JPH09277293A - Production of plate-shaped product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a flaw caused by air bubbles on the surface of a product after molding even if a slight amt. of air remains in a mixture of a filler and a liquid resin in a method for producing a plate-shaped product by subjecting the mixture to press molding under heating and pressure by using a hermetically closed type mold to mold the same into an almost plate shape. SOLUTION: A mixture 3 of a filler and a liquid resin is pressed by a mold consisting of upper and lower molds 1, 2 to mold a plate-shaped product. A sheet 5 is interposed between the mixture 3 and the upper mold 1 and a sheet 6 is interposed between the mixture 3 and the lower mold 2. The sheets 5, 6 are composed of a polymeric film and a large number of small holes are regularly or irregularly bored in the entire surfaces of the sheets.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a plate-like product by mixing a filler such as a lump of stone or a lump of glass and a liquid resin and heating and pressing the mixture in a mold. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of a plate-shaped product of this type, when a filler and a liquid resin are agitated and kneaded, a large amount of air is mixed in the mixture, and air bubbles in the air are generated. Since it is exposed on the surface of the product after pressing and causes a bubble-like defect, which impairs the appearance of the product, in order to prevent this, the mixture is vacuum degassed before press molding or pressed using a vibration press device. It is common to perform degassing in parallel with the work, or to form while compressing air bubbles by a high pressure press (for example, 50 kg / cm 2).

[0003]

However, even if the various degassing methods as described above are performed alone or in combination,
It is still difficult to completely perform deaeration with the closed mold, and there is a problem that foam-like defects may occur on the surface of the product.

According to a trial calculation, when the size of the plate-shaped product is 1 m width × 1 m length × 10 mm thickness, only 10 mm (2) of compressed air, which is one millionth of its volume, remains. Even if it is, it corresponds to 10 bubbles of 1 mm ▲ 3, and the bubbles expand due to the heat during the heat-molding press, and this tends to float in the thickness direction of the plate-shaped product, that is, on the surface of the product. Therefore, a slight degassing failure leads to surface defects of the product.

As can be seen from the above, it was extremely difficult to degas the mixture "completely" after stirring and kneading.

In addition to the above-mentioned lack of deaeration, a trace amount of a reaction product (volatile gas) accompanying the polymerization reaction of the resin during heating and pressurization is a cause of such bubble-like defects. It may occur.

As another type of technique for preventing the formation of the above-mentioned bubble-like defects, there is known a technique of opening the periphery of the molding die to the atmosphere and letting the generated bubbles escape to the outside. However, if such an open mold is adopted, a part of the volatile liquid resin is diffused,
There is an inconvenience in that a resin-deficient region is generated especially in the outer peripheral portion of the finished product, and physical properties such as strength and appearance are different from those in the central portion, and the product quality is deteriorated. The closed mold does not have such a defect, but has a problem that the above-mentioned bubble-like defect occurs.

The present invention has been made in view of the above problems, and is a method for producing a plate-shaped product in which a mixture of a filler and a liquid resin is heated and pressed into a substantially plate-like shape by using a closed mold. Then, it aims at providing the manufacturing method of the plate-shaped product which does not generate the defect by an air bubble on the surface of the product after shaping | molding, even if some air remains in the said mixture.

[0009]

In order to achieve the above object, in the method for producing a plate-shaped product of the present invention, a boundary surface between a mold and a mixture for accommodating air bubbles generated and floated during molding. I decided to intervene.

Therefore, in the method for manufacturing a plate-shaped product according to claim 1, a method for manufacturing a plate-shaped product in which a mixture of a filler and a liquid resin is heat-pressed into a substantially plate shape in a closed mold. In the above, the heating and pressing press molding is performed by interposing a flexible sheet in which a large number of small holes are regularly or irregularly provided between the mixture and the inner wall surface of the mold. Is characterized by.

In this case, as described in claim 2, it is preferable to use a polymer film as the material of the sheet. Specifically, polypropylene, polyester, resin-impregnated paper or the like can be used. Needless to say, it is preferable that the sheet has heat resistance to a predetermined high temperature at the time of hot-pressing, but this is not always essential, and what is more important is the releasability of the molded product. Therefore, the material of the sheet should be determined in relation to the material of the mixture as the molded article (particularly the material of the liquid resin).

Further, as described in claim 3, it is desirable that the small holes formed in the sheet have a diameter of 3 mm or less. Actually, this diameter is preferably about 1 mm or less for the reason described later, but if it is 3 mm or less, the effect of the present invention can be obtained to some extent.

Further, as described in claim 4, the present invention can be effectively applied to the molding of a plate having a thickness of 5 mm or more and a width and a length of 250 mm or more. In the prior art, it was possible to suppress the generation of bubbles to some extent when the size of the product was small, but the occurrence rate of defective products (molded products with bubble-like defects) was high for large products. .
The present invention is also extremely effective for large products that exceed the above dimensions.

Further, as described in claim 5, it is preferable to use a thermopolymerizable resin as the liquid resin. The thermopolymerization resin is also called a reaction type resin, and is a resin such as an acrylic resin or a styrene resin that causes a polymerization reaction when heated. In the present invention, it is preferable to use the monomer (monomer) or one having a low degree of polymerization or a mixture thereof.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a plate-like product manufacturing method according to the present invention will be described below with reference to the accompanying drawings. FIG.
Is a sectional front view showing a main part of a press molding apparatus used for manufacturing a plate-like product, and FIG. 2 is a perspective view showing a sheet used in the present invention.

In the figure, reference numeral 1 is an upper die arranged horizontally, and is formed by processing both upper and lower surfaces of a square metal plate into highly accurate flat surfaces.

Reference numeral 2 denotes a lower die which is horizontally disposed below the upper die 1 so as to face the upper die 1, and a slightly thick metal plate made of the same material as the upper die 1 and having substantially the same size is machined. A cavity 2a for molding a plate-shaped product is formed in the center of the upper surface. The cavity 2a has a shape in which a square plate body can be completely accommodated, and in the present embodiment, the dimensions are slightly larger than 1000 mm in each length and width and 10 mm in depth.

Reference numeral 3 is a mixture which is a raw material for the plate-like product, and is a mixture of a filler and a liquid resin, and a specific composition and an example of the production method will be described later.

Reference numeral 4 denotes an elastic packing made of an elastic material such as heat-resistant rubber, which is mounted over the entire circumference along the inner circumference of the side wall 2b of the cavity 2a.
The size is slightly higher than the depth of a. That is,
When the upper mold 1 is pressed against the upper surface of the lower mold 2, the elastic packing 4 comes into close contact with the molding surface 1a which is the lower surface of the upper mold 1, and the periphery of the cavity 2a is hermetically sealed without any gap. Become.

Numerals 5 and 6 are sheets characteristic of the present invention, which are made of a polymer film, and as shown in FIG.
A large number of small holes 5a and 6a are formed on the entire surface so as to form a vertical and horizontal lattice pattern. In this embodiment,
The material of the sheet is stretched polyester, the thickness is 20 μm, the diameter of the small holes is 0.5 mm, and the lattice rows are 10 mm apart in both length and width.

Reference numeral 7 denotes a heating device closely attached to the upper surface of the upper die 1, which is attached to the lower end of an elevating shaft (not shown) of the pressing device and is integrated with the elevating shaft and the upper die 1. Move up and down. A heating device 8 is closely attached to the lower surface of the lower mold 2, and is fixed to the base of the pressing device. The heating devices 7 and 8 respectively heat the upper mold 1 and the lower mold 2 to a predetermined molding temperature.

An artificial stone was manufactured by the following procedure using the press molding apparatus having the above-mentioned structure.

First, the filler and the liquid resin are mixed. As the filler, glass lumps, ceramic lumps, glass powder, and a mixture of ceramic powders were used. The size of the lump is 0.3-
Some 10 mm are mixed. The particle size of the powder is 0.05 mm or less. An acrylic resin monomer was used as the liquid resin. The weight ratio of the filler to the liquid resin was 83:13. These were stirred and mixed with a mixer having a strong stirring ability to obtain a uniform mixture. The resulting mixture is
Since the content of the resin is small, the fluidity and the flowability are hardly seen, and it is in a state of containing a considerable amount of air with stirring.

Next, this mixture is housed in a vacuum decompression device, depressurized and deaerated for a predetermined time, and then preformed into a flat plate using a vibration press device. As a result, the mixture became a flat plate in which most of the air was degassed and discharged, except for a small amount of residue.

The plate-like mixture thus obtained is set in the above-mentioned press-molding apparatus and heat-pressed and press-molded. The pressure applied was 15 kg / cm2, the heating temperature was 150 ° C, and the molding time was 10 minutes. The artificial stone to be formed has a thickness of 10 mm and a width and a length of 1000 mm.

Here, in order to confirm the effect of the present invention, a comparative example using no sheet and an example of the present invention using a sheet were manufactured under the same conditions.

(Comparative example)

When the sheet was not used, about 7 to 10 bubble-like defects having a diameter of about 1 mm were formed on the surface of the molded product taken out from the mold.

(Example)

On the other hand, when the sheet having the size shown in FIG. 2 was laid on the upper and lower surfaces of the mixture and then heat and pressure press molding was performed, the sheet was stuck to the surface of the molded product taken out. As a result, a small amount of resin was protruding into the small hole portion of the sheet. Then, when the sheet was peeled off, these protruding resins were peeled off together with the sheet while being attached to the sheet. Then, no bubble-like defects were observed on the surface of the molded product.

The reason why the occurrence of bubble-like defects is suppressed by interposing the sheet can be presumed as follows.

That is, the residual air and the generated gas floating on the surface of the molded product during the heating and pressurization and the trace amount of resin flowing out together with these are originally no escape areas, and the surface of the molded product is in the form of bubbles. However, in the present invention, since these gases are accommodated in the minute spaces inside the small holes formed in the sheet, no defects occur on the surface of the molded product.

Therefore, the size and number of the small holes to be formed in the sheet should be experimentally determined to some extent in accordance with the vibration press in the previous step, the vacuum treatment, the size of the plate-like product to be formed, and the like. As a tentative guide, it seems that the size and number of bubbles generated when the sheet is molded without using the sheet as in the comparative example can be used as a guide.

That is, to explain in comparison with the above-mentioned Examples and Comparative Examples, in the above-mentioned Examples, the total volume of the space formed in the small holes of the sheet is (1000)
mm / 10mm) ▲ 2 = 10000, hole diameter 0.5mm,
The thickness of the sheet is changed from 20 μm to 157 mm (3), which is sufficiently larger than the volume of bubbles generated in the comparative example.

However, the total volume of the pore space should not be excessive. This is because if the space is made larger than necessary, the amount of resin in the molded product will be reduced by the amount that flows out from the mixture into the small holes. Roughly speaking, the total volume of the space formed by the small holes is preferably 0.001 to 0.0001% or less of the volume of the plate-shaped product.

When the diameter of the holes is 3 mm or more, the effect of suppressing the occurrence of bubble-like defects can be obtained, but when the sheet is peeled from the surface of the molded product, the small holes of the sheet There is a disadvantage that the resin that overflows in the sheet does not come off with the sheet and remains on the molded product side.

The present invention is not limited to the above embodiment, and the following modifications may be made.

(1) In the above embodiment, the sheet is interposed between the upper and lower surfaces of the product, but the sheet may be laid only on the upper side which is the front surface of the product.

(2) In the above embodiment, an example of manufacturing a plate-shaped product by mixing a filler such as a lump of stone or a lump of glass with a liquid resin has been described, but the present invention is not limited to this, and the present invention is not limited to this. It can also be applied to the production of plate-shaped products.

(3) As the plate-shaped product, not only a flat plate but also a curved product can be applied.

[0041]

As described above, according to the method for manufacturing a plate-shaped product of the present invention, the surface of the molded product can be obtained while taking advantage of the fact that a molded product having a uniform composition can be obtained by the closed mold. It is possible to effectively suppress the occurrence of bubble-like defects. As a result, the yield of products can be significantly improved.

Therefore, since an extremely low-priced means of interposing a sheet such as an inexpensive polymer film between the mixture and the inner wall surface of the mold, the cost does not increase.

Further, as a result of adopting the above means, it becomes possible to prevent the occurrence of bubble-like defects even when the press pressure is low pressure (15 kg / cm 2 or less), and it is possible to achieve a large high pressure (50 kg).
/ cm ▲ 2 or more) Compared with the conventional technology in which residual air is forcedly compressed by a pressing device to suppress the formation of bubbles, the same or higher effect can be obtained with simple manufacturing equipment.

[Brief description of drawings]

FIG. 1 is a sectional front view showing a main part of a press molding apparatus used in a method for manufacturing a plate-shaped product according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a seat used in an embodiment of the present invention.

[Explanation of symbols]

 1 Upper mold 1a Molding surface 2 Lower mold 2a Cavity 3 Mixture 4 Elastic packing 5,6 Sheets 5a, 6a Small hole 7,8 Heating device

Claims (5)

[Claims] 1. A method for producing a plate-shaped product, which comprises press-molding a mixture of a filler and a liquid resin into a substantially plate-like shape in a closed mold, wherein the mixture and the inner wall surface of the mold are separated from each other. In the method for producing a plate-shaped product, the heat and pressure press molding is performed by interposing a flexible sheet having a large number of small holes regularly or irregularly provided therein. 2. The method for manufacturing a plate-shaped product according to claim 1, wherein the sheet is made of a polymer film. 3. The method for producing a plate-shaped product according to claim 1, wherein the small hole has a diameter of 3 mm or less. 4. The method for producing a plate-shaped product according to claim 1, wherein a plate having a thickness of 5 mm or more and a width and a length of 250 mm or more is formed. 5. The method for manufacturing a plate-shaped product according to claim 1, wherein the liquid resin is a thermopolymerizable resin.