阅读说明：本技术 橡胶胶乳及水系粘接剂组合物 (Rubber latex and aqueous adhesive composition ) 是由 大串元 小野冢正雄 小林直纪 安藤辽太郎 于 2020-03-11 设计创作，主要内容包括：橡胶胶乳,其含有接枝共聚物和表面活性剂,接枝共聚物具有氯丁二烯聚合物链和接枝链,所述接枝链结合于该氯丁二烯聚合物链且包含来自烯键式不饱和羧酸的结构单元,接枝共聚物中的氧原子的含量相对于氯原子的含量而言的摩尔比为0.04～1。(A rubber latex contains a graft copolymer and a surfactant, wherein the graft copolymer has a chloroprene polymer chain and a graft chain, the graft chain is bonded to the chloroprene polymer chain and contains a structural unit derived from an ethylenically unsaturated carboxylic acid, and the molar ratio of the content of oxygen atoms to the content of chlorine atoms in the graft copolymer is 0.04-1.)

1. A rubber latex containing a graft copolymer and a surfactant,

the graft copolymer has a chloroprene polymer chain and a graft chain bonded to the chloroprene polymer chain and containing a structural unit derived from an ethylenically unsaturated carboxylic acid,

the graft copolymer has a molar ratio of the content of oxygen atoms to the content of chlorine atoms of 0.04 to 1.

2. The rubber latex according to claim 1, wherein the ethylenically unsaturated carboxylic acid contains at least one selected from the group consisting of acrylic acid and methacrylic acid.

3. The rubber latex according to claim 1 or 2, wherein the acetone-soluble component in the graft copolymer is 3% by mass or less as measured by the following (1) to (4),

(1) the rubber latex was frozen at-60 ℃ for 24 hours and then freeze-dried, thereby obtaining a dried product,

(2) the dried material (1.00 g) was cut into 2mm squares, the obtained pieces were immersed in 100mL of acetone to obtain an acetone solution, and the acetone solution was stirred for 24 hours using a magnetic stirrer,

(3) removing insoluble substances in the acetone solution by filtration, then concentrating and drying the acetone solution by using an evaporator, measuring the mass of the residue,

(4) the acetone-soluble component was calculated by the following formula,

the acetone-soluble component is equal to the mass of the residue [ g ]/the mass of the dried product 1.00[ g ] × 100.

4. The rubber latex as claimed in any one of claims 1 to 3, which further comprises a tackifier resin, a thickener and an isocyanate.

5. An aqueous adhesive composition comprising the rubber latex according to any one of claims 1 to 4.

Technical Field

The present invention relates to a rubber latex and an aqueous adhesive composition.

Background

As an adhesive containing a chloroprene polymer (hereinafter, referred to as "polychloroprene" in some cases) as a base, a solvent-based adhesive in which chloroprene rubber is dissolved in an organic solvent has been mainly used. However, solvent adhesives have a problem of danger of fire and environmental pollution caused by organic solvents during production and use, and the demand for desolvation has been increasing. As a means of desolvation, a method of replacing an aqueous adhesive based on a chloroprene polymer latex is effective.

As an aqueous adhesive containing a chloroprene polymer latex as a base, for example, the following two-pack type aqueous adhesive is known: an aziridine-based, carbodiimide-based, or blocked isocyanate-based crosslinking agent is further used by blending an aqueous polyurethane resin having a crosslinking density of 0.02 to 1.00 per 1000 atomic weight with respect to the chloroprene polymer latex (see patent document 1 below).

In addition, there are known: a two-pack type aqueous adhesive in which a liquid polychloroprene is blended with an aqueous urethane resin as a main component and a water-dispersible isocyanate compound is used as a curing agent (see patent document 2); an aqueous adhesive obtained by blending an aqueous polyurethane emulsion obtained by reacting a specific isocyanate compound, a polyol, a chain extender, and a carboxylic acid-containing low-molecular-weight polyol with a polychloroprene latex (see patent document 3 below); and so on.

Further, an adhesion method using an aqueous primer composed of a chloroprene-based rubber latex, an olefin-based resin emulsion, a polyurethane latex, and a tackifier resin is known (see patent document 4 below).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2-127491

Patent document 2: japanese laid-open patent publication No. 4-323292

Patent document 3: japanese laid-open patent publication No. 10-273587

Patent document 4: japanese laid-open patent publication No. 5-320601

Disclosure of Invention

Problems to be solved by the invention

In these conventional water-based adhesives and bonding methods, initial bonding strength is insufficient when members made of vinyl chloride resin are bonded to each other.

An object of one aspect of the present invention is to provide a rubber latex that can obtain excellent initial adhesion strength when members made of vinyl chloride resin are adhered to each other. Another object of the present invention is to provide an aqueous adhesive composition containing the rubber latex.

Means for solving the problems

The present inventors have conducted extensive studies and, as a result, have found that the above-mentioned problems can be solved by a rubber latex containing a graft copolymer obtained by grafting an ethylenically unsaturated carboxylic acid onto a chloroprene polymer and a surfactant, wherein the molar ratio of the content of oxygen atoms to the content of chlorine atoms in the graft copolymer is 0.04 to 1.

One aspect of the present invention provides a rubber latex containing a graft copolymer and a surfactant, the graft copolymer having a chloroprene polymer chain and a graft chain bonded to the chloroprene polymer chain and containing a structural unit derived from an ethylenically unsaturated carboxylic acid, wherein the graft copolymer has a molar ratio of an oxygen atom content to a chlorine atom content of 0.04 to 1.

Another aspect of the present invention provides an aqueous adhesive composition containing the rubber latex.

ADVANTAGEOUS EFFECTS OF INVENTION

According to an aspect of the present invention, it is possible to provide a rubber latex which can obtain excellent initial adhesion strength when members made of a vinyl chloride resin are adhered to each other. According to another aspect of the present invention, there is provided an aqueous adhesive composition containing the rubber latex.

Detailed Description

The present invention will be described in detail below. The embodiments described below are merely examples of representative embodiments of the present invention, and the scope of the present invention is not to be narrowly construed in accordance therewith.

In the present specification, a numerical range represented by "to" includes ranges in which the numerical values recited before and after "to" are respectively the minimum value and the maximum value. The numerical range "a or more" means a and a range exceeding a. The numerical range "below A" means the range of A and less than A. In the numerical ranges recited in the present specification, the upper limit or the lower limit of the numerical range in one stage may be arbitrarily combined with the upper limit or the lower limit of the numerical range in another stage. In the numerical ranges described in the present specification, the upper limit or the lower limit of the numerical range may be replaced with the values shown in the examples. "a or B" may include either or both of a and B. Unless otherwise specified, 1 kind of the material exemplified in the present specification may be used alone, or 2 or more kinds may be used in combination. The content of each component in the composition means the total amount of a plurality of substances present in the composition, unless otherwise specified, when a plurality of substances belonging to each component are present in the composition. The term "(meth) acrylic acid" means at least one of acrylic acid and methacrylic acid corresponding thereto. The same applies to other similar expressions such as "(meth) acrylate".

< rubber latex >

The rubber latex according to the present embodiment contains a graft copolymer and a surfactant, the graft copolymer having a chloroprene polymer chain (polychloroprene chain) and a graft chain bonded to the chloroprene polymer chain and containing a structural unit derived from an ethylenically unsaturated carboxylic acid (ethylenically unsaturated carboxylic acid), and the molar ratio of the content of oxygen atoms to the content of chlorine atoms in the graft copolymer being 0.04 to 1.

According to the rubber latex of the present embodiment, excellent initial adhesion strength (initial adhesion force) can be obtained when members made of vinyl chloride resin are adhered to each other. The rubber latex according to the present embodiment has a double bond of the chloroprene polymer in the chloroprene polymer chain and a carboxyl group derived from an ethylenically unsaturated carboxylic acid in the molecule, and thus can be suitably used for bonding various members. The rubber latex according to the present embodiment can be used as it is as an adhesive. The rubber latex according to the present embodiment may contain no organic solvent and may be used as an aqueous adhesive (aqueous adhesive composition).

According to the rubber latex of the present embodiment, when members made of a vinyl chloride resin are bonded to each other, excellent initial adhesion strength and excellent normal state adhesion strength (normal state adhesive force) can be obtained. The "normal adhesion strength" is the adhesion strength after the members are held at 23 ℃ and 50% RH for 5 days after they are pressure-bonded to each other. The rubber latex according to the present embodiment can obtain these adhesion strengths without requiring a primer treatment operation or the like, and is not easily limited by adhesion conditions. The rubber latex according to the present embodiment can be used for bonding members made of natural rubber to each other and/or bonding members made of vinyl chloride resin to members made of natural rubber. The rubber latex according to the present embodiment can also be used for adhesion of members made of nylon to each other and adhesion of members made of nylon to other members.

(graft copolymer)

The graft copolymer has a chloroprene polymer chain (polychloroprene chain) and a graft chain bonded to the chloroprene polymer chain and containing a structural unit derived from an ethylenically unsaturated carboxylic acid. The chloroprene polymer chain is a backbone polymer with respect to the graft chain, and may be the backbone of the graft copolymer.

The graft copolymer can be obtained by grafting (graft polymerization) an ethylenically unsaturated carboxylic acid to a chloroprene polymer (polychloroprene). That is, the method for producing a graft copolymer includes a graft polymerization step of grafting (graft polymerization) an ethylenically unsaturated carboxylic acid to a chloroprene polymer. The method for producing the graft copolymer may include a chloroprene polymerization step of polymerizing chloroprene to obtain a chloroprene polymer, and in the chloroprene polymerization step, chloroprene and another monomer copolymerizable with chloroprene may be polymerized (copolymerized).

(chloroprene Polymer)

The chloroprene polymer (polychloroprene) of the chloroprene polymer chain has a structural unit derived from chloroprene (2-chloro-1, 3-butadiene). The chloroprene polymer may be: homopolymers of chloroprene, copolymers of chloroprene and other monomers copolymerizable with chloroprene, or mixtures of these polymers. The chloroprene polymer may be a chloroprene latex.

The content of the structural unit derived from chloroprene is preferably 50 mass% or more, 70 mass% or more, 90 mass% or more, 95 mass% or more, 98 mass% or more, or 99 mass% or more based on the whole chloroprene polymer, from the viewpoint of easily obtaining excellent initial adhesion strength and easily obtaining excellent normal state adhesion strength. The chloroprene polymer may be a form formed of a constituent unit derived from chloroprene (a form in which 100% by mass of the chloroprene polymer is substantially a constituent unit derived from chloroprene).

Examples of the monomer copolymerizable with chloroprene include esters of (meth) acrylic acid (e.g., methyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate), hydroxy (meth) acrylates (e.g., 2-hydroxyethyl (meth) acrylate, 2-hydroxymethyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate), 2, 3-dichloro-1, 3-butadiene, 1-chloro-1, 3-butadiene, isoprene, ethylene, styrene, and acrylonitrile.

When a copolymer of chloroprene and another monomer copolymerizable with chloroprene is used as the chloroprene polymer, the copolymerization amount of the other monomer is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, per 100 parts by mass of chloroprene. By adjusting the copolymerization amount of the other monomer to the above range, the effect of the copolymerization of these monomers can be easily exhibited without impairing the characteristics of the rubber latex (for example, the aqueous adhesive composition).

The other monomer copolymerizable with chloroprene is not limited to 1 type, and for example, 3 or more types of monomers including chloroprene may be copolymerized. The polymer structure of the chloroprene polymer is not particularly limited. The chloroprene polymer may be a thiol-modified chloroprene polymer, a xanthic acid-modified chloroprene polymer, a sulfur-modified chloroprene polymer, a dithiocarbonate-based chloroprene polymer, a trithiocarbonate-based chloroprene polymer, a urethane-based chloroprene polymer, or the like.

The chloroprene polymer can be obtained by, for example, emulsion polymerization of a raw material monomer containing chloroprene as a main component in the presence of a polymerization catalyst, a catalyst activator, a polymerization initiator, a chain transfer agent, and the like. In obtaining the chloroprene polymer, rosin or the like can be used as an emulsifying dispersant.

Examples of the catalyst for the polymerization reaction include organic peroxides such as ketone peroxides, hydroperoxides (e.g., t-butyl hydroperoxide), dialkyl peroxides, and diacyl peroxides.

Examples of the catalyst activator include sodium sulfite, sodium bisulfite, potassium sulfite, iron (II) oxide, anthraquinone, β -sodium sulfonate, formamidinesulfinic acid, and L-ascorbic acid.

The polymerization initiator is not particularly limited, and known polymerization initiators generally used for emulsion polymerization of chloroprene monomers can be used. Examples of the polymerization initiator include inorganic peroxides (potassium persulfate, ammonium persulfate, sodium persulfate, etc.), hydrogen peroxide, and the like.

The chain transfer agent is not particularly limited, and a chain transfer agent generally used for emulsion polymerization of chloroprene can be used. Examples of the chain transfer agent include: long-chain alkyl mercaptans such as n-dodecyl mercaptan (also known as 1-dodecyl mercaptan), t-dodecyl mercaptan, and n-octyl mercaptan; xanthic acid compounds such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide; iodoform; benzyl 1-pyrroledithiocarbamate (alias: benzyl 1-pyrroledithiocarbamate), benzyl phenyldithiocarbamate, 1-benzyl-N, N-dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethylimidazolium dithiocarbamate (alias: 1-phenylethylimidazolium dithioformate), benzyl 1- (2-pyrrolidinone) dithiocarbamate (alias: benzyl 1- (2-pyrrolidinone) dithiocarbamate), benzyl phthalimidyldithiocarbamate (alias: benzyl phthalimidyldithiocarbamate), 2-cyanoprop-2-yl-1-pyrroledithiocarbamate (alias: 2-cyanoprop-2-yl-1- Pyrrole dithioformate), 2-cyanobut-2-yl-1-pyrrole dithiocarbamate (alternative name: 2-cyanobut-2-yl-1-pyrrole dithiocarbamate), benzyl 1-imidazole dithiocarbamate (alternative name: benzyl 1-imidazoledithiocarbamate), 2-cyanoprop-2-yl-N, N-dimethyldithiocarbamate, benzyl N, N-diethyldithiocarbamate, cyanomethyl-1- (2-pyrrolidinone) dithiocarbamate, 2- (ethoxycarbonylbenzyl) propan-2-yl-N, N-diethyldithiocarbamate, 1-phenylethyldithiobenzoate, 2-phenylprop-2-yl dithiobenzoate, 1-acetoxy-1-yl-ethyldithiobenzoate, 1- (4-methoxyphenyl) ethyldithiobenzoate, benzyl dithioacetate, ethoxycarbonylmethyldithioacetate, 2- (ethoxycarbonyl) propan-2-yl dithiobenzoate, methyl-N, N-dimethyldithiocarbamate, N-N, N-diethyldithiocarbamate, N-1-phenylethyl-2-yl dithiobenzoate, 1-acetoxy-1-yl-ethyldithiobenzoate, 1- (4-methoxyphenyl) ethyldithiobenzoate, benzyl-ethoxycarbonylmethyldithioacetate, 2- (ethoxycarbonyl) propan-2-yl dithiobenzoate, N-dimethyldithiocarbamate, N-2-dimethyldithiocarbamate, N-1-pyrrolidinone, N-1-ethyldithiobenzoate, N-ethyldithiocarbamate, N-1-ethyldithiobenzoate, N-one, N, 2-cyanoprop-2-yldithiocarbenzoate, t-butyl dithiobenzoate, 2,4, 4-trimethylpent-2-yldithiocarbenzoate, 2- (4-chlorophenyl) -prop-2-yldithiocarbenzoate, 3-vinylbenzyldithiobenzoate, 4-vinylbenzyldithiobenzoate, diethoxyphosphinyldithiocarbonate, t-butyl trithioperoxybenzoate, 2-phenylprop-2-yl-4-chlorodithiobenzoate, 1-methyl-1-phenyl-ethyl naphthalene-1-carboxylate, 4-cyano-4-methyl-4-thiobenzylsulfanylbutanoic acid, dibenzyl tetrathioterephthalate, thiodipropylbenzoate, tert-butyl dithiobenzoate, tert-butyl ester of a compound having a structure represented by the formula, Carboxymethyl dithiobenzoate, poly (ethylene oxide) having a dithiobenzoate end group, poly (ethylene oxide) having a 4-cyano-4-methyl-4-thiobenzylsulfanyl butanoic acid end group, 2- [ (2-phenylethanothyl) sulfanyl ] propanoic acid, 2- [ (2-phenylethanothyl) sulfanyl ] succinic acid, potassium 3, 5-dimethyl-1H-pyrazole-1-dithiocarbamate, cyanomethyl- (phenyl) dithiocarbamate, benzyl 4-chlorodithiobenzoate, phenylmethyl-4-chlorodithiobenzoate, methyl-2-thiobenzyl-2-thioalkyl-thioacetate, and the like, 4-nitrobenzyl-4-chlorodithiobenzoate, phenylprop-2-yl-4-chlorodithiobenzoate, 1-cyano-1-methylethyl-4-chlorodithiobenzoate, 3-chloro-2-butenyl-4-chlorodithiobenzoate, 2-chloro-2-butenyl dithiobenzoate, benzyl dithioacetate, 3-chloro-2-butenyl-1H-pyrrole-1-dithiocarboxylic acid, 2-cyanobutan-2-yl-4-chloro-3, 5-dimethyl-1H-pyrazole-1-dithioformate, cyanomethyl (phenyl) dithiocarbamate, methyl (phenyl) dithiobenzoate, methyl (ethyl) dithiobenzoate, methyl-ethyl-1-dithiobenzoate, methyl-2-methyl-4-butenyl-2-butenyl-3, 5-dimethyl-1H-pyrazole-1-dithioformate, methyl-2-methyl-ethyl-1-methyl-1-ethyl-2-butenyl-4-propyl-4-chloro-2-butenyl-2-dimethyl-1H-pyrazole-1-dithioformate, methyl-1-methyl-ethyl-methyl-1-ethyl-methyl-ethyl-2-methyl-2-ethyl-2-methyl-ethyl-2-methyl-propyl-2-methyl-ethyl-2-propyl-dithiobenzoate, 2-methyl-ethyl-2-methyl-ethyl-2-methyl-ethyl-2-methyl-2-methyl-ethyl-2-methyl-2-methyl-2-ethyl-methyl-2-methyl-ethyl-2-methyl-2-ethyl-2-methyl-2-methyl-2-methyl-2-ethyl-methyl-2-ethyl-2-methyl-2-methyl-2-methyl-ethyl-methyl-ethyl-2-methyl-2-, 2-cyano-2-propyldodecyltrithiocarbonate, dibenzyltrithiocarbonate, butylbenzyltrithiocarbonate, 2- [ [ (butylthio) thiolmethyl ] thio ] propanoic acid, 2- [ [ dodecylthio) thiolmethyl ] thio ] propanoic acid, 2- [ [ (butylthio) thiolmethyl ] thio ] succinic acid, 2- [ [ dodecylthio) thiolmethyl ] thio ] -2-methylpropanoic acid, 2' - [ methylthiobis (thio) ] bis [ 2-methylpropanoic acid ], 2-amino-1-methyl-2-oxoethylbutyltrithiocarbonate, benzyl-2- [ (2-hydroxyethyl) amino ] -1-methyl-2-oxoethyltrithiocarbonate Thiocarbonyl compounds such as thiocarbonate, 3- [ [ [ (tert-butyl) thio ] thiolmethyl ] thio ] propanoic acid, cyanomethyldodecyltrithiocararbonate, diethylaminobenzyl trithiocarbonate and dibutylaminobenzyltrithiocarbonate.

The polymerization temperature is not particularly limited, and may be a temperature at which emulsion polymerization can be usually carried out, and is preferably in the range of 0 to 50 ℃ and more preferably in the range of 10 to 50 ℃. The final polymerization rate of the chloroprene polymer obtained in the above-mentioned chloroprene polymerization step is not particularly limited, but is preferably arbitrarily adjusted within a range of 30 to 100%. In order to adjust the final conversion, when a desired conversion is achieved, the polymerization may be stopped by adding a polymerization terminator to stop the polymerization reaction.

The polymerization terminator is not particularly limited, and a commonly used polymerization terminator can be used. Examples of the polymerization terminator include thiodiphenylamine, 4-tert-butylcatechol, and 2, 2-methylenebis-4-methyl-6-tert-butylphenol.

The graft copolymer may be a graft copolymer obtained by grafting a monomer containing an ethylenically unsaturated carboxylic acid as a main component to a chloroprene polymer. The graft copolymer may have a graft chain having a content of the structural unit derived from the ethylenically unsaturated carboxylic acid in the following range. The content of the structural unit derived from an ethylenically unsaturated carboxylic acid is preferably 50 mass% or more, 70 mass% or more, 90 mass% or more, 95 mass% or more, 98 mass% or more, or 99 mass% or more based on the whole graft chain, from the viewpoint of easily obtaining excellent initial adhesion strength and easily obtaining excellent normal state adhesion strength. The graft chain may be formed of a structural unit derived from an ethylenically unsaturated carboxylic acid (a mode in which substantially 100% by mass of the graft chain is a structural unit derived from an ethylenically unsaturated carboxylic acid). The graft chain may have no structural unit derived from chloroprene.

Examples of the ethylenically unsaturated carboxylic acid grafted to the chloroprene polymer include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, and the like. The ethylenically unsaturated carboxylic acid is not limited to 1 species, and 2 or more species may be used in combination. From the viewpoint of easily obtaining excellent initial adhesion strength and easily obtaining excellent normal state adhesion strength, it is preferable that the ethylenically unsaturated carboxylic acid contains at least one selected from the group consisting of acrylic acid and methacrylic acid.

As a method for grafting an ethylenically unsaturated carboxylic acid to a chloroprene polymer, the following emulsion polymerization method is generally used: the chloroprene polymer (latex) obtained by the above method is mixed with an ethylenically unsaturated carboxylic acid, and the ethylenically unsaturated carboxylic acid is grafted to the chloroprene polymer in the presence of a radical polymerization initiator. In addition, the following solution polymerization method may also be used: a chloroprene polymer rubber is obtained by freeze-drying a chloroprene polymer (latex), an ethylenically unsaturated carboxylic acid is added to a solution obtained by dissolving the chloroprene polymer rubber in an organic solvent, and the ethylenically unsaturated carboxylic acid is grafted to the chloroprene polymer in the presence of a radical polymerization initiator. As the radical polymerization initiator, for example, potassium persulfate can be used.

The graft copolymer has a molar ratio of the content of oxygen atoms to the content of chlorine atoms (content of oxygen atoms/content of chlorine atoms) of 0.04 to 1 (i.e., the molar ratio of chlorine atoms to oxygen atoms in the graft copolymer is 1:0.04 to 1: 1). The molar ratio of chlorine atoms to oxygen atoms is a molar ratio representing the amount of chlorine atoms contained in the chloroprene polymer and the amount of oxygen atoms contained in the ethylenically unsaturated carboxylic acid, and represents the graft amount of the ethylenically unsaturated carboxylic acid in the graft copolymer. For example, in order to increase the content of oxygen atoms, the amount of ethylenically unsaturated carboxylic acid to be grafted or the polymerization time may be increased, or the amount of ethylenically unsaturated carboxylic acid to be grafted to the chloroprene polymer may be increased.

The content of chlorine atoms and oxygen atoms in the graft copolymer can be measured by the following method.

(1) The rubber latex was frozen at-60 ℃ for 24 hours and then freeze-dried, thereby obtaining a dried product.

(2) 1.00g of the above dried product was cut into 2mm squares (cubes of 2mm in length. times.2 mm in width. times.2 mm in height), the obtained pieces were immersed in 100mL of acetone to obtain an acetone solution, and then the acetone solution was stirred for 24 hours using a magnetic stirrer (for example, manufactured by AS ONE Corporation, CHPS-170DS, size: 175 mm. times.178 mm). This operation (2) can be carried out, for example, at 23 ℃.

(3) The insoluble matter in the acetone solution is recovered by filtration and then dried (for example, the insoluble matter is dried by leaving it to stand for 24 hours in a vacuum dryer).

(4) The measurement is carried out using a scanning electron microscope (e.g., SU6600 manufactured by Hitachi High-Technologies Corporation) equipped with an energy dispersive X-ray analyzer (e.g., INCAX-act manufactured by Oxford Instruments).

The molar ratio of the content of oxygen atoms to the content of chlorine atoms in the graft copolymer is preferably 0.05 or more, 0.06 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.35 or more, 0.38 or more, 0.39 or more, 0.4 or more, 0.41 or more, 0.42 or more, 0.45 or more, 0.48 or more, 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more, from the viewpoint of easily obtaining excellent initial adhesion strength and easily obtaining excellent normal state adhesion strength. The molar ratio of the content of oxygen atoms to the content of chlorine atoms in the graft copolymer is preferably 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.48 or less, 0.45 or less, 0.42 or less, 0.41 or less, 0.4 or less, 0.39 or less, 0.38 or less, 0.35 or less, 0.3 or less, 0.2 or less, 0.1 or less, or 0.06 or less, from the viewpoint of easily obtaining excellent initial adhesion strength and easily obtaining excellent normal state adhesion strength.

In the graft copolymer, the acetone-soluble component measured in the following (1) to (4) is preferably 3 mass% or less, 2 mass% or less, 1 mass% or less, or less than 1 mass% from the viewpoint of easily obtaining excellent initial adhesion strength and easily obtaining excellent normal state adhesion strength. The acetone-soluble component may be 0 mass% or more and may exceed 0 mass. The graft copolymer may contain acetone-soluble components measured by the following (1) to (4) in a range of more than 0% by mass and not more than 3% by mass.

(1) The rubber latex was frozen at-60 ℃ for 24 hours and then freeze-dried, thereby obtaining a dried product.

(2) 1.00g of the above dried product was cut into 2mm squares (cubes of 2mm in length. times.2 mm in width. times.2 mm in height), the obtained pieces were immersed in 100mL of acetone to obtain an acetone solution, and then the acetone solution was stirred for 24 hours using a magnetic stirrer (for example, manufactured by AS ONE Corporation, CHPS-170DS, size: 175 mm. times.178 mm). This operation (2) can be carried out, for example, at 23 ℃.

(3) Insoluble matter in the acetone solution was removed by filtration, and then the acetone solution was concentrated and dried by an evaporator, and the mass (a) of the residue was measured (accurately weighed).

(4) The acetone-soluble component was calculated by the following formula.

The mass of acetone-soluble component (a) [ g ]/the mass of the dried product 1.00[ g ] × 100

The acetone-soluble component can be used as an index of the amount of a polymer (such as a homopolymer of methacrylic acid) obtained by polymerizing ethylenically unsaturated carboxylic acids used in obtaining a graft copolymer. By adjusting the acetone-soluble component to this range, the initial adhesive strength and the normal adhesive strength can be easily improved.

(surfactant)

The surfactant is not particularly limited, and examples thereof include polyvinyl alcohol; rosin acid soaps, disproportionated rosin soaps, and other resin acid soaps; alkyl sulfates such as sodium lauryl sulfate; alkyl benzene sulfonates such as sodium dodecylbenzenesulfonate; alkyl naphthalene sulfonate; a dialkyl sulfosuccinate salt; polyoxyethylene alkyl ether sulfates; salts of arylsulfonic acid-formaldehyde condensates such as salts of β -naphthalenesulfonic acid-formaldehyde condensates; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene higher alcohol ethers and polyoxyethylene nonyl phenyl ethers.

The content of the surfactant (surfactant amount) is preferably in the following range based on the total amount of the rubber latex (in terms of solid content) from the viewpoint of improving the stability of the rubber latex. The content of the surfactant is preferably 0.5% by mass or more, 0.7% by mass or more, 0.8% by mass or more, 1% by mass or more, 1.2% by mass or more, 1.4% by mass or more, 1.5% by mass or more, 1.6% by mass or more, 1.8% by mass or more, or 2% by mass or more. The content of the surfactant is preferably 2.5% by mass or less, 2% by mass or less, 1.8% by mass or less, 1.6% by mass or less, 1.5% by mass or less, 1.4% by mass or less, 1.2% by mass or less, 1% by mass or less, 0.8% by mass or less, or 0.7% by mass or less. From these viewpoints, the content of the surfactant is preferably 0.5 to 2.5% by mass. The content of the surfactant can be measured by the method described in examples.

The surfactant may be added after the graft copolymer is obtained by the above-mentioned method, or may be added at the time of polymerization of the chloroprene polymer (chloroprene polymerization step) or at the time of obtaining the graft copolymer (graft polymerization step).

(other Components)

The rubber latex according to the present embodiment may optionally contain a tackifier resin, a thickener, isocyanate, an ultraviolet absorber, an antioxidant, a plasticizer, a filler, a vulcanizing agent, a vulcanization accelerator, an antifoaming agent, a rust preventive, and the like, depending on required performance. For example, the rubber latex according to the present embodiment may contain a tackifier resin, a thickener, and an isocyanate.

[ tackifying resins ]

The tackifier resin may be blended to improve the initial adhesive strength. The tackifier resin is not particularly limited, and examples thereof include rosin resins, polymerized rosin resins, α -pinene resins, β -pinene resins, terpene phenolic resins, C5 fraction petroleum resins, C9 fraction petroleum resins, C5/C9 fraction petroleum resins, DCPD petroleum resins, alkylphenol resins, xylene resins, coumarone indene resins, and the like.

The method of adding the tackifier resin is not particularly limited, and it is preferable to add the tackifier resin after preparing an emulsion so that the resin is uniformly dispersed in the rubber latex.

The content (amount of addition) of the tackifier resin is preferably 20 to 80 parts by mass per 100 parts by mass (in terms of solid content) of the rubber latex. By adjusting the content (addition amount) of the tackifier resin to the above range, both the initial adhesive strength and the normal state adhesive strength are easily improved.

[ thickening agent ]

The thickener may be added to increase the viscosity of the adhesive and improve the applicability and workability of the adhesive. The tackifier resin is not particularly limited, and examples thereof include an aqueous solution of carboxymethyl cellulose (CMC), an aqueous solution of hydroxyethyl cellulose, polyvinyl alcohol, and a synthetic resin emulsion containing a hydrophilic group.

The content (addition amount) of the thickener is preferably 0.01 to 1.0 part by mass or 0.05 to 0.5 part by mass per 100 parts by mass (in terms of solid content) of the rubber latex. By adjusting the content (addition amount) of the thickener to this range, good stability of the adhesive over time can be easily obtained.

[ isocyanate ]

The isocyanate may be blended to improve the adhesive strength. The isocyanate is not particularly limited, and methyl isocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone isocyanate, and the like can be mentioned.

The content (amount of addition) of the isocyanate is preferably 1 to 10 parts by mass or 2 to 5 parts by mass based on 100 parts by mass of the rubber latex (in terms of solid content). By adjusting the content (addition amount) of the thickener to this range, good adhesive strength can be easily obtained.

< aqueous adhesive composition >

The aqueous adhesive composition according to the present embodiment is an aqueous adhesive composition containing the rubber latex according to the present embodiment, and the rubber latex according to the present embodiment is an aqueous adhesive (an aqueous adhesive composition composed of the rubber latex according to the present embodiment). The aqueous adhesive composition according to the present embodiment may contain no organic solvent. The content of the organic solvent may be 1.0 mass% or less, 0.5 mass% or less, or 0.1 mass% or less, and may be 0 mass% based on the total mass of the aqueous adhesive composition.

Examples

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

< example 1 >

(production of chloroprene latex A)

Into a reactor having an internal volume of 10L, 150 parts by mass of water, 4.0 parts by mass of sodium dodecylbenzenesulfonate (NEOPELEX G-65 (purity: 65 mass%)), 0.7 parts by mass of sodium naphthalenesulfonate formaldehyde condensate (DEMOL N, manufactured by Kao corporation) and 0.5 parts by mass of sodium hydrogensulfite were charged under a nitrogen stream, and then the solid components were dissolved to obtain a solution. Then, while stirring the solution, 100 parts by mass of chloroprene and 0.55 part by mass of 1-dodecanethiol were added to the solution. The polymerization was started at 10 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 75%, the polymerization was stopped by adding an emulsion containing 0.02 parts by mass of thiodiphenylamine. The unreacted monomers were removed under reduced pressure to obtain a latex. Water was added thereto to adjust the solid content concentration (mass concentration) in the latex to 20 mass%, thereby obtaining chloroprene latex a (thiol-modified). The solid content concentration in the chloroprene latex was calculated from the mass change before and after drying when 2g of the chloroprene latex was dried with a 125 ℃ hot air dryer for 1 hour.

(production of graft copolymer rubber latex a)

To 100 parts by mass of the chloroprene latex a, 0.5 part by mass of methacrylic acid and 0.005 part by mass of 1-dodecylmercaptan were added while stirring. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. The polymerization was terminated when the polymerization rate reached 100%. Thus, a graft copolymer rubber latex a was obtained.

< example 2 >

A graft copolymer rubber latex b was obtained in the same manner as in example 1 except that the amount of methacrylic acid used in example 1 was changed to 4 parts by mass and the amount of 1-dodecanethiol used was changed to 0.04 part by mass.

< example 3 >

A graft copolymer rubber latex c was obtained in the same manner as in example 1 except that the amount of methacrylic acid used in example 1 was changed to 8 parts by mass and the amount of 1-dodecanethiol used was changed to 0.08 part by mass.

< example 4 >

(production of chloroprene latex B)

Chloroprene latex B (modified with xanthate) was obtained in the same manner as in example 1, except that 0.55 part by mass of 1-dodecanethiol in example 1 was changed to 0.55 part by mass of diethylxanthogen disulfide (manufactured by daikon chemical industries, ltd.).

(production of graft copolymer rubber latex d)

While stirring 100 parts by mass of the chloroprene latex B, 4 parts by mass of methacrylic acid and 0.04 part by mass of 1-dodecylmercaptan were added to the chloroprene latex B. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 100%, the polymerization was terminated. Thus, a graft copolymer rubber latex d was obtained.

< example 5 >

(production of chloroprene latex C)

Chloroprene latex C (sulfur-modified) was obtained in the same manner as in example 1, except that 0.55 part by mass of 1-dodecanethiol in example 1 was changed to 0.55 part by mass of sulfur.

(production of graft copolymer rubber latex e)

While stirring 100 parts by mass of the chloroprene latex C, 4 parts by mass of methacrylic acid and 0.04 part by mass of 1-dodecylmercaptan were added to the chloroprene latex C. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 100%, the polymerization was terminated. Thus, a graft copolymer rubber latex e was obtained.

< example 6 >

A graft copolymer rubber latex f was obtained in the same manner as in example 2, except that methacrylic acid in example 2 was changed to acrylic acid.

< example 7 >

(production of chloroprene latex D)

Chloroprene latex D (thiol-modified) was obtained in the same manner as in example 1, except that the amount of sodium dodecylbenzenesulfonate (NEOPELEX G-65 (purity: 65 mass%) manufactured by Kao corporation) used in example 1 was changed from 4.0 parts by mass to 2.0 parts by mass.

(production of graft copolymer rubber latex g)

To the chloroprene latex D, 4 parts by mass of methacrylic acid and 0.04 part by mass of 1-dodecylmercaptan were added while stirring 100 parts by mass of the chloroprene latex D. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 100%, the polymerization was terminated. Thus, a graft copolymer rubber latex g was obtained.

< example 8 >

(production of chloroprene latex E)

Chloroprene latex E (thiol-modified) was obtained in the same manner as in example 1 except that the amount of sodium dodecylbenzenesulfonate (nepelex G-65 (purity: 65 mass%)) used in example 1 was changed from 4.0 parts by mass to 6.0 parts by mass.

(production of graft copolymer rubber latex h)

While stirring 100 parts by mass of the chloroprene latex E, 4 parts by mass of methacrylic acid and 0.04 part by mass of 1-dodecylmercaptan were added to the chloroprene latex E. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 100%, the polymerization was terminated. Thus, a graft copolymer rubber latex h was obtained.

< example 9 >

(production of chloroprene latex F)

Chloroprene latex F was obtained in the same manner as in example 1 except that 4.0 parts by mass of sodium dodecylbenzenesulfonate (NEOPELEX G-65 (purity: 65% by mass)) in example 2 was changed to 4.0 parts by mass of polyvinyl alcohol (B-05, manufactured by Denka).

(production of graft copolymer rubber latex i)

While stirring 100 parts by mass of the chloroprene latex F, 4 parts by mass of methacrylic acid and 0.04 part by mass of 1-dodecylmercaptan were added to the chloroprene latex F. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 100%, the polymerization was terminated. Thus, a graft copolymer rubber latex i was obtained.

< example 10 >

(production of chloroprene latex G)

A chloroprene latex G (thiol-modified) was obtained in the same manner as in example 2 except that the polymerization initiation temperature in example 2 was changed to 40 ℃.

(production of graft copolymer rubber latex j)

While stirring 100 parts by mass of the chloroprene latex G, 4 parts by mass of methacrylic acid and 0.04 part by mass of 1-dodecylmercaptan were added to the chloroprene latex G. The polymerization was started at 40 ℃ under a nitrogen atmosphere using potassium persulfate as a polymerization initiator. When the polymerization rate reached 100%, the polymerization was terminated. Thus, a graft copolymer rubber latex j was obtained.

< comparative example 1 >

A graft copolymer rubber latex k was obtained in the same manner as in example 1 except that the amount of methacrylic acid used in example 1 was changed to 0.3 part by mass and the amount of n-dodecylmercaptan used was changed to 0.003 part by mass.

< comparative example 2 >

A graft copolymer rubber latex l was obtained in the same manner as in example 1 except that the amount of methacrylic acid used in example 1 was changed to 12 parts by mass and the amount of n-dodecylmercaptan used was changed to 0.12 part by mass.

< comparative example 3 >

A rubber latex m was used, which was obtained by mixing water with a carboxyl-modified chloroprene latex (manufactured by Denka Co., Ltd.: LC-501) to adjust the solid content concentration to 20 mass%.

< comparative example 4 >

Chloroprene latex a was produced in the same manner as in example 1. To 100 parts by mass of the obtained chloroprene latex A, 4.0 parts by mass of polymethacrylic acid (PMA, manufactured by FUJIFILM Wako Pure Chemical Corporation) was added, followed by stirring at 25 ℃ until the polymethacrylic acid was dissolved. Thereby, a rubber latex n was obtained.

< evaluation of rubber latex >

(molar ratio of chlorine atom/oxygen atom in Polymer)

The above rubber latex was frozen at-60 ℃ for 24 hours and then freeze-dried, thereby obtaining a dried product. 1.00g of the dried product was cut into 2mm square cubes (length: 2 mm. times. width: 2 mm. times. height: 2mm) to obtain chips. The small pieces were dipped (dispersed) in 100mL of acetone at 23 ℃ to give an acetone solution, which was then stirred for 1 hour using a magnetic stirrer (manufactured by AS ONE Corporation, CHPS-170DS, size: 175 mm. times.178 mm).

Insoluble matter (polymer) in the acetone solution was recovered by filtration, and then dried by allowing the insoluble matter to stand in a vacuum dryer for 24 hours. The content of chlorine atoms and oxygen atoms in the polymer was measured by using a scanning electron microscope (SU 6600, manufactured by Hitachi High-Technologies Corporation) equipped with an energy dispersive X-ray analyzer (manufactured by Oxford Instruments, INCAX-act). Based on the measurement results, the molar ratio of chlorine atom/oxygen atom in the polymer was calculated. The results are shown in tables 1 and 2.

< acetone soluble component >

The above rubber latex was frozen at-60 ℃ for 24 hours and then freeze-dried, thereby obtaining a dried product. 1.00g of the dried product was cut into 2mm square cubes (length: 2 mm. times. width: 2 mm. times. height: 2mm) to obtain chips. The small pieces were dipped (dispersed) in 100mL of acetone at 23 ℃ to give an acetone solution, which was then stirred for 1 hour using a magnetic stirrer (manufactured by AS ONE Corporation, CHPS-170DS, size: 175 mm. times.178 mm).

Insoluble matter (polymer) in the acetone solution was removed by filtration. The acetone solution was concentrated and dried using an evaporator, and then the mass (a) of the residue was measured (accurately weighed). The acetone-soluble component was calculated by dividing the mass (a) of the residue by the mass of the dried product, as shown in the following formula. The results are shown in tables 1 and 2.

Acetone-soluble component [% by mass ] - [ mass of residue (a) [ g ]/mass of dried product (1.00[ g ]) × 100

< surfactant dose >

The rubber latex was diluted to 200 times with pure water, and then centrifuged, and 25. mu.L of the obtained supernatant was quantitatively analyzed by liquid chromatography. The surfactant amount in the rubber latex was calculated from the measured value using a standard curve. The results are shown in tables 1 and 2.

< polymerization Rate >

The polymerization rate of the copolymer in the rubber latex is calculated by the following formula. The amount of the monomer is 100 parts by mass, and the evaporation residue represents a nonvolatile matter from which the copolymer contained in the rubber latex has been removed.

The polymerization rate [% ] of the copolymer is (amount of monomer [ mass ] × (solid content concentration [ mass%) ] -evaporation residue [ mass ])/amount of monomer [ mass ] × 100

< preparation of aqueous adhesive composition >

An aqueous adhesive composition was obtained by mixing 50 parts by mass of TAMANOL E-100 (53% by mass emulsion of terpene-phenolic resin, manufactured by Mitsuka chemical industries, Ltd.) as a tackifier resin, 0.5 part by mass of RM-8W (17.5% by mass solid content, manufactured by Rohm and Haas Company, Ltd.) as a thickener, and 2 parts by mass of TAKENATE WD-730 (water-dispersible polyisocyanate, manufactured by Mitsui chemical Co., Ltd.) as an isocyanate with respect to 100 parts by mass (in terms of solid content) of the rubber latex of examples 1 to 10 and comparative examples 1 to 4. The adhesive strength was evaluated by the following method using the aqueous adhesive composition.

< adhesion Strength >

(evaluation test of initial adhesion Strength)

200g (wet)/m (wet) of a vinyl chloride artificial leather (manufactured by Yamato chemical industries, Ltd., trade name: 30 ester gray stain (Japanese: 30 エステル gray stain), type: Y321-715A, size of glue coated portion: 20mm wide × 70mm long) was coated with a brush on 2 sheets of the artificial leather²The aqueous adhesive composition of (3). After drying at 90 ℃ for 10 minutes in an atmosphere, the coated surfaces were bonded to each other and pressure-bonded with a hand roller. After the pressure bonding, the sheet was left to stand at 23 ℃ under an atmosphere of 50% RH for 10 minutes, and the 180 DEG peel strength was measured at a tensile rate of 200mm/min using a tensile tester. The results are shown in tables 1 and 2. When the vinyl chloride artificial leather as an adherend was broken, it was indicated as "material breakage" in the table.

(evaluation test of Normal adhesion Strength)

2 vinyl chloride artificial leathers (manufactured by Yamato chemical industries, Ltd., trade name: 30 ester gray stain, type: Y321-715A, size of coated portion 20mm wide by 70mm long) were coated with 200g (wet)/m by brush, respectively²The aqueous adhesive composition of (3). After drying at 90 ℃ for 10 minutes in an atmosphere, the coated surfaces were bonded to each other and pressure-bonded with a hand roller. After the pressure bonding, the sheet was left to stand at 23 ℃ under an atmosphere of 50% RH for 5 days, and the 180 DEG peel strength was measured at a tensile rate of 200mm/min using a tensile tester. The results are shown in tables 1 and 2. When the vinyl chloride artificial leather as an adherend was broken, it was indicated as "material breakage" in the table.

[ Table 1]

[ Table 2]

Although not shown in the table, the aqueous adhesive composition of the above examples can be applied to the adhesion of a high-polar material such as vinyl chloride artificial leather to a diene rubber sheet such as a natural rubber sheet, and the adhesion of natural rubber sheets to each other (except for the kind of adherend, the adherend is destroyed (the result of the "material breakage" described above) when the same evaluation test as the evaluation test of the initial adhesion strength and the normal adhesion strength described above is performed).