Cellulosic fiber for polyamide resin reinforcement

Abstract

To provide a cellulosic fiber for polyamide resin reinforcement which can reduce a resin pressure in production.SOLUTION: There are provided a cellulosic fiber for polyamide resin reinforcement which contains isophoronediamine; a polyamide resin composition which contains the fiber and an aliphatic polyamide resin; and a molding which contains the polyamide resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cellulosic fiber for reinforcing polyamide resin. [Background technology]

[0002] Fiber-reinforced resin compositions have the advantage of being lightweight, and are therefore used in place of metal materials in fields such as automobile parts, aircraft interior parts, household appliances, construction materials, etc. Furthermore, from the viewpoint of reducing the weight of structures formed from fiber-reinforced resin compositions, resin compositions reinforced with natural fibers having a low specific gravity have been proposed as fibers for reinforcing the resin composition.

[0003] Patent Document 1 discloses a polyamide resin composition containing polyamide 6, cellulosic fibers, and a compatibilizer having one or more amino groups or acid anhydride groups, wherein the melting point of the compatibilizer is 40°C to 260°C. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-84999 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the findings of the present inventors, the polyamide resin composition disclosed in Patent Document 1 has room for improvement in terms of reducing the resin pressure during the production of the composition.

[0006] Therefore, an object of the present invention is to provide a cellulosic fiber for reinforcing a polyamide resin, which can reduce the resin pressure during production. [Means for solving the problem]

[0007] The present inventors have found that when cellulosic fibers containing isophoronediamine are used, the resin pressure during production of a polyamide resin composition can be reduced.

[0008] The present invention relates to the following [1] to [6]. [1] Cellulosic fibers containing isophorone diamine for reinforcing polyamide resins. [2] The cellulose fiber for reinforcing a polyamide resin according to [1], wherein the cellulose fiber is an acetylated cellulose fiber. [3] A polyamide resin composition comprising the cellulose fiber for reinforcing polyamide resins according to [1] or [2] and an aliphatic polyamide resin. [4] The polyamide resin composition according to [3], wherein the aliphatic polyamide resin is polyamide 6. [5] A molded article comprising the polyamide resin composition according to [3] or [4]. [6] A method for producing a polyamide resin composition, comprising: (1A) a step of contacting cellulosic fibers with isophorone diamine to obtain cellulosic fibers containing isophorone diamine at least in their crystals; (1B) a step of melt-kneading the cellulose-based fibers obtained in step (1A) with an aliphatic polyamide resin to obtain a polyamide resin composition; A method for producing a polyamide resin composition, comprising: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a cellulosic fiber for reinforcing a polyamide resin, which can reduce the resin pressure during production. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Cellulosic fiber for reinforcing polyamide resin] The cellulose-based fiber for reinforcing polyamide resin contains isophorone diamine. Specifically, the cellulose-based fiber for reinforcing polyamide resin contains cellulose fiber and isophorone diamine. The cellulose-based fiber for reinforcing polyamide resin is a fiber component used to reinforce polyamide resin.

[0011] The cellulose-based fiber for reinforcing polyamide resin can reduce the resin pressure during the production of a polyamide resin composition containing the fiber, and in addition, the molded article containing the polyamide resin composition containing the fiber may have excellent mechanical properties (e.g., tensile strength, flexural modulus, and flexural strength).

[0012] [Cellulosic fibers] Cellulosic fibers are fibers made of at least one polymer (hereinafter also referred to as "cellulosic polymer") selected from the group consisting of cellulose, holocellulose, and lignocellulose. Lignocellulose refers to a substance in which lignin and cellulose are bonded together, and / or a mixture of lignin and cellulose, present in plants regardless of the amount of lignin content.

[0013] Cellulosic fibers include unmodified cellulosic fibers and acetylated cellulosic fibers. Unmodified cellulosic fibers are fibers in which the hydroxyl groups of the polysaccharides and lignin in the cellulosic polymers that make up the cellulosic fibers are not modified. Acetylated cellulosic fibers are fibers in which at least some of the hydroxyl groups of the polysaccharides and lignin in the cellulosic polymers that make up the unmodified cellulosic fibers are acetylated.

[0014] "Acetylated" means that at least some of the hydroxyl groups of the polysaccharides and lignin in the cellulose polymers that make up the acetylated cellulose fiber have been modified with acetyl groups (i.e., the hydrogen atoms of the hydroxyl groups have been replaced with acetyl groups (CH3C(=O)-)).

[0015] In acetylated cellulose-based fibers, the degree of acetyl substitution (also referred to as "DS") of hydroxyl groups in the polysaccharides and lignin constituting cellulose, holocellulose, and / or lignocellulose is not particularly limited and can be appropriately set depending on the desired properties. Here, the degree of acetyl substitution refers to the degree to which hydroxyl groups present in the polysaccharide and lignin units (repeating units) constituting cellulose, holocellulose, and / or lignocellulose in the acetylated cellulose-based fibers are modified with acetyl groups.

[0016] When the cellulosic polymer is cellulose, the repeating unit is a glucopyranose residue, and the number of hydroxyl groups per unit is 3. Therefore, when the cellulosic polymer constituting the acetylated cellulosic fiber is composed of only cellulose, the upper limit of the degree of acetyl group substitution is 3.

[0017] Lignocellulose also includes cellulose, hemicellulose, and lignin. When the cellulosic polymer is hemicellulose, the repeating unit is a xylose residue in xylan or a galactose residue in arabinogalactan, and the number of hydroxyl groups per unit is two. In addition, the repeating unit in standard lignin is a standard lignin residue, and the number of hydroxyl groups per unit is two. Therefore, when the cellulose polymer that constitutes the acetylated cellulose fiber is lignocellulose, the upper limit of the degree of acetyl group substitution is less than 3, and is usually 2.7 to 2.8, depending on the contents of hemicellulose and lignin contained in the lignocellulose.

[0018] Holocellulose also includes cellulose and hemicellulose. The number of hydroxyl groups per repeating unit of cellulose and hemicellulose is 3 and 2, respectively. Therefore, when the cellulose polymer constituting the acetylated cellulose fiber is holocellulose, the upper limit of the degree of acetyl group substitution is less than 3.

[0019] In the acetylated cellulose fiber, the degree of acetyl substitution is preferably 0.4 to 2.55. When the degree of acetyl substitution is 0.4 to 2.55, the acetylated cellulose fiber can have excellent dispersibility in polyamide resins. The degree of acetyl substitution is more preferably 0.56 to 2.52, and particularly preferably 0.60 to 0.90.

[0020] The degree of acetyl substitution (DS) was measured by elemental analysis, neutralization titration, FT-IR, and two-dimensional NMR ( 1 H and 13 The degree of acetyl group substitution can be adjusted by adjusting the amount of acetylating agent (i.e., acetic anhydride or acid chloride, etc.) used in the acetylation, the reaction temperature, the reaction time, etc.

[0021] (raw material for cellulosic fibers) The raw material for the unmodified cellulose fibers includes an unmodified cellulose fiber-containing material, which is preferably cellulose pulp (an aggregate of unmodified cellulose fibers).

[0022] Cellulosic pulp refers to a fiber aggregate composed of cellulose polymers separated from plant materials. Examples of plants include wood, bamboo, hemp, jute, kenaf, cotton, beet, agricultural waste, etc. Examples of wood include wood derived from conifers or broad-leaved trees such as Sitka spruce, pine (such as Abies sachalinensis and red pine), cedar, cypress, eucalyptus, and acacia.

[0023] Cellulosic pulp includes pulp that does not contain lignin (such as pulp made of cellulose or pulp made of holocellulose) and pulp that contains lignin (lignopulp). Here, lignopulp includes pulp that contains only trace amounts of lignin, as long as lignin is detectable. The amount of lignin in lignopulp can be quantified by the Klason method. The lignin content in lignopulp is not particularly limited, but is preferably 0.1 to 40% by mass, more preferably 0.1 to 35% by mass, and particularly preferably 0.1 to 30% by mass.

[0024] The cellulosic pulp is preferably pulp obtained from wood (wood pulp), and is preferably lignopulp.

[0025] Cellulosic pulp can be obtained by treating the above-mentioned plant-derived raw materials by mechanical pulping, chemical pulping, or a combination of mechanical and chemical pulping. Pulps obtained in this manner include kraft pulp (KP) and mechanical pulp (MP). Kraft pulp (KP) includes unbleached softwood kraft pulp (NUKP), oxygen-bleached softwood kraft pulp (NOKP), and bleached softwood kraft pulp (NBKP). Mechanical pulp (MP) includes groundwood pulp (GP), refined pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and the like.

[0026] Acetylated cellulose-based fibers can be obtained by acetylating an unmodified cellulose-based fiber-containing material. Acetylation can be performed using known methods for acetylating hydroxyl groups in cellulose-based polymers. For example, an acetylation reaction in which hydrogen atoms of hydroxyl groups in a cellulose-based polymer are converted into acetyl groups can be performed by suspending the unmodified cellulose-based fiber-containing material in an anhydrous aprotic polar solvent capable of swelling the unmodified cellulose-based fiber-containing material, and reacting the unmodified cellulose-based fiber-containing material with an acetylating agent in the presence of a base. Examples of the acetylating agent include acetic anhydride and acid chloride. Examples of aprotic polar solvents include N-methylpyrrolidone and N,N-dimethylformamide. Examples of bases include pyridine, N,N-dimethylaniline, sodium carbonate, sodium bicarbonate, and potassium carbonate. The acylation reaction is preferably performed, for example, at room temperature (e.g., 25°C) to 100°C while stirring the raw material components.

[0027] The degree of acetyl group substitution of the acetylated cellulose fiber can be adjusted by adjusting the amount of acetylating agent, reaction temperature, reaction time, etc.

[0028] (Average fiber diameter of cellulosic fibers) The average fiber diameter of the cellulose-based fibers is not particularly limited, but is preferably 10 to 500 μm. With such an average fiber diameter, the compatibility with isophorone diamine is enhanced, and isophorone diamine is more likely to be present between the crystals of the cellulose-based fibers. Furthermore, with such an average fiber diameter, defibration (microfibrillation) can be efficiently performed when kneaded with a polyamide resin.

[0029] (Preferred embodiment of cellulosic fiber) From the viewpoint of uniform dispersion, the cellulose-based fibers are preferably acetylated cellulose-based fibers. The cellulosic fibers may be one type or a combination of two or more types.

[0030] [Isophoronediamine] Isophorone diamine has a melting point of 10°C. Isophorone diamine can function as a swelling agent for cellulosic fibers. Furthermore, when a significant amount of isophorone diamine is incorporated into the crystals of the cellulosic fibers, the crystal lattice spacing of the cellulosic fibers increases (this may be the basis for the increase in crystal lattice spacing in the Examples). This reduces the cohesive strength of the cellulosic fibers, and substitution of isophorone diamine with polyamide resin occurs, resulting in the incorporation of polyamide resin into the cellulosic fibers and the promotion of compounding of the cellulosic fibers and polyamide resin. As a result, the cellulosic fibers are more uniformly dispersed in the polyamide resin. Therefore, it is believed that the resin pressure can be reduced when producing a composition containing cellulosic fibers for reinforcing polyamide resin and an aliphatic polyamide resin. Isophorone diamine may be produced by a known method, or a commercially available product may be used.

[0031] [Crystal lattice spacing] In the cellulose-based fiber for reinforcing polyamide resins, the crystal lattice spacing of the cellulose-based fiber is preferably greater than 14.6 Å, and particularly preferably greater than 14.6 Å but not greater than a range in which the crystalline state of the cellulose-based fiber is not disrupted. This is because disruption of the crystalline state prevents the cellulose-based fiber from exhibiting its functions and properties. When the crystal lattice spacing of the cellulose-based fiber is within the above range, the cohesive force of the cellulose-based fiber tends to be further suppressed. This tends to further reduce the resin pressure during the production of a polyamide resin composition. The crystal lattice spacing of the cellulose-based fiber can be adjusted by increasing or decreasing the content of isophoronediamine. The crystal lattice spacing of the cellulose-based fiber can also be measured using X-ray diffraction, an electron microscope, or the like (see, for example, Sen to Kogyo, Vol. 62, No. 7 (2006), pp. 183-187).

[0032] [Content of each ingredient] The content of each component in the cellulose-based fiber for reinforcing polyamide resin is not particularly limited as long as it is sufficient to impregnate the cellulose-based fiber with isophoronediamine, but the following contents are preferred.

[0033] In the cellulose-based fiber for reinforcing a polyamide resin, the content of isophorone diamine is preferably 50 to 300 parts by mass, particularly preferably 100 to 250 parts by mass, per 100 parts by mass of the cellulose-based fiber (i.e., the cellulose-based fiber not containing isophorone diamine).

[0034] [Polyamide resin composition] The polyamide resin composition contains the above-described cellulose-based fiber for reinforcing polyamide resin and an aliphatic polyamide resin. Because the polyamide resin composition contains the above-described cellulose-based fiber for reinforcing polyamide resin, the mechanical properties of the polyamide resin composition are improved compared to a case where the polyamide resin composition contains only an aliphatic polyamide resin.

[0035] [Aliphatic polyamide resin] Aliphatic polyamide resins are polyamide resins that do not have an aromatic ring, and include aliphatic homopolyamide resins and aliphatic copolymer polyamide resins.

[0036] (Aliphatic homopolyamide resin) Aliphatic homopolyamide resin refers to a polyamide resin that contains one type of monomer component. Examples of the monomer component that constitutes the aliphatic polyamide resin include a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, or an aminocarboxylic acid. When the monomer component that constitutes the aliphatic polyamide resin is a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, the combination of one type of aliphatic diamine and one type of aliphatic dicarboxylic acid is considered to be one type of monomer component.

[0037] The aliphatic diamine preferably has 2 to 20 carbon atoms, and more preferably 4 to 12. The aliphatic dicarboxylic acid preferably has 2 to 20 carbon atoms, and more preferably 6 to 12. The lactam preferably has 5 to 12 carbon atoms. The aminocarboxylic acid preferably has 5 to 12 carbon atoms.

[0038] Examples of aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, and eicosanediamine. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedionic acid, dodecanedionic acid, tridecanedionic acid, tetradecanedionic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedionic acid.

[0039] Examples of the combination of an aliphatic diamine and an aliphatic dicarboxylic acid include a combination of hexamethylenediamine and adipic acid, a combination of hexamethylenediamine and sebacic acid, and a combination of hexamethylenediamine and dodecanedioic acid. The combination of an aliphatic diamine and an aliphatic dicarboxylic acid is preferably an equimolar salt of the combination.

[0040] Examples of lactams include γ-butyrolactam, δ-valerolactam, ε-caprolactam, enantholactam, undecanelactam, and dodecanelactam. Examples of aminocarboxylic acids include 5-aminopentanoic acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. From the viewpoint of productivity, the lactam is preferably ε-caprolactam, undecanelactam, or dodecanelactam.

[0041] Specific examples of aliphatic homopolyamide resins include polybutyrolactam (polyamide 4), polyvalerolactam (polyamide 5), polycaprolactam (polyamide 6), polyenantholactam (polyamide 7), polyundecane lactam (polyamide 11), polylauryllactam (polyamide 12), polytetramethylene adipamide (polyamide 46), polytetramethylene azelamide (polyamide 49), and polytetramethyl ethylene diamethylene terephthalate (polyamide 48). Methylene sebacamide (Polyamide 410), Polytetramethylene dodecamide (Polyamide 412), Polypentamethylene adipamide (Polyamide 56), Polypentamethylene azelamide (Polyamide 59), Polypentamethylene sebacamide (Polyamide 510), Polypentamethylene dodecamide (Polyamide 512), Polyhexamethylene adipamide (Polyamide 66), Polyhexamethylene azelamide (Polyamide 69) ), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polynonameethylene adipamide (polyamide 96), polynonameethylene azelamide (polyamide 99), polynonameethylene sebacamide (polyamide 910), polynonameethylene dodecamide (polyamide 912), polydecamethylene adipamide (polyamide 106), polydecamethylene azelamide (polyamide Polyamide 109), polydodecamethylene decamide (polyamide 1010), polydodecamethylene dodecamide (polyamide 1012), polydodecamethylene adipamide (polyamide 126), polydodecamethylene azelamide (polyamide 129), polydodecamethylene sebacamide (polyamide 1210), polydodecamethylene dodecamide (polyamide 1212), polydodecamethylene oxamide (polyamide 122), and the like.

[0042] (Aliphatic copolyamide resin) Aliphatic copolyamide resins are aliphatic polyamide resins that contain two or more types of monomer components and do not have an aromatic ring. Examples of aliphatic copolyamide resins include a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, and an aliphatic copolyamide resin that is a copolymer of two or more types of monomers selected from the group consisting of lactams and aminocarboxylic acids.

[0043] Specific examples of aliphatic copolymer polyamide resins include caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 66), caprolactam / hexamethylenediaminoazelaic acid copolymer (polyamide 6 / 69), caprolactam / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 610), caprolactam / hexamethylenediaminoundecanoic acid copolymer (polyamide 6 / 611), caprolactam / hexamethylenediaminododecanoic acid copolymer (polyamide 6 / 612), and caprolactam / aminoundecanoic acid copolymer (polyamide 6 / 11). , caprolactam / lauryllactam copolymer (polyamide 6 / 12), caprolactam / hexamethylenediaminoadipic acid / lauryllactam copolymer (polyamide 6 / 66 / 12), caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 66 / 610), caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 66 / 612), hexamethylenediaminoadipic acid / caprolactam copolymer (polyamide 66 / 6), etc.

[0044] From the viewpoint of moldability, the aliphatic polyamide resin is preferably polyamide 6.

[0045] (relative viscosity) From the viewpoint of mechanical properties, the relative viscosity of the aliphatic polyamide resin is preferably 2.00 or more, more preferably 2.00 to 2.50, and particularly preferably 2.20 to 2.50. The relative viscosity of the aliphatic polyamide resin can be measured in accordance with JIS K-6920 under conditions of a polyamide concentration of 1% by weight in 96% by weight sulfuric acid at a temperature of 25°C.

[0046] (carboxyl end group concentration) From the viewpoint of mechanical properties, the carboxyl end group concentration of the aliphatic polyamide resin is 2.0 × 5.0 -5 eq / g or more, preferably 2.0 x 10-5 ~4.0×10 -5 eq / g is more preferable, and 2.0×10 -5 ~3.0×10 -5 eq / g is particularly preferred. The carboxyl end group concentration of the aliphatic polyamide resin can be measured by dissolving the aliphatic polyamide resin in benzyl alcohol and titrating with a 0.05N sodium hydroxide solution. The carboxyl end group concentration of the aliphatic polyamide resin can be adjusted by adding a dicarboxylic acid or a diamine during the production of the aliphatic polyamide resin.

[0047] [Other ingredients] The polyamide resin composition may contain other components within the range that does not impair the effects of the present invention, such as compatibilizers, surfactants, polysaccharides (starch, alginic acid, etc.), natural proteins (gelatin, glue, casein, etc.), inorganic compounds (tannin, zeolite, ceramics, metals, etc.), colorants, plasticizers, fragrances, pigments, flow adjusters, leveling agents, conductive agents, antistatic agents, UV absorbers, UV dispersants, and deodorizers.

[0048] [Content of each ingredient] The content of each component relative to the total 100% by mass of the polyamide resin composition is not particularly limited as long as it is a content sufficient to disperse the cellulose-based fiber for reinforcing the polyamide resin in the polyamide resin composition, but the following contents are preferred.

[0049] The content of the aliphatic polyamide resin relative to the total 100% by mass of the polyamide resin composition is preferably 20% by mass to 99% by mass, more preferably 40% by mass to 95% by mass, and particularly preferably 40% by mass to 60% by mass.

[0050] The content of the cellulose fiber for reinforcing the polyamide resin relative to the total 100% by mass of the polyamide resin composition is preferably 1% by mass to 80% by mass, more preferably 5% by mass to 60% by mass, and particularly preferably 10% by mass to 30% by mass.

[0051] The total content of the cellulose fiber for reinforcing polyamide resin and the aliphatic polyamide resin is preferably 60% to 100% by mass relative to 100% by mass of the total polyamide resin composition, with the remainder being the content of other components.

[0052] [Method of producing polyamide resin composition] The method for producing the polyamide resin composition is not particularly limited as long as it is a method that can produce a desired polyamide resin composition. The method for producing the polyamide resin composition includes the following steps: (1A) a step of contacting cellulosic fibers with isophorone diamine to obtain cellulosic fibers containing isophorone diamine at least in their crystals; (1B) a step of melt-kneading the cellulose-based fibers obtained in step (1A) with an aliphatic polyamide resin to obtain a polyamide resin composition; It is preferred that the compound contains:

[0053] [Process (1A)] In step (1A), the method for contacting the cellulosic fibers with isophorone diamine is not particularly limited, and examples thereof include a method in which the cellulosic fibers are impregnated with isophorone diamine.

[0054] The contact temperature between the cellulosic fibers and isophorone diamine is preferably equal to or higher than the melting point of isophorone diamine (10°C), and is preferably around room temperature (25°C) (for example, 10°C to 40°C).

[0055] Step (1A) produces cellulose fibers containing isophorone diamine at least in their crystals. The cellulose fibers produced by step (1A) may contain isophorone diamine on the surface of the cellulose fibers, as long as the cellulose fibers contain isophorone diamine at least in their crystals. The cellulose fibers produced by step (1A) are as described above, including preferred embodiments.

[0056] [Process (1B)] The melt-kneading temperature in step (1B) can be appropriately set depending on the type of aliphatic polyamide resin, but is preferably 225 to 240° C. When the temperature during melt-kneading is within the above range, the aliphatic polyamide resin and the cellulosic fibers can be uniformly mixed.

[0057] In step (1B), shear stress during kneading promotes defibration (microfibrillation) of the cellulosic fibers. Furthermore, step (1B) suppresses aggregation of the defibrated cellulosic fibers, thereby producing a polyamide resin composition in which the cellulosic fibers (B) are well dispersed in the aliphatic polyamide resin.

[0058] The polyamide resin composition obtained by the production method including steps (1A) and (1B) may be obtained as a masterbatch. The desired polyamide resin composition can be obtained by a step of melt-kneading the thus obtained masterbatch with an additional aliphatic polyamide resin so as to dilute it (dilution-kneading step).

[0059] In this case, the method for producing the polyamide resin composition comprises the following steps: (2A) contacting cellulosic fibers with isophorone diamine to obtain cellulosic fibers containing isophorone diamine in their crystals; (2B) a step of melt-kneading the cellulose-based fiber obtained in step (2A) with an aliphatic polyamide resin to obtain a masterbatch (masterbatch kneading step); (2C) A step of melt-kneading the masterbatch with an additional aliphatic polyamide resin to obtain a polyamide resin composition (dilution and kneading step).

[0060] Here, the steps (2A) and (2B) are the same as those described above for the steps (1A) and (1B), and the conditions for dilution kneading in the step (2C) are the same as those described above for the step (1B).

[0061] [Usage amount] The amounts of the cellulose-based fibers and isophorone diamine used in step (1A), and the amounts of the cellulose-based fibers and aliphatic polyamide resin obtained in step (1A) used in step (1B) may be amounts that correspond to the contents of each component in the polyamide resin composition.

[0062] When a masterbatch is obtained, the amounts of the components used in steps (2A) and (2B) are the same as those in steps (1A) and (1B). The amount of the aliphatic polyamide resin used in step (2C) is preferably 50 to 150 parts by mass, particularly preferably 75 to 125 parts by mass, per 100 parts by mass of the masterbatch obtained in step (2B).

[0063] (Polyamide resin composition obtained by the production method) A polyamide resin composition can be obtained by the above-described production method.

[0064] [Uses of polyamide resin composition] The polyamide resin composition can be used to form a molded article, which may be in the form of a film, sheet, plate, pellet, rod, powder, hollow, or the like.

[0065] A molded article using the polyamide resin composition (a molded article containing the polyamide resin composition) can be produced by molding the polyamide resin composition using any of various known molding methods such as mold molding, injection molding, extrusion molding, blow molding, and foam molding.

[0066] Molded articles made using polyamide resin compositions are lighter in weight and have superior strength characteristics compared to molded articles made using polyamide resin compositions containing only inorganic fibers such as glass fibers or carbon fibers.

[0067] The molded article can be used for interior, exterior, and structural materials for transport vehicles such as automobiles, trains, ships, and airplanes; housings, structural materials, and internal parts for electrical appliances such as personal computers, televisions, and telephones; building materials; and the like. [Example]

[0068] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0069] <Evaluation> 1) Crystal lattice spacing of cellulose fibers (unit: Å): The crystal lattice spacing of cellulose fibers was measured by X-ray diffraction. 2) Relative viscosity of polyamide resin: In accordance with JIS K-6920, 1 g of aliphatic polyamide resin was dissolved in 100 ml of 96% concentrated sulfuric acid, and the relative viscosity was measured at 25°C. 3) Carboxy end group concentration: The aliphatic polyamide resin was dissolved in benzyl alcohol and titrated with 0.05N (normal) sodium hydroxide solution to measure the carboxy end group concentration. 4) Tensile strength: Testing was performed in accordance with the test method described in ISO 527-1, 2 at room temperature (25°C) at a tensile speed of 5 mm / min. The average value was calculated for 10 test pieces (n=10). In addition, the tensile strength of Comparative Example 1, which did not contain a swelling agent, was set at 100.0%, and the value was calculated and reported in the table as the percentage of the tensile strength of each example (tensile strength improvement rate). A tensile strength improvement rate of more than 100.0% was determined to be "excellent in tensile strength." 5) Flexural modulus: Tests were conducted in accordance with the test method described in ISO 178 at room temperature (25°C) using 4 mm thick test pieces at a bending speed of 2 mm / min. The average value was calculated for five test pieces (n=5). Values ​​were also calculated relative to the value of Comparative Example 1, which did not contain a swelling agent, taken as 100.0%, and the values ​​were reported in the table as the percentage of the flexural modulus of each example (improvement in flexural modulus). Improvements in flexural modulus exceeding 100.0% were judged to have "excellent flexural modulus." 6) Flexural strength: Tests were conducted in accordance with the test method described in ISO 178 at room temperature (25°C) using 4 mm thick test pieces at a bending speed of 2 mm / min. The average value was calculated for five test pieces (n=5). Values ​​were also calculated relative to the flexural strength of Comparative Example 1, which did not contain a swelling agent, taken as 100.0%, and these values ​​are reported in the table as the percentage of flexural strength for each example (flexural strength improvement rate). Flexural strength improvement rates exceeding 100.0% were judged to be "excellent in flexural strength."

[0070] <Ingredients used> The following ingredients were used: Cellulosic fibers (A): Acetylated unbleached softwood pulp (A-1): 20 kg (10 kg solids) of wet unbleached softwood kraft pulp (NUKP), which had been beaten to a Canadian Standard Freeness (CSF) of 180 mL, was placed in a mixer (Nippon Coke & Engineering Co., Ltd., "FM150L"), and stirring was initiated. The mixture was dehydrated under reduced pressure at 80°C. Next, 4.0 kg of acetic anhydride was added, and the mixture was reacted at 80°C for 2 hours. After the reaction, the mixture was washed with water. The resulting washed pulp was placed in a dryer and dried under reduced pressure at 60-70°C to obtain acetylated unbleached softwood pulp (A-1). The moisture content of the resulting acetylated unbleached softwood pulp was measured using an infrared moisture meter, and found to be 2.5 wt% and the degree of acetyl substitution (DS) to be 0.86. The average fiber diameter was measured using a fiber tester (L&W) to be 35 μm. Swelling agent (B): Isophoronediamine (B-1): Fujifilm Wako Pure Chemical Industries, Ltd. (melting point: 10°C) 80% aqueous solution of hexamethylenediamine (B-2): manufactured by Asahi Kasei Chemicals Corporation (melting point of hexamethylenediamine: 38°C) ε-Caprolactam (B-3): manufactured by UBE Corporation (melting point: 69°C) Polyamide resin (C): Polyamide 6 (C-1): manufactured by UBE Corporation (relative viscosity: 2.47, carboxyl end group concentration: 2.5 × 10 -5 eq / g)

[0071] [Example 1] (1) Manufacture of cellulosic fibers for reinforcing polyamide resins 500 g of acetylated unbleached softwood pulp (A-1) and 1,000 g of isophoronediamine (B-1) (200 parts by mass of isophoronediamine per 100 parts by mass of acetylated unbleached softwood pulp) were mixed in a Henschel mixer at room temperature (25°C; the same applies below) for 5 minutes to obtain cellulose fiber (a-1) for reinforcing polyamide resins in Example 1.

[0072] (2) Masterbatch mixing (MB mixing) 1,000 g of cellulose fiber (a-1) for reinforcing polyamide resin and 1,000 g of polyamide 6 (C-1) were blended at room temperature for 10 minutes, fed into a twin-screw melt kneader (manufactured by Coperion Co., Ltd., model ZSK32Mc), melt-kneaded at a cylinder temperature of 230°C, and the molten resin was extruded into strands, which were then introduced into a water tank, cooled, cut, and vacuum-dried to obtain pellets of a masterbatch (MB-C1) for fiber-reinforced polyamide resin.

[0073] (3) Dilution and kneading Next, 1,000 g of the obtained fiber-reinforced polyamide resin masterbatch (MB-C1) pellets and 1,000 g of polyamide 6 (C-1) were pre-blended and fed into a twin-screw melt kneader (manufactured by Coperion Co., Ltd., model ZSK32Mc), melt-kneaded at a cylinder temperature of 230 ° C., and the molten resin was extruded into a strand shape, which was then introduced into a water tank, cooled, cut, and vacuum-dried to obtain pellets of fiber-reinforced polyamide resin composition (c-1). In addition, the resin pressure during dilution kneading when kneaded at 10 kg / h and 100 rpm was measured using a resin pressure meter attached to the twin-screw melt kneader.

[0074] [Comparative Example 1] (1) Masterbatch mixing (MB mixing) Pellets of a masterbatch (MB-C2) for fiber-reinforced polyamide resin were obtained in the same manner as in Example 1, except that the cellulose-based fiber (a-1) for reinforcing polyamide resin was changed to acetylated unbleached softwood pulp (A-1) and the amount was changed from 1,000 g to 500 g.

[0075] (2) Dilution and kneading Except for changing the masterbatch for fiber-reinforced polyamide resin (MB-C1) to the masterbatch for fiber-reinforced thermoplastic resin (MB-C2), pellets of fiber-reinforced polyamide resin composition (c-2) were obtained in the same manner as in Example 1. In addition, the resin pressure during dilution and kneading was measured when kneading at 10 kg / h and 100 rpm.

[0076] Comparative Example 2 (1) Manufacture of cellulosic fibers for reinforcing polyamide resins 500 g of acetylated unbleached softwood pulp (A-1) and 1,250 g of an 80% aqueous solution of hexamethylenediamine (B-1) (200 parts by mass of hexamethylenediamine per 100 parts by mass of acetylated unbleached softwood pulp (A-1)) were mixed in a Henschel mixer at room temperature for 5 minutes to obtain cellulose fiber (a-2) for reinforcing polyamide resins in Comparative Example 2.

[0077] (2) Masterbatch mixing (MB mixing) Pellets of a masterbatch (MB-C3) for fiber-reinforced polyamide resin were obtained in the same manner as in Example 1, except that the cellulose-based fiber (a-1) for reinforcing polyamide resin was changed to the cellulose-based fiber (a-2) for reinforcing polyamide resin and the amount was changed from 1,000 g to 1,250 g.

[0078] (3) Dilution and kneading Next, 1,000 g of the obtained pellets of the masterbatch (MB-C3) for fiber-reinforced polyamide resin and 1,000 g of polyamide 6 (C-1) were blended in advance and fed into a twin-screw melt mixer (manufactured by Coperion Co., Ltd., model ZSK32Mc), melt-mixed at a cylinder temperature of 230 ° C., and the molten resin was extruded into a strand shape, which was then introduced into a water tank, cooled, cut, and vacuum-dried to obtain pellets of fiber-reinforced polyamide resin composition (c-3). In addition, the resin pressure during dilution mixing was measured when mixing at 10 kg / h and 100 rpm.

[0079] Comparative Example 3 (1) Manufacture of cellulosic fibers for reinforcing polyamide resins The cellulose-based fiber (a-2) for reinforcing polyamide resin of Comparative Example 2 was immersed in water at 25°C for 15 minutes to remove hexamethylenediamine remaining in the pellets. After that, vacuum drying was performed to obtain the cellulose-based fiber (a-3) for reinforcing polyamide resin of Comparative Example 3.

[0080] (2) Masterbatch mixing (MB mixing) Pellets of a masterbatch (MB-C4) for fiber-reinforced polyamide resin were obtained in the same manner as in Example 1, except that the cellulose-based fiber (a-1) for reinforcing polyamide resin was changed to the cellulose-based fiber (a-3) for reinforcing polyamide resin and the amount was changed from 1,000 g to 500 g.

[0081] (3) Dilution and kneading Except for changing the masterbatch for fiber-reinforced polyamide resin (MB-C1) to the masterbatch for fiber-reinforced polyamide resin (MB-C4), pellets of fiber-reinforced polyamide resin composition (c-4) were obtained in the same manner as in Example 1. In addition, the resin pressure during dilution and kneading was measured when kneading at 10 kg / h and 100 rpm.

[0082] Comparative Example 4 (1) Manufacture of cellulosic fibers for reinforcing polyamide resins 500 g of acetylated unbleached softwood pulp (A-1), 1,000 g of ε-caprolactam (B-3) (200 parts by mass of ε-caprolactam (B-3) per 100 parts by mass of acetylated unbleached softwood pulp (A-1)), and 250 g of water were mixed in a Henschel mixer at room temperature for 5 minutes to obtain cellulose fiber (a-4) for reinforcing polyamide resins in Comparative Example 4.

[0083] (2) Masterbatch mixing (MB mixing) Pellets of a masterbatch (MB-C5) for fiber-reinforced polyamide resin were obtained in the same manner as in Example 1, except that the cellulose-based fiber (a-1) for reinforcing polyamide resin was changed to the cellulose-based fiber (a-4) for reinforcing polyamide resin.

[0084] (3) Dilution and kneading Except for changing the masterbatch for fiber-reinforced polyamide resin (MB-C1) to the masterbatch for fiber-reinforced polyamide resin (MB-C5), pellets of fiber-reinforced polyamide resin composition (c-5) were obtained in the same manner as in Example 1. In addition, the resin pressure during dilution and kneading was measured when kneading at 10 kg / h and 100 rpm.

[0085] The results are shown in Tables 1 and 2.

[0086] [Table 1]

[0087] [Table 2]

[0088] The cellulose fiber for reinforcing polyamide resin of Example 1 contains isophorone diamine. As can be seen from the table, when the cellulose fiber for reinforcing polyamide resin of Example 1 was used, the resin pressure during production (dilution and kneading) of the polyamide resin composition could be reduced. Furthermore, as can be seen from the table, the molded article of the polyamide resin composition containing the cellulose fiber for reinforcing polyamide resin of Example 1 had an improvement rate of 100.0% or more in tensile strength, flexural modulus, and flexural strength, and these mechanical properties were excellent.

[0089] The cellulose fiber for reinforcing polyamide resin of Comparative Example 2 contains hexamethylenediamine. The cellulose fiber for reinforcing polyamide resin of Comparative Example 3 is a fiber obtained by washing cellulose fiber containing hexamethylenediamine with water. When the cellulose fiber for reinforcing polyamide resin of Comparative Examples 2 and 3 was used, the reduction in resin pressure during the production of the polyamide resin composition was insufficient. The cellulose fiber for reinforcing polyamide resin of Comparative Example 4 contains ε-caprolactam. When the cellulose fiber for reinforcing polyamide resin of Comparative Example 4 was used, the resin pressure during the production of the polyamide resin composition increased rather than decreased.

Claims

1. Cellulosic fibers containing isophorone diamine for reinforcing polyamide resins.

2. The cellulose-based fiber for reinforcing a polyamide resin according to claim 1 , wherein the cellulose-based fiber is an acetylated cellulose-based fiber.

3. A polyamide resin composition comprising the cellulose-based fiber for reinforcing a polyamide resin according to claim 1 or 2 and an aliphatic polyamide resin.

4. The polyamide resin composition according to claim 3, wherein the aliphatic polyamide resin is polyamide 6.

5. A molded article comprising the polyamide resin composition according to claim 3.

6. A molded article comprising the polyamide resin composition according to claim 4.

7. A method for producing a polyamide resin composition, comprising: (1A) a step of contacting cellulosic fibers with isophorone diamine to obtain cellulosic fibers containing isophorone diamine at least in their crystals; (1B) a step of melt-kneading the cellulose-based fibers obtained in step (1A) with an aliphatic polyamide resin to obtain a polyamide resin composition; A method for producing a polyamide resin composition, comprising:

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