Cellulose fiber composition production method and cellulose fiber-blended resin composition production method

Abstract

[Problem] To provide a cellulose fiber composition production method and a cellulose fiber-blended resin composition production method, with which it becomes possible to improve both elastic modulus and impact strength of a molded product of a cellulose fiber-blended resin composition. [Solution] A method for producing a cellulose fiber composition using, as starting materials, 100 parts by mass of cellulose fibers (A), 5-30 parts by mass of a hydrophobic compound (B) that is any one of a (meth)acrylic resin, a styrene-(meth)acrylic resin, and a polyolefin resin each having at least one structure selected from among an epoxy group, a carboxyl group, a carbamoyl group, a carboxylic anhydride, and a carboxylic acid salt in the molecule thereof, and 1-10 parts by mass of an alkaline inorganic compound (C), the method being characterized by including a step in which the total solid content concentration of a mixture containing the components (A), (B), and (C) is adjusted to 25-85%, and the mixture is sheared at a shear rate of 1,500 s-1 or more.

Description

Method for producing a cellulose fiber composition and method for producing a cellulose fiber-containing resin composition

[0001] The present invention relates to a method for producing a cellulose fiber composition and a method for producing a cellulose fiber-reinforced resin composition that can improve the elastic modulus and impact strength of a molded article of a cellulose fiber-reinforced resin composition.

[0002] Traditionally, fibrous additives such as glass fibers, carbon fibers, aramid fibers, and cellulose fibers have been used to improve the strength of resin molded products. Among these, cellulose fibers have characteristics such as low density, high elastic modulus, and low coefficient of linear thermal expansion. Furthermore, because cellulose fibers are "carbon neutral" and a sustainable resource, they are expected to be a material that contributes to reducing environmental impact.

[0003] However, because cellulose fibers are hydrophilic and commonly used thermoplastic resins are hydrophobic, the adhesion between cellulose fibers and resin is poor, and the strength of the cellulose fibers is not fully reflected in the molded product. Furthermore, because it is difficult to highly disperse cellulose fibers in the resin, sufficient reinforcing effect on the molded product has sometimes not been obtained. To date, various compositions and manufacturing methods have been proposed as means to fully demonstrate the effect of adding cellulose fibers, i.e., the strength of the molded product, in cellulose fiber composite resins.

[0004] Patent Document 1 shows that using a resin composition containing cellulose fibers, an acrylic resin and / or styrene-acrylic resin having a specific solubility in water and glass transition temperature, and a thermoplastic resin results in good elastic modulus and fiber dispersibility in the resin of a molded article. However, in Patent Document 1, it was necessary to use a high-boiling point organic solvent such as propylene glycol monomethyl ether in order to adsorb the acrylic resin and / or styrene-acrylic resin having a specific solubility in water and glass transition temperature onto the hydrophilic cellulose fiber surface. These solvents are more expensive than water, and if they remain in the final resin composition, they may be gradually released into the air as volatile organic compounds (VOCs), so it is desirable to avoid using them as much as possible.

[0005] Furthermore, in Patent Document 1, it was necessary to apply strong force to the cellulose fibers using a twin-screw kneader or the like in order to uniformly disperse the cellulose fibers in the molten resin. However, this causes the fibers to break during kneading with the resin, so even if the elastic modulus of the resulting resin composition is improved, the impact strength of the molded article decreases, making it difficult to use for structural materials that require both elastic modulus and impact strength.

[0006] International Publication No. 2020 / 235310

[0007] The present invention aims to provide a method for producing a cellulose fiber composition and a method for producing a cellulose fiber-containing resin composition that can improve both the elastic modulus and impact strength of a molded article of the cellulose fiber-containing resin composition, even when strong force is applied to the cellulose fibers in an aqueous system using a twin-screw kneader or the like.

[0008] As a result of diligent research, the inventors of this invention discovered that the above problems can be solved by forming a cellulose fiber composition by mixing cellulose fibers with a specific hydrophobic compound and an alkaline inorganic compound in an aqueous mixture and shearing it at a specific shear rate, thereby completing the present invention.

[0009] In other words, the present invention provides a method for producing a cellulose fiber composition using at least the following as raw materials: (1) 100 parts by mass of cellulose fiber (A), 5 to 30 parts by mass of a hydrophobic compound (B) which is a (meth)acrylic resin, styrene-(meth)acrylic resin, or polyolefin resin having one or more structures in its molecule consisting of an epoxy group, carboxyl group, carbamoyl group, carboxylic acid anhydride, or carboxylate, and 1 to 10 parts by mass of an alkaline inorganic compound (C), wherein the total solids content after preparation of a mixture containing at least (A), (B), and (C) is 25 to 85%, and the mixture is subjected to a shear rate of 1,500 s defined by the following formula. －１ A method for producing a cellulose fiber composition, characterized by including a step of shearing as described above, (formula) shear rate (s －１): Peripheral speed (m / s) ÷ clearance (m) <2> A method for producing a cellulose fiber composition according to <1>, characterized in that the alkaline inorganic compound (C) contains at least one alkaline earth metal compound. <3> A method for producing a cellulose fiber composition according to <1>, further characterized in that 0.3 to 5 parts by mass of a surfactant (D) with a surface tension of 42 mN / m or less is used as a raw material. <4> A method for producing a cellulose fiber-containing resin composition, comprising the step of kneading the cellulose fiber composition obtained by the method according to <1> with a thermoplastic resin, and characterized in that it contains 5 to 50 parts by mass of cellulose fibers.

[0010] According to the manufacturing method of the present invention, a cellulose fiber-reinforced resin composition can be obtained that achieves both elastic modulus and impact strength in the molded article.

[0011] Embodiments of the present invention will be described in detail below. The following description is merely an example of embodiments of the present invention and is not limited to this description. Furthermore, in this application, "(meth)acrylic" means methacrylic and / or acrylic.

[0012] <Raw Materials for Cellulose Fiber Composition> In the method for producing the cellulose fiber composition of the present invention, the raw materials for the cellulose fiber composition refer to the components that make up the mixture before shearing. In the method for producing the cellulose fiber composition of the present invention, the components that make up the mixture before shearing include, at a minimum, cellulose fibers (A), a hydrophobic compound (B) which is one of the following: (meth)acrylic resin, styrene-(meth)acrylic resin, or polyolefin resin having one or more structures of epoxy group, carbamoyl group, carboxyl group, carboxylic acid anhydride, or carboxylate salt in its molecule (hereinafter sometimes simply referred to as "hydrophobic compound (B)"), and an alkaline inorganic salt compound (C).

[0013] Cellulose fibers (A) are known to originate from plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., sea squirts), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc., and any of these can be used in the present invention. Preferably, the cellulose fiber is derived from plants or microorganisms, and more preferably, from plants. Among plant-derived cellulose fibers, pulp (particularly unbleached coniferous kraft pulp (NUKP) and bleached coniferous kraft pulp (NBKP)) is especially preferred. The raw material cellulose fiber may also be modified cellulose in which some of the functional groups of cellulose have been substituted. For example, acetyl-modified cellulose fiber obtained by substituting some of the hydroxyl groups of cellulose with acetic anhydride, or carboxymethyl cellulose fiber obtained by substituting some of the hydroxyl groups of cellulose with sodium monochloroacetate, etc., may be used.

[0014] The hydrophobic compound (B) is a (meth)acrylic resin, styrene-(meth)acrylic resin, or polyolefin resin that has one or more of the following structures in its molecule: epoxy group, carboxyl group, carbamoyl group, carboxylic acid anhydride, or carboxylate salt, and has a solubility of less than 1 g in 100 g of water at 25°C after drying the sample at 150°C. Epoxy groups, carboxyl groups, carbamoyl groups, carboxylic acid anhydrides, and carboxylate salts are highly polar and hydrophilic functional groups, and having one or more of these functional groups facilitates adhesion to the surface of cellulose fibers.

[0015] In this invention, (meth)acrylic resin is a polymer containing acrylic monomers as polymerization components, and styrene-(meth)acrylic resin is a copolymer containing acrylic monomers and styrene monomers as polymerization components. These resins may be used as is or as aqueous dispersions.

[0016] Acrylic monomers refer to (meth)acrylic acid and its derivatives, specifically including linear saturated alkyl group-containing monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, and stearyl (meth)acrylate; and branched saturated alkyl group-containing monomers such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples include alicyclic alkyl group-containing monomers such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; aromatic monomers such as phenyl (meth)acrylate and benzyl (meth)acrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and 2-methacryloyloxyethyl succinic acid; (meth)acrylates having functional groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycidyl (meth)acrylate, and ethoxydiethylene glycol (meth)acrylate; and (meth)acrylamides such as (meth)acrylamide, N-isopropyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, (meth)acryloylmorpholine, diacetone acrylamide, N-methylolacrylamide, and N-hydroxyethylacrylamide.

[0017] Styrene monomers refer to styrene and its derivatives. Specifically, examples of styrene monomers include styrene, α-methylstyrene, divinylbenzene, 4-methylstyrene, 4-t-butylstyrene, 4-n-octylstyrene, sodium styrenesulfonate, 4-vinylbenzoic acid, 4-aminostyrene, 4-methoxystyrene, 4-nitrostyrene, stilbene, and 4,4'-dimethylstilbene.

[0018] Polyolefin resins are homopolymers or copolymers of ethylene monomer, propylene monomer, or α-olefin monomer having 4 or more carbon atoms, or copolymers of the aforementioned acrylic monomers and / or styrene monomers with ethylene monomer, propylene monomer, or α-olefin monomer having 4 or more carbon atoms, and mixtures thereof.

[0019] There are no particular limitations on the method for introducing one or more structures from among epoxy groups, carboxyl groups, carbamoyl groups, carboxylic acid anhydrides, and carboxylate salts into the molecule of hydrophobic compound (B). A monomer having the structure may be selected and the polymerization reaction carried out, or a compound having the structure may be introduced by an addition reaction after the polymerization reaction. However, due to the ease of introduction, it is preferable to select a monomer having the structure and carry out the polymerization reaction.

[0020] While there are no particular limitations on the monomer having an epoxy group, examples include glycidyl (meth)acrylate, methyl (3,4-epoxycyclohexyl)acrylate, allyl glycidyl ether, and 4-hydroxybutyl acrylate glycidyl ether, with glycidyl (meth)acrylate being preferred.

[0021] The monomer having a carbamoyl group is not particularly limited, but (meth)acrylamide is preferred.

[0022] While there are no particular limitations on the monomer having a carboxyl group, examples include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxyethyl succinic acid; and unsaturated dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid, and citraconic acid, among which (meth)acrylic acid and maleic acid are preferred. Examples of carboxylate salts include alkali metal salts, alkaline earth metal salts, and ammonium salts of the monomer having a carboxyl group.

[0023] Examples of monomers having the structure of a carboxylic acid anhydride include crotonic acid anhydride and maleic acid anhydride, with maleic acid anhydride being preferred.

[0024] There are no restrictions on the method of polymerizing acrylic resins and / or styrene-acrylic resins; conventionally known methods such as solution polymerization, suspension polymerization, emulsion polymerization, and solvent-free bulk polymerization can be used. The reaction mechanism is also not particularly limited, and radical polymerization, anionic polymerization, cationic polymerization, coordination polymerization, and various living polymerizations can be used. Conventionally known compounds can be used as polymerization initiators and polymerization solvents.

[0025] In the case of hydrophobic compound (B), (meth)acrylic resins, styrene-(meth)acrylic resins, and polyolefin resins, it is preferable that monomers having these functional group structures are present in an amount of 10% to 40% by mass of the total polymerization components. An amount of 10% by mass or more improves the affinity with cellulose fibers and makes them easier to adsorb onto the cellulose surface, while an amount of 40% by mass or less facilitates the uniform dispersion of cellulose fibers.

[0026] In this invention, the hydrophobic compound (B) needs to be used in amounts of 5 to 30 parts by mass per 100 parts by mass of cellulose fiber (A), and using 15 to 30 parts by mass is preferable as it improves affinity with the cellulose fiber. If the amount is less than 5 parts by mass, it is insufficient to cover the surface of the cellulose fiber with the hydrophobic compound, and if it is more than 30 parts by mass, it becomes difficult to achieve both the elastic modulus and impact properties of the cellulose fiber resin composition.

[0027] Alkaline inorganic compounds (C) are inorganic compounds that, when dissolved or dispersed in water, cause the pH of the aqueous solution or dispersion to be greater than 7. Specifically, examples include carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, and barium carbonate; bicarbonates such as lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, and barium bicarbonate; metal oxides such as magnesium oxide and calcium oxide; and hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, zinc hydroxide, and aluminum hydroxide. By using alkaline inorganic compounds (C), when the obtained cellulose fiber composition is kneaded with a thermoplastic resin to obtain a cellulose fiber-containing resin composition, thermal degradation of the fibers due to organic acids derived from the cellulose fibers can be suppressed. In order to apply the cellulose fiber resin composition to a wide range of fields, it is preferable that the alkaline inorganic compound (C) has low solubility in water. The solubility in 100 g of water at 20°C is preferably 6 g or less, and more preferably 1 g or less. Examples of alkaline inorganic compounds include alkaline earth metal compounds such as magnesium carbonate, calcium carbonate, barium carbonate, magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, and barium hydroxide. Magnesium carbonate, calcium carbonate, magnesium oxide, calcium oxide, magnesium hydroxide, and calcium hydroxide are more preferred due to their availability. The solubility in 100 g of water at 20°C is 0.04 g for magnesium carbonate, 0.01 g for calcium carbonate, 0.01 g for magnesium oxide, 0.12 g for calcium oxide, less than 0.01 g for magnesium hydroxide, and 0.17 g for calcium hydroxide.

[0028] In the present invention, the amount of alkaline inorganic compound (C) used is 1 to 10 parts by mass, preferably 1 to 5 parts by mass, per 100 parts by mass of cellulose fiber (A).

[0029] <Mixing of Raw Materials> There are no particular restrictions on the mixing order or equipment for the raw materials that constitute the mixture before shearing, however, the total solid content concentration of the mixture containing cellulose fibers (A), hydrophobic compounds (B), and alkaline inorganic compounds (C) must be adjusted by adding water to be between 25% and 85%. The total solid content concentration can be calculated from the formula: weight of components other than solvent (kg) ÷ total weight including solvent (kg) × 100. It is preferable that the solvent be entirely water, and if other organic solvents are included, it is desirable that they constitute less than 5% of the total solvent. If the total solid content concentration is less than 25%, the resulting cellulose fiber composition will contain an excess of solvent, requiring excessive energy to remove the solvent, which is undesirable, and it is preferable to have a concentration of 40% or more. Furthermore, if the total solid content concentration is greater than 85%, the swelling of the cellulose fibers will be insufficient, and in the subsequent shearing process, the hydrophobic compound (B), which has one or more structures of epoxy groups, carboxyl groups, carbamoyl groups, carboxylic acid anhydrides, or carboxylate salts in its molecule, will have difficulty penetrating into the cellulose fibers.

[0030] Furthermore, by mixing a surfactant (D) having a surface tension of 42 mN / m or less, in addition to (A), (B), and (C) above, the dispersion of the cellulose fiber composition into the thermoplastic resin in subsequent processes becomes easier, and the material properties of the final cellulose resin composition are improved. A surface tension meter (DY-300, manufactured by Kyowa Interface Science Co., Ltd.) can be used to measure the surface tension. The surface tension of surfactant (D) is preferably 25 mN / m or more. It is preferable to use 0.1 to 5 parts by mass of surfactant (D) per 100 parts by mass of cellulose fiber (A), and more preferably 0.3 to 5 parts by mass. By using the above amounts, a sufficient surface tension reduction effect can be obtained, and the cellulose fibers can be appropriately fluffed during shearing, allowing the hydrophobic compound (B) to effectively penetrate into the cellulose fibers.

[0031] In addition to (A), (B), and (C) described above, fillers such as silicon dioxide and carbon black, and maleic anhydride-modified polyolefins may be mixed in, to the extent that they do not impair the effects of the present invention. The amount added is not particularly limited as long as it does not hinder the effects of the invention, but from the viewpoint of cost-effectiveness, the amount of maleic anhydride-modified polyolefin added is preferably 5 parts by mass or more and less than 50 parts by mass per 100 parts by mass of cellulose fiber (A). When maleic anhydride-modified polyolefin is used as (B), it is preferable to add it so that the total amount of maleic anhydride-modified polyolefin used as (B) is 5 parts by mass or more and less than 60 parts by mass per 100 parts by mass of cellulose fiber (A).

[0032] Next, a mixture containing at least (A), (B), and (C) is subjected to a shearing rate of 1,500 s. －１ A cellulose fiber composition is obtained by subjecting it to the above shearing treatment. Examples of apparatus for performing the above shearing treatment include single disc refiners, conical refiners, Henschel mixers (Nippon Coke Industries Co., Ltd.), Super Mixers (Kawata Co., Ltd.), Redigge mixers, PAM Apex mixers (Taiheiyo Kiko Co., Ltd.), Amixon mixers (Toyo High-Tech Co., Ltd.), co-directional twin-screw kneaders, and heterodirectional twin-screw kneaders, all of which have rotating parts. Using these apparatus, a mixture containing at least (A), (B), and (C) is subjected to 1,500 s. －１ When shearing is performed at such a high shear rate, the surface of the cellulose fibers swells with water and becomes fuzzy. Furthermore, hydrophobic compounds penetrate into the gaps in the fuzzy surface, allowing for hydrophobic treatment of the cellulose fiber surface even in an aqueous system. The shear rate is 1,500 s. －１ There are no particular restrictions as long as it is above 1,800s －１ Preferably, the above. Also, the shear rate is 250,000 s. －１ The following is preferable. The shear rate is defined by the following formula: (Formula) Shear rate (s －１ ): Peripheral speed (m / s) ÷ Clearance (m)

[0033] Specifically, in the case of a single disk refiner, a conical refiner, a Henschel mixer, a super mixer, a Lodige mixer, a Pumapex mixer, and an Amixon mixer, it is calculated from the peripheral speed of the stirring blade at the location with the highest peripheral speed on the outer periphery of the stirring blade and the size of the gap (clearance) between the stirring blade and the stirring tank. In the case of a co-rotating or counter-rotating twin-screw kneader, it is calculated from the peripheral speed at the outermost periphery of the rotating shaft and the size of the gap (clearance) between the outermost periphery and the kneader barrel portion. The clearance is preferably a value lower than 0.02 from the perspective of the shear efficiency of the mixture, and a value higher than 0.0001 can prevent excessive force from being applied to the fibers and causing them to be cut, which is preferable because it can achieve both the elastic modulus and impact strength of the molded body of the cellulose fiber-containing resin composition. The peripheral speed is preferably 0.4 m / s or more and 250 m / s or less within the range of the specifications of the device for applying the shear treatment. When the shear rate is lower than 1,500 s －１ -1, the fibrillation on the surface of the cellulose fibers becomes insufficient, and the hydrophobic compound cannot enter the gaps formed by the fibrillation. When the cellulose fiber composition obtained in this way is compounded with a thermoplastic resin, excessive force is applied to the fibers and they are cut, resulting in the inability to achieve both the elastic modulus and impact strength of the molded body of the cellulose fiber-containing resin composition.

[0034] In the present invention, a cellulose fiber-reinforced resin composition can be obtained by kneading a cellulose fiber composition obtained by the method described above with a thermoplastic resin. The thermoplastic resin is not particularly limited as long as it is one that is commonly used in molded articles. The thermoplastic resin may be the same type as the hydrophobic compound (B) or a different type. Specific examples of thermoplastic resins include polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers, and modified polyolefins obtained by reacting these polyolefins with maleic anhydride; polyamides such as polyacetal, nylon 6, nylon 66, nylon 11, and nylon 12; polyesters such as polylactic acid, polyethylene terephthalate, and polybutylene terephthalate; chlorine resins such as polyvinyl chloride and polyvinylidene chloride; fluororesins such as polyvinyl fluoride and polyvinylidene fluoride; polystyrene; ABS resin; petroleum resin, coumarone resin; terpene resin; rosin resin; thermoplastic elastomers such as olefin-based elastomers, vinyl chloride-based elastomers, urethane-based elastomers, polyester-based elastomers, and polyamide-based elastomers; polycarbonates such as ionomer resins, polyacrylonitrile, ethylene-vinyl acetate resin, ethylene-vinyl alcohol resin, polypropylene carbonate, and polycarbonate diol; modified polyphenylene ether; and methylpentene resin. Examples of the modified polyolefins mentioned above include maleic anhydride-modified polyolefins such as maleic anhydride-modified polyethylene and maleic anhydride-modified polypropylene.

[0035] Among these, polylactic acid and polyolefins are preferred because their low melting points make them less susceptible to thermal degradation of cellulose fibers. One or more of these can be used in combination.

[0036] In this process, the cellulose fibers are dispersed while the obtained cellulose fiber composition and thermoplastic resin are kneaded to obtain a cellulose fiber-containing resin composition. The kneader can be either a batch type or a continuous type. The kneading temperature should preferably be such that the cellulose fibers do not deteriorate due to heat. Specifically, kneading should preferably be done in the range of 100 to 250°C.

[0037] In the cellulose fiber-containing resin composition obtained by the present invention, within a range that does not interfere with the effects of the present invention, in the kneading step with a thermoplastic resin, resins other than the thermoplastic resin, various fillers such as talc, clay, glass fiber, crystal nucleating agents, crosslinking agents, hydrolysis inhibitors, antioxidants, lubricants, waxes, colorants, stabilizers, etc. may be blended.

[0038] To obtain a molded article using the cellulose fiber-containing resin composition obtained as described above, general molding methods can be used. For example, injection molding, extrusion molding, blow molding, compression molding, foam molding, etc. can be mentioned.

[0039] Also, the uses of the molded article using the cellulose fiber-containing resin composition of the present invention are not particularly limited. For example, interior and exterior materials and housings for transportation machinery such as automobiles, motorcycles, bicycles, railways, drones, rockets, aircraft, ships, etc., energy machinery such as wind turbines and hydraulic generators, home appliance housings such as air conditioners, refrigerators, vacuum cleaners, microwave ovens, AV equipment, digital cameras, personal computers, etc., electronic substrates, communication equipment housings such as mobile phones and smartphones, medical instruments such as walking canes and wheelchairs, shoes such as sneakers and business shoes, tires, balls for ball sports, ski boots, snowboard boards, golf clubs, protectors, fishing lines, artificial lures, etc. for sports goods, outdoor goods such as tents and hammocks, civil engineering and building materials such as wire coatings, water pipes, gas pipes, etc., building materials such as column materials, floor materials, decorative panels, window frames, heat insulating materials, etc., furniture such as bookshelves, desks, chairs, etc., industrial robots, household robots, hot melt adhesives, filaments and support agents for laminated 3D printers, packaging materials such as films and tapes, resin containers such as PET bottles, spectacle frames, trash cans, sharp pencil cases, etc. for daily sundries, etc. can be mentioned.

[0040] Hereinafter, examples of the present invention will be described. Note that the present invention is not limited to these examples.

[0041] <Manufacture of Hydrophobic Compound (B)> (Production Example 1)700 parts of water, 140 parts of styrene, 40 parts of α-methylstyrene, 60 parts of 2-ethylhexyl acrylate, 30 parts of acrylamide, 30 parts of glycidyl methacrylate, and 10 parts of Take Surf A-2821-S (manufactured by Takemoto Yushi) were added to a reaction vessel, and the mixture was heated to 90°C while blowing nitrogen. 3 parts of ammonium persulfate and 3 parts of sodium bisulfite were added as initiators, and the mixture was stirred for 4 hours to produce an aqueous solution of hydrophobic compound (B1).

[0042] (Production Example 2) 20 parts of acrylic acid, 80 parts of styrene, 2.0 parts of azobisisobutyronitrile, and 100 parts of isopropyl alcohol were charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube. The temperature was raised to 80°C while blowing nitrogen, and then 1.0 part of azobisisobutyronitrile was charged and held at the same temperature for 3 hours. Then, 51.9 parts of a 30% by mass aqueous potassium hydroxide solution was added, followed by 300 parts of water, and the temperature was further raised to distill off isopropyl alcohol, producing an aqueous solution of hydrophobic compound (B2).

[0043] (Production Example 3) 100 parts of xylene, 25 parts of 1-hexadecene, 25 parts of diisobutylene, and 50 parts of maleic anhydride were added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the mixture was heated to 150°C while blowing nitrogen. 3 parts of di-t-butyl peroxide was added as an initiator, and the mixture was stirred for 4 hours. Then, after distilling off xylene under reduced pressure, 69 parts of 25% aqueous ammonia and 300 parts of water were added to produce an aqueous solution of hydrophobic compound (B3).

[0044] (Example 1) [Steps to obtain cellulose fiber composition] 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 150 parts by mass of water, 30 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, 2 parts by mass of calcium carbonate (C), and 30 parts by mass of maleic anhydride-modified polypropylene (Hardren® PMA H-1000P, manufactured by Toyobo MC Co., Ltd.) were placed in a container and mixed. The total solid content concentration of the mixture was 44.1%. Next, the mixture was discharged from a twin-screw kneader (manufactured by Technovel Co., Ltd.) while applying the shear rate shown in Table 1 to obtain a cellulose fiber composition. The shear rate was calculated using the following formula: (Formula) Shear rate (s －１ ): Peripheral speed (m / s) ÷ Clearance (m)

[0045] (Example 2) A cellulose fiber composition was obtained by performing the same procedure as in Example 1, except that 20 parts by mass of hydrophobic compound (B1) were used and the mixture was discharged using a twin-screw kneader (manufactured by Japan Steel Works Ltd.) while applying the shear rate shown in Table 1.

[0046] (Example 3) 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 140 parts by mass of water, 30 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, and 1 part by mass of calcium hydroxide (C) were placed in a container and mixed. The total solid content concentration of the mixture was 40.1%. The mixture was then mixed for 80 minutes in a Henschel mixer (manufactured by Nippon Coke Industries, Ltd.) at the shear rate shown in Table 1 to obtain a cellulose fiber composition.

[0047] (Example 4) A cellulose fiber composition was obtained by the same procedure as in Example 1, except that 20 parts by mass of hydrophobic compound (B1) were used. The total solid content concentration of the mixture was 44.8%.

[0048] (Example 5) 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 150 parts by mass of water, 20 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, 2 parts by mass of calcium carbonate (C), and 30 parts by mass of maleic anhydride-modified polypropylene (Hardren® PMA H-1000P, manufactured by Toyobo MC Co., Ltd.) were placed in a container and mixed. The total solid content concentration of the mixture was 44.8%. The mixture was then discharged from a twin-screw kneader (manufactured by Japan Steel Works Ltd.) at the shear rate shown in Table 1 to obtain a cellulose fiber composition.

[0049] (Example 6) 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 67 parts by mass of water, 20 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, and 2 parts by mass of calcium carbonate (C) were placed in a container and mixed. The total solid content concentration of the mixture was 56.9%. The mixture was then extruded through a single disc refiner (manufactured by Aikawa Iron Works Co., Ltd.) at the shear rate shown in Table 1 to obtain a cellulose fiber composition.

[0050] (Example 7) The same procedure as in Example 1 was carried out except that 20 parts by mass of (B2) and 2 parts by mass of calcium hydroxide (C) were used as the hydrophobic compound to obtain a cellulose fiber composition. The total solid content concentration of the mixture was 42.0%.

[0051] (Example 8) The same procedure as in Example 1 was carried out except that 20 parts by mass of (B3) and 2 parts by mass of calcium hydroxide were used as the hydrophobic compound to obtain a cellulose fiber composition. The total solid content concentration of the mixture was 42.0%.

[0052] (Example 9) The same procedure as in Example 1 was carried out except that 2 parts by mass of calcium hydroxide (C) was used to obtain a cellulose fiber composition. The total solid content concentration of the mixture was 44.8%.

[0053] (Example 10) 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 33 parts by mass of water, 20 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, 2 parts by mass of calcium carbonate (C), 0.7 parts by mass of KM73 (manufactured by Shin-Etsu Chemical Co., Ltd., surface tension 41.9 mN / m) as surfactant (D), and 30 parts by mass of maleic anhydride-modified polypropylene (Hardren® PMA H-1000P, manufactured by Toyobo MC Co., Ltd.) were placed in a container and mixed. The total solid content concentration of the mixture was 68.0%. The mixture was then extruded using a twin-screw kneader (manufactured by Technovel Co., Ltd.) while applying the shear rate shown in Table 1 to obtain a cellulose fiber composition. [Surface tension measurement of surfactant] A surface tensile meter (DY-300, manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the surface tension of surfactant (D). Aqueous solutions of surfactants at different concentrations were prepared, their surface tensions were measured, and the lowest surface tension value was defined as the surface tension of the surfactant.

[0054] (Comparative Example 1) 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 33 parts by mass of water, 20 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, 2 parts by mass of calcium carbonate (C), and 30 parts by mass of maleic anhydride-modified polypropylene (Hardren® PMA H-1000P, manufactured by Toyobo MC Co., Ltd.) were placed in a container and mixed. The total solid content concentration of the mixture was 68.3%. The mixture was then mixed for 80 minutes in a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.) at the shear rate shown in Table 1 to obtain a cellulose fiber composition.

[0055] (Comparative Example 2) The same procedure as in Example 1 was carried out except that the hydrophobic compound (B) was 0 parts by mass and the calcium carbonate (C) was 0 parts by mass to obtain a cellulose fiber composition. The total solid content concentration of the mixture was 46.4%.

[0056] (Comparative Example 3) The same procedure as in Example 1 was carried out except that the hydrophobic compound (B1) was 20 parts by mass and calcium carbonate (C) was 0 parts by mass to obtain a cellulose fiber composition. The total solid content concentration of the mixture was 39.1%.

[0057] Table 1 shows the calculated shear rate for each example, and Table 2 shows the amount of material used, the shear rate, and the solid content during shearing for each example.

[0058]

[0059]

[0060] Explanation of terms in the table: Ca: Calcium

[0061] (Example 11) [Steps to obtain a cellulose fiber-reinforced resin composition] 65 parts by mass of the cellulose fiber composition from Example 1 (of which 40 parts by mass are cellulose fibers) and 35 parts by mass of polypropylene resin (Prime Polypro® J108M, manufactured by Prime Polymer Co., Ltd.) as a thermoplastic resin were put into a twin-screw kneader (manufactured by Technobel Co., Ltd.) and melt-kneaded at 170°C to obtain a cellulose fiber-reinforced resin composition containing 40 parts by mass of cellulose fibers.

[0062] (Example 12) The same procedure as in Example 11 was followed, except that the cellulose fiber composition of Example 2 was used as 61 parts by mass (of which 40 parts by mass was cellulose fiber) and polypropylene resin was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 40 parts by mass of cellulose fiber.

[0063] (Example 13) 52 parts by mass of the cellulose fiber composition from Example 3 (of which 40 parts by mass are cellulose fibers), 12 parts by mass of maleic anhydride-modified polypropylene (Hardren® PMA H-1000P, manufactured by Toyobo MC Co., Ltd.), and 36 parts by mass of polypropylene resin (Prime Polypro® J108M, manufactured by Prime Polymer Co., Ltd.) as a thermoplastic resin were put into a twin-screw kneader (manufactured by Technobel Co., Ltd.) and melt-kneaded at 170°C to obtain a cellulose fiber-containing resin composition containing 40 parts by mass of cellulose fibers.

[0064] (Example 14) The same procedure as in Example 11 was followed, except that 30 parts by mass of the cellulose fiber composition of Example 4 (of which 20 parts by mass are cellulose fibers) and 70 parts by mass of polypropylene resin were used as the cellulose fiber composition to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fibers.

[0065] (Example 15) The same procedure as in Example 11 was followed, except that 30 parts by mass of the cellulose fiber composition of Example 5 (of which 20 parts by mass are cellulose fibers) and 70 parts by mass of polypropylene resin were used as the cellulose fiber composition to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fibers.

[0066] (Example 16) The same procedure as in Example 13 was followed to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fiber, except that the cellulose fiber composition of Example 6 was used as the cellulose fiber composition (of which 20 parts by mass were cellulose fibers), 6 parts by mass of maleic anhydride-modified polypropylene (Hardren® PMA H-1000P manufactured by Toyobo MC Co., Ltd.), and 70 parts by mass of polypropylene resin.

[0067] (Example 17) The same procedure as in Example 14 was followed, except that the cellulose fiber composition of Example 7 was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fibers.

[0068] (Example 18) The same procedure as in Example 14 was followed, except that the cellulose fiber composition of Example 8 was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fibers.

[0069] (Example 19) The same procedure as in Example 14 was followed, except that the cellulose fiber composition of Example 9 was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fibers.

[0070] (Example 20) The same procedure as in Example 11 was followed, except that the cellulose fiber composition of Example 10 was used as 61 parts by mass (of which 40 parts by mass was cellulose fiber) and polypropylene resin was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 40 parts by mass of cellulose fiber.

[0071] (Comparative Example 4) The same procedure as in Example 11 was followed, except that the cellulose fiber composition of Comparative Example 1 was used as 61 parts by mass (of which 40 parts by mass was cellulose fiber) and polypropylene resin was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 40 parts by mass of cellulose fiber.

[0072] (Comparative Example 5) The same procedure as in Example 11 was followed, except that 26 parts by mass of the cellulose fiber composition of Comparative Example 2 (of which 20 parts by mass are cellulose fibers) and 74 parts by mass of polypropylene resin were used as the cellulose fiber composition to obtain a cellulose fiber-containing resin composition containing 20 parts by mass of cellulose fibers.

[0073] (Comparative Example 6) The same procedure as in Example 11 was followed, except that the cellulose fiber composition of Comparative Example 3 was used as 60 parts by mass (of which 40 parts by mass was cellulose fiber) and polypropylene resin was used as the cellulose fiber composition, to obtain a cellulose fiber-containing resin composition containing 40 parts by mass of cellulose fiber.

[0074] The cellulose fiber-reinforced resin compositions obtained in Examples 11-20 and Comparative Examples 4-6 were evaluated by the following method.

[0075] [Evaluation of Resin Composition] Using the obtained cellulose fiber-reinforced resin composition, bar-type test specimens described in JIS standard K7171 were molded using an injection molding machine, and the flexural modulus was measured in accordance with JIS K7171 using a universal testing machine Tensilon® RTM-50 (manufactured by Orientec Co., Ltd.). In addition, the Charpy impact strength was measured using a Charpy impact testing machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a 2.0 J hammer without making a notch in the same test specimen.

[0076] The results are shown in Tables 3 and 4. Note that the mechanical properties of cellulose fiber-reinforced resin compositions depend heavily on the cellulose concentration in the resin. Therefore, it is appropriate to compare resin compositions with the same cellulose concentration. Table 3 shows the evaluation results for a cellulose fiber-reinforced resin composition containing 40 parts by mass of cellulose, and Table 4 shows the evaluation results for a cellulose fiber-reinforced resin composition containing 20 parts by mass of cellulose.

[0077]

[0078]

[0079] Explanation of terms in Tables 3 and 4: PP: Polypropylene resin

[0080] Comparing Examples 11, 12, 13, and 20, in which the cellulose fiber content in the resin is 40%, with Comparative Example 4, 1,500s －１ When the cellulose fiber composition is manufactured using the above shear rates, the resulting molded cellulose fiber-containing resin composition exhibits higher elastic modulus and impact strength than the molded article in Comparative Example 1. In particular, in Example 20, the addition of surfactant (D) makes it possible to achieve both higher elastic modulus and impact strength in the molded article. Furthermore, comparing Examples 11, 12, 13, and 20 with Comparative Example 6, it can be seen that there is a difference in the impact strength of the molded article depending on the presence or absence of alkaline inorganic salts. Comparing Examples 14 to 19, in which the cellulose fiber content in the resin is 20%, with Comparative Example 5, it can be seen that there is a difference in the elastic modulus and impact strength of the molded article depending on the presence or absence of hydrophobic compounds and alkaline inorganic salts.

[0081] (Example 21) [Steps to obtain a cellulose fiber composition] A cellulose fiber composition was obtained by performing the same procedure as in Example 10.

[0082] (Example 22) [Steps to obtain cellulose fiber composition] 100 parts by mass of bleached coniferous kraft pulp (NBKP), which is cellulose fiber (A), 33 parts by mass of water, 20 parts by mass of the hydrophobic compound (B1) obtained in Production Example 1, 2 parts by mass of calcium carbonate (C), and 0.7 parts by mass of KM73 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a surfactant (D) were placed in a container and mixed. The mixture was then processed in a twin-screw kneader (manufactured by Technovel Co., Ltd.) at a shear speed of approximately 2,600 s. －１ A cellulose fiber composition was obtained by extruding while applying a certain process. The total solid content concentration during the shearing treatment was 63.1%.

[0083] (Comparative Example 7) The same procedure as in Comparative Example 2 was performed to obtain a cellulose fiber composition.

[0084] (Comparative Example 8) [Steps to obtain a cellulose fiber composition] The same procedure as in Comparative Example 2 was carried out, except that maleic anhydride-modified polypropylene (Hardlen® PMA H-1000P manufactured by Toyobo MC Co., Ltd.) was set to 0 parts by mass, to obtain a cellulose fiber composition.

[0085] Table 5 shows the calculated shear rate for each embodiment, and Table 6 shows the amount of material used, the shear rate, and the solid content during shearing for each embodiment.

[0086]

[0087]

[0088] Explanation of terms in the table: Ca: Calcium

[0089] (Example 23) [Steps to obtain a cellulose fiber-reinforced resin composition] 76 parts by mass of the cellulose fiber composition of Example 21 (of which 50 parts by mass are cellulose fibers) and 24 parts by mass of polyethylene resin (Suntech HD J320, manufactured by Asahi Kasei Chemicals Corporation) as a thermoplastic resin were put into a twin-screw kneader (manufactured by Technovel Co., Ltd.) and melt-kneaded at 170°C to obtain a cellulose fiber-reinforced resin composition containing 50 parts by mass of cellulose.

[0090] (Example 24) As the cellulose fiber composition, 49 parts by mass of the cellulose fiber composition of Example 22 (of which 40 parts by mass are cellulose fibers), and as the thermoplastic resin, polylactic acid (Ingeo, manufactured by NatureWorks Co., Ltd.) ＴＭ 51 parts by mass of biopolymer 4032D was placed into a twin-screw kneader (manufactured by Technovel Co., Ltd.) and melt-kneaded at 170°C to obtain a cellulose fiber-reinforced resin composition containing 40 parts by mass of cellulose.

[0091] (Comparative Example 9) [Step to obtain a cellulose fiber-reinforced resin composition] 65 parts by mass of the cellulose fiber composition of Comparative Example 7 (of which 50 parts by mass are cellulose fibers) and 35 parts by mass of polyethylene resin (Suntech HD J320, manufactured by Asahi Kasei Chemicals Corporation) as a thermoplastic resin were put into a twin-screw kneader (manufactured by Technovel Co., Ltd.) and melt-kneaded at 170°C to obtain a cellulose fiber-reinforced resin composition containing 50 parts by mass of cellulose.

[0092] (Comparative Example 10) [Step to obtain a cellulose fiber-containing resin composition] 40 parts by mass of the cellulose fiber composition of Comparative Example 8 as the cellulose fiber composition, and polylactic acid (Ingeo, manufactured by NatureWorks Co., Ltd.) as the thermoplastic resin. ＴＭ 60 parts by mass of biopolymer 4032D was placed into a twin-screw kneader (manufactured by Technovel Co., Ltd.) and melt-kneaded at 170°C to obtain a cellulose fiber-reinforced resin composition containing 40 parts by mass of cellulose.

[0093] Tables 7 and 8 show the evaluation results of the cellulose fiber-reinforced resin compositions obtained in Examples 23-24 and Comparative Examples 9-10.

[0094]

[0095]

[0096] Explanation of terms in Tables 7 and 8: PE: Polyethylene resin PLA: Polylactic acid

[0097] The molded articles of the cellulose fiber-reinforced resin composition obtained by the manufacturing method of the present invention exhibit higher elastic modulus and impact strength compared to the molded articles of the comparative examples, regardless of whether polyethylene resin or polylactic acid is used as the thermoplastic resin, indicating that the method can be applied to a variety of thermoplastic resins.

Claims

1. A method for producing a cellulose fiber composition using at least 100 parts by mass of cellulose fiber (A), 5 to 30 parts by mass of a hydrophobic compound (B) which is one of (meth)acrylic resin, styrene-(meth)acrylic resin, or polyolefin resin having one or more structures of epoxy group, carboxyl group, carbamoyl group, carboxylic acid anhydride, or carboxylate salt in its molecule, and 1 to 10 parts by mass of an alkaline inorganic compound (C) as raw materials, wherein the total solid content concentration after preparation of a mixture containing at least (A), (B), and (C) is 25 to 85%, and the mixture is subjected to a shear rate of 1,500 s defined by the following formula. －１ A method for producing a cellulose fiber composition, characterized by including a step of shearing as described above. (Formula) Shear rate (s －１ ): Peripheral speed (m / s) ÷ Clearance (m) 2. A method for producing a cellulose fiber composition according to claim 1, characterized in that the alkaline inorganic compound (C) contains at least one alkaline earth metal compound.

3. A method for producing a cellulose fiber composition according to claim 1, further characterized in that 0.3 to 5 parts by mass of a surfactant (D) with a surface tension of 42 mN / m or less is used as a raw material.

4. A method for producing a cellulose fiber-containing resin composition, comprising the step of kneading a cellulose fiber composition obtained by the manufacturing method described in claim 1 with a thermoplastic resin, characterized in that the composition contains 5 to 50 parts by mass of cellulose fibers.

Images