JPS627778A - Adhesive composition - Google Patents

Abstract

PURPOSE:The titled composition capable of bonding wood with a water content in a wide range, having a small change in viscosity of blended paste with time, containing a formaldehyde condensed resin, aqueous latex, isocyanate compound, maize protein and urea in a specific ratio. CONSTITUTION:The aimed composition containing (A) 100pts.wt. formaldehyde condensed resin(mixture of phenolic formaldehyde resin obtained by reacting 1mol phenol with 1.5-3.0mols formaldehyde at 8.0-11.0pH and amino resin) having 1-25wt% phenol, (B) 2-40pts.wt. aqueous latex, (C) 1-30pts.wt. isocyanate compound (e.g., tolylene diisocyanate, etc.), (D)2-50pts.wt. maize protein containing >=60wt% prolamine and (E) 0.2-5pts.wt. urea.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for bonding wood, can bond wood with a wide range of moisture content, has good workability in use, and is excellent in economy. Regarding adhesives.

[Conventional technology]

Currently, formaldehyde-based condensation resins are used in the production of plywood, but in order to develop sufficient adhesive performance, the veneer used must be sufficiently dried, and the moisture content of the veneer is usually kept below 10% by weight. It is necessary to control the However, the amount of moisture that logs retain varies;
Furthermore, since the ease of drying varies depending on the type of wood, the moisture content of the veneer after drying is widely distributed, which in turn causes the adhesive strength of the manufactured plywood to fluctuate greatly, making it impossible to obtain plywood of stable quality. There was a problem. Also, if you dry too much,
Depending on the type of raw wood used, the veneer may warp or twist, making it unsuitable for normal plywood production equipment, or the veneer may crack, making it unusable.

In order to solve this problem, for example, when using high moisture content veneer, there are methods to reduce the amount of filler such as wheat flour and water added to the adhesive, and addition of soybean flour, powder, corn protein, etc. Although methods have been used in which the bonding time is increased or the heat-pressing time is lengthened, adhesion strength sufficient for practical use has not yet been achieved.

Furthermore, Japanese Patent Publication No. 57-19148 discloses an adhesive comprising a compound having an isocyanate group dissolved in a hydrophobic organic solvent and a surfactant in an aqueous emulsion.
It is stated that in some cases, a formaldehyde-based condensation resin can be used in combination. However, although this method is effective for adhering wood with a high moisture content, it is not sufficient, and since the main component is an aqueous emulsion, when adhering wood with a low moisture content, it is difficult to bond the adhesive after applying the adhesive. If the time required to press the adhesive is long, or if the adhesive is applied to hot wood, the adhesive layer tends to dry out, resulting in the problem of so-called dry adhesion, where sufficient adhesive strength is not developed. There is. Furthermore, since the main component is water-based latex, there is also a problem in terms of economic efficiency.

He discovered that an adhesive composition containing formaldehyde thread, water-based latex, incyanate compound, and protein in specific proportions had excellent performance, and filed a patent application (Japanese Patent Application No. 59-65850). ).

[Problem that the invention seeks to solve]

By using the above adhesive composition, it became possible to bond wood having a wide range of moisture contents, and problems such as dry adhesion did not occur, but it was found that such an adhesive composition had poor workability. That is, the viscosity of such adhesives changes significantly over time after the formulation is adjusted, and the increase in viscosity tends to impede application control, especially under high temperatures in summer, which is a problem in terms of work.

In addition, since it has thixotropic flow characteristics, it tends to exhibit a higher viscosity when it is left standing than when it is stirred.

Therefore, in areas where the flow rate is slow in the adhesive supply line or where stress is not easily applied to the adhesive, replacement with lower viscosity adhesives is less likely to occur and the adhesive remains for a long time, which tends to exacerbate the viscosity increase problem mentioned above. There is also a problem.

[Means for solving problems]

As a result of various studies aimed at solving the above-mentioned problems, the present inventor discovered that urea has an extremely large improvement effect on the stability and structural viscosity of these adhesives, and has thus arrived at the present invention. be.

That is, in the present invention, (1) 100 parts by weight of a formaldehyde condensation resin containing 1 to 25% by weight of phenol;
■ 2 to 40 parts by weight of aqueous Latinx, ■ 1 to 30 parts by weight of incyanate compound, ■ 2 to 50 parts by weight of corn starch containing 60 parts by weight or more of prolamin, ■ 0.2 to 50 parts by weight of urea
This is an adhesive composition containing 5 parts by weight.

The formaldehyde condensation resin containing 1 to 25% by weight of phenol in the present invention is a phenol formaldehyde condensation resin such as urea phenol formaldehyde cocondensation resin, melamine phenol formaldehyde cocondensation resin, and urea melamine pheno-formaldehyde cocondensation resin. A condensation resin with a phenol content of 1 to 25% by weight, or a phenol formaldehyde resin or the above phenol formaldehyde condensation resin and a urea formaldehyde resin, a melamine formaldehyde resin,
A formaldehyde condensation resin mixture with an amino resin such as urea melamine formaldehyde resin, in which the content of phenol in the mixture is 1 to 25% by weight, and usually has a nonvolatile content of 40 to 70% by weight. means. Preferably, a formaldehyde-based condensation resin obtained by mixing a phenol-formaldehyde resin obtained by reacting 1.5 to 3.0 moles of formaldehyde with 1 mole of phenol at pH 8.0 to 11.0 and an amino resin, more preferably is a urea-formaldehyde resin obtained by reacting such a phenol formaldehyde resin with an amino resin of 1.0 to 1.8 mol of cyformaldehyde per 1 mol of urea and/or 1.5 to 3.0 mol of formaldehyde per 1 mol of melamine. It is a formaldehyde-based condensation resin obtained by mixing melamine formaldehyde resin obtained by reacting moles. The formaldehyde condensation resin used in the present invention may be a uniform dispersion system, and when prepared by mixing, the phenol resin and/or amino resin may be in the form of powder or emulsion.

When the content of phenol is less than 1%, the adhesive composition exhibits large changes in viscosity over time and tends to exhibit thixotropic flow, which tends to cause problems in practical use. If the phenol content exceeds 25%, the curing of the adhesive composition according to the present invention will be extremely slow, and it will not be able to cure sufficiently under the curing conditions under which it is generally used. When the pH value of the blended glue is lowered, partial aggregation and gelation occur, making it inconvenient to use as an adhesive. In addition, when preparing a formaldehyde-based condensation resin with a phenol content of 1 to 25% by weight by mixing,
As for the phenol-formaldehyde resin used, the number of moles of formaldehyde per mole of phenol is 1.
5 to 3.0 is good, and the pH during resin production is 8.0 to 11.
．． 0i: (Good. When the number of moles of formaldehyde per mole of 2' phenol is less than 1.5 and/or when the pH during resin production is less than 8.0, the resulting phenolic resin has poor water solubility, It has the disadvantage that it is difficult to obtain a uniform composition when preparing the adhesive composition according to the present invention.

Further, when the number of moles of formaldehyde per mole of phenol exceeds 30, when the adhesive composition according to the present invention is prepared, the composition increases in viscosity over time and has a strong formalin odor, which causes practical problems. If the pH at the time of resin production exceeds 11.0, the curing of the adhesive composition of the present invention will be delayed, and sufficient curing will not be obtained under the curing conditions commonly used, and adhesive strength will not be developed.

The amino resin used to prepare a formaldehyde-based condensation resin having a phenol content of 1 to 25% by weight by mixing is urea-formaldehyde obtained by reacting 1 mole of urea with 1.0 to 1.8 moles or less of formaldehyde. It is desirable to use a melamine-formaldehyde resin obtained by reacting 15 to 3.0 moles of formaldehyde with 1 mole of resin and/or melamine.

When formaldehyde is less than 1.8 mole per mole of urea and when formaldehyde is less than 3.8 mole per mole of melamine.
If it exceeds 0 mol, the adhesive composition not only has a strong formalin odor but also greatly thickens over time, making it impractical. Also, the number of moles of formaldehyde per mole of melamine is 1.
If it is less than 5, a problem arises in that adhesive strength is not sufficiently developed.

In the present invention, the aqueous latex refers to a latex obtained by copolymerizing a conjugated diene such as butadiene or isoprene with a monomer copolymerized therewith, such as various vinyl hexamers such as styrene, methyl methacrylate, or acrylonitrile, chloroprene latex, or butyl rubber. latex, polyvinyl chloride emulsion, polybutadiene latex, ethylene vinyl acetate copolymer emulsion,
polyvinyl acetate emulsion, or these latexes containing a carboxyl group, an N-methylol group, an N-alkoxymethyl group, a glycidyl group, a β-methylglycidyl group, a hydroxyl group, an amino group, an amide group, and an acid anhydride group. It includes a so-called modified latex obtained by emulsion polymerization of at least one reactive monomer having at least one crosslinking reactive group in its side chain. Furthermore, two or more types of aqueous latex may be used in combination.

Furthermore, in the present invention, the mixing ratio of () aqueous latex to (1) formaldehyde condensed resin containing 1 to 25 parts by weight of phenol is 02 to 100 parts by weight.
It should be 40 parts by weight, preferably in the range 3 to 35 parts by weight.

If the blending ratio is less than 2 parts by weight, adhesion to high moisture content wood will be insufficient, punctures may occur during plywood production, and only extremely low adhesion can be expected. If the blending ratio exceeds 40 parts by weight, when using wood with low moisture content or high temperature wood, or when the blended glue is deposited for a long time after application and before metal pressure, This causes a so-called dry adhesion problem in which the adhesive layer dries and does not exhibit sufficient adhesive strength.

Furthermore, the isocyanate compound referred to in the present invention may be any compound containing two or more incyanate groups in the molecule, such as tolylene diisocyanate (TDI),
4-4'-Diphenolmethane diisocyanate (MD
I), hexamethylene diisocyanate (HMDI
), xylene diisocyanate (MDI), inphorone diisocyanate (IDI), polymethylene polyphenyl polyisocyanate (polymeric MDI), and the like.

Further, as compounds having an incyanate group, for example,
Mixtures of polyisocyanates and polyols, prepolymers, i.e., NCO-terminated prepolymers prepolymerized with polyol and excess polyinsyanate, or OH-terminated prepolymers prepolymerized with excess polyol, in which the polyisocyanate is used There is no problem even if a polymer obtained by adding an excess amount is used.

The amount of the incyanate compound in the present invention must be 1 to 60 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the formaldehyde condensation resin (2). If the amount of the incyanate compound is less than 1 part by weight, good adhesion to wood with a high moisture content as mentioned in the present invention cannot be expected, and if it exceeds 30 parts by weight, the viscosity of the adhesive after compounding may increase over time. It is not practical because it is large and has poor economic efficiency. As for the addition method, the incyanate compound may be added alone or after being diluted in a suitable solvent. Alternatively, the incyanate compound may be emulsified and added.

The corn protein used in the present invention is a protein contained in corn, and a typical example is gluten meal, which is obtained as a by-product when starch is extracted from corn, and contains 60% by weight or more of prolamin. It includes. The manufacturing method includes, for example, soaking corn in an aqueous sulfite solution and crushing it in a crusher to separate and remove the germ, and then grinding it in a crusher to separate a milky substance. Next, starch is separated from the emulsion, and the remaining liquid is concentrated, filtered, dried,
By grinding, a gluten meal is obtained, which usually contains 60 to 80% by weight of prolamins, and the remainder consists of starch, ash, and water. When using a large amount of corn flour with a low protein content to obtain adhesive properties for wood with a high moisture content, the fluidity of the blended glue deteriorates and the viscosity increases over time, causing problems for practical use. The prolamin content should be at least 60% by weight in order to occur. It is desirable that the corn protein has a particle size of 80 mesh or less in order to improve miscibility with the blended powder and uniform application of the blended paste.

The corn protein in the present invention contains 1 to 1 phenol.
Formaldehyde condensation resin 100 containing 25% by weight
Must be added in an amount of 2 to 50 parts by weight,
Desirably, it is 5 to 30 parts by weight. If the amount added is less than 2 parts by weight, the adhesion to wood with a high moisture content as mentioned in the present invention will be poor, and if it exceeds 50 parts by weight, the fluidity of the blended glue will be impaired, or the roll spreader used in commonly used - This causes the problem that the applicability is significantly poor. Corn protein may be added alone at the time of blending, or may be mixed in advance with a filler added at the time of blending.

In the present invention, 0.2 parts by weight of urea is added to 100 parts by weight of formaldehyde resin containing 1 to 25% by weight of phenol.
Add up to 5 parts by weight, preferably 0.5 to 3.0 parts by weight. The addition of urea not only suppresses the conventionally known increase in viscosity of adhesive compositions over time, but also improves fluidity when the stress applied to the adhesive is small, making it less likely to stagnate in equipment. There is an advantage. It is well known that urea has the effect of reducing free formalin, for example, but this advantage of the present invention was completely unknown and was discovered for the first time by the present inventor. . If less than 0.2 parts by weight of urea is added to 100 parts by weight of water-soluble formaldehyde resin containing 1 to 25% by weight of phenol, the above-mentioned advantages cannot be obtained, and if more than 5 parts by weight is added. , the water-resistant adhesive strength decreases.

In carrying out the present invention, a method is adopted in which water-based latex, incyanate compound, corn protein, urea, commonly used fillers such as wheat flour, rice flour, and talc, water, and a hardening agent are added and mixed to formaldehyde-based condensation resin. be done. The mixing order is not particularly limited, and the stirring time during mixing, the finished viscosity of the blended composition, etc. may be controlled under the same conditions as in a normal method. In the practice of the present invention, in addition to wheat flour as a bulking agent conventionally used in plywood production, coconut flour, walnut flour, barley flour, rice flour, cornstarch, wood flour, talc, clay, etc. can be used. . Furthermore, polyvinyl alcohol is added for the purpose of improving temporary adhesion.
A water-retaining polymer compound and a deliquescent inorganic substance may be added to prevent dry adhesion.

Further, the amount of adhesive composition applied and bonding conditions such as cold pressure and hot pressure can all be the same as usual conditions.

The fluidity of the compounded glue obtained by the present invention is equivalent to that of commonly used adhesives made by adding fillers, water, hardening agents, etc. to formaldehyde-based condensation resins, so it can be used in commonly used mixers, spreaders, presses, etc. It can be used with equipment such as

〔Example〕

Next, the present invention will be explained by examples. Departments and sections are based on weight unless otherwise specified.

Reference Example 1 94 parts of phenol and 200 parts of 67% formalin were adjusted to pH 10.5 with a 48% caustic soda aqueous solution, reacted at 85° C. for 2 hours with stirring, and cooled.

The nonvolatile content of the obtained phenol resin was 47.2%. Hereinafter, this resin will be abbreviated as PFL.

Reference Example 2 120 parts of urea and 325 parts of 67% formalin were adjusted to pH Z5 with a 20% aqueous solution of caustic soda, heated with stirring and reacted at 85°C for 30 minutes, and then adjusted to pH 5 using an aqueous solution of 40% thiacetic acid. The temperature was adjusted to .0 and the reaction was carried out at 85°C for 60 minutes. After that, the pH was adjusted to 7.0 with a 20% caustic soda aqueous solution, 45 parts of urea was added, and the mixture was reacted at 75°C for 30 minutes.
The pH was adjusted to 8.0 and cooled. The nonvolatile content of the obtained urea resin was 52.3%. Hereinafter, this resin will be abbreviated as UFl.

Reference example 3 250 parts of melamine, 450 parts of 37% formalin at 20%
The pH was adjusted to 10.0 with an aqueous caustic soda solution, heated with stirring, and reacted at 85°C for 2 hours, followed by cooling.

The nonvolatile content of the obtained melamine resin was 57.7%. Hereinafter, this resin will be abbreviated as MFI.

Reference example 4 94 parts of phenol, 285 parts of 67-thiformin at 48%
The pH was adjusted to 11.0 with an aqueous caustic soda solution, and the reaction was carried out at 85° C. for 2 hours with stirring, followed by cooling.

The nonvolatile content of the obtained phenol resin was 43.7%. Hereinafter, this resin will be abbreviated as PF2.

Reference Example 5 120 parts of urea and 555 parts of 57% formalin were adjusted to pH 15 with a 20% caustic soda aqueous solution, and heated with stirring to give 85%
After reacting at 85° C. for 30 minutes, the pH was adjusted to 50 using a 40° C. acetic acid aqueous solution and reacting at 85° C. for 30 minutes. Thereafter, the pH was adjusted to ZO with a 20% caustic soda aqueous solution, and 22 parts of urea was added and reacted at 75°C for 30 minutes.
H was adjusted to 8.0 and cooled. The nonvolatile content of the obtained urea resin was 50.1 inches. Hereinafter, this resin will be abbreviated as UF2.

Reference Example 6 250 parts of melamine and 585 parts of 37% formalin were adjusted to pH 10.0 with a 20% aqueous solution of caustic soda, heated with stirring, reacted at 85° C. for 2 hours, and then cooled. The nonvolatile content of the obtained melamine resin was 553%. Hereinafter, this resin will be abbreviated as MF2.

Reference Examples 7 to 9 Each mixture having the composition shown in Table 1 was placed in a tank equipped with a stirrer,
A monomer emulsion was created.

62 parts of water, 0.1 part of tetrasodium salt of ethylene diamino tetraacetic acid, 0.1 part of sodium lauryl sulfate, and 0.2 parts of potassium persulfate were placed in an autoclave equipped with a stirrer, and 10 parts of the monomer emulsion was placed in the autoclave. The mixture was transferred, heated to 80°C, and reacted for 1 hour. After 1 hour, 0.8 parts of potassium persulfate was charged together with 20 parts of water, and the remaining monomer emulsion was continuously added to the autoclave over a period of 4 hours. During this time, the autoclave was kept at 80°C. After continuing the reaction at 80° C. for an additional hour, residual monomers were removed by steam distillation, and aqueous ammonia was added to adjust the pH of the latex to 90. Below, the latex synthesized according to Reference Example 7 is Latex A1 The latex synthesized according to Reference Example 8 is Latex B1 Reference Example 9
The latex synthesized by the following is referred to as latex C.

Table-1 Examples PFl, PF2, UFl, UF'2, MFl, M synthesized in Reference Examples 1 to 6 as formaldehyde-based condensation resins
P2゜ Latex synthesized in Reference Examples 7 to 9 as aqueous latex A1 B1 C1 CR as isocyanate compound
-300 (manufactured by Mitsui Nisso Urethane Co., Ltd.).

Gluten meal (containing 70% prolamin manufactured by Shikishima Cornstarch Co., Ltd.) was ground into 80 mesh or less as corn protein, urea, flour (made by Nippon Flour Mills Co., Ltd.) and water as a filler.

Table-2 to Table-7 using ammonium chloride as a hardening agent
Adhesive compositions were prepared by mixing in the proportions shown in 1.0 mm + 2.0 mm using these adhesive compositions.
+1.0 penalty veneer composition (lauan veneer, moisture content 4% or less and 20 to 25 inches) with a coating amount of 370II/m
(both sides), cold pressure 12 kg/cd 20 minutes, hot pressure 10-A
It was manufactured under the conditions of 117° C. and 60 seconds, and its adhesive strength as Type 1 plywood was measured based on the Japanese Agricultural Standards. When plywood is manufactured with a veneer moisture content of 4 ℃ or less, cold pressing immediately after applying the adhesive composition to the veneer, followed by hot pressing (indicated as 4%-1 in the table) and 60℃ The adhesive composition was applied to a preheated veneer, left to stand for 30 minutes before cold pressing, and then cold pressing and hot pressing were performed (indicated as 4 CH 2 in the table). Evaluation was performed using two methods.

In addition, the ratio of the viscosity immediately after adjustment and the viscosity after being left at 35°C for 6 hours is used as a measure of the viscosity of the adhesive composition, and as a measure of the fluidity under low stress, the ratio of the viscosity immediately after adjustment and the viscosity after being left at 35°C for 6 hours is used as a measure of the viscosity of the adhesive composition. The yield viscosity was measured using a formula viscometer. The results are in the table-
As shown in Tables 2 to 7.

In addition, when adjusting the adhesive composition, the amount of filler and water was changed and the amount of filler and water was changed and
It was measured and adjusted to 18 to 23 poise.

〔Effect of the invention〕

The adhesive composition of the present invention has excellent performance in bonding high moisture content wood, and it is possible to produce high quality plywood even when using high moisture content veneer. In addition, even if a veneer with a low moisture content is used or a veneer with a relatively high temperature is used, the problem of so-called dry adhesion is unlikely to occur. That is, it has the advantage of being applicable to wood with a wide range of moisture content, which is of great significance when used in actual plywood production. Furthermore, the adhesive composition of the present invention has a small change in viscosity over time of the compounded glue, and
It also has excellent workability, such as the ability to apply compounded glue to veneers extremely well, and has the same fluidity as conventional formaldehyde-based resins, making it applicable to current plywood production lines. I'm here.

Furthermore, since a formaldehyde-based condensation resin can be used as the main component in the formulation, it is effective in reducing the cost of the compounded glue, and is economical enough to enable practical use in plywood production. Further, the formaldehyde-based condensation resin can be selected according to the required water resistance, and by selecting an appropriate condensation resin, it is also possible to optimize the cost of the blended glue.

Claims (3)

[Claims] (1) (a) 100 parts by weight of formaldehyde condensation resin containing 1 to 25% by weight of phenol, (b) 2 to 40 parts by weight of aqueous latex, (c) 1 to 30 parts by weight of isocyanate compound, and (d) 2 to 50 parts by weight of corn starch containing 60% by weight or more of prolamins, (e)
An adhesive composition comprising 0.2 to 5 parts by weight of urea. (2) A formaldehyde condensation resin containing 1 to 25% by weight of phenol is obtained by reacting 1 mole of phenol with 1.5 to 3.0 moles of formaldehyde at pH 8.0 to 11.0, and a phenol formaldehyde resin and an amino acid The adhesive composition according to claim 1, which is a mixture of resins. (3) A urea-formaldehyde resin obtained by reacting an amino resin with 1 mole of urea and 1.8 moles or less of formaldehyde, and/or a melamine obtained by reacting 1 mole of melamine with 1.5 to 3.0 moles of formaldehyde. The adhesive composition according to claim 2, which is a formaldehyde resin.