JPH0262209A - Manufacture of artificial marble product - Google Patents

Abstract

PURPOSE:To form a molded item, on which no sinking develops and which has a shape as designed, by a method wherein unsaturated monomer mainly consisting of filler-containing methyl methacrylate is poured in a mold under the condition that a favorably releasable sheet, which is shaped so as to lie parallel with at least a part of the molding surface for forming the rear side of a product, is lain parallel with said part of the molding surface. CONSTITUTION:The loadings of filler is 20 - 80wt% on the basis of the gross weight of polymer mainly consisting of methyl methacrylate and the filler. In addition, the sheet concerned prevents sinking, which is developed from developing through the separation of the front side of said monomer from the molding surface in the midway of polymerization due to the separation of its rear side from the molding surface for forming its rear side during the shrinkage of the polymer. Accordingly, the sheet must be soft and easily deformable. The thickness of the sheet depends upon its material and its normal and favorable thickness is 0.01 - 2mm. Further, the peeling strength between a product and the sheet is 2kg/cm or less. The shaped sheet must be arranged so as to come into close contact with the molding surface without gap caused by wrinkle, floating and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for casting an acrylic artificial marble product having a front surface with excellent surface properties and a back surface conforming to a designed shape.

[Conventional technology]

Acrylic resin containing fillers has a beautiful appearance and excellent physical properties, so it is used as acrylic artificial marble products such as various tabletops, countertops, bathroom vanities, sinks, bathtubs, shower trays, and waterproof pans. It is widely used for flooring, wall materials, temporary partitions, arts and crafts, etc. The manufacturing of acrylic artificial marble products is easy to introduce cross-linking necessary to improve physical properties, it is easy to manufacture large products and change the product shape, and the manufacturing equipment is relatively inexpensive. For this reason, it is often done by cast molding. However, when casting complex-shaped products other than flat plates, so-called irregular-shaped cast products, polymerization shrinkage causes dull defects called "sink marks" mainly around the convex parts of the product surface, which reduces the aesthetic value. This is a problem because it exists.

Conventionally, as a method to prevent whiskers, a special mold with a fitting mechanism installed on the parting line of the mold (■) is used, and a technology (Mode
rn Plastics International
, 1979 (November), p. 20), a technology that heats only the part that forms the front side of the product to harden the front side first and concentrate sink marks only on the back side (PLAST).
IC5DESIGN & PROCESSING, 1st
Volume 5, November 1975, pages 19-21),
■Technology for attaching a film with good mold releasability to the mold surface of the upper mold that forms the back side of the product (Japanese Patent Laid-Open No. 59-232813
(mentioned in the specification of the No. 1) are known.

[Problem to be solved by the invention]

However, the above-mentioned conventional techniques (2) and (3) require special molds, pressure equipment, and special heating equipment, which not only result in high equipment costs, but also may not completely prevent hair growth depending on the shape of the product. . On the other hand, although method (■) does not require expensive equipment, it is difficult to attach the film to the upper mold with a complicated shape, and even if it is attached, there are many wrinkles and cannot help but stand out. As a result, the back side of the product may have a shape different from the design, thin parts, wrinkles, etc., which may impede installation, reduce strength, or even cause wrinkles to show through the front side, impairing its aesthetic value. As a result, inconveniences arise, and repairs become necessary and end up being expensive.

An object of the present invention is to provide a method for manufacturing a cast-molded acrylic artificial marble product without whiskers and having a designed shape at a low cost without requiring expensive equipment or complicated operations.

[Means to solve the problem]

According to the present invention, the above purpose is to form the back surface of an artificial marble product when manufacturing an artificial marble product by cast molding using an unsaturated monomer mainly composed of methyl methacrylate containing a filler. This is achieved by casting a sheet with good mold releasability that is shaped along at least a portion of the mold surface and casting along the mold surface.

[For production]

The unsaturated 441 monomer mainly composed of methyl methacrylate referred to in the present invention is methyl methacrylate alone or less than 50% by weight, preferably less than 30% by weight of methyl methacrylate is substituted with another unsaturated monomer. The unsaturated monomer that substitutes methyl methacrylate is not particularly limited as long as it can be copolymerized with methyl methacrylate. Examples of such include 1-18 carbon atoms.
ester of monohydric alcohol with acrylic acid, ester of monohydric alcohol with 2 to 18 carbon atoms and methacrylic acid, monoester of dihydric alcohol with 2 to 4 carbon atoms with acrylic acid or methacrylic acid, acrylic acid, methacrylic acid, maleic anhydride, maleic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, styrene, α-methylstyrene, vinyl acetate, glycidyl methacrylate, vinyl chloride, vinylidene chloride, vinyl fluoride, ethylene, etc. Functional unsaturated monomers, acrylic acid and/or methacrylic acid with ethylene glycol, polyethylene glycol, polypropylene glycol, 1,3-phthanediol, neopentyl glycol, 1,6-hexanediol, trimethylolethane, Examples include polyhydric esters with polyhydric alcohols such as methylolpropane, tetramethylolmethane, pentaerythritol and dipentaerythritol, and polyfunctional unsaturated monomers such as divinylbenzene and triallyl isocyanurate. The unsaturated monomers substituting methyl methacrylate can be used in combination of two or more types.In addition, the unsaturated monomers mainly composed of methyl methacrylate are
It is also possible to pre-polymerize a part of the composition and use it as a sill. It should be noted that if the substitution of methyl methacrylate with other unsaturated monomers exceeds 50% by weight, the weather resistance of the artificial marble product will decrease, which is not preferable.

The filler used in the present invention is not particularly limited as long as it is insoluble in the unsaturated monomer mainly composed of methyl methacrylate. aluminum oxide, aluminum oxide,
Examples include, but are not limited to, powders of calcium carbonate, calcium silicate, calcium aluminate, calcium sulfate, magnesium hydroxide, silica, talc, clay, glass, ceramics, wood, and the like.

Note that two or more types of fillers can also be used in combination. The particle size of the filler is usually 0.1 to 100 μm, preferably 0.
．． It is 5 to 50 μm, more preferably 1 to 30 μm.

Particle size is 100I! If it exceeds m, unclear and minute spots may appear on the artificial marble product, spoiling its aesthetic appearance.
Moreover, if the particle size is less than 0.1 μm, it is not preferable because it causes disadvantages such as being expensive and making it difficult to fill a large amount. The amount of filler added is determined by the performance required for the artificial marble product, but it is usually 20 to 80% based on the total amount of the filler and the unsaturated monomer polymer mainly composed of methyl methacrylate. % by weight, preferably 40-70% by weight.

If the amount of filler added exceeds 80% by weight, the strength and other performance of the artificial marble product will deteriorate, and if it is less than 20% by weight, a marble-like appearance will not appear, which is not preferable.

The artificial marble product of the present invention is a cast molded product having a marble-like appearance, which is obtained by introducing an unsaturated monomer mainly composed of methyl methacrylate containing the filler into a mold and polymerizing it. Usually, the entire surface of a product is not the usable side (the front side is the usable side where a beautiful appearance is required and the product value will be significantly reduced if there is a beard, and the other side is the usable side where the appearance is not given much importance and there are defects such as sink marks). It has two types of surfaces: a back surface that is allowed to As an example,
Examples include, but are not limited to, various countertops, kitchen tops, tabletops, sinks, washstands, bathtubs, waterproof pans, and the like.

The cast-molded products described above are often cast-molded using a mold for forming the front side and a mold for forming the back side, but each mold is not necessarily one mold. It does not have to be, and depending on the case, it may be divided into two or more pieces. Also, the mold that forms the front side and the mold that forms the back side are
They do not necessarily have to be separated; a part of the mold forming the back side may be integrated with part or all of the mold forming the front side, or a part of the mold forming the front side may be part of the mold forming the front side. It may be something that is integrated with part or all of the mold that forms the mold.

There are no particular limitations on the material of the mold used in the present invention. Examples of mold materials include glass, which is commonly used.
Examples include metal, resin, plaster, etc., but are not limited to these.

The sheet referred to in the present invention needs to be insoluble in unsaturated monomers mainly composed of methyl methacrylate. However, there is no problem with swelling as long as the swelling does not reach the surface that does not come into contact with the artificial marble until the end of polymerization and hardening, and the sheet does not undergo deformation such as wrinkles. In addition, when the unsaturated monomer containing the filler, mainly methyl methacrylate, decreases in thickness due to polymerization shrinkage, this sheet deforms and separates from the mold surface that forms the back surface. Since the surface side, which is the surface used for artificial marble products, has the effect of preventing the generation of whiskers due to peeling off from the mold surface during polymerization, it needs to be soft and easily deformable.

In other words, the fact that the sheet is soft means that
Place a sheet with a width of 1 cm and a length of 10 cm on two supporting points set at a distance of 5 cm, and 0.2 cm from the straight line connecting the supporting points.
The load required to be applied to the center between the supports to produce a deflection of m is 1000 g or less, preferably 500 g or less, more preferably 100 g or less, even more preferably 2
It means 0g or less.

A sheet that requires a large load is undesirable because it is more likely to generate whiskers. Therefore, the thickness of the shaped sheet with good mold releasability as referred to in the present invention cannot be determined in part because it varies depending on the material of the sheet, that is, its softness.
Usually 0.01 to 2 fl, preferably 0.04 to 11, more preferably 0.07 to 0.5 fl. If the thickness of the sheet is less than 0.01 mm, the sheet will lack strength and stiffness, making it difficult to install it along the mold surface. If the thickness of the sheet exceeds 2 m1, it will be difficult to deform and the artificial marble product will tend to have whiskers, which is not preferable.

The sheet used in the present invention must have good mold releasability. In the present invention, the term "good mold releasability" means that the peel strength between the sheet and the artificial marble product cast-molded using the sheet is 2 kg/(to) or less, preferably 0.5 kir/cm. Below, more preferably Q, 1kg
/a++ or less.

If the peel strength exceeds 2 kg/cffI, it will be difficult to remove the sheet from the artificial marble product, and if it is left as is, it will warp due to the difference in thermal expansion coefficient, and the colored sheet will deteriorate due to the heat of polymerization. This is undesirable because it causes disadvantages such as being transparent from the front side, being economically disadvantageous because the sheet cannot be reused, and having problems with adhesive strength when attaching a pedestal etc. to the back side of an artificial marble product. .

Examples of the material of the sheet with good mold releasability that can be used in the present invention include polyester resin, polyamide resin, fluororesin, polyvinyl alcohol, preferably polyethylene, nylon 12, ethylene-vinyl alcohol copolymer resin, etc. However, it is not limited to these. Note that this sheet does not necessarily need to be made of a uniform material; for example, it may be a laminate sheet in which a sheet with good formability is bonded to the side that does not come into contact with the artificial marble product. Examples of sheet materials with good shapeability include, but are not limited to, polyvinyl chloride, polypropylene, polymethyl methacrylate, polystyrene, and ABS resin.

There are no particular restrictions on the method for shaping the sheet described above along the mold surface, and any method suitable for the purpose can be used. Examples of such methods include shaping a flat sheet by vacuum forming, pressure forming, or press forming, obtaining a shaped sheet by extrusion molding, and forming by applying a solution on the mold surface and drying it. Examples include, but are not limited to, methods for obtaining a mold sheet.

The meaning of the term "along" or "along" as used in the present invention is to install or make the artificial marble product in the designed shape closely adhere to the mold surface without any gaps such as wrinkles or raised parts. That's true. In other words, as a result of placing this sheet along the mold surface, the sheet surface takes on the shape of the mold surface that provides an artificial marble product with the designed shape.

Therefore, even if the sheet of the present invention is interposed between the mold surface and the artificial marble product, the artificial marble product can be molded into the intended shape as designed.

In this way, the shape of the back side of the artificial marble product of the present invention is
The shape of the sheet is determined by the shape of the sheet, so the mold surface that forms the back side does not necessarily need to be in close contact with the entire surface of one side of the sheet (the mold surface may have some missing parts as long as the sheet does not deform). Good too.

In other words, for example, to reduce weight or to vent air when installing a sheet, the mold surface may have many small holes that are not designed for artificial marble products, or the mold surface may have a mesh shape that is different from the designed surface of artificial marble products. It is also possible that there is. In the scope of the present invention, the term ``along'' or ``along'' includes:
This also includes the case where a sheet having a designed shape is placed on a mold surface having such a surface condition.

The sheet of the present invention does not necessarily need to be installed on the entire surface of the mold surface that forms the back surface of the artificial marble product, and can be installed only on a portion of the mold surface depending on the degree of hair growth. Furthermore, when the sheet is placed along the mold surface, it may be partially fixed to the mold surface using an adhesive or the like.

The unsaturated monomer mainly composed of methyl methacrylate containing the filler of the present invention may optionally include dyes and pigments, reinforcing materials, modifiers, stabilizers, mold release agents, flame retardants, antistatic agents, etc. It is okay to add agents etc.

Further, there is no particular restriction on the method for polymerizing the unsaturated monomer mainly composed of thymer methacrylate containing the filler of the present invention, and any suitable method can be used.

Examples include a method of heating in the presence or absence of a radical polymerization initiator, a method using a so-called redox system consisting of a radical polymerization initiator and an accelerator, and a method of irradiating with ultraviolet rays or radiation. It is not limited to.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 A countertop was made of a square plate with sides of about 370 am, having a vertically rising water return on one side with a height of about 50 m, and an apron of about 701 m in height folded vertically on the opposite side. For this purpose, two chrome-plated molds were prepared by bending both ends of rectangular stainless steel plates with a thickness of 3 fins by 90 degrees in opposite directions.

Both ends of a rectangular polyethylene terephthalate sheet having a thickness of 0.07 mm were bent 90 degrees in opposite directions by thermoforming, and molded to fit an upper mold forming the back side of the countertop.

A gasket made of foamed polyethylene is placed around the lower mold that forms the front side of the countertop, excluding the tip of the front sag, and the upper mold is placed along with the above-mentioned molded sheet, and the space between the surfaces is adjusted by tightening with a clamp. The length was adjusted to 10 m and the mold was assembled. The mold was installed so that the front sagging part was above the center plane when the center plane was made horizontal, and the front sagging part was slightly raised to tilt the center plane at about 15 degrees with respect to the horizontal.

Shirabu obtained by partial polymerization of methyl methacrylate (2
The viscosity at 5°C is 3 Boise), 38 parts by weight, 2 parts by weight of ethylene glycol dimethacrylate, and 0 parts by weight of stearic acid.
．． 0.2 parts by weight of N,N-dimethyl-p-toluidine were dissolved, and then 60 parts by weight of aluminum hydroxide powder (Hisilite H-310, manufactured by Showa Denko) was uniformly mixed. Further, 0.2 parts by weight of benzoyl peroxide was uniformly dissolved and poured into the above-mentioned mold from the tip of the apron.

This was heated together with the mold to 50°C in a hot air oven. Thirty minutes after the exothermic peak of polymerization was observed, the temperature was raised to 120°C and further heated for 2 hours. When the countertop was removed from the mold, the front side had a sharp pattern (and the back side was also finished in the shape as designed).

Comparative Example 1 A countertop was obtained in the same manner as in Example 1, except that an unmolded polyethylene terephthalate sheet was used instead of the formed sheet. The rising part of the water return on the back side of the resulting countertop is
The curvature was larger than the design value, so the wall thickness in this part was 61 m, 411 points thinner than the design value.

Example 2 The front surface has a bulge extending 100 mm at the maximum in an arc across the center 800 fins of one long side.
It consists of a rectangular flat part with a length of 400g and a short side of 600 fins, with a water return of 50 mm in height standing vertically on the long straight side, and a height of 8011 mm hanging vertically on the long side with a bulge. Furthermore, the flat part is 350 ++n from the short side, and the center part, which is 100 ridges away from the mizugae and the front edge, is 8 cranes lower than the surrounding area, and the back side is the same as the front side. It consists of a rectangular flat part, with a water return hanging vertically from the straight long side, and a front drop rising vertically from the bulging long side, and is further expanded by 20 mm from the part corresponding to the water cutter on the front side. In order to obtain a washstand whose parts are 81cm higher than the surrounding area, a lower mold is used to form the front side as shown in Figure 1, and a back side as shown in Figure 2. An upper mold for forming was prepared. Each mold is approximately 10m thick
The molding surface of the lower mold was chrome plated.

An ethylene-vinyl alcohol copolymer resin (Eval F, manufactured by Kuraray) sheet having a thickness of 0.1 mm was shaped by vacuum forming so as to follow the surface of the upper mold.

Gaskets made of foamed polyethylene were installed on both sides of the lower mold and at the tip of the water return, and the upper mold with the above-mentioned vacuum forming sheet placed along it was fitted and tightened with clamps to adjust the surface spacing to 15 fins. Assembled the mold. The mold was installed with the front hanging part raised and the flat part inclined at about 15 degrees with respect to the horizontal.

Polymethyl methacrylate (Rose beads HR.

7.6 parts by weight of Kyowa Gas Chemical Industry ■) were dissolved in 30.4 parts by weight of methyl methacrylate and 2 parts by weight of trimethylolpropane trimethacrylate, and aluminum hydroxide powder (Hisilite H-310, manufactured by Showa Denko ■) was dissolved.
5% by weight, 45 parts by weight of silica powder (Crystallite AA, @Tatsumori), 0.02 parts by weight of stearic acid, and 2.
0.02 parts by weight of 2'-azobis(4-methoxy-2,4-valeronitrile) was mixed uniformly and poured into the mold described above.

The flat part of the mold was returned to the horizontal position and heated to 50°C in a hot air oven.

Thirty minutes after the exothermic peak of polymerization was observed, the temperature was raised to 120°C, and the mixture was further heated for 2 hours. The resulting bathroom vanity had a wall thickness of approximately 13.5 m, and there were no sink marks on the front side.
The back side was also finished in the shape as designed.

Comparative Example 2 Ethylene-vinyl alcohol copolymer resin The bathroom vanity was obtained by the same method. In addition, approximately 10
The polyvinyl alcohol film was fixed by pasting 1011 square double-sided adhesive tape at 0n intervals. The back surface of the obtained bathroom vanity had wrinkles all over it, and was particularly severe in the bulging part of the apron. In addition, the curvature of the rising corners of the water return and drainer on the back side was larger than the designed value.

〔Effect of the invention〕

The acrylic artificial marble cast molded product of the present invention is cast by placing a sheet with good mold releasability along the mold surface that forms the back surface, so that the use surface, that is, the front surface. It does not stand out and has high aesthetic value.

In addition, since the above sheet is shaped according to the designed shape of the cast-molded product, the back side is finished according to the designed shape, and there are no wrinkles or thick walls that occur when unshaped sheets or films are rolled. There are no thin parts or parts with shapes different from the design.

Furthermore, the above sheet has good mold releasability, so it can be easily removed from the cast molded product, and since the sheet is attached, it can warp due to the difference in thermal expansion coefficient, and discolor due to heat. The stained sheet remains attached, damaging the aesthetic value.
Because of the sheet, there are no problems such as inconvenience in adhering parts.

According to the present invention, it is possible to obtain an acrylic artificial marble product that is inexpensive and simple to operate, has the dimensions as designed, is free from hairs, and has excellent aesthetic value.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a lower mold forming the front side of a bathroom vanity according to an embodiment of the present invention, and Fig. 2 is a perspective view of an upper mold forming the back side.The scale of each part is arbitrary. be. 1... Return water, 2... Drop in front, 3... Drain, 4
...Flat area, 5...Bulge. Figure 1 Figure 2

Claims (1)

[Claims] When manufacturing artificial marble products by cast molding using an unsaturated monomer mainly composed of methyl methacrylate containing fillers, A method for producing an artificial marble product, comprising casting a shaped sheet with good mold releasability along the mold surface.