JP2001048622A - Admixture for hydraulic composition and hydraulic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve properties with respect to extrusion of a hydraulic composition and water retention properties, of an admixture for a hydraulic composition by using a water-soluble cellulose ether and a polyvinylacetamide-based compound as components of the admixture. SOLUTION: This admixture contains a water-soluble cellulose ether and a polyvinylacetamide-based compound, wherein as the cellulose ether, methylcellulose, hydroxyethyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, hydroxyethyl ethylcellulose, or the like, the 1 wt.% aqueous solution of which has an about 100-50,000 mPa.s viscosity, can be used, however, such a cellulose ether having comparatively high viscosity is desired; as the polyvinylacetamide-based compound, such a compound which has a repeating unit represented by the formula and also a weight average molecular weight of 2×104 to 2×107 and the 5 wt.% aqueous solution of which has about several tens of thousands to several hundreds of thousands mPa.s viscosity is desirably used; the blending ratio by weight of the cellulose ether to the polyvinylacetamide-based compound is desirably 5:95 to 95:5; and the admixture is added to a hydraulic composition desirably in an amount sufficient to provide a 0.2-1.5 pts.wt. ratio of the admixture to 100 pts.wt. of the total of a hydraulic material-(s) and an aggregate in the hydraulic composition. Further, the admixture can also be used for a wide variety of concrete products.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic composition admixture and a hydraulic composition useful as a thickener and the like, which is used as a cement or gypsum-based extrusion molding aid.

[0002]

2. Description of the Related Art
In the hydraulic composition, as a thickener used for extrusion molding, alkyl cellulose such as methyl cellulose,
Hydroxyalkylcellulose such as hydroxyethylcellulose and hydroxyalkylalkylcellulose such as hydroxypropylmethylcellulose and hydroxyethylmethylcellulose have been exclusively used widely.

[0003] The reason is excellent plasticity and water retention performance, and by using these cellulose ethers,
Extrusion molding was easily possible even in extrusion molding not containing asbestos.

[0004] However, these cellulose ethers have a problem in that the cost increases because the purified pulp, which is a natural product, is further subjected to chemical treatment. In order to avoid this, it has been attempted to replace a part of the cellulose ether with a thickening agent which is a chemically synthesized product such as relatively inexpensive poval, starch, polyacrylamide, polyethylene glycol and the like. For example, Patent No. 2
Japanese Patent No. 884118 discloses a method in which a water-soluble cellulose ether and an acrylic copolymer are used in combination to form an admixture for asbestos-free cement extrusion molding. Patent No. 2812837 discloses a water-soluble cellulose ether. A method using a thickener obtained by combining ether and poval is described.

However, these thickeners of chemically synthesized products are very inferior in viscosity and water retention compared to cellulose ethers, so that they are used in large amounts and the water distribution of extruded products becomes uneven. In some cases, the quality as an extruded product is deteriorated, for example, resulting in reduced strength.

[0006] The present invention is an improvement of the above circumstances, and it is possible to improve the extrudability and water retention by using it as a thickener used as a cement or gypsum-based extrusion molding aid. It is an object of the present invention to provide a hydraulic composition admixture which can be obtained and a hydraulic composition prepared by blending the same.

[0007]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to solve the above-mentioned problems of the prior art, and as a result, by using a water-soluble cellulose ether in combination with a polyvinylacetamide compound. The present inventors have found that water-soluble cellulose ether can be reduced, and at the same time, extrudability and water retention are excellent, and the present invention has been accomplished.

Accordingly, the present invention provides (1) an admixture for a hydraulic composition, comprising (1) a water-soluble cellulose ether and a polyvinylacetamide compound, and (2) an alkyl cellulose, a hydroxyalkyl The present invention provides the hydraulic composition admixture characterized by being cellulose or hydroxyalkylalkylcellulose, and (3) a hydraulic composition comprising the admixture.

Hereinafter, the present invention will be described in detail. As the water-soluble cellulose ether used for the admixture for a hydraulic composition of the present invention, alkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkylalkyl cellulose are preferable. , Hydroxyethyl cellulose, hydroxypropyl methyl cellulose,
Hydroxyethyl methylcellulose, hydroxyethylethylcellulose and the like are used. In the case of extrusion molding, the viscosity of this water-soluble cellulose ether is about 100 to 50,000 mPa · s in the case of a 1% aqueous solution. Is preferred.

On the other hand, the polyvinylacetamide-based compound is preferably a water-soluble one because it exhibits excellent water retention performance. Specifically, those having a weight average molecular weight of 2 × 10 ⁴ to 2 × 10 ⁷ having a repeating unit represented by the following formula are preferred.

[0011]

Embedded image

This polyvinyl acetamide compound is
Several to several hundred thousand m in 5% by weight aqueous solution viscosity depending on the degree of polymerization
It is preferably about Pa · s. These may be a homopolymer type or a copolymer with acrylic acid. Further, in consideration of cost, it is preferable to use a material having a relatively high viscosity as in the case of the water-soluble cellulose ether.

The mixing ratio of the water-soluble cellulose ether and the polyvinylacetamide compound may be arbitrarily selected because they have excellent water retention performance, but preferably the water-soluble cellulose ether / polyvinylacetamide compound = 1/9.
It is in the range of 9 to 99/1 (weight ratio), and more preferably in the range of 5/95 to 95/5 (weight ratio).

When the water-soluble cellulose ether and the polyvinyl acetamide compound are added to the hydraulic composition, the amount of the water-soluble cellulose ether and the polyvinylacetamide compound is usually 100 wt. 0.1 per part
Although it is used in the range of 5 to 5 parts by weight, the range of 0.2 to 1.5 parts by weight is preferable in consideration of cost and the like. Since these are used as assistants for extrusion molding, they may be used to such an extent that water retention and plasticity required for extrusion molding are provided. If the addition amount is too small, the required water retention cannot be obtained, or the plasticity is insufficient, and extrusion molding becomes difficult. On the other hand, if the amount is too large, the cost increases and the extrusion molding pressure becomes unnecessarily high due to the increase in the adhesive strength.

Here, as the cement used in the hydraulic composition to which the admixture of the present invention is blended, ordinary portland cement, blast furnace cement, early-strength cement, fly ash cement, alumina cement and the like are used. In the case of a gypsum system, gypsum dihydrate, gypsum hemihydrate and the like are mainly used.
The amount of the cement or gypsum-based hydraulic substance used may be such that the required strength is obtained.

In the present invention, an aggregate can be added as required. Specifically, silica powder or the like is mainly used for extrusion molding, and silica sand, river sand, crushed sand, crushed stone, cobblestone and the like are used for general mortar and concrete. In order to reduce the weight, expanded perlite, high-grade aqueous resin, styrene beads, inorganic hollow microspheres, organic hollow microspheres, and the like are used. The amount used is
In a total amount of 100 parts by weight of the hydraulic substance and the aggregate, 0 to 90 parts by weight, particularly 10 to 90 parts by weight in the case of a normal aggregate.
Used in the range of parts by weight, 0 to 10 for lightweight aggregate
It is used in a range of 0.1 to 10 parts by weight, especially 0.1 to 10 parts by weight.

Further, if necessary, a setting retarder, a setting accelerator, a high performance water reducing agent, a high performance A
An E water reducing agent is also used. Setting retarders and setting accelerators are
The amount to be used may be determined in consideration of the state until the curing after extrusion molding, but usually the total amount of the hydraulic substance and the aggregate is 1
It is used in the range of 0.01 to 10 parts by weight with respect to 00 parts by weight. The high-performance water reducing agent and the AE water reducing agent may be used in such an amount that the fluidity of the system can be ensured, and is usually 0.05 to 6 parts by weight based on 100 parts by weight of the total of the hydraulic substance and the aggregate. Used in the range.

In the case of extrusion molding, it is preferable to add a reinforcing fiber. In addition to conventionally used chrysotile mineral fibers, wollastonite and mica are also used. In addition, pulp fibers, vinylon fibers, polypropylene Fibers and aramid fibers are used. The amount used in this case depends on the desired bending strength and impact strength, but is generally used in the range of 0.1 to 30 parts by weight based on 100 parts by weight of the total amount of the hydraulic substance and the aggregate. You. In particular, when the amount is less than the above range, a sufficient reinforcing effect cannot be obtained, and when the amount is too large, the fibers are not sufficiently dispersed, so that the strength may be reduced. Water is added to the hydraulic composition, and the amount of water is selected according to the type of the hydraulic composition and the like, and can be a normal amount.

The admixture of the present invention is used not only as a thickening agent for extrusion molding, but also as a cement mortar composition such as a cement mortar composition for plasterers, a high-fluidity concrete and a water-inseparable concrete. It can be widely used for concrete products in general.

[0020]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Example I, Comparative Example I] The following materials were used as the cement-based extrusion composition to obtain the compositions shown in Tables 1 and 2. (1) Cement: ordinary Portland cement (manufactured by Taiheiyo Cement) (2) Silica powder: 250 mesh pass product of silica (3) Pulp: average fiber length 1 mm (4) Polypropylene fiber: fiber length 6 mm (5) Water-soluble cellulose ether: Metros SHV-
PF (hydroxypropyl methylcellulose) (20
C, 1% by weight aqueous solution viscosity: 14,500 mPa · s, manufactured by Shin-Etsu Chemical Co., Ltd.) (6) Polyvinylacetamide compound: GE191
(Molecular weight 4 × 10 ⁶ , manufactured by Showa Denko) GE191L (molecular weight 8 × 10 ⁵ , manufactured by Showa Denko) (7) Polyvinyl alcohol: PA-18S (manufactured by Shin-Etsu Chemical) (8) Polyacrylamide: SS-200 (manufactured by Himo) (9) Hydroxypropylated starch: Sorbitose HDF
P (Matsuya Chemical) (10) Water: tap water

<Extrusion molding> Materials other than water were mixed by a Henschel mixer for 3 minutes, a predetermined amount of water was added, and the mixture was further mixed for 2 minutes. Thereafter, the mixture was kneaded in a 10 L kneader-ruder for 5 minutes, and extruded. In this case, a flat plate was prepared using a die shape of 6 × 75 mm, and the surface state was observed. The surface condition was measured visually, and it was observed whether the extruded product had a smooth surface without cracks.

Also, using a die shape of 20 × 40 mm,
The above kneaded material was extruded, primary cured at 65 ° C. for 10 hours, and then autoclaved at 170 ° C. for 8 hours, and then the flexural strength and compressive strength were measured. The measuring method is JI
According to SR5201. The results are shown in Tables 1 and 2.

[0024]

[Table 1] * Material parts displayed * strength N / mm ² Display

[0025]

[Table 2] * Material parts displayed * strength N / mm ² Display

From these results, it can be seen that when a thickener other than the polyvinylacetamide compound used in combination with the water-soluble cellulose ether is used in combination, extrusion molding is difficult or impossible with the same amount of use.

[Example II, Comparative Example II] The following materials were used as the mortar to be tiled, and compositions having the formulations shown in Tables 3 and 4 were obtained. (1) Cement: ordinary Portland cement (manufactured by Taiheiyo Cement) (2) Silica sand: Mikawa silica sand No. 5.6 (3) Water-soluble cellulose ether: Metroose 90SH
-30000 (hydroxypropyl methylcellulose)
(20 ° C., 2% by weight aqueous solution viscosity: 32000 mPa ·
(4) Polyvinylacetamide compound: GE191L
H (molecular weight 2 × 10 ⁶ , manufactured by Showa Denko) (5) Polyvinyl alcohol: PA-18S (manufactured by Shin-Etsu Chemical) (6) Polyacrylamide: SS-500 (manufactured by Hyomo) (7) Water: tap water

Materials other than water were mixed with a 5 L mortar mixer for 1 minute, a predetermined amount of water was added, and kneaded for 3 minutes.

Immediately after kneading the mortar, the following measurements were made. (1) Table flow: According to JIS A 6916. (2) Water retention rate: Based on the Residential City Development Corporation and tiled mortar. The measurement time was after 60 minutes. (3) Tile adhesion strength: Tile adhesion strength at the age of 7 years was measured according to the Residential Urban Development Corporation Law. Tiling is
Immediately after the mortar was applied to the sealant-treated concrete pavement plate with a predetermined thickness, the mortar was attached. The results are shown in Tables 3 and 4.

[0030]

[Table 3] * Material parts displayed * strength N / mm ² Display

[0031]

[Table 4] * Material parts displayed * strength N / mm ² Display

The results show that when a thickener other than the polyvinylacetamide compound used in combination with the water-soluble cellulose ether is used, the water retention rate is low and the tile adhesion strength is remarkably poor.

[0033]

According to the present invention, by using a water-soluble cellulose ether in combination with a polyvinylacetamide-based compound, better plasticity can be obtained and high water retention performance can be obtained as compared with a case where another thickener is used in combination with a water-soluble cellulose ether. Can be obtained.

Claims (3)

[Claims] 1. An admixture for a hydraulic composition, comprising a water-soluble cellulose ether and a polyvinylacetamide compound. 2. The admixture for hydraulic compositions according to claim 1, wherein the water-soluble cellulose ether is an alkyl cellulose, a hydroxyalkyl cellulose or a hydroxyalkyl alkyl cellulose. 3. A hydraulic composition comprising the admixture according to claim 1 or 2.