JP2756484B2 - Adhesive composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an adhesive composition, and particularly to a vinyl acetate polymer emulsion adhesive suitable as an adhesive for wood.

[Prior Art] and [Problems to be Solved] A vinyl acetate polymer emulsion adhesive using acetoacetylated polyvinyl alcohol as a protective colloid is a vinyl acetate polymer using polyvinyl alcohol not acetoacetylated as a protective colloid. It is used as an adhesive for paper, furniture, thin veneers, etc., because it has better water resistance than emulsion adhesives. However, fields such as laminated wood, where high water resistance is required, including the applications described above,
In applications such as high-grade furniture, thick veneers, and water-resistant flash boards that require water resistance, the water resistance of the emulsion tends to be insufficient in adhesion performance, and thus poses a practical problem. As a means for solving this point, at present, formalin-based resins such as urea-formalin-based resins and melamine-formalin-based resins are blended in a vinyl acetate-based polymer emulsion to improve the water resistance of the emulsion. However, these methods have the drawbacks that the pot life is short and pollution problems such as emission of formalin from furniture are caused.

On the other hand, Japanese Patent Publication No. 59-1581 discloses a vinyl acetate polymer emulsion using the acetoacetylated polyvinyl alcohol as a protective colloid, an isocyanate compound,
An adhesive composition for wood has been proposed in which an epoxy compound, a compound having a radical-forming ability, and an oxidizing agent are added as a water-resistant agent (water-resistance improving agent).

However, the addition of such a water-proofing agent deteriorates the pot life (preservability), and there is a need for a water-proofing agent that does not have these disadvantages from the viewpoint of workability. Further, when an isocyanate compound or the like is added, the adhesive force decreases with time.

JP-A-48-72235 proposes a polyvinyl acetate-based emulsion adhesive obtained by adding zirconyl nitrate and zirconyl chloride to a polyvinyl acetate-based emulsion containing a hydrophilic protective colloid.

However, adhesive compositions to which metal salts such as zirconyl nitrate and zirconyl chloride are added exhibit strong acidity at pH, cause wood contamination and deterioration, and are used in areas where water resistance is highly required. Power is weak and there is a problem.

[Problem to be Solved by the Invention] The present invention solves the disadvantages of the prior art, and in particular,
Provide an adhesive composition which is excellent in water-resistant adhesiveness and hot water-resistant adhesiveness, has little change in adhesive force with time, and is particularly useful in bonding wood, in fields where water-resistant adhesiveness and hot-water adhesiveness are highly required. The purpose is to:

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a vinyl acetate polymer emulsion containing acetoacetylated polyvinyl alcohol as a protective colloid, a composition ratio of calcium oxide and silicon dioxide (CaO / SiO ₂ ) is present in an adhesive composition containing 5/95 to 60/40 calcium silicate.

The acetoacetylated polyvinyl alcohol in the present invention can be obtained, for example, by reacting polyvinyl alcohol with diketene. The average degree of saponification and average degree of polymerization of the polyvinyl alcohol containing the acetoacetyl group are not particularly limited, but from the viewpoint of the effect as a protective colloid, the residual acetic acid group is 0.1 to 15 mol%, and the average degree of polymerization is 500 to 500. 26
A range of 00 is preferred.

Here, the content of the acetoacetyl group is suitably in the range of 0.05 to 15 mol%, preferably 2 to 8 mol%. When the content of the acetoacetyl group is less than 0.05 mol%, the contribution to the water resistance and stability of the emulsion is reduced. On the other hand, when the content of the acetoacetyl group exceeds 15 mol%, the dispersion in the emulsion polymerization is insufficient, and a homogeneous emulsion cannot be obtained, or the obtained emulsion has poor stability and is not suitable for practical use. Not preferred as a product.

Examples of the vinyl acetate polymer emulsion in the present invention include (homo) vinyl acetate resin emulsion, ethylene-vinyl acetate copolymer resin emulsion, vinyl acetate-acrylate copolymer resin emulsion, and vinyl acetate-methacrylate copolymer. Examples of the resin emulsion such as a resin emulsion containing a vinyl acetate component can be given.

The vinyl acetate polymer emulsion using acetoacetylated polyvinyl alcohol (hereinafter sometimes referred to as AA-PVA) used as a protective colloid in the present invention, for example,
Using the AA-PVA as a protective colloid, a vinyl acetate monomer alone, or in the presence of another polymerizable monomer as exemplified above, can be obtained by emulsion polymerization by a known method. it can.

The amount of AA-PVA used as the protective colloid is suitably from 6 to 20% by weight based on the solid content of the vinyl acetate polymer emulsion for the desired purpose of the present invention.

The polymerization temperature during emulsion polymerization is 60 to 80 ° C,
The reaction time is preferably 2 to 8 hours.

As the emulsion polymerization catalyst required for the polymerization, a normal emulsion polymerization catalyst can be used, and in particular, a redox catalyst is preferable, and specific examples include hydrogen peroxide and formaldehyde, zinc sulfoxylate, and peroxide. Examples include a combination of hydrogen and tartaric acid, hydrogen peroxide, ammonium peroxy acid or potassium peroxy acid and sodium metal bisulfite.

In the above polymerization, other water-soluble protective colloids such as hydroxyethyl cellulose, starch, carboxymethyl cellulose and gum arabic can be used in combination with AA-PVA.

Further, a nonionic activator, an anionic activator, or the like as an emulsifier can be used in combination with AA-modified PVA.

Further, pH adjusters such as calcium carbonate; slaked lime; acetates such as calcium acetate, sodium acetate, zinc acetate and aluminum acetate; acids such as malonic acids and β-keto acid esters; β-diketones and acid sulfites are polymerized. Can be used for

In addition, various additives used for emulsion polymerization can be used.

The calcium silicate used in the present invention is a compound having a composition in which calcium oxide (CaO) and silicon dioxide (SiO ₂ ) are bonded.

Calcium silicate includes calcium metasilicate (CaO
・ SiO ₂ ), calcium orthosilicate (dicalcium silicate, 2Ca)
O.SiO ₂ ) and tricalcium silicate (3CaO.SiO ₂ ).

Calcium silicate can be formed by firing or melting CaO and SiO ₂ at high temperatures.

As the calcium silicate in the present invention, synthetic products,
Can be used regardless of natural products.

The composition ratio of CaO and SiO ₂ of the calcium silicate is suitably CaO / SiO ₂ = 5/95 to 60/40.

When CaO / SiO ₂ = 5 or less / 95 or more, water resistance, heat-resistant adhesive strength, and holding time become short, and when CaO / SiO ₂ = 60 or more / 40 or less, the viscosity changes sharply.

The amount of the calcium silicate in the present invention is AA
The amount is 0.5 to 100 Wt parts, preferably 2 to 60 Wt parts per 100 Wt parts of the solid content of the vinyl acetate polymer emulsion using PVA chloride as a protective colloid. When the amount (addition amount) of calcium silicate is less than 0.5 Wt, the water-resistant adhesive strength and the heat-resistant adhesive strength are poor. Performance degrades, causing problems in use.

The adhesive composition of the present invention includes fillers such as clay, kaolin, talc, and wood flour; fillers such as flour and starch; boric acid; reaction accelerators such as aluminum sulfate; pigments such as titanium oxide; and preservatives. Various additives such as insecticides and rust preventives can be added as necessary.

The adhesive composition of the present invention is suitable for bonding various kinds of adhesives, and is particularly suitable for use as an adhesive composition for wood.

For example, it is useful as an adhesive in the wood field where high water resistance is required, such as laminated wood, high-quality furniture, thick veneer, and water-resistant flash board.

In addition to bonding between woods, it can be used for bonding wood to paper, textiles, inorganic plate film, and the like.

Next, the present invention will be described based on examples and comparative examples.

In the following examples, the unit is a Wt unit unless otherwise specified.

Example 1 Acetoacetylated Polyvinyl Alcohol “GOSEFIMER Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 5 (parts) Vinyl acetate monomer 35 1% aqueous potassium peroxide solution 9 Water 51 Sodium acetate 0.05 Acetoacetyl according to the above composition A vinyl acetate-based polymer emulsion containing pyridinated alcohol as a protective colloid was obtained as follows.

The preparation of the emulsion was performed by using a glass separable flask equipped with a stirrer, a dropping funnel, a cooler, and a thermometer.
Performed in aqueous solution.

First, 50 parts of a 10% acetoacetylated polyvinyl alcohol aqueous solution, 6 parts of water, 0.05 parts of sodium acetate and 3.5 parts of vinyl acetate monomer are charged into a separable flask, and the inner temperature of the separable flask is raised to 70 ° C. while stirring. Temperature.

After the internal temperature of the separable flask reached 70 ° C., dropping of a 1% aqueous potassium peracid solution was started. 9 parts of 1% potassium peroxyacid was added dropwise over 4 hours.

One hour later, the internal temperature of the separable flask was adjusted to 75 to 80 ° C, and 31.5 parts of a vinyl acetate monomer was added dropwise over 3 hours.

After dropping the vinyl acetate monomer, the inner temperature of the separable flask was aged at 75-80 ° C for 1 hour, then cooled,
An acetoacetylated vinyl acetate polymer emulsion of 948 Ps (poise) / 30 ° C. was obtained (hereinafter referred to as Em-1).

An adhesive composition was prepared by dispersing 15 parts of Chemolit ABS-3 (48% CaO, 49% SiO ₂ , manufactured by Maruwa Biochemical) as calcium silicate in 100 parts of Em-1.

Example 2. As calcium silicate, Solex CM (CaO21%,
An adhesive composition was prepared in the same manner as in Example 1 except that 3 parts of SiO _{2 (} 57%, manufactured by Tokuyama Soda Co., Ltd.) was dispersed.

Example 3 As calcium silicate, Florite R (CaO22%,
An adhesive composition was prepared in the same manner as in Example 1 except that 3 parts of SiO _{2 (} 60%, manufactured by Tokuyama Soda Co., Ltd.) was dispersed.

Comparative Example 1. In Example 1, Em- was used without using calcium silicate.
The adhesive composition had only one composition.

Comparative Example 2 An adhesive was prepared in the same manner as in Example 1 except that calcium silicate was not used and 15 parts of an isocyanate compound (trade name: Sumidur 44V-20, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was used. The composition was prepared.

Comparative Example 3. Epoxy resin emulsion [100 parts of bisphenol A liquid epoxy resin, 4 parts of nonionic emulsifier, and 100 parts of water were forcibly dispersed in 100 parts of Em-1 used in Example 1] After dispersing 35 parts, 15 parts of an MDI-based isocyanate compound (trade name: Sumidur 44V-20, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was mixed and dispersed to prepare an adhesive composition [without addition of calcium silicate].

Comparative Example 4. An adhesive composition was prepared in the same manner as in Example 1, except that 5 parts of quicklime (CaO 98% or more, first-class reagent, manufactured by Junsei Chemical Co., Ltd.) was used instead of calcium silicate in Example 1. .

Comparative Example 5. An adhesive composition was prepared in the same manner as in Example 1 except that 15 parts of silicic acid (99% or more of SiO _2, manufactured by Crystallite AI Tatsumori) was used instead of calcium silicate. It was adjusted.

Comparative Example 6. Aerosil 20 having a SiO ₂ content of 99% or more as silicic acid
An adhesive composition was prepared in the same manner as in Comparative Example 5, except that 1 part of 0 (ultrafine anhydrous silica [manufactured by Nippon Aerosil Co., Ltd.]) was used.

Comparative Example 7. 15 parts of calcium carbonate (Whiteton P-30, manufactured by Shiraishi Industry Co., Ltd.) was dispersed in 100 parts of Em-1 used in Example 1, and then the isocyanate compound 15 used in Comparative Example 3 was dispersed.
An adhesive composition in which parts were mixed and dispersed was prepared.

Comparative Example 8 An adhesive composition was prepared in the same manner as in Comparative Example 7, except that 15 parts of talc (Talc 3S, manufactured by Nippon Talc) was used instead of calcium carbonate.

Comparative Example 9 An adhesive composition was prepared in the same manner as in Comparative Example 8 except that 15 parts of kaolin clay (Burges Kaolin Clay No. 10, manufactured by Burgess Pigment) was used instead of calcium carbonate.

Comparative Example 10. An adhesive composition was prepared in the same manner as in Comparative Example 9 except that 10 parts of zirconium silicate (Micropax 20-A, manufactured by Shirasu Chemical Industry Co., Ltd.) was used instead of calcium carbonate.

Comparative Example 11. In Example 1, partially saponified PVA having an average degree of polymerization of 1700 was used instead of acetoacetylated polyvinyl alcohol.
Emulsion polymerization was carried out in the same manner as in Example 1 except that (Nippon Synthetic Chemical Industry, PVA NH-17) was used.
0Ps / 30 ° C vinyl acetate emulsion (hereinafter referred to as Em-
2).

An adhesive composition was prepared by dispersing 15 parts of Chemolit ABS-3 (48% CaO, 49% SiO ₂ , manufactured by Maruwa Biochemical) as calcium silicate in 100 parts of Em-2.

Comparative Example 12. A comparative example except that 3 parts of Solex CM (CaO 21%, SiO ₂ 57%, manufactured by Tokuyama Soda Co.) was dispersed as calcium silicate in 100 parts of Em-2 obtained in Comparative Example 11. In the same manner as in 11, an adhesive composition was prepared.

Comparative Example 13. An adhesive was prepared in the same manner as in Comparative Example 11, except that 100 parts of Em-2 obtained in Comparative Example 11 was dispersed with 3 parts of Florite R used in Example 3 as calcium silicate. The composition was prepared.

The adhesive performance and the change in adhesive force with time of the adhesive compositions shown in the above Examples and Comparative Examples were measured.

 The results are shown in Tables 1 and 2.

[Adhesion performance] test was performed under the following conditions: adhesion: 10 m / m thick rice pine wood Coating amount: 250 g / m ² (both sides coated) Pressing: 10 kg / cm ² × 2 hours, 20 ° C Raw: Bonded by leaving it at 20 ° C. for 10 days, and the test conditions were as follows.

(1) Compressive shear strength A test piece was treated under the following conditions, and measured in accordance with JIS K6806 “Aqueous polymer-isocyanate-based wood adhesive”, paragraphs 4, 11, and 1 compressive shear strength.

i> Normal condition: After preparing the test piece, perform the test in an atmosphere of 20 ° C. and 65% RH.

ii) Warm water: The test piece is immersed in warm water at 60 ± 3 ° C. for 3 hours, then immersed in room temperature water until it cools, and the test is performed in a wet state.

iii) Heat resistance: Immediately after the test piece is left in an atmosphere of 100 ± 1.5 ° C for 16 hours, the test is performed.

iv) Repeat boiling; After immersing the test piece in boiling water for 4 hours,
Dry in air at 60 ± 3 ° C for 20 hours, immerse it in boiling water for 4 hours, immerse it in water at room temperature until it cools down, and use it as it is in the wet state.

 Next, a test method of [Change in adhesive force with time] will be described.

The adhesive composition was left in an atmosphere of 20 ° C. and adhered to each day under the following conditions. Substrate: 10 m / m thick rice pine material Coating amount: 250 g / m ² (both sides coated) ) Compression; 10 kg / cm ² × 2 hours, curing at 20 ° C .; left at 20 ° C. for 10 days The test pieces were subjected to a normal state and boil-back treatment, and the compressive shear strength was measured.

From the results shown in Tables 1 and 2, it can be seen that according to the examples of the present invention, it is possible to provide an excellent adhesive which is excellent in water resistance and hot water resistance and has little change in adhesive force with time.

[Effects of the Invention] As described above, according to the present invention, it was possible to provide an excellent adhesive which is excellent in water resistance and hot water resistance, has little change in adhesive force with time, and surpasses the conventional example.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-1581 (JP, A) JP-A-57-202364 (JP, A) JP-A-57-59971 (JP, A) 18622 (JP, B1)

Claims (1)

(57) [Claims] 1. A vinyl acetate polymer emulsion containing acetoacetylated polyvinyl alcohol as a protective colloid is added to a composition of calcium oxide and silicon dioxide (CaO / Si
An adhesive composition comprising O ₂ ) containing calcium silicate of 5/95 to 60/40.