JPH1192734A - Wood adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive free from drawbacks inherent in a vinyl acetate resin emulsion and being excellent in properties such as workability, heat resistance, water resistance, storage stability and adhesiveness by incorporating a vinyl acetate resin emulsion prepared by the seed polymerization of vinyl acetate in an emulsion of an ethylene/vinyl acetate copolymer resin having a specified ethylene content. SOLUTION: The ethylene content of the ethylene/vinyl acetate copolymer resin (EVA) in the emulsion is 15-35 wt.%. In order to keep the stability of the emulsion formed in the seed polymerization, a polyvinyl alcohol(PVA) is used. The amount of EVA uses is desirably 15-40 wt.% based on the entire resin. The content of the resin contained in the vinyl acetate resin emulsion formed by the seed polymerization is 25-65 wt.% (in terms of the solid matter). The seed polymerization is carried out by charging a reactor with water and the EVA emulsion and adding a vinyl acetate monomer while polymerizing it in the presence of a polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to workability, heat resistance,
The present invention relates to a woodworking adhesive containing a vinyl acetate resin-based emulsion which is excellent in properties such as water resistance, storage stability, and adhesiveness, and which essentially does not contain a conventionally required plasticizer as a component.

[0002]

2. Description of the Related Art Vinyl acetate resin emulsions obtained by emulsion polymerization of vinyl acetate monomers using polyvinyl alcohol as a protective colloid have been widely used in adhesives, paints, paper processing, textile processing and the like. In particular, it is widely used as an adhesive for woodworking.

[0003]

As described above, vinyl acetate resin emulsions widely used for adhesives, paints and the like also have various disadvantages. That is, the viscosity has a large temperature dependency, and the viscosity is significantly increased at a low temperature such as in winter, so that the workability is deteriorated. In particular, poor film formation at low temperatures,
It is necessary to add a plasticizer such as dibutyl phthalate (DBP). Therefore, the obtained film becomes flexible by the addition of the plasticizer, but the strength is weakened and the heat resistance is reduced. In particular, when used for winter, the amount of DBP added becomes large, and this tendency becomes remarkable. Further, when the concentration is high, the viscosity rises remarkably, the workability is poor, and the handling is inconvenient.
On the other hand, if the viscosity is reduced, sedimentation and sedimentation occurs, and storage stability deteriorates. In addition, polyvinyl alcohol (PV)
Since A) is used, the resulting film has poor water resistance.

The present invention eliminates the disadvantages of the above-mentioned vinyl acetate resin emulsion and provides an adhesive for woodwork containing a vinyl acetate resin emulsion excellent in workability, heat resistance, water resistance, storage stability and adhesiveness. It is intended to provide an agent.

[0005]

That is, the present invention comprises a vinyl acetate resin-based emulsion obtained by seed-polymerizing vinyl acetate with an ethylene-vinyl acetate copolymer-based resin emulsion having an ethylene content of 15 to 35% by weight. An adhesive for woodwork, characterized in that:

In the present invention, the content of the ethylene-vinyl acetate copolymer resin is preferably 15 to 40% by weight based on the whole resin. Further, the woodworking adhesive of the present invention is characterized in that it does not contain a plasticizer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The woodworking adhesive of the present invention comprises a resin composition containing a vinyl acetate resin-based emulsion obtained by seed-polymerizing vinyl acetate with an ethylene-vinyl acetate copolymer-based resin (hereinafter, referred to as EVA) emulsion. .

In order to obtain such a vinyl acetate resin emulsion, an EVA emulsion is used as a seed.
The vinyl acetate monomer may be seed polymerized. Specifically, it is preferable to add a vinyl acetate monomer to the EVA emulsion and polymerize it.

The EVA emulsion of one component used is not particularly limited, but a low solid content of 10% by weight or less is industrially disadvantageous. The ethylene content in EVA is preferably from 15 to 35% by weight, particularly from 23 to 35% by weight.
Preferably it is 29% by weight. If the ethylene content is within the range, a commercially available EVA can be used. If the ethylene content is less than 15% by weight, the film forming temperature of a vinyl acetate resin-based emulsion produced by seed polymerization of a vinyl acetate monomer is undesirably high, exceeding 0 ° C. On the other hand, if the ethylene content exceeds 35% by weight, the adhesive becomes a woodworking adhesive, and the adhesive strength is undesirably lowered.

In order to maintain the stability of the emulsion formed during seed polymerization, it is preferable to add an emulsifier, a surfactant, or PVA. Especially P
VA is preferably used.

[0011] The amount of PVA to be added is such that PVA is 2 to 20 in the solid content of the vinyl acetate resin emulsion to be formed.
% Is preferred. In this case, if PVA is already contained in the EVA emulsion, the total amount is added. If the amount of PVA is less than 2% by weight, the polymerization stability during seed polymerization is reduced, and if it is more than 20% by weight, the polymerization stability is not further improved.

The PVA used is not particularly limited, and PVA generally used for polymerizing a vinyl acetate emulsion or an EVA emulsion can be used. A partially saponified product or a completely saponified product can be used alone or in combination. Further, PVAs having different molecular weights can be used in combination.

As the other component used for the seed polymerization, a vinyl acetate monomer is used. In addition to the vinyl acetate, a known component capable of copolymerizing with vinyl acetate such as vinyl propionate, vinyl versatate, and acrylic acid ester is used. Polymerization using a small amount of the monomer in combination with vinyl acetate can also be carried out within a range that does not impair the physical properties of the adhesive for woodworking.

The content of the EVA resin is preferably 15 to 40% by weight based on the total (all resins) of the vinyl acetate resin, the EVA resin and the PVA to be seed-polymerized. When the amount of the EVA resin is less than 15% by weight, not only the film formation temperature of the vinyl acetate resin-based emulsion to be formed becomes 0 ° C. or higher but also the viscosity becomes too high. If the proportion of the EVA resin exceeds 40% by weight, the adhesive strength as a woodworking adhesive is undesirably reduced.

The content of the resin contained in the vinyl acetate resin emulsion produced by the seed polymerization is desirably 25 to 65% by weight, preferably 40 to 60% by weight as a solid content. If it is less than 25% by weight, the viscosity is too low,
Conversely, if it exceeds 65% by weight, the viscosity becomes too high or the polymerization does not proceed smoothly. It is preferable to adjust the amounts of the EVA emulsion, the vinyl acetate monomer to be polymerized, and water so as to have such a ratio.

In order to perform seed polymerization, water and EVA elusion are charged into a polymerization vessel, and polymerization is preferably carried out using a polymerization initiator used for ordinary radical polymerization while adding a vinyl acetate monomer. In this case, part or all of the vinyl acetate monomer may be added to the polymerization vessel together with water and EVA elution before the start of the polymerization, or part or all of the vinyl acetate monomer may be continuously or intermittently added during the polymerization. It may be added.

The polymerization temperature depends on the type of the initiator used. For example, when using ammonium persulfate, potassium persulfate, etc., and the polymerization is promoted by the thermal decomposition of the reaction initiator, the temperature is preferably 60 ° C. or higher. Alternatively, when the polymerization is promoted by a combination of a peroxide and a reducing agent, a temperature lower than 60 ° C. is appropriate.

The vinyl acetate resin-based emulsion obtained by subjecting vinyl acetate to the EVA emulsion in this manner can be used as an adhesive for woodworking.
This vinyl acetate resin-based emulsion forms a film without a plasticizer even at 0 ° C., has a small increase in viscosity at low temperatures, and has excellent normal-state adhesiveness, heat-resistant adhesiveness as an adhesive for woodworking,
And water-resistant adhesion.

The vinyl acetate resin emulsion of the present invention can be used as a woodworking adhesive without adding a plasticizer which adversely affects the working environment and the woodworking material to be bonded. , A filler, a solvent, a pigment, a dye, a preservative, an antifoaming agent, a water-soluble polymer, and the like can be used.

The woodworking adhesive containing the vinyl acetate resin emulsion of the present invention is formed at 0 ° C. Thus, the EV of the present invention having an ethylene content of 15 to 35% by weight.
A vinyl acetate resin-based emulsion obtained by seed polymerization of vinyl acetate to emulsion A exhibits excellent film-forming properties and adhesiveness without a plasticizer as an adhesive for woodworking, has a small increase in viscosity at low temperatures, and is used in winter. Is also excellent in workability.

[0021]

The present invention will be described more specifically with reference to the following examples. A commercially available EVA emulsion can be used, but it can also be produced as shown in the following Production Examples.

Production Example 1 PVA (manufactured by Denki Kagaku Kogyo Co., Ltd.) was placed in a high-pressure reactor with a stirrer.
Combined use of trade names B-05 and B-17, weight ratio: B-0
5 / B-17 = 1/1) 2061 g and Rongalit 22
45.8 kg of pure water in which 9 g was dissolved and 30.1 vinyl acetate
8 kg was charged. The temperature in the system was 55 ° C., and 11.45 kg of ethylene was introduced and pressurized. The pressure in the system is 53k
gG / cm ² . Polymerization was carried out by continuously adding 5% ammonium persulfate and 15.6 kg of vinyl acetate. The pressure increased to 60 kgG / cm ^{2 in the} second hour of polymerization and then decreased. After about 8 hours, the polymerization was completed, and an EVA emulsion was obtained.

The solid content of the emulsion was 55.8%, and the viscosity was 4,400 mPa · s. The ethylene content in the resin was 20%. Table 1 shows the physical properties.

Production Example 2 EVA emulsion was obtained by polymerization in the same manner as in Production Example 1 except that 5.73 kg of ethylene was added intermittently after the start of polymerization. The ethylene content in the resin was 26%. Table 1 shows the physical properties.

Production Example 3 An EVA emulsion was obtained by polymerization in the same manner as in Production Example 1 except that the amount of ethylene initially added was 14.6 kg, and the amount of ethylene intermittently added after the start of polymerization was 7.95 kg. Was. The ethylene content in the resin was 31%. Table 1 shows the physical properties.

In the present invention, the ethylene content of the EVA emulsion used is preferably from 15 to 35% by weight.
For comparison in the case where the ethylene content deviates from this range, an example of the production of an EVA emulsion having a low ethylene content will be described below.

Production Example 4 Polymerization was carried out in the same manner as in Production Example 1 except that the amount of ethylene initially added was changed to 6.25 kg to obtain an EVA emulsion.
The ethylene content in the resin was 12%. Table 1 shows the physical properties.

[0028]

[Table 1]

(Note) 1) The viscosity is a value measured at 30 ° C. and 30 rotations using a BM type viscometer. 2) The average particle diameter indicates a value measured by a laser method. 3) The minimum film formation temperature is JIS K 6804 7.6.
The values measured by the minimum film forming temperature are shown. 4) The glass transition temperature indicates a value measured by DSC. 5) Commercial product A is a product of Denka EV manufactured by Denki Kagaku Kogyo Co., Ltd.
3 shows an EVA emulsion of Atex # 55. 6) Commercial product B is manufactured by Denki Kagaku Kogyo Co., Ltd., trade name Denka EV
3 shows an EVA emulsion of Atex # 56.

Next, the E obtained in Production Examples 1 to 3 and Production Example 4
An example of seed polymerization in which a VA emulsion and EVA emulsions of commercial products A and B are used as a seed (seed) emulsion and a vinyl acetate shell is used.

Example 1 344 parts by weight of water was placed in a reaction vessel equipped with a stirrer, and PVA was added.
50 parts by weight (trade name: B-17, manufactured by Denki Kagaku Kogyo KK) were added, and the mixture was heated to 80 ° C. After the PVA was completely dissolved, 200 parts by weight of the EVA emulsion of Production Example 1 was added.
When the temperature in the system was raised to 80 ° C., a catalyst (a solution in which 1 part by weight of ammonium persulfate and 20 parts by weight of sodium hydrogen carbonate were dissolved in 20 parts by weight of water) and vinyl acetate were added dropwise to carry out polymerization. The amount of vinyl acetate added was 384 parts by weight.

The film formation temperature of the produced emulsion was measured to be 0 ° C. When the viscosity at 5 ° C. was measured using a BM type viscometer, it was 110 Pa · s. Also,
The viscosity at 23 ° C. was 52 Pa · s. The ratio of the viscosity at 5 ° C. to the viscosity at 23 ° C. was 2.1 times, and the rise in viscosity at low temperature was small.

Next, the adhesive strength when the vinyl acetate resin emulsion produced in Example 1 was used as an adhesive for woodworking was measured. In the test, the compression shear adhesive strength was measured based on JIS K 6852. The test piece used was a combination of a birch material and a birch material. A normal test, a heat resistance test (60 ° C., 1 hour) and a water resistance test (30 ° C., 3 hours) were performed.

The test results are shown in Table 2. As shown in Table 2, the adhesiveness was comparable to that of a commercially available vinyl acetate emulsion containing a plasticizer (Reference Examples 1 and 2).

Comparative Example 1 Seed polymerization was carried out in the same manner as in Example 1 except that the EVA emulsion produced in Production Example 4 was used. The ratio of the viscosity at 5 ° C. to the viscosity at 23 ° C. of the resulting emulsion was as good as 2.6 times, and the results of the adhesion test were not inferior to those of commercial products, but the film formation temperature was as high as 5 ° C.

Examples 2 to 5 In Example 2, seed polymerization was carried out in the same manner as in Example 1 by using an EVA emulsion of a commercial product A (trade name: Denka EVA Tex # 55, manufactured by Denki Kagaku Kogyo KK).

In Example 3, the EVA emulsion produced in Production Example 2 was used. In Example 4, an EVA emulsion of a commercially available product B (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name Denka EVA Tex # 56) was used. Seed polymerization was carried out in the same manner as in Example 1 by using each of the EVA emulsions produced in Example 3.

The film forming temperature of the produced emulsion,
The viscosity and adhesive strength were measured in the same manner as in Example 1. The measurement results are shown in Table 2, and all were good results.

Comparative Example 2 The amount of water to be added was 386 parts by weight, and the EVA emulsion to be used was EVA emulsion of commercial product B (Denka EVA Tex # 56, manufactured by Denki Kagaku Kogyo KK), and the added amount was 100 parts by weight. Seed polymerization was carried out in the same manner as in Example 1 except that the amounts of vinyl acetate and vinyl acetate were changed to 442 parts by weight, and the resulting emulsion was measured for film formation temperature, viscosity and adhesive strength in the same manner as in Example 1. Table 2 shows the measurement results.

This emulsion was obtained by reducing the amount of the EVA emulsion, but had good adhesion. However, no film was formed at 0 ° C, and the viscosity at 5 ° C was 520P.
As high as a, there was a problem in workability.

Comparative Example 3 The amount of water to be added was 218 parts by weight, and the EVA emulsion to be used was EVA emulsion of commercial product B (trade name: Denka EVA Tex # 56, manufactured by Denki Kagaku Kogyo Co., Ltd.), and the added amount was 500 parts by weight. The seed polymerization was carried out in the same manner as in Example 1 except that the amounts of vinyl acetate and vinyl acetate were changed to 210 parts by weight, and the film formation temperature, viscosity and adhesive strength of the resulting emulsion were measured in the same manner as in Example 1. Table 2 shows the measurement results.

This emulsion had a high EVA content and was formed at 0 ° C. However, the viscosity at 5 ℃ is 15P
a · s was a little high. In addition, the adhesiveness is reduced, the normal adhesive strength, heat and water resistant adhesive strength are significantly reduced,
The value was lower than that of the commercially available products (Reference Examples 1 and 2).

Comparative Example 4 Without using the EVA emulsion, the amount of water was 498 parts by weight, the amount of PVA was 100 parts by weight, and the amount of vinyl acetate was 3 parts.
Polymerization was carried out at 80 parts by weight, and the film formation temperature and viscosity of the resulting emulsion were measured in the same manner as in Example 1. Table 2 shows the measurement results.

This emulsion did not use an EVA emulsion, and was formed at 0 ° C. However, 5 ° C
Viscosity is 2000 Pa · s and viscosity at 23 ° C is 100 Pa
-Viscosity increased sharply compared to s, and workability at low temperature was poor.

[0045]

[Table 2]

(Note) 1) EVA content is expressed by ΔEVA / (EVA + VA + PV)
A) Indicates Δ × 100 (solid content). 2) Reference Example 1 is manufactured by Konishi Co., Ltd., trade name: Bond CH150.
0 shows a homovinyl acetate resin emulsion. 3) Reference Example 2 shows a homovinyl acetate resin emulsion having a trade name of Bond CH18 manufactured by Konishi Co., Ltd.

[0047]

As described above, the adhesive containing the vinyl acetate resin emulsion obtained by seed-polymerizing vinyl acetate to the ethylene vinyl acetate copolymer resin emulsion having an ethylene content of 15 to 35% by weight according to the present invention. The agent can be used as a woodworking adhesive having excellent film forming properties, workability and adhesive strength without adding a plasticizer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuko Takeshita 4-3-3-808 Motonakayama, Funabashi City, Chiba Prefecture (72) Inventor Hiroki Yamamoto 6 Goi South Coast, Ichihara City, Chiba Prefecture Electrochemical Industry Co., Ltd. Chiba Plant (72) Inventor Kazuhiro Ote 6, Goi-minamikaigan, Ichihara-shi, Chiba Chiba Works, Chiba Pref. (72) Inventor Masami Higurashi, Goi-minamikachi, Ichihara-shi, Chiba Chiba Works, Chiba

Claims (3)

[Claims] 1. A woodworking adhesive comprising a vinyl acetate resin emulsion obtained by seed polymerization of vinyl acetate with an ethylene vinyl acetate copolymer resin emulsion having an ethylene content of 15 to 35% by weight. 2. The content of the ethylene-vinyl acetate copolymer resin is 15 to 40% by weight in the total resin.
The woodworking adhesive described. 3. The woodworking adhesive according to claim 1, which does not contain a plasticizer.