JP3108431B2 - Molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molded product made of a hydraulic substance used as a material for buildings, civil engineering, ships, and the like.

(Prior art) A polyvinyl alcohol polymer (hereinafter abbreviated as PVA) is added to improve the mechanical properties and moldability of a molded product made of a hydraulic substance such as cement, gypsum or slag slag. It is generally known that For example, JP-A-49-45934 discloses that PVA is blended for improving the bending strength and impact strength of a pulp cement board, and JP-A-61-77655 and JP-A-61-77655 disclose. No. 209950 discloses the use of PVA to improve the bending strength, impact strength and dimensional stability of slag and gypsum board and to prevent cracks.

JP-A-49-5017 and JP-A-60-239377
The use of PVA is disclosed in JP-A-51-137 for cement moldings and JP-A-51-137719 for the use of lightweight concrete for improving their mechanical strength, improving their surface and preventing cracks.

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

JP-A-47-13628 discloses that the amount of PVA can be reduced by adding a boron-based substance to a water slurry composition comprising cement and PVA powder.

Japanese Patent Application Laid-Open No. 59-184754 discloses cement and PVA.
It is disclosed that in a water slurry composition comprising a powder, the strength of a molded product is improved by changing the PVA powder to a silyl group-modified PVA.

2. Description of the Related Art In recent years, molded products of hydraulic substances have been mass-produced in factories of the same standard. Conditions required for mass production of hydraulic materials in factories include good mechanical strength and dimensional stability, no cracks in molded products, and good productivity. However, it has been found that a method for producing a molded article made of a hydraulic substance satisfying all of these conditions and a molded article made of a hydraulic substance have not been found.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and is a molded article made of a hydraulic material having excellent mechanical strength and dimensional stability. The purpose is to provide.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have found out that hydraulic substances (A), PVA (B) and PVA (B)
PVA consisting of substance (D) that thickens aqueous solution
The compounding ratio of (B) is 0.1 to 20 with respect to the hydraulic substance (A).
% By weight, and the compounding ratio of the substance (D) is 1 to 50% by weight with respect to the PVA (B), and the polyvinyl alcohol-based polymer ( B) found a molded product having a structure dispersed in an island shape, and completed the present invention.

(Embodiment of the Invention) First, a method for producing a molded product made of a hydraulic substance of the present invention will be described.

The hydraulic substance (A) in the present invention is not particularly limited as long as it is an inorganic compound that cures by reaction with water.
Examples include various portland cements, gypsum, slag slag, rock wool, inorganic substances such as magnesium carbonate and calcium silicate.

As the PVA (B) in the present invention, ordinary unmodified PVA, silyl group-modified PVA, and powders of various modified PVAs are used. The degree of polymerization of PVA (B) is not particularly limited, but is preferably 500 or more, more preferably 1500
That is all. When the degree of polymerization of PVA (B) is 500 or more,
Due to the strong PVA (B) film and the increased bonding strength of the PVA (B) powder, various properties such as the mechanical strength of the molded product obtained by autoclaving at a temperature of 100 ° C or more are significantly improved. I do. The saponification degree of PVA (B) is not particularly limited, but is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. When the saponification degree of PVA (B) is 80 mol% or more, the dispersion of the PVA (B) powder in the aqueous composition becomes uniform, and the aqueous composition is obtained by autoclaving at a temperature of 100 ° C or more. Of PVA (B) powder and P
Due to the strength of the VA (B) film, the bending strength of the obtained molded article is remarkably improved.

The particle size of the PVA (B) powder is not particularly limited, but is preferably 16 mesh pass, more preferably 42 mesh pass, and the smaller the average particle size, the better.

In the aqueous composition of the present invention, the mixing ratio of the PVA (B) powder is 0.1 to 20% by weight, and preferably 0.5 to 5% by weight, based on the hydraulic substance (A). If the blending ratio of PVA (B) is less than 0.1% by weight, the effect of reinforcing the molded product by adding PVA (B) cannot be obtained, and if it exceeds 20% by weight, the water resistance and flame retardancy decrease. May not be preferred.

Furthermore, in order to improve the effect of PVA (B), a substance (D) that thickens the aqueous PVA (B) solution is added to the aqueous composition of the present invention.

The substance (D) that thickens the PVA (B) aqueous solution is 20 ° C
The substance (D) in a 10% aqueous solution of PVA (B) in
By adding 5% of solid content to (B), PVA
(B) A substance whose viscosity increases twice or more, preferably four times or more, of the aqueous solution, and more preferably a substance which gels the PVA (B) aqueous solution. Among the substances (D) that thicken the aqueous solution of PVA (B), PVA (B) is cross-linked to form a cross-linked product insoluble in water at a temperature lower than 100 ° C. Dissolved in and 10
P dissolved in autoclave curing at temperatures above 0 ° C
A crosslinking agent for PVA that thickens the aqueous VA (B) solution is preferred.

Examples of the substance (D) that thickens the PVA (B) aqueous solution include boric acid, borax, calcium borate, magnesium borate,
Trivalent chromium generated when an alkali metal salt of aluminate, zirconium salt, chromic acid or dichromic acid is reduced, tetravalent titanium generated by oxidation of titanium trichloride, vanadate, copper ion, etc. Is mentioned. Dyes such as Congo Red and organic substances such as gallic acid can also be used. Among these substances (D) that thicken the PVA (B) aqueous solution, boric acid compounds are preferable,
Among them, calcium borate is particularly preferred. In the case where the hydraulic substance (A) generates calcium ions in the presence of water, 100% of boric acid, borax or calcium borate may be used.
When the temperature is lower than 100 ° C, a crosslinked product insoluble in PVA (B) and water is formed.
Most preferred is a crosslinking agent for PVA (B) that thickens the aqueous PVA (B) solution dissolved at the above temperature. That is, in the present invention, the substance (D) that thickens the PVA (B) aqueous solution is used in the step before the autoclave curing.
It has the property of suppressing the dissolution of A (B) powder and dissolving the PVA (B) powder in autoclave curing at a temperature of 100 ° C or higher.

Further, in the present invention, it is preferable to use the reinforcing fiber (C) as one of the additives in order to express the strength of a high-performance molded article. The amount of the reinforcing fibers added is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the total solid content. By adding 0.1% by weight or more of the reinforcing fiber, the effect of reinforcing the molded product and the effect of connecting the green sheets are remarkably improved. However, if added in an amount of 10% by weight or more, there is a problem in the dispersibility of the reinforcing fibers, and the reinforcing effect may be impaired. As the type of reinforcing fiber,
Examples thereof include those usually used as a reinforcing material such as cement. Preferably, as a reinforcing fiber of a molded product composed of a hydraulic substance (A), vinylon-based, acrylic-based,
Pulps such as olefin-based, carbon- and aramid-based fibers, synthetic pulp, wood pulp, and high-beaten wood pulp (these are also referred to as fibers in the present invention). May be used in combination.

In the present invention, PVA (B) is used in the form of a powder and hardly dissolves in water in an aqueous composition. Therefore, even when the aqueous composition is used in the form of a water slurry, the viscosity of the water slurry Almost all of the PVA (B) powder remains in the aqueous composition even when produced by the papermaking method without increasing the temperature. After that, when the autoclave curing (moist heat condition) is performed at a temperature of 100 ° C. or more, the PVA (B) It is considered that the powder is dissolved and the reinforcing effect is exhibited. In particular, when a cross-linking agent for PVA (B) is used in combination with the substance (D), the PVA (B) dissolved in the autoclave curing does not significantly move (migrate) into the molded product, but is moved to that location. It is supposed that the reinforcing effect is remarkably increased due to the remaining adhesive force.

The effect of adding the substance (D), which increases the viscosity of the aqueous solution of PVA (B), is greater as the amount of the added substance (D) increases.
20% by weight.

The method for producing the molded product of the present invention may be any of wet papermaking, flow-on, extrusion, and dry methods.

The aqueous composition of the present invention may contain any additives which are optionally added to the aqueous composition comprising the normal hydraulic substance (A), such as powdered silica and fly ash. A filler such as an inorganic filler, sand, gravel, and lightweight aggregate may be included as an additive, and may further include air bubbles.

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

Next, the above aqueous composition is autoclaved at a temperature of 100 ° C. or higher. It is necessary that the temperature be 100 ° C or higher, preferably 120 to 180 ° C, more preferably
140-170 ° C. The time for the autoclave curing is not particularly limited, but is preferably 1 to 30 hours, more preferably 8 hours.
~ 20 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 be deteriorated.

The molded product thus obtained is particularly excellent in mechanical strength and dimensional stability.

The curing conditions (hereinafter abbreviated as primary curing) before performing the autoclave curing are not particularly limited, and the conditions for directly performing the autoclave curing without performing the primary curing or 10 conditions.
Conditions for performing primary curing at a temperature lower than 0 ° C. are used. Among them, the conditions for performing the primary curing at a temperature of 10 ° C or more and less than 100 ° C are preferable, and the conditions for performing the primary curing at a temperature of 70 ° C or more and less than 100 ° C are particularly preferable. There is no particular limitation on the water vapor pressure of the gas phase during the primary curing, but the higher the water vapor pressure, the more preferable the saturated water vapor pressure.
As a method of controlling the water vapor pressure in the gas phase, there is a method such as steaming. There is no particular limitation on the time for the 1:00 curing, but it is preferable to perform the primary curing until the mold is cured 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 below 100 ° C.

Of these primary curing conditions, specific temperature conditions (70
After primary curing at a temperature of 100 ° C or higher and lower than 100 ° C), a substance (D) for thickening an aqueous solution of PVA (B) is preferably used in combination under a wet heat condition of 100 ° C or higher (condition under which the PVA powder dissolves). If the autoclave curing is carried out at a temperature of 100 ° C. or higher, a molded article having surprisingly high strength is obtained.

 Next, the structure of the molded product of the present invention will be described.

The molded article of the present invention comprises a hydraulic substance (A), a PVA (B), and a substance that thickens an aqueous PVA (B) solution.
The mixing ratio of VA (B) is 0.1 to 2 with respect to hydraulic substance (A).
The molded product is 0% by weight, and the compounding ratio of the substance (D) is 1 to 50% by weight based on the polyvinyl alcohol-based polymer (B). A molded article having a structure in which the polyvinyl alcohol-based polymer (B) is dispersed in an island shape.

As the hydraulic substance (A) and the PVA (B), those described in the section of the above-mentioned aqueous composition molding method are used. The molded article of the present invention is a PV described in the above-mentioned production method.
It is preferable from the viewpoint of the strength of the molded article that the substance (D) which thickens the aqueous solution A (B) or the reinforcing fiber (C) is further contained therein. The amount of the reinforcing fiber (C) added is preferably 0.1 to 10% by weight based on the total solid content. The compounding ratio of substance (D) is 1% by weight based on PVA (B)
Or more, preferably 1 to 50% by weight, more preferably 5 to 20% by weight.
% By weight is particularly preferred. It is important that the molded product of the present invention has a structure in which the solidified PVA (B) is dispersed in an island shape after being melted in the molded product. ) Are preferably substantially uniformly dispersed. The shape of the island of PVA (B) is not particularly limited, and is spherical or deformed spherical, spherical or deformed spherical having a hollow portion, and from the center to the periphery.
Spherical or deformed spheres in which the PVA concentration decreases are mentioned. Although there is no particular limitation on the size of the island, the average major axis of the island is preferably 0.05 to 3 mm, more preferably 0.1 to 3 mm.
1 mm. PVA (B) is not a structure that is dispersed in the form of discontinuous islands in the molded product {PVA (B) is continuous, etc.} or PVA (B) is not solidified after melting, PVA ( In the case of を including the case where B) is incompletely melted, the strength of the molded product is reduced.

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

The method for producing the molded article of the present invention is not particularly limited, and examples thereof include a method for producing a molded article comprising the aqueous composition.

The molded product of the present invention is used as a molding material for a plate-like material used for a roof, an outer wall, an inner wall, and the like, a road and a revetment block, and the like.

(Examples) The effects of the present invention will be described below with reference to examples. In Examples, "%" and "part" mean "% by weight" and "part by weight", respectively, unless otherwise specified.

Examples 1 to 10 and Comparative Examples 1 to 10 (1) Sample molding method (papermaking method) Normal Portland cement was used as a hydraulic substance, and the degree of polymerization was 1700, the saponification degree was 98 mol%, and the PVA powder was 60.
A mesh pass was used, and the other additives shown in Table 1 were used. Using these blended components, Table 1
An aqueous composition was prepared at the compounding ratio shown in (Examples 1 to 10) and Table 2 (Comparative Examples 1 to 10), and a water slurry having a solid content concentration of 40% was prepared and poured into a mold. Concentration 70-80
% (Wet base) and squeeze, thickness
0.8cm board was made. This corresponds to the range of the thickness of the product obtained by the usual fourdrinier single layering.

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

(2) Evaluation method Bulk specific gravity: In accordance with JIS A 5413, the test piece was placed in a hot air drier and determined from the weight and volume after drying at 105 ± 5 ° C for 24 hours.

Bending strength and bending: Measured at a span length of 5 cm in accordance with JIS A 1408 "Bending test method for building boards". The maximum deflection at the center of the span was defined as bending deflection. (Incidentally, the larger the bending deflection, the more the molded product has flexibility and is useful as a molded product.) Length change rate (dimensional stability): In accordance with JIS A5416,
The rate of change was determined by measuring the length of water immersed in water at 20 ° C. overnight, based on the product dried at 60 ° C. overnight.

(3) Results Table 1 (Examples 1 to 10) and Table 2 (Comparative Examples 1 to 10)
See 10).

(4) Microscopic observation When the cross section of the molded product obtained in Examples 1 to 10 was observed by a scanning electron microscope, after melting in the molded product, the solidified PVA was discontinuous island shape (the shape of the island was Deformed sphere)
It was confirmed that the particles were dispersed uniformly and uniformly.

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

In addition, the dispersion state of PVA in the molded article could be observed by using a stereoscopic microscope after the PVA was colored by iodine coloration.

When the cross section of the molded product obtained in Comparative Examples 1 to 4 was observed by a scanning electron microscope, in the molded product, PVA was dispersed in an island shape, but the PVA was observed only in traces of incomplete dissolution. I couldn't.

Comparative Examples 11 and 12 (1) Sample molding method (papermaking method) In Examples 1 and 3, except that a PVA aqueous solution was used instead of PVA powder, and an aqueous composition to which boric acid was added or not added was adjusted. A sample was formed in the same manner as in Examples 1 and 3. When the PVA aqueous solution was used, the viscosity of the water slurry was increased, the drainage was poor, and a problem occurred in the process passability.

(2) Evaluation method Same as in Examples 1 to 10.

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

(4) Microscopic Observation When the cross section of the molded product obtained in Comparative Examples 11 and 12 was observed with a scanning electron microscope, it was confirmed that PVA was not dispersed in an island shape in the molded product. Was.

Example 11, Comparative Examples 13 to 18 (1) Sample molding method (dry method) Using the same PVA powder, boric acid and ordinary Portland cement and Toyoura standard sand as used in Examples 1 to 10, Table 3 The aqueous composition was adjusted at the mixing ratio shown in Table 2 and mixed under the condition of a water / cement ratio (w / c) of 40%, and 25 cm × 25 c
It was poured into a m × 0.8 cm mold and molded. Table 3 shows the curing conditions of the obtained plate material.

(2) Evaluation method Same as in Examples 1 to 10.

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

(4) Microscopic Observation When the cross section of the molded product obtained in Example 11 was observed by a scanning electron microscope, after melting in the molded product, the solidified PVA was discontinuous island shape (the shape of the island was deformed). (Spherical) and uniformly dispersed.

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

In addition, the dispersion state of PVA in the molded article could be observed by using a stereoscopic microscope after the PVA was colored by iodine coloration.

When the cross section of the molded product obtained in Comparative Examples 13, 14, 17 and 18 was observed by a scanning electron microscope, in the molded product,
Although PVA was dispersed in the form of islands, the PVA showed only traces of incomplete melting.

Comparative Examples 19 to 20 (1) Method of Forming Sample (Dry Method) A method similar to that of Example 11 except that an aqueous PVA solution was used instead of the PVA powder used in Example 11, and boric acid was added or not added. A sample was prepared with.

(2) Evaluation method Same as in Example 11.

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

(4) Microscopic Observation When the cross sections of the molded products obtained in Comparative Examples 19 and 20 were observed with a scanning electron microscope, it was confirmed that PVA was not dispersed in an island shape in the molded products. Was.

(Effect of the Invention) A molded product made of a hydraulic substance provided by the present invention has high mechanical strength and dimensional stability, and has extremely high industrial value.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C04B 22:08) (56) References JP-A-3-1933651 (JP, A) JP-A-1-244808 (JP, A) JP-A Sho JP-A-53-21244 (JP, A) JP-A-49-45934 (JP, A) JP-A-61-77655 (JP, A) JP-A-61-209950 (JP, A) A) JP-A-49-5017 (JP, A) JP-A-60-239377 (JP, A) JP-A-51-137719 (JP, A) JP-A-47-13628 (JP, A) −184754 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 28/00 C04B 22/08 C04B 24/26

Claims (5)

(57) [Claims] 1. A polyvinyl alcohol-based polymer (B) comprising a hydraulic substance (A), a polyvinyl alcohol-based polymer (B) and a substance (D) that thickens an aqueous solution of a polyvinyl alcohol-based polymer (B). Is 0.1 to 20% by weight based on the hydraulic substance (A), and the substance (D)
Is 1 to 50% by weight with respect to the polyvinyl alcohol-based polymer (B), wherein the polyvinyl alcohol-based polymer (B) which has been melted and then solidified is an island. A molded article having a structure dispersed in a shape. 2. The substance (D) which thickens the aqueous solution of the polyvinyl alcohol polymer (B) is prepared by adding the substance (D) to a 10% aqueous solution of the polyvinyl alcohol polymer (B) at 20 ° C. The molded product according to claim 1, wherein the viscosity of the aqueous solution of the polyvinyl alcohol-based polymer (B) becomes twice or more by adding 5% of the solid content to (B). 3. The molded article according to claim 1, wherein the substance (D) for thickening the aqueous solution of the polyvinyl alcohol-based polymer (B) is a boric acid-based compound. 4. The reinforcing fiber (C) is used in an amount of 0.1 to 1 with respect to the total solid content.
The molded product according to any one of claims 1 to 3, which contains 0% by weight. 5. The molded article according to claim 1, which has tobermorite gel.