JPH11255551A - Hydraulic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydraulic composition with improved cracking-proofness and mechanical strength such as flexural strength by including a hydraulic material and a polyvinyl alcohol with saponification degree and polymerization degree each of specific level or higher so as to specify the polyvinyl alcohol content of the composition on the whole solid basis. SOLUTION: The saponification degree and polymerization degree of the polyvinyl alcohol are >=80 mol.% and >=1,200, respectively, and the content of the polyvinyl alcohol in this hydraulic composition is 0.1-20 wt.% on the whole solid basis. It is preferable that the polyvinyl alcohol to be used is a silyl group-modified polyvinyl alcohol, a thickening matter (pref. boric acid or borax) is included at 1-20 wt.% based on the polyvinyl alcohol, reinforcing fibers (pulp is also used other than Vinylon-based fibers) are included at 0.1-10 wt.% on the whole solid basis, and the degree of the silyl group modification is 0.1-10 mol.%. The hydraulic material is an organic matter such as one of various kinds of Portland cement or gypsum. This hydraulic composition is used as a molding material for roofs, external walls, board-like materials for inner walls, roads, shore protective blocks and others.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic composition having high performance and used as a material for buildings, civil engineering, ships, and the like.

[0002]

2. Description of the Related Art In order to improve the mechanical properties and moldability of a molded product made of a hydraulic substance such as cement, gypsum, slag, etc., it is common to add polyvinyl alcohol (hereinafter abbreviated as PVA). Is known. For example, JP-A-49-45934 discloses the use of PVA for improving the bending strength and impact strength of a pulp cement board, and JP-A-61-77655 and JP-A-61-20.
No. 9950 describes that PVA is used for bending strength, impact strength, dimensional stability, and crack prevention of slag and gypsum board.

[0003] Further, Japanese Patent Application Laid-Open Nos. 49-50017 and 60-239377 disclose, for cement molded products,
Japanese Patent No. 51-137719 discloses that for lightweight concrete, the mechanical strength, surface improvement and crack prevention of PV are used.
The use of A is described.

The reason is that PVA is stable at high pH, does not inhibit the hydration reaction of hydraulic substances, dissolves in water, is uniformly dispersed in a matrix such as cement, This is because the physical properties of the hydraulic composition can be improved by bonding between the particles or forming a strong coating.

[0005] However, although there are many types and brands of PVA and their performances are remarkably different, in these known examples, the results when various types of polyvinyl alcohol are variously examined are particularly examined. However, the obtained mechanical properties and workability are not sufficiently improved, and there are problems with uniformity, yield, and wastewater treatment.

[0006]

The necessary improvements of hydraulic molded products represented by concrete are mechanical strength, crack prevention, waterproofness, workability, and the like.

The present inventors have intensively studied these improvements from various viewpoints and focused on silyl group-modified PVA as the most effective PVA to be added to the hydraulic composition. By selecting the degree of polymerization, the mechanical strength of a cured molded product obtained from such a hydraulic composition was successfully improved. In addition, it has been found that the molding performance is good and the effect of improving crack prevention and the like is remarkable. It is also surprising that even when ordinary unmodified PVA is used, a molded article having a higher mechanical strength than a known molded article containing PVA can be obtained by selecting the same degree of polymerization and saponification degree. I found it.

[0008]

The present invention uses a specific PVA as a hydraulic composition. More specifically, the degree of saponification is 80 mol% or more, preferably 88 mol% or more, and the polymerization degree is 1200 or more. , Preferably a P of 1500 or more
VA, more preferably, a silyl group-modified PVA having the above-mentioned conditions is used, and a blend of the PVA and a hydraulic substance, more preferably, a mixture of the PVA and a thickening substance and / or a reinforcing fiber is used.

There are various types of modification of PVA such as cation, anion and nonion modification. We have developed various modified PVA
Were synthesized, and as a result of intensive studies on the effect of adding PVA, they showed a strong affinity with hydraulic substances, strongly bonded between particles of hydraulic substances, etc., and in particular, a nonionic-based material whose properties were remarkable in alkali. Silyl group-modified PVA has been found to be particularly suitable for this purpose.

For example, it is manufactured by the method described in Japanese Patent Publication No. 64-2684. That is, the modified PVA can be produced by (1) a method of introducing a silyl group into PVA by post-modification using a silylating agent, and (2) a method of introducing a silyl group into a modified polyvinyl ester having a hydroxyl group using a silylating agent. A method of saponifying the silyl-modified polyvinyl ester obtained, (3) a method of saponifying a copolymer of a vinyl ester and a silyl group-containing olefinically unsaturated monomer, and (4) the presence of a mercaptan having a silyl group. A method of saponifying a terminal silyl-modified polyvinyl ester obtained by polymerizing a vinyl ester by hydrolysis is exemplified, but the ease of industrial production and the resulting modified P
The methods (3) and (4) described above are preferably used from the viewpoint of VA homogeneity.

Examples of the silyl group-containing olefinically unsaturated monomer used in the above method (3) include vinyl silane such as vinyl methoxy silane, vinyl ethoxy silane, vinyl acetoxy silane, vinyl methyl dimethoxy silane, and 3- (meth) And (meth) acrylamido-alkylsilanes such as acrylamido-propylmethoxysilane and 3- (meth) acrylamido-propylmethyldimethylmethoxysilane. Vinylmethoxysilane is usually preferably used.

Examples of the mercaptan having a silyl group used in the above method (4) include, for example, 3-trimethoxysilyl-propylmercaptan, 3-methyldimethoxysilyl-propylmercaptan, and 3-triethoxysilyl-propylmercaptan. Usually, 3-trimethoxysilyl-propylmercaptan is preferably used.

The vinyl ester used in the above (3) or (4) includes vinyl acetate, vinyl formate, vinyl propionate and the like, but usually vinyl acetate is preferably used. The polymerization or copolymerization of the vinyl ester can be carried out by a known method using a radical initiator in a bulk or in a lower alcohol solvent such as methanol, and saponification of the resulting vinyl ester polymer or copolymer. Can be carried out by a conventional method of adding an alkali or acid catalyst to an alcohol solution of the polymer or the like.

The degree of silyl group modification of the silyl group modified PVA is preferably 0.1 to 10 mol%. 0.
If it is less than 1 mol%, the reinforcing effect by addition to the hydraulic molded article is not always sufficient, and if it exceeds 10 mol%, the reinforcing effect is similarly reduced. If it exceeds 10 mol%, the reason why the reinforcing effect is lowered is not clear, but is presumed to be due to gelation even if dissolved, and poor spreading. If the degree of saponification of the modified PVA is 80 mol% or more, the dispersion in the matrix (hydraulic substance) becomes uniform, and the bending strength and waterproofness of the final product are remarkably improved by its particle bonding strength and coating strength. I do. Conversely, if it is less than 80 mol%, P
Since the number of hydrophilic groups in VA decreases and an insoluble portion is generated,
Uniformity of physical properties is hindered, and the improvement in bending strength and waterproofness is small.

In the present invention, the degree of polymerization of PVA is 1
It is important that it is 200 or more, and the degree of polymerization is 1200
By the above, since the coating is strong and the particle bonding force is large, the characteristics of the molded product obtained from the hydraulic composition can be greatly improved.

Further, as mentioned above, in the course of these studies, more surprisingly, the above-mentioned specific degree of saponification,
It has been found that the tendency obtained by using modified PVA in the polymerization degree range also applies to ordinary PVA. Although there is a slight decrease in the effect, the reinforcing effect when using PVA within the range of the present invention (that is, the above-mentioned polymerization degree range and saponification degree range) is clearly better than using the other PVA. Shows the results. In the present invention, P
It is important that the amount of VA added is 0.1 to 20% by weight based on the total solids. If the amount is less than 0.1% by weight, the reinforcing effect of the addition cannot be obtained, and if it exceeds 20% by weight, the viscosity of the matrix increases extremely and the workability decreases.
Also, when expressed as a ratio to the hydraulic substance in the matrix, it is preferably 0.2 to 40% by weight.

Further, PVA is used to improve the effect of PVA.
It is preferable to add a thickening substance that causes the aqueous solution to thicken. PVA is generally quite stable against strong acids and strong bases, but precipitates and agglomerates against salts, and is known to be thickened and gelled by chemical bonding, especially with boric acid and borax. I have. In addition, thickening of PVA aqueous solution,
Examples of substances that cause gelation include trivalent chromium generated when an alkali metal salt of chromic acid or dichromic acid is reduced, tetravalent titanium or vanadate formed by oxidation of titanium trichloride, and copper. Ions and the like also form complex compounds. As other organic substances, dyes such as Congo Red, gallic acid and the like are known, but the above-mentioned boric acid or borax is practically preferable.

For example, in the case of manufacturing by a papermaking method, if the viscosity of the slurry is too high, the drainage becomes poor and there is a problem in the processability. However, when powdered PVA or boric acid which causes thickening is added, it hardly dissolves in water and thus does not thicken, and most of it is formed on a wire mesh. And it melt | dissolves by heating in the following curing process, and reinforcement performance is exhibited. It also appears to be effective in heating during the curing step, particularly in preventing heat deterioration during so-called autoclave treatment. In general, the larger the amount of the thickening substance added, the greater the viscosity increase, but it is 1 to 20% by weight, preferably 5 to 20% by weight based on PVA. If it is less than 1% by weight, the practical effect is insufficient.

Further, it is desirable to use a reinforcing fiber in order to develop a high-performance product strength. The amount of the reinforcing fiber added is 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the total solid content. If it is less than 0.1% by weight, it is difficult to obtain the effect of reinforcing the hydraulic substance and the effect of connecting the green sheets. Further, if the content exceeds 10% by weight, there is a problem in dispersibility, and the reinforcing effect is impaired. Examples of the type of reinforcing fiber include all those usually used as a reinforcing material such as cement, but preferably vinylon-based, acrylic-based, olefin-based, carbon, and aramid-based, which are proven as reinforcing fibers for hydraulic substances. Each fiber, synthetic pulp, wood pulp, pulp such as high beaten pulp of wood (in the present invention, these are also referred to as fibers), and may be used alone or in combination of two or more. . The molding method may be any of a wet papermaking method, a dry method, and the like. In the case of the wet papermaking method, it is desirable that any one of pulp such as pulp, beaten pulp, and synthetic pulp be contained.

The curing conditions vary depending not only on the properties and applications to be obtained, but also on the type of matrix and the reinforcing fibers, but may be any of natural curing, steam curing and autoclave curing. In order for the obtained hydraulic molded product to have good dimensional stability, autoclave curing is effective.
That is, in order to have good dimensional stability as a building material,
In order to uniformly disperse the modified PVA in the matrix, the autoclave curing method is a simple and effective method. In particular, it is best when PVA is used in powder form.

Here, the hydraulic substance refers to an inorganic substance having hydraulic properties such as various kinds of Portland cement, gypsum, slag slag, magnesium carbonate, calcium silicate and the like. The composition of the present invention, if necessary, may contain, in addition to the above-mentioned components, additives usually used for hydraulic moldings.
For example, an inorganic filler such as powdered silica or fly ash, or a filler such as sand, gravel or lightweight aggregate may be contained as an additive, and may further contain air bubbles.

The hydraulic composition of the present invention is used as a molding material for plate-like materials used for roofs, outer walls, inner walls, etc., roads, seawalls, and the like.

[0023]

EXAMPLES The effects of the present invention will be described below with reference to examples. In the examples,% is a value based on weight unless otherwise specified. The physical properties of the products in the following examples were evaluated by the following evaluation methods. Flexural strength, flexure; measured in accordance with JIS A 1408 "Bending test method for building boards", with a span of 5 cm. The maximum deflection at the center of the span was defined as bending deflection. Bulk specific gravity: According to JIS A 5413, the test piece was placed in an air dryer equipped with a stirrer, and determined from the weight and volume after drying at 105 ± 5 ° C for 24 hours. Length change rate: Based on JAS A 5416, the length at the time of absorption of water immersed in water at 20 ° C and day and night was measured based on the sample dried at 60 ° C and day and night to determine the change rate.

Example 1, Comparative Examples 1-3 As modified PVA, vinylmethoxysilane was used as a modified monomer, and in a methanol solvent, an initiator of 2,2 e-azobisisobutyronitrile was used. After copolymerization with vinyl acetate, saponification was carried out by a conventional method, and unreacted substances were removed, followed by drying to obtain a product having a polymerization degree of 1700 and a saponification degree of 98 mol%. The modification degree was adjusted to 0.3 mol% by adjusting the copolymerization amount of vinylmethoxysilane. This modified PVA was added to a matrix of Portland cement and Toyoura standard sand in a ratio of 1: 1 by an aqueous solution method.
%, W / C (ratio of water to cement) = 40%, cast into a 25 × 25 × 0.6 cm formwork, standardized for 4 weeks (20 ° C., 65% pH) After curing, the strength was measured (Example 1). For comparison, a 0.3 mol% modified PVA produced by the same method as described above, but having a polymerization degree of 500 and a saponification degree of 75% was tested under the same conditions (Comparative Example 1). For comparison, unmodified PVA
(Polymerization degree: 500, saponification degree: 75%) (Comparative Example 2) The same method was used for those using PVA and those not using PVA (Comparative Example 3), and the results are shown in Table 1.

[0025]

[Table 1]

From the above, the product using the silyl group-modified PVA (Example 1) has a remarkable 80% improvement in strength as compared with the product not using PVA, and the polymerization degree and the saponification degree even when PVA is used. It can be seen that there is a large improvement in strength of 50 to 62% compared to the case where the range of the present invention is not satisfied.

Examples 2 and 3 and Comparative Examples 4 and 5 Comparisons were made with non-asbestos slate plates by wet papermaking. Here, as an example, a 100-mesh powder having a silyl group modification degree of 0.3 mol%, a polymerization degree of 1700 and a saponification degree of 98 mol% was used in an amount of 2% by weight based on the solid content. Matrix is made of Portland cement, and beaten pulp (CSF = 100) 3 as an additive
In addition, 2% by weight of vinylon fiber was added, and wet papermaking was performed by the Hachiek method. One day of curing at 80 ° C. of the steam, and after natural curing for 4 weeks, the strength was measured (Example 2). At the same time, the freeze-thaw behavior was examined by ASTM C-666 as a waterproof property. Similarly, as an example, when unmodified PVA having a degree of polymerization of 1700 and a degree of saponification of 98 mol% was used (Example 3), and for comparison, the degree of polymerization and degree of saponification of unmodified PVA were Table 2 shows the merging (Comparative Example 4) using a material out of the range of the invention (polymerization degree 500, saponification degree 75 mol%) and no PVA (Comparative Example 5).
Side by side.

[0028]

[Table 2]

As shown in Table 1, the modified PVA having a degree of polymerization and saponification within the range of the present invention has improved the strength by nearly 80% as compared with Comparative Example 5, and the unmodified PVA has the range of the present invention even in the case of unmodified PVA. Among them, those having a degree of polymerization and a degree of saponification show an improvement in strength close to 50%. In the case of a product using unmodified PVA having a degree of polymerization and a degree of saponification outside the range of the present invention, the strength is improved only by about 10%.

Example 4 and Comparative Examples 6 and 7 Based on the following composition, namely, siliceous (55% by weight), calcareous (38% by weight), PP fiber (2% by weight) and pulp (5% by weight) Then, 2% by weight of the following unmodified PVA 100 mesh powder was added or not added, and wet papermaking was performed using a Hachiek machine, and autoclaving was performed at 180 ° C. for 8 hours to obtain a calcium silicate lightweight plate. Produced.

Here, Example 4 uses the above PVA having a degree of polymerization of 1700 and a saponification degree of 98 mol%, and Comparative Example 6 shows a case using the above PVA having a degree of polymerization of 500 and a saponification degree of 75 mol%. Is a case where PVA is not added. Table 3 shows the specific gravity and bending strength of the lightweight plate obtained in each example.

[0032]

[Table 3]

Also in this case, when the bending strength is compared, PVA
Compared with no addition, unmodified PVA shows an improvement of nearly 50%, proving that the effect on reinforcing properties is high.

Examples 5, 6 and Comparative Example 8 An asbestos-free board made by wet papermaking was prepared for comparison.
In the formulation of Example 5, 2% of powdered PVA having a degree of polymerization of 1700, a degree of saponification of 98% and 100 mesh was used as a reinforcing agent.
In addition, beaten pulp was 5% as a reinforcing fiber, pearlite was 15% as a lightening material, and the rest was ordinary Portland cement. Example 6 is 0.2% as a thickener in the composition of Example 5
(10% based on PVA) boric acid was added.

In Comparative Example 8, neither PVA nor boric acid was added. A slurry having a solid content concentration of 40% was adjusted according to the above-mentioned composition, poured into a mold, and then pressed to a thickness of about 0.8 c.
m, a plate having a bulk specific gravity of about 1.0 was prepared. This is equivalent to the usual fourdrinier single layering. Thereafter, after steam curing at 80 ° C. for 24 hours, autoclaving was performed at 140 ° C. or 160 ° C. for 6 hours, and further dried at 90 ° C. for 16 hours to obtain an asbestos-free board material product. Table 4 shows the composition and physical properties of the product.

[0036]

[Table 4]

In Example 5, both 140 ° C. and 160 ° C. autoclave treatments had higher flexural strength than Comparative Example 8,
The toughness is clearly superior due to the large bending deflection. In Example 6 to which a small amount of boric acid was further added, the bending strength and bending deflection were further improved, and a remarkable difference from Comparative Example 8 was recognized. The physical properties of the product change depending on the autoclave processing temperature. The treatment at 160 ° C. improves the dimensional stability, but the bending strength and bending deflection tend to decrease. However, Example 6 had a small decrease in bending strength and bending deflection. It is considered that this is because the degree of thermal deterioration of PVA is small.

[0038]

The present invention is excellent in mechanical strength such as bending strength, and also excellent in crack prevention.

Claims (4)

[Claims] 1. A hydraulic substance and a polyvinyl alcohol having a degree of saponification of 80 mol% or more and a polymerization degree of 1200 or more, and the content of the polyvinyl alcohol is 0.1 to 20% by weight based on the total solid content. A hydraulic composition characterized in that: 2. The hydraulic composition according to claim 1, wherein the polyvinyl alcohol is a silyl group-modified polyvinyl alcohol. 3. The hydraulic composition according to claim 1, wherein the thickening substance of polyvinyl alcohol is contained in an amount of 1 to 20% by weight based on polyvinyl alcohol. 4. The reinforcing fiber is used in an amount of 0.1 to 10% based on the total solid content.
The hydraulic composition according to any one of claims 1 to 3, wherein the composition contains 1% by weight.