Cellulose fiber composite material

Abstract

The purpose of the present invention is to provide a cellulose fiber composite material with which it is possible to produce a molded body that has excellent mechanical properties. One embodiment of the present invention is a cellulose fiber composite material containing cellulose fibers, an acid-modified polypropylene, and an acid-modified olefinic elastomer. The cellulose fiber composite material has a cellulose fiber content of 5.0-60.0 mass%, an acid-modified polypropylene content of 15.0-90.0 mass%, and an acid-modified olefinic elastomer content of 1.0-30.0 mass%.

Description

Cellulose fiber composite

[0001] The present invention relates to a cellulose fiber composite.

[0002] Polypropylene is known as a resin component suitable for producing molded articles with excellent functionality. To improve the performance of such resin components, cellulose fibers and other materials are sometimes used in combination.

[0003] For example, Patent Document 1 discloses a polypropylene composition for producing molded articles, which contains (A) polypropylene, (B) a rubber-containing polymer, and (C) a compatibilizer, and further contains 5 to 45 parts by mass of (D) cellulose fibers per 100 parts by mass of the total amount of components (A) to (C), wherein the (D) cellulose fibers have an α-cellulose content of 80% by mass or more, an average fiber length of 1 to 100 μm, and an average fiber diameter of 1 to 50 μm. It is claimed that use of such a polypropylene composition for producing molded articles results in molded articles that are excellent in rigidity, elongation, colorability, etc., and have little odor.

[0004] JP 2011-231237 A

[0005] The technology disclosed in Patent Document 1 requires the use of cellulose fibers containing 80% by mass or more of highly crystalline α-cellulose, and the cellulose fibers function as a crystal nucleating agent, which increases the crystallinity of the resin and can reduce impact strength. Thus, with the conventional technology, it has been difficult to obtain a cellulose fiber composite material that can be used to produce a molded product with a good balance of various mechanical properties (e.g., high rigidity, elongation, impact strength, etc.).

[0006] Therefore, an object of the present invention is to provide a cellulose fiber composite material that can be used to produce a molded article with excellent mechanical properties.

[0007] The present inventors have conducted extensive research and found that the above-mentioned problems can be solved by using a cellulose fiber composite material containing a predetermined component, and have thus completed the present invention.

[0008] One aspect of the present invention is a cellulose fiber composite material containing cellulose fibers, an acid-modified polypropylene, and an acid-modified olefin-based elastomer, wherein the cellulose fiber content is 5.0 to 60.0% by mass, the acid-modified polypropylene content is 15.0 to 90.0% by mass, and the acid-modified olefin-based elastomer content is 1.0 to 30.0% by mass relative to the cellulose fiber composite material.

[0009] It is preferable that the acid-modified polypropylene is a carboxylic acid anhydride-modified polypropylene, and the acid-modified olefin-based elastomer is a carboxylic acid anhydride-modified olefin-based elastomer. It is preferable that the acid-modified olefin-based elastomer is at least one selected from acid-modified ethylene-propylene rubber, acid-modified ethylene-propylene-non-conjugated diene rubber, acid-modified ethylene-1-butene rubber, acid-modified ethylene-1-butene-non-conjugated diene rubber, and acid-modified ethylene-1-octene rubber. It is preferable that the average fiber length of the cellulose fibers is 100 to 300 μm. It is preferable that the standard deviation of the cellulose area ratio measured under the following measurement conditions is 15% or less. (Measurement conditions) In a cross section of the cellulose fiber composite, ５ μm ２ The area of ​​the cellulose fibers in this range is defined as the cellulose area ratio. The cellulose area ratios are calculated for 10 arbitrary cross sections of the cellulose fiber composite, and the standard deviation is calculated to define the cellulose area ratio standard deviation. It is preferred that the cellulose fiber composite is a particle having a major axis and a minor axis, and that the cellulose fibers are oriented in the major axis direction of the cellulose fiber composite. It is preferred that the average diameter of the region formed by the acid-modified olefin elastomer in the cross section of the cellulose fiber composite is 0.7 to 1.2 μm, and that the standard deviation of the diameters of the region is 1.0 μm or less.

[0010] According to the present invention, a cellulose fiber composite material is provided that can be used to produce a molded article having excellent mechanical properties.

[0011] FIG. 1 shows an SEM photograph of a cross section of the cellulose fiber composite particle according to Example 1, which is perpendicular to the orientation direction (long axis direction) of the fibers.

[0012] Hereinafter, when an upper limit value and a lower limit value are separately described, it is considered that a numerical range combining any upper limit value and any lower limit value is substantially disclosed.

[0013] In the following, unless otherwise specified, various measurements are carried out at room temperature (23° C.).

[0014] The components, structure / physical properties / shape, production method, uses, etc. of the cellulose fiber composite material according to the present disclosure will be described below, but the present invention is not limited to the following in any way.

[0015] <<<Components>>> The cellulose fiber composite preferably contains cellulose fibers, acid-modified polypropylene (acid-modified polypropylene), and acid-modified olefin-based elastomer (acid-modified olefin-based elastomer). The cellulose fiber composite may also contain other components. Each component will be described below.

[0016] <<Cellulose Fibers>> Examples of cellulose fibers include plant-derived cellulose fibers, animal-derived cellulose fibers such as those derived from acetic acid bacteria, regenerated fibers (fibers artificially produced by dissolving natural cellulose from trees or wood pulp in a solvent to form thin, long, continuous fibers), etc. The type of cellulose fiber is not particularly limited, and multiple types may be used in combination.

[0017] Pulp that can be used as a raw material for cellulose fibers may be either wood pulp or non-wood pulp, and may be either mechanical pulp or chemical pulp.

[0018] Examples of wood pulp include MP, CP, GP, RGP, CGP, SP, AP, KP, and SCP obtained from softwoods such as fir and pine, and hardwoods such as eucalyptus and poplar. The wood pulp may be unbleached or bleached.

[0019] Non-wood pulp includes natural fibers other than wood, such as cotton, straw, bamboo, esparto, bagasse, linter, kenaf, Manila hemp, flax, hemp, jute, gampi, etc. Other pulps include recycled paper pulp made from recycled paper and scraps.

[0020] The average fiber length of the cellulose fibers is preferably 10 μm or more, 50 μm or more, 100 μm or more, 120 μm or more, 150 μm or more, or 200 μm or more, and is preferably 500 μm or less, 400 μm or less, 350 μm or less, or 300 μm or less. By setting the average fiber length of the cellulose fibers within this range, the dispersibility of the cellulose fibers is improved, aggregation of the cellulose fibers is suppressed, and a composite material with excellent MFR is easily obtained. As a result, various mechanical properties of the obtained molded article can be improved.

[0021] The average fiber diameter of the cellulose fibers is preferably 1 to 50 μm. By setting the average fiber diameter of the cellulose fibers in this range, aggregation of the cellulose fibers is suppressed, and it is easy to obtain a composite material with an excellent MFR. As a result, various mechanical properties of the obtained molded article can be improved.

[0022] The average fiber length and average fiber diameter of the cellulose fibers are number average values ​​calculated by observing the cross section of a cellulose composite material using a scanning electron microscope, randomly selecting 50 cellulose fibers contained in the cross section, and observing them.

[0023] The cellulose fiber content in the cellulose fiber composite is preferably 5.0% by mass or more, 10.0% by mass or more, 15.0% by mass or more, 20.0% by mass or more, or 25.0% by mass or more, and is preferably 63.0% by mass or less, 60.0% by mass or less, or 55.0% by mass or less. By setting the cellulose fiber content within this range, the reinforcing effect derived from the cellulose fiber is fully exhibited, and it is easy to obtain a composite material with excellent MFR. As a result, various mechanical properties of the obtained molded article can be improved. In addition, the environmental impact is easily reduced.

[0024] <<Acid-Modified Polypropylene>> Acid-modified polypropylene is polypropylene that has been acid-modified.

[0025] In the present disclosure, acid modification may refer to graft polymerization of an acid-modified monomer onto the main chain of a polymer or the like, or acid modification of an end portion of a polymer or the like with an acid-modified monomer. Acid modification is carried out by reacting a polymer or the like with an acid-modified monomer in a molten state, solution state, slurry state, gas phase state, or the like. Examples of acid-modified monomers include unsaturated carboxylic acids or derivatives of unsaturated carboxylic acids. Examples of unsaturated carboxylic acids include maleic acid, fumaric acid, itaconic acid, and (meth)acrylic acid. Examples of derivatives of unsaturated carboxylic acids include acid anhydrides such as maleic anhydride and itaconic anhydride, and unsaturated carboxylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and monoalkyl maleates.

[0026] The polypropylene constituting the acid-modified polypropylene may be a conventionally known one. The polypropylene may be a homopolymer consisting of only propylene, or may be a block copolymer or random copolymer mainly consisting of propylene.

[0027] The acid-modified polypropylene is preferably a carboxylic acid anhydride-modified polypropylene, more preferably a maleic anhydride-modified polypropylene. The use of such a component can improve compatibility with other components. As a result, various mechanical properties of the resulting molded article can be improved.

[0028] The content of the acid-modified polypropylene in the cellulose fiber composite is preferably 15.0 mass% or more, 20.0 mass% or more, 25.0 mass% or more, or 30.0 mass% or more, and is preferably 90.0 mass% or less, 80.0 mass% or less, 70.0 mass% or less, or 60.0 mass% or less. By setting the content of the acid-modified polypropylene within this range, a molded product having an excellent balance of various mechanical properties can be easily obtained.

[0029] <<Acid-Modified Olefin Elastomer>> The acid-modified olefin elastomer is an olefin elastomer that has been acid-modified. The acid modification is as described above. The olefin elastomer is one in which a polyolefin resin component and a rubber component are dispersed together or crosslinked together, for example.

[0030] The olefin-based elastomer constituting the acid-modified olefin-based elastomer may be any conventionally known elastomer and is not particularly limited. Examples of the olefin-based elastomer include ethylene-based elastomers, propylene-based elastomers, and 1-butene-based elastomers. Examples of the olefin-based elastomer include those made from ethylene or propylene and an α-olefin having 3 or more carbon atoms as raw materials. Further, examples of the olefin-based elastomer include those made from non-conjugated dienes (e.g., 1,4-hexadiene, dicyclopentadiene, ethylidene norbornene, etc.) as raw materials. Specific examples of the olefin-based elastomer include ethylene-propylene rubber, ethylene-1-butene rubber, ethylene-propylene-1-butene rubber, ethylene-1-hexene rubber, ethylene-1-octene rubber, ethylene-norbornene rubber, propylene-1-butene rubber, ethylene-propylene-non-conjugated diene rubber, ethylene-1-butene-non-conjugated diene rubber, and ethylene-propylene-1-butene-non-conjugated diene rubber.

[0031] The acid-modified olefin elastomer is preferably at least one selected from acid-modified ethylene-propylene rubber, acid-modified ethylene-propylene-non-conjugated diene rubber, acid-modified ethylene-1-butene rubber, acid-modified ethylene-1-butene-non-conjugated diene rubber, and acid-modified ethylene-1-octene rubber. The use of such an acid-modified olefin elastomer not only provides excellent compatibility with other components (e.g., acid-modified polypropylene) but also excellent reactivity with dispersants, compatibilizers, and the like. As a result, various mechanical properties of the resulting molded article can be improved.

[0032] The acid-modified olefinic elastomer is preferably a carboxylic acid anhydride-modified olefinic elastomer, and more preferably a maleic anhydride-modified olefinic elastomer. The use of such a component can improve compatibility with other components. As a result, various mechanical properties of the resulting molded article can be improved. In particular, this effect can be easily achieved by combining a carboxylic acid anhydride-modified olefinic elastomer with a carboxylic acid anhydride-modified polypropylene.

[0033] The content of the acid-modified olefin-based elastomer in the cellulose fiber composite is preferably 1.0 mass% or more, 3.0 mass% or more, 5.0 mass% or more, or 10.0 mass% or more, and is preferably 30.0 mass% or less, 25.0 mass% or less, or 20.0 mass% or less. By setting the content of the acid-modified olefin-based elastomer within this range, a molded product excellent in impact strength, tensile properties, flexural strength, elastic modulus, etc. can be easily obtained.

[0034] In the cellulose fiber composite, the ratio [(cellulose fiber content) / (acid-modified olefin elastomer content)] is preferably 0.5 or more, 1.0 or more, 1.5 or more, or 2.0 or more, and is preferably 10.0 or less, 8.0 or less, 6.0 or less, or 4.0 or less.

[0035] In the cellulose fiber composite, the ratio [(content of acid-modified polypropylene) / (content of acid-modified olefin-based elastomer)] is preferably 1.0 or more, 1.5 or more, 2.0 or more, or 2.5 or more, and is preferably 15.0 or less, 10.0 or less, 8.0 or less, 6.0 or less, or 4.0 or less.

[0036] In the cellulose fiber composite, the ratio [(acid-modified polypropylene content) / (cellulose fiber content)] is preferably 0.1 or more, 0.2 or more, 0.5 or more, or 1.0 or more, and is preferably 5.0 or less, 4.0 or less, 3.0 or less, or 2.0 or less.

[0037] By setting the ratio of the blending amounts of each component within this range, the various mechanical properties of the resulting molded article can be improved in a balanced manner.

[0038] <<Other Components>> Examples of other components include known additives, such as flame retardants, release agents, flow modifiers, antistatic agents, compatibilizers, UV absorbers, fillers, surfactants, coupling agents, colorants, antioxidants, antifoaming agents, leveling agents, and plasticizers.

[0039] The content of other components in the cellulose fiber composite material is, for example, 30.0% by mass or less, 20.0% by mass or less, 10.0% by mass or less, or 5.0% by mass or less.

[0040] <<<Structure / Properties / Shape>>> In the cellulose fiber composite, the cellulose fibers may be present dispersed in a matrix component (e.g., acid-modified polypropylene), and the acid-modified olefin-based elastomer may be present in the form of islands in the cellulose fiber composite.

[0041] The cellulose fiber composite preferably has a cellulose area ratio standard deviation of 15% or less, 13% or less, or 10% or less, as measured under the following measurement conditions. When the cellulose area ratio standard deviation is within such a range, various mechanical properties of the resulting molded article can be improved.

[0042] (Measurement conditions for standard deviation of cellulose area ratio) In the cross section of the cellulose fiber composite material, ５ μm ２ The area of ​​cellulose fiber in the range of 0.01 mm is defined as the cellulose area ratio. The cellulose area ratio is calculated for 10 arbitrary cross sections of the cellulose fiber composite, and the standard deviation is calculated to define the cellulose area ratio standard deviation. More specifically, the thermoplastic resin composite is cut to form a cross section, and the cross section is observed from vertically above the cross section at a magnification of 250 times using a scanning electron microscope, and an image is taken. Next, the area occupied by cellulose fiber, as observed from vertically above, within a predetermined area on the cross section surface of the thermoplastic resin composite in the image taken is measured using commercially available software. Here, the predetermined area on the cross section surface of the thermoplastic resin composite is 2.0 x 10 ５ μm ２The area occupied by the cellulose fibers is divided by a predetermined area on the cross-sectional surface of the thermoplastic resin composite, and the result is multiplied by 100 to obtain the cellulose area ratio in the cross section of the thermoplastic resin composite. Similar measurements are performed on 10 arbitrary locations on the cross section of the thermoplastic resin composite, and the standard deviation of the cellulose area ratios obtained at the 10 locations is calculated, which is used as the standard deviation of the area ratio occupied by cellulose fibers.

[0043] The standard deviation of the cellulose area ratio can be adjusted by the kneading conditions (for example, the rotation speed of the mixer) during kneading, which will be described later.

[0044] In the cross section of the cellulose fiber composite, the region formed with the acid-modified olefin-based elastomer preferably has an average diameter of 0.7 to 1.2 μm. Furthermore, the standard deviation of the diameter of the region formed with the acid-modified olefin-based elastomer is preferably 1.0 μm or less, 0.8 μm or less, or 0.5 μm or less. The average diameter and standard deviation of the diameter are calculated by the following method.

[0045] The thermoplastic resin composite was cut, subjected to osmium electron staining, and observed from vertically above the cross section using a scanning electron microscope at a magnification of 250x, and images were taken. The particle sizes of 100 elastomer components (regions formed by acid-modified olefin-based elastomer) were measured, and the average particle size and standard deviation were calculated.

[0046] Such average diameter and standard deviation of diameter can be adjusted by the degree of acid modification (amount of acid modifying agent) and the like.

[0047] The shape of the cellulose fiber composite is not particularly limited. The cellulose fiber composite may constitute a molded body having a predetermined shape, or may be a raw material for producing a predetermined molded body. The cellulose fiber composite is preferably in the form of particles such as resin pellets used to produce a molded body.

[0048] When the cellulose fiber composite is a particle having a short axis and a long axis (e.g., an oval-spherical or cylindrical particle), the cellulose fibers are preferably oriented in the long axis direction of the cellulose fiber composite. Using such a cellulose fiber composite can improve various mechanical properties of the resulting molded article. Note that "cellulose fibers oriented in the long axis direction of the particle" refers to a state in which the cellulose fibers tend to be oriented in one direction (the long axis direction of the cellulose fiber composite) throughout the cellulose fiber composite. This state also includes states in which the axial directions of the cellulose fibers are not parallel, or the axial direction of the cellulose fibers does not coincide with the long axis direction of the cellulose fiber composite. Examples of particles with high cellulose fiber orientation include those in which, upon longitudinal cross-section observation of the particle, the proportion of fibers whose longitudinal axis forms an angle of ±30° or less (oriented fiber proportion) is 80% or more, 85% or more, or 90% or more. The oriented fiber proportion is calculated, for example, by observing 50 cellulose fibers. The observation of the cellulose fibers in the particles is carried out using, for example, an X-ray CT analyzer.

[0049] The axial direction of the cellulose fibers can be easily oriented by melting a composition containing various raw materials and then forming a granular cellulose fiber composite material using an extruder or the like.

[0050] When the cellulose fiber composite material is made into particles (pellets, etc.), the major axis diameter, minor axis diameter, cross-sectional shape, etc. of the particles can be adjusted appropriately depending on the application.

[0051] <<<Manufacturing Method>>> A cellulose fiber composite is produced by mixing and kneading the raw materials (cellulose fibers, acid-modified polypropylene, acid-modified olefin elastomer, etc.) at a predetermined temperature (above the softening point of the resin component). When the cellulose fiber composite is formed into granules (pellets, etc.), a method such as extrusion molding the kneaded resin composition and cutting the resulting rod-shaped material can be carried out. After molding the cellulose fiber composite, a stretching step or a step of immersing in water or the like to rapidly cool the cellulose fiber composite may be carried out. For the method of producing a cellulose fiber composite, reference can be made to the methods disclosed in, for example, WO 2021 / 256471.

[0052] The raw materials may be mixed using a mixer such as a Henschel mixer, a super mixer, or a ribbon mixer.

[0053] Examples of the method for kneading the raw materials include a method using a Banbury mixer and a method using a pressure roller. Kneading may also be performed using an extrusion molding machine such as a twin-screw extruder. In this case, kneading and extrusion molding can be performed simultaneously.

[0054] The method for producing a cellulose fiber composite material may be a method for producing a cellulose fiber composite material containing cellulose fibers by kneading pulp pieces with acid-modified polypropylene, acid-modified olefin elastomer, or the like, and simultaneously defibrating the pulp pieces into cellulose fibers. For such a method of simultaneously defibrating pulp pieces into cellulose fibers with resin kneading, reference may be made to the methods disclosed in WO 2021 / 256471, etc. In this case, the amount of cellulose fiber in the cellulose fiber composite material can be adjusted based on the amount of pulp pieces. Furthermore, the average fiber length, average fiber diameter, etc. of the cellulose fibers obtained using the pulp pieces can be adjusted based on the kneading conditions (kneading speed, time, etc.).

[0055] The method for producing a cellulose fiber composite may also involve using unmodified polypropylene and / or an unmodified olefinic elastomer and an acid-modified monomer as raw materials, and simultaneously kneading and acid-modifying each component. In this case, the blending amounts (blending ratios) of the polypropylene and / or olefinic elastomer and the acid-modified monomer used as raw materials can be adjusted based on the content of the acid-modified polypropylene and / or acid-modified olefinic elastomer in the cellulose fiber composite.

[0056] By changing the conditions (temperature, pressure, etc.) during extrusion molding, etc., the orientation and dispersibility of the cellulose fibers can be adjusted.

[0057] <<<<Applications>>> The cellulose fiber composite material is preferably used as a raw material for resin molded products. The cellulose fiber composite material is used, for example, as a raw material (pellets, etc.) for resin molded products made using a mold such as injection molding or for resin molded products made using a 3D printer.

[0058] Furthermore, the cellulose fiber composite material (or a molded product obtained using the cellulose fiber composite material) is preferably used as a component for molded parts for vehicles, machines, devices, etc., industrial materials such as containers, pallets, plastic cores, and building materials, daily necessities, miscellaneous goods, etc.

[0059] The cellulose fiber composite material of the present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

[0060] <<Raw Materials>> <Cellulose Fibers> Cellulose fiber 1: Average fiber length 210 μm Cellulose fiber 2: Average fiber length 120 μm Cellulose fiber 3: Average fiber length 280 μm Cellulose fiber 4: Average fiber length 60 μm Cellulose fiber 5: Average fiber length 340 μm

[0061] <Acid-modified polypropylene> Acid-modified PP1: Maleic anhydride-modified polypropylene (block) Acid-modified PP2: Propanoate-modified polypropylene (block)

[0062] <Acid-modified olefin elastomers> Acid-modified OE1: Maleic anhydride-modified ethylene-propylene rubber Acid-modified OE2: Maleic anhydride-modified ethylene-propylene-conjugated diene rubber Acid-modified OE3: Maleic anhydride-modified ethylene-1-butene rubber Acid-modified OE4: Propanoate ester-modified ethylene-propylene rubber Acid-modified OE5: Propanoate ester-modified ethylene-octene rubber

[0063] <<Production of Cellulose Fiber Composite Material>> <Example 1> A mixture was obtained by dry blending the raw materials (cellulose fiber, acid-modified polypropylene, and acid-modified olefin-based elastomer) in the raw materials and amounts (mass%) shown in Table 1. Each of the obtained mixtures was kneaded using a twin-screw kneader (PCM30 manufactured by Ikegai Corporation) under the conditions shown in Table 3 below. The obtained kneaded product was discharged from the extruder and stretched to about 1 m in the air, then immersed in water to cool and cut, thereby obtaining cylindrical cellulose fiber composite particles (pellets) according to Example 1 with a length of 6 mm and a width of 3 mm.

[0064] Fig. 1 shows an SEM photograph of a cross section perpendicular to the fiber orientation direction (long axis direction) of the cellulose fiber composite particle according to Example 1. As shown in Fig. 1, in the cross section of the cellulose fiber composite particle, cellulose fibers (CF) are distributed, and granular elastomer regions (EA) formed by the acid-modified olefin-based elastomer are formed in the acid-modified polypropylene (AP).

[0065] <Examples 2-13, Comparative Examples 1-4> Cellulose fiber composite particles (pellets) according to Examples 2-13 and Comparative Examples 1-4 were obtained in the same manner as in Example 1, except that the raw materials used and their blending amounts were changed to those shown in Tables 1 and 2.

[0066] <<Structure>> For the cellulose fiber composite particles according to each Example and Comparative Example, the standard deviation of the cellulose area ratio, the orientation of the cellulose fibers, and the average diameter and standard deviation of the diameter of the region formed by the acid-modified olefin-based elastomer in the cross section of the cellulose fiber composite material were measured. The measurement results are shown in Tables 1 and 2.

[0067] Furthermore, longitudinal cross sections of the cellulose fiber composite particles were observed based on the above-mentioned method, and the proportion of cellulose fibers whose orientation angle between the long axis direction of the cellulose fiber composite particle and the axial direction of the cellulose fiber was within ±30° (oriented fiber proportion) was calculated and evaluated according to the following criteria: A: Oriented fiber proportion of 90% or more B: Oriented fiber proportion of 85% or more but less than 90% C: Oriented fiber proportion of 80% or more but less than 85% D: Oriented fiber proportion less than 80%

[0068] <<Evaluation>> The moldability of the cellulose fiber composite particles according to each Example and Comparative Example was evaluated under the following conditions. Furthermore, those that were judged to be moldable in the moldability evaluation were further subjected to a tensile test, a bending test, and a Charpy impact strength test. The evaluation results are shown in Tables 1 and 2.

[0069] <Moldability> Using an injection molding machine (J80ADS, manufactured by The Japan Steel Works, Ltd.), dumbbell test pieces (Type A1 in accordance with ISO 527) were prepared under the following conditions: raw material temperature 200°C or less, mold temperature 60°C, injection speed 40 to 60 mm / s, and holding pressure 35 MPa. If a sufficiently filled molded product was obtained under the above molding conditions, it was evaluated as "moldable," and if molding was not possible under the above molding conditions because the injection pressure exceeded the limit, it was evaluated as "unmoldable."

[0070] <Tensile test> The test was carried out in accordance with ISO 527. The tensile strength of each dumbbell-shaped test piece was measured using an Instron material testing machine (Shimadzu Corporation: Autograph AG25 TA), and the test was evaluated based on the following evaluation criteria: A: 40 MPa or more B: 20 ​​MPa or more but less than 40 MPa C: Less than 20 MPa

[0071] <Bending test> The test was carried out in accordance with ISO 178. The bending modulus of each dumbbell-shaped test piece was measured using an Instron material testing machine (Shimadzu Corporation: Autograph AG25 TA), and the test piece was evaluated based on the following evaluation criteria: A: 3 GPa or more B: 2 GPa or more but less than 3 GPa C: Less than 2 GPa

[0072] <Charpy Impact Strength Test> The test was conducted in accordance with ISO 179 / 1eU. Using a test specimen having a notch (ISO 527, Type A), impact measurements were conducted by the edgewise test method at a temperature of 23°C, and evaluation was conducted based on the following evaluation criteria. A: 10 kJ / m ２ More than B: 5kj / m ２ More than 10kj / m ２ Less than C: 3kj / m ２ More than 5kj / m ２ Less than D: 3 kJ / m ２ less than

[0073] <Overall evaluation> For the evaluation results of the tensile test, bending test, and Charpy impact strength test, those that had only B or A were rated as "A", those with one C and the rest being B or A were rated as "B", those with two or more Cs and no Ds were rated as "C", and those that could not be molded (those for which each test could not be performed) and those with Ds in any of the tests were rated as "D".

[0074]

[0075]

[0076]

[0077] In Table 3, NDW indicates that kneading disc W was used, NDL indicates that kneading disc L was used, and NDR indicates that kneading disc R was used. NDW means that the kneading strength was relatively strong, NDL means that the kneading strength was relatively medium, and NDR means that the kneading strength was relatively weak.

[0078] Since the cellulose fiber composite material according to the present invention can be used to produce molded articles with various excellent mechanical properties, it is preferably used as a raw material (e.g., pellets) for resin molded articles using a mold such as injection molding or resin molded articles using a 3D printer. CROSS-REFERENCE TO RELATED APPLICATIONS

[0079] This application claims priority based on Japanese Patent Application No. 2024-50386, filed with the Japan Patent Office on March 26, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A cellulose fiber composite material comprising cellulose fibers, acid-modified polypropylene, and an acid-modified olefin-based elastomer, wherein the content of the cellulose fibers is 5.0 to 60.0 mass%, the content of the acid-modified polypropylene is 15.0 to 90.0 mass%, and the content of the acid-modified olefin-based elastomer is 1.0 to 30.0 mass%.

2. The cellulose fiber composite material according to claim 1, wherein the acid-modified polypropylene is a carboxylic acid anhydride-modified polypropylene, and the acid-modified olefin-based elastomer is a carboxylic acid anhydride-modified olefin-based elastomer.

3. The cellulose fiber composite material according to claim 1 or 2, wherein the acid-modified olefin-based elastomer is at least one selected from the group consisting of acid-modified ethylene-propylene rubber, acid-modified ethylene-propylene-non-conjugated diene rubber, acid-modified ethylene-1-butene rubber, acid-modified ethylene-1-butene-non-conjugated diene rubber, and acid-modified ethylene-1-octene rubber.

4. The cellulose fiber composite material according to claim 1 or 2, wherein the cellulose fibers have an average fiber length of 100 to 300 μm.

5. The cellulose fiber composite material according to claim 1 or 2, wherein the standard deviation of the cellulose area ratio measured under the following measurement conditions is 15% or less. (Measurement conditions) In a cross section of the cellulose fiber composite material, ５ μm ２ The area of ​​the cellulose fibers in the range is defined as the cellulose area ratio. The cellulose area ratios are calculated for 10 arbitrary cross sections of the cellulose fiber composite, and the standard deviation is calculated to define the cellulose area ratio standard deviation.

6. A cellulose fiber composite according to claim 1 or 2, wherein the cellulose fiber composite is a particle having a major axis and a minor axis, and the cellulose fibers are oriented in the major axis direction of the cellulose fiber composite.

7. A cellulose fiber composite according to claim 1 or 2, wherein the average diameter of the region formed by the acid-modified olefin-based elastomer in the cross section of the cellulose fiber composite is 0.7 to 1.2 μm, and the standard deviation of the diameter of said region is 1.0 μm or less.

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