JPH06182780A - Manufacture of artificial marble molding - Google Patents

Abstract

PURPOSE:To obtain an artificial marble molding with an excellently finished appearance having no luster unevenness of air bubbles or like defects in its surface by performing mold-release in a state of a thermoplastic resin skin film in close contact with the molding, and permitting it to be hardened through heat. CONSTITUTION:On the mold surface of a mold 1, thermoplastic resin solution is applied and then dried in order to form a thermoplastic resin film 2, and thereafter a thermoplastic resin composite is poured therein, and a cast molded product 3a is cured and then mold-released, and subsequently a semicured molded product 3b having the thermoplastic resin film closely stuck thereto is taken out to be subjected to further heat curing, resulting in obtaining a fully cured molding 3c.

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 an artificial marble molded product used for a wash basin, a countertop for kitchen equipment, a bathtub member, furniture, interior equipment and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for producing artificial marble molded products, especially non-plate-shaped artificial marble molded products having curved or uneven surfaces, a compound obtained by kneading unsaturated polyester resin, glass fiber, calcium carbonate, etc. is heated. A press molding method in which the material is filled in a die and then pressed by a hydraulic press machine to cure. A casting method in which a liquid resin composition comprising a methylmethacrylic resin containing a curing agent and a filler such as aluminum hydroxide powder, silica powder, calcium carbonate powder is poured into a closed mold and heated to cure. A mold release agent is applied to the inner surface of a mold made of reinforced plastics (hereinafter referred to as FRP) made of glass fiber and unsaturated polyester resin, epoxy resin, etc., and then an unsaturated polyester resin containing a curing agent and a curing accelerator is applied. Apply by spraying, etc.
After forming a resin film and curing it to form a so-called gel coat layer, a liquid resin composition consisting of an unsaturated polyester resin containing a curing agent and a curing accelerator and a filler is cast to obtain a demoldable state. Until then, there was a gel coat casting method in which after curing and demolding at room temperature, heating was completed to complete curing.

[0003]

[Problems to be Solved by the Invention] When manufacturing an artificial marble molded product by a press molding method, it is suitable for labor saving by a large-scale facility and for mass production of a small variety, but generally a temperature of 150 ° C and a pressure of 100 kg / cm ² A large hydraulic press that can withstand molding conditions,
Equipment costs such as molds were high, and it was not suitable for producing artificial marble molded products of various shapes in small lots.

Although the physical properties of the cured product are improved as compared with the method of casting a liquid resin in a molding die, it is difficult to obtain a high degree of designability such as a semi-transparent texture and a clear stone pattern. there were.

The method of casting in a mold and heating and curing is mainly carried out in the case of producing an artificial marble molded product using a methylmethacrylic resin composition, but the mold production is expensive, Further, it is difficult to uniformly heat the material, and a so-called sink mark phenomenon in which the mold and the molding material are separated from each other due to curing shrinkage is liable to occur, and gloss unevenness is likely to occur. Since the mold is heavy and requires a precision because it uses a closed mold, it is expensive, and the adaptability to the product shape is poor.

Using the FRP mold, the surface of the mold is previously
In the method of forming the gel coat layer of the resin and then casting the unsaturated polyester resin composition, an open type molding die can be used, and the production of the die is simpler and less expensive than the die. In addition, since it can be easily duplicated by using the master mold that is the basis of the shape, it can be applied to various different sizes and shapes, and was suitable for the production of a large variety of small lots.

The FRP type has many advantages such as light weight and easy handling, but on the other hand, in the gel coating method, a resin liquid is applied to the surface of the molding die and semi-cured to form a gel coat layer. It required extra material, process, and labor. In particular, the gel coat work requires a skill because it is a manual work, and there is a problem that the quality tends to vary depending on the operator and the working conditions.

Further, since the molded product has a transparent or nearly transparent gel coat layer on the surface thereof, it generally has an excellent appearance and a high degree of texture, but the gel coat layer is yellowed due to aging, and the impact property is deteriorated. Was likely to occur, scratches were conspicuous, and repair was difficult. Further, it has a defect that blisters and cracks are easily generated by hot water or the like.

When the unsaturated polyester resin composition is directly cast and cured at room temperature to a low temperature of 50 ° C. without gel coating using the FRP mold, the cast product is still completely removed after demolding. Volatile substances such as unreacted styrene monomer which are not hardened and are contained near the surface are deaerated as pinholes in the heating and curing process for after-cure.

Due to the occurrence of the pinhole, the gloss of the surface is lowered, the gloss and the skin are roughened, and the appearance is remarkably lowered. In addition, physical properties such as water resistance and stain resistance are deteriorated, which is not practical.

When the FRP mold is used, without gel coating and heated while being cast and completely cured, the FRP mold is distorted by heat, and the dimensional stability of the molded product cannot be obtained. It is difficult to remove a molded product having a complicated shape due to shrinkage.

Even when the curing is sufficiently advanced at room temperature for a long time, it is difficult to remove the mold and the molding time is prolonged,
It had a problem that productivity was lowered.

Further, in any of the above methods,
When changing the gloss of the surface of a molded product, it is necessary to prepare a mold with a gloss surface that matches the required gloss. I had to make a mold.

The present invention has a mold release property and mold releasability from a molded product, and more preferably to the mold surface than to the molded product surface.
After forming a thermoplastic resin film with good releasability on the mold surface,
A thermosetting resin composition is cast and cured, and the thermoplastic resin film is released from the mold in a state where it is in close contact with the molded product, and heat-cured, so that there is no bubble or gloss unevenness on the surface, and a good finished appearance. The purpose is to obtain an artificial marble molded product.

[0015]

Means for Solving the Problems In the present invention, a radical polymerization type thermosetting resin composition is injected into a molding die and cured,
In the process of obtaining an artificial marble molded product, a thermoplastic resin that has releasability from the casting mold and the molded product and that has good releasability from the surface of the molded product toward the mold surface. A method for producing an artificial marble molded article, comprising forming a film on a mold surface and then casting the thermosetting resin composition. Particularly, the thermoplastic resin film formed on the mold surface is polyvinyl alcohol. And a film composed of an aqueous acrylic resin and / or vinyl acetate resin emulsion impart appropriate adhesiveness and releasability to the mold surface and the surface of the molded product. Furthermore, by incorporating the inorganic powder in an amount of 0 to 30% by weight with respect to the resin of the thermoplastic resin film formed on the mold surface, molded articles of various glossiness can be obtained without changing the glossiness of the molding die surface. It becomes possible to obtain.

The mold used in the present invention may be a metal mold or a reinforced plastic mold (hereinafter referred to as "FRP mold"), but the FRP is lightweight, easy to manufacture and economical.
The use of molds is preferred.

The radical-polymerization type thermosetting resin composition of the present invention is a slurry-like material which comprises a resin, a filler, a coloring agent, a curing agent, a curing accelerator, etc. and is suitable for room temperature curing type casting. Yes, the resin is an unsaturated polyester resin, a vinyl ester resin, a triazine ring-containing (meth) acrylate polymer, a methylmethacrylic resin, or the like, or
Resins combining these can be used.

The ratio of the resin to the filler in the present invention is generally preferably 20 to 40 parts by weight of the resin component and 80 to 60 parts by weight of the filler. Hereinafter, all parts and% are expressed by weight ratio. When the amount of the resin component is 20 parts or less, the fluidity of the resin composition is lowered and the defoaming property is lowered. When the amount of the filler is 60 parts or less, shrinkage due to shrinkage, deterioration of texture, increase in material price are not preferable, but
These compounding ratios differ depending on the viscosity of the resin, the type of the filler, the particle size, etc., and can be appropriately selected.

In the present invention, the thermosetting resin composition must be injected into a mold having a thermoplastic resin film formed on the surface of the mold, cured, and released from the mold. It is necessary that the releasability from the thermoplastic resin film is better than that. Further, the thermoplastic resin film should not be peeled off during handling in the demolding and heating steps, and should be capable of easily and forcibly peeling after the completion of curing.

It is essential that the thermoplastic resin used for forming a film on the surface of the molding die is in a liquid state, is easy to apply, has a good film-forming property, has strength for handling, and has an appropriate releasability. The above characteristics are obtained by blending polyvinyl alcohol with an aqueous acrylic resin and / or vinyl acetate resin emulsion and using a liquid containing water as a medium.

This thermoplastic resin liquid dissolves 5 to 20% of polyvinyl alcohol using water as a medium, and to the polyvinyl alcohol, an aqueous acrylic resin such as hydroxyalkyl (meth) acrylate, polypropylene glycol methacrylate, The polyethylene glycol monomethacrylate and / or vinyl acetate resin emulsion is prepared by dissolving or dispersing 5 to 30% by itself or in combination. Although water is used as the medium, it is also possible to add alcohols, acetone, and other mediums having an affinity for water and the resin to be blended to the water.

Aqueous acrylic resin and / or vinyl acetate resin emulsion is added to polyvinyl alcohol in an amount of 5 to 3
By adding 0%, it is possible to easily release from the molding die and adhere to the molded article with an adhesive force capable of forced peeling.

When the amount of the water-based acrylic resin and / or vinyl acetate resin emulsion added is 5% or less, the adhesiveness to the molded product decreases, and when it exceeds 30%, the drying property of the film, the toughness, and the molded product are deteriorated. Peelability is reduced.

Further, by adding an inorganic powder such as silica, alumina or calcium carbonate to the above thermoplastic resin liquid, the glossiness of the surface of the molded product can be arbitrarily changed without changing the glossiness of the mold surface. It is possible to obtain molded articles of various glossiness with the same mold. By adding the inorganic powder additive in the range of 0 to 30% with respect to the thermoplastic resin, it is possible to obtain a finished surface having various glossiness from gloss finish to semi-gloss to matte finish. I can.

Prior to the application of the thermoplastic resin, a mold release agent is applied to the molding die surface. As the release agent, a silicone resin type, a fluororesin type, a wax type, etc. are used, and particularly, the wax type is preferable because it is less repulsive in applying the thermoplastic resin liquid.

Next, the surface of the mold is coated with the thermoplastic resin liquid by a brush, uniformly applied using a small-diameter sifon type spray gun, and dried at room temperature or by heating to form a film. The thermoplastic resin film is formed at least on the front side where the design and appearance of the molded product are important.

The mold may be either a hermetic mold or an open mold. After the thermoplastic resin film is formed, the mold is assembled as necessary and the thermosetting resin composition is used. Pour a slurry into the mold, room temperature to 50 ℃
It is cured at the following temperatures.

In the cast molding method of the present invention, it is not necessary to perform gel coating on the mold surface, and even if the mold is directly cast, bubbles,
A surface finish without gloss can be obtained.

The cast material is hardened to the extent that it can maintain the hardness and strength that can be handled, but is removed from the mold when it is not completely hardened. As a result, shrinkage is less than that of a completely cured product, and even a complicated shape can be demolded relatively easily. In addition, since it is cured at normal temperature to low temperature, the mold has little distortion and deformation due to heat. Further, the cycle of the mold becomes faster, and the productivity is improved. The proper degree of curing of the cast material at the time of demolding can be grasped based on the separately measured curing characteristic data.

Since the molded thermosetting resin composition is cured by contacting with the thermoplastic synthetic resin film formed on the mold surface, the surface of the molded product is finished in the same condition as the surface state of this film. In particular, the polyvinyl alcohol aqueous solution provides a good result because it forms a tough and smooth film on the mold surface. The film and the molded product are demolded in a state of being in close contact with each other, heated in a heating furnace to 60 ° C. to 100 ° C., and further subjected to aftercure until a practically sufficient performance is obtained.

When the after cure temperature is 60 ° C. or lower, it takes a long time to obtain the required physical properties of the molded product,
Productivity and quality are likely to deteriorate. When the after-cure is performed at a temperature of 100 ° C. or higher, the thermoplastic film is dehydrated and becomes brittle, and it becomes difficult to forcibly peel it off.

Since the molded product is heated in a state where the thermoplastic resin film is in close contact with the molded product, deaeration of volatile substances such as unreacted styrene monomer contained in the vicinity of the surface of the molded product,
This thermoplastic resin film blocks the occurrence of pinholes and uneven glossiness, and improves the stain resistance.

By forcibly peeling off the thermoplastic resin film adhered to the surface of the molded article that has undergone after-cure, an artificial marble molded article having excellent surface properties and appearance can be obtained. Incidentally, the state in which the thermoplastic resin film is adhered has a protective effect against the generation of scratches during handling.

[0034]

【Example】

Example 1 An example of the present invention will be described below with reference to the drawings.
Figure 1 shows the inside surface of the sink of a sink in a domestic sink,
That is, it is a cross-sectional view showing a state where a thermoplastic resin film is formed on the surface of the molding die (lower die) 11 on the side that becomes a visible portion when assembled. The molding die (lower die) 11 is made of FRP of glass fiber and unsaturated polyester resin, combined with the upper die, and used as a closed die.

As the thermoplastic resin film 2, a polyvinyl alcohol-based film which can be released from the mold and the molded product and has good adhesion to the moldable product is formed on the mold surface.

Prior to the formation of this film, a carnauba wax release agent is applied and thinly and uniformly applied while being wiped with a cloth.

Next, polyvinyl alcohol is added at a concentration of 20.
%, Dissolved in 90 ° C. hot water, 15% polyethylene glycol monomethacrylate is added to polyvinyl alcohol, stirred and uniformly dispersed to obtain a coating liquid.

A lower mold 1 of the molding die was used to spray the coating solution with a suction type spray gun having a coating nozzle diameter of 0.8 mm at a spraying pressure of 2 kgf / cm ^{2 so} that the thickness of the film after drying was about 30 μm.
1 is evenly applied, and hot air at 80 ° C. is applied to dry it for 30 minutes to form a polyvinyl alcohol film which is a thermoplastic resin film 2 having high smoothness.

This lower mold 11 and the upper mold 1 coated with a release agent
After combining the two, inject the thermosetting resin composition into the mold,
It is cured to obtain a molded product. FIG. 2 is a cross-sectional view showing a cast state, and the molded product 3 a is hardened in the molding die 1.

The thermosetting resin composition comprises 6 parts of a melamine (meth) acrylate prepolymer obtained by condensing melamine, paraformaldehyde and 2-hydroxyethyl (meth) acrylate, fumaric acid, phthalic anhydride,
24 parts of unsaturated polyester consisting of 50% styrene monomer solution of polyester obtained by condensing isophthalic acid and propylene glycol, aluminum hydroxide powder 40
Parts, silicic acid anhydride powder 20 parts, calcium carbonate powder 10 parts, dibutyl phthalate 50% solution of a curing agent methyl ethyl ketone peroxide 0.4 parts, and cobalt naphthenate 6% styrene monomer solution 0.2 parts as a curing accelerator. In addition, the internal pressure is Hg 100 mm
It is a uniform slurry-like material obtained by stirring for 30 minutes while depressurizing and degassing.

After casting, it is left at room temperature of 30 ° C. for 3 hours to cure. The molded product 3a being cured is the thermoplastic resin film 2
Curing progresses in contact with the polyvinyl alcohol film which is
While the surface is formed, it adheres with moderate strength.

The cast molding 3a is hardened and can be demolded, and has reached the hardness and strength that does not hinder the handling work, but is demolded at a stage where it is not completely hardened and is thermoplastic. A semi-cured molded product 3b with the resin film 2 adhered thereto is obtained.

This semi-cured molded product 3b is heated in a heating and curing room at a temperature of 80 ° C. for 2 hours to perform after-cure to remove the polyvinyl alcohol film, and the resin is a sufficiently hardened molded product 3c for an artificial marble sink. Got a sink. The sink had a uniform gloss, had no pinholes, and had a good gloss finish.

Example 2 A mold release agent containing dammer wax as a main component was applied to the lower surface of a mold for a sink vanity sink made of FRP, and polyvinyl alcohol containing inorganic powder was applied to the surface of the mold. The aqueous solution was applied and dried to form a film. still,
The composition of the polyvinyl alcohol aqueous solution and the coating conditions are as follows.

After being dissolved in warm water at 90 ° C. so that the polyvinyl alcohol concentration becomes 15%, a vinyl acetate resin emulsion is added so that the nonvolatile content becomes 10% with respect to the solid content of polyvinyl alcohol. 6% of silica powder having an average particle diameter of 3.5 μm was added, well stirred and uniformly dispersed to obtain a coating liquid.

This coating solution was sprayed at a spraying pressure of 3 kgf / cm ² using a suction type spray gun having a paint nozzle diameter of 1.0 mm.
The dried film was evenly applied to the lower mold of the mold so that the film had a thickness of 25 μm, and was dried by applying warm air at 90 ° C. for 20 minutes to form a polyvinyl alcohol film having a matte surface.

Next, this lower mold was combined with the upper mold, and 30 parts of an unsaturated polyester resin consisting of a 50% styrene monomer solution of a polyester obtained by condensing isophthalic acid, phthalic anhydride, fumaric acid, and propylene glycol was used. 30 parts of aluminum hydroxide powder, 20 parts of calcium carbonate powder,
10 parts of particles having an average particle diameter of 2 mm obtained by pulverizing a cured product of an unsaturated polyester resin colored with carbon black and 1 part of titanium oxide are mixed, and further, a curing agent methyl ethyl ketone peroxide 55% dibutyl phthalate 55% solution 0. 4 parts and 0.2 part of a styrene monomer solution containing 6% cobalt naphthenate as a curing accelerator are added and stirred to form a uniform slurry.

This slurry was poured into a mold to obtain 70
After being left to cure at a temperature of ℃ for 2.5 hours, it is demolded, placed in a heating chamber at a temperature of 80 ℃ and subjected to aftercure for 3 hours to remove the polyvinyl alcohol film adhered to the surface of the molded product. It was peeled off to obtain a sink for artificial vanity made of artificial marble with a stone pattern. This sink has a uniform matte finish, giving it a dull appearance, according to JIS A4401.
It had the quality specified in.

[0049]

EFFECT OF THE INVENTION Since the thermoplastic resin film adheres to the surface of the molded product and forms a barrier layer, pinholes and gloss unevenness due to volatilization of unreacted styrene monomer are eliminated, and a beautiful finish is obtained. , Stain resistance is improved.

Since the gel coat is not required, the production can be performed without the skill required for forming the gel coat, the process can be shortened, and the material can be saved.

Due to the protective action of the thermoplastic resin film, even if the molded product is released from the mold before it is completely cured, scratches are unlikely to occur during handling. Also, since the mold is removed before the curing is completed,
Mold cycle is faster and productivity is higher.

Since the surface of the molded product is finished in contact with the surface of the thermoplastic resin film, the uniformity of gloss is improved. Also, by adding an inorganic powder to the thermoplastic resin, the same mold can be used without changing the glossiness of the mold surface.
Molded products with different gloss can be made. Depending on the particle size and the amount of the inorganic powder to be added, it is possible to easily obtain a molded article having a desired gloss level from glossy finish to semi-glossy to matte finish.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a molding die on which a thermoplastic resin film of the present invention is formed.

FIG. 2 is a sectional view showing a state where a thermosetting resin is cast.

FIG. 3 is a cross-sectional view of a molded product having a thermoplastic resin film adhered thereto after releasing from the mold.

FIG. 4 is a cross-sectional view of a molded product from which a thermoplastic resin film has been peeled off after aftercure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Thermoplastic resin film 3a Molded product 3b Semi-cured product 3c Fully cured product 11 Mold (lower mold) 12 Mold (upper mold)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display area B29L 31:10 4F (72) Inventor Yusuke Misawa Osamu, Kamezu-cho, Kaifu-gun, Aichi Prefecture Kagamizu character Fukami 24 Address Aika Kogyo Co., Ltd. (72) Inventor Mineo Hayakawa 2288 Nishihorie, Shinkawa-cho, Nishikasugai-gun, Aichi Address Aika Kogyo Co., Ltd.

Claims (4)

[Claims] 1. In the step of injecting a radical polymerization type thermosetting resin composition into a molding die and curing the composition to obtain an artificial marble molded article, the composition has releasability from the molding die and the molded article. And an artificial marble characterized by forming a thermoplastic resin film on the mold surface, which has a better releasability to the mold surface than to the molded product surface, and then casting the thermosetting resin composition. Manufacturing method of molded products. 2. The thermoplastic resin film formed on the mold surface,
The method for producing an artificial marble molded article according to claim 1, which comprises polyvinyl alcohol and an aqueous acrylic resin and / or vinyl acetate resin emulsion. 3. The thermoplastic resin film is peeled off after the cast thermosetting resin composition is cured to a state that does not hinder the handling work and released from the mold, and then heated and cured. Item 1. A method for producing an artificial marble molded article according to item 1 or 2. 4. The inorganic powder is contained in an amount of 0 to 30% by weight relative to the resin of the thermoplastic resin film formed on the mold surface, according to any one of claims 1 to 3. Manufacture of artificial marble moldings.