JPH07329005A - Production of plywood - Google Patents

Abstract

PURPOSE:To enhance the warm water resistance, heat boiling resistant strength of plywood by bonding hardly adhesive material plywood of a Japanese larch or the like by an adhesive containing a thermo-setting formalin-based adhesive and an adhesive composed of synthetic rubber latex in a predetermined ratio. CONSTITUTION:A thermosetting formalin-based adhesive B and synthetic rubber latex C are used as an adhesive in a ratio of B:C=100:30-50% to bond a hardly adhesive material A of a Japanese larch or the like being a plywood material. The adhesive is composed of a co-condensation resin of urea and formalin and the latex C is a copolymer of butadiene, an aromatic vinyl monomer, an acrylic monomer having an amide group and unsaturated carboxylic acid and the glass transition temp. of the latex C is set to 0-90 deg.C. The plywood produced by this method is excellent in warm water resistance and heat boiling resistant strength.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing plywood,
More specifically, it relates to a method for producing a plywood having excellent adhesive strength against hot water and boiling resistance, which uses a hard-to-adhere material such as Karamatsu, a coniferous tree typified by Douglas fir, and a southern hardwood typified by Apiton (Kruin). .

[0002]

2. Description of the Related Art Conventionally, melanty is used as a material for plywood, and an amino-based condensation resin or a phenol-based condensation resin represented by urea-based condensation resin, melamine-based condensation resin, or urea-melamine-based condensation resin as an adhesive. And blends of fillers typified by wheat flour have been used.

[0003]

However, in recent years, due to the environmental protection problem in Southeast Asia and the accompanying export restrictions on logs, the price of raw timber for meranty wood, which has been used conventionally, has risen, making it difficult to obtain high-quality timber. It's coming. Among them, plywood manufacturers have been forced to use various materials such as Southeast Asia Apiton (Kruin) Russian Kara pine and American and Canadian Douglas fir. However, coniferous trees represented by Karamatsu and Douglas fir, and southern hardwoods represented by Apiton (Kruin) are normally used when an adhesive composition containing a conventional amino-based condensation resin or phenol-based condensation resin is used as a main component. However, there is a problem in that it is difficult to meet public standards such as JAS because the hot water / boiling resistance (hereinafter abbreviated as water resistant adhesion) is insufficient.

[0004]

[Means for Solving the Problems] Even when the present inventors have used plywood materials such as softwood typified by Karamatsu and Douglas fir, which are difficult-to-adhere materials, and South Pacific hardwood typified by Apiton (Kruin), as plywood materials. , JAS with sufficient water resistant adhesive strength
We have repeatedly studied the manufacturing method of plywood that clears the standard. As a result, in order to solve the above problems, it is effective to add synthetic rubber latex to conventional amino-based condensation resin or phenol-based condensation resin. More specifically, Tg of synthetic rubber latex is generally used to improve hot water adhesive strength. It was found that the influence of the functional group monomer, which is commonly said, is extremely large. That is, it is most effective to copolymerize an acrylic monomer having an amide group in order to impart water-resistant adhesive strength, but the miscibility with wheat flour blended as an extender is hindered. However, it has been found that this miscibility can be achieved by copolymerizing an unsaturated carboxylic acid.

That is, the present invention is as follows (a) to (f). (A) At least one difficult-to-adhesive material (A) selected from larch as a material for plywood, softwood typified by Douglas fir, and Southern Ocean hardwood typified by Apiton (Kruin); thermosetting formalin as an adhesive The three components of the adhesive system (B) and the synthetic rubber latex (C) are essential, and the weight ratio of the active components of (B) and (C) is B: C = 10.
The method for manufacturing plywood is characterized in that it is 0: 3 to 50. (B) The method for producing plywood according to (ii), wherein the thermosetting formalin-based adhesive (B) is a co-condensation resin of at least one selected from urea, melamine and phenol with formalin. (C) The synthetic rubber latex (C) has (1) butadiene, (2) at least one kind of monomer selected from aromatic vinyl-based monomer, unsaturated carboxylic acid ester monomer, and acrylonitrile, and (3) amide group. (4) A method for producing plywood, which is a copolymer of an acrylic monomer and (4) an unsaturated carboxylic acid. (D) Glass transition temperature of synthetic rubber latex (C) (T
g) is 0- + 90 degreeC, The manufacturing method of the plywood as described in (A) characterized by the above-mentioned. (E) The synthetic rubber latex (C) has an amide group-containing acrylic monomer in an amount of 1 to 10 in 100 parts by weight of the total amount of the monomers.
(3) The method for producing plywood according to (3) above, wherein the plywood is copolymerized by weight. (F) The unsaturated carboxylic acid of the synthetic rubber latex (C) is copolymerized in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total amount of the monomers, (c).

Examples of the material used for the poorly-adhesive material (A) include Karamatsu, Douglas fir, and Apiton (cruin) as described above. These may be used alone or in combination of two or more kinds as a composite plywood.

Examples of the thermosetting formalin adhesive (B) include urea condensation resins, melamine condensation resins, amino condensation resins represented by urea-melamine condensation resins, and phenol condensation resins. These may be used alone or in combination of two or more. Specifically, in the plywood JAS standard, a phenol resin or a co-condensation resin of phenol and melamine and / or urea is used for special plywood, and a melamine and urea is used for T-1 and T-2 plywood. A co-condensation resin is preferable in terms of cost performance.

(2) Aromatic vinyl monomers used for emulsion polymerization of synthetic rubber latex (C) are styrene,
As unsaturated carboxylic acid ester monomers, α-methylstyrene, divinylbenzene and the like are used as methyl methacrylate, ethyl acrylate, isobutyl methacrylate, tertbutyl methacrylate, vinyl acetate, acrylonitrile, isobutyl acrylate, n-butyl acrylate, 2 ethylhexyl acrylate. Examples thereof include acrylic acid or methacrylic acid ester having 4 to 12 alkyl groups such as 2-ethylhexyl methacrylate and lauryl methacrylate. Of these, styrene is preferred because of its economy and ease of emulsion polymerization.

(3) Acryl monomers having an amide group include acrylamide, methacrylamide, maleimide, N-methylol acrylamide, N-methylol methacrylamide, N-methoxymethyl acrylamide, N-isopropoxymethyl acrylamide and N-butoxymethyl acrylamide. , N-isobutoxymethyl acrylamide, N-octyloxymethyl acrylamide, N-carboxymethyl acrylamide and the like. Among them, N-methylol acrylamide and N-methylol having a methylol group from the viewpoint of adhesive strength, warm water resistance, boiling resistance and the like. Methacrylamide is preferred.

Examples of the (4) unsaturated carboxylic acid monomer of the synthetic rubber latex (C) include acrylic acid, methacrylic acid, crotonic acid, etc. as monocarboxylic acid, and itaconic acid, maleic acid, etc. as dicarboxylic acid. Examples include fumaric acid. Among these acrylic monomers having a carboxyl group, a monocarboxylic acid is preferable because of the copolymerizability with the acrylic monomer having an amide group.

Tg of synthetic rubber latex (C) is 0 to +
90 ° C. More preferably, Tg is 30 to + 70 ° C. If Tg is less than 0 ° C, water resistant adhesive strength cannot be obtained,
If it exceeds 90 ° C, the stability during emulsion polymerization is insufficient, and in some cases there is a risk of gelation during emulsion polymerization.

The amount of the amide group-containing acrylic monomer in the synthetic rubber latex (C) is 1 to 6 parts by weight based on 100 parts by weight of the total amount of the monomers. The amount is preferably 2 to 5 parts by weight in view of the stability during emulsion polymerization and the water resistant adhesive strength. When the amount is less than 1 part by weight, the water-resistant adhesive strength cannot be obtained, and when the amount is more than 6 parts by weight, the stability during emulsion polymerization is remarkably reduced and gelation occurs during the emulsion polymerization. The unsaturated carboxylic acid monomer amount of the synthetic rubber latex (C) is 1 in 100 parts by weight of the total amount of the monomers.
10 to 10 parts by weight. It is preferably 2 to 5 parts by weight.
If the amount is less than 1 part by weight, the polymerization stability and the mechanical stability during coating will be poor. When the amount is more than 10 parts by weight, the emulsion polymerization rate is remarkably reduced, the polymerization is not completed within a predetermined emulsion polymerization time, the amount of residual monomer is increased, and the water-resistant adhesive strength is not obtained.

The pH of the synthetic rubber latex (C) is neutralized with an alkali. As the alkali, those generally used may be used, but it is preferable to use a volatile amine represented by ammonia rather than an inorganic alkali such as caustic soda for improving the hot water resistance. The pH for neutralization is 4-9, more preferably 5-8. Four
If it is less than the above, the mechanical stability cannot be obtained and a stable coating state on the adherend cannot be obtained, and if it exceeds 9, the curing of the thermosetting formalin adhesive (B) used in combination is delayed, which is not preferable.

The ratio of the thermosetting formalin adhesive (B) and the synthetic rubber latex (C) used is B: C = 100: 3 to 50, preferably 10 as the weight ratio of the active ingredients.
It is 0: 5 to 30. If it is less than 3, the water-resistant adhesive strength is not obtained, and if it exceeds 50, the miscibility with additives typified by wheat flour is remarkably reduced, and a stable coating state on an adherend by a roll coater or the like cannot be obtained. Cause trouble.

As described above, according to the method for producing plywood of the present invention, the water-resistant adhesive strength, which has been insufficient with the conventional amino-based condensation resin or phenol-based condensation resin alone, is raised to a sufficient level, and the conventional meranty plywood is obtained. It has a very high practical value as an inexpensive plywood substitute for, and its significance is significant.

The synthetic rubber latex (C) used in the present invention may be produced by an emulsion polymerization method, such as water, the above-mentioned monomer mixture, a surfactant, a chain transfer agent (polymerization degree modifier), and a radical polymerization initiator. As a surfactant, fatty acid soap, rosin acid soap, alkyl sulfonate, alkylbenzene sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl Anionic surfactants such as aryl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene sorbitan fatty acid esters, nonionic surfactants such as oxyethyleneoxypropylene block copolymers, and the like,
Usually, it is used in the anionic surfactant alone or in a mixed system of anionic surfactant and nonionic surfactant, and the proportion of the monomer mixture is generally 0.01 to 5% by weight. Examples of the chain transfer agent include mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan and mercaptoethanol, and halogenated hydrocarbons such as carbon tetrachloride. Examples of the radical polymerization initiator include persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, hydrogen peroxide, benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide and other peroxides, and 2, 2. Examples thereof include azobis compounds such as azobisisobutyronitrile, with persulfate being most preferred.

The polymerization temperature is usually in the range of 60 to 90 ° C., but low temperature redox polymerization in which a reducing agent such as sodium bisulfite, ascorbic acid (salt) and Rongalit is combined with a radical polymerization initiator is also used. be able to. If desired, a polymerization regulator such as a pH regulator such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate or the like can be added. The synthetic rubber latex (C) in the present invention contains an antiseptic agent, water, a dispersant, a defoaming agent, a film-forming aid, a plasticizer, a coloring agent, polyvinyl alcohol, and an antifreezing agent within a range that does not impair the desired effect. You may use together.

[0018]

EXAMPLES The present invention will be described below with reference to production examples, examples and comparative examples, but the present invention is not limited thereto. Parts and% in the examples are by weight unless otherwise specified. The numbers in the table represent parts by weight unless otherwise specified.

Stability indication during emulsion polymerization (results are shown in Table-1) G: Very little adherence in the flask and coarse particles (good) LP: Coarse particles GL: Gelation NP: Unreacted (large amount of residual monomer) ) Name of monomer BD: Butadiene ST: Styrene nBA: n-Butyl acrylate N-MAM: N-methylol acrylamide N-MMAM: N-methylol methacrylamide MAM: Methacrylamide AA: Acrylic acid IA: Itaconic acid HEMA: Hydroxyethyl methacrylate tDM: tert dothecil mercaptan

Production Examples 1 to 10 A mixture of a mixed monomer (excluding butadiene) and a chain transfer agent (tDM) having the composition ratios shown in Table 1 was weighed in advance, and 500 parts of distilled water and 2 parts of sodium dodecylbenzenesulfonate were used. Was added dropwise under stirring conditions to obtain a pre-emulsified monomer. Next, in a 3 liter autoclave equipped with a stirrer, 500 g of distilled water, 1 g of sodium dodecylbenzenesulfonate,
5 g of potassium persulfate was charged and sealed, the internal pressure of the autoclave was set to 5 kg / cm 2 with nitrogen, and a leak test was performed for 5 minutes, and then the pressure was reduced to 500 mmHg. After repeating this operation twice, the mixture was stirred in a nitrogen stream at a rotation speed of 250 rpm and the temperature was raised to 65 ° C. After the temperature was raised to 65 ° C. with stirring under a nitrogen blanket, a small amount of butadiene and the above-mentioned emulsifying monomer were charged in order to form seeds of emulsion, and the mixture was reacted for 30 minutes to form seeds of emulsion particles. Then, the pre-emulsified monomer was continuously added dropwise over 8 hours, the reaction of the residual monomer was carried out for 12 hours, then cooled to 40 ° C., adjusted to pH 7.5 with 14% ammonia water, and filtered through a 100 mesh wire mesh. Then, a synthetic rubber latex having a solid content of 50% was obtained. In addition, as for Production Examples 7, 8 and 10, the subsequent evaluation was not carried out because of gelation or excessive residual monomer.

[0021]

[Table 1]

Examples 1 to 10 100 parts of the resin shown in Table 2 was placed in a 1-liter flask, and synthetic rubber latex was mixed with stirring in the proportions shown in the table. Next, 15 parts of flour "Sugi" (manufactured by Nippon Milling Co., Ltd.) was added with stirring. Further, 1 part of ammonium chloride (powder) was added and mixed as a curing agent to obtain an adhesive for plywood. In the table, U-350 is a thermosetting formalin resin for T-1 (Mitsui Toatsu Chemical Co., Ltd .; melamine-urea co-condensation resin).
And U-883 is a special thermosetting formalin-based resin (manufactured by Mitsui Toatsu Chemicals, Inc .; phenol-melamine co-condensation resin). With a spreader, the adhesive for the main plywood,
Using the grades shown in Table-2, 3 per 3 mm thick veneer
After applying 5 g (core) and sandwiching with a 3 mm thick single plate (face back), press at 115 ° C. heat press at a pressing pressure of 10 Kg / cm 2 for 3 minutes and 30 seconds, cool to room temperature, and ply plywood with 3 plies Got Subsequently, the evaluation tests shown below were performed, and the results are shown in Tables 2 and 3.

[0023]

[Table 2]

[0024]

[Table 3]

Comparative Examples 1 and 6 100 parts of the resin shown in Table 2 was placed in a 1-liter flask, and then 15 parts of flour "sugi" was added with stirring. Further, 1 part of ammonium chloride (powder) was added and mixed as a curing agent to obtain an adhesive for plywood. Hereinafter, a 3-ply plywood was obtained in the same manner as in the example, and subsequently subjected to the evaluation test shown below, and the results are shown in Tables 2 and 3. Comparative Examples 2 to 5, 7 to 101 100 parts of the resin shown in Table 2 was placed in a 1-liter flask, and synthetic rubber latex was further mixed with stirring at the ratio in the table. Then 15 parts of flour "sugi" was added with stirring. Further, 1 part of ammonium chloride (powder) was added and mixed as a curing agent to obtain an adhesive for plywood. Hereinafter, a 3-ply plywood was obtained in the same manner as in the example, and subsequently subjected to the evaluation test shown below, and the results are shown in Tables 2 and 3.

<Evaluation test> 1. Workability The presence or absence of fluidity when blending flour was visually observed and displayed as shown below. ◯: Easy to mix and has fluidity and sufficient roll coater coating is possible. Δ: Mixable, but roll coater can be coated although it has high viscosity and lacks fluidity. X: Mixing is difficult and powder is left as it is, and roll coater coating is not possible. Possible

2. JAS normal state test According to "Japanese Agricultural Standards for Structural Plywood; Method of Making Test Pieces", 20 pieces of 25 mm wide test piece were cut from the sample,
An adhesive strength test was conducted. The results are shown in terms of average strength and wood fracture rate.

3. JAS T-1 test From the above sample, 2. Twenty test pieces were cut by the same method. After soaking the test piece in boiling water for 4 hours,
It was dried at a temperature of 3 ° C. for 20 hours, further dipped in boiling water for 4 hours, dipped in water at room temperature until cooled, and an adhesive strength test was performed in a wet state. The result is the average intensity,
The wood fracture rate and the number of accepted pieces were displayed. The number of passed pieces was judged according to the "Compliance criteria of test pieces" in JAS, and 90% or more of passed pieces were regarded as passed.

4. JAS special test From the above sample, 2. Twenty test pieces were cut by the same method. The test piece was dipped in boiling water for 72 hours, then dipped in water at room temperature until it was dipped, and an adhesive strength test was performed in a wet state. The results are shown in terms of average strength, wood fracture rate, and number of passing pieces. The number of passed pieces was judged according to the "Compliance criteria of test pieces" in JAS, and 90% or more of passed pieces were regarded as passed.

[0030]

EFFECTS OF THE INVENTION The plywood manufacturing method of the present invention can raise the hot water / boiling resistance, which was insufficient with conventional amino-based condensation resins or phenol-based condensation resins alone, to a level that clears the JAS standard. did it. .

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Takeshi Ito 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. Within the corporation

Claims (6)

[Claims] 1. At least one difficult-to-adhesive material (A) selected from pine pine as a plywood material, softwood typified by Douglas fir, and South Pacific hardwood typified by Apiton (cruin), and thermosetting as an adhesive. Formalin adhesive (B) and synthetic rubber latex (C) are essential, and the effective component weight ratio of (B) and (C) is B: C = 10.
The method for manufacturing plywood is characterized in that it is 0: 3 to 50. 2. The production of plywood according to claim 1, wherein the thermosetting formalin adhesive (B) is a cocondensation resin of at least one selected from urea, melamine and phenol with formalin. Method. 3. A synthetic rubber latex (C) comprising (1) butadiene and (2) at least one kind of monomer selected from aromatic vinyl monomers, unsaturated carboxylic acid ester monomers, acrylonitrile, and (3) amide groups. The method for producing plywood according to claim 1, which is a copolymer of an acrylic monomer having (4) and an unsaturated carboxylic acid (4). 4. The method for producing plywood according to claim 1, wherein the glass transition temperature (Tg) of the synthetic rubber latex (C) is 0 to + 90 ° C. 5. A synthetic rubber latex (C) containing an amide group-containing acrylic monomer in an amount of 1 in 100 parts by weight of the total amount of the monomers.
The method for producing a plywood according to claim 3, wherein 10 to 10 parts by weight are copolymerized. 6. The method for producing plywood according to claim 3, wherein the unsaturated carboxylic acid of the synthetic rubber latex (C) is copolymerized in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total amount of the monomers.