JP2012126867A - Synthetic resin emulsion, re-emulsifying emulsion powder, and adhesive composition for woodworking using the synthetic resin emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition for woodworking, which shows excellent adhesiveness and high material fracture ratio in conducting splitting strength evaluation, and to provide a synthetic resin emulsion useful for the adhesive composition.SOLUTION: The synthetic resin emulsion is made by dispersing for stabilization, a synthetic resin (A) in a polyvinyl alcohol resin (B) having 1,2-diol bond on a side chain. The glass transition temperature of the synthetic resin (A) is -20°C or lower. The adhesive composition for woodworking mainly comprises the synthetic resin emulsion.

Description

  The present invention relates to a synthetic resin emulsion, a re-emulsifiable emulsion powder, and an adhesive composition for woodworking. More specifically, the present invention relates to a synthetic resin emulsion capable of obtaining sufficient splitting strength when used as an adhesive composition for woodworking, It relates to an emulsifiable emulsion powder. The present invention also relates to an adhesive composition for woodworking, comprising at least one of the synthetic resin emulsion of the present invention, the re-emulsifiable emulsion powder of the present invention, and the synthetic resin emulsion obtained by re-emulsifying the powder.

  As an adhesive for woodworking or paper, an adhesive containing an aqueous emulsion that has no danger of ignition and is environmentally friendly and relatively safe is often used. Conventionally, polyvinyl alcohol has been used as a protective colloid agent to impart mechanical stability and freeze stability to an aqueous emulsion. However, although the mechanical stability and freezing stability of the emulsion are improved, the polymerization stability is insufficient particularly when polymerizing mainly with a hydrophobic monomer, or the stability of the resulting emulsion is insufficient. Often it was. In particular, the tendency was strong when the nonvolatile content of the emulsion was higher than 50% by weight.

  Therefore, even when the nonvolatile content of the emulsion is 50% by weight or more, a stable emulsion with a relatively small particle size can be obtained, and the film has excellent water resistance, warm water resistance, boiling resistance, toughness and long-term durability. Patent Document 1 discloses an aqueous synthetic resin emulsion for forming a resin. In the aqueous synthetic resin emulsion described in Patent Document 1, a synthetic resin composed of a polymerizable monomer containing a predetermined amount of a styrene monomer is dispersed and stabilized in a polyvinyl alcohol resin having a 1,2-diol bond in the side chain. An aqueous synthetic resin emulsion.

  On the other hand, there are shearing and splitting as the stress applied to the bonding surface. Unlike the shearing that is applied uniformly to the entire bonding surface, the splitting is applied to one or the end of the bonding surface, so it is a stress different from shear. It is. In the evaluation of adhesiveness using an adhesive for woodworking, for example, evaluation of wood panel adhesiveness, splitting strength evaluation is regarded as an important evaluation, and Patent Document 2 also performs adhesive evaluation by a splitting test.

  In addition, as one of the methods for evaluating the performance of the adhesive, there is a method of destroying the adhesion surface of the adherend bonded through the adhesive. There are three forms of breakage, interfacial breakage that peels off at the interface between the adherend and the adhesive, and cohesive breakage that breaks down the adhesive itself. Among these destruction situations, it can be said that the adhesive that causes material destruction has strong adhesiveness because not only the bonding of the adhesive itself but also the bonding between the adhesive and the adherend must be strong. Accordingly, in the evaluation of the splitting strength of the adhesive for woodworking, it is desirable that the ratio of the area where the wood is broken to the bonded area in the broken state (material breakage rate) is high.

  When the present inventors performed split strength evaluation on the adhesive for woodworking using the aqueous synthetic resin emulsion of Patent Document 1, although adhesiveness and material breakage rate equal to or higher than conventional adhesives for woodworking are obtained, The inventors of the present invention have intensively conducted research and development in order to develop an adhesive for woodworking that can provide better adhesiveness and a high material breakage rate.

JP 2009-40994 A JP 2006-282951 A

  The present invention has been made in view of the above circumstances, and its purpose is to provide a woodworking adhesive composition capable of expressing good adhesiveness and high material breakage rate in split strength evaluation, and its main component. And providing a synthetic resin emulsion.

  By using a polyvinyl alcohol resin having a 1,2-diol bond in the side chain as a dispersant, and using a synthetic resin having a glass transition temperature adjusted lower than that of a conventional synthetic resin. The present inventors have found that the above problems can be solved.

  That is, the present invention provides a synthetic resin emulsion in which the synthetic resin (A) is dispersed and stabilized with a polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain. The present invention relates to a synthetic resin emulsion having a glass transition temperature of −20 ° C. or lower. The present invention also includes a re-emulsifiable emulsion powder that is a dried product of this synthetic resin emulsion, a synthetic resin emulsion obtained by re-emulsifying this re-emulsifiable emulsion powder, and these synthetic resin emulsions and re-emulsifiable emulsion powders. The present invention relates to an adhesive composition for woodworking.

According to the synthetic resin emulsion of the present invention, when applied to an adhesive composition for woodworking, good adhesiveness and high material breakage rate can be expressed in split strength evaluation. In addition, the synthetic resin emulsion of the present invention or the synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder is water resistant, warm water resistant, boiling resistant, toughness and long-term when a film is formed. It has an effect excellent in durability.
Note that “for woodworking” in the present invention refers to application to not only a wood part or an adherend of wood itself, but also an adherend containing a wood part such as paper or wood, for example, woodwork, furniture, architecture. Represents application to interior, packaging, paper processing, decorative plywood, composite members, panels, etc.

Hereinafter, although the synthetic resin emulsion of this invention is demonstrated in detail, these show an example of a desirable embodiment.
The synthetic resin emulsion of the present invention is a synthetic resin emulsion in which the synthetic resin (A) is dispersed and stabilized with a polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain.

[Synthetic resin emulsion]
First, the synthetic resin (A) used in the present invention will be described.
If the synthetic resin (A) is a synthetic resin having a glass transition temperature of −20 ° C. or lower that can be dispersed and stabilized with a polyvinyl alcohol-based resin (B) having a 1,2-diol bond in the side chain described later and become an emulsion. Well, the production method is not particularly limited, but in particular, the polymerizable (copolymerization) monomer component constituting the synthetic resin (A) has a 1,2-diol bond in the side chain. It is preferably a synthetic resin produced by emulsion polymerization in the presence of the system resin (B).

The synthetic resin (A) in the present invention preferably contains a copolymer of a hydrophobic monomer and a hydrophilic monomer, a polymer of a hydrophobic monomer, or a copolymer of hydrophobic monomers.
Here, as the hydrophobic monomer, those usually handled by those skilled in the art as a hydrophobic monomer may be used. However, if the physical properties are defined, the solubility in water at 20 ° C. is 0.1% or less. Specific examples include polymerizable monomers such as (meth) acrylic monomers, styrene monomers, vinyl monomers, and the like, which can be used alone or in combination of two or more. In the present invention, a monomer that does not belong to the definition of the hydrophobic monomer is treated as a hydrophilic monomer.

  Examples of the (meth) acrylic monomer include n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, Alkyl groups such as lauryl (meth) acrylate, octyl (meth) acrylate and stearyl (meth) acrylate have 4 or more carbon atoms, preferably 6 to 18 (meth) acrylates, particularly aliphatic (meth) acrylates, phenoxy Aromatic (meth) acrylates such as acrylate, trifluoroethyl methacrylate, ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1 , 4- Aliphatic di (meth) acrylates such as tandiol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) An acrylate etc. are mentioned. These are used alone or in combination of two or more. “(Meth) acrylate” means acrylate or methacrylate.

  Examples of the styrene monomer include styrene and α-methylstyrene. These are used alone or in combination of two or more.

  Examples of such vinyl monomers include vinyl laurate, vinyl stearate, vinyl versatate, and divinylbenzene. These are used alone or in combination of two or more.

  Among these, (meth) acrylic monomers and styrene monomers are preferable, and styrene, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are particularly preferable.

In the present invention, a synthetic resin (A) can be obtained by polymerizing or copolymerizing a polymerization (copolymerization) component comprising the above monomer components. It is preferable to contain 30% by weight or more of a monomer, particularly preferably 40% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more.
The upper limit of the content ratio of the hydrophobic monomer is not particularly limited, but is usually 100% by weight or less, preferably 99.5% by weight or less, particularly preferably 99% by weight or less, and contains a small amount of a hydrophilic monomer. May be. If the content of the hydrophobic monomer is too small, the desired water resistance and weather resistance tend to be insufficient.

  Further, in the present invention, a synthetic resin (A) obtained by copolymerizing a copolymer component containing at least styrene as a hydrophobic monomer is preferable, and the content of styrene is the solubility in water at 20 ° C. in the copolymer component. Is not more than 70% by weight, preferably not more than 65% by weight, and more preferably not more than 60% by weight, based on the entire hydrophobic monomer having a ratio of 0.1% or less. The lower limit of the styrene content is preferably 1% by weight or more. When there is too much content of this styrene, there exists a tendency for superposition | polymerization stability to fall.

  The synthetic resin (A) of the present invention needs to have a glass transition temperature of −20 ° C. or less, preferably less than −20 ° C., and more preferably −22 ° C. or less. The lower limit of the glass transition temperature is usually −80 ° C. or higher, more preferably −75 ° C. or higher. When the glass transition temperature is too high, it tends to be difficult to express good adhesiveness and a high material breakage rate in the split strength evaluation.

  In addition, the glass transition temperature of a synthetic resin (A) calculates the glass transition temperature of the homopolymer which consists of each copolymerization component which comprises a synthetic resin (A), and each copolymerization component which comprises a synthetic resin (A) It can adjust by adjusting a weight ratio suitably.

  In the present invention, examples of the copolymerizable monomer copolymerized with the hydrophobic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate as (meth) acrylic monomers. A (meth) acrylate having an alkyl group of 3 or less, preferably 2 or less, particularly an aliphatic (meth) acrylate, can be used. Examples of vinyl monomers that can be used include vinyl acetate and vinyl propionate.

In the present invention, it is preferable to copolymerize a functional monomer together with a hydrophobic monomer at the time of emulsion polymerization from the viewpoint of warm water resistance and boiling resistance with respect to xylem and wood materials. The functional monomer is preferably at least one selected from the group consisting of the following (1) to (6).
(1) allyl group-containing monomer (2) glycidyl group-containing monomer (3) hydrolyzable silyl group-containing monomer (4) acetoacetyl group-containing monomer (5) carbonyl group-containing monomer (6) hydroxy group-containing monomer

  Specific examples of the allyl group-containing monomer (1) include, for example, monomers having two or more allyl groups such as triallyloxyethylene, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, allyl Examples thereof include glycidyl ether and allyl acetate. Among these, allyl glycidyl ether is preferable from the viewpoint of adhesiveness when wet.

  Specific examples of the glycidyl group-containing monomer (2) include glycidyl (meth) acrylate, glycidyl (meth) allyl ether, 3,4-epoxycyclohexyl (meth) acrylate, and the like. Among these, glycidyl (meth) acrylate is preferable from the viewpoint of improving the water resistance of the woodworking adhesive.

  Specific examples of the hydrolyzable silyl group-containing monomer (3) include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. , Γ-methacryloxypropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, etc. . Of these, vinyltrimethoxysilane is preferred from the viewpoint of wet adhesion.

  Specific examples of the acetoacetyl group-containing monomer (4) include, for example, vinyl acetoacetate, allyl acetoacetate, allyl acetoacetate, acetoacetoxyethyl (meth) acrylate, acetoacetoxyethyl crotonate, acetoacetoxypropyl (meta) ) Acrylate, acetoacetoxypropyl crotonate, 2-cyanoacetoacetoxyethyl (meth) acrylate and the like. Among these, acetoacetoxyethyl (meth) acrylate is preferable from the viewpoint of improving the water resistance of the adhesive for woodworking.

  Specific examples of the carbonyl group-containing monomer (5) include, for example, diacetone acrylamide.

  Specific examples of the hydroxy group-containing monomer (6) include aliphatic (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate. Among these, 2-hydroxyethyl methacrylate is preferable from the viewpoint of improving the water resistance of the adhesive for woodworking.

  According to a preferred embodiment of the present invention, the functional monomer comprises a glycidyl group-containing monomer (2), a hydrolyzable silyl group-containing monomer (3), an acetoacetyl group-containing monomer (4), and a hydroxy group-containing monomer (6). It is preferably selected from the group consisting of, in particular, comprising at least one of the glycidyl group-containing monomer (2) and the hydroxy group-containing monomer (6). This is particularly preferable from the viewpoint of improving the boiling property.

  The amount of the functional monomer used is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, particularly preferably 0.1 to 5% by weight, based on the entire copolymerizable monomer. More preferably, it is 0.1 to 1% by weight. If the amount used is too small, improvement in water resistance and wet adhesion tends to be insufficient, and if it is too large, polymerization tends to be poor. In addition, these functional monomers can be used in combination of 2 or more types.

  Further, in the present invention, the following copolymerizable monomers can be used in combination as copolymerizable monomers other than those described above, as long as the object of the present invention is not impaired. For example, olefinic monomers such as ethylene; halogenated olefinic monomers such as vinyl chloride; acrylamides such as (meth) acrylamide, N, N-dimethylacrylamide, t-butylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid Monomers; Nitrile monomers such as (meth) acrylonitrile; vinyl ether monomers such as methyl vinyl ether; ethylenically unsaturated carboxylic acids such as (meth) acrylic acid and (anhydrous) itaconic acid and ester monomers thereof can be used.

  The polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain in the present invention (hereinafter sometimes referred to as “PVA resin (B)”) is usually represented by the following formula (1). PVA-based resin containing a 1,2-diol structural unit.

  Such a PVA-based resin (B) includes, for example, (I) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, and (II) of vinyl acetate and vinyl ethylene carbonate. A method of saponifying and decarboxylating a copolymer, (III) a method of saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, (IV ) A method of saponifying a copolymer of vinyl acetate and glyceryl monoallyl ether, and the like.

  The amount of 1,2-diol bonded to the PVA resin (B) is preferably 1 to 15 mol%, more preferably 1 to 12 mol%, still more preferably 2 to 10 mol%, still more preferably 2 ~ 8 mol%. Here, the 1,2-diol bond amount is, for example, the above formula (1) included in the PVA resin (B) when the 1,2-diol structural unit is represented by the above formula (1). It means the molar ratio of the represented 1,2-diol bond structural unit. If the amount of 1,2-diol bond is too small, the mechanical stability of the emulsion and the water resistance of the film tend to be lowered, and if too large, the stability during polymerization is lowered, and a stable emulsion having a high nonvolatile content. Tends to be difficult to obtain.

  The non-volatile content means a residue remaining after heat-drying the emulsion, and the weight before and after normal heat-drying can be determined according to the calculation method described in JISK6828-1.

  Moreover, it is preferable that the average saponification degree of PVA-type resin (B) is 85 mol% or more, More preferably, it is 90 mol% or more, Most preferably, it is 95-99.8 mol%. If the degree of saponification is too small, the stability of the emulsion during polymerization tends to decrease, making it difficult to obtain the desired emulsion.

  In the present specification, the average saponification degree can be determined according to the saponification degree calculation method described in JISK6726.

  Furthermore, the average polymerization degree of the PVA resin (B) is preferably 50 to 3000, more preferably 100 to 2500, still more preferably 100 to 1500, and particularly preferably 200 to 500. If the degree of polymerization is too small, it tends to be difficult to industrially produce a PVA resin, and if it is too large, the viscosity of the emulsion tends to be too high, or the polymerization stability of the emulsion tends to decrease.

  In the present specification, the average degree of polymerization can be determined according to the method for calculating the average degree of polymerization described in JIS K6726.

  In the present invention, the amount of PVA resin (B) used as a protective colloid (dispersion stabilizer) in the process of emulsion polymerization when producing a synthetic resin emulsion is based on the total amount of polymerizable monomers used. It is preferably 3 to 20% by weight, more preferably 8 to 15% by weight. If the amount used is too small, the amount of protective colloid at the time of emulsion polymerization tends to be insufficient and the polymerization stability tends to be poor, and if too large, the water resistance tends to decrease as an adhesive for woodworking. .

  Here, the whole amount of the PVA resin (B) used is usually present in the synthetic resin emulsion formed by polymerization. That is, 3 to 20% by weight, more preferably 8 to 15% by weight of the PVA resin (B) is present in the emulsion with respect to the synthetic resin.

  In the present invention, as a protective colloid (dispersion stabilizer), in addition to the PVA resin (B), an unmodified type part, a completely saponified PVA resin, and various modified type parts as long as the object of the present invention is not impaired. -A completely saponified PVA resin may be used in combination.

  In the present invention, the PVA resin (B) is usually made into an aqueous solution using an aqueous medium, and this is used in the process of emulsion polymerization. Here, the aqueous medium refers to water or an alcoholic solvent mainly composed of water, preferably water. The amount of PVA resin (B) in this aqueous solution (in terms of non-volatile content) is not particularly limited, but is preferably 5 to 30% by weight from the viewpoint of ease of handling.

  In addition, PVA type | system | group means what modified | denatured by PVA itself or various modified species (modified species other than the modified species which has a 1, 2- diol bond in this invention), for example, the modification | denaturation degree is Usually, it is 20 mol% or less, preferably 15 mol% or less, more preferably 10 mol% or less. If the degree of modification becomes too high, it tends to thicken and gel during emulsion polymerization, and it tends to be difficult to obtain a stable emulsion.

  Examples of such modified species include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid and the like. Unsaturated acids or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or the like Salt, alkyl vinyl ethers, polyoxyethylene (meth) allyl ether, polyoxyalkylene (meth) allyl ether such as polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) acrylate, Polyoxyalkylene (meth) acrylates such as reoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamides such as polyoxypropylene (meth) acrylamide, polyoxyethylene [1- (meta ) Acrylamide-1,1-dimethylpropyl] ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, N-acrylamidomethyltrimethylammonium Chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylallyl vinyl ketone N- vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like. In addition to the above, modified species containing active hydrogen such as acetoacetyl group modification, mercapto group modification, diacetone acrylamide modification, and the like are also included.

  The synthetic resin emulsion of the present invention is obtained by dispersing and stabilizing a synthetic resin (A) with a polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain. For example, a PVA resin (B ) As a protective colloid and can be produced by emulsion polymerization of a hydrophobic monomer, preferably a functional monomer, and optionally a copolymerizable monomer containing a hydrophilic monomer.

  The synthetic resin emulsion of the present invention is produced by emulsion polymerization of the polymerizable (copolymerizable) monomer component constituting the synthetic resin (A) in the presence of the PVA resin (B). Preferably, in this case, in addition to the polymerizable (copolymerization) monomer component and the PVA resin (B), other components can be further used as necessary.

  Such other components are not particularly limited as long as the properties as a synthetic resin emulsion are not deteriorated, and can be appropriately selected according to the purpose. Examples of other components include a polymerization initiator, a polymerization regulator, an auxiliary emulsifier, a plasticizer, and a film forming aid.

  Any polymerization initiator can be used without particular limitation as long as it can be used for ordinary emulsion polymerization. For example, inorganic peroxides such as potassium persulfate, sodium persulfate, and ammonium persulfate; organic peroxides, azo initiators Agents, peroxides such as hydrogen peroxide and butyl peroxide; and redox polymerization initiators combining these with reducing agents such as acidic sodium sulfite and L-ascorbic acid. Two or more of these may be used in combination. In the present invention, among these, ammonium persulfate and potassium persulfate are preferable from the viewpoint of easy polymerization without adversely affecting the film properties and strength enhancement.

  There is no restriction | limiting in particular as a polymerization regulator, It can select suitably from well-known things. Examples of such a polymerization regulator include a chain transfer agent and a buffer.

  Here, examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol and butanol; aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, furfural and benzaldehyde; and dodecyl mercaptan, lauryl mercaptan, and normal mercaptan. And mercaptans such as thioglycolic acid, octyl thioglycolate, and thioglycerol. Two or more of these may be used in combination. The use of a chain transfer agent is effective in terms of stabilizing the polymerization, but it reduces the degree of polymerization of the synthetic resin, so the water resistance of the resulting film and the adhesive strength for woodworking are reduced. there's a possibility that. For this reason, when using a chain transfer agent, it is desirable to adjust the usage-amount suitably.

  Here, examples of the buffer include sodium acetate, ammonium acetate, dibasic sodium phosphate, and sodium citrate. Two or more of these may be used in combination.

  Any auxiliary emulsifier can be used as long as it is known to those skilled in the art as being usable for emulsion polymerization. Therefore, auxiliary emulsifiers include, for example, known anionic, cationic and nonionic surfactants, water-soluble polymers having protective colloid ability other than PVA resin (B), and water-soluble oligomers. Can be appropriately selected.

  Preferred specific examples of the surfactant include, for example, anionic surfactants such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate, and nonions such as those having a pluronic structure and those having a polyoxyethylene structure. Surfactants. A reactive surfactant having a radical polymerizable unsaturated bond in the structure can also be used as the surfactant.

  The use of an emulsifier makes the emulsion polymerization proceed smoothly and facilitates control. In addition, there is an effect of suppressing the generation of coarse particles and block-like substances generated during the polymerization. However, when many of these surfactants are used as emulsifiers, the water resistance tends to decrease. For this reason, when using surfactant, it is desirable that the usage-amount is an auxiliary | assistant amount with respect to PVA-type resin (B), ie, to reduce as much as possible.

  Examples of the water-soluble polymer having protective colloid ability other than the PVA resin (B) include PVA resins other than the PVA resin (B), hydroxyethyl cellulose, polyvinyl pyrrolidone, and methyl cellulose. These are effective in that the viscosity is changed by increasing the viscosity of the emulsion or changing the particle size of the emulsion. However, since the water resistance of the film may be lowered depending on the amount used, it is desirable to use a small amount when used.

  As the water-soluble oligomer, for example, a polymer or copolymer having a hydrophilic group such as a sulfonic acid group, a carboxyl group, a hydroxyl group, and an alkylene glycol group and having a degree of polymerization of about 10 to 500 is preferably exemplified. Specific examples of water-soluble oligomers include, for example, amide copolymers such as 2-methacrylamide-2-methylpropanesulfonic acid copolymer, sodium methacrylate-4-styrenesulfonate copolymer, styrene / maleic acid copolymer. Examples include polymers, melamine sulfonic acid formaldehyde condensates, poly (meth) acrylates, and the like. Furthermore, specific examples include a monomer having a sulfonic acid group, a carboxyl group, a hydroxyl group, an alkylene glycol group, and a water-soluble oligomer obtained by copolymerizing a radical polymerizable reactive emulsifier alone or in advance with another monomer. It is done. In the present invention, among these, 2-methacrylamide-2-methylpropane sulfonic acid copolymer, sodium methacrylate-4-styrene sulfonate, from the viewpoint of mixing stability with fillers such as pigments and charcoal cal described below. A copolymer is preferred. As the water-soluble oligomer, those previously polymerized before starting the emulsion polymerization may be used, or commercially available products may be used. Two or more of these may be used in combination.

  Moreover, as a plasticizer, an adipate type plasticizer, a phthalic acid type plasticizer, a phosphoric acid type plasticizer etc. can be used, for example, Dibutyl phthalate etc. can be used especially. A film-forming aid having a boiling point of 260 ° C. or higher can also be used. The amount of these other components used is not particularly limited as long as the object of the present invention is not impaired, and can be appropriately selected according to the object.

  Examples of the emulsion polymerization method include, for example, a monomer dropping type emulsion polymerization method in which water and an emulsifier are charged into a reaction vessel and the temperature is raised and a copolymerizable monomer and a polymerization initiator are dropped; An emulsion monomer dropping type emulsion polymerization method in which the resultant is dispersed and emulsified with water and then dropped is mentioned, but the monomer dropping type is convenient in terms of control of the polymerization process and controllability.

  Usually, emulsion polymerization is carried out using other components as described above such as a polymerization initiator, a polymerization regulator, and an auxiliary emulsifier as needed in addition to the emulsifier and the polymerizable monomer component. The polymerization reaction conditions are not particularly limited, and can be appropriately selected according to the type and purpose of the polymerizable monomer.

The emulsion polymerization process will be described more specifically as follows.
First, water, an emulsifier and, if necessary, an auxiliary emulsifier are charged in a reaction can, and after raising the temperature (usually 65 to 90 ° C.), a part of the polymerizable monomer component and a polymerization initiator are added to the reaction can. Initial polymerization is carried out. Next, the remaining polymerizable monomer components are added to the reaction can in one batch or dropwise, and polymerization is allowed to proceed while further adding a polymerization initiator as necessary. When it is determined that the polymerization reaction is completed, the reaction can is cooled, and the target synthetic resin emulsion can be taken out.

  In the present invention, the synthetic resin emulsion obtained by emulsion polymerization is typically uniform milky white, and its average particle size is preferably 0.2 to 3 μm from the viewpoint of emulsion stability. Preferably it is 0.3-2 micrometers. Here, the average particle size of the emulsion can be measured by a conventional method, for example, a laser analysis / scattering type particle size distribution analyzer “LA-910” (manufactured by Horiba, Ltd.).

  Thus, the synthetic resin emulsion of the present invention can be obtained, but when used for various purposes, it is preferably adjusted to 40 to 60% by weight as the nonvolatile content.

  Moreover, in this invention, you may further add various additives to the synthetic resin emulsion after emulsion polymerization as needed. Examples of such additives include organic pigments, inorganic pigments, water-soluble additives, pH adjusters, preservatives, and antioxidants.

  The water-soluble additive is added for the purpose of improving the re-emulsibility in water when the re-emulsifiable emulsion powder obtained by drying the synthetic resin emulsion of the present invention is dispersed in water.

  When the water-soluble additive is used, the water-soluble additive is usually added to the synthetic resin emulsion after emulsion polymerization and before drying. The amount of the water-soluble additive is preferably 2 to 30% by weight, preferably 5 to 20% by weight, particularly preferably 8 to 15% by weight, based on the solid content of the synthetic resin emulsion before drying. . When the amount used is too large, the water resistance of the re-emulsifiable emulsion powder tends to be insufficient, and when it is too small, the re-emulsification property tends not to be improved sufficiently.

  Examples of water-soluble additives include PVA resins, hydroxyethyl cellulose, methyl cellulose, starch derivatives, polyvinyl pyrrolidone, polyethylene oxide, water-soluble alkyd resins, water-soluble phenol resins, water-soluble urea resins, water-soluble melamine resins, water-soluble guanamines. Resin, water-soluble naphthalenesulfonic acid resin, water-soluble amino resin, water-soluble polyamide resin, water-soluble acrylic resin, water-soluble polycarboxylic acid resin, water-soluble polyester resin, water-soluble polyurethane resin, water-soluble polyol resin, and water-soluble An epoxy resin etc. are mentioned. Two or more of these may be used in combination.

  Among these, PVA-based resins are effective for improving the re-emulsification property in water. The PVA-based resin to be used may be the same as that used as an emulsifier in the emulsion polymerization process, or may be different. During polymerization, a PVA resin having a high degree of polymerization is difficult to use because of its polymerization stability, but even such a PVA resin can be used without any problems as long as it is added after polymerization. However, those having low solubility in water may adversely affect the re-emulsification property, so it is desirable to use them after confirming the solubility in water in advance.

  Furthermore, in the present invention, functional groups such as acetoacetyl group, mercapto group, carboxyl group, sulfonic acid group, alkoxyl group, diacetone acrylamide group, group having 1,2-diol bond in the side chain as water-soluble additives. Modified PVA-based resin modified with can also be used.

  PVA or acetoacetyl group-modified PVA, diacetone acrylamide group-modified PVA as a water-soluble additive effective for improving re-emulsification in water, PVA containing a side chain 1,2-diol bond, Isocyanate compounds, (poly) hydrazide compounds, aziridine compounds, epoxy group-containing compounds, amine compounds, aldehyde compounds, methylol melamine polymers, polyvalent polymers used as crosslinking agents for re-emulsifiable emulsion powders It can be used in appropriate combination with a metal compound (aluminum salt, zircozole salt, calcium salt, etc.) and the like.

  When the cross-linking agent is a powder or powder, it is also possible to obtain a one-part re-emulsifiable emulsion powder composition in which a necessary amount is blended in advance with the re-emulsifiable emulsion powder.

[Re-emulsifiable emulsion powder]
In the present invention, a re-emulsifiable emulsion powder can be obtained by drying the synthetic resin emulsion obtained by the emulsion polymerization. Examples of the drying method include spray drying, freeze drying, and warm air drying after coagulation. Among these, spray drying is preferable from the viewpoint of production cost and energy saving.

  In the case of spray drying, the spray format can be implemented by a format such as a disk type or a nozzle type. Examples of the heat source for spray drying include hot air and heated steam. The conditions for spray drying can be appropriately selected according to the size and type of the spray dryer, the solid content of the emulsion, the viscosity, the flow rate, and the like. The temperature of spray drying is usually about 80 to 150 ° C.

  The spray drying process will be further described with specific examples. First, the solid content in the synthetic resin emulsion is adjusted, and this is continuously supplied from the nozzle of the spray dryer, and the mist is dried with warm air. To powder.

  In the present invention, the anti-caking agent can be used in combination by mixing it with a re-emulsifiable emulsion powder after spray drying or spraying it from a different nozzle from the synthetic resin emulsion during spray drying. . The addition of the anti-caking agent is to prevent particles from caking and agglomerating and blocking during storage, for example, when the emulsion powder is coated with the anti-caking agent.

  As the anti-caking agent, known inert inorganic or organic powders such as calcium carbonate, talc, clay, dolomite, anhydrous silicic acid, white carbon, alumina white and the like can be used. Among these, anhydrous silicic acid, calcium carbonate, clay and the like are preferable. The amount of the anti-caking agent used is preferably about 2 to 30% by weight, more preferably 5 to 20% by weight, particularly preferably 8 to 15% by weight, based on the re-emulsifiable emulsion powder obtained. It is.

  Thus, the re-emulsifiable emulsion powder of the present invention can be obtained. However, when used in various applications, it is basically used after re-emulsifying in water to return to the original synthetic resin emulsion state.

[Adhesive composition for woodwork]
The synthetic resin emulsion of the present invention, the re-emulsifiable emulsion powder, and further the synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder are useful as an adhesive for woodworking, and have good adhesiveness in split strength evaluation. Moreover, a high material breakage rate can be expressed. The synthetic resin emulsion of the present invention, the re-emulsifiable emulsion powder, and the synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder are not only used as adhesives for woodworking, but also water such as various cements and gypsum. It can also be used for various applications such as additives to hard materials, powder paints, and inorganic finishes.

  Furthermore, in the present invention, the synthetic resin emulsion of the present invention, the re-emulsifiable emulsion powder, and the synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder are mixed with a crosslinking agent and a filler to be used for woodworking. It can be used as a composition.

  As the crosslinking agent, for example, an isocyanate compound or a prepolymer thereof, an epoxy compound or a prepolymer thereof is preferably used. It is preferable that the usage-amount of a crosslinking agent is 1 to 40 weight% with respect to the synthetic resin (A) in a synthetic resin emulsion, More preferably, it is 5 to 25 weight%. If the amount of the crosslinking agent is too small, the crosslinking effect is small and the expected adhesive strength tends to be difficult to obtain. If the amount is too large, the usable time of the adhesive tends to be extremely short and the workability tends to be hindered.

  As the filler, fine particle type calcium carbonate, talc, dolomite and the like are generally used alone or in combination depending on the purpose and purpose.

  Thus, the synthetic resin emulsion of the present invention, the re-emulsifiable emulsion powder, and the synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder are excellent in splitting strength evaluation when applied to an adhesive composition for woodworking. In addition to exhibiting excellent adhesiveness and high material breakage rate, when the film was formed, the resulting film was excellent in water resistance, warm water resistance, boiling resistance, toughness and long-term durability. It has an effect and is particularly useful for an adhesive composition for woodworking.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded. In the examples, “parts” and “%” mean weight basis.

The following were prepared as the polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain.
・ PVA resin (B-1)
PVA-based resin having an average saponification degree of 99.1 mol%, an average polymerization degree of 300, and a side chain 1,2-diol bond content of 8 mol%

Moreover, the following were prepared as polyvinyl alcohol-type resin (B ') which does not have a 1, 2- diol bond in a side chain. -PVA-type resin (B'-1)
PVA resin having an average degree of polymerization of 300 and an average degree of saponification of 88 mol%

[Example 1]
In a 2L stainless steel reaction can equipped with a stirrer and a reflux condenser, 870 parts of water and PVA resin (B-1) as a protective colloid (average saponification degree 99.1 mol%, average polymerization degree 300) , 60 parts of a 1,2-diol bond in the side chain / manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and the reaction can is heated to 85 ° C. to obtain the PVA resin (B-1). Dissolved in water. Next, the temperature of the reactor was kept at 80 ° C., and the premixed mixed monomer (600 parts of n-butyl acrylate (BA) / 214 parts of styrene / 2-hydroxyethyl methacrylate (2HEMA)) 22. 5 parts = 71.7 / 25.6 / 2.7 (weight ratio)) and 30% of an ammonium persulfate aqueous solution in which 1.8 g of ammonium persulfate was dissolved in 30 g of water as a polymerization initiator was added. The initial polymerization reaction was performed for 1 hour. Next, the remaining mixed monomer and 60% of the ammonium persulfate aqueous solution as a polymerization initiator were dropped into the reaction vessel over 4 hours to proceed the polymerization. After completion of dropping, 10% of the aqueous ammonium persulfate solution was added and aged for 1 hour at the same temperature to obtain a synthetic resin emulsion (synthetic resin emulsion 1) having a nonvolatile content of 50%.

  The calculated glass transition temperature (Tg) of the synthetic resin having this monomer composition (BA / styrene / 2HEMA = 71.7 / 25.6 / 2.7 (weight ratio)) is the Tg of each homopolymer − In the case of 52 ° C., + 100 ° C., and + 55 ° C., it is −24 ° C.

[Example 2]
A synthetic resin emulsion 2 was produced in the same manner as in Example 1 except that the type and composition ratio of the mixed monomer were changed to BA / styrene / 2HEMA = 80.1 / 17.2 / 2.7 (weight ratio). .

  The calculated glass transition temperature (Tg) of a synthetic resin having this monomer composition (BA / styrene / 2HEMA = 80.1 / 17.2 / 2.7 (weight ratio)) is the Tg of each homopolymer − It is -34 degreeC when it is set to 52 degreeC, +100 degreeC, and +55 degreeC.

[Example 3]
A synthetic resin emulsion 3 was produced in the same manner as in Example 1 except that the type and composition ratio of the mixed monomer were changed to BA / styrene / 2HEMA = 90.8 / 6.5 / 2.7 (weight ratio). .

  The calculated glass transition temperature (Tg) of a synthetic resin having this monomer composition (BA / styrene / 2HEMA = 90.8 / 6.5 / 2.7 (weight ratio)) is the Tg of each homopolymer − It is -44 degreeC when it is set to 52 degreeC, +100 degreeC, and +55 degreeC.

[Comparative Example 1]
A synthetic resin emulsion 4 was produced in the same manner as in Example 1 except that the type and composition ratio of the mixed monomer were changed to BA / styrene / 2HEMA = 55.7 / 41.6 / 2.7 (weight ratio). .

  The calculated glass transition temperature (Tg) of the synthetic resin having this monomer composition (BA / styrene / 2HEMA = 55.7 / 41.6 / 2.7 (weight ratio)) is the Tg of each homopolymer − When 52 ° C, + 100 ° C, and + 55 ° C, the temperature is -4 ° C.

[Comparative Example 2]
A synthetic resin emulsion 5 was produced in the same manner as in Example 1 except that the type and composition ratio of the mixed monomer were changed to BA / styrene / 2HEMA = 63.2 / 34.1 / 2.7 (weight ratio). .

  The calculated glass transition temperature (Tg) of the synthetic resin having this monomer composition (BA / styrene / 2HEMA = 63.2 / 34.1 / 2.7 (weight ratio)) is the Tg of each homopolymer − In the case of 52 ° C., + 100 ° C., and + 55 ° C., it is −14 ° C.

[Comparative Example 3]
A synthetic resin emulsion 6 was produced in the same manner as in Example 1 except that the PVA resin (B′-1) was used instead of the PVA resin (B-1).

  Using the synthetic resin emulsions 1 to 6 of Examples 1 to 3 and Comparative Examples 1 to 3 described above, an average polymerization degree of 1400 and a saponification degree of 88 mol% prepared in advance for 200 parts of each synthetic resin emulsion 8 parts of partially saponified PVA, 45 parts of calcium carbonate as filler, and 2.5 parts of hydroxyethyl cellulose were added to each of the three components and stirred well, and 27 parts of water was added, and the viscosity was adjusted to 5-6. After adjusting to 10,000, 15 parts of a cross-linking agent (polydimethyldiphenyl diisocyanate / manufactured by Nippon Polyurethane Industry Co., Ltd.) was added and stirred sufficiently to give adhesives for woodworking examples 1 to 3 and comparative examples 1 to 3. A composition was obtained.

<Split strength evaluation test>
About the obtained adhesive composition for woodworking, the split adhesive strength was measured according to JIS K 6853: 1994 [the split adhesive strength test method of an adhesive] using the wood board as a test piece.

The specific test method is as follows.
After using the “hips” plate specified in JIS K 6848-4: 1999, the adhesive composition was applied to the bonding surface at a rate of 200 g / m ² , and the plates were bonded to each other. It compressed after 10 minutes by the load of 8 MPa, and was hold | maintained as it was at 23 degreeC for 24 hours. After depressurization, 48 hours elapsed and then used for measurement.

  The test piece was mounted on a testing machine with a test piece mounting tool, a test was performed with a load applied, and the maximum load when the test piece was broken was recorded as the adhesive strength (N / 25 mm). The destruction state at this time was examined, and the ratio of the broken area to the bonded area was read and used as the material breakage rate (%). The evaluation results are as shown in Table 1.

  As shown in Table 1, in the adhesive compositions for woodworking examples 1 to 3 in which the glass transition temperature (Tg) of the synthetic resin in the synthetic resin emulsion is −20 ° C. or less, the glass transition temperature (Tg) is −20. The adhesive strength for woodworking Comparative Examples 1 and 2 higher than ° C. is higher in adhesive strength and the material breakage rate. Moreover, the adhesive composition for woodworking of Comparative Example 3 in which the PVA resin in the synthetic resin emulsion is not a PVA resin having a 1,2-diol bond in the side chain has a glass transition temperature (Tg) of −20 of the synthetic resin. Even if it is below ℃, the adhesive strength is lower than in Examples 1 to 3, and the material breakage rate is also low. Therefore, the advantages of the effects of the present invention are also apparent from Table 1.

  The synthetic resin emulsion of the present invention, the re-emulsifiable emulsion powder, and the synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder are good in splitting strength evaluation when applied to an adhesive composition for woodworking. Adhesiveness and high material breakage rate can be expressed. In addition, it has an excellent effect on water resistance, warm water resistance, boiling resistance, toughness and long-term durability of the obtained film, in particular, adhesives for woodworking, inorganic finishing agents, paints, It is useful for various applications such as admixtures for hydraulic materials such as cement and plaster.

Claims (7)

  The synthetic resin (A) is a synthetic resin emulsion dispersed and stabilized with a polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain, and the glass transition temperature of the synthetic resin (A) is -20. A synthetic resin emulsion having a temperature of ℃ or less.   The polyvinyl alcohol resin (B) having a 1,2-diol bond in the side chain has a 1,2-diol bond amount of 1 to 15 mol%, an average saponification degree of 85 mol% or more, and an average polymerization degree of 50 to 3000. The synthetic resin emulsion according to claim 1, wherein   A re-emulsifiable emulsion powder, which is a dried product of the synthetic resin emulsion according to claim 1 or 2.   A synthetic resin emulsion obtained by re-emulsifying the re-emulsifiable emulsion powder according to claim 3.   The synthetic resin emulsion according to claim 1, 2, or 4, which is used for an adhesive for woodworking.   An adhesive composition for woodworking, comprising the synthetic resin emulsion according to any one of claims 1, 2, 4, and 5, or the re-emulsifiable emulsion powder according to claim 3.   The woodworking adhesive composition according to claim 6, further comprising a crosslinking agent.