JPH03162447A - Production of synthetic wood - Google Patents

Abstract

PURPOSE:To obtain a synthetic wood, excellent in strength in spite of a low specific gravity and having a smooth surface and toughness resistant to nailing, sawing and planing by blending chaff powder with a specific urethane resin. CONSTITUTION:(A) Chaff powder having a particle size passing through a 30-mesh screen in an amount of 40-95wt.% is blended with (B) a resin raw material which is a reaction product of a polyoxyalkylene polyol having 50-10000 number-average molecular weight with polymethylene polyphenyl polyisocyanate and has 0.05-3.0 crosslinking density in an amount of 60-5wt.%.

Description

[Detailed description of the invention] [Purpose of the invention]

[Industrial Application Field] The wood invention relates to a method for producing synthetic wood from rice husk and thermosetting urethane resin. [Prior art] Conventional synthetic wood includes, for example, Jiwei wood, which is made by gluing together small pieces of wood, and wood made of polyvinyl chloride, polystyrene, acrylonitrile, butadiene, and styrene copolymer resins that resemble wood only in appearance. It is known that
Besides being expensive, the former could not be molded into complex shapes or curved surfaces. On the other hand, although the latter can be molded freely, secondary processing such as planing and nailing is difficult, so it is not very popular. Furthermore, rice husk powder is processed into urea-formalin resin, melamine resin,
Some are mixed into thermosetting or thermoplastic resins such as phenolic resins or polypropylene resins, but high-quality products have drawbacks such as high specific gravity (specific gravity of 1.00 or more) or brittle materials. there were. In addition to the above, JP-A No. 55-88738 and JP-B No. 62-40491 describe a method of manufacturing a template from rice husks and urethane prepolymer, but in this case, the rice husks are not crushed. Because the product is used in its original form (major axis: 5-6 am, minor axis: 2-31111 mm), the product has a flat pattern of rice husks, and cannot be called laminated wood at all. Moreover, the surface is uneven, even if polished,
Painting does not provide a beautiful surface. [Problem n to be solved by the invention] Therefore, the problem to be solved by the present invention is to use rice husk and a special urethane resin as materials, which have excellent strength despite having a small specific gravity, and which can be easily nailed or sawed. Another object of the present invention is to provide laminated wood that not only has toughness suitable for planing but also has a smooth surface.

[Structure of the invention]

(+) Overview In order to achieve the above-mentioned objects, the method for producing synthetic wood according to the present invention is based on the method for producing synthetic wood from rice husk powder and thermosetting urethane resin. 95% by weight and ■ As a urethane resin, the number average molecular weight is 50~! It is a reaction product of polyoxyalkylene polyol of 0,000 and polymethylene polyphenyl polyisocyanate, and is characterized by being blended with 60 to 5% by weight of a resin raw material having a crosslink density of 0.05 to 3.0. The main matters related to the structure of the invention will be explained in sections below. (2) Crosslinking density In the method for producing synthetic wood of the present invention, the raw material urethane resin is a reaction product of polyoxyalkylene polysilicate with a number average molecular weight of 50 to 10,000 and polymethylene polyphenyl polyincyanate, The crosslinking density is O. O
It is necessary that the value is S~3.0. Here, the "crosslinking density (CD)" is a value calculated as follows, for example. That is, the molecular weight Wl. A polyisocyanate compound Wlg having a functional group number F+ and a molecular weight NW2. Number of functional groups F
The crosslink density per too molecular weight of the polyurethane resin obtained by reacting 2 g of polyol No. 2 with 2 g of polyol No. 2 is calculated as follows. (Left below) Urethane resins with a CD of 0.05 or less have poor bending performance, peel strength, and wet strength; conversely, with a CD of 3.0 or more,
The f& type board becomes brittle. (3) Rice husk powder The rice husk used in the present invention is ordinary rice husk that has been crushed to 30 J pass. Moisture content immediately before use is 1O%
Below, it is preferable to dry it to 5% or less. Note that the smaller the particle size, the better. The appearance of the precept-shaped products becomes beautiful. (4) Polymethylene polyphenyl polyisocyanate Polymethylene polyphenyl polyisocyanate, which constitutes the urethane resin used in the wood invention, is generally called polymeric MDI, and is a crude product obtained by phosgenating a condensate of aniline and formalin. is used. (5) Polyoxyalkylene polyol Polyoxyalkylene polyol, which is another component constituting the urethane resin used in the present invention, is a polyhydric alcohol such as glycerin, trimethylolpropane, pentaerythritol, sorbitol, sugar, and bisphenol A. Polyfunctional polyether polyols obtained by reacting 7-rukylene oxides such as propylene oxide, butylene oxide, etc., and those having a number average molecular weight of 50 to 10,000 are used. (6) Blending urethane resin into rice husk The urethane resin raw material may be blended into the rice husk in the form of a reaction product (prebolymer) of each equivalent of polymethylene polyphenyl polyisocyanate and polyoxyalkylene polyol, or in the form of a reaction product (prebolymer) of each equivalent amount of polymethylene polyphenyl polyisocyanate and polyoxyalkylene polyol, or the former over the latter. It may be in the form of a prepolymer having NCOTS at the end using an excess amount of incyanate, or equivalent amounts of unreacted incyanate and polyether polyol, or a method in which the former is blended with rice husk powder in excess of the latter. No matter which resin raw material is used, the blending ratio is determined on the assumption that the mixture of prepolymer or polyol and polyisocyanate will completely react during the next heat pressing step. (7) Blending ratio The blending ratio of rice husk powder and urethane resin raw material is 40 to 95! i amount %, preferably 50-90 weight 2, urethane resin raw material 5-601 i amount %, preferably 10-5
It is 0% by weight. If the urethane resin raw material is less than 5% by weight, bending strength, compressive strength, peel strength, wet strength, etc. are low. On the other hand, 60% by weight
In this case, not only does the unit price of synthetic wood become high, but it also loses its wood feel. (8) Production The resin raw material of the present invention is first mixed with rice husk alone or optionally in the form of a solvent solution or emulsion using a tumbler or blender device, or sprayed onto rice husk powder. It is mixed with rice husk powder. Next, this mixture was charged into a mold, and the temperature was 80 to 180°C.
Preferably 120~180℃, pressure 5~50kg/
cm2, preferably 10 to 20 kg/cm2. At this time, the density can be easily adjusted by adjusting the density and amount of the rice husk powder and urethane resin raw materials. [Function] The R& type product produced by the method of the present invention has a density of 1.0 g/c compared to products using resins such as phenol and polypropylene.
■It has a low density of less than 3, and although it is filled with rice husks, it has a smooth and beautiful surface with a woody feel, and can be nailed or planed. In addition, it has excellent physical properties such as bending strength, peel strength, and water resistance, and can be painted freely using urethane paints, acrylic paints, etc. [Examples] The embodiments and effects of the invention will be described below using Examples and Comparative Examples, but the examples are merely for illustrative purposes. It is not intended to limit or restrict inventive thinking. 150 parts of rice husk powder (bulk specific gravity: 0.4
35 parts of polymethylene polyphenyl polyinsyanate and 3 parts of polyoxypropylene triol (average molecular weight 410) were placed in a rotary blower drum L/7 while rotating.
A prepolymer (crosslinking density: 1.70), which had been premixed and reacted with 5 parts, was sprayed. The obtained rice husk powder to be treated was placed in a mold and heated at 160°C for 13k.
Heat pressed for 5 minutes under g/cm2 condition, 200m*X2
An impressive product with dimensions of 00mm x 511m was obtained. The resulting dignified product has a beautiful surface with a woody feel, and is
'; When physical properties were tested according to A 5908, the density was 0. Hg/cm3. The bending strength was 320 kg/cm3 and the peel strength was 83 kg/cm2. This molded board could be nailed and planed. Example 2 Rice husk powder (particle size 30-50Ay x bulk specific gravity 0.501
/cs3, moisture 3.5%), glycerin•propylene oxide adduct (molecular 13,000) in the same manner as in Example 1.
) After mixing a prepolymer (crosslinking density: 0.53) consisting of 89 parts of polymethylene polyphenyl polyisocyanate and 31 parts, a synthetic wood having a density of 0.89 g/c was obtained in the same manner as in Example 1. This synthetic wood. Bending strength 295kg
/cm2. It had a peel strength of 70 kg/c+w2, and no cracking occurred even when nailed to it. Furthermore, even when the surface of this molded product is painted with acrylic urethane, the paint film does not swell or peel, and the grid adhesion test (1 ts x 1 am) shows 100/100, indicating good adhesion to the paint film. It had a sexual nature. Comparative Example 1 Rice husk with a moisture content of 7% (long axis 6 am, short axis 3 a+m)
100 parts of poly7enylmethane polyisocyanate 70
IJ-2-(F-
A molded plate was obtained in the same manner as in Example 1 by mixing 15 parts of NCO (15.0%). When the physical properties of the obtained *template were measured, the density was 0.85.
1/cs3 and bending strength of 110 kg/cm2, but the shape of rice husk appeared on the surface of the molded plate, making it difficult to call it a wood product. Furthermore, painting with acrylic urethane paint was difficult due to the liquid-repellent nature of the surface. Note (U raw main sur powder (particle size 30~50fit x. Bulk specific gravity 0.5
A mixture of 100 parts of 0 g/cm3, moisture 3.5%), 85 parts of 7 borac resin (average molecular weight 1000) and 15 parts of hexamethylenetetramine was treated in the same manner as in Example 1 to obtain a template. The physical properties of this template are density 1.41g/cm3, bending strength 315kg/cm2, and peel strength 58kg/cm2.
．． The hardness was 060. Moreover, in the grid peeling test of the acrylic urethane coated product, the score was 95/100, with some peeling occurring.

【Effect of the invention】

As explained and demonstrated above, the present invention uses rice husks and a special urethane resin as materials, and has excellent strength despite its low specific gravity, as well as toughness that can withstand nailing, sawing, and planing. By being able to provide synthetic wood with a smooth surface as well as a smooth surface, we can contribute to the development of synthetic wood-related industries. Patent is the applicant Daiichi Kogyo Seiyaku Co., Ltd.

Claims (1)

[Claims] 1. In producing synthetic wood from rice husk powder and thermosetting urethane resin, (1) 40 to 95% by weight of rice husk powder with a particle size of 30 mesh pass; (2) number average as urethane resin; Molecular weight 50-100
00 polyoxyalkylene polyol and polymethylene polyphenyl polyisocyanate,
60-5% by weight of a resin raw material having a crosslinking density of 0.05-3.0.