JPS6056604B2 - Filled thermoplastic resin injection molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filled thermoplastic resin injection molded article that is soft, highly glossy, and has a good appearance.

Thermoplastic resin injection molded products containing various fillers such as glass fiber, inorganic materials, metal powder, etc. have better tensile strength, bending strength, flexural modulus, and heat resistance than molded products without fillers. As a useful material with improved dimensional stability etc., it has been used as parts for automobile parts and electrical appliances.

On the other hand, thermoplastic resin molded products were made by utilizing its plasticity and using the steps of heating fluidization, shaping, and cooling solidification, but since the filler mentioned above does not have fluidity, thermoplastic resin molded products containing filled materials are molded. The surface of the product is severely rough and the beauty of the exterior is required.
1 is often used only for internal structural parts. The manufacturing method of these molded products generally utilizes the plasticity of the thermoplastic resin in injection molding of thermoplastic resin molded products, in other words, uses a screw etc. to heat and fluidize the thermoplastic resin, shape it, and then mold it. The basic principle is to obtain a molded product by cooling and solidifying within the mold.

In other words, in order to release and take out the molded product from the mold after solidification, it is cooled below the heating deformation temperature of the filled thermoplastic resin and taken out of the mold.Therefore, the mold is generally kept at a temperature lower than the heating deformation temperature. Hold. In order to further increase productivity, a refrigerant is used to cool the mold to a temperature on the verge of condensation. In other words, in the current injection molding process, even when the mold is cooled and heated and stored at the temperature of the molten resin, the mold temperature does not, in principle, exceed the heating deformation temperature of the filled thermoplastic resin. control and shape. For this reason, when the mold surface contacts the thermoplastic resin and the filler, the thermoplastic resin is rapidly cooled at the contact surface, and the fluidity of the thermoplastic resin becomes extremely poor, resulting in poor adhesion of the thermoplastic resin to the mold surface. The surface of the molded product is extremely uneven. Furthermore, since fillers and thermoplastic resins generally do not have good compatibility, it is thought that fine voids are formed at the interface between the filler and thermoplastic resins, resulting in silver streaks when injection molding is performed. In other words, the filler material appears on the surface of the injection molded product, making it extremely uneven and having silver streaks and the like, resulting in an injection molded product with poor gloss and poor appearance. When using a thermoplastic resin as an injection molded product that requires a beautiful appearance, there are other methods such as painting, pasting a film, or attaching a thin film material to the surface of the filled thermoplastic resin molded product. It has been adopted.

However, this method has the disadvantage that it is not possible to obtain a molded product with a soft glossy appearance inherent to thermoplastic resins, and that it is expensive because it takes time and effort to manufacture. In the case of painting, mechanical strength such as impact strength is reduced because the thermoplastic resin is melted to form a paint film. Also, when applying a film, if the shape of the injection molded product is complex, it is almost impossible to cover the entire surface of the molded product in terms of industrial production. The present inventors have discovered that by integrally forming a thin skin layer of thermoplastic resin without exposed filler on the surface of a filled thermoplastic resin injection molded product during injection molding, the thermoplastic resin is naturally present on the surface of the molded product. The above-mentioned problems were solved by obtaining a filled thermoplastic resin injection molded product having a high gloss and a good appearance without defective appearance phenomena such as flow marks and silver streaks.

The present invention is a filled thermoplastic resin molded article, and the surface of the molded article has a smooth thermoplastic resin skin layer with a thickness of 1 to 100 μm that does not contain filler and substantially covers the bonding interface. Flow Mark, Silver It is a filled thermoplastic resin injection molded product with no streaks.

If the thermoplastic resin skin layer is less than 1 μm, the filler tends to appear on the surface and the appearance tends to lose its so-called smooth appearance such as gloss. ．． Further, it is not necessary to have a skin layer of 100 μm or more, and when the skin layer becomes 1000 μm or more, the effect of adding a filler decreases. This thermoplastic resin skin layer has a smooth surface without any roughness or unevenness that causes poor appearance even when observed using an optical microscope at a magnification of 44@.

Furthermore, this skin layer has a gloss level of Qs (60) on the surface of the molded product.
% is smooth enough to give a high gloss of 80% or more, and it gives injection molded products not only a high gloss but also a soft gloss. Because it has such a skin layer structure with a thickness of 1 to 100 μm, filler material appears on the surface, which is a major drawback of filled thermoplastic resin injection molded products, and
Thermoplastic resin injection molded products with high gloss and excellent appearance can be obtained without defects in appearance caused by flow and uneven flow of filled thermoplastic resin in injection molded products such as Silver Streak and Flow Mark. . The method for obtaining the injection molded product of the present invention is as follows.In order to improve the adhesion between the resin and the mold, the mold surface is maintained at a temperature higher than the heating deformation temperature of the filled thermoplastic resin. On the other hand, it is impossible to release the mold while keeping the surface of the mold at a temperature higher than the heating deformation temperature of the filled thermoplastic resin, and it is impossible to obtain the desired molded product without deformation. In order to obtain this, the mold is cooled to a temperature lower than the heating deformation temperature of the thermoplastic resin, and the molded product is released from the mold in a solidified state.High-frequency induction heating is used for this heating and cooling. Utilizing the principle, by selectively heating the surface layer of the mold,
The injection molded product of the present invention can be obtained by rapidly heating and rapidly cooling the surface of the mold. Next, the injection molded product according to the present invention and its molding method will be explained with reference to the drawings.

In injection molding of filled thermoplastic resin, a high-frequency induction heating inductor is installed between a stationary mold and a movable mold as shown in FIG.

When an inductor was sandwiched between the movable mold and the stationary mold and a high frequency was oscillated while the inductor was sandwiched, the temperature of only the mold surface (points A and B) suddenly increased as shown in Figure 2. It can be confirmed that the temperature inside the mold (point C and point D) increases almost no temperature due to high-frequency induction heating. In the case of the example shown in FIG. 2, the mold is not cooled with cooling water, but simply shows an example of the change over time in the temperature distribution of the mold due to high-frequency induction heating. After that, the mold was opened once, the inductor was extracted from between the fixed and movable molds, the mold was closed again, and the filled thermoplastic resin was injected in the same manner as normal injection molding, resulting in the desired appearance. A beautiful filled thermoplastic resin injection molded product was obtained. An injection molded article according to the present invention was obtained using a glass fiber-reinforced acrylonitrile-styrene copolymer resin (acrylonitrile-styrene copolymer resin is hereinafter abbreviated as AS resin) as a filled thermoplastic resin. Optical micrographs of the cross section of this molded article in the thickness direction are shown in FIGS. 3 and 4. The magnification is 44 mm. For reference, the same material was injection molded using the same mold at a mold temperature of 60° C., and photographs of the same cross section were taken in the same manner as shown in FIGS. 5 and 6. The magnification is 44@. In both photos, the island pattern is made of glass fiber, and the horizontal line is the surface of the molded product. Figures 3, 4 and 5
As is clear from comparing Figures 6 and 6, in the case of the injection molded product of the present invention, filler glass fibers do not appear on the surface of the injection molded product, and at least 1 to 30 p of the thermoplastic It can be seen that the resin layer is formed on the surface layer of the molded product.

Also, as shown in Figures 3 and 4, when the glass fibers are located relatively close to the surface of the molded product, the thermoplastic resin layer or skin layer is formed, and at the same time the skin layer becomes slightly uneven due to the influence of the glass fibers. 6, an injection molded product having a glossy appearance can be obtained because it shows gentle unevenness compared to the case shown in FIG.
On the other hand, in the case of normal injection molded products, as shown in Figures 5 and 6, if the glass fibers protrude from the surface of the molded product, or if the glass fibers are located near the surface layer, the flow of resin on the mold surface may occur. Perhaps because of this alienation, silver streak-like irregularities occur on the surface, and only molded products with so-called dull and rough surfaces can be obtained. In order to quantify the appearance and gloss of the glass fiber-reinforced AS resin injection molded product of the present invention, the glossiness G of the molded product was determined by ASTM D523.
The result of measuring s(600)% was 98%.

On the other hand, the molded product produced at a mold temperature of 60° C. had a gloss level of 45%, indicating the smoothness and gloss of the injection molded product appearance of the present invention. In addition, the molded product of the present invention has low flow resistance during injection molding, and orientation distortion is less likely to occur.
Measurement of the heating deformation temperature specified in It was confirmed that this also improved. The filler used in the present invention refers to powders and hollow bodies of inorganic materials such as glass fiber, glass bulb calcium carbonate, mica, and asbestos, and metals such as iron, copper, zinc, aluminum, and their oxides. This refers to particles with a small particle size of 5 mesh or less.

In the present invention, thermoplastic resins include polystyrene, rubber-reinforced polystyrene (hereinafter collectively referred to as PS), acrylonitrile-styrene polymer (AS resin), acrylonitrile-butadiene-styrene polymer, acrylonitrile-butadiene-styrene-α-methylstyrene. , acrylonitrile-methyl methacrylate-butadiene-styrene (
It includes all so-called thermoplastic resins such as ABS resin (hereinafter collectively referred to as ABS resin), polyethylene, polypropylene, polycarbonate, polyphenylene ether, polyoxymethylene, and nylon.

Example 1 A glass fiber having a diameter of 13p and an AS resin containing 2% by weight were molded using a normal in-line injection molding machine.

The mold is made of ordinary S-45C steel, and has a diameter of 10 cm, a depth of 2 CIn, and an average wall thickness of 3 according to the conceptual diagram shown in Figure 1.
．． The mold is capable of molding a 5wm dish-shaped product, and the gate is a center direct gate. The inductor is made by molding a 3-frame diameter copper tube into a dish shape in a spiral pattern with 5-frame intervals, then casting it with epoxy resin to a thickness of 3Crf1 and solidifying it into a flat plate.

The injection molding conditions are that the temperature of the AS resin with 0 glass fiber addition is 2.
The cylinder temperature was set to 40°C.

Before injecting the glass fiber-reinforced AS resin into a mold, the above-mentioned inductor was inserted between the molds and a 400KC. ．． 6
The mold was heated by oscillating for 15 seconds using a KW high-frequency oscillator as shown in FIG. Thereafter, the mold was opened, the inductor was extracted from between the molds, and the mold was closed again. During this time, the mold cooling water is prevented from flowing inside the mold, and then the filler-containing resin is poured into the mold as in normal injection molding.
The molded product was injected at an injection pressure of 0k9/Clt for 2 hours, and then cooled by passing cooling water through the mold for a few seconds, and then the molded product was taken out.
The total cycle time was 6@. There are no surface scratches. This injection molded product has the same appearance as an AS resin injection molded product that does not contain glass fiber, and has silver streaks,
The molded product had a very good appearance with no glass fibers protruding from the surface, and was soft and had a high gloss. Example 2 An ABS resin containing 15μ of glass fiber in an amount of 2% was molded using a conventional injection molding machine at a resin temperature of 240°C.

The mold is a mold capable of producing dumbbells and strips having shapes specified in JIS K687l, and is made of S-55C. The inductor is 377I77! 5T1r diameter copper pipe! They were arranged in a spiral shape at intervals of Ft, and this was cast into a 2 cm thick flat plate with epoxy resin and fixed and solidified. The molding method was the same as in Example 1, but at 400K.
C,. 6KW1 high frequency oscillation time 10 seconds, injection 1, cooling 1 second, molding cycle 5 [phase], injection pressure 50k9/C into the mold with elevated surface temperature as described above (see Figure 2).
Injection molded at 7lf. Obtained glass fiber reinforced ABS
It was confirmed that the surface of the molded product was covered with a smooth skin layer of ABS resin with a thickness of 1 to 50 μm, and that no glass fibers were protruding or exposed on the surface of the molded product. The gloss and physical properties of the molded product are as shown in Table 1. As is clear from the results in Table 1, the gloss of this injection molded product is extremely high and its physical properties are also excellent. Comparative Example 1 Using the same molding machine and mold as in Example 2, using the same molding material, resin temperature 240°C, mold temperature 60°C, injection 1
0 seconds, cooling 1 melt, whole molding cycle 10 seconds, injection pressure 50k9
The results of measuring the physical properties of the molded product are shown in Comparative Example 1 in Table 1.

Example 3 11PS resin with 50% by weight of 200 mesh iron powder added,
Molding was carried out using a normal in-line injection molding machine at a resin temperature of 220°C.

The mold is a box-shaped molded product measuring 5 cm x 80 x 0.5 d deep, and a pair of these can be molded at the same time, and by fitting them together, a case with a hinge can be created. It is a type. The gate is also a restricted side gate. The inductor is 5T! Copper tubes with a diameter of Rm were arranged in a spiral shape at 5Tm intervals in a planar manner, and this was cast with epoxy resin to form a flat plate with a thickness of 2cff1, and the copper tubes were fixed and solidified.

This inductor was inserted between the molds and the 400KC. After oscillating a high frequency of 6 kW for 1 to 2 minutes, the inductor was extracted from between the molds, and injection molding was performed in the same manner as in Example 1.

No iron powder was observed on the surface of the obtained molded product, and there were no sill particles, flow marks, jetting, etc., and the surface gloss Gs (60%) of the molded product was 100%, in other words, there was no gloss gradient. A uniform, high-gloss molded product was obtained.

Furthermore, the specific gravity of the molded product was 1.8, making it possible to mold a heavy, heavy, soft, and high-gloss product that was not found in conventional PS molded products. As described above, the thermoplastic resin injection molded product containing a filler according to the present invention has a structure in which a skin layer of thermoplastic resin with a smooth surface and a thickness of 1 to 100 μm is formed to cover the layer containing the filler. Therefore, the molded product surface is smooth and soft without flow marks or silver streaks, and the molded product has a highly glossy appearance.

The ability to produce filled thermoplastic resin injection molded articles with such excellent appearance by stamped injection molding significantly increases the productivity of injection molding. The molded product of the present invention is a filled thermoplastic resin injection molded product with a highly smooth surface and excellent rigidity and dimensional stability, so it can be advantageously used for structural parts that have fitting parts or sliding parts. can. For example, in a tape recorder chassis made of glass fiber reinforced AS resin, the sliding resistance of the bush button portion is small. Furthermore, when the cap of a lipstick case is made of glass fiber-reinforced ABS resin, a molded product with an unprecedented balance of rigidity, soft glossy appearance, and snap-fitting properties (fitting properties when the cap is tightened) can be obtained. The usefulness of the present invention is immeasurable.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram for manufacturing a molded article according to the present invention. FIG. 2 shows an example of the temperature distribution of the mold in the apparatus shown in FIG. FIG. 3 and FIG. 4 are cross-sectional photographs in the thickness direction of a glass fiber-reinforced AS resin molded product according to one embodiment of the present invention. Fifth
Figure 6 is a comparison photograph, which is a cross-sectional photograph in the thickness direction of a glass fiber-reinforced 5AS resin molded product made by a conventional molding method. Reference numeral 1 denotes a stationary mold, and 2 a movable mold.

Claims (1)

[Claims] 1 A filler-containing thermoplastic resin injection molded product, in which the surface of the molded product has a smooth thermoplastic resin skin layer with a thickness of 1 to 100 μm that does not contain a filler and substantially has a bonding interface. It is formed integrally during injection molding, and the surface of the molded product has a gloss level Gs (60°)% of 80 or higher at an incident angle of 60° as defined by ASTM D523, and has a flow mark, silver Streak-free filled thermoplastic injection molded product.