JPH0649573B2 - Aluminum hydroxide for artificial marble and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides an onyx tone obtained by filling aluminum hydroxide into an unsaturated polyester resin, an acrylic resin, or the like,
TECHNICAL FIELD The present invention relates to aluminum hydroxide for producing artificial marble such as marble and a method for producing the same.

[Conventional technology]

It is well known to fill an unsaturated polyester resin or acrylic resin with aluminum hydroxide to obtain an onyx-like or marble-like molding.

Recently, aluminum hydroxide having a small particle size has been used as a filler for the purpose of improving the strength, surface smoothness, boiling resistance, and sedimentation of the filler in a paste state of the molded body.

In order to obtain a molded product by press molding of BMC (bulk molding compound) and SMC (sheet molding compound), use aluminum hydroxide having a small particle size as a filler to prevent separation of resin and filler at the time of pressing. Is advantageous.

[Problems to be Solved by the Invention]

However, when the particle size is small, that is, when aluminum hydroxide having a large specific surface area is used as the resin filler, there are problems such as poor dispersion of the filler in the resin and high resin filling viscosity, making it difficult to highly fill the filler. It cannot be avoided.

In addition, the unsaturated polyester resin composition having a large specific surface area of aluminum hydroxide as a filler has a gel time because an oil-soluble curing accelerator such as cobalt naphthenate used as a curing accelerator is trapped on the surface of aluminum hydroxide. However, there is a problem in that the productivity is reduced, the molded product becomes yellowish, and the like.

[Means for Solving the Problems]

As a result of intensive studies to solve the above problems, the inventor has found that the primary particle size of precipitated aluminum hydroxide, which is a raw material for pulverization, has a very large effect on the specific surface area and resin filling viscosity of the pulverized material. Based on this, the present invention has been completed.

That is, the present invention crushes aluminum hydroxide having a low specific surface area and low resin filling viscosity and secondary agglomerated precipitated aluminum hydroxide having a primary particle diameter substantially equal to the average particle diameter of the intended crushed aluminum hydroxide. Another object of the present invention is to provide a method for producing aluminum hydroxide for artificial marble, which is characterized in that the raw material is crushed and produced.

That is, the gist of the present invention is that the average particle size measured by the sedimentation method exceeds 8 μm and 30 μm or less, the specific surface area measured by the nitrogen adsorption method is 1.5 m ² / g or less, and the viscosity of 10 poise at 20 ° C. 100 parts by weight of unsaturated polyester resin having 200 parts by weight of aluminum hydroxide filled therein was measured with a Brookfield viscometer at 35 ° C. to obtain a resin filling viscosity of 1000.
The ratio of particles having a particle size of less than or equal to 75 μm and less than poise is 1
% Or less, the whiteness is 95 or more, and the average particle diameter composed of primary particles in the range of 20 μm or less and aluminum hydroxide for artificial marble and the average diameter measured by the pressure crushing method. Another object of the present invention is to provide a method for producing aluminum hydroxide for artificial marble, characterized by crushing secondary aggregated particles of aluminum hydroxide having a size of 30 to 70 μm.

Here, the whiteness means a value measured by a photoelectric whiteness meter. 1
The average form of the secondary particle diameter is a value obtained by crushing under pressure of 0.75 t / cm ² and measuring the average diameter by the air permeation method.

The method for pulverizing the secondary aggregated particles of aluminum hydroxide is not particularly limited, but a general method such as a ball mill for pulverizing powder particles is adopted.

First, the reasons for limiting the numerical values of the aluminum hydroxide of the present invention will be described.

The average particle size measured by the sedimentation method is in the range of more than 8 μm and 30 μm or less. When the average particle size is 8 μm or less, the strength and surface smoothness when formed into a molded article are good, but 8 μm or less and
When it exceeds 30 μm, the resin filling viscosity becomes high. Further 30μ
If m is exceeded, the spinnability of the resin paste will deteriorate, so
When a flow pattern artificial marble is manufactured by the casting method, the flow pattern is easily broken in the middle, and the strength and surface smoothness of the molded product are deteriorated. In addition, BMC and S
It becomes difficult to prevent the separation of the resin and the filler during press molding of the MC.

It is essential that the specific surface area measured by the BET method is 1.5 m ² / g or less, and if it exceeds this, the dispersion of the filler in the resin or the unsaturated polyester resin when cured with a peroxide curing catalyst Causes a significant delay in gel time. It is essential that the resin filling viscosity is 1000 poise or less, and if it exceeds this, it will be difficult to knead the resin and filler or molding by casting, and the target color cannot be increased because the filling amount of the filler cannot be increased. I don't get a feeling of volume,
In BMC and the like, the amount of glass fiber mixed cannot be increased, so that the target strength cannot be obtained, and high filling of the filler cannot be achieved, resulting in poor flow characteristics during pressing.

It is essential that the proportion of particles with a particle size of 75 μm or more is 1% or less, and if it exceeds this, the spinnability of the resin paste deteriorates. Therefore, when manufacturing a flow pattern artificial marble by the casting method. , The flow pattern is easy to cut in the middle,
The surface smoothness of the molded product deteriorates.

It is essential that the whiteness measured with a photoelectric whiteness meter is 95 or more, and if the whiteness is less than this, the obtained molded product is colored in a light yellow or light brown color and has a good color tone suitable for artificial marble. Will not be obtained.

Next, the reasons for limiting the numerical values of the secondary aggregated particles of aluminum hydroxide, which is the raw material to be crushed in the method for producing aluminum hydroxide of the present invention, will be described.

It is essential that the average particle size measured by the sedimentation method is within the range of 30 to 70 μm, and if it is less than 30 μm, the particle size distribution of the ground product becomes too narrow, resulting in an increase in resin filling viscosity, and
If it exceeds 70 μm, the coarse particle residue of the pulverized product increases,
The surface is inferior in smoothness, and it becomes difficult to prevent the separation of the resin and the filler during press molding of BMC and SMC.

The average primary particle diameter obtained by crushing under pressure of 0.75 t / cm ² and measuring the average diameter by the air permeation method is 8 μm.
The average diameter is 8 μm.
The specific surface area when pulverized to more than 30 μm and more than μm, and the resin filling viscosity become high.

Specifically, the average primary particle diameter of aluminum hydroxide is measured by the following method. That is, in a mold (cylindrical crucible type, diameter 30 mm, depth 50 mm) as shown in FIG.
15 g of aluminum hydroxide left for 1 hour in an atmosphere of RH of 65% is charged, and the pressure of 0.75 t / cm ² is applied for 30 seconds by a hydraulic press. Then, aluminum hydroxide is taken out from the mold, put in a bag made of a resin film to loosen a pressure lump by finger pressure, and the resulting crushed powder is measured for its average particle size (brain size) by an air permeation method.

[Action]

The reason why the primary particle size of the precipitated aluminum hydroxide has a great influence on the specific surface area of the pulverized product and the resin filling viscosity is considered as follows. Fig. 2 shows that the average particle size is 70 μm and the average primary particle size is 25 μm. FIG. 3 of the deposited aluminum hydroxide is an electron micrograph of aluminum hydroxide obtained by pulverizing the aluminum hydroxide to a mean particle size of 16 μm with a forced stirring type mill using alumina balls of 5 mmφ. Fig. 4 shows precipitated aluminum hydroxide having an average particle diameter of 42 µm and primary particle average diameter of 15 µm. It is an electron micrograph of the formed aluminum hydroxide. As is clear from the photograph, 1
The average particle size of aluminum hydroxide with an average particle size of 25 μm is 16
Since crushing of the primary particles naturally occurs when the particles are pulverized to a size of μm, the cleavability of aluminum hydroxide causes a plate-like and irregular particle shape, resulting in an increase in viscosity when highly filled with resin. Further, since the primary particles have to be destroyed, the crushing time becomes long, the particle surface becomes rough, and a large amount of chipping particles are generated, so that the specific surface area becomes large. On the other hand, crushing aluminum hydroxide having an average primary particle diameter of 15 μm to an average particle diameter of 16 μm is, so to speak, crushing of secondary agglomerated particles, and there is almost no destruction of primary particles. As for the particle shape, since the rounded particle shape of the primary particles of the precipitated aluminum hydroxide is well maintained, the viscosity when the resin is highly filled is low. Furthermore, since the crushing time is short, the specific surface area is also small.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples shown in Table 1 and Comparative Examples shown in Table 2. Evaluation of the resin / aluminum hydroxide composite composition in the table was performed as follows. .

1. Resin filling viscosity and 2. Dispersion time (blending) Unsaturated polyester resin ^{* 1} 100 parts Aluminum hydroxide 200 parts Stirring and kneading with the above blending is the time until completely paste-like, and the viscosity at that time (using a BS type viscometer, 35 ° C) is the resin filling viscosity. The resin filling viscosity is preferably 1000 poise or less, and the dispersion time is preferably 10 minutes or less.

* 1 Showa High Polymer Co., Ltd. Rigolac 2004 WM-2 3. 3. Color tone of molded product and 4. Gel time (blended) unsaturated polyester resin ^{* 2} 100 parts MEKPO (Methyl ethyl ketone peroxide trade name Permek N NOF CORPORATION) 1 part 6% cobalt naphthenate 0.2 parts aluminum hydroxide 150 parts * 2 Refractive index 1.52, viscosity 18p (25 ° C) Stir kneading with the above composition, continuously measuring the viscosity of the composition in a constant temperature bath at 25 ° C, the time until the viscosity begins to rise due to resin curing Is the gel time.

The gel time is preferably 60 minutes or less.

Also, defoaming and kneading with the above composition, casting in a 3 mφ × 15 mm thick molding die, and curing at room temperature (25 ° C.) overnight, then at 50 ° C., 3
The color tone of the cured product heat-cured for a period of time was measured with a color tester SM-4-CH manufactured by Suga Test Instruments Co., Ltd. and represented by Hunter color tone coordinates Lab. This is the color tone of the molded body. Hunter chromaticity coordinates are represented by (L, a, b), axis L represents lightness, and a and b are perceptual chromaticity indices having side and side, which represent red, green, and yellow, respectively. As artificial marble, b representing yellow is important, and it is preferably 10 or less.

5. Spinnability (blended) unsaturated polyester resin ^{* 2} 100 parts MEKPO (Methyl ethyl ketone peroxide Trade name Permec N Nippon Oil & Fats
1 part 6% Cobalt naphthenate 0.2 part Aluminum hydroxide coarse particles (70 μm) 70 parts Aluminum hydroxide fine particles 160 parts * 2 Refractive index 1.52, viscosity 18p (25 ° C) After stirring and kneading, The resin slurry was scooped with a spatula and the pulling condition when dropped was called the spinnability and judged as follows.

・ Drops in a lump without pulling the thread: × ・ Pulls the thread, but it is easy to break in the middle: △ ・ Pulls the thread and drips smoothly: ○ From these results, the fine-grained aluminum hydroxide according to the present invention has a smaller specific surface area as compared with the conventional one, so that the dispersibility in the resin is good, and the suppression effect against the delay of the gel time when the unsaturated polyester resin is filled. Therefore, the color tone of the molded product is less likely to have a yellowish tint, and since the viscosity when filled with the resin is low, high filling is possible. In addition, since there are few coarse-grained residues, the spinnability is excellent, and it is understood that the flow pattern is not cut off in the middle when the flow pattern artificial marble is manufactured by the casting method.

〔The invention's effect〕

The aluminum hydroxide thus obtained is quality-designed especially as a filler for artificial marble, and exhibits excellent properties when used in this application.

For example, when the aluminum hydroxide of the present invention is used as a filler when an unsaturated polyester resin is filled and a vanity or kitchen countertop is manufactured by a casting method, the dispersibility in the resin is good, and thus the mixture is stirred and kneaded. But in a short time. Further, even if the filler is highly filled to reduce the resin content for the purpose of cost reduction, the viscosity is low, and therefore the casting operation is easy to perform. Further, the curing time of the unsaturated polyester resin is remarkably short as compared with the case where conventional fine-grained aluminum hydroxide is filled, so that the productivity is excellent. in addition,
Since the cured product has little yellowness, a product with a beautiful color tone can be obtained with or without the addition of a pigment.

Due to its excellent spinnability, beautiful flow pattern artificial marble can be obtained.

Further, when a vanity, bathtub or the like is manufactured by a BMC or SMC press molding method, if the aluminum hydroxide of the present invention is used as a filler, high filling is possible and the flow characteristics at the time of pressing are excellent. Further, since the obtained molded body has excellent surface smoothness, it has a high-class feeling and, in addition, has excellent stain resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a mold used in a pressure crushing method for measuring the average primary particle diameter, and FIGS. 2 to 5 are electron micrographs showing the particle structure of aluminum hydroxide.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Kawai 8 Ebisu-cho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Showa Denko KK Yokohama factory (72) Inventor Mitsuhiko Morihira 8 Ebisu-cho, Kanagawa-ku, Yokohama, Showa Denko KK Yokohama factory (56) Reference JP-A-1-275422 (JP, A)

Claims (2)

[Claims] 1. An average particle diameter of more than 8 μm and less than 30 μm measured by a sedimentation method, a specific surface area of less than 1.5 m ² / g measured by a nitrogen adsorption method (BET method), and a viscosity of 10 poise at 20 ° C. Particles having a resin filling viscosity of 1000 poise or less and a particle size of 75 μm or more measured by a Brookfield viscometer at 35 ° C. with a mixture of 100 parts by weight of an unsaturated polyester resin containing 200 parts by weight of aluminum hydroxide. Is 1%
Hereinafter, aluminum hydroxide for artificial marble, which has a whiteness of 95 or more. 2. A secondary agglomerate of aluminum hydroxide having an average particle diameter of 30 to 70 μm, which is composed of primary particles having an average diameter of more than 8 μm and not more than 20 μm measured by a pressure crushing method, is crushed. A method for producing the aluminum hydroxide for artificial marble according to claim 1.