Resin composition, pellet, and molded article

Abstract

To provide a resin composition, a pellet containing the same, and a molded article, enabling a molded article to achieve superior flowability during molding and excellent mechanical properties.SOLUTION: A resin composition comprises a thermoplastic resin (A) including a polyacetal resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min, and regenerated cellulose fibers (B). It is preferable that the regenerated cellulose fibers (B) include solvent-spun regenerated cellulose fibers. A proportion of the thermoplastic resin (A) relative to the total mass of the resin composition is preferably 30 to 95 mass%, and a proportion of the regenerated cellulose fibers (B) is preferably 5 to 70 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, pellets, and molded articles. More specifically, the present invention relates to a resin composition containing a polyacetal resin and regenerated cellulose fibers, pellets thereof, and molded articles of the resin composition. [Background technology]

[0002] Toward the creation of a sustainable society, composite resin materials that combine petroleum-derived resin components with biomass components are increasingly being utilized. Examples of such composite resin materials include regenerated cellulose fiber-containing resin compositions in which regenerated cellulose fibers are filled into a thermoplastic resin (see, for example, Patent Documents 1 and 2). Lightweight molded articles with excellent mechanical properties can be obtained from such regenerated cellulose fiber-containing resin compositions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-091775 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-020465 Summary of the Invention [Problem to be solved by the invention]

[0004] Since regenerated cellulose fiber-containing resin compositions sometimes exhibit poor fluidity during injection molding, there is a demand for improved fluidity during molding, particularly during injection molding. Polyacetal resin is known as a typical engineering resin with excellent physical properties, such as mechanical and electrical properties, and chemical properties, such as chemical resistance and heat resistance. Combining such polyacetal resin with regenerated cellulose fibers is expected to produce molded products with even better mechanical properties. However, the inventors' research has revealed that the combination of polyacetal resin and regenerated cellulose fibers results in a lower fluidity during injection molding, making it difficult to achieve the desired mechanical properties.

[0005] An object of the present disclosure is to provide a resin composition that allows for the production of molded articles that have excellent flowability during molding and excellent mechanical properties, as well as pellets and molded articles containing the same. [Means for solving the problem]

[0006] As a result of extensive research, the inventors of the present application have found that the above-mentioned problems can be solved by a resin composition containing a thermoplastic resin (A) including a polyacetal resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min, and regenerated cellulose fibers (B). [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a resin composition that allows a molded article to be obtained that has excellent flowability during molding and excellent mechanical properties, as well as pellets and molded articles containing the same. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the present disclosure will be described in detail below, but the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Furthermore, when multiple numerical ranges are described for a specific parameter, any of the numerical values ​​described therein can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limits of a numerical range described in this disclosure are numerical values ​​within that range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less." When a specific description given for one embodiment also applies to other embodiments, that description may be omitted in other embodiments.

[0009] [Resin composition] A first embodiment of the present disclosure relates to a resin composition comprising a thermoplastic resin (A) containing a polyacetal resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min, and regenerated cellulose fibers (B). The resin composition according to the first embodiment can provide a molded article that exhibits excellent flowability during molding and excellent mechanical properties.

[0010] <Thermoplastic resin (A)> The resin composition according to the first embodiment contains a thermoplastic resin (A) containing a polyacetal resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min. The inclusion of the thermoplastic resin (A) (hereinafter referred to as "resin (A)") containing the polyacetal resin (a1) having a specific melt flow rate results in a resin composition with excellent fluidity during molding, particularly during injection molding. Furthermore, by combining the resin (A) with regenerated cellulose fibers (B) described below, a molded product with excellent mechanical properties can be obtained.

[0011] (Polyacetal resin (a1)) The resin composition according to the first embodiment contains a polyacetal resin (a1) (hereinafter referred to as "resin (a1)") having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min. From the viewpoint of achieving both good fluidity during injection molding and mechanical properties of the molded product, it is preferable that the resin (A) contains the resin (a1) as a main component. Here, "containing the resin (a1) as a main component" means that the proportion of the resin (a1) relative to the total mass of the resin (A) is greater than 50 mass%. The proportion of the resin (a1) relative to the total mass of the resin (A) is preferably 70 mass% or more, more preferably 90 mass% or more. Alternatively, the resin (A) may contain only the resin (a1).

[0012] Melt flow rate The melt flow rate of resin (a1) (190°C, 2.16 kg load) is 20 to 60 g / 10 min. The inventors' investigations revealed that regenerated cellulose fiber-containing resin compositions containing polyacetal resins exhibit reduced fluidity, particularly during injection molding, leading to poor moldability and resulting in insufficient mechanical properties. To improve fluidity during injection molding, the cylinder temperature of the molding machine is typically adjusted. However, polyacetal resins are prone to thermal decomposition, which can result in the generation of formaldehyde, making this common approach unacceptable. After further intensive investigations, the inventors discovered that combining polyacetal resin (a1) with regenerated cellulose fibers, whose melt flow rate measured at 190°C and a 2.16 kg load is controlled within the range of 20 to 60 g / 10 min, can improve fluidity, particularly during injection molding. Surprisingly, they also found that combining solvent-process regenerated cellulose fibers with resin (a1) as the regenerated cellulose fibers (B), further improves fluidity. Furthermore, a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min is preferable because pellets of the resin composition according to the first embodiment can be stably produced. The melt flow rate of the thermoplastic resin may be measured at different temperatures (for example, 190°C, 200°C, 210°C, 230°C, etc.) and compared and evaluated, but the melt flow rate of resin (a1) is measured at 190°C. Among the above temperatures, for example, at 230°C, thermal decomposition occurs, generating bubbles, which may prevent accurate measurement.

[0013] The melt flow rate of the resin (a1) (190°C, 2.16 kg load) can be measured in accordance with ISO 1133 (condition D). The melt flow rate can be measured using a melt flow rate tester (for example, product name "Melt Indexer L220" manufactured by Tateyama Scientific High-Technologies Co., Ltd.).

[0014] The melt flow rate (190°C, 2.16 kg load) of resin (a1) is not particularly limited as long as it is in the range of 20 to 60 g / 10 min. However, from the viewpoint of achieving a better balance between fluidity during injection molding and mechanical properties of the molded product, it is preferably 25 to 60 g / 10 min, more preferably 30 to 60 g / 10 min, and even more preferably 40 to 60 g / 10 min. In one embodiment, the melt flow rate (190°C, 2.16 kg load) of resin (a1) may be 20 to 50 g / 10 min, or may be 20 to 45 g / 10 min. The melt flow rate (190°C, 2.16 kg load) of resin (a1) can be adjusted to the above range by adding a known molecular weight modifier during polymerization.

[0015] Melting point The melting point of resin (a1) is not particularly limited as long as it has the effects of the present disclosure, and can be appropriately adjusted within a range in which the melt flow rate (190°C, 2.16 kg load) is 20 to 60 g / 10 min. In one embodiment, the melting point of resin (a1) may be 155 to 164°C. The melting point of resin (a1) can be measured using a differential scanning calorimeter (DSC).

[0016] Resin (a1) contains oxymethylene units (—CHO—) as its main structural unit. In this disclosure, the term “main structural unit” refers to a monomer unit that accounts for more than 50% by mass, preferably 70% by mass or more, of all structural units (100% by mass) that constitute resin (a1). Resin (a1) may be a homopolymer containing only oxymethylene units, or a copolymer containing comonomer units other than oxymethylene units, as long as the melt flow rate satisfies the above range. Here, “comonomer unit” refers to a monomer unit derived from a monomer (comonomer) that is copolymerizable with the monomer (main monomer) that constitutes the oxymethylene unit.

[0017] Homopolymer The homopolymer can be obtained by anionic polymerization of formaldehyde in the presence of a polymerization catalyst. The terminals of the crude polyoxymethylene obtained in the polymerization step must be stabilized using an etherifying agent, an esterifying agent, or the like. When resin (a1) is a homopolymer, the degree of polymerization of the homopolymer can be appropriately adjusted within the range that satisfies the above-mentioned melt flow rate.

[0018] Copolymer The copolymer can be obtained by copolymerizing trioxane with a comonomer copolymerizable with trioxane in the presence of a polymerization catalyst. Trioxane is a cyclic trimer of formaldehyde. Trioxane is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acid catalyst, and can be purified by distillation or other methods.

[0019] The comonomer is preferably selected from the group consisting of cyclic ethers and cyclic formals having at least one carbon-carbon bond. Examples include 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, ethylene oxide, propylene oxide, epichlorohydrin, etc. Among these, from the viewpoint of polymerization stability, 1,3-dioxolane and 1,4-butanediol formal are preferred, and 1,3-dioxolane is more preferred. Furthermore, as the comonomer, a compound having two polymerizable cyclic ether groups or cyclic formal groups, such as diglycidyl ether of alkylene glycol, e.g., butanediol diglycidyl ether, or diformal, or a compound having three or more polymerizable cyclic ether groups or cyclic formal groups, such as glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, or pentaerythritol tetraglycidyl ether, may be used.

[0020] The copolymer can be polymerized by a known method using a known polymerization apparatus such as a batch type or continuous type.

[0021] When the resin (a1) is a copolymer, the copolymer may be a random copolymer, a block copolymer, or a graft copolymer. From the viewpoint of thermal stability, a random copolymer is preferred. The polymerization degree, branching degree, and crosslinking degree of the copolymer can be appropriately adjusted within the range satisfying the above-mentioned melt flow rate.

[0022] As described above, resin (a1) may be a homopolymer or a copolymer, but a copolymer is preferred from the viewpoint of thermal stability. In one embodiment, the proportion of comonomer units in resin (a1) is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, based on the total structural units of the copolymer (100% by mass), from the viewpoint of thermal stability. In a preferred embodiment, resin (a1) comprises a copolymer containing one or more comonomer units selected from 1,3-dioxolane and 1,4-butanediol formal in an amount of 1 to 20% by mass, based on the total structural units. The proportion of comonomer units in resin (a1) can be calculated by H-NMR. For example, a sample is prepared by dissolving resin (a1) in deuterated 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) to a concentration of 5% by mass. The sample is analyzed by 1H-NMR to determine the ratio of the integral value of the comonomer unit to the integral value of the peaks of all the monomers in the resin (a1).

[0023] (Other thermoplastic resins (a2)) In one embodiment, the resin (A) may contain a thermoplastic resin other than the resin (a1) (another thermoplastic resin (a2), hereinafter also referred to as "resin (a2)"). Any thermoplastic resin can be selected as resin (a2) as long as it does not impair the effects of the present disclosure. Examples of suitable resins include olefin-based resins (polyethylene resin, polypropylene resin, etc.), vinyl alcohol-based resins, vinyl ester-based resins, styrene-based resins, (meth)acrylic resins, polyester-based resins, polycarbonate-based resins, polyamide-based resins, polysulfone-based resins, polyphenylene-based resins, polyacetal-based resins other than resin (a1), and thermoplastic elastomers. Biodegradable resins and biomass resins can also be used. Among these, resin (a2) may contain an olefin-based resin, which has a slower solidification rate than polyacetal resin, or a polypropylene resin, from the viewpoint of improving the resin impregnation into fibers during pellet production and fluidity during molding. When resin (A) contains resin (a2), the amount of resin (a2) is preferably 10% by mass or less, and more preferably 7% by mass or less, of the total mass of resin (A), from the viewpoint of the mechanical properties of the molded product. In a particularly preferred embodiment, from the viewpoint of easily obtaining a molded article having excellent flowability during molding and excellent mechanical properties, the resin (A) contains only the resin (a1).

[0024] In one embodiment, the proportion of resin (A) relative to the total mass of the resin composition is preferably 30 to 95 mass%, more preferably 40 to 90 mass%, even more preferably 50 to 80 mass%, and particularly preferably 60 to 75 mass%. When the proportion of resin (A) is within the above range, it is easy to achieve both flowability during molding and mechanical properties of the molded article.

[0025] <Regenerated cellulose fiber (B)> The resin composition according to the first embodiment contains the aforementioned resin (A) and regenerated cellulose fibers (B). The term "regenerated cellulose fibers" refers to artificially spun cellulose fibers made from natural cellulose fibers (such as plant-derived cellulose fibers, animal-derived cellulose fibers (such as sea squirt cellulose), and bacterial-derived cellulose fibers).

[0026] Methods for obtaining regenerated cellulose fibers from natural cellulose fibers include, for example, the viscose method, the cuprammonium method, and the solvent spinning method (a method in which cellulose is directly spun without first being chemically converted; hereinafter referred to as the "solvent method"). Examples of regenerated cellulose fibers obtained by the viscose method include viscose rayon, polynosic, and modal. Examples of regenerated cellulose fibers obtained by the cuprammonium method include cupra. Examples of regenerated cellulose fibers obtained by the solvent method include lyocell and regenerated cellulose fibers obtained by the ionic liquid method. As the regenerated cellulose fiber (B), one type of regenerated cellulose fiber obtained by these methods may be used alone, or two or more types may be used in combination. In addition, spun fibers made by twisting short regenerated cellulose fibers into long threads may also be used.

[0027] The resin composition according to the first embodiment preferably contains viscose-process regenerated cellulose fiber and / or solvent-process regenerated cellulose fiber as the regenerated cellulose fiber (B). From the viewpoint of easily obtaining a resin composition having excellent flowability during molding, it is preferable to contain solvent-process regenerated cellulose fiber. Furthermore, from the viewpoint of easily obtaining a molded product having excellent mechanical properties, it is preferable to contain viscose-process regenerated cellulose fiber. Furthermore, from the viewpoint of easily achieving a balance between the flowability during injection molding and the mechanical properties of the molded product, it is more preferable to contain solvent-process regenerated cellulose fiber.

[0028] In one embodiment, the tensile breaking elongation of a single yarn (monofilament) of the regenerated cellulose fiber (B) at a pulling speed of 1 mm / min is preferably less than 10%, more preferably 8% or less. By including the regenerated cellulose fiber (B) with a tensile elongation of less than 10%, appropriate fiber breakage occurs, which tends to improve processability in injection molding or extrusion molding. The tensile breaking elongation can be measured specifically by the following method. (Method for measuring tensile elongation at break of single yarn) Using a Tensilon universal material testing machine (for example, A&D Corporation, product name "RTG-1310"), measure the tensile breaking elongation of the cellulose single yarn five times under the conditions of load cell capacity: 0.15 N, chuck distance: 20 mm, and tensile speed: 1 mm / min, and calculate the average value.

[0029] In one embodiment, the regenerated cellulose fibers (B) preferably have an average fiber diameter of 5 to 30 μm and an X-ray orientation degree of 86% or more. Such an average fiber diameter and X-ray orientation degree facilitate impregnation of the regenerated cellulose fibers (B) with the resin (A). Furthermore, the mechanical strength of the resulting molded article also tends to be improved. The average fiber diameter is more preferably 6 to 20 μm, and even more preferably 7 to 15 μm. The average fiber diameter of the regenerated cellulose fibers (B) can be calculated from the average diameter of a plurality of fibers observed with an SEM or the like. The degree of X-ray orientation is more preferably 90% or more. The degree of X-ray orientation of the regenerated cellulose fibers (B) can be determined from the formulas described in JP-A-9-31744 and JP-A-9-256216.

[0030] In one embodiment, the tensile modulus (Young's modulus) of the regenerated cellulose fiber (B) is preferably 10 GPa or more, more preferably 15 GPa or more, and even more preferably 20 GPa or more. From the viewpoint of easily achieving the above tensile modulus, the regenerated cellulose fiber (B) preferably includes solvent-process regenerated cellulose fiber. The tensile modulus of the regenerated cellulose fiber (B) can be determined by measuring the fiber using a tensile tester with a chuck distance of 20 mm and a pulling speed of 1 mm / min after storing the fiber in an air-conditioned room at 23°C and 50% RH for 24 hours.

[0031] In one embodiment, the proportion of the regenerated cellulose fibers (B) relative to the total mass of the resin composition is preferably 5 to 70 mass%, more preferably 10 to 60 mass%, even more preferably 20 to 50 mass%, and particularly preferably 25 to 40 mass%. When the proportion of the regenerated cellulose fibers (B) is within the above range, it is easy to achieve both good fluidity during molding and good mechanical properties of the molded product.

[0032] (Thermoplastic resin impregnated regenerated cellulose fiber bundle (B-1)) The resin composition according to the first embodiment preferably contains a thermoplastic resin-impregnated regenerated cellulose fiber bundle (B-1) (hereinafter referred to as "fiber bundle (B-1)") in which a fiber bundle of regenerated cellulose fibers (B) aligned in the longitudinal direction is impregnated with a resin (A). When the resin composition according to the first embodiment contains the fiber bundle (B-1), a molded article with more excellent mechanical properties can be obtained. In one embodiment, the resin composition may contain the fiber bundle (B-1) and any thermoplastic resin (for example, the above-mentioned resin (a2)), or may contain only the fiber bundle (B-1).

[0033] The fiber bundle (B-1) is a composite material obtained by impregnating a fiber bundle of regenerated cellulose fibers (B) aligned in the longitudinal direction with a resin (A) and then cutting the fiber bundle. As a result of studies by the present inventors, it was found that the resin-impregnated fiber bundle can be easily produced by using a resin (A) containing a resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min as the impregnating resin. A resin composition containing the fiber bundle (B-1) can easily produce a molded product that has excellent flowability during injection molding and excellent mechanical properties. In a particularly preferred embodiment, the fiber bundle (B-1) comprises a fiber bundle formed by bundling solvent-process regenerated cellulose fibers aligned in the longitudinal direction and impregnated with only resin (a1) as the thermoplastic resin (A).

[0034] The resin (A) contained in the fiber bundle (B-1) can be exemplified in the same manner as the resin (A) described above, and preferred examples are also the same. That is, the proportion of the resin (a1) in the resin (A) is preferably more than 50% by mass, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The proportion of the resin (a1) in the impregnated resin (A) may be 100% by mass.

[0035] The proportion of resin (A) in fiber bundle (B-1) is preferably 30 to 95 mass%, more preferably 40 to 90 mass%, even more preferably 50 to 80 mass%, and particularly preferably 60 to 75 mass%. The proportion of regenerated cellulose fiber (B) in fiber bundle (B-1) is preferably 5 to 70 mass%, more preferably 10 to 60 mass%, even more preferably 20 to 50 mass%, and particularly preferably 25 to 40 mass%. When the proportion of resin (A) and regenerated cellulose fiber (B) is within the above range, it is easy to achieve both good fluidity during molding and good mechanical properties of the molded product.

[0036] The number of regenerated cellulose fibers (B) in the fiber bundle (B-1) is preferably adjusted to a range of 100 to 30,000. In one embodiment, the number of regenerated cellulose fibers (B) is preferably 2,000 to 30,000, more preferably 3,000 to 25,000, and even more preferably 5,000 to 25,000.

[0037] The average length of the regenerated cellulose fibers (B) in the fiber bundle (B-1) is preferably 3 to 30 mm, more preferably 3 to 15 mm, and even more preferably 3 to 9 mm. By including such regenerated cellulose fibers (B), the mechanical strength of the molded article obtained by injection molding the resin composition according to the first embodiment is more likely to be improved. The average length of the regenerated cellulose fibers (B) in the fiber bundle (B-1) can be calculated by measuring the major axis lengths of approximately 100 pellets of the fiber bundle (B-1) with a vernier caliper or the like and averaging the measurements.

[0038] When the resin composition according to the first embodiment contains fiber bundles (B-1) and other thermoplastic resins, the average length of the regenerated cellulose fibers (B) in the resin composition is also preferably 3 to 30 mm, more preferably 3 to 15 mm, and even more preferably 3 to 9 mm. The average length of the regenerated cellulose fibers (B) in the resin composition can be calculated as the average value of the fiber lengths measured by dissolving and removing the resin of the resin composition with an organic solvent (such as xylene), dispersing the regenerated cellulose fibers (B) in a medium, and subjecting the regenerated cellulose fibers (B) to image processing.

[0039] (Method for producing thermoplastic resin-impregnated regenerated cellulose fiber bundle (B-1)) In one embodiment, the fiber bundle (B-1) can be produced by a known production method using a die. Specifically, the production methods described in JP-A-6-313050, JP-A-2007-176227, JP-B-6-2344, etc. can be applied.

[0040] <Other ingredients> The resin composition according to the first embodiment may contain components other than the resin (A) and the regenerated cellulose fibers (B) (other components) within the range that does not impair the effects of the present invention. Examples of other components include the aforementioned resin (a2), as well as additives such as softeners, surface lubricants, leveling agents, antioxidants, surfactants, corrosion inhibitors, light stabilizers, UV absorbers, heat stabilizers, reaction catalysts, polymerization inhibitors, silane coupling agents, lubricants, plasticizers, crystallization accelerators, hydrolysis inhibitors, inorganic fillers, colorants, mold release agents, antistatic agents, organic fillers other than the regenerated cellulose fibers (B), metal powders, pigments, and epoxy compounds. These additives may be used alone or in combination of two or more.

[0041] When the resin composition contains the additives, the amount of the additives can be 1% by mass or less based on the total mass of the resin composition. The additives may be added during the production of the fiber bundle (B-1), or may be attached to at least a part of the surface of the pellets of the resin composition described below. In one embodiment, the resin composition preferably contains an antioxidant and a reaction catalyst. Examples of preferred antioxidants include hindered phenol-based antioxidants and phosphorus-based antioxidants. Examples of preferred reaction catalysts include quaternary phosphonium salts (e.g., methyltriphenylphosphonium bromide). When the resin composition contains an antioxidant, the proportion of the antioxidant is preferably 0.01 to 1 mass% relative to the total mass of the resin composition. When the resin composition contains a reaction catalyst, the proportion of the reaction catalyst is preferably 0.001 to 0.05 mass% relative to the total mass of the resin composition. When the resin composition contains a reaction catalyst, the Charpy impact strength of the molded article is likely to be improved.

[0042] <Method of manufacturing resin composition> The method for producing the resin composition according to the first embodiment is not particularly limited, and the resin composition may be produced by a method including mixing resin (A), regenerated cellulose fibers (B), and, if necessary, optional components by a conventional method. For example, the components may be mixed, kneaded, and extruded using a single- or twin-screw extruder to obtain pellets of the resin composition. In one embodiment, a resin composition comprising fiber bundle (B-1) (or a resin composition containing fiber bundle (B-1) and other components) may be obtained by a method including obtaining fiber bundle (B-1) by the above-described method for producing fiber bundle (B-1) (e.g., a method in which a molten impregnation resin containing resin (A) and, if necessary, optional components is impregnated into a fiber bundle of regenerated cellulose fibers (B) that has been passed through a crosshead die and aligned in the length direction, thereby preparing fiber bundle (B-1)), and optionally mixing the fiber bundle (B-1) with other components (e.g., resin (a2), etc.).

[0043] [pellet] A second embodiment of the present disclosure relates to pellets. The pellets according to the second embodiment can be obtained by producing the resin composition according to the first embodiment, for example, by the method for producing the resin composition described above. The pellets according to the second embodiment are prepared from a resin composition that combines the resin (a1) having the specific melt flow rate described above with regenerated cellulose fibers (B), and can also have the effect of reducing fiber breakage during the production of the pellets.

[0044] [Molded products and their manufacturing methods] A third embodiment of the present disclosure relates to a molded article. The molded article according to the third embodiment is obtained by molding the resin composition according to the first embodiment (or the pellets according to the second embodiment). The molded article according to the third embodiment may be obtained by injection molding the resin composition according to the first embodiment (or the pellets according to the second embodiment). The molded article according to the third embodiment has excellent mechanical properties.

[0045] In one embodiment, the tensile strength of the molded article measured in accordance with ISO 527 is preferably 85 MPa or more, more preferably 90 MPa or more. The molded article according to the third embodiment can achieve a tensile strength that is 1.5 times or more that of a molded article made of a conventional polypropylene resin-impregnated regenerated cellulose fiber bundle (such as Comparative Example 3 described below), for example.

[0046] In one embodiment, the molded article may have a Charpy notched impact strength, measured in accordance with ISO179 / 1eA, of 20 kJ / m 2 or more, or 25 kJ / m 2 or more.

[0047] [Application] The molded article according to the third embodiment has excellent mechanical properties and can be suitably used for applications such as cases and frames used in automobiles, home appliances, toys, furniture, etc., or structural members such as gear parts.

[0048] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] A resin composition comprising a thermoplastic resin (A) containing a polyacetal resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min, and regenerated cellulose fibers (B). [2] The resin composition according to [1], wherein the regenerated cellulose fibers (B) include solvent-process regenerated cellulose fibers. [3] The resin composition according to [1] or [2], wherein the proportion of the thermoplastic resin (A) is 30 to 95 mass% and the proportion of the regenerated cellulose fiber (B) is 5 to 70 mass% relative to the total mass of the resin composition. [4] A resin composition according to any one of [1] to [3], wherein the resin composition comprises a thermoplastic resin-impregnated regenerated cellulose fiber bundle (B-1) in which the regenerated cellulose fiber (B) is aligned in the longitudinal direction and impregnated with the thermoplastic resin (A). [5] The resin composition according to any one of [1] to [4], wherein the regenerated cellulose fibers (B) in the resin composition have an average length of 3 to 9 mm. [6] The resin composition according to any one of [1] to [5], wherein the regenerated cellulose fiber (B) has a tensile breaking elongation of a single yarn of less than 10% at a tensile speed of 1 mm / min. [7] The resin composition according to any one of [1] to [6], wherein the polyacetal resin (a1) has a melt flow rate (190°C, 2.16 kg load) of 40 to 60 g / 10 min. [8] The resin composition according to any one of [1] to [7], wherein the proportion of the polyacetal resin (a1) relative to the total mass of the thermoplastic resin (A) is 90 mass% or more. [9] The resin composition according to any one of [1] to [8], which is for injection molding.

[10] A pellet comprising the resin composition according to any one of [1] to [8].

[11] A molded article comprising the resin composition according to any one of [1] to [8]. [Example]

[0049] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

[0050] The following materials were used as raw materials for the resin composition. <Thermoplastic resin (A)> (Resin (a1)) Polyacetal resin (polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane) (melt flow rate (190°C, 2.16 kg load): 45 g / 10 min). (resin (a2)) Resin (a2-1): Polyacetal resin (polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane) (melt flow rate (190°C, 2.16 kg load): 9 g / 10 min). Resin (a2-2): Polyacetal resin (polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane) (melt flow rate (190°C, 2.16 kg load): 70 g / 10 min). Resin (a2-3): Propylene homopolymer (PP homopolymer, manufactured by SunAllomer Co., Ltd., product name "PMB02A"). Resin (a2-4): Maleic anhydride modified polypropylene resin (SK Functional Polymer, product name "OREVAC (registered trademark) CA100"). <Regenerated cellulose fiber (B)> Regenerated cellulose fiber (B1): Solvent-process regenerated cellulose fiber (manufactured by BioMid Fiber, average fiber diameter (long diameter): 11 μm, tensile elongation at break: 5.4%). Regenerated cellulose fiber (B2): Viscose regenerated cellulose fiber (manufactured by Cordenka, product name "CR500TEX", average fiber diameter (long diameter): 11 μm, tensile breaking elongation: 15.5%).

[0051] The tensile breaking elongation of the regenerated cellulose fibers (B1) to (B2) is the tensile breaking elongation of a single yarn measured by the following method. Using a Tensilon universal material testing machine (manufactured by A&D Co., Ltd., product name "RTG-1310"), the tensile breaking elongation of the regenerated cellulose fiber single yarn was measured five times under the conditions of load cell capacity: 0.15 N, chuck distance: 20 mm, and tensile speed: 1 mm / min, and the average value was calculated.

[0052] <Other ingredients> Antioxidant (1): Hindered phenol-based antioxidant (manufactured by BASF Japan Ltd., product name "Irganox (registered trademark) 1010"). Antioxidant (2): Phosphorus-based antioxidant (manufactured by BASF Japan Ltd., product name "Irgafos (registered trademark) 168"). Reaction catalyst: methyltriphenylphosphonium bromide (MTPB) (Tokyo Chemical Industry Co., Ltd.).

[0053] [Example 1] 74.9% by mass of resin (a1) and 0.1% by mass of antioxidant (1) were mixed and charged into a twin-screw extruder, and then melt-kneaded at a cylinder temperature of 210 ° C. to obtain a molten mixture. The solvent-processed regenerated cellulose fiber (B1) was passed through a crosshead die and impregnated into a fiber bundle aligned in the length direction so that the solvent-processed regenerated cellulose fiber (B1) was 25% by mass. The fiber bundle was then shaped using a shaping nozzle at the crosshead die outlet, shaped using a shaping roll, and cut into 7 mm lengths using a pelletizer to obtain the resin composition of Example 1 consisting of pelletized fiber bundle (B-1).

[0054] Next, the resin composition (pellets) of Example 1 was injection molded under the following conditions to obtain a molded article (ISO tensile test piece). Various mechanical properties of the obtained molded article were measured under the following conditions. Furthermore, the flowability during injection molding was measured under the following conditions. (Molding conditions) Molding machine: Sumitomo Heavy Industries, Ltd., product name "EC40SE100EV-A". Specimen: ISO tensile specimen. Molding temperature: 200℃. Mold temperature: 90℃.

[0055] <Evaluation of mechanical properties> Measurement of tensile strength and elongation The obtained ISO tensile test specimen was used to perform measurements in accordance with ISO 527. Specifically, a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph (registered trademark) AG-20kNXDplus") was used to perform measurements under the following conditions: temperature: 23°C, test speed: 5 mm / min, and chuck distance (span) 115 mm.

[0056] Charpy impact strength measurement The obtained ISO tensile test specimens were used to measure in accordance with ISO179 / 1eA. Specifically, a digital impact tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd., product name "Impact Tester No. 258-L IMPACT TESTER") was used under the following conditions: test temperature: 23°C, measurement mode: V-notched, hammer capacity: 4J.

[0057] <Liquidity evaluation> The fluidity during injection molding was evaluated based on the filling pressure (molding filling pressure) during molding of the ISO tensile test specimens, using the following evaluation criteria: 1-2: excellent, 3-4: good, 5: fair, 6: poor. (Evaluation criteria) 1: Molding filling pressure is 100 MPa or less. 2: Molding filling pressure is over 100 MPa and up to 130 MPa. 3: Molding filling pressure is over 130 MPa and up to 140 MPa. 4: Molding filling pressure is over 140 MPa and up to 150 MPa. 5: Molding filling pressure is over 150 MPa and up to 160 MPa. 6: Molding filling pressure is over 160 MPa.

[0058] [Examples 2 to 6 and Comparative Examples 1 to 5] Pellet-shaped resin compositions were prepared under the same conditions as in Example 1, except that the formulations of the resin compositions were as shown in Tables 1 and 2. Molded articles were prepared from the resin compositions (pellets) of each example under the same conditions as in Example 1. The fluidity and mechanical properties of the resulting molded articles were evaluated under the same conditions as in Example 1. The results are shown in Tables 1 and 2.

[0059] [Table 1]

[0060] [Table 2]

[0061] Examples 1 to 4 are examples in which solvent-process regenerated cellulose fibers (B1) were blended as the regenerated cellulose fibers (B), and Examples 5 and 6 are examples in which viscose-process regenerated cellulose fibers (B2) were blended. As shown in Tables 1 and 2, by combining resin (a1) and regenerated cellulose fiber (B), molded articles with excellent fluidity and mechanical properties during injection molding could be obtained. Furthermore, the resin compositions of Examples 1 to 6 had better mechanical properties than the resin compositions of Comparative Examples 3 to 5, which contained polypropylene as resin (A). Furthermore, the resin compositions of Examples 1 to 4, which combined solvent-process regenerated cellulose fiber (B1) with resin (a1), had improved fluidity compared to the resin compositions of Examples 5 and 6. On the other hand, the resins of Examples 5 and 6, which combined viscose-process regenerated cellulose fiber (B2), had slightly reduced fluidity but improved mechanical properties, particularly Charpy impact strength. On the other hand, in Comparative Example 1, which combined a polyacetal resin with a melt flow rate (190°C, 2.16 kg load) of less than 20 g / 10 min, breakage of the regenerated cellulose fibers occurred during production, and pellets (fiber bundle (B-1)) could not be produced. Furthermore, in Comparative Example 2, which combined a polyacetal resin with a melt flow rate (190°C, 2.16 kg load) of more than 60 g / 10 min, the resin had low toughness, causing frequent pellet cracking during strand cutting, and it was not possible to produce pellets (fiber bundle (B-1)) of a quality suitable for injection molding. From the above results, it was found that the resin composition according to the first embodiment can provide molded products with excellent flowability during molding and excellent mechanical properties.

Claims

1. A resin composition comprising a thermoplastic resin (A) containing a polyacetal resin (a1) having a melt flow rate (190°C, 2.16 kg load) of 20 to 60 g / 10 min, and regenerated cellulose fibers (B).

2. The resin composition according to claim 1 , wherein the regenerated cellulose fibers (B) include solvent-process regenerated cellulose fibers.

3. The resin composition according to claim 1 or 2, wherein the proportion of the thermoplastic resin (A) is 30 to 95% by mass and the proportion of the regenerated cellulose fiber (B) is 5 to 70% by mass relative to the total mass of the resin composition.

4. The resin composition according to claim 1 or 2, comprising a thermoplastic resin-impregnated regenerated cellulose fiber bundle (B-1) in which the regenerated cellulose fiber (B) is aligned in the longitudinal direction and impregnated with the thermoplastic resin (A).

5. 3. The resin composition according to claim 1, wherein the regenerated cellulose fibers (B) in the resin composition have an average length of 3 to 9 mm.

6. 3. The resin composition according to claim 1, wherein the regenerated cellulose fiber (B) has a tensile breaking elongation of a single yarn of less than 10% at a pulling rate of 1 mm / min.

7. The resin composition according to claim 1 or 2, wherein the polyacetal resin (a1) has a melt flow rate (190°C, 2.16 kg load) of 40 to 60 g / 10 min.

8. The resin composition according to claim 1 or 2, wherein a proportion of the polyacetal resin (a1) relative to the total mass of the thermoplastic resin (A) is 90 mass% or more.

9. The resin composition according to claim 1 or 2, which is for injection molding.

10. A pellet comprising the resin composition according to claim 1 or 2.

11. A molded article comprising the resin composition according to claim 1 or 2.

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