Cellulose-fiber-containing resin composition and method for producing the same

Abstract

To provide a resin composition that improves compatibility between highly hydrophilic microfibrillated cellulose and a highly hydrophobic resin, thereby achieving superior tensile strength and flexural strength.SOLUTION: A resin composition contains cellulose fibers, a modified polyolefin resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof, urea or a derivative thereof, and a thermoplastic resin having no hydrophilic functional group, wherein the modified polyolefin resin has an acid-value reduction rate of 2% or more in ethanol extraction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition containing cellulose fibers. [Background technology]

[0002] Fine fibrous cellulose obtained by finely disintegrating plant fibers includes microfibril cellulose and cellulose nanofibers, and is a fine fiber with a fiber diameter of about 1 nm to several tens of μm. Fine fibrous cellulose is lightweight, has high strength, a high elastic modulus, and a low coefficient of linear thermal expansion, and is therefore suitable for use as a reinforcing material for resin compositions.

[0003] However, since fine fibrous cellulose is hydrophilic while resin is hydrophobic, there is a problem with the dispersibility of the fine fibrous cellulose when using it as a reinforcing material for resin.

[0004] In Patent Document 1, a cellulose raw material and urea are heat-treated to obtain a cellulose raw material in which some of the hydroxyl groups of the cellulose are substituted with carbamate groups, and this is then micronized by mechanical processing to obtain fine fibrous cellulose. The fine fibrous cellulose obtained by this method is less hydrophilic than conventional fine fibrous cellulose and has a high affinity with low-polarity resins, etc., and therefore disperses highly uniformly in resins, resulting in a resin composition with high tensile strength. It is also disclosed that a compatibilizer such as maleic acid-modified polypropylene may be added as a dispersant to further improve dispersion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-1876 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there has been insufficient research into what kind of compatibilizer should be used to further enhance the effect of improving the strength of the resin composition.

[0007] An object of the present invention is to provide a resin composition having excellent tensile strength and flexural strength by improving the compatibility between highly hydrophilic fine fibrous cellulose and highly hydrophobic resin. [Means for solving the problem]

[0008] The present invention provides the following: [1] A resin composition comprising (A) cellulose fibers, (B) a modified polyolefin resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof, (C) urea or a derivative thereof, and (D) a thermoplastic resin having no hydrophilic functional groups, wherein the modified polyolefin resin (B) exhibits an acid value reduction rate of 2% or more upon ethanol extraction. [2] The resin composition according to claim 1, wherein the content of the (D) thermoplastic resin not having a hydrophilic functional group in the resin composition is 100 to 1900 mass% relative to 100 mass% of the (A) cellulose fiber contained in the resin composition. [3] A method for producing a resin composition, comprising the steps of kneading (A) cellulose fibers, (B) a modified polyolefin resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof, (C) urea or a derivative thereof, and (D) a thermoplastic resin having no hydrophilic functional groups. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the compatibility between highly hydrophilic fine fibrous cellulose and highly hydrophobic resins, and to provide a resin composition excellent in tensile strength and flexural strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for producing the resin composition of the present invention will be described below. In the present invention, "to" includes the extreme values. That is, "X to Y" includes the values ​​X and Y at both ends.

[0011] (Resin composition) The resin composition of the present invention contains at least cellulose fibers, a modified polyolefin resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof (hereinafter referred to as "modified polyolefin resin"), urea or a derivative thereof, and a thermoplastic resin having no hydrophilic functional groups. According to the present invention, the resin composition of the present invention contains 2 parts by mass or more of an α,β-unsaturated carboxylic acid or a derivative thereof that is not graft-polymerized to the polyolefin resin per 100 parts by mass of the modified polyolefin resin, thereby improving compatibility with the cellulose fibers and enabling the production of a homogeneous resin composition. Furthermore, according to the present invention, a resin composition having excellent tensile strength and flexural strength can be obtained.

[0012] (Cellulose fiber (A)) The cellulose fiber (A) used in the present invention can be obtained by pulping a pulp raw material. The pulp raw material may be either wood or non-wood. Examples of wood raw materials used to produce wood pulp include softwood and hardwood. Examples of non-wood raw materials used to produce non-wood pulp include cotton, hemp, sisal, Manila hemp, flax, straw, bamboo, bagasse, and kenaf. The pulp raw materials (wood raw materials and non-wood raw materials) may be unbleached (before bleaching) or bleached (after bleaching). The method for pulping a wood raw material is not particularly limited, and examples include pulping methods commonly used in the papermaking industry. Wood pulp can be classified by the pulping method, and examples include chemical pulp obtained by cooking using methods such as the kraft method, sulfite method, soda method, and polysulfide method; mechanical pulp (TMP) obtained by pulping using mechanical forces such as a refiner or grinder; semi-chemical pulp obtained by pre-treatment with chemicals followed by mechanical pulping; recycled paper pulp; and deinked pulp.

[0013] The Canadian Standard Freeness of the cellulose fiber (A) used in the present invention is not particularly limited. A freeness of more than 600 mL is preferable from the viewpoint of contributing to cost reduction because the beating step can be omitted. The upper limit of the freeness is not particularly limited, but in reality it is 800 mL or less. The Canadian Standard Freeness of the cellulose fiber (A) can be measured according to JIS P 8121-2:2012.

[0014] (chemical modification) The cellulose fiber (A) used in the present invention may be chemically modified by acetylation, oxidation, esterification, etherification, or the like. However, the use of non-chemically modified cellulose fiber is preferred from the viewpoint of contributing to reducing the environmental load and reducing costs, since the chemical modification step can be omitted.

[0015] (acetylated denaturation) The acetylated modified pulp that can be used in the present invention (sometimes simply referred to as "acetylated pulp") has the hydrogen atoms of the hydroxyl groups present on the surface of the cellulose in the pulp raw material substituted with acetyl groups (CH3-CO-). The substitution with acetyl groups increases hydrophobicity and reduces aggregation during drying, improving workability and facilitating dispersion and defibration in the resin after kneading. Furthermore, the substitution of highly reactive hydroxyl groups with acetyl groups suppresses thermal decomposition of cellulose, improving heat resistance during kneading. The degree of acetyl group substitution (DS) of the acetylated pulp is preferably adjusted to 0.4 to 1.3, more preferably 0.6 to 1.1, from the viewpoints of workability and maintaining the crystallinity of the cellulose fibers.

[0016] (Acetylation reaction) The acetylation reaction can be carried out in a short time by suspending the cellulose raw material in an anhydrous aprotic polar solvent capable of swelling the raw material, such as N-methylpyrrolidone (NMP) or N,N-dimethylformamide (DMF), and using acetic anhydride, acetyl chloride, or other acetyl halides in the presence of a base. The base used in this acetylation reaction is preferably pyridine, N,N-dimethylaniline, sodium carbonate, sodium bicarbonate, or potassium carbonate, with potassium carbonate being more preferred. Alternatively, the reaction can be carried out without the use of an anhydrous aprotic polar solvent or base by using an excess of an acetylating reagent such as acetic anhydride. The acetylation reaction is preferably carried out, for example, at room temperature to 100°C with stirring. After the reaction, vacuum drying may be performed to remove the acetylating reagent. If the target degree of acetyl substitution is not achieved, the acetylation reaction and subsequent vacuum drying may be repeated any number of times.

[0017] (Washing) The acetylated pulp obtained by the acetylation reaction is preferably subjected to a washing treatment such as water replacement after the acetylation treatment.

[0018] (dehydration) The washing treatment may be carried out with dehydration as needed. Dehydration can be carried out by pressurized dehydration using a screw press or reduced-pressure dehydration by evaporation, but centrifugal dehydration is preferred from the viewpoint of efficiency. Dehydration is preferably carried out until the solid content in the solvent is about 10 to 60%.

[0019] (Dry) The acetylated pulp that can be used in the present invention may be dried after the dewatering step. The drying can be carried out using, for example, a microwave dryer, a blower dryer, or a vacuum dryer, but a dryer that can dry while stirring, such as a drum dryer, a paddle dryer, a Nauta mixer, or a batch dryer with a stirring blade, is preferred. When drying is carried out, the moisture content of the acetylated pulp is preferably 1 to 40%, more preferably 1 to 10%, and even more preferably 1 to 5%.

[0020] (Modified polyolefin resin (B) modified with α,β-unsaturated carboxylic acid and / or its derivative) The modified polyolefin resin (B) (hereinafter referred to as "modified polyolefin resin"), which has been modified with an α,β-unsaturated carboxylic acid and / or its derivative, functions as a compatibilizing resin (compatibilizer). The compatibilizing resin functions to improve the uniform mixing and adhesion between cellulose fibers with different hydrophobicity and a thermoplastic resin (D) without hydrophilic functional groups, which will be described later. When a resin is modified with an α,β-unsaturated carboxylic acid and / or its derivative, it becomes highly hydrophilic, which means that it has good affinity with water and the surface of cellulose.

[0021] A modified polyolefin resin can be obtained by modifying a polyolefin resin with an α,β-unsaturated carboxylic acid and / or a derivative thereof. Examples of the modified polyolefin resin (B) include maleic anhydride-modified polypropylene (MAPP) and maleic anhydride-modified polyethylene (MAPE).

[0022] (α,β-unsaturated carboxylic acid and / or its derivative) The term "α,β-unsaturated carboxylic acid" refers to an α,β-unsaturated compound having a carboxy group. The term "derivative of α,β-unsaturated carboxylic acid" refers to an anhydride, mono- or diester, amide, imide, etc. of the unsaturated compound.

[0023] Examples of α,β-unsaturated carboxylic acids or derivatives thereof include fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, aconitic acid, and anhydrides thereof; monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, monomethyl maleate, monoethyl maleate, monopropyl maleate, monobutyl maleate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, maleimide, and N-phenylmaleimide.

[0024] When obtaining a modified polyolefin resin, the α,β-unsaturated carboxylic acid or its derivative may be used alone or in combination of two or more. In the latter case, the compounding ratio of each compound is not particularly limited.

[0025] The α,β-unsaturated carboxylic acid and / or its derivative preferably includes an α,β-unsaturated dicarboxylic acid, and more preferably includes one or more selected from the group consisting of itaconic anhydride, maleic anhydride, and maleic acid, with maleic anhydride being more preferred.

[0026] (α,β-unsaturated carboxylic acid or its derivative (unreacted substance) that does not graft polymerize onto polyolefin resin) During the production of modified polyolefin resins, α,β-unsaturated carboxylic acids or derivatives thereof that do not graft polymerize onto the polyolefin resin, i.e., unreacted materials, may be generated. Examples of unreacted materials include α,β-unsaturated carboxylic acids or derivatives thereof (monomers) and oligomers thereof. The modified polyolefin resin (B) of the present invention preferably exhibits an acid value reduction rate of 2% or more, more preferably 10% or more, upon ethanol extraction. A high acid value reduction rate upon ethanol extraction indicates that the modified polyolefin resin contains a large amount of unreacted materials. The presence of a certain amount of unreacted materials in the modified polyolefin resin improves the strength of the resin composition. Although the reason for this is unclear, it is thought that in addition to the modified polyolefin as a compatibilizer, low-molecular-weight monomers and oligomers are present at the interface between the cellulose fibers and the thermoplastic resin, filling in the areas where the modified polyolefin molecular chain is not present. This plays a supporting role as a compatibilizer, improving uniform mixing and adhesion, and improving the strength of the resin composition.

[0027] (Acid value reduction rate) The rate of decrease in acid value by ethanol extraction can be calculated by the following formula using the degree of acid modification of the modified polyolefin before and after ethanol extraction of the modified polyolefin resin by the method described below. The degree of acid modification of the modified polyolefin resin can be measured by alkali titration. Acid value reduction rate by ethanol extraction (%) = (acid denaturation degree before ethanol extraction - acid denaturation degree after ethanol extraction) / acid denaturation degree before ethanol extraction × 100

[0028] (Ethanol extraction method) Weigh out 200g of ethanol (99.5%) and place it in a disposable cup, then drop in 20g of a 10% solution of modified polyolefin resin dissolved in p-xylene and stir with a stirrer for at least 15 minutes to precipitate the modified polyolefin resin.Recover the precipitated modified polyolefin resin and vacuum dry it overnight in a vacuum dryer set at 40°C.

[0029] Factors that determine the characteristics of the modified polyolefin resin (B) used in the present invention as a compatibilizing resin (compatibilizer) include, for example, the amount of maleic anhydride added and the weight-average molecular weight of the base polyolefin resin in the case of maleic anhydride-modified polyolefin. Polyolefin resins with a high amount of maleic anhydride added enhance compatibility with hydrophilic polymers such as cellulose, but the molecular weight of the resin decreases during the addition process, resulting in reduced strength of the molded product. The optimal balance is an amount of maleic anhydride added of 20 to 100 mg KOH / g, more preferably 45 to 65 mg KOH / g. A low amount of maleic anhydride added results in fewer points of interaction with the hydroxyl groups of cellulose and the hydroxyl groups and modified functional groups contained in the modified cellulose. Furthermore, a high amount of maleic anhydride added can lead to self-aggregation due to hydrogen bonding between carboxyl groups in the resin, or to a reduction in the molecular weight of the base olefin resin due to excessive addition reactions, resulting in insufficient strength as a reinforced resin.

[0030] From the viewpoint of easy dispersibility, the melting point of the modified polyolefin resin (B) used in the present invention is preferably equal to or lower than the melting point of the thermoplastic resin (D) having no hydrophilic functional group. For example, the melting point of maleic anhydride-modified polypropylene (MAPP) is 150°C, and the melting point of maleic anhydride-modified polyethylene (MAPE) is 120°C. Furthermore, for example, the melting point of polyamide resin (PA6) is 220°C.

[0031] The modified polyolefin resin (B) may be further modified, for example, with a (meth)acrylic acid ester. By further modifying a thermoplastic resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof with a (meth)acrylic acid ester, compatibility is improved.

[0032] A (meth)acrylic acid ester is a compound containing at least one (meth)acryloyl group in the molecule. In this specification, "(meth)acryloyl group" means an acryloyl group and / or a methacryloyl group. The (meth)acrylic acid ester is preferably a compound represented by the following general formula (1): CH2=CR1COOR2 (1)

[0033] In general formula (1), R1 represents a hydrogen atom or a methyl group, preferably a methyl group, and R2 represents CnH2n+1, where n represents an integer of 1 to 18, preferably an integer of 1 to 15, and more preferably an integer of 1 to 13.

[0034] Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, glycidyl (meth)acrylate, octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 1-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, acetoacetoxyethyl (meth)acrylate, and (meth)acryloylmorpholine. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, and tridecyl (meth)acrylate are preferred, and octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, and tridecyl (meth)acrylate are more preferred.

[0035] The (meth)acrylic acid ester may be one kind or a combination of two or more kinds, in which case the compounding ratio of each compound is not particularly limited.

[0036] The amount of modified polyolefin resin (B) is not particularly limited, but is preferably 1 to 100% by mass, and more preferably 10 to 80% by mass, relative to the mass (100% by mass) of cellulose fiber (A). If the amount added exceeds 100% by mass, the amount exceeds the amount necessary to form an interface between cellulose and resin, which is thought to result in a decrease in strength when formed into a composite. The modified polyolefin resin (B) may be used alone or as a mixed resin of two or more types. When used as a graft composite of one or more polymers and polyolefins, the polyolefin resin that constitutes the graft composite is not particularly limited, but polyethylene, polypropylene, polybutylene, etc. can be used from the viewpoint of ease of production of the graft composite.

[0037] (Urea or its derivatives (C)) In the present invention, from the viewpoint of improving the strength of the resulting resin composition, urea or a derivative thereof (C) is used as a low molecular weight auxiliary that provides a primary amine.

[0038] Urea has a thermal decomposition temperature of 135°C and decomposes into ammonia and isocyanic acid above this temperature. By kneading urea simultaneously with cellulose fibers, the unmodified hydroxyl groups newly revealed from within the fibers react with the generated isocyanic acid, promoting the formation of urethane bonds. This is thought to enhance the hydrophobicity of cellulose fibers compared to untreated cellulose fibers. By simultaneously melt-kneading urea with modified polyolefin resin (B), the amino groups newly introduced on the surface of the cellulose fibers by urea treatment interact hydrophilically with the acid groups of modified polyolefin resin (B), forming a stronger composite between the cellulose fibers and the modified polyolefin resin.

[0039] The amount of urea or its derivatives to be blended is not particularly limited. However, from the viewpoint of preventing the fibers from agglomerating and reducing strength due to an excessive amount of urea or its derivatives to be blended, the ratio of the mass of urea or its derivatives (C) to the mass of cellulose fibers (A) is preferably less than 0.8, more preferably 0.05 or more but less than 0.75, and even more preferably 0.1 or more but less than 0.7.

[0040] (dispersion medium) Examples of the dispersion medium include water and organic solvents, and a mixture thereof may also be used. From the viewpoints of compatibility with pulp and safety, water is preferably used. The amount of dispersion medium is preferably an amount that results in a solids concentration of the cellulose fibers fed into the kneader of 10 to 50% by mass, more preferably an amount that results in a solids concentration of 20 to 40% by mass. If the solids concentration of the cellulose fibers at the start of kneading is too low below the lower limit, the drying load increases, resulting in insufficient drying, which may result in a decrease in the strength of the final resin composition. If the solids concentration of the cellulose fibers at the start of kneading is too high above the upper limit, the penetration of the dispersion medium, such as water containing urea, into the cellulose fibers is poor, resulting in non-uniformity.

[0041] (Thermoplastic resin (D) having no hydrophilic functional group) Examples of the thermoplastic resin (D) having no hydrophilic functional group include the following general thermoplastic resins having a melting temperature of 250° C. or less.

[0042] Common thermoplastic resins that can be used include polyolefin resins, polyamide resins, polyvinyl chloride, polystyrene, polyvinylidene chloride, fluororesins, (meth)acrylic resins, polyesters, polylactic acid, copolymer resins of lactic acid and esters, polyglycolic acid, acrylonitrile-butadiene-styrene copolymers (ABS resins), polyphenylene oxide, polyurethanes, polyacetals, vinyl ether resins, polysulfone resins, and cellulose resins (such as triacetylated cellulose and diacetylated cellulose).

[0043] As the polyolefin resin, polyethylene, polypropylene (hereinafter also referred to as "PP"), ethylene-propylene copolymer, polyisobutylene, polyisoprene, polybutadiene, etc. can be used.

[0044] Polyamide resins (PA) are also expected to interact with hydroxyl groups of cellulose that have not been affected by urea, making them suitable for use. Examples of PA include aliphatic PAs such as polyamide 6 (nylon 6, PA6), polyamide 11 (nylon 11, PA11), polyamide 12 (nylon 12, PA12), polyamide 66 (nylon 66, PA66), polyamide 46 (nylon 46, PA46), polyamide 610 (nylon 610, PA610), and polyamide 612 (nylon 612, PA612), as well as aromatic PAs composed of aromatic diamines such as phenylenediamine and aromatic dicarboxylic acids such as terephthaloyl chloride or isophthaloyl chloride, or derivatives thereof. From the viewpoint of high affinity with cellulose fibers and cellulose nanofibers, aliphatic PAs are preferred, with PA6, PA11, and PA12 being more preferred, and PA6 being particularly preferred. Furthermore, one type of polyamide resin may be used alone, or two or more types of polyamide resins may be mixed together.

[0045] The resins exemplified above can be used as homopolymers or as block copolymers containing resins having various known functions in a half amount or less.

[0046] The melting point of the thermoplastic resin (D) having no hydrophilic functional group is preferably 230°C or lower from the viewpoint of thermal decomposition of cellulose. In consideration of the expected components to be used, the melting point is preferably 100°C or higher, and more preferably 80°C or higher.

[0047] The amount of the thermoplastic resin (D) not having a hydrophilic functional group to be blended is not particularly limited, but is preferably 1 to 50 mass % and more preferably 5 to 40 mass % relative to the mass (100 mass %) of the cellulose fibers (A).

[0048] (melt kneading) The mixture is melt-kneaded in a kneader to obtain a resin composition.

[0049] To suppress the decomposition of urea, which is expected to have the effect of inhibiting cellulose aggregation while removing water as a dispersion medium, the barrel temperature of the kneader is set to a temperature range of at least 100°C to 130°C, preferably 110°C to 130°C, from the viewpoint of being above the boiling point of water but below the decomposition temperature of urea. The raw material composition is heated while stirring, and the dispersion medium is removed to obtain a mixture. If the heating temperature is too high, the urea decomposes, reducing the effect of the urea and preventing successful kneading. Furthermore, if the urea, which inhibits aggregation by penetrating between cellulose particles, decomposes, agglomerates are more likely to remain.

[0050] In the melt-kneading, the dispersion medium is preferably removed until the solid content of the resulting mixture reaches 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less. As the removal of the dispersion medium progresses, a shear force is applied to the cellulose fibers containing the urea water, and the final resin composition has excellent strength.

[0051] After the dispersant is removed, the urea-treated cellulose fibers, the modified polyolefin resin (B), and the thermoplastic resin (D) without hydrophilic functional groups are melt-kneaded, which promotes the nano-ization of the pulp.

[0052] Examples of a device for heating the raw material composition to a predetermined temperature while stirring include a single-screw or multi-screw kneader (extruder). From the viewpoint of versatility, a twin-screw kneader is preferably used. Furthermore, the kneader (extruder) is preferably equipped with parts that constitute a screw.

[0053] As the melt-kneading device, a single-screw or multi-screw kneader (extruder) is preferably used. From the viewpoint of being able to melt-knead the cellulose fiber (A), the modified polyolefin resin (B), the urea or its derivative (C), and the thermoplastic resin (D) without a hydrophilic functional group, as well as having a strong kneading force that promotes nano-pulp formation, a multi-screw kneader (extruder) such as a twin-screw kneader (extruder) or a four-screw kneader (extruder) is preferably configured to include multiple kneading screws, rotors, etc.

[0054] The resin composition produced by the production method of the present invention may further contain additives such as surfactants, polysaccharides such as starches and alginic acid, natural proteins such as gelatin, glue and casein, inorganic compounds such as tannin, zeolite, ceramics and metal powder, colorants, plasticizers, fragrances, pigments, flow control agents, leveling agents, conductive agents, antistatic agents, UV absorbers, UV dispersants, deodorizers, antioxidants, etc. The content of any additive may be appropriately determined within a range that does not impair the effects of the present invention.

[0055] According to the present invention, a resin composition having excellent tensile strength and flexural strength can be obtained.

[0056] (Application) The resin composition produced by the production method of the present invention can be used to produce molding materials and molded articles (molding materials and molded articles). Examples of the shape of the molded article include films, sheets, plates, pellets, powders, and various shapes such as three-dimensional structures. Molding methods that can be used include mold molding, injection molding, extrusion molding, blow molding, and foam molding.

[0057] The molded body (molded body) can be used not only in the field of fiber-reinforced plastics where matrix molded bodies (molded bodies) containing cellulose fibers are used, but also in fields where thermoplasticity and mechanical strength (tensile strength, etc.) are required.

[0058] They can be effectively used as interior, exterior and structural materials for transportation equipment such as automobiles, trains, ships and airplanes; cases, structural materials and internal parts for electrical appliances such as computers, televisions, telephones and watches; cases, structural materials and internal parts for mobile communication devices such as mobile phones; cases, structural materials and internal parts for portable music players, video players, printing equipment, copying equipment, sporting goods and the like; building materials; office equipment such as stationery, containers and the like. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] (Measuring Canadian Standard Freeness (CSF)) The Canadian standard freeness of the cellulose fibers used in the examples and comparative examples was measured in accordance with JIS P 8121-2:2012.

[0061] (Measurement of lignin content) The lignin content of the cellulose fibers used in the examples and comparative examples was measured based on the Klason method, which is a commonly used quantitative method (Klason lignin).

[0062] (Measurement of tensile strength) 150 g of the pellet-like resin molded body obtained in the Examples, Comparative Examples, and Reference Examples was placed in a small molding machine ("MC15" manufactured by Xplore Instruments) and molded into dumbbell-shaped test specimens (Type A12, JIS K7139) under conditions of a heating barrel (cylinder) temperature of 200°C and a mold temperature of 40°C. The resulting test specimens were measured for modulus of elasticity, maximum stress (yield strength), and fracture displacement (strain and elongation until fracture) using a precision universal testing machine ("Autograph AG-Xplus" manufactured by Shimadzu Corporation) at a test speed of 1 mm / min and an initial gauge length of 30 mm. The modulus of elasticity and maximum stress were measured for each sample, and the reinforcement ratio was calculated by setting the modulus of elasticity and maximum stress of the diluting resin to 100. The results are shown in Table 1.

[0063] (Bending strength measurement) 150 g of the pellet-like resin molded body obtained in the Examples, Comparative Examples, and Reference Examples was placed in a small molding machine ("MC15" manufactured by Xplore Instruments) and molded into bar test specimens (4 mm thick, parallel section length 80 mm) at a heating barrel (cylinder) temperature of 250°C and a mold temperature of 40°C. The elastic modulus, maximum stress, and fracture displacement of the obtained test specimens were measured using a precision universal testing machine ("Autograph AG-Xplus" manufactured by Shimadzu Corporation) at a test speed of 10 mm / min and a support distance of 64 mm. For the elastic modulus and maximum stress, the reinforcement ratio was calculated by the ratio of the measured values ​​of each sample to the values ​​of the elastic modulus and maximum stress of the diluting resin, respectively, which were set to 100. The results are shown in Table 1.

[0064] (Materials used in producing the resin composition) (A) Cellulose fiber (decomposition temperature: 299°C): NUKP (unbleached softwood kraft pulp) ·(C) Urea: Powder, manufactured by Mitsui Chemicals (D) Thermoplastic resin not having a hydrophilic functional group: homopolypropylene (hPP): (PP MA04A manufactured by Japan Polypropylene Corporation, melting point: 165°C) Antioxidants: Hindered phenol antioxidant (Irganox 1010, manufactured by BASF Japan Ltd.)

[0065] (Production Example 1: Modified Polyolefin (B) (MAPP1)) 100 parts of an α-olefin copolymer (propylene content: 98 mol%, ethylene content: 2 mol%, Tm: 145°C), 4.0 parts of maleic anhydride, and 2.0 parts of di-t-butyl peroxide were reacted in a twin-screw extruder set at 170°C to obtain a reaction product with a weight-average molecular weight of 60,000 and a Tm of 145°C. The graft weight of maleic anhydride was measured by alkali titration and found to be 3.4% by weight. The acid value reduction rate of the produced modified polyolefin (MAPP1) upon ethanol extraction is shown in Table 1.

[0066] (Production Example 2: Modified Polyolefin (B) (MAPP2)) 100 parts of an α-olefin copolymer (propylene content: 97 mol%, ethylene content: 3 mol%, Tm: 125°C), 5.0 parts of maleic anhydride, and 3.0 parts of di-t-butyl peroxide were kneaded and reacted using a twin-screw extruder set at 170°C to obtain a reaction product with a weight-average molecular weight of 80,000 and a Tm of 125°C. The graft weight of maleic anhydride was measured by alkali titration and found to be 4.2% by weight. The acid value reduction rate of the produced modified polyolefin (MAPP2) upon ethanol extraction is shown in Table 1.

[0067] (Production Example 3: Modified Polyolefin (B) (MAPP3) 100 parts of an α-olefin copolymer (97 mol% propylene, 3 mol% ethylene, Tm = 125°C), 8.0 parts of maleic anhydride, 1.0 part of lauryl methacrylate (acrylic monomer), and 3.0 parts of di-t-butyl peroxide were kneaded and reacted using a twin-screw extruder set at 170°C to obtain a reaction product with a weight-average molecular weight of 75,000 and a Tm = 125°C. The graft weight of maleic anhydride was measured by alkali titration and found to be 5.1 wt%. The acid value reduction rate of the produced modified polyolefin (MAPP3) upon ethanol extraction is shown in Table 1.

[0068] Example 1 (Production of Resin Composition) 26.4 g of solids of unbeaten softwood unbleached kraft pulp (NUKP) as cellulose fiber (Canadian Standard Freeness of more than 600 mL, lignin content of 1% by mass or more, solids concentration of 30% by mass or less), 7.2 g of solids of MAPP1 produced in Production Example 1, 7.2 g of urea, and an antioxidant were kneaded using a twin-screw kneader under conditions of 100°C or higher and 130°C or lower, and a screw peripheral speed of 212 mm / sec, to obtain a mixture with a solids concentration of 98.0% by mass. Next, 80 g of homopolypropylene (hPP) as a thermoplastic resin (D) having no hydrophilic functional groups was added to the mixture, and the mixture was kneaded using a twin-screw kneader under heating conditions of 180° C. or less. The molten mixture was then pelletized using a pelletizer to obtain pellets of a resin composition.

[0069] Example 2 Resin kneading was carried out in the same manner as in Example 1 to obtain a mixture with a solid content concentration of 97.6 mass%, except that MAPP2 of Production Example 2 was used as the modified polyolefin resin (B) modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof. Pellets of a resin composition were obtained in the same manner as in Example 1, except that the obtained mixture was used.

[0070] Example 3 Resin kneading was carried out in the same manner as in Example 1 to obtain a mixture with a solid content concentration of 98.3 mass %, except that MAPP3 of Production Example 3 was used as the modified polyolefin resin (B) modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof. Pellets of a resin composition were obtained in the same manner as in Example 1, except that the obtained mixture was used.

[0071] (Comparative Example 1) Resin kneading was carried out in the same manner as in Example 1, except that maleic anhydride-modified polypropylene (MAPP): (TOYOTAC PMA-H1000P manufactured by Toyobo Co., Ltd.: dicarboxylic acid addition amount 57 mg KOH / g, melting point: 150°C, acid value reduction rate 1.1%) was used as the modified polyolefin resin (B) modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof, to obtain a mixture with a solid content concentration of 98.3 mass%. Pellets of a resin composition were obtained in the same manner as in Example 1, except that the obtained mixture was used.

[0072] [Table 1]

[0073] As can be seen from Table 1, the resin compositions of Examples 1 to 3, which used modified polyolefins (MAPP1 to MAPP3) characterized by an acid value reduction rate of 2% or more upon ethanol extraction, were superior in tensile strength (elastic modulus, maximum stress) and flexural strength (elastic modulus, maximum stress) compared to Comparative Example 1.

Claims

1. A resin composition comprising (A) cellulose fibers, (B) a modified polyolefin resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof, (C) urea or a derivative thereof, and (D) a thermoplastic resin having no hydrophilic functional group, A resin composition characterized in that the modified polyolefin resin (B) exhibits an acid value reduction rate of 2% or more upon ethanol extraction.

2. 2. The resin composition according to claim 1, wherein the content of the (D) thermoplastic resin having no hydrophilic functional group in the resin composition is 100 to 1900% by mass relative to 100% by mass of the (A) cellulose fiber contained in the resin composition.

3. A method for producing a resin composition, comprising the steps of kneading (A) cellulose fibers, (B) a modified polyolefin resin modified with an α,β-unsaturated carboxylic acid and / or a derivative thereof, (C) urea or a derivative thereof, and (D) a thermoplastic resin having no hydrophilic functional group.

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