JPH04147820A - Production of artificial marble by extrusion molding - Google Patents

Abstract

PURPOSE:To continuously produce artificial marble excellent in appearance and quality characteristics by applying specific slip imparting treatment to an extrusion die and a forming die and setting an extrusion temp. condition and a cooling temp. condition to specific ranges. CONSTITUTION:Solidifying extrusion molding is performed in such a way that an acrylic resin powder as a matrix resin and an aluminum hydroxide powder as a powdery inorg. filler are uniformly mixed with a small amount of a liquid plasticizer to be extruded in a predetermined shape from the extrusion die of an extrusion molding machine and immediately passed through a forming die equipped with a cooling jacket to be subjected to solidifying extrusion molding. At this time, extrusion temp. is set to 180-220 deg.C and the cooling temp. of the molded body is set to 150 deg.C or less. A slip imparting layer with the coefficient of friction of 0.3 or less and tensile strength of 50kg.f/(10mm width) or more is formed to the contact surfaces of the extrusion die and forming die with the molding material to perform solidifying extrusion molding to prepare artificial marble. As the slip imparting layer, a tetrafluoroethylene resin is used alone or a film or sheet consisting of said resin and a tensile fiber core material is used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing artificial marble used as building materials, washstands, sink tops, etc. This invention relates to a method for manufacturing artificial marble, which has a natural astronomical stone appearance by dispersing aluminum hydroxide powder, by extrusion molding.

Prior Art The inventors of the present invention have previously filed Japanese Patent Application No. 63-228048.
No. (Japanese Unexamined Patent Publication No. 2-74317), we proposed an efficient extrusion method for manufacturing artificial marble. The manufacturing method according to this prior proposal selectively uses magnesium hydroxide as the powdered inorganic filler. However, it is known that it is preferable to use aluminum hydroxide as an inorganic filler for artificial marble. That is, aluminum hydroxide is
Because the refractive index is similar to that of the acrylic resin used as the matrix resin, powder-filled products have the advantage of giving the product a deep appearance with both transparency and concealment properties, and can be easily cut. It is most suitable as the main material of wood.

Problems to be Solved by the Invention However, aluminum hydroxide powder, which is most suitable as an inorganic filler, has a low thermal decomposition temperature, and when the temperature exceeds 180°C, thermal decomposition gradually progresses to form water and alumina.
Acrylic resin extrusion processing temperature (200-250℃)
It was naturally foreseen that the decomposed water would foam and it would be impossible to obtain the desired astronomical stone-like molded product, and for this reason, even though the advantages of extrusion molding were recognized, it was considered impossible to adopt it. The reality is that

In the background of the above-mentioned prior art, this invention uses aluminum hydroxide powder as a powdered inorganic filler, and uses a continuous extrusion method to create artificial marble with excellent appearance and quality characteristics. This was done with the aim of making continuous manufacturing possible.

Means for Solving the Problem The inventors conducted various experiments and research based on the above-mentioned desired problem, and found that as mentioned above, when the temperature exceeds 180℃, water and alumina gradually decompose. Even when aluminum hydroxide powder, which changes into The solidification extrusion method is used to complete extrusion in a solidified state, and the extrusion die and forming die are subjected to a specific lubricant treatment, and the extrusion conditions, especially the extrusion temperature condition and the cooling temperature condition by the forming die, are adjusted. By setting each to a specific range,
It is possible to perform continuous extrusion molding without any problems by suppressing the generation of bubbles and voids caused by thermal decomposition of aluminum hydroxide powder, and the molded product has a transparent appearance, depth, and concealment effect, making it possible to produce natural marble. It was discovered that something very similar to can be obtained, and the present invention was completed.

That is, the basis of this invention is that a mixture of acrylic resin powder as a matrix resin and aluminum hydroxide powder as a powdered inorganic filler is uniformly mixed together with a small amount of a liquid plasticizer as a molding material. used as
Immediately after the molding material is extruded into a predetermined shape from an extrusion die of an extrusion molding machine, it is passed through a forming die with a cooling jacket to form a solidified state. The extrusion temperature by the extruder is 180 to 220°C (preferably 190 to 210°C)
), the cooling temperature of the molded body by the forming die was set to 150
℃ or less (preferably 120℃ or less), and the entire contact surface with the molding material on the inner surface of the extrusion die and forming die is coated with a friction coefficient of 0.3 or less and a tensile strength of 50 kg-f/ (10 (2) A method for producing artificial marble by extrusion molding, characterized in that the above-mentioned solidification extrusion molding operation is performed in a state in which a lubricant layer of width) or more is coated.

The above-mentioned lubricant layer preferably uses a fluororesin, particularly a tetrafluoroethylene resin as a lubricant, and a film or sheet made of the resin alone or in combination with a tensile fiber core material.

Next, each component, formulation, and extrusion molding conditions of the molding material used in the present invention will be explained in more detail.

(Matrix Resin) As the matrix resin, acrylic resin is used because it has excellent properties such as transparency, weather resistance, hardness, and heat resistance. Specifically, thermoplastic acrylic resins and thermoplastic methacrylic resins having various monomer compositions can be used as the resin, but in particular, a homopolymer of methyl methacrylate or a methyl methacrylate containing 50% of the total monomer composition can be used. Suitable are copolymers formed by copolymerizing at least one methacrylic acid ester and at least one vinyl monomer copolymerizable with methyl methacrylate in an amount of at least 70% by weight, preferably at least 70% by weight. Beads or pulverized powders thereof are used as molding material elements. Although the particle size is not particularly limited,
Generally 5 to 200 μm, particularly preferably 20 to 100 μm
A material having a diameter of about m is preferably used.

The above acrylic resin has a melt flow rate (MFR, 23
0℃, 3. 8kg) (Test method/unit, ASTM
D 1238) of 0.5 g/10 min or more and a weight average molecular weight iw of less than 300,000 should be used. Melt flow rate (M
If a material with a FR) of less than 0°5 g/10 m1n or an average molecular weight Qw of more than 300,000 is used, the melt viscosity will increase and the fluidity will decrease when mixed with the filler in the extruder.
As a result, a power load exceeding the capacity of the extruder is generated, causing problems such as involuntary stoppage of operation, resin leakage, and screw damage, making smooth extrusion molding difficult. However, when the artificial marble that is a molded product is used for applications requiring heat resistance, it is necessary to use a weight average molecular weight Qw of 80,000 or more as the lower limit. In other words, if an acrylic resin with a MW of less than 80,000 is used, the heat resistance will decrease and the surface may be damaged if a hot pot is placed on top of the molded product or a lit cigarette is accidentally dropped. occurs. The most preferable range of melt flow rate (MFR) and weight average molecular weight (MW) is MFR: 1° Og/10 m1n or more, and the richness w is in the range of 120,000 to 170,000.

(Powdered Inorganic Filler) As the powdered inorganic filler, it is particularly necessary to use aluminum hydroxide powder as the main material. Moreover, the aluminum hydroxide powder has an average particle diameter of 10 μm or more and a specific surface area of 2 rr! / g or less, and more preferably, the particle shape is approximately spherical.

If the average particle diameter is 10 μm or less, the concealing properties of the sheet will be too high and the texture of the sheet will be inferior to that of artificial marble.

Furthermore, if the specific surface area becomes too large, exceeding 2 rd/g, the hiding property will become too high due to fine bubbles at the interface between aluminum hydroxide and the matrix resin.

Furthermore, due to the increase in specific surface area, contaminants are more likely to be adsorbed, causing problems in the stain resistance of artificial marble.

By using aluminum hydroxide powder as a filler that meets the above requirements, the hardness of aluminum hydroxide is 2.5 on the Mohs scale, making it possible to continuously form artificial marble with a good appearance by extrusion. The factors such as relatively low particle size, large particle size and small specific surface area, refractive index similar to that of matrix resin, and poor leakage compared to acrylic resin all work together to make it effective. It is thought that it is working.

(Plasticizer) Addition of plasticizer is useful for reducing the melt viscosity of acrylic resin and improving moldability by acting as an original plasticizer, and it shows compatibility with acrylic resin. Requires liquid plasticizer. In other words, if a plasticizer is incompatible with acrylic resin, even if the molding material to which it is added can be extruded, the molded product will easily bleed or develop microcracks, making it difficult to maintain practical durability. It becomes inferior to sex. Furthermore, the plasticizer is required to be in a liquid state in order to wet the acrylic resin powder during kneading and cause the aluminum hydroxide powder to adhere thereto, thereby making it easier to obtain a homogeneous mixture.

The transparency of the plasticizer used does not matter much when colored molded articles are to be produced. However, when trying to obtain solid white artificial marble, transparency is
It is not preferable to use a plasticizer exceeding 100 in HA because it may cause yellowing or other harmful coloring in the molded product. Therefore, in this case, the plasticizer should have a transparency of APHA of 100 or less, particularly preferably 50 or less.

The type of plasticizer used is not particularly limited.

Examples of plasticizers that can be used include phthalate ester-based plasticizers such as DMP, DOP, and DBP, and fatty acid (dibasic) ester-based plasticizers such as DIOA and DBSXDO.
8 etc., and T as a trimellitic acid ester type.
OTM etc. can be mentioned.

(Blend) The blending ratio of the molding material is 100% by weight based on the total amount of the mixture of acrylic resin powder and aluminum hydroxide powder, and 20 to 5% of the acrylic resin powder.
Qvj%, aluminum hydroxide powder should range from 80 to 5Qvj%. If the blending ratio of acrylic resin powder is less than 20vt% and therefore the blending ratio of aluminum hydroxide exceeds 80v4%, the matrix resin will not be uniformly dispersed in the aluminum hydroxide powder, resulting in dispersion in the extruder. Melting and softening does not proceed sufficiently, making extrusion molding difficult. On the other hand, the amount of acrylic resin powder not included is 50vt%.
If the relative proportion of aluminum hydroxide powder is less than 5Q,v+%, even if the extrusion process is facilitated, the molded product will have insufficient hiding power and will be too transparent. , it becomes impossible to express a feeling of weight similar to that of natural marble, and the heat resistance becomes insufficient. The most preferable blending ratio is in the range of 25 to 40W1% in the acrylic resin powder.

The blending amount of the plasticizer is 100 parts by weight based on the total amount of the powder mixture of the acrylic resin powder and aluminum hydroxide powder, and if it is less than 0.5 parts by weight, the desired addition effect may not be sufficiently achieved. can't get to it. That is, the acrylic resin cannot be sufficiently leaked out, and the aluminum hydroxide powder may undergo secondary aggregation or coarse particles may segregate, making it impossible to obtain a uniform mixture. In addition, the role of plasticizing efficiency is not fully demonstrated, and during extrusion molding, the extrusion fluidity is unstable, making it difficult to perform long-term uniform continuous extrusion molding, and even if extrusion molding is performed, hydroxylation occurs in the molded product. The distribution of the aluminum powder becomes non-uniform, and its agglomerates act as cores, resulting in a drawback that the aluminum powder has extremely poor strength against external impacts.

On the other hand, if the amount of plasticizer added exceeds 5 parts by weight, even if a homogeneous mixture is obtained, the heat resistance of the molded article will be significantly reduced. Therefore, the amount of plasticizer to be added should be in the range of 0.5 to 5 parts by weight, and preferably in the range of 1.0 to 3 parts by weight.

In addition to the above-mentioned essential ingredients, the molding material used in this invention contains a coloring agent to obtain colored artificial marble, a small amount of higher fatty acids such as stearic acid and palmitic acid, and alkaline earth metals as lubricants. salt (calcium salt, magnesium salt, etc.) or montan acid wax,
It is naturally permissible to add amides of higher fatty acids. Furthermore, if necessary, the aluminum hydroxide powder may be previously surface-treated with a fatty acid metal salt, a silane coupling agent, a titanate coupling agent, or the like. Furthermore, part of the aluminum hydroxide powder may be replaced with another type of powdered inorganic filler to reduce material costs and adjust the appearance of the molded product, within a range that does not impair the effects of the present invention. It is also permissible to do so.

(Molding conditions) When molding, first the premixed materials are premixed. This mixing operation is carried out by using, for example, a Henschel mixer with stirring blades, a ribbon blender, a V-type tumbler, etc., and adding the acrylic resin powder, aluminum hydroxide powder, and liquid plasticizer to the above-mentioned mixing ratio. Mix evenly until there is no powder-like material left.

I will do it. Second, it is inappropriate to use a dry blender or the like without a stirring blade as a mixer because the "flour"-like lumps will not disappear even after a long mixing operation. Furthermore, the order in which the mixed materials are added to the right side of the mixer does not pose much of a problem.

Next, the adulterated substance obtained by the above premixing operation is used as a molding material, and is solidified and extruded into a predetermined cross-sectional shape using a solidification extrusion molding device. The extrusion molding equipment used is generally used to extrude shoulder polymer materials into round bars, plate pipes, or irregularly shaped products.The extruder extrudes the polymer material while melting it, and then The molten polymer material is distributed as necessary to the die, and is solidified and formed into the desired shape and size by cooling while passing through a forming die attached to the tip. The solidification extrusion method using such an apparatus is suitable for molding not only general resins but also materials with particularly high melt viscosity and poor fluidity, and materials with high filler content.

In other words, since the molten material is solidified in the forming die and extruded, the inside of the die is under extremely high pressure, which suppresses the formation of voids and bubbles in the molded product, resulting in good quality. It has certain characteristics.

A typical example of the solidification extrusion molding apparatus used in the present invention is shown in FIG. In the figure, (1) is the extruded body, (2) is its cylinder (3)
The extrusion screw (4A) (4B) (
4C) (4D) is the first to fourth heating device of the cylinder (2), (5) is the material supply hopper, (6) is the drive device, (7) is the constriction part at the tip of the cylinder (2), (8) (9) is a forming die with a water cooling jacket (9a) connected in front of the extrusion die, (]0) is a molded body take-off device made of a rubber roll or a caterpillar, etc.; If) (+2) is a heating device for the above-mentioned constriction section (7) and extrusion die (8), and (13) is a measuring device for the resin pressure at the constriction section at the tip of the cylinder.

By the way, in carrying out this invention, the extrusion die (
8) and the inner surface of the forming die (9) that comes in contact with the extruded material must be subjected to a specific lubricating treatment to prevent the forming material from sticking. This lubrication treatment is essential in order to enable continuous extrusion molding for a long time while maintaining the surface quality and texture of the artificial marble at a constant and good quality, and the coefficient of static to dynamic friction is 0°. By applying a lubricant layer (14) having a tensile strength of 3 or less and a tensile strength of 50 kg-f/ (10 mm width) or more to the entire inner surface of the extrusion die (8) and the forming die (9) by pasting or the like. It is something to do. If the lubricant layer (14) has a coefficient of friction exceeding 0°3, the pressing pressure of the molding material will increase, making it impossible to maintain the preferred predetermined pressure described below, making molding practically difficult. . The preferred coefficient of friction is 0.
．． 15 or less.

In addition, if the tensile strength is less than 50 kg-f/ (10 kg-f), the lubricant layer (14) will be damaged early due to strong rubbing of the molding material during extrusion molding, and the lubricating effect will be lost, resulting in propulsion. The force decreases and continuous molding becomes difficult. Preferably, the tensile strength is 100 kg-f/(1OIIO1 width) or more.

The material and composition of the lubricating material layer (14) are not particularly limited as long as they have the above-mentioned coefficient of friction and tensile strength, but fluororesin is preferably used in view of the low coefficient of friction. It is suitable for use as a lubricant. Especially 4
Preferably, fluorinated ethylene resin (PTFE) is used.

The required tensile strength can be achieved by increasing the thickness of the resin film or sheet used as the lubricating material, but it is also possible to obtain the required strength while using a thin resin film itself as the lubricating material. It is advantageous to provide a composite material in which the resin film is laminated to a core layer made of tensile fibers such as glass fibers, Kepra fibers, or metal fibers.

In the above-mentioned solidification extrusion molding apparatus, the molding material is charged from the hopper (5), is kneaded by the screw (3) while being melted and softened by heating in the cylinder (2), and is extruded through the constriction part (7). It is extruded into a predetermined shape from a die (8). The extrudate extruded from the extrusion die is cooled by a water cooling jacket (9a) equipped thereon while passing through the forming die (9), and is shaped into a predetermined cross-sectional shape and solidified (A), That is, it is manufactured into artificial marble.

By the way, as mentioned above, aluminum hydroxide has 18
When the temperature exceeds 0°C, it gradually begins to decompose into water and alumina, but this water causes foaming in the normal extrusion molding method, which significantly impairs the appearance of the product. On the other hand,
By using the solidification extrusion method and molding under high pressure, it is possible to obtain good quality artificial marble without foaming even if aluminum hydroxide is used as a filler, but if the solidification extrusion method is used, Molding cannot be performed at any temperature, and is only possible under limited conditions.

The first condition is the extrusion temperature. That is, the extrusion temperature is within the range of 180°C to 220°C in any part of the extruder main body (1), including the cylinder (2), the cylinder tip constriction part (7), and the extrusion die (8). ,
Preferably it must be set in the range of 190°C to 210°C. If the set temperature is less than 180°C, the acrylic resin will not sufficiently melt and soften, and the back pressure of the extruder will become too large, making extrusion molding difficult. On the other hand, if the set temperature exceeds 220° C., the decomposition of aluminum hydroxide is accelerated, so foaming cannot be suppressed even in the solidification extrusion method, and the value of the product is significantly reduced.

Moreover, the second condition is the cooling temperature of the molded article (A) by the cooling jacketed forming die (9). That is,
Sufficient cooling must be performed so that the temperature of the molded body (A) at the exit of the forming die (9) is below 150°C, preferably below 120°C. If this cooling temperature exceeds 150°C, the artificial marble molded product extruded from the cooling jacketed forming die (9) will be in a softened state, and the surface will have appearance defects such as foaming and blistering, as well as The shape is also difficult.

Also, the third condition is that the extrusion die (8
) and the entire inner surface of the forming die (9) is coated with a lubricant layer (I4) having predetermined physical properties to perform a specific lubricating process, and then the solidifying extrusion molding operation is performed. be.

Under conditions without this lubricating treatment, it is not possible to perform long-term continuous extrusion molding of artificial marble with stable surface properties.

Furthermore, as another condition, the cylinder throttle part (7)
The extrusion resin pressure is 50kg/cj to 500kg/a
d, preferably within the range of 70 kg/at to 350 kg/cd.

If the resin pressure is less than 50 kg/cd, cavities and foaming are likely to occur (reducing the quality of the product as artificial marble).If it exceeds 500 kg/al, there is a mechanical limit and the extruder or extruder There is a risk of damaging the die forming die.

Effects of the Invention According to the present invention, in addition to selecting an acrylic resin powder with excellent transparency and heat resistance as the matrix resin, aluminum hydroxide powder is particularly selected as the powder inorganic filler, and these powders and Using a mixture with a liquid plasticizer as a molding material, adopting a solidification extrusion method, setting a specific range of extrusion temperature conditions and cooling temperature conditions by a forming die, and further adding specific attachments to the extrusion die and forming die. In combination with slipping treatment, high-quality artificial marble can be continuously molded without any problems using extrusion molding, which was previously thought to be impossible.

Therefore, it is possible to manufacture artificial marble of any desired length and desired cross-sectional shape with high efficiency, and the manufactured artificial marble has a good balance of transparency and concealment, has excellent depth and solidity, and has a natural appearance. It is possible to obtain a high-quality product that has an appearance similar to marble and is uniform throughout.

Example Matrix resins, powdered inorganic fillers, and plasticizers listed in Table 1 below were prepared.

Table 1 On the other hand, as a solidification extrusion molding device, a full-flight molding machine (caliber: 50III!II, L
/D=32, screw compression ratio: 2°5), and lubricant made of various materials as shown in Table 2 was applied to the entire inner surface of the pushing die (8) and forming die (9). A layer (14) was formed as a cover.

Table 2 The materials listed in Table 1 above were placed in a Henschel mixer in the proportions shown in Table 3 below, and mixed at room temperature for 30 minutes.

Then, the mixture was solidified and extruded using the solidification extrusion molding machine described above under various extrusion conditions as shown in Table 3 to obtain various plate-shaped molded products with a thickness of 12mm and a width of 790mm.

Then, the extrusion moldability during extrusion molding was evaluated, and the appearance of each molded product was examined. The evaluation method was as follows, and the evaluation results are also shown in Table 3.

〔Evaluation methods〕 Product appearance × Cracks and voids caused by foaming A smooth and beautiful surface is obtained. What was given.

Due to foaming, nests may get inside, voids or uneven surfaces. Something convex.

Extrudability ○...Extruder load is within the rated value Yes, stable for more than 24 hours Something that can be extruded continuously.

×...The load on the extruder is too high and the load is too high. If the crew stops during operation, Significant fluctuations over 24 hours It is not possible to extrude more stably than Something.

[Margin below]

As shown in the evaluation in Table 3 above, in the production methods of Examples 1 to 4 according to the specified conditions of the present invention, continuous solidification extrusion molding operation can be continued for 24 hours or more. , it was possible to obtain artificial marble with high efficiency and good appearance quality.

On the other hand, if the extrusion temperature conditions are too high or too low according to Comparative Example 5.6, the extruder load may be excessive or fluctuate, making it impossible to make a plate, or even if the extruder can be made, foaming or voids may occur. Therefore, it was not possible to obtain molded products of good quality.

Also, Comparative Example 7 in which the temperature of the molded product at the die exit is too high due to insufficient cooling of the molded product by the water cooling jacket of the forming die, and Comparative Example in which molding was performed using a forming die that does not have (does not use) a cooling jacket. 8
In all cases, it was not possible to suppress the occurrence of voids and blisters due to foaming, and it was still not possible to obtain a molded product with excellent quality.

Furthermore, in Comparative Example 9 in which no lubricant layer was applied to the extrusion die and forming die, extrusion molding could not be performed at all from the initial stage, and the physical properties of the lubricant layer were not as good as those of the present invention. In all cases of Comparative Examples 10 and 11 which deviated from the specified values, the resin film of the lubricant layer was damaged less than 24 hours after the start of operation, and subsequent molding became difficult.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a solidification extrusion molding apparatus used in the extrusion molding operation of the present invention. (1)...Extruder main body, (2)...Cylinder (8
)...Extrusion die, (9)...Forming die, (
9a)...Water cooling jacket, (14)...Lubricant layer. that's all

Claims (2)

[Claims] (1) A mixture of acrylic resin powder as a matrix resin and aluminum hydroxide powder as a powdered inorganic filler, mixed uniformly with a small amount of liquid plasticizer, is used as a molding material. Immediately after extrusion into a predetermined shape from an extrusion die of an extrusion molding machine, solidification extrusion molding is performed by passing through a forming die with a cooling jacket to form a solidified state, and when performing solidification extrusion molding, the extrusion temperature of the extruder The cooling temperature of the molded body by the forming die is set to 180 to 220°C, and the cooling temperature of the molded body by the forming die is set to 150°C or less, and the entire contact surface with the molding material on the inner surface of the extrusion die and forming die has a coefficient of friction of 0.
A method for manufacturing artificial marble by extrusion molding, characterized in that the solidification extrusion molding operation is performed under a state in which a lubricant layer with a tensile strength of 3 or less and a tensile strength of 50 kg・f/(10 mm width) or more is coated. . (2) The method for producing artificial marble by extrusion molding according to claim (1), wherein the lubricant layer comprises a film or sheet using tetrafluoroethylene resin as a lubricant.