JPS5918339B2 - Method for manufacturing wood cement molded bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a wood cement molded body mainly used as a building material.

Conventionally, composite molded products of wood materials and cement, such as wood wool cement boards and wood chip cement boards, i.e., wood cement molded products, have been mainly used as building materials. It has advantages such as good hardness and durability, and its usage is expected to increase in the future.

However, this wooden molded body has major problems in manufacturing.

The first problem is that depending on the type of wood, components eluted from the wood may inhibit the hardening of cement.

This fact has been known for a long time, and it is said that among the eluted components, organic substances such as sugars mainly inhibit the hardening of cement, and there are significant differences in the type and amount of these inhibiting components depending on the tree species.

For example, coniferous trees such as hemlock, rainbow pine, and red pine are generally suitable as wood materials, but cedar and larch are not suitable, and broad-leaved trees such as redwood and beech are suitable, but merabi is unsuitable and cannot be used.

Furthermore, depending on the type of wood, one of the sapwood cores may be usable, but the other may not be usable.

As described above, the wood that can be safely used for wood cement moldings is extremely limited, which is inconvenient and increases manufacturing costs.

A second drawback is that productivity is very low.

Commonly used cement takes a long time to harden, and although various improvements have been made such as adding hardening accelerators, it still takes at least one day and night to remove from the mold after molding, resulting in high costs. It was causing this.

This invention was made to solve the above-mentioned problems, and the gist thereof is to provide a wood material shredded into a cement composition containing portland cement, alumina cement, anhydrite, or (and) hemihydrate gypsum. and water, molding the composition into a predetermined shape, and curing it by heating.

This invention is characterized by the use of a cement composition containing portland cement, alumina cement, anhydrite or (and) hemihydrate, which has a hardening speed at room temperature even in the presence of moisture. Calcium sulfoaluminate (3CaO・Al2O3・3CaS04・30～
32H20) is a cement composition that hardens by producing needle-like crystals, and the desirable composition range is 50 to 96 (80 to 96) parts by weight of Portland cement;
25-2.0 (10-2.0) parts by weight of alumina cement, 15-1.5 (5-1) parts of anhydrite or/and hemihydrate
．． 5) Parts by weight (more preferred ranges are in parentheses).

Further, if necessary, slaked lime may be added in an amount of 10 parts by weight or less, more preferably 5 parts by weight or less.

If 0.2 to 2.0 parts by weight of an alkali metal salt of an organic carboxylic acid or 9.4 to 2.5 parts by weight of an alkali metal salt of phosphoric acid are added to 100 parts by weight of this mixture, a cement paste can be obtained. The pot life is extended, the strength immediately after heat curing is improved, and early demolding can be carried out without any trouble.

As the Portland cement, ordinary Portland cement, early strength Portland cement, ultra early strength Portland cement, white Portland cement, etc. are used.

In addition, if the Portland cement component is less than the above composition range, it will not only be economically disadvantageous, but also the amount of calcium sulfoaluminate will be too large, resulting in poor durability after curing, for example, at 50°C or higher. Problems such as large drying shrinkage occur at high temperatures.

Conversely, if the Portland cement component exceeds 96 parts by weight, early strength will be insufficient.

In this invention, wood chips of various types of wood, wood flour, wood wool, etc. are used as the wood material cut into pieces.

Furthermore, in this invention, in addition to the above-mentioned cement composition and wood materials, for example, waterproofing agents, water repellents, foaming agents, corrosion inhibitors for wood materials, combustion inhibitors, etc. can be used as necessary. Furthermore, for the purpose of reinforcement and weight increase, substances such as various aggregates and fibers may be mixed in addition to the wood material.

In this invention, the above-mentioned mixture is molded into a predetermined shape and heated to harden. However, the molding method is not particularly different from that of conventional wood cement molded bodies, and the mixture is placed in a mold and pressurized. The most common method is to mold the material under pressure, and then heat it under pressure or with the pressure released.

Heating is preferably carried out so that the temperature of the molded mixture is 60 to 90°C.

If the temperature is lower than 60°C, the curing rate will be slow, and if the heating condition exceeds 90°C, the long-term strength of the molded product obtained will tend to be low.

In this invention, since the above-mentioned components are mixed and heated while being molded, curing proceeds quickly before the curing-inhibiting components of the wood are substantially eluted, and there are limitations depending on the wood species. It is now possible to use woods that were previously considered unsuitable, such as larch and cedar.
In addition, the curing becomes faster and demolding time is extremely short, productivity is improved, and wood cement molded bodies can be produced economically.

Next, the present invention will be explained in detail.

Examples 1 to 12 100 parts by weight of a cement composition having the composition shown in Table 1, 15 parts by weight of wood material and 50 parts by weight of water (if an organic carboxylic acid or sodium salt of phosphoric acid is added as an additive) (as shown in Table 1) and mix, put this mixture into a double formwork of 4X4X16crfL, form it by hand, then put a patch plate on it and form it to a thickness of 2cr.
The material was pressed to I'L, placed in a heating chamber in the pressed state, and after the material temperature reached 80°C, it was maintained at that temperature for 10 minutes, and then demolded to obtain a wood cement molded body.

The compressive strength and bending strength of each wood cement molded body after 1 hour of demolding and after 7 days were measured according to JIS R5201 (
Table 2 shows the results of measurements conducted in accordance with the Physical Test Method for Cement.

Table 2 also shows the results of measuring the starting time of each cement paste according to JIS R5201 as a guide to the pot life of the cement paste.

The wood material used was obtained by carving each piece of wood using an electric planer into pieces of about 0.15 m71 L in thickness, about 5 mm in width, and about 7 mm in length.

As a comparative example, tests were carried out in the same manner as in the examples using only ordinary Portland cement or ultra-early strength Portland cement as a cement composition.

However, the curing conditions are 20℃65%R without heating and in a pressed state.
It was left in the room of H for 3 days and then removed from the mold.

The measured physical properties are shown in Table 2. As can be seen from these results, in the method of the present invention, wood materials such as larch and cedar, which were conventionally unsuitable, can be used, and the material can be cured and removed from the mold in an extremely short period of time.

Claims (1)

[Claims] 1. A cement composition containing Portland cement, alumina cement, anhydrite, or (and) hemihydrate gypsum is mixed with finely chopped wood material and water, and this mixture is molded into a predetermined shape. A method for producing a wood cement molded body, which is characterized by curing by heating. 2. The method for producing a wood cement molded body according to claim 1, wherein the cement composition contains an alkali metal salt of an organic carboxylic acid or an alkali metal salt of phosphoric acid.