JP2000273410A - Pressure-sensitive adhesive sheet and pressure sensitive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a pressure-sensitive adhesive sheet excellent in quality as the pressure-sensitive adhesive sheet and having recycling aptitude by formulating a specific tacky agent layer with a specific amount of pigment. SOLUTION: This sheet has an adhesive layer on at least one surface of a substrate body and can be made to adhere by being pressurized in a state that coated surfaces of adhesive layers face each other. The adhesive layer comprises (A) 100 pts.wt. pressure-sensitive adhesive having water dispersibility and a glass transition temperature of -30 deg.C to 20 deg.C and (B) 20-100 pts.wt. pigment. The ingredient A is preferably a copolymer obtained from (i) 4-20 wt.% ethylenic unsaturated carboxylic acid-containing monomer, (ii) 40-70 wt.% 4-18C alkyl (meth)acrylate, (iii) 5-50 wt.% hydrophilic monomer having a glass transition temperature of <=-20 deg.C and (iv) 1-15 wt.% other comonomer and formulated with an alkali metal hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a pressure-sensitive adhesive sheet. More specifically, the adhesive-coated surfaces of the pressure-sensitive adhesive sheet are opposed to each other, and exhibit a strong adhesive force only when pressed with high pressure, and the pressure-sensitive adhesive sheet has excellent re-disintegration properties with water, The present invention relates to a pressure-sensitive adhesive sheet that can be easily re-disintegrated without adversely affecting an adhesive and a base material during regeneration and can be mixed in a recycling process.

[0002]

2. Description of the Related Art In recent years, a sheet obtained by applying or printing a pressure-sensitive adhesive on a sheet is processed into a postcard, an envelope, a slip, or the like by applying the adhesive or printing the surfaces so as to face each other and by pressure bonding. Demand for pressure-sensitive adhesive sheets for business forms is increasing. These types of pressure-sensitive adhesive sheets are usually subjected to processing such as printing, cutting, bending, etc. in the pre-joining process.If an electrophotographic printer is used for this printing method, The latent image is heated by the heating element in the fixing stage of the toner that makes the latent image visible, and the adhesive layer is plasticized and adheres to the paper feed roll, etc., causing troubles such as misfeeds and paper jams. There is.

[0003] Further, when the pressure-sensitive adhesive sheet for business forms is Z-folded and overlapped before the joining process, there is a disadvantage that the surfaces to which the adhesive is applied are likely to be joined unexpectedly. In addition, even when the substrate is stored in a state where the adhesive-coated surface and the substrate are in contact with each other, blocking easily occurs, which causes a problem in handling operation. To solve these problems, JP-A-61-34552, JP-A-61-34552, JP-A-61-34553, and JP-A-61-34
No. 550, JP-A-2-151493 and the like, a method of adding an anti-blocking agent such as an inorganic or organic pigment, a lubricant, and a release agent to an adhesive has also been proposed, but it is not always sufficient. (A) High pressure adhesion,
At present, it has not yet been obtained that satisfy both [b] heat resistance and [c] blocking resistance.

On the other hand, regarding the recycling of waste paper, in Japan, the amount of waste paper including recycled waste paper as a raw material for pulp production currently exceeds 50% of the raw material for producing paper and paperboard, and the main raw material is already used. Occupy the position. Recycled pulpable waste paper includes newspapers, cardboard, magazines, imitations, high-quality (including art), fine white, cards, special whites, white and white, white manila, tickets, Chinese old paper, and brown paper ), Mounts, ground tickets, balls, heat-sensitive recording paper, pressure-sensitive copy paper, OCR paper, and the like.

[0005] In general, a disintegration step of disintegrating waste paper to obtain a pulp suspension, a rough selection for separating foreign matter in the pulp suspension,
Recycling pulping is performed through a selective process, a deinking process of separating printing ink, and a bleaching process of whitening the color. However, wax-processed paper, pressure-sensitive adhesive sheets, pressure-sensitive adhesive sheets and pressure-sensitive labels cannot separate water-insoluble wax, pressure-sensitive adhesives, pressure-sensitive adhesives, etc. from pulp fibers, making it difficult to recycle pulp. Used paper.

In particular, in the case of a pressure-sensitive adhesive sheet, a water-insoluble pressure-sensitive adhesive contains 1 to 30% of the weight of waste paper. Further, since this pressure-sensitive adhesive has a strong adhesive force, pulp fiber Is considered impossible to separate from When making paper using recycled pulp containing an adhesive component, the adhesive closes the eyes of the wire, stains press rolls and blankets in the paper making process, causing paper breakage and significantly reducing paper making efficiency. There is a problem that the formation of the paper layer or the quality is adversely affected, such as a problem or formation of spots on the paper surface.

[0007] Recently, due to problems of forest resources, environmental protection, etc., there have been reported several cases in which the above-mentioned non-recyclable pressure-sensitive adhesive sheet products have been successfully recycled by devising them physically or by equipment. Have been. For example, JP-A-4-
As in 174787, a method of adding an inorganic pigment to the disaggregation step to eliminate the adhesiveness of the paste and performing a screen treatment,
As disclosed in Japanese Patent Application Laid-Open No. 4-163383, there is a method of removing the glue by making the holes of the screen after defibration fine. However, each is a special processing method.

Further, recently, there has been an increasing demand for products using recycled paper as a base material for the purpose of promoting interest in environmental protection-related products and promoting environmental protection activities.
However, most of these recycled papers are neutral papers containing a large amount of calcium carbonate. Therefore, when used in combination with these pressure-sensitive adhesives containing a large amount of carboxylic acid in the pressure-sensitive adhesive composition, it takes several months. In the above-mentioned long-term storage, there was a disadvantage that the adhesive strength was significantly reduced.

[0009]

SUMMARY OF THE INVENTION The present invention provides a pressure-sensitive adhesive sheet having excellent quality as a pressure-sensitive adhesive sheet and having recyclability. As for the quality of the pressure-sensitive adhesive sheet, it shows excellent adhesiveness only under a high pressure, and furthermore, the adhesive-applied surfaces are in contact with each other, but do not adhere when pressed with a low pressure. Even if pressure is applied between the surface on which the adhesive is applied and the substrate on which the adhesive is not applied, the surface does not adhere. Adhesive even when the surface coated with adhesive comes in contact with hot objects,
The purpose is not to cause blocking.

[0010] As for recyclability, when regenerating pulp from a pressure-sensitive adhesive sheet or the like as used paper as it is, the adhesive can be re-disintegrated easily without any adverse effect, and the adjusted water for disintegration can be recycled without contamination. The pulp can be regenerated in the pulping process, and even if coated paper or neutral paper containing a large amount of calcium carbonate is used as the base material, there is no significant decrease in adhesive strength or deterioration in water redispersibility even after long-term storage. The purpose is to:

[0011]

In order to obtain such a recyclable pressure-sensitive adhesive sheet, the present inventors have determined that an adhesive having water redispersibility and having a specific glass transition temperature has a specific amount. Is characterized in that a pressure-sensitive adhesive layer containing the above pigment is provided.

(1) That is, the present invention relates to a pressure-sensitive adhesive sheet which has an adhesive layer on at least one surface of a substrate, and which can be adhered by applying pressure to the coated surfaces of the adhesive layer so as to face each other. Has water redispersibility, and has a glass transition temperature −
Pressure-sensitive adhesive at 30 to 20 ° C., and pressure-sensitive adhesive 1
A pressure-sensitive adhesive sheet comprising 20 to 150 parts by weight of a pigment with respect to 00 parts by weight.

Further, the present inventors have conducted research on a pressure-sensitive adhesive suitable for a pressure-sensitive adhesive sheet, and found that a copolymer containing a specific amount of an ethylenically unsaturated carboxylic acid-containing monomer is suitable. I understood. (2) That is, the pressure-sensitive adhesive according to (1) comprises (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer,
(B) alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, (c) glass transition point -20
It is preferably a copolymer obtained by copolymerizing a hydrophilic monomer having a temperature of not more than ° C and (d) other copolymerizable monomers. Particularly preferred monomer components of the copolymer include (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer and (b) 40 to 40% by weight of a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms. 70% by weight,
(C) a hydrophilic monomer 5 having a glass transition point of −20 ° C. or lower.
50% by weight, (d) other copolymerizable monomers 1-1
5% by weight.

Further, the present inventors, by neutralizing the pressure-sensitive adhesive, improve the water redispersibility of the adhesive,
And found that it is possible to prevent the deterioration of the adhesive when using coated paper or neutral paper containing a large amount of calcium carbonate as a base material, and further performing a neutralization reaction using an alkali metal hydroxide. It has been found that this is preferable because a change in the adhesive performance over time can be prevented. (3) That is, the pressure-sensitive adhesive according to (2) comprises (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer,
(B) 40 to 70% by weight of an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, (c) 5 to 50% by weight of a hydrophilic monomer having a glass transition point of −20 ° C. or less, (d) Others 1 to 15% by weight of copolymerizable monomer
It is preferable to use a pressure-sensitive adhesive obtained by copolymerizing the above and blending an alkali metal hydroxide. The alkali metal hydroxide is compounded in a proportion of 50 to 1 of the carboxyl group in the copolymer.
It is preferable to add an amount corresponding to 20 mol%, particularly preferably potassium hydroxide.

(4) The pressure-sensitive adhesive preferably further contains an alkanolamine. (5) Furthermore, it is preferable that the pressure-sensitive adhesive contains a hydrophilic plasticizing substance. The hydrophilic plasticizing substance is preferably added in an amount of 10% by weight or less based on the copolymer. (6) The pressure-sensitive adhesive preferably contains a chelating agent. Chelating agent is 10% by weight based on the copolymer.
The following additions are preferred. (7) The base material is preferably paper containing calcium carbonate as a pigment in the coating layer or as an ash / filler in the paper layer.

(8) The present invention also relates to a method for producing a polymer comprising an alkali neutralized salt of a polymer containing a vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride as an essential monomer component. Copolymerizing a monomer component containing 4 to 20% by weight of an unsaturated carboxylic acid-containing monomer,
50 to 120 mol% based on the carboxyl groups in the copolymer
Is a pressure-sensitive adhesive obtained by adding an alkali metal hydroxide and then adding 10% by weight or less of a hydrophilic plasticizing substance to the copolymer.

(9) In the pressure-sensitive adhesive described in (8), the monomer components are (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer, and (b) 4-1 to 4 carbon atoms.
(Meth) acrylic acid alkyl ester having an alkyl group of 8 to 40 to 70% by weight, (c) glass transition point -20 ° C
It is preferable that 5 to 50% by weight of the following hydrophilic monomer and 1 to 15% by weight of (d) other copolymerizable monomers are used.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pressure-sensitive adhesive used in the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it can be defibrated in water, but its glass transition temperature is adjusted to a range of -30 to 20 ° C. There is a need to. If the glass transition temperature of the adhesive is lower than −30 ° C., the tack on the coated surface becomes too strong, which is not preferable. On the other hand, when the glass transition temperature is higher than 20 ° C., the self-adhesiveness is undesirably lowered.

Among them, the pressure-sensitive adhesive comprises (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer,
(B) alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, (c) glass transition point -20
It is preferably a copolymer obtained by copolymerizing a hydrophilic monomer having a temperature of not more than ° C and (d) other copolymerizable monomers. In particular, (a) ethylenically unsaturated carboxylic acid-containing monomer 4
(B) 40 to 70% by weight of an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, and (c) 5 to 50% by weight of a hydrophilic monomer having a glass transition point of -20 ° C or lower. , (D) and a copolymer obtained by copolymerizing 1 to 15% by weight of a copolymerizable monomer, and more preferably a copolymer obtained by neutralizing the copolymer. In particular, a pressure-sensitive adhesive obtained by blending an alkali metal hydroxide with this copolymer is preferable.

(A) Examples of the monomer containing an ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid,
Examples include itaconic acid, crotonic acid, maleic acid, fumaric acid, monoalkyl maleic acid, monoalkyl itaconic acid, monoalkyl fumaric acid, and the like. This monomer must be copolymerized to account for 4-20% by weight of the copolymer. By the way, when the content is less than 4% by weight, the water redispersibility of the adhesive becomes insufficient, and when it exceeds 20% by weight, the self-adhesive strength becomes insufficient and the adhesive is liable to deteriorate with time.

(B) As the alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, butyl (meth) acrylate, hexyl (meth) acrylate,
Octyl (meth) acrylate, (meth) acrylic acid-2
-Ethylhexyl, stearyl (meth) acrylate and the like. This monomer is preferably copolymerized so as to occupy 40 to 70% by weight of the copolymer in order to balance the self-adhesiveness of the adhesive and the water redispersibility.

(C) The hydrophilic monomer having a glass transition point of −20 ° C. or lower is a homopolymer (homopolymer) in order to exhibit good water redispersibility without impairing the self-adhesiveness of the adhesive. A hydrophilic monomer having a glass transition point (Tg) of −20 ° C. or lower at that time may be copolymerized. Examples of the hydrophilic monomer which becomes a homopolymer having a glass transition point (Tg) of −20 ° C. or lower include methoxyethyl acrylate, methoxypropyl acrylate, ethoxyethyl acrylate, ethoxypropyl acrylate, methoxyethyl methacrylate, and ethoxyethyl methacrylate. Alkyl (meth) acrylates, caprolactone adducts of (meth) acrylic acid represented by the following general formula [formula 1], carboxylic acid-modified rosin esters represented by the following general formula [formula 2], ( Poly) ethylene glycol (meth) acrylate and the like.

[0023]

Embedded image

Wherein R ₁ is a methyl group or a hydrogen atom,
n shows the integer of 1-10. ]

[0025]

Embedded image

Wherein m represents an integer of 1 to 8. ]

These hydrophilic monomers may be used alone or in combination. In order to develop good water redispersibility without deteriorating the self-adhesiveness, 5 to 50%
It is preferable to copolymerize so as to account for the weight%.

(D) Other copolymerizable monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, cyclohexyl (meth) acrylate, vinyl acetate, propion Vinyl acid, vinyl chloride, vinylidene chloride, styrene,
Ethylene, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, divinyl Benzene, N, N'-methylenebis (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, N-butoxymethyl (meth) acrylamide, etc. Monomers can also be copolymerized. This monomer is preferably copolymerized so as to account for 1 to 15% by weight of the copolymer in terms of the balance between the adhesive strength, cohesive strength, and water redispersibility of the adhesive.

Among the monomers constituting the above-mentioned copolymer, components for imparting water redispersibility of the adhesive include:
(A) Ethylenically unsaturated carboxylic acid containing monomers are important. In addition, other monomers (b), (c),
By blending (d), the balance of adhesion, cohesion, and water redispersibility is achieved.

Further, by subjecting the copolymer to a neutralization reaction with an alkali metal hydroxide, water redispersibility can be further improved, and a base paper based on coated paper or neutral paper containing a large amount of calcium carbonate can be used. It is possible to prevent the deterioration of the adhesive when used for the material. In the neutralization treatment, ammonia or the like may be used.However, since the water redispersibility of the pressure-sensitive adhesive deteriorates with their volatilization, the adhesive performance by volatilization over time after being processed into a pressure-sensitive adhesive sheet is reduced. The use of an alkali metal hydroxide is also preferred from the viewpoint of preventing change and deterioration of water redispersibility.

Examples of the alkali metal hydroxide to be added to these copolymers include potassium hydroxide and sodium hydroxide. These alkali metal hydroxides are used to form 50 to 12 carboxyl groups in the copolymer.
It is preferable to add so as to correspond to 0 mol%. Incidentally, if it is less than 50 mol%, the adhesive film tends to deteriorate with time, and if it exceeds 120 mol%, sufficient self-adhesiveness tends not to be exhibited. In addition, among the hydroxides of alkali metals, especially when potassium hydroxide is added, even when using coated paper or neutral paper containing a large amount of calcium carbonate as the base material, deterioration over time can be significantly prevented, More preferred.

The alkanolamine which can be used in combination with the alkali metal hydroxide includes monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, monoisopropanolamine, diisopropanolamine, and the like. Triisopropanolamine, N
-Methyldiethanolamine, N, N-dibutylethanolamine and the like. The use of an alkanolamine in combination is preferable because it has a role of promoting plasticization of the copolymer resin and suppressing a decrease in adhesive strength.

Further, by adding a hydrophilic plasticizing substance, plasticization of the copolymer and water redispersibility can be assisted. That is, to optimize the amount of the ethylenically unsaturated carboxylic acid-containing monomer in the adhesive composition and the neutralization reaction of the carboxyl group by the hydroxide of the alkali metal, to supplement the adhesiveness, and to help the water redispersibility By blending a hydrophilic plasticizing substance and a well-balanced blend with other copolymerizable monomers, the copolymer can be redispersible in water without impairing the adhesive strength. Agent. Further, the hydrophilic plasticizing substance also has an action of preventing discoloration and deterioration of the adhesive with time.

Examples of the hydrophilic plasticizing substance include sugar alcohols such as glycerin, sorbit, mannitol, dursit, idit, erythrit, arabit, adnit, polyethylene oxide or polypropylene oxide and glycerin, xylitol trioxyisobutane, Copolymers with polyhydric alcohols such as sorbit, polyether polyols such as polyethylene glycol and polypropylene glycol, copolymers of ethylene oxide and propylene oxide, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxy Nonionic surfactants such as ethylene polyoxypropylene glycol are exemplified.

The plasticizing substance has a self-adhesive property of the adhesive,
Considering the water redispersibility, the amount added is 1 to the copolymer.
The content is preferably 0% by weight or less. In addition, among these hydrophilic plasticizing substances, nonionic surfactants are particularly preferable because a pressure-sensitive adhesive having good adhesiveness and storage stability can be finished.

Further, a chelating agent can be further added to the above-mentioned adhesive. Examples of the chelating agent to be added include polyaminocarboxylic acids such as EDTA, oxycarboxylic acids such as citric acid, condensed phosphates, and the like. Coated paper or neutral paper containing a large amount of calcium carbonate is used as a base material. Polyaminocarboxylic acids such as EDTA are preferred because they have a large effect of preventing deterioration due to calcium ions when used. The chelating agent is preferably added at a ratio of 10% by weight or less, more preferably 5% by weight or less based on the adhesive copolymer in consideration of the self-adhesiveness of the adhesive.

The method for producing the above adhesive copolymer is not particularly limited.
Solvent, chain transfer agent, a known method such as a method of solution polymerization in the presence of a polymerization initiator, and a known method such as a method of emulsion polymerization in an aqueous system in the presence of an emulsifier, a chain transfer agent, a polymerization initiator, a dispersant, and the like. Can be manufactured.

In particular, the above-mentioned monomer component is emulsion-polymerized in the presence of a polymer dispersant comprising an alkali neutralized salt of a polymer containing a vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride. The way to get
It is particularly preferable because it is suitable for producing an adhesive for a pressure-sensitive adhesive sheet. The polymer dispersant is used as an emulsifier at the time of emulsion polymerization, promotes emulsion polymerization smoothly, and acts to keep the obtained emulsion stable. It is believed that the resulting emulsion has an effect of enhancing self-adhesion at the contact interface between the coated surfaces of the emulsion, and that the adhesion of the emulsion at the contact interface such as a conventionally used emulsifier is small, and the resulting emulsion has a high self-adhesion. It has adhesiveness, and has low tackiness and self-adhesiveness.

Specific examples of the vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride which is a monomer component of the polymer used as the polymer dispersant include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid. , Itaconic acid, maleic anhydride, itaconic anhydride and the like. Each of these monomers can be used alone or in combination as appropriate.

The polymer used as the polymer dispersant in the present invention may be a polymer containing only the above-mentioned vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride as a monomer component, or a polymer other than the vinyl unsaturated monomer. In addition, a copolymer containing, as a monomer component, another vinyl-based unsaturated monomer copolymerizable with the monomer.

Examples of the vinyl unsaturated monomer copolymerizable with the vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride include alkyl (meth) acrylates such as methyl methacrylate and ethyl acrylate; Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, (meth) acrylamide derivatives such as (meth) acrylonitrile and acrylamide, sulfonic acid monomers such as sodium vinyl sulfonate and sodium styrene sulfonate, dibutyl maleate, Maleic esters such as dioctyl maleate; vinyl acetate; styrene;

The polymer used as the polymer dispersant preferably has a number average molecular weight of about 400 to 10000. If the molecular weight is out of this range, the stability during emulsion polymerization is poor, and the stability of the obtained emulsion is poor. Is also not desirable. The polymer preferably has an acid value of 200 or more. In addition to the vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride, the polymer may have a vinyl unsaturated monomer copolymerizable therewith. In the case of a copolymer containing a saturated monomer as a monomer component, it is appropriate to select the type and amount of the monomer component so that the acid value becomes 200 or more.

Among the polymers containing a vinyl-based unsaturated monomer in the form of a carboxylic acid or an acid anhydride as an essential monomer component, those which can be suitably used in the present invention include polyacrylic acid, polymethacrylic acid and ( (Meth) acrylic acid / alkyl (meth) acrylate copolymer, (meth) acrylic acid / styrene copolymer, (meth) acrylic acid / alkyl (meth) acrylate / styrene copolymer, styrene / maleic anhydride Acid copolymers and the like can be exemplified. Among these polymers, polymethacrylic acid, methacrylic acid copolymer and the like are particularly preferable because they are excellent in self-adhesiveness.

The polymer containing the vinyl unsaturated monomer in the form of the carboxylic acid or acid anhydride as an essential monomer component is
For example, it can be obtained by polymerizing the above monomer in water, in a hydrophilic organic solvent, or in a mixed solution of water and a hydrophilic organic solvent using a radical polymerization initiator. Examples of the hydrophilic organic solvent that can be used at this time include alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, acetone, ketones such as methyl ethyl ketone, ethylene glycol monomethyl ether,
Glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and propylene glycol monomethyl ether can be mentioned.

Examples of the radical polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,2
Azo-based polymerization initiators such as 4-dimethylvaleronitrile),
A peroxide-based polymerization initiator such as t-butyl hydroperoxide, benzoyl peroxide, and lauroyl peroxide can be used. The amount of the radical polymerization initiator used is 0.2 to 1 with respect to the total amount of the polymerization monomers.
It may be about 0% by weight, preferably about 0.5 to 5% by weight. The reaction temperature during the polymerization may be usually about 50 to 120 ° C., and the reaction time is usually about 1 to 16 hours.
Preferably, it may be about 2 to 8 hours. Since the used organic solvent acts as a chain transfer agent when an acrylic emulsion is obtained by emulsion polymerization, it is preferable to evaporate after polymerization by raising the temperature and, if necessary, reducing the pressure.

The carboxyl group contained in the polymer containing a vinyl unsaturated monomer in the form of a carboxylic acid or an acid anhydride as an essential monomer component is partially or entirely neutralized,
It is used as a polymer dispersant in the form of an alkali neutralized salt.
Examples of the alkali compound used for neutralization include amine compounds such as monoethylamine, diethylamine, triethylamine, monoethanolamine, dimethylaminoethanol and morpholine, and inorganic alkali compounds such as ammonia, sodium hydroxide and potassium hydroxide. The degree of neutralization may be in the range of about 30 to 100%. If the degree of neutralization is less than this, it is not preferable because hydrophilicity is insufficient and it is difficult to obtain a stable emulsion.

Specific examples of the polymer dispersant that can be used in the present invention include, for example, commercially available Tuftic AD (trademark: manufactured by Toyobo Co., Ltd.) and SN-4 (trademark: manufactured by Sumitomo Dow). You can use what is. In addition, Tokiko Sho 46
The oligomer having a terminal alkyl sulfide group described in JP-A-10786 can also be used as a polymer dispersant.

The amount of the polymer dispersant used may be about 0.1 to 5.0% by weight based on the total amount of the monomers.
Preferably, it may be about 0.2 to 2.5% by weight. If the amount of the polymer dispersant is too small, a stable emulsion cannot be obtained. If the amount is too large, the self-adhesiveness decreases, which is not preferable.

In the present invention, a common emulsifier used for ordinary emulsion polymerization can be used in combination with the above-mentioned polymer dispersant in the emulsion polymerization. However, if the used amount of these emulsifiers is too large, when the obtained emulsion is used as a self-adhesive adhesive, the emulsifier migrates to the coating surface and inhibits the self-adhesion, which is not preferable. . In addition, when an emulsifier having an ethylene oxide group, a propylene oxide group, or the like in a molecular structure is used, a low molecular weight polymer component is easily generated by a chain transfer reaction during emulsion polymerization, and such a low molecular weight polymer is formed. When done
There is a problem that this transfers to the coating surface and inhibits self-adhesion. Therefore, it is appropriate that the amount of the emulsifier other than the above-mentioned polymer dispersant to be used is within the same range as the amount of the polymer dispersant used.

Examples of such emulsifiers include potassium oleate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium alkane sulfonate, sodium alkylnaphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, Anionic emulsifiers such as sodium polyoxyethylene alkyl allyl ether sulfate, polyoxyethylene alkyl ether phosphate and polyoxyethylene alkyl allyl ether phosphate; polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oxypropylene block Polymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester Nonionic emulsifiers and the like; stearylamine hydrochloride, lauryl trimethylammonium chloride, cationic emulsifiers such as trimethyl octadecyl ammonium chloride; lauryl betaine, amphoteric emulsifiers such as lauryl dimethyl amine oxide may be cited.

Among these emulsifiers, the emulsifier having a polymerizable double bond in the molecular structure, which is commercially available as a so-called reactive emulsifier, is bonded to the polymer particles to suppress migration of the emulsifier, It is particularly preferable for the purpose of auxiliary use in combination with a polymer dispersant, since the adhesiveness is hardly reduced. Examples of such a reactive emulsifier include Adecaria Soap SE-10N (trademark: Asahi Denka Kogyo KK)
Manufactured), Latemul S-180 (trademark: manufactured by Kao Corporation), Eleminor JS-2 (trademark: manufactured by Sanyo Chemical Industry Co., Ltd.),
Aqualon HS-10 (trademark: Daiichi Kogyo Seiyaku Co., Ltd.)
And Antox MS-60 (trademark: manufactured by Nippon Emulsifier Co., Ltd.).

Emulsion polymerization for producing the acrylic emulsion of the present invention may be performed according to a conventional method. That is, in the presence of the polymer dispersant and, if necessary, other emulsifiers, the monomer and the polymerization initiator are supplied at a predetermined temperature under stirring in an aqueous medium, or are supplied continuously. Done. The monomer can be supplied as it is, or can be supplied as a monomer emulsion with water and an emulsifier. The monomer concentration is
The amount may be generally about 30 to 70% by weight, preferably about 35 to 65% by weight, based on the total amount of the charged amount.

As the polymerization initiator, generally used radical polymerization initiators, for example, ammonium persulfate,
Persulfates such as potassium persulfate; azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile); t-butyl hydroperoxide And peroxide-based initiators such as benzoyl peroxide and lauroyl peroxide. The amount of the radical polymerization initiator used is 0.05 to 5% by weight based on the total amount of the polymerization monomers.
Degree, preferably about 0.2 to 3% by weight.

In order to carry out redox polymerization, a reducing agent may be used in combination with a radical polymerization initiator. Examples of the reducing agent include sodium hyposulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate and the like. The amount of the reducing agent to be used is usually in the range of about 1/10 to 1/1 by weight relative to the polymerization initiator.

The reaction temperature during the emulsion polymerization is usually 20 to 90 ° C.
However, if the polymerization temperature is too high, a low molecular weight component is easily generated during the polymerization reaction.
It is preferable to set the range. The reaction time is usually 1
The time may be about 16 hours, preferably about 2 to 8 hours.

Examples of the polymerization initiator used in the polymerization include persulfates such as potassium persulfate and ammonium persulfate, 2,2′-azobisisobutyronitrile,
From azo compounds such as 2′-azobis (2,4-dimethylvaleronitrile), peroxides such as hydrogen peroxide, benzoyl peroxide, lauryl peroxide, and combinations of ammonium persulfate with sodium sulfite, acidic sodium sulfite, etc. , A so-called redox-based polymerization initiator. The amount of the polymerization initiator to be used is generally about 0.2 to 2% by weight, more preferably about 0.3 to 1% by weight, based on the total amount of the monomers commonly used for polymerization.

Examples of the chain transfer agent to be added at the time of the copolymerization include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, octyl thioglycolate, nonyl thioglycolate, 2-ethylhexyl thioglycolate, β Thioglycolic acid esters such as 2-ethylhexyl mercaptopropionate; 2,4-diphenyl-4-methyl-1-pentene; 1-methyl-4-isopropylidene-1-cyclohexene; In particular, thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-pentene
When isopropylidene-1-cyclohexene is used, the obtained copolymer has a low odor, which is preferable. The amount of the chain transfer agent is adjusted to about 0.001 to 3% by weight of all monomers to be polymerized.

The monomer concentration during the polymerization is usually from 30 to 70.
% By weight, preferably about 40 to 60% by weight. Further, the polymerization reaction is usually performed at a temperature of 60 to 100 ° C. for 2 to 8 hours. Further, a wetting agent, a leveling agent, a thickener, an antifoaming agent, a preservative and the like can be appropriately added.

The copolymer obtained by the above method is desirably neutralized with an alkali metal hydroxide corresponding to 50 to 120 mol% of the carboxyl groups in the copolymer.
By performing the neutralization treatment, the mechanical stability can be improved and the viscosity can be adjusted. Further, it is possible to prevent deterioration when coated paper or neutral paper containing a large amount of calcium carbonate is used as the base material.

An alkanolamine capable of exhibiting the function of the copolymer as a plasticizer can be used together with the alkali metal hydroxide. In order to neutralize the carboxyl groups in the copolymer, ammonia or the like may be used.However, the water redispersibility of the pressure-sensitive adhesive deteriorates with their volatilization, and thus, the time after processing into a pressure-sensitive adhesive sheet is reduced. It is also preferable to use a hydroxide of an alkali metal and, at the same time, an alkanolamine at the same time, in order to prevent a change in adhesion performance and a deterioration in water redispersibility due to volatilization in water.

According to the present invention, by using such a copolymer as a pressure-sensitive adhesive, it is possible to obtain a pressure-sensitive adhesive sheet which can be mixed in a waste paper recycling process.

Next, as the base material used for the pressure-sensitive adhesive sheet, for example, films (cellophane, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polyester, etc.) and papers (fine paper, art paper, Coated paper, cast coated paper, foil paper, kraft paper, polyethylene laminated paper, impregnated paper, vapor-deposited paper, low-size paper, water-soluble paper, etc.), metal foil, synthetic paper, non-woven fabric, etc. Recording layer, thermal transfer recording image receiving layer,
Various recording layers such as an ink receiving layer for ink jet recording,
Those provided with layers such as various printing layers, coloring layers and concealing layers can be suitably used.

Considering the recyclability of the pressure-sensitive adhesive sheet, the above papers can be used as high quality paper, art paper, coated paper, cast paper, kraft paper, impregnated paper, low size paper, water soluble paper, kraft paper or high quality paper. For example, casein, dextrin, starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer Paper such as a base material provided with a filler layer mainly composed of a natural or synthetic resin and / or a pigment such as a coalescable or acrylate copolymer, and a water-soluble base such as polyvinyl alcohol, carboxymethylcellulose and methylcellulose. Water formed from molecules Or a lactic acid or lactide and glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxycarboxylic acid such as hydroxyheptanoic acid or molded from lactic acid-based polymer such as polylactic acid. It is desirable to use a film or the like that is easily hydrolyzed with an alkaline aqueous solution.

The above papers are not particularly limited, and acidic papers, neutral papers, and the like made by using virgin pulp, and recycled paper made from used paper may be used. In particular, use calcium carbonate as a pigment in the coating layer or ash in the paper layer.
Even paper containing filler can be suitably used with little deterioration in adhesive performance.

The pigment contained in the pressure-sensitive adhesive layer of the present invention further improves the heat resistance and blocking resistance of the adhesive, and includes inorganic pigments and organic pigments. Specifically, silica, kaolin, clay, calcium carbonate,
Examples thereof include aluminum hydroxide, titanium oxide, zinc oxide, melamine resin particles, benzoguanamine resin particles, and starch particles, which can be used alone or in combination. The pigment can be used in an amount of 30 to 150 parts by weight, preferably 30 to 100 parts by weight, per 100 parts by weight of the adhesive.
Parts by weight. By the way, when the amount is less than 30 parts by weight, the adhesive strength becomes too strong and blocking easily occurs. on the other hand,
If the amount exceeds 150 parts by weight, the blocking resistance and the heat resistance are improved, but the adhesion is reduced.

In the present invention, it is also possible to use a tackifier in combination. Examples of such tackifiers include rosin-based resins and derivatives thereof, terpene-based resins, cumarone-indene resins, xylene resins, alkylphenol resins, C5 and C9-based petroleum resins, and the like. It can be added within a range that does not impair heat resistance. Further, it is also possible to use a release agent, for example, various paraffins, waxes, fatty acids and derivatives thereof, higher alcohols, metal soaps, silicones and the like can be exemplified as long as the adhesiveness is not impaired. Can be added. Furthermore, auxiliary agents such as an antistatic agent, a thickener, a preservative, an antioxidant, an ultraviolet absorber, a fluorescent dye, a colorant, and an antifoaming agent are added to the pressure-sensitive adhesive layer of the present invention as necessary. May be.

The coating amount of the pressure-sensitive adhesive is 4 to 20 g / m ^2.
And preferably 6 to 17 g / m ² . Incidentally 4
When the amount is less than g / m ² , the adhesiveness is reduced, and when the amount exceeds 20 g / m ² , there is a possibility that the adhesion of the residue to the heat roll during thermal fixing of the toner may be deteriorated. The method of applying and printing the pressure-sensitive adhesive includes an air knife coater, a blade coater, a bar coater, a screen printing, a flexo printing, and the like.
Conventionally known methods can be used.

[0068]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but of course, the present invention is not limited to these examples. Unless otherwise specified, all parts, ratios, coating amounts, and the like in the examples are indicated by solid content weight.

Example 1 (Production of Adhesive) First, as a mixture of emulsified monomers, methoxyethyl acrylate: 75 parts, caprolactone acrylate adduct (trade name: Aronix M-5300 / Toagosei Co., Ltd.): 20 parts, 2-ethylhexyl acrylate: 220 parts, acrylic acid: 45 parts, vinyl acetate: 20
Parts, methyl (meth) acrylate: 20 parts, anionic emulsifier (trade name: Emar NC-35 / Kao Corporation): 6
Parts, ion-exchanged water: 150 parts.

Next, 150 parts of ion-exchanged water, 3 parts of potassium peroxide, and 3 parts of octyl mercaptan were charged into a flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction pipe, and a thermometer. After the temperature rises,
The emulsified monomer mixture was dropped by 1/6. Reaction rate 9
When it reached 0%, the remaining monomer mixture was dropped over 3 hours to carry out polymerization. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 3 hours to complete the reaction. Next, the contents of the flask were
And neutralized by adding a 10% aqueous solution of KOH and triethanolamine in an amount corresponding to 50 mol% of the carboxyl groups in the copolymer.
Nonionic surfactant (trade name: Emulgen 810 / manufactured by Kao Soap Co.): 4 parts with respect to 100 parts of the adhesive body
Ethylene-vinyl acetate-acrylic copolymer (trade name: Sumikaflex S-3110 / Sumitomo Chemical Co., Ltd.): 27 parts,
2 parts of an ammonium salt of EDTA (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was vigorously stirred to produce an adhesive used in the present invention.

(Preparation of Pressure Sensitive Adhesive Sheet) Adhesive 10
To 0 part by weight, 30 parts by weight of synthetic silica (trade name: Mizuka Seal P-526 / manufactured by Mizusawa Chemical Industry Co., Ltd.) and 15 parts by weight of wheat starch are blended as pigments, and the solid content is adjusted to 35% by weight. A pressure-sensitive adhesive composition was obtained. Coated with an air knife coater so that 8 g / m ² by dry weight of this pressure-sensitive adhesive composition on a high-quality paper 64 g / m ^2, to obtain a pressure-sensitive adhesive sheet of the present invention and dried.

Example 2 The pressure-sensitive adhesive sheet of the present invention was prepared in the same manner as in Example 1 except that the pigment was changed to 130 weight of synthetic silica (trade name: Mizuka Seal P-526 / manufactured by Mizusawa Chemical Industry Co., Ltd.). I got

Example 3 (Preparation of pressure-sensitive adhesive sheet) Aluminum hydroxide (trade name: Heidilite H) was used as a pigment in 100 parts by weight of the above adhesive.
-42 / manufactured by Showa Denko KK, and adjusted to a solid content concentration of 35% by weight to obtain a pressure-sensitive adhesive composition of the present invention. Coated with an air knife coater so that 8 g / m ² by dry weight of this pressure-sensitive adhesive composition on a high-quality paper 64 g / m ^2, to obtain a pressure-sensitive adhesive sheet of the present invention and dried.

Example 4 A pressure-sensitive adhesive sheet of the present invention was obtained in the same manner as in Example 1, except that neutral paper-made high-quality paper containing calcium carbonate was used as the base material.

Comparative Example 1 Ethylene-vinyl acetate copolymer resin (trade name: Sumikaflex 753 / Sumitomo Chemical Co., Ltd.) as an adhesive
100 parts by weight (glass transition temperature: -15 ° C.) of 150 parts by weight of synthetic silica (trade name: Mizukasil P-832 / manufactured by Mizusawa Chemical Industry Co., Ltd.) as a pigment were mixed with 100 parts by weight, and the solid content was adjusted to 45% by weight. A pressure-sensitive adhesive composition was obtained. This pressure-sensitive adhesive composition was applied to a high quality paper of 64 g / m ² by dry weight of 8 g / m ^2.
Was applied with an air knife coater and dried to obtain a pressure-sensitive adhesive sheet.

Comparative Example 2 Modified natural rubber-based block copolymer resin (trade name: Furtite FB-DO-3 / manufactured by Mitsui Fuller) 1 as an adhesive
36 parts by weight of synthetic silica (trade name: Mizukasil P-832 / manufactured by Mizusawa Chemical Industry), 40 parts by weight of wheat starch, SBR latex (trade name: Polylac 750K-101 / manufactured by Mitsui Chemicals) in 00 parts by weight Blending parts by weight,
The pressure-sensitive adhesive composition was obtained by adjusting the solid content to 35% by weight. Coated with an air knife coater so that the pressure-sensitive adhesive composition becomes 8 g / m ² by dry weight to high-quality paper of 64 g / m ^2, to obtain a pressure-sensitive adhesive sheet is dried.

(Evaluation Test Items) [Adhesion] Adhesion after storage under the following two conditions was measured according to JIS-Z-0237 measuring method of normal adhesion (unit: g / 25 mm). ). In addition, PB was described in the case where the surface substrate was broken. Condition A: After the production of the pressure-sensitive adhesive sheet, the sheet was stored for 7 days in an atmosphere at a temperature of 23 ± 2 ° C. and a relative humidity of 65 ± 5%, and then its adhesive strength was measured. Condition B: After production of the pressure-sensitive adhesive sheet, the sheet was stored in an atmosphere at a temperature of 40 ± 2 ° C. and a relative humidity of 90 ± 5% for 7 days, and then its adhesive strength was measured.

[Pressure-sensitive adhesive water redispersibility] The surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was immersed in water at 20.degree.
The behavior of the pressure-sensitive adhesive upon repeated rubbing was evaluated according to the following evaluation criteria. ：: The pressure-sensitive adhesive layer was redispersed into fine particles having no adhesive property. Δ: Although the adhesiveness of the pressure-sensitive adhesive layer is reduced, it is not finely dispersed or agglomerated. X: The adhesiveness of the pressure-sensitive adhesive layer did not change, and the pressure-sensitive adhesive layer film aggregated.

[Recyclability] The recyclability after storage under the following two conditions was evaluated. Condition A: After manufacturing the pressure-sensitive adhesive sheet, the sheet was stored for 7 days in an atmosphere at a temperature of 23 ± 2 ° C. and a relative humidity of 65 ± 5%, and then its suitability for recycling was evaluated. Condition B: After manufacturing the pressure-sensitive adhesive sheet, the sheet was stored in an atmosphere at a temperature of 40 ± 2 ° C. and a relative humidity of 90 ± 5% for 7 days, and then its suitability for recycling was evaluated.

(Evaluation) A 45 g sample of the pressure-sensitive adhesive sheet cut into a size of about 20 mm
After adding 1 g of NaOH and adding 1 g of NaOH and subjecting it to 150,000 rotations using a TAPPI disintegrator, the pulp concentration becomes 15%.
%, And 1.5 g of an 18% NaOH aqueous solution and 1.8 g of a 10% solution of a deinking agent (trade name: DI-600, manufactured by Kao Corporation) are added. At 40 ° C. for 20 minutes, and then dehydrated with a 60-mesh nylon screen until the pulp concentration became 25%. Then, 3.85 g of a 30% aqueous NaSiO ₃ solution and 6% aqueous H ₂ O ₂ were added. 5 g of each was added, and then a kneading treatment was performed for 5 minutes using a double arm kneader.

Next, the mixture was stirred for 120 minutes while maintaining the temperature at 55 ° C., diluted with water until the pulp concentration became 17.5%, and the second kneading treatment was performed in the same manner. Thereafter, the mixture was further diluted with water until the pulp concentration became 1%. next,
This 1% pulp dispersion is put in a flotator for 10 minutes.
The mixture was subjected to a flotation treatment for 1 minute, bubbles generated at that time were removed with a scraper, dewatered again with a 60-mesh nylon screen, washed with 1000 ml of water and dehydrated to a concentration of 13%. Water was added to the pulp dispersion liquid thus obtained to a concentration of 0.3% to prepare a hand-made sheet, the remaining state of the undisintegrated material was visually observed, and stickiness by finger touch was observed. In accordance with the following evaluation criteria.

(Evaluation Criteria for Recycling Suitability) ：: Almost no undisintegrated material and no stickiness. Δ: There is a little undisintegrated matter, but there is no stickiness and there is no practical problem. X: The undisintegrated material is conspicuous or sticky.

[Overall Evaluation] The above evaluations were combined to evaluate the performance as a recyclable pressure-sensitive adhesive sheet of the present invention. ：: Sufficient waste paper recycling is possible even with the pressure-sensitive adhesive sheet even after long-term storage, and the adhesive performance of the pressure-sensitive adhesive is good, with little deterioration due to heat and humidity. ：: Undisintegrated material remains after disintegration, but has no adhesiveness, recycling of waste paper is possible, and the adhesive performance of the pressure-sensitive adhesive has good adhesive strength and little heat and moisture deterioration. Δ: Recycling of used paper is possible even with the pressure-sensitive adhesive sheet, but there is a problem in the adhesive performance of the pressure-sensitive adhesive. ×: Recycling of used paper is impossible from the viewpoint of storage stability regardless of the adhesive performance.

[0084]

[Table 1]

[0085]

As shown in Table 1, the pressure-sensitive adhesive sheet of the present invention has excellent recyclability of pulp because the pressure-sensitive adhesive is easily redispersed in water, and the adhesive strength required at the time of application. This indicates that even if the pressure-sensitive adhesive sheet is mixed into the recycling process as it is, it is easily removed outside the process, and furthermore, it contains a large amount of calcium carbonate that could not be used in the past due to the storage stability of the pressure-sensitive adhesive sheet It was a pressure-sensitive adhesive sheet in which the adhesive performance and disintegration of the adhesive did not deteriorate even when paper or neutral paper was used.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C005 WA03 4F100 AA08A AA18B AA18C AK25B AK25C AK70B AK70C AL01B AL01C AT00A BA02 BA03 BA06 BA07 BA10B BA10C CA13B CA13C CB05B CB05C DG10A EH05B13J05 J05 J05 J05 J05 J05 J05 J05 J05 J05 AB01 CA02 CA04 CA05 CA06 CA07 CA08 CB01 CB02 CC02 CD01 FA01 GA01 4J040 BA142 DF011 DF041 DF051 EE012 GA07 HA146 HB11 HC09 HD43 JA09 JB09 KA22 KA31 KA38 LA07 LA08 LA11 PA23

Claims (9)

[Claims] 1. A substrate having an adhesive layer on at least one side of the substrate,
In a pressure-sensitive adhesive sheet capable of adhering by applying pressure while facing the application surfaces of the adhesive layer, the adhesive layer has water redispersibility and a glass transition temperature of -30 to 20 ° C. And a pressure-sensitive adhesive sheet containing 20 to 150 parts by weight of a pigment with respect to 100 parts by weight of the pressure-sensitive adhesive. 2. A pressure-sensitive adhesive comprising: (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer, and (b) an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet is a copolymer obtained by copolymerizing (c) a hydrophilic monomer having a glass transition point of -20 ° C or lower, and (d) other copolymerizable monomers. 3. A pressure-sensitive adhesive comprising: (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer, and (b) 4 carbon atoms.
(Meth) acrylic acid alkyl ester having an alkyl group of from 18 to 18% by weight, (c) glass transition point -2
A pressure-sensitive adhesive obtained by copolymerizing 5 to 50% by weight of a hydrophilic monomer having a temperature of 0 ° C. or less and (d) 1 to 15% by weight of another copolymerizable monomer, and blending an alkali metal hydroxide with the copolymer. Item 3. The pressure-sensitive adhesive sheet according to Item 2. 4. The pressure-sensitive adhesive sheet according to claim 2, wherein the pressure-sensitive adhesive contains an alkanolamine. 5. The pressure-sensitive adhesive sheet according to claim 2, wherein the pressure-sensitive adhesive contains a hydrophilic plasticizing substance. 6. The pressure-sensitive adhesive sheet according to claim 2, wherein the pressure-sensitive adhesive contains a chelating agent. 7. The pressure-sensitive material according to claim 1, wherein the base material is paper containing calcium carbonate as a pigment in a coating layer or as an ash / filler in a paper layer. Adhesive sheet. 8. In the presence of a polymer dispersant comprising an alkali neutralized salt of a polymer having a vinyl-based unsaturated monomer in the form of a carboxylic acid or an acid anhydride as an essential monomer component, contains an ethylenically unsaturated carboxylic acid. A monomer component containing 4 to 20% by weight of a monomer is copolymerized, and 50 to 120 mol% of an alkali metal hydroxide is added to the carboxyl group in the copolymer. A pressure-sensitive adhesive obtained by adding up to wt.% Of a hydrophilic plasticizing substance. 9. A monomer component comprising: (a) 4 to 20% by weight of an ethylenically unsaturated carboxylic acid-containing monomer, and (b) 40 to 70% by weight of an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms. %, (C) glass transition point−
9. The pressure-sensitive adhesive according to claim 8, wherein 5 to 50% by weight of a hydrophilic monomer having a temperature of 20 ° C. or less and 1 to 15% by weight of (d) other copolymerizable monomers.