JP4425110B2 - Steam and / or autoclave curing hydraulic composition, and molded article - Google Patents

Description

  The present invention relates to a hydraulic molded article suitably used as a material for buildings, civil engineering, ships, and the like, and a hydraulic composition used for manufacturing the hydraulic molded article.

  In order to improve the mechanical properties, dimensional stability, moldability, etc. of molded products made of hydraulic materials such as cement, gypsum and starch slag, and to improve the surface condition, polyvinyl alcohol ( It is conventionally known to add (hereinafter also referred to as PVA) (for example, see Patent Document 1).

  Further, it is known that PVA is added to a hydraulic material in the form of powder and molded, and then steam curing and / or autoclave curing is performed to improve the strength, frost damage resistance, etc. of the hydraulic molded product ( For example, see Patent Document 2).

  In addition, there is a method in which a hydraulic substance, PVA powder, and a substance that thickens PVA (thickening substance) are mixed at a predetermined blending ratio, and the mixture is autoclaved at a temperature of 100 ° C. or higher to produce a molded product. It is described in Patent Document 3.

  In these methods, the PVA layer formed in the molded article is difficult to pass not only water but also carbon dioxide gas, thereby preventing neutralization of the substrate. Further, it is considered that pores that adversely affect frost damage resistance are sealed, and pores newly formed by dissolution of PVA have an effect of buffering the internal pressure generated when water is frozen and thawed. Furthermore, the PVA layer has the characteristics that the adhesive strength between the matrix and the aggregate and the reinforcing fibers is improved, the bending strength, the tensile strength, and the impact strength are improved, and at the same time, the breaking strain of the bending and the tensile becomes large.

  However, none of the above methods is necessarily satisfactory in workability. In particular, in the method described in Patent Document 3, when a thickening material is added, PVA slightly dissolved in water during mixing of the slurry is obtained. The viscosity of the entire slurry becomes very high due to the thickening substance, and the workability is adversely affected, for example, the drainage during paper making becomes extremely poor. For this reason, there are problems that the concentration of the slurry cannot be increased and the amount of PVA added cannot be increased. Moreover, since a step of adding a thickening substance is required at the time of production, there is a problem in that it takes time and labor for the work and increases costs. Boron-based substances such as boric acid, which are the most effective thickeners, are designated substances in the Industrial Safety and Health Law, the Chemical Substance Management Promotion Law (PRTR Law), and the Water Pollution Control Law. There is also a problem.

On the other hand, hydraulic moldings have recently been required to have higher performance, and conventional methods cannot satisfy the requirements of mechanical properties such as frost resistance, strength, and elongation. Therefore, development of a method capable of obtaining higher frost resistance and mechanical properties is desired.
JP 61-209950 A JP-A-8-245257 JP 2000-44318 A

  The present invention provides a hydraulic composition that has good workability and that can be molded with steam and / or autoclave curing to provide a molded article having excellent frost resistance and mechanical properties (for example, bending strength, bending deflection, etc.). The purpose is to provide it at low cost. Moreover, it aims at providing the hydraulic molding obtained using this hydraulic composition, and its manufacturing method.

  As a result of intensive studies to achieve the above object, the present inventors have found that the elution amount with respect to water at 40 ° C. or lower is 5% by mass or less, the particle size passes through a sieve having an aperture of 0.6 mm, and the looseness appears. If PVA-based resin powder having a specific gravity of 0.35 g / ml or less is used, the workability is good, and water that can provide a molded product having excellent frost damage resistance and mechanical properties by curing with steam and / or autoclave. It has been found that a hard composition can be obtained at low cost. Further, it has been found that such a PVA-based resin powder is a PVA-based resin powder having a saponification degree of 98 mol% or more prepared by a kneader saponification method and having an average polymerization degree of 1000 or more, and further investigation is made. Over time, the present invention has been completed.

That is, the present invention
(1) The elution rate with respect to the hydraulic substance (A) and water at 40 ° C. is 5% by mass or less, is a particle size that passes through a sieve of 0.6 mm opening of JIS standard, and has a loose apparent specific gravity of 0.35 g. / Ml or less of polyvinyl alcohol resin powder (B), and the content of component (B) is 0.1 to 20% by mass with respect to the total solid content, and / Or hydraulic composition for autoclave curing,
(2) The polyvinyl alcohol resin of the powder (B) is a saponified product of an aliphatic polyvinyl ester, having a saponification degree of 98 mol% or more and an average polymerization degree of 1000 or more, and produced by a kneader saponification method The hydraulic composition for curing steam and / or autoclave according to the above (1),
(3) A hydraulic substance (A), a polyvinyl alcohol resin powder (B), and reinforcing fibers (C) are contained, and the reinforcing fibers are contained in an amount of 0.1 to 10% by mass based on the total solid content. The steam and / or autoclave curing hydraulic composition according to (1) or (2),
(4) The hydraulic composition according to any one of (1) to (3) is dispersed in water to form a slurry, which is molded, and then obtained by steam and / or autoclave curing. (5) The hydraulic composition according to any one of (1) to (3) is dispersed in water to form a slurry, and then molded, and then steam and / or autoclave curing is performed. The present invention relates to a method for producing a hydraulic molded product.

  The water-curable composition of the present invention is excellent in workability, and the hydraulic composition of the present invention is cured with steam and / or autoclave to obtain a hydraulic molded product excellent in frost resistance and mechanical properties. be able to.

  The steam and / or autoclave curing hydraulic composition of the present invention has an elution rate of 5 mass% or less with respect to the hydraulic substance (A) and water at 40 ° C., and passes through a sieve having an aperture of 0.6 mm according to JIS standard. The PVA resin powder (B) having a loose apparent specific gravity of 0.35 g / ml or less, and the content of the component (B) is 0.1 to 20% by mass relative to the total solid content It is characterized by being.

(Component A)
The hydraulic substance (A) which is one component of the present invention is not particularly limited as long as it does not hinder the object of the present invention, and may be any inorganic substance that can be cured by reacting with water. Examples of the hydraulic substance (A) include various portland cements, blast furnace cements, alumina cements, gypsum, starch syrup, calcium silicate, magnesium carbonate, etc., and these include only one type or two or more types. You may use it in combination.

(Component B)
The PVA resin powder (B), which is another component of the present invention, has an elution rate of 5% by mass or less with respect to water at 40 ° C., and has a particle size that passes through a sieve having an aperture of 0.6 mm according to JIS standard. The loose apparent specific gravity is 0.35 g / ml or less.

The elution rate of the PVA resin powder (B) with respect to water at 40 ° C. is 5% by mass or less. When the elution rate exceeds 5% by mass, when the slurry is dispersed in water to form a slurry, the dissolution of the PVA resin increases, and the viscosity of the slurry increases, resulting in poor workability, and the dispersibility of the PVA resin powder. This causes a problem that a molded product having high mechanical properties and dimensional stability cannot be obtained. In particular, when molding is performed by a papermaking method, there is a problem that drainage is deteriorated and workability and productivity are extremely deteriorated.
In the present invention, “elution rate with respect to water at 40 ° C.” is defined as an elution rate represented by the following mathematical formula with respect to water at 40 ° C. Specifically, 450 g of 40 ° C. pure water and 50 g of PVA (solid mass) are put in a container immersed in a constant temperature bath at 40 ° C., and stirring is continued for 24 hours in a sealed state to obtain a slurry. The slurry is then filtered with suction through an 11-G4 glass filter and the filtrate is collected. The concentration of the collected filtrate is measured to determine the mass of PVA eluted in water, and the elution rate is calculated from the mass of PVA eluted in water and 50 g (solid content mass) of PVA.
[Equation 1]
Elution rate (mass%) = (mass of sample eluted in water / sample solid mass before elution) × 100

The particle size of the PVA-based resin powder (B) is a particle size that passes through a sieve having an aperture of 0.6 mm according to JIS standard. Preferably, the particle size passes through a sieve having an aperture of 0.25 mm. If the particle size is larger than this, the slurry cannot be uniformly dispersed, and the dispersion state of the PVA resin becomes worse when formed into a molded product. A molded product with specific physical properties cannot be obtained.
The “particle size” is defined by JIS K6726 3.10: Particle size, and is measured according to the method described in the dry screening test of JIS Z8815.

The loose apparent specific gravity of the PVA resin powder (B) is 0.35 g / ml or less, preferably 0.1 g / ml or more and 0.35 g / ml or less. More preferably, it is 0.1 g / ml or more and 0.3 g / ml or less.
The “loose apparent specific gravity” is defined as the mass per unit volume occupied by the powder, and can be determined by following the method for measuring the loose apparent specific gravity of a powder tester manufactured by Hosokawa Micron Corporation.

When the apparent specific gravity of the PVA resin powder is small, the dispersibility when it is made into a slurry is good, and a sufficient amount of pores formed by dissolution of the PVA powder can be obtained with a small amount of PVA. Therefore, it is possible to obtain a molded article having high frost resistance and mechanical properties without causing adverse effects that occur when a large amount of PVA resin is added.
When the loose apparent specific gravity is 0.35 g / ml or more, the dispersibility of the PVA resin powder when dispersed in water to form a slurry deteriorates, and a molded product having high mechanical properties and dimensional stability can be obtained. Can not.
Moreover, if it is less than 0.1 g / ml, the volume of PVA-type resin powder will become high too much, and the problem that the handleability of PVA-type resin powder will worsen arises.

  For example, the PVA resin powder (B) according to the present invention is obtained by polymerizing an aliphatic vinyl ester monomer in a solvent such as alcohol in the presence of a radical initiator. A catalyst such as an alkaline substance or an acidic substance was added with stirring, and stirring was continued after the addition to saponify the aliphatic polyvinyl ester, and the resulting PVA resin was precipitated from a solvent such as alcohol. The fine powdery PVA-based resin is manufactured by heating and drying at a temperature of 100 ° C. or more, and further sieving with a sieve having an aperture of 0.6 mm or less according to JIS standard.

  Various types of aliphatic vinyl ester monomers are used, and examples thereof include known aliphatic vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl stearate. . For the purpose of industrial production, vinyl acetate is particularly preferred.

  Further, the PVA resin according to the present invention may be one obtained by copolymerization with an unsaturated monomer copolymerizable with the aliphatic vinyl ester monomer within a range not impairing the effects of the present invention. Examples of unsaturated monomers copolymerizable with aliphatic vinyl ester monomers include α-olefins such as ethylene, propylene, n-butene and 1-hexene; acrylamide, dimethylacrylamide, methacrylamide, N- Amides such as methylolacrylamide, N-vinylformamide, N-vinylacetamide, diacetone acrylamide; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl glycidyl ether , A monomer having a glycidyl group such as glycidyl methacrylate; polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, methyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl Vinyl ethers such as vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; allyl acetate, dimethylallyl acetate, isopropenyl allyl acetate, allyl alcohol, dimethylallyl alcohol, Allyl compounds such as isopropenyl allyl alcohol, allyl chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether; vinylsilyl compounds such as diphenylmethylvinylsilane, trimethoxyvinylsilane, trivinylbutylvinylsilane; N-vinyl Cyclic N-vinyl compounds such as 2-pyrrolidone and N-vinyl-2-caprolactam; Maleic anhydride; mono or dialkyl maleic acid ester; itaconic acid or its alkyl ester; acrylic acid; allyl carboxylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, polyoxyethylene (meta ) (Meth) acrylic acid esters derived from carboxylic acids such as acrylates, polyoxypropylene (meth) acrylates or salts thereof; 2-acrylamido-2-methylpropanesulfonic acid or alkali metal salts thereof; 2-acrylamide-1 -Methylpropane sulfonic acid or alkali metal salt thereof; 2-methacrylamide-2-methylpropane sulfonic acid or alkali metal salt thereof; olefin sulfur such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, etc. Although such phosphate or a metal salt thereof including but not limited to.

A chain transfer agent may be used to modify the polymer terminal. Examples of the chain transfer agent for modifying the polymer terminal include, but are not limited to, aldehydes, mercaptans, and halogen-containing compounds.
Two or more types of PVA resins may be used in combination.

  As a saponification method of the produced aliphatic polyvinyl ester, a kneader saponification method using a kneader is preferable because stable PVA resin particles can be obtained. When a PVA resin is produced by this method, a fine powder of PVA having a small particle size and a fibrous shape, that is, an apparent specific gravity can be obtained.

  The saponification degree of the PVA resin is not particularly limited, but is preferably 98 mol% or more in order to lower the solubility of PVA in water at 40 ° C. Furthermore, it is more preferable that it is 99 mol% or more.

  The average degree of polymerization of the PVA-based resin is not particularly limited, but is preferably 1000 or more, and more preferably 1300 or more, in order to increase the reinforcing effect of the molded product.

  Content of PVA-type resin powder is 0.1-20 mass% with respect to the total solid of a hydraulic composition. Preferably, it is 0.3-10 mass%. If it is less than 0.1% by mass, the effect of addition cannot be achieved. Further, even if added in an amount of more than 20% by mass, the reinforcing effect corresponding to the addition cannot be obtained, which is uneconomical, the viscosity of the slurry becomes extremely high, and workability such as drainage at the time of papermaking is extremely reduced. .

(Component C)
Moreover, it is preferable to use a reinforcing fiber (C) in order to develop a higher performance product strength. The content of the reinforcing fiber is 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the total solid content. If it is less than 0.1% by mass, it is difficult to obtain the effect of reinforcing the hydraulic substance and the effect of improving the strength of the green sheet, and if it exceeds 10% by mass, there is a problem of dispersibility, and conversely, the effect of reinforcement is lowered. Examples of the types of reinforcing fibers include all those usually used as reinforcing materials such as cement. For example, vinylon-based, acrylic-based, olefin-based, carbon, aramid-based fibers, synthetic pulp, wood pulp, wood These are pulps such as highly beaten pulp, and these may be used alone or in combination of two or more.

(Other ingredients)
The hydraulic composition of the present invention may contain additives usually used for hydraulic molded products in addition to the above components, if necessary. Examples of such additives include inorganic fillers such as powdered silica, glass balloons, shirasu balloons, fly ash, and pearlite, and fillers such as sand, gravel, and lightweight aggregates. The hydraulic composition of the present invention may further contain bubbles.

(Method for producing hydraulic composition)
The hydraulic composition of the present invention can be obtained by mixing a hydraulic substance (A), a PVA resin powder (B), and optionally a reinforcing fiber (C).

(Hydraulic molding)
The hydraulic molded article of the present invention is obtained by dispersing the hydraulic composition in water to form a slurry (slurry preparation process), molding (molding process), and then curing with steam and / or autoclave (curing process). Is obtained.

(Slurry preparation process)
The hydraulic composition slurry of the present invention is prepared by mixing the hydraulic composition and water to prepare a slurry. For mixing, conventionally known mixing methods can be used. For example, a concrete mixer, a screw-type kneader, a peller-type kneader, or the like can be used.
The solid content concentration of the slurry of the present invention is appropriately set depending on the molding method and the like, and is not particularly limited, but is usually 2 to 90% by mass.

(Molding process)
Next, the slurry is formed. The molding method is not particularly limited, and conventionally known methods (for example, a mold method, an extrusion method, a wet papermaking method, a flow-on method, a dry method, etc.) can be appropriately used. When the forming method is a wet papermaking method, it is desirable that any of pulps such as pulp, beaten pulp, and synthetic pulp is contained in the slurry.

(Curing process)
Furthermore, the molded product obtained in the molding step is subjected to steam curing at a temperature of 100 ° C. or lower and / or autoclave curing in an autoclave at a temperature of 100 ° C. or higher. Either steam curing or autoclave curing may be performed, or after performing steam curing, further autoclave curing may be performed.
The steam curing temperature is preferably 80 ° C. or higher. When the temperature is less than 80 ° C., the PVA resin powder is not sufficiently dissolved, and the effect of improving frost resistance and mechanical properties is insufficient.
The temperature of the autoclave curing is preferably 120 to 180 ° C, more preferably 140 to 170 ° C. The time for steam curing and autoclave curing is not particularly limited, but is preferably 1 to 30 hours, more preferably 8 to 20 hours. If the curing time is less than 1 hour, the hydraulic reaction may be insufficient. In the case of autoclave curing, if it exceeds 24 hours, the PVA resin powder (B) may be deteriorated.

  After the molding step and the curing step, the hydraulic molded product may be further processed into a desired size and shape using a machine tool or the like, and the hydraulic molded product of the present invention has various shapes (for example, multi-faced, circular, etc. Columnar, cylindrical, etc.).

  The hydraulic molded article of the present invention can be widely used in various fields such as architecture, civil engineering, and ships, and in particular, roofing materials, outer wall materials, inner wall materials, floor materials, gates, road blocks, revetment blocks, etc. Can be used extremely effectively.

The present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.
The physical property values in the following examples were evaluated by the following evaluation methods.

<Method for measuring physical properties of PVA resin powder>
(Saponification degree, average polymerization degree)
The degree of saponification and the average degree of polymerization were measured according to JIS K6726 3.5: degree of saponification, 3.7: average degree of polymerization.

(Elution rate for 40 ° C water)
Into a container immersed in a constant temperature bath at 40 ° C., 450 g of pure water at 40 ° C. and 50 g of PVA resin powder are put, and stirring is continued for 24 hours in a sealed state. After 24 hours, the slurry is suction filtered through an 11-G4 glass filter, and the filtrate is collected. The concentration of the collected filtrate was measured, and the elution rate was calculated.

(Loose apparent specific gravity)
Using a powder tester manufactured by Hosokawa Micron Co., Ltd., the measurement was performed according to the method for measuring the apparent apparent specific gravity of this apparatus.

(Granularity)
Measured according to JIS K6726 3.10: particle size.

<Method for measuring physical properties of molded product>
(specific gravity)
According to JIS A5413, the test piece was put into an air dryer equipped with a stirrer, and obtained from the mass and volume after drying at 105 ° C. ± 5 ° C. for 24 hours.

(Bending strength, bending deflection)
Measured according to JISA 1408 “Bending test method for building boards”.
<Test conditions>
Sample size: width 40mm, thickness 5-8mm
Span width: 100 mm, crosshead speed: 20 mm / min
Temperature / Humidity: 20 ° C / 65% RH
The maximum deflection at the center of the span was taken as the bending deflection.

(Frost-resistant volume expansion rate)
A specimen (length 100 mm × width 100 mm × thickness 8 mm) was immersed in water for 24 hours, then placed in a furnace, and subjected to a freeze / thaw cycle test according to ASTM C666. That is, the specimen is held at 4.4 ° C. for 2 hours, then held at −17.8 ° C. for 2 hours, and again held at 4.4 ° C. for 2 hours. The volume expansion coefficient after 20 temperature cycles were measured.

(Workability of slurry)
○: The state of the slurry is uniform and the drainage at the time of dehydration is good. Δ: Either or both of the properties of the slurry and the drainage at the time of dehydration are slightly poor.
X: Either one or both of the properties of the slurry and the drainage during dehydration are considerably poor.

(Comprehensive evaluation)
○: The workability of the slurry is good, and the frost damage resistance, bending strength, and bending deflection of the molded product are very high.
X: There are any problems in the workability of the slurry, the frost damage resistance of the molded article, the bending strength, and the bending deflection.

<Method for creating PVA>
(PVA-1)
An average polymerization degree of 1700 and saponification were obtained by adding sodium hydroxide while stirring a 40 mass% methanol solution of polyvinyl acetate in a kneader at a rotation speed of 30 rpm at 40 ° C. to saponify the polyvinyl acetate. A methanol slurry of PVA having a degree of 99.2 mol% was obtained.
The slurry was separated from the slurry by a centrifugal separator, and the solid content was dried at 110 ° C. for 1 hour to obtain PVA powder. By sieving this PVA powder with a sieve having an aperture of 0.18 mm, a PVA powder (PVA-1) passing through the sieve having an aperture of 0.18 mm was obtained.
It was 2.2 mass% when the elution rate with respect to the water of 40 degreeC of this PVA powder was measured.
Moreover, it was 0.29 g / ml when the loose specific gravity was measured.

(PVA-2)
Using polyvinyl acetate, PVA powder having an average polymerization degree of 1300 and a saponification degree of 99.5 mol% was obtained in the same manner as (PVA-1). This PVA powder was sieved with a sieve having an aperture of 0.30 mm to obtain PVA powder (PVA-2) passing through the sieve having an aperture of 0.30 mm.
It was 2.8 mass% when the elution rate with respect to 40 degreeC water of this PVA powder was measured.
The apparent apparent specific gravity was 0.31 g / ml.
The characteristic values of this PVA powder are shown in Table 1.

(PVA-3)
Using polyvinyl acetate, a PVA powder having an average polymerization degree of 2000 and a saponification degree of 98.8 mol% was obtained in the same manner as (PVA-1). By sieving this PVA powder with a sieve having an opening of 0.25 mm, a PVA powder (PVA-3) passing through the sieve having an opening of 0.25 mm was obtained.
It was 3.8 mass% when the elution rate with respect to the 40 degreeC water of this PVA powder was measured.
Moreover, it was 0.27 g / ml when the loose specific gravity was measured.

(PVA-4)
Using polyvinyl acetate, PVA powder having an average polymerization degree of 1700 and a saponification degree of 99.2 mol% was obtained in the same manner as (PVA-1). This PVA powder was sieved with a sieve having an opening of 1.5 mm to obtain a PVA powder (PVA-4) passing through the sieve having an opening of 1.5 mm.
It was 2.0 mass% when the elution rate with respect to the 40 degreeC water of this PVA powder was measured.
The apparent apparent specific gravity was 0.31 g / ml.

(PVA-5)
Sodium hydroxide was added to and mixed with a 40 mass% methanol solution of polyvinyl acetate at 40 ° C. Thereafter, the mixture was allowed to stand at 40 ° C., and polyvinyl acetate was saponified in a standing state, thereby obtaining a PVA methanol swelled product having an average polymerization degree of 1700 and a saponification degree of 99.2 mol%.
The methanol swelled product was crushed by cutting and pulverizing, and further dried at 110 ° C. for 1 hour to obtain coarse particles of PVA resin. The PVA coarse particles were further pulverized to obtain PVA powder (PVA-5) that passed through a sieve having an aperture of 0.18 mm.
It was 25.3 mass% when the elution rate with respect to the 40 degreeC water of this PVA powder was measured.
Moreover, it was 0.47 g / ml when the loose specific gravity was measured.

(PVA-6)
PVA-5 PVA powder was heat treated at 110 ° C. for 1 hour to obtain PVA powder (PVA-6). In addition, the particle size of this PVA powder was a particle size which passes a sieve with an opening of 0.18 mm.
The elution rate of this PVA powder with respect to water at 40 ° C. was measured to be 4.3% by mass.
Moreover, it was 0.47 g / ml when the loose specific gravity was measured.

Example 1
In addition to the mixed composition shown below, the hydraulic composition was manufactured by adding and mixing 2 mass% of PVA-1 PVA powder with respect to the total solid content. To this hydraulic composition, water at room temperature (about 30 ° C.) is added to prepare a slurry having a solid content of 40% by mass, poured into a mold, and then pressed to a bulk specific gravity of about 1.0 with a thickness of 8 mm. A plate was created. This corresponds to a normal long knitting type one-sheet papermaking. Then, the autoclave was cured at 160 ° C. for 6 hours, and further dried at 90 ° C. for 16 hours to produce a molded product sample. Table 1 shows the characteristics of the molded sample. The dispersibility of the slurry was good, the workability was good, the frost damage resistance, and the mechanical properties such as bending strength and bending deflection were also good.

(Mixed composition)
Cement (ordinary Portland cement) 45% by mass
Fly ash (Kanden fly ash) 35% by mass
Pulp 10% by mass
Perlite (Topco Perlite 51) 10% by mass

Example 2
A hydraulic composition and a molded product sample were produced in the same manner as in Example 1 except that the amount of PVA powder (PVA-1) added was 1% by mass with respect to the total solid content. Table 1 shows the characteristics of the molded sample.
The dispersibility of the slurry was good, the workability was good, the frost damage resistance, and the mechanical properties such as bending strength and bending deflection were also good.

Example 3
A hydraulic composition and a molded product sample were produced in the same manner as in Example 1 except that the amount of PVA powder (PVA-1) added was 5% by mass with respect to the total solid content. Table 1 shows the characteristics of the molded sample.
The dispersibility of the slurry was good, the workability was good, the frost damage resistance, and the mechanical properties such as bending strength and bending deflection were also good.

Example 4
A hydraulic composition and a molded product sample were produced in the same manner as in Example 1 except that PVA powder (PVA-2) was used. Table 1 shows the characteristics of the molded sample.
The dispersibility of the slurry was good, the workability was good, the frost damage resistance, and the mechanical properties such as bending strength and bending deflection were also good.

Example 5
A hydraulic composition and a molded product sample were produced in the same manner as in Example 1 except that PVA powder (PVA-3) was used. Table 1 shows the characteristics of the molded sample.
The dispersibility of the slurry was good, the workability was good, the frost damage resistance, and the mechanical properties such as bending strength and bending deflection were also good.

Comparative Example 1
A molded product sample was produced in the same manner as in Example 1 except that no PVA powder was added. Table 1 shows the characteristics of the molded sample.
When PVA was not added, frost damage resistance and mechanical properties such as bending strength and bending deflection were very low.

Comparative Example 2
A molded product sample was produced in the same manner as in Example 1 except that the amount of PVA powder (PVA-1) added was 40% by mass with respect to the total solid content. Table 1 shows the characteristics of the molded sample.
Since the amount of PVA added was too large, the dispersibility of the slurry was poor and the workability was poor. In addition, frost damage resistance, mechanical properties such as bending strength and bending deflection were not so high.

Comparative Example 3
A molded product sample was produced in the same manner as in Example 1 except that PVA powder (PVA-4) was used. Table 1 shows the characteristics of the molded sample.
Since the particle size of PVA was too large, the dispersibility of PVA was also bad. As a result, the frost damage resistance and mechanical properties such as bending strength and bending deflection were not so high.

Comparative Example 4
A molded product sample was produced in the same manner as in Example 1 except that PVA powder (PVA-5) was used. Table 1 shows the characteristics of the molded sample.
Since the PVA melted out greatly, the viscosity of the slurry was very high and the workability was poor, and the apparent specific gravity of the PVA was high, so the dispersibility of the PVA was also poor. As a result, frost damage resistance and mechanical properties such as bending strength and bending deflection were not so high.

Comparative Example 5
A molded product sample was produced in the same manner as in Example 1 except that PVA powder (PVA-6) was used. Table 1 shows the characteristics of the molded sample.
Since the apparent specific gravity of PVA was high, the dispersion state of PVA in the molded product was poor, and the formation of pores was insufficient. As a result, the frost damage resistance and mechanical properties such as bending strength and bending deflection were not so high.

Example 6
The hydraulic composition was manufactured by adding 2 mass% of PVA powder (PVA-1) with respect to the total solid in addition to the mixed composition shown below, and mixing. Normal temperature (about 30 ° C.) water was added to the hydraulic composition to prepare a slurry having a solid content of 15% by mass. This slurry was used for wet papermaking by the Hatschek method (circular knitting papermaking machine) to obtain an intermediate having a thickness of 6 mm. Subsequently, this intermediate was cured at 80 ° C. for 24 hours to produce a molded product sample. Table 2 shows the characteristics of the molded sample. The dispersibility of the slurry was good, the workability was good, the frost damage resistance, and the mechanical properties such as bending strength and bending deflection were also good.
(Mixed composition)
Cement (ordinary Portland cement) 50% by mass
Fly ash (Kanden fly ash) 30% by mass
Pulp (NUKP csf500ml) 5% by mass
Perlite (fine powder perlite) 15% by mass

Comparative Example 6
A molded product sample was produced in the same manner as in Example 6 except that PVA powder (PVA-5) was used. Table 2 shows the characteristics of the molded sample.
Since the PVA melted out greatly, the viscosity of the slurry was very high and the workability was poor, and the apparent specific gravity of the PVA was high, so the dispersibility of the PVA was also poor. As a result, the frost damage resistance and mechanical properties such as bending strength and bending deflection were not so high.

By using the hydraulic composition of the present invention, it is possible to obtain a molded product excellent in frost damage resistance, mechanical properties and dimensional stability, and a hydraulic molded product for steam and / or autoclave curing with good workability. Can be obtained at low cost.
Since the method of the present invention does not require the use of a thickener such as boric acid, it is excellent in workability, low in cost, and excellent in terms of environment and safety and health.

Claims (5)

The elution rate with respect to the hydraulic substance (A) and water at 40 ° C. is 5% by mass or less, the particle size passes through a sieve with an aperture of 0.6 mm of JIS standard, and the loose apparent specific gravity is 0.35 g / ml or less. in it contains a powder (B) of the polyvinyl alcohol resin, vapor and / or autoclave curing, wherein the amount of component (B) is 0.1 to 20% by mass of the total solid content Hydraulic composition.   The polyvinyl alcohol resin of the powder (B) is a saponified product of an aliphatic polyvinyl ester, has a saponification degree of 98 mol% or more and an average polymerization degree of 1000 or more, and is produced by a kneader saponification method. Item 2. The hydraulic composition for curing steam and / or autoclave according to item 1. It contains a hydraulic substance (A), a polyvinyl alcohol resin powder (B) and reinforcing fibers (C), and contains reinforcing fibers in an amount of 0.1 to 10% by mass based on the total solid content. The hydraulic composition for steam and / or autoclave curing according to claim 1 or 2.   A hydraulic molded article obtained by dispersing the hydraulic composition according to any one of claims 1 to 3 in water to form a slurry, then molding, and then curing with steam and / or autoclave.   A method for producing a hydraulic molded article, wherein the hydraulic composition according to any one of claims 1 to 3 is dispersed in water to form a slurry, and then molded, and then cured by steam and / or autoclave.