Fibrous cellulose-containing product, fibrous cellulose composite resin, and method for producing fibrous cellulose-containing product

Abstract

The present invention provides a fibrous cellulose-containing substance excellent in dispersibility even when drying is performed, a manufacturing method thereof, and a fibrous cellulose composite resin excellent in strength. A fibrous cellulose-containing substance added to a resin, the average fiber width of fibrous cellulose being 0.1 to 19 μm, and the hydroxyl group being substituted with a urethane group, the fibrous cellulose-containing substance containing a powder that interacts with the fibrous cellulose. In addition, a fibrous cellulose composite resin uses the above fibrous cellulose-containing substance as fibrous cellulose. Furthermore, in the manufacturing method of the fibrous cellulose-containing substance, the fibrous cellulose in which the hydroxyl group is substituted with a urethane group is exfoliated so as to have an average fiber width of 0.1 to 19 μm, and a powder that interacts with the fibrous cellulose is mixed to obtain a mixed solution, and the mixed solution is dried.

Description

Technical Field

[0001] This invention relates to fibrous cellulose inclusions, fibrous cellulose composite resins, and methods for manufacturing fibrous cellulose inclusions. Background Technology

[0002] In recent years, the use of microfibers such as cellulose nanofibers and microfibrillated cellulose (microfibrillated cellulose) as resin reinforcing materials has attracted much attention. However, microfibers are hydrophilic, while resins are hydrophobic, thus causing problems with the dispersibility of microfibers when used as resin reinforcing materials. Therefore, the inventors have proposed a scheme that replaces the hydroxyl groups of microfibers with urethane groups (see Patent Document 1). According to this scheme, the dispersibility of microfibers is improved, thereby improving the reinforcing effect of the resin. However, microfibers aggregate during drying, but this aggregation is strong, thus causing problems with dispersibility when using dried microfibers as resin reinforcing materials.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-1876 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The main problem to be solved by the present invention is to provide a fibrous cellulose inclusion with excellent dispersibility even when dried, a method for manufacturing the same, and a fibrous cellulose composite resin with excellent strength.

[0008] Methods for solving problems

[0009] In existing developments, such as those described in the aforementioned patent literature, the main focus is on the dispersibility of microfibers when they are held in a dispersion state. Among various modification methods, including esterification, etherification, amidation, and sulfidation, the introduction of urethane esters (urethane esterification) has been found to be superior. In contrast, this invention focuses on the dispersibility of microfibers when they are temporarily dried and then mixed with resin. It was discovered that by exploring other substances and properties used with microfibers in various experiments based on the introduction of urethane esters, the aforementioned problem can be solved, leading to the development of this invention. The method for this invention is as follows.

[0010] (The means described in Option 1)

[0011] A fibrous cellulose inclusion, which is added to a resin, is characterized in that...

[0012] The average fiber width of the aforementioned fibrous cellulose is 0.1 μm to 19 μm, and some or all of the hydroxyl groups are replaced by urethane groups.

[0013] The fibrous cellulose content includes powder that interacts with the aforementioned fibrous cellulose.

[0014] (The means described in Option 2)

[0015] The fibrous cellulose inclusions as described in Scheme 1, wherein the 90% / 10% particle size of the interacting powder is 2 to 1000.

[0016] (The means described in Option 3)

[0017] The fibrous cellulose inclusion as described in Scheme 1 or Scheme 2, wherein the volume average particle size of the interacting powder is 0.01 μm to 10000 μm, and the volume average particle size (μm) of the interacting powder / the average fiber length (μm) of the fibrous cellulose is 0.005 to 5000.

[0018] (The means described in Option 4)

[0019] The fibrous cellulose content as described in any one of Schemes 1 to 3, wherein the proportion of the fibrous cellulose with a fiber length less than 0.2 mm is 5% or more, and the proportion of the fibrous cellulose with a fiber length of 0.2 mm to 0.6 mm is 10% or more.

[0020] (The means described in Option 5)

[0021] The fibrous cellulose contained in any one of Schemes 1 to 4, wherein the average fiber length of the fibrous cellulose is 1.0 mm or less, the average fiber width is 10 μm or less, and the fibrillation rate is 2.5% or more.

[0022] (The means described in Option 6)

[0023] The fibrous cellulose content as described in any one of Schemes 1 to 5, wherein the interacting powder is an acid-modified resin with an acid value of 2.0% or higher.

[0024] (The means described in Scheme 7)

[0025] The fibrous cellulose content as described in any one of Schemes 1 to 6, wherein the powder involved in the interaction is maleic anhydride-modified polypropylene.

[0026] (The means described in Scheme 8)

[0027] A fibrous cellulose composite resin, comprising a mixture of fibrous cellulose and resin, characterized in that...

[0028] The fibrous cellulose contained in any one of Schemes 1 to 7 is used as the above-mentioned fibrous cellulose.

[0029] (The means described in Scheme 9)

[0030] A method for manufacturing a fibrous cellulose inclusion, characterized in that fibrous cellulose with some or all of its hydroxyl groups replaced by carbamate groups is opened to an average fiber width of 0.1 μm to 19 μm, and then mixed with a powder that interacts with the fibrous cellulose to obtain a mixture.

[0031] The mixture is then dried.

[0032] The effects of the invention

[0033] According to the present invention, a fibrous cellulose inclusion with excellent dispersibility even when dried, a method for manufacturing the same, and a fibrous cellulose composite resin with excellent strength are obtained. Detailed Implementation

[0034] The specific implementation method is described below. It should be noted that this implementation method is only one example of the present invention. The scope of the present invention is not limited to the scope of this implementation method.

[0035] In this method, a fibrous cellulose inclusion is added to a resin. The fibrous cellulose (hereinafter also referred to as "cellulose fiber") is a urethane-modified microfiber cellulose with an average fiber width of 0.1 μm to 19 μm, and where some or all of the hydroxyl groups (-OH groups) are substituted with urethane groups. Furthermore, the fibrous cellulose inclusion contains a powder that interacts with the fibrous cellulose (hereinafter also simply referred to as "interacting powder"). This powder is preferably an acid-modified resin, wherein the acid groups of the acid-modified resin are ionicly bonded to some or all of the urethane groups. Additionally, by adding this fibrous cellulose inclusion to the resin, a fibrous cellulose composite resin is obtained. Furthermore, in the method for manufacturing the fibrous cellulose inclusion, fibrous cellulose with some or all of the hydroxyl groups substituted with urethane groups is opened to an average fiber width of 0.1 μm to 19 μm, and the powder that interacts with the fibrous cellulose is added to obtain a mixture, which is then dried. Detailed explanation follows.

[0036] (Fibrous cellulose)

[0037] In this method, the fibrous cellulose as microfibrils is microfibril cellulose (microfibrillated cellulose) with an average fiber diameter of 0.1 μm to 19 μm. If microfibril cellulose is used, the reinforcing effect of the resin is significantly improved. Furthermore, compared to cellulose nanofibers, which are also microfibrils, microfibril cellulose is easier to modify using urethane groups (urethane oxidation). More preferably, the cellulose raw material before microfiberization is urethane-oxidized; in this case, microfibril cellulose and cellulose nanofibers are equivalent.

[0038] In this method, microfibrillated cellulose refers to fibers with an average fiber width that is thicker than that of cellulose nanofibers. Specifically, the average fiber diameter (width) is, for example, 0.1 μm to 19 μm, preferably 0.2 μm to 10 μm, and more preferably more than 0.5 to 10 μm. If the average fiber diameter of the fibrous cellulose is less than 0.1 μm, it is indistinguishable from cellulose nanofibers, and the effect of improving the strength (especially the flexural modulus) of the resin may not be fully achieved. In addition, the fiber-opening time becomes longer, requiring a large amount of energy. Furthermore, the dehydration properties of the cellulose fiber slurry deteriorate. If the dehydration properties deteriorate, a large amount of energy is required during drying, and when a large amount of energy is applied during drying, the fibrous cellulose will undergo thermal degradation, and the strength may decrease. Moreover, if the fiber opening reaches an average fiber diameter of less than 0.1 μm, the deviation in fiber length of the fibrous cellulose becomes smaller, making it difficult to achieve the effect of this method in specifying the particle size distribution of the powders that interact.

[0039] On the other hand, if the average fiber diameter of the fibrous cellulose is higher than 19 μm, it becomes indistinguishable from pulp, and the reinforcing effect may become insufficient. Furthermore, in open-fiber processes with an average fiber diameter higher than 19 μm, the deviation in fiber length of the fibrous cellulose is small, making it difficult to achieve the desired effect of this method, which specifies the particle size distribution of the interacting powders. In particular, if the average fiber diameter is 10 μm or less, it combines well with the powders that have an average fiber length of 1.0 mm or less and a fibrillation rate of 2.5% or more, resulting in good entanglement with the interacting powders.

[0040] Furthermore, the mode diameter (width) of the fibrous cellulose is preferably 0.1 μm to 19 μm, more preferably 0.5 μm to 10 μm, and particularly preferably 1 μm to 6 μm. Regarding this, as will be explained later, in this method where the fiber length of the fibrous cellulose is uneven, since fibers with large fiber widths exist in a certain proportion during the fiber opening process, it is preferable to determine the fibrous cellulose based on the mode diameter, which has the largest quantity, compared to determining it based on the average fiber diameter. From this perspective, it can be said that if the mode diameter is less than 0.1 μm, the proportion of cellulose nanofibers tends to increase, causing the cellulose nanofibers to aggregate and potentially resulting in insufficient reinforcement. On the other hand, if the mode diameter exceeds 19 μm, the proportion of pulp tends to increase, and the reinforcement effect may also become insufficient.

[0041] The method for determining the average fiber diameter of microfibers (microfiber cellulose and cellulose nanofibers) is described below.

[0042] First, 100 ml of an aqueous dispersion of microfibers with a solid content of 0.01%–0.1% by mass was filtered through a Teflon (registered trademark) membrane filter. The solution was then subjected to one solvent exchange with 100 ml of ethanol and three solvent exchanges with 20 ml of tert-butanol. Next, the solution was freeze-dried and coated with osmium to prepare a sample. This sample was then observed using SEM (Self-Electron Microscopy) images at any magnification of 3,000x to 30,000x, depending on the width of the fibers. Specifically, two diagonal lines were drawn on the observed image, and three straight lines were arbitrarily drawn passing through the intersection of the diagonal lines. The width of a total of 100 fibers intersecting these three straight lines was then visually measured. The median diameter of the measured values ​​was taken as the average fiber diameter.

[0043] In addition, the mode diameter of the microfibers was determined using a fiber analyzer "FS5" manufactured by Valmet.

[0044] However, when the fibrous cellulose is microfibrillated cellulose, it exhibits a greater degree of variation in fiber length and other characteristics. This is based on the following reasons.

[0045] First, pulp is manufactured, for example, by boiling wood chips under pressure with alkali and then unraveling them upon returning to normal pressure, without applying mechanical fiber-opening. Therefore, wood cells are directly separated to form pulp, resulting in relatively uniform fiber length. In contrast, the fuzzing portion of cellulose nanofibers is independently separated, and most of the pulp consists of fibers from these individual fuzzing portions. Consequently, fiber length is also relatively uniform. In contrast, microfiber cellulose is in the middle stage of fiber fuzzing caused by applying mechanical fiber-opening force to the pulp, resulting in a wider distribution of fiber length.

[0046] Microfibrillated cellulose typically contains at least 5% fibers with a length less than 0.2 mm, and at least 10% fibers with a length between 0.2 mm and 0.6 mm. Preferably, the proportion of fibers with a length less than 0.2 mm is at least 8%, and at least 13% fibers with a length between 0.2 mm and 0.6 mm. More preferably, the proportion of fibers with a length less than 0.2 mm is at least 20%, and at least 16% fibers with a length between 0.2 mm and 0.6 mm. If the fiber length of the microfibrillated cellulose is uneven as described above, the effect of this method of specifying the particle size distribution of the powders that interact with each other is fully realized.

[0047] Furthermore, especially if the proportion of fibers with a length less than 0.2 mm is too high, the entanglement of powders interacting with larger particle sizes becomes insufficient, potentially leading to reduced dispersibility. On the other hand, if the proportion of fibers with a length greater than 0.6 mm is too high, the entanglement of powders interacting with smaller particle sizes becomes insufficient, potentially leading to reduced dispersibility.

[0048] As mentioned above, the variation in fiber length and other parameters of microfibrillated cellulose is relatively large. However, if the proportion of fibers with a length less than 0.2 mm is too high, or the proportion of fibers with a length greater than 0.6 mm is too high, the reinforcing effect of the resin itself as a fiber may deteriorate. Therefore, it is preferable that the proportion of fibrous cellulose with a fiber length of 0.2 mm to 0.6 mm is 10% to 90%, more preferably 14% to 70%, and particularly preferably 16% to 50%. If the proportion of fibers with a length of 0.2 mm to 0.6 mm is less than 14%, the entanglement with the interacting powder becomes insufficient, and as a result, the reinforcing effect may not be fully realized.

[0049] Microfiber cellulose can be obtained by opening (microfiberizing) cellulose raw materials (hereinafter also referred to as "raw material pulp"). Raw material pulp can be selected from one or more of the following: wood pulp made from broadleaf trees, coniferous trees, etc.; non-wood pulp made from rice straw, bagasse, cotton, hemp, bast fibers, etc.; and waste paper pulp (DIP) made from recycled waste paper, damaged paper, etc. It should be noted that the above-mentioned raw materials can be in the form of pulverized matter (powder), such as cellulose-based powder.

[0050] In order to minimize the introduction of impurities, wood pulp is preferred as the raw material pulp. As wood pulp, one or more types can be selected from chemical pulps such as broadleaf sulfate pulp (LKP) and softleaf sulfate pulp (NKP), as well as mechanical pulp (TMP).

[0051] Broadleaf sulfate pulp can be bleached broadleaf sulfate pulp, unbleached broadleaf sulfate pulp, or semi-bleached broadleaf sulfate pulp. Similarly, coniferous sulfate pulp can be bleached coniferous sulfate pulp, unbleached coniferous sulfate pulp, or semi-bleached coniferous sulfate pulp.

[0052] As mechanical pulp, one or more of the following can be selected: stone mill pulp (SGP), pressure stone mill pulp (PGW), wood chip pulp (RGP), chemical fine pulp (CGP), thermomechanical pulp (TGP), GP, thermomechanical pulp (GP), thermomechanical pulp (TMP), chemothermal-mechanical pulp (CTMP), disc-milled mechanical pulp (RMP), bleached thermomechanical pulp (BTMP), etc.

[0053] Raw pulp can be pretreated chemically before fiber opening. Examples of chemical pretreatment include polysaccharide hydrolysis using acid (acid treatment), polysaccharide hydrolysis using enzymes (enzyme treatment), polysaccharide swelling using alkali (alkali treatment), polysaccharide oxidation using oxidizing agents (oxidation treatment), and polysaccharide reduction using reducing agents (reduction treatment). Among these, enzyme treatment is preferred as a chemical pretreatment, and one or more treatments selected from acid treatment, alkali treatment, and oxidation treatment are more preferred. Enzyme treatment will be described in detail below.

[0054] The enzymes used in the enzymatic treatment are preferably at least one of cellulase-based enzymes and hemicellulase-based enzymes, and more preferably a combination of both. When these enzymes are used, the decomposition of cellulose raw materials becomes easier. It should be noted that cellulase-based enzymes cause the decomposition of cellulose in the presence of water. Similarly, hemicellulase-based enzymes cause the decomposition of hemicellulose in the presence of water.

[0055] Cellulase system enzymes can be produced by fungi such as *Trichoderma*, *Acremonium*, *Aspergillus*, *Phanerochaete*, *Trametes*, *Humicola*, *Bacillus*, *Schizophyllum*, *Streptomyces*, and *Pseudomonas*. These cellulase system enzymes can be purchased as reagents or commercially available products. Commercially available products include, for example, Cellulosin T2 (manufactured by HBI Corporation), Meicelase (manufactured by Meiji Seika Corporation), Novozyme 188 (manufactured by Novozyme Corporation), Multifect CX10L (manufactured by Genencor Corporation), and cellulase GC220 (manufactured by Genencor Corporation).

[0056] In addition, either EG (endoglucanase) or CBH (exoglucanase) can be used as a cellulase system enzyme. EG and CBH can be used alone or in combination. Alternatively, they can be used in combination with hemicellulase system enzymes.

[0057] As hemicellulase enzymes, examples include xylanase (an enzyme that breaks down xylan), mannanase (an enzyme that breaks down mannan), and arabanase (an enzyme that breaks down arabinogalactan). Additionally, pectinase (an enzyme that breaks down pectin) can also be used.

[0058] Hemicellulose is a polysaccharide, excluding pectin, located between cellulose microfibrils in plant cell walls. The types of hemicellulose are diverse and vary depending on the type of wood and the interlayer structure of the cell wall. In the secondary cell walls of coniferous trees, glucomannan is the main component; in the secondary cell walls of broadleaf trees, 4-O-methylglucuronide xylan is the main component. Therefore, in the case of obtaining fine fibers from bleached sulfate pulp (NBKP) of coniferous trees, mannanase is preferred. Similarly, in the case of obtaining fine fibers from bleached sulfate pulp (LBKP) of broadleaf trees, xylanase is preferred.

[0059] The amount of enzyme added relative to the cellulose raw material is determined by factors such as the type of enzyme, the type of wood (coniferous or broadleaf), and the type of mechanical pulp. Preferably, the amount of enzyme added relative to the cellulose raw material is 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 effects of the enzyme addition may not be fully realized. On the other hand, if the amount of enzyme added is greater than 3% by mass, the cellulose may be saccharified, and the yield of fine fibers may decrease. Furthermore, there is the problem that the improvement in effect corresponding to the increase in the amount added may not be observed.

[0060] When using cellulase-based enzymes, the pH during enzyme treatment is preferably in a weakly acidic range (pH = 3.0–6.9) from the perspective of enzyme reactivity. On the other hand, when using hemicellulase-based enzymes, the pH during enzyme treatment is preferably in a weakly alkaline range (pH = 7.1–10.0).

[0061] When using either cellulase-based or hemicellulase-based enzymes as the enzyme, the temperature for enzyme treatment is preferably 30°C to 70°C, more preferably 35°C to 65°C, and particularly preferably 40°C to 60°C. If the temperature during enzyme treatment is above 30°C, the enzyme activity is less likely to decrease, preventing prolonged treatment time. On the other hand, when the temperature during enzyme treatment is below 70°C, enzyme inactivation can be prevented.

[0062] The enzyme treatment time is determined by factors such as the type of enzyme, the temperature of the enzyme treatment, and the pH during the enzyme treatment. Generally, the enzyme treatment time ranges from 0.5 hours to 24 hours.

[0063] After enzyme treatment, it is preferable to inactivate the enzyme. Methods for inactivating 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°C to 100°C.

[0064] Next, the method of alkali treatment will be explained.

[0065] When alkaline treatment is performed before fiber opening, the hydroxyl groups of hemicellulose and cellulose in the pulp partially dissociate, and the molecules become anionic. This weakens the intramolecular and intermolecular hydrogen bonds, promoting the dispersion of cellulose raw materials during fiber opening.

[0066] Examples of alkalis used in alkaline treatment include sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia solution, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, and other organic alkalis. Among these, sodium hydroxide is preferred from a manufacturing cost perspective.

[0067] Enzyme treatment, acid treatment, and oxidation treatment before fiber opening can reduce the water retention of microfiber cellulose, increase its crystallinity, and improve its homogeneity. In this respect, if the water retention of microfiber cellulose is low, it is easier to dehydrate, thus improving the dehydration properties of the cellulose fiber pulp.

[0068] When raw pulp is subjected to enzymatic, acid, or oxidative treatments, the amorphous regions of hemicellulose or cellulose in the pulp are decomposed. This results in a reduction of fiber-opening energy and an improvement in the uniformity and dispersibility of cellulose fibers. However, pretreatment reduces the aspect ratio of microfiber cellulose; therefore, when used as a resin reinforcing material, excessive pretreatment is preferable to avoid.

[0069] The fiber opening of raw pulp can be achieved by using homogenizers such as refiners, high-pressure homogenizers, high-pressure homogenization devices, mills, grinding mills, mortar and pestle mills, single-screw mixers, multi-screw mixers, kneading mills, and jet mills. Among these methods, kneading mills and jet mills are preferred.

[0070] The average fiber length (average length of a single fiber) of the microfiber cellulose is preferably 0.10 mm to 2.00 mm, more preferably 0.12 mm to 1.50 mm, and particularly preferably 0.15 mm to 1.00 mm. If the average fiber length is less than 0.10 mm, a three-dimensional network of fibers cannot be formed, and the reinforcing effect of the composite resin (especially the flexural modulus) may be reduced. Furthermore, it may not be able to fully entangle with the interacting powder. On the other hand, if the average fiber length is greater than 2.00 mm, the length is no different from that of the raw pulp, and therefore the reinforcing effect may be insufficient. Additionally, fiber agglomeration may occur, and it may not be able to fully entangle with the interacting powder.

[0071] The average fiber length of the cellulose raw material used as the raw material for microfiber cellulose is preferably 0.50 mm to 5.00 mm, more preferably 1.00 mm to 3.00 mm, and particularly preferably 1.50 mm 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 during the fiber-opening process may not be sufficiently obtained. On the other hand, if the average fiber length is greater than 5.00 mm, it may become disadvantageous in terms of manufacturing costs during fiber opening.

[0072] The average fiber length of microfibril cellulose can be arbitrarily adjusted, for example, by selecting the raw pulp, pretreatment, and fiber opening.

[0073] The aspect ratio of the microfibril 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 constructed, and therefore the reinforcing effect may be insufficient even if the average fiber length exceeds 0.10 mm. Furthermore, if the aspect ratio is less than 2, the number of points that can interact with the spherical powder becomes too small, resulting in insufficient interaction and failing to fully utilize the compatibility between the interacting powder and the fiber, thus the reinforcing effect may be insufficient. On the other hand, if the aspect ratio is greater than 15,000, the microfibrils cellulose become more entangled with each other, and the dispersion in the resin may be insufficient. Additionally, the interaction between the fibers and the interacting powder may not occur sufficiently, resulting in an insufficient reinforcing effect.

[0074] The aspect ratio is the value obtained by dividing the average fiber length by the average fiber width. It is known that the larger the aspect ratio, the more hooking points there are, and therefore the better the reinforcing effect. However, on the other hand, the resin's ductility decreases accordingly with the increase in hooking.

[0075] The fibrillation rate of microfibrillated cellulose is preferably 1.0% to 30.0%, more preferably 1.5% to 20.0%, and particularly preferably 2.5% to 15.0%. If the fibrillation rate is higher than 30.0%, the contact area with water becomes too large, so even if fiber opening can be carried out within a range where the average fiber width is maintained at 0.1 μm or more, dehydration may be difficult. In addition, if the fibrillation rate is higher than 30.0%, the surface area becomes too large, and the fibers easily retain water, so it may be difficult for them to interact with the powders that will interact with each other. On the other hand, if the fibrillation rate is lower than 1.0%, there are fewer hydrogen bonds between the fibrils, and it may be impossible to form a strong three-dimensional network. In addition, if the fibrillation rate is lower than 2.5%, the entanglement with the powders that will interact with each other tends to be worse.

[0076] The fiber length and fibrillation rate were determined using a Valmet FS5 fiber analyzer.

[0077] The crystallinity of microfibrillated cellulose is preferably 50% or more, more preferably 55% or more, and particularly preferably 60% or more. If the crystallinity is less than 50%, although the miscibility with other cellulose fibers, such as pulp or cellulose nanofibers, is improved, the strength of the fibers themselves decreases, and therefore the strength of the resin may not be improved. On the other hand, the crystallinity of microfibrillated cellulose is preferably 95% or less, more preferably 90% or less, and particularly preferably 85% or less. If the crystallinity is greater than 95%, the proportion of strong hydrogen bonds within the molecules increases, the fibers themselves become rigid, and the dispersibility deteriorates.

[0078] The crystallinity of microfibrillated cellulose can be arbitrarily adjusted, for example, by selecting the raw pulp, pretreatment, and micronization.

[0079] Crystallinity was determined according to JIS K 0131 (1996).

[0080] The pulp viscosity of microfibrillated cellulose is preferably 2 cps or more, and more preferably 4 cps or more. If the pulp viscosity of microfibrillated cellulose is lower than 2 cps, it may be difficult to suppress the aggregation of microfibrillated cellulose. In addition, if the pulp viscosity is lower than 2 cps, even if the interaction with the interacting powder is achieved, the reinforcing properties of the resin may become insufficient.

[0081] The pulp viscosity is a value determined according to TAPPI T 230.

[0082] The degree of freeness of microfibrillated cellulose is preferably 500 ml or less, more preferably 300 ml or less, and particularly preferably 100 ml or less. If the degree of freeness of microfibrillated cellulose is higher than 500 ml, the effect of improving the strength of the resin may not be fully obtained. In addition, the mutual entanglement of the interacting powders deteriorates, which may not be able to sufficiently suppress the aggregation of fibers.

[0083] The freeness was measured according to JIS P8121-2 (2012).

[0084] The zeta potential of the microfibril cellulose is preferably -150mV to 20mV, more preferably -100mV to 0mV, and particularly preferably -80mV to -10mV. If the zeta potential is below -150mV, the compatibility with the resin is significantly reduced, and the reinforcing effect may become insufficient. On the other hand, if the zeta potential is above 20mV, the dispersion stability may decrease.

[0085] The water retention of microfiber cellulose is preferably 80% to 400%, more preferably 90% to 350%, and particularly preferably 100% to 300%. If the water retention is below 80%, it is no different from the raw pulp, and therefore the reinforcing effect may be insufficient. On the other hand, if the water retention is above 400%, the dehydration properties tend to deteriorate, and aggregation is prone to occur. In this regard, since the hydroxyl groups of the fiber are replaced with urethane groups, the water retention of microfiber cellulose can be further reduced, thereby improving dehydration and drying properties.

[0086] The water retention of microfiber cellulose can be adjusted arbitrarily, for example, by selecting the raw pulp, pretreatment, and fiber opening.

[0087] The water retention is measured according to JAPAN TAPPI No.26 (2000).

[0088] The microfibrillated cellulose produced in this manner has urethane groups. There are no particular limitations on how urethane groups are formed. For example, urethane groups can be formed by urethane esterification of cellulose raw materials, or by urethane esterification of microfibrillated cellulose (micronized cellulose raw materials).

[0089] It should be noted that the presence of a urethane group refers to the state in which urethane (an ester of carbamate) is introduced into fibrous cellulose. The urethane group is a group represented by -O-CO-NH-, such as -O-CO-NH2, -O-CONHR, -O-CO-NR2, etc. That is, the urethane group can be represented by the following structural formula (1).

[0090] [Chemistry 1]

[0091]

[0092] Here, R is each independently at least one of a saturated straight-chain hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated straight-chain hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, and their derivative groups.

[0093] Examples of saturated straight-chain hydrocarbon groups include methyl, ethyl, and propyl, which are straight-chain alkyl groups with 1 to 10 carbon atoms.

[0094] Examples of saturated branched hydrocarbon groups include isopropyl, sec-butyl, isobutyl, tert-butyl, and other branched alkyl groups with 3 to 10 carbon atoms.

[0095] Examples of saturated cyclic hydrocarbon groups include cyclopentyl, cyclohexyl, and norbornyl cycloalkyl groups.

[0096] Examples of unsaturated straight-chain hydrocarbon groups include vinyl, propen-1-yl, propen-3-yl, and other straight-chain alkenyl groups with 2 to 10 carbon atoms, as well as ethynyl, propyn-1-yl, propyn-3-yl, and other straight-chain alkynyl groups with 2 to 10 carbon atoms.

[0097] Examples of unsaturated branched hydrocarbon groups include branched alkenyl groups with 3 to 10 carbon atoms, such as propen-2-yl, buten-2-yl, and buten-3-yl, and branched alkyne groups with 4 to 10 carbon atoms, such as butyn-3-yl.

[0098] Examples of aromatic groups include phenyl, tolyl, xylyl, and naphthyl.

[0099] As a derived group, examples include groups formed by replacing one or more hydrogen atoms of the above-mentioned saturated straight-chain hydrocarbon groups, saturated branched hydrocarbon groups, saturated cyclic hydrocarbon groups, unsaturated straight-chain hydrocarbon groups, unsaturated branched hydrocarbon groups, and aromatic groups with substituents (such as hydroxyl, carboxyl, halogen atoms, etc.).

[0100] In microfibrillated cellulose containing urethane groups (with urethane incorporated), some or all of the highly polar hydroxyl groups are replaced with relatively less polar urethane groups. Therefore, microfibrillated cellulose with urethane groups exhibits low hydrophilicity and high affinity for resins with low polarity. Consequently, microfibrillated cellulose with urethane groups exhibits excellent uniform dispersibility with resins. Furthermore, slurries made from microfibrillated cellulose with urethane groups have low viscosity and good processability.

[0101] The substitution rate of the urethane groups for the hydroxyl groups in microfibrillated cellulose is preferably 1.0 mmol / g to 5.0 mmol / g, more preferably 1.2 mmol / g to 3.0 mmol / g, and particularly preferably 1.5 mmol / g to 2.0 mmol / g. A substitution rate of 1.0 mmol / g or higher ensures the effective introduction of the urethane, particularly improving the flexural elongation of the resin. Conversely, if the substitution rate exceeds 5.0 mmol / g, the cellulose fibers may not maintain their shape, potentially resulting in insufficient resin reinforcement.

[0102] It should be noted that the substitution rate of the carbamate group (mmol / g) refers to the amount of carbamate group contained in 1g of cellulose raw material containing carbamate groups. Furthermore, cellulose is a polymer with dehydrated glucose as its structural unit, and each structural unit has three hydroxyl groups.

[0103] <Carbamate>

[0104] Regarding the introduction of carbamates (carbamate esterification) into microfiber cellulose (a cellulose raw material that has undergone carbamate esterification before fiber splitting; hereinafter also referred to as "microfiber cellulose, etc."), there are methods described above for both carbamate esterification followed by micronization of the cellulose raw material and carbamate esterification followed by micronization of the cellulose raw material. In this specification, the fiber splitting of the cellulose raw material will be described first, followed by carbamate esterification (modification). However, either fiber splitting or carbamate esterification can be performed in any order. However, it is preferable to perform carbamate esterification first, followed by fiber splitting. This is because the cellulose raw material has high dehydration efficiency before fiber splitting, and the heating accompanying carbamate esterification makes the cellulose raw material easier to split.

[0105] The process of urethane esterification of microfibrils, cellulose, etc., can be mainly divided into mixing treatment, removal treatment, and heat treatment. It should be noted that the mixing treatment and removal treatment can also be collectively referred to as conditioning treatment for preparing a mixture for heat treatment.

[0106] In the mixing process, microfibrillated cellulose and the like (as mentioned above, there are also cases where cellulose raw materials are used, and the same applies below) are mixed with urea and / or urea derivatives (hereinafter also simply referred to as "urea and the like") in a dispersion medium.

[0107] Urea or urea derivatives can be used, for example, urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and compounds obtained by substituting the hydrogen atoms of urea with alkyl groups. These ureas or urea derivatives can be used alone or in combination. Urea is preferred.

[0108] The lower limit of the mixing mass ratio of urea, etc., to microfibrillated cellulose, etc. (urea, etc. / microfibrillated 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 making the mixing mass ratio 10 / 100 or higher, the efficiency of carbamate esterification is improved. On the other hand, even if the mixing mass ratio is higher than 300 / 100, carbamate esterification reaches its limit.

[0109] The dispersion medium is usually water. However, other dispersion media such as alcohols and ethers, or mixtures of water and other dispersion media can also be used.

[0110] In the mixing process, for example, microcellulose and urea can be added to water, microcellulose can be added to an aqueous solution of urea, or urea can be added to a slurry containing microcellulose. Furthermore, stirring can be performed after addition to ensure uniform mixing. Additionally, other components can be included in the dispersion containing microcellulose and urea.

[0111] In the removal process, the dispersion medium is removed from the dispersion containing microfibrils, cellulose, and urea obtained from the mixing process. By removing the dispersion medium, urea and the like can be effectively reacted in the subsequent heat treatment.

[0112] The removal of the dispersion medium is preferably carried out by heating to volatilize the dispersion medium. According to this method, only the dispersion medium can be effectively removed while the residual components such as urea remain.

[0113] Regarding the lower limit of the heating temperature during the removal process, when the dispersion medium is water, 50°C is preferred, 70°C is more preferred, and 90°C is particularly preferred. By raising the heating temperature to 50°C or higher, the dispersion medium can be effectively 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 is higher than 120°C, the dispersion medium reacts with the urea, and the urea may decompose independently.

[0114] The heating time during the removal process can be appropriately adjusted according to factors such as the concentration of solid components in the dispersion. Specifically, for example, it can be 6 to 24 hours.

[0115] In the subsequent heat treatment following the removal process, a mixture of microfibrillated cellulose and urea is subjected to heat treatment. In this heat treatment, some or all of the hydroxyl groups of the microfibrillated cellulose react with urea and are replaced with urethane groups. More specifically, when urea is heated, it decomposes into isocyanate and ammonia as shown in reaction formula (1) below. Furthermore, isocyanate is highly reactive and, for example, forms urethane with the hydroxyl groups of cellulose as shown in reaction formula (2) below.

[0116] NH2-CO-NH2→HN=C=O+NH3…(1)

[0117] Cell-OH+HN=C=O→Cell-O-CO-NH2…(2)

[0118] 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), further preferably 140°C, and most preferably 150°C. By heating at a temperature of 120°C or higher, urethane esterification can be effectively carried out. 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, microfibrils and the like may decompose, and the reinforcing effect may be insufficient.

[0119] The lower limit of the heating time in the heat treatment is preferably 1 minute, more preferably 5 minutes, particularly preferably 30 minutes, further preferably 1 hour, and most preferably 2 hours. By making the heating time 1 minute or more, the carbamate reaction can be reliably carried out. On the other hand, the upper limit of the heating time is preferably 15 hours, more preferably 10 hours. If the heating time is higher than 15 hours, it is uneconomical, and 15 hours is sufficient to carry out carbamate esterification.

[0120] However, prolonged heating time leads to the deterioration of cellulose fibers. Therefore, the pH conditions during heat treatment are important. The pH is preferably 9 or higher, more preferably 9-13, and particularly preferably alkaline conditions of pH 10-12. As a second-best alternative, acidic or neutral conditions of pH 7 or lower, preferably pH 3-7, and particularly preferably pH 4-7 are preferred. If neutral conditions of pH 7-8 are used, the average fiber length of the cellulose fibers becomes shorter, and the reinforcing effect of the resin may deteriorate. Conversely, alkaline conditions of pH 9 or higher increase the reactivity of the cellulose fibers, promoting reactions with urea, etc., and efficiently carrying out the carbamate esterification reaction, thus ensuring a sufficiently high average fiber length. On the other hand, acidic conditions of pH 7 or lower allow the reaction of urea, etc., into isocyanate and ammonia to proceed, promoting the reaction with the cellulose fibers and efficiently carrying out the carbamate esterification reaction, thus ensuring a sufficiently high average fiber length. However, if possible, heat treatment under alkaline conditions is preferred. This is because acidic conditions may lead to acid hydrolysis of cellulose.

[0121] pH can be adjusted by adding acidic compounds (such as acetic acid, citric acid, etc.) or alkaline compounds (such as sodium hydroxide, calcium hydroxide, etc.) to the mixture.

[0122] As a device for heating in heat treatment, a hot air dryer, a paper machine, a pulp dryer, etc. can be used.

[0123] The mixture after heat treatment can be washed. This washing can be done with water or similar substances. This washing removes any unreacted residues of urea, etc.

[0124] (slurry)

[0125] Microcellulose fibers are dispersed in an aqueous medium to form a dispersion (slurry). The aqueous medium is preferably entirely water, but other liquids compatible with water can also be used as a component. As other liquids, lower alcohols with 3 or fewer carbon atoms can be used.

[0126] 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 below 0.1% by mass, excessive energy may be required during dehydration and drying. On the other hand, if the solids concentration is above 10.0% by mass, the fluidity of the slurry itself decreases, and it may not be able to mix uniformly when using a dispersant.

[0127] (Powders that interact)

[0128] The fibrous cellulose inclusions of this method contain powder that interacts with the fibrous cellulose. By including this interacting powder in the fibrous cellulose inclusions, the fibrous cellulose can be made to exert the reinforcing properties of the resin. That is, when using fibrous cellulose in slurry form, it is preferable to remove the aqueous medium contained in the slurry before compounding with the resin. However, when removing the aqueous medium, the cellulose fibers irreversibly aggregate together through hydrogen bonds, which may prevent them from fully exerting their reinforcing effect as fibers. Therefore, by including the interacting powder in the fibrous cellulose slurry, the hydrogen bonds between the cellulose fibers are physically prevented. In addition, in the case of powders that do not interact, the powders that do not interact may aggregate together during drying, but this possibility is low in the case of powders that interact. From this point of view, the interacting powder is preferably an acid-modified resin, more preferably a maleic anhydride-modified resin, and particularly preferably maleic anhydride-modified polypropylene (MAPP). Details of the acid-modified resin are described below.

[0129] Here, "interaction" refers to a strong bond between cellulose and covalent bonds, ionic bonds, or metallic bonds (i.e., bonds based on hydrogen bonds or van der Waals forces are not included in the concept of interaction). Preferably, a strong bond is one with a bond energy of 100 kJ / mol or higher.

[0130] The volume average particle size of the interacting powder is preferably 0.01 μm to 10000 μm, more preferably 50 μm to 750 μm, and particularly preferably 150 μm to 450 μm. If the volume average particle size exceeds 10000 μm, the interacting powder may enter the gaps between the cellulose fibers and may not be able to exert an anti-agglomeration effect. On the other hand, if the volume average particle size is less than 0.01 μm, it may not be able to suppress the hydrogen bonds between the microfibrils due to its fine size.

[0131] The 90% particle size / 10% particle size ratio of the interacting powder is preferably 2 to 1000, more preferably 10 to 200. By keeping the particle size ratio within this range, the aggregation inhibition effect of the interacting powder can be fully utilized even when the fibrous cellulose is microfibrillated cellulose and there are deviations in fiber length. Specifically, if the 90% particle size / 10% particle size ratio is less than 2, the particle size is too uniform, and it may be difficult to achieve an interaction effect only with fibers of a specific fiber length. On the other hand, if the 90% particle size / 10% particle size ratio exceeds 1000, the deviation in particle size becomes extreme, and the length of the interacting fiber may be limited.

[0132] The 90% particle size refers to the particle size measured sequentially from the smallest particles, reaching a proportion of 90%. The 10% particle size refers to the particle size measured sequentially from the smallest particles, reaching a proportion of 10%.

[0133] The arithmetic standard deviation of the interacting powders is preferably 0.01 μm to 10000 μm, more preferably 1 μm to 5000 μm, and particularly preferably 10 μm to 1000 μm. As described above, although the particle size of the powder is varied, fibrous cellulose has a range in the sense that it is microfibrillary cellulose, and therefore the arithmetic standard deviation of a particular powder is possible. In this regard, if the arithmetic standard deviation is less than 0.01 μm, the particle size becomes uniform, and it may be difficult to achieve an interaction effect only with fibers of a specific fiber length. On the other hand, if the arithmetic standard deviation exceeds 10000 μm, the particle size becomes excessively non-uniform, and the range of fiber lengths that can interact becomes wider, which may make it difficult to achieve an interaction effect.

[0134] The arithmetic standard deviation is a value measured using a particle size distribution measuring device (such as the laser diffraction / scattering particle size distribution measuring device of Horiba Corporation).

[0135] Furthermore, the volume average particle size (μm) of the interacting powders / the average fiber length (μm) of the fibrous cellulose is preferably 0.005 to 5000, more preferably 0.01 to 1000. Within this range, the powder and fibers become further entangled, and fiber aggregation is suppressed. More specifically, if the volume average particle size of the interacting powders / the average fiber length of the fibrous cellulose is less than 0.005, the fibers interact with each other, and sufficient interaction with the interacting powders cannot be achieved, potentially resulting in insufficient reinforcement. On the other hand, if the volume average particle size of the interacting powders / the average fiber length of the fibrous cellulose exceeds 5000, the number of points capable of interacting with the spherical interacting powders becomes too small, thus insufficient interaction cannot be achieved, potentially resulting in insufficient reinforcement.

[0136] In this specification, the volume average particle size of the interacting powders is calculated from the volume average particle size distribution measured directly or in an aqueous dispersion using a particle size distribution measuring device (e.g., a laser diffraction / scattering particle size distribution measuring device from Horiba Manufacturing Co., Ltd.).

[0137] In this method, the interacting powder is preferably a resin powder. If the interacting powder is a resin powder, it melts rather than granulates during mixing, so the presence of particles with different particle sizes has no effect. For example, the same resin powder used to obtain the composite resin can be used as the resin powder. Of course, different types can also be used.

[0138] The amount of the interacting powders mixed relative to the fibrous cellulose is preferably 1% to 9,900% by mass, more preferably 5% to 1,900% by mass, and particularly preferably 10% to 900% by mass. If the amount mixed is less than 1% by mass, the effect of inhibiting aggregation by entering the gaps between the cellulose fibers may not be fully realized. On the other hand, if the amount mixed is greater than 9,900% by mass, the function as a cellulose fiber may not be realized.

[0139] In addition, inorganic powders can be combined with interacting powders. When interacting powders and inorganic powders are combined, even if the inorganic powders themselves or the interacting powders aggregate, the inorganic powders and interacting powders will mutually prevent agglomeration. Furthermore, small-particle-size powders have a large surface area and are more susceptible to intermolecular forces than gravity, resulting in easy agglomeration. Therefore, when mixing powders with microfibrillated cellulose slurries, the powders may not dissolve smoothly in the slurry, or they may aggregate upon removal from the aqueous medium, thus failing to fully exert the effect of preventing microfibrillated cellulose agglomeration. However, combining inorganic powders and interacting powders is considered to mitigate their own agglomeration.

[0140] Examples of inorganic powders include, for example, the elemental forms, oxides, hydroxides, carbonates, sulfates, silicates, sulfites, and various clay minerals composed of these compounds of metallic elements in Groups I to VIII of the periodic table, such as Fe, Na, K, Cu, Mg, Ca, Zn, Ba, Al, Ti, and silicon. Specifically, examples include barium sulfate, calcium sulfate, magnesium sulfate, sodium sulfate, calcium sulfite, zinc oxide, heavy calcium carbonate, light calcium carbonate, aluminum borate, aluminum oxide, iron oxide, calcium titanate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, sodium hydroxide, magnesium carbonate, calcium silicate, clay, wollastonite, glass beads, glass powder, silica gel, dry silica, colloidal silica, silica sand, silica, quartz powder, diatomaceous earth, silica fume, and glass fiber. These inorganic powders can contain a variety of substances. Additionally, they can be substances contained in waste paper pulp or so-called recycled fillers used to regenerate inorganic matter from papermaking sludge.

[0141] However, it is preferable to use at least one inorganic powder selected from calcium carbonate, talc, silica, clay, calcined clay, titanium dioxide, aluminum hydroxide, and recycled fillers, which are suitable for use as fillers or pigments in papermaking. More preferably, it is preferable to use at least one selected from calcium carbonate, talc, and clay. Particularly preferred is at least one of light calcium carbonate and heavy calcium carbonate. Using calcium carbonate, talc, or clay facilitates compounding with a matrix such as resin. Furthermore, as these are general-purpose inorganic materials, they have the advantage of having few limitations in application. In addition, calcium carbonate is particularly preferred for the following reasons: When using light calcium carbonate, it is easy to control the size and shape of the powder to be constant. Therefore, by adjusting the size and shape according to the size and shape of the cellulose fibers in a way that easily creates gaps and inhibits the aggregation of cellulose fibers, it is advantageous to be able to achieve the desired effect with precision. In addition, if heavy calcium carbonate is used, since heavy calcium carbonate is amorphous, it has the following advantages: even when there are fibers of various sizes in the slurry, it can enter the gaps and inhibit the aggregation of cellulose fibers during the fiber aggregation process when the aqueous medium is removed.

[0142] When using both inorganic powder and interacting powder, the ratio of the average particle size of the inorganic powder to the average particle size of the interacting powder is preferably 1:0.1 to 1:10000, more preferably 1:1 to 1:1000. It can be considered that if within this range, problems arising from the strength of their own cohesive forces will not occur (e.g., the powder cannot be easily separated in the slurry when mixed with microfibrillated cellulose, or the powder aggregates when removed by an aqueous medium), thus maximizing the effect of preventing the aggregation of microfibrillated cellulose.

[0143] When using both inorganic powder and interacting powder, the mass percentage of inorganic powder to the mass percentage of interacting powder is preferably 1:0.01 to 1:100, more preferably 1:0.1 to 1:10. It is considered that within this range, dissimilar powders can inhibit their own aggregation. It is also considered that within this range, problems arising from the strength of their own cohesive forces (e.g., the inability of the powder to dissolve smoothly in the slurry when mixed with microfibrillated cellulose, or the aggregation of powders during removal from an aqueous medium) will not occur, thus fully realizing the effect of preventing the aggregation of microfibrillated cellulose.

[0144] (Acid-modified resin)

[0145] As described above, the powders involved in the interaction are preferably resin powders. Furthermore, the resin is preferably an acid-modified resin. The acid groups of the acid-modified resin can ionicly bond with some or all of the urethane groups. Through this ionic bonding, the agglomeration-inhibiting function of the resin powder is effectively achieved.

[0146] Acid-modified resins can be, for example, acid-modified polyolefin resins, acid-modified epoxy resins, and acid-modified styrene-based elastomer resins. Acid-modified polyolefin resins are preferred. Acid-modified polyolefin resins are copolymers of unsaturated carboxylic acid components and polyolefin components.

[0147] As a polyolefin component, one or more polymers of olefins such as ethylene, propylene, butadiene, and isoprene can be selected. Polypropylene resin, as a propylene polymer, is preferred.

[0148] As the unsaturated carboxylic acid component, one or more can be selected from maleic anhydride, phthalic anhydride, itaconic anhydride, citraconic anhydride, citric anhydride, etc. Among them, maleic anhydride is preferred. That is, maleic anhydride-modified polypropylene resin is particularly preferred.

[0149] The mixing amount of the acid-modified resin relative to 100 parts by weight of microfiber cellulose is preferably 0.1 to 1,000 parts by weight, more preferably 1 to 500 parts by weight, and particularly preferably 10 to 200 parts by weight. Especially when the acid-modified resin is maleic anhydride-modified polypropylene resin, it is preferably 1 to 200 parts by weight, more preferably 10 to 100 parts by weight. If the mixing amount of the acid-modified resin is less than 0.1 parts by weight, the aggregation inhibition effect is insufficient. On the other hand, if the mixing amount is greater than 1,000 parts by weight, there is a tendency for the aggregation inhibition effect to decrease.

[0150] The weight-average molecular weight of maleic anhydride-modified polypropylene is, for example, 1,000 to 100,000, preferably 3,000 to 50,000.

[0151] In addition, the acid value of maleic anhydride modified polypropylene is preferably 0.5 mg KOH / g or more and 100 mg KOH / g or less, more preferably 1 mg KOH / g or more and 50 mg KOH / g or less.

[0152] The acid value of maleic anhydride modified polypropylene is determined by titration with potassium hydroxide according to JIS-K2501.

[0153] (Dispersant)

[0154] Microfibrillated cellulose is more preferably mixed with a dispersant. As a dispersant, compounds having amino and / or hydroxyl groups in aromatic compounds and compounds having amino and / or hydroxyl groups in aliphatic compounds are preferred.

[0155] Examples of aromatic compounds containing an amino group and / or a hydroxyl group include aniline, toluidine, trimethylaniline, anisidine, tyramine, histamine, tryptamine, phenol, butylated hydroxytoluene, bisphenol A, cresol, eugenol, gallic acid, guaiacol, picric acid, phenolphthalein, serotonin, dopamine, adrenaline, noradrenaline, thymol, tyrosine, and water. Salicylic acid derivatives, methyl salicylate derivatives, anisyl alcohol derivatives, salicylol derivatives, sinigrin derivatives, difenidol derivatives, diphenylmethanol derivatives, cinnamyl alcohol derivatives, scopolamine derivatives, chromol derivatives, vanillyl alcohol derivatives, 3-phenyl-1-propanol derivatives, phenethyl alcohol derivatives, phenoxyethanol derivatives, resveratrol derivatives, benzyl alcohol derivatives, benzoin derivatives, mandelic acid derivatives, mandeonitrile derivatives, benzoic acid derivatives, phthalic acid derivatives, isophthalic acid derivatives, terephthalic acid derivatives, benzohexacarboxylic acid derivatives, cinnamic acid derivatives, etc.

[0156] In addition, examples of compounds containing amino and / or hydroxyl groups in aliphatic groups include octanols, 2-ethylhexanols, nonanols, decanols, undecanools, lauryl alcohols, tridecanools, myristols, pentadecanools, cetyl alcohols, stearyl alcohols, transoleyl alcohols, oleyl alcohols, linoleyl alcohols, methylamines, dimethylamines, trimethylamines, ethylamines, diethylamines, ethylenediamines, triethanolamines, and N,N-diisopropylamines. Ethylethylamine, tetramethylethylenediamine, 1,6-hexanediamine, spermidine, spermine, rimantaline, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, heptadecanic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, sorbic acid, etc.

[0157] The dispersants described above inhibit hydrogen bonds between cellulose fibers. Therefore, during the compounding of microfibrillated cellulose and resin, the microfibrillated cellulose is reliably dispersed in the resin. Furthermore, these dispersants also improve the compatibility between the microfibrillated cellulose and the resin. From this perspective, the dispersibility of microfibrillated cellulose in the resin is improved.

[0158] It should be noted that when compounding fibrous cellulose and resin, compatibilizers (chemicals) are also considered to be added separately. However, compared to adding chemicals at this stage, when fibrous cellulose is mixed with dispersant (chemical) beforehand, the chemical wraps around the fibrous cellulose more evenly, and the compatibility with resin is further improved.

[0159] Furthermore, polypropylene, for example, has a melting point of 160°C, so the mixing of fibrous cellulose and resin is carried out at around 180°C. However, when a dispersant (liquid) is added at this temperature, it dries instantly. Therefore, there is a method that uses a resin with a low melting point to prepare a masterbatch (a composite resin with a high concentration of microfibrillated cellulose), and then uses a common resin to reduce the concentration. However, resins with low melting points generally have low strength. Therefore, when using this method, the strength of the composite resin may be reduced.

[0160] The mixing amount of the dispersant relative to 100 parts by weight of microfiber cellulose is preferably 0.1 to 1,000 parts by weight, more preferably 1 to 500 parts by weight, and particularly preferably 10 to 200 parts by weight. If the mixing amount of the dispersant is less than 0.1 parts by weight, the improvement in resin strength may be insufficient. On the other hand, if the mixing amount is greater than 1,000 parts by weight, it becomes excessive, and the resin strength tends to decrease.

[0161] Regarding this point, it is believed that the aforementioned acid-modified resin improves compatibility and reinforcement by ionic bonding between the acid groups and the urethane groups of the microfibrils. Due to its large molecular weight, it also easily integrates with the resin (improved adhesion), which helps to increase strength. On the other hand, the aforementioned dispersant is sandwiched between the hydroxyl groups of the microfibrils, preventing aggregation, thus improving dispersibility in the resin. Furthermore, because its molecular weight is smaller than that of the acid-modified resin, it can penetrate into the narrow spaces between the microfibrils that the acid-modified resin cannot reach, thereby improving dispersibility and enhancing strength. Based on the above aspects, it is suitable that the molecular weight of the aforementioned acid-modified resin is 2 to 2,000 times, preferably 5 to 1,000 times, the molecular weight of the dispersant.

[0162] To explain this in more detail, the interacting powder is physically sandwiched between the microfibrils of cellulose, thereby inhibiting hydrogen bonding and thus improving the dispersibility of the microfibrils. In particular, the acid groups in the acid-modified resin form ionic bonds with the urethane groups of the microfibrils. Therefore, it exists around the fibers preferentially over other substances, exerting an effect of inhibiting fiber aggregation. Moreover, when a composite resin is made by mixing fibrous cellulose contents with resin, it plays a role in making the composite resin closely bonded to the microfibrils, improving the mechanical strength of the composite resin. In this respect, dispersants are similar in inhibiting hydrogen bonding between microfibrils, but since the interacting powder is on the order of micrometers, it is physically sandwiched in to inhibit hydrogen bonding. Therefore, although the dispersibility is lower than that of dispersants, especially in the case of resin powder, it melts itself to form a matrix, so it does not contribute to the reduction of 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 microfibrils and improving the dispersibility of the microfibrils. However, their residue in the resin may lead to a reduction in physical properties.

[0163] (Manufacturing method of composite resin)

[0164] A mixture of fibrous cellulose components, dispersants, etc., can be dried and pulverized into a powder before being compounded with resin. This method eliminates the need to dry the fibrous cellulose during compounding with resin, resulting in good thermal efficiency. Furthermore, when the mixture contains interacting powders or dispersants, the likelihood of the fibrous cellulose (microfibrillated cellulose) failing to redisperse is low, even after drying the mixture.

[0165] The mixture is dehydrated as needed before drying to produce a dehydrated product. This dehydration can be achieved by selecting one or more dehydration devices such as belt presses, screw presses, filter presses, twin-roll mills, mesh forming machines, valveless filters, central disc filters, membrane treatments, and centrifuges.

[0166] The drying of the mixture can be carried out by selecting one or more of the following methods: rotary kiln drying, plate drying, airflow drying, medium flow drying, spray drying, drum drying, screw conveyor drying, impeller drying, single screw mixing drying, multi-screw mixing drying, vacuum drying, and stirring drying.

[0167] The dried mixture (dried material) is pulverized to produce a powder. The pulverization of the dried material can be performed using one or more of the following: bead mill, kneader, disperser, shredder, shredder, hammer mill, etc.

[0168] The average particle size of the powder is preferably 1 μm to 10,000 μm, more preferably 10 μm to 5,000 μm, and particularly preferably 100 μm to 1,000 μm. If the average particle size of the powder is higher than 10,000 μm, the compatibility with the resin may deteriorate. On the other hand, a large amount of energy is required to reduce the average particle size of the powder to less than 1 μm, which is uneconomical.

[0169] In addition to controlling the degree of pulverization, the average particle size of powdered materials can also be controlled by using grading devices such as filters and cyclone separators.

[0170] 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 cellulose fibers are stronger, making them less likely to disperse in the resin. On the other hand, a bulk density below 0.03 is disadvantageous from the perspective of transportation costs.

[0171] The bulk density is a value determined according to JIS K7365.

[0172] 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 is higher than 50%, the energy required for mixing with the resin is enormous and uneconomical.

[0173] The moisture content is calculated as follows: Using a constant temperature dryer, the sample is kept at 105℃ for more than 6 hours, and the mass at the moment when the mass change is no longer confirmed is taken as the mass after drying, and calculated by the following formula.

[0174] Fiber moisture content (%) = [(mass before drying - mass after drying) ÷ mass before drying] × 100

[0175] The powder (containing fibrous cellulose) obtained above is compounded with resin as needed to obtain a fibrous cellulose composite resin. This compounding can be achieved by, for example, mixing granular resin with the powder, or by first melting the resin and then adding the powder to the melt. It should be noted that when using resin powders such as acid-modified resins as the interacting powder, the composite resin can also be prepared by immediately compounding without mixing with the resin.

[0176] When the total amount of the mixture (powder, fibrous cellulose content) is set to 100 parts by mass, it is preferable to contain fibrous cellulose in a proportion of more than 55 parts by mass, particularly more than 60 parts by mass. Generally, if a mixture with a fibrous cellulose concentration exceeding 55 parts by mass is mixed with a resin, the dispersibility and mixability of the mixture in the resin deteriorate. On the other hand, the mixture of the present invention contains fibrous cellulose with some or all of its hydroxyl groups substituted with urethane groups, and powder that interacts with the aforementioned fibrous cellulose. Therefore, even if the fibrous cellulose exceeds 55 parts by mass, high dispersibility can be maintained when the mixture is mixed with a resin. From the viewpoint of reducing the amount of mixture used to contain any proportion of fibrous cellulose in the composite resin, it is also preferable to increase the fibrous cellulose concentration of the mixture.

[0177] In the mixing process, one or more types of mixers can be selected, such as single-screw or twin-screw multi-screw mixers, mixing rollers, kneaders, roller mills, Banbury mixers, screw presses, and dispersers. Among these, twin-screw or multi-screw mixers are preferred. Two or more twin-screw or multi-screw mixers can also be used in parallel or in series.

[0178] The mixing temperature is above the glass transition temperature of the resin, and varies depending on the type of resin. Preferably it is 80°C to 280°C, more preferably 90°C to 260°C, and particularly preferably 100°C to 240°C.

[0179] As the resin, at least one of thermoplastic resin or thermosetting resin may be used.

[0180] As a thermoplastic resin, one or more of the following can be selected: polyolefins such as polypropylene (PP) and polyethylene (PE), polyester resins such as aliphatic polyester resins and aromatic polyester resins, polystyrene, polyacrylic resins such as methacrylates and acrylates, polyamide resins, polycarbonate resins, polyacetal resins, etc.

[0181] Preferably, at least one of polyolefins and polyester resins is used. Polypropylene is preferred as the polyolefin. Furthermore, regarding the polyester resin, examples of aliphatic polyester resins include polylactic acid and polycaprolactone, and examples of aromatic polyester resins include polyethylene terephthalate. Biodegradable polyester resins (also simply referred to as "biodegradable resins") are preferred.

[0182] As a biodegradable resin, one or more of the following can be selected: hydroxycarboxylic acid aliphatic polyesters, caprolactone aliphatic polyesters, dicarboxylic acid polyesters, etc.

[0183] As a hydroxycarboxylic acid-based aliphatic polyester, one or more of the following can be selected: homopolymers of hydroxycarboxylic acids such as lactic acid, malic acid, gluconic acid, and 3-hydroxybutyric acid, or copolymers using at least one of these hydroxycarboxylic acids. Among these, polylactic acid, copolymers of lactic acid with the aforementioned hydroxycarboxylic acids other than lactic acid, polycaprolactone, and copolymers of at least one of the aforementioned hydroxycarboxylic acids with caprolactone are preferred, with polylactic acid being particularly preferred.

[0184] As this lactic acid, for example, L-lactic acid, D-lactic acid, etc. can be used. These lactic acids can be used alone or two or more can be selected for use.

[0185] As a caprolactone-based aliphatic polyester, one or more of the following can be selected: homopolymers of polycaprolactone, copolymers of polycaprolactone and the aforementioned hydroxycarboxylic acids.

[0186] As a dicarboxylic acid polyester, one or more of the following can be selected: polybutylene succinate, polyethylene succinate, polybutylene adipate, etc.

[0187] Biodegradable resins can be used alone or in combination with two or more types.

[0188] Examples of thermosetting resins include phenolic resins, urea resins, melamine resins, furan resins, unsaturated polyesters, diallyl phthalate resins, vinyl ester resins, epoxy resins, polyurethane resins, silicone resins, and thermosetting polyimide resins. These resins can be used alone or in combination of two or more.

[0189] The preferred mixing ratio of fibrous cellulose and resin is 1 part by weight or more of fibrous cellulose and 99 parts by weight or less of resin; more preferably, 2 parts by weight or more of fibrous cellulose and 98 parts by weight or less of resin; and particularly preferably, 3 parts by weight or more of fibrous cellulose and 97 parts by weight or less of resin. Furthermore, it is preferable that fibrous cellulose is 50 parts by weight or less of fibrous cellulose and 50 parts by weight or more of resin; more preferably, 40 parts by weight or less of fibrous cellulose and 60 parts by weight or more of resin; and particularly preferably, 30 parts by weight or less of fibrous cellulose and 70 parts by weight or more of resin. In particular, if the fibrous cellulose content is 10 to 50 parts by weight, the strength of the resin composition, especially the flexural strength and tensile modulus of elasticity, can be significantly improved.

[0190] It should be noted that the final resin composition typically contains the same proportion of fibrous cellulose and resin as described above.

[0191] Solubility parameters of microfibrils, cellulose, and resin (cal / cm³) 3 ) 1 / 2The difference in (SP value), that is, in SP values ​​expressed as microfibrillary cellulose. MFC SP value of resin POL When the value is equal to the difference between SP values, it can be calculated as SP = SP MFC Value - SP POL The SP value difference is preferably 10 to 0.1, more preferably 8 to 0.5, and particularly preferably 5 to 1. If the SP value difference exceeds 10, the microfibrils of cellulose will not disperse in the resin, and a reinforcing effect may not be obtained. On the other hand, if the SP value difference is less than 0.1, the microfibrils of cellulose will dissolve in the resin and cannot function as a filler, and a reinforcing effect may not be obtained. Regarding this, the SP value of the resin (solvent)... POL SP values ​​of microfibrillated cellulose (solute) MFC The smaller the difference in values, the greater the enhancement effect.

[0192] It should be noted that the solubility parameter (cal / cm³) 3 ) 1 / 2 The SP value is a measure of the intermolecular forces that act between the solvent and the solute. The closer the SP values ​​of the solvent and solute are, the greater their solubility.

[0193] (Molding process)

[0194] The compound containing fibrous cellulose and resin can be further compounded as needed, and then molded into the desired shape. There are no particular limitations on the size, thickness, shape, etc. of the molded product; for example, it can be made into flakes, granules, powders, fibers, etc.

[0195] The temperature during molding is above the glass transition temperature of the resin, and varies depending on the type of resin, for example, 90℃~260℃, preferably 100℃~240℃.

[0196] The compound can be molded using methods such as die molding, injection molding, extrusion molding, blow molding, and foam molding. Alternatively, the compound can be spun into fibers, and then blended with the aforementioned plant materials to form mats or sheets. Fiber blending can be achieved, for example, by using airflow to simultaneously deposit the fibers.

[0197] As an apparatus for forming a compound, one or more of the following can be selected: injection molding machine, blow molding machine, blow molding machine, compression molding machine, extrusion molding machine, vacuum forming machine, air compression molding machine, etc.

[0198] The above molding process can be carried out after mixing, or the mixture can be cooled first, crushed into fragments using a crusher or similar device, and then fed into a molding machine such as an extrusion molding machine or injection molding machine for molding. Of course, molding is not a necessary condition for this invention.

[0199] (Other compositions)

[0200] The fibrous cellulose composition may contain cellulose nanofibers along with microfibrillated cellulose. Cellulose nanofibers, like microfibrillated cellulose, are fine fibers and complement microfibrillated cellulose in improving resin strength. However, where possible, it is preferable to use only microfibrillated cellulose as the fine fiber, without including cellulose nanofibers. It should be noted that the average fiber diameter (average fiber width, average diameter of a single fiber) of the cellulose nanofibers is preferably 4 nm to 100 nm, more preferably 10 nm to 80 nm.

[0201] In addition, the fibrous cellulose contents may include pulp. Pulp has the effect of significantly improving the dewatering properties of cellulose fiber pulp. Regarding pulp, similar to the case of cellulose nanofibers, it is best to avoid mixing, i.e., its content is 0% by mass.

[0202] In addition to microfibers and pulp, the resin composition (composite resin) can also contain fibers from various plant materials obtained from plants such as hibiscus, jute, Manila hemp, sisal, gampi, daphne, paper mulberry, banana, pineapple, coconut, corn, sugarcane, bagasse, coconut, papyrus, reed, fine-stemmed needlegrass, Indian grass, wheat, rice, bamboo, various coniferous trees (such as fir and cypress), broad-leaved trees, and cotton. It is also possible for the resin composition to contain the above-mentioned fibers.

[0203] One or more of the following can be selected from antistatic agents, flame retardants, antibacterial agents, colorants, free radical scavengers, foaming agents, etc., and added to the resin composition, without impairing the effects of the present invention. These raw materials can be added to a dispersion of fibrous cellulose, added during the mixing of fibrous cellulose and resin, added to their mixture, or added by other methods. From the perspective of manufacturing efficiency, it is preferable to add them during the mixing of fibrous cellulose and resin.

[0204] The resin composition may contain ethylene-α-olefin copolymer elastomer or styrene-butadiene block copolymer as a rubber component. Examples of α-olefins include butene, isobutene, pentene, hexene, methylpentene, octene, decene, dodecene, etc.

[0205] Example

[0206] The embodiments of the present invention will now be described.

[0207] 22.0 g of maleic anhydride-modified polypropylene (MAPP) with uniform particle size or a mixture of maleic anhydride-modified polypropylene (MAPP) with different particle sizes was added to 1,570 g of microfibrillated cellulose with a solid content concentration of 2.8% by mass. The mixture was then heated using a contact dryer at 140°C to obtain a urethane-modified microfibrillated cellulose composition. The moisture content of this urethane-modified microfibrillated cellulose composition was 5%–22%.

[0208] The method for modifying fibers with urethane is described below.

[0209] Specifically, coniferous sulfate pulp with a moisture content of less than 10%, a urea aqueous solution with a solids concentration of 10%, and a citric acid aqueous solution are mixed in a mass ratio of pulp:urea:citric acid = 100:50:0.1 based on the solids content, and then dried at 105°C. Next, the mixture is heated at a specified reaction temperature and time to obtain urethane-modified pulp (urethane-treated pulp). The obtained urethane-modified pulp is diluted with distilled water and stirred, and the dewatering process is repeated twice. The washed urethane-modified pulp is then beaten using a beater to achieve a specified ratio of particles smaller than 0.2 mm and particles between 0.2 mm and 0.6 mm, yielding urethane-modified microcellulose fibers (urethane-treated MFC (microfibers)).

[0210] Alternatively, 22.0 g of polypropylene powder was used instead of maleic anhydride-modified polypropylene to obtain a carbamate-modified microfibrillated cellulose inclusion as a comparative example. The water content of this carbamate-modified microfibrillated cellulose inclusion was 5%–22%.

[0211] Polypropylene granules were added to the urethane-modified microfiber cellulose composition obtained above at a ratio of urethane-modified microfiber: other components = 10:90 and mixed. The mixture was then kneaded using a twin-screw mixer at 180°C and 200 rpm to obtain a urethane-modified microfiber cellulose composite resin with a fiber blending rate of 10%.

[0212] The urethane-modified microfiber cellulose composite resin obtained above was granulated into cylindrical pieces with a diameter of 2 mm and a length of 2 mm using a granulator. These cylindrical pieces were then injection molded at 180°C into cuboid test specimens (length 59 mm, width 9.6 mm, thickness 3.8 mm). The flexural modulus of elasticity was investigated for each test specimen. The results, along with the particle size (particle diameter) of the MAPP and the fiber size (fiber length) of the fibrous cellulose, are shown in Table 1 according to the following criteria.

[0213] (Flexural modulus)

[0214] The flexural modulus of elasticity was determined according to JIS K7171:2008. The evaluation results are shown in the table based on the following criteria.

[0215] When the flexural modulus of the resin itself is set to 1, and the flexural modulus (multiplier) of the composite resin is 1.45 or higher: ○

[0216] With the flexural modulus of the resin itself set to 1, and the flexural modulus (multiplier) of the composite resin being greater than 1.40 but less than 1.45: △

[0217] Setting the resin's own flexural modulus to 1, the case where the composite resin's flexural modulus (multiplier) is less than 1.40: ×

[0218] [Table 1]

[0219]

[0220] Industrial applicability

[0221] This invention can be used as a fibrous cellulose inclusion, a fibrous cellulose composite resin, and a method for manufacturing fibrous cellulose inclusions. For example, the fibrous cellulose composite resin can be used in: interior materials, exterior materials, and structural materials for transportation equipment such as automobiles, trams, ships, and airplanes; housings, structural materials, and internal components for electrical products such as personal computers, televisions, telephones, and watches; housings, structural materials, and internal components for mobile communication devices such as mobile phones; housings, structural materials, and internal components for portable music playback devices, video playback devices, printing equipment, photocopying equipment, sporting goods, office equipment, toys, and other similar products; interior materials, exterior materials, and structural materials for buildings and furniture; office equipment such as stationery; and packaging, trays, and other storage containers, protective components, and partitions.

Claims

1. A fibrous cellulose inclusion, which is a fibrous cellulose inclusion added to a resin, characterized in that, The fibrous cellulose has a fiber width of 2 μm to 4 μm, a fiber length of 0.2 mm to 0.6 mm accounting for 14% to 40% of the total, a fiber length less than 0.2 mm accounting for 8% to 73% of the total, an average fiber length of 0.18 mm to 1.46 mm, and some or all of the hydroxyl groups are replaced by urethane groups. The fibrous cellulose content includes powder that interacts with the fibrous cellulose. The interacting powder is an acid-modified resin with a 90% particle size / 10% particle size ratio of 10–93.

08. The amount of the interacting powders mixed in is 10% to 900% by mass relative to the fibrous cellulose. The arithmetic standard deviation of the interacting powders is 68.15 μm to 503.01 μm. The volume average particle size of the interacting powders is 50 μm to 450 μm.

2. The fibrous cellulose inclusion as described in claim 1, wherein, The volume average particle size of the interacting powder / the average fiber length of the fibrous cellulose is 0.005 to 5000, wherein the units of the volume average particle size and the average fiber length are μm.

3. The fibrous cellulose inclusion as described in claim 1 or 2, wherein, The fibrous cellulose has an average fiber length of less than 1.0 mm, an average fiber width of less than 10 μm, and a fibrillation rate of more than 2.5%.

4. The fibrous cellulose inclusion as described in claim 1 or 2, wherein, The interacting powder is an acid-modified resin with an acid value of 2.0% or higher.

5. The fibrous cellulose inclusion as described in claim 1 or 2, wherein, The interacting powder is maleic anhydride-modified polypropylene.

6. A fibrous cellulose composite resin, comprising fibrous cellulose and resin, characterized in that, The fibrous cellulose content of any one of claims 1 to 5 is used as the fibrous cellulose.

7. A method for manufacturing a fibrous cellulose inclusion, characterized in that, Fibrous cellulose, in which some or all of the hydroxyl groups have been substituted with urethane groups, is opened with the following specifications: a fiber width with a mode diameter of 2 μm to 4 μm, a fiber length of 0.2 mm to 0.6 mm in proportions of 14% to 40%, a fiber length less than 0.2 mm in proportions of 8% to 73%, and an average fiber length of 0.18 mm to 1.46 mm. The fibrous cellulose and a powder that interacts with the fibrous cellulose are mixed in a ratio of 10% to 900% by mass relative to the fibrous cellulose to obtain a mixture. The interacting powder is an acid-modified resin with a 90% particle size / 10% particle size ratio of 10 to 93.08, an arithmetic standard deviation of 68.15 μm to 503.01 μm, and a volume average particle size of 50 μm to 450 μm. The mixture is then dried.

Images