JP2011148853A - Double-sided pressure-sensitive adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive tape that has good adhesion to an adherend, and can be suitably released without leaving any adhesive tails or destroying a supporting substrate when released. <P>SOLUTION: This double-sided pressure-sensitive adhesive tape has a structure including a pressure-sensitive adhesive layer with a release sheet formed on both sides of a nonwoven fabric material, which is made by laminating a water-dispersed pressure-sensitive acrylic adhesive composition applied on the release sheet to both sides of the nonwoven fabric material. The total light transmittance of the nonwoven fabric material is ≥70%, and tensile strength of the MD and TD direction is 25-40 N/20 mm. The pressure-sensitive adhesive composition includes emulsion particles of an acrylic copolymer, dispersed in an aqueous medium, containing n-butyl acrylate, 2-ethylhexyl acrylate and a carboxyl group-bearing vinyl monomer as monomer components. A gel fraction of the adhesive composition, upon lamination, measured after removal of the aqueous medium is ≤10%, and the total light transmittance of the double-sided pressure-sensitive adhesive tape is ≥75%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape having adhesive layers made of a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed in an aqueous medium, on both surfaces of a nonwoven fabric substrate.

  Adhesive tape is used as a bonding means with excellent workability and high bonding reliability in parts such as office automation equipment, home appliances, and automobiles for parts fixing and labeling for displaying product information. On the other hand, from the viewpoint of protecting the global environment, assembly products such as OA equipment are often disassembled after use and recycled and reused. At this time, when the parts are joined with the adhesive tape or when the label is attached, an operation for peeling the adhesive tape or the label is required, and the adhesive can be removed without breaking the residue or the supporting substrate. Characteristics (so-called removability) are required. Further, in recent years, suppression of emission of volatile organic compounds (so-called VOC) has been strongly demanded. In the pressure-sensitive adhesive tape, a solventless type pressure-sensitive adhesive has attracted attention, and replacement of a solvent-type pressure-sensitive adhesive with a water-dispersed pressure-sensitive adhesive has been desired.

  Conventionally, as a double-sided pressure-sensitive adhesive tape having high adhesion reliability and removability, (a) (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms, (b) nitrogen-containing vinyl (C) an acrylic copolymer comprising, as a main component, an acrylic copolymer comprising a hydroxyl group-containing monomer or a carboxyl group-containing monomer that reacts with a crosslinking agent (c), and (d) an isocyanate crosslinking agent. There is disclosed a double-sided pressure-sensitive adhesive tape composed of a PSA-based pressure-sensitive adhesive composition and a nonwoven core having a specific strength (see Patent Document 1). However, when the double-sided pressure-sensitive adhesive tape of the present technology is constituted by an emulsion polymerization method, it has been difficult to develop excellent removability.

  Further, a re-peelable pressure-sensitive adhesive tape using an emulsion-type pressure-sensitive adhesive and using a nonwoven fabric base material as a base material is disclosed (see Patent Document 2). The pressure-sensitive adhesive tape has excellent adhesion and removability to adherends such as SUS and ABS. Improvement of removability has been demanded.

JP-A-8-209086 JP2008-239872A

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive tape that has a good adhesive force to an adherend and can be suitably peeled off without causing adhesive residue or destruction of the support substrate. .

  In the present invention, an adhesive composition with good removability is laminated on a specific nonwoven fabric substrate having high tensile strength at a low initial gel fraction, and the total light transmittance of the resulting adhesive tape is increased. As a result, the adhesion and impregnation between the layers of the pressure-sensitive adhesive tape are improved, and excellent removability can be realized while having excellent adhesive performance.

  That is, the present invention is a double-sided pressure-sensitive adhesive tape in which a water-dispersed acrylic pressure-sensitive adhesive composition applied on a release sheet is laminated on both surfaces of a nonwoven fabric substrate, and a pressure-sensitive adhesive layer with a release sheet is formed on both surfaces of the nonwoven fabric substrate. The nonwoven fabric substrate has a total light transmittance of 70% or more, a tensile strength in the MD direction and TD direction of 25 to 40 N / 20 mm, and the water-dispersed acrylic pressure-sensitive adhesive composition is 2-ethylhexyl. Water-dispersed acrylic pressure-sensitive adhesive in which emulsion particles of an acrylic copolymer containing an acrylate, a (meth) acrylate having a C 4-8 alkyl group, and a carboxyl group-containing vinyl monomer as monomer components are dispersed in an aqueous medium The gel fraction measured by removing the aqueous medium of the water-dispersed acrylic pressure-sensitive adhesive composition at the time of lamination is 10% or less. , The total light transmittance of the double-sided adhesive tape is to provide a double-sided adhesive tape is 75% or more.

  The double-sided pressure-sensitive adhesive tape of the present invention can significantly reduce the emission of volatile organic compounds (so-called VOC) and organic solvent odor, adheres firmly to the adherend, and is difficult to remove. A so-called adhesive residue and a pressure-sensitive adhesive tape that does not destroy the supporting substrate can be obtained.

<Water-dispersed acrylic pressure-sensitive adhesive composition>
(Acrylic copolymer)
In the water-dispersed acrylic pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention, 2-ethylhexyl acrylate, carbon number 4 is used as the acrylic copolymer that forms the acrylic copolymer emulsion particles. An acrylic copolymer containing (meth) acrylate having 8 to 8 alkyl groups and a carboxyl group-containing vinyl monomer as monomer components is used.

  In the present invention, by using 2-ethylhexyl acrylate as a monomer component, the pressure-sensitive adhesive is easily impregnated into the nonwoven fabric, and the nonwoven fabric is difficult to break during re-peeling. As content of 2-ethylhexyl acrylate, it is preferable that it is 10-90 mass%, and it is more preferable that it is 20-80 mass%. By keeping the content of 2-ethylhexyl acrylate within this range, it is easy to suppress the adhesion between the pressure-sensitive adhesive and the adherend over time, and the adhesive strength hardly rises excessively. it can.

  Moreover, by using together with 2-ethylhexyl acrylate and using the (meth) acrylate which has a C4-C8 alkyl group, strong adhesiveness can be improved greatly, maintaining removability. Examples of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isooctyl (meth) acrylate, and n-octyl (meta ) (Meth) acrylates such as acrylates can be used. Among them, acrylate monomers having an alkyl group having 4 to 8 carbon atoms are preferably used, and n-butyl acrylate can be particularly preferably used. It is also preferable to use n-butyl acrylate and t-butyl methacrylate in combination. The amount of (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably 10 to 80% by mass, and more preferably 20 to 70% by mass.

  In the present invention, the 2-ethylhexyl acrylate and the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms can be expressed more suitably in the monomer component forming the acrylic copolymer. The sum of the contents of ethylhexyl acrylate and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably 50 to 98% by mass, and particularly preferably 80 to 98% by mass. The ratio of the content of 2-ethylhexyl acrylate in the monomer component forming the acrylic copolymer and the (meth) acrylate having a C 4-8 alkyl group is (2-ethylhexyl acrylate / C 4 -C The mass ratio represented by (meth) acrylate having 8 alkyl groups is preferably 9/1 to 2/8, and particularly preferably 75/25 to 25/75.

  In the present invention, (meth) acrylate monomers other than those described above may be used in combination as the (meth) acrylate monomer that forms the acrylic copolymer. Examples of other (meth) acrylate monomers include (meth) acrylate monomers such as methyl (meth) acrylate and ethyl (meth) acrylate, and one or more of these may be used in combination. . Especially, it is preferable to use together (meth) acrylate which has a C2-C2 alkyl group, such as methyl (meth) acrylate and ethyl (meth) acrylate, and it is preferable that it is 1-10 mass% as usage-amount. .

  In the present invention, by using a carboxyl group-containing vinyl monomer in combination with the above monomer, the cohesive force of the pressure-sensitive adhesive layer can be improved, and suitable adhesiveness and removability can be combined. Examples of the carboxyl group-containing vinyl monomer include one or two selected from carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, phthalic acid, phthalic anhydride, and crotonic acid. The above can be used. Among them, it is preferable to use at least one of acrylic acid and methacrylic acid, and it is particularly preferable to use acrylic acid and methacrylic acid in combination. The carboxyl group of acrylic acid and methacrylic acid is easy to ensure cohesive force by interaction between carboxyl groups, there are many means for increasing cohesive force with many reactive crosslinking agents, and interaction with the nitrogen-containing vinyl monomer described later. It has the advantage that it can be expressed. Furthermore, in the present invention, acrylic acid tends to be oriented in the vicinity of the particle surface and methacrylic acid is oriented inside the particle by using acrylic acid having relatively high hydrophilicity and methacrylic acid that is more hydrophobic than acrylic acid. The acid groups can be arranged in a well-balanced manner on the surface and inside of the acrylic copolymer emulsion particles. The presence of acid groups in the vicinity of the particle surface can ensure cohesion between emulsion particles, and the presence of acid groups present in the particles can improve cohesion within emulsion particles. As a result, the pressure-sensitive adhesive layer obtained can reduce a portion having a low cohesive force and can suitably suppress deterioration of re-peelability over time. . Moreover, the combined use of methacrylic acid and acrylic acid has the effect of greatly improving the constant load performance necessary for strong adhesion.

  As for the content of the carboxyl group-containing vinyl monomer, the sum of the contents of the carboxyl group-containing vinyl monomer in the monomer component forming the acrylic copolymer is preferably 0.5 to 10% by mass. More preferably, it is 0.5-5 mass%, More preferably, it is 1.5-3.5 mass%. By setting it within this range, the crosslinking reaction with the crosslinking agent easily proceeds well. Furthermore, when the pressure-sensitive adhesive layer is formed, a cohesive force suitable for the pressure-sensitive adhesive layer is ensured, and it is easy to achieve both removability and strong adhesiveness. Furthermore, the cohesive force necessary for ensuring water resistance and the hydrophobicity of the pressure-sensitive adhesive layer surface can be ensured.

  When the methacrylic acid and acrylic acid are used in combination, the molar equivalent ratio of methacrylic acid / acrylic acid is preferably 0.2 or more, more preferably 3 or more, and further preferably 4 or more. Preferably, it is 6 or more. By setting the combined ratio within the above range, the amount of surface acid groups and the amount of internal acid groups in the acrylic copolymer emulsion particles can be suitably controlled.

  In the present invention, it is preferable to further use a nitrogen-containing vinyl monomer as the monomer component of the acrylic copolymer. The nitrogen-containing vinyl monomer is presumed to produce an effect of drawing a carboxyl group that is easily oriented on the particle surface into the particle by interacting with an acid group, particularly a carboxyl group, in the acrylic copolymer emulsion particles. In order to produce this effect, the content of the nitrogen-containing vinyl monomer is preferably set to the above lower limit or more. On the other hand, when the content is increased, the reactivity with the crosslinking agent described later tends to decrease, but by setting the content to the upper limit or less, necessary reactivity can be ensured. When the content is within this range, the acid group distribution in the acrylic copolymer emulsion particles can be easily converged to a suitable distribution range.

  Examples of the nitrogen-containing vinyl monomer include one or more selected from N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylonitrile, acrylamide, N, N-dimethylacrylamide and dimethylaminoethyl (meth) acrylate. Can be used.

  Among these, as the nitrogen-containing vinyl monomer, it is more preferable to use a monomer having an amide group. In the case of amine-based nitrogen-containing monomers, the interaction with acid groups becomes too strong, so the amount of acid groups on the particle surface tends to decrease, the interaction between emulsion particles weakens, and a cohesive force as an adhesive is obtained. It becomes difficult to be.

  When the nitrogen-containing vinyl monomer is used, the content of the nitrogen-containing vinyl monomer in the monomer component forming the acrylic copolymer is preferably 0.1 to 4.5% by mass, and more preferably, 0.1%. By adjusting in the range of 5 to 4% by mass, more preferably 0.5 to 3.5% by mass, the effects of the present invention can be suitably expressed.

  When the nitrogen-containing vinyl monomer is used, the ratio of the nitrogen-containing vinyl monomer to the vinyl monomer having a carboxyl group in the acrylic copolymer is not particularly limited, but the monomer component constituting the acrylic copolymer The molar ratio X / Y is preferably 1/1 to 1/20, where X is the number of moles of the nitrogen-containing vinyl monomer and Y is the number of moles of the vinyl monomer having a carboxyl group, 1/5 is more preferable, and 1/1 to 1/3 is still more preferable. If it is in the said range, reaction with the vinyl monomer which has a carboxyl group, and the crosslinking agent mentioned later will advance easily. Furthermore, it becomes easy to converge the distribution of carboxyl groups in the acrylic copolymer emulsion to a range described later.

  In the acrylic copolymer used in the present invention, monomers other than those described above can be used as necessary. Examples of such monomers include a hydroxyl group-containing monomer, (meth) acrylic acid 2-hydroxy Alcoholic hydroxyl group-containing monomers such as ethyl, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like can be used as appropriate. As keto group or aldehyde group-containing monomer, diacetone acrylamide, diacetone methacrylamide, acrolein, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone acrylate, diacetone methacrylate, acetonitrile acrylate, 2-hydroxypropyl Examples include acrylate acetoacetate and butanediol acrylate acetate. As the silane monomer, 3-methacryloxypropylmethyldimethoxysilane [for example, KBM-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltrimethoxysilane [for example, KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3 -Methacryloxypropylmethyldiethoxysilane [for example, KBE-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltriethoxysilane [for example, KBE-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-acryloxypropyltri And methoxysilane [for example, KBM-5103 manufactured by Shin-Etsu Chemical Co., Ltd.]. Moreover, N methylol acrylamide etc. are mentioned as a methylol group containing monomer. Examples of the phosphoric acid group-containing monomer include Sipomer PAM-100, PAM-200, and PAM-300 manufactured by Rhodia Nikka Co., Ltd., and 20% by mass or less in the monomer component forming the acrylic copolymer. It can be used at a ratio of 1 type or 2 types or more.

  The weight average molecular weight of the acrylic copolymer used in the present invention is preferably 500 to 1,200,000, more preferably 60 to 1,000,000. By setting it within the range, it is possible to balance both the flexibility when the pressure-sensitive adhesive impregnates the nonwoven fabric and the cohesive force necessary for removability. The said weight average molecular weight is standard polystyrene conversion by a gel permeation chromatography (GPC). As measurement conditions, TSKgel GMHXL [manufactured by Tosoh] is used as the column, the column temperature is 40 ° C., the eluent is tetrahydrofuran, the flow rate is 1.0 mL / min, and the standard polystyrene is TSK standard polystyrene.

  In order to adjust the molecular weight, a chain transfer agent may be used in the polymerization. Examples of the chain transfer agent include known chain transfer agents such as lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. Can be used.

(Type of tackifying resin)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a tackifying resin in order to adjust the strong adhesiveness of the resulting pressure-sensitive adhesive layer. As the tackifier resin used in the present invention, an emulsion type tackifier resin can be preferably used from the viewpoint of use in an aqueous dispersion type pressure-sensitive adhesive composition. Examples of the emulsion-type tackifying resin include rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, disproportionated rosin ester, terpene, terpene phenol, petroleum resin, etc. Can be illustrated.

  Among these, a polymerized rosin ester-based tackifier resin and a rosin phenol-based tackifier resin are preferable, and it is particularly preferable to blend these in combination. Specifically, polymerized rosin ester-based tackifier resins are Superester E-650 [Arakawa Chemical Industries, Ltd.], Superester E-788 [Arakawa Chemical Industries, Ltd.], Superester E-786. 60 [Arakawa Chemical Industries, Ltd.], Super Ester E-865 [Arakawa Chemical Industries, Ltd.], Super Ester E-865NT [Arakawa Chemical Industries, Ltd.], Harrier Star SK-508 [Harima Chemicals ( Co., Ltd.] Harrier Star SK-508H [Harima Kasei Co., Ltd.], Harrier Star SK-816E [Harima Kasei Co., Ltd.], Harrier Star SK-822E [Harima Kasei Co., Ltd.], Harrier Star SK- 323NS [manufactured by Harima Chemicals Co., Ltd.] and the like, and rosin phenolic tackifying resins are Tamanoru E-100 [manufactured by Arakawa Chemical Industries, Ltd.], Tamanoru E 200 [(manufactured by Arakawa Chemical Industry Ltd.), Tamanol E-200NT Arakawa Chemical Industries, Ltd.], and the like.

  When these are used in combination, the ratio of the polymerized rosin ester-based tackifier resin (A) to the rosin phenol-based tackifier resin (B) is 5 / in a mass ratio represented by (A) / (B). It is preferably 1 to 1/5, more preferably 3/1 to 1/3, and still more preferably 1/1 to 1/3. If it is in the said range, re-peelability and strong adhesiveness can be improved with good balance.

  The softening point of the tackifying resin is preferably 120 to 180 ° C, more preferably 140 to 180 ° C. By adding a tackifying resin having a high softening point, strong adhesiveness is improved.

  In the blend ratio of the acrylic copolymer / tackifying resin, the acrylic copolymer / tackifying resin = 100/10 to 100/40 is preferable, and the acrylic copolymer / tackifying resin = 100 is more preferable. / 15 to 100/35. If it is in the said range, re-peelability and strong adhesiveness can be improved with good balance.

(Crosslinking agent)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a crosslinking agent for the purpose of improving the cohesive strength of the resulting pressure-sensitive adhesive layer. Examples of the crosslinking agent include known isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, polyvalent metal salt crosslinking agents, metal chelate crosslinking agents, keto-hydrazide crosslinking agents, oxazoline crosslinking agents, and carbodiimide crosslinking agents. A crosslinking agent, a silane crosslinking agent, a glycidyl (alkoxy) epoxysilane crosslinking agent, or the like can be used. Among them, a type of crosslinking agent that is added after the completion of polymerization and causes the crosslinking reaction to proceed is preferable. Examples thereof include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, a carbodiimide-based crosslinking agent, and a glycidyl (alkoxy) epoxysilane-based crosslinking agent. Specifically, in the isocyanate-based cross-linking agent, Bernock DNW-5000 [manufactured by DIC Corporation], Bernock DNW-5010 [manufactured by DIC Corporation], Bernock DNW-5100 [manufactured by DIC Corporation], Bernock DNW- 5500 [manufactured by DIC Corporation], Aquanate 100 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 105 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 110 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 120 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 130 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 200 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 210 [manufactured by Nippon Polyurethane Industry Co., Ltd.], LS2319 [manufactured by Sumika Bayer Urethane Co., Ltd.], LS2336 [Sumika Bayer Ure Tanhydr Co., Ltd.], Bayhydur 3100 [manufactured by Sumika Bayer Urethane Co., Ltd.] and the like, and epoxy crosslinking agents include Denacol EX-832 [Nagase Kasei Kogyo Co., Ltd.], Denacol EX-841 [Nagase Kasei] Kogyo Co., Ltd.], Tetrad C [Mitsubishi Gas Chemical Co., Ltd.], Tetrad X [Mitsubishi Gas Chemical Co., Ltd.], etc. Catalyst manufactured], Epocross WS-700 [manufactured by Nippon Shokubai Co., Ltd.], Epocross K-2010E [manufactured by Nippon Shokubai Co., Ltd.], Epocross K-2020E [manufactured by Nippon Shokubai Co., Ltd.], Epocross K-2030E [(stock) ) Manufactured by Nippon Shokubai Co., Ltd., and carbodiimide-based crosslinking agents include Carbodilite SV-02 [Nisshinbo Co., Ltd.], Carbodilite V-02 [Nisshinbo ( )], Carbodilite V-02-L2 [Nisshinbo Co., Ltd.], Carbodilite V-04 [Nisshinbo Co., Ltd.], Carbodilite E-01 [Nisshinbo Co., Ltd.], Carbodilite E-02 [Nisshinbo Co., Ltd.] )], Carbodilite E-03A [Nisshinbo Co., Ltd.], Carbodilite E-04 [Nisshinbo Co., Ltd.], and glycidyl (alkoxy) epoxysilane crosslinking agents, 2- (3,4-epoxycyclohexylethyltrimethoxy) Silane [KBM-303; Shin-Etsu Silicone Co., Ltd.], γ-glycidoxypropyltrimethoxysilane [KBM-403; Shin-Etsu Silicone Co., Ltd.], γ-glycidoxypropylmethyldiethoxysilane [KBE-402 Manufactured by Shin-Etsu Silicone Co., Ltd.], γ-glycidoxypropyltriethoxysilane [KBE-403; Manufactured by Co., Ltd.] and the like. As an index of the degree of cross-linking, the degree of cross-linking is adjusted using the value of the gel fraction that measures the insoluble content after the pressure-sensitive adhesive layer has been immersed in toluene for 24 hours. The gel fraction is preferably 20 to 45% by mass. More preferably in the range of 25 to 45% by mass, and still more preferably in the range of 28 to 38% by mass, re-peelability and strong adhesiveness can be ensured with a good balance.

  Especially, it is preferable to use the crosslinking agent which reacts with the above-mentioned carboxyl group-containing vinyl monomer, and the above-mentioned isocyanate-based crosslinking agent, epoxy compound, oxazoline compound, carbodiimide-based crosslinking agent, glycidyl (alkoxy) epoxysilane compound and the like are preferable. The present invention is a technique characterized by ensuring the cohesive force of the acrylic copolymer over the whole by orienting an appropriate amount of acid groups both on the emulsion particle surface and inside the particle. By using a cross-linking agent that reacts with an acid group, an improvement in cohesion can be suitably achieved.

(Additive)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, as an additive, a base (such as aqueous ammonia) for adjusting the pH within a range that does not impair the desired effect of the present invention, if necessary, Acids, plasticizers, softeners, antioxidants, fillers such as glass and plastic fibers, balloons, beads, and metal powders, colorants such as pigments and dyes, pH adjusters, film formation aids, leveling agents, Known materials such as thickeners, water repellents, and antifoaming agents can be optionally added to the pressure-sensitive adhesive composition.

(Production method)
The water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention can be produced by an emulsion polymerization method for obtaining an emulsion-type pressure-sensitive adhesive. In the emulsion polymerization, an appropriate amount of an anionic or nonionic emulsifier or other dispersion stabilizer is used in order to ensure polymerization stability. Especially an emulsifier is not restrict | limited, A well-known emulsifier can be used. Examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate and the like. Examples thereof include ethylene alkyl ether and polyoxyethylene alkyl phenyl ether.
Furthermore, it is preferable to use an emulsifier having a polymerizable unsaturated group in the molecule, which is known as a “reactive emulsifier”. Specifically, Latemul S-180 [manufactured by Kao Corporation], Latemu PD-104 [manufactured by Kao Corporation], Aqualon HS-10 [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon HS-20 [No. Ichi Kogyo Seiyaku Co., Ltd.], Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon KH-05 [Daiichi Kogyo Seiyaku Co., Ltd. )], Aqualon RN-10 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon RN-20 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon ER-10 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon ER-20 [Daiichi Kogyo Seiyaku Co., Ltd.], New Frontier A-229E [Daiichi Kogyo Seiyaku Co., Ltd.], Adeka Soap SE-10 [Asahi Denka Kogyo Co., Ltd.], Adeka Soap SE -20 [Asahi Denka Kogyo Co., Ltd.], Adeka Asopu SR-10 N [Asahi Denka Co., Ltd.], ADEKAREASOAP SR-20 N [Asahi Denka Co., Ltd.], and the like. It is preferable to use a reactive emulsifier because the water resistance of the coating is improved in addition to the polymerization stability.

  Among the emulsion polymerization methods, it is preferable to use a dropping polymerization method. Moreover, in order to make it easy to introduce an acid group into the particle, a dropping polymerization method may be selected and controlled by changing the composition of the emulsion to be dropped in the first half and the second half of the dropping. Specifically, the acid monomer can be introduced into the particles by increasing the ratio of the acid monomer in the first half of the dropping and decreasing the ratio of the acid monomer in the second half of the dropping.

  The polymerization initiator used in the emulsion polymerization is not limited, and a known polymerization initiator can be used. Specifically, 2,2 ′,-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (2-amidinopropane) ) Dihydrochloride, 2,2′-azobis [N- (2-arboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) Azo initiators such as hydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, persulfate initiators such as potassium persulfate, ammonium persulfate, sodium persulfate Agents, benzoyl peroxide, t-butyl hydroperoxide, peroxide initiators such as hydrogen peroxide, carbonyl initiators such as aromatic carbonyl compounds, persulfate and sodium hydrogensulfite Combination with helium, and the like redox initiators such as a combination of a peroxide and sodium ascorbate.

  In addition, the solid content concentration of the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention is not particularly limited, but in terms of manufacturing costs and transportation costs, and when used after drying. From the viewpoint of excellent drying properties, the solid content concentration is preferably 40 to 70% by weight.

  The aqueous medium used in the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention may be water alone or a mixed solvent of water and a water-soluble solvent. The above-mentioned “mixed solvent of water and water-soluble solvent” usable in the present invention is a mixed solvent of a water-soluble solvent mainly composed of water, and the water-soluble solvent with respect to the total amount of the mixed solvent. The content of is preferably 10% by weight or less, more preferably 5% by weight or less. Examples of the water-soluble solvent include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, butyl cellosolve, or polar solvents such as N-methylpyrrolidone, which may be used alone. Two or more kinds may be used in combination.

  In addition, the average particle diameter of the acrylic copolymer emulsion particles in the present invention is not particularly limited, but if it is 150 nm or less, it may be difficult to introduce acid groups into the emulsion particles, so that it exceeds 150 nm. The particle size is preferably 200 to 1000 nm, more preferably 200 to 800 nm, still more preferably 200 to 600 nm, and even more preferably 250 to 400 nm.

  Here, the average particle diameter of the particles means a 50% median diameter of the emulsion particles on the volume basis, and the numerical values are based on values obtained by measurement by a dynamic light scattering method. If the average particle size becomes too small, the surface area of the particles increases and the proportion of the particle surface in contact with water increases. As a result, for example, when a carboxyl group is used as the acid group, the carboxyl group is easily ionized into a carboxylate anion, and the tendency of the carboxyl group to localize on the particle surface is increased.

For this reason, the ratio (AN _IN ) / (AN _SUR ) between the amount of acid groups on the surface of the resulting acrylic copolymer emulsion and the amount of acid groups inside (AN _SUR ) may not be within the desired range as described above. . Accordingly, the average particle diameter is preferably more than 150 nm. On the other hand, when the average particle size becomes too large, an excessively large average particle size is not preferable in order to promote fusion between the emulsion particles after forming the pressure-sensitive adhesive layer, and it is preferable to suppress the average particle size to 1000 nm or less.

(Distribution of acid groups)
Acrylic copolymer emulsion particles in the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention include the amount of acid groups (AN _SUR ) on the surface of the acrylic copolymer emulsion particles and the acrylic copolymer emulsion particles. It is desirable that the ratio (AN _IN ) / (AN _SUR ) to the internal acid group amount (AN _IN ) is one or more acrylic copolymer emulsion particles. In the present invention, by using an acrylic copolymer in which the amount of acid groups inside is equal to or greater than the amount of acid groups on the surface, adhesive residue can be reduced and excessive increase in adhesive strength over time can be suppressed. Thus, an adhesive tape having suitable removability can be realized. According to the water-dispersed acrylic pressure-sensitive adhesive composition using such acrylic copolymer emulsion particles, excellent removability is achieved even when a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer is used. Therefore, it is possible to realize a pressure-sensitive adhesive tape excellent in both characteristics of conflicting strong adhesion and re-peeling. Furthermore, adhesive tapes with excellent water resistance can be obtained by securing cohesive force by acid group orientation both between and within the particles and reducing the hydrophilicity of the pressure-sensitive adhesive layer surface by improving the amount of acid groups on the particle surface (improving hydrophobicity). be able to. The acid group amount ratio (AN _IN ) / (AN _SUR ) is preferably 1.3 or more, more preferably 1.5 or more, and further preferably 2.0 or more. On the other hand, the upper limit is not particularly limited as long as there is a surface acid group amount (A _SUR ) that can ensure cohesion between the acrylic copolymer emulsion particles, but the ratio is preferably 10 or less, and preferably 5 or less. Is more preferable. When it is within the above-mentioned upper limit range, the interaction between the particles easily proceeds, the cohesive force between the particles is easily increased, and the removability and water resistance are improved.

(Measurement method of acid group distribution)
The distribution of acid groups in the acrylic copolymer emulsion particles used in the present invention is measured by the following method. The method for measuring the distribution of acid groups in the acrylic copolymer emulsion particles in the present invention is preferably a potentiometric titration because it is a simple operation with little measurement error. The acid group can be measured by potentiometric titration according to the method disclosed in Japanese Patent Application Laid-Open No. 2007-003454, and is measured in detail by the following method.

(Measurement method of acid group distribution using potentiometric titration)
In the present invention, a method for measuring the distribution of acid groups in the acrylic copolymer emulsion particles using potentiometric titration is shown below.

  The acidic sample dispersion used for potentiometric titration can be prepared by mixing acrylic copolymer emulsion particles (solid content) and ion-exchanged water at a mass ratio represented by (acrylic copolymer emulsion / ion-exchanged water). Adjust to / 100. Extraction of the acrylic copolymer emulsion particles from the water-dispersed acrylic pressure-sensitive adhesive composition may be performed in a state of being dispersed in an aqueous medium or in a state of being separated from the aqueous medium. The acidic sample dispersion to be adjusted is preferably an acidic sample dispersion having a pH of 4 or less. From the water-dispersed acrylic pressure-sensitive adhesive composition neutralized with ammonia water or the like, acrylic acid is dispersed in an aqueous medium. When extracting the copolymer emulsion, it is preferable to adjust the pH to 4 or less by adding a weak acid such as formic acid or butyric acid to the sample dispersion as necessary.

  For titration, an automatic potentiometric titrator can be used. Examples of the automatic potentiometric titrator include AT-610, AT-420N-WIN manufactured by Kyoto Electronics Co., Ltd.

Calculation of the acid group amount (AN _SUR ) and the internal acid group amount (AN _IN ) on the surface of the acrylic copolymer emulsion particles is calculated based on a titration curve obtained by potentiometric titration. When potentiometric titration is performed with the X-axis as the base dropping amount and the Y-axis as the pH, between the titration start point P ₀ and the titration end point P ₃ , the minimum point P ₁ and the minimum point P at which the pH becomes minimum after the base titration starts. titration curve having an inflection point P ₂ appearing next to ₁ (FIG. 1) is obtained. The local minimum point P ₁ and the inflection point P ₂ are more clearly converted to a differential curve (FIG. 2) of a titration curve in which the X-axis is a base dropping amount (mL) and the Y-axis is ΔE / mL. easily read the ₁ and _{P 2.}

The region of P _{0 to} P ₁ in the titration curve is a region where the free acid in the aqueous phase of the sample dispersion is neutralized, and the pH value decreases as the free acid in the aqueous phase is neutralized. shows the minimum value P ₁ that the pH value becomes minimum when neutralized. Therefore, the amount of base dripped in this region is the titration amount required to neutralize the acid in the aqueous phase. From the base titration and the base concentration of the inorganic base solution used for the titration, the acid group amount (AN _AQUA ) [meq / g] in the aqueous phase in the sample dispersion is calculated.

In the water-dispersed acrylic pressure-sensitive adhesive composition, since the acid used for polymerizing the acrylic copolymer generally remains, the acrylic copolymer emulsion particles are extracted in a state dispersed in an aqueous medium. Free acid is present in the aqueous phase of the sample dispersion. On the other hand, when only the acrylic copolymer emulsion particles are separated and dispersed in ion-exchanged water, there is a possibility that P ₀ = P ₁ because there is theoretically no acid in the aqueous phase. .

When the acid in the aqueous phase is neutralized, the acid groups on the surface of the acrylic copolymer emulsion particles that are easily neutralized are then neutralized. Since this becomes the region of P _{1 to} P ₂ of the titration curve, the amount of base dripped in this region is the titration amount required to neutralize the acid groups on the surface of the acrylic copolymer emulsion particles. The acid group amount (AN _SUR ) [meq / g] on the surface of the acrylic copolymer emulsion particles is calculated from the base titration and the base concentration of the inorganic base solution used for the titration.

When the acid groups on the surface of the acrylic copolymer emulsion particles are neutralized, neutralization of the acid groups inside the acrylic copolymer emulsion particles, which are difficult to neutralize, begins. This is the inflection point P ₂ in the titration curve. Appears as The amount of acid groups (AN _IN ) inside the acrylic copolymer emulsion particles is determined by titration of the total amount of acid groups present inside the emulsion particles when the emulsion particles form particles stably. Therefore, it is preferable to calculate from the above calculation result and the total acid group amount (AN _TOTAL ) in the sample dispersion by the following formula.
AN _IN = AN _TOTAL- (AN _SUR + AN _AQUA )

  In the inorganic base solution used for the titration, potassium hydroxide or sodium hydroxide can be preferably used as the inorganic base used for titration, and potassium hydroxide is particularly preferably used. The concentration of the inorganic base used for titration is preferably adjusted in the range of 0.1 to 2 mol / L.

  As other titration conditions, it is preferable to perform titration by intermittent constant rate titration, the intermittent time is 10 seconds, the maximum dripping amount is 20 mL, the single injection amount at the intermittent injection is preferably 0.16 mL / time, and the injection speed Is preferably 5 seconds / mL, the potential for collecting data is 4 mL, and the titration for detecting pH is preferably performed every 0.16 mL.

  To illustrate a specific measurement method, a water-dispersed acrylic pressure-sensitive adhesive composition containing 3 g of acrylic copolymer emulsion particles (solid content) was weighed into a 300 mL polyethylene beaker with a dropper, Ion exchange water is poured into the polyethylene beaker until the total amount of the test sample reaches 100 g and stirred. Then, the electrode and the temperature assurance electrode are immersed. The tip of the titration nozzle is higher than the liquid level, and is 2 cm away from the electrode so that the titration reagent does not reach the electrode. Under the above conditions, automatic potentiometric titration is started with stirring. After the measurement is completed, meq / g is calculated from the titration amount at the equivalent point automatically printed on the obtained titration curve.

(Method of measuring the total amount of acid groups)
The total acid group amount (AN _TOTAL ) in the acidic sample dispersion can be obtained by a measurement method based on potentiometric titration with an inorganic acid solution as shown below, even when calculated from the theoretical amount of acid groups calculated from the charged amount. The obtained value may be used. A method for measuring the total amount of acid groups (AN _TOTAL ) in the sample dispersion by potentiometric titration is described below.

  For the preparation of the sample dispersion, potassium hydroxide is added to a sample dispersion equivalent to the acidic sample dispersion used above until pH 13 and all acid groups including the inside of the particles are neutralized. When the dispersion of acrylic copolymer emulsion particles is a basic sample dispersion having a pH of 13, all acid groups inside are drawn out to the surface of the emulsion particles by electrostatic interaction. Therefore, by performing back titration of the basic sample dispersion with an inorganic acid solution, the acid groups on the surface of the acrylic copolymer emulsion particles and the acid groups on the inside can be titrated equally, and the total amount of acid groups in the sample dispersion Can be calculated.

  The acid used for the titration is preferably sulfuric acid, and the concentration is preferably 0.1 mol / L. As the potentiometric titration apparatus, an apparatus similar to the above can be preferably used.

When potentiometric titration is performed with the X-axis being the acid dropping amount and the Y-axis being the pH, the inflection points Q ₁ , Q ₂ , Q _{3 are in the} order of the acid titration from the titration start point Q ₀ to the titration end point Q _4. A titration curve is obtained (FIG. 3). By converting these inflection points into differential curves (FIG. 4) of titration curves in which the X axis is the acid drop amount (mL) and the Y axis is ΔE / mL, the inflection points can be read more clearly. X-coordinate at these inflection points _{Q1, Q} 2, _{Q 3} is an acid dropped quantity at each _point, acid dropping amount in Q 0 to Q ₁ neutralizing the residue of potassium hydroxide used in adjusting to pH13 This is the titration amount required to do this. The acid dripping amount in Q _{1 to} Q ₂ is a titration amount required to neutralize all acid groups present in the acrylic copolymer emulsion particles, and the acid dripping amount in Q _{2 to} Q ₃ is the water phase. This is a titration amount required to neutralize the acid groups therein. Therefore, the total amount of acid groups in the acidic sample dispersion is converted into meq / g based on the amount of acid dropped in Q _{1 to} Q ₃ and the concentration of acid used for titration. (AN _TOTAL ) is calculated.

  As a specific measurement method, a water-dispersed acrylic pressure-sensitive adhesive composition containing 3 g of acrylic copolymer emulsion particles (solid content) was weighed into a 300 mL polyethylene beaker with a dropper, and then Ion exchange water is poured into a polyethylene beaker until the total amount of the test sample reaches 100 g and stirred. Subsequently, 1N potassium hydroxide is added and stirred until the test sample reaches pH 13. Then, the electrode and the temperature assurance electrode are immersed. The potentiometric automatic titration is started in the same manner as the titration conditions described above. After the measurement is completed, meq / g is calculated from the titration amount at the equivalent point automatically printed on the obtained titration curve.

  The introduction of acid groups into the acrylic copolymer emulsion particles can be controlled by appropriately selecting the monomer composition and polymerization method. As the monomer composition, acid groups can be introduced into the particles by increasing the hydrophobicity of the acid monomer. Moreover, an acid group can also be introduce | transduced inside a particle | grain by copolymerizing the nitrogen-containing monomer which interacts with an acid group. On the other hand, as the polymerization method, a so-called dropping polymerization method can be selected and controlled by changing the composition of the emulsion to be dropped in the first half and the second half of the dropping. Specifically, the acid monomer can be introduced into the particles by increasing the ratio of the acid monomer in the first half of the dropping and decreasing the ratio of the monomer having an acid group in the second half of the dropping.

<Nonwoven fabric substrate>
In the double-sided pressure-sensitive adhesive tape of the present invention, a nonwoven fabric base material having a total light transmittance of 70% or more and a tensile strength in the MD direction and TD direction of 25 to 40 N / 20 mm is used as the center.

  The tensile strength of the nonwoven fabric is 10 to 50 N / 20 mm, preferably 15 to 40 N / 20 mm, more preferably 25 to 40 N / 20 mm in both the MD direction (longitudinal direction; flow direction) and the TD direction (transverse direction; width direction). By doing so, it is difficult for the tape to break at the time of re-peeling, and it is also difficult to peel off when pasted on a curved surface or the like. The tensile strength described above was measured using a Tensilon tensile tester on a sample having a vote line length of 100 mm and a width of 20 mm under a measurement condition of a tensile speed of 300 mm / min in an environment of 23 ° C. and 50% RH. The maximum intensity.

  Moreover, an adhesive composition can impregnate suitably because the total light transmittance of a nonwoven fabric base material shall be 70% or more, and the total light transmittance of the adhesive tape obtained can be made high.

[Measurement method of total light transmittance]
The total light transmittance can be measured by, for example, a reflection / transmittance meter HR-100 manufactured by Murakami Color Research Laboratory in accordance with JIS K 7105.

  The tear strength of the nonwoven fabric is preferably 1 N or more as the tear strength specified in JIS-P-8116. By setting the tear strength to 1 N or more, it is possible to remarkably suppress the breakage of the nonwoven fabric that occurs when the starting point of breakage occurs due to the instantaneous tearing in the peeling process and expands, and the base material is difficult to cut. As a result, the removability of the double-sided pressure-sensitive adhesive tape adhered to the adherend for a long time can be greatly improved. The upper limit of the tear strength is not particularly defined, but a tear strength of about 3N is usually assumed as the upper limit for a substrate using a nonwoven fabric. Preferably it is 1.2-2.5N, More preferably, it is 1.5-2.5N.

  The interlayer strength of the nonwoven fabric is preferably 1 N / 15 mm or more. The interlayer strength is measured by first sticking a 24 mm wide adhesive film (Nichiban CT405AP-24) on both sides of a 25 × 150 mm non-woven fabric. The length of the adhesive film is longer than that of the nonwoven fabric. Both ends of the sample are cut off, the adhesive film is peeled off from one end of the sample adjusted to 15 × 150 mm, and the nonwoven fabric layer is peeled off by about 30 mm. Three samples of each of the vertical direction and the horizontal direction are prepared. Measurement temperature and humidity: 23 ° C., 50% RH, Measuring instrument: Tensilon RTA-100 manufactured by Orientec, specimen gripping interval: 20 mm, the sample is sandwiched between chucks, speed: 100 mm / min, measurement distance: 50 mm The integrated average load is read, and the average value of the three sheets in the vertical direction and the horizontal direction is set as the interlayer strength (N / 15 mm). The upper limit of interlaminar strength is not particularly specified, but an interlaminar strength of about 4N is usually assumed as the upper limit for a substrate using a nonwoven fabric.

  As a material of the nonwoven fabric, a known and conventional nonwoven fabric used as a nonwoven fabric for an adhesive tape can be used. Typical examples include Manila hemp; pulp; chemical fibers such as rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber; and mixtures thereof. Furthermore, you may perform the impregnation process which used the viscose impregnation and the thermoplastic resin as a binder as needed.

  Among these, hemp alone or a mixture of hemp and vinylon, rayon, polyester, pulp or the like is preferable. As the hemp, Manila hemp is preferable from the viewpoint of strength. The content of Manila hemp is preferably 50% by mass or more, and more preferably 70% by mass or more.

  For the purpose of improving the strength of the nonwoven fabric, it is preferable to add a known and usual reinforcing agent in the nonwoven fabric manufacturing process. As the reinforcing agent, an internal additive reinforcing agent or an external additive reinforcing agent may be used alone or in combination. As the internal reinforcement, polyacrylamide resins, urea-formaldehyde resins, melamine-formaldehyde resins, epoxy-polyamide resins, and the like can be used. In particular, a polyamidoamine / epichlorohydrin resin which is an epoxy-polyamide resin is preferable because it significantly increases the interlayer strength of the nonwoven fabric. The addition amount of the internal additive reinforcing agent is preferably 0.2 to 1%, more preferably 0.3 to 0.5% with respect to the nonwoven fabric. On the other hand, as the external additive reinforcing agent, a thermoplastic resin such as starch; viscose, carboxymethylcellulose, polyvinyl alcohol, polyacrylamide or the like can be used. Especially, in order to raise the interlayer strength of a nonwoven fabric base material, it is preferable to use the above-mentioned internal additive reinforcement agent.

The basis weight of the nonwoven fabric described above is preferably from 10 to 30 g / ^{m 2,} it is rather more preferable is 13~25g / ^{m 2,} and still more preferably 14~20g / ^{m 2.} It is preferable that density is 0.15~0.35g / ^{m 2,} and more preferably 0.2 to 0.3 g / ^{m 2.} In the case of this range, it is possible to improve the balance between the difficulty of cutting the nonwoven fabric and the impregnation property of the pressure-sensitive adhesive into the nonwoven fabric, and the removability can be further improved.

  The paper making method of the nonwoven fabric is not particularly limited, but can be obtained by a known wet method, and various paper machines using a circular net paper machine, a short net paper machine, a long net paper machine, an inclined short net paper machine, etc. The method is used. Among them, in order to make it difficult to cut the nonwoven fabric, it is preferable to increase the isotropy of strength and elongation in the MD direction and the TD direction, and an inclined short net paper machine that easily increases the isotropy is preferable.

  The thickness of the nonwoven fabric substrate is not particularly limited as long as it has the above-mentioned total light transmittance, tensile strength, and the above-mentioned basis weight, but a thickness of 65 to 80 μm is suitable for the effect of the present invention. It is preferable because it is easily expressed.

  It is preferable that an acrylic copolymer having a glass transition temperature (Tg) of −10 ° C. or lower is fixed to the nonwoven fabric used to form the double-sided pressure-sensitive adhesive tape. Compared to ordinary non-woven fabric that does not have an acrylic copolymer fixed, when the acrylic copolymer is fixed, the surface of the non-woven fabric is coated with acrylic, so it has a chemical affinity with the acrylic pressure-sensitive adhesive composition. Property is improved, and the effect of strengthening the bond between the nonwoven fabric substrate and the pressure-sensitive adhesive is born. As a result, in the re-peeling process of peeling the pressure-sensitive adhesive tape that has been stuck to the adherend for a long period of time, the pressure-sensitive adhesive is less likely to fall off the nonwoven fabric substrate. Moreover, usually, when a nonwoven fabric is treated with an acrylic fiber processing agent, the tensile strength of the nonwoven fabric tends to increase, but the tear strength is greatly reduced, and it becomes easy to break. However, when an acrylic copolymer having a low glass transition temperature is used, the tear strength is increased at a temperature in the vicinity of −10 ° C., which greatly contributes to the improvement of removability.

  Furthermore, the glass transition temperature of the acrylic copolymer fixed to the nonwoven fabric is preferably −10 ° C. or lower, preferably −15 ° C. or lower, and more preferably −20 ° C. or lower. When an acrylic copolymer having a high glass transition temperature exceeding −10 ° C. is fixed to a nonwoven fabric substrate, the brittleness of the nonwoven fabric substrate becomes strong and the tear strength of the nonwoven fabric substrate decreases. As a result, the nonwoven fabric substrate is significantly easily broken when re-peeling. On the other hand, in the case of an acrylic copolymer having a low glass transition temperature of −10 ° C. or lower, an effect of relaxing the stress applied to the nonwoven fabric substrate during the re-peeling process is produced, and the nonwoven fabric substrate is difficult to break.

<Double-sided adhesive tape>
(Constitution)
The pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer composed of the above water-dispersed acrylic pressure-sensitive adhesive composition on both surfaces of the nonwoven fabric substrate, and has a total light transmittance of 75% or more, preferably 80% or more. Double-sided adhesive tape. By setting the total light transmittance of the double-sided pressure-sensitive adhesive tape to 75% or more, suitable removability can be realized.

(Adhesive layer)
The pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the present invention is a layer obtained by removing the solvent from the water-dispersed acrylic pressure-sensitive adhesive composition. The preferable thickness of the pressure-sensitive adhesive layer added to both sides when the double-sided pressure-sensitive adhesive tape is formed is 30 to 300 μm, more preferably 50 to 200 μm.

  The pressure-sensitive adhesive layer in the present invention preferably has a temperature having a convex peak value on the tangent loss in the dynamic viscoelastic spectrum, which is −60 ° C. to −5 ° C., and is −30 ° C. to −10 ° C. It is more preferable. When it exists in this range, it becomes easy to balance re-peelability and strong adhesiveness in a well-balanced manner.

  The above-mentioned dynamic viscoelastic characteristics are measured between the parallel disks that are the measuring unit of the test machine using a viscoelasticity tester (manufactured by Rheometrics, trade name: Ares 2KSTD) in the measurement of dynamic viscoelasticity. A test piece is sandwiched in between and a storage elastic modulus (G ′) and a loss elastic modulus (G ″) from −50 ° C. to 150 ° C. are measured at a frequency of 1 Hz. The test piece is an adhesive having a thickness of 0.5 to 2.5 mm. May be sandwiched between the parallel disks alone, but the laminate of the base material and the adhesive may be stacked in layers and sandwiched between the parallel disks. When the thickness of the pressure-sensitive adhesive is adjusted to the above range, the present inventors have no influence on the dynamic viscoelastic spectrum of the pressure-sensitive adhesive even if the substrate is sandwiched between them. Has confirmed.

(Manufacturing process of adhesive tape)
As a method of laminating the pressure-sensitive adhesive layer on the nonwoven fabric, the pressure-sensitive adhesive solution is coated on the separator once using a roll coater, a die coater, etc. Transfer method). In this invention, it is preferable that the lamination temperature at the time of the said lamination shall be 80-150 degreeC. The laminating pressure is preferably 30 to 500 N / cm, more preferably 40 to 300 N / cm. The laminating speed is preferably 2 to 50 m / min, and more preferably 2 to 25 m / min. In particular, it is preferable to increase the pressure during lamination, and the pressure / speed ratio is preferably 4 to 20. It becomes easy to adjust the total light transmittance of an adhesive tape to a suitable range by adjusting the lamination conditions at the time of adhesive tape manufacture on the said conditions.

  The gel fraction for measuring the insoluble content after immersing the pressure-sensitive adhesive layer in toluene at the end of the drying process for 24 hours is preferably 10% or less, and more preferably 5% or less. When the gel fraction at the end of the drying step is 10% or less, the pressure-sensitive adhesive is easily impregnated into the nonwoven fabric, the total light transmittance is easily adjusted, and the removability can be improved. This gel fraction can be adjusted by appropriately selecting the reaction temperature, reaction time, type and amount of initiator used, and type and amount of chain transfer agent when synthesizing the acrylic copolymer emulsion. it can.

(Characteristics of adhesive tape)
The tensile strength of the pressure-sensitive adhesive tape of the present invention is preferably 20 N / 20 mm or more and less than 50 N / 20 mm in both the MD direction (longitudinal direction; flow direction) and the TD direction (transverse direction; width direction). More preferably, it is 20 N / 20 mm or more and less than 40 N / 20 mm, More preferably, it is 30 N / 20 mm or more and less than 40 N / 20 mm. In the case of 20 N / 20 mm or more, the adhesive tape is stuck for a long period of time, and becomes remarkably difficult to tear when peeled again. On the other hand, when the tensile strength is excessively high, the so-called waist as the adhesive tape becomes strong, and therefore, it tends to occur without being able to withstand the repulsive force, and is preferably less than 50 N / 20 mm. In particular, in the case where an adhesive tape is used for an application that requires a repulsive force such as a curved surface, it is preferably less than 40 N / 20 mm.

  In addition, the above-mentioned tensile strength was measured using a Tensilon tensile tester on a sample having a vote line length of 100 mm and a width of 20 mm under a measurement condition of a tensile speed of 300 mm / min in an environment of 23 ° C. and 50% RH. The maximum intensity.

  The 180 degree peel adhesive strength of the adhesive tape is measured in accordance with JIS-Z-0237 (2000 version), and the galvanized steel sheet is used as an adherend. [A] A sample that was left in an environment of 23 ° C. and 50% for 1 hour, and [B] a sample that was left in an environment of 60 ° C. and 0 to 5% for 20 days, and then 23 ° C. and 50 % Of the adhesive tape sample for 1 hour was prepared, and the adhesive force when the adhesive tape samples [A] and [B] were peeled off at a speed of 1000 m / min in the direction of 180 degrees ([A] and [B ]), The [A] adhesive strength is preferably 15 to 20 N / 20 mm, and the [B]-[A] adhesive strength difference is preferably within 10 N / 20 mm. In the case of the adhesive strength in this range, it becomes easy to achieve both re-peelability and strong adhesiveness in a balanced manner. In addition, the adhesive tape at the time of evaluation adjusts an adhesive tape sample by cut | disconnecting to 20 mm width x 100 mm length, and in the case of a double-sided adhesive tape, a double-sided adhesive tape is lined with a 25-micrometer-thick PET film, and 20-mm width A double-sided adhesive tape sample is prepared by cutting to a length of × 100 mm.

<Application>
The pressure-sensitive adhesive tape of the present invention has a peeling resistance that can withstand the repulsive force of the adherend, a resistance that can withstand a load applied in the shear direction, an adhesive reliability under severe environmental conditions such as a high humidity environment, and a space between parts in a small area. It is also excellent in strong adhesive force that can stably fix between members, such as fixing. In addition, it has excellent removability in the case of inadequate adhesion in the work process and separation between members during recycling. Unlike conventional adhesives based on solution-polymerized acrylic resins, the use of water-dispersed acrylic adhesive compositions can also be expected to reduce volatile organic compounds. It can be suitably used as an adhesive tape that fixes parts in various products in industrial applications such as building materials, OA, and home appliance industries.

  Next, the present invention will be described in detail with reference to examples and comparative examples.

[Method for preparing water-dispersed acrylic pressure-sensitive adhesive composition]
Example 1
<Preparation of emulsion>
In a container, 75 g of ion-exchange water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20 g and surfactant Latemul PD-104 [Kao Corporation; active ingredient 20%] 37.5 g was added and dissolved uniformly. Then, 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25 g of methyl methacrylate, 7.5 g of N-vinyl pyrrolidone, 12.5 g of acrylic acid and 0.2 g of lauryl mercaptan were added to emulsify, and an emulsion solution 632.7 g was obtained.

<Manufacture of acrylic copolymer emulsion>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 340 g of ion-exchanged water was added, and the temperature was raised to 60 ° C. while blowing nitrogen. While stirring, part of the emulsion [3.2 g], ammonium persulfate aqueous solution 5.0 g [active ingredient 3%], and sodium hydrogen sulfite aqueous solution 5.0 g [active ingredient 3%] were added. Polymerized in time. Subsequently, the remaining emulsion (629.5 g) and ammonium persulfate aqueous solution (40 g [active ingredient: 1.25%]) were dropped and polymerized over 8 hours using a separate funnel while keeping the reaction vessel at 60 ° C. After completion of dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled to obtain an acrylic copolymer emulsion (A). Then, it adjusted with ammonia water (active ingredient 10%) so that pH might be set to 7.5. This was filtered through a 200-mesh wire mesh to obtain an acrylic copolymer emulsion (B). Here, the obtained water-dispersed acrylic polymer had a solid concentration of 50% and an average particle size of 338 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
To the acrylic copolymer emulsion (B) 1000 g [dry; 500 g], Surfynol PSA-336 [produced by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as a leveling agent, antifoaming agent Surfinol DF-110D [manufactured by Air Products Japan; active ingredient 100%] 2.5 g, emulsion type polymerized rosin ester tackifier resin superester E-865NT [Arakawa Chemical Industries, Ltd. as tackifier resin ); Softening point 160 ° C.] 50 g in solid content, emulsion type rosin phenolic tackifier resin Tamanol E-200NT [manufactured by Arakawa Chemical Industries, Ltd .; softening point 150 ° C.] 50 g in solid content is added as a crosslinking agent. Epoxy compound tetrad C [Mitsubishi Gas Chemical Co., Ltd.] 0.15 g, 100 mesh Filtered through a mesh to obtain aqueous acrylic PSA composition of the present invention.

[Method for preparing non-woven fabric substrate]
A solution containing 90% Manila hemp, 10% polyester, and 0.5% polyamidoamine / epichlorohydrin resin was made with an inclined short net paper machine to a basis weight of 17 g / m ² and a density of 0.28 g / cm ³ , A nonwoven fabric base material having a tensile strength of 25.3 N / 20 mm in the MD direction and 23.5 N / 20 mm in the TD direction was obtained. The total light transmittance of the nonwoven fabric substrate was 73%.

<Method for preparing double-sided adhesive tape>
A pressure-sensitive adhesive obtained by coating the water-dispersed acrylic pressure-sensitive adhesive composition on a 75 μm-thick polyester film having a thickness of 65 μm after drying and drying at 100 ° C. for 5 minutes. The sheet was transferred to both surfaces of the above-mentioned nonwoven fabric substrate, and laminated with a hot roll at 100 ° C. at a pressure of 40 N / cm and a speed of 10 m / min to obtain a double-sided pressure-sensitive adhesive tape. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 78.3%. The double-sided pressure-sensitive adhesive tape was tested after aging at 40 ° C for 2 days.

(Example 2)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1.

<Method for preparing double-sided adhesive tape>
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that lamination was performed at a pressure of 40 N / cm and a speed of 2 m / min with a hot roll at 100 ° C. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 80.3%.

(Example 3)
<Preparation of emulsion>
In a container, 75 g of ion-exchange water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20 g and surfactant Latemul PD-104 [Kao Corporation; active ingredient 20%] 37.5 g was added and dissolved uniformly. Emulsified by adding 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25 g of methyl methacrylate, 7.5 g of N-vinylpyrrolidone, 1.5 g of acrylic acid, 11 g of methacrylic acid, and 0.2 g of lauryl mercaptan. As a result, 632.7 g of an emulsion was obtained.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid content concentration of 50% and an average particle size of 341 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer emulsion obtained above was used.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 40 N / cm with a hot roll at 80 ° C. at a speed of 10 m / min, the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 80.5%.

Example 4
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 40 N / cm and a speed of 10 m / min with a hot roll at 100 ° C., the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 81.3%.

(Example 5)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 120 N / cm with a hot roll at 100 ° C. at a speed of 10 m / min, the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 83.0%.

(Example 6)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 40 N / cm and a speed of 10 m / min with a 120 ° C. hot roll, the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 84.2%.

(Example 7)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 200 N / cm and a speed of 20 m / min with a hot roll at 100 ° C., the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 85.4%.

(Comparative Example 1)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 40 N / cm and a speed of 25 m / min with a hot roll at 100 ° C., the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 70.8%.

(Comparative Example 2)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, and laminating at a pressure of 40 N / cm and a speed of 10 m / min with a heat roll at 25 ° C., the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 68.1%.

(Comparative Example 3)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1.

<Method for preparing double-sided adhesive tape>
Except for laminating at a pressure of 10 N / cm and a speed of 10 m / min with a hot roll at 100 ° C. using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, in the same manner as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 69.9%.

(Comparative Example 4)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 340 g of ion-exchanged water was added, and the temperature was raised to 60 ° C. while blowing nitrogen. While stirring, a part [3.2 g] of the emulsion obtained above, 5.0 g of ammonium persulfate aqueous solution [3% active ingredient], and 5.0 g of sodium hydrogen sulfite aqueous solution [3% active ingredient] were added. Polymerization was carried out in 1 hour while maintaining the temperature. Subsequently, the remaining emulsion (629.5 g) and ammonium persulfate aqueous solution (40 g [active ingredient: 1.25%]) were dropped and polymerized using a separate funnel over 8 hours while maintaining the reaction vessel at 70 ° C. After completion of dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 70 ° C., and then the contents were cooled to obtain an acrylic copolymer emulsion (A). Then, it adjusted with ammonia water (active ingredient 10%) so that pH might be set to 7.5. This was filtered through a 200-mesh wire mesh to obtain an acrylic copolymer emulsion (B). Here, the obtained water-dispersed acrylic polymer had a solid concentration of 50% and an average particle size of 338 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer emulsion obtained above was used.

<Method for preparing double-sided adhesive tape>
Using the water-dispersed acrylic pressure-sensitive adhesive composition obtained above, except for laminating at a pressure of 40 N / cm and a speed of 10 m / min with a hot roll at 100 ° C., the same method as in Example 1, A double-sided adhesive tape was obtained. The total light transmittance of the double-sided pressure-sensitive adhesive tape was 62.7%.

[Evaluation method (water-dispersed acrylic pressure-sensitive adhesive composition)]
(Measurement method of carboxyl group distribution in acrylic copolymer emulsion)
Acrylic copolymer emulsion (A) obtained in Example 1 (A) (solid content 50%) 6.0 g (solid content 3 g) was weighed into a 300 mL polyethylene beaker with a dropper, and then the polyethylene product was made. Into a beaker, 94.0 g of ion-exchanged water is poured and stirred (the total amount of the test sample is 100 g). Then, the electrode and the temperature assurance electrode are immersed. The tip of the titration nozzle was higher than the liquid level, and was placed 2 cm away from the electrode so that the titration reagent did not reach the electrode. The method file is set to intermittent titration at the titration mode, the intermittent time is 10 seconds, the maximum drop volume is 20 mL, the single injection volume at the time of intermittent injection is 0.16 mL / time, the injection speed is 5 seconds / mL, The potential for collecting data was designated as 4 mL, and the titer for collecting data was designated as 0.16 mL. While stirring, potentiometric automatic titration was performed. The amount of acid groups present on the surface of the acrylic copolymer emulsion particles calculated from the obtained titration curve is 0.173 meqv. / G, the amount of acid groups present inside the particles is 0.122 meqv. / G.

  The acrylic copolymer emulsions of Examples 2 to 7 and Comparative Examples 1 to 5 were measured in the same manner, and the amount of acid groups present on the surface of the acrylic copolymer emulsion particles calculated from the titration curve was present inside the particles. The amount of acid group to be calculated was calculated. The obtained results are shown in Table 1.

(Average particle size of acrylic copolymer emulsion)
The value of the average particle diameter (50% median diameter on a volume basis) measured with a Nikkiso Co., Ltd. Microtrac UPA type particle size distribution analyzer was determined.

[Evaluation method (double-sided adhesive tape)]
(Evaluation of removability)
The double-sided pressure-sensitive adhesive tape sample was prepared by backing the double-sided pressure-sensitive adhesive tape with a PET film having a thickness of 25 μm and cutting it into a width of 20 mm × 100 mm. Next, polycarbonate / ABS alloy plate (hereinafter PC / ABS plate) (manufactured by Nippon Test Panel Co.) or galvanized steel sheet (manufactured by Nippon Test Panel Co., Ltd.) is used as an adherend and is 2 kg under an environment of 23 ° C. and 50% One-way reciprocating pressure application was performed with a roller, and the mixture was allowed to stand in an environment of 60 ° C. for 20 days. Then, it left still in 23 degreeC * 50% RH environment for 1 hour, and the removability at the time of peeling a double-sided adhesive tape sample at a speed | rate of 25 m / min in the direction of 135 degree | times was evaluated. The re-peelability was evaluated according to the following criteria.
A: The adhesive residue on the adherend and the remaining area of the adhesive tape due to the cutting of the nonwoven fabric are less than 3% of the pasting area.
A to B: The adhesive residue on the adherend and the remaining area of the adhesive tape due to the cutting of the nonwoven fabric are 3% or more and less than 10% of the sticking area.
○: The adhesive residue on the adherend and the residual area of the adhesive tape by cutting the nonwoven fabric are 10% or more and less than 30% of the pasting area.
Δ: The adhesive residue on the adherend and the remaining area of the adhesive tape due to the cutting of the nonwoven fabric are 30% or more and less than 80% of the pasting area.
X: The adhesive residue on the adherend and the remaining area of the adhesive tape by cutting the nonwoven fabric are 80% or more of the pasting area.

(Evaluation of strong adhesiveness and increase in adhesive strength over time after application of adherend)
The double-sided pressure-sensitive adhesive tape sample was prepared by backing the double-sided pressure-sensitive adhesive tape with a PET film having a thickness of 25 μm and cutting it into a width of 20 mm × 100 mm. Next, PC / ABS plate (manufactured by Nippon Test Panel Co.) or galvanized steel plate (manufactured by Nippon Test Panel Co., Ltd.) is used as an adherend, and pressure is applied once and again with a 2 kg roller in an environment of 23 ° C and 50%. [A] sample left for 1 hour in an environment of 23 ° C. and 50%, and [B] left for 20 days in an environment of 60 ° C. and 0 to 5%, and then in an environment of 23 ° C. and 50%. A sample was prepared for 1 hour.
Thereafter, the adhesive strength ([A] and [B]) when the double-sided pressure-sensitive adhesive tape samples [A] and [B] were peeled off at a speed of 1000 m / min in the 180 ° direction was measured. Next, the increased adhesive strength ([B]-[A]) was calculated. In addition, the measurement of adhesive force was implemented based on JIS-Z-0237 (2000 version).

(Evaluation of constant load peelability)
A 10 mm wide double-sided adhesive tape sample lined with a 25 μm thick polyester film is applied to a PC / ABS plate (manufactured by Nippon Test Panel) or a galvanized steel plate (manufactured by Nippon Test Panel) so that the length is 50 mm. A 2 kg roller was pressurized and adhered by reciprocating once on the double-sided PSA sheet. After being left for 1 hour in an atmosphere of 23 ° C. and 50% RH, a load of 300 g is applied so that the direction is 90 ° with respect to the peeling direction, and the time until a 50 mm long tape sample falls is measured. Evaluation was made according to the following criteria. The constant load peelability evaluation is a substitute evaluation method that assumes a case where deformation stress is applied to the double-sided pressure-sensitive adhesive tape for a long time from the outside, and the longer the time until dropping, the more the peel resistance, that is, the strong adhesiveness. Expresses superiority.
○: The falling time was 3 hours or more.
Δ: Dropped within 3 hours.
X: It fell within 1 hour.

  As is clear from the above table, the pressure-sensitive adhesive tapes of the present inventions of Examples 1 to 7 have good adhesion and rebound resistance to adherends and have excellent removability. there were. On the other hand, the adhesive tapes of Comparative Examples 1 to 4 were poor in removability.

It is a conceptual diagram of a titration curve obtained by potentiometric titration with a basic solution of an acrylic copolymer emulsion. It is a conceptual diagram of a differential curve based on a titration curve obtained by potentiometric titration with a basic solution of an acrylic copolymer emulsion. It is a conceptual diagram of a titration curve obtained by potentiometric titration with an acidic solution of an acrylic copolymer emulsion. It is a conceptual diagram of a differential curve based on a titration curve obtained by potentiometric titration with an acidic solution of an acrylic copolymer emulsion. It is a schematic diagram of the water resistance evaluation method in the Example of this invention.

1 Stainless steel plate 2 Urethane foam 3 Peeling distance

Claims (5)

A double-sided pressure-sensitive adhesive tape in which a water-dispersed acrylic pressure-sensitive adhesive composition applied on a release sheet is laminated on both surfaces of a nonwoven fabric substrate, and a pressure-sensitive adhesive layer with a release sheet is formed on both surfaces of the nonwoven fabric substrate,
The total light transmittance of the nonwoven fabric substrate is 70% or more, the tensile strength in the MD direction and the TD direction is 25 to 40 N / 20 mm,
The water-dispersed acrylic pressure-sensitive adhesive composition is an aqueous dispersion in which emulsion particles of an acrylic copolymer containing n-butyl acrylate, 2-ethylhexyl acrylate and a carboxyl group-containing vinyl monomer as monomer components are dispersed in an aqueous medium. Type acrylic pressure-sensitive adhesive composition,
The gel fraction measured by removing the aqueous medium of the water-dispersed acrylic pressure-sensitive adhesive composition at the time of lamination is 10% or less,
The double-sided pressure-sensitive adhesive tape, wherein the double-sided pressure-sensitive adhesive tape has a total light transmittance of 75% or more. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein a lamination temperature at the time of lamination is 80 to 150 ° C, a lamination pressure is 40 to 500 N / cm, and a lamination speed is 2 to 50 m / min. The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the acrylic copolymer contains a nitrogen-containing vinyl monomer as a monomer component. The sum of the contents of 2-ethylhexyl acrylate and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component forming the acrylic copolymer is 50 to 98% by mass of the carboxyl group-containing vinyl monomer. Content is 0.5-10 mass%, The double-sided adhesive tape in any one of Claims 1-3. The acrylic copolymer emulsion particles are titrated by performing potentiometric titration by dropping an inorganic base solution on an acidic sample dispersion prepared by adjusting the mass ratio of acrylic copolymer emulsion particles / ion exchange water = 3/100. A titration curve (X axis: base dripping amount, Y axis: pH) having an inflection point P ₂ that appears after the start point P ₀ , the minimum point P _{1 at} which the pH becomes minimum after the start of titration, and the minimum point P ₁ was measured. When
Acid group amount (AN _SUR ) on the surface of acrylic copolymer emulsion particles calculated from the amount of base dropped in P _{1 to} P ₂ ,
And inside the acrylic copolymer emulsion particles calculated by subtracting the amount of acid groups calculated from the amount of base dropped in P _{0 to} P ₂ from the total amount of acid groups (AN _TOTAL ) in the acidic sample dispersion The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the ratio (AN _IN ) / (AN _SUR ) of the acid group amount (AN _IN ) is 1 or more acrylic copolymer emulsion particles.

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