JPH0716962B2 - Method for manufacturing composite molded body - Google Patents

Description

The present invention relates to a method for producing a composite molded article having excellent mechanical strength and water resistance.

[Problems to be Solved by Prior Art and Invention]

The molded body of inorganic powder is widely used as a heat insulating material, a heat insulating material, a fireproof coating material, an interior / exterior material for buildings, and the like. Generally, a specific strength obtained by dividing bending strength by the square of specific gravity is used as an index representing the mechanical strength of a material, and a high specific strength is also required for the above-mentioned inorganic powder compact. As a method for improving the specific strength of a molded body of inorganic powder, there is known a method of impregnating the molded body of inorganic powder with a polymerizable monomer and then polymerizing the polymerizable monomer to obtain a composite molded body. Has been. For example, Japanese Unexamined Patent Publication (Kokai) No. 48-61527 discloses that a molded product mainly composed of calcium silicate hydrate is impregnated with a methacrylic acid ester and polymerized by heating. According to this method, a composite molded article having both high specific strength and absolute strength and excellent water resistance can be obtained.

However, the composite molded article obtained by such a manufacturing method is not sufficiently impregnated with methacrylic acid ester in all the voids of the calcium silicate molded article, and particularly, in the surface layer portion of the composite molded article, Many unimpregnated voids remain. Therefore, there is still room for improving the specific strength and absolute strength of the composite molded body.

[Means for solving problems]

The inventors of the present invention have conducted extensive studies to improve the specific strength and absolute strength of the above-mentioned composite molded body and to improve water resistance and surface hardness. As a result, between the step of impregnating the molded body of the inorganic powder with the polymerizable monomer and / or the partial polymer and the step of polymerizing the above-mentioned polymerizable monomer and / or the partial polymer, It has been found that the above object can be achieved by adding a step of molding a molded body of an inorganic powder impregnated with a polymer and / or a partial polymer at a high pressure, and has completed the present invention.

That is, the present invention, after impregnating the inorganic powder or a molded body thereof with a polymerizable monomer and / or a partial polymer, 70 to 10,000 kg
A method for producing a composite molded article, which comprises molding at a pressure of / cm ² and then polymerizing the polymerizable monomer and / or a partial polymer thereof.

That is, in the present invention, it is important to impregnate the inorganic powder or its preliminary molded body with the polymerizable monomer and / or the partial polymer and then pressurize or press-mold the inorganic powder or the inorganic polymer. The effect of the present invention cannot be expected when a molded product is impregnated with the polymerizable monomer and / or partial polymer and polymerized without pressurizing.

As the inorganic powder used in the present invention, known inorganic powders can be used without any limitation as long as they can be molded into a molded body. Generally, in order to improve the specific strength of the obtained composite molded body, the bulk density in the dry state is 0.01 to 1.0 g / cc, particularly 0.05
Inorganic powders of ~ 0.4 g / cc are preferred. From the viewpoint of the impregnating property of the polymerizable monomer and / or its partial polymer, an inorganic powder having an oil absorption of 0.5 to 10 cc / g is preferable.

Specific examples of the inorganic powder preferably used in the present invention include aluminum oxide; calcium oxide; silicon oxide; calcium aluminate such as 3CaO.Al ₂ O ₃ , CaO.Al ₂ O ₃ ; 3CaO.SiO. _2, inorganic oxides such as calcium silicate ₂ such 2CaO · SiO and the like. Moreover, these hydrates are also preferably used in the present invention. Among these inorganic powders, silicon oxide or calcium silicate is preferable because it has excellent moldability and the resulting composite molded body has high specific strength. Furthermore, it has a gyrolite type crystal structure, the SiO ₂ / CaO molar ratio is 1.6 to 3.2, the average diameter in the longitudinal direction is 0.1 to 30 microns, and the thickness is 0.005 to 0.1 microns. Alternatively, silicon oxide in which the calcium content is dissolved and removed by contacting the calcium silicate with a mineral acid is most preferably used. Such petal-like calcium silicate and silicon oxide can be produced by the methods described in JP-A-54-93698 and JP-A-54-118399.

Addition of other components to the above inorganic powder can be carried out as necessary. Examples thereof include fibrous substances such as glass fibers, carbon fibers, aramid fibers, vinylon fibers, and metal fibers; organic admixtures such as paraffin, tar, polyethylene, polypropylene, and rubber.
The fibrous material is effective in further improving the specific strength and absolute strength of the obtained composite molded article, and it is usually preferable to mix the inorganic powder in the proportion of 0.1 to 5.0% by weight. Further, the organic admixture is effective in improving the processability and freeze-thaw resistance of the obtained composite molded body, and it is preferable to mix it in the inorganic powder at a ratio of 0.5 to 10% by weight.

The inorganic powder used in the present invention has a granular shape, a plate shape, or a spherical shape. It is easy to handle if it is molded into a columnar shape. The molded body can be molded from the above-mentioned inorganic powder by a known molding method without particular limitation. For example, for molding the dried inorganic powder, a uniaxial pressure molding method using a die press molding machine, an isostatic press molding method, or the like is adopted. For molding the inorganic powder in the form of slurry, a mold injection method, a dehydration pressure molding method or the like is adopted, and drying is performed after the molding. In molding the inorganic powder, the bulk density of the molded product is 0.1 to 0.6 g in consideration of the impregnability of the polymerizable monomer and / or partial polymer described below and the absolute strength of the resulting composite molded product. It is preferable to mold so as to be / cc.

The polymerizable powder and / or the partial polymer is impregnated into the inorganic powder or the molded product of the inorganic powder obtained as described above. As the polymerizable monomer and / or partial polymer used in the present invention, known ones can be used without particular limitation as long as they can impregnate an inorganic powder or a molded product thereof. Considering the impregnating property of the inorganic powder or its molded product, the viscosity of the polymerizable monomer and / or the partial polymer is preferably 0.2 to 100 cps. Specific examples of the polymerizable monomer and the partial polymer which can be preferably used in the present invention are as follows. For example, vinyl halides such as vinyl chloride and vinylidene chloride; aromatic vinyls such as styrene and divinylbenzene; vinyl nitriles such as acrylonitrile and methacrylonitrile; acrylic acid esters such as methyl acrylate and diethylene glycol bisallyl carbonate. Methacrylic acid esters such as methyl methacrylate and glycidyl methacrylate; vinyl ketones such as methyl vinyl ketone; or partial polymers of these polymerizable monomers;
Examples include oligomers having a radically polymerizable unsaturated group such as unsaturated polyester; uncured products such as epoxy resin, urethane resin and melamine resin. These polymerizable monomers and partial polymers may be used alone or in admixture of two or more. Particularly in the present invention, aromatic vinyls such as styrene and methacrylic acid esters such as methyl methacrylate are preferably used because a more excellent composite molded body can be obtained.

For the polymerization of these polymerizable monomers and / or partial polymers, a polymerization initiator may be mixed with the polymerizable monomers and / or partial polymers, if necessary. As the polymerization initiator, known compounds can be used without any limitation. For example,
Azonitriles such as azobisisobutyronitrile; ketone peroxides such as methyl ethyl ketone peroxide; hydroperoxides such as cumene hydroperoxide; diacyl peroxides such as benzoyl peroxide and lauroyl peroxide . Among these, azobisisobutyronitrile and benzoyl peroxide are preferably used. The amount of these polymerization initiators used is preferably selected from the range of 0.001 to 10% by weight, preferably 0.3 to 4% by weight, based on the polymerizable monomer and / or partial polymer.

The amount of the polymerizable monomer and / or the partial polymer to be impregnated into the inorganic powder or its molded product is 2 to 35% by weight, preferably 5 to 20%.
It is preferably set to wt%.

The method of impregnating the inorganic powder or the molded body thereof with the polymerizable monomer and / or the partial polymer is not particularly limited. And / or a method of immersing in the partial polymer, a method of deaerating or pressurizing after that, a method of applying, a method of spraying and the like can be mentioned. Among these impregnation methods, the spray method is particularly preferably used.

According to the above method, the inorganic powder or the molded product impregnated with the polymerizable monomer and / or the partial polymer has a viscosity of 70 to 10,000 kg / c.
It is molded into a predetermined shape under a pressure of m ² , preferably 150 to 2,000 kg / cm ² . Although the absolute strength and durability of the obtained composite molded article are improved by increasing the molding pressure, when the content exceeds the above range, not only the pressing effect reaches a ceiling but also it becomes technically difficult. On the other hand, if the molding pressure is further reduced below 70 kg / cm ² , the bending strength and specific strength of the molded body will decrease, and the practicality will be poor. As a molding method, a known method is carried out without particular limitation. For example, a compression molding method such as a uniaxial pressure molding method using a die press molding machine or an isostatic press molding method can be used.

The composite molded article of the present invention can be obtained by polymerizing the polymerizable monomer and / or partial polymer impregnated in the molded article obtained by the above method by a known method. The method for polymerizing the polymerizable monomer and / or the partial polymer is, for example,
Methods such as heating and radiation irradiation are used.

When the fibrous material or the organic admixture described above is mixed with the inorganic powder, it is preferable to heat the fibrous material or the organic admixture in order to improve the adhesiveness between the inorganic powder and the fibrous material. . Therefore, if a heating method is adopted as a method of polymerizing the above-mentioned polymerizable monomer and / or partial polymer, it is possible to serve also as adhesion between the fibrous material or the organic admixture and the inorganic powder. . The heating temperature is generally 50 to 160
It is preferable to select from the range of ° C.

The shape of the composite molded article of the present invention is not particularly limited and can be used in the form of granules, plates, spheres, columns, etc. For example, when it is used as a building material, it is generally a plate.

〔effect〕

According to the method of the present invention, it is possible to obtain a composite molded article having excellent specific strength and absolute strength. Moreover, the obtained composite molded article is also excellent in water resistance and surface hardness. The present inventors presume the reason why such high specific strength and good water resistance are obtained as follows. That is, a polymerizable monomer and / or a partial polymer is impregnated in a molded body of an inorganic powder and then molded at a specific pressure, so that the polymerizable monomer and / or the partial polymer is converted into a composite molded body. It is considered that a dense layer formed by forming a dense layer on the surface layer portion contributes to the improvement of mechanical strength and water resistance.

〔Example〕

Examples and comparative examples are shown below to more specifically describe the present invention, but the present invention is not limited to these examples.

Each test in Examples and Comparative Examples was carried out by the following method.

(1) Bending test A span of 80 mm and a load speed of 0.5 mm / min were measured by the three-point bending method.

(2) Specific strength The flexural strength is shown by the value obtained by dividing the air-dry specific gravity of the test piece by the squared value.

(3) Water absorption length change rate The dimension of the air-dried sample was L ₁ and the dimension after immersion in water for 24 hours was L _2, and the rate was calculated by the following formula.

Water absorption length change rate (%) = (L ₂ −L ₁ ) / L ₁ × 100 (4) Surface water absorption rate After measuring the mass W ₁ of the air-dried sample, measure the inner diameter on one side of the sample. A glass tube with a height of 25 mm and a height of 40 mm is sealed and fixed by rubber packing to prevent water leakage.
Water of 5 cc was injected into the glass tube, a water absorption test was conducted for 1 hour, and then the mass W ₂ of the sample was measured to obtain the value by the following formula.

(5) Surface hardness: Martens type scratch tester, hardness tester ball diameter 3mm
The test piece was scratched on one surface of the test piece, the test point was magnified 400 times with an electron microscope, and the width of the streak was measured.

Examples 1 to 6 As an inorganic powder, petal-like calcium silicate powder (Fluorite R (trade name) having a gyro-light type crystal structure, a bulk density of 0.10 g / cc and an oil absorption of 5 g / cc ); Manufactured by Tokuyama Soda Co., Ltd.), the inorganic powder is press-molded with a die press at a pressure of 50 kg / cm ² to obtain a bulk density of 0.35 g /
With cc, a 100 × 100 × 5 mm plate-shaped molded body was obtained. Then, the surface of the molded body was impregnated with 2.07% by weight of azobisisobutyronitrile having a viscosity of 0.57 cps methyl methacrylate in 100 parts by weight of the molded body at a ratio shown in Table 1 by a spray method, and The molded body was press-molded with a die press molding machine under the pressure shown in Table 1 and then polymerized at 120 ° C. for 2 hours to obtain a composite molded body. The test results of the obtained composite molded body are shown in Table 1.

Examples 7 to 10 Examples except that the polymerizable monomer or partial polymer shown in Table 2 was used instead of methyl methacrylate which is the polymerizable monomer used in Examples 1 to 6 A composite molded body was obtained in the same manner as in 1 to 6. The test results of the obtained composite molded body are shown in Table 2.

Examples 11 to 13 The bulk density obtained by contacting the petal-like calcium silicate used in Examples 1 to 6 with hydrochloric acid has a bulk density of 0.13 g / cc and an oil absorption of 4 g / cc. Composite molded bodies were obtained in the same manner as in Examples 1 to 6 except that the silica powder of No. 1 was used. The test results of the obtained composite molded body are shown in Table 3.

Examples 14 to 17 Composite molded articles were prepared in the same manner as in Examples 1 to 6 except that the inorganic powders used in Examples 1 to 6 were mixed with the fibrous substances shown in Table 4 to form mixed powders. Got The test results of the obtained composite molded body are shown in Table 4.

Examples 18 to 20 Instead of the petal-shaped calcium silicate used in Examples 1 to 6, lime raw materials and silicic acid raw materials were mixed so that the molar ratio of CaO / SiO ₂ was 1.0, and water was further added. The resulting raw material slurry was hydrothermally reacted in an autoclave under the conditions of 14 kg / cm ² and 194 ° C for 10 hours with stirring, and then dried to obtain a bulk density of 0.25 g / cc and an oil absorption of 2.4 cc. Example 1 except that an inorganic powder mainly composed of / xonotolite was used.
A composite molded body was obtained in the same manner as described above. The test results of the obtained composite molded body are shown in Table 5.

Comparative Example 1 A composite molded body was obtained in the same manner as in Example 1 except that the molding pressure was 60 kgf / cm ² . The test results of the obtained molded body are shown below.

Comparative Example 2 As the inorganic powder, calcium silicate powder mainly composed of zonolite was used as in Examples 18 to 20, and the inorganic powder was press-molded by a die press molding machine at a pressure of 500 kg / cm ^2. Then, 7.2 parts by weight of methyl methacrylate containing 2.0 parts by weight of azobisisobutyronitrile and having a viscosity of 0.57 cps was impregnated into the molded body by a spray method, and further 120 ° C.
Polymerization was carried out for 2 hours to obtain a composite molded body. The test results of the obtained composite molded body are shown in Table 5.

Claims (1)

[Claims] 1. After impregnating an inorganic powder or a molded product thereof with a polymerizable monomer and / or a partial polymer, 70 to 10,000 kg / cm ²
A method for producing a composite molded article, which comprises molding at a pressure of 1, and then polymerizing the polymerizable monomer and / or the partial polymer thereof.