Method for manufacturing resin molded products

Abstract

To provide a method for manufacturing resin molded products that can reduce the risk of deterioration in fine appearance.SOLUTION: The manufacturing method for resin molded products comprises an intermediate step of producing an intermediate product 110 by incorporating a first predetermined amount of zinc oxide powder 100 into a first resin 102, and a final step of melt-molding a second resin 104, which is the same type of resin as the first resin, and the intermediate product 110 to produce a final molded product. The zinc oxide powder 100 has a particle size (d50) of 10 nanometers (nm) or more and 100 nanometers (nm) or less, the content of the zinc oxide powder 100 in the intermediate product 110 is 10 weight percent (wt.%) or more and 30 weight percent (wt.%) or less, and the content of the zinc oxide powder 100 in the final molded product is 0.1 weight percent (wt.%) or more and 2.5 weight percent (wt.%) or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a resin molded product. [Background technology]

[0002] Zinc oxide is known as a metal having trace metal action. As a molding method for producing a resin molded product containing zinc oxide, for example, a method is known in which a resin composition containing zinc oxide having a particle size (d50) of about 0.2 to 3.0 micrometers (μm) is melt-molded to produce the desired molded product (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-515319 Summary of the Invention [Problem to be solved by the invention]

[0004] When zinc oxide is ultrafine particles with a particle diameter (d50) of less than about 0.2 to 3.0 micrometers (μm), for example, ultrafine particles with a particle diameter (d50) of 100 nanometers (nm) or less, the primary particles tend to aggregate to form relatively large secondary particles, affecting the appearance of the product. Generally, the impact of such aggregation on the appearance is within the acceptable range for a product and has not previously been considered a problem. However, based on many years of experience in the manufacture of cosmetic containers, the inventors of the present invention have discovered that even extremely minor deterioration in appearance can be a fatal problem for products whose appearance is closely watched by users.

[0005] In light of the above, the present invention provides a method for producing a resin molded product that can reduce the possibility of minor deterioration in appearance. [Means for solving the problem]

[0006] The first invention is a method for producing a resin molded product, comprising: an intermediate step of incorporating a predetermined amount of zinc oxide powder into a first resin to produce an intermediate; and a final step of molding the intermediate and a second resin that is the same type of resin as the first resin to produce a final molded product, wherein the zinc oxide powder has a particle diameter (d50) of 10 nanometers (nm) or more and 100 nanometers (nm) or less, the content of the zinc oxide powder in the intermediate is any value between 10 weight percent (wt%) and 30 weight percent (wt%), and the content of the zinc oxide powder in the final molded product is any value between 0.1 weight percent (wt%) and 2.5 weight percent (wt%).

[0007] According to the first aspect of the present invention, an intermediate containing zinc oxide powder is produced, and then the intermediate is molded with a second resin to produce a final molded product. Because the first and second resins are the same type of resin, the zinc oxide contained in the intermediate is effectively dispersed in the second resin along with the first resin. As a result, the aggregation of zinc oxide powder that occurs when the final molded product is produced by directly adding zinc oxide powder to the second resin is no longer visible. Furthermore, by adjusting the content ratio of the second resin and the intermediate, the content of zinc oxide powder in the final molded product can be adjusted depending on the antibacterial performance required for the final molded product.

[0008] A second invention is a method for producing a resin molded product according to the first invention, wherein the first resin has greater fluidity than the second resin.

[0009] According to the second aspect of the invention, the zinc oxide, together with the first resin having a relatively high fluidity, can be incorporated between the pellets of the second resin which is not completely fluidized in the final step. Then, since the second resin is completely fluidized when the zinc oxide is incorporated between the pellets of the second resin, the zinc oxide can be more reliably and uniformly dispersed in the second resin.

[0010] A third invention is a method for producing a resin molded product according to the first invention, wherein the fluidity of the first resin is three times or more greater than the fluidity of the second resin.

[0011] A fourth invention is a method for producing a resin molded product according to the first invention, wherein the fluidity of the first resin is at least five times greater than the fluidity of the second resin.

[0012] A fifth invention is a method for producing a resin molded product according to the first invention, wherein the fluidity of the first resin is at least 10 times greater than the fluidity of the second resin.

[0013] A sixth invention is a method for producing a resin molded product according to the first invention, wherein the particle size (d50) of the zinc oxide is 50 nanometers (nm) or less.

[0014] According to the sixth aspect of the present invention, the ultrafine zinc oxide particles can effectively exert their trace metal function while preventing aggregation of the primary particles.

[0015] A seventh invention is a method for producing a resin molded product according to the first invention, wherein the zinc oxide powder contains fine particles having a plurality of particle sizes (d50).

[0016] Zinc oxide powder is composed of numerous fine particles. The powder contains the most fine particles with the same particle diameter (d50), but the fine particles have a predetermined distribution (typically a normal distribution) and include fine particles smaller and larger than the particle diameter (d50). Furthermore, even if zinc oxide powder with a predetermined particle diameter (d50, hereinafter referred to as the "catalog value") is purchased, the particle diameter may not necessarily be the same as the catalog value at any position (position within the zinc oxide bag). Therefore, the particle diameter of the zinc oxide powder actually used in the manufacturing process (hereinafter referred to as the "actual value") is likely to differ from the catalog value. Resin molded products manufactured using powder with an actual value larger than the catalog value may have different antibacterial performance than those manufactured using powder with a smaller value than the catalog value. In this regard, according to the seventh aspect of the present invention, the zinc oxide powder contains fine particles with multiple particle diameters (d50). For example, if the large and small particle diameters (d50) are A and B, respectively, according to the configuration of the seventh invention, when focusing on individual fine particles, the majority of fine particles have a particle diameter in the range of A to B, so it is highly likely that the particle diameter (d50) at any position in the purchased zinc oxide powder will be A to B. This allows the antibacterial performance of resin molded products to be averaged, enabling more reliable quality assurance.

[0017] An eighth invention is a method for producing a resin molded product according to the first or second invention, wherein the intermediate step and the final step are carried out continuously.

[0018] According to the eighth aspect of the present invention, an intermediate product that is not completely solidified is introduced into the final step, so that zinc oxide can be more effectively dispersed in the second resin.

[0019] A ninth invention is a method for manufacturing a resin molded product, in which, in the configuration of the eighth invention, a heat-retaining means is arranged between the intermediate step and the final step to prevent the intermediate body manufactured in the intermediate step from completely solidifying.

[0020] A tenth invention is a method for producing a resin molded product, in which, in the configuration of either the first or second invention, the intermediate is input into the final process in a state in which it is not completely solidified.

[0021] An eleventh invention is a method for producing a resin molded product, in which, in the configuration of either the first or second invention, the intermediate is introduced into the final process in a melted state by a melting means that melts the intermediate. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a method for manufacturing a resin molded product that can reduce the possibility of minor deterioration in appearance. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a conceptual diagram showing a manufacturing facility for carrying out a manufacturing process for a resin molded product according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a conceptual diagram showing a manufacturing facility for carrying out a manufacturing process for a resin molded product according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a conceptual diagram showing a manufacturing facility for carrying out a manufacturing process for a resin molded product according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a conceptual diagram showing a manufacturing facility for carrying out a manufacturing process for a resin molded product according to a fourth embodiment of the present invention. [Figure 5] FIG. 10 is a conceptual diagram showing a manufacturing facility for carrying out a manufacturing process for a resin molded product according to a fifth embodiment of the present invention. [Figure 6] FIG. 1 shows experimental results (confirmation of aggregation). [Figure 7] FIG. 1 shows experimental results (confirmation of aggregation). [Figure 8] FIG. 1 is a diagram showing experimental results (antibacterial test). [Figure 9] FIG. 1 is a diagram showing experimental results (antibacterial test). [Figure 10] FIG. 1 is a diagram showing experimental results (antibacterial test). [Figure 11] FIG. 1 is a diagram showing experimental results (antibacterial test). DETAILED DESCRIPTION OF THE INVENTION

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Note that only the basic configuration of the present invention will be described, omitting explanations of configurations that can be implemented by those skilled in the art.

[0025] First Embodiment FIG. 1 is a conceptual diagram showing a manufacturing facility 1 (hereinafter referred to as "facility 1") for carrying out a manufacturing process for a resin molded product according to a first embodiment of the present invention.

[0026] The facility 1 is composed of an extrusion unit 10 and a molding unit 50. The extrusion unit 10 is a device for carrying out an intermediate step of manufacturing an intermediate 110 by incorporating zinc oxide powder 100 into a first resin 102. The molding unit 50 is a device for carrying out a final step of melt-molding a second resin 104, which is the same type of resin as the first resin 102, and the intermediate 110 to manufacture a final molded product.

[0027] The extrusion unit 10 is an extruder, and its main components are a base 12, a drive source housing 14, a barrel 16, a screw 18, a front section 20, a die 22, a cylindrical section 24, and a hopper 30. A screen 20a is disposed in the front section 20. A heater (not shown) is disposed on the cylindrical peripheral wall of the cylindrical section 24, so that the intermediate body 110 is maintained in an unsolidified state. The cylindrical section 24 is an example of a heat retention means. A motor (not shown) for rotating the screw 18 is housed in the drive source housing 14.

[0028] A predetermined amount of first resin 102 and a predetermined amount of powder 100 are supplied to hopper 30. First resin 102 is composed of a large number of pellets. First resin 102 may be, for example, a polyolefin resin such as polypropylene, a polystyrene resin, or a polyester resin, but is not limited to these. In this embodiment, resin 102 is, for example, a highly fluid polypropylene resin.

[0029] The powder 100 is a zinc oxide powder having a particle diameter (d50) of 10 nanometers (nm) or more and 100 nanometers (nm) or less. In this embodiment, the particle diameter (d50) of the powder 100 is 35 nanometers (nm). The particle size distribution of the powder 100 is a normal distribution. In addition to the first resin 102 and the powder 100, an appropriate coupling agent such as a silane coupling agent and other additives as needed are supplied to the hopper 30. In this embodiment, the median diameter is used as the particle diameter, but this is not limited to this. For example, the average diameter or the mode diameter may be used as the particle diameter.

[0030] The content of the powder 100 in the intermediate 110 is any value between 10 weight percent (wt%) and 30 weight percent (wt%), inclusive, and is 20 weight percent (wt%) in this embodiment. In this embodiment, the content of the zinc oxide powder 100 in the intermediate 110 means the weight of the powder 100 relative to the total weight of the first resin 102 and the powder 100, without taking into account the content of additives. In the intermediate 110, the powder 100 is dispersed throughout the resin. That is, the powder 100 is not concentrated on the surface or center of the intermediate 110, but is dispersed substantially uniformly.

[0031] When a predetermined amount of first resin 102 and a predetermined amount of powder 100 are supplied to the hopper 30, the first resin 102 and the powder 100 move into the barrel 16. The first resin 102 is melted in the barrel 16 and is sent to the front section 20 while being mixed with the powder 100 by the screw 18. The first resin 102 with the powder 100 dispersed therein is formed into a thread-like shape by the die 22 to become an intermediate body 110. The intermediate body 110 moves inside the cylindrical section 24 and is sent into the molding unit 50. Because a heater is provided in the cylindrical section 24, the intermediate body 110 is sent into the molding unit 50 while remaining in an incompletely solidified state.

[0032] The molding unit 50 is an injection molding machine, and its main components are a base 52, an injection unit moving cylinder 54, a drive source storage section 56, a motor 58, an injection cylinder 60, a barrel 62, a screw 64, a screw head 66, a mold 68, a mold clamping unit 70, and a hopper 80.

[0033] A predetermined amount of second resin 104 is supplied into the barrel 62 via a hopper 80. The second resin 104 is the same type of resin as the first resin 102 and is composed of a large number of pellets. In this embodiment, the second resin 104 is a polypropylene resin. However, the first resin 102 has a higher fluidity than the second resin 104. Liquidity indicates the behavior of a synthetic resin when pressure is applied during heating and melting for molding. In this embodiment, liquidity is measured as a melt flow rate (MFR). That is, the melt flow rate (MFR) of the first resin 102 is higher than that of the second resin 104. The melt flow rate of the first resin 102 is preferably at least three times higher than that of the second resin 104, more preferably at least five times higher, and even more preferably at least ten times higher. The upper limit of the melt flow rate of the second resin 104 relative to the melt flow rate of the first resin 102 is, for example, 15 times or less.

[0034] In this embodiment, YUHWA POLYPRO 4018, a polypropylene resin manufactured by KOREA PETROCHEMICAL IND.CO., LTD., is used as the first resin 102, and SB-520, a polypropylene resin manufactured by LOTTE Chemical Corporation, is used as the second resin 104. Zinc oxide is a material manufactured by HKK SOLUTION. The melt flow rate of YUHWA POLYPRO 4018, the first resin 102, is 19 g / 10 min (ASTM D1238), and the melt flow rate of SB-520, the second resin 104, is 1.8 g / 10 min (ASTM D1238).

[0035] Unlike the present embodiment, when polystyrene is used as the first resin 102 and the second resin 104, for example, HI 425TVL, a polystyrene resin manufactured by Kumho Petrochemical Corporation, is used as the first resin 102, and Styrolution PS476L, a polystyrene resin manufactured by Ineos Styrolution, is used as the second resin 104. Furthermore, for example, G100C, a polystyrene resin manufactured by Toyo Styrene Corporation, is used as the first resin 102, and G200C, a polystyrene resin manufactured by the same company, is used as the second resin 104. In this way, the first resin 102 and the second resin 104 are the same type of resin, and the fluidity of the first resin 102 is greater than the fluidity of the second resin 104.

[0036] As described above, a predetermined amount of second resin 104 is supplied into the barrel 62 via the hopper 80. Meanwhile, a predetermined amount of intermediate 110 is supplied into the barrel 62 via the cylindrical portion 24. The second resin 104 and intermediate 110 are mixed and melt-molded, and then sent to the screw head 66 by the screw 64, where a final molded product is formed in the mold 68. The content of powder 100 in the final molded product is any value between 0.1 weight percent (wt%) and 2.5 weight percent (wt%). In this embodiment, the content of powder 100 in the final molded product is 0.1 weight percent (wt%). In this embodiment, the content of zinc oxide powder 100 in the final molded product refers to the weight of powder 100 relative to the total weight of the first resin 102, the second resin 104, and the powder 100, without taking into account the content of additives.

[0037] In the final molded product, the powder 100 is dispersed uniformly throughout the resin, i.e., the primary particles of the powder 100 do not agglomerate and are dispersed substantially uniformly throughout the final molded product.

[0038] Second Embodiment Next, a second embodiment will be described with reference to Fig. 2. Explanation of matters common to the first embodiment will be omitted, and the explanation will focus on the parts that are different from the first embodiment.

[0039] The manufacturing equipment 1 of the second embodiment is the same as that of the first embodiment. However, the zinc oxide powder fed into the extrusion unit 10 contains fine particles with a plurality of particle diameters (d50). In addition to a predetermined amount of a first resin 102, predetermined amounts of powders 100A and 100B are supplied to a hopper 30.

[0040] The total weight of powders 100A and 100B is the same as that of powder 100 in the first embodiment. Powders 100A and 100B differ in particle size (d50). In this embodiment, powder 100A has a particle size (d50) of 25 nanometers (nm), and powder 100B has a particle size (d50) of 35 nanometers (nm). Furthermore, in this embodiment, the particle sizes (d50) of powder 100A and powder 100B are the same in weight. Unlike this embodiment, the number of microparticles with multiple types of particle size (d50) is not limited to two, but may be three or more. Furthermore, unlike this embodiment, the number of microparticles with multiple types of particle size (d50) does not have to be the same, and one may be larger than the other.

[0041] <Third embodiment> Next, a third embodiment will be described with reference to Fig. 3. Explanation of matters common to the first embodiment will be omitted, and the following will focus on the differences from the first embodiment.

[0042] A manufacturing facility 1A (hereinafter referred to as "facility 1A") of the third embodiment is composed of an extrusion unit 10A and a molding unit 50. The molding unit 50 is the same as that of the first embodiment.

[0043] In contrast, the extrusion unit 10A, unlike the extrusion unit 10 of the first embodiment, processes the intermediate 110 into intermediate particles 111. The extrusion unit 10A has a cooling water tank 24, a water draining device 26, and a particle manufacturing device 28. The cooling water tank 24 has multiple rollers 24a arranged therein, which maintain and cool the filamentous intermediate 110 in water while sending it toward the water draining device 26. After the water on the surface of the filamentous intermediate 110 is removed by the water draining device 26, the filamentous intermediate 110 is cut by a rotary blade 28b of the particle manufacturing device 28 and processed into intermediate particles 111. The intermediate particles 111 are in the form of pellets. The intermediate 100 is pulled from the die 22 by two rollers 28a, 28a of the particle manufacturing device 28 through the cooling water tank 24 and the water draining device 26 to the particle manufacturing device 28.

[0044] A predetermined amount of second resin 104 and a predetermined amount of intermediate particles 111 are supplied into the barrel 62 via a hopper 80. The second resin 104 and the intermediate particles 111 are melt-molded while being mixed, and a final molded product is formed in a mold 68.

[0045] <Fourth embodiment> Next, a fourth embodiment will be described with reference to Fig. 4. Explanation of matters common to the third embodiment will be omitted, and the following will focus on differences from the third embodiment.

[0046] The manufacturing equipment 1A of the fourth embodiment is the same as that of the third embodiment. However, the zinc oxide powder fed into the extrusion unit 10A includes fine particles of multiple particle diameters (d50). For example, in addition to a predetermined amount of a first resin 102, predetermined amounts of powders 100A and 100B are supplied to the hopper 30. The total weight of the powders 100A and 100B is the same as that of the powder 100 of the third embodiment. In this embodiment, the particle diameter (d50) of the powder 100A is 25 nanometers (nm), and the particle diameter (d50) of the powder 100B is 35 nanometers (nm). Furthermore, in this embodiment, the particle diameter (d50) of the powder 100A and the particle diameter (d50) of the powder 100B are the same by weight. Unlike the present embodiment, the number of fine particles of multiple particle diameters (d50) is not limited to two, but may be three or more. Also, unlike this embodiment, the fine particles having different particle diameters (d50) do not have to be of the same amount by weight.

[0047] <Fifth embodiment> Next, a fifth embodiment will be described with reference to Fig. 5. Explanation of matters common to the fourth embodiment will be omitted, and the following will focus on the differences from the fourth embodiment.

[0048] The manufacturing equipment 1B of the fifth embodiment includes, in addition to the equipment 1A of the fourth embodiment, a melting device 90. The melting device 90 is an apparatus for melting the intermediate particles 111A and feeding the melted intermediate particles 111A into the molding unit 50, and is an example of a melting means.

[0049] The melting device 90 has a housing 92, a hollow cylindrical passage 94, and a hopper 96. A heater (not shown) is disposed on the cylindrical peripheral wall of the passage 94. The intermediate particles 111A fed into the hopper 96 are sent to the passage 94, melted in the passage, and become a melt 110AX, which is supplied into the barrel 62 of the molding machine 50.

[0050] <First Experimental Example> <<Confirmation of aggregation>> 6 and 7 are diagrams showing experimental examples in which sample plates were molded. S1 (Fig. 6) is a plate made only of normal flow polypropylene resin (second resin 104), S2 (Figs. 6 and 7) is a plate made by melt molding a mixture of normal flow polypropylene resin and zinc oxide powder, and S3 (Fig. 7) is a plate made by melt molding a mixture of an intermediate and normal flow polypropylene. The intermediate was made from high flow polypropylene (first resin 102) and zinc oxide powder.

[0051] The high-fluidity polypropylene (first resin 102) was YUHWA POLYPRO4018, a polypropylene resin manufactured by KOREA PETROCHEMICAL IND.CO., LTD., and the normal-fluidity polypropylene (second resin 104) was SB-520, a polypropylene resin manufactured by LOTTE Chemical Corporation. The zinc oxide powder used was a material manufactured by HKK SOLUTION, with a particle size (d50) of 35 nanometers (nm).

[0052] The content of zinc oxide powder in the intermediate was 20 weight percent (wt / %), and the content of zinc oxide powder in sample plates S2 and S3 was 1.0 weight percent (wt / %).

[0053] Each plate was photographed against a black background. The upper half of each plate is used for gripping, is thicker than the lower half, and has a finely textured surface. The lower half of each plate, enclosed by a dashed line, is the object of comparison. Each plate was manufactured using the manufacturing process of the third embodiment described above.

[0054] Comparing S1 and S2 in Figure 6, S2 appears slightly whiter overall than S1 due to the influence of zinc oxide. In addition, S2 has noticeable scattered white clumps due to the aggregation of zinc oxide particles.

[0055] Comparing S2 and S3 in Figure 7, S2 shows noticeable scattered white lumps due to aggregation of zinc oxide microparticles. S2 in Figure 7 is the same photograph as S2 in Figure 6, but arrows indicate particularly noticeable aggregation areas. The areas near the tips of the arrows that appear whiter than the surrounding area are the aggregation areas. In S2, many aggregation areas are present in the symmetrical lower half, but aggregation areas are also visible in the upper half of the grip. In contrast, no aggregation is visible in S3.

[0056] <<Antibacterial test results>> Test pieces (herein, these test pieces are also referred to as "sample plate S2" and "sample plate S3") were prepared using the same manufacturing method and ingredients as sample plates S2 and S3. Sample plates S2 and S3 were prepared with zinc oxide powder contents of 0.1 weight percent (wt / %), 0.25 weight percent (wt / %), 0.5 weight percent (wt / %), and 1.0 weight percent (wt / %), respectively, and antibacterial tests were conducted. Figure 8 is a photograph of the results of the antibacterial test on sample plate S2, and Figure 9 is a photograph of the results of the antibacterial test on sample plate S3. The antibacterial test was conducted in accordance with JIS Z2801. Specifically, the following procedure was followed. 1. Drop 0.4 ml of test bacteria liquid onto a test piece (5 cm x 5 cm) in a petri dish, cover it with film (4 cm x 4 cm), and then put the lid on the petri dish. 2. Incubate the dish at 35°C and 90% RH or higher for 24 hours. 3. After 24 hours, wash off the test bacteria from the film and test specimen. 4. Measure the number of bacteria in the rinse solution. Calculate the antibacterial activity value according to the following formula (calculating the number of digits): Antibacterial activity value = log(1cm of untreated sample) 2 Number of viable bacteria after incubation per 1cm of processed sample) - log( 2 (Number of viable bacteria after incubation per 100ml)

[0057] As shown in Figures 8 and 9, antibacterial effects were observed in both sample plates S2 and S3 when the zinc oxide content was 0.5 weight percent or more. No significant difference in antibacterial effect was observed between sample plates 2 and S3. In the photographs of Figures 8 and 9, sample plate S3 appears to have a higher antibacterial effect, but if a difference in the number of bacteria is considered significant, no significant difference was observed.

[0058] In addition, zinc oxide powder with a particle size (d50) of 100 nanometers (nm) was used, and aggregation confirmation and antibacterial tests were conducted in the same manner as in the first experimental example described above, and the results were similar to those of the first experimental example.

[0059] <Second Experimental Example> Similar coagulation confirmation and antibacterial tests were conducted using polystyrene resin instead of the polypropylene resin used in the first experimental example. S2ps in Figure 10 is a plate formed by melt-molding zinc oxide powder directly into polystyrene resin with normal fluidity, while S3ps in Figure 11 is a plate formed by melt-molding a mixture of an intermediate and polystyrene resin with normal fluidity. The intermediate was made from high-fluidity polystyrene resin (first resin 102) and zinc oxide powder.

[0060] The results of the confirmation of aggregation (not shown) were the same as in Experimental Example 1. The results of the antibacterial test are shown in Figures 10 and 11. Figure 10 is a photograph of the results of the antibacterial test on sample plate S2ps, and Figure 11 is a photograph of the results of the antibacterial test on sample plate S3ps.

[0061] 10 and 11, the antibacterial effect was observed in both sample plates S2ps and S3ps when the zinc oxide content was 0.1 weight percent or more. No significant difference in the antibacterial effect was observed between sample plates S2ps and S3ps.

[0062] The method for manufacturing a resin molded product of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Furthermore, the above-described embodiments can be combined as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0063] 1,1A,1B manufacturing equipment 10,10A Extrusion Unit 50 molding units 80 Hopper 90 Melting Device 100, 100A, 100B Zinc oxide powder 102 First Resin 104 Second Resin 110,110A intermediate 111,111A intermediate particles

Claims

1. an intermediate step of incorporating a predetermined amount of zinc oxide powder into a first resin to produce an intermediate; a final step of molding a second resin, which is the same type of resin as the first resin, and the intermediate product to produce a final molded product; The zinc oxide powder has a particle diameter (d50) of 10 nanometers (nm) or more and 100 nanometers (nm) or less, The content of the zinc oxide powder in the intermediate is any value between 10 weight percent (wt%) and 30 weight percent (wt%), The content of the zinc oxide powder in the final molded product is any value between 0.1 weight percent (wt%) and 2.5 weight percent (wt%). A method for manufacturing resin molded products.

2. The method for producing a resin molded product according to claim 1 , wherein the first resin has a higher fluidity than the second resin.

3. 2. The method for producing a resin molded product according to claim 1, wherein the fluidity of the first resin is at least three times greater than the fluidity of the second resin.

4. 2. The method for producing a resin molded product according to claim 1, wherein the fluidity of the first resin is at least five times greater than the fluidity of the second resin.

5. 2. The method for producing a resin molded product according to claim 1, wherein the fluidity of the first resin is at least 10 times greater than the fluidity of the second resin.

6. 2. The method for producing a resin molded product according to claim 1, wherein the particle diameter (d50) of the zinc oxide is 50 nanometers (nm) or less.

7. The method for producing a resin molded product according to claim 1 , wherein the zinc oxide powder contains fine particles having a plurality of particle sizes (d50).

8. The method for producing a resin molded product according to claim 1 or 2, wherein the intermediate step and the final step are carried out continuously.

9. 9. The method for producing a resin molded product according to claim 8, wherein a heat-retaining means is disposed between the intermediate step and the final step to prevent the intermediate body produced in the intermediate step from completely solidifying.

10. 3. The method for producing a resin molded product according to claim 1, wherein the intermediate product is introduced into the final step in a state where it is not completely solidified.

11. 3. The method for producing a resin molded product according to claim 1, wherein the intermediate is introduced into the final step in a state where the intermediate is melted by a melting means for melting the intermediate.

Images