Resin composition, resin molded article, automotive part, and method for producing resin composition

Abstract

To provide a resin composition capable of forming a resin molded article having high impact strength, and a resin molded article having high impact strength.SOLUTION: The method according to claim 1, wherein the cellulose fibers have an acid number of 60mgKOH / g or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Cellulose fibers are known to have a high modulus of elasticity comparable to that of aramid fibers and a linear expansion coefficient lower than that of glass fibers. Furthermore, cellulose fibers have a low true density and are extremely light compared to glass fibers and other materials commonly used as fillers. Cellulose fibers are abundantly available on Earth as a natural resource, and their use is expected from the perspective of carbon neutrality.

[0003] In view of the above circumstances, the use of cellulose fibers has been investigated, and one example of such a method is to incorporate cellulose fibers into a resin to increase the mechanical strength of a resin molded product. For example, Patent Document 1 discloses a resin composition containing cellulose fibers, a resin, and an alkali metal-containing compound. The resin molded product described in Patent Document 1 is said to have improved tensile strength and tensile modulus. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-066789 Summary of the Invention [Problem to be solved by the invention]

[0005] There are situations where impact resistance is required for resin molded articles. One example of an impact-resistant molded article is expected to be used in automobile bumpers. Therefore, an object of the present disclosure is to provide a resin composition capable of forming a resin molded article having high impact strength, and a resin molded article having high impact strength.

[0006] The present disclosure includes the following aspects. <1> A resin composition comprising cellulose fibers, a resin, and an additive having an acid value of 60 mgKOH / g or more. <2> The additive has a hydrophilic group and a hydrophobic group. <1> The resin composition according to claim 1. <3> The hydrophobic group includes an α-olefin moiety. <2> The resin composition according to claim 1. <4> the hydrophilic group includes at least one selected from the group consisting of a hydroxyl group, a carboxylic acid group, and a carboxylic acid anhydride group; <2> or <3> The resin composition according to claim 1. <5> The content of the additive is 0.1% by mass to 20% by mass. <1> ~ <4> The resin composition according to any one of the above. <6> The average fiber length of the cellulose fibers is 1.5 mm or more. <1> ~ <5> The resin composition according to any one of the above. <7> The average fiber diameter of the cellulose fibers is 100 μm or less. <1> ~ <6> The resin composition according to any one of the above. <8> The cellulose fibers include viscose rayon. <1> ~ <7> The resin composition according to any one of the above. <9> The resin includes a thermoplastic resin. <1> ~ <8> The resin composition according to any one of the above. <10> The thermoplastic resin includes polypropylene. <9> The resin composition according to claim 1. <11> A resin composition comprising cellulose fibers having an average fiber length of 3 mm or more and a resin. <12> <1> ~ <11> A resin molded article formed from the resin composition according to any one of claims 1 to 4. <13> <12> An automobile part comprising the resin molded article according to claim 1. <14> A step of preparing a masterbatch by mixing a resin and an additive having an acid value of 60 mgKOH / g or more; mixing the masterbatch with cellulose fibers; Including, <1> ~ <11> 10. A method for producing the resin composition according to claim 9. <15> cellulose fibers, a high acid value additive, and a resin are mixed together; <1> ~ <11> 10. A method for producing the resin composition according to claim 9. [Effects of the Invention]

[0007] According to the present disclosure, a resin composition capable of forming a resin molded article having high impact strength, and a resin molded article having high impact strength are provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are scanning electron microscope (SEM) images of fracture surfaces of test pieces for Izod impact strength. (A) is an SEM image of Comparative Example 1, and (B) is an SEM image of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple substances corresponding to the component. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.

[0010] <Resin composition> The resin composition of the present disclosure includes cellulose fibers, a resin, and an additive having an acid value of 60 mgKOH / g or more. Hereinafter, the "additive having an acid value of 60 mgKOH / g or more" is also referred to as a high acid value additive. The resin composition of the present disclosure may contain other additives as needed. The main components constituting the resin composition of the present disclosure will be described below.

[0011] [Cellulose fiber] The cellulose fibers may be obtained from various cellulose fiber sources selected from the group consisting of natural cellulose and regenerated cellulose. Examples of natural cellulose that can be used include wood pulp obtained from wood species (broadleaf trees or conifers), 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, microorganisms (e.g., acetic acid bacteria), etc. Examples of regenerated cellulose that can be used include regenerated cellulose fibers (viscose rayon, cupra, Tencel, Lyocell, etc.), cellulose derivative fibers, and ultrafine threads of regenerated cellulose or cellulose derivatives obtained by electrospinning.

[0012] The cellulose fiber is preferably a regenerated cellulose fiber, more preferably viscose rayon or lyocell, and even more preferably viscose rayon. Viscose rayon is a fiber regenerated using the viscose method. Compared to other regenerated cellulose fibers, it is less susceptible to fiber breakage due to shear stress generated during kneading and molding. When fibers with a fiber length of 3 mm or more are used, the proportion of short fibers with a fiber length of 1 mm or less in the resin molded product is low, and the resin molded product tends to have excellent impact resistance.

[0013] If necessary, the cellulose fiber raw material may be mechanically beaten, fibrillated, refined, or the like using a grinder, refiner, or the like to adjust the fiber diameter, fiber length, degree of fibrillation, etc., or may be bleached or purified using chemicals to adjust the content of components other than cellulose (acid-insoluble components such as lignin, alkali-soluble polysaccharides such as hemicellulose, etc.). In one embodiment, the cellulosic fiber feedstock may be chemically modified.

[0014] The average fiber length of the cellulose fibers is preferably 1.5 mm or more, more preferably 2 mm or more, even more preferably 3 mm or more, and particularly preferably 4 mm or more. When the average fiber length of the cellulose fibers is equal to or greater than the above lower limit, they tend to effectively contribute to the impact resistance of the resin molded product. The average fiber length of the cellulose fibers is preferably 20 mm or less, more preferably 15 mm or less, and even more preferably 10 mm or less. When the average fiber diameter of the cellulose fibers is equal to or less than the above upper limit, the resin molded article tends to have excellent impact resistance. This is presumably because, when an impact is applied to the resin molded article, the cellulose fibers tend to be pulled out, resulting in an increase in the amount of energy.

[0015] The resin composition of the present disclosure may contain cellulose fibers having an average fiber length of 3 mm or more and a resin. The use of cellulose fibers having an average fiber length of 3 mm or more provides a good balance between the effective contribution to impact resistance of a resin molded product and the amount of energy required for pulling out when an impact is applied, which tends to result in excellent impact resistance.

[0016] The average fiber diameter of the cellulose fibers is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less. When the average fiber diameter of the cellulose fibers is equal to or less than the above upper limit, the fiber diameter tends to be not too large and to effectively contribute to impact resistance. The average fiber diameter of the cellulose fibers is preferably 10 nm or more, more preferably 100 nm or more, and even more preferably 1 μm or more. When the average fiber diameter of the cellulose fibers is equal to or greater than the above lower limit, the crystallinity of the cellulose is well maintained, and the mechanical strength tends to be excellent.

[0017] In this disclosure, the fiber length and fiber diameter of cellulose fibers are observed using a high-resolution scanning electron microscope (SEM). Measurement samples can be prepared by dissolving only the resin component of a resin molded product containing cellulose fibers in high-temperature xylene and extracting only the fibers.

[0018] In order to obtain a good effect of improving impact resistance, the content of cellulose fibers in the resin composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 10% by mass or more. In addition, the content of cellulose fibers in the resin composition is preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of achieving a balance with other physical properties when made into a resin molded body.

[0019] 〔resin〕 Examples of the resin include thermoplastic resin, thermosetting resin, photocurable resin, elastomer (rubber), etc., and it is preferable to include a thermoplastic resin.

[0020] Specific examples of thermoplastic resins include, but are not limited to, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; polyamide resins such as nylon 6.6 and nylon 6.10; vinyl chloride resins such as polyvinyl chloride and polyvinylidene chloride; vinyl resins such as polyvinyl acetate, ethylene-vinyl acetate copolymer, and polyvinyl alcohol; polyacetal resins; fluororesins such as polyvinylidene fluoride; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene resins such as polystyrene, styrene-butadiene block copolymer, and styrene-isoprene block copolymer; polyacrylonitrile, styrene-acrylonitrile copolymer, and nitrile resins; polyphenylene ether resins; polyamides; polyurethanes; polyimides; polyamideimides; acrylic resins such as polymethacrylic acid and polyacrylic acid; polycarbonates; polyphenylene sulfide; polysulfones; polyethersulfones; polyethernitriles; polyetherketones; polyketones; liquid crystal polymers; silicone resins; and ionomers. The thermoplastic resin may be used alone or in combination of two or more kinds.

[0021] Specific examples of thermosetting resins are not particularly limited, and include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, and bisphenol Z type epoxy resin; novolac type epoxy resins such as bisphenol A novolac type epoxy resin, phenol novolac type epoxy resin, and cresol novolac epoxy resin; biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, aryl alkylene type epoxy resin, tetraphenylol ethane type epoxy resin, naphthalene type epoxy resin, and anthracene type epoxy resin. Epoxy resins, phenoxy-type epoxy resins, dicyclopentadiene-type epoxy resins, norbornene-type epoxy resins, adamantane-type epoxy resins, fluorene-type epoxy resins, glycidyl methacrylate copolymer epoxy resins, cyclohexylmaleimide and glycidyl methacrylate copolymer epoxy resins, epoxy-modified polybutadiene rubber derivatives, CTBN-modified epoxy resins, trimethylolpropane polyglycidyl ether, phenyl-1,3-diglycidyl ether, biphenyl-4,4'-diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol or propylene glycol diglycidyl ether, sorbitol polyglycidyl ether, tris(2,Examples of suitable phenolic resins include phenolic resins such as 3-epoxypropyl)isocyanurate, triglycidyl tris(2-hydroxyethyl)isocyanurate, novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin; unmodified resol phenolic resins; and resol-type phenolic resins such as oil-modified resol phenolic resins modified with tung oil, linseed oil, and walnut oil; triazine ring-containing resins such as phenoxy resin, urea resin, and melamine resin; unsaturated polyester resin, bismaleimide resin, diallyl phthalate resin, silicone resin, resins having a benzoxazine ring, norbornene resin, cyanate resin, isocyanate resin, urethane resin, benzocyclobutene resin, maleimide resin, bismaleimide triazine resin, polyazomethine resin, and thermosetting polyimide. The thermosetting resin may be used alone or in combination of two or more kinds.

[0022] Specific examples of photocurable resins include, but are not limited to, well-known general (meth)acrylate resins, vinyl resins, epoxy resins, etc. These are generally classified according to the reaction mechanism into radical reaction types in which monomers react with radicals generated by light, and cationic reaction types in which monomers undergo cationic polymerization. Radical reaction type monomers include (meth)acrylate compounds and vinyl compounds (e.g., certain vinyl ethers). Cationic reaction types include epoxy compounds and certain vinyl ethers. For example, epoxy compounds that can be used as cationic reaction types can be monomers for both thermosetting resins and photocurable resins. The photocurable resin may be used alone or in combination of two or more kinds.

[0023] Specific examples of elastomers (rubber) include, but are not limited to, natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), acrylonitrile-styrene-butadiene copolymer rubber (ABS), chloroprene rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, chlorosulfonated polyethylene rubber, modified natural rubber (epoxidized natural rubber (ENR), hydrogenated natural rubber, deproteinized natural rubber, etc.), ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, etc. The elastomer (rubber) may be used alone or in combination of two or more kinds.

[0024] Among the above resins, polyolefin resins, polyamide resins, polycarbonate, and ABS are preferred, and from the viewpoints of handleability and cost, polyolefin resins and ABS are more preferred, and polyolefin resins are even more preferred.

[0025] The polyolefin resin preferred as the thermoplastic resin is a polymer obtained by polymerizing olefins (e.g., α-olefins) or further alkenes as monomer units. Specific examples of the polyolefin resin include ethylene (co)polymers such as low-density polyethylene (e.g., linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, and ultra-high-molecular-weight polyethylene, polypropylene (co)polymers such as polypropylene, ethylene-propylene copolymer, and ethylene-propylene-diene copolymer, and ethylene-α-olefin copolymers such as ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-glycidyl methacrylate copolymer. Among these, polypropylene is particularly preferred as the polyolefin resin.

[0026] The content of the resin in the resin composition may be the balance of the cellulose fiber and the high acid value additive, as well as other additives.

[0027] [High acid value additives] High acid value additives are additives with an acid value of 60 mgKOH / g or more. They are thought to increase the affinity with cellulose fibers and contribute to improving impact resistance.

[0028] The acid value of the high acid value additive is preferably 65 mgKOH / g or more, more preferably 70 mgKOH / g or more, and even more preferably 75 mgKOH / g or more. The acid value of the high acid value additive is preferably 300 mgKOH / g or less, more preferably 200 or less, and even more preferably 100 or less. When the acid value of the high acid value additive is equal to or less than the above upper limit, the affinity with cellulose falls within a more appropriate range, and the impact resistance tends to be better.

[0029] The acid value is measured in accordance with JIS K0070:1992.

[0030] The high acid value additive preferably has a hydrophilic group and a hydrophobic group. The high acid value additive is amphiphilic, which tends to have affinity with both the cellulose fiber and the resin and improve impact resistance.

[0031] The hydrophobic group preferably contains a hydrocarbon group. The hydrophobic group may contain an oxygen atom, but preferably does not contain an oxygen atom.

[0032] The hydrophobic group preferably contains an α-olefin moiety. The α-olefin moiety is a moiety derived from an α-olefin. In particular, when the resin contains a polyolefin-based resin, the hydrophobic group containing an α-olefin moiety has excellent affinity with the resin. The hydrophobic group may contain an aromatic ring, but when the hydrophobic group contains an aromatic ring, the resin preferably contains an aromatic ring.

[0033] The hydrophilic group preferably contains at least one selected from the group consisting of a hydroxyl group, a carboxylic acid group, and a carboxylic acid anhydride group, more preferably contains a carboxylic acid anhydride group, and even more preferably contains a structure derived from maleic anhydride.

[0034] The ratio of the hydrophobic group to the hydrophilic group may be adjusted so that the acid value of the high acid value additive falls within the above range.

[0035] A preferred example of the high acid value additive is a copolymer represented by the following general formula (1).

[0036] [ka]

[0037] In the general formula (1), R represents a hydrocarbon group, and n represents an integer of 1 or more.

[0038] In the resin composition, the content of the high acid value additive is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more. In addition, the content of the high acid value additive in the resin composition is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, taking into account physical property values ​​other than impact resistance.

[0039] [Other ingredients] The resin composition of the present disclosure may further contain other components as needed to improve its performance. Examples of such other components include, but are not limited to, dispersants, fibers other than cellulose fibers (e.g., fibrillated or fine aramid fibers), compatibilizers, plasticizers, polysaccharides such as starches and alginic acid, natural proteins such as gelatin, glue, and casein, inorganic compounds such as zeolites, ceramics, talc, silica, metal oxides, and metal powders, colorants, fragrances, pigments, flow control agents, leveling agents, conductive agents, antistatic agents, UV absorbers, UV dispersants, and deodorizers. When the resin composition contains other components, the content of the other components in the resin composition is appropriately selected within a range that does not impair the desired effects of the present invention, and may be, for example, 0.01 to 50 mass %, or 0.1 to 30 mass %.

[0040] <Method of manufacturing resin composition> The method for producing the resin composition of the present disclosure is not particularly limited. For example, the resin composition may be produced by mixing cellulose fibers and a high acid value additive to prepare a masterbatch (first step), and mixing the masterbatch with a resin (second step). In this embodiment, the cellulose fibers and the high acid value additive may each be added in their entirety in the first step, or a portion thereof may be added in the first step and the remainder in the second step, and the resin may each be added in their entirety in the second step, or a portion thereof may be added in the first step and the remainder in the second step.

[0041] In another embodiment, for example, the resin composition may be produced by including a step (first step) of mixing a resin and a high acid value additive to prepare a masterbatch, and a step (second step) of mixing the masterbatch with cellulose fibers. In this embodiment, the resin and the high acid value additive may each be added in their entirety in the first step, or a portion thereof may be added in the first step and the remainder in the second step, and the cellulose fibers may each be added in their entirety in the second step, or a portion thereof may be added in the first step and the remainder in the second step.

[0042] In yet another embodiment, the resin composition may be produced by mixing the cellulose fibers, the high acid value additive, and the resin all at once. In this embodiment, the cellulose fibers, the high acid value additive, and the resin may all be mixed at once, or a portion of them may be mixed and the remainder may be added separately at any timing.

[0043] The cellulose fibers may be mixed with the high acid value additive and resin as a dry powder or in the form of a dispersion (slurry) containing water.

[0044] The shape of the resin composition of the present disclosure is not particularly limited, and may be any of resin pellets, sheets, fibers, plates, rods, and the like.

[0045] <Resin molded body> The resin molded article of the present disclosure is formed from the resin composition of the present disclosure. The shape of the resin molded body may be a three-dimensional shape, or may be a sheet, film, or fiber shape. For example, a portion (e.g., several locations) of the resin molded body may be melted by heat treatment and then bonded to, for example, a resin or metal substrate. The resin molded body may be a coating film applied to a resin or metal substrate, or may form a laminate with the substrate. Furthermore, the sheet-, film-, or fiber-shaped resin molded body may be subjected to secondary processing such as annealing, etching, corona treatment, plasma treatment, embossing, cutting, and surface polishing.

[0046] The Izod impact strength of the resin molded body is 15kJ / m 2 It is preferable that the concentration is 20 kJ / m or more. 2 a or more, and 25 kJ / m 2 It is more preferable that the upper limit of the Izod impact strength of the resin molded product is not particularly limited.

[0047] The Izod impact strength is measured at 23°C using a notched test piece in accordance with JIS K7110:1999.

[0048] The tensile modulus of elasticity of the resin molded product is preferably 2000 MPa or more, more preferably 2500 MPa or more, and even more preferably 3000 MPa or more. There is no particular upper limit to the tensile modulus of elasticity of the resin molded product.

[0049] The tensile modulus is measured in accordance with JIS K7161:2014 at a tension speed of 5.0 mm / min.

[0050] The flexural modulus of the resin molded product is preferably 2000 MPa or more, more preferably 2500 MPa or more, and even more preferably 3000 MPa or more. There is no particular upper limit to the flexural modulus of the resin molded product.

[0051] The flexural modulus is measured using a three-point bending tester in accordance with JIS K7171: 2016. The measurement conditions are a support distance of 64 mm and a test speed of 2.0 mm / min.

[0052] The resin composition of the present disclosure is highly heat resistant and lightweight, and therefore can be used as a substitute for steel plates, fiber-reinforced plastics such as carbon fiber-reinforced plastics and glass fiber-reinforced plastics, resin composites containing inorganic fillers, and the like. For example, they can be used for industrial machinery parts (e.g., electromagnetic equipment housings, roll materials, transport arms, medical equipment components, etc.), general machinery parts, automobile, railway, and vehicle parts (e.g., outer panels, bumpers, chassis, aerodynamic components, seats, friction materials inside transmissions, etc.), ship components (e.g., hulls, seats, etc.), aviation-related parts (e.g., fuselages, main wings, tails, moving surfaces, fairings, cowls, doors, seats, interior materials, etc.), spacecraft and artificial satellite components (motor cases, main wings, structures, antennas, etc.), electronic and electrical components (e.g., personal computer housings, mobile phone housings, office equipment, audiovisual equipment, telephones, facsimiles, home appliances, toys, etc.), construction and civil engineering materials (e.g., rebar substitutes, truss structures, cables for suspension bridges, etc.), daily necessities, sports and leisure goods (e.g., golf club shafts, fishing rods, tennis or badminton rackets, etc.), wind power generation housing components, and container and packaging materials. A suitable example is automobile parts, and from the viewpoint of excellent impact resistance, it can be suitably used for impact-resistant parts such as bumpers. [Example]

[0053] The present disclosure will be specifically described below using examples, but the scope of the present disclosure is not limited to these examples.

[0054] (Preparation of Resin Composition) A resin composition was obtained by blending 30% by mass of viscose rayon (average fiber diameter 10 μm, average fiber length 4 mm) as a cellulose resin, 68% by mass of a polypropylene resin as a resin, and 2% by mass of the components shown below as additives in a single-screw mixer at a mixing temperature of 190°C and a screw rotation speed of 100 rpm.

[0055] Comparative Example 1: No additives Comparative Example 2: Maleic anhydride modified polypropylene, acid value 26 mg KOH / g Comparative Example 3: Maleic anhydride modified polypropylene, acid value 52 mg KOH / g Example 1: α-olefin maleic anhydride copolymer, acid value 79 mg KOH / g Example 2: Styrene maleic anhydride copolymer, acid value 188 mg KOH / g

[0056] (Measurement of tensile modulus) Test specimens were prepared by injection molding based on JIS K7161:2014. The tensile modulus was measured using an AGX-50kNV manufactured by Shimadzu Corporation at a head speed of 5.0 mm / min, a gauge length of 50 mm, and a grip distance of 115 mm.

[0057] (Measurement of flexural modulus) Test specimens were prepared by injection molding in accordance with JIS K7171:2016, and the flexural modulus was determined by three-point bending measurement using a Shimadzu AGX-50kNV golf club head at a head speed of 2.0 mm / min and a support distance of 64 mm.

[0058] (Measurement of Izod impact strength) The resulting resin composition was injection molded to prepare a test piece for Izod impact strength. The Izod impact strength was measured using a DG-IB manufactured by Toyo Seiki Seisakusho Co., Ltd., with a hammer swing angle of 150° and a hammer force of 2.75 J.

[0059] [Table 1]

[0060] As shown in Table 1, Examples 1 and 2, which contain cellulose fibers, resin, and an additive with an acid value of 60 mgKOH / g or more, have higher Izod impact strength than Comparative Example 1, which does not contain any additive. It is also apparent that Examples 1 and 2 have higher Izod impact strength than Comparative Examples 2 and 3, which contain additives with acid values ​​of less than 60 mgKOH / g. In particular, Example 1 had an Izod impact strength that was about twice as high as those of Comparative Examples 1 to 3. It is also apparent that, compared with Comparative Examples 1 to 3, Examples 1 and 2 maintain the same level of tensile modulus and flexural modulus.

[0061] Scanning electron microscope (SEM) images of the fracture surfaces of the test pieces for Izod impact strength are shown in Figure 1. Figure 1(A) is an SEM image of Comparative Example 1, and (B) is an SEM image of Example 1. In Figure 1(A) of Comparative Example 1, where no additive was added, it is clear that the cellulose fibers are broken. In contrast, in Figure 1(B) of Example 1, where a high acid value additive was added, there is little breakage of the cellulose fibers, and it is clear that the cellulose fibers are being pulled out. In Example 1, it is presumed that the cellulose fibers are predominantly pulled out at the time of breakage, which increases the amount of energy involved, thereby improving impact resistance.

Claims

1. A resin composition comprising cellulose fibers, a resin, and an additive having an acid value of 60 mgKOH / g or more.

2. The resin composition according to claim 1 , wherein the additive has a hydrophilic group and a hydrophobic group.

3. The resin composition according to claim 2, wherein the hydrophobic group includes an α-olefin moiety.

4. The resin composition according to claim 2 , wherein the hydrophilic group comprises at least one selected from the group consisting of a hydroxyl group, a carboxylic acid group, and a carboxylic acid anhydride group.

5. The resin composition according to claim 1, wherein the content of the additive is 0.1% by mass to 20% by mass.

6. The resin composition according to claim 1, wherein the cellulose fibers have an average fiber length of 1.5 mm or more.

7. The resin composition according to claim 1, wherein the cellulose fibers have an average fiber diameter of 100 μm or less.

8. The resin composition of claim 1 , wherein the cellulose fibers comprise viscose rayon.

9. The resin composition according to claim 1 , wherein the resin comprises a thermoplastic resin.

10. The resin composition according to claim 9 , wherein the thermoplastic resin comprises polypropylene.

11. A resin composition comprising cellulose fibers having an average fiber length of 3 mm or more and a resin.

12. A resin molded product formed from the resin composition according to any one of claims 1 to 11.

13. An automobile part formed from the resin molded article according to claim 12.

14. a step of preparing a masterbatch by mixing a resin and an additive having an acid value of 60 mgKOH / g or more; mixing the masterbatch with cellulose fibers; A method for producing the resin composition according to any one of claims 1 to 11, comprising:

15. The method for producing the resin composition according to any one of claims 1 to 11, wherein the cellulose fibers, the high acid value additive, and the resin are mixed together.

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