WO2021251216A1 - Production method for carbamated cellulose fibers, and production method for carbamated filaments - Google Patents

Abstract

[Problem] To provide a production method for carbamated cellulose fibers and a production method for carbamated filaments whereby it is possible to achieve sufficient carbamation in a short period of time. [Solution] Provided is a production method for carbamated cellulose fibers, said method being characterized by having a step in which cellulose fibers are subjected to a heat treatment such that the hydroxy groups in the cellulose fibers are substituted with carbamate groups at a substitution rate of at least 1.0 mmol/g, wherein the heat treatment is carried out a 150-170°C. Also provided is a production method for carbamated filaments that has a step in which cellulose fibers are fibrillated until the average fiber width is at most 19 µm to produce filaments.

Description

Method for Producing Carbamate Cellulose Fiber and Method for Producing Carbamate Fine Fiber

The present invention relates to a method for producing a carbamate-ized cellulose fiber and a method for producing a carbamate-ized fine fiber.

In recent years, fine fibers such as cellulose nanofibers and microfiber cellulose (microfibrillated cellulose) have been in the limelight for use as reinforcing materials for resins. However, since the fine fibers are hydrophilic while the resin is hydrophobic, there is a problem in the dispersibility of the fine fibers in order to use the fine fibers as a reinforcing material for the resin. Therefore, the present inventors have proposed to replace the hydroxyl group of the fine fiber with a carbamate group (carbamate) (see Patent Document 1). According to this proposal, the dispersibility of the fine fibers is improved, and thus the reinforcing effect of the resin is improved.

After that, through repeated tests, it was found that when the substitution rate of the carbamate group is 1 mmol / g or more, the reinforcing effect of the resin, for example, the bending elongation is improved. Therefore, based on this finding, it has become possible to search for the possibility of carbamate formation in a shorter time. This is because the substitution rate of the carbamate group does not exceed 1 mmol / g simply by performing the carbamate formation in a short time.

Japanese Unexamined Patent Publication No. 2019-1876

A main problem to be solved by the present invention is to provide a method for producing a carbamate-ized cellulose fiber and a method for producing a carbamate-ized fine fiber, which can be sufficiently carved and can be carved in a short time.

As a general theory, it is conceivable to raise the reaction temperature in order to carry out the reaction in a short time. However, increasing the substitution rate of the carbamate group makes the cellulose fibers more susceptible to damage. Therefore, in Patent Document 1, the upper limit of the heat treatment temperature is 200 ° C., but when increasing the substitution rate of the carbamate group, the heat treatment is usually performed at about 140 ° C. from the viewpoint of suppressing damage to the cellulose fibers. Was there. That is, there was no idea of raising the reaction temperature when increasing the substitution rate of the carbamate group, especially when the substitution rate was 1 mmol / g or more. Of course, there was no finding that the substitution rate of the carbamate group could be increased to 1 mmol / g or more even in a short time by increasing the temperature.

However, as a result of repeated numerous tests, if the temperature of the heat treatment is within a predetermined range, the substitution rate of the carbamate group is 1 mmol / / even if the heat treatment time is short while suppressing damage to the cellulose fibers. It has been found that the temperature can be increased to g or more. The following means have led to the idea based on such knowledge.

(Means according to claim 1)
It has a step of heat-treating the cellulose fiber and substituting the hydroxy group of the cellulose fiber with a carbamate group so that the substitution rate is 1.0 mmol / g or more.
The heat treatment is carried out at 150 to 170 ° C.
A method for producing a carbamate-ized cellulose fiber.

(Means according to claim 2)
The heat treatment is carried out under the condition that at least one of urea and a derivative of urea and citric acid are added to the cellulose fiber.
The amount of the citric acid added to the cellulose fibers is 0.1 to 10,000 ppm.
The method for producing a carbamate-ized cellulose fiber according to claim 1.

(Means according to claim 3)
The amount of the urea and the derivative of the urea added to the cellulose fibers is 1 to 70%.
The method for producing a carbamate-ized cellulose fiber according to claim 2.

(Means according to claim 4)
A step of heat-treating the cellulose fiber to replace the hydroxy group of the cellulose fiber with a carbamate group so that the substitution rate is 1.0 mmol / g or more.
It has a step of defibrating cellulose fibers so that the average fiber width is 19 μm or less to form fine fibers.
The heat treatment is carried out at 150 to 170 ° C.
A method for producing carbamate fine fibers.

(Means according to claim 5)
The heat treatment is performed so that the crystallinity of the fine fibers remains at 50% or more.
The method for producing a carbamate fine fiber according to claim 4.

According to the present invention, it is a method for producing a carbamate-ized cellulose fiber and a method for producing a carbamate-ized fine fiber, which can be sufficiently carved and can be carved in a short time.

Next, a mode for carrying out the invention will be described. The embodiment of the present invention is an example of the present invention. The scope of the present invention is not limited to the scope of the present embodiment.

The method for producing a carbamate-ized cellulose fiber of the present embodiment includes a step of heat-treating the cellulose fiber to replace a part or all of the hydroxy group (-OH group) of the cellulose fiber with the carbamate group. This substitution is performed so that the substitution rate is 1.0 mmol / g or more from the viewpoint of the reinforcing effect of the resin. The heat treatment for carbamate is performed at 150 to 170 ° C. Further, the method for producing carbamate fine fibers includes, in addition to the above, a step of defibrating the cellulose fibers so that the average fiber width is 19 μm or less to obtain fine fibers. This defibration may be performed after the raw material pulp is carbamate or before the raw material pulp is carbamate. However, it is preferable to defibrate the raw material pulp after carbamate it. Hereinafter, it will be described in detail. The carbamate-ized cellulose fiber in the method for producing a carbamate-ized cellulose fiber does not mean that the carbamate-ized fine fiber is excluded.

(Cellulose fiber)
Fine fibers can be obtained by defibrating (miniaturizing) the raw material pulp (cellulose raw material). This defibration may be carried out so that the fine fibers become cellulose nanofibers or microfiber cellulose (microfibrillated cellulose). However, it is preferable to use microfiber cellulose. Microfiber cellulose improves the reinforcing effect of the resin. Further, although the microfiber cellulose is a fine fiber, it is easier to modify (carbamate) with a carbamate group than the cellulose nanofiber which is also a fine fiber. However, it is preferable to carbamate the raw material pulp before it is miniaturized, and in this case, the microfiber cellulose and the cellulose nanofiber are equivalent.

In this embodiment, the microfiber cellulose means a fiber having an average fiber diameter (width) thicker than that of cellulose nanofibers. Specifically, the average fiber diameter is, for example, 0.1 to 19 μm, preferably 0.2 to 15 μm, and more preferably more than 0.5 to 10 μm. When the average fiber diameter of the microfiber cellulose is less than 0.1 μm (less than 0.1 μm), it is no different from that of cellulose nanofibers, and the effect of improving the strength (particularly bending elastic modulus) of the resin may be inferior. In addition, the defibration time becomes long and a large amount of energy is required. Further, the dehydration property of the cellulose fiber slurry is deteriorated. When the dehydration property deteriorates, a large amount of energy is required for drying, and when a large amount of energy is applied to drying, the microfiber cellulose is thermally deteriorated and the strength may decrease. On the other hand, if the average fiber diameter of the microfiber cellulose exceeds (exceeds) 19 μm, it is no different from pulp, and the reinforcing effect may not be sufficient.

In this embodiment, 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 having a solid content concentration of 0.01 to 0.1% by mass is filtered through a membrane filter made of Teflon (registered trademark), and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. do. Next, it is freeze-dried and coated with osmium to prepare a sample. This sample is observed with an electron microscope SEM image at a magnification of 3,000 to 30,000 times depending on the width of the constituent fibers. Specifically, two diagonal lines are drawn on the observation image, and three straight lines passing through the intersections of the diagonal lines are arbitrarily drawn. Further, the width of a total of 100 fibers intersecting with these three straight lines is visually measured. Then, the median diameter of the measured value is taken as the average fiber diameter.

Fine fibers can be obtained by defibrating (miniaturizing) the raw material pulp. The raw material pulp includes, for example, wood pulp made from broadleaf trees, coniferous trees, etc., non-wood pulp made from straw, bagasse, cotton, hemp, carrot fiber, etc., recycled paper pulp made from recovered waste paper, waste paper, etc. One type or two or more types can be selected and used from (DIP) and the like. The above-mentioned various raw materials may be, for example, in the state of a crushed product (powder) called a cellulosic powder or the like.

However, in order to avoid contamination with impurities as much as possible, it is preferable to use wood pulp as the raw material pulp. As the wood pulp, for example, one kind or two or more kinds can be selected and used from chemical pulp such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), mechanical pulp (TMP) and the like.

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

Examples of the mechanical pulp include stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), chemi-grand pulp (CGP), thermo-grand pulp (TGP), and ground pulp (GP). One or more of the thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), bleached thermomechanical pulp (BTMP) and the like can be selected and used.

Raw pulp can be pretreated by a chemical method prior to defibration. Pretreatment by chemical method includes, for example, hydrolysis of polysaccharide with acid (acid treatment), hydrolysis of polysaccharide with enzyme (enzyme treatment), swelling of polysaccharide with alkali (alkali treatment), oxidation of polysaccharide with oxidizing agent (acid treatment). Oxidation treatment), reduction of polysaccharides with a reducing agent (reduction treatment), and the like can be exemplified. However, as the pretreatment by a chemical method, it is preferable to carry out an enzyme treatment, and in addition, it is more preferable to carry out one or more treatments selected from an acid treatment, an alkali treatment and an oxidation treatment. Hereinafter, the enzyme treatment will be described in detail.

As the enzyme used for the enzyme treatment, it is preferable to use at least one of the cellulase-based enzyme and the hemicellulase-based enzyme, and it is more preferable to use both in combination. The use of these enzymes facilitates the defibration of cellulose raw materials. The cellulase-based enzyme causes the decomposition of cellulose in the coexistence of water. In addition, hemicellulose-based enzymes induce the decomposition of hemicellulose in the presence of water.

Examples of the cellulase-based enzymes include Trichoderma (Filamentous fungus), Acremonium (Filamentous fungus), Aspergillus (Filamentous fungus), Fanerochaete (Phanerochaete), Tramethes (Tra). Genus Humicola, genus Humicola, genus Bacillus, genus Schizophyllum, genus Streptomyces, genus Pseudomonas, bacteria produced by Pseudomonas, etc. Enzymes can be used. These cellulase-based enzymes can be purchased as reagents or commercial products. Commercially available products include, for example, cellulosein T2 (manufactured by HPI), Meicerase (manufactured by Meiji Seika), Novozyme 188 (manufactured by Novozyme), Multifect CX10L (manufactured by Genencore), and cellulase-based enzyme GC220 (manufactured by Genecore). Manufactured by) and the like can be exemplified.

Further, as the cellulase-based enzyme, either EG (endoglucanase) or CBH (cellobiohydrolase) can be used. EG and CBH may be used alone or in combination. Further, it may be used in combination with a hemicellulase-based enzyme.

As the hemicellulase-based enzyme, for example, xylanase, which is an enzyme that decomposes xylan, mannase, which is an enzyme that decomposes mannan, and arabanase, which is an enzyme that decomposes araban, can be used. can. In addition, pectinase, which is an enzyme that decomposes pectin, can also be used.

Hemicellulose is a polysaccharide excluding pectins between the cellulose microfibrils of the plant cell wall. Hemicellulose is diverse and varies between wood types and cell wall layers. Glucomannan is the main component in the secondary walls of conifers, and 4-O-methylglucuronoxylan is the main component in the secondary walls of hardwoods. Therefore, when fine fibers are obtained from softwood bleached kraft pulp (NBKP), it is preferable to use mannase. Further, when fine fibers are obtained from hardwood bleached kraft pulp (LBKP), it is preferable to use xylanase.

The amount of enzyme added to the cellulose raw material is determined by, for example, the type of enzyme, the type of wood used as the raw material (conifer or hardwood), the type of mechanical pulp, and the like. However, the amount of the 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 the enzyme added is less than 0.1% by mass, the effect of the addition of the enzyme may not be sufficiently obtained. On the other hand, if the amount of the enzyme added exceeds 3% by mass, cellulose may be saccharified and the yield of fine fibers may decrease. In addition, there is also a problem that the improvement of the effect corresponding to the increase in the addition amount cannot be recognized.

When a cellulase-based enzyme is used as the enzyme, the pH at the time of enzyme treatment is preferably in a weakly acidic region (pH = 3.0 to 6.9) from the viewpoint of the reactivity of the enzyme. On the other hand, when a hemicellulase-based enzyme is used as the enzyme, the pH at the time of enzyme treatment is preferably in a weak alkaline region (pH = 7.1 to 10.0).

The temperature during the enzyme treatment is preferably 30 to 70 ° C, more preferably 35 to 65 ° C, and particularly preferably 40 to 60 ° C, regardless of whether the cellulase-based enzyme or the hemicellulase-based enzyme is used as the enzyme. .. When the temperature at the time of 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 at the time of enzyme treatment is 70 ° C. or lower, inactivation of the enzyme can be prevented.

The enzyme treatment time is determined by, for example, the type of enzyme, the temperature of the enzyme treatment, the pH at the time of the enzyme treatment, and the like. However, the general enzyme treatment time is 0.5 to 24 hours.

It is preferable to inactivate the enzyme after the enzyme treatment. As a method for inactivating the enzyme, for example, there are a method of adding an alkaline aqueous solution (preferably pH 10 or higher, more preferably pH 11 or higher), a method of adding hot water at 80 to 100 ° C., and the like.

Next, the method of alkali treatment will be described.
When alkali treatment is performed prior to defibration, some of the hydroxyl groups of hemicellulose and cellulose in pulp are dissociated, and the molecules are anionized, weakening intramolecular and intermolecular hydrogen bonds and promoting dispersion of cellulose raw materials in defibration. Ru.

Examples of the alkali used for the alkali treatment include sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide and the like. Organic alkali or the like can be used. However, from the viewpoint of manufacturing cost, it is preferable to use sodium hydroxide.

By performing enzyme treatment, acid treatment, and oxidation treatment prior to defibration, the water retention of the fine fibers can be lowered, the crystallization degree can be increased, and the homogeneity can be increased. In this respect, if the water retention level of the fine fibers is low, dehydration is likely to occur, and the dehydration property of the cellulose fiber slurry is improved.

When the raw material pulp is subjected to enzyme treatment, acid treatment, or oxidation treatment, the hemicellulose and the amorphous region of cellulose that the pulp has are decomposed. As a result, the energy of defibration can be reduced, and the uniformity and dispersibility of the cellulose fibers can be improved. However, since the pretreatment reduces the aspect ratio of the fine fibers, it is preferable to avoid excessive pretreatment when used as a reinforcing material for the resin.

For defibration of raw pulp, for example, beaters, high-pressure homogenizers, homogenizers such as high-pressure homogenizers, stone mill type friction machines such as grinders and grinders, single-screw kneaders, multi-screw kneaders, kneader refiners, jet mills, etc. It can be done by beating the raw pulp using. However, it is preferable to use a refiner or a jet mill.

The average fiber length of the fine fibers (average length of the single fibers) 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, the flexural modulus of the composite resin may decrease, and 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 material pulp.

The average fiber length of the cellulose raw material as a raw material for fine fibers 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 effect of reinforcing the resin of the defibrated fine fibers 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 cost at the time of defibration.

The average fiber length of fine fibers can be arbitrarily adjusted by, for example, selection of raw material pulp, pretreatment, defibration, and the like.

In this embodiment, the average fiber length of the fine fibers is a value measured by a fiber analyzer "FS5" manufactured by Valmet. The same applies to the fine rate (Fine rate) described below.

The fine ratio of the fine fibers is preferably 30% or more, more preferably 35 to 99%, and particularly preferably 40 to 95%. When the fine ratio is 30% or more, the proportion of homogeneous fibers is large, and the destruction of the composite resin is difficult to proceed. However, if the fine ratio exceeds 99%, the flexural modulus may be insufficient.

The above is the fine ratio of fine fibers, but it is more preferable to keep the fine ratio of the cellulose raw material, which is the raw material of fine fibers, within a predetermined range. Specifically, the fine ratio of the cellulose raw material as a raw material for fine fibers is preferably 1% or more, more preferably 3 to 20%, and particularly preferably 5 to 18%. If the fine ratio of the cellulose raw material before defibration is within the above range, it is considered that even if the fine fibers are defibrated so that the fine ratio is 30% or more, the damage to the fibers is small and the reinforcing effect of the resin is improved. ..

The fine rate can be adjusted by pretreatment such as enzyme treatment. However, especially in the case of enzyme treatment, the fiber itself may become tattered and the reinforcing effect of the resin may be reduced. Therefore, the amount of the enzyme added from this point of view is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less. Further, it is also one of the selection frames that the enzyme treatment is not performed (addition amount: 0% by mass).

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

The aspect ratio of the fine fibers is preferably 2 to 15,000, more preferably 10 to 10,000. If the aspect ratio is less than 2, the 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 fine fibers becomes high, and the dispersion in the resin may be insufficient.

In this embodiment, the aspect ratio is a value obtained by dividing the average fiber length by the average fiber width. It is considered that the larger the aspect ratio, the more places where catching occurs, so that the reinforcing effect increases, but on the other hand, the more catching, the lower the ductility of the resin.

The fibrillation rate of the fine fibers 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 dehydration may become difficult even if the fibers are defibrated within the range where the average fiber width remains 0.1 μm or more. be. On the other hand, if the fibrillation rate is lower than 1.0%, there are few hydrogen bonds between the fibrils, and there is a possibility that a strong three-dimensional network cannot be formed.

In this embodiment, the fibrillation rate means that fine fibers are dissociated in accordance with JIS-P-8220: 2012 "Pulp-dissolution method", and the obtained dissociated pulp is referred to as FiberLab. (Kajaani) means a value measured using.

The crystallinity of the fine fibers is preferably 50% or more, more preferably 55% or more, and particularly preferably 60% or more. When the crystallinity is less than 50%, the mixability with other fibers such as pulp is improved, but the strength of the fibers themselves is lowered, so that the strength of the resin may not be improved. In this respect, in this embodiment, the heating temperature in carbamate formation is increased, but in the past, it was considered that the fibers would be damaged by this increase in temperature, and the temperature was not increased. However, when the heating temperature is raised to a high temperature, the heating time is shortened, so that the fibers are not exposed to heat for a long time, damage accumulation to the fibers can be suppressed, and a decrease in crystallinity can be suppressed. Therefore, according to this embodiment, the reinforcing effect of the resin is excellent, and it is extremely easy to set the crystallinity to 50% or more. On the other hand, the crystallinity of the fine fibers is preferably 95% or less, more preferably 90% or less, and particularly preferably 85% or less. When the crystallinity exceeds 95%, the ratio of strong hydrogen bonds in the molecule increases, the fiber itself becomes rigid, and the dispersibility becomes inferior.

The crystallinity of the fine fibers can be arbitrarily adjusted by, for example, selection of raw material pulp, pretreatment, and micronization treatment.

In this embodiment, the crystallinity is a value measured according to JIS K 0131 (1996).

The pulp viscosity of the fine fibers is preferably 2 cps or more, more preferably 4 cps or more. If the pulp viscosity of the fine fibers is less than 2 cps, it may be difficult to suppress the aggregation of the fine fibers.

In this embodiment, the pulp viscosity is a value measured according to TAPPI T 230.

The freeness of the fine fiber is preferably 500 ml or less, more preferably 300 ml or less, and particularly preferably 100 ml or less. If the freeness of the fine fibers exceeds 500 ml, the effect of improving the strength of the resin may not be sufficiently obtained.

In this embodiment, the freeness is a value measured in accordance with JIS P8121-2 (2012).

The zeta potential of the fine fiber is preferably −150 to 20 mV, more preferably -100 to 0 mV, and particularly preferably -80 to -10 mV. If the zeta potential is lower than −150 mV, the compatibility with the resin may be significantly reduced and the reinforcing effect may be insufficient. On the other hand, if the zeta potential exceeds 20 mV, the dispersion stability may decrease.

The water retention of the fine fibers is preferably 80 to 400%, more preferably 90 to 350%, and particularly preferably 100 to 300%. If the water retention level is less than 80%, the reinforcing effect may be insufficient because it is the same as the raw material pulp. On the other hand, when the degree of water retention exceeds 400%, the dehydration property tends to be inferior and the agglutination tends to occur. In this respect, the water retention degree of the fine fiber can be lowered by substituting the hydroxy group of the fiber with the carbamate group, and the dehydration property and the dryness can be improved.

The water retention of fine fibers can be arbitrarily adjusted by, for example, selection of raw material pulp, pretreatment, defibration, etc.

In this embodiment, the degree of water retention is JAPAN TAPPI No. It is a value measured according to 26 (2000).

The fine fiber of this embodiment has a carbamate group. How it is supposed to have a carbamate group is not particularly limited. For example, the cellulose raw material may be carbamate to have a carbamate group, or the fine fibers (defibrated cellulose raw material) may be carbamate to have a carbamate group.

The term "having a carbamic acid group" means a state in which a carbamic acid group (ester of carbamic acid) is introduced into the cellulose fiber. The carbamate group is a group represented by —O—CO-NH—, for example, a group represented by —O—CO—NH ₂ , —O—CONHR, —O—CO—NR _{2, and the} like. That is, the carbamate group can be represented by the following structural formula (1).

Here, R is independently a saturated linear hydrocarbon group, a saturated branched chain hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched chain hydrocarbon group, and the like. An aromatic group and at least one of these inducing groups.

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

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

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

Examples of the unsaturated linear hydrocarbon group include a linear alkenyl group having 2 to 10 carbon atoms such as an ethenyl group, a propene-1-yl group and a propene-3-yl group, an ethynyl group and a propyne-1. Examples thereof include a linear alkynyl group having 2 to 10 carbon atoms such as an yl group and a propyne-3-yl group.

Examples of the unsaturated branched chain hydrocarbon group include a branched chain alkenyl group having 3 to 10 carbon atoms such as a propene-2-yl group, a butene-2-yl group, and a butene-3-yl group, and butin-3. -A branched chain alkynyl group having 4 to 10 carbon atoms such as an yl group can be mentioned.

Examples of the aromatic group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group and the like.

Examples of the inducing group include the above-mentioned saturated linear hydrocarbon group, saturated branched chain hydrocarbon group, saturated cyclic hydrocarbon group, unsaturated linear hydrocarbon group, unsaturated branched chain hydrocarbon group and aromatic. Examples thereof include a group in which one or more hydrogen atoms contained in the group are substituted with a substituent (for example, a hydroxy group, a carboxy group, a halogen atom, etc.).

In the fine fiber having a carbamate group (in which a carbamate group is introduced), a part or all of the highly polar hydroxy group is replaced with a relatively low polarity carbamate group. Therefore, the fine fiber having a carbamate group has low hydrophilicity and high affinity with a resin having low polarity. As a result, the fine fiber having a carbamate group is excellent in uniform dispersibility with the resin. Further, the slurry of fine fibers having a carbamate group has low viscosity and good handleability.

The substitution rate of the carbamate group with respect to the hydroxy group of the fine fiber 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. Is. When the substitution rate is 1.0 mmol / g or more, the effect of introducing the carbamate group, particularly the effect of improving the flexural modulus of the resin can be surely exhibited. On the other hand, if the substitution rate exceeds 5.0 mmol / g, the cellulose fibers may not be able to maintain the shape of the fibers, and the reinforcing effect of the resin may not be sufficiently obtained. Further, when the substitution rate of the carbamate group exceeds 2.0 mmol / g, the average fiber length of the pulp becomes short when the raw material pulp is carbamate, and as a result, the average fiber length of the fine fibers tends to be less than 0.1 mm. There is a risk that sufficient resin reinforcement effect cannot be obtained. In the case of carbamate of the raw material pulp, the above substitution rate directly applies to the substitution rate of the carbamate group of the raw material pulp.

Explaining the above in more detail, first, the hydroxyl group existing in the cellulose contributes to the hydrogen bond of the cellulose itself, and when it is compounded with the resin, the cellulose fibers aggregate by the hydrogen bond and act as a reinforcing fiber. Is hindered. Therefore, by substituting the hydroxyl group with a carbamate group (particularly, the substitution rate is 1.0 mmol / g or more), the hydrogen bond is weakened, the aggregation of the fiber is suppressed, and the fiber is effectively functioned as a reinforcing material. However, if the hydroxyl group is replaced with a carbamate group too much, the affinity with the resin is improved too much and there is a possibility that the hydroxyl group will be dissolved in the resin when it is compounded with the resin. When dissolved, it does not exist as a fiber but exists as a molecule, so it is considered that the reinforcing property is lost. Therefore, by setting the substitution rate to 1.0 to 2.0 mmol / g, it is possible to suppress excessive agglutination of the fibers themselves and to exist in the resin in the form of the reinforcing fibers and exhibit reinforcing properties. Think about it.

In this embodiment, the substitution rate of the carbamate group (mmol / g) means the amount of substance of the carbamate group contained in 1 g of the cellulose raw material having the carbamate group. The substitution rate of the carbamate group is measured by measuring the N atoms present in the carbamate pulp by the Kjeldahl method, and the carbamateization rate per unit weight is calculated. Cellulose is a polymer having anhydrous glucose as a structural unit, and has three hydroxy groups per structural unit. As described above, in the case of carbamate before making fine fibers, that is, before defibration, the above substitution rate is the substitution rate of the carbamate group in the cellulose raw material.

<Carbamate>
Here, carbamate formation will be described in detail.
As described above, the point of introducing a carbamate group (carbamate formation) into fine fibers (cellulose raw material when carbamate before defibration; the same applies hereinafter, also simply referred to as "cellulose fiber") is cellulose. There are a method of carbamating the raw material and then making it finer, and a method of making the cellulose raw material finer and then making it into carbamate. In this regard, in the present specification, the defibration of the cellulose raw material will be described first, and then the carbamate formation (modification) will be described. However, either defibration or carbamate can be done first. However, it is preferable to carry out carbamate first and then defibrate. This is because the cellulose raw material before defibration has high dehydration efficiency, and the cellulose fibers are easily defibrated by heating accompanying carbamate formation. Regarding the case of carbamating first, it can be said that it is a method for producing carbamated cellulose fibers even after the carbamating and before the defibration.

The step of carbamate-forming cellulose fibers can be mainly classified into, for example, a mixing treatment, a removal treatment, and a heat treatment. The mixing treatment and the removing treatment can also be referred to as an adjustment treatment for preparing a mixture to be subjected to the heat treatment. Carbamateization also has the advantage that it can be chemically modified without the use of organic solvents.

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

As the derivative of urea or urea, for example, urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, a compound in which the hydrogen atom of urea is replaced with an alkyl group or the like can be used. can. These ureas and urea derivatives can be used alone or in combination of two or more. However, it is preferable to use urea.

The total amount (mixed amount) of urea or the like added to the cellulose fibers is preferably 1 to 70 (w / w)%, more preferably 5 to 50 (w / w)%, and particularly preferably 10 to 50 (w / w). )%. By increasing the addition amount to 1% or more, the efficiency of carbamate formation is improved. On the other hand, even if the addition amount exceeds 70%, the carbamate formation reaches a plateau.

The dispersion medium is usually water. However, other dispersion media such as alcohol and ether, or a mixture of water and another dispersion medium may be used.

In the mixing treatment, for example, cellulose fibers and urea may be added to water, cellulose fibers may be added to an aqueous solution of urea or the like, or urea or the like may be added to a slurry containing cellulose fibers. Further, in order to mix uniformly, the mixture may be stirred after the addition. Further, the dispersion liquid containing the cellulose fibers and urea or the like may contain other components.

In the removal treatment, the dispersion medium is removed from the dispersion liquid containing the cellulose fibers and urea obtained in the mixing treatment. By removing the dispersion medium, urea and the like can be efficiently reacted in the subsequent heat treatment.

It is preferable to remove the dispersion medium by volatilizing the dispersion medium by heating. According to this method, only the dispersion medium can be efficiently removed while leaving components such as urea.

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

The heating time in the removal treatment can be appropriately adjusted according to the solid content concentration of the dispersion liquid and the like. Specifically, for example, 6 to 24 hours.

In the heat treatment following the removal treatment, a mixture of cellulose fibers and urea or the like is heat-treated. In this heat treatment, a part or all of the hydroxy groups of the cellulose fibers react with urea or the like and are replaced with carbamate groups. More specifically, when urea or the like is heated, it is decomposed into isocyanic acid and ammonia as shown in the following reaction formula (1). Isocyanic acid is very reactive, and for example, a carbamate group is formed at the hydroxyl group of the cellulose fiber as shown in the following reaction formula (2).
NH _2- CO-NH ₂ → H-N = C = O + NH ₃ ... (1)
Cell-OH + HN = C = O → Cell-CO-NH ₂ … (2)

The heating temperature in the heat treatment is preferably 150 to 170 ° C, more preferably 150 to 165 ° C, and particularly preferably 150 to 160 ° C. By setting the heating temperature to 150 ° C. or higher, the substitution rate of the carbamate group can be set to 1 mmol / g or higher even in a short-time reaction. On the other hand, by setting the heating temperature to 170 ° C. or lower, damage to the fibers can be suppressed. The melting point of urea is about 134 ° C.

The heating time in the heat treatment is preferably 0.5 to 2.0 hours, more preferably 0.6 to 1.5 hours, and particularly preferably 0.7 to 1.0 hours. By setting the heating time to 0.5 hours or more, the carbamate formation reaction can be reliably carried out. However, if the heating time exceeds 2.0 hours, the cellulose fibers may be damaged (deteriorated).

Thus, prolonged heating time causes deterioration of cellulose fibers. Therefore, the pH condition in the heat treatment becomes important. The pH is preferably an alkaline condition of pH 9 or higher, more preferably pH 9 to 13, and particularly preferably pH 10 to 12. Further, as the next best measure, the pH is 7 or less, preferably pH 3 to 7, and particularly preferably pH 4 to 7, which is an acidic condition or a neutral condition. Under neutral conditions of pH 7 to 8, the average fiber length of the cellulose fibers becomes short, and the reinforcing effect of the resin may be inferior. On the other hand, under alkaline conditions of pH 9 or higher, the reactivity of the cellulose fibers is enhanced, the reaction with urea or the like is promoted, and the carbamate-forming reaction is carried out efficiently, so that the average fiber length of the cellulose fibers should be sufficiently secured. Can be done. On the other hand, under acidic conditions of pH 7 or less, the reaction of decomposing urea or the like into isocyanic acid and ammonia proceeds, the reaction with cellulose fibers is promoted, and the carbamate formation reaction is performed efficiently, so that the average fiber length of the cellulose fibers is sufficient. Can be secured. However, if possible, it is preferable to heat-treat under alkaline conditions. This is because acid hydrolysis of cellulose may proceed under acidic conditions.

The pH can be adjusted by adding an acidic compound (for example, acetic acid, citric acid, etc.) or an alkaline compound (for example, sodium hydroxide, calcium hydroxide, etc.) to the mixture.

However, the heat treatment for acidifying the pH is preferably carried out under the condition that 0.001 mmol or more of the organic acid ion is added to 1 g of the urea and the urea derivative (total mass of the urea and the urea derivative). It is more preferable to carry out under the condition of addition of 0.1 to 10.0 mmol, and particularly preferably to carry out under the condition of addition of 1.0 to 5.0 mmol. When the organic acid is added, the reaction of decomposing urea or the like into isocyanic acid and ammonia proceeds, the reaction with the cellulose fiber is promoted, and the carbamate formation reaction is carried out efficiently. However, if the organic acid ion is less than 0.001 mmol / g, such an effect may not be exhibited. On the other hand, when the organic acid ion exceeds 10.0 mmol / g, the effect of the organic acid ion reaches a plateau, unnecessary organic acid ion remains, and the carbamate formation reaction by urea may be inhibited.

However, when citric acid is used as the organic acid, the amount of citric acid added to the cellulose fibers is preferably 0.1 to 10,000 ppm, more preferably 1 to 7,000 ppm, and 10 to 5 It is particularly preferable to set it to 000 ppm. If the amount added is less than 0.1 ppm, the reaction of decomposing urea or the like into isocyanic acid and ammonia does not proceed well, so that the carbamate formation reaction may not proceed. On the other hand, if the addition amount exceeds 10,000 ppm, the hydroxyl group or carboxyl group of the organic acid may react with urea or the like and isocyanic acid, and urea or the like or isocyanic acid that contributes to carbamate formation may be consumed.

As the organic acid, in addition to citric acid, for example, malic acid, tartrate acid, oxalic acid, acetic acid, formic acid, fumaric acid, lactic acid, butyric acid, succinic acid, organic acid salts of these organic acids and the like can be used. However, it is preferable to use hydroxy acid and hydroxy salt in combination, and it is more preferable to use citric acid and citrate in combination. Under acidic conditions, urea and the like are decomposed into isocyanic acid and ammonia as described above, but this ammonia is neutralized by a hydroxy acid such as citric acid, and ammonia is reduced. When the amount of ammonia decreases, the production of ammonia progresses and carbamate formation progresses. However, if the amount of hydroxy acid such as citric acid is simply increased, the hydroxy acid such as citric acid is consumed only for advancing acidification. However, when a hydroxy acid salt is used in combination, this hydroxy acid salt becomes a buffer, a hydroxy acid is produced from the hydroxy acid salt, neutralization of ammonia, production of ammonia progresses, and carbamate formation proceeds.

In addition to citric acid, hydroxy acids include, for example, aliphatic hydroxy acids such as glycolic acid, lactic acid, tarthronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartrate acid, isocitrate acid, mevalonic acid, pantoic acid, and ricinolic acid, and salicylic acid. , Vanillic acid, aromatic hydroxy acids such as citric acid and the like can be exemplified.

From the above viewpoint, the addition ratio of the hydroxy acid salt to the hydroxy acid is preferably 1,000 parts by mass or less, more preferably 750 parts by mass or less, and 500 parts by mass or less with respect to 100 parts by mass of the hydroxy acid. Is particularly preferable. The hydroxy salt is meaningful in combination with a hydroxy acid, and the lower limit can be said to be more than 0 parts by mass, but preferably 10 parts by mass or more.

Further, it is desirable that the organic acid salt is added so that the pH in the system is within the above-mentioned pH. By satisfying such conditions, the flexural modulus and bending elongation of the fibrous cellulose composite resin are improved. If the amount of hydroxy acid such as citric acid added is simply increased, the average fiber length of cellulose or the like may be shortened, but the combined use of hydroxy acid and hydroxy acid salt suppresses this possibility.

As a device for heating in the heat treatment, for example, a hot air dryer, a paper machine, a dry pulp machine, or the like can be used.

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

(slurry)
If necessary, the cellulose fibers are dispersed in an aqueous medium to form a dispersion liquid (slurry). It is particularly preferable that the total amount of the aqueous medium is water, but an aqueous medium which is another liquid which is partially compatible with water can also be used. As the other liquid, lower alcohols having 3 or less carbon atoms can be used.

The solid content concentration of the slurry is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 5.0% by mass. If the solid content concentration is less than 0.1% by mass, excessive energy may be required for dehydration and drying. On the other hand, if the solid content concentration exceeds 10.0% by mass, the fluidity of the slurry itself is lowered, and for example, when a dispersant is used, it may not be possible to mix uniformly.

(Acid-modified resin)
If the carbamate-ized cellulose fiber is not defibrated, it is defibrated to obtain fine fibers (hereinafter, the same applies), and then mixed with an acid-modified resin. In the acid-modified resin, the acid group is ionically bonded to a part or all of the carbamate group. This ionic bond improves the reinforcing effect of the resin.

As the acid-modified resin, for example, an acid-modified polyolefin resin, an acid-modified epoxy resin, an acid-modified styrene-based elastomer resin, or the like can be used. However, it is preferable to use an acid-modified polyolefin resin. The acid-modified polyolefin resin is a copolymer of an unsaturated carboxylic acid component and a polyolefin component.

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

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

The mixed amount of the acid-modified resin 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 with respect to 100 parts by mass of the fine fibers. In particular, when the acid-modified resin is a maleic anhydride-modified polypropylene resin, the amount is preferably 1 to 200 parts by mass, more preferably 10 to 100 parts by mass. If the mixed amount of the acid-modified resin is less than 0.1 parts by mass, the improvement in strength may not be sufficient. On the other hand, if the mixing amount exceeds 1,000 parts by mass, it becomes excessive and the strength tends to decrease.

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

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

Further, the MFR (melt flow rate) of the acid-modified resin is preferably 2,000 g / 10 minutes (190 ° C. / 2.16 kg) or less, more preferably 1,500 g / 10 minutes or less, and 500 g / 10 minutes or less. It is particularly preferably 10 minutes or less. If the MFR exceeds 2,000 g / 10 minutes, the dispersibility of the cellulose fibers may decrease.

The acid value is measured in accordance with JIS-K2501 and titrated with potassium hydroxide. The MFR measurement is based on JIS-K7210, and is determined by the weight of the sample flowing out in 10 minutes with a load of 2.16 kg at 190 ° C.

(Dispersant)
The fine fibers are preferably mixed with a dispersant. As the dispersant, a compound having an amine group and / or a hydroxyl group in an aromatic group and a compound having an amine group and / or a hydroxyl group in an aliphatic group are preferable.

Examples of compounds having an amine group and / or a hydroxyl group in aromatics include aniline, toluidin, trimethylaniline, anisidin, tyramine, histamine, tryptamine, phenol, dibutylhydroxytoluene, and bisphenol A. Classes, cresols, eugenols, gallic acid, guaiacol, picrinic acid, phenolphthalene, serotonin, dopamine, adrenaline, noradrenaline, timol, tyrosine, salicylic acid, methyl salicylate, anis alcohol. , Salicyl alcohols, cinapyl alcohols, diphenidols, diphenylmethanols, cinnamyl alcohols, scopolamines, tryptofols, vanillyl alcohols, 3-phenyl-1-propanols, phenethyl alcohols, phenoxyethanols , Veratril alcohols, benzyl alcohols, benzoins, mandelic acids, manderonitriles, benzoic acids, phthalic acids, isophthalic acids, terephthalic acids, melitonic acids, silicic acids and the like.

Examples of compounds having an amine group and / or a hydroxyl group in aliphatics include capryl alcohols, 2-ethylhexanols, pelargone alcohols, caprin alcohols, undecyl alcohols, lauryl alcohols, and tridecyl alcohols. , Myristyl alcohols, pentadecyl alcohols, cetanols, stearyl alcohols, erizyl alcohols, oleyl alcohols, linoleyl alcohols, methylamines, dimethylamines, trimethylamines, ethylamines, diethylamines, ethylenediamine , Triethanolamines, N, N-diisopropylethylamines, tetramethylethylenediamines, hexamethylenediamines, spermidins, spermins, amantadins, formic acids, acetic acids, propionic acids, butyric acids, valeric acids, Caproic acids, enanth acids, capricic acids, pelargonic acids, capric acids, lauric acids, myristic acids, palmitic acids, margalic acids, stearic acids, oleic acids, linoleic acids, linolenic acids, arachidonic acids, eicosapentaenoic acids, docosahexaenoic acids, sorbins. Examples include acids.

The above dispersants inhibit hydrogen bonds between cellulose fibers. Therefore, when the fine fibers and the resin are kneaded, the fine fibers are surely dispersed in the resin. Further, the above dispersant also has a role of improving the compatibility of the fine fibers and the resin. In this respect as well, the dispersibility of the fine fibers in the resin is improved.

It is conceivable to add a phase solvent (drug) separately when kneading the fine fibers and the resin, but rather than adding a chemical at this stage, the fine fibers and the dispersant (drug) are mixed in advance. When the fibrous cellulose-containing material is used, the chemicals are more uniformly attached to the fine fibers, and the effect of improving the compatibility with the resin is enhanced.

Further, for example, polypropylene has a melting point of 160 ° C., and therefore, kneading of fine fibers and resin is performed at about 180 ° C. However, if a dispersant (liquid) is added in this state, it dries in an instant. Therefore, there is a method of producing a masterbatch (composite resin having a high concentration of fine fibers) using a resin having a low melting point, and then lowering the concentration with a normal resin. However, a resin having a low melting point generally has a low strength. Therefore, according to this method, the strength of the composite resin may decrease.

The mixing amount of the dispersant 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 with respect to 100 parts by mass of the fine fibers. If the mixing amount of the dispersant is less than 0.1 parts by mass, it may be considered that the improvement of the resin strength is not sufficient. On the other hand, if the mixing amount exceeds 1,000 parts by mass, the amount becomes excessive and the resin strength tends to decrease.

In this respect, the above-mentioned acid-modified resin is intended to improve the compatibility by ionic bonding between the acid group and the carbamate group of the fine fiber, thereby enhancing the reinforcing effect, and because of its large molecular weight, it is easy to be compatible with the resin. It is considered that it contributes to the improvement of strength. On the other hand, the above-mentioned dispersant intervenes between the hydroxyl groups of the fine fibers to prevent aggregation and thus improves the dispersibility in the resin, and has a smaller molecular weight than the acid-modified resin. It can enter a narrow space between fine fibers that an acid-modified resin cannot enter, and plays a role of improving dispersibility and strength. From the above viewpoint, the molecular weight of the acid-modified resin is preferably 2 to 2,000 times, preferably 5 to 1,000 times, the molecular weight of the dispersant.

(Powder that does not interact)
The fine fibers of this embodiment are preferably mixed with a powder that does not interact with the cellulose fibers. By mixing with non-interacting powder, the reinforcing effect is improved. In this respect, in this embodiment, the aqueous medium is removed to obtain a fibrous cellulose-containing material whose water content is adjusted to a predetermined range before the fine fibers are composited with the resin. However, when the aqueous medium is removed, the cellulose fibers may irreversibly aggregate due to hydrogen bonds, and the reinforcing effect as the fibers may not be sufficiently exhibited. Therefore, by mixing a powder that does not interact with the cellulose fibers, hydrogen bonds between the cellulose fibers are physically inhibited.

Here, "non-interacting" is included in the concept that covalent bonds, ionic bonds, and strong bonds by metal bonds do not occur with cellulose (that is, hydrogen bonds and van der Waals force bonds do not interact). .). Preferably, the strong bond is a bond having a binding energy of more than 100 kJ / mol.

The non-interacting powder is preferably at least one of an inorganic powder and a resin powder having little action of dissociating the hydroxyl group of the cellulose fiber into hydroxide ions when coexisting in the slurry. More preferably, it is an inorganic powder. Having such physical characteristics makes it possible to easily disperse the powder that does not interact with the cellulose fibers into the resin or the like when the fibrous cellulose-containing material is formed and then compounded with the resin. Further, particularly when it is an inorganic powder, it is advantageous in terms of operation. Specifically, as a method for adjusting the water content of the fibrous cellulose-containing material, for example, a method of directly applying an aqueous dispersion (a mixture of fibrous cellulose and non-interacting powder) to a metal drum as a heat source is used for drying (a mixture of fibrous cellulose and non-interacting powder). For example, a method of drying with a Yankee dryer or a cylinder dryer, etc.) and a method of heating without directly contacting the water dispersion with a heat source, that is, a method of drying in air (for example, drying with a constant temperature dryer, etc.). And exists. However, when resin powder is used, when it is brought into contact with a heated metal plate (for example, a Yankee dryer, a cylinder dryer, etc.) and dried, a film is formed on the surface of the metal plate, the heat conduction deteriorates, and the drying efficiency becomes remarkable. descend. Inorganic powders are advantageous in that such problems are unlikely to occur.

The average particle size of the non-interacting 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 exceeds 10,000 μm, when the aqueous medium is removed from the fibrous cellulose slurry, it may enter into the gaps between the fine fibers and the effect of inhibiting aggregation may not be exhibited. On the other hand, if the average particle size is less than 1 μm, hydrogen bonds between the fine fibers may not be inhibited due to the fineness.

In particular, when the powder that does not interact with the powder is a resin powder, the effect of inhibiting aggregation by entering the gaps between the fine fibers is effectively exhibited when the average particle size is in the above range. Moreover, it is economical because it has excellent kneadability with a resin and does not require a large amount of energy. Since the resin powder melts when kneaded with the resin and does not affect the appearance as particles, a powder having a large particle size can be effectively used. On the other hand, even when the resin powder is an inorganic powder, the average particle size of the inorganic powder is in the above range, so that the effect of entering the gaps between the fine fibers and inhibiting aggregation is exhibited, but the inorganic powder is kneaded. However, the size does not change significantly, so if the particle size is too large, it may affect the appearance as grains.

The resin powder physically intervenes between the fine fibers to inhibit hydrogen bonds, thereby improving the dispersibility of the fine fibers. On the other hand, the acid-modified resin described above improves compatibility by ionic bonding an acid group and a carbamate group of fine fibers, thereby enhancing a reinforcing effect. In this respect, the dispersant inhibits hydrogen bonds between fine fibers in the same manner, but since the resin powder is micro-order, it physically intervenes and suppresses hydrogen bonds. Therefore, although the dispersibility is lower than that of the dispersant, the resin powder itself melts into a matrix, which does not contribute to deterioration of physical properties. On the other hand, since the dispersant is at the molecular level and is extremely small, it has a high effect of covering the fine fibers to inhibit hydrogen bonds and improving the dispersibility of the fine fibers. However, it may remain in the resin and work to reduce the physical properties.

The average particle size of non-interacting powder is a volume standard measured using a particle size distribution measuring device (for example, a laser diffraction / scattering type particle size distribution measuring device manufactured by Horiba Seisakusho Co., Ltd.) with the powder as it is or in the state of an aqueous dispersion. It is a medium diameter calculated from the particle size distribution.

Examples of the inorganic powder include simple substances and oxides of metal elements in Groups I to VIII of the Periodic Table of the Periodic Table, such as Fe, Na, K, Cu, Mg, Ca, Zn, Ba, Al, Ti, and silicon elements. , Hydroxides, carbon salts, sulfates, silicates, sulfites, various clay minerals composed of these compounds, and the like can be exemplified. Specifically, for example, barium sulfate, calcium sulfate, magnesium sulfate, sodium sulfate, calcium sulfite, zinc oxide, heavy calcium carbonate, light calcium carbonate, aluminum borate, alumina, iron oxide, calcium titanate, aluminum hydroxide, etc. Magnesium hydroxide, calcium hydroxide, sodium hydroxide, magnesium carbonate, calcium silicate, clay, wallastnite, glass beads, glass powder, silica gel, dry silica, colloidal silica, silica sand, silica stone, quartz powder, diatomaceous earth, white carbon , Glass fiber and the like can be exemplified. A plurality of these inorganic fillers may be contained. Further, it may be contained in recycled paper pulp, or may be a so-called recycled filler obtained by regenerating an inorganic substance in paper sludge.

However, at least one inorganic powder selected from calcium carbonate, talc, white carbon, clay, calcined clay, titanium dioxide, aluminum hydroxide, recycled filler, etc., which are suitably used as fillers and pigments for papermaking. It is preferable to use at least one selected from calcium carbonate, talc, and clay, and it is more preferable to use at least one of light calcium carbonate and heavy calcium carbonate. Especially preferable. When calcium carbonate, talc, or clay is used, it is easy to combine with a matrix such as a resin. Further, since it is a general-purpose inorganic material, there is an advantage that there are few restrictions on its use. Further, calcium carbonate is particularly preferable for the following reasons. When light calcium carbonate is used, it becomes easier to control the size and shape of the powder to be constant. For this reason, there is a merit that the size and shape can be adjusted so as to easily generate the effect of suppressing the aggregation of the fine fibers by entering the gap according to the size and shape of the fine fibers, and the effect can be easily exerted in a pinpoint manner. There is. In addition, when heavy calcium carbonate is used, since the heavy calcium carbonate is amorphous, even if fibers of various sizes are present in the slurry, they enter the gap in the process of agglomeration of the fibers when the aqueous medium is removed. There is a merit that the aggregation of fine fibers can be suppressed.

On the other hand, as the resin powder, the same resin as that used when obtaining the composite resin can be used. Of course, they may be different, but they are preferably the same.

The blending amount of the non-interacting powder is preferably 1 to 9900% by mass, more preferably 5 to 1900% by mass, and particularly preferably 10 to 900% by mass with respect to the fine fibers (cellulose fibers). If the blending amount is less than 1% by mass, it may enter into the gaps between the fine fibers and the action of suppressing aggregation may be insufficient. On the other hand, if the blending amount exceeds 9900% by mass, the function as fine fibers may not be exhibited. When the powder that does not interact with the powder is an inorganic powder, it is preferable to mix the powder in a ratio that does not interfere with thermal recycling.

Inorganic powder and resin powder can be used in combination as the non-interacting powder. When the inorganic powder and the resin powder are used in combination, the inorganic powder and the resin powder exert an effect of preventing each other from agglutination even when the inorganic powder and the resin powder are mixed under the condition of agglutination. In addition, powder with a small particle size has a large surface area and is more susceptible to the influence of intermolecular force than the influence of gravity, and as a result, it is more likely to aggregate. There is a risk that the powders will not loosen well in the slurry, or that the powders will aggregate when the water content is adjusted, and the effect of preventing the aggregation of fine fibers will not be fully exhibited. However, it is considered that the combined use of the inorganic powder and the resin powder can alleviate the agglutination of the powder itself.

When the inorganic powder and the resin powder are used in combination, the ratio of the average particle size of the inorganic powder to the average particle size of the resin powder is preferably 1: 0.1 to 1: 10,000, preferably 1: 1 to 1: 1,000. Is more preferable. Within this range, problems arise from the strength of its own cohesive force (for example, when mixing powder and fine fiber slurry, the powder does not loosen well in the slurry, or when adjusting the water content, the powder It is considered that the effect of preventing the agglomeration of fine fibers can be sufficiently exerted without causing the problem of agglomeration of fine fibers.).

When the inorganic powder and the resin powder are used in combination, the ratio of the mass% of the inorganic powder to the mass% of the resin powder is preferably 1: 0.01 to 1: 100, more preferably 1: 0.1 to 1:10. Within this range, it is considered possible for dissimilar powders to inhibit their own aggregation. In other words, if it is within this range, problems arise from the strength of its own cohesive force (for example, when the powder and the fine fiber slurry are mixed, the powder does not loosen well in the slurry, or when the water content is adjusted. It is considered that the effect of preventing the agglomeration of fine fibers can be sufficiently exerted without causing the problem that the powders agglomerate with each other.).

(Manufacturing method of composite resin)
In producing the fibrous cellulose composite resin, a mixture of fine fibers (cellulose fibers), acid-modified resin, dispersant, non-interacting powder and the like is contained prior to kneading with the resin as described in detail below. It is preferable to use a fibrous cellulose-containing material having a water content of less than 18%. This fibrous cellulose-containing material is usually a dried product. Further, this dried product is preferably pulverized into a powder. According to this form, the coloring of the fibrous cellulose composite resin obtained by kneading with the resin is reduced. In addition, it is not necessary to dry the fibrous cellulose when kneading with the resin, and the thermal efficiency is good. Further, when a powder that does not interact with the mixture or a dispersant is mixed, there is a low possibility that the cellulose fibers (fine fibers) will not be redispersed even if the mixture is dried.

The mixture is dehydrated if necessary prior to drying. For this dehydration, for example, one or two or more types are selected from dehydrators such as belt presses, screw presses, filter presses, twin rolls, twin wire formers, valveless filters, center disk filters, membrane treatments, and centrifuges. Can be done using.

Drying of the mixture or dehydrated product is, for example, rotary kiln drying, disk drying, air flow drying, medium flow drying, spray drying, drum drying, screw conveyor drying, paddle drying, uniaxial kneading drying, multiaxial kneading drying, vacuum. It can be carried out by selectively using one kind or two or more kinds from drying, stirring drying and the like.

The dried mixture (dried product) is preferably crushed into a powder. The pulverization of the dried product can be carried out by selecting or using one or more of, for example, a bead mill, a kneader, a disper, a twist mill, a cut mill, a hammer mill and the like.

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 powdery substance exceeds 10,000 μm, the kneadability with the resin may be inferior. On the other hand, it is not economical because a large amount of energy is required to make the average particle size of the powdery substance less than 1 μm.

The average particle size of the powder can be controlled not only by controlling the degree of crushing, but also by classifying using a classifying device such as a filter or a cyclone.

The bulk specific gravity 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. When the bulk specific density exceeds 1.0, it means that the hydrogen bonds between the fine fibers are stronger and it is not easy to disperse them in the resin. On the other hand, making the bulk specific density less than 0.03 is disadvantageous in terms of transfer cost.

The bulk specific density is a value measured according to JIS K7365.

The water content of the mixture (fibrous cellulose-containing material) is preferably less than 18%, more preferably 0 to 17%, and particularly preferably 0 to 16%. When the water content is 18% or more, it may not be possible to reduce the coloring of the fibrous cellulose composite resin due to the components derived from the cellulose fibers. In particular, when the substitution rate of the carbamate group is 1 mmol / g or more, it may not be possible to reduce the coloring.

When the water content is 18% or more, the microfiber cellulose and high-temperature water come into contact with each other when exposed to a high temperature of, for example, 180 ° C. or higher by melt-kneading or the like, resulting in a low molecular weight reaction of the microfiber cellulose. Is generated, a low-molecular-weight compound that causes coloring is generated, and it is considered that coloring by the low-molecular-weight compound proceeds in the kneading step. However, when the carbamate group is carbamate so that the substitution rate is 1 mmol / g or more, for example, the coloring-causing substance is removed in the washing step of the carbamate pulp, and the water content is further reduced to 18% or less. Therefore, it becomes possible to evaporate the high-temperature water before it comes into contact with the microfiber cellulose, and it is possible to prevent coloring.

By the way, when the originally existing coloring-causing substance (hemicellulose, etc.) has a low molecular weight, it becomes water-soluble, and it becomes possible to remove the coloring-causing substance in the washing process of the carbamate pulp. When the coloring-causing substance remains in the microfiber cellulose, the above-mentioned high-temperature water and the coloring-causing substance come into contact with each other, and the coloring becomes remarkable.

The water content content is a value calculated by the following formula, where the mass at the time when the sample is held at 105 ° C. for 6 hours or more using a constant temperature dryer and no change in mass is observed is taken as the mass after drying.
Moisture content (%) = [(mass before drying-mass after drying) ÷ mass before drying] x 100

The dehydrated and dried fine fibers may contain a resin other than the resin powder as a powder that does not interact with each other. When the resin is contained, the hydrogen bonds between the dehydrated and dried fine fibers are inhibited, and the dispersibility in the resin at the time of kneading can be improved.

Examples of the form of the resin contained in the dehydrated / dried fine fibers include powder, pellets, and sheets. However, powder (powder resin) is preferable.

In the case of powder, the average particle size of the powdered resin contained in the dehydrated and dried fine fibers 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, it may not enter the kneading device due to the large particle size. On the other hand, if the average particle size is less than 1 μm, hydrogen bonds between the fine fibers may not be inhibited due to the fineness. The resin such as the powder resin used here may be the same type as or different from the resin to be kneaded with the fine fibers (resin as the main raw material), but it is preferable that the resin is the same type.

The powder resin having an average particle diameter of 1 to 10,000 μm is preferably mixed in an aqueous dispersed state before dehydration and drying. By mixing in an aqueous-based dispersed state, the powder resin can be uniformly dispersed among the fine fibers, the fine fibers can be uniformly dispersed in the composite resin after kneading, and the strength physical characteristics can be further improved. ..

The fibrous cellulose-containing material (resin reinforcing material) obtained as described above is kneaded with a resin to obtain a fibrous cellulose composite resin. This kneading can be performed, for example, by a method of mixing the pellet-shaped resin and the reinforcing material, or by a method of first melting the resin and adding the reinforcing material to the melt. The acid-modified resin, dispersant and the like can also be added at this stage.

For the kneading process, for example, one or two or more types are selected and used from a single-screw or two-screw multi-screw kneader, a mixing roll, a kneader, a roll mill, a Banbury mixer, a screw press, a disperser, and the like. be able to. Among these, it is preferable to use a multi-screw kneader having two or more shafts. Two or more multi-axis kneaders with two or more axes may be used in parallel or in series.

The temperature of the kneading treatment is equal to or higher than the glass transition point 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 100 to 240 ° C. Is particularly preferable.

As the resin, it is preferable to use at least one of a thermoplastic resin and a thermosetting resin.

Examples of the thermoplastic resin include 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, and polyamide resins. One kind or two or more kinds can be selected and used from the polycarbonate resin, the polyacetal resin and the like.

However, it is preferable to use at least one of polyolefin and polyester resin. Moreover, it is preferable to use polypropylene as the polyolefin. Further, as the polyester resin, examples of the aliphatic polyester resin include polylactic acid and polycaprolactone, and examples of the aromatic polyester resin include polyethylene terephthalate, which are biodegradable. It is preferable to use a polyester resin having a above (simply also referred to as “biodegradable resin”).

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

As the hydroxycarboxylic acid-based aliphatic polyester, for example, a homopolymer of a hydroxycarboxylic acid such as lactic acid, malic acid, glucose acid, or 3-hydroxybutyric acid, or at least one of these hydroxycarboxylic acids is used. One type or two or more types can be selected and used from the polymers and the like. However, it is preferable to use polylactic acid, a polymer of the above hydroxycarboxylic acid excluding lactic acid and lactic acid, polycaprolactone, and a polymer of at least one of the above hydroxycarboxylic acids and caprolactone, and polylactic acid is preferably used. Especially preferred to use.

As this lactic acid, for example, L-lactic acid, D-lactic acid and the like can be used, and these lactic acids may be used alone or two or more kinds may be selected and used.

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

As the dibasic acid polyester, for example, one or more of polybutylene succinate, polyethylene succinate, polybutylene adipate and the like can be selected and used.

The biodegradable resin may be used alone or in combination of two or more.

Examples of the thermosetting resin include phenol resin, urea resin, melamine resin, furan resin, unsaturated polyester, diallyl phthalate resin, vinyl ester resin, epoxy resin, urethane resin, silicone resin, thermosetting polyimide resin and the like. Can be used. These resins can be used alone or in combination of two or more.

The resin may preferably contain an inorganic filler in a proportion that does not interfere with thermal recycling.

Examples of the inorganic filler include simple substances of metal elements in Groups I to VIII of the Periodic Table, such as Fe, Na, K, Cu, Mg, Ca, Zn, Ba, Al, Ti, and silicon elements, and oxidation. Examples thereof include substances, hydroxides, carbon salts, sulfates, silicates, sulfites, and various clay minerals composed of these compounds.

Specifically, for example, 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, hydroxylation. Examples of aluminum, magnesium hydroxide, calcium hydroxide, sodium hydroxide, magnesium carbonate, calcium silicate, claywa lastnite, glass beads, glass powder, silica sand, silica stone, quartz powder, diatomaceous earth, white carbon, glass fiber and the like are exemplified. be able to. A plurality of these inorganic fillers may be contained. Further, it may be contained in recycled paper pulp.

The mixing ratio of the resin to the fibrous cellulose (cellulose fiber) is preferably 9900 to 1, preferably 1900 to 66, and more preferably 900 to 100 with respect to 100 parts by mass of the fibrous cellulose. In particular, when the blending ratio of the fibrous cellulose in 100 parts by mass of the fibrous cellulose composite resin is 10 to 50 parts by mass, the strength of the resin composition, particularly the bending strength and the tensile elastic modulus can be remarkably improved.

The content ratio of the fibrous cellulose and the resin contained in the finally obtained resin composition is usually the same as the above-mentioned compounding ratio of the fibrous cellulose and the resin.

When the fine fiber is microfiber cellulose, ^{the difference between the solubility parameter (cal / cm 3} ) ^1/2 (SP value) of the microfiber cellulose and the resin is the SP _{MFC value of the microfiber cellulose and the SP POL} value of the resin. , SP value difference = 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 5-1. If the difference in SP value exceeds 10, microfiber cellulose may not be dispersed in the resin and the reinforcing effect may not be obtained. On the other hand, if the difference in SP value is less than 0.1, the microfiber cellulose dissolves in the resin and does not function as a filler, so that the reinforcing effect cannot be obtained. _{In this respect, the smaller the difference between the SP POL} value of the resin (solvent) _{and the SP MFC} value of the microfiber cellulose (solute), the greater the reinforcing effect.

The solubility parameter (cal / cm ³ ) ^1/2 (SP value) is a measure of the intramolecular force acting between the solvent and the solute, and the closer the SP value is to the solvent and solute, the higher the solubility. ..

(Molding process)
The kneaded product of the fine fibers and the resin can be formed into a desired shape after being kneaded again if necessary. The size, thickness, shape, etc. of this molding are not particularly limited, and may be, for example, sheet-shaped, pellet-shaped, powder-shaped, fibrous-shaped, or the like.

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

Molding of the kneaded product can be performed by, for example, mold molding, injection molding, extrusion molding, hollow molding, foam molding, or the like. Further, the kneaded product may be spun into a fibrous form and mixed with the above-mentioned plant material or the like to form a mat shape or a board shape. The mixed fiber can be, for example, a method of simultaneous deposition by an air ray or the like.

As an apparatus for molding a kneaded product, for example, one or two from injection molding machines, blow molding machines, hollow molding machines, blow molding machines, compression molding machines, extrusion molding machines, vacuum forming machines, pneumatic molding machines and the like. You can select and use more than one species.

The above molding can be performed after kneading, or the kneaded product is once cooled and made into chips by using a crusher or the like, and then the chips are put into a molding machine such as an extrusion molding machine or an injection molding machine. You can also do it. Of course, molding is not an essential requirement of the present invention.

(Other compositions)
The fibrous cellulose may contain cellulose nanofibers together with microfiber cellulose. Cellulose nanofibers are fine fibers like microfiber cellulose, and have a role of complementing microfiber cellulose for improving the strength of the resin. However, if possible, it is preferable to use only microfiber cellulose without containing cellulose nanofibers as fine fibers. The average fiber diameter (average fiber width; average diameter of single fibers) of the cellulose nanofibers is preferably 4 to 100 nm, more preferably 10 to 80 nm.

Further, the fibrous cellulose may contain pulp. Pulp has a role of significantly improving the dehydration property of the cellulose fiber slurry. However, as in the case of cellulose nanofibers, it is most preferable that pulp is not blended, that is, the content is 0% by mass.

In addition to fine fibers and pulp, the resin composition includes kenaf, jute hemp, Manila hemp, sisal, ganpi, sansho, 楮, banana, pineapple, coco palm, corn, sugar cane, bagasse, palm, papyrus, reeds, esparto, etc. Fibers derived from plant materials obtained from various plants such as sisal, wheat, rice, bamboo, various coniferous trees (sugi and hinoki, etc.), broadleaf trees and cotton may be contained or may be contained.

For the resin composition, for example, one or more selected from antistatic agents, flame retardants, antibacterial agents, colorants, radical scavengers, foaming agents, etc., and a range that does not impair the effects of the present invention. Can be added with. These raw materials may be added to the dispersion liquid of fibrous cellulose, added at the time of kneading the fine fibers and the resin, added to these kneaded products, or added by other methods. .. However, from the viewpoint of production efficiency, it is preferable to add it at the time of kneading the fine fibers and the resin.

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, methyl-pentene, octene, decene, dodecene and the like.

Next, an embodiment of the present invention will be described.
Using coniferous kraft pulp with a water content of 10% or less, an aqueous urea solution with a solid content concentration of 10%, and a 20% aqueous solution of citric acid, the mass ratio in terms of solid content is pulp: urea: citric acid = 100: 50: 0.1. After mixing so as to be, it was dried at 105 ° C. Next, heat treatment was performed at a predetermined reaction temperature and reaction time to obtain carbamate-modified pulp (carbamate-modified pulp). The obtained carbamate-modified pulp was diluted with distilled water and stirred, and dehydration washing was repeated twice. The washed carbamate-modified pulp is beaten using a beating machine until the Fine ratio (the ratio of fibers of 0.2 mm or less in the fiber length distribution measurement by FS5) becomes 77% or more, and the carbamate-modified microfiber cellulose (carbamate formation) is beaten. MFC (fine fiber)) was obtained.

For the obtained carbamate MFC, the carbamate ratio, the average fiber length after carbamation and before beating, and the average fiber length after beating were measured. The results are shown in Table 1. The carbamate ratio was calculated by FTIR measurement of the carbamate pulp after the reaction and based on the ratio of the peak heights of the absorption spectra of C = O and OH. As the carbamation progresses, OH decreases and O = C increases. However, in the table, the case where the carbamateization rate is 1 mmol / g or more is shown as ◯, and the case where the carbamateization rate is less than 1 mmol / g is shown as x. Regarding the average fiber length before beating, the case of 1.0 mm or more is shown as ◯, and the case of less than 1.0 mm is shown as x. Regarding the average fiber length after beating, the case of 0.8 mm or more was shown as ⊚, the case of 0.5 mm or more and less than 0.8 mm was shown as ◯, and the case of less than 0.5 mm was shown as x.

(Discussion)
For example, when heated at 170 ° C., the carbamate formation rate could be 1 mmol / g or more even when the reaction time was 1 hour and 30 minutes. Therefore, it can be seen that when this carbamate MFC is used as a reinforcing material for the resin, the flexural modulus of the resin can be improved. Further, even when the heat treatment was performed at 170 ° C. for 3 hours, the average fiber length was 0.5 mm or more, indicating that the damage to the fibers was suppressed.

Further, it can be seen that if the reaction temperature is 150 ° C. or higher, the carbamate formation rate can be 1 mmol / g or higher.

Table 2 shows the relationship between the carbamate formation rate and the flexural modulus. In this test, a composite resin was prepared by the following method and the flexural modulus was measured. The measurement of flexural modulus was based on JIS K 7171: 1994. However, in the table, the flexural modulus of the resin itself is set to 1, and the case where the flexural modulus of the composite resin is 1.3 times or more is described as ◯, and the case where the flexural modulus of the composite resin is less than 1.3 times is described as x.

(Making composite resin)
A mixture of coniferous kraft pulp with a water content of 10% or less, an aqueous urea solution with a solid content concentration of 10%, and various pH adjustment solutions in a mass ratio in terms of solid content of pulp: urea: citric acid = 100: 50: 0.4. After mixing so as to be, it was dried at 105 ° C. Then, it was heat-treated at a reaction time of 160 ° C. for a reaction time of 1 hour to obtain a carbamate-modified pulp (carbamate conversion rate 1.0 mmol / g).

The obtained carbamate-modified pulp was diluted with distilled water and stirred, and dehydration washing was repeated twice.

The washed carbamate-modified pulp (concentration 3%) is refined using a beating machine (SDR) until the Fine ratio (the ratio of fibers of 0.2 mm or less in the fiber length distribution measurement by FS5) becomes 77% or more. By doing so, a carbamateized MFC aqueous dispersion was obtained.

Next, PP powder and MAPP powder were added to this aqueous dispersion (fiber concentration 3%) (carbamate MFC: PP powder: MAPP = 55.0: 17.5: 27.5) and mixed to form a slurry. .. This slurry was heated and dried (140 ° C., 3 rpm) with a drum dryer to obtain a carbamate MFC dried product. As the PP powder, Novatec PPMA3 pellets manufactured by Japan Polypropylene Corporation were processed into powder (500 μm or less through a sieve, medium diameter 123 μm). Further, as the MAPP powder, SCONA9212FA manufactured by BYK was used.

Next, the carbamateized MFC dried product was kneaded with a twin-screw kneader (180 ° C., 200 rpm) to obtain pellets. These pellets are mixed with PP pellets so as to have a carbamate MFC of 10% (carbamate MFC pellets: PP pellets = 10:45), kneaded with a twin-screw kneader (180 ° C., 200 rpm), and processed into pellets. , Injection molding was performed to prepare a bending test piece.

The present invention can be used as a method for producing a carbamateized cellulose fiber and a method for producing a carbamateized fine fiber.

Claims (5)

1. It has a step of heat-treating the cellulose fiber and substituting the hydroxy group of the cellulose fiber with a carbamate group so that the substitution rate is 1.0 mmol / g or more.
   The heat treatment is carried out at 150 to 170 ° C.
   A method for producing a carbamate-ized cellulose fiber.
2. The heat treatment is carried out under the condition that at least one of urea and a derivative of urea and citric acid are added to the cellulose fiber.
   The amount of the citric acid added to the cellulose fibers is 0.1 to 10,000 ppm.
   The method for producing a carbamate-ized cellulose fiber according to claim 1.
3. The amount of the urea and the derivative of the urea added to the cellulose fibers is 1 to 70%.
   The method for producing a carbamate-ized cellulose fiber according to claim 2.
4. A step of heat-treating the cellulose fiber to replace the hydroxy group of the cellulose fiber with a carbamate group so that the substitution rate is 1.0 mmol / g or more.
   It has a step of defibrating cellulose fibers so that the average fiber width is 19 μm or less to form fine fibers.
   The heat treatment is carried out at 150 to 170 ° C.
   A method for producing carbamate fine fibers.
5. The heat treatment is performed so that the crystallinity of the fine fibers remains at 50% or more.
   The method for producing a carbamate fine fiber according to claim 4.