JPS6241449B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an injection molded polyester product having a deeper pearly surface luster and a flowing pattern on the surface. Polyester resin is hygienic, strong, chemical resistant,
Due to its excellent fragrance retention, transparency, and surface gloss, it is being widely used in cosmetics, pharmaceuticals, food containers, etc. However, in specific fields of use, for example, it has excellent decorative properties such as pearl surface gloss. There is also a demand for molded products with a unique appearance. By the way, as resin compositions with pearly surface luster, mixed resin compositions of polycarbonate and polymethyl methacrylate, mixed resin compositions of acrylonitrile-styrene copolymer and methacrylic resin, etc. are well known. Although it is widely used because it produces glossy molded products, its range of use is currently limited due to poor chemical resistance, strength, aroma retention, etc. On the other hand, we found that a mixed resin composition of polyester resin and methacrylic resin can be used to produce molded products with pearly surface gloss and excellent chemical resistance, strength, and fragrance retention. Products formed by molding resin and methacrylic resin in one step have a weak pearlescent feel, and improvements in this respect have been strongly desired. In view of the current situation, the present inventors aimed to obtain a polyester injection molded product that has a deep pearly surface gloss with a stronger pearl feeling without impairing the properties of the polyester resin, and also has a flow pattern on the surface. As a result of intensive studies, we mixed polyester resin into extruded pellets made of polyester resin and methacrylic resin in a specific composition range so that the amount of methacrylic resin in the injection molded product was within a specific range, and then injection molded the product. The inventors have discovered that by doing so, it is possible to create a deep and beautiful molded product with a more colorful pearl surface luster and surface flow pattern, and have arrived at the present invention. In other words, the gist of the present invention is that the intrinsic viscosity is
A polyester resin having an intrinsic viscosity of 0.6 or more is extruded into 100 parts by weight of a polyester resin having an intrinsic viscosity of 0.6 or more into extruded pellets having a resin composition of 10 to 99% by weight of a polyester resin of 0.6 or more and 90 to 1% by weight of a methacrylic resin. The methacrylic resin in the injection molded product is blended in a composition of 16 parts by weight or more, and then injection molded.It has a pearly surface luster and a surface flow pattern. A method of manufacturing polyester injection molded products. In the method of the present invention, in the first step, polyester resin and methacrylic resin are blended in amounts within a specific range and melt-extruded to form pellets to obtain extruded shaped pellets.Then, in the second step, By blending this shaped pellet with a predetermined amount of polyester resin and performing two-stage injection molding, it is possible to stably and reproducibly develop an even stronger and deeper pearly surface luster. It is. As mentioned above, even when a polyester resin and a methacrylic resin are mixed and molded at the same time, a pearly surface luster is produced, although it is weak. It is thought that the development of this pearly surface luster is based on the flattening of the methacrylic resin layer. Until now, when mixing the polyester resin and methacrylic resin, it was thought that pearlescent surface luster would be difficult to develop in two-stage molding as in the present invention.
Surprisingly, it has been discovered that, contrary to expectations, there is a unique phenomenon in which a pearl surface luster with even greater depth and depth appears. Furthermore, it has been found that the molded product has an excellent feature of clearly expressing a surface flow pattern. The polyester resin used in the present invention is one in which 60 mol% or more of the repeating units that constitute it consist of ethylene terephthalate, and the copolymerized components include isophthalic acid, adipic acid, sebacic acid, and P-β-oxyethoxybenzoic acid. , dicarboxylic acid components such as diphenyl ether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, etc. or their alkyl ester derivatives, propylene glycol, butanediol, hexamethylene glycol, neopentyl Glycols such as 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 polymer thus obtained can be used, but its intrinsic viscosity [η] must be 0.6 or more, preferably in the range of 0.65 to 1.4. It is preferable to use a polyester resin with a large [η] because the pearl surface gloss and luster tend to be good. If [η] is less than 0.6, it is not preferable because the mechanical strength of the final molded product will be extremely low, and the luster will be lost and the beauty will be impaired. On the other hand, [η] is for example
If it exceeds 1.4, it is not preferable because its moldability deteriorates. Note that [η] is phenol/tetrachloroethane = 50/50 (weight ratio) solution at 25°C.
This value was determined from the solution viscosity measured in . In addition, [η] of the polyester resin in a mixed composition of polyester resin and methacrylic resin is obtained by pulverizing the composition at a temperature of -30°C or lower, and then extracting the methacrylic resin using an acetone/ethanol mixed solvent. This value was determined in the same manner as above after removal and drying. In the present invention, the polyester resin mixed with the methacrylic resin and used for extrusion shaping and the polyester resin used in the second stage may be the same or different. good. In particular, it is preferable to use polyester resins with different [η] values because their flow behavior will be different and a strong surface flow pattern will tend to appear. The methacrylic resin in the present invention refers to a homopolymer of methyl methacrylate, a copolymer of 50 mol% or more of methyl methacrylate and another vinyl monomer that can be copolymerized with it, or a mixture of these polymers. be. Other vinyl monomers that can be copolymerized with methyl methacrylate include acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, butyl acrylate, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, etc. It will be done. In the present invention, it is preferable to use a homopolymer of methyl methacrylate or a copolymer with methyl acrylate or ethyl acrylate because a molded article having particularly excellent pearly surface gloss can be obtained. The resin composition of the extruded pellets made of polyester resin and methacrylic resin is 10 to 99% by weight of polyester resin, preferably 40 to 97% by weight, and 90 to 1% by weight of methacrylic resin, preferably 60 to 99% by weight. It is necessary that the composition be in the range of 3% by weight. The extrusion-shaped pellets may be obtained by mixing pellets of each resin within the above composition range in a blender or the like, and then shaping the pellets in an extruder. If the proportion of polyester resin in the extruded pellets is less than 10% by weight, not only the mechanical strength of the final molded product will be low, but also delamination will easily occur, making it difficult to obtain the desired product. Things that I can no longer do often occur, which is not good. On the other hand, the proportion of polyester resin is 99% by weight
Exceeding this is not preferable because it becomes difficult to develop the pearly surface gloss of the final molded product. What is important when preparing these extrusion-formed pellets is to sufficiently dry the polyester resin, methacrylic resin, and methacrylic resin. η], which not only impairs the mechanical strength and chemical resistance of the final molded product, but also
This is not preferable because it also weakens the development of pearl surface luster. Any commonly used extruder can be used, but an extruder that provides sufficient kneading will give better results. For example, an extruder with a relatively large L/D and a compression ratio of 1.6 to 3.5 is preferable. Furthermore, measures to enhance the kneading effect, such as adding dalmage to the tip of the screw, are preferably implemented. The temperature during extrusion molding must be at a temperature that sufficiently melts the polyester resin; for example, for polyethylene terephthalate, the cylinder temperature is
A temperature of 260℃ or higher is desired. It is often better to use a so-called forward tapered profile where the temperature gradient of the cylinder is low on the hopper side and high on the nozzle side, but if the polyester resin content is high, the cylinder temperature on the hopper side should be increased. A reverse tapered profile may also be used. In the present invention, extruded pellets having a specific composition ratio as described above are combined with extruded pellets having a specific composition ratio as described above.
Injection molding by blending polyester resin with [η] of 0.6 or more so that the composition is 16 parts by weight or more per 100 parts by weight, and the methacrylic resin in the injection molded product is 0.5 to 40% by weight. One of its major characteristics is that The extruded pellets and the newly blended polyester resin can be mixed uniformly using a commonly used blender, etc. In this case, it is preferable that the shapes of the pellets be close in size. . The composition of the methacrylic resin in the injection molded product is 0.5 as described above.
The content of the methacrylic resin is required to be 40% by weight.If the methacrylic resin content is less than 0.5% by weight, the transparent feeling of the molded product will be strong and the pearly feeling will hardly be observed. On the other hand, if the methacrylic resin exceeds 40% by weight, the pearl surface luster becomes weak, the mechanical strength becomes poor, and the chemical resistance becomes extremely poor, which is not preferable. In addition, the amount of the polyester resin blended into the extruded pellets is 16 parts by weight or more based on 100 parts by weight of the extruded pellets, and if it is less than 16 parts by weight, the pearlescent luster and appearance will be weakened. So I don't like it. In carrying out the present invention, any commonly used injection molding machine may be used, but the degree of pearl surface gloss and surface flow pattern tends to be affected by the screw shape and injection molding conditions. Therefore, it is preferable that the screw has a compression zone and a metering zone each having at least 3 pitches and a compression ratio of 1.5 to 4. Also important in injection molding conditions are injection speed and mold temperature.
As the injection speed increases, the surface flow pattern becomes more pronounced. However, if the injection speed is extremely high, the gloss around the gate will disappear, stains will occur, and the flow pattern on the upper surface will tend to lose its elegance, so a moderate injection speed is required. On the other hand, it is preferable that the mold temperature is set to 50℃ or less.If the mold temperature exceeds 50℃, it will take a long time to cool and solidify the injection molded product, which will lengthen the molding cycle. When molded, crystallization of the molded product may occur and the pearl surface luster may disappear, which is not preferable. The wall thickness of injection molded products is 1 to 12 from the viewpoint of moldability.
It is preferably in the range of
If it exceeds 12 mm, the polyester resin will crystallize, which will not only cause loss of pearl surface luster but also cause sink marks, which is not preferred. According to the method of the present invention, it is possible to maintain a high [η] of the polyester resin in the final molded product by reducing deterioration during molding, and it is possible to maintain a high [η] of the polyester resin in the final molded product, resulting in a bottle with excellent surface appearance, drop strength, etc. It also has the added benefit of being easier to manufacture. When carrying out the present invention, dyes and pigments, ultraviolet absorbers, antistatic agents,
Additives such as nucleating agents may be added. The injection molded product of the present invention has a strong pearly surface luster and a surface flow pattern different from conventional products due to the two-stage molding as described above, and can be used for cosmetic products such as cream containers, compacts, lipstick containers, and caps. It can be used for various products such as tabletop seasoning containers, daily necessities, pharmaceutical containers, and electrical parts such as knobs. The present invention will be specifically explained below using Examples. Examples 1 to 5, Comparative Example 1 6.5 kg of polyethylene terephthalate pellets with [η] of 1.2 were vacuum-dried at 150°C for 10 hours using a box-type vacuum dryer, and [η] (dl) was measured in chloroform at 25°C. 3.5 kg of polymethyl methacrylate pellets with a ratio of 0.6 (L/D = 24, supply zone 11D, compression zone) were added after vacuum drying at 85°C for 50 hours and mixed well using a blender.
6D, metaling zone 7D, pitch 1D, compression ratio 2.5
The pellets were fed into a 40 mmφ extruder manufactured by Toshiba Machine Co., Ltd. equipped with a screw of 100 mm and extruded to obtain pellets having an average size of 3φ×3 mm. At this time, the cylinder temperature was 260°C in the rear, 270°C in the middle, 280°C in the front, 280°C in the die, and the screw rotation speed was 60 rpm. The measured value of [η] of polyethylene terephthalate in the obtained extruded pellets was 1.03. Next, the extruded pellets that had been vacuum-dried at 150°C for 10 hours and polyethylene terephthalate pellets with [η] of 1.0 that had been vacuum-dried at 150°C for 10 hours were mixed in the proportions shown in Table 1. After mixing well with a blender, L/D=17, supply zone
8.5D, compression zone 5.3D, metalling zone
A flat plate weighing 48.5 g, average wall thickness 3 mm, and outer diameter 130 mm was molded into two molded cold molded plates with a gate diameter of 1.8 mm φ using an SJ-40C injection molding machine manufactured by each machine factory equipped with a screw of 3.2D, pitch 0.9D, and compression ratio 1.8. It was molded using a runner type mold. 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) 50Kg/cm ² , secondary injection pressure (gauge pressure) 35Kg/
cm ² , injection speed 50 g/sec, molding cycle 40 seconds,
The mold temperature was 10°C. The obtained molded product was evaluated for pearl surface gloss, surface flow pattern, and appearance change by 1 month ethanol immersion test at 40°C. The results are shown in Table 1. In addition, as Comparative Examples 2 to 5, the dried polyethylene terephthalate pellets with [η] of 1.2 used in the first stage and polymethyl methacrylate pellets with [η] of 0.6 were mixed in the proportions shown in Table 2. A single-stage mixture was injection molded in the same manner as in Example 1 to obtain a molded product. Table 2 shows the evaluation results for these molded products. The evaluation display of pearl surface gloss and surface flow pattern in Tables 1 and 2 is as follows (these evaluation methods are common to the following Examples and Comparative Examples). Pearl surface gloss ◎: Very strong pearl surface gloss expression 〇: Fairly strong pearl surface gloss expression △: Weak pearl surface gloss expression ×: Pearl surface no gloss Surface flow pattern ◎: Very strong surface flow pattern present 〇: Fairly strong surface Flow pattern present △: Weak surface flow pattern present ×: Surface flow pattern slightly observed or not present at all

【table】

[Table] Examples 6 to 9, Comparative Example 6 Pellet of ethylene (terephthalate-isophthalate) copolymer with [η] of 1.0, in which 3 mol% of isophthalic acid component was vacuum-dried at 170°C for 5 hours. , a (methyl methacrylate-methyl acrylate) copolymer with [η] (dl/g) of 0.6 measured in chloroform at 25 °C, in which 10 mol% of methyl acrylate was copolymerized, vacuum-dried at 80 °C for 25 hours. The combined pellets were mixed in the proportions shown in Table 3, and extrusion molded using the extruder and molding conditions used in Example 1 to obtain pellets having dimensions of 3 mm x 3 mm. [ Polyethylene terephthalate pellets with η] of 0.9 were mixed, and the outside diameter of the threaded part was
50mmφ, height 55mm, body average thickness 3.5mm, weight 52
Two cream containers with a capacity of 65 c.c. were molded using a hot runner mold. The molding conditions were as follows. Cylinder temperature is C ₁ 265℃,
C ₂ 270℃, C ₃ 280℃, nozzle 290℃, manifold
280℃, hot runner 290℃, mold temperature 7℃, primary injection pressure (gauge pressure) 60Kg/cm ² , secondary injection pressure (gauge pressure) 40Kg/cm ² , injection speed 55g/sec, molding cycle 27 seconds. It was hot. The obtained molded article was evaluated in the same manner as in Example 1. Those results in the third
Shown in the table.

[Table] Easy to wake up.
Examples 10 to 13, Comparative Example 7 Extruded pellets of (methyl methacrylate-methyl acrylate) copolymer/ethylene (terephthalate-isophthalate) copolymer = 20/80 (wt%) obtained in Example 7 and pellets of polyethylene terephthalate with different [η] as shown in Table 4 were mixed in equal amounts, and after thoroughly drying, injection molding was performed in the same manner as in Example 7, and molding was performed using the mold and conditions. Summer. The obtained molded article was evaluated in the same manner as in Example 1. The results are shown in Table 4.

[Table] Example 14 The extruded pellets of (methyl methacrylate-methyl acrylate) copolymer/ethylene (terephthalate-isophthalate) copolymer = 60/40 (wt%) obtained in Example 9 were As shown in the table, polyethylene terephthalate with [η] of 1.15 was mixed so that the content of methacrylic resin in the final molded product varied, and after thoroughly drying, the same injection molding machine, mold, and conditions as in Example 9 were used. Molding was carried out using
The obtained molded article was evaluated in the same manner as in Example 1. The results are shown in Table 5.

【table】

Claims (1)

[Claims] 1 Polyester resin with an intrinsic viscosity of 0.6 or more10
To extruded pellets having a resin composition of ~99% by weight and 90 to 1% by weight of methacrylic resin, add 16 parts by weight or more of a polyester resin with an intrinsic viscosity of 0.6 or more to 100 parts by weight of the extruded pellets. , and the methacrylic resin in the injection molded product is 0.5 to 40% by weight.
A method for producing an injection molded polyester product having a pearly surface luster and a surface flow pattern, the method comprising blending the polyester to have the following composition and then injection molding the product.