JP2786898B2 - Method for producing a synthetic resin molded article having an uneven thickness with excellent matting properties - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a synthetic resin molded article having excellent matting properties.

(Prior Art) Conventionally, methods for reducing the surface gloss of a synthetic resin molded product include (1) a method of performing fine unevenness processing on a surface of a mold such as a mold, and (2) a method of using an inorganic or organic fine powder. A method of adding to a synthetic resin (for example, JP-A-58-52339,
JP-A-8-113242, JP-A-59-193950, JP-A-63
-260960).

(Problems to be Solved by the Invention) However, in these conventional methods, not only the method (1) does not provide a sufficient matting effect, but also a thick-walled part in the case of a molded article having an uneven thickness. Part of the surface does not have a good matte shape, and in the method (2), the fluidity of the synthetic resin material,
The gloss of the molded product changes due to molding pressure, mold temperature, etc.
Not only is it difficult to obtain a uniform matte surface, but also in the case of a molded product having an uneven thickness, there is a problem that a part of the surface of the thick portion does not have a good matte shape.

Therefore, an object of the present invention is to provide a method for producing a synthetic resin molded article having an excellent matting property and having a uniform matte surface even in the case of a molded article having an uneven thickness, eliminating the above-mentioned disadvantages of the prior art. Is to do.

(Means for Solving the Problems) The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, using a mold having fine unevenness on the cavity surface and a molding material containing fine powder in combination. It has been found that the present invention can be achieved by molding, and the present invention has been completed.

That is, the gist of the present invention is that, when producing a synthetic resin molded article having an uneven thickness, the particle size is 1 to 30.
A synthetic resin material containing polymer fine particles having a weight distribution of particles having a particle size of less than 10 μm and a particle size of less than 10 μm is subjected to a fine unevenness treatment with a surface roughness of 1 to 50 μm on at least a part of the cavity surface. A method for producing a synthetic resin molded article having an uneven thickness with excellent matting characteristics, wherein the molded article is filled in a molding die and injection molded.

 Hereinafter, the present invention will be described in detail.

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

As the polymer fine particles in the present invention, fine powder obtained by pulverizing a crosslinked or high polymerization degree resin, or JP-A-48-49838
And high-polymerized polymer particles produced by the method and suspension method disclosed in JP-A-62-307238 and JP-A-62-307238. From the viewpoints of mechanical properties and matting properties of molded articles containing these fine powders, crosslinked polymethylmethacrylate spherical fine particles, crosslinked polystyrene spherical fine particles, and high polymerization type polymethylmethacrylate spherical fine particles are preferably used.

The polymer fine particles in the present invention are particles having a particle size of 1 to 30 μm, preferably 1 to 25 μm, and a particle size of less than 10 μm from the viewpoint of the stability of the matte appearance and the uniformity of the matte surface with respect to the change in the fine particle content. Occupies 60% or more, preferably 75% or more in weight distribution. The average particle diameter of the polymer fine particles is preferably less than 10 μm. It is preferable in terms of uniformity to use a fine powder having a particle size that matches the roughness of the mold. The average particle size here means a particle size equivalent to 50% of the total weight by integrating each particle size by weight. For example, a transmission type particle size distribution measuring device by gravity sedimentation method (manufactured by Seishin Enterprise Co., Ltd .: SKA5000), etc. Can be measured. Spherical fine particles are preferably used from the viewpoint of the uniformity of the matting state and the texture, and a narrower particle size distribution is more preferably used because uniform matting properties can be obtained. If the particle size of the weight fine particles exceeds 30 μm or if the particles having a particle size of less than 10 μm are less than 60% in weight distribution, the surface will not be fine and uniform, which is not preferable. In addition,
It is not necessary to add a large amount because the surface of the mold is roughened, and it depends on the intended use.To obtain good anti-glare properties, 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight is synthesized. It is desirable to mix it per 100 parts by weight of resin.

The mold of the present invention in which the surface of the cavity is subjected to a fine unevenness treatment, a chemical etching method, using a surface processing means such as a sand blast method, at least a part of the cavity surface has a surface roughness of 1 to 50 μm, preferably Is 1
This refers to a molded body with irregularities of 10μm, with irregularities all over the cavity surface, irregularities only on the cavity surface corresponding to the visible part of the molded product, or uneven thickness molding It is assumed that only the cavity surface corresponding to the thick portion where the matte state of the product is not uniform is subjected to unevenness treatment. The surface roughness as referred to in the present invention means a center line average roughness (Ra). If the roughness of the surface of the cavity is less than 1 μm, the surface of the molded product will not be in a good matte state, which is not preferable. If the depth of the roughness of the surface of the cavity exceeds 50 μm, the surface of the molded product will be poor. It is not preferable because a fine and uniform matte state is not obtained.

In the production method of the present invention, the synthetic resin has a particle size of 1 to 30 μm.
m, or a synthetic resin material containing fine powder such as a mixture obtained by stirring and mixing polymer fine particles with a Hensyl mixer or the like, and then mixing and extruding the mixture into a pellet form into a molding die. In obtaining a molded product, it is possible to obtain a synthetic resin molded product having excellent matting properties by molding using the above-mentioned mold in which at least a part of the cavity surface is subjected to a fine unevenness treatment.

As the injection molding method of the synthetic resin molded article in the present invention, a commonly used injection molding method, injection compression molding method, or the like can be applied. As for the molding conditions, molding conditions suitable for the type of the synthetic resin can be adopted, and the unevenness of the molding die and the fine powder in the synthetic resin material are combined to have a uniform matte surface after molding. it can.

(Effects of the Invention) As described above, according to the present invention, since a molding method in which fine irregularities are applied to the cavity surface and a synthetic resin material containing fine powder are used in combination, a general method is used. It is useful because a synthetic resin molded article having a uniform matte appearance and excellent matting properties can be easily manufactured even if the molded article has an uneven wall thickness due to product design, strength, and the like.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples.

In Examples and Comparative Examples, “%” and “parts” all represent “% by weight” and “parts by weight”, respectively.
Further, the performance of the synthetic resin molded products obtained in the examples and comparative examples was measured and evaluated by the following methods.

Surface condition A fluorescent lamp was reflected on a sample in a room and visually observed, and the matte state of the sample was represented by the following symbols.

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

Δ: The outline of the fluorescent lamp is recognized but unclear, and the surface has irregularities.

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

Glossiness Measured according to JISK7105 glossiness meter (Suga Test Instruments Co., Ltd .: Digital variable angle glossmeter UGV-40), 60 ゜ -6
Measured at 0 ° reflection.

Surface roughness Surface roughness meter based on JISB0601 (Kosaka Laboratory Co., Ltd .;
Center line average roughness (Ra) by surface roughness measuring instrument SE-30D)
Was measured.

Example 1 The polymerization degree was 930 based on 100 parts of polymethyl methacrylate.
0 and a particle size distribution of 1 to 24 μm, and an average particle size of 7 μm (10
Using a molding material filled with 5 parts of highly polymerized polymethyl methacrylate fine particles having a particle size of less than μm (82% by weight distribution) (manufactured by Sekisui Chemical Co., Ltd .: Technopolymer MB-8, true specific gravity 1.19). Gold having a cavity with a thickness of 2 mm and a thickness of 4 mm as shown in FIGS. 1 and 2 and having a thickness of 4 mm, and the entire surface of the cavity corresponding to the outer portion of the molded product is subjected to 1 μm unevenness treatment. Molding is performed with an injection molding machine equipped with a mold (manufactured by Sumitomo Heavy Industries, Ltd .: Neomat 350/120) under the conditions of a molding temperature of 200 to 240 ° C and a mold temperature of 50 ° C to form a cylindrical container having one bottom surface. Product was obtained.

The performance evaluation results of these molded products are shown in Table 1. As a result, a molded product having a uniform matte surface over the entire surface of the uneven thickness molded product was obtained.

Example 2 A polymerization degree of 900 was added to 100 parts of polymethyl methacrylate.
0 and a particle size distribution of 1 to 20 μm, and an average particle size of 4.5 μm (10
Except for using a molding material filled with 14 parts of highly polymerized polymethyl methacrylate fine particles having a particle size of less than 95 μm and a weight distribution of 95%) and 1 part of titanium oxide powder (R-680, manufactured by Ishihara Sangyo Co., Ltd.). Injection molding in the same manner as in Example 1,
A molded product in the shape of a cylindrical container was obtained.

The performance evaluation results of these molded products are shown in Table 1. As a result, a molded product having a uniform matte surface over the entire surface of the uneven thickness molded product was obtained.

Example 3 2 to 40 μm per 100 parts of polymethyl methacrylate
Crosslinked polymethyl methacrylate fine powder (Microsphere M, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) having a particle size distribution of m and an average particle size of 11 μm (particles having a particle size of less than 10 μm are 65% by weight distribution).
-305) is filled with 5 parts of molding material, and the surface roughness of the mold is
Except for 5.0 μm, injection molding was performed in the same manner as in Example 1 to obtain a cylindrical container-shaped molded product.

The performance evaluation results of these molded products are shown in Table 1. As a result, a molded product having a uniform matte surface over the entire surface of the uneven thickness molded product was obtained.

Comparative Example 1 Injection molding was performed in the same manner as in Example 1 except that polymethyl methacrylate that was not filled with fine powder was used as a molding material to obtain a molded product in the shape of an uneven thickness cylindrical container.

The performance evaluation results of these molded products are shown in Table 1. As a result, a good matte surface was not formed in the thick portion due to uneven shrinkage of the resin in the thickness direction, and the mattability of the uneven thickness molded product was uneven. The surface with the surface was shown.

Comparative Example 2 A molded product in the shape of an uneven thickness cylindrical container 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 molded product surface was uneven at the thick portion and the thin portion of the molded product, and uneven gloss was observed over the entire surface of the molded product. The erased state was indicated.

[Brief description of the drawings]

FIG. 1 is a perspective view of an uneven thickness cylindrical container shape which is one embodiment of the uneven thickness shape, and FIG. 2 is a sectional view thereof.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Joe Yuzu 3-8-2 Nihombashi, Chuo-ku, Tokyo Examiner at Kyowa Gas Chemical Industry Co., Ltd. Tomoya Kato (56) References JP-A-62-95345 JP, A) JP-A-61-271302 (JP, A) JP-A-56-59228 (JP, A) U.S. Pat.

Claims (1)

(57) [Claims] 1. A synthetic resin containing a polymer fine particle having a particle size of 1 to 30 μm and a particle size of less than 10 μm in a weight distribution of 60% or more in producing a synthetic resin molded article having an uneven wall thickness. Injection molding by filling the material into a mold having at least a part of the cavity surface subjected to a fine unevenness treatment having a surface roughness of 1 to 50 μm and injection molding, characterized by an excellent matting property. The method for producing a synthetic resin molded product of the above.