TWI595010B - Water-based emulsion, method of manufacturing water-based emulsion, water-based adhesive composition, and adhesive - Google Patents

Description

Aqueous emulsion, method for producing aqueous emulsion, aqueous adhesive composition and adhesive sheet

The present invention relates to an aqueous emulsion and an aqueous adhesive composition containing an aqueous emulsion, and an adhesive sheet having an adhesive layer formed using the aqueous adhesive composition.

The present application claims priority based on Japanese Patent Application No. 2015-114012, filed on Jan. 4, 2015, in Japan, the content of which is incorporated herein.

In recent years, in order to reduce the burden on the global environment, development of an adhesive using a solvent-free aqueous emulsion has been carried out.

For the aqueous emulsion to be used as the adhesive, for example, Patent Document 1 describes an aqueous dispersion of a multistage emulsion polymer which exhibits improved water resistance and water whitening resistance.

Further, Patent Document 2 describes an optical film water-dispersible pressure-sensitive adhesive composition which can form an adhesive layer capable of suppressing peeling and peeling in a humidified environment.

Further, from the past, techniques for polymerizing monomers in the presence of an addition-cleaving chain transfer agent are well known.

For example, Patent Document 3 describes a light-diffusing film obtained by polymerizing an unsaturated monomer in the presence of an addition-cracking type chain transfer agent to obtain an emulsion, and applying the emulsion to a transparent film.

Further, Patent Documents 4 to 6 disclose a coating composition containing an emulsion obtained by polymerizing an unsaturated monomer in the presence of an addition-cleaving type chain transfer agent.

Further, Patent Document 7 describes an acrylic rubber obtained by polymerizing a monomer mixture in the presence of an addition-cleaving type chain transfer agent.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-299260

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2012-128391

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2014-134735

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2006-193680

[Patent Document 5] Japanese Laid-Open Patent Publication No. 2006-143763

[Patent Document 6] Japanese Patent No. 5258293

[Patent Document 7] International Publication No. 2007/114108

In recent years, it has strong adhesion and can be formed The need for an adhesive for the adhesive layer to be peeled off from the adherend residue and the adhesive layer is increased. Thus, an aqueous emulsion which can be used as a raw material of the adhesive is required.

However, it is known that an adhesive having a strong adhesive force using an aqueous emulsion is less likely to form an adhesive layer which is not peeled off by the residual residue of the adherend and the stick.

The present invention has been made in view of the above-mentioned facts, and provides an adhesive sheet having a strong adhesive force and having an adhesive layer which can be peeled off from the adhesive residue and the adhesive residue, and an adhesive layer used for the adhesive sheet. The aqueous adhesive composition and the aqueous emulsion suitable for the aqueous adhesive composition described above are problems.

In order to solve the above problems, the inventors of the present invention have focused on an emulsion containing a polymer of a plurality of monomer components having different glass transition temperatures (Tg: glass transition temperatures) in a homopolymer form. Specifically, an emulsion of a polymer is produced in the presence of an addition-cleaving type chain transfer agent using a monomer component which can provide a soft polymer and a monomer component which can provide a hard polymer. Soft polymers have a low Tg and a strong adhesion. The hard polymer has a high Tg and is expected to have an effect of reducing the residue and sticking of the adherend. The inventors of the present invention evaluated the properties of the manufactured emulsion and conducted research in turn.

As a result, it has been found that the present invention can be considered by forming an adhesive layer of an adhesive sheet by using an emulsion of a polymer obtained by the method shown below. It is a method of adding a cracking type chain transfer agent in a prescribed amount. In the presence of the monomer component of the soft polymer, the monomer component which can provide the hard polymer is added and polymerized in a predetermined ratio.

That is, the present invention relates to the following matters:

[1] An aqueous emulsion comprising the step (I) of emulsifying and polymerizing a first polymerizable component in the presence of an addition-cleaving type chain transfer agent, and the step (I) obtained in the above step (I) The step (II) in which the polymer is supplied to the second polymerizable component and polymerized, and the production method satisfying the following conditions (1) to (3) is obtained: (1) the amount of the addition-cleaving chain transfer agent, relative to 100 parts by mass of the total polymerizable component in total of the first polymerizable component and the second polymerizable component is 0.05 to 1 part by mass; and (2) the first polymerizable component provides a glass transition temperature of -20 ° C or lower. The polymer is 70 to 95% by mass of the total polymerizable component; (3) the second polymerizable component provides a polymer having a glass transition temperature of 50 ° C or higher, and is 5 of the total polymerizable components. ~30% by mass.

[2] The aqueous emulsion according to [1], which has a gel fraction of 90% or more.

[3] The aqueous emulsion according to [1] or [2] wherein the first polymerizable component provides a polymer having a glass transition temperature of -40 ° C or lower.

[4] The aqueous emulsion according to any one of [1] to [3] wherein the second polymerizable component provides a glass having a glass transition temperature of 70 ° C or higher. Compound.

[5] The aqueous emulsion according to any one of [1] to [4] wherein the second polymerizable component contains more than 50% by mass of methyl methacrylate and/or n-butyl acrylate.

[6] The aqueous emulsion according to any one of [1] to [5] wherein the first polymerizable component contains more than 50% by mass of n-butyl acrylate and/or 2-ethylhexyl acrylate.

[7] An aqueous adhesive composition comprising the aqueous emulsion according to any one of [1] to [6].

[8] An adhesive sheet comprising an adhesive layer on one side or both sides of a substrate, wherein the adhesive layer is formed using the aqueous adhesive composition of [7].

[9] A method for producing an aqueous emulsion comprising the step (I) of emulsifying and polymerizing a first polymerizable component in the presence of an addition-cleaving type chain transfer agent, and the obtained in the above step (I) The step of supplying the second polymerizable component to the polymer and carrying out the polymerization (II), and satisfying the following conditions (1) to (3): (1) the amount of the addition-cracking chain transfer agent, relative to the first 100 parts by mass of the total polymerizable component in total of the polymerizable component and the second polymerizable component is 0.05 to 1 part by mass; (2) the first polymerizable component provides a polymer having a glass transition temperature of -20 ° C or lower, and 70 to 95% by mass of the total polymerizable component; (3) the second polymerizable component provides a glass transition temperature of 50 The polymer of °C or more is 5 to 30% by mass of the total polymerizable component.

[10] An aqueous emulsion comprising a soft polymer and a hard polymer as a structural unit, the two polymer systems having a functional group derived from an addition-cleaving type chain transfer agent, wherein the soft polymer has a glass transition temperature of -20 C ° or less, 70 to 95% by mass of the structural unit of the polymer, and the glass transition temperature of the hard polymer is 50° C. or higher, and 5 to 30% by mass of the structural unit of the polymer, and the soft polymerization is carried out. The soft polymer portion composed of the material and the hard polymer portion composed of the aforementioned hard polymer have a two-layer structure.

According to the present invention, an aqueous emulsion suitable for use in an aqueous adhesive composition for an adhesive layer of an adhesive sheet can be provided.

An adhesive sheet comprising an aqueous adhesive composition containing the aqueous emulsion of the present invention, which has an adhesive layer formed on one or both sides of the substrate, has a strong adhesive force and can be peeled off from the adhesive residue and the adhesive residue. .

Hereinafter, the aqueous emulsion, the aqueous adhesive composition and the adhesive sheet of the present invention will be described in detail.

<aqueous emulsion>

The aqueous emulsion of the present embodiment is a step (I) comprising: emulsion-polymerizing a first polymerizable component in the presence of an addition-cleaving type chain transfer agent, and polymerization obtained in the above step (I) The step (II) of supplying the second polymerizable component and polymerizing, and the aqueous emulsion of the polymer obtained by the production method of the following conditions (1) to (3).

The polymer contained in the aqueous emulsion of the present embodiment is a soft polymer obtained by polymerizing a first polymerizable component and a hard polymer obtained by polymerizing a second polymerizable component. Since the polymer in the aqueous emulsion contains a hard polymer, when the adhesive layer is formed using the aqueous adhesive composition containing the aqueous emulsion, the adhesive layer can be peeled off from the adherend without leaving the adhesive residue and the stick. Further, since a soft polymer is present in the polymer of the aqueous emulsion, strong adhesion to the adherend can be obtained by the flexibility of the soft polymer.

(1) The amount of the addition-cracking type chain transfer agent is 0.05 to 1 part by mass based on 100 parts by mass of the total polymerizable component in total of the first polymerizable component and the second polymerizable component; (2) First polymerization property The component provides a polymer having a Tg of -20 ° C or less and is 70 to 95% by mass in the total polymerizable component; (3) the second polymerizable component provides a polymer having a Tg of 50 ° C or more, and is a total polymerization. 5 to 30% by mass of the sexual components.

(additional cleavage chain transfer agent)

Addition cleavage used in the production of the aqueous emulsion of the present embodiment The chain transfer agent may, for example, be α-bromomethylstyrene, α-phenoxymethylstyrene, α-alkylthiomethylstyrene, α-tert-butylperoxymethylstyrene, α. - benzyloxystyrene, methyl-α-phenoxy methacrylate, methyl-α-alkylthiomethacrylate, methyl-α-tertiary butyl peroxymethacrylate, A Alpha-substituted unsaturated monomer such as benzyl-α-benzyloxy acrylate or α-bromomethyl acrylonitrile, α-methyl styrene dimer, methyl methacrylate dimer, methacryl Alpha-substituted dimers such as nitrile dimers, benzyl dithiobenzoate, 1-phenylethyl dithiobenzoate, 2-phenyl-2-propynyl dithiobenzoate , 1-Ethyloxyethyl dithiobenzoate, benzyl dithioacetate, dimethyl butyl dithiobenzoate, 2-cyano-2-propynyl dithiobenzoate, a disulfide compound such as cumene thiobenzoate, a dithio fatty acid ester or a derivative thereof, a dithiobenzoic acid ester or a derivative thereof.

Among the above-mentioned addition-cracking type chain transfer agents, in particular, since the odor is small and the treatment is easy to take, which is inexpensive and easily obtained industrially, it is preferred to use an α-substituted dimer. As the α-substituted dimer, an α-methylstyrene dimer is preferred.

The above-mentioned addition-cleaving type chain transfer agent may be used singly or in combination of two or more.

In the production of the aqueous emulsion of the present embodiment, an addition-cracking chain transfer agent is used in an amount of 0.05 to 1 part by mass based on 100 parts by mass of the total polymerizable component in total of the first polymerizable component and the second polymerizable component. . When the amount of the addition-cracking chain transfer agent is 0.05 parts by mass or more based on 100 parts by mass of the total polymerizable component, when an adhesive layer is formed using an aqueous adhesive composition containing an aqueous emulsion, it is difficult to form a sticky layer. Adhesive layer and/or adhesive layer. Therefore, the amount of the addition-cracking type chain transfer agent is 0.05 parts by mass or more, preferably 0.1 parts by mass or more based on 100 parts by mass of the total polymerizable component. Further, when the amount of the addition-cracking type chain transfer agent is 1 part by mass or less based on 100 parts by mass of the total polymerizable component, when the adhesive layer is formed using the aqueous adhesive composition containing the aqueous emulsion, the adhesive layer is less likely to cohesive. damage. Therefore, the amount of the addition-cracking type chain transfer agent is 1 part by mass or less, preferably 0.6 part by mass or less, more preferably 0.4 part by mass or less based on 100 parts by mass of the total polymerizable component.

(polymerizable component)

When the aqueous emulsion of the present embodiment is produced, the monomer used as the first polymerizable component and/or the second polymerizable component is preferably an ethylenically unsaturated monomer.

In the following description, (meth) acrylate means acrylate or methacrylate.

Examples of the ethylenically unsaturated monomer include those conventionally shown below.

Methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, (meth)acrylic acid ring a (meth) acrylate such as hexyl ester, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate or isobornyl (meth)acrylate; 2-hydroxyethyl methacrylate, (meth) propylene a hydroxyalkyl (meth) acrylate such as 2-hydroxypropyl acrylate; a polyalkylene glycol (meth) acrylate such as ethylene glycol (meth) acrylate or butylene glycol (meth) acrylate; , alkylamino (meth) acrylate such as N-dimethylaminoethyl (meth) acrylate or N,N-dimethylaminopropyl (meth) acrylate; vinyl formate, vinyl acetate a vinyl ester compound such as ester, vinyl propionate or vinyl neodecanoate; an aromatic vinyl compound such as styrene, α-methylstyrene, p-methylstyrene or ethylvinylbenzene; vinylpyrrolidone or the like; Heterocyclic vinyl compound; monoolefin compound of ethylene, propylene, butylene, isobutylene, etc.; conjugated diene compound of butadiene, isoprene, chloroprene, etc.; 1,1,1-trimethylamine a vinyl compound containing an amine quinone imine such as methacrylimide; a vinyl cyanide compound such as acrylonitrile or methacrylonitrile; (meth) acrylamide, N-methyl acrylamide, α,β-B containing an indenyl group or a substituted amidino group such as N,N-dimethyl(meth)acrylamide or N,N-dimethylaminopropyl(meth)acrylamide Ethylenically unsaturated compound; acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxyethyl acrylate oligomer, 2-propene oxime An α,β-unsaturated mono or dicarboxylic acid such as oxyethyl succinic acid; a carboxyl group-containing vinyl compound such as monohydroxyethyl (meth) acrylate or monohydroxypropyl (meth) acrylate; a sulfonic acid allyl ester or a sodium p-styrene sulfonate An α,β-ethylenically unsaturated compound of a sulfonic acid group.

The monomer used as the first polymerizable component and/or the second polymerizable component may further contain a crosslinkable monomer capable of forming a polymer having a crosslinked structure.

Examples of the crosslinkable monomer include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl ether, and epoxypropyl group. An epoxy group-containing α,β-ethylenically unsaturated compound such as (meth)allyl ether or 3,4-epoxycyclohexyl (meth) acrylate; vinyl triethoxy decane, vinyl An α,β-ethylenically unsaturated compound containing a hydrolyzable alkoxyalkylene group such as β-methoxyethoxy decane or γ-methyl propylene oxypropyltrimethoxy decane; a polyfunctional vinyl compound such as (meth) acrylate, trimethylolpropane tri(meth) acrylate, allyl (meth) acrylate, divinyl benzene or diallyl phthalate; For example, a carbonyl group-containing α,β-ethylenically unsaturated compound such as diacetone acrylamide.

When the crosslinkable monomer is contained in the first polymerizable component and/or the second polymerizable component, the crosslinked structure of the polymer obtained after the polymerization depends on the kind of the crosslinkable monomer to be used.

For example, it may be a crosslinked structure formed by polymerizing a crosslinkable monomer, or may be an active hydrogen group contained in a functional group based on a crosslinkable monomer and another monomer or a crosslinking agent. A crosslinked structure formed by bonding.

The first polymerizable component used in the production of the aqueous emulsion of the present embodiment provides a polymer having a Tg of -20 ° C or lower. When a polymer having a Tg of -20 ° C or less is used as the first polymerizable component, an excellent adhesion can be obtained when an adhesive layer is formed using an aqueous adhesive composition containing an aqueous emulsion. Therefore, the first polymerizable component is preferably a polymer which provides a polymer having a Tg of -20 ° C or less, preferably -40 ° C or less. On the other hand, the first polymerizable component is preferably one having a Tg of -70 ° C or more in terms of high cohesive strength and strong peel strength when an adhesive layer is formed using an aqueous adhesive composition containing an aqueous emulsion. The object is more preferably a polymer which can provide -55 ° C or more.

The first polymerizable component may be a polymer having a Tg of -20 ° C or lower, and may be a single monomer or a mixture of two or more monomers. When the first polymerizable component is a mixture of two or more kinds of monomers, two or more kinds of monomers which provide a polymer having a Tg of -20 ° C or less may be used in combination, or one or two or more kinds may be combined. A monomer having a polymer having a Tg of -20 ° C or lower and one or more monomers having a polymer having a Tg of more than -20 ° C are provided.

Among the monomers used as the first polymerizable component and/or the second polymerizable component, the first polymerizable component is preferably ethyl acrylate or n-butyl acrylate in terms of excellent stability during polymerization. , n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, acrylic acid 2- Ethyl acrylate having an alkyl group having 2 to 10 carbon atoms, and methoxyethyl acrylate, 2-hydroxyethyl acrylate, and methacrylic acid 2-, such as ethylhexyl acrylate, n-octyl acrylate, and isooctyl acrylate; A substituted alkyl acrylate having an alkyl group having 1 to 10 carbon atoms which is substituted with an alkoxy group or a hydroxyl group, such as hydroxyethyl ester.

As the first polymerizable component, among the above monomers, n-butyl acrylate and/or 2-ethylhexyl acrylate are particularly preferably used.

Further, the first polymerizable component preferably contains acrylic acid, methacrylic acid, fumaric acid, maleic acid, and itaconic acid in order to improve the adhesion of the adhesive layer formed using the aqueous adhesive composition containing the aqueous emulsion. The unsaturated carboxylic acid having 3 to 5 carbon atoms is particularly preferably contained in any one or more selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid.

The first polymerizable component is preferably mainly composed of n-butyl acrylate and/or 2-ethylhexyl acrylate (in other words, n-butyl acrylate and/or 2-ethylhexyl acrylate in the first polymerizable component) It is more than 50% by mass in total, and more preferably 70% by mass or more in the first polymerizable component.

Further, the first polymerizable component preferably contains a carbonic acid of 3 to 5 as a copolymerization component with n-butyl acrylate and/or 2-ethylhexyl acrylate. In this case, the unsaturated carboxylic acid having 3 to 5 carbon atoms in the first polymerizable component is preferably contained in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass.

When the first polymerizable component contains n-butyl acrylate and/or 2-ethylhexyl acrylate and an unsaturated carboxylic acid having 3 to 5 carbon atoms, the copolymerized polymer is formed into an aqueous emulsion. a soft polymer of the polymer. As a result, an aqueous emulsion can be obtained, which can be formed as strong The adhesive layer of the adhesive is used as an aqueous adhesive composition.

The second polymerizable component used in the production of the aqueous emulsion of the present embodiment provides a polymer having a Tg of 50 ° C or higher. When a polymer having a Tg of 50 ° C or higher is used as the second polymerizable component, when an adhesive layer is formed using an aqueous adhesive composition containing an aqueous emulsion, sufficient adhesion is easily obtained. Therefore, the second polymerizable component is a polymer which provides a Tg of 50 ° C or more, and a polymer which can provide 70 ° C or more is preferable from the viewpoint of re-peelability (less residual rubber).

The second polymerizable component may be a polymer having a Tg of 50 ° C or higher, and may be a single monomer or a mixture of two or more monomers. When the second polymerizable component is a mixture of two or more kinds of monomers, two or more kinds of monomers which provide a polymer having a Tg of 50 ° C or higher may be used in combination, or one type or two or more types may be used in combination. A monomer having a Tg of 50 ° C or more, and one or more monomers which provide a polymer having a Tg of less than 50 ° C.

In the second polymerizable component, among the monomers used as the first polymerizable component and/or the second polymerizable component, methyl methacrylate, butyl methacrylate, and 2-ethyl acrylate are preferably used. One or two or more kinds of hexyl hexyl acrylate and n-butyl acrylate.

When the second polymerizable component is two kinds of monomers, a combination of methyl methacrylate and butyl methacrylate or a combination of n-butyl acrylate and 2-ethylhexyl acrylate is preferred.

The second polymerizable component is preferably mainly composed of methyl methacrylate and/or n-butyl acrylate (in other words, methyl methacrylate and/or The n-butyl acrylate is contained in a total amount of more than 50% by mass in the second polymerizable component, and more preferably 70% by mass or more in the second polymerizable component.

The first polymerizable component is contained in the total polymerizable component (the total of the first polymerizable component and the second polymerizable component) in an amount of 70 to 95% by mass. The second polymerizable component is contained in the total polymerizable component in an amount of 5 to 30% by mass. Further, the first polymerizable component is preferably contained in the total polymerizable component in an amount of from 80 to 95% by mass. The second polymerizable component preferably contains 5 to 20% by mass of the total polymerizable component.

When the content of the first polymerizable component in the total polymerizable component is 70% by mass or more (the second polymerizable component is 30% by mass or less), a soft polymer obtained by sufficiently polymerizing the first polymerizable component can be sufficiently contained. A polymer in an aqueous emulsion. Therefore, when an aqueous adhesive composition containing an aqueous emulsion is used to form an adhesive layer, there is an advantage that sufficient adhesion can be obtained.

In addition, when the content of the first polymerizable component in the total polymerizable component is 95% by mass or less (the second polymerizable component is 5% by mass or more), the hard polymer obtained by polymerizing the second polymerizable component can be sufficiently formed. Therefore, when an aqueous adhesive composition containing an aqueous emulsion is used to form an adhesive layer, cohesive failure is less likely to occur, and it is not easy to form a residue for the adherend.

Further, the glass transition temperature (Tg) of the polymer in the present embodiment is a theoretical value calculated from the FOX formula shown below from the respective monomer components constituting the polymer and the ratio thereof.

Tg=T-273

However, 1/T=(W1/T1+W2/T2+W3/T3+‧‧‧+Wn/Tn) (where Tg is the glass transition temperature (Celsius temperature) of the polymer, and T is the glass transition of the polymer Temperature (absolute temperature): W1, W2, W3, and Wn are the weight fraction of each monomer component, and T1, T2, T3, and Tn are the glass transition temperature (absolute temperature) of the homopolymer of each monomer component.

In the present invention, the calculation of the Tg of the polymer (soft polymer) obtained from the first polymerizable component and the polymer (hard polymer) obtained from the second polymerizable component is calculated based on a monofunctional monomer. That is, even if the first polymerizable component and/or the second polymerizable component contains a polyfunctional monomer, the content thereof is small; thus, the polyfunctional component contained in the first polymerizable component and/or the second polymerizable component The monomer has less effect on the Tg of the polymer. Therefore, the calculation of the Tg of the polymer does not include the influence of the polyfunctional monomer.

Further, the theoretical value of Tg obtained from the above FOX equation is in good agreement with the glass transition temperature calculated based on the measured value obtained by differential scanning calorimetry (DSC).

(gel fraction)

The aqueous emulsion of the present embodiment preferably has a gel fraction of 90% or more, more preferably 93% or more. An aqueous emulsion having a gel fraction of 90% or more is an adhesive layer formed using an aqueous adhesive composition containing the same, and it is more difficult to leave residual glue and stick marks on the adherend during peeling.

<Method for Producing Aqueous Emulsion>

The aqueous emulsion of the present embodiment can be carried out under the above conditions: step (I) of emulsifying and polymerizing the first polymerizable component in the presence of an addition-cleaving type chain transfer agent, and in the step (I) The obtained polymer is supplied to the second polymerizable component and polymerized in the step (II).

In the step (I), for example, an addition-cracking type chain transfer agent and water are fed into the reactor, and the first polymerizable component (monomer) is supplied to the reactor as needed to carry out emulsion polymerization. The other component may be one or more selected from the group consisting of water, an emulsifier, a polymerization initiator, a reducing agent, a non-additive cleavage type chain transfer agent, and a crosslinking agent.

As the emulsifier used in the step (I), a surfactant is exemplified. Examples of the surfactant include nonionic properties such as an anionic surfactant such as sodium dodecylbenzenesulfonate or sodium dodecyl sulfate, polyoxyethylene alkyl ether, and polyoxyethylene nonylphenyl ether. Surfactant, cationic surfactant such as hexadecyltrimethylammonium bromide or lauryl pyridine, amphoteric surfactant such as lauryl betaine, polyoxyethylene-1-(allyloxyethylene) a reactive surfactant such as an alkyl ether sulfate ammonium salt or the like.

Among these emulsifiers, a reactive surfactant is particularly preferably used in order to introduce into the interior of the polymer by polymerization. An aqueous adhesive composition containing an aqueous emulsion produced using a reactive surfactant has less bleed out from the adhesive layer to the adherend when the adhesive layer is formed using the same. Therefore, contamination of the adherend due to the component oozing out from the adhesive layer is less likely to occur, which is preferable. These emulsifiers may be used singly or in combination.

As the polymerization initiator used in the step (I), it can be mentioned A water-soluble azo initiator such as a persulfate-based initiator such as potassium persulfate or ammonium persulfate or a hydrogen peroxide-based initiator such as 2,2'-azobis(2-methylpropionamidine) dihydrochloride An organic peroxide such as a tertiary butyl group or a cumene hydroperoxide or hydrogen peroxide. These polymerization initiators may be used singly or in combination.

Examples of the reducing agent used in the step (I) include a reducing organic compound such as ascorbic acid, tartaric acid, citric acid, glucose, or formaldehyde sulfoxylate metal salt, sodium thiosulfate, sodium sulfite, sodium hydrogen sulfite, and partial A reducing inorganic compound such as sodium disulfite or the like.

Examples of the non-addition-cleaving type chain transfer agent used in the step (I) include 2-ethylhexylthioglycolate, n-dodecyl mercaptan, tertiary dodecanethiol, and n-butyl mercaptan. , 2-mercaptoethanol, β-mercaptopropionic acid, methanol, n-propanol, isopropanol, tertiary butanol, benzyl alcohol, and the like. Among these chain transfer agents which are not addition-type cleavage type, 2-ethylhexyl thioglycolate is particularly preferably used because of the excellent effect of adjusting the molecular weight of the polymer. These non-additional cleavage type chain transfer agents may be used singly or in combination.

The type of the crosslinking agent used in the step (I) is appropriately determined depending on the kind of the monomer used in the production of the aqueous emulsion. Specifically, as the crosslinking agent, a decane coupling agent, a polyfluorene compound, a polyfunctional epoxy compound, a polyfunctional isocyanate compound, or the like can be used. Among these crosslinking agents, a crosslinked structure can be formed by merely performing copolymerization, and a decane coupling agent is particularly preferably used for easy handling.

When an α,β-ethylenically unsaturated compound containing a carbonyl group is used as the crosslinkable monomer, it is preferred to use two of bismuth oxalate, diterpene succinate, diammonium adipate, and polyacrylic acid bismuth. Multiple combinations of the above sulfhydryl groups The substance acts as a crosslinking agent to form a crosslinked structure.

In the step (I), the entire amount of the first polymerizable component and/or other components used in the step (I) may be fed into the reactor in advance for emulsion polymerization. In the step (I), the emulsion polymerization may be carried out while continuously or intermittently supplying the first polymerizable component and/or other components. In the step (I), in order to obtain an aqueous emulsion containing particles of a polymer having a uniform particle diameter, it is preferred to carry out emulsion polymerization while continuously or intermittently supplying the first polymerizable component and other components to the reactor.

The emulsion polymerization in the step (I) is preferably carried out by adjusting the temperature in the reactor to 5 to 100 ° C, preferably 50 to 90 ° C, while stirring the solution in the reactor.

In the step (I), when the first polymerizable component and the other component are continuously or intermittently supplied to the reactor for emulsion polymerization, the supply of the first polymerizable component and other components to the reactor may be completed. The polymerization is carried out for 0.5 to 5 hours at a temperature of, for example, 5 to 100 ° C, preferably 50 to 90 ° C.

The emulsion polymerization in the step (I) can be carried out under an air atmosphere or an inert gas atmosphere.

In the present embodiment, in the step (I), it is preferred to add the emulsion containing the polymer in the emulsion polymerization or the emulsion polymerization after the supply of the first polymerizable component and the other components to the reactor is completed. One or two or more acids or bases are adjusted to a pH of 6.5 to 9.0. By adjusting the pH of the emulsion to 6.5 to 9.0, it is possible to obtain an effect of improving the stability of the aqueous emulsion and further reducing the coarse particles of the obtained aqueous emulsion.

The acid used for the pH adjustment of the emulsion containing the polymer in the emulsion polymerization or the emulsion polymerization in the step (I) may, for example, be acetic acid, lactic acid, hydrochloric acid, phosphoric acid or sulfuric acid. Further, examples of the base used for adjusting the pH of the emulsion include an amine compound such as triethylamine, ammonia, diethanolamine or diethylaminoethanol; and an alkali metal such as potassium hydroxide, sodium hydroxide or lithium hydroxide. hydroxide.

In the step (II), the second polymerizable component is supplied to the polymerization system containing the polymer obtained in the step (I) and polymerized. In the step (II), the polymerization system containing the polymer obtained in the step (I) may be supplied to the other components simultaneously with the second polymerizable component (monomer) as needed. The other component may be one or more selected from the group consisting of water, an emulsifier, a polymerization initiator, a reducing agent, a non-additive cleavage type chain transfer agent, and a crosslinking agent.

In the step (II), when the polymerization system comprising the polymer obtained in the step (I) is supplied to the other components simultaneously with the second polymerizable component (monomer), the second polymerizable component may be used by using a mixer or the like. After mixing with one or more of the other components described above to prepare an emulsion, it is supplied to the polymerization system of the step (I).

In the step (II), in the case of using an emulsifier, a polymerization initiator, a reducing agent, a non-addition-cleaving type chain transfer agent, and a crosslinking agent as other components, it can be used in the above step (I). The other ingredients used are the same.

In addition, in the step (I) and the step (II), if other components are used, the other components of the two components may be identical, and some or all of the phases may be used. different.

In the step (II), the entire amount of the second polymerizable component and/or other components used in the step (II) may be supplied to the polymerization system of the step (I) and polymerized. In the step (II), the polymerization may be carried out while continuously or intermittently supplying the second polymerizable component and/or other components. In the step (II), in order to obtain an aqueous emulsion containing particles of a polymer having a uniform particle diameter, it is preferred to carry out the second polymerizable component and other components continuously or intermittently to the polymerization system of the step (I). polymerization.

The polymerization in the step (II) is preferably carried out by adjusting the temperature in the reactor to 5 to 100 ° C, preferably 50 to 90 ° C, while stirring the solution in the reactor.

In the present embodiment, in the step (II), when the second polymerizable component and the other component are continuously or intermittently supplied to the polymerization system of the step (I), the second polymerizable component is preferably used. After the supply of the other components to the polymerization system of the step (I) is completed, the polymerization is continued for 0.5 to 5 hours at a temperature of, for example, 5 to 100 ° C, preferably 50 to 90 ° C.

The emulsion polymerization in the step (II) can be carried out under an air atmosphere or an inert gas atmosphere.

The reaction conditions in the step (II) may be identical to the step (I), and may be partially or completely different.

In the present embodiment, it is preferred to add one or more kinds of acids or bases to the aqueous emulsion obtained after the polymerization in the step (II), and adjust the pH to 4 to 10. By adjusting the pH of the aqueous emulsion to 4~ 10, can increase the surface charge of the aqueous emulsion, can give stability.

The acid used for the adjustment of the pH of the aqueous emulsion is the same as the acid used for the pH adjustment of the emulsion used in the emulsion polymerization or the polymer after the emulsion polymerization in the step (I). Moreover, the base used for the adjustment of the pH of the aqueous emulsion is the same as the base used for pH adjustment in the step (I).

By carrying out the above steps, an aqueous emulsion of the present embodiment comprising particles of a polymer having a two-layer structure derived from a functional group of a addition-cleaving type chain transfer agent can be obtained. The polymer having the two-layer structure described above has a soft polymer obtained by polymerizing a first polymerizable component and a hard polymer obtained by polymerizing a second polymerizable component as a structural unit. Examples of the two-layer structure of the polymer include a core shell type, a snowman type, and a gold flat type. The two-layer structure of the polymer varies depending on the type, ratio, and the like of the first polymerizable component and/or the second polymerizable component.

The nonvolatile content of the polymer in the aqueous emulsion thus obtained is usually from 30 to 70% by mass, preferably from 40 to 65% by mass.

<Aqueous Adhesive Composition>

The aqueous adhesive composition of the present embodiment contains the aqueous emulsion of the present embodiment.

In the present embodiment, the aqueous emulsion obtained by the polymerization in the above step (II) can be directly used as an aqueous adhesive composition. Further, the solid content concentration of the aqueous emulsion obtained by the polymerization in the above step (II) may be adjusted by dilution with a solvent or the like as the aqueous viscosity. The composition of the agent is used.

Further, as the aqueous adhesive composition, the pH of the aqueous emulsion obtained by the polymerization in the above step (II) can be adjusted to 4 to 10 by the above method.

Further, as the aqueous adhesive composition, a tackifier such as a rosin-based, terpene-based or petroleum-based adhesive may be added to the aqueous emulsion of the present embodiment. These tackifiers may be used singly or in combination of two or more.

Further, as the aqueous adhesive composition, one or two or more kinds of additives may be added to the aqueous emulsion of the present embodiment. Examples of the additive include a crosslinking agent (a polyfunctional epoxy, a polyfunctional isocyanate, a decane coupling agent, etc.), a viscosity improving agent, a tackifier, an antifoaming agent, and a pigment (a body pigment, a coloring pigment, a hollow balloon, etc.). , dispersing agents, wetting agents, light stabilizers, ultraviolet absorbers, preservatives, antibacterial agents, and the like.

The aqueous adhesive composition of the present embodiment can be suitably used as an adhesive.

Examples of the adherend when the aqueous adhesive composition is used as an adhesive include paper, plastic film, metal, glass, woven fabric, non-woven fabric, foam of plastic or rubber, and the like. Further, the aqueous adhesive composition of the present embodiment is also suitable as an adhesive for automotive products, home electric appliances, and electronic parts.

<adhesive sheet>

The adhesive sheet of the present embodiment has an adhesive layer on one side or both sides of the substrate.

The adhesive layer forming the adhesive sheet is formed using the aqueous adhesive composition of the present embodiment. The thickness of the adhesive layer can be appropriately determined depending on the use of the adhesive sheet, the material of the adherend, and the like. The thickness of the adhesive layer can be, for example, 5 to 200 μm, preferably 10 to 100 μm.

The base material used for the adhesive sheet is not particularly limited, and examples thereof include paper, a plastic film, a resin foam, a rubber foam, a metal, a glass, a woven fabric, a nonwoven fabric, and an inorganic plate.

In the adhesive sheet of the present embodiment, in order to protect the adhesive layer, a release protective layer may be provided on the adhesive layer.

The protective layer may be, for example, a porous material such as a plastic film, paper, cloth, or nonwoven fabric, a mesh, a foamed sheet, a metal foil, or a suitable sheet such as a laminate thereof.

The plastic film used for the protective layer may, for example, be a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, or the like. A polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene-vinyl acetate copolymer film, or the like.

The thickness of the plastic film used for the protective layer can be, for example, 5 to 200 μm, preferably 5 to 100 μm.

The pressure-sensitive adhesive sheet of the present embodiment can be produced, for example, by applying the aqueous pressure-sensitive adhesive composition of the present embodiment to one side or both surfaces of the substrate, followed by drying to form an adhesive layer.

For the surface of the substrate to be coated with the aqueous adhesive composition, in order to enhance the adhesion between the substrate and the adhesive layer before applying the aqueous adhesive composition The anchor layer may be formed, or various easy-to-handle treatments such as corona treatment or plasma treatment may be performed.

As a method of applying the aqueous adhesive composition, various methods can be employed. Specifically, examples of the coating method include roll coating, contact roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip coating, bar coating, and knife. A method such as coating, air knife coating, curtain coating, lip coating, or an extrusion coating method using a die coater or the like.

When the aqueous adhesive composition is applied to the substrate, the coating amount is controlled so that the adhesive layer formed after drying reaches a predetermined thickness.

Next, the applied aqueous adhesive composition is dried to form an adhesive layer in accordance with a usual method.

Thereafter, the surface of the adhesive layer can be easily processed as needed. Further, a release protective layer may be provided on the adhesive layer as needed.

According to the above steps, the adhesive sheet of the present embodiment can be obtained.

The adhesive sheet of the present embodiment can be used for daily necessities such as tape, double-sided tape, adhesive label, wallpaper, floor tile, floor tile (cushion floor), carpet, ceiling material, window adhesive sheet (for example, heat shield). It is suitable for use in areas such as residential materials such as reflective sheets and anti-theft patches. Further, the adhesive sheet of the present embodiment can be used, for example, in the manufacture of automobile products, home electric appliances, electronic parts, and the like.

[Examples]

Hereinafter, the present invention will be described in detail based on examples. The invention is not limited by the examples shown below.

In addition, "parts" and "%" in the examples and comparative examples indicate "mass parts" and "mass%" unless otherwise stated.

"Example 1"

In a reactor equipped with a polymerization apparatus of a stirrer, a thermometer, and a reflux condenser, ion-exchanged water and NOFMER MSD as an addition-cracking type chain transfer agent were fed in the ratio shown in Table 1, and the temperature was raised. Then, while maintaining the internal temperature of the reactor at 80 ° C in an air atmosphere, the solution in the reactor was stirred at about 120 rpm, and potassium persulfate as a polymerization initiator was added as described in Table 1.

Further, each component shown in the item (A) of the emulsion of Table 1 and (B) of the emulsion was mixed at a ratio shown in Table 1, and emulsified by a homogenizer to prepare (A) an emulsion and (B) Emulsion.

"Step (I)"

The emulsion (A) and the 2.5% potassium persulfate aqueous solution (catalyst for dropping) were continuously dropped into the reactor of the above polymerization apparatus, and the emulsion polymerization was carried out while stirring at about 120 rpm at a temperature of 80 °C. Further, polymerization was continued for 30 minutes from the end of the dropwise addition of the (A) emulsion to obtain an emulsion.

Further, the dropping rate of the (A) emulsion was set to about 233 parts/hour (about 233 g/hour). Also, 2.5% potassium persulfate aqueous solution (dropping touch The dropping speed of the medium was set to be about 11.1 parts/hour (about 11.1 g/hour). Thereafter, after the completion of the dropwise addition of the (A) emulsion and the dropping catalyst, ammonia water as a neutralizing agent was added to adjust the pH to 7 to 8.

"Step (II)"

Step (II) is started 30 minutes after the end of the dropping of the (A) emulsion. In the step (II), the (B) emulsion was continuously dropped into the reactor of the polymerization apparatus containing the emulsion obtained in the step (I), and the emulsion polymerization was carried out while stirring at about 120 rpm at a temperature of 80 °C. (B) The dropping rate of the emulsion was set to about 194 parts/hour (about 194 g/hour). Further, the polymerization was continued for 1 hour from the completion of the dropwise addition of the (B) emulsion, and then cooled to room temperature (25 ° C). According to the above procedure, the aqueous emulsion of Example 1 was obtained.

"Examples 2 to 5, Comparative Examples 1 to 8"

An aqueous emulsion was prepared in the same manner as in Example 1 except that the amount of the split chain transfer agent and/or the composition of the (A) emulsion and (B) emulsion were changed as shown in Table 1 or Table 2. .

The values of (A) emulsion and (B) emulsion, addition-cleaving chain transfer agent, polymerization initiator, dropping catalyst, and neutralizing agent shown in Tables 1 and 2 are masses, and the unit is (g). ).

The ratio of the first polymerizable component (A) shown in Table 1 and Table 2 is the first polymerizable component among the total polymerizable components in which the first polymerizable component (A) and the second polymerizable component (B) are combined. (A) ratio (% by mass). In addition, the ratio of the second polymerizable component (B) is a ratio (% by mass) of the second polymerizable component (B) in the total polymerizable component.

The values of the first polymerizable component (A) Tg and the second polymerizable component (B) Tg shown in Tables 1 and 2 are as follows. Tables 1 and 2 and the following are shown. The glass transition temperature (absolute temperature) Tn of the homopolymer (homopolymer) of each monomer component was calculated based on the FOX equation described above.

MMA (methyl methacrylate): 378K

BuA (n-butyl acrylate): 221K

2EHA (2-ethylhexyl acrylate): 203K

Aa (acrylic acid): 379K

β-CEA (β-carboxyethyl acrylate): 310K

2HEMA (2-hydroxyethyl methacrylate): 328K

The materials shown in Tables 1 and 2 other than the monomer components used in the production of the aqueous emulsions of the examples and the comparative examples are as follows: NOFMER MSD (α-methylstyrene dimer): addition-cleaving chain transfer agent (Nippon Oil Co., Ltd.)

SILICON SCA-503: decane coupling agent (Zhangjiagang Guotai-Huarong New Chemical Materials Co., Ltd.)

Aqualon KH-10 (polyoxyethylene-1-(allyloxyethylene) alkyl ether sulfate ammonium salt): surfactant (manufactured by Daiichi Kogyo Co., Ltd.)

Next, the properties of the aqueous emulsions of Examples 1 to 5 and Comparative Examples 1 to 8 were evaluated according to the methods shown below. The results are shown in Tables 1 and 2.

(The nature of the aqueous emulsion)

(A) Nonvolatile fraction: The aqueous emulsion was dried at 105 ° C for 1 hour, and was calculated according to the following formula.

Non-volatile fraction (%) = [mass after drying / quality before drying] × 100

(B) Viscosity: Measured at 23 ° C and 10 rpm using a BH type viscometer.

(C) pH: determined by a pH meter.

Further, each of the aqueous emulsions of Examples 1 to 5 and Comparative Examples 1 to 8 was used as an aqueous adhesive composition, and an adhesive sheet was produced by the following method.

As the substrate, a polyester film having a thickness of 50 μm which was subjected to corona treatment on one side was prepared. Thereafter, the surface of the polyester film subjected to the corona treatment was applied with an aqueous emulsion (aqueous adhesive composition) so that the thickness of the adhesive layer after drying became 35 μm, and dried at 105 ° C for 2 minutes to form an adhesive. Layer, get the adhesive sheet.

The peel strength of the obtained adhesive sheet was measured according to the method shown below. Put it The results are shown in Tables 1 and 2.

(Measurement of peel strength (adhesion))

The adhesion evaluation method according to JIS-Z-0237 is adopted. Specifically, the adhesive layer of the 25 mm × 250 mm adhesive sheet produced by the above method was laminated with the stainless steel (SUS304) plate as the adherend, and the bonding area was 25 mm × 125 mm. On the adhesive sheet, the 2 kg roller was rolled back and forth once in a temperature of 23 ° C and a relative humidity of 50%, thereby adhering the adhesive sheet to the stainless steel plate and placing it in the same environment. After the bonding, the 180° peel strength (N/25 mm) was measured under the conditions of a peeling speed of 300 mm/min for those who were allowed to stand for 20 minutes and for 24 hours.

Further, in the measurement of the peel strength, when the adhesive layer of the adhesive sheet was cohesively broken, "c" was added to the end of the numerical value of the 180 peel strength described in Tables 1 and 2.

Further, the 180° peel strength (N/25 mm) of the adherend (stainless steel plate) placed for 20 minutes after the bonding was evaluated according to the following criteria.

"baseline"

◎: 12.0 (N/25mm) or more

○: 10.0 (N/25mm) or more

×: not up to 10.0 (N/25mm)

(re-peelability (residue))

It was visually judged whether or not the adherend (stainless steel plate) which measured the peeling force after the bonding which was used for the measurement of the adhesive force was left for 24 hours, and it was evaluated based on the following criteria.

"baseline"

○: no residue of sticky material

△: Residual glue is available in the area of less than 5% of the total adherend

×: 5% or more of the entire adherend has residual glue

(with or without blurring)

The adherend (stainless steel sheet) in which the peeling force was measured after being placed for 24 hours after the bonding was measured by visual observation was visually judged to be illegible (sticking), and evaluated according to the following criteria.

"baseline"

○: The sticky object is unclear (sticky)

×: The sticky object is blurred (sticky)

(Measurement of gel fraction)

A sample (aqueous emulsion) dried at 105 ° C was weighed to about 1.0 g, and it was immersed in about 30 ml of toluene at room temperature for 1 day. Thereafter, the toluene-insoluble matter was taken out, dried at 110 ° C for about 1 hour, and weighed, and the gel fraction was calculated using the following formula.

Gel fraction (%) = [toluene insoluble mass / sample quality] × 100

As shown in Table 1, the adhesive sheets of the aqueous emulsions (aqueous adhesive compositions) of Examples 1 to 5 were used, at the initial stage of bonding (20). Peeling force after a minute) or high adhesion after 24 hours. In particular, the adhesive sheets of Example 1 and Example 3 had an adhesive force of 12.5 (N/25 mm) or more after bonding for 20 minutes, and showed an extremely high adhesive force.

Further, in the adhesive sheets of Examples 1 to 5, the amount of residual glue to the adherend was small, and peeling was possible without leaving a sticking mark.

On the other hand, as shown in Table 2, the adhesive sheet for the adherend was produced using the adhesive sheet of the aqueous emulsion of Comparative Example 1 which was produced without using the addition-cleaving type chain transfer agent (NOFMER MSD). Further, in the adhesive sheet of Comparative Example 1, cohesive failure occurred in the evaluation of the adhesion after 24 hours of bonding.

Further, an adhesive sheet of the aqueous emulsion of Comparative Example 2 which was produced without using an addition-cleaving type chain transfer agent, and an adhesive sheet of the aqueous emulsion of Comparative Example 3 which was used in a small amount using an addition-cracking type chain transfer agent, were coagulated. Although the gel fraction is 90% or more, there is a stick residue.

Further, the adhesive sheet to the adherend was generated using the adhesive sheet of the aqueous emulsion of Comparative Example 4 in which the (B) emulsion was not used. Further, in the adhesive sheet of Comparative Example 4, cohesive failure occurred at the time of evaluation of the adhesive force after bonding for 20 minutes and 24 hours.

Using the adhesive sheet of the aqueous emulsion of Comparative Example 5 in which the (B) emulsion had a Tg of -52 ° C, a residue against the adherend occurred. Further, in the adhesive sheet of Comparative Example 5, the adhesion at the initial bonding (peeling force after 20 minutes) was insufficient, and cohesive failure occurred at the time of evaluation of the adhesive force after 24 hours of bonding.

Also, the use of an addition-cleaving type chain transfer agent is excessively used. In the adhesive sheet of the aqueous emulsion of Comparative Example 6, the residue of the adherend occurred. Further, in the adhesive sheet of Comparative Example 6, the adhesion at the initial bonding (peeling force after 20 minutes) was insufficient, and cohesive failure occurred in the evaluation of the adhesion after 24 hours of bonding.

Further, the adhesive sheet to the adherend was generated using the adhesive sheet of the aqueous emulsion of Comparative Example 7 in which the (A) emulsion was not used. Further, in the adhesive sheet of Comparative Example 7, cohesive failure occurred in the evaluation of the adhesion after 20 minutes of bonding and after 24 hours.

Further, the adhesive sheet of the aqueous emulsion of Comparative Example 8 in which the (A) emulsion had a Tg of -8 ° C had insufficient adhesion at the initial bonding (peeling force after 20 minutes), and adhesion after bonding for 24 hours. The power is not sufficient.

Claims (9)

An aqueous adhesive composition comprising an aqueous emulsion comprising: step (I) of emulsifying and polymerizing a first polymerizable component in the presence of an addition-cleaving chain transfer agent, and The step (II) in which the polymer obtained in the above step (I) is supplied to the second polymerizable component and polymerized, and the production method satisfying the following conditions (1) to (3) is obtained: (1) addition-cracking type The amount of the chain transfer agent is 0.05 to 1 part by mass based on 100 parts by mass of the total polymerizable component in total of the first polymerizable component and the second polymerizable component; (2) the first polymerizable component provides glass. a polymer having a transition temperature of -20 ° C or lower and 70 to 95% by mass of the total polymerizable component; (3) the second polymerizable component provides a polymer having a glass transition temperature of 50 ° C or higher, and 5 to 30% by mass of the total polymerizable component. The aqueous adhesive composition according to claim 1, wherein the aqueous emulsion has a gel fraction of 90% or more. The aqueous adhesive composition of claim 1 or claim 2, wherein the first polymerizable component provides a polymer having a glass transition temperature of -40 ° C or less. The aqueous adhesive composition of claim 1 or claim 2, wherein the second polymerizable component provides a polymer having a glass transition temperature of 70 ° C or higher. The aqueous adhesive composition of claim 1 or claim 2, wherein the second polymerizable component comprises more than 50% by mass of methyl methacrylate and/or n-butyl acrylate. The aqueous adhesive composition according to claim 1 or claim 2, wherein the first polymerizable component comprises more than 50% by mass of n-butyl acrylate and/or 2-ethylhexyl acrylate. An adhesive sheet having an adhesive layer on one or both sides of a substrate, the adhesive layer being formed using the aqueous adhesive composition according to any one of claims 1 to 6. A method for producing an aqueous adhesive composition, comprising a step of producing an aqueous emulsion, the step of producing the aqueous emulsion comprising: step of emulsion-polymerizing the first polymerizable component in the presence of an addition-cracking chain transfer agent (I), and the step (II) of supplying the second polymerizable component to the polymer obtained in the above step (I) and carrying out the polymerization, and satisfying the following conditions (1) to (3): (1) addition cracking The amount of the chain transfer agent is 0.05 to 1 part by mass based on 100 parts by mass of the total polymerizable component in total of the first polymerizable component and the second polymerizable component; (2) the first polymerizable component is provided a polymer having a glass transition temperature of -20 ° C or lower and 70 to 95% by mass of the total polymerizable component; (3) the second polymerizable component provides a polymer having a glass transition temperature of 50 ° C or higher, and It is 5 to 30% by mass in the above all-polymerizable component. An aqueous adhesive composition comprising an aqueous emulsion containing a soft polymer and a hard polymer as a structural unit, the two polymer systems having a functional group derived from an addition-cleaving type chain transfer agent, the soft polymerization The glass transition temperature of the material is -20 ° C or lower, 70 to 95% by mass of the structural unit of the polymer, and the glass transition temperature of the hard polymer is 50 ° C or higher, and the structural unit of the polymer contains 5 to 5 30% by mass, the soft polymer portion composed of the aforementioned soft polymer and the hard polymer portion composed of the above-mentioned hard polymer have a two-layer structure.