JP2011021071A - Water-based adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based adhesive which is free from an odor and an injurious property, when used, maintains an excellent ordinary adhesive strength, and is excellent in roll coater suitability. <P>SOLUTION: This water-based adhesive not containing a volatile organic compound is characterized by comprising an aqueous solution of a polyurethane resin having at least one silanol group in the molecule. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is an aqueous adhesive that can be applied when bonding substrates made of various materials such as plastic, natural leather, artificial leather, synthetic leather, rubber, foam, textiles, paper, glass, metal, and wood. It relates to the agent.

  Conventionally, as an adhesive for bonding a table tennis rubber sheet and a sponge, a synthetic rubber such as natural rubber or chloroprene rubber is used as an aromatic hydrocarbon solvent such as toluene, or a volatile organic compound such as a ketone solvent such as acetone. Dissolved adhesives (hereinafter sometimes referred to as VOCs) have been used.

  However, because VOCs are harmful to the human body, the International Table Tennis Federation (hereinafter abbreviated as ITTF) has stated in the Olympic Charter 21 “Products that pollute the environment that are considered harmful or toxic to humanity are not allowed”. In view of this, the Board of Directors has decided to prohibit the use of adhesives that are harmful to the human body after September 1, 2008.

  However, the VOC contained in the adhesive that bonds the sponge and the sheet used by the racket manufacturer when manufacturing the rubber may react to the racket inspection machine.

  At present, when using a new rubber, it is thought that VOCs that may remain on the rubber can be removed by removing the rubber from the packaging material, exposing it to air for 72 hours, and then adhering it to the racket. Yes. However, there is actually a problem with the preparation of players before the match, and not all players are able to do this, and this is not a fundamental solution.

  Under these circumstances, non-organic solvent-based adhesives that are free from odors and harmfulness during use, maintain excellent normal adhesive strength, and have excellent roll coater suitability are desired.

As an adhesive that can be used for the above-mentioned applications,
(A) having a stable normal adhesive strength;
(B) Suitability for roll coater,
(C) No odor,
The characteristics are required.

  The adhesive is required to be suitable for a roll coater. In general, a roll coater is used for a sticking operation, and a long pot life is required. In addition, since a two-component adhesive is assumed to cause poor adhesion due to poor mixing, mismeasurement, or the like, a one-component adhesive is required.

  Also, from the viewpoint of improving the working environment, the adhesive has been required to reduce odors.

JP 2007-2848573 A

ITTF Handbook 2008/2009, 2.04.07

  The problem to be solved by the present invention is to provide an aqueous adhesive which has no odor and no harmfulness at the time of use, maintains an excellent normal adhesive strength, and is excellent in roll coater suitability.

The present invention for solving the above problems is as follows.
(1) A water-based adhesive comprising a polyurethane resin having at least one silanol group in a molecule and a styrene-butadiene copolymer latex.
(2) The aqueous adhesive according to claim 1, wherein the polyurethane resin is a reaction product of a polyisocyanate component, a polyol component and a hydrolyzable silicon group-containing compound. The polyisocyanate component is an alicyclic diisocyanate. The water-based adhesive according to claim 2, wherein the polyol component is a polyether-based polyol or a polyester-based polyol.
(4) The aqueous adhesive according to any one of claims 1 to 3, further comprising a strongly basic tertiary amine.
(5) The aqueous adhesive according to any one of claims 1 to 4, wherein the styrene-butadiene copolymer latex has a gel fraction of 30 to 100%.

  The water-based adhesive of the present invention has no odor or harmfulness at the time of use, maintains excellent normal adhesive strength, and is excellent in roll coater suitability. It is extremely useful and can be used for bonding plastics such as vinyl chloride (PVC), natural leather, synthetic leather, artificial leather, rubber, foam, textiles, paper, metal, and glass.

  The best mode for carrying out the invention will be described in detail below.

  The aqueous adhesive of the present invention contains a polyurethane resin containing at least one silanol group in the molecule (hereinafter also referred to as a silanol group-containing polyurethane resin) as an essential component. As this urethane resin, a resin in which a silanol group-containing polyurethane resin is dissolved in an aqueous phase, or a colloidal dispersion system (dispersion) in which fine particles are dispersed is used.

  The silanol group in the silanol group-containing polyurethane resin is a hydrolyzable silicon in a compound containing an active hydrogen group capable of reacting with at least one isocyanate group and a hydrolyzable silicon group in one molecule used in the reaction. The group is produced by hydrolysis in the aqueous phase. Silanol groups are introduced into the silanol group-containing polyurethane resin by urethane bonds, which bonds have a compound having at least two active hydrogen groups per molecule (preferably a polyol component) and at least two isocyanates per molecule. A group-containing compound (isocyanate component) and a compound (hydrolyzable silicon group-containing compound) containing an active hydrogen group capable of reacting with at least one isocyanate group and a hydrolyzable silicon group in one molecule Is formed. More preferably, it is obtained by the method described in paragraphs [0031] to [0064] of JP-A-9-12864.

  The presence (bonding) site of the silanol group contained in the silanol group-containing polyurethane resin is not particularly limited, and is present (bonded) at both ends, any one end, or any intermediate portion of the polyurethane resin. Also good. In addition, a silanol group-containing polyurethane resin into which a hydrophilic group is introduced is preferable, and examples of the hydrophilic group include a carboxyl group, a sulfonic acid group, a sulfonate group, an epoxy group, and a polyoxyethylene group. However, among them, a carboxyl group and a sulfonic acid group are preferably introduced from the viewpoint of the stability of the resin in the aqueous phase.

  The molecular weight of the silanol group-containing polyurethane resin is not particularly limited, but is preferably 3000 or more. Further, the content of the silanol group-containing polyurethane resin in the aqueous polyurethane composition is preferably 60% by mass or less, more preferably about 10 to 50% by mass in order to maintain storage stability without increasing the viscosity. .

  Examples of the compound having at least two active hydrogen groups per molecule include compounds having an amino group, a hydroxyl group, a mercapto group, and the like as the group having an active hydrogen group, and the reaction rate with an isocyanate group, and A compound having a hydroxyl group, particularly a polyol is preferred from the viewpoint of mechanical properties of the resulting film. The molecular weight of the compound having a hydroxyl group is preferably from 200 to 10,000, particularly preferably from 300 to 5,000, from the viewpoint of film performance and workability during production.

  Examples of the compound having a hydroxyl group include polyester polyol, polyether polyol, polyether ester polyol, polyester amide polyol, acrylic polyol, polycarbonate polyol, polyhydroxyalkane, castor oil, polyurethane polyol, and mixtures thereof. Among the polyols, polyether polyols and polyester polyols are preferable.

  Examples of the polyester polyol include dibasic acids such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, and sebacic acid, or mixtures thereof, ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, and neopentyl glycol. , 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3′-dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol and other glycols or their Examples thereof include polyester polyols obtained by reacting with a mixture.

  As the polyether polyol, for example, a low molecular weight polyol such as water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin or the like is used as an initiator to polymerize an oxirane compound such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran or the like. The polyether polyol obtained by making it to be mentioned.

  Examples of the polyether ester polyol include polyether ester polyols obtained by reacting the dibasic acids or their dialkyl esters or mixtures thereof with the polyether polyol. The polyesteramide polyol is obtained by reacting in addition to the raw material of the polyesterification reaction product using, as a raw material, an aliphatic diamine having an amino group such as ethylenediamine, propylenediamine, hexamethylenediamine, or the like in the polyesterification reaction. And the like.

  Examples of the acrylic polyol include polymerizable monomers having one or more hydroxyl groups in one molecule, such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and the like. Examples thereof include those obtained by copolymerizing (meth) acrylic acid or its ester.

  Examples of the polycarbonate polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 3-methyl-1,5-pentane. Diol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol-A and hydrogenated bisphenol-A And the like obtained by reacting one or more glycols selected from the group consisting of dimethyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene and the like.

  Examples of the polyhydroxyalkane include isoprene, butadiene, or liquid rubber obtained by copolymerizing butadiene and acrylamide.

  Examples of the polyurethane polyol include a polyol having a urethane bond in one molecule, and the polyol includes, for example, a polyether polyol, a polyester polyol, a polyether ester polyol, and the like, and at least two isocyanate groups per molecule described later. Examples thereof include those obtained by reacting an isocyanate group-containing compound having an NCO group / OH group with a molar number of less than 1.

  In addition to the compound having a hydroxyl group, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, Glycols such as 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol; low molecular weight polyols such as glycerin, trimethylolpropane, pentaerythritol; Monools such as methanol, ethanol, propanols, butanols, 2-ethylhexanol, lauryl alcohol, stearyl alcohol, etc. may be mixed.

  The compound having at least two isocyanate groups per molecule may be any of aliphatic, alicyclic, aromatic and araliphatic. Alternatively, a mixture thereof may be used. Examples of the aliphatic diisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, and 1,3-butylene diisocyanate. 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methylcaproate and the like or a mixture thereof; examples of the alicyclic diisocyanate include 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (Isophorone diisocyanate), 4,4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane or 1,3- Bis (isocyanatemethyl) cyclohexane or a mixture thereof (hydrogenated xylylene diisocyanate) or a mixture thereof; examples of aromatic diisocyanates include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5 Naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, 4,4'-toluic Diisocyanate, dianisidine diisocyanate, 4,4′-diphenyl ether diisocyanate, etc., or mixtures thereof; examples of araliphatic diisocyanates include 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω, ω′-diisocyanate -1,4-diethylbenzene, 1,3- or 1,4-bis (1-isocyanate-1-methylethyl) benzene or a mixture thereof; as the triisocyanate, for example, triphenylmethane-4,4 ′, 4 ″ -Triisocyanate, 1,3,5-triisocyanate benzene, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate hexane, etc .; As polyisocyanate monomer, for example, 4,4'-diphenyl Dimethylmethane-2,2 5,5'-tetra-isocyanates; the polyisocyanate dimers derived from monomers, trimers, and the like. Among the isocyanate components, alicyclic diisocyanates are preferable, and hydrogenated xylylene diisocyanate is most preferable.

  A compound containing an active hydrogen group capable of reacting with at least one isocyanate group and a hydrolyzable silicon group in one molecule is hydrolyzed with at least one active hydrogen group capable of reacting with an isocyanate group in one molecule. The hydrolyzable silicon group in the hydrolyzable silicon group-containing compound is a hydrolyzable group that is hydrolyzed by moisture in the presence or absence of a silanol condensation catalyst. A group bonded to a silicon atom. Examples of the hydrolyzable group include a hydrogen atom, a halogen atom, an alkoxy group, an acyloxy group, a ketoximate group, an amino group, an amide group, an aminooxy group, a mercapto group, and an alkenyl. An oxy group etc. are mentioned. Among these, an alkoxy group is preferable because hydrolyzability is relatively small and handling is easy. The hydrolyzable group is usually bonded to one silicon atom in the range of 1 to 3, in terms of reactivity of the hydrolyzable silyl group after coating, water resistance, solvent resistance and the like. What couple | bonded 2-3 pieces is preferable.

  Examples of the active hydrogen group capable of reacting with an isocyanate group include a mercapto group, a hydroxyl group, and an amino group. Examples of hydrolyzable silicon group-containing compounds having a mercapto group as an active hydrogen group and an alkoxy group as a hydrolyzable group include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-mercapto. Examples of hydrolyzable silicon group-containing compounds having an amino group as an active hydrogen group and an alkoxy group as a hydrolyzable group include propyltriethoxysilane and γ-mercaptopropylmethyldiethoxysilane. -(2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyldimethoxysilane, γ- (2-aminoethyl) aminopropyl Diethoxysilane, γ-aminopropylto Silane, .gamma.-aminopropyltriethoxysilane, .gamma.-aminopropyl dimethoxysilane, .gamma.-aminopropyl diethoxy silane and the like, those having two or more active hydrogen groups are preferred.

  The ratio of the polyisocyanate compound to the active hydrogen group-containing compound is preferably such that the ratio of the isocyanate group in the polyisocyanate group-containing compound to the active hydrogen group in the active hydrogen group-containing compound exceeds 1.0. The amount of the hydrolyzable silicon group-containing compound used is such that, for example, an active hydrogen group-containing compound and a polyisocyanate group-containing compound are reacted to terminate the isocyanate group in order to develop sufficient curability in the aqueous paste composition. In the case where a polyurethane prepolymer having a hydrolyzable silicon group-containing compound is then reacted, the ratio of active hydrogen groups in the hydrolyzable silicon group-containing compound to the isocyanate group in the polyurethane prepolymer is 0.05. An amount of ~ 1.0 is preferred.

  Examples of the hydrophilic group-containing compound include at least one active hydrogen group in the molecule and a hydrophilic group such as a carboxyl group, a sulfonic acid group, a sulfonate group, an epoxy group, or a polyoxyalkylene group. Compounds. There is no particular limitation on the timing of reacting the hydrophilic group-containing compound.

  Examples of the hydrophilic group-containing compound include 2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisophthalic acid, sulfanilic acid, 1,3-phenylenediamine-4,6-disulfonic acid, Sulfonic acid-containing compounds such as 2,4-diaminotoluene-5-sulfonic acid or derivatives thereof, or polyester polyols obtained by copolymerization thereof; 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, Carboxyl group-containing compounds such as 2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid, 3,4-diaminobenzoic acid or derivatives thereof, maleic anhydride, phthalic anhydride, succinic anhydride , Trimellitic anhydride, pyromellitic anhydride and other acid anhydrides and active hydrogen groups A carboxyl group-containing compound or a derivative thereof obtained by reacting with a compound, or a polyester polyol obtained by copolymerizing these compounds; containing a repeating unit of ethylene oxide, and containing at least one active hydrogen group in the polymer Nonionic group-containing compounds such as polyoxyalkylene compounds to be contained, or polyester ether polyols obtained by copolymerizing these compounds.

  When copolymerization is performed using a compound containing an anionic hydrophilic group such as a carboxyl group or a sulfonic acid group, a neutralizing agent is used to dissolve or disperse the generated polyurethane resin well. .

  Examples of the neutralizing agent include tertiary amines such as ammonia, triethylamine, triethanolamine, triisopropanolamine, trimethylamine, and dimethylethanolamine, alkali metals such as sodium hydroxide, potassium hydroxide, and calcium hydroxide, or Examples thereof include hydroxides of alkaline earth metals. These are used alone or in a mixture of two or more. The addition time of a neutralizing agent is not specifically limited, The addition amount is preferable 0.1-2.0 equivalent with respect to a hydrophilic group.

  In the production of the aqueous polyurethane composition, the reaction sequence of these compounds and the addition timing of the strongly basic tertiary amine as a curing catalyst are not particularly limited, but examples thereof include the following production methods. It is done.

  A polyurethane prepolymer is produced by reacting an active hydrogen group-containing compound, a polyisocyanate compound, and a compound having a hydrophilic group in the molecule and having at least one active hydrogen group. Next, the hydrophilic group in the polyurethane prepolymer was neutralized with a neutralizing agent, a strong base tertiary amine was added as a curing catalyst, and this neutralizing agent and a strong basic tertiary amine were added. An aqueous composition of the polyurethane resin can be produced by dissolving or dispersing the polyurethane prepolymer in water in which the hydrolyzable silicon group-containing compound and other chain extenders are dissolved.

  It is also possible to increase the molecular weight by reacting with another chain extender. As the chain extender, for example, a known polyamine compound is used. Examples of the polyamine compound include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'- Diamines such as dimethyl-4,4′-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, polyamines such as diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepentamine, hydroxyethylhydrazine, hydroxyethyldiethylenetriamine, 2 -[(2-aminoethyl) amino] ethanol, compounds having an amino group and a hydroxyl group such as 3-aminopropanediol, hydrazines, acid hydrazides and the like. The said polyamine compound is used individually or in mixture of 2 or more types.

  The strongly basic tertiary amine contained in the aqueous adhesive of the present invention acts as a catalyst for forming a siloxane bond when a silanol group-containing polyurethane resin is formed into a film, so that crosslinking is efficiently promoted even at a temperature of about room temperature. And an aqueous adhesive excellent in water resistance and solvent resistance can be obtained.

  The strongly basic tertiary amine is not particularly limited, but preferably has a pKa of 11 or more from the viewpoint of promoting crosslinking in a room temperature region. Examples of these strongly basic tertiary amines include 1,8-diazabicyclo [5.4.0] undecene-7 (DBU), 1,6-diazabicyclo [3.4.0] nonene-5, and the like. .

  0.001-10 parts are preferable with respect to 100 mass parts (henceforth a part) of silanol group containing polyurethane resin (solid content), and, as for content of the said strong basic tertiary amine, 0.001-7 parts Is more preferable, and 0.001 to 5 parts is more preferable. When a strongly basic tertiary amine is contained in such an amount, the curing rate is good, and the solvent resistance and water resistance of the formed coating film tend to be good.

  Examples of self-emulsifying urethane resins thus obtained, that is, water-based urethane resins (compositions) containing a silanol group-containing polyurethane resin, include, for example, an anionic type containing a silanol group in the side chain. “Takelac WS Series” (manufactured by Takeda Pharmaceutical Co., Ltd.).

  Moreover, in this invention, you may use various dispersion stabilizers in the range which does not inhibit the effect of this invention. Examples of the dispersion stabilizer include polyvinyl alcohol, fiber ether, starch, maleated polybutadiene, maleated alkyd resin, water-soluble polyester resin, water-soluble polyamide resin, water-soluble polyurethane resin, water-soluble acrylic resin, and the like. It can be used alone or in combination of two or more. These may be added and used during the production of the silanol group-containing polyurethane resin, or may be mixed after completion of the reaction.

  In the aqueous adhesive of the present invention, in addition to the above silanol group-containing polyurethane resin, the adhesiveness and feel at impact can be further improved by using a styrene-butadiene copolymer latex in combination.

  As is well known, the styrene-butadiene copolymer latex is a latex made of a copolymer of an aromatic vinyl monomer and a conjugated diene monomer. Various conventionally known styrene-butadiene copolymer latexes are appropriately used.

  As such styrene-butadiene copolymer latex, typically, 10 to 70% by weight of an aromatic vinyl monomer, 10 to 70% by weight of a conjugated diene monomer, 0.5% Examples thereof include those obtained by emulsion polymerization of 10 to 10% by weight of ethylenically unsaturated carboxylic acid monomers and 0 to 50% by weight of other vinyl monomers copolymerizable therewith. Furthermore, it is possible to use a latex containing a partially crosslinked polymer. Further, among such styrene-butadiene copolymer latexes, those having a gel fraction of about 30 to 100% can be suitably employed. Of course, such styrene-butadiene copolymer latexes can be used. It goes without saying that the present invention is not limited to these.

  In addition, examples of the aromatic vinyl monomer used for the production of the above styrene-butadiene copolymer latex include styrene and vinyl toluene, while examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2-ethyl-1,3-butadiene, chloroprene, and the like. Examples of the ethylenically unsaturated carboxylic acid monomer include itaconic acid, fumaric acid, maleic acid, acrylic acid, methacrylic acid, and other vinyl monomers that can be copolymerized. Exemplify vinyl cyanides such as acrylonitrile and methacrylonitrile; (meth) acrylic acid esters such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, etc. I can do it.

  The styrene-butadiene copolymer latex preferably has a gel fraction of 30 to 100%, more preferably 40 to 90%. The gel fraction is the gel fraction of the styrene-butadiene copolymer latex, the weight ratio of the cured film of the sufficiently dried styrene-butadiene copolymer latex to the insoluble content of the cured film immersed in acetone for 8 hours. .

  The blending ratio of the silanol group-containing polyurethane resin and the styrene-butadiene copolymer latex is 100% by weight of the water-based adhesive, and the silanol group-containing polyurethane resin: styrene-butadiene copolymer latex = 95: 5 to 5: 95% by weight, Preferably, it may be appropriately selected within the range of 80:20 to 20: 80% by weight, more preferably 60:40 to 40: 60% by weight.

  In the aqueous adhesive of the present invention, it is preferable to adjust the viscosity according to various coating methods when applying to the sponge, and it is preferable to use a thickener as the viscosity adjusting method.

  As a thickener, cellulose derivatives such as HEC (hydroxyethylcellulose), MC (methylcellulose), CMC (carboxymethylcellulose), polyacrylate, polyacrylate, PVP (polyvinylpyrrolidone), urethane-based, polyether-based Associative thickeners and the like.

  These thickeners may be used alone or in combination of two or more.

  The thickener may be used in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the aqueous adhesive.

  In addition, acrylic emulsion, vinyl acetate emulsion, etc. can be added within a range that does not affect the adhesion.

  The aqueous adhesive of the present invention may have a non-volatile content of 10 to 70%, preferably 30 to 50%, and a viscosity of 20 to 50000 mPa · s, preferably 100 to 10000 mPa · s.

  As a method of laminating a sheet and a sponge in the aqueous adhesive of the present invention, 3 to 5 grams of the aqueous adhesive of the present invention was applied to a sponge of about 30 cm square with a roll coater, and the sheet was adhered immediately after that. It shall be dried under reduced pressure for 12 to 72 hours between plates. The table tennis rubber is a single rubber sheet only, a soft rubber back with a tab and a sponge, and a flat surface and a sponge so that the tab has a ball striking surface. Although there are three types of soft rubber, the water-based adhesive of the present invention can be used for the production of a back soft rubber and a front soft rubber. In order to produce the back soft rubber, the aqueous adhesive of the present invention may be applied to the sponge and bonded to the surface with the tab of the sheet. To produce the front soft rubber, the aqueous adhesive of the present invention is applied to the sponge. Apply and stick to the flat surface of the sheet.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Production Example 1
Production method of acrylic emulsion In a container, 50 parts by weight of ion exchange water, 5 parts by weight of sodium dodecyl sulfate, 1.5 parts by weight of acrylic acid, 52 parts by weight of 2-ethylhexyl acrylate, 46.5 parts by weight of methyl methacrylate, 10% excess A monomer emulsion was prepared by weighing and stirring 2.0 parts by weight of an aqueous ammonium sulfate solution. A four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube and a thermometer was charged with 50 parts by weight of ion-exchanged water, and the internal temperature was raised to 75 ° C. while stirring. And 0.5 part by weight of 10% aqueous ammonium persulfate solution. The remaining monomer emulsion was dropped at the same temperature, and a polymerization reaction was performed for 3 hours. The polymerization reaction was carried out after 1 hour while maintaining the internal temperature. After completion of the post-polymerization reaction, the mixture was cooled to room temperature and neutralized by adding 3 parts by weight of 25% aqueous ammonia solution to obtain an acrylic emulsion (A) having a viscosity of 200 mPa · s and a nonvolatile content of 50.7%.

  Silanol group-containing polyurethane resin dispersion containing 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) (trade name “Takelac WS-5100”, manufactured by Mitsui Takeda Chemical Co .; isophorone diisocyanate / polycarbonate system; 60 parts of solid content (solid content 30%), 40 parts of styrene-butadiene copolymer latex (trade name “A7269”, manufactured by Asahi Kasei Chemicals Corporation; gel fraction 50%), thickener (polyacrylate emulsion, trade name “ Primal ASE60 ", manufactured by Rohm & Haas Co.) was added and stirred for 30 minutes to adjust the aqueous adhesive.

  Example 1 except that a silanol group-containing polyurethane resin dispersion containing DBU (trade name “Takelac WS-5320”, manufactured by Mitsui Takeda Chemical Co .; isophorone diisocyanate / polyether system; solid content 30%) was used. A water-based adhesive was prepared by the method of

  Except for using a DBU-containing silanol group-containing polyurethane resin dispersion (trade name “Takelac WS-6021”, manufactured by Mitsui Takeda Chemicals; hydrogenated xylylene diisocyanate / polyether system; solid content 30%). A water-based adhesive was prepared in the same manner as in 1.

  Example 1 except that a silanol group-containing polyurethane resin dispersion (trade name “Takelac WS-4000”, manufactured by Mitsui Takeda Chemicals; hydrogenated xylylene diisocyanate / polycarbonate system; solid content 30%) containing DBU was used. A water-based adhesive was prepared in the same manner as described above.

  Example 1 except that DBU-containing silanol group-containing polyurethane resin dispersion (trade name “Takelac WS-5000”, manufactured by Mitsui Takeda Chemical Co .; isophorone diisocyanate / polyester system; solid content 30%) was used. A water-based adhesive was prepared in the same manner.

Comparative Example 1
0.5 parts by weight of Primal ASE60 was added to 100 parts by weight of the acrylic emulsion (A) prepared in Production Example 2 and stirred for 30 minutes to prepare an acrylic emulsion adhesive (A-1).

Comparative Example 2
100 parts by weight of chloroprene latex (trade name “Skyprene Latex SL-360”, manufactured by Tosoh Corporation, nonvolatile content of about 52%) and urethane associative thickener (polyurethane resin, trade name Adecanol UH-420, ADEKA) 0.5 parts by weight was added and stirred for 30 minutes to prepare a chloroprene latex adhesive (B-1).

Comparative Example 3
A chloroprene rubber solvent type adhesive was prepared by blending chloroprene rubber with 72% toluene and 8.9% methyl ethyl ketone.

  The aqueous adhesives of Examples 1 to 3 and the adhesives of Comparative Examples 1 to 3 were applied to the surface of the sponge with a roll coater, and the sheet and the sponge were bonded together. The sponge and the sheet are based on natural rubber obtained by vulcanizing sulfur, and the sponge and the sheet used in the table tennis rubber “Blythe” of Tamas Co., Ltd. were used.

  Thereafter, it was further dried for 12 hours in an environment of slightly reduced pressure at 30 ° C. to prepare a table tennis rubber test body. Each evaluation was measured as follows.

<Normal bond strength>
Evaluation ◎ ・ ・ ・ If you try to peel, the sheet or sponge will be destroyed.
○ ・ ・ ・ Partial destruction of the sheet or sponge when peeling is attempted.
X: Not bonded.

<Roll coater suitability>
The applicability when the adhesive was applied to the sponge with a roll coater was evaluated as workability.
Evaluation ○: Can be applied satisfactorily.
X: Cannot be applied.

<Odor>
Evaluation by evaluating the odor of the adhesive by olfaction ○ ・ ・ ・ There is almost no odor.
X: There is a strong odor.

  Table 1 shows the results of formulation and evaluation of the aqueous adhesives of Examples 1 to 5 and the evaluation results of Comparative Examples 1 to 3.

  As is apparent from the results shown in Table 1, the water-based adhesive of the present invention is substantially free of VOC, but the normal adhesive strength is a conventional chloroprene rubber solvent-based adhesive containing VOC. It was the same or more than the table tennis rubber manufactured in (Comparative Example 3). Moreover, the table tennis rubber manufactured with the acrylic emulsion adhesive (Comparative Example 1) is inferior to the normal adhesive strength, and the table tennis rubber manufactured with the chloroprene latex adhesive (Comparative Example 2) is the normal adhesive strength and roll coater. It was inferior to aptitude.

  The rubber prepared with the aqueous adhesives of the present invention of Examples 1 to 5 and the conventional chloroprene rubber solvent type adhesive of Comparative Example 3 was subjected to VOC using a racket inspection machine (trade name “ENEZ”, manufactured by WASSING). The presence or absence was judged. The results are shown in Table 2.

Racket inspection machine criteria
OK ... The racket inspection machine does not respond.
NG ... The racket inspection machine reacts.

  As is clear from the results shown in Table 2, the table tennis rubber prepared with the aqueous adhesive of the present invention did not react with the racket inspection machine and could be evaluated as substantially free of VOC.

  Since the water-based adhesive of the present invention does not substantially contain VOC, the VTF regulation of ITTF can be cleared, and the adhesiveness of an adhesive containing conventional VOC is not impaired.

Claims (5)

A water-based adhesive comprising a polyurethane resin having at least one silanol group in a molecule and a styrene-butadiene copolymer latex. The aqueous adhesive according to claim 1, wherein the polyurethane resin is a reaction product of a polyisocyanate component, a polyol component, and a hydrolyzable silicon group-containing compound. The aqueous adhesive according to claim 2, wherein the polyisocyanate component is an alicyclic diisocyanate, and the polyol component is a polyether polyol or a polyester polyol. Furthermore, the water-based adhesive in any one of Claims 1-3 containing a strongly basic tertiary amine. The aqueous adhesive according to any one of claims 1 to 4, wherein the styrene-butadiene copolymer latex has a gel fraction of 30 to 100%.