JPH03243322A - Manufacture of artificial marble by extrusion molding - Google Patents

Abstract

PURPOSE:To manufacture artificial marble having excellent appearance and quality characteristics continuously by mixing acrylic resin powder and alumi num hydroxide powder with a liquefied plasticizer, using the mixture as a material for molding, conducting solidification extrusion molding and specifying an extrusion temperature and the cooling temperature of a molded form by a forming die. CONSTITUTION:A mixture obtained by uniformly mixing acrylic resin powder as a matrix resin and aluminum hydroxide powder as powdered inorganic fillers with a small quantity of a liquefied plasticizer is employed as a material for molding. Electricity is conducted through a forming die 9 with a cooling jacket 9a immediately after the material for molding is extruded in a specified shape from the extrusion die 8 of an extrusion molding machine, and solidification extrusion molding molding the material under a solidified state is executed. An extrusion temperature by an extruder is set and controlled at 180-220 deg.C and the cooling temperature of a molded form A by the forming die 9 at 150 deg.C or lower at that time. An acrylic resin having a melt flow rate of 0.5g/10min or more and weight average molecular weight of 80000-300000 is used as an acrylic resin as the matrix resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the manufacturing method of 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 as a material, by extrusion molding.

Conventional technology Conventionally, this type of artificial marble has been made using an acrylic resin matrix that has excellent properties such as transparency, hardness, weather resistance, and heat resistance, and powder fillers such as aluminum hydroxide, magnesium hydroxide, etc. It is known that calcium carbonate, silica, etc. are uniformly dispersed singly or in combination of two or more. Among these, aluminum hydroxide has a refractive index similar to that of acrylic resin as a matrix resin, so it gives products a deep appearance with both transparency and hiding properties, and is also easy to cut. Toshizuru dot is the most commonly used main material for powder fillers.

Many examples of the structure of conventional artificial marble as described above can be found in, for example, Japanese Patent Application Laid-Open Nos. 53-104621, 61-141653, and 61-178458.

Problems to be Solved by the Invention However, due to its composition or the materials used, conventional artificial marble has been limited in its manufacturing method to either cast molding or press moldability. Of course, these conventional manufacturing methods not only require a long time for molding, but also involve batch molding, resulting in poor productivity and high costs. Furthermore, depending on the size of the molded product, a large molding device is required, which limits the product size, makes it impossible to manufacture long products, and requires joining during use. There were fundamental problems such as an increase in the number of cases.

In view of these problems, it is naturally foreseeable that it would be advantageous to continuously produce artificial marble by extrusion molding. However, aluminum hydroxide powder, which is most commonly used as an inorganic filler, has a low thermal decomposition temperature, and when the temperature exceeds 180°C, thermal decomposition gradually progresses to water and alumina, so acrylic resin It is naturally predicted that at the extrusion processing temperature (200 to 250°C), the decomposed water will foam and it will be impossible to obtain the desired astronomical stone-like molded product.For this reason, the advantages of extrusion molding are recognized. The reality is that it was considered impossible to adopt any of them.

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 By adopting a solidification extrusion method that completes extrusion to a solidified state, and by setting the extrusion conditions, especially the extrusion temperature conditions and the cooling temperature conditions by the forming die, to specific ranges, it is possible to eliminate bubbles caused by thermal decomposition of the aluminum hydroxide powder. We discovered that it is possible to perform continuous extrusion molding without any problems by suppressing the generation of voids, and that it is possible to obtain a molded product that is extremely similar to natural marble by having transparency, depth, and hiding effects in appearance. This led to the completion of the present invention.

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°C.
This is a method for producing artificial marble by extrusion molding, characterized in that the solidification extrusion molding operation is performed with the setting controlled at a temperature below (preferably 120° C. or lower).

The acrylic resin used in this invention has a melt flow rate (
MFR, 230°C, 3.8Ky load) is 0. 5g/
10 min or more, and the weight average molecular ffi (Pvlw
) is preferably 80,000 to 300,000.

In addition, aluminum hydroxide powder as a powder filler is
It is desirable to use relatively coarse particles with an average particle diameter of 10 μm or more and a specific surface area of 2 Trt/g or less, and a small surface area.

Furthermore, the blending ratio of the mixture used as the molding material is
Acrylic resin powder 20-50% based on the total amount of the mixture of acrylic resin powder and aluminum hydroxide powder
The mixing ratio should be set within the range of νt% and aluminum hydroxide from 80 to 50vt%.

Furthermore, the solidification extrusion molding operation must be carried out by setting the extrusion resin pressure from the extruder to at least 50/(yf/Ci), preferably 70 to 350 to 9
It should be set within the range of f/ai.

Next, each component, formulation, and extrusion molding method 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 is melt flow rate 4 (MFR, 23
0℃, 3. 8Ky) (Test method/unit, ASTM
D 1238) or more than 0.5 g/10 min and the weight average molecular weight ILFvlW is less than 300.000. Melt flow rate (MF
R) is 0. If less than 5g/10w1n or with an average molecular weight MW of more than 300,000 is used, the melt viscosity will increase and the fluidity will decrease when kneaded 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 Mw 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 w1n or more, and a calm w 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 preferably has an average particle size of 10 μm or more and a specific surface area of 2 rrt/g or less, and more preferably has a substantially spherical particle shape.

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

Moreover, if the specific surface area becomes too large exceeding 2 Trt/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. It is effective in combination with the following: relatively low particle size, large particle size and small specific surface area, similar refractive index to matrix resin, and inferior leakage to acrylic resin. It is thought that it is acting on

(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. Needs to be an eaves 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 wavy shape of the plasticizer is necessary in order to make it easier to obtain a uniform mixture by loosening the acrylic resin powder and adhering the aluminum hydroxide powder to it during kneading.

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 with an HA of more than 100 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 DMPSDOPSDBP, and fatty acid (dibasic) ester-based plasticizers such as DIOASDBS and DO.
S etc., and trimellitic acid ester type T
OTM etc. can be mentioned.

(Composition) When the blending ratio of the molding material is 100 wt% based on the total amount of the mixture of acrylic resin powder and aluminum hydroxide powder, 20 to 5% of the acrylic resin powder is mixed.
0 wt%, aluminum hydroxide powder should be in the range of 80-50 wt%. If the blending ratio of the acrylic resin powder is less than 20wt% and therefore the blending ratio of aluminum hydroxide exceeds 80wt%, 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 without acrylic resin powder is 50wt%.
If the blending ratio of aluminum hydroxide powder exceeds 50 wt%, even if the extrusion molding operation is facilitated, the molded product will have insufficient hiding power and will be too transparent. It no longer exhibits a heavy feel similar to marble, and its heat resistance becomes insufficient.

The most preferable blending ratio is in the range of 25 to 4 wt% 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, resulting in condensation or nucleation, which results in a disadvantage of extremely poor strength against external impact.

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, and a small amount of higher fatty acids such as stearic acid and valmitic acid as a lubricant, and alkaline earth metals thereof. 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 method) When molding, first, premixing 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 branched plasticizer to the above-mentioned mixing ratio. This is done by uniformly mixing until there are no powder-like lumps.

In this case, it is inappropriate to use a dry blender or the like without stirring blades as a mixer, since the "flour"-like lumps will not disappear even if the mixing operation is performed for a long time. Furthermore, the order in which the blended materials are introduced into the mixer does not matter much.

Next, the mixture 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 here is generally used to extrude polymer materials into round rods, plate vibrators, 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 extrusion die, and is solidified and formed into the desired shape and size by cooling while passing through a forming die attached to the tip of the extrusion die. The solidification extrusion method using such an apparatus can be suitably used 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, in order to solidify the molten material in the forming die and extrude it, the inside of the die becomes under extremely high pressure.
It has the feature that it can suppress the generation of voids and bubbles in the molded product and can provide good quality.

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 main 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, (10) is a molded body take-off device made of a rubber roll or a caterpillar, (11) ) (12) 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.

On the inner surfaces of the extrusion die (8) and forming die (9) that come into contact with the extrusion material, a release film (as shown) made of glass fiber laminated with a fluororesin is attached to prevent sticking.

The molding material is introduced from the hopper (5), melted and softened by heating in the cylinder (2), kneaded by the screw (3), passed through the drawing part (7), and then extruded into the extrusion die (8). It is extruded into a predetermined shape. The extrudate extruded from the extrusion die passes through the forming die (9) and is then equipped with a water cooling jacket (9a).
), and is shaped into a predetermined cross-sectional shape to produce a solidified molded product (A), that is, artificial marble.

By the way, as mentioned above, aluminum hydroxide has 18
When the temperature exceeds 0°C, it gradually begins to decompose and transforms into water and alumina, but this water causes foaming in normal extrusion molding methods, which significantly impairs the appearance of the product. In contrast,
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.

One such condition is 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, the molded article (A) at the exit of the forming die (9)
Sufficient cooling must be carried out so that the temperature 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.

Furthermore, as another condition, the cylinder throttle part (7)
The extrusion resin pressure is 50Kg/ad~500Ky/
ad, preferably 7oKy/ad to 350 to 9/
must be operated within the ad range.

If the resin pressure is less than 50 Ky/l:4, foaming is likely to occur if there are cavities, reducing the quality of the product as artificial marble. Moreover, if it exceeds 9/cri of 500, it is mechanically at its limit and there is a risk of damaging the extruder or extrusion 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 By using a mixture with a liquid plasticizer as a molding material, adopting a solidification extrusion method, and setting a specific range of extrusion temperature conditions and cooling temperature conditions using a forming die, extrusion that was previously thought to be impossible. The molding method allows continuous molding of high-quality artificial marble without any problems.

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 good transparency and concealability (excellent harmony, depth, and profound feeling). It is possible to obtain a high-quality product that has an appearance similar to natural marble and is uniform throughout.

Further, the melt flow rate (MFR) of claim (2),
By using an acrylic resin powder having a weight average molecular weight o; tW as a matrix, artificial marble with excellent heat resistance can be produced without any problems by extrusion molding.

Furthermore, by using aluminum hydroxide powder having a particle size and specific surface area as specified in claims (3) and (4) and by adopting a specific blending ratio, it is possible to produce a product of high quality that has the above-mentioned characteristics. The extrusion moldability of artificial marble allows for long-term continuous molding.

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

[Margin below]

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

×: Foaming causes cavities or voids inside the product, or the surface becomes uneven.

Extrudability O...The load on the extruder is within the rated value. Yes, stable and continuous extrusion Something that came.

×...The load on the extruder is too high and the If the crew stops during operation, Stable extrusion with significant fluctuations What could not be done.

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

Then, the mixture was extruded using the solidification extrusion molding machine shown in Figure 1 (caliber = 50 mm, L/D-32, screw: full flight type with compression ratio of 2.5), and the extrusion conditions were changed as shown in Table 2. This was solidified and extruded to obtain a plate-shaped molded product with a thickness of 12 m and a width of 790 m.

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 2.

As shown in the evaluation in Table 2 above, in the production methods of Examples 1 to 4 that comply with the specified conditions of the present invention, artificial marble with good appearance quality was produced by continuous solidification extrusion molding operations. I was able to get it.

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 too high or fluctuate, making it impossible to make the plate, or even if the extruder is made, foaming or voids may occur. However, it was not possible to obtain molded products of good quality.

In addition, in the case of Comparative Example 7, the temperature of the molded product at the die exit was too high due to insufficient cooling of the molded product by the water cooling jacket of the forming die, and in the case of Comparative Example 7, which was formed using a forming die that does not have (does not use) a cooling jacket. Example 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 of excellent quality.

[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. That's it - Mi~V

Claims (4)

[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 A method for producing artificial marble by extrusion molding, characterized in that the solidification extrusion molding operation is performed by controlling the cooling temperature of the molded product by a forming die to 180 to 220 °C and 150 °C or less. (2) The acrylic resin as the matrix resin has a melt flow rate (MFR, 230°C, 3.8 kg load) of 0.5 g/10 min or more, and a weight average molecular weight (@M@w) of 80,000 or more. 300,000. The method for producing artificial marble by extrusion molding according to claim (1). (3) The aluminum hydroxide powder used as the powdered inorganic filler has an average particle size of 10 μm or more and a specific surface area of 2 m^2/
The method for producing artificial marble by extrusion molding according to claim (1) or (2), which uses a marble having a particle size of less than g. (4) The mixture used as a molding material has a blending ratio of 20 to 50 wt% of acrylic resin powder and 80 to 50 wt% of aluminum hydroxide powder, based on the total amount of the powder mixture of acrylic resin powder and aluminum hydroxide powder. The method for producing artificial marble by extrusion molding according to any one of claims (1) to (3).