WO2022168459A1

WO2022168459A1 - Resin composite, method for producing resin composite, and pre-fibrillated cellulose fibers

Info

Publication number: WO2022168459A1
Application number: PCT/JP2021/046164
Authority: WO
Inventors: 雄二郎福田; 惟緒角田; 健一郎佐々木; 伸彦山本
Original assignee: 日本製紙株式会社
Priority date: 2021-02-03
Filing date: 2021-12-15
Publication date: 2022-08-11
Also published as: TW202231962A; JP7108727B1; TWI807559B; JP2022118772A

Abstract

A resin composite which comprises a resin and cellulose fibers, and is obtained by kneading the resin and pre-fibrillated cellulose fibers with a single- or multi-screw kneader. The pre-fibrillated cellulose fibers are ones which are obtained by mechanically processing a pulp and in which the content of fibers having a length of 0.1-0.5 mm, excluding 0.5 mm, is 40% or higher but less than 58% and the content of fibers having a length of 1.5-2.0 mm, excluding 2.0 mm, is 5% or higher but less than 10%. The cellulose fibers contained in the resin composite comprise 50 vol% or more cellulose fibers having an average fiber width of 1 μm or less.

Description

Resin composite, method for producing resin composite, and cellulose fiber pre-fibrillated material

The present invention relates to a resin composite containing finely divided cellulose fibers, a method for producing this resin composite, and a cellulose fiber pre-fibrillated material used for this resin composite.

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

Methods for producing a resin composite containing finely divided cellulose fibers include a method in which cellulose that has been finely refined to a nano-level is combined with a resin, and a method in which light pre-fibrillation is performed by a method such as mechanical fibrillation. There is a method of fibrillating cellulose together with a resin using a kneader, and Patent Document 1 discloses a beating treatment of pulp under low-concentration conditions regarding the latter method. Moreover, Patent Document 1 describes that a resin composite containing cellulose preliminarily fibrillated by the method is superior in tensile modulus and tensile strength as compared to the resin alone.

Further, in Patent Document 2, by heat-treating a cellulose raw material and urea, a cellulose raw material in which a part of the hydroxy groups of cellulose is substituted with a carbamate group is obtained, and this is mechanically treated (preliminary fibrillation) to obtain fine particles. to obtain fine fibrous cellulose. Although there is no description of the solid content concentration of the cellulose raw material at the time of preliminary fibrillation, the fine fibrous cellulose obtained by this method has a freeness of 100 mL or less, and is more hydrophilic than conventional fine fibrous cellulose. Since it has a high affinity with low-polarity resins and the like, it disperses in resins with high uniformity and provides a composite with high tensile strength. In addition, Patent Documents 3 and 4 disclose a technique for increasing the solid content concentration by lowering the pH of fibril cellulose that has been beaten and refined to reduce water retention and increase the concentration. It is

However, there has been 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.

JP 2016-176052 A JP 2019-1876 A Japanese Patent Publication No. 2015-508839 Japanese Patent Application Publication No. 2017-527660

An object of the present invention is to provide a resin composite that has a high tensile modulus and a high tensile strength, and furthermore has an excellent balance with tensile elongation. Another object of the present invention is to provide a method for producing a resin composite that can obtain this resin composite. Another object of the present invention is to provide a pre-fibrillated cellulose fiber material for use in this resin composite.

The present invention provides the following.
(1) A resin composite containing a resin and cellulose fibers, wherein the resin composite is obtained by kneading the resin and a cellulose fiber pre-fibrillated material using a uniaxial or multiaxial kneader, and the cellulose The pre-fibrillated cellulose fiber material is obtained by mechanically treating pulp, and the cellulose fiber pre-fibrillated material has a fiber length of 0.1 mm or more and less than 0.5 mm in 40% or more and less than 58%, and a fiber length of 1.5 mm or more. .0 mm is present at a rate of 5% or more and less than 10%, and the cellulose fibers contained in the resin composite have an average fiber width of 1 μm or less at a rate of 50% or more by volume. Complex.
(2) The resin composite according to (1), wherein the pulp has a solid content concentration of 10% by mass or more during the mechanical treatment.
(3) The resin composite according to (1) or (2), wherein the mechanical treatment is performed using at least one of a disc refiner and a conical refiner.
(4) A method for producing a resin composite containing a resin and cellulose fibers, comprising a mechanical treatment step of mechanically treating pulp to obtain a cellulose fiber pre-fibrillation product, the resin and the cellulose fiber pre-fibrillation. and a kneading step of obtaining a resin composite by kneading the material with a uniaxial or multiaxial kneader, and the cellulose fiber pre-disentangled material has a fiber length of 0.1 mm or more and less than 0.5 mm at 40% or more. Less than 58%, a fiber length of 1.5 mm or more and less than 2.0 mm exists at a rate of 5% or more and less than 10%, and the cellulose fibers contained in the resin composite have an average fiber width of 1 μm or less. % or more, a method for producing a resin composite.
(5) A cellulose fiber pre-fibrillated material used for a resin composite, in which the fiber length is 0.1 mm or more and less than 0.5 mm is 40% or more and less than 58%, and the fiber length is 1.5 mm or more and less than 2.0 mm is 5%. A cellulose fiber pre-fibrillated material present at a rate of not less than 10%.

According to the present invention, it is possible to provide a resin composite that has a high tensile modulus and a high tensile strength, and is excellent in balance with tensile elongation. In addition, it is possible to provide a method for producing a resin composite by which this resin composite can be obtained. Moreover, it is possible to provide a cellulose fiber pre-fibrillated material used for this resin composite.

The resin composite of the present invention will be described below. In the present invention, "-" includes end values. That is, "X through Y" includes the values X and Y at both ends.

The resin composite of the present invention contains a resin and cellulose fibers, and the resin composite is obtained by kneading the resin and a cellulose fiber pre-fibrillated material using a uniaxial or multiaxial kneader, The cellulose fiber pre-fibrillated material is obtained by mechanically treating pulp, and the cellulose fiber pre-fibrillated material has a fiber length of 0.1 mm or more and less than 0.5 mm in 40% or more and less than 58%, and a fiber length of 1.5 mm. More than 2.0 mm and less than 2.0 mm are present at a rate of 5% or more and less than 10%, and the rate of the cellulose fibers contained in the resin composite having an average fiber width of 1 μm or less is 50% or more by volume. The fiber length distribution and fine content measurement of the cellulose fiber pre-fibrillated product indicates the number average fiber length based on ISO16065, and is measured using a fiber tester manufactured by Lorentzen & Wettre, a fiber tester manufactured by ABB, and a flak manufactured by Valmet. The average fiber length can be determined by image analysis such as Sionator.

(cellulose fiber)
In the present invention, the cellulose fiber is fibrous cellulose, and may further contain a fibrous cellulose derivative. The cellulose fiber contained in the resin composite of the present invention has an average fiber width of 1 μm or less, and is 50% by volume or more, and 55% by volume or more from the viewpoint of obtaining a sufficient balance between strength improvement effect and elongation. is preferred, 60% by volume or more is more preferred, and 65% by volume or more is even more preferred. Here, the average fiber width of the cellulose fibers contained in the resin composite can be measured by X-ray computed tomography (hereinafter sometimes abbreviated as X-CT).

The content of the cellulose fiber contained in the resin composite of the present invention is preferably 0.5 to 30% by mass, preferably 1.0 to 25% by mass, with respect to the entire resin composite from the viewpoint of obtaining a sufficient reinforcing effect. % is more preferred, and 3.0 to 20% by mass is even more preferred.

(resin)
As resins used in the present invention, the following general thermoplastic resins having a melting temperature of 250° C. or less can be mentioned.

General 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, poly Glycolic acid, acrylonitrile-butadiene-styrene copolymer (ABS resin), polyphenylene oxide, polyurethane, polyacetal, vinyl ether resin, polysulfone resin, cellulose resin (triacetylated cellulose, diacetylated cellulose, etc.), etc. can be used. can.

As the polyolefin resin, it is possible to use polyethylene, polypropylene (hereinafter also referred to as "PP"), ethylene-propylene copolymer, polyisobutylene, polyisoprene, polybutadiene, and the like.

Polyamide resin (PA) is also expected to interact with hydroxyl groups and acetyl groups of cellulose that are not affected by urea, so it can be used favorably. PA includes 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, PA612)), etc., aromatic diamines such as phenylenediamine and aromatic dicarboxylic acids such as terephthaloyl chloride and isophthaloyl chloride, or aromatic PAs composed of derivatives thereof etc. can be mentioned. From the viewpoint of high affinity with cellulose fibers and cellulose nanofibers, it is preferable to use aliphatic PA, more preferably PA6, PA11, and PA12, and particularly preferably PA6. Moreover, a polyamide resin may be used individually by 1 type, and may be used in mixture of 2 or more types of polyamide resins.

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

Also, as the "masterbatch resin" described later, one containing a compatibilizing resin may be used. Here, the compatibilizing resin is used for the purpose of improving uniform mixing and adhesion between the cellulose fibers and the diluent resin.

(Compatibilizing resin)
Compatibilizing resins that can be used in the present invention include low-molecular-weight dicarboxylic acids capable of forming acid 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) added with maleic acid together with a diluent resin. .

The factors that determine the characteristics of a compatibilizing resin include the amount of dicarboxylic acid added and the weight average molecular weight of the base material polyolefin resin. A polyolefin resin having a large amount of dicarboxylic acid added increases compatibility with a hydrophilic polymer such as cellulose, but the molecular weight of the resin decreases during the addition process, resulting in a decrease in the strength of the molded product. As an optimum balance, the amount of dicarboxylic acid added is 20-100 mgKOH/g, more preferably 45-65 mgKOH/g. When the amount added is small, the number of points that interact with the hydroxyl groups of cellulose and the hydroxyl groups and modified functional groups contained in modified cellulose in the resin decreases. Further, when the addition amount is large, self-aggregation due to hydrogen bonding between carboxyl groups in the resin, or reduction in the molecular weight of the base material olefin resin due to excessive addition reaction, the strength as a reinforced resin is not achieved. The molecular weight of the polyolefin resin is preferably 35,000 to 250,000, more preferably 50,000 to 100,000. If the molecular weight is smaller than this range, the strength of the resin is lowered, and if it is larger than this range, the viscosity increases significantly when melted, resulting in poor workability during kneading and molding defects.

The amount of the compatibilizing resin having the above characteristics is 10 to 70% by mass with respect to the amount of cellulose fiber (hereinafter sometimes referred to as "cellulose amount"), which is the total amount of cellulose and hemicellulose contained in the cellulose fiber. is preferred, and 20 to 50% by mass is more preferred. If the amount added exceeds 70% by mass, it is thought that the introduction of urea-derived isocyanic acid into cellulose fibers is inhibited and the formation of a complex between the compatibilizer and urea is promoted.

Also, the compatibilizing resin may be used singly or as a mixed resin of two or more. In the case of use as a graft of one or more polymers and polyolefin, the polyolefin resin constituting the graft is not particularly limited. can be used.

In the present invention, when the resin contains the above-mentioned compatibilizing resin, a low-molecular-weight auxiliary agent that imparts primary amines such as urea may be added from the viewpoint of improving the strength of the resulting resin composite. Urea is decomposed into ammonia and isocyanic acid when the temperature exceeds 135°C. is considered to promote the formation of urethane bonds by reaction, and it is speculated that the hydrophobicity increases compared to cellulose fibers that are not treated with urea. Furthermore, by melt-kneading at the same time as the compatibilizing resin containing an acid anhydride, the ionic bonds between the amino groups newly introduced on the surface of the cellulose fiber by the urea treatment and the carboxylic acid possessed by the compatibilizing resin are promoted, and the cellulose is further strengthened. It is believed that it is possible to form a composite of the fiber and the compatibilizing resin.

When urea is used as an auxiliary agent, the blending amount is cellulose, which is a combination of cellulose and hemicellulose contained in cellulose fibers, from the viewpoint of suppressing the decrease in strength due to aggregation of fibers due to too much urea. It is preferably 10 to 100% by mass, more preferably 15 to 80% by mass, and even more preferably 20 to 70% by mass based on 100% by mass of the amount of fiber (hereinafter sometimes referred to as "cellulose amount").

(Method for producing resin composite)
The method for producing a resin composite of the present invention includes a mechanical treatment step of mechanically treating pulp to obtain a cellulose fiber pre-fibrillated product, and a uniaxial or multiaxial treatment of the resin and the obtained cellulose fiber pre-fibrillated product. and a kneading step of obtaining a resin composite by kneading using a kneader.

(Mechanical treatment process)
In the mechanical treatment step of the present invention, the pulp of the cellulose raw material is mechanically treated to obtain a cellulose fiber pre-disentanglement product.

(raw material for cellulose)
In the present invention, the cellulose raw material refers to various forms of materials mainly composed of cellulose, including lignocellulose (NUKP), pulp (bleached or unbleached wood pulp, bleached or unbleached non-wood pulp, Refined linters, jute, Manila hemp, kenaf and other herbaceous pulps), natural cellulose such as cellulose produced by microorganisms such as acetic acid bacteria, reprecipitation after dissolving cellulose in some solvent such as cuprammonium solution, morpholine derivative, etc. Regenerated cellulose, fine cellulose obtained by depolymerizing cellulose by subjecting the above cellulose raw material to hydrolysis, alkaline hydrolysis, enzymatic decomposition, explosion treatment, mechanical treatment such as vibration ball mill, etc., and acetylation denaturation are not affected. Various cellulose derivatives and the like are exemplified.

Lignocellulose is a complex carbohydrate polymer that makes up the cell walls of plants, and is mainly composed of polysaccharides cellulose and hemicellulose, and aromatic polymer lignin. The content of lignin can be adjusted by delignifying or bleaching the raw material pulp or the like.

In the present invention, pulp is used as a cellulose raw material, and the pulp is subjected to mechanical treatment to obtain a cellulose fiber pre-fibrillated material. In the present invention, the mechanical treatment generally refers to mixing fibers in a dispersion medium represented by water and further pulverizing or fibrillating, and includes beating, fibrillation, dispersion, and the like. Refinement means that the fiber length, fiber diameter, etc. are reduced, and fibrillation means that the fiber becomes more fluffy. Apparatuses used for mechanical treatment are not limited, but examples include apparatus of types such as high-speed rotary, colloid mill, high pressure, roll mill, ultrasonic, high pressure or ultrahigh pressure homogenizers, refiners, single disc refiners and Disc refiners such as double disc refiners, conical refiners, beaters, PFI mills, ball mills, stone mill mills, sand grinder mills, impact mills, dyno mills, ultrasonic mills, canda grinders, attritors, vibration mills, cutter mills, jet mills, home use Juicer Mixer, mortar, kneader, disperser, high-speed disaggregator, top finisher, etc. Using a rotating shaft to make wet pulp act on a metal or a blade and pulp fibers, or by friction between pulp fibers be able to. In the present invention, the mechanical treatment is preferably beating using a Niagara beater, a refiner, or a kneader, and a disc refiner or conical refiner capable of high-concentration treatment, since the fibrillation of the fibers can be efficiently advanced. It is more preferable to be a beating treatment using.

The mechanical treatment is performed using a mixture containing the above pulp and a dispersion medium, and the solid content concentration at that time is 10% by mass or more, preferably 15% by mass or more, 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. Solids concentration is the concentration of solids in the mixture subjected to mechanical treatment. By subjecting the pulp to mechanical treatment such as beating under conditions of a high solid content concentration of 10% by mass or more, merits such as improved treatment efficiency and improved handling properties can be obtained. As handling properties, for example, after high-concentration mechanical treatment, it can be transported as it is at high concentration without dilution, and the viscosity of the pulp dispersion that has undergone high-concentration mechanical treatment is not high and can be pumped. Another advantage is that the dispersion is less likely to stick to the inside of the storage container. Furthermore, when the drying step is performed after the high-concentration mechanical treatment, the amount of volatilized dispersion medium is small and the drying efficiency is good. Furthermore, it is preferable to subject the pulp of the present invention to chemically modified pulp to high-concentration mechanical treatment because the viscosity of the dispersion is less likely to increase.
By setting the pulp concentration at the time of mechanical treatment to a high value, it is possible to suppress an increase in the fine content, which will be described later, due to excessive swelling of the pulp, and to leave suitable long fibers in the resin composite.

If the solid content concentration during mechanical treatment exceeds 50% by mass, drying proceeds in the apparatus during the treatment and scorching of the material is likely to occur. A condition of mass % or less is more preferable.

As for the degree of mechanical treatment, the freeness (C.S.F) is preferably about 100 mL to 500 mL, more preferably about 120 mL to 450 mL, still more preferably about 150 mL to 250 mL. By setting the freeness to the upper limit or lower, the effect can be exhibited. 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 inhibited due to the acceleration of the hardening.

In the present invention, the cellulose fiber pre-fibrillated product has a wide fiber length distribution due to high-concentration mechanical treatment, and the final resin composite has long fibers that are advantageous for reinforcing strength properties and a state in which high reinforcing properties are maintained. From the viewpoint that the structure contains a moderate amount of fine fibers that are advantageous for improving the tensile elongation value of the resin, the fiber length distribution has a fiber length distribution of 40% or more and less than 58% of the fibers with a fiber length of 0.1 mm or more and less than 0.5 mm, and Fibers with a length of 1.5 mm or more and less than 2.0 mm are present in 5% or more and less than 10%, preferably fibers with a fiber length of 0.1 mm or more and less than 0.5 mm are present in 50% or more and less than 55%, and fibers Fibers with a length of 1.5 mm or more and less than 2.0 mm are present at 6% or more and less than 10%. In addition, the fiber length in the present invention indicates the number average fiber length based on ISO16065.

In the present invention, the cellulose fiber pre-fibrillated material preferably contains 35 to 50% fines, more preferably 37 to 48%. Here, the fine portion refers to fibers having a fiber length of 0.2 mm or less. If the fines content is large, fibrillation proceeds by kneading, which will be described later, but if the condition exceeds 50%, it becomes difficult to leave long fibers in the resin composite, so an appropriate amount is preferable.

In addition, in the present invention, the cellulose fiber pre-fibrillated material may be used in an undenatured state, but may be chemically denatured by acetylation, oxidation, etherification, esterification, or the like.

(acetylation modification)
In the acetylation-modified cellulose fiber pre-fibrillated product (sometimes simply referred to as “acetylated pulp”) that can be used in the present invention, the hydrogen atoms of the hydroxyl groups present on the cellulose surface of the cellulose raw material are acetyl groups ( CH ₃ —CO—). Substitution with an acetyl group increases hydrophobicity and reduces aggregation during drying, thereby improving workability and facilitating dispersion and fibrillation in the resin after kneading. In addition, since highly reactive hydroxyl groups are substituted with acetyl groups, thermal decomposition of cellulose is suppressed and heat resistance during kneading is improved. The degree of acetyl group substitution (DS) of the acetylated pulp is preferably 0.4 to 1.3, more preferably 0.6 to 1.1, from the viewpoint of workability and maintaining the crystallinity of cellulose fibers. adjust.

(acetylation reaction)
The acetylation reaction is carried out by suspending the raw material in an anhydrous aprotic polar solvent capable of swelling the cellulose raw material, such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), adding acetic anhydride, acetyl chloride, It is possible to carry out the reaction in a short time by using an acetyl halide such as, for example, in the presence of a base. As the base used in this acetylation reaction, pyridine, N,N-dimethylaniline, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, etc. are preferred, and potassium carbonate is more preferred. Also, by using an excess amount of an acetylation reagent such as acetic anhydride, the reaction can be carried out under conditions that do not use an anhydrous aprotic polar solvent or a base.

The acetylation reaction is preferably carried out with stirring, for example, at room temperature to 100°C. After the reaction treatment, drying may be performed under reduced pressure to remove the acetylation reagent. If the target degree of acetyl group substitution is not reached, the acetylation reaction and subsequent vacuum drying may be repeated any number of times.

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

(dehydration)
In the washing treatment, dehydration may be performed as necessary. As the dehydration method, a pressurized dehydration method using a screw press, a vacuum dehydration method using volatilization or the like can be used, but the centrifugal dehydration method is preferable from the viewpoint of efficiency. Dehydration is preferably carried out until the solid content in the solvent reaches approximately 10 to 60%.

(dry)
The acetylated pulp that can be used in the present invention is subjected to a drying treatment after the dehydration step. The drying treatment can be performed, for example, by using a microwave dryer, a blow dryer or a vacuum dryer, but a drum dryer, a paddle dryer, a Nauta mixer, a batch dryer with stirring blades, etc., can be used. A dryer that can dry while drying is preferred. Drying is preferably carried out until the moisture content of the acetylated pulp reaches about 1 to 40%, more preferably 1 to 10%, even more preferably 1 to 5%. By using the dried pulp, it is possible to reduce the influence of hydrolysis of the pulp by water in the kneading step, which will be described later.

(oxidative modification)
Oxidation can be carried out as known. Oxidation treatment improves the handling when increasing the density of the pulp during preliminary fibrillation. For example, there is a method of oxidizing raw 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. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to generate a group selected from the group consisting of an aldehyde group, a carboxyl group and a carboxylate group. Alternatively, an ozone oxidation method may be mentioned. According to this oxidation reaction, at least the hydroxyl groups at the 2nd and 6th positions of the glucopyranose rings constituting cellulose are oxidized, and the cellulose chain is decomposed.

An example of the method for measuring the amount of carboxyl groups is described below. Prepare 60 mL of a 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose, add 0.1 M hydrochloric acid aqueous solution to adjust the pH to 2.5, and then drop 0.05 N sodium hydroxide aqueous solution to adjust the pH to 11. Measure the electrical conductivity until the It can be calculated using the following formula from the amount (a) of sodium hydroxide consumed in the neutralization stage of the weak acid whose electrical conductivity changes slowly.
Carboxyl group amount [mmol/g oxidized cellulose] = a [mL] x 0.05/oxidized cellulose mass [g]

The amount of carboxyl groups in the oxidized cellulose measured in this way is preferably 0.1 mmol/g or more, more preferably 0.3 mmol/g or more, still more preferably 0.5 mmol/g, relative to the absolute dry mass. 0.8 mmol/g or more, more preferably 0.8 mmol/g or more. The upper limit of the amount 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 0.1 to 3.0 mmol/g, more preferably 0.3 to 2.5 mmol/g, still more preferably 0.5 to 2.5 mmol/g, and 0.8 to 2.0 mmol /g is even more preferred.

(Etherification and esterification)
As etherification and esterification, modification can be performed by known methods such as carboxymethylation, phosphate esterification, phosphite esterification, and sulfate esterification.

(Carboxymethylation modification)
Carboxymethylation can be carried out as known. The carboxymethylation treatment improves the handling of the pulp during preliminary fibrillation to increase the density of the pulp. The degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose is measured, for example, by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose (absolute dry) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a common stopper. 2) Add 100 mL of methanol nitrate (100 mL of special grade concentrated nitric acid added to 1000 mL of methanol) and shake for 3 hours to convert carboxymethyl cellulose salt (carboxymethyl cellulose) into hydrogen carboxymethyl cellulose. 3) About 1.5 g to 2.0 g of hydrogen-form carboxymethylated cellulose (absolute dry) is accurately weighed and placed in a 300 mL conical flask equipped with a common stopper. 4) Wet hydrogen carboxymethyl cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. ₅ ) Back _- titrate excess NaOH with 0.1N H2SO4 using phenolphthalein as indicator. 6) Calculate the degree of carboxymethyl substitution (DS) by the formula:
A = [(100 × F'-(0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1]/(absolute dry weight of hydrogen-form carboxymethylated cellulose (g))
DS = 0.162 x A/(1 - 0.058 x A)
A: Amount of 1N NaOH (mL) required to neutralize 1 g of hydrogen-type carboxymethylated cellulose
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 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. The upper limit of the degree of substitution is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less. Therefore, the degree of carboxymethyl group substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, even more preferably 0.10 to 0.35.

(Kneading process)
In the kneading step of the present invention, a resin composite is obtained by kneading a resin and a cellulose fiber pre-fibrillated material using a uniaxial or multiaxial kneader. In the present invention, a resin composite may be obtained by a method of collectively kneading a cellulose fiber pre-fibrillated material and a resin, or a cellulose fiber pre-fibrillated material and a resin (hereinafter referred to as "masterbatch resin") may be obtained. ), and then kneading (diluting and kneading) this masterbatch and a resin (dilution resin) to obtain a resin composite. Moreover, in the kneading step, urea or the like may be kneaded together, if necessary.

When feeding into the kneader, various commercially available feeders and side feeders can be used. If the resin and optionally used urea are powdered in advance, the cellulose fiber pre-fibrillated product, the resin, and the urea can be mixed with a commercially available mixer or the like before being added. Even if the resin or the like is not pulverized, it can be fed by preparing a plurality of feeders, such as a feeder for pellets and a feeder for pre-fibrillated cellulose fibers. In the kneading step for producing the masterbatch, the amount of the cellulose fiber content of the cellulose fiber preliminary defibrated material to be fed into the kneader is the sum of the cellulose fiber preliminary defibrated material, resin, and optionally used urea. It is preferably 35 to 85% by mass, more preferably 40 to 65% by mass, based on the amount.

(kneader)
In the kneading step of the present invention, a single-screw or multi-screw kneader is used. In addition to being able to melt and knead the resin and the cellulose fiber pre-fibrillated material, from the viewpoint of having a strong kneading power that promotes nanoization of the cellulose fiber pre-fibrillated material, a multi-axis kneader such as a twin-screw kneader or a four-screw kneader is used. It is desirable that a shaft kneader is used and that the parts constituting the screw include a plurality of kneaders, rotors, and the like.

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

In the present invention, the resin, the cellulose fiber pre-fibrillated material, and optionally used urea or the like that are put into the kneader in the kneading step are melt-kneaded, and at least a portion of the resin is melted and kneaded by the shearing force generated during this melt-kneading. is subjected to main defibration to prepare a resin composite containing cellulose fibers having an average fiber width of 1 μm or less at a rate of 50% by volume or more.

(Dilution kneading process)
The method for producing a resin composite of the present invention may further include a dilution kneading step of kneading the resin composite obtained in the kneading step and a diluent resin. When the dilution kneading step is included, the resin composite prepared by the kneading step can be used as a masterbatch. Moreover, when the dilution-kneading step is included, the resin composite obtained after the dilution-kneading step may contain cellulose fibers having an average fiber width of 1 μm or less at a rate of 50% by volume or more.

(Resin for dilution)
As the diluent resin used in the present invention, a general thermoplastic resin having a melting temperature of 250° C. or lower can be used. The diluent resin may be used singly or as a mixture of two or more resins.

When the resin composite obtained in the kneading step is used as a masterbatch, a resin composite further containing the diluent resin can be obtained by adding a diluent resin to the masterbatch and melt-kneading it. When the diluent resin is added and melt-kneaded, the two components may be mixed at room temperature without heating and then melt-kneaded, or may be mixed with heating and melt-kneaded.

The same kneader as used in the kneading process can be used as the kneader for melting and kneading by adding the resin for dilution. Also, the melt-kneading temperature can be adjusted according to the resin used in the kneading step. The heating setting temperature during melt-kneading is preferably about ±10° C., the lowest processing temperature recommended by the supplier of the thermoplastic resin. By setting the temperature within this temperature range, the cellulose fiber pre-defibrated material and the resin can be uniformly mixed.

The resin composite produced by the production method of the present invention further includes, for example, surfactants; polysaccharides such as starches and alginic acid; natural proteins such as gelatin, glue and casein; tannins, zeolites, ceramics, metal powders, etc. colorants; plasticizers; fragrances; pigments; flow control agents; leveling agents; conductive agents; may The content of any additive may be appropriately contained within a range that does not impair the effects of the present invention.

(resin composite)
The resin composite obtained by the production method of the present invention may be obtained by a method of kneading the resin and the cellulose fiber pre-fibrillated material at once, or may be obtained by kneading the resin and the cellulose fiber pre-fibrillated material together. It may be a resin composite obtained in a dilution kneading step of kneading a masterbatch obtained by kneading and a resin for dilution.

(Application)
A molding material and a molded article (molding material and molded article) can be produced using the resin composite of the present invention. Examples of the shape of the molded body include various shaped bodies such as film-like, sheet-like, plate-like, pellet-like, powder-like, and three-dimensional structures. As a molding method, die molding, injection molding, extrusion molding, blow molding, foam molding, etc. can be used.

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

Interior materials, exterior materials, structural materials, etc. for transportation equipment such as automobiles, trains, ships, and airplanes; housings, structural materials, internal parts, etc. for electrical appliances such as personal computers, televisions, telephones, and clocks; mobile communications such as mobile phones Housings, structural materials, internal parts, etc. of equipment; housings, structural materials, internal parts, etc. of portable music players, video players, printers, copiers, sporting goods; building materials; office equipment such as stationery, etc. It can be effectively used as a vessel, container, or the like.

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

(Fiber length distribution of cellulose fiber pre-fibrillated product, measurement of fine content)
The fiber length distribution and fine content of the cellulose fiber pre-fibrillated product were measured using a fiber tester manufactured by Lorentzen & Wettre. In the present invention, the fiber length indicates the number average fiber length based on ISO16065. Specifically, 0.1 g of pulp dry mass was stirred and disaggregated with 300 mL of water, and measured with a fiber tester.

In the present invention, the fine portion refers to fibers having a fiber length of 0.2 mm or less. The higher the value, the more the defibration proceeds by kneading, which will be described later. However, if the value exceeds 50%, it is difficult to leave long fibers in the resin composite, which is not preferable. Its content is preferably 35 to 50%, more preferably 37 to 48%, of the total fibers including fines.

(Method for measuring degree of acetyl group substitution (DS))
(DS measurement by back titration method)
A sample of acetylated cellulose pulp was dried and accurately weighed 0.5 g (A). 75 mL of ethanol and 50 mL of 0.5N NaOH (0.025 mol) (B) were added thereto and stirred for 3 to 4 hours. This was filtered, washed with water and dried, and the sample on the filter paper was subjected to FT-IR measurement, 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 back titration below.
The filtrate contains sodium acetate resulting from hydrolysis and NaOH added in excess. This NaOH neutralization titration was performed using 1N HCl (using phenolphthalein as an indicator).

・ 0.025 mol (B) - (number of moles of HCl used for neutralization)
= Number of moles of acetyl groups ester-bonded to hydroxyl groups of cellulose, etc. (C)
(Cellulose repeating unit molecular weight 162
× number of moles of cellulose repeating units (unknown (D))
+ (molecular weight of acetyl group 43 × (C))
= 0.5 g (A) of weighed sample
The number of moles (D) of repeating units of cellulose was calculated from the above formula.

DS was calculated by the following formula.
・DS = (C)/(D)

(Average fiber width of acetylated cellulose fibers in resin composite)
Regarding the acetylated cellulose fibers in the resin composite, the ratio of the average fiber width of 1 μm or less was obtained by X-ray computed tomography (hereinafter abbreviated as X-CT) (SKYSCAN1272 (manufactured by Bruker): resolution 0.5 μm). It was done by Specifically, this apparatus cut out a 1 cm square from the inside of the resin composite containing 10% of the produced cellulose fiber, and measured this under the above-mentioned conditions of 1 voxel of 0.5 μm. After reconstructing this three-dimensionally, a plane of 200×200 μm or more was selected, and after separating the fiber portion and the non-fiber portion from the shape, this image was binarized to remove fibers and noise of 2 voxels or less. Using 10 planes or more of this planar image in the range of 200 μm in the Z-axis direction, the average of the fiber portion (undisentangled fiber amount) was obtained. The fibers displayed in the image by the above operation mean fibers having a fiber width of more than 1 μm. The ratio of cellulose fibers having an average fiber width of 1 μm or less was determined by the following formula using this averaged amount of unfibrillated fibers.

In the above formula, the cellulose content was 10% and the cellulose density was 1.5 g/cm ³ because the example contained 10% cellulose fiber.

(Measurement of tensile modulus, tensile strength, and tensile elongation)
150 g of pellet-shaped resin moldings obtained in Examples and Comparative Examples were put into a small molding machine ("MC15" manufactured by Xplore Instruments), and the temperature of the heating cylinder (cylinder) was 200 ° C., and the mold temperature was 40 ° C. A dumbbell-shaped test piece (type A12, JIS K 7139) was molded under the conditions. Using a precision universal testing machine (manufactured by Shimadzu Corporation, "Autograph AG-Xplus"), the obtained test piece was tested at a test speed of 1 mm/min and an initial distance between marked lines of 30 mm. Strength and tensile elongation (strain and elongation until breakage) were measured. Table 1 shows the tensile elongation results. Also, using only the diluent resin, a dumbbell-shaped test piece was molded 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. The ratio of the measured values of each sample to the modulus of elasticity and tensile strength of 100 is defined as the reinforcement ratio, and Table 1 shows the results.

(Kneader and operating conditions used for manufacturing masterbatch and resin composite)
"MFU15TW-45HG-NH" twin-screw kneader manufactured by Technobell Co., Ltd. Screw diameter: 15 mm, L/D: 45, Processing speed: 300 g/h, Screw rotation speed: 200 rpm, Set temperature: Operating at the melting point of each resin + 5 ° C. .

(Example 1)
(Beating treatment of pulp)
Unbleached softwood kraft pulp containing 50% water (NUKP: lignin content 8% by mass) was adjusted to a solid concentration of 20%, and 20 kg of this was treated with a single disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd., plate blade width: 4 mm, Groove width: 5 mm), clearance: 0.25 mm, passing twice, and processing so that the measured value of freeness at 5 points is 350 mL to 450 mL (beating treatment), cellulose fiber pre-fibrillation prepared things. The fiber length distribution of the obtained cellulose fiber pre-fibrillated product was measured using Lorentzen & Wettre. Table 1 shows the results.

(Preparation of acetylated pulp)
20.0 kg (solid content: 4.0 kg) of hydrous softwood unbleached kraft pulp (NUKP) that has been subjected to the above-mentioned cellulose fiber pre-fibrillation, that is, beating treatment, is added to a stirrer ("FM150L" manufactured by Nippon Coke Industry Co., Ltd.) , stirring was started and dehydration was carried out under reduced pressure at 50°C. Then, 4.0 kg of acetic anhydride was added and reacted at 80° C. for 2 hours. After the reaction, the pulp was sufficiently washed with water, dehydrated, and dried under reduced pressure to obtain acetylated pulp having a pulp solid content concentration of 98% by mass, that is, an acetylated cellulose fiber pre-fibrillated material. The degree of acetyl group substitution (DS) of the acetylated cellulose fiber pre-fibrillated product was 0.5.

(Materials used for manufacturing masterbatch A and resin composite A)
(a) Pre-fibrillated acetylated cellulose fiber (b) Resin for masterbatch PA6: (PA6 P1011F manufactured by Ube Industries, Ltd.)
(c) Resin for dilution PA6: (PA6 1011FB manufactured by Ube Industries, Ltd.)

(Production of masterbatch A)
The above acetylated cellulose fiber pre-fibrillated product (460 g as absolute dry product) and masterbatch resin (PA6: 720 g) were placed in a polyethylene bag and mixed by shaking. 1180 g of the obtained mixture was put into a kneader using a feeder (manufactured by Technobell Co., Ltd.) attached to the above-mentioned twin-screw kneader, and kneaded at a heating temperature to mix the acetylated cellulose fiber pre-fibrillated material with the resin. A masterbatch A containing the acetylated cellulose fibers obtained by main disentanglement by kneading and a masterbatch resin was produced.

(Production of resin composite A)
60 g of the obtained masterbatch A and 120 g of the diluent resin (PA6) were mixed and kneaded at the heating temperature in the twin-screw kneader. The melt-kneaded product was then pelletized using a pelletizer to obtain a resin composite (molded product) A in the form of pellets containing the acetylated cellulose fibers, the masterbatch resin, and the diluent resin. In the acetylated cellulose fibers contained in the resin composite A, the ratio of the average fiber width of 1 μm or less was 67% by volume. As for the acetylated cellulose fiber after kneading with the resin, it was difficult to separate the resin from the fiber, so it was difficult to measure the fiber length.

(Materials used for manufacturing masterbatch B and resin composite B)
(a) Pre-fibrillated acetylated cellulose fiber (b) Masterbatch resin MAPP: (MAPP PMAH1000P manufactured by Toyobo)
(c) Urea: (manufactured by Wako Pure Chemical Industries)
(d) Dilution resin PP: (PP MA04A manufactured by Japan Polypropylene Corporation)

(Production of masterbatch B)
The above acetylated cellulose fiber pre-fibrillation product (460 g as absolute dry product), masterbatch resin (MAPP: 110 g) and powdered urea (180 g) were placed in a polyethylene bag and mixed by shaking. 750 g of the obtained mixture was put into the kneader using a feeder (manufactured by Technobell Co., Ltd.) attached to the above-mentioned twin-screw kneader, and kneaded at a heating temperature, and the pre-defibrated product of the acetylated cellulose fibers was mixed with the resin. A masterbatch B containing the acetylated cellulose fibers obtained by the main defibration by kneading and the masterbatch resin was produced.

(Production of resin composite B)
38 g of the obtained masterbatch B and 142 g of diluent resin (PP) were mixed and kneaded at the heating temperature by the twin-screw kneader. The melt-kneaded product was then pelletized using a pelletizer to obtain a pellet-shaped resin composite (molded product) B containing the acetylated cellulose fibers, the masterbatch resin, and the diluent resin. The acetylated cellulose fibers contained in the resin molding B had a ratio of 60% by volume having an average fiber width of 1 μm or less.

(Example 2)
Cellulose fiber pre-defibrated material in the same manner as in Example 1 except that in the beating treatment of pulp, the number of passes through the single disc refiner was set to 3 times, and the measured value of freeness at 5 points was changed to 150 mL to 250 mL. prepared. Also, an acetylated cellulose fiber pre-fibrillated material was prepared in the same manner as in Example 1 except that this pre-fibrillated cellulose fiber material was used. Masterbatches A and B and resin composites A and B were produced in the same manner as in Example 1 except that the pre-fibrillated material obtained in Example 2 was used. In the acetylated cellulose fibers contained in the resin composites A and B, the proportions having an average fiber width of 1 μm or less were 71% by volume and 65% by volume, respectively.

(Comparative example 1)
Masterbatch A, B and resin composites A and B were produced. The acetylated cellulose fibers contained in the resin composites A and B had an average fiber width of 1 μm or less at 59% by volume and 51% by volume, respectively.

(Comparative example 2)
Cellulose fiber pre-defibrated material in the same manner as in Example 1 except that in the beating treatment of pulp, the number of passes through the single disc refiner was set to 1 time, and the measured value of freeness at 5 points was changed to 450 mL to 550 mL. prepared. Also, an acetylated cellulose fiber pre-fibrillated material was prepared in the same manner as in Example 1 except that this pre-fibrillated cellulose fiber material was used. Masterbatches A and B and resin composites A and B were produced in the same manner as in Example 1, except that the pre-fibrillated material obtained in Comparative Example 2 was used. In the acetylated cellulose fibers contained in the resin composites A and B, the proportions having an average fiber width of 1 μm or less were 61% by volume and 54% by volume, respectively.

(Comparative Example 3)
In the pulp beating treatment, NUKP adjusted to a solid content concentration of 3% is treated five times under the condition of a single disc refiner clearance of 0.15 mm, and the measured value of freeness at 5 points is 150 mL to 250 mL. A cellulose fiber pre-fibrillated material was prepared in the same manner as in Example 1, except that a pre-fibrillated material was obtained. Also, an acetylated cellulose fiber pre-fibrillated material was prepared in the same manner as in Example 1 except that this pre-fibrillated cellulose fiber material was used. Masterbatches A and B and resin composites A and B were produced in the same manner as in Example 1, except that the pre-fibrillated material obtained in Comparative Example 3 was used. In the acetylated cellulose fibers contained in the resin composites A and B, the proportions having an average fiber width of 1 μm or less were 75% by volume and 71% by volume, respectively.

As shown in Table 1, 40% or more and less than 58% of the cellulose fiber pre-defibrated material obtained by mechanically treating the pulp of the present invention has a fiber length of 0.1 mm or more and less than 0.5 mm, and a fiber length of 1 A resin composite obtained by kneading a cellulose fiber pre-fibrillated product in which 5 mm or more and less than 2.0 mm is present at a ratio of 5% or more and less than 10% with a resin using a uniaxial or multiaxial kneader is When the ratio of cellulose fibers having an average fiber width of 1 μm or less contained in is 50% by volume or more, the balance between tensile strength or tensile elastic modulus and tensile elongation is excellent.

Claims

A resin composite comprising a resin and cellulose fibers,
The resin composite is obtained by kneading the resin and a cellulose fiber pre-fibrillated material using a uniaxial or multiaxial kneader,
The cellulose fiber pre-fibrillated material is obtained by mechanically treating pulp,
The cellulose fiber pre-fibrillated material has a fiber length of 0.1 mm or more and less than 0.5 mm at a rate of 40% or more and less than 58%, and a fiber length of 1.5 mm or more and less than 2.0 mm at a rate of 5% or more and less than 10%,
A resin composite, wherein the cellulose fibers contained in the resin composite have an average fiber width of 1 μm or less at a rate of 50% by volume or more.
The resin composite according to claim 1, wherein the pulp has a solid content concentration of 10% by mass or more during the mechanical treatment.
The resin composite according to claim 1 or 2, wherein the mechanical treatment is performed using at least one of a disc refiner and a conical refiner.
A method for producing a resin composite containing a resin and cellulose fibers,
a mechanical treatment step of mechanically treating the pulp to obtain a cellulose fiber pre-fibrillated product;
a kneading step of obtaining a resin composite by kneading the resin and the cellulose fiber pre-fibrillated material using a uniaxial or multi-axial kneader,
The cellulose fiber pre-fibrillated material has a fiber length of 0.1 mm or more and less than 0.5 mm at a rate of 40% or more and less than 58%, and a fiber length of 1.5 mm or more and less than 2.0 mm at a rate of 5% or more and less than 10%,
The method for producing a resin composite, wherein the cellulose fibers contained in the resin composite have an average fiber width of 1 μm or less at a rate of 50% by volume or more.
A cellulose fiber pre-fibrillated material used for a resin composite,
A cellulose fiber pre-defibrated material having a fiber length of 0.1 mm or more and less than 0.5 mm at a rate of 40% or more and less than 58% and a fiber length of 1.5 mm or more and less than 2.0 mm at a rate of 5% or more and less than 10%.