JPH06157104A - Grained artificial marble - Google Patents

Abstract

PURPOSE:To obtain a natural stone-like grained artificial marble having a masking transparency look by mixing an acrylic resin, powdery inorg. filler, transparent frit powder and plasticizer in a specified ratio to obtain a forming material. CONSTITUTION:20-50 pts.wt. matrix resin powder (acrylic resin) and 80-50 pts.wt a powdery inorg. filler (aluminum hydroxide powder) are mixed. Meanwhile, the raw materials such as feldspar, quartzite and borax are melted, solidified and crushed to prepare a transparent frit powder having 1.48-1.6 refractive index. Further, 100 pts.wt. of the mixed powder, 0.1-10 pts.wt. of the frit powder and a small amt. of a liq. plasticizer (e.g. phthalic ester and trimellitic ester) are uniformly mixed to obtain the forming material, which is extruded and heat-treated to obtain the marble.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stone-grained artificial marble used as a building material, a vanity, a top plate of a system kitchen, or the like.

[0002]

2. Description of the Related Art A conventional artificial marble is composed of, for example, a mixture obtained by uniformly mixing an inorganic filler with an acrylic resin as a matrix resin as a molding material, and the molding material is subjected to a casting method or solidification extrusion molding. It was formed by. Further, for the purpose of imparting a stone-like appearance similar to natural stone to such artificial marble, in the molding material, fine crushed stone particles of natural stone, metal flakes, and colored resin particles having heat resistance, In some cases, heat-resistant colored synthetic resin fibers or the like are contained so as to be uniformly dispersed, and the content of these materials causes the appearance of a stone-like appearance.

[0003]

However, the conventional stone-grained artificial marble has a slightly different taste from the appearance of natural stone, and has the impression that it is an imitation product.
In other words, the natural marble stone tone has a transparency with a proper concealing property, and also has a deep shade pattern and scattered radiance, whereas the conventional artificial marble stone. Regarding the tone, there was a problem that the above-mentioned peculiar transparency, dark and light patterns, brilliance, etc. peculiar to natural stone were subtly different, and the natural feeling was poor.

An object of the present invention is to solve the above problems of the prior art and to provide a stone-grained artificial marble that exhibits a natural stone-like stone tone and is full of natural feeling.

[0005]

[Means for Solving the Problems] The inventors of the present invention have conducted various experiments and researches under the above-mentioned problems. As a result, in addition to the matrix resin and the inorganic filler, the inventors have specified that the stone tone is expressed. The present invention has been completed by discovering that natural stone-like stone tone can be expressed by adding materials.

That is, the present invention is a stone-grained artificial marble formed by extrusion molding, in which a matrix resin containing methacrylic resin powder as a main component, aluminum hydroxide powder as a powdery inorganic filler, and feldspar. , Silica stone,
A mixture of a transparent frit powder having a refractive index of 1.48 to 1.60 obtained by melting, solidifying, and crushing a raw material such as borax and a small amount of a liquid plasticizer, as a molding material. It is configured.

Further, in the molding material, when the total amount of the powder mixture of the matrix resin powder and the aluminum hydroxide powder is 100 parts by weight, 100
20 to 50 parts by weight of the matrix resin powder
By weight, the aluminum hydroxide powder is set in the range of 80 to 50 parts by weight, and 0.1 to 10 parts by weight of the frit powder is mixed with 100 parts by weight of the powder mixture.

Particularly in the present invention, it is preferable to set the average particle diameter of the frit powder to 3.0 mm or less.

Next, each component of the molding material used in the present invention, the compounding thereof, and the extrusion molding method for carrying out the present invention will be described in detail.

<Matrix Resin> In the present invention, an acrylic resin is used as the matrix resin because it is excellent in various properties such as transparency, weather resistance, hardness and heat resistance.

Examples of the acrylic resin include general-purpose acrylic resins such as thermoplastic acrylic resins having different monomer compositions and thermoplastic methacrylic resins. In particular, in the present invention, a homopolymer of methyl methacrylate or methyl methacrylate is 5
A copolymer obtained by copolymerizing at least 0% by weight, preferably at least 70% by weight, with other methacrylic acid ester and at least one vinyl monomer copolymerizable with methyl methacrylate is suitable. .

Among the acrylic resins, carboxyl group-containing methacrylic resin, glutarimide group-containing methacrylic resin and the like can improve the heat resistance of the molded product and are preferably used as a molding material.

Here, the carboxyl group-containing methacrylic resin is a copolymer of methyl methacrylate (MMA) and an ethylenically unsaturated carboxylic acid. A typical example of the ethylenically unsaturated carboxylic acid is acrylic acid. , Methacrylic acid, and others, itaconic acid, maleic acid,
Maleic anhydride etc. can be mentioned. The ethylenically unsaturated carboxylic acid is usually 1 to 1 in the matrix resin.
Copolymerized in the range of 5%, preferably 3 to 7% is used. If it is less than 1%, the desired adhesiveness between the matrix resin and the inorganic filler cannot be obtained, and the heat resistance is poor.
On the other hand, if it exceeds 15%, the fluidity of the molding material decreases, and extrusion molding becomes difficult. Further, for the purpose of improving heat resistance, a vinyl aromatic compound copolymerizable with methyl methacrylate may be copolymerized with this polymer in an amount of 5% or less. Examples of this vinyl aromatic compound include styrene, vinyltoluene, α-methylstyrene and the like.

The glutarimide group-containing methacrylic resin means that methyl methacrylate (MMA) is heated and melted,
It is a copolymer that can be obtained by mixing and reacting an imidizing agent. Examples of the imidizing agent include ammonia, methylamine, ethylamine, butylamine, hexylamine, octylamine, nolylamine, decylamine, benzylamine, cyclohexylamine, aniline, halogenated aniline, urea and dimethylurea.

The glutarimide unit in the glutarimide group-containing methacrylic resin is represented by the following chemical formula 1.

[0016]

[Chemical 1] Here, R1 and R2 represent a hydrogen atom or a methyl group, and R3 represents a hydrogen atom or an aliphatic, aromatic or alicyclic hydrocarbon having 1 to 20 carbon atoms. Among these, those in which R3 is hydrogen or a methyl group are particularly excellent in heat resistance.

The glutarimide unit must be contained in the glutarimide group-containing methacrylic resin in an amount of 5 to 100 mol%, preferably 20 mol% or more. If the glutarimide unit content is less than 5 mol%, thermal cracking and thermal deformation are likely to occur in the molded product, resulting in insufficient heat resistance.

The above-mentioned general-purpose acrylic resin, carboxyl group-containing methacrylic resin, glutarimide group-containing methacrylic resin, etc. do not necessarily have to constitute the matrix resin by themselves, and it is possible to form a matrix resin by mixing two or more kinds. Absent.

For example, a carboxyl group-containing methacrylic resin and a general-purpose acrylic resin such as methyl methacrylate may be used in combination to form a matrix resin. In this case, the general-purpose acrylic resin is added in an ethylenic amount. Unsaturated carboxylic acid is 1 to 15% of the matrix resin
It is desirable to add it within the range. When a glutarimide group-containing methacrylic resin and a general-purpose acrylic resin are used together, the compounding ratio of the glutarimide group-containing methacrylic resin and the general-purpose acrylic resin is 100: 0 to 10:90.
Is desirable, and particularly 100: 0 to 50 to 50: 5
It is preferably 0. Within this range, the heat resistance of the molded product can be improved.

As the matrix resin, a powdered one is used, and its particle size is not particularly limited,
Generally from 5 to 200 μm, particularly preferably from 20 to 100 μm
Those having a size of about m are preferably used.

Further, the matrix resin has a melt flow rate (MFR, 230 ° C., 3.8 k) in order to carry out the melt-kneading operation in the extruder at the time of extrusion molding without hindrance.
g) (test method / unit; ASTM D 1238) is 0.
It is preferably 5 g / 10 min or more, particularly 1.0 g / 10 min or more. Furthermore, the weight average molecular weight Mw is 80,
000 or more and less than 300,000, particularly 90,000
Above, those less than 170,000 are preferable. In this case, for example, the melt flow rate (MFR) is 0.5 g /
If it is less than 10 min or the average molecular weight Mw exceeds 300,000, the melt viscosity is increased and the fluidity is lowered during kneading with the filler in the extruder, and accordingly, a power load more than the capability of the extruder is generated, Operation may be stopped unintentionally, or problems such as resin leakage and screw damage may occur, making smooth extrusion molding difficult. Further, when a matrix resin having a weight average molecular weight Mw of less than 80,000 is used, the heat resistance is lowered, so that when a hot pot is placed on the molded product or an ignited cigarette is accidentally dropped, the surface is There is a risk of being damaged.

<Powdered inorganic filler> As the powdered inorganic filler, it is particularly necessary to use aluminum hydroxide powder as a main material. This aluminum hydroxide powder is
The average particle size is 1 μm or more and the specific surface area is 6 m ^2.
/ G or less is preferably used, and it is more preferable to use a particle having a substantially spherical shape.

If the average particle size is 1 μm or less, the sheet may have too high a hiding property and the texture of the artificial marble may be poor. Further, if the specific surface area exceeds 6 m ² / g and becomes too large, the hiding property also becomes too high due to fine bubbles at the interface between the aluminum hydroxide and the matrix resin. Furthermore, the increase in the specific surface area facilitates the adsorption of pollutant properties, which causes a problem in the stain resistance of the artificial marble.

By using an aluminum hydroxide powder satisfying the above requirements as a filler, continuous molding by extrusion of an artificial marble having a good appearance can be carried out without any trouble.
The hardness of aluminum hydroxide is relatively low at Mohs hardness of 2.5, the particle size is large and the specific surface area is small, the refractive index is close to that of the matrix resin, and the leakage property to the matrix resin is poor. Are believed to be interrelated and work effectively together.

<Frit Powder> In the present invention, the frit powder is mixed in the molding material in order to give the molded product a natural stone-like grain tone.

The term "frit" as used herein means that raw materials obtained by crushing feldspar, silica stone, borax, etc. are once melted into glass form at high temperature in a heating furnace such as a continuous furnace, tank furnace, etc. It is a formulation that is solidified by quenching, and this formulation is ground into powder and used as a frit powder. A typical example of such frit powder is XM-1099N (49 μm) manufactured by Nippon Frit Co., Ltd.

The average particle size of the frit powder is preferably set to 3.0 mm or less, particularly 5 to 100 μm. In this case, when the average particle size exceeds 3.0 mm, the dispersion rate of the frit powder in the molding material decreases, unevenness in the stone tone occurs, and the workability during extrusion molding deteriorates. The surface smoothness of the product may deteriorate.

In the present invention, the frit powder is
It is as transparent as glass, and has a refractive index in a relatively wide range, that is, in the range of 1.48 to 1.60. The refractive index of the frit powder can be set to a desired refractive index within the above range by appropriately changing the constituent components of the frit. When a frit powder having a refractive index similar to that of the matrix resin is used, a deep and transparent stone tone can be expressed in the molded product. On the contrary, when frit powder having a refractive index far from the refractive index of the matrix resin is used, it is appropriately concealed and a stone tone having a different taste can be expressed.

If necessary, the frit powder may be surface-treated with a silane coupling agent in advance, or may be further colored. By blending the frit powder colored in various colors in this way, it becomes possible to express a rich stone tone.

<Plasticizer> The addition of a plasticizer is useful for reducing the melt viscosity of the matrix resin by its original function as a plasticizer and improving the moldability, and is compatible with the matrix resin. It is necessary to be a liquid plasticizer showing. In other words, with a plasticizer that is not compatible with the matrix resin, bleeding and microcracks are likely to occur in the molded product even if the molding material containing it is extrudable, making it practically durable. Inferior in sex. Further, the liquidity of the plasticizer is necessary in order to wet the matrix resin powder at the time of kneading and adhere the aluminum hydroxide powder to the matrix resin powder to facilitate obtaining a uniform mixture.

The transparency of the plasticizer is less of an issue when trying to produce colored moldings. However, in the case of obtaining a white pure artificial marble, it is not preferable to use a plasticizer having a transparency of APHA of more than 100 because the molded product may become yellowed or cause other harmful coloring. Therefore, in this case, it is necessary to use a plasticizer having a transparency of APHA of 100 or less, particularly preferably 50 or less.

Other types of plasticizers are not particularly limited. Examples of usable plasticizers include phthalic acid ester-based DMP, DOP and DBP, and fatty acid (dibasic) ester-based DIOA and DB.
S, DOS and the like, and TOTM and the like can be listed as a trimellitic acid ester type.

<Compounding> The mixing ratio of the molding material is based on the total amount of the powder mixture of the matrix resin powder and the aluminum hydroxide powder, and the total amount is 100 parts by weight. 2 powder
0-50 parts by weight, 80-50 aluminum hydroxide powder
It should be in the range of parts by weight. If the blending ratio of the matrix resin powder is less than 20 parts by weight, and thus the blending amount of aluminum hydroxide exceeds 80 parts by weight, the matrix resin will not be uniformly dispersed in the aluminum hydroxide powder,
As a result, melt softening does not proceed sufficiently in the extruder and extrusion molding becomes difficult. On the other hand, when the blending amount of the matrix resin powder exceeds 50 parts by weight and the blending ratio of the aluminum hydroxide powder becomes less than 50 parts by weight, even if the extrusion molding operation is facilitated, the concealing property in the molded product is reduced. Insufficient and too transparent, the weight feeling similar to natural marble cannot be expressed, and heat resistance becomes insufficient. The most preferable mixing ratio is in the range of 25 to 40 parts by weight in the matrix resin powder.

The frit powder needs to be added in an amount of 0.1 to 10 parts by weight, particularly 0.5 to 10 parts by weight, based on 100 parts by weight of the powder mixture of the matrix resin powder and aluminum hydroxide powder. It is preferable to add 5 parts by weight. In this case, if the blending amount is less than 0.1 part by weight, a sufficient grain tone is not exhibited in the molded product, and conversely 1
If it exceeds 0 parts by weight, although the grain tone is expressed, the smoothness of the surface of the molded product is deteriorated and the workability during extrusion molding is also deteriorated.

The plasticizer is in the range of 0.5 to 5 parts by weight, particularly 1.0 part by weight, based on 100 parts by weight of the powder mixture of the matrix resin powder and aluminum hydroxide powder.
It is preferably added in the range of 3 to 3 parts by weight. In this case, if the addition amount is less than 0.5 part by weight, the desired addition effect cannot be obtained sufficiently. That is, the matrix resin cannot be sufficiently leaked, the aluminum hydroxide powder is secondarily aggregated, and coarse particles are segregated, so that a uniform mixture cannot be obtained. In addition, the role of plasticization efficiency is not fully exerted, the extrusion fluidity is not stable during extrusion molding, and it becomes difficult to perform uniform continuous extrusion molding for a long time. The distribution of the aluminum powder becomes non-uniform, and its agglomerates serve as nuclei, resulting in a defect that the strength becomes extremely inferior to the impact from the outside. On the other hand, when the compounding amount of the plasticizer exceeds 5 parts by weight, the heat resistance of the molded product may be significantly reduced even if a uniform mixture is obtained.

The molding material used in the present invention contains, in addition to the above essential components, a colorant to obtain a colored artificial marble, and a small amount of a higher fatty acid such as stearic acid or palmitic acid as a lubricant and its alkali. Naturally, addition of earth metal salts (calcium salt, magnesium salt, etc.), montanic acid wax, amides of higher fatty acids, etc. is allowed. If necessary, the aluminum hydroxide powder may be surface-treated with a fatty acid metal salt, a silane coupling agent, a titanate coupling agent, or the like in advance. Further, in order not to impair the effects of the present invention, a part of the aluminum hydroxide powder is replaced with another type of powdered inorganic filler to reduce the material cost and adjust the appearance of the molded product. Is also acceptable.

<Molding Method> In molding, first, the above-mentioned compounded materials are premixed. For this mixing operation, for example, using a Henschel mixer having a stirring blade, a ribbon blender, a V-type tumbler, etc., the matrix resin powder, the aluminum hydroxide powder, the frit powder, and the liquid plasticizer are added in the respective mixing ratios described above, This is done by mixing uniformly until there are no "powder" like agglomerates. It is not appropriate to use a dry blender or the like having no stirring blade as a mixer here because the "as-is" powder-like agglomerate does not disappear even after performing a mixing operation for a long time. Further, the order of feeding the blended materials to the mixer does not matter so much.

Then, the mixture obtained by the above premixing operation is used as a molding material, and this is solidified and extruded into a predetermined cross-sectional shape.

The extrusion molding apparatus used at the time of molding is
It is generally used to extrude polymeric materials into round bars, plate pipes, and other shaped products.It is necessary to extrude polymeric materials while they are being melted by an extruder, and then to use the molten polymeric materials in an extrusion die. According to the above, and cooling is performed while passing through a forming die attached to the tip of the die to solidify and mold it into a desired shape and size. The solidification extrusion method using such an apparatus can be suitably used for molding not only general resins but also materials having particularly high melt viscosity and poor fluidity, and materials having a high filler content. That is, since the molten material is solidified and extruded in the forming die, the pressure inside the die becomes extremely high. Therefore, it is possible to suppress the occurrence of voids and bubbles in the molded product, and obtain good quality. It has features.

Here, an example of a typical solidification extrusion molding apparatus is shown in FIG. As shown in the figure, (1) is the extruder body, (2) is its cylinder, (3) is the extrusion screw installed inside it, (4A) (4B) (4C) (4
D) is the first to fourth heating devices of the cylinder (2),
(5) is a material supply hopper, (6) is a drive unit, (7)
Is a squeezing portion at the tip of the cylinder (2), (8) is an extrusion die provided subsequently to it, (9) is a forming die with a water-cooling jacket (9a) further provided in front of it, and (10) is A device for retracting a molded body made of a rubber roll or a caterpillar, etc.
And a heating device for the extrusion die (8), (13) a measuring device for the resin pressure at the end of the cylinder, and (15) a heating device arranged subsequent to the take-up device (10).

On the inner surfaces of the extrusion die (8) and the forming die (9) which come into contact with the extruded material, there is provided a lubricant layer (14) for preventing sticking of the molding material.
This slip layer (14) makes it possible to carry out continuous extrusion molding for a long time while keeping the surface properties and the texture of the artificial marble constant and good. Attached lubricant layer (14)
Has a static or dynamic friction coefficient of 0.3 or less, preferably 0.
Below 15 and tensile strength is 50kgf / (10mm
Width) or more, preferably 100 kg · f / (10 mm width) or more, and such a material is attached to the entire inner surface of the extrusion die (8) and the forming die (9) by sticking or the like. ing.

When the friction coefficient of the attached lubricant layer (14) exceeds 0.3, the extrusion pressure of the molding material increases and it becomes impossible to maintain a predetermined pressure described later, which makes the actual molding operation difficult. . If the tensile strength of the lubricant layer (14) is less than 50 kgf / (10 mm width), the molding material is strongly rubbed during extrusion molding, so that the lubricant layer (14) is early. To be damaged. As a result, the lubrication effect disappears, the propulsive force decreases, and continuous molding operation becomes difficult.

As the constituent material of the lubricant layer (14), it is preferable to use a fluororesin having a low coefficient of friction as a lubricant, from the viewpoint of the friction coefficient. Particularly, among the fluororesins, tetrafluoroethylene resin is preferable. It is better to use.

Further, in order to impart the required tensile strength to such a resin, glass fiber, Kevlar fiber (du Pont)
Alternatively, a core layer made of a tensile fiber such as a metal fiber is laminated with the resin film or sheet having low friction,
It is preferable to use the composite material as a sliding material. However, the tensile strength may be increased by increasing the thickness of the low-friction resin film or sheet.

The heating device (15) is arranged close to the front of the forming die (9) in the extruder.
The heating device (15) includes a heating furnace body (16) that allows the molded body (A) sent from the forming die (9) to pass therethrough over 20 minutes, and a heating furnace body (1).
The transfer device (19) is composed of a large number of roller conveyors, while transferring from (6) the inlet side to the outlet side. Then, a large number of hot air blow-out holes (1
8), hot air is blown into the furnace,
It is kept in the range of 200 ° C. As a result, the entire surface of the molded body (A) passing through the inside of the heating furnace body (16) is uniformly heat-treated.

In this embodiment, an air bath type heating device using hot air is used, but a water bath type heating device using hot water may be used. However, since post-treatment work such as removal of water after the heat treatment is required, it is possible to reduce the post-treatment work by configuring the heating device by the air bath type rather than the water bath type.

In the extruder thus constructed, the premixed molding material is charged from the hopper (5) and melted and softened by heating in the cylinder (2) by the screw (3). Kneaded,
It is extruded into a predetermined shape from the extrusion die (8) through the narrowed portion (7). Subsequently, the extrudate extruded from the extrusion die (8) is cooled by a water-cooling jacket (9a) provided therein while passing through the forming die (9), shaped into a predetermined cross-sectional shape and solidified. (A) is formed.

Subsequently, the molded body (A) was heated by the heating device (1
It is sent to the heating furnace main body (16) of 5), heat-treated there for a predetermined time, and then gradually cooled at room temperature, whereby a stone-grained artificial marble is formed.

By the way, as described above, when aluminum hydroxide exceeds 180 ° C., it gradually decomposes and changes into water and alumina, and this water content is foamed by the usual extrusion molding method to give the appearance of the product. This will cause significant inhibition. On the other hand, by using the solidification extrusion method and molding under high pressure, it is possible to obtain an artificial marble of good quality without foaming even when aluminum hydroxide is used as the filler. In this case, the solidification extrusion method can be carried out smoothly, especially under the following conditions.

The first condition is the extrusion temperature. That is, the extrusion temperature is the cylinder (2) portion of the extruder body (1),
It is desirable to set the temperature in the range of 180 ° C. to 220 ° C., and preferably in the range of 190 ° C. to 210 ° C. in any part of the cylinder tip narrowing part (7) and the extrusion die (8) part. If the set temperature is less than 180 ° C., the melting and softening of the matrix resin does not proceed sufficiently, so that the back pressure of the extruder becomes too large and extrusion molding becomes difficult. On the other hand, when the set temperature exceeds 220 ° C., the decomposition of aluminum hydroxide is promoted, so that foaming cannot be suppressed even in the solidification extrusion method, which may significantly reduce the value of the product.

The second condition is the cooling temperature of the compact (A) by the forming die (9) with a cooling jacket. That is, the temperature of the molded body (A) at the outlet of the forming die (9) is 150 ° C. or lower, preferably 120 ° C.
It is better to perform sufficient cooling so that the temperature becomes as follows. When this cooling temperature exceeds 150 ° C., the artificial marble molded body extruded from the forming die with a cooling jacket (9) is in a softened state, and foaming and appearance defects such as blistering occur on its surface, and Shape is also difficult.

The third condition is that the lubricant layer (14) is formed on the inner surfaces of the extrusion die (8) and the forming die (9) as described above. When such a sliding treatment is not applied, artificial marble with a stable surface texture,
It becomes difficult to continuously mold for a long time.

As other conditions, the pressure of the extruded resin in the cylinder throttle portion (7) is 50 kg / cm ² to 50.
0 kg / cm ² , preferably 70 kg / cm ^{2 to} 350
It has to be operated in the range of kg / cm ² . If the resin pressure is less than 50 kg / cm ² , nest formation and foaming are likely to occur, and the quality of the product as artificial marble deteriorates. ^{On the other hand} , if it exceeds 500 kg / cm ² , there is a mechanical limit, and the extruder, the extrusion die and the forming die may be damaged.

On the other hand, the molded body (A) sent out from the forming die (9) often has a residual strain inside, and is particularly used under severe conditions where heating and cooling are repeated, such as a stove. When used as a top plate of a sink used near the heat source of No. 3, cracks may occur due to the influence of the internal strain.

In order to prevent such defects, the above-mentioned molded body (A) is introduced into the heating device (15) immediately after molding and heat-treated. In this case, the heat treatment condition is 80 to
It is desirable that the temperature is 200 ° C. and the time is 20 minutes or more.
It is preferably at 20 to 150 ° C. for about 30 to 60 minutes. If the heat treatment temperature is lower than 80 ° C, internal strain cannot be sufficiently removed. On the other hand, if the temperature exceeds 200 ° C., foaming, deformation, etc. may occur to deteriorate the appearance quality of the molded product. On the other hand, if the heating time is less than 20 minutes, the internal strain cannot be sufficiently removed.

The heat treatment time depends on the delivery speed of the molded body (A) delivered from the forming die (9),
That is, the heating furnace body (1
It is advantageous to determine by setting the effective effective length of 6).

By carrying out such a heat treatment, the dimensional change hardly occurs in the molded body (A) before and after the heat treatment, and the deformation of the molded product can be effectively prevented. On the other hand, for example, a molded body continuously molded by the solidification extrusion molding method is cut into a predetermined size to form a single rectangular plate, and when the rectangular plate is subjected to heat treatment in a batch type, the rectangular plate after heating is Compared to the square plate before heat treatment, the plate is
As the width and length shrink together, deformation also occurs.
Therefore, in order to obtain artificial marble of a specified size, it is necessary to prepare a molding plate larger than that size in advance and cut it to a specified size after heat treatment, resulting in waste of material and economical loss. growing.

Although the reason why such a difference occurs is not clear, in the case of the present embodiment, the heat treatment is carried out in a state where it is not completely cooled immediately after the solidification extrusion, and the molded body is extruded in the extrusion direction. It is continuous, the periphery is fixed, and the whole body is heated gradually and continuously without being locally heated. It is considered that the internal strain can be removed without causing

[0059]

As described above, according to the stone-grained artificial marble of the present invention, a matrix resin containing acrylic resin powder as a main component, aluminum hydroxide powder as a powdery inorganic filler, feldspar, A transparent frit powder having a refractive index of 1.48 to 1.60 obtained by melting and solidifying raw materials such as silica stone and borax is mixed uniformly with a small amount of liquid plasticizer to form a molding material. In addition, since the blending amount of each component of the molding material is specified, in the molded product, a natural stone-like stone tone such as transparency with appropriate concealing property, deep shade pattern, scattered glitter etc. Is expressed and the effect of being full of natural feeling is obtained.

Particularly, by specifying the average particle size of the frit powder, a more vivid stone tone can be expressed.

[0061]

EXAMPLE A matrix resin, powdered inorganic filler, frit powder, and plasticizer shown in Table 1 below were prepared.

[0062]

[Table 1] These materials shown in Table 1 were put into a Henschel mixer at the compounding ratio shown in Table 2 below, and mixed at room temperature for 30 minutes.

Then, the respective extruding temperature and the extruding die temperature of each mixture were set to 200 by using a solidification extruding machine (diameter: 50 mm, L / D = 32, compression ratio 2.5) shown in FIG. ℃, the cooling temperature of the molded body by the forming die (9) is set to 120 ° C., solidification extrusion molding is performed to obtain a plate-shaped molded product having a thickness of 12 mm and a width of 790 mm, and the molded product is continuously heated by a heating device. According to (15), heat treatment was performed at 140 ° C. for 60 minutes. In this extrusion molding machine, as the lubricant layer (14) provided on the inner surfaces of the extrusion die (8) and the forming die (9), a tetrafluoroethylene film was laminated on a core layer made of glass fiber woven cloth. I used one.

[0064]

[Table 2] And for each molded product, extrusion moldability, product appearance,
The stone tone of the product was evaluated. The evaluation method is as follows, and the evaluation results are also shown in Table 2.

(Evaluation method) 1. Extrudability is good. The load of the extruder was within the rated value, and stable and continuous extrusion was possible. The load of the extruder was within the rated value, but the stability was a little lacking regarding continuous extrusion. 1. Excessive load on the extruder caused the screw to stop during operation, and the fluctuations became extremely large, which prevented stable extrusion. Good appearance of the product: No foaming or deformation was found, and a smooth and beautiful surface was obtained. Possible ... No problem in appearance under normal observation, but careful observation revealed some foaming. What was not observed: Foaming or deformation was observed, and the surface was rough, such as uneven surface. Observing the stone tone of the product. Good… Transparency with appropriate concealing properties, deep shade patterns, scattered glitters, etc. that have a natural stone-like tone, not… have a natural stone-like tone As shown in the evaluation of Table 2, among Examples 1 to 7 according to the prescribed conditions of the present invention, those according to Examples 1 to 6 can perform continuous solidification extrusion molding operation without any trouble. The appearance quality was good, and it was possible to bring out a natural stone-like vivid stone tone. At this time, the resin pressure is 290 to 32
It was stable at 0 kg / cm ² . Further, in Example 7, although some instability was observed in the resin pressure, the appearance quality was not so serious and a vivid stone tone similar to natural stone was able to be expressed.

On the other hand, in the case of Comparative Example 1 in which the amount of the frit powder blended was less than the specified range of the present invention, there was no problem in extrusion moldability and appearance quality, but a natural stone-like stone tone was exhibited. I couldn't do it. Further, in the case of Comparative Example 2 in which the amount of the frit powder exceeds the specified range of the present invention, not only stable solidification extrusion molding cannot be performed for a long time, but also unevenness such as rough skin is recognized on the surface, and a good molded product is obtained. Couldn't get

As described above, according to the present invention, it is possible to obtain a stone-grained artificial marble that is full of natural feeling without any problems in workability during molding and appearance quality.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an example of a solidification extruder used in an extrusion molding operation of the present invention.

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Claims (2)

[Claims] 1. A matrix resin powder having an acrylic resin powder as a main component, an aluminum hydroxide powder as a powdery inorganic filler, and raw materials such as feldspar, silica stone, and borax are melted and solidified, and pulverized. The obtained refractive index 1.48 to 1.
60 transparent frit powder and a small amount of a liquid plasticizer are uniformly mixed to form a mixture as a molding material, and the powder mixture of the matrix resin powder and the aluminum hydroxide powder in the molding material. The total amount of 1
When the amount is 100 parts by weight, the matrix resin powder is set to 20 to 50 parts by weight and the aluminum hydroxide powder is set to 80 to 50 parts by weight, and 100 parts by weight of the powder mixture is used. On the other hand, a stone-grained artificial marble comprising 0.1 to 10 parts by weight of the frit powder. 2. The average particle diameter of the frit powder is 3.0 mm
The stone-grained artificial marble according to claim 1, which is set below.