JP6870400B2 - Resin composition and molded article - Google Patents

Description

The present invention relates to resin compositions and molded articles. More specifically, the present invention relates to a molded product having excellent thermal conductivity that can be suitably used for building materials and housing applications, and a resin composition for obtaining the molded product.

In recent years, the use of unused energy such as geothermal energy has been progressing from the viewpoints of responding to global environmental conservation and utilizing unused energy. For example, Patent Document 1 comprises a geothermal heat exchanger in which a flow path is formed by heat collection and heat dissipation pipes to utilize geothermal heat, and a heat pump connected to the geothermal heat exchanger. A geothermal heat pump is disclosed in which a geothermal heat exchanger is buried in the ground to exchange heat in the ground. In the geothermal heat pump, the piping is coated with a porous foamed polyethylene or styrofoam or a cushioning tape as a heat insulating material in order to improve the thermal efficiency. However, since the pipe is made of polyethylene or polybutylene, there is a problem that the thermal conductivity is low and the heat loss is large. Patent Documents 2 and 3 disclose pipes in which carbon fibers and carbon nanofibers are blended with resin to increase the thermal conductivity of the pipes, but carbon fibers are widely used in large quantities due to their high price. It is not suitable for infrastructure related applications. Further, when inexpensive graphite is used, since bending physical properties are low by itself, an inorganic filler such as glass fiber or talc is required as a physical property enhancer. (Patent Document 4)

On the other hand, in recent years, research on a technique for using relatively inexpensive plant fiber (hereinafter, also referred to as cellulose fiber) as a reinforcing material for a thermoplastic resin has been advanced (Patent Document 5). Plant fibers are inexpensive and have a low environmental impact because they are used by loosening the fine fibers of plants, rather than artificially synthesizing them into fibers like carbon fibers and glass fibers. There are advantages. In addition, glass fiber remains as ash when incinerated, and there is concern about health damage to humans and organisms, but since plant fiber hardly remains as ash, there are no problems such as health damage or landfill treatment, and it is environmentally friendly. It is attracting attention as a material that does not give a load.

Japanese Unexamined Patent Publication No. 2001-289533 Japanese Unexamined Patent Publication No. 2004-198098 Japanese Unexamined Patent Publication No. 2010-190471 Japanese Unexamined Patent Publication No. 2015-193735 Japanese Unexamined Patent Publication No. 2014-193959

The graphite-only pipe containing no reinforcing material has a problem of insufficient mechanical strength. Further, the pipe using carbon fiber has a problem that the thermal conductivity is insufficient, and also has a problem that it is not suitable for practical use because it is expensive. Further, when low-density polyolefin is added, there is a problem that bending strength and elastic modulus are insufficient, and it is necessary to include an inorganic reinforcing material such as glass fiber or mica. However, the resin composition using the glass fiber has a problem that the thermal conductivity is low, the dispersion is liable to be poor, and the glass fiber is crushed during kneading to obtain the desired physical properties.

An object of the present invention is to provide a resin composition and a molded product having good thermal conductivity and molding processability and capable of forming a molded product having good mechanical strength.

The present inventor has completed the present invention as a result of diligent studies to solve the above problems. That is, the present invention contains a cellulose fiber (A) having an average fiber diameter of 10 to 3000 nm, a graphite (B) having an average particle size of 50 to 150 μm, and a polyolefin resin (C), and the cellulose fiber (A) is used as a resin composition. The present invention relates to a resin composition containing 1 to 30% by mass in 100% by mass and 5 to 30% by mass of graphite (B) in 100% by mass of the resin composition.

The present invention also relates to the above resin composition, wherein the total amount of the cellulose fibers (A) and graphite (B) is 6 to 45% by mass in 100% by mass of the resin composition.

Further, the present invention is a polyolefin resin (C) comprises a density 930 kg / m ³ of less than the polyolefin resin (D) and the density 930 kg / m ³ or more of the polyolefin resin (E), about the resin composition.

The present invention also relates to the above resin composition containing 10 to 40% by mass of the polyolefin resin (D) and 30 to 84% by mass of the polyolefin resin (E) in 100% by mass of the resin composition.

The present invention also relates to a molded product obtained by molding the above resin composition.

INDUSTRIAL APPLICABILITY According to the present invention, it has become possible to provide a resin composition and a molded product capable of forming a molded product having good thermal conductivity and mechanical strength.

The resin composition of the present invention contains cellulose fibers (A) having an average fiber diameter of 10 to 3000 nm, graphite (B) having an average particle diameter of 50 to 150 μm, and a polyolefin resin (C).

<Cellulose fiber (A)>
Cellulose is a carbohydrate represented by the molecular formula (C ₆ H ₁₀ O ₅ ) _n , but unlike the cellulose fiber (A) referred to in the present specification, it is difficult to use a solvent. It refers to fibrous cellulose having an average dissolved fiber diameter of 10 to 3000 nm.

The cellulose fiber (A) has an average fiber diameter of 10 to 3000 nm, preferably 10 to 1000 nm, more preferably 100 to 500 nm, and even more preferably 100 to 300 nm. When the average particle size is 10 nm or more, a network structure between cellulose fibers can be easily formed, the flexural modulus of the molded product can be improved, and the surface of the molded product can be made smoother. Further, when the average particle size is 3000 nm or less, the number of fibers per weight is increased and the mechanical properties are excellent. When the surface of the molded product is smooth, the appearance is excellent, so that it can be suitably used for applications that are visible to the human eye, such as personal computers, mobile phones, and indoor units of air conditioners.

The aspect ratio of the cellulose fiber (A) is preferably 30 to 10000, more preferably 50 to 5000, and even more preferably 50 to 1000. The aspect ratio is a value obtained by dividing the average fiber length by the average fiber diameter.
Within the above range, the cellulose fibers can be easily dispersed, and performances such as good appearance and improved mechanical properties are likely to be exhibited. The average fiber length and the average fiber diameter are the average values of 10 arbitrary cellulose fibers observed with an electron microscope.

In order to produce the cellulose fiber (A), it is generally solved by grinding and / or beating the cellulose fiber-containing material with a refiner, a high-pressure homogenizer, a medium stirring mill, a millstone, a grinder, a twin-screw extruder, or the like. Manufactured as fiber or finely divided. It can also be produced using microorganisms (for example, acetic acid bacteria (Acetobacter)). Furthermore, it is also possible to use a commercially available product. Examples of the raw material of the cellulose fiber (A) include plants (for example, wood made of hardwood and conifer, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp, recycled pulp, corn, waste paper). In particular, a method of defibrating pulp produced from recycled paper or wood with a high-pressure homogenizer or a twin-screw extruder is preferable because it is inexpensive, has less fiber agglutination, and can be defibrated. In particular, when defibrating to the nano level, it is preferable to defibrate in stages by using the above device a plurality of times, and when increasing the fiber diameter, it can be adjusted by reducing the number of times the device is used.

The cellulose fiber (A) in the present invention may contain lignin. Lignin is a high molecular weight phenolic compound contained in plants. Cellulose fibers containing lignin are sometimes called lignocellulose.

The cellulose fiber (A) in the present invention preferably contains 1 to 30% by mass, more preferably 5 to 20% by mass, in 100% by mass of the resin composition. Within the above range, the cellulose fibers are easily dispersed, and performances such as good appearance and improved mechanical properties are likely to be exhibited.

The cellulose fiber (A) may be one in which a carboxyl group in which the hydroxyl group on the surface of the cellulose fiber is partially modified is introduced. As a method for introducing a carboxyl group into a cellulose fiber, a cellulose fiber, a compound having a carboxyl group, an acid anhydride of a compound having a carboxyl group, an acid imide of a compound having a carboxyl group, or a derivative of a compound having a carboxyl group can be used. Examples thereof include a method of reacting with and a method of oxidizing the hydroxyl group of cellulose.

The derivative of the compound having a carboxyl group is not particularly limited, and examples thereof include an acid anhydride of the compound having a carboxyl group, an acid imide, a derivative of a compound having a carboxyl group such as an acid halide and an ester.

Examples of the acid anhydride of the compound having a carboxyl group include dimethylmaleic anhydride, diethylmalic anhydride, diphenylmaleic anhydride and the like.
Examples of the acid imide of the compound having a carboxyl group include imides of dicarboxylic acids such as maleimide, succinate imide, and phthalate imide.
Examples of the acid halide of the compound having a carboxyl group include acetate halides such as chloroacetic acid and bromoacetic acid.

On the other hand, examples of the method of oxidizing the hydroxyl group of cellulose include a method of using an N-oxyl compound as an oxidation catalyst and allowing an copolymer to act (TEMPO oxidation), a method of irradiating with ultraviolet rays, a corona discharge treatment and the like. Among these, TEMPO oxidation, which can oxidize hydroxyl groups without deteriorating cellulose fibers, is preferable.

In order to improve the affinity of the cellulose fiber (A) with the polyolefin resin, a surface treatment agent (for example, a silane compound) may be used to form a coating layer on the surface of the cellulose fiber (A).
Examples of the silane compound include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and N-β (aminoethyl) γ. -Amino group-containing silane coupling agent such as aminopropylmethyldimethoxysilane; γ-glycidyl group-containing silane coupling agent such as γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropylmethyldimethoxysilane; γ-mercaptopropyltri Mercapto group-containing silane coupling agent such as methoxysilane; vinyl group-containing silane coupling agent such as vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (methoxyethoxy) silane; γ- (meth) acryloyloxypropyltrimethoxysilane, Examples thereof include (meth) acryloyl group-containing silane coupling agents such as γ- (meth) acryloyloxypropyltriethoxysilane and γ- (meth) acryloyloxypropyldimethoxymethylsilane. Examples of alkoxysilanes include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, and n-. Examples thereof include propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, and trifluoropropyltrimethoxysilane. When the silane compound is reacted, it is preferable to introduce an oxidation or carboxyl group in advance because the silane compound facilitates the introduction of an organic substituent by oxidizing or acetylating the cellulose fiber. The surface treatment agent may be used alone or in combination of two or more.

For the formation of the coating layer, known methods such as a direct treatment method (for example, a dry method, a slurry method, a spray method, etc.), an integral blend method (for example, a direct method, a masterbatch method, etc.), a dry concentrate method, and the like can be used. .. Further, a method of adding a surface treatment agent in the defibration process in water, which is the production process of the cellulose fiber (A), can be adopted.

Since the cellulose fiber (A) is generally defibrated while using water, it is in a state of being dispersed in water immediately after defibration. However, since the temperature is often 100 ° C. or higher during melt-kneading with a resin, it is preferable to use powdered cellulose fibers in a state where water has been removed. Examples of the powdered cellulose fiber include a dried product obtained by drying the aqueous dispersion of the cellulose fiber as it is, a powder obtained by mechanically treating the dried product, and a non-aqueous solvent such as acetone and alcohol for the aqueous dispersion of the cellulose fiber. The cellulose fibers are agglomerated by mixing with, and the agglomerates are dried, the aqueous dispersion of cellulose fibers is powdered by a known spray-drying method, and the aqueous dispersion of cellulose fibers is prepared by a known freeze-drying method. Examples include powdered ones. The spray-drying method is a method of spraying and drying an aqueous dispersion of cellulose nanofibers in the air. In particular, when the cellulose fibers are oxidized or have a carboxyl group introduced, a method of mixing with a non-aqueous solvent such as acetone or alcohol to aggregate the cellulose fibers and drying the aggregates is preferable. Examples of commercially available powdered cellulose fibers include KC Flock manufactured by Nippon Paper Chemicals Co., Ltd., Theoras manufactured by Asahi Kasei Chemicals Co., Ltd., and Abyssel manufactured by FMC Co., Ltd.

<Graphite (B)>
Graphite (B) has an average particle size of 50 to 150 μm, preferably 80 to 120 μm. Good thermal conductivity can be obtained when the average particle size is 50 μm or more. Further, when the average particle size is 150 μm or less, good mechanical properties can be obtained and the surface of the molded product can be smoothed. The average particle size is an average value of 10 maximum lengths of graphite particles observed with an electron microscope.

Graphite (B) is preferably contained in the resin composition in an amount of 5 to 30% by mass, more preferably 5 to 20% by mass.

As the graphite (B), scaly graphite, flaky graphite, pyrolyzed graphite, and graphite subjected to thermal expansion treatment (hereinafter, also referred to as expanded graphite) can be used, and they can be used alone or in combination of two or more. It is preferable to use expanded graphite or pyrolyzed graphite.

Expanded graphite refers to natural graphite such as scaly graphite, soil graphite, and massive graphite, which are naturally produced as minerals, and petroleum coke, petroleum pitch, amorphous carbon, etc., which are heat-treated at 2000 ° C or higher and have an irregular arrangement. It is graphite obtained by artificially orienting the micrographite crystals of No. 1 and subjecting it to chemical immersion or electrooxidation treatment. In chemical immersion, a graphite raw material is immersed in a large amount of concentrated sulfuric acid or the like, and an oxidizing agent such as concentrated nitric acid, potassium dichromate, ammonium peroxodisulfate, sodium peroxodisulfate, or hydrogen peroxide is added to treat graphite. This is a method in which an interlayer compound is formed, then washed with water, and then rapidly heated at 800 to 1000 ° C. to expand. The electrooxidation treatment method is a method in which a graphite raw material is treated in an electrolytic solution such as sulfuric acid, then washed with water, and then rapidly heated at 800 to 1000 ° C. to expand.
The graphite that has been pulverized after being subjected to the thermal expansion treatment in this way is the graphite that has been subjected to the thermal expansion treatment. The pulverization may be performed by pressurizing and compressing the graphite subjected to the thermal expansion treatment using a roll, a press or the like to form a sheet, and then pulverizing the graphite. It can be adjusted to any bulk density during pressure compression and pulverization. Examples of commercially available products include the expanded graphite EC series manufactured by Ito Graphite Industry Co., Ltd. On the other hand, pyrolysis graphite is graphite obtained by heat-treating powdered coke at 3000 ° C., graphitizing it, and then pulverizing it.

Graphite (B) is preferably a bulk density of 0.1 to 0.5 g / cm ^3, more preferably 0.15~0.2g / cm ^3. Moldability is further improved by setting the bulk density to 0.1 g / cm ^{3 or more.} Further, by reducing the bulk density to 0.4 g / cm ³ or less, the thermal conductivity is further improved. The bulk density is a numerical value measured in accordance with ASTM32990.

The graphite (B) has a specific surface area is preferably from 1 to 100 m ² / g, more preferably not more than ^{80m 2 / g, 40m 2 /} g or less is more preferred. By setting the specific surface area to 100 m ² / g or less, the dispersibility of graphite is further improved, and the smoothness of the molded product is further improved. The specific surface area is a numerical value measured according to ASTM3037-89.

In order to improve the affinity of graphite (B) with the polyolefin resin, a surface treatment agent (for example, the silane compound) may be used to form a coating layer on the surface of the graphite (B).

For the formation of the coating layer, known methods such as a direct treatment method (for example, a dry method, a slurry method, a spray method, etc.), an integral blend method (for example, a direct method, a masterbatch method, etc.), a dry concentrate method, and the like can be used. .. Of these, as a method capable of simple treatment, the direct treatment method is preferable, and the dry method is more preferable.

An example of the dry method may be described as a method in which graphite is mixed by dropping or spraying a surface treatment agent while stirring and mixing with a Henschel mixer, and heat treatment is performed if necessary. Since the graphite after forming the coating layer may aggregate, it is preferable to pulverize it with a ball mill or the like. It is also preferable to form the coating layer after diluting with an organic solvent such as alcohol when dropping or spraying the surface treatment agent.

The total amount of the cellulose fibers (A) and the graphite (B) is preferably 6 to 45% by mass, more preferably 15 to 30% by mass, based on 100% by mass of the resin composition. Within the above range, the dispersibility becomes simpler and the occurrence of lumps can be suppressed.

<Polyolefin resin (C)>
The polyolefin resin (C) preferably comprises a density 930 kg / m ³ of less than the polyolefin resin (D) and the density 930 kg / m ³ or more of the polyolefin resin (E). The density refers to a value measured in accordance with JIS K 7112. The polyolefin resin (D) / polyolefin resin (E) is preferably in the range of 1/99 to 50/50 (mass ratio), and more preferably in the range of 5/95 to 30/70. Further, it is preferable that the resin composition contains 10 to 40% by mass of the polyolefin resin (D) and 30 to 84% by mass of the polyolefin resin (E) in 100% by mass of the resin composition.

The polyolefin resin (D) includes linear low-density polyethylene resin, linear ultra-low-density polyethylene resin, polypropylene resin, ethylene-propylene copolymer, and copolymer of α-olefin and ethylene or propylene. It may be mentioned, and may be used alone or in combination of two or more. By using the polyolefin resin (D), the graphite (B) can be easily dispersed. Among these, linear low-density polyethylene and linear ultra-low-density polyethylene are preferable. The low density means 920 kg / m ³ or less, and the ultra-low density means 900 kg / m ³ or less.

The polyolefin resin (E) is, for example, a high-density polyethylene resin, a polypropylene resin, polybutene-1, poly-4-methylpentene, a random block or graft copolymer of ethylene-propylene, or a combination of α-olefin and ethylene or propylene. Examples thereof include polymers, which may be used alone or in combination of two or more. Among these, high-density polyethylene resin is preferable. The high density means that the density exceeds ^{930 g / m 3.}

As the polyolefin resin (C), a polar polyolefin resin obtained by modifying the polyolefin resin to impart polarity may be used, if necessary. This is because the cellulose fibers (A) and graphite (B) have polar groups (hydroxyl groups) on their surfaces, so that the polar polyolefin acts as a dispersant. Examples of the polar polyolefin resin include maleic acid-modified ethylene oligomers such as polyethylene oxide, montan wax, and maleic anhydride-modified ethylene oligomer that have been reacted with oxygen at high pressure and high temperature; ethylene-acrylic acid copolymer and ethylene-methacrylic acid. Unsaturated carboxylic acid-modified polyethylene resin such as polymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, maleic acid-modified polyethylene such as maleic anhydride-modified polyethylene; maleic anhydride-modified propylene oligomer, etc. Maleic acid-modified propylene oligomer; propylene-acrylic acid copolymer, propylene-methacrylic acid copolymer, propylene-acrylic acid ester copolymer, propylene-methacrylic acid ester copolymer, maleic acid such as maleic anhydride-modified polypropylene Examples thereof include unsaturated carboxylic acid-modified polypropylene-based resins such as modified polypropylene, and maleic acid-modified polyolefin-based resins such as maleic acid-modified polyethylene-based resin and maleic acid-modified polypropylene-based resin are preferable, and maleic anhydride-modified polyethylene-based resin and maleine anhydride are preferable. Maleic anhydride-modified polyolefin-based resins such as acid-modified polypropylene-based resins are more preferable. The maleic acid-modified polyethylene-based resin is obtained by graft-polymerizing maleic acid on the polyethylene-based resin, and the maleic acid-modified polypropylene-based resin is obtained by graft-polymerizing maleic acid on the polypropylene-based resin. Examples of the maleic anhydride-modified propylene include the Youmex series manufactured by Sanyo Chemical Industries, Ltd., and examples of the maleic acid-modified polyethylene include the Olevac series manufactured by Arkema. The polar polyolefin resin is preferably blended in an amount of 1 to 7% when the entire resin composition is taken as 100%.

The resin composition of the present invention contains 1 to 30% by mass of cellulose fibers (A), 5 to 30% by mass of graphite (B), and 40 to 94% by mass of polyolefin resin (C) in 100% by mass of the resin composition. It is more preferable to contain 5 to 15% by mass of the cellulose fiber (A), 5 to 20% by mass of the graphite (B), and 65 to 90% by mass of the polyolefin resin (C).

The resin composition of the present invention can contain various additives as long as the object of the present invention is not impaired.

Various additives can be appropriately selected depending on the application in which the molded product is used, etc., and are heat stabilizers, plasticizers, dispersants, compatibilizers, lubricants, antioxidants, light stabilizers, ultraviolet absorbers, crystal nucleating agents, blocking agents. Preventive agents, sealability improvers, mold release agents, lubricants such as polyethylene wax, pigments, inorganic fillers (talc, mica, clay, wallastonite, calcium carbonate, etc.), foaming agents (organic, inorganic, microcapsules, etc.) Flame retardants (halogen, phosphoric acid ester, metal salt, red phosphorus, metal hydrate, etc.) Flame retardants, lubricants (PTFE particles, etc.), optical brighteners, phosphorescent pigments, etc. Fluorescent dyes, antistatic agents, flow modifiers, crystal nucleating agents, inorganic and organic antibacterial agents, impact modifiers typified by graft rubber, infrared absorbers, photochromic agents, etc., alone or in combination of two or more Can be mixed.

The resin composition of the present invention can be produced by melt-kneading cellulose fibers (A), graphite (B), and polyolefin resin (C). For the melt kneading, a batch type kneader such as a Banbury mixer and a known kneading device such as a twin-screw extruder, a single-screw extruder and a rotor type twin-screw kneader can be used. The form of the resin composition is not limited, but is generally in the form of pellets, powder, or beads.

The molded product of the present invention can be obtained by melting and kneading the resin composition and using a molding machine. As a molding method, a known method can be used. For example, extrusion molding, injection molding, blow molding, press molding, calendar molding, T-die molding, inflation molding, compression molding, pipe extrusion molding, laminate molding, vacuum molding and the like can be mentioned.

When the molded product of the present invention is used as a building material, for example, a heat exchange pipe for underground heat exchange, a transport material [container, flexible container, trolley, tray, carrier tape, pallet, seat skid (for automobile seat transport)). , Stretch film (to prevent load collapse), binding band, foam cushioning material, air cap (cushioning material), etc.], Molded products for daily life materials [Furniture (chairs, desks, hangers, etc.), building materials for houses (entrance / indoor) Various doors such as, inner / outer wall materials, ceiling materials, roofing materials, tiles, etc.).

Examples of housing applications include containers and packaging materials for containers and packaging materials [food (fresh foods, processed foods, soft drinks, etc.), miscellaneous goods (tableware, toys, stationery, electrical parts, home appliances, furniture, etc.). , Luxury goods, etc.) Containers and packaging materials, Chemicals (industrial chemicals, pharmaceuticals, etc.) containers and packaging materials, Automotive parts [Instrument panels, door trims, pillars and other interior materials, bumpers and other exterior materials, gasoline Internal parts such as tanks and valves], home appliances [TVs, recorders / players (videos, hard disks, DVDs, BDs, etc.), computer equipment [computers, displays (CRT, liquid crystal, plasma, projectors, organic EL, etc.), etc.) Laptop computers, printers, recording medium drives (hard disks, MOs, memory cards, CDs, DVDs, BDs, flexible disks, etc.), recording media (USB memory, IC cards, etc.) housings, mouse housings, and internal parts] Housing, small portable devices [radio, mobile phones, PHS, PDA, smartphones, portable game machines and game software, TVs, navigation devices, GPS devices, headphone stereos, optical cameras, digital cameras electronic dictionaries and computers, lithium ion charging Housings for vessels and internal parts, etc.], office equipment [copying, facsimiles, scanners and their combined machines, shredders, paper folding machines, electronic blackboards, time recorders, network cameras, smoking counters, label writers, etc. Electronic registers, electronic checkwriters, laminators, bookbinding machines, etc.] housings, game machines [arcade-type game machines, pachinko, slot machines, etc.] housings, medical equipment [dry imagers, medical printers, medical recorders, medical cameras, etc.] , X-ray television system, CT scanner system, mammograph system, angiography system, ultrasonic diagnostic system, and other housings.

Among these, molded products used for geothermal heat exchange heat exchange pipes and housings are preferable because of their excellent thermal conductivity and mechanical properties.

Hereinafter, the present invention will be described in more detail, but the present invention is not limited to these examples as long as it does not deviate from the technical idea of the present invention. In addition, hereinafter, "mass%" is described as "%". The raw materials used in the following examples and comparative examples will be described. The properties of the cellulose fiber (A) are shown in Table 1.

<Manufacturing of cellulose fibers (A-1 to A-4)>
100 g of Theoras KG-1000 manufactured by Asahi Kasei Chemical Co., Ltd. and 1000 mL of ethanol were added, and the fibers were vacuum-dried after being repeatedly passed 20 times using a 3-roll mill [BR-230V] manufactured by Imex Co., Ltd. A-1) was obtained. By adjusting the number of times of passing through the machine repeatedly, A-2, A-3, and A-4 having different average fiber diameters were obtained.

<Manufacturing of acetylated cellulose fiber (A-5)>
50 g of KC floc manufactured by Nippon Paper Chemicals Co., Ltd., 150 mg of TEMPO (manufactured by Sigma Aldrich) and 500 ml of an aqueous solution in which 1000 mg of sodium bromide were dissolved were added, and the mixture was stirred until uniformly dispersed. After adding 50 ml of an aqueous sodium hypochlorite solution (5% effective chlorine) and an aqueous sodium chlorite solution (5% effective chlorine) to the reaction system, the pH was adjusted to 10 and the oxidation reaction was started. After reacting for 2 hours while adjusting the pH to 10, the mixture was filtered through a glass filter, thoroughly washed with water, and vacuum dried to obtain powdered cellulose oxide fibers (A-5).

<Manufacturing of hydrophobicized cellulose fiber (A-6)>
50 g of acetylated cellulose fiber (A-5) and 5 g of hexyltriethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) were heated and stirred in 300 mL of ethanol at 60 ° C. using a magnetic stirrer for 1 hour. Then, the solvent was removed by vacuum drying to obtain a hydrophobic cellulose fiber (A-6).

(A-7) Cellulose fiber (Asahi Kasei Chemical Co., Ltd., Theoras KG-1000, average fiber system 4500 nm)
The properties of graphite (B) are shown in Table 2.

<Polyolefin resin (D)>
D-1: Linear low-density polyethylene (KJ640T manufactured by Japan Polyethylene Corporation, density 880 kg / m ³ , MFR = 30 g / 10 min, melting point 58 ° C.)
D-2: Linear low-density polyethylene (Evolu SP0510 manufactured by Prime Polymer Co., Ltd., density 903 kg / m ³ , MFR = 1.2 g / 10 min, melting point 98 ° C.)
E-3: Polypropylene resin (PP, density 900 kg / m ³ , MFR = 5 g / 10 min, melting point 120 ° C)

<Polyolefin resin (E)>
E-1: High-density polyethylene resin (Prime Polymer Co., Ltd. Hi-Zex 7000F, density 952 kg / m ³ , MFR = 0.04 g / 10 min, melting point 131 ° C)
E-2: High-density polyethylene resin (Prime Polymer Co., Ltd. Hi-Zex 3300, density 958 kg / m ³ , MFR = 1 g / 10 min, melting point 133 ° C)

<Additive (F)>
F-1: Maleic anhydride-modified polypropylene (Youmex 1001 manufactured by Sanyo Chemical Industry Co., Ltd.)
F-2: Glass fiber (Nitto Boseki cut fiber E-301, average fiber system 10 μm)

[Example 1]
[Manufacturing of resin composition]
10% by mass of cellulose fiber (A-1), 10% by mass of graphite (B-2), 15% by mass of polyolefin resin (D-1), and 65% by mass of polyolefin resin (E-1) are put into a Henschel mixer. After premixing under the conditions of a temperature of 20 ° C. and a time of 3 minutes, the mixture is supplied to an extruder having a screw diameter of 30 mm and L / D (screw diameter / screw length) = 38 to 42, and has a rotation speed of 200 rpm and a set temperature of 190. The mixture was melt-kneaded under the condition of ° C., and the extruded product was cut with a pelletizer to obtain a pellet-shaped resin composition.

〔Evaluation method〕
The following evaluation items were tested using the obtained resin composition. The results are shown in Tables 5 and 6.

〔Thermal conductivity〕
The resin composition was put into a hot press sheet forming machine and heated to 200 ° C. to prepare eight sheets having a length of 40 mm, a width of 40 mm and a thickness of 1.5 mm, and a hot disk heat dissipation physical property measuring device (TPS-500 Kyoto Electronics Industry). The thermal conductivity (unit: W / m · K) was measured by stacking four sheets on the top and bottom of a sensor having a diameter of 7 mmφ. The higher the thermal conductivity, the better the heat exchange efficiency and heat dissipation.

[Tension fracture point elongation rate]
The resin composition was put into a hot press sheet molding machine and heated to 200 ° C. to prepare a press sheet having a length of 200 mm, a width of 200 mm and a thickness of 1.5 mm, and then punched into a No. 2 dumbbell mold to prepare a test piece. The tensile fracture point elongation rate was measured according to JIS K-7127 under the condition of a tensile speed of 100 mm / min. The test piece before the test had an elongation rate of 100%. When the elongation rate is large, the flexibility of the molded product is increased, and cracks and cracks are less likely to occur when an impact is applied. 200% or more is preferable.

[Bending strength and flexural modulus]
Using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.), the resin composition was molded into strip test pieces at a temperature of 190 ° C. The strip test piece conformed to the standard of type B2 (length 80 mm × width 10 mm × thickness 4 mm) described in JIS K 7139. The strip test piece produced was measured for bending strength and flexural modulus using a fully automatic bending tester Bentgraph II (manufactured by Toyo Seiki Co., Ltd.) according to JIS K 7171. The higher the bending strength and flexural modulus, the higher the rigidity, and the less likely it is to deform when a load is applied to the molded product. The bending strength is preferably 20 MPa or more. The flexural modulus is preferably 1000 MPa or more.

[Specific gravity measurement]
The resin composition was put into a hot press sheet molding machine and heated to 200 ° C. to prepare a press sheet having a length of 200 mm, a width of 200 mm and a thickness of 1.5 mm. It was measured by the Archimedes method according to JIS K 7112.

[Surface smoothness]
The resin composition is put into a spiral die pipe molding machine (manufactured by Toyo Seiki Co., Ltd.), melted at a molding temperature of 190 ° C. and a screw rotation speed of 80 rpm, and extruded to form a pipe shape having a diameter of 20 mm and a thickness of 1.5 mm. I got the goods.
The surface of the obtained pipe was observed, and the surface smoothness was evaluated according to the following criteria. The evaluation criteria A and B are practical levels.
A: The surface of the pipe is smooth Good B: The surface of the pipe has irregularities with a height of less than 0.2 mm Practical use C: The surface of the pipe has irregularities or holes with a height of 0.2 mm or more Not practical use Cellulose fiber The presence of aggregates of (A) and graphite (B) affects surface smoothness. If the surface smoothness is good, it means that the cellulose fibers and graphite are uniformly dispersed in the resin.

[Examples 2 to 17, Comparative Examples 1 to 5]
A pellet-shaped resin composition was prepared by performing in the same manner as in Example 1 except that the raw materials of Example 1 were changed to the compositions shown in Tables 3 and 4, and evaluated in the same manner as in Example 1. The results are shown in Tables 5 and 6. The numerical values in Tables 3 and 4 represent mass%, and the blanks indicate that they are not blended.
From the results shown in Tables 5 and 6, the thermal conductivity, mechanical properties, and surface smoothness were improved by blending the specific cellulose fiber in the specific polyolefin as compared with the case of blending graphite alone. It was suggested that the combination of graphite and cellulose fibers in a specific amount has a surprising effect of improving not only mechanical strength but also thermal conductivity.
On the other hand, none of the molded products using the resin compositions of Comparative Examples 1 to 5 satisfied all of the thermal conductivity, surface smoothness, and mechanical strength.
However, Examples 2, 3, and 13 are reference examples.

Claims (5)

A cellulose fiber (A) having an average fiber diameter of 10 to 3000 nm, a graphite (B) having an average particle diameter of 50 to 120 μm, and a polyolefin resin (C) are contained, and the cellulose fiber (A) is contained in 100% by mass of the resin composition. A resin composition containing 5 to 20 % by mass and containing 5 to 30% by mass of graphite (B) in 100% by mass of the resin composition. The resin composition according to claim 1, wherein the total amount of the cellulose fibers (A) and graphite (B) is 6 to 45% by mass in 100% by mass of the resin composition. The polyolefin resin (C) comprises a density 930 kg / m ³ of less than the polyolefin resin (D) and the density 930 kg / m ³ or more of the polyolefin resin (E), according to claim 1 or 2 resin composition. The resin composition according to claim 3, wherein the resin composition contains 10 to 40% by mass of the polyolefin resin (D) and 30 to 84% by mass of the polyolefin resin (E) in 100% by mass of the resin composition. A molded product obtained by molding the resin composition according to any one of claims 1 to 4.