Cellulose composite resin

Abstract

[Problem] To provide a cellulose composite resin which has a stone-like appearance and, despite this, is inhibited from having reduced strength properties. [Solution] A cellulose composite resin comprising a resin and, combined therewith, microfibrous cellulose having an average fiber length of 0.05-0.5 mm, said cellulose composite resin being characterized by having spots of dirt each comprising an aggregate of microfibrous cellulose, the number of the spots of dirt being 5-1,000 per 9 cm2 and the areal proportion of the spots of dirt being 10-100,000 mm2 / m2.

Description

Cellulose composite resin

[0001] In recent years, nanotechnology, which aims to reduce the size of substances to the nanometer level and obtain new physical properties that differ from the conventional properties of the substances, has been attracting attention. Fine cellulose fibers produced from pulp, a cellulosic raw material, by chemical treatment, pulverization, etc., are excellent in strength, elasticity, thermal stability, etc., and are therefore expected to be used in a variety of applications. In particular, taking advantage of the greatest features of fine cellulose fibers, namely light weight, high strength, and recyclability, it has been proposed to use fine cellulose fibers, including cellulose nanofibers obtained by pulverizing plant fibers and microfibrous cellulose, as reinforcing materials for thermoplastic resins (see Patent Document 1).

[0002] Currently, there are proposals to use fibrous cellulose, including cellulose nanofibers and microfibrous cellulose obtained by pulverizing plant fibers, as a reinforcing material for thermoplastic resins. When using fibrous cellulose as a reinforcing material for thermoplastic resins, it is desirable that the fibrous cellulose be uniformly dispersed in the resin, as this uniform dispersion can improve strength properties. There are various methods for improving dispersibility, such as chemically modifying the fibrous cellulose to make it hydrophobic or adding a compatibilizer.

[0003] JP 2019-131774 A

[0004] On the other hand, there is a need for thermoplastic resins to have a designable appearance, but it has been difficult to provide a designable appearance while maintaining strength properties. In light of the above background art, an object of the present invention is to provide a cellulose composite resin that has a stone-like appearance while suppressing a decrease in strength properties.

[0005] The inventors have conducted extensive research and have succeeded in inventing a cellulose composite resin that is not only designed but also inhibits deterioration in strength and other physical properties even when the fibrous cellulose is not necessarily uniformly dispersed. Therefore, the following aspects of the invention are presented to solve the above problems. (First Aspect) A cellulose composite resin is a composite of a resin and microfibrous cellulose having an average fiber length of 0.05 to 0.5 mm, and has darts made of aggregates of the microfibrous cellulose, with the number of darts being 5 to 1,000 per 9 cm. ２ , and the dirt area ratio is 10 to 100,000 mm ２ / m ２ A cellulose composite resin characterized by:

[0006] A technique for obtaining a cellulose composite resin with improved strength properties by mixing and kneading cellulose fibers into a resin has been used for some time, as shown in Patent Document 1. For a cellulose composite resin to have high strength properties, it is preferable that the cellulose is contained in the cellulose composite resin in a dispersed state, and the more uniformly dispersed the cellulose, the higher the strength properties of the cellulose composite resin.

[0007] Conventional cellulose composite resin technologies have focused on dispersing cellulose fibers in the cellulose composite resin in order to improve its strength properties, without placing importance on the design of the resulting product. In contrast, when attempting to produce a cellulose composite resin with a design, one approach to achieve this is to incorporate a substance (e.g., granular material) different from the resin or cellulose fiber into the cellulose composite resin and then mold it. In this case, since the cellulose composite resin originally contains a substance different from the resin or cellulose fiber, when external pressure is applied to the cellulose composite resin, such as by bending it, the portion containing the substance is more brittle than other portions and more susceptible to cracking. As a result, the cellulose composite resin does not have high strength properties.

[0008] However, the cellulose composite resin of the present invention has strength properties because it is a composite of resin and microfibrous cellulose, and also has design properties with a stone-like appearance due to the presence of dirt. Furthermore, because one of the components of the dirt is an aggregate of microfibrous cellulose and one of the components constituting the cellulose composite resin is also microfibrous cellulose, the area where the dirt is located is not inferior in strength compared to other areas, and cracks are not likely to occur in the area where the dirt is located. Therefore, the present invention provides a cellulose composite resin that has design properties while suppressing a decrease in strength properties.

[0009] (Second Aspect) The cellulose composite resin according to the first aspect, which has a stone-like color tone.

[0010] The granite-like color tone provides an aesthetically pleasing cellulose composite resin.

[0011] (Third Aspect) The cellulose composite resin of the first aspect, which comprises modified microfibrous cellulose in which all or part of the hydroxy groups of the cellulose are substituted with carbamate groups.

[0012] The cellulose composite resin of this embodiment has darts scattered throughout a substrate containing resin and modified microfibrous cellulose. Since the modified microfibrous cellulose, which is one component of the substrate, has excellent dispersibility, the cellulose composite resin of this embodiment exhibits the effect of further suppressing or reinforcing the deterioration of strength properties.

[0013] (Fourth Aspect) The cellulose composite resin of the first aspect, comprising modified microfibrous cellulose in which all or a portion of the hydroxyl groups of cellulose are substituted with carbamate groups, and the substitution rate of the carbamate groups of the modified microfibrous cellulose is 0.5 mmol / g or more and 2.0 mmol / g or less.

[0014] Since the substitution rate of the carbamate group in the modified microfibrous cellulose is within the above range, the effect of further suppressing the decrease in strength properties or of reinforcing the properties is remarkable.

[0015] (Fifth Aspect) The cellulose composite resin according to the first aspect, wherein the resin is a polyolefin-based resin.

[0016] If the resin contained in the composite resin is a polyolefin resin, it has thermal plasticity and therefore exhibits excellent processability.

[0017] (Sixth Aspect) The cellulose composite resin according to the first aspect, wherein the resin is an organic acid anhydride-modified polyolefin resin.

[0018] The organic acid anhydride-modified polyolefin resin has an organic acid anhydride group, and the organic acid group easily bonds with the cellulose portion of the microfibrous cellulose, thereby improving the interfacial adhesion between the resin and the microfibrous cellulose and improving the strength properties of the composite material.

[0019] (Seventh Aspect) The cellulose composite resin of the first aspect, wherein the ratio of the flexural strength of the cellulose composite resin to the flexural strength of the resin itself is 1.05 to 2.0.

[0020] Since the ratio is 1.05 to 2.0, the cellulose composite resin of this embodiment can be used as a resin material that can replace conventional resins in terms of strength as well.

[0021] (Eighth Aspect) The cellulose composite resin of the first aspect, wherein the mass ratio of the resin to the microfibrous cellulose is 99:1 to 50:50.

[0022] If the mass ratio of resin to microfibrous cellulose is 99:1 to 50:50, the number of darts per unit area and the total area will be appropriate, resulting in an aesthetically excellent appearance.

[0023] (9th Aspect) The cellulose composite resin according to the 1st aspect, further comprising a white pigment.

[0024] The inclusion of the white pigment imparts a hue to the base of the cellulose composite resin, increasing the difference in hue between the base and the dirt, making the dirt more visible and resulting in an excellent design.

[0025] According to the present invention, a cellulose composite resin can be obtained that has a stone-like appearance while suppressing a decrease in strength properties.

[0026] 1 is a diagram showing a production example of a cellulose composite resin, 2 is a diagram showing test examples 1 to 4 of a cellulose composite resin, and 3 is a diagram showing test examples 5 to 7 of a cellulose composite resin.

[0027] Next, an embodiment of the present invention will be described. Note that this embodiment is an example of the present invention. The scope of the present invention is not limited to the scope of this embodiment.

[0028] The cellulose composite resin of the present embodiment is a cellulose composite resin in which a resin and microfibrous cellulose having an average fiber length of 0.05 to 0.5 mm are composited, and has darts 3 made of aggregates of microfibrous cellulose, and the number of darts is 5 to 1,000 per 9 m. ２ , and the dirt area ratio is 10 to 100,000 mm ２ / m ２ First, the microfibrous cellulose, which is the material of the cellulose composite resin, will be described.

[0029] (Microfibrous Cellulose) Microfibrous cellulose is a fiber obtained by pulverizing cellulose. In addition to microfibrous cellulose, other categories of pulverized cellulose fibers include cellulose nanofibers, which have a smaller fiber width. Composite resins can be produced using either microfibrous cellulose, cellulose nanofibers, or a mixture thereof. Microfibrous cellulose significantly improves the reinforcing effect of the resin. Furthermore, in the washing process performed after the carbamate reaction to remove unreacted residual reagents, urea, etc., dehydration is extremely poor when the fibers to be washed are cellulose nanofibers. On the other hand, microfibrous cellulose is easier to modify with carbamate groups (carbamation) than cellulose nanofibers from the perspective of dehydration. However, from the perspective of promoting the chemical reaction, it is more preferable to carbamate the cellulose fiber to be carbamate-modified from the cellulose raw material before pulpization, such as pulp or a paper substrate made from pulp. Of course, unmodified microfibrous cellulose that has not been modified by carbamate or other methods can also be used in the cellulose composite resin of this embodiment.

[0030] The average fiber length of the microfibrous cellulose (average length of single fibers) is preferably 0.05 to 0.5 mm, more preferably 0.1 to 0.45 mm, and particularly preferably 0.15 to 0.40 mm. If the average fiber length is less than 0.05 mm, the reinforcing effect of the resin may not be fully exerted. On the other hand, if the average fiber length exceeds 1.0 mm, the microfibrous cellulose may become entangled with each other, making it difficult to handle.

[0031] The microfibrous cellulose used in the cellulose composite resin of this embodiment has an average fiber width of, for example, 0.1 to 25 μm, preferably 0.2 to 20 μm, and more preferably 0.5 to 18 μm. When the average fiber width of the microfibrous cellulose is within this range, the decrease in the strength properties of the resin (particularly the flexural modulus) is suppressed or the strength properties of the resin are maintained, which is preferable. Furthermore, since it does not defibrate as finely as cellulose nanofibers, it does not require the time, cost, and energy required for production. It also has the advantage of being easy to dry. It has a moderate moisture content. Fibers with small diameters, such as cellulose nanofibers, have poor dehydration properties, requiring significant energy consumption for drying, and the cellulose fibers are degraded by heat, which may result in a decrease in strength. On the other hand, if the average fiber width of the microfibrous cellulose exceeds 25 μm, it becomes no different from pulp, and the reinforcing effect may be insufficient.

[0032] The average fiber length of the cellulose raw material used to produce microfibrous cellulose is preferably 0.50 to 5.00 mm, more preferably 1.00 to 3.00 mm, and particularly preferably 1.50 to 2.50 mm. If the average fiber length of the cellulose raw material exceeds 5.00 mm, there is a risk of being disadvantageous in terms of costs during defibration and beating.

[0033] The average fiber length of the microfibrous cellulose can be adjusted as desired by, for example, selecting the cellulose raw material, pre-treating, beating, etc.

[0034] Microfibrous cellulose can be obtained by macerating and beating a cellulose raw material, for example, a paper substrate made from raw pulp or pulp slurry. The cellulose raw material can be one or more selected from wood pulp made from broadleaf trees, coniferous trees, etc.; non-wood pulp made from straw, bagasse, cotton, hemp, bast fibers, etc.; and recycled paper pulp (DIP) made from recycled waste paper, broke, etc. The above-mentioned raw materials may be in the form of a pulverized material (powder), such as cellulose powder.

[0035] However, in order to minimize the contamination of impurities, it is preferable to use wood pulp as the cellulose raw material. As the wood pulp, for example, one or more types can be selected from chemical pulps such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), and mechanical pulp (TMP), etc.

[0036] The hardwood kraft pulp may be bleached hardwood kraft pulp, unbleached hardwood kraft pulp, or semi-bleached hardwood kraft pulp. Similarly, the softwood kraft pulp may be bleached softwood kraft pulp, unbleached softwood kraft pulp, or semi-bleached softwood kraft pulp.

[0037] As the mechanical pulp, for example, one or more types can be selected and used from stone ground pulp (SGP), pressed stone ground pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo-ground pulp (TGP), ground pulp (GP), thermo-mechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), refiner mechanical pulp (RMP), bleached thermo-mechanical pulp (BTMP), etc.

[0038] For the microfibrous cellulose, it is preferable to use a cellulose raw material having a lignin content of 1.0% or less, and more preferably 0.8% or less. When carbamate-treated microfibrous cellulose is used, for example, if the lignin content exceeds 1.0%, discoloration is likely to occur when the cellulose fibers are heat-treated so that the carbamate group substitution rate is 0.5 mmol / g or more. However, if the lignin content of the cellulose raw material is within the above range, discoloration caused by lignin can be suppressed, and discoloration can also be suppressed when the cellulose composite resin is formed. Furthermore, when the cellulose raw material is carbamate-treated, the lignin contained in the cellulose is also carbamate-treated. In other words, the reagent used in the carbamate reaction reacts not only with the cellulose portion of the cellulose raw material but also with the lignin. When the carbamate reaction is completed and the remaining reagent is washed off from the cellulose, the carbamate-treated lignin also flows out and is removed. In this series of operations, the reagents for the carbamate reaction are consumed not only in the cellulose but also in the lignin, which may result in a decrease in the carbamate conversion rate of the cellulose remaining in the fibers. From this perspective, if the lignin content in the microfibrous cellulose is within the above range, the amount of carbamate that flows out and does not contribute to fiber reinforcement can be reduced, resulting in the effect of achieving excellent strength when converted into a composite resin.

[0039] The lignin content is a value measured in accordance with the Lignin Content Test Method (JAPAN-TAPPI-No. 61 (2000)).

[0040] From the viewpoint of preventing discoloration, the kappa number of the cellulose raw material is preferably 2 or less, and more preferably 1 or less.

[0041] The kappa number is a value measured in accordance with the kappa number test method (JIS-P-8211 (2011)).

[0042] The lignin content and kappa number can be adjusted, for example, by selecting the cellulose raw material, cooking, bleaching, etc.

[0043] In this embodiment, the whiteness of the cellulose raw material is preferably 50% or more, more preferably 80% or more, and particularly preferably 82% or more. If the whiteness of the cellulose raw material itself is less than 50%, the sample will be further discolored during melt-kneading, and the whiteness of the composite resin itself will be low.

[0044] The whiteness is a value measured in accordance with JIS-P-8148:2001.

[0045] The cellulose raw material can be pretreated by a chemical method before being converted into microfibrous cellulose. Examples of pretreatment by a chemical method include hydrolysis of polysaccharides with an acid (acid treatment), hydrolysis of polysaccharides with an enzyme (enzyme treatment), swelling of polysaccharides with an alkali (alkali treatment), oxidation of polysaccharides with an oxidizing agent (oxidation treatment), and reduction of polysaccharides with a reducing agent (reduction treatment). As a pretreatment by a chemical method, an enzyme treatment is preferably carried out, and it is more preferable to additionally carry out one or more treatments selected from an acid treatment, an alkali treatment, and an oxidation treatment. The enzyme treatment will be described in detail below.

[0046] As the enzyme used in the enzymatic treatment, it is preferable to use at least one of cellulase enzymes and hemicellulase enzymes, and more preferably to use both in combination. The use of these enzymes makes it easier to convert cellulose raw materials into microfibrous cellulose. Note that cellulase enzymes cause the decomposition of cellulose in the presence of water. Also, hemicellulase enzymes cause the decomposition of hemicellulose in the presence of water.

[0047] Examples of cellulase enzymes that can be used include enzymes produced by species of the Trichoderma (filamentous fungi), Acremonium (filamentous fungi), Aspergillus (filamentous fungi), Phanerochaete (basidiomycetes), Trametes (basidiomycetes), Humicola (filamentous fungi), Bacillus (bacteria), Schizophyllum (basidiomycetes), Streptomyces (bacteria), and Pseudomonas (bacteria). These cellulase enzymes are available as reagents or commercially available products. Examples of commercially available products include Celluleucin T2 (manufactured by HPI), Meicerase (manufactured by Meiji Seika Kaisha), Novozyme 188 (manufactured by Novozyme), Multifect CX10L (manufactured by Genencor), and cellulase enzyme GC220 (manufactured by Genencor).

[0048] As the cellulase enzyme, either EG (endoglucanase) or CBH (cellobiohydrolase) can be used. EG and CBH can be used alone or in combination. They can also be used in combination with a hemicellulase enzyme.

[0049] Examples of hemicellulase enzymes that can be used include xylanase, which is an enzyme that decomposes xylan, mannase, which is an enzyme that decomposes mannan, and arabanase, which is an enzyme that decomposes araban. Pectinase, which is an enzyme that decomposes pectin, can also be used.

[0050] The amount of enzyme added to the cellulose raw material is determined by, for example, the type of enzyme, the type of wood used as the raw material (coniferous or broadleaf), the type of mechanical pulp, etc. However, the amount of enzyme added to the cellulose raw material is preferably 0.1 to 3 mass%, more preferably 0.3 to 2.5 mass%, and particularly preferably 0.5 to 2 mass%. If the amount of enzyme added is less than 0.1 mass%, the effect of adding the enzyme may not be fully obtained. On the other hand, if the amount of enzyme added is more than 3 mass%, the cellulose may be saccharified, and the yield of microfibrous cellulose may decrease. There is also the problem that the improvement in effect may not be commensurate with the increase in the amount added.

[0051] When a cellulase enzyme is used as the enzyme, the pH during the enzymatic treatment is preferably in the weak acidic range (pH = 3.0 to 6.9) from the viewpoint of the reactivity of the enzymatic reaction. On the other hand, when a hemicellulase enzyme is used as the enzyme, the pH during the enzymatic treatment is preferably in the weak alkaline range (pH = 7.1 to 10.0).

[0052] The temperature during the enzyme treatment is preferably 30 to 70°C, more preferably 35 to 65°C, and particularly preferably 40 to 60°C, regardless of whether a cellulase enzyme or a hemicellulase enzyme is used as the enzyme. If the temperature during the enzyme treatment is 30°C or higher, the enzyme activity is less likely to decrease, and prolongation of the treatment time can be prevented. On the other hand, if the temperature during the enzyme treatment is 70°C or lower, deactivation of the enzyme can be prevented.

[0053] The time for the enzyme treatment is determined depending on, for example, the type of enzyme, the temperature of the enzyme treatment, the pH during the enzyme treatment, etc. However, the time for the enzyme treatment is generally 0.5 to 24 hours.

[0054] After the enzymatic treatment, it is preferable to inactivate the enzyme. Examples of methods for inactivating the enzyme include adding an alkaline aqueous solution (preferably pH 10 or higher, more preferably pH 11 or higher) and adding hot water at 80 to 100°C.

[0055] Furthermore, enzyme treatment breaks down cellulose into oligosaccharides and monosaccharides, which turn brown and discolored like caramel when heated. Therefore, it is preferable to thoroughly wash the cellulose raw material with water after enzyme treatment.

[0056] Next, the alkali treatment method will be explained. When cellulose raw materials are subjected to alkali treatment prior to conversion into microfibrous cellulose, some of the hydroxyl groups in the hemicellulose and cellulose contained in the pulp are dissociated, and the molecules are anionized, weakening intramolecular and intermolecular hydrogen bonds and promoting the dispersion of the fibers in the cellulose raw materials.

[0057] Examples of the alkali used in the alkali treatment include organic alkalis such as sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and benzyltrimethylammonium hydroxide. However, from the viewpoint of production costs, it is preferable to use sodium hydroxide.

[0058] If the cellulose raw material is subjected to an enzyme treatment, acid treatment, or oxidation treatment prior to conversion into microfibrous cellulose, the water retention of the microfibrous cellulose can be reduced, the crystallinity can be increased, and the homogeneity can be improved. In this regard, microfibrous cellulose with low water retention is preferred because steam explosion is less likely to occur during kneading, and a cellulose composite resin with reduced strength reduction can be obtained.

[0059] When cellulose raw materials are treated with enzymes, acids, or oxidation, the hemicellulose and amorphous regions of cellulose in the pulp are decomposed. As a result, the energy required to produce microfibrous cellulose can be reduced, and the uniformity of the cellulose fibers can be improved. However, because pretreatment reduces the aspect ratio of microfibrous cellulose, excessive pretreatment is preferably avoided when using it as a reinforcing material for resins.

[0060] The cellulose raw material can be defibrated by beating the cellulose raw material using, for example, a homogenizer such as a beater, a high-pressure homogenizer, or a high-pressure homogenizer, a millstone-type friction machine such as a grinder or a grinder, a single-screw kneader, a multi-screw kneader, a kneader refiner, a jet mill, etc. However, it is preferable to use a refiner or a jet mill.

[0061] The fine A ratio of the microfibrous cellulose is preferably 3% or more and 60% or less, more preferably 10% or more and 55% or less, and particularly preferably 15% or more and 50% or less. When the fine A ratio is within the above range, the cellulose composite resin has a high proportion of homogeneous fibers and is suppressed from decreasing in strength.

[0062] Furthermore, when the fine A ratio of the microfibrous cellulose is set within the above range, the fine B ratio of the microfibrous cellulose is preferably 15 to 50%, more preferably 16 to 40%. When the fine B ratio is within the above range, the decrease in strength when the microfibrous cellulose is used as a composite resin can be further suppressed.

[0063] The above is the fineness ratio of microfibrous cellulose, but it is more preferable if the fineness ratio of the cellulose raw material used as the raw material for microfibrous cellulose is also within a specified range. Specifically, the fine A ratio of the cellulose raw material used as the raw material for microfibrous cellulose is preferably 1% or more, more preferably 3 to 20%, and particularly preferably 5 to 18%. If the fine A ratio of the cellulose raw material is within the above range, even if the microfibrous cellulose is defibrated so that the fine A ratio is 3% or more, it is thought that the damage to the fibers will be small and the reinforcing effect of the resin will be improved.

[0064] The fine A ratio and fine B ratio can be adjusted by pretreatment such as enzyme treatment. However, especially when enzyme treatment is performed, the fiber itself may become brittle and fall apart, reducing the reinforcing effect of the resin. Therefore, from this perspective, the amount of enzyme added is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less. Also, not performing enzyme treatment (addition amount 0% by mass) is also an option.

[0065] In this embodiment, the "fine A rate" refers to the percentage of the total mass of pulp fibers having a fiber width of 75 μm or less and a fiber length of 0.2 mm or less relative to the total mass of pulp fibers. The "fine B rate" refers to the percentage of the total mass of pulp fibers having a fiber width of 10 μm or less and a fiber length of more than 0.2 mm relative to the total mass of pulp fibers.

[0066] The aspect ratio of the microfibrous cellulose is preferably 5 to 10,000, more preferably 10 to 5,000, and particularly preferably 15 to 3,000. When the aspect ratio is within this range, a three-dimensional network is formed, and the microfibrous cellulose is less likely to be unevenly distributed in localized areas in the composite resin. In addition, excessive entanglement of the microfibrous cellulose with itself is also less likely to occur.

[0067] The fibrillation rate of the microfibrous cellulose is preferably 1.0 to 30%, more preferably 2.0 to 25%, and particularly preferably 2.5 to 20%. If the fibrillation rate is within the above range, the contact area with water is appropriate and dehydration is facilitated, thereby reducing the energy required for the dehydration treatment.

[0068] In this embodiment, the fibrillation rate refers to a value obtained by disintegrating cellulose fibers in accordance with JIS-P-8220:2012 "Pulp Disintegration Method" and measuring the obtained disintegrated pulp using a fiber analyzer "FS5" manufactured by Valmet.

[0069] The crystallinity of the microfibrous cellulose is preferably 50% or more, more preferably 55% or more, and particularly preferably 60% or more. On the other hand, the crystallinity of the microfibrous cellulose is preferably 95% or more, more preferably 90% or more, and particularly preferably 85% or more. If the crystallinity is within the above range, the strength of the microfibrous cellulose itself is sufficiently maintained, and a decrease in the strength properties of the cellulose composite resin is unlikely to occur.

[0070] The crystallinity of the microfibrous cellulose can be adjusted as desired by, for example, selecting the cellulose raw material, pre-treating it, and pulverizing it.

[0071] The pulp viscosity of the microfibrous cellulose is preferably 2 cps or more, more preferably 4 cps or more. If the pulp viscosity of the microfibrous cellulose is less than 2 cps, it may be difficult to suppress aggregation of the microfibrous cellulose.

[0072] The freeness of the microfibrous cellulose is preferably 500 ml or less, more preferably 300 ml or less, and particularly preferably 100 ml or less. If the freeness of the microfibrous cellulose exceeds 500 ml, the effect of improving the strength of the resin may not be sufficiently obtained.

[0073] The zeta potential of the microfibrous cellulose is preferably −150 to 20 mV, more preferably −100 to 0 mV, and particularly preferably −80 to −10 mV. If the zeta potential is below −150 mV, compatibility with the resin may be significantly reduced, resulting in insufficient reinforcing effect. On the other hand, if the zeta potential is above 20 mV, dispersion stability may be reduced.

[0074] The water retention of the microfibrous cellulose is preferably 400 to 80%, more preferably 350 to 90%, and particularly preferably 300 to 100%. When the water retention is within this range, the cellulose composite resin becomes flexible and does not suffer from poor dehydration. In particular, when the water retention is 300 to 100%, it becomes easy to adjust the moisture content of the composite granules, and the fibers are less likely to be damaged, which contributes to improving the strength of the composite resin. Furthermore, the water retention of the microfibrous cellulose can be further reduced by substituting the hydroxy groups of the fibers with carbamate groups, thereby improving dehydration and drying properties.

[0075] The water retention of microfibrous cellulose can be adjusted as desired by, for example, selecting the cellulose raw material, pre-treating, defibrating, etc.

[0076] Microfibrous cellulose can be modified by substituting a portion of the cellulose with a functional group in order to impart additional properties to the original properties of the cellulose. Examples of modifications of microfibrous cellulose include carbamate conversion, esterification, etherification, amidation, and sulfidation. Carbamate conversion is particularly preferred because it improves the dispersibility of the microfibrous cellulose during the production process. The microfibrous cellulose constituting the cellulose composite resin may be modified by carbamate conversion to have carbamate groups, or it may be one that has no carbamate groups and has not been modified at all.

[0077] In the process of producing a cellulose composite resin, the timing of substituting the hydroxy groups of the microfibrous cellulose with carbamate groups is not particularly limited as long as it is before the kneading step. For example, a carbamate reaction may be carried out on a cellulose raw material to provide the carbamate groups, or a carbamate reaction may be carried out on a microfibrous cellulose (a pulverized cellulose raw material) to provide the carbamate groups.

[0078] The term "having a carbamate group" means that a carbamate group (an ester of carbamic acid) has been introduced into the microfibrous cellulose. The carbamate group can be represented by the following structural formula (Chemical Formula 1), and is represented, for example, by -O-CO-NH-. ２ , -O-CONHR, -O-CO-NR ２ Examples include:

[0079]

[0080] Here, n represents an integer of 1 or greater. Each R is independently at least one of a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, and a group derived therefrom.

[0081] Examples of the saturated linear hydrocarbon group include linear alkyl groups having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, and a propyl group.

[0082] Examples of saturated branched hydrocarbon groups include branched alkyl groups having 3 to 10 carbon atoms, such as an isopropyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group.

[0083] Examples of the saturated cyclic hydrocarbon group include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, and a norbornyl group.

[0084] Examples of the unsaturated linear hydrocarbon group include linear alkenyl groups having 2 to 10 carbon atoms, such as ethenyl (vinyl), propen-1-yl, and propen-3-yl groups, and linear alkynyl groups having 2 to 10 carbon atoms, such as ethynyl, propyn-1-yl, and propyn-3-yl groups.

[0085] Examples of the unsaturated branched hydrocarbon group include branched alkenyl groups having 3 to 10 carbon atoms, such as a propen-2-yl group, a buten-2-yl group, and a buten-3-yl group, and branched alkynyl groups having 4 to 10 carbon atoms, such as a butyn-3-yl group.

[0086] Examples of the aromatic group include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0087] Examples of the derivative group include groups in which one or more hydrogen atoms of the above-mentioned saturated linear hydrocarbon group, saturated branched hydrocarbon group, saturated cyclic hydrocarbon group, unsaturated linear hydrocarbon group, unsaturated branched hydrocarbon group, and aromatic group have been substituted with a substituent (for example, a hydroxy group, a carboxy group, a halogen atom, etc.).

[0088] In microfibrous cellulose having carbamate groups (introduced with carbamate groups), some or all of the highly polar hydroxyl groups are substituted with relatively less polar carbamate groups. Therefore, microfibrous cellulose having carbamate groups has low hydrophilicity and high affinity with resins having low polarity. As a result, microfibrous cellulose having carbamate groups has excellent uniform dispersibility with resins having similarly low polarity. In addition, a slurry of microfibrous cellulose having carbamate groups has low viscosity and good handleability.

[0089] The substitution rate of carbamate groups relative to hydroxy groups in microfibrous cellulose is preferably 0.5 mmol / g or more and 2.0 mmol / g or less, more preferably 0.6 mmol / g or more and 1.8 mmol / g or less, and particularly preferably 0.7 mmol / g or more and 1.6 mmol / g or less. When the substitution rate is within this range, the hydrogen bonds between cellulose fibers caused by the hydroxyl groups of the cellulose are weakened (aggregation relaxation effect). In addition, the introduction of carbamate groups, which are more hydrophobic than hydroxyl groups, increases the affinity with the resin powder (affinity improvement effect). As a result, the resin powder and the microfibrous cellulose become entangled with each other, and the microfibrous cellulose that does not form dirt 3 is less likely to aggregate, thereby enhancing the resin reinforcement effect. Furthermore, by having the substitution rate within this range, the heat resistance of the composite resin is less likely to decrease. In this regard, when cellulose fibers are exposed to heat, hydroxyl groups are usually detached, and the molecular chain can shorten from the point where the detachment occurs. Furthermore, if some of the hydroxyl groups are modified by carbamate or the like, elimination of the hydroxyl groups becomes more likely. Therefore, if the substitution rate of the carbamate group is increased too much, the molecular chain becomes too short, the decomposition temperature decreases, and heat resistance decreases. Furthermore, if the substitution rate of the carbamate group is increased too much, the average fiber length of the pulp becomes short when the cellulose fiber is carbamate-modified, and there is a risk that sufficient resin reinforcement effect will not be achieved.

[0090] In this embodiment, the carbamate group substitution rate (mmol / g) refers to the amount of carbamate groups contained per gram of cellulose raw material containing carbamate groups. The carbamate group substitution rate is calculated by measuring the N atoms present in the carbamate-modified pulp using the Kjeldahl method and calculating the carbamate conversion rate per unit weight. Cellulose is a polymer with anhydroglucose as a structural unit, and has three hydroxy groups per structural unit.

[0091] Examples of methods for obtaining carbamate-modified microfibrous cellulose include a method in which a cellulose raw material is subjected to a carbamate reaction and then pulverized (disintegrated, beaten, and / or defibrated) to obtain carbamate-modified microfibrous cellulose, and a method in which the cellulose raw material is pulverized and then pulverized to obtain carbamate-modified microfibrous cellulose. Here, the pulverization of the cellulose raw material is described first, followed by the carbamation reaction (modification). However, either the pulverization or the carbamation may be performed first. In particular, it is preferable to perform the carbamation reaction first and then the pulverization. This is because the cellulose raw material before pulverization has high dehydration efficiency and is in a state in which the cellulose raw material is easily pulverized by heating associated with the carbamation reaction.

[0092] The process of carbamate conversion of microfibrous cellulose or the like (which may be a cellulose raw material as mentioned above, the same applies hereinafter) can be mainly divided into, for example, a mixing treatment, a removal treatment, and a heat treatment. The mixing treatment and the removal treatment can be collectively referred to as a conditioning treatment for preparing a mixture to be subjected to a heat treatment. Furthermore, carbamate conversion has the advantage that the reactant can be chemically modified without using an organic solvent.

[0093] In the mixing treatment, microfibrous cellulose or the like and urea or a derivative of urea (hereinafter simply referred to as "urea or the like") are mixed in a dispersion medium.

[0094] Examples of urea and urea derivatives that can be used include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and compounds in which the hydrogen atoms of urea are substituted with alkyl groups. These ureas and urea derivatives can be used alone or in combination. However, it is preferable to use urea.

[0095] The upper limit of the mixing mass ratio of urea etc. to microfibrous cellulose etc. (urea etc. / microfibrous cellulose etc.) is preferably 300 / 100, more preferably 200 / 100. On the other hand, the lower limit is preferably 10 / 100, more preferably 20 / 100. By making the mixing mass ratio 10 / 100 or more, the efficiency of carbamate formation is improved. On the other hand, even if the mixing mass ratio exceeds 300 / 100, carbamate formation is not further promoted.

[0096] The dispersion medium is usually water, although other dispersion media such as alcohols and ethers, as well as mixtures of water with other dispersion media, may also be used.

[0097] In the mixing treatment, for example, microfibrous cellulose etc. and urea etc. may be added to water, microfibrous cellulose etc. may be added to an aqueous solution of urea etc., or urea etc. may be added to a slurry containing microfibrous cellulose etc. Furthermore, stirring may be performed after addition to achieve uniform mixing. Furthermore, other components may be contained in the dispersion containing microfibrous cellulose etc. and urea etc. When the microfibrous cellulose etc. is a sheet-shaped cellulose raw material, a method may be adopted in which the cellulose raw material is impregnated in a mixed liquid of urea etc. and a dispersion medium and mixed. When the cellulose raw material is in sheet form, heat is conducted within the sheet, which is expected to lower the heating temperature and shorten the heating time in the heat treatment.

[0098] In the removal treatment, the dispersion medium is removed from the dispersion liquid containing the microfibrous cellulose etc. and urea etc. obtained in the mixing treatment. By removing the dispersion medium, the urea etc. can be reacted efficiently in the subsequent heat treatment.

[0099] The dispersion medium is preferably removed by volatilizing it by heating, which allows efficient removal of the dispersion medium while leaving behind components such as urea.

[0100] When the dispersion medium is water, the lower limit of the heating temperature in the removal treatment is preferably 50°C, more preferably 70°C, and particularly preferably 90°C. By setting the heating temperature to 50°C or higher, the dispersion medium can be efficiently volatilized (removed). On the other hand, the upper limit of the heating temperature is preferably 120°C, more preferably 100°C. If the heating temperature exceeds 120°C, the dispersion medium and urea may react, resulting in the urea decomposing independently.

[0101] The heating time in the removal treatment can be adjusted appropriately depending on the solid content concentration of the dispersion, etc. Specifically, it is, for example, 6 to 24 hours.

[0102] In the heat treatment following the removal treatment, a mixture of microfibrous cellulose and urea is heat-treated. In this heat treatment, some or all of the hydroxyl groups of the microfibrous cellulose are reacted with urea and substituted with carbamate groups. More specifically, when urea is heated, it is decomposed into isocyanic acid and ammonia as shown in the following reaction formula (1). Isocyanic acid is highly reactive, and for example, carbamate groups are formed on the hydroxyl groups of cellulose as shown in the following reaction formula (2). NH ２ —CO—NH ２ → H-N=C=O + NH ３ ...(1) Cell-OH + H-N=C=O → Cell-O-CO-NH ２ …(2)

[0103] The lower limit of the heating temperature in the heat treatment is preferably 120°C, more preferably 130°C, particularly preferably above the melting point of urea (about 134°C), even more preferably 140°C, and most preferably 150°C. By setting the heating temperature to 120°C or higher, carbamate formation is carried out efficiently. The upper limit of the heating temperature is preferably 200°C, more preferably 180°C, and particularly preferably 170°C. If the heating temperature exceeds 200°C, the microfibrous cellulose and the like may decompose, resulting in an insufficient reinforcing effect.

[0104] The lower limit of the heating time in the heat treatment is preferably 1 minute, more preferably 5 minutes, particularly preferably 30 minutes, even more preferably 1 hour, and most preferably 2 hours. By setting the heating time to 1 minute or more, the carbamate reaction can be carried out reliably. On the other hand, the upper limit of the heating time is preferably 5 hours, more preferably 3 hours. A heating time of more than 5 hours is not economical, and 5 hours is sufficient for carbamate formation.

[0105] However, prolonged heating times can lead to degradation of the cellulose fibers. Therefore, it is desirable to adjust the pH of the reaction system to minimize degradation of the cellulose fibers during heat treatment. Specifically, the pH is preferably 9 or higher, more preferably 9 to 13, and particularly preferably 10 to 12, under alkaline conditions. Alternatively, a second-best option is acidic or neutral conditions of pH 7 or lower, preferably 3 to 7, and particularly preferably 4 to 7. Neutral conditions of pH 7 to 8 may shorten the average fiber length of the cellulose fibers, potentially resulting in a poor reinforcing effect of the resin. In contrast, alkaline conditions of pH 9 or higher enhance the reactivity of the cellulose fibers, promoting the reaction with urea and other compounds, resulting in efficient carbamate formation, thereby ensuring a sufficient average fiber length of the cellulose fibers. On the other hand, acidic conditions of pH 7 or lower promote the decomposition of urea and other compounds into isocyanic acid and ammonia, promoting the reaction with cellulose fibers, resulting in efficient carbamate formation, thereby ensuring a sufficient average fiber length of the cellulose fibers. However, if possible, heat treatment under alkaline conditions is preferable. This is because acidic conditions may cause acid hydrolysis of cellulose.

[0106] The pH can be adjusted by adding an acidic compound (e.g., acetic acid, citric acid, etc.) or an alkaline compound (e.g., sodium hydroxide, calcium hydroxide, etc.) to the mixture.

[0107] As the heating device in the heat treatment, for example, a hot air dryer, a paper machine, a dry pulp machine, etc. can be used.

[0108] The mixture after the heat treatment may be washed. This washing may be carried out with water or the like. By this washing, unreacted urea and the like remaining can be removed.

[0109] (Slurry) If necessary, the microfibrous cellulose is dispersed in an aqueous medium to form a dispersion (slurry). The aqueous medium is particularly preferably entirely water, but an aqueous medium containing other liquids that are partially compatible with water can also be used. As the other liquid, lower alcohols having 3 or less carbon atoms can be used.

[0110] The solids concentration of the slurry is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 5.0% by mass. If the solids concentration is less than 0.1% by mass, excessive energy may be required for dehydration and drying. On the other hand, if the solids concentration is more than 10.0% by mass, the fluidity of the slurry itself may decrease, making it difficult to uniformly mix the slurry when a dispersant is used.

[0111] (Resin powder) Microfibrous cellulose may aggregate depending on storage conditions, and once aggregated, it takes time and effort to re-disperse it. In order to suppress the aggregation of microfibrous cellulose and to facilitate re-dispersion, it is advisable to mix resin powder with the microfibrous cellulose. When microfibrous cellulose and resin powder are mixed to form a mixture, the microfibrous cellulose remains dispersed and stable, making it less likely to aggregate. In particular, when microfibrous cellulose is dried, aggregation of the microfibrous cellulose is likely to occur, so by dispersing and mixing resin powder, aggregation can be suppressed.

[0112] The resin component of the cellulose composite resin of this embodiment is not particularly limited, and mixing a general resin with microfiber cellulose to form a composite can suppress the decrease in strength properties or reinforce the structure. This effect can be considered similar to the effect of reinforcing a mud wall with straw. Therefore, even if the resin is a polyolefin-based resin, polyester-based resin, AS-based resin, polyamide-based resin, or other resin, forming the composite resin can suppress the decrease in strength properties or reinforce the structure.

[0113] The resin powder is preferably a resin that serves as the matrix of the fiber masterbatch. If the resin powder is, for example, a polyolefin resin, when compounded with microfiber cellulose, the interfacial adhesion between the polyolefin resin and the fiber can be improved, thereby improving the physical properties of the composite material.

[0114] A compatibilizer can be added to improve the compatibility of the resin powder mixed with the microfibrous cellulose. An acid-modified resin powder is preferred as the compatibilizer. The acid-modified resin is a polymer having a polymer backbone and a side chain of an organic acid anhydride group, and the polymer backbone is selected from polyolefin-based resins, polyester-based resins, AS-based resins, polyamide-based resins, etc. When considering compounding with a general-purpose polyolefin-based resin, the polymer backbone of the acid-modified resin powder is preferably a polyolefin-based resin. The side chain may be an organic acid capable of forming an acid anhydride, but from a cost perspective, an unsaturated carboxylic acid is preferred. In the acid-modified resin powder, the acid groups ionically bond with some or all of the carbamate groups of the microfibrous cellulose. This ionic bond improves the reinforcing effect of the resin.

[0115] As the polyolefin component, for example, one or more types can be selected and used from polymers of alkenes such as ethylene, propylene, butadiene, isoprene, etc. However, it is preferable to use a polypropylene resin, which is a polymer of propylene.

[0116] As the unsaturated carboxylic acid component, for example, one or more selected from maleic anhydrides, phthalic anhydrides, itaconic anhydrides, citraconic anhydrides, citric anhydrides, etc. can be used. However, it is preferable to use maleic anhydrides, and it is suitable to use a maleic anhydride-modified polypropylene resin.

[0117] From the above, the resin powder is preferably one having a polyolefin main chain and containing a polymer having an organic acid anhydride group on the side chain, that is, an organic acid anhydride-modified polyolefin.

[0118] The resin powder to be mixed with the microfibrous cellulose may be a mixture of an acid-modified resin powder and a non-acid-modified resin powder, or the entire amount of the resin powder may be an acid-modified resin powder, or the entire amount of the resin powder may be a non-acid-modified resin powder. When a mixture of an acid-modified resin powder and a non-acid-modified resin powder is used, the amount of the non-acid-modified resin powder mixed is preferably 0 to 200 parts by mass, more preferably 1 to 100 parts by mass, and particularly preferably 10 to 70 parts by mass, per 100 parts by mass of the acid-modified resin powder.

[0119] The average particle size of the resin powder mixed with the microfibrous cellulose of this embodiment is preferably 0.1 to 1,000 μm, more preferably 1 to 800 μm, and even more preferably 10 to 600 μm. The ratio of the average particle size of the resin powder to the average fiber width of the microfibrous cellulose used for mixing (average particle size (μm) of the resin powder / average fiber width (μm) of the microfibrous cellulose) is preferably 50 to 80,000, more preferably 500 to 60,000. If the above ratio is less than 50, the resin powder is too small relative to the microfibrous cellulose, which may cause the microfibrous cellulose particles to come into contact with each other in a mixture containing the resin powder and the microfibrous cellulose, making it difficult to uniformly disperse them. Furthermore, if the above ratio exceeds 60,000, the resin powder is too large relative to the microfibrous cellulose, making it difficult for the microfibrous cellulose particles to physically approach each other and form dirt particles 3.

[0120] The weight average molecular weight of the maleic anhydride-modified polypropylene is, for example, 1,000 to 100,000, preferably 3,000 to 50,000.

[0121] The acid value of the maleic anhydride-modified polypropylene is preferably 0.5 mgKOH / g or more and 100 mgKOH / g or less, and more preferably 1 mgKOH / g or more and 50 mgKOH / g or less.

[0122] Furthermore, the acid-modified resin powder preferably has an MFR (melt flow rate) of 2000 g / 10 min (190°C / 2.16 kg) or less, more preferably 1500 g / 10 min or less, and particularly preferably 500 g / 10 min or less. When the MFR is in the above range, the microfibrous cellulose is dispersed in the resin powder with good dispersibility, which is preferable.

[0123] The acid value is measured in accordance with JIS-K2501 by titration with potassium hydroxide.

[0124] The resin powder used to form the composite granules by mixing with the microfibrous cellulose and the resin pellets mixed in the kneading step s60 preferably have a smaller average particle size than the resin pellets. The resin powder and the resin pellets may be made of the same resin compound or different resin compounds.

[0125] (Dispersant) The mixture of resin powder and microfibrous cellulose of this embodiment preferably contains a dispersant. Preferred dispersants are aromatic compounds having an amine group and / or a hydroxyl group, and aliphatic compounds having an amine group and / or a hydroxyl group.

[0126] Examples of compounds having an amine group and / or a hydroxyl group in an aromatic group include anilines, toluidines, trimethylanilines, anisidines, tyramines, histamines, tryptamines, phenols, dibutylhydroxytoluenes, bisphenol A, cresols, eugenols, gallic acids, guaiacols, picric acids, phenolphthalein, serotonins, dopamines, adrenalines, noradrenalines, thymols, tyrosines, salicylic acids, methyl salicylates, and aliphatic alcohols. Examples of the alcoholic beverage include varnish alcohols, salicylic alcohols, sinapyl alcohols, diphenidol, diphenylmethanols, cinnamyl alcohols, scopolamines, tryptophols, vanillyl alcohols, 3-phenyl-1-propanols, phenethyl alcohols, phenoxyethanols, veratryl alcohols, benzyl alcohols, benzoins, mandelic acids, mandelonitriles, benzoic acids, phthalic acids, isophthalic acids, terephthalic acids, mellitic acids, and cinnamic acids.

[0127] Furthermore, examples of compounds having an amine group and / or a hydroxyl group in an aliphatic group include capryl alcohols, 2-ethylhexanols, pelargonic alcohols, capric alcohols, undecyl alcohols, lauryl alcohols, tridecyl alcohols, myristyl alcohols, pentadecyl alcohols, cetanols, stearyl alcohols, elaidyl alcohols, oleyl alcohols, linoleyl alcohols, methylamines, dimethylamines, trimethylamines, ethylamines, diethylamines, and ethylenediamines. , triethanolamines, N,N-diisopropylethylamines, tetramethylethylenediamines, hexamethylenediamines, spermidines, spermines, amantadines, formic acids, acetic acids, propionic acids, butyric acids, valeric acids, caproic acids, enanthic acids, caprylic acids, pelargonic acids, capric acids, lauric acids, myristic acids, palmitic acids, margaric acids, stearic acids, oleic acids, linoleic acids, linolenic acids, arachidonic acids, eicosapentaenoic acids, docosahexaenoic acids, and sorbic acids.

[0128] The above dispersants inhibit hydrogen bonding between the microfibrous cellulose particles in the mixture. Therefore, when a dispersant is added to a mixture containing a powdered resin and microfibrous cellulose, the microfibrous cellulose particles are dispersed without agglomerating together, resulting in a cellulose composite resin with uniform strength.

[0129] Furthermore, since polypropylene has a melting point of approximately 160°C, the kneading step s60 is performed, for example, at a temperature higher than that. At high temperatures, the resin components melt, and if a dispersant (liquid) is added in this state, the dispersion medium evaporates and dries in an instant. Therefore, a method can be adopted in which a masterbatch (a composite resin with a high concentration of microfibrous cellulose) is prepared using resin pellets with a low melting point, and then regular resin pellets are fed into the kneader to reduce the concentration of microfibrous cellulose. However, resins with low melting points generally have low strength. Therefore, this method may reduce the strength of the composite resin.

[0130] The amount of dispersant mixed is preferably 0.1 to 1,000 parts by mass, more preferably 1 to 500 parts by mass, and particularly preferably 10 to 200 parts by mass, per 100 parts by mass of microfibrous cellulose. If the amount of dispersant mixed is less than 0.1 parts by mass, the improvement in resin strength may be insufficient. On the other hand, if the amount mixed exceeds 1,000 parts by mass, the amount becomes excessive and the resin strength tends to decrease.

[0131] In this regard, the acid-modified resin powder described above improves compatibility by forming ionic bonds between the acid groups and the carbamate groups of the microfibrous cellulose, thereby enhancing the reinforcing effect. Its large molecular weight makes it easily compatible with resin pellets, which is thought to contribute to improving strength. Meanwhile, the dispersant described above intervenes between the hydroxyl groups of the microfibrous cellulose to prevent aggregation, thereby improving dispersibility in the resin. Furthermore, because its molecular weight is smaller than that of the acid-modified resin, it can enter the narrow spaces between the microfibrous cellulose that the acid-modified resin cannot enter, thereby improving dispersibility and improving strength. From these perspectives, the molecular weight of the acid-modified resin is preferably 2 to 2,000 times, and preferably 5 to 1,000 times, the molecular weight of the dispersant.

[0132] (Production Method) A mixture containing microfibrous cellulose and resin powder (a mixture further containing a dispersant, a non-interacting powder, etc., when adjusting the dispersibility of the microfibrous cellulose) is preferably dried to a moisture content of 10% or less prior to kneading with resin pellets, as described in detail below. This dried mixture is usually in the form of pellets. This pellet-like mixture is preferably pulverized into a powder. When made into a powder, the materials constituting the mixture are not uniform, so that the composite granules are uniformly kneaded during the kneading process, and the resulting cellulose composite resin is less discolored. In addition, excessive heating to remove moisture from the microfibrous cellulose during kneading with resin pellets is not required, resulting in good thermal efficiency. Furthermore, when a non-interacting powder or a dispersant is mixed into the mixture, there is little risk that the microfibrous cellulose will not redisperse even if the mixture is dried.

[0133] (Example of manufacturing method) An example of a manufacturing method for a cellulose composite resin will be described with reference to Figure 1. First, microfibrous cellulose is prepared. The microfibrous cellulose may be substituted in whole or in part with a carbamate group, or may not be substituted. The manufacturing operation is facilitated when the microfibrous cellulose is prepared as dispersion 1 having a solids concentration of 3 mass%, for example.

[0134] (Mixing step) The microfibrous cellulose dispersion 1 is supplied to the mixing step s10. In the mixing step s10, the microfibrous cellulose dispersion 1 and the resin powder 2 are introduced into a mixer 11 and mixed to obtain a mixture. To ensure a uniform mixture, it is preferable to arrange two mixers (mixers 11 and 12) in series.

[0135] (Dehydration Step) The mixture may be supplied to the dehydration step s20, or the dehydration step s20 may be omitted and the mixture may be supplied to the pulverization step s30. When the mixture is supplied to the dehydration step s20, the mixture is dehydrated by a dehydration means to produce a dehydrated product. The dehydration means 21 may be, for example, one or more dehydration devices selected from a belt press, a screw press, a filter press, a twin roll, a twin wire former, a valveless filter, a center disc filter, a membrane treatment, a centrifuge, and the like. Dehydration using a belt press or a screw press is particularly preferred because it provides high productivity and makes it easy to adjust the design. The dehydrated product may have a moisture content of, for example, 10 to 60% by mass.

[0136] (Crushing Step) The dehydrated product (or the mixture when the dehydration step s20 is omitted) is supplied to crushing means 31 in crushing step s30 and crushed to form a powder. If the mixture is small enough to be smoothly supplied to compression means 51 in the compression step s50, the mixture can be supplied to the drying step s40 without the dehydration step s20 and crushing step s30. The crushing of the dehydrated product (or the mixture) can be carried out using, for example, one or more selected from a crusher, a bead mill, a kneader, a disperser, a twist mill, a cut mill, a hammer mill, etc.

[0137] The average particle size of the powdery material is preferably 50 to 30,000 μm, more preferably 100 to 20,000 μm, and particularly preferably 150 to 10,000 μm. When the average particle size of the powdery material is within the above range, the composite granules formed by compression are unlikely to crumble easily even when subjected to an external force, and the bulk density of the formed composite granules is also prevented from becoming too small.

[0138] The average particle size of the powdery material can be controlled by controlling the degree of pulverization, as well as by classification using a classifying device such as a filter or cyclone.

[0139] (Drying Step) The powdery material (or mixture, dehydrated material) is supplied to drying means 41 in drying step s40 and dried to produce a dry powdery material with a moisture content of 0.1 to 20% by mass. The dry powdery material is composed of microfibrous cellulose and resin. The drying means 41 can be, for example, one or more selected from rotary kiln drying, disk drying, airflow drying, media fluidized drying, spray drying, drum drying, screw conveyor drying, paddle drying, uniaxial kneading drying, multiaxial kneading drying, vacuum drying, stirring drying, etc.

[0140] The moisture content of the dried powder is 20% or less, preferably 0.2 to 15%, more preferably 0.5 to 10%. If the moisture content exceeds 20%, the subsequent compression process becomes difficult.

[0141] The moisture content was calculated using the following formula: moisture content (%) = [(mass before drying - mass after drying) / mass before drying] x 100 after holding the sample at 105°C for 6 hours or more in a constant temperature dryer and determining the mass at which no change in mass was observed.

[0142] (Compression Step) The dried powder material is subjected to a compression step s50. In the compression step s50, the dried powder material is compressed by compression means 51 and processed into a pellet-shaped composite granulated material. Examples of the compression means 51 include a biomass pellet manufacturing device from Earth Engineering Co., Ltd., a press pelletizer from Chiyoda Machinery Co., Ltd., a wood pellet manufacturing device from Apte Japan Co., Ltd., a biomass pellet manufacturing device from Shinko Koki Co., Ltd., a pelletizer from Tosa Tech Co., Ltd., a briquette from WELHOUSE Co., Ltd., and a briquette machine from Nippon Steel Corporation.

[0143] Since the dry powder contains resin and microfibrous cellulose, the composite granules obtained by compression treatment are formed by compressing the dry powder with resin and microfibrous cellulose.

[0144] A granulation device, which is an example of the compression means 51, has a (ring) die with a large number of cylindrical through-holes formed substantially parallel to and perpendicular to the ring surface. A dry powder material containing a resin powder and microfibrous cellulose is forced into the through-holes from one end of the through-holes using a roller while applying pressure, compressing the dry powder material into a granule and releasing it from the other end. To produce the composite granules of this embodiment, for example, the through-holes may have a shape in which multiple holes of different diameters are connected in the axial direction. Alternatively, the through-holes may have the same diameter from one end to the other. The compression ratio of the composite granules can be adjusted by changing the pressure transmitted from the roller, the shape of the through-holes, the speed at which the mixture passes through the through-holes, the amount of dry powder material introduced into the through-holes, and the (ring) die temperature.

[0145] The number of darts 3 scattered in the cellulose composite resin of this embodiment can be adjusted by the presence or absence of a compatibilizer, or by undergoing the dehydration step s20, the drying step s40, and the compression step s50. The microfibrous cellulose in the cellulose composite resin has a very small fiber diameter of the smallest unit of microfibrous cellulose, so that each smallest unit of microfibrous cellulose cannot be seen with the naked eye. However, when the microfibrous cellulose aggregates to form aggregates with a certain diameter or larger, the aggregates can be seen as darts 3 by humans.

[0146] The dirt 3 in the cellulose composite resin of this embodiment is formed by agglomeration of microfibrous cellulose in a mixture of resin powder and microfibrous cellulose, but it is preferable that the mixture of resin powder and microfibrous cellulose be dispersed as uniformly as possible before the dirt 3 is formed. If the microfibrous cellulose is unevenly distributed in the mixture, the distribution of the dirt 3 will be uneven in the cellulose composite resin, resulting in a cellulose composite resin with an uneven pattern having dense and sparse areas of the dirt 3. On the other hand, if the mixture of resin powder and microfibrous cellulose is uniformly dispersed before the dirt 3 is formed, the distribution of the dirt 3 in the cellulose composite resin will be dispersed overall, resulting in an aesthetically pleasing appearance.

[0147] On the other hand, in producing a cellulose composite resin, a mixture in which microfibrous cellulose is uniformly dispersed in resin powder is subjected to compression or heat treatment, whereby adjacent microfibrous cellulose particles aggregate to form dirt 3, while microfibrous cellulose particles that do not contribute to the formation of dirt 3 remain dispersed in the resin. In other words, the cellulose composite resin contains microfibrous cellulose that is dispersed in the resin to form the base, and aggregated microfibrous cellulose that forms dirt 3.

[0148] The size and number of dirt 3, i.e., microfibrous cellulose aggregates, can be adjusted by changing the presence or absence of a compatibilizer and the processing conditions of each of the dehydration step s20, drying step s40 and compression step s50, and the inventors speculate that the processing conditions of the compression step s50 in particular have the greatest impact.

[0149] The reason why dirt 3 is formed, particularly in the compression step s50, is not precisely understood, but can be roughly explained as follows: When the dry powder material is supplied to the compression means in the compression step s50, the microfibrous cellulose contained in the dry powder material is subjected to compression pressure during the process of forming the composite granules, causing microfibrous cellulose particles that are physically close to each other to aggregate. At this time, the higher the compression pressure, the more the aggregation is promoted. Then, aggregates of a certain size can be visually recognized by humans.

[0150] Incidentally, the dry powder material supplied to the compression means 51 in the compression step s50 is somewhat dry but has a predetermined moisture content. Based on this, when a heated compression means is used to compress the dry powder material, the microfibrous cellulose is exposed to high temperatures while being subjected to compression pressure, and it is thought that the moisture contained in the microfibrous cellulose evaporates, and the microfibrous cellulose aggregates by physical aggregation and hydrogen bonding, etc. At this time, the higher the temperature, the more active the evaporation of moisture becomes, and the more aggregates are formed.

[0151] The temperature of the dry powder material in the compression step s50 is not particularly limited, but is preferably 10 to 200°C, more preferably 15 to 180°C. If the temperature is too high, the microfibrous cellulose will undergo thermal decomposition. The temperature of the (ring) die provided with through-holes in the compression means can be adjusted, and heat is transferred from the (ring) die to the dry powder material supplied to the through-holes, so the temperature of the dry powder material can be adjusted by adjusting the temperature of the (ring) die.

[0152] The volume of each composite granule is 4 to 4000 mm ３ It is preferable that the length is 20 to 1500 mm. ３ More preferably, it is 50 to 1000 mm ３ It is more preferable that the bulk density of each composite granule is 0.10 to 0.40 g / cm. ３ It is preferable that the density is 0.20 to 0.37 g / cm ３ More preferably, it is 0.25 to 0.35 g / cm ３ It is more preferable that:

[0153] The volume and bulk density of the composite granules are correlated, and if either the volume or the bulk density is within the above range, the cellulose composite resin can be produced with good productivity. For example, when the volume of the composite granules is 4 mm ３ If the volume is 4000 mm or more, it is easy to handle and loss occurring in the manufacturing process can be suppressed. ３ If the bulk density of the composite granules is 0.40 g / cm or less, the composite granules are less bulky and can be filled into the kneader with as few gaps as possible, which is preferable. ３ If the bulk density is below this value, fragments are less likely to remain even if the composite granules are broken down by kneading. If the bulk density is too high, the number of fiber agglomerates in the granules increases, which increases the load during extrusion kneading and may result in poor operability. On the other hand, if the bulk density is too low, the composite granules may lose a certain degree of hardness, losing their disintegrability during kneading and making it difficult to relax the fiber agglomerations. Furthermore, since the compressed mixture easily breaks down and turns into powder, it may be blown out of the kneader vent together with steam, which may result in poor operability.

[0154] The bulk density is a value measured in accordance with JIS K7365.

[0155] The shape of the composite granules is not particularly limited, but examples thereof include geometric three-dimensional shapes such as an approximately cylindrical, approximately rectangular prism, approximately cube, approximately rectangular prism, or shapes similar to these or a combination of these shapes, but are not limited to these.

[0156] The composite granules may have a moisture content of 20% or less, preferably 0 to 20%, more preferably 1 to 15%, and even more preferably 2 to 10%. A moisture content of 20% or less is preferable because steam explosion is less likely to occur during heating in a kneader. When the microfibrous cellulose mixture is compressed, the moisture contained in the microfibrous cellulose is squeezed out, and the moisture content of the composite granules is lower than that of the dry powder material before compression.

[0157] If the moisture content exceeds 20%, when the microfibrous cellulose is exposed to high temperatures, for example, 180°C or higher, during melt kneading or the like, contact between the microfibrous cellulose and high-temperature water occurs frequently, causing a reaction to depolymerize the microfibrous cellulose, producing low-molecular-weight compounds that cause discoloration, and it is thought that discoloration due to the low-molecular-weight compounds progresses during the kneading process. However, when carbamate conversion is performed so that the carbamate group substitution rate is 0.5 mmol / g or higher, for example, discoloration-causing substances are removed in the carbamate pulp washing process, and further, by setting the moisture content to 10% or less, it becomes possible to evaporate the high-temperature water before it comes into contact with the microfibrous cellulose, thereby preventing discoloration.

[0158] Incidentally, when the discoloration-causing substances (hemicellulose, etc.) originally present are broken down into smaller molecules, they become water-soluble, making it possible to remove the discoloration-causing substances during the carbamate pulp washing process. If the discoloration-causing substances remain in the microfibrous cellulose, they come into contact with high-temperature water during the kneading process, causing significant discoloration.

[0159] The composite granules of this embodiment are easy to granulate and have sufficient strength when made into a cellulose composite resin, provided that the mass ratio of the resin to the microfibrous cellulose is preferably 1:99 to 99:1, more preferably 5:95 to 95:5, and even more preferably 10:90 to 90:10, based on the solid content.

[0160] The composite granules (resin reinforcing material) obtained as described above are kneaded with resin pellets to finally obtain a cellulose composite resin. This kneading can be performed, for example, by mixing the pellet-shaped resin with the reinforcing material, or by first melting the resin pellets and adding the composite granules to the melt. Acid-modified resins, dispersants, etc. can also be added at this stage.

[0161] (Kneading Step) The kneading step s60 is a step in which a composite granule (or a dry powder) is kneaded, or a composite granule (or a dry powder) is kneaded with resin pellets 62 to obtain a cellulose composite resin. Conventionally, when cellulose nanofibers are mixed with a resin as a reinforcing material, a cellulose raw material is defibrated into cellulose nanofibers as a preliminary step, which are then fed into a kneader 61 together with the resin. However, the defibrated and dried cellulose nanofibers are in a powder form, which makes them bulky and leads to poor absorption, making it difficult to feed large amounts. Therefore, with conventional powder samples, the discharge speed can be slow when using a twin-screw extruder with a diameter of 15 mm, for example. Furthermore, the composite resin containing cellulose nanofibers and resin discharged from the kneader 61 is discharged, for example, in the form of strands. However, it can be difficult to stabilize the supply rate, resulting in brittle strands, insufficient strands, or colored strands.

[0162] On the other hand, in this embodiment, the sample supplied to the kneader 61 is a composite granule containing resin and microfibrous cellulose, so the amount supplied to the kneader 61 is stable, the thermal conductivity to the sample during kneading is excellent, the strands formed by kneading are stable, and there is less discoloration than in the past.

[0163] To adjust the amount of microfibrous cellulose contained in the final cellulose composite resin, additional resin pellets 62 can be supplied during the mixing process and kneaded with the composite granules. The resin pellets 62 fed to the kneader 61 preferably have an average particle diameter of 1 to 10 mm, more preferably 2 to 5 mm. If the average particle diameter is too small, the resin may melt before reaching the shaft and adhere to the wall, hindering the supply of subsequent resin pellets 62, resulting in a lack of quantitative kneading. Furthermore, poor thermal conductivity between the resin pellets results in a significant amount of energy being consumed before melting. If the average particle diameter is too large, poor thermal conductivity between the resin pellets results in a significant amount of energy being consumed before melting, making them difficult to supply to the kneader 61, and uneven heat conduction, resulting in a long melting time.

[0164] The resin pellets 62 may be supplied at the beginning of the kneading process by the kneader 61, or may be supplied after the kneading process has progressed to a certain extent. Here, "after the kneading process has progressed to a certain extent" refers to, for example, half the total time required from when the composite granules are supplied to the initial sample supply section of the kneader 61 until they are kneaded and discharged as a cellulose composite resin from the discharge section of the kneader 61. The cellulose composite resin discharged from the kneader 61 is processed into a molded body in a pelletizing step 70, sent to a packaging step 80, and packaged to become a final product 81.

[0165] In the kneading step s60, when new resin pellets 62 are supplied to the kneader 61 in addition to the composite granules and kneaded, the amount of newly supplied resin pellets 62 is preferably 0 to 10,000 parts by mass, and more preferably 0 to 1,000 parts by mass, per 100 parts by mass of microfibrous cellulose. By supplying new resin pellets 62, the blending ratio of microfibrous cellulose can be adjusted as desired.

[0166] The kneading step s60 may be repeated two or more times. For example, when the first kneading step s60 is repeated twice, in the first kneading step s60, the composite granules are supplied to the kneader 61 and kneaded without newly supplying the resin pellets 62 to obtain a cellulose composite resin. Then, in the second kneading step s60, the obtained cellulose composite resin may be supplied to the kneader 61 again, and newly supplied resin pellets 62 may be kneaded during the kneading process to obtain a cellulose composite resin (kneaded twice).

[0167] The temperature of the kneading treatment in this embodiment is equal to or higher than the glass transition point of the resin pellets 62, and although it differs depending on the type of resin pellets 62, it is preferably 80 to 280° C., more preferably 90 to 260° C., and particularly preferably 100 to 240° C. In addition to melting the resin pellets 62, the kneading treatment also melts the resin powder contained in the composite granules.

[0168] In the kneading process of this embodiment, when a twin-screw extruder having a diameter of 15 mm is used, for example, the composite granules and resin pellets 62 are supplied to the kneader 61 so as to achieve a discharge rate of preferably 1.0 to 10.0 kg / h, more preferably 1.5 to 7.0 kg / h, and even more preferably 2.0 to 5.0 kg / h, and water may be additionally supplied.

[0169] For the kneading treatment, one or more types of kneaders can be selected from, for example, a single-screw or multi-screw kneader having two or more screws, a multi-screw kneading extruder, a mixing roll, a kneader, a roll mill, a Banbury mixer, a screw press, a disperser, etc. Among these, it is preferable to use a multi-screw kneader having two or more screws. Two or more multi-screw kneaders having two or more screws may be used in parallel or in series.

[0170] The resin used for the resin pellets 62 is preferably at least one of a thermoplastic resin and a thermosetting resin.

[0171] As the thermoplastic resin, for example, one or more selected from polyolefins such as polypropylene (PP) and polyethylene (PE), polyester resins such as aliphatic polyester resins and aromatic polyester resins, polyacrylic resins such as polystyrene, methacrylate, and acrylate, polyamide resins, polycarbonate resins, polyacetal resins, etc. can be used.

[0172] However, it is preferable to use at least one of polyolefin and polyester resin. Furthermore, it is preferable to use polypropylene as the polyolefin. Furthermore, as the polyester resin, examples of aliphatic polyester resins include polylactic acid and polycaprolactone, and examples of aromatic polyester resins include polyethylene terephthalate. However, it is preferable to use a biodegradable polyester resin (also simply referred to as a "biodegradable resin").

[0173] As the biodegradable resin, for example, one or more selected from hydroxycarboxylic acid-based aliphatic polyesters, caprolactone-based aliphatic polyesters, dibasic acid polyesters, and the like can be used.

[0174] The hydroxycarboxylic acid-based aliphatic polyester can be one or more selected from homopolymers of hydroxycarboxylic acids such as lactic acid, malic acid, glucose acid, 3-hydroxybutyric acid, etc., and copolymers using at least one of these hydroxycarboxylic acids. However, it is preferable to use polylactic acid, copolymers of lactic acid and the above hydroxycarboxylic acids other than lactic acid, polycaprolactone, and copolymers of caprolactone with at least one of the above hydroxycarboxylic acids, and it is particularly preferable to use polylactic acid.

[0175] As the lactic acid, for example, L-lactic acid, D-lactic acid, etc. can be used, and these lactic acids may be used alone or in combination of two or more.

[0176] As the caprolactone-based aliphatic polyester, for example, one or more selected from homopolymers of polycaprolactone and copolymers of polycaprolactone or the like with the above-mentioned hydroxycarboxylic acids can be used.

[0177] As the dibasic acid polyester, for example, one or more selected from polybutylene succinate, polyethylene succinate, polybutylene adipate, etc. can be used.

[0178] The biodegradable resins may be used alone or in combination of two or more.

[0179] Examples of thermosetting resins that can be used include phenolic resins, urea resins, melamine resins, furan resins, unsaturated polyesters, diallyl phthalate resins, vinyl ester resins, epoxy resins, urethane resins, silicone resins, thermosetting polyimide resins, etc. These resins can be used alone or in combination of two or more.

[0180] The resin pellets 62 may contain an inorganic filler, preferably in a proportion that does not interfere with thermal recycling.

[0181] Examples of inorganic fillers include simple substances, oxides, hydroxides, carbonates, sulfates, silicates, sulfites of metal elements in Groups I to VIII of the periodic table, such as Fe, Na, K, Cu, Mg, Ca, Zn, Ba, Al, Ti, and silicon, as well as various clay minerals composed of compounds of these elements.

[0182] Specific examples include barium sulfate, calcium sulfate, magnesium sulfate, sodium sulfate, calcium sulfite, zinc oxide, silica, heavy calcium carbonate, light calcium carbonate, aluminum borate, alumina, iron oxide, calcium titanate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, sodium hydroxide, magnesium carbonate, calcium silicate, clay wollastonite, glass beads, glass powder, silica sand, silica stone, quartz powder, diatomaceous earth, white carbon, and glass fiber. A plurality of these inorganic fillers may be contained. Also, those contained in recycled paper pulp may be used.

[0183] The blending ratio of resin pellets 62 to microfibrous cellulose is preferably 0 to 50, more preferably 0 to 20, and even more preferably 0 to 10, parts by mass of resin pellets 62 per part by mass of microfibrous cellulose. When the blending ratio is within the above range, the strength of the resin composition, particularly the bending strength and tensile modulus, can be significantly improved.

[0184] Solubility parameters of microfibrous cellulose and resin (cal / cm ３ ) １／２ The difference in SP value is the SP of microfibrous cellulose. ＭＦＣ Value, resin SP ＰＯＬ value, the difference in SP value = SP ＭＦＣ Value - SP ＰＯＬ The difference in SP value is preferably 0.1 to 10.0, more preferably 0.5 to 8.0, and particularly preferably 1.0 to 5.0. If the difference in SP value is within the above range, the microfibrous cellulose does not dissolve in the resin during the kneading treatment, but is dispersed throughout the resin, resulting in a cellulose composite resin in which the decrease in strength properties is suppressed. In particular, the SP of the resin (solvent) ＰＯＬ value and SP of microfibrous cellulose (solute) ＭＦＣ The smaller the difference in values, the greater the reinforcing effect.

[0185] The solubility parameter (cal / cm ３ ) １／２The SP value is a measure of the intermolecular force acting between a solvent and a solute, and the closer the SP values ​​of the solvent and solute are, the greater the solubility.

[0186] (Pelletizing Step) The microfiber cellulose composite resin discharged in the kneading step s60 is processed into pellets in the pelletizing step s70 as required, and sent to the packaging step s80, where it is packaged to become a final product 81.

[0187] (Cellulose composite resin) The darts 3 contained in the cellulose composite resin of this embodiment preferably have a diameter of 0.1 to 5 mm, more preferably 0.2 to 4 mm. The number of darts 3 is preferably 5 to 1000 per 9 cm. ２ , more preferably 7 to 800 pieces / 9 cm ２ The dirt area is preferably 10 to 100,000 mm ２ / m ２ , more preferably 20 to 80,000 mm ２ / m ２ If the number of dirt particles and the area of ​​the dirt particles are within the above ranges, the cellulose composite resin will have a dark-colored dirt 3, i.e., a form in which aggregates of microfibrous cellulose are scattered in a pale-colored composite resin containing microfibrous cellulose and resin (for example, a form with a shading like a night sky with stars), and the resin will have an overall design quality, particularly a stone-like color tone.

[0188] As explained above, the number of dirt particles 3 can be adjusted by changing the processing conditions of the dehydration step s20, the drying step s40, and the compression step s50. However, when producing a cellulose composite resin with a small number of dirt particles 3, the dried powder obtained in the drying step s40 can be supplied to the kneading step s60 without the compression step s50. The size of the dirt particles 3 can be adjusted by the degree of dehydration in the dehydration step s20, the method and degree of drying in the drying step s40, the shape of the composite granules in the compression step s50, the compression pressure, the temperature, etc. The number, diameter, and area of ​​the dirt particles 3 can also be adjusted by changing the mass ratio of the resin to the microfibrous cellulose.

[0189] The number of dirt particles and the dirt area in the cellulose composite resin are values ​​measured in accordance with JIS-P8145:2011 "Paper and paperboard - Evaluation method for foreign matter" (threshold value 150), with the foreign matter in this test method being dirt 3.

[0190] The cellulose composite resin of this embodiment has a mass ratio of resin to microfibrous cellulose of 99:1 to 50:50, preferably 98:2 to 55:45, and more preferably 97:3 to 60:40. When the mass ratio is within this range, the deterioration of the strength properties of the resin is suppressed, the size and number of the darts 3 fall within appropriate ranges, the stone-like color tone is visible, and the design is excellent.

[0191] (White pigment) The cellulose composite resin of this embodiment is formed by adding dirt 3 to a base made of a cellulose composite resin containing a resin and microfibrous cellulose, giving it a stone-like color tone, but a white pigment may also be added to the base. By adding a white pigment, the cellulose composite resin has the color of the white pigment, further enhancing the design. A cellulose composite resin that does not contain a white pigment in the first place will have an amber color, which is the color of the microfibrous cellulose itself. The degree of amber color can be adjusted to a lighter or darker color depending on the concentration of the microfibrous cellulose. If the color of the resin itself is transparent, the lower the concentration of microfibrous cellulose contained in the cellulose composite resin, the closer the cellulose composite resin will be to a transparent color.

[0192] In the production of cellulose composite resins, the white pigment primarily functions to impart color to the cellulose composite resin and secondarily to inhibit the aggregation of microfibrous cellulose. The color-imparting function is as described above, and the aggregation-inhibiting function is as follows.

[0193] In microfibrous cellulose, the cellulose molecules forming the microfibrous cellulose may irreversibly aggregate due to hydrogen bonding. When the microfibrous cellulose is mixed with a white pigment, the presence of the white pigment between the cellulose molecules in the microfibrous cellulose physically inhibits the hydrogen bonding, suppressing the aggregation of the microfibrous cellulose. In other words, the microfibrous cellulose becomes more easily dispersed. Considering this effect, by changing the mass ratio of the microfibrous cellulose to the white pigment, it is possible to promote the aggregation of the microfibrous cellulose or, conversely, promote its dispersion.

[0194] On the other hand, the use of a white pigment makes it easy to composite it with a matrix such as a resin. Furthermore, since white pigments are general-purpose inorganic materials, they have the advantage of being less subject to limitations on their application. Furthermore, the size and shape of the white pigment can be selected and prepared according to the application. Therefore, by preparing a white pigment according to the size and shape of the resin powder or microfibrous cellulose, it is possible to adjust the size and shape so that the white pigment penetrates into the gaps in the microfibrous cellulose and more easily exerts the effect of suppressing aggregation. Therefore, when a white pigment is contained in a cellulose composite resin, the dispersibility of the microfibrous cellulose is improved, and as a result, the strength of the cellulose composite resin is improved more than that of the resin itself.

[0195] The white pigment may be added at any stage during the cellulose composite resin production process. Adding it during the mixing step s10, for example, is preferable because it is well mixed with the microfibrous cellulose and resin powder, resulting in a uniformly dispersed mixture. Alternatively, it may be added during the compression step s50. The compression step s50 allows for adjustment of the size and number of dirt particles 3, so adding the white pigment to the compression means 51 along with the sample makes it easier to adjust the size and number of dirt particles 3. Meanwhile, in the kneading step s60, the resin is melted, so adding the white pigment allows for the production of a cellulose composite resin with reduced color unevenness. A color masterbatch composed of a white pigment and a resin can also be used as a method for adding the white pigment.

[0196] Examples of white pigments that can be used include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, satin white, etc. In particular, a cellulose composite resin obtained by mixing titanium dioxide has a color tone and color that combines the white color derived from titanium dioxide with the amber color derived from microfibrous cellulose.

[0197] The amount of white pigment per part by mass of microfibrous cellulose is preferably 30 parts by mass or less, more preferably 0.05 to 20 parts by mass, and even more preferably 0.1 to 10 parts by mass. When the ratio of white pigment per part by mass of microfibrous cellulose is within the above range, the dirt 3 scattered in the cellulose composite resin can be easily seen, the stone-like color tone stands out, and the design is excellent.

[0198] The average particle size of the white pigment is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, and particularly preferably 0.1 to 1 μm. If the average particle size of the white pigment is within the above range, the white pigment is dispersed uniformly in the cellulose composite resin, and color unevenness is unlikely to occur, which is preferable.

[0199] In this specification, the average particle size of the white pigment is a median diameter calculated from a volume-based particle size distribution measured using a particle size distribution measuring device (for example, a laser diffraction / scattering particle size distribution measuring device manufactured by Horiba, Ltd.) on the white pigment powder as is or in the form of a water dispersion.

[0200] (Flexural Modulus) In the cellulose composite resin of this embodiment, the ratio of the flexural modulus of the cellulose composite resin to the flexural modulus of the resin itself (the ratio calculated by Formula 1) is preferably 1.1 to 3.0, more preferably 1.15 to 2.5, and even more preferably 1.2 to 2.0. Cellulose composite resins with a flexural modulus ratio within the above range are preferred because they maintain flexibility compared to the flexural modulus of conventional resins themselves. Here, "resin itself" refers to a resin that does not contain impurities such as cellulose. (Flexural Modulus Ratio) = (Flexural Modulus of Cellulose Composite Resin) / (Flexural Modulus of Resin itself) Formula 1

[0201] The flexural modulus is a value measured in accordance with JIS-K-7171:2022.

[0202] (Bending strength) In the cellulose composite resin of this embodiment, the ratio of the bending strength of the cellulose composite resin to the bending strength of the resin itself (the ratio calculated by Formula 2) is preferably 1.05 to 2.0, more preferably 1.06 to 1.9, and even more preferably 1.08 to 1.8. A cellulose composite resin having a bending strength ratio within the above range is preferable because it is less susceptible to breakage compared to the bending strength of conventional resins themselves. (Bending strength ratio) = (Bending strength of cellulose composite resin) / (Bending strength of resin itself) Formula 2

[0203] The bending strength is a value measured in accordance with JIS-K-7171:2022.

[0204] (Charpy impact strength) The cellulose composite resin of the present embodiment preferably has a Charpy impact strength of 0.5 to 30 kJ / m ２ , more preferably 0.8 to 25 kJ / m ２ , more preferably 1.0 to 20 kJ / m ２ A cellulose composite resin having a Charpy impact strength within the above range is preferable because it is not significantly inferior in impact resistance compared to the Charpy impact strength of conventional resins themselves.

[0205] The Charpy impact strength is a value measured in accordance with JIS-K-7111:2012.

[0206] (Deflection temperature under load) The cellulose composite resin of the present embodiment preferably has a deflection temperature under load of 60 to 200° C., more preferably 70 to 190° C., and even more preferably 80 to 180° C. A cellulose composite resin having a deflection temperature under load within the above range is preferred because it has excellent heat resistance and elasticity at high temperatures.

[0207] The deflection temperature under load is a value measured in accordance with JIS-K-7210-1:2014 under a load of 0.45 MPa.

[0208] (Melt Flow Rate (MFR)) The cellulose composite resin of the present embodiment preferably has a melt flow rate of 0.1 to 200 g / 10 min, more preferably 0.2 to 175 g / 10 min, and even more preferably 0.3 to 150 g / 10 min. A cellulose composite resin having a melt flow rate within the above range is preferred because it has excellent fluidity and can be easily processed into a wide variety of molded products.

[0209] The melt flow rate (MFR) is a value measured in accordance with JIS-K-7210-1:2014, under conditions of 190°C and a load of 2.16 kg, by measuring the weight of a sample that flows out in 10 minutes.

[0210] The cellulose composite resin of the present embodiment can be molded into a desired shape after being kneaded again as necessary. The size, thickness, shape, etc. of the molded product are not particularly limited, and may be, for example, a sheet, pellet, powder, fiber, etc.

[0211] The temperature during the molding process is equal to or higher than the glass transition point of the resin, and varies depending on the type of resin, but is, for example, 90 to 260°C, preferably 100 to 240°C.

[0212] The kneaded material can be molded by, for example, mold molding, injection molding, extrusion molding, blow molding, foam molding, etc. Alternatively, the kneaded material can be spun into fibers and mixed with the above-mentioned plant materials to form a mat or board. The mixing can be performed by, for example, simultaneous deposition by air laying.

[0213] As the apparatus for molding the kneaded product, for example, one or more selected from an injection molding machine, a blow molding machine, a hollow molding machine, a blow molding machine, a compression molding machine, an extrusion molding machine, a vacuum molding machine, a pressure molding machine, etc. can be used.

[0214] The above molding can be carried out following kneading, or the kneaded mixture can be cooled, crushed into chips using a crusher or the like, and the chips can then be fed into a molding machine such as an extrusion molding machine or an injection molding machine. Of course, molding is not an essential requirement of the present invention.

[0215] (Other Compositions) The microfibrous cellulose may contain cellulose nanofibers together with the microfibrous cellulose. The cellulose nanofibers play a role in complementing the microfibrous cellulose in improving the strength of the resin. However, it is preferable to use only microfibrous cellulose without including cellulose nanofibers. The average fiber width of the cellulose nanofibers (average fiber width; average diameter of a single fiber) is preferably 4 to 100 nm, more preferably 10 to 80 nm.

[0216] The cellulose composite resin may contain, in addition to cellulose nanofibers, fibers derived from plant materials obtained from various plants such as kenaf, jute, Manila hemp, sisal, gampi, mitsumata, kozo, banana, pineapple, coconut, corn, sugarcane, bagasse, palm, papyrus, reed, esparto, sabaigrass, wheat, rice, bamboo, various conifers (such as cedar and cypress), broad-leaved trees, and cotton.

[0217] One or more selected from, for example, antistatic agents, flame retardants, antibacterial agents, colorants, radical scavengers, foaming agents, etc. can be added to the cellulose composite resin within a range that does not impair the effects of the present invention. These raw materials may be added to the microfibrous cellulose dispersion 1 in the mixing step s10, or may be added to the materials supplied in the compression step s50 or kneading step s60, or may be added by other methods. However, from the standpoint of production efficiency, it is preferable to add them to the microfibrous cellulose dispersion 1.

[0218] The cellulose composite resin may contain an ethylene-α-olefin copolymer elastomer or a styrene-butadiene block copolymer as a rubber component. Examples of α-olefins include butene, isobutene, pentene, hexene, methylpentene, octene, decene, and dodecene.

[0219] The cellulose composite resin of the present embodiment has excellent design characteristics not found in conventional resins and can be used in a variety of applications. Examples of applications include agricultural materials, piping, everyday items such as toothbrushes, shoe soles, glasses, binoculars, toys, masks, and hoses, films, sheets, synthetic paper, filters, cosmetics such as powders, puffs, containers, and wax, building materials such as flooring and architectural films, liquid crystal materials, organic EL materials, organic semiconductor materials, electronic materials, electronic devices, communication equipment, aircraft parts, machine parts, electronic components, electronic substrates, packaging materials, robot parts, optical components, road materials such as asphalt, guardrails, poles, and signs, exterior parts for electrical equipment, exterior parts for office automation equipment, and sealants.

[0220] (Definitions, Measurement Methods, etc.) (Average Fiber Width) The average fiber width of fine fibers (microfibrous cellulose and cellulose nanofibers) is measured as follows. First, 100 ml of an aqueous dispersion of fine fibers with a solid content of 0.01 to 0.1% by mass is filtered through a Teflon (registered trademark) membrane filter, and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. Next, the sample is freeze-dried and osmium-coated to obtain a sample. This sample is observed using an electron microscope SEM image at a magnification of 3,000 to 30,000 times depending on the width of the constituent fibers. Specifically, two diagonal lines are drawn on the observed image, and three straight lines passing through the intersections of the diagonal lines are arbitrarily drawn. Furthermore, the widths of a total of 100 fibers intersecting with these three straight lines are measured visually. The median diameter of the measured value is then taken as the average fiber width.

[0221] (Aspect Ratio) The aspect ratio is the value obtained by dividing the average fiber length by the average fiber width. The larger the aspect ratio, the more points at which snagging occurs, resulting in a greater reinforcing effect. However, on the other hand, the increased number of snagging points is thought to reduce the ductility of the resin.

[0222] (Water Retention) The water retention is a value measured in accordance with JAPAN TAPPI No. 26 (2000).

[0223] (Fiber Analysis) The fine ratio, fibrillation ratio, average fiber length, etc. are values ​​measured using a fiber analyzer "FS5" manufactured by Valmet.

[0224] (Crystallization degree) The crystallinity degree is a value measured in accordance with JIS K 0131 (1996).

[0225] (Viscosity) The pulp viscosity is a value measured in accordance with TAPPI T230.

[0226] (Freeness) The freeness is a value measured in accordance with JIS P8121-2 (2012).

[0227] In the examples, composite granules and cellulose composite resins were produced using resin and pulp as raw materials, and evaluation tests were carried out. The results are shown in Table 1.

[0228] <Production of Test Examples, etc.> The production procedures for the test examples were as follows. Procedure (1) A predetermined sizing agent was added to the pulp slurry, and paper was made in the wire part to achieve a predetermined Cobb sizing degree, and then the paper was passed through the press part and pre-dryer part to obtain a paper base material with a predetermined basis weight. The pulp used was a mixture of bleached hardwood kraft pulp and bleached softwood kraft pulp.

[0229] Step (2) Next, the obtained paper substrate was impregnated and coated with an aqueous urea solution of a predetermined concentration in the coater part, and then dried in the after-dryer part to obtain urea-coated paper.

[0230] Step (3) The obtained urea-coated paper was reacted in a roll-to-roll reactor at a predetermined temperature for a predetermined residence time to obtain carbamate-modified paper.

[0231] Step (4): The resulting carbamate-modified paper was then diluted with water to a solids concentration of 5% using a disintegrator and disintegrated. The disintegrating solution was dehydrated and washed twice to obtain washed carbamate-modified pulp. The carbamate-modified pulp was beaten in a refiner to obtain carbamate-modified microfibrous cellulose with a Fine A ratio of 40% or more. The average fiber length of the carbamate-modified microfibrous cellulose was 0.5 mm.

[0232] Step (5) 15 g of maleic anhydride-modified polypropylene (MAPP) powder was added as a compatibilizer to 1000 g of a carbamate-modified microfibrous cellulose aqueous dispersion adjusted to a solids concentration of 3.0% by mass, and the mixture was stirred, dehydrated, and dried to obtain a dry powder containing MAPP powder and microfibrous cellulose. The maleic anhydride-modified polypropylene powder was either "MG400W" (average particle diameter: about 500 μm) manufactured by Riken Vitamin Co., Ltd., "Admer AT2606" (average particle diameter: about 700 μm) manufactured by Mitsui Chemicals, Inc., or "Modic P928" (average particle diameter: about 500 μm) manufactured by Mitsubishi Chemical Corporation.

[0233] Procedure (6) The obtained dry powder material was divided into two types: one that was compressed and one that was not. The procedure for the compressed material was as follows. The dry powder material was compressed using a compressor (TS-55, manufactured by Tosa Tech Co., Ltd.) to obtain a composite granule containing resin powder and microfibrous cellulose. The composite granule was an approximately cylindrical pellet with a diameter of 3 to 5 mm and a height of 3 to 5 mm.

[0234] Procedure (7) The material compressed in the above procedure (6) was melt-kneaded using a φ15 mm twin-screw extruder at 160 ° C. to 180 ° C. and 75 rpm, resulting in a high-concentration cellulose composite resin with a mass ratio of resin to microfibrous cellulose of 33.3:66.7 based on solids. The obtained high-concentration cellulose composite resin was again fed to a φ15 mm twin-screw extruder together with resin pellets (PP-1 or PP-2) and melt-kneaded at 160 ° C. to 180 ° C. and 200 rpm to obtain a cellulose composite resin with a cellulose concentration of 10%. The mixed resin pellets were commercially available polypropylene homopolymers (PP-1) or block polymers (PP-2). The obtained cellulose composite resin was cut into cylindrical shapes with a diameter of 2 mm and a height of 2 mm using a pelletizer. The same melt-kneading was performed on the material that was not compressed in procedure (6), and the obtained cellulose composite resin was similarly cut into cylindrical shapes.

[0235] Step (8): 1 g of the cut cellulose composite resin was weighed out and pressed in a press at 180°C to form a circular sheet approximately 9 cm in diameter, yielding Test Examples 1 to 7 and Comparative Example 3. The resulting Test Examples 1 to 7 are shown in Figures 2 and 3. The following measurements were performed on these Test Examples. Measurement of dirt 3 was performed in accordance with JIS-P8145:2011 "Paper and paperboard - Evaluation method for foreign matter" (threshold value 150), and the number of dirt particles and the dirt area were measured. Note that the blackened areas in the figure were not included in the calculations for measuring the number of dirt particles and the dirt area.

[0236] In the above series of procedures, the test examples are produced by modifying the microfibrous cellulose to form carbamates, but the test examples can also be produced without the modification treatment. In this case, the test examples can be produced by the following procedure.

[0237] Step (1)' The prepared pulp is beaten in a refiner to obtain unmodified microfibrous cellulose having a Fine A ratio of 40% or more. The average fiber length of the microfibrous cellulose is 0.5 mm.

[0238] Step (2)' The obtained microfibrous cellulose is subjected to the same steps as steps (5) to (8) above to form a circular sheet.

[0239] Comparative Example 1 was produced by the following procedure. Commercially available polypropylene resin pellets (PP-1) were pressed in a press at 180°C and processed into a circular sheet with a diameter of approximately 9 cm to obtain Comparative Example 1. Comparative Example 4 was also produced by the same procedure as Comparative Example 1, except that the prepared resin was changed.

[0240] Comparative Example 2 was produced by the following procedure. 15 g of propylene powder obtained by pulverizing polypropylene resin pellets (PP-1) was added to 1000 g of an unmodified microfibrous cellulose aqueous dispersion adjusted to a solids concentration of 3.0% by mass, in terms of bone dry weight, and after stirring, a drying treatment was performed to obtain a dry powder containing propylene powder and microfibrous cellulose. The drying treatment was an oven drying treatment at a temperature of 105 ° C for 120 minutes or more. Comparative Example 3 was also produced by the same procedure as Comparative Example 2, except that the carbamate-modified microfibrous cellulose of the above test example was used instead of the unmodified microfibrous cellulose used in Comparative Example 2.

[0241] The unmodified microfibrous cellulose refers to microfibrous cellulose produced without subjecting raw material pulp to chemical modification treatment such as carbamate conversion.

[0242] The dried powder obtained above was melt-kneaded using a φ15 mm twin-screw extruder at 160 ° C to 180 ° C and 75 rpm, and a high-concentration cellulose composite resin was obtained in which the mass ratio of resin to microfibrous cellulose was 33.3:66.7 based on the solid content. The obtained high-concentration cellulose composite resin was again fed to a φ15 mm twin-screw extruder together with resin pellets (PP-1), and melt-kneaded at 160 ° C to 180 ° C and 200 rpm to obtain a cellulose composite resin with a cellulose concentration of 10%. The obtained cellulose composite resin was cut into a cylindrical shape with a diameter of 2 mm and a height of 2 mm using a pelleter.

[0243] 1 g of the cut cellulose composite resin was weighed out and pressed in a press at 180° C. to form a circular sheet having a diameter of about 9 cm, to obtain Comparative Example 2.

[0244] <Evaluation Test 1> For the test examples produced by the above procedure, the number of darts, dart area, flexural modulus, flexural strength, Charpy impact strength, deflection temperature under load, and MFR were measured. The results are shown in Table 1.

[0245]

[0246] The present invention can be used as a cellulose composite resin.

[0247] REFERENCE SIGNS LIST 1 Microfibrous cellulose dispersion 2 Resin powder 3 Dirt 11 Mixer 12 Mixer 21 Dehydration means 31 Pulverization means 41 Drying means 51 Compression means 61 Kneader 62 Resin pellets 81 Final product s10 Mixing process s20 Dehydration process s30 Pulverization process s40 Drying process s50 Compression process s60 Kneading process s70 Pelletization process s80 Packaging process

Claims

1. A cellulose composite resin in which resin and microfibrous cellulose with an average fiber length of 0.05 to 0.5 mm are combined, and the darts are composed of aggregates of microfibrous cellulose, and the number of darts is 5 to 1,000 per 9 cm. ２ , and the dirt area ratio is 10 to 100,000 mm ２ / m ２ A cellulose composite resin characterized by:

2. The cellulose composite resin according to claim 1, which has a stone-like color tone.

3. The cellulose composite resin according to claim 1, which comprises modified microfibrous cellulose in which all or part of the hydroxyl groups of the cellulose have been substituted with carbamate groups.

4. The cellulose composite resin according to claim 1, comprising modified microfibrous cellulose in which all or part of the hydroxyl groups of cellulose are substituted with carbamate groups, and the substitution rate of the carbamate groups in the modified microfibrous cellulose is 0.5 mmol / g or more and 2.0 mmol / g or less.

5. The cellulose composite resin according to claim 1, wherein the resin is a polyolefin resin.

6. The cellulose composite resin according to claim 1, wherein the resin is an organic acid anhydride-modified polyolefin resin.

7. The cellulose composite resin according to claim 1, wherein the ratio of the flexural strength of the cellulose composite resin to the flexural strength of the resin itself is 1.05 to 2.

0.

8. The cellulose composite resin according to claim 1, wherein the mass ratio of the resin to the microfibrous cellulose is 99:1 to 50:

50.

9. The cellulose composite resin according to claim 1, further comprising a white pigment.

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