Fibrous cellulose composite resin and method for producing fibrous cellulose

Abstract

To provide a fibrous cellulose having high reinforcing effect of a resin, a fibrous cellulose composite resin having high intensity, and a method for producing the fibrous cellulose having the high reinforcing effect of the resin.SOLUTION: A fibrous cellulose has an average fiber width of 0.1 μm or more, has some or all of hydroxyl groups substituted with carbamate groups, has a carbamate group substitution rate of 1.0 mmol / g or more, and has a fine rate of 10% or more and 35% or less. The fibrous cellulose composite resin comprises fibrous cellulose and a resin, the fibrous cellulose being the aforementioned fibrous cellulose. Moreover, when producing the fibrous cellulose, a cellulose raw material and urea or the like are heat-treated and some or all of the hydroxyl groups in the cellulose raw material are substituted by the carbamate groups, the fibers are separated until the average fiber width is 0.1 μm or more, the heat treatment is performed such that the carbamate group substitution rate reaches 1.0 mmol / g or more, and the fibers are separated until the fine rate is 10% or more and 35% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention Fibrous cellulose composite resin This also relates to a method for producing fibrous cellulose. [Background technology]

[0002] In recent years, fine fibers such as cellulose nanofibers and microfiber cellulose (microfibrillated cellulose) have attracted attention for their use as reinforcing materials for resins. However, since fine fibers are hydrophilic while resins are hydrophobic, there has been a problem with the dispersibility of the fine fibers when using them as reinforcing materials for resins. Therefore, the present inventors proposed substituting the hydroxyl groups of the fine fibers with carbamate groups (see Patent Document 1). According to this proposal, the dispersibility of the fine fibers is improved, thereby improving the reinforcing effect of the resin. However, even now, further improvements in the reinforcing effect are desired, and various research is continuing. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-1876 [Overview of the project] [Problems that the invention aims to solve]

[0004] The main problem that the invention aims to solve is , strength High-quality fibrous cellulose composite resin, and Fibrous cellulose composite resin The objective is to provide a method for manufacturing [the product]. [Means for solving the problem]

[0005] In conventional development, such as the development described in the above-mentioned patent document, the focus was on modifying the microfibers, and among the numerous modification methods such as esterification, etherification, amidation, and sulfidation, it was found that the introduction of carbamate groups (carbamation) was superior. In contrast, the present invention does not focus on the introduction of carbamate groups, but rather, through numerous tests based on the premise of introducing carbamate groups, it was discovered that the above problem could be solved by pursuing the physical properties of the microfibers, and thus the invention was conceived. More specifically, the causes of insufficient reinforcement effect of the resin were examined in detail, and it was first discovered that one of the factors was the non-uniformity of the microfibers. However, it was also discovered that if the uniformity of the microfibers is increased too much, the fluidity of the composite resin formed by kneading the microfibers and resin decreases, and this decrease in fluidity leads to a decrease in the homogeneity of the composite resin, resulting in insufficient reinforcement effect. The means conceived through these findings are described below.

[0006] ( First aspect ) The average fiber width is 0.1 μm or more, and some or all of the hydroxyl groups are substituted with carbamate groups represented by the "-CO-NH2" group. The substitution rate of the carbamate group is 1.0 mmol / g or more. The fine rate is 10% or more and 35% or less. The average fiber length is 1.0 to 1.68 mm. A fibrous cellulose characterized by the following features.

[0007] ( Second aspect ) The fine content of the cellulose raw material is 1% or more. First aspect Fibrous cellulose as described above.

[0008] ( Third aspect ) The cellulose raw material is either untreated with enzymes, or the amount of enzymes added is limited to 2% by mass or less of the cellulose raw material. Second aspect Fibrous cellulose as described above.

[0009] ( Fourth aspect ) The pulp viscosity is 4 cps or more, The fibrous cellulose according to any one of Aspects 1 to 3.

[0010] ( Fifth aspect ) Containing fibrous cellulose and a resin, The fibrous cellulose is The average fiber width is 0.1 μm or more, and part or all of the hydroxyl groups are substituted with carbamate groups represented by "-CO-NH2" groups, The substitution rate of the carbamate group is 1.0 mmol / g or more, The fines rate is 10% or more and 35% or less, The average fiber length is 1.0 to 1.68 mm, A fibrous cellulose composite resin characterized by this.

[0011] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​[Effects of the Invention]

[0013] According to the present invention, strength High-quality fibrous cellulose composite resin, and Fibrous cellulose composite resin This will be the manufacturing method. [Modes for carrying out the invention]

[0014] Next, embodiments for carrying out the invention will be described. Note that this embodiment is just one example of the present invention. The scope of the present invention is not limited to this embodiment.

[0015] The fibrous cellulose in this form (hereinafter also referred to as "cellulose fiber") has an average fiber width (diameter) of 0.1 μm or more, and some or all of its hydroxyl groups (-OH groups) are substituted with carbamate groups. In addition, the carbamate group substitution rate is 1.0 mmol / g or more, and the fineness rate is 10% or more and 35% or less. Furthermore, a fibrous cellulose composite resin is formed by including this fibrous cellulose and a resin. Moreover, the method for producing fibrous cellulose includes a step of heat-treating at least one of the cellulose raw material and urea and a urea derivative to substitute some or all of the hydroxyl groups of the cellulose raw material with carbamate groups, and a step of defibrating the cellulose raw material to a range in which the average fiber width is 0.1 μm or more to produce microfiber cellulose. The heat treatment is carried out so that the carbamate group substitution rate is 1.0 mmol / g or more, and the defibration is carried out so that the fineness rate is 10% or more and 35% or less. A detailed explanation follows below.

[0016] (fibrous cellulose) The fibrous cellulose composite resin in this embodiment comprises fibrous cellulose (hereinafter also referred to as "cellulose fibers"), a resin, and preferably an acid-modified resin. When an acid-modified resin is included, some or all of the carbamate groups are ionically bonded to the acid groups of the acid-modified resin.

[0017] In this embodiment, the fibrous cellulose, which is a fine fiber, is microfibrillated cellulose (microfiber cellulose) with an average fiber diameter of 0.1 μm or more. Using microfibrillated cellulose significantly improves the reinforcing effect of the resin. Furthermore, microfibrillated cellulose is easier to modify with carbamate groups (carbamate) than cellulose nanofibers, which are also fine fibers. However, it is more preferable to carbamate the cellulose raw material before micronization, in which case microfibrillated cellulose and cellulose nanofibers are equivalent.

[0018] In this embodiment, microfiber cellulose refers to fibers with a wider average fiber width than cellulose nanofibers. Specifically, the average fiber diameter is, for example, 0.1 to 20 μm, preferably 0.2 to 19 μm, and more preferably greater than 0.5 to 18 μm. If the average fiber diameter of microfiber cellulose falls below 0.1 μm, it becomes indistinguishable from cellulose nanofibers, and the effect of improving the strength (especially the flexural modulus) of the resin may not be sufficiently obtained. In addition, the defibration time becomes longer, requiring a large amount of energy. Furthermore, the dewatering ability of the cellulose fiber slurry deteriorates. If the dewatering ability deteriorates, a large amount of energy is required for drying, and if a large amount of energy is applied to drying, the microfiber cellulose may degrade due to heat, potentially reducing its strength. On the other hand, if the average fiber diameter of microfiber cellulose exceeds 20 μm, it becomes indistinguishable from pulp, and the reinforcing effect may not be sufficient.

[0019] Microfiber cellulose can be obtained by defibrating (finely reducing) cellulose raw material (hereinafter also referred to as "raw material pulp"). As raw material pulp, one or more types can be selected and used from among wood pulp made from hardwoods, softwoods, etc., non-wood pulp made from straw, bagasse, cotton, hemp, pulp fibers, etc., recycled paper pulp (DIP) made from recycled waste paper, waste paper, etc., etc. The above raw materials may also be in the form of crushed material (powdered material), such as cellulose powder.

[0020] However, in order to avoid the inclusion of impurities as much as possible, it is preferable to use wood pulp as the raw material pulp. As for wood pulp, one or more types can be selected and used from chemical pulps such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), and mechanical pulp (TMP), etc.

[0021] Hardwood kraft pulp may be bleached hardwood kraft pulp, unbleached hardwood kraft pulp, or semi-bleached hardwood kraft pulp. Similarly, softwood kraft pulp may be bleached softwood kraft pulp, unbleached softwood kraft pulp, or semi-bleached softwood kraft pulp.

[0022] As mechanical pulp, one or more types can be selected and used from, for example, stone gland pulp (SGP), pressure stone gland pulp (PGW), refiner gland pulp (RGP), chemigland pulp (CGP), thermo gland pulp (TGP), gland pulp (GP), thermomechanical pulp (TMP), chemothermetic pulp (CTMP), refiner mechanical pulp (RMP), bleached thermomechanical pulp (BTMP), etc.

[0023] The raw pulp can be pretreated by chemical methods prior to defibration. Examples of chemical pretreatments include hydrolysis of polysaccharides with acid (acid treatment), hydrolysis of polysaccharides with enzymes (enzyme treatment), swelling of polysaccharides with alkali (alkali treatment), oxidation of polysaccharides with an oxidizing agent (oxidation treatment), and reduction of polysaccharides with a reducing agent (reduction treatment). However, as a chemical pretreatment, enzymatic treatment is preferred, and it is even more preferable to apply one or more treatments selected from acid treatment, alkali treatment, and oxidation treatment. Enzyme treatment will be described in detail below.

[0024] For enzymatic treatment, it is preferable to use at least one of cellulase-type enzymes and hemicellulase-type enzymes, and more preferably both in combination. Using these enzymes makes defibration of cellulose raw materials easier. Cellulase-type enzymes induce the decomposition of cellulose in the presence of water. Hemicellulase-type enzymes induce the decomposition of hemicellulose in the presence of water.

[0025] Examples of cellulase enzymes that can be used include those produced by genera such as 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 cellulocine T2 (manufactured by HPI Corporation), Meicerase (manufactured by Meiji Seika Co., Ltd.), Novozyme 188 (manufactured by Novozyme Inc.), Multifect CX10L (manufactured by Genencor Inc.), and cellulase enzyme GC220 (manufactured by Genencor Inc.).

[0026] Furthermore, either EG (endoglucanase) or CBH (cellobiohydrolase) can be used as the cellulase enzyme. EG and CBH may be used individually or in combination. They may also be used in combination with hemicellulase enzymes.

[0027] Examples of hemicellulase enzymes that can be used include xylanase, which breaks down xylan; mannase, which breaks down mannan; and arabanase, which breaks down araban. Pectinase, which breaks down pectin, can also be used.

[0028] Hemicellulose is a polysaccharide that is obtained by removing pectins from between cellulose microfibrils in plant cell walls. Hemicellulose is diverse and varies depending on the type of wood and the layer of the cell wall. In the secondary wall of coniferous trees, glucomannan is the main component, while in the secondary wall of hardwoods, 4-O-methylglucuronoxylan is the main component. Therefore, when obtaining fine fibers from bleached coniferous kraft pulp (NBKP), it is preferable to use mannase. Similarly, when obtaining fine fibers from bleached hardwood kraft pulp (LBKP), it is preferable to use xylanase.

[0029] The amount of enzyme added to the cellulose raw material is determined by factors such as the type of enzyme, the type of wood used as the raw material (coniferous or hardwood), and the type of mechanical pulp. However, the amount of enzyme added to the cellulose raw material is preferably 0.1 to 3% by mass, more preferably 0.3 to 2.5% by mass, and particularly preferably 0.5 to 2% by mass. If the amount of enzyme added is less than 0.1% by mass, the effect of the enzyme addition may not be sufficiently obtained. On the other hand, if the amount of enzyme added exceeds 3% by mass, the cellulose may be saccharified, and the yield of fine fibers may decrease. There is also the problem that the improvement in effect may not be commensurate with the increase in the amount of enzyme added.

[0030] When using a cellulase-type enzyme, the pH during enzyme treatment is preferably in the weakly acidic range (pH=3.0~6.9) from the viewpoint of the reactivity of the enzymatic reaction. On the other hand, when using a hemicellulase-type enzyme, the pH during enzyme treatment is preferably in the weakly alkaline range (pH=7.1~10.0).

[0031] The temperature during enzyme treatment is preferably 30-70°C, more preferably 35-65°C, and particularly preferably 40-60°C, regardless of whether a cellulase-type enzyme or a hemicellulase-type enzyme is used. If the temperature during enzyme treatment is 30°C or higher, the enzyme activity is less likely to decrease, and the treatment time can be prevented from being prolonged. On the other hand, if the temperature during enzyme treatment is 70°C or lower, enzyme inactivation can be prevented.

[0032] The duration of enzyme treatment depends on factors such as the type of enzyme, the treatment temperature, and the pH during treatment. However, the typical treatment time is between 0.5 and 24 hours.

[0033] After enzyme treatment, it is preferable to deactivate the enzyme. Methods for deactivating the enzyme include, for example, adding an alkaline aqueous solution (preferably pH 10 or higher, more preferably pH 11 or higher) or adding hot water at 80-100°C.

[0034] Next, we will explain the alkaline treatment method. Alkaline treatment prior to defibration partially dissociates the hydroxyl groups of hemicellulose and cellulose in the pulp, causing the molecules to become anionic. This weakens intramolecular and intermolecular hydrogen bonds, promoting the dispersion of cellulose raw materials during defibration.

[0035] Examples of alkalis that can be used for alkaline treatment include sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia solution, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and benzyltrimethylammonium hydroxide, among other organic alkalis. However, from the viewpoint of manufacturing cost, sodium hydroxide is preferred.

[0036] Enzyme treatment, acid treatment, or oxidation treatment prior to defibration can lower the water retention of microfiber cellulose, increase its crystallinity, and improve its homogeneity. In this respect, lower water retention of microfiber cellulose makes it easier to dehydrate, improving the dewatering properties of the cellulose fiber slurry.

[0037] Enzymatic, acidic, or oxidative treatment of raw pulp breaks down the amorphous regions of hemicellulose and cellulose in the pulp. As a result, the energy required for defibration can be reduced, improving the uniformity and dispersibility of cellulose fibers. However, since pretreatment reduces the aspect ratio of microfiber cellulose, it is preferable to avoid excessive pretreatment when using it as a reinforcing material for resins.

[0038] The defibration of raw pulp can be carried out by beating it using, for example, a homogenizer such as a beater, high-pressure homogenizer, or high-pressure homogenization device; a millstone-type friction machine such as a grinder or crusher; a single-screw kneader; a multi-screw kneader; a kneader refiner; or a jet mill. However, it is preferable to use a refiner or a jet mill.

[0039] The average fiber length (average length of individual fibers) of microfiber cellulose is preferably 0.10 to 2.00 mm, more preferably 0.12 to 1.50 mm, and particularly preferably 0.15 to 1.00 mm. If the average fiber length is less than 0.10 mm, a three-dimensional network of fibers cannot be formed, which may reduce the flexural modulus of the composite resin, and even if homogeneity is improved by increasing the fineness ratio to over 35%, the reinforcing effect may not be improved. On the other hand, if the average fiber length exceeds 2.00 mm, the reinforcing effect may be insufficient because the length is the same as that of the raw pulp.

[0040] The average fiber length of the cellulose raw material used to make microfiber 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 is less than 0.50 mm, the reinforcing effect of the resin after defibration treatment may not be sufficiently obtained. On the other hand, if the average fiber length exceeds 5.00 mm, it may be disadvantageous in terms of manufacturing costs during defibration.

[0041] The average fiber length of microfiber cellulose can be arbitrarily adjusted, for example, by selecting raw pulp, pre-treatment, defibration, etc.

[0042] The fineness ratio of microfiber cellulose is preferably 10% or more and 35% or less, more preferably 11-33%, and particularly preferably 13-31%. When the fineness ratio is 10% or more, a certain proportion of homogeneous fibers is ensured, and the homogeneity of the composite resin is ensured. As a result, the flexural modulus is ensured. However, if the fineness ratio exceeds 35%, the fluidity of the composite resin decreases, and this decrease in fluidity may lead to a decrease in the homogeneity of the composite resin and an insufficient reinforcing effect. In this regard, the inventors have found that if the fineness ratio is 35% or less, the fluidity of the composite resin is high, and strands can be drawn even when the fiber content ratio is 55%.

[0043] The above describes the fineness ratio of microfiber cellulose, but it is more preferable to keep the fineness ratio of the cellulose raw material used to make the microfiber cellulose within a specified range. Specifically, it is preferable that the fineness ratio of the cellulose raw material used to make the microfiber cellulose be 1% or more, more preferably 3-20%, and particularly preferable 5-18%. If the fineness ratio of the cellulose raw material before defibration is within the above range, it is thought that there will be less damage to the fibers after defibration, and the reinforcing effect of the resin will be improved.

[0044] The fineness ratio can be adjusted by pretreatment such as enzymatic treatment. However, especially when enzymatic treatment is performed, the fibers themselves may become brittle, potentially 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. Alternatively, not performing enzymatic treatment (addition amount 0% by mass) is also an option.

[0045] In this embodiment, "fine ratio" refers to the mass-based proportion of pulp fibers with a fiber length of 0.2 mm or less.

[0046] The aspect ratio of the microfiber cellulose is preferably 2 to 15,000, more preferably 10 to 10,000. If the aspect ratio is less than 2, a three-dimensional network cannot be sufficiently constructed, and even if the average fiber length is 0.10 mm or more, the reinforcing effect may be insufficient. On the other hand, if the aspect ratio exceeds 15,000, the entanglement of the microfiber cellulose increases, and dispersion in the resin may be insufficient.

[0047] The fibrillation rate of microfiber cellulose is preferably 1.0 to 30.0%, more preferably 1.5 to 20.0%, and particularly preferably 2.0 to 15.0%. If the fibrillation rate exceeds 30.0%, the contact area with water becomes too large, and even if defibration is performed within the range where the average fiber width remains 0.1 μm or more, dehydration may become difficult. On the other hand, if the fibrillation rate falls below 1.0%, there are few hydrogen bonds between fibrils, and it may not be possible to form a strong three-dimensional network.

[0048] In this context, fibrillation rate refers to the value obtained by dissociating cellulose fibers in accordance with JIS-P-8220:2012 "Pulp - Dissociation Method" and measuring the resulting dissociated pulp using FiberLab. (Kajaani).

[0049] The crystallinity of the microfiber cellulose is preferably 50% or higher, more preferably 55% or higher, and particularly preferably 60% or higher. If the crystallinity falls below 50%, although the miscibility with pulp and cellulose nanofibers improves, the strength of the fibers themselves decreases, which may prevent improvement in the strength of the resin. On the other hand, the crystallinity of the microfiber cellulose is preferably 95% or lower, more preferably 90% or lower, and particularly preferably 85% or lower. If the crystallinity exceeds 95%, the proportion of strong hydrogen bonds within the molecule increases, the fibers themselves become rigid, and the dispersibility deteriorates.

[0050] The degree of crystallinity of microfiber cellulose can be arbitrarily adjusted, for example, by selecting the raw pulp, pre-treatment, and micronization process.

[0051] The pulp viscosity of the microfiber cellulose is preferably 4 cps or higher, more preferably 5 cps or higher. If the pulp viscosity of the microfiber cellulose is below 4 cps, it may become difficult to suppress the aggregation of the microfiber cellulose. In this respect, if the pulp viscosity is 4 cps or higher, even if the fineness ratio of the microfiber cellulose is 35% or less, and therefore long fibers may be present, the aggregation of long fibers is suppressed, and the reinforcing effect of the resin is reliably achieved.

[0052] The freeness of the microfiber 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 microfiber cellulose exceeds 500 ml, the average fiber diameter of the microfiber cellulose will exceed 20 μm, and the effect of improving the strength of the resin may not be sufficiently obtained.

[0053] The zeta potential of microfiber cellulose is preferably -150 to 20 mV, more preferably -100 to 0 mV, and particularly preferably -80 to -10 mV. If the zeta potential falls below -150 mV, the compatibility with the resin may decrease significantly, potentially resulting in insufficient reinforcement. On the other hand, if the zeta potential exceeds 20 mV, the dispersion stability may decrease.

[0054] The water retention capacity of microfiber cellulose is preferably 80-400%, more preferably 90-350%, and particularly preferably 100-300%. If the water retention capacity falls below 80%, it is no different from the raw pulp, and the reinforcing effect may be insufficient. On the other hand, if the water retention capacity exceeds 400%, it tends to have poor dewatering properties and is prone to aggregation. In this regard, the water retention capacity of microfiber cellulose can be made lower by substituting the hydroxyl groups of the fibers with carbamate groups, thereby improving dewatering properties and drying properties.

[0055] The water retention capacity of microfiber cellulose can be arbitrarily adjusted, for example, by selecting the raw pulp, pre-treatment, and defibration.

[0056] Microfiber cellulose has carbamate groups. The method by which it is considered to have carbamate groups is not particularly limited. For example, it may have carbamate groups because the cellulose raw material has been carbamateized, or it may have carbamate groups because the microfiber cellulose (finely processed cellulose raw material) has been carbamateized.

[0057] The term "having a carbamate group" refers to a state in which a carbamate group (an ester of carbamic acid) has been introduced into fibrous cellulose. A carbamate group is a group represented by -O-CO-NH-, such as -O-CO-NH2, -O-CONHR, -O-CO-NR2, etc. In other words, a carbamate group can be represented by the following structural formula (1).

[0058] [ka]

[0059] Here, 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 derivative thereof.

[0060] Examples of saturated linear hydrocarbon groups include linear alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, and propyl groups.

[0061] Examples of saturated branched hydrocarbon groups include branched alkyl groups having 3 to 10 carbon atoms, such as isopropyl, sec-butyl, isobutyl, and tert-butyl groups.

[0062] Examples of saturated cyclic hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, and norbornyl groups.

[0063] Examples of unsaturated linear hydrocarbon groups include linear alkenyl groups having 2 to 10 carbon atoms, such as ethenyl group, propen-1-yl group, and propen-3-yl group, and linear alkynyl groups having 2 to 10 carbon atoms, such as ethynyl group, propyne-1-yl group, and propyne-3-yl group.

[0064] Examples of unsaturated branched hydrocarbon groups include branched alkenyl groups having 3 to 10 carbon atoms, such as propen-2-yl, buten-2-yl, and buten-3-yl groups, and branched alkynyl groups having 4 to 10 carbon atoms, such as butyne-3-yl groups.

[0065] Examples of aromatic groups include phenyl groups, tolyl groups, xylyl groups, and naphthyl groups.

[0066] Examples of derivative groups include groups in which one or more hydrogen atoms of the saturated linear hydrocarbon group, saturated branched hydrocarbon group, saturated cyclic hydrocarbon group, unsaturated linear hydrocarbon group, unsaturated branched hydrocarbon group, and aromatic group are substituted with substituents (e.g., hydroxyl groups, carboxyl groups, halogen atoms, etc.).

[0067] In microfiber cellulose containing carbamate groups (introduced with carbamate groups), some or all of the highly polar hydroxyl groups are replaced with relatively less polar carbamate groups. Therefore, microfiber cellulose containing carbamate groups has low hydrophilicity and high affinity for low-polarity resins. As a result, microfiber cellulose containing carbamate groups exhibits excellent uniform dispersibility with resins. Furthermore, slurry made from microfiber cellulose containing carbamate groups has low viscosity and good handling properties.

[0068] The substitution rate of carbamate groups for hydroxyl groups in microfiber cellulose is preferably 1.0 to 5.0 mmol / g, more preferably 1.2 to 3.0 mmol / g, and particularly preferably 1.5 to 2.0 mmol / g. A substitution rate of 1.0 mmol / g or higher ensures the effect of introducing carbamate groups, particularly the improvement of the resin's flexural modulus. On the other hand, if the substitution rate exceeds 5.0 mmol / g, the cellulose fibers may lose their shape, potentially resulting in insufficient resin reinforcement. Furthermore, if the carbamate group substitution rate exceeds 2.0 mmol / g, the average fiber length of the pulp becomes shorter when the raw material pulp is carbamateized, resulting in an average fiber length of less than 0.1 mm for the microfiber cellulose, potentially preventing sufficient resin reinforcement.

[0069] In this embodiment, the carbamate group substitution rate (mmol / g) refers to the amount of carbamate groups contained in 1 g of cellulose raw material containing carbamate groups. The carbamate group substitution rate is calculated by measuring the amount of N atoms present in the carbamateized pulp using the Kjeldahl method and determining the carbamateization rate per unit weight. Furthermore, cellulose is a polymer with anhydrous glucose as its structural unit, and each structural unit has three hydroxyl groups.

[0070] <Carbamate> Regarding the introduction of carbamate groups into microfiber cellulose (or cellulose raw material if carbamateization is performed before defibration; the same applies hereinafter, and it is also referred to as "microfiber cellulose, etc."), as mentioned above, there are two methods: one in which the cellulose raw material is carbamateized first and then refined, and another in which the cellulose raw material is refined first and then carbamateized. In this specification, the defibration of the cellulose raw material is explained first, followed by the carbamateization (modification). However, defibration and carbamateization can be performed in either order. However, it is preferable to perform carbamateization first and then defibration. This is because the cellulose raw material has high dehydration efficiency before defibration, and the heating associated with carbamateization makes the cellulose raw material more easily defibrated.

[0071] The process of carbamate microfiber cellulose, etc., can be mainly divided into, for example, mixing, removal, and heat treatment. The mixing and removal treatments together can also be referred to as preparation treatments for preparing the mixture to be subjected to heat treatment.

[0072] In the mixing process, microfiber cellulose or the like (which may be cellulose raw material as described above; the same applies hereinafter) and urea or a derivative of urea (hereinafter simply referred to as "urea, etc.") are mixed in a dispersion medium.

[0073] Examples of urea and urea derivatives that can be used include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and compounds in which hydrogen atoms of urea are substituted with alkyl groups. These ureas or urea derivatives can be used individually or in combination. However, the use of urea is preferred.

[0074] The lower limit of the mixed mass ratio of urea, etc. to microfiber cellulose, etc. (urea, etc. / microfiber cellulose, etc.) is preferably 10 / 100, more preferably 20 / 100. On the other hand, the upper limit is preferably 300 / 100, more preferably 200 / 100. By increasing the mixed mass ratio to 10 / 100 or higher, the efficiency of carbamate formation is improved. On the other hand, even if the mixed mass ratio exceeds 300 / 100, carbamate formation plateaus.

[0075] The dispersion medium is usually water. However, other dispersion mediums such as alcohol or ether, or mixtures of water and other dispersion mediums may also be used.

[0076] In the mixing process, for example, microfiber cellulose and urea may be added to water, or microfiber cellulose may be added to an aqueous solution of urea, or urea may be added to a slurry containing microfiber cellulose. Furthermore, stirring may be performed after addition to ensure uniform mixing. In addition, the dispersion containing microfiber cellulose and urea may contain other components.

[0077] In the removal process, the dispersion medium is removed from the dispersion containing microfiber cellulose and urea obtained in the mixing process. By removing the dispersion medium, the urea can be reacted efficiently in the subsequent heat treatment.

[0078] The dispersion medium is preferably removed by volatilizing it through heating. This method allows for the efficient removal of only the dispersion medium while leaving components such as urea intact.

[0079] The lower limit of the heating temperature in the removal process is preferably 50°C, more preferably 70°C, and particularly preferably 90°C, when the dispersion medium is water. By heating 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 will react, and there is a risk that the urea will decompose on its own.

[0080] The heating time in the removal process can be adjusted as appropriate depending on the solid content concentration of the dispersion. Specifically, for example, it can be 6 to 24 hours.

[0081] In the heat treatment following the removal process, a mixture of microfiber cellulose and urea is heat-treated. During this heat treatment, some or all of the hydroxyl groups of the microfiber cellulose react with urea and are replaced by carbamate groups. More specifically, when urea is heated, it decomposes into isocyanic acid and ammonia as shown in reaction equation (1) below. Isocyanic acid is highly reactive, and for example, as shown in reaction equation (2) below, carbamate groups are formed on the hydroxyl groups of cellulose. NH2-CO-NH2→ HN=C=O + NH3…(1) Cell-OH + HN=C=O → Cell-CO-NH2…(2) 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. Heating to 120°C or higher allows for efficient carbamate formation. 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, microfiber cellulose and the like may decompose, potentially resulting in insufficient reinforcement.

[0082] 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. Heating for 1 minute or more ensures that the carbamate reaction can be carried out reliably. On the other hand, the upper limit of the heating time is preferably 15 hours, more preferably 10 hours. Heating for more than 15 hours is not economical, and carbamate can be sufficiently carried out in 15 hours.

[0083] However, prolonged heating time leads to deterioration of cellulose fibers. Therefore, the pH conditions during heat treatment are important. Preferably, the pH is 9 or higher, more preferably 9 to 13, and particularly preferably 10 to 12, which are alkaline conditions. As a second-best option, an acidic or neutral condition of 7 or lower, preferably 3 to 7, and particularly preferably 4 to 7, is also acceptable. Under neutral conditions of 7 to 8 pH, the average fiber length of the cellulose fibers may be shortened, potentially resulting in a reduced reinforcing effect of the resin. In contrast, under alkaline conditions of 9 or higher pH, the reactivity of the cellulose fibers increases, promoting the reaction with urea, etc., and efficiently carrying out the carbamate reaction, thus ensuring a sufficient average fiber length of the cellulose fibers. On the other hand, under acidic conditions of 7 or lower pH, the reaction of decomposition from urea, etc., into isocyanic acid and ammonia proceeds, promoting the reaction with cellulose fibers, and efficiently carrying out the carbamate reaction, thus ensuring a sufficient average fiber length of the cellulose fibers. However, if possible, it is preferable to heat treat under alkaline conditions. This is because acidic conditions may cause acid hydrolysis of cellulose to proceed.

[0084] pH adjustment can be performed by adding acidic compounds (e.g., acetic acid, citric acid, etc.) or alkaline compounds (e.g., sodium hydroxide, calcium hydroxide, etc.) to the mixture.

[0085] For the heat treatment, heating equipment such as a hot air dryer, paper machine, or dry pulp machine can be used.

[0086] The mixture after heat treatment may be washed. This washing can be done with water or the like. This washing can remove any unreacted urea or other residual substances.

[0087] (slurry) Microfiber cellulose is dispersed in an aqueous medium to form a dispersion (slurry) as needed. While it is particularly preferable that the aqueous medium is entirely water, an aqueous medium containing a portion of another liquid that is compatible with water can also be used. Other liquids that can be used include lower alcohols with 3 or fewer carbon atoms.

[0088] The solid content concentration of the slurry is preferably 2 to 10% by mass, more preferably 3 to 8% by mass. If the solid content concentration is less than 2% by mass, excessive energy may be required during dewatering and drying. On the other hand, if the solid content concentration exceeds 10% by mass, the fluidity of the slurry itself decreases, and uniform mixing may not be possible even when using a dispersant. In this regard, for example, if the fine content ratio exceeds 35%, the upper limit of the slurry solid content concentration from the viewpoint of ensuring fluidity is 4.0% by mass. In contrast, if the fine content ratio is 35% or less, the upper limit is 10% (preferably 6.0%) by mass, as described above. Therefore, if the fine content ratio is 35% or less and the slurry solid content concentration is 10% by mass or less, the amount of aqueous medium that needs to be removed from the slurry can be reduced, and the solid content concentration can be increased, which has advantages such as cost reduction.

[0089] (Acid-modified resin) As mentioned above, in acid-modified resins, the acid groups ionically bond with some or all of the carbamate groups. This ionic bonding improves the reinforcing effect of the resin.

[0090] Examples of acid-modified resins that can be used include acid-modified polyolefin resins, acid-modified epoxy resins, and acid-modified styrene-based elastomer resins. However, it is preferable to use acid-modified polyolefin resins. Acid-modified polyolefin resins are copolymers of an unsaturated carboxylic acid component and a polyolefin component.

[0091] As the polyolefin component, one or more polymers of alkenes such as ethylene, propylene, butadiene, and isoprene can be selected and used. However, it is preferable to use polypropylene resin, which is a polymer of propylene.

[0092] As the unsaturated carboxylic acid component, one or more can be selected from, for example, maleic anhydrides, phthalic anhydrides, itaconic anhydrides, citraconic anhydrides, citric anhydrides, etc. However, maleic anhydrides are preferably used. In other words, it is preferable to use maleic anhydride-modified polypropylene resin.

[0093] The amount of acid-modified resin to be 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 microfiber cellulose. In particular, when the acid-modified resin is maleic anhydride-modified polypropylene resin, the amount is preferably 1 to 200 parts by mass, and more preferably 10 to 100 parts by mass. If the amount of acid-modified resin mixed is less than 0.1 parts by mass, the improvement in strength is insufficient. On the other hand, if the amount mixed exceeds 1,000 parts by mass, it becomes excessive and tends to decrease the strength.

[0094] The weight-average molecular weight of maleic anhydride-modified polypropylene is, for example, 1,000 to 100,000, preferably 3,000 to 50,000.

[0095] Furthermore, the acid value of the maleic anhydride-modified polypropylene is preferably 0.5 mg KOH / g or more and 100 mg KOH / g or less, and more preferably 1 mg KOH / g or more and 50 mg KOH / g or less.

[0096] Furthermore, the MFR (melt flow rate) of the acid-modified resin is preferably 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. If the MFR exceeds 2000 g / 10 min, the dispersibility of the cellulose fibers may decrease.

[0097] The acid value is measured in accordance with JIS-K2501 by titration with potassium hydroxide. The MFR is measured in accordance with JIS-K7210 by applying a load of 2.16 kg at 190°C and determining the weight of the sample that flows out in 10 minutes.

[0098] (Dispersant) Cellulose raw materials or microfiber cellulose are more preferable when mixed with a dispersant. Preferred dispersants are compounds having an amine group and / or a hydroxyl group in aromatic compounds, and compounds having an amine group and / or a hydroxyl group in aliphatic compounds.

[0099] Compounds having an amine group and / or a hydroxyl group in aromatic compounds include, for example, anilines, toluidines, trimethylanilines, anisidines, tyramines, histamines, tryptamines, phenols, dibutylhydroxytoluenes, bisphenol A, cresols, eugenols, gallic acids, guaiacols, picric acids, phenolphthaleins, serotonins, dopamins, adrenaline, noradrenaline, thymols, tyrosines, salicylic acids, methyl salicylates, and Examples include vinyl alcohols, salicyl alcohols, cinnapyr alcohols, diphenidols, diphenylmethanols, cinnamyl alcohols, scopolamines, tryptofols, vanillyl alcohols, 3-phenyl-1-propanols, phenethyl alcohols, phenoxyethanols, veratril alcohols, benzyl alcohols, benzoins, mandelic acids, mandelonitriles, benzoic acids, phthalic acids, isophthalic acids, terephthalic acids, melitic acids, and cinnamic acids.

[0100] Examples of compounds having an amine group and / or a hydroxyl group in an aliphatic compound include caprylic alcohols, 2-ethylhexanols, pelargone alcohols, caprin 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. Examples include 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.

[0101] The dispersants described above inhibit hydrogen bonding between cellulose fibers. Therefore, when mixing microfiber cellulose and resin, the microfiber cellulose is reliably dispersed in the resin. Furthermore, these dispersants also play a role in improving the compatibility between microfiber cellulose and resin. In this respect, the dispersibility of microfiber cellulose in resin is improved.

[0102] While it is possible to add a phase solvent (chemical) separately during the kneading of fibrous cellulose and resin, mixing the fibrous cellulose and dispersant (chemical) beforehand results in more uniform adhesion of the chemical to the fibrous cellulose, thus improving compatibility with the resin.

[0103] Furthermore, for example, polypropylene has a melting point of 160°C, and therefore the mixing of fibrous cellulose and resin is carried out at around 180°C. However, if a dispersant (liquid) is added in this state, it dries out instantly. Therefore, there is a method of preparing a masterbatch (a composite resin with a high concentration of microfiber cellulose) using a resin with a low melting point, and then lowering the concentration with a normal resin. However, resins with low melting points generally have low strength. Therefore, this method may reduce the strength of the composite resin.

[0104] The amount of dispersant to be 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 microfiber cellulose. If the amount of dispersant mixed is less than 0.1 parts by mass, the improvement in resin strength may not be sufficient. On the other hand, if the amount of dispersant mixed exceeds 1,000 parts by mass, it becomes excessive and tends to decrease the resin strength.

[0105] In this regard, the aforementioned acid-modified resin improves compatibility by ionic bonding between the acid groups and the carbamate groups of microfiber cellulose, thereby increasing the reinforcing effect. Because of its large molecular weight, it readily blends with the resin and is thought to contribute to improved strength. On the other hand, the above-mentioned dispersant intervenes between the hydroxyl groups of microfiber cellulose to prevent aggregation and thereby improve 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 microfiber cellulose that the acid-modified resin cannot penetrate, thus improving dispersibility and contributing to improved strength. From these viewpoints, the molecular weight of the above-mentioned acid-modified resin is preferably 2 to 2,000 times, more preferably 5 to 1,000 times, that of the dispersant.

[0106] To explain this point in more detail, resin powder physically intervenes between microfiber cellulose molecules, inhibiting hydrogen bonding and thereby improving the dispersibility of microfiber cellulose. In contrast, acid-modified resins improve compatibility by ionic bonding between acid groups and the carbamate groups of microfiber cellulose, thereby enhancing the reinforcing effect. In this respect, dispersants also inhibit hydrogen bonding between microfiber cellulose molecules, but because resin powder is on the micro-order, it suppresses hydrogen bonding by physically intervening. Therefore, although its dispersibility is lower than that of dispersants, the resin powder itself melts and forms a matrix, so it does not contribute to a decrease in physical properties. On the other hand, dispersants are at the molecular level and are extremely small, so they are highly effective in inhibiting hydrogen bonding by covering the microfiber cellulose and improving the dispersibility of microfiber cellulose. However, they may remain in the resin and contribute to a decrease in physical properties.

[0107] (Manufacturing method) A mixture of fibrous cellulose, acid-modified resin, and dispersant can be dried and pulverized into a powder before being kneaded with the resin. This form eliminates the need to dry the fibrous cellulose during kneading with the resin, resulting in good thermal efficiency. Furthermore, if a dispersant is mixed into the mixture, there is a low risk that the fibrous cellulose (microfiber cellulose) will not redisperse even if the mixture is dried.

[0108] The mixture may be dehydrated before drying, if necessary. This dehydration can be carried out by selecting one or more types of dehydration equipment from among, for example, a belt press, screw press, filter press, twin roll, twin wire former, valveless filter, center disc filter, membrane processing, and centrifuge.

[0109] The drying of the mixture can be carried out by selecting one or more of the following methods: rotary kiln drying, disc drying, airflow drying, fluidized bed drying, spray drying, drum drying, screw conveyor drying, paddle drying, single-screw kneading drying, multi-screw kneading drying, vacuum drying, agitation drying, etc.

[0110] The dried mixture (dried material) is ground into a powder. The dried material can be ground using one or more types of equipment selected from, for example, a bead mill, kneader, disper, twist mill, cut mill, hammer mill, etc.

[0111] The average particle size of the powder is preferably 1 to 10,000 μm, more preferably 10 to 5,000 μm, and particularly preferably 100 to 1,000 μm. If the average particle size of the powder exceeds 10,000 μm, it may result in poor kneadability with the resin. On the other hand, reducing the average particle size of the powder to less than 1 μm requires a large amount of energy, making it uneconomical.

[0112] The average particle size of powdered materials can be controlled not only by controlling the degree of grinding, but also by classification using classification devices such as filters and cyclones.

[0113] The bulk density of the mixture (powder) is preferably 0.03 to 1.0, more preferably 0.04 to 0.9, and particularly preferably 0.05 to 0.8. A bulk density exceeding 1.0 means that the hydrogen bonds between the fibrous celluloses are stronger, making it difficult to disperse them in the resin. On the other hand, a bulk density below 0.03 is disadvantageous in terms of transportation costs.

[0114] The bulk density is a value measured in accordance with JIS K7365.

[0115] The moisture content of the mixture (powder) is preferably 50% or less, more preferably 30% or less, and particularly preferably 10% or less. If the moisture content exceeds 50%, the energy required for kneading with the resin becomes enormous, making it uneconomical.

[0116] The moisture content was calculated using the following formula, after drying the sample in a constant-temperature dryer, holding it at 105°C for 6 hours or more and taking the mass at which no further mass fluctuation was observed. Fiber moisture content (%) = [(Mass before drying - Mass after drying) ÷ Mass before drying] × 100

[0117] Dehydrated and dried microfiber cellulose may contain resin. The presence of resin inhibits hydrogen bonding between the dehydrated and dried microfiber cellulose molecules, improving dispersibility within the resin during mixing.

[0118] Examples of resin forms that can be contained in dehydrated and dried microfiber cellulose include powder, pellets, and sheets. However, powder form (powdered resin) is preferred.

[0119] When in powder form, the average particle size of the resin powder contained in the dehydrated and dried microfiber cellulose is preferably 1 to 10,000 μm, more preferably 10 to 5,000 μm, and particularly preferably 100 to 1,000 μm. If the average particle size exceeds 10,000 μm, the particles may be too large to enter the mixing device. On the other hand, if the average particle size is less than 1 μm, the particles may be too fine to inhibit hydrogen bonding between microfiber cellulose cells. The resin used here, such as the powdered resin, may be the same type as the resin mixed with the microfiber cellulose (the resin as the main raw material) or a different type, but it is preferable that they be the same type.

[0120] Resin powders with an average particle size of 1 to 10,000 μm are preferably mixed in an aqueous dispersion state before dehydration and drying. Mixing in an aqueous dispersion state allows for uniform dispersion of the resin powder between microfiber cellulose molecules, enabling uniform dispersion of microfiber cellulose in the composite resin after kneading, thereby further improving the strength and physical properties.

[0121] The powdered material (resin reinforcing agent) obtained as described above is kneaded with the resin to obtain a fibrous cellulose composite resin. This kneading can be done, for example, by mixing pelletized resin with the powdered material, or by first melting the resin and then adding the powdered material to the molten material. Acid-modified resins and dispersants can also be added at this stage.

[0122] For the mixing process, one or more types of equipment can be selected and used from, for example, single-screw or multi-screw mixers, mixing rolls, kneaders, roll mills, Banbury mixers, screw presses, dispersers, etc. Among these, it is preferable to use a multi-screw mixer with two or more shafts. Two or more multi-screw mixers with two or more shafts may be used in parallel or in series.

[0123] The mixing temperature is above the glass transition temperature of the resin and varies depending on the type of resin, but is preferably 80 to 280°C, more preferably 90 to 260°C, and particularly preferably 100 to 240°C.

[0124] As the resin, at least one of thermoplastic resins or thermosetting resins can be used.

[0125] As thermoplastic resins, one or more can be selected and used from, for example, 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, and polyacetal resins.

[0126] However, it is preferable to use at least one of polyolefin and polyester resin. Furthermore, as polyolefin, polypropylene is preferred. In addition, as polyester resin, aliphatic polyester resins such as polylactic acid and polycaprolactone can be exemplified, and aromatic polyester resins such as polyethylene terephthalate can be exemplified, but it is preferable to use a biodegradable polyester resin (also simply called "biodegradable resin").

[0127] As for biodegradable resins, one or more can be selected and used from, for example, hydroxycarboxylic acid-based aliphatic polyesters, caprolactone-based aliphatic polyesters, dibasic acid polyesters, etc.

[0128] As the hydroxycarboxylic acid aliphatic polyester, one or more can be selected and used from among homopolymers of hydroxycarboxylic acids such as lactic acid, malic acid, glucose acid, and 3-hydroxybutyric acid, or 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 excluding lactic acid, polycaprolactone, or copolymers of at least one of the above hydroxycarboxylic acids and caprolactone, and it is particularly preferable to use polylactic acid.

[0129] For example, L-lactic acid or D-lactic acid can be used as the lactic acid, and these lactic acids may be used individually or two or more types may be selected and used together.

[0130] As the caprolactone-based aliphatic polyester, one or more can be selected and used from, for example, a homopolymer of polycaprolactone or a copolymer of polycaprolactone or the above-mentioned hydroxycarboxylic acid.

[0131] As the dibasic acid polyester, one or more types can be selected and used from, for example, polybutylene succinate, polyethylene succinate, and polybutylene adipate.

[0132] Biodegradable resins may be used individually or in combination of two or more types.

[0133] 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, and thermosetting polyimide resins. These resins can be used individually or in combination of two or more types.

[0134] The resin may contain inorganic fillers, preferably in a proportion that does not hinder thermal recycling.

[0135] Examples of inorganic fillers include elemental metal elements from 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 oxides, hydroxides, carbon salts, sulfates, silicates, sulfites, and various clay minerals composed of these elements.

[0136] Specifically, 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 worlastonite, glass beads, glass powder, silica sand, silica, quartz powder, diatomaceous earth, white carbon, glass fiber, etc. Multiple inorganic fillers may be included. They may also be found in recycled paper pulp.

[0137] The blending ratio of fibrous cellulose and resin is preferably 1 part by mass or more of fibrous cellulose and 99 parts by mass or less of resin, more preferably 2 parts by mass or more of fibrous cellulose and 98 parts by mass or less of resin, and particularly preferably 3 parts by mass or more of fibrous cellulose and 97 parts by mass or less of resin. Also preferably 50 parts by mass or less of fibrous cellulose and 50 parts by mass or more of resin, more preferably 40 parts by mass or less of fibrous cellulose and 60 parts by mass or more of resin, and particularly preferably 30 parts by mass or less of fibrous cellulose and 70 parts by mass or more of resin. In particular, when the amount of fibrous cellulose is 10 to 50 parts by mass, the strength of the resin composition, especially the flexural strength and tensile modulus, can be significantly improved.

[0138] The final resin composition will typically contain the same proportions of fibrous cellulose and resin as described above.

[0139] Dissolution parameters of microfiber cellulose and resin (cal / cm 3 ) 1 / 2 (SP value), that is, the SP of microfiber cellulose MFC value, the SP of the resin POL value, then the difference in SP value = SP MFC value - SP POL value. The difference in SP value is preferably 10 to 0.1, more preferably 8 to 0.5, and particularly preferably 5 to 1. If the difference in SP value exceeds 10, microfiber cellulose may not disperse in the resin and it may not be possible to obtain a reinforcing effect. On the other hand, if the difference in SP value is less than 0.1, microfiber cellulose will dissolve in the resin and will not function as a filler, and a reinforcing effect cannot be obtained. In this regard, the smaller the difference between the SP POL value of the resin (solvent) and the SP MFC value of microfiber cellulose (solute), the greater the reinforcing effect.

[0140] Note that the dissolution parameter (cal / cm 3 ) 1 / 2 (SP value) is a measure representing the intermolecular force acting between the solvent and solute. The closer the SP values of the solvent and solute are, the higher the solubility.

[0141] (Forming process) The kneaded product of fibrous cellulose and resin can be shaped into a desired shape after kneading again if necessary. The size, thickness, shape, etc. of this shaping are not particularly limited, and for example, it can be in the form of a sheet, pellet, powder, fiber, etc.

[0142] The temperature during the forming process is above the glass transition point of the resin and varies depending on the type of resin. For example, it is 90 to 260 °C, preferably 100 to 240 °C.

[0143] The compound can be molded by methods such as die molding, injection molding, extrusion molding, hollow molding, and foam molding. Alternatively, the compound can be spun into fibers and blended with the aforementioned plant materials to form mats or boards. Blending can be done by methods such as simultaneous deposition using an air ray.

[0144] As a device for molding the kneaded material, one or more types can be selected and used from, for example, injection molding machines, blow molding machines, hollow molding machines, blow molding machines, compression molding machines, extrusion molding machines, vacuum molding machines, and pressure molding machines.

[0145] The molding described above can be performed immediately after kneading, or the kneaded material can be cooled, chipped using a crusher or the like, and then fed into a molding machine such as an extruder or injection molder. Of course, molding is not an essential requirement of this invention.

[0146] (Other compositions) Fibrous cellulose may contain cellulose nanofibers along with microfiber cellulose. Cellulose nanofibers are fine fibers, similar to microfiber cellulose, and play a complementary role to microfiber cellulose in improving the strength of the resin. However, if possible, it is preferable to use only microfiber cellulose without including cellulose nanofibers as fine fibers. The average fiber diameter (average fiber width; average diameter of a single fiber) of the cellulose nanofibers is preferably 4 to 100 nm, more preferably 10 to 80 nm.

[0147] Furthermore, fibrous cellulose may contain pulp. The pulp plays a role in significantly improving the dewatering properties of the cellulose fiber slurry. However, as with cellulose nanofibers, it is most preferable not to include pulp, i.e., to have a pulp content of 0% by mass.

[0148] The resin composition may also contain, or may contain, fibers derived from plant materials obtained from various plants, including, in addition to fine fibers and pulp, kenaf, jute, Manila hemp, sisal, ganpi, mitsumata, kozo, banana, pineapple, coconut, corn, sugarcane, bagasse, palm, papyrus, reed, esparto, survivalgrass, wheat, rice, bamboo, various coniferous trees (such as cedar and cypress), broad-leaved trees, and cotton.

[0149] The resin composition may contain one or more of the following, for example, antistatic agents, flame retardants, antibacterial agents, colorants, radical scavengers, and foaming agents, insofar as they do not hinder the effects of the present invention. These raw materials may be added to a dispersion of fibrous cellulose, added during the kneading of fibrous cellulose and resin, added to the resulting mixture, or added by other methods. However, from the standpoint of manufacturing efficiency, it is preferable to add them during the kneading of fibrous cellulose and resin.

[0150] The resin composition 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.

[0151] The MFR (melt flow rate) of the resin composition (preferably when the fiber content is 55%) is preferably 0.01 to 20 g / 10 min, more preferably 0.02 to 10 g / 10 min, and particularly preferably 0.03 to 5 g / 10 min. If the MFR is 0.01 g / 10 min or higher, strands can be reliably drawn. However, if the MFR exceeds 1.0 g / 10 min, the molecular weight of the base resin may decrease too much, potentially making it impossible to meet the required strength properties.

[0152] The measurement of MFR is the same as in the case of acid-modified resins described above. In this specification, the determination of whether or not strands can be drawn is made using a small experimental machine (a small twin-screw kneader with shaft length L and shaft diameter D, where D=15mm and shaft ratio L / D=15). If strands can be drawn without problems using a simple device with an L / D of around 15, it can be said that strands can also be drawn using a normal device. Furthermore, the fact that a small test machine can be used means that the device is not limited in type, which has the advantage of not requiring additional capital investment. Incidentally, if the L / D is large, the composite resin will be kneaded more thoroughly, which will improve the dispersion of MFCs and the homogenization of the composite resin, as well as the fluidity of the composite resin. According to the inventors' findings, strands can be drawn using any device with D=48 and L / D=48, or with D=30 and L / D=60.

[0153] (Definition, measurement method, etc.) (Average fiber diameter) The method for measuring the average fiber diameter of fine fibers (microfiber cellulose and cellulose nanofibers) is as follows: First, 100 ml of an aqueous dispersion of fine fibers with a solid content concentration of 0.01-0.1% by mass is filtered through a Teflon® membrane filter, and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. Next, the dispersion is freeze-dried and coated with osmium to prepare the sample. This sample is observed using an electron microscope (SEM) at a magnification of 3,000x to 30,000x depending on the width of the constituent fibers. Specifically, two diagonal lines are drawn on the observed image, and three arbitrary straight lines are drawn passing through the intersection of the diagonals. Furthermore, the width of a total of 100 fibers that intersect these three straight lines is measured visually. The median diameter of the measured values ​​is then taken as the average fiber diameter.

[0154] (Aspect ratio) The aspect ratio is the value obtained by dividing the average fiber length by the average fiber width. A larger aspect ratio increases the number of points where snagging occurs, thus increasing the reinforcement effect. On the other hand, it is thought that the ductility of the resin decreases as more snagging occurs.

[0155] (Water retention) The water retention rate was measured according to JAPAN TAPPI No.26 (2000).

[0156] (Fiber analysis) The fineness rate, fibrillation rate, and average fiber length were measured using the Valmet FS5 fiber analyzer.

[0157] (Degree of crystallinity) The degree of crystallinity was measured in accordance with JIS K 0131 (1996).

[0158] (viscosity) Pulp viscosity was measured according to TAPPI T 230.

[0159] (B type viscosity) The B-type viscosity (solid content concentration 1%) of the dispersion was measured in accordance with JIS-Z8803 (2011) "Method for Measuring the Viscosity of Liquids". B-type viscosity is the resistance torque when the dispersion is stirred, and a higher value means that more energy is required for stirring.

[0160] (Freeness) Freeness is a value measured in accordance with JIS P8121-2(2012). [Examples]

[0161] Next, embodiments of the present invention will be described. Coniferous kraft pulp with a moisture content of 10% or less, a urea aqueous solution with a solid content of 10%, and various pH adjusting solutions were mixed in the mass ratio on a solid content basis as shown in Table 1 (the amount of pH adjusting solution is not specified. Since urea is a weak base, the amount of pH adjusting solution is small (approximately 0.02-0.2 g / g of urea)). The mixture was then dried at 105°C. Subsequently, it was heat-treated for 3 hours at a reaction temperature of 140°C to obtain carbamate-modified pulp. The obtained carbamate-modified pulp was diluted and stirred with distilled water, and dewatering and washing were repeated twice. The washed carbamate-modified pulp was beaten in a Niagara beater for 1 hour to obtain carbamate-modified microfiber cellulose with a fineness of 24%.

[0162] 2750 g of a carbamate-modified microfiber cellulose aqueous dispersion with a solid content of 2% by mass was mixed with 27.5 g of maleic anhydride-modified polypropylene and 17.5 g of polypropylene powder, and heated and dried at 105°C to obtain a carbamate-modified microfiber cellulose-containing material. The water content of this carbamate-modified microfiber cellulose-containing material was less than 20%.

[0163] The carbamate-modified microfiber-containing material obtained as described above was kneaded in a twin-screw kneader at 180°C and 200 rpm to obtain a carbamate-modified microfiber cellulose composite resin with a fiber content of 55%. Polypropylene pellets were added to this carbamate-modified microfiber cellulose composite resin in a ratio of carbamate-modified microfibers to other components of 10:90 and mixed in a twin-screw kneader at 180°C and 200 rpm to obtain a carbamate-modified microfiber cellulose composite resin with a fiber content of 10%.

[0164] Carbamate-modified microfiber cellulose composite resin with a fiber content of 10% was cut into cylindrical shapes with a diameter of 2 mm and a length of 2 mm using a pelletizer, and injection molded into rectangular test specimens (length 59 mm, width 9.6 mm, thickness 3.8 mm) at 180°C. The composite resin with a fiber content of 55% was visually inspected to determine whether strands could be drawn, and the flexural modulus of the composite resin with a fiber content of 10% was examined. The results are shown in Table 1.

[0165] The flexural modulus was measured in accordance with JIS K7171:2008. In the table, the flexural modulus of the composite resin (magnification) is set to 1 (1.38 GPa), and "○" indicates that the flexural modulus (magnification) of the composite resin is 1.40 times or higher, while "×" indicates that it is less than 1.40 times. For the strands, tests were conducted using the aforementioned small experimental machine, and "○" indicates that they could be shrunk, while "×" indicates that they could not.

[0166] [Table 1] [Industrial applicability]

[0167] The present invention relates to fibrous cellulose, fibrous cellulose composite resin, and fibrous cellulose. Composite resin It can be used as a manufacturing method. For example, fibrous cellulose composite resin can be used as interior, exterior, and structural materials for transportation equipment such as automobiles, trains, ships, and airplanes; as casings, structural materials, and internal components for electrical appliances such as personal computers, televisions, telephones, and watches; as casings, structural materials, and internal components for mobile communication equipment such as mobile phones; as casings, structural materials, and internal components for portable music players, video players, printing machines, photocopiers, sporting goods, office equipment, toys, and sporting goods; as interior, exterior, and structural materials for buildings and furniture; as office equipment such as stationery; and for other applications such as packaging, trays, protective components, and partition components.

Claims

1. It contains fibrous cellulose, maleic anhydride-modified polypropylene resin, and polypropylene resin. The fibrous cellulose is, The average fiber width is 0.1 μm or more, and some or all of the hydroxyl groups are "-CO-NH ２ It is substituted with a carbamate group represented by the " group, The substitution rate of the carbamate group is 1.0 mmol / g to 5.0 mmol / g. The fine rate is between 10% and 35%. The average fiber length is 0.10 to 2.00 mm. A fibrous cellulose composite resin characterized by the following features.

2. The fine content of the cellulose raw material is 1% or more. The fibrous cellulose composite resin according to claim 1.

3. The cellulose raw material is either untreated with enzymes, or the amount of enzymes added is limited to 2% by mass or less of the cellulose raw material. The fibrous cellulose composite resin according to claim 1.

4. The pulp viscosity of the fibrous cellulose is 4 cps or more. The fibrous cellulose composite resin according to claim 1.

5. A cellulose raw material and at least one of urea and a urea derivative are heat-treated to remove some or all of the hydroxyl groups of the cellulose raw material from the "-CO-NH" group. ２ The process involves substitution with a carbamate group represented by the " group, The process includes a step of defibrating the cellulose raw material to obtain fibrous cellulose in a range where the average fiber width is 0.1 μm or more and the average fiber length is 0.10 to 2.00 mm. The heat treatment is carried out such that the substitution rate of the carbamate group is 1.0 mmol / g to 5.0 mmol / g. The aforementioned defibration is carried out such that the fineness ratio is 10% or more and 35% or less. A fibrous cellulose composite resin is obtained from the fibrous cellulose, maleic anhydride-modified polypropylene resin, and polypropylene resin. A method for producing a fibrous cellulose composite resin characterized by the above.

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