JP3979657B2 - Adhesive composition - Google Patents

Description

  The present invention relates to an adhesive composition, and more specifically, an adhesive based on a resin emulsion that does not contain a plasticizer that is suspected of being an environmental hormone and has good low-temperature adhesiveness, water resistance, adhesive strength, and extrudability from a container. It relates to a composition.

Conventionally, resin emulsions such as vinyl acetate resin emulsions, acrylic resin emulsions or ethylene / vinyl acetate copolymer resin emulsions are used for woodworking because they have good adhesion and can be used easily, and are easy to store. It has been widely used as an adhesive for paper industry and textiles.
In particular, an adhesive based on a vinyl acetate resin emulsion is widely used as a general-purpose product because it is excellent in low cost and workability in addition to adhesive performance.

Although vinyl acetate resin emulsion is used in this way, it is indispensable to add a plasticizer to ensure low-temperature film-forming properties, but phthalic acid, which has been commonly used as a plasticizer. Suspected environmental hormones have been pointed out for esters and the like, and there is a strong demand for adhesives that do not contain plasticizers.
Moreover, since the plasticizer is a volatile organic compound (VOC component) and has been pointed out to cause sick house syndrome, there is a demand for an adhesive that does not contain the plasticizer.

Under such circumstances, an adhesive composition based on a resin emulsion obtained by seed polymerization of vinyl acetate in the presence of an ethylene vinyl acetate copolymer resin emulsion as disclosed in JP-A-11-92734 is proposed. Has been.
However, this type of resin emulsion is still inadequate for film formation at low temperatures, so adhesion to adherends at low temperatures is poor, viscosity increase at low temperatures is extremely poor, and workability from containers is poor. There are still issues such as difficulties.

  From the above situation, vinyl acetate is seed-polymerized in the presence of acrylic resin emulsion as a resin emulsion with good low-temperature film-forming properties and having normal adhesive strength, water resistance, heat resistance, storage stability, etc. A method is proposed in Japanese Patent Application Laid-Open No. 2003-213235. The adhesive composition based on the resin emulsion obtained by this method has good low-temperature film-forming properties, normal adhesive strength, water resistance, heat resistance, storage stability, etc., but the resin film after film formation is hard Therefore, the adhesive performance at low temperature was not sufficient. Also, the extrudability from the container was not sufficiently good.

Thus, there is a strong demand for a type having good low temperature adhesiveness, water resistance, heat resistance, normal adhesive strength, storage stability, and extrudability from a container, which is indispensable as an adhesive composition based on a resin emulsion. It was.


Japanese Patent No. 11-92734 JP 2003-213235 A

  An object of the present invention is not to provide an adhesive composition comprising a resin emulsion that does not contain a plasticizer that is suspected of being an environmental hormone, and that is excellent in low-temperature adhesiveness, adhesive strength, water resistance, heat resistance, and extrudability from a container. It is what.

In order to achieve low-temperature adhesion, water resistance, heat resistance, and extrusion from a container, the resin emulsion A and the resin emulsion B are not included in the present invention. Adhesive composition comprising 100: 1 to 100: 100 based on solid content
Resin Emulsion A Acrylic resin emulsion (hereinafter sometimes referred to as seed emulsion a1) and a vinyl acetate resin emulsion synthesized using polyvinyl alcohol as a protective colloid or a resin emulsion obtained by emulsion copolymerization of vinyl acetate and other monomers ( A resin emulsion obtained by polymerizing vinyl acetate or vinyl acetate and other copolymerizable monomers in the presence of seed emulsion a2), the acrylic resin emulsion and polyvinyl alcohol. A resin emulsion in which the total solid content of a vinyl acetate resin emulsion polymerized using as a protective colloid is 5 to 30% by weight based on the total solid content of the resin emulsion. (However, unless the seed emulsion a1 and the seed emulsion a2 are the same emulsion)
Resin Emulsion B An acrylic resin emulsion, vinyl acetate acrylic copolymer resin emulsion, or ethylene vinyl acetate copolymer resin emulsion having a minimum film forming temperature of 2 ° C. or lower solves the above-mentioned problems.

Since the resin emulsion according to the present invention is an adhesive composition containing 100: 1 to 100: 100 based on the solid content of the resin emulsion A and the resin emulsion B , the low temperature adhesion It is excellent in water resistance, heat resistance and extrudability from containers, and is extremely useful as an adhesive for woodworking. Moreover, since it does not contain a plasticizer that is suspected of being an environmental hormone, it is convenient for production and processing of various environmentally friendly products.

Hereinafter, the present invention will be described in detail.
The adhesive composition according to the present invention is an adhesive composition containing 100: 1 to 100: 100 based on the solid content of the resin emulsion A and the resin emulsion B.

The raw material etc. which are employ | adopted in this invention below are demonstrated.
The seed emulsion a1 includes methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, lauryl (meth) acrylate, (meth) (Meth) acrylic acid esters such as 2-ethylhexyl acrylate, octyl (meth) acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, polyethylene glycol Acrylic monomers containing hydroxyl groups such as acrylate and polyethylene glycol methacrylate, (meth) acrylonitrile and acrylamide Alternatively, styrene, vinyl acetate, vinyltoluene, (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid and other monomers added are known to use surfactants as emulsifiers or PVA as protective colloids. Those obtained by emulsion polymerization by various methods are used.

Among these, the preferred seed emulsion a1 is preferably in the range glass transition temperature of 0 to-60 ° C. of dry film, there is the monomer composition so that the temperature range is set, like this If it is a thing, the low-temperature film-forming property of adhesive composition will be ensured, and the adhesiveness with respect to a to-be-adhered body in low temperature, heat resistant adhesive force, water resistance, normal state adhesive force, etc. will be ensured.

The seed emulsion a2 used together with the seed emulsion a1 is a vinyl acetate resin emulsion synthesized using polyvinyl alcohol (hereinafter abbreviated as PVA) as a protective colloid, or a resin emulsion obtained by emulsion copolymerization of vinyl acetate and other monomers. It is preferable from the viewpoints of extrudability to the body, adhesion, and adhesion performance.

Other monomers that are emulsion copolymerized with vinyl acetate include methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, butyl (meth) acrylate, ethylene glycol di (meth) acrylate, glycidyl ( In addition to (meth) acrylates such as (meth) acrylate and propylene glycol (meth) acrylate, vinyl propionate, (meth) acrylic acid, methylolacrylamide, vinyl versatate, vinyl butyrate, vinyl stearate, allyl acetate, methyl vinyl ether , Ethyl vinyl ether, isopropyl vinyl ether, acrylonitrile and the like.
Further, in order to improve the water resistance, strength, stain resistance, etc. of the resin emulsion and the adhesive composition, a silyl group-containing monomer can be added to participate in the emulsion copolymerization. Examples of the silyl group-containing monomer include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, tris-2-methoxyethoxyvinylsilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. Can be mentioned.

The resin emulsion A is prepared by polymerizing vinyl acetate or vinyl acetate and other monomers in the presence of a seed resin emulsion comprising a seed emulsion a1 and a seed emulsion a2 .
For polymerization, for example, water and PVA as a protective colloid are dissolved in a reaction vessel equipped with a stirrer, a heating device, a thermometer and a temperature control device, a monomer dropping hole, a reflux condenser, etc. In addition to the addition, the temperature is raised to 60 to 80 ° C., and then an aqueous solution of a polymerization initiator and vinyl acetate can be added dropwise.
Further, a part of the polymerization initiator or monomer can be added at the initial stage of polymerization, or the polymerization initiator or monomer can be added in portions during the polymerization.

In addition, the ratio of the solid content of the resin emulsion for seeds to the solid content of the resin emulsion A is preferably 5 to 30% by weight. In this range, if it is less than 5% by weight, the low-temperature adhesiveness of the prepared adhesive composition is not inferior, and the normal adhesive force of the adhesive composition exceeding 30% by weight tends to decrease. Not .

  PVA used as a protective colloid in the polymerization of resin emulsions has an average polymerization degree of 400 to 4000 and a saponification degree of 87 to 98 mol%, which is a balance of polymerization stability, structural viscosity, water resistance, storage stability, etc. And can be used alone or in combination of two or more. If the average degree of polymerization is less than 400, the initial adhesiveness and tackiness are insufficient, which is not preferable. If the average degree of polymerization exceeds 4000, the viscosity of the resin emulsion becomes too high, but this is not suitable when used in combination with other PVA. Not as long. Moreover, protective colloids and surfactants other than PVA may be added as long as the polymerizability and performance as an adhesive are not impaired.

Surfactants that can be used include cationic, anionic, and nonionic surfactants that are blended in an amount of 0.01 to 5% by weight based on the total amount of monomers.
In addition, the blending amount of the surfactant with respect to all monomers tends to increase the average particle size of the resin emulsion as the amount decreases, and the average particle size tends to decrease as the amount increases, affecting the size of the average particle size of the prepared resin emulsion. It is recognized that there is. It is preferable to set the average particle diameter of the resin emulsion to 300 to 700 nm in order to adjust the emulsion polymerization property, storage stability, water resistance, initial adhesive force, etc. in a well-balanced manner. 0.01 to 0.5% by weight is desirable. Thus, the water resistance of an adhesive composition improves by suppressing the addition amount of surfactant.

Examples of the cationic surfactant include alkyltrimethylammonium, bromide, alkylpyridium bromide, imidazolium laurate, and the like. Examples of anionic compounds include higher fatty acid salts such as sodium octoate, sodium decanoate, sodium laurate, sodium oleate and sodium stearate, alkyl sulfates such as sodium lauryl sulfate and sodium oleyl sulfate, and lauryl alcohol sulfate. Higher alcohol sulfates such as oleyl sulfate, stearyl alcohol sulfate, α-olefin sulfate, alkyl benzene sulfonate, α-olefin sulfonate, alkane sulfonate, α-sulfo fatty acid ester salt, etc. And higher alkyl polyethylene glycol sulfates. Nonionic compounds include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block polymer alkyl benzene sulfonate, alkyl aryl sulfonate, alkyl sulfosuccinic acid, polyoxyethylene alkyl sulfate. , Polyoxyethylene alkyl ether, polyoxyethylene oxypropylene block polymer, fatty acid soap and the like.
In order to improve the water resistance of the resin emulsion, the use of reactive surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene higher fatty acid esters having an ethylenically unsaturated bond is considered. May be.

As the polymerization initiator, 0.01 to 1.0 weight of peroxide initiator, azo initiator, and persulfate initiator is used with respect to 100 parts by weight of the monomer. Examples of the peroxide initiator include benzoyl peroxide, lauryl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, butyl hydroperoxide, and hydrogen peroxide. Examples of the azo initiator include azobisisobutyronitrile, azobiscyanovaleric acid, azobiscyanopentanoic acid, and the like. Examples of the persulfate-based initiator include ammonium persulfate, potassium persulfate, and sodium persulfate.
As the polymerization regulator, for example, thioglycolic acid, butyl mercaptan, dodecyl mercaptan, octyl mercaptan, lauryl mercaptan and the like can also be used as appropriate.

  The temperature at which polymerization proceeds is different from the type of polymerization initiator used. For example, when emulsion polymerization is advanced by thermal decomposition such as ammonium persulfate, a temperature of 60 ° C. or higher is suitable, and in a redox system in which a peroxide and a reducing agent are combined, 60 is used. Emulsion polymerization can proceed even at a temperature of ℃ or less.

  Examples of the resin emulsion B having an MFT of 2 ° C. or less mixed with the resin emulsion A include vinyl acetate / acrylic copolymer resin emulsion, acrylic resin emulsion, and ethylene / vinyl acetate copolymer resin emulsion. For the synthesis of these resin emulsions, in addition to general emulsion polymerization, a known method such as seed polymerization is adopted, and MFT is set to 2 ° C. or lower. If MFT is not set to 2 ° C. or less, there is a tendency that good low-temperature adhesiveness cannot be obtained.

The mixing ratio of the resin emulsion A and the resin emulsion B is 100 to 1 to 100, preferably 2 to 100, as a solid content ratio. In this range, it is not recognized that the low-temperature adhesiveness is less than 100 to 1, and the normal adhesive force of the adhesive composition exceeding 100 to 100 does not tend to decrease.

  The resin emulsion prepared from the resin emulsion A and the resin emulsion B having an MFT of 2 ° C. or lower can be used as it is as an adhesive composition, but has an applicability, tackiness, viscosity, initial adhesive strength, etc. If further properties are required, or if special properties are required depending on the coating method or the like, it is necessary to add and adjust various compounding materials according to each use mode. Such compounding materials include tackifiers, fillers, thickeners, dispersants, ph adjusters, leveling agents, water resistance agents, preservatives, antifoaming agents, surfactants, isocyanate compounds as crosslinking agents, etc. Is mentioned.

  When considering the compounding of an isocyanate compound as a crosslinking agent in order to improve the performance as an adhesive, the water resistance, hot water resistance, and heat resistance can be increased by blending 5 to 20% by weight based on the solid content of the adhesive composition. In addition, the effect of significantly improving the adhesive strength can be obtained. In addition, when mix | blending an isocyanate compound as a crosslinking agent, if 0.1-5 weight% is added with respect to an adhesive composition sodium sulfanilate as a reaction retarding agent, a pot life can be extended further. It has been confirmed that the adhesion workability is greatly improved by the addition.

  Examples of the isocyanate compounds include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, triphenylmethane triisocyanate, polymethylene phenyl polyisocyanate, xylene diisocyanate, hexa Examples thereof include methylene diisocyanate and crude MDI containing 4,4-diphenylmethane diisocyanate and liquid polymeric MDI. In particular, it has been confirmed that a stable adhesive force can be obtained when the crude MDI is used as a curing agent for an adhesive that adheres hard wood to an adherend. The reason for this is not necessarily clear, but it is presumed that the penetration to a hard adherend is good.

Other effective examples of thickeners and tackifiers include cellulose resins such as methylcellulose, ethylcellulose, hydroxycellulose, and carboxylcellulose, starch, casein, polyethylene glycol, chitosan, and gum arabic.
Moreover, kaolin, clay, talc, calcium carbonate, wheat flour, eggplant powder, etc. can be used effectively as fillers. Among them, calcium carbonate is inexpensive and has no functional group, so there is no thickening when a curing agent is blended, and since it is inorganic and relatively soft, it does not damage the blade when cutting bonded products. Convenient.

Hereinafter, the present invention will be further described by the preparation of resin emulsion A, resin emulsion B having an MFT of 2 ° C. or less, and examples and comparative examples. In addition, a weight part represents only a part and the numerical value displayed on Table 1, 2, and 3 represents a weight part. Needless to say, the present invention is not limited to the examples and comparative examples.
(A) Preparation of resin emulsion A C-70 (manufactured by Gantz Kasei Co., Ltd., solid content) as an acrylic resin emulsion in a reaction vessel equipped with a stirrer, a heating device, a thermometer and a temperature control device, a monomer dropping hole, and a reflux condenser. 55%, MFT 0 ° C.), 95 parts of water, B-17 as PVA (manufactured by Denki Kagaku Kogyo Co., Ltd., average polymerization degree 1700, saponification degree 88 mol%), acetic acid prepared using PVA as protective colloid AK-914 as a vinyl resin emulsion (manufactured by Aika Kogyo Co., Ltd., solid content 55%, MFT 12 ° C.), ethylene vinyl acetate copolymer resin emulsion prepared using PVA as a protective colloid # 140 (manufactured by Denki Kagaku Kogyo Co., Ltd.) , Solid content 55%, MFT 0 ° C or less) and PVA prepared without using protective colloid ECOS3000 (manufactured by Dainippon Ink Industries, Ltd., solid content 40%, MFT 0 ° C. or lower) as a resin resin emulsion is mixed and stirred, and then heated to 80 ° C. to dissolve hydrogen peroxide and tartaric acid in 5 parts of water. The emulsion polymerization was advanced while adding vinyl acetate dropwise over 3 hours together with the aqueous solution. After completion of the dropwise addition of vinyl acetate, the polymerization reaction was further continued at 80 ° C. and then cooled to room temperature. The properties of the prepared resin emulsion A are shown in Table 1.

(B) Resin emulsion B with MFT of 2 ° C. or less As an example sample of resin emulsion B with MFT of 2 ° C. or less, (a) C-70 as an acrylic resin emulsion (manufactured by Ganz Kasei Co., Ltd., solid content 55%, MFT) 0) and (b) ethylene vinyl acetate copolymer resin emulsion # 140 (manufactured by Denki Kagaku Kogyo Co., Ltd., solid content 55%, MFT 0 ° C. or less) was used. Moreover, as a sample of the resin emulsion B of the comparative example, a vinyl acetate resin emulsion AK-914 (manufactured by Aika Industry Co., Ltd., solid content 55%, MFT 12 ° C.) was used.

Note) Measurement / test method (1) Solid content : dried at 110 ° C. for 3 hours to obtain the solid content .
(2) Normal adhesive strength: The compression shear adhesive strength of the birch material was measured according to JISK6804 (2003 edition), and 10 N / mm ² or more was evaluated as ◯ and less than 10 N / mm ² was evaluated as ×.
(3) Low temperature adhesion: In an atmosphere of 2 ° C., the adhesive composition was applied to lauan plywood at an application amount of 150 g / m ² , and a particle board was immediately bonded and pressed at a pressure of 0.1 MPa for 12 hours. Thereafter, the bonded body was forcibly broken and the material breakage rate was measured, and 80% or more of the material breakage was evaluated as ◯, and less than 80% was evaluated as x.
(4) Extrudability 500 g of cylindrical plastic tube (opening diameter: 3 mm) was filled with the adhesive composition, and the extrudability when the central part of the cylindrical plastic tube was pushed by hand at room temperature was evaluated. . Good was evaluated as ◯, and poor was evaluated as ×.

The adhesive composition according to the present invention is excellent in adhesive performance such as low-temperature adhesiveness, water resistance and heat resistance, and excellent in workability such as extrudability and coatability. Because it is easy to use and does not contain plasticizers that are suspected of being an environmental hormone, it can be used safely for various purposes such as woodworking and paperworking.

Claims (1)

An adhesive composition comprising 100: 1 to 100: 100 based on the solid content of resin emulsion A and resin emulsion B.
Resin Emulsion A Acrylic resin emulsion (hereinafter referred to as seed emulsion a1) and vinyl acetate resin emulsion synthesized using polyvinyl alcohol as a protective colloid or a resin emulsion obtained by emulsion copolymerization of vinyl acetate and other monomers (hereinafter referred to as seed emulsion a2) A resin emulsion obtained by polymerizing vinyl acetate or vinyl acetate and other copolymerizable monomers in the presence of a vinyl acetate resin emulsion polymerized using the acrylic resin emulsion and polyvinyl alcohol as protective colloids. A resin emulsion in which the total solid content is 5 to 30% by weight based on the total solid content of the resin emulsion. (However, unless the seed emulsion a1 and the seed emulsion a2 are the same emulsion)
Resin emulsion B An acrylic resin emulsion, a vinyl acetate acrylic copolymer resin emulsion, or an ethylene vinyl acetate copolymer resin emulsion having a minimum film forming temperature of 2 ° C. or lower.