Resin composition, resin molded article, electronic device, and method for producing resin composition

Abstract

To provide a resin composition capable of enabling recycled polycarbonate to be reutilized as a new product.SOLUTION: The resin composition contains a recycled polycarbonate, a general-purpose polystyrene, and an elastic polymer having an ester group and a styrene polymer block.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a resin molded article, an electronic device, and a method for producing a resin composition. [Background technology]

[0002] Toward the realization of a low-carbon society, it is important to promote the conversion of resin materials into biomass and the recycling of these materials, and in addition to legal regulations and promotional measures, technological development is being actively pursued. In particular, with regard to recycling, along with the development of virgin resins with excellent recyclability, progress is being made in the development of technologies that can improve the performance of recycled resins, which are generated in large quantities but have deteriorated, so that they can be reused by improving their practical performance. As an example of such a technology, Patent Document 1 below discloses a method for producing a recycled resin composition, which comprises melt-kneading 100 parts by weight of resin pieces (A) obtained by crushing molded products made of polycarbonate resin with 0.1 to 30 parts by weight of an epoxidized (partially hydrogenated) diene polymer (B). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-245756 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although the polycarbonate resin has excellent initial impact resistance, it has poor fluidity and is susceptible to hydrolysis, making it a material that deteriorates rapidly. The recycled resin composition of Patent Document 1, which uses such a polycarbonate resin, is difficult to reuse as a material having impact resistance as its main property, and also has insufficient fluidity, making it difficult to reuse it as a new product.

[0005] Therefore, an object of the present invention is to provide a resin composition, a resin molded article, an electronic device, and a method for producing a resin composition that allows recycled polycarbonate to be reused as a new product. [Means for solving the problem]

[0006] To achieve this object, the present invention provides a resin composition containing recycled polycarbonate, general-purpose polystyrene, and an elastic polymer having an ester group and a styrene polymer block. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a resin composition, a resin molded article, an electronic device, and a method for producing a resin composition that enable recycled polycarbonate to be reused as a new product. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the resin composition, the resin molded article, the electronic device, and the method for producing the resin composition of the present invention will be described.

[0009] <Resin composition> The resin composition of the present embodiment contains recycled polycarbonate (R-PC), general polystyrene (GPPS), and elastomeric polymer (MBS). Of these, the elastomeric polymer (MBS) is added as an impact modifier, and is an elastomeric polymer having an ester group and a styrene polymer block.

[0010] Here, recycled polycarbonate refers to a resin recovered from molded products that use polycarbonate as a base material. Recycled polycarbonate includes polycarbonate recovered from used molded products that have been shipped to the market.

[0011] The general polystyrene may be a virgin resin as a raw material before molding into a product, or may be recycled general polystyrene (R-GPPS) as a commercially recovered resin. By using recycled general polystyrene as a constituent material of the resin composition, the utilization rate of recycled resin in the resin composition can be increased.

[0012] [Material Mixture Ratio] The blending ratio of each material in the resin composition described above is such that the content of the elastomeric polymer is 4% by mass or more and 7% by mass or less, when the total mass of the recycled polycarbonate, general-purpose polystyrene, and elastomeric polymer is taken as 100% by mass. In other words, this resin composition makes it possible to keep the content of virgin resin as a raw material before product molding to a very small amount, 4 to 7% by mass, which is the elastomeric polymer content.

[0013] The blending ratio of each material in the resin composition is preferably such that the recycled polycarbonate content is 50% by mass or more and 83% by mass or less, and the general-purpose polystyrene content is 10% by mass or more and 46% by mass or less, based on the total amount. This gives the resin composition sufficient impact strength for use as a housing part for an electronic device, and fluidity sufficient to form a resin molded product by injection molding.

[0014] Furthermore, it is more preferable that the blending ratio of each material in the resin composition is such that the recycled polycarbonate content is 50% by mass or more and 65% by mass or less, and the general-purpose polystyrene content is 30% by mass or more and 46% by mass or less, based on the total amount. This gives the resin composition high fluidity and therefore excellent moldability, making it possible to form resin molded products with complex shapes.

[0015] Furthermore, the blending ratio of each material in the resin composition may be such that the recycled polycarbonate content is 65% by mass or more and 83% by mass or less, and the general-purpose polystyrene content is 10% by mass or more and 30% by mass or less, based on the total amount. This gives the resin composition sufficient impact strength for use as a housing part constituting the exterior of an electronic device.

[0016] In the resin composition described above, the greater the content of recycled polycarbonate within the above-mentioned blending ratio range, the higher the impact strength, and the greater the content of ordinary polystyrene, the higher the fluidity.

[0017] Although polycarbonate is a resin with excellent initial impact resistance, it has poor fluidity and is easily hydrolyzed. Therefore, the recycled polycarbonate that constitutes the resin composition experiences a broadening of its molecular weight distribution toward the low molecular weight side due to hydrolysis, significantly reducing its toughness (impact strength) to a fraction of its original value. However, the degree of this reduction varies significantly depending on its market history. Therefore, it is preferable to determine the blending ratio of recycled polycarbonate, general-purpose polystyrene, and elastomeric polymer within the above-mentioned blending ratio ranges in accordance with the characteristics of the recycled polycarbonate. The characteristics of the recycled polycarbonate in this case are impact strength and fluidity. Specifically, if the fluidity of the recycled polycarbonate is low, the blending ratio of general-purpose polystyrene in the resin composition should be increased, thereby facilitating injection molding using the resin composition.

[0018] Furthermore, general-purpose polystyrene is a more chemically stable resin than polycarbonate. However, even with general-purpose polystyrene, the degree of deterioration relative to initial performance varies depending on its history in the market. For this reason, when using recycled general-purpose polystyrene as the general-purpose polystyrene that constitutes the resin composition, it is preferable to adjust the blending ratio of each material, taking into account its characteristic values, so that the characteristic values ​​(impact strength and fluidity) of the resin composition reach the target values.

[0019] The compounding ratio of each material in the resin composition as described above can be confirmed using an infrared spectroscopy (IR) device or a nuclear magnetic resonance (NMR) device.

[0020] <Method of manufacturing resin composition> The resin composition described above is produced as follows. First, recycled polycarbonate, general-purpose polystyrene, and an elastomeric polymer are prepared as raw materials. Next, the recycled materials are dried, and then the raw materials are weighed to achieve the above-mentioned blending ratio and thoroughly mixed. When determining the component ratio, the characteristic values ​​of the recycled polycarbonate are first obtained. Then, the component ratio of each material is determined based on the characteristic values ​​so that the characteristic values ​​of the resin composition reach the target values. The mixture is then placed in a screw extruder and melt-kneaded to obtain the resin composition.

[0021] In this manufacturing method, when the mixture of materials is melt-kneaded, an ester exchange reaction occurs between the recycled polycarbonate and the ester groups of the elastomeric polymer. This is thought to restore the molecular weight of the recycled polycarbonate, improve its compatibility with other resins, and significantly increase its impact strength. Furthermore, while both virgin and recycled polycarbonates (recovered resins) have low fluidity, even after the ester exchange reaction, the addition of highly fluid general-purpose polystyrene improves the resin composition to a practical level of fluidity. Furthermore, the high compatibility between the styrene polymer block contained in the elastomeric polymer and general-purpose polystyrene provides the resin composition with practical strength and uniformity.

[0022] <Resin molded products and electronic devices> The resin molded article of the embodiment is formed using the resin composition of the embodiment described above and can be used as an exterior or interior part of an electronic device. The electronic device is a device that includes an electronic circuit. Such electronic devices include, for example, a scanner that reads an original image, and a copier that prints the original image read by the scanner. The electronic device is also a printer or facsimile machine that prints image data input from the outside, or a multifunction device that combines these functions. The printer may be, for example, an electronic photography (EP) type or an inkjet type.

[0023] Such electronic devices include exterior and interior components that are resin molded articles formed using the resin composition of the above-described embodiment. These exterior and interior components constitute, for example, a housing, such as an exterior housing or a part thereof, or an interior housing or a part thereof for accommodating individual components and materials to be placed inside the exterior housing.

[0024] The resin molded product is produced by injection molding using the resin composition of the above-described embodiment.

[0025] <Effects of the embodiment> The resin composition described above contains recycled polycarbonate, general-purpose polystyrene, which has a fluidity-enhancing effect, and an elastomeric polymer, which has an impact strength-enhancing effect. This allows the resin composition to have sufficient impact strength and moldable fluidity for a product, even though it contains recycled polycarbonate, which has inherently low fluidity and whose impact strength has deteriorated in the market. As a result, this resin composition allows recycled polycarbonate to be upcycled and reused in new products.

[0026] Furthermore, the general polystyrene contained in this resin composition is an inexpensive material, both as a virgin resin and as a recycled resin (recovered resin from the market). The amount of elastomeric polymer added to this resin composition is a small amount, 4 to 7 mass %. Therefore, even if the price of recycled polycarbonate is relatively high, the overall cost of the resin composition can be kept low. Furthermore, by using recycled general polystyrene instead of general polystyrene, the utilization rate of recycled resin in the resin composition can be increased. [Example]

[0027] Resin compositions of examples to which the present invention is applied and resin compositions of comparative examples were prepared as follows, and evaluation tests were carried out.

[0028] <Preparation of Resin Composition> For Examples 1 to 3 and Comparative Examples 1 to 3, resin compositions containing R-PC, R-GPPS, and MBS in the blending ratios shown in Table 1 below were prepared. For Comparative Example 4, polycarbonate (V-PC: virgin polycarbonate) was used as a raw material before molding into a product. In each of the Examples and Comparative Examples, the R-PC and R-GPPS were the same recycled product. The MBS used was Metablen C-223A manufactured by Mitsubishi Chemical Corporation.

[0029] The resin compositions in Examples 1 to 3 and Comparative Examples 1 to 3 were prepared as follows. First, as a pre-drying step, the thermoplastic resins R-PC and R-GPPS were each dried at 80°C for 4 hours. Next, the components shown in Table 1 below were weighed out at their respective component ratios (mass%) and dry-blended.

[0030] The dry-blended mixture was then fed through the raw material supply port (hopper) of a twin-screw extrusion kneader, and melt-kneaded at a cylinder temperature of 240°C and a screw rotation speed of 400 rpm. The twin-screw extrusion kneader used was a HAAKE Rheomex PTW 16 OS twin-screw extruder manufactured by Thermo Scientific. The kneaded molten resin was cooled and then pelletized using a pelletizer, yielding the resin compositions of Examples 1 to 3 and Comparative Examples 1 to 3.

[0031] <Evaluation test> [Rating 1: Impact strength] The Izod impact strength of each of the resin compositions of Examples 1 to 3 and Comparative Examples 1 to 4 was measured according to the procedure in accordance with ISO 180 as follows. First, each resin composition was dried at 80°C for 4 hours. Then, using an injection molding machine (Babyplast manufactured by Rambaldi) with a cylinder temperature set at 240°C and a mold temperature of 50°C, notched test specimens measuring 80 mm in length, 10 mm in width, and 4.0 mm in height were obtained. The test specimens were molded using 10 throwaway shots, followed by 15 consecutive shots for shaping. The Izod impact strength of each of the 15 test specimens obtained was measured, and the average of the measured values ​​is shown in Table 1 below as the impact strength.

[0032] Impact strength is 8kJ / m 2 If the impact strength is 16kJ / m or more, the impact resistance is sufficient for use as an interior part of an electronic device. 2 If the impact resistance is equal to or greater than this, it is sufficient for use as an exterior part of an electronic device.

[0033] [Rating 2: Liquidity] The melt mass flow rate (MFR) of each resin composition of Examples 1 to 3 and Comparative Examples 1 to 4 was measured as follows. Each prepared resin composition was measured using a capillary rheometer (Capillograph 1D, manufactured by Toyo Seiki Seisakusho, Ltd.), and the viscosity at 240°C and a shear rate of 10,000 (1 / sec) was calculated by interpolation. The calculated viscosities are shown in Table 1 below.

[0034] If the viscosity is 120 Pa·S or less at 240°C, the fluidity is such that simple resin molded products can be formed by injection molding. If the viscosity is 60 Pa·S or less at 240°C, the fluidity is such that complex resin molded products can be formed by injection molding.

[0035] [Table 1]

[0036] <Evaluation results> As shown in Table 1 above, the resin compositions of Examples 1 to 3, in which the R-PC content was 50 to 83 mass%, the R-GPPS content was 10 to 46 mass%, and the MBS content was 4 to 7 mass%, had an impact strength of 8 kJ / m 2 The results were as above. Furthermore, the resin compositions of Examples 1 to 3 had a fluidity of a viscosity of 120 Pa·S or less. This confirmed that the resin compositions of Examples 1 to 3 to which the present invention was applied had sufficient impact strength for use as interior components for electronic devices, and also had fluidity sufficient to allow the formation of resin molded products with simple structures by injection molding. Furthermore, this confirmed that application of the present invention made it possible to reuse R-PC as new products.

[0037] Furthermore, the resin compositions of Examples 1 and 2, in which the R-PC content is 50 to 65% by mass and the R-GPPS content is 30 to 46% by mass, have an impact strength of 8 kJ / m 2 The resin compositions of Examples 1 and 2 had sufficient impact strength, but were also extremely easy to process by injection molding, and were capable of forming resin molded articles of complex shapes.

[0038] The resin compositions of Examples 1 and 3, in which the R-PC content was 65 to 83% by mass and the R-GPPS content was 10 to 30% by mass, had an impact strength of 16 kJ / m 2The viscosity was 120 Pa S or less, and the fluidity was 120 Pa S or less. This confirmed that the resin compositions of Examples 1 and 3 were easy to process by injection molding, and also had sufficient impact strength for use as exterior parts for electronic devices.

[0039] In contrast, the resin composition of Comparative Example 2 has increased impact strength compared to the R-PC of Comparative Example 1, but does not achieve the same level of impact strength as the V-PC of Comparative Example 4. Moreover, its low fluidity makes it difficult to reuse it as a new product. Furthermore, the resin composition of Comparative Example 3 has sufficient fluidity, but its low impact strength makes it difficult to reuse it as a new product.

Claims

1. Contains recycled polycarbonate, general-purpose polystyrene, and an elastomeric polymer having ester groups and styrene polymer blocks. Resin composition.

2. The general-purpose polystyrene is recycled general-purpose polystyrene. The resin composition according to claim 1.

3. The content of the elastic polymer is 4 to 7% by mass relative to 100% by mass of the total of the polycarbonate, the general-purpose polystyrene, and the elastic polymer. The resin composition according to claim 1.

4. The content of the polycarbonate is 50 to 83% by mass and the content of the general-purpose polystyrene is 10 to 46% by mass relative to 100% by mass of the total of the polycarbonate, the general-purpose polystyrene, and the elastic polymer. The resin composition according to claim 3.

5. The content of the polycarbonate is 50 to 65% by mass and the content of the general-purpose polystyrene is 30 to 46% by mass relative to 100% by mass of the total of the polycarbonate, the general-purpose polystyrene, and the elastic polymer. The resin composition according to claim 3.

6. The content of the polycarbonate is 65 to 83 mass% and the content of the general-purpose polystyrene is 10 to 30 mass% relative to 100 mass% of the total of the polycarbonate, the general-purpose polystyrene, and the elastic polymer. The resin composition according to claim 3.

7. A molded product made from the resin composition according to any one of claims 1 to 6. Resin molded product.

8. Forming at least a part of the housing of an electronic device The resin molded product according to claim 7.

9. A housing molded using the resin composition according to any one of claims 1 to 6. electronic equipment.

10. Recycled polycarbonate, general-purpose polystyrene, and an elastic polymer having an ester group and a styrene polymer block are melt-kneaded. A method for producing a resin composition.

11. The compounding ratio of the polycarbonate, the general-purpose polystyrene, and the elastic polymer is adjusted according to the characteristic values ​​of the polycarbonate. A method for producing the resin composition according to claim 10.

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