JPH04187552A - Production of formed material - Google Patents

Abstract

PURPOSE:To obtain a formed article having remarkably high mechanical strength and good dimensional stability by producing an aqueous composition composed of a hydraulic substance and a specific amount of a powdery polyvinyl alcohol polymer and curing the composition in an autoclave. CONSTITUTION:An aqueous composition composed of a hydraulic substance A and 0.1-20wt.% (based on the component A) of a powdery polyvinyl alcohol polymer B is cured at >=100 deg.C in an autoclave. The above aqueous composition is preferably further added with reinforcing fiber C to improve the strength of the formed article. A substance D capable of thickening the aqueous solution of the component B is preferably added in an amount of >=1wt.% (based on the powdery component B) to improve the effect of the component B. The component D is especially preferably a boric acid-type compound.

Description

Detailed Description of the Invention (Industrial Field of Application) - The present invention relates to a method for manufacturing a molded product made of a hydraulic material used as a material for architecture, civil engineering, ships, etc., and a molded product made of a hydraulic material. .

(Prior art) In order to improve the mechanical properties and formability of molded products made of hydraulic substances such as cement, gypsum, or water slag,
It is generally known to add a polyvinyl alcohol polymer (hereinafter abbreviated as PVA). for example,
JP-A No. 49-45934 discloses the use of PVA to improve the bending strength and impact strength of pulp cement boards, and JP-A No. 61-7765
No. 5 and Japanese Unexamined Patent Publication No. 61-209950 disclose the use of PVA to improve the bending strength, impact strength and dimensional stability of slag and gypsum boards, and to prevent cracks.

Also, JP-A-49-50017 and JP-A-60-
No. 239377 discloses the patent application for cement moldings,
1-'137719, for lightweight concrete,
The use of PVA to increase their mechanical strength, improve their surface and prevent cracking is disclosed.

The reason for this is that PVA is stable even in high pH systems, inhibits the hydration reaction of hydraulic substances, dissolves in water, is uniformly dispersed in matrices such as cement, and particles of hydraulic substances, etc. This is because it is possible to improve various physical properties of the hydraulic composition by bonding between particles and by forming a strong PVA film.

Further, JP-A-47-13628 discloses that the amount of PVA used can be reduced by adding a boron-based substance to an aqueous slurry composition consisting of cement and PVA powder.

Furthermore, in JP-A-59-184754, in a water slurry composition consisting of cement and PVA powder, PV
It is disclosed that the strength of molded products is improved by replacing powder A with silyl group-modified PVA.

In recent years, molded products of hydraulic materials have come to be mass-produced in factories to the same specifications. When mass producing hydraulic materials in a factory, the required conditions are II: good mechanical strength and dimensional stability, no cracks in the molded product, and good productivity. However, the reality is that no method for manufacturing a molded article made of a hydraulic material and a molded article made of a hydraulic material satisfying all of these conditions have been found.

(Problems to be Solved by the Invention) The purpose of the present invention is to provide a method for manufacturing a molded product made of a hydraulic material that does not have any of the above-mentioned problems particularly when producing a molded product in a factory, and a method for producing a molded product made of a hydraulic material. Our goal is to provide the following.

(Means for Solving the Problems) As a result of intensive studies in order to solve the above problems, the present inventors have found that the present inventors have developed a method that consists of a hydraulic substance (A) and a polyvinyl alcohol polymer (B) powder, and a polyvinyl alcohol polymer powder. It consists of a hydraulic substance characterized by curing in an autoclave at a temperature of 100°C or higher an aqueous composition in which the blending ratio of combined (B) powder is 0.1 to 20% by weight based on the hydraulic substance (A). The method for molding will be explained.

The hydraulic substance (A) in the present invention is not particularly limited as long as it is an inorganic compound that hardens by reaction with water; examples thereof include various types of portland cement, gypsum, water slag, rock wool, magnesium carbonate, and Examples include inorganic substances such as acid carnoum.

As the PVA (B) powder in the present invention, unmodified ordinary PVA, noryl group-modified PVA, and various modified PVA powders are used. PV A (B
) is not particularly limited, but preferably 50
It is 0 or more, more preferably 1500 or more. pV
If the degree of polymerization of A (B) is 500 or more, PV A
(B) The film is strong and the PVA (B) The binding strength of the powder is strong, but the physical properties such as mechanical strength of the molded product obtained by autoclave curing at a temperature of 100°C or higher is significantly improved. There is no particular restriction on the degree of saponification of PVA (B), but it is preferably 80 mol%.
The content is more preferably 90 mol% or more, still more preferably 95 mol% or more.

In the present invention, when the substance (D) that thickens the P V A (B) aqueous solution is not used, p V A (B)
The degree of saponification is particularly preferably 98 mol% or more. PV
When the degree of saponification of A (B) is 80 mol% or more, the dispersion of P V A (B) powder into the aqueous composition becomes uniform, and the aqueous composition is autoclaved at a temperature of 100 ° C. or higher. Due to the bonding strength of the PVA(B) powder and the strength of the PVA(B) film, the bending strength of the resulting molded product is significantly improved.

The average particle size of the P V A (B) powder is not particularly limited, but is preferably 16 mesh particles, more preferably 42 mesh particles, and the smaller the average particle size is, the more preferable it is.

The aqueous composition of the present invention comprises a hydraulic substance (A) and PV A
(B) Powder, and the blending ratio of PVA (B) powder is 0.1 to 20% by weight based on the hydraulic substance (A).
and preferably 05 to 5% by weight. pV A
If the blending ratio of (B) is less than 0.1% by weight, p
The effect of reinforcing the molded article cannot be obtained by adding V A (B), and if it exceeds 20% by weight, water resistance and flame retardancy may decrease, which may be undesirable.

In order to further develop the strength of the molded product, it is preferable to use reinforcing fiber (C) as one of the additives. The amount of reinforcing fiber added is 0.1 based on the total solid content.
-10% by weight is preferred, and 05-5% by weight is more preferred. By adding 0.1% by weight or more of reinforcing fibers, the reinforcing effect of the molded product and the effect of connecting green roots are significantly improved.

However, if it is added in an amount of 10% by weight or more, there will be a problem in the dispersibility of reinforcing fibers, which may even impair the reinforcing effect. Types of reinforcing fibers include those normally used as reinforcing materials for cement, etc., but preferred are hinilon, acrylic, and olefin fibers that have a proven track record as reinforcing fibers for molded products made of hydraulic substances (A). , carphone and aramid fibers, synthetic valves, wood valves, and valves such as highly refined wood valves (these are also collectively referred to as fibers in the present invention), and when used, these may be used alone or in combination of two or more types. You may also use it.

Furthermore, in order to improve the effect of P V A (B), P
~' A (B) It is preferable to add a substance (D) that thickens the aqueous solution.

A substance (D) that thickens an aqueous solution of P V A (B) is a substance (D) that is added to a 10% aqueous solution of P, V A CB) at 20'C in an amount of 5% based on PV A (B). (The addition ratio is the solid content ratio), p v p, (
B) A substance that increases the viscosity of an aqueous solution by at least twice, preferably four times or more, and more preferably a substance that causes the aqueous solution to gel. P V A (B) Water -
Among the substances (D) that thicken solutions, P VA (
B) is crosslinked to form a crosslinked product that is insoluble in water at temperatures below 100°C, dissolves in water during autoclave curing at temperatures above 100°C, and dissolves during autoclave curing at temperatures above IH°C. P V A (B
) PVA crosslinkers are preferred which thicken the aqueous solution.

p V A (B) Examples of substances (D) that thicken aqueous solutions include boric acid, borax, calcium borate, magnesium borate, aluminates, zirconium salts, and alkali metal salts of chromic acid or dichromic acid. trivalent chromium, which is produced when titanium trichloride is oxidized;
titanium, vanadate, copper ions, and the like. Furthermore, dyes such as Congo red and organic substances such as gallic acid can also be used. These p V A (B
) Among the substances (D) that thicken an aqueous solution, boric acid compounds are preferred, and among these, calcium borate is particularly preferred.

When the hydraulic substance (A) generates calcium ions in the presence of water, it is possible to form a water-insoluble cross-linker with PVA (B) at a temperature below 1°C, such as boric acid, borax or calcium borate. PvA (B) which forms a substance, dissolves in water at a temperature of 100°C or higher, and thickens an aqueous solution of PVA (B) dissolved at a temperature of 100°C or higher.
) is also preferred. That is, in the present invention, a substance (D
) is P V in the process before autoclave curing.
It has the property of suppressing the dissolution of the A (B) powder and allowing the PVA (B) powder to dissolve during autoclave curing at a temperature of 100° C. or higher.

In the present invention, P V A (B) is used in powder form, and since it hardly dissolves in water in an aqueous composition, even when the aqueous composition is used in the form of a water slurry, the viscosity of the aqueous slurry is Even if the aqueous composition is produced by a paper-making method without increasing the PVA (
B) PVA (
B) It is thought that the powder dissolves and develops a reinforcing effect. In particular, when a cross-linking agent such as PVA (B) among substance (D) is used together, PVA (B) dissolved during autoclave curing will migrate extensively into the molded product (
It is inferred that the reinforcing effect is significantly increased because the adhesive remains in place and develops adhesive strength without migration (migration).

In addition, P V A (B) Substance that thickens the aqueous solution (D)
The greater the amount of PVA (
1% by weight or more, preferably 1 to 50% by weight based on B)
The above content is preferably 5 to 20% by weight.

The manufacturing method of the present invention may be a wet papermaking method, a flow-on method, an extrusion method, a dry method, or the like.

The aqueous composition of the present invention may contain any additives that are added to an aqueous composition made of a normal hydraulic substance (A) as required, such as powdered glue, fly ash, etc. It may contain fillers such as inorganic fillers, sand, gravel, and lightweight aggregates as additives, and may further contain air bubbles.

The solid content concentration of the aqueous composition of the present invention varies depending on the manufacturing method and is not particularly limited. The solid content concentration of the aqueous composition is, for example, 2 to 90% by weight, depending on the manufacturing method.

The feature of the production method of the present invention is that the above aqueous composition is
It consists in curing in an autoclave at a temperature above ℃. The temperature needs to be 100°C or higher, preferably 120 to 180°C, more preferably 140 to 17°C.
It is 0°C. The autoclave curing time is not particularly limited, but is preferably 1 to 30 hours, more preferably 8 to 2 hours.
It is 0 hours. If the autoclave curing time is less than 1 hour, the hydraulic reaction may be insufficient, and if it exceeds 24 hours, the PVA (B) may deteriorate.

The molded product obtained by the production method of the present invention has particularly excellent mechanical strength and dimensional stability.

There are no particular restrictions on the curing conditions before autoclave curing (hereinafter abbreviated as 1st curing), and conditions for direct autoclave curing without 1st curing or 10
Conditions are used in which primary curing is performed at a temperature below 0°C. Among these, conditions in which the primary curing is performed at a temperature of 10°C or more and less than 100°C are preferred, and conditions in which the primary curing is performed at a temperature of 70°C or more and less than 100°C are particularly preferred. There is no particular restriction on the water vapor pressure in the gas phase during the primary curing, but a higher water vapor pressure is preferable, and a saturated water vapor pressure of Iwao is also preferable. Methods such as steaming can be cited as a method for controlling the water vapor pressure in the gas phase.

Although there is no particular restriction on the time for the primary curing, it is preferable to carry out the primary curing until the mold is hardened to the extent that the mold can be removed. The time for the primary curing is, for example, about 1 day to 1 week in the case of room temperature curing, and 5 to 48 hours in the case of heat curing at less than 100°C.

Among these primary curing conditions, certain temperature conditions (70
After primary curing at 100°C or above and below 100°C,
When autoclave curing is performed at a temperature of 100°C or higher under moist heat conditions (conditions in which PVA powder dissolves) at a temperature of 100°C or higher, more preferably in combination with pVA (B) and a substance (D) that thickens the aqueous solution. , a molded product with surprisingly high strength can be obtained.

Next, the molded article J of the present invention will be explained.

The molded article of the present invention comprises a hydraulic substance (A) and PVA (
B), and the blending ratio of PVA (B) is 01 to 20% by weight based on the hydraulic substance (A), in which P is melted and then solidified in the molded product.
This is a molded product having a single structure in which V A (B) is dispersed in an island shape.

As the aqueous substance (A) and PVA (B), those described in the column of the method for molding the aqueous composition above may be used. The molded product of the present invention contains reinforcing fibers (C) and/or pvp, (B) a substance that thickens the aqueous solution (D) described in the manufacturing method column above, which improves the strength of the molded product. preferred from the viewpoint of The amount of reinforcing fiber (C) added is preferably 0.1 to 10% by weight based on the total solid content. The blending ratio of substance (D) is preferably 1% by weight or more, more preferably 1 to 50% by weight, and particularly preferably 5 to 20% by weight based on PVA (B). The molded product of the present invention is made of P V that is solidified after being melted in the molded product.
The characteristic is that A (B) is dispersed in the form of islands and has a single-layer structure, and it is preferable that the island-like P V A (B) is generally uniformly dispersed in the molded product. pV A
There is no particular restriction on the shape of the island in (B), and examples include spherical or deformed spherical shapes, spherical or deformed spherical shapes with hollow parts, and spherical or deformed spherical shapes in which the PVA concentration decreases from the center to the periphery. It will be done. There is no particular restriction on the size of the islands, but the average long axis of the islands is preferably 0.05 to 3 mm, more preferably 0.1 to 1 m.
It is m. When P V A (B) does not have a structure dispersed in discontinuous islands in the molded article (p V A (B)
) is continuous) or when P V A (B) is not solidified after melting (P V A (B)
(including incomplete melting), the strength of the molded product decreases.

In the molded product of the present invention, when the hydraulic substance (A) is made of cement, the molded product contains tobermorite gel. This tobermorite gel can be observed using a scanning electron microscope. When the molded article contains tobermorite gel, the strength and dimensional stability of the molded article are significantly improved.

Although there are no particular restrictions on the method for manufacturing the molded product of the present invention,
A method for manufacturing a molded article made of the aqueous composition described above may be mentioned.

The molded product of the present invention is used as a molding material for plate-like products used for roofs, outer walls, inner walls, etc., blocks for roads and seawalls, and the like.

(Example) The effects of the present invention will be explained below using examples.

In the examples, "%J" and "part J" mean "% by weight" and "parts by weight", respectively, unless otherwise specified.

Example 1-14, Comparative Example 1~! 0 (1) Sample molding method (paper making method) Using ordinary Portland cement as the hydraulic material,
Polymerization degree 1700, saponification degree 98 mol% as PVA powder
, 60 Metsuyupass was used, and as other additives, those shown in Table 1 were used. Using these ingredients,
Table-■ (Examples j to 1+) and Table-2 (Comparative Example 1-1
After adjusting the aqueous composition according to the mixing ratio shown in 0) and pouring it into a formwork, an aqueous slurry with a solid content concentration of 40% was pressed so that the solid content concentration was 70 to 80% (wet Hebe). A board with a thickness of 0.8 cm was produced by squeezing.This corresponds to the thickness range of products obtained by ordinary Fourdrinier-layer papermaking.

The curing conditions of the obtained plate materials are shown in Table 1 (Examples 1 to 14) and Table 2 (Comparative Examples 1 to 10).

(2) Evaluation method Bulk specific gravity: Based on JISA5413, the test piece was placed in a hot air dryer and was determined from the weight and volume after drying at 105±5°C for 24 hours.

Bending strength, bending deflection: JISA 140
Measurements were made with a span length of 5 cm in accordance with the 8ril Bending Test Method for Building Boards. The maximum deflection at the center of the span was defined as the bending deflection. (The larger the bending deflection, the more flexible the molded product is, and the more useful it is as a molded product.) Length change rate (dimensional stability) - Dry at 60°C day and night in accordance with JISA5416. The rate of change was determined by measuring the length of water absorption after being immersed in water at 20° C. day and night.

(3) Results The results are shown in Table 1 (Examples 1 to 14) and Table 2 (Comparative Examples 1 to 10).

(4) i! i Microscopic Observation When the cross section of the molded product obtained in Example 1-14 was observed using a scanning electron microscope, it was found that the PVA that had solidified after melting in the molded product had a discontinuous island shape (the shape of the island was deformed). It was confirmed that the particles were dispersed uniformly and in a spherical shape.

It was also confirmed that the molded product contained tobermorite gel.

Further, the dispersion state of PVA in the molded product can be observed using a stereomicroscope after coloring the PVA by iodine coloring.

When the cross sections of the molded products obtained in Comparative Examples 1 to 4 were observed using a scanning electron microscope, PVA was dispersed in the form of islands in the molded products, but the PVA was incompletely melted and there was no evidence of f2. I just couldn't accept it.

Comparative Example lt-14 (1) Sample molding method (paper making method) Examples 1, 2.4.5i, mite, except that the aqueous composition was prepared using a PVA aqueous solution instead of PVA powder. Samples were molded in the same manner as in Examples 1, 2, and 4.5. When a PVA aqueous solution was used, the viscosity of the water slurry became high, and the aqueous property was poor, causing problems in processability.

(2) Evaluation method Same as Example 1-14.

(3) Results The results are shown in Table-2.

(4) Microscope Observation When the cross section of the molded product obtained in Comparative Examples 11-14 was observed using a scanning electron microscope, it was confirmed that PVA was not dispersed in the form of islands in the molded product. Ta.

Examples 15-16, Comparative Examples 15-20 (1) Sample molding method (dry method) Using the same PVA powder, boric acid, ordinary Bortland cement, and Toyoura standard sand as used in Examples 1-14. , an aqueous composition was prepared in the proportions shown in Table 3,
The mixture was mixed at a water to cement ratio (w/c) of 40%, and poured into a mold of 25 cm x 25 cm x 0.8 cm. Table 3 shows the curing conditions for the plate material obtained.

(2) Evaluation method Same as Examples 1-14.

(3) Results The results are shown in Table-3.

(4) Microscopic Observation When the cross section of the molded products obtained in Examples 15 to 16 was observed using a scanning electron microscope, it was found that after melting in the molded products,
It is important to confirm that the solidified PVA is uniformly dispersed in the form of discontinuous islands (the shape of the islands is a deformed sphere).

It was also confirmed that the molded product contained tobermorite gel.

Furthermore, the dispersion state of PVA in the molded article could be observed using a stereomicroscope after coloring the PVA by iodine coloring.

When the cross sections of the molded products obtained in Comparative Examples 15, 17, 19 and 20 were observed using a scanning electron microscope, it was found that the PVA was dispersed in the form of islands in the molded products, but the PVA was not completely melted. Only traces of this were observed.

Comparative Examples 21-22 (1) Sample molding method (dry method) Instead of the PVA powder used in Examples 15-16,
A sample was prepared in the same manner as in Example 15.16 except that a PVA aqueous solution was used.

(2) Evaluation method Example 15~ Same as 6.

(3) Results The results are shown in Table-3.

(4) Microscope Observation When the cross sections of the molded products obtained in Comparative Examples 21 and 22 were observed using a scanning electron microscope, it was found that PV
Is it that A is not dispersed like an island? *itz'''2''-・
The manufacturing method for the square margin moldings allows for the easy production of molded bodies with extremely high mechanical strength and good dimensional stability through autoclave curing, and has extremely high industrial value. A molded product made of a hydraulic material provided by the present invention at a height of 0° (having high mechanical strength and extremely high industrial value).

Patent applicant RiRashi Co., Ltd.

Claims (12)

[Claims] (1) Consisting of a hydraulic substance (A) and a polyvinyl alcohol polymer (B) powder, and the blending ratio of the polyvinyl alcohol polymer (B) powder to the hydraulic substance (A) is 0.1 to 20 % by weight of an aqueous composition is autoclaved at a temperature of 100° C. or higher. (2) Claim 1 wherein the aqueous composition contains reinforcing fiber (C)
A method for producing the described molded article. (3) The aqueous composition contains a polyvinyl alcohol polymer (
The method for producing a molded article according to claim 1 or 2, wherein B) the substance (D) that thickens the aqueous solution is contained in an amount of 1% by weight or more based on the powder of the polyvinyl alcohol polymer (B). (4) A method for producing a molded article, which comprises curing the aqueous composition according to claim 1 or 2 at a temperature of less than 100°C, and then curing it in an autoclave at a temperature of 100°C or higher. (5) A method for producing a molded article, which comprises curing the aqueous composition according to claim 3 at a temperature of less than 100°C, and then curing it in an autoclave at a temperature of 100°C or higher. (6) Claims 1 to 5, wherein the hydraulic substance (A) is cement.
A method for producing a molded article according to any one of the above. (7) The substance (D) that thickens the aqueous solution of the polyvinyl alcohol polymer (B) is a crosslinking agent for the polyvinyl alcohol polymer (B), and is a crosslinked product of the polymer (B) and the substance (D). does not dissolve in water at temperatures below 100°C;
The substance according to any one of claims 1 to 6, which is a substance that dissolves in water during autoclave curing at a temperature of 100°C or higher and thickens an aqueous solution of the polymer (B) dissolved during autoclave curing at a temperature of 100°C or higher. A method for producing a molded article as described in section. (8) Claims 1 to 7 wherein the substance (D) that thickens the aqueous solution of the polyvinyl alcohol polymer (B) is a boric acid compound.
A method for producing a molded article according to any one of the above. (9) Consisting of a hydraulic substance (A) and a polyvinyl alcohol polymer (B), and the blending ratio of the polyvinyl alcohol polymer (B) to the hydraulic substance (A) is 0.
1 to 20% by weight of a molded article, the molded article having a structure in which a polyvinyl alcohol polymer (B) solidified after being melted in the molded article is dispersed in island shapes. (10) The molded article according to claim 9, containing reinforcing fiber (C). (11) Claim 9 or 1, wherein the polyvinyl alcohol polymer (B) contains a substance (D) that thickens the aqueous solution in an amount of 1% by weight or more based on the polyvinyl alcohol polymer (B).
The molded article described in 0. (12) The molded article according to any one of claims 9 to 11, comprising tobermorite gel.