Resin composition, resin molded article and structure

Abstract

To provide a resin composition capable of improving tensile yield point strength compared to conventional compositions.SOLUTION: There is provided a resin composition comprising a matrix resin containing a recycled polypropylene and homopolypropylene and a fiber, wherein the content rate of the recycled polypropylene relative to the total of the matrix resin is 1 mass% or more and less than 80 mass%. The content rate of the fiber relative to the resin composition is 5 mass% or more and 40 mass% or less. The homopolypropylene is at least one of virgin homopolypropylene composed of a virgin material and recovered homopolypropylene recovered from an unused waste material.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Patent Document 1 describes "FRP recycled pellets made from thermoplastic FRP waste as a raw material, in which 80 wt% or more of the entire matrix resin made of thermoplastic resin is recycled resin, the average fiber length of the reinforcing fibers is 300 μm to 700 μm, the proportion of fibers over 1000 μm in the fiber length distribution is 5% or more, and the fiber volume content is 10% to 40%." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-114091 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, recycled resin accounts for 80 mass % or more of the total matrix resin. However, the inventors of the present invention have found that when recycled resin is included in this proportion, the tensile yield strength (the stress value when the resin changes from elastic to inertial deformation) is low, and there is room for improvement in the tensile yield strength. The problem to be solved by the present disclosure is to provide a resin composition, a resin molded article, and a structure that can improve the tensile yield strength compared to conventional resin compositions. [Means for solving the problem]

[0005] The resin composition of the present disclosure is a resin composition comprising a matrix resin containing recycled polypropylene and homopolypropylene, and fibers, wherein the recycled polypropylene content of the matrix resin is 1% by mass or more and less than 80% by mass. Other solutions will be described later in the description of the preferred embodiments of the present invention. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to provide a resin composition, a resin molded article, and a structure that can improve the tensile yield strength compared to conventional resin compositions. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of a structure including a resin molded product according to the present disclosure. [Figure 2] FIG. 10 is a perspective view of a structure including a resin molded product according to another embodiment. [Figure 3] 1 is a graph showing the magnitude of the tensile yield strength relative to the usage rate of recycled polypropylene in the matrix resin. [Figure 4] FIG. 1 is a perspective view of a jig used to measure unscrewing torque. [Figure 5] 1 is a graph showing the magnitude of unscrewing torque relative to the usage rate of recycled polypropylene in the matrix resin. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, modes for carrying out the present disclosure (hereinafter referred to as "embodiments") 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 described 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 redundant 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.

[0009] The resin composition of the present disclosure comprises a matrix resin containing recycled polypropylene and homopolypropylene, and fibers. Hereinafter, polypropylene will be abbreviated as PP, recycled polypropylene as recycled PP, and homopolypropylene as homoPP, as appropriate. The resin composition of the present disclosure may be a composition consisting only of the matrix resin and fibers, or may contain other components (colorants, antioxidants, etc.). The fibers are components that strengthen the matrix resin and are usually dispersed throughout the matrix resin.

[0010] Recycled PP is PP obtained by recycling, for example, recycled waste PP. Such PP can be obtained, for example, as PCR-PP, by crushing, cleaning, melting, and molding recycled waste PP into pellets. Recycled PP may optionally contain fibers (e.g., glass fiber, carbon fiber, etc.).

[0011] 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 (tensile strength (tensile yield strength, etc.), unscrewing torque, rigidity, etc.) are easy to predict and can be easily used as a material for resin compositions having desired physical properties.

[0012] The PP used in household electrical appliances is often block PP (block copolymer of polypropylene), so by determining the block PP content in the matrix resin, the recycled PP (PP derived from household electrical appliances) content can be determined.

[0013] 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 above-mentioned functions of the homo PP can be exhibited. 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.

[0014] In the resin composition of the present disclosure, virgin homo PP and recycled homo PP are contained in a ratio that corresponds to the lot-to-lot variation in the physical properties of recycled homo PP so that the physical properties of the resin composition meet the target values. Because both virgin PP and recycled homo PP are unused, they have high physical properties. However, recycled homo PP has inferior physical properties to virgin PP due to the processing steps it has undergone for assembly. In other words, while both virgin PP and recycled homo PP have excellent physical properties, there are some differences in their physical properties. Furthermore, the physical properties of recycled homo PP also vary somewhat depending on, for example, the location, origin, and time of collection. In other words, the physical properties of recycled homo PP may vary depending on the lot of recycled homo PP.

[0015] Therefore, the ratio of virgin PP to recycled homo PP is adjusted according to the target values ​​of physical properties of the resin composition of the present disclosure (e.g., tensile strength, unscrewing torque, etc.). This makes it possible to prevent over-specification and insufficient performance relative to the target values ​​of physical properties. A specific adjustment method involves measuring the physical properties of the virgin PP and recycled homo PP using any method, and then determining the ratio of their use based on these measurements so that the resin composition of the present disclosure achieves the target values.

[0016] The recycled PP content of the entire matrix resin is 1% by mass or more but less than 80% by mass (for example, 79% by mass or less), preferably 1% by mass or more but 75% by mass or less, more preferably 1% by mass or more but 50% by mass or less, and even more preferably 1% by mass or more but 30% by mass or less. By including recycled PP in this proportion, tensile strength, unscrewing torque, etc. can be improved compared to conventional products.

[0017] The fibers are so-called reinforcing fibers. The inclusion of fibers can, for example, strengthen the physical properties of the resin composition of the present disclosure. The fibers are, for example, at least one of virgin fibers (fibers made from virgin materials) or recycled fibers. The use of at least one of these fibers can strengthen the matrix resin. Among these, when it is desired to particularly improve the physical properties of the resin composition of the present disclosure, it is preferable to use virgin fibers. On the other hand, it is preferable to use recycled fibers in order to reduce the production cost of the resin composition of the present disclosure or to increase the usage rate of recycled materials in the resin composition of the present disclosure.

[0018] The fiber is at least one of glass fiber and carbon fiber. By using at least one of these, the matrix resin can be reinforced. Among them, glass fiber is preferably used to reduce the manufacturing cost of the present disclosure.

[0019] The fibers can be used by mixing them with a matrix resin in the form of a masterbatch, for example.

[0020] The fiber content of the resin composition of the present disclosure is 5% by mass or more and 40% by mass or less, preferably 1% by mass or more and 35% by mass or less, more preferably 15% by mass or more and 30% by mass or less, and particularly preferably 15% by mass or more and 25% by mass or less. By including fibers in this proportion, the matrix resin can be reinforced with the fibers.

[0021] FIG. 1 is a perspective view of a structure 20 including a resin molded article 21 according to the present disclosure. The resin molded article 21 is an article molded from a resin composition according to the present disclosure. In the example of FIG. 1, the structure 20 is a household electrical appliance, specifically a washing machine (including a washer-dryer). The resin molded article 21 is an outer tub, an outer tub cover, or the like of the washing machine.

[0022] The resin molded product 21 is, for example, an injection molded product. As an injection molded product, it can be molded into a desired shape. The resin molded product 21 is a component provided in one of the structures of a washing machine or a vacuum cleaner. In the example of FIG. 1, the outer tub, outer tub cover, etc., which are the resin molded products 21, are components that make up the washing machine as described above. Because a washing machine has a rotating drum 22, the resin molded product 21 is required to have strength (an example of a physical property). Therefore, by using the resin molded product 21 of the present disclosure, it is possible to achieve both the use of recycled PP and high strength.

[0023] Fig. 2 is a perspective view of a structure 20 including a resin molded product 21 of another embodiment. In the example of Fig. 2, the structure 20 is a vacuum cleaner, and the resin molded product 21 is a part that requires high strength (for example, a head, a pipe connected to the head, etc.).

[0024] Although not shown in the drawings, the structure 20 may also be a refrigerator, a cooking appliance, a rice cooker, an air conditioner, an air purifier, or the like. [Example]

[0025] The present disclosure will be described more specifically below with reference to examples.

[0026] The tensile yield strength (an example of tensile strength) was measured by varying the recycled PP content in the matrix resin. Glass fiber was used, and the glass fiber content was 20 mass% of the entire resin composition. The tensile yield strength was measured by conducting a tensile test based on JIS K 7161-1:2014, and is the stress value (strength) when the resin composition deforms from elastic to plastic. The measurement results are shown in Figure 3.

[0027] FIG. 3 is a graph showing the tensile yield strength versus the recycled PP content in the matrix resin. The recycled PP content of 80% by mass or more and 100% by mass or less is the technology described in Patent Document 1. The MD direction is the machine direction, and the TD direction is the transverse direction. In both the MD and TD directions, the tensile yield strength generally decreased as the recycled PP content increased, and increased as the recycled content decreased. In particular, the TD direction tensile yield strength tended to decrease at 50% by mass or more, but remained similar between 30% and 50% by mass. Therefore, if a tensile yield strength between 30% and 50% by mass in the TD direction is required, increasing the recycled PP content to, for example, 50% by mass can increase the recycled PP content and reduce the production cost of the resin composition of the present disclosure.

[0028] On the other hand, in the MD direction, the degree of change (tendency; slope of the tangent) in tensile yield strength at 50% by mass or more and 100% by mass or less was similar to the degree of increase in tensile yield strength at 0% by mass or more and 30% by mass or less. However, at 30% by mass or more and 50% by mass or more, the degree of change in tensile yield strength was greater than the degree of change in tensile yield strength at 0% by mass or more and 30% by mass or less and 50% by mass or more and 100% by mass or less. Thus, the degree of change differed between the MD direction and the TD direction. Therefore, it is preferable to design the resin composition of the present disclosure by focusing on such differences.

[0029] Next, using the same resin composition as that used in the measurement of the tensile yield strength, the unscrewing torque was measured. The unscrewing torque was measured in accordance with the tightening torque inspection method (unscrewing torque method). After tightening the screw with a torque of 1.5 N, the screw was loosened with a torque wrench, and the torque value when the screw started to turn was measured as the unscrewing torque.

[0030] FIG. 4 is a perspective view of the jig 30 used to measure the unscrewing torque. The jig 30 has a conical shape with a notched top. An opening 31 extending in the axial direction is formed in the center of the cone (near the center of the circle when viewed from above). The opening 31 has a circular shape when viewed from above and tapers downward. The center of the jig 30 when viewed from above coincides with the center of the opening 31 when viewed from above. The dimensions of the jig 30 were: diameter a at the top surface was 7.3 mm; diameter b of the opening 31 was 3.4 mm; diameter c of the opening at the bottom surface of the jig 30 was 3.2 mm; and height d of the jig 30 was 15 mm.

[0031] The jig 30 was made of resin, and a screw (a tapping screw for resin (PC screw) with a nominal diameter of M4) was inserted into the opening 31 of the jig 30, which was integrally molded with a resin base material (not shown), and tightened with a tightening torque of 1.5 N as described above. Then, the unscrewing torque was measured as described above.

[0032] Figure 5 is a graph showing the magnitude of unscrewing torque relative to the percentage of recycled PP used in the matrix resin. There was a tendency for the unscrewing torque to decrease as the percentage of recycled PP used increased, and for the unscrewing torque to increase as the percentage of recycled PP used decreased. When the unscrewing torque is large, the torque required to unscrew a tightened screw is large, making it difficult to unscrew (disengage). Therefore, when the percentage of recycled PP used is high, the unscrewing torque is small, and tightened screws are easy to unscrew.

[0033] However, the trend changed depending on the recycled PP usage rate. For example, when the usage rate was 80% by mass or more and 100% by mass or less (the technology of Patent Document 1 above), the unscrewing torque was almost the same, approximately 0.7 kN. Similarly, when the usage rate was 30% by mass or more and 50% by mass or less, the unscrewing torque was almost the same, approximately 0.8 kN. Therefore, if an unscrewing torque of, for example, 30% to 50% by mass is required, the recycled PP usage rate can be increased by, for example, setting the recycled PP usage rate to 50% by mass, thereby reducing the production cost of the composition of the present disclosure.

[0034] Furthermore, the degree of increase was greater from 0% to 30% by mass than from 50% to 80% by mass. Therefore, it can be said that the effect of the amount of recycled PP used on the change in unscrewing torque is small when the amount is 50% to less than 80% by mass, but is large when the amount is 0% to 30% by mass.

[0035] Furthermore, the inventors' investigations have revealed a strong correlation between the unscrewing torque shown in Figure 5 and the tensile yield strength shown in Figure 3, such that the greater the recycled PP content, the smaller the physical properties (unscrewing torque, tensile yield strength). Therefore, the measurement results of either the unscrewing torque or the tensile yield strength can be used to predict the measurement results of the other. This improves the efficiency of determining the recycled PP content in the composition of the present disclosure in order to achieve target physical property values. [Explanation of symbols]

[0036] 20 Structures 21 Resin molded products 22 Rotating drum 30 Jig 31 Aperture

Claims

1. A resin composition comprising: A matrix resin including recycled polypropylene and homopolypropylene; and a fiber, The content of the recycled polypropylene relative to the entire matrix resin is 1% by mass or more and less than 80% by mass. A resin composition characterized by:

2. The resin composition according to claim 1, The content of the fibers in the resin composition is 5% by mass or more and 40% by mass or less. A resin composition characterized by:

3. The resin composition according to claim 1, The homopolypropylene is at least one of virgin homopolypropylene made from virgin material and recovered homopolypropylene recovered from unused waste material. A resin composition characterized by:

4. The resin composition according to claim 3, The virgin homopolypropylene and the recovered homopolypropylene are contained in a ratio corresponding to the lot-to-lot variation in the physical properties of the recovered homopolypropylene so that the physical properties of the resin composition satisfy the target values. A resin composition characterized by:

5. The resin composition according to claim 4, The physical property is tensile strength A resin composition characterized by:

6. The resin composition according to claim 1, The recycled polypropylene is polypropylene derived from household electrical appliances. A resin composition characterized by:

7. The resin composition according to claim 1, The fibers are at least one of virgin fibers and regenerated fibers. A resin composition characterized by:

8. The resin composition according to claim 7, The fiber is at least one of glass fiber and carbon fiber. A resin composition characterized by:

9. A resin molded product, A molded article made of the resin composition according to claim 1. A resin molded product characterized by:

10. The resin molded product according to claim 9, The resin molded product is an injection molded product. A resin molded product characterized by:

11. The resin molded product according to claim 9, The resin molded product is a component included in either a washing machine or a vacuum cleaner. A resin molded product characterized by:

12. A structure comprising: The resin molded product according to claim 9 is provided. A structure characterized by:

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