JP4572720B2 - Method for producing water-dispersed acrylic resin, and water-dispersed acrylic pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet produced thereby - Google Patents

Description

  The present invention relates to a method for producing a water-dispersed acrylic resin. In particular, the present invention relates to a method for producing a water-dispersed acrylic pressure-sensitive adhesive resin excellent in initial adhesion to an adherend having an uneven surface such as urethane foam, and a water-dispersed acrylic pressure-sensitive adhesive produced thereby. The present invention relates to a composition and an adhesive sheet.

  In industrial fields such as automobiles, building materials, OA, and home appliance industries, adhesive tapes are used in large quantities for the purpose of bonding to parts and members such as metals, various plastics, and foam bodies. In these industrial applications, more demanding performance is required, such as adhesion to adherends that are very difficult to bond, adhesion reliability under severe environmental conditions, and adhesion in a small area. In order to meet such demanding performance requirements, conventionally, a pressure-sensitive adhesive composition mainly composed of a solution polymerization type acrylic resin has been used. However, since the pressure-sensitive adhesive composition using these solution polymerization type acrylic resins is synthesized in an organic solvent, the volatilization of the solvent when producing a pressure-sensitive adhesive product such as pressure-sensitive adhesive synthesis, stirring, and coating, Due to the volatilization of the solvent remaining in the adhesive when the adhesive product is used in the market, the effects on the human body and the environment are becoming problems. In addition, organic solvents themselves, and low-molecular weight monomers in adhesives that volatilize with organic solvents, as well as irritating odors such as additives, are regarded as problems, and there is a demand for solventless adhesive compositions that do not use organic solvents. ing. Among these, pressure-sensitive adhesive compositions using water-dispersed acrylic resins that can use existing production equipment and have high safety are demanded.

  A water-dispersed acrylic resin is produced by forming fine particles of a monomer in an aqueous medium by using an emulsifier or a surfactant, and polymerizing in the fine particles. In such a production method, Generally, it is difficult to control the molecular weight and the resin structure. In a state where the monomer is highly concentrated compared to solution polymerization, even if only a monofunctional monomer is used, radicals are easily generated at sites other than radically polymerizable unsaturated double bonds by the polymerization initiator, A branched or cross-linked resin is likely to be formed. Therefore, the pressure-sensitive adhesive resin containing a resin having a branched or crosslinked structure has a molecular chain that is not flexible and has an excessive cohesive force. For example, it is difficult to adhere to a material that has unevenness on the surface such as urethane foam. Was hardly deformed according to the unevenness of the surface, and the adhesiveness, particularly the initial adhesiveness, was poor.

  As means for improving the adhesion and peel resistance of the adhesive tape to the adherend, the solvent-soluble content in the total solid content is 20 to 90% by weight, the glass transition temperature is -20 ° C or less, and the weight An acrylic pressure-sensitive adhesive composition containing an acrylic resin having an average molecular weight of 100,000 or more has been proposed (see Patent Document 1). However, the pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition obtained by this technique has insufficient initial adhesion to an adherend having an uneven surface such as urethane foam. In addition, in the disclosed production method, depending on the type of initiator and polymerization conditions, it is easy to generate amorphous aggregates in which emulsified fine particles are fixed or fused together. May be difficult.

JP 2003-105298 A (Claims)

Therefore, an object of the present invention is to provide a method for producing a water-dispersed acrylic resin in which the branched or crosslinked structure is reduced as much as possible, which has been difficult with the conventional method for producing a water-dispersed acrylic resin. is there.
Another object of the present invention is to provide a method for producing a water-dispersed acrylic resin in which fine particles emulsified at the time of production are fixed or fused together to generate an amorphous aggregate. .
Moreover, the other object of this invention is to provide the manufacturing method of the acrylic resin for water dispersion type adhesives which solves the said subject.
In addition, another object of the present invention is to solve the above-mentioned problems, and even a material that has unevenness on the surface, such as urethane foam, is easily deformed according to the unevenness of the surface, and has an adhesive property. Another object of the present invention is to provide a method for producing a water-dispersed acrylic resin for pressure-sensitive adhesives having particularly good initial adhesion.
Furthermore, another object of the present invention is to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using a water-dispersed acrylic resin for pressure-sensitive adhesives that solves the above problems.

  Various studies have been made to solve the above problems. In the emulsion polymerization, a redox system, a thermal decomposition system, and other catalyst systems are used. In the case of an acrylic resin, a redox initiator is widely used. The reason for this is that the catalyst is easily decomposed even at low temperatures, and the polymerization proceeds stably (hardly influenced by the temperature), and the amount of catalyst can be reduced. Initiators are widely used.

  However, it has been found that when emulsion polymerization is performed using a redox initiator, a large number of branched or crosslinked polymers are produced. Such a pressure-sensitive adhesive resin containing a lot of resins having a branched or crosslinked structure has a molecular chain that is not flexible and has an excessive cohesive force. On the other hand, deformation according to the unevenness of the surface hardly occurs, and the adhesiveness, particularly the initial adhesiveness, is poor. The inventors of the present invention have studied an initiator that replaces the redox initiator, and have found that the branching reaction can be suppressed by using a water-soluble azo initiator. The water-dispersed acrylic resin produced using an azo initiator has a low content of branched or cross-linked resin compared to the case where other initiators are used, and has high flexibility. A water-dispersed acrylic resin can be obtained. As a result, it is possible to develop a high initial adhesive force for an adherend having an uneven surface. Further, as a result of further investigation, when a cationic water-soluble azo initiator is used as the azo initiator, the emulsion stability is somewhat unstable, and the emulsified fine particles are fixed or fused together to form an irregular shape. In addition, it was found that it is effective to use a nonionic or anionic water-soluble azo initiator in order to prevent aggregation of emulsified fine particles. The present invention has been completed.

  That is, the present invention emulsifies a (meth) acrylic acid ester monomer and a vinyl monomer copolymerizable therewith with an acidic group in an aqueous medium using a nonionic or anionic water-soluble azo initiator. A method for producing a water-dispersed acrylic resin to be polymerized is provided.

The present invention also includes a (meth) acrylic acid ester monomer, a vinyl monomer copolymerizable with the monomer, a surfactant A having a copolymerizable double bond, and a nonionic or anionic water solution. A first step of initiating emulsion polymerization in an aqueous medium using a water-soluble azo initiator,
It is a method for producing a water-dispersed acrylic resin by sequentially performing the second step of adding one or more surfactants B having a copolymerizable double bond,
Provided is a method for producing a water-dispersed acrylic resin in which the copolymerizable Ra of the surfactant A and the copolymerizable Rb of the surfactant B are Ra <Rb with respect to the (meth) acrylic acid ester monomer. Is.

  The present invention also provides a water-dispersed acrylic pressure-sensitive adhesive composition using the water-dispersed acrylic resin obtained by the above production method.

  Moreover, this invention provides the adhesive sheet provided with the water-dispersed acrylic adhesive composition as an adhesive layer.

  According to the production method of the present invention, it is possible to produce a water-dispersed acrylic resin in which the branched or crosslinked structure is reduced as much as possible without generating aggregates. The pressure-sensitive adhesive composition containing the acrylic pressure-sensitive adhesive resin obtained by this method has high initial adhesion to an adherend having irregularities on the surface and can exhibit appropriate cohesiveness.

  A known compound can be used as the (meth) acrylic acid alkyl ester used in producing the water-dispersed acrylic resin by the production method of the present invention. Examples of such compounds include ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) ) Acrylate, isoamyl (meth) acrylate, isodecyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-chloro-2-hydroxy Propyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, nonylphenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) Acrylate, glycidyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, nonyl phenoxyethyl tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl (meth) acrylate. In this specification, (meth) acrylic acid means acrylic acid or methacrylic acid, and the same applies to derivatives of acrylic acid or methacrylic acid.

  Among these, it is preferable to use a compound represented by the following formula (1).

（式中、R₁は分岐鎖を有していても良い炭素数４〜１８のアルキル基を表し、Ｘは水素原子又はメチル基を表す。）

(In the formula, R ₁ represents an alkyl group having 4 to 18 carbon atoms which may have a branched chain, and X represents a hydrogen atom or a methyl group.)

  The copolymerization ratio of the monomer represented by the formula (1) in the acrylic copolymer resin is preferably 60 to 98% by mass, more preferably 80 to 97% by mass with respect to all monomers. If it is the said range, adhesive force is favorable.

In order to use a water-dispersed acrylic resin as a pressure-sensitive adhesive resin, among the monomers represented by the formula (1), R ¹ in the formula (1) may have a branched chain having 8 to 8 carbon atoms. It is preferable that the monomer represented by formula (1) is a polymer represented by formula (1), and the monomer represented by formula (1) is polymerized alone to produce a homopolymer. A monomer having a glass transition point of −10 ° C. or lower is preferable. Such monomers include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, dodecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, isodecyl acrylate, isostearyl acrylate, cyclohexyl acrylate, and the like. The use ratio of such a monomer is preferably 10 to 70% by mass with respect to the total monomers. More preferably, it is 20-50 mass%. If it is the said range, adhesive force is favorable.

  Examples of vinyl monomers that can be copolymerized and have an acidic group include (meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, and the like. Among these, one or more monomers are used.

  It is preferable to use the addition amount of the above-mentioned copolymerizable vinyl monomer having an acidic group in the range of 0.5 to 15 parts by mass with respect to all monomers. More preferably, it is 1.5-10 mass parts, More preferably, it is the range of 2-8 mass parts. If it is the said range, the stability (polymerization stability) of the emulsion at the time of water-dispersion type acrylic resin emulsion polymerization will be favorable. Furthermore, when the pressure-sensitive adhesive composition is applied, it can be applied without agglomeration of the resin, and the mechanical stability during application is excellent.

  In the present invention, a nonionic or anionic water-soluble azo initiator is used instead of a cationic water-soluble azo initiator. Specific examples of the cationic water-soluble azo initiator include 2,2′-azobis (2-methylpropionamidine) disulfate and 2,2′-azobis (2-amidinopropane) dihydrochloride. However, when these are used, for example, when an anionic surfactant is used, an ion pair is likely to be generated, the stability of the emulsion is lowered, and as a result, aggregates are generated and production is difficult. On the other hand, the nonionic or anionic water-soluble azo initiator does not generate an ion pair with the anionic surfactant, so that the stability of the emulsion is maintained and the production without the generation of aggregates becomes possible. .

  As the nonionic or anionic water-soluble azo initiator used in the present invention, known ones can be used. For example, as an anionic water-soluble azo initiator, an azo initiator having a carboxyl group or a hydroxyl group can be mentioned. Specifically, V-501 [made by Wako Pure Chemical Industries Ltd.] etc. are mentioned. The structural formula of V-501 is represented by Formula 2. V-501 is an anionic water-soluble azo initiator.

  The 10-hour half-life temperature of the nonionic or anionic water-soluble azo initiator used in the production method of the present invention is preferably 80 ° C. or lower. More preferably, the 10-hour half-life temperature is 70 ° C. or lower.

  The polymerization temperature in the production method of the present invention is preferably set to a temperature lower than the 10-hour half-life temperature of the initiator (however, limited to the range in which the initiation reaction is performed). By carrying out the polymerization at a temperature lower than the 10-hour half-life temperature of the initiator, the radical concentration can be kept low and the branching reaction can be restrained, so that a highly flexible adhesive resin can be produced. High initial adhesion to an adherend having irregularities on the surface such as foam, and excellent peeling resistance can be exhibited. Preferably, the temperature is set to a temperature lower by 5 to 30 ° C, more preferably 10 to 30 ° C lower than the 10-hour half-life temperature. However, it is not preferable at a temperature lower than 30 ° C. because polymerization hardly proceeds.

  In the case of an azo initiator having a 10-hour half-life temperature of 69 ° C, the polymerization temperature is preferably 64 ° C to 39 ° C. More preferably, it is 59 degreeC-39 degreeC.

  The initiator addition amount is preferably in the range of 0.01 part to 5.0 parts with respect to the total monomer amount. When the amount is 0.5 parts or less, the polymerization reaction does not easily proceed and the production becomes difficult. If it is 5.0 parts or more, the branching reaction tends to proceed, and the flexibility of the pressure-sensitive adhesive is lowered.

  As an emulsifier used in emulsion polymerization, an anionic surfactant is widely used. In general, anionic surfactants have a higher surface charge on the formed particles than nonionic or cationic surfactants, and the use of anionic surfactants improves the stability of the emulsion during emulsion polymerization. It becomes good. In the production method of the present invention, a known surfactant can be used, but an anionic surfactant is preferably used.

As the anionic surfactant, known and publicly used ones are used. Examples include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl sulfosuccinate, etc. It is done.
One or more of these are used.

  In an anionic surfactant, particles are present independently due to electrical repulsion, so that even when the radical concentration is low, the polymerization stability is kept high and production without occurrence of aggregates becomes possible. The anionic surfactant is preferably used in the range of 0.5 part to 2.0 parts by weight with respect to 100 parts by weight of the acrylic monomer. If it is the said range, emulsification stability, adhesive force, and water resistance will be favorable.

  Among the anionic surfactants, an anionic surfactant having a copolymerizable double bond is preferable. When manufacturing water-dispersed acrylic pressure-sensitive adhesive resins, it is widely used to use surfactants during emulsification, but the surfactants are not subjected to chemical or physical constraints and are adhered in a free state. If it remains in the agent, the adhesive force to the adherend tends to decrease, and the cohesive force of the pressure-sensitive adhesive itself tends to decrease. In addition, the water resistance tends to be adversely affected. However, an anionic surfactant having a copolymerizable double bond is copolymerized with a (meth) acrylic acid ester monomer that becomes a pressure-sensitive adhesive resin, and is incorporated and fixed in the molecular chain. Adhesive performance such as force and influence on water resistance are small, and a high initial adhesion force to an adherend having irregularities on the surface and an excellent cohesive force can be expressed.

  In addition, anionic surfactants having a copolymerizable double bond can be used in a larger amount than known ionic surfactants. Therefore, higher emulsifying power can be obtained, and production without the generation of aggregates is possible.

  As the anionic surfactant having a copolymerizable double bond, it is possible to use two or three or more types having different copolymerizability with the (meth) acrylic acid ester which is the main raw material of the adhesive resin. preferable. In particular, it is preferable to use one type or two or more types of anionic surfactant A and relatively high anionic surfactant B, which are relatively low in copolymerizability with the main component monomer. In addition, when using the anionic surfactant B having a relatively high copolymerizability with the main component monomer, it is preferable to avoid the use at the start of the polymerization and to add it as needed after the polymerization has progressed. When an anionic surfactant having a copolymerizable double bond is added to the end of the molecular chain where the polymerization reaction is proceeding, the anionic surfactant tries to add polymerization to the end (meta). Inhibits the reaction of the acrylate monomer. That is, the anionic surfactant having a copolymerizable double bond inhibits the copolymerization reaction of the (meth) acrylate monomer. Therefore, among the anionic surfactants having a copolymerizable double bond, the anionic surfactant B, which is relatively easy to react with the (meth) acrylate monomer, is used at the initial stage of polymerization of the (meth) acrylate monomer. If used, the reactivity at the start of polymerization is significantly reduced, and the initiation reaction may not proceed. Further, as the polymerization proceeds, the anionic surfactant B is incorporated into the main chain, and the surface active power may be reduced in the later stage of the polymerization time, which may reduce the stability of the emulsion.

  Therefore, it is preferable to use an anionic surfactant A having a relatively low copolymerization property in the initial stage of polymerization. By doing so, the amount of the surfactant in the aqueous medium does not decrease at the initial stage of polymerization, and emulsion polymerization can be performed relatively stably while the polymerization reaction proceeds. However, since the anionic surfactant A is also taken into the main chain by the polymerization reaction and decreases, the anionic surfactant B having a relatively high copolymerizability with the main component monomer is added at the end of the polymerization. It is preferable. By doing so, the amount of the unreacted surfactant at the end of the polymerization reaction can be reduced, and the amount of the surfactant remaining in the pressure-sensitive adhesive in a free state can be suppressed as much as possible. Furthermore, at the end of the polymerization, it is preferable to add a polymerization initiator, since unreacted surfactant present in the aqueous medium can be incorporated into the polymer chain of the acrylic resin. As a result, it is possible to further reduce the impact on adhesive performance and water resistance such as adhesive strength and cohesive strength of acrylic resin, higher initial adhesive strength for adherends having irregularities on the surface, And an excellent cohesive force can be expressed.

Therefore, as a method for producing the water-dispersed acrylic resin of the present invention,
(1) a (meth) acrylic acid ester monomer, a vinyl monomer copolymerizable therewith and having an acidic group, a surfactant A having a copolymerizable double bond, and a nonionic or anionic water-soluble azo type A first step of initiating emulsion polymerization in an aqueous medium using an initiator;
(2) A production method for sequentially performing the second step of adding one or more surfactants B having a copolymerizable double bond,
(3) For the (meth) acrylic acid ester monomer, the copolymerizable Ra of the surfactant A and the copolymerizable Rb of the surfactant B are:
It is preferable to use a method for producing a water-dispersed acrylic resin in which Ra <Rb.

Comparison of the copolymerizability of anionic surfactants A and B having a copolymerizable double bond can be confirmed by the following method.
(1) In the composition of the (meth) acrylic acid ester monomer for producing the water-dispersed acrylic resin and the polymerization reaction conditions, the polymerization reaction is performed using the surfactant X having a copolymerizable double bond. performed, (based on the charged total monomer weight, the ratio of the mass of the monomer was converted to polymer) conversion ratio of (meth) acrylic acid ester monomer after the polymerization initiation time T after obtaining the P _X.
(2) A polymerization reaction is performed using a surfactant Y having a copolymerizable double bond in the same composition and polymerization reaction conditions of the (meth) acrylic acid ester monomer as in (1). after T time (meth) obtaining the conversion ratio P _Y acrylic acid ester monomer.

If the surfactant having a copolymerizable double bond for the (meth) acrylate monomer is relatively high in copolymerizability, it easily enters the polymer chain and inhibits the progress of the polymerization reaction of the (meth) acrylate monomer. . As a result, the polymerization ratio of the (meth) acrylic acid ester monomer at T time after the start of polymerization is lowered. Therefore, when P _X > P _Y , the copolymerizability of the surfactant X is lower than that of the surfactant Y. In this case, the surfactant X is a surfactant A having a relatively low copolymerization property, and the surfactant Y is a surfactant B having a relatively high copolymerization property.

  Examples of the anionic surfactant having a copolymerizable double bond include compounds of formula (3) and formula (4).

（式中、Rはアルキル基、ｎは１以上の整数を示す。）

(In the formula, R represents an alkyl group, and n represents an integer of 1 or more.)

  Commercially available products include Aqualon KH-10 (Daiichi Kogyo Seiyaku Co., Ltd.), Latemuru S-180 (Kao Co., Ltd.) and the like. The structure of Aqualon KH-10 is shown in Formula (5), and the structure of Latemul S-180 is shown in Formula 6.

  Next, examples of the polymerization method of the acrylic pressure-sensitive adhesive composition of the present invention include a batch polymerization method, a pre-emulsion method, a monomer dropping method, and the like. Among these, the pre-emulsion method in which water, a monomer, and an emulsifier previously mixed are added dropwise is preferable because of high polymerization stability.

In the pre-emulsion method, after dropping a part of an emulsion prepared in advance, an anionic surfactant having higher copolymerizability with the (meth) acrylic acid ester is dropped together with the remaining emulsion. It is preferable to perform additional dropwise addition within the range of 10 to 90% of the total dropwise addition amount from the start to polymerize the reactive monomer.
By adding an anionic surfactant that is highly copolymerizable with (meth) acrylic acid ester, the adhesive strength to adherends with irregularities on the surface, such as urethane foam, is maintained without sacrificing polymerization stability. It can be improved further. In addition, by additional dropping in the range of 10 to 90% of the total dropping amount from the start of dropping, the influence on polymerization stability can be reduced, and production without occurrence of aggregates is possible. Become.

  Moreover, you may use a chain transfer agent for superposition | polymerization. By using a chain transfer agent, the molecular weight of the acrylic polymer can be adjusted. Examples of the chain transfer agent include known chain transfer agents such as lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. Can be used.

  Moreover, a crosslinking agent can be used in order to improve the cohesive force of an adhesive. As the crosslinking agent, known isocyanates, epoxy compounds, aziridine compounds, polyvalent metal salts, metal chelates, organic peroxides, and the like can be used.

  As an index of the degree of cross-linking, the value of the gel fraction for measuring the insoluble content after the pressure-sensitive adhesive layer is immersed in toluene for 24 hours is used. The gel fraction is preferably 20 to 50% by mass. More preferably, it is 25-40 mass%, More preferably, it is 27-35 mass%. If it is the range of 20-50 mass%, both the initial stage adhesive force and the cohesion force to the to-be-adhered body which has an unevenness | corrugation on the surface like a urethane foam are favorable.

  Moreover, tackifying resin can be added for the purpose of improving the adhesiveness to the to-be-adhered body which has an unevenness | corrugation on the surface like a urethane foam.

  As tackifying resins, known aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins and other petroleum resins, rosin resins, rosin ester resins, disproportionated rosin resins, polymerized rosin resins, polymerization Rosin resin such as rosin ester resin and rosin phenol resin, terpene resin, terpene phenol resin, coumarone indene resin and the like can be used.

  As for the addition amount of tackifying resin, 10-40 mass parts is preferable. More preferably, it is 15-35 parts, More preferably, it is 20-35 parts. Good initial adhesion, low-temperature adhesion, and cohesive strength to adherends and polyolefin-based materials that have irregularities on the surface, such as urethane foam, by adding the amount of tackifying resin in the range of 10 to 40 parts by mass It is.

  In addition, the pressure-sensitive adhesive composition includes, as necessary, plasticizers, softeners, antioxidants, glass and plastic fibers, balloons, beads, metal powders and the like as long as the desired effects of the present invention are not impaired. Known materials such as fillers, colorants such as pigments and dyes, pH adjusters, film forming aids, leveling agents, thickeners, water repellents and antifoaming agents can be optionally added.

  Next, an adhesive sheet provided with the water-dispersed adhesive composition of the present invention as an adhesive layer will be described.

  The pressure-sensitive adhesive composition may be used as a pressure-sensitive adhesive layer for a substrate-less double-sided sheet that does not have a substrate. Moreover, it is good also as an adhesive sheet on which the adhesive layer was laminated | stacked on at least one surface of the support body, for example, there exists a single-sided adhesive sheet in which the adhesive layer was laminated | stacked only on one surface, and a double-sided adhesive sheet laminated | stacked on both surfaces.

  The pressure-sensitive adhesive composition may be used as a pressure-sensitive adhesive layer for a substrate-less double-sided sheet that does not have a substrate. Moreover, it is good also as an adhesive sheet by which the adhesive layer was laminated | stacked on the at least one surface of the support body. For example, there are a single-sided pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is laminated on only one side, and a double-sided pressure-sensitive adhesive sheet laminated on both sides.

  To form a pressure-sensitive adhesive layer on a support, a method of directly applying a pressure-sensitive adhesive solution on a support with a roll coater or a die coater, or once forming a pressure-sensitive adhesive layer on a separator and then transferring it to the support Use the method. The preferable thickness of the pressure-sensitive adhesive layer after drying is 30 to 300 μm, preferably 50 to 200 μm.

  The support used for the pressure-sensitive adhesive sheet is a known film such as a polyester film, a polypropylene film, a polyethylene film, a polyimide film or the like, a foam body such as urethane, polyethylene or rubber, a nonwoven fabric, a cloth, a metal foil or paper. Can be used.

  The form of the pressure-sensitive adhesive sheet is not particularly limited, and may be a sheet or roll-like product form, or may be a tape form.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
(Experiment to confirm copolymerization ratio)

(Confirmation experiment 1)
In a container, 10 parts of an anionic surfactant Latemul S-180 (manufactured by Kao Corporation; active ingredient 50%) having a copolymerizable double bond and 100 parts of deionized water were uniformly dissolved. Thereto, 245 parts of 2-ethylhexyl acrylate, 245 parts of n-butyl acrylate, 15 parts of acrylic acid and 0.5 part of lauryl mercaptan were added and emulsified to prepare Emulsion A (625.5 parts). Next, 0.1 part of E-118B and 350 parts of deionized water are placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, and the temperature is raised to 55 ° C. while blowing nitrogen. Warm up. Under stirring, an anionic water-soluble polymerization initiator V-501 [manufactured by Wako Pure Chemical Industries, Ltd .; active ingredient 100%] 5 parts of an aqueous solution (active ingredient 5%) was added, and then emulsion A was 6.2. The polymerization reaction was carried out for 1 hour while maintaining 55 ° C. Subsequently, a part (619.3 parts) of the remaining emulsion A and 40 parts of an anionic water-soluble polymerization initiator V-501 aqueous solution (active ingredient 5%) were placed in a reaction vessel using a separate dropping funnel. While maintaining at 55 ° C., the polymerization was carried out by dropping over 6 hours. It was 98% or more when the conversion 1 hour after completion | finish of dripping was measured.

(Confirmation experiment 2)
Instead of adding 10 parts of anionic surfactant Latemul S-180 having a copolymerizable double bond, anionic surfactant Aqualon KH-10 having a copolymerizable double bond [Daiichi Kogyo Seiyaku Co., Ltd. , 100% active ingredient] The same operation as in (Confirmation Experiment 1) was performed except that 5 parts were used. It was 70% or less when the conversion of 1 hour after completion | finish of dripping was measured.

In Confirmation Experiment 1 using the anionic surfactant Latemul S-180 having a copolymerizable double bond, the conversion after 1 hour after the completion of dropping was 98% or more.
In Confirmation Experiment 2 using the anionic surfactant Aqualon KH-10 having a copolymerizable double bond, the conversion after 1 hour after the completion of dropping was 70% or less.
From this result, it was confirmed that the copolymerizability (R _S ) of Latemulu S-180 in the above monomer composition and the copolymerization property (R _K ) of Aqualon KH-10 were R _S <R _K. AQUALON KH-10 has better copolymerization with respect to the monomer composition than LATEMUL S-180, and is thus more easily copolymerized and easily incorporated into the polymer chain. As a result, the copolymerization reaction between the monomers is inhibited, and the conversion ratio after a certain time is lowered.

At the end of the polymerization reaction, it is theoretically assumed that all the charged monomers are converted into a polymer (conversion) and become a non-volatile substance. Therefore, when the total mass of the aqueous medium and all the charged raw materials is W _A and the total charged mass of the monomers is W _M , the theoretical non-volatile fraction R _EP (%) of the polymer at the end of the polymerization reaction is expressed by the following formula (1) It can ask for.
R _EP (%) = (W _M / W _A ) × 100 (1)

On the other hand, the total mass of the sample when sampling at any time the course of the polymerization reaction and W _tA, when the nonvolatile content of the mass in the sample was W _t, during W _t, and generated so far The mass W _{tP of the} polymer and the mass W _tS of non-volatile components other than the monomer, such as the residue of the surfactant and polymerization initiator contained from the time of preparation, are included. Here, if the mass ratio of components other than the monomers to total aqueous media and charged all raw material and R _S, W _tS is a value obtained by multiplying the R _S to W _tA. Therefore, the non-volatile fraction R _tP (%) of the produced polymer at an arbitrary time during the polymerization reaction can be obtained by subtracting W _tS from W _t and can be obtained by the following equation (2).
R _tP (%) = (W _t −W _tS ) × 100 / W _tA (2)
(W _tS = W _tA × R _S )
It becomes.
From the above, the conversion at an arbitrary time during the polymerization reaction is calculated by the following equation (3).
Conversion [%] = (R _tP / R _EP ) × 100 (3)

Specifically, conversion during polymerization is determined by the following method. The reactant is sampled from the reaction vessel, and the mass (W _tA ) is measured. After drying at 108 ° C. for 90 minutes to remove volatile substances such as water and acrylic monomer, the mass (W _t ) of the residue is measured. Then, a conversion by _R EP (%) calculated by the equation (1).

Example 1
(1) Preparation of Emulsion A A container was charged with 20 parts of the anionic surfactant Latemul E-118B (Kao Corporation; active ingredient 25%) and 100 parts of deionized water and dissolved uniformly. Thereto, 245 parts of 2-ethylhexyl acrylate, 245 parts of n-butyl acrylate, 15 parts of acrylic acid and 0.5 part of lauryl mercaptan were added and emulsified to obtain an emulsion A (625.5 parts).

(2) Production of water-dispersed acrylic polymer 0.1 parts of E-118B and 350 parts of deionized water were placed in a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel. The temperature was raised to 55 ° C. while blowing nitrogen. Under stirring, an anionic water-soluble polymerization initiator V-501 [manufactured by Wako Pure Chemical Industries, Ltd .; active ingredient 100%] 5 parts of an aqueous solution (active ingredient 5%) was added, and then emulsion A was 6.2. Polymerization was performed for 1 hour while maintaining 55 ° C. Subsequently, a part of the remaining emulsion A (619.3 parts) and 40 parts of V-501 aqueous solution (active ingredient 5%) were added for 8 hours while maintaining the reaction vessel at 55 ° C. using a separate dropping funnel. The solution was dropped and polymerized.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with ammonia water so that the pH was 7.5. This was filtered through a 200-mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 49.5%, a viscosity of 460 mPa · s, and an average particle size of 270 nm.

(3) Production of water-dispersed acrylic pressure-sensitive adhesive composition 1.2 parts of Surfinol 420 (produced by Air Products Japan; active ingredient 100%) as a leveling agent in the water-dispersed acrylic polymer described above, Epocross WS-500 (manufactured by Nippon Shokubai Co., Ltd .; active ingredient 50%), 1 part was added, followed by filtration through 100 mesh wire netting, and rosin resin E-200 [Arakawa Chemical Industries, Ltd.] as a tackifying resin. 20 parts by mass of solid content was added to obtain the water-dispersed acrylic pressure-sensitive adhesive composition of the present invention.

(4) Preparation of double-sided pressure-sensitive adhesive sheet On a polyester film having a thickness of 75 μm obtained by subjecting the water-dispersed acrylic pressure-sensitive adhesive composition to a release treatment, coating was performed so that the thickness after drying was 65 μm. The pressure-sensitive adhesive layer obtained by drying for 3 minutes was transferred onto both sides of a rayon nonwoven fabric having a basis weight of 14 g / m ² and laminated at 80 ° C. with a pressure of 4 kgf / cm to obtain a double-sided pressure-sensitive adhesive sheet. The obtained double-sided PSA sheet was used for the test after aging in an oven at 40 ° C. for 2 days. The gel fraction of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet was 34%.

(Example 2)
(1) Preparation of Emulsion A Anionic surfactant in Example 1 was changed to 10 parts of anionic surfactant Latemul S-180 (produced by Kao Corporation; active ingredient 50%) having a copolymerizable double bond. An emulsion A (615.5 parts) was obtained by the same operation as in Example 1 except that the content was changed to.

(2) Production of water-dispersed acrylic polymer In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 0.1 part of anionic surfactant Latemul E-118B was removed. 350 parts of ionic water was added, and the temperature was raised to 55 ° C. while blowing nitrogen. Under stirring, an anionic water-soluble polymerization initiator V-501 [manufactured by Wako Pure Chemical Industries, Ltd .; active ingredient 100%] 5 parts of an aqueous solution (active ingredient 5%) was added, and then emulsion A was 6.2. Polymerization was performed for 1 hour while maintaining 55 ° C. Subsequently, the remaining emulsion A (609.3 parts) and anionic water-soluble V-501 aqueous solution 40 parts (active ingredient 5%) were added while maintaining the reaction vessel at 55 ° C. using a separate dropping funnel. Drop polymerization was performed over time.

  Subsequently, a water-dispersed acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1. Subsequently, an adhesive tape was produced in the same manner as in Example 1.

(Example 3)
(1) Preparation of Emulsion Liquid A Emulsion A (615.5 parts) was prepared by the same operation as in Example 2.

(2) Manufacture of water-dispersed acrylic polymer Anionic surfactant S-180 having a copolymerizable double bond in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel .1 part and 350 parts of deionized water were added and the temperature was raised to 55 ° C. while blowing nitrogen. Under stirring, an anionic water-soluble polymerization initiator V-501 [manufactured by Wako Pure Chemical Industries, Ltd .; active ingredient 100%] 5 parts of an aqueous solution (active ingredient 5%) was added, and then emulsion A was 6.2. Polymerization was performed for 1 hour while maintaining 55 ° C. Subsequently, a part (300 parts) of the remaining emulsion A and 20 parts of an anionic water-soluble V-501 aqueous solution (active ingredient 5%) were kept at 55 ° C. using a separate dropping funnel. The polymerization was conducted dropwise over 4 hours. During this time, the emulsion A (310.3 parts) which was not added dropwise was added to the anionic surfactant Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd., active ingredient 100%] having a copolymerizable double bond 5 Part was added and stirred until uniform to prepare Emulsion B (315.3 parts).

  Immediately after the addition of emulsion A, emulsion B (315.3 parts) and anionic water-soluble V-501 aqueous solution 20 parts (active ingredient 5%) were placed in a reaction vessel at 55 ° C. using separate dropping funnels. While maintaining, dropwise polymerization was carried out over 4 hours to produce a water-dispersed acrylic polymer. Subsequently, a water-dispersed acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1. Subsequently, an adhesive tape was produced in the same manner as in Example 1.

(Comparative Example 1)
An acrylic polymer emulsion was obtained in the same manner as in Example 1 except that the polymerization initiator was changed to a redox initiator composed of 1.0 part of ammonium persulfate and 0.5 part of sodium hydrogen sulfite. Subsequently, a water-dispersed acrylic pressure-sensitive adhesive composition was obtained in the same manner as in Example 1. Subsequently, an adhesive tape was produced in the same manner as in Example 1.

(Comparative Example 2)
(1) Preparation of Emulsion A A Emulsion A was prepared in the same manner as in Example 1.

(2) Production of water-dispersed acrylic polymer In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 0.1 part of anionic surfactant Latemul E-118B was removed. 350 parts of ionic water was added, and the temperature was raised to 55 ° C. while blowing nitrogen. Under stirring, a water-based cationic initiator 2,2′-azobis (2-amidinopropane) dihydrochloride [manufactured by Wako Pure Chemical Industries, Ltd .; trade name V-50] 5 parts of an aqueous solution (active ingredient 5%) was added. Subsequently, 6.2 parts of Emulsion A was charged and polymerized in 1 hour while maintaining 55 ° C. Subsequently, the remaining emulsion A (619.3 parts) and 40 parts of V-50 aqueous solution (active ingredient 5%) were dropped over 8 hours while maintaining the reaction vessel at 55 ° C. using a separate dropping funnel. When polymerized, a large amount of aggregates were generated, making filtration impossible, making it difficult to produce.

  Table 1 shows the evaluation results of the filterability of each water-dispersed acrylic polymer and the urethane foam initial adhesiveness, adhesive force, holding force, and tack of each adhesive tape.

The official names of the abbreviations in Table 1 are shown below.
2EHA; 2-ethylhexyl acrylate BA; n-butyl acrylate AA; acrylic acid L-SH; lauryl mercaptan V-501; (manufactured by Wako Pure Chemical Industries, Ltd.) V-501
V-50; (Wako Pure Chemical Industries, Ltd.) V-50
APS; ammonium persulfate SMS; sodium hydrogen sulfite E-118B; (made by Kao Corporation) Latemul S-180
KH-10; (Daiichi Kogyo Seiyaku Co., Ltd.) Aqualon KH-10
S-180; (manufactured by Kao Corporation) Latemul S-180

[Productivity (filterability)]
When filtering with a 200-mesh wire mesh, it was possible to filter without clogging, and a 200-mesh wire mesh with no aggregates was evaluated as “good”. Further, when no agglomerates adhered to the shaft of the stirrer and the inner wall of the polymerization vessel, it was evaluated as “very good”. When the 200 mesh wire mesh was clogged and could not be filtered, it was evaluated that “cannot be filtered”.

[Measurement method of adhesion to urethane foam]
A water-dispersed acrylic pressure-sensitive adhesive composition was applied to the surface of a polyethylene terephthalate film having a thickness of 25 μm so that the thickness after drying was 65 μm, thereby preparing a pressure-sensitive adhesive tape. The pressure-sensitive adhesive tape was bonded to an ECS urethane foam with a 2 kg roll in an atmosphere of 23 ° C. and 50% RH, and immediately after that, it was slowly peeled off by hand. The destruction state of the urethane foam surface at this time was evaluated according to the following criteria.

○: Urethane foam material breakage △: Transfer of urethane foam surface to adhesive layer ×: No transfer of urethane foam surface to adhesive layer

[Measurement method of adhesive strength]
A pressure-sensitive adhesive tape was produced in the same manner as in the method for measuring adhesiveness to urethane foam. Using this adhesive tape and a mirror-finished stainless steel plate as the adherend, the 180-degree peel strength was measured in an atmosphere of 23 ° C. and 50% RH in accordance with JIS Z-0237 to obtain the adhesive strength.

[Method for measuring holding force]
A pressure-sensitive adhesive tape was produced in the same manner as in the method for measuring adhesiveness to urethane foam. Adhesive tape was affixed to the stainless steel plate so that the adhesive area would be 20 mm × 20 mm, and the time until it slipped by applying a load of 500 g at 70 ° C. was measured. In addition, when it was retained after 24 hours, the retention time was set to 24 hours or longer.

[Tack measurement method]
A pressure-sensitive adhesive tape was produced in the same manner as in the method for measuring adhesiveness to urethane foam. It was measured in an atmosphere of 23 ° C. and 50% RH according to the ball rolling method of JIS Z-0237.

[Method for measuring gel fraction]
A water-dispersed acrylic pressure-sensitive adhesive composition was applied to the surface of a 25 μm-thick polyethylene terephthalate film so that the thickness after drying was 65 μm, and dried at 100 ° C. for 3 minutes to prepare a pressure-sensitive adhesive tape. A sample cut into a size of 40 mm × 50 mm was used as a sample. Next, the mass (G1) of the above-mentioned sample before being immersed in toluene and the mass (G0) of the nonwoven fabric serving as the core substrate were measured in advance and immersed in a toluene solution at room temperature for 24 hours. And the toluene insoluble matter of the sample after immersion is separated by filtering with a 300 mesh wire mesh, the mass (G2) of the residue after drying at 105 ° C. for 1 hour is measured, and the gel is measured according to the following formula (3) The fraction was determined.

Gel fraction (mass%) = [(G2-G0) / (G1-G0)] × 100 (3)

Claims (4)

Using a (meth) acrylic acid ester monomer, a vinyl monomer copolymerizable therewith and having an acidic group, a surfactant A having a copolymerizable double bond, and an anionic water-soluble azo initiator, A first step of starting emulsion polymerization in an aqueous medium;
It is a method for producing a water-dispersed acrylic resin by sequentially performing the second step of adding one or more surfactants B having a copolymerizable double bond,
A method for producing a water-dispersed acrylic resin in which the copolymerizable Ra of the surfactant A and the copolymerizable Rb of the surfactant B are Ra <Rb with respect to the (meth) acrylate monomer. The (meth) acrylic acid ester monomer has the formula (1)

(Wherein R ₁ represents an alkyl group having 4 to 18 carbon atoms which may have a branched chain, and X represents a hydrogen atom or a methyl group), and represented by the formula (1) The method for producing a water-dispersed acrylic resin according to claim 1, comprising a monomer having a glass transition point of -10 ° C or lower as a main constituent when the monomer to be polymerized alone is polymerized. A water-dispersed acrylic pressure-sensitive adhesive composition using the water-dispersed acrylic resin obtained by the production method according to claim 1 . A pressure-sensitive adhesive sheet comprising the water-dispersed acrylic pressure-sensitive adhesive composition according to claim 3 as a pressure-sensitive adhesive layer.