Acrylic resin emulsion and method for producing the same, and method for producing aqueous polymer-isocyanate-based adhesive obtained by using the emulsion

Abstract

To provide acrylic resin emulsion having good storage stability of emulsion and providing aqueous polymer-isocyanate-based adhesive which has a long pot life and has improved adhesive force.SOLUTION: A method for producing acrylic resin emulsion includes: a polymerization step of emulsion polymerizing a monomer component including an aromatic vinyl monomer and alkyl (meth)acrylate, in the presence of an emulsifier and a polymerization initiator, at a polymerization temperature exceeding 50°C; and an emulsifier addition step of adding a nonionic emulsifier (A1) having a linear alkyl group and / or branched alkyl group and no aromatic hydrocarbon ring, after the temperature of the solution obtained in the polymerization step is equal to or lower than 50°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an acrylic resin emulsion, a method for producing the same, and a method for producing an aqueous polymer-isocyanate adhesive using the emulsion. [Background technology]

[0002] Aqueous polymer-isocyanate adhesives do not generate formaldehyde, can bond at room temperature, and have excellent water resistance and durability, so they are widely used for bonding wood, etc. Aqueous polymer-isocyanate adhesives are generally obtained by blending an isocyanate compound, which serves as a curing agent, with a base agent containing an aqueous emulsion, polyvinyl alcohol, and water.

[0003] For example, Patent Document 1 describes that water resistance and heat resistance can be improved by using, as the aqueous emulsion contained in an aqueous polymer-isocyanate adhesive, an aqueous emulsion obtained by emulsion polymerization of a monomer composition containing (A) one or more monomers (a1) selected from aromatic vinyl monomers and / or (meth)acrylic acid ester monomers, and a hydroxyl group-containing vinyl monomer (a2), (B) a compound having a polymerizable double bond group selected from sodium p-styrenesulfonate or sodium methallylsulfonate, and (C) a polymerizable monomer composition containing an anionic surfactant and / or a nonionic surfactant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4155736 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in aqueous polymer-isocyanate adhesives using aqueous emulsions obtained by adding a surfactant (i.e., an emulsifier) ​​during polymerization of an aromatic vinyl monomer and a (meth)acrylic acid ester monomer, as in Patent Document 1, there is a demand for further improvement in adhesive strength, as well as for improvement in the storage stability of the aqueous emulsion and the pot life of the resulting adhesive.

[0006] Therefore, an object of the present invention is to provide an acrylic resin emulsion that has good emulsion storage stability, that provides a long pot life for the resulting aqueous polymer-isocyanate-based adhesive, and that provides an aqueous polymer-isocyanate-based adhesive with improved adhesive strength. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the present inventors have discovered that by emulsion polymerizing monomer components including an aromatic vinyl monomer and a (meth)acrylic acid alkyl ester, cooling the resulting solution to a predetermined temperature or below, and then adding a specific nonionic emulsifier, it is possible to provide an acrylic resin emulsion that has good storage stability, a long pot life for the resulting adhesive, and an improved adhesive strength for the resulting adhesive, and have completed the present invention.

[0008] That is, the present invention is as follows. [1] A polymerization step of emulsion-polymerizing a monomer component including an aromatic vinyl monomer and a (meth)acrylic acid alkyl ester in the presence of an emulsifier and a polymerization initiator at a polymerization temperature of more than 50°C; an emulsifier addition step of adding a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring after the temperature of the solution obtained in the polymerization step has reached 50°C or less. [2] The production method according to [1], wherein the amount of the nonionic emulsifier (A1) added in the emulsifier addition step is 0.05 to 8.0 parts by mass per 100 parts by mass of the total of the monomer components. [3] The monomer component further contains a hydroxyl group-containing monomer, The production method according to [1] or [2], wherein the content of the hydroxyl group-containing monomer is 0.1 to 2.8% by mass in 100% by mass of the monomer components. [4] The method according to any one of [1] to [3], wherein the emulsion particles constituting the acrylic resin emulsion have an average particle size based on the scattering intensity distribution (cumulant average particle size) of 100 to 350 nm. [5] A method for producing an aqueous polymer-isocyanate adhesive, comprising a step of mixing a main component composition containing the acrylic resin emulsion obtained by the production method according to any one of [1] to [4], polyvinyl alcohol, and water with an isocyanate crosslinking agent. [6] An acrylic resin emulsion comprising emulsion particles containing structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester, a nonionic emulsifier (A), and water, the nonionic emulsifier (A) comprises a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring, the content of the nonionic emulsifier (A1) is 90% by mass or more in 100% by mass of the nonionic emulsifier (A), The acrylic resin emulsion has a content of the nonionic emulsifier (A) of 0.3 parts by mass or more per 100 parts by mass of the emulsion particles. [7] An acrylic resin emulsion comprising emulsion particles containing structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester, a nonionic emulsifier (A), and water, the nonionic emulsifier (A) comprises a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring, An acrylic resin emulsion that has a peeling rate of 10% or less as determined by the boiling peeling test below. (Boiling peel test) The acrylic resin emulsion, a 15% polyvinyl alcohol aqueous solution, calcium carbonate, and water were mixed in a mass ratio of 20:15:20:45 (acrylic resin emulsion:polyvinyl alcohol aqueous solution:calcium carbonate:water). Next, 15 parts by mass of polymethylene polyphenyl polyisocyanate was added to 100 parts by mass of the base composition to prepare an adhesive. The adhesive's adhesion to Douglas fir was tested in accordance with the "Boiling Peel Test" for structural laminated lumber specified by the Japanese Agricultural Standards, and the peel rate was calculated. [Effects of the Invention]

[0009] According to the present invention, it is possible to produce an acrylic resin emulsion that has good storage stability, and in which the resulting aqueous polymer-isocyanate-based adhesive has a long pot life and improved adhesive strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] One embodiment of the present invention will be described below, but the present invention is not limited thereto. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less." Furthermore, "(meth)acrylic acid" means acrylic acid or methacrylic acid, and "(meth)acrylate" means acrylate or methacrylate. The same applies to terms such as "(meth)acryloxy" and "(meth)acryloyl."

[0011] [1. Acrylic resin emulsion manufacturing method] The method for producing the acrylic resin emulsion of the present invention includes the steps of: a polymerization step of emulsion-polymerizing a monomer component including an aromatic vinyl monomer and a (meth)acrylic acid alkyl ester in the presence of an emulsifier and a polymerization initiator at a polymerization temperature of more than 50°C; The method is characterized by including an emulsifier addition step of adding a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring after the temperature of the solution obtained in the polymerization step has reached 50°C or less. Each step will be explained below in order.

[0012] [1-1. Polymerization process] In the polymerization step, the monomer components are emulsion-polymerized in the presence of an emulsifier and a polymerization initiator at a polymerization temperature of more than 50° C. Any conventionally known emulsion polymerization method can be used as long as the specific monomer components are used and the polymerization temperature is more than 50° C.

[0013] The monomer component contains an aromatic vinyl monomer, which can enhance the water resistance of the resulting aqueous polymer-isocyanate adhesive (hereinafter sometimes simply referred to as "adhesive").

[0014] The aromatic vinyl monomer is preferably a monomer having at least one aromatic hydrocarbon ring and at least one terminal ethylenically unsaturated group in the molecule. The aromatic hydrocarbon ring refers to a hydrocarbon ring having aromaticity and consisting of a single ring or condensed rings, and specific examples thereof include a benzene ring, a naphthalene ring, a phenanthrene ring, an anthracene ring, etc., with a benzene ring being preferred. In the following description, the term "aromatic hydrocarbon ring" has the same meaning as above. The number of aromatic hydrocarbon rings per molecule of the aromatic vinyl monomer is preferably 1 to 2, and more preferably 1. Examples of the terminal ethylenically unsaturated group include a vinyl group, a (meth)acryloyl group, etc. The number of terminal ethylenically unsaturated groups per molecule of the aromatic vinyl monomer is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1.

[0015] Examples of the aromatic vinyl monomer include styrene-based monomers, aryl(meth)acrylates, aralkyl(meth)acrylates, and aryloxy group-containing alkyl(meth)acrylates.

[0016] The styrene-based monomers include styrene; C alkyl groups such as halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms); and alkyl groups (e.g., methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, and tert-butyl groups). 1-4 alkyl group), vinyl group, alkoxysilyl group (e.g., tri-C such as trimethoxysilyl group, triethoxysilyl group, etc. 1-4 and styrene having one or more substituents such as an alkoxysilyl group. The substituent is preferably at least one selected from a halogen atom and an alkyl group. Specific examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene, chlorostyrene, chloromethylstyrene, divinylbenzene, p-styryltrimethoxysilane, and 2-styrylethyltrimethoxysilane.

[0017] Examples of the aryl (meth)acrylate include aryl (meth)acrylates having an aryl group having 6 to 18 carbon atoms, such as phenyl (meth)acrylate, o-tolyl (meth)acrylate, m-tolyl (meth)acrylate, p-tolyl (meth)acrylate, 2,3-xylyl (meth)acrylate, 2,4-xylyl (meth)acrylate, 2,5-xylyl (meth)acrylate, 2,6-xylyl (meth)acrylate, 3,4-xylyl (meth)acrylate, 3,5-xylyl (meth)acrylate, 1-naphthyl (meth)acrylate, and 2-naphthyl (meth)acrylate.

[0018] Examples of the aralkyl (meth)acrylate include aralkyl (meth)acrylates having an aralkyl group having 7 to 18 carbon atoms, such as benzyl (meth)acrylate, phenylethyl (meth)acrylate, methylbenzyl (meth)acrylate, and naphthylmethyl (meth)acrylate.

[0019] Examples of the aryloxy group-containing alkyl (meth)acrylate include C acrylates such as phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, methylphenoxyethyl (meth)acrylate, and 2-(2-naphthyloxy)ethyl (meth)acrylate. 6-18 Aryloxy C 2-4 Examples include alkyl (meth)acrylates.

[0020] The aromatic vinyl monomers may be used alone or in combination of two or more.

[0021] The aromatic vinyl monomer is preferably a styrene-based monomer, more preferably styrene or styrene having at least one substituent selected from a halogen atom and an alkyl group, and even more preferably styrene.

[0022] The amount of the aromatic vinyl monomer is, for example, 15 to 80 mass%, preferably 40 to 60 mass%, and more preferably 40 to 55 mass%, based on 100 mass% of all monomer components used in the polymerization step. By adjusting the amount of the aromatic vinyl monomer to be equal to or greater than the above-mentioned lower limit, the water resistance of the resulting adhesive can be improved, and by adjusting the amount of the aromatic vinyl monomer to be equal to or less than the above-mentioned upper limit, it is possible to design a Tg appropriate for the required performance while maintaining water resistance.

[0023] The monomer component further includes a (meth)acrylic acid alkyl ester. Specific examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, 2-pentyl (meth)acrylate, isopentyl (meth)acrylate, and neobutyl (meth)acrylate. Pentyl (meth)acrylate, 3-methyl-2-butyl (meth)acrylate, 3-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-hexyl (meth)acrylate, 3,3-dimethyl-2-butyl (meth)acrylate, 3-methyl-2-pentyl (meth)acrylate, 4-methyl-2-pentyl (meth)acrylate, 2,4-dimethyl-3-pentyl (meth)acrylate, n-heptyl (meth)acrylate, 2-heptyl (meth)acrylate ) acrylate, 2-methyl-3-hexyl (meth)acrylate, 3-heptyl (meth)acrylate, 5-methyl-2-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2,2-dimethyl-3-hexyl (meth)acrylate, 2,5-dimethyl-3-hexyl (meth)acrylate, 3-octyl (meth)acrylate, 4-octyl (meth)acrylate, Examples of the acrylate include 5-methyl-2-heptyl (meth)acrylate, 5-methyl-3-heptyl (meth)acrylate, 6-methyl-2-heptyl (meth)acrylate, 6-methyl-3-heptyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, tridecyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, henicosyl (meth)acrylate, and tetracosyl (meth)acrylate.

[0024] The (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0025] Among them, (meth)acrylic acid alkyl esters include (meth)acrylic acid C 1-20 Also preferred are (meth)acrylic acid alkyl esters having a homopolymer glass transition temperature (Tg) of −20° C. or lower (hereinafter, sometimes referred to as low Tg (meth)acrylic acid alkyl esters), and methacrylic acid C 1-5 At least one selected from alkyl esters is also preferred. Structural units derived from low Tg (meth)acrylic acid alkyl esters and / or methacrylic acid C 1-5 By appropriately adjusting the content of structural units derived from alkyl esters, it becomes easy to adjust the glass transition temperature of the resulting emulsion particles to fall within the range described below.

[0026] In this specification, the "glass transition temperature of a homopolymer" may be, for example, the value (if multiple Tg values ​​are listed, the lowest value) described in "POLYMER HANDBOOK THIRD EDITION" (by J. BRANDRUP and EHIMMERGUT, 1989, published by John Wiley & Sons, Inc., pp. VI / 209-VI / 277). For compounds not described in "POLYMER HANDBOOK THIRD EDITION," a value (calculated value) determined by computer using commercially available glass transition temperature calculation software (e.g., "MATERIALS STUDIO" manufactured by Accelrys Software Inc., version 4.0.0.0, module: Synthia, calculation conditions: weight average molecular weight 100,000) may be used.

[0027] The Tg of the low Tg (meth)acrylic acid alkyl ester is −20° C. or lower, preferably −100 to −20° C., and more preferably −80 to −30° C. Examples of the low Tg (meth)acrylic acid alkyl ester include ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, and isononyl acrylate. Of these, n-butyl acrylate, 2-octyl acrylate, and 2-ethylhexyl acrylate are preferred, and n-butyl acrylate is more preferred. By using a low Tg (meth)acrylic acid alkyl ester, the Tg of the emulsion particles can be lowered, and the adhesive properties of the resulting adhesive can be further improved.

[0028] Also, methacrylic acid C 1-5 As alkyl esters, methacrylic acid C 1-3 Alkyl esters are preferred, with methyl methacrylate being more preferred. Methacrylic acid C 1-5 The use of alkyl esters can increase the reactivity in emulsion polymerization.

[0029] The amount of the (meth)acrylic acid alkyl ester (particularly, the low Tg (meth)acrylic acid alkyl ester and the methacrylic acid C 1-5 The amount of the alkyl esters (total amount of alkyl esters) may be appropriately adjusted so that the Tg of the resulting emulsion particles falls within the range described below, and is, for example, 20 to 200 parts by mass, preferably 50 to 160 parts by mass, and more preferably 110 to 130 parts by mass relative to 100 parts by mass of the aromatic vinyl monomer.

[0030] From the viewpoint of achieving both water resistance and adhesiveness of the resulting adhesive, the amount of the low Tg (meth)acrylic acid alkyl ester is preferably 20 to 160 parts by mass, more preferably 50 to 140 parts by mass, and even more preferably 90 to 120 parts by mass, per 100 parts by mass of the aromatic vinyl monomer. Methacrylic acid C1-5 The amount of alkyl ester is, for example, 0 to 30 parts by mass relative to 100 parts by mass of the aromatic vinyl monomer, and from the viewpoint of achieving both water resistance and polymerization reactivity, it is preferably 3 to 30 parts by mass, and more preferably 5 to 20 parts by mass. The amount of the (meth)acrylic acid alkyl ester (particularly, the low Tg (meth)acrylic acid alkyl ester and the methacrylic acid C 1-5 The amount of the alkyl esters (total amount) is, for example, 15 to 80 mass %, preferably 25 to 70 mass %, and more preferably 35 to 60 mass % relative to 100 mass % of all the monomer components used in the polymerization step. The amount of the low Tg alkyl (meth)acrylate is, for example, 15 to 80 mass %, preferably 25 to 65 mass %, and more preferably 35 to 55 mass %, based on 100 mass % of all monomer components used in the polymerization step. The methacrylic acid C 1-5 The amount of alkyl ester is, for example, 1 to 15 mass %, preferably 1 to 10 mass %, and more preferably 2 to 7 mass %, relative to 100 mass % of all monomer components used in the polymerization step.

[0031] The total amount of the aromatic vinyl monomer and the (meth)acrylic acid alkyl ester is, for example, 60 to 100 mass%, preferably 80 to 99.5 mass%, and more preferably 90 to 99.0 mass%, based on 100 mass% of all monomer components used in the polymerization step.

[0032] The monomer component preferably further contains a hydroxyl group-containing monomer, which enables crosslinking between the isocyanate-based crosslinking agent and the emulsion particles, thereby achieving a high crosslink density.

[0033] The hydroxyl group-containing monomer is preferably a monomer having at least one hydroxyl group and at least one polymerizable unsaturated group in the molecule (but not having an aromatic hydrocarbon ring). Examples of the polymerizable unsaturated group include a (meth)acryloyl group, a vinyl group, and a maleimide group, and among these, a (meth)acryloyl group is preferred.

[0034] Specific examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; halogen-substituted hydroxyalkyl (meth)acrylates such as 3-chloro-2-hydroxypropyl (meth)acrylate; modified hydroxyalkyl (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate and 2-(meth)acryloyloxyethyl 2-hydroxyethyl phthalate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; and hydroxyl group-containing vinyl monomers such as vinyl alcohol and allyl alcohol.

[0035] The hydroxyl group-containing monomers may be used alone or in combination of two or more.

[0036] Among them, the hydroxyl group-containing monomer is preferably hydroxyalkyl (meth)acrylate, and hydroxy C 1-4 Alkyl (meth)acrylates are more preferred, and 2-hydroxyethyl (meth)acrylate is even more preferred.

[0037] The amount of the hydroxyl group-containing monomer may be, for example, 0 to 5 mass% based on 100 mass% of all monomer components used in the polymerization step, but is preferably 0.1 to 2.8 mass%, more preferably 1.0 to 2.8 mass%, and even more preferably 1.5 to 2.5 mass%. By adjusting the amount of the hydroxyl group-containing monomer to be equal to or greater than the above-mentioned lower limit, the crosslink density of the adhesive can be increased, and by adjusting the amount of the hydroxyl group-containing monomer to be equal to or less than the above-mentioned upper limit, the pot life of the resulting adhesive can be extended.

[0038] The amount of the hydroxyl group-containing monomer may be, for example, 0 to 10 parts by mass, preferably 1.0 to 6.5 parts by mass, and more preferably 3.0 to 6.0 parts by mass, relative to 100 parts by mass of the aromatic vinyl monomer.

[0039] The monomer component may further contain a crosslinking monomer, which allows for the construction of a crosslinking system other than that achieved by an isocyanate-based crosslinking agent.

[0040] The crosslinkable monomer is preferably a monomer that has neither an aromatic hydrocarbon ring nor a hydroxyl group, and has at least one crosslinkable functional group and at least one polymerizable unsaturated group in the molecule. Examples of the crosslinkable functional group include a polymerizable unsaturated group, an epoxy group, and a hydrolyzable silyl group, and among these, a hydrolyzable silyl group is preferred. The hydrolyzable silyl group refers to a silyl group to which a hydrolyzable group (e.g., an alkoxy group, a halogen atom, etc.) is bonded. Examples of the polymerizable unsaturated group include a (meth)acryloyl group, a vinyl group, and a maleimide group, and among these, a (meth)acryloyl group is preferred.

[0041] Examples of crosslinkable monomers include monomers having two or more polymerizable unsaturated groups, silane coupling agents having a hydrolyzable silyl group and a polymerizable unsaturated group, and epoxy group-containing crosslinkable monomers having an epoxy group and a polymerizable unsaturated group (but excluding hydrolyzable silyl groups).

[0042] Specific examples of the monomer having two or more polymerizable unsaturated groups include: Alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate (preferably C 1-10alkanediol di(meth)acrylate); Dialkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate (preferably diC 2-4 alkylene glycol di(meth)acrylate); Polyalkylene glycol di(meth)acrylates such as polyethylene glycol di(meth)acrylates having an added mole number of ethylene oxide of 2 to 50, and polypropylene glycol di(meth)acrylates having an added mole number of propylene oxide of 2 to 50 (preferably C 2-4 PolyC with 2 to 50 moles of alkylene oxide added 2-4 alkylene glycol di(meth)acrylate); trihydric alcohol tri(meth)acrylates such as ethoxylated glycerin tri(meth)acrylate, propylene oxide-modified glycerol tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and trimethylolpropane triethoxytri(meth)acrylate; tetra(meth)acrylates of tetrahydric alcohols such as pentaerythritol tetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate; Hexa(meth)acrylates of hexahydric alcohols such as dipentaerythritol hexa(meth)acrylate; 2-(2'-vinyloxyethoxyethyl)(meth)acrylate; and the like.

[0043] Specific examples of the silane coupling agent include (meth)acryloyl group-containing silane coupling agents such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, and 3-(meth)acryloxyethoxypropyltrimethoxysilane; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; and epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0044] Specific examples of the epoxy group-containing crosslinkable monomer include epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate, α-methylglycidyl (meth)acrylate, and 2-glycidyloxyethyl (meth)acrylate; epoxy group-containing vinyl monomers such as allyl glycidyl ether; and the like.

[0045] The crosslinkable monomers may be used alone or in combination of two or more.

[0046] Among them, the crosslinkable monomer is preferably a silane coupling agent, more preferably a (meth)acryloyl group-containing silane coupling agent, and more preferably a (meth)acryloxy C 2-4 Alkyltri C 1-4 Alkoxysilane is more preferred.

[0047] The amount of the crosslinkable monomer may be, for example, 0 to 5.0% by mass, preferably 0.1 to 3.0% by mass, and more preferably 0.3 to 1.0% by mass, based on 100% by mass of all monomer components used in the polymerization step. By adjusting the amount of the crosslinkable monomer to be equal to or greater than the above-mentioned lower limit, the crosslink density can be increased. Furthermore, by adjusting the amount of the crosslinkable monomer to be equal to or less than the above-mentioned upper limit, the pot life can be further extended.

[0048] The amount of the crosslinkable monomer may be, for example, 0 to 8.0 parts by mass, preferably 0.3 to 5.0 parts by mass, and more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the aromatic vinyl monomer.

[0049] The monomer component may further contain a monomer other than the aromatic vinyl monomer, the (meth)acrylic acid alkyl ester, the hydroxyl group-containing monomer, and the crosslinkable monomer (hereinafter referred to as other monomer). The other monomers are monomers other than aromatic vinyl monomers, (meth)acrylic acid alkyl esters, hydroxyl group-containing monomers, and crosslinkable monomers, and have at least one polymerizable unsaturated group in the molecule.

[0050] Specific examples of other monomers include: cycloaliphatic group-containing monomers such as cycloalkyl(meth)acrylates (e.g., cyclopropyl(meth)acrylate, cyclopentyl(meth)acrylate, cyclohexyl(meth)acrylate, cycloheptyl(meth)acrylate, cyclooctyl(meth)acrylate), esters of (meth)acrylic acid and polycyclic alcohols (e.g., isobornyl(meth)acrylate, adamantyl(meth)acrylate), and cycloalkyl group-containing maleimides (N-cyclohexylmaleimide); acid group-containing monomers such as unsaturated monocarboxylic acids (e.g., (meth)acrylic acid, cinnamic acid, crotonic acid), unsaturated dicarboxylic acids (e.g., maleic acid, fumaric acid, itaconic acid, and citraconic acid), monoesters of unsaturated dicarboxylic acids (e.g., maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monomethyl ester, itaconic acid monobutyl ester, etc.), anhydrides of unsaturated dicarboxylic acids (e.g., maleic anhydride), 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl hexahydrophthalic acid, etc.); Vinyl lactam monomers (e.g., N-methylvinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone), maleimide monomers (e.g., maleimide, N-ethylmaleimide), piperidyl (meth)acrylic monomers (e.g., 2,2,6,6-tetramethyl-4-piperidyl (meth)acrylate, 1,2 , 2,6,6-pentamethyl-4-piperidyl (meth)acrylate), aziridinyl group-containing (meth)acrylic monomers (e.g., (meth)acryloylaziridine, (meth)acrylic acid 2-aziridinylethyl), addition-polymerizable oxazolines (e.g., 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2- nitrogen atom-containing monomers such as isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline), amino group-containing (meth)acrylic monomers (e.g., N,N-dimethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate), and amide group-containing monomers (e.g., (meth)acrylamide, N-monomethyl (meth)acrylamide, N-monoethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, Nn-propyl (meth)acrylamide, N-isopropyl (meth)acrylamide, methylenebis(meth)acrylamide, N-butoxymethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl acrylamide, and diacetone acrylamide); Fluoroalkyl (meth)acrylates such as trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and octafluoropentyl (meth)acrylate; alkoxyalkyl group-containing (meth)acrylates such as methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and trimethylolpropane tripropoxy (meth)acrylate; carbonyl group-containing (meth)acrylates such as (meth)acryloxyalkylpropenal, acetonyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate acetylacetate, butanediol-1,4-acrylate acetylacetate, and 2-(acetoacetoxy)ethyl (meth)acrylate; vinyl monomers such as vinyl acetate, vinyl chloride, and vinyl benzoate; Olefin monomers such as ethylene and propylene; and the like.

[0051] The other monomers may be used alone or in combination of two or more.

[0052] The amount of the other monomers is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of all monomer components used in the polymerization step, and may be 0% by mass.

[0053] The emulsifier used in the polymerization step is not limited, but includes nonionic emulsifiers, anionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, polymeric emulsifiers, etc., and conventionally known emulsifiers can be used. These emulsifiers may be used alone or in combination of two or more. Furthermore, an emulsifier containing a polymerizable unsaturated group in the molecule may also be used. Examples of the polymerizable unsaturated group include a group having an ethylenically unsaturated double bond. Incidentally, an emulsifier containing a polymerizable unsaturated group is also referred to as a reactive emulsifier. Among these, the emulsifier used in the polymerization step is preferably a nonionic emulsifier and / or an anionic emulsifier, and more preferably a combination of a nonionic emulsifier and an anionic emulsifier. Of the total emulsifiers used in the polymerization step (100% by mass), the total amount of nonionic emulsifier and anionic emulsifier is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.

[0054] The nonionic emulsifier (hereinafter referred to as nonionic emulsifier (A)) refers to a compound having a nonionic group and a hydrophobic group (but not having a cationic group).

[0055] Examples of the nonionic group include groups known as emulsifiers (surfactants), such as polyether groups and ester groups. The nonionic group is preferably a polyether group, more preferably a polyoxyalkylene group, and more preferably a polyoxy C 2-4 An alkylene group is more preferred, and a polyoxyethylene group and a polyoxypropylene group are particularly preferred.

[0056] Examples of the hydrophobic group include groups known as emulsifiers (surfactants), such as linear or branched alkyl groups and aromatic hydrocarbon ring-containing hydrocarbon groups. Of these, linear or branched alkyl groups are preferred, and linear alkyl groups are more preferred. The linear or branched alkyl group preferably has 8 to 40 carbon atoms, more preferably 8 to 30 carbon atoms, and even more preferably 8 to 20 carbon atoms. The aromatic hydrocarbon ring-containing hydrocarbon group is preferably a hydrocarbon group having a benzene ring, and the aromatic hydrocarbon ring-containing hydrocarbon group preferably has 10 to 40 carbon atoms, more preferably 18 to 30 carbon atoms.

[0057] Examples of the nonionic emulsifier (A) include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyalkylene alkylaryl ethers such as polyoxyethylene nonylphenyl ether and polyoxyethylene dibutylphenyl ether; condensates of polyethylene glycol and polypropylene glycol; sorbitan fatty acid esters such as sorbitan monostearate, sorbitan distearate, sorbitan tristearate and sorbitan monolaurate; polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan tristearate, and the like. Examples of suitable hydroxyalkylene sorbitan fatty acid esters include polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan stearate; fatty acid monoglycerides such as glycerol monostearate and glycerol monooleate; condensation products of ethylene oxide and aliphatic amines; and compounds containing a polyoxyalkylene group and an alkenyl group having a terminal double bond, such as polyoxyethylene styrenated propenyl phenyl ether, allyloxymethyl alkoxyethyl hydroxypolyoxyethylene, polyoxyethylene alkylpropenyl phenyl ether, allyloxymethyl nonylphenoxyethyl hydroxypolyoxyethylene, and polyoxyalkylene alkenyl ether.

[0058] The nonionic emulsifier used in the polymerization step is not particularly limited, but from the viewpoint of the storage stability of the emulsion, a nonionic emulsifier having a linear alkyl group and / or a branched alkyl group as the hydrophobic group and not having an aromatic hydrocarbon ring is preferred, and a nonionic emulsifier having a linear alkyl group as the hydrophobic group and not having an aromatic hydrocarbon ring is more preferred. Hereinafter, the "nonionic emulsifier having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring" may be referred to as nonionic emulsifier (A1). The linear alkyl group contained in the nonionic emulsifier (A1) preferably has 8 to 40 carbon atoms, more preferably 8 to 30, and even more preferably 8 to 20. The branched alkyl group contained in the nonionic emulsifier (A1) preferably has 8 to 40 carbon atoms, more preferably 8 to 30, and even more preferably 8 to 20. The hydrophilic group possessed by the nonionic emulsifier (A1) is as described above, and the preferred embodiments thereof are also the same.

[0059] Specific examples of the nonionic emulsifier (A1) include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether (particularly, polyoxy C 2-4 Alkylene C 8-30 alkyl ethers); esters of sorbitan with saturated fatty acids such as sorbitan monostearate, sorbitan distearate, sorbitan tristearate, and sorbitan monolaurate (especially sorbitan with C 8-30 Esters of saturated fatty acids; compounds in which a polyoxyalkylene chain is added to an ester of sorbitan and saturated fatty acids, such as polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan tristearate, and polyoxyethylene sorbitan monolaurate (especially compounds in which sorbitan and C 8-30 Polyoxy C esters with saturated fatty acids 2-4 Compounds with alkylene chains added); glycerin C such as glycerol monostearate 8-30 saturated fatty acid monoesters; etc., among which polyoxyalkylene alkyl ethers are preferred, and polyoxy C 2-4 Alkylene C 8-30 Alkyl ethers are more preferred, and polyoxyethylene C 8-30 Alkyl ethers are more preferred, and linear alkyl groups (particularly linear C 8-30 Polyoxyethylene alkyl ethers having alkyl groups are particularly preferred.

[0060] The amount of nonionic emulsifier (A1) in 100% by mass of nonionic emulsifier (A) used in the polymerization step is, for example, 30% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.

[0061] The anionic emulsifier (hereinafter referred to as anionic emulsifier (B)) refers to a compound having an anionic group and a hydrophobic group. Examples of the anionic group include groups known as emulsifiers (surfactants), such as a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a sulfate ester residue, a phosphate ester residue, etc. The anionic group is preferably a sulfonic acid group, a carboxylic acid group, or a sulfate ester residue, and more preferably a sulfate ester residue. Examples of the hydrophobic group include the groups exemplified as the hydrophobic group contained in the nonionic emulsifier, and preferred embodiments are also the same.

[0062] Specific examples of the anionic emulsifier (B) include alkyl sulfate salts such as ammonium dodecyl sulfate and sodium dodecyl sulfate; alkyl sulfonate salts such as ammonium dodecyl sulfonate, sodium dodecyl sulfonate and sodium alkyl diphenyl ether disulfonate; alkyl aryl sulfonate salts such as ammonium dodecyl benzene sulfonate, sodium dodecyl benzene sulfonate and sodium dodecyl naphthalene sulfonate; polyoxyethylene alkyl sulfonate salts; polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate and ammonium polyoxyethylene lauryl ether sulfate; polyoxyethylene alkyl aryl ether sulfate esters or salts thereof containing an alkenyl group having a terminal double bond, such as bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salts, propenyl-alkyl sulfosuccinate salts, (meth)acrylic acid polyoxyethylene sulfonate salts, (meth)acrylic acid polyoxyethylene phosphonate salts, sulfonate salts of allyloxymethyl alkyloxy polyoxyethylene, sulfate salts of allyloxymethyl alkoxyethyl polyoxyethylene, and polyoxyalkylene alkenyl ether ammonium sulfate salts.

[0063] Among the anionic emulsifiers (B), those having a linear alkyl group and / or a branched alkyl group as the hydrophobic group and having no aromatic hydrocarbon ring are preferred, and those having a linear alkyl group as the hydrophobic group and having no aromatic hydrocarbon ring are more preferred. Hereinafter, the "anionic emulsifier having a linear alkyl group and / or a branched alkyl group and having no aromatic hydrocarbon ring" may be referred to as anionic emulsifier (B1). The linear alkyl group contained in the anionic emulsifier (B1) preferably has 8 to 40 carbon atoms, more preferably 8 to 30, and even more preferably 8 to 20. The branched alkyl group contained in the anionic emulsifier (B1) preferably has 8 to 40 carbon atoms, more preferably 8 to 30, and even more preferably 8 to 20. The hydrophilic group contained in the anionic emulsifier (B1) is as described above, and the preferred embodiments thereof are also the same.

[0064] Specific examples of the anionic emulsifier (B1) include alkyl sulfate salts such as ammonium dodecyl sulfate and sodium dodecyl sulfate (particularly, C 8-30 Alkyl sulfate salts; alkyl sulfonate salts such as ammonium dodecyl sulfonate and sodium dodecyl sulfonate (especially C 8-30 Alkyl sulfonate salts; polyoxyalkylene alkyl sulfonate salts such as polyoxyethylene alkyl sulfonate salts (especially polyoxy C 2-4 Alkylene C 8-30 Alkyl sulfonate salts; polyoxyalkylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate and ammonium polyoxyethylene lauryl ether sulfate (especially polyoxy C 2-4 Alkylene C 8-30 alkyl ether sulfate salts); ammonium laurate, sodium stearate, etc. 8-30 Among them, polyoxyalkylene alkyl ether sulfate salts are preferred, and polyoxy C 2-4 Alkylene C 8-30 Alkyl ether sulfate salts are more preferred, and polyoxyethylene C 8-30 Alkyl ether sulfate salts are more preferred, and linear alkyl groups (especially linear C 8-30 Particularly preferred are polyoxyethylene alkyl ether sulfate salts having alkyl groups.

[0065] In 100% by mass of the anionic emulsifier (B) used in the polymerization step, the amount of the anionic emulsifier (B1) is, for example, 30% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.

[0066] The total amount of emulsifier used in the polymerization step is preferably 0.05 to 10.0 parts by mass, more preferably 0.05 to 5.0 parts by mass, and even more preferably 0.05 to 2.0 parts by mass, relative to 100 parts by mass of the monomer components. By adjusting the amount of emulsifier used within the above range, polymerization can be stabilized. In particular, it is preferable to adjust the total amount of the nonionic emulsifier (A) and the anionic emulsifier (B) to fall within the above range, and it is more preferable to adjust the total amount of the nonionic emulsifier (A1) and the anionic emulsifier (B1) to fall within the above range.

[0067] In addition, the ratio of the nonionic emulsifier (A) to the anionic emulsifier (B) used in the polymerization step (nonionic emulsifier:anionic emulsifier) ​​is preferably 5:1 to 1:5 by mass, more preferably 3:1 to 1:3. By adjusting the ratio of the nonionic emulsifier (A) to the anionic emulsifier (B) used within the above range, an emulsion that is stable against mechanical energy, such as the influence of shear during stirring, can be obtained. In particular, it is preferable to adjust the ratio of the nonionic emulsifier (A1) to the anionic emulsifier (B1) used (nonionic emulsifier (A1):anionic emulsifier (B1)) within the above range.

[0068] Furthermore, the total amount of the nonionic emulsifier (A1) and the anionic emulsifier (B1) in 100% by mass of all emulsifiers used in the polymerization step is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

[0069] If necessary, a protective colloid such as polyvinyl alcohol may be used together with the emulsifier.

[0070] The polymerization initiator used in the polymerization step is not limited, but examples thereof include azo-based polymerization initiators such as azobisisobutyronitrile, 2,2-azobis(2-methylbutyronitrile), 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-diaminopropane) hydrochloride, 4,4-azobis(4-cyanovaleric acid), and 2,2-azobis(2-methylpropionamidine); persulfates such as ammonium persulfate and potassium persulfate; and peroxide-based polymerization initiators such as hydrogen peroxide, benzoyl peroxide, t-butyl peroxybenzoate, parachlorobenzoyl peroxide, lauroyl peroxide, and ammonium peroxide. These polymerization initiators may be used alone or in combination of two or more. Among the above polymerization initiators, persulfate and / or peroxide-based polymerization initiators are preferred, and it is more preferred to use a combination of persulfate and peroxide-based polymerization initiators.

[0071] The amount of polymerization initiator used in the emulsion polymerization is preferably 0.01 to 5.0 parts by mass, more preferably 0.01 to 4.0 parts by mass, and even more preferably 0.01 to 3.0 parts by mass, per 100 parts by mass of the monomer components. If it is necessary to increase the polymerization rate or lower the reaction temperature, a reducing agent such as a soluble sulfite or ascorbic acid, or a metal compound that generates heavy metal ions in water, such as ferrous sulfate, can be combined with the peroxide polymerization initiator or persulfate to form a redox initiator.

[0072] The emulsion polymerization is usually carried out in an aqueous solvent. Examples of the aqueous solvent include water and a mixed solvent of water and a water-soluble organic solvent. The water-soluble organic solvent refers to an organic solvent that dissolves in water at a concentration of 0.01% by mass or more at room temperature and normal pressure. In this specification, room temperature means 25°C, and normal pressure means 1 atmosphere. From the viewpoint of further improving the storage stability of the emulsion, the water content in the aqueous solvent is preferably 10 to 100% by mass, more preferably 25% by mass or more, even more preferably 60% by mass or more, and particularly preferably 90% by mass or more. The remainder is preferably the water-soluble organic solvent. As the water, ion-exchanged water (deionized water), distilled water, pure water, etc. can be used.

[0073] Examples of the water-soluble organic solvent include: Lower alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and tert-butyl alcohol (preferably C 1-4 alcohol); glycols such as propylene glycol, 1,3-propanediol, 1,2-hexanediol, dipropylene glycol, tripropylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; Glycerin; Ethylene glycol monoalkyl ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, etc.) 1-4 alkyl ether), propylene glycol monoalkyl ether (e.g., propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, propylene glycol monoisobutyl ether, etc.) 1-4alkylene glycol monoalkyl ethers (preferably C alkyl ethers) 2-4 Alkylene glycol mono C 1-4 alkyl ethers); Diethylene glycol monoalkyl ethers (e.g., diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, etc.) 1-4 alkyl ether), dipropylene glycol monoalkyl ether (e.g., dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monoisobutyl ether, etc.) 1-4 Dialkylene glycol monoalkyl ethers (preferably diC alkyl ethers) 2-4 Alkylene glycol mono C 1-4 alkyl ethers); Polyethylene glycol monoalkyl ethers (e.g., polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polyethylene glycol monopropyl ether, polyethylene glycol monoisopropyl ether, polyethylene glycol monobutyl ether, polyethylene glycol monoisobutyl ether, etc.) 1-4 alkyl ether), polypropylene glycol monoalkyl ether (e.g., polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monopropyl ether, polypropylene glycol monoisopropyl ether, polypropylene glycol monobutyl ether, polypropylene glycol monoisobutyl ether, etc.) 1-4alkyl ethers) (preferably polyC 2-4 Alkylene glycol mono C 1-4 alkyl ethers); Heterocycles such as 2-pyrrolidone and N-methyl-2-pyrrolidone; Ketones such as acetone and methyl ethyl ketone; The number of moles of alkylene oxide added to the polyalkylene glycol monoalkyl ether is preferably 2 to 10, and more preferably 2 to 4. These water-soluble organic solvents may be used alone or in combination of two or more kinds.

[0074] The amount of the aqueous solvent used in carrying out the emulsion polymerization is not particularly limited, but may be, for example, 20 to 200 parts by mass per 100 parts by mass of the monomer component. When a water-soluble organic solvent is used, the amount of the water-soluble organic solvent used in the emulsion polymerization is not particularly limited, but may be, for example, 1 to 10 parts by mass per 100 parts by mass of the monomer component.

[0075] Specific examples of the emulsion polymerization method include conventionally known methods such as monomer dropping polymerization, pre-emulsion dropping polymerization, seed polymerization, and multi-stage polymerization.

[0076] The seed polymerization method is a method in which the above-mentioned monomer components are emulsion-polymerized in the presence of seed particles. When employing the seed polymerization method, the seed particles used may be those produced in the same reaction vessel prior to the above-mentioned polymerization step, or seed particles polymerized in a different reaction vessel. The seed particles provide a site for emulsion polymerization in the polymerization step, and are ultimately included in the emulsion particles in the acrylic resin emulsion of the present invention.

[0077] The seed particles are not particularly limited, but preferably contain structural units derived from aromatic vinyl monomers and / or structural units derived from (meth)acrylic acid alkyl esters, and more preferably contain structural units derived from aromatic vinyl monomers and structural units derived from (meth)acrylic acid alkyl esters. Examples of the aromatic vinyl monomer constituting the seed particles include the compounds exemplified as the aromatic vinyl monomer in the monomer component described above, and the preferred embodiments thereof are also the same. Examples of the (meth)acrylic acid alkyl ester constituting the seed particles include the compounds exemplified as the (meth)acrylic acid alkyl ester in the above-mentioned monomer component, and among them, (meth)acrylic acid C 1-5 Alkyl esters are preferred, and methacrylic acid C 1-5 Alkyl esters are more preferred, with methyl methacrylate being especially preferred. The total content of the structural units derived from the aromatic vinyl monomer and the structural units derived from the (meth)acrylic acid alkyl ester in the seed particles is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may be 100% by mass. The seed particles may also contain structural units derived from monomers other than aromatic vinyl monomers and (meth)acrylic acid alkyl esters, such as the hydroxyl group-containing monomers, crosslinkable monomers, and other monomers described above.

[0078] The average particle size of the seed particles is, for example, 20 to 100 nm, and preferably 30 to 70 nm, and can be determined from the average particle size (cumulant average particle size) based on the scattering intensity distribution measured at a measurement temperature of 23°C.

[0079] The amount of the seed particles may be adjusted appropriately depending on the particle size of the desired emulsion particles, and is, for example, 0 to 10 parts by mass, and preferably 0 to 5 parts by mass, relative to 100 parts by mass of the monomer component.

[0080] In the emulsion polymerization reaction system, additives such as chain transfer agents such as tert-dodecyl mercaptan, pH adjusters, chelating agents, etc. may be added in appropriate amounts as needed. The amount of additive varies depending on the type of additive and cannot be determined in general, but is usually preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the monomer components.

[0081] The polymerization temperature during the emulsion polymerization can be appropriately set taking into consideration the weight-average molecular weight of the resulting emulsion particles, the blending ratio of the monomer components, the type of polymerization initiator, and the like. The reaction temperature is usually above 50°C, preferably 55 to 100°C, more preferably 60 to 95°C, and even more preferably 65 to 90°C.

[0082] The polymerization time for carrying out the emulsion polymerization is not particularly limited, but from the viewpoint of productivity, it is preferably 0.5 to 30 hours, more preferably 1 to 20 hours, and even more preferably 3 to 10 hours.

[0083] The reaction pressure is not particularly limited, and may be normal pressure (atmospheric pressure), reduced pressure, or increased pressure. The emulsion polymerization is desirably carried out in an atmosphere of an inert gas such as nitrogen gas.

[0084] [1-2. Emulsifier addition process] In the emulsifier addition step, a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring is added after the temperature of the solution obtained in the polymerization step has reached 50° C. or below. Specifically, the nonionic emulsifier (A1) is added after the solution obtained in the polymerization step has been cooled to 50° C. or below. The nonionic emulsifier (A1) may be added during the cooling operation of the solution obtained in the polymerization step (when the temperature of the solution has reached 50° C. or below). The temperature of the solution when the nonionic emulsifier (A1) is added is preferably 0 to 50°C, more preferably 5 to 40°C, and even more preferably 10 to 35°C.

[0085] The difference between the polymerization temperature in the polymerization step and the temperature of the solution when the nonionic emulsifier (A1) is added is preferably from 35 to 75°C, more preferably from 50 to 60°C.

[0086] The method for lowering the temperature of the solution obtained in the polymerization step to 50°C or less is not particularly limited, and a normal cooling procedure may be used. For example, the solution may be cooled in a water bath or ice bath, in a cold place (e.g., 1°C or higher but lower than 15°C), or left to cool to room temperature (e.g., 15 to 30°C).

[0087] The pH of the solution when the nonionic emulsifier (A1) is added is preferably 5 to 10, more preferably 6 to 9.5. By adjusting the pH to the above-mentioned lower limit or higher, the dispersion stability and mechanical stability of the emulsion can be improved, and by adjusting the pH to the above-mentioned upper limit or lower, the decrease in water resistance and the generation of odor can be suppressed. The method for adjusting the pH of the solution to the aforementioned range upon addition of the nonionic emulsifier (A1) is not particularly limited. For example, a pH adjuster may be added after the temperature of the solution obtained in the polymerization step has dropped to 50°C or below, before the addition of the nonionic emulsifier (A1). Examples of the pH adjuster include alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; and water-soluble organic amines such as dimethylaminoethanol, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. These pH adjusters may be used alone or in combination of two or more.

[0088] Examples of the nonionic emulsifier (A1) used in the emulsifier addition step include the same ones as the nonionic emulsifier (A1) explained in the polymerization step, and the preferred embodiments thereof are also the same.

[0089] The amount of the nonionic emulsifier (A1) added in the emulsifier addition step is preferably 0.05 to 8.0 parts by mass, more preferably 0.3 to 5.0 parts by mass, even more preferably 0.5 to 4.0 parts by mass, and particularly preferably 0.8 to 3.0 parts by mass, relative to 100 parts by mass of the total of the monomer components used in the polymerization step. By adjusting the amount of the nonionic emulsifier (A1) added to be equal to or greater than the above-mentioned predetermined lower limit, the adhesive strength of the resulting adhesive can be further increased, and by adjusting the amount of the nonionic emulsifier (A1) added to be equal to or less than the above-mentioned predetermined upper limit, the interaction between particles can be reduced, thereby further improving the storage stability of the emulsion.

[0090] In the emulsifier addition step, an emulsifier other than the nonionic emulsifier (A1) (hereinafter referred to as emulsifier (A2)) may be added, but it is preferable to use a small amount thereof, and it is more preferable not to use emulsifier (A2). Examples of the emulsifier (A2) include emulsifiers that do not fall under the category of the nonionic emulsifier (A1) among the emulsifiers described above as emulsifiers used in the polymerization step.

[0091] The proportion of the nonionic emulsifier (A1) in 100% by mass of all emulsifiers used in the emulsifier addition step is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. By adjusting the proportion of the nonionic emulsifier (A1) within the above range, the adhesiveness and bonding strength of the resulting adhesive to substrates can be further improved, the pot life can be further extended, and the storage stability of the emulsion can also be improved.

[0092] The amount of the emulsifier used in the emulsifier addition step is preferably 5.0 to 30 parts by mass, more preferably 5.0 to 20 parts by mass, and even more preferably 7.5 to 15 parts by mass, relative to 1 part by mass of the emulsifier used in the polymerization step. In particular, it is preferable to adjust the amount of the nonionic emulsifier (A1) used in the emulsifier addition step to within the above range, relative to 1 part by mass of the total of the nonionic emulsifier (A1) and the anionic emulsifier (B1) used in the polymerization step.

[0093] The acrylic resin emulsion obtained by the production method of the present invention has the same form as that described later in "2. Acrylic resin emulsion," including its preferred form.

[0094] [2. Acrylic resin emulsion] The above-mentioned production method provides an acrylic resin emulsion containing emulsion particles containing structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester, a nonionic emulsifier (A), and water, wherein the nonionic emulsifier (A) contains a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring. The emulsion particles containing structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester are emulsion particles obtained by polymerizing an aromatic vinyl monomer and a (meth)acrylic acid alkyl ester, in other words, emulsion particles containing a polymer having structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester. By being emulsion particles containing the polymer, the emulsion of the present disclosure can be a resin emulsion.

[0095] The acrylic resin emulsion preferably satisfies at least one of the following requirements (1) and (2), and more preferably satisfies both of them. Requirement (1): The content of the nonionic emulsifier (A1) is 90% by mass or more in 100% by mass of the nonionic emulsifier (A), and the content of the nonionic emulsifier (A) is 0.3 parts by mass or more per 100 parts by mass of the emulsion particles. Requirement (2): The peeling rate determined by the boiling peeling test described below is 10% or less.

[0096] A preferred embodiment of the acrylic resin emulsion will now be described.

[0097] The shape of the emulsion particles is not particularly limited, but they are usually spherical. The shape can be measured using a transmission electron microscope or a scanning electron microscope. The emulsion particles may have a single-layer structure or a multi-layer structure (e.g., a core-shell structure), but a single-layer structure is preferred.

[0098] The average particle size of the emulsion particles is, for example, 100 to 350 nm, preferably 200 to 350 nm, more preferably 250 to 340 nm, and even more preferably 270 to 330 nm. By adjusting the average particle size within the above range, the storage stability of the acrylic resin emulsion and the pot life of the resulting adhesive can be improved. The average particle size can be determined as the average particle size (cumulant average particle size) based on the scattering intensity distribution measured at a measurement temperature of 23°C. The average particle size of the emulsion particles can be appropriately adjusted by changing the amount of emulsifier or seed particles used in the polymerization step, etc. For example, the average particle size of the resulting emulsion particles can be reduced by increasing the amount of emulsifier or seed particles used in the polymerization step.

[0099] The glass transition temperature (Tg (°C)) of the emulsion particles is preferably −10 to 25°C, more preferably 0 to 20°C, and even more preferably 0 to 10°C. By adjusting the Tg to the above-mentioned upper limit or less, the performance of the resulting adhesive can be improved regardless of the ambient temperature. The glass transition temperature (°C) of the emulsion particles is calculated by the Fox equation shown below: A This can be calculated by converting from (K). 1 / Tg A =Σ(Wm / Tgm) / 100 [In the formula, Tg A indicates the glass transition temperature (absolute temperature: K) of the emulsion particle, Wm indicates the content (mass%) of monomer m in all monomer components constituting the emulsion particle (including the monomer components constituting the seed particle when seed particles are used), and Tgm indicates the glass transition temperature (absolute temperature: K) of a homopolymer of monomer m.

[0100] The emulsion particles are particles composed of the above-mentioned monomer components and seed particles used as needed, and as described above, essentially contain structural units derived from an aromatic vinyl monomer and structural units derived from an alkyl (meth)acrylate ester.

[0101] The aromatic vinyl monomer constituting the emulsion particles is the same as the aromatic vinyl monomer described as the monomer component used in the polymerization step, and the preferred embodiments thereof are also the same. The content of the structural unit derived from the aromatic vinyl monomer in the emulsion particles is, for example, 15 to 80 mass %, preferably 40 to 60 mass %, and more preferably 40 to 55 mass %. By adjusting the content to be equal to or greater than the above-mentioned lower limit, the water resistance of the resulting adhesive can be increased, and by adjusting the content to be equal to or less than the above-mentioned upper limit, it is possible to design a Tg appropriate for the required performance while maintaining water resistance.

[0102] The (meth)acrylic acid alkyl ester constituting the emulsion particles is the same as the (meth)acrylic acid alkyl ester explained as the monomer component used in the polymerization step, and the preferred embodiments thereof are also the same. The content of the structural units derived from the (meth)acrylic acid alkyl ester in the emulsion particles (particularly, the content of the structural units derived from the low Tg (meth)acrylic acid alkyl ester and the methacrylic acid C1-5 The total content of the structural units derived from alkyl esters may be appropriately adjusted so that the Tg of the resulting emulsion particles falls within the aforementioned range, and is, for example, 20 to 200 parts by mass, preferably 50 to 160 parts by mass, and more preferably 110 to 130 parts by mass, relative to 100 parts by mass of the structural units derived from the aromatic vinyl monomer. From the viewpoint of achieving both water resistance and adhesiveness of the resulting adhesive, the content of the structural units derived from the low Tg (meth)acrylic acid alkyl ester is preferably 20 to 160 parts by mass, more preferably 50 to 140 parts by mass, and even more preferably 90 to 120 parts by mass, per 100 parts by mass of the structural units derived from the aromatic vinyl monomer. Methacrylic acid C 1-5 The content of the structural units derived from alkyl esters is, for example, 0 to 30 parts by mass relative to 100 parts by mass of the structural units derived from the aromatic vinyl monomers. From the viewpoint of achieving both water resistance and polymerization reactivity, the content is preferably 3 to 30 parts by mass, and more preferably 5 to 20 parts by mass.

[0103] The content of the structural units derived from the (meth)acrylic acid alkyl ester (particularly, the structural units derived from the low Tg (meth)acrylic acid alkyl ester and methacrylic acid C 1-5 The amount of structural units derived from alkyl esters (total content) is, for example, 15 to 80% by mass, preferably 25 to 70% by mass, and more preferably 35 to 60% by mass, based on 100% by mass of the emulsion particles. The content of the structural units derived from the low Tg alkyl (meth)acrylate is, for example, 15 to 80 mass %, preferably 25 to 65 mass %, and more preferably 35 to 55 mass %, based on 100 mass % of the emulsion particles. The methacrylic acid C 1-5 The content of the structural unit derived from alkyl ester is, for example, 1 to 15% by mass, preferably 1 to 10% by mass, and more preferably 2 to 7% by mass, based on 100% by mass of the emulsion particles.

[0104] The total content of the structural units derived from the aromatic vinyl monomer and the structural units derived from the (meth)acrylic acid alkyl ester in the emulsion particles is, for example, 60 to 100 mass %, preferably 80 to 99.5 mass %, and more preferably 90 to 99.0 mass %.

[0105] The emulsion particles preferably further contain structural units derived from a hydroxyl group-containing monomer. The hydroxyl group-containing monomer is the same as the hydroxyl group-containing monomer described as the monomer component used in the polymerization step, and preferred embodiments thereof are also the same.

[0106] The content of structural units derived from hydroxyl group-containing monomers in the emulsion particles may be, for example, 0 to 5 mass%, but is preferably 0.1 to 2.8 mass%, more preferably 1.0 to 2.8 mass%, and even more preferably 1.5 to 2.5 mass%. By adjusting the content to be equal to or greater than the above-mentioned lower limit, the crosslink density can be increased, and by adjusting the content to be equal to or less than the above-mentioned upper limit, the pot life of the resulting adhesive can be extended. The content of the structural units derived from the hydroxyl group-containing monomer may be, for example, 0 to 10 parts by mass, but is preferably 1.0 to 6.5 parts by mass, and more preferably 3.0 to 6.0 parts by mass, per 100 parts by mass of the structural units derived from the aromatic vinyl monomer.

[0107] The emulsion particles may further contain a structural unit derived from a crosslinkable monomer. The crosslinkable monomer is the same as the crosslinkable monomer described as the monomer component used in the polymerization step, and preferred embodiments thereof are also the same.

[0108] The content of the structural unit derived from the crosslinkable monomer in the emulsion particles may be, for example, 0 to 5.0% by mass, preferably 0.1 to 3.0% by mass, and more preferably 0.3 to 1.0% by mass. By adjusting the content to be equal to or greater than the above-mentioned lower limit, the crosslink density can be increased, and by adjusting the content to be equal to or less than the above-mentioned upper limit, the pot life can be further extended. The content of the structural units derived from the crosslinkable monomer may be, for example, 0 to 8.0 parts by mass, preferably 0.3 to 5.0 parts by mass, and more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the structural units derived from the aromatic vinyl monomer.

[0109] The emulsion particles may further contain structural units derived from other monomers, which are the same as the other monomers described as the monomer components used in the polymerization step.

[0110] The content of structural units derived from other monomers in the emulsion particles is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and may be 0% by mass.

[0111] The content of the emulsion particles is preferably 80 to 99.7 mass %, more preferably 85 to 99.5 mass %, and even more preferably 90 to 99.3 mass %, based on 100 mass % of the solid content contained in the acrylic resin emulsion.

[0112] As described above, the acrylic resin emulsion contains a nonionic emulsifier (A). The nonionic emulsifier (A) is the same as the emulsifier described as the nonionic emulsifier (A) used in the polymerization step, and preferred embodiments thereof are also the same. The content of the nonionic emulsifier (A) is preferably 0.3 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.7 to 2 parts by mass, relative to 100 parts by mass of the emulsion particles.

[0113] As described above, the nonionic emulsifier (A) includes a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring. The nonionic emulsifier (A1) is the same as the emulsifier described as the nonionic emulsifier (A1) used in the polymerization step, and preferred embodiments thereof are also the same. The content of the nonionic emulsifier (A1) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably 100% by mass, based on a total of 100% by mass of the nonionic emulsifier (A) contained in the acrylic resin emulsion. By adjusting the content of the nonionic emulsifier (A1) within the above range, the storage stability of the emulsion, the pot life of the resulting adhesive, and the adhesive strength of the resulting adhesive can be further improved.

[0114] The acrylic resin emulsion may contain an emulsifier other than the nonionic emulsifier (A). Examples of the emulsifier other than the nonionic emulsifier (A) include anionic emulsifier (B), cationic emulsifier, amphoteric emulsifier, and polymer emulsifier, and among these, anionic emulsifier (B) is preferred. Of the total 100% by mass of emulsifiers contained in the acrylic resin emulsion, the total amount of the nonionic emulsifier (A) and the anionic emulsifier (B) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.

[0115] The anionic emulsifier (B) that may be contained in the acrylic resin emulsion is the same as the emulsifier described as the anionic emulsifier (B) used in the polymerization step, and the preferred embodiments thereof are also the same. That is, the anionic emulsifier (B) preferably contains the anionic emulsifier (B1). The content of the anionic emulsifier (B1) is, for example, 30% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass, based on 100% by mass of the anionic emulsifier (B) contained in the acrylic resin emulsion. By adjusting the content of the anionic emulsifier (B1) within the above range, the storage stability of the emulsion, the pot life of the resulting adhesive, and the adhesive strength of the resulting adhesive can be further improved.

[0116] The content ratio ((A):(B)) of the nonionic emulsifier (A) to the anionic emulsifier (B) contained in the acrylic resin emulsion is preferably 2:1 to 80:1 by mass, and more preferably 5:1 to 40:1. By adjusting the usage ratio of the nonionic emulsifier (A) to the anionic emulsifier (B) within the above range, the emulsion particles can be stabilized. In particular, it is preferable to adjust the use ratio ((A1):(B1)) of the nonionic emulsifier (A1) and the anionic emulsifier (B1) contained in the acrylic resin emulsion to fall within the above range.

[0117] Furthermore, the total amount of the nonionic emulsifier (A1) and the anionic emulsifier (B1) is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on 100% by mass of all emulsifiers contained in the acrylic resin emulsion. By adjusting the total amount of the nonionic emulsifier (A1) and the anionic emulsifier (B1) within the above range, the storage stability of the emulsion, the pot life of the resulting adhesive, and the adhesive strength of the resulting adhesive can be further improved.

[0118] The acrylic resin emulsion further contains water. The amount of water is not particularly limited, and may be adjusted so that the nonvolatile content of the acrylic resin emulsion falls within the range described below.

[0119] The acrylic resin emulsion may further contain a water-soluble organic solvent. The water-soluble organic solvent is the same as the water-soluble organic solvent described above, and preferred embodiments thereof are also the same. The content of the water-soluble organic solvent is preferably 40% by mass or less, more preferably 10% by mass or less, and even more preferably 6% by mass or less, based on 100% by mass of the total of water and the water-soluble organic solvent, and may be 0% by mass.

[0120] The total content of the emulsion particles, emulsifier, water, and water-soluble organic solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the acrylic resin emulsion, and may be 100% by mass.

[0121] The acrylic resin emulsion may further contain appropriate amounts of additives such as a chain transfer agent such as tert-dodecyl mercaptan, a pH adjuster, a chelating agent, etc. The content of the additives varies depending on the type of additive and cannot be determined in general, but is usually preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the emulsion particles.

[0122] From the viewpoint of handleability, the nonvolatile content of the acrylic resin emulsion is preferably 30 to 60 mass %, more preferably 35 to 60 mass %, and even more preferably 40 to 55 mass %. The nonvolatile content can be measured by the method described in the examples below.

[0123] The acrylic resin emulsion enhances the adhesive strength of the adhesive obtained using the acrylic resin emulsion. The adhesive strength of the adhesive can be measured, for example, according to the "boiling peel test" specified by the Japanese Agricultural Standards, and the acrylic resin emulsion preferably has a peel rate of 10% or less, more preferably 5% or less, and even more preferably less than 3% as determined by the boiling peel test described below. (Boiling peel test) The acrylic resin emulsion, a 15% polyvinyl alcohol aqueous solution, calcium carbonate, and water were mixed in a mass ratio of 20:15:20:45 (acrylic resin emulsion:polyvinyl alcohol aqueous solution:calcium carbonate:water). Next, 15 parts by mass of polymethylene polyphenyl polyisocyanate was added to 100 parts by mass of the base composition to prepare an adhesive. The adhesive's adhesion to Douglas fir was tested in accordance with the "Boiling Peel Test" for structural laminated lumber specified by the Japanese Agricultural Standards, and the peel rate was calculated.

[0124] [3. Water-based polymer-isocyanate adhesive] The aqueous polymer-isocyanate adhesive can be produced by mixing a base composition containing a resin emulsion with an isocyanate-based crosslinking agent. The base composition containing the resin emulsion typically contains a hydroxyl-containing compound. The base composition may contain the above-mentioned acrylic resin emulsion and a hydroxyl-containing aqueous polymer (preferably polyvinyl alcohol), or it may contain the above-mentioned acrylic resin emulsion having emulsion particles containing a polymer having structural units derived from a hydroxyl-containing monomer, or it may contain an acrylic resin emulsion obtained by performing the above-mentioned polymerization process using a hydroxyl-containing polymer as a protective colloid. In particular, the aqueous polymer-isocyanate adhesive of the present invention is preferably produced by mixing a base composition containing the above-mentioned acrylic resin emulsion, polyvinyl alcohol, and water with an isocyanate-based crosslinking agent, i.e., the aqueous polymer-isocyanate adhesive of the present invention preferably comprises a base composition containing the above-mentioned acrylic resin emulsion, polyvinyl alcohol, and water, and an isocyanate-based crosslinking agent. Below, the aqueous polymer-isocyanate adhesive obtained by a preferred production method will be described in detail, but the present invention is not limited thereto.

[0125] In the production of an aqueous polymer-isocyanate adhesive, it is preferable to first prepare a base composition. The base composition is preferably prepared by mixing an acrylic resin emulsion, polyvinyl alcohol, water, and optionally a filler and other additives. That is, the base composition preferably contains an acrylic resin emulsion, polyvinyl alcohol, water, and optionally a filler and / or other additives.

[0126] The acrylic resin emulsion used in the base composition is as described above, and the preferred embodiments thereof are also the same. In preparing the base composition, the acrylic resin emulsion may be used alone or in combination of two or more.

[0127] The acrylic resin emulsion is preferably used so that the amount of emulsion particles contained in the acrylic resin emulsion is 5 to 40 mass %, more preferably 10 to 30 mass %, of the total solid content (100 mass %) of the resulting base composition. By adjusting the amount of emulsion particles within the above range, higher adhesive performance can be maintained.

[0128] The polyvinyl alcohol used in the base composition includes not only polyvinyl alcohol but also modified products of polyvinyl alcohol such as ethylene-modified polyvinyl alcohol and silanol-modified polyvinyl alcohol.

[0129] The polyvinyl alcohol can be obtained, for example, by saponifying a vinyl acetate homopolymer or a vinyl acetate copolymer. The polyvinyl alcohol may be partially saponified polyvinyl alcohol (for example, polyvinyl alcohol having a saponification degree of 85 to 90 mol%) or completely saponified polyvinyl alcohol (for example, polyvinyl alcohol having a saponification degree of more than 97 mol%).

[0130] The degree of saponification and the degree of modification of the polyvinyl alcohol may be appropriately adjusted depending on the required adhesive performance and pot life. For example, the use of modified polyvinyl alcohol or polyvinyl alcohol with a high degree of saponification increases the crosslink density, which tends to result in higher adhesive performance.

[0131] The degree of polymerization of the polyvinyl alcohol is preferably 1,000 to 3,000, and more preferably 1,500 to 2,500.

[0132] In preparing the base composition, the polyvinyl alcohol may be used alone or in combination of two or more kinds.

[0133] The amount of the polyvinyl alcohol is preferably 5 to 30 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of emulsion particles contained in the acrylic resin emulsion. By adjusting the amount of polyvinyl alcohol to be equal to or greater than the above-mentioned lower limit, the adhesive strength can be further increased, and by adjusting the amount of polyvinyl alcohol to be equal to or less than the above-mentioned upper limit, the pot life of the resulting adhesive can be further increased.

[0134] The polyvinyl alcohol is preferably used in the form of an aqueous solution, the water constituting the aqueous solution being a part of the water contained in the base composition.

[0135] The water used in the base composition may be any of ion-exchanged water (deionized water), distilled water, pure water, etc. The water may be water derived from the acrylic resin emulsion described above or other aqueous emulsions described below, water added separately during preparation of the base composition, or a mixture thereof.

[0136] The amount of water is preferably 40 to 70% by mass, more preferably 40 to 65% by mass, and even more preferably 45 to 60% by mass, based on 100% by mass of the main composition. By adjusting the amount of water to be equal to or greater than the above-mentioned lower limit, the dispersibility of each component can be increased, and by adjusting the amount of water to be equal to or less than the above-mentioned upper limit, the drying time can be shortened.

[0137] It is preferable that a filler is further mixed into the base composition. By using a filler, the solid content of the resulting adhesive can be increased, and the drying time can be shortened.

[0138] Examples of the filler include inorganic fillers such as clay, kaolin, talc, zeolite, silica, calcium carbonate, barium sulfate, aluminum oxide, and titanium oxide; and organic fillers such as regenerated rubber, cellulose powder, wheat flour, soybean powder, blood powder, wood powder, and walnut shell powder; and among these, inorganic fillers are preferred, and calcium carbonate is more preferred.

[0139] In preparing the base composition, the filler may be used alone or in combination of two or more.

[0140] The amount of the filler may be adjusted as appropriate so that the solid content of the base composition falls within the range described below, but is preferably 50 to 300 parts by mass, and more preferably 100 to 200 parts by mass, per 100 parts by mass of emulsion particles contained in the acrylic resin emulsion.

[0141] In 100% by mass of the main composition, the total content of the acrylic resin emulsion, polyvinyl alcohol, water, and filler is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.

[0142] Examples of other additives that can be used in the base composition include other aqueous emulsions other than the above-mentioned acrylic resin emulsions, such as vinyl acetate resin emulsions, ethylene-vinyl acetate copolymer resin emulsions, acrylic resin emulsions other than the above-mentioned acrylic resin emulsions, styrene-butadiene copolymer resin emulsions, acrylonitrile-butadiene copolymer resin emulsions, and urethane resin emulsions; organic solvents such as the water-soluble organic solvents exemplified above; plasticizers; antifoaming agents; thickeners; leveling agents; dispersants; colorants such as dyes and pigments; water-resistant agents; lubricants; pH adjusters; preservatives; surfactants; and the like.

[0143] The order of mixing in the preparation of the base composition is not particularly limited. For example, the acrylic resin emulsion and the filler can be mixed in advance, and then the aqueous solution of polyvinyl alcohol, the remainder of the water, and other additives used as needed can be added and mixed to prepare the base composition.

[0144] The mixing temperature in the preparation of the base composition is not particularly limited, but is preferably 5 to 40° C. The mixing time in the preparation of the base composition is also not particularly limited, but is preferably 10 to 35° C. from the viewpoint of productivity.

[0145] The solid content of the base composition is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and even more preferably 50 to 65% by mass. By adjusting the solid content of the base composition to fall within the above range, the drying time when the adhesive is formed can be shortened, and productivity can be improved.

[0146] Next, the base composition is mixed with an isocyanate-based crosslinking agent to produce an aqueous polymer-isocyanate adhesive. The isocyanate-based crosslinking agent is preferably a compound containing at least two isocyanate groups per molecule.

[0147] Examples of the isocyanate-based crosslinking agent include organic polyisocyanates such as aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates; and modified products of the organic polyisocyanates such as biuret products, isocyanurate products, and adduct products of the organic polyisocyanates.

[0148] Examples of the aromatic polyisocyanate include tolylene diisocyanate (TDI), 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.

[0149] Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate.

[0150] Examples of the alicyclic polyisocyanate include isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatemethyl)cyclohexane.

[0151] Examples of the modified organic polyisocyanate include: Adducts of organic polyisocyanates such as "Sumidur L" (manufactured by Sumitomo Bayer Urethane Co., Ltd.), "Coronate L" and "Coronate HL" (all manufactured by Tosoh Corporation); Biuret form of organic polyisocyanate such as "Sumidur N" (manufactured by Sumitomo Bayer Urethane Co., Ltd.); Examples include isocyanurates of organic polyisocyanates such as "Desmodur IL" and "Desmodur HL" (both manufactured by Bayer AG); "Coronate EH" and "Coronate HX" (both manufactured by Tosoh Corporation), "Takenate D110N" and "Takenate D120N" (both manufactured by Mitsui Chemicals, Inc.).

[0152] Also usable are so-called blocked isocyanates, which are obtained by inactivating the isocyanate groups in these isocyanate crosslinking agents by reacting them with a masking agent having active hydrogen.

[0153] Among the isocyanate-based crosslinking agents, organic polyisocyanates such as aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates are preferred, aromatic polyisocyanates are more preferred, and 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, and polymethylene polyphenyl polyisocyanate are even more preferred.

[0154] The isocyanate-based crosslinking agents may be used alone or in combination of two or more.

[0155] The amount of the isocyanate crosslinking agent used is preferably 1 to 30 parts by mass, more preferably 5 to 25 parts by mass, and even more preferably 10 to 20 parts by mass, relative to 100 parts by mass of the main composition. By adjusting the amount of the isocyanate crosslinking agent to be equal to or greater than the above-mentioned lower limit, the adhesive strength of the resulting adhesive can be further improved, and by adjusting the amount of the isocyanate crosslinking agent to be equal to or less than the above-mentioned upper limit, the pot life of the resulting adhesive can be further extended.

[0156] The mixing temperature of the base composition and the isocyanate-based crosslinking agent is not particularly limited, but is preferably 5 to 40° C. Furthermore, the mixing time of the base composition and the isocyanate-based crosslinking agent is preferably 10 to 35° C. from the viewpoint of ensuring working time.

[0157] The aqueous polymer-isocyanate adhesive obtained by the above-described production method has excellent pot life and adhesive strength. [Example]

[0158] The present invention will now be described in more detail based on examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0159] The physical properties and performance were measured as follows.

[0160] (1) Cumulant mean particle size Using a particle size measuring device (nanoSAQLA, manufactured by Otsuka Electronics Co., Ltd.), the scattering intensity distribution was determined by dynamic light scattering at a measurement temperature of 23°C, and the average particle size was determined by cumulant analysis.

[0161] (2) Non-volatile content (NV value) The nonvolatile content of the emulsion was calculated based on the following formula by weighing 1 g of the emulsion, drying it in a hot air dryer at 125°C for 1 hour, and using the resulting residue as the nonvolatile content. Formula: [Non-volatile content in emulsion (mass%)] = ([mass of residue] ÷ [mass of emulsion (1 g)]) × 100

[0162] (3) Emulsion storage stability The emulsion was placed in a 250 ml polyethylene container, sealed, and three samples were prepared, which were then left to stand for 60 days in thermostatic chambers maintained at 5°C, 23°C, and 50°C, respectively. The obtained samples were visually observed, and if no precipitate was observed in any of the samples, they were rated as ◯, and if precipitate was observed in one or more samples, they were rated as ×.

[0163] (4) Adhesiveness (Preparation of adhesive) 20 parts of calcium carbonate was added to 20 parts of the emulsion while stirring, and the mixture was stirred for 10 minutes. Next, 15 parts of a 15% aqueous polyvinyl alcohol solution and 45 parts of water were added while stirring, and the mixture was stirred for another 10 minutes to prepare a base composition. 15 parts of polymethylene polyphenyl polyisocyanate were blended with 100 parts of the resulting base composition, and the mixture was mixed until uniform to prepare an adhesive. (Preparation of test specimens) Apply 250 g / m2 of the adhesive prepared above to one side of the Douglas fir board. 2 Within one minute, another Douglas fir board was attached to the board and pressed at 23°C and 1.0 MPa for 30 minutes to obtain a test sample. The test sample was then cut to 75 mm lengths, leaving the cross-sectional dimensions of the end grain intact, to create three test pieces. The Douglas fir boards used were approximately 250 mm long, 60 mm wide, and 25 mm thick. All had been planed within 24 hours, and the moisture content of the Douglas fir boards was less than 10%. (Boiling peel test) The delamination rate was calculated in accordance with the provisions of the "boiling delamination test" for structural laminated timber specified by the Japanese Agricultural Standards. Specifically, each of the three test specimens was immersed in boiling water for four hours, followed by another hour in water at 10°C to 25°C. The specimens were then removed from the water and placed in a thermostatic oven at 70±3°C. The specimens were dried overnight, avoiding moisture buildup, until the mass was within 100–110% of the pre-test mass. The length of delamination on both buttocks of each specimen was then measured. The delamination rate on both buttocks was calculated for each specimen using the formula below, and the average was calculated and evaluated according to the following criteria. The smaller the delamination rate, the better the adhesive strength. According to the Japanese Agricultural Standards, a delamination rate of 5% or less is considered to be in compliance with the standard. Adhesives that meet the following criteria with a rating of ○ are considered to have particularly excellent adhesive strength. Note that when measuring the delamination length, wood damage due to cracking or knots, or peeling in areas where knots are present, are not considered delamination. Peeling rate (%) = (total length of peeling on both buttocks / total length of adhesive layer on both buttocks) x 100 [Evaluation criteria] ○: Peeling rate is less than 3% △: Peeling rate is between 3% and 10% ×: Peeling rate exceeds 10%

[0164] (5) Pot life The base composition prepared by the method described in (4) Adhesion Evaluation was adjusted to 35°C, and then 15 parts of polymethylene polyphenyl polyisocyanate was blended with 100 parts of the base composition and mixed until uniform to obtain an adhesive. The resulting adhesive was adjusted to 35°C using a thermostatic bath capable of maintaining a uniform temperature, and the viscosity was measured using a Brookfield viscometer at a rotation speed of 20 rpm. The viscosity 90 minutes after the start of measurement was evaluated according to the following evaluation criteria. [Evaluation criteria] Good: Viscosity after 90 minutes is 25,000 mPa·s or less ×: Viscosity after 90 minutes exceeds 25,000 mPa·s

[0165] [Examples 1 to 4, 6] Water was added to the monomer components and polymerization emulsifier shown in Table 1 so that the concentration of the monomer components became 74%, and the mixture was stirred with a homomixer to prepare a pre-emulsion. Separately, a flask equipped with a dropping funnel, a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 2.0 parts of seed particles (styrene / methyl methacrylate copolymer, solids concentration 35%, average particle size 45 nm) and 35 parts of water, the internal temperature was raised to 83°C, and 0.04 parts of potassium persulfate was added. The pre-emulsion and 0.46 parts of potassium persulfate were added at a constant flow rate over 3.5 hours, and the temperature was then maintained at 83°C for 2 hours. The mixture was then cooled to 10-45°C, and aqueous sodium hydroxide solution was added to adjust the pH to 6. To the obtained solution, 2.0 parts (solid content equivalent) of a post-added emulsifier shown in Table 1 was added per 100 parts of the monomer components used, and then the solution was filtered using a 100-mesh wire screen to obtain an emulsion.

[0166] [Examples 5, 7 to 8] Water was added to the monomer components and polymerization emulsifier shown in Table 1 so that the concentration of the monomer components became 74%, and the mixture was stirred with a homomixer to prepare a pre-emulsion. Separately, a flask equipped with a dropping funnel, a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 35 parts of water and 0.02 parts of Kao Corporation's Latemul E-118B, the internal temperature was raised to 83°C, and 0.04 parts of potassium persulfate was added. The pre-emulsion and 0.46 parts of potassium persulfate were added at a constant flow rate over 3.5 hours, and the temperature was then maintained at 83°C for 2 hours. The mixture was then cooled to 10-45°C, and aqueous sodium hydroxide solution was added to adjust the pH to 6. To the resulting solution, 2.0 parts of a post-added emulsifier shown in Table 1 was added per 100 parts of the monomer components used, and the mixture was filtered using a 100-mesh wire screen to obtain an emulsion.

[0167] [Comparative Examples 1 to 2, 9 to 12] Emulsions were obtained in the same manner as in Examples 5 and 7 to 10, except that the types and amounts of the monomer components, polymerization emulsifier, and post-added emulsifier were changed as shown in Table 2.

[0168] [Comparative Examples 3 to 8] Emulsions were obtained in the same manner as in Examples 1 to 4 and 6, except that the types and amounts of the monomer components were changed as shown in Table 2 and no post-added emulsifier was added.

[0169] The properties of the emulsions obtained in each of the Examples and Comparative Examples were evaluated, and the results are shown in Tables 1 and 2.

[0170] [Table 1]

[0171] [Table 2]

[0172] The terms used in Tables 1 and 2 have the following meanings. St: styrene MMA: Methyl methacrylate BA: butyl acrylate HEA: Hydroxylethyl acrylate HEMA: Hydroxyethyl methacrylate KBM-503: γ-methacryloxypropyltrimethoxysilane Latemul E-118B: Kao Corporation Latemul E-118B, sodium polyoxyethylene alkyl ether sulfate (anionic emulsifier (B1)) (solid content 26%) Emulgen 120: Kao Corporation Emulgen 120, polyoxyethylene lauryl ether (nonionic emulsifier (A1)) (solids 100%) Newcol 562SN: Newcol 562SN manufactured by Nippon Nyukazai Co., Ltd., polyoxyethylene nonylphenyl ether sulfate sodium salt (anionic emulsifier other than anionic emulsifier (B1)) (solids content 30%) Newcol 568SN: Nippon Nyukazai Co., Ltd. Newcol 568SN, a mixture (26% solids) of polyoxyethylene nonylphenyl ether sulfate sodium salt (anionic emulsifier other than anionic emulsifier (B1)) and polyoxyethylene nonylphenyl ether (nonionic emulsifier other than nonionic emulsifier (A1)). Newcol 504: Nippon Nyukazai Co., Ltd. Newcol 504, polyoxyethylene nonylphenyl ether (nonionic emulsifier other than nonionic emulsifier (A1)) (solids content 100%) Latemul D27S: Latemul D27S manufactured by Nippon Nyukazai Co., Ltd., polyoxyethylene dibutylphenyl ether (nonionic emulsifier other than nonionic emulsifier (A1)) (solids content 50%)

[0173] The emulsions of Examples 1 to 8 were excellent in storage stability, and when the emulsions were used to make adhesives, the adhesiveness was good and the pot life was practically satisfactory. In Comparative Examples 1 to 2 and 11 to 12, emulsifiers other than the nonionic emulsifier (A1) were added after cooling, but the adhesiveness was inferior to that of the above Examples. In addition, the pot life and emulsion storage stability were poor, which is problematic in practical use. In addition, in Comparative Examples 3 to 10, no emulsifier was added after cooling, and although the pot life and emulsion storage stability were comparable to those of the Examples of the present invention, the adhesiveness was poor, which is problematic in practical use.

Claims

1. a polymerization step of emulsion-polymerizing a monomer component containing an aromatic vinyl monomer and a (meth)acrylic acid alkyl ester in the presence of an emulsifier and a polymerization initiator at a polymerization temperature of more than 50°C; an emulsifier addition step of adding a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring after the temperature of the solution obtained in the polymerization step has reached 50°C or less.

2. The production method according to claim 1, wherein the amount of the nonionic emulsifier (A1) added in the emulsifier addition step is 0.05 to 8.0 parts by mass per 100 parts by mass of the total of the monomer components.

3. the monomer component further contains a hydroxyl group-containing monomer, The method according to claim 1, wherein the content of the hydroxyl group-containing monomer is 0.1 to 2.8% by mass based on 100% by mass of the monomer components.

4. 2. The method according to claim 1, wherein the average particle size of emulsion particles constituting the acrylic resin emulsion based on a scattering intensity distribution is 100 to 350 nm.

5. A method for producing an aqueous polymer-isocyanate adhesive, comprising a step of mixing a base composition containing the acrylic resin emulsion obtained by the production method of claim 1, polyvinyl alcohol, and water with an isocyanate crosslinking agent.

6. An acrylic resin emulsion comprising emulsion particles containing structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester, a nonionic emulsifier (A), and water, the nonionic emulsifier (A) comprises a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring, the content of the nonionic emulsifier (A1) is 90% by mass or more in 100% by mass of the nonionic emulsifier (A), The acrylic resin emulsion has a content of the nonionic emulsifier (A) of 0.3 parts by mass or more per 100 parts by mass of the emulsion particles.

7. An acrylic resin emulsion comprising emulsion particles containing structural units derived from an aromatic vinyl monomer and structural units derived from a (meth)acrylic acid alkyl ester, a nonionic emulsifier (A), and water, the nonionic emulsifier (A) comprises a nonionic emulsifier (A1) having a linear alkyl group and / or a branched alkyl group and not having an aromatic hydrocarbon ring, An acrylic resin emulsion having a peeling rate of 10% or less as determined by the boiling peeling test described below. (Boiling peel test) The acrylic resin emulsion, a 15% by weight aqueous polyvinyl alcohol solution, calcium carbonate, and water were mixed in a mass ratio of 20:15:20:45 (acrylic resin emulsion:polyvinyl alcohol aqueous solution:calcium carbonate:water). Next, 15 parts by weight of polymethylene polyphenyl polyisocyanate was added to 100 parts by weight of the base composition to prepare an adhesive. The adhesive's adhesion to Douglas fir was tested in accordance with the "Boiling Peel Test" for structural laminated lumber specified by the Japanese Agricultural Standards, and the peel rate was calculated.

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