JPH01242451A - Pulp fiber-reinforced cement board - Google Patents

Abstract

PURPOSE:To lower water absorptivity by compounding a specific ratio of a powdery thermoplastic resin with a cement admixture composed of cement, silica, pulp fibers, pigment, etc. CONSTITUTION:The powdery thermoplastic resin is compounded at 3-7wt.% with the cement admixture consisting of the cement, silica, pulp fibers for reinforcement, pigment and other fillers. PVC, PE, acrylic resin, etc., are usable as the thermoplastic resin. The effect of lowering the water absorptivity of the board material is insufficient if the compounding ratio thereof is <3%. The above-mentioned effect is not so much improved even if the ratio exceeds 7%. The resin is melted to flow by heating at the time of curing so as to flow into the gaps included in the board material when the board material is molded of the above-mentioned compd. and is cured in an autoclave. The resin solidifies in the gaps after the curing. The volume of the gaps is thereby decreased and the closed cells are formed simultaneously in the board material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulp fiber-reinforced cement temporary for construction, which is used as roofing material, wall material, etc.

[Conventional technology]

Traditionally, asbestos fiber-reinforced cement boards have been used as this type of building material, but as asbestos fiber pollution has become a major problem in recent years, pulp fiber-reinforced cement boards that contain pulp fibers instead of asbestos fibers have become widespread. came into use.

[Problems with conventional technology]

However, pulp fiber-reinforced cement boards, which are made by blending pulp fibers as a reinforcing material into a cement mixture made of a mixture of cement and silica, mixed with inorganic fillers, pigments, etc. as necessary, have less pulp compared to asbestos. Due to its high water absorption, pulp-containing cement board material has a high water absorption property, which causes warping, expansion and contraction due to repeated water absorption and drying, and poor dimensional stability as a building material. There are various problems such as a large decrease in strength, and when exposed to low temperatures, water absorption freezes, resulting in poor frost damage resistance as a plate material.

[Problem to be solved by the invention]

In order to solve the above-mentioned problems caused by the water absorption of pulp, the present inventors have found that an effective means is to reduce the volume of voids in the pulp-containing cement board, and to make the voids into closed cells. This goal was achieved by blending cement, silica, pulp, and other fillers with thermoplastic resin powder and molding a pulp-blended cement board.

[Technology that led to solving the problem]

That is, the pulp fiber-reinforced cement board of the present invention contains a powdered thermoplastic resin in a cement mixture consisting of cement, silica, reinforcing pulp fibers, pigments, and other fillers.
It is characterized by containing 4% heavy weight.

[Effect]

In this invention, commercially available inexpensive resins such as vinyl chloride resin, polyethylene, acrylic resin, etc. can be used as the thermoplastic resin.

In the present invention, the blending amount of the powdered thermoplastic resin is 3 to 7.
The reason for limiting the weight percentage is that if the amount is less than 3% by weight, the effect of reducing the water absorption rate of the board material is not sufficient (on the other hand, if the amount exceeds 7% by weight, the effect of reducing the water absorption rate is not improved much). This is because, in some cases, other physical properties of the cement board may be adversely affected.

When a board is formed by blending thermoplastic resin powder with a cement-based mixture consisting of cement, silica, pulp, and other fillers and pigments if necessary, and the board is cured in an autoclave, the resin is released by heating during curing. It melts and flows, flows into the micro parts of the voids contained in the plate material by capillary action, and when the temperature drops after autoclave curing, it solidifies within the voids, reducing the void volume and at the same time breaking up the continuous voids. Can be independent bubbles.

Therefore, even if the pulp has a high water absorbency, the water absorbency of the board does not increase, and the above problems can be solved.

〔Example〕

A cement mixture having the composition shown in Table 1 (parts by weight) was molded and then cured in an autoclave to obtain a pulp-blended cement board.

Table 1 (Parts by weight) Table 2 shows the results of measuring the physical properties of the cement board samples A, B, and C.

In Table 2, the strength is the bending strength of sample A in an air-dried state, which is 10
It is shown as an index set to 0.

Table 2 〔effect〕

Claims (1)

[Claims] A pulp fiber-reinforced cement board characterized by blending 3 to 7% by weight of a powdered thermoplastic resin to a cement mixture consisting of cement, silica, reinforcing pulp fibers, pigments, and other fillers.