Resin masterbatch and method for producing resin composition

Abstract

Provided is a resin masterbatch containing a cellulose material (A), an acid-modified polypropylene (B), and a thermoplastic resin (C), wherein the cellulose material (A) has a kappa value of 30 or less, the thermoplastic resin (C) has a melting point of less than 100°C and a Charpy impact strength of 30 kJ / m2 or more, and the brightness of a molded body obtained by pressing the resin masterbatch for 1 minute at 150°C and 0.5 MPa is 29 or more.

Description

Method for producing resin masterbatch and resin composition

[0001] The present invention relates to a resin masterbatch and a method for producing a resin composition using the resin masterbatch.

[0002] Cellulose fiber is a natural filler derived from plants, and has attracted attention as a low-density, high-strength reinforcing material for resins.

[0003] Currently, a resin masterbatch containing cellulose fibers as a reinforcing material is obtained, then transported to a user, who then dilutes the masterbatch to a desired concentration for use. From the viewpoints of ease of handling and transportation efficiency, it is desirable to prepare a resin masterbatch containing as high a content of cellulose fibers as possible as a reinforcing material. For example, Patent Document 1 describes the preparation of a resin masterbatch containing 50% by mass of cellulose fibers, and describes that a molded article made using a resin composition obtained by diluting and kneading this resin masterbatch has excellent mechanical properties.

[0004] Furthermore, since it is desirable for users to have a high degree of freedom in toning the color of the final resin composition, there is a demand for resin masterbatches that are less colored.

[0005]

[0003] Incidentally, a method for obtaining a resin composition by melt-kneading a resin and pulp, which is a raw material for cellulose fibers, using a kneader to form a composite is known, but there is a problem in that the resulting resin composition is noticeably discolored due to kneading, depending on the production conditions. In particular, when a resin masterbatch containing a high amount of cellulose fibers is produced using bleached pulp with a low lignin content, the resulting resin masterbatch is highly discolored, even though the kneading conditions are not particularly high. Furthermore, there is a problem in that a molded article using the final resin composition obtained by diluting and kneading this resin masterbatch has reduced strength properties.

[0006] JP 2022-012875 A

[0007] In Patent Document 1, carbon-based particles containing carbon black as a main component are added to improve the dispersibility of cellulose fibers in a resin composition, thereby obtaining a highly black appearance, but it was not possible to obtain a resin composition that can be toned to a bright color tone.

[0008] Therefore, an object of the present invention is to provide a resin masterbatch that is less colored, allows for bright color toning, and enables the production of molded articles with excellent mechanical properties, and to provide a method for producing a resin composition using the resin masterbatch that does not require the application of strong shear force.

[0009] As a result of extensive research into achieving this object, the inventors have discovered that it is extremely effective to use a cellulose material with a predetermined kappa number in a predetermined amount and to blend it with a thermoplastic resin having specific properties, and have completed the present invention.

[0010] The present invention provides the following: (1) A resin masterbatch comprising (A) a cellulose material, (B) an acid-modified polypropylene, and (C) a thermoplastic resin, wherein the cellulose material (A) has a kappa number of 30 or less, and the thermoplastic resin (C) has a melting point of less than 100°C and a Charpy impact strength of 30 kJ / m ２(2) The resin masterbatch according to (1), wherein the content of the (A) cellulose material is 25 to 55 parts by mass and the content of the (C) thermoplastic resin is 20 to 65 parts by mass, per 100 parts by mass of the resin masterbatch. (3) The resin masterbatch according to (1), wherein the blending amount of the (B) acid-modified polypropylene relative to 100 parts by mass of the (A) cellulose material is 6 parts by mass or more. (4) A method for producing a resin composition, comprising a step of continuously melt-mixing and molding a resin masterbatch and a thermoplastic resin for dilution in a molding machine, wherein the resin masterbatch comprises (A) a cellulose material, (B) an acid-modified polypropylene, and (C)' a thermoplastic resin, the (A) cellulose material having a kappa number of 30 or less, and the content of the (A) cellulose material in 100 parts by mass of the resin masterbatch being 25 to 55 parts by mass.

[0011] According to the present invention, it is possible to provide a resin masterbatch that has a small degree of coloring, allows for toning to a bright color tone, and enables the production of a molded product with excellent mechanical properties. Furthermore, according to the present invention, it is possible to provide a method for producing a resin composition using the resin masterbatch, which does not require the application of a strong shear force.

[0012] The present invention will be described in detail below. In the present invention, "to" includes the end values. That is, "X to Y" includes the values ​​X and Y at both ends.

[0013] (Resin Masterbatch) The present invention relates to a resin masterbatch containing (A) a cellulose material, (B) an acid-modified polypropylene, and (C) a thermoplastic resin, wherein the (A) cellulose material has a kappa number of 30 or less, and the (C) thermoplastic resin has a melting point of less than 100°C and a Charpy impact strength of 30 kJ / m ２ The resin masterbatch is pressed at 150° C., 0.5 MPa, and for 1 minute to obtain a molded body having a brightness of 29 or more.

[0014] (Lightness) From the viewpoint of coloring flexibility, the lightness of a molded body obtained by pressing 0.1 g of the resin masterbatch of the present invention under conditions of 150°C, 0.5 MPa, and 1 minute is 29 or more, and preferably 30 to 100. If the lightness of the molded body is too lower than the above lower limit, the desired hue may not be obtained when a pigment or the like is added. The lightness can be determined as the L value, for example, by using a spectrophotometer on the surface of the molded body. The higher the lightness value, the closer to white the body is. The thickness of the molded body obtained by pressing is not particularly limited as long as light does not bleed through during lightness measurement, but it is preferably 1 mm or more.

[0015] (A) Cellulose Material The cellulose material (A) used in the present invention must have a kappa number of 30 or less from the viewpoint of whiteness. Furthermore, the kappa number is preferably 25 or less, and more preferably 20 or less. Generally, the lower the kappa number, the more bleached the material is. While there is no particular lower limit, the kappa number is 0 or more. The kappa number is an index of lignin content, and by keeping the kappa number within the above range, discoloration is suppressed when the material is molded into a molded product. In this specification, the kappa number can be determined in accordance with JIS P 8211.

[0016] The (A) cellulose material used in the present invention can be obtained by pulping a pulp raw material. The pulp raw material may be either wood or non-wood. Examples of wood raw materials used to produce wood pulp include softwood and hardwood. Examples of non-wood raw materials used to produce non-wood pulp include cotton, hemp, sisal, Manila hemp, flax, straw, bamboo, bagasse, and kenaf. The kappa number can be adjusted by delignifying or bleaching the pulp raw material that is the source of the cellulose material.

[0017] The method for pulping wood raw materials is not particularly limited, and examples include pulping methods commonly used in the papermaking industry. Wood pulp can be classified by pulping method, and examples include chemical pulp prepared by methods such as the kraft method, sulfite method, soda method, and polysulfide method; mechanical pulp (TMP) obtained by pulping using mechanical force such as a refiner or grinder; semi-chemical pulp obtained by chemical pretreatment followed by mechanical pulping; recycled paper pulp; and deinked pulp.

[0018] The cellulose material (A) used in the present invention may be used in an unmodified state, or may be chemically modified by acetylation, oxidation, esterification, etherification, or the like.

[0019] From the viewpoints of productivity and suppression of discoloration, the content of the cellulose material (A) in 100 parts by mass of the resin masterbatch is preferably 25 to 55 parts by mass, and more preferably 28 to 52 parts by mass. If the content of the cellulose material is too high, discoloration may occur due to frictional heat, and conversely, if the content is too low, it may not contribute to improving productivity.

[0020] (B) Acid-Modified Polypropylene Examples of the acid-modified polypropylene used in the present invention include maleic anhydride-modified polypropylene and acrylic acid-modified polypropylene. Although there are no particular limitations, it is preferable to use the commonly used maleic anhydride-modified polypropylene.

[0021] Acid-modified polypropylene functions as a compatibilizing resin. A compatibilizing resin enhances the uniform mixing and adhesion between cellulose materials with different hydrophobicities and the diluent thermoplastic resin described below. Factors determining the characteristics of a compatibilizing resin include, for example, the amount of dicarboxylic acid added and the weight-average molecular weight of the base polyolefin resin in the case of maleic anhydride-modified polyolefin. Polyolefin resins with a high amount of dicarboxylic acid added enhance compatibility with hydrophilic polymers such as cellulose, but the molecular weight of the resin decreases during the addition process, resulting in reduced strength of the molded product. The optimal balance for the amount of dicarboxylic acid added is 20 to 100 mg KOH / g, more preferably 45 to 65 mg KOH / g. A low addition amount reduces the number of points in the resin where the hydroxyl groups of cellulose, the hydroxyl groups contained in the modified cellulose, and the modified functional groups interact. Furthermore, a high addition amount can lead to self-aggregation due to hydrogen bonding between carboxyl groups in the resin, or a reduction in the molecular weight of the base olefin resin due to excessive addition reactions, resulting in insufficient strength as a reinforced resin. The molecular weight of the polyolefin resin is preferably 35,000 to 250,000, and more preferably 50,000 to 100,000. If the molecular weight is below this range, the strength of the resin will decrease, while if it is above this range, the viscosity will increase significantly when melted, which will decrease workability during kneading and cause molding defects.

[0022] The amount of (B) acid-modified polypropylene is not particularly limited, but is preferably 6 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 12 parts by mass or more, per 100 parts by mass of (A) cellulose material. The upper limit is preferably 80 parts by mass or less, more preferably 60 parts by mass or less. If the amount exceeds 100 parts by mass, the amount exceeds the amount necessary to form an interface between the cellulose and the resin, and it is thought that the strength of the composite will decrease.

[0023] (C) Thermoplastic Resin The (C) thermoplastic resin contained in the resin masterbatch of the present invention has a melting point of less than 100°C, preferably 15 to 95°C, more preferably 15 to 90°C, even more preferably 20 to 85°C, and even more preferably 25 to 75°C, so as to suppress damage to the cellulose fibers, even taking into account the temperature rise due to frictional heat during kneading. In this specification, the melting point of the (C) thermoplastic resin is the melting point derived from the endothermic peak when the temperature is increased at 5°C / min under a nitrogen atmosphere using a differential scanning calorimeter (DSC). If the melting point is too high above the upper limit, the fibers may be damaged by frictional heat during melt kneading. Conversely, if the melting point is too low, the masterbatches may be more likely to adhere to each other.

[0024] The thermoplastic resin (C) has a Charpy impact strength of 30 kJ / m in order to improve the impact strength of the final resin composition. ２ or more, 32 kJ / m ２ More preferably, it is 35 kJ / m or more. ２ It is more preferable that the Charpy impact strength is equal to or greater than the above lower limit. If the Charpy impact strength is lower than the above lower limit, the impact strength of the final resin composition may be low. In this specification, the Charpy impact strength is determined by performing an impact test on a notched test piece based on JIS K 7111-1.

[0025] The thermoplastic resin (C) that can be used in the present invention is not particularly limited as long as the melting point and Charpy impact strength are within the above-mentioned ranges, and examples thereof include olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers.

[0026] Examples of olefin-based thermoplastic elastomers include EPR (ethylene-propylene copolymer), ethylene-butene copolymer, ethylene-octene copolymer, polyethylene homopolymer, modified ethylene-butene copolymer, EEA (ethylene-ethyl acrylate copolymer), modified EEA, modified EPR, modified EPDM (ethylene-propylene-diene terpolymer), ionomer, α-olefin copolymer, modified IR (isoprene rubber), modified SEBS (styrene-ethylene-butylene-styrene copolymer), halogenated isobutylene-paramethylstyrene copolymer, ethylene-acrylic acid modified product, ethylene-vinyl acetate copolymer, and acid-modified product thereof, and mixtures containing these as main components. These may be used alone or in combination of two or more. From the viewpoint of compatibility with polypropylene-based resins, ethylene-octene copolymer and ethylene-propylene copolymer are preferred.

[0027] Examples of styrene-based thermoplastic elastomers include block copolymers such as styrene-butadiene-styrene (SBS) copolymer, styrene-isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer, styrene-ethylene-propylene-styrene (SEPS) copolymer, and styrene-butadiene-butylene-styrene (SBBS) copolymer. These may be used alone or in combination of two or more.

[0028] Preferred thermoplastic elastomers for use in the present invention include ethylene-octene copolymers, ethylene-propylene copolymers, and styrene-butadiene block copolymers. Ethylene-octene copolymers are particularly preferred. The thermoplastic elastomers may be modified with maleic anhydride, fumaric anhydride, or the like. In the styrene-butadiene block copolymers, the styrene content is preferably 15 to 30% by mass.

[0029] The content of the thermoplastic resin (C) in 100 parts by mass of the resin masterbatch is preferably 20 to 65 parts by mass, more preferably 30 to 64 parts by mass, in order to achieve both productivity and suppression of damage to the fibers. If the content of the thermoplastic resin is too high, productivity may decrease, and conversely, if it is too low, damage to the fibers may occur.

[0030] The resin masterbatch of the present invention may further contain an antioxidant. Examples of the antioxidant that can be used include a thioether-based antioxidant and a hindered phenol-based antioxidant, and an example of the hindered phenol-based antioxidant is Irganox 1010 manufactured by BASF Japan Ltd.

[0031] (Method for Producing Resin Masterbatch) The method for producing the resin masterbatch of the present invention is not particularly limited. For example, the resin masterbatch can be obtained by kneading (A) a cellulose material, (B) an acid-modified polypropylene, (C) a thermoplastic resin, and secondary materials such as an antioxidant that are used as needed.

[0032] As the kneading device, it is preferable to use a single-screw or multi-screw kneader (extruder). In order to be able to melt-knead (A) the cellulose material, (B) the acid-modified polypropylene, and (C) the thermoplastic resin, and also to have a strong kneading force that promotes nano-pulp formation, multi-screw kneaders (extruders) such as twin-screw kneaders (extruders) and four-screw kneaders (extruders) are preferably configured to include multiple kneaders, rotors, etc. in the parts that make up the screws.

[0033] The temperature set during kneading is preferably 160°C or less, more preferably 50 to 150°C, from the viewpoint of suppressing damage to the fibers.

[0034] (Method for producing resin composition) The method for producing a resin composition of the present invention includes a step of continuously melt-mixing and molding a resin masterbatch and a thermoplastic resin for dilution in a molding machine, wherein the resin masterbatch includes (A) a cellulose material, (B) an acid-modified polypropylene, and (C)' a thermoplastic resin, wherein the (A) cellulose material has a kappa number of 30 or less, and the content of the (A) cellulose material in 100 parts by mass of the resin masterbatch is 25 to 55 parts by mass.

[0035] The (A) cellulose material contained in the resin masterbatch used in the production method of the present invention has a kappa number of not more than 30, preferably not more than 25, and more preferably not more than 20. As the (A) cellulose material, those exemplified in the description of the resin masterbatch of the present invention can be used.

[0036] As the acid-modified polypropylene (B) contained in the resin masterbatch used in the production method of the present invention, those exemplified in the explanation of the resin masterbatch of the present invention can be used.

[0037] The thermoplastic resin (C)' contained in the resin masterbatch used in the production method of the present invention is not limited to the thermoplastic resin (C) exemplified in the description of the resin masterbatch of the present invention, as long as it can be continuously melt-mixed and molded together with the diluent thermoplastic resin using a molding machine without applying strong shear force. For example, an olefin-based thermoplastic elastomer, a styrene-based thermoplastic elastomer, etc. can be used. Note that the thermoplastic resin (C)' used in the production method of the present invention may also be the thermoplastic resin (C) exemplified in the description of the resin masterbatch of the present invention.

[0038] Examples of olefin-based thermoplastic elastomers include EPR (ethylene-propylene copolymer), ethylene-butene copolymer, ethylene-octene copolymer, polyethylene homopolymer, modified ethylene-butene copolymer, EEA (ethylene-ethyl acrylate copolymer), modified EEA, modified EPR, modified EPDM (ethylene-propylene-diene terpolymer), ionomer, α-olefin copolymer, modified IR (isoprene rubber), modified SEBS (styrene-ethylene-butylene-styrene copolymer), halogenated isobutylene-paramethylstyrene copolymer, ethylene-acrylic acid modified product, ethylene-vinyl acetate copolymer, and acid-modified product thereof, and mixtures containing these as main components. These may be used alone or in combination of two or more. From the viewpoint of compatibility with polypropylene-based resins, ethylene-octene copolymer and ethylene-propylene copolymer are preferred.

[0039] Examples of styrene-based thermoplastic elastomers include block copolymers such as styrene-butadiene-styrene (SBS) copolymer, styrene-isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer, styrene-ethylene-propylene-styrene (SEPS) copolymer, and styrene-butadiene-butylene-styrene (SBBS) copolymer. These may be used alone or in combination of two or more.

[0040] Preferred thermoplastic elastomers for use in the production method of the present invention include ethylene-octene copolymers, ethylene-propylene copolymers, and styrene-butadiene block copolymers. Ethylene-octene copolymers are particularly preferred. The thermoplastic elastomers may also be modified with maleic anhydride, fumaric anhydride, or the like. In the styrene-butadiene block copolymers, the styrene content is preferably 15 to 30% by mass.

[0041] The resin masterbatch used in the production method for a resin composition of the present invention must contain 25 to 55 parts by mass of cellulose material per 100 parts by mass of the resin masterbatch, preferably 27 to 52 parts by mass, and more preferably 30 to 50 parts by mass. If the content of cellulose material is too high, there is a risk of damage to the fibers due to frictional heat, and conversely, if the content is too low, there is a risk of reduced productivity. As the resin masterbatch used in the production method of the present invention, it is preferable to use the resin masterbatch described above.

[0042] (Thermoplastic Resin for Dilution) Examples of the thermoplastic resin for dilution used in the present invention include the following general thermoplastic resins having a melting temperature of 250°C or less. The thermoplastic resin for dilution may be used alone or in combination of two or more resins. From the viewpoint of adjusting physical properties, it is preferable to use, as the thermoplastic resin for dilution, the following general thermoplastic resin in combination with a (C)' thermoplastic resin, preferably a thermoplastic elastomer, contained in the resin masterbatch.

[0043] Common thermoplastic resins that can be used include polyolefin resins, polyamide resins, polyvinyl chloride, polystyrene, polyvinylidene chloride, fluororesins, (meth)acrylic resins, polyesters, polylactic acid, copolymer resins of lactic acid and esters, polyglycolic acid, acrylonitrile-butadiene-styrene copolymers (ABS resins), polyphenylene oxide, polyurethanes, polyacetals, vinyl ether resins, polysulfone resins, and cellulose resins (such as triacetylated cellulose and diacetylated cellulose).

[0044] As the polyolefin resin, polyethylene, polypropylene (hereinafter also referred to as "PP"), ethylene-propylene copolymer, polyisobutylene, polyisoprene, polybutadiene, polymethylpentene (hereinafter also referred to as "PMP"), etc. can be used.

[0045] Polyamide resins (PA) are also expected to interact with the hydroxyl groups of cellulose and are therefore suitable for use. Examples of PA include aliphatic PAs such as polyamide 6 (nylon 6, PA6), polyamide 11 (nylon 11, PA11), polyamide 12 (nylon 12, PA12), polyamide 66 (nylon 66, PA66), polyamide 46 (nylon 46, PA46), polyamide 610 (nylon 610, PA610), and polyamide 612 (nylon 612, PA612), as well as aromatic PAs composed of aromatic diamines such as phenylenediamine and aromatic dicarboxylic acids such as terephthaloyl chloride or isophthaloyl chloride, or derivatives thereof. From the viewpoint of high affinity with cellulose fibers and cellulose nanofibers, aliphatic PAs are preferred, with PA6, PA11, and PA12 being more preferred, and PA6 being particularly preferred. Furthermore, one type of polyamide resin may be used alone, or two or more types of polyamide resins may be used in combination.

[0046] The resins exemplified above can be used as homopolymers or as block copolymers containing resins having various known functions in a half amount or less.

[0047] The content of a general thermoplastic resin such as a polyolefin resin or a polyamide resin in 100 parts by mass of the resin composition is preferably 10 to 95 parts by mass, more preferably 15 to 85 parts by mass, from the viewpoint of moldability.

[0048] The total amount of the (C)' thermoplastic resins in the resin composition relative to 100 parts by mass of a general thermoplastic resin such as a polyolefin resin or a polyamide resin is preferably 5 to 70 parts by mass, and more preferably 10 to 65 parts by mass. From the viewpoint of enabling continuous melt mixing and molding using an injection molding machine or the like without requiring a kneading process using a strong shear force using a twin-screw kneader (extruder) or the like, the total amount of the (C)' thermoplastic resins in the resin composition relative to 100 parts by mass of the (A) cellulose material is preferably 15 to 400 parts by mass, and more preferably 25 to 350 parts by mass.

[0049] (Process for Continuous Melt-Mixing and Molding) In this process, for example, a mixture of a resin masterbatch, a general thermoplastic resin as a diluting thermoplastic resin, and the (C)' thermoplastic resin as a diluting thermoplastic resin, all in the form of pellets, is shaken and charged into a molding machine such as an injection molding machine, and the mixture is melted and liquefied in the heating cylinder of the molding machine.The screw built into the cylinder is then rotated, and the molten resin is injected into, for example, a mold, and cooled to obtain a molded resin composition.

[0050] Examples of molding machines that can be used in this step include injection molding machines, extrusion molding machines, and blow molding machines.

[0051] When using a molding machine such as an injection molding machine, the cylinder temperature and molding temperature are preferably set to the recommended molding temperature of the dilution thermoplastic resin, or if there are multiple dilution thermoplastic resins, to the highest temperature among them.

[0052] In the method for producing a resin composition of the present invention, additives such as surfactants, polysaccharides such as starches and alginic acid, natural proteins such as gelatin, glue and casein, inorganic compounds such as tannin, zeolite, ceramics and metal powder, colorants, plasticizers, fragrances, pigments, flow control agents, leveling agents, conductive agents, antistatic agents, UV absorbers, UV dispersants, deodorants, antioxidants, etc. The blending ratio of any additive may be appropriately adjusted within a range that does not impair the effects of the present invention.

[0053] According to the present invention, a resin masterbatch can be provided that uses a cellulose material having a predetermined kappa number in a predetermined amount and contains a (C) thermoplastic resin, preferably a thermoplastic elastomer, having specific properties, thereby enabling a small degree of coloration, bright color toning, and enabling the production of molded articles with excellent mechanical properties such as tensile strength and flexural strength. Furthermore, according to the present invention, a specific amount of (C)' thermoplastic resin, preferably a thermoplastic elastomer, is blended with a specific cellulose material, so that a resin composition can be obtained by continuously melt-mixing and molding using a molding machine, without the need to apply strong shear force using a kneader.

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, unless the method for measuring / calculating each value in each example is specifically stated, it was measured / calculated by the method described in the specification.

[0055] (MB Fiber Ratio) The masterbatch (MB) fiber ratio indicates the mass ratio of pulp contained in the total mass of the resin masterbatch.

[0056] (Fiber ratio after dilution) The fiber ratio after dilution indicates the mass ratio of pulp contained in the total mass of the resin composition after blending the thermoplastic resin for dilution.

[0057] (Lightness) 0.1 g of the resin master batch obtained in each of the examples and comparative examples was pressed in a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd.) at 150°C, 0.5 MPa, and for 1 minute to produce a molded body with a thickness of 1.1 mm. The lightness (L value) of the obtained molded body was measured using a spectrophotometer (SE200, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 1. The higher the lightness value, the closer to white the resin is, i.e., the less colored the resin master batch is.

[0058] (Tensile Test) 200 g of a mixture of pellet-shaped resin master batches and diluting thermoplastic resins obtained in the Examples and Comparative Examples was placed in an injection molding machine ("NEX50-IV" manufactured by Nissei Plastic Industrial Co., Ltd.), and a dumbbell-shaped test piece (Type A1, JIS K 7139) was molded under conditions of a heating barrel (cylinder) temperature of 210°C and a mold temperature of 40°C. The elastic modulus, maximum stress, and strain to break of the obtained test piece were measured using a precision universal testing machine ("Autograph AG-Xplus" manufactured by Shimadzu Corporation) at a test speed of 20 mm / min and an initial gauge length of 50 mm. The results are shown in Table 1.

[0059] (Bending Test) 200 g of a mixture of pellet-shaped resin master batches and diluting thermoplastic resins obtained in the Examples and Comparative Examples was placed in an injection molding machine ("NEX50-IV" manufactured by Nissei Plastic Industrial Co., Ltd.), and a dumbbell-shaped test piece (Type A1, JIS K 7139) was molded under conditions of a heating barrel (cylinder) temperature of 210°C and a mold temperature of 40°C. The elastic modulus and maximum stress of the obtained test piece were measured using a precision universal testing machine ("Autograph AG-Xplus" manufactured by Shimadzu Corporation) at a test speed of 2 mm / min and a support distance of 64 mm. The results are shown in Table 1.

[0060] (Impact Test) Based on JIS K 7111-1, an impact test was carried out on a notched test piece to determine the Charpy impact strength.

[0061] (Density) The density of the resin compositions obtained in the examples and comparative examples was measured using a dry automatic density meter, Accupyc II 1340-10CC (manufactured by Shimadzu Corporation).

[0062] (Materials used in Examples and Comparative Examples) Various cellulose materials: Hardwood bleached kraft pulp (LBKP, kappa number: 11.3) Softwood bleached kraft pulp (NBKP, kappa number: 15) Softwood unbleached kraft pulp (NUKP, kappa number: 62.7) The kappa number of the pulp is a value measured in accordance with JIS P 8211. Acid-modified polypropylene: maleic anhydride modified polypropylene (MAPP), manufactured by Toyobo Co., Ltd., H1000P Antioxidant: Irganox 1010 manufactured by BASF Thermoplastic resin for masterbatch (MB) / thermoplastic resin for dilution: Polyolefin elastomer: ethylene-octene copolymer (EOC), manufactured by The Dow Chemical Company, Engage 8200, melting point: 48°C, Charpy impact strength: 40 kJ / m ２The above (The melting point of EOC is the melting point derived from the endothermic peak in differential thermal analysis when the temperature is increased at 5°C / min under a nitrogen atmosphere.) Thermoplastic resin for masterbatch (MB): Hydrogenated styrene-based plastic elastomer (styrene-ethylene-butylene-styrene copolymer, SEBS): manufactured by Asahi Kasei Corporation, Tuftec H1041, styrene content: 30 mass%, melting point: 26°C, Charpy impact strength: 40 kJ / m ２ The above (The melting point of SEBS is the melting point derived from the endothermic peak in differential thermal analysis when the temperature is increased at 5°C / min under a nitrogen atmosphere.) Thermoplastic resins for dilution: Homopolypropylene (hPP): J108M, manufactured by Prime Polymer Co., Ltd. Polymethylpentene (PMP): TPX (registered trademark), RT18, manufactured by Mitsui Chemicals, Inc.

[0063] Example 1 Production of Resin Masterbatch Sheet-shaped LBKP (kappa number: 11.3) was dried and crushed using a Henschel mixer. 1.7 parts by mass of MAPP as acid-modified polypropylene and 0.3 parts by mass of an antioxidant were placed in a polyethylene bag and mixed by shaking. 10 parts by mass of dried and crushed LBKP, the entire mixture of MAPP and antioxidant, and 21.3 parts by mass of ethylene-octene copolymer (EOC) as a thermoplastic resin for MB were charged into a twin-screw kneader (manufactured by Technovel Corporation: screw diameter φ15 mm, L / D 45 (L / D is the ratio of the screw length (L) to the screw diameter (D)), rotors used at three locations in the screw configuration) using a feeder attached to the kneader, and kneaded at a temperature set to 160°C to produce a pellet-shaped resin masterbatch (hereinafter also simply referred to as "MB") containing LBKP, MAPP, antioxidant, and a thermoplastic resin for MB.

[0064] (Production of Resin Composition) The entire amount of the obtained resin masterbatch, 61 parts by mass of homopolypropylene as a diluting thermoplastic resin, and 5.7 parts by mass of ethylene-octene copolymer (EOC) were mixed in the form of pellets, and the mixture was directly charged into an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., 50 t), and melt-mixed and injection-molded continuously at a temperature set at 210°C to obtain a test piece (resin composition).

[0065] (Example 2) A resin masterbatch was produced in the same manner as in Example 1, except that in the production of the resin masterbatch, the blending amount of EOC as the thermoplastic resin for MB was changed to 8 parts by mass. A test piece (resin composition) was obtained in the same manner as in Example 1, except that the obtained resin masterbatch was used and the blending amount of EOC as the thermoplastic resin for dilution was changed to 19 parts by mass.

[0066] (Example 3) A resin masterbatch was produced in the same manner as in Example 1, except that NBKP (kappa number: 15) was used instead of LBKP in the production of the resin masterbatch, and the amount of EOC used as the thermoplastic resin for MB was changed to 8 parts by mass. A test piece (resin composition) was obtained in the same manner as in Example 1, except that the obtained resin masterbatch was used and the amount of EOC used as the thermoplastic resin for dilution was changed to 19 parts by mass.

[0067] (Example 4) (Production of Resin Masterbatch) A resin masterbatch was produced in the same manner as in Example 1, except that the blending amount of acid-modified polypropylene (MAPP) was changed to 2.5 parts by mass, the blending amount of antioxidant was changed to 0.5 parts by mass, and the blending amount of LBKP was changed to 15 parts by mass, and that 15 parts by mass of hydrogenated styrenic thermoplastic elastomer (SEBS) was used instead of 21.3 parts by mass of EOC as the thermoplastic resin for MB.

[0068] (Production of Resin Composition) The entire amount of the obtained resin master batch and 67 parts by mass of polymethylpentene (PMP) as a diluting thermoplastic resin were mixed in the form of pellets, and the mixture was directly charged into an injection molding machine. A test piece (resin composition) was obtained in the same manner as in Example 1.

[0069] Example 5 A resin masterbatch was produced in the same manner as in Example 4, except that in the production of the resin masterbatch, the blending amount of hydrogenated styrene thermoplastic elastomer (SEBS) as the thermoplastic resin for MB was set to 25 parts by mass. A test piece (resin composition) was obtained in the same manner as in Example 4, except that the obtained resin masterbatch was used and the blending amount of polymethylpentene (PMP) as the thermoplastic resin for dilution was set to 57 parts by mass.

[0070] Comparative Example 1 A resin masterbatch was produced in the same manner as in Example 1, except that NUKP (kappa number: 62.7) was used instead of LBKP and the amount of EOC used as the thermoplastic resin for MB was changed to 8 parts by mass in the production of the resin masterbatch. A test piece (resin composition) was obtained in the same manner as in Example 1, except that the obtained resin masterbatch was used and the amount of EOC used as the thermoplastic resin for dilution was changed to 19 parts by mass.

[0071] Comparative Example 2 A resin masterbatch was produced in the same manner as in Example 1, except that the blending amount of EOC as the thermoplastic resin for MB was changed to 4.7 parts by mass in the production of the resin masterbatch. A test piece (resin composition) was obtained in the same manner as in Example 1, except that the obtained resin masterbatch was used and the blending amount of EOC as the thermoplastic resin for dilution was changed to 22.3 parts by mass.

[0072]

[0073] As can be seen from Table 1, in Examples 1 to 5, a cellulose material having a kappa number of 30 or less, an acid-modified polypropylene, and a polyethylene terephthalate (PE) having a melting point of less than 100°C and a Charpy impact strength of 30 kJ / m ２ A resin masterbatch containing the above thermoplastic resin was obtained, and the molded body obtained by pressing this resin masterbatch under conditions of 150°C, 0.5 MPa, and 1 minute had a brightness of 29 or more and was little discolored.

[0074] In Comparative Example 1, pulp with a high kappa number, i.e., a high lignin content, was used, and therefore the molded body obtained by pressing the resin masterbatch had a brightness of less than 29 and was heavily discolored. Furthermore, compared with Examples 2 and 3, which had the same MB fiber ratio, the resin composition obtained after dilution had inferior breaking strain characteristics in a tensile test.

[0075] In Comparative Example 2, the MB fiber content was higher than in Examples 1 and 2, which used the same type of cellulose material, and the molded body obtained by pressing the resin masterbatch had a brightness of less than 29 and was significantly discolored. Furthermore, the resin composition obtained after dilution was inferior in maximum stress and breaking strain in a tensile test, and in maximum stress in a bending test.

Claims

1. A resin master batch comprising (A) a cellulose material, (B) an acid-modified polypropylene, and (C) a thermoplastic resin, wherein the cellulose material (A) has a kappa number of 30 or less, and the thermoplastic resin (C) has a melting point of less than 100°C and a Charpy impact strength of 30 kJ / m ２ and a molded product obtained by pressing the resin masterbatch under conditions of 150° C., 0.5 MPa, and 1 minute has a lightness of 29 or more.

2. The resin master batch according to claim 1, wherein the content of the (A) cellulose material is 25 to 55 parts by mass and the content of the (C) thermoplastic resin is 20 to 65 parts by mass, per 100 parts by mass of the resin master batch.

3. The resin master batch according to claim 1, wherein the amount of the acid-modified polypropylene (B) per 100 parts by mass of the cellulose material (A) is 6 parts by mass or more.

4. A method for producing a resin composition, comprising a step of continuously melt-mixing and molding a resin master batch and a thermoplastic resin for dilution in a molding machine, wherein the resin master batch comprises (A) a cellulose material, (B) an acid-modified polypropylene, and (C)' a thermoplastic resin, the (A) cellulose material having a kappa number of 30 or less, and the content of the (A) cellulose material in 100 parts by mass of the resin master batch is 25 to 55 parts by mass.