TWI807559B - Resin composite, method for producing resin composite, and cellulose fiber prefibrillated product - Google Patents

Abstract

A resin composite, comprising resin and cellulose fibers, wherein the resin composite is formed by kneading the resin and a cellulose fiber pre-defibrated product by using a single-shaft or multi-shaft kneading machine, the cellulose fiber pre-defibrated product is formed by mechanically treating pulp, in the cellulose fiber pre-defibrated product, the fibers with a length of 0.1 mm or more and less than 0.5 mm exist in a proportion of 40% or more and less than 58%, and the fibers with a length of 1.5 mm or more and less than 2.0 mm exist in a proportion of more than 5% and less than 10%. The proportion of the cellulose fibers contained in the resin composite having an average fiber width of 1 μm or less is 50% by volume or more.

Description

Resin composite, method for producing resin composite, and cellulose fiber prefibrillated product

The present invention relates to a resin composite containing micronized cellulose fibers, a method for producing the resin composite, and a cellulose fiber predefibrated product used in the resin composite.

The fine fibrous cellulose obtained by 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. Microfibrous cellulose is light, has high strength, high modulus of elasticity, and low coefficient of linear thermal expansion, and thus can be suitably used as a reinforcing material for a resin composition.

As a method of producing a resin composite containing micronized cellulose fibers, there are a method of compounding cellulose that has been micronized in advance to a nanometer level in a resin, and a method of defibrating cellulose that has been lightly predefibrated by a method such as mechanical defibration with a resin using a kneader. Regarding the latter method, Patent Document 1 discloses a beating treatment of pulp under low concentration conditions. In addition, Patent Document 1 describes that a resin composite including cellulose subjected to predefibration by this method is superior in tensile modulus of elasticity and tensile strength compared to resin alone.

In addition, in Patent Document 2, cellulose in which a part of the hydroxyl groups of cellulose are substituted with carbamate groups is obtained by heat-treating cellulose raw materials and urea. The raw material is micronized by mechanical treatment (prefibrillation) to obtain fine fibrous cellulose. Although the solid content concentration of the cellulose raw material at the time of prefibrillation is not described, the fine fibrous cellulose obtained by this method has a freeness of 100 mL or less, has lower hydrophilicity than conventional fine fibrous cellulose, and has a high affinity with low-polarity resins, etc., and thus is dispersed in the resin with high uniformity, thereby providing a composite with high tensile strength. In addition, Patent Document 3 and Patent Document 4 disclose techniques for increasing the solid content concentration by lowering the pH of fibril cellulose that is beated and miniaturized, thereby lowering water retention and increasing the concentration.

However, there is a demand for a resin composite that not only has high tensile strength but also has an excellent balance with other properties such as tensile elongation.

[Prior art literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2016-176052

[Patent Document 2] Japanese Patent Laid-Open No. 2019-1876

[Patent Document 3] Japanese Patent Application Publication No. 2015-508839

[Patent Document 4] Japanese Patent Application Publication No. 2017-527660

An object of the present invention is to provide a resin composite which has a high tensile modulus of elasticity and high tensile strength, and has an excellent balance with tensile elongation. Moreover, the object of this invention is to provide the manufacturing method of the resin composite which can obtain this resin composite. In addition, the object of the present invention is to provide a method for the resin Cellulose fiber prefibrillation in composites.

The present invention provides the following.

(1) A resin composite body comprising resin and cellulose fibers, wherein the resin composite body is characterized in that the resin composite body is obtained by kneading the resin and cellulose fiber pre-defibrated material using a uniaxial or multi-axial kneading machine, the cellulose fiber pre-defibrated material is obtained by mechanically treating pulp, and in the cellulose fiber pre-defibrated material, fibers with a length of 0.1 mm or more and less than 0.5 mm are present in a proportion of 40% or more and less than 58%, and fibers with a length of 1.5 mm or more and less than 2.0 mm are present at a ratio of 5% or more And the ratio of less than 10% exists, and the ratio of the average fiber width of the said cellulose fiber contained in the said resin composite is 1 micrometer or less is 50 volume% or more.

(2) The resin composite according to (1), wherein the solid content concentration of the pulp during the mechanical treatment is 10% by mass or more.

(3) The resin composite according to (1) or (2), wherein the mechanical treatment is performed using at least one of a disk refiner and a conical refiner.

(4) A method for manufacturing a resin composite body, which is a method for manufacturing a resin composite body including resin and cellulose fibers. The manufacturing method of the resin composite body includes: a mechanical treatment step of mechanically processing pulp to obtain a cellulose fiber pre-defibrated product; and a kneading step of kneading the resin and the cellulose fiber pre-defibrated product using a single-shaft or multi-shaft kneading machine to obtain a resin composite body, and in the cellulose fiber pre-defibrated product, the fiber length is 0.1 mm or more and less than 0.5 mm and is 40% or more And the ratio of less than 58% exists, the fiber length of 1.5 mm or more and less than 2.0 mm exists in the ratio of 5% or more and less than 10%, and the ratio of the average fiber width of the cellulose fibers contained in the resin composite is 1 μm or less is 50% by volume or more.

(5) A pre-defibrated cellulose fiber for use in a resin composite, wherein the pre-defibrated cellulose fiber has a fiber length of 0.1 mm to less than 0.5 mm in a proportion of 40% to less than 58%, and a fiber length of 1.5 mm to less than 2.0 mm exists in a proportion of 5% to less than 10%.

According to the present invention, it is possible to provide a resin composite having a high tensile modulus of elasticity, high tensile strength, and an excellent balance with tensile elongation. In addition, a method for producing a resin composite capable of obtaining the resin composite can be provided. In addition, prefibrillated cellulose fibers used in the resin composite can be provided.

Hereinafter, the resin composite of the present invention will be described. In the present invention, "~" includes end values. That is, "X~Y" includes the value X and the value Y at both ends thereof.

The resin composite of the present invention includes resin and cellulose fibers. The resin composite is obtained by kneading the resin and cellulose fiber pre-defibrated material by using a single-shaft or multi-shaft kneader. The cellulose fiber pre-defibrated material is obtained by mechanically treating pulp. In the cellulose fiber pre-defibrated material, the fiber length of 0.1 mm or more and less than 0.5 mm exists in a proportion of 40% or more and less than 58%, and the fiber length is 1.5 mm or more and not less than 58%. The ratio of 2.0 mm to 5% to less than 10% exists, and the ratio of the average fiber width of the cellulose fibers contained in the resin composite to 1 μm or less is 50% by volume or more. The fiber length distribution and fine component measurement of the cellulose fiber predefibrated product represent the number average fiber length based on the International Standards Organization (ISO) 16065, and the average fiber length can be obtained by image analysis of a fiber tester manufactured by Lorentzen & Wettre, a fiber tester manufactured by ABB Co., Ltd., and a fractionator manufactured by Valmet Corporation.

(cellulose fiber)

In the present invention, cellulose fibers refer to fibrous cellulose, and may further include fibrous cellulose derivatives. From the viewpoint of achieving a sufficient balance between the strength-improving effect and elongation, the ratio of the average fiber width of the cellulose fibers contained in the resin composite of the present invention is 50% by volume or more, preferably 55% by volume or more, more preferably 60% by volume or more, and still more preferably 65% by volume or more. Here, the average fiber width of the cellulose fibers contained in the resin composite can be measured by X-ray computerized tomography (hereinafter, it may be abbreviated as X-CT (X-ray computed tomography)).

From the viewpoint of obtaining a sufficient reinforcing effect, the content of the cellulose fibers contained in the resin composite of the present invention is preferably 0.5% by mass to 30% by mass, more preferably 1.0% by mass to 25% by mass, and still more preferably 3.0% by mass to 20% by mass, based on the entire resin composite.

(resin)

Examples of the resin used in the present invention include general thermoplastic resins having a melting temperature of 250° C. or lower.

Common thermoplastic resins include polyolefin resin, polyamide resin, polyvinyl chloride, polystyrene, polyvinylidene chloride, fluororesin, (meth)acrylic resin, polyester, polylactic acid, copolymer resin of lactic acid and ester, polyglycolic acid, acrylonitrile-butadiene-styrene copolymer (ABS (acrylonitrile butadiene styrene) resin), polyphenylene ether, polyurethane, polyacetal, vinyl ether resin, poly Pine-based resins, cellulose-based resins (triacetylated cellulose, diacetylated cellulose, etc.) and the like.

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

In addition, polyamide resin (polyamide, PA) is also expected to interact with hydroxyl groups or acetyl groups of cellulose that are not affected by urea, and can be preferably used. Examples of PA include 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), polyamide 612 (nylon 612, Aliphatic PA such as PA612), aromatic PA containing aromatic diamine such as phenylenediamine and aromatic dicarboxylic acid such as terephthaloyl chloride or isophthaloyl chloride, or derivatives thereof. From the viewpoint of high affinity with cellulose fibers and cellulose nanofibers, aliphatic PA is preferably used, PA6, PA11, and PA12 are more preferably used, and PA6 is particularly preferably used. In addition, one type of polyamide resin may be used alone, or two or more types of polyamide resin may be used in combination.

The exemplified resins described above can be used not only as homopolymers but also as block copolymers made of copolymers containing half or less of resins having various known functions.

In addition, a resin containing a compatibilizing resin can be used as the "resin for masterbatch" described later. Here, the compatibilizing resin is a resin used for the purpose of uniformly mixing the cellulose fiber and the thinning resin or improving adhesion.

(Compatibilized resin)

Examples of compatibilizing resins that can be used in the present invention include polymer resins having a low-molecular-weight dicarboxylic acid capable of forming anhydrides such as maleic acid, succinic acid, and glutaric acid on polyolefin chains such as polypropylene and polyethylene. Among them, it is preferable to use a resin mainly composed of maleic anhydride-modified polypropylene (MAPP) or maleic anhydride-modified polyethylene (MAPE) with maleic acid added thereto, respectively, together with a thinning resin.

Factors that determine the characteristics of the compatibilizing resin include the added amount of dicarboxylic acid and the weight average molecular weight of the polyolefin resin as the base material. A polyolefin resin having a large amount of added dicarboxylic acid improves the compatibility with hydrophilic polymers such as cellulose, but the molecular weight of the resin decreases during the addition, and the strength of the molded product decreases. As the best balance, the added amount of dicarboxylic acid is 20 mgKOH/g~100 mgKOH/g, more preferably 45 mgKOH/g~65 mgKOH/g. When the added amount is small, there are fewer interaction points in the resin with the hydroxyl group of cellulose, the hydroxyl group contained in the modified cellulose, or the modified functional group. In addition, when the amount of addition is large, the molecular weight of the polyolefin resin as the base material decreases due to self-aggregation caused by hydrogen bonds between carboxyl groups in the resin, etc., or the molecular weight of the polyolefin resin as the base material decreases, and the reinforcement as a reinforcement cannot be achieved. The strength of the resin. The molecular weight of the polyolefin resin is preferably from 35,000 to 250,000, more preferably from 50,000 to 100,000. When the molecular weight is less than this range, the strength of the resin decreases, and when it exceeds this range, the viscosity rises greatly during melting, the workability during kneading decreases, and it becomes a cause of molding failure.

The amount of the compatibilizing resin having the above characteristics is preferably 10% by mass to 70% by mass, more preferably 20% by mass to 50% by mass, relative to 100% by mass of the total amount of cellulose fiber components (hereinafter sometimes referred to as "the amount of cellulose") contained in the cellulose fibers. It is considered that if the added amount exceeds 70% by mass, the introduction of urea-derived isocyanic acid into the cellulose fiber will be inhibited, or the complex formation of the compatibilizer and urea will be promoted.

In addition, one kind of compatibilizing resin may be used alone, or may be used as a mixture of two or more kinds of resins. In addition, when used as a graft body of one or more polymers and polyolefin, the polyolefin resin constituting the graft body is not particularly limited, and polyethylene, polypropylene, polybutene, etc. can be used from the viewpoint of easy production of the graft body.

In the present invention, when the compatibilizing resin is included in the resin, a low-molecular-weight auxiliary agent imparting a primary amine, such as urea, may be added from the viewpoint of improving the strength of the obtained resin composite. Urea is decomposed into ammonia and isocyanic acid when the temperature exceeds 135°C. It is considered that by kneading urea and cellulose fibers at the same time, the unmodified hydroxyl groups newly appearing from the inside of the cellulose fibers react with the generated isocyanic acid through kneading to promote the formation of urethane bonds. It is speculated that the hydrophobicity is improved compared to cellulose fibers that have not been treated with urea. Furthermore, by compatibilizing resin with acid anhydride Simultaneously, melt kneading can promote the ionic bonding between the newly introduced amine group and the carboxylic acid of the compatibilizing resin on the surface of the cellulose fiber through urea treatment, thereby forming a composite of the cellulose fiber and the compatibilizing resin more firmly.

From the viewpoint of suppressing fiber aggregation and strength reduction due to excessive compounding amount of urea, the compounding amount when urea is used as an auxiliary agent is preferably 10 mass % to 100 mass %, more preferably 15 mass % to 80 mass %, and still more preferably 20 mass % to 70 mass %, based on 100 mass % of the total amount of the cellulose fiber component (hereinafter sometimes referred to as "cellulose amount") contained in the cellulose fiber contained in cellulose and hemicellulose.

(Manufacturing method of resin composite)

The manufacturing method of the resin composite body of the present invention includes: a mechanical treatment step of mechanically processing the pulp to obtain a cellulose fiber predefibrate; and a kneading step of kneading the resin and the obtained cellulose fiber predefibrate by using a single-shaft or multi-shaft kneader to obtain a resin composite.

(mechanical processing step)

In the mechanical treatment step of the present invention, the pulp in the cellulose raw material is mechanically treated to obtain a cellulose fiber predefibrated product.

(cellulose raw material)

In the present invention, the so-called cellulose raw material refers to materials in various forms mainly composed of cellulose, including lignocellulose (needle unbleached kraft pulp (NUKP)) of conifers, examples of which include: pulp (bleached or unbleached wood pulp, bleached or unbleached non-wood pulp, refined cotton linters, jute (jute), manila hemp (manila hemp), kenaf (kenaf) and other herbal sources pulp, etc.), borrow Natural cellulose such as cellulose produced by microorganisms such as acetic acid bacteria, regenerated cellulose obtained by dissolving cellulose in a certain solvent such as cuproammonia solution or morpholine derivatives and then precipitating, microfine cellulose obtained by depolymerizing cellulose by hydrolysis, alkali hydrolysis, enzymatic decomposition, blasting treatment, vibration ball milling and other mechanical treatments of the cellulose raw material, various cellulose derivatives that do not affect the degree of acetylation modification, etc.

Furthermore, lignocellulose is a complex carbohydrate polymer constituting the cell wall of plants, and mainly includes polysaccharide cellulose, hemicellulose, and lignin which is an aromatic polymer. The lignin content can be adjusted by delignifying or bleaching pulp as a raw material.

In the present invention, pulp is used as a cellulose raw material, and the pulp is mechanically treated to obtain a cellulose fiber predefibrated product. In the present invention, the so-called mechanical treatment generally refers to mixing fibers in a dispersion medium represented by water and further miniaturizing or fibrillating, including beating, defibrating, and dispersing. Micronization means reduction in fiber length, fiber diameter, etc., and fibrillation means increase in fluff of fibers. The device used for mechanical treatment is not limited, for example, high-speed rotary type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, etc. can be used. High-pressure or ultra-high pressure homogenizers, refiners, disc refiners such as single-disc refiners or double-disc refiners, conical refiners, beaters, PFI mills, ball mills, stone mortar mills, sand grinders, impact mills, and Dyno mills can be used. Dyno mill, ultrasonic mill, Kanda grinder, attritor, vibration mill, cutter mill, jet mill, household juicer mixer, mortar, kneader, disperser, high-speed disintegrator, top refiner, etc. A person who uses water-containing pulp and metal or a knife to act on pulp fibers, or uses pulp fibers to rub against each other. In the present invention, the mechanical treatment is preferably a beating treatment using a Niagara beater, a refiner, or a kneader because fibrillation of fibers can be efficiently performed, and further preferably a beating treatment using a disc refiner or a conical refiner capable of high-concentration treatment.

The mechanical treatment is carried out using a mixture containing the above-mentioned pulp and a dispersion medium, and the solid content concentration at this time is 10% by mass or more, preferably 15% by mass or more, and more preferably 18% by mass or more (mechanical treatment at this concentration is also referred to as "high-concentration mechanical treatment"). The dispersion medium is not limited, and an organic solvent or water can be used, but water is preferred. The solid content concentration refers to the concentration of solid content in the mixture subjected to mechanical treatment. Mechanical treatment such as beating is performed on the pulp under the condition that the solid content concentration is as high as 10% by mass or more, so that the advantages of improving processing efficiency and improving operability can be obtained. As operability, for example, it is possible to directly transport high-concentration pulp without diluting treatment after high-concentration mechanical treatment, or the viscosity of pulp dispersion liquid after high-concentration mechanical treatment is not high, the transport efficiency in the pump is good, and the dispersion liquid has little sticking in the storage container, etc. Furthermore, when performing a drying process after a high-concentration mechanical process, the amount of the dispersion medium which volatilizes is small, and drying efficiency is also mentioned. Furthermore, in the pulp of the present invention, when the chemically modified pulp is subjected to a high-concentration mechanical treatment, the viscosity of the dispersion is less likely to increase, which is preferable.

By setting the pulp concentration at the time of mechanical treatment to be high, it is possible to suppress the increase of the fine components described later caused by the excessive swelling of the pulp, so that the residual resin in the resin composite can be suppressed. Leave proper long fibers.

If the solid content concentration during the mechanical treatment exceeds 50% by mass, the material is likely to be scorched as the process is dried in the device. Therefore, it is preferable to process under the conditions of 50% by mass or less, and more preferably 40% by mass or less.

As the degree of mechanical treatment, the freeness (C.S.F) is preferably about 100mL~500mL, more preferably about 120mL~450mL, and more preferably about 150mL~250mL. By setting the freeness below the upper limit, the effect can be exhibited, and by setting the freeness above the lower limit, the operation is excellent, and furthermore, it is possible to suppress the phenomenon that the effect of improving the strength of the resin composite obtained by kneading with the resin is hindered due to the damage to the cellulose fiber and the shortening of the fibers.

In the present invention, in the cellulose fiber pre-defibrated product, the fiber length distribution is expanded by high-concentration mechanical treatment, and the final resin composite appropriately contains long fibers that contribute to the enhancement of physical properties and fine fibers that contribute to the improvement of the tensile elongation value of the resin while maintaining high reinforcement. 5% to less than 10% of fibers having a fiber length of 0.1 mm to less than 0.5 mm are present at 50% to less than 55%, and fibers having a fiber length of 1.5 mm to less than 2.0 mm are present at 6% to less than 10%. In addition, in this invention, a fiber length shows the number average fiber length based on ISO16065.

In the present invention, the cellulose fiber predefibrate preferably contains 35%-50% of fine components, more preferably contains 37%-48% of fine components. Here, the so-called The fine component means fibers having a fiber length of 0.2 mm or less. If there are many fine components, although defibration will be performed by the kneading mentioned later, if it exceeds 50%, it will become difficult to leave long fibers in the resin composite, so it is preferable to use an appropriate amount.

Furthermore, in the present invention, the predefibrated cellulose fiber can be used in an unmodified state, or can be chemically modified by acetylation, oxidation, etherification, esterification, or the like.

(Acetylation modification)

The acetylated cellulose fiber predefibrate (sometimes simply referred to as "acetylated pulp") that can be used in the present invention is one in which the hydrogen atoms of the hydroxyl groups present on the cellulose surface of the cellulose raw material are substituted with acetyl groups (CH ₃ —CO—). By substituting with acetyl group, the hydrophobicity is improved, and the aggregation during drying is reduced, so the workability is improved, and it is easy to disperse or defibrate in the resin after kneading. In addition, since the highly reactive hydroxyl group is substituted with an acetyl group, thermal decomposition of cellulose can be suppressed, and heat resistance during kneading is improved. The degree of substitution (degree of substitution, DS) of the acetylated pulp is adjusted to preferably 0.4 to 1.3, more preferably 0.6 to 1.1, from the viewpoint of workability and maintenance of crystallinity of the cellulose fiber.

(acetylation reaction)

Regarding the acetylation reaction, when the raw material is suspended in an anhydrous aprotic polar solvent capable of swelling the cellulose raw material, such as N-methylpyrrolidone (NMP) or N,N-dimethylformamide (N,N-dimethylformamide, DMF), the reaction can be carried out in the presence of a base using acetic anhydride, acetyl chloride and other halogenated acetylides, etc., in the presence of a base. As the base used in the acetylation reaction, pyridine, N,N-dimethylaniline, sodium carbonate, sodium bicarbonate, potassium carbonate, etc. are preferred, and more Potassium carbonate is preferred. In addition, by using an acetylation reagent such as acetic anhydride in excess, the reaction can also be performed without using an anhydrous aprotic polar solvent or a base.

The acetylation reaction is preferably carried out, for example, at room temperature to 100° C. while stirring. After the reaction treatment, it can also be dried under reduced pressure to remove the acetylation reagent. In addition, if the target acetylation degree of substitution is not reached, the acetylation reaction and subsequent vacuum drying can be repeated any number of times.

(cleaning)

The acetylated pulp obtained by the acetylation reaction is preferably subjected to washing treatment such as water replacement after the acetylation treatment.

(dehydration)

Dehydration may be performed as necessary during the washing process. The dehydration method can also be implemented by a pressure dehydration method using a screw press, a vacuum dehydration method using volatilization, etc., but a centrifugal dehydration method is preferable in terms of efficiency. Dehydration is preferably performed until the solid content in the solvent becomes about 10% to 60%.

(dry)

The acetylated pulp usable in the present invention is subjected to a drying treatment after the dewatering step. The drying treatment can be performed using, for example, a microwave dryer, a blower dryer, or a vacuum dryer, but a drum dryer, a paddle dryer, a nauta mixer, a batch dryer with stirring blades, and the like that can dry while stirring are preferred. Drying is preferably performed until the moisture content of the acetylated pulp becomes about 1% to 40%, more preferably until 1% to 10%, and still more preferably until 1% to 5%. implemented by using Dried pulp can reduce the influence of water on the hydrolysis of pulp in the kneading step described later.

(oxidation modification)

Oxidation can be performed as known. Oxidation treatment improves the handling when pulp concentration is increased during predefibration. For example, a method of oxidizing raw material pulp in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromides, iodides, and mixtures thereof is exemplified. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of cellulose is selectively oxidized to generate a group selected from the group consisting of aldehyde groups, carboxyl groups, and carboxylate groups. Alternatively, an ozonation method may be mentioned. According to this oxidation reaction, at least the hydroxyl groups at the 2-position and 6-position of the glucopyranose ring constituting cellulose are oxidized, and the cellulose chain is decomposed.

An example of a method for measuring the amount of carboxyl groups will be described below. 60 mL of a 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose was prepared, adjusted to pH 2.5 by adding 0.1 M hydrochloric acid aqueous solution, and then 0.05 N aqueous sodium hydroxide solution was added dropwise to measure conductivity until the pH reached 11. It can be calculated using the following formula from the amount (a) of sodium hydroxide consumed in the neutralization stage of a weak acid in which the change in electrical conductivity is gentle.

Carboxyl group amount [mmol/g oxidized cellulose] = a [mL] × 0.05/ oxidized cellulose mass [g]

The amount of carboxyl groups in oxidized cellulose measured in the above manner is preferably at least 0.1 mmol/g, more preferably at least 0.3 mmol/g, still more preferably at least 0.5 mmol/g, and still more preferably at least 0.8 mmol/g, relative to the absolute dry mass. the amount of The limit is preferably 3.0 mmol/g or less, more preferably 2.5 mmol/g or less, still more preferably 2.0 mmol/g or less. Therefore, the amount is preferably 0.1mmol/g~3.0mmol/g, more preferably 0.3mmol/g~2.5mmol/g, still more preferably 0.5mmol/g~2.5mmol/g, even more preferably 0.8mmol/g~2.0mmol/g.

(Etherification and Esterification)

As etherification and esterification, modification can be carried out by known methods such as carboxymethylation, phosphorylation, phosphorylation, and sulfation.

(carboxymethylation modification)

Carboxymethylation can be carried out as known. By carboxymethylation treatment, the handling at the time of predefibration when the pulp concentration is increased becomes favorable. The measurement of the carboxymethyl substitution degree per glucose unit of carboxymethylated cellulose is performed by the following method, for example. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dry) was precisely weighed, and it put into the Erlenmeyer flask with a stopper of 300 mL capacity. 2) Add 100 mL of methanol nitric acid (a liquid obtained by adding 100 mL of special-grade concentrated nitric acid to 1000 mL of methanol), and shake for 3 hours to make carboxymethylcellulose salt (carboxymethylated cellulose) into hydrogen-form carboxymethylated cellulose. 3) Accurately weigh about 1.5 g to 2.0 g of hydrogen-form carboxymethylated cellulose (absolutely dry), and put it into a 300-mL Erlenmeyer flask with a stopper. 4) Wet hydrogen carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. 5) Back titration _of excess NaOH with 0.1N _H2SO4 using phenolphthalein as indicator. 6) Calculate the carboxymethyl substitution degree (DS) by the following formula: A=[(100×F’-(0.1N H ₂ SO ₄ )(mL)×F)×0.1]/(absolute dry mass of hydrogen carboxymethylated cellulose (g))

DS=0.162×A/(1-0.058×A)

A: The amount of 1N NaOH required to neutralize 1 g of hydrogen-form carboxymethylated cellulose (mL)

F: Factor _of 0.1N _H2SO4

F': factor of 0.1N NaOH

The degree of carboxymethyl substitution per anhydroglucose unit in carboxymethylated cellulose is preferably at least 0.01, more preferably at least 0.05, still more preferably at least 0.10. The upper limit of the degree of substitution is preferably at most 0.50, more preferably at most 0.40, still more preferably at most 0.35. Therefore, the carboxymethyl substitution degree is preferably from 0.01 to 0.50, more preferably from 0.05 to 0.40, and still more preferably from 0.10 to 0.35.

(mixing steps)

In the kneading step of the present invention, the resin composite is obtained by kneading the resin and the predefibrated cellulose fiber by using a single-shaft or multi-shaft kneader. In the present invention, the resin composite can be obtained by kneading the predefibrated cellulose fibers and the resin together. It is also possible to prepare a masterbatch containing the predefibrated cellulose fibers and the resin (hereinafter, sometimes referred to as "resin for masterbatch"), and then knead (dilution and knead) the masterbatch and the resin (resin for dilution) to obtain the resin composite. In addition, in the kneading step, if necessary, urea or the like may be kneaded together.

When feeding into the kneader, various commercially available feeders or side feeders can be used. The resin and optionally used urea may be powdered in advance, and the cellulose fiber predefibrated product, resin, and urea may be mixed with a commercially available mixer or the like before inputting. Even in the case where the resin etc. are not powdered, for example, by Like the feeder for pellets and the feeder for cellulose fiber predefibrate, prepare multiple feeders and put them in. In the kneading step for preparing the masterbatch, the blending amount of the cellulose fiber component of the cellulose fiber prefibrillated material charged into the kneading machine is preferably 35% by mass to 85% by mass, more preferably 40% by mass to 65% by mass, based on the total amount of the cellulose fiber prefibrillated material, resin, and optionally urea.

(mixing machine)

In the kneading step of the present invention, a single-shaft or multi-shaft kneading machine is used. From the viewpoint of having a strong kneading force capable of melting and kneading the resin and the cellulose fiber predefibrated material and promoting the nanonization of the cellulose fiber predefibrated material, it is desirable to use a multi-shaft kneading machine such as a biaxial kneading machine, a four-shaft kneading machine, and have a structure including a plurality of kneading or rotors in members constituting the screw.

The set temperature for melt kneading can be adjusted according to the melting temperature of the resin used. The heating setting temperature during melting and kneading is preferably about ±10° C. from the lowest processing temperature recommended by the thermoplastic resin supplier. By setting the mixing temperature in this temperature range, the prelyzed cellulose fiber and resin can be uniformly mixed.

In the present invention, the resin, the predefibrated cellulose fibers, and optionally urea, etc. put into the kneading machine in the kneading step are melted and kneaded, and at least a part of the predefibrated cellulose fibers are mainly defibrated by the shear force generated during the melted kneading, thereby preparing a resin composite containing 50% by volume or more of cellulose fibers having an average fiber width of 1 μm or less.

(dilute mixing step)

The manufacturing method of the resin composite of the present invention may further include a dilution and kneading step, In the dilution kneading step, the resin composite obtained in the kneading step is kneaded with the resin for dilution. When the dilution and kneading process is included, the resin composite prepared by the kneading process can be used as a masterbatch. In addition, when the dilution and kneading step is included, the resin composite obtained after the dilution and kneading step only needs to contain 50% by volume or more of cellulose fibers having an average fiber width of 1 μm or less.

(resin for thinning)

As the diluting resin used in the present invention, a general thermoplastic resin having a melting temperature of 250° C. or lower can be used. The diluting resin may be used alone or in combination of two or more resins.

When the resin composite obtained in the kneading step is used as a masterbatch, a resin composite further containing a dilution resin can be obtained by adding a dilution resin to the masterbatch and performing melt kneading. In the case of adding the resin for dilution and performing melt-kneading, the two components may be mixed without heating at room temperature and then melt-kneaded, or may be mixed while heating to perform melt-kneading.

As a kneader for melt-kneading by adding the resin for dilution, the same kneader as that used in the above-mentioned kneading step can be used. In addition, the melt kneading temperature can be adjusted according to the resin used in the kneading step. The heating setting temperature during melting and kneading is preferably about ±10° C. from the lowest processing temperature recommended by the thermoplastic resin supplier. By setting the temperature in this temperature range, the cellulose fiber predefibrate and the resin can be uniformly mixed.

The resin composite manufactured by the manufacturing method of the present invention can be further Deploying surfactants; polysaccharides such as starch and alginic acid; natural proteins such as gelatin, animal glue, and casein; inorganic compounds such as tannin, zeolite, ceramics, and metal powder; colorants; plasticizers; fragrances; pigments; flow regulators; leveling agents; conductive agents; antistatic agents; UV absorbers; UV dispersants; As the content rate of an arbitrary additive, it can contain suitably within the range which does not impair the effect of this invention.

(resin composite)

The resin composite obtained by the production method of the present invention may be a resin composite obtained by kneading a resin and predefibrated cellulose fibers together, or may be a resin composite obtained by a dilution kneading step of kneading a masterbatch obtained by kneading a resin and predefibrated cellulose fibers.

According to the present invention, it is possible to provide a resin composite having a high tensile modulus of elasticity, high tensile strength, and an excellent balance with tensile elongation. In addition, a method for producing a resin composite capable of obtaining the resin composite can be provided. In addition, prefibrillated cellulose fibers used in the resin composite can be provided.

(use)

A molding material and a molded article (molding material and molded article) can be produced using the resin composite of the present invention. As for the shape of the molded body, molded bodies of various shapes such as a film shape, a sheet shape, a plate shape, a granular shape, a powder shape, and a three-dimensional structure are exemplified. As the molding method, mold molding, injection molding, extrusion molding, blow molding, foam molding, and the like can be used.

Shaped bodies (formed bodies) other than for use in matrices containing cellulose fibers In addition to the field of fiber-reinforced plastics for moldings (moldings), it can also be used in fields requiring thermoplasticity and mechanical strength (tensile strength, etc.).

It can be effectively used as interior materials, exterior materials, structural materials, etc. of transportation equipment such as automobiles, trams, ships, and airplanes; frames, structural materials, and internal parts, etc., of electrical appliances such as personal computers, televisions, telephones, and watches; frames, structural materials, internal parts, etc., of mobile communication devices such as mobile phones; Frames, structural materials, internal parts, etc.; building materials; office equipment such as stationery, containers, containers, etc.

[Example]

Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Fiber length distribution and fine component measurement of cellulose fiber prefibrillation)

The fiber length distribution and fine component measurement of the cellulose fiber predefibrated product were measured using a fiber tester manufactured by Lorentzen & Wettre. In the present invention, the fiber length means the number average fiber length based on ISO16065. Specifically, 0.1 g of pulp dry mass was stirred and dissociated in 300 mL of water, and measured with a fiber tester.

In the present invention, the fine component refers to fibers having a fiber length of 0.2 mm or less. The higher the value, the more defibrillation will be achieved by kneading described later, but if it exceeds 50%, it will be difficult to leave long fibers in the resin composite Dimensions, so it is not good. Its content is preferably 35%~50%, more preferably 37%~48% in all fibers including fine components.

(Measurement method of acetyl substitution degree (DS))

(Measurement of DS by back titration method)

A sample of acetylated cellulose pulp was dried, and 0.5 g was accurately weighed (A). 75 mL of ethanol and 50 mL (0.025 mol) of 0.5N NaOH (B) were added thereto, followed by stirring for 3 to 4 hours. It was filtered, washed with water, and dried, and the sample on the filter paper was measured by Fourier Transform Infrared Spectroscopy (FT-IR), and it was confirmed that the absorption peak based on the carbonyl of the ester bond disappeared, that is, the ester bond was hydrolyzed.

The filtrate was used for the back titration described below.

The sodium acetate salt formed as a result of hydrolysis and NaOH added in excess were present in the filtrate. This NaOH neutralization titration was performed using 1N HCl (phenolphthalein was used as an indicator).

． 0.025mol (B) - (the number of moles of HCl used in neutralization) = the number of moles of acetyl groups ester-bonded with hydroxyl groups such as cellulose (C). (The molecular weight of cellulose repeating unit 162×the number of moles of cellulose repeating unit (unknown (D))+(the molecular weight of acetyl group 43×(C))=weighted sample 0.5g(A)

From the formula, the molar number (D) of the repeating unit of cellulose was calculated.

DS is calculated by the following formula.

． DS=(C)/(D)

(average fiber width of acetylated cellulose fibers in the resin composite)

For the acetylated cellulose fibers in the resin composite, the ratio of the average fiber width to 1 μm or less was determined by X-ray computer tomography (hereinafter abbreviated as X-CT) (SKYSCAN 1272 (manufactured by Bruker): resolution 0.5 μm). Specifically, this apparatus cut out the inside of the produced resin composite containing 10% cellulose fibers in a 1 cm square, and measured it under the conditions of 0.5 μm per voxel. After three-dimensional reconstruction, select a plane of 200 μm × 200 μm or more, separate the fibrous part and non-fibrous part according to the shape, and then binarize the image to remove fibers and noise below 2 voxels. For this planar image, the average value of the fiber portion (undefibrated fiber amount) was obtained using 10 or more planes within a range of 200 μm in the Z-axis direction. The fibers displayed in the image by the above operation refer to fibers having a fiber width greater than 1 μm. The ratio of the cellulose fibers having an average fiber width of 1 μm or less was obtained by the following formula using the average obtained value of the amount of undefibrated fibers.

In addition, in the said formula, since 10% of cellulose fibers were contained in the Example, the amount of cellulose was set to 10%, and the density of cellulose was set to 1.5 g/cm ³ .

(Determination of Tensile Elasticity Modulus, Tensile Strength, and Tensile Elongation)

150 g of the granular resin moldings obtained in Examples and Comparative Examples were put into a small molding machine ("MC15" manufactured by Xplore Instruments Co., Ltd.), and a dumbbell-shaped test piece (type A12, Japanese Industrial Standards (JIS) K 7139) was molded under the conditions of a heating cylinder (cylinder) temperature of 200° C. and a mold temperature of 40° C. For the obtained test piece, the tensile modulus of elasticity, tensile strength, and tensile elongation (strain and elongation until fracture) were measured using a precision universal testing machine ("autograph AG-Xplus" manufactured by Shimadzu Corporation) at a test speed of 1 mm/min and a distance between initial marking lines of 30 mm. Table 1 shows the results of tensile elongation. In addition, using only the diluting resin, a dumbbell-shaped test piece was formed in the same manner as described above, and the tensile modulus and tensile strength of the obtained test piece were measured in the same manner as described above.

(Kneading machines and operating conditions used in the production of masterbatches and resin composites)

"MFU15TW-45HG-NH" twin-shaft kneading machine manufactured by Technovel Co., Ltd.

Screw diameter: 15mm, L/D: 45, processing speed: 300g/hour

The screw rotation speed was 200 rpm, and the set temperature was operated at +5°C, the melting point of each resin.

(Example 1)

(Pulp beating treatment)

Conifer unbleached kraft pulp (NUKP: lignin content 8% by mass) containing 50% water was adjusted to a solid content concentration of 20%, and 20 kg of it was passed through a single disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd., plate blade width: 4mm, groove width: 5mm) twice under the condition of a gap of 0.25mm, and the measured value at five points of freeness was 350mL~450mL. Prepare the cellulose fiber prefibrillate. For the obtained cellulose fiber predefibrated product, the fiber length distribution was measured using a fiber tester manufactured by Lorentzen & Wettre. The results are shown in Table 1.

(Preparation of acetylated pulp)

The cellulose fiber prefibrillated product, that is, 20.0 kg (solid content: 4.0 kg) of hydrous softwood unbleached kraft pulp (NUKP) subjected to beating treatment, was put into a mixer ("FM150L" manufactured by Nippon Coke Industry Co., Ltd.), and stirring was started, followed by dehydration under reduced pressure at 50°C. Then, 4.0 kg of acetic anhydride was added, and it was made to react at 80 degreeC for 2 hours. After the reaction, the pulp was fully washed with water, dehydrated, and dried under reduced pressure to obtain acetylated pulp with a pulp solid content concentration of 98% by mass, that is, acetylated cellulose fiber predefibrated product. The degree of acetyl substitution (DS) of the acetylated cellulose fiber prefiber was 0.5.

(Materials used in the production of masterbatch A and resin composite A)

(a) Acetylated cellulose fiber prefibrillation

(b) Resin for masterbatch

． PA6: (PA6 P1011F manufactured by Ube Industries Co., Ltd.)

(c) Diluting resin

． PA6: (PA6 1011FB manufactured by Ube Industries, Ltd.)

(Manufacture of Master Batch A)

The acetylated cellulose fiber predefibrate (460 g as an absolute dry matter) and the resin for a masterbatch (PA6: 720 g) were put in a polyethylene bag, shaken and mixed. Using a feeder (manufactured by Technovel Co., Ltd.) attached to the twin-shaft kneader, 1180 g of the obtained mixture was put into the kneader, and kneaded at a heating temperature to manufacture a masterbatch A containing acetylated cellulose fibers obtained by main-defibrating acetylated cellulose fiber predefibrated by kneading with a resin, and a masterbatch resin.

(Manufacture of resin composite A)

60 g of the obtained masterbatch A and 120 g of the resin for dilution (PA6) were mixed, and it kneaded at heating temperature using the said biaxial kneader. Next, the molten kneaded product was granulated using a granulator to obtain a granular resin composite (molded article) A containing acetylated cellulose fibers, a resin for masterbatch, and a resin for dilution. In addition, the ratio of the average fiber width of the acetylated cellulose fiber contained in the resin composite A to 1 micrometer or less was 67 volume%. Furthermore, it is difficult to measure the fiber length of the acetylated cellulose fibers kneaded with the resin because it is difficult to separate the resin from the fibers.

(Materials used in the production of masterbatch B and resin composite B)

(a) Acetylated cellulose fiber prefibrillation

(b) Resin for masterbatch

． MAPP: (MAPP PMAH1000P made by Toyobo)

(c) Urea: (manufactured by Wako Pure Chemical Industries)

(d) Diluting resin

． PP: (PP MA04A manufactured by Japan Polypro)

(manufacturing of masterbatch B)

The acetylated cellulose fiber predefibrate (460 g as an absolute dry product), resin for masterbatch (MAPP: 110 g), and powdery urea (180 g) were put in a polyethylene bag, shaken and mixed. Using a feeder (manufactured by Technovel Co., Ltd.) attached to the twin-shaft kneader, 750 g of the obtained mixture was put into the kneader, and kneaded at a heating temperature to manufacture a masterbatch B containing acetylated cellulose fibers obtained by main-defibrating the predefibrated product of acetylated cellulose fibers by kneading with a resin, and a masterbatch resin.

(Manufacture of resin composite B)

38 g of the obtained masterbatch B and 142 g of the resin for dilution (PP) were mixed, and kneaded at heating temperature using the above-mentioned twin-screw kneader. Next, the molten kneaded product was granulated using a granulator to obtain a granular resin composite (molded body) B containing acetylated cellulose fibers, a resin for masterbatch, and a resin for dilution. In addition, the ratio of the average fiber width of the acetylated cellulose fiber contained in the resin molded body B to 1 micrometer or less was 60 volume%.

(Example 2)

In the beating process of pulp, the number of passes through the single-disk refiner is set to three times, and the measured value at the fifth point of freeness is 150mL~250mL. A cellulose fiber predefibrated product was prepared in the same manner as in Example 1 except for the change. Moreover, except having used this cellulose fiber predefibrate, it carried out similarly to Example 1, and prepared the acetylated cellulose fiber predefibrate. Except having used the predefibrated material obtained in Example 2, it carried out similarly to Example 1, and produced masterbatch A, masterbatch B, resin composite A, and resin composite B. In addition, the proportions of the average fiber width of the acetylated cellulose fibers contained in the resin composite A and the resin composite B were 1 μm or less were 71% by volume and 65% by volume, respectively.

(comparative example 1)

Masterbatch A, masterbatch B, resin composite A, and resin composite B were produced in the same manner as in Example 1 except that the pulp was not subjected to beating treatment and was acetylated under the conditions of Example 1 instead of the acetylated cellulose fiber predefibrate. In addition, the ratios of the average fiber width of the acetylated cellulose fibers included in the resin composite A and the resin composite B were 59% by volume and 51% by volume, respectively.

(comparative example 2)

In the beating treatment of pulp, the number of passes through the single-disk refiner was set to one, and the measured value of freeness at five points was changed so that it was 450 mL to 550 mL, and the cellulose fiber predefibrated product was prepared in the same manner as in Example 1. Moreover, except having used this cellulose fiber predefibrate, it carried out similarly to Example 1, and prepared the acetylated cellulose fiber predefibrate. Except using the predefibrated product obtained in Comparative Example 2, masterbatch A, masterbatch B, resin composite A, and resin composite B were produced in the same manner as in Example 1. In addition, the proportion of the average fiber width of the acetylated cellulose fibers contained in the resin composite A and the resin composite B is 1 μm or less is 61 volumes, respectively. %, 54% by volume.

(comparative example 3)

In the beating treatment of pulp, NUKP with a solid content concentration adjusted to 3% was treated five times under the condition that the gap of the single disc refiner was 0.15 mm, and a cellulose fiber predefibrated product with a measured value of 150 mL to 250 mL of freeness at five places was obtained. The cellulose fiber predefibrated product was prepared in the same manner as in Example 1 except that. Moreover, except having used this cellulose fiber predefibrate, it carried out similarly to Example 1, and prepared the acetylated cellulose fiber predefibrate. Except using the predefibrated product obtained in Comparative Example 3, masterbatch A, masterbatch B, resin composite A, and resin composite B were produced in the same manner as in Example 1. In addition, the ratios of the average fiber width of the acetylated cellulose fibers included in the resin composite A and the resin composite B were 75% by volume and 71% by volume, respectively.

As shown in Table 1, the resin composite obtained by kneading a cellulose fiber predefibrated product obtained by mechanically treating pulp with a fiber length of 0.1 mm to less than 0.5 mm to 40% to less than 50% by volume of the cellulose fiber predefibrated product obtained by mechanically treating pulp when the ratio of the average fiber width of the cellulose fiber contained therein is 1 μm or less to 50% by volume or more. A ratio of 58% or more exists, and a fiber length of 1.5 mm or more and less than 2.0 mm exists in a ratio of 5% or more and less than 10%.

Claims (5)

A resin composite comprising a resin and cellulose fibers, wherein the resin composite is characterized in that the melting temperature of the resin is a thermoplastic resin of 250° C. or lower, the resin composite is obtained by a production method having a step of kneading the resin and a cellulose fiber prelyzed product using a single-shaft or multi-shaft kneader, the freeness of the cellulose fiber pre-lyzed product is 120 mL to 450 mL, and the fiber length is 0.1 mm or more and less than 0.5 mm and is 40% or more and less than 58%. The ratio exists, the fiber length is 1.5 mm or more and less than 2.0 mm, the ratio is 5% or more and less than 10%, the average fiber width of the cellulose fibers contained in the resin composite is 50% by volume or more, and the content of the cellulose fibers contained in the resin composite is 0.5% by mass to 30% by mass relative to the entire resin composite. The resin composite according to claim 1, wherein the cellulose fibers are acetylated cellulose fibers. A method for manufacturing a resin composite body, which is a method for manufacturing a resin composite body including resin and cellulose fibers, the method for manufacturing the resin composite body includes: a beating treatment step, performing a beating treatment on pulp with a solid content concentration of 10% by mass or more at a freeness of 120mL to 450mL to obtain a cellulose fiber pre-defibrated product; A resin composite is obtained by kneading a cellulose fiber predefibrated product in which the fiber length is 0.1 mm to less than 0.5 mm in a proportion of 40% to less than 58%, and the fiber length is 1.5 mm to less than 2.0 mm in a proportion of 5% to less than 10%, and the ratio of the average fiber width of the cellulose fibers contained in the resin composite is 1 μm or less is 50% by volume or more. The method for manufacturing a resin composite according to claim 3, wherein the beating treatment is performed using at least one of a disc refiner and a cone refiner. A cellulose fiber predefibrated product for use in a resin composite, in which the fiber length of 0.1 mm to less than 0.5 mm is present in a proportion of 40% to less than 58%, and the fiber length of 1.5 mm to less than 2.0 mm is present in a proportion of 5% to less than 10%.