JP2007224184A - Acrylic polymer-containing composition emulsion and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet having an adhesive layer having excellent transparency, concretely ≤4 haze at 20 μm thickness, and exhibiting a large adhesive strength, concretely ≥6 N/25 mm adhesive strength to a polyethylene plate at 180° peeling; and to provide an acrylic polymer-containing composition emulsion preferably usable for the formation of the adhesive layer of the pressure-sensitive adhesive sheet. <P>SOLUTION: The acrylic polymer-containing composition emulsion is obtained by polymerizing a composition emulsion containing a monomer having ≤2 μm of 50% particle diameter. The composition emulsion contains 6-30 pts.wt. of (B) a stickiness-imparting resin containing ≥60 wt.% of a rosin-based stickiness-imparting resin, and 0.2-1.5 pts.wt. of (C) a nonreactive surfactant based on 100 pts.wt. of (A) a radically polymerizable unsaturated monomer capable of forming a polymer having ≤0°C glass transition temperature, and consisting essentially of a (meth)acrylic ester. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention is an aqueous emulsion of a composition containing a polymer formed from a radical polymerizable monomer and a tackifying resin, and more specifically, a composition in which the polymer and the tackifying resin are combined is dispersed in water. And an acrylic polymer-containing composition emulsion. More specifically, the present invention relates to an acrylic polymer-containing composition emulsion capable of forming an adhesive layer having excellent transparency.
The present invention also relates to a method for producing the acrylic polymer-containing composition emulsion.
Furthermore, the present invention relates to a pressure-sensitive adhesive containing the acrylic polymer-containing composition emulsion and a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive.

The pressure-sensitive adhesive is used for forming a pressure-sensitive adhesive sheet.
The basic laminate structure of the pressure-sensitive adhesive sheet is a single-sided pressure-sensitive adhesive sheet such as a sheet-like substrate / pressure-sensitive adhesive layer / release sheet, or both sides such as a release sheet / pressure-sensitive adhesive layer / sheet-like substrate / pressure-sensitive adhesive layer / release sheet. It is an adhesive sheet. At the time of use, the release sheet is peeled off, and the pressure-sensitive adhesive layer is attached to the adherend.
The pressure-sensitive adhesive sheet is used for various applications, and various adhesive strengths are required.
In addition, the pressure-sensitive adhesive layer may be required to be transparent. For example, after using a transparent plastic film as a sheet-like base material and sticking an adhesive sheet on an adherend, it may be required that the surface state of the adherend can be visually recognized from the transparent plastic film side. Or after sticking to a transparent adherend, it may be required that the state of the sticking interface can be visually recognized from the transparent adherend side.

In general, the pressure-sensitive adhesive is roughly classified into a solvent-type pressure-sensitive adhesive and an aqueous emulsion-type pressure-sensitive adhesive, and both of them are mainly composed of an acrylic polymer.
When a large adhesive force is required (for example, when an adhesive force of 6 N / 25 mm or more is required when peeling 180 degrees against a polyethylene plate), a solvent-type pressure-sensitive adhesive containing a tackifying resin is mainly used conventionally. I came. The tackifying resin is dissolved in an organic solvent. Therefore, in the case of a solvent-type acrylic pressure-sensitive adhesive, it is easy to dissolve a tackifier resin in an organic solvent solution of an acrylic polymer. And since an acrylic polymer and tackifying resin are fully compatible, the dry coating film of a solvent-type acrylic adhesive, ie, an adhesive layer, is generally excellent in transparency.

  The acrylic water-based emulsion type pressure-sensitive adhesive is mainly composed of an acrylic polymer emulsion and water as a dispersion medium. On the other hand, tackifying resins do not dissolve in water. Accordingly, it is very difficult to obtain an acrylic aqueous emulsion-type pressure-sensitive adhesive by mixing the tackifying resin as it is with an acrylic polymer emulsion, and even if obtained, the dispersion stability is very poor.

Therefore, various ideas have been made for introducing the tackifier resin into the acrylic aqueous emulsion adhesive.
For example, it has been proposed to pre-emulsify a tackifier resin and blend it into an acrylic polymer emulsion. This method makes it possible to blend a tackifying resin, which is mostly solid, into an acrylic polymer emulsion.
However, according to this method, the pressure-sensitive adhesive layer obtained after drying the pressure-sensitive adhesive becomes cloudy and opaque. In the process of drying the pressure-sensitive adhesive, the polymer particles derived from the acrylic polymer emulsion and the tackifying resin are difficult to mix, and the tackifying resin forms an independent domain, and a uniform phase is not formed. It is considered that the agent layer becomes cloudy.

In Patent Documents 1 to 3, an emulsion composed of a radical polymerizable unsaturated monomer, a tackifier resin, a surfactant (preferably a reactive surfactant) and water is obtained in advance, and the emulsion is polymerized. Thus, a method of introducing a tackifying resin into an emulsion-type pressure-sensitive adhesive has been proposed.
For example, in Example 4 of JP 2000-313865 A (Patent Document 1), 100 parts by weight of a radical polymerizable unsaturated monomer, 5 parts of a tackifying resin, about 1.6 parts of a reactive surfactant and water are added. It is described that an emulsion containing it is obtained and the emulsion is polymerized to obtain an emulsion-type pressure-sensitive adhesive. Since the surfactant is a reactive surfactant and the amount thereof is large, the pressure-sensitive adhesive layer obtained from such an emulsion-type pressure-sensitive adhesive is insufficient in terms of transparency. Furthermore, since the amount of tackifying resin is small, it is not possible to obtain a pressure-sensitive adhesive sheet that can exhibit a large adhesive force of 6 N / 25 mm or more when peeled 180 degrees from a polyethylene plate.

  Examples 1 and 2 of JP 2001-031708 (Patent Document 2) include 100 parts by weight of a radical polymerizable unsaturated monomer, 10 parts of a tackifying resin, 1.5 parts of a reactive surfactant, and water. Is obtained, and the emulsion is dropped and polymerized in water containing 1.5 parts of a reactive surfactant to obtain an emulsion-type pressure-sensitive adhesive. Since the surfactant is a reactive surfactant and the total amount used is large, the pressure-sensitive adhesive layer obtained from such an emulsion-type pressure-sensitive adhesive is insufficient in terms of transparency.

Furthermore, Example 1 of JP 2001-348551 A (Patent Document 3) contains 100 parts by weight of a radical polymerizable unsaturated monomer, 15 parts of a tackifying resin, 2.5 parts of a reactive surfactant and water. It is described that an emulsion is obtained and the emulsion is polymerized to obtain an emulsion-type pressure-sensitive adhesive. Since the surfactant is a reactive surfactant and the amount thereof is large, the pressure-sensitive adhesive layer obtained from such an emulsion-type pressure-sensitive adhesive is insufficient in terms of transparency.
JP 2000-313865 A JP 2001-031708 A JP 2001-348551 A

  The present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having excellent transparency, specifically having a HAZE (cloudiness value) of 4 or less at a thickness of 20 μm. An object of the present invention is to provide a pressure-sensitive adhesive sheet that can exhibit an adhesive force of 6 N / 25 mm or more upon peeling at 180 ° and an acrylic polymer-containing composition emulsion that can be preferably used for forming a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet. .

In order to solve the above-mentioned problems, the present inventor has intensively studied to arrive at the present invention.
That is, the first invention is based on rosin with respect to 100 parts by weight of the radically polymerizable unsaturated monomer (A) mainly composed of (meth) acrylic acid ester, which can form a polymer having a glass transition temperature of 0 ° C. or less. 6 to 30 parts by weight of a tackifier resin (B) containing at least 60% by weight of a tackifier resin, 0.2 to 1.5 parts by weight of a non-reactive surfactant (C) and water, 50 The present invention relates to an acrylic polymer-containing composition emulsion obtained by polymerizing a monomer-containing composition emulsion having a% particle size of 2 μm or less.

  In the second invention, the proportion of small particle diameter particles of 0.05 μm or more and less than 0.4 μm is 60 to 98 (volume%) in the total 100 (volume%) of the volume of all dispersed particles. The acrylic polymer-containing composition emulsion described in the above invention is characterized in that the proportion of particles having a large particle diameter of 0.4 μm or more and 5 μm or less is 40 to 2 (volume%).

The third invention is a radically polymerizable unsaturated monomer (A) mainly composed of (meth) acrylic acid ester capable of forming a polymer having a glass transition temperature of 0 ° C. or lower: 100 parts by weight, rosin-based adhesive Tackifying resin (B) containing 60% by weight or more of imparting resin: 6 to 30 parts by weight and non-reactive surfactant (C): 0.2 to 1.5 parts by weight are emulsified in the presence of water. A monomer-containing composition emulsion having a 50% particle size of 2 μm or less,
Next, a method for producing an acrylic polymer-containing composition emulsion, wherein the monomer-containing composition emulsion is polymerized,
4th invention is related with the acrylic polymer containing composition emulsion obtained by the manufacturing method as described in the said invention.

The fifth invention relates to an emulsion-type pressure-sensitive adhesive characterized by containing the polymer-containing emulsion described in any of the above inventions,
6th invention is related with the emulsion type adhesive as described in the said invention characterized by containing the crosslinking agent (D) which can react with the functional group in an acrylic polymer containing composition emulsion.

  Furthermore, the seventh invention is a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer formed from the emulsion-type pressure-sensitive adhesive described in the above invention is provided on at least one surface of a sheet-like substrate other than a foam (however, Except when the amount of water-soluble component contained in the pressure-sensitive adhesive layer is 3% by weight or less).

  According to the present invention, a pressure-sensitive adhesive layer having excellent transparency that can have a HAZE (cloudiness value) of 4 or less at a thickness of 20 μm is provided, and adheres to a polyethylene plate at 6 N / 25 mm or more when peeled 180 degrees. It is now possible to provide an acrylic polymer-containing composition emulsion that can be preferably used for forming a pressure-sensitive adhesive sheet capable of expressing force and a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet.

  In the present invention, the radically polymerizable unsaturated monomer (A) used for the formation of the monomer-containing composition emulsion is preferably mainly composed of (meth) acrylic acid alkyl ester having 1 to 14 carbon atoms in the alkyl group. . Such alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, iso-propyl (meth) acrylate, butyl (meth) acrylate, (meth) Linear or branched aliphatic such as iso-butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate Examples include acrylate esters of alcohol and the corresponding methacrylate esters. The alkyl group of the (meth) acrylic acid alkyl ester used preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 2-ethylhexyl acrylate as a main component. . The (meth) acrylic acid alkyl ester is contained in 70 to 99.9% by weight in a total of 100% by weight of the radical polymerizable unsaturated monomer (A), and is contained in one or more kinds.

  The radically polymerizable unsaturated monomer (A) preferably contains 0.1 to 20% by weight of a carboxyl group-containing monomer in a total of 100% by weight of the radically polymerizable unsaturated monomer (A). More preferably, it is contained in an amount of 0.2% to 2% by weight. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic acid, and crotonic acid. When the proportion of the carboxyl group-containing monomer is less than 0.1% by weight, the particles that are dispersoids constituting the monomer-containing composition emulsion to be formed (hereinafter, the particles that are dispersoids are referred to as “emulsion particles”) in water. This dispersion state tends to be unstable, and the polymerization tends to become unstable. On the other hand, when the proportion of the carboxyl group-containing monomer exceeds 20% by weight, the adhesion between the emulsion particles of the acrylic polymer-containing composition emulsion is inhibited when the pressure-sensitive adhesive is dried, and the transparency of the pressure-sensitive adhesive layer is likely to be lowered.

In addition, as the radically polymerizable unsaturated monomer (A) used in the present invention, monomers other than those described above can be used as necessary. Examples of such monomers include (meth) acrylic acid 2-hydroxy Ethyl, alcohol-containing hydroxyl group-containing monomers such as 2-hydroxypropyl (meth) acrylate and 2-hydroxybutyl (meth) acrylate, polyethylene glycol (meth) acrylate,
Epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate,
(Meth) acrylamide monomers such as N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, methylolated acrylamide, N- (1,1-dimethyl-3oxobutyl) acrylamide, diacetone acrylamide,
Examples thereof include vinyl monomers such as phosphoric acid group-containing vinyl monomers, vinyl acetate, styrene, butadiene and the like, acetoacetoxyethyl methacrylate, alkoxysilyl group-containing monomers, etc., and 0 to 10% in total of 100% by weight of the radical polymerizable unsaturated monomer (A). It can be used at a ratio of% by weight, and one or more can be used.

By the way, an adhesive sheet forms an adhesive layer by apply | coating the adhesive in a liquid state to a sheet-like base material, and drying and removing the liquid medium contained in the adhesive.
In the case of a solvent-type pressure-sensitive adhesive, by removing the liquid medium, the contained polymer component is formed as it is to form a pressure-sensitive adhesive layer. On the other hand, in the case of an emulsion-type pressure-sensitive adhesive, when the liquid medium is removed, the emulsion particles approach, adhere to, and fuse together to form a film. Therefore, in order to improve the transparency of the pressure-sensitive adhesive layer, it is important to promote the fusion of the emulsion particles. Therefore, it is preferable to use interparticle crosslinking in order to promote fusion between the emulsion particles.
In order to generate interparticle cross-linking, the radical polymerizable unsaturated monomer (A) is preferably used in combination with a monomer having a functional group capable of causing a cross-linking reaction. Among these, it is preferable to use a monomer having a carboxyl group or a hydroxyl group in combination with a monomer having a functional group that can undergo a crosslinking reaction during film formation. These functional groups may have self-crosslinking properties.
Furthermore, cross-linking between particles can be generated also by using a crosslinking agent (D) described later.
Monomers that are preferably used to form interparticle crosslinks include epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, methylolated acrylamide, dye Examples include monomers such as (meth) acrylamide monomers such as acetone acrylamide, alkoxysilyl group-containing monomers, and acetoacetoxyethyl methacrylate.

In the present invention, when the above-mentioned various radically polymerizable unsaturated monomers (A) are polymerized, it is important that the glass transition temperature (Tg) of the obtained polymer is 0 ° C. or less, and −10 ° C. or less. It is preferable that the temperature is −20 ° C. or lower. Even if an acrylic polymer-containing composition emulsion with a tackifying resin is obtained using a radical polymerizable unsaturated monomer whose glass transition temperature exceeds 0 ° C., such an acrylic polymer-containing composition emulsion An adhesive cannot be obtained.
The glass transition temperature of a polymer obtained by polymerizing a radical polymerizable unsaturated monomer can be calculated by a known theoretical formula.

Next, the tackifier resin (B) will be described.
In the present invention, as the tackifying resin (B), a total of 100% by weight of the tackifying resin (B) containing at least 60% by weight of a rosin resin is the total of the radical polymerizable unsaturated monomer (A). It is important to use 6 to 30 parts by weight with respect to 100 parts by weight, preferably 8 to 25 parts by weight, more preferably 10 to 20 parts by weight.
When the tackifying resin (B) is less than 6 parts by weight, a pressure-sensitive adhesive layer capable of exhibiting sufficient adhesive strength, specifically, an adhesive strength of 6 N / 25 mm or more when peeled by 180 degrees against a polyethylene plate. It becomes difficult to form.
On the other hand, when the tackifying resin (B) exceeds 30 parts by weight, the transparency of the resulting adhesive layer is lowered, and it becomes difficult to obtain an adhesive layer that can have a HAZE of 4 or less at a thickness of 20 μm. . Moreover, since there are too many tackifying resins (B) contained in the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer becomes too soft and a strong adhesive force cannot be obtained.

Even if the tackifying resin (B) is used in a range of 6 to 30 parts by weight with respect to 100 parts by weight of the radical polymerizable unsaturated monomer (A), the rosin resin occupying the tackifying resin (B). When the ratio is less than 60% by weight, a pressure-sensitive adhesive layer having excellent transparency cannot be obtained. From the viewpoint of transparency, it is preferable to use only a rosin resin, but from the viewpoint of economy, it is preferable to use another tackifier resin in combination.
Examples of other tackifying resins that can be used in combination with the rosin resin include terpene resins, aromatic petroleum resins, aliphatic petroleum resins, and the like, and it is preferable to use a terpene resin in combination from the viewpoint of adhesive strength.
Examples of the rosin resin include natural rosin, rosin ester, hydrogenated rosin, hydrogenated rosin ester, polymerized rosin, polymerized rosin ester, disproportionated rosin, and disproportionated rosin ester.
Examples of the terpene resin include α-pinene resin, β-pinene resin, terpene phenol resin, hydrogenated terpene phenol resin and the like.
Examples of aromatic petroleum resins include styrene oligomers and α-methylstyrene / styrene copolymers.

Next, the non-reactive surfactant (C) will be described.
In the present invention, the type and amount of the surfactant used are extremely important.
If the mixed liquid of the radical polymerizable unsaturated monomer (A) and the tackifier resin (B) is simply emulsified in an aqueous medium, the so-called reactive surfactant having a radical polymerizable functional group also has the above functional group. Any non-reactive surfactant (C) that is not included can be used.
However, in order to obtain an adhesive layer having excellent transparency, it is necessary to use a non-reactive surfactant (C).

  When the monomer-containing composition emulsion containing the radical polymerizable unsaturated monomer (A) and the tackifier resin (B) is polymerized, the reactive surfactant is copolymerized with the radical polymerizable unsaturated monomer (A). It is considered that the reactive surfactant that has lost the degree of freedom is immobilized in the vicinity of the surface of the emulsion particles of the resulting acrylic polymer-containing composition emulsion. The emulsion particles are mainly composed of a radically polymerizable unsaturated monomer (A) and a tackifying resin (B) that are relatively rich in lipophilicity. Therefore, when the emulsion-type pressure-sensitive adhesive containing the acrylic polymer-containing composition emulsion is dried to form a pressure-sensitive adhesive layer, the hydrophilic part derived from the immobilized surfactant is large in the emulsion particles because of its hydrophilicity. It is presumed that the fusion between the emulsion particles is inhibited without affinity with the lipophilic part occupying the part. As a result, it becomes difficult to obtain a pressure-sensitive adhesive layer excellent in transparency from a pressure-sensitive adhesive containing an acrylic polymer-containing composition emulsion obtained using a reactive surfactant.

  On the other hand, when the non-reactive surfactant (C) is used, the surfactant is present in the vicinity of the emulsion particle surface of the acrylic polymer-containing composition emulsion, but is not immobilized. It can move in the film in the process of film formation during drying. That is, since the non-reactive surfactant (C) does not inhibit the fusion between the lipophilic emulsion particles, an acrylic polymer-containing composition emulsion obtained using the non-reactive surfactant (C) is used. A dense and uniform pressure-sensitive adhesive layer can be formed from the pressure-sensitive adhesive contained. Since the pressure-sensitive adhesive layer is dense and uniform, it has excellent transparency.

  Examples of the non-reactive surfactant (C) used in the present invention include ionic and non-ionic surfactants, which can be used alone or in combination.

  Nonionic surfactants (C) include nonionic surfactants such as polyoxyalkylene alkyl ethers typified by polyoxyethylene alkyl ethers and polyoxyalkylene polycyclic phenyl ethers and other ether types. Examples thereof include oxyethylene glyceryl ether fatty acid ester, polyoxyethylene hydrogenated castor oil fatty acid ester, polyoxyethylene trimethylolpropane fatty acid ester, amino acid derivative, polyglycerin fatty acid ester, and silicon surfactant.

  As the ionic surfactant among the non-reactive surfactant (C), an ionic surfactant such as a sulfate ester obtained by anionizing the nonionic surfactant or a salt thereof can be used.

The amount of the non-reactive surfactant (C) used is important to be 0.2 to 1.5 parts by weight with respect to 100 parts by weight of the total of the radical polymerizable unsaturated monomer (A). It is preferably 5 to 1 part by weight. When the non-reactive surfactant (C) is less than 0.2 parts by weight, the dispersion stability of the monomer-containing composition emulsion is poor, and the radical polymerizable unsaturated monomer (A) and the tackifier resin (B) It becomes easy to separate into a containing layer and an aqueous layer. Furthermore, when a monomer-containing composition emulsion having poor dispersion stability is to be polymerized, the polymerization becomes unstable and a large amount of aggregates are generated.
On the other hand, although the surfactant is not immobilized in the vicinity of the surface of the emulsion particles, when the non-reactive surfactant (C) exceeds 1.5 parts by weight, the resulting acrylic polymer-containing composition emulsion In drying, the excessive amount of the non-reactive surfactant (C) tends to inhibit the fusion of the emulsion particles and reduce the transparency of the pressure-sensitive adhesive layer.
In the present invention, in order to control the emulsion particle size of the acrylic polymer-containing composition emulsion to be produced, a part of the surfactant to be used may be added in advance to the polymerization vessel.

A monomer-containing composition emulsion containing a specific amount of a tackifying resin (B), a specific amount of a non-reactive surfactant (C) and water with respect to the radical polymerizable monomer (A) is 50% of emulsion particles. It is important that the diameter is 2 μm or less, preferably 0.5 to 1.7 μm, and more preferably 0.8 to 1.5 μm. The particle size of the emulsion particles of the monomer-containing composition emulsion can be controlled by controlling the stirring conditions and the like.
In the present invention, “50% particle diameter” refers to a median diameter on a volume basis.

From the viewpoint of transparency of the pressure-sensitive adhesive layer to be formed, it is preferable that the emulsion particle diameter of the acrylic polymer-containing composition emulsion is smaller. However, if the 50% particle size of the emulsion particles of the monomer-containing composition emulsion is too small, the stability of the monomer-containing composition emulsion tends to decrease, and the polymerization stability also tends to decrease.
In general, a relatively large amount of surfactant is required to ensure the dispersion stability of smaller emulsion particles. If the amount of the non-reactive surfactant (C) to be used is increased with respect to the radical polymerizable monomer (A) or the tackifier resin (B), the stability can be improved even in a monomer-containing composition emulsion having a small particle size. The stability of the resulting acrylic polymer-containing composition emulsion can also be improved.
However, when the amount of the non-reactive surfactant (C) is excessive, the transparency of the formed pressure-sensitive adhesive layer is lowered.

On the other hand, when the 50% particle diameter of the emulsion particles of the monomer-containing composition emulsion exceeds 2 μm, it is difficult to obtain a pressure-sensitive adhesive layer excellent in transparency from a pressure-sensitive adhesive containing a polymer emulsion obtained by polymerizing the emulsion particles. is there.
When the composition containing the radical polymerizable monomer (A) and the tackifier resin (B) is polymerized in water, the difference in the diffusion rate of the radical polymerizable monomer (A) and the tackifier resin (B) in water Therefore, it is considered that the radical polymerizable monomer (A) preferentially forms a polymer emulsion alone, and the tackifying resin (B) is easily left behind.
When a monomer-containing composition emulsion having a 50% particle size larger than 2 μm is polymerized, this tendency becomes stronger, and the acrylic polymer emulsion derived from the radical polymerizable monomer (A) and the tackifier resin ( It becomes a state close to a simple mixture with the emulsion of B). In such a case, since the fusion between the two emulsion particles is difficult to proceed, the formed pressure-sensitive adhesive layer tends to be inferior in transparency.

Next, the method for obtaining the acrylic polymer-containing composition emulsion of the present invention will be described in more detail.
The acrylic polymer-containing composition emulsion of the present invention is, for example, a radically polymerizable monomer (A) mainly composed of (meth) acrylic acid ester capable of forming a polymer having a glass transition temperature of 0 ° C. or less, and the radical polymerization. 6 to 30 parts by weight of a tackifier resin (B) containing 60% by weight or more of a rosin-based tackifier resin with respect to 100 parts by weight of the monomer (A), preferably a tackifier resin (B) Is sufficiently dissolved in the radically polymerizable monomer (A), 0.2 to 1.5 parts by weight of the non-reactive surfactant (C) and water are added to this mixture, and the mixture is stirred and mixed. Using a disperser such as an emulsifier or a homomixer, a monomer-containing composition emulsion having a 50% particle size of emulsion particles of 2 μm or less is obtained, and the monomer-containing composition emulsion is placed in a dropping device. That.
Then
Water is put into a reaction vessel equipped with heating and stirring means, and the monomer-containing composition emulsion is dropped into the water to polymerize,
Water and a part of the monomer-containing composition emulsion are placed in a reaction vessel equipped with heating and stirring means, and the remaining monomer-containing composition emulsion is dropped therein to polymerize,
Water and a non-reactive surfactant can be placed in a reaction vessel equipped with heating and stirring means, and the monomer-containing composition emulsion can be dropped into the surfactant aqueous solution for polymerization.
In the case of the third exemplified method, the amount of the non-reactive surfactant that can be blended in the water in the reaction vessel is preferably an amount that does not decrease the transparency of the pressure-sensitive adhesive layer formed. Combined with the amount of the non-reactive surfactant used for forming the composition emulsion, the amount is 0.2 to 1.5 parts by weight per 100 parts by weight of the radical polymerizable monomer (A). Is preferred.

The acrylic polymer-containing composition emulsion obtained by polymerizing the monomer-containing composition emulsion is a particle having a small particle diameter of 0.05 μm or more and less than 0.4 μm in a total of 100 (volume%) of the volume of all dispersed particles. Is preferably 60 to 98 (volume%), preferably the ratio of 0.4 to 5 μm of large particle diameter is 40 to 2 (volume%), and the ratio of small particle diameter is It is 75-95 (volume%), and it is more preferable that the ratio for which a large particle diameter particle accounts is 25-5 (volume%).
Of the total volume (100% by volume) of the total dispersed particles of the acrylic polymer-containing composition emulsion, the proportion of small particle diameters of 0.05 μm or more and less than 0.4 μm is less than 60 (% by volume), that is, relatively When the proportion of large particle diameters of 0.4 μm or more and 5 μm or less is larger than 40 (volume%), the transparency of the formed pressure-sensitive adhesive layer tends to be lowered.
On the other hand, in the total 100 (volume%) of the volume of all dispersed particles of the acrylic polymer-containing composition emulsion, when the proportion of small particle diameter particles of 0.05 μm or more and less than 0.4 μm exceeds 98 (volume%), The particle filling rate at the time of drying decreases, and eventually the adhesiveness between the emulsion particles and the adhesion to the sheet-like substrate decrease, so the water resistance and adhesion of the resulting pressure-sensitive adhesive layer tend to decrease It is in.

The polymerization initiator used when obtaining the acrylic polymer-containing composition emulsion of the present invention will be described.
As the polymerization initiator, either a water-soluble or water-insoluble one can be used, and a water-soluble polymerization initiator is preferably used. As those generally used, water-soluble thermal decomposition polymerization initiators such as persulfates such as potassium persulfate and ammonium persulfate, azobis cation salts or hydroxyl adducts, and redox initiators can be used. . Redox initiators include combinations of organic peroxides such as t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide and reducing agents such as Rongalite, sodium metabisulfite, or sodium persulfate, ammonium persulfate and Rongalite. A combination of sodium thiosulfate, a combination of hydrogen peroxide and ascorbic acid, or the like can be used. The amount of the polymerization initiator used is preferably 0.02 to 3 parts by weight and more preferably 0.1 to 1 part by weight with respect to 100 parts by weight of the radical polymerizable unsaturated monomer (A). .
As a method for adding a polymerization initiator, the whole amount is charged in a reaction vessel, the reaction may be started, a part thereof is charged in a reaction vessel, and the remainder may be added in portions or added dropwise. The entire amount may be added in portions or added dropwise. In the case of divided addition or dropwise addition, it may be used in a state of being mixed with the monomer-containing composition emulsion.

Moreover, in order to control the molecular weight and molecular weight distribution of the emulsion particles of the acrylic polymer-containing composition emulsion of the present invention, a mercaptan-based, thioglycol-based, or β-mercaptopropionic acid-based alkyl ester should be used as a chain transfer agent. Can do. When using a chain transfer agent, the addition amount can be used, adjusting molecular weight at 0-0.1 weight part with respect to 100 weight part of radically polymerizable unsaturated monomers (A).
The polymerization reaction for obtaining the acrylic polymer-containing composition emulsion is usually carried out in the temperature range of 40 ° C. to 90 ° C. over 2 to 6 hours.

An emulsion-type pressure-sensitive adhesive can be obtained by adding various additives and the like to the acrylic polymer-containing composition emulsion of the present invention as necessary. Specific additives include wetting agents (surfactant for preventing repellency, etc.), antifoaming agents, neutralizing agents, plasticizers, thickeners, colorants, preservatives, rust inhibitors, solvents, water repellents. Etc.
In addition, when adding various additives, it is preferable to disperse the additives well using a homomixer or the like.

The pressure-sensitive adhesive containing the acrylic polymer-containing composition emulsion of the present invention preferably crosslinks the emulsion particles with each other in the course of drying.
For this purpose, after radical polymerization of the radically polymerizable unsaturated monomer (A), the functional groups derived from the monomer (A) can undergo a crosslinking reaction in the drying process and the aging process performed as necessary. , Selecting the type of functional group in the radical polymerizable unsaturated monomer (A),
It is preferable to contain a crosslinking agent (D) capable of reacting with the functional group derived from the monomer (A).
For example, when a monomer having an acetoacetoxy group is used as one of the radically polymerizable unsaturated monomers (A), acrylic polymers constituting the emulsion particles can self-crosslink in the drying process or the like.

The crosslinking agent (D) reacts with a functional group derived from the radical polymerizable unsaturated monomer (A) in the acrylic polymer-containing composition emulsion, such as a hydroxyl group, a carboxyl group, an epoxy group, etc., during the drying process or aging. The resulting compound can be used.
Examples of such a crosslinking agent (D) include hydrazide compounds, semicarbazide derivatives, isocyanate compounds, carbodiimide compounds, aziridine compounds, complexable metal compounds, and the like.
The amount of the crosslinking agent (D) used is preferably 10 parts by weight or less based on 100 parts by weight of the total of the acrylic polymer and the tackifier resin (B) contained in the acrylic polymer-containing composition emulsion. The amount is more preferably 5 parts by weight or less, and further preferably 3 parts by weight or less.
In the drying process and the aging process, it is considered that fusion between emulsion particles and cross-linking between particles proceed in a competitive manner. Therefore, if the interparticle cross-linking proceeds before the fusion between the emulsion particles hardly progresses, it is considered that the cross-linked portion becomes a kind of barrier for the fusion between the emulsion particles. Therefore, it is preferable that there is not too much crosslinking agent (D).

A pressure-sensitive adhesive sheet can be obtained by coating the emulsion-type pressure-sensitive adhesive of the present invention on a sheet-like substrate other than a foam and drying it.
As the sheet-like substrate, various plastic films having transparency are preferably used. Moreover, various base materials can also be used independently, and the thing in the multilayer state formed by laminating | stacking a several thing can also be used.
In the pressure-sensitive adhesive sheet of the present invention, an emulsion-type pressure-sensitive adhesive is coated on a release sheet (separator), and a pressure-sensitive adhesive layer is provided. Then, the pressure-sensitive adhesive layer and the sheet-like base material are bonded together, and the pressure-sensitive adhesive layer is formed into a sheet shape. It can also be obtained by a method of transferring onto a substrate, a so-called transfer method.
The method of coating the emulsion-type pressure-sensitive adhesive on the sheet-like substrate or release sheet is not particularly limited, and includes a roll coater such as a comma coater, a blade coater, and a gravure coater, a slot die coater, a lip coater, and a curtain coater. A conventionally known coating apparatus can be used.
As for the adhesive layer which comprises the adhesive sheet of this invention, it is preferable that HAZE is 4 or less in thickness 20 micrometers, and it is more preferable that it is 3.5 or less. In addition, the pressure-sensitive adhesive sheet of the present invention can exhibit a large adhesive force of 6 N / 25 mm or more, preferably 8 N / 25 mm or more, more preferably 9 N / 25 mm or more with respect to a polyethylene plate when it is peeled 180 degrees.

However, in the pressure-sensitive adhesive sheet of the present invention, the case where the amount of the water-soluble component contained in the pressure-sensitive adhesive layer is 3% by weight or less is excluded.
Here, “water-soluble component contained in the pressure-sensitive adhesive layer” refers to the various components contained in the pressure-sensitive adhesive layer formed by applying and drying the pressure-sensitive adhesive on the substrate and removing the volatile components. , Which is water-soluble.
For example, in the surfactant used in emulsion polymerization to obtain an acrylic polymer, the surfactant itself does not have radical polymerizability, so-called non-reactive surfactant that is water-soluble,
Among neutralizing agents for neutralizing emulsions of acrylic polymers, those remaining in the pressure-sensitive adhesive layer to be formed in order not to exhibit volatility such as ammonia,
In addition, the water-soluble component contained in an antifoamer, a wetting agent, antiseptic | preservative, a thickener etc. which is mix | blended with an adhesive is mentioned.
However, the reactive surfactant used in emulsion polymerization to obtain an acrylic polymer, the polymerization initiator, and the crosslinking agent blended in the pressure-sensitive adhesive are not soluble at the time of polymerization, even if they are water-soluble. Alternatively, since the water-solubility disappears by being incorporated into the acrylic polymer when the pressure-sensitive adhesive is dried, it is excluded from the “water-soluble component contained in the pressure-sensitive adhesive layer”.
The amount of the “water-soluble component contained in the pressure-sensitive adhesive layer” can be calculated from the weight ratios of various components constituting the pressure-sensitive adhesive layer.

Since the pressure-sensitive adhesive layer formed from the emulsion-type pressure-sensitive adhesive of the present invention has good transparency, when using various plastic films having excellent transparency as the sheet-like substrate, the pressure-sensitive adhesive sheet of the present invention is a laminate film, It is useful for a wide range of applications that require transparency and high adhesive strength, from general-purpose products such as labels, tapes, and window films to optical members such as packaging materials and polarizing plates.
The “sheet” and “sheet shape” referred to in the present invention are intended to include not only a relatively short length but also a so-called long web state.

  Specific examples of the present invention will be described below together with comparative examples, but the present invention is not limited to the following examples. In the following examples and comparative examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively. In addition, the number of ethylene oxide repeating polyethylene oxide is defined as “EO number”.

Example 1
As radical polymerizable monomers, 2-ethylhexyl acrylate: 50.5 parts, butyl acrylate: 40.3 parts, ethyl acrylate: 5 parts, methyl methacrylate: 3 parts, acrylic acid: 1 part, acetoacetoxyethyl methacrylate: 0.2 part, “Superester A-125” (made by Arakawa Chemical Co., Ltd.) which is a rosin resin as a tackifying resin: 10 parts, “YS resin PX1250” (made by Yasuhara Chemical Co., Ltd.) which is a terpene resin : 5 parts were mixed, the tackifying resin was dissolved in the radical polymerizable monomer, and a mixture of both was obtained.
To this mixture, 1 part of polyoxyethylene alkyl ether sulfate having 12 alkyl carbon atoms and 18 EO number, which is a water-soluble non-reactive surfactant, and 50 parts of deionized water are added, followed by stirring with a homomixer. A monomer-containing composition emulsion having a particle size of 1.2 μm was obtained, and the monomer-containing composition emulsion was charged into a dropping tank.
In addition, the glass transition temperature calculated | required theoretically of the polymer obtained from the composition of the said radically polymerizable monomer is -57.1 degreeC.

In a polymerization vessel equipped with a heating device, a stirrer, a reflux cooling device, a thermometer, a nitrogen introduction tube and a dropping tank, deionized water: 49 parts, polyoxyethylene alkyl ether sulfate having 12 alkyl carbons and 18 EOs: 0 .1 part was charged, stirred under a nitrogen atmosphere and heated to an internal temperature of 78 ° C., and 0.105 part of 5% potassium persulfate aqueous solution was added as a solid content. After 5 minutes, the above monomer-containing composition emulsion and 5% ammonium persulfate aqueous solution were used as solids, and 0.315 parts were added dropwise from separate dropping tanks over 4 hours to carry out polymerization.
After completion of dropping, the temperature is kept at 80 ° C. for 30 minutes, and then the internal temperature is set to 60 to 65 ° C. over 30 minutes, and t-butyl hydroperoxide: 0.1 part and Rongalite: 0.12 part are added every 10 minutes. Added in batches. The mixture was further reacted with stirring for 1 hour, neutralized with aqueous ammonia, and filtered through a 175 mesh nylon filter cloth to obtain an acrylic polymer-containing composition emulsion having a nonvolatile content of 50.1% and a viscosity of 120 mPa · s. It was.
The emulsion particles of the resulting acrylic polymer-containing composition emulsion have a small particle size component (peak) and a large particle size component (peak), each having a maximum value at a particle size of 0.204 μm and 1.156 μm, The 50% particle size was 0.185 μm. The emulsion particles contained in the small particle size component (peak) having a maximum value at a particle size of 0.204 μm have a particle size of 0.05 μm or more and less than 0.4 μm, and the content ratio thereof is the obtained acrylic polymer When the total volume of the emulsion particles contained in the contained composition emulsion is 100 (volume%), the number of particles occupying 87 (volume%) and the remaining 13 (volume%) is a maximum of 1.156 μm. It was an emulsion particle contained in a large particle size component (peak) having a value and having a particle size of 0.4 μm or more and 5 μm or less.

Antifoaming agent: 0.1 part (50% by weight is a water-soluble component) and water-soluble sodium dioctylsulfosuccinate: 1 part are added to 100 parts of the acrylic polymer-containing composition emulsion obtained above. Furthermore, the thickener (30% by weight is a water-soluble component): 1 part is increased to 5000 mPa · s (measured at # 4 rotor / 60 rpm at 25 ° C., BL type viscometer) to give the emulsion type adhesive. Obtained. The pressure-sensitive adhesive was prepared with a homomixer.
The obtained emulsion-type adhesive was applied on a separator using a doctor blade so as to have a dry film thickness of 20 μm, dried at 100 ° C. for 75 seconds, and a 50 μm PET film was laminated to prepare a coated product. Immediately the evaluation described later was performed.
The 50% particle size of the monomer-containing composition emulsion, the particle size distribution of the acrylic polymer-containing composition emulsion, the transparency of the pressure-sensitive adhesive layer, and the adhesive strength were determined by the following methods. The results are listed in Table 1.

<50% particle size><particle size distribution>
The particle size of the monomer-containing composition emulsion and the acrylic polymer-containing composition emulsion was measured by “Microtrack” manufactured by Nikkiso Co., Ltd. The nonvolatile content was measured by weight after drying at 150 ° C. for 20 minutes in an electric oven. The ratio was measured.

<Transparency evaluation>
Remove the separator from the coated product, and subtract the HAZE of the PET film itself using a multi-light source spectrocolorimeter (manufactured by Suga Test Instruments Co., Ltd.). The HAZE of the layer was measured.

<Adhesive strength evaluation>
The coated product was cut into a strip with a width of 25 mm, the separator was peeled off, attached to a polyethylene plate, reciprocated once with a 2 kg roll, and a measurement sample was obtained. Twenty-four hours after application, the adhesive strength when peeled in the 180 ° direction at a rate of 300 mm / min in an atmosphere at 23 ° C. was measured.

(Example 2)
A monomer-containing composition emulsion having a 50% particle size of 1.3 μm was prepared in the same manner as in Example 1 except that 0.2 parts of acetoacetoxyethyl methacrylate was used instead of 0.2 parts of diacetone acrylamide. In the same manner, polymerization and filtration were performed to obtain an acrylic polymer-containing composition emulsion having a nonvolatile content of 50.2% and a viscosity of 110 mPa · s. The theoretical Tg of the acrylic polymer constituting the acrylic polymer-containing composition emulsion is −57.1 ° C.
Next, 0.1 part by weight of adipic acid dihydrazide was mixed and dissolved as a cross-linking agent with respect to 100 parts by weight of the acrylic polymer and tackifying resin contained in the resulting acrylic polymer-containing composition emulsion. .
Furthermore, an antifoaming agent, a wetting agent, and a thickening agent were added in the same manner as in Example 1 to prepare an emulsion-type pressure-sensitive adhesive, and the same experiment as in Example 1 was performed.

(Comparative Example 1)
In Example 1, the same experiment as in Example 1 was performed except that the 50% particle size of the monomer-containing composition emulsion was adjusted to 8 μm.

(Comparative Example 2)
A monomer-containing composition emulsion was obtained in the same manner as in Example 1 except that 0.1 part of the polyoxyethylene alkyl ether sulfate having 12 alkyl carbon atoms and 18 EO number, which is a non-reactive surfactant, was used. When the stirring was stopped, the layer was separated into a layer containing a radical polymerizable monomer and a tackifying resin and an aqueous layer, and the subsequent polymerization was stopped.

(Comparative Example 3)
A monomer containing a 50% particle size of 1.2 μm is included in the same manner as in Example 1 except that 2 parts of a polyoxyethylene alkyl ether sulfate having 12 alkyl carbon atoms and 18 EO atoms, which is a non-reactive surfactant, is used. A composition emulsion was obtained and polymerized and filtered in the same manner to obtain an acrylic polymer-containing composition emulsion having a nonvolatile content of 50.4% and a viscosity of 130 mPa · s. Thereafter, the same experiment as in Example 1 was performed.

(Comparative Example 4)
The polyoxyethylene alkyl ether sulfate having an alkyl carbon number of 12 and an EO number of 18 which is a non-reactive surfactant used in Example 1 is replaced with a polyoxyethylene-1- (allyloxymethyl) alkyl which is a reactive surfactant. The same experiment as in Example 1 was performed except that the ammonium salt of ether sulfate was used.

(Comparative Example 5)
The tackifier resin is rosin resin "Superester A-125" (Arakawa Chemical Co., Ltd.): 3.3 parts, terpene resin "YS resin PX1250" (Yasuhara Chemical Co., Ltd.): 1 7 parts, except that the polyoxyethylene alkyl ether sulfate having 12 carbon atoms and 18 EO number, which is the non-reactive surfactant used in Example 1, was changed to 1.5 parts. A similar experiment was conducted

(Comparative Example 6)
The non-reactive surfactant polyoxyethylene alkyl ether sulfate having 12 carbon atoms and 18 EO used in Example 5 was used as the reactive surfactant polyoxyethylene-1- (allyloxymethyl) alkyl. The same experiment as in Example 5 was performed, except that the ammonium salt of ether sulfate was used.

(Comparative Example 7)
Tackifying resin, rosin resin "Super Ester A-125" (Arakawa Chemical Co., Ltd.): 25 parts, terpene resin "YS Resin PX1250" (Yasuhara Chemical Co., Ltd.): 15 parts Except that, the same experiment as in Example 1 was performed.

(Comparative Example 8)
Tackifying resin, rosin resin "Superester A-125" (Arakawa Chemical Co., Ltd.): 5 parts, terpene resin "YS Resin PX1250" (Yasuhara Chemical Co., Ltd.): 10 parts In the same manner as in Example 1, a monomer-containing composition emulsion having a 50% particle size of 1.1 μm was obtained, polymerized and filtered in the same manner, and an acrylic having a nonvolatile content of 50.3% and a viscosity of 120 mPa · s. A system polymer-containing composition emulsion was obtained. Thereafter, the same experiment as in Example 1 was performed.

(Comparative Example 9)
Non-reactive surfactant used in Example 1 with 15 parts of “superester A-125” (produced by Arakawa Chemical Co., Ltd.), which is a rosin resin, without using a terpene resin. Instead of polyoxyethylene alkyl ether sulfate having 12 alkyl carbon atoms and 18 EO atoms, a reactive surfactant, polyoxyethylene-1- (allyloxymethyl) alkyl ether sulfate ammonium salt is 2.5. The same experiment as in Example 1 was performed except that a part of the sample was used.

(Comparative Example 10)
Without using a tackifying resin, the same radical polymerizable monomer mixture as in Example 1 and a non-reactive surfactant polyoxyethylene alkyl ether sulfate having 12 alkyl carbon atoms and 18 EO atoms were used. Thus, a monomer emulsion having a 50% particle size of 1.2 μm was obtained, and thereafter an acrylic polymer emulsion having a nonvolatile content of 50.2% and a viscosity of 110 mPa · s was obtained in the same manner as in Example 1.
Regarding the particle size distribution of the obtained acrylic polymer emulsion, the number of particles contained in a peak having a maximum value only at a particle size of 0.180 μm is 100 (% by volume), and the particle size is all 0.05 μm or more and 0.00. It was less than 4 μm. The 50% particle size was 0.185 μm.
Next, 15 parts by weight of solidified rosin-based tackifier resin with an emulsified softening point of 150 ° C. and an average particle size of 0.52 μm is added to 100 parts by weight of the solid content of the obtained acrylic polymer emulsion and mixed. did.
After mixing, the particle size distribution was determined in the same manner as in Example 1.
Thereafter, an experiment similar to that of Example 1 was performed based on 100 parts of a mixture of an acrylic polymer emulsion and a tackifier resin emulsion.

Claims (7)

60% by weight of rosin-based tackifying resin with respect to 100 parts by weight of radically polymerizable unsaturated monomer (A) mainly composed of (meth) acrylic acid ester capable of forming a polymer having a glass transition temperature of 0 ° C. or less. A monomer having a 50% particle size of 2 μm or less, containing 6 to 30 parts by weight of the tackifying resin (B), 0.2 to 1.5 parts by weight of the non-reactive surfactant (C) and water. An acrylic polymer-containing composition emulsion obtained by polymerizing a composition-containing emulsion. The proportion of small particle diameter particles of 0.05 μm or more and less than 0.4 μm in the total 100 (volume%) of all dispersed particles is 60 to 98 (volume%), and a large size of 0.4 μm or more and 5 μm or less. 2. The acrylic polymer-containing composition emulsion according to claim 1, wherein the proportion of the particle size particles is 40 to 2 (volume%). Radical polymerizable unsaturated monomer (A) mainly composed of (meth) acrylic acid ester capable of forming a polymer having a glass transition temperature of 0 ° C. or less: 100 parts by weight, containing rosin-based tackifying resin at 60% by weight or more Tackifying resin (B): 6-30 parts by weight and non-reactive surfactant (C): 0.2-1.5 parts by weight are emulsified in the presence of water, and 50% particle size is 2 μm or less. A monomer-containing composition emulsion of
Next, a method for producing an acrylic polymer-containing composition emulsion, wherein the monomer-containing composition emulsion is polymerized. An acrylic polymer-containing composition emulsion obtained by the production method according to claim 3. An emulsion-type pressure-sensitive adhesive comprising the polymer-containing emulsion according to claim 1. The emulsion-type pressure-sensitive adhesive according to claim 5, comprising a crosslinking agent (D) capable of reacting with a functional group in the acrylic polymer-containing composition emulsion. A pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer formed from the emulsion-type pressure-sensitive adhesive according to claim 5 or 6 is provided on at least one surface of a sheet-like substrate other than a foam (however, water-soluble contained in the pressure-sensitive adhesive layer) Except when the amount of the sex component is 3% by weight or less).