Cellulose fine fiber and method for producing the same

Abstract

To provide a cellulose fine fiber which can suppress decomposition of a resin upon compounding of a cellulose fine fiber and a resin while being derived from a plant, thereby is excellent in stability in long-term storage, can give a resin composition which is stable trough a plurality of heat histories such as material recycling accompanied by melt-kneading, and can also suppress corrosion of a device caused by the cellulose fine fiber, and a method for producing the same.SOLUTION: A cellulose fine fiber is derived from a plant, and has a content of halogen coupled to cellulose of 250 mass ppm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to cellulose fine fibers and a method for producing the same. [Background technology]

[0002] In recent years, cellulose fine fibers have been utilized as a plant resource that can be utilized in a wide range of applications from the viewpoints of environmental protection and the expression of various unique performance characteristics. For example, cellulose fine fibers whose surfaces have been chemically modified have the fiber properties of a high elastic modulus, excellent thermal dimensional stability, and excellent interface formation with resins, and therefore have attracted attention as fillers for automotive composites and core materials for fiber-reinforced plastics. However, since special and complicated processes are required to obtain cellulose fine fibers, there are many challenges in producing cellulose fine fibers stably and inexpensively.

[0003] Patent Document 1 describes a method in which lignocellulose is chemically modified, added to a molten resin, and then kneaded and pulverized (fibrillated).

[0004] Patent Document 2 describes fibrous cellulose having an average fiber diameter of 0.1 μm or more, an average fiber length of 0.02 to 3.0 mm, and a fibrillation rate of 1.0% or more, and describes a technology in which the fibrous cellulose is subjected to a hydrophobic treatment and then blended with a resin to increase the flexural modulus of the fibrous cellulose composite resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 148233 [Patent Document 2] International Publication No. 2019 / 230573 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when plant-derived cellulose fine fibers are composited with a resin, the presence of the cellulose fine fibers can sometimes cause problems such as resin decomposition and corrosion inside equipment such as kneading equipment and molding equipment. The technologies described in Patent Documents 1 and 2 use cellulose raw materials that may be plant-derived, but do not address the above problems. As such, the prior art has not yet fully explored plant-derived cellulose fine fibers that can be produced without corrosion of equipment and that can impart excellent properties to resin compositions.

[0007] The present invention aims to solve the above-mentioned problems and to provide cellulose fine fibers and a method for producing the same, which are plant-derived and yet can suppress decomposition of the resin when the cellulose fine fibers are combined with the resin, thereby providing a resin composition that is stable during long-term storage and remains stable even after multiple thermal cycles associated with melt-kneading, such as in material recycling, and which can also suppress corrosion of equipment caused by the cellulose fine fibers. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the inventors have found that the configuration disclosed herein can solve the problems, and have thus completed the present invention. That is, the present disclosure includes the following items.

[0009] [1] Cellulose fine fibers are derived from plants and have a content of halogens bonded to cellulose of 250 mass ppm or less. [2] Cellulose fine fibers are derived from plants and have a chlorine content bound to cellulose of 250 mass ppm or less. [3] 3. The cellulose fine fibers according to item 1 or 2, having a whiteness of 50% or more. [4] Item 1. A method for producing cellulose fine fibers, A method for producing cellulose fine fibers, comprising a step of defibrating a cellulose raw material having a content of halogen bonded to cellulose of 300 mass ppm or less. [5] Item 2. The method for producing cellulose fine fibers, A method for producing cellulose fine fibers, comprising a step of defibrating a cellulose raw material having a chlorine content bonded to cellulose of 300 mass ppm or less. [6] Item 6. The method for producing cellulose fine fibers according to Item 4 or 5, wherein the cellulose raw material is a chemically modified product. [7] Item 7. The method for producing cellulose fine fibers according to Item 6, wherein the chemically modified product is an acetylated product. [8] 7. The method for producing cellulose fine fibers according to any one of items 4 to 6, wherein the cellulose raw material is derived from cotton. [9] 9. The method for producing cellulose fine fibers according to any one of items 4 to 8, wherein the defibrating is a beating treatment using a disc refiner.

[10] A resin composition comprising the cellulose fine fibers according to any one of items 1 to 3 and a resin.

[11] A step of obtaining cellulose fine fibers by the method described in any one of Items 4 to 9; a step of mixing the cellulose fine fibers and a resin to obtain a resin composition; A method for producing a resin composition, comprising:

[12] A molded article obtained by molding the resin composition according to item 10.

[13] Item 13. The molded body according to item 12, which is a profile extrusion molded body.

[14] A method for producing a profile extrusion molded body, Item 11. A method comprising a step of profile extruding the resin composition according to item 10.

[15] Item 11. A 3D printing material comprising the resin composition according to item 10.

[16] Item 16. The 3D printing material according to item 15, having the form of a filament or powder.

[17] A shaped object formed by using the resin composition according to item 10 or the 3D printing material according to item 15 or 16 with a 3D printer.

[18] A method for manufacturing a shaped object, comprising: A method comprising a step of modeling the resin composition according to item 10 or the 3D printing modeling material according to item 15 or 16 using a 3D printer. [Effects of the Invention]

[0010] According to one aspect of the present invention, a cellulose fine fiber and a method for producing the same can be provided, which are plant-derived and yet can suppress decomposition of the resin when the cellulose fine fiber is combined with the resin, thereby providing a resin composition that is stable during long-term storage and remains stable even after multiple thermal cycles associated with melt-kneading, such as in material recycling, and can also suppress corrosion of equipment caused by the cellulose fine fiber. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of the arrangement of blades and grooves of a disc refiner. [Figure 2] FIG. 2 is a diagram illustrating the blade width, groove width, and blade distance of a disc refiner. [Figure 3] FIG. 1 is a diagram showing the cross-sectional shape of the die of the single-screw extruder used in Examples 11 to 13. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described by way of example, but the present invention is not limited to these embodiments and can be practiced in various modifications within the scope of the invention.

[0013] <Cellulose microfibers> The cellulose fine fibers of this embodiment include both unmodified cellulose fine fibers and chemically modified cellulose fine fibers.

[0014] In the cellulose fine fibers of this embodiment, the content of halogen bonded to cellulose is 250 ppm by mass or less. In one embodiment, the content of chlorine bonded to cellulose is 250 ppm by mass or less. In this disclosure, the content of halogen bonded to cellulose (chlorine in one embodiment) in the cellulose fine fibers means the halogen content (chlorine content in one embodiment) after the cellulose fine fibers are subjected to the "immersion and filtration treatment" described below. In this disclosure, the content of halogen (chlorine in one embodiment) is a value measured according to the "halogen content measurement" described below. When the content of halogen bonded to cellulose (chlorine in one embodiment) is within the above range, decomposition of the resin during compounding of the cellulose fine fibers with the resin can be suppressed, resulting in a resin composition that is stable during long-term storage and stable even after multiple thermal cycles associated with melt-kneading, such as material recycling. In addition, a halogen content (chlorine content in one embodiment) within the above range is advantageous for suppressing corrosion inside equipment such as kneading equipment and molding equipment.

[0015] When halogens are present in the cellulose fine fibers, the halogens may be strongly bound to the cellulose by chemical or physical bonds. In one embodiment, when the cellulose fine fibers are immersed in pure water at 25°C for 48 hours, followed by filtration and drying, as in the [immersion and filtration treatment] of the present disclosure, 80% or more by mass of the halogens before the treatment may remain in the cellulose fine fibers. Due to their strong binding to the cellulose, these halogens continue to remain even when the cellulose fine fibers are composited with a resin, causing problems such as resin decomposition and corrosion of the equipment. The cellulose fine fibers of this embodiment are characterized by a low content of halogens firmly bound to the cellulose. The content of halogens remaining in the cellulose fine fibers after the [immersion and filtration treatment] of the present disclosure is used as an indicator of this.

[0016] [Soaking and filtration process] The cellulose fine fibers are immersed in pure water at 25°C for 48 hours. Specifically, the cellulose fine fibers are immersed in pure water at a solid content of 2% by mass in a 200 mL glass beaker, stirred for 1 hour with a 3-1 motor (HEIDON BL-600 type, SUS propeller blade, 100 rpm), and then allowed to stand. Next, the mixture is filtered under reduced pressure using a Teflon (registered trademark) membrane filter (1 μm mesh size) to obtain a mass of 10 g / m. 2 A sheet of the above is prepared and filtered and dried in a ventilated oven at 70°C until the moisture content is 10% by mass or less, yielding treated cellulose fine fibers. The moisture content is measured as follows: 2.00 g of a cellulose sample is placed in a glass weighing bottle, dried at 60°C for 15 hours, then at 105°C for 2 hours, weighed to a constant value in a desiccator, and then the weight is measured and calculated using the following formula: Moisture content (mass%) = (sample weight before drying - sample weight after drying) / (sample weight before drying) x 100

[0017] [Halogen content measurement] 50 mg of the above-described treated cellulose fine fibers was weighed into a quartz sample boat. The sample boat was placed in an electric furnace (manufactured by Mitsubishi Chemical Analytic Co., Ltd.) and combusted at 1000°C. The gas generated by combustion was cooled to room temperature through a cooling section and then bubbled through a fluororesin tube into an absorption solution (the absorption solution was prepared by dissolving 10 mg / L of tartrate ions, 600 mg / L of hydrogen peroxide, 2.7 mmol / L of sodium carbonate, and 0.3 mmol / L of sodium bicarbonate in ion-exchange water). This absorption solution was passed through a fluororesin tube and the halogen content was quantified using an ion chromatograph (THERMOFISHER INTEGRION CT model). The moisture content measured above was subtracted from the amount of the treated cellulose fine fibers. Finally, the value (ppm by mass) converted to the dry mass (i.e., water-free state) of the treated cellulose fine fibers was used as the halogen content of the cellulose in this embodiment.

[0018] In one aspect, the halogen that may be contained in the cellulose fine fibers of this embodiment may be in the form of a compound containing fluorine, chlorine, bromine, iodine, and / or astatine (i.e., a halogen compound). The halogen compound may be a halide (i.e., a compound of a halogen and an element with a lower electronegativity), a halogen salt, or the like, and may be an inorganic halogen compound or an organic halogen compound. Considering bleaching and the like in the production process of cellulose raw materials, cellulose fine fibers often contain fluorine and / or chlorine among halogens, and particularly often contain chlorine. When a cellulose raw material with a high halogen content (chlorine content in one aspect) is used, the benefits of reducing the halogen content (chlorine content in one aspect) in the production process of cellulose fine fibers are more pronounced.

[0019] In one embodiment, the cellulose microfibers are chemically modified cellulose microfibers. In the present disclosure, chemically modified cellulose microfibers refer to cellulose microfibers in which at least a portion of the three hydroxyl groups contained in the glucopyranose units in the backbone of the cellulose molecules present in the cellulose fibers have been chemically modified. The term "a portion" as used herein refers to the fact that at least one hydroxyl group of at least one glucopyranose unit in the cellulose structure formed by polymerizing multiple glucopyranose units has been chemically modified. In a typical embodiment, the cellulose as a whole is not chemically modified, and the chemically modified cellulose microfibers retain the crystalline structure of the cellulose prior to chemical modification. For example, when analyzed by X-ray diffraction (XRD), the crystalline structure of cellulose type I can be confirmed.

[0020] (cellulose raw material) The cellulose raw material is of plant origin, and softwood chips, hardwood chips, or non-wood cellulose raw materials (cotton-derived, hemp-derived, bagasse-derived, kenaf-derived, bamboo-derived, straw-derived, etc.) can be used, but it is preferable to use a cellulose raw material with a high degree of type I crystallinity.

[0021] Furthermore, in order to suppress discoloration and deterioration of physical properties due to heat when compositing the cellulose fine fibers with a resin, the glucose content of the cellulose raw material of this embodiment, as determined by analysis of the constituent sugars, is preferably 90% by mass or more, more preferably 91% by mass or more, and even more preferably 93% by mass or more. There is no particular upper limit to the glucose content, but considering the limits of impurities (e.g., components other than polysaccharides, such as fats and oils, various contaminants, etc.) that may be mixed into the cellulose raw material during harvesting or the purification process, or during the production process of the cellulose fine fibers, it is preferable that the glucose content be 99.5% by mass or less. In a cellulose raw material, a high glucose content usually indicates high cellulose purity. Cellulose fine fibers obtained using a cellulose raw material with high cellulose purity have the advantage of having low amounts of lignin, hemicellulose, and other components that can reduce elastic modulus and heat resistance.

[0022] The glucose content in the structural sugar analysis was measured as follows. Structural sugar analysis was performed according to the analytical procedure of the National Renewable Energy Laboratory (NREL), USA, 2008.) 3 ml of 72% sulfuric acid was added to 200 mg of sample, and the mixture was allowed to swell at 30°C for 1 hour. The mixture was then poured into a 125 ml pressure bottle with 84 ml of purified water and hydrolyzed at 120°C for 1 hour. The mixture was then suction-filtered while still hot through a 1G-3 glass filter (pre-weighed at 105°C). After solid-liquid separation, the filtrate was adjusted to a constant volume of 100 ml and the structural sugars were quantified by high-performance liquid chromatography (HPLC) with FL detection.

[0023] The purified cellulose raw material can be purified pulp or cotton-like purified product obtained from the aforementioned cellulose raw materials, such as softwood chips, hardwood chips, or non-wood cellulose raw materials (such as those derived from cotton, hemp, bagasse, kenaf, bamboo, or straw), through a digestion process for delignification, a purification step for removing hemicellulose, and a bleaching process. Furthermore, cut yarns of regenerated cellulose fibers and cut yarns of regenerated cellulose obtained by electrospinning can also be used as purified cellulose raw materials. It is preferable to set appropriate purification treatment conditions (e.g., digestion temperature, alkali concentration during digestion, bleaching agent concentration, or bleaching time) depending on the type of cellulose raw material, produce purified cellulose fibers that retain high cellulose purity, and use them as raw materials.

[0024] Among these, from the viewpoints of high cellulose purity, industrial availability, and quality stability, cellulose raw materials derived from cotton (cotton lint or cotton linter) are preferred, and cotton linter pulp is particularly preferred.

[0025] In response to recent demands for a sustainable society, recycled materials such as recycled cotton and recycled wood can also be used as cellulose raw materials. Recycled cotton, as used herein, refers to fibers made by collecting and crushing cotton scraps and waste cotton discarded at spinning and sewing factories, and fibers obtained by crushing cotton that has been once processed into cloth, clothing, etc. Furthermore, recycled wood refers to materials obtained by chipping sawmill waste, construction wood, thinned wood, forest residues, etc., and pulping them using conventional methods. Of the above-mentioned recycled materials, recycled cotton is preferred as the cellulose raw material of this embodiment.

[0026] Furthermore, further immersing the cellulose raw material or the above-mentioned purified cellulose raw material (e.g., purified pulp) in water and subjecting it to heat treatment at a temperature of 100°C or higher, and also performing an alkali treatment in which the cellulose raw material or the above-mentioned purified cellulose raw material is immersed in a strong alkaline aqueous solution (alkali concentration: 1% by mass to 10% by mass) such as an aqueous sodium hydroxide solution and left to stand or stirred for a certain period of time at a temperature in the range of 0°C to 60°C, followed by repeated washing with water, are effective in reducing the halogen content in the cellulose raw material.

[0027] In addition, it may also be effective to obtain a highly pure purified cellulose raw material by further immersing the cellulose raw material or the above-mentioned purified cellulose raw material in water and performing an enzymatic treatment using a hemicellulose-degrading enzyme such as xylases or mannanase or cellulases at a temperature in the range of 35°C to 55°C.

[0028] In particular, combining two or more of the above-mentioned heat treatment, alkali treatment, and enzyme treatment for purification can be effective for obtaining a purified cellulose raw material with a higher purity. These treatments can be significantly effective because they not only reduce the load of the pulverization treatment but also expel impurities such as lignin and hemicellulose present on the surfaces and between the microfibrils that constitute the cellulose raw material into the aqueous phase, thereby increasing the cellulose purity of the purified cellulose raw material.

[0029] The glucose content determined by analysis of constituent sugars is preferably high not only in the cellulose raw material but also in the cellulose fine fibers. The glucose content of the cellulose fine fibers is preferably 85% by mass or more, more preferably 90% by mass or more, and although there is no particular upper limit, in one embodiment it is 99.5% by mass or less.

[0030] (Whiteness of cellulose fine fibers) The cellulose fine fibers of this embodiment preferably have a whiteness of 50% or more. The whiteness here refers to a value measured using a spectrophotometer / color difference meter (Model PF700 manufactured by Nippon Denshoku Industries Co., Ltd.) according to the "Method for measuring ISO whiteness diffuse blue light reflectance of paper, paperboard and pulp (JIS P8148, ISO 2470)." When the cellulose raw material or cellulose fine fibers are obtained in the form of a sheet, they are subjected to the measurement as is. On the other hand, when in a wet state, the cellulose raw material or cellulose fine fibers are used in a sheet having a basis weight of 50 g / m. 2 The cellulose fine fibers are made into paper using a suction filtration device equipped with a polytetrafluoroethylene (PTFE) membrane filter, and dried at 80°C until the moisture content reaches equilibrium, to prepare a cellulose sheet. The whiteness of this sheet is measured using the above-mentioned device. Higher whiteness is preferable because the cellulose fine fibers have better heat resistance, and therefore improve the strength, elastic modulus, and dimensional stability when the resin composition obtained by compounding with a resin through melt kneading is mechanically recycled. The whiteness of the cellulose fine fibers is more preferably 60% or more, even more preferably 70% or more, particularly preferably 80% or more, significantly more preferably 90% or more, and most preferably 95% or more. The higher this value, the greater the effect of this embodiment, so there is no upper limit, but a practically obtainable range is preferably 99% or less.

[0031] (Whiteness of cellulose raw materials) In order to achieve the above-mentioned whiteness of the cellulose fine fibers, the cellulose raw material is preferably subjected to a bleaching treatment or the like prior to the defibration treatment. In the defibration process of this embodiment, the whiteness does not decrease significantly, so the whiteness of the cellulose raw material subjected to defibration matches the whiteness of the cellulose fine fibers. That is, the whiteness of the cellulose raw material is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, particularly preferably 80% or more, significantly more preferably 90% or more, and most preferably 95% or more. The higher this value, the greater the effect of this embodiment, so there is no upper limit, but 99% or less is preferable as a range that can be substantially obtained.

[0032] (Halogen content of cellulose raw materials) From the viewpoint of achieving the above-mentioned whiteness of the cellulose fine fibers, the content of halogen bonded to cellulose in the cellulose raw material to be defibrated (chlorine content in one embodiment) is preferably 300 ppm by mass or less, more preferably 250 ppm by mass or less, even more preferably 200 ppm by mass or less, particularly preferably 150 ppm by mass or less, and most preferably 100 ppm by mass or less. The content of halogen bonded to cellulose (chlorine content in one embodiment) is preferably as low as possible, but from the viewpoint of the production efficiency of cellulose fibers, in one embodiment, it may be 10 ppm by mass or more, or 25 ppm by mass or more. The halogen content is the amount per dry mass of the cellulose raw material, measured by the same method as described above for the cellulose fine fibers.

[0033] (Bleaching method for cellulose raw materials) In one embodiment, the method for bleaching the cellulose raw material can be one or more selected from the group consisting of chlorine treatment, alkali extraction treatment, hypochlorite treatment, chlorine dioxide treatment, oxygen bleaching treatment, hydrogen peroxide bleaching treatment, and ozone bleaching treatment.

[0034] Chlorine treatment (hereinafter also referred to as "C" treatment) is a bleaching method using chlorine gas, which solubilizes the lignin in plant-derived cellulose raw materials (typically unbleached pulp) by chlorinating the lignin.

[0035] The alkali extraction treatment (hereinafter also referred to as "E" treatment) is a treatment in which alkali-soluble chlorinated lignin is dissolved and extracted with an alkali (caustic soda, etc.).

[0036] Hypochlorite treatment (hereinafter also referred to as "H" treatment) is a treatment that bleaches carbohydrates such as cellulose and hemicellulose using sodium hypochlorite.

[0037] Chlorine dioxide treatment (hereinafter also referred to as "D" treatment) is a treatment that uses chlorine dioxide to selectively decompose and remove lignin without destroying carbohydrates.

[0038] Oxygen bleaching treatment (hereinafter also referred to as "O" treatment) is a treatment in which lignin is oxidatively decomposed and extracted using oxygen.

[0039] Hydrogen peroxide bleaching treatment (hereinafter also referred to as "P" treatment) is a treatment that involves oxidative decomposition and extraction of lignin using hydrogen peroxide.

[0040] Ozone bleaching treatment (hereinafter also referred to as "Z" treatment) is a treatment in which lignin is oxidatively decomposed and extracted using ozone.

[0041] Effective combinations of bleaching methods include CEH treatment, CEHH treatment, CEHD treatment, CEHED treatment, CEHDED treatment, and CEDED treatment. These alphabetical arrangements indicate the sequence of each treatment, but the order may be reversed depending on the purpose. Other examples include C / D treatment, in which part of the chlorine used in the chlorine treatment is replaced with chlorine dioxide (here, " / " indicates that both treatments are performed simultaneously), treatment in which C in the above-mentioned sequence is replaced with C / D, E / O treatment or E / P treatment, in which a small amount of oxygen or hydrogen peroxide is added to strengthen the alkalinity during E treatment, treatment in which E in the above-mentioned sequence is replaced with E / O treatment or E / P treatment, treatment in which oxygen is further added to E / O treatment or E / P treatment, and treatment in which E in the above-mentioned sequence is replaced with E / OH treatment. These can be combined appropriately depending on the application and purpose.

[0042] Alternatively, equivalent ECF (Elemental Chlorine Free, i.e., DE / ODD, E / OEDP) treatment, TCF (Total Chlorine Free, i.e., E / OP-ZP) treatment, etc. may also be used.

[0043] In order to reduce the halogen concentration (chlorine concentration in one embodiment) in the cellulose raw material, a treatment that uses as little chlorine as possible is preferred, and from this viewpoint, alkali extraction treatment, oxygen treatment, ozone treatment, chlorine dioxide treatment, hypochlorite treatment, or a combination of these, ECF treatment, or TCF treatment is preferred. In order to achieve high whiteness while maintaining the degree of polymerization of the cellulose raw material, i.e., strength, alkali extraction treatment, ozone treatment, ECF treatment, or TCF treatment is preferred, and among these, ECF treatment or TCF treatment is more preferred.

[0044] (Fiber length distribution of cellulose raw materials) In one embodiment, the cellulose raw material has an average fiber length (specifically, a length-weighted average fiber length, described below) of 3 mm or less as measured by an automatic fiber shape analyzer, and / or the number ratio of fibers having a fiber length of 3 mm or more is 20% or less. When the cellulose raw material has a specific fiber length distribution, the energy transfer to the finer or beating section during the defibration step (for example, beating using a disc refiner or high-pressure homogenizer) is improved, and clogging is less likely to occur, so that stable defibration processing can be achieved even when the cellulose concentration is relatively high.

[0045] The average fiber length is more preferably 2.5 mm or less, even more preferably 2.0 mm or less, and particularly preferably 1.6 mm or less. The smaller the average fiber length, the greater the above-mentioned effect, so there is no particular lower limit, but in consideration of the mechanical properties when the cellulose fine fibers after beating are used as a resin filler, the average fiber length is preferably 0.1 mm or more, and more preferably 0.5 mm or more.

[0046] The proportion of fibers having a length of 3 mm or more is more preferably 15% or less, and even more preferably 10% or less. The smaller this value, the greater the effect described above. Therefore, there is no particular lower limit, but a range that can be obtained by practical pretreatment is preferably 0.5% or more, and more preferably 1% or more.

[0047] The fiber length of the above-mentioned cellulose raw material can be measured using an automatic fiber shape analyzer (Morfi Neo manufactured by Techpap). The measurement procedure is described below.

[0048] The cellulose raw material is dispersed in pure water to prepare 1 L of aqueous dispersion. The final solids concentration of the cellulose raw material is 0.003 to 0.005% by mass. If the aqueous dispersion contains less than 2% by mass of the cellulose raw material before dilution, simple mixing with a spatula or the like is sufficient. However, if the aqueous dispersion contains 2% by mass or more, or if the cellulose raw material is in the form of a wet cake or powder, dispersion is performed using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18") under the following processing conditions: rotation speed 25,000 rpm x 5 minutes. If the material is dispersed in a medium other than water, it is dispersed in a sufficient amount of pure water using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18") at 25,000 rpm for 5 minutes, after which the medium is removed by means of suction filtration or the like, and the material is dispersed again in pure water using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18") at 25,000 rpm for 5 minutes to a final solids concentration of 0.003 to 0.005% by mass, thereby replacing the medium with water.

[0049] Next, the aqueous dispersion prepared above is placed in an autosampler and measured. The measurement results are output in txt format (or csv format), and each shape parameter is extracted or calculated from the measurement results. The following values ​​from the measurement results are used for each parameter.

[0050] 1) Length-weighted average fiber length: Mean length-weighted length [μm] 2) Proportion of fibers with a fiber length of 3 mm or more: From the histogram of the fiber length distribution in 1), calculate the proportion of fibers with a fiber length of 3 mm or more to all fibers using the following formula. Percentage of fibers with a fiber length of 3 mm or more (%) = Number of fibers with a fiber length of 3 mm or more / Total number of fibers measured x 100 3) Mean fiber width [μm]

[0051] (Pretreatment of cellulosic raw materials) The cellulose raw material of this embodiment may be subjected to one or more pretreatments selected from pulverization, grinding, and classification in order to control the fiber length within a specific range, and then used for defibration (e.g., beating treatment). The pretreatment according to one embodiment is a treatment for producing a pretreated cellulose raw material having an average fiber length of 3 mm or less and / or having a number proportion of fibers having a fiber length of 3 mm or more of 20% or less from a cellulose raw material having an average fiber length of more than 3 mm and having a number proportion of fibers having a fiber length of 3 mm or more of 20% or less.

[0052] The pulverization treatment of this embodiment is a treatment of pulverizing the cellulose raw material in a dry manner, and a coarse pulverizer, an intermediate pulverizer, a fine pulverizer, or the like can be used as the pulverizer.

[0053] Examples of coarse crushers include jaw crushers (i.e., crushers that bite the raw material between fixed and movable plates and crush it with a strong compressive force), gyratory crushers (i.e., crushers that bite the raw material between a fixed cone cave and an eccentrically rotating mantle and crush it with a compressive force), and impact crushers (i.e., crushers that impact-crush the raw material with impact blades attached to a rapidly rotating cylindrical rotor and then impact-crush the raw material by hitting it again against a repulsion plate at high speed).

[0054] Examples of intermediate crushers include roll crushers (i.e., crushers that have multiple horizontal cylindrical rolls, pass the raw material through the gap between them, and crush it using the pressure of the two rolls, which rotate in different directions and at different speeds), edge runners (i.e., crushers that use two large, heavy rollers that roll on a horizontal plate to compress and shear the raw material, thereby crushing, mixing, and kneading it), disintegrators (i.e., crushers that use two steel cage-type rotors that rotate in opposite directions around a concentric axis, and crush the raw material supplied from the inner rotor by applying impact force through centrifugal force and rotational action), SAG (Semi-Autogenous Grinding) mills, and autogenous grinding mills.

[0055] A SAG mill is a grinding machine that uses both large stones and metal balls for grinding. SAG mills typically use the smallest balls, which are 6-15% electrically charged. As the drum rotates, the large stones and steel balls inside are thrown up and collide with the object, grinding it into smaller particles. Friction then breaks them down into smaller particles. SAG mills are characterized by their large diameter and short barrel, and the interior of the mill contains an array of plates for mixing the materials.

[0056] In an autogenous grinding mill (also known as a Run of Mine (ROM) mill), large stones are thrown up by a rotating drum, and the stones collide with each other to compress the particles. The principle is similar to the SAG mill described above, but differs in that metal balls are not used.

[0057] Examples of fine grinding mills include screen type (screen mill), rotating disk type, axial flow type, and ball mill type grinders, as well as rod mills and jet mills.

[0058] In a ball mill, sand or metal balls are usually packed inside a horizontal or slightly inclined rotating cylinder, and grinding is carried out by collision and friction with the balls. The material to be ground is fed from one end of the cylinder, and the ground product is discharged from the other end.

[0059] Rod mills have a structure similar to that of ball mills, but use rods (metal cylinders) instead of balls as the grinding medium. The material to be ground is pulverized by the impact of the rods on the rotating drum (body). Compared to ball mills, they are less likely to over-pulverize, and produce ground products with a relatively uniform particle size.

[0060] Jet mills use compressed air to generate a supersonic airflow to pulverize the material to be pulverized. Jet mills come in two types: pancake type, in which jet nozzles are arranged in a spiral, and collision type, in which the supersonic airflow from the jet nozzles is sprayed onto a collision plate.

[0061] Among the above, an intermediate grinder or a fine grinder is preferred for processing the cellulose raw material in this embodiment, and a fine grinder is more preferred. Among fine grinders, a screen type is preferred because it has excellent processing capacity.

[0062] Next, the grinding treatment of this embodiment is a treatment in which a cellulose raw material is dispersed in an aqueous medium and the resulting aqueous dispersion is subjected to a grinding treatment. This treatment is different from the grinding treatment of this embodiment in that it is a wet treatment. Examples of aqueous media include water itself, or a mixture of water and one or more organic solvents selected from the group consisting of monohydric alcohols such as ethanol, n-propanol, isopropanol, and butanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin, ketones such as acetone, nitrile solvents such as acetonitrile, and pyrrolidone solvents. The blending ratio of the organic solvent in the above-mentioned organic solvent-water mixture is preferably less than 50% by mass, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. The higher the water ratio, the better the grindability, and the higher the organic solvent ratio, the more suppressed the aggregation of fine fibers during the drying process after grinding. Therefore, the ratio of the organic solvent is preferably set in consideration of the balance between grindability and suppression of aggregation. Examples of the grinding machine that can be used in this embodiment include a rotary mill, a grinding machine, a planetary mixer, a single-screw extruder, a twin-screw extruder, and a bead mill.

[0063] A bead mill is a media agitation grinder that uses beads to nano-disperse or finely grind powder. The material to be processed and beads (media) are placed in a grinding chamber (vessel), which is then rotated at high speed by an agitation mechanism, imparting energy to the beads through centrifugal force, and grinding the material particles through shear stress, frictional force, and impact force.

[0064] Among these grinders, rotary mills, mortars, and planetary mixers are preferred because they are excellent at adjusting the fiber length distribution. The cellulose concentration in the aqueous dispersion used for grinding is preferably 50% by mass or less, more preferably 25% by mass or less, and particularly preferably 20% by mass or less. Considering the efficiency of grinding, the lower limit is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more.

[0065] Furthermore, the classification process of this embodiment refers to an operation of separating cellulose raw materials by fiber length with the aim of aligning the fiber length, and either dry classification or wet classification can be used. Examples of dry classification include gravity field classification, inertial field classification, and centrifugal field classification (natural vortex type or forced vortex type). Examples of wet classification include gravity field classification, centrifugal field classification (free vortex type), and centrifugal field classification (forced vortex type), and any of these can be used. Classification using mesh sizes in sieves, screens, wires (edge ​​wires), nets, etc., and classification by centrifugation can also be used. Considering production efficiency, classification using mesh sizes is preferred, and among these, using a dry cyclone or screen, or a wet screen or edge wire is more preferred, a wet screen or edge wire is even more preferred, and a wet edge wire is particularly preferred.

[0066] (Chemical modification of cellulose raw materials) The cellulose raw material of this embodiment is preferably chemically modified in a state before defibration (in one embodiment, in a pulp state) and then subjected to the defibration treatment described below. When pretreatment is performed before defibration, the chemical modification can be carried out before the pretreatment, but it is easier and more preferable to carry out the chemical modification after the pretreatment.

[0067] Chemical modification methods include esterification, etherification, and urethanization, with esterification being preferred. Among these, saturated monocarboxylic acid esterification, such as acetate esterification (acetylation), propionate esterification, pentanoic acid (valeric acid) esterification, and hexanoic acid (caproic acid) esterification, is preferred. Among these, acetate esterification (acetylation) is preferred in terms of the heat resistance of the cellulose fine fibers after chemical modification, but esterification using a dicarboxylic acid, such as phthalic acid esterification, may also be used. For chemical modification, a general esterification reaction method using a saturated carboxylic acid or its acid anhydride or acid chloride, or a saturated monocarboxylic acid vinyl, such as vinyl acetate or vinyl propionate, can be used.

[0068] When chemically modifying the cellulose raw material before defibration, it is preferable to carry out the chemical modification in a solvent that effectively swells the cellulose raw material in order to chemically modify the surface of the fibers inside the cellulose raw material. In one embodiment, the solvent that effectively swells the cellulose raw material is an aprotic polar solvent, and preferred are dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and mixtures of any of these.

[0069] (Chemical modification of cellulose microfibers) In another embodiment, cellulose may be chemically modified after being converted into fine fibers. In this case, the cellulose fine fibers are concentrated by suction filtration or the like to form a wet cake, which is then diluted and dispersed in a solvent for chemical modification. The chemical modification method may be the same as that used for chemically modifying cellulose raw materials.

[0070] However, when chemically modifying cellulose fine fibers, excessive drying can cause aggregation of the cellulose fine fibers, so the solids concentration is preferably 30% by mass or less, more preferably 20% by mass or less. On the other hand, since the esterifying agent also reacts with water, the less water carried over, the better, and the lower limit of the solids concentration is preferably 5% by mass or more, more preferably 10% by mass or more. If the presence of water makes chemical modification difficult, it is recommended to suction-filter the dispersion slurry diluted and dispersed in the above-mentioned solvent, and then repeatedly add more solvent to reduce the water content in the system before chemical modification. Furthermore, when chemically modifying cellulose after fine fiberization, it is preferable to use a solvent that effectively swells the cellulose raw material as described above in order to achieve uniform chemical modification, but since the surface of the cellulose fine fibers is exposed, other solvents can be used.

[0071] (Degree of substitution of cellulose raw material or cellulose fine fibers) In one embodiment, the chemically modifying group may be an acyl group. The degree of substitution (DS) of the acyl group in the cellulose raw material or cellulose fine fibers is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more. The upper limit of DS is preferably 1.3 or less, more preferably 1.1 or less, and even more preferably 1.0 or less, because if the DS is too high, the crystallinity decreases and the mechanical properties of the resin composition obtained by compounding the cellulose fine fibers with a resin decrease.

[0072] The degree of acyl substitution (DS) can be calculated from the reflection infrared absorption spectrum of the esterified cellulose fiber based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton. The peak of the absorption band of C=O derived from the acyl group is at 1730 cm -1 The absorption band of CO based on the cellulose backbone appears at 1030 cm -1The DS of esterified cellulose fibers was determined by creating a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose fibers (described later) and the modification rate (IR index 1030), which is defined as the ratio of the peak intensity of the absorption band of C=O based on acyl groups to the peak intensity of the absorption band of CO in the cellulose backbone chain, and then calculating a calibration curve from the correlation graph. Degree of substitution DS = 4.13 × IR index (1030) It can be found by using

[0073] The method for calculating the DS of esterified cellulose fiber by solid-state NMR is as follows: 13 C solid-state NMR measurements were performed, and the chromaticity can be calculated using the following formula, which is the ratio of the chromatic intensity (Inf) of a signal assigned to one carbon atom derived from the modifying group to the total chromatic intensity (Inp) of signals assigned to carbons C1-C6 derived from the pyranose ring of cellulose, which appear in the range from 50 ppm to 110 ppm. DS=(Inf)×6 / (Inp) For example, when the modifying group is an acetyl group, the signal at 23 ppm assigned to -CH3 can be used.

[0074] Use 13 The conditions for the C solid-state NMR measurement are, for example, as follows: Equipment:Bruker Biospin Avance500WB Frequency: 125.77MHz Measurement method: DD / MAS method Waiting time: 75 seconds NMR sample tube: 4mmφ Accumulation times: 640 times (approx. 14 hours) MAS: 14,500Hz Chemical shift reference: glycine (external reference: 176.03 ppm)

[0075] (DS of cellulose fine fibers s / DS) In one embodiment, the cellulose fine fibers may be cellulose fine fibers whose surfaces have been chemically modified. In one embodiment, the DS heterogeneity ratio (DSs / DS), defined as the ratio of the degree of substitution (DSs) on the fiber surface to the degree of substitution (DS) of the entire fiber, of the chemically modified cellulose fine fibers is 1.05 or more.

[0076] When the chemically modifying group is an acyl group, the DS heterogeneity ratio (DSs / DS), defined as the ratio of the degree of acyl substitution (DSs) on the fiber surface to the degree of acyl substitution (DS) in the entire fiber, is preferably 1.05 or greater. The higher the DS heterogeneity ratio, the more pronounced the sheath-core-like heterogeneity (i.e., a structure in which the fiber surface is highly chemically modified while the fiber center retains a cellulose structure close to the original, unmodified structure). This allows for the high tensile strength and dimensional stability inherent in cellulose, while improving the affinity with resins when composited with resins and the dimensional stability of resin compositions. The DS heterogeneity ratio is more preferably 1.1 or greater, or 1.2 or greater, or 1.3 or greater, or 1.5 or greater, or 2.0 or greater. From the viewpoint of ease of production of chemically modified cellulose fine fibers, the DS heterogeneity ratio is preferably 30 or less, or 20 or less, or 10 or less, or 6 or less, or 4 or less, or 3 or less.

[0077] DS s The value of varies depending on DS, but as an example, it is preferably 0.1 or more, or 0.2 or more, or 0.3 or more, or 0.5 or more, and preferably 3.0 or less, or 2.5 or less, or 2.0 or less, or 1.5 or less, or 1.2 or less, or 1.0 or less.

[0078] DSs is determined as follows. Specifically, esterified cellulose fibers powdered by freeze-pulverization are placed on a 2.5 mm diameter dish-shaped sample stage, pressed down to flatten the surface, and then measured by X-ray photoelectron spectroscopy (XPS). The XPS spectrum reflects the constituent elements and chemical bonding state of only the surface layer of the sample (typically a few nm thick). Peak separation is performed on the obtained C1s spectrum, and DSs can be calculated using the following formula: the integrated intensity (Ixf) of the peak assigned to one carbon atom derived from the chemical modification group relative to the integrated intensity (Ixp) of the peak assigned to carbons C2-C6 derived from the pyranose ring of cellulose (289 eV, C-C bond). DSs = (Ixf) × 5 / (Ixp) When the chemical modifying group is an acetyl group, after peak separation of the C1s spectrum at 285 eV, 286 eV, 288 eV, and 289 eV, the peak at 289 eV can be used for Ixp, and the peak (286 eV) derived from the O-C=O bond of the acetyl group can be used for Ixf. The conditions for the XPS measurement used are, for example, as follows. Equipment used: ULVAC-Phi VersaProbe II Excitation source: mono. AlKα 15kV x 3.33mA Analysis size: approx. 200 μmφ Photoelectron extraction angle: 45° Capture Area Narrow scan: C 1s, O 1s Pass Energy: 23.5 eV

[0079] (Crystallization degree of cellulose raw material or cellulose fine fibers) The crystallinity of the cellulose raw material or cellulose fine fibers is preferably 55% or more. When the crystallinity is within this range, the mechanical properties (strength, dimensional stability) of the cellulose itself are high, and therefore, when the cellulose fine fibers are dispersed in a resin, the strength and dimensional stability of the resin composition tend to be high. A more preferred lower limit of the crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular upper limit for the crystallinity of the cellulose raw material or cellulose fine fibers, and the higher the better, but from the viewpoint of production, a preferred upper limit is 99%.

[0080] When the cellulose is cellulose type I crystal (derived from natural cellulose), the degree of crystallinity can be calculated by the Segal method from the diffraction pattern (2θ / deg. 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction, using the following formula: Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) : Diffraction peak intensity due to the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous in cellulose type I crystals, which is the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ=18.0°)

[0081] When the cellulose is cellulose type II crystal (derived from regenerated cellulose), the degree of crystallinity can be calculated from the absolute peak intensity h0 at 2θ=12.6° assigned to the (110) plane peak of cellulose type II crystal in wide-angle X-ray diffraction and the peak intensity h1 from the baseline at this interplanar spacing, using the following formula: Crystallinity (%) =h1 / h0 ×100

[0082] Known crystalline forms of cellulose include type I, type II, type III, and type IV, of which type I and type II are particularly commonly used, while type III and type IV are obtained on a laboratory scale but are not commonly used on an industrial scale. The cellulose raw material or cellulose fine fibers of the present disclosure preferably contain cellulose type I crystals or cellulose type II crystals, since these have relatively high structural mobility and, by dispersing the cellulose fine fibers in a resin, a resin composition can be obtained that has a lower linear expansion coefficient and superior strength and elongation during tensile and bending deformation. More preferably, the cellulose raw material or cellulose fine fibers contain cellulose type I crystals and have a crystallinity of 55% or more.

[0083] (Morphological changes in cellulose raw materials or cellulose microfibers before and after chemical modification) In the chemical modification of this embodiment, stirring conditions, temperature, and the like are adjusted as appropriate. However, the fiber length retention rate of the cellulose raw material or cellulose fine fibers before and after chemical modification (fiber length retention rate (%) = average fiber length (nm) after modification / average fiber length (nm) before modification × 100) is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. The average fiber length here refers to the length-weighted average fiber length measured using an automatic fiber shape analyzer (Morfi Neo, manufactured by Techpap). Maintaining a long fiber length after chemical modification also maintains the fiber length of the resulting cellulose fine fibers, which is advantageous in improving the strength and heat resistance of the resin composition obtained by compounding the cellulose fine fibers with a resin. The higher the fiber length retention rate, the greater the effect, so there is no particular upper limit. However, considering realistic modification treatments, 99.5% or less is preferred.

[0084] (Defibrillation of cellulose raw materials) In this embodiment, cellulose raw materials can be defibrated to obtain cellulose fine fibers. In one aspect, the defibration may be a beating treatment. Defibration may be performed on cellulose raw materials that have or have not undergone the pretreatment of this embodiment, but is preferably performed on cellulose raw materials that have undergone pretreatment. In one aspect, the cellulose raw materials that have been adjusted to a specific fiber length by the pretreatment step, i.e., an average fiber length of 3 mm or less and / or a number ratio of fibers 3 mm or more of 20% or less, are dispersed in an aqueous medium, and the resulting dispersion is subjected to the following treatment to perform the beating treatment. Examples of aqueous media include water itself, or a mixture of water and one or more organic solvents selected from monohydric alcohols such as ethanol, n-propanol, isopropanol, and butanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin, ketones such as acetone, nitrile-based solvents such as acetonitrile, and pyrrolidone-based solvents. The blending ratio of the organic solvent in the mixture of the organic solvent and water is preferably less than 50% by mass, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. The higher the water ratio, the better the defibration performance, and the higher the organic solvent ratio, the more effectively the aggregation of fine fibers is suppressed during the drying process after defibration. Therefore, it is preferable to set the ratio of organic solvent in consideration of the balance between defibration performance and aggregation suppression. Beating is distinguished from the pulverization as a pretreatment of this embodiment in that it is a wet process, and from the grinding as a pretreatment of this embodiment in that the fiber length of the cellulose subjected to the treatment is different.

[0085] In this beating treatment, the cellulose raw material (for example, a pulp sheet) is dispersed in an aqueous medium using a pulper or homomixer, etc. as necessary, and then refined using a beating device such as a beater, disc refiner, high-pressure homogenizer, water jet, disc mill, ball mill, bead mill, mass colloider, homomixer, etc. The beating treatment may be carried out in one stage or multiple stages, and when carried out in multiple stages, the same device may be used multiple times, or different devices may be used in combination.

[0086] Furthermore, prior to the beating treatment, it is preferable to homogeneously disperse the cellulose raw material in an aqueous medium using the above-mentioned pulper or homomixer. In particular, when the cellulose raw material is first chemically modified and then beaten, the hydrophilicity of the cellulose raw material is reduced, so it is preferable to perform the dispersion treatment using a mixer such as a homomixer at a peripheral speed of 10 m / s or more in one embodiment, preferably 20 m / s or more, more preferably 25 m / s or more, and 90 m / s or less in one embodiment, preferably 80 m / s or less, more preferably 50 m / s or less. By reducing lumps and the like in the dispersion treatment, homogeneous cellulose fine fibers can be obtained by a homogeneous beating treatment. Note that the water in the aqueous medium used in this case can effectively be highly pure water such as distilled water or ion-exchanged water.

[0087] (Multi-stage beating) When beating cellulose in multiple stages, it is effective to combine two or more types of beating devices with different shear rates or micronization mechanisms. Here, the multistage beating method preferably involves multistage beating using disc refiners with different disc configurations, or beating in a disc refiner followed by beating in a high-pressure homogenizer. As the disc refiner, any of single-disc refiners, double-disc refiners, and conical refiners may be used, but in order to highly control beating, a single-disc refiner is preferred, as it has high accuracy in controlling the clearance between the fixed blade and the rotary blade.

[0088] (Beating with a disc refiner) Beating is particularly preferably carried out using a disc refiner. When using a disc refiner, pulp or cotton-like cellulose raw material is dispersed and stored in a tank so as to have an appropriate solids concentration in an aqueous medium, and then beaten using the disc refiner. The lower limit of the solids concentration can be adjusted to preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and even more preferably 1.0% by mass or more. The upper limit of the concentration is preferably 6% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less. As the water used in this process, highly pure water such as distilled water or ion-exchanged water can be effectively used.

[0089] When operating a disc refiner, the defibration process can be carried out using a continuous circulation process in which the slurry stored in a tank is returned to the original tank via the disc refiner. However, it is preferable to prepare two tanks connected by piping via a disc refiner (Tank A and Tank B), and first transfer the slurry from Tank A to Tank B via the disc refiner and store it there. Once the processing of the slurry in Tank A is complete, the process is switched to continuously transfer the slurry from Tank B to Tank A via the disc refiner and store it there. If the defibration process is then carried out using a continuous process in which these steps are repeated alternately, the slurry will reliably pass through the disc refiner every time it is processed, allowing a uniform number of passes to be performed on the entire amount of slurry. This is more preferable from the perspective of uniformity of the degree of defibration, i.e., the quality stability of cellulose fine fibers.

[0090] When beating is performed using a disc refiner, it may be performed in multiple stages (treatment with multiple types of blades) or in one stage (treatment with one type of blade).

[0091] Fig. 1 is a diagram illustrating an example of the arrangement of blades and grooves of a disc refiner, and Fig. 2 is a diagram illustrating the blade width, groove width, and blade-to-blade distance of a disc refiner. When multiple disc refiners are used for multi-stage beating, it is preferable to use refiners with at least two different types of blades. Referring to Figs. 1 and 2, a specific blade configuration is as follows: in a disc refiner having blades 11 and grooves 12 as shown in Fig. 1, the blade width W B , groove width W G , and cutting width W B groove width W G The value obtained by dividing the fiber length by the groove ratio (hereinafter referred to as the flute ratio) is important, and it is particularly preferable to perform a beating process (hereinafter referred to as the first stage) using a refiner equipped with blades having a blade width of 1.5 mm or more and a groove ratio of 0.1 to 1.0 (hereinafter referred to as the first stage), and then perform a beating process (hereinafter referred to as the second stage) using a refiner equipped with blades having a blade width of 0.1 mm or more and a groove ratio of 0.5 to 1.0 (hereinafter referred to as the second stage). Defibrating using a disc refiner with such a configuration reduces the number of long fibers that cause aggregation in the resin and produces cellulose fibers with a low fibrillation rate (i.e., low fuzz). In this case, a separate beating step may be added between the first and second stages.

[0092] Furthermore, when using one type of blade to perform disc refiner processing in one stage, it is particularly preferable to perform the beating process using a refiner having a blade with a blade width of 0.1 mm or more and 1.0 mm or less and a blade groove ratio of 0.5 or more and 1.0 or less.

[0093] (Blade distance in disc refiner processing) Also, referring to FIG. 2, in beating with a disc refiner, the blade distance W between two blades (specifically, the rotary blade 21 and the fixed blade 22 in FIG. 2) is LIt is advantageous to control the clearance (hereinafter simply referred to as the blade distance). By controlling the blade distance, it is possible to control the fiber length and degree of beating of the cellulose fine fibers. When processing in multiple stages, it is preferable to set the blade distance to 0.05 mm or more and 0.5 mm or less in the first stage of processing, and to set the blade distance to 0.05 mm or more and 0.3 mm or less in the second stage of processing. Furthermore, when processing in one stage, it is preferable to set the blade distance to 0.05 mm or more and 0.3 mm or less. When adjusting the blade distance, it is preferable to start with a wider blade distance and gradually narrow the blade distance while keeping the current value of the device below a certain level. By controlling in this manner, clogging and overloading of the device can be prevented, and highly uniform cellulose fine fibers can be obtained.

[0094] Thus, precise control of the blade distance between the fixed blade and the rotary blade during cellulose beating using a disc refiner is advantageous for producing homogeneous cellulose fine fibers with good mechanical properties suitable for filler. For example, the blade distance of conventional single-disc refiners is usually adjusted using a screw-type jack, which results in play in the runner section that secures the rotary blade. Therefore, if the runner section is pulled strongly in the thrust direction, it will move by approximately 0.3 mm. Therefore, a small amount of this movement (play) is preferable for obtaining beaten cellulose with high precision and good reproducibility. The movement amount is preferably 0.1 mm or less, more preferably 0.08 mm or less, and even more preferably 0.05 mm or less. In one embodiment, a single-disc refiner with the above-mentioned thrust direction movement amount of 0.03 mm may be used by using a ball screw jack as the blade distance adjustment mechanism. Furthermore, to adjust the blade distance with high precision, it is preferable to attach a reducer to the ball screw jack to enable fine adjustment of the blade distance. The use of such a single-disc refiner enables fine adjustment of the blade distance and enables beating while maintaining a constant blade distance without blade vibration during the beating process. This prevents the blades from coming into contact with each other when the blade distance is reduced, thereby preventing the fiber length from becoming too short and reducing coarse fibers. As a result, it becomes possible to reproducibly produce cellulose fine fibers with a highly uniform shape distribution that imparts excellent mechanical properties to the resin composition obtained by compounding the cellulose fine fibers with a resin.

[0095] (Number of passes in disc refiner processing) The beating process can also be controlled by the number of times the cellulose fibers pass between the rotary blade and the fixed blade (hereinafter referred to as the number of passes). By increasing the number of passes, cellulose fibers with a uniform fiber diameter and fiber length distribution can be obtained. Here, the number of passes refers to the number of times the refining process is performed (i.e., the number of times the fibers pass between the rotary blade and the fixed blade) after the blade distance is reduced to the desired distance.

[0096] The number of passes through the disc refiner is preferably 5 or more, more preferably 20 or more, and even more preferably 40 or more. As the number of passes increases, the distribution of fiber shapes gradually converges to a constant value, so a higher number is preferable, but considering productivity, the upper limit of the number of passes is preferably 300 or less.

[0097] (Method for determining beating conditions using a disc refiner) The shape of cellulose fine fibers obtained by disc refiner processing is controlled by the combined effects of the aforementioned disc refiner blade type, blade distance, number of passes, concentration, and other factors. To obtain a shape of cellulose fine fibers suitable for use in fiber-reinforced resins, it is preferable to increase the number of passes under viscous beating conditions. Viscous beating is a beating method that tends to fluff and refine fibers, while beating methods that tend to cause cutting in the fiber length direction are called free beating. The greater the number of blades, the longer the blade length, the greater the ratio of blade width to groove width (blade groove ratio), and the greater the contact angle, the greater the number of intersections between the rotating and fixed blades. This disperses the force applied to the fibers at each intersection, increasing the number of impacts on the fibers and resulting in a tendency toward viscous beating. On the other hand, when the above conditions are reversed, a tendency toward free beating is demonstrated. The blade distance of the disc refiner is preferably widened when blades that exhibit a tendency toward free beating are used, and is preferably narrowed when blades that exhibit a tendency toward free beating are used, but a blade distance that is too narrow can lead to clogging, fiber shortening due to fiber length cutting, and excessive refinement, so the blade distance is preferably 0.05 mm or more. By adjusting the blade distance and the number of passes described above depending on the shape of the cellulose raw material (fiber length and fiber diameter), the treatment concentration, and the blades used, it is possible to control the fiber shape, such as the average fiber diameter and fiber length distribution, within a preferred range.

[0098] (Multi-stage beating process using a combination of a disc refiner and a high-pressure homogenizer) In one preferred embodiment, the cellulose fibers beaten with the disc refiner are further subjected to a beating treatment with a high-pressure homogenizer. A high-pressure homogenizer is more effective at thinning fibers than a disc refiner. The high-pressure homogenizer treatment is preferably carried out at a pressure of 30 MPa or more, more preferably 50 MPa or more, and even more preferably 80 MPa or more. The upper limit of the pressure may be preferably 300 MPa or less, more preferably 250 MPa or less, and even more preferably 150 MPa or less, depending on the characteristics of the apparatus.

[0099] Examples of high-pressure homogenizers include the NS-type high-pressure homogenizer from Niro Soavi (Italy), the Lanier-type (R model) pressure homogenizer from SMT Co., Ltd., and the high-pressure homogenizer from Sanwa Machine Co., Ltd., and examples of ultra-high-pressure homogenizers include high-pressure collision type beating machines such as the Microfluidizer from Mizuho Kogyo Co., Ltd., the Nanomizer from Yoshida Kikai Kogyo Co., Ltd., and the Ultimizer from Sugino Machine Co., Ltd. However, other devices may also be used as long as they perform micronization using a mechanism similar to that of these devices.

[0100] In high-pressure homogenizer treatment, as in disc refiner treatment, defibration treatment can be carried out using a continuous circulation process in which the slurry stored in a tank is returned to the original tank via the high-pressure homogenizer. However, it is preferable to prepare two tanks connected by piping via a high-pressure homogenizer (Tank A and Tank B), and first transfer the slurry from Tank A to Tank B via the high-pressure homogenizer and store it there. When processing of the slurry in Tank A is completed, the process is switched to continuously transfer the slurry from Tank B to Tank A via the high-pressure homogenizer and store it there. If defibration treatment is carried out using a continuous process in which these steps are repeated alternately, the slurry will reliably pass through the high-pressure homogenizer every time it is treated, allowing a uniform number of passes to be performed on the entire amount of slurry, which is more preferable from the perspective of uniformity of the degree of defibration, i.e., the quality stability of the cellulose fine fibers.

[0101] [Shape of cellulose microfibers] (average fiber length) The cellulose fine fibers of this embodiment preferably have a longer average fiber length because they have better mechanical properties when used as a reinforcing material for resins and the like. That is, when the fiber length is long, the fibers become entangled when blended into the resin, allowing the cellulose fine fibers to be uniformly dispersed in the resin without forming aggregates. This improves the stress transmission of the resin composition, resulting in increased strength and fracture strain. The average fiber length, as measured by an automatic fiber shape analyzer, is preferably 400 μm or more, more preferably 500 μm or more, even more preferably 600 μm or more, and particularly preferably 700 μm or more. The length-weighted average fiber length is defined in ISO / FDIS 16065-2:2006 and is the average value of the fiber length corresponding to the actual fiber length taking into account the bent shape of the bent fiber. Since the longer the fiber length, the greater the above-mentioned effects, and therefore the upper limit is not particularly limited. However, in one aspect, the fiber length is 3 mm or less, and a preferred range is 1000 μm or less.

[0102] (average fiber diameter) The cellulose fine fibers of this embodiment preferably have an average fiber diameter of 300 nm or less as measured by an automatic fiber shape analyzer. Having an average fiber diameter within this range makes it easy to sufficiently increase the L / D of each individual cellulose fiber. When the L / D is large, the cellulose fine fibers become entangled with each other in the resin, thereby increasing the strength of the resin composition. The average fiber diameter of the cellulose fine fibers is more preferably 200 nm or less, even more preferably 150 nm or less, and most preferably 130 nm or less. Since a smaller average fiber diameter is preferred because it allows for a larger L / D, there is no particular lower limit. However, since a certain thickness is desired to increase the bending elasticity of the resin composition, the average fiber diameter is preferably 10 nm or more, more preferably 40 nm or more.

[0103] (Coefficient of variation (CV) of average fiber length) In the cellulose fine fibers of this embodiment, when the variation in the fiber length is small, the anisotropy of mechanical properties (tensile strength, flexural strength, tensile modulus, flexural modulus, thermal expansion coefficient, etc.) is small, which is preferable among the reinforcing effects when added to a resin. The variation in fiber length is expressed as the coefficient of variation CV by the following formula. CV (%) = (standard deviation of fiber length (μm) / average fiber length (μm)) x 100 The CV is preferably 20% or less, more preferably 15% or less, and particularly preferably 12% or less. The lower this value, the greater the above-mentioned effect, so there is no particular lower limit, but realistically, 1% or more is preferable.

[0104] (Concentration and drying of cellulose microfibers) The cellulose fine fibers of this embodiment can be obtained in the form of a wet molded body (wet cake) by dehydrating the slurry using a filter or a paper machine. Among these, the papermaking method using a paper machine is advantageous in that it reduces drying shrinkage of the cellulose fine fibers. In one aspect, the slurry is dehydrated by filtering it on a porous substrate. In the papermaking method, any papermaking machine can be used that is equipped with wires of a mesh size that dehydrates the slurry and retains the cellulose fine fibers. When a flat sheet-shaped composite molded body is to be obtained, a papermaking machine such as an inclined wire papermaking machine, a Fourdrinier papermaking machine, or a cylinder papermaking machine can be used.

[0105] When cellulose fine fibers are used as a dry filler, they can be dried using a known drying device such as a hot air dryer or a spray dryer. Because cellulose tends to aggregate during the drying process and is difficult to redisperse afterwards, it is preferable to use a dispersant. By increasing the redispersibility, the mechanical properties and stability of the resulting resin composition can be improved. It is desirable to add a dispersant to a cellulose aqueous dispersion, and then dry it under shear to obtain a cellulose powder.

[0106] The dispersant can be at least one selected from the group consisting of surfactants, organic compounds with a boiling point of 100° C. or higher, and resins having a chemical structure that can highly disperse cellulose.

[0107] The surfactant may have a chemical structure in which a moiety having a hydrophilic substituent and a moiety having a hydrophobic substituent are covalently bonded. As the surfactant, surfactants used for various purposes such as food and industrial use can be used, and for example, the following can be used alone or in combination of two or more:

[0108] Any of anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants can be used as the surfactant. However, in terms of affinity with cellulose, anionic surfactants and nonionic surfactants are preferred, and nonionic surfactants are more preferred.

[0109] Among the above, surfactants having a polyoxyethylene chain, a carboxyl group, or a hydroxyl group as a hydrophilic group are preferred in terms of affinity with cellulose, polyoxyethylene surfactants (polyoxyethylene derivatives) having a polyoxyethylene chain as a hydrophilic group are more preferred, and nonionic polyoxyethylene derivatives are even more preferred. The polyoxyethylene chain length of the polyoxyethylene derivative is preferably 3 or more, more preferably 5 or more, even more preferably 10 or more, and particularly preferably 15 or more. The longer the chain length, the higher the affinity with cellulose, but in terms of the balance with coatability, the upper limit is preferably 60 or less, more preferably 50 or less, even more preferably 40 or less, particularly preferably 30 or less, and most preferably 20 or less.

[0110] Among the surfactants described above, alkyl ether, alkylphenyl ether, rosin ester, bisphenol A, β-naphthyl, styrenated phenyl, and hydrogenated castor oil hydrophobic groups are particularly suitable due to their high affinity with resins. The preferred alkyl chain length (in the case of alkylphenyl, the number of carbon atoms excluding the phenyl group) is 5 or more, more preferably 10 or more, even more preferably 12 or more, and particularly preferably 16 or more. The higher the number of carbon atoms in the alkyl chain, the higher the affinity with typical resins, so there is no upper limit, but the upper limit for the number of carbon atoms is preferably 30 or less, and more preferably 25 or less.

[0111] Among these hydrophobic groups, those having a cyclic structure or those having a bulky and multifunctional structure are preferred. As those having a cyclic structure, alkylphenyl ether type, rosin ester type, bisphenol A type, β-naphthyl type, and styrenated phenyl type are preferred, and as those having a multifunctional structure, hydrogenated castor oil type is preferred. Among these, rosin ester type and hydrogenated castor oil type are particularly more preferred.

[0112] In addition, organic compounds with a boiling point of 100°C or higher may be effective as non-surfactant dispersants. Examples of such organic compounds include polyethylene glycol, polypropylene glycol, and organic compounds having a glycerin structure. Furthermore, depending on the type of resin, for example, if the resin is a polyolefin, high-boiling organic solvents such as liquid paraffin and decalin are effective. Furthermore, if the resin is a polar resin such as nylon or polyacetate, it may be effective to use a solvent similar to the aprotic solvent that can be used in producing cellulose microfibers, such as dimethyl sulfoxide.

[0113] (Applications of cellulose microfibers) In one aspect, the cellulose fine fibers of this embodiment may have an appropriate fineness that is neither too coarse nor too fine, and may have good homogeneity. The cellulose fine fibers of this embodiment can be suitably used as a reinforcing filler for fiber-reinforced resins. Furthermore, they can be molded into a sheet and impregnated with resin to be used as a prepreg material, or as a building material such as concrete. Alternatively, various molded articles of any shape can be obtained using a resin composition containing the cellulose fine fibers of this embodiment and a resin.

[0114] <Resin composition> One aspect of the present invention provides a resin composition containing the cellulose fine fibers of the present disclosure and a resin, i.e., a fiber-reinforced resin. Another aspect of the present invention provides a method for producing a resin composition, comprising the steps of obtaining cellulose fine fibers using the method of the present embodiment and mixing the cellulose fine fibers with a resin to obtain a resin composition. Methods for obtaining the resin composition are not particularly limited, but include mixing the cellulose fine fibers with a resin dissolved in a solvent and drying the solvent; mixing the cellulose fine fibers with a dispersant or the like, drying the mixture, and adding it to a melt-kneaded resin using a twin-screw extruder; wet-laid papermaking of the cellulose fine fibers, forming a sheet, and then impregnating the sheet with a resin to form a composite; and mixing the cellulose fine fibers with synthetic fibers, forming a nonwoven fabric by, for example, wet-laid papermaking, and then heat-pressing the mixture at a temperature above the melting point of the synthetic fibers.

[0115] (resin) The resin contained in the resin composition may be a thermosetting resin, a photocurable resin, or a thermoplastic resin. Among these, thermoplastic resins are preferred because the cellulose fine fibers of this embodiment have excellent heat resistance. The cellulose fine fibers of this embodiment can be suitably composited with resins having a melting point of 200°C or higher and a melt-kneading temperature of 250°C or higher. In this disclosure, the melting point refers to the peak-top temperature of the endothermic peak (the highest peak if two or more peaks are present) that appears when the temperature is increased at a rate of 10°C / min using a differential scanning calorimeter (DSC). Examples of thermoplastic resins include one or more selected from the group consisting of polyolefins (polyethylene, polypropylene, etc.), polyesters (polyethylene terephthalate, polylactic acid, etc.), polyamides (PA6, PA66, PA4, PA12, aromatic polyamides, etc.), polyacrylonitrile, polymethyl methacrylate, polystyrene, polyvinyl alcohol, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide. These thermoplastic resins may be used alone or in combination of two or more.

[0116] (Content of cellulose fine fibers in resin composition) The content of cellulose fine fibers in the resin composition is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, even more preferably 10% by mass or more, and even more preferably 20% by mass or more. From the viewpoint of avoiding performance degradation due to separation of the continuous resin layer and molding defects due to reduced fluidity during molding of the resin composition, it is preferable that the content of cellulose fine fibers is not too high, and the upper limit of the content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0117] (Combination using nonwoven fabric method) In one embodiment, a resin composition containing cellulose fine fibers and a resin may be obtained, for example, by a nonwoven fabric forming method. In one embodiment, the nonwoven fabric contains the cellulose fine fibers of the present disclosure, and in another embodiment, the nonwoven fabric contains the cellulose fine fibers of the present disclosure and synthetic fibers. By using the nonwoven fabric forming method, the cellulose fine fibers are formed into continuous layers in the resin by hydrogen bonding, and the continuous layers form a structure highly oriented in a two-dimensional plane direction, resulting in a material with excellent strength.

[0118] A preferred example of the content of the cellulose fine fibers in the nonwoven fabric may be in the same range as the content of the cellulose fine fibers in the resin composition from the same viewpoint as described above.

[0119] The synthetic fiber content in the nonwoven fabric is preferably 50% by mass or more, or 60% by mass or more, from the viewpoint that the synthetic fibers can be melted to form a continuous layer during the production of the resin composition, which makes it easier to increase the strength of the resin composition, and that the dehydration load during the papermaking process during the production of the nonwoven fabric is small, and from the viewpoint of ensuring that the cellulose fine fiber content is not too low and thus obtaining a good reinforcing effect from the cellulose fine fibers, the synthetic fiber content is preferably 99% by mass or less, or 95% by mass or less, or 90% by mass or less.

[0120] (synthetic fiber) In one embodiment, the synthetic fibers used in the nonwoven fabric production method are synthetic staple fibers. In one embodiment, the synthetic staple fibers may have an average fiber length of 20 mm or less. The synthetic staple fibers may be fibrillated fibers obtained by fibrillating cut fibers after spinning by a beating treatment or the like, or fibrillated fibers obtained by spinning fibers with a multi-branched structure obtained by spinning by a flash spinning or electrospinning method and then cutting the fibers.

[0121] The average fiber diameter of the synthetic fibers is preferably 0.1 μm or more, or 0.3 μm or more, or 1.0 μm or more from the viewpoint of easy availability of synthetic fibers, and is preferably 50 μm or less, or 40 μm or less, or 25 μm or less from the viewpoint of facilitating uniform blending with cellulose fine fibers and the formation of a homogeneous nonwoven fabric. When the synthetic fibers have a relatively small average fiber diameter (for example, 10 μm or less), the difference in fiber diameter between the cellulose fine fibers and the synthetic fibers is small, so the coefficient of variation of air resistance is low and the uniformity of the structure within the nonwoven fabric is good. On the other hand, when the synthetic fibers have a relatively large average fiber diameter (for example, more than 40 μm), the difference in fiber diameter between the cellulose fine fibers and the synthetic fibers is large, so the structure within the nonwoven fabric tends to vary widely, but the nonwoven fabric can be made to have a high basis weight (for example, 200 g / m 2 or more), a good (i.e., low) coefficient of variation of air resistance can be exhibited.

[0122] The average fiber length of the synthetic fibers is preferably 0.5 mm or more, or 1.0 mm or more, or 1.5 mm or more, from the viewpoint of obtaining a nonwoven fabric with good mechanical properties, and is preferably 20 mm or less, or 15 mm or less, or 10 mm or less, from the viewpoint of facilitating uniform dispersion of the cellulose fine fibers among the synthetic fibers. The average fiber diameter and average fiber length of synthetic fibers are measured using the following method. Each synthetic fiber sample is dispersed in water to a concentration of 0.01 to 0.1% by mass, ultrasonicated (for several minutes) if necessary, and then dropped onto a glass slide. The dispersion is sandwiched between a cover glass to prevent air from entering, and the periphery of the cover glass is sealed with nail polish (the concentration of the aqueous dispersion is adjusted so that the fibers do not become entangled during microscopic imaging). Images are then taken using a microscope (Keyence Corporation, Model VHX-7000; the magnification is adjusted so that the long sides of the fibers fit within the image). The major and minor diameters of 100 fibers for each sample are measured, and the averages are used to determine the average fiber length and average fiber diameter.

[0123] The melting point of the synthetic fiber is preferably 300°C or lower, more preferably 250°C or lower, from the viewpoint of preventing thermal degradation of the cellulose fine fiber during heat pressing. On the other hand, if the melting point is too low, the practical use as a fiber-reinforced resin is low, so the melting point is preferably 90°C or higher, more preferably 160°C or higher.

[0124] Examples of polymers constituting synthetic fibers include those mentioned above as resins. Among them, preferred polymers are polyamide, polyester (polyethylene terephthalate, polylactic acid, etc.), polyoxymethylene, polyacrylonitrile, etc., because they have high affinity with cellulose fine fibers and are easy to blend uniformly. Furthermore, polyphenylene sulfide, polyphenylene ether, polyester, aromatic polyamide, etc. are suitable for applications requiring heat resistance.

[0125] The method for producing a composite by the nonwoven fabric method is described below. The nonwoven fabric method includes a slurry preparation step in which cellulose fine fibers and synthetic fibers are stirred and mixed in a medium containing water to obtain a slurry, a papermaking step in which a wet molded body is obtained from the slurry by a wet papermaking method, a drying step in which the wet molded body is dried to obtain a nonwoven fabric, and a heat pressing step in which the nonwoven fabric is heat pressed at a temperature equal to or higher than the melting point of the synthetic fibers in the nonwoven fabric to obtain a fiber-reinforced resin.

[0126] (Slurry preparation process) In this process, the cellulose fine fibers and synthetic fibers are stirred in a medium containing water to monodisperse the bundled synthetic fibers and highly distribute them among the cellulose fine fibers. Known stirring devices such as a homomixer or blender mixer can be used as the stirring device. The total solids concentration of the cellulose fine fibers and synthetic fibers is preferably 3.0% by mass or less, 1.0% by mass or less, or 0.8% by mass or less to increase the elastic modulus of the final fiber-reinforced resin by highly dispersing the cellulose fine fibers and synthetic fibers and to increase the two-dimensional orientation of the cellulose fine fibers and thereby increase the strength and breaking strain. The total solids concentration is preferably 0.05% by mass or more, 0.1% by mass or more, or 0.25% by mass or more to shorten the filtration time and improve productivity. A dispersant such as a surfactant or thickener may be used to improve the dispersibility of the synthetic fibers or the mixability of the synthetic fibers with the cellulose fibers.

[0127] (Paper making process) In this process, the slurry is dehydrated by a wet papermaking method to obtain a wet molded body. In one embodiment, the slurry is dehydrated by suction filtration on a porous substrate. In the papermaking method, any filter medium having a pore size that allows the slurry to be dehydrated and retains the cellulose fine fibers and synthetic fibers can be used. Specific filter mediums include filter paper, filter cloth, and metal mesh. In this case, a more effective dehydration effect can be obtained by combining suction filtration with a pressing process in which the wet molded body is contact-pressed from above with a roll or the like.

[0128] As the papermaking equipment, a machine such as an inclined wire paper machine, a Fourdrinier paper machine, or a cylinder paper machine can be used to obtain a wet molded body in a flat sheet shape with few defects. Also, a metal mold for pulp molding can be used to obtain a wet molded body in a desired shape.

[0129] Although continuous or batch papermaking may be used depending on the purpose, when obtaining a flat sheet, from an industrial point of view, it is preferable to produce a long sheet by continuous papermaking using a papermaking machine and then form it into a roll product form, from the viewpoint of cost. In particular, in the case of continuous papermaking using a papermaking machine, in conventional papermaking (for example, papermaking using beaten pulp fibers and synthetic fibers), the fibers in the aqueous dispersion of fibers fed onto the papermaking wire are oriented in the running direction of the wire belt due to the generation of shear stress caused by the running of the wire belt and the resulting flat sheet, and as a result, anisotropy of physical properties (strength, elastic modulus, etc.) occurs between the running direction (machine direction, MD) and the perpendicular direction (transverse direction, TD) due to the orientation of the fibers. However, the continuous papermaking of this embodiment is characterized in that differences in physical properties between the MD and TD directions are less likely to occur. This characteristic is thought to be due to the fact that when a flat sheet as a nonwoven fabric is produced using a papermaking machine, the cellulose fine fibers form isotropic soft agglomerates based on inter-fiber association in an aqueous dispersion containing cellulose fine fibers and synthetic fibers that is fed into the papermaking machine, and the synthetic fibers are incorporated into the soft agglomerates (i.e., integrated) to form composite soft agglomerates, so that even if the synthetic fibers have an anisotropic shape, they are incorporated into the composite soft agglomerates in an unoriented state (i.e., in a disordered, non-anisotropic state).

[0130] The composite soft agglomerate has sufficient strength to withstand the shear stress applied to the aqueous dispersion due to belt travel, as in conventional papermaking. Therefore, the composite soft agglomerate can be deposited and dehydrated on a belt while the synthetic fibers remain unoriented and fixed, and then subjected to a drying process or other process to form a non-anisotropic sheet. In continuous papermaking, the MD / TD property ratios, such as tensile strength, tensile modulus, flexural strength, flexural modulus, and coefficient of linear thermal expansion, typically increase with the running speed during papermaking (usually 5 m / min or higher). However, when the flat sheet of the present embodiment is produced by a continuous papermaking method, the MD / TD property ratio can be, in one aspect, 1.6 or less, preferably 1.4 or less, and more preferably 1.2 or less. Furthermore, the method of the present embodiment exhibits the advantageous feature of being less likely to exhibit anisotropy, not only in highly flat areas but also in highly curvilinear areas, even during three-dimensional molding such as pulp molding.

[0131] (drying process) In this step, the wet molded body is at least dried to obtain a nonwoven fabric. The drying method is not particularly limited, but it is preferable to use a fixed-length drying type dryer, such as a drum dryer or pin tenter, that can dry the liquid medium while maintaining the width of the wet molded body at a fixed length. The air resistance of the nonwoven fabric can be controlled by the composition ratio of the cellulose fine fibers and synthetic fibers that make up the slurry, the overall basis weight, the dispersion method of the raw material, the blending conditions of various additives, the average fiber diameter of the cellulose fine fibers, etc.

[0132] The drying temperature is preferably 45°C or higher, or 60°C or higher, or 80°C or higher, or 85°C or higher, or 90°C or higher from the viewpoint of drying efficiency (particularly from the viewpoint of increasing the evaporation rate of the liquid medium to achieve good productivity). It is also preferably 180°C or lower, or 150°C or lower, or 120°C or lower, or 115°C or lower, or 110°C or lower from the viewpoints of preventing thermal denaturation of the hydrophilic polymers (specifically, cellulose fine fibers and other components) constituting the nonwoven fabric, preventing a decrease in energy efficiency that affects costs, and further preventing the reaction of a reactive crosslinking agent, if used. For example, multi-stage drying, in which low-temperature drying at a temperature of 100°C or lower is first performed, followed by drying at a temperature above 100°C, is also effective in obtaining a highly uniform nonwoven fabric. For example, the above conditions are suitable when a blocked polyisocyanate is used as the reactive crosslinking agent.

[0133] (heat press process) In this process, the nonwoven fabric obtained in the drying process is pressed using a heated mold to melt and flow the synthetic fibers contained in the nonwoven fabric, filling the voids and producing a fiber-reinforced resin, which is a composite of cellulose fibers and resin. Because the cellulose fibers do not melt due to heat, they can remain highly oriented in the two-dimensional plane direction within the nonwoven fabric. The heating temperature can be any temperature above the melting point of the synthetic fibers; however, near the melting point, the viscosity of the resin is high, and voids may remain within the composite. Therefore, the heating temperature is preferably at least 10°C higher than the melting point of the synthetic fibers. To adjust the thickness of the molded body, multiple nonwoven fabrics may be stacked and subjected to the heat-pressing process.

[0134] <Molded body and its uses> Another aspect of the present invention provides a molded article obtained by molding the resin composition of the present disclosure. The resin composition can be molded into various molded articles by conventionally known molding methods (e.g., injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.), and is particularly suitable for injection molding.

[0135] In one aspect, the molding method may be a profile molding. That is, in one aspect, the molded article of the present embodiment may be a profile-shaped article. Another aspect of the present invention also provides a method for producing a profile-extruded article, including a step of profile-extruding the resin composition of the present embodiment.

[0136] A known method can be used for the profile extrusion molding. Specific examples of profile extrusion molding methods include feeding a resin composition into an extrusion molding machine, kneading it while heating it inside, and extruding it through a profile extrusion die to obtain an uncooled molded product. The uncooled molded product is then continuously introduced into a cooling zone and cooled to obtain a profile extrusion molded product. Another method is to perform melt kneading to obtain a resin composition, extrude the resin composition using the die of the kneader as a die for profile extrusion to obtain an uncooled molded product, and then continuously introduce the uncooled molded product into a cooling zone to cool it and obtain a profile extrusion molded product.

[0137] The lower limit of the extrusion temperature during profile extrusion is preferably +5°C, more preferably +10°C, relative to the melting point if the thermoplastic resin in the resin composition is a crystalline resin, or +5°C, more preferably +10°C, relative to the glass transition point if the thermoplastic resin is an amorphous resin. By controlling the lower limit within this range, the productivity of profile extrusion can be improved. The upper limit of the extrusion temperature during profile extrusion is preferably +100°C, more preferably +80°C, more preferably +70°C, or more preferably +60°C, relative to the melting point if the thermoplastic resin in the resin composition is a crystalline resin, or +70°C, more preferably +60°C, relative to the glass transition point if the thermoplastic resin is an amorphous resin. By controlling the upper limit within this range, deterioration of the cellulose fine fibers can be suppressed, thereby maintaining the mechanical properties of the resin composition. Furthermore, drawdown of the resin between the profile extrusion die and the cooling zone can be suppressed, resulting in good dimensional accuracy of the profile extrusion molded product.

[0138] The cross-sectional shape of the profile extrusion molded product is not particularly limited, but preferable cross-sectional shapes include sheet, pipe, tube, and angular shapes. In the case of a sheet shape, the sheet thickness can be 0.2 to 50 mm, and the sheet width can be 10 to 1500 mm. In the case of a pipe or tube shape, the thickness can be 0.1 to 30 mm, and the inner diameter can be 1 to 1000 mm. In the case of an angular shape, the angle of the corner can be 30 to 150 degrees. Furthermore, the minimum radius of curvature on the root side of the corner can be 0.1 mm.

[0139] Furthermore, the obtained molded articles can be used for a variety of purposes, such as automobile parts, electrical and electronic parts, building materials, lifestyle, cosmetic and medical parts, rails, pipes, sashes, door frames, window frames, handrails, decking materials, fences and various building materials.

[0140] Specifically, automotive parts include interior parts such as inner handles, fuel trunk openers, seat belt buckles, assist wraps, various switches, knobs, levers, and clips, electrical system parts such as meters and connectors, in-vehicle electrical and electronic parts such as audio equipment and car navigation equipment, parts that come into contact with metal such as window regulator carrier plates, door lock actuator parts, mirror parts, wiper motor system parts, and mechanical parts such as fuel system parts.

[0141] Electrical and electronic components include parts or components of devices that are made of resin molded bodies and have many metal contacts, such as audio equipment, video equipment, office automation equipment such as telephones, copy machines, facsimiles, word processors, and computers, and parts or components of toys, specifically chassis, gears, levers, cams, pulleys, and bearings.

[0142] Furthermore, it can be suitably used for a wide range of lifestyle, cosmetic and medical parts, including lighting fixtures, fittings, pipes, cocks, faucets, toilet peripheral parts and other building materials and piping parts, fasteners, stationery, lip balm and lipstick containers, cleaners, water purifiers, spray nozzles, spray containers, aerosol containers, general containers and syringe needle holders. Among these, it is more preferably usable for gears, which are used in high temperature environments and are subjected to high loads.

[0143] <3D printing materials and objects> <3D printing materials and their manufacturing methods> One aspect of the present invention provides a 3D printing material comprising the resin composition of this embodiment. In one aspect, the 3D printing material may have a desired form, such as a filament or powder, and is preferably in the form of a filament or powder. Known methods can be used to mold the resin composition into a 3D printing material of the desired form. For example, the filament may be a monofilament or a multifilament, but a monofilament is preferred for ease of molding.

[0144] The diameter of the filamentary modeling material is preferably 0.5 to 5.0 mm, more preferably 1.0 to 3.5 mm, and most preferably 1.5 to 3.0 mm. The length of the filamentary modeling material is preferably greater than 1 m, more preferably greater than 10 m, more preferably greater than 100 m, and most preferably greater than 300 m. Controlling the shape of the filamentary modeling material within this range allows for a wide selection of applicable 3D printers, and allows for appropriate design of the modeling time, size, and precision of the modeled object. In one embodiment, the length of the filamentary modeling material may be 20,000 m or less.

[0145] In one embodiment, the filamentous shaping material can be produced by heating and melting a resin composition, passing it through a nozzle or other fine hole, cooling it, and winding it up. The diameter of the fine hole can be selected appropriately depending on the diameter of the filament and the winding speed. From the viewpoints of production efficiency and the frequency of thread breakage, it is preferably 0.5 to 10.0 mm, more preferably 0.8 to 5.0 mm, and most preferably 1.0 to 3.0 mm. The cooling method can be selected appropriately from known methods such as air cooling and water cooling. From the viewpoints of production efficiency and the frequency of thread breakage, air cooling is preferred. From the viewpoints of production efficiency and the frequency of thread breakage, the winding speed of the filament is preferably 0.1 to 10 m / s, more preferably 0.15 to 5 m / s, and most preferably 0.2 to 1 m / s. The production apparatus for the filamentous shaping material and the production apparatus for the resin composition may be the same or different.

[0146] The particle size, particle shape, and aspect ratio of the powdered modeling material can be appropriately selected depending on the 3D printer used. In one embodiment, the particle size is preferably 1 to 10,000 μm, more preferably 10 to 500 μm, and most preferably 30 to 200 μm, from the viewpoints of handling as a modeling material and surface smoothness of the modeled object. The particle shape may be spherical or irregular, but irregular shapes are preferred from the viewpoint of suppressing voids during modeling. The aspect ratio is preferably 1.001 to 3.0, preferably 1.01 to 2.0, and most preferably 1.1 to 1.8, from the viewpoint of suppressing voids by reducing interparticle gaps.

[0147] In one embodiment, the powdered modeling material can be produced by pulverizing or reprecipitating a resin composition. The method for pulverizing the resin composition is not particularly limited, and may be wet pulverization, dry pulverization, cryo-pulverization, freeze-pulverization, heat-pulverization, etc. A pulverizing medium may be used to control the shape of the powdered modeling material.

[0148] <Modeled object and its manufacturing method> One aspect of the present invention provides a shaped object produced by using a 3D printer to model the resin composition (e.g., resin composition pellets) or 3D printing material of the present embodiment. Another aspect of the present invention provides a method for producing a shaped object, including the step of using a 3D printer to model the resin composition or 3D printing material of the present embodiment. 3D printer modeling methods include fused deposition modeling, stereolithography, material jetting, powder bonding, and powder bed fusion. When a filamentary modeling material is used, fused deposition modeling is preferred, and when a powdered modeling material is used, powder bonding and powder bed fusion are preferred.

[0149] <Uses of 3D printing materials and models> The shaped object may be applied directly to various applications, or may be molded into a desired shape alone or with other components to produce a desired molded product. The method of combining the components and the molding method are not particularly limited and may be selected depending on the desired molded product. Molding methods include, but are not limited to, cutting molding and foam molding. The shaped object or molded product is useful as a substitute for steel plates, fiber-reinforced plastics (e.g., carbon fiber-reinforced plastics, glass fiber-reinforced plastics, etc.), resin composites containing inorganic fillers, etc. Suitable applications for 3D printing materials, shaped objects, and molded products include industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical parts, construction and civil engineering materials, household goods, sports and leisure goods, wind power generation housing components, containers and packaging materials, etc.

[0150] <Characteristics of resin composition, 3D printing materials, and objects> The resin composition, the 3D printing modeling material, and the modeled object can have the following properties.

[0151] <Tensile yield strength> In one embodiment, the tensile yield strength of the resin composition, 3D printing modeling material, or modeled object may be 20 MPa or more, or 50 MPa or more, or 80 MPa or more, and may be 300 MPa or less, or 200 MPa or less, or 150 MPa or less.

[0152] <Tensile elongation at break> In one embodiment, the tensile elongation at break of the resin composition, 3D printing modeling material, or modeled object may be 2% or more, or 3% or more, or 5% or more, and may be 200% or less, or 100% or less, or 20% or less.

[0153] <Flexural modulus> In one embodiment, the flexural modulus of the resin composition, 3D printing modeling material, or modeled object may be 2.0 GPa or more, or 2.5 GPa or more, or 3.0 GPa or more, or 3.5 GPa or more, or 3.7 GPa or more, or 3.9 GPa or more, and may be 20.0 GPa or less, or 10.0 GPa or less, or 8.0 GPa or less.

[0154] <250℃ weight loss rate (T 250℃ )> Resin composition, 3D printing material or modeled object weight loss rate at 250°C (T 250℃ ) is preferably 1.5% or less, or 1.4% or less, or 1.3% or less, from the viewpoint of avoiding thermal degradation during molding and improving the mechanical strength of the shaped object. A lower weight loss rate at 250°C is desirable, but from the viewpoint of ease of production of the resin composition, the 3D printing modeling material, or the shaped object, in one embodiment, it may be 0.01% or more, or 0.1% or more, or 0.3% or more. The weight loss rate at 250°C (T 250℃) is the weight loss rate when a sample of a resin composition, 3D printing material, or modeled object is held at 250°C for two hours under a nitrogen flow in a TG analysis. The sample is heated from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for one hour, then heated from 150°C to 250°C at a rate of 10°C / min and held at 250°C for two hours. The weight W0 at the time of reaching 250°C is taken as the starting point, and the weight after holding at 250°C for two hours is taken as W1, and is calculated using the following formula. Weight change rate at 250°C (%): (W1-W0) / W0 x 100

[0155] <Surface roughness> The resin composition, 3D printing material, or shaped object of this embodiment has low surface roughness, resulting in excellent decorative properties and appearance. The arithmetic mean surface roughness Ra of the resin composition, 3D printing material, or shaped object is preferably 0.5 μm or less, or 0.4 μm or less, or 0.3 μm or less. In one aspect, from the viewpoint of ease of production of the resin composition, 3D printing material, or shaped object, the arithmetic mean surface roughness Ra may be 0.001 μm or more, or 0.01 μm or more, or 0.1 μm or more. [Example]

[0156] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these examples.

[0157] <Measurement method> [Whiteness measurement] Using a spectrophotometer and color difference meter (Nippon Denshoku Industries Co., Ltd., Model PF700), measurements were taken according to the "ISO whiteness diffuse blue light reflectance measurement method for paper, paperboard, and pulp (JIS P8148 / ISO 2470)." Cellulose raw material or cellulose fine fiber slurry was mixed with a 50g / m2 fiber weight. 2 To obtain the above results, a cellulose sheet was prepared using a suction filtration device equipped with a polytetrafluoroethylene (PTFE) membrane filter, and dried at 80°C until the moisture reached equilibrium, and the sheet was subjected to the above measurements.

[0158] [Measurement of the content of halogens bound to cellulose in cellulose raw materials or cellulose fine fibers] (soaking and filtration treatment) The cellulose raw material or cellulose fine fibers were immersed in pure water at 25°C for 48 hours. Specifically, the cellulose raw material or cellulose fine fibers were immersed in pure water at a solid content of 2% by mass in a 200 mL glass beaker, stirred for 1 hour with a 3-1 motor (HEIDON BL-600 type, SUS propeller blade, 100 rpm), and then allowed to stand. Next, the mixture was filtered under reduced pressure using a Teflon (registered trademark) membrane filter (1 μm mesh size) to obtain a mass of 10 g / m. 2 The sheet was then filtered and dried in a ventilated oven at 70°C until the moisture content was 10% by mass or less, thereby obtaining a treated cellulose raw material or treated cellulose fine fibers.

[0159] (Halogen content measurement) 50 mg of the treated cellulose raw material or treated cellulose fine fibers was weighed into a quartz sample boat. The sample boat was placed in an electric furnace (manufactured by Mitsubishi Chemical Analytic Co., Ltd.) and combusted at 1000 °C. The gas generated by combustion was cooled to room temperature through a cooling section and then bubbled through a fluororesin tube into an absorption solution (the absorption solution was prepared by dissolving 10 mg / L of tartrate ions, 600 mg / L of hydrogen peroxide, 2.7 mmol / L of sodium carbonate, and 0.3 mmol / L of sodium bicarbonate in ion-exchange water). The absorption solution was passed through a fluororesin tube and subjected to ion chromatography (THERMOFISHER INTEGRION CT model) to quantify halogens. In this case, the moisture content in the treated cellulose raw material or treated cellulose fine fibers was subtracted using the loss on drying method (2.00 g of a cellulose sample was placed in a glass weighing bottle, dried at 60°C for 15 hours, then at 105°C for 2 hours, weighed to a constant weight in a desiccator, and calculated using the following formula: moisture content (mass%) = (sample weight before drying - sample weight after drying) / (sample weight before drying) x 100). Finally, the value (ppm by mass) converted to the dry mass (i.e., water-free state) of the treated cellulose raw material or treated cellulose fine fibers was taken as the content of halogen bonded to cellulose.

[0160] [Measurement by automatic fiber shape analyzer] The shape characteristics of the cellulose raw material or cellulose fine fibers were evaluated using an automatic fiber shape analyzer (MorfiNeo manufactured by TechPap) by the following method.

[0161] The sample (cellulose raw material or cellulose fine fibers) was dispersed in pure water to prepare 1 L of aqueous dispersion. The final solids concentration of the sample was 0.003 to 0.005% by mass. If the sample before dilution was an aqueous dispersion of less than 2% by mass, it was stirred with a spatula. If the sample was an aqueous dispersion of 2% by mass or more, or in the form of a wet cake or powder, it was dispersed using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18") at 25,000 rpm for 5 minutes.

[0162] Next, the aqueous dispersion prepared above was subjected to measurement using an autosampler. The measurement results were output in txt format, and each shape parameter was extracted or calculated from the measurement results. The following values ​​from the measurement results were used for each parameter.

[0163] 1) Length-weighted average fiber length: Mean length-weighted length [μm] 2) Proportion of fibers with a fiber length of 3 mm or more: From the histogram of the fiber length distribution in 1), the proportion of fibers with a fiber length of 3 mm or more to all fibers was calculated using the following formula. Percentage of fibers with a fiber length of 3 mm or more (%) = Number of fibers with a fiber length of 3 mm or more / Total number of fibers measured x 100 3) Mean fiber width [μm]

[0164] [Glucose content measurement] The glucose content of the cellulose raw materials was determined by analyzing their constituent sugars using the following method, based on the analytical procedures of the National Renewable Energy Laboratory of the U.S. Department of Energy (Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., Crocker, D.: Determination of structural carbohydrates and lignin in biomass. National Renewable Energy Laboratory (NREL), USA, 2008.). 200 mg of sample was added to 3 ml of 72% sulfuric acid and allowed to swell at 30 °C for 1 hour. The mixture was then poured into a 125 ml pressure bottle with 84 ml of pure water and hydrolyzed at 120 °C for 1 hour. The mixture was then suction filtered while still hot through a 1G-3 glass filter (pre-weighed at 105 °C). After solid-liquid separation, the filtrate was adjusted to a constant volume of 100 ml and the sugar components were quantified by high-performance liquid chromatography (HPLC) (FL detection method) under the following conditions. The measurement conditions for high-performance liquid chromatography were as follows: Apparatus: Shimadzu HPLC-20A; Column: Shodex Asahipak NH2P-50 4E; Mobile phase: water / acetonitrile = 20 / 80 (volume ratio); Flow rate: 1.0 mL / min; Detector: RI; Column temperature: 30 °C.

[0165] [DS] The degree of substitution (DS) of the chemically modified cellulose raw material and the chemically modified cellulose fine fibers was evaluated using an infrared spectrometer (manufactured by JASCO Corporation, FT / IR-6200) by the following method. (Preparation of porous sheet) First, the wet cake was added to tert-butanol, and further dispersed using a mixer or the like until no aggregates remained. The concentration was adjusted to 0.5% by mass per 0.5g of fine cellulose fiber solids. 100g of the resulting tert-butanol dispersion was filtered on filter paper. Without peeling the filtered material from the filter paper, it was sandwiched between two larger pieces of filter paper, and dried in an oven at 150°C for 5 minutes while pressing down the edges of the larger filter paper with weights. The filter paper was then peeled off to obtain a porous sheet with little distortion. The air resistance of this sheet was 10g / m². 2 The porous sheet with a permeability of 100 sec / 100 ml or less was used as the measurement sample. The basis weight W (g / m) of the sample left standing for one day in an environment of 23°C and 50% RH 2 After measuring the air permeability, the air permeability resistance R (sec / 100 ml) was measured using an Oken type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, the air permeability resistance R was calculated according to the following formula: 2 The value per unit area was calculated. Weight 10g / m 2Air resistance per unit (sec / 100ml) = R / W x 10

[0166] (measurement) The infrared spectrum of the porous sheet was measured by the ATR-IR method at five points using a Fourier transform infrared spectrophotometer (FT / IR-6200 manufactured by JASCO) under the following conditions. Accumulation times: 64 times, Wavenumber resolution: 4cm -1 , Measurement wavenumber range: 4000 to 600 cm -1 , ATR crystal: diamond, Incident angle: 45°

[0167] From the obtained IR spectrum, the IR index was calculated using the following formula: IR index = H1730 / H1030 In the formula, H1730 and H1030 are the values ​​at 1730 cm -1 , 1030cm -1 (absorption band of CO stretching vibration of cellulose backbone chain) -1 and 1500cm -1 The line connecting the -1 and 1500cm -1 The line connecting these points is taken as the baseline, and the absorbance is calculated when this baseline is taken as 0. The average degree of substitution at each measurement point was calculated from the IR index according to the following formula, and the average value was taken as DS. DS = 4.13 × IR index

[0168] [Crystallization] The crystallinity of the cellulose raw material was evaluated using an X-ray diffractometer (MiniFlex II, manufactured by Rigaku Corporation) by the following method. The porous sheet was subjected to X-ray diffraction measurement, and the crystallinity was calculated using the following formula. Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) : Diffraction peak intensity due to the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous in cellulose type I crystals, which is the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ=18.0°) (X-ray diffraction measurement conditions) Device: MiniFlex (manufactured by Rigaku Corporation) Operation axis 2θ / θ Source CuKα Measurement method: Continuous Voltage 40kV Current 15mA Starting angle 2θ=5° End angle 2θ=30° Sampling width 0.020° Scan speed 2.0° / min Sample: A porous sheet is attached to the sample holder.

[0169] [Resin foaming] The resulting resin compositions (dumbbell-shaped bodies cut into 5mm wide x 10mm long pieces or pellets 2mm in diameter x 4mm long) were measured using a high-resolution 3D X-ray microscope (Rigaku nano3D) under the following conditions: X-ray tube voltage / tube current 40kV / 30mA (X-ray target: Cu), 180° rotation, 1500 projections, exposure time 24 seconds per projection, and spatial resolution 0.54μm / pix. The void fraction was measured using software. A void fraction of 0.1% by volume or less was evaluated as ◎, greater than 0.1% by volume but less than 0.5% by volume as 〇, greater than 0.5% by volume but less than 1.0% by volume as △, and greater than 1.0% by volume as ×.

[0170] [Thermal stability of resin] The resin composition (dumbbell molded body) obtained by kneading was placed in a polyethylene bag with a zipper and stored at 100°C for one month, then returned to room temperature and left for one day, after which the flexural strength was measured according to the ISO method.Compared to before storage, a flexural strength retention rate of 95% or more was evaluated as ◎, 90% to less than 95% as ◯, 85% to less than 90% as △, and less than 85% as ×.

[0171] [Recyclability of resin] The resin composition (dumbbell molded body) molded by the method described in Example 1 was cut with a cutter to a diameter of 5 mm or less and subjected to two passes in an ultracentrifugal grinder (Retsch ZM200 model, screen opening 2 mm, rotation speed 10,000 rpm). Melt-kneading and injection molding were performed by the method described in Example 1, and after repeating this five times, the bending strength was measured. In comparison with the bending strength before storage, a bending strength retention of 95% or more was evaluated as ◎, 90% or more but less than 95% as ◯, 85% or more but less than 90% as △, and less than 85% as x.

[0172] [Device corrodes] The internal metal surface of the kneading section of a small kneader (DSM, Xplore MC 15HT) was visually evaluated for scorching before and after melt-kneading. After melt-kneading, the polyethylene was melted (kneaded for 20 minutes at a temperature of 140°C and a rotation speed of 200 rpm), and the inside of the extruder was washed. The kneading section was then cooled to room temperature, and the inside was wiped clean with acetone. In comparing the metallic gloss before and after melt-kneading, a completely comparable metallic gloss was evaluated as ◎, a partial dullness was observed as ○, a light dullness was observed overall as △, and a heavy dullness was observed overall as ×.

[0173] <Production of Cellulose Fine Fibers and Resin Composition> Example 1: Cotton linter pulp (CLP) Cotton crude linters were dry screened in the laboratory to extract the 2-8 mm fraction. Next, 400 g of the resulting crude linters were placed in a 4 L autoclave and cooked at an active alkali addition rate of 18 ((NaOH (g) + NaS (g)) / 1 L of water), a sulfidity of 28% (NaS (g) / total alkali (g) x 100), a liquor ratio of 4.5 (liquid / solids), an initial temperature of 90 °C, a cooking temperature of 155 °C, and a cooking time of 150 min. The cooked crude linters were diluted 10-fold with pure water and washed by decantation four times. The crude linters were then dehydrated to a solids content of 25% by mass using a centrifugal dehydrator equipped with a 200 μm mesh filter cloth.

[0174] The crude linter obtained above was dried, and 70.0 g of the dried product was placed in a polyethylene (PE) plastic bottle. Pure water was added so that the solid content concentration during the reaction was 10% by mass, and the bottle was sealed. The container was then immersed in a thermostatic water bath and preheated at 70°C. After preheating, sodium hydroxide was added to the water in the container so that the solid content was 10% by mass, and the mixture was stirred with a 3-1 motor to dissolve the sodium hydroxide. This slurry was introduced into a 2-L autoclave equipped with a stirring blade, heated to 90°C, and then oxygen was introduced, the internal pressure was increased to 500 kPa, and the reaction was carried out for 60 minutes. After the reaction, the linter was washed with ion-exchanged water and then dehydrated to a solid content of 25% by mass using a centrifugal dehydrator (equipped with a filter cloth with a mesh size of 200 μm) to obtain a cellulose raw material.

[0175] The resulting cellulose raw material had a crystallinity of 85% and a glucose content of 98% by mass. Table 1 shows the measurement results of the halogen content and whiteness of this cellulose raw material.

[0176] The above procedure was repeated multiple times, and the recovered cellulose raw material was immersed in water to a solids content of 1.0% by mass. The cellulose raw material was then dispersed using a lab pulper (manufactured by Aikawa Iron Works Co., Ltd.) and defibrated using a single-disc refiner (manufactured by Aikawa Iron Works Co., Ltd., SDR14 type lab refiner, pressure-type disc refiner). This disc refiner had two tanks (Tank A and Tank B) connected by piping. The slurry was first transferred from Tank A to Tank B via the disc refiner and stored there. After the slurry in Tank A was processed, the slurry was continuously transferred from Tank B to Tank A via the disc refiner and stored there. This method controlled the number of passes through the disc refiner. The disc refiner's blade spacing adjustment mechanism was equipped with a ball screw jack and a reducer, allowing for precise blade spacing adjustment with micrometer accuracy. Furthermore, after the target blade distance was reached, the deviation of the blade distance during beating was measured using a displacement sensor and was found to be less than 0.005 mm. The disc refiner blades used were 4.0 mm in width and 0.89 in groove ratio, and after 30 passes at a blade distance of 0.25 mm, blades with a blade width of 0.8 mm and groove ratio of 0.53 were used, and after 30 passes at a blade distance of 0.30 mm, blades with a blade width of 0.8 mm and groove ratio of 0.53 were used.

[0177] The resulting slurry was subjected to 10 passes at 80 MPa in a high-pressure homogenizer (NS3015H, manufactured by Niro Soavi Co., Ltd.). Similar to the disc refiner treatment, the high-pressure homogenizer treatment was also performed using two tanks, and the number of passes was controlled.

[0178] Using the obtained cellulose fine fibers, a composite was produced by injection molding according to the following procedure. 1) The wet cake of cellulose fine fibers was dispersed in hexafluoroisopropanol (hereinafter referred to as HFIP) (as a cellulose dispersion medium) by a dispersion treatment using a homogenizer (IKA Ultra Turrax T18) at a rotation speed of 12,000 rpm for 3 minutes so that the solid content concentration became 1% by volume. 2) A solution was prepared by dissolving polyamide 6 (1013B, manufactured by Ube Industries, Ltd.) in HFIP (as a resin solvent) at a solid content of 1% by mass. 3) The solutions 1) and 2) were placed in a container so that the solid mass ratio of cellulose fine fibers to polyamide 6 was 1:9, and mixed for 5 minutes at 2000 rpm using a centrifugal mixer (Thinky Corporation, Awatori Rentaro ARE-310). 4) The mixture obtained in 3) was cast onto a release film (Mitsui Chemicals Tocello, X88B) and dried in an oven at 80°C for 1 hour. 5) The solid matter on the release film obtained in 4) was pulverized using a tabletop pulverizer (Mini Speed ​​Mill MS-05, manufactured by LaboNext Co., Ltd.). 6) The powder obtained in 5) was dried in a vacuum dryer for 24 hours or more. 7) The dried product obtained in 6) was kneaded in a small kneader (manufactured by DSM, Xplore MC 15HT) at a temperature of 250°C and a rotation speed of 200 rpm for 20 minutes. 8) After kneading, the resulting resin composition was poured into an injection molding machine (Xplore IM12) to prepare a multipurpose test piece in accordance with ISO-37.

[0179] The obtained test pieces were evaluated by a bending test in accordance with ISO 178 and a tensile test in accordance with ISO 527. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0180] This resin composition was evaluated for foaming property, thermal stability, recyclability, and corrosion of equipment. The results are shown in Table 1.

[0181] (Example 2) Bleached Softwood Kraft Pulp (KBKP) In the method for producing the cellulose raw material of Example 1, the crude linter was replaced with coniferous wood chips, and a cellulose raw material was obtained in the same manner. The crystallinity of the obtained cellulose raw material was 82%, and the glucose content was 92% by mass. The measurement results of the halogen content and whiteness of this cellulose raw material are shown in Table 1.

[0182] Using this cellulose raw material, cellulose fine fibers and a resin composition were prepared in the same manner as in Example 1. The resulting resin composition was evaluated by a bending test and a tensile test. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0183] This resin composition was evaluated for foaming property, thermal stability, recyclability, and corrosion of equipment. The results are shown in Table 1.

[0184] (Example 3) Bleached Hardwood Kraft Pulp (LBKP) In the method for producing the cellulose raw material of Example 1, the crude linter was replaced with hardwood chips, and a cellulose raw material was obtained in the same manner. The crystallinity of the obtained cellulose raw material was 80%, and the glucose content was 89% by mass. The measurement results of the halogen content and whiteness of this cellulose raw material are shown in Table 1.

[0185] Using this cellulose raw material, cellulose fine fibers and a resin composition were prepared in the same manner as in Example 1. The resulting resin composition was evaluated by a bending test and a tensile test. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0186] The resin composition was measured for foaming property, thermal stability, recyclability, and corrosion of equipment, and the results are shown in Table 1.

[0187] Example 4: Cotton linter pulp (CLP) A cellulose raw material was prepared using bleached cotton linter pulp (produced in China, chlorine bleached) using the following method. 400 g of linter pulp, shredded into 10 mm cubes, was placed in a 4 L autoclave and cooked at an initial temperature of 90°C, a cooking temperature of 155°C, and a cooking time of 150 minutes. The cooked linter was diluted 10-fold with pure water and washed by decantation four times. The cellulose raw material was then dehydrated to a solids content of 25% by mass using a centrifugal dehydrator (equipped with a filter cloth with 200 μm openings) to obtain a cellulose raw material. The crystallinity of the resulting cellulose raw material was 85%, and the glucose content was 98% by mass. The halogen content and whiteness of this cellulose raw material were measured and shown in Table 1.

[0188] Using this cellulose raw material, cellulose fine fibers and a resin composition were prepared in the same manner as in Example 1. The resulting resin composition was evaluated by a bending test and a tensile test. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0189] This resin composition was evaluated for foaming property, thermal stability, recyclability, and corrosion of equipment. The results are shown in Table 1.

[0190] Example 5: Cotton linter pulp (CLP) Using the cellulose raw material obtained in Example 1, 400 g of the cellulose raw material was introduced into a 4 L autoclave and digested at an initial temperature of 90°C, a digestion temperature of 155°C, and a cooking time of 150 minutes. The digested linter was diluted 10 times with pure water and washed by decantation four times. Next, it was dehydrated to a solid content of 25% by mass using a centrifugal dehydrator (equipped with a filter cloth with a mesh size of 200 μm). This procedure was repeated nine times to obtain a heat-purified cellulose raw material. The crystallinity of the obtained cellulose raw material was 72%, and the glucose content was 98% by mass. The halogen content and whiteness of this cellulose raw material were measured and the results are shown in Table 1.

[0191] Using this cellulose raw material, cellulose fine fibers and a resin composition were prepared in the same manner as in Example 1. The resulting resin composition was evaluated by a bending test and a tensile test. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0192] This resin composition was evaluated for foaming property, thermal stability, recyclability, and corrosion of equipment. The results are shown in Table 1.

[0193] (Example 6) Cotton linter pulp (CLP) In the manufacturing method of Example 5, the heat purification operation using Okurave was repeated a total of five times to obtain a heat-purified cellulose raw material. The crystallinity of the obtained cellulose raw material was 83%, and the glucose content was 98% by mass. The measurement results of the halogen content and whiteness of this cellulose raw material are shown in Table 1.

[0194] Using this cellulose raw material, cellulose fine fibers and a resin composition were prepared in the same manner as in Example 1. The resulting resin composition was evaluated by a bending test and a tensile test. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0195] This resin composition was evaluated for foaming property, thermal stability, recyclability, and corrosion of equipment. The results are shown in Table 1.

[0196] (Comparative Example 1) Cotton linter pulp (CLP) The bleached cotton linter pulp (produced in China, chlorine bleached) of Example 4 was shredded into 10 mm square pieces using a shredder. This was used as the cellulose raw material (the crystallinity of the resulting cellulose raw material was 85%, and the glucose content was 98% by mass. The measurement results for the halogen content and whiteness of this cellulose raw material are shown in Table 1). Cellulose fine fibers and a resin composition were prepared in the same manner as in Example 1.

[0197] The resulting resin composition was evaluated by bending test and tensile test. The results showed that the flexural modulus was 4.0 MPa or more, the flexural strength was 80 MPa or more, the tensile modulus was 3.5 GPa or more, and the tensile strength was 90 MPa or more, indicating that a good resin composition was obtained.

[0198] This resin composition was evaluated for foaming ability, thermal stability, recyclability, and corrosion of the equipment, and the results are shown in Table 1. For this resin composition, the results for none of the items were satisfactory for practical use. In particular, when the inside of the equipment after melt-kneading was observed, slight traces of oxides adhering to the metal surface were observed.

[0199] Example 7: Acetylated cotton linter pulp The cellulose raw material obtained in Example 1 was dispersed in dimethyl sulfoxide (DMSO) to a solids content of 5.8% by mass and potassium carbonate of 1.1% by mass. 30 L of this slurry was placed in a 50 L reactor and heated to 60°C with homogeneous stirring. Vinyl acetate (4.4% by mass relative to the reaction solution) was added and acetylation was continued until the desired degree of substitution was achieved. The degree of substitution (DS) was measured appropriately during the reaction. When the DS reached 1.0 or greater, 3 L of water was added to terminate the reaction. The reaction solution was thoroughly washed to remove the solvent by repeated stirring and filtration using pure water in a pressure filter in an amount 50 times the mass of the cellulose solids, yielding a wet cake of acetylated cellulose fibers. The average fiber length after chemical modification was 95% of that before chemical modification.

[0200] This acetylated cellulose was subjected to a micronization treatment using the method of Example 1 to obtain cellulose fine fibers. The DS of the cellulose fine fibers was 0.85. A resin composition was prepared using these fine fibers using the same method as in Example 1. The resulting resin composition was evaluated by bending test and tensile test. The results showed a flexural modulus of 4.0 MPa or more, a flexural strength of 80 MPa or more, a tensile modulus of 3.5 GPa or more, and a tensile strength of 90 MPa or more, indicating that a good resin composition was obtained. This resin composition was evaluated for foamability, thermal stability, recyclability, and equipment corrosion. The foamability, thermal stability, and recyclability were rated as ◎, and the equipment corrosion was rated ○, resulting in a resin that was satisfactory for practical use.

[0201] Example 8 The same procedure as in Example 1 was carried out, except that the resin used in Example 1 was changed to a polyacetal copolymer (containing 4 mol% of oxyethylene units in addition to oxymethylene units), to produce a resin composition, which was then evaluated for foamability, thermal stability, recyclability, and equipment corrosion. All items were rated as good or better (specifically, foamability and equipment corrosion were rated good, and thermal stability and recyclability were rated excellent), resulting in a satisfactory product.

[0202] (Comparative Example 2) The same procedure as in Comparative Example 1 was carried out except that the resin used was changed to a polyacetal copolymer (containing 4 mol% of oxyethylene units in addition to oxymethylene units), and a resin composition was prepared and evaluated for foamability, thermal stability, recyclability, and equipment corrosion. All items were rated fair or worse (specifically, foamability was poor, and thermal stability, recyclability, and equipment corrosion were fair), and no product satisfactory for practical use was obtained.

[0203] Example 9 In the manufacturing method of Example 1, the resin used was changed to polypropylene, and the cellulose dispersion medium and resin solvent used were changed to toluene. The same procedure was followed as in Example 1 to prepare a resin composition, and foaming properties, thermal stability, recyclability, and corrosion of the equipment were evaluated. All items were rated as ⊚, and no problems were observed.

[0204] (Comparative Example 3) A resin composition was prepared in the same manner as in Comparative Example 1, except that the resin used in the manufacturing method of Comparative Example 1 was changed to polypropylene, and the cellulose dispersion medium and resin solvent used were changed to toluene. The foamability, thermal stability, recyclability, and corrosion of the equipment were evaluated for this resin composition. As a result of evaluating the foamability, thermal stability, recyclability, and corrosion of the equipment, all items were rated as fair, and a practically unsatisfactory product was not obtained.

[0205] Example 10 Using the aqueous dispersion of cellulose fine fibers obtained in Example 1, a composite was produced according to the following procedure. The resulting aqueous dispersion of cellulose fine fibers was filtered under pressure to obtain an aqueous dispersion with a solid content of 10% by mass. 30 parts by mass of PEG20000 was added to this aqueous dispersion of cellulose fine fibers per 70 parts by mass of cellulose fine fibers, and the mixture was then vacuum dried at approximately 40°C using a revolution-rotation mixer (Hibismix 2P-1, manufactured by Primix Corporation) to obtain cellulose fine fiber powder. A twin-screw extruder (a TEM SX series extruder manufactured by Toshiba Machine Co., Ltd.) with 13 cylinder blocks and an L / D of 52 was used. A side feed port was installed in cylinder 5 to enable the supply of raw materials from that position, and a vent port for vacuum suction was installed in cylinder 12 to enable the removal of volatile components and coexisting air. The screw configuration was as follows: cylinders 1-2 were used as conveying screws; cylinders 3-4 were equipped with two clockwise kneading discs (feed type kneading discs: hereinafter referred to as RKDs), followed by one neutral kneading disc (non-conveying type kneading disc: hereinafter referred to as NKDs), followed by a counterclockwise screw, forming a pre-mixing zone; cylinder 5, which was the side feed zone, was used as a conveying screw; cylinders 6-7 were equipped with one RKD, two NKDs, followed by one counterclockwise screw, forming a melt-kneading zone; cylinders 8-9 were used as conveying screws; cylinder 10 was equipped with one RKD, followed by one NKD, followed by a counterclockwise screw, forming a kneading zone; cylinders 11-13 were used as conveying screws, forming a devolatilization zone. A mixture of 85.7 parts by mass of polyamide 6 (1013B, manufactured by Ube Industries, Ltd.) and 14.3 parts by mass of cellulose fine fiber powder was fed through cylinder 1 of an extruder, with cylinder 1 water-cooled and the other cylinders set at 250°C, and the mixture was kneaded and extruded into strands. The strands were cut with a strand cutter to obtain resin composition pellets. The foamability of these resin composition pellets was evaluated, resulting in an excellent result, with no problems.

[0206] Comparative Example 4 Using the cellulose fine fiber aqueous dispersion obtained in Comparative Example 1, resin composition pellets were obtained in the same manner as in Example 10. The foamability of these resin composition pellets was evaluated and they were rated fair, meaning that they were not satisfactory for practical use.

[0207] <Production of profile extrusion molded body> Example 11 Irregular extrusion molding was carried out using the resin composition pellets of Example 10. Using a 40 mm diameter single-screw extruder equipped with a die having the cross-sectional shape shown in Figure 3 (values ​​in the figure are in millimeters), the pellets were extruded at a molding temperature of 250°C and a screw rotation speed of 20 rpm, and then shaped using a sizing die having the same cross section as the die in a 2 m long water tank filled with cooling water at 25°C to obtain an irregular extrusion molded product.

[0208] Example 12 Resin composition pellets were obtained in the same manner as in Example 10, except that a mixture of 92.8 parts by mass of glass fiber reinforced polyamide 6 (1015GC3, manufactured by Ube Industries, Ltd.) and 7.2 parts by mass of cellulose fine fiber powder was fed and kneaded. Then, irregular extrusion molding was performed in the same manner as in Example 11, and an irregular extrusion molded product was obtained.

[0209] Example 13 Resin composition pellets were obtained in the same manner as in Example 10, except that a mixture of 82.8 parts by mass of polyamide 6 (1013B, manufactured by Ube Industries, Ltd.), 10 parts by mass of carbon fiber (Toray, Torayca T300), and 7.2 parts by mass of cellulose fine fiber powder was fed and kneaded, and then irregular extrusion molding was performed in the same manner as in Example 11 to obtain an irregular extrusion molded product.

[0210] <Production of objects using 3D printing> Example 14 Using the resin composition pellets of Example 10, a 3devo filament extruder (nozzle diameter 1.7 mm) manufactured by 3D Printing Corporation was used, and the extrusion was carried out under automatically controlled conditions of a nozzle temperature of 250°C, a screw rotation speed of 3.5 rpm, and a winding speed of 0.02 to 0.1 m / s under air-cooled conditions to obtain a monofilament of filament-shaped modeling material. Next, the above filamentous modeling material was used in a Canon FUNMAT HT fused deposition modeling 3D printer to obtain a model with the same shape as a multipurpose test piece conforming to ISO294-3 under the following conditions: nozzle temperature 210°C, platform temperature 80°C, layer pitch 0.3 mm, and modeling speed 30 mm / sec.

[0211] [Table 1] [Industrial Applicability]

[0212] By using the cellulose fine fibers and the method for producing the same of the present invention in the production of a resin composition, it is possible to suppress decomposition of the resin when the cellulose fine fibers are combined with the resin, and to suppress corrosion inside the kneading equipment, molding equipment, etc. This makes it possible to provide a resin composition that is excellent in stability during long-term storage and remains stable even after multiple thermal cycles associated with melt-kneading, such as in material recycling.

Claims

1. Cellulose fine fibers are derived from plants and have a content of halogen bonded to cellulose of 250 mass ppm or less.

2. Cellulose fine fibers are derived from plants and have a content of chlorine bonded to cellulose of 250 mass ppm or less.

3. The cellulose fine fibers according to claim 1 or 2, having a whiteness of 50% or more.

4. The method for producing cellulose fine fibers according to claim 1, A method for producing cellulose fine fibers, comprising a step of defibrating a cellulose raw material having a content of halogen bonded to cellulose of 300 mass ppm or less.

5. The method for producing cellulose fine fibers according to claim 2, A method for producing cellulose fine fibers, comprising a step of defibrating a cellulose raw material having a chlorine content bonded to cellulose of 300 mass ppm or less.

6. The method for producing cellulose fine fibers according to claim 4 or 5, wherein the cellulose raw material is a chemically modified product.

7. The method for producing cellulose fine fibers according to claim 6, wherein the chemically modified product is an acetylated product.

8. The method for producing cellulose fine fibers according to claim 4 or 5, wherein the cellulose raw material is derived from cotton.

9. The method for producing cellulose fine fibers according to claim 4 or 5, wherein the defibrating is a beating treatment using a disc refiner.

10. A resin composition comprising the cellulose fine fibers according to claim 1 or 2 and a resin.

11. A step of obtaining cellulose fine fibers by the method according to claim 4 or 5; a step of mixing the cellulose fine fibers and a resin to obtain a resin composition; A method for producing a resin composition, comprising:

12. A molded article obtained by molding the resin composition according to claim 10.

13. The molded article according to claim 12, which is a profile extrusion molded article.

14. A method for producing a profile extrusion molded body, A method comprising the step of profile extruding the resin composition of claim 10.

15. A 3D printing modeling material comprising the resin composition according to claim 10.

16. The 3D printing modeling material according to claim 15, which is in the form of a filament or a powder.

17. A shaped object produced by molding the resin composition according to claim 10 or a 3D printing material comprising the resin composition using a 3D printer.

18. A method for manufacturing a shaped object, comprising: A method comprising the step of modeling the resin composition according to claim 10 or a 3D printing modeling material composed of the resin composition using a 3D printer.

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