JP3474303B2 - Wood adhesive - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a preserved stability, initial adhesion, relates <br/> the excellent wood adhesive bonding strength and water resistance.

[0002]

2. Description of the Related Art Unlike conventional aminoplast-based adhesives, adhesives containing water-soluble polymers, aqueous emulsions and isocyanate-based compounds as main components do not generate formalin and are compressed at room temperature for a relatively short time. Since it can obtain extremely high adhesive strength and water resistance by itself, it has been prized as an adhesive for wood (for example, JP-A-48-947).
39, 50-69139). As a similar adhesive, an aqueous adhesive composition comprising a copolymer emulsion of a hydroxyl group-containing monomer such as allyl alcohol, 2-hydroxyethyl acrylate, N-methylol acrylamide and vinyl acetate, and a divalent isocyanate compound. (JP-A-49-26346), a polyvinyl acetate emulsion containing polyvinyl alcohol as a dispersant (protective colloid), and a water-resistant adhesive composition comprising a polyvalent isocyanate compound (JP-A-3-33178).
Issue). Furthermore, it consists of an emulsion polymer stabilized with polyvinyl alcohol, the emulsion polymer producing a vinyl acetate copolymer having a glass transition temperature in the range of 10 to 40 ° C. in the first stage and 50 to 120 in the second stage. An adhesive produced by a two-step polymerization process consisting of producing a methyl methacrylate copolymer having a glass transition temperature of ℃, wherein the ratio of vinyl acetate copolymer to methyl methacrylate copolymer is in the range of 10: 1 to 10: 6 is reported. (JP-A-2-302485). Under such circumstances, in recent years, JIS for wood adhesives composed of an aqueous polymer and an isocyanate compound has been established.

However, as the objects to be bonded expand,
In some cases, it is necessary to further improve the current adhesive performance level. Specifically, higher structural durability may be required for the structural adhesive, and further improvement in initial adhesiveness may be required for individual applications. In the latter case, polyvinyl alcohol (hereinafter, PVA
However, when an aqueous emulsion of a vinyl acetate-based resin is used as a dispersant, the initial adhesiveness is improved but the water resistance is insufficient. In addition, PV, which is an aqueous polymer blended in this type of adhesive,
A also contributes significantly to the performance of the adhesive. Specifically, PVA having completely saponified or acetoacetyl groups
When used, the water-resistant adhesion is improved, but partially saponified P
Aqueous emulsion and PVA compared to using VA
However, there is a problem that the low temperature viscosity stability and the storage stability of the main agent consisting of In addition, although the conventional adhesives as described above exhibit some degree of performance, those having satisfactory performances in terms of viscosity stability of the main agent, initial adhesiveness, adhesive strength, and water resistance are not available. The current situation is that it has not been developed yet.

[0004]

[SUMMARY OF THE INVENTION The present invention, said to solve the problems in the conventional art, the storage stability of the base resin is excellent in adhesive strength and water resistance, yet initial adhesion of good wood
The purpose is to provide an adhesive for materials .

[0005]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors on the above-mentioned object, (A) a water-soluble or water-dispersible modified polyvinyl with an ethylene unit content of 1 to 24 mol%. Alcohol blended with (B) aqueous emulsion
In addition, (C) polyisocyanate compound is further added, and the solid content ratio is (A) component / (B) component = 99 /
1 to 5/95 (weight ratio), and (C) per 100 parts by weight (as solid content) of the mixture of the components (A) and (B).
The present invention has been completed by finding a wood adhesive containing 1 to 200 parts by weight of components.

The present invention also provides a wood product obtained by adhering with the above adhesive.

The water-soluble or water-dispersible modified PVA having an ethylene unit content of 1 to 24 mol% which constitutes the composition of the present invention can be obtained by saponifying a copolymer of vinyl ester and ethylene. As vinyl ester,
Examples thereof include vinyl formate, vinyl acetate, vinyl propionate and vinyl pivalate, with vinyl acetate being preferred.

The modified PVA of the present invention may be a copolymer of an ethylenically unsaturated monomer within a range not impairing the effects of the present invention. Such ethylenically unsaturated monomers, e.g., acrylic acid, methacrylic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, Lee itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl - (3-acrylamide-3-
Dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinylpyrrolidone, vinyl chloride, vinyl bromide,
Vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate,
Examples include sodium allyl sulfonate and the like. Also,
A terminal-modified PVA obtained by copolymerizing ethylene with a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid and saponifying the same can also be used. The modified PVA of the present invention is most preferably modified with ethylene only. From the viewpoint of water solubility or water dispersibility of the modified PVA, the modified P of the present invention is prepared by using a comonomer other than ethylene.
When further modified to VA, the content of the comonomer is preferably less than 2.0 mol%, more preferably less than 1.0 mol%, favorable preferable to further less than 0.5 mol%. The saponification degree of the modified PVA is preferably 50 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, although it depends on the ethylene content. In addition, modified P
The degree of polymerization of VA is preferably in the range of 100 to 8000,
300-2000 are more preferable.

The aqueous emulsion constituting the composition of the present invention comprises a conventionally known anionic, cationic, amphoteric or nonionic low molecular surfactant as a dispersant and various water-soluble polymers such as polyvinyl alcohol and hydroxyethyl cellulose. Representative of emulsion polymerization type aqueous emulsions and polyurethane emulsions obtained by emulsion polymerization of radically polymerizable ethylenically unsaturated monomers and diene monomers in an aqueous solution containing (protective colloid) alone or in combination of two or more kinds. The aqueous emulsion obtained by the post-emulsification method of the polymer is used alone or in combination of two or more kinds.

The ethylenically unsaturated monomer constituting the emulsion polymerization type aqueous emulsion dispersoid of the present invention includes olefins such as ethylene, propylene and isobutene, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and the like. Vinyl esters such as halogenated olefins, vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, vinyl pivalate, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-acrylic acid Acrylic esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, hydroxypropyl trimethyl ammonium chloride acrylate, methacryl , Methyl methacrylate, ethyl methacrylate, n- propyl methacrylate i- propyl, n- butyl methacrylate, i- butyl methacrylate, t- butyl methacrylate, 2
-Methacrylic acid esters such as ethylhexyl, dodecyl methacrylate, octadecyl methacrylate, hydroxypropyl trimethyl ammonium chloride, acrylamide, methacrylamide, N-methylol acrylamide, N, N-dimethyl acrylamide, acrylamido-2-methyl propane sulfonic acid And its sodium salt acrylamide, trimethyl-
(3-Acrylamido-3-dimethylpropyl) -ammonium chloride, 3-acrylamidopropyltrimethylammonium chloride, 3-methacrylamidopropyltrimethylammonium chloride, N-methylacrylamide, N-ethylacrylamide, diacetoneacrylamide, acrylonitrile, methacrylonitrile. , Allyl compounds such as allyl acetate and allyl chloride, styrene, α-methylstyrene, p-methylstyrene sulfonic acid and styrene-based monomers such as sodium and potassium salts thereof, and others such as N-vinylpyrrolidone The monomer of is mentioned. Examples of the diene-based monomer include butadiene, isoprene, chloroprene and the like.

In carrying out emulsion polymerization for obtaining the aqueous emulsion of the present invention, the above-mentioned monomer is added temporarily or continuously in the presence of water, the above-mentioned dispersant, and a polymerization initiator, A usual emulsion polymerization method such as heating and stirring may be carried out, or a method of continuously mixing and emulsifying a monomer with an aqueous dispersant solution and continuously adding it may be carried out.

The amount of the dispersant used in the present invention is
Although not particularly limited, it is usually 0.2 to 50 parts by weight, preferably 0.5 to 20 parts by weight, relative to 100 parts by weight of the monomer. When the amount of the dispersant is less than 0.2 parts by weight, the polymerization stability is lowered, and when it exceeds 50 parts by weight, the viscosity becomes too high.

The polymerization initiator is not particularly limited, and examples thereof include potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 2,2'-azobis (2-amidinopropane) dihydrochloride, Cumene hydroperoxide, benzoyl peroxide, isopropylbenzene peroxide and the like are used alone or in a redox system in combination with a reducing agent such as sodium bisulfite, tartaric acid, L-ascorbic acid, formaldehyde sodium sulfoxylate and ferrous sulfate. .

The composition of the present invention comprises the above (A) modified PV
A, (B) aqueous emulsion and the polyvalent isocyanate compound which is the (C) component are compounded. Where (C)
The polyvalent isocyanate compound has two or more isocyanate groups in the molecule, and for example, tolylene diisocyanate (TDI); hydrogenated TDI; trimethylolpropane-TDI adduct (for example, manufactured by Bayer Co.,
Trade name: Desmodur L); triphenylmethane triisocyanate; methylenebisdiphenyl isocyanate (MDI); hydrogenated MDI; polymerized MDI; hexamethylene diisocyanate; xylylene diisocyanate; 4,4-dicyclohexylmethane diisocyanate; isophorone diisocyanate. In addition, a prepolymer obtained by polymerizing a polyol with an excess of polyisocyanate and having an isocyanate group as an end group may be used.

The composition of the present invention comprises the above-mentioned (A) modified PV.
It comprises A, (B) aqueous emulsion and (C) polyvalent isocyanate compound. Here, (A) modified PV
The blending ratio of the (A) modified PVA and the (B) aqueous emulsion in the main agent composed of A and the (B) aqueous emulsion is (A) / (B) = 99/1 to 5/95 (weight ratio) in terms of solid content ratio. )
Is more preferable, and the range of 95/5 to 10/90 is more preferable. Further, the compounding ratio of the polyisocyanate compound as the component (C) to the main agent composed of the component ( A) and the component (B) is 100 parts by weight of the mixture of the component ( A) and the component (B) (solid content conversion). Therefore, the polyvalent isocyanate compound (C) is preferably 1 to 200 parts by weight, and particularly preferably 5 to 100 parts by weight. If the amount of the polyvalent isocyanate compound is less than this range, the adhesive strength and water resistance will be low, and if it exceeds the range, the pot life after compounding the polyvalent isocyanate will be shortened, which is not practical.

In the composition of the present invention, if necessary, starch, modified starch, oxidized starch, sodium alginate, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, maleic anhydride-
Water-soluble polymer compounds such as isobutene copolymer, maleic anhydride-styrene copolymer, maleic anhydride-methyl vinyl ether copolymer, urea-formalin resin, urea-
Thermosetting resins generally used as adhesives such as melamine-formalin resin and phenol-formalin resin can be appropriately used. Furthermore, the composition of the present invention includes clay, kaolin, talc, calcium carbonate, fillers such as wood flour, extenders such as wheat flour, boric acid, reaction accelerators such as aluminum sulfate, pigments such as titanium oxide and others. Various additives such as antiseptics, rust preventives, etc. can be appropriately added as necessary.

[0017] The adhesive of the present invention is suitable for bonding wood. The coating amount may be appropriately selected according to various situations.
Examples of the coating method include coating with a brush and coating with a roll. Drying after applying the adhesive may be drying by heating at room temperature to 200 ° C., but the adhesive of the present invention exhibits sufficient adhesive force even when dried at room temperature. The adhesive of the present invention is characterized in that it is excellent in leaving stability of the main component and excellent in both initial adhesiveness and water-resistant adhesiveness in boiling water. The drying time after applying the adhesive is preferably about 30 minutes to 5 hours. It is preferable to dry the adhesive while it is pressed.
The pressure at the time of pressing is selected in the range of 5 to ²⁰ kg / cm ² , and when the hard wood is the adherend, the higher the pressing pressure is, the softer wood is the adherend. In this case, it is preferable that the pressure is high enough not to destroy the wood.

The wood-based product of the present invention is a wood-based product bonded with the above-mentioned adhesive agent, and examples thereof include laminated wood and furniture. There is no particular limitation on the type of wood in the wood product, and examples thereof include birch, hemlock, cedar, rawan, zelkova, pelpok, rubber, oak, and the like.

[0019]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. In the examples and comparative examples,
Unless otherwise specified, "part" and "%" are based on weight. Example 1 Modified PVA having a content of ethylene units of 5.5 mol% (PV
A-1: degree of polymerization 1400, degree of saponification 99.0 mol%) 1
35 parts of 5% aqueous solution and 65 parts of calcium carbonate were mixed, and ethylene-vinyl acetate copolymer emulsion (O
M-4200, solid content concentration 55%, manufactured by Kuraray) was added to 100 parts to prepare a main agent. In addition, polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Company, trade name:
A composition was prepared by adding 30 parts of Millionate MR-100). Using this, a test was conducted under the following conditions. The results are shown in Tables 1 and 2.

[Test Conditions] 1. Stability of the main agent left to stand: The above main agent was placed in a closed container and allowed to stand in a constant temperature bath at 5 ° C and 40 ° C for 2 weeks. The state before and after leaving was observed. A: No change B: Slight increase in viscosity or sedimentation was observed. X: No gelation or fluidity of sediment. Adhesion Test An adhesion test was conducted using the above composition under the following conditions. Substrate: Hippo / Hippo (Heat) 8% Water content: 250g / m ² (both sides coating) Deposition time: 1 minute Clamping condition: 20 ° C, 24 hours, pressure 10kg / cm ² (normal strength, Repeated boiling test piece only) Measure compression shear adhesive strength according to JIS K-6852 Normal strength: Measured as it is after curing at 20 ° C for 7 days. Repeated boiling strength : After curing at 20 ° C for 7 days, test piece is placed in boiling water. After soaking for 4 hours, it was dried in air at 60 ° C. for 20 hours, further soaked in boiling water for 4 hours, then soaked in water at room temperature until cooled, and subjected to the test in a wet state. Initial adhesive strength : 10 kg / cm at 20 ° C after bonding
Pressing at ² pressure for 10 minutes, immediately measuring compression shear adhesive strength

Example 2 Modified PVA having an ethylene unit content of 7.1 mol% (PV
A-2: degree of polymerization 1700, degree of saponification 95.4 mol%) 1
35 parts of a 5% aqueous solution and 65 parts of calcium carbonate were mixed, and styrene-butadiene copolymer emulsion (D
L-612, solid content concentration 50%, manufactured by Asahi Kasei) was added to prepare a main agent. Then, 30 parts of polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Millionate MR-100) was added to prepare a composition. Using this, a test was conducted in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 3 A PVA having a mercapto group at its end (polymerization degree: 5) was placed in a glass polymerization container equipped with a stirrer, a nitrogen blowing port, and a thermometer.
00, saponification degree 88.2 mol%, content of mercapto group unit 4.5 × 10 ⁻⁵ mol / g-PVA) and 100 parts of deionized water were added and dissolved by heating. After cooling it, the pH was adjusted to 3.0 with sulfuric acid, and the temperature was raised to 70 ° C. while bubbling nitrogen. With stirring at 150 rpm, 10 parts of methyl methacrylate and 10 parts of n-butyl acrylate were added, and further 10 parts of a 1% potassium persulfate aqueous solution was added to initiate polymerization. One hour after the initiation of polymerization, 40 parts of methyl methacrylate, 38 parts of n-butyl acrylate and 2 parts of hydroxyethyl methacrylate were uniformly added dropwise over 2 hours. After the dropping was completed, the temperature was raised to 80 ° C. and the mixture was left for 1 hour. A methyl methacrylate-n-butyl acrylate-hydroxyethyl methacrylate copolymer emulsion (acrylic Em) having a solid content concentration of 48.5% was obtained. Modified PVA with an ethylene unit content of 9.0 mol% (PVA-
3: Polymerization degree 1400, saponification degree 99.2 mol%) 15%
35 parts of an aqueous solution and 65 parts of calcium carbonate were mixed, and the above-mentioned acrylic Em was added thereto to prepare a main agent. in addition,
Polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Company, trade name: Millionate MR-100) 3
A composition was prepared by adding 0 part. Using this, Example 1
The test was conducted in the same manner as. The results are shown in Tables 1 and 2.

Example 4 In Example 1, the content of ethylene units in place of PVA-1 was 2.3 mol% (PVA-4: polymerization degree 1200,
Except using 15% aqueous solution of a saponification degree of 98.0 mol%) were tested in the same manner as in Example 1. The results are shown in Table 1 and Table 2.
Shown in.

Example 5 In Example 1, a 15% aqueous solution having an ethylene unit content of 4.5 mol% (PVA-5: polymerization degree 500, saponification degree 98.5 mol%) was used in place of PVA-1. except,
The same test as in Example 1 was carried out. The results are shown in Tables 1 and 2.

Example 6 In Example 1, the content of ethylene units was 12.0 mol% instead of PVA-1 (PVA-6: degree of polymerization 500,
Except using 15% aqueous solution of saponification degree 98.5 mol%) were tested in the same manner as in Example 1. The results are shown in Table 1 and Table 2.
Shown in.

Example 7 In Example 1, the content of ethylene units in place of PVA-1 was 18.0 mol% (PVA-7: polymerization degree 700,
Degree of saponification 71.0 mole%, except for using a 15% aqueous solution of allyl sulfonate sodium 0.2 mol% modified), was tested in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 In Example 1, non-modified PVA was used instead of PVA-1.
(PVA-8: degree of polymerization 1700, degree of saponification 98.5 mol%), except using 15% aqueous, was tested in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 2 In Example 1, unmodified PVA was used instead of PVA-1.
(PVA-9: polymerization degree 1700, saponification degree 88.2 mol%), except using 15% aqueous, it was tested in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 3 In Example 1, 15% of modified PVA (PVA-10: degree of polymerization 1400, degree of saponification 98.5 mol%) having an ethylene unit content of 0.5 mol% instead of PVA-1 was used. The same test as in Example 1 was carried out except that an aqueous solution was used. The results are shown in Table 1 and Table 2.

Comparative Example 4 In Example 1, modified PVA having a content of ethylene units of 30.0 mol% instead of PVA-1 (PVA-11:
Polymerization degree 500, saponification degree 98.5 mol%, except for using a 15% aqueous solution of sodium allyl sulfonate 1.0 mol% modified), was tested in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0031]

[Table 1]

PVA-1: Content of ethylene unit 5.5
Mol%, degree of polymerization 1400, degree of saponification 99.0 mol% PVA-2: ethylene unit content 7.1 mol%, degree of polymerization 1700, degree of saponification 95.4 mol% PVA-3: content of ethylene unit 9 0.0 mol%, degree of polymerization 1400, degree of saponification 99.2 mol% PVA-4: content of ethylene units 2.3 mol%, degree of polymerization 1200, degree of saponification 98.0 mol% PVA-5: content of ethylene units Amount 4.5 mol%, degree of polymerization 500, degree of saponification 98.5 mol% PVA-6: content of ethylene unit 12.0 mol%, degree of polymerization 500, degree of saponification 98.5 mol% PVA-7: ethylene unit Content of 18.0 mol%, sodium allyl sulfonate 0.2 mol%, degree of polymerization 70
0, degree of saponification 71.0 mol% PVA-8: degree of polymerization 1700, degree of saponification 98.5 mol% PVA-9: degree of polymerization 1700, degree of saponification 88.2 mol% PVA-10: content of ethylene unit 0.1. 5 mol%, degree of polymerization 1400, degree of saponification 98.5 mol% PVA-11: content of ethylene units 30.0 mol%,
Sodium allyl sulfonate 1.0 mol%, degree of polymerization 50
0, saponification degree 98.5 mol% OM-4200: ethylene-vinyl acetate copolymer emulsion (solid content 55%) DL-612: styrene-butadiene copolymer emulsion (solid content 50%) Acrylic Em: methyl methacrylate / N-Butyl acrylate / hydroxyethyl methacrylate copolymer emulsion (solid content 48.5%)

[0033]

[Table 2]

[0034]

EFFECT OF THE INVENTION The adhesive of the present invention is excellent in leaving stability of the main component, excellent in initial adhesive strength, and dramatically improved in adhesive strength and water resistance, and can be suitably used especially for wood adhesives. .

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) C09J 175/04 C08L 29/04 C08L 101/00

Claims (2)

(57) [Claims] 1. A (A) water-soluble at a content of 1 to 24 mol% of ethylene units or water-dispersible modified polyvinyl alcohol (B) is formulated in an aqueous emulsion, further (C)
A polyisocyanate compound is blended, and (A) component / (B) component = 99/1 to 5/95 (weight ratio) in solid content ratio, and blending of (A) component and (B) component Thing 100
An adhesive for wood, which is 1 to 200 parts by weight of the component (C) per part by weight (converted to solid content). 2. A wood product obtained by adhering with the adhesive according to claim 1.