JPS63234078A - Water-dispersed type pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition having excellent film-forming properties, stabilized adhesive force, etc., with a low viscosity in spite of a high solid concentration, by adding a specific acrylic monomeric mixture with an emulsifying agent into water containing a water-soluble polymerization initiator dissolved therein and carrying out polymerization. CONSTITUTION:The aimed composition, obtained by initially blending (A) 90-99.9wt.% main monomer, consisting of an alkyl (meth)acrylate having a 1-4C alkyl and capable of providing a homopolymer thereof, exhibiting pressure-sensitive properties and having <=250 deg.K glass transition point with (B) 10-0.1wt.% crosslinking monomer consisting of a polyfunctional ester of a polyhydric alcohol with (meth)acrylic acid or divinylbenzene to provide a monomeric mixture, then adding the above-mentioned monomeric mixture with an emulsifying agent into water containing a water-soluble polymerization initiator dissolved therein and carrying out polymerization and consisting of 5-40wt.% particles having 0.05-0.3mum average particle diameter and 95-60wt.% particles having 0.3-1mum average particle diameter.

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 provide relatively high cohesive strength as pressure-sensitive adhesives.

[Problem that the invention seeks to solve]

However, the conventional acrylic water-dispersed adhesive mentioned above is
This is still unsatisfactory when applied to applications where a high degree of cohesive force is desired, 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. Due to the non-uniformity, the cohesive force is not very large compared to the degree of crosslinking, and even if the cohesive force can be increased, the adhesive force will decrease accordingly, resulting in high adhesive force and high cohesive force. It has been difficult to obtain such pressure-sensitive adhesive compositions.

Furthermore, if the cohesive force is increased by the above-mentioned means (if
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. Furthermore, when this type of adhesive is applied to a support and dried to produce an adhesive tape, etc., the above-mentioned adhesive properties, especially adhesive strength and repulsion resistance, may change over time. However, there was also the problem that it was difficult to exhibit stable adhesive properties.

The above change in adhesive properties is thought to be due to poor film forming properties when forming a film by coating and drying on a support.
For this reason, attempts have been made to improve film-forming properties by increasing the drying temperature or adding film-forming aids. However, in this case, problems of thermal energy and adverse effects on adhesive properties due to the remaining film-forming agent cannot be avoided.

In addition, attempts have been made to reduce the particle size of polymer particles in water-dispersed adhesives in order to improve film-forming properties, but in this case, the viscosity of the adhesive becomes extremely high, and colorants and adhesives Drying after application may impair mixing workability when blending various additives such as imparting agents and workability during application, and the concentration of polymer particles in water, that is, the solid content concentration, must be lowered. It took a long time to complete the process, which resulted in a loss of workability.

From the above, this invention has the advantage of being able to maintain a low viscosity that poses no practical problem even with a high solids concentration that contributes to shortening drying time, and to raise the drying temperature when forming a tape or the like to form a film. It is possible to obtain good film-forming properties without adding any auxiliary agents, and therefore it is possible to exhibit stable adhesive properties that do not change over time as described above. The object of the present invention is to provide an acrylic water-dispersed pressure-sensitive adhesive composition that has significantly superior strength and repulsion resistance.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors discovered that an acrylic monomer mixture containing a small amount of a specific crosslinking monomer in an aqueous medium in which a water-soluble polymerization initiator was dissolved. When polymer particles with a relatively large particle size and polymer particles with a smaller particle size are produced in a specific ratio by continuously adding an emulsifier in small amounts at the same time and carrying out emulsion polymerization, it is possible to A water-dispersed pressure-sensitive adhesive composition with low viscosity can be obtained even if the concentration in water (that is, the solid content concentration) is increased, and when it is made into a tape, the drying temperature must be particularly high or a film-forming aid must be used. Good film-forming properties can be obtained without the addition of auxiliary means such as the addition of This led to the completion of this invention after learning that the adhesive strength, cohesive force, and repulsion resistance were all significantly superior.

That is, in this invention, a (meth) alkyl group having 1 to 14 carbon atoms is added to water in which a water-soluble polymerization initiator is dissolved.
Acrylic acid alkyl ester alone or its homopolymer or copolymer consisting of this ester and a monoethylenically unsaturated monomer copolymerizable with it has a glass transition point of 250°K or less that exhibits pressure-sensitive adhesive properties, and the main monomer is 90 to 99.97 JIit% and a small amount (both a kind of crosslinking monomer) selected from polyvalent esters of polyhydric alcohols and (meth)acrylic acid and divinylbenzene.
A monomer mixture consisting of ~0.1% by weight is added together with an emulsifier and polymerized, and the average particle size is 0.05%.
5-40% by weight of particles of ~0.3 μm and an average particle size of 0.3 μm.
The present invention relates to a water-dispersed pressure-sensitive adhesive composition characterized in that it contains polymer particles consisting of 95 to 60% by weight of particles having a particle size of more than 3 μm and 1.0 μm or less.

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

Furthermore, in this specification, the gel fraction of the polymer particles is an index indicating the extent to which the polymer constituting the polymer particles is involved in crosslinking, and this is the ratio of the solvent-insoluble portion of the polymer mentioned above. (% by weight). 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 matter. This measurement is as shown in Examples below.

[Structure and operation of the invention]

The monomer mixture used in this invention includes an acrylic main monomer and at least one crosslinking monomer selected from polyvalent esters of polyhydric alcohols and (meth)acrylic acid, and divinylbenzene. It consists of the body.

The above acrylic main monomer is composed of a (meth)acrylic acid alkyl ester having an alkyl group of 1 to 14 carbon atoms alone, or this ester and a monoethylenically unsaturated monomer copolymerizable therewith. It is what it is. As (meth)acrylic acid alkyl ester, from the viewpoint of adhesive properties,
An alkyl group having 1 to 14 carbon atoms is used, and particularly preferred examples include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, ethyl methacrylate,
Examples include butyl methacrylate and lauryl methacrylate.

In addition, examples of copolymerizable monoethylenically unsaturated monomers include acrylonitrile, methacrylonitrile, vinyl acetate, styrene or its derivatives, (meth)acrylic acid,
Examples include itaconic acid, maleic acid, 2-hydroxyethyl (meth)acrylate, N/N-dimethylaminoethyl methacrylate, and these monomers contribute as modifying components of the polymer constituting the polymer particles. .

The main monomer consisting of such (meth)acrylic acid alkyl ester alone or the copolymerizable monoethylenically unsaturated monomer described above is a homopolymer or copolymer that exhibits pressure-sensitive adhesive properties. Glass transition point is 250
``It is necessary that the composition is as follows.By having such a composition, it is possible to create an adhesive that has high cohesive strength, high adhesive strength, and excellent repulsion resistance. It becomes possible to prepare a composition.For this purpose, the copolymerizable monoethylenically unsaturated monomer is (meth)
It is preferable that the amount of the copolymerizable unsaturated monomer is kept to a small amount relative to the acrylic acid alkyl ester, and it is generally preferable that the amount of the copolymerizable unsaturated monomer in the main monomers is usually 10% by weight or less.

The above-mentioned crosslinkable monomer used in combination with such a main monomer is an essential component in order to make polymer particles have a suitable crosslinked structure, and among these monomers, the above-mentioned polyvalent monomer Specific examples of esters include ethylene glycol di(
meth)acrylate, diethylene glycol di(meth)
More than diesters such as acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polybrobylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, etc. Generally, polyvalent esters up to tetraesters (the molecular weight thereof is usually 1°000 or less) are mentioned. As the crosslinking monomer, one or more of these polyvalent esters and divinylbenzene can be used.

The ratio of the main monomer to the crosslinkable monomer is 90 to 99.9% by weight for the main monomer and 10 to 0.9% by weight for the crosslinkable monomer.
The amount may be adjusted appropriately within the range of 1% by weight depending on the type and desired cohesive force. If the amount of crosslinking monomer used is too small, the cohesive force cannot be set within the desired range, and conversely, if it is too large, the cohesive force will be too high, causing problems in terms of adhesive strength and repulsion resistance, and polymerization. Stability may be impaired.

In this invention, the use of the above-mentioned crosslinkable monomer makes the polymer particles have a cross-linked structure, thereby contributing to the improvement of the cohesive force.As a guideline for forming the above-mentioned cross-linked structure, It is desirable that the amount is about 10 to 70% by weight, preferably about 15 to 60% by weight. Such a gel fraction can be easily set mainly by adjusting the amount of the crosslinkable monomer used.

In this invention, a monomer mixture consisting of such a main monomer and a crosslinkable monomer is added to water in which a water-soluble polymerization initiator is dissolved together with an emulsifier, and polymerized. , 5 to 40% by weight of relatively small particles with an average particle size in the range of 0.05 to 0.3 μm, and relatively small particles with an average particle size in the range of more than 0.3 μm and 1°0 μm or less. Polymer particles consisting of 95-60% by weight of large-sized particles are produced.

By generating such polymer particles, there is no need to worry about increasing the viscosity of the aqueous dispersion because relatively large particles exist in larger numbers than small particles, and the overall polymer particle size increases. Even if the concentration in water is as high as 50 to 70% by weight, the viscosity can be made low enough to cause no practical problems.
It can also have low thixotropy. What's more, when it is made into tape, etc., it takes on a structure in which small particles are inserted into the gaps between large particles, making it possible to form a uniform coating film, making it possible to In this way, stable adhesive properties without any change in oral adhesive properties can be exhibited without raising the drying temperature or adding film-forming aids.

In addition, due to the above-mentioned uniform coating properties, good results can be obtained in terms of adhesion and repulsion resistance as well as cohesive force, and in addition, the polymer particles are cross-linked with an appropriate gel fraction due to the use of the cross-linkable monomer. Because it is structured, it is possible to obtain sufficient cohesive strength even without adding an external cross-linking agent, and there is no noticeable decrease in adhesive strength or repulsion resistance. It can provide excellent effects.

On the other hand, if the particle size distribution of the polymer particles falls outside the above range, it becomes difficult to obtain the above-mentioned effects, regardless of whether or not a crosslinking monomer is used. That is, relatively small particles have an average particle size of less than 0.205 μm,
If the amount exceeds 40% by weight, or if the relatively large particles have an average particle size of 0.3 μm or less, the viscosity of the aqueous dispersion increases, making it difficult to achieve a high polymer concentration. Become. In addition, if the average particle size of relatively small particles exceeds 0.3 μm or the amount thereof becomes less than 5% by weight, the relatively large particles become 1.0 μm.
If the average particle diameter exceeds m, the film-forming properties when formed into a tape or the like will deteriorate, the adhesive properties will change significantly over time, and it will be difficult to obtain good results in terms of improving cohesive force and the like.

In this invention, the particle size distribution of the produced polymer particles is determined as described above (in order to do this, a single polymer is added to water in which a water-soluble polymerization initiator is dissolved, under a condition in which radicals based on the initiator are sufficiently generated). The polymer mixture and the emulsifier are continuously added little by little, and the polymer particles dispersed in the aqueous phase during the initial polymerization grow and thicken, and new polymer particles form during the polymerization. This will grow and become thicker (
The polymerization may be allowed to proceed in such a manner that a relatively large particle size is produced in the first stage and a relatively small particle size is produced in the second stage.

In order to control such polymerization, the amount of water-soluble polymerization initiation elbow and the polymerization temperature (water temperature) must be appropriately set to ensure that the amount of radicals generated from the initiator is sufficient. It is necessary to adjust the addition rate of the monomer mixture so that the added monomer mixture polymerizes quickly and does not remain in the water in an unreacted state. Also important is the amount of emulsifier added together with the monomer mixture; The amount of addition should be determined.

In addition, regarding the effect of the emulsifier, in the early stage of polymerization when the monomer mixture is added, the produced polymer appears as particles in the aqueous phase, and the monomer mixture added thereafter is used for the growth of the polymer particles. During this process, the emulsifier added is adsorbed onto the surface of the growing polymer particles and acts to stabilize the particles and prevent the formation of new polymer particles.

Thus, when at least 60% by weight of the monomer mixture has been added, the particle size of the polymer particles increases, resulting in a gradual increase in the particle surface area, so that a portion of the emulsifier added in a certain amount becomes It remains in the aqueous phase without being adsorbed on the surface of the particles, forming micelles. Due to the formation of micelles, the monomer mixture subsequently added is solubilized, and the micelles serve as sites for polymerization to generate new polymer particles. Therefore, the monomer mixture that is subsequently added is used for the growth of the initial polymer particles and the above-mentioned new polymer particles, and the emulsifier that is added at the same time is adsorbed on the surface of these particles and contributes to the stabilization of the particles. be.

As a water-soluble polymerization initiator for carrying out such a polymerization reaction, any of those used in general emulsion polymerization such as potassium persulfate, ammonium persulfate, and hydrogen peroxide can be used. Particularly preferred are persulfates. The ionic terminal group of this persulfate contributes to stabilizing the polymer particles, thereby enabling more stable emulsion polymerization. The amount of such a polymerization initiator used is related to the polymerization temperature, but -a has a monomer mixture of 10
0.1 to 1 part by weight, preferably 0.2 to 1 part by weight
The proportion may be set to 0.6 parts by weight.

The polymerization temperature may be any condition as long as the generation of radicals from the initiator occurs quickly, and is usually 60 to 90°C.
, preferably 65 to 80°C. In the case of a redox system that uses a reducing agent in combination, the temperature may be lower than this.

Furthermore, the emulsifier to be added little by little together with the monomer mixture into the water in which the polymerization initiator is dissolved may be either anionic or nonionic, and conventionally known emulsifiers are widely applicable. be. As a material that does not inhibit the adhesive properties of the resulting water-dispersed pressure-sensitive adhesive composition and is particularly effective for stabilizing polymer particles and forming micelles,
It is preferable to use anionic emulsifiers. The amount of these emulsifiers used is usually 131 parts by weight, preferably 0.1 to 0.5 parts by weight, based on 100 parts by weight of the monomer mixture.
Parts by weight. Of course, it is necessary to determine the above usage amount depending on the emulsifying ability of the emulsifier; if it is too little or too much, it will be difficult to produce polymer particles with the above particle size distribution, and if it is too much, the adhesive properties will deteriorate, especially water resistance. This is not desirable because it causes problems.

Note that this emulsifier is added together with the monomer mixture, but at that time, it may be added after being dissolved in the monomer mixture,
It may be added alone. It is particularly preferable to use a small amount of water and add the monomer mixture and emulsifier to this as an emulsion, which makes the monomer mixture and emulsifier uniformly emulsified. Good results are obtained for stabilization.

The average particle diameter obtained in this way is 0.05 to 0.3
μm1 Particularly preferably 5 to 40% by weight of relatively small particles in the range of 0.1 to 0.2 μm, preferably 10 to 3
0% by weight and the average particle size is more than 0.3μm and 1.0μm
Hereinafter, particularly preferably 95 to 60% by weight of relatively large particles in the range of 0.4 to 0.8 μm, preferably 90 to 60%
An aqueous dispersion containing polymer particles consisting of 70% by weight is
The gel fraction of the polymer particles is usually about 10 to 70% by weight, and the concentration of the polymer particles, that is, the solid content concentration, can be set in the range of 50 to 70% by weight, as described above. Even at such a high concentration, its viscosity is low, it has low thixotropy, and it has excellent film forming properties for 4Wi such as tape formation, and has excellent adhesive strength, cohesive strength, and repulsion resistance properties. also highly satisfied,
Furthermore, it has the characteristic that stable adhesive properties can be expressed with little oral change in these adhesive properties.

Therefore, in this invention, the aqueous dispersion obtained by the above method can be used as it is as a water-dispersed pressure-sensitive adhesive composition, but this composition may be colored if necessary. Conventionally known additives such as additives, fillers, anti-aging agents, and tackifiers may be appropriately blended, and the blending amount may be a normal amount.The above composition alone has a high adhesive strength. It exhibits good cohesive force, but if it is desired to further increase this cohesive force, various conventionally known external crosslinking agents can be added within a range that does not impair the characteristics of the present invention.

When blending these additives and external crosslinking agents, the low thixotropy of the aqueous dispersion provides the advantage of easy uniform mixing, and the good film-forming properties of the aqueous dispersion make it possible to add Another advantage is that the functions of agents and the like can be expressed even better.

〔Effect of the invention〕

As described above, in this invention, particles of relatively small diameter and particles of larger diameter are separated by using an acrylic monomer mixture containing a small amount of a specific crosslinking monomer and an emulsifier. By producing polymer particles with a moderately crosslinked structure in which the polymer particles are mixed in a specific ratio, the viscosity is low even when the concentration of the polymer particles is high, and it is easy to form a film when forming into tape. An acrylic water-dispersed pressure-sensitive adhesive composition that has excellent adhesive properties, highly satisfies adhesive strength, cohesive force, and repulsion resistance, and can exhibit stable adhesive properties that do not change over time. can be provided. In addition, this composition has the advantage that various additives and external crosslinking agents can be easily and uniformly mixed therein, so that the functions of these additives can be better expressed. Therefore, the water-dispersed pressure-sensitive adhesive composition of the present invention is extremely useful for applications such as general pressure-sensitive adhesive tapes, sheets, labels, and other applications that particularly require rebound resistance. It can be applied to

〔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.

In addition, adhesive force, cohesive force, repulsion resistance, and gel fraction were measured using the following methods, and viscosity was measured using a B-type rotational viscometer (number of rotations: 2 Or, p, w). It is.

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. As a test piece, JIS Z-1528
The 180 degree peeling adhesive strength (g/20 crane width) was measured.

Cohesive strength> Make double-sided adhesive tape similar to the adhesive strength test, and
It was bonded to two Bakelite plates with an adhesive area of 25n x 25 fl, 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 a 0.3 m thick aluminum plate so that the thickness after drying was 50 μm.
After drying at 00℃ for 3 minutes, cut it into a size of 101m x 80fi to make a test piece.
Bending and pasting it on an aluminum cylinder of 4 m in length, then 4
When the test piece was left at 0°C for 24 hours, the distance (crane) that the test piece rose from the cylinder was measured.

Gel fraction> A pressure-sensitive adhesive composition 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,
A test piece was prepared by cutting it into a size of 1, and this test piece was immersed in heated acetone for 24 hours, and the gel fraction was determined by the following method.

Dry weight of At8 test piece after immersion AO; Weight of test piece before immersion Example 1 In a 500 ml reactor equipped with a thermometer, stirrer, nitrogen inlet tube and reflux condenser, 0.0. Add 70 parts of distilled water prepared by dissolving 5 parts of
After heating to ℃, the main monomer consisting of 40 parts of n-butyl acrylate and 60 parts of 2-ethylhexyl acrylate (
A monomer mixture prepared by adding 2 parts of triethylene glycol dimethacrylate as a crosslinkable monomer to the glass transition point of the copolymer (205°K), 0.2 parts of sodium lauryl sulfate.
36 parts of water and 20 parts of water are mixed and uniformly emulsified using ultrasonic waves, and an emulsion is continuously added over 3 hours to carry out a polymerization reaction, and after the addition is completed, the emulsion is maintained at 80°C for 2 hours. As a result, an aqueous dispersion having a polymer particle concentration of 53% was obtained.

The aggregate content of this aqueous dispersion was 0.06%, and this was taken out.
The aqueous dispersion after removing the water was used as the water-dispersible pressure-sensitive adhesive composition of the present invention. The particle size distribution of the polymer particles of this composition was measured using a submicron particle analyzer NASD model (
Coulter Electronic Inc.), it was found that large particles with an average particle size of 0.58 μm and small particles with an average particle size of 0.21 μm coexisted. . When the rain particles were separated using a centrifugal separator and their weight ratios were measured, 81% of the rain particles were large particles and 19% were small particles.

Comparative Example 1 An aqueous dispersion having a polymer particle concentration of 53% was obtained in the same manner as in Example 1, except that 2 parts of triethylene glycol dimethacrylate as a crosslinkable monomer was not used. This aqueous dispersion contained 0.07% of aggregates, and the aqueous dispersion after removing this was used as a water-dispersed pressure-sensitive adhesive composition for comparison. In addition, when the particle size distribution of the polymer particles of this composition was measured in the same manner as in Example 1, 80% of the particles had an average particle size of 0.60 μm, and 80% had an average particle size of 0.20 μm.
It was found that the particles consisted of 20% of the particles.

Comparative Example 2 Into a reactor similar to Example 1, 90 parts of distilled water containing 0.5 part of potassium persulfate was charged, and 8 parts of distilled water was added under a nitrogen stream.
After heating to 0°C, monomer mixture 1 similar to Example 1
02 parts were continuously added over 3 hours to carry out a polymerization reaction, and after the addition was completed, the mixture was maintained at 80°C for 2 hours to obtain an aqueous dispersion having a polymer particle concentration of 53%. ``This aqueous dispersion contained 3.5% aggregates, and after removing these, the aqueous dispersion was used as a water-dispersed pressure-sensitive adhesive composition for comparison. Furthermore, when the particle size distribution of the polymer particles of this composition was measured in the same manner as in Example 1, it was found that the composition consisted of polymer particles having a single particle size with an average particle size of 0.36 μm. Ta.

Example 2 Into a reactor similar to Example 1, 50 parts of distilled water containing 0.5 part of potassium persulfate was charged, and the mixture was heated to 8 parts under a nitrogen stream.
After heating to 0°C, monomer mixture 1 similar to Example 1
0.2 parts of sodium lauryl sulfate, 0.36 parts of sodium lauryl sulfate, and 40 parts of water were mixed and uniformly emulsified using ultrasonic waves, and an emulsion was added continuously over 3 hours to perform a polymerization reaction.
After the addition was completed, the mixture was maintained at 80° C. for 2 hours to obtain an aqueous dispersion having a polymer particle concentration of 53%.

This aqueous dispersion contained 0.06% of aggregates, and the aqueous dispersion after removing this was used as the water-dispersed pressure-sensitive adhesive composition of the present invention. In addition, when the particle size distribution of the polymer particles of this composition was examined in the same manner as in Example 1, 74% of the particles had an average particle size of 0.55 μm, and the average particle size was 0.23 μm.
It was found that the particles consisted of 26% of micrometer particles.

Example 3 In a reactor similar to Example 1, 0.0% ammonium persulfate was added.
3 parts of distilled water and heated to 80°C under a nitrogen stream, the main unit consisting of 90 parts of n-butyl acrylate, 10 parts of ethyl acrylate, and 1 part of acrylic acid was added. A monomer mixture prepared by adding 1.8 parts of divinylbenzene as a crosslinking monomer to a copolymer (glass transition point of 222°K), 0.36 parts of sodium lauryl sulfate, and 50 parts of water, By continuously adding an emulsion formed by uniformly emulsifying with sonic waves over a period of 5 hours to carry out a polymerization reaction, and holding it at 80 ° C. for 2 hours after the addition is completed,
An aqueous dispersion having a polymer particle concentration of 51% was obtained.

The aqueous dispersion contained 0.08% aggregates, and the aqueous dispersion after removing this was used as the water-dispersed pressure-sensitive adhesive composition of the present invention. In addition, when the particle size distribution of the polymer particles of this composition was investigated in the same manner as in Example 1, 71% of particles had an average particle size of 0.75 μm, and 71% had an average particle size of 0.25 μm.
It was found that the particles consisted of 29% of micrometer particles.

The viscosity (25° C.), gel fraction, adhesive force, cohesive force, and repulsion resistance of each of the compositions of Examples 1 to 3 and Comparative Example 1.2 above were examined. In addition, as an oral change in adhesive properties, after the preparation of the test piece for the adhesive force and repulsion resistance test (that is, after the formation of the adhesive layer), it was stored at 70 ° C. for 8 days,
After this storage, adhesive strength and repulsion resistance were examined. These results were as shown in the table below.

As is clear from the results in the table above, the water-dispersed pressure-sensitive adhesive composition of the present invention has a low viscosity, and has a high adhesive strength.
It can be seen that the cohesive force and repulsion resistance are sufficiently satisfied, and that these adhesive properties hardly change over time, demonstrating stable adhesive properties. On the other hand, the composition of Comparative Example 1 was inferior in cohesive force and repulsion resistance, and the composition of Comparative Example 2, although both of the above properties were improved to some extent, was not sufficient, and moreover, the viscosity was relatively high. In addition, since the adhesive properties change orally, it is presumed that in order to prevent this, a troublesome process such as making it into a tape and then subjecting it to aging treatment at high temperature is necessary.

Claims (8)

[Claims] (1) A monoethylenically unsaturated (meth)acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms alone or copolymerizable with this ester in water in which a water-soluble polymerization initiator is dissolved. 90 to 99.9% by weight of a main monomer whose homopolymer or copolymer can exhibit pressure-sensitive adhesiveness and have a glass transition point of 250°K or less, a polyhydric alcohol, and (meth)acrylic acid. A monomer mixture consisting of 10 to 0.1% by weight of at least one crosslinking monomer selected from polyhydric esters and divinylbenzene is added together with an emulsifier and polymerized. Particles 5 to 5 with an average particle diameter of 0.05 to 0.3 μm
40% by weight and the average particle size is over 0.3μm and 1.0μm
A water-dispersed pressure-sensitive adhesive composition comprising polymer particles consisting of 95 to 60% by weight of the following particles. (2) The water-dispersed pressure-sensitive adhesive composition according to claim (1), wherein the water-soluble polymerization initiator is a persulfate. (3) The water-soluble polymerization initiator is present in an amount of 0.1 to 1 part by weight based on 100 parts by weight of the monomer mixture.
) or (2). (4) The water-dispersed pressure-sensitive adhesive composition according to any one of claims (1) to (3), wherein the emulsifier is an anionic emulsifier. (5) The emulsifier is 0.00 parts by weight per 100 parts by weight of the monomer mixture.
Claims Nos. (1) to (4) which are 05 to 1 part by weight
The water-dispersed pressure-sensitive adhesive composition according to any one of Items 1 to 3. (6) The water-dispersed pressure-sensitive adhesive composition according to any one of claims (1) to (5), which is obtained by adding a monomer mixture and an emulsifier to water as an emulsion. thing. (7) The water-dispersed pressure-sensitive adhesive composition according to any one of claims (1) to (6), which has a polymerization temperature of 60 to 90°C. (8) The water-dispersed pressure-sensitive adhesive composition according to any one of claims (1) to (7), wherein the concentration of the polymer particles in water is 50 to 70% by weight.