WO2023162433A1 - Fibrous cellulose, fibrous cellulose composite resin, and method for producing fibrous cellulose - Google Patents

Abstract

[Problem] To provide fibrous cellulose having a high resin reinforcing effect, a high-strength fibrous cellulose composite resin, and a method for producing fibrous cellulose having a high resin reinforcing effect. [Solution] This fibrous cellulose has an average fiber width of 0.1-20 μm, wherein part or all of hydroxy groups are substituted by carbamate groups, the rate of substitution by carbamate groups is 0.5 mmol/g or more, and fine ratio A/fine ratio B is 1.5-10. This fibrous cellulose composite resin contains said fibrous cellulose and a resin. In production of the fibrous cellulose, a disc refiner is used for miniaturization, and the initial load factor of the disc refiner is set to 65% or more.

Description

Fibrous cellulose, fibrous cellulose composite resin, and method for producing fibrous cellulose

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

In recent years, the use of fine fibers such as cellulose nanofibers and microfiber cellulose (microfibrillated cellulose) as a reinforcing material for resins has been in the spotlight. However, since the fine fibers are hydrophilic and the resin is hydrophobic, there is a problem in the dispersibility of the fine fibers when using the fine fibers as a reinforcing material for the resin. Accordingly, the present inventors proposed substituting the hydroxy groups of fine fibers with carbamate groups (see Patent Document 1). According to this proposal, the dispersibility of the fine fibers is improved, thereby improving the reinforcing effect of the resin. However, even now, there is a desire to further improve the reinforcing effect, and various researches are continuing.

JP 2019-1876 A

The main problem to be solved by the invention is to provide a method for producing fibrous cellulose with a high resin reinforcing effect, a fibrous cellulose composite resin with high strength, and a fibrous cellulose with a high resin reinforcing effect.

In the conventional development, for example, the development of the above patent document, the main focus is on the modification of fine fibers, and among the numerous modification methods such as esterification, etherification, amidation, and sulfidation, the introduction of carbamate groups (carbamation) was found to be excellent. In contrast, the present invention does not focus on the introduction of carbamate groups, but conducts numerous tests on the premise of introducing carbamate groups. The inventors have found that the above problems can be solved by pursuing them, and have arrived at the idea.

(Means according to claim 1)
The average fiber width is 0.1 to 20 μm, and some or all of the hydroxy groups are substituted with carbamate groups,
The substitution rate of the carbamate group is 0.5 mmol/g or more,
Fine rate A/Fine rate B is 1.5 to 10,
A fibrous cellulose characterized by:

(Means according to claim 2)
The Fine rate A is 20 to 60%,
The fibrous cellulose according to claim 1.

(Means according to claim 3)
The average fiber length is 0.10 to 2.0 mm,
The fibrous cellulose according to claim 1 or 2.

(Means according to claim 4)
comprising the fibrous cellulose and resin according to any one of claims 1 to 3,
A fibrous cellulose composite resin characterized by:

(Means according to claim 5)
A method of miniaturizing raw material pulp and converting it to carbamate so that the average fiber width is 0.1 to 20 μm and the substitution rate of carbamate groups is 0.5 mmol/g or more,
In the miniaturization, a disc refiner (DR) is used, and the initial load factor of the disc refiner is set to 65% or more,
A method for producing fibrous cellulose, characterized by:

(Means according to claim 6)
Heat treatment during the carbamate conversion, and washing after the heat treatment so that the replacement washing rate is 80% or more.
The method for producing fibrous cellulose according to claim 5.

According to the present invention, a method for producing fibrous cellulose with a high resin reinforcing effect, a fibrous cellulose composite resin with high strength, and a fibrous cellulose with a high resin reinforcing effect.

Next, the mode for carrying out the invention will be explained. Note that this embodiment is an example of the present invention. The scope of the present invention is not limited to the scope of this embodiment.

The fibrous cellulose of this embodiment (hereinafter also referred to as “cellulose fiber”) has an average fiber width (diameter) of 0.1 to 20 μm, and part or all of the hydroxy groups (—OH groups) are carbamate groups. has been replaced. Further, the carbamate group substitution rate is 0.5 mmol/g or more, and the Fine rate A/Fine rate B is 1.5-10. Furthermore, a fibrous cellulose composite resin is constituted by including this fibrous cellulose and resin. On the other hand, in the method of producing fibrous cellulose, the raw material pulp is pulverized and converted to carbamate so as to have an average fiber width of 0.1 to 20 μm and a substitution ratio of carbamate groups of 0.5 mmol/g or more. In miniaturization, a disc refiner (DR) is used, and the initial load factor (initial DR load factor) of this disc refiner is set to 65% or more. A detailed description will be given below.

(fibrous cellulose)
The fibrous cellulose composite resin of the present embodiment contains the fibrous cellulose of the present embodiment (hereinafter also referred to as "cellulose fiber"), a resin, preferably an acid-modified resin. When an acid-modified resin is included, some or all of the carbamate groups are ionically or covalently bonded to the acid groups of the acid-modified resin.

The fibrous cellulose, which is fine fibers in this embodiment, is microfiber cellulose (microfibrillated cellulose) with an average fiber diameter of 0.1 to 20 μm. Microfiber cellulose significantly improves the reinforcing effect of the resin. In addition, in the washing step for the purpose of removing urea or the like remaining unreacted after the carbamate reaction, if the fibers to be washed are cellulose nanofibers, the dehydration is very poor. In contrast, microfiber cellulose is easier to modify with carbamate groups (carbamate formation) than cellulose nanofiber, which is also a fine fiber, from the viewpoint of dehydration. However, it is more preferable to carbamate the cellulose raw material prior to micronization, in which case the cellulose raw material will be washed, so microfiber cellulose and cellulose nanofibers are equivalent.

In the present embodiment, microfiber cellulose means fibers with a larger average fiber width than cellulose nanofibers. Specifically, the average fiber diameter is, for example, 0.1 to 20 μm, preferably 0.2 to 19 μm, more preferably over 0.5 to 18 μm. If the average fiber diameter of the microfiber cellulose is less than 0.1 μm (below), it is no different from cellulose nanofiber, and there is a possibility that the effect of improving the strength (especially bending elastic modulus) of the resin cannot be sufficiently obtained. . In addition, defibration takes a long time, and a large amount of energy is required. Furthermore, the dewaterability of the cellulose fiber slurry deteriorates. When dehydration deteriorates, a large amount of energy is required for drying, and if a large amount of energy is applied to drying, the microfiber cellulose may be thermally degraded, resulting in a decrease in strength. On the other hand, if the average fiber diameter of the microfiber cellulose exceeds (exceeds) 20 μm, it is no different from pulp, and there is a risk that the reinforcing effect will not be sufficient.

The method for measuring the average fiber diameter of microfiber cellulose is as follows.
First, 100 ml of an aqueous dispersion of fine fibers (microfiber cellulose) having a solid content concentration of 0.01 to 0.1% by mass was filtered through a Teflon (registered trademark) membrane filter, filtered once with 100 ml of ethanol, and then filtered with 20 ml of t-butanol. Replace the solvent with 3 times. It is then freeze-dried and coated with osmium to form a sample. This sample is observed with an electron microscope SEM image at a magnification of 3,000 times 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. Furthermore, the width of a total of 100 fibers intersecting with these three straight lines is visually measured. Then, the median diameter of the measured values is taken as the average fiber diameter.

Microfiber cellulose can be obtained by defibrating (miniaturizing) cellulose raw material (hereinafter also referred to as "raw material pulp"). Raw material pulp includes, for example, wood pulp made from broad-leaved trees, coniferous trees, etc., non-wood pulp made from straw, bagasse, cotton, hemp, pistil fibers, etc., and waste paper pulp made from recovered waste paper, waste paper, etc. (DIP) or the like can be selected and used. The various raw materials described above may be, for example, in the form of pulverized (powdered) material such as cellulose powder.

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

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

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

The raw material pulp can be pretreated by chemical methods prior to being refined. Examples of chemical pretreatments include hydrolysis of polysaccharides with acid (acid treatment), hydrolysis of polysaccharides with enzymes (enzyme treatment), swelling of polysaccharides with alkali (alkali treatment), and oxidation of polysaccharides with an oxidizing agent ( oxidation treatment), reduction of polysaccharides with a reducing agent (reduction treatment), and the like. However, as the chemical pretreatment, it is preferable to perform enzyme treatment, and in addition, it is more preferable to perform one or more treatments selected from acid treatment, alkali treatment, and oxidation treatment. The enzymatic treatment will be described in detail below.

As the enzyme used for enzymatic treatment, it is preferable to use at least one of a cellulase enzyme and a hemicellulase enzyme, and more preferably to use both together. The use of these enzymes makes the fibrillation of cellulosic raw materials easier. Cellulase enzymes cause decomposition of cellulose in the presence of water. In addition, hemicellulase enzymes cause decomposition of hemicellulose in the presence of water.

Cellulase enzymes include, for example, Trichoderma genus, Acremonium genus, Aspergillus genus, Phanerochaete genus, Trametes genus genus Humicola, genus Bacillus, genus Schizophyllum, genus Streptomyces, genus Pseudomonas, etc. Enzymes can be used. These cellulase enzymes can be purchased as reagents or commercial products. Commercially available products include, for example, cellulucine T2 (manufactured by HPI), Meicerase (manufactured by Meiji Seika Co., Ltd.), Novozym 188 (manufactured by Novozym), Multifect CX10L (manufactured by Genencore), cellulase enzyme GC220 (manufactured by Genencore). ) etc. can be exemplified.

In addition, both EG (endoglucanase) and CBH (cellobiohydrolase) can be used as cellulase enzymes. EG and CBH may be used alone or in combination. It may also be used in combination with a hemicellulase enzyme.

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

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

The amount of enzyme added to the cellulose raw material is determined, for example, by the type of enzyme, the type of wood used as the raw material (coniferous or hardwood), the type of mechanical pulp, etc. However, the amount of enzyme added to the cellulose raw material is preferably 0.1 to 3% by mass, more preferably 0.3 to 2.5% by mass, and particularly preferably 0.5 to 2% by mass. If the added amount of the enzyme is less than 0.1% by mass, there is a possibility that the effect of the addition of the enzyme cannot be sufficiently obtained. On the other hand, if the added amount of the enzyme exceeds 3% by mass, cellulose may be saccharified and the yield of fine fibers may decrease. Moreover, there is also a problem that an improvement in the effect commensurate with an increase in the amount added cannot be recognized.

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

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

The time for enzymatic treatment is determined, for example, by the type of enzyme, temperature of enzymatic treatment, pH during enzymatic treatment, etc. However, the general enzymatic treatment time is 0.5 to 24 hours.

It is preferable to deactivate the enzyme after enzymatic treatment. Methods for inactivating the enzyme include, for example, 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 explained.

Alkaline treatment prior to fibrillation dissociates some of the hydroxyl groups of hemicellulose and cellulose in the pulp, anionizing the molecules, weakening intramolecular and intermolecular hydrogen bonds, and promoting the dispersion of cellulose raw materials during fibrillation. be.

Alkali used for alkali treatment include, for example, sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia solution, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, and the like. An organic alkali or the like can be used. However, from the viewpoint of production cost, it is preferable to use sodium hydroxide.

If enzymatic treatment, acid treatment, or oxidation treatment is performed prior to defibration, the water retention of microfiber cellulose can be lowered, the degree of crystallinity can be increased, and homogeneity can be increased. In this regard, when the water retention of the microfiber cellulose is low, it becomes easy to dewater, and the dewaterability of the cellulose fiber slurry is improved.

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

Defibrillation (miniaturization) of the raw material pulp is performed by, for example, homogenizers such as beaters, high-pressure homogenizers, high-pressure homogenizers, grinders, stone mills such as grinders, single-screw kneaders, multi-screw kneaders, kneader refiners, It can be carried out by beating the raw material pulp using a jet mill or the like. However, it is preferable to use a refiner or a jet mill, more preferably a disc refiner (DR), and particularly preferably a single disc refiner (SDR).

The average fiber length (average length of single fibers) of the microfiber cellulose is preferably 0.10 to 2.0 mm, more preferably 0.2 to 1.5 mm, and particularly preferably 0.3 to 1.2 mm. be. If the average fiber length is less than 0.10 mm, the fibers cannot form a three-dimensional network, and the bending elastic modulus of the composite resin may decrease. There is a possibility that the reinforcing effect will not improve even if On the other hand, if the average fiber length exceeds 2.0 mm, there is a risk that the reinforcing effect will be insufficient because the fiber length is the same as that of raw material pulp.

The average fiber length of the cellulose raw material, which is the raw material of the microfiber cellulose, is preferably 0.50 to 5.00 mm, more preferably 1.00 to 3.00 mm, and particularly preferably 1.50 to 2.50 mm. If the average fiber length of the cellulose raw material is less than 0.50 mm, the reinforcing effect of the resin may not be sufficiently obtained during defibration treatment. On the other hand, if the average fiber length exceeds 5.00 mm, it may be disadvantageous in terms of production cost during fibrillation.

The average fiber length of microfiber cellulose can be arbitrarily adjusted, for example, by selecting raw material pulp, pretreatment, defibration, etc.

The fine rate A (fine rate A) of the microfiber cellulose is preferably 10 to 90%, more preferably 20 to 60%, and particularly preferably 25 to 50%. If the Fine A is 10% or more, the ratio of homogeneous fibers is high, and the breakage of the composite resin becomes difficult to proceed. However, when the Fine modulus A exceeds 90%, the flexural modulus may become insufficient.

The above is the fine rate A of the microfiber cellulose, but it is more preferable if the fine rate A of the cellulose raw material, which is the raw material of the microfiber cellulose, is also within a predetermined range. Specifically, the fine ratio A of the cellulose raw material, which is the raw material of the microfiber cellulose, is preferably 1% or more, more preferably 3 to 25%, and particularly preferably 5 to 20%. . If the fine rate A of the cellulose raw material before defibration is within the above range, even if the fine rate A of the microfiber cellulose is fibrillated to 10% or more, the fibers are less damaged and the reinforcing effect of the resin is improved. It is thought that

On the other hand, the fine rate B (fine rate B) of the microfiber cellulose is preferably 1 to 75%, more preferably 10 to 75%, and particularly preferably 35 to 75%. If the fine ratio B is less than 1%, there are many fibers with a short fiber length or many fibers with a large fiber width, so there is a possibility that the reinforcing effect will be insufficient. On the other hand, if the fine rate B exceeds 75%, the number of thin and long fibers increases, and the fibers become entangled with each other. It may break, resulting in deterioration of bending physical properties and impact resistance.

　Fine ratios A and B can be adjusted by pretreatment such as enzyme treatment. However, especially in the case of enzymatic treatment, the molecular weight is reduced and the rigidity is thought to be lost, which may reduce the reinforcing effect of the resin. Therefore, from this point of view, the amount of enzyme added is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less. In addition, no enzymatic treatment (addition amount 0% by mass) is also one option.

Furthermore, in the present embodiment, the Fine rate A/Fine rate B (Fine rate ratio) is preferably 1.5 to 10, more preferably 1.8 to 9.5, and particularly preferably 2.0 to 9.0. be. Especially when the Fine rate A is within a predetermined range (preferably 20 to 60%), if the Fine rate ratio is less than 1.5, tertiary The original network cannot be constructed, and there is a possibility that the reinforcement effect will be insufficient. On the other hand, especially when the Fine rate A is within a predetermined range (preferably 20 to 60%), when the Fine rate ratio exceeds 10, fibers are separated from each other as in the case where long and hard fibers such as NKP are abundant. When an impact is applied from the outside, the entangled portion of the fibers acts like a foreign object and breaks from there, which may reduce the bending physical properties and impact resistance.

(Adjustment of fine rate ratio)
Here, a method for adjusting the Fine ratio will be described.
The fine rate ratio can be adjusted by, for example, mixing two or more types of microfiber cellulose with different fine rates. However, simply pulverizing one cellulose raw material and adjusting the Fine rate ratio is superior in production efficiency. Therefore, for example, a mixture of a plurality of pulp raw materials can be used as the cellulose raw material.

Specifically, for example, it is preferable to use pulp raw materials in which NKP (softwood kraft pulp) and LKP (hardwood kraft pulp) are mixed, NKP (preferably NBKP) 5 to 95% by mass, LKP (preferably LBKP.) It is more preferable to use a pulp raw material composed of 5 to 95% by mass, and it is particularly preferable to use a pulp raw material composed of 25 to 75% by mass of NKP and 25 to 75% by mass of LKP. NKP is characterized by having many long and hard (thick) fibers, and LKP is characterized by having many short and soft (thin) fibers. can be adjusted.

However, in this embodiment, the following method is further recommended.
That is, in refining the cellulose raw material, a disc refiner (DR) is used, and the initial load factor (initial DR load factor) of this disc refiner is 65 to 100%, preferably 65 to 90%, more preferably 65 to 85%. By adjusting the initial load factor in this manner, the fine factor ratio can be adjusted as will be apparent from the examples described later.

The initial DR load factor is an index showing how much pressure is applied to the pulp (because of the initial stage, the beating has hardly progressed) against the teeth of the refiner. It is a value calculated from power (Kw)/rated power (Kw).

In the present embodiment, "Fine rate A" refers to the mass-based ratio of cellulose fibers having a fiber length of 0.2 mm or less and a fiber width of 75 µm or less. In addition, "fine rate B (Fine rate B)" refers to the mass-based ratio of cellulose fibers having a fiber length of more than 0.2 mm and a fiber width of 10 µm or less.

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

The aspect ratio is the value obtained by dividing the average fiber length by the average fiber width. As the aspect ratio increases, the number of locations where catching occurs increases, so that the reinforcing effect increases.

The fiber length, fine rate, etc. of microfiber cellulose are values measured by a fiber analyzer "FS5" manufactured by Valmet.

The fibrillation rate of the microfiber cellulose is preferably 1.0-30.0%, more preferably 1.5-20.0%, and particularly preferably 2.0-15.0%. If the fibrillation rate exceeds 30.0%, the contact area with water becomes too large, so even if defibration is performed in a range in which the average fiber width remains at 0.1 μm or more, dehydration may become difficult. be. On the other hand, if the fibrillation rate is less than 1.0%, hydrogen bonding between fibrils is reduced, and a strong three-dimensional network may not be formed.

In the present embodiment, the fibrillation rate means that the cellulose fibers are defibered in accordance with JIS-P-8220:2012 "Pulp - defiberization method", and the defiberized pulp obtained is subjected to FiberLab. (Kajaani Co.).

The crystallinity of microfiber cellulose is preferably 50% or higher, more preferably 55% or higher, and particularly preferably 60% or higher. If the degree of crystallinity is less than 50%, although the miscibility with pulp and cellulose nanofibers is improved, the strength of the fibers themselves is lowered, so there is a risk that the strength of the resin cannot be improved. On the other hand, the crystallinity of the microfibrous cellulose is preferably 95% or less, more preferably 90% or less, particularly preferably 85% or less. If the degree of crystallinity exceeds 95%, the ratio of strong hydrogen bonds in the molecule increases, the fiber itself becomes rigid, and the dispersibility deteriorates.

The crystallinity of microfiber cellulose can be arbitrarily adjusted, for example, by selecting raw material pulp, pretreatment, and refining treatment.

The crystallinity of microfiber cellulose is a value measured in accordance with JIS K 0131 (1996).

The pulp viscosity of the microfiber cellulose is preferably 1 cps or more, more preferably 2 cps or more. The pulp viscosity is the viscosity of the solution after dissolving cellulose in the copper ethylenediamine solution, and the higher the pulp viscosity, the higher the degree of polymerization of cellulose. If the pulp viscosity of the microfiber cellulose is 1 cps or more, the dehydration property is imparted to the slurry, the decomposition of the cellulose nanofibers is suppressed when kneading with the resin, and a sufficient reinforcing effect can be obtained.

The pulp viscosity of microfiber cellulose is a value measured in accordance with TAPPI T230.

The freeness of the microfiber cellulose is preferably 500 ml or less, more preferably 300 ml or less, and particularly preferably 100 ml or less. If the freeness of the cellulose microfibers exceeds 500 ml, the average fiber diameter of the cellulose microfibers exceeds 20 μm, and there is a risk that the effect of improving the strength of the resin will not be sufficiently obtained.

The freeness of microfiber cellulose 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 less than -150 mV, the compatibility with the resin may be significantly reduced and the reinforcing effect may be insufficient. On the other hand, when the zeta potential exceeds 20 mV, the dispersion stability may deteriorate.

Microfiber cellulose has carbamate groups. There is no particular limitation on how it is determined to have a carbamate group. For example, the cellulose raw material may be carbamate to have carbamate groups, or the microfiber cellulose (micronized cellulose raw material) may be carbamate to have carbamate groups. .

In addition, having a carbamate group means a state in which a carbamate group (ester of carbamic acid) is introduced into the fibrous cellulose. A carbamate group is a group represented by --O--CO--NH--, for example, a group represented by --O--CO--NH ₂ , --O--CONHR, --O--CO--NR ₂ and the like. That is, the carbamate group can be represented by the following structural formula (1).

where n represents an integer of 1 or more. Each R is independently hydrogen, a saturated straight-chain hydrocarbon group, a saturated branched-chain hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated straight-chain hydrocarbon group, an unsaturated branched-chain hydrocarbon group, It is at least one of an aromatic group and a derivative group thereof.

Examples of saturated straight-chain hydrocarbon groups include straight-chain alkyl groups having 1 to 10 carbon atoms such as methyl group, ethyl group, and propyl group.

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

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

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

Examples of unsaturated branched hydrocarbon groups include branched chain alkenyl groups having 3 to 10 carbon atoms such as propen-2-yl group, buten-2-yl group and buten-3-yl group, butyne-3 A branched alkynyl group having 4 to 10 carbon atoms such as -yl group can be mentioned.

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

The derivative group includes, for example, the above saturated straight-chain hydrocarbon group, saturated branched-chain hydrocarbon group, saturated cyclic hydrocarbon group, unsaturated straight-chain hydrocarbon group, unsaturated branched-chain hydrocarbon group and aromatic A group in which one or more hydrogen atoms of the group are substituted with a substituent (eg, a hydroxy group, a carboxy group, a halogen atom, etc.) can be mentioned.

In microfiber cellulose with carbamate groups (carbamate groups introduced), some or all of the highly polar hydroxy groups are substituted with carbamate groups, which are considered to be relatively less polar. As a result, affinity with low-polarity resins and the like increases. Therefore, microfibrous cellulose with carbamate groups has excellent uniform dispersibility with the resin. Also, slurries of microfibrous cellulose with carbamate groups are less viscous and easier to handle.

The substitution ratio of carbamate groups to hydroxy groups of the microfiber cellulose is preferably 0.5 to 5.0 mmol/g, more preferably 0.6 to 3.0 mmol/g, particularly preferably 0.7 to 2.0 mmol/g. is g. When the substitution rate is 0.5 mmol/g or more, the effect of introducing a carbamate group, particularly the effect of improving the flexural modulus of the resin, can be reliably exhibited. On the other hand, if the substitution rate exceeds 5.0 mmol/g, the cellulose fibers will not be able to maintain the shape of the fibers, and there is a risk that the reinforcing effect of the resin will not be obtained sufficiently. Further, when the carbamate group substitution rate exceeds 2.0 mmol/g, the average fiber length of the pulp is shortened when the raw material pulp is carbamated, and as a result, the average fiber length of the microfiber cellulose becomes less than 0.1 mm, There is a possibility that a sufficient resin reinforcing effect cannot be obtained.

In the present embodiment, the carbamate group substitution ratio (mmol/g) refers to the amount of carbamate groups contained per 1 g of cellulose raw material having carbamate groups. The degree of carbamate group substitution is determined by measuring the N atoms present in the carbamate pulp by the Kjeldahl method and calculating the degree of carbamate conversion per unit weight. Cellulose is a polymer having anhydroglucose as a structural unit, and has three hydroxy groups per structural unit.

<Carbamate formation>
Regarding the point of introducing carbamate groups into microfiber cellulose (the cellulose raw material when carbamate-ized before fibrillation; hereinafter the same, also referred to as "microfiber cellulose, etc.") (carbamation), as described above. There are two methods, one is a method of carbamate-izing a cellulose raw material and then pulverizing, and the other is a method of pulverizing a cellulose raw material and then carbamate-forming. In this regard, in this specification, defibration of the cellulose raw material is described first, and then carbamate formation (modification) is described. However, defibration and carbamate can be performed either first. However, it is preferable to perform carbamate formation first and then defibrate. This is because the cellulose raw material before defibration has a high dehydration efficiency, and the cellulose raw material is easily defibrated by the heating accompanying carbamate formation.

The process of carbamate-izing microfiber cellulose can be mainly divided into, for example, mixing treatment, removal treatment, and heat treatment. In addition, the mixing process and the removal process can also be collectively referred to as a preparation process for preparing a mixture to be subjected to heat treatment. By the way, as a method of carbamate conversion, for example, there is a method of forming a sheet of microfiber cellulose or the like, applying urea or the like to the sheet-like microfiber cellulose or the like, and heat-treating it, that is, a method that is not a mixing treatment. . The present embodiment does not deny this sheet-like method, and hereinafter, as an example, a detailed description will be given of an embodiment in which microfiber cellulose or the like and urea or the like are mixed.

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

Examples of urea and urea derivatives include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and compounds in which hydrogen atoms of urea are substituted with alkyl groups. can. These urea or urea derivatives can be used singly or in combination. However, it is preferred to use urea.

The lower limit of the mixing mass ratio of urea, etc. to microfiber cellulose, etc. (urea, etc./microfiber cellulose, etc.) is preferably 10 kg/pt, more preferably 20 kg/pt. On the other hand, the upper limit is preferably 300 kg/pt, more preferably 200 kg/pt. By setting the mixing mass ratio to 10 kg/pt or more, the efficiency of carbamate formation is improved. On the other hand, even if the mixing mass ratio exceeds 300 kg/pt, carbamate formation plateaus.

The dispersion medium is usually water. However, other dispersion media such as alcohols and ethers, and mixtures of water and other dispersion media may also be used.

In the mixing process, for example, microfiber cellulose or the like and urea or the like are added to water, microfiber cellulose or the like is added to an aqueous solution of urea or the like, or urea or the like is added to a slurry containing microfiber cellulose or the like. may Moreover, in order to mix uniformly, you may stir after addition. Further, the dispersion containing microfiber cellulose or the like and urea or the like may contain other ingredients.

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

The removal of the dispersion medium is preferably carried out by volatilizing the dispersion medium by heating. According to this method, only the dispersion medium can be efficiently removed while leaving components such as urea.

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

The heating time in the removal process can be adjusted as appropriate according to the solid content concentration of the dispersion. Specifically, it is, for example, 6 to 24 hours.

In the heat treatment that follows the removal treatment, a mixture of microfiber cellulose etc. and urea etc. is heat treated. In this heat treatment, some or all of the hydroxy groups of the microfiber cellulose or the like react with urea or the like and are substituted with carbamate groups. More specifically, when urea or the like is heated, it decomposes into isocyanic acid and ammonia as shown in the following reaction formula (1). Isocyanic acid is highly reactive, and forms a carbamate group on the hydroxyl group of cellulose, for example, as shown in the following reaction formula (2).

NH ₂ —CO—NH ₂ → H—N=C=O + NH ₃ (1)

Cell-OH + H-N=C=O → Cell-O-CO-NH ₂ (2)

The lower limit of the heating temperature in the heat treatment is preferably 120°C, more preferably 130°C, particularly preferably higher than the melting point of urea (about 134°C), still more preferably 150°C, most preferably 160°C. By setting the heating temperature to 120° C. or higher, carbamate formation is efficiently performed. The upper limit of the heating temperature is preferably 280°C, more preferably 260°C. If the heating temperature exceeds 280° C., urea and the like may be thermally decomposed, and coloring may become noticeable.

The heating time in the heat treatment varies depending on the heating temperature and method, but is preferably 1 second to 5 hours, more preferably 3 seconds to 3 hours, and particularly preferably 5 seconds to 2 hours. If the heating time exceeds 5 hours, there is a possibility that the coloring will become remarkable, and the productivity will be poor.

The heat treatment can also be carried out by a contact method such as contact with a heating roll. In this case, the heating temperature in the heat treatment is 180 to 280° C., more preferably 200 to 270° C., particularly preferably 220 to 260° C., and the heating time is preferably 1 to 60 seconds, more preferably 1 to 30 seconds, particularly preferably 1 to 20 seconds.
The heat treatment can also be performed by a non-contact heating method such as hot air heating or far infrared heating. In this case, the carbamate-forming reaction can proceed efficiently by raising the reaction temperature.

However, prolonged heating time causes deterioration of cellulose fibers. Therefore, the pH condition in the heat treatment becomes important. The pH is preferably pH 9 or higher, more preferably pH 9-13, and particularly preferably pH 10-12 under alkaline conditions. Also, as a second best measure, pH 7 or less, preferably pH 3 to 7, particularly preferably pH 4 to 7, acidic or neutral conditions. Under neutral conditions of pH 7 to 8, the average fiber length of the cellulose fibers may be shortened, and the reinforcing effect of the resin may be inferior. On the other hand, under alkaline conditions of pH 9 or higher, the cellulose fibers swell and the urea dissolved in the dispersion medium permeates into the interior of the fibers, resulting in an efficient carbamate reaction. can be secured to On the other hand, under acidic conditions of pH 7 or less, the reaction of decomposing urea and the like into isocyanic acid and ammonia proceeds, and the reaction to cellulose fibers is accelerated, resulting in an efficient carbamate reaction. can be secured to However, if possible, it is preferable to heat-treat under alkaline conditions. This is because acid hydrolysis of cellulose may proceed under acidic conditions.

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

For example, a hot air dryer, a paper machine, a dry pulp machine, etc. can be used as a device for heating in the heat treatment.

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

Here, whether or not the washing was sufficiently performed can be confirmed by measuring the nitrogen concentration and transparency of the filtrate (slurry), but it is better to evaluate by the "displacement washing rate" defined below. preferable. In addition, the following "first stage" means the first time in which the pulp slurry before dehydration (after disintegration) is subjected to the dehydration step. Further, "the second and subsequent stages" means that the first stage is completely completed, and the same dehydration process is performed again after addition of diluent water and stirring.

Replacement cleaning rate D0 (first stage) = (A0)/(X0 + Y0)
X0: Amount of water contained in pulp before dehydration = Amount of aqueous pulp dispersion before dehydration - Pulp concentration before dehydration x Amount of aqueous pulp dispersion before dehydration Y0: Amount of water contained in pulp after dehydration = after dehydration Amount of aqueous pulp dispersion - Pulp concentration after dehydration × Amount of aqueous pulp dispersion after dehydration A0: Amount of filtrate after dehydration

Replacement cleaning rate Dn (from the second stage onwards) = Dn-1 + An x (1-Dn-1) / (Xn + Yn)
Dn-1: Replacement cleaning rate of the previous stage Xn: Amount of water contained in pulp before dehydration = Amount of aqueous pulp dispersion before dehydration - Pulp concentration before dehydration x Amount of aqueous pulp dispersion before dehydration Yn: Pulp after dehydration Amount of water contained in = Amount of aqueous pulp dispersion after dehydration - Concentration of pulp after dehydration x Amount of aqueous pulp dispersion after dehydration An: Amount of filtrate after dehydration

In this embodiment, the replacement cleaning rate is preferably 80% or more. If it is difficult to achieve a washing ratio of 80% or more in one dehydration washing, it is preferable to repeat the dehydration washing several times until the washing ratio reaches 80% or more, followed by diluted dehydration washing.

(slurry)
The microfiber cellulose is optionally dispersed in an aqueous medium to form a dispersion (slurry). It is particularly preferred that the entire amount of the aqueous medium is water, but it is also possible to use an aqueous medium that is partly another liquid that is compatible with water. Other liquids that can be used include lower alcohols having 3 or less carbon atoms.

The solid content concentration of the slurry is preferably 0.1-10.0% by mass, more preferably 0.5-5.0% by mass. If the solid content concentration is less than 0.1% by mass, excessive energy may be required during dehydration and drying. On the other hand, when the solid content concentration exceeds 10.0% by mass, the fluidity of the slurry itself is lowered, and when a dispersant is used, there is a possibility that uniform mixing may not be possible.

(Acid-modified resin)
In the acid-modified resin, as described above, the acid groups form ionic bonds or covalent bonds with some or all of the carbamate groups. This ionic bond or covalent bond improves the reinforcing effect of the resin.

As acid-modified resins, for example, acid-modified polyolefin resins, acid-modified epoxy resins, acid-modified styrene-based elastomer resins, etc. can be used. However, it is preferable to use an acid-modified polyolefin resin. An 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 more of alkene polymers such as ethylene, propylene, butadiene and isoprene can be selected and used. However, it is preferable to use polypropylene resin, which is a polymer of propylene.

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

The amount of the acid-modified resin to be mixed is preferably 0.1 to 1,000 parts by mass, more preferably 1 to 500 parts by mass, and particularly preferably 10 to 200 parts by mass with respect to 100 parts by mass of the microfiber cellulose. Particularly 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 part by mass, the strength is not sufficiently improved. 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.

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

Furthermore, the MFR (melt flow rate) of the acid-modified resin is preferably 2000 g/10 min (190° C./2.16 kg) or less, more preferably 1500 g/10 min or less, and 500 g/10 min or less. It is particularly preferred to have If the MFR exceeds 2000 g/10 minutes, the dispersibility of cellulose fibers may decrease.

The acid value is measured by titrating with potassium hydroxide in accordance with JIS-K2501. The MFR is measured in accordance with JIS-K7210, and is determined by the weight of the sample that flows out in 10 minutes under a load of 2.16 kg at 190°C.

(dispersant)
Cellulose raw materials or microfibrous cellulose are more preferred when mixed with a dispersant. As the dispersing agent, a compound having an aromatic compound having an amine group and/or a hydroxyl group and an aliphatic compound having an amine group and/or a hydroxyl group are preferable.

Examples of compounds having an amine group and/or hydroxyl group in aromatics include anilines, toluidines, trimethylanilines, anisidines, tyramines, histamines, tryptamines, phenols, dibutylhydroxytoluenes, bisphenol A cresols, eugenols, gallic acids, guaiacols, picric acids, phenolphthaleins, serotonins, dopamines, adrenaline, noradrenaline, thymols, tyrosines, salicylic acids, methyl salicylates, anise alcohols , salicyl alcohols, sinapyl alcohols, diphenidols, diphenylmethanols, cinnamyl alcohols, scopolamines, tryptophors, vanillyl alcohols, 3-phenyl-1-propanols, phenethyl alcohols, phenoxyethanols , veratryl alcohols, benzyl alcohols, benzoins, mandelic acids, mandelonitriles, benzoic acids, phthalic acids, isophthalic acids, terephthalic acids, mellitic acids, and cinnamic acids.

Examples of compounds having an amine group and/or a hydroxyl group in an aliphatic group include capryl alcohols, 2-ethylhexanols, pelargon alcohols, capric alcohols, undecyl alcohols, lauryl alcohols, and tridecyl alcohol. , myristyl alcohols, pentadecyl alcohols, cetanols, stearyl alcohols, elaidyl alcohols, oleyl alcohols, linoleyl alcohols, methylamines, dimethylamines, trimethylamines, ethylamines, diethylamines, ethylenediamine triethanolamines, N,N-diisopropylethylamines, tetramethylethylenediamines, hexamethylenediamines, spermidines, spermines, amantadine, formic acids, acetic acids, propionic acids, butyric acids, valeric acids, Caproic acids, enanthic acids, caprylic acids, pelargonic acids, capric acids, lauric acids, myristic acids, palmitic acids, margaric acids, stearic acids, oleic acids, linoleic acids, linolenic acids, arachidonic acids, eicosapentaenoic acids, docosahexaenoic acids, sorbin acids and the like.

The above dispersants inhibit hydrogen bonding between cellulose fibers. Therefore, the microfiber cellulose is reliably dispersed in the resin when the microfiber cellulose and the resin are kneaded. The above dispersants also play a role in improving the compatibility of the microfiber cellulose and the resin. In this respect, the dispersibility of the microfiber cellulose in the resin is improved.

It is conceivable to separately add a compatibilizer (drug) when kneading the fibrous cellulose and the resin, but rather than adding the drug at this stage, the fibrous cellulose and the dispersing agent (drug) are mixed in advance. In this case, the drug is evenly attached to the fibrous cellulose, and the effect of improving the compatibility with the resin is enhanced.

Also, for example, polypropylene has a melting point of 160°C, so fibrous cellulose and resin are kneaded at about 180°C. However, if the dispersing agent (liquid) is added in this state, it dries up in an instant. Therefore, there is a method of using a resin with a low melting point to prepare a masterbatch (composite resin with a high concentration of microfiber cellulose), and then reducing the concentration with a normal resin. However, resins with low melting points generally have low strength. Therefore, according to this method, the strength of the composite resin may decrease.

The amount of the dispersant mixed is preferably 0.1 to 1,000 parts by mass, more preferably 1 to 500 parts by mass, and particularly preferably 10 to 200 parts by mass with respect to 100 parts by mass of the microfiber cellulose. If the amount of the dispersant mixed is less than 0.1 part by mass, there is a possibility that the improvement in resin strength will be insufficient. On the other hand, if the mixing amount exceeds 1,000 parts by mass, it becomes excessive and tends to lower the resin strength.

In this regard, the above-mentioned acid-modified resin is intended to improve compatibility by forming an ionic or covalent bond between the acid group and the carbamate group of the microfiber cellulose, thereby enhancing the reinforcing effect. It is easy to get used to both, and it is thought that it contributes to strength improvement. On the other hand, the above-mentioned dispersant intervenes between the hydroxyl groups of the microfiber cellulose to prevent aggregation, thereby improving the dispersibility in the resin. , it can enter the narrow spaces between microfiber cellulose where the acid-modified resin cannot enter, and plays a role of improving dispersibility and strength. From the above viewpoints, 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.

To explain this point in more detail, the resin powder physically intervenes between the cellulose microfibers to inhibit hydrogen bonding, thereby improving the dispersibility of the cellulose microfibers. In contrast, acid-modified resins improve compatibility by forming ionic or covalent bonds between acid groups and carbamate groups of microfiber cellulose, thereby enhancing reinforcing effects. In this respect, the dispersing agent inhibits the hydrogen bonding between microfiber celluloses, but since the resin powder is micro-order, it physically intervenes to suppress the hydrogen bonding. Therefore, although the dispersibility is lower than that of the dispersant, the resin powder itself melts and becomes a matrix, so it does not contribute to deterioration of physical properties. On the other hand, since the dispersant is at the molecular level and is extremely small, it has a high effect of covering the cellulose microfibers, inhibiting hydrogen bonding, and improving the dispersibility of the cellulose microfibers. However, it may remain in the resin and work to reduce physical properties.

(Production method)
The mixture of fibrous cellulose, acid-modified resin, dispersant, etc. can be dried and ground into a powder prior to kneading with the resin. According to this form, it is not necessary to dry the fibrous cellulose when kneading with the resin, and the heat efficiency is good. Further, when a dispersant is mixed in the mixture, even if the mixture is dried, there is a low possibility that the fibrous cellulose (microfiber cellulose) will not be redispersed. In addition, in order to increase the productivity during kneading, it may be compressed into a fibrous cellulose solid.

If necessary, the mixture is dehydrated into a dehydrated product prior to drying. For this dehydration, for example, one or more types are selected from dehydration devices such as belt presses, screw presses, filter presses, twin rolls, twin wire formers, valveless filters, center disk filters, membrane processing, and centrifugal separators. can be done using

Drying of the mixture includes, for example, rotary kiln drying, disk drying, air stream drying, medium fluidized drying, spray drying, drum drying, screw conveyor drying, paddle drying, uniaxial kneading drying, multi-screw kneading drying, vacuum drying, and stirring drying. It can be carried out by selecting and using one or more of these.

The dry mixture (dry matter) is ground to a powder. Pulverization of the dried product can be carried out by selecting and using one or more of, for example, bead mills, kneaders, dispersers, twist mills, cut mills, hammer mills, and the like.
However, when compressing into fibrous cellulose solid matter, it is preferable to use, for example, an apparatus that applies external pressure to a powdery or granular matter to compress it and granulate it into pellets. The equipment includes biomass pellet manufacturing equipment from Earth Engineering Co., Ltd., press pelleter from Chiyoda Machinery Co., Ltd., wood pellet manufacturing equipment from Apte Japan, biomass pellet manufacturing equipment from Shinko Koki Co., Ltd., and pelletizer from Tosa Tech Co., Ltd. , WELHOUSE, and a briquette machine of NIPPON STEEL BUSSAN CO., LTD. The mixture is loaded into the device and compressed into pelleted microfibrous cellulose solids.

The average particle size of the powder is preferably 1-10,000 μm, more preferably 10-5,000 μm, and particularly preferably 100-1,000 μm. If the average particle size of the powder exceeds 10,000 μm, the kneadability with the resin may be poor. On the other hand, it is not economical because a large amount of energy is required to reduce the average particle size of the powder to less than 1 μm.

In addition to controlling the degree of pulverization, the average particle size of the powder can be controlled by classification using a classification device such as a filter or cyclone.

The bulk specific gravity of the mixture (powder) is preferably 0.03-1.0, more preferably 0.04-0.9, and particularly preferably 0.05-0.8. A bulk specific gravity of more than 1.0 means that the hydrogen bonding between fibrous celluloses is stronger and it is not easy to disperse the fibrous cellulose in the resin. On the other hand, setting the bulk specific gravity below 0.03 is disadvantageous in terms of transportation costs. However, when fibrous cellulose solids are used, the bulk specific gravity per piece is preferably 0.4 to 0.8.

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

The moisture content of the mixture (powder) is preferably 50% or less, more preferably 30% or less, and particularly preferably 10% or less. If the moisture content exceeds 50%, the energy required for kneading with the resin is enormous, which is not economical.

The moisture content is a value calculated by the following formula, using a constant temperature drier, holding the sample at 105° C. for 6 hours or more, and using the mass after drying as the mass when no change in mass is observed.
Fiber moisture content (%) = [(mass before drying - mass after drying) / mass before drying] x 100

The dehydrated and dried microfiber cellulose may contain resin. When the resin is contained, the hydrogen bonding between the dehydrated and dried microfiber cellulose is inhibited, and the dispersibility in the resin during kneading can be improved.

Forms of the resin contained in the dehydrated and dried microfiber cellulose include, for example, powder, pellet, and sheet. However, the powder form (powder resin) is preferable.

When powdered, the average particle size of the resin powder contained in the dehydrated and dried microfiber cellulose is preferably 1 to 10,000 μm, more preferably 10 to 5,000 μm, and particularly preferably 100 to 1,000 μm. If the average particle size exceeds 10,000 μm, the particles may not enter the kneading device due to the large particle size. On the other hand, when the average particle size is less than 1 μm, there is a possibility that hydrogen bonding between microfiber celluloses cannot be inhibited due to fineness. The resin such as the powdered resin used here may be of the same type or different from the resin to be kneaded with the microfiber cellulose (the resin as the main raw material), but is preferably of the same type.

The resin powder with an average particle size of 1 to 10,000 μm is preferably mixed in an aqueous dispersion state before dehydration and drying. By mixing in an aqueous dispersion state, the resin powder can be uniformly dispersed between the microfiber celluloses, and the microfiber cellulose can be uniformly dispersed in the composite resin after kneading, and the strength properties can be further improved. can be done.

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

For the kneading treatment, for example, one or more selected from single-screw or multi-screw kneaders with two or more screws, mixing rolls, kneaders, roll mills, Banbury mixers, screw presses, dispersers, etc. are used. be able to. Among them, it is preferable to use a multi-screw kneader with two or more screws. Two or more multi-screw kneaders with two or more screws may be used in parallel or in series.

The temperature of the kneading treatment is 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 more preferably 100 to 240°C. is particularly preferred.

At least one of thermoplastic resin and thermosetting resin can be used as the resin.

Examples of thermoplastic resins 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, methacrylates and acrylates, polyamide resins, One or more of polycarbonate resins, polyacetal resins and the like can be selected and used.

However, it is preferable to use at least one of polyolefin and polyester resin. Polypropylene is preferably used as the polyolefin. Furthermore, as polyester resins, aliphatic polyester resins such as polylactic acid and polycaprolactone can be exemplified, and aromatic polyester resins such as polyethylene terephthalate can be exemplified. It is preferable to use a polyester resin having

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

Hydroxycarboxylic acid-based aliphatic polyesters include, for example, homopolymers of hydroxycarboxylic acids such as lactic acid, malic acid, glucose acid, and 3-hydroxybutyric acid, and copolymers using at least one of these hydroxycarboxylic acids. One or two or more may be selected and used from among polymers and the like. However, it is preferable to use polylactic acid, a copolymer of lactic acid and the above hydroxycarboxylic acids other than lactic acid, polycaprolactone, and a copolymer of at least one of the above hydroxycarboxylic acids and caprolactone. It is particularly preferred to use

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

As the caprolactone-based aliphatic polyester, for example, one or more of polycaprolactone homopolymers and copolymers of polycaprolactone and the above hydroxycarboxylic acids can be selected and used. .

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 singly or in combination of two or more.

Examples of thermosetting resins include phenol resins, urea resins, melamine resins, furan resins, unsaturated polyesters, diallyl phthalate resins, vinyl ester resins, epoxy resins, urethane resins, silicone resins, thermosetting polyimide resins, 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, preferably in a proportion that does not interfere with thermal recycling.

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

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, hydroxide Examples include aluminum, magnesium hydroxide, calcium hydroxide, sodium hydroxide, magnesium carbonate, calcium silicate, clay wollastonite, glass beads, glass powder, silica sand, silica stone, quartz powder, diatomaceous earth, white carbon, and glass fiber. be able to. A plurality of these inorganic fillers may be contained. It may also be contained in waste paper pulp.

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

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

The difference in the solubility parameter (cal/cm ³ ) ^1/2 (SP value) of microfiber cellulose and resin, that is, the SP _MFC value of microfiber cellulose, the SP _POL value of resin, the difference in SP value = SP _MFC value - can be the SP _POL value. The SP value difference is preferably 10 to 0.1, more preferably 8 to 0.5, and particularly preferably 5 to 1. If the difference in SP value exceeds 10, the microfiber cellulose may not be dispersed in the resin and the reinforcing effect may not be obtained. On the other hand, if the difference in SP value is less than 0.1, the microfiber cellulose will dissolve in the resin and will not function as a filler, failing to obtain a reinforcing effect. In this regard, the smaller the difference between the SP _POL value of the resin (solvent) and the SP _MFC value of the microfiber cellulose (solute), the greater the reinforcing effect.

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

(Molding process)
The kneaded product of fibrous cellulose and resin can be kneaded again, if necessary, and then molded into a desired shape. The size, thickness, shape, and the like 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 during the molding process is above the glass transition point of the resin, and varies depending on the type of resin, but is for example 90 to 260°C, preferably 100 to 240°C.

The kneaded product can be molded by, for example, mold molding, injection molding, extrusion molding, blow molding, foam molding, and the like. Alternatively, the kneaded product may be spun into a fibrous form and mixed with the above-described plant material or the like to form a mat or board. Mixing can be carried out by, for example, a method of simultaneous deposition by air laying.

As a device for molding the kneaded material, for example, one or two of injection molding machines, blow molding machines, blow molding machines, blow molding machines, compression molding machines, extrusion molding machines, vacuum molding machines, air pressure molding machines, etc. More than one species can be selected and used.

The above molding may be carried out after kneading, or the kneaded product may be cooled once, chipped using a crusher or the like, and then the chips may be put into a molding machine such as an extruder or an injection molding machine. can also be done. Of course, molding is not an essential requirement of the invention.

The fibrous cellulose composite resin obtained as described above preferably has a standard deviation of flexural modulus of 30 MPa or less, more preferably 29 MPa or less, and particularly preferably 28 MPa or less. If the standard deviation exceeds 30 MPa, when using it as a material, take measures such as increasing the thickness of the material more than necessary or using a reinforcing material in order to maintain the minimum necessary physical properties considering the variation. need arises, which may lead to an increase in cost.

The flexural modulus in this embodiment is a value measured according to JIS K 7171.

(Other compositions)
In addition to fine fibers and pulp, resin compositions include kenaf, jute hemp, manila hemp, sisal hemp, gampi, mitsumata, kozo, banana, pineapple, coconut palm, corn, sugar cane, bagasse, palm, papyrus, reed, esparto, Fibers derived from plant materials obtained from various plants such as surviving grass, barley, rice, bamboo, various conifers (such as cedar and cypress), broad-leaved trees, and cotton can and may be contained.

For the resin composition, for example, one or more selected from among antistatic agents, flame retardants, antibacterial agents, colorants, radical scavengers, foaming agents, etc., within a range that does not impede the effects of the present invention. can be added at These raw materials may be added to the fibrous cellulose dispersion, added during kneading of the fibrous cellulose and resin, added to the kneaded product, or added by other methods. good. However, from the viewpoint of production efficiency, it is preferable to add the fibrous cellulose and the resin during kneading.

The resin composition may contain an ethylene-α-olefin copolymer elastomer or a styrene-butadiene block copolymer as a rubber component. Examples of α-olefins include, for example, butene, isobutene, pentene, hexene, methyl-pentene, octene, decene, dodecene, and the like.

Next, examples of the present invention will be described.
(Test Examples 1 to 6)
First, test examples for clarifying the relationship between the Fine rate A/Fine rate B, the carbamate conversion rate, and the flexural modulus will be shown.
Specifically, first, a cellulose raw material made of bleached softwood kraft pulp and bleached hardwood kraft pulp with a moisture content of 10% or less is used with an aqueous urea solution with a solid content concentration of 30%, and the mass ratio of pulp: urea in terms of solid content is was mixed so as to have a predetermined ratio, and then dried at 105°C. After that, the mixture was reacted at a predetermined reaction temperature and reaction time to obtain a carbamate-modified pulp. The resulting carbamate-modified pulp was diluted with distilled water, stirred, and dehydrated and washed twice. The washed carbamate-modified pulp is beaten using a beater until the Fine rate (ratio of fibers with a fiber length distribution measurement of 0.2 mm or less by FS5) reaches a predetermined rate or higher, thereby producing carbamate-modified microfiber cellulose. Obtained. The resulting carbamate-modified microfiber cellulose was adjusted to a predetermined pulp blending ratio of softwood bleached kraft pulp and hardwood bleached kraft pulp. 22.0 g of maleic acid modified polypropylene was added, and 14.0 g of polypropylene powder was added to each and heated using a contact dryer heated to 140° C. to obtain carbamate modified microfiber cellulose inclusions. The moisture content of the carbamate-modified microfibrous cellulose inclusions was 5-22%. To the carbamate-modified microfiber cellulose-containing material, polypropylene pellets were added and mixed so that the carbamate-modified microfiber: other components = 10:90, and kneaded with a twin-screw kneader at 180 ° C. and 200 rpm. A carbamate-modified microfiber cellulose composite resin with a compounding ratio of 10% was obtained. A carbamate-modified microfiber cellulose composite resin with a fiber content of 10% was cut into a cylindrical shape with a diameter of 2 mm and a length of 2 mm with a pelleter, and a rectangular parallelepiped test piece (length 59 mm, width 9.6 mm, thickness 3.8 mm) was made at 180 ° C. injection molded into. Table 1 shows the results (flexural modulus).

In the bending test, first, the bending elastic modulus was examined according to JIS K7171:2008. In the table, the bending elastic modulus (magnification) of the composite resin is shown with the bending elastic modulus (1.48 GPa) of the resin itself (blank) being 1.

(Test Examples 7-9)
Next, a test example will be shown to clarify that the Fine rate A/Fine rate B can be adjusted by the initial DR load rate.

Specifically, first, a cellulose raw material made of bleached softwood kraft pulp and bleached hardwood kraft pulp with a moisture content of 10% or less is used with an aqueous urea solution with a solid content concentration of 30%, and the solid content ratio is pulp: urea at a predetermined level. After mixing to proportion, it was dried at 105°C. After that, the mixture was reacted at a predetermined reaction temperature and reaction time to obtain a carbamate-modified pulp. The resulting carbamate-modified pulp was diluted with distilled water and stirred, and the dehydration step was repeated twice. After dehydration, the carbamate-modified pulp diluted and stirred to a concentration of about 3.0% is treated at a temperature of 80 ° C. or less and the load power of the beater is adjusted so that the initial load factor is 65% or more. The ratio of fibers having a fiber length distribution measurement of 0.2 mm or less) was beaten to a predetermined ratio or more to obtain carbamate-modified microfiber cellulose. Table 2 shows the results. Test Example 8 corresponds to Test Example 5 described above, and Test Example 9 corresponds to Test Example 6 described above.

By adjusting the initial load factor of the beater to 65% or more, it was found that the Fine A/B ratio was 1.5 to 10.0. Cuboid test pieces were prepared in the same manner as in Test Examples 1 to 6, except that the initial load factor of the beater was adjusted, and the flexural modulus of the composite resin was measured. The initial load factor referred to here is a value relative to the rated value of the load power (kw) from the start of beating until the fiber length decreases by 25% or more when the rated value is 100%.

The present invention can be used as a method for producing fibrous cellulose, fibrous cellulose composite resin, and fibrous cellulose. For example, fibrous cellulose composite resins are used for interior materials, exterior materials, structural materials, etc. of transportation equipment such as automobiles, trains, ships, and airplanes; Parts, etc.; Housings, structural materials, internal parts, etc. of mobile communication devices such as mobile phones; Structural materials, internal parts, etc.; interior materials, exterior materials, structural materials, etc. for buildings and furniture; office equipment, etc. such as stationery; Available.

Claims (6)

1. The average fiber width is 0.1 to 20 μm, and some or all of the hydroxy groups are substituted with carbamate groups,
   The substitution rate of the carbamate group is 0.5 mmol/g or more,
   Fine rate A/Fine rate B is 1.5 to 10,
   A fibrous cellulose characterized by:
2. The Fine rate A is 20 to 60%,
   The fibrous cellulose according to claim 1.
3. The average fiber length is 0.10 to 2.0 mm,
   The fibrous cellulose according to claim 1 or 2.
4. comprising the fibrous cellulose and resin according to any one of claims 1 to 3,
   A fibrous cellulose composite resin characterized by:
5. A method of miniaturizing raw material pulp and converting it to carbamate so that the average fiber width is 0.1 to 20 μm and the substitution rate of carbamate groups is 0.5 mmol/g or more,
   In the miniaturization, a disc refiner (DR) is used, and the initial load factor of the disc refiner is set to 65% or more,
   A method for producing fibrous cellulose, characterized by:
6. Heat treatment during the carbamate conversion, and washing after the heat treatment so that the replacement washing rate is 80% or more.
   The method for producing fibrous cellulose according to claim 5.