JPH04154652A - Production of inorganic molded article - Google Patents

Abstract

PURPOSE:To obtain hydraulic inorganic molded articles having high strength and excellent dimensional stability by molding a mixture of sulfur-containing acrylic fire-resistant fibers having a specific shape with a hydraulic substance and hardening the molded articles in an autoclave. CONSTITUTION:A mixture of sulfur-containing acrylic flame-resistant fibers cut so as to have <=7 denier fineness and <=90 aspect ratio with a hydraulic substance is molded and then hardened in an autoclave. The fibers have preferably <=50 aspect ratio. The amount of the hydraulic substance is preferably <=50 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a hydraulic inorganic molded product that has high strength and excellent dimensional stability as a building member.

[Prior Art] Conventionally, inorganic molded products for construction, such as asbestos cement boards, calcium silicate boards, and lightweight aerated concrete boards (A
When a hydraulic inorganic material consisting of calcareous material and silicic acid material, such as L C), is cured in an autoclave under high temperature steam, a highly crystalline hydrate called tobermorite is formed. Roofing materials, flooring materials, exterior walls, partition materials, etc. made of such highly crystalline hydraulic inorganic materials have excellent insulation properties and thermal stability, and in addition, they reduce drying shrinkage and are chemically resistant. It is said that resistance can be increased.

Therefore, asbestos, reinforcing steel, and the like have been used as reinforcing fibers for the above-mentioned high-performance hydraulic inorganic molded products that must be cured in high-temperature steam.

However, asbestos, which is a natural material, is mostly imported and its price fluctuates widely.In addition, in recent years it has become clear that asbestos is harmful to health and hygiene, so its use has increased. are being avoided or restricted.

Therefore, the present inventors previously proposed in Japanese Patent Application Laid-Open No. 63-45155 that high-strength acrylic fibers were used as asbestos substitute fibers that could withstand curing in high-temperature steam, that is, autoclave curing. We proposed a sulfur-containing acrylic flame-resistant fiber that was heated and sulfurized in a sulfur-containing atmosphere.

[Problems to be Solved by the Invention] In general, in order to obtain a high-strength hydraulic inorganic product using the premix method, the amount of water added to a hydraulic substance such as cement is minimized, and the voids in the molded product are minimized. It is necessary to reduce the rate.

However, if the amount of water added is small, the viscosity of the hydraulic substance increases significantly, making it difficult to disperse the reinforcing fibers. Therefore,
When the fiber length is shortened in order to improve dispersibility, there is a problem in that adhesiveness with hydraulic substances decreases and a sufficient reinforcing effect cannot be obtained.

By the way, since the above-mentioned asbestos substitute fibers have a significantly larger fiber diameter than asbestos, sufficient adhesiveness, that is, a sufficient reinforcing effect cannot be obtained unless the fiber length is increased to a certain extent. Therefore, the ratio of the fiber length to the fiber diameter, that is, the aspect ratio, is required to be at least a certain value. For example, JP-A-62-223046 discloses that the fiber length is 5 mm or less and the aspect ratio is 100 or more, preferably 200 or more.

Therefore, the present inventors investigated reinforcing fibers and their aspect ratios in order to improve dispersibility and adhesion to hydraulic substances and exhibit excellent reinforcing performance in the premix method. It has arrived.

An object of the present invention is to provide a method for producing a hydraulic inorganic molded article having high strength and excellent dimensional stability.

[Means for Solving the Problems] The object of the present invention is to provide a material having a fineness of 7 deniers or less,
This can be achieved by forming a mixture of a sulfur-containing acrylic flame-resistant fiber cut to have an aspect ratio of 90 or less and a hydraulic substance, and then curing it in an autoclave. can.

[Function] The manufacturing method of the present invention will be explained in more detail below.

The reinforcing fiber used in the present invention is a sulfur-containing acrylic flame-resistant fiber that can withstand autoclave curing, that is, has excellent high-temperature alkali resistance, and exhibits excellent adhesion to hydraulic substances.

The sulfur-containing acrylic flame-resistant fiber (hereinafter simply referred to as flame-resistant fiber) contains a cyclized structure and a crosslinked structure consisting of sulfur bonds in the molecular chain of polyacrylonitrile.

Here, a specific example of a method for producing the flame-resistant fiber used in the present invention will be explained.

First, the acrylic fiber used as a starting material is not particularly limited, but in order to obtain a flame-resistant fiber with high strength and high modulus, it is desirable that the acrylic fiber has high strength and high modulus. For example, the degree of polymerization is at least 1.
5. Preferably, a high polymerization degree acrylonitrile (hereinafter abbreviated as AN) polymer having a polymerization degree of 2°0 to 5.0 is used, and the tensile strength is at least 7 g/d, preferably 9 g/d or more,
More preferably, it is desirable to form acrylic fibers of 10 g/d or more.

Next, as the AN-based polymer used for producing acrylic fibers, AN alone or at least 90 mol% of AN-based polymers are used.
and 10 mol% or less of monomers copolymerizable with the AN, such as carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, and their lower alkyl esters, hydroxymethyl acrylate, hydroxyethyl acrylate, and hydroxymethyl methacrylate. Hydroxyalkyl acrylate containing a hydroxyl group of carboxylic acid such as acrylate, acrylamide, methacrylamide, α-chloroacrylonitrile, hydroxyethyl acrylic acid,
Examples of copolymerized monomers include allylsulfonic acid and methacrylsulfonic acid. Among these copolymerized monomers, acrylamides have a fast sulfurization reaction, little oxidative deterioration due to oxygen, and can yield high-strength flame-resistant fibers. is particularly desirable.

These AN-based polymers are dimethyl sulfoxide (DM
organic solvents such as SO), dimethylformamide (DMF), and dimethylacetamide (DMAc); concentrated aqueous solutions of inorganic salts such as calcium chloride, zinc chloride, and rhodan soda;
When dissolved in an inorganic solvent such as nitric acid, the solution viscosity is 2000.
Boise or more, preferably 3000 to 10000 boise,
A spinning dope having a polymer concentration of 5 to 20% is prepared.

In order to produce dense fibers with as high strength and high modulus as possible and with little difference in internal and external structures from the solvent solution (spinning stock solution) of the high polymerization degree AN polymer thus obtained, it is necessary to use this high polymerization degree AN polymer. A so-called dry-wet spinning method is adopted, in which a polymer spinning solution is discharged through a spinneret into an inert atmosphere such as air, and then the discharged spinning solution is introduced into a coagulation bath to complete coagulation. Stretching is desirable.

The specific conditions for this dry-wet spinning are as follows: The spinning solution is spun between the spinneret surface and the coagulation bath, the distance between which is set within a range of 1 to 20 mm, preferably 3 to 1Q mm. After discharging it into a microspace formed by the liquid surface, it is introduced into a coagulation bath and coagulated, and then the obtained fiber thread is washed with water, desolventized, first stretched, dried and densified, and then subjected to a second It is made into a drawn fiber thread by passing through post-processing steps such as drawing and heat treatment. The fiber yarn obtained by this dry-wet spinning has extremely excellent drawability. Preferably, as a secondary drawing method, at least one
．． 1 times, preferably 1.5 times or more, the total effective stretching ratio is at least 10 times, preferably 12 times or more, and the fineness is 0.5 to 7 denier (d), preferably 1 It is preferable to set it within the range of ~5d.

If the fineness is smaller than 0.5d, there will be many yarn breakages during the drawing process, and if it is larger than 7d, not only will high strength not be expected, but sulfurization will become uneven in the cross-sectional direction of the fiber in the heating sulfurization process described below. Therefore, it is undesirable.

The acrylic fiber thus obtained is exposed to a sulfur-containing atmosphere,
For example, a sulfur-containing gas consisting of sulfur dioxide, sulfur gas, carbon disulfide, hydrogen sulfide, carbonyl sulfide, etc. alone or a mixture thereof, or a mixture of the above-mentioned sulfur-containing gas and an inert gas, especially sulfur dioxide. is preferably used because it has excellent reactivity with acrylic fibers and can uniformly sulfurize the cross section of the fibers. Further, the inert gas is a gas that does not cause a chemical reaction with the acrylic fibers, and examples thereof include nitrogen, argon, helium, carbon dioxide, water vapor, and the like alone or in a mixture thereof.

Next, the temperature of the sulfur-containing gas in the sulfur-containing atmosphere is 2
The heating temperature in the sulfurization process may be from 30 to 400°C, and may be at a constant temperature or at an elevated temperature, and the acrylic fiber bundle may be under tension, constant length, or relaxed. −
As an example, the first stage heating is performed in a heating furnace maintained at a temperature range of 230 to 280 °C, and the second stage heating is performed at a temperature of 280 to 40 °C.
A method of completing sulfidation within a temperature range of 0° C. in a heating furnace in which temperature raising conditions are set in stages can be mentioned.

The flame-resistant fiber thus obtained for use in the present invention has a sulfur content of at least 0.5% by weight, preferably at least 1.0% by weight. Sulfur content is 0. If it is less than 5% by weight, it will not be able to withstand autoclave curing and the reinforcing effect will decrease.

Furthermore, if the sulfur content becomes too large, the strength of the flame-resistant fiber will decrease, so the upper limit is 25% by weight or less, preferably 15% by weight or less. And its tensile strength is 3
．． The fineness of the flame-resistant fiber is 5 g/d or more, preferably 4.5 g/d or more.The fineness of the flame-resistant fiber is 7 denier (d) or less, preferably 0.5 to 5 d. If it is larger than 7d, high strength cannot be expected and sufficient reinforcing performance cannot be obtained for the inorganic molded product. Further, the ratio of fiber length to fiber diameter, that is, the aspect ratio, is 90 or less, preferably 50 or less. Here, if the aspect ratio is larger than 90, the dispersibility in the hydraulic substance becomes poor and high reinforcing performance cannot be obtained. Such effects become more obvious as the amount of fiber added increases.

By the way, in order to obtain the above aspect ratio, the fiber length should be 2 mm or less, preferably 1 mm or less, and more preferably 0.5 mm or less, especially for high-speed rotary blades, refiners, high-speed hammers, high-speed jet streams, etc. Flame-resistant fibers cut by a pulverizer so that the fiber length of 0°5 mm or less is 30% by weight or more, preferably 50% by weight or more is preferably used. At this time, the fiber length can be controlled by adjusting the grinding time and the output of the grinder, or by classifying the fibers using screens of different diameters.

The hydraulic substances used in the present invention include inorganic substances having hydraulic properties such as calcareous and silicic substances, such as silica stone, diatomaceous earth, blast furnace slag, fly ash, lime,
Examples include various cements such as gypsum and Portland cement.

Furthermore, in order to impart porosity to the inorganic molded product and reduce its weight, pearlite, shirasu balloons, glass balloons, etc. can be mixed as appropriate. In order to roughly improve the fluidity of the hydraulic substance, wood pulp, fibrillated acrylic fibers or aromatic polyamide fibers, inorganic fibers, and other fillers can be added and blended.

Thus, the above-mentioned composition consisting of the flame-resistant fiber, hydraulic substance and various fillers is mixed with water in a mixer, kneaded, and then molded into a desired shape. At this time, the blending amount of flame-resistant fiber is 0.1 to 10% by weight, preferably 0.5% by weight.
~5% by weight.

Also, as a mixer, Omni mixer, Eirich,
A kneader, mortar mixer, etc. are used. Further, as a molding method, a premix method, that is, gravity molding, press molding, injection molding, extrusion molding, etc. is used.

Incidentally, the amount of water added to the hydraulic material (W/c) is 50 parts by weight, preferably 30 parts by weight. Here, if the amount of water added is more than 50 parts by weight, a high-performance inorganic molded product cannot be obtained.

The molded product thus obtained is placed in an autoclave and cured under steam at 180°C. Of course, there is no problem in using a curing temperature of over 180°C or a temperature range of 100 to 180°C. Further, the curing time varies depending on the curing temperature, but a range of 3 to 15 hours is used.

[Example〕 EXAMPLES Hereinafter, the effects of the present invention will be specifically explained with reference to Examples.

Examples 1-2, Comparative Examples 1-2 An AN-based copolymer having an intrinsic viscosity of 3.2, consisting of 99 mol% acrylonitrile (AN) and 1 mol% acrylamide, was solution-polymerized in dimethyl sulfoxide (DMSO). The resulting spinning stock solution was subjected to dry-wet spinning. As a coagulation bath, 2
A 55% DMSO aqueous solution at 0°C was used. The obtained undrawn fiber yarn was stretched 5 times in hot water, washed with water, and then
Secondary stretching was performed in a dry heat tube at ~200°C at a maximum stretching ratio of 90%, with a fineness of 2 denier and a strength of 13.2 g/d.

Acrylic fibers with an elongation of 12.8% were obtained.

Next, this acrylic fiber was exposed to 20% nitrogen 8% sulfur dioxide gas.
The mixture was heated and sulfided at 295° C. for 20 minutes in a 0% mixed gas. The obtained flame-resistant fiber has a fineness of 2 denier and a strength of 9.2 g/
d, elongation was 10.3%, and sulfur content was 3.2% by weight.

This sulfur-containing acrylic flame-resistant fiber has a fiber length of 1.2.5.
A portion of the cut yarn with a fiber length of 5 mm was crushed into a fiber length of 0.0 mm using a crusher using a high-speed rotating blade. The pulverized yarn was made up of 83% by weight of yarn having a diameter of 5 mm or less.

Next, 1% by weight of these cut yarns and crushed yarns, 2% by weight of methyl cellulose, and 97% by weight of a hydraulic substance consisting of cement and fly ash were mixed in an Eirich, and then 20 parts of water was added and kneaded.

The obtained viscous material was extrusion molded, left in a wet state for 24 hours, and then steam-cured at 5°C for 5 hours in an autoclave at 180°C.

The bending strength, impact strength, etc. of the obtained molded plate were measured in an air-dried state.

The results are shown in Table 1.

From Table 1, it can be seen that the molded plate manufactured according to the present invention has excellent reinforcing performance.

[Effects of the Invention] The method for producing an inorganic molded article according to the present invention uses reinforcing fibers that have a fineness of 7 deniers or less and an aspect ratio of 90.
By using the following sulfur-containing acrylic flame-resistant fibers, excellent dispersibility and adhesion to hydraulic substances can be obtained in the premix method, that is, when molding hydraulic compounds with a small amount of water and high viscosity. Therefore, fiber-reinforced inorganic molded products with high strength and high impact strength can be manufactured.

Therefore, the inorganic molded product produced according to the present invention can be used for many purposes such as building materials and civil engineering materials due to its excellent performance.

Patent application Daitoshi Co., Ltd.

Claims (3)

[Claims] (1) Fineness is 7 denier or less and aspect ratio is 9
1. A method for producing an inorganic molded article, which comprises molding a mixture of a sulfur-containing acrylic flame-retardant fiber cut to 0 or less and a hydraulic substance, and then curing in an autoclave. (2) The method for producing an inorganic molded article according to claim 1, wherein the aspect ratio of the sulfur-containing acrylic flame-resistant fiber is 50 or less. (3) The method for producing an inorganic molded article according to claim 1 or 2, wherein the amount of water added to the hydraulic substance is 50 parts by weight or less.