KR950001986B1 - Preparation method of artificial marble - Google Patents

Abstract

None.

Description

Manufacturing method of epoxy artificial marble

1 is a schematic view of the washbasin produced by the present invention.

2 is a cross-sectional view of the mold used in the present invention.

The present invention relates to a method for producing an epoxy artificial marble molded article.

Industrial Applicability The present invention can produce a large molded article, which has been impossible with the conventional molding method of a resin composition, with good productivity.

Artificial marble molded products made of plastic can express various colors to meet the needs of consumers, but in order to be used in molded products such as washbasins, sinks, bathtubs, etc., they must be hard and have high heat resistance, and the appearance of the beautiful surface, wear resistance and impact strength must be high. Can be used.

In addition, the chemical resistance must be high enough to maintain durability in household detergents or chemicals used at home.

Conventionally, artificial marble molded articles prepared on the basis of unsaturated polyesters or acrylics have a large shrinkage rate, which makes the process complicated and does not have high physical properties. In order to prepare artificial marble, natural marble powder is cured by mixing natural polyester powder with unsaturated polyester resin (cf. Korean Patent Publication No. 68-264), or cured by mixing aluminum hydroxide (cf. Japanese Patent Publication No. 84-11968 No.), inorganic powders such as calcium carbonate, talc and the like were mixed and cured to prepare a plate-like artificial marble. Unsaturated polyester, however, had a large shrinkage during curing and was weak in impact, so that the molding process was not simple, such as using glass fiber as a reinforcing agent.

In addition, acrylic resins are also used a lot, but even if a large amount of minerals are filled, the shrinkage rate is large. Therefore, a complicated process is required to reduce this. In addition, it takes a long time for molding until demolding. Is low.

However, epoxy resins have a small shrinkage rate and a short molding time, but are expensive and poor in formability compared to other resins, and thus have a lot of difficulties in manufacturing large molded articles. Thus, acrylic resins have been mainly used until now.

British Patent No. 1,323,343, developed by Ciba-Geigy, relates to a method for producing thick molded articles by gelling and curing inorganic filled epoxy resins with a mold. The patent used a method of supplying additional compositions under pressure after molding the resin composition to prevent shrinkage, which should have at least one portion of at least 4 cm in diameter. The products obtained by this method were mainly used as electrical insulators.

Therefore, a relatively thick molded article is manufactured by the methods known to date, and these methods have a disadvantage in that productivity is reduced due to a complicated manufacturing process and a post-process.

Accordingly, an object of the present invention is to provide a method for producing an epoxy-based artificial marble molded article excellent in heat resistance, fouling resistance and surface hardness, and particularly thin in the final molded article.

The epoxy resin used in the present invention is a known epoxy resin compound having two or more active epoxy groups in a molecule, for example, a cyclic form such as diglycidyl ether or cyclohexene derivative derived from bisphenol-A or bisphenol-F. Known such as diepoxy compounds of olefin compounds, diglycidyl ethers of polyphenols or polyhydroxyphenols, diglycidyl ethers of aromatic oxycarboxylic acids or aromatic dicarboxylic acids or diglycidyl esters Conventional epoxy resins produced by industrial production processes and mixtures of two or more thereof.

As the curing agent, methylhexahydrophthalic anhydride which is liquid at room temperature, maleic anhydride of metacyclopentadiene, methyltetraphthalic anhydride and mixtures thereof can be used.

Although a curing catalyst can also be used, an imidazole compound can be used as a curing catalyst, For example, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1- Vinyl-2-hydroxyethylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-hydroxyethyl-2-methylimidazole and the like.

In the present invention, inorganic fillers are used for the purpose of lowering the coefficient of thermal expansion, reducing heat generation during curing, improving mechanical properties, and the like. The inorganic fillers that can be used include crystalline silica, fused silica, talc, calcium carbonate, miter, alumina, and hydroxide. Aluminum, kaolin and the like.

The present invention relates to a method for producing a large molded article having a thin thickness by defoaming while preheating the curable epoxy resin composition in 60 minutes and injecting at a pressure of at least 300 g / cm ² in a mold higher than the temperature of the composition.

When the epoxy composition is injected into the mold, the gas in the mold is discharged, and no gas enters again while the composition is cured, and the composition compensates for the curing shrinkage by maintaining the injection pressure. At this time, the temperature gradient of the composition is adjusted to be kept constant, about 12 ℃ is preferred. The template preheats at least 10 ° C. above the temperature of the composition when the preheated epoxy composition is injected. The composition is cured faster as the mold and the temperature of the composition is higher, but shrinks relatively large, and when the temperature is low, the viscosity is low, making it difficult to supply uniform raw materials and slowing down the curing speed.

The mold can be installed horizontally or vertically, and the input by the injected composition depends on the shape of the product. Since the composition to be injected into the mold is injected from the bottom of the mold, the injection pressure must be greater than these and the mold holding pressure must be greater than the injection pressure.

The injection pressure should consider both injection time, mold holding pressure and molding time.

For example, in the case of manufacturing a washbasin, injection into the mold at a pressure of 700 g / cm ² takes 4 minutes for injection and curing takes about 20 minutes at 150 ° C. Even if the molded product is not completely cured, only the gelation is performed, so that the molded product can be demoulded and the maximum physical properties of the epoxy can be obtained by post curing.

For this purpose, anhydride curing agents are suitable, and post-curing is preferably carried out at 120 to 140 ° C. for 2 to 8 hours.

In addition, in order to increase the surface hardness and abrasion, silica, alumina, and the like are suitable, and may be mixed or used alone depending on the color, and to increase the whiteness, titanium dioxide may be added in an amount of 0.1 to 3% by weight of other fillers. In addition, the filler may not stain the product when the particles are settled or the density distribution is different, so that the suspension is evenly dispersed to prevent the settling.

Staining or discoloration (especially yellowing) can be prevented by keeping the injection time of the composition as short as possible and controlling the temperature used for injection and curing. It is preferable to proceed with curing after being sufficiently cured in the mold as much as possible.

Epoxy resin composition is maintained at 50 to 70 ℃, avoiding maintenance for more than 24 hours because the viscosity is increased, the mold can be used up to 80 to 180 ℃ but considering the workability and productivity is suitable 120 to 160 ℃.

The mold depends on the molded part because it must be able to precisely control the temperature, but it is relatively accurate to measure and heat in many places, it is preferable to use a dry heating cartridge.

Referring to the drawings, in FIG. 2, (1) is a position where the epoxy resin composition is injected, and the mold is installed vertically with this portion down. (2) represents a cartridge heating rod, and (3) collects the gas which comes out when filling the mold of a composition.

Epoxy resins have strong adhesion to metals, so care must be taken when releasing them. It is better to use a silicone release agent, and before applying the release agent to the inner surface of the mold, it is necessary to cleanly remove those that may occur in the previous molding, so that the surface is clean and there is no difficulty in release.

The epoxy resin composition so minerals is high is charged at room temperature, due to high viscosity injection it is difficult, insert the curing agent heated under degassing for about 30 minutes in a vacuum, and under pressure, of the temperature and 700g / cm ² to approximately 60 ℃ second FIG. As shown in Fig. 1, injection is performed through the runner of (1).

The mold is then preheated so that the temperature gradient from the runner to the top of the runner increases uniformly within 12 ° C. The injection takes 4 minutes and the mold is kept at 160 ° C and it takes about 15 minutes to cure and reach a stable state.

At this time, it is important to maintain the injection pressure. Otherwise, shrinkage may occur and wrinkles may appear on the surface, or in severe cases, the molded article may crack.

In addition, if the curing time and temperature is short, the uncured portion is relatively weak, which may cause the product to break when demolding. When the epoxy composition is injected into the mold, air or gases are collected in (3). The front part of (3) is thinly designed to accelerate the temperature rise by heat transfer from the mold, and to cure gas faster than other parts of the molding. It should be blocked.

Since the mold needs precise temperature control when heating, it is necessary to install heating rods (2) to facilitate heating and temperature control so as to prevent overheating and supercooling while maintaining the required temperature gradient. At this time, the female frame and the frame maintain the temperature differently. In other words, the frame is the front part of the product to be noticeable to humans, so the surface condition should be excellent and therefore about 10 ℃ higher than the female frame.

When demolding the molded article, the runner and the part of (3), in particular, the passage leading to (3) should be cleanly cleaned, and the demolded molded article needs heat treatment. Heat treatment for complete curing is carried out in an oven at 130 ℃ for 2 hours to reduce this time, if you want to add a curing accelerator when mixing the curing agent.

There is almost no discoloration due to oxidation during heat treatment, but it is preferable to put nitrogen in a heating oven to prevent color change. The reason for the color change is that the residence time in the mold was short and the mold was demolded at too low a degree of curing.

Epoxy-based artificial marble molded article manufactured according to the present invention is not contaminated by household detergents, chemicals or food in addition to the heat resistance temperature of 200 ℃ or more and has a high surface hardness. In addition, when the impact strength is high, when forming a large molded article, for example, a sink, a wash basin, a bath, etc., it is possible to sufficiently make a solid product of the same volume in an amount of 1/2 to 2/3 of unsaturated polyester or acrylic type. In addition, the product is excellent in color and texture.

Hereinafter, the present invention will be described in more detail with reference to Examples, and the present invention is not limited thereto.

Example 1

The epoxy composition which added 2 weight part of red pigments (for example, Araldite DW-0133 of Ciba-Geigy Age) is injected at 60 degreeC by the pressure of 1,000 g / cm <^2> .

In this case, the mold is injected at 150 ° C. and the frame is preheated at 160 ° C. and demolded 25 minutes after the injection. In order to prevent deformation after demolding, it is completely cured by installing in a jig for 3 hours at 125 ° C.

Example 2

The epoxy composition is injected at 70 ° C., at a pressure of 1,200 g / cm ² , while the female frame is injected at 145 ° C. and the frame is preheated to 155 ° C. and demolded 30 minutes after the injection. After demolding, the jig was installed at 130 ° C. for 2 hours, heat treated in an oven, and demolded.

Claims (9)

The curing agent is added to the epoxy composition, which can be cured in a preheated mold in 60 minutes, degassed while mixing, injecting pressure into the mold, and the pressure is maintained during the curing, and the composition in the mold has a constant temperature gradient from the inlet to the top of the mold. Method of producing an artificial marble characterized in that it has a. The method of claim 1, wherein the temperature gradient of the molding is maintained at about 10 ° C. and the temperature of the molding at injection is maintained at 40-100 ° C. 7. The method of claim 1 wherein the passage before the place where the gas is evacuated and the gas is collected when the composition is injected is thinned. The method of claim 3 wherein the composition is injected from below and the injection pressure is at least 400 g / cm ² . The method of claim 1, wherein the temperature of the frame is maintained about 10 ° C. higher than the temperature of the female frame to allow for easy release from the frame. The method of claim 1, wherein at least four heating zones are provided to control the heating of the mold well. The method of claim 1 comprising bisphenol A resin of the epoxy composition and wherein an anhydride curing agent is used in admixture. 8. The method of claim 7, wherein the composition contains at least 50% by weight inorganic filler. The method of claim 1 wherein the resin composition is injected under a pressure of 400 to 2,400 g / cm ² and the mold is preheated to 120 to 180 ° C. 7.