JPH05194009A - Method for manufacturing hydraulic molded article - Google Patents

Abstract

(57) [Summary] [Purpose] Asbestos has been used as a reinforcing material in hydraulically molded products for autoclave curing.
An object of the present invention is to provide a method for producing a hydraulically molded product at low cost without using this asbestos. [Structure] Inexpensive, cross-linked synthetic fiber is used as a reinforcing fiber in an amount of 0.3 to 10% by weight, and has a surface hardness of 80% after molding.
Primary curing is performed until the above temperature is reached, and autoclaving is performed at 140 ° C. or higher after primary curing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydraulic molded article which is cured by autoclave using a crosslinked synthetic fiber as a reinforcing material.

[0002]

2. Description of the Related Art In recent years, health problems caused by asbestos have been clarified and their use is being regulated. Carbon fibers are partially used as an alternative material in this field. It is difficult to obtain bending toughness because of low value, and it is very expensive, so that only a very small amount is used.

On the other hand, an attempt has been made to use a relatively inexpensive general-purpose synthetic fiber for the purpose, and it is disclosed in Japanese Patent Laid-Open No. 12905/1990.
No. 3 and Japanese Patent Laid-Open No. 3-207606.

In Japanese Patent Laid-Open No. 129053/1990, a high molecular weight acrylonitrile polymer (hereinafter abbreviated as PAN) is used.
Made from a high-strength, highly-oriented acrylic fiber consisting of
Although it has been shown to be cured at ℃, the bending strength of the concrete plate is low for the fiber obtained, although the strength is high. Further, the present inventors have found that when such a fiber is immersed in a cement extract (pH about 12.5) at 160 ° C. for 1 hour, it is completely dissolved. Therefore, such a fiber essentially does not withstand the autoclave curing of cement, and the description of JP-A No. 2-129053 has to be construed as giving good data by chance.

In Japanese Patent Laid-Open No. 3-207606, polypropylene fiber, polyethylene fiber, polyvinyl alcohol (hereinafter abbreviated as PVA) fiber is used, and a molded product is first prepared.
A method of autoclave curing at -3 atmG (120 to 143 ° C), followed by curing in water for 15 days or more and then drying is shown. The method is intended to provide a manufacturing method that does not cause melt deterioration of the fiber, and therefore relaxes autoclave curing conditions and combines underwater curing, but at a high temperature of at least 140 ° C or higher. Not only is it not possible to shorten the curing time, which is a major feature of autoclave curing, but it is also difficult to obtain the dimensional stability of the obtained product. Unless the temperature is 140 ° C. or higher, calcium oxide and silica cannot react sufficiently and tobermorite is not formed, so that satisfactory dimensional stability cannot be obtained.

Further, in order to withstand autoclave curing and to obtain a sufficient reinforcing effect, it is effective to introduce crosslinks into the fiber. Regarding PVA type fiber, it is disclosed in JP-A-3-213.
Japanese Unexamined Patent Publication No. 510-8 and Japanese Patent Laid-Open No. 60-8
1309 publication. However, only the fiber properties such as strength, water resistance, and alkali resistance are shown, and when used as a reinforcing material for a hydraulic molded product that is to be cured by an autoclave, let alone the most important requirement, what is the effect? There is no specific description as to whether a hydraulic molded product can be produced by such a method.

As described above, there is no example in which conventional general-purpose fibers or crosslinked products thereof actually withstand autoclave curing at 140 ° C. and have a sufficient reinforcing effect, and the hydraulic property of autoclave curing using such fibers is not. There is no example of producing a molded product.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a hydraulic molded product that is low in cost and excellent in dimensional stability and strength.

[0009]

In order to obtain excellent dimensional stability, it is necessary to carry out autoclave curing at least at 140 ° C or higher. Therefore, the reinforcing fibers must withstand such curing. The present inventors have conducted detailed condition studies using various synthetic fibers, and as a result, have found the following two important requirements and arrived at the present invention.

One is to use a cross-linked synthetic fiber as a reinforcing component, and the other is to have a surface hardness of 80% or more after molding using such a fiber and before carrying out autoclave curing. It is to carry out primary curing.

Synthetic fibers that have not been subjected to crosslinking treatment are severely deteriorated by alkali and moist heat, and cannot withstand curing at 140 ° C. or higher. If the crystallinity of the fiber is high, a certain degree of alkali resistance and resistance to moist heat can be obtained, but it will melt, melt or decompose under the severe conditions of an autoclave. Such a phenomenon can be avoided by introducing cross-linking to prevent water or alkali from entering or by raising the melting point.

Primary curing is extremely important in using such fibers. If this primary curing is insufficient, the fibers will deteriorate during autoclave curing and the reinforcing effect will be lost. The details are unknown, but
It is considered that the matrix is hardened to some extent by the primary curing and the fibers are firmly adhered to prevent the deterioration of the fibers.

The crosslinked synthetic fiber used in the present invention may be a crosslinked product of an olefinic synthetic fiber such as polypropylene or polyethylene in addition to the PAN type and PVA type. In this respect, PAN-based and PVA-based are particularly preferable.

Although the crosslinking treatment is not particularly limited,
In the method of generating radicals such as radiation or electron beam, the main chain is broken and the strength is lowered, so that crosslinking using a chemical reaction is preferable.

In the PAN system, a method in which a crosslinkable vinyl monomer and acrylonitrile are copolymerized to form fibers and then crosslinked is effective. As the crosslinkable vinyl monomer, for example, acrylamide, N-methylacrylamide, N-methylolacrylamide and the like are preferable, and
Copolymerize about 20% by weight. After spin-drawing such a polymer according to a conventional method, acrylamide may be formalin, and in the case of N-methylacrylamide or N-methylolacrylamide, an acid may be mainly added and heat-fixed. It is also possible to add dimethylol dihydroxyethylene urea, dimethylol melamine, or the like to the fiber as a crosslinking aid.

On the other hand, with respect to the PVA type, although not particularly limited, a method in which an acid such as phosphoric acid or hydrochloric acid or a salt such as ammonium phosphate or ammonium sulfate is applied to the fiber and heat treated, or 100 g / l or more of formaldehyde, There is a method of acetalization under special conditions of sulfuric acid 100 g / l or less, or a method of acetalization by using a dialdehyde and a monoaldehyde together. In particular, a method of using a dialdehyde and a monoaldehyde together, more specifically to a fiber On the other hand, a method in which a mixed solution of glutaraldehyde and formaldehyde is first applied to the fibers in the first step and crosslinking treatment is performed in a mixed bath of formaldehyde and sulfuric acid in the second step is preferable.

Such fibers can be used in any form depending on the manufacturing method and the construction method of the molded product. For example, short-cut short fibers or chopped strands may be used, or filament yarns or bundled filament yarns may be used in the form of long fibers, or so-called fiber rods. Further, it can be used as a non-woven fabric, a mat-like product, a mesh-like product, a knit-like product, a two-dimensional or three-dimensional woven fabric, and the like. Further, such synthetic fibers can be used in combination with other reinforcing materials such as carbon fibers and reinforcing bars. When short-cutting fibers and using them as short fibers, it is necessary for the fibers to be uniformly dispersed and distributed in the matrix in order to sufficiently exert the reinforcing effect. For that purpose, the aspect ratio of the short fibers (fiber The ratio of the fiber length to the average diameter of the) is 150 to 1500,
Particularly, it is desirable to set it to 300 to 800.

The addition ratio of the synthetic fiber in the hydraulic molded product of the present invention is 0.3 to 10% by weight, preferably 0.5 to 5%.
%, And more preferably 1.0 to 3.0% by weight.
If it is lower than this range, the reinforcing property is poor, and in the high adding region, the dispersibility is poor, and the reinforcing effect is difficult to obtain. Further, when pulp is used as a molding aid, it is used in order to facilitate molding, improve the curing speed in primary curing, and maintain the nonflammability of the molded product.
Weight% or less is desirable.

Cement is typical as the hydraulic material of the present invention, and Portland cement and various other cements can be used. Further, a calcareous raw material and a siliceous raw material can be mixed and used. A siliceous raw material is indispensable for producing a tobermorite crystal having excellent dimensional stability as a matrix, and its Blaine specific surface area is 2000 cm ↑ 2 / g or more, preferably 4
000 cm ↑ 2 / g or more, more preferably 6000 cm
↑ 2 / g or more, the higher the Blaine value, the more easily tobermorite crystals are formed, the higher the matrix strength, and the more remarkable the fiber reinforcing effect. Further, these hydraulic materials may be mixed with sand or gravel to be used as mortar or concrete. Gypsum, gypsum slag, magnesia, etc. may be added as other hydraulic substances. In addition, mica, sepiolite, attabarugite,
An auxiliary material such as perlite can be used.

There is no need to use any special method for producing the molded article, and a general FRC production method may be used. For example, in the case of a thin plate, there is a wet papermaking method such as the Haschek method, and mortar, concrete, etc. In the case of, there are vibration molding, centrifugal molding, extrusion molding and the like.

The conditions such as the temperature and the time for carrying out the primary curing until the surface hardness of the molded product after molding is 80% or more may be appropriately selected depending on the molding method.
0 ° C to 60 ° C is suitable. In order to bring out the reinforcing effect of the fiber, it is necessary to carry out primary curing until the surface hardness of the molded product reaches 80% or more. However, if the curing is excessively advanced in the primary curing, it may be difficult to generate tobermorite even if the autoclave curing is performed.

Subsequently, autoclave curing is performed. In autoclave curing, it is necessary to cause a hydrothermal reaction between siliceous and calcareous substances, and the curing is performed at 140 ° C or higher, preferably 155 ° C or higher. In addition, the higher the temperature, the higher the reaction rate, so that the time can be shortened, which is preferable.

EXAMPLES The present invention will be described below with reference to examples. In the examples,% is a value based on weight unless otherwise specified. In addition, in the examples, the effect of autoclave curing is expressed by dimensional stability, and the reinforcing effect of fibers is expressed by the toughness ratio of the molded product after autoclave curing. These are measured by the following methods. Surface hardness of moldings; Hardnes manufactured by Kyoto Kobunshi Keiki Co., Ltd.
Measured by Tester Type C Asker Dimensional stability; Measured according to length change test by water absorption of JIS A-5418 Toughness ratio; Bending in wet state (after immersion in water for 3 days) according to JIS K-6911 Strength span 5 cm
When the maximum point where the linear relationship between the bending strength and the rise of the bending curve is maintained is LOP, and the maximum point of the bending strength extracted by the reinforcement of the fiber is MOR, the bending strength and the bending strength at each point are measured. Let LOP toughness and MOR toughness be the product of
And MOR toughness ratio = (MOR toughness) / (LO
(P toughness). Since the toughness ratio of LOP and MOR becomes larger in the wet state as well as in the dry state, the toughness ratio of LOP and MOR in the wet state was measured in the present invention. When the value is 1.0, there is no reinforcing effect.

Examples 1, 2 and Comparative Example 1 5% by weight of acrylamide and 95% by weight of acrylonitrile
A spinning dope was prepared by dissolving the copolymer of (1) in a 65% by weight aqueous nitric acid solution so that the polymer concentration was 20% by weight. The stock solution was extruded from a nozzle into a 33 wt% nitric acid aqueous solution, solidified, and washed with water, and drawn 4.0 times and 3.5 times under boiling water and steam, respectively. Subsequently, the fibers were impregnated with formaldehyde, dried in an air bath at 150 ° C to cause a crosslinking reaction at the same time, and further heat-treated at 230 ° C. The obtained fiber has a strength of 10.3 g / d at 2d, and in a filtrate of Portland cement having a pH of 11.5,
Even after the treatment at 100 ° C. for 24 hours, the crosslinking was performed until the strength of 10.1 g / d was maintained. 6m of the fiber
cut into m and 2% by weight of the fiber with a Hascheck machine,
3% by weight pulp, 55% by weight Portland cement, 40% by weight silica powder with a Blaine value of 5400 cm ↑ 2 / g
Wet papermaking with the following composition, primary curing at 50 ° C for different time, and then autoclave curing at 160 ° C for 10 hours,
A slate plate having a thickness of 4 mm was obtained. Table 1 shows the physical properties of the molded product obtained under each condition.

[0025]

[Table 1] As shown in Table 1, when primary curing is insufficient, the fiber does not contribute to the toughness (reinforcing effect) at all.

Comparative Example 2 Example 1 except that the fiber not subjected to the crosslinking treatment was used.
Fibers were obtained and a slate plate was prepared by the same method as described above.
The strength of the fiber was 10.5 g / d, but it was lowered to 6.2 g / d by the alkali treatment. Also,
The toughness ratio of the slate plate was as low as 1.1.

Examples 3, 4 and Comparative Examples 3, 4 Fully saponified PVA having a degree of polymerization of 1800 was dissolved in water at a concentration of 15%, and boric acid and nonylphenol ethylene oxide 40 mol adducts were added to PVA at 1% each. .5
% And 3.0% were added to prepare a spinning dope. The spinning solution was wet-spun into a coagulation bath of sodium hydroxide 15 g / l and mirabilite 350 g / l at 60 ° C., followed by roller stretching, neutralization, wet heat stretching, washing with water, and 3 g / l phosphate bath. And then dried. Subsequently, the film was dry-heated and wound at 230 ° C. so that the total draw ratio was 23 times. Subsequently, the fiber is in the form of a cassette and is immersed in a bath of 2 g / l of glutaraldehyde, 50 g / l of formaldehyde and 70 ° C. and appropriately squeezed, and then 100 g / l of formaldehyde, 70 g / l of sulfuric acid, 30 g / l of mirabilite 80 Treated in a bath at 0 ° C. The fiber thus obtained had a strength of 1.5d, a strength of 15.1 g / d, and a strength after the alkali treatment of 14.9 g / d. This is 6mm
Cut into 0.1% by weight (Comparative Example 3), and the addition ratio was 0.1.
5% by weight (Example 3), 5.0% by weight (Example 4), 1
A slate plate was made in the same manner as in Example 1 with 1% by weight (Comparative Example 4). Table 2 shows the dispersibility of the fibers and the physical properties of the slate plate.
Shown in.

[0028]

[Table 2]

If the fiber addition rate is too lower than the range of the present invention, it will not contribute to the improvement of toughness, and if it is too high, the dispersibility will be poor and neither dimensional stability nor toughness will be improved.

Examples 5, 6 and Comparative Example 5 In Example 1, the autoclave curing conditions were changed.
Table 3 shows each condition and slate physical properties.

[0031]

[Table 3]

As is apparent from the table, when the curing temperature is low, the dimensional stability is insufficient even if the time is extended.

[0033]

Industrial Applicability According to the present invention, it becomes possible to manufacture at low cost a hydraulic molded article having excellent performance such as dimensional stability and strength by using inexpensive synthetic fiber, and it is possible to comply with the regulation of the use of asbestos.

Claims (1)

[Claims] 1. A cross-linked synthetic fiber is mixed as a reinforcing component in an amount of 0.3 to 10% by weight, and the mixture is molded. After primary curing so that the surface hardness of the molded product becomes 80% or more, 14
A method for producing a hydraulic molded article, which comprises performing autoclave curing at 0 ° C or higher.