Resin composition, resin molded article, and household electrical appliance

Abstract

To improve design, tensile strength and impact resistance of a resin composition containing polypropylene and used for an exterior component of a household electrical appliance or the like.SOLUTION: The resin composition includes a thermoplastic resin containing polypropylene and a white pigment added to the thermoplastic resin, wherein the tensile elongation at break measured by a tensile test according to ASTMD638 is larger than that of a non-added resin composition in which the white pigment is not added to the thermoplastic resin.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition, a resin molded article, and a home appliance. [Background technology]

[0002] Thermoplastic resins are used in large quantities in various electrical appliances, including household electrical appliances. Among these, resin compositions containing polypropylene as a main component are by far the most widely used thermoplastic resins because they are inexpensive yet have practically satisfactory levels of durability and impact resistance.

[0003] To minimize the impact on the natural environment after disposal, thermoplastic resins are required to be recycled horizontally rather than simply disposed of. However, the more often they are recycled, the greater the risk of foreign matter from the waste being mixed in, so measures must be taken to make the foreign matter invisible from the outside.

[0004] Patent Document 1 discloses a light-colored recycled thermoplastic resin composition with excellent appearance design on the surface of a molded article, which contains 100 parts by weight of a used thermoplastic resin composition containing residual solid foreign matter, 0.1 to 5 parts by weight of a foreign matter concealing pigment, and 0.05 to 10 parts by weight of a heat stabilizer. Patent Document 1 also discloses that test pieces deteriorated in a thermal oxidation stability test were subjected to a tensile test to measure the tensile breaking elongation, and the tensile breaking elongation retention rate, compared with the tensile breaking elongation value (initial value) before the stability test, was used to determine deterioration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-189629 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, from the viewpoint of thermal oxidation stability, the tensile elongation at break is used to determine the deterioration of the recycled thermoplastic resin composition.

[0007] As a result of extensive research, the present inventors have found that the addition of a white pigment improves the tensile strength and impact resistance of a resin composition.

[0008] An object of the present disclosure is to improve the designability, tensile strength, and impact resistance of a resin composition containing polypropylene used for exterior parts of home appliances and the like. [Means for solving the problem]

[0009] The resin composition of the present disclosure includes a thermoplastic resin containing polypropylene and a white pigment added to the thermoplastic resin. The resin composition has a tensile elongation at break measured by a tensile test in accordance with ASTM D638 that is greater than the tensile elongation at break of an additive-free resin composition in which the white pigment is not added to the thermoplastic resin. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to improve the design properties, tensile strength, and impact resistance of a resin composition containing polypropylene used for exterior parts of home appliances and the like. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a washing machine / dryer as an example of a home electric appliance according to the present disclosure. [Figure 2] 1 is a perspective view showing a vacuum cleaner as an example of a home electric appliance according to the present disclosure. [Figure 3] 1 is a table showing the measurement results of tensile strength at yield point and the like when the content of white pigment in a resin composition using recycled PP is changed. [Figure 4] 1 is a graph showing the results of DSC measurements of a resin composition in which a predetermined amount of white pigment is added to recycled block PP. [Figure 5]1 is a graph showing the results of DSC measurement of a resin composition in which a predetermined amount of white pigment is added to recycled random PP. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description of one embodiment, other embodiments applicable to the one embodiment will also be described as appropriate. The present disclosure is not limited to the one embodiment below, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. Furthermore, the same components will be given the same reference numerals, and duplicate descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for convenience of illustration, changes may be made from the actual configuration within the scope of not significantly impairing the effects of the present disclosure, and some components may be omitted or modified between drawings. Furthermore, the same embodiment does not necessarily have to include all of the configurations.

[0013] The resin composition of the present disclosure includes a matrix resin containing recycled polypropylene and homopolypropylene. Hereinafter, polypropylene will be abbreviated as "PP," recycled polypropylene as "recycled PP," and homopolypropylene as "homoPP."

[0014] Recycled PP is PP obtained by recycling waste PP collected on the market. Such PP can be obtained as PCR-PP by, for example, crushing, cleaning, melting, and molding the waste PP collected on the market into pellets. Recycled PP may contain fibers (e.g., glass fiber, carbon fiber, etc.). Here, PCR is an abbreviation for Post-Consumer Recycled Resin.

[0015] Recycled PP is, for example, PP derived from household electrical appliances. PP is often used in household electrical appliances. Furthermore, recycled PP derived from household electrical appliances has the advantage that its physical properties (such as tensile yield strength) are easy to predict and it can be easily used as a material for resin compositions with desired physical properties.

[0016] The PP used in household electrical appliances is often block PP (block copolymer of polypropylene). Therefore, by determining the block PP content in the matrix resin, the recycled PP (PP derived from household electrical appliances) content can be determined.

[0017] On the other hand, the homo PP contained in the resin composition of the present disclosure is a homopolymer of propylene. The inclusion of homo PP can improve physical properties (such as tensile strength) that are reduced by using recycled PP. The homo PP is at least one of virgin homo PP made from virgin materials and recovered homo PP recovered from unused waste materials. Recovered homo PP is also called post-industrial recycled material (PIR). These PPs have excellent physical properties. Therefore, by using at least one of these, the excellent physical properties of the homo PP can be utilized. Unused waste materials are, for example, materials discarded without being shipped to the market. Examples include waste materials discarded during factory production due to manufacturing defects, etc.

[0018] FIG. 1 is a perspective view showing a washer / dryer as an example of a home electric appliance according to the present disclosure.

[0019] The washer-dryer 10 shown in the figure is a drum-type household appliance and includes a rotating drum 11, a housing front part 12, a door 13, and an operation panel 14.

[0020] The housing front part 12 is a molded product (resin molded product) made using the resin composition of the present disclosure. The housing front part 12 is usually produced by injection molding.

[0021] Housing front surface portion 12 is required to have strength (one example of a physical property) because it transmits vibrations from rotating drum 11. Housing front surface portion 12 can achieve both design and strength by being formed from the resin composition of the present disclosure.

[0022] FIG. 2 is a perspective view showing a vacuum cleaner as an example of a home electric appliance according to the present disclosure.

[0023] The vacuum cleaner 20 shown in this figure is a rechargeable stick-type household appliance. The vacuum cleaner 20 comprises a suction head 21, an extension tube 22, a main body 23, and a charging base 24.

[0024] The suction head 21 must be strong because it will collide with walls, furniture, etc. during operation. The extension tube 22 must also be strong because it will be subjected to a strong force during a collision.

[0025] Although not shown, the home electric appliances of the present disclosure may be refrigerators, cooking appliances (microwave ovens, induction cooking heaters, etc.), rice cookers, air conditioners, air purifiers, etc. in addition to the above-mentioned washer-dryers and vacuum cleaners.

[0026] The present disclosure will be described in more detail below with reference to examples.

[0027] In the examples, the ratio of the white pigment added to the recycled PP, which is the matrix resin constituting the resin composition of the present disclosure, was changed, and the tensile strength at yield point and the like were measured.

[0028] Figure 3 is a table showing the results of measurements of tensile yield strength and other properties when the white pigment content in a resin composition using recycled PP is changed. Recycled block PP or recycled random PP was used as the recycled PP. The white pigment was a 9:1 mixture of titanium dioxide and zinc stearate (metallic soap) by weight. In the table, the amount (content) of the white pigment added is by weight, and is expressed as a percentage (wt%) of the proportion of the total resin composition. Here, a resin composition without added white pigment (white pigment added amount 0 wt%) will be referred to as an "additive-free resin composition."

[0029] The tensile strength at yield was measured by a tensile test in accordance with ASTM D638. The tensile strength at yield is the stress value (strength) when the resin composition deforms from elastic to plastic. During this test, the tensile elongation at break was also measured.

[0030] In addition, flexural strength and flexural modulus were measured by a flexural test in accordance with ASTM D790. IZOD impact strength was measured at room temperature (23°C) and -10°C in accordance with ASTM D256. Heat distortion temperature was measured at a load of 4.6 MPa in accordance with ASTM D648. Melt flow rate (MFR) was measured in accordance with ASTM D1238.

[0031] As shown in this table, in both the recycled block PP and recycled random PP, the addition of white pigment significantly improved the tensile elongation at break and the IZOD impact strength (impact resistance).

[0032] From this table, it can be seen that in the case of recycled block PP, the tensile elongation at break and IZOD impact strength are improved when the amount of white pigment added is in the range of 1 to 20 wt%. In the case of recycled block PP, the amount of white pigment added is preferably in the range of 2 to 15 wt%, and more preferably in the range of 2 to 10 wt%.

[0033] On the other hand, in the case of recycled random PP, the tensile elongation at break and IZOD impact strength are also improved when the amount of white pigment added is in the range of 1 to 20 wt%. In the case of recycled random PP, the amount of white pigment added is preferably in the range of 1 to 15 wt%, and more preferably in the range of 5 to 15 wt%.

[0034] The following reasons can be considered for this.

[0035] Adding zinc stearate to the white pigment makes it easier to mix with PP. In addition, adding zinc stearate changes the crystalline structure of the PP-PE copolymer matrix resin, reducing the amount of rigid PP crystal components. This is thought to make the resin composition more flexible and more resistant to impacts.

[0036] The mixing ratio of titanium dioxide to zinc stearate constituting the white pigment is not limited to the above example, and may be in the range of 7:3 to 9.5:0.5 by weight, preferably in the range of 8:2 to 9.5:0.5, and more preferably in the range of 8.5:1.5 to 9.5:0.5.

[0037] In this way, by setting the amount of white pigment added within a predetermined range, it is possible to improve the design, tensile strength and impact resistance.

[0038] 4 is a graph showing the results of DSC measurements of a resin composition in which a predetermined amount of white pigment has been added to recycled block PP, where DSC stands for Differential Scanning Calorimeter.

[0039] This figure shows the cases where the content of the white pigment is 0 wt%, 1 wt%, 10 wt%, and 20 wt%. The composition of the white pigment is the same as in Figure 3.

[0040] As shown in this figure, regardless of the content of the white pigment, there is an endothermic peak at approximately 173°C, which is near the melting point of PP.

[0041] FIG. 5 is a graph showing the results of DSC measurement of a resin composition in which a predetermined amount of white pigment is added to recycled random PP.

[0042] This figure shows the cases where the content of the white pigment is 0 wt%, 1 wt%, 10 wt%, and 20 wt%. The composition of the white pigment is the same as in Figure 3.

[0043] In this figure, regardless of the content of the white pigment, there are endothermic peaks at about 170°C, which is near the melting point of PP, and at about 130°C, which is near the melting point of PE.

[0044] Preferred embodiments of the present disclosure will be described below.

[0045] As the amount of white pigment added to the resin composition increases, the crystallinity of the polypropylene in the resin composition tends to decrease.

[0046] The thermoplastic resin constituting the resin composition includes recycled resin.

[0047] The thermoplastic resin may include recycled resin made from crushed waste materials.

[0048] The thermoplastic resin constituting the resin composition may contain a block copolymer or random copolymer composed of propylene and ethylene.

[0049] The white pigment includes titanium dioxide and a metal soap.

[0050] The metal soap includes zinc stearate. [Explanation of symbols]

[0051] 10: washer-dryer, 11: rotating drum, 12: front part of the housing, 13: door, 14: operation panel, 20: vacuum cleaner, 21: suction head, 22: extension tube, 23: main body, 24: charging stand.

Claims

1. a thermoplastic resin including polypropylene; A resin composition comprising: a white pigment added to the thermoplastic resin; The resin composition has a tensile elongation at break measured by a tensile test in accordance with ASTM D638 that is greater than the tensile elongation at break of an additive-free resin composition in which the white pigment is not added to the thermoplastic resin.

2. a thermoplastic resin including polypropylene; A resin composition comprising: a white pigment added to the thermoplastic resin; The resin composition has an IZOD impact strength at room temperature measured in accordance with ASTM D256 that is greater than the IZOD impact strength of an additive-free resin composition in which the white pigment is not added to the thermoplastic resin.

3. a thermoplastic resin including polypropylene; a white pigment added to the thermoplastic resin; The resin composition, wherein the white pigment contains titanium dioxide and a metal soap.

4. The resin composition according to claim 1 or 2, wherein the white pigment comprises titanium dioxide and a metal soap.

5. The resin composition according to claim 3 , wherein the metal soap comprises zinc stearate.

6. The resin composition according to claim 4 , wherein the metal soap comprises zinc stearate.

7. The resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin comprises a recycled resin.

8. The resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin comprises a block copolymer or a random copolymer composed of propylene and ethylene.

9. The resin composition according to any one of claims 1 to 3, wherein the content of the white pigment is 2 to 10 wt%.

10. A resin molded product formed from the resin composition according to any one of claims 1 to 3.

11. A home electric appliance comprising the resin molded product according to claim 10.

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