WO2022091580A1

WO2022091580A1 - Method for producing fibrous cellulose and method for producing fibrous cellulose composite resin

Info

Publication number: WO2022091580A1
Application number: PCT/JP2021/032647
Authority: WO
Inventors: 貴章今井; 一紘松末; 隆之介青木
Original assignee: 大王製紙株式会社
Priority date: 2020-10-26
Filing date: 2021-09-06
Publication date: 2022-05-05

Abstract

[Problem] To provide: a method for producing fibrous cellulose, wherein the substitution rate of a modification treatment is improved; and a method for producing a fibrous cellulose composite resin. [Solution] This method for producing fibrous cellulose comprises: a step for carbamating cellulose fibers; and a step for fibrillating the cellulose fibers into fibrous cellulose. The carbamating step comprises: a mixing step wherein the cellulose fibers and at least one agent selected from among urea and a urea derivative are mixed with each other; and a heating step wherein the cellulose fibers are heated after the mixing step. The mixing step comprises: a step for adding the agent to the cellulose fibers; and a step for mixing up the cellulose fibers and the added agent, said step being carried out such that the precipitation rate of disintegrated cellulose fibers at the interface after 10 minutes standing is less than 60% if a 0.2 mass% disintegration liquid that is obtained by disintegrating the cellulose fibers, which have been obtained by the mixing step, in water is made to have a uniform concentration and subsequently left at rest. In a method for producing a fibrous cellulose composite resin according to the present invention, fibrous cellulose is obtained by the above-descried method, and the fibrous cellulose and a resin are mixed with each other.

Description

Method for producing fibrous cellulose and method for producing fibrous cellulose composite resin

The present invention relates to a method for producing fibrous cellulose and a method for producing a fibrous cellulose composite resin.

In recent years, cellulose nanofibers obtained by defibrating raw pulp and fine fibers such as microfiber cellulose (microfibrillated cellulose) have attracted attention for their use as reinforcing materials for resins, and research and development are underway. Although fine fibers are useful as a reinforcing material, they are hydrophilic and repel each other with a resin having hydrophobic properties, so that it may not be possible to sufficiently bring out the effect of the resin as a reinforcing material. There is a problem of not being there. To solve this problem, a technique of performing modification treatment such as imparting a hydrophobic group to fine fibers to impart hydrophobicity similar to that of a resin and enhancing the affinity with the resin to have a reinforcing effect. Has been proposed.

Patent Document 1 describes, as a technique for imparting a hydrophobic group to fine fibers, "modified cellulose fiber esterified by adding cyclic polybasic acid anhydride (a) having a hydrophobic group to the cellulose fiber and having 15 or more carbon atoms. (A) ”is disclosed, and the modified cellulose fiber-containing resin composition containing the modified cellulose fiber (A) and the dispersion resin (B) is excellent in dispersibility and mechanical strength with respect to the resin for molding material. I am proposing that it will be.

In Patent Document 2, "a step of reacting cellulose having a hydroxyl group with a resin having an anhydrous polybasic acid structure in the molecule to obtain modified cellulose and a step of refining the obtained modified cellulose are performed in the same step. A method for producing a modified cellulose nanofiber, wherein the anhydrous polybasic acid structure is a cyclic anhydrous polybasic acid structure in which a carboxyl group is dehydrated and condensed in the molecule to form a cyclic structure. According to this technology, it is possible to easily produce modified cellulose nanofibers that are easily dispersed in a solvent.

WO2015 / 040884 Japanese Unexamined Patent Publication No. 2016-216605

Patent Document 1 states that it is desirable that the substitution rate (reaction rate) of the acid anhydride with respect to the cellulose fiber is within a predetermined range, but it is sufficient regarding what kind of production method should be adopted to improve the substitution rate. No consideration has been given. Patent Document 2 states that cellulose and a resin having an anhydrous polybasic acid structure in the molecule are reacted at a predetermined ratio to produce modified cellulose nanofibers, but this also relates to improving the substitution rate. However, sufficient consideration has not been given. Based on these points, the present inventor thinks that there may be room for further improvement of the substitution rate, and the problem to be solved by the present invention is a fibrous form obtained by improving the substitution rate of the modification treatment. A method for producing cellulose and a method for producing a fibrous cellulose composite resin will be provided.

The present inventors have obtained the finding that the substitution rate is affected by the mixing condition of the cellulose fiber and the drug, and if the mixture is sufficiently mixed, the substitution rate will be improved. Therefore, the aspects of the invention completed based on this finding are as follows.

[First aspect]
It has a step of carbamate the cellulose fiber and a step of defibrating the cellulose fiber into fibrous cellulose.
The carbamate step comprises a mixing step of mixing the cellulose fiber and at least one of urea and a derivative of urea, and a heating step of heating the cellulose fiber after the mixing step.
The mixing step includes a step of adding the drug to the cellulose fiber and a step of mixing the cellulosic fiber and the added drug.
The mixing step is
When 0.2% by mass of the dissociated liquid prepared by dissociating the cellulose fibers obtained by mixing with water to a uniform concentration and then allowing it to stand, the sedimentation rate at the interface of the dissociated cellulose fibers However, it should be less than 60% after 10 minutes of standing.
A method for producing fibrous cellulose, which is characterized by the above.
Here, the sedimentation rate can be obtained by the following formula.
(Precipitation rate (%)) = {(Water volume of dissociation liquid)-(Depth from the liquid surface of dissociation liquid to the interface of cellulose fibers in dissociation liquid)} / (Water volume of dissociation liquid) × 100

When a carbamate group is added to the cellulose fibers of pulp, the cellulose fibers become hydrophobic, the hydrogen bonds between the cellulose fibers are weakened, and the fibers are easily defibrated. Carbamate formation of the cellulose fiber can be carried out through a mixing step of mixing the cellulose fiber and the above-mentioned agent and a heating step of promoting the reaction. In the mixing step, it is preferable to add a chemical to the cellulose fibers and mix them.

Conventionally, when making cellulose fibers hydrophobic, a chemical reaction was carried out by adding a chemical for making the cellulose fibers hydrophobic, but as a result of proceeding with research, the cellulose fibers and the chemicals are sufficient as a prerequisite for the chemical reaction. I came to the view that it might not be mixed with. For example, even if a chemical is added to a slurry-like cellulose fiber, the chemical that adheres to the cellulose fiber adheres to the surface of the cellulose fiber and its surroundings, but hardly penetrates into the inside of the cellulose fiber and does not adhere so much. It is presumed. It is considered that carbamate formation is not promoted even if a chemical reaction is attempted by heating the inside of the cellulose fiber, that is, the portion where the amount of the chemical adhered is small or not, because the chemical as a reactant is small or absent in the first place. As a result, the easy dissociation of cellulose fibers due to carbamization is less likely to occur because they are not carbamated.

Specifically, it can be thought of as follows. The hydroxyl groups of the individual fibers that form the unmodified cellulose fibers are hydrogen bonded to each other. When the cellulose fiber is carbamate-treated, the hydroxyl group of the cellulose fiber is replaced with a carbamate group to obtain a modified cellulose fiber. Since the hydroxyl group of the modified cellulose fiber is substituted with a carbamate group, the hydrogen bond is weakened and the modified cellulose fiber is more easily dissociated than the unmodified cellulose fiber. On the other hand, in the case of a cellulose fiber in which a drug has penetrated into the fiber, not only the hydroxyl group on the fiber surface but also the hydroxyl group inside the fiber is replaced with a carbamate group, so that the hydrogen bond is weakened more easily and the fiber is dissociated more easily. Will be done.

When the dissociated liquid prepared by dispersing the dissociated cellulose fibers in a solvent is made uniform and then allowed to stand, the cellulose fibers begin to precipitate and are separated into a cellulose fiber phase and a supernatant phase to form an interface of the cellulose fibers. It will settle over time. Specifically, it can be considered as follows. Cellulose fibers before the addition of the drug contain air inside the fibers. Most of the chemicals adhering to the fiber adhere to the surface of the fiber, and the cellulose fiber which hardly adheres to the inside of the fiber retains air inside the fiber even after the carbamate step. This cellulose fiber is difficult to settle because air still remains inside the fiber. On the other hand, in the cellulose fiber in which the chemical has penetrated into the fiber, air is pushed out to the outside of the fiber by the penetration of the chemical in the fiber, and the amount of air remaining in the fiber is small, so that it is easy to settle.

According to the production method of this embodiment, the effect of the drug permeating into the inside of the cellulose fiber is obtained, and carbamate formation is promoted not only on the surface of the cellulose fiber but also inside, so that the substitution rate of the carbamate group is improved. It has become.

[Second aspect]
It has a step of carbamate the cellulose fiber and a step of defibrating the cellulose fiber into fibrous cellulose.
The carbamate step comprises a mixing step of mixing the cellulose fiber and at least one of urea and a derivative of urea, and a heating step of heating the cellulose fiber after the mixing step.
The mixing step is
(1) When the mixing step includes a step of adding the drug to the cellulose fiber and a step of mixing the cellulosic fiber and the added drug, the sedimentation rate becomes less than 60% after 10 minutes of standing.
(2) When the mixing step comprises only the step of adding the drug to the cellulose fibers, the sedimentation rate becomes 60% or more after 10 minutes of standing.
To do,
A method for producing fibrous cellulose, which is characterized by the above.
Here, the sedimentation rate is determined when 0.2% by mass of the dissociated liquid prepared by dissociating the cellulose fibers obtained by performing a mixing step with water to a uniform concentration and then allowing it to stand. It is the sedimentation rate of the interface of the cellulose fiber, which can be obtained by the following formula.
(Precipitation rate (%)) = {(Water volume of dissociation liquid)-(Depth from the liquid surface of dissociation liquid to the interface of cellulose fibers in dissociation liquid)} / (Water volume of dissociation liquid) × 100

When the mixing step consists only of the step of adding the drug to the cellulose fiber, the effect of the drug permeating into the cellulose fiber is less likely to be so, and air remains inside the fiber, making it difficult to settle. The sedimentation rate differs depending on the presence or absence of the mixing step, and the carbamate group substitution rate is superior in the case where the mixing step has a mixing step than in the case where the mixing step consists only of the step of adding the drug to the cellulose fibers. It becomes a thing.

Further, since the sedimentation rate in the case of (1) above is less than 60% and the sedimentation rate in the case of (2) above is 60 or more, even a type of cellulose fiber that does not easily react with a drug is (1). ) Has the effect of penetrating the inside of the fiber, so that the production method has an improved substitution rate of the carbamate group.

[Third aspect]
The step of adding the drug is carried out with the addition amount of the drug per 1 g of the cellulose fiber being 10 g or less.
The method for producing fibrous cellulose according to claim 1 or 2.

In the conventional carbamate method, in order to increase the substitution rate, the amount of the drug added was increased or the heat energy in the heating process was increased. However, there was concern that this method would lead to an increase in manufacturing costs. On the other hand, this embodiment has the effect of increasing the replacement rate while reducing the cost of the drug.

[Fourth aspect]
The heating step is performed at a heating temperature of 200 ° C. or lower and a heating time of 15 hours or less.
A method for producing fibrous cellulose according to any one of the first to third aspects.

Cellulose fibers cause irreversible thermal denaturation when exposed to high temperatures for a long time, which may make it difficult to use as a material for fibrous cellulose composite resin. Under the conditions of the above aspect, heat denaturation is unlikely to occur. Further, even under the conditions of the above embodiment, since the drug has penetrated into the cellulose fiber, the reaction conversion rate of the carbamate-forming reaction does not decrease.

[Fifth aspect]
The carbamate step is performed without adding an organic solvent.
A method for producing fibrous cellulose according to any one of the first to fourth aspects.

In the conventional carbamate method, in order to promote the substitution reaction and / or addition reaction of the hydrophobic group to the cellulose fiber, it may be carried out in the presence of an organic solvent. However, organic solvents have a risk of ignition and a risk of leakage, and are complicated to handle. In this embodiment, such a risk can be avoided, and it is not necessary to provide equipment such as a fume hood that is desired to be installed at the time of handling.

[Sixth aspect]
The mixing step is performed by adding 0.1 g or more and 99 g or less of the dispersion medium per 1 g of the cellulose fiber.
A method for producing fibrous cellulose according to a third aspect.

It is preferable to add a dispersion medium because the cellulose fibers are less likely to aggregate, but adding a large amount of the dispersion medium may dilute the drug and reduce the reaction efficiency. With the above addition amount, the permeation of the drug into the cellulose fiber is not suppressed, and it is easy to adjust the substitution rate to a desired value.

[7th aspect]
The substitution rate of the carbamate group with respect to the fibrous cellulose is 1 to 2 mmol / g.
The method for producing fibrous cellulose according to any one of the first to sixth aspects.

If the fibrous cellulose has the above substitution rate, the fibrous cellulose composite resin produced from this as a raw material has excellent strength and is preferable.

[Eighth aspect]
Fibrous cellulose is obtained by the method according to any one of the first to seventh aspects, and the fibrous cellulose and the resin are mixed.
A method for producing a fibrous cellulose composite resin.

In the production method of the first to seventh aspects, the chemical permeates the inside of the cellulose fiber to produce fibrous cellulose, so that the substitution efficiency of the carbamate group is improved and the desired strength is obtained. It is possible to manufacture the provided fibrous cellulose composite resin.

[9th aspect]
The step of defibrating the cellulose fiber into fibrous cellulose is a step of defibrating the fibrous cellulose so that the average fiber width is 0.1 to 19 μm.
The method for producing fibrous cellulose according to any one of the first to eighth aspects.

By defibrating the fibrous cellulose so that the average fiber width is within the range of 0.1 to 19 μm, the strength of the fibrous cellulose composite resin is increased.

According to the present invention, it is a method for producing a fibrous cellulose obtained by improving the substitution rate of the modification treatment, and a method for producing a fibrous cellulose composite resin.

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 fibrous cellulose of the present embodiment includes a step of carbamate the cellulose fiber and a step of defibrating the cellulose fiber into fibrous cellulose, and the step of carbamate is the cellulose fiber, urea and the like. It has a mixing step of mixing at least one of the agents of the urea derivative and a heating step of heating the cellulose fibers after the mixing step, and the mixing step includes a step of adding the agent to the cellulose fibers. It is carried out by having a step of mixing the cellulose fiber and the added agent. Hereinafter, it will be described in detail.

(Fibrous cellulose)
In the method of this embodiment, the raw material pulp (cellulose raw material) is defibrated to obtain fibrous cellulose. The average fiber width of the fibrous cellulose is not particularly limited. However, it is more preferable to defibrate so as to obtain microfiber cellulose (microfibrillated cellulose) having an average fiber width of 0.1 to 19 μm. The microfiber cellulose having an average fiber width in the above range has an effect of reinforcing the resin used for the composite, and the strength of the composite resin produced from the microfiber cellulose as a material is remarkably improved. Microfibers Cellulose is easier to modify (carbamate) with carbamate groups than fine fibers with a smaller average fiber width, that is, cellulose nanofibers. Carbamate can be carried out using either undefibrated cellulose fibers or defibrated microfiber cellulose or cellulose nanofibers, but in the step of mixing, the fibers are to some extent. It is more preferable to carbamate the cellulose fibers before defibration because the lumpy state is easier to mix.

In this embodiment, fibrous cellulose having an average fiber width (diameter) of 0.1 to 19 μm is referred to as microfiber cellulose, microfibrillated cellulose, or MFC.

In this embodiment, microfiber cellulose means a fiber having an average fiber diameter (width) larger than that of cellulose nanofiber. 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. If the average fiber diameter of the microfiber cellulose is less than 0.1 μm, it can be said that it is an equivalent of cellulose nanofibers, and the effect of improving the strength (particularly bending elastic modulus) of the resin may not be sufficiently exhibited. In addition, it is uneconomical because it takes a lot of time and a large amount of energy to defiber. Further, when the fibers are made into a slurry, the dehydration property deteriorates. Deterioration of dehydration requires a large amount of energy for drying when it is desired to obtain a dried product of fibers, and excessive energy application may damage the fibers and may not have the effect of improving the strength of the resin. be. In particular, when the average fiber diameter is 50 nm or less, the thermal decomposition temperature is remarkably lowered, so that the heat resistance is lowered, which makes it unsuitable for kneading with a resin. On the other hand, when the average fiber diameter of the microfiber cellulose exceeds 19 μm, there is almost no difference from the pulp, and there is a possibility that the reinforcing effect cannot be obtained.

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 Teflon (registered trademark) membrane filter, and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. 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 medium diameter of the measured value is taken as the average fiber diameter.

As described above, microfiber cellulose can be obtained by defibrating (miniaturizing) the cellulose raw material. 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.

As the hardwood kraft pulp, hardwood bleached kraft pulp, hardwood unbleached kraft pulp, hardwood semi-bleached kraft pulp and the like can be used. As the softwood kraft pulp, softwood bleached kraft pulp, softwood unbleached kraft pulp, and softwood semi-bleached kraft pulp can be used.

The mechanical pulp can be used without particular limitation, and for example, stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), chemi-grand pulp (CGP), thermo-grand pulp ( Select one or more from TGP), ground pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), bleached thermomechanical pulp (BTMP), etc. Can be used.

Cellulose fiber (raw material 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. Of these treatments, enzyme treatment is particularly preferable because the fibers are not damaged. It is preferable to perform one or more treatments selected from acid treatment, alkali treatment, and oxidation treatment in addition to the enzyme treatment because defibration is facilitated.

The pretreatment is a treatment for facilitating the defibration of the cellulose fiber (raw material pulp), and may be performed before the step of carbamate-forming the cellulose fiber, or may be performed after the pretreatment after the step of carbamate formation. The step of defibrating may be performed.
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, EG (endoglucanase) and CBH (cellobiohydrolase) can also 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 alabang, 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 fiber is determined by, for example, the type of enzyme, the type of wood used as a raw material (conifer or hardwood), the type of mechanical pulp, and the like. However, the amount of the enzyme added to 100 parts by mass of the cellulose raw material is preferably 0.1 to 3 parts by mass, more preferably 0.3 to 2.5 parts by mass, and particularly preferably 0.5 to 2 parts by mass. If the amount of the enzyme added is less than 0.1 parts by mass, the effect of adding 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 cellulose 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 reaction. 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 likely to be activated, and the enzyme treatment is completed in a short time. 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, the hydroxyl groups of hemicellulose and cellulose in pulp are partially 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 solution, 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.

The above is an example of the pretreatment prior to defibration, but when the pretreatment is applied, the water retention degree of the microfiber cellulose can be lowered, the crystallinity can be increased, and the homogeneity can be increased. If the water retention level of the microfiber cellulose is low, dehydration is likely to occur, and the dehydration property of the cellulose fiber slurry is improved. In addition, the pretreatment decomposes hemicellulose and the amorphous region of cellulose contained in pulp. When the amorphous region is decomposed, the energy of defibration can be reduced, and the uniformity and dispersibility of the defibrated microfiber cellulose can be improved. However, since the pretreatment lowers the aspect ratio of the microfiber cellulose, it is preferable to avoid excessive pretreatment when it is used as a reinforcing material for the resin.

(Dissociation process)
Cellulose fibers may be dissociated prior to defibration. The dissociation step is a step of dispersing pulp (cellulose fibers) in which fibers are aggregated to form a sheet shape or the like into independent fibers, and can be performed by a dissociation device. Examples of the disassembling device include a hand mixer, a tab type pulper, a drum type pulper, and a household mixer.

(Process of defibrating)
For defibration of cellulose fibers, 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 cellulose fibers using. In particular, it is preferable to use a refiner or a jet mill because damage to the fibers can be suppressed and the fibers become homogeneous.

Microfiber obtained by defibrating cellulose fibers The average fiber length (average length of single fibers) of cellulose is preferably 0.10 to 2.00 mm, more preferably 0.12 to 1.50 mm, and particularly preferably 0.12 to 1.50 mm. It is 0.15 to 1.00. 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 pulp (cellulose fiber) used as a raw material in this embodiment is preferably 1.0 to 5.0 mm, more preferably 1.2 to 4.5 mm, and particularly preferably 1.5 to 4. It is 0 mm. If the average fiber length is less than 1.0 mm, the effect of reinforcing the resin by the microfiber cellulose obtained by defibrating the cellulose fiber may not be sufficiently obtained. On the other hand, if the average fiber length exceeds 5.0 mm, the energy required for defibration between the cellulose fibers is large, which may be disadvantageous in terms of manufacturing cost.

Further, the defibration of the cellulose fibers is preferably performed so that the average fiber length ratio is less than 30, more preferably 2 to 20, and 1.5 to 10. Especially preferable. When the average fiber length ratio is 30 or more, the mechanical shearing to the fiber becomes excessive and the damage to the fiber increases. Therefore, the fiber may become too short or the strength of the fiber itself may decrease, and as a result, the resin reinforcing effect when composited with the resin may not be exhibited.

In this embodiment, the average fiber length ratio is a value obtained by dividing the average fiber length of the cellulose fibers before defibration by the average fiber length of the cellulose fibers after defibration (average fiber length before defibration / average after defibration). Fiber length).

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

The average size of pulp (cellulose fiber) used as a raw material in this embodiment is preferably 8 × 10 ^-5 to 1 × 10 ⁻² mm ³ , more preferably 1 × 10 ^-4 to 2, in terms of average volume. It is preferably 1 × 70 ^-3 mm ³ , more preferably 3 × 10 ^-4 to 5 × 10 ^-3 mm ³ . If the average volume of the cellulose fibers is less than 8 × 10 ^-5 mm ³ , the cellulose fibers may not come into contact with each other or be pressed against each other (difficult to be pressed) in the mixing process. It becomes difficult for the drug to penetrate into the inside. On the other hand, if the average volume of the cellulose fibers exceeds 1 × 10 ⁻² mm ³ , the pressure applied to the cellulose fibers will be biased in the mixing process, resulting in uneven penetration of the drug and deflated microfiber cellulose. May not be homogeneous.

The fine ratio of the microfiber cellulose obtained by defibration 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 microfiber cellulose, that is, the cellulose fiber after defibration, but it is more preferable to keep the fine ratio of the cellulose fiber before defibration within a predetermined range. Specifically, the fine ratio of the cellulose fibers before defibration is preferably 1% or more, more preferably 3 to 20%, and particularly preferably 5 to 18%. If the fine ratio of the cellulose fiber before defibration is within the above range, even if the fine ratio of the microfiber cellulose is defibrated to be 30% or more, the damage to the fiber is small and the reinforcing effect of the resin is considered to be improved. Be done.

The fine rate can be adjusted by pretreatment such as enzyme treatment. However, especially in the case of enzymatic treatment, the bonded state in the fiber may be partially destroyed, and the reinforcing effect of the resin may be reduced. Therefore, it is better to reduce the addition rate of the enzyme, for example, it 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 microfiber cellulose 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 microfiber celluloses are often entangled with each other, 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 microfiber cellulose is preferably 1 to 30%, more preferably 1.5 to 20%, and particularly preferably 2 to 15%. If the fibrillation rate exceeds 30%, there are many bonds between microfiber cellulose and water molecules per unit area, which may make dehydration difficult. On the other hand, when the fibrillation rate is less than 1%, the amount of fibrils bonded to water molecules is small, and the three-dimensional network formed by hydrogen bonds may not be rigid.

In this embodiment, the fibrillation rate refers to the dissociation of cellulose fibers 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 microfiber cellulose is preferably 50% or more, more preferably 55% or more, and particularly preferably 60% or more. If the crystallinity is less than 50%, the strength of the fiber itself may decrease, and the strength of the resin may not be improved. Further, if the crystallinity is less than 50%, the heat resistance of the carbamate microfiber cellulose may be insufficient. If the crystallinity is low, the thermal decomposition reaction of the microfiber cellulose immediately proceeds due to the heat applied from the outside. On the other hand, the crystallinity of the microfiber cellulose is preferably 95% or less, more preferably 90% or less, and particularly preferably 85% or less. When the crystallinity exceeds 95%, the amount of hydrogen bonds in the cellulose molecule and between the cellulose molecules becomes large, and the dispersibility becomes inferior.

The crystallinity of microfiber cellulose 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 microfiber cellulose is preferably 2 cps or more, more preferably 4 cps or more. If the pulp viscosity of the microfiber cellulose is less than 2 cps, the dispersibility of the microfiber cellulose may be deteriorated.

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

The freeness of the microfiber cellulose is preferably 500 ml or less, more preferably 300 ml or less, particularly preferably 100 ml or less, and the lower limit is not particularly limited, and is preferably 10 ml or more. If the freeness of the microfiber cellulose 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 microfiber cellulose is preferably −150 to 20 mV, more preferably -100 to 0 mV, and particularly preferably -80 to -10 mV. If the zeta potential 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 microfiber cellulose 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 water retention level is the same as that of the raw material pulp, and the reinforcing effect may be insufficient. On the other hand, if the water retention level exceeds 400%, it becomes difficult to dry. The water retention rate of the microfiber cellulose tends to be lower as the substitution rate of the carbamate group in the microfiber cellulose is higher. Therefore, the water retention rate can be set to a desired value by adjusting the substitution rate.

The water retention level of the microfiber cellulose can be arbitrarily adjusted by, for example, selection of raw material pulp, pretreatment, defibration, and the like.

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

The microfiber cellulose of this embodiment has a carbamate group. The carbamate-ized microfiber cellulose may be, for example, one in which the raw material cellulose fiber is carbamateized and defibrated to become microfiber cellulose, or the microfiber cellulose is carbamateized to be carbamate. It may be made into microfiber cellulose.

Having a carbamate group (ie, carbamate) means that a carbamate group (ester of carbamic acid) has been introduced into the cellulose fiber or microfiber cellulose. The carbamate group is a group represented by -O-CO-NH-, and examples thereof include a group represented by -O-CO-NH ₂ , -O-CONHR, -O-CO-NR ₂ , and the like. can. 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 microfiber cellulose having a carbamate group (in which a carbamate group is introduced), a part or all of the hydroxy group as a polar group is replaced with a carbamate group which is a relatively non-polar group. Microfiber cellulose having a carbamate group is more non-polar than microfiber cellulose which is not carbamate as a single substance, that is, is hydrophobic, and therefore has a weak repulsion with a resin having a hydrophobic property. Therefore, the microfiber cellulose having a carbamate group mixed with the resin does not easily aggregate with each other, has good dispersibility, and adheres to the resin. Further, the slurry of microfiber cellulose 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 microfiber cellulose (or cellulose fiber) (the mmol ratio of the substituted carbamate group with respect to 1 g of the microfiber cellulose) is preferably 1 to 2 mmol / g, more preferably 1.1 to 1. It is 9.9 mmol / g, particularly preferably 1.2 to 1.8 mmol / g. 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. This is because microfiber cellulose having a substitution rate of 1.0 mmol / g or more has hydrophobicity, so that it has a weak repulsion with the resin and is appropriately dispersed in the resin. It is considered that the strength of the resin is unlikely to occur and the strength is uniform. On the other hand, when the substitution rate of the carbamate group exceeds 2 mmol / g, the strength of the composite resin decreases. This is because microfiber cellulose forms a strong three-dimensional network by hydrogen bonding, but if the substitution rate of the carbamate group is too high, the hydroxy groups that contribute to the formation of the three-dimensional network are relatively reduced. Therefore, it is considered that it becomes difficult to form a three-dimensional network rigidly.

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 fiber 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.

(Carbamate)
Regarding the method of introducing a carbamate group (carbamate) into microfiber cellulose (cellulose raw material when carbamate before defibration; the same applies hereinafter, also simply referred to as "cellulose fiber"), the cellulose raw material is carbamate. There are a method of making the cellulose material finer and then making it finer, and a method of making the cellulose raw material finer and then making it into a carbamate. 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 raw material is easily defibrated by heating accompanying carbamate formation.

The step of carbamate-forming cellulose fibers can be divided into a mixing step and a heating step, and the mixing step can be further subdivided into a step consisting of only an addition step and a step consisting of a step of mixing with the addition step. Further, for carbamate formation, a mixing step may be performed, and a heating step may be performed through a disintegration step and / or a defibration step.

The carbamate step may or may not be carried out with the addition of an organic solvent. When an organic solvent is added, it is preferable to use an organic solvent that does not have reactivity with the carboxy group of the cellulose fiber. Examples of the organic solvent include hydrocarbon solvents such as cyclohexane, toluene and xylene, halogen solvents such as methylene chloride, chloroform and dichloroethane, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, N, N-. Amid solvents such as dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone, carboxylic acid solvents such as acetic acid, propionic acid and butyric acid, ether solvents such as tetrahydrofuran, diethyl ether, isopropyl ether and 1,4-dioxane. A solvent can be mentioned. However, when an organic solvent is added, the concentration of the drug in the reaction system decreases, the encounter rate between the cellulose fiber as the reactant and the drug decreases, which may lead to a decrease in the substitution rate of the carbamate group. It is desirable to do this without adding an organic solvent.

(Mixing process)
The mixing step is a step of mixing the drug with the cellulose fibers. It consists of a process of putting a cellulose raw material (cellulose fiber) and a drug in a container such as a container, a bag, and a tank, and mixing the cellulose fiber and the drug.

(Addition process)
The addition step is a step of adding a drug to the cellulose fiber. The whole amount of the drug may be added to the container containing the cellulose fiber at a time, or it may be divided into several portions and added little by little.

In the addition step, the amount of the drug added per 1 g of cellulose fiber is preferably 10 g or less, more preferably 5 g or less, still more preferably 1 g or less. Since this embodiment has a step of mixing, carbamate formation is promoted by the above addition amount. The lower limit of the addition amount is preferably 0.05 g, more preferably 0.1 g. If the addition rate is 0.01 g, this embodiment has an excellent substitution rate for carbamate formation.

(Mixing process)
The mixing step is a step of mixing the cellulose fibers and the added chemicals. In the mixing process, the drug is infiltrated into the surface and inside of the cellulose fibers. By mixing, the chemicals adhere to the surface of the cellulose fibers, and the chemicals on the surface gradually permeate the inside of the cellulose fibers in the process of mutual contact, rubbing, and pressing of the cellulose fibers to which the chemicals have adhered. It will come to go. Whether or not the drug has sufficiently penetrated into the cellulose fibers can be evaluated by, for example, putting the cellulose fibers subjected to the mixing step into the aqueous phase and measuring the degree of sedimentation. Since the drug, for example urea, has a higher specific density than water, the cellulose fibers subjected to the mixing step settle faster than the cellulose fibers not subjected to the step. Even if the cellulose fibers that have undergone the mixing step are rinsed with water or the like, the chemicals that adhere to the fiber surface easily run off, but the chemicals that have penetrated into the fibers do not easily run off.

In the mixing step, 0.2% by mass of the dissociated liquid prepared by dissociating the cellulose fibers obtained by mixing the cellulose fibers with water to a uniform concentration is allowed to stand, and then the dissociated cellulose fibers are allowed to stand. The sedimentation rate at the interface of the above can be set to less than 60%, preferably 59% or less, more preferably 58% or less after 10 minutes of standing. The sedimentation rate can be calculated by the following formula.
[Number 1]
(Precipitation rate (%)) = {(Water volume of dissociation liquid)-(Depth from the liquid surface of dissociation liquid to the interface of cellulose fibers in dissociation liquid)} / (Water volume of dissociation liquid) × 100
If the sedimentation rate 10 minutes after standing is 60% or more, the penetration of the drug into the cellulose fibers is not sufficient. This is because chemicals, especially urea and the like, have a large specific gravity with respect to water, and cellulose fibers with insufficient penetration of chemicals are less likely to settle in water. Cellulose fibers in which the chemicals have sufficiently penetrated into the fibers contain a large amount of chemicals having a relatively large specific gravity, so that they tend to settle in water. The sedimentation rate was measured in accordance with JIS M 0201: 1974 (coal preparation wastewater test method). A certain amount of slurry was put into a container and allowed to stand for a certain period of time, and the amount of change in the sedimentation interface per unit time was used. You can ask. Further, the settling speed can also be measured in accordance with JIS M 0201: 1974, and can be obtained from the amount of change in the settling interface per unit time by putting a certain amount of slurry into a container and allowing it to stand for a certain period of time. The water volume of the dissociated liquid means the depth from the liquid surface to the bottom surface of the dissociated liquid when the dissociated liquid is placed in a container for measuring the sedimentation rate.

When the mixing step comprises (1) a step of adding the drug to the cellulose fiber and a step of mixing the cellulosic fiber and the added drug, the sedimentation rate is 60 after 10 minutes of standing. %, Preferably 59% or less, more preferably 58% or less. (2) When the mixing step comprises only the step of adding the drug to the cellulose fibers, the sedimentation rate is 10 minutes after standing. It may be 60% or more, more preferably 63% or more, still more preferably 65% or more. At this time, the settling rate in the case of (1) is expressed as "Pmix +", and the settling rate in the case of (2) is expressed as "Pmix-".

Further, the [settlement rate (Pmix +)]-[settlement rate (Pmix-)] (that is, the difference in the settling rate) is preferably 1% or more, more preferably 2% or more, still more preferably 3% or more. When the mixing step is performed, the cellulose fibers are sufficiently infiltrated with the drug, and the substitution efficiency of the carbamate group is improved, which is desirable.

Also, regarding the sedimentation rate, the cellulose fiber in which the drug is sufficiently permeated into the cellulose fiber is more than the cellulose fiber in which the drug is sufficiently permeated (manufactured without the mixing step). It will be big. It is considered that this is because the chemical having a high specific density permeated into the inside of the cellulose fiber and the specific gravity of the cellulose fiber as a whole increased. The sedimentation rate (d (%) / dt) is the amount of change in the sedimentation rate per unit time.

Although it is difficult to strictly define a cellulose fiber in which the drug has sufficiently penetrated into the inside of the cellulose fiber depending on the degree of penetration of the drug, for example, the drug is preferably 0.5 mmol or more per 1 g of the cellulose fiber. It can be said that it contains more preferably 1.0 mmol or more, still more preferably 1.5 mmol or more. Whether or not the drug has sufficiently penetrated into the fibers of cellulose (that is, the degree of penetration) can be evaluated by, for example, the following mathematical formula.
[Number 2]
(Permeability) = (Mass g of cellulose fiber containing drug)-(Mass g of dried cellulose fiber)
Here, the mass of the cellulose fiber containing the drug means the mass of the cellulose fiber that has undergone the mixing step after being dried (105 ° C., 1 hour). The mass g of the drug and the substance amount mmol of the drug are appropriately converted and obtained.

Cellulose fibers produced without the mixing step are relatively difficult to settle, and the reaction conversion rate between the cellulose fibers and the drug is also low.

When the cellulose fiber obtained by performing the addition step and the mixing step in the mixing step was put into water and the cellulose fiber liquid having a solid content concentration of 0.2% by mass was dissociated at 800 rpm, the dissociation occurred. It is advisable to carry out the mixing step so that the time required for completion is preferably 15 minutes or less, more preferably 12 minutes or less, still more preferably 10 minutes or less. If the time required for the disaggregation to be completed exceeds 15 minutes, the drug may not sufficiently penetrate into the cellulose fibers. On the other hand, a cellulose fiber liquid obtained by adding the cellulose fiber obtained in the case where the mixing step (2) consists only of the step of adding the drug to the cellulose fiber into water to have a solid content concentration of 0.2% by mass is prepared. When the fibers are disintegrated at 800 rpm, the time required for the dissolution to be completed is 20 minutes or more.

The method of mixing is not particularly limited, but can be performed as follows as an example. It is possible to put the cellulose fibers and the chemicals into a cylindrical tank equipped with a mixing mixer such as a concrete mixer or a mortar mixer, a stirring blade or a circulation machine, and mix them. If you want to do a small amount, put the cellulose fiber and the medicine in the container and mix them with a mixing mixer such as a hand mixer, or put the cellulose fiber and the medicine in the bag and pickle the pickles from the outside of the bag. It can be a method of mixing the materials as if they were kneaded or kneaded.

The time for mixing the cellulose fiber and the drug is not particularly limited, but preferably 1 minute or more, more preferably 5 minutes or more, still more preferably 10 minutes or more, because the drug sufficiently penetrates into the cellulose fiber. The mixing time may be preferably 24 hours or less, more preferably 12 hours or less, still more preferably 6 hours or less. Even if it is mixed for more than 24 hours, the effect corresponding to it is not achieved. The rotation speed at the time of mixing is not particularly limited, but the lower limit is preferably 1 rpm or more, more preferably 10 rpm or more, further preferably 100 rpm or more, and the upper limit is preferably 100,000 rpm or less, more preferably 10000 rpm or less. It is good to say.

Examples of the drug used in the mixing step include urea or a derivative of urea (hereinafter, also simply referred to as "urea or the like"). 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 or derivatives of urea can be used alone or in combination of two or more. However, it is preferable to use urea.

The lower limit of the mixed mass ratio of urea or the like (urea or the like / cellulose fiber) to the cellulose fiber is preferably 10/100 or more, more preferably 20/100 or more. On the other hand, the upper limit is preferably 300/100 or less, more preferably 200/100 or less. By setting the mixed mass ratio to 10/100 or more, the efficiency of carbamate formation is improved. On the other hand, even if the mixed mass ratio exceeds 200/100, the carbamation reaches a plateau.

(Dispersion medium)
The step of mixing can be performed only with cellulose fibers and a chemical, but a dispersion medium which is a liquid medium may be further added. Water is usually preferable as the dispersion medium. Further, another liquid medium such as alcohol or ether, or a mixture of water and another dispersion medium may be used.

In the mixing step, for example, cellulose fibers, urea or the like may be added to the dispersion medium, cellulose fibers may be added to an aqueous solution of urea or the like, or urea or the like may be added to the slurry containing the cellulose fibers. Further, the dispersion liquid containing the cellulose fibers and urea or the like may contain other components. When a dispersion medium is added to the cellulose fibers and urea to prepare a dispersion liquid, a step of adding 99 g or less, more preferably 66 g or less, still more preferably 49 g or less of the dispersion medium per 1 g of the cellulose fibers and mixing them is performed. It is preferable to add 0.1 g or more, more preferably 1 g or more, still more preferably 2 g or more, and mix them. If the amount of the dispersion medium per 1 g of the cellulose fiber exceeds 99 g, the amount of the cellulose fiber in the entire dispersion liquid is small, so that it is difficult for the chemicals to adhere to the entire cellulose fiber evenly, and the defibration may not be uniform. There is. Further, if the amount of the dispersion medium per 1 g of the cellulose fiber is less than 0.1 g, the effect of adding the dispersion medium may not be expected.

(Drying process)
After the mixing step, the heating step is performed, but a drying step can be inserted between the mixing step and the heating step. The drying step is a step of removing the dispersion medium from the dispersion liquid containing the cellulose fibers and urea obtained in the mixing step, and can also be referred to as a removal step. By removing the dispersion medium, urea and the like can be efficiently reacted in the subsequent heat treatment. Even after the drying step, the chemical remains on the surface and inside of the fiber.

It is preferable to remove the dispersion medium by volatilizing the dispersion medium by heating. According to this method, it is possible to efficiently remove only the dispersion medium while leaving almost all the components such as urea.

When the dispersion medium is water, the set temperature in the drying step is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, and particularly preferably 90 ° C. or higher. By setting the set temperature to 50 ° C. or higher, the dispersion medium can be efficiently volatilized (removed). On the other hand, the upper limit of the set temperature is preferably 120 ° C, more preferably 100 ° C. If the heating temperature exceeds 120 ° C., the dispersion medium and urea chemically react with each other, and the reaction conversion rate between the cellulose fibers and urea may decrease.

The drying time applied to the drying step can be appropriately adjusted according to the solid content concentration of the dispersion liquid and the like. Specifically, the drying time is, for example, 24 hours or less, preferably 20 hours or less, more preferably 18 hours or less, and particularly preferably 16 hours or less. On the other hand, it is better to dry for at least 6 hours to remove the dispersion medium. When the drying time is within the above range, almost the entire amount of the dispersion medium is removed from the cellulose fibers, and the thermal denaturation of the fibers due to long-term drying can be reliably suppressed.

As described above, it is preferable to provide a drying step prior to the heating step. In particular, in this drying step, the cellulose fibers subjected to the heating step are dried so that the moisture content is 10% or less, preferably 0 to 9%, and more preferably 0 to 8%. Is preferable. By drying the cellulose fibers so that the moisture content is 10% or less prior to the heating step, the substitution rate of the carbamate group can be easily set to 1 mmol / g or more. By performing the drying step prior to the heating step, there is an advantage that the substitution efficiency of the carbamate group is improved.

(Heating process)
The heating step is a step of heating a mixture of cellulose fibers and a drug (urea or the like) after the mixing step (or drying step). In the heating step, a part or all of the hydroxy groups of the cellulose fiber chemically react with urea or the like and are replaced with carbamate groups. The reaction process is as follows. 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 unstable, for example, the carboxy group of cellulose is replaced with a carbamate group 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-O-CO-NH ₂ … (2)

The cellulose fiber used in the heating step of this embodiment has a large number of reaction sites between the hydroxy group and the drug in the cellulose fiber because the drug adheres to and permeates the fiber surface and the inside, and is relatively large. It is believed that the drug reacts with the hydroxy group. Further, although the water content of the cellulose fibers that have undergone the drying step has evaporated, the chemicals remain on the surface and inside, so that the hydrogen bonds are weakened by the chemicals at the places where the chemicals remain. Therefore, the cellulose fiber is excellent in the substitution efficiency of carbamate formation, and is easily dissociated and defibrated. It is considered that the action of weakening the hydrogen bond by the drug is due to the fact that a part of the water molecule forming the hydrogen bond is replaced with the urea molecule.

In the heating step, the temperature for heating the mixture (heating temperature) is preferably 120 ° C. or higher, more preferably 130 ° C. or higher, particularly preferably urea melting point (about 134 ° C.) or higher, still more preferably 140 ° C. or higher, most preferably. The temperature should be 150 ° C. or higher. When the heating temperature is lower than 120 ° C., the substitution reaction is less likely to be promoted. On the other hand, the heating temperature is preferably 200 ° C. or lower, more preferably 180 ° C. or lower, and particularly preferably 170 ° C. or lower. If the heating temperature exceeds 200 ° C., the cellulose fibers may be decomposed or heat-denatured, and the reinforcing effect of the resin may be insufficient.

The heating time in the heating step is preferably 1 minute or longer, more preferably 5 minutes or longer, and particularly preferably 30 minutes. If the heating time is less than 1 minute, the chemical reaction may not be completed. On the other hand, the heating time is preferably 15 hours or less, more preferably 10 hours or less, and particularly preferably 5 hours or less. Since the chemical reaction is completed by heating for 15 hours, there is no advantage in heating beyond that time.

As described above, the temperature and time conditions are mainly different between the drying process and the heating process. Since the main purpose of the drying step is to vaporize and remove the dispersion medium adhering to the cellulose fibers, the treatment is performed at a low temperature and for a long time. Since the main purpose of the heating step is to promote the chemical reaction within the range where the cellulose fibers do not deteriorate, the treatment is performed at a high temperature and for a short time. The drying step may be omitted, but it is better to do so. If the heating step is performed in a non-drying state, water or steam exposed to a high temperature state may break the acetal bond to which glucose constituting cellulose is bound and damage the fiber. In addition, urea or the like to be used for carbamate formation of the cellulose fiber may chemically react with the water adhering to the cellulose fiber and be consumed, and further addition of urea may be required.

In the heating step, it is preferable to adjust the pH in addition to the reaction temperature and the reaction time because the chemical reaction is promoted. 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. Alternatively, the pH may be 7 or less, preferably pH 3 to 7, particularly preferably pH 4 to 7, under acidic or neutral conditions. However, under weakly alkaline conditions of more than 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, it is preferable to heat-treat under alkaline conditions because a part of cellulose may be acid hydrolyzed 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.

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

The mixture after the heating step may be washed for use in the next step. This washing may be performed with water or the like. By this washing, residual unreacted urea and the like and by-products can be removed. However, as described above, both defibration and carbamating can be performed first, but in the case of the washing, it is preferable to deflate after carbamating rather than carbamate after defibration. This is because when the cellulose fiber is defibrated, the water retention (degree) increases and it becomes difficult to dehydrate, and when the fiber is finely divided, it tends to irreversibly aggregate when it dries. For example, assuming that the water retention of pulp is 100%, the water retention of microfiber cellulose after defibration is as high as about 300%.

(slurry)
It is preferable to disperse the microfiber cellulose in an aqueous medium to prepare a dispersion liquid (slurry) because it can be easily stored and handled. As the water-based medium, it is particularly preferable that the whole amount is water, but an water-based medium which is a liquid which is partially compatible with water can be used. As the 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, a large amount of slurry is prepared for producing the composite resin, which is complicated and may require excessive energy 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 the slurry itself cannot be mixed uniformly, which is not convenient.

(Acid-modified resin)
The microfiber cellulose is preferably mixed with an acid-modified resin. When the acid-modified resin is mixed, the acid group ionically bonds with 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 can be selected and used from among maleic anhydrides, phthalic anhydrides, itaconic anhydrides, citraconic anhydrides, citrate anhydrides and the like. However, it is preferable to use maleic anhydrides. That is, it is 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 microfiber cellulose. 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 is not 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 2000 g / 10 minutes (190 ° C. / 2.16 kg) or less, more preferably 1500 g / 10 minutes or less, and 500 g / 10 minutes or less. It is particularly preferable to have it. If the MFR exceeds 2000 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 microfiber cellulose of this embodiment is preferably mixed with a dispersant. When a dispersant is mixed with the microfiber cellulose, it becomes difficult for the microfiber cellulose to aggregate with each other. This is because the dispersant has a function of inhibiting hydrogen bonds between microfiber celluloses. By mixing the dispersant, the dispersibility of the microfiber cellulose with respect to the resin is improved when the microfiber cellulose and the resin are kneaded. The dispersant also has a role of improving the compatibility of the microfiber cellulose and the resin.

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 acids, guaiacols, picric acids, phenolphthalenes, serotonins, dopamines, adrenaline, noradrenaline, timoles, tyrosine, salicylic acids, methyl salicylates, anis alcohols. , Salicylic 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, tridecyl alcohols, and the like. Myristyl alcohols, pentadecyl alcohols, cetanols, stearyl alcohols, eleidyl alcohols, oleyl alcohols, linoleil alcohols, methylamines, dimethylamines, trimethylamines, ethylamines, diethylamines, ethylenediamines, Triethanolamines, N, N-diisopropylethylamines, tetramethylethylenediamines, hexamethylenediamines, spermidins, spermins, amantadins, formic acids, acetic acids, propionic acids, butyric acids, valeric acids, caproic acids. , Enant 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, eikosapentaenoic acids, docosahexaenoic acids, sorbic acids, etc. Can be mentioned.

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 microfiber cellulose. If the mixing amount of the dispersant is less than 0.1 parts by mass, the effect of adding the dispersant is weak, and the strength of the resin may not be sufficiently improved. On the other hand, if the mixing amount exceeds 1,000 parts by mass, the dispersibility of the microfiber cellulose may decrease due to the excess dispersant.

The above-mentioned acid-modified resin is intended to improve compatibility by ionic bonding between an acid group and a carbamate group of microfiber cellulose, thereby enhancing a reinforcing effect, and because of its large molecular weight, it is dispersed together with a resin for kneading. Cheap. The dispersant intervenes between the hydroxy groups between the microfiber celluloses to prevent aggregation, and since the molecular weight is smaller than that of the acid-modified resin, the space between the microfiber celluloses is narrow so that the acid-modified resin cannot enter. It can enter the space and plays a role in improving the dispersibility of microfiber cellulose. Therefore, 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)
It is preferable to mix the microfiber cellulose of this embodiment with the powder. By mixing with the powder, the microfiber cellulose is suppressed from agglomeration and can be in a form capable of exhibiting the reinforcing property of the resin. It is advisable to adjust the water content of the microfiber cellulose to a predetermined range until it is compounded with the resin. As a result, the dispersibility with the resin deteriorates, and the effect of reinforcing the resin may not be sufficiently exerted.

The powder used should have poor reactivity with microfiber cellulose. Poor reactivity means that it is difficult to promote chemical reactions such as covalent bonds, ionic bonds, metal bonds, hydrogen bonds, and van der Waals forces. It can also be said that the powder has an activation energy of more than 100 kJ / mol when the powder and the microfiber cellulose chemically react with each other.

As the powder, an inorganic powder or a resin powder can be selected and used, but an inorganic powder is preferable. Inorganic powder is preferable because it has a reaction suppressing effect because it is difficult to dissociate the carboxy group of the cellulose fiber into hydroxide ion. Inorganic powder is particularly advantageous in terms of operation. This is because, as a method for adjusting the water content of the fibrous cellulose-containing material, for example, a method of directly applying a mixed solution of fibrous cellulose and powder to a metal drum as a heat source and drying the mixture, or a method of mixing the mixture with a heat source. A method of heating the liquid without directly touching it can be mentioned as a method of adjusting the water content. However, when the 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 is deteriorated, and the drying efficiency is remarkably high. If it is an inorganic powder, there is a concern that it will decrease. Such a problem is unlikely to occur.

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 exceeds 10,000 μm, the effect of inhibiting aggregation by entering the gaps between the fibers of cellulose may be impaired. If the average particle size is less than 1 μm, the particle size of the powder is too small for the cellulose fibers, and the effect of inhibiting the aggregation of the cellulose fibers with each other may not be exhibited.

The resin powder has the role of inhibiting hydrogen bonds by physically intervening in the gaps between the cellulose fibers and improving the dispersibility of the microfiber cellulose. On the other hand, the acid-modified resin described above improves compatibility and enhances the reinforcing effect by ionic bonding an acid group and a carbamate group of microfiber cellulose. The dispersant has the same action of inhibiting hydrogen bonds between microfiber celluloses, but since the particle size of the resin powder is micro-order, it physically intervenes and suppresses hydrogen bonds. Although the dispersibility of the resin powder is lower than that of the dispersant, the resin powder itself melts and forms a matrix, so that it does not contribute to deterioration of physical properties. On the other hand, since the dispersant has a particle size at the molecular level and is extremely small, it has a high effect of covering the microfiber cellulose to inhibit hydrogen bonds and improving the dispersibility of the microfiber cellulose. However, it may remain in the resin and cause deterioration of physical properties.

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

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.

Uses at least one inorganic powder selected from calcium carbonate, talc, white carbon, clay, calcined clay, titanium dioxide, aluminum hydroxide, recycled fillers, etc., which are suitably used as fillers and pigments for papermaking. It is more preferable to use at least one selected from calcium carbonate, talc, and clay, and it is particularly preferable to use at least one of light calcium carbonate and heavy calcium carbonate. .. Calcium carbonate, talc, and clay are easy to combine with a matrix such as a resin, and since they are general-purpose inorganic materials, they have merits such as less limitation of use. In addition, calcium carbonate is particularly preferred. The size and shape of the light calcium carbonate powder can be controlled as desired, and the powder can be molded so as to enter the gap according to the size and shape of the cellulose fibers, so that the effect of suppressing the aggregation of the cellulose fibers can be easily produced. .. In addition, since heavy calcium carbonate is amorphous, even if fibers of various sizes are present in the slurry, the cellulose fibers enter the gaps in the process of removing the aqueous medium during the drying step and aggregating the fibers. Mutual aggregation can be suppressed.

The resin used for the resin powder is not particularly limited, and various resins can be used, but it is preferable to use the same resin as the resin used for obtaining the composite resin because the use can be selected with one resin.

The mixing ratio of the powder is preferably 0.01 to 99 parts by mass, more preferably 0.05 to 19 parts by mass, and particularly preferably 0.1 to 9 parts by mass with respect to 1 part by mass of fibrous cellulose (microfiber cellulose). It is a mass part. If the mixing ratio of the powder to the fibrous cellulose is less than 0.01 parts by mass, the powder may be insufficient, and the action of entering the gaps between the cellulose fibers to suppress aggregation may be insufficient. If the mixing ratio exceeds 99 parts by mass, the fibers may be buried in the powder, which may hinder the kneading process of the fibrous cellulose and the resin.

Both the inorganic powder and the resin powder exemplified as the powder can be used in combination. When the inorganic powder and the resin powder are used together, even if either the inorganic powder or the resin powder is mixed under the condition of agglomeration, the effect of preventing the agglomeration is exhibited by mixing both the inorganic powder and the resin powder. Will be done. In general, powder with a small particle size has a relatively large surface area and tends to be easily aggregated due to the action of intramolecular force in addition to the action of gravity. However, when the inorganic powder and the resin powder are used in combination, the particle size is small. Aggregation of powders is suppressed. From this point of view, 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: 10000, and is preferably 1: 1 to 1: 1000. Is more preferable.

(Production method)
The mixture of fibrous cellulose (microfiber cellulose), acid-modified resin, dispersant, powder and the like to be kneaded with the resin is preferably a dried product having a moisture content of less than 18%. The dried product is preferably pulverized into a powder. In the form of a powder, the coloring of the fibrous cellulose composite resin obtained by kneading with the resin is reduced. Generally, when a composite resin is produced from a cellulose fiber and a resin, the composite resin exhibits a yellowish color. However, the composite resin produced from the powdery substance exhibits a color close to the original color of the resin. Further, in the form of a powdery substance, it is easily dried, and it is not necessary to dare to dry the fibrous cellulose when kneading with the resin, and the thermal efficiency of kneading is good. When a powder or a dispersant is mixed in the mixture, there is a low possibility that the fibrous cellulose (microfiber cellulose) will not be redispersed even if the mixture is dried.

When the mixture is dried to make a dried product, it is recommended to dehydrate it to make a dehydrated product before drying. This dehydration can be performed using a dehydrator. Examples of the dehydrating device include a belt press, a screw press, a filter press, a twin roll, a twin wire former, a valveless filter, a center disk filter, a membrane treatment, a centrifuge and the like.

The mixture or dehydrated product can be dried using a drying device. Examples of the drying device include 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 drying, and stirring drying. And so on.

The above-mentioned powdery substance can be crushed by using a crushing device. Examples of the crushing device include 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 10,000 μm or less, 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 be easily dried. On the other hand, it is not necessary to strictly set the lower limit of the average particle size, but for example, it is not economical to make the average particle size less than 1 μm because a large amount of energy is required.

The average particle size of the powder can be controlled by classification using a classification device (filter, cyclone, etc.).

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, strong aggregation is formed by hydrogen bonds between the fibrous celluloses, and it becomes difficult to disperse them in the resin. On the other hand, when the bulk specific density is less than 0.03, the mixture and the fibrous cellulose are separated by gravity in the kneading process, and excellent dispersibility is not maintained. Poor composite resin, etc. may be manufactured and the product may not be uniform.

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, the fibrous cellulose composite resin may be colored. 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.

In order to reduce coloring, for example, hemicellulose, which is one of the constituent substances of cellulose (coloring causative substance), can be reduced in molecular weight to make it water-soluble, and the coloring causative substance can be removed in the washing step of carbamate pulp. If the coloring-causing substance remains in the microfiber cellulose, the resin and the coloring-causing substance come into contact with each other during the kneading step, and the coloring becomes remarkable.

The moisture 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

(Kneading process)
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 from a single-screw kneader, a multi-screw kneader with two or more shafts, a mixing roll, a kneader, a roll mill, a Banbury mixer, a screw press, a disperser, and the like. Can be used. 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 step is preferably 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. It is particularly preferable to do so.

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 of hydroxycarboxylic acid-based aliphatic polyester, caprolactone-based aliphatic polyester, dibasic acid polyester and the like can be selected and used.

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 the 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 contain an inorganic filler, and the inorganic filler may be, for example, a periodic table of Fe, Na, K, Cu, Mg, Ca, Zn, Ba, Al, Ti, silicon element and the like. Examples thereof include elemental substances of metal elements in groups I to VIII, oxides, 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 blending ratio of the fibrous cellulose (microfiber cellulose) and the resin is preferably fibrous cellulose: resin = 1 to 99% by mass: 99 to 1% by mass, more preferably 5 to 95% by mass: 95 to 5% by mass. , More preferably 10 to 90% by mass: 90 to 10% by mass. When the ratio of the fibrous cellulose is lower than the above range of the compounding ratio, the amount of the fibrous cellulose is small, so that the strength of the three-dimensional network formed by the fibrous celluloses connecting the resins in the composite resin is weak and the resin is reinforced. It will be less effective. On the other hand, when the ratio of the fibrous cellulose is higher than the above range of the blending ratio, even if the fibrous cellulose has a reinforcing effect of the resin, the strength inherent in the resin is not exhibited, and when the composite resin is used. It may not have the desired strength.

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

The difference between the solubility parameter (cal / cm ³ ) ^1/2 (SP value) of the microfiber cellulose and the resin is the SPMLC value of the microfiber cellulose and the SPPOL value of the resin. can do. 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, the dispersibility of the microfiber cellulose in the resin is insufficient, and it may not be possible to obtain the reinforcing effect. 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. It can be said that the smaller the difference between the SPPOL value of the resin (solvent) and the SPMFC 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 fibrous cellulose-containing substance and the kneaded resin can be kneaded again if necessary, and then formed into a desired shape. The size, thickness, shape, etc. of this molding are not particularly limited, and may be, for example, sheet-like, pellet-like, powder-like, fibrous-like, or the like.

The temperature at which the molding step is performed is preferably equal to or higher than the glass transition point of the resin, and varies depending on the type of resin, but for example, 90 to 260 ° C, preferably 100 to 240 ° C may be sufficient for kneading.

Molding of the kneaded product can be performed by, for example, mold molding, injection molding, extrusion molding, hollow molding, foam molding, or the like. It is also possible to spin the kneaded material into a fibrous form and mix it with a 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 molding machines, pressure molding machines and the like. You can select and use more than one species.

Examples of materials that are mixed as plant materials include kenaf, jute hemp, Manila hemp, sisal hemp, ganpi, mitsumata, cypress, banana, pineapple, coco palm, corn, sugar cane, bagasse, palm, papyrus, reeds, esparto, and surviving glass. Examples thereof include fibers derived from plant materials obtained from various plants such as wheat, rice, bamboo, various coniferous trees (such as cedar and cypress), broad-leaved trees and cotton.

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.

Next, an embodiment of the present invention will be described. The sheet of coniferous bleached kraft pulp used in the examples was made into a sheet shape having a solid content concentration of about 50% and a solid content concentration of about 100 to 2000 g / m ² by removing water from the pulp dispersion liquid to a size of about 5 x 5 cm. It is cut out and has a volume of 8 to 20 cm ³ .

The test examples used in the examples were prepared by the following procedure.
[Test Example 1]
(1) A sheet of coniferous bleached kraft pulp (NBKP) was placed in a container, urea, citric acid, and water were added and mixed to obtain a mixed solution. The mixing amount was the amount shown in Table 1. The mixing method was to put a mixing mixer (Blender Vitaprep 3 manufactured by Vitamix Co., Ltd. for home use) in the mixed solution and mix at 3000 rpm for 10 minutes.
(2) After the operation of (1) above, the liquid component was removed from the mixed liquid, and the residue was taken out and dried to obtain a dried product. The drying method was a method of leaving the residue at 105 ° C. for 3 hours in a constant temperature device.
(3) After heating the dried product, it was allowed to cool to room temperature to obtain a modified cellulose fiber (Test Example 1). The heating method was a method of leaving the dried product at 140 ° C. for 3 hours in a constant temperature device.

[Test Example 2]
(1) A sheet of coniferous bleached kraft pulp (NBKP) was placed in a container, urea, citric acid, and water were added to prepare a mixed solution, and the mixture was left for 10 minutes. The mixing amount was the amount shown in Table 1.
(2) After the operation of (1) above, the liquid component was removed from the mixed liquid, and the residue was taken out and dried to obtain a dried product. The drying method was a method of leaving the residue at 105 ° C. for 3 hours in a constant temperature device.
(3) After heating the dried product, it was allowed to cool to room temperature to obtain a modified cellulose fiber (Test Example 2). The heating method was a method of leaving the dried product at 140 ° C. for 3 hours in a constant temperature device.

(Replacement rate comparison test)
The test operation and procedure are as follows.
FTIR measurement was performed on the test examples prepared as described above. The FTIR measurement was performed with the measuring device "Thermo, model number NICOLET iS10".
Calculate the ratio (% _{C = O} ) / (% _OH ) of the absorption spectrum transmittance (% _{C = O} ) of C = O obtained by the measurement and the absorption spectrum transmittance (% _OH ) of OH. The substitution rate (mmol / g) of the carbamate group was determined. Regarding the results of the substitution rate comparative test, the substitution rate was 1.29 mmol / g in Test Example 1 and 0.95 mmol / g in Test Example 2.

(Dissociation test)
Test examples were prepared as follows.
[Test Example 3]
(1) Put 9 g of a sheet of softwood bleached kraft pulp (NBKP) having a solid content concentration of 50% by mass in a container, add 9 g of 25% urea water, 0.005 mg of citric acid, and 90 g of water to prepare a mixed solution, and mix the mixture. The liquid was mixed. The mixing method was to put a mixing mixer (Blender Vitaprep 3 manufactured by Vitamix Co., Ltd. for home use) in the mixed solution and mix at 3000 rpm for 10 minutes.
(2) After the operation of (1) above, the liquid component was removed from the mixed liquid, and the residue was taken out and dried to obtain cellulose fibers (Test Example 3). The drying method was a method of leaving the residue at 105 ° C. for 3 hours in a constant temperature device.

[Test Example 4]
(1) Put 9 g of a sheet of softwood bleached kraft pulp (NBKP) having a solid content concentration of 50% by mass in a container, add 9 g of 25% urea water, 0.005 mg of citric acid, and 90 g of water to prepare a mixed solution, and mix the mixture. The liquid was allowed to stand for 10 minutes.
(2) After the operation of (1) above, the liquid component was removed from the mixed liquid, and the residue was taken out and dried to obtain cellulose fibers (Test Example 4). The drying method was a method of leaving the residue at 105 ° C. for 3 hours in a constant temperature device.

0.1 g of the obtained cellulose fiber (Test Example 3 or Test Example 4) was put into a container containing 50 g of water, stirred at a rotation speed of 800 rpm, and the elapsed time until the dissociation was completed was measured. The dissociation was judged to be completed when the number of agglomerates having a major axis of 5 mm or more present in the dispersion was less than one. The results are shown in Table 2. As the container, a clear wide-mouthed bottle (transparent) manufactured by Sanpo Kasei Co., Ltd. was used.

It is probable that in Test Example 3, urea permeated into the inside of the cellulose fiber, hydrogen bonds between the cellulose fibers were inhibited by the urea and weakened, and water molecules entered the inside of the fiber, so that it became easy to disintegrate.

(Settling rate test)
0.1 g of the cellulose fiber (Test Example 3 or Test Example 4) prepared in the above-mentioned dissociation test is put into a container containing 50 g of water, and the mixture is stirred at a rotation speed of 1500 rpm for 10 minutes to completely dissociate and dissociate the liquid. I made it. After making the concentration of the dissociated liquid uniform, it was allowed to stand, and the depth from the liquid surface of the dissociated liquid to the interface of the cellulose fibers with the passage of time was measured to calculate the sedimentation rate. The results are shown in Table 3. Here, the sedimentation rate was calculated by the following formula [Equation 1]. As the container, a clear wide-mouthed bottle (transparent) manufactured by Sanpo Kasei Co., Ltd. was used.
[Number 1]
(Precipitation rate (%)) = {(Water volume of dissociation liquid)-(Depth from the liquid surface of dissociation liquid to the interface of cellulose fibers in dissociation liquid)} / (Water volume of dissociation liquid) × 100

Urea penetrated into the fiber and remained inside the fiber even after dissociation, so Test Example 3 was easier to settle.

(Bending strength test)
[Test Example 5] to [Test Example 9]
(1) A sheet of coniferous bleached kraft pulp (NBKP) was placed in a container, urea, citric acid, and water were added and mixed to obtain a mixed solution. The mixing amount was the amount shown in Table 4. The mixing method was to put a mixing mixer (Blender Vitaprep 3 manufactured by Vitamix Co., Ltd. for home use) in the mixed solution and mix at 3000 rpm for 10 minutes.
(2) After the operation of (1) above, the liquid component was removed from the mixed liquid, and the residue was taken out and dried to obtain a dried product. The drying method was a method of leaving the residue at 105 ° C. for 3 hours in a constant temperature device.
(3) After heating the dried product, it was allowed to cool to room temperature to obtain cellulose fibers. The heating method was a method of leaving the dried product at 140 ° C. for 3 hours in a constant temperature device. The obtained cellulose fiber was diluted and stirred with distilled water, dehydrated and washed twice, and then distilled water was added to adjust the solid content concentration to 3% to obtain an aqueous dispersion of cellulose fiber. rice field.
(4) The aqueous dispersion of cellulose fibers was defibrated so that the average fiber width was 16 μm to obtain an aqueous dispersion of fibrous cellulose having a solid content concentration of 3%. The carbamate formation rate was measured for the obtained aqueous dispersion of fibrous cellulose dehydrated and then dried at 105 ° C. for 3 hours.
(5) An aqueous dispersion of fibrous cellulose, polypropylene resin powder (Novatec PP MA3), and maleic anhydride-modified polypropylene are mixed in a dry weight ratio of 10:85: 5, and dried by heating at 105 ° C. I got something. This was kneaded with a twin-screw kneader under the conditions of 180 ° C. and 200 rpm to obtain a kneaded product.
(6) The kneaded product was molded at 180 ° C. to obtain a rectangular parallelepiped fibrous cellulose composite resin (Test Examples 5 to 9). The dimensions of the fibrous cellulose composite resin were 59 mm in length × 9.6 mm in width × 3.8 mm in thickness.
(7) For the fibrous cellulose composite resin, the flexural modulus was measured according to JIS K7171: 2008.

The measured flexural modulus was evaluated as follows. The flexural modulus ratio calculated by dividing the flexural modulus of Test Example X (X is any of 6, 7, 8 or 9) by the flexural modulus of Test Example 5, that is, the flexural modulus of Test Example X. The ratio is
1.1 or less is "△",
Those with more than 1.1 to less than 1.2 are "○",
Those with 1.2 or more were marked with "◎".
The fibrous cellulose composite resin having a carbamating rate of 1 to 2 mmol / g, for example, Test Example 7 and Test Example 8, has an improved flexural modulus as compared with Test Example 5 which is a non-carbamate fibrous cellulose composite resin. It has a favorable strength.

The present invention can be used as a method for producing fibrous cellulose and a method for producing a fibrous cellulose composite resin.

Claims

It has a step of carbamate the cellulose fiber and a step of defibrating the cellulose fiber into fibrous cellulose.
The carbamate step comprises a mixing step of mixing the cellulose fiber and at least one of urea and a derivative of urea, and a heating step of heating the cellulose fiber after the mixing step.
The mixing step includes a step of adding the drug to the cellulose fiber and a step of mixing the cellulosic fiber and the added drug.
The mixing step is
When 0.2% by mass of the dissociated liquid prepared by dissociating the cellulose fibers obtained by mixing with water to a uniform concentration and then allowing it to stand, the sedimentation rate at the interface of the dissociated cellulose fibers However, it should be less than 60% after 10 minutes of standing.
A method for producing fibrous cellulose, which is characterized by the above.
Here, the sedimentation rate can be obtained by the following formula.
(Precipitation rate (%)) = {(Water volume of dissociation liquid)-(Depth from the liquid surface of dissociation liquid to the interface of cellulose fibers in dissociation liquid)} / (Water volume of dissociation liquid) × 100
It has a step of carbamate the cellulose fiber and a step of defibrating the cellulose fiber into fibrous cellulose.
The carbamate step comprises a mixing step of mixing the cellulose fiber and at least one of urea and a derivative of urea, and a heating step of heating the cellulose fiber after the mixing step.
The mixing step is
(1) When the mixing step includes a step of adding the drug to the cellulose fiber and a step of mixing the cellulosic fiber and the added drug, the sedimentation rate becomes less than 60% after 10 minutes of standing.
(2) When the mixing step comprises only the step of adding the drug to the cellulose fibers, the sedimentation rate becomes 60% or more after 10 minutes of standing.
To do,
A method for producing fibrous cellulose, which is characterized by the above.
Here, the sedimentation rate is determined when 0.2% by mass of the dissociated liquid prepared by dissociating the cellulose fibers obtained by performing a mixing step with water to a uniform concentration and then allowing it to stand. It is the sedimentation rate of the interface of the cellulose fiber, which can be obtained by the following formula.
(Precipitation rate (%)) = {(Water volume of dissociation liquid)-(Depth from the liquid surface of dissociation liquid to the interface of cellulose fibers in dissociation liquid)} / (Water volume of dissociation liquid) × 100
The step of adding the drug is carried out with the addition amount of the drug per 1 g of the cellulose fiber being 10 g or less.
The method for producing fibrous cellulose according to claim 1 or 2.
The heating step is performed at a heating temperature of 200 ° C. or lower and a heating time of 15 hours or less.
The method for producing fibrous cellulose according to any one of claims 1 to 3.
The carbamate step is performed without adding an organic solvent.
The method for producing fibrous cellulose according to any one of claims 1 to 4.
The mixing step is performed by adding 0.1 g or more and 99 g or less of the dispersion medium per 1 g of the cellulose fiber.
The method for producing fibrous cellulose according to claim 3.
The substitution rate of the carbamate group with respect to the fibrous cellulose is 1 to 2 mmol / g.
The method for producing fibrous cellulose according to any one of claims 1 to 6.
A fibrous cellulose is obtained by the method according to any one of claims 1 to 7, and the fibrous cellulose and a resin are mixed.
A method for producing a fibrous cellulose composite resin.
The step of defibrating the cellulose fiber into fibrous cellulose is a step of defibrating the fibrous cellulose so that the average fiber width is 0.1 to 19 μm.
The method for producing fibrous cellulose according to any one of claims 1 to 8.