JP6975539B2 - Water-based resin composition for adhesives - Google Patents

Description

The present invention relates to a water-based resin composition for a pressure-sensitive adhesive, and more specifically, a water-based resin composition for a pressure-sensitive adhesive that can be suitably used for a pressure-sensitive adhesive product such as a paper label or a pressure-sensitive adhesive tape, and a water-based resin composition for the pressure-sensitive adhesive. The present invention relates to an adhesive product having an adhesive layer obtained by using an object.

The water-based resin composition for an adhesive containing an emulsion resin has a low impact on the environment and is safe for the human body, and exhibits high adhesive strength by volatilizing the water-based dispersion medium after application and fusing the emulsion particles to each other. It is possible to form a pressure-sensitive adhesive layer. In recent years, water-based resin compositions for pressure-sensitive adhesives containing such emulsion resins have been used for forming a pressure-sensitive adhesive layer in the production of many pressure-sensitive adhesive products such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, and labels. Various studies have been conducted with the aim of improving the performance. For example, an emulsion-type pressure-sensitive adhesive composition capable of exhibiting good adhesive properties with respect to both a poorly adhesive polyolefin-based adherend such as polyethylene and polypropylene and an adherend having a rough surface such as corrugated cardboard. Has been proposed (see, for example, Patent Document 1).

By the way, in a specific emulsion resin composition, by setting the residual content of persulfate used as a polymerization initiator to 200 ppm or less, paints such as indoor paints, outdoor paints and building material paints and adhesives can be used. It is disclosed that the emission amount of formaldehyde can be suppressed to a low level and is useful in applications where emission is a problem (see, for example, Patent Document 2).

Japanese Patent No. 4795766 Japanese Patent No. 4109595

As described above, a resin composition containing an emulsion resin is used as an adhesive, but especially when the adhesive is applied to an adhesive product such as a paper label or an adhesive tape, the adhesiveness to the curved surface of the adherend (hereinafter referred to as “adhesive”). , Also referred to as “curved surface adhesion”) and resistance to displacement of the pressure-sensitive adhesive layer (hereinafter, also referred to as “holding force”), there was room for further improvement.
If the holding power of the pressure-sensitive adhesive is good, the pressure-sensitive adhesive layer can be sufficiently prevented from being displaced or protruding from a predetermined position. This makes it possible to sufficiently suppress the deterioration of the blade used for cutting the adhesive product to the desired dimensions and making cuts in the base material, etc., and maintenance of equipment such as blade replacement can be performed. Less.

Patent Document 1 discloses that in an emulsion-type pressure-sensitive adhesive composition, the physical properties of the pressure-sensitive adhesive are adjusted by adjusting the addition amount of the aqueous cross-linking agent within a predetermined range (paragraph [0034]). etc). However, even if an attempt is made to achieve both curved surface adhesion and holding power depending on the amount of the water-based cross-linking agent added, the adhesive's followability to the curved surface, that is, softness is required for the curved surface adhesion, and the holding power of the adhesive is required. Since cohesive force, that is, hardness is required, both performances are in a trade-off relationship with each other, and it is difficult to achieve both performances in a well-balanced manner only by adjusting the amount of the aqueous cross-linking agent added.

The above-mentioned Patent Document 2 does not specifically disclose the application of the invention described in Patent Document 2 to an aqueous resin composition for a pressure-sensitive adhesive.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a method for achieving both curved surface adhesion and holding power in an aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin.

The present inventor has focused on an aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin that has a low impact on the environment and is safe for the human body, and has the curved surface adhesion and holding power of the pressure-sensitive adhesive layer obtained by using the composition. As a result, the content of the persulfate used as the polymerization initiator in the composition containing the (meth) acrylic polymer having a specific glass transition temperature was reduced to an extremely small amount. I came up with a new water-based resin composition for adhesives. The present inventor has found that the pressure-sensitive adhesive layer obtained by using this water-based resin composition for a pressure-sensitive adhesive can achieve both curved surface adhesion and holding power in a well-balanced manner, and has conceived that the above problems can be brilliantly solved. However, the present invention has been reached.

That is, the present invention is an aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin and an aqueous dispersion medium, wherein the emulsion resin has a glass transition temperature of −80 to 10 ° C. and contains a (meth) acrylic polymer. The composition is an aqueous resin composition for a pressure-sensitive adhesive containing 1 ppb to 100 ppm of persulfate.

By using the aqueous resin composition for a pressure-sensitive adhesive of the present invention, it is possible to obtain a pressure-sensitive adhesive product that can achieve both curved surface adhesion and holding power in a well-balanced manner.

The present invention will be described in detail below. It should be noted that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

<Water-based resin composition for adhesive of the present invention>
(Persulfate remaining in the composition)
The above-mentioned aqueous resin composition for a pressure-sensitive adhesive of the present invention contains 1 ppb to 100 ppm of a persulfate used as a polymerization initiator. If the amount of persulfate remaining in the composition is extremely small as described above, the adhesive layer obtained by using the composition has a particularly excellent holding power while sufficiently improving the adhesiveness to the curved surface. It is possible to achieve both curved surface adhesion and holding power in a well-balanced manner. This is because the pressure-sensitive adhesive layer containing a persulfate that does not bind to the polymer terminal absorbs moisture more easily than the pressure-sensitive adhesive layer containing a group derived from the persulfate that is bonded to the polymer terminal, and thus is plasticized by water. It is presumed that the balance between the holding power and the adhesiveness to the curved surface was lost. However, by using a very small amount of persulfate remaining in the composition, the obtained pressure-sensitive adhesive layer was made difficult to absorb moisture. It is considered that this is because it is possible to specifically prevent the imbalance from being lost.

The content of the persulfate is preferably, for example, 80 ppm or less, more preferably 50 ppm or less, further preferably 40 ppm or less, and further preferably 20 ppm, from the viewpoint of improving the holding power and the like. It is more preferably less than or equal to, particularly preferably 10 ppm or less, and most preferably 1 ppm or less. When a persulfate is used as the polymerization initiator, the content of the persulfate is usually 1 ppb or more even if the content of the persulfate is sufficiently reduced. In this respect, the aqueous resin composition for a pressure-sensitive adhesive of the present invention is polymerized. It is also distinguished from the aqueous resin composition for a pressure-sensitive adhesive obtained without using a persulfate as an initiator in terms of composition.
The content of persulfate is measured by the method described in Examples.

Examples of the persulfate include sodium persulfate, potassium persulfate, ammonium persulfate and the like, and one or more of these can be used.

In the aqueous resin composition for a pressure-sensitive adhesive of the present invention, even if the liberated persulfate cannot be detected (0 ppb), the (meth) acrylic polymer contained in the emulsion resin in the composition contains the persulfate at the polymer terminal. As long as it has a structure in which the derived groups are bonded, it can be distinguished from the conventional aqueous resin composition for a pressure-sensitive adhesive obtained without using a persulfate as a polymerization initiator. That is, the present invention is an aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin and an aqueous dispersion medium, wherein the emulsion resin has a glass transition temperature of −80 to 10 ° C. and is derived from a persulfate at the polymer terminal. The composition comprises a (meth) acrylic polymer having a structure in which groups are bonded, and the composition is also an aqueous resin composition for a pressure-sensitive adhesive having a persulfate content of 100 ppm or less.
Here, the preferable upper limit value of the content of persulfate is as described above.
The method for measuring the content of persulfate and the type of persulfate are as described above.

The structure to which the group derived from the persulfate is bonded may be any structure formed by polymerizing the monomer component using the persulfate as the polymerization initiator.
Hereinafter, matters common to the above-mentioned technically closely related inventions will be described.

(Emulsion resin)
The water-based resin composition for a pressure-sensitive adhesive of the present invention contains an emulsion resin, and the emulsion resin has a glass transition temperature of −80 to 10 ° C. and contains a (meth) acrylic polymer.
The emulsion resin is usually obtained by emulsion polymerization of a monomer component, but an emulsion resin may be obtained by adding an emulsifier to the polymer obtained by polymerization. In the present specification, the emulsion resin refers to a polymer that forms emulsion particles in an aqueous resin composition for a pressure-sensitive adhesive.

The emulsion resin preferably has a glass transition temperature of −70 to 0 ° C. When an emulsion resin having such a glass transition temperature is used, the adhesive strength can be further improved. The glass transition temperature of the emulsion resin is more preferably −65 to −15 ° C., further preferably −60 to −30 ° C., and particularly preferably −55 to −45 ° C.
When the emulsion resin according to the present invention contains two or more kinds of emulsion resins, Tg (total Tg) calculated from all the monomer compositions used for preparing the emulsion resin according to the present invention is within the above range. However, it is preferable that the Tg of each of the two or more emulsion resins is within the above range.
For example, one of the preferred forms in the present invention is that the emulsion resin contains an emulsion resin having a glass transition temperature of −70 to −45 ° C. and an emulsion resin having a glass transition temperature of −10 to 10 ° C. ..
The glass transition temperature (Tg) can be calculated by the method described in Examples described later.

The emulsion resin contains a (meth) acrylic polymer. The (meth) acrylic polymer means a polymer having a structural unit derived from the (meth) acrylic monomer. The (meth) acrylic monomer refers to a monomer having an acryloyl group or a methacryloyl group, or a group in which a hydrogen atom in these groups is replaced with another atom or an atomic group, or a derivative of such a monomer.

The (meth) acrylic polymer preferably contains a (meth) acrylic acid-based polymer. The (meth) acrylic acid-based polymer refers to a polymer having a structural unit derived from a (meth) acrylic acid-based monomer, and the (meth) acrylic acid-based monomer is an acryloyl group or a methacryloyl group, or hydrogen in these groups. An atom has a group in which another atom or atomic group is replaced, and a carboxylic acid group (-COOH group), a carboxylic acid base (-COOM group), or an acid anhydride group thereof (-C (= O)). It is a monomer having −O—C (= O) − group). The above M represents a metal salt, an ammonium salt, or an organic amine salt. Examples of the metal atom forming the metal salt include a monovalent metal atom such as an alkali metal atom such as lithium, sodium and potassium; a divalent metal atom such as calcium and magnesium; and a trivalent metal such as aluminum and iron. Atoms are preferred. As the organic amine forming the organic amine salt, alkanolamines such as ethanolamine, diethanolamine and triethanolamine, and triethylamine are suitable. The (meth) acrylic acid-based monomer is preferably (meth) acrylic acid (salt). The (meth) acrylic acid (salt) is a monomer having an acryloyl group or a methacryloyl group and having a carboxylic acid group (-COOH group) or a carboxylic acid base (-COOM group).

The monomer component for obtaining the (meth) acrylic polymer is preferably composed of a (meth) acrylic acid-based monomer and other copolymerizable unsaturated monomers. When the monomer component contains a (meth) acrylic acid-based monomer, the dispersibility of various additives described later is improved in the aqueous resin composition for a pressure-sensitive adhesive of the present invention, and the function of the obtained pressure-sensitive adhesive layer is more excellent. It becomes a thing. Further, when the monomer component contains other copolymerizable unsaturated monomers, it becomes easy to adjust the glass transition temperature and other physical properties.

The monomer components for obtaining the (meth) acrylic polymer are 0.01 to 5% by mass of the (meth) acrylic acid-based monomer and 0.01 to 5% by mass with respect to 100% by mass of all the monomer components used as the raw material of the emulsion resin. It preferably contains 95-99.99% by mass of other copolymerizable unsaturated monomers. It is more preferable that the monomer component contains 0.05% by mass or more of the (meth) acrylic acid-based monomer and 99.95% by mass or less of other copolymerizable unsaturated monomers, and the (meth) acrylic acid-based monomer is contained. It is more preferable to contain 0.1% by mass or more and 99.9% by mass or less of other copolymerizable unsaturated monomers. Further, it is more preferable that the monomer component contains 3% by mass or less of the (meth) acrylic acid-based monomer and 97% by mass or more of other copolymerizable unsaturated monomers. Within such a range, the monomer components are stably copolymerized.

The other copolymerizable unsaturated monomer is not particularly limited, and examples thereof include (meth) acrylic monomers other than the (meth) acrylic acid-based monomers and other unsaturated monomers.

The (meth) acrylic monomer other than the above (meth) acrylic acid-based monomer has, for example, an acryloyl group or a methacryloyl group, or a group in which a hydrogen atom in these groups is replaced with another atom or an atomic group. A (meth) acrylic monomer having a carboxylic acid ester group, a derivative of such a monomer, for example, a monomer further having an alkylene glycol group, a hydroxy group, an allyl group, an epoxy group, a nitrogen atom, a halogen atom, or the like. , (Meta) acrylic monomer having an acrylamide group, (meth) acrylic monomer having a benzotriazole group, (meth) acrylic monomer having a benzophenone group, (meth) acrylic monomer having a piperidine group and the like. These can be used alone or in combination of two or more, respectively.

Examples of the (meth) acrylic monomer having a carboxylic acid ester group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl ( Meta) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) Meta) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl ( Examples thereof include meth) acrylate, phenylethyl (meth) acrylate, methylbenzyl (meth) acrylate, and naphthylmethyl (meth) acrylate.

Examples of the derivative of the (meth) acrylic monomer having a carboxylic acid ester group include ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, and 1,6-hexanediol di (meth). (Meta) acrylic monomer having an alkylene glycol group such as acrylate and diethylene glycol di (meth) acrylate; (meth) acrylic monomer having a hydroxy group such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Monomer; (meth) acrylic monomer having an allyl group such as allyl (meth) acrylate; (meth) acrylic monomer having an epoxy group such as glycidyl (meth) acrylate; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth). ) Nitrogen atom-containing (meth) acrylate compounds such as acrylate; trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, trichloroethyl (meth) acrylate, tetrachloropropyl (meth) Examples thereof include (meth) acrylic monomers having a halogen atom such as acrylate and octachloropentyl (meth) acrylate.

Examples of the (meth) acrylic monomer having an acrylamide group include (meth) acrylamide, diacetone (meth) acrylamide, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide, and N, N-dimethyl ( Meta) acrylamide, N-n-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, methylenebis (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylaminoethyl (meth) ) Acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, diacetone (meth) acrylamide and other (meth) acrylamide compounds and the like can be mentioned.

Examples of the (meth) acrylic monomer having a benzotriazole group include 2- [2'-hydroxy-5'-(meth) acryloyloxyethylphenyl] -2H-benzotriazole.

Examples of the (meth) acrylic monomer having a benzophenone group include 2-hydroxy-4- (meth) acryloyloxybenzophenone.

Examples of the (meth) acrylic monomer having a piperidine group include 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine and 4- (meth) acryloyloxy-1,2,2. Examples thereof include 6,6-pentamethylpiperidine.

As the monomer component used as a raw material for the (meth) acrylic acid-based polymer, a (meth) acrylic monomer other than the above-mentioned (meth) acrylic acid-based monomer is used as a raw material for the (meth) acrylic acid-based polymer. It is preferably contained in an amount of 20% by mass or more, more preferably 40% by mass or more, further preferably 60% by mass or more, and particularly preferably 80% by mass or more with respect to 100% by mass of the component. .. Further, the (meth) acrylic monomer other than the above (meth) acrylic acid-based monomer is preferably contained in an amount of 99.99% by mass or less, and 99.95% by mass or less, based on 100% by mass of all the monomer components. It is more preferable, and it is further preferable that the content is 99.9% by mass or less.

Examples of the other unsaturated monomer include an unsaturated monomer having a nitrogen atom, an unsaturated monomer having an aromatic ring, an unsaturated monomer having a silane group, and other polyfunctional unsaturated monomers. One type or two or more types can be used.

Examples of the unsaturated monomer having a nitrogen atom include N-vinylpyrrolidone and (meth) acrylonitrile.

Examples of the unsaturated monomer having an aromatic ring include divinylbenzene, styrene, α-methylstyrene, vinyltoluene, ethylvinylbenzene and the like.

Examples of the unsaturated monomer having a silane group include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (methoxyethoxy) silane, 2-styrylethyltrimethoxysilane, and vinyltrichlorosilane.

Examples of the other polyfunctional unsaturated monomer include trimethylolpropane diallyl ether, diallyl phthalate, and triallyl cyanurate.

The water-based resin composition for a pressure-sensitive adhesive of the present invention may contain one kind of emulsion resin obtained by polymerizing a monomer component, or may contain two or more kinds. When the aqueous resin composition for a pressure-sensitive adhesive of the present invention contains two or more types of emulsion resins, it may be a mixture obtained by mixing (blending) two or more types of emulsion resins, and is used in a series of manufacturing steps. It may be an emulsion resin in which two or more kinds of polymer chains are composited, which is obtained by producing a resin containing two or more kinds of polymer chains (for example, multi-stage polymerization or the like). When two or more kinds of emulsion resins are mixed, at least one of the two or more kinds of emulsion resins may be a (meth) acrylic polymer, and the other emulsion resins are (diene-based polymers, vinyl acetate-based polymers, etc.). Meta) A polymer other than the acrylic polymer may be used. Further, in order to produce a product containing two or more kinds of polymer chains in a series of production steps, production conditions such as monomer dropping conditions may be appropriately set. The composite of the two or more kinds of polymer chains includes, for example, a form having a core portion and a shell portion. The emulsion resin according to the present invention has a core portion and a shell portion. For example, the emulsion resin according to the present invention comprises two types of emulsion resins according to the present invention, and the two types of emulsions according to the present invention. Examples thereof include one in which one of the resins forms a core portion and the other forms a shell portion. The emulsion resin is a (meth) acrylic polymer obtained by using a monomer component containing a (meth) acrylic monomer. For example, a (meth) acrylic monomer forms a monomer component forming a core portion of an emulsion. , May be contained in any of the monomer components forming the shell portion, or may be contained in both of them. Further, at least one of the two or more types of emulsion resins forming the emulsion particles may be in the form of a composite of two or more types of polymer chains.

When the emulsion resin is in the form of a composite of two or more kinds of polymer chains, one polymer chain and the other polymer chain may be completely compatible with each other and have a homogeneous structure in which these cannot be distinguished. , These may be inhomogeneously formed without being completely incompatible (for example, a core-shell composite structure or a microdomain structure).
In the core-shell composite structure, it is preferable that the surface of the core portion is covered with the shell portion. In this case, it is preferable that the surface of the core portion is completely covered by the shell portion, but it does not have to be completely covered. The portion may be exposed.

The solid content of the emulsion resin is preferably 20% by mass or more, more preferably 30% by mass or more, based on 100% by mass of the solid content of the aqueous resin composition for a pressure-sensitive adhesive of the present invention. It is more preferably 40% by mass or more, and particularly preferably 50% by mass or more. The content is preferably 99% by mass or less, more preferably 90% by mass or less, further preferably 80% by mass or less, and particularly preferably 70% by mass or less.
The solid content means a component other than the aqueous dispersion medium.

The emulsion resin preferably has a weight average molecular weight of 30,000 to 5,000,000. When the emulsion resin has such a weight average molecular weight, the effect of the present invention can be more fully exhibited. The weight average molecular weight of the emulsion resin is more preferably 50,000 or more, further preferably 80,000 or more, and particularly preferably 100,000 or more. The weight average molecular weight is more preferably 4 million or less, still more preferably 3 million or less.
The weight average molecular weight (Mw) of the emulsion resin is measured by GPC (gel permeation chromatography) under the following conditions.
Measuring equipment: HLC-8120GPC (trade name, manufactured by Tosoh Corporation)
Column used: TSK-GEL GMHXL-L and TSK-GELG5000HXL (both manufactured by Tosoh) connected in series Standard material for calibration curve: Polystyrene (manufactured by Tosoh)
Measuring method: The object to be measured is dissolved in an eluent (tetrahydrofuran) so that the solid content is 0.2% by mass, and filtered through a filter is measured.

The average particle size of the emulsion resin is preferably 80 to 600 nm.
By using the emulsion particles having the average particle size in this range, the adhesive performance can be further improved. The average particle size of the emulsion particles is more preferably 500 nm or less. The average particle size is more preferably 100 nm or more.
The average particle size of the emulsion particles can be measured using a particle size distribution measuring device (FPAR-1000, Otsuka Electronics Co., Ltd.) by a dynamic light scattering method.

The method for producing the emulsion resin is not particularly limited, but for example, it can be produced by a general emulsion polymerization method. Further, the method for producing the emulsion resin may be a method other than emulsion polymerization, for example, a method in which an emulsifier is allowed to act on a polymer polymerized by suspension polymerization to form an emulsion.
In the above method for producing an emulsion resin, the amount of persulfate used as a polymerization initiator is preferably 0.1 to 20% by mass with respect to 100% by mass of all the monomer components used as the raw material of the emulsion.

When producing the emulsion resin, a chain transfer agent such as a mercaptan compound may be used. This makes it possible to improve the adhesiveness to the curved surface. Examples of commercially available chain transfer agents include thiocalcol 20 (trade name, n-dodecyl mercaptan, manufactured by Kao Corporation). In the above method for producing an emulsion resin, the amount of the chain transfer agent used is preferably 0.001 to 10% by mass with respect to 100% by mass of all the monomer components used as the raw material of the emulsion.

As described above, as a method for reducing the amount of persulfate used as the polymerization initiator in the production of the aqueous resin composition for a pressure-sensitive adhesive of the present invention, the amount of persulfate can be as small as possible. The present invention is not particularly limited, and a method of removing the persulfate by using a conventionally known purification method, a method of reducing or decomposing the persulfate, or a method in which these are combined can be used. For example, as a method for reducing / decomposing persulfate, if necessary, a reducing agent such as sodium hydrogen sulfite or sodium disulfite or a decomposing agent such as iron sulfate is used and appropriately heated to reduce the persulfate.・ Can be disassembled. Here, when a reducing agent (decomposing agent) is used, the reducing agent (decomposing agent) may be contained in the raw material (pre-emulsion) of the emulsion, and is added after the dropping of the raw material of the emulsion into the reaction system (done). It may be post-added) or both. Further, it is preferable that the amount of the reducing agent (decomposing agent) used is 0.1 to 10% by mass with respect to 100% by mass of all the monomer components used as the raw material of the emulsion.

(Aqueous dispersion medium)
The water-based resin composition for a pressure-sensitive adhesive of the present invention contains an water-based dispersion medium, and the emulsion resin is usually dispersed in the water-based dispersion medium without being dissolved. In the present specification, the aqueous dispersion medium may contain an organic dispersion medium such as ethylene glycol, butyl cellosolve, butyl carbitol, and butyl carbitol acetate as long as it contains water, but water is preferable. By adjusting the amount of the aqueous dispersion medium, the solid content of the aqueous resin composition for a pressure-sensitive adhesive can be appropriately adjusted.
The solid content of the aqueous resin composition for a pressure-sensitive adhesive of the present invention is not particularly limited, but is preferably, for example, 20 to 80% by mass, more preferably 25 to 75% by mass, and even more preferably. It is 30 to 70% by mass.

(Emulsifier component)
The aqueous resin composition for a pressure-sensitive adhesive of the present invention preferably further contains an emulsifier component. The water-based resin composition for a pressure-sensitive adhesive of the present invention contains an emulsifier component, which may be contained as an emulsifier at the time of emulsion polymerization, and as an emulsifier acting on a polymer polymerized by a method other than emulsion polymerization. Although it may contain the component, it is preferable to contain the component as an emulsifier during emulsion polymerization. The emulsifier at the time of emulsion polymerization may be an ordinary emulsifier (a compound different from the emulsion resin), or may be a structural unit constituting a part of the polymer forming the emulsion resin.

The emulsifier component means all of the agents contained in the emulsion composition that can function as an emulsifier, regardless of the purpose of use thereof. That is, the emulsifier component in the emulsion composition may have other functions as long as it can function as an emulsifier.

As the emulsifier component, one or more of an anionic emulsifier, a cationic emulsifier, a nonionic emulsifier, an amphoteric emulsifier, and a polymer emulsifier can be used.
Examples of the anionic emulsifier include fatty acids (salts), alkyl ether carboxylic acids (salts), N-acylamino acids (salts), alkane sulfonic acid (salts), α-olefin sulfonic acid (salts), and α-sulfoalkyl esters. (Salt), Alkyl sulfosuccinic acid (salt), acyl isethionic acid (salt), N-acyl-N-alkyl taurine (salt), alkyl sulfate ester (salt), alkyl ether sulfate ester (salt), alkyl phosphate ester (salt) ), Polyoxyalkylene alkyl ether phosphate ester (salt), polyoxyalkylene alkyl ether sulfate (salt), alkyldiphenyl ether disulfonic acid (salt), alkylbenzene sulfonic acid (salt), polyoxyalkylene polycyclic phenyl ether sulfate ester (salt) ) Etc. are mentioned as suitable ones, and one or more of these can be used.

Commercially available products of the anionic emulsifier include, for example, Hytenol LA-16 (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Softanol MES-9 (trade name, manufactured by Nippon Shokubai Co., Ltd.), and Newcol 297 (commodity name). Name, manufactured by Nippon Emulsifier Co., Ltd.), Perex TA, Perex SS-H, Emar O (trade name, manufactured by Kao Corporation) and the like can be mentioned.

Among the above anionic emulsifiers, examples of the anionic emulsifier having a reactive unsaturated double bond include Adecaria Soap SR-10, Adecaria Soap SR-20, and Adecaria Soap SR-30 (trade name, (trade name,). Ethersulfate-type reactive anion-based emulsifiers such as (manufactured by ADEKA Corporation); , Sanyo Kasei Kogyo Co., Ltd.) and other sulfosuccinate-type reactive anion-based emulsifiers; (Methyl) Polyoxyethylene alkylpropenylphenyl ether ammonium sulfate such as polyoxyethylene sulfonate salt, Aqualon HS-10, Aqualon BC-10 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Aqualon KH-10 (commodity) Name, sulfonate salt of allyloxymethylalkyloxypolyoxyethylene such as Daiichi Kogyo Seiyaku Co., Ltd., allyloxymethylnonylphenoxyethyl hydroxy such as Adecaria Soap SE-10 (trade name, manufactured by ADEKA Corporation) Polyoxyethylene sulfonate salt, bis (polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salt such as Antox MS-60 (trade name, manufactured by Nippon Emulsorium Co., Ltd.), ADEKA RIA Soap ER-20 (trade name, Allyloxymethylalkoxyethyl hydroxypolyoxyethylene such as ADEKA), polyoxyethylene alkylpropenylphenyl ether such as Aqualon RN-20 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adecaria Soap NE- Examples thereof include allyloxymethylnonylphenoxyethyl hydroxypolyoxyethylene such as 10 (trade name, manufactured by ADEKA Corporation).

The nonionic emulsifier is not particularly limited, and for example, polyoxyethylene alkyl ether; polyoxyethylene alkylaryl ether; sorbitan aliphatic ester; polyoxyethylene sorbitan aliphatic ester; aliphatic monoglyceride such as glycerol monolaurate; Polyoxyethyleneoxypropylene copolymer; examples thereof include a condensation product of ethylene oxide and an aliphatic amine, amide or acid. For example, examples of commercially available products include Emargen 1118S (manufactured by Kao Corporation). In addition, allyloxymethylalkoxyethyl hydroxypolyoxyethylene (for example, "Adecaria Soap ER-20" manufactured by ADEKA Corporation), polyoxyalkylene alkenyl ether (for example, "Latemuru PD-420", "Latemuru" manufactured by Kao Co., Ltd.). Reactive nonionic emulsifiers such as PD-430 ”) can also be used. One or more of these can be used.

The cationic emulsifier is not particularly limited, and examples thereof include dialkyldimethylammonium salt, ester-type dialkylammonium salt, amide-type dialkylammonium salt, and dialkylimidazolinium salt, and one or more of these may be used. be able to.

The amphoteric emulsifier is not particularly limited, and examples thereof include alkyldimethylaminoacetic acid betaine, alkyldimethylamine oxide, alkylcarboxymethylhydroxyethyl imidazolinium betaine, alkylamide propyl betaine, and alkylhydroxysulfobetaine. Species or two or more species can be used.

The polymer emulsifier is not particularly limited, and for example, polyvinyl alcohol and its modified product; (meth) acrylic water-soluble polymer; hydroxyethyl (meth) acrylic water-soluble polymer; hydroxypropyl (meth) acrylic water-soluble polymer. Sexual polymers; polyvinylpyrrolidone and the like can be mentioned, and one or more of these can be used.

The emulsifier component may further have a substituent. Examples of the substituent include a hydrocarbon group, an amino group, an alkoxy group, an alkylamino group, an alkoxysulfonyl group, a sulfoalkyl group, an aminoalkyl group, a carboxylic acid group, a polyalkylene oxide chain-containing group, an alkenyloxy group and the like. Be done.

Above all, it is preferable that the aqueous resin composition for a pressure-sensitive adhesive of the present invention further contains a component derived from an emulsifier having a reactive unsaturated double bond. When the aqueous resin composition for a pressure-sensitive adhesive of the present invention contains two or more emulsion resins, the component derived from an emulsifier having a reactive unsaturated double bond is contained in at least one of the emulsion resins. Just do it. Thereby, more excellent holding power can be exhibited.
The emulsifier having a reactive unsaturated double bond more preferably contains a compound having a reactive carbon-carbon unsaturated bond.

The emulsifier component can be obtained by appropriately using a conventionally known method. Further, as described above, it is also possible to use a commercially available product as an emulsifier component, or to use a commercially available product in which an aqueous dispersion medium is added and the solid content concentration is appropriately adjusted.

The aqueous resin composition for a pressure-sensitive adhesive of the present invention preferably has an emulsifier component content of 0.01 to 20% by mass with respect to 100% by mass of all the monomer components used as a raw material for the emulsion resin. From the viewpoint of exerting the effect of the present invention, the content of the emulsifier component is more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, and 0.2% by mass or more. Is more preferable, and 0.3% by mass or more is particularly preferable. The content of the emulsifier component is more preferably 10% by mass or less, further preferably 5% by mass or less, further preferably 2% by mass or less, and 1% by mass or less. Is particularly preferable.

In addition, in this specification, the total monomer component used as a raw material of an emulsion resin does not include an emulsifier which is a constituent unit constituting a part of a polymer forming an emulsion resin.

The content of the emulsifier component in the above-mentioned aqueous resin composition for a pressure-sensitive adhesive of the present invention is the amount of the emulsifier (a compound different from the emulsion resin) in the aqueous resin composition for a pressure-sensitive adhesive of the present invention and the emulsifier is an emulsion. It is the total amount with the amount of the constituent unit constituting a part of the polymer forming the resin.
The amount of the emulsifier (a compound different from the emulsion resin) in the water-based resin composition for a pressure-sensitive adhesive of the present invention is a component extracted from the pressure-sensitive adhesive layer obtained by using the water-based resin composition for a pressure-sensitive adhesive of the present invention. Can be obtained by analyzing with a high-speed liquid chromatograph.

(Pigment)
The water-based resin composition for a pressure-sensitive adhesive of the present invention may further contain a pigment. By coloring white or the like with a pigment, the visibility of the pressure-sensitive adhesive layer obtained by using the composition becomes good.
As the pigment, for example, one kind or two or more kinds of inorganic colorants, organic colorants and the like can be used. Examples of the inorganic colorant include titanium oxide, carbon black, and a valve handle. Examples of the organic colorant include dyes and natural dyes. Among them, the pigment is preferably an inorganic colorant, and for example, titanium oxide is more preferable.
The pigment preferably has an average particle size of 1 to 50 μm. The average particle size of the pigment can be measured by a laser diffraction type particle size distribution measuring device, and is a value of 50% by weight from the particle size distribution.
The blending amount of the pigment is preferably 1 to 100 parts by mass, more preferably 3 to 80 parts by mass, still more preferably 5 to 100 parts by mass with respect to 100 parts by mass of the solid content of the emulsion resin according to the present invention. It is 50 parts by mass.

(Thickener)
The water-based resin composition for a pressure-sensitive adhesive of the present invention may further contain a thickener.
Examples of the thickener include polyurethane resins, polycarboxylic acid resins, polyvinyl alcohols, cellulosic derivatives and the like. Examples of commercially available thickeners include Adecanol UH-420 (trade name, polyurethane resin, manufactured by ADEKA Corporation).
The blending amount of the thickener may be appropriately adjusted so that the aqueous resin composition for a pressure-sensitive adhesive of the present invention has a desired viscosity as a pressure-sensitive adhesive, but the solid content of the emulsion resin according to the present invention is 100 parts by mass. On the other hand, for example, the solid content is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, still more preferably 1 to 10 parts by mass.

(Defoamer)
The water-based resin composition for a pressure-sensitive adhesive of the present invention may further contain an antifoaming agent.
When an antifoaming agent is used, it is possible to suppress the generation of foam generated during the preparation of the pressure-sensitive adhesive layer. The defoaming agent is not particularly limited, and examples thereof include silicone-based defoaming agents and organic (non-silicone) -based defoaming agents, and one or more of these defoaming agents can be used. Examples of commercially available defoaming agents include, for example, manufactured by Big Chemy Japan Co., Ltd., product numbers: BYK-088, BYK-063, BYK-065, BYK-066N, BYK-067A, BYK-077, BYK-141 and the like. Silicone defoaming agent; manufactured by Big Chemy Japan Co., Ltd., product numbers: BYK-054, BYK-057, BYK-354, BYK-392, BYK-1752, BYK-1790, BYK-1791, BYK-1794, etc. Examples include (non-silicone) antifoaming agents.
When the water-based resin composition for a pressure-sensitive adhesive of the present invention contains a defoaming agent, the blending amount of the defoaming agent may be appropriately adjusted, but for example, it is solid with respect to 100 parts by mass of the solid content of the emulsion resin according to the present invention. In minutes, 0.01 to 5 parts by mass is preferable, 0.1 to 4 parts by mass is more preferable, and 0.3 to 2 parts by mass is further preferable.

(Adhesive-imparting resin)
The water-based resin composition for a pressure-sensitive adhesive of the present invention may further contain a pressure-sensitive adhesive resin.
As the tackifying resin, a resin having a softening point of 60 ° C. or higher is preferable, and examples thereof include a rosin ester resin, a terpene resin, a phenol resin, a styrene resin, a xylene resin, a silicone resin, and an aliphatic petroleum resin. And one or more of these can be used. Examples of commercially available products of the tackifier resin include Super Ester E (trade name, manufactured by Arakawa Chemical Industry Co., Ltd.) and the like.
The blending amount of the tackifier resin may be appropriately adjusted, but the solid content is preferably 1 to 10 parts by mass, preferably 2 to 6 parts by mass, based on 100 parts by mass of the solid content of the emulsion resin according to the present invention. More preferred.

(Other ingredients)
The water-based resin composition for a pressure-sensitive adhesive of the present invention may further contain other components.
Other components include, for example, cross-linking agents; wetting agents; viscosity modifiers; modifiers; fillers; antistatic agents; UV absorbers; UV stabilizers; dispersants; gelling agents; plasticizers; stabilizers; Preservatives; antifungal agents; antistatic agents can be mentioned, and one or more of these can be used. In addition, other components include oligomers and monomers derived from the monomers used as raw materials for emulsion resins, chain transfer agents, and those in which a reducing agent remains. In addition, the other component referred to here means a non-volatile content (solid content) remaining in the pressure-sensitive adhesive layer obtained by using the water-based resin composition for a pressure-sensitive adhesive of the present invention, and volatilization of an water-based dispersion medium or the like. Contains no ingredients.
The pigment, thickener, defoaming agent, tackifier resin, and other components are mixed with the emulsion resin according to the present invention using, for example, a butterfly mixer, a planetary mixer, a spiral mixer, a kneader, a dissolver, and the like. Can be done.

When the water-based resin composition for a pressure-sensitive adhesive of the present invention contains other components, the ratio of the other components to the entire water-based resin composition for a pressure-sensitive adhesive of the present invention is not particularly limited, but is, for example, 10% by mass or less. It is preferably 5% by mass or less, more preferably 5% by mass or less.

(PH)
The pH of the aqueous resin composition for a pressure-sensitive adhesive of the present invention is not particularly limited, but is preferably 2 to 10, more preferably 3 to 9.5, and even more preferably 7 to 9. The pH of the aqueous resin composition for a pressure-sensitive adhesive of the present invention can be adjusted by adding aqueous ammonia, an aqueous solution of an alkali metal hydroxide, water-soluble amines, or the like to the emulsion resin.
In the present specification, pH can be measured by the method described in Examples described later.

(viscosity)
The viscosity of the aqueous resin composition for a pressure-sensitive adhesive of the present invention may be suitable as a pressure-sensitive adhesive, but is preferably 1000 to 100,000 mPa · s, more preferably 3,000 to 80,000 mPa · s, for example. It is more preferably 5,000 to 60,000 mPa · s, further preferably 7,000 to 40,000 mPa · s, and particularly preferably 9000 to 20,000 mPa · s.
In the present specification, the viscosity can be measured under the conditions described in Examples described later.

Hereinafter, the inventions that are technically closely related to the present invention described above will also be further described.

(Polymer initiator remaining in the composition)
As described above, by setting the content of the persulfate remaining in the water-based resin composition for the pressure-sensitive adhesive to an extremely small amount, the effect of the present invention that achieves both curved surface adhesion and holding power in a well-balanced manner can be exhibited. As described above, even when a polymerization initiator other than the persulfate is used together with or instead of the persulfate as the polymerization initiator, the polymerization initiation remaining in the aqueous resin composition for an adhesive is started. Similar effects of the present invention can be exhibited by setting the content of the agent to a very small amount. In addition, this makes it difficult for the obtained pressure-sensitive adhesive layer to absorb moisture by using a very small amount of the polymerization initiator remaining in the composition, as in the case of using a very small amount of persulfate, and the above balance is achieved. It is considered that this is because it is possible to specifically prevent the collapse. Therefore, the preferable content range of the persulfate remaining in the above-mentioned composition can be rephrased as the preferable content range of the polymerization initiator. That is, the present invention is an aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin and an aqueous dispersion medium, wherein the emulsion resin has a glass transition temperature of −80 to 10 ° C. and contains a (meth) acrylic polymer. The composition is also an aqueous resin composition for a pressure-sensitive adhesive containing 1 ppb to 100 ppm of a polymerization initiator.

The preferable content range of the polymerization initiator remaining in the composition is the same as the above-mentioned preferable content range of the persulfate remaining in the composition. When a polymerization initiator is used, the content of the polymerization initiator is usually 1 ppb or more even if the content is sufficiently reduced. In this respect, the conventional aqueous resin composition for a pressure-sensitive adhesive has started polymerization. It is structurally distinguished from the water-based resin composition for an adhesive obtained without using an agent.
The content of the polymerization initiator is measured by a known method.

Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylbutyronitrile), and 2,2'-in addition to the above-mentioned persulfate. Azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2-diaminopropane) hydroxide, 4,4' -Azobis (4-cyanovaleric acid), 2,2'-azobis (2-methylpropionamidine), azo-based polymerization initiators such as high-molecular-weight azo-based polymerization initiators; hydrogen peroxide, ammonium peroxide, benzoyl peroxide , Peroxides such as p-chlorobenzoyl peroxide and lauroyl peroxide can be mentioned, and one or more of these can be used.

In the aqueous resin composition for a pressure-sensitive adhesive of the present invention, even if a liberated polymerization initiator cannot be detected (0 ppb), the (meth) acrylic polymer contained in the emulsion resin in the composition is a polymerization initiator at the polymer terminal. As long as it has a structure in which the derived group is bonded, it can be distinguished from the conventional aqueous resin composition for a pressure-sensitive adhesive obtained without using a polymerization initiator. That is, the present invention is an aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin and an aqueous dispersion medium, wherein the emulsion resin has a glass transition temperature of −80 to 10 ° C. and is derived from a polymerization initiator at the polymer terminal. The composition comprises a (meth) acrylic polymer having a structure in which a group is bonded, and the composition is also an aqueous resin composition for a pressure-sensitive adhesive having a content of a polymerization initiator of 100 ppm or less.
Here, the preferable upper limit value of the content of the polymerization initiator is as described above.
The method for measuring the content of the polymerization initiator and the type of the polymerization initiator are as described above.

The structure to which the group derived from the polymerization initiator is bonded may be any structure formed by polymerizing the monomer components using the polymerization initiator.

When producing the aqueous resin composition for a pressure-sensitive adhesive of the present invention, the method of using a very small amount of the polymerization initiator as described above is not particularly limited as long as the amount of the polymerization initiator can be used in a very small amount. A method of removing using a known purification method, a conventionally known method of reducing or decomposing a polymerization initiator, or a method in which these are combined can be used.

<Adhesive product of the present invention>
The present invention is also a pressure-sensitive adhesive product having a pressure-sensitive adhesive layer obtained by using the water-based resin composition for a pressure-sensitive adhesive of the present invention.

The pressure-sensitive adhesive layer preferably has an average thickness of 1 to 1000 μm. By setting the thickness to 1 μm or more, the functions required for the pressure-sensitive adhesive layer can be more fully exhibited. Further, when the thickness is 1000 μm or less, the drying property becomes better and a good pressure-sensitive adhesive layer can be formed. The average thickness of the pressure-sensitive adhesive layer is more preferably 3 μm or more, still more preferably 8 μm or more. The average thickness of the pressure-sensitive adhesive layer is more preferably 100 μm or less.
The average thickness is calculated by arbitrarily measuring 5 points with a micrometer.

The pressure-sensitive adhesive product of the present invention may be composed of only a pressure-sensitive adhesive layer, but may further have a base material and a mold release material, if necessary. When the pressure-sensitive adhesive product of the present invention further has a base material, the pressure-sensitive adhesive layer is formed on the surface of the base material. The material of the base material is not particularly limited, and may be any of paper; plastic material; fiber material; metal material such as steel plate. For example, the fact that the base material is paper is one of the preferred forms of use of the aqueous resin composition for a pressure-sensitive adhesive of the present invention. The paper is not particularly limited, and examples thereof include high-quality paper, kraft paper, crepe paper, gloss paper, glassine paper, and the like, and one or more of these can be used. ..
A mold release material may be further formed on the pressure-sensitive adhesive layer. The release material is attached separately from the base material and peeled off to expose the pressure-sensitive adhesive layer when the pressure-sensitive adhesive product is used. Examples of the release material include a release paper such as K-80HS (trade name, manufactured by Sun A. Kaken Co., Ltd.) and a resin film such as a fluororesin and a polyolefin resin.
The thickness of the base material and the release material can be appropriately designed.

For example, the pressure-sensitive adhesive product of the present invention can be suitably obtained by applying the water-based resin composition for a pressure-sensitive adhesive of the present invention on, for example, a substrate, heating it as necessary, and drying it. After forming the pressure-sensitive adhesive layer on the release material, the pressure-sensitive adhesive layer may be transferred onto the base material.
The water-based resin composition for an adhesive of the present invention can be applied using, for example, a brush, a spatula, an air spray, an airless spray, a mortar gun, a ricing gun, or the like.

The pressure-sensitive adhesive product of the present invention has a curved surface adhesion because the amount of persulfate (polymerization initiator) remaining in the water-based resin composition for a pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is reduced to an extremely small amount. It has a well-balanced holding power and can be suitably used as an adhesive tape, an adhesive sheet, a label, or the like. Examples of the adhesive tape include a single-sided tape having an adhesive layer on one side of the base material and a double-sided tape having an adhesive layer on both sides of the base material. Further, the adhesive tape may be a curing tape. As described above, the adhesive product of the present invention is particularly preferably used as a paper label.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "part" means "part by weight" and "%" means "mass%".

In the following, the content of the persulfate in the aqueous resin composition for a pressure-sensitive adhesive was measured as follows.
<Measuring method of persulfate content>
A residual initiator persulfate ion _{(S 2} ^{O 8 -2)} is manufactured by Dionex Thermo Ion Chromatograph DX-320: was measured using a (column manufactured by Dionex AS-16).

Various resin properties were evaluated as follows.
<Non-volatile content (NV)>
About 1 g of the obtained emulsion resin was weighed, and after 150 ° C. × 1 hour in a hot air dryer, the remaining amount of drying was defined as a non-volatile content, and the ratio to the mass before drying was expressed in%.
<pH>
The value at 25 ° C. was measured with a pH meter (“F-23” manufactured by HORIBA, Ltd.).
<Viscosity>
Measurement was performed using a B-type rotational viscometer (“VISCOMETER TVB-10” manufactured by Toki Sangyo Co., Ltd.) under the conditions of 25 ° C. and 12 rpm.

<Polymer glass transition temperature (Tg)>
The Tg of the polymer was calculated from the monomer composition used in each stage using the following formula (1).

In the formula, Tg'is the Tg (absolute temperature) of the polymer. W ₁ ′, W ₂ ′, ... Wn ′ are mass fractions of each monomer with respect to all the monomer components. T ₁ , T ₂ , ... Tn is the glass transition temperature (absolute temperature) of the homopolymer (single polymer) composed of each monomer component.

In addition, Tg calculated from the monomer composition used in all steps was described as "total Tg".
The Tg value of each homopolymer used to calculate the glass transition temperature (Tg) of the polymerizable monomer component by the above calculation formula (1) is shown below.
Methyl methacrylate (MMA): 105 ° C
2-Ethylhexyl acrylate (2EHA): -70 ° C.
Butyl acrylate (BA): -54 ° C
Acrylic acid (AA): 106 ° C
Hydroxyethyl methacrylate (HEMA): 55 ° C.

1. 1. Emulsion resin synthesis example (Synthesis example 1)
19 parts of deionized water was placed in a flask equipped with a dropping funnel, a stirrer, a nitrogen introduction tube, a thermometer, and a reflux condenser. 4.8 parts of 2-ethylhexyl acrylate (2EHA), 91.5 parts of butyl acrylate (BA), 1 part of methyl methacrylate (MMA), 2.5 parts of hydroxyethyl methacrylate (HEMA), 0 part of acrylic acid (AA) in the dropping funnel. .2 parts, 0.1 part of n-dodecyl mercaptan (manufactured by Kao Co., Ltd., trade name: thiocalcol 20), 28.5 parts of deionized water, 0.5 parts of anionic emulsifier reactive with monomer components A preemulsifier (manufactured by ADEKA Corporation, solid content 25%, trade name: Adecaria Soap SR-20) was prepared.
0.4% of the obtained preemulsion was added into the flask, the temperature was raised to 70 ° C. while gently blowing nitrogen gas, and 0.1 part of an 8% ammonium persulfate aqueous solution (8% APS) was added to the flask. Was added to, and emulsion polymerization was started.
Next, the rest of the preemulsion, 5 parts of 8% APS and 5 parts of 4% aqueous sodium sulfite solution (4% SMBS) were uniformly added dropwise into the flask over 320 minutes.
Immediately after the completion of the dropping, 5 parts of a 4% aqueous sodium sulfite solution (4% SMBS) was added, and then the mixture was aged at 70 ° C. for 480 minutes. Then, the mixture was cooled at room temperature and filtered through a 200-mesh wire mesh to obtain the emulsion resin of Synthesis Example 1 (solid content 60%, Tg-52 ° C.).

(Synthesis Examples 2-9)
Emulsion resins of Synthesis Examples 2 to 9 were obtained in the same manner as in Synthesis Example 1 except that the composition was changed as shown in Table 1 below. The Tg of the emulsion resin of Synthesis Examples 2 to 4 and 7 to 9 was −52 ° C., the Tg of the emulsion resin of Synthesis Example 5 was −61 ° C., and the Tg of the emulsion resin of Synthesis Example 6 was −59 ° C. Is.

In each synthesis example, 0.4% of the pre-emulsion was added into the flask in the initial stage (initial state), and the rest of the pre-emulsion was dropped at the time of dropping. However, in Table 1 below, the pre-emulsion is described. The total of these usage amounts is shown separately under the item of "pre-emulsion".
In Table 1 below, 25% SR-20 means an anionic emulsifier (manufactured by ADEKA Corporation, solid content 25%, trade name: Adecaria Soap SR-20) having reactivity with the above-mentioned monomer component. However, 25% LA-16 means polyoxyethylene alkyl ether ammonium sulfate (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solid content 25%, trade name: Hytenol LA-16).

2. 2. Manufacturing method of Example (Example 1)
100 parts of the emulsion resin of Synthesis Example 1 was stirred well and neutralized with 25% aqueous ammonia solution. Subsequently, Superester (registered trademark) E-788 (manufactured by Arakawa Chemical Industry Co., Ltd .; solid content 50%), which is a tackifying resin, was added so as to have a solid content of 4.0 parts, and a thickening agent "Adecanol UH" was further added. -420 "(manufactured by ADEKA Co., Ltd.) 0.5 to 5 parts are added in two or three steps while observing the state of viscosity (after addition, 30 minutes to 60 minutes to stabilize the viscosity). (Continued stirring for minutes), the viscosity was adjusted to obtain an emulsion-type pressure-sensitive adhesive composition having a solid content of 60%, a pH of 8.0, and a viscosity of 13,000 mPa · s (25 ° C., a value measured with a B-type viscometer). ..
Using this emulsion-type pressure-sensitive adhesive composition, apply it to a release paper (“K-80HS”; manufactured by Sun A. Kaken Co., Ltd.) so that the thickness after drying becomes 16.5 μm, and dry it at 105 ° C. for 90 seconds. By doing so, a pressure-sensitive adhesive layer was formed. ^{A commercially available gloss paper (90 g / m 2} ) as a base material is attached to the surface of this pressure-sensitive adhesive layer (the coated surface after drying), and cured at 23 ° C. in a 65% RH atmosphere for 3 days, and then the pressure-sensitive adhesive sheet (adhesive sheet (90 g / m 2)) is attached. (With release paper) was prepared.

(Examples 2 to 7)
An adhesive sheet (with a paper pattern) was produced in the same manner as in Example 1 except that the emulsion resin of Synthesis Example 1 was changed to the emulsion resin of Synthesis Examples 2 to 7.
(Comparative Examples 1 and 2)
An adhesive sheet (with a paper pattern) was produced in the same manner as in Example 1 except that the emulsion resin of Synthesis Example 1 was changed to the emulsion resin of Synthesis Examples 8 and 9.

3. 3. Evaluation method for adhesive properties, etc. <Curved surface adhesion>
As the adherend, a round bar made of polypropylene (denoted as PP in the column of curved surface adhesion in Table 1 above) and a round bar made of polyethylene (denoted as PE in the column of curved surface adhesion in Table 1 above) having a diameter of 15 mm. A round bar was used.
Attach the adhesive sheet to the curved surface of the adherend along the circumference of the adherend with a width of 20 mm, which corresponds to the length of half a circumference, in an atmosphere with a temperature of 23 ° C and a relative humidity of 65%. After standing for 7 days, the state of the test piece was visually observed, and the curved surface adhesion was evaluated based on the following evaluation criteria.

(Evaluation criteria)
25 points: No peeling of the end 20 points: Peeling of the end is less than 0.5 mm 15 points: Peeling of the end is 0.5 mm to 5 mm
0 point: Peeling of the end is larger than 5 mm

<Holding power>
The holding force was measured according to the method described in JIS: Z0237: 2009 Adhesive Tape / Adhesive Sheet Test Method. Specifically, a stainless steel sheet is used as an adherend, and after wiping off the dirt on the surface of the stainless steel sheet, the surface is washed with acetone and dried in an oven, and the temperature is 23 ° C. and the relative humidity is 65%. The adherend was stored in the atmosphere for 24 hours or more.
The adhesive sheet was cut to a width of 25 mm, and the obtained test piece was placed on the stainless steel plate in an atmosphere having a temperature of 23 ° C. and a relative humidity of 65%. The test piece was crimped by reciprocating. The crimped test piece was left in an atmosphere with a temperature of 40 ° C. and a relative humidity of 65% for 20 minutes, and then a 1 kg weight was attached to the end of the adhesive sheet and hung and allowed to stand in the atmosphere for 1000 minutes. The time required for the adhesive sheet to peel off and the misalignment length of the adhesive sheet 1000 minutes after the start of the test were measured, and the holding power was evaluated based on the following evaluation criteria.

(Evaluation criteria)
50 points: Adhesive sheet does not peel off after 1200 minutes 40 points: Adhesive sheet peels off in 800 minutes or more and less than 1200 minutes 30 points: 400 minutes or more, adhesive sheet peels off in less than 800 minutes 0 points: 400 Adhesive sheet peels off in less than a minute

<Comprehensive evaluation>
Comprehensive evaluation was performed by totaling the evaluation scores for each physical property. An adhesive sheet having a curved surface adhesion (PP, PE) of 15 points or more and a holding power of 30 points or more and an overall evaluation of 60 points or more has a good balance between curved surface adhesion and holding power. It is compatible and has passed. Further, from the viewpoint of curved surface adhesion (PP, PE) and holding power, it can be said that the higher the total evaluation score is, the better it is. An adhesive sheet having at least one evaluation of 0 points for any of the physical properties is rejected.

In the pressure-sensitive adhesive sheets of Examples 1 to 7, the amount of residual APS in the emulsion-type pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer is 100 ppm or less (within the range of 0.1 to 90 ppm), and all of them are poorly adhesive polyolefins. It has a well-balanced balance between curved surface adhesion to the system adherend and holding power. The pressure-sensitive adhesive sheet of Comparative Example 1 had good curved surface adhesion, but the residual APS amount was 170 ppm, and it is considered that the holding power was lowered because the adhesive sheet was plasticized by water. The pressure-sensitive adhesive sheet of Comparative Example 2 has a residual APS amount of 200 ppm, and in order to increase the holding power in a system having a large residual APS amount, the molecular weight is adjusted without using a chain transfer agent (thiocalcol 20) during the production of the emulsion resin. Although it is increased, as a result, it is considered that the holding power is good but the adhesiveness to the curved surface is lowered. That is, when the amount of the remaining APS is large, the holding force and the adhesiveness to the curved surface cannot be balanced.
Since all of the emulsion resins according to this example are obtained by polymerizing a (meth) acrylic monomer using an ammonium persulfate aqueous solution as a polymerization initiator, ammonium persulfate is derived from the terminal of the (meth) acrylic polymer. It has a structure in which the groups of

Claims (6)

An aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin and an aqueous dispersion medium.
The emulsion resin has a glass transition temperature of −80 to 10 ° C. and contains a (meth) acrylic polymer.
The monomer component for obtaining the (meth) acrylic polymer is 0.01 to 5% by mass of the (meth) acrylic acid-based monomer and 0.01 to 5% by mass of the (meth) acrylic acid-based monomer in 100% by mass of the total monomer component, and other than the (meth) acrylic acid-based monomer. Contains 95-99.99% by mass of (meth) acrylic monomer
The composition is an aqueous resin composition for a pressure-sensitive adhesive, which further contains 1 ppb to 100 ppm of a persulfate. An aqueous resin composition for a pressure-sensitive adhesive containing an emulsion resin and an aqueous dispersion medium.
The emulsion resin contains a (meth) acrylic polymer having a glass transition temperature of −80 to 10 ° C. and a structure in which a group derived from a persulfate is bonded to the polymer terminal.
The monomer component for obtaining the (meth) acrylic polymer is 0.01 to 5% by mass of the (meth) acrylic acid-based monomer and 0.01 to 5% by mass of the (meth) acrylic acid-based monomer in 100% by mass of the total monomer component, and other than the (meth) acrylic acid-based monomer. Contains 95-99.99% by mass of (meth) acrylic monomer
The composition is an aqueous resin composition for a pressure-sensitive adhesive, characterized in that the content of persulfate is 100 ppm or less. The aqueous resin composition for a pressure-sensitive adhesive according to claim 1 or 2 , wherein the composition further contains a component derived from an emulsifier having a reactive unsaturated double bond. The method for producing an aqueous resin composition for an adhesive according to any one of claims 1 to 3.
The production method is a method for producing an aqueous resin composition for a pressure-sensitive adhesive, which comprises a step of adding a reducing agent to the reaction system after the completion of dropping the raw material of the emulsion into the reaction system. The pressure-sensitive adhesive according to claim 4, wherein in the step of adding the reducing agent, the amount of the reducing agent added is 0.1 to 10% by mass with respect to 100% by mass of all the monomer components used as the raw material of the emulsion. A method for producing an aqueous resin composition. A pressure-sensitive adhesive product comprising a pressure-sensitive adhesive layer obtained by using the aqueous resin composition for a pressure-sensitive adhesive according to any one of claims 1 to 3.