KR950014704B1 - Extrusion-moldable hydraulic cement-based composition - Google Patents

Abstract

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Description

Hydraulic Cement Substrate Composition for Extrusion

The present invention provides a hardening cement base composition having a high mechanical strength with a relatively small amount of an organic binder as an additive compared to a hydraulic cement base composition for extrusion molding, or more particularly, compared to a conventional hydraulic cement base composition for extrusion molding. The present invention relates to a hydraulic cement base composition for extrusion molding which can provide a product.

As is well known, preformed cement based boards and other products reinforced with asbestos fibers are widely used in construction as exterior wall materials, roofing materials, flooring materials and the like. This preformed cement based product is cured into a product form of a composition consisting of a mixture of water-based cement, asbestos fibers, aggregates (e.g. fine sand), and other additives with water, about 10% by weight of cement. The desired cross section is obtained by extruding into the die of the extruder.

Although various kinds of reinforcements have been proposed and widely used in addition to the above-mentioned asbestos fibers, most of the reinforcements used so far have been occupied by asbestos fibers having very good properties. In other words, the asbestos fibers have a very good dispersibility to the cement base composition, and can obtain an extruded raw molded body having excellent shape retention and water retention. In addition, the asbestos fibers have a high heat resistance sufficient to withstand the curing conditions of extruded bodies usually carried out in autoclaves under overpressure of water vapor at 170 ° C. or higher, so that the dimensional stability and mechanical properties of hardened cement-based boards are necessary for building materials. Strength can be given. Therefore, nothing can be compared with asbestos fibers in view of the various requirements (dispersibility in the composition, form- and water-retaining properties, heat resistance, etc.) as reinforcing materials combined in the extrusion-based cement based composition.

However, asbestos fibers have recently been suspected of carcinogenicity due to their unique fiber morphology, which is a serious problem for the public. Soon, asbestos fibers will be completely banned as reinforcements in cement-based compositions for extrusion. Therefore, by first reducing the amount of asbestos fibers blended into the cement-based compound immediately and using a substitute material for the asbestos fibers, it is eager to produce an extruded cement-based composition that does not use asbestos fibers as a reinforcing material. It is hoped to be.

To date, various types of synthetic organic fibers have been proposed and tested as an asbestos fiber replacement strengthening agent in extrusion-based cement based compositions, but none of them satisfy all of the above requirements. Apart from the fact that synthetic organic fibers are relatively much more expensive than asbestos fibers, i.e., there is no satisfactory synthetic organic fiber in terms of dispersibility in the composition and the form-and water-retainability of the extruded body. In addition, some synthetic organic fibers are poorly heat resistant to the point that they cannot withstand the conditions of autoclaving at atmospheric pressure of high pressure steam. In particular, synthetic organic fibers, which can impart high mechanical strength to cured objects, are usually very expensive.

Apart from synthetic organic fibers, proposals have been made to use pulp fibers, a type of natural organic fibers, as an asbestos fiber substitute. Besides the advantages of being relatively inexpensive compared to synthetic organic fibers, pulp fibers, although less than asbestos fibers, have good dispersibility in cement based compositions. In addition, the pulp fibers are suitable for sawing, nailing and reinforcing together with reinforcing cement-based boards, which can exhibit their own advantages that are hardly available in asbestos fibers.

As a result of the recent trend to achieve higher efficiency in extrusion of cement based compositions for producing preformed moldings, cement based compositions reinforced with asbestos fibers or pulp fibers are subjected to high compressive forces during extrusion. In spite of the excellent water-retaining properties sometimes imparted by these reinforcing fibers, the water is separated and covered with a layer of free water on the surface of the extruded body so that the extruded parts are attached to each other before the extruded body is completely solidified and cured, thus slightly deforming the extruded body do.

For the purpose of solving the above-mentioned problems in the moldability of cement-based compositions reinforced with asbestos or pulp fibers under high pressure extrusion, it has been proposed to mix extrusion-based cement-based compositions with binders and water-soluble organic polymers. Until now, Japanese Patent Publication No. 43-7134, in addition to methyl cellulose, hydroxypropyl methyl cellulose, etc., various kinds including hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose, polyethylene oxide, poly (sodium acrylate), casein and the like Water-soluble organic polymers have been proposed, of which hydroxyalkyl alkyl celluloses are the most widely used in terms of good dispersibility imparted to cement and aggregate particles, and good adhesion and water-retaining properties to the extruded bodies combined with them. Used.

Many proposals have been made by previous practitioners for blending extruded cementitious compositions with pulp fibers as reinforcements and mixing them with organic binders and the like. For example, Japanese Patent Laid-Open No. 63-1276 discloses cement-based compositions incorporating pulp fibers, spherical particles of synthetic resin having a bubble structure formed by primary foaming, and binders such as methyl cellulose, which are to be extruded. It can be and can be cured to obtain a hardened cement based molded body suitable for sawing or nailing.

However, the pulp commonly used in the prior art is a wood pulp obtained by grinding coniferous or hardwood, or a pulp recycled from the highland of such wood pulp, so that it contains a large amount of lignin derived from wood containing 30-50% by weight of lignin. Since the lignin component of the pulp has the adverse effect of delaying the curing time of the hydraulic cement, the time required for curing the compacted body by the autoclave treatment is excessively increased, resulting in an increase in the production cost. The use of pulp fibers as an asbestos fiber replacement reinforcement in the base composition is also not without any problems.

The adverse effect of pulp by lignin is of course not a serious problem when using chemical pulp containing small amounts of lignin after chemical treatment as reinforcing material, if the price is not so expensive compared to wood pulp, the chemical pulp is very suitable for the purpose. . That is, when the chemical pulp is used in a large amount enough to exhibit a reinforcing effect in the cement-based composition for compression molding, the composition is more expensive than the composition blended with asbestos fibers, so it is not practically useful.

On the other hand, Japanese Laid-Open Patent Publication No. 63-256558 discloses an extrusion molding cement substrate composition characterized by consisting of a ground wood pulp and a hydraulic cement added with a curing accelerator. However, such a composition is lowered in price by using inexpensive groundwood pulp as compared to chemical pulp, but does not provide a solution to the problem in pulp-reinforced compositions because the curing accelerator is expensive enough to offset this.

Furthermore, groundwood pulp is much shorter than chemical pulp with fiber lengths of up to 6 mm when used in conifers, up to 2 mm in hardwoods and up to 25 mm, and has a particularly poor reinforcement effect on the impact strength of hardened cement-based moldings that are reinforced together. This is also a problem. The recycled pulp at high altitudes does not exhibit the desired reinforcing effect because the fiber length of the recycled pulp is sometimes much shorter than that of fresh ground wood pulp, at least in part due to the reduced ligline content.

When the pulp is groundwood pulp, in addition to increasing the cost for the pulp fibers by blending it in large quantities, another factor that increases the cost of the pulp-reinforced cementitized composition is that the amount of organic binder must be increased to balance the pulp fibers. It is. In addition, the fire resistance of the hardened cement based molded body is reduced by the amount of pulp fibers blended into the cement based composition for extrusion molding.

In view of the situations described above, it is desperately desired to develop cement-based compositions for extrusion that meet various requirements, including: the amount of organic fibers added to the composition as a reinforcing agent is as small as possible; The preformed cement based moldings obtained from the composition by molding and curing should be suitable for sawing and nailing; The preformed molded and hardened cement based molded parts of the composition must have a high resistance to mechanical impact in order to be less damaged during transport; The preformed molded and hardened cement based molded articles of the composition must have sufficient and required mechanical strength, including impact strength, in use; The amount of organic binder required for the composition should be small enough to not adversely affect the moldability of the composition; The composition should be able to be produced at the lowest possible cost throughout the production process.

It is therefore an object of the present invention to provide a novel and improved cementitious composition for extrusion molding which is reinforced with fiber reinforcement without the disadvantages and problems of the above mentioned former fiber-reinforced cementitious composition.

Therefore, the cement-based composition for extrusion molding of the present invention is:

(a) hydraulic cement;

(b) inorganic aggregate in powder form;

(c) organic polymers as binders;

(d) crude crude linter pulp fibers; And

(e) containing as a mixture a composition of a concentration suitable for extrusion.

As mentioned above, the essential components in the cementitious composition for extrusion molding of the present invention are components (a) to (e), the most characteristic of which is component (d).

In the composition of the present invention, the basic component is hydraulic cement, which is component (a), although Portland cement is relatively inexpensive and most preferably used, Portland cement, blast furnace cement, flash cement, alumina There are no particular restrictions on the type specific to various hydraulic cements, including cement. If appropriate, two or more types of hydraulic cement may be used in combination.

Component (b) in the composition of the present invention may be any aggregate material of known inorganic aggregate material, including fine sand, silica powder, etc., having a particle size equivalent to hydrocement cement, pearlite, vermiculite, fly ash and the like. Fine silica sand can also be used in limited quantities. The particle size of the aggregate material depends on the special forms of preformed and hardened cemented bodies made from the compositions of the present invention. The amount of aggregate material relative to hydraulic cement is common as in normal cement mortar compositions.

Component (c) is a water soluble organic polymer used as binder. Examples of suitable binder materials include methyl cellulose and hydroxyalkyl alkylcelluloses such as methyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, hydroxyethyl ethylcellulose and the like. Although not particularly limited, the cellulose ether used as component (c) has an average degree of polymerization capable of obtaining a 2% by weight aqueous solution having a viscosity of at least 20.000 ° C poise at least 20 ° C, preferably at least 30,000 center poise. The amount of organic binder added to the composition of the present invention should be as small as possible so that good extrudability can be imparted to the composition because the organic polymer is relatively expensive. Typically, in most cases, the amount of the organic polymer as the binder is 0.2 to 10 parts by weight, preferably 0.3 to 0.5 parts by weight per 100 parts by weight of the total amount of the hydraulic cement as component (a) and the inorganic aggregate material as component (b). to be.

The most characteristic component (b) among the components of the composition of the present invention is crude linter pulp, which is short-haired fibers which stick cotton seeds after taking out cotton seeds before purification treatment such as degreasing. Normally before degreasing, the crude linter contains up to about 10% by weight of oleaginous material. Unexpectedly, the oleaginous material does not adversely affect the curing of the cement based composition of the present invention but rather acts as a kind of lubricating oil that enables more smooth extrusion, thereby providing the possibility of reducing the amount of water-soluble organic polymer as a binder. Has a beneficial effect. In the present composition, the amount of the crude linter as component (d) is preferably 2-5 parts by weight per 100 parts by weight of the total amount of the hydraulic cement as component (a) and the inorganic aggregate material as component (b), and thus good impact strength. Can be imparted to the molded article and the cured molded article of the present cement based composition.

If acceptable, asbestos fibers may be used as auxiliary reinforcement in a coarse printer in a limited amount of up to 5 parts by weight per 100 parts by weight of component (a) hydraulic cement and component (b) inorganic aggregate material.

Component (e) is water essential for carrying out hydroponic curing of the cement based composition. The amount of water in this composition should be as small as possible so that the composition can have a concentration suitable for extrusion and the uniformity of the composition can be maintained. Usually, the amount of water in the present invention is in the range of 20 to 50 parts by weight per 100 parts by weight of the hydraulic cement of component (a) and the inorganic aggregate material of component (b).

In the following, the hydraulic cement composition for extrusion molding of the present invention is described in more detail in the comparative examples except for this, but this does not limit the scope of the present invention in any way. In the following description, the term "parts" always means "parts by weight".

EXAMPLE

Six hydraulic cement-based compositions, referred to hereinafter as Compositions I, II, III, IV, V and VI, are usually 70 parts of Portland cement, 30 parts of silica with an average particle diameter of 12 μm, and 2-10 mm in length. Crude crude linters of 10-40 μm in diameter are referred to as 1, 2, 3, 3, 4, and 5 parts for each in lint-free form, binders I, II, III and IV below and shown in Table 1 0.5 parts (compositions I, II, IV, V and VI) or 0.4 parts (composition III) in cellulose ethers present, and an amount of water capable of obtaining a water ratio of 25-30% / cement as shown in Table 1 Mix for 3 minutes at 500rpm by Henschel mixer and re-dough for 5 minutes with a double arm dough.

The cellulose ethers mentioned above as binders I-IV are depicted as follows.

I: Hydroxypropyl methyl cellulose (90SH-100000, manufactured by Shin-Etst Chemical Co.), capable of giving a 2% by weight aqueous solution with a viscosity of 80,000 centipoise at 20 ° C.

II: hydroxypropyl methyl cellulose (90SH-15000, same company as above) which can give 2 wt% aqueous solution with viscosity of 15,000 centipoise at 20 ℃

III: hydroxypropyl methyl cellulose capable of giving a 2 wt% aqueous solution with a viscosity of 15,000 centipoise at 20 ° C. (SEW-15T, manufactured by the same company as above)

IV: Methyl cellulose which can give 2 weight% aqueous solution of viscosity 8,000 centipoise at 20 degreeC (SM-8000, the same company product mentioned above)

Each of the compositions I-VI is transferred to an extruder, and the raw molded body in the form of a board having a continuous length is extruded through a slit die having a hole having a width of 75 mm and a thickness of 6 mm. The state of the thus-extruded green compacts is visually observed by recording A or B when no cracks or cracks are found, respectively.

To test the length of time needed to cure the composition, take 30 g from the extruded raw molded body, make it into round balls, put it in a plastic film bag and hold it in a 45 ° C. constant temperature device, so that the plastic in the ball when compressed to a weight of 20 kg Measure the length of time until no deformation occurs.

The raw molded body of the board extruded from the extruder is first cured at 45 ° C. and 100% of atmospheric pressure at atmospheric pressure for 24 hours, and then cured for 8 hours in an autoclave at 170 ° C. and 9 kg / cm 2 G pressure. The cured boards obtained were measured for Charpy impact strength according to the method specified in JIS K 6971 and for bending strength and compressive strength according to the method specified in JIS R 5201.

Nailing suitability assessments were also conducted for hardened boards prepared by extrusion molding with a 15 mm thick opening and then curing under the same curing schedule. Therefore, after hammering the iron nail of 2 mm diameter and nailed to the board, the state of the board was visually observed, and the case where no crack appeared or the crack appeared, respectively, was recorded as A or B. The results are shown in Table 1.

TABLE 1

Comparative Example 1

For comparison, four extruded cement based compositions, referred to hereinafter as compositions RI, R-II, R-III and R-IV, have a fiber length of 0.5-3 mm and a fiber diameter instead of crude crude linter pulp. 5 parts or 7 parts of pulp recycled from the highland of 10-30 μm, the binder is formulated in the amounts shown in Table 2, the binder I, water / cement ratio in the Examples described above except increasing as shown in Table 2 It is prepared in the same manner as.

The results of the formulation and evaluation tests for each composition of R-I-R-IV are summarized in Table 2 below.

TABLE 2

Comparative Example 2

For further comparison, four extruded cementitious compositions, referred to hereinafter as compositions BI, B-II, B-III and B-IV, have a fiber length of 0.5-4 mm and a fiber diameter of 10 instead of recycled pulp. Replaced with a hardwood wood pulp of ˜40 μm, the binder was prepared in the same manner as in Comparative Example 1 except that the binder I and water / cement ratios each formulated in the amounts shown in Table 3 below.

TABLE 3

Comparative Example 3

For further comparison, four extruded cementitious compositions, referred to hereinafter as compositions CI, C-II, C-III and C-IV, have a fiber length of 0.9-0.6 mm and a fiber diameter instead of recycled paper pulp. Replaced with hardwood wood pulp of 10-70 μm, the binder was prepared in the same manner as in Comparative Example 1 except that the bound I and water / cement ratios were each formulated in the amounts shown in Table 4 below. do.

The formulations and results of the evaluation tests of each of Compositions C-I-C-IV are summarized in Table 4 below.

TABLE 4

[Comparative Examples 4 and 5]

In Comparative Example 4, for the sake of further comparison, four cement-based compositions for extrusion molding, hereinafter referred to as compositions PI, P-II, P-III and P-IV, have a fiber length of 1-7 instead of recycled paper pulses. Mm and a fiber diameter of 10-40 μm, replaced with crude linter pulp, the binder is bound I each formulated in the amounts shown in Table 5 and the water / cement ratio is shown in Table 5 except that Prepared in the same manner as in.

In Comparative Example 5, asbestos fibers having a fiber length of 1 to 10 mm and a fiber diameter of 1 to 10 μm, instead of pulp, were used as comparative compositions, referred to below as AI, and the binder was an amount of binder I shown in Table 5 below. The water / cement ratio is prepared in the same manner as above except that shown in Table 5.

Formulation and evaluation test results for each of the compositions P-I P-IV and A-I are summarized in Table 5 below.

TABLE 5

Claims (3)

(a) hydraulic cement; (b) inorganic aggregate in powder form; (c) 0.2-1.0 weight part of organic polymer as a binder per 100 weight part of components (a) and (b) gross weight; (d) 2 to 5 parts by weight of crude crude linter pulp fibers per 100 parts by weight of the components (a) and (b) total weight; And (e) a mixture consisting of 20 to 50 parts by weight of water to provide a composition having a concentration suitable for extrusion molding per 100 parts by weight of the components (a) and (b) total weight. The cement based composition for extrusion molding according to claim 1, wherein the organic polymer as a binder is a water-soluble cellulose ether. 3. The cement-based composition for extrusion molding according to Claim 2, wherein the 2% by weight aqueous solution of the water-soluble cellulose ether has a degree of polymerization of at least 15,000 centipoise at 20 ° C.