JP2001107006A - Aqueous adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aqueous adhesives which excel in low temperature film- formability, quick exhibition of adhesive strength, adhesive strength, water- resistant adhesive strength, and boiling water-resistant adhesive strength and can suitably be used as the wood adhesive. SOLUTION: Aqueous adhesives comprise (A) an emulsion obtained by seed polymerization of 100-600 pts.wt., based on 100 pts.wt. solids content in an ethylene/vinyl acetate copolymer based resin emulsion having an ethylene content of 10-45 wt.%, sum of vinyl acetate and 0-40 pts.wt., based on 100 pts.wt. vinyl acetate, other vinyl polymerizable monomers in the presence of a polyvinyl alcohol aqueous solution and an ethylene/vinyl acetate copolymer based resin emulsion, (B) an aqueous solution containing a water-soluble polymer such as polyvinyl alcohol, (C) a filler to react with an isocyanate compound, and (D) a polyvalent isocyanate compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention can be suitably used as an adhesive for wood having excellent low-temperature film-forming properties, rapid development of adhesive strength, adhesive strength, water-resistant adhesive strength, and boiling adhesive strength. It relates to a water-based adhesive.

[0002]

2. Description of the Related Art An aqueous polymer isocyanate adhesive comprising an aqueous polymer aqueous solution and / or an aqueous emulsion and / or an aqueous latex, an inorganic filler and an isocyanate compound does not contain formaldehyde and has a temperature of 0 ° C.
It is widely used as an adhesive for structural glue for JAS standard construction and use environment 2 because of its excellent water-resistant adhesive strength, which is capable of bonding at near normal temperature and for wood.

[0003]

However, in order to further improve the productivity per unit time, it is required to further shorten the pressing time required for bonding and to further improve the water-resistant and boiling-resistant adhesive strength. However, conventional aqueous polymer-isocyanate adhesives are still insufficient for these requirements. For example, when a vinyl acetate resin emulsion is used as the aqueous emulsion, the adhesive strength is quickly expressed but the water-resistant adhesive strength and the boiling adhesive strength are inferior, and the film forming temperature is high. It is necessary to add a plasticizer or a film-forming aid to adhere at room temperature.

On the other hand, when a styrene-butadiene copolymer latex is used as the aqueous latex, the room-temperature bonding performance near 0 ° C., the water-proof bonding strength, and the boiling bonding strength are excellent, but the speed of developing the bonding strength is extremely slow. It has drawbacks and is rarely used due to recent demands for increased productivity. In addition, when the ethylene-vinyl acetate copolymer resin emulsion is used as the aqueous emulsion, the room-temperature bonding performance near 0 ° C. is better than that when the vinyl acetate resin emulsion is used, but the water-resistant bonding strength and the boiling bonding resistance are sufficient. However, there was a drawback that the speed of developing the adhesive strength was inevitably lower than that of the vinyl acetate resin emulsion.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and is an aqueous adhesive comprising the following components (A) to (D). (A) In the presence of an aqueous solution of polyvinyl alcohol and an ethylene-vinyl acetate copolymer resin emulsion having an ethylene content of 10 to 45% by weight, vinyl acetate and ethylene acetate are added per 100 parts by weight of solids in the copolymer resin emulsion. Emulsion obtained by seed polymerization of 100 to 600 parts by weight of another vinyl polymerizable monomer in total from 0 to 40 parts by weight per 100 parts by weight of vinyl acetate, and (B) a water-soluble polymer such as polyvinyl alcohol. An aqueous solution, (C) a filler that reacts with an isocyanate compound, and (D) a polyvalent isocyanate compound. Hereinafter, the present invention will be described in detail.

[0006] In the presence of polyvinyl alcohol (A), an ethylene-vinyl acetate copolymer emulsion is used as a seed emulsion, and vinyl acetate and 0 to 40 parts by weight of another vinyl-polymerizable monomer per 100 parts by weight of vinyl acetate are added. A method of seed polymerization of 100 to 600 parts by weight in total is described in JP-A-60-235875 and JP-B-60-313.
A publicly known method shown in, for example, No. 49 can be used. In the presence of an ethylene-vinyl acetate copolymer resin emulsion having an ethylene content of 10 to 45% by weight, vinyl acetate per 100 parts by weight of solids in the copolymer resin emulsion and 0 to 40 per 100 parts by weight of vinyl acetate are used. The reason why the emulsion is obtained by seed polymerization of parts by weight of another vinyl-polymerizable monomer is as follows. An ethylene-vinyl acetate copolymer having an ethylene content of less than 10% is used in an amount of from 0 to 100 parts by weight of solids in the copolymer resin emulsion, and from 0 to 100 parts by weight of vinyl acetate and vinyl acetate.
40 parts by weight of another vinyl polymerizable monomer in a total of 10
This is because, when the seed polymerization is performed outside the range of 0 to 600 parts by weight, the minimum film forming temperature becomes high, and it becomes impossible to bond at room temperature near 0 ° C. When an ethylene-vinyl acetate copolymer resin emulsion having an ethylene content of more than 45% by weight is used, the cohesive strength, which is important as an adhesive, becomes poor because the ethylene content is too large, resulting in inferior boiling adhesive strength. Results.

A wood adhesive excellent in low-temperature film-forming property, rapid expression of adhesive strength, adhesive strength, water-resistant adhesive strength and boiling-resistant adhesive strength, which are the characteristics of the present invention, is obtained in the presence of polyvinyl alcohol. A remarkable effect is exhibited by using the ethylene-vinyl acetate copolymer emulsion as a seed emulsion and using an emulsion obtained by seed polymerization and / or seed copolymerization of a vinyl compound containing vinyl acetate. The possible reason is that vinyl acetate is seed-polymerized with an ethylene-vinyl acetate copolymer emulsion,
Since the minimum film forming temperature can be lowered compared to the case where a vinyl acetate resin emulsion is used as an adhesive, there is no need to add a plasticizer or a film forming auxiliary agent, thereby providing excellent water and boiling resistance. It is presumed that it was done. Also, compared with the case where only an ethylene-vinyl acetate copolymer emulsion is used, by performing seed polymerization, a grafting reaction occurs inside the polyvinyl alcohol or the emulsion, so that an important cohesive force as an adhesive is improved, and adhesion is improved. It is considered that the speed of onset, water resistance, and boiling adhesive strength were improved.

The ethylene content used as a seed is 10
The ethylene-vinyl acetate copolymer emulsion having a non-volatile content of 30 to 74% by weight,
This can be obtained as a commercial product, or can be easily produced by a commonly used emulsion polymerization method. In order to maintain the stability of the emulsion formed during seed polymerization, it is more preferable to use polyvinyl alcohol as an aqueous solution. An emulsifier and a surfactant may be used in combination. The amount of polyvinyl alcohol to be added is preferably such that polyvinyl alcohol is 2 to 30% by weight in the solid content of the resulting emulsion. In this case, when polyvinyl alcohol is already contained in the ethylene-vinyl acetate copolymer emulsion, the total amount is used. If the amount of the polyvinyl alcohol is less than 2% by weight, the polymerization stability during seed polymerization is reduced, and
If the amount is more than 10% by weight, the polymerization stability is not further improved. The polyvinyl alcohol used is not particularly limited, and is generally a vinyl acetate emulsion or ethylene-
Polyvinyl alcohol used when polymerizing a vinyl acetate copolymer 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.

To perform seed polymerization, water and an ethylene-vinyl acetate copolymer emulsion are placed in a polymerization vessel,
Using a polymerization initiator used for ordinary radical polymerization,
The polymerization is preferably performed 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 the ethylene-vinyl acetate copolymer emulsion before the start of the polymerization, or part or all of the vinyl acetate monomer may be continuously added during the polymerization. It may be added intermittently or intermittently. The polymerization temperature depends on the type of reaction initiator used. For example, when using ammonium persulfate, potassium persulfate, or the like, 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 compound used for the seed polymerization has a vinyl carboxylate other than vinyl acetate, for example, vinyl acetate such as vinyl formate, vinyl propionate and vinyl versatate, and an alcohol residue having 1 to 8 carbon atoms. (Meth) acrylates are preferred,
Other examples include unsaturated carboxylic acid compounds such as acrylic acid, itaconic acid, maleic acid and fumaric acid, and halogenated unsaturated hydrocarbons such as vinyl chloride and vinylidene chloride.

(B) The aqueous solution containing a water-soluble polymer such as polyvinyl alcohol has an average degree of saponification of 80 to 99.5 mol% and a degree of polymerization of 300 to 4500 with respect to a water-soluble polymer such as polyvinyl alcohol. In addition to general polyvinyl alcohol, acrylamide modification having an average saponification degree of 80 to 99.5% and a polymerization degree of 300 to 4500, alkyl vinyl ether copolymerization modification, amino group modification, acetoacetyl modification, diacetone acryl modification, Modified polyvinyl alcohol such as amide modification and cationization modification, or polyvinyl alcohol which has been modified with a sulfonic acid group even when the average saponification degree is lower than 80 mol% and which can be completely or partially water-soluble can also be used. In addition, any water-soluble modified cellulose-based polymer such as hydroxyethyl cellulose or carboxymethyl-modified or any other polymer that can be completely or partially made water-soluble by heating at room temperature or by heating can be used. . The compounding amount of the water-soluble polymer such as polyvinyl alcohol is 2 to 50 in solid content per 100 parts by weight of solid content of the seed polymerization emulsion (A).
Parts are preferred. If the amount is less than 2 parts, the cross-linking density with the isocyanate compound will be insufficient, possibly resulting in poor boiling resistance. Also, if the amount exceeds 50 parts, the hydrophilicity as an adhesive becomes too high, or the boiling adhesion resistance is poor.

The filler which reacts with the isocyanate compound (C) is, for example, an inorganic filler such as calcium carbonate, talc, kaolin, clay, silica, calcium sulfate or the like which contains a small amount of water at room temperature and reacts. Any substance that reacts with the isocyanate compound, such as a substance reacting by bonding, can be used. Flour or as an organic filler as well as an inorganic filler,
Any of starches such as corn starch and tapioca denbun, coconut shell powder, and the like can be used as long as they react with the isocyanate compound. These inorganic fillers and organic fillers may be used alone or in combination. The amount of the filler that reacts with these isocyanate compounds is preferably 5 to 300 parts by weight based on 100 parts by weight of the solid content of the seed polymerization emulsion (A). If the amount is less than 5 parts, the water-based adhesive and the boiling-resistant adhesive strength may be reduced because the water-based adhesive excessively permeates the wood. Also, when the amount exceeds 300 parts by weight, the water-resistant and boiling-resistant adhesive strength is reduced due to a decrease in the ratio of components relating to adhesion.

The polyvalent isocyanate compound (D) is
A compound having two or more isocyanate groups in the molecule, for example, tolylene diisocyanate (TDI); hydrogenated TDI; trimethylolpropane-TDI adduct (for example, Desmodur, manufactured by Bayer AG)
L); triphenylmethane triisocyanate; methylenebisdiphenyl isocyanate (MDI); hydrogenated M
DI; polymerized MDI; hexamethylene diisocyanate;
Xylylene diisocyanate; 4,4-dicyclohexylmethane diisocyanate; isophorone diisocyanate, and the like. In addition, a prepolymer having a terminal group having an isocyanate group, which is previously polymerized with an excess of polyisocyanate in a polyol, may be used. These polyvalent isocyanate compounds are preferably liquid at room temperature, but can be liquefied by using together with an organic solvent or other liquid isocyanate compound which can be dissolved even at room temperature, such as solid 4,4'-methylenediphenyl diisocyanate. May be used. These polyvalent isocyanate compounds may be used alone or in combination. By blending the polyvalent isocyanate compound (D), excellent adhesive strength and water resistance are imparted. The polyvalent isocyanate compound is preferably used in an amount of 20 to 200 parts by weight per 100 parts by weight of the solid content of the seed polymerization emulsion (A). If the amount is less than 20 parts, sufficient water resistance and boiling resistance of the present invention cannot be exhibited, and if the amount exceeds 200 parts by weight, the viscosity rise after compounding is extremely fast, and the workability of bonding is significantly reduced.

The water-based adhesive of the present invention can be mixed with various additives such as a pigment such as titanium white or red iron oxide, a defoamer, a dispersant, a preservative, a thickener, and a flame retardant. In addition, if necessary, various synthetic resin emulsions such as acrylic, vinyl acetate, vinyl chloride, vinylidene chloride, styrene-acryl copolymer, vinyl acetate-acryl copolymer, styrene-butadiene rubber, Natural rubber, chloroprene rubber, polyisoprene rubber, acrylonitrile
Various rubber-based resin latexes such as butadiene-based copolymer rubber can be mixed and used. Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto.

Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Example of seed polymerization 70 parts of ion-exchanged water and 5 parts of Denkapovar B-17 (polyvinyl alcohol having an average saponification degree of 88%, manufactured by Denki Kagaku Kogyo KK) were charged into a 2 L four-necked flask at 80 ° C.
And the contents were completely dissolved. Then, 20 parts of Evadic EP-11 (ethylene-vinyl acetate copolymer emulsion having an ethylene content of 20% by weight, manufactured by Dainippon Ink and Chemicals, Inc.) was charged, 10 parts of vinyl acetate was injected, and the reaction vessel was charged with nitrogen gas. The air was completely replaced. Next, an aqueous solution in which 0.25 part of sodium bicarbonate was dissolved in 2 parts of ion-exchanged water was charged, an aqueous solution in which 0.04 part of potassium persulfate was dissolved in 3 parts of ion-exchanged water was added, and the contents were stirred at 80 ° C. for 15 minutes. Thereafter, an aqueous solution in which 90 parts of vinyl acetate and 0.36 part of potassium persulfate were dissolved in 5 parts of ion-exchanged water was added dropwise over about 3 hours. Thereafter, the mixture was aged at 80 ° C. for 1 hour to complete the polymerization, and then cooled to 30 ° C. or lower to obtain 10
After passing through a 0 mesh net, the emulsion was taken out to obtain an emulsion of a seed polymerization example. Next, 250 parts of ion-exchanged water and 50 parts of Denka Povar B-17 (polyvinyl alcohol having an average saponification degree of 88%, manufactured by Denki Kagaku Kogyo Co., Ltd.) were charged into a 2 L four-necked flask and heated to 80 ° C. Was completely dissolved. Then, after cooling the melt to 40 ° C., 300 parts of Whiteton SB (trade name, manufactured by Shiraishi Calcium Co., Ltd.), which is heavy calcium carbonate having an average particle size of about 2 μm, was added, and stirring was continued for 30 minutes. 400 parts of the emulsion of the polymerization example was added and stirred for 30 minutes. Stirring was further continued while cooling, and when the temperature became 30 ° C. or lower, the mixture was taken out through a 60-mesh net. Immediately before use, 100 parts by weight of the removed composition was treated with Millionate MR-100 manufactured by Nippon Polyurethane Industry Co., Ltd. (viscosity 125 mPa at 25 ° C. containing 31% by weight of isocyanate groups).
(S) of polymeric methylene diphenyl diisocyanate (15 parts by weight) was mixed and stirred to obtain an aqueous adhesive of Example 1.

[0016]

Example 2 Example of seed polymerization In Example 1, Evadic EP of the example of seed polymerization was used.
An emulsion of a seed polymerization example was obtained in exactly the same manner as the seed polymerization example, except that the charged amount of −11 was changed to 40 parts instead of 20 parts. Except for using this emulsion, it was produced in the same manner as in Example 1 to obtain a water-based adhesive of Example.

[0017]

Example 3 Example of seed polymerization 70 parts of ion-exchanged water and 5 parts of Denkapovar B-17 (polyvinyl alcohol having an average saponification degree of 88%, manufactured by Denki Kagaku Kogyo Co., Ltd.) were charged into a 2 L four-necked flask at 80 ° C.
And the contents were completely dissolved. Then Denka EVA
20 parts of Tex # 55 (ethylene-vinyl acetate copolymer emulsion having an ethylene content of 22% by weight and a nonvolatile content of 55%) manufactured by Denki Kagaku Kogyo Co., Ltd.
Then, the air in the reaction vessel was completely replaced with nitrogen gas. Next, 0.25 parts of sodium bicarbonate was replaced with ion-exchanged water 2
The dissolved aqueous solution was charged in
Aqueous solution obtained by dissolving 3 parts by weight of ion-exchanged water was added, and the contents were stirred at 80 ° C. for 15 minutes. Then, 70 parts of vinyl acetate and a vinyl ester of versatic acid having 9 carbon atoms manufactured by Shell Chemical Co., Ltd. An aqueous solution in which 20 parts of Veova 9 (trade name) and 0.36 parts of potassium persulfate were dissolved in 5 parts of ion-exchanged water was dropped over about 3 hours. Thereafter, the mixture was aged at 80 ° C. for 1 hour to complete the polymerization, and then cooled to 30 ° C. or lower to obtain 10
After passing through a 0 mesh net, the emulsion was taken out to obtain an emulsion of a seed polymerization example. Next, a water-based adhesive was prepared in the same manner as in Example 1 except that the emulsion of the seed polymerization example was used instead of the seed polymerization example.

Table 1 shows the seed polymerization emulsion of the present invention and emulsions and latexes used in Comparative Examples.

[Table 1] Notes in Table 1 a) Polyvinyl alcohol is used as a protective colloid, and dibutyl phthalate is used as a plasticizer.
B) A vinyl acetate resin emulsion containing polyvinyl alcohol (a product of Aika Kogyo Co., Ltd.) containing polyvinyl alcohol as a protective colloid and containing neither a plasticizer nor a film-forming aid. Ethylene-vinyl acetate copolymer resin emulsion as protective colloid (Dai Nippon Ink Chemical Industry Co., Ltd.) d) Styrene-butadiene copolymer latex (Asahi Kasei Corporation)

Comparative Examples 1 to 4 Similarly, in Table 2, general emulsions which cannot be combined with all of those having good low-temperature adhesiveness, quick adhesive strength development, and excellent water and boiling resistances are shown in Table 2. And Comparative Examples 1 to 4 using latex are also shown.

Measurement Methods for Physical Properties (1) Non-volatile content was measured according to JIS K6806 4.5. (2) The viscosity indicates a value measured at 25 ° C. at 12 rotations using a BM type viscometer. (3) The minimum film forming temperature was measured according to JIS K 6804 7.6 minimum film forming temperature. (4) The pH was measured according to JIS K6806 4.7. (5) Speed of onset of adhesion A water-based adhesive having a water content of 10% was used, and both sides parallel to the coating material axis were uniformly coated with a water-based adhesive at a rate of 125 ± 25 g / m ^{2 on} each of the surfaces to be bonded. 981 to 1471 kN @ 10 to 15 kgf / c
Pressing was carried out at 20 to 25 ° C. for 20 minutes at a pressure of m ² ｝, and the pressure was released. Immediately after depressurization, JISK6806
The test specimen was finished to the shape and dimensions of the compression shear bond strength test specimen shown in FIG. 4.11 and the compression shear bond strength was measured to compare the development speed of the bond strength. (6) Compression shear bond strength Using a square mesh with a water content of 10%, water-based adhesive is uniformly applied to each of the surfaces to be bonded at a rate of 125 ± 25 g / m ^{2 so} that both sides parallel to the coating material axis coincide. The bonding surface is brought into close contact with each other so that the pressure is 981 kN {10 kgf / cm ² }.
Pressing was performed at 0 to 25 ° C. for 24 hours, and the pressure was released. Subsequently, after standing for 72 hours, the test piece was finished to the shape and dimensions of the compressive shear bond strength test piece shown in FIG. 1 of JIS K6806 4.11, and the compressive shear bond strength under normal conditions and after repeated boiling was measured. (7) JAS test of laminated wood 7-1) One lamina size has a thickness of 25 mm and a width of 100
mm, length 450mm, water content 10%, bulk density 0.7
5 g / cm ³ of the oak Masami was bonded by 5 ply lamination. 125 ± 25 g / m2 of water-based adhesive on each of the surfaces to be bonded
The adhesive surfaces are brought into close contact with each other so that the two sides parallel to the coating material axis are evenly aligned at a ratio of ² at 1471 kN ｛15 kgf.
The sample was pressed at 20 to 25 ° C. for 20 minutes at a pressure of / cm ² ｝, and depressurized. Subsequently, after standing for 72 hours, a JAS laminated timber was subjected to a constructive immersion peeling test. 7-2) One lamina size has a thickness of 22 mm and a width of 105
5 mm spruce material with a water content of 8%
ply laminate bonding. A water-based adhesive is uniformly applied to each of the surfaces to be bonded at a rate of 125 ± 25 g / m ² so that both sides parallel to the coating material axis are brought into close contact with each other so that the adhesive surfaces are adhered to each other.
Pressing was performed at a pressure of 85 kN {8 kgf / cm ² } at 20 to 25 ° C. for 20 minutes, and the pressure was released. Subsequently, after standing for 72 hours, a structural immersion peeling test and a boiling peeling test of the JAS laminated wood were performed.

Table 2 shows the compositions of Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3.

[Table 2]

Table 3 shows the evaluation results.

[Table 3]

[0023]

According to the present invention, it is possible to provide a water-based adhesive excellent in low-temperature adhesiveness, quick development of adhesive strength, water-resistant adhesive strength, and boiling-resistant adhesive strength. The adhesive of the present invention,
In particular, it can be suitably used as an adhesive for wood and plywood. Also,
In addition to bonding between woods, it can be used for bonding wood to paper, textiles, inorganic boards and the like.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Daijiro Asai 24 Fukami, Kamiyazu, Jinmeji-cho, Kaifu-gun, Aichi Prefecture F term (reference) 4J040 BA102 EF181 EF191 EF291 EF301 EF301 EF311 EF321 EF331 GA03 GA05 GA07 HA126 HA196 HA256 HA306 HA316 HA356 JA03 JB11 KA42 LA05 LA06 LA07 LA08 MA01 MA08 MA09 NA12 NA13

Claims (1)

[Claims] An aqueous adhesive comprising the following (A) to (D) (A): an aqueous solution of polyvinyl alcohol and an ethylene-vinyl acetate copolymer resin emulsion having an ethylene content of 10 to 45% by weight. 100 to 600 parts by weight of vinyl acetate and 100 to 600 parts by weight of another vinyl polymerizable monomer in total per 100 parts by weight of vinyl acetate are seed-polymerized per 100 parts by weight of solids in the copolymer resin emulsion. (B) an aqueous solution containing a water-soluble polymer such as polyvinyl alcohol, (C) a filler that reacts with an isocyanate compound, and (D) a polyvalent isocyanate compound.