JPH0822565B2 - Method of manufacturing artificial marble by extrusion - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an artificial marble used for building materials, a vanity, a top plate of a system kitchen, etc. by an extrusion molding method.

[0002]

2. Description of the Related Art The inventors of the present invention have proposed, in Japanese Patent Application No. 2-393934 (Japanese Patent Application Laid-Open No. 3-243322), which has been previously filed, a method of manufacturing an artificial marble by an extrusion molding method which is highly efficient. . The manufacturing method related to this prior proposal is
As the matrix resin, an acrylic resin, specifically, a thermoplastic acrylic resin having various monomer compositions,
And a thermoplastic methacrylic resin are used, and particularly preferably, a homopolymer of methyl methacrylate, or methyl methacrylate is 50% by weight or more of the total amount of monomers,
It is preferable to use at least 70% by weight of a copolymer obtained by copolymerizing at least one other vinyl monomer copolymerizable with other methacrylic acid ester or other methyl methacrylate, and solidifying under specific conditions. Extrusion molding is performed.

[0003]

However, the artificial marble obtained by filling the polymethylmethacrylate resin powder with the inorganic filler is 90 ° C. for use as a top plate of a kitchen range or the like.
It has been found that when exposed to the relatively high temperature as described above, thermal cracks are likely to occur and there is a problem in durability.

The cause of this thermal cracking is that the bonding force between the resin phase and the inorganic filler is weak, whereas the difference between the thermal expansion coefficient and the thermal contraction coefficient of the resin phase and those of the inorganic filler is large. It is thought to be because. Therefore, as a known general method for increasing the bonding force at this interface, a method of surface-treating the surface of the inorganic filler by silane coupling or the like was tried, but the sufficient effect could not be obtained yet.

In view of the above background, the present invention makes it possible to manufacture an artificial marble which is free from thermal cracks and has excellent durability even in a relatively high temperature atmosphere by an extrusion molding method. To that end.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various experiments and studies under the above-mentioned problems, and as a result of using a specific acrylic resin powder as a matrix resin, heat resistance is improved, The present invention has been completed by finding that no thermal crack occurs.

That is, the basis of the present invention is to use a matrix resin containing carboxyl group-containing methacrylic resin powder as a main component, and the matrix resin and aluminum hydroxide powder as a powdery inorganic filler. Is used as a molding material using a mixture that is uniformly mixed with a small amount of a liquid plasticizer, and immediately after the molding material is extruded into a predetermined shape from an extrusion die of an extrusion molding machine, it is conducted to a forming die with a cooling jacket and solidified. Solidification extrusion molding is performed, and in performing the solidification extrusion molding, the extrusion temperature by the extruder is set to 180 to 220 ° C., and the cooling temperature of the formed body by the forming die is controlled to be 150 ° C. or less, and the solidification is performed. It is a method of manufacturing an artificial marble by extrusion molding, which comprises performing an extrusion molding operation.

The above matrix resin used in the present invention has a melt flow rate (MFR, 230 ° C., 3.8 kg load) from the viewpoints of moldability and heat resistance of molded products.
Is 0.5 g / 10 min or more and the weight average molecular weight (Mw) is preferably 80,000 to 300,000.

As the powdered inorganic filler, it is preferable to use aluminum hydroxide powder having an average particle size of 10 μm or more and a specific surface area of 2 m ² / g or less.

Further, the mixture used as the molding material is 20 to 50% by weight of the matrix resin powder and 80 to 50% by weight of the aluminum hydroxide powder, based on the total amount of the powder mixture of the matrix resin powder and the aluminum hydroxide powder. It should be set within the range of the compounding ratio.

Furthermore, in the solidification extrusion molding operation, the pressure of the extruded resin from the extruder is at least 50 kgf / cm.
It is necessary to set it to ² or more, preferably 7
It should be set within the range of 0 to 350 kgf / cm ² .

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

(Matrix Resin) The present invention is characterized in that a methacrylic resin containing a carboxyl group is a main component as a matrix resin.

The carboxyl group-containing methacrylic resin is
A copolymer of methyl methacrylate (MMA) and an ethylenically unsaturated carboxylic acid. Typical examples of the ethylenically unsaturated carboxylic acid include acrylic acid and methacrylic acid, and other itaconic acid, Maleic acid, maleic anhydride, etc. can be mentioned. The ethylenically unsaturated carboxylic acid is usually 1 to 15% of the matrix resin,
It is preferable to use a copolymerized product in the range of 3 to 7%. If it is less than 1%, the desired improvement in the adhesiveness between the matrix resin and the inorganic filler cannot be obtained, and the effect of improving thermal cracking is low. On the other hand, if it exceeds 15%, the fluidity in the extruder decreases, extrusion molding becomes difficult, and the water absorption rate increases, which adversely affects the physical properties. Furthermore, for the purpose of improving heat resistance, a vinyl aromatic compound copolymerizable with methyl methacrylate may be copolymerized with the polymer in an amount of 5% or less. Examples of this vinyl aromatic compound include styrene, vinyltoluene, α-methylstyrene and the like.

The matrix resin is not limited to the carboxyl group-containing methacrylic resin described above, but may be a commonly used methacrylic resin such as methyl methacrylate described above. In this case, the addition amount of the general-purpose methacrylic resin needs to be such that the ethylenically unsaturated carboxylic acid is added within the range of 1 to 15% of the matrix resin.

As the above matrix resin, a powdered one is used, and the particle size thereof is not particularly limited, but is generally 5 to 200 μm, particularly preferably 20 to 10 μm.
Those having a size of about 0 μm are preferably used.

Further, the matrix resin has a melt flow rate (MFR, 230 ° C., 3.8 kg) (test method / unit;
Those having an ASTM D 1238) of 0.5 g / 10 min or more and a weight average molecular weight Mw of less than 300,000 should be used. Melt flow rate (MF
R) is less than 0.5 g / 10 min or average molecular weight M
When w exceeding 300,000 is used, when kneading with the filler in the extruder, the melt viscosity increases and the fluidity decreases, and accordingly, a power load exceeding the capacity of the extruder occurs, and the operation is Problems such as unintentional stoppage, resin leakage, and screw damage occur, making smooth extrusion molding difficult.
However, when the artificial marble, which is a molded product, is used for applications requiring heat resistance, the lower limit of the weight average molecular weight Mw is Mw of 80,000 or more. That is, if a matrix resin having an Mw of less than 80,000 is used, the surface may be damaged when a hot pot is placed on a molded product or when a lit cigarette is accidentally dropped due to a decrease in heat resistance. Occurs. The most preferable ranges of the melt flow rate (MFR) and the weight average molecular weight (Mw) are MFR: 1.0 g / 10 min or more and Mw in the range of 120 to 170,000.

(Powdered inorganic filler) As the powdered inorganic filler, it is necessary to use aluminum hydroxide powder as a main material. Moreover, it is preferable to use the aluminum hydroxide powder having an average particle diameter of 10 μm or more and a specific surface area of 2 m ² / g or less, and further it is preferable to use one having a substantially spherical particle shape. .

When the average particle size is 10 μm or less, the sheet has a too high hiding property, resulting in poor texture as an artificial marble.

If the specific surface area exceeds 2 m ² / g and becomes too large, the hiding property will be 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 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.

(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 acrylic resin. It is necessary to be a liquid plasticizer showing. That is, with a plasticizer that is incompatible with the matrix resin, even if a molding material containing it is extrudable, bleeding or microcracks are likely to occur in the molded product, and it is practically durable. Will be inferior to. The liquidity of the plasticizer is necessary in order to wet the matrix resin powder during kneading and adhere the aluminum hydroxide powder to the matrix resin powder so that a uniform mixture can be easily obtained.

The transparency of the plasticizer used does not matter so much in the production of colored moldings. However, in the case of obtaining a white pure artificial marble, when a plasticizer having a transparency of APHA of more than 100 is used, the molded product is yellowed or causes other harmful coloring, which is not preferable. Therefore, in this case, as the plasticizer, APHA having a transparency of 100 or less, particularly preferably 50 or less, should be used.

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 compounding ratio of the molding material is 20 to 50 wt% of the matrix resin powder and aluminum hydroxide when the total amount of the mixture of the matrix resin powder and the aluminum hydroxide powder is 100 wt%. The powder should be in the range of 80 to 50 wt%. The blending ratio of the matrix resin powder is less than 20 wt%,
Therefore, when the blending amount of aluminum hydroxide exceeds 80 wt%, the matrix resin is not uniformly dispersed in the aluminum hydroxide powder, and 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 wt% and the blending ratio of the aluminum hydroxide powder is relatively less than 50 wt%, the hiding property of the molded product is insufficient even if the extrusion molding operation is facilitated. Therefore, the transparency becomes too strong, the weight feeling similar to natural marble cannot be exhibited, and the heat resistance becomes insufficient. The most preferable blending ratio is 25-40 wt% in the matrix resin powder.
Range.

The amount of the plasticizer blended is 100 parts by weight based on the total amount of the powder mixture of the matrix resin powder and aluminum hydroxide powder, and if it is less than 0.5 parts by weight, the desired addition effect is obtained. Can't get enough. 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 continuous extrusion molding in a uniform manner 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,
If the blending amount of the plasticizer exceeds 5 parts by weight, the heat resistance of the molded product will be significantly reduced even if a uniform mixture is obtained. Therefore, the blending amount of the plasticizer should be in the range of 0.5 to 5 parts by weight, and it is particularly preferable to add it in the range of 1.0 to 3 parts by weight.

The molding material used in the present invention contains, in addition to the above-mentioned 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. Furthermore, within the range that does not impair the effects of the present invention,
It is also permissible to replace a part of the aluminum hydroxide powder with another type of powdered inorganic filler to reduce the material cost and adjust the appearance of the molded product.

(Molding Method) At the time of molding, first, premixed materials are premixed. For this mixing operation, for example, using a Henschel mixer with a stirring blade, a ribbon blender, a V-type tumbler, etc., the matrix resin powder, the aluminum hydroxide powder, and the liquid plasticizer are added to the above mixing ratios, respectively, This is done by mixing uniformly until there are no lumps. It is not appropriate to use a dry blender or the like having no stirring blade as the mixer, because the "mass powder" -like lumps do not disappear even after the mixing operation for a long time. Further, the order of feeding the blended materials to the mixer does not matter so much.

Next, 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 by a solidification extruding apparatus. The extrusion molding equipment used here is generally used to extrude polymeric materials into round bars, plate pipes, or other shaped products. The molten polymer material is distributed to an extrusion die as needed, and is cooled while passing through a forming die attached to the tip of the extrusion 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 with high filler filling. 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 generation of voids and bubbles in the molded product, and obtain good quality. It has features.

A typical example of the solidification extrusion molding apparatus used in the present invention is shown in FIG. In the figure, (1) is the extruder body, (2) is its cylinder, (3) is the extrusion screw installed inside it, and (4)
A) (4B) (4C) (4D) are first to fourth heating devices of the cylinder (2), (5) is a material supply hopper,
(6) is a driving device, (7) is a throttle portion at the tip of the cylinder (2), (8) is an extrusion die provided subsequently to it,
(9) is a water cooling jacket (9
Forming die with a), (10) take-up device for molded body consisting of rubber roll, track, etc., (11) (12)
Is a heating device for the drawing portion (7) and the extrusion die (8),
(13) is a measuring device for the resin pressure at the throttle of the cylinder tip.

On the inner surfaces of the extrusion die (8) and the forming die (9) that come into contact with the extruded material, a release film (not shown) in which glass fiber is laminated with a fluororesin is attached to prevent sticking. To be done.

Then, the molding material is introduced from the hopper (5), is kneaded by the screw (3) while being melted and softened by being heated in the cylinder (2), and is extruded through the drawing section (7). It is extruded into a predetermined shape from (8). The extrudate extruded from the extrusion die is cooled by a water-cooling jacket (9a) provided in the extrudate while passing through the forming die (9), shaped into a predetermined cross-sectional shape and solidified (A), That is, it is manufactured into artificial marble.

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 a usual extrusion molding method to remarkably improve the appearance of the product. It causes the inhibition.
On the other hand, by using the solidification extrusion method, by molding under high pressure, even when using aluminum hydroxide as a filler,
It is possible to obtain a good quality artificial marble without foaming, but the solidification extrusion method does not allow molding at any temperature and can be carried out only under limited conditions.

One of the conditions is the extrusion temperature. That is, the extrusion temperature is 180 ° C. or higher in any of the cylinder (2) portion, the cylinder tip narrowed portion (7), and the extrusion die (8) portion of the extruder body (1).
It should be set in the range of 220 ° C, preferably in the range of 190 ° C to 210 ° C. This set temperature is 180
If the temperature is lower than 0 ° 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 and the value of the product is significantly reduced.

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.
Sufficient cooling must be provided to maintain the temperature below ℃. 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 The shape is also difficult.

As still another condition, the pressure of the extruded resin in the cylinder drawing portion (7) is 50 kg / cm ² to
500 kg / cm ² , preferably 70 kg / cm ^{2 to} 3
It must be operated within the range of 50 kg / cm ² . When 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 an artificial marble is deteriorated. ^{On the other hand} , if it exceeds 500 kg / cm ² , there is a mechanical limit, and there is a risk of damaging the extruder and the extrusion die forming die.

[0037]

According to the present invention, the carboxyl group-containing methacrylic resin is selected as the main component of the matrix resin, and the aluminum hydroxide powder is selected as the powdery inorganic filler, and the powder and the liquid plasticizer are added. By using the mixture as a molding material, adopting the solidification extrusion method, and setting the specific range of the extrusion temperature condition and the cooling temperature condition, continuous molding of high-quality artificial marble can be performed without any trouble.

In particular, by using a carboxyl group-containing methacrylic resin as the main component of the matrix resin, it is possible to obtain an artificial marble excellent in durability without cracking due to heat even in a relatively high temperature atmosphere. It can be widely used.

[0039]

Example A matrix resin, a powdered inorganic filler, and a plasticizer shown in Table 1 below were prepared.

[0040]

[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.

The mixture was solidified and extruded as shown in FIG. 1 (diameter: 50 mm, L / D = 32, compression ratio: 2.5).
Full flight type), the extrusion conditions were changed as shown in Table 2 and solidification extrusion was performed, and the thickness was 12 mm and the width was 790 m.
A plate-shaped molded product of m was obtained.

[0042]

[Table 2] Then, the extrusion moldability during extrusion molding was evaluated, and the appearance of each molded product was examined. The evaluation method is as follows, and the evaluation results are also shown in Table 2.

(Evaluation method) 1. Appearance of product: ○… A smooth and beautiful surface was obtained without the formation of cavities due to foaming and voids. ×… The surface of the surface was uneven due to cavities and voids inside due to foaming. Extrudability: ○… Extruder load was within the rated value and could be extruded stably and continuously. ×… Extruder load was excessive, the screw stopped during operation, and fluctuation was extremely large and stable Extrusion Things I couldn't do 3. Thermal cracking: As shown in FIG. 2, the obtained plate-shaped molded product was manufactured into a processed product similar to the top plate used in an actual kitchen stove. This processed product is 1300 × 650 × 1
In the central part of the plate-like body (21) with a size of 2 mm, 560 × 5
It has a frame-like shape with a 30 mm opening (22) cut out. This is left for 2 hours at 110 ℃ atmosphere, 110
One cycle consists of cooling from ℃ to -15 ℃ in 1 hour, leaving in -15 ℃ atmosphere for 2 hours, and further heating from -15 ℃ to 110 ℃ in 1 hour. After repeating this for 100 cycles, the appearance is shown. The following evaluations were made by visual observation.

○: No cracks are observed ×: Cracks are observed As shown in the evaluation of Table 2, in each of the manufacturing methods of Examples 1 to 6 according to the specified conditions of the present invention, By continuous solidification extrusion molding operation, it was possible to obtain an artificial marble with good appearance quality without generation of thermal cracks.

On the other hand, in the case of Comparative Example 1 in which the carboxyl group-containing methacrylic resin was not used as the matrix resin, a good appearance was obtained, but thermal cracking occurred and it could not be used at high temperature. It was a thing. From this, it can be seen that in the present invention, the occurrence of thermal cracks is suppressed by including the carboxyl group-containing methacrylic resin in the matrix resin.

When the extrusion temperature conditions are out of the values specified in the present invention and in Comparative Examples 2 and 3, plate formation cannot be performed due to excessive load of the extruder or fluctuation, or even if plate formation is possible, foaming or voids occur. And a molded product of good quality could not be obtained.

Further, in the case of Comparative Example 4 in which the temperature of the molded body at the die outlet is too high due to insufficient cooling of the molded body by the water cooling jacket of the forming die, and when the forming die having no cooling jacket (not used) is used. In the case of the molded Comparative Example 5, it was not possible to suppress the occurrence of voids and blisters due to foaming, and it was not possible to obtain a molded product having excellent 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.

FIG. 2 is a perspective view showing the shape of a sample used for a thermal crack evaluation test.

[Explanation of symbols]

 (1) ... Extruder body (2) ... Cylinder (8) ... Extrusion die (9) ... Forming die (9a) ... Water cooling jacket

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Claims (4)

[Claims] 1. A molding material, which is a mixture of a matrix resin containing a carboxyl group-containing methacrylic resin powder as a main component and an aluminum hydroxide powder as a powdery inorganic filler uniformly mixed with a small amount of a liquid plasticizer. Immediately after the molding material is extruded from an extrusion die of an extrusion molding machine into a predetermined shape, it is conducted to a forming die with a cooling jacket to perform solidification extrusion molding, and the solidification extrusion molding is performed. At this time, the solidification extrusion molding operation is carried out by setting the extrusion temperature by the extruder to 180 to 220 ° C. and controlling the cooling temperature of the formed body by the forming die to 150 ° C. or less, and the method for producing an artificial marble by extrusion molding. . 2. The matrix resin has a melt flow rate (MFR, 230 ° C., 3.8 kg load) of 0.5 g.
/ 10 min or more and the weight average molecular weight (Mw) is 8
The method for producing an artificial marble by extrusion according to claim 1, wherein the number of the artificial marble is from 10,000 to 300,000. 3. The aluminum hydroxide powder as the powder inorganic filler has an average particle size of 10 μm or more and a specific surface area of 2 m.
^The method for producing an artificial marble by extrusion molding according to claim 1 or 2, which has a content of ² / g or less. 4. The matrix resin powders 20 to 50, based on the total amount of the powder mixture of the matrix resin powder and the aluminum hydroxide powder.
The method for producing an artificial marble by extrusion according to claim 1, wherein the blending ratio is such that the weight percentage is 80 to 50 wt% of the aluminum hydroxide powder.