JPS6296566A - Resin molding - Google Patents

Abstract

PURPOSE:To provide a resin molding which does not have a failue in appearance due to weld-mark, etc. and has a galaxy-like appearance, containing a thermoplastic resin and specified lustrous particles. CONSTITUTION:100pts.vol. thermoplastic resin (e.g., PS) is blended with 0.05-5.0 pts.vol. lustrous particles having a mean equivalent diameter of 10-300mum and a mean geometric ratio of 1/8-1 (e.g., Al particles) and optionally 0.1-12.0 pts.vol. colorant (e.g., carbon black), a stabilizer, a parting agent, an antistatic agent, etc. The resulting resin material is molded to obtain a resin molding whose reflectance is increased by at least 15% as compared with the case where no lustrous particle is contained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to cameras, VTRs, OA equipment, electric razors,
Related to resin molded products used for interior and exterior materials, containers, etc. of cosmetics, etc.

[Conventional technology]

Many molded products have been known in which a thermoplastic resin is mixed with, for example, metal particles as a filler to give a glossy appearance and then melt-molded. There are two types of these molded products depending on the shape of the gloss imparting particles. The first is a molded product that has a uniform metallic appearance over its entire surface by filling it with fine to ultrafine metal particles, as disclosed in Japanese Patent Application Laid-Open No. 58-37045. . When manufacturing this molded product by injection molding, the flow cross section of the molten resin in the mold is as shown in Figures 2 and 3. Since a layer 22 that does not contain the resin is formed, a weld mark 23 (FIG. 3) made of only resin is formed at the flange of the flow comrades. Since this weld mark does not contain metal particles, it absorbs light and appears black, significantly detracting from its appearance. Therefore,
Such molded products could not be used as high-grade molded products such as camera exterior covers.

The second type uses metal flake powder with an average equivalent diameter of 30 μm or more and an average shape ratio of 1710 or less. In this molded product, the flakes are damaged by shearing force during kneading and molding of the resin and metal flakes. If it is not destroyed, the weld mark on the molded product will not be noticeable (but if it is destroyed, the weld mark will become noticeable as seen in the first type mentioned above).

Incidentally, the particle size distribution of aluminum flake powder with an average equivalent diameter of 50 μm and an average shape ratio of 1710 or less before and after kneading and forming is shown in the fourth table.
As shown in FIG. In this case as well, the weld mark becomes conspicuous, making it difficult to use it for high-grade molded products with complex shapes.

In addition to weld marks, causes of poor appearance of molded products include uneven gloss, sink marks, silver streaks, etc. For example, if a molded product with a basic wall thickness of 2fi has a local thin wall part of 1.5 w* as shown in FIG.
A step difference of 10 μm appears as uneven gloss. Also,
If there is a local thick wall part of 3,0 Tsuru shown in FIG.
A micrometer level difference occurs and is noticeable as a sink mark.

In order to make such uneven gloss and sink marks less noticeable, attempts have been made to perform high-temperature molding, but high-temperature molding increases molding time and reduces productivity. The uneven gloss and sink marks are somewhat noticeable (but
It cannot be completely erased.

Therefore, as a means to eliminate appearance defects, secondary processing such as painting has been required, and design adjustments have been made to prevent appearance defects, but product design constraints have become extremely large.

Another problem when obtaining a final molded product only by injection molding is that the resin itself has a low surface hardness and is easily scratched. Once scratched, it has a significant impact on the exterior, often detracting from its luxurious appearance.

[Purpose and outline of the invention]

A first object of the present invention is to provide a resin molded product that eliminates appearance defects such as weld marks that are found in conventional resin molded products filled with gloss imparting particles.

The second object of the present invention is to eliminate such weld marks, make appearance defects such as uneven gloss, sink marks, silver streaks, etc. less noticeable, and even if scratches occur, there will be no significant damage to the appearance. Our goal is to provide resin molded products.

The third objective of the present invention is to eliminate such appearance defects and to provide an excellent appearance that can be used for high-quality molded products with complex shapes such as camera exterior covers and VTR covers, in other words, to provide an appearance that shines when scattered in the clear night sky. The object of the present invention is to provide a resin molded product having a galaxy-like appearance (hereinafter referred to as galaxy-like).

A fourth object of the present invention is to provide a resin molded product that can eliminate design constraints for eliminating appearance defects when designing the molded product.

The above purpose is to contain 0.05 to 5.0 parts by volume of glossy particles with an average equivalent diameter of 10 to 300 μm and an average shape ratio of 178 to 1 per 100 parts by volume of a thermoplastic resin, and the reflectance of the particles is higher than the gloss. This is achieved by the resin molded article of the present invention, which is characterized in that the resin molded article of the present invention is 15% or more higher than the state without particles.

[Detailed description and examples of the invention]

The glossy particles used in the present invention (hereinafter referred to as glossy particles) have an average equivalent diameter of 10 to 300 μm and an average shape ratio of 178 to 1.

The average equivalent diameter herein refers to the value obtained by taking the arithmetic mean of the longest diameter and the shortest diameter of the glossy particles as the equivalent diameter, and averaging this equivalent diameter for the test particle group. To measure the equivalent diameter, place the molded product or the molded product dissolved in a solvent on a glass plate.
This can be carried out using a particle distribution measuring device Luzex (trade name, manufactured by Nippon Regulator@).

Moreover, the average shape ratio is the ratio of the longest diameter to the shortest diameter of particles, that is, the arithmetic mean of (shortest diameter)/(longest diameter). To calculate the average shape ratio, a particle distribution measuring device such as Luzex can be used.

Assuming that the glossy particles are spheres, in a system where the distances between the centers of the spheres are all equally distributed, the average gap between the glossy particles is calculated by the following formula (
1).

In formula (1), D: Average gap between glossy particles R: Average equivalent diameter of glossy particles ■: The volume ratio of all glossy particles to the total volume of thermoplastic resin and glossy particles is an index of the conspicuousness of the weld mark. , D becomes larger, the weld mark becomes less noticeable. In other words, the width of the weld mark of a metallic mold is usually 30 mm.
Since it is less than μm, if D is made larger than 35 μm, the weld mark becomes less noticeable.

The optimum average diameter for D to be 35 μm or more and to exhibit a galaxy-like appearance is 10 to 300 μm. If the average equivalent diameter is less than 10 μm, appearance defects such as weld marks will be noticeable, and individual particles will be difficult to visually distinguish, resulting in merely changing color tone. It also has a small effect on making scratches less noticeable.

If the average equivalent diameter exceeds 300 μm, the glossy particles will look like foreign matter, impairing the balance of appearance and making it impossible to obtain a good appearance.

A particularly preferable range of the average equivalent diameter is 20 to 100 μm.

In addition, the flat shape ratio of the glossy particles used in the present invention is 178
~] is because if it is less than 178, the glossy particles are likely to be destroyed during kneading and molding, and weld marks are likely to be noticeable. The average shape ratio is particularly preferably 173-1.

Further, the content of the glossy particles is required to be 0.05 to 5.0 parts by volume, particularly preferably 0.3 to 3.0 parts by volume, based on 100 parts by volume of the thermoplastic resin. If the amount of glossy particles is less than 0.05 part by volume, the particles will be too sparse and will not be very effective in eliminating poor appearance or the conspicuousness of scratches. It becomes impossible to create a galaxy-like appearance because the color tone is determined.

In addition, in the resin molded product of the present invention, another essential condition for eliminating appearance defects and forming an excellent appearance is that the reflectance of the resin molded product is 15% or more than that of a state without glossy particles. One example is that it is elevated.

Here, the reflectance was measured using a photonic sensor (trade name, manufactured by Photonics) by placing the molded product on a support stand, placing the probe vertically, emitting light, and measuring the reflected light. Refers to reflectance.

If the rate of increase in reflectance is less than 15%, it is insufficient to eliminate poor appearance and conspicuous scratches, and the galaxy-like appearance is incomplete. The rate of increase in reflectance is more preferably 25 to 80%.

The base material of the glossy particles used in the present invention does not matter as long as the particles have a glossy surface. For example, at least the surface layer is made of metals such as aluminum, soot, copper, or iron; alloys made of these metals such as brass or stainless steel;
Glossy particles made of mica, certain shells, inorganic or organic polymer crystals that exhibit birefringence, phosphors, etc. can be used.

For example, using aluminum particles will give you a silvery, sparkling appearance, and using brass particles will give you a golden, moist appearance. Moreover, various appearances can be formed by changing the gloss appearance of the surface of the metal particles.

Examples of the thermoplastic resin used in the present invention include acrylic resin, polystyrene resin, polyolefin resin such as polypropylene, vinyl chloride resin, methylpentene resin,
Resins such as polycarbonate resin, copolyester, copolyamide, ABS, etc. may be mixed with each other or may be colored. Further, the resin molded product of the present invention may be added with a coloring agent in an amount of, for example, 0.1 to 12.0 parts per 100 parts by volume of the resin.
By mixing volume parts, more diverse appearances can be formed.

Furthermore, various stabilizers, mold release agents, antistatic agents, flame retardants, etc. that can be added to the thermoplastic resin can be added within a range that does not impair the effects of the present invention.

The resin molded article of the present invention is particularly effective when manufactured by injection molding or injection compression molding, but other melt molding methods such as extrusion molding may be used.

It has been said for some time that silver streaks, which are a type of appearance defect, are likely to occur when molding with a metallic appearance, but it is important to keep the drying time at least 2 hours and to avoid lowering the mold temperature. If this is followed, silver streaks will not occur in the case of a galaxy-like appearance. Further, in the case of a metal-like appearance, a pinpoint gate is likely to cause silver streaks, but in the case of a galaxy-like appearance of the present invention, even a pinpoint gate does not cause silver streaks.

It is preferable to use a composition in which the thermoplastic resin and the glossy particles are mixed in advance by melting the resin, for example, in the form of pellets, in order to uniformly disperse the glossy particles in the molded product.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 A resin molded product 1 shown in FIG. 1 ((a) plan view (b) AA' sectional view) was injection molded. Molded product 1 is a flat plate with a length of 100 m and a width of 801 m1, the basic wall thickness is 1.6n, the thickness of thick parts 2 and 3 is 2.6 mm and 2.0 mm, respectively, and the thickness of thin parts 4 and 5 is 2.6 mm and 2.0 mm, respectively. are 1.211 m, Q, and 31 m, respectively, and the average equivalent diameter is 5 m for 100 volume parts of colored ABS resin.
1 aluminum particle with a diameter of 2 μm and an average shape ratio of 1/3.7
．． It contained 0 parts by volume and was molded under the following molding conditions.

The reflectance of the obtained molded product is 56.7% higher than that without aluminum particles, and there are no appearance defects such as weld marks, uneven gloss, or sink marks, and there are no scratches. The result is a sparkling, high-class appearance that can be used as a camera cover.

Example 2.3 The average equivalent diameter of the aluminum particles used was 92 μm or 210 μm
A molded article was obtained in the same manner as in Example 1 except that the diameter was changed to μm. As in Example 1, the obtained molded product had no appearance defects and had a high-quality appearance.

Examples 4 and 5 The content of aluminum particles was determined based on 100 parts by volume of ABS resin.
Example 1 except that it was changed to 0.1 part by volume or 2.5 parts by volume
A molded article was obtained in the same manner as above. As in Example 1, the obtained molded product had no appearance defects and had a high-quality appearance.

Examples 6 and 7 The average shape ratio of aluminum particles was 1/7.2 or 171.
A molded article was obtained in the same manner as in Example 1 except that the sample was changed to No. 6.

The obtained molded product had no defects in appearance as in Example 1, and
It had a high-class appearance.

Example 8.9 100 parts by volume of colored polycarbonate resin and average shape ratio of 1
The molded product of Example 1 was made using 1.5 parts by volume of two types of aluminum particles: /1.6 (average equivalent diameter 42 μm) and 1/7.2 (average equivalent diameter 50 μm). The reflectance increase rate of the molded product was 28% for the 1/1.6 product, and 28% for the 1/1.6 product.
7.2 was 97%. As in Example 1, the obtained molded product had no defects in appearance and had a high-quality appearance.

Comparative Example 1 Average equivalent diameter 8 μm for 100 volume parts of colored ABS resin
, aluminum particles with an average shape ratio of 1/1.4 were
03 parts by volume was contained, and molding was carried out under the same molding conditions as in Example 1.

The reflectance of the obtained molded article was 7% higher than that without aluminum particles.

However, welds, uneven gloss, sink marks, etc. were noticeable, and the scratches were not much different from ordinary ABS, so it could not be used as a material with a high-class appearance.

Comparative Example 2 The same procedure as in Example 1 was carried out using A without aluminum particles.
This was done using BS resin. The unevenness, sink marks, etc. were clearly noticeable and the product could not be used as a product.

(Surface hardness 3B) [Effects of the invention] The resin molded product of the present invention has no weld marks, no appearance defects due to uneven gloss, sink marks, silver streaks, etc., and no significant damage to the appearance due to scratches, which could not be achieved conventionally. It exhibits a galaxy-like appearance that can be used for high-quality molded products such as camera exterior covers, typewriter exteriors, and OAi device exteriors, which have not been available before, making it possible to expand the boundaries of plastic exterior design. In particular, the effect is remarkable when dye-colored thermoplastic resin is used, and it can be applied to products with complex shapes.

In addition, design constraints for alleviating appearance defects are removed, the degree of freedom in design is expanded, and productivity is high.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of the resin molded product of the present invention produced in the example, and FIG. 1(b) is A-A in FIG. 1(a).
'This is a cross-sectional view. Figure 2 is a cross-sectional view of the flow of a conventional metal-filled resin, Figure 3 is a cross-sectional view of the metal-filled resin after molding, and Figures 4 and 5 are a flow diagram of a conventional metal-filled resin using glossy particles with an average shape ratio of 1/10 or less. It is a graph showing particle size distribution (frequency distribution) before and after molding.
6 and 7 are cross-sectional views showing locations where uneven gloss, sink marks, etc. occur in a resin molded product, respectively. 1... Resin molded product, 2.3... Thick wall part, 4.5...
- Thin wall part, 21...Metal powder, 22...Layer made only of resin, 23...Weld mark. Agent Patent Attorney Minoru Yamashita Children Figure 1 (0) (b) 81 Figure 2 Figure 3 Kusu

Claims (1)

[Claims] Average equivalent diameter 10 to 100 parts by volume of thermoplastic resin
Contains 0.05 to 5.0 parts by volume of glossy particles with a diameter of 300 μm and an average shape ratio of 1/8 to 1, and the reflectance is increased by 15% or more compared to the state without the glossy particles. Characteristic resin molded products.