JPH07107150B2 - Emulsion type pressure sensitive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an emulsion-type pressure-sensitive adhesive, specifically, adhesive strength,
Excellent balance of tack and cohesion, especially -10 ℃
The present invention relates to an emulsion-type pressure-sensitive adhesive that exhibits excellent adhesive force and cohesive force over a wide temperature range of + 40 ° C.

Prior Art Pressure sensitive adhesives are rated by adhesion, tack and cohesion. As a pressure-sensitive adhesive, it is desirable that both adhesive strength and cohesive strength are excellent. However, in general, adhesive strength and cohesive strength are contradictory properties. When the cohesive force is improved, the adhesive force tends to decrease. Therefore, it is extremely difficult to improve the adhesive strength and cohesive strength in a well-balanced manner, and it is usually necessary to consider whether the adhesive strength or cohesive strength is important depending on the application of the adhesive, It is the actual situation that corresponds to.

Also, the adhesive strength at low temperature and the adhesive strength at high temperature are
There is the same tendency as described above. When the low temperature adhesive strength is improved, the high temperature adhesive strength is lowered, and conversely, when the high temperature adhesive strength is improved, the low temperature adhesive strength is lowered.

Therefore, the pressure-sensitive adhesive has a good balance of adhesive strength, tackiness and cohesive strength, and excellent adhesive strength and cohesive strength over a wide temperature range from a low temperature of about -10 ° C to a high temperature of about + 40 ° C. Was desired to be developed.

(Problems to be Solved by the Invention) The present invention solves the problems of the conventional pressure-sensitive adhesives as described above, and is excellent in well-balanced adhesive force, tack and cohesive force, and over a wide temperature range. It is an object of the present invention to provide a pressure-sensitive adhesive having excellent adhesive force and cohesive force.

(Means for Solving the Problems) That is, the present invention relates to an acrylic acid ester monomer or a methacrylic acid ester monomer 80 to 9 having a chain alkyl group having 4 to 12 carbon atoms.
Monomer mixture consisting of 5.9 wt%, vinyl acetate monomer 4-15 wt%, unsaturated mono- or dicarboxylic acid monomer 0.1-5 wt% and other copolymerizable monomer 0-10 wt% Obtained by emulsion polymerization in the presence of an anionic surfactant and / or a nonionic surfactant, the glass transition temperature of the copolymer is less than -55 ° C, and the number average molecular weight (polystyrene conversion) is 110,000 to 500,000. 20 to 80 parts by weight of the copolymer emulsion (A) and an acrylic acid ester monomer or a methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms 60 to 9
9.9% by weight, unsaturated mono or dicarboxylic acid monomer 0.1
Copolymer weight of 5% by weight and other copolymerizable monomer 0-40% by weight, obtained by emulsion polymerization in the presence of an anionic surfactant and / or a nonionic surfactant. A polymer mixture comprising 80 to 20 parts by weight of a copolymer emulsion (B) having a glass transition temperature of −55 ° C. or higher and a number average molecular weight (in terms of polystyrene) of 10,000 to 100,000. The present invention relates to an emulsion-type pressure-sensitive adhesive characterized in that 1 to 30 parts by weight of a thermoplastic tackifier resin having a softening point of 50 to 180 ° C. is blended per 100 parts by weight.

Hereinafter, the present invention will be described in detail.

The copolymer emulsion (A) used in the present invention contributes to imparting low-temperature adhesive force and cohesive force. The acrylic acid ester monomer or methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms used for the production of this copolymer emulsion (A) includes acrylic acid 2-
Examples thereof include ethylhexyl, butyl acrylate, isononyl acrylate, 2-ethylhexyl methacrylate, butyl methacrylate and isononyl methacrylate. Of these, 2-ethylhexal acrylate,
Butyl acrylate is particularly preferred. These acrylic acid ester monomers or methacrylic acid ester monomers are
They can be used alone or in combination of two or more.

The amount of the acrylic acid ester monomer or methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms is 80 to 80% of that of the monomer mixture used for producing the copolymer latex (A). It is 95.9% by weight, preferably 85 to 95% by weight. If it is less than 80% by weight, the low-temperature adhesive strength will decrease, while if it exceeds 98.9% by weight, the high-temperature adhesive strength, the room-temperature adhesive strength will decrease, and the cohesive strength will also decrease.

Vinyl acetate monomer is an essential component for improving adhesive strength and cohesive force, and the effect of the present invention can be achieved only by using a specific amount of vinyl acetate monomer among vinyl monomers. It is a thing. The amount of the vinyl acetate monomer used is 4 to 15% by weight, preferably 5 to 10% by weight of the monomer mixture used for producing the copolymer emulsion (A). If it is less than 4% by weight, the balance between the room-temperature adhesive strength and the high-temperature adhesive strength and the cohesive strength is unbalanced, and especially the room-temperature adhesive strength and the high-temperature adhesive strength decrease, while if it exceeds 15% by weight, the low-temperature adhesive strength decreases.

Examples of the unsaturated mono- or dicarboxylic acid monomer used for producing the copolymer emulsion (A) include acrylic acid, methacrylic acid, itaconic acid, maleic acid and crotonic acid. These monomers may be used alone or in combination of two or more.

The amount of the unsaturated mono- or dicarboxylic acid monomer used is 0.1 to 5% by weight, preferably 0.5 to 4% by weight, of the monomer mixture used for producing the copolymer emulsion (A). If it is less than 0.1% by weight, the cohesive force is lowered, while if it exceeds 5% by weight, the adhesive force at high temperature, room temperature and low temperature is lowered, and particularly the low temperature adhesive force is poor.

Other copolymerizable monomers used in the production of the copolymer emulsion (A) include acrylamide,
Methacrylamide, N-methylolacrylamide, N
-Amids such as methylolmethacrylamide, nitriles such as acrylonitrile and methacrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, allyl phthalate, allyl acrylate, allyl methacrylate and the like having 4 carbon atoms
Examples thereof include carboxylic acid esters other than acrylic acid ester monomers or methacrylic acid ester monomers having a chain alkyl group of up to 12 and aromatic vinyl compounds such as styrene. These monomers may be used alone or in combination of two or more.

The amount of the above-mentioned other copolymerizable monomer to be used is 0 for the monomer mixture used for producing the copolymer emulsion (A).
-10 wt%, preferably 1-8 wt%. 10% by weight
If it exceeds, the low temperature adhesive strength will decrease.

The copolymer emulsion (B) used in the present invention imparts room temperature adhesive strength and high temperature adhesive strength. As the acrylic acid ester monomer or methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms, which is used in the production of this copolymer emulsion (B), the above copolymer emulsion (A) is used. Those listed in can be used. The acrylic acid ester monomer or methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms may be the same as or different from that used in the production of the copolymer emulsion (A). It may be one.
These monomers can be used alone or in combination of two or more.

The amount of the acrylic acid ester monomer or the methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms is 60 to 60% of that of the monomer mixture used for producing the copolymer emulsion (B). It is 99.9% by weight, preferably 70 to 95% by weight. If it is less than 60% by weight, the low-temperature adhesiveness will decrease, while if it exceeds 99.9% by weight, the room-temperature adhesiveness and the high-temperature adhesiveness will decrease, and the cohesive force will also decrease.

As the unsaturated mono- or dicarboxylic acid monomer used in the production of the copolymer emulsion (B), those mentioned in the copolymer emulsion (A) can be used. The unsaturated mono- or dicarboxylic acid monomer may be the same as or different from the monomer used for producing the copolymer emulsion (A). These monomers may be used alone or in combination of two or more.

The amount of the unsaturated mono- or dicarboxylic acid monomer used is 0.1 to 5% by weight, preferably 0.5 to 4% by weight of the monomer mixture used for producing the copolymer emulsion (B). If it is less than 0.1% by weight, the cohesive force is lowered, while if it exceeds 5% by weight, the adhesive force at high temperature, room temperature and low temperature is lowered, and especially the low temperature adhesive force is poor.

Examples of the other copolymerizable monomer used for producing the copolymer emulsion (B) are exemplified as other copolymerizable monomers used for producing the copolymer emulsion (A). The above-mentioned monomers can be used.
This copolymerizable monomer may be the same as or different from the monomer used for producing the copolymer emulsion (A). These monomers may be used alone or in combination of two or more.

The above-mentioned other copolymerizable monomers are used in an amount of 0 of the monomer mixture used for producing the copolymer emulsion (B).
-40% by weight, preferably 5-30% by weight. 40% by weight
If it exceeds, the low temperature adhesive strength will decrease.

The glass transition temperature of the copolymer of the copolymer emulsion (A) used in the present invention is lower than -55 ° C, preferably -70 ° C to
-56 ° C, number average molecular weight (polystyrene equivalent)
Is 110,000 to 500,000, preferably 150,000 to 300,000. When the glass transition temperature of the copolymer is −55 ° C. or higher, the low temperature adhesive strength is lowered, which is not preferable. Further, if the number average molecular weight of the copolymer (in terms of polystyrene) is less than 110,000, the cohesive force is insufficient.
On the other hand, when it exceeds 500,000, the adhesive strength at high temperature, room temperature and low temperature is insufficient.

The copolymer of the copolymer latex (B) used in the present invention has a glass transition temperature of -55 ° C or higher, preferably -54 ° C to-.
The temperature is 35 ° C., and the number average molecular weight (in terms of polystyrene) is 10,000 to 100,000, preferably 20,000 to 90,000. When the glass transition temperature of the copolymer is less than -55 ° C, the cohesive force is lowered, which is not preferable. Further, when the number average molecular weight of the copolymer (in terms of polystyrene) is less than 10,000, the cohesive force is greatly reduced as in the case where the glass transition temperature is less than -55 ° C. On the other hand, when it exceeds 100,000, the low temperature adhesive strength and the high temperature adhesive strength are reduced.

For the copolymer latex (A) and the copolymer latex (B), the composition of the monomer mixture is determined so that the glass transition temperature of the obtained copolymer is within the above range, and the monomer mixture is For example, it can be obtained by emulsion polymerization using hydrogen peroxide or a redox reducing agent as a polymerization initiator. As the emulsifier, an anionic surfactant and / or a nonionic surfactant is used.

Anionic surfactants include sodium alkyl diphenyl ether disulfonate, sodium alkyl sulfate, sodium lauryl alcohol sulfate, sodium dodecylbenzene sulfonate, and the like, and nonionic surfactants include polyoxyethylene nonyl phenyl ether and polyoxyethylene ocryl. Examples thereof include phenyl ether and polyethylene glycol sorbitan monolaurate. These surfactants may be used alone or in combination of two or more. Among these, sodium alkylsulfate is particularly preferable as the anionic surfactant, and polyoxyethylene nonylphenyl ether is particularly preferable as the nonionic surfactant. The amount of the anionic surfactant used is 0.1% of the monomer mixture.
~ 5.0 wt%, preferably 0.3-2.0 wt%, and the amount of the nonionic surfactant used is 0.
It is 1 to 5.0% by weight, preferably 0.3 to 4.0% by weight.

The glass transition temperature in the present invention was determined by the following formula (see “Polymer Handbook”, 2nd edition, edited by Jay Brand Wrap et al., Published by Jay Willy).

Tg: Glass transition temperature of copolymer (absolute temperature display) Tgi: Glass transition temperature of homopolymer of monomer component (i) (absolute temperature display) Wi: Polymerization amount of component (i) in copolymer The above-mentioned copolymer latex (A) and copolymer Laex (B) are mixed in a proportion of 20 to 80 parts by weight and 80 to 20 parts by weight, preferably 30 to 70 parts by weight and 70 to 30 parts by weight, respectively. Then, a polymer mixture is prepared. When the mixing ratio of the copolymer latex (A) is less than 20 parts by weight, the low-temperature adhesive force is low and the cohesive force is insufficient. On the other hand, if it exceeds 80 parts by weight, the room temperature adhesive strength and the high temperature adhesive strength are not sufficiently high, which is not practical.

Generally, the adhesive strength is improved in proportion to the amount of the copolymer latex (B) used, but the cohesive strength tends to be decreased, so that the adhesive strength from the low temperature to the high temperature required in actual use is increased. Considering the force and the cohesive force, the usage ratio of the copolymer latex (A) and the copolymer latex (B) may be appropriately determined within the above range.

In the present invention, with respect to 100 parts by weight of the polymer mixture obtained as described above, the softening point is 1 to 30 parts by weight, preferably 5 to 20 parts by weight of the thermoplastic tackifier resin having a softening point of 50 to 180 ° C. Compound. This thermoplastic tackifier resin is used to further improve the adhesive force, and specific examples thereof include rosin, polymerized rosin, hydrogenated rosin, partially hydrogenated rosin and esterified products of these polyhydric alcohols. Resin obtained by polymerization or copolymerization of rosins such as terpene resin, terpene phenol resin, aliphatic petroleum resin, aromatic petroleum resin, copolymerized petroleum resin composed of aliphatic hydrocarbon and aromatic hydrocarbon, and cyclopentadiene Examples thereof include hydrides of system resins. These resins may be used alone or in combination of two or more. Rosin resin is particularly preferable. The softening point of the thermoplastic tackifying resin is 50 to 180 ° C., preferably 70.
A decrease in cohesive strength is observed at a softening point of 50 ° C or lower at ~ 150 ° C. On the other hand, if it exceeds 180 ° C., the adhesive strength at high temperature, normal temperature and low temperature is lowered, and especially the low temperature adhesive strength is lowered, which is not preferable.

The thermoplastic tackifier resin is usually used as an emulsion.

The amount of the thermoplastic tackifier resin used is the above polymer mixture.
If the amount is less than 1 part by weight with respect to 100 parts by weight, the high temperature adhesive strength and the room temperature adhesive strength are lowered. On the other hand, if it exceeds 30 parts by weight, the low temperature adhesive strength is lowered and the tack is lowered, which is not preferable.

In the emulsion-type pressure-sensitive adhesive of the present invention, in addition to the above-mentioned components, known additives such as a filler, a pigment, a thickener, a defoaming agent, an antiaging agent, a cross-linking agent, and a wetting agent, if necessary. Can be blended.

The emulsion-type pressure-sensitive adhesive of the present invention has a good balance of adhesive strength, tackiness and cohesive strength, and exhibits excellent adhesive strength and cohesive strength in a wide temperature range of -10 ° C to + 40 ° C. Further, the emulsion-type pressure-sensitive adhesive of the present invention is also excellent in adhesive strength to a non-polar adherend such as polyethylene, which is lacking in the conventional acrylic acid ester-based pressure-sensitive adhesive.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, part and% mean a weight part and weight%, respectively.

The number average molecular weight was measured using a H-type column (manufactured by Toyo Soda Co., Ltd.) with a 150 type liquid chromatography device (manufactured by Waters Co.).

Production Example Production of Copolymer Emulsion (A) (1) Copolymer Emulsion (A-1) 1.0 part of sodium lauryl sulfate (anionic surfactant) and 60 parts of polyoxyethylene nonyl phenyl ether (nonion) in 60 parts of ion-exchanged water. 3 parts by weight of a surface active agent) to prepare an aqueous solution of an emulsifier, and thereto are added 9 parts of 2-ethylhexyl acrylate, 7 parts of vinyl acetate, 2 parts of acrylic acid and 0.02 part of n-dodecyl mercaptan as a polymerization degree controlling agent. The emulsifier aqueous solution was emulsified.

On the other hand, 40 parts of ion-exchanged water and 0.3 part of sodium persulfate are charged into a four-necked flask having an internal volume equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, and the temperature is raised to 70 ° C. while replacing with nitrogen. . When the liquid temperature reached 70 ° C., the above emulsion was added dropwise over 3 hours. After finishing the dropping, 2 at 80 ℃
The reaction was completed by continuing stirring for an hour.

The properties of the obtained copolymer emulsion (A-1) are as follows:
Shown in the table. It was extremely stable with almost no aggregates.

(2) Copolymer emulsions (A-2) to (A-5) The composition of the monomer mixture used and the amounts of n-dodecyl mercaptan, sodium persulfate and nonionic surfactant added are as shown in Table 1. Copolymer emulsions (A-2) to (A-5) were prepared in the same manner as in the production method of the copolymer latex (A-1) except that the above was changed.

Obtained copolymer emulsions (A-2) to (A-5)
The properties are shown in Table 1. It was extremely stable with almost no aggregates.

Production of copolymer emulsion (B) (1) Copolymer latex (B-1) 40 parts of ion-exchanged water, sodium dodecylbenzene sulfonate
0.1 part and 0.7 part of hydrogen peroxide were placed in a 1-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a lowering funnel, heated to 80 ° C., and then 60 parts of ion-exchanged water and 90 parts of butyl acrylate. , 8 parts methyl methacrylate, 2 acrylic acid
Parts, n-dodecyl mercaptan 0.05 parts, ferrous sulfate 0.05
Parts, 0.9 parts of sodium dodecylbenzene sulfonate and 0.5 parts of polyoxyethylene alkylphenyl ether were emulsified and added dropwise over 5 hours. 85 ℃ after dropping
The reaction was completed by continuing stirring for 2 hours.

The properties of the obtained copolymer emulsion (B-1) are as follows:
Shown in the table.

(2) Copolymer emulsion (B-2) to (B-4)
Except that the composition of the monomers used and the amount of n-dodecyl mercaptan added were changed as shown in Table 1, the copolymer emulsion (B-1) was prepared in the same manner as in the production method of the copolymer emulsion (B-1). -2) to (B-4) were prepared.

Obtained copolymer emulsions (B-2) to (B-4)
The properties are shown in Table 1.

Production of Comparative Copolymer Emulsion (1) Comparative Copolymer Emulsions (a-1) to (a)
-3) A copolymer for comparison in the same manner as in the method for producing the copolymer emulsion (A-1) except that the monomer composition used and the amount of n-dodecyl mercaptan used were changed as shown in Table 1. Emulsions (a-1) to (a-3) were prepared.

The obtained comparative copolymer emulsions (a-1) to (a)
The properties of -3) are shown in Table 1.

(2) Comparative copolymer emulsion (b-1), (b
-2) In the same manner as in the method for producing the copolymer emulsion (B-1), except that the monomer composition used, the amounts of n-dodecyl mercaptan, sodium persulfate and the like used were changed as shown in Table 1. Comparative copolymer emulsion (b-1), (b
-2) was prepared.

The obtained comparative copolymer emulsions (b-1) and (b
The properties of -2) are shown in Table 1.

Examples 1 to 7 and Comparative Examples 1 to 7 The copolymer emulsions (A) and (B) obtained in the above production examples were prepared by adding emulsions of stabilized rosin ester as a thermoplastic tackifier resin as shown in Table 2. Blended into
Emulsion type pressure sensitive adhesive of the present invention (Examples 1 to 10) and comparative emulsion type pressure sensitive adhesive (Comparative Examples 1 to 7)
Was prepared and its performance was tested.

The test method is as follows.

(Preparation of adhesive sheet) Each emulsion-type pressure-sensitive adhesive is applied to high-quality paper (64 g / m ² basis weight) so that the dry weight is 25 g / m ² , dried, and release paper is applied to this adhesive-coated surface. The pressure-sensitive adhesive sheet was prepared by stacking and bonding.

(Tack Test) The tack was evaluated by touching the finger with the following three grades.

◎: Very large ○: Large ×: Small (Room temperature adhesive strength test) A high-density polyethylene plate with a thickness of 2 mm, a width of 50 mm, and a length of 125 mm is used.
Polished by the method of JIS-Z-0237, width 25mm, length 250
A pressure-sensitive adhesive sheet (mm) of 5 mm was reciprocated 5 times with a 3 kg roller in a room at 20 ° C and 60% RH, and after 2 hours, a tensile tester (S-500 manufactured by Shimadzu Corporation) was used at a pulling speed of 300 mm / min.
The adhesive force when peeled at an angle of 0 ° was measured. The larger the value, the higher the adhesive strength.

(Cohesive strength test) A SUS steel plate with a thickness of 3 mm, a width of 50 mm and a length of 80 mm is JIS-Z-0237.
Polished by the method specified in, and the overlapping part is 25 mm x 2
The pressure-sensitive adhesive sheet was placed so as to have a length of 5 mm, and was reciprocated 6 times with a 3 kg roller, a 1 kg weight was hung on the lower end of the pressure-sensitive adhesive sheet, and the time until the pressure-sensitive adhesive sheet slipped off in an atmosphere of 40 ° C. was measured in time units (minutes). However, for 1200 minutes or more, it was described as "not falling". The larger the guess, the higher the cohesive force.

(Low temperature adhesive strength test) The measurement was performed in the same manner as the above room temperature adhesive strength test method except that the sticking temperature and the measurement temperature were set to -10 ° C.

(High temperature adhesive strength test) The measurement was performed in the same manner as the above room temperature adhesive strength test method except that the sticking temperature was 23 ° C and the measuring temperature was 40 ° C.

The results are shown in Table 2.

In Comparative Example 1, the number average molecular weight of the copolymer emulsion (A) is outside the range of the present invention, and the cohesive force is poor.

In Comparative Example 2, the vinyl acetate monomer content and the glass transition temperature of the copolymer emulsion (A) are outside the ranges of the present invention, and the low temperature adhesive strength is poor.

In Comparative Example 3, the glass transition temperature of the copolymer emulsion (B) is outside the range of the present invention, and the cohesive force is poor.

In Comparative Example 4, the copolymer emulsion (A) / copolymer emulsion (B) ratio is outside the range of the present invention, and both the low temperature adhesive strength and the cohesive strength are poor.

In Comparative Example 5, the copolymer emulsion (A) / copolymer emulsion (B) ratio was outside the range of the present invention, and the high temperature adhesive strength was poor.

Comparative Example 6 is an example in which the thermoplastic tackifier resin was not blended, and the high temperature adhesive strength was poor.

In Comparative Example 7, the vinyl acetate monomer content of the copolymer emulsion (A) is outside the range of the present invention, and the low temperature adhesive strength and cohesive strength are poor.

(Effect of the present invention) The emulsion-type pressure-sensitive adhesive of the present invention is excellent in well-balanced adhesive strength, tackiness and cohesive strength, and particularly -10 ° C to + 40 ° C.
It exhibits excellent adhesion and cohesion over a wide temperature range. Further, it exhibits a good adhesive force even for non-polar adherends such as polyethylene. Therefore, the emulsion-type pressure-sensitive adhesive of the present invention can be effectively used in various applications such as pressure-sensitive adhesive tapes and sheets.

Claims (1)

[Claims] 1. Acrylic ester monomer or methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms 80 to 95.9% by weight, vinyl acetate monomer 4 to 15% by weight, unsaturated monoester. Alternatively, a monomer mixture consisting of 0.1 to 5% by weight of a dicarboxylic acid monomer and 0 to 10% by weight of another copolymerizable monomer is emulsion polymerized in the presence of an anionic surfactant and / or a nonionic surfactant. 20-80 parts by weight (solid content) of a copolymer emulsion (A) having a glass transition temperature of less than −55 ° C. and a number average molecular weight (polystyrene conversion) of 110,000 to 500,000, which is obtained by And acrylic acid ester monomer or methacrylic acid ester monomer having a chain alkyl group having 4 to 12 carbon atoms 60 to 9
9.9% by weight, unsaturated mono or dicarboxylic acid monomer 0.1
Copolymer weight of 5% by weight and other copolymerizable monomer 0-40% by weight, obtained by emulsion polymerization in the presence of an anionic surfactant and / or a nonionic surfactant. A polymer mixture having a glass transition temperature of -55 ° C or higher and a copolymer emulsion (B) having a number average molecular weight (polystyrene conversion) of 10,000 to 100,000 (80 to 20 parts by weight (solid content conversion)). An emulsion-type pressure-sensitive adhesive characterized in that 1 to 30 parts by weight (in terms of solid content) of a thermoplastic tackifier resin having a softening point of 50 to 180 ° C. is mixed with 100 parts by weight of the polymer mixture.