JP2021183658A - Polyamide resin composition, and method of producing the same - Google Patents

Abstract

To provide a resin composition, small in heat degradation of a cellulose nanofiber, and further excellent in elongation characteristics also, and a method of producing the same.SOLUTION: One aspect of the present invention is to provide a resin composition including polyamide and a cellulose nanofiber, where the polyamide in the resin composition exhibits a melting point lower than a melting point of the independent polyamide by 5°C-20°C. Also, one aspect of the present invention is to provide a method of producing a resin composition including mixing polyamide, a cellulose nanofiber, and a univalent metal halide.SELECTED DRAWING: None

Description

The present invention relates to a resin composition containing polyamide and cellulose nanofibers and a method for producing the same.

Since resin materials are light and have excellent processing characteristics, they are widely used in various fields such as automobile parts, electrical / electronic parts, office equipment housings, precision parts, etc., but resin alone has mechanical properties, dimensional stability, etc. Since it is often insufficient, a composite of a resin and various fillers is generally used. In recent years, it has been studied to use nanofibers such as cellulose nanofibers (CNF) as such fillers. Since nanofibers such as CNF tend to aggregate in a dry state, they are often produced as a dispersion liquid capable of stable dispersion.

For example, Patent Document 1 states that when lactams are polymerized in the presence of an alkali catalyst and an initiator, a solid filler having any size of 1 μm or less is polymerized in the lactams in a dispersed manner. A method for producing a polyamide composite material as a feature is described, and carbon black, carbon nanotubes, and cellulose nanofibers are exemplified as solid fillers.

Japanese Unexamined Patent Publication No. 2018-162363

Since both polyamide and cellulose nanofibers are excellent in mechanical properties, heat resistance, chemical resistance and the like, a resin composition containing a combination thereof can be applied to various uses. However, since polyamide has a relatively high melting point, there is a problem that the cellulose nanofibers exposed to high temperature in the molten polyamide are thermally deteriorated during the production and processing of the resin composition, resulting in coloring or deterioration of physical properties. there were. Further, although the resin composition containing polyamide is excellent in tensile strength, bending strength, abrasion resistance, heat resistance and the like, it has a drawback of low elongation, and improvement thereof has been desired.

An object of the present invention is to solve the above-mentioned problems and to provide a resin composition having less thermal deterioration of cellulose nanofibers and having excellent elongation characteristics and a method for producing the same.

The present disclosure includes the following aspects.
[1] A resin composition containing polyamide and cellulose nanofibers.
A resin composition in which the polyamide in the resin composition has a melting point that is 5 ° C. to 20 ° C. lower than the melting point of the polyamide alone.
[2] The resin composition according to the above aspect 1, which comprises a monovalent metal halide.
[3] The resin composition according to the above aspect 2, wherein the monovalent metal halide is a bromide or an iodide.
[4] The resin composition according to the third aspect, which comprises 100 parts by mass of the polyamide, 1 to 40 parts by mass of the cellulose nanofibers, and 0.1 to 50 parts by mass of the potassium iodide.
[5] The resin composition according to any one of the above aspects 1 to 4, wherein the polyamide is one or more selected from the group consisting of polyamide 6, polyamide 66 and polyamide 6I.
[6] The resin composition according to any one of embodiments 1 to 5, wherein the cellulose nanofibers have an average fiber diameter of 2 nm to 1000 nm.
[7] The resin composition according to any one of the above aspects 1 to 6, wherein the fiber length (L) / fiber diameter (D) ratio of the cellulose is 30 to 5000.
[8] The resin composition according to any one of the above embodiments 1 to 7, wherein the cellulose has a weight average molecular weight (Mw) of 100,000 or more and a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 6 or less. ..
[9] The resin composition according to any one of the above aspects 1 to 8, wherein the degree of crystallinity of the cellulose is 60% or more.
[10] The resin composition according to any one of embodiments 1 to 9, wherein the content of the alkali-soluble polysaccharide in the cellulose is 12% by mass or less.
[11] The resin composition according to any one of the above aspects 1 to 10, wherein the average content of the acid-insoluble component of the cellulose is 10% by mass or less.
[12] The resin composition according to any one of the above aspects 1 to 11, wherein the cellulose is chemically modified.
[13] The resin composition according to the above aspect 12, wherein the chemical modification is esterification.
[14] The resin composition according to the above aspect 13, wherein the esterification is acetylation.
[15] The resin composition according to any one of the above aspects 12 to 14, wherein the average degree of substitution (DS) of the cellulose is 0.3 to 1.2.
[16] The method for producing a resin composition according to any one of the above aspects 1 to 15.
A method comprising mixing a polyamide, cellulose nanofibers, and a monovalent metal halide.

According to the present invention, it is possible to provide a resin composition and a method for producing the same, which have less thermal deterioration of cellulose nanofibers and are also excellent in elongation characteristics.

It is a figure explaining the melting point measurement by a differential scanning calorimeter (DSC). It is an explanatory view of a method of measuring the thermal decomposition temperature (T _D) and 1% weight loss temperature (T _1%). It is explanatory drawing of the calculation method of IR index 1730 and IR index 1030.

Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited to these aspects.

<Resin composition>
One aspect of the present invention provides a resin composition containing a polyamide and cellulose nanofibers. In one embodiment, the polyamide in the resin composition exhibits a melting point lower than the melting point of the polyamide alone. According to the resin composition having such peculiar properties, the resin composition can be produced and processed at a relatively low temperature while using polyamide which is a polymer having a relatively high melting point. It is possible to suppress thermal deterioration of cellulose nanofibers during production and processing. Further, the resin composition in which the polyamide in the resin composition exhibits a melting point lower than the melting point of the polyamide alone can have good elongation characteristics even though the polyamide is used. Although not bound by theory, in such resin compositions, the polyamide has a looser molecular chain structure (eg, lower crystallinity, lower ratio of α crystal phase and lower γ crystal phase). (Due to the high ratio, etc.).

FIG. 1 is a diagram illustrating melting point measurement by a differential scanning calorimeter (DSC). With reference to FIG. 1, in the present disclosure, the melting point is measured in the temperature range of −20 ° C. to 270 ° C. at a temperature increase / decrease rate of 20 ° C./min using a differential scanning calorimetry device (DSC). The peak top temperature of the peak of the maximum area that appears. In one embodiment, the enthalpy of the endothermic peak is 10 J / g or more, more preferably 20 J / g or more. In the measurement, the sample is once heated to a temperature condition of melting point + 20 ° C or higher (STEP 1 (heating) in the figure), the resin is melted, and then the temperature is lowered to -20 ° C at 20 ° C / min. Using a sample cooled to (STEP 2 (lowering temperature) in the figure), the peak top temperature (STEP 3 (lowering temperature) in the figure) when the temperature was raised at 20 ° C./min (STEP 3 (heating) in the figure). Read the peak top). The resin composition and the polyamide may each have one or more endothermic peaks. When there are at least two endothermic peaks, the peak top temperature of the endothermic peak on the highest temperature side is defined as the melting point of the present disclosure. In the differential scanning calorific value analysis spectrum of the resin composition, the peak derived from the target polyamide is found after confirming the polyamide species in the resin composition by Fourier conversion infrared spectroscopy, gas chromatography mass analysis, etc., and then the polyamide species. It can be confirmed as a heat absorption peak having an enthalpy of 10 J / g or more near the literature value of the melting point (in one embodiment, the value described in the section of polyamide resin of "Plastic Material Course" (Nikkan Kogyo Shimbun)). Further, the melting point of the polyamide alone is a value measured by using the polyamide used for producing the resin composition, or if the measurement cannot be performed, the above-mentioned document value is used instead.

From the viewpoint of improving the heat resistance of the resin composition, the melting point of the polyamide alone is preferably 220 ° C. or higher, or 230 ° C. or higher, or 240 ° C. or higher, or 245 ° C. or higher, or 250 ° C. or higher, and cellulose nano. From the viewpoint of suppressing thermal deterioration of the fiber and easiness of producing the resin composition, the melting point is preferably 350 ° C. or lower, 320 ° C. or lower, or 300 ° C. or lower.

In one embodiment, the difference between the melting point of the polyamide in the resin composition and the melting point of the polyamide alone (hereinafter, also referred to as melting point difference) is that it can be melt-processed at a relatively low temperature while using the polyamide. In one embodiment, the temperature may be 5 ° C. or higher, 10 ° C. or higher, 15 ° C. or higher, or 20 ° C. or higher in that the effect of suppressing thermal deterioration of the cellulose nanofibers is good. On the other hand, the melting point difference may be 20 ° C. or lower, 15 ° C. or lower, 10 ° C. or lower, or 5 ° C. or lower in one embodiment in that the physical properties of the resin composition are well maintained. In one embodiment, the melting point difference is 5 ° C. or higher and 20 ° C. or lower from the viewpoint of obtaining the above advantages. Further, in one embodiment, the melting point of the polyamide in the resin composition may be 160 ° C. or higher, 180 ° C. or higher, or 200 ° C. or higher, and may be 300 ° C. or lower, 280 ° C. or lower, or 260 ° C. or lower. ..

As the polyamide: a polyamide obtained by a polycondensation reaction of lactams (for example, polyamide 6, polyamide 11, polyamide 12, etc.); diamines (for example, 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 1, , 7-Heptanediamine, 2-methyl-1-6-hexanediamine, 1,8-octanediamine, 2-methyl-1,7-heptanediamine, 1,9-nonandiamine, 2-methyl-1,8-octane Diamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, m-xylylene diamine, etc.) and dicarboxylic acids (eg, butanedioic acid, pentandioic acid, hexanediacid, heptanedioic acid, etc.) , Octanedioic acid, nonanedioic acid, decanedioic acid, benzene-1,2-dicarboxylic acid, benzene-1,3-dicarboxylic acid, benzene-1,4 dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane- Polyamides obtained as copolymers with 1,4-dicarboxylic acids (eg, polyamides 6,6, polyamides 6,10, polyamides 6,11, polyamides 6,12, polyamides 6, T, polyamides 6, I, polyamides) 9, T, polyamide 10, T, polyamide 2M5, T, polyamide MXD, 6, polyamide 6, C, polyamide 2M5, C, etc.); and copolymers in which these are copolymerized (for example, polyamide 6, T / 6). , I, etc.), etc.

In a preferred embodiment, the polyamide is one or more selected from the group consisting of polyamide 6, polyamide 6, 6 and polyamide 6, I. Since the polyamides 6 and I are difficult to mold alone, they are usually used in combination with other polyamides.

For example, when the polyamide 6 is used, the above-mentioned melting point difference can be 1 ° C. to 5 ° C., or 5 ° C. to 18 ° C., or 18 ° C. to 30 ° C., and when the polyamides 6 and 6 are used, the above-mentioned melting point difference can be obtained. Can be 1 ° C to 5 ° C, or 5 ° C to 18 ° C, or 18 ° C to 30 ° C, and when polyamides 6 and I are used, the melting point difference is 1 ° C to 5 ° C, or 5 ° C to 5 ° C. It can be 18 ° C, or 18 ° C to 30 ° C.

The concentration of the terminal carboxyl group of the polyamide is not particularly limited, but is preferably 20 μmol / g or more, or 30 μmol / g or more, and preferably 150 μmol / g or less, 100 μmol / g or less, or 80 μmol. It is less than / g.

In polyamide, the ratio of carboxyl end groups to all end groups ([COOH] / [all end groups]) is preferably 0.30 or more, or 0, from the viewpoint of dispersibility of the cellulose nanofibers in the resin composition. It is .35 or more, 0.40 or more, or 0.45 or more, and is preferably 0.95 or less, or 0.90 or less, or 0.85 or less, or 0. It is 80 or less.

The terminal group concentration of the polyamide can be adjusted by a known method. As a preparation method, a terminal adjuster (for example, a diamine compound, a monoamine compound, a dicarboxylic acid compound, a monocarboxylic acid compound, an acid anhydride, or a mono) that reacts with a terminal group so as to have a predetermined terminal group concentration during the polymerization of polyamide. Examples thereof include a method of adding (isocyanate, monoacid halide, monoester, monoalcohol, etc.) to the polymerization solution.

Examples of the terminal modifier that reacts with the terminal amino group include acetic acid, propionic acid, butylic acid, valeric acid, caproic acid, capric acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, isobutylic acid and the like. Alicyclic monocarboxylic acid such as aliphatic monocarboxylic acid; alicyclic monocarboxylic acid such as cyclohexanecarboxylic acid; aromatic monocarboxylic acid such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid and phenylacetic acid. ; And a plurality of mixtures arbitrarily selected from these. Among these, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, etc. One or more end regulators selected from the group consisting of valeric acid and valeric acid are preferable, and acetic acid is most preferable.

Examples of the terminal modifier that reacts with the terminal carboxyl group include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine and dibutylamine; Alicyclic monoamines such as cyclohexylamines and dicyclohexylamines; aromatic monoamines such as aniline, toluidine, diphenylamines and naphthylamines and any mixtures thereof. Among these, one or more terminals selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine and aniline from the viewpoints of reactivity, boiling point, stability of sealed terminal, price and the like. Regulators are preferred.

The concentration of the amino-terminal group and the carboxyl-terminal group of the polyamide ^{can be determined by 1} H-NMR from the integrated value of the characteristic signal corresponding to each terminal group. This method is preferable in terms of accuracy and simplicity. More specifically, it is recommended to use the method described in JP-A-7-228775, use heavy trifluoroacetic acid as the measurement solvent, and set the number of integrations to 300 scans or more.

The intrinsic viscosity [η] of the polyamide measured under the condition of 30 ° C. in concentrated sulfuric acid is from the viewpoint that the fluidity in the mold is good and the appearance of the molded piece is good when the resin composition is injection-molded, for example. Therefore, it is preferably 0.6 to 2.0 dL / g, or 0.7 to 1.4 dL / g, or 0.7 to 1.2 dL / g, or 0.7 to 1.0 dL / g. In the present disclosure, "intrinsic viscosity" is synonymous with viscosity generally called intrinsic viscosity. For the intrinsic viscosity, ηsp / c of several measuring solvents having different concentrations was measured in 96% concentrated sulfuric acid under a temperature condition of 30 ° C., and the relational expression between each ηsp / c and the concentration (c) was obtained. It is obtained by the method of deriving and extrapolating the concentration to zero. The value extrapolated to zero is the intrinsic viscosity. Details of the above method are described, for example, on pages 291 to 294 of Prentice-Hall, Inc. 1994. It is accurate that the concentration in some of the above-mentioned measuring solvents having different concentrations is at least 4 points (for example, 0.05 g / dL, 0.1 g / dL, 0.2 g / dL, 0.4 g / dL). Desirable from the point of view.

[Cellulose nanofibers]
As a raw material for cellulose nanofibers, natural cellulose and regenerated cellulose can be used. Natural cellulose includes wood pulp obtained from wood species (hardwood or coniferous tree), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linter, sisal, walla, etc.), animals (eg, straw). Cellulose fiber aggregates produced by kenaf), algae, and microorganisms (eg, acetic acid bacteria) can be used. As the regenerated cellulose, regenerated cellulose fibers (viscose, cupra, tencel, etc.), cellulose derivative fibers, regenerated cellulose obtained by an electrospinning method, or ultrafine threads of a cellulose derivative can be used.

Cellulose nanofibers are made by treating pulp or the like with hot water at 100 ° C or higher, hydrolyzing hemicellulose to make it fragile, and then using a high-pressure homogenizer, microfluidizer, ball mill, disc mill, mixer (for example, homomixer), etc. Refers to fine cellulose deflated by the crushing method of. In one embodiment, the cellulose nanofibers have a number average fiber diameter of 1 nm or more and 1000 nm or less. Cellulose may be chemically modified as described below.

The slurry can be prepared, for example, by dispersing the cellulose nanofibers obtained through the above defibration in a liquid medium, and the dispersion is carried out using a high-pressure homogenizer, a microfluidizer, a ball mill, a disc mill, a mixer (for example, a homomixer) or the like. You may go. The liquid medium in the slurry may include, for example, water and optionally another liquid medium (eg, an organic solvent), either alone or in combination of two or more. Examples of the organic solvent include commonly used water-miscible organic solvents: alcohols having a boiling point of 50 ° C to 170 ° C (eg, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s). -Butanol, t-butanol, etc.); Ether (eg, propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); Carous acid (eg, formic acid, acetic acid, lactic acid, etc.); (For example, ethyl acetate, vinyl acetate, etc.); Ketone (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); Nitrogen-containing solvent (dimethylformamide, dimethylacetamide, acetonitrile, etc.), etc. can be used. In a typical embodiment, the liquid medium in the slurry is substantially only water. In addition to the cellulose nanofibers and the liquid medium, the slurry may contain additional components (dispersant, antioxidant, preservative, thickener, etc.) described below.

Since the cellulose raw material contains an alkali-soluble component and a sulfuric acid-insoluble component (lignin, etc.), the alkali-soluble component and the sulfuric acid-insoluble component may be reduced through a purification step such as delignin by a cooking treatment and a bleaching step. .. On the other hand, the purification step such as delignin and the bleaching step by the steaming treatment cuts the molecular chain of cellulose and changes the weight average molecular weight and the number average molecular weight. It is desirable that the weight average molecular weight and the ratio of the weight average molecular weight to the number average molecular weight are controlled to the extent that they do not deviate from an appropriate range.

In addition, since the purification step such as delignin and the bleaching step by the steaming treatment reduce the molecular weight of the cellulose molecule, these steps reduce the molecular weight of the cellulose and change the quality of the cellulose raw material to the presence of an alkali-soluble component. There is concern that the ratio will increase. Since the alkali-soluble content is inferior in heat resistance, the purification step and bleaching step of the cellulose raw material are controlled so that the amount of the alkali-soluble content contained in the cellulose raw material is within a certain range. desirable.

In one embodiment, the number average fiber diameter of the cellulose nanofibers is preferably 2 to 1000 nm from the viewpoint of satisfactorily obtaining the effect of improving the physical properties of the cellulose nanofibers. The number average fiber diameter of the cellulose nanofibers is more preferably 4 nm or more, 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 500 nm or less, 450 nm or less, 400 nm or less, or 350 nm. Below, or below 300 nm, or below 250 nm.

The number average fiber diameter of the cellulose nanofibers can be obtained as the number average fiber diameter calculated from the specific surface area obtained by the BET method by adsorption of nitrogen. An average fiber diameter of 1000 nm or less ^{corresponds to a specific surface area of 2.667 m 2} / g or more.

The method for calculating the number average fiber diameter by nitrogen adsorption is as follows. That is, an aqueous dispersion of cellulose nanofibers is subjected to solvent substitution with tBuOH to prepare a porous sheet, and the specific surface area of the porous sheet is measured by using the BET method by nitrogen adsorption. When the cellulose is in an ideal state in which fusion between fibers does not occur at all, and the cellulose density is d (g / cm ³ ) and the fiber diameter is D (nm), the specific surface area and the fiber diameter are determined. The relationship between is expressed by the following formula.
Specific surface area (m ² / g) = 4000 / (dD)
Then, when the cellulose density is 1.50 g / cm ³ , the number average fiber diameter is expressed by the following formula.
D (nm) = 2667 / specific surface area (m ² / g)
The specific surface area when D is 1 μm is 2.667 m ² / g.

The average fiber diameter of the cellulose nanofibers in the resin composition is determined by dissolving the resin component in the resin composition in an organic or inorganic solvent capable of dissolving the resin component of the resin composition, and separating the cellulose nanofibers. After being thoroughly washed with a solvent, it is replaced with a water-soluble solvent (for example, water, ethanol, tert-butanol, etc.) to prepare a 0.01 to 0.1% by mass dispersion, and a high shear homogenizer (for example, manufactured by IKA) is prepared. Redisperse under the trade name "Ultra Tarax T18"). The average fiber diameter can be confirmed by preparing a porous sheet from the redispersion liquid and measuring by the above-mentioned measuring method.

The average L / D of the cellulose nanofibers is preferably 50 or more, 80 or more, or 100 or more, from the viewpoint of satisfactorily improving the mechanical properties of the resin composition containing the cellulose nanofibers with a small amount of cellulose nanofibers. Or 120 or more, or 150 or more. The upper limit is not particularly limited, but is preferably 5000 or less from the viewpoint of handleability.

In the present disclosure, the length, diameter, and L / D ratio of each of the cellulose nanofibers are such that the aqueous dispersion of the cellulose nanofibers is a high shear homogenizer (for example, manufactured by Nippon Seiki Co., Ltd., trade name "Excel Auto Homogenizer ED". −7 ”), Treatment conditions: An aqueous dispersion dispersed at a rotation speed of 15,000 rpm × 5 minutes was diluted with pure water to 0.1 to 0.5% by mass, cast on mica, and air-dried. The sample is used as a measurement sample and measured with a high-resolution scanning microscope (SEM) or an atomic force microscope (AFM). Specifically, the length (L) and diameter (D) of 100 randomly selected celluloses are measured in an observation field in which the magnification is adjusted so that at least 100 cellulose nanofibers can be observed. Then, the ratio (L / D) is calculated. For cellulose, the number average value of the length (L), the number average value of the diameter (D), and the number average value of the ratio (L / D) are calculated.

Alternatively, the length, diameter, and L / D ratio of the cellulose nanofibers in the resin composition can be confirmed by measuring the solid resin composition as a measurement sample by the above-mentioned measuring method.

Alternatively, the length, diameter, and L / D ratio of the cellulose nanofibers in the resin composition are determined by dissolving the resin component in the resin composition in an organic or inorganic solvent capable of dissolving the resin component of the resin composition, and cellulose. To prepare an aqueous dispersion in which the solvent is replaced with pure water, dilute the cellulose concentration with pure water to 0.1 to 0.5% by mass, and put it on mica. It can be confirmed by casting and air-drying the sample as a measurement sample by the above-mentioned measuring method. At this time, the cellulose to be measured is measured with 100 or more randomly selected celluloses.

The crystallinity of the cellulose nanofibers is preferably 55% or more. When the crystallinity is in this range, the mechanical properties (strength, dimensional stability) of the cellulose itself are high, so when the cellulose nanofibers are dispersed in the resin, the strength and dimensional stability of the resin composition tend to be high. be. The lower limit of the more preferable crystallinity is 60%, even more preferably 70%, and most preferably 80%. The upper limit of the crystallinity of the cellulose nanofibers is not particularly limited, and a higher value is preferable, but a preferable upper limit is 99% from the viewpoint of production.

Alkaline-soluble polysaccharides such as hemicellulose and acid-insoluble components such as lignin are present between microfibrils of plant-derived cellulose and between microfibril bundles. Hemicellulose is a polysaccharide composed of sugars such as mannan and xylan, and plays a role of hydrogen-bonding with cellulose to connect microfibrils. Lignin is a compound having an aromatic ring and is known to be covalently bound to hemicellulose in the cell wall of a plant. If the residual amount of impurities such as lignin in cellulose is large, discoloration may occur due to heat during processing. Therefore, from the viewpoint of suppressing discoloration of the resin composition during extrusion processing and molding processing, cellulose nanofibers are also used. It is desirable that the degree of crystallinity of is within the above range.

The degree of crystallinity referred to here is Segal from the diffraction pattern (2θ / deg. 10 to 30) when the sample is measured by wide-angle X-ray diffraction when the cellulose is a cellulose type I crystal (derived from natural cellulose). By law, it is calculated by the following formula.
Crystallinity (%) = ([Diffraction intensity due to (200) plane of 2θ / deg. = 22.5]-[Diffraction intensity due to amorphousness of 2θ / deg. = 18]) / [2θ / Deg. = Diffraction intensity due to 22.5 (200) plane] × 100

The degree of crystallinity is 2θ = 12.6 °, which is assigned to the (110) plane peak of the cellulose type II crystal in wide-angle X-ray diffraction when the cellulose is a cellulose type II crystal (derived from regenerated cellulose). From the absolute peak intensity h0 and the peak intensity h1 from the baseline at this surface spacing, it is calculated by the following equation.
Crystallinity (%) = h1 / h0 × 100

As the crystal form of cellulose, type I, type II, type III, type IV and the like are known, and among them, type I and type II are widely used, and type III and type IV are obtained on a laboratory scale. Although it has been used, it is not widely used on an industrial scale. The cellulose nanofibers of the present disclosure have relatively high structural mobility, and by dispersing the cellulose nanofibers in a resin, the linear expansion coefficient is lower, and the strength and elongation during tensile and bending deformation are more excellent. Cellulose nanofibers containing cellulose type I crystals or cellulose type II crystals are preferable, and cellulose nanofibers containing cellulose type I crystals and having a degree of crystallization of 55% or more are more preferable. preferable.

The degree of polymerization of the cellulose nanofibers is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, and even more preferably 450 or more. Is 3500 or less, more preferably 3300 or less, more preferably 3200 or less, more preferably 3100 or less, and even more preferably 3000 or less.

From the viewpoint of processability and expression of mechanical properties, it is desirable that the degree of polymerization of the cellulose nanofibers is within the above range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of developing mechanical properties, it is desirable that the degree of polymerization is not too low.

The degree of polymerization of cellulose nanofibers means the average degree of polymerization measured according to the reduction specific viscosity method using a copper ethylenediamine solution described in the confirmation test (3) of the "15th Revised Japanese Pharmacy Manual (published by Hirokawa Shoten)". do.

In one embodiment, the weight average molecular weight (Mw) of the cellulose nanofibers is 100,000 or more, more preferably 200,000 or more. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) is 6 or less, preferably 5.4 or less. The larger the weight average molecular weight, the smaller the number of terminal groups of the cellulose molecule. Further, since the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, it means that the smaller the Mw / Mn, the smaller the number of ends of the cellulose molecule. Since the end of the cellulose molecule is the starting point of thermal decomposition, not only the weight average molecular weight is large, but also when the weight average molecular weight is large and the width of the molecular weight distribution is narrow, the cellulose nanofibers and cellulose nanos with high heat resistance are particularly high. A resin composition containing a fiber and a resin can be obtained. The weight average molecular weight (Mw) of the cellulose nanofibers may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of availability of the cellulose raw material. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more, from the viewpoint of ease of producing cellulose nanofibers. The Mw can be controlled within the above range by selecting a cellulose raw material having Mw according to the purpose, appropriately performing physical treatment and / or chemical treatment on the cellulose raw material within an appropriate range, and the like. Mw / Mn also has the above range by selecting a cellulose raw material having Mw / Mn according to the purpose, appropriately performing physical treatment and / or chemical treatment on the cellulose raw material within an appropriate range, and the like. Can be controlled. In both Mw control and Mw / Mn control, the physical treatment includes dry or wet pulverization of microfluidizers, ball mills, disc mills, etc., grinders, homomixers, high-pressure homogenizers, ultrasonic devices. A physical treatment for applying a mechanical force such as impact, shearing, shearing, and friction due to the above can be exemplified, and the chemical treatment can be exemplified by cooking, bleaching, acid treatment, regenerated cellulose formation, and the like.

The weight average molecular weight and the number average molecular weight of the cellulose nanofibers referred to here are gel permeations in which cellulose is dissolved in N, N-dimethylacetamide to which lithium chloride is added, and then N, N-dimethylacetamide is used as a solvent. It is a value obtained by chromatography.

Examples of the method for controlling the degree of polymerization (that is, the average degree of polymerization) or the molecular weight of the cellulose nanofibers include hydrolysis treatment and the like. By the hydrolysis treatment, the depolymerization of the amorphous cellulose inside the cellulose proceeds, and the average degree of polymerization becomes small. At the same time, the hydrolysis treatment removes impurities such as hemicellulose and lignin in addition to the above-mentioned amorphous cellulose, so that the inside of the fiber becomes porous.

The method of hydrolysis is not particularly limited, and examples thereof include acid hydrolysis, alkaline hydrolysis, hot water hydrolysis, steam explosion, and microwave hydrolysis. These methods may be used alone or in combination of two or more. In the acid hydrolysis method, for example, α-cellulose obtained as pulp from a fibrous plant is used as a cellulose raw material, and in a state where the cellulose is dispersed in an aqueous medium, an appropriate amount of protonic acid, carboxylic acid, Lewis acid, heteropolyacid, etc. is added. In addition, the average degree of polymerization can be easily controlled by heating while stirring. The reaction conditions such as temperature, pressure, and time at this time differ depending on the cellulose type, cellulose concentration, acid type, acid concentration, etc., but are appropriately prepared so as to achieve the desired average degree of polymerization. For example, there is a condition that cellulose is treated with a mineral acid aqueous solution of 2% by mass or less at 100 ° C. or higher and under pressure for 10 minutes or longer. Under this condition, the catalyst component such as acid permeates into the inside of the cellulose, hydrolysis is promoted, the amount of the catalyst component used is reduced, and the subsequent purification is facilitated. In addition to water, the dispersion liquid of the cellulose raw material at the time of hydrolysis may contain a small amount of an organic solvent as long as the effect of the present invention is not impaired.

Alkaline-soluble polysaccharides that cellulose can contain include hemicellulose, as well as β-cellulose and γ-cellulose. The alkali-soluble polysaccharide is a component (that is, a component obtained by removing α-cellulose from holocellulose) obtained as an alkali-soluble portion of holocellulose obtained by solvent extraction and chlorine treatment of a plant (for example, wood). Understood by those skilled in the art. Alkaline-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, and have the inconveniences of decomposing when heated, causing yellowing during heat aging, and causing a decrease in the strength of cellulose. It is preferable that the content of the alkali-soluble polysaccharide in the cellulose is low because it can be invited.

In one embodiment, the average content of alkali-soluble polysaccharides in the cellulose nanofibers is preferably 20% by mass or less with respect to 100% by mass of the cellulose nanofibers from the viewpoint of obtaining good dispersibility of the cellulose nanofibers. Or 18% by mass or less, 15% by mass or less, or 12% by mass or less. The content may be 1% by mass or more, 2% by mass or more, or 3% by mass or more from the viewpoint of ease of producing cellulose nanofibers.

The average content of alkali-soluble polysaccharides can be determined by the method described in non-patent literature (Wood Science Experiment Manual, edited by Japan Wood Society, pp. 92-97, 2000), and the holocellulose content (Wise method). It is obtained by subtracting the α-cellulose content from. This method is understood in the art as a method for measuring the amount of hemicellulose. The alkali-soluble polysaccharide content is calculated three times for one sample, and the number average of the calculated alkali-soluble polysaccharide content is defined as the alkali-soluble polysaccharide average content.

In one embodiment, the average content of the acid-insoluble component in the cellulose nanofibers is preferably 10% by mass with respect to 100% by mass of the cellulose nanofibers from the viewpoint of avoiding a decrease in heat resistance of the cellulose nanofibers and the accompanying discoloration. Below, or 5% by mass or less, or 3% by mass or less. The content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more from the viewpoint of ease of producing cellulose nanofibers.

The average content of acid-insoluble components is determined as a quantification of acid-insoluble components using the Clarson method described in a non-patent document (Wood Science Experiment Manual, edited by Japan Wood Society, pp. 92-97, 2000). This method is understood in the art as a method for measuring the amount of lignin. The sample is stirred in a sulfuric acid solution to dissolve cellulose, hemicellulose and the like, and then filtered through a glass fiber filter paper, and the obtained residue corresponds to an acid-insoluble component. The acid-insoluble component content is calculated from the weight of the acid-insoluble component, and the number average of the acid-insoluble component contents calculated for the three samples is taken as the acid-insoluble component average content.

Cellulose nanofibers of the thermal decomposition temperature (T _D), from the viewpoint of heat resistance and mechanical strength desired in-vehicle use or the like can be exhibited, and at 270 ° C. or higher in one aspect, preferably 275 ° C. or higher, more preferably It is 280 ° C. or higher, more preferably 285 ° C. or higher. The higher the thermal decomposition start temperature is, the more preferable it is, but from the viewpoint of ease of producing cellulose nanofibers, for example, it may be 320 ° C. or lower, or 300 ° C. or lower.

In the present disclosure, T _D is a value obtained from a graph in which the horizontal axis is temperature and the vertical axis is% weight residual ratio in thermogravimetric (TG) analysis, as shown in the explanatory diagram of FIG. 2 (B) is an enlarged view of FIG. 2 (A). Starting from the weight (weight loss of 0 wt%) of the cellulose nanofibers at 150 ° C. (with almost all water removed), the temperature continues to rise, and the temperature (T _1% ) and 2 wt% weight at the time of 1 wt% weight loss. Obtain a straight line through the decreasing temperature (T _2%). The temperature at the intersection of this straight line and the horizontal line (baseline) passing through the starting point of the weight loss amount of 0 wt% is defined _{as T D.}

The 1% weight loss temperature (T _1% ) is the temperature at which the weight is reduced by 1% by weight starting from the weight of 150 ° C. when the temperature is continuously _{increased by the method of T D.}

The 250 ° C. weight loss rate (T _{250 ° C.} ) of the cellulose nanofibers is the weight loss rate when the cellulose nanofibers are held at 250 ° C. under a nitrogen flow for 2 hours in TG analysis.

(Chemical modification)
The cellulose nanofibers may be chemically modified cellulose nanofibers. Cellulose nanofibers may be chemically modified in advance, for example, at the stage of raw pulp or linter, during defibration treatment, or after defibration treatment, during or after the slurry preparation step, or during the drying (granulation) step. It may be chemically modified during or after that.

As the modifying agent for cellulose nanofibers, a compound that reacts with the hydroxyl group of cellulose can be used, and examples thereof include an esterifying agent, an etherizing agent, and a silylating agent. In a preferred embodiment, the chemical modification is acylation with an esterifying agent. As the esterifying agent, acid halides, acid anhydrides, carboxylic acid vinyl esters, and carboxylic acids are preferable.

The acid halide may be at least one selected from the group consisting of the compounds represented by the following formula (1).
R ^1- C (= O) -X (1)
(In the formula, R ¹ represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, or an aryl group having 6 to 24 carbon atoms, and X represents Cl. , Br or I.)
Specific examples of acid halides include acetyl chloride, acetyl bromide, acetyl iodide, propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl chloride, benzoyl bromide, and iodide. Examples include, but are not limited to, benzoyl chloride. Above all, the acid chloride can be suitably adopted from the viewpoint of reactivity and handleability. In the reaction of acid halides, one or more alkaline compounds may be added for the purpose of neutralizing an acidic substance which is a by-product at the same time as acting as a catalyst. Specific examples of the alkaline compound include, but are not limited to, tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine.

As the acid anhydride, any suitable acid anhydride can be used. for example,
Saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso) butyric acid and valeric acid; unsaturated aliphatic monocarboxylic acid anhydrides such as (meth) acrylic acid and oleic acid;
Alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid and tetrahydrobenzoic acid;
Aromatic monocarboxylic acid anhydrides such as benzoic acid and 4-methylbenzoic acid;
Examples of the dibasic carboxylic acid anhydride include anhydrous saturated aliphatic dicarboxylic acid such as succinic acid anhydride and adipic acid, anhydrous unsaturated aliphatic dicarboxylic acid anhydride such as maleic anhydride and itaconic acid anhydride, and 1-cyclohexene anhydride-1. , 2-Dicarboxylic acid, Hexahydrophthalic anhydride, Anhydrous alicyclic dicarboxylic acid such as methyltetrahydrophthalic anhydride, and Aromatic dicarboxylic acid anhydride such as phthalic acid anhydride and naphthalic acid anhydride;
Examples of the polybasic carboxylic acid anhydrides having 3 or more bases include (anhydrous) polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride.
In the reaction of the acid anhydride, as a catalyst, an acidic compound such as sulfuric acid, hydrochloric acid, or phosphoric acid, or a Lewis acid (for example, a Lewis acid compound represented by MYn, M is B, As, Ge, etc.). Represents a semi-metal element, a base metal element such as Al, Bi, In, a transition metal element such as Ti, Zn, Cu, or a lanthanoid element, and n is an integer corresponding to the atomic value of M and is 2 or 3. , Y represents a halogen atom, OAc, OCOCF ₃ , ClO ₄ , SbF ₆ , PF ₆ or OSO ₂ CF ₃ (OTf)), or one or more alkaline compounds such as triethylamine and pyridine are added. You may.

The carboxylic acid vinyl ester has the following formula (1):
R-COO-CH = CH ₂ ... Equation (1)
{In the formula, R is either an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 24 carbon atoms. } Is preferred. The carboxylic acid vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, cyclohexanevinyl carboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, and pivalin. More preferably, it is at least one selected from the group consisting of vinyl acid acid, vinyl octylate divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl pivalate, vinyl octylate, vinyl benzoate, and vinyl cinnamic acid. .. In the esterification reaction with carboxylic acid vinyl ester, alkali metal hydroxide, alkaline earth metal hydroxide, alkali metal carbonate, alkaline earth metal carbonate, alkali metal hydrogen carbonate, grades 1 to 3 can be used as catalysts. One or more selected from the group consisting of amines, quaternary ammonium salts, imidazoles and derivatives thereof, pyridines and derivatives thereof, and alkoxides may be added.

Examples of the alkali metal hydroxide and alkaline earth metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide and the like. Alkali metal carbonate, alkaline earth metal carbonate, alkali metal hydrogen carbonate include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, carbonic acid. Examples include potassium hydrogen, cesium hydrogen carbonate, and the like.

The 1st to 3rd grade amines are primary amines, secondary amines, and tertiary amines, and specific examples thereof include ethylenediamine, diethylamine, proline, N, N, N', N'-tetramethylethylenediamine, and the like. N, N, N', N'-tetramethyl-1,3-propanediamine, N, N, N', N'-tetramethyl-1,6-hexanediamine, tris (3-dimethylaminopropyl) amine, Examples thereof include N, N-dimethylcyclohexylamine and triethylamine.

Examples of the imidazole and its derivative include 1-methylimidazole, 3-aminopropylimidazole, carbonyldiimidazole and the like.

Examples of pyridine and its derivatives include N, N-dimethyl-4-aminopyridine, picoline and the like.

Examples of the alkoxide include sodium methoxide, sodium ethoxide, potassium-t-butoxide and the like.

Examples of the carboxylic acid include at least one selected from the group consisting of compounds represented by the following formula (1).
R-COOH ... (1)
(In the formula, R represents an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms.)

Specific examples of the carboxylic acid include acetic acid, propionic acid, butyric acid, caproic acid, cyclohexanecarboxylic acid, capric acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid and pivalin. Included is at least one selected from the group consisting of acid, octyl acid, benzoic acid, and cinnamic acid.

Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid, particularly acetic acid, is preferable from the viewpoint of reaction efficiency.
In the reaction of the carboxylic acid, the catalyst may be an acidic compound such as sulfuric acid, hydrochloric acid or phosphoric acid, or a Lewis acid (for example, a Lewis acid compound represented by MYn, in which M is B, As, Ge or the like. It represents a semi-metal element, a base metal element such as Al, Bi, In, a transition metal element such as Ti, Zn, Cu, or a lanthanoid element, and n is an integer corresponding to the atomic value of M, and 2 or 3 is used. Representing, Y represents a halogen atom, OAc, OCOCF ₃ , ClO ₄ , SbF ₆ , PF ₆ or OSO ₂ CF ₃ (OTf)), or one or more alkaline compounds such as triethylamine and pyridine are added. May be.

Among these esterification reactants, in particular, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, and vinyl butyrate and acetic acid, among which acetic anhydride and vinyl acetate are used. It is preferable from the viewpoint of reaction efficiency.

When the cellulose nanofibers are chemically modified (eg, by hydrophobicity such as acylation), the dispersibility of the cellulose nanofibers in the resin tends to be good, but the cellulose nanofibers are unsubstituted or low. Even with the degree of substitution, good dispersibility in the resin can be shown. When the cellulose nanofiber is esterified cellulose, the acyl substitution degree (DS) is 1.0 or less in one embodiment, preferably 0.1 or more and 1.0 or less. When the DS is 0.1 or more, an esterified cellulose having a high thermal decomposition start temperature and a resin composition containing the same can be obtained. On the other hand, when the DS is 1.0 or less, an unmodified cellulose skeleton remains in the esterified cellulose, so that it has both high tensile strength and dimensional stability derived from cellulose and a high thermal decomposition start temperature derived from chemical modification. , Esterified cellulose and a resin composition containing the same can be obtained. The DS is more preferably 0.2 or more, still more preferably 0.25 or more, particularly preferably 0.3 or more, most preferably 0.5 or more, more preferably 0.8 or less, still more preferably 0.7. Below, it is particularly preferably 0.6 or less, and most preferably 0.5 or less.

When the modifying group of the chemically modified cellulose is an acyl group, the degree of acyl substitution (DS) is based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton from the reflected infrared absorption spectrum of the esterified cellulose. Can be calculated. The peak of the C = O absorption band based on the acyl group ^{appears at 1730 cm -1,} and the peak of the C—O absorption band based on the cellulose skeleton chain appears at 1030 cm ^-1 (see FIG. 3). The DS of esterified cellulose is the ratio of the peak intensity of the absorption band of C = O based on the acyl group to the peak intensity of the absorption band of the cellulose skeleton chain C—O and the DS obtained from the solid NMR measurement of the esterified cellulose described later. A correlation graph with the modification rate (IR index 1030) defined in is prepared, and the calibration curve substitution degree DS = 4.13 × IR index (1030) calculated from the correlation graph.
Can be obtained by using.

The method for calculating the DS of esterified cellulose by solid NMR is ^{to perform 13} C solid NMR measurement on frozen and pulverized esterified cellulose, and the signal attributed to carbon C1-C6 derived from the pyranose ring of cellulose appearing in the range of 50 ppm to 110 ppm. It can be obtained by the following formula from the area intensity (Inf) of the signal assigned to one carbon atom derived from the modifying group with respect to the total area intensity (Inp) of.
DS = (Inf) x 6 / (Inp)
For example, if the modifying group is an acetyl group, a 23 ppm signal attributed to _{−CH 3 may be used.}
^{The conditions for the 13} C solid-state NMR measurement used are as follows, for example.
Equipment: Bruker Biospin Avance 500WB
Frequency: 125.77MHz
Measurement method: DD / MAS method Waiting time: 75 sec
NMR sample tube: 4 mmφ
Total number of times: 640 times (about 14 hours)
MAS: 14,500Hz
Chemical shift standard: Glycine (external standard: 176.03 ppm)

DS non-uniformity ratio (DSs) defined by the ratio of the degree of modification (DSs) of the fiber surface to the degree of modification (DSt) of the entire fiber of chemically modified cellulose (which is synonymous with the above-mentioned degree of acyl substitution (DS)). / DSt) is preferably 1.05 or more. The larger the value of the DS non-uniformity ratio, the more non-uniform structure like the sheath core structure (that is, the fiber surface layer is highly chemically modified, while the fiber center retains the original unmodified cellulose structure. (Structure) is remarkable, and while having high tensile strength and dimensional stability derived from cellulose, it is possible to improve the affinity with the resin at the time of compounding with the resin and the dimensional stability of the resin composition. be. The DS non-uniformity ratio is more preferably 1.1 or more, 1.2 or more, 1.3 or more, 1.5 or more, or 2.0, from the viewpoint of ease of production of chemically modified cellulose. , Preferably 30 or less, or 20 or less, or 10 or less, or 6 or less, or 4 or less, or 3 or less.
The value of DSs varies depending on the degree of modification of the esterified cellulose, but as an example, it is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.3 or more, still more preferably 0.5 or more. It is preferably 3.0 or less, more preferably 2.5 or less, particularly preferably 2.0 or less, still more preferably 1.5 or less, particularly preferably 1.2 or less, and most preferably 1.0 or less. be. The preferred range of DSt is as described above for acyl substituents (DS).

The smaller the coefficient of variation (CV) of the DS non-uniformity ratio of the chemically modified cellulose is, the smaller the variation in various physical properties of the resin composition is, which is preferable. The coefficient of variation is preferably 50% or less, 40% or less, 30% or less, or 20% or less. The fluctuation coefficient can be further reduced by, for example, a method of defibrating a cellulose raw material and then chemically modifying to obtain chemically modified cellulose (that is, a sequential method), while a method of simultaneously defibrating and chemically modifying a cellulose raw material. (Ie, simultaneous method) can be increased. Although the mechanism of this action has not been clarified, it is understood that the simultaneous method facilitates chemical modification in fine fibers produced in the early stage of defibration, and that the chemical modification reduces hydrogen bonds between cellulose microfibrils. As a result of the further progress of the fibers, it is considered that the fluctuation coefficient of the DS non-uniformity ratio increases.

For the coefficient of variation (CV) of the DS non-uniformity ratio, 100 g of an aqueous dispersion of chemically modified cellulose (solid content of 10% by mass or more) was sampled and frozen and crushed by 10 g, and 10 samples of DSt and DSs were used as measurement samples. After calculating the DS non-uniformity ratio from, it can be calculated by the following formula from the standard deviation (σ) and the arithmetic average (μ) of the DS non-uniformity ratio among the obtained 10 samples.
DS non-uniform ratio = DSs / DSt
Coefficient of variation (%) = standard deviation σ / arithmetic mean μ × 100

The calculation method of DSs is as follows. That is, the esterified cellulose powdered by freeze pulverization is placed on a dish-shaped sample table having a diameter of 2.5 mm, the surface is suppressed and flattened, and measurement is performed by X-ray photoelectron spectroscopy (XPS). The XPS spectrum reflects the constituent elements and chemical bond states of only the surface layer of the sample (typically about several nm). Peak separation was performed on the obtained C1s spectrum, and the peak (289eV, CC bond) attributed to carbon C2-C6 derived from the pyranose ring of cellulose was assigned to one carbon atom derived from the modifying group with respect to the area intensity (Ipp). It can be obtained by the following formula from the area intensity (Ixf) of the peak to be formed.
DSs = (Ixf) x 5 / (Ixp)
For example, when the modifying group is an acetyl group, the C1s spectrum is separated into peaks at 285 eV, 286 eV, 288 eV, and 289 eV, and then a peak of 289 ev is used for Ipp and an OC = O bond of the acetyl group is used for Ixf. A peak (286 eV) may be used.
The conditions for XPS measurement used are as follows, for example.
Equipment used: ULVAC-PHI VersaProbeII
Excitation source: mono. AlKα 15kV x 3.33mA
Analysis size: Approximately 200 μmφ
Photoelectron extraction angle: 45 °
Capture area Now scan: C 1s, O 1s
Pass Energy: 23.5eV

In the resin composition, the amount of the cellulose nanofibers with respect to 100 parts by mass of the polyamide is preferably 1 part by mass or more or 5 parts by mass or more from the viewpoint of satisfactorily obtaining the effect of improving the physical properties of the resin composition by using the cellulose nanofibers. , 10 parts by mass or more, or 15 parts by mass or more, and preferably 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less, or from the viewpoint of satisfactorily dispersing cellulose nanofibers in polyamide. It is 20 parts by mass or less.

[Monovalent metal halide]
In one embodiment, the resin composition comprises a monovalent metal halide. The monovalent metal halide has the ability to satisfactorily lower the melting point of the polyamide in the resin composition. Although not bound by theory, monovalent metal halides can have the effect of changing the crystal structure of the polyamide (eg, changing from the α crystal phase to the γ crystal phase), thus lowering the melting point of the polyamide. It is considered to be excellent in the effect of making it. By containing a monovalent metal halide in the resin composition, the elongation characteristics of the resin composition can be improved. In one embodiment, the monovalent metal halide can also have an effect of suppressing oxidative deterioration of the polyamide, so that the durability of the resin composition can be improved. The monovalent metal halide is also advantageous in that the effect of improving the characteristics of the resin composition by the cellulose nanofibers can be further improved by improving the dispersibility of the cellulose nanofibers in the polyamide. In the resin composition, the amount of the monovalent metal halide with respect to 100 parts by mass of the polyamide is preferably 0.1 part by mass or more, or 1 part by mass or more, or from the viewpoint of obtaining a good effect of lowering the melting point of the polyamide. It is 10 parts by mass or more, or 20 parts by mass or more, and is preferably 50 parts by mass from the viewpoint of maintaining good the excellent properties (tensile strength, bending strength, abrasion resistance, heat resistance, etc.) inherent in polyamide. It is less than a part, 40 parts by mass or less, or 30 parts by mass or less.

Examples of the monovalent metal halide include copper iodide (CuI), sodium iodide (NaI), potassium iodide (KI), sodium chloride (NaCl), potassium chloride (KCl), sodium bromide (NaBr), and bromide. Potassium (KBr) and the like can be exemplified. In one embodiment, the monovalent metal halide is preferably bromide or iodide, particularly preferably potassium iodide.

[Additional ingredients]
In addition to the above-mentioned components (polyamide, cellulose nanofibers, and potassium iodide), the resin composition may further contain additional components such as dispersants, antioxidants, preservatives, and thickeners.

(Dispersant)
The dispersant contributes to improving the dispersibility of the cellulose nanofibers in the resin. The dispersant may be one substance or a mixture of two or more substances. In the latter case, the characteristic values of the present disclosure (eg, melting point, molecular weight, HLB value, SP value) mean the value of the mixture.

The melting point of the dispersant may be 80 ° C. or lower, or 70 ° C. or lower, -100 in that the dispersant can more uniformly coat the periphery of the cellulose and disperse the cellulose more uniformly in the resin. The temperature may be ℃ or higher, or -50 ° C or higher. The number average molecular weight of the dispersant may be 1000 or more, or 2000 or more, and 50,000 or less in that the dispersant can more uniformly coat the periphery of the cellulose and disperse the cellulose more uniformly in the resin. , Or may be 20000 or less. The number average molecular weight of the dispersant is a value obtained in terms of standard polystyrene using gel permeation chromatography.

The dispersant is preferably a water-soluble polymer from the viewpoint of suppressing the aggregation of cellulose. In the present disclosure, "water-soluble" means that 0.1 g or more is dissolved in 100 g of water at 23 ° C. Further, it is more preferable that the dispersant has a hydrophilic segment and a hydrophobic segment (that is, it is an amphipathic molecule) from the viewpoint of more uniformly dispersing cellulose in the resin. Examples of amphipathic molecules include those having a carbon atom as a basic skeleton and having a functional group composed of an element selected from carbon, hydrogen, oxygen, nitrogen, chlorine, sulfur, and phosphorus. If the molecule has the above-mentioned structure, a chemical bond between the inorganic compound and the above-mentioned functional group is also preferable. The hydrophilic segment has a good affinity with the surface of cellulose, and the hydrophobic segment has a characteristic that it suppresses agglutination between celluloses via the hydrophilic segment and is easily compatible with the resin. Therefore, in the dispersant, it is preferable that the hydrophilic segment and the hydrophobic segment are present in the same molecule.

The HLB value of the dispersant is preferably 0.1 or more and less than 8.0. The HLB value is a value indicating the balance between the hydrophobicity and the hydrophilicity of the surfactant, and takes a value from 1 to 20, and the smaller the value, the stronger the hydrophobicity, and the larger the value, the stronger the hydrophilicity. Is shown. In the present disclosure, the HLB value is a value obtained from the following formula by the Griffin method. In the following formula, the "total / molecular weight of the formulas of the hydrophilic groups" is the mass% of the hydrophilic groups.
Formula 1) Griffin method: HLB value = 20 × (sum of formulas of hydrophilic groups / molecular weight)

The lower limit of the HLB value of the dispersant is preferably 0.1, more preferably 0.2, and most preferably 1 from the viewpoint of easy solubility in water. The upper limit of the HLB value is preferably less than 8, more preferably 7.5, and most preferably 7 from the viewpoint of uniform dispersibility of cellulose in the resin.

In a typical embodiment, the hydrophilic segment comprises a hydrophilic structure (eg, one or more hydrophilic groups selected from a hydroxyl group, a carboxy group, a carbonyl group, an amino group, an ammonium group, an amide group, a sulfo group, etc.). This is the part that shows good affinity with cellulose. Hydrophilic segments include polyethylene glycol segments (ie, multiple oxyethylene unit segments) (PEG blocks), segments containing repeating units containing quaternary ammonium salt structures, polyvinyl alcohol segments, polyvinylpyrrolidone segments, poly. Examples thereof include an acrylic acid segment, a carboxyvinyl polymer segment, a cationized guagam segment, a hydroxyethyl cellulose segment, a methyl cellulose segment, a carboxymethyl cellulose segment, and a polyurethane soft segment (specifically, a diol segment). In a preferred embodiment, the hydrophilic segment comprises an oxyethylene unit.

Examples of the hydrophobic segment include a segment having an alkylene oxide unit having 3 or more carbon atoms (for example, a PPG block), a segment containing the following polymer structure, and the like:
Acrylic polymer, styrene resin, vinyl chloride resin, vinylidene chloride resin, polyolefin resin, polyhexamethylene adipamide (6,6 nylon), polyhexamethylene azelamide (6,9 nylon), polyhexamethylene Organic dicarboxylic acids with 4 to 12 carbon atoms and 2 to 13 carbon atoms such as sebacamide (6,10 nylon), polyhexamethylenedodecanoamide (6,12 nylon), polybis (4-aminocyclohexyl) methadodecane, etc. Polycondensate with organic diamine, ω-amino acid (eg, ω-aminoundecanoic acid) polycondensate (eg, polyundecaneamide (11 nylon), etc.), polycapramid, which is a ring-opening polymer of ε-aminocaprolactam (eg, polyundecaneamide (11 nylon), etc.) 6 nylon), polylauric lactam (12 nylon) which is a ring-opening polymer of ε-aminolaurolactum, amino acid lactam containing a ring-opening polymer of lactam, polymer composed of diamine and dicarboxylic acid, polyacetal Nylon-based resin, polycarbonate-based resin, polyester-based resin, polyphenylen sulfide-based resin, polysulfone-based resin, polyether ketone-based resin, polyimide-based resin, fluorine-based resin, hydrophobic silicone-based resin, melamine-based resin, epoxy-based resin, phenol-based resin.

In a preferred embodiment, the dispersant has a PEG block as a hydrophilic group and a PPG block as a hydrophobic group in the molecule.

The dispersant can have a graft copolymer structure and / or a block copolymer structure. These structures may be one kind alone or two or more kinds. In the case of two or more kinds, a polymer alloy may be used. Further, a partially modified product of these copolymers or a terminal modified product (acid modification) may be used.

The structure of the dispersant is not particularly limited, but when the hydrophilic segment is A and the hydrophobic segment is B, the AB type block copolymer, the ABA type block copolymer, the BAB type block copolymer, and the ABAB type Block copolymer, ABABA type block copolymer, BABAB type copolymer, tribranched copolymer containing A and B, tetrabranched copolymer containing A and B, star type copolymer containing A and B Examples thereof include a polymer, a monocyclic copolymer containing A and B, a polycyclic copolymer containing A and B, and a cage-type copolymer containing A and B.

The structure of the dispersant is preferably an AB-type block copolymer, an ABA-type triblock copolymer, a tri-branched copolymer containing A and B, or a quaternary-branched copolymer containing A and B. More preferably, it is an ABA-type triblock copolymer, a tri-branched structure (that is, a tri-branched copolymer containing A and B), or a 4-branched structure (that is, a 4-branched copolymer containing A and B). be. In order to ensure good affinity with cellulose, it is desirable that the structure of the dispersant is the above structure.

Preferable examples of the dispersant include a compound that gives a hydrophilic segment (for example, polyethylene glycol), a compound that gives a hydrophobic segment (for example, polypropylene glycol, poly (tefa tramethylene ether) glycol (PTMEG), polybutadiene diol, and the like. ) Can be used as one or more (for example, a block copolymer of propylene oxide and ethylene oxide, a block copolymer of tetrahydrofuran and ethylene oxide) and the like. The dispersant may be used alone or in combination of two or more. When two or more kinds are used in combination, it may be used as a polymer alloy. Further, a modified polymer described above (for example, modified with at least one compound selected from an unsaturated carboxylic acid, an acid anhydride thereof or a derivative thereof) can also be used.

Among these, from the viewpoint of heat resistance (odor) and mechanical properties, polyethylene glycol and polypropylene glycol copolymers, polyethylene glycol and poly (tetramethylene ether) glycol (PTMEG) copolymers, and mixtures thereof are used. Preferred are mentioned, and a copolymer of polyethylene glycol and polypropylene glycol is more preferable from the viewpoint of handleability and cost.

In a typical embodiment, the dispersant has a cloud point. When the temperature of the aqueous solution of a nonionic surfactant having a polyether chain such as a polyoxyethylene chain as a hydrophilic part is raised, the temperature of a transparent or translucent aqueous solution (this temperature is called a cloud point). ), The phenomenon of cloudiness is seen. That is, when a transparent or translucent aqueous solution is heated at a low temperature, the solubility of the nonionic surfactant drops sharply at a certain temperature, and the surfactants that have been dissolved until then aggregate and become cloudy. And separate from water. It is considered that this is because the nonionic surfactant loses its hydration power at high temperature (the hydrogen bond between the polyether chain and water is broken and the solubility in water drops sharply). The cloud point tends to be lower as the polyether chain is longer. At temperatures below the cloud point, the cloud point is a measure of hydrophilicity in the dispersant, as it dissolves in water at any rate.

The cloud point of the dispersant can be measured by the following method. Using a sound fork type vibration viscous meter (for example, SV-10A manufactured by A & D Co., Ltd.), adjust the aqueous solution of the dispersant to 0.5% by mass, 1.0% by mass, and 5% by mass, and adjust the temperature. Measure in the range of 0 to 100 ° C. At this time, the portion showing the inflection point (the increase in viscosity or the clouding point of the aqueous solution) at each concentration is defined as the cloud point.

The lower limit of the cloud point of the dispersant is preferably 10 ° C., more preferably 20 ° C., and most preferably 30 ° C. from the viewpoint of handleability. The upper limit of the cloud point is not particularly limited, but is preferably 120 ° C, more preferably 110 ° C, still more preferably 100 ° C, and most preferably 60 ° C. In order to ensure good affinity with cellulose, it is desirable that the cloud point of the dispersant is within the above range.

As the dispersant, those having a dissolution parameter (SP value) of 7.25 or more are more preferable. When the dispersant has an SP value in this range, the dispersibility of cellulose in the resin is improved.

The SP value depends on both the aggregation energy density of the substance and the molar molecular weight, according to the Papers literature (RFFodors: Polymer Engineering & SCienCe, vol.12 (10), p.2359-2370 (1974)). However, these are considered to depend on the type and number of substituents of the substance, and according to the literature of Ueda et al. (Paint Study, No. 152, OCt. 2010), the existing existing examples shown in Examples described later are shown. SP values (Cal / Cm ³ ) ^1/2 for major solvents have been published.

The SP value of the dispersant can be experimentally obtained from the boundary between soluble and insoluble when the dispersant is dissolved in various solvents having a known SP value. For example, when 1 mL of the dispersant is dissolved in various solvents (10 mL) having different SP values at room temperature under stirrer stirring for 1 hour, it can be determined whether or not the entire amount is dissolved. For example, when the dispersant is soluble in diethyl ether, the SP value of the dispersant is 7.25 or more.

As the dispersant (particularly amphipathic molecule), one having a boiling point higher than that of water is preferable, and one having a boiling point higher than the melting point of the resin is more preferable from the viewpoint of uniformly dispersing cellulose in the resin during melt kneading. .. The boiling point higher than that of water means a boiling point higher than the boiling point at each pressure in the vapor pressure curve of water (for example, 100 ° C. under 1 atm).

By selecting a dispersant having a boiling point higher than that of water, for example, in the process of evaporating water when a slurry containing water as a liquid medium is dried to obtain a cellulose dry body in the presence of a dispersant. Since the water and the dispersant are replaced and the dispersant is present inside the cellulose, the effect of significantly suppressing the aggregation of the cellulose nanofibers can be achieved.

<Manufacturing method of resin composition>
One aspect of the present invention provides a method for producing a resin composition containing cellulose nanofibers and polyamide. A resin composition can be produced by melt-kneading cellulose nanofibers (which may be in the form of a dispersion liquid, a dried product, or a redispersion liquid obtained by dispersing the dried product in a dispersion medium) with polyamide. As a more specific manufacturing method of the resin composition,
-A method of mixing a resin monomer and cellulose nanofibers, carrying out a polymerization reaction, extruding the obtained resin composition into strands, cooling and solidifying in a water bath, and obtaining a pellet-shaped molded product.
-A method of melt-kneading a mixture of resin and cellulose nanofibers using a single-screw or twin-screw extruder, extruding it into strands, and cooling and solidifying it in a water bath to obtain a pellet-shaped molded product.
-A method of melt-kneading a mixture of resin and cellulose nanofibers using a single-screw or twin-screw extruder, extruding it into a rod or cylinder and cooling it to obtain an extruded body.
-A method of melt-kneading a mixture of resin and cellulose nanofibers using a single-screw or twin-screw extruder to obtain an extruded sheet or film-shaped molded product from a T-die.
And so on. In a preferred embodiment, a mixture of resin and cellulose nanofibers is melt-kneaded using a single-screw or twin-screw extruder, extruded into strands, and cooled and solidified in a water bath to obtain a pellet-shaped molded product.
Specific examples of the method for melt-kneading the resin and the cellulose nanofibers include a method in which the resin and the cellulose nanofibers transported at a desired ratio are mixed and then melt-kneaded.

The minimum processing temperature recommended by the thermoplastic resin supplier is, for example, 255 to 270 ° C. for the polyamide 66 and 225 to 240 ° C. for the polyamide 6. Normally, the set heating temperature is in the range of a temperature about 20 ° C. higher than these recommended minimum processing temperatures. In the resin composition of the present embodiment, the melting point is lower than the melting point of the polyamide alone contained in the resin composition, so that the heating set temperature is higher than the melting point of the polyamide in the resin composition as described above. It may be set in a temperature range as high as about 20 ° C. In one embodiment, the processing temperature may be preferably 195 ° C. to 300 ° C., for example, in polyamide 6, preferably 195 ° C. to 210 ° C., or 210 ° C. to 230 ° C., or 230 ° C. to 260 ° C. For polyamides 6 and 6, the temperature is preferably 250 ° C to 270 ° C, or 270 ° C to 290 ° C, or 290 ° C to 300 ° C.

The resin composition can be provided in various shapes. Specific examples thereof include a resin pellet shape, a sheet shape, a fibrous shape, a plate shape, a rod shape, and the like, but the resin pellet shape is more preferable because of the ease of post-processing and the ease of transportation. Preferred pellet shapes at this time include a round shape, an elliptical shape, a cylindrical shape, and the like, which differ depending on the cutting method at the time of extrusion processing. Pellets cut by a cutting method called underwater cut often have a round shape, and pellets cut by a cutting method called hot cut often have a round or oval shape, which is called a strand cut. Pellets cut by the method are often cylindrical. In the case of a round pellet, the preferable size is 1 mm or more and 3 mm or less as the pellet diameter. Further, in the case of columnar pellets, the preferable diameter is 1 mm or more and 3 mm or less, and the preferable length is 2 mm or more and 10 mm or less. It is desirable that the above diameter and length be at least the lower limit from the viewpoint of operational stability during extrusion, and preferably at least the upper limit from the viewpoint of biting into the molding machine in post-processing.

The resin composition of the present embodiment can be used as various resin molded bodies. The method for manufacturing the resin molded product is not particularly limited, and any manufacturing method may be used, but an injection molding method, an extrusion molding method, a blow molding method, an inflation molding method, a foam molding method, or the like can be used. Of these, the injection molding method is the most preferable from the viewpoint of design and cost. Further, the resin composition may be used by heat-treating a part (for example, several places) thereof to melt it and adhering it to a resin or metal substrate, for example. Further, the resin composition may be a coating film applied to a resin or metal substrate. With these, a laminated body of a resin composition and a substrate can be formed. Further, the sheet-like, film-like or fibrous resin composition may be subjected to secondary processing such as annealing treatment, etching treatment, corona treatment, plasma treatment, grain transfer, cutting and surface polishing.

Although the resin composition of the present embodiment can be suitably applied to various uses, it is particularly suitable for applications such as high-pressure gas tanks in that it is excellent in elongation characteristics while using polyamide.

The present invention will be further described based on examples, but the present invention is not limited to these examples.

≪Material used≫
[polyamide]
Polyamide 6: UBE NYLON 1013B (melting point: 215-225 ° C.)

[Cellulose Nanofiber (CNF-A)]
1 part by mass of cotton linter pulp was stirred at 500 rpm for 1 hour at room temperature in 30 parts by mass of dimethyl sulfoxide (DMSO) using a uniaxial stirrer (DKV-1 φ125 mm dissolver manufactured by IMEX). Subsequently, the slurry was fed to a bead mill (NVM-1.5 manufactured by IMEX) with a hose pump and circulated for 180 minutes using only DMSO to form a fine cellulose fiber slurry having a solid content of 3.2% by mass of slurry S1 (DMSO solvent). ) Was obtained.

During the circulation operation, the rotation speed of the bead mill was 2500 rpm and the peripheral speed was 12 m / s, and the beads used were made of zirconia, φ2.0 mm, and a filling rate of 70% (the slit gap of the bead mill was 0.6 mm). Further, during the circulation operation, the slurry temperature was controlled to 40 ° C. by a chiller in order to absorb heat generated by friction.

After the slurry S1 is put into an explosion-proof disperser tank, 3.2 parts by mass of vinyl acetate and 0.49 parts by mass of sodium hydrogen carbonate are added, the temperature in the tank is set to 50 ° C., stirring is performed for 120 minutes, and the solid content ratio is 2. A 9.9% by mass slurry (DMSO solvent) was obtained.

In order to stop the reaction, 30 parts by mass of pure water was added, the mixture was sufficiently stirred, and then the mixture was placed in a dehydrator for concentration. By repeating the washing operation of dispersing, stirring, and concentrating the obtained wet cake in 30 parts by mass of pure water again a total of 5 times, unreacted reagents, solvents, etc. are removed, and acetylation with a solid content of 10% by mass is performed. 10 parts by mass of a fine cellulose fiber cake (water solvent) was obtained. When a porous sheet was prepared from this cake and the degree of acyl substitution (DS) was determined, DS = 1.0.

≪Preparation of resin composition≫
[Example 1]
Potassium iodide was added to 10 g (solid content 1 g) of a 10 mass% cellulose nanofiber slurry and stirred, and then dried and powdered under the following conditions to obtain a CNF / KI powder. 2 g of the obtained powder and 10 g of the polyamide 6 were put into a tabletop small kneader and melt-kneaded for 5 minutes to obtain a resin composition.

(Conditions for drying and powdering)
The material was put into a drying apparatus and dried under the following conditions. The moisture content was measured using an infrared heating moisture meter (MX-50 (manufactured by A & D)), and the time when the moisture content became 7% by mass or less (solid content mass 93% or more) was dried. It was the end point. The conditions are as follows.
Equipment: Lai Gemixer manufactured by Chuo Kiko Co., Ltd. (Model number: VT-20)
Conditions: At a jacket temperature of 100 ° C., the pressure was reduced to −90 kPa with a vacuum pump while stirring with an agitator (peripheral speed 16 m / s) and a chopper (3000 rpm). Decompression drying was carried out until the product temperature reached 50 ° C. The drying time was 160 minutes. As the drying temperature, the surface temperature of the jacket was measured at three points and used as the average value.

[Example 2]
A resin composition was obtained in the same manner as in Example 1 except that potassium iodide of Example 1 was used as sodium iodide.

[Example 3]
A resin composition was obtained in the same manner as in Example 1 except that potassium iodide of Example 1 was used as potassium chloride.

[Example 4]
A resin composition was obtained in the same manner as in Example 1 except that potassium iodide of Example 1 was used as sodium chloride.

[Example 5]
A resin composition was obtained in the same manner as in Example 1 except that potassium iodide of Example 1 was used as potassium bromide.

[Example 6]
A resin composition was obtained in the same manner as in Example 1 except that potassium iodide of Example 1 was used as sodium bromide.

[Comparative Example 1]
The pellets of polyamide 6 as a raw material were put into a small tabletop kneader and melt-kneaded for 5 minutes.

[Comparative Example 2]
A resin composition was obtained in the same manner as in Example 1 except that potassium iodide was not used.

≪Evaluation≫
<Cellulose nanofibers>
[Preparation of porous sheet]
First, the wet cake was added to tert-butanol, and further dispersed with a mixer or the like until there were no aggregates. The concentration was adjusted to 0.5% by mass with respect to the cellulose solid content weight of 0.5 g. 100 g of the obtained tert-butanol dispersion was filtered on a filter paper and dried at 150 ° C., and then the filter paper was peeled off to obtain a sheet. A porous sheet having an air permeation resistance of 100 sec / 100 ml or less per ^{10 g / m 2 of the sheet was used as a measurement sample.
After measuring the basis weight W (g / m 2} ) of the sample left to stand in an environment of 23 ° C. and 50% RH for 1 day, a Wangken type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01) was used. The air permeability resistance R (sec / 100 ml) was measured. ^{At this time, the value per 10 g / m 2} basis weight was calculated according to the following formula.
Air permeability resistance per 10 g / m ² basis weight (sec / 100 ml) = R / W × 10

[Acyl Substitution Degree (DS)]
The infrared spectroscopic spectra of the porous sheet at five locations by the ATR-IR method were measured with a Fourier transform infrared spectrophotometer (FT / IR-6200 manufactured by JASCO). The infrared spectroscopic spectrum measurement was performed under the following conditions.
Accumulation number: 64 times,
Wavenumber resolution: 4 cm ^-1 ,
Wavenumber range: 4000-600cm ^-1 ,
ATR crystal: diamond,
Incident angle: 45 °
From the obtained IR spectrum, the IR index was calculated by the following equation (1):
IR index = H1730 / H1030 ... (1)
Calculated according to. In the formula, H1730 and H1030 are the absorbances at 1730 cm ^-1 and 1030 cm ^-1 (absorption band of cellulose skeleton chain CO stretching vibration). However, each of the line connecting the lines and 800 cm ^-1 and 1500 cm ^-1 connecting 1900 cm ^-1 and 1500 cm ^-1 as a baseline, means absorbance when the baseline was zero absorbance.
Then, the average degree of substitution at each measurement location was calculated from the IR index according to the following equation (2), and the average value was taken as DS.
DS = 4.13 x IR index ... (2)

<Polyamide and resin composition>
[Melting point]
For the polyamide 6 and the resin composition, a differential scanning calorimeter (DSC8000 manufactured by PerkinElmer) was used for measuring the melting point. The shredded sample was weighed in a special aluminum pan to a size of about 5 mg, and the sample sealed with a special jig was used for measurement. The measurement conditions are described below. Measurement temperature range: -20 ° C to 280 ° C, temperature rise / fall rate: 20 ° C / min. The measurement program was carried out in three steps of temperature rise → temperature decrease → temperature rise, and the peak top of the peak (the peak on the highest temperature side) that appeared at the time of the second temperature rise was set as the melting point. The melting point (the above-mentioned measuring method) of the polyamide 6 used in Examples 1 to 6 and Comparative Example 2 with the resin alone was 218.4 ° C.

[Tensile breaking strength, tensile elastic modulus]
From the obtained pellets, a multipurpose test piece conforming to ISO294-3 was molded using an injection molding machine.
Polyamide-based material: Conditions conforming to JIS K6920-2 Tensile breaking strength and tensile elastic modulus were measured for a multipurpose test piece in accordance with ISO527. Since the polyamide resin changes due to moisture absorption, it was stored in an aluminum moisture-proof bag immediately after molding to suppress moisture absorption.

[Ease of kneading]
Table 1 shows "ease of kneading". When a mixture containing cellulose nanofibers and polyamide is melt-kneaded, the kneading is performed near the melting point of the polyamide, so that a carbonization phenomenon due to thermal decomposition of the cellulose nanofibers may occur. If the melting point of the polyamide is lowered, the kneading temperature can also be lowered, and the cellulose nanofibers can be melt-kneaded without being thermally decomposed. Further, for example, when the melting point of the polyamide in the resin composition is lowered by 20 ° C. as compared with the case where the polyamide alone is used, the torque at the time of kneading can be reduced by lowering the kneading temperature by 10 ° C., and kneading is easy. become.

The resin composition provided by the present invention, which has excellent elongation characteristics and has little thermal deterioration, can be suitably applied to various resin molded body applications.

Claims (16)

A resin composition containing polyamide and cellulose nanofibers.
A resin composition in which the polyamide in the resin composition has a melting point that is 5 ° C. to 20 ° C. lower than the melting point of the polyamide alone. The resin composition according to claim 1, which comprises a monovalent metal halide. The resin composition according to claim 2, wherein the monovalent metal halide is bromide or iodide. The resin composition according to claim 3, which comprises 100 parts by mass of the polyamide, 1 to 40 parts by mass of the cellulose nanofibers, and 0.1 to 50 parts by mass of the potassium iodide. The resin composition according to any one of claims 1 to 4, wherein the polyamide is at least one selected from the group consisting of polyamide 6, polyamide 66 and polyamide 6I. The resin composition according to any one of claims 1 to 5, wherein the cellulose nanofibers have an average fiber diameter of 2 nm to 1000 nm. The resin composition according to any one of claims 1 to 6, wherein the fiber length (L) / fiber diameter (D) ratio of the cellulose is 30 to 5000. The resin composition according to any one of claims 1 to 7, wherein the cellulose has a weight average molecular weight (Mw) of 100,000 or more and a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 6 or less. The resin composition according to any one of claims 1 to 8, wherein the degree of crystallinity of the cellulose is 60% or more. The resin composition according to any one of claims 1 to 9, wherein the content of the alkali-soluble polysaccharide of the cellulose is 12% by mass or less. The resin composition according to any one of claims 1 to 10, wherein the average content of the acid-insoluble component of the cellulose is 10% by mass or less. The resin composition according to any one of claims 1 to 11, wherein the cellulose is chemically modified. The resin composition according to claim 12, wherein the chemical modification is esterification. The resin composition according to claim 13, wherein the esterification is acetylation. The resin composition according to any one of claims 12 to 14, wherein the average degree of substitution (DS) of the cellulose is 0.3 to 1.2. The method for producing a resin composition according to any one of claims 1 to 15.
A method comprising mixing a polyamide, cellulose nanofibers, and a monovalent metal halide.

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