Resin composition and method for producing the same

Abstract

One embodiment of the present invention provides: a resin composition which contains a polypropylene resin and cellulose fibers and has excellent transparency; a method for producing this resin composition; and a molded body which is formed of this resin composition. Another embodiment of the present invention provides: a resin composition which has a low linear expansion coefficient and high toughness, while having excellent transparency; a method for producing this resin composition; and a molded body which is formed of this resin composition. Another embodiment of the present invention provides: a resin composition which contains a polypropylene resin, a styrene elastomer and cellulose fibers, wherein if the polypropylene resin is molded into a sheet that has a thickness of 0.2 mm and the sheet is measured by an Abbe method, the ratio (C2 / P1) of the refractive index (C2) of the cellulose fibers as calculated by structure-property relationship on the basis of the molecular structure of the cellulose fibers to the refractive index (P1) of the polypropylene resin is 0.950 to 1.050.

Description

[Technical Field]

[0001] The present invention relates to a resin composition comprising a polypropylene resin and cellulose fibers, a method for producing the same, and a molded article formed from the resin composition. [Background technology]

[0002] Polypropylene (PP) resins have been widely used in various applications due to their excellent balance of various mechanical properties such as tensile strength and impact resistance, as well as advantages such as transparency, ease of molding, light weight, and low environmental impact during disposal. In recent years, with growing concern for environmental issues, there has been research into using polypropylene resins in ways that further reduce the environmental impact, such as using dope-dyed materials that can be used as is without the need for painting.

[0003] Styrene elastomers are known as modifiers that improve the toughness and impact resistance of polypropylene resins. In composites of polypropylene resin and styrene elastomers, the styrene elastomer is finely dispersed in the polypropylene resin, contributing to improved impact resistance.

[0004] For example, Patent Document 1 describes a polypropylene resin composition suitable for use as an unpainted resin molding material because it has scratch resistance that is compatible with impact resistance, comprising 75-90% by weight of a polypropylene resin, 7-15% by weight of a hydrogenated styrene-butadiene-styrene copolymer elastomer (A) with a styrene content of 18-42% by weight, and 3-10% by weight of a hydrogenated styrene-butadiene-styrene copolymer elastomer (B) with a styrene content of 12-15% by weight.

[0005] On the other hand, various fillers are used in resin compositions to improve their mechanical properties. In the case of fillers, various methods for reducing environmental impact are being considered, and the use of cellulose is being explored, focusing on its advantages as a low-density and renewable material. Among these, cellulose fibers are advantageous because they provide a good improvement in physical properties per unit of usage.

[0006] Patent Document 2 describes a cellulose composite resin that has high impact strength and suppresses resin discoloration to an extent that does not pose a problem in coloring to a desired color, and is characterized in that it comprises a main resin, cellulose fibers, a dispersant, and a rubber-containing polymer, wherein the α-cellulose content in the cellulose fibers is 50% by mass or more and less than 80% by mass.

[0007] Patent Document 3 aims to provide a resin composition with excellent environmental properties, minimal reduction in impact strength, low specific gravity, high rigidity, and excellent molded appearance by uniformly dispersing nanonatural polymers in a matrix component such as a resin, and further aims to provide a resin composition with suppressed coloration. It describes a molten mixture characterized by containing a nanonatural polymer and an oligomer mainly composed of a vinyl aromatic compound. Patent Document 3 states that the nanonatural polymer may be cellulose nanofiber and the oligomer may be a styrene-based oligomer. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2012 / 160869 [Patent Document 2] Japanese Patent Publication No. 2020-33541 [Patent Document 3] International Publication No. 2020 / 240935 [Overview of the project] [Problems that the invention aims to solve]

[0009] In molded articles containing polypropylene resin and styrene elastomer, when cellulose nanofibers are used as fillers, property improvements due to cellulose nanofibers (e.g., reduction of the coefficient of thermal expansion and improvement of elastic modulus or toughness) can be achieved. However, the presence of cellulose nanofibers has the problem of reducing the transparency of the molded article.

[0010] One aspect of the present invention aims to solve the above problems and provide a resin composition comprising a polypropylene resin and cellulose fibers and having excellent transparency, a method for producing the same, and a molded article formed from the resin composition. Another aspect of the present invention aims to solve the above problems and provide a resin composition having a low coefficient of thermal expansion, high toughness, and excellent transparency, a method for producing the same, and a molded article formed from the resin composition. [Means for solving the problem]

[0011] This disclosure includes the following items: [Item 1] A resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose fibers, A resin composition in which the polypropylene resin is formed into a sheet with a thickness of 0.2 mm, and the ratio (C2 / P1) of the refractive index (C2) of the cellulose fibers, calculated by the structural-property correlation method based on the molecular structure of the cellulose fibers, to the refractive index (P1) of the polypropylene resin measured by the Abbe formula is 0.950 to 1.050. [Item 2] A resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose fibers, A resin composition in which the polypropylene resin is formed into a sheet with a thickness of 0.2 mm, and the difference (|C2-P1|) between the refractive index (P1) of the polypropylene resin when the sheet is measured by the Abbe formula and the refractive index (C2) of the cellulose fibers calculated by the structural-property correlation method based on the molecular structure of the cellulose fibers is 0.025 to 0.090. [Item 3] When a control composition is formed into a sheet with a thickness of 0.2 mm, and the refractive index (R1) of the sheet is measured using the Abbe formula, the ratio (C2 / R1) of the refractive index (C2) of the cellulose fibers, calculated by the structural-property correlation method based on the molecular structure of the cellulose fibers, to the refractive index (R1) of the sheet is 0.970 to 1.050. The control composition consists of the same polypropylene resin and styrene elastomer as the resin composition, and The resin composition according to item 1 or 2, wherein the mass ratio of polypropylene resin to styrene elastomer in the control composition is equal to the mass ratio of polypropylene resin to styrene elastomer in the resin composition. [Item 4] When a control composition is formed into a sheet with a thickness of 0.2 mm, the difference (|C2-R1|) between the refractive index (R1) of the sheet measured by the Abbe formula and the refractive index (C2) of the cellulose fibers calculated by the structural-property correlation method based on the molecular structure of the cellulose fibers is between 0.001 and 0.100. The control composition consists of the same polypropylene resin and styrene elastomer as the resin composition, and A resin composition according to any of items 1 to 3, wherein the mass ratio of polypropylene resin to styrene elastomer in the control composition is equal to the mass ratio of polypropylene resin to styrene elastomer in the resin composition. [Item 5] The resin composition according to item 3 or 4, wherein the refractive index (R1) of the control composition is 1.450 to 1.550. [Item 6] The resin composition according to item 1 or 2, wherein the refractive index (P1) of the polypropylene resin is 1.450 to 1.550. [Item 7] A resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose fibers, A resin composition in which the ratio (C2 / P2) of the refractive index (C2) of the cellulose fiber, calculated by the structural-property correlation method based on molecular structure, to the refractive index (P2) of the polypropylene resin, calculated by the structural-property correlation method based on molecular structure, is 1.020 to 1.080. [Item 8] A resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose fibers, A resin composition in which the difference (|C2-P2|) between the refractive index (P2) of the polypropylene resin calculated by the structural-property correlation method based on its molecular structure and the refractive index (C2) of the cellulose fiber calculated by the structural-property correlation method based on its molecular structure is 0.050 to 0.100. [Item 9] The resin composition according to any one of items 1 to 8, wherein the refractive index (C2) of the cellulose fiber is 1.480 to 1.600. [Item 10] The cellulose fiber is a modified cellulose fiber, The resin composition according to item 9, wherein the refractive index (C2) of the cellulose fibers is 1.480 to 1.580. [Item 11] The cellulose fiber is an acetylated cellulose fiber, The resin composition according to any one of items 1 to 10, wherein the degree of acetyl substitution of the acetylated cellulose fiber is 0.1 to 1.5. [Item 12] The resin composition according to any one of items 1 to 11, wherein the average fiber diameter of the cellulose fibers is 1000 nm or less. [Item 13] The specific surface area of ​​the cellulose fiber is 40 to 200 m². 2 A resin composition according to any of items 1 to 12, which is / g. [Item 14] A resin composition according to any one of items 1 to 13, wherein the ratio of the SP value of the cellulose fiber to the SP value of the polypropylene resin is 1.3 to 1.9. [Item 15] The resin composition according to any one of items 1 to 14, wherein the polypropylene resin is homopolypropylene. [Item 16] The resin composition according to any one of items 1 to 15, wherein the melt mass flow rate (MFR) of the polypropylene resin at 230°C and a load of 21.2 N is 10 to 80 g / 10 min. [Item 17] The resin composition according to any one of items 1 to 16, wherein the styrene-based elastomer has a melt mass flow rate (MFR) of 0.5 to 20 g / 10 min at 230°C and a load of 21.2 N. [Item 18] In the aforementioned resin composition, a volume of 110 μm 3 A resin composition according to any of items 1 to 17, wherein the volume ratio of coarse aggregates is 5% or less. [Item 19] Polypropylene resin 50% to 94.5% by mass, Styrene-based elastomer 5% to 40% by mass, Cellulose fiber 0.5% to 30% by mass, As optional components, liquid rubber 0% to 30% by mass, and As an optional component, surfactant 0% to 30% by mass, A resin composition containing any of the items 1 to 18. [Item 20] A resin composition according to any one of items 1 to 19, further comprising liquid rubber. [Item 21] A resin composition according to any one of items 1 to 20, further comprising a surfactant. [Item 22] The resin composition comprises a styrene-based resin containing the styrene-based elastomer, The resin composition is The aforementioned polypropylene resin, 50% to 89.5% by mass, The styrene-based elastomer, 10% to 40% by mass, and The aforementioned cellulose fibers: 0.5% to 30% by mass A resin composition containing any of the items 1 to 21. [Item 23] The resin composition according to item 22, wherein the polypropylene resin is molded into a sheet with a thickness of 0.2 mm, and the ratio (S1 / P1) of the refractive index (S1) of the styrene resin, when molded into a sheet with a thickness of 0.2 mm and measured by the Abbe formula, to the refractive index (P1) of the polypropylene resin, when the sheet is measured by the Abbe formula, is 0.950 to 1.050. [Item 24] A method for producing a resin composition as described in any of items 1 to 23, A method comprising a mixing step of mixing a polypropylene resin, a styrene elastomer, and cellulose fibers. [Item 25] The aforementioned mixing step, A process to obtain an elastomer masterbatch containing styrene-based elastomer and cellulose fibers, The process involves kneading the elastomer masterbatch with the polypropylene resin, The method described in item 24, including the method described in item 24. [Item 26] The resin composition further comprises one or more selected from the group consisting of liquid rubber and surfactant, and the method is The process further includes obtaining a cellulose masterbatch containing one or more selected from the group consisting of cellulose fibers, liquid rubber, and surfactants. The method according to item 25, wherein a styrene-based elastomer and the cellulose masterbatch are mixed to obtain the elastomer masterbatch. [Item 27] The resin composition comprises a styrene-based resin containing the styrene-based elastomer, In the mixing step, the polypropylene resin, the styrene resin, and the cellulose fibers are mixed. The method according to any one of items 24 to 26, wherein the polypropylene resin is molded into a sheet with a thickness of 0.2 mm, and the ratio (S1 / P1) of the refractive index (S1) of the styrene resin, when molded into a sheet with a thickness of 0.2 mm and measured by the Abbe formula, to the refractive index (P1) of the polypropylene resin, when the sheet is measured by the Abbe formula, is 0.950 to 1.050. [Item 28] A resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose nanofibers, In the resin composition, the polypropylene resin forms a continuous phase. A dispersed phase is formed in the continuous phase, comprising the cellulose nanofibers and a polymer coating the cellulose nanofibers. The polymer is a resin composition containing the styrene-based elastomer. [Item 29] A method for producing the resin composition described in item 28, A method comprising a mixing step of mixing a polypropylene resin, a styrene elastomer, and cellulose nanofibers. [Item 30] A method for producing a resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose nanofibers, A process for obtaining an elastomer masterbatch containing a styrene-based elastomer and cellulose nanofibers, and A step of kneading the elastomer masterbatch with the polypropylene resin, Methods that include... [Item 31] Automotive body panels comprising the resin composition described in any of items 1-23 and 28. [Effects of the Invention]

[0012] According to one aspect of the present invention, a resin composition comprising a polypropylene resin and cellulose fibers and having excellent transparency, a method for producing the same, and a molded article formed from the resin composition can be provided. According to another aspect of the present invention, a resin composition having a low coefficient of thermal expansion, high toughness, and excellent transparency, a method for producing the same, and a molded article formed from the resin composition may be provided. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows a scanning electron microscope (SEM) image of a cross-section of the resin composition obtained in Example 2-1. [Modes for carrying out the invention]

[0014] The following describes exemplary embodiments of the present invention (hereinafter abbreviated as "Embodiments"), but the present invention is not limited to these embodiments. Unless otherwise specified, the characteristic values ​​of this disclosure are measured by the methods described in the [Examples] section of this disclosure or by methods that are understood to be equivalent to those of a person skilled in the art.

[0015] ≪Resin Composition: First Embodiment≫ One aspect of the present invention provides a resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose fibers. In one aspect, the resin composition comprises a styrene resin containing the styrene elastomer. In a typical aspect, the polypropylene resin may form a continuous phase and the styrene elastomer (or styrene resin) may form a dispersed phase in the resin composition. Cellulose is inherently hydrophilic due to its hydroxyl groups, but if at least some of the hydroxyl groups of cellulose fibers are modified, they may be more hydrophobic than unmodified cellulose fibers.

[0016] In a composite of a polypropylene resin and a styrene elastomer, the styrene elastomer not only improves the toughness of the polypropylene resin and thus its impact resistance, but can also contribute to maintaining or improving the excellent transparency inherent in the polypropylene resin. The inventors have investigated various methods for obtaining a resin composition with high transparency (i.e., high ultraviolet and visible light transmittance) while obtaining the desired reinforcing effect from the filler when further compounding such a composite for the purpose of improving mechanical properties. When trying to obtain a resin composition containing a filler and having excellent transparency, it is useful to bring the refractive index of the filler close to that of other components in the resin composition. The inventors have focused on the fact that in a composition containing a polypropylene resin, a styrene elastomer, and cellulose fibers, in particular, controlling the refractive index ratio or refractive index difference between the polypropylene resin and the cellulose fibers contributes to the high transparency of the resin composition as a whole, and have found that controlling the refractive index of the cellulose fibers by controlling the modified state of the cellulose fibers is advantageous in achieving a high degree of compatibility between the mechanical properties and transparency of the resin composition. The resin composition of this embodiment can have high transparency in one aspect, and when such a resin composition is used as a dope material, excellent color development and / or brilliance can be exhibited.

[0017] <Refractive index> In this disclosure, the refractive index of the polypropylene resin is, in one embodiment, the refractive index evaluated by the following procedure 1, and in one embodiment, the refractive index evaluated by the following procedure 2. Also in this disclosure, the refractive index of the styrene resin is the refractive index evaluated by the following procedure 1. Also in this disclosure, the refractive index of the cellulose fiber is the refractive index evaluated by the following procedure 2.

[0018] [Step 1] In this procedure, 1 g of material is preheated at 200°C under vacuum for 5 minutes, then pressed at 10 MPa and held for 1 minute, and then rapidly cooled at room temperature to form a sheet with a thickness of 0.2 mm. The refractive index of the sheet is then measured using an Abbe refractometer. In one embodiment, the above material is a starting material used in the production of a resin composition. However, if evaluation using the starting material is not possible, a sample isolated by treating the resin composition with an organic or inorganic solvent that dissolves polypropylene or styrene resins to dissolve the resin, removing impurities by filtration extraction, and then distilling off the solvent from the resulting solution may be used.

[0019] [Step 2] In this procedure, the refractive index is calculated using the structure-property correlation method based on the molecular structure of the material (more specifically, the monomer composition) for polypropylene resins and the molecular structure of the material (more specifically, the presence or absence of substitution, the type of substituent, and the degree of substitution) for cellulose fibers. Specifically, the refractive index is determined by calculation using the Synthia module of Materials Studio manufactured by BIOVIA Corporation. Details of the calculation method will be described later in the [Examples] section of this disclosure.

[0020] [Refractive index of cellulose fibers] In one embodiment, the refractive index of the cellulose fibers is adjusted to a range close to that of the polypropylene resin. This can suppress interfacial reflection between the cellulose fibers and the polypropylene resin in the resin composition. Reflection occurring at localized areas, such as the interface between the resin component and the filler component, in the resin composition leads to increased light scattering throughout the resin composition, and therefore to increased haze. Suppressing interfacial reflection contributes to improved transparency by reducing haze in the resin composition. From the above viewpoint, in one embodiment, the refractive index (C2) of the cellulose fibers is 1.480 or higher, or 1.500 or higher, or 1.510 or higher, or 1.520 or higher, and in one embodiment, 1.600 or lower, or 1.590 or lower, or 1.580 or lower, or 1.570 or lower, or 1.560 or lower.

[0021] When cellulose fibers are modified cellulose fibers, the refractive index (C2) can typically be between 1.480 and 1.580.

[0022] In one embodiment, the refractive index of the cellulose fiber may be adjusted to a desired range by controlling the type and / or degree of substitution of substituents on the cellulose fiber.

[0023] [Refractive index of polypropylene resins] The refractive index (P1) of the polypropylene resin evaluated in Procedure 1 of this disclosure is, in one embodiment, 1.450 or higher, or 1.490 or higher, or 1.500 or higher, and in another embodiment, 1.550 or lower, or 1.530 or lower, or 1.520 or lower. When performing the evaluation according to Procedure 1 on the polypropylene resin in a resin composition, the resin composition may be treated with an organic or inorganic solvent that dissolves the polypropylene resin to dissolve the resin, and the polypropylene resin isolated by removing the solvent from the solution obtained by removing impurities by filtration extraction may be used for sample sheet preparation and refractive index measurement according to Procedure 1.

[0024] The refractive index (P2) of the polypropylene resin evaluated in Procedure 2 of this disclosure is, in one embodiment, 1.410 or higher, or 1.440 or higher, or 1.450 or higher, and in one embodiment, 1.510 or lower, or 1.490 or lower, or 1.480 or lower.

[0025] The refractive index (S1) of the styrene-based resin evaluated in Procedure 1 of this disclosure (or the refractive index of each of the polymers corresponding to the styrene-based resin if there are two or more polymers in the resin composition) is, in one embodiment, 1.450 or higher, or 1.470 or higher, or 1.480 or higher, or 1.490 or higher, and in one embodiment, 1.550 or lower, or 1.520 or lower, or 1.510 or lower, or 1.500 or lower.

[0026] [Relationship between the refractive index of polypropylene resin and cellulose fiber] The ratio (C2 / P1) of the refractive index (C2) of the cellulose fiber evaluated in Procedure 2 of this Disclosure to the refractive index (P1) of the polypropylene resin evaluated in Procedure 1 of this Disclosure is, in one embodiment, 0.950 or more, or 0.970 or more, or 0.980 or more, or 0.990 or more, and in one embodiment, 1.050 or less, or 1.040 or less, or 1.035 or less, or 1.030 or less, or 1.025 or less, or 1.020 or less, from the viewpoint of obtaining a highly transparent resin composition.

[0027] From the viewpoint of obtaining a highly transparent resin composition, the ratio (C2 / P2) of the refractive index (C2) of the cellulose fiber evaluated in Procedure 2 of this disclosure to the refractive index (P2) of the polypropylene resin evaluated in Procedure 2 of this disclosure is, in one embodiment, 1.020 or more, or 1.030 or more, or 1.035 or more, or 1.040 or more, or 1.045 or more, and in one embodiment, 1.080 or less, or 1.070 or less, or 1.065 or less, or 1.060 or less, or 1.055 or less, or 1.050 or less.

[0028] The difference (|C2-P1|) (i.e., absolute value) between the refractive index (P1) of the polypropylene resin evaluated in Procedure 1 of this disclosure and the refractive index (C2) of the cellulose fiber evaluated in Procedure 2 of this disclosure is preferably 0.090 or less, or 0.080 or less, or 0.070 or less, from the viewpoint of obtaining a highly transparent resin composition. From the viewpoint of transparency of the resin composition, a smaller difference is preferable, but from the viewpoint of simplifying the combination operation of cellulose fiber and polypropylene resin, in one embodiment it may be 0.025 or more, or 0.030 or more, or 0.040 or more, or 0.050 or more.

[0029] The difference (|C2-P2|) between the refractive index (P2) of the polypropylene resin evaluated in Procedure 2 of this disclosure and the refractive index (C2) of the cellulose fiber evaluated in Procedure 2 of this disclosure is preferably 0.100 or less, or 0.090 or less, or 0.080 or less, from the viewpoint of obtaining a highly transparent resin composition. From the viewpoint of transparency of the resin composition, a smaller difference is preferable, but from the viewpoint of simplifying the combination operation of cellulose fiber and polypropylene resin, in one embodiment it may be 0.050 or more, or 0.060 or more, or 0.070 or more.

[0030] [Refractive index of a mixture of polypropylene resin and styrene elastomer] The refractive index of a mixture of polypropylene resin and styrene elastomer, as described later, when evaluated in Procedure 1 of this disclosure, is in one embodiment 1.45 or higher, or 1.47 or higher, or 1.48 or higher, or 1.49 or higher, and in one embodiment 1.55 or lower, or 1.53 or lower, or 1.52 or lower, or 1.51 or lower. When the evaluation is performed on the mixture of polypropylene resin and styrene elastomer in the resin composition, the resin composition may be treated with an organic or inorganic solvent that dissolves the polypropylene resin and styrene elastomer to dissolve the resin, and the polypropylene resin and styrene elastomer isolated by distilling off the solvent from the solution obtained by removing impurities by filtration extraction may be used for sample sheet preparation and refractive index measurement according to Procedure 1.

[0031] [Relationship between the refractive index of the control composition and cellulose fibers] The ratio (C2 / R1) of the refractive index (C2) of the cellulose fiber evaluated in Step 2 to the refractive index (R1) of the control composition evaluated in Step 1 is, in one embodiment, 0.970 or more, or 1.000 or more, or 1.020 or more, or 1.025 or more, or 1.030 or more, and in one embodiment, 1.050 or less, or 1.040 or less, or 1.035 or less. In this disclosure, the control composition means a composition consisting of the same polypropylene resin and styrene elastomer as the resin composition of this disclosure, and in which the mass ratio of the polypropylene resin to the styrene elastomer in the control composition is equal to the mass ratio of the polypropylene resin to the styrene elastomer in the resin composition of this disclosure.

[0032] The difference (|C2-R1|) between the refractive index (R1) of the control composition evaluated in step 1 and the refractive index (C2) of the cellulose fiber evaluated in step 2 is preferably 0.100 or less, or 0.050 or less, or 0.030 or less, or 0.020 or less, from the viewpoint of obtaining a highly transparent resin composition. From the viewpoint of transparency of the resin composition, a smaller difference is preferable, but from the viewpoint of simplifying the operation of combining the resin and cellulose fiber, in one embodiment it may be 0.001 or more, or 0.003 or more, or 0.005 or more, or 0.007 or more.

[0033] The refractive index (R1) of the control composition evaluated in step 1 is, in one embodiment, 1.450 or higher, or 1.480 or higher, or 1.490 or higher, and in one embodiment, 1.550 or lower, or 1.520 or lower, or 1.510 or lower.

[0034] [Relationship between the refractive index of polypropylene resins and styrene resins] The ratio (S1 / P1) of the refractive index (S1) of the styrene-based resin evaluated in Step 1 to the refractive index (P1) of the polypropylene-based resin evaluated in Step 1 is preferably 0.950 or higher, or 0.970 or higher, or 0.980 or higher, or 0.990 or higher, and preferably 1.050 or lower, or 1.020 or lower, or 1.010 or lower, or 1.000 or lower.

[0035] The difference (|S1-P1|) between the refractive index (P1) of the polypropylene resin evaluated in Step 1 and the refractive index (S1) of the styrene resin evaluated in Step 1 is preferably 0.100 or less, or 0.050 or less, or 0.030 or less, or 0.020 or less, from the viewpoint of obtaining a highly transparent resin composition. From the viewpoint of transparency of the resin composition, a smaller difference is preferable, but from the viewpoint of simplifying the combination operation of the polypropylene resin and the styrene resin, in one embodiment it may be 0.001 or more, or 0.003 or more, or 0.005 or more, or 0.007 or more.

[0036] [Relationship between the refractive index of polypropylene resins and styrene elastomers] The ratio (s1 / P1) of the refractive index (s1) of the styrene elastomer evaluated in Step 1 to the refractive index (P1) of the polypropylene resin evaluated in Step 1 is preferably within the same range as described above for the ratio of the refractive index of the styrene resin evaluated in Step 1 to the refractive index of the polypropylene resin evaluated in Step 1.

[0037] The difference (|s1-P1|) between the refractive index (P1) of the polypropylene resin evaluated in Step 1 and the refractive index (s1) of the styrene elastomer evaluated in Step 1 is preferably within the same range as described above for the difference between the refractive index of the polypropylene resin evaluated in Step 1 and the refractive index of the styrene resin evaluated in Step 1.

[0038] The following describes preferred examples of each component of the resin composition of this embodiment.

[0039] <Cellulose fiber> The cellulose fibers of this disclosure may have modified groups, which are formed by modifying a portion of the hydroxyl groups, such as one or more selected from the group consisting of acetyl groups, propionyl groups, butyryl groups, carboxymethyl groups, methyl groups, ethyl groups, hydroxyethyl groups, hydroxypropyl groups, and carboxyl groups. In one embodiment, hydrophobization by modification is advantageous for improving the heat resistance of the cellulose fibers. The cellulose fibers may be obtained from various cellulose fiber raw materials selected from natural cellulose and regenerated cellulose. As natural cellulose, wood pulp obtained from wood species (hardwood or softwood), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linter, sisal, straw, etc.), and cellulose fiber aggregates produced by animals (e.g., ascidians), algae, and microorganisms (e.g., acetic acid bacteria) can be used. As regenerated cellulose, regenerated cellulose fibers (viscose, cupro, Tencel, etc.), cellulose derivative fibers, and ultrafine threads of regenerated cellulose or cellulose derivatives obtained by electrospinning can be used. In one embodiment, linters are preferred in terms of heat resistance. These raw materials can be adjusted as needed by beating, fibrillation, and micronization using mechanical force such as grinders and refiners to control fiber diameter, fiber length, degree of fibrillation, etc., or by bleaching and purifying with chemicals to adjust the content of components other than cellulose (acid-insoluble components such as lignin, alkali-soluble polysaccharides such as hemicellulose, etc.).

[0040] Cellulose fibers are obtained by mechanically micronizing cellulose raw materials in a dry or wet manner. Modification may be performed before, during, and / or after micronization. The micronization process may be carried out using a single apparatus once or more times, or using multiple apparatuses, each used once or more times.

[0041] The equipment used for micronization is not particularly limited, but examples include high-speed rotary, colloidal mill, high-pressure, roll mill, and ultrasonic types of equipment. High-pressure or ultra-high-pressure homogenizers, refiners, beaters, PFI mills, kneaders, dispersers, high-speed defibrators, grinders (stone mill type grinders), ball mills, vibratory mills, bead mills, conical refiners, disc refiners, single-screw, twin-screw or multi-screw kneaders / extruders, homomixers under high-speed rotation, refiners, defibrators, beaters, friction grinders, high-shear fibrilators (e.g., Cavitron rotor / starter devices), dispersers, homogenizers (e.g., microfluidizers), etc., which use metal or blades to act on pulp fibers around a rotating shaft, or those that use friction between pulp fibers.

[0042] In one embodiment, the cellulose fibers before or after modification can be obtained as a slurry. The slurry can be prepared by dispersing the cellulose fiber raw material in water and / or other media (e.g., organic solvents, inorganic acids, bases and / or ionic liquids) and micronizing it.

[0043] The organic solvent used in the aforementioned micronization process is not particularly limited, but examples include: alcohols with 1 to 20 carbon atoms, preferably 1 to 4 carbon atoms, such as methanol, ethanol, and propanol; glycol ethers with 2 to 20 carbon atoms, preferably 2 to 6 carbon atoms, such as methyl cellosolve and propylene glycol monomethyl ether; ethers with 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, such as propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, and 1,4-dioxane; acetone; methyl ethyl ketone; and Examples include ketones with 3 to 20 carbon atoms, preferably 3 to 6 carbon atoms, such as ethyl isobutyl ketone; linear or branched saturated or unsaturated hydrocarbons with 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as methylene chloride and chloroform; carboxylic acids with 1 to 20 carbon atoms, such as formic acid, acetic acid, and lactic acid; esters with 2 to 20 carbon atoms, preferably 2 to 6 carbon atoms, such as ethyl acetate and vinyl acetate; nitrogen-containing solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and sulfur-containing solvents such as dimethyl sulfoxide. These can be used individually or in combination of two or more, but from the viewpoint of ease of operation in the micronization process, alcohols with 1 to 6 carbon atoms, glycol ethers with 2 to 6 carbon atoms, ethers with 2 to 8 carbon atoms, ketones with 3 to 6 carbon atoms, lower alkyl ethers with 2 to 5 carbon atoms, carboxylic acids with 1 to 8 carbon atoms, esters with 2 to 6 carbon atoms, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide are preferred.

[0044] Examples of inorganic acids include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, and boric acid. However, from the viewpoint of efficiency of defibrillation and ease of handling, it is preferable to use one or more selected from the group consisting of hydrochloric acid, sulfuric acid, and phosphoric acid.

[0045] Examples of bases include hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; carbonates such as sodium carbonate, potassium carbonate, and calcium carbonate; and organic amines such as ammonia, triethylamine, and triethanolamine. However, from the viewpoint of efficiency of defibrillation and ease of handling, it is preferable to use one or more selected from the group consisting of hydroxides, carbonates, and organic amines.

[0046] In this disclosure, an ionic liquid refers to a salt of a liquid containing an organic ion in at least one of its cation and anion portions, with a melting point of ions only of 100°C or lower. Preferably, the ionic liquid has at least one cation selected from the group consisting of imidazolium cation, pyrrolidinium cation, piperidinium cation, morpholinium cation, pyridinium cation, quaternary ammonium cation, and phosphonium cation in its cation portion.

[0047] In particular, ionic liquids having an imidazolium skeleton, for example, the following formula (1): [ka] (In the formula, R1 and R2 each independently represent an alkyl group or allyl group having 1 to 8 carbon atoms, and X represents an anion.) The imidazolium-based ionic liquid shown is more preferable than other ionic liquids because it has a relatively low melting point, a wide temperature range in which it exists as a liquid, maintains fluidity even at low temperatures, and has excellent thermal stability. From the viewpoint of defibrillability, the number of carbon atoms in R1 and R2 is more preferably 4 or less, even more preferably 3 or less, and most preferably 2 or less.

[0048] The anionic component is a halide ion (Cl - , Br - , I - (etc.), carboxylate anions (for example, carboxylate anions with a total of 1 to 3 carbon atoms, e.g., C2H5CO2) - CH3CO2 - , HCO2 -Pseudohalide ions (i.e., monovalent ions having properties similar to halide ions, such as CN - , SCN - , OCN - , ONC - , N3 - etc.), sulfonic acid anions, organic sulfonic acid anions (such as methanesulfonic acid anions), phosphate anions (such as ethyl phosphate anions, methyl phosphate anions, hexafluorophosphate anions), borate anions (such as tetrafluoroborate anions), perchlorate anions, etc. From the perspective of fibrillation properties, halide ions and carboxylate anions are preferred.

[0049] Examples of imidazolium-based ionic liquids include 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium formate, 1-allyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium dimethyl phosphate, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium diethyl phosphate, 1,3-dimethylimidazolium acetate, 1-ethyl-3-methylimidazolium propionate, 1-propyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium bromide, etc.

[0050] Although it is possible to defibrate the cellulose fiber raw material only with an ionic liquid, when the dissolving power for cellulose is too high and there is a risk of dissolving the cellulose fibers, it is preferable to add water and / or an organic solvent to the ionic liquid for use. The type of organic solvent to be added may be appropriately selected considering the compatibility with the ionic liquid, the affinity with cellulose, the solubility of the mixed solvent in the cellulose fiber raw material, viscosity, etc., but one or more selected from the group consisting of N,N-dimethylacetamide, N,N-dimethylformamide, 1-methyl-2-pyrrolidone, dimethyl sulfoxide, acetonitrile, methanol, and ethanol are preferred.

[0051] The total amount of water and / or other media used in the micronization process is not particularly limited, as long as it is an effective amount that can disperse the cellulose fiber raw material. However, it is preferably 1 mass or more, more preferably 10 mass or more, even more preferably 50 mass or more, preferably 10,000 mass or less, more preferably 5,000 mass or less, even more preferably 2,000 mass or less, and particularly preferably 1,000 mass or less, relative to the cellulose fiber raw material.

[0052] Since cellulose fiber raw materials contain alkali-soluble components and sulfuric acid-insoluble components (such as lignin), these components may be reduced through purification processes such as deligninization by pulping and bleaching. On the other hand, purification processes such as deligninization by pulping and bleaching cleave the molecular chains of cellulose, changing the weight-average molecular weight and number-average molecular weight. Therefore, it is desirable that the purification and bleaching processes of cellulose fiber raw materials be controlled so that the weight-average molecular weight of the cellulose fiber and the ratio of weight-average molecular weight to number-average molecular weight are within an appropriate range.

[0053] Furthermore, there are concerns that the cellulose fibers will become lower in molecular weight due to purification processes such as lignin removal through pulping, and that the cellulose fiber raw material will be altered, increasing the proportion of alkali-soluble components. Since alkali-soluble components have poor heat resistance, it is desirable that the purification and bleaching processes of the cellulose fiber raw material be controlled so that the amount of alkali-soluble components contained in the cellulose fiber raw material remains below a certain value.

[0054] In one embodiment, the cellulose fiber raw material may be modified (chemically modified), and inorganic esters such as nitrate esters, sulfate esters, phosphate esters, silicate esters, and borate esters, organic esters such as acetylated and propionylated esters, ethers such as methyl ethers, hydroxyethyl ethers, hydroxypropyl ethers, hydroxybutyl ethers, carboxymethyl ethers, and cyanoethyl ethers, and TEMPO oxides obtained by oxidizing the primary hydroxyl groups of cellulose can be used as the cellulose fiber raw material.

[0055] [SP value] From the viewpoint of good dispersion of cellulose fibers in polypropylene resin to improve the mechanical properties and transparency of the resin composition, it is preferable that the SP value of the cellulose fibers be adjusted to a range close to that of the polypropylene resin. From the above viewpoint, the SP value of the cellulose fibers is preferably 22 or higher, or 24 or higher, or 26 or higher, and preferably 32 or lower, or 30 or lower, or 28 or lower. In this disclosure, the SP value is the value obtained by the fedors method in the Synthia module of Materials Studio manufactured by BIOVIA Corporation.

[0056] The ratio of the SP value of cellulose fibers to the SP value of polypropylene resin is preferably 1.3 or higher, or 1.4 or higher, or 1.5 or higher, and preferably 1.9 or lower, or 1.8 or lower, or 1.7 or lower. It should be noted that the resin composition of this embodiment includes a styrene elastomer, and it is known to those skilled in the art that the SP value of the styrene elastomer is generally around 15 to 20, for example, the SP value of SEBS (hydrogenated styrene-butadiene-styrene) elastomer is generally around 16 to 18. Such SP values ​​are typically close to the SP value of the polypropylene resin or fall between the SP value of the polypropylene resin and the SP value of the cellulose fibers. Therefore, controlling the relationship between the SP values ​​of the polypropylene resin and the cellulose fibers greatly contributes to improving the dispersibility of the cellulose fibers.

[0057] [Number-average fiber length, number-average fiber diameter, and L / D ratio] In one embodiment, the number-average fiber length of the cellulose fibers is preferably 30 μm or more, 50 μm or more, or 100 μm or more, from the viewpoint of obtaining a good effect of improving the physical properties of the resin composition, and preferably 750 μm or less, 700 μm or less, 650 μm or less, or 600 μm or less, from the viewpoint of reducing light scattering of the resin composition and obtaining good transparency of the resin composition.

[0058] In one embodiment, the number-average fiber diameter of the cellulose fibers is 1000 nm or less, or 900 nm or less, or 800 nm or less, or 700 nm or less, or 600 nm or less, or 500 nm or less, or 400 nm or less, or 300 nm or less, or 200 nm or less, from the viewpoint of reducing light scattering of the resin composition and obtaining good transparency of the resin composition, and in one embodiment, it is 2 nm or more, or 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, from the viewpoint of obtaining a good effect of improving the physical properties of the resin composition. In one embodiment, the cellulose fibers may be nanofibers, and the average fiber diameter of the nanofibers is 2 to 1000 nm in one embodiment.

[0059] The number-average fiber length (L) / number-average fiber diameter (D) ratio of cellulose fibers is preferably 30 or more, or 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more, from the viewpoint of obtaining a good effect on improving the physical properties of the resin composition, and preferably 5000 or less, or 3000 or less, or 2000 or less, or 1000 or less, from the viewpoint of reducing light scattering of the resin composition and obtaining good transparency of the resin composition.

[0060] In one embodiment, the number-average fiber diameter (D), number-average fiber length (L), and L / D ratio of the cellulose fibers of this disclosure are values ​​measured using a scanning electron microscope (SEM) by the following procedure. An aqueous dispersion of cellulose fibers is replaced with tert-butanol, diluted to 0.001-0.1% by mass, dispersed using a high-shear homogenizer (e.g., IKA product, trade name "Ultra-Turrax T18") under processing conditions: rotation speed 15,000 rpm × 3 minutes, cast onto an osmium-deposited silicon substrate, air-dried, and used as a measurement sample, which is then measured using a high-resolution scanning electron microscope (SEM). Specifically, the length (L) and diameter (D) of 100 randomly selected fibrous materials are measured in an observation field adjusted to the magnification so that at least 100 fibrous materials can be observed, and the ratio (L / D) is calculated. For the cellulose fibers, the number-average values ​​of length (L), diameter (D), and ratio (L / D) are calculated.

[0061] The fiber length, fiber diameter, and L / D ratio of cellulose fibers contained in the resin composition can be confirmed by measuring them using the measurement method described above, with these as measurement samples. Alternatively, the fiber length, fiber diameter, and L / D ratio of cellulose fibers contained in the resin composition can be confirmed by dissolving the polymer components contained therein in an organic or inorganic solvent capable of dissolving the polymer components, separating the cellulose fibers, thoroughly washing them with the solvent, preparing an aqueous dispersion by replacing the solvent with pure water, diluting the cellulose fiber concentration with pure water to 0.1-0.5% by mass, casting it onto mica, air-drying it, and measuring it using the measurement method described above as a measurement sample.

[0062] [Volume ratio of coarse aggregates (volume fraction)] From the viewpoint of suppressing light scattering caused by cellulose fibers in a resin composition and improving the transparency of the resin composition, it is preferable that the cellulose fibers are highly and uniformly finely granulated. From this viewpoint, in the resin composition, the volume 110 μm 3The volume fraction of the aggregates is preferably 5% or less, or 4% or less, or 3% or less, or 2% or less, or 1.5% or less. The volume fraction of aggregates is a value measured using X-ray CT measurement for the resin composition by the following method. The 3D data obtained from X-ray CT measurements is binarized, and pixels containing only aggregates are extracted. Then, the ratio of the total volume of aggregates larger than a cube with sides of 4.8 μm to the total volume of the X-ray CT observation area is calculated as the volume fraction of the aggregates.

[0063] [Specific surface area] The specific surface area of ​​the cellulose fibers is preferably 40 m², as this allows for good transparency of the resin composition due to the highly fine cellulose fibers. 2 / g or more, or 45m 2 / g or more, or 50m 2 / g or more, or 55m 2 / g or more, or 60m 2 / g or more, or 70m 2 The amount is 200m or more, and from the viewpoint of ease of manufacturing and handling cellulose fibers, it is preferably 200m 2 / g or less, or 170m 2 / g or less, or 160m 2 The specific surface area is less than or equal to / g. The specific surface area is determined using a specific surface area and pore distribution analyzer (e.g., Nova-4200e, manufactured by Quantachrome Instruments) by drying approximately 0.2g of the sample under vacuum at 120°C for 5 hours, and then measuring the amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen at 5 points (multi-point method) within the range of relative vapor pressure (P / P0) of 0.05 to 0.2. The BET specific surface area (m²) is then calculated using the instrument's program. 2 It is measured by calculating ( / g).

[0064] [Degree of crystallinity] The degree of crystallinity of the cellulose fibers is preferably 55% or higher. When the degree of crystallinity is within this range, the mechanical properties (strength, dimensional stability) of the cellulose itself are high, and therefore, when cellulose fibers are dispersed in the resin, the strength and dimensional stability of the resin composition tend to be high. A more preferable lower limit for the degree of crystallinity is 60%, even more preferably 70%, and most preferably 80%. While a higher degree of crystallinity of the cellulose fibers is preferable in terms of improving physical properties, from the viewpoint of easily adjusting the degree of substitution of the cellulose fibers to obtain the desired refractive index, it is preferably 99% or less, 95% or less, or 90% or less.

[0065] The degree of crystallinity referred to here, when the cellulose is type I cellulose crystal (derived from natural cellulose), can be determined by the Segal method from the diffraction pattern (2θ / deg. of 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction, using the following formula. Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) :Diffraction peak intensity at the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous material in type I cellulose crystals, specifically the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°).

[0066] Furthermore, if the cellulose is a type II cellulose crystal (derived from regenerated cellulose), the degree of crystallinity can be determined by the following formula using wide-angle X-ray diffraction, from the absolute peak intensity h0 at 2θ=12.6°, which is attributed to the (110) plane peak of the type II cellulose crystal, and the peak intensity h1 from the baseline at this interplanar spacing. Crystallinity (%) =h1 / h0 ×100

[0067] [Crystal polymorphism] Known crystalline polymorphs of cellulose include type I, type II, type III, and type IV. Among these, types I and II are particularly widely used, while types III and IV, although obtained on a laboratory scale, are not widely used on an industrial scale. The cellulose fibers of this disclosure have relatively high structural mobility, and by dispersing these cellulose fibers in a resin, a resin composition with a lower coefficient of thermal expansion and superior strength and elongation during tensile and bending deformation can be obtained. Therefore, cellulose fibers containing cellulose type I crystals or cellulose type II crystals are preferred, and cellulose fibers containing cellulose type I crystals and having a crystallinity of 55% or higher are more preferred.

[0068] [Degree of polymerization] Furthermore, the degree of polymerization of the cellulose fibers is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, preferably 3500 or less, more preferably 3300 or less, more preferably 3200 or less, more preferably 3100 or less, and more preferably 3000 or less.

[0069] From the viewpoint of processability and mechanical property development, it is desirable to keep the degree of polymerization of the cellulose fibers within the above-mentioned range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of mechanical property development, it is desirable that it is not too low.

[0070] The degree of polymerization of cellulose fibers refers to the average degree of polymerization measured according to the reduction ratio viscosity method using copper ethylenediamine solution, as described in the confirmation test (3) of the "Fifteenth Revised Japanese Pharmacopoeia Commentary (published by Hirokawa Shoten)". Furthermore, the degree of polymerization of modified cellulose fibers may not be accurately calculated due to the presence of modifying groups. In such cases, the degree of polymerization of the cellulose fiber immediately before modification or the cellulose raw material immediately before modification, which is the raw material for the cellulose fiber, may be considered as the degree of polymerization of the cellulose fiber.

[0071] [Mw,Mn,Mw / Mn] In one embodiment, the weight-average molecular weight (Mw) of the cellulose fiber is 100,000 or more, or 200,000 or more. In another embodiment, the ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) is 6 or less, or 5.4 or less. A larger weight-average molecular weight means fewer end groups in the cellulose molecule. Also, since the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer end groups in the cellulose molecule. Since the end groups of cellulose molecules are the starting points for thermal decomposition, a particularly heat-resistant cellulose fiber can be obtained when the weight-average molecular weight of the cellulose molecules in the cellulose fiber is not only large, but also when the width of the molecular weight distribution is narrow. From the viewpoint of the availability of cellulose fiber raw materials, the weight-average molecular weight (Mw) of the cellulose fiber may be, for example, 600,000 or less, or 500,000 or less. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) may be, for example, 1.5 or higher, or 2 or higher, from the viewpoint of ease of manufacturing cellulose fibers. Mw can be controlled to the above range by selecting a cellulose fiber raw material having an Mw appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose fiber raw material within an appropriate range. Mw / Mn can also be controlled to the above range by selecting a cellulose fiber raw material having an Mw / Mn appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose fiber raw material within an appropriate range. In one embodiment, each of the Mw and Mw / Mn of the cellulose raw material may be within the above range. In both the control of Mw and the control of Mw / Mn, examples of the above physical treatments include dry or wet grinding using microfrudizers, ball mills, disc mills, etc., and physical treatments that apply mechanical forces such as impact, shear, shear, and friction using grinders, homomixers, high-pressure homogenizers, ultrasonic devices, etc. Examples of the above chemical treatments include pulverization, bleaching, acid treatment, enzymatic treatment, and regenerative cellulose formation. Note that accurate calculation of Mw, Mn, and Mw / Mn for modified cellulose fibers may not be possible due to the presence of modifying groups. In such cases, the Mw, Mn, and Mw / Mn of the cellulose fiber immediately before modification or the cellulose raw material immediately before modification, which are the raw materials for the cellulose fibers, may be considered as the Mw, Mn, and Mw / Mn of the cellulose fibers.

[0072] The weight-average molecular weight and number-average molecular weight of cellulose fibers referred to here are values ​​obtained by dissolving cellulose fibers in N,N-dimethylacetamide to which lithium chloride has been added, and then determining them by gel permeation chromatography using N,N-dimethylacetamide as the solvent.

[0073] [Control of degree of polymerization and molecular weight] Methods for controlling the degree of polymerization (i.e., average degree of polymerization) or molecular weight of cellulose fibers include hydrolysis. Hydrolysis promotes the depolymerization of amorphous cellulose inside the cellulose fibers, reducing the average degree of polymerization. At the same time, hydrolysis removes impurities such as hemicellulose and lignin in addition to the amorphous cellulose mentioned above, resulting in a porous structure inside the fibrous material.

[0074] The hydrolysis method is not particularly limited, but examples include acid hydrolysis, alkaline hydrolysis, hydrothermal decomposition, steam explosion, and microwave decomposition. These methods may be used individually or in combination of two or more. In the acid hydrolysis method, for example, α-cellulose obtained as pulp from fibrous plants is used as the cellulose fiber raw material, and while dispersed in an aqueous medium, an appropriate amount of protic acid, carboxylic acid, Lewis acid, heteropoly acid, etc. is added, and the average degree of polymerization can be easily controlled by heating while stirring. The reaction conditions such as temperature, pressure, and time vary depending on the cellulose species, cellulose concentration, acid species, acid concentration, etc., but are adjusted appropriately to achieve the desired average degree of polymerization. For example, one condition is to use an aqueous solution of mineral acid with a concentration of 2% by mass or less and treat the cellulose fibers at 100°C or higher under pressure for 10 minutes or more. Under these conditions, the catalytic component such as the acid penetrates into the cellulose fiber, promoting hydrolysis, reducing the amount of catalytic component used, and making subsequent purification easier. Furthermore, the dispersion of cellulose fiber raw materials during hydrolysis may contain a small amount of organic solvent in addition to water, as long as it does not impair the effects of the present invention.

[0075] [Alkali-soluble polysaccharides and acid-insoluble components] Between the microfibrils of cellulose fibers and between the bundles of microfibrils, there are alkali-soluble polysaccharides such as hemicellulose and acid-insoluble components such as lignin. Hemicellulose is a polysaccharide composed of sugars such as mannan and xylan, and it plays a role in linking microfibrils together by hydrogen bonding with cellulose. Lignin is a compound with an aromatic ring, and it is known to be covalently bonded with hemicellulose in the cell walls of plants.

[0076] The alkali-soluble polysaccharides that cellulose fibers may contain include not only hemicellulose but also β-cellulose and γ-cellulose. Alkali-soluble polysaccharides are understood by those skilled in the art to be components obtained as the alkali-soluble part of holocellulose obtained by solvent extraction and chlorine treatment of plants (e.g., wood) (i.e., components obtained by removing α-cellulose from holocellulose). Since alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, they can cause problems such as decomposition when heated, yellowing during thermal aging, and a decrease in the strength of cellulose fibers. Therefore, it is preferable to have a low alkali-soluble polysaccharide content in cellulose fibers.

[0077] In one embodiment, the average content of alkali-soluble polysaccharides in cellulose fibers is preferably 20% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, based on 100% by mass of cellulose fibers, from the viewpoint of maintaining the mechanical strength of the cellulose fibers during melt kneading and suppressing yellowing. The above content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 3% by mass or more, from the viewpoint of ease of manufacturing the cellulose fibers.

[0078] The average alkali-soluble polysaccharide content can be determined using the method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000), by subtracting the α-cellulose content from the holocellulose content (Wise method). This method is understood in the industry as a method for measuring hemicellulose content. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content is taken as the average alkali-soluble polysaccharide content. However, the alkali-soluble polysaccharide content of modified cellulose fibers may not be accurately calculated due to the presence of modifying groups. In this case, the average alkali-soluble polysaccharide content of the cellulose fiber immediately before modification or the cellulose raw material immediately before modification, which is the raw material for the cellulose fiber, may be considered as the average alkali-soluble polysaccharide content of the cellulose fiber.

[0079] Acid-insoluble components that cellulose fibers may contain are understood by those skilled in the art as insoluble components remaining after sulfuric acid treatment of a degreased sample obtained by solvent extraction of plants (e.g., wood). Specifically, these acid-insoluble components are, but are not limited to, aromatic lignin. Acid-insoluble components are often colored themselves, which can impair the appearance of the resin composition and cause yellowing during thermal aging. Therefore, it is preferable to have a low average content of acid-insoluble components in cellulose fibers.

[0080] In one embodiment, the average content of acid-insoluble components in cellulose fibers is preferably 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on 100% by mass of cellulose fibers, from the viewpoint of avoiding a decrease in the heat resistance of cellulose fibers and the resulting discoloration. From the viewpoint of ease of manufacturing cellulose fibers, the above content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more.

[0081] The average acid-insoluble component content is determined using the Claesson method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). This method is understood in this industry as a method for measuring lignin content. After stirring the sample in sulfuric acid solution to dissolve cellulose and hemicellulose, etc., the sample is filtered through glass fiber filter paper, and the resulting residue contains the acid-insoluble components. The acid-insoluble component content is calculated from the weight of these acid-insoluble components, and the number average of the acid-insoluble component content calculated for three samples is taken as the average acid-insoluble component content. In the case of modified cellulose fibers, it may not be possible to accurately calculate the average acid-insoluble component content due to the presence of modifying groups. In this case, the average alkali-soluble polysaccharide content of the cellulose fiber immediately before modification or the cellulose raw material immediately before modification, which is the raw material for cellulose fibers, may be considered as the average alkali-soluble polysaccharide content of the cellulose fiber.

[0082] [Thermal decomposition onset temperature (T D )] The thermal decomposition onset temperature of cellulose fibers (T DIn one embodiment, the thermal decomposition start temperature is preferably 250°C or higher, or 260°C or higher, or 270°C or higher, or 275°C or higher, or 280°C or higher, from the viewpoint of avoiding thermal degradation during melt kneading and being able to exhibit mechanical strength. A higher thermal decomposition start temperature is preferable, but from the viewpoint of ease of manufacturing cellulose fibers, it may be, for example, 320°C or lower, or 310°C or lower, or 300°C or lower.

[0083] [Temperature at 1% weight loss (T 1% ), 250℃ weight loss rate (T 250℃ )] Temperature (T) when cellulose fiber loses 1 wt% of its weight. 1% In one embodiment, the temperature is preferably 260°C or higher, or 270°C or higher, or 275°C or higher, or 280°C or higher, or 285°C or higher, or 290°C or higher, from the viewpoint of avoiding thermal degradation during melting and kneading and being able to exhibit mechanical strength. 1% Higher temperatures are preferable, but from the viewpoint of ease of manufacturing cellulose fibers, temperatures of, for example, 330°C or lower, 320°C or lower, or 310°C or lower may also be acceptable.

[0084] Weight loss rate of cellulose fibers at 250°C (T 250℃ From the viewpoint of avoiding thermal degradation during melting and kneading and being able to exhibit mechanical strength, in one embodiment, it is preferably 15% or less, or 12% or less, or 10% or less, or 8% or less, or 6% or less, or 5% or less, or 4% or less, or 3% or less. 250℃ While a lower concentration is preferable, from the viewpoint of ease of manufacturing cellulose fibers, it may be, for example, 0.1% or more, or 0.5% or more, or 0.7% or more, or 1.0% or more.

[0085] In this disclosure, T DThis value is obtained from a graph in thermogravimetric (TG) analysis under nitrogen flow, where the x-axis is temperature and the y-axis is weight retention percentage. Cellulose fibers are heated from room temperature to 150°C at a heating rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, and then heated to 450°C at a heating rate of 10°C / min. The weight at 150°C (when moisture is almost completely removed) (weight loss of 0 wt%) is used as the starting point, and the temperature at which a 1 wt% weight loss occurs (T 1% ) and temperature (T) when weight decreases by 2 wt% 2% Obtain a straight line passing through ( ). The temperature at the point where this line intersects with the horizontal line (baseline) passing through the starting point of the weight loss of 0 wt% is T. D This is how it is defined.

[0086] 1% weight loss temperature (T 1% ) is the above T D This is the temperature at which the weight decreases by 1% by weight, starting from the weight at 150°C, when the temperature is continuously increased using this method.

[0087] Weight loss rate of cellulose fibers at 250°C (T 250℃ ) is the weight loss rate when cellulose fibers are held at 250°C under a nitrogen flow for 2 hours in TG analysis. Cellulose fibers are heated from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, then heated from 150°C to 250°C at a rate of 10°C / min, and held at 250°C for 2 hours. The weight W0 at the time of reaching 250°C is taken as the starting point, and the weight after being held at 250°C for 2 hours is taken as W1, which is calculated using the following formula. Weight change rate at 250℃ (%): (W0-W1) / W0×100

[0088] [Porous Sheet] The properties of cellulose fibers (crystallinity, polymorphism, degree of polymerization, Mw, Mn, Mw / Mn, average content of alkali-soluble polysaccharides, average content of acid-insoluble components, T D , T 1% , T 250℃Measurements of (etc.) can vary significantly depending on the form of the sample being measured. To ensure stable and reproducible measurements, a distortion-free porous sheet should be used as the measurement sample. The method for preparing the porous sheet is as follows.

[0089] First, a concentrated cellulose fiber cake with a solid content of 10% by mass or more is added to tert-butanol, and then dispersed using a mixer or similar device until no aggregates remain. The concentration is adjusted to 0.5% by mass for every 0.5g of cellulose fiber solid content. 100g of the resulting tert-butanol dispersion is filtered on filter paper. Without removing the filtrate from the filter paper, it is sandwiched between two larger sheets of filter paper, and the edges of the larger sheets are pressed down with weights, and dried in a 150°C oven for 5 minutes. After that, the filter paper is peeled off to obtain a porous sheet with minimal distortion. The air permeability resistance R of this sheet is 10g / m² 2 Materials with a density of 100 sec / 100 ml or less are treated as porous sheets and used as measurement samples.

[0090] The air permeability resistance R was measured by measuring the basis weight W (g / m²) of a porous sheet sample that had been left standing for one day in an environment of 23°C and 50%RH. 2 After measuring the air permeability resistance (R) (sec / 100ml), the air permeability resistance is measured using a Wangyan-type air permeability resistance tester (for example, Asahi Seiko Co., Ltd., model EG01). At this time, 10 g / m³ is used according to the following formula. 2 Calculate the value per unit area. Weight: 10g / m 2 Air permeability resistance (sec / 100ml) = R / W × 10

[0091] [Physical properties of cellulose fibers in resin compositions] Various physical properties of cellulose fibers in resin compositions (refractive index, number-average fiber length, number-average fiber diameter, L / D ratio, volume fraction of coarse aggregates, specific surface area, degree of crystallinity, crystalline polymorphism, degree of polymerization, Mw, Mn, Mw / Mn, average content of alkali-soluble polysaccharides, average content of acid-insoluble components, T D , T 1% , T 250℃The resin components of the resin composition, and the DS described later, are analyzed by the following method: The resin components of the resin composition are dissolved in an organic or inorganic solvent capable of dissolving the resin components of the resin composition, the cellulose fibers are separated, and after thorough washing with the solvent, the solvent is replaced with tert-butanol. Subsequently, the tert-butanol slurry of cellulose fibers is analyzed using the same measurement method as described above, and various physical properties of the cellulose fibers in the resin composition are calculated.

[0092] [Degenerate] The cellulose fibers contained in the resin composition of this embodiment may be modified, for example, at the stage of cellulose fiber raw material preparation, during or after defibration treatment, or they may be modified during or after the preparation of the slurry as a dispersion containing cellulose fibers, or during or after the drying and granulation process.

[0093] In one embodiment, cellulose fibers may be subjected to acetylation using an acetylating agent as a modifying agent, and optionally, modifications other than acetylation using a modifying agent other than an acetylating agent. As modifying agents, compounds that react with the hydroxyl groups of cellulose can be used, such as esterifying agents, etherifying agents, and silylating agents. Preferred esterifying agents used for acetylation and optionally other esterifications are acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids.

[0094] The acid halide may be at least one compound selected from the group consisting of compounds represented by the following formula. R 1 -C(=O)-X (In the formula, R 1 (where X represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, or an aryl group having 6 to 24 carbon atoms, and X is Cl, Br, or I.) Specific examples of acid halides include, but are not limited to, acetyl chloride, acetyl bromide, acetyl iodide, propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl chloride, benzoyl bromide, and benzoyl iodide. Among these, acid chlorides are particularly suitable due to their reactivity and ease of handling. In the reaction of acid halides, one or more alkaline compounds may be added to act as a catalyst and to neutralize the acidic by-products. Specific examples of alkaline compounds include, but are not limited to, tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine.

[0095] Any suitable acid anhydride can be used as the acid anhydride. For example, Saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso)butyric acid, and valeric acid; unsaturated aliphatic monocarboxylic acid anhydrides such as (meth)acrylic acid and oleic acid; Alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid and tetrahydrobenzoic acid; Aromatic monocarboxylic anhydrides such as benzoic acid and 4-methylbenzoic acid; Examples of dibasic carboxylic acid anhydrides include saturated aliphatic dicarboxylic anhydrides such as succinic anhydride and adipic acid, unsaturated aliphatic dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride, alicyclic dicarboxylic anhydrides such as 1-cyclohexene-1,2-dicarboxylic anhydride, hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride, and aromatic dicarboxylic anhydrides such as phthalic anhydride and naphthalic anhydride; Examples of polybasic carboxylic acid anhydrides with three or more bases include (anhydride) polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride. Furthermore, in the reaction of acid anhydrides, one or more acidic compounds such as sulfuric acid, hydrochloric acid, or phosphoric acid, or Lewis acids (for example, Lewis acid compounds represented as MYn, where M represents a metalloid element such as B, As, or Ge, or a base metal element such as Al, Bi, or In, or a transition metal element such as Ti, Zn, or Cu, or a lanthanide element; n is an integer corresponding to the valence of M, representing 2 or 3; and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)), or alkaline compounds such as triethylamine or pyridine may be added as catalysts.

[0096] Examples of vinyl carboxylates include those with the following formula: R-COO-CH=CH2 A vinyl carboxylate ester represented by the formula {wherein R is any of an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 24 carbon atoms} is preferred. The vinyl carboxylate ester is more preferably at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octoate, divinyl adipate, vinyl methacrylate, vinyl crotate, vinyl octoate, vinyl benzoate, and vinyl cinnamate. In esterification reactions with vinyl carboxylates, one or more catalysts selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, primary to tertiary amines, quaternary ammonium salts, imidazoles and their derivatives, pyridines and their derivatives, and alkoxides may be added.

[0097] Examples of alkali metal hydroxides and alkaline earth metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and barium hydroxide. Examples of alkali metal carbonates, alkaline earth metal carbonates, and alkali metal bicarbonates include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, and cesium bicarbonate.

[0098] Primary, secondary, and tertiary amines refer to primary, secondary, and tertiary amines, and specific examples include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, N,N-dimethylcyclohexylamine, and triethylamine.

[0099] Examples of imidazoles and their derivatives include 1-methylimidazole, 3-aminopropylimidazole, and carbonyldiimidazole.

[0100] Examples of pyridine and its derivatives include N,N-dimethyl-4-aminopyridine and picoline.

[0101] Examples of alkoxides include sodium methoxide, sodium ethoxide, and potassium t-butoxide.

[0102] The carboxylic acid is selected from the group consisting of compounds represented by the following formula. R-COOH (In the formula, R represents an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms.)

[0103] Specific examples of carboxylic acids include at least one selected from the group consisting of acetic acid, propionic acid, butyric acid, caproic acid, cyclohexanecarboxylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid, octic acid, benzoic acid, and cinnamic acid.

[0104] Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid is preferred. In particular, the use of at least acetic acid is preferred from the viewpoint of reaction efficiency.

[0105] Furthermore, in the reaction of carboxylic acids, one or more acidic compounds such as sulfuric acid, hydrochloric acid, or phosphoric acid, or Lewis acids (for example, Lewis acid compounds represented as MYn, where M represents a metalloid element such as B, As, or Ge, or a base metal element such as Al, Bi, or In, or a transition metal element such as Ti, Zn, or Cu, or a lanthanide element; n is an integer corresponding to the valence of M, representing 2 or 3; and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)), or alkaline compounds such as triethylamine or pyridine may be added as catalysts.

[0106] Among these esterification reagents, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid is particularly preferred. In particular, using at least acetic anhydride and / or vinyl acetate is preferred from the viewpoint of reaction efficiency.

[0107] [Substitution degree (DS)] The degree of substitution (DS) of cellulose fibers is determined as the average degree of substitution. From the viewpoint of bringing the refractive index of the cellulose fibers close to that of the polypropylene resin, the degree of acetyl substitution when the cellulose fibers are acetylated cellulose fibers is preferably 0.1 or higher, or 0.3 or higher, or 0.5 or higher, or 0.6 or higher, or 0.7 or higher, or 0.8 or higher, and preferably 3.0 or lower, or 2.0 or lower, or 1.5 or lower, or 1.0 or lower. Similarly, from the viewpoint of bringing the refractive index of the cellulose fibers into line with that of the polypropylene resin, the degree of carboxymethyl substitution when the cellulose fibers are carboxymethylated cellulose fibers is preferably 0.2 or higher, or 0.6 or higher, or 1.0 or higher, and preferably 3.0 or lower, or 2.0 or lower, or 1.5 or lower. Similarly, when the cellulose fiber is a butyrylated cellulose fiber, the degree of butyryl substitution is preferably 0.1 or more, or 0.3 or more, or 0.5 or more, or 0.8 or more, and preferably 3.0 or less, or 2.0 or less, or 1.5 or less, or 1.0 or less. Similarly, when the cellulose fiber is a hydroxypropylated cellulose fiber, the degree of hydroxypropyl substitution is preferably 0.1 or more, or 0.5 or more, or 0.9 or more, and preferably 3.0 or less, or 2.0 or less, or 1.0 or less. According to the inventors' studies, the refractive index of unmodified cellulose fibers is approximately 1.551 in one embodiment, the refractive index of cellulose fibers with an acetyl substitution degree of 3 is approximately 1.509 in one embodiment, the refractive index of cellulose fibers with a carboxymethyl substitution degree of 3 is approximately 1.502 in one embodiment, the refractive index of cellulose fibers with a butyryl substitution degree of 3 is approximately 1.490 in one embodiment, and the refractive index of cellulose fibers with a hydroxypropyl substitution degree of 3 is approximately 1.506 in one embodiment. Cellulose fibers with an acetyl substitution degree, carboxymethyl substitution degree, butyryl substitution degree, or hydroxypropyl substitution degree within the above range are advantageous from the viewpoint of obtaining a resin composition with excellent transparency by bringing the refractive index of the cellulose fiber and the refractive index of the polypropylene resin close together.Furthermore, from the viewpoint that retaining an unmodified cellulose skeleton in the cellulose fibers allows for adjustment of the refractive index through modification and improvement of the thermal decomposition initiation temperature while maintaining the good physical properties derived from cellulose, the degree of acetyl substitution, carboxymethyl substitution, butyryl substitution, or hydroxypropyl substitution is preferably 2.0 or less, or 1.8 or less, or 1.5 or less, or 1.2 or less, or 1.0 or less. Having the above-mentioned degree of substitution below the above-mentioned upper limit is also advantageous in terms of suppressing discoloration of the cellulose fibers.

[0108] The degree of substitution is determined by reflection-type infrared absorption spectroscopy and 13 This can be determined by 13C solid-state NMR measurement. For example, the degree of acyl substitution when the modifying group is an acyl group can be calculated from the reflectivity infrared absorption spectrum of esterified cellulose fibers based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton. The peak of the C=O absorption band based on the acyl group is at 1730 cm⁻¹. -1 The peak of the CO absorption band based on the cellulose backbone chain appears at 1030 cm⁻¹. -1 It appears in [location]. The DS of esterified cellulose fibers is obtained by creating a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose fibers (described later) and the denaturation rate (IR index 1030), which is defined as the ratio of the peak intensity of the absorption band of C=O based on the acyl group to the peak intensity of the absorption band of CO in the cellulose backbone chain, and a calibration curve calculated from the correlation graph. Degree of substitution DS = 4.13 × IR index (1030) This can be obtained by using [this method].

[0109] The method for calculating the DS of esterified cellulose fibers using solid-state NMR is as follows: For freeze-pulverized esterified cellulose fibers... 13 The following formula can be used to determine the signal intensity (Inf) from a single carbon atom derived from the modifying group, based on the total area intensity (Inp) of the signals attributed to carbon atoms C1-C6 derived from the pyranose ring of cellulose, which appear in the range of 50 ppm to 110 ppm. DS = (Inf) × 6 / (Inp) If the modifying group is an acetyl group, you can use the 23 ppm signal assigned to -CH3. Use 13 The conditions for 13C solid-state NMR measurement are as follows, for example: Equipment:Bruker Biospin Avance500WB Frequency: 125.77MHz Measurement method: DD / MAS method Waiting time: 75 seconds NMR sample tube: 4mmφ Total number of times: 640 (approximately 14 hours) MAS: 14,500Hz Chemical shift reference: Glycine (External reference: 176.03 ppm)

[0110] The amount of cellulose fibers per 100 parts by mass of polypropylene resin in the resin composition is preferably 0.001 parts by mass or more, or 0.01 parts by mass or more, or 0.1 parts by mass or more, or 1 part by mass or more, from the viewpoint of obtaining a good reinforcing effect, and preferably 100 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 50 parts by mass or less, or 30 parts by mass or less, from the viewpoint of stably achieving good dispersion of cellulose fibers in the resin composition.

[0111] From the viewpoint of obtaining a good reinforcing effect, the amount of cellulose fibers per 100% by mass of the resin composition is preferably 0.001% by mass or more, or 0.01% by mass or more, or 0.1% by mass or more, or 0.5% by mass or more, or 1% by mass or more. From the viewpoint of stably achieving good dispersion of cellulose fibers in the resin composition, it is preferably 50% by mass or less, or 40% by mass or less, or 30% by mass or less, or 20% by mass or less.

[0112] <Polypropylene resin> The polypropylene resin may be a propylene homopolymer or a propylene unit-containing copolymer, and may have a modified group. Examples of propylene unit-containing copolymers include ethylene-propylene copolymers and ethylene-propylene-diene copolymers. In a typical embodiment, the polypropylene resin is homopolypropylene.

[0113] In one embodiment, the SP value of the polypropylene resin is 16.5 or higher, or 16.6 or higher, or 16.7 or higher, and in another embodiment, it is 17.5 or lower, or 17.4 or lower, or 17.3 or lower.

[0114] The weight-average molecular weight of the polypropylene resin is preferably 10,000 or more, or 15,000 or more, or 20,000 or more, from the viewpoint of obtaining good mechanical properties of the resin composition, particularly toughness, and preferably 300,000 or less, or 200,000 or less, or 100,000 or less, from the viewpoint of stably realizing the desired form of the cellulose / elastomer dispersion phase.

[0115] The melt mass flow rate (MFR) of the polypropylene resin, measured at 230°C and under a load of 21.2 N in accordance with ISO 1133, is preferably 0.1 g / 10 min or more and 100 g / 10 min or less. The lower limit of the MFR is more preferably 1 g / 10 min, or 5 g / 10 min, or 10 g / 10 min, or 20 g / 10 min, or 30 g / 10 min, and the upper limit of the MFR is more preferably 80 g / 10 min, or 70 g / 10 min, or 60 g / 10 min, or 50 g / 10 min. From the viewpoint of improving the toughness of the resin composition, it is desirable that the MFR does not exceed the above upper limit, and from the viewpoint of the fluidity of the resin composition, it is desirable that it does not fall below the above lower limit.

[0116] In one embodiment, the glass transition temperature of polypropylene (particularly unmodified polypropylene) is preferably -50°C or higher, or 0°C or higher, or 50°C or higher, from the viewpoint of good mechanical properties of the resin composition, and preferably 200°C or lower, or 150°C or lower, or 100°C or lower, from the viewpoint of the availability of these polypropylenes.

[0117] In this disclosure, the melting point refers to the peak top temperature of the endothermic peak that appears when the temperature is increased from 23°C at a heating rate of 10°C / min using a differential scanning calorimetry (DSC). If two or more endothermic peaks appear, the peak top temperature of the highest-temperature endothermic peak is referred to. The enthalpy of the endothermic peak at this time is preferably 10 J / g or more, and more preferably 20 J / g or more. When measuring, it is preferable to use a sample that has been heated to a temperature condition of melting point + 20°C or higher to melt the resin, and then cooled to 23°C at a cooling rate of 10°C / min. In this disclosure, the glass transition temperature refers to the peak top temperature of the peak where the storage modulus decreases significantly and the loss modulus is at its maximum when measured using a dynamic viscoelasticity analyzer while increasing the temperature from 23°C at a heating rate of 2°C / min at an applied frequency of 10 Hz. If two or more loss modulus peaks appear, the peak top temperature of the highest-temperature peak is referred to. To improve measurement accuracy, it is desirable to perform measurements at least once every 30 seconds. While there are no particular restrictions on the preparation method of the measurement samples, it is preferable to use cut pieces from hot-pressed products to eliminate the effects of molding distortion, and from the standpoint of heat conduction, the size (width and thickness) of the cut pieces should be as small as possible.

[0118] The content of polypropylene resin in the resin composition is preferably 50% by mass or more, or 55% by mass or more, or 60% by mass or more, or 70% by mass or more, and preferably 99% by mass or less, or 95% by mass or less, or 94.5% by mass or less, or 94% by mass or less, or 93% by mass or less, or 92% by mass or less, or 91% by mass or less, or 90% by mass or less, or 89.5% by mass or less, or 85% by mass or less, or 80% by mass or less.

[0119] <Styrene-based elastomers, styrene resins> In one embodiment, the resin composition comprises a styrene elastomer, and in another embodiment, a styrene resin comprising a styrene elastomer. The styrene resin may consist solely of a styrene elastomer, or it may be a combination of a styrene elastomer and another styrene resin (for example, one or more selected from the group consisting of polystyrene, acrylonitrile styrene copolymer, and acrylonitrile butadiene styrene copolymer).

[0120] In this disclosure, "elastomer" in one embodiment means a material that is elastic at room temperature (23°C). In one embodiment, being elastic means that the storage modulus of elasticity measured by dynamic viscoelasticity measurement at 23°C and 10 Hz is between 1 MPa and 100 MPa.

[0121] The styrene-based elastomer may be a hydrogenated product. Examples of styrene-based elastomers include SBS (styrene-butadiene-styrene), SEBS (hydrogenated styrene-butadiene-styrene), SIS (styrene-isoprene-styrene), SEPS (styrene-ethylene-propylene-styrene), SBR (styrene-butadiene rubber), and hydrogenated SBR, with SEBS being preferred, and high-vinyl SEBS being even more preferred. From the viewpoint of suppressing thermal degradation during processing, the hydrogenation rate of the hydrogenated product is preferably 50% or more, or 80% or more, or 98% or more, and from the viewpoint of low-temperature toughness, it is preferably 50% or less, or 20% or less.

[0122] In SEBS elastomers, the ratio of 1,2- or 3,4-bonds of butadiene is preferably 5 mol% or more, or 10 mol% or more, or 13 mol% or more, or 15 mol% or more, and preferably 80 mol% or less, or 75 mol% or less, or 65 mol% or less, or 50 mol% or less, or 40 mol% or less, from the viewpoint of suppressing crystallization of soft segments.

[0123] The number-average molecular weight (Mn) of the styrene-based elastomer is preferably 10,000 or more, or 40,000 or more, or 100,000 or more, or 150,000 or more, or 200,000 or more, from the viewpoint of obtaining a resin composition with excellent storage modulus, etc. From the viewpoint of ease of dispersion of cellulose fibers into the styrene-based elastomer, and from the viewpoint of the styrene-based elastomer not becoming too hard and the resin composition having good toughness, it is preferably 800,000 or less, or 750,000 or less, or 700,000 or less, or 600,000 or less, or 500,000 or less, or 250,000 or less. Unless otherwise specified, the number-average molecular weight and weight-average molecular weight of the elastomer or rubber in this disclosure are values ​​obtained in terms of standard polystyrene using gel permeation chromatography with chloroform as the solvent and a measurement temperature of 40°C.

[0124] The melt mass flow rate (MFR) of the styrene-based elastomer at 230°C and a load of 21.2 N is preferably 0.5 g / 10 min or more, or 1.5 g / 10 min or more, or 3.0 g / 10 min or more, from the viewpoint of ease of dispersion of cellulose fibers into the styrene-based elastomer and the fact that the styrene-based elastomer does not become too hard and the resin composition has good toughness. From the viewpoint of obtaining a resin composition with excellent storage modulus, it is preferably 20 g / 10 min or less, or 15 g / 10 min or less, or 10 g / 10 min or less.

[0125] Of the total 100% by mass of styrene-based elastomer and cellulose fibers, the content of styrene-based elastomer is preferably 25% by mass or more, 30% by mass or more, or 40% by mass or more, from the viewpoint of obtaining good toughness of the resin composition, and preferably 99% by mass or less, 95% by mass or less, or 90% by mass or less, from the viewpoint of exhibiting a good reinforcing effect by cellulose fibers.

[0126] The content of styrene-based elastomer in the resin composition is preferably 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more, or 30% by mass or more, and preferably 50% by mass or less, or 45% by mass or less, or 40% by mass or less.

[0127] <Liquid rubber> In one embodiment, the resin composition may contain liquid rubber. In one embodiment, the liquid rubber may form a dispersed phase in the resin composition. In this disclosure, liquid rubber means a substance that is fluid at 23°C and forms a rubber elastic body by crosslinking (more specifically vulcanization) and / or chain extension. That is, in one embodiment, the liquid rubber is an uncured product. Furthermore, fluidity means that, in one embodiment, liquid rubber dissolved in cyclohexane is placed in a vial with a diameter of 21 mm and a total length of 50 mm at 23°C and dried, so that the liquid rubber fills the vial to a height of 1 mm, seals it, and when the vial is left upside down for 24 hours, a movement of 0.1 mm or more of the substance in the height direction can be observed.

[0128] Liquid rubber can function as a dispersant for effectively dispersing cellulose fibers in polypropylene resins, and tends to have superior cellulose fiber aggregation suppression ability and heat resistance compared to, for example, liquid non-rubber materials. When such liquid rubber is used, heating and kneading can be carried out sufficiently during the production of the resin composition without concern for thermal degradation of each component, thus enabling good dispersion of cellulose fibers in the polypropylene resin. Molded articles formed from resin compositions produced in this way have excellent mechanical properties and can also have excellent decorative properties and aesthetic appeal due to their high surface smoothness.

[0129] The liquid rubber may have the monomer composition of a general rubber, and is preferably relatively low in molecular weight from the viewpoint of ease of handling and good dispersibility of cellulose fibers. In one embodiment, the liquid rubber exhibits a liquid form due to having a number-average molecular weight (Mn) of 80,000 or less.

[0130] In one embodiment, liquid rubber may be combined with cellulose fibers to form a masterbatch, and such a masterbatch may be further combined with a styrene-based elastomer to form another masterbatch.

[0131] The number-average molecular weight (Mn) of the liquid rubber is preferably 1,000 or more, or 1,500 or more, or 2,000 or more, from the viewpoint of thermal stability and the effect of improving the dispersibility of cellulose fibers in the resin. It is preferably 80,000 or less, or 50,000 or less, or 40,000 or less, or 30,000 or less, or 10,000 or less, in terms of having high fluidity suitable for good dispersion when dispersing cellulose fibers in liquid rubber.

[0132] The weight-average molecular weight (Mw) of the liquid rubber is preferably 1,000 or more, or 2,000 or more, or 4,000 or more, from the viewpoint of thermal stability and the effect of improving the dispersibility of cellulose fibers in the resin. It is preferably 240,000 or less, or 150,000 or less, or 30,000 or less, in terms of having high fluidity suitable for good dispersion when dispersing cellulose fibers in liquid rubber.

[0133] The ratio (Mw / Mn) of the number-average molecular weight (Mn) to the weight-average molecular weight (Mw) of the liquid rubber is preferably 1.5 or higher, or 1.8 or higher, or 2 or higher, in that the degree of variation in molecular weight allows for a high degree of compatibility of multiple properties (in one embodiment, a high degree of compatibility between good dispersion of cellulose fibers in the resin and a good flexural modulus of the resin composition). In that the variation in molecular weight is not excessively large and the desired physical properties of the resin composition can be obtained stably, for example, in terms of compatibility between fluidity and impact resistance, it is preferably 10 or lower, or 8 or lower, or 5 or lower, or 3 or lower, or 2.7 or lower.

[0134] Liquid rubber can have good thermal stability. The thermal decomposition onset temperature of liquid rubber (T DIn terms of good thermal stability, the temperature at which thermal decomposition begins is, in one embodiment, 200°C or higher, 250°C or higher, or 300°C or higher. A higher thermal decomposition onset temperature is preferable, but from the viewpoint of the availability of liquid rubber, in one embodiment it may be 500°C or lower, 450°C or lower, or 400°C or lower.

[0135] The glass transition temperature of liquid rubber is preferably -150°C or higher, or -120°C or higher, or -100°C or higher, in terms of good thermal stability, and preferably 25°C or lower, or 10°C or lower, or 0°C or lower, in terms of good fluidity.

[0136] In one embodiment, the liquid rubber comprises a diene rubber, and in another embodiment, a conjugated diene polymer or a non-conjugated diene polymer or a hydrogenated version thereof. The polymer or its hydrogenated version may be an oligomer. The monomers constituting the liquid rubber may be unmodified or modified (e.g., acid-modified, hydroxyl-modified, etc.). In one embodiment, the liquid rubber may have reactive groups at both ends (e.g., one or more selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, thio groups, amino groups, and halo groups), and therefore may be bifunctional. These reactive groups contribute to crosslinking and / or chain extension of the liquid rubber.

[0137] Conjugated diene polymers The conjugated diene polymer may be a homopolymer, or a copolymer of two or more conjugated diene monomers, or a copolymer of a conjugated diene monomer and another monomer. The copolymer may be random or block-shaped.

[0138] Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-heptadiene, and 1,3-hexadiene, which may be used individually or in combination of two or more.

[0139] In one embodiment, the conjugated diene polymer is a copolymer of the above-mentioned conjugated diene monomer and an aromatic vinyl monomer. The aromatic vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with a conjugated diene monomer. Examples include styrene, p-methylstyrene, α-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, and divinylbenzene, which may be used individually or in combination of two or more. From the viewpoint of moldability of the resin composition and impact resistance of the molded article, styrene is preferred.

[0140] Examples of random copolymers include butadiene-isoprene random copolymers, butadiene-styrene random copolymers, isoprene-styrene random copolymers, and butadiene-isoprene-styrene random copolymers. Regarding the compositional distribution of each monomer in the copolymer chain, examples include perfectly random copolymers with a composition close to statistically random, and tapered random copolymers with a gradient in the compositional distribution. The bonding mode of the conjugated diene polymer, i.e., the composition of 1,4-bonds, 1,2-bonds, etc., may be uniform or different between molecules.

[0141] A block copolymer may be a copolymer consisting of two or more blocks. For example, a block copolymer may have a structure such as AB, ABA, or ABAB, where block A is an aromatic vinyl monomer and block B is a block of conjugated diene monomer and / or a copolymer of aromatic vinyl monomer and conjugated diene monomer. The boundaries between each block do not necessarily need to be clearly distinguishable; for example, if block B is a copolymer of aromatic vinyl monomer and conjugated diene monomer, the aromatic vinyl monomer in block B may be distributed uniformly or tapered. Furthermore, block B may have multiple portions where the aromatic vinyl monomer is uniformly distributed and / or tapered. In addition, block B may have multiple segments with different aromatic vinyl monomer content. When multiple blocks A and block B exist in the copolymer, their molecular weights and compositions may be the same or different.

[0142] The block copolymer may be a mixture of two or more types in which one or more of the following are different: bond type, molecular weight, aromatic vinyl compound species, conjugated diene compound species, 1,2-vinyl content or the total amount of 1,2-vinyl content and 3,4-vinyl content, aromatic vinyl compound component content, hydrogenation rate, etc.

[0143] In conjugated diene polymers, the amount of vinyl bonds in the conjugated diene bond units (e.g., 1,2- or 3,4- bonds of butadiene) is preferably 10 mol% or more and 75 mol% or less, or 13 mol% or more and 65 mol% or less. The amount of vinyl bonds in a conjugated diene bond unit (e.g., the amount of 1,2-bonds in butadiene) is, 13 This can be determined by 13C-NMR (quantitative mode). That is, 13 In 1C-NMR, integrating the peak areas shown below yields a value proportional to the carbon content of each structural unit, which can then be converted to the mass percentage of each structural unit. Styrene 145-147 ppm Vinyl 110-116 ppm Diene (cis) 24-28 ppm Diene (trans) 29-33 ppm

[0144] In a copolymer of a conjugated diene monomer and an aromatic vinyl monomer, the amount of aromatic vinyl monomer bonded to the conjugated diene monomer (hereinafter also referred to as the amount of aromatic vinyl bonded) may be preferably 5 mol% to 70 mol%, or 10 mol% to 50 mol%, based on 100% of the total moles of the conjugated diene polymer.

[0145] Examples of hydrogenated conjugated diene polymers include those exemplified above, such as hydrogenated butadiene homopolymers, isoprene homopolymers, styrene-butadiene copolymers, and acrylonitrile-butadiene copolymers.

[0146] In a preferred embodiment, the liquid rubber is one or more selected from the group consisting of polybutadiene, butadiene-styrene copolymer, polyisoprene, and polychloroprene. These may be derivatives (e.g., maleic anhydride modified, methacrylic acid modified, terminal hydroxyl group modified, hydrogenated, and combinations thereof).

[0147] Non-conjugated diene polymers The non-conjugated diene polymer may be a homopolymer, or a copolymer of two or more non-conjugated diene monomers, or a copolymer of a non-conjugated diene monomer and another monomer. The copolymer may be random or block. Examples of non-conjugated diene polymers include: Olefin polymers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, and ethylene-α-olefin copolymers. Examples include butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylic acid ester-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber.

[0148] In ethylene-α-olefin copolymers, monomers that can copolymerize with ethylene units include propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, or eicosene-1, aliphatic substituted vinyl monomers such as isobutylene, and styrene. Examples include aromatic vinyl monomers such as substituted styrene, vinyl acetate, acrylic acid esters, methacrylic acid esters, glycidyl acrylic acid esters, glycidyl methacrylic acid esters, hydroxyethyl methacrylic acid esters, nitrogen-containing vinyl monomers such as acrylamide, allylamine, vinyl-p-aminobenzene, and acrylonitrile, and dienes such as butadiene, cyclopentadiene, 1,4-hexadiene, and isoprene.

[0149] The ethylene-α-olefin copolymer is preferably a copolymer of ethylene and one or more α-olefins having 3 to 20 carbon atoms, more preferably a copolymer of ethylene and one or more α-olefins having 3 to 16 carbon atoms, and most preferably a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms.

[0150] From the viewpoint of exhibiting impact resistance, the molecular weight of the ethylene-α-olefin copolymer is preferably 10,000 or more, more preferably 10,000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 20,000 to 60,000, as measured by a gel permeation chromatography analyzer using 1,2,4-trichlorobenzene as a solvent at 140°C with a polystyrene standard.

[0151] Furthermore, from the viewpoint of ease of handling during processing, the ethylene unit content of the ethylene-α-olefin copolymer is preferably 30 to 95% by mass relative to the total amount of the ethylene-α-olefin copolymer.

[0152] Ethylene-α-olefin copolymers can be produced by conventionally known manufacturing methods, such as those described in Japanese Patent Publication No. 4-12283, Japanese Unexamined Patent Publication No. 60-35006, Japanese Unexamined Patent Publication No. 60-35007, Japanese Unexamined Patent Publication No. 60-35008, Japanese Unexamined Patent Publication No. 5-155930, Japanese Unexamined Patent Publication No. 3-163088, and U.S. Patent No. 5,272,236.

[0153] In one embodiment, the liquid rubber comprises one or more selected from the group consisting of diene rubber, silicone rubber, urethane rubber, and polysulfide rubber, as well as hydrogenated versions thereof.

[0154] The viscosity of the liquid rubber at 25°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 200,000 mPa·s or less, from the viewpoint of good dispersion of cellulose fibers in the liquid rubber, and preferably 100 mPa·s or more, or 300 mPa·s or more, or 500 mPa·s or more, from the viewpoint of thermal stability, effect on improving the dispersibility of cellulose fibers in the resin, and mechanical properties of the resin composition.

[0155] The viscosity of the liquid rubber at 80°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 250,000 mPa·s or less, or 100,000 mPa·s or less, from the viewpoint of good dispersion of cellulose fibers in the liquid rubber and good dispersion of cellulose fibers in the resin by heating and kneading, and preferably 50 mPa·s or more, or 100 mPa·s or more, or 300 mPa·s or more, from the viewpoint of thermal stability, effect of improving the dispersibility of cellulose fibers in the resin, and mechanical properties of the resin composition.

[0156] The viscosity of the liquid rubber at 0°C is preferably 2,000,000 mPa·s or less, or 1,000,000 mPa·s or less, or 400,000 mPa·s or less, from the viewpoint of good dispersion of cellulose fibers in the liquid rubber, and preferably 200 mPa·s or more, or 600 mPa·s or more, or 1,000 mPa·s or more, from the viewpoint of thermal stability, effect on improving the dispersibility of cellulose fibers in the resin, and mechanical properties of the resin composition.

[0157] The low temperature dependence of the viscosity of the liquid rubber is preferable because it allows for good dispersion of cellulose fibers in the liquid rubber over a wide mixing temperature range. From this viewpoint, it is particularly preferable that the viscosity of the liquid rubber at 80°C, 25°C, and 0°C is within the above range.

[0158] The viscosity of liquid rubber is measured using a Type B viscometer at a rotation speed of 10 rpm.

[0159] Liquid rubber may be combined with cellulose fibers to form a masterbatch. In the masterbatch, the mass ratio of cellulose fibers to liquid rubber may be 0.1 / 99.9~99.9 / 0.1, or 1 / 99~99 / 1, or 5 / 95~95 / 5, or 10 / 90~90 / 10, or 20 / 80~80 / 20, or 30 / 70~70 / 30, or 40 / 60~60 / 40.

[0160] The masterbatch containing cellulose fibers and liquid rubber may or may not contain additional components. Examples of additional components include one or more of those exemplified in this disclosure as additional components that may be included in the resin composition of this embodiment. The content of the additional components in the masterbatch may be, for example, 0.01 to 50% by mass, or 0.1 to 30% by mass.

[0161] In the resin composition, the amount of liquid rubber per 100 parts by mass of polypropylene resin is preferably 0.001 parts by mass or more, or 0.01 parts by mass or more, or 0.1 parts by mass or more, or 1 part by mass or more, preferably 100 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 50 parts by mass or less, or 30 parts by mass or less, or 10 parts by mass or less, or 8 parts by mass or less, from the viewpoint of balancing processability and mechanical properties.

[0162] In the resin composition, the content of cellulose fibers relative to 100% by mass of the total of cellulose fibers and liquid rubber is preferably 0.5% by mass or more, or 1% by mass or more, or 3% by mass or more, from the viewpoint of obtaining a good reinforcing effect from cellulose fibers, and preferably 80% by mass or less, or 60% by mass or less, or 33% by mass or less, or 30% by mass or less, or 20% by mass or less, or 10% by mass or less, from the viewpoint of obtaining the advantages of using liquid rubber.

[0163] The liquid rubber content in the resin composition is preferably 0% by mass or more, or 0.5% by mass or more, or 1.0% by mass or more, or 1.4% by mass or more, or 1.8% by mass or more, or 2.2% by mass or more, or 2.6% by mass or more, and preferably 30% by mass or less, or 15% by mass or less, or 12% by mass or less, or 10% by mass or less, or 6.0% by mass or less, or 4.5% by mass or less, or 4.0% by mass or less, or 3.5% by mass or less, or 3.0% by mass or less.

[0164] <Sulfurizing agents, sulfurizing accelerators> When the resin composition contains liquid rubber and / or other uncured rubber, the resin composition typically contains a vulcanizing agent and may optionally contain a vulcanization accelerator. Conventionally known vulcanizing agents and vulcanization accelerators may be appropriately selected depending on the type of uncured rubber in the resin composition. Examples of vulcanizing agents include organic peroxides, azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and high-molecular-weight polysulfur compounds. The amount of vulcanizing agent is preferably 0.01 to 20 parts by mass, or 0.1 to 15 parts by mass, per 100 parts by mass of uncured rubber in the resin composition.

[0165] Examples of vulcanization accelerators include sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. Zinc oxide, stearic acid, etc., may also be used as vulcanization aids. The amount of vulcanization accelerator is preferably 0.01 to 20 parts by mass, or 0.1 to 15 parts by mass, per 100 parts by mass of uncured rubber in the resin composition.

[0166] <Surfactants> In one embodiment, the resin composition contains a surfactant. In one embodiment, the surfactant is a nonionic surfactant. The nonionic surfactant can penetrate the voids in the cellulose fiber aggregate, making the aggregate porous. For example, if a nonionic surfactant is impregnated into the aggregate in a wet state and then dried to form a dried product, the shrinkage during drying can be reduced compared to a dried product obtained by drying the aggregate without using the nonionic surfactant. Using such a dried product to manufacture the resin composition is advantageous from the viewpoint of good dispersion of cellulose fibers.

[0167] Nonionic surfactants are preferably compounds having a hydrophilic group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and an amino group, and a hydrocarbon group.

[0168] In one embodiment, the nonionic surfactant has an aliphatic group with 6 to 30 carbon atoms as its hydrophobic portion. Such a nonionic surfactant has good affinity with polypropylene resins and styrene elastomers due to the contribution of the carbon chain of the hydrophobic portion, and tends to easily penetrate the voids of cellulose fiber aggregates because the carbon chain of the hydrophobic portion is not too long. The aliphatic group may be linear, alicyclic, or a combination thereof. In one embodiment, the number of carbon atoms in the aliphatic group is 6 or more, or 8 or more, or 10 or more, from the viewpoint of obtaining good dispersibility of cellulose fibers in the resin, and in one embodiment, it is 30 or less, or 25 or less, or 20 or less, from the viewpoint of penetration into the voids of cellulose fiber aggregates.

[0169] Nonionic surfactants preferably have one or more structures selected from the group consisting of oxyethylene, glycerol, and sorbitan as the hydrophilic portion (specifically, a repeating structure in which one or more of these are repeated units). These structures are preferred because they exhibit high hydrophilicity and can easily form various nonionic surfactants in combination with various hydrophobic portions. In the nonionic surfactant having the hydrophilic portion described above, the number of carbon atoms n in the hydrophobic portion and the number of repeating units m in the hydrophilic portion preferably satisfy the following formula: n > m from the viewpoint of obtaining good dispersibility of cellulose fibers in the resin. The number of repeating units m in the hydrophilic portion is preferably 1 or more, or 2 or more, or 3 or more, or 5 or more from the viewpoint of good penetration of the nonionic surfactant into the voids of the cellulose fiber aggregate, and preferably 30 or less, or 25 or less, or 20 or less, or 18 or less from the viewpoint of obtaining good dispersibility of cellulose fibers in the resin.

[0170] Nonionic surfactants are preferably, The following general formula (1): R-(OCH2CH2) m -OH (1) Compounds represented by [wherein R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms in R.], and The following general formula (2): R1OCH2-(CHOH)4-CH2OR2(2) [In the formula, R1 and R2 are independently a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR3{in the formula, R3 represents an aliphatic group having 1 to 30 carbon atoms}, or -(CH2CH2O) y The compound represented by -R4{wherein R4 represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer from 1 to 30} represents... It is one or more species selected from the group consisting of the following:

[0171] In general formula (1), R corresponds to the hydrophobic portion described above, and (OCH2CH2) (i.e., the oxyethylene unit) corresponds to the hydrophilic portion described above. Preferably, the number of carbon atoms in R and the number of repeating units m of (OCH2CH2) are within the same range as described above for the number of carbon atoms n of the hydrophobic portion and the number of repeating units m of the hydrophilic portion.

[0172] In general formula (2), for each of R1, R2, R3, and R4, the number of carbon atoms in the aliphatic group having 1 to 30 carbon atoms is preferably 6 or more, or 8 or more, or 10 or more, and 24 or less, or 20 or less, or 18 or less. Furthermore, y is 1 or greater, preferably 2 or greater, or 4 or greater, preferably 30 or less, or 25 or less, or 20 or less.

[0173] The amount of surfactant in the resin composition is preferably 10 parts by mass or more, or 15 parts by mass or more, or 20 parts by mass or more, per 100 parts by mass of cellulose fiber, and preferably 200 parts by mass or less, or 150 parts by mass or less, or 100 parts by mass or less, or 90 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 60 parts by mass or less, or 50 parts by mass or less, or 45 parts by mass or less, or 40 parts by mass or less.

[0174] The surfactant content in the resin composition is preferably 0.1% by mass or more, or 0.5% by mass or more, or 1% by mass or more, and preferably 10% by mass or less, or 5% by mass or less, or 1% by mass or less.

[0175] <Additional ingredients> The resin composition may further contain additional components in addition to the components described above. Examples of additional components include additional polymers, dispersants other than the surfactants mentioned above, organic or inorganic fillers, heat stabilizers, antioxidants, antistatic agents, colorants, and the like. The content ratio of any additional component in the resin composition is appropriately selected within a range that does not impair the desired effects of the present invention, but may be, for example, 0.01 to 50% by mass, or 0.1 to 30% by mass.

[0176] In one embodiment, the resin composition does not contain a coloring agent. On the other hand, since the resin composition can achieve a high degree of compatibility between good mechanical properties and high transparency, in one embodiment it is useful as a dope-dyeing material. That is, the resin composition according to one embodiment can be configured as a dope-dyeing material by including a coloring agent.

[0177] Additional polymers include thermoplastic resins other than polypropylene resins, such as one or more of polyamide resins, polyester resins, polyacetal resins, polyphenylene ether resins, and polyphenylene sulfide resins. In one embodiment, these thermoplastic resins may have a melting point of 100°C to 350°C or a glass transition temperature of 100°C to 250°C. From the viewpoint of improving the heat resistance of the resin composition, the melting point may, in one embodiment, be 100°C or higher, or 140°C or higher, or 150°C or higher, or 160°C or higher, or 170°C or higher, or 180°C or higher, or 190°C or higher, or 200°C or higher, or 210°C or higher, 220°C or higher, or 230°C or higher, or 240°C or higher, or 245°C or higher, or 250°C or higher. From the viewpoint of ease of manufacturing the resin composition, in one embodiment, it may be 350°C or lower, or 320°C or lower.

[0178] The total content of polymer components in the resin composition (in one embodiment, the total content of polypropylene resin, styrene elastomer, any liquid rubber, and any additional polymer) is preferably 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more, or 85% by mass or more, or 90% by mass or more, and preferably 99.5% by mass or less, or 99% by mass or less, or 98% by mass or less, or 95% by mass or less, or 90% by mass or less.

[0179] The total mass ratio of cellulose fibers to polymer components in the resin composition is preferably 1 / 99 to 50 / 50, or 2 / 98 to 40 / 60, or 3 / 97 to 30 / 70.

[0180] In a preferred embodiment, the resin composition is Polypropylene resin 50% to 94.5% by mass, Styrene-based elastomer 5% to 40% by mass, Cellulose fiber 0.5% to 30% by mass, As optional components, liquid rubber 0% to 30% by mass, and As an optional component, surfactant 0% to 30% by mass, Includes.

[0181] In a preferred embodiment, the resin composition comprises a styrene-based resin containing a styrene-based elastomer, and Polypropylene resin 50% to 89.5% by mass, 10% to 40% by mass of styrene-based elastomer, and Cellulose fiber 0.5% to 30% by mass Includes.

[0182] <<Resin composition: Second aspect>> One aspect of the present invention provides a resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose nanofibers. Cellulose nanofibers are inherently hydrophilic due to their hydroxyl groups, while polypropylene resins and styrene elastomers are inherently hydrophobic. The inventors have found that in a resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose nanofibers, by dispersing the styrene elastomer and cellulose nanofibers in a unique form within the polypropylene resin, it is possible to achieve both excellent mechanical properties such as a low coefficient of thermal expansion and high toughness, and high transparency.

[0183] In one embodiment, a polypropylene resin forms a continuous phase in the resin composition, and in one embodiment, a dispersed phase (hereinafter also referred to as the cellulose / polymer dispersed phase) composed of cellulose nanofibers and a polymer coating the cellulose nanofibers is formed in the continuous phase. In one embodiment, the polymer includes a styrene elastomer.

[0184] In one embodiment, the coating of cellulose nanofibers by a polymer means that, in cross-sectional morphology observation of the resin composition, the polymer is in contact with substantially the entire outer circumference of the cellulose nanofibers. Therefore, the polymer can coat the cellulose nanofibers in such a manner that the cellulose nanofibers do not come into contact with the polypropylene resin. However, there may be areas on the outer circumference of the cellulose nanofibers that are not in contact with the polymer, as long as the effects of the present invention are not impaired. In one embodiment, 70% or less, 60% or less, or 50% or less of the outer circumference length of the cellulose nanofibers measured on the cross-sectional observation image of the resin composition may not be in contact with the polymer. The above coating state is determined by observing the cross-sectional morphology of the resin composition with a scanning electron microscope (SEM) at a magnification of 20,000x or 50,000x, observing one or more fields of view, and for each of 30 randomly selected cellulose nanofibers, measuring the outer circumference length and determining whether or not there is contact with the polymer, and determining that cellulose nanofibers are in contact with the polymer for 30% or more of their outer circumference length are determined to be polymer-coated cellulose nanofibers. If 15 or more of the 30 cellulose nanofibers are determined to be coated with polymer, then it is determined that the polymer is coating the cellulose nanofibers in the resin composition.

[0185] In a composite of a polypropylene resin and a styrene elastomer, the styrene elastomer not only improves the toughness and impact resistance of the polypropylene resin, but can also contribute to maintaining or improving the excellent transparency inherent in the polypropylene resin. The inventors investigated various methods for obtaining the desired reinforcing effect of a filler without impairing the excellent transparency of the composite when further compounding a filler to improve the mechanical properties of such a composite. As a result, they found that a high degree of compatibility between mechanical properties and transparency can be achieved by dispersing cellulose nanofibers coated with a polymer containing a styrene elastomer in the continuous phase (i.e., matrix phase) of the polypropylene resin.

[0186] Since the polymer in the cellulose / polymer dispersed phase coats the cellulose nanofibers while intervening between the cellulose nanofibers and the polypropylene-based resin continuous phase, it contributes to good mechanical properties of the resin composition, particularly a low coefficient of linear expansion and high toughness, and also contributes to low haze (i.e., high transparency) of the resin composition because light scattering hardly occurs. Also, when attempting to simply disperse cellulose nanofibers in a polypropylene-based resin, it is difficult to finely disperse them in the essentially hydrophobic polypropylene-based resin and aggregates may form, which may deteriorate the mechanical properties and transparency of the resin composition. However, the fact that the cellulose nanofibers are coated with a polymer is also advantageous for improving the mechanical properties and transparency of the resin composition by suppressing aggregation of the cellulose nanofibers.

[0187] The polymer constituting the cellulose / polymer dispersed phase may be only a styrene-based elastomer or may further contain an additional polymer. Examples of the additional polymer include liquid rubber described below. The polymer in the cellulose / polymer dispersed phase only needs to coat the cellulose nanofibers as the whole polymer.

[0188] Examples of each component of the resin composition according to the second aspect will be described below. Regarding configurations other than the following description, they may be the same as those of the resin composition according to the first aspect, and the description will not be repeated.

[0189] <Cellulose nanofibers> [Number average fiber length, number average fiber diameter, and L / D ratio] In one embodiment, the number-average fiber length of cellulose nanofibers can contribute to the dispersion of polymers in an elongated shape within the cellulose / polymer dispersion phase. In one embodiment, the number-average fiber length of cellulose nanofibers is preferably greater than or equal to the lower limit exemplified in the first embodiment, from the viewpoint of effectively exhibiting the property-improving effect of cellulose nanofibers and effectively controlling the morphology of the cellulose / polymer dispersion phase, and is preferably less than or equal to the upper limit exemplified in the first embodiment, from the viewpoint of ease of controlling the morphology of the cellulose / polymer dispersion phase.

[0190] The number-average fiber diameter of the cellulose nanofibers is preferably the same as that exemplified in the first embodiment, from the viewpoint of obtaining a good effect of improving physical properties by the cellulose nanofibers and from the viewpoint of creating fine fibers that are advantageous for good coating by the styrene-based elastomer.

[0191] The number-average fiber length (L) / number-average fiber diameter (D) ratio of cellulose nanofibers is preferably above the lower limit exemplified in the first embodiment, from the viewpoint of exhibiting the property-improving effect of cellulose nanofibers and effectively controlling the morphology of the cellulose / polymer dispersed phase, and preferably below the upper limit exemplified in the first embodiment, from the viewpoint of ease of controlling the morphology of the cellulose / polymer dispersed phase.

[0192] [Degree of crystallinity] The degree of crystallinity of cellulose nanofibers is preferably above the lower limit exemplified in the first embodiment, because cellulose itself has high mechanical properties (strength, dimensional stability), and when cellulose nanofibers are dispersed in a resin, the resin composition tends to have high strength and dimensional stability. The upper limit of the degree of crystallinity is not particularly limited, but from a production standpoint, it may be below the upper limit exemplified in the first embodiment.

[0193] [Physical properties of cellulose nanofibers in resin compositions] Various physical properties of cellulose nanofibers in resin compositions (number-average fiber length, number-average fiber diameter, L / D ratio, degree of crystallinity, crystalline polymorphism, degree of polymerization, Mw, Mn, Mw / Mn, average content of alkali-soluble polysaccharides, average content of acid-insoluble components, T D , T 1% , T 250℃ The DS, DSs, DS heterogeneity ratio, coefficient of variation of the DS heterogeneity ratio, etc., described later, are analyzed in the same manner as described in the section on [Physical properties of cellulose fibers in resin composition] with respect to the first embodiment, except for those described later.

[0194] [Chemical modification] Cellulose nanofibers may be chemically modified cellulose nanofibers (also called chemically modified cellulose nanofibers). Cellulose nanofibers may be chemically modified beforehand, for example, at the cellulose fiber raw material stage, during the defibrillation process, or after the defibrillation process, or they may be chemically modified during or after the preparation of the slurry as a dispersion, or during or after the drying and granulation process.

[0195] As a modifying agent for cellulose nanofibers, compounds that react with the hydroxyl groups of cellulose can be used, such as esterifying agents, etherifying agents, and silylating agents. In a preferred embodiment, the chemical modification is acylation using an esterifying agent, and particularly preferably acetylation. Preferred esterifying agents are acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids. The details of the esterifying agent may be the same as in the first embodiment.

[0196] [Degree of acyl substitution (DS)] When cellulose nanofibers are chemically modified (e.g., by hydrophobization such as acylation), they tend to have good dispersibility in resins. However, the cellulose nanofibers of this disclosure, especially when combined with a dispersant, easily exhibit good dispersibility in resins even when unsubstituted or with a low degree of substitution. When the cellulose nanofibers are esterified cellulose nanofibers, the degree of acyl substitution (DS) is preferably 0.1 or higher, or 0.2 or higher, or 0.25 or higher, or 0.3 or higher, or 0.5 or higher, in order to obtain esterified cellulose nanofibers with a high thermal decomposition onset temperature. Furthermore, since an unmodified cellulose skeleton remains in the esterified cellulose nanofibers, the degree of acyl substitution (DS) is preferably 2.0 or lower, or 1.8 or lower, or 1.5 or lower, or 1.2 or lower, or 1.0 or lower, or 0.8 or lower, or 0.7 or lower, or 0.6 or lower, or 0.5 or lower, in order to obtain esterified cellulose nanofibers that combine high tensile strength and dimensional stability derived from cellulose with a high thermal decomposition onset temperature derived from chemical modification. The degree of acyl substitution (DS) can be determined by the same method as described above in the first embodiment.

[0197] The DS non-uniformity ratio (DSs / DSt), defined as the ratio of the degree of modification of the fiber surface (DSs) to the degree of modification of the entire fiber (DSt) (which is synonymous with the degree of acyl substitution (DS) above) of chemically modified cellulose nanofibers, is preferably 1.05 or higher. The larger the value of the DS non-uniformity ratio, the more pronounced the sheath-core-like non-uniform structure (i.e., a structure in which the fiber surface is highly chemically modified while the fiber center retains a structure close to the original unmodified cellulose), and while possessing high tensile strength and dimensional stability derived from cellulose, it is possible to improve the affinity with the resin when compounded with the resin, and improve the dimensional stability of the resin composition. The DS non-uniformity ratio is more preferably 1.1 or higher, or 1.2 or higher, or 1.3 or higher, or 1.5 or higher, or 2 or higher, and from the viewpoint of ease of manufacturing chemically modified cellulose nanofibers, it is preferably 30 or lower, or 20 or lower, or 10 or lower, or 6 or lower, or 4 or lower, or 3 or lower. The value of DSs varies depending on the degree of modification of the esterified cellulose nanofiber, but as an example, it is preferably 0.1 or higher, more preferably 0.2 or higher, even more preferably 0.3 or higher, even more preferably 0.5 or higher, preferably 3.0 or lower, more preferably 2.5 or lower, particularly preferably 2.0 or lower, even more preferably 1.5 or lower, particularly preferably 1.2 or lower, and most preferably 1.0 or lower. The preferred range for DSt is as described above for acyl substituents (DS).

[0198] A smaller coefficient of variation (CV) of the DS heterogeneity ratio of chemically modified cellulose nanofibers is preferable because it reduces the variation in various physical properties of the resin composition. Preferably, the coefficient of variation is 50% or less, or 40% or less, or 30% or less, or 20% or less. The coefficient of variation can be further reduced in a method in which chemical modification is performed after defibrillation of the cellulose fiber raw material to obtain chemically modified cellulose nanofibers (i.e., sequential method), while it can be increased in a method in which defibrillation and chemical modification of the cellulose fiber raw material are performed simultaneously (i.e., simultaneous method). Although the mechanism of action is not clear, it is thought that in the simultaneous method, chemical modification proceeds more easily in the fine fibers generated in the initial stages of defibrillation, and as the hydrogen bonds between cellulose microfibrils decrease due to chemical modification, defibrillation proceeds further, resulting in an increase in the coefficient of variation of the DS heterogeneity ratio.

[0199] The coefficient of variation (CV) of the DS heterogeneity ratio can be calculated using the following formula: 100g of an aqueous dispersion of chemically modified cellulose nanofibers (solid content of 10% by mass or more) is taken, frozen and pulverized in 10g portions, and the DS heterogeneity ratio is calculated from the DSt and DSs of 10 samples. Then, the standard deviation (σ) and arithmetic mean (μ) of the DS heterogeneity ratios among the 10 samples are used. DS heterogeneity ratio = DSs / DSt Coefficient of variation (%) = Standard deviation σ / Arithmetic mean μ × 100

[0200] The method for calculating DSs is as follows: Esterified cellulose nanofibers, powdered by freeze-grinding, are placed on a 2.5 mmφ dish-shaped sample stage, the surface is pressed down to flatten it, and X-ray photoelectron spectroscopy (XPS) is performed. The XPS spectrum reflects the constituent elements and chemical bonding state of only the surface layer of the sample (typically a few nm). Peak separation is performed on the obtained C1s spectrum, and the area intensity (Ixp) of the peak attributed to a single carbon atom derived from the modifying group is used to determine the DSs using the following formula, compared to the area intensity (Ixf) of the peak attributed to a single carbon atom derived from the pyranose ring of cellulose (289 eV, CC bond). DSs = (Ixf) × 5 / (Ixp) For example, if the modifying group is an acetyl group, after separating the C1s spectrum at 285eV, 286eV, 288eV, and 289eV, the 289eV peak can be used for Ixp and the peak derived from the OC=O bond of the acetyl group (286eV) can be used for Ixf. The conditions used for XPS measurement are as follows, for example: Equipment used: ULVAC-FI VersaProbeII Excitation source: mono.AlKα 15kV × 3.33mA Analysis size: Approximately 200 μmφ Photoelectron extraction angle: 45° Capture area Narrow scan: C 1s, O 1s Pass Energy: 23.5 eV

[0201] <Polypropylene resin> The polypropylene-based resin may be the same as that exemplified in the first aspect except as follows. In the second aspect, the melt mass flow rate (MFR) of the polypropylene-based resin measured at 230 °C and a load of 21.2 N in accordance with ISO 1133 is preferably 3 g / 10 min or more and 30 g / 10 min or less. The lower limit of the MFR is more preferably 5 g / 10 min, or 6 g / 10 min, or 8 g / 10 min, and the upper limit of the MFR is more preferably 25 g / 10 min, or 20 g / 10 min, or 18 g / 10 min. From the perspective of improving the toughness of the resin composition, it is desirable that the MFR does not exceed the above upper limit value, and from the perspective of the fluidity of the resin composition, it is desirable that the MFR does not fall below the above lower limit value.

[0202] [Modified polypropylene] The polypropylene-based resin may contain modified polypropylene or may be modified polypropylene. In one aspect, the resin composition contains unmodified polypropylene and modified polypropylene. Modified polypropylene can improve the dispersibility of cellulose nanofibers in the resin composition due to the contribution of good affinity with styrene-based elastomers and / or cellulose nanofibers. From the perspective of affinity with styrene-based elastomers and / or cellulose nanofibers, the modified polypropylene is preferably acid-modified polypropylene. As the acid used for acid modification, mono- or polycarboxylic acids can be used, and examples include maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, and citric acid. Maleic acid or its anhydride is particularly preferred because of the ease of increasing the modification rate. There is no particular limitation on the modification method, but a method of heating polypropylene above its melting point and melt-kneading it in the presence or absence of a peroxide is common.

[0203] From the perspective of obtaining the advantages of using acid-modified polypropylene well, the acid value of the acid-modified polypropylene is preferably 1 mgKOH / g or more, or 3 mgKOH / g or more, or 10 mgKOH / g or more, and from the perspective of maintaining good chemical stability of the resin composition, it is preferably 20 mgKOH / g or less, or 100 mgKOH / g or less, or 50 mgKOH / g or less.

[0204] The melt mass flow rate (MFR) of acid-modified polypropylene, measured at 230°C and under a load of 21.2 N in accordance with ISO 1133, is preferably 50 g / 10 min or more, or 100 g / 10 min or more, or 150 g / 10 min or more, or 200 g / 10 min or more, from the viewpoint of increasing affinity at the interface between the continuous phase and the dispersed phase. There is no particular upper limit, but it is preferably 500 g / 10 min to maintain mechanical strength. On the other hand, the MFR of unmodified polypropylene may be within the range exemplified above as the MFR of polypropylene-based resins.

[0205] In one embodiment, the melting points of unmodified polypropylene and modified polypropylene are preferably 100°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, or 170°C or higher, from the viewpoint of good mechanical properties of the resin composition, and preferably 190°C or lower, or 180°C or lower, from the viewpoint of the availability of polypropylene.

[0206] In one embodiment, the glass transition temperatures of unmodified polypropylene and modified polypropylene are preferably -50°C or higher, 0°C or higher, or 50°C or higher, from the viewpoint of good mechanical properties of the resin composition, and preferably 200°C or lower, 150°C or lower, or 100°C or lower, from the viewpoint of the availability of these polypropylenes.

[0207] <Styrene-based elastomers, styrene resins> Styrene elastomers and styrene resins containing them may be the same as those exemplified in the first embodiment, except as described below. In the second embodiment, the styrene elastomer may be a modified product, and may have modified groups such as epoxy groups, acid anhydride groups, carboxyl groups, carboxylate groups, sulfo groups, aldehyde groups, hydroxyl groups, alkoxy groups, amino groups, amide groups, imide groups, nitro groups, isocyanate groups, mercapto groups, etc. The amount of modified groups per 100 mol% of total monomer units is preferably 0.1 mol% or more, or 0.2 mol% or more, or 0.3 mol% or more, and preferably 5 mol% or less, or 3 mol% or less, from the viewpoint of affinity between cellulose nanofibers and styrene elastomers. The amount of modified groups can be confirmed by FT-IR (Fourier transform infrared spectroscopy), solid-state NMR (nuclear magnetic resonance), solution NMR, or by calculating the molar ratio of modified groups by combining a predetermined monomer composition and elemental analysis of elements not contained in the unmodified product.

[0208] In one embodiment, at least a portion of the styrene-based elastomer may have an acidic functional group. In this disclosure, "a styrene-based elastomer having an acidic functional group" means that the acidic functional group is added to the molecular backbone of the elastomer via a chemical bond. In this disclosure, an acidic functional group means a functional group that can react with basic functional groups, etc. Specific examples include acid anhydride groups, carboxyl groups, carboxylate groups, sulfo groups, hydroxyl groups, and the like.

[0209] The amount of acidic functional groups added to the styrene-based elastomer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, based on 100% by mass of the styrene-based elastomer, from the viewpoint of affinity between cellulose nanofibers and styrene-based elastomers. The number of acidic functional groups is obtained by measuring a calibration curve prepared by measuring a calibration sample mixed with an acidic substance using an infrared absorption spectrum analyzer, and then measuring the sample based on the calibration curve created using the characteristic absorption band of the acid.

[0210] Examples of styrene-based elastomers having acidic functional groups include modified elastomers obtained by grafting α,β-unsaturated dicarboxylic acids or their derivatives onto an unmodified styrene-based elastomer in the presence or absence of peroxides. In a preferred embodiment, the styrene-based elastomer is an acid anhydride-modified elastomer.

[0211] Specific examples of α,β-unsaturated dicarboxylic acids and their derivatives include maleic acid, fumaric acid, maleic anhydride, and fumaric anhydride, with maleic anhydride being particularly preferred among these.

[0212] In one embodiment, the styrene-based elastomer may be a mixture of a styrene-based elastomer having acidic functional groups and a styrene-based elastomer not having acidic functional groups. The mixing ratio of the styrene-based elastomer having acidic functional groups and the elastomer not having acidic functional groups is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and most preferably 40% by mass or more, when the total of both is 100% by mass, from the viewpoint of maintaining high toughness and physical stability of the resin composition. There is no particular upper limit, and substantially all styrene-based elastomers may be elastomers having acidic functional groups, but from the viewpoint of not causing problems with fluidity, 80% by mass or less is desirable.

[0213] Of the total 100% by mass of styrene-based elastomer and cellulose nanofibers, the content of styrene-based elastomer is preferably 35% by mass or more, or 40% by mass or more, or 50% by mass or more, or 70% by mass or more, from the viewpoint of coating the cellulose nanofibers with styrene-based elastomer to obtain good toughness of the resin composition, and preferably 99% by mass or less, or 95% by mass or less, or 90% by mass or less, from the viewpoint of exhibiting a good reinforcing effect by cellulose nanofibers.

[0214] The content of styrene-based elastomer in the resin composition is preferably 10% by mass or more, or 11% by mass or more, or 13% by mass or more, or 15% by mass or more, and preferably 50% by mass or less, or 45% by mass or less, or 40% by mass or less, or 35% by mass, to have good impact resistance of the resin composition.

[0215] <Liquid rubber> In one embodiment, the resin composition may contain liquid rubber. The liquid rubber may exist as a polymer constituting the cellulose / polymer dispersion phase. Liquid rubber has the same meaning as described above in the first embodiment. The liquid rubber may be the same as those exemplified in the first embodiment.

[0216] Liquid rubber can function as a dispersant for effectively dispersing cellulose nanofibers in polypropylene resins, and tends to exhibit superior ability to suppress cellulose nanofiber aggregation and heat resistance compared to, for example, liquid non-rubber materials. In particular, because liquid rubber has a high affinity for styrene elastomers, it is suitable for coating cellulose nanofibers with styrene elastomers without causing aggregation. When using such liquid rubber, heating and kneading can be carried out sufficiently during the production of the resin composition without concern for thermal degradation of each component, thus enabling good dispersion of cellulose nanofibers in the polypropylene resin. Molded articles formed from resin compositions produced in this way have excellent mechanical properties and can also possess excellent decorative properties and aesthetics due to their high surface smoothness.

[0217] In the resin composition of the second embodiment, the details of the components other than those mentioned above may be the same as those described above in the first embodiment.

[0218] In the second embodiment, the resin composition is preferably, Polypropylene resin 50% to 89.5% by mass, Styrene-based elastomer 10% to 40% by mass, Cellulose nanofiber 0.5% to 30% by mass, As optional components, liquid rubber 0% to 30% by mass, and As an optional component, surfactant 0% to 30% by mass, Includes.

[0219] ≪Method for manufacturing resin compositions≫ The resin composition of this embodiment can be manufactured in one embodiment by a method including a mixing step of mixing a polypropylene resin, a styrene elastomer (in one embodiment, a styrene resin containing a styrene elastomer), and cellulose fibers (in one embodiment, cellulose nanofibers). Mixing may be carried out using stirring means such as a rotation-orbit mixer, a planetary mixer, a homogenizer, a propeller-type stirrer, a rotary stirrer, an electromagnetic stirrer, an open roll mixer, a Banbury mixer, a single-screw extruder, or a twin-screw extruder. Furthermore, stirring may be carried out under heating to efficiently perform shearing. Mixing by a homogenizer is preferred because it can promote dispersion by applying high shearing force and pressure. Examples of mixing methods in the mixing step include: (1) A method for obtaining a resin composition by simultaneously adding and mixing cellulose fibers, polypropylene resin, styrene elastomer, and optionally additional components. (2) A method comprising the steps of obtaining an elastomer masterbatch containing a styrene-based elastomer and cellulose fibers, and kneading the elastomer masterbatch with a polypropylene-based resin. These are some examples. In the first embodiment, the method described in (2) above is useful for finely dispersing cellulose fibers in a polypropylene resin. In a second embodiment, the method of (2) described above is useful for forming the cellulose / polymer dispersed phase of the present disclosure.

[0220] In (2) above, the method for manufacturing the elastomer masterbatch is: (a) A method comprising obtaining a cellulose masterbatch containing cellulose fibers and a surfactant and / or liquid rubber, then mixing this with a styrene-based elastomer and optionally drying it to obtain an elastomer masterbatch, (b) A method for obtaining an elastomer masterbatch by simultaneously mixing a resin composition containing a surfactant and / or liquid rubber with cellulose fibers, a surfactant and / or liquid rubber, and a styrene-based elastomer, and optionally drying the mixture. These are some examples. In (a) above, a suitable method for obtaining a cellulose masterbatch is one in which the resin composition contains a surfactant and liquid rubber, the surfactant is mixed with the cellulose fibers to impregnate the voids in the cellulose fiber aggregate, then the liquid rubber is added and mixed to impregnate the voids, and the mixture is dried as needed to obtain a cellulose masterbatch.

[0221] <Powder> Cellulose fibers or cellulose masterbatch may be used as a powder in the production of the resin composition. The powder may have one or more of the following properties. This allows the powder to have excellent processing properties and the cellulose fibers to exhibit excellent dispersion in the polypropylene resin.

[0222] [Powder manufacturing] An example of a method for producing the powder is a method that includes a slurry preparation step of preparing a slurry containing cellulose fibers, a liquid medium, and optionally additional components, and a drying step of drying the slurry to form a powder.

[0223] (Slurry preparation process) In this step, a slurry is prepared. As the liquid medium, water-miscible organic solvents can be used, such as: alcohols with a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (dimethylformamide, dimethylacetamide, acetonitrile, etc.). In a typical embodiment, the liquid medium in the slurry is substantially water only. The slurry may consist of cellulose fibers and the liquid medium, or it may contain surfactants and / or liquid rubber, and any additional components.

[0224] From the viewpoint of process efficiency in the subsequent drying step, the concentration of cellulose fibers in the slurry is preferably 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more. From the viewpoint of avoiding excessive increase in the viscosity of the slurry and solidification due to aggregation, and maintaining good handling properties, it is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, or 45% by mass or less. For example, cellulose fibers are often produced in a dilute dispersion, but the concentration of cellulose fibers in the slurry may be adjusted to the above preferred range by concentrating such a dilute dispersion. Methods such as suction filtration, pressure filtration, centrifugal deliquidation, and heating can be used for concentration.

[0225] (drying process) In this process, the slurry is dried under controlled drying conditions to form a powder. The timing of adding components other than cellulose fibers may be before, during, and / or after drying the slurry. Drying equipment such as spray dryers and extruders can be used for drying. The drying equipment may be commercially available, for example, a micro-mist spray dryer (manufactured by Fujisaki Electric Co., Ltd.), a spray dryer (manufactured by Okawara Chemical Machinery Co., Ltd.), or a twin-screw extruder (manufactured by Japan Steel Works, Ltd.). Among the drying conditions, appropriately controlling the drying speed, drying temperature, and / or pressure (degree of reduced pressure), especially the drying speed, may be advantageous in achieving the desired shape of the powder.

[0226] The drying rate, which is the amount of liquid medium (parts by mass) removed per minute per 100 parts by mass of slurry, may be, for example, 10% / min or more, 50% / min or more, or 100% / min or more, from the viewpoint of rapidly drying the slurry to form a powder of a desired particle size, and may be, for example, 10000% / min or less, 1000% / min or less, or 500% / min or less, from the viewpoint of avoiding excessive pulverization of cellulose fibers, thereby suppressing aggregation of the cellulose fibers and obtaining good handling properties. The drying rate is given by the following formula: Drying rate (% / min) = (Slurry moisture content at the start of drying (mass%) - Powder moisture content at the end of drying (mass%)) / Time taken from the start of drying to the end of drying (minutes) This is the value obtained according to (i.e., the average value throughout the drying process). Here, "start of drying" refers to the point at which the slurry or cake to be dried is supplied to the apparatus and the drying process begins at the desired drying temperature, reduced pressure, and shear rate. The time spent pre-mixing under conditions different from the drying process (drying temperature, reduced pressure, and shear rate) is not included in the drying time. Furthermore, the drying endpoint is defined as the point at which the moisture content first falls below 7% by mass, based on sampling taken at intervals of no more than 10 minutes from the start of drying. In the case of a continuous drying apparatus, the time required from the start of drying to the end of drying can be interpreted as the residence time. In the case of a spray dryer, the residence time can be calculated from the heating air volume and the volume of the drying chamber. Furthermore, when an extruder is used as a drying apparatus, the residence time can be calculated from the screw rotation speed and the total number of screw pitches.

[0227] The drying temperature may be, for example, 20°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher, from the viewpoint of drying efficiency and appropriately agglomerating the cellulose fibers to form a powder of a desired particle size, and may be, for example, 200°C or lower, 150°C or lower, 140°C or lower, 130°C or lower, or 100°C or lower, from the viewpoint of making it less likely for the cellulose fibers and additional components to undergo thermal degradation and avoiding excessive pulverization of the cellulose fibers. The drying temperature is the temperature of the heat source in contact with the slurry, and is defined, for example, by the surface temperature of the temperature-controlled jacket of the drying apparatus, the surface temperature of the heating cylinder, or the temperature of the hot air.

[0228] The degree of reduced pressure may be -1kPa or less, -10kPa or less, -20kPa or less, -30kPa or less, -40kPa or less, or -50kPa or less, from the viewpoint of drying efficiency and appropriately agglomerating cellulose fibers to form a powder of a desired particle size, and may be -100kPa or more, -95kPa or more, or -90kPa or more, from the viewpoint of avoiding excessive pulverization of cellulose fibers.

[0229] In the drying process, the residence time at a slurry temperature of 20°C to 200°C may preferably be set to 0.01 minutes to 10 minutes, 0.05 minutes to 5 minutes, or 0.1 minutes to 2 minutes. Drying under these conditions allows for rapid drying of the cellulose fibers, resulting in the successful production of powder with the desired particle size.

[0230] For example, when using a spray dryer, the slurry is sprayed into a drying chamber through which hot gas is circulated using a spray mechanism (rotating disc, pressurized nozzle, etc.) to dry it. The size of the slurry droplets at the time of spray introduction may be, for example, 0.01 μm to 500 μm, or 0.1 μm to 100 μm, or 0.5 μm to 10 μm. The hot gas may be an inert gas such as nitrogen or argon, or air, etc. The hot gas temperature may be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C. The contact between the slurry droplets and the hot gas in the drying chamber may be parallel flow, counterflow, or parallel-counterflow. The particulate powder generated by the drying of the droplets is collected using a cyclone, drum, etc.

[0231] Furthermore, for example, when using an extruder, the slurry is introduced from a hopper into a kneading section equipped with a screw, and the slurry is dried by continuously transporting it by the screw within the kneading section under reduced pressure and / or heating. The screw configuration may consist of a transport screw, a counterclockwise screw, and a kneading disc, combined in any order. The drying temperature may be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C.

[0232] <Elastomer Masterbatch> [Elastomer masterbatch of the first embodiment] In the first embodiment, an elastomer masterbatch containing cellulose fibers, a styrene-based elastomer or a styrene-based resin containing the same, and optionally additional components may be used to produce the resin composition. The amount of cellulose fibers in the elastomer masterbatch is preferably 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more, and preferably 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less, per 100 parts by mass of styrene-based elastomer, or per 100 parts by mass of the total of styrene-based elastomer and liquid rubber in one embodiment.

[0233] In the elastomer masterbatch, the total content of cellulose fibers and any liquid rubber is preferably 5% by mass or more, or 15% by mass or more, or 30% by mass or more, or 40% by mass or more, or 50% by mass or more, and in one embodiment it may be 80% by mass or less, or 70% by mass or less, or 60% by mass or less.

[0234] In one embodiment, the elastomer masterbatch may be formed by kneading a cellulose masterbatch, a styrene-based elastomer or a styrene-based resin containing the same, and optionally additional components. The kneading temperature may be, for example, 100°C to 300°C. From the viewpoint of ease of processing, it is preferably 150°C or higher, and from the viewpoint of suppressing the decomposition of the resin and cellulose fibers, it is preferably 270°C or lower.

[0235] [Elastomer masterbatch of the second embodiment] In a second embodiment, an elastomer masterbatch containing cellulose nanofibers, a styrene-based elastomer or a styrene-based resin containing the same, and optionally additional components may be used to produce the resin composition. The total content of cellulose nanofibers, styrene-based elastomer, and any liquid rubber in the elastomer masterbatch is preferably 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more, or 90% by mass or more, and in one embodiment may be 100% by mass or less, or 99% by mass or less, or 95% by mass or less.

[0236] In one embodiment, the elastomer masterbatch may be formed by kneading a cellulose masterbatch, a styrene-based elastomer or a styrene-based resin containing the same, and optionally additional components. The kneading temperature may be, for example, 150°C to 280°C.

[0237] [Masterbatch mixing] In the first and second embodiments, the mixing means is not particularly limited, but examples of mixing means include a rotating / revolving mixer, a planetary mixer, a homogenizer, a propeller-type agitator, a rotary agitator, an electromagnetic agitator, an open roll mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, and so on. Furthermore, mixing may be performed under heating in order to efficiently carry out shearing.

[0238] <Mixing of elastomer masterbatch and polypropylene resin> The above elastomer masterbatch can be melt-kneaded with a polypropylene resin to obtain a resin composition. The mass ratio of the elastomer masterbatch to the polypropylene resin (elastomer masterbatch / polypropylene resin) may, in one embodiment, be 1 / 99 to 99 / 1, or 5 / 95 to 95 / 5, or 10 / 90 to 90 / 10, or 20 / 80 to 80 / 20, or 30 / 70 to 70 / 30, or 40 / 60 to 60 / 40.

[0239] [Mixing in the first form] In the first embodiment, a general-purpose kneader such as a Banbury mixer or open roll may be used for melt kneading. The kneading temperature may be, for example, 100°C to 300°C. From the viewpoint of ease of processing, it is preferably 150°C or higher, and from the viewpoint of suppressing the decomposition of the resin and cellulose fibers, it is preferably 270°C or lower. The elastomer masterbatch may be subjected to kneading with the polypropylene resin while the styrene elastomer remains in a fluid state. Alternatively, in a preferred embodiment, melt kneading may be performed in a twin-screw extruder.

[0240] In the first embodiment, an elastomer masterbatch, transported to a desired ratio with a polypropylene resin, may be added to the polypropylene resin, mixed, and then melt-kneaded. In one embodiment, the production of the elastomer masterbatch and the kneading of the elastomer masterbatch with the polypropylene resin are carried out continuously in the same apparatus. This allows for good dispersion of cellulose fibers, styrene elastomers, etc., in the polypropylene resin. The kneading means for the elastomer masterbatch and the polypropylene resin is preferably a single-screw extruder or a twin-screw extruder, but a twin-screw extruder is preferred from the viewpoint of controlling the dispersibility of cellulose fibers. When the process of producing the elastomer masterbatch and the process of kneading the elastomer masterbatch with the polypropylene resin are carried out continuously, the L / D ratio, obtained by dividing the cylinder length (L) of the extruder by the screw diameter (D) throughout both processes, is preferably 20 or more, and particularly preferably 40 or more. The screw rotation speed for both processes is preferably in the range of 50 to 800 rpm, and more preferably in the range of 100 to 600 rpm. Each screw inside the extruder cylinder may be optimized by combining elements such as an elliptical, two-bladed screw-shaped conveying screw and a kneading disc, which is a kneading element.

[0241] [Mixing in the second form] In a second embodiment, a general-purpose kneader such as a single-screw extruder, twin-screw extruder, or multi-screw extruder may be used for melt kneading. The kneading temperature may be, for example, 150°C to 280°C. The elastomer masterbatch may be kneaded with the polypropylene resin while the styrene elastomer remains in a fluid state. Alternatively, in a preferred embodiment, a kneader such as a Banbury mixer or open roll may be used. When a polypropylene resin and a styrene elastomer are mixed, generally one forms a continuous phase and the other a substantially spherical dispersed phase. However, in the method of this embodiment, by appropriately adjusting the conditions when mixing the styrene elastomer, which is mixed with cellulose nanofibers, with the polypropylene resin, the styrene elastomer can be dispersed in the continuous phase of the polypropylene resin.

[0242] In a second embodiment, an elastomer masterbatch, transported to a desired ratio with a polypropylene resin, may be added to the polypropylene resin, mixed, and then melt-kneaded. In one embodiment, the production of the elastomer masterbatch and the kneading of the elastomer masterbatch with the polypropylene resin are performed continuously in the same apparatus. This allows for the stable realization of the desired distribution state of cellulose nanofibers and the desired dispersed phase form of the styrene elastomer. The kneading means for the elastomer masterbatch and the polypropylene resin is preferably a single-screw extruder or a twin-screw extruder, but a twin-screw extruder is preferred from the viewpoint of controlling the dispersibility of cellulose nanofibers. When the process of producing the elastomer masterbatch and the process of kneading the elastomer masterbatch with the polypropylene resin are performed continuously, the L / D ratio, obtained by dividing the cylinder length (L) of the extruder by the screw diameter (D) throughout both processes, is preferably 30 or more, and particularly preferably 40 or more. The screw rotation speed for both processes is preferably in the range of 50 to 800 rpm, and more preferably in the range of 100 to 600 rpm. Each screw inside the extruder cylinder may be optimized by combining elements such as an elliptical, two-bladed screw-shaped conveying screw and a kneading disc, which is a kneading element.

[0243] <Shape of resin composition> The resin composition of this embodiment can be provided in various shapes such as pellets, sheets, fibers, plates, and rods. For example, the resin composition may be extruded into strands and cooled and solidified in a water bath to form pellets, or the resin composition may be extruded into rods or cylinders and cooled to form extruded products, or the resin composition may be extruded from a T-die to form sheets or films. Pellet shapes are preferred for ease of post-processing and transport. Preferred pellet shapes include round, elliptical, and cylindrical shapes, and the shape may vary depending on the cutting method during extrusion. For example, pellets cut using a method called underwater cutting are often round, pellets cut using a method called hot cutting are often round or elliptical, and pellets cut using a method called strand cutting are often cylindrical. The preferred diameter of round pellets is 1 mm to 3 mm. The preferred diameter of cylindrical pellets is 1 mm to 3 mm, and the preferred length is 2 mm to 10 mm. The diameter and length mentioned above should preferably be above the lower limit from the viewpoint of operational stability during extrusion, and below the upper limit from the viewpoint of ease of engagement with the molding machine during post-processing.

[0244] A desired molded article may be manufactured by molding a resin composition alone or together with other components into a desired shape. The combination of components and the molding method are not particularly limited and may be selected according to the desired molded article. The molding method is not limited to these, but injection molding, extrusion molding, blow molding, inflation molding, and foam molding can be used. Among these, injection molding is particularly preferred from the viewpoint of design and cost.

[0245] Uses of resin compositions The resin composition of this embodiment is useful as a substitute for steel plates, fiber-reinforced plastics (e.g., carbon fiber reinforced plastics, glass fiber reinforced plastics, etc.), resin composites containing inorganic fillers, etc. Suitable applications of the resin composition include industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing components, containers and packaging components, etc.

[0246] The resin composition of the first embodiment is particularly useful as a dope-dye material that can be applied to applications requiring high mechanical properties (e.g., automotive body panels) because it achieves a high degree of balance between mechanical properties and transparency, and can also have excellent color development and luster when colored. A preferred embodiment provides an automotive body panel containing the resin composition of the present disclosure. The resin composition of the second embodiment is particularly useful as a dope-dyed material that can achieve a high degree of both mechanical properties and transparency, and is therefore applicable to applications requiring high mechanical properties (for example, automotive body panels).

[0247] ≪Characteristics of Resin Compositions≫ <Refractive index> The refractive index of the resin composition (particularly the resin composition of the first embodiment) is such that, in one embodiment, the arithmetic mean value obtained when five different points in the test specimen are evaluated in Procedure 1 of the present disclosure is 1.500 or higher, or 1.503 or higher, or 1.505 or higher, and in one embodiment, 1.515 or lower, or 1.513 or lower, or 1.510 or lower.

[0248] <Light transmittance> The light transmittance of the resin composition (particularly the resin composition of the first embodiment) is, in one embodiment, 1% or more, or 2% or more, or 3% or more, or 5% or more, or 8% or more, or 10% or more, or 15% or more. A higher light transmittance is desirable, but from the viewpoint of ease of manufacturing the resin composition, in one embodiment it is 50% or less, or 40% or less, or 30% or less, or 25% or less. The above transmittance is the light transmittance at a wavelength of 780 nm measured using a UV-Vis spectrophotometer (e.g., JASCO Corporation, V-670) on a 2 mm thick dumbbell-shaped test piece conforming to ISO 37 type 3 standard, which is made by kneading the resin composition in a small kneader (e.g., Xplore Instruments, product name "Xplore") and producing it with an attached injection molding machine.

[0249] <Tensile Yield Strength> The tensile yield strength of the resin composition (particularly the resin composition of the first embodiment) may, in one embodiment, be 20 MPa or more, or 21 MPa or more, or 22 MPa or more, and in one embodiment, it may be 40 MPa or less, or 35 MPa or less, or 30 MPa or less.

[0250] <Tensile elongation at breaking> The tensile elongation at break of the resin composition (particularly the resin composition of the first embodiment) may, in one embodiment, be 100% or more, 200% or more, or 300% or more, and in one embodiment, it may be 1000% or less, 900% or less, or 800% or less.

[0251] <Flexural modulus> The flexural modulus of the resin composition (particularly the resin composition of the second embodiment) may, in one embodiment, be 1.0 GPa or more, 1.1 GPa or more, or 1.2 GPa or more, and may be 4.0 GPa or less, 3.5 GPa or less, or 3.0 GPa or less. [Examples]

[0252] The following describes illustrative embodiments of the present invention with reference to examples, but the present invention is not limited to these examples.

[0253] (1) First aspect ≪Evaluation Method≫ <Polypropylene resins and styrene elastomers> [Melt flow rate (MFR) at 230°C] The measurement was performed using the method described in JIS K7210.

[0254] <Liquid rubber> [Amount of vinyl, amount of aromatic styrene] Dissolve the sample in deuterated chloroform, 13 The measurement was performed using 1C-NMR (JEOL ECZ500) under the following conditions. Resonance frequency: 125MHz Pulse width: 90° Repeat time: 8 sec Total: 5120 times Temperature: room temperature Chemical shift reference: CDCl 377.0 ppm

[0255] [Viscosity at 25°C] The viscosity of the liquid rubber was measured using a Type B viscometer at a rotation speed of 10 rpm.

[0256] [Number-average molecular weight (Mn) and weight-average molecular weight (Mw)] Chromatograms were measured using GPC with three polystyrene gel-packed columns linked together, and molecular weight (Mn, Mw) and molecular weight distribution (Mw / Mn) were calculated using a calibration curve with standard polystyrene. Tetrahydrofuran was used as the solvent.

[0257] <Cellulose fiber> The following evaluations were performed on acetylated and unacetylated cellulose fibers. [Fabrication of porous sheets] First, the concentrated cake was added to tert-butanol and then dispersed using a mixer or similar device until no aggregates remained. The concentration was adjusted to 0.5% by mass for every 0.5 g of cellulose fiber solids. 100 g of the resulting tert-butanol dispersion was filtered on filter paper. Without removing the filtrate from the filter paper, it was sandwiched between two larger sheets of filter paper, and the edges of the larger sheets were pressed down with weights while it was dried in a 150°C oven for 5 minutes. After that, the filter paper was peeled off to obtain a porous sheet with minimal distortion. The air permeability resistance of this sheet was 10 g / m². 2 Porous sheets with a flow rate of 100 sec / 100 ml or less were used as measurement samples. The basis weight (W) of the sample after standing for 1 day in an environment of 23℃ and 50%RH (g / m²) 2 After measuring the air permeability resistance (R) (sec / 100ml), the air permeability resistance was measured using a Wangyan-type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, 10 g / m was measured according to the following formula. 2 The value per unit area was calculated. Weight: 10g / m 2 Air permeability resistance (sec / 100ml) = R / W × 10

[0258] [Weight-average molecular weight (Mw), number-average molecular weight (Mn), and Mw / Mn ratio] 0.88 g of porous sheet was weighed, cut into small pieces with scissors, lightly stirred, and then 20 mL of pure water was added and left for 1 day. Next, the water and solids were separated by centrifugation. Then 20 mL of acetone was added, lightly stirred, and left for 1 day. Next, the acetone and solids were separated by centrifugation. Then 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. After separating the N,N-dimethylacetamide and solids again by centrifugation, 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. The N,N-dimethylacetamide and solids were separated by centrifugation, and 19.2 g of N,N-dimethylacetamide solution, prepared so that lithium chloride was 8 mass percent, was added to the solids, stirred with a stirrer, and visually confirmed to be dissolved. The solution containing the dissolved cellulose fibers was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The equipment and measurement conditions used are as follows. Equipment: Tosoh Corporation HLC-8120 Column: TSKgel SuperAWM-H (6.0mm I.D. × 15cm) × 2 tubes Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%) Flow rate: 0.6mL / min Calibration curve: Pullulan equivalent For cellulose fibers, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and Mw / Mn ratio of the raw material before acetylation were used.

[0259] [Average content of alkali-soluble polysaccharides] The alkali-soluble polysaccharide content was determined for cellulose fibers by subtracting the α-cellulose content from the holocellulose content (Wise method) using the method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). The alkali-soluble polysaccharide content was calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content was taken as the average alkali-soluble polysaccharide content of the cellulose fiber. For acetylated cellulose fibers CNF-3 and CNF-4, the average alkali-soluble polysaccharide content of the raw materials CNF-1 and CNF-2 before acetylation was used.

[0260] [Average content of acid-insoluble components] The acid-insoluble components were quantified using the Claesson method described in a non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000) for cellulose fibers. Absolutely dried cellulose fibers were accurately weighed, placed in a designated container, and 72% by mass concentrated sulfuric acid was added. After pressing the contents uniformly with a glass rod, the mixture was autoclaved to dissolve the cellulose and hemicellulose in the acid solution. After cooling, the contents were filtered through glass fiber filter paper to obtain the acid-insoluble components as residue. The acid-insoluble component content was calculated from the weight of this residue, and the number average of the acid-insoluble component content calculated for three samples was taken as the average acid-insoluble component content. For acetylated cellulose fibers CNF-3 and CNF-4, the average acid-insoluble component content of the raw materials CNF-1 and CNF-2 before acetylation was used.

[0261] [Degree of crystallinity] X-ray diffraction measurements were performed on the porous sheet, and the degree of crystallinity was calculated using the following formula. Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) :Diffraction peak intensity at the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous): The halo peak intensity due to amorphous material in type I cellulose crystals, specifically the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°). (X-ray diffraction measurement conditions) MiniFlex device (manufactured by Rigaku Corporation) Operation axis 2θ / θ Source CuKα Measurement method: Continuous Voltage 40kV Current 15mA Starting angle 2θ=5° Ending angle 2θ = 30° Sampling width 0.020° Scan speed 2.0° / min Sample: A porous sheet is attached to the sample holder.

[0262] [Number average fiber diameter] The concentrated cake was diluted with tert-butanol to 0.01% by mass, dispersed using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 15,000 rpm for 3 minutes, cast onto an osmium-deposited silicon substrate, and air-dried. The resulting sample was then measured using a high-resolution scanning electron microscope (Hitachi High-Tech Corporation, Regulus 8220). The measurement was performed by adjusting the magnification so that at least 100 cellulose fibers could be observed. The diameter (D) of 100 randomly selected cellulose fibers was measured, and the number-average fiber diameter was calculated by adding the average of the 100 cellulose fibers.

[0263] [Specific surface area] Using a specific surface area and pore distribution analyzer (Nova-4200e, manufactured by Quantachrome Instruments), approximately 0.2 g of a porous sheet was dried under vacuum at 120°C for 5 hours. Then, the amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen was measured at 5 points within a relative vapor pressure (P / P0) range of 0.05 to 0.2 (multi-point method). The BET specific surface area (m²) was then calculated using the analyzer's program. 2 The value per gram ( / g) was calculated.

[0264] [Acyl substitution degree DS] The degree of acetyl substitution was measured. Infrared spectral measurements were taken from five locations on the porous sheet using the ATR-IR method with a Fourier transform infrared spectrophotometer (JASCO FT / IR-6200). The infrared spectral measurements were performed under the following conditions. Total number of times: 64 Wavenumber resolution: 4cm -1 , Measurement wavefrequency range: 4000~600cm -1 , ATR crystal: diamond, Incident angle: 45°

[0265] From the obtained IR spectrum, the IR index is calculated using the following formula: IR Index = H1730 / H1030 The calculation was performed according to the formula. In the formula, H1730 and H1030 are 1730 cm. -1 , 1030cm -1 This is the absorbance in the absorption band of the CO stretching vibration of the cellulose skeleton chain. However, each value is 1900 cm². -1 and 1500cm -1 The line connecting them is 800cm -1 and 1500cm -1 The line connecting these points is used as the baseline, and this value represents the absorbance when this baseline is set to 0. Then, the average degree of replacement at each measurement location was calculated from the IR index according to the following formula, and the average value was defined as DS. DS = 4.13 × IR Index

[0266] [Thermal decomposition onset temperature (T D )] Thermal analysis of the porous sheet was performed using the following measurement method. Device: Rigaku Thermo plus EVO2 Sample: Circular pieces cut from a porous sheet were stacked in aluminum sample pans, with 10 mg of each piece placed on top. Sample amount: 10 mg Measurement conditions: Under a nitrogen flow of 100 ml / min, the temperature was raised from room temperature to 150 °C at a rate of 10 °C / min, held at 150 °C for 1 hour, and then directly raised to 450 °C at a rate of 10 °C / min. T D Calculation method: Obtained from a graph with temperature on the horizontal axis and weight retention percentage on the vertical axis. Starting from the weight of the porous sheet at 150 °C (state where moisture was almost removed) (weight loss amount 0 wt%), the temperature was further raised. A straight line passing through the temperature at 1 wt% weight loss and the temperature at 2 wt% weight loss was obtained. The temperature at the point where this straight line intersects the horizontal line (baseline) passing through the starting point of 0 wt% weight loss was defined as the thermal decomposition start temperature (T D ).

[0267] [Temperature at 1 wt% weight loss] The temperature at 1 wt% weight loss used in the calculation of the above T D was defined as the temperature at 1 wt% weight loss.

[0268] [Weight loss rate at 250 °C] Apparatus: Thermo plus EVO2 manufactured by Rigaku Sample: A circular piece cut from the porous sheet was stacked and placed in an aluminum sample pan with a weight of 10 mg. Sample amount: 10 mg Measurement conditions: Under a nitrogen flow of 100 ml / min, the temperature was raised from room temperature to 150 °C at a rate of 10 °C / min, held at 150 °C for 1 hour, then raised from 150 °C to 250 °C at a rate of 10 °C / min, and directly held at 250 °C for 2 hours. Starting from the weight W0 at the time of reaching 250 °C, after holding at 250 °C for 2 hours, the weight was W1, and it was calculated from the following formula. Weight loss rate at 250 °C (%): ((W0 - W1) / W0) × 100

[0269] <Cellulose fiber, polypropylene resin and resin composition> [Refractive index] (Procedure 1: Refractive index by Abbe method) For the sample sheet prepared by the following procedure, the refractive index was measured using an Abbe refractometer 2T manufactured by Atago. A polypropylene resin sample sheet and a resin composition sample sheet were prepared according to the following procedure. After preheating 1 g of the material at 200 °C for 5 minutes under vacuum, it was pressed at 10 MPa and held for 1 minute, and then rapidly cooled at room temperature to obtain a sample sheet with a thickness of 0.2 mm.

[0270] (Measurement conditions) Test method: JIS K 7142 Test piece: 8 mm × 20 mm Test conditions: Temperature; 23 °C Light source; Na (D line / 589 nm) Contact liquid; diiodomethane

[0271] (Procedure 2: Refractive index calculated from molecular structure) The refractive index was calculated according to the following procedure. Using the Synthia module of Materials Studio manufactured by BIOVIA, for each polymer, it was calculated based on the structure-property correlation method from the chemical structure of the monomer, and a calibration curve was created to obtain it. The detailed theory is based on the following formula described on page 303 of the following reference, and the description is incorporated herein by reference for the purpose of this case: Jozef Bicerano, "Prediction of Polymer Properties, 3rd Edition", published by Marcel Dekker. n(298K) ≒ 1.885312 + 0.024558 × (17 × 0 χ V -20 × 0 χ - 12 × 1 χ V -9 × N rot +N ref ) / N 0 χ V : Zero-order (atomic) connectivity index for the whole molecule 0 χ: Zero-order (atomic) connectivity index 1 χ V : First-order (bond) connectivity index for the whole molecule N rot : Total number of rotational degrees of freedom of the repeating unit N ref : Correction factor N: Number of vertices in the graph after removing hydrogen

[0272] The refractive index of acetylated cellulose fibers is determined by using a repeating unit in which the hydroxyl group of the β-D-glucopyranose unit is replaced with an acetyl group, resulting in a degree of acetyl group substitution of DS. A For the cases where the refractive index is 0 (i.e., unchanged), 1.0, 2.0, and 3.0, the refractive index was determined, and the following formula was derived and calculated using linear regression by the least squares method. Refractive index = -0.0151 × DS A +1.55 The refractive index of polypropylene resins was calculated using the molar ratio of propylene units (RP) and ethylene units (RE) in the total polymer. The refractive index was determined for RP = 0 (i.e., polyethylene homopolymer), 0.3, 0.5, 0.7, and 1.0 (i.e., polypropylene homopolymer). The following formula was derived and calculated using linear regression by the least squares method. Refractive index = 0.0069 × (RP / (RP + RE)) + 1.46

[0273] [SP value] The chemical structure of each component was determined using the Synthia module of BIOVIA's Materials Studio, following Fedors' method. For the SP value of cellulose fibers, the degree of acetyl group substitution (DS) was used. A Using the values ​​obtained for the cases =0 (i.e., unvaried), 1.0, 2.0, and 3.0, the following equation was derived and calculated by linear regression using the least squares method. SP value = -3.2428 × DS A +31.7

[0274] <Resin composition> [Light transmittance] From a dumbbell-shaped test specimen conforming to ISO 37 type 3 standards, a rectangular parallelepiped sample measuring 2 mm thick, 4 mm wide, and 15 mm long was cut using a precision saw. The light transmittance at a wavelength of 780 nm was measured using a UV-Vis spectrophotometer (JASCO Corporation, V-670) and calculated as the light transmittance.

[0275] [Volume fraction of coarse aggregates] Samples measuring 2 mm thick, 4 mm wide, and 2 mm long were cut from a dumbbell-shaped test specimen conforming to ISO 37 type 3 standards using a precision saw, and X-ray CT measurements were performed using an X-CT scanner (Bruker Japan, Skyscan 1272). The measurement conditions were as follows. Tube voltage: 40kV Tube current: 100μA Pixel resolution: 1.2 μm Detector pixel count: 2452 × 1640 pixels Total number of times: 4 Measurement angle step: 0.2 degrees Scan range: 0-180 degrees Furthermore, the data obtained after measurement was smoothed by applying a Kuwahara filter across two pixels in the 3D direction to improve image quality. The 3D data thus obtained was then binarized to extract pixels containing only aggregates. Subsequently, the ratio of the total volume of aggregates larger than a cube with sides of 4.8 μm to the total volume of the X-ray CT observation area was calculated as the volume fraction of the aggregates.

[0276] [Tensile yield strength and tensile fracture strain] Tensile yield strength and tensile fracture strain were measured in accordance with ISO 527-1. For molded pieces that fractured before reaching yield, the maximum strength was used as a substitute.

[0277] [Coefficient of linear expansion] A rectangular prism sample measuring 2 mm vertically, 4 mm horizontally, and 10 mm in length was cut from the center of a dumbbell-shaped test specimen conforming to ISO 37 type 3 standard using a precision saw. Thermomechanical analysis (TMA) was performed in accordance with ISO 11359-2 within the measurement temperature range of -20°C to 120°C, and values ​​were calculated between 0°C and 60°C.

[0278] ≪Materials used≫ <Polypropylene resin> PP: Polypropylene homopolymer (MA04A, available from Nippon Polypropylene Co., Ltd.), refractive index (P1) according to Procedure 1: 1.510, refractive index (P2) according to Procedure 2: 1.471, SP value: 16.06, MFR: 40g / 10min

[0279] <Styrene-based elastomers and styrene-based resins> SEBS H1062: Product name "ToughTec H1062", manufactured by Asahi Kasei Corporation, MFR: 4.5g / 10 min SEBS H1221: Product name "ToughTec H1221", manufactured by Asahi Kasei Corporation, MFR: 4.5g / 10 minutes SEBS S1613: Product name "SOE S1613", manufactured by Asahi Kasei Corporation, MFR: 4.5g / 10 mins Polystyrene (PS) SX100: Product name "YS Resin SX100", manufactured by Yasuhara Chemical Co., Ltd.

[0280] <Liquid rubber> Liquid rubber-1: Butadiene-styrene random copolymer (RICON 184, available from Clay Valley), viscosity 40,000 cP at 25°C, number-average molecular weight (Mn) 3,200, weight-average molecular weight (Mw) 14,000, Mw / Mn 4.3, vinyl content 19 mol%, aromatic styrene content 8 mol% Liquid rubber-2: Butadiene-styrene random copolymer (RICON 100, available from Clay Valley), viscosity at 25°C 75,000 cP, number-average molecular weight (Mn) 2,100, weight-average molecular weight (Mw) 4,500, Mw / Mn 2.1, vinyl content 42 mol%, aromatic styrene content 9 mol%

[0281] <Cellulose fiber> CNF-1: Unmodified Cellulose Fiber (miniaturization) Three parts by mass of cotton linter pulp were immersed in 27 parts by mass of water and dispersed using a pulper. 30 parts by mass of the pulper-treated cotton linter pulp slurry (of which three parts by mass were cotton linter pulp) were dispersed in 170 parts by mass of water to obtain an aqueous dispersion (solid content 1.5% by mass). Using an SDR14 type laboratory refiner (pressure-type disk type) manufactured by Aikawa Iron Works Co., Ltd. as a disc refiner, the aqueous dispersion was beaten for 30 minutes with a clearance of 1 mm between the disks. Subsequently, thorough beating was performed under conditions where the clearance was reduced to almost zero to obtain a beaten aqueous dispersion (solid content concentration: 1.5% by mass). The obtained beaten aqueous dispersion was then subjected to three micronization processes using a high-pressure homogenizer (NSO15H manufactured by Nilo Soavi (Italy)) at an operating pressure of 100 MPa to obtain a fine cellulose fiber slurry (solid content concentration: 1.5% by mass). Then, the solids were concentrated to 20% by mass using a dehydrator to obtain CNF-1.

[0282] CNF-2: Unmodified Cellulose Fiber CNF-2 was obtained using the same method as CNF-1, except that the number of micronization processes using a high-pressure homogenizer was changed to 10.

[0283] CNF-3: Acetylcellulose fiber Five parts by mass of CNF-1 (solid content 20% by mass) and ninety-five parts by mass of DMSO were added to a KAPPA VITA® homomixer (tank size 35L) manufactured by NETZSCH Vakumix. The mixture was dispersed in the homomixer at 2500 rpm (peripheral speed 12 m / s) to obtain 100 parts by mass of DMSO slurry (solid content 1.0% by mass). Subsequently, two parts by mass of vinyl acetate and 0.3 parts by mass of potassium carbonate were added, and the mixture was stirred at 40°C for 3 hours. To stop the reaction, 100 parts by mass of water was added while stirring. The solids were then filtered off. The obtained solids were washed by adding 100 parts by mass of water, dispersing them in the homomixer, and then filtering six times to obtain 5 parts by mass of concentrated acetylated cellulose fiber cake (solid content 20% by mass).

[0284] CNF-4: Acetylcellulose fiber CNF-4 was obtained by acetylation using the same method as for CNF-3, except that CNF-1 was replaced with CNF-2.

[0285] CNF-5: Cellulose fiber Daicel Mirise Co., Ltd.'s Celish KY-100G (solid content concentration 10% by mass) was concentrated in a dehydrator to a solid content concentration of 20% by mass. The properties of cellulose fibers are shown in Table 1.

[0286] <Nonionic surfactant> Surfactant-1: Sorbitan monolaurate (Leodol SP-L10, available from Kao Corporation) Surfactant-2: Polyoxyethylene(2) monolauryl ether (Emulgen 102KG, available from Kao Corporation) (Number in parentheses indicates the number of repeating oxyethylene chains) Surfactant-3: Ethylene glycol-propyn glycol copolymer (PEG-PPG) (Sannix GL-3000, available from Sanyo Chemical Industries, Ltd.)

[0287] Preparation of resin compositions <Examples 1-1 to 1-14> 25 parts by mass of cellulose fiber with a solid content of 20% by mass was mixed with 75 parts by mass of purified water. A nonionic surfactant and liquid rubber were added to this mixture according to the composition shown in Table 2, and the mixture was mixed for 5 minutes using a Shinky ARE-310 rotary-orbit mixer to obtain a dispersion of the cellulose fiber composition. The obtained dispersion was dried at 80°C using an ESPEC SPH-201. The resulting dried material was pulverized with a Labonect MS-05 mini-speed mill to obtain CNF powder. The obtained CNF powder and SEBS elastomer were mixed in a small kneader (manufactured by Xplore Instruments, product name "Xplore") at 200°C and 200 rpm for 3 minutes according to the composition shown in Table 3, and then discharged to obtain a masterbatch. Next, the obtained masterbatch and polypropylene resin were mixed in a small kneader (manufactured by Xplore Instruments, product name "Xplore") at 200°C and 200 rpm for 3 minutes according to the composition shown in Table 5. After that, they were melted at 200°C in the attached injection molding machine to produce dumbbell-shaped test specimens conforming to ISO 37 TYPE 3 standards.

[0288] <Comparative Example 1-1> Polypropylene resin was mixed using a small kneader (Xplore Instruments, product name "Xplore") at 200°C and 200 rpm for 3 minutes in a circulating kneading process. The resulting material was then melted at 200°C using the attached injection molding machine to produce dumbbell-shaped test specimens conforming to ISO 37 TYPE 3 standards.

[0289] <Comparative Examples 1-2 to 1-5> SEBS elastomer or masterbatch and polypropylene resin were mixed in a small kneader (manufactured by Xplore Instruments, product name "Xplore") at 200°C and 200 rpm for 3 minutes according to the composition shown in Table 6. The mixture was then melted at 200°C in the attached injection molding machine to produce dumbbell-shaped test specimens conforming to ISO 37 TYPE 3 standards.

[0290] The results are shown in Tables 1-6.

[0291] [Table 1]

[0292] [Table 2]

[0293] [Table 3]

[0294] [Table 4]

[0295] [Table 5]

[0296] [Table 6]

[0297] (2) Second aspect ≪Evaluation Method≫ <Resin composition> [Presence or absence of coating with styrene elastomer] The following conditions were used for evaluation using a scanning electron microscope (SEM). Multipurpose test specimens formed using an injection molding machine were trimmed to an appropriate size, and MD-ND cross-sectional samples were prepared using a cryomicrotome. These samples were then block-stained with osmium tetroxide and ruthenium tetroxide, and observed using SEM. Device: SU8200 (manufactured by Hitachi, Ltd.) Acceleration voltage: 1.5kV Detector: LA-BSE (compositional image) For example, Figure 1 is a scanning electron microscope (SEM) image of a cross-section of the resin composition obtained in Example 2-1, in which polypropylene (1), cellulose nanofibers (2), styrene elastomer (3), and liquid rubber (4) were observed. In the obtained image, the dispersed phase was defined as styrene elastomer or liquid rubber, the continuous phase as polypropylene resin, and the fibrous material was defined as cellulose nanofiber, and the following observations were made. Twenty images were taken at a magnification of 50,000x in an arbitrary field of view. For each of 30 cellulose nanofibers randomly selected from the image, cellulose nanofibers that were in contact with the polymer at a rate of 30% or more were determined to be cellulose nanofibers coated with styrene elastomer. If 15 or more of the 30 cellulose nanofibers were determined to be coated with styrene elastomer, it was determined that the polymer was coating the cellulose nanofibers in the resin composition, and the following evaluation was performed. A: Styrene elastomer is coating cellulose nanofibers. B: The styrene elastomer does not coat the cellulose nanofibers. -: Not evaluated because it does not contain cellulose nanofibers or styrene-based elastomers.

[0298] [Flexural modulus] Multipurpose test specimens conforming to ISO 294-3 were molded from resin composition pellets using an injection molding machine under conditions conforming to JIS K6921-2. The injection molding temperature was 200°C. The flexural modulus was measured in accordance with JIS K7171.

[0299] [Coefficient of linear expansion] The coefficient of linear thermal expansion was measured in accordance with ISO 11359-2, using a precision saw to cut a rectangular sample measuring 4 mm in length, 4 mm in width, and 10 mm in length from the center of a multipurpose test specimen, within the measurement temperature range of -10°C to 80°C, and values ​​between 0°C and 60°C were calculated.

[0300] [Charpy impact strength] Charpy impact strength was measured using a multi-purpose test specimen in accordance with JIS K7111.

[0301] [Evaluation of coarse aggregates] The number of aggregates visible to the naked eye was measured in a 1 cm square area in the center of the multipurpose test specimen and evaluated according to the following criteria. A: There are no visible aggregates. B: 1 to 5 aggregates visible to the naked eye C: Six or more aggregates visible to the naked eye

[0302] ≪Materials used≫ <Polypropylene resin> Polypropylene homopolymer (MA04A) (same as in the first embodiment)

[0303] <Styrene-based elastomer> SEBS H1062 (same as the first aspect)

[0304] <Liquid rubber> Butadiene-styrene random copolymer (RICON 184) (same as the first embodiment)

[0305] <Cellulose nanofiber> CNF-1: Unmodified cellulose fiber, and CNF-3: Acetylated cellulose fiber (same as the first embodiment)

[0306] <Nonionic surfactant> Surfactant: Sorbitan monooleate (Leodol SP-O10V, available from Kao Corporation)

[0307] <Production of CNF dry body> To the CNF concentrated cake (solid content mass 20%), surfactant and liquid rubber were added in amounts corresponding to the parts by mass shown in Table 7 per 100 parts by mass of the fine cellulose fiber solid content, and they were thoroughly stirred with an industrial mixer (Kenmix Eye Cook Chef PRO) manufactured by Aikosha Co., Ltd. to obtain a concentrated cake containing a dispersant. Using these as raw materials, they were charged into a drying device, and drying was carried out at a predetermined shear rate, degree of vacuum, and heating temperature (jacket temperature or hot air temperature). The moisture content was measured using an infrared heating type moisture meter (MX-50 (manufactured by A&D)), and the time when the moisture content became 7% by mass or less (solid content mass 93% or more) was taken as the end point of drying. The conditions were as follows. Device: High-speed vacuum dryer (model number: FS10) manufactured by Earth Technica Co., Ltd. Conditions: While stirring with a jacket temperature of 80°C, an agitator (peripheral speed 2 m / s), and a chopper (3,500 rpm), the pressure was reduced to -70 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 70°C to obtain a CNF dry body.

[0308] ≪Preparation of resin composition≫ <Examples 2-1 to 2-4, Comparative Examples 2-3, 2-4> Using a twin-screw extruder, the CNF dry material was melt-kneaded with SEBS elastomer at 200°C in the proportions listed in Table 7 to obtain a masterbatch. Subsequently, using the twin-screw extruder again, the masterbatch was melt-kneaded with polypropylene at 200°C in the proportions listed in Table 7 to obtain resin pellets. Multipurpose test specimens were prepared from the obtained resin pellets using an injection molding machine, and various physical properties were evaluated.

[0309] <Example 2-5> Using a twin-screw extruder, CNF dry material, SEBS elastomer, and polypropylene were melt-kneaded at 200°C in the proportions listed in Table 7 to obtain resin pellets. Multipurpose test specimens were prepared from the obtained resin pellets using an injection molding machine, and various physical properties were evaluated.

[0310] <Comparative Example 2-1> Using a twin-screw extruder, SEBS elastomer and polypropylene were melt-kneaded at 200°C in the proportions listed in Table 7 to obtain resin pellets. Multipurpose test specimens were prepared from the obtained resin pellets using an injection molding machine, and various physical properties were evaluated.

[0311] <Comparative Example 2-2> Using a twin-screw extruder, CNF dry material and polypropylene were melt-kneaded at 200°C in the proportions listed in Table 7 to obtain resin pellets. Multipurpose test specimens were prepared from the obtained resin pellets using an injection molding machine, and various physical properties were evaluated.

[0312] The results are shown in Table 7.

[0313] [Table 7] [Industrial applicability]

[0314] The resin composition relating to this disclosure can form molded articles with good physical properties and can therefore be suitably applied to a wide range of applications, such as industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing components, containers and packaging components, etc.

Claims

1. A resin composition comprising a polypropylene resin, a styrene elastomer, and cellulose nanofibers, In the resin composition, the polypropylene resin forms a continuous phase. A dispersed phase is formed in the continuous phase, comprising the cellulose nanofibers and a polymer coating the cellulose nanofibers. The polymer is a resin composition containing the styrene-based elastomer.

2. The polypropylene resin in an amount of 50% to 89.5% by mass, The styrene-based elastomer in an amount of 10% to 40% by mass, and The cellulose nanofibers, 0.5% to 30% by mass, The resin composition according to claim 1, comprising:

3. The resin composition according to claim 1, wherein the content of styrene-based elastomer is 35% by mass or more of the total 100% by mass of styrene-based elastomer and cellulose nanofiber contained in the resin composition.

4. The resin composition according to claim 1, wherein the polypropylene resin is a propylene homopolymer.

5. The resin composition according to claim 1, wherein the cellulose nanofibers are chemically modified cellulose nanofibers.

6. The resin composition according to claim 5, wherein the chemically modified cellulose nanofiber is acetylated cellulose nanofiber.

7. The resin composition according to claim 1, wherein the resin composition further comprises liquid rubber as the polymer constituting the dispersed phase.

8. The resin composition according to claim 1, further comprising a surfactant.

9. A method for producing a resin composition according to any one of claims 1 to 8, A method comprising a mixing step of mixing a polypropylene resin, a styrene elastomer, and cellulose nanofibers.

10. The mixing step is A process for obtaining an elastomer masterbatch containing a styrene-based elastomer and cellulose nanofibers, and A step of kneading the elastomer masterbatch with the polypropylene resin, The method according to claim 9, including the method described in claim 9.

11. Automotive exterior panel comprising the resin composition according to any one of claims 1 to 8.

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