JPH0387213A - Manufacture of synthetic resin molded product of superior flatting properties - Google Patents

Abstract

PURPOSE:To provide a flatting surface even in case of an uneven wall-shaped molded product by using a mold with fine recess and projection processing on its cavity and molding a molding material containing fine powder. CONSTITUTION:When a molded product is manufactured by filling a synthetic resin material containing fine powder of 1 - 50mum grain diameter in a mold, a mold with fine recess and projection processing applied at least on a part of the cavity surface is used for molding. As for the synthetic resin, acryl resin is preferred, and as for the fine powder, polymerized fine particles are preferred, and spherical particles of crosslinking polymethyl methacrylate crosslinking polystyrene and highly polymerized type polymethyl methacrylate are used. The mold with surface roughness of 1 - 50mum, preferably 1 - 10mum formed at least on a part of the cavity surface formed by means of the chemical etching process, and blast process or the like is used, and the injection molding process is preferred from the viewpoints of productivity and flatting surface properties.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a synthetic resin molded article with excellent matte properties.

(Prior art) Conventionally, methods for reducing the surface gloss of synthetic resin molded products include (1) applying fine irregularities to the surface of a mold such as a metal mold, (2) applying inorganic or organic fine powder, etc. Addition method to synthetic resin (for example, JP-A-58-52339, JP-A-58-113242, JP-A-59-1939)
50, Japanese Unexamined Patent Publication No. 63-260960), etc. are known. (Problems to be Solved by the Invention) However, with these conventional methods, (method 11) not only does not provide a sufficient matting effect, but also has problems with thick-walled parts in the case of molded products with uneven thickness. Some parts of the surface do not have a good matte finish, and in method (2), the glossiness of the molded product changes depending on the fluidity of the synthetic resin material, molding pressure, mold temperature, etc., and it is difficult to obtain a uniform matte surface. Not only is it difficult to obtain, but in the case of molded products with uneven thickness, there are also problems such as a part of the surface of the thick wall portion not having a good matte finish.

Therefore, an object of the present invention is to provide a method for manufacturing a synthetic resin molded product that eliminates the drawbacks of the above-mentioned prior art, has excellent matte properties, and has a uniform matte surface even in the case of a molded product with uneven thickness. It's about doing.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the inventors of the present invention used a mold with a cavity surface treated with fine irregularities in combination with a molding material containing fine powder. It was discovered that the present invention can be achieved by forming the bottom shape, and the present invention was completed.

That is, the gist of the present invention is that the particle size is 1 to 50.
When a mold is filled with a synthetic resin material containing μm fine powder to obtain a molded product, a mold with a fine unevenness treatment applied to at least a portion of the cavity surface is used to create a matte bottom shape. This is a method for manufacturing synthetic resin molded products with excellent properties.

The present invention will be explained in detail below.

As the synthetic resin in the present invention, thermoplastic resins such as acrylic resin, polycarbonate resin, styrene resin, ABS resin, and vinyl chloride resin, and thermosetting resins such as epoxy resin, phenol resin, and unsaturated polyester resin can be used. Acrylic resin is preferably used in consideration of beauty, injection moldability, etc.

The fine powder of the present invention is not particularly limited, and inorganic and organic fine powders can be used.

Specific examples of inorganic fine powders include fine powders and particles of silica, calcium carbonate, aluminum, barium sulfate, titanium oxide, etc., and organic X! Specific examples of the powder include fine powder obtained by pulverizing a crosslinked or highly polymerized resin, or by the formulation and suspension method shown in Japanese Patent Application Laid-Open No. 48-49838, Japanese Patent Application No. 62-307238, etc. Examples include crosslinked or highly polymerized polymer fine particles produced.

From the viewpoint of mechanical properties and matte properties of molded products containing these fine powders, it is preferable to use polymer fine particles, such as cross-linked polymethyl methacrylate spherical fine particles, cross-linked polystyrene spherical fine particles, and high polymerization degree type polymethyl methacrylate spherical fine particles. Fine particles are preferably used.

The particle size of the fine powder used in the present invention is 1 to 50 μm,
Preferably it is 1 to 30 μm, and the average particle size is 3 to 25 μm.
μm, preferably 3 to IO μm, and more preferably the particle size is 1 to 30 μm, preferably 1 to IO μm, from the viewpoint of stability of the matte appearance against fluctuations in the fine powder content and uniformity of the matte surface. Particles in the range of 25 μm and less than 10 μm in diameter account for 60% or more, preferably 75% or more of the weight distribution. From the viewpoint of uniformity, it is preferable to use a fine powder having a particle size that matches the roughness of the unevenness of the mold. The average particle size here means the particle size that corresponds to 50% of the total weight by adding up each particle size by weight.
5KA5000), etc. Spherical fine particles are preferably used from the viewpoint of uniformity of matte state and texture, and narrower particle size distribution is more preferably used because uniform matteness can be obtained. Particle size of polymer fine particles is 50μ
If the average particle size exceeds m or 25 μm, the surface will not become fine and uniformly matte, which is not preferable. In addition, since the surface of the mold is textured, there is no need to add a large amount, and the amount varies depending on the intended use, but in order to obtain good anti-glare properties, it is preferably 0.5 to 15 parts by weight. It is desirable to blend 1 to 10 parts by weight per 100 parts by weight of the synthetic resin.

The mold in which the cavity surface of the present invention has been subjected to fine unevenness treatment means that at least a portion of the cavity surface has a surface roughness of 1 to 50 μm using a surface treatment method such as a chemical etching method or a sandblasting method. Preferably 1~
This refers to a mold that has an unevenness of 10 μm, such as one in which the entire surface of the cavity is treated with unevenness, one in which only the cavity surface corresponding to the visible part of the molded product is treated with unevenness, or molded with uneven thickness. This includes products in which only the cavity surface corresponding to the thick wall part where the matte state of the product does not appear uniformly is textured. The surface roughness as used in the present invention means center line average roughness (Ra). If the roughness of the unevenness on the cavity surface is less than 1 μm, the surface of the molded product will not be in a good matte state, which is undesirable. If the depth of the unevenness on the cavity surface exceeds 50 μm, the surface of the molded product will be It is not desirable because it does not become a fine and uniform matte state.

In the production method of the present invention, the synthetic resin has a particle size of 1 to 50 μm.
A mold is filled with a synthetic resin material containing fine powder, such as one obtained by stirring and mixing the above-mentioned fine powder of m with a Henshil mixer or the like, or a mixture made by extrusion molding into pellets after mixing. When obtaining molded products,
A synthetic resin molded article with excellent matteness can be obtained by molding using the mold described above, in which at least a portion of the cavity surface has been subjected to fine unevenness treatment.

As a molding method for the synthetic resin molded article in the present invention, commonly used injection molding methods, compression molding methods, injection compression molding methods, etc. can be applied, but the injection molding method is preferably used from the viewpoint of productivity and matte surface property. It will be done.

In addition, molding conditions suitable for the type of synthetic resin can be adopted, and the unevenness of the mold and the fine powder in the synthetic resin material combine to ensure that the surface has a uniform matte state after molding. can.

(Effects of the Invention) As described above, according to the present invention, the molding method uses a mold in which the cavity surface is treated with fine irregularities and a synthetic resin material containing fine powder. The present invention is useful because it allows easy production of synthetic resin molded products with uniform matte appearance and excellent matte properties even if the shape of the molded product has uneven thickness due to product design, strength, etc.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, "%" and "parts" in Examples and Comparative Examples all represent "% by weight" and "Parts by weight", respectively, and the performance of the synthetic resin molded products obtained in Examples and Comparative Examples was determined by the following method. Measured and evaluated.

Table 10 Visual observation by reflecting a fluorescent light onto the sample in the L toilet room,
The matte state of the sample was expressed by the following symbol.

○...The outline of the fluorescent lamp is not recognized or is hardly recognized.

△: The outline of the fluorescent lamp is recognized, but it is unclear, and the surface is uneven.

×: The outline of the fluorescent lamp is clearly recognized, and there are almost no irregularities on the surface.

The gloss was measured at 60°-600 reflection using a gloss meter (Suga Test Instruments - Two Digital Variable Angle Gloss Meter UGV-40) in accordance with the gloss measurement of JIS K7105.

The centerline average roughness (Ra) was measured using a surface roughness meter (-Koita Research Institute; Surface Roughness Measuring Instrument 5E-30D) in accordance with JISBO601.

Example 1 Polymerization degree 9 for 100 parts of polymethyl methacrylate
300 with a particle size distribution of 1 to 24 μm and an average particle size of 7 μm
m (particles less than 10 μm are 82% in weight distribution) high polymerization degree polymethyl methacrylate fine particles (Tasui Kaseihin Kogyo ■
Using a molding material filled with 5 parts of Technopolymer MB-8 (true specific gravity: 1.19), a cavity shaped like an unevenly walled cylindrical container with a thin wall part of 2 fl and a thick wall part of 4 km as shown in Figs. 1 and 2 was made. An injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.: Neomaso) 3 equipped with a mold in which the entire surface of the cavity corresponding to the outer part of the molded product is treated with lIIm irregularities.
50/120) at a molding temperature of 200 to 240°C and a mold temperature of 50°C to obtain a molded product in the shape of a cylindrical container with a -bottom surface.

The performance evaluation results of these molded products are shown in Table 1, and the uneven thickness molded products had a uniform matte surface over the entire surface.

Example 2 Polymerization degree 9 for 100 parts of polymethyl methacrylate
000 with a particle size distribution of 1 to 20 μm and an average particle size of 4.
Other than using a molding material filled with 14 parts of highly polymerized polymethyl methacrylate fine particles of 5 μm (particles less than 10 μm are 95% in weight distribution) and 1 part of titanium oxide powder (manufactured by Ishiya Sangyo ■: R-680). was injection molded in the same manner as in Example 1 to obtain a molded product in the shape of a cylindrical container.

The performance evaluation results of these molded products are shown in Table 1, and the uneven thickness molded products had a uniform matte surface over the entire surface.

Example 3 2 to 40 parts per 100 parts of polymethyl methacrylate
Five parts of cross-linked polymethyl methacrylate fine powder (manufactured by Matsumoto Yushi Pharmaceutical Group Co., Ltd.: Microsphere-M-305) with a particle size distribution of 11 μm and an average particle diameter of 11 μm (particles less than 10 μm account for 65% of the weight distribution) was filled. The molding material was injection molded in the same manner as in Example 1 except that the surface roughness of the mold was 5.0 μm to obtain a molded product in the shape of a cylindrical container.

The performance evaluation results of these molded products are shown in Table 1, and the uneven thickness molded products had a uniform matte surface over the entire surface.

Comparative Example 1 A molded article in the shape of a cylindrical container with uneven thickness was obtained by injection molding in the same manner as in Example 1 except that polymethyl methacrylate not filled with fine powder was used as the molding material.

The performance evaluation results of these molded products are shown in Table 1. Due to uneven shrinkage of the resin in the thickness direction, a good matte surface cannot be formed in thick-walled parts, resulting in uneven matte properties of molded products with uneven thickness. The surface with .

Comparative Example 2 A molded product in the shape of a cylindrical container with uneven thickness was obtained in the same manner as in Example 1 except that the mold surface was a mirror surface.

The performance evaluation results of these molded products are shown in Table 1. The dispersion state of the fine powder on the surface of the molded product is uneven between the thick and thin parts of the molded product, resulting in uneven gloss over the entire surface of the molded product. Indicates erased state.

4,

[Brief explanation of drawings]

Figure 1 shows An uneven thickness circle that is an embodiment of an uneven thickness shape Perspective view of cylindrical container shape, Figure 2 shows its cross-sectional view. Shown below.

Claims (6)

[Claims] (1) When filling a mold with a synthetic resin material containing fine powder with a particle size of 1 to 50 μm to obtain a molded product, use a mold that has at least a portion of the cavity surface treated with fine irregularities. 1. A method for producing a synthetic resin molded product with excellent matte properties. (2) The manufacturing method according to claim 1, wherein the fine irregularities have a surface roughness of 1 to 50 μm. (3) The manufacturing method according to claim 1, wherein the fine powder is a polymer fine particle having a particle size of 1 to 10 μm. (4) The manufacturing method according to claim 1, which comprises injection molding. (5) The manufacturing method according to claim 1, wherein the synthetic resin molded product is a molded product having uneven thickness. (6) The manufacturing method according to any one of claims 1 to 5, wherein the synthetic resin is an acrylic resin.