JPS60258221A - Molded chaff article having improved water resistance and elasticity - Google Patents

Abstract

PURPOSE:A molded chaff article, obtained by kneading chaff with an ethylene- vinyl acetate based copolymer emulsion containing a polyisocyanate compound, molding the resultant mixture, and heat-treating the molded article, and suitable to TATAMI mats, cushion and nursery beds. CONSTITUTION:A molded chaff article obtained by kneading chaff with a mixture of (A) a polyisocyanate compound with (B) an ethylene-vinyl actate based copolymer, molding the resultant mixture, and heat-treating the molded article, preferable at 140-160 deg.C. Preferably, the total amount of the components (A) and (B) is 40-60wt%, and the weight ratio between the components (A) and (B) is 0.3-0.6:1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rice husk molded product having excellent water resistance and elasticity.

Conventionally, when molding mats with excellent water resistance and elasticity, such as tatami floor or carpet under mats, using rice husks as a raw material, strict requirements were placed on the performance and cost of the adhesive used, so water resistance up to the level of gold and white was required. There is no known method for producing rice husk molded products with excellent strength and elasticity at low cost.

Rice husks are naturally hydrophobic and have the property of being resistant to rot, but when compression molded and used as tatami flooring, the adhesive used to hold the shape must have excellent water resistance. . In other words, when making tatami floors using rice husks, moisture in the atmosphere is absorbed by the voids in the tatami mats, which can sometimes lead to water seepage, so the adhesive used must be highly water resistant. However, from the viewpoint of water resistance, conventional urea-based adhesives and vinyl acetate-based adhesives are generally unsuitable. Furthermore, tatami floors are required to have strong elasticity with a unique tactile feel, and from this elasticity point of view, thermosetting adhesives based on phenol resins or urea resins are unsuitable. Furthermore, in the case of tatami floors made from rice husks, in order to maintain their breathability, the compression ratio cannot be increased during molding, and the compression ratio must be kept within a certain limited range. However, in this case, since the contact density between the rice husks is reduced, the adhesive used must have a stronger adhesive force.

In general, there are isocyanate-based, rubber-based, and epoxy resin-based adhesives that are superior in water resistance, elasticity, and strong adhesion, but these are all expensive and do not require rice husk matting. It is not suitable for mass processing such as floor preparation, and has the disadvantage that it is difficult to uniformly wet the fine particles due to its high viscosity.

In view of the above-mentioned circumstances, the present inventor has conducted extensive research on the development of rice husk molded products with excellent water resistance and elasticity using a special adhesive, and as a result has completed the present invention. It has arrived.

That is, according to the present invention, rice husks are mixed with an ethylene-vinyl acetate copolymer emulsion containing a polyisocyanate compound, molded into a desired shape, and heat treated to produce rice husks with excellent water resistance and elasticity. A shell molding is provided.

As the ethylene-vinyl acetate copolymer emulsion used in the present invention, various commercially available emulsions can be used, such as Denka EVA Tex (manufactured by Denki Kagaku Kogyo ■). In this case, the copolymer component may contain other components such as acrylic acid, maleic acid, fumaric acid, etc., if necessary. Examples of polyisocyanate compounds include common isocyanate compounds having two or more isocyanate groups (NGO), such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and triphenylmethane triisocyanate (TTI). etc. In the case of the present invention, these polyisocyanate compounds can be used in the form of a prepolymer prepared using a polyol. In the case of the present invention, various products commercially available as polyurethane adhesive components can be used as they are as the polyisocyanate compound.

The adhesive used in the present invention is mainly composed of an ethylene-vinyl acetate copolymer emulsion, which is combined with a polyisocyanate compound.

The adhesive of the present invention is used in the form of a mixture by mixing the two, but in this case, the composition of the mixture is the ethylene-vinyl acetate copolymer (solid content in the emulsion) and Total amount with polyisocyanate compound is 30~
80% by weight, preferably 40-6o1%, □1 water, 7o-2o weight, good. 1) It is best to adjust the content to 60 to 40% by weight. In addition, the polyisocyanate compound is ethylene-vinyl acetate copolymer 1
0.1 to 0.8 parts by weight, preferably 0.1 to 0.8 parts by weight.
It is preferable to use it in a proportion of 3 to 0.6 parts by weight. In the present invention, when adding a polyisocyanate compound to an ethylene-vinyl acetate copolymer emulsion, the water content can be adjusted arbitrarily.For example, by mixing an appropriate amount of water with the polyisocyanate compound, A method of adding and mixing the mixture to an ethylene-vinyl acetate copolymer emulsion, a method of adding water to an ethylene-vinyl acetate copolymer emulsion, and adding and mixing a polyisocyanate compound thereto, etc. can be adopted. .

To carry out the method of the invention, rice husks are mixed with the adhesive. In this case, the mixing method is as follows.

In addition to the method of stirring and mixing the rice husks and the adhesive, there are methods such as spraying the adhesive onto the rice husks. The amount of adhesive used is
The amount is about 100 to 400 g, preferably about 200 to 300 g, per 1 kg of rice husk. Next, the rice husks to which this adhesive has been added are formed into an appropriate desired shape. In this case, the shape can be appropriately selected depending on the product use, and can be made into various shapes such as a plate shape, a mat shape, a cylindrical shape, and a prismatic shape. Next, this molded product is heat treated while being held in the molding machine. Heat treatment temperature is 120-180°C, preferably 140°C
The temperature is 160° C. and the heat treatment can be carried out using various heating means, but for practical purposes it is preferable to carry out the heat treatment using hot air.

Through this heat treatment, the polyisocyanate compound and the ethylene-vinyl acetate copolymer undergo a crosslinking reaction, thereby fixing the rice grain particles to each other.

The rice husk molded product of the present invention has excellent water resistance and elasticity, and is inexpensive, since the above-mentioned special adhesive is used to fix the rice grain particles to each other. The rice husk molded product of the present invention can be used for various purposes such as tatami floors, mats, cushions, and nursery beds.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Commercially available ethylene-vinyl acetate copolymer emulsion (hereinafter referred to as EVA) [trade name: Denka EVA #60 (
manufactured by Denki Kagaku Kogyo), solid content 55%, viscosity (cps)
2500, pH 4, 5) 200g of polyisocyanate [Product name: Coronate C-3053 (Japan Polyurethane Products), NCO content 29.4%, viscosity 240cp
/25℃] and 50 g of water, mixed this with rice husk 11Q (apparent specific gravity approximately 0.1), and tested in a hot air blow-out type tester (30 cm x 30 cm, press pressure 3 kg).
/cd) to a thickness of 5cm (compression ratio approx. 2.2) L, hot air (temperature 140℃, wind force 0.3kg/c♂) from one porous pressure plate to the other porous pressure plate. ) to 5
It was molded by blowing through it for about 30 minutes at an air flow rate of NM"/hour.Next, for a water resistance test, this molded product was immersed in cold water for 3 hours and taken out, but the volume of the molded product (4500 cc
), the amount of water that entered the void was approximately 2,100 cc, and the rate of water release was 1,700 cc in approximately 20 minutes.If this was left at room temperature for 2 days, the water content would be 150 cc before the start of the test.
During this period, no collapse, melting, or dissolution of the adhesive resin coating was detected, and no deformation such as blistering or crumbling of the molded product occurred, and no partial peeling occurred.

Further, after drying, this molded product was immersed in warm water at 60° C. for 3 hours and then pulled out, but in this case as well, almost no change was observed as in the above case.

Comparative Example 300 g of EVA shown in Example 1 was mixed with rice husks 11Q, compressed to 5 cm using a hot air blowing test machine (same machine as Example 1), and hot air (120°C, 5 NM''/hour) was blown through for 30 minutes. The obtained molded product had a strong shape and appearance with air permeability and elasticity as in Example 1, but when it was immersed in cold water for a water resistance test, the adhesive resin was removed in just 15 minutes. The coating was dissolved in water and washed away, lost its compressive force and adhesion to the rice husks, swelled, and completely disintegrated after 30 minutes.

Example 2 A mixed solution of 3600 g of EVA shown in Example 1, 900 g of polyisocyanate shown in Example 1, and 900 g of water was mixed and stirred, mixed with rice husks 190Q, and heated in a full-scale hot air blower type tester (91 cm x 182 cm). ) to a thickness of 5 cm, -1.5°, i, a3. Yo,. . , Ka. Engineering [
L:! jut (14o 1・□℃, 1100N” /
time) was blown through for 30 minutes and molded. The obtained molded product was subjected to a water resistance test in the same manner as in Example 1, and as a result, it showed excellent water resistance, almost the same as in Example 1.

Although the rice husk tatami floor obtained as described above is a new product and no JIS standard has been set for it, the standard for foam polystyrene sandwich tatami flooring was applied mutatis mutandis, and the amount of deflection was determined by the bending test specified therein. , and the amount of local compression was measured by local tests.

The results are shown in the table below.

The dimensions of the test product are the same as the standard product (91JI): length 182 cm, width 91c+n, and thickness 5 cm.

Table 1 In addition, in the case of the adhesive used in the present invention, the volume is increased (approximately 30%) by foaming by mixing EVA, polyisocyanate, and water. In addition, when the polyisocyanate shown in Example 1 is used alone, the heating temperature for the reaction is 16%.
The adhesive of the present invention reacts completely at 140°C to 150°C, whereas the adhesive of the present invention is advantageous in terms of thermal energy.

Patent applicant: Toshiaki Ikeura, patent attorney, Kindai Jisui Center Co., Ltd.

Claims (1)

[Claims] (1) A rice husk molded product with excellent water resistance and elasticity, which is obtained by mixing rice husk with an ethylene-vinyl acetate copolymer emulsion blended with a polyisocyanate compound, molding it into a desired shape, and heat-treating it.