JPS63297430A - Synthetic polymer molded article - Google Patents

Abstract

PURPOSE:To obtain the titled molded article having excellent dispersibility of filler, moldability and mechanical strength, free from generation of matte unevenness, giving matte feeling and suitable as a container for cosmetic, etc.,, by compounding a specific organic filler to a thermoplastic polymer. CONSTITUTION:The objective molded article can be produced by compounding (A) a thermoplastic polymer such as polyethylene, polypropylene, polystyrene, AS, ABS, MMA, MS, polycarbonate, polyacetal, nylon, etc., with (B) 0.5-45wt.% of beads of crosslinked polystyrene, acrylic polymer or polyethylene having particle diameter of 3-600mum and molding the composition by injection molding, extrusion molding, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to various synthetic resin containers such as cosmetic containers and other synthetic resin molded articles having matte surfaces.

(Prior art) When considering the design of synthetic resin containers, etc., containers with matte surfaces are used to give a softer color tone or create contrast with glossy parts. etc. can be seen in large numbers. As a means of forming a matte on the surface of a synthetic resin container, etc., there are two methods: ■ Making the mold surface equivalent to the cavity uneven by some means, ■ Applying a matte coating to the molded product, ■ Sandblasting the molded product. (1) Transferring the matte onto the molded product; (2) Adding a highly heat-resistant inorganic filler or organic piece to the molding material as a matting agent. That is, in the case of (■) above, the mold surface corresponding to the cavity is made finely uneven by sandblasting or electric discharge machining, and molten resin is poured into the mold cavity.
This method involves cooling, solidifying, and transferring the unevenness. In the case of (2), a predetermined amount of a matting agent is mixed into the paint, and the paint is sprayed onto the effective surface of the molded article using an air gun or the like, and then dried. In the case of ■, blow the desired mesh sand onto the molded product with strong air force, reproduce the unevenness on the surface of the molded product with sand particles, blow the adhering sand with air, then wash with water, This is a drying method. In the case of (2), the matte-printed plastic film is transferred onto a synthetic resin molded product using a hot rubber roll or the like. ■In the case of
Inorganic fillers such as calcium carbonate are used as matting agents, and beads of polyethylene, polystyrene, MMA, etc. are used as organic matting agents.

(Problem to be Solved by the Invention) In the case of (2) above, productivity is relatively high because a mat is formed on the surface of the molded product at the same time as molding with the mold.
If the molding conditions are poor, there are drawbacks such as poor reproducibility of the unevenness and uneven gloss depending on the location of the product. Particularly in areas where sink marks occur on the product, such as near thick corners, the transfer effect on the mold surface may be lost and the matte feel may not appear in some areas. Furthermore, when a small amount of air remains in the cavity, etc., the transfer accuracy on the mold surface deteriorates and mud unevenness occurs. Furthermore, when the mold is released, depending on the shape of the molded product, it may easily scratch, so it is not suitable for complex shapes and is limited to relatively flat shapes. Moreover, the product is difficult to handle because scratches and scratches are likely to occur during handling. In blow molding, fine irregularities cannot be reproduced due to air pressure limitations. In the case of (2), when applying matte coating to the molded product, it is necessary to mask functional parts such as caps and bottle threads in advance, resulting in poor productivity and high costs. In the case of (2), after sand is blown with air, the blown surface is blown with air, and then washing, drying, etc. is a laborious process, resulting in high costs.

Also, the sandblasted surface is easily scratched, and the quality is poor considering the high cost. In case (2), thermal transfer is limited to surfaces with simple shapes such as flat surfaces and circumferential surfaces of the molded product, resulting in a partially matte appearance of the product.

Also, because high heat and pressure are applied locally to the product,
Distortion occurs only in the surface layer, and cracks occur on the surface over time or due to the adhesion of chemicals such as alcohol. In the case of ■, if an inorganic filler with high heat resistance is mixed into the molding material as a matting agent, the shape of the inorganic filler is a crystal such as a plate or needle, and although it has high heat resistance, it may cause damage to the molding material. It has very poor dispersibility and adhesion, and there are problems such as poor appearance and mud unevenness depending on the molding conditions and location. In particular, when calcium carbonate is used as a matting agent and is filled into a molding material, there are problems such as rusting of the mold and filling of air vent gaps due to the gas generated by the calcium carbonate. In addition, there are product stains such as red rust, material shortages, and fading phenomena, and the cost of the mold increases due to the use of stainless steel materials to prevent mold corrosion.

On the other hand, when organic beads such as polyethylene, polystyrene, and MMA are filled into a molding material as a matting agent, the heat resistance is 90% even though the beads themselves are finely spherical.
The disadvantage is that the temperature is only about 100°C to 100°C, and the beads dissolve when kneaded with the resin, making them useless.

The present invention was made to solve the above problems all at once, and as a condition for the matting agent to be filled into the molding material, (
b) Uniform, thin particles with a constant shape (spherical);
(b) Good dispersibility in resin, (c) High heat resistance, (d) High resin adhesion and no separation from resin even under different molding conditions. By developing a specific organic filler, it is possible to obtain molded products with very good dispersibility, less occurrence of mud spots, and a beautiful matte feel, as well as increased mechanical strength such as surface hardness and bending strength. The purpose of the present invention is to provide an economical synthetic resin molded product with good moldability and high production efficiency.

(Means for Solving the Problems) The synthetic resin molded product according to the present invention is made of polyethylene, polypropylene, polystyrene, AS, ASS, MMAlM.
S, polycarbonate, polyacetal, nylon, or other thermoplastic resin mixed with 0.5 to 45% by weight of crosslinked polystyrene beads, crosslinked acrylic beads, and crosslinked polyethylene beads with a particle size of 3μ to 600μ, alone or in combination. It is.

The thermoplastic resin used in the present invention can be polyethylene, polypropylene, polystyrene,
AS, ABSlMMA, MS; Various resins such as polycarbonate, polyacetal, and nylon are selected. In addition, we decided to use cross-linked polystyrene beads, cross-linked acrylic beads, and cross-linked polyethylene beads as matting agents because they are all fine, transparent, perfectly spherical particles with a particle size of 3 to 600μ, and have a high surface hardness. (9H),
This is because it has properties such as excellent surface smoothness, excellent heat resistance of 300° C., very good chemical resistance, ability to be colored, and a matting effect.

The synthetic resin molded product may be various synthetic resin containers such as cosmetic containers molded by injection molding, extrusion molding, blow molding, etc., or molded products in various shapes for various uses. When blending the above-mentioned crosslinked polymer beads into thermoplastic resins such as polyethylene, polypropylene, and polystyrene, it is important to select beads that have good dispersibility in the resin and have high adhesion to the resin. can be,
Examples include polyethylene resin and crosslinked polyethylene beads, and polystyrene and crosslinked polystyrene beads. In addition, the particle size of the crosslinked polymer beads was specified to be in the range of 3μ to 600μ because this range is not only easy to manufacture, but also has high surface hardness and relatively uniform thin particles. This is based on the fact that it can be obtained with a constant shape (spherical), has good dispersibility with resin, and has high adhesion.

Particles with a particle size of less than 3 microns not only have problems in manufacturing technology, but also have good dispersibility with resin, but have a small surface area, so there are problems with adhesion strength with resin, etc. On the other hand, if the particle size exceeds 600 μm, the surface area increases and the adhesion strength with the resin increases, but not only does the dispersibility in the resin deteriorate, but there is also a problem with the surface strength of the beads themselves. Furthermore, each of the crosslinked polymer beads described above is blended singly in the thermoplastic resin, but the invention is not necessarily limited to this, and for example, two or more types of crosslinked polymer beads may be blended in combination. The reason why the blending ratio of the crosslinked polymer beads is specified to be in the range of 0.5 to 45% by weight is because if the blending ratio is too small, the beautiful matte feeling on the surface of the molded product intended by the present invention cannot be obtained. On the other hand, if the amount is too large, the dispersibility and adhesion to the resin will not only deteriorate, but it will also cause problems in molding and increase costs.

<Example 1> Polyethylene resin 80fflffi%, particle size 200μ
20% cross-linked polyethylene beads were blended.

This polyethylene resin containing cross-linked polyethylene beads was melted and dispersed using an injection molding machine under the temperature conditions necessary for molding, and then molded under a predetermined molding pressure.
A polyethylene cap 1 shown in ) was obtained. Figure 1 (
b) shows an enlarged sectional view of the cap 1, 2 shows the polyethylene resin after molding, and 3 shows the crosslinked polyethylene beads. The surface of the obtained polyethylene cap 1 had a beautiful matte feel with good dispersibility and no muddy unevenness.

<Example 2> As in Example 1, 5% by weight of crosslinked acrylic beads having a particle size of 50 μm were blended with 95% by weight of impact-resistant polystyrene resin. A powder container 10 shown in FIG. 2 was molded using a blow molding machine. The surface of the container 10 is the same as in Example 1.
A beautiful matte finish with no mud spots was obtained. Especially Ki? The surface of the fitting portion 10a with the protrusion 11 is a thin, uniform spherical protrusion with good sliding properties, resulting in a ball bearing effect and improving the operability of the fitting cap 11.

<Example 3> Similarly to Example 1, 75% by weight of polypropylene resin,
15% by weight of crosslinked polystyrene beads with a particle size of 15μ were blended. A lipstick cap 21 shown in FIG. 3 was molded using an injection molding machine. As in Example 1, the surface of the cap 21 had a beautiful matte appearance without muddy unevenness. In particular, the surface of the fitting part 22 with the lipstick main body 20 is as shown in Example 2.
The same effect as above was obtained, and the operability of the cap 21 was improved.

(Effects of the Invention) As is clear from the above description, the present invention is applicable to polyethylene, polypropylene, polystyrene, and AS.

Thermoplastic resins such as ABS, MMA, MS, polycarbonate, polyacetal, nylon, etc., with particle sizes of 3 μ to 60
Since it is a synthetic resin molded product containing 0.5 to 45% by weight of crosslinked polyethylene beads, crosslinked acrylic beads, and crosslinked polyethylene beads of 0μ, it has the following unprecedented effects: play. That is, (1) A beautiful matte surface without unevenness can be obtained on the surface of the synthetic resin molded product.

■Due to the very good dispersibility of the matting agent during material production,
Unlike conventional inorganic fillers, it is easy to mix at high concentrations. Furthermore, since the matting agent is heat resistant, it will not melt depending on the molding temperature, so there is no risk of heat aging.

■Since the beads themselves, which are matting agents, are hard, the surface hardness of the molded product is slightly improved, making it less likely to be scratched.

■The surface of the molded product has fine, uniform spherical protrusions, and has good sliding properties, so the fitting part with the lid of various containers such as cosmetic containers has a ball bearing effect, making the operation of the fitting cap etc. Improvements will be made.

■The matting agent also serves as a mobile filler, and can be easily filled into the fine and deep parts of the molded product. Therefore, it has the effect of significantly alleviating thermal strain after molding.

■Compared to conventional matting agents, stains are less likely to adhere to the surface, even on white fabrics. Further, attached dirt can be easily removed.

■Excellent effects such as no effect on hot stamping or stamping.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view of a molded cap according to an embodiment of the present invention, FIG. 1(b) is a partially enlarged sectional view thereof, and FIG. 2 is a perspective view of a molded cap according to an embodiment of the present invention. FIG. 3 is a front view of a container for powder, and FIG. 3 is a front view of a container for lipstick. 1.11.21... Cap, 2...
Thermoplastic resin, 3...Crosslinked polymer beads. Patent applicant Yoshida Kogyo Co., Ltd. Agent
Patent attorney - Kensuke Shiro Patent attorney Usuri Matsumoto @ Figure 1 (a) Figure 2 II Figure 3 j

Claims (2)

[Claims] (1) Polyethylene, polypropylene, polystyrene,
Thermoplastic resins such as AS, ABS, MMA, MS, polycarbonate, polyacetal, nylon, etc. with a particle size of 3μ
A molded article made of synthetic resin, characterized in that it contains 0.5 to 45% by weight of crosslinked polystyrene beads, crosslinked acrylic beads, and crosslinked polyethylene beads of ~600μ, either alone or in combination. (2) The synthetic resin molded product according to claim 1, wherein the synthetic resin molded product is various synthetic resin containers such as cosmetic containers molded by injection molding, extrusion blow molding, etc.