Composite materials and methods for manufacturing composite materials

Abstract

In order to meet the recent demands for carbon neutrality, improvements in the recyclability of composite materials are desired. [Solution] The method for producing a composite material includes a first step S1a in which nanofibers are mixed with polyethylene resin to obtain a masterbatch, a second step S2a in which polyethylene resin is further mixed with the masterbatch obtained in the first step S1a to obtain an intermediate, and a third step S3a in which a styrene-based thermoplastic elastomer is mixed with the intermediate obtained in the second step S2a to obtain a composite material. The blending amount in the masterbatch is 15 to 30 parts by mass of nanofibers per 100 parts by mass of polyethylene resin. The blending amount in the composite material is 1 to 20 parts by mass of nanofibers and 5 to 35 parts by mass of styrene-based thermoplastic elastomer per 100 parts by mass of polyethylene resin.

Description

[Technical Field]

[0001] This invention relates to a composite material containing nanofibers and a method for producing the composite material. [Background technology]

[0002] Automakers are constantly demanding weight reduction for automotive interior and exterior parts such as bumpers and instrument panels. However, conventional automotive interior and exterior parts mainly use polyolefin resin reinforced with powders such as talc, which has a high specific gravity. Although the specific gravity of polyolefin resin is light (less than 1), the specific gravity of the talc powder is heavy (more than 2), so the specific gravity of the interior and exterior parts exceeds 1. On the other hand, these interior and exterior parts are required to have mechanical properties such as rigidity (elastic modulus), strength (yield stress), and impact resistance (impact value). Furthermore, in recent years, there has been a demand for carbon neutrality in products using plastics.

[0003] A method for producing a composite material by compounding carbon nanotubes with a thermoplastic resin has been proposed (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-173036 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, thermoplastic resin composites compounded with carbon nanotubes have problems such as poor impact resistance and difficulty in recycling. Automotive interior and exterior parts require impact resistance (impact value) in addition to rigidity (elastic modulus) and strength (yield stress) as mechanical properties, so it was necessary to develop a material that possessed all of these properties. For this reason, attempts were made to compound thermoplastic resins such as polyethylene resin with materials such as rubber and elastomers, but although impact resistance was improved to some extent, rigidity (elastic modulus) and strength (yield stress) decreased, so it was not possible to find a condition that satisfied both properties. Furthermore, in order to meet the recent demand for carbon neutrality, improvements in the recyclability of composite materials are desired. [Means for solving the problem]

[0006] The present invention has been made to solve at least some of the aforementioned problems and can be realized in the following embodiments or applications.

[0007] [1] One embodiment of the composite material according to the present invention is: The product contains 1 to 20 parts by mass of nanofibers and 5 to 35 parts by mass of styrene-based thermoplastic elastomer per 100 parts by mass of polyethylene resin. The aforementioned nanofibers are carbon nanotubes with an average diameter of 5 nm to 30 nm. The storage modulus at 25°C in a dynamic viscoelasticity test at a frequency of 1 Hz, in accordance with JIS K7244, is 1.4 GPa or higher, and the Charpy impact value measured by a Charpy impact test in accordance with JIS K7111 is 10.0 kJ / m². 2 The above is the characteristic feature.

[0008] [2] In one embodiment of the composite material, The storage modulus (GPa) and the Charpy impact value (kJ / m 2 The product of ) can be 10 or more.

[0009] [3] In one embodiment of the composite material, The specific gravity is less than 1, and the storage modulus (E') at 130°C is between 1 MPa and 10 MPa.

[0010] [4] One embodiment of the method for producing a composite material according to the present invention is: Step 1a involves mixing nanofibers with polyethylene resin to obtain a masterbatch, Step 2a involves further mixing the polyethylene resin with the masterbatch obtained in step 1a to obtain an intermediate, A third step involves mixing the intermediate obtained in step 2a with a styrene-based thermoplastic elastomer to obtain a composite material, Includes, The proportion of the nanofibers in the masterbatch is 15 to 30 parts by mass per 100 parts by mass of the polyethylene resin. The proportions of the composite material are 1 to 20 parts by mass of the nanofibers and 5 to 35 parts by mass of the styrene-based thermoplastic elastomer per 100 parts by mass of the polyethylene resin. The aforementioned nanofibers are carbon nanotubes with an average diameter of 5 nm to 30 nm. The first a step and the second a step include a process of thinning the polyethylene resin using an open roll in which the outer surface temperature of the polyethylene resin is set to 140°C to 155°C and the roll spacing is set to more than 0 mm and less than or equal to 0.5 mm. The third step (3a) is characterized by including a step of thinning the intermediate using an open roll in which the outer surface temperature of the intermediate is set to 150°C to 165°C and the roll spacing is set to be greater than 0 mm and less than or equal to 0.5 mm.

[0011] [5] Another embodiment of the method for producing a composite material according to the present invention is: Step 1b involves mixing nanofibers with a styrene-based thermoplastic elastomer to obtain a masterbatch, Step 2b involves mixing polyethylene resin with the masterbatch obtained in step 1b to obtain a composite material, Includes, The compounding amount in the masterbatch is 40 to 60 parts by mass of the nanofiber with respect to 100 parts by mass of the styrene-based thermoplastic elastomer, The compounding amount in the composite material is 1 to 20 parts by mass of the nanofiber and 5 to 35 parts by mass of the styrene-based thermoplastic elastomer with respect to 100 parts by mass of the polyethylene resin, The nanofiber is a carbon nanotube with an average diameter of 5 nm or more and 30 nm or less, The first b step and the second b step include a step of thinning using an open roll in which the outer surface temperature of the styrene-based thermoplastic elastomer or the polyethylene resin is 150°C to 165°C and the roll interval is set to exceed 0 mm and be 0.5 mm or less.

Effects of the Invention

[0012] According to one aspect of the composite material according to the present invention, it is excellent in recyclability and also excellent in mechanical properties. According to one aspect of the method for producing the composite material according to the present invention, a composite material excellent in recyclability and mechanical properties can be obtained.

Brief Description of the Drawings

[0013] [Figure 1] It is a flowchart of the method for producing the composite material according to the first embodiment. [Figure 2] It is a diagram schematically showing the first a step. [Figure 3] It is a flowchart of the method for producing the composite material according to the second embodiment. [Figure 4] It is a diagram schematically showing the first b step.

Embodiments for Carrying Out the Invention

[0014] Embodiments of the present invention are described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited in any way to the embodiments described below and includes various modifications that are implemented without changing the gist of the present invention. Not all of the configurations described below are necessarily essential to the present invention.

[0015] A. Composite material The composite material according to this embodiment contains 1 to 20 parts by mass of nanofibers and 5 to 35 parts by mass of styrene-based thermoplastic elastomer per 100 parts by mass of polyethylene resin.

[0016] The amount of nanofibers in the composite material is preferably 1 part by mass or more and 20 parts by mass or less, for example, it can be 1 part by mass or more and 15 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less, and particularly 3 parts by mass or more and less than 10 parts by mass. The nanofibers are dispersed throughout the composite material in a defibrated state. By incorporating an appropriate amount of nanofibers, it is possible to improve the storage modulus while maintaining a high elongation at break.

[0017] The amount of styrene-based thermoplastic elastomer in the composite material is preferably 5 parts by mass or more and 35 parts by mass or less, for example, it can be 8 parts by mass or more and 32 parts by mass or less, and more preferably 10 parts by mass or more and 30 parts by mass or less. By incorporating an appropriate amount of styrene-based thermoplastic elastomer, the Charpy impact value is improved, and products made from the composite material have excellent impact resistance.

[0018] The composite material has a storage modulus of 1.4 GPa or higher at 25°C in a dynamic viscoelasticity test at a frequency of 1 Hz in accordance with JIS K7244, and a Charpy impact value of 10.0 kJ / m² measured in a Charpy impact test in accordance with JIS K7111. 2This concludes the explanation. Each test method will be described in detail in the Examples section, along with other test methods. The storage modulus of the composite material is 1.4 GPa or higher, which is the same as or higher than the storage modulus of polyethylene resin alone. Generally, when thermoplastic elastomers are blended with polyethylene resin, the storage modulus tends to decrease significantly. However, by blending nanofibers and styrene-based thermoplastic elastomers in predetermined amounts with the polyethylene resin, the decrease in storage modulus is suppressed. Furthermore, the Charpy impact value of the composite material is 10.0 kJ / m². 2 The above is the result, and the Charpy impact value of polyethylene resin alone is 3.1 kJ / m². 2 This value is significantly higher. Generally, blending thermoplastic elastomers with polyethylene resin does not tend to increase the Charpy impact value very much. However, blending a predetermined amount of nanofibers and styrene-based thermoplastic elastomers with polyethylene resin increases the Charpy impact value. Composite materials excel in mechanical properties, particularly stiffness (elastic modulus) and impact resistance (impact value).

[0019] Here, "parts by mass" refers to "phr" unless otherwise specified, and "phr" is an abbreviation for "parts per hundred of resin or rubber," representing the percentage of additives applied to rubber, thermoplastic resins, etc.

[0020] Composite materials can have a tensile yield stress of 19 MPa or higher in tensile strength tests. A tensile yield stress of 19 MPa or higher makes the composite material less susceptible to deformation under external forces. For example, it can withstand use as an interior or exterior part of an automobile. The tensile strength test will be explained in the examples section.

[0021] Composite materials can exhibit a fracture elongation of 400% or more in tensile strength tests. This high fracture elongation results in high fracture energy and resistance to tearing, making composite materials, such as automotive interior and exterior parts, highly reliable.

[0022] Composite materials are measured by their storage modulus (GPa) and Charpy impact value (kJ / m²). 2 The product of () and can be 10 or more, and furthermore, can be 13 or more, and especially can be 15 or more. Composite materials have a high storage modulus and a high Charpy impact value. Therefore, the storage modulus (GPa) and the Charpy impact value (kJ / m 2 The fact that the product of ) is 10 or more indicates that the composite material possesses well-balanced mechanical properties.

[0023] Composite materials are characterized by their storage modulus (GPa) per part by the amount of nanofibers present in the composite material (1 part by mass) and their Charpy impact value (kJ / m²). 2 The product of () can be 3 or more. By calculating this product per part by mass of nanofiber, it can be seen that the influence of nanofibers on the mechanical properties is significant. If this product per part by mass of nanofiber is high, the amount of nanofibers can be reduced, making it possible to lighten the composite material.

[0024] The composite material has a specific gravity of less than 1 and a storage modulus (E’) at 130°C that can be 1 MPa or more and 10 MPa or less. The test for obtaining the storage modulus can be carried out in accordance with JIS K7244 by changing the temperature in the above dynamic viscoelasticity test. Even when nanofibers as a reinforcing agent are blended, the composite material is light. The composite material with a specific gravity of less than 1 can float in water, and separation during recycling is also easy. Since the storage modulus (E’) of the composite material at 130°C is 1 MPa or more and 10 MPa or less, it can be reprocessed for reuse after use. In order to maintain the mechanical properties as a composite material even after reprocessing, the nanofibers in the composite material need to be dispersed throughout in a defibrated state similar to that before reprocessing. When the storage modulus (E’) at 130°C is less than 1 MPa, the composite material is in a state close to melting, and kneading using the elasticity described later becomes difficult. Therefore, during reprocessing, the nanofibers in the composite material aggregate to form agglomerates, which affects the mechanical properties such as tensile strength and elongation at break after reprocessing. Also, when the storage modulus (E’) at 130°C exceeds 10 MPa, the rigidity of the composite material is too high and reprocessing is difficult.

[0025] As described above, the composite material is excellent in recyclability and also in mechanical properties. By being excellent in recyclability, the composite material can meet the requirements for carbon neutralization.

[0026] B. Raw materials The polyethylene resin is, for example, high-density polyethylene (HDPE) with a density of 0.941 g / cm -3 or more, medium-density polyethylene (MDPE) with a density of from 0.926 g / cm -3 to 0.940 g / cm -3 and low-density polyethylene (LDPE) with a density of from 0.910 g / cm -3 to 0.920 g / cm -3Examples include low-density polyethylene (LDPE). These polyethylene resins can be used individually or in combination of two or more. Note that ultra-high molecular weight polyethylene (UHMWPE), with a molecular weight of 1 million or more, is not included in the polyethylene used in this invention because it is difficult to process using general molding methods. Density is obtained by measurement in accordance with JIS K7112. High-density polyethylene is preferred for automotive interior and exterior parts.

[0027] Polyethylene resin can be, for example, biomass-derived polyethylene resin. Biomass-derived polyethylene resin is obtained by polymerizing ethylene derived from biomass such as plant residues and food waste. Biomass-derived ethylene monomer can be obtained by known production methods. This can be done. The raw material monomer for polyethylene resin may contain 100% by mass of biomass-derived ethylene, or 100% by mass of fossil fuel-derived ethylene, or it may contain both biomass-derived ethylene and fossil fuel-derived ethylene.

[0028] Nanofibers are carbon nanotubes with an average diameter of 5 nm to 30 nm.

[0029] The average diameter of the carbon nanotubes is preferably between 5 nm and 30 nm, and can be, for example, between 5 nm and 20 nm, or between 10 nm and 15 nm. The average diameter and average length of the carbon nanotubes can be obtained by measuring the diameter and length at 200 or more points from an electron microscope image taken at, for example, 5,000x magnification (the magnification can be appropriately changed depending on the size of the carbon nanotubes), and calculating the arithmetic mean of these measurements.

[0030] Carbon nanotubes can be so-called multi-wall carbon nanotubes (MWNTs), which have a shape formed by rolling up a single sheet of graphite with a hexagonal carbon network (graphene sheet) into a tubular shape.

[0031] Furthermore, carbon materials that partially have a carbon nanotube structure can also be used. These materials are sometimes referred to as graphite fibril nanotubes or vapor-grown carbon fibers.

[0032] While catalytic chemical vapor deposition (CCVD) and the solid carbon method can be used as synthesis methods for carbon nanotubes, they are not particularly limited. Carbon nanotubes can be obtained, for example, by thermally decomposing hydrocarbons in contact with a catalyst to produce carbon nanotubes and hydrogen. For example, the method disclosed in Japanese Patent Publication No. 2021-58848 can be used. This method is called the Direct Methane Reforming (DMR) method and can efficiently produce carbon nanotubes and hydrogen using methane gas as the hydrocarbon and hematite particles as the catalyst. Since this production method can produce hydrogen, it can contribute to carbon neutrality.

[0033] A styrene-based thermoplastic elastomer is an elastomer containing at least styrene units or styrene derivative units.

[0034] Styrene-based thermoplastic elastomers may contain, in addition to styrene units, at least one other unit selected from the group consisting of olefin units, (meth)acrylic acid units, (meth)acrylic acid ester units, and (meth)acrylonitrile units. Each of the olefin units, (meth)acrylic acid units, (meth)acrylic acid ester units, and (meth)acrylonitrile units may be present individually or in pairs or more.

[0035] There are no particular limitations on the styrene-based thermoplastic elastomer, and examples include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-butylene-styrene copolymer (SBBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and hydrogenated versions thereof. Hydrogenated styrene-based thermoplastic elastomers are preferred, and hydrogenated SEPS is particularly preferred.

[0036] The styrene-based thermoplastic elastomer is not particularly limited in terms of the content of styrene units or styrene derivative units. For example, the content of styrene units or styrene derivative units in the styrene-based elastomer can be 10% by mass or more and 80% by mass or less, the styrene content can be 13% by mass or more and 65% by mass or 20% by mass or more and 40% by mass or less.

[0037] C. Manufacturing method C-1. First Embodiment Figure 1 is a flowchart of the manufacturing method for the composite material according to the first embodiment. Figure 2 is a schematic diagram showing step 1a. The raw materials used in the manufacturing method are those described in B above.

[0038] As shown in Figure 1, the method for manufacturing a composite material according to the first embodiment includes a first a step (S1a), a second a step (S2a), and a third a step (S3a).

[0039] S1a: Step 1a is a step of mixing nanofibers with polyethylene resin to obtain a masterbatch. The amount of nanofibers in the masterbatch is 15 parts by mass or more and 30 parts by mass or less per 100 parts by mass of polyethylene resin.

[0040] As shown in Figure 2, the first step (S1a) and the second step (S2a) include a thin-passing step using an open roll 10 in which the outer surface temperature of the polyethylene resin 30 is set to 140°C to 155°C and the roll spacing is set to more than 0 mm and less than or equal to 0.5 mm. For example, in the first step (S1a), it is preferable to pass the polyethylene resin 30 through at an outer surface temperature of 140°C to 155°C. Prior to the thin-passing step, a kneading step of mixing the polyethylene resin 30 and nanofibers 40 may be performed. The roll spacing is the distance between the closest positions of roll 11 and roll 12. Rolls 11 and 12 rotate in opposite directions (directions of the arrows). The thin-passing step generates a high shear force inside the polyethylene resin 30 by passing the polyethylene resin 30 and nanofibers 40 between the narrow rolls 11 and 12, and also deforms the polyethylene resin 30 significantly due to the restoring force due to the elasticity of the polyethylene resin 30. This large deformation causes the nanofibers 40 to move significantly, and the aggregated nanofibers 40 to defibrate, allowing them to be dispersed in the polyethylene resin 30. The outer surface temperature is the outer surface temperature of the polyethylene resin 30. The polyethylene resin 30 may also be heated by setting the rolls 11 and 12 to 140°C to 155°C. By passing the polyethylene resin 30 through the open roll at an outer surface temperature that has appropriate elasticity near the melting point of the polyethylene resin 30, the restoring force of the polyethylene resin 30 is obtained when it is extruded between the rolls 11 and 12. By performing the thin-passing process multiple times, a masterbatch 60 in which the nanofibers 40 have defibrated and dispersed throughout is obtained. Although the open roll 10 was described as a two-roll example, it may also be a three-roll system.

[0041] S2a: Step 2a is a process in which polyethylene resin is further mixed with the masterbatch 60 obtained in step 1a (S1a) to obtain an intermediate. The nanofiber content in the intermediate is less than the nanofiber content in the masterbatch 60.

[0042] Step 2a may include, for example, a step of kneading the masterbatch 60, and a step of further adding polyethylene resin to the kneaded masterbatch 60 and kneading to obtain an intermediate. These two kneading steps are preferably carried out when the outer surface temperature of the polyethylene resin (masterbatch) is 140°C to 155°C. These two kneading steps can be carried out in an open roll 10, but are not limited to this and can be carried out in any known kneading apparatus.

[0043] S3a: Step 3a is a step in which a styrene-based thermoplastic elastomer is mixed with the intermediate obtained in step 2a (S2a) to obtain a composite material. The proportions of the composite material are set so that, per 100 parts by mass of polyethylene resin, there are 1 to 20 parts by mass of nanofiber and 5 to 35 parts by mass of styrene-based thermoplastic elastomer.

[0044] Step 3a (S3a) preferably includes a step of thin-passing using an open roll set to an outer surface temperature of 150°C to 165°C and a roll spacing greater than 0 mm and less than or equal to 0.5 mm. The thin-passing step can be basically carried out in the same way as in Step 1a (S1a) described above, using Figure 2, by replacing the polyethylene resin 30 and nanofiber 40 with the intermediate and a styrene-based thermoplastic elastomer. Note that Step 3a (S3a) can be carried out in the same way as Step 1a (S1a), so redundant explanations will be omitted.

[0045] The composite material obtained by step 3a (S3a) is the composite material described in detail in "A. Composite Material" above. Therefore, when products molded from the composite material, such as automotive interior and exterior parts, are collected after being distributed in the market, the collected products can be reprocessed. In reprocessing, it is preferable to knead the polyethylene resin of the collected product (chips obtained by crushing the collected product, etc.) so that the outer surface temperature is 150°C to 165°C, and then perform a thin-passing process. Since the aggregation of nanofibers 40 is suppressed by the thin-passing process, products can be manufactured again while maintaining the mechanical properties of the composite material.

[0046] C-2. Second Embodiment Figure 3 is a flowchart of the manufacturing method for the composite material according to the second embodiment. Figure 4 is a schematic diagram showing the 1b step.

[0047] As shown in Figure 3, the method for manufacturing the composite material includes a first b step (S1b) and a second b step (S2b).

[0048] S1b: Step 1b is a step of mixing nanofibers with a styrene-based thermoplastic elastomer to obtain a masterbatch. The amount of nanofibers in the masterbatch is 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of styrene-based thermoplastic elastomer.

[0049] As shown in Figure 4, steps 1b (S1b) and 2b (S2b) include a step of thin-passing the styrene-based thermoplastic elastomer 50 using an open roll 10 set to an outer surface temperature of 150°C to 165°C and a roll spacing greater than 0 mm and less than or equal to 0.5 mm. The thin-passing step can be basically carried out in the same way as in step 1a (S1a) described above using Figure 2, by replacing the polyethylene resin 30 with the styrene-based thermoplastic elastomer 50. By performing the thin-passing step multiple times, a masterbatch 60 in which the nanofibers 40 are defibrated and dispersed throughout is obtained. Note that step 1b (S1b) can be carried out in the same way as step 1a (S1a), so redundant explanations are omitted.

[0050] If the nanofiber 40 is a carbon nanotube, the kneading step and the thin-passing step described in step 1a (S1a) above can be performed.

[0051] S2b: Step 2b is a step in which polyethylene resin is mixed with the masterbatch 60 obtained in step 1b (S1b) to obtain a composite material. The proportions of the composite material are set so that, per 100 parts by mass of polyethylene resin, there are 1 to 20 parts by mass of nanofiber and 5 to 35 parts by mass of styrene-based thermoplastic elastomer.

[0052] Step 2b (S2b) involves the outer layer of the styrene-based thermoplastic elastomer and polyethylene resin. It is preferable to include a step of thin-passing using an open roll 10 with a surface temperature of 150°C to 165°C and a roll spacing greater than 0 mm and less than or equal to 0.5 mm. The thin-passing step can be performed in basically the same way as in the first step (S1a) described above, by replacing the nanofiber 40 with a masterbatch 60 using Figure 2. Note that the second step (S2b) can be performed in the same way as the first step (S1a), so redundant explanations will be omitted.

[0053] The composite material obtained in step 2b (S2b) is the composite material described in detail in "A. Composite Material" above. Therefore, when products molded from the composite material, such as automotive interior and exterior parts, are collected after being distributed in the market, the collected products can be reprocessed. In reprocessing, it is preferable to knead the polyethylene resin of the collected product (chips obtained by crushing the collected product, etc.) so that the outer surface temperature is 150°C to 165°C, and then perform a thin-passing process. Since the aggregation of nanofibers 40 is suppressed by the thin-passing process, products can be manufactured again while maintaining the mechanical properties of the composite material. [Examples]

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0055] (1) Sample preparation (1-1) Preparation of the masterbatch Masterbatches MB1 to MB5 were prepared using the formulations shown in Table 1 and the open roll 10 shown in Figures 2 and 4.

[0056] The raw materials used in the examples and comparative examples are: BioHDPE: Plant-derived high-density polyethylene manufactured by Braskem, SHC7260HDPE: Petroleum-derived high-density polyethylene manufactured by Nippon Polyethylene Co., Ltd., Novatec HD HJ560 SEPS: Septon 2002 (hydrogenated styrene-ethylene-propylene-styrene copolymer), a styrene-based thermoplastic elastomer manufactured by Kuraray Co., Ltd. BioSF: Septon SF904 (hydrogenated styrene-farnesene block copolymer), a styrene-based thermoplastic elastomer manufactured by Kuraray Co., Ltd. TPO: Santoprene 251-92W232, an olefin-based thermoplastic elastomer manufactured by Celanese. EVA: Ethylene vinyl acetate copolymer manufactured by Tosoh Corporation, UltraCene 625 TPU: BASF's urethane-based thermoplastic elastomer, Elastran 1180A CNT: Carbon nanotubes manufactured by Toda Kogyo Co., Ltd., average diameter 10nm-15nm, TC-2000 Talc: Talc manufactured by Nippon Talc Co., Ltd., Simgon That is all.

[0057] [MB1] Step 1a was performed. Specifically, BioHDPE was kneaded in an open roll until the outer surface temperature reached 140°C-155°C, then CNTs were added, and the material was passed through multiple times with the roll spacing set to more than 0 mm and less than or equal to 0.5 mm to obtain MB1.

[0058] [MB2] The 1b process was carried out. Specifically, the SEPS was kneaded in an open roll until the outer surface temperature reached 150°C-165°C, then CNTs were added, and the material was passed through multiple times with the roll spacing set to more than 0 mm and less than or equal to 0.5 mm to obtain MB2.

[0059] [MB3] The first b step was performed. Specifically, BioSF was applied to the outer surface in an open roll. The mixture was kneaded to a temperature of 150°C-165°C, pre-treated carbon nanotubes (CNTs) were added, and then the mixture was passed through multiple times with the roll spacing set to between 0 mm and 0.5 mm to obtain MB3.

[0060] [Table 1]

[0061] (1-2) Fabrication of composite materials [Example 1-3] Step 2a was performed. Specifically, MB1 was kneaded in an open roll until the outer surface temperature reached 140°C-155°C, and BioHDPE was added and kneaded in the amount of CNTs shown in Table 2 to obtain the intermediate for Example 1-3. Next, step 3a was performed. Specifically, the intermediate was kneaded in an open roll until the outer surface temperature reached 150°C-165°C, and SEPS was added in the amount shown in Table 2. Then, the material was passed through multiple times with the roll spacing set to more than 0 mm and less than or equal to 0.5 mm to obtain the composite material for Example 1-3. Furthermore, the composite material was pressure-molded at 180°C for 3 minutes to obtain a sheet-like sample of Example 1-3 with a thickness of 0.4 mm.

[0062] [Comparative Example 1] BioHDPE was kneaded in an open roll until the outer surface temperature reached 140°C-155°C, then removed and pressure-molded at 180°C for 3 minutes to obtain a sheet-like sample of Comparative Example 1 with a thickness of 0.4 mm.

[0063] [Comparative Example 2] BioHDPE was kneaded in an open roll until the outer surface temperature reached 140°C-155°C. CNTs were then added in the amounts shown in Table 2 and kneaded, after which the mixture was dispensed. The dispensed mixture was pressure-molded at 180°C for 3 minutes to obtain a sheet-like sample of Comparative Example 2 with a thickness of 0.4 mm.

[0064] [Comparative Example 3-5] Step 2a was performed. Specifically, MB1 was kneaded in an open roll until the outer surface temperature reached 140°C-155°C, and BioHDPE was added and kneaded in the amount of CNTs shown in Table 3 to obtain the intermediate for Comparative Example 3-5. Next, step 3a was performed. Specifically, the intermediate was kneaded in an open roll until the outer surface temperature reached 150°C-165°C, and TPO, EVA, or TPU was added in the amount of CNTs shown in Table 3. Then, the mixture was passed through multiple times with the roll spacing set to more than 0 mm and less than or equal to 0.5 mm to obtain the mixture for Comparative Example 3-5. Furthermore, the mixture was pressure-molded at 180°C for 3 minutes to obtain a sheet-like sample of Comparative Example 3-5 with a thickness of 0.4 mm.

[0065] [Comparative Example 6] BioHDPE was kneaded in an open roll until the outer surface temperature reached 140°C-155°C. Talc was then added in the amounts shown in Table 3 and kneaded, after which the mixture was dispensed. The dispensed mixture was pressure-molded at 180°C for 3 minutes to obtain a sheet-like sample of Comparative Example 6 with a thickness of 0.4 mm.

[0066] [Example 4-6] Step 2b was performed. Specifically, MB2 was kneaded in an open roll until the outer surface temperature reached 150°C-165°C, and then Bi was added in the proportions shown in Table 4. After adding oHDPE and kneading, the composite material samples of Example 4-6 were obtained by performing a process of passing the material through multiple times with the roll spacing set to more than 0 mm and less than or equal to 0.5 mm. Furthermore, the composite material was pressure-molded at 180°C for 3 minutes to obtain a sheet-like sample of Example 4-6 with a thickness of 0.4 mm.

[0067] [Examples 7, 8] Step 2b was performed. Specifically, MB3 was kneaded in an open roll until the outer surface temperature reached 150°C-165°C, then BioHDPE was added in the proportions shown in Table 4 and kneaded. After that, the material was passed through multiple times with the roll spacing set to more than 0 mm and less than or equal to 0.5 mm to obtain the composite material samples of Examples 7 and 8. Furthermore, the composite material was pressure-molded at 180°C for 3 minutes to obtain the sheet-like samples of Examples 7 and 8 with a thickness of 0.4 mm.

[0068] (2) Evaluation method (2-1) Tensile strength test For the samples of the examples and comparative examples, test specimens punched into the shape of a No. 7 dumbbell according to JIS K-7113-1 were subjected to tensile strength tests according to JIS K7127 using a Shimadzu Autograph AG-X tensile testing machine at 25°C and a tensile speed of 50 mm / min. The elongation at break (Eb (%)) and yield point tensile stress (Ty (MPa)) were measured. The measurement results are shown in the "Elongation (Eb)" and "Yield (Ty)" columns of Tables 2 to 4.

[0069] (2-2) DMA test For the examples and comparative examples, test specimens cut into strips (40 x 4 mm width) were subjected to DMA testing (dynamic viscoelasticity testing) in accordance with JIS K7244 using a Hitachi High-Tech Science Corporation DMA7100 dynamic viscoelasticity tester, with a chuck distance of 20 mm, a measurement temperature of -30 to 200°C, a dynamic strain of ±0.05%, and a frequency of 1 Hz.

[0070] Based on these test results, the storage modulus (E') was measured at measurement temperatures of 25°C and 130°C. The storage modulus is shown in the "E'(25°C)(GPa)" and "E'(130°C)(MPa)" columns of Tables 2 to 4. In each table, samples that melted at 130°C are indicated as "Melted".

[0071] (2-3) Charpy impact test For the examples and comparative examples, samples were molded at 180°C using an injection molding machine (Imoto Seisakusho IMC-19EE) to the size of JIS K 7139 B1 strip test pieces (with notches). A Charpy impact test was then performed using an impact testing machine from Toyo Seiki Seisakusho Co., Ltd. under the conditions of n=5, hammer weighing 1, 2, and 4 J, in accordance with JIS K7111. The Charpy impact value (I) was measured from the test results. The Charpy impact value (I) is shown in the "Impact Value (I)" column of Tables 2 to 4.

[0072] Furthermore, the DMA test results E'(25℃)(GPa) and Charpy impact value (I)(kJ / m2 The product of () was calculated. The calculation results are shown in the "E' × I" column of Tables 2 to 4.

[0073] Furthermore, the "E'×I" value was divided by the amount of CNT or CNF (phr) to calculate the "E'×I" value per unit mass part. The calculation results are shown in the "E'×I / C" column of Tables 2 to 4.

[0074] (2-4) Specific gravity calculation The specific gravity of the samples in the examples and comparative examples was measured at room temperature using an ELECTRONIC DENSIMETER SD-200L manufactured by ALFA MIRAGE. The calculation results are shown in the "Specific Gravity" column of Tables 2 to 4.

[0075] [Table 2]

[0076] [Table 3]

[0077] [Table 4]

[0078] (3) Evaluation The samples in Examples 1-8, which used BioHDPE as a base, had a storage modulus (E'(25℃)) of 1.4 GPa or higher and a Charpy impact value of 10.2 kJ / m 2 The above concludes the findings. The sample in Comparative Example 1, which is BioHDPE alone, has a storage modulus (E'(25°C)) of 1.4 GPa. Therefore, the storage modulus (E'(25°C)) of the samples in Examples 1-8 was improved by compounding them with nanofibers and thermoplastic elastomers. In addition, the Charpy impact of Comparative Example 1 was 3.1 kJ / m 2 The Charpy impact values ​​for Comparative Example 2, which was a composite of only CNTs, and Comparative Example 6, which was a composite of talc, were 3.7 kJ / m². 2 , 4.3 kJ / m 2In contrast, Examples 1-8 showed a reading of 10.4 kJ / m³. 2 As described above, the improvement is significant. Furthermore, while incorporating thermoplastic elastomers other than styrene-based thermoplastic elastomers, such as TPO, EVA, and TPU, as in Comparative Examples 3 and 5, improves the Charpy impact value somewhat, the storage modulus (E'(25°C)) decreases significantly, resulting in insufficient rigidity, which is undesirable.

[0079] The samples in Examples 1-8 had an "E'×I" value of 18.7 or higher. This indicates that the samples in Examples 1-8 have a good balance of rigidity and impact resistance even when nanofibers are incorporated.

[0080] The samples in Examples 1-8 had an "E'×I" value of 3.71 or higher per 1 phr of nanofiber. This indicates that the samples in Examples 1-8 were highly effective even with a small amount of nanofiber. Therefore, it was found that weight reduction is possible by reducing the amount of nanofiber used.

[0081] The samples in Examples 1-8 had a specific gravity of less than 1 and a (E'(130℃)) of 2.5 MPa to 6.4 MPa. It was found that the samples in Examples 1-8 were lightweight. Furthermore, it was found that the samples in Examples 1-8 were reprocessable.

[0082] The samples in Examples 1-8 had a yield point tensile stress (Ty) of 19.0 MPa or higher. This indicates that the samples in Examples 1-8 are suitable for use as automotive interior and exterior parts.

[0083] The samples in Examples 1-8 had an elongation at break (Eb) of 504% or more. The samples from Examples 1-8 were found to be excellent toughness and highly reliable materials.

[0084] The present invention includes configurations substantially identical to those described in the embodiments, for example, configurations with the same function, method, and results, or configurations with the same purpose and effect. Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Finally, the present invention includes configurations that add known technology to the configurations described in the embodiments. [Explanation of symbols]

[0085] 10…Open roll, 11,12…Roll, 30…Polyethylene resin, 40…Nanofiber, 50…Styrene-based thermoplastic elastomer, 60…Masterbatch

Claims

1. The product contains 1 to 20 parts by mass of nanofibers and 5 to 35 parts by mass of styrene-based thermoplastic elastomer per 100 parts by mass of polyethylene resin. The aforementioned nanofibers are carbon nanotubes with an average diameter of 5 nm to 30 nm. The storage modulus at 25°C in a dynamic viscoelasticity test at a frequency of 1 Hz in accordance with JIS K7244 is 1.4 GPa or higher, and the Charpy impact value measured by a Charpy impact test in accordance with JIS K7111 is 10.0 kJ / m ２ That concludes the explanation of composite materials.

2. In the composite material according to claim 1, The storage modulus (GPa) and the Charpy impact value (kJ / m ２ A composite material whose product with ) is 10 or more.

3. In the composite material according to claim 1 or claim 2, A composite material having a specific gravity of less than 1 and a storage modulus (E') at 130°C of 1 MPa or more and 10 MPa or less.

4. Step 1a involves mixing nanofibers with polyethylene resin to obtain a masterbatch, Step 2a involves further mixing the polyethylene resin with the masterbatch obtained in step 1a to obtain an intermediate, A third step involves mixing the intermediate obtained in step 2a with a styrene-based thermoplastic elastomer to obtain a composite material, Includes, The amount of nanofiber in the masterbatch is 15 to 30 parts by mass per 100 parts by mass of polyethylene resin. The proportions of the composite material are 1 to 20 parts by mass of the nanofibers and 5 to 35 parts by mass of the styrene-based thermoplastic elastomer per 100 parts by mass of the polyethylene resin. The aforementioned nanofibers are carbon nanotubes with an average diameter of 5 nm to 30 nm. The first a step and the second a step include a process of thinning the polyethylene resin using an open roll in which the outer surface temperature of the polyethylene resin is set to 140°C to 155°C and the roll spacing is set to more than 0 mm and less than or equal to 0.5 mm. A method for manufacturing a composite material, wherein step 3a includes a step of thinning the intermediate using an open roll set to an outer surface temperature of 150°C to 165°C and a roll spacing greater than 0 mm and less than or equal to 0.5 mm.

5. Step 1b involves mixing nanofibers with a styrene-based thermoplastic elastomer to obtain a masterbatch, Step 2b involves mixing polyethylene resin with the masterbatch obtained in step 1b to obtain a composite material, Includes, The proportion of the nanofibers in the masterbatch is 40 to 60 parts by mass per 100 parts by mass of the styrene-based thermoplastic elastomer. The proportions of the composite material are 1 to 20 parts by mass of the nanofibers and 5 to 35 parts by mass of the styrene-based thermoplastic elastomer per 100 parts by mass of the polyethylene resin. The aforementioned nanofibers are carbon nanotubes with an average diameter of 5 nm to 30 nm. A method for manufacturing a composite material, comprising the steps of the first b and the second b, which include a step of thinly passing the styrene-based thermoplastic elastomer or polyethylene resin through an open roll set to an outer surface temperature of 150°C to 165°C and a roll spacing greater than 0 mm and less than or equal to 0.5 mm.

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