JP2002225088A - Mirror surface finished mold to which surface treatment is applied and molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mold releasability without using a release agent without changing a product design. SOLUTION: Metal film surface treatment, a nonmetal film surface treatment or composite film surface treatment of them is applied to a mold and, if necessary, the surface of the mold is polished to set the surface roughness Rz (ten- score average roughness) of the mold to 0.001-0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment mold in which a mold for injection molding of a thermoplastic resin requiring a mirror surface treatment is subjected to a surface treatment to improve releasability, and a molding method using the same. It is. The present invention is effective for molding a light reflecting component.

[0002]

2. Description of the Related Art The surface roughness of a molded product such as a conventional injection molding die, particularly a light reflection component molding die, is, for example, Rz (ten-point average roughness). ) In a very small mirror mold of 0.001 to 0.5 μm,
When a thermoplastic resin such as polybutylene terephthalate or polyphenylene sulfide is injection-molded, the molded product has poor releasability, and has a problem in that the molded product is deformed or broken at the time of release. Conventionally, as a method for solving this problem, there is a method of increasing a draft angle of a mold, adding an ejector pin, or applying a release agent. It is also possible to improve the releasability by increasing the surface roughness of the molded part to some extent. However, these methods have a problem that a product design is modified or changed, a release agent is used, and a surface state is roughened, and these methods do not always meet the requirements. On the other hand, mold surface treatment is also conventionally performed, but the purpose is to increase the hardness of the surface to reduce wear and prevent corrosion,
It is necessary to use the same release agent as in the past.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, the present inventor has found that a thermoplastic resin such as polybutylene terephthalate and polyphenylene sulfide resin, particularly a resin containing no glass, inorganic filler, etc. After extensive research and investigation into the improvement of mold release properties, the mold release properties were significantly improved without changing the product design and using a mold release agent by applying a specific surface treatment to the mold surface. They have found that they can do this and have completed the present invention.

That is, a first aspect of the present invention is that a metal coating surface treatment, a non-metal coating surface treatment, or a composite coating surface treatment thereof is applied to an injection molding die for thermoplastic resin, and polishing is performed as necessary. A processing die, the surface roughness Rz of the die
Provided is a processing mold having a (ten-point average roughness) of 0.001 to 0.5 μm. A second aspect of the present invention is the treatment according to the first aspect of the present invention, wherein the surface treatment is any one of a hard chromium plating treatment, a chromium nitride treatment, a titanium nitride treatment, and a chromium film treatment in which nitrogen is supersaturated. Provide mold. A third aspect of the present invention provides the treatment mold according to the second aspect, wherein the surface treatment is a chromium nitride treatment. A fourth aspect of the present invention provides the processing die according to the second aspect of the present invention, wherein the surface treatment is a surface treatment of applying a chromium film in which nitrogen is supersaturated as a solid solution by a sputtering method. A fifth aspect of the present invention provides the molding die according to any one of the first to fourth aspects of the present invention, wherein the draft angle of the molded product is within 5 degrees. A sixth aspect of the present invention provides the treatment mold according to the fifth aspect, wherein the thermoplastic resin is polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, or polyacetal. According to a seventh aspect of the present invention, there is provided a processing mold according to any one of the first to sixth aspects of the present invention, which is used for molding a light reflecting component.
According to an eighth aspect of the present invention, there is provided a molding method with improved releasability, in which a thermoplastic resin is injection-molded using the processing mold according to any one of the first to seventh aspects of the present invention. According to a ninth aspect of the present invention, there is provided the molding method according to the eighth aspect of the present invention, wherein the molding is performed on the mold surface without using a release agent.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. JIS B0601 (1)
994), Ra (arithmetic mean roughness),
There are Ry (maximum height), Rz (ten point average roughness), etc.
In the present invention, a suitable index is Rz (ten-point average roughness). The reason why Rz is an index is that the releasability is more affected by unevenness that is partially present than the average roughness of the mold surface. That is, although Ra used normally gives a stable result of surface roughness, unevenness which affects the releasability is averaged, so that there is a case where correlation is not obtained with the releasability. Further, Ry is the difference between the maximum height and the maximum depth within the measurement range, so that the measurement error is large, and similarly, it is not appropriate because the correlation with the mold releasability cannot be obtained. On the other hand, Rz
Is a parameter that reflects the unevenness that is partially present on the surface, and therefore has a very good correlation with the releasability. Therefore, it is important to adjust the surface using Rz as an index.

[0006] The surface coating treatment according to the present invention is (1) a general surface treatment or (2) a specific surface treatment. (1) General surface treatments include metal coating treatments such as electroplating, diffusion plating, vapor deposition plating, electroless plating, and thermal spraying; non-coating such as ceramic coating by CVD, PVD, ion plating, sputtering, and vacuum deposition. Metal coating treatment, or a composite coating treatment thereof, and the like can be given. Specifically, electrolytic plating and electroless plating of hard chromium or the like; titanium nitride (TiN), chromium nitride (Cr
N), a ceramic coating treatment of titanium aluminum nitride (TiAlN) or the like. (2) The specific surface treatment is a surface treatment using “a chromium film in which nitrogen is dissolved in supersaturation”. This is a surface treatment in which chromium, which is generally said to not dissolve nitrogen at room temperature by a sputtering method, is dissolved in a non-equilibrium reaction process to coat an amorphous chromium film in a nitrogen supersaturated state. E. FIG. F. (France) technology. The surface hardness obtained in this way can be 1,000 or more in terms of micro Vickers hardness, and can be used as a surface treatment of a resin molding die. The film thickness can be selected from several μm to several tens μm, but may be, for example, about 10 μm.

The metal used as the base of the injection mold used in the present invention is not particularly limited. For example, stainless steel such as SUS420J2, SKD11, SKD12, SKD6
1, alloy tool steels such as SK3, high-speed steels such as SKH151, structural carbon steels such as S55C and SCM440, aluminum alloys, and non-ferrous alloys such as beryllium copper. Although there is no particular limitation on the surface hardness of the mold, since the present invention is characterized by the surface roughness of the molded product part of the mold, from the need to prevent disturbance of the mold surface assembly due to wear during molding, It is preferable to increase the surface hardness to some extent. For this reason, the mold can be subjected to heat treatment such as carburizing and quenching, induction hardening, and surface nitriding.

The mold of the present invention is obtained by subjecting a mirror-finished mold surface to a surface treatment. When the surface roughness of the mold before performing the surface treatment is represented by Rz (ten-point average roughness), Rz is in the range of 0.001 to 0.5 μm, preferably 0.001 to 0.2 μm. It is. If the surface roughness Rz before performing the surface treatment is more than 0.5 μm, the surface roughness is not in a desired range of the smooth surface roughness, and the surface is too rough to improve the mold release, and it is difficult to find the effect of the surface treatment.
Since the surface roughness after the surface treatment is almost the same as that before the surface treatment, it is important to make the target surface roughness almost the target before the surface treatment. Since the surface roughness after the surface treatment is almost the same as that before the surface treatment, the surface roughness of the mold after the surface treatment or, if necessary, the polishing after the polishing is also Rz (10%). Rz is 0.001 to 0.5 μm, preferably 0.001 to 0.
It is in the range of 2 μm.

As the thermoplastic resin used in the present invention, any resin can be injection-molded as long as it can be generally injection-molded. As a thermoplastic resin,
For example, aromatic polyester, liquid crystalline polyester, polycarbonate, polyolefin, polyamide, polyacetal, polystyrene, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-butadiene-acrylic acid (or ester thereof) copolymer , Acrylonitrile-styrene copolymer, polyurethane, fluororesin, polyphenylene oxide, polyarylene sulfide resin, polysulfone,
Polyether sulfone, polyketone, polyetherketone, polyimide, polyetherimide, polybenzimidazole, polybutadiene, butyl rubber, silicone resin, styrene-based elastomer, urethane-based elastomer, ester-based elastomer, amide-based elastomer,
Olefin-based elastomers and the like can be mentioned. Among these, aromatic polyesters and liquid crystalline polyesters are composed of, for example, aromatic dicarboxylic acids; aliphatic or aromatic dihydroxy compounds; or aliphatic or aromatic hydroxycarboxylic acids. Specific examples of the aromatic polyester include polyethylene terephthalate, polybutylene terephthalate, polycyclohexylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.

[0010] These synthetic resins also contain, as fillers and reinforcing agents, magnesium oxide, calcium oxide, zinc oxide, magnesium hydroxide, magnesium carbonate, calcium carbonate, talc, mica, clay, kaolin, bentonite, dolomite, silica. Inorganic acid salts such as oxides, hydroxides, carbonic acid, phosphoric acid, boric acid, silicic acid and the like or silicon dioxide of the periodic table II or III metal such as, alumina, hydrotalcite etc. Formulated, plate-like or spherical powder, fiber such as glass fiber, carbon fiber, aramid fiber and their crushed products, and whisker such as calcium carbonate, titanium oxide, potassium titanate, wollastonite, graphite etc. It is also possible.

The mold of the present invention is not particularly limited as long as it can exert the effects of the present invention, and can be applied to injection molding, extrusion molding, compression molding and the like. It is particularly effective when applied to molds. The shape of the cylindrical nest is not particularly limited as long as the effects of the present invention can be exerted. For example, the diameter of the cylindrical nest is 5 to 50 mm, preferably 10 to 30 mm, and the length of the cylindrical portion is 10 to 300 mm, preferably. Is 20 to 200 mm, the thickness of the molded product is 0.3 to 2.0 mm, preferably 0.5 to
1.0 mm. The cylindrical nest may have an arbitrary cross section such as a circle, an ellipse, a polygon, and an oval. The draft angle of the cylindrical portion is possible even within 5 degrees, particularly 0 to 2 degrees. In the mold surface, the portion exhibiting the above surface roughness Rz may be the entire surface of the cavity, but may be at least the surface portion that greatly affects the releasability, for example, only the surface portion of the cylindrical mold insert.

When the above-described resin is molded by the mold of the present invention, molding is performed with little or no use of a release agent even in the case where the surface roughness of the molded product is reduced. It is possible. Therefore, the present invention relates to containers for food, medicine, cosmetics, etc .; covers for OA / AV equipment, electronic equipment, etc.
Housings and chassis; light reflecting parts such as lamp reflectors and lamp extensions; electronic parts such as connectors and relay cases; effective for molding gears for OA / AV equipment, automobiles, etc., and is particularly effective for continuous molding. It is preferably used for molding light reflecting parts and lenses.

[0013]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. The surface roughness of the nest and the mold cavity surface was measured by JI
Performed according to SB0601-1994.

[Embodiments 1 to 12] FIG. 1C shows the use of the nesting type movable side mold shown in FIG. 1A and the movable side nest shown in FIG. 1B. A hat-shaped product was molded, and the mold release was performed by projecting a flange portion of the hat-shaped molded product with an ejector pin. FIG. 2 shows an experimental mold diagram for measuring the release resistance. The release resistance measured the stress applied to the ejector pin at the time of release as a release resistance value.
In the present invention, the smaller the release resistance is, the easier the release is. As a pressure sensor for measuring the release resistance value, MM1094 manufactured by Nireco Co., Ltd. was used. The data measured by the sensor was converted and monitored using MOBAK MM2055 manufactured by Nireco Corporation. The moving side insert was made of Hitachi Metals' HPM1 and polished with sandpaper at No. 2000, and then subjected to six types of surface treatments shown in Table 1. For comparison, an untreated surface was also manufactured. The surface roughness is important in confirming the effect of this surface treatment. This is because the release resistance changes significantly due to the difference in surface roughness. For this reason, the surface roughness of the nest and the mold cavity surface is measured by a contour shape measuring machine Surf Test SV600.
It measured using 3D (made by Mitutoyo). Table 2 shows the results of each surface treatment and the surface roughness. The thermoplastic resins used are polyacetal resin (POM), polybutylene terephthalate resin (PBT), and polyphenylene sulfide resin (hereinafter, PPS), all manufactured by Polyplastex Corporation. In addition, what added 25, 30 or 40% (to the total mass) of GF (glass fiber) as a reinforcing agent was also used. Table 3 shows the molding machines and molding conditions used.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

FIG. 3 shows the measured PBT without added toughening agent.
Is plotted with respect to the surface roughness (horizontal axis). Each point shown in the figure is the actually measured release resistance value in each surface treatment. The solid line shows the mold release resistance value with respect to the surface roughness of the movable side nest obtained empirically. As shown in Table 2, the actual surface roughness differs depending on each treatment even if the same pretreatment is performed. Since the release resistance changes depending on the difference in the surface roughness, the release resistance cannot be evaluated uniformly. However, as shown by the solid line, since the release resistance against the surface roughness of the nest on the moving side is empirically known, the difference in the release resistance between the solid line and each point at the same surface roughness is the surface resistance. This is considered to be the effect of the processing. That is, No. Taking No. 4 as an example, the arrow in FIG. 3 can be said to be the effect of the surface treatment according to the present invention.

Table 4 shows the results of the reduction rate of the release resistance of PBT containing no reinforcing agent and PBT containing 30% glass filler. The release resistance reduction rate is a ratio of the reduced release resistance value described with reference to FIG. 3 to the untreated release resistance value.
For this reason, it can be said that a surface treatment having a larger demolding reduction rate is a better surface treatment. As in Examples 11 and 12, there are surface treatments that have a small effect on PBT with no filler added, but Examples 1 and 2 show a release resistance reduction rate of 20 to 30% or more. The reduction rate is remarkable and can be said to be unique. In the present invention, it is sufficient that the release resistance reduction rate is improved. However, in order to be able to release by extrusion without using a release agent, the release resistance reduction rate is 10% depending on the resin and the structure of the molded product. The content is preferably at least 20%, more preferably at least 30%, particularly preferably at least 50%.

Table 5 shows the difference in the rate of reduction in release resistance depending on the type of molding resin. The demolding resistance is reduced in various molding materials. Above all, No. in PBT 4 and N
o. The reduction rate of 7 shows a specifically high release resistance reduction rate, and it is clear that it works effectively. On the other hand, in POM and PPS resins, No. 4, No. Only 7 protrudes, and the release resistance reduction rate is not high. The mold releasability of the present invention can be improved by changing the chemical properties of the surface layer obtained by subjecting the material of the substrate to a surface treatment (for example, lowering the affinity for the resin) and the surface roughness in a specific range. It is thought to be due to

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

According to the present invention, the product design is modified,
It is possible to obtain a mold surface that can be easily released without changing or using a release agent while maintaining the surface state in a mirror state. As a result, removal of the resin after molding is facilitated, the molding cycle is shortened, and the incidence of defective products is reduced.

[Brief description of the drawings]

FIG. 1A is a top view of a moving mold used in the present invention. (B) It is a side view of a moving side nest. (C) It is sectional drawing of the moving side insert and the product formed on it.

FIG. 2 is a schematic view of an experimental mold for measuring a release resistance used in the present invention.

FIG. 3 shows mold surface roughness Rz (μm) and mold release resistance (N)
6 is a graph showing the relationship of.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Moving-side mold 2 Nesting 3 Ejector pin 4 Surface treatment part 5 Product

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Claims (9)

[Claims] 1. A treatment mold obtained by subjecting a thermoplastic resin injection molding mold to a metal film surface treatment, a non-metal film surface treatment, or a composite film surface treatment thereof, and polished as required. The surface roughness Rz (ten-point average roughness) of the mold is 0.
A processing mold having a size of 001 to 0.5 μm. 2. The processing mold according to claim 1, wherein the surface treatment is any one of a hard chromium plating treatment, a chromium nitride treatment, a titanium nitride treatment, and a chromium film treatment in which nitrogen is dissolved in a supersaturated state. 3. The processing mold according to claim 2, wherein the surface treatment is a chromium nitride treatment. 4. The processing die according to claim 2, wherein the surface treatment is a surface treatment in which a chromium film in which nitrogen is supersaturated as a solid solution is applied by a sputtering method. 5. The molding die according to claim 1, wherein a draft angle of the molded product is within 5 degrees. 6. The processing mold according to claim 5, wherein the thermoplastic resin is polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, or polyacetal. 7. The method according to claim 1, which is used for molding light reflecting parts.
6. The processing mold according to any one of 6. 8. A molding method with improved mold releasability, wherein a thermoplastic resin is injection-molded using the processing mold according to claim 1. 9. The molding method according to claim 8, wherein the molding is performed on the surface of the mold without using a release agent.