JPS6257487B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an injection molded polyester product that has been subjected to an anodic coating treatment and has a surface gloss similar to that of matte aluminum. Satin aluminum molded products treated with anodic coating have a deep and elegant surface gloss, and have been used in fields that require a high-class image such as cosmetic bottle caps, compacts, luxury fountain pens, and decorative plates. Widely used. By the way, the method for producing these matte aluminum molded products is to first create the aluminum material into the desired shape by cold working, remove burrs, perform a satin finish using sandplast, etc., and then clean it, degrease it, and wash it with water. However, if necessary, electrolytic polishing or chemical polishing is performed, followed by an anodic coating treatment, and furthermore, a coloring treatment is performed. At this time, it is necessary to thicken the anodic coating in order to give the molded product a high-class image, and as a result, a long period of anodic coating treatment is required. However, due to the various complicated manufacturing steps and long-time electrical processing, the manufacturing cost of such molded products is extremely high. Therefore, even for molded products with high added value such as cosmetic containers, the manufacturing cost becomes an issue, and it is difficult to develop molded products that are cheaper and easier to obtain and have a satin aluminum appearance that has been subjected to an anodic coating treatment. It was strongly desired. In view of the current situation, the inventors of the present invention conducted intensive studies to easily obtain a plastic molded product having an appearance similar to the matte aluminum molded product subjected to the anodic coating treatment at a low cost. An injection mold having a satin-like surface in which the inner surface of the mold is treated with a satin-like surface using a resin composition blended with at least one selected from the group consisting of a polyolefin resin and a methacrylic resin in a specific range amount. The inventors have discovered that an injection molded article formed by the method can satisfy the above object, and have arrived at the present invention. That is, the gist of the present invention is that the intrinsic viscosity is
It is composed of a resin composition consisting of 60 to 99.5% by weight of a polyester resin of 0.6 or higher and 40 to 0.5% by weight of at least one type selected from the group consisting of polyolefin resins and methacrylic resins, and the inner surface of the mold has a satin finish. This is a polyester injection molded product molded using a molded injection mold. The polyester resin used in the present invention is one in which 60 mol% or more of the repeating units constituting the resin consists of ethylene terephthalate, and also includes copolymers. Copolymerization components include isophthalic acid, adipic acid, sebacic acid, P-β-oxyethoxybenzoic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, etc. Dicarboxylic acid components such as alkyl ester derivatives of , glycols such as propylene glycol, butanediol, hexamethylene glycol, neopentyl glycol, and cyclohexanedimethanol are used. Polyester resins can be produced by any of the following methods: polycondensation via transesterification, direct esterification and polycondensation, or solid phase polymerization of the polymers obtained by these methods. The resulting polymer can be used, but its intrinsic viscosity [η] is 0.6 or more, preferably 0.65.
A range of ~1.4 is desirable. [η] is 0.6
If it is less than that, the appearance of the final molded product will be impaired and the desired deep and elegant surface gloss will not be developed, which is not preferable. On the other hand, if [η] is too high, for example exceeding 1.4, the melt viscosity of the resin will increase and its injection moldability will deteriorate, which is not preferable. Note that [η] is a value determined from the solution viscosity measured at 25°C in a phenol/tetrachloroethane=50/50 (weight ratio) solution. Furthermore, the polyolefin resin in the present invention refers to a homopolymer of ethylene, propylene, butene-1,4-methylpentene-1, isobutylene, etc., or a copolymer containing these α-olefins as a main component with other comonomers. It is. Specific examples of copolymers include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-vinyl acetate copolymer.
Examples include methyl acrylate copolymer and ethylene-propylene copolymer. When carrying out the present invention, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer,
Methyl acrylate copolymers, polypropylene, etc. exhibit excellent effects and are particularly preferred. Furthermore, the methacrylic resin in the present invention refers to a homopolymer of methyl methacrylate or a copolymer of 50 mol% or more of methyl methacrylate and another vinyl monomer. Other vinyl monomers that can be copolymerized with methyl methacrylate include methyl acrylate,
Acrylic acid alkyl esters such as ethyl acrylate and butyl acrylate, ethyl methacrylate,
Examples include methacrylic acid alkyl esters such as butyl methacrylate, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, and the like. In carrying out the present invention, it is preferable to use a homopolymer of methyl methacrylate or a copolymer with methyl acrylate or ethyl acrylate because particularly excellent effects can be obtained. In carrying out the present invention, the above-mentioned polyolefin resin and methacrylic resin may be used alone, or in combination with polyolefin resins or methacrylic resins, or in combination with at least one polyolefin resin and at least one methacrylic resin. It can be used in combination with the polyester resin in an amount of 60 to 99.5% by weight of the above polyester resin and 40% by weight of at least one selected from the group consisting of polyolefin resin and methacrylic resin. It is necessary that the content be in the range of ~0.5% by weight. If the resin composition constituting the injection molded article of the present invention deviates from the above range, it may be molded using a specific satin-finished injection mold described later. This is not preferable because it becomes difficult to develop a surface gloss similar to that of matte aluminum that has been subjected to film treatment.
That is, when the content of the polyester resin in the resin composition exceeds 99.5% by weight, the final injection molded product has a strong transparency and becomes cloudy glass-like. On the other hand, if the content of polyester resin is less than 60% by weight, the desired surface gloss is difficult to obtain, such as a deep and elegant luster that does not develop and the appearance resembles unglazed pottery. Prolonged exposure to alcohol, fragrances, etc. is not preferable because cracks tend to occur and the strength decreases significantly. In the present invention, any suitable method can be used to mix at least one of a polyolefin resin and a methacrylic resin with the polyester resin, but the resin powders and pellets of each of the above resins are mixed in a mixer and then pelletized using a melt extruder. The method is preferred. At this time, a mixing zone may be provided at the screw tip of the extruder to enhance the kneading effect, or, for example, L/D may be 20 or more and the compression ratio may be 2.0.
It is preferable to use the above-mentioned screw or a biaxial screw because a good appearance can be obtained. Next, the injection molded product of the present invention is molded from the above-mentioned specific resin composition using an injection mold whose inner surface is satin finished, and the inner surface of the mold used at that time has the desired appearance. Depending on the pattern, part or all of the surface of the mold product may be satin finished. The satin finish on the inside of these molds is a corrosion process.
This can be done by electrical discharge machining or the like. The surface roughness of the satin pattern on the inner surface of the mold can be selected depending on the appearance of the desired molded product, but specific examples include Miyamori Metal Seisakusho's textured sample numbers: B39D, B39CD, B39C, B39BC, B39B,
B39AB, B684, B9A, etc. are preferable, but are not limited thereto. In carrying out the present invention, any commonly used injection molding machine may be used, but the degree of surface gloss of the molded product tends to be affected by the screw shape and injection molding conditions. Therefore, the screw has a compression zone and a metering zone of at least 3 pitches each, and a compression ratio of 1.5 to 3.
4 is preferred. Also important in injection molding conditions are injection speed and mold temperature. This is preferable because as the injection speed increases, a deeper surface gloss can be obtained. However, if the injection speed is excessively increased, the surface gloss around the gate will disappear, dirt will occur, and a strong flow pattern will appear, resulting in a loss of elegance, so a moderate injection speed is required. On the other hand, it is preferable that the mold temperature is set at 50℃ or less. If the temperature is higher than this, it will take a long time to cool and solidify the injection molded product, resulting in a longer molding cycle, and molding in such conditions This is not preferable because crystallization occurs in the molded product, and the deep satin aluminum-like surface gloss that has been subjected to the anodic coating treatment, which is the object of the present invention, cannot be obtained. The injection molded product of the present invention is made by injection molding a resin composition composed of a specific amount of resin as described above, so that the surface of the molded product has a pearl-like surface gloss and a satin pattern is formed on the inner surface of the mold. This is obtained for the first time by the synergistic effect of applying this to the surface of the molded product during injection molding, and the presence of a resin layer that gives a pearl-like surface gloss under the matte surface of the molded product surface is the characteristic of the present invention. It is thought that this gives a matte aluminum-like surface gloss appearance. In the present invention, additives such as dyes and pigments, ultraviolet absorbers, antistatic agents, and nucleating agents may be added without departing from the purpose of the present invention. The injection molded product of the present invention has a beautiful deep surface gloss similar to that of satin aluminum that has been subjected to the anodic coating treatment as described above, and is free from alcohol, fragrance, and other materials.
It has excellent chemical resistance to weak acids, etc., mechanical strength such as impact strength and bending strength, fragrance retention, and hygienic properties, so it is used as caps for containers for cosmetics and pharmaceuticals.
It can be preferably used for compacts, lipstick containers, fountain pen shafts, knobs of electrical appliances, etc. The present invention will be specifically explained below using Examples. Examples 1 to 5, Comparative Examples 1 to 2 [η] (dl Pellets of methacrylic copolymer having a composition of methyl methacrylate/methyl acrylate = 90/10 (weight ratio) with a ratio of 0.6 (g) to 85°C.
After drying for 20 hours at L/D = 24, supply zone 11D,
Compression zone 6D, metaling zone 7D, pitch
1D, supplied to a Toshiba Machine 40mmφ extruder equipped with a screw with a compression ratio of 2.5, and extruded to an average size of 3φ×
Pellets with dimensions of 3 mm were obtained. At this time, the cylinder temperature is 260℃ in the rear, 270℃ in the middle, and 280℃ in the front.
℃, die 280℃, and screw rotation speed 60 rpm. The measured value of [η] of polyethylene terephthalate in the obtained pellets was in the range of 0.83 to 0.87. Based on these pellets 10
Blue masterbatches with double concentration were shaped respectively, 10 parts by weight of these masterbatches and 90 parts by weight of the above-mentioned mixed resin composition pellets were mixed, vacuum dried at 150°C for 5 hours, L/D = 17, supply zone
8.5D, compression zone 5.3D, metalling zone
The inner surface is textured by Miyamori Metal Manufacturing Co., Ltd. using a Meiki Seisakusho SJ-40C injection molding machine equipped with a screw of 3.2D, pitch 0.9D, and compression ratio 3.0.
A B39C satin-finished side gate that can be molded in two pieces at the same time using a cold runner mold, weighing 15g, half of the flat plate having a wall thickness of 3mm, and the other half having a thickness of 1.5mm, and one side with a stepped matte finish. manufactured
A flat plate of 50 x 100 mm was molded. The molding conditions were as follows. Cylinder temperature is C ₁ 270℃, C ₂ 280
℃, C ₃ 290℃, nozzle 290℃, primary injection pressure (gauge pressure) 30Kg/cm ² , secondary injection pressure (gauge pressure) 20Kg/cm 2
cm ² , injection speed 50 g/sec, molding cycle 30 seconds,
The mold temperature was 10°C. The obtained molded product was evaluated for its surface appearance and changes in appearance by an ethanol immersion test at 40°C for one month. These results are shown in Table 1 along with [η] of PET in each plate. The display of appearance evaluation in Table 1 is as follows (these display methods are common to the following Examples and Comparative Examples). ◎: Those with surface gloss equivalent to the surface gloss of satin-finished aluminum that has been subjected to anodic coating treatment 〇: Those that have surface gloss that is quite close to the surface gloss of satin-finished aluminum that has been subjected to anodized coating treatment △: Those that have surface gloss that is quite similar to the surface gloss of satin-finished aluminum that has been subjected to anodic coating treatment A surface gloss that is quite similar to the surface gloss of the applied satin aluminum is observed, but its condition is weak.

[Table] Examples 6 to 8, Comparative Examples 3 to 4 Moisture content with various [η] shown in Table 2
At 70℃ with 90 parts by weight of PET pellets below 50ppm
A mixture of 10 parts by weight of ethylene-ethyl acrylate copolymer that had been vacuum-dried for 20 hours was molded using the extruder used in Example 1 under the same molding conditions to obtain mixed resin pellets. Next, these mixed resin pellets were injection molded using the injection molding machine and mold used in Example 1 under the same molding conditions to obtain a satin-finished, uncolored flat plate of the same size as the flat plate obtained in Example 1. . Table 2 shows the evaluation results for the surface appearance of the obtained molded product and the change in appearance after a one month ethanol immersion test at 40°C.

【table】

Claims (1)

[Claims] 1 Polyester resin 60 with an intrinsic viscosity of 0.6 or more
-99.5% by weight and at least 40% to 0.5% by weight of at least one type selected from the group consisting of polyolefin resins and methacrylic resins, using an injection molding mold with a matte finish on the inner surface of the mold. Molded polyester injection molded product.