JPH11116351A - Production of molded product of foamed resin-containing cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a specific gravity-reduced molded product that has uniform and stable physical properties between those of resin and cement by soaking its intermediate molded product comprising a thermoplastic resin and hydraulic cement in a mixture of an organic solvent with water and heat-treating the soaked product at a temperature higher than the boiling point of water in a shortened curing time. SOLUTION: In this case, a thermoplastic resin having a softening point or heat distortion temperature lower than the boiling point of water under the normal or elevated pressure is suitably used, for example, polyethylene or polypropylene. The cement is mainly a hydraulic cement (e.g: usual portland cement). As the organic solvent, are used two or more kinds of organic solvents one of which is compatible with water, for example, acetone, dioctyl phthalate. The weight ratio of the thermoplastic resin to the hydraulic cement is 100:(50-900). In the heat treatment, the temperature is set to 20-60 deg.C, then raised over the boiling point of water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foamed resin-containing cement molded product, and more particularly, to a method comprising a thermoplastic resin and cement as main components and having intermediate properties between the two.
The present invention relates to a method for producing a foamed resin-containing cement molded body suitable for applications such as building materials and civil engineering materials.

[0002]

2. Description of the Related Art In recent years, as a building or civil engineering material of a cement-based molded body, for example, a plate, a block, or other forms, a thermoplastic resin is mixed with a cement as a main component and heated and molded. After that, a so-called resin-containing cement molded product obtained by curing and curing with water has been awarded. In addition to the original physical properties of the cement material, this molded product has improved bending strength and compressive strength, and has fewer defects such as deformation, shrinkage, and cracks. While it has advantages such as increased resistance, the cement curing process by hydration during the molding process is obtained by heating and molding a mixture of cement and thermoplastic resin at a temperature equal to or higher than the melting temperature of the thermoplastic resin. Since the method is based on the so-called post-hydration method, which comprises immersing the intermediate molded product in water, the degree of hydration varies between the parts of the molded product, for example, the surface layer and the inside, and uniform physical properties are obtained. There is a disadvantage that it cannot be done. As such a molding method, for example, JP-A-4-114978 can be mentioned.

[0003] Further, as a molding method in which the molding technique of a resin-containing cement molded article by the above-mentioned post-hydration method is improved, a hydrophilic substance is added to a thermoplastic resin and cement which are main components, or a water-absorbing fiber is added. There is known a method of obtaining a resin-containing cement molded article by adding a large amount of such a compound. In these methods, the step of curing the cement by hydration during the molding step involves immersing the intermediate molded product after heat molding the mixture in water, and the additive wets the thermoplastic resin with water. It is effective in giving hydration efficiently in the curing process, but depending on the desired shape, the hardening of the cement partially becomes excessive or insufficient,
Sufficient and uniform physical properties cannot always be obtained. As such a molding method, for example, JP-A-7-10626 is cited.

[0004] Further, the present inventors have solved the above problems by curing an intermediate molded product by a post-hydration method.
It is necessary that the thermoplastic resin in the intermediate molded product does not hinder contact with water essential for cement curing,
If this is in a swelling or dissolving state, the curing of the intermediate molded product can be accelerated.
No. 169, a method for producing a resin-containing cement molded product in which an intermediate molded product composed of a thermoplastic resin and hydraulic cement is immersed in a mixed solution of an organic solvent and water to thereby swell and cure the thermoplastic resin Suggested. However, in the resin-containing cement molded article obtained by this method, although the physical properties are relatively uniform and stable mechanical strength can be obtained, a long curing time by hydration is required to obtain such mechanical strength. Remains. Moreover, the obtained molded body still has a large specific gravity as a mixture of a thermoplastic resin and a hydraulic cement, and is still difficult to handle.

In order to solve the above-mentioned problem, the inventors of the present invention basically employ the structure of Japanese Patent Application No. 8-82169 and further combine an organic solvent impregnated with an intermediate molded product with water. It has been found that if the mixed solution is heated to a certain temperature or higher, the curing time can be shortened, and the thermoplastic resin can be in a foamed state to reduce the specific gravity, thus completing the present invention.

[0006]

That is, the present invention is based on the above-mentioned background and, in principle, utilizes a conventional method for producing a resin-containing cement molded body by a post-hydration method, It is possible to harden an intermediate molded product made of a thermoplastic resin and cement in a shorter time, to have intermediate physical properties between a thermoplastic resin and cement, and to have uniform and stable mechanical strength, It is an object of the present invention to provide a method for producing a foamed resin-containing cement molded article capable of obtaining a resin-containing cement molded article having a reduced specific gravity.

[0007]

In order to solve the above-mentioned problems, the present invention provides an intermediate molded product comprising a thermoplastic resin and a hydraulic cement, which is immersed in a mixed solution of an organic solvent and water. By providing heat treatment at a temperature equal to or higher than the boiling point of water, a method for producing a foamed resin-containing cement molded body, characterized by curing the hydraulic cement while swelling and foaming the thermoplastic resin, is provided. .

That is, in the present invention, an intermediate molded product composed of a thermoplastic resin and a hydraulic cement is immersed in the mixed solution having a temperature equal to or higher than the boiling point of water, and an organic solvent penetrating into the intermediate molded product is obtained. While swelling the thermoplastic resin and foaming with at least water, it facilitates water penetration and promotes the hydration reaction of hydraulic cement with water to uniformly cure the entire intermediate molded product. .

The thermoplastic resin used in the present invention is, for example, polyethylene, polypropylene, polyvinyl chloride, ABS or the like. The thermoplastic resin has a softening temperature or a heat deformation temperature at a temperature lower than the boiling point of water under normal pressure or under pressure. Certain thermoplastic resins are preferably applied. Above all, from the viewpoint of obtaining an intermediate molded product, the softening temperature is less than 100 ° C,
Polyvinyl chloride is suitable as a material having a relatively wide range of heat conditions at the time of heat processing and excellent heat workability. Further, the thermoplastic resin is not limited to the same kind, and may be used by mixing with a different kind. Further, the present invention can be applied to the remaining synthetic resin waste obtained by roughly sorting and removing metals, soil, sand, and other contaminants from the synthetic resin waste mainly composed of the thermoplastic resin.

Further, the cement used in the present invention is mainly hydraulic cement, for example, Portland cement hydraulic cement such as ordinary Portland cement, blast furnace cement, fly ash cement, white cement, etc. It is a hydraulic cement such as an early-strength cement, an alumina cement, an oxychloride cement, an acid-resistant cement, and a gypsum. It is also composed of two or more components and reacts with water to become hydraulic, for example, activated silica and water. Calcium oxide, activated alumina and calcium hydroxide are also applicable, and furthermore, two or more of the above cements can be mixed and applied.

The organic solvent used in the present invention is one or more organic solvents capable of swelling or dissolving the thermoplastic resin, and at least one of them is compatible with water. In the case of a mixed solution comprising two or more organic solvents, a mixing ratio in which this is well compatible with water is selected. For example, organic solvents that swell the thermoplastic resin include acetone, dioctyl phthalate (DOP), and butyl phthalate (DB).
P) and the like. When the thermoplastic resin is a polyvinyl chloride resin, examples of the organic solvent for dissolving the same include tetrahydrofuran (THF), cyclohexanone, nitrobenzene, dioxane, dichloromethane, carbon tetrachloride and the like. Examples of the organic solvent having compatibility with water include tetrahydrofuran (THF), acetone, and methyl ethyl ketone (MEK). Here, the water-compatible organic solvent is not only water-soluble organic solvent itself but also water-insoluble but is compatible with other water-compatible organic solvents. Including those who do For example, it is a mixed solution composed of 70% by volume of acetone that is compatible with water, 10% by volume of cyclohexanone that is incompatible with water alone, and 20% by volume of water.

Here, the mixing ratio of the organic solvent to water is such that the ratio of the organic solvent to water is within a range in which the thermoplastic resin swells. That is, the mixing ratio is such that the mixed solution of the organic solvent and water is sufficient to swell the thermoplastic resin and does not dissolve the thermoplastic resin. In this case, the upper limit of the proportion of the organic solvent is not necessarily strict, and it is assumed that the proportion is such that a slight portion of the thermoplastic resin is dissolved.

Next, a specific example of a combination of a thermoplastic resin and an organic solvent will be described. For a polyvinyl chloride resin, tetrahydrofuran (THF) or acetone is desirable, and further, cyclohexanone, nitrobenzene, methyl ethyl ketone (MEK), dioxane Or one added with at least one selected from so-called plasticizers such as dioctyl phthalate and dibutyl phthalate is preferably used.

The mixing ratio of the thermoplastic resin and the cement in the present invention varies depending on the type of the thermoplastic resin, but the range is from 50 to 900 parts by weight of the hydraulic cement to 100 parts by weight of the thermoplastic resin. I do.

In order to obtain the intermediate molded product of the present invention, in addition to the mixture of the thermoplastic resin and the cement, additives such as glass fiber and metal fiber for improving the brittleness of the cement are added. Further, additives such as a foaming agent, a pigment, a light stabilizer, and a heat stabilizer can be added according to the application. The mixture may be heated and kneaded to form a plate-shaped intermediate molded product, or an intermediate molded product obtained by laminating and integrating this with a glass net or a metal net by heating and laminating means.

Next, the mixing means and the molding means for obtaining the intermediate molded product in the present invention will be described. First, as a means for mixing the thermoplastic resin and the hydraulic cement, a commonly used mortar mixer or blender is applied. In this case, in order to improve the mixing degree of the thermoplastic resin and the above-mentioned additives other than the hydraulic cement, the thermoplastic resin is heated to a temperature lower than the melting temperature, preferably a softening temperature or a temperature lower than the heat deformation temperature. Is also good. Then, as a means for heat molding the mixture to obtain an intermediate molded product, the thermal properties at the time of heat molding of the mixture, which are expressed by the type of the thermoplastic resin used, the mixing ratio, the type and amount of the additive, etc. Any known means can be selected as a means for heat-molding a thermoplastic resin as long as the method conforms to the above, and molding methods such as injection molding, extrusion molding, press molding, and compression molding can be applied. For example,
In the press molding, first, the mixture was heated and kneaded at a temperature equal to or higher than the melting temperature of the thermoplastic resin by a mixing roll used for kneading a normal thermoplastic resin as a device for heating and kneading, and this was rolled into a sheet. Thereafter, the sheet is further subjected to compression molding while heating using a press in a single layer or in a laminated state to obtain a plate-like resin-containing cement molded article. It is essential that the heating temperature in the thermoforming be a temperature equal to or higher than the melting temperature of the thermoplastic resin to be used. Further, the set temperature is changed according to the type of each component of the mixture, the mixing ratio, the thermoforming means and the like. be able to. For example, when the thermoplastic resin is a vinyl chloride resin, the heat molding temperature of the pressing machine is set to 120.
The temperature is in the range of ~ 180 ° C.

The intermediate molded product obtained above is immersed in a mixed solution of an organic solvent and water, and the mixed solution is heated at a temperature equal to or higher than the boiling point of water to swell the thermoplastic resin. In addition, the hydraulic cement is hardened by facilitating the penetration of water. At this time, the thermoplastic resin in the intermediate molded product is swollen by the organic solvent that infiltrates from the surface of the intermediate molded product to the interior, and at the same time, water is hardened. As a result of vaporization or foaming due to vaporization of water and the organic solvent, water penetrates into the interior of the intermediate molded product more easily and in a shorter time than when it is simply swollen, and the intermediate molded product It comes into contact with the hydraulic cement therein and hydrates it in a short time. Then, as a natural result of the foaming state, the specific gravity can be reduced.

In the above-mentioned treatment with the mixed solution of the intermediate molded product, after the intermediate molded product is immersed, a relatively low temperature (for example, 20 to 60 ° C.) at which the organic solvent does not vaporize for a certain period of time.
And then heating to a temperature above the boiling point of water. The time in this case depends on the thickness of the intermediate molded product, but is, for example, about 1 hour if the thickness is about 5 mm.

During the heating of the mixed solution, the treatment system using the mixed solution may be subjected to a pressure exceeding atmospheric pressure, for example, 5-6 kg /
By setting the boiling point of water higher than that at normal pressure by placing it under pressure of about ² cm2 and setting the heat treatment temperature of the mixed solution higher, the degree of softening and foaming of the thermoplastic resin in the intermediate molded product As a result, the penetration of water into the intermediate molded product becomes easier, and the hydration of the hydraulic cement can be more effectively promoted.

Further, in the present invention, after the intermediate molded product is heat-treated in the mixed solution, it is immediately immersed in cold water at a temperature equal to or lower than room temperature to generate fine voids due to body contraction. It is also possible to promote the infiltration of water to further promote the hydration of the hydraulic cement.

It should be noted that, if the organic solvent remains in the molded product hydrated by the method of the present invention, it causes a decrease in mechanical properties. Therefore, it is desirable to remove these surplus organic solvents. This removing method can be performed by placing the molded body in a heated state or a reduced pressure state.

The foamed resin-containing cement molded body thus obtained may be slightly deformed from the desired shape. In that case, it is desirable to correct by known heating correction means. For example, when the plate-like foamed resin-containing cement molded body is in a warped state, it is corrected by hot pressing or the like.

[0023]

EXAMPLES Examples of the present invention will be described below along with comparative examples.

The evaluation of the degree of hydration of the foamed resin-containing cement moldings obtained in each of the Examples and Comparative Examples was performed by observing the cross section of the moldings with an electron microscope and examining ettringite or monocrystalline formed on the cement particle surfaces in a crystalline form. Evaluation was made by confirming the presence or absence of products such as sulfate, and the results are shown in Table 1. The evaluation criteria are as follows.

◎: In any part from the surface layer to the inner layer, a hydration product was found in 5 or more of the 10 randomly selected cement particles, and at a depth of 1.0 mm or more from the surface layer, 9 out of 10 cement particles selected
More than one hydration product can be seen.

：: In any part from the surface layer to the inner layer, 5 or more arbitrarily selected cement particles show hydration products in 5 or more cement particles, and at a depth of 0.5 mm or more from the surface layer, 9 out of 10 cement particles selected
More than one hydration product can be seen.

△: A hydrated product is observed in 5 or more of 10 randomly selected cement particles only at a depth of less than 1.0 mm from the surface layer.

×: A hydration product is observed in 5 or more of 10 randomly selected cement particles only at a depth of less than 0.5 mm from the surface layer.

The foamed resin-containing cement moldings obtained in each of Examples and Comparative Examples were measured for specific gravity and flexural modulus [N / mm ² ] and are shown in Table 1.

Example 1 Vinyl chloride resin (degree of polymerization: 700, particle size: 100 μm) 10
0 parts by weight, 200 parts by weight of ordinary Portland cement,
3 parts by weight of the tin-based stabilizer was charged into a mixer, and the mixer jacket was heated to 40 ° C. and mixed with stirring. This mixture was heated and kneaded with a mixing roll at 170 ° C. for 10 minutes, and then rolled to obtain a sheet-shaped intermediate molded product having a thickness of 5 mm. The obtained plate-shaped intermediate molded product was immersed in an aqueous solution containing 30% of tetrahydrofuran (THF) at a temperature of 45 ° C. for 1 hour, and then heated to 70 ° C. and refluxed for 5 hours to continue immersion. Thereafter, the molded body after the completion of the immersion treatment was dried at a temperature of 75 ° C. for 12 hours in order to remove excess tetrahydrofuran (THF). As shown in Table 1, the molded article thus obtained was a resin-containing cement molded article in which hydration progressed well from the surface layer to the inner layer, and the specific gravity was 1.98. The modulus of elasticity of this molded product is 5
It was 500 [N / mm ² ].

Example 2 An intermediate molded product having a thickness of 5 mm was obtained in the same manner as in Example 1, and was immersed and dried under the same conditions as in Example 1 except that the temperature was raised to 90 ° C. . The obtained molded body is shown in Table 1.
As shown in the figure, the resin-containing cement molded body in which hydration progressed very well from the surface layer to the inner layer, and the specific gravity was 1.8
It was 5. Further, the elastic modulus of this molded body is 5000 [N
/ Mm ² ].

Example 3 An intermediate molded product having a thickness of 5 mm was obtained in the same manner as in Example 2, and was then converted to an aqueous solution containing 10% of tetrahydrofuran (THF) under the same conditions as in Example 2. Dipped and dried. As shown in Table 1, the obtained molded article was a resin-containing cement molded article in which hydration progressed well from the surface layer to the inner layer, and the specific gravity was 1.98. The elastic modulus of this molded product was 5,500 [N / mm ² ].

Example 4 An intermediate molded product having a thickness of 5 mm was obtained in the same manner as in Example 2, and then immersed and dried under the same conditions as in Example 2 except that this was used as an aqueous solution containing 80% of acetone. . As shown in Table 1, the obtained molded article was a resin-containing cement molded article in which hydration progressed well from the surface layer to the inner layer, and the specific gravity was 1.91. The elastic modulus of this molded product is 550.
0 [N / mm ² ].

Example 5 An intermediate molded product having a thickness of 5 mm was obtained in the same manner as in Example 2, and this was mixed with 70% acetone and 10% cyclohexanone.
Immersion and drying were carried out under the same conditions as in Example 2 except that an aqueous solution containing As shown in Table 1, the obtained molded article was a resin-containing cement molded article in which hydration progressed very well from the surface layer to the inner layer, and the specific gravity was 1.90. The elastic modulus of the molded product is 5300 [N / m
m ² ].

Comparative Example 1 A 5 mm thick sheet-like intermediate molded product obtained in the same manner as in Example 1 was immersed in the mixed solution of Example 1 maintained at a temperature of 45 ° C. The same procedure was followed.
As shown in Table 1, only the surface layer portion of the obtained molded body was hydrated, and the specific gravity was 2.11. Also,
The flexural modulus was 4000 [N / mm ² ].

Comparative Example 2 The 5 mm thick sheet-like intermediate product obtained in Comparative Example 1 was immersed in boiling water for 5 hours, and then dried at a temperature of 75 ° C. for 12 hours. The obtained molded article had only a surface layer hydrated and had a smaller degree of hydration than Comparative Example 1,
The specific gravity was 2.12. The flexural modulus is 3000
[N / mm ² ].

[0037]

[Table 1]

[0038]

As described above, according to the present invention, an intermediate molded product obtained by heating and kneading a mixture of a thermoplastic resin and a hydraulic cement is immersed in a mixed solution of an organic solvent and water. By performing a heat treatment of the mixed solution at a temperature equal to or higher than the boiling point of water, while swelling and foaming the thermoplastic resin, facilitating the penetration of water and promoting the hydration reaction of hydraulic cement with water, Since the hydraulic cement is hardened, the specific gravity can be reduced, and furthermore, the foamed resin-containing cement molded body having uniform physical properties and stable mechanical strength can be easily produced in a shorter time. There is an effect that can be.

Claims (5)

[Claims] An intermediate molded product comprising a thermoplastic resin and hydraulic cement is immersed in a mixed solution of an organic solvent and water, and then the mixed solution is heated at a temperature equal to or higher than the boiling point of water. A method for producing a foamed resin-containing cement molded product, wherein the hydraulic cement is cured while swelling and foaming the thermoplastic resin. 2. The method according to claim 1, wherein the thermoplastic resin is a polyvinyl chloride resin. 3. The foamed resin-containing cement according to claim 1, wherein the temperature of the mixed solution is kept at 20 to 60 ° C. for a certain period of time after immersing the intermediate molded product, and then heated to a temperature higher than the boiling point of water. A method for producing a molded article. 4. The foamed resin-containing composition according to claim 1, wherein when the intermediate molded product is treated with a mixed solution of an organic solvent and water, the treatment system is placed under a pressure exceeding atmospheric pressure. A method for producing a cement molding. 5. The intermediate molded product according to claim 1, wherein the intermediate molded product is immersed in a mixed solution of an organic solvent and water, and after completion of the heat treatment, immediately immersed in cold water at a temperature equal to or lower than room temperature.
The method for producing a foamed resin-containing cement molded product according to the above item.