JP2007238840A - Adhesive composition for lumber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition for lumber which has excellent formability (curability) and adhesiveness and is stable against thickening of the adhesive with time. <P>SOLUTION: The adhesive composition for lumber contains (a) a resol-type phenol aldehyde resin, (b) an isocyanate compound and (c) an inorganic filler. The contents of the isocyanate compound (b) and the inorganic filler (c) are 20-100 pts.wt. and 40-100 pts.wt. respectively relative to 100 pts.wt. of the resol-type phenol aldehyde resin (a). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive composition for wood, and more particularly, to an adhesive composition for wood that is fast-curing at low temperature.

  In recent years, the utilization of coniferous resources has been considered as a material for structural plywood due to the difficulty in obtaining hardwood resources. However, softwood plywood using amino resin adhesives such as melamine / formaldehyde resin and urea / formaldehyde resin is insufficient in terms of adhesion, durability and stability, and plywood made from softwood In order to increase the reliability of the resin, it is said that it is preferable to use a phenol / formaldehyde resin adhesive having excellent adhesiveness, durability and stability.

  Conventional phenol-formaldehyde resin adhesives (hereinafter referred to as phenol adhesives) require higher temperature and longer time for hot pressing (pressing) when manufacturing plywood than amino resin adhesives. For this reason, workability is reduced, the thickness of the product after pressing is reduced, and surface deterioration is caused. Furthermore, compared with the moisture content tolerance of the amino resin adhesive, the tolerance width tends to be narrow, and as a result, the moldability (curability) tends to deteriorate.

  As a method of rapidly curing at low temperature using a phenol adhesive, if the molar ratio of formaldehyde (F) and phenol (P) (hereinafter referred to as F / P molar ratio) is 2.5 to 3.0, Although it is known that the effect can be obtained to some extent, this method is not practical because the usable time of the paste is extremely short, and formaldehyde emission amount (hereinafter referred to as F emission amount) from the produced plywood is sometimes referred to. ) Was a problem.

In addition, techniques for adding resorcinol, lignin, tannin and the like to a phenol adhesive have been proposed (see, for example, Patent Documents 1 and 2). However, these techniques have a small effect unless they are added in a large amount. If they are added in a large amount, the viscosity increase of the paste liquid before pressing becomes extremely fast, and there is a problem in productivity.
Furthermore, there is also a method of widening the moisture tolerance by simply blending an inorganic filler such as calcium carbonate to accelerate the drying of the paste liquid. However, if added in a large amount, the paste solution dries before hot pressing, resulting in poor adhesion, so the amount added was within a limited range.

  In addition, the present inventors set the F / P molar ratio of the primary reaction to a high level by sequential reaction when synthesizing the phenol resin, and added phenol when the resin viscosity reached a certain level, thereby adding F / P mole. By lowering the ratio and blending the isocyanate when preparing the paste liquid, it was possible to produce at a set temperature of 125 ° C. and a pressure time of 25 seconds / mm (see, for example, Patent Document 3). . However, when using a high moisture content veneer whose veneer moisture content exceeds 16%, a conventional melamine / formaldehyde resin adhesive (hereinafter referred to as melamine adhesion) is used at a hot plate temperature of 115 ° C. where the vapor pressure can be kept low. It was still difficult to produce at a hot pressing time of 20 seconds / mm, which can maintain productivity equivalent to that of the agent.

JP 2000-63787 A JP 2003-41225 A JP 2001-254066 A

  The present invention provides an adhesive composition for wood having excellent moldability (curability), adhesiveness, and stability of thickening over time.

Such an object is achieved by the following present inventions (1) to (5).
(1) An adhesive composition for wood comprising a resol type phenol / formaldehyde resin (a), an isocyanate compound (b), and an inorganic filler (c), the resol type phenol / formaldehyde resin (a) An adhesive composition for wood, wherein the isocyanate compound (b) is 20 to 100 parts by weight and the inorganic filler (c) is 40 to 100 parts by weight with respect to 100 parts by weight.
(2) The resol type phenol / formaldehyde resin (a) is obtained by reacting within a molar ratio of formaldehyde (F) to phenol (P) (F / P) of 1.5 to 2.5. The adhesive composition for wood as described in said (1).
(3) The adhesive composition for wood according to the above (1) or (2), wherein the pH of the resol type phenol-formaldehyde resin (a) is in the range of 9-13.
(4) The wood adhesive according to any one of the above (1) to (3), wherein the isocyanate compound (b) is any one of 4,4-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, or a mixture thereof. Composition.
(5) The wood adhesive composition according to any one of (1) to (4) above, wherein the inorganic filler (c) is calcium carbonate, talc, or a mixture thereof.

  The wood adhesive composition of the present invention is excellent in formability (curability), adhesiveness, and paste for softwood veneer while maintaining productivity of amino resin adhesive for conventional hardwood materials. It has liquid thickening stability over time.

Hereinafter, embodiments of the adhesive composition for wood according to the present invention will be described.
The wood adhesive composition according to the present invention is a wood adhesive composition comprising a resol-type phenol-formaldehyde resin (a), an isocyanate compound (b), and an inorganic filler (c), The isocyanate compound (b) is 20 to 100 parts by weight and the inorganic filler (c) is 40 to 100 parts by weight with respect to 100 parts by weight of the resol type phenol / formaldehyde resin (a).

The resol-type phenol / formaldehyde resin (a) used in the wood adhesive composition of the present invention is usually composed of phenols (P) and aldehydes (F) in an F / P molar ratio of 1.5 to 2.5. Preferably, a value obtained by reacting to a predetermined viscosity in the presence of a basic catalyst as 1.6 to 2.2 can be preferably applied.
Here, if the F / P molar ratio is less than the above lower limit, the curing of the resol type phenol-formaldehyde resin (a) may be slow, and if it exceeds the above upper limit, the amount of F emission from the plywood may increase. In addition, the pot life may be shortened.

  Examples of the phenols used to obtain the resol type phenol / formaldehyde resin (a) used in the wood adhesive composition of the present invention include phenol, cresol, xylenol, resorcinol, etc. You may do it. As formaldehyde, any of formalin (formaldehyde aqueous solution) and paraformaldehyde (solid) may be used, or they may be used alone or in combination.

  As the catalyst, a strong base catalyst such as sodium hydroxide or potassium hydroxide is usually used. When sodium hydroxide is used as the catalyst, the amount of the catalyst is not particularly defined, but the molar ratio of sodium hydroxide to phenol (hereinafter referred to as sodium hydroxide / phenol molar ratio) is 0 in order to improve water solubility. .1 or more is desirable, and it is desirable not to exceed 0.8. If this molar ratio is less than 0.1, the curing of the resol type phenol-formaldehyde resin (a) may be slow, and if it exceeds 0.8, the water resistance of the adhesive layer may be lowered. Reaction conditions for reacting phenols with aldehydes are not particularly limited, but it is preferable to carry out a condensation reaction under normal reflux or at a temperature of 70 ° C. or higher until a predetermined viscosity is reached.

  About pH of resol type phenol * formaldehyde resin (a), 9-13 are preferable. As a result, the water-solubility of the resol-type phenol / formaldehyde resin (a) can be improved, and the curability and water resistance of the wood adhesive composition can be improved. When pH is less than 9, the water solubility and curability of the adhesive may be reduced. On the other hand, if it exceeds 13, the water resistance of the adhesive layer may decrease.

The isocyanate compound (b) blended in the wood adhesive composition of the present invention is not particularly limited as long as it contains two or more isocyanate groups in the molecule. For example, 4,4-diphenylmethane diisocyanate, 1-chloro-2,4-phenylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-TDI, 3,3′-dimethyl-4,4′-biphenylene diisocyanate Polymers such as dimers and trimers thereof, such as polymethylene polyphenyl polyisocyanate, are applied. In consideration of toxicity, 4,4-diphenylmethane diisocyanate (hereinafter referred to as MDI) or polymethylene polyphenyl polyisocyanate is preferable.
In addition, a prepolymer having an isocyanate group as a terminal group previously polymerized with an excess of polyisocyanate in a polyol may be used. These can be used alone or in combination of two or more.

  The compounding quantity of an isocyanate compound (b) is 20-100 weight part with respect to 100 weight part of resol type | mold phenol formaldehyde resin (a). Preferably it is 25-50 weight part. Thereby, while making sclerosis | hardenability and workability | operativity at the time of plywood production favorable, adhesiveness can further be improved. Moreover, the moisture content tolerance of the veneer used for a plywood can be taken widely. When the amount of the isocyanate compound (b) is less than the above lower limit value, sufficient curability may not be obtained. When the amount is more than the above upper limit value, the increase in the viscosity of the compounding paste increases and it is applied to plywood production. Can be difficult.

The inorganic filler (c) to be blended in the wood adhesive composition of the present invention is not particularly limited. For example, calcium carbonate, talc, clay, calcium oxide, cinnabar sand, slate powder, mica powder, glass Powder, zinc white, titanium dioxide, kaolin, aragonite powder (quartz), diatomaceous earth, bentonite, mica, cold water, pumice, aluminum hydroxide, aluminum oxide, magnesium oxide, gypsum, barium sulfate, magnesium hydroxide, calcium sulfate, There is Shirasu balloon. These can be used alone or in combination of two or more.
Preferred is calcium carbonate and / or talc, and particularly preferred is calcium carbonate. Thereby, the adhesive composition for wood can be manufactured at low cost.

  The compounding quantity of an inorganic filler (c) is 40-100 weight part with respect to 100 weight part of resol type | mold phenol formaldehyde resin (a). Preferably, it is 50-80 weight part. Thereby, sclerosis | hardenability and adhesiveness can be made favorable. If it is less than the above lower limit value, sufficient curability may not be obtained, and if it is more than the above upper limit value, sufficient adhesiveness may not be obtained, and the paste liquid is dried before hot press. May result in poor adhesion.

  Resorcinol, formamide, m-cresol, alkylresorcinol, tannin, lignin, polyvinylbutyral, ethylene glycol, diethylene glycol and the like can be added to the wood adhesive composition of the present invention for the purpose of promoting curing. . In the wood adhesive composition of the present invention, a filler (starch such as wheat flour, corn starch, Takapio starch, coconut shell powder, etc.), a bulking agent, water, a curing accelerator, etc. may be added and mixed as necessary. Is also possible.

  Next, as a method for preparing an adhesive composition for wood and a paste solution, a predetermined amount of an isocyanate compound (b) and an inorganic filler (c) are blended in the above-described resol-type phenol formaldehyde resin (a) to adhere to wood. An adhesive composition is prepared, and a paste liquid is prepared by further blending a filler such as wheat flour.

The plywood obtained using this glue solution is a softwood veneer that cannot be sufficiently durable with an amino resin adhesive, and F emission (standard in JAS wood edition) F toaster (1.5 mg / L or less) When using a single plate with a single plate moisture content exceeding 16% under the same heating conditions as the amino resin adhesive (heating plate set temperature 115 ° C., heating time 20 seconds / mm) However, the conventional phenol adhesive is used, and it has an adhesive performance equivalent to that of a plywood obtained under normal heating conditions (hot plate set temperature 140 ° C., heating time 40 seconds / mm).
And by making F / P molar ratio at the time of synthesize | combining a resole type and phenol formaldehyde resin (a) into 1.5-2.5, in addition to the said effect, to express the outstanding low formaldehyde emission property Specifically, the amount of F emission can satisfy F forster (0.3 mg / L or less).

  In the present specification, the production examples, examples, and modes are for supporting the understanding of the contents of the invention according to the present application, and the present invention is not limited in any way by the description. “Parts” indicates “parts by weight” and “%” indicates “% by weight”.

Production Example of Resol Type Phenol / Formaldehyde Resin (a) 259 parts of phenol, 446 parts of 37% formalin (F / P molar ratio: 2.0), 220 parts of 30% aqueous sodium hydroxide solution (sodium hydroxide / phenol molar ratio) = 0.6), and 75 parts of water are charged and reacted at 80 ° C. with a B-type viscometer until the viscosity at 25 ° C. is about 2 dPa · s to obtain a resol type phenol / formaldehyde resin having a pH of 11.5. It was.

Examples 1-8
In 100 parts of the resol-type phenol / formaldehyde resin (a) obtained in the above production example, MDI as the isocyanate compound (b), calcium carbonate as the inorganic filler (c), or talc is blended in the number of parts shown in Table 1, respectively. An adhesive composition for wood was obtained.
Furthermore, 15 parts of wheat flour was added as a filler to the obtained adhesive composition for wood, and the viscosity was adjusted to 2 Pa · s with water to obtain a paste solution.

Comparative Examples 1-4
100 parts of the resol-type phenol / formaldehyde resin (a) obtained in the above production example is blended with MDI as the isocyanate compound (b), calcium carbonate and talc as the inorganic filler (c), respectively, in the amount shown in Table 2, respectively. Got.
Furthermore, 15 parts of flour as a filler was added to the resulting composition, and the viscosity was adjusted to 2 Pa · s with water to obtain a paste solution.

Comparative Example 5
Add 100 parts of melamine adhesive (MA-209, manufactured by Sumitomo Bakelite Co., Ltd.) having a molar ratio of formaldehyde to melamine (formaldehyde / melamine) of 0.6, 10 parts of flour, and add 1 part of ammonium chloride. The viscosity was adjusted to 2 Pa · s with water to obtain a paste.

Evaluation was carried out using the pastes obtained in the above examples and comparative examples. The stability with time of the paste was determined to be acceptable when the viscosity after standing for 2 hours at 35 ° C. was less than 2.0 times the initial viscosity, and rejected when the viscosity was 2.0 times or more. Moreover, the plywood was produced using a larch material having a thickness of 2.5 mm. That is, after the original plate was completely dried, the moisture content was adjusted to 16 to 20%, and the paste was applied to both sides to prepare a paste plate. Plywood was produced with 5 ply using this glue plate for the second and fourth. The molding conditions were as follows: the amount of paste solution applied: 28 g / angle, cold pressure condition: 10 kg / cm ² , heating condition: 10 kg / cm ² , 115 ° C., 20 seconds / mm. And it measured about the moldability of a plywood, the adhesive strength after special treatment (JAS wood edition description) of the obtained plywood, and F emission amount, and the result is shown in Table 3.

  Formability (= curability) was determined by visual observation of puffed and peeled plywood after hot pressing, and those that did not swell and peeled were accepted, and some were rejected. The measuring method of the adhesive strength (special adhesive strength) was measured according to the test method (steaming repeated test) described in the JAS wood edition, and passed or failed was determined according to this JAS. The measurement method of F emission amount was measured according to the test method (formaldehyde emission amount test) described in JAS Wood.

From the results of Examples shown in Table 3, the adhesive composition for wood of the present invention has excellent moldability (curability), adhesiveness, stability with thickening with time of paste solution, low formaldehyde emission, and low temperature. It is apparent that the adhesive composition for wood for plywood has a low formaldehyde odor and can be produced even when the moisture content of the applied veneer exceeds 16%.
Therefore, by producing plywood using the wood adhesive composition of the present invention, it is not necessary to dry the glue plate to a completely dry state, and the drying process can be shortened, thus realizing improved productivity of plywood. can do.
Comparative Examples 1 and 2 are cases where the blending amount of the isocyanate compound (b) is outside the specified range. When the amount is small, sufficient moldability cannot be obtained, and when the amount is large, the viscosity increase with time of the paste is too large. End up. Comparative Examples 3 and 4 are cases where the blending amount of the inorganic filler (c) is out of the specified range. When the amount is small, the viscosity increase with time of the paste is too large, and when the amount is large, the special adhesive strength is unacceptable. turn into. Comparative Example 5 is a case of a conventional amino-based adhesive, which results in a failure of special adhesive strength and a large amount of formaldehyde emission.

  The present invention has excellent adhesiveness to a softwood veneer while maintaining the productivity of an amino resin adhesive with respect to conventional hardwood materials for productivity, from the plywood previously developed by the present inventors. Adhesive composition for wood that can be produced at a lower temperature than the hot-pressing condition of phenol adhesive with reduced formaldehyde odor, and can be produced even if the moisture content of the applied veneer exceeds 16% And is useful as an adhesive for wood, particularly for plywood.

Claims (5)

  An adhesive composition for wood comprising a resol type phenol / formaldehyde resin (a), an isocyanate compound (b), and an inorganic filler (c), comprising 100 parts by weight of the resol type phenol / formaldehyde resin (a) The wood adhesive composition, wherein the isocyanate compound (b) is 20 to 100 parts by weight and the inorganic filler (c) is 40 to 100 parts by weight.   The resol type phenol-formaldehyde resin (a) is obtained by reacting within a molar ratio (F / P) of formaldehyde (F) to phenol (P) of 1.5 to 2.5. The adhesive composition for wood described in 1.   The wood adhesive composition according to claim 1 or 2, wherein the pH of the resol-type phenol-formaldehyde resin (a) is in the range of 9 to 13.   The wood adhesive composition according to any one of claims 1 to 3, wherein the isocyanate compound (b) is 4,4-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, or a mixture thereof.   The adhesive composition for wood according to any one of claims 1 to 4, wherein the inorganic filler (c) is any one of calcium carbonate and talc or a mixture thereof.