JPH0661814B2 - Method of manufacturing artificial marble by extrusion - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing artificial marble used in building materials, vanity tops, sink tops, etc., and particularly to a powdery inorganic filler in an acrylic resin matrix. The present invention relates to a method for producing an artificial marble having an appearance of natural marble by dispersing aluminum hydroxide powder by an extrusion molding method.

Conventional technology Conventionally, as this type of artificial marble, an acrylic resin having excellent properties such as transparency, hardness, weather resistance, and heat resistance is used as a matrix, and aluminum hydroxide, magnesium hydroxide as a powder filler is added to the matrix. It is known that calcium carbonate, silica and the like are uniformly dispersed in one kind or in a combination of two or more kinds. Among them, aluminum hydroxide, which has a refractive index similar to that of acrylic resin as a matrix resin, gives the product a deep appearance that is both transparent and concealing, and is easy to cut. It is most commonly used as the main material of powder fillers.

Examples of the constitution of the conventional artificial marble as described above include, for example, JP-A-53-104621 and JP-A-61-141653.
Many examples can be found in Japanese Patent Publication No. 61-178458.

However, the conventional artificial marble is limited in its production method to either the cast molding method or the press molding method from the viewpoint of the composition or the material used. Of course, in all of these conventional manufacturing methods, not only the time required for molding is long, but also the molding is performed by a batch method, so that the productivity is poor and the cost is high. Further, depending on the size of the molded product, a large molding device is required, the product size is limited by the device, and it is impossible to manufacture a long product, and bonding is required at the time of use. There were many essential problems such as increasing the number of cases.

With respect to such problems, the advantage of continuously producing artificial marble by an extrusion molding method is naturally expected. However, in the aluminum hydroxide powder most commonly used as an inorganic filler, the thermal decomposition temperature is low, and when it exceeds 180 ° C, the thermal decomposition gradually progresses into water and alumina. It is foreseeable that a desired marble-like molded product in which decomposed water is foamed cannot be obtained at the extrusion processing temperature (200 to 250 ° C.), and the advantage of extrusion is not recognized. The fact is that even ゝ could not be adopted.

Among the background of the prior art as described above, the present invention uses an aluminum hydroxide powder as a powdery inorganic filler, and a continuous extrusion molding method to produce an artificial marble excellent in appearance and quality characteristics. This is an intended task to enable continuous production.

Means for Solving the Problems Under the above-mentioned intended problems, the inventors of the present invention have conducted various experiments and researches, and as described above, when the temperature exceeds 180 ° C., decomposition gradually starts and water and alumina are gradually decomposed. Even when the aluminum hydroxide powder that changes to is used as an inorganic filler, a solidification extrusion method for performing extrusion molding under extremely high pressure, that is, the molding material is passed through a forming die with a cooling jacket immediately after extrusion by the extrusion die. By adopting the solidification extrusion method that completes the extrusion in the solidified state, and further by setting the extrusion conditions, particularly the extrusion temperature condition and the cooling temperature condition by the forming die, to the respective specific ranges, bubbles and bubbles due to the thermal decomposition of the aluminum hydroxide powder can be obtained. It is possible to carry out continuous extrusion molding without any problem while suppressing the generation of voids, and the transparency, depth and concealing effect on the appearance of the molded product. The present invention has been completed by discovering that a material that has both of the above and that is extremely similar to natural marble can be obtained.

That is, the basic point of the present invention is to form a mixture of an acrylic resin powder as a matrix resin and an aluminum hydroxide powder as a powdery inorganic filler, together with a small amount of a liquid plasticizer, into a molding material. Used as
Immediately after extruding the molding material into a predetermined shape from an extrusion die of an extrusion molding machine, solidification extrusion molding is conducted to form a solidified state by conducting to a forming die with a cooling jacket, and when performing the solidification extrusion molding, The extrusion temperature by the extruder is 180 to 220 ° C (preferably 190 to 210).
℃), the cooling temperature of the molded body by the forming die is 15
A method for producing an artificial marble by extrusion molding, characterized in that the solidification extrusion molding operation is performed by setting and controlling at 0 ° C or lower (preferably 120 ° C or lower).

The acrylic resin used in the present invention has a melt flow rate (MFR, 230 ° C., 3.8 kg load) of 0.5 g / 10 from the viewpoint of moldability and heat resistance of a molded product.
min or more, and weight average molecular weight (w) is 80,000
It is preferable to use one having a value of 0 to 300,000.

Further, aluminum hydroxide powder as a powder filler,
It is desirable to use those having an average particle size of 10 μm or more and a specific surface area of 2 m ² / g or less, which is relatively coarse and has a small surface area.

And again, the mixing ratio of the mixture as the molding material is
Acrylic resin powder 20 to 50 based on the total amount of the mixture of acrylic resin powder and aluminum hydroxide powder.
The blending ratio should be set in the range of wt% and aluminum hydroxide 80 to 50 wt%.

Furthermore, the solidification extrusion molding operation needs to be carried out by setting the pressure of the extruded resin from the extruder to at least 50 kgf / cm ² or more, preferably 70 to 350 kgf / cm ^2. Should do

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

(Matrix Resin) As the matrix resin, an acrylic resin is used because it is excellent in various properties such as transparency, weather resistance, hardness and heat resistance. Specific examples of the resin include thermoplastic acrylic resins having different monomer compositions and thermoplastic methacrylic resins, and in particular, a homopolymer of methyl methacrylate or methyl methacrylate is used as the total monomer content. A copolymer obtained by copolymerizing at least 1% of other vinyl ester monomer copolymerizable with other methacrylic acid ester and other methyl methacrylate in a proportion of at least 70% by weight, preferably at least 70% by weight, is preferable. These beads or ground powders are used as molding material elements. The particle size 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.

The above-mentioned acrylic resin has a melt flow rate (MFR, 23) in order to perform the melt-kneading operation in the extruder without any trouble.
0 ° C, 3.8 kg) (Test method / unit: ASTM D 12
38) should be 0.5 g / 10 min or more and the weight average molecular weight w should be less than 300,000. Melt flow rate (MFR) is 0.5g / 1
If less than 0 min or if the average molecular weight w exceeds 300,000, when kneading with the filler in the extruder, the melt viscosity increases and the fluidity decreases, and the power load more than the capacity of the extruder is accordingly increased. If it occurs, the operation will be stopped unintentionally, or problems such as resin leakage and screw damage will occur, making smooth extrusion molding difficult. However, when the artificial marble, which is a molded product, is used for heat resistance-required applications, it is necessary to use a weight average molecular weight w having a lower limit w of 80,000 or more. That is, when an acrylic resin having a w of less than 80,000 is used,
The decrease in heat resistance may damage the surface when a hot pot is placed on the molded product or the lit cigarette is accidentally dropped. Melt flow rate (MF
The most preferable range of R) and the weight average molecular weight (w) is MFR: 1.0 g / 10 min or more, w12 to 17
It is in the range of 10,000.

(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 a material having a substantially spherical particle shape. .

When the average particle size is 10 μm or less, the sheet has too high a hiding property and the texture of the artificial marble becomes poor.

On the other hand, if the specific surface area exceeds 2 m ² / g and becomes too large, the hiding property becomes too high due to the 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 performed without any problem, because the hardness of aluminum hydroxide is Mohs hardness of 2.5. Relatively low, large particle size and small specific surface area, close refractive index to the matrix resin, poor leak resistance to acrylic resin, etc. It is thought to be working.

(Plasticizer) Addition of a plasticizer is useful for reducing the melt viscosity of an acrylic resin by its original function as a plasticizer and improving moldability, and shows compatibility with an acrylic resin. It needs to be a liquid plasticizer. That is, with a plasticizer that is not compatible with acrylic resin, bleeding or microcracks are likely to occur in a molded product even if a molding material containing the plasticizer can be extruded. It becomes inferior in sex. The liquidity of the plasticizer is necessary in order to wet the acrylic resin powder at the time of kneading and adhere the aluminum hydroxide powder to the acrylic resin powder to facilitate obtaining a uniform mixture.

The transparency of the plasticizer used does not matter so much in the production of colored moldings. However, when trying to obtain white pure artificial marble, the transparency is AP
It is not preferable to use a plasticizer having an HA of more than 100, because it causes yellowing of the molded product and causes other harmful coloring. 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 phthalate-based ones such as DMP, DOP and DBP, and fatty acid (dibasic) ester-based ones such as DIOA, DBS and DO.
S or the like, or T as a trimellitic ester type
OTM etc. can be listed.

(Mixing) The mixing ratio of the molding material is 20 to 50% of the acrylic resin powder when the total amount of the mixture of the acrylic resin powder and the aluminum hydroxide powder is 100 wt%.
It should be in the range of wt% and aluminum hydroxide powder 80 to 50 wt%. 20 wt% of acrylic resin powder
%, And therefore the content of aluminum hydroxide is 8
When it exceeds 0 wt%, the matrix resin is not uniformly dispersed in the aluminum hydroxide powder, and as a result, the melt softening does not proceed sufficiently in the extruder and the extrusion molding becomes difficult. On the other hand, if the acrylic resin powder content exceeds 50 wt% and the aluminum hydroxide powder content is relatively less than 50 wt%, the concealing property of the molded product will be poor even if the extrusion molding operation is facilitated. Sufficient and too strong transparency makes it impossible to express the weight feeling similar to natural marble, and heat resistance becomes insufficient. The most preferable blending ratio is 25-40 wt% in acrylic resin powder.
% Range.

When the amount of the plasticizer is 100 parts by weight based on the total amount of the powder mixture of the acrylic resin powder and the aluminum hydroxide powder, if the amount is less than 0.5 parts by weight, the desired addition effect is sufficient. Can't get to. That is, the acrylic resin cannot be sufficiently leaked, the aluminum hydroxide powder is secondarily aggregated, and the 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 compounding amount of the plasticizer exceeds 5 parts by weight, the heat resistance of the molded product is significantly lowered 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 this invention includes, in addition to the above essential components, a colorant added to obtain an ignition artificial marble, and a small amount of higher fatty acid such as stearic acid and palmitic acid as a lubricant, and its alkaline earth metal. Naturally, addition of salts (calcium salts, magnesium salts, 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 a range that does not impair the effects of the present invention, 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. It is also acceptable to do.

(Molding method) Before molding, premixing of the pre-blended materials is first performed. For this mixing operation, for example, using a Henschel mixer with a stirring blade, a ribbon blender, a V-type tumbler, etc., the acrylic resin powder, the aluminum hydroxide powder, and the liquid plasticizer are added to the above mixing ratios, respectively. It is done by mixing uniformly until there is no "-like" agglomerate. It is unsuitable to use a dry blender or the like having no stirring blade as the mixer because the "mass powder" -like lumps will not disappear even after a long mixing operation. 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 extrusion molding device. 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, and (3)
Is an extrusion screw installed in it, (4A) (4B)
(4C) and (4D) are first to fourth of the cylinder (2).
A heating device, (5) a material supply hopper, (6) a drive device, (7) a narrowed portion at the tip of the cylinder (2), (8)
Is an extrusion die provided subsequently thereto, (9) is a forming die with a water-cooling jacket (9a) further provided in front of it, (10) is a device for pulling a molded body composed of a rubber roll or a caterpillar, (11 ) (12) is a heating device for the drawing part (7) and the extrusion die (8), and (13) is a measuring device for the resin pressure at the drawing part of the cylinder tip.

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

Then, the molding material is charged 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) and the extrusion die (8). Is extruded into a predetermined shape. The extrudate extruded from the extrusion die passes through the forming die (9) and is equipped with a water cooling jacket (9).
It is cooled in a), shaped into a predetermined cross-sectional shape, and manufactured into a solidified compact (A), that is, an artificial marble.

By the way, as mentioned above, aluminum hydroxide is
When the temperature exceeds 0 ° C, decomposition gradually starts and changes into water and alumina, and this water content causes foaming in a usual extrusion molding method, which causes a significant inhibition of the appearance of the product. In contrast,
By using the solidification extrusion method, by molding under high pressure, even when using aluminum hydroxide as a filler, it is possible to obtain an artificial marble of good quality without foaming, but if the solidification extrusion method is used, It cannot be molded at any temperature and can only be performed under limited conditions.

One of the conditions is the extrusion temperature. That is, the extrusion temperature is in the range of 180 ° C to 220 ° C 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 preferably be set in the range of 190 ° C to 210 ° C. If the set temperature is lower than 180 ° C., the melting and softening of the acrylic 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.

Further, the second condition is the cooling temperature of the molded body (A) by the forming die (9) with a cooling jacket. That is, sufficient cooling must be performed so that the temperature of the molded body (A) at the outlet of the forming die (9) is 150 ° C. or lower, preferably 120 ° C. or lower. If 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, causing foaming, appearance defects such as blisters, and the like on the surface thereof. The shape is also difficult.

Furthermore, as other conditions, the cylinder throttle (7)
Extrusion resin pressure ^{in, 50kg / cm 2 ~500kg / cm} 2, preferably should be operated within the range of ^{70kg / cm 2 ~350kg / cm 2} . If the resin pressure is less than 50 kg / cm ² , the quality of the artificial marble of the product in which nest formation and foaming are likely to occur 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.

EFFECTS OF THE INVENTION According to the present invention, in addition to selecting an acrylic resin powder having excellent transparency and heat resistance as a matrix resin, aluminum hydroxide powder is particularly selected as a powder inorganic filler, and By using a mixture with a liquid plasticizer as a molding material, and by adopting a solidification extrusion method and setting a specific range of an extrusion temperature condition and a cooling temperature condition by a forming die, extrusion that was conventionally considered unmoldable By the molding method, high-quality artificial marble can be continuously molded without any trouble.

Therefore, it is possible to efficiently manufacture an artificial marble of any length and a required cross-sectional shape, and the manufactured artificial marble has a good harmony of transparency and concealment, and is excellent in depth and profoundness. It is possible to obtain a high-quality product that has an appearance similar to that of marble and that is uniform in quality as a whole.

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

Furthermore, by using an aluminum hydroxide powder having a particle size and a specific surface area as defined in claims (3) and (4) and adopting a specific blending ratio, it is possible to obtain a very high quality having the above-mentioned characteristics. It enables continuous molding for a long time by extrusion molding method of artificial marble.

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

The materials shown in Table 1 above 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 is then solidified and extruded as shown in FIG. 1 (caliber: 50 mm, L / D = 32, screw: 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 mm.
A plate-shaped molded product of

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 methods〕

Product Appearance: A smooth and beautiful surface with no nests caused by foaming and no voids.

× ... due to foaming, nesting inside or voids occurred,
The surface is uneven.

Extrudability: Good: The extruder load was within the rated value, and stable and continuous extrusion was possible.

X: The extruder was overloaded and the screw stopped during operation, and the fluctuation was so large that stable extrusion could not be performed.

As shown in the evaluation of Table 2 above, in each of the manufacturing methods of Examples 1 to 4 according to the prescribed conditions of the present invention, an artificial marble with good appearance quality was produced by continuous solidification extrusion molding operation. I was able to get it.

On the other hand, when the extrusion temperature conditions are too high or too low, Comparative Examples 5 and 6 prevent the plate making due to excessive load or fluctuation of the extruder, or even if the plate making can cause foaming or voids. It was not possible to obtain a molded product of good quality. Further, in the case of Comparative Example 7 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 Comparative Example molded using the forming die having no cooling jacket (not used). In the case of No. 8, it was not possible to suppress the generation of voids and blisters due to foaming, and it was also impossible to obtain a molded product having excellent quality.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a solidification extrusion molding apparatus used for the extrusion molding operation of the present invention. (1) …… Extruder body, (2) …… Cylinder, (8) …… Extrusion die, (9) …… Forming die, (9a) …… Water cooling jacket.

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Claims (4)

[Claims] 1. An acrylic resin powder as a matrix resin and an aluminum hydroxide powder as a powdery inorganic filler, which are uniformly mixed together with a small amount of a liquid plasticizer, are used as a molding material. Immediately after the material is extruded into a predetermined shape from the extrusion die of the extrusion molding machine, solidification extrusion molding is conducted in which the material is conducted into a solidified state by passing through a forming die with a cooling jacket, and when performing the solidification extrusion molding, Extrusion temperature is 180-220 ℃,
A method for producing an artificial marble by extrusion molding, wherein the solidification extrusion molding operation is performed by setting and controlling the cooling temperature of the molded body by a forming die to 150 ° C. or lower. 2. An acrylic resin as a matrix resin has a melt flow rate (MFR, 230 ° C., 3.8 kg).
The method for producing an artificial marble by extrusion molding according to claim 1, wherein a material having a load of 0.5 g / 10 min or more and a weight average molecular weight (w) of 80,000 to 300,000 is used. 3. An aluminum hydroxide powder as a powdery 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, wherein the content is ² / g or less. 4. The acrylic resin powder is 20 to 50 wt% based on the total amount of the powder mixture of the acrylic resin powder and the aluminum hydroxide powder.
The method for producing an artificial marble by extrusion molding according to any one of claims (1) to (3), wherein the blending ratio is 80 to 50 wt% of aluminum hydroxide.