JP2003213235A - Adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that, though an adhesive comprising a vinyl acetate resin emulsion has been widely used as it is water-based and easily used, the adhesive has undesirable film forming properties in winter and is not used without mixing a plasticizer, the plasticizer used decreases strengths and reduces heat resistance, the plasticizer is suspicious to be an environmental hormone and anxious to be used and so forth. <P>SOLUTION: This adhesive composition comprises the vinyl acetate emulsion produced by seed polymerizing vinyl acetate monomer to an acrylic resin emulsion prepared by emulsion polymerization using an acrylic monomer. The adhesive composition solves the above problems. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel water-based adhesive composition, and more specifically, it has an excellent film-forming property without increasing viscosity even at low temperature, and has an excellent adhesive property for adhesives, especially for woodworking and paper. It relates to an aqueous adhesive composition comprising a vinyl acetate resin emulsion useful as an agent.

[0002]

2. Description of the Related Art Conventionally, vinyl acetate resin emulsions obtained by emulsion polymerization of vinyl acetate monomers have been widely used for adhesives, paints, paper processing, textile processing and the like. However, when it is used as an adhesive, the temperature dependence of the viscosity is large, the viscosity rises significantly at low temperatures such as in winter, resulting in poor workability. Also, since the film-forming property at low temperatures is poor, plastic such as dibutyl phthalate is used. Addition of agents is required. The film formed from the emulsion becomes flexible by adding a plasticizer to the emulsion, but the strength and heat resistance of the film are reduced. This tendency becomes more remarkable as the amount of plasticizer added increases, especially when used for winter. Furthermore, in recent years, there has been concern about the use of phthalate plasticizers as chemical substances suspected of having endocrine disrupting effects.

As an attempt to reduce the amount of plasticizer, Japanese Unexamined Patent Publication No. Hei 11
-Ethylene content of 15-35 as in No. 092734
An adhesive for woodworking is disclosed which comprises a vinyl acetate resin emulsion obtained by seed polymerization of vinyl acetate in an ethylene vinyl acetate copolymer resin emulsion in a weight percentage. However, it has been pointed out that this adhesive also has insufficient film forming properties at low temperatures, and that it has a marked increase in viscosity at low temperatures and poor workability.

[0004]

In view of such a situation, the present invention solves the problems of the conventional vinyl acetate resin emulsion, that is, the problems such as the decrease in strength and heat resistance of the bonded portion due to the use of the plasticizer, and environmental pollution. Provided is an adhesive composition composed of a vinyl acetate resin emulsion which is excellent in low-temperature film-forming property, storage stability, good workability with little increase in viscosity at low temperature, and excellent adhesive properties such as initial adhesiveness and water resistance. It is something to do.

[0005]

As a result of various studies to solve the above-mentioned problems, the present inventors have found that a vinyl acetate resin emulsion obtained by seed polymerization of a vinyl acetate monomer into an acrylic resin emulsion is obtained. It was found that the water-based adhesive composition consisting of (3) solves the problem, and further studies have been conducted to complete the present invention. That is, the present invention provides (1) a water-based adhesive composition comprising a vinyl acetate resin emulsion obtained by seed-polymerizing an acrylic resin emulsion with a vinyl acetate monomer,
(2) The water-based adhesive composition according to (1), wherein the acrylic resin has a glass transition temperature of 0 ° C. or lower. (3) Acrylic resin is contained in an amount of 5 to 30% by weight based on the whole solid (1)
The water-based adhesive composition as described above, (4) the water-based adhesive composition as described in (1), wherein the weight ratio of the acrylic resin and the vinyl acetate resin is 1: 0.4 to 20, and (5) JISK6804.
The water-based adhesive composition according to any one of (1) to (4), which has a film forming temperature of 2 ° C. or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic resin emulsion used in the present invention is obtained by emulsion-polymerizing an acrylic monomer or a comonomer copolymerizable therewith in the presence of an emulsifier, a polymerization initiator, a polymerization modifier and the like. Further, it can be prepared by further performing seed polymerization of the vinyl acetate resin emulsion using the acrylic resin emulsion as a seed.

Examples of acrylic monomers used include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, lauryl (meth) acrylate, and (meth) acrylate. (Meth) acrylic acid ester such as 2-ethylhexyl acrylate and octyl (meth) acrylate, for example, having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate (meth) In addition to acrylic acid esters, (meth) acrylonitrile, (N-methylol) acrylamide, etc. may be mentioned. If desired, a polymerizable monomer may be used in combination with the acrylic monomer. Examples of comonomers that can be used in combination include ethylenic monomers copolymerizable with acrylic monomers such as styrene, modified styrene, vinyl acetate, (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid. To be

The acrylic resin emulsion obtained by emulsion polymerization has a dry film having a glass transition temperature of 0 ° C. or lower, preferably 0 to −60 ° C. Therefore,
It is preferable to prepare an acrylic monomer alone or in combination so that the glass transition temperature falls within this temperature range.
When the glass transition temperature is 0 ° C or higher, the film forming temperature of the vinyl acetate resin emulsion may not be 2 ° C or lower. Further, when the glass transition temperature is lower than -60 ° C, the cohesive force of the aqueous adhesive composition comprising the vinyl acetate resin emulsion becomes poor and the adhesive performance is deteriorated, which is not preferable.

In the emulsion polymerization of the above monomers, any of nonionic, anionic, cationic and amphoteric emulsifiers can be used. Examples of the nonionic ones include polyoxyethylene alkylphenol ether sulfates or sulfonates, alkylbenzene sulfonates, olefin sulfonates and the like, alone or in combination, and further in combination with polyoxyethylene alkylphenol ethers, polyoxyethylene stearates, polyoxyethylene stearates, Combination use with oxyethylene, polyoxyethylene-polyoxypropylene block copolymer and the like can be mentioned.

Examples of the anionic substance include potassium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium alkanesulfonate and sodium polyoxyethylene alkyl ether phosphate.

Examples of cationic compounds include stearylamine hydrochloride, lauryltrimethylammonium chloride, trimethyloctadecylammonium chloride and the like. Examples of zwitterionic compounds include lauryl betaine and lauryl dimethylamine oxide. These emulsifiers are
They can be used alone or in combination of two or more. The amount of these emulsifiers used is appropriately 0.1 to 10% by weight based on the monomer components.

As the emulsion polymerization initiator (catalyst), 0.01 to 1.0% by weight of a peroxide initiator, an azo type initiator or a persulfate type initiator is used with respect to 100% by weight of the monomer. It

Examples of peroxide type initiators include benzoyl peroxide, lauryl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, butyl hydroperoxide and hydrogen peroxide.

Examples of the azo-based initiator include azobisisobutylnitrile, azobiscyanovalerianic acid and azobiscyanopentanoic acid.

Examples of persulfate type initiators include ammonium persulfate, potassium persulfate, sodium persulfate and the like.

In addition to the above, thioglycolic acid, butyl mercaptan, dodecyl mercaptan, octyl mercaptan, lauryl mercaptan, etc. may be appropriately used as the polymerization regulator.

The emulsion polymerization of the acrylic emulsion can be carried out by a method known per se. For example, a polymerization initiator is added to an aqueous emulsifier solution, and the monomer emulsion is added dropwise thereto at a temperature of 20 to 80 ° C. It is performed until the addition rate reaches 90% or more, preferably 95% or more.

Next, in the seed polymerization, for example, water and polyvinyl alcohol as a protective colloid are added and dissolved in a reaction vessel for polymerization, the acrylic resin emulsion obtained above is added, and acetic acid is added using a polymerization initiator. It is possible to proceed while adding the vinyl monomer. In this case, part or all of the vinyl acetate monomer may be added to the polymerization container together with the polymerization initiator, water and the acrylic emulsion, or a part or all of the vinyl acetate monomer may be continuously or intermittently added to the acrylic emulsion. It is also possible to proceed with the reaction while being added. In addition to the vinyl acetate monomer, a comonomer such as (meth) acrylic acid ester, vinyl propionate, vinyl versatate, (meth) acrylic acid, (N-methylol) acrylamide may be added for copolymerization. If necessary, a filler, a pigment, a defoaming agent, a preservative, etc. can be added at appropriate times.

PVA used as protective colloid is
Those having a saponification degree of 87 to 99% and a polymerization degree of 400 to 4000 are excellent in the balance of polymerization stability, leaving stability, low temperature film-forming property, structural viscosity, water resistance and the like, and are used alone or in combination. PV as a component to form protective colloid
In addition to A, a surfactant may be used.

The proportion of the acrylic resin emulsion used as seeds is set so that the film-forming temperature of the aqueous adhesive composition is preferably 2 ° C. or less, based on 100 parts by weight of the total solid content in the aqueous adhesive composition. It is preferably 5 to 30% by weight, preferably 8 to 25% by weight. If the proportion of the acrylic resin emulsion used is 5% by weight or less, the film-forming temperature of the aqueous adhesive composition may not be sufficiently lowered, and the viscosity becomes too high, resulting in poor workability.
The plasticizing effect also tends to diminish. On the other hand, 30% by weight
If it is above, the plasticization tends to be excessive, and the adhesive performance tends to deteriorate.

The proportion of the acrylic resin emulsion and vinyl acetate monomer used in the seed polymerization is 1: 0.4 to 20, preferably 0.8 to 15, in terms of solid content. The solid content in the aqueous adhesive composition is suitably 25 to 65% by weight based on the total amount of the aqueous adhesive composition. If it is 25% by weight or less, the viscosity of the composition may be lowered, and a problem may occur in film-forming property. If it is 65% by weight or more, the viscosity becomes too high and the polymerization stability may be deteriorated.

The temperature during the polymerization depends on the kind of the polymerization initiator used. For example, a temperature of 60 ° C. or higher is suitable for proceeding the polymerization by thermal decomposition such as ammonium persulfate. Further, in a redox system in which a peroxide and a reducing agent are combined, it can proceed at 60 ° C. or lower. The average particle size of the emulsion obtained by seed polymerization is 5
It is 0 to 500 nm, preferably 80 to 450 nm.

[0023]

The present invention will be described in detail with reference to the following examples. "Parts" and "%" are based on weight unless otherwise specified. A reaction vessel equipped with a synthetic stirrer for acrylic emulsion 1 (hereinafter referred to as AE1), a temperature controller, a reflux condenser, a thermometer and a nitrogen inlet tube was charged with 345 parts of water, and the inside was replaced with nitrogen gas. Then, 1025 parts of solution A in which 220 parts of water was dissolved in 5 parts of sodium lauryl sulfate was added, and 20 parts of water was dissolved in 4.5 parts of ammonium persulfate. Add the liquid,
A seed emulsion was prepared by reacting at 70 ° C. for 20 minutes. Next, a solution C prepared by dissolving 2.5 parts of ammonium persulfate in 70 parts of water was supplied to the reaction vessel over 3 hours, and further reacted at 85 ° C. for 1.5 hours to prepare AE1.

Acrylic resin emulsion 2 (hereinafter referred to as AE2
AE) using the monomers, water, sodium lauryl sulfate, etc. described in the column AE2 of Table 1 under the same conditions as in the preparation of the synthetic AE1.
2 was prepared.

Acrylic resin emulsion 3 (hereinafter referred to as AE3
AE3 was prepared using the monomers described in the column of AE3 in Table 1, water, sodium dodecylbenzenesulfonate, and the like under the same conditions as in the preparation of the synthetic AE1 in (1).

Acrylic resin emulsion 4 (hereinafter referred to as AE4
AE4 using the monomers described in the column AE4 of Table 1, water, and sodium lauryl sulfate under the same conditions as in the preparation of synthetic AE1
Was prepared.

Acrylic resin emulsion 5 (hereinafter referred to as AE5
AE) using the monomers, water, sodium lauryl sulfate, etc. described in the column AE5 of Table 1 under the same conditions as in the preparation of the synthetic AE1.
5 was prepared.

Acrylic resin emulsion 6 (hereinafter referred to as AE6
AE) using the monomers, water, sodium lauryl sulfate, etc. described in the column AE6 of Table 1 under the same conditions as in the preparation of the synthetic AE1.
6 was prepared.

[0029]

[Table 1]

Example 1 558 parts by weight of water was placed in the same reaction vessel used for the synthesis of AE1, and polyvinyl alcohol (saponification degree 88%,
Add 50 parts of average degree of polymerization of 500, hereinafter referred to as PVA,
After heating to 80 ° C. for dissolution, 37 parts of AE1 was added. While maintaining the temperature in the system at 80 ° C., a catalyst prepared by dissolving 1 part of ammonium persulfate in 20 parts of water and 335 parts by weight of vinyl acetate monomer were added dropwise over 3 hours to proceed with polymerization. The content (solid content) of the acrylic resin in the obtained vinyl acetate polymer emulsion was 5% by weight based on the total solid content.

Example 2 Emulsion polymerization of the vinyl acetate emulsion of Example 2 was carried out in the same manner as in Example 1 except that 492 parts of water, 50 parts of PVA, 184 parts of AE2 and 254 parts of vinyl acetate monomer were used. The content (solid content) of the acrylic resin in the vinyl acetate polymer emulsion was 25% by weight.

Example 3 The vinyl acetate emulsion of Example 3 was emulsion polymerized in the same manner as in Example 1 except that 548 parts of water, 50 parts of PVA, 59 parts of AE3 and 323 parts of vinyl acetate monomer were used. The content (solid content) of the acrylic resin in the vinyl acetate emulsion was 8% by weight.

Example 4 A vinyl acetate emulsion was emulsion polymerized in the same manner as in Example 1 except that 530 parts of water, 50 parts of PVA, 100 parts of AE4 and 300 parts of vinyl acetate monomer were used. The content (solid content) of the acrylic resin in the vinyl acetate emulsion was 14% by weight.

Example 5 A vinyl acetate emulsion was emulsion polymerized under the same conditions as in Example 1 except that 476 parts of water, 50 parts of PVA, 221 parts of AE5 and 233 parts of vinyl acetate monomer were used. The content (solid content) of the acrylic resin in the vinyl acetate emulsion was 30% by weight.

Comparative Example 1 The vinyl acetate emulsion of Comparative Example 1 was emulsion polymerized in the same manner as in Example 1 except that 530 parts of water, 50 parts of PVA, 100 parts of AE6 and 300 parts of vinyl acetate monomer were used. The content of acrylic resin in the vinyl acetate emulsion was 14% by weight based on the total solid content.

Comparative Example 2 The vinyl acetate emulsion of Comparative Example 2 was emulsion polymerized in the same manner as in Example 1 except that 566 parts of water, 50 parts of PVA, 20 parts of AE1 and 344 parts of vinyl acetate monomer were used. The content of acrylic resin in the vinyl acetate emulsion was 3% by weight based on the total solid content.

Comparative Example 3 The vinyl acetate emulsion of Comparative Example 3 was emulsion polymerized in the same manner as in Example 1 except that 462 parts of water, 50 parts of PVA, 250 parts of AE3 and 218 parts of vinyl acetate monomer were used. The content of acrylic resin in the vinyl acetate emulsion was 34% by weight based on the total solid content.

Comparative Example 4 552 parts of water and 50 parts of PVA (saponification degree 88%, average degree of polymerization 500) were heated to 80 ° C. in the reaction vessel used in Example 1 to dissolve them, and then the temperature was changed to 80 ° C. The polymerization catalyst (a solution of 1 part of ammonium persulfate dissolved in 20 parts of water) and 328 parts of vinyl acetate monomer were added dropwise over 3 hours to maintain emulsion polymerization. After completion of the reaction, 50 parts of dibutyl phthalate (hereinafter referred to as DBP) was mixed as a plasticizer to prepare an emulsion of Comparative Example 4.

Test Example 1 The vinyl acetate emulsions prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were used to measure the normal adhesive strength, water resistant adhesive strength, initial adhesive strength and film forming temperature, and the results are shown in Table 2. I got the result.

[0040]

[Table 2] (1) Viscosity indicates a value measured at 25 ° C. and 10 rotations using a BH type viscometer. (2) Measuring method of adhesive strength and film forming temperature (° C)

Adhesive force measurement method: Using adherends according to JIS K 6852 and test pieces adhered according to the method of preparing test pieces, according to JIS K6804, normal state and water resistance (soaking in water at 30 ° C. for 3 hours) ) Tested and measured. Measuring method of film forming temperature (° C.): Measured at the minimum film forming temperature specified in JIS K6804. Initial adhesive strength measurement method: 5.5 mm thick plywood (Lauan material), 12 mm thick medium density fiberboard (MDF) and 5.5 mm thick plywood (Lauan material) are laminated as shown in FIG. Bonded by.
The amount of adhesive applied is 150 g / m ² (one side of MDF applied), and the adhesion area is 80 mm × 80 mm, 23 ° C., 0.5.
It was clamped at MPa for 10 minutes, and immediately after releasing the clamp, the adhesive force was measured by an Instron tensile tester.

[0042]

EFFECTS OF THE INVENTION The water-based adhesive composition of the present invention has excellent initial adhesive strength, normal adhesive strength, and water-resistant adhesive strength, and does not increase viscosity even at low temperatures and has excellent film-forming properties. It can be used for various purposes without problems. Moreover, since it does not contain a plasticizer such as dibutyl phthalate, which is suspected to have an endocrine disrupting action, it can be used by the user as an adhesive in various applications such as woodworking, paper processing, and fiber processing with peace of mind.

[0043]

[Brief description of drawings]

FIG. 1 is a perspective view of a plywood used for measuring an initial adhesive force.

[Explanation of symbols]

1.5.5 mm thick plywood 2.12 mm thick MDF 3.5.5mm thick plywood The arrow indicates the split load direction.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuki Kaede             24 Fukami, Kamigatsu-ji, Jinmeji-cho, Kaifu-gun, Aichi Prefecture             Address Aika Industry Co., Ltd. (72) Inventor Naomi Ishii             960 Shimokokura, Kashiwara-cho, Hikami-gun, Hyogo Prefecture             Tsukasei Co., Ltd. (72) Inventor Masayuki Matsumoto             960 Shimokokura, Kashiwara-cho, Hikami-gun, Hyogo Prefecture             Tsukasei Co., Ltd. F-term (reference) 4J011 KA16 KB19 KB29                 4J026 AA17 AA45 BA20 BB01 DA04                       DA07 DA14 DB04 DB08 DB14                       GA06                 4J040 DE021 DF041 DF051 DF061                       DF081 DF101 DL041 HA126                       JA03 LA02 LA08 LA11 MA08                       MA09

Claims (5)

[Claims] 1. An aqueous adhesive composition comprising a vinyl acetate resin emulsion obtained by seed polymerization of an acrylic resin emulsion with a vinyl acetate monomer. 2. The water-based adhesive composition according to claim 1, wherein the acrylic resin has a glass transition temperature of 0 ° C. or lower. 3. Acrylic resin is used in an amount of 5 to 3 based on the whole solid matter.
The aqueous adhesive composition according to claim 1, which contains 0% by weight. 4. The aqueous adhesive composition according to claim 1, wherein the weight ratio of the acrylic resin and the vinyl acetate resin is 1: 0.4 to 20. 5. The water-based adhesive composition according to any one of claims 1 to 4, wherein a film forming temperature according to JIS K6804 is 2 ° C. or lower.