JPH04139044A - Cement composition - Google Patents

Abstract

PURPOSE:To improve the shock resistance, bending strength and compressive strength of a cement compsn. and to make it possible to work a molded product of the compsn. by nailing, sawing and other method by incorporating a small amt. of crude linters as reinforcing fibers. CONSTITUTION:This cement compsn. contains crude linters as reinforcing fibers in place of asbestos. The crude linters are low-cost short fibers separated from the shells of cottonseeds after reaping long fibers. The amt. of the crude linters used is 2-5 pts.wt. per 100 pts.wt. inorg. components such as cement.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

TECHNICAL FIELD The present invention relates to a cement composition, and particularly to a cement composition that provides a cement molded article with strength equal to or greater than that of conventional cement compositions. [0002]

[Conventional technology]

Conventionally, cement boards reinforced with asbestos fibers have been widely used as exterior wall materials, roof materials, floor materials, etc. of buildings. This is made by adding water to a mixture of cement and about 10% by weight of asbestos fibers, aggregates, etc., kneading it, and extruding it using a die of the desired shape, or diluting it with water to form a slurry, and making it into paper. It was manufactured by methods such as molding and mold casting. [0003] This asbestos fiber has extremely good dispersibility during mixing and mixing, and the resulting mixed material has good shape retention during extrusion molding. It has the ability to easily produce thick paper sheets. Furthermore, even when cured in a steam pressure cooker at a high temperature of 170°C or higher to impart dimensional stability and necessary strength to molded products, this fiber has excellent heat resistance, so it can fully perform as a strength reinforcing fiber. He is showing his full potential. In this way, asbestos fibers are unique in that they simultaneously satisfy the various properties required for manufacturing molded products, such as dispersibility, shape retention, water retention, retention of inorganic particles in slurry, and heat resistance. Because it is a reinforcing fiber that does not have any carbon dioxide, it has been used exclusively for the production of various molded products by extrusion molding, paper forming, etc. [0004] However, in recent years, asbestos 1 fiber is said to be carcinogenic due to its unique fiber shape. It is becoming necessary to do so. Organic synthetic fibers were first considered as fibers to replace asbestos, but all of them had poor dispersibility, shape retention, water retention, and retention of inorganic particles in slurry. Therefore, their heat resistance is poor, and some fibers cannot be subjected to the steam pressure curing described above. In addition, from a cost perspective, some materials with high reinforcement strength are considerably more expensive than asbestos fibers, and it is difficult to find any material that is truly satisfactory. [0005] On the other hand, pulp fiber, which is an organic natural fiber, is relatively cheap in cost, and although it is not as good as asbestos fiber in terms of dispersibility, it is superior to other organic fibers. The obtained molded product can be processed by nailing, sawing, etc., which was difficult to do with conventional asbestos fiber-containing cement molded products, and has the advantage of being easy to install as an exterior material for buildings. For this reason, it has been attracting attention in recent years as an alternative material to asbestos fibers. [0006] On the other hand, in extrusion molding of a cement mortar composition,
In general, a lot of pressure is applied during molding, and even in the case of cement compositions containing asbestos fibers or pulp fibers, the water retention properties of these fibers alone cannot uniformly retain water within the molded body, and extrusion Since the water is separated and the molded products adhere to each other until the molded product is solidified and hardened, it has been difficult to maintain the shape of the molded product discharged from the die. [0007] In order to improve this moldability, a method has been proposed in which an organic binder is used in a composition for extrusion molding. Examples of this organic binder include methylcellulose, hydroxypropylmethylcellulose, etc. described in Japanese Patent Publication No. 43-7134, as well as hydroxyethylcellulose, carboxymethylhydroxyethylcellulose, polyethylene oxide, sodium polyacrylate, casein, etc. Among these, hydroxyalkylalkyl cellulose is widely used because it has good dispersibility in cement, aggregate, etc., and has excellent water retention and adhesive properties. [0008] Several proposals have been made so far regarding molding compositions containing pulp fibers to which such binders are added. For example, Japanese Patent Publication No. 63-1276 discloses that a cement composition containing pulp fibers, a primarily foamed spherical resin, and a binder such as methylcellulose is extruded and molded into a mold that can be sawed or nailed. It has been shown that the body can be obtained. [0009] However, the pulp fibers disclosed in the prior art of Kotada et al.
It is either wood pulp from hardwoods of about 500 yen in size or waste paper pulp recycled from this. Especially when wood pulp is used, if the content of lignin in the pulp is high, it slows down the hardening time of cement and takes a lot of time for curing. Therefore, pulp from which 30 to 50% of lignin has been removed by chemical treatment is usually used. [0010] Pulp subjected to this chemical treatment is expensive and has a shorter fiber length, so compared to asbestos fibers that can be observed up to 25 mm, it is significantly inferior in its effectiveness as a reinforcing fiber, especially its impact strength reinforcement effect. Become. On the other hand, recycled waste paper pulp eliminates the hardening delay caused by lignin, but many have shorter fiber lengths and lack strength reinforcing effects. [0011] In order to achieve this fiber reinforcing effect on par with asbestos using wood pulp, a considerable amount must be added.
This resulted in higher costs. Pulp with such short fiber length has poor retention of inorganic particles in cement slurry (unlike when asbestos fibers are used), so when making thick paperboards, polymer flocculants such as polyacrylamide are used. Therefore, it is necessary to agglomerate inorganic particles such as cement to form paper, which also leads to higher costs. Similarly, JP-A-63-256558 discloses extrusion molding of cement/wood pulp with the addition of a hardening accelerator, but this method becomes more expensive due to the use of the hardening accelerator. . This increase in wood pulp also reduced the nonflammability of the cement molded body. [0012]

[Problem to be solved by the invention]

Due to these circumstances, ■ The amount of organic fiber added is as small as possible; ■ Nailing and sawing are possible; ■ The molded board is less likely to be damaged during transportation; ■ In use,
It has been desired to develop an organic fiber-containing molding cement composition that satisfies the following requirements: - has the necessary and sufficient impact, bending, and compressive strengths; - can be molded with as little organic binder as possible; - has low manufacturing costs. . [0013]

[Means to solve the problem]

The present invention was achieved as a result of intensive studies to solve these problems, and its gist is that a cement composition for molding contains unrefined crude linter as a reinforcing fiber. To explain the present invention in detail below, unrefined crude linter used as reinforcing fiber in the present invention refers to the maximum length of long hair fiber (lint) that is separated from the cottonseed shell after cutting the long hair fibers (lint) from the cottonseed. Low-priced short fibers (crude linters) with a diameter of about 10 mm are obtained by extrusion or paper-forming without being purified with alkaline solution or chlorine bleach. It has been shown that impact strength comparable to that of asbestos/cement-based molded products can be obtained in molded products by adding only 2 to 5 parts by weight of unrefined crude linter to 100 parts by weight of inorganic components such as cement and gay stone powder. This is the heading that led to the present invention. [0014] Although this short-haired fiber (crude linter) contains less than 10% of oil and fat components, this does not have a negative effect on the hardening of cement, but rather works as a lubricant to facilitate molding. , the amount of organic binder required during molding can be reduced. As mentioned above, the amount of this crude linter added to 100 parts by weight of the total inorganic components such as cement and silica powder is 2 to 2.
Amounts as low as 5 parts by weight are effective. [0015] As the binder used in combination during extrusion molding, water-soluble alkyl cellulose and/or hydroxyalkylalkyl cellulose that have been generally used in conventional cement compositions for extrusion molding can be used, and specifically, methyl cellulose, hydroxy Examples include propyl methyl cellulose, hydroxyethyl methyl cellulose and hydroxyethyl ethyl cellulose. [0016] It is desirable that the amount added be as small as possible in order to reduce costs, but if it is too low, the molding condition will deteriorate, so the total amount of inorganic components such as cement and silica powder should be 10
It is preferable to set it as 0.3-0.5 weight part with respect to 0 weight part. Further, as a viscosity index corresponding to the degree of polymerization of the binder used, the higher the viscosity in a 2% aqueous solution, the more preferable it is because the amount added can be reduced. Specifically, 2%
The viscosity of an aqueous solution at 20° C. is 15,000 cps or more, particularly 30,000 cps or more. [0017] The flocculant used during paper forming may be a commonly used water-soluble polymer flocculant such as polyacrylamide, or an inorganic flocculant such as aluminum sulfate. The addition amount is sufficient to be 0.5% or less to a slurry that can be easily molded to a desired thickness. Water-soluble alkyl cellulose and/or hydroxyalkyl alkyl cellulose can be used as admixtures for improving fluidity and preventing breathing in mold casting, and specifically methyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose. , hydroxyethyl ethyl cellulose and the like. In order to improve shape retention, lubricity, water retention, inorganic particle retention, etc. during molding, asbestos fibers can be added in addition to coarse linter; If so, the object of the present invention can be achieved even if it is added in a small amount, specifically 5% by weight or less, without affecting the cost. [0018] Cement mortar, which is the main component of the cement composition of the present invention, is a well-known cement material consisting of aggregate, water, other additives, etc. The cement mortar used here includes ordinary Portland cement. In addition, special cement such as alumina cement can also be used as long as it does not affect the cost. Silica stone, preferably silica powder with a grain size comparable to cement, can also be used as an aggregate, as well as lightweight aggregates such as perlite, vermiculite, and fly ash, as well as silica sand.
No. 12 can also be used as long as it does not interfere with the present invention. There is no problem with the amount of water to be added as long as it is within the range that can be used for extrusion or paper forming.For example, for 100 parts by weight of inorganic components such as cement and silica stone, in the case of extrusion molding, it is approximately 20 to 50 parts by weight, and for paper forming and forming. In the case of mold casting, it is preferably added in a proportion of 50 to 400 parts by weight. [0019]

【Example】

Hereinafter, specific embodiments of the present invention will be explained using Examples and Comparative Examples, but the present invention is not limited to these Examples. Example 1 Unrefined crude linter, which is short-haired fibers that remain separated after cutting the long-haired fibers (lint) from cottonseed, was mixed with 70 parts by weight of ordinary Portland cement, silica stone (manufactured by Toriyana Co., Ltd.), and 70 parts by weight of ordinary Portland cement. ), water and a binder were further added under the conditions shown in Table 1, and 5 parts by weight were added using a Henschel mixer.
After mixing at 00 rpm for 3 minutes, the mixture was kneaded for 5 minutes using a double-arm kneader with a capacity of 10 liters, and then extruded into a sheet using an extruder (manufactured by Ishikawa Ji Seisakusho Co., Ltd.) through a die with a width of 75 mm and a gap of 6 mm. The molding state was observed. At this time, the state in which no cracks were formed at both ends of the sheet was evaluated as ○, and the case in which cracks were formed was evaluated as ×. [0020] In addition, 30 g of the molded product immediately after being discharged from the extrusion molding machine was collected, rolled up, placed in a plastic bag, cured in a thermostat at 45°C, and deformed by placing a 20 kg weight on the rolled molded product. The time required for it to disappear was measured and defined as the curing time. Furthermore, for the obtained molded body (sheet), first 45
After curing for 24 hours at 100% relative humidity in an autoclave at 170°C for 8 hours under a pressure of 9 kg/cm2, the impact strength, bending strength,
Compressive strength and nailing properties were measured. In addition, the pulp cost in the table is expressed as a ratio when the cost of the molded article in the amount of 5 parts by weight of waste paper pulp added is 1. The details of the binder used are also shown below. [0021] (Measurement method) Impact strength: Based on Charpy impact strength according to JIS K-6971. Bending strength and compressive strength: Based on bending compressive strength according to JIS R-5201. Nailing property: The molded product (in the case of extrusion molding, molded using a die with a gap of 15 mm) was heated at 45°C and 100% relative humidity for 24 hours.
After curing for an hour, further autoclave at 170℃ for 9k.
For those cured for 8 hours under a pressure of g/cm2, when the molded product did not crack when driven with a nail of 2 mm in diameter, it was rated ○, and when it cracked, it was rated x. [0022] (Binder) A: 90SH-100000 (manufactured by Shin-Etsu Chemical Co., Ltd., hydroxypropyl methylcellulose, 2% aqueous solution at 20°C
Viscosity at 80,000 cps) B: 90SH-1
5000 (manufactured by the same company, the viscosity of a 2% aqueous solution at 20°C is 15°000 cps) C: 5EW-15T (manufactured by the same company, hydroxyethyl methyl cellulose, the viscosity of a 2% aqueous solution at 20°C is 15°C,
000 cps) D: 5M-8000 (manufactured by the same company, methylcellulose, 2% aqueous solution with a viscosity of 8,000 at 20°C
cps) [0023] Comparative Example 1 Waste paper pulp (from unbleached groundwood pulp) Unbleached hardwood and softwood groundwood pulp, and linter pulp (linters obtained from cotton were boiled in dilute aqueous sodium hydroxide solution, sodium chlorite) (obtained by a series of treatments such as bleaching with a chlorine bleach and deashing with an acid) were predispersed in water 16 times the weight of each sheet, and then the sheets shown in Tables 1 and 2 were prepared. Dehydrated to the same amount of water (water ratio), added the indicated binder along with 70 parts by weight of cement and 530 parts by weight of silicone, and poured into a Henschel mixer.
It was treated in the same manner as in the example and measured in the same manner. [0024] Comparative Example 2 Molding was performed in the same manner as in Example 1 except that asbestos 6D-3 (manufactured by Lake Co., Ltd.) was added instead of the unrefined crude linter, and the same measurements were performed under the conditions shown in Table 2. The above results are shown in Tables 1 and 2. [0025]

[Table 1]

[Table 2] [0027] Example 2 The same unrefined crude linter used in Example 1 was mixed with 70 parts by weight of ordinary Portland cement and 30 parts by weight of silica stone (manufactured by Toriyana Co., Ltd.) under the conditions shown in Table 3. After mixing with a Henschel mixer at 500 rpm for 3 minutes, the mixture was placed in an Eirich mixer filled with the water shown in the table and stirred and mixed for 5 minutes. The mixture was transferred to a tank, added with the indicated amount of polyacrylamide as a coagulant, and pressed with a Nowa 2 press roll having a diameter of 500 mm and a length of 8480 mm to form a sheet with a thickness of 10 mm. [0028] After curing this molded product for 24 hours at 45° C. and 100% relative humidity, the molded product is cured to such an extent that even if the surface of the molded product is rubbed with a B pencil, it will not be scratched, and the time required for this is defined as the curing time. And so. This molded product was further heated at 170℃ and 950kg/cm.
After curing in the autoclave No. 2 for 8 hours, impact strength, bending strength, and nailing performance were measured in the same manner as in the previous example, and these results are listed in Table 3 together with the pulp cost determined in the same manner as in the previous example. [0029] Comparative Example 3 Waste paper, unbleached hardwood and softwood pulp, and linter pulp (linter obtained from cotton were boiled in a dilute aqueous sodium hydroxide solution, bleached with a chlorine bleach such as sodium chlorite, and bleached with an acid) (obtained by a series of treatments such as deashing) were dispersed in 16 times their weight in water, and then 70 parts by weight of cement and 530 parts by weight of silicon were added, and the conditions shown in Table 3 were obtained. Water was added thereto, mixed in an Eirich mixer, molded in the same manner as in Example 2, and measured. [0030] Comparative Example 4 Molding and measurement were carried out in the same manner as in Example 2, except that asbestos 6D-3 was used in place of the unrefined crude linter and the conditions shown in Table 3 were used. [0031]

[0032] Example 3 The same unrefined crude linter as used in Example 1 was used under the conditions shown in Table 4 together with 70 parts by weight of ordinary Portland cement and 30 parts by weight of silica (described above). Add the binder with the abbreviation shown in Example 1 in the amount shown in Table 4, mix it with a Henschel mixer at 500 rpm for 3 minutes, then put it into an Omni mixer (manufactured by Chiyoda Giken Co., Ltd.), and add water at the water ratio shown in Table 4. and rotated at maximum speed to mix for 5 minutes. The slurry obtained by mixing is 15 mm thick and 20 mm wide.
Pour into a mold with a depth of 40 mm and heat at 25°C for 10
The molded product was cured under 0% humidity to harden it to the extent that it would not be scratched even when rubbed with a B pencil (the time required for this was defined as the curing time). The cured molded product was demolded, and its impact strength, bending strength, and nailing performance were measured, and these results are shown in Table 4 together with the pulp cost determined in the same manner as in the previous example. [0033] Comparative Example 5 Waste paper, unbleached hardwood and softwood pulp, and linter pulp (linter obtained from cotton were boiled in a dilute aqueous sodium hydroxide solution, bleached with a chlorine bleach such as sodium hypochlorite, and bleached with an acid) (obtained through a series of treatments such as deashing) were used in place of the crude linters shown in Example 3, and molded under the conditions shown in Table 4 and measured. [0034] Comparative Example 6 Molding and measurement were carried out in the same manner as in Example 3, except that asbestos 6D-3 was used in place of the unrefined crude linter and the conditions shown in Table 4 were used. [0035] [0036]

【Effect of the invention】

According to the present invention, although the cost is equivalent to or about 1/3 that of conventional asbestos/cement-based molded products, it has impact, bending, and compressive strengths comparable to those of conventional asbestos/cement-based molded products, and has excellent extrusion, paper forming, and molding properties. It can ensure frame casting moldability and provide workability such as nailing and sawing to the resulting molded product.

Claims (1)

[Claims] 1. A cement composition containing unrefined crude linter as a reinforcing fiber.