JPS62100573A - Water-dispersed pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:A composition, based on a specific acrylic (co)polymer emulsion and a pressure-sensitive acrylic (co)polymer emulsion and having high adhesive and cohesive force without adding an external crosslinking agent thereto. CONSTITUTION:A composition containing a polymer emulsion obtained by adding (B) a polymer emulsion prepared by polymerizing (i) a main monomer, consisting of a 1-14C alkyl ester of (meth)acrylic acid or an unsaturated monomer having no functional group copolymerizable therewith in the molecule and capable of giving the (co)polymer having <=250 deg.K glass transition point exhibiting pressure-sensitive adhesive property thereof to (A) a polymer emulsion, obtained by polymerizing (i) the main monomer with (ii) a monomer mixture containing an unsaturated monomer containing N-methylol group of N-alkoxymethyl group added thereto in the presence of a persulfate in an aqueous medium without using an emulsifying agent and containing 20-60wt% gel fraction of polymer particles as a base.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to an acrylic water-dispersed pressure-sensitive adhesive composition.

[Conventional technology]

In recent years, acrylic pressure-sensitive adhesives have replaced conventional natural rubber-based adhesives due to their superior adhesive properties and durability.

It has become widely used as an alternative to synthetic rubber-based pressure-sensitive adhesives. Also, among this type of adhesive, recently water-dispersible adhesives that do not use organic solvents are resource-saving.

It is being researched and developed from the perspective of environmental hygiene.

Such water-dispersed adhesives are generally prepared by emulsion polymerization. That is, it is prepared by emulsion polymerization of a (meth)acrylic acid alkyl ester in an aqueous medium together with a modifying monomer such as acrylic acid, styrene, or vinyl acetate as necessary, and the room temperature obtained by this method is It is known that acrylic polymers with adhesive properties have a relatively large molecular weight compared to polymers obtained by solution polymerization, and therefore can be used as pressure-sensitive adhesives7 with relatively high cohesive strength. There is.

[Problem that the invention seeks to solve]

However, the conventional acrylic water-dispersed adhesive mentioned above is
When applied to applications where a high degree of cohesive force is desired, it is still unsatisfactory, and when the bonded area is exposed to relatively high temperatures, the cohesive force is significantly reduced.
could hardly be put to use. Therefore, in order to further improve the cohesive force of this type of adhesive, external crosslinking agents similar to those used in organic solvent types, such as melamine compounds, epoxy compounds, metal salts, etc., are added to the polymer emulsion after emulsion polymerization. Attempts have been made.

However, with these improvement measures, it is difficult to select the type and amount of crosslinking agent to be used, and there are productivity problems such as the thermal energy for crosslinking which cannot be ignored. As a result, the cohesive force is not so thick compared to the degree of crosslinking (and even if the cohesive force can be increased, the adhesive force will decrease accordingly, and in the end, the adhesive force will be high and It has been difficult to obtain pressure sensitive adhesive compositions that have cohesive strength.

Furthermore, when the cohesive force is increased by the above-mentioned means,
Apart from the decrease in adhesive strength, there was also the problem that the adhesive had poor repulsion resistance.

In other words, in applications such as bonding a metal plate or plastic plate in a bent state to an adherend with a curved surface, a restoring force acts on the bent metal or plastic plate, so it is difficult to resist this restoring force. This repulsion resistance is expressed by the balance between adhesive strength and cohesive force. It was not possible to satisfy them.

As described above, the conventional acrylic water-dispersed adhesive has a problem in that it is difficult to obtain one that highly satisfies both adhesive strength and cohesive force and also has excellent repulsion resistance. Moreover, this type of adhesive uses an emulsifier to stabilize the polymer particles during emulsion polymerization, and this emulsifier is mixed into the adhesive composition, resulting in poor moisture and water resistance. There was also the problem that the adhesive properties were adversely affected.

Therefore, the present invention provides a water-dispersed pressure-sensitive adhesive composition that does not contain any emulsifier that causes the deterioration of the adhesive properties, and that has high adhesive strength and high cohesive strength even without the addition of an external crosslinking agent. It is an object of the present invention to provide an acrylic water-dispersed pressure-sensitive adhesive composition that exhibits the above properties and also has excellent repulsion resistance.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors conducted two-step polymerization in an aqueous medium that eliminated the use of emulsifiers by using a specific polymerization initiator instead of conventional emulsion polymerization. In the first stage of polymerization, a specific acrylic monomer mixture, a part of which is a self-crosslinking monomer, is used to produce polymer particles with a gel fraction within a specific range. When a combined emulsion is produced and a specific acrylic monomer is added to it to perform the second stage of polymerization, it does not contain an emulsifier, so it is moisture resistant,
An acrylic water-dispersed pressure-sensitive adhesive composition that has excellent water resistance, exhibits high adhesive strength and high cohesive strength even without the addition of an external crosslinking agent, and has excellent repulsion resistance can be obtained. After discovering that this was the case, he completed this invention.

That is, in this invention, the alkyl group has 1 to 14 carbon atoms.
A glass transition in which a homopolymer or copolymer of (meth)acrylic acid alkyl ester alone or its homopolymer or copolymer consisting of this ester and an unsaturated monomer having no functional group in the molecule that can be copolymerized with the ester exhibits pressure-sensitive adhesive properties. point is 250°K
The main monomer that can be the following is N as a self-crosslinking monomer.
- The gel fraction obtained by polymerizing a monomer mixture prepared by adding an unsaturated monomer containing a methylol group or an N-alkoxymethyl group in an aqueous medium in the presence of a persulfate without using an emulsifier is A (meth)acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms alone or an unsaturated monomer copolymerizable with this ester is added to a polymer emulsion containing 20 to 60% of weight particles. J$ for post-polymerization, the homopolymer or copolymer of which is composed of
The present invention relates to a water-dispersed pressure-sensitive adhesive composition based on a polymer emulsion obtained by adding and polymerizing a polymer.

As described above, in this invention, polymerization in an aqueous medium is carried out without using an emulsifier by using a persulfate as a polymerization initiator, and the persulfate decomposes into ions. This generates terminal groups that greatly contribute to polymerization stability and the stability of the emulsion after polymerization. Therefore, the pressure-sensitive adhesive composition based on the polymer emulsion obtained by this method has excellent moisture resistance and water resistance because it does not contain an emulsifier. The stability of the emulsion is comparable to that of other compositions.

In addition, in this invention, the polymerization in an aqueous medium as described above is divided into two stages, and an acrylic Sit mixture containing the above-mentioned specific self-crosslinking monomer is used as a monomer for the first stage polymerization. By using a polymeric compound, an emulsion containing specific polymer particles with a controlled gel fraction is produced, and to this, an acrylic monomer with excellent pressure-sensitive adhesive properties is added as a second stage. Since post-polymerization is performed, in other words, the polymer particles produced by this method have a crosslinked structure inside and a structure made of acrylic pressure-sensitive adhesive polymer as the surrounding part. It is estimated that the gel fraction of the entire polymer constituting the particles is regulated within a specific range due to the particle structure. It exhibits high adhesive strength and high cohesive strength even without the addition of agents, and also has excellent repulsion resistance.

In addition, the gel fraction of polymer particles in this specification is
It serves as an index indicating the extent to which the polymer constituting the polymer particles is involved in crosslinking, and is expressed by measuring the solvent-insoluble content (% by weight) of the polymer. Specifically, it is actually measured by forming a polymer film from an emulsion containing polymer particles, immersing it in a solvent to elute the polymer that does not participate in crosslinking, and measuring the remaining solvent-insoluble content. .

This measurement is as shown in Examples below.

Furthermore, in this specification, (meth)acrylic acid refers to acrylic acid and/or methacrylic acid, (meth)acrylic acid alkyl ester refers to acrylic acid alkyl ester and/or methacrylic acid alkyl ester, and (meth)acrylic acid alkyl ester refers to acrylic acid alkyl ester and/or methacrylic acid alkyl ester. ) Acrylate means acrylate and/or methacrylate, respectively.

[Structure and operation of the invention]

In this invention, the gel fraction is regulated within a specific range by first using the first-stage polymerization monomer and polymerizing it in the presence of persulfate in an aqueous medium without using an emulsifier. A polymer emulsion containing polymer particles is produced.

The above monomer for polymerization has an alkyl group having 1 to 14 carbon atoms.
A main monomer consisting of a (meth)acrylic acid alkyl ester alone or this ester and an unsaturated monomer having no functional group in the molecule that can be copolymerized with the ester, and N as a self-crosslinking monomer. A monomer mixture containing an unsaturated monomer containing a -methylol group or an N-alkoxymethyl group is used.

As the (meth)acrylic acid alkyl ester as the main monomer, from the viewpoint of adhesive properties, those in which the alkyl group has 1 to 14 carbon atoms are used, and particularly preferred examples include:
Ethyl acrylate, butyl acrylate, acrylic acid 2-
Ethylhexyl, isononyl acrylate, isodecyl acrylate, ethyl methacrylate, butyl methacrylate,
Examples include lauryl methacrylate. In addition, examples of copolymerizable unsaturated monomers that do not have a functional group in the molecule include acrylonitrile, methacrylonitrile, vinyl acetate, styrene or derivatives thereof, and these monomers can be used to form polymer particles. It mainly contributes as a component that increases the cohesive force of the polymers that make up the polymer.

The main monomer consisting of such (meth)acrylic acid argyl ester alone or the above-mentioned copolymerizable unsaturated medium has a glass transition point such that its homopolymer or copolymer exhibits pressure-sensitive adhesive properties. It is necessary that the composition be such that 250' or less. With such a composition, it is possible to prepare an adhesive composition that has both high cohesive strength and high adhesive strength. For this purpose, the above copolymerizable unsaturated monomer is (meta)
The copolymerizable unsaturated monomer is usually contained in a monomer mixture consisting of a main monomer and a self-crosslinking monomer, and is preferably kept in a small amount relative to the acrylic acid alkyl ester. The content is preferably 10% by weight or less.

The self-crosslinking monomer used in combination with this main monomer is an essential component for making the polymer particles have an appropriate gel fraction, and contains N-methylol or N-alkoxymethyl groups. using unsaturated monomers. The amount of these monomers to be used is within the range of 1 to 10% by weight in the monomer mixture, and is appropriately determined depending on the type and desired gel fraction of the polymer particles. If the amount used is too small, the gel fraction of the polymer particles cannot be set within the desired range, and conversely, if it is too large, the gel fraction of the polymer particles becomes too high, resulting in poor adhesion and repulsion resistance. A difficulty arises.

Specific examples of the unsaturated monomer containing an N-methylol group or an N-alkoxymethyl group include N-methylol acrylamide, N-methylol methacrylamide, N-n-
Examples include butoxymethylacrylamide, N-n-butoxymethylacrylamide, and the like. The number of carbon atoms in the alkoxy group of the N-alkoxymethyl group is preferably about 5 or less from the viewpoint of reactivity.

In the first stage of polymerization, persulfate as a polymerization initiator is usually added and dissolved in water, heated to a temperature of 60 to 90°C, and the above-mentioned monomer is stirred into the aqueous medium. The polymer mixture may be added dropwise at a predetermined rate and allowed to react for a predetermined period of time while being maintained at a constant temperature.

Examples of persulfates used here include potassium persulfate, ammonium persulfate, and sodium persulfate. This persulfate acts as a weight initiator 1, giving shape to the molecular weight and even the mountain fraction of the produced polymer, and the ionic end groups produced by its decomposition in the aqueous medium. It contributes to the polymerization stability during the polymerization and the stability of the emulsion after polymerization. In addition, this persulfate usually plays a role as a polymerization initiator in the second stage of polymerization in the subsequent step, and also plays a role in polymerization stability and emulsion stability.

Therefore, the amount of the persulfate used is desirably set within an appropriate range from the above-mentioned viewpoint, that is, from the viewpoint of the molecular stars, gel fraction, and stability of the produced polymer. Generally, the proportion of persulfate is preferably 0.1 to 5 parts by weight per 100 parts by weight of the monomer mixture used in the first stage polymerization.

It is important that the polymer emulsion thus obtained has a gel fraction M of the polymer particles contained therein in a range of 20 to 60% by weight. This setting can be easily achieved mainly by adjusting the type and amount of the self-crosslinking monomer, and in addition, by appropriately selecting the amount of persulfate used and polymerization conditions as described above. be.

By setting the gel fraction of the polymer particles within the above range, an adhesive composition with high adhesive strength, high cohesive strength, and excellent repulsion resistance can be obtained. If the ratio is less than 20% by weight, the cohesive force decreases5, and if it exceeds 60% by weight, the adhesive strength decreases and it becomes difficult to obtain an adhesive composition with excellent rebound resistance.

Note that the solid content concentration of the polymer emulsion obtained in this first stage polymerization, that is, the concentration of polymer particles, is not particularly limited, but the amount of the monomer used for the second stage polymerization is In order to ensure the polymerization stability of the first and second stages and the stability of the emulsion, generally 20
It is preferable to adjust the weight to about 50% by weight.

In this invention, a monomer for post-polymerization is further added to the polymer emulsion containing polymer particles having a gel fraction of 20 to 60% by weight, obtained as described above, to carry out the second stage polymerization. This produces a polymer emulsion containing polymer particles with a suitably crosslinked structure.

The above monomer for post-polymerization has an alkyl group having 1 to 1 carbon atoms.
It consists of four (meth)acrylic acid alkyl esters alone or this ester and an unsaturated monomer copolymerizable therewith. As the (meth)acrylic acid alkyl ester, the same monomers as those in the first stage are used. In addition, unsaturated monomers that can be copolymerized with this include (meth)acrylic acid, itaconic acid, fumaric acid, maleic acid, 2-hydroxyethyl (meth)acrylate, acrylonitrile, methacrylonitrile, styrene, and acetic acid. Examples include vinyl.

Such a monomer for post-polymerization is selected such that its homopolymer or copolymer has a glass transition point of 250°K or less at which it exhibits pressure-sensitive adhesive properties, as in the case of the main monomer in the first stage. It is necessary to have a composition that provides a polymer with a temperature higher than the glass transition temperature mentioned above, which tends to cause problems in terms of adhesive strength.

Therefore, even when an unsaturated monomer copolymerizable with the (meth)acrylic acid alkyl ester is used, the amount of the latter monomer used is within a range of 10% by weight or less in the monomer for post-polymerization. The proportion used should be such that the above glass transition point is satisfied.

The amount of monomer used for the subsequent polymerization depends on the composition of the monomer mixture used in the first stage polymerization, the gel fraction of the polymer particles composed of this mixture, and the final solid state. It is determined appropriately so that the concentration of the components is at an appropriate ratio,
Usually, the ratio of the post-polymerization monomer to 100 parts by weight of the first-stage monomer mixture is 10 to 500 parts by weight.

The second stage polymerization is carried out by dropping the above monomer for post-polymerization into the polymer emulsion produced in the first stage at a predetermined dropping rate while stirring. The polymerization temperature at this time may be in the range of 60 to 90°C as in the case of the first stage. Incidentally, during this second stage polymerization, it is not necessary to intentionally add a persulfate as a polymerization initiator. However, they may be added if specifically desired.

The polymer emulsion obtained in this manner generally has a concentration of polymer particles having an appropriate crosslinked structure, that is, a solid content concentration of 50 to 70, from the viewpoint of emulsion stability and viscosity characteristics. It is desirable to set it within a range of % by weight.

The water-dispersed pressure-sensitive adhesive composition of the present invention is based on the polymer emulsion obtained in the second stage polymerization, and the composition may contain colorants and fillers as necessary. , anti-aging agents, tackifiers, and other conventionally known additives may be appropriately blended. The blending amount may be a normal amount. Furthermore, although the above composition exhibits high adhesive strength and high cohesive strength by itself, if it is desired to further increase the cohesive strength, various conventionally known external crosslinking agents may be used within a range that does not impair the characteristics of the present invention. There is no problem in combining them.

〔Effect of the invention〕

As described above, since the water-dispersed pressure-sensitive adhesive composition of the present invention does not contain an emulsifier, the moisture resistance and water resistance are reduced due to emulsifiers (no deterioration of adhesive properties is observed, and external crosslinking is not observed). It exhibits high adhesive strength and high cohesive strength even without the addition of agents, and shows no decline in cohesive strength, especially at high temperatures.
Furthermore, it has the characteristic of being extremely resistant to repulsion, and can be used for general pressure-sensitive adhesive tapes, sheets, labels, etc., as well as applications that require particularly high repulsion resistance. is also very useful.

〔Example〕

EXAMPLES Below, examples of the present invention will be described in more detail. In addition, in the following, "part" means part by weight, and "%" means weight %, respectively.

Moreover, adhesive force, cohesive force, repulsion resistance, and gel fraction were measured by the following methods.

<Adhesive strength> A pressure-sensitive adhesive composition was applied to both sides of a 25 μm thick polyester film so that the thickness after drying was 50 μm on one side, and dried at 100°C for 3 minutes to make a double-sided adhesive tape, and JIS Z- 1528, the 180 degree peeling adhesive strength (g/20** width) was measured.

Cohesive strength> Make double-sided adhesive tape similar to the adhesive strength test, and
It was attached to two Bakelite plates with an adhesive area of 25 m x 25 mm, and a load of 1 kg was applied at 40°C and 80°C, and the time (minutes) until the Bakelite plate fell was measured.

Repulsion resistance> A pressure-sensitive adhesive composition was applied to one side of an aluminum plate of 0.3 sIFJ so that the thickness after drying was 50 μm,
After drying at 100℃ for 3 minutes, lQm+iX3Qii
A test piece is made by cutting it into a size of m, and this test piece is
When the test piece was bent and attached to an aluminum cylinder with a 0 fin diameter and then stored at 40°C for 24 hours, the distance (frame) that the test piece rose from the cylinder was measured.

Gel fraction> A polymer emulsion was applied to one side of a 25 μm thick polyester film so that the thickness after drying was 50 μm, and after drying at 100°C for 3 minutes, the test piece was cut into a size of 5Q+nX5QH. The test piece was immersed in heated acetone for 24 hours, and the gel fraction was determined by the following method.

Ao -P At; Dry weight of the test piece after immersion AO; Weight of the test piece before immersion Example 1 A After adding 100 parts of distilled water in which 0.5 parts of sulfuric acid was dissolved and heating it to 80°C under a nitrogen stream, a main mixture consisting of 44 parts of n-butyl acrylate and 53 parts of 2-ethylhexyl acrylate was added. The glass transition point of the monomer copolymer (221'K) is N-n-
A monomer mixture prepared by adding 3 parts of butoxymethylmethacrylamide was continuously added dropwise over 5 hours while maintaining the above temperature, and after the dropwise addition, the temperature was further maintained at 80°C for 2 hours to form the first stage polymer. Obtained Emulsicon. The gel fraction of the polymer particles contained in this emulsion was 27.5%.

Next, the above polymer emulsion was heated to 80°C under a nitrogen stream, and then n-butyl acrylate 21
27 parts of 2-ethylhexyl acrylate and 1.5 parts of methacrylic acid (copolymer glass transition point 224"K) were added to
The mixture was continuously added dropwise over a period of time, and after the addition, the temperature was further maintained at 80° C. for 2 hours to perform the second stage polymerization.

The solid content concentration of the polymer emulsion thus obtained was 59.8%, and this emulsion was used as it was as the water-dispersed pressure-sensitive adhesive composition of the present invention.

Comparative Example 1 A water-dispersed pressure-sensitive adhesive composition was obtained in exactly the same manner as in Example 1, except that N-n-butoxymethylmethacrylamide was omitted from the monomer mixture in the first stage. . Note that the gel fraction of the polymer particles of the emulsion obtained in the first stage polymerization was 0%.

Comparative Example 2 As a monomer mixture in the first stage, 0.2 parts of N-butoxymethylmethacrylamide was added to the main monomer consisting of 45.8 parts of n-butyl acrylate and 54 parts of 2-ethylhexyl acrylate. A water-dispersed pressure-sensitive adhesive composition was obtained in exactly the same manner as in Example 1, except that a water-dispersed pressure-sensitive adhesive composition was used. The gel fraction of the polymer particles of the emulsion obtained in the first stage polymerization was 1). It was 5%.

Comparative Example 3 As the first stage monomer mixture, 15 parts of N-n-butoxymethylmethacrylamide was added to the main monomers consisting of 42 parts of n-butyl acrylate and 43 parts of 2-ethylhexyl acrylate. A water-dispersed pressure-sensitive adhesive composition was obtained in exactly the same manner as in Example 1, except that a water-dispersed pressure-sensitive adhesive composition was used. Note that the gel fraction of the polymer particles of the emulsion obtained in the first stage polymerization was 70.5%.

Examples 2 to 6 First-stage polymer emulsions were obtained in exactly the same manner as in Example 1, except that the monomer mixture shown in Table 1 below was used as the first-stage monomer mixture. .

The gel fraction of the polymer particles contained in this emulsion was as shown in Table 1. In addition, in Table 1, A
is the main monomer, B is a self-crosslinking monomer, and the glass transition point means the glass transition point of the copolymer consisting of the main monomer.

Next, for the first stage polymer emulsion,
A second stage polymer emulsion was obtained in the same manner as in Example 1, except that the monomers for post-polymerization shown in Table 2 below were used. This emulsion was directly used as the water-dispersed pressure-sensitive adhesive composition of the present invention. Furthermore, what is the solid content in the second stage polymer emulsion? twice, second
It was as shown in the table. Moreover, the glass transition point in Table 2 means the glass transition point of the copolymer composed of the monomer for post-polymerization.

The results of examining the adhesive strength, cohesive force, and repulsion resistance of each of the adhesive compositions of Examples 1 to 6 and Comparative Examples 1 to 3 below are as follows:
The results were as shown in Table 3 below.

Table 3 As is clear from the above results, the water-dispersed pressure-sensitive adhesive composition of the present invention has high adhesive strength and high cohesive strength,
Furthermore, it has very good rebound resistance, and since it does not contain an emulsifier, it has excellent moisture resistance and water resistance, and this together with the fact that it is an adhesive composition with extremely high practical value.

Patent applicant: Nitto Electric Industry Co., Ltd.; Patent applicant address: 1-1-2, Ibaraki-shi, Osaka Prefecture Name: 1-1-2 Hozumi (396) Representative of Nitto Electric Industry Co., Ltd.
Goro Kamai 4, agent postal code 530 "Detailed explanation of the invention" in the specification 7. Contents of amendment A, specification (1) page 22, line 5 1";"221°K" 1 -210°K” is corrected.

(2) No. 22 @ line 16; “224°K” will be corrected to “213°K”.

(3) Glass transition temperature (°K) column in Table 1 on page 25; Example 2 is r223J, r204j, Example 4 is r221j, r-21), 1, Examples 5 is r2
27J will be corrected to r207J, and Example 6 will correct r222J to r213j.

(4) Glass transition temperature (°K) column in Table 2 on page 27; Example 2 has r229J, r209J, Example 4 has r226j, 1-206J, and Example 5 has r'. 22
5J has been corrected to r206J1゜

Claims (6)

[Claims] (1) A (meth)acrylic acid alkyl ester with an alkyl group having 1 to 14 carbon atoms alone or its homologue consisting of this ester and an unsaturated monomer having no functional group in the molecule that can be copolymerized with the ester An unsaturated monomer containing an N-methylol group or an N-alkoxymethyl group as a self-crosslinking monomer is added to the main monomer whose glass transition point at which the polymer or copolymer exhibits pressure-sensitive adhesiveness can be 250°K or less. The gel fraction obtained by polymerizing a monomer mixture obtained by adding
A (meth)acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms alone or an unsaturated monomer copolymerizable with the ester and this ester is added to a polymer emulsion containing 0 to 60% by weight of polymer particles. The homopolymer or copolymer consisting of
A water-dispersible pressure-sensitive adhesive composition based on a polymer emulsion obtained by polymerization with addition of a monomer for post-polymerization that can have a temperature of 50°K or less. (2) A patent claim in which, in a monomer mixture for obtaining a polymer emulsion containing polymer particles having a gel fraction of 20 to 60% by weight, the self-crosslinking monomer is present in an amount of 1 to 10% by weight in the mixture. The water-dispersed pressure-sensitive adhesive composition according to item (1). (3) A patent claim in which the amount of persulfate is 0.1 to 5 parts by weight per 100 parts by weight of a monomer mixture for obtaining a polymer emulsion containing polymer particles with a gel fraction of 20 to 60% by weight. The water-dispersed pressure-sensitive adhesive composition according to item (1) or item (2). (4) A patent in which the amount of the monomer for post-polymerization is 10 to 500 parts by weight based on 100 parts by weight of the monomer mixture to obtain a polymer emulsion containing polymer particles with a gel fraction of 20 to 60% by weight. The water-dispersed pressure-sensitive adhesive composition according to any one of claims (1) to (3). (5) The polymerization temperature is 60 to 90% to obtain a polymer emulsion containing polymer particles with a gel fraction of 20 to 60% by weight.
The water-dispersed pressure-sensitive adhesive composition according to any one of claims (1) to (4), which has a temperature of .degree. (6) A polymer emulsion obtained by adding a monomer for post-polymerization and polymerizing the emulsion, the solid content of which is 50 to 70% by weight in the emulsion.
) to (5).