Resin composition and molded body using same

Abstract

A resin composition according to the present disclosure contains: a cellulose having a surface roughness with an arithmetic average height of 0.1 μm or less at a cutoff value of 5 μm, a thermoplastic resin, and titanium oxide. The content of the cellulose is 60 wt. % or less. The present disclosure makes it possible to provide a resin composition that has excellent environmental compatibility, suppresses thermal discoloration of cellulose during molding, and allows to obtain a light-colored molded body.

Description

Resin composition and molded article using same

[0001] The present disclosure relates to a resin composition and a molded article using the same.

[0002] In recent years, environmental issues have led to a desire to move away from fossil fuels in the materials field, and the use of biomass has been attracting attention. Biomass materials are one of the means that can reduce carbon dioxide emissions toward achieving carbon neutrality. Specifically, for example, by adding biomass materials to resins to obtain resin molded products, it is possible to reduce the carbon dioxide emitted from fossil fuels during combustion.

[0003] Among biomass materials, cellulose can be added to resins to improve the rigidity of resin molded bodies, and is therefore used as a resin reinforcing material. Cellulose has attracted attention for its low cost and environmental friendliness compared to other resin reinforcing materials such as glass fiber, carbon fiber, and aramid fiber.

[0004] However, in order to obtain a molded article using a resin composition containing cellulose, the resin needs to be heated to a temperature at which the resin melts (injection molding).However, a resin composition containing cellulose is prone to discoloration when heated, making it difficult to obtain a light-colored resin molded article.

[0005] To address this problem, for example, Patent Document 1 describes that discoloration during injection molding can be suppressed by coating the surface of cellulose in a resin composition containing a cellulose fiber aqueous dispersion or a dried cellulose fiber and a thermoplastic resin. The cellulose fiber aqueous dispersion contains cellulose fibers, polyurethane, and water, and the dried cellulose fiber is a dried product of the cellulose fiber aqueous dispersion.

[0006] Japanese Patent Application Laid-Open No. 2020-176157

[0007] However, in order to coat the surface of cellulose, as described in Patent Document 1, for example, it is necessary to disperse cellulose fibers in an aqueous solvent and then carry out a coating step with a surface treatment agent, which is a complicated process.

[0008] Furthermore, in a manufacturing process for producing a molded article using a resin composition containing cellulose, for example, if the operation of the manufacturing equipment is temporarily stopped due to some kind of trouble, the residence time of the resin composition containing cellulose at high temperatures may be longer than usual, making it difficult to suppress thermal discoloration of the cellulose.

[0009] The present disclosure aims to provide a resin composition that is environmentally friendly, suppresses thermal discoloration of cellulose during molding, and enables the production of a light-colored molded article. Another object of the present disclosure is to provide a molded article using the resin composition.

[0010] A resin composition according to one embodiment of the present disclosure includes cellulose having a surface roughness of 0.1 μm or less in arithmetic mean height at a 5 μm cutoff value, a thermoplastic resin, and titanium oxide, wherein the cellulose content is 60 wt% or less.

[0011] According to the present disclosure, it is possible to provide a resin composition that is excellent in environmental friendliness, suppresses thermal discoloration of cellulose during molding, and can obtain a light-colored molded article. Furthermore, according to the present disclosure, it is possible to provide a light-colored molded article using the resin composition.

[0012] Hereinafter, embodiments of the present disclosure will be described.

[0013] <Resin Composition> As described above, the resin composition according to this embodiment contains cellulose having a surface roughness of 0.1 μm or less in arithmetic mean height at a cutoff value of 5 μm, a thermoplastic resin, and titanium oxide. The cellulose content is 60 wt% or less. The resin composition having this configuration is environmentally friendly, suppresses thermal discoloration of the cellulose during molding, and allows for the production of a light-colored molded product.

[0014] In the past, when producing molded articles using a resin composition containing cellulose, it was difficult to obtain light-colored molded articles due to thermal discoloration of the cellulose during melt-kneading and injection molding. However, the present inventors have discovered that by using cellulose having a surface roughness of 0.1 μm or less with an arithmetic mean height (cutoff value 5 μm) and setting the content of the cellulose in the resin composition to 60 wt % or less, it is possible to suppress thermal discoloration of the cellulose during melt-kneading and injection molding, and to obtain light-colored molded articles.

[0015] The resin composition according to the present embodiment can suppress thermal discoloration without the steps of dispersing cellulose in an aqueous solvent and coating the surface of the cellulose, which have been conventionally performed to suppress thermal discoloration of cellulose, and therefore can produce a light-colored molded product by a simple method.

[0016] Furthermore, the resin composition according to this embodiment can suppress thermal discoloration of cellulose even when the resin composition is retained at high temperatures for a long period of time during melt-kneading and injection molding.

[0017] In the present disclosure, the L of the molded body ＊ , a ＊ , b ＊ As a result of measuring the color difference using a color difference meter (for example, "RM200QC" manufactured by X-Rite Inc.), ＊ (Black to White) is +90.0 or more, a ＊ (green to red) is greater than or equal to -4.0 and less than or equal to +4.0, b ＊ A molded product having a value of (blue to yellow) of -4.0 or more and +8.0 or less is defined as being light-colored. ＊ , a ＊ , b ＊ In color space, lightness is L ＊ and chromaticity is expressed as a ＊ , b ＊ Chromaticity indicates hue and saturation.

[0018] [Cellulose] The cellulose contained in the resin composition according to this embodiment will be described in detail below.

[0019] As described above, the surface roughness of the cellulose according to this embodiment is 0.1 μm or less in terms of arithmetic mean height (cutoff value: 5 μm). This configuration makes it possible to suppress thermal discoloration of the cellulose during molding, thereby obtaining a light-colored molded product. It is more preferable that the arithmetic mean height (cutoff value: 5 μm) is 0.08 μm or less.

[0020] In this embodiment, in order to exclude surface irregularities of large wavelengths due to cellulose undulations, etc., the measurement data was subjected to cutoff processing using a phase compensation filter (cutoff value: 5 μm) to calculate the arithmetic mean height.

[0021] In the present disclosure, the arithmetic mean height refers to the arithmetic mean height (Sa) calculated by measuring the surface roughness of a cellulose surface at a cutoff value of 5 μm based on a method in accordance with JIS B 0601: 1994 and JIS B 0031: 1994. The arithmetic mean height can be measured, for example, by the method described in the Examples below.

[0022] The cellulose content of the present embodiment is 60% by weight or less relative to the resin composition. When the cellulose content is 60% by weight or less relative to the resin composition, the resin composition has good fluidity. Therefore, thermal discoloration of the cellulose during melt-kneading and injection molding is suppressed, and a light-colored molded product can be obtained.

[0023] When the cellulose content of the resin composition is 60% by weight or less, large parts can be molded without excessively increasing the temperature during melt-kneading and injection molding. Therefore, even when molding large parts, thermal discoloration of the cellulose during melt-kneading and injection molding can be suppressed, and light-colored molded products can be obtained.

[0024] When the content of the cellulose is 60% by weight or less relative to the resin composition, the generation of aggregates during melt-kneading and injection molding is suppressed, and a molded article having a good appearance can be obtained.

[0025] When the thermoplastic resin is a polyolefin and the molded article made from the resin composition is a handheld dryer, vacuum cleaner, or the like, the cellulose content of the resin composition is set to 60% by weight or less, which reduces the specific gravity and makes the article lighter, thereby reducing the burden on the user during use.

[0026] The cellulose content of the resin composition is preferably 50% by weight or less, more preferably 45% by weight or less, even more preferably 30% by weight or less, and most preferably 15% by weight or less.

[0027] The content of the cellulose is preferably 10% by weight or more relative to the resin composition. When the content of the cellulose is 10% by weight or more relative to the resin composition, a molded article with excellent environmental friendliness can be more reliably obtained. When the content of the cellulose is 10% by weight or more relative to the resin composition, the rigidity of a molded article using the resin composition can be improved.

[0028] The average particle size of the cellulose according to this embodiment is preferably 100 μm or less. When the average particle size is 100 μm or less, a light-colored molded product can be obtained, and the generation of cellulose aggregates during kneading and molding of the resin composition can be suppressed. This allows a molded product with a good appearance to be obtained. The average particle size is more preferably 80 μm or less, and even more preferably 60 μm or less.

[0029] The average particle size of the cellulose is preferably 5 μm or more. When the average particle size is 5 μm or more, a light-colored molded article can be obtained and the rigidity of the molded article using the resin composition can be improved. The average particle size is more preferably 10 μm or more, and even more preferably 15 μm or more.

[0030] The maximum particle size of the cellulose is not particularly limited, but is preferably 200 μm or more and 400 μm or less. When the maximum particle size is 200 μm or more, the rigidity of a molded article using the resin composition can be improved. When the maximum particle size is 400 μm or less, a molded article having a good appearance can be obtained.

[0031] The minimum particle size of the cellulose is preferably 0.1 μm or more and 4 μm or less. When the minimum particle size is 0.1 μm or more, the rigidity of a molded article made using the resin composition can be improved. When the minimum particle size is 4 μm or less, a molded article having a good appearance can be obtained.

[0032] The aspect ratio of the cellulose is preferably 2 to 10. When the aspect ratio is within this range, the rigidity of a molded article made using the resin composition can be improved.

[0033] The average particle size, minimum particle size, maximum particle size, and aspect ratio of the cellulose can be measured, for example, by the following method.

[0034] A portion of the cellulose to be measured is dispersed on a glass slide and a magnified photograph is taken. A total of several dozen cellulose samples are used for the photograph. The photographed image is processed using image analysis software (Image-Pro PLUS, manufactured by Nippon Rover Co., Ltd.). The obtained digital microscope observation photograph (data) is binarized using a contrast threshold to extract only the cellulose image.

[0035] The extracted image is used to determine the minor axis length, major axis length, and aspect ratio, which is the ratio of the major axis length to the minor axis length, of the cellulose. The minor axis length refers to the smallest diameter (minimum diameter) that passes through the center of gravity of the object being measured and connects two points on the periphery of the object being measured. The major axis length can be calculated by (circumferential diameter of the object being measured) / (2 - minor axis length). The major axis length indicates the particle size of the cellulose. The lower limit of the major axis length that can be calculated using this method is 3 μm.

[0036] In the distribution of major axis lengths, the average particle size is the average value of the major axis lengths, the minimum particle size is the minimum value of the major axis lengths, and the maximum particle size is the maximum value of the major axis lengths.

[0037] Various properties of the cellulose contained in the resin composition or molded article, such as the arithmetic mean height and particle size, are measured after extracting the cellulose from the resin composition or molded article. To extract the cellulose from the resin composition or molded article, for example, about 0.2 g of a sample (resin composition or molded article) is prepared, and the thermoplastic resin is removed using any chemical in an automatic high-speed solvent extraction device, and the resulting insoluble matter is dried under reduced pressure.

[0038] For example, to remove polypropylene from a sample, o-xylene containing dibutylhydroxytoluene (BHT) can be used at high temperature (135°C). For example, to remove polystyrene (PS), polycarbonate (PC), acrylonitrile styrene (AS), etc., chloroform, toluene, tetrahydrofuran (THF), etc. can be used.

[0039] In this embodiment, the amount of hemicellulose in the cellulose is preferably 10% by weight or less. Hemicellulose present in the cellulose is one of the causes of thermal discoloration during molding. Therefore, by setting the amount of hemicellulose in the cellulose to 10% by weight or less, thermal discoloration during molding can be suppressed, and a light-colored molded product can be more reliably obtained.

[0040] The cellulose according to the present embodiment may be unmodified cellulose in which the hydroxyl groups derived from cellulose are not modified with any substituents, or may be modified cellulose in which the hydroxyl groups derived from cellulose (particularly a part of them) are modified (or substituted). However, the cellulose is preferably unmodified cellulose that is not chemically modified.

[0041] Chemical modification of cellulose requires a dehydration and drying process, which increases the environmental impact and costs. On the other hand, chemical modification increases heat resistance. However, with the cellulose of the present embodiment having the above-described configuration, thermal discoloration of the cellulose during molding can be suppressed even without chemical modification, and a light-colored molded product can be more reliably obtained.

[0042] The form of the cellulose according to this embodiment is not particularly limited, and may be, for example, powder or fiber.

[0043] [Method for producing cellulose] The cellulose contained in the resin composition according to this embodiment is produced by applying various production methods to cellulose raw materials. The raw materials and production methods for cellulose are not particularly limited. An example of a method for producing cellulose will be described below.

[0044] The raw material for cellulose may be naturally derived or regenerated (recycled material). However, from the viewpoint of environmental friendliness, recycled material is preferred as the raw material for cellulose. Examples of naturally derived cellulose include wood-derived pulp and non-wood-derived pulp such as rice, cotton, kenaf, bagasse, abaca, hemp, and bamboo. Examples of regenerated cellulose include paper-derived pulp obtained by finely grinding previously made paper.

[0045] The paper in this case may be new paper or recycled paper. Regenerated cellulose also includes, for example, cellulose obtained from the cellulose-containing molded article according to the present embodiment. The raw material for cellulose may contain only one type of material, or may contain two or more types of materials.

[0046] The raw material for cellulose is preferably bleached pulp. By bleaching the pulp, the hemicellulose content in the pulp can be reduced. Wood and other raw materials for pulp usually contain hemicellulose, lignin, and the like in addition to cellulose.

[0047] However, if hemicellulose is present in the pulp used as the raw material for the cellulose, the hemicellulose contributes to the thermal discoloration that occurs during molding, as described above. Therefore, if bleached pulp is used as the raw material for the cellulose, thermal discoloration can be suppressed, and a light-colored molded product can be more reliably obtained.

[0048] It is believed that hemicellulose remains in the pulp even after bleaching treatment. In the resin composition according to the present embodiment, even if the cellulose raw material contains pulp with residual hemicellulose, thermal discoloration of the cellulose during molding can be suppressed, and a light-colored molded product can be obtained.

[0049] The chemicals used in the bleaching treatment are not particularly limited, but examples thereof include sodium hypochlorite (NaClO), hydrogen peroxide (H ２ O ２ ), ozone (O ３ ), oxygen (O ２ ), sodium hydroxide (NaOH), and mixtures thereof.

[0050] The method for producing cellulose is not particularly limited, and includes a method of mechanically pulverizing (refining) a cellulose raw material, a method of subjecting a cellulose raw material to acid hydrolysis, etc. However, it is preferable to produce cellulose by mechanically pulverizing a cellulose raw material.

[0051] Mechanical refining causes less damage to the surface of cellulose than acid hydrolysis, which requires many steps and produces a lot of carbon dioxide emissions. Therefore, mechanical refining is less expensive and more environmentally friendly.

[0052] There are no particular limitations on the cellulose mills that can be used for mechanical treatment, and examples include counter jet mills, Micron Jet (registered trademark), Inomizer (registered trademark) (all manufactured by Hosokawa Micron Corporation), impact jet mills, etc. The conditions for the mechanical treatment can be appropriately set so as to obtain the desired cellulose.

[0053] The pulverized cellulose can be passed through a classifier and a sieve to obtain cellulose having a desired particle size. The classifier is not particularly limited, but examples thereof include Micron Separator (registered trademark), Turboplex (registered trademark) (a centrifugal airflow classifier), and Coarse Powder Classifier (all manufactured by Hosokawa Micron Corporation), and Elbow Jet (registered trademark) (manufactured by Nittetsu Mining Co., Ltd.).

[0054] There are no particular limitations on the sieving device for sieving coarse particles, but examples include Ultrasonic (manufactured by Koei Sangyo Co., Ltd.), Resonaseave, Gyrosifter (all manufactured by Tokuju Kosakusho Co., Ltd.), Vibrasonic System (manufactured by Dalton Co., Ltd.), circular sieve, etc.

[0055] [Thermoplastic Resin] The thermoplastic resin contained in the resin composition according to this embodiment will be described in detail below.

[0056] The thermoplastic resin according to this embodiment has a viscosity of 1×10 at 200° C. ６ It is preferable that the viscosity at 200°C is 1 x 10 Pa·s or less. ６ When the viscosity is Pa s or less, it is possible to suppress the temperature rise of the resin due to shear heat generation during melt-kneading and injection molding, thereby suppressing thermal discoloration of the cellulose during melt-kneading and injection molding, and more reliably obtaining a light-colored molded product.

[0057] Furthermore, the viscosity is 1×10 ６ When the viscosity is 5×10 Pa s or less, the temperature rise of the resin due to shear heating during melt kneading and injection molding can be suppressed. Therefore, molding of large parts for home appliances, automobiles, building materials, etc. is easy. ５ It is more preferable that the viscosity is not more than Pa·s.

[0058] The viscosity is 1×10 ３ It is preferable that the viscosity is 5×10 Pa s or more. This makes it possible to ensure the rigidity of a molded product while maintaining a certain degree of flowability during molding when the resin composition is used for molding. ３ It is more preferable that the viscosity is 1×10 Pa·s or more. ４ It is more preferable that the viscosity is Pa·s or more.

[0059] The viscosity can be measured by a method conforming to JIS K 7210 and JIS K 7311. Specifically, the viscosity can be measured using, for example, a constant test force extrusion type capillary rheometer flow tester (manufactured by Shimadzu Corporation).

[0060] The thermoplastic resin according to this embodiment preferably has a melting temperature (melting point) of 200° C. or less. When the melting temperature is 200° C. or less, the resin temperature during melt-kneading can be kept at 200° C. or less. This makes it possible to suppress thermal discoloration and decomposition of cellulose, and more reliably obtain a light-colored molded product.

[0061] The thermoplastic resin according to this embodiment preferably has a melt flow rate (MFR) of 2.5 g / 10 min or more at a temperature of 230° C. and a load of 2.16 kgf. When the MFR is 2.5 g / 10 min or more, the resin composition has good fluidity. Therefore, the injection pressure during melt-kneading and injection molding can be reduced, and heat generation due to shear is less likely to occur.

[0062] Even when molding large parts, molding can be performed without excessively increasing the molding temperature. Therefore, when the MFR is 2.5 g / 10 min or more, thermal discoloration of the cellulose during melt-kneading and injection molding can be suppressed, and light-colored molded products can be more reliably obtained.

[0063] When the MFR is 2.5 g / 10 min or more, even when molding a relatively large part, it is possible to use an injection molding machine with a relatively low clamping force. Therefore, a molded article can be obtained using relatively inexpensive equipment. In the present disclosure, the MFR of a thermoplastic resin is measured by a method in accordance with JIS K 7210.

[0064] The flexural modulus of the thermoplastic resin according to the present embodiment is not particularly limited, but is preferably 1200 MPa or more, and more preferably 1400 MPa or more. In the present disclosure, the flexural modulus of the thermoplastic resin is measured by a method in accordance with JIS K 7171.

[0065] The thermoplastic resin according to the present embodiment may be a virgin resin, a recycled resin (recycled material) obtained from waste materials, or both a virgin resin and a recycled material. From the viewpoint of environmental friendliness, it is preferable that the thermoplastic resin contains a recycled material.

[0066] Examples of the thermoplastic resin include polyolefin, polystyrene, acrylonitrile butadiene styrene (ABS), polycarbonate, polyamide, and acrylic. Among these, polyolefin is preferably used. Examples of polyolefin include polyethylene, polypropylene, polybutene, and polymethylpentene. Among these, polypropylene is preferable.

[0067] The thermoplastic resin may be composed of only one type of resin, or may be composed of two or more types of resin.

[0068] According to the resin composition of the present embodiment, even if the thermoplastic resin has no affinity for cellulose, it is possible to obtain a molded article that is light in color and has a good appearance by using the resin composition. Thermoplastic resins that have no affinity for cellulose include, for example, polypropylene, polyethylene, polystyrene, and ABS.

[0069] The content of the thermoplastic resin in the resin composition according to the present embodiment is preferably 40% by weight or more, more preferably 60% by weight or more, based on the weight of the resin composition, and is preferably 90% by weight or less, more preferably 88% by weight or less, based on the weight of the resin composition.

[0070] When the content of the thermoplastic resin is 88% by weight or less relative to the resin composition, the rigidity of the molded article obtained using the resin composition can be ensured, and the resin composition is also excellent in environmental friendliness.

[0071] When the content of the thermoplastic resin is 60% by weight or more relative to the resin composition, the concentration of cellulose is reduced and fluidity is improved. This makes molding easier and allows for the molding of larger parts. When the content of the thermoplastic resin is 60% by weight or more relative to the resin composition and the specific gravity of the thermoplastic resin is lower than that of cellulose, weight reduction is also expected.

[0072] [Titanium Oxide] The titanium oxide contained in the resin composition according to this embodiment will be described in detail below.

[0073] The titanium oxide according to this embodiment is a white pigment. When the resin composition contains titanium oxide, the pale color of the molded article made using the resin composition can be ensured.

[0074] The crystal structure of the titanium oxide includes, for example, rutile and anatase. Although not particularly limited, a rutile crystal structure is preferred. The rutile crystal structure has a higher refractive index than other crystal structures and can scatter light to enhance the ability to conceal foreign matter such as black spots.

[0075] The particle size of the titanium oxide is preferably 1 μm or less. When the particle size of the titanium oxide is 0.5 μm or less, the dispersibility of the titanium oxide in the molded body is improved compared to when titanium oxide with a larger particle size is added to the molded body at the same weight percentage. This improves the ability to conceal foreign matter and improves the appearance of the molded body. The titanium oxide may or may not be surface-treated.

[0076] The content of the titanium oxide is preferably 5% by weight or less relative to the resin composition. When the content of the titanium oxide is 5% by weight or less, the cost can be reduced while ensuring the light color of the molded article using the resin composition. Furthermore, the rigidity and impact resistance of the molded article can be maintained.

[0077] If the resin composition contains titanium oxide, the specific gravity increases and the lightness is impaired. Therefore, it is preferable to keep the content as low as possible. Although there is no particular lower limit for the titanium oxide content, it is preferably 1.5 wt % or more of the resin composition.

[0078] [Other Components] In addition to the components described above, the resin composition according to the present embodiment may appropriately contain at least one of maleic acid-modified polypropylene, antioxidant, UV absorber, light resistance stabilizer, antistatic agent, metal deactivator, plasticizer, nucleating agent, flame retardant, lubricant, etc., in order to bind the thermoplastic resin and cellulose. Furthermore, the resin composition according to the present embodiment may appropriately contain, in addition to the components described above, an additive for coating the surface of cellulose, etc.

[0079] <Molded Product> The molded product according to this embodiment is light-colored. Specifically, in this embodiment, the L ＊ , a ＊ , b ＊ As a result of measuring the color difference using a color difference meter (RM200QC, manufactured by X-Rite Inc.), ＊ (Black to White) is +90.0 or more, a ＊ (green to red) is greater than or equal to -4.0 and less than or equal to +4.0, b ＊ A molded product having a value (blue to yellow) of -4.0 or more and +8.0 or less is defined as being light-colored.

[0080] The method for producing the molded article according to this embodiment will be exemplified below. However, as long as a molded article can be obtained by injection molding the resin composition, there are no particular limitations on the various conditions.

[0081] First, the above-mentioned components such as cellulose, thermoplastic resin, and titanium oxide are mixed in the desired amounts and then melt-kneaded in a twin-screw kneading extruder. A mixer or the like may be used to premix the components. The twin-screw kneading extruder is, for example, a twin-screw kneading extruder manufactured by Technovel Co., Ltd.

[0082] The temperature during the melt-kneading is preferably 200° C. or lower. When the temperature during the melt-kneading is 200° C. or lower, the resin temperature does not become too high, and heat generation due to shear can be suppressed. Therefore, thermal discoloration of the cellulose is suppressed, and a light-colored molded product can be more reliably obtained.

[0083] To suppress heat generation due to shear, the screw configuration can be adjusted to reduce the rotation speed. However, this can reduce the dispersibility of the cellulose and affect the appearance, so it is best to adjust the screw configuration while keeping a balance in mind. If the dispersibility of the cellulose decreases, resin degradation products may accumulate in the die at the discharge section. In this case, strands may break more easily, potentially affecting the productivity of the kneading process.

[0084] During the melt-kneading, cellulose easily absorbs water and generates steam due to the heat of the kneader, so it is preferable that the kneader be equipped with a vent to allow the steam to escape.

[0085] The kneaded product is dried to prepare pellets, and the pellets are then fed into an injection molding machine to prepare a molded product. The cylinder temperature during molding is preferably 200°C or lower. Setting the cylinder temperature to 200°C or lower can suppress thermal discoloration of the cellulose, and more reliably obtain a light-colored molded product.

[0086] As described above, the present disclosure discloses various aspects of the technology, the main aspects of which are summarized below.

[0087] The resin composition according to a first aspect of the present invention comprises cellulose having a surface roughness of 0.1 μm or less as an arithmetic mean height at a cutoff value of 5 μm, a thermoplastic resin, and titanium oxide, and the cellulose content is 60 wt % or less.

[0088] In the resin composition according to the second aspect, in addition to the first aspect, the content of the cellulose is 10% by weight or more.

[0089] In the resin composition according to the third aspect, in addition to the first or second aspect, the cellulose contains recycled material.

[0090] In a resin composition according to a fourth aspect, in addition to any one of the first to third aspects, the amount of hemicellulose in the cellulose is 10% by weight or less.

[0091] In a resin composition according to a fifth aspect, in addition to any one of the first to fourth aspects, the cellulose is not chemically modified.

[0092] In a resin composition according to a sixth aspect, in addition to any one of the first to fifth aspects, the cellulose has an average particle size of 100 μm or less.

[0093] In a resin composition according to a seventh aspect, in addition to any one of the first to sixth aspects, the viscosity of the thermoplastic resin at 200°C is 1 x 10 ６ It is less than Pa·s.

[0094] In the resin composition according to an eighth aspect, in addition to any one of the first to seventh aspects, the melting temperature of the thermoplastic resin is 200° C. or less.

[0095] In the resin composition according to the ninth aspect, in addition to any one of the first to eighth aspects, the melt flow rate (MFR) at a temperature of the thermoplastic resin of 230 ° C. and a load of 2.16 kgf is 2.5 g / 10 min or more.

[0096] In a resin composition according to a tenth aspect, in addition to any one of the first to ninth aspects, the thermoplastic resin includes a polyolefin.

[0097] In a resin composition according to an eleventh aspect, in addition to any one of the first to tenth aspects, the thermoplastic resin contains recycled material.

[0098] In a resin composition according to a twelfth aspect, in addition to any one of the first to eleventh aspects, the content of the titanium oxide is 5% by weight or less relative to 100% by weight of the resin composition.

[0099] A light-colored molded article according to a thirteenth aspect is formed by injection molding the resin composition according to any one of the first to twelfth aspects.

[0100] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0101] [Methods for Measuring Cellulose] In the following examples, methods for measuring the arithmetic mean surface height (Sa) and particle size of cellulose will be described.

[0102] (Method for measuring arithmetic mean height) The surface roughness of cellulose was measured using a non-contact laser microscope (LEXT OLS4100, manufactured by Olympus Corporation) at a cutoff value of 5 μm according to a method conforming to JIS B 0601:1994 and JIS B 0031:1994, and the arithmetic mean height (Sa) was calculated. Specifically, the fibers of the measurement sample were measured, and the surface roughness of the obtained height data (arithmetic mean height (Sa)) was calculated. The objective lens of the laser microscope was set to 100x, and the optical zoom was set to 3x.

[0103] (Method of measuring particle size (average particle size, maximum particle size, minimum particle size)) The method of measuring the average particle size, minimum particle size, and maximum particle size of cellulose is as described above.

[0104] Next, the components used to prepare the resin compositions in Examples 1 to 9 and Comparative Example 1 will be described.

[0105] [Cellulose] Cellulose A: Bleached pulp was milled and then passed through a classifier and a sieve to obtain Cellulose A, which had an average particle size of 15 μm and a surface roughness of 0.05 μm (arithmetic mean height (Sa) cutoff value: 5 μm). The maximum particle size was 121 μm and the minimum particle size was 3 μm. Cellulose B: Bleached pulp was milled and then passed through a classifier and a sieve to obtain Cellulose B, which had an average particle size of 47 μm and a surface roughness of 0.06 μm (arithmetic mean height (Sa) cutoff value: 5 μm). The maximum particle size was 279 μm and the minimum particle size was 4 μm. Cellulose C: After the bleached pulp was ground in a mill, the pulp was passed through a classifier and a sieve to obtain Cellulose C, which had an average particle size of 140 μm and a surface roughness of 0.05 μm (arithmetic mean height (Sa) cutoff value: 5 μm). The maximum particle size was 500 μm and the minimum particle size was 60 μm. Cellulose P: After the bleached pulp was acid hydrolyzed, filtered, washed, dehydrated, and dried, the pulp was passed through a classifier and a sieve to obtain Cellulose P, which had an average particle size of 23 μm and a surface roughness of 0.11 μm (arithmetic mean height (Sa) cutoff value: 5 μm). The maximum particle size was 130 μm and the minimum particle size was 4 μm.

[0106] [Thermoplastic Resins] Resin 1: Polypropylene (PP) (block PP, MFR: 30 g / 10 min, flexural modulus: 1800 MPa) Resin 2: Polypropylene (PP) (block PP, MFR: 2.5 g / 10 min, flexural modulus: 1650 MPa) Resin 3: Polypropylene (PP) (block PP, MFR: 60 g / 10 min, flexural modulus: 1300 MPa) [Titanium Oxide] Product Number "R-FC-5", manufactured by Venator Materials PLC <Evaluation Test 1> [Example 1] In Example 1, a molded body was produced using a resin composition obtained by mixing the above-mentioned components in the blending ratios (contents) listed in Table 1. That is, pellets were produced using resin 1 as the thermoplastic resin, cellulose, and titanium oxide as raw materials. Specifically, the above raw materials were weighed and dry-blended so that the contents in the resin composition would be the contents (wt%) listed in Table 1.

[0107] Next, the dry-blended raw materials were melt-kneaded in a twin-screw kneading extruder (KZW15TW-45MG-NH(-700), manufactured by Technovel Co., Ltd.) at a temperature of 170°C and an output of 2 kg / hour. The kneaded raw materials were cooled with water to produce pellets, which were then molded at 185°C to obtain molded products. The light color and heat discoloration resistance of the obtained molded products were examined using the following methods. The results are shown in Table 1.

[0108] [Examples 2 to 9, Comparative Examples 1 and 2] In Examples 2 to 9 and Comparative Examples 1 and 2, molded articles were produced using resin compositions prepared by mixing the above-described components in the blending ratios (contents) shown in Table 1 in the same manner as in Example 1, and the pale color and heat discoloration resistance of the resulting molded articles were investigated by the following methods. The results are shown in Table 1.

[0109] (Light Color, Heat Discoloration Resistance) The above-mentioned components were mixed in the blending ratios (contents) shown in Table 1, and then melt-kneaded at 190°C using a twin-screw kneading extruder (KZW15TW-45MG-NH(-700), manufactured by Technovel Co., Ltd.). The resulting kneaded mixture was dried to obtain pellets. Measurement of Light Color The resulting pellets were placed in an injection molding machine (J50ADS-60U, manufactured by The Japan Steel Works, Ltd.), and the cylinder temperature was set to 185°C to prepare a test piece I measuring 60 mm x 70 mm x 1.6 mm. The L of test piece II obtained after 10 shots was ＊ , a ＊ , b ＊ was measured using a color difference meter (RM200QC, manufactured by X-Rite Inc.).

[0110] The result is L ＊ (Black to White) is +90.0 or more, a ＊ (green to red) is greater than or equal to -4.0 and less than or equal to +4.0, b ＊ If the difference (blue to yellow) was -4.0 or more and +8.0 or less, it was judged as acceptable, and if not, it was judged as unacceptable. These results are shown in Table 1. - Heat discoloration resistance Furthermore, test piece II prepared after 10 shots was taken out, and the pellets from the 11th shot were filled into a cylinder, and the cylinder temperature was set to 185°C. After 15 minutes, molding was carried out to prepare test piece III, and the L of the obtained test piece III was ＊ , a ＊ , b ＊ was measured using a color difference meter (RM200QC, manufactured by X-Rite Inc.).

[0111] The color difference ΔE between the 11th shot test piece III and the 10th shot test piece II was determined. ΔE is a value expressed by the following formula (1), and a ΔE value of 2.5 or less was judged as acceptable, and a ΔE value of more than 2.5 was judged as unacceptable. These results are shown in Table 1. ΔE=[(ΔL ＊ ) ２ + (Δa ＊ ) ２ + (Δb ＊ ) ２ ] １／２ (1)

[0112] [Example 10] One hundred molded articles obtained using the resin composition of Example 1 were crushed using a crusher to produce flakes. Each of these molded articles corresponds to Test Piece I. The obtained flakes were melt-kneaded at 190°C using a twin-screw kneading extruder (KZW15TW-45MG-NH(-700), manufactured by Technovel Co., Ltd.). The obtained kneaded product was dried to obtain pellets. Using the obtained pellets, the light color and heat discoloration resistance of the molded articles were evaluated using the same method as in Example 1. The results are shown in Table 1.

[0113] The properties of cellulose D obtained by extraction from the pellets in Example 10 were measured by the method described above. The results were an average particle size of 14 μm, a maximum particle size of 114 μm, a minimum particle size of 3 μm, and a surface roughness of 0.08 μm in arithmetic mean height (Sa) (cutoff value 5 μm). The thermoplastic resin contained in the pellets in Example 10 was the same resin as resin 1 used in Example 1, and is referred to as resin 4 in Table 1.

[0114]

[0115] [Discussion] From the results shown in Table 1, it was found that in Examples 1 to 10, in which the arithmetic mean height of the cellulose surface (cutoff value 5 μm) and the cellulose content were appropriately adjusted, the yellowness of the molded articles was suppressed and the molded articles were light in color. From the above test results for thermal discoloration resistance, it was found that the resin compositions of Examples 1 to 10 suppressed thermal discoloration of cellulose even when the residence time during injection molding was long.

[0116] Even in Example 2, in which a resin with a relatively low MFR and low flowability was used, thermal discoloration of the cellulose during injection molding was suppressed, and a light-colored molded article was obtained.

[0117] In Example 10, the cellulose used was the cellulose (recycled material) obtained from the molded body of Example 1. In Example 10, the arithmetic mean height (cutoff value: 5 μm) of the cellulose surface was also appropriately adjusted, so discoloration could be suppressed even when the heat load caused by kneading and molding was applied again, and a light-colored molded body could be achieved.

[0118] In contrast, when the resin composition of Comparative Example 1, which contained 65% by weight of cellulose relative to the resin composition, was used, the evaluation of light color and heat discoloration resistance was unsuccessful. The molded article of Comparative Example 2, which used cellulose having a surface roughness of 0.11 μm with an arithmetic mean height (cutoff value 5 μm), also had a strong yellowish tinge, and the light color was unsuccessful. In Comparative Example 2, the evaluation of heat discoloration resistance was also unsuccessful due to the strong yellowish tinge.

[0119] <Evaluation Test 2> The resin compositions of Examples 1 to 9 and Comparative Example 1 were further tested for appearance quality of molded articles using the resin compositions by the following method. The results are shown in Table 2.

[0120] [Appearance quality: number of aggregates] 1 g of the above test piece I was cut out and sheeted by heat pressing at a temperature of 180°C and a pressure of approximately 5 MPa. Using a digital microscope (VHX-6000, manufactured by Keyence Corporation), the number of aggregates having a size of 300 μm or less was counted. If the number of aggregates was 0 to 10, it was evaluated as "excellent," if it was 10 to 30, it was evaluated as "fair," and if it was 30 or more, it was evaluated as "poor."

[0121] <Evaluation Test 3> The resin compositions of Examples 1 to 9 and Comparative Example 1 were further tested for flexural modulus of molded articles using the resin compositions by the method described below. The results are shown in Table 2.

[0122] [Flexural Modulus] The pellets obtained by the kneader were charged into an injection molding machine (J50ADS-60U, manufactured by The Japan Steel Works, Ltd.), and the cylinder temperature was set to 185°C to prepare dumbbell test pieces. The flexural modulus was measured according to JIS 7171.

[0123]

[0124] [Discussion] The results in Table 2 show that in Examples 1 to 8, in which the cellulose content and shape were appropriately adjusted, molded articles with fewer aggregates and better appearance were obtained. In contrast, the results in Table 2 show that in Example 9, in which cellulose with an average particle size of 140 μm was used, the number of aggregates was large and the appearance was poor.

[0125] In the case of Comparative Example 1, in which the cellulose content relative to the resin composition was 65% by weight, the number of aggregates was greater than in Examples 1 to 8.

[0126] The results in Table 2 show that the molded article of Example 4, which used cellulose at a content of 5 wt% relative to the resin composition, was inferior in bending elasticity. In contrast, the results in Table 2 show that by using the resin compositions of Examples 1 to 3 and 5 to 9, which contained an appropriate amount of cellulose, molded articles with even better bending elasticity could be obtained.

[0127] <Evaluation Test 4> The resin compositions of Examples 1, 6, and 7 were further subjected to a test for impact resistance of molded articles using the resin compositions by the method described below. The results are shown in Table 3.

[0128] [Impact Resistance] The pellets obtained by the above kneader were charged into an injection molding machine, and a cylinder temperature was set to 185°C to prepare dumbbell test pieces. Notches were made in the dumbbell test pieces according to a method in accordance with JIS 7111, and the Charpy impact value was measured at 23°C.

[0129]

[0130] [Discussion] The results in Table 3 show that molded articles with even better impact resistance can be obtained by using the resin compositions of Examples 1 and 6, which contain an appropriate amount of titanium oxide. In contrast, the results in Table 3 show that the molded article of Example 7, which contained 7.5 wt % titanium oxide, was inferior in impact resistance.

[0131] Test Example 5 The weather resistance of molded articles made using the resin compositions of Examples 1, 10, and Comparative Examples 1 and 2 was further tested by the method described below. The results are shown in Table 4.

[0132] [Weather Resistance Test] The pellets obtained in Examples 1, 10, and Comparative Examples 1 and 2 were loaded into an injection molding machine, and the cylinder temperature was set to 185°C to prepare test pieces X measuring 60 mm x 70 mm x 2 mm. Test piece Y obtained after 10 shots was subjected to an accelerated weather resistance test (Sunshine Carbon Test). Specifically, the test pieces were dimmed for 12 hours in a 120-minute cycle using a Sunshine Weather Meter (S80, manufactured by Suga Test Instruments Co., Ltd.). During this test, the dimming was performed under the condition of spraying ion-exchanged water for the first 18 minutes.

[0133] The color difference of test piece Y before and after dimming was measured using a color difference meter (RM200QC, manufactured by X-Rite Inc.). Based on the color difference measurement results, the following evaluations were made. These results are shown in Table 4.

[0134]

[0135] [Discussion] From the results in Table 4, it was found that the resin composition of Example 1, which contained 13.5 wt% of cellulose having an arithmetic mean height (Sa) (cutoff value 5 μm) of 0.05 μm in the resin composition, suppressed discoloration of the molded body even when subjected to a weather resistance test. Also, it was found that the resin composition of Example 10, which contained 13.5 wt% of cellulose having an arithmetic mean height (Sa) (cutoff value 5 μm) of 0.08 μm in the resin composition, suppressed discoloration of the molded body even when subjected to a weather resistance test.

[0136] In contrast, the results in Table 4 show that the resin composition of Comparative Example 1, which contained 65% by weight of cellulose having an arithmetic mean height (Sa) (cutoff value 5 μm) of 0.05 μm, could not be evaluated in the weather resistance test and was found to have poorer weather resistance than the resin composition of Example 1. Furthermore, the resin composition of Comparative Example 2, which contained 13.5% by weight of cellulose having an arithmetic mean height (Sa) (cutoff value 5 μm) of 0.11 μm, was found to have poorer weather resistance than the resin composition of Example 10.

Claims

A resin composition comprising cellulose having a surface roughness of 0.1 μm or less in arithmetic mean height at a cutoff value of 1.5 μm, a thermoplastic resin, and titanium oxide, wherein the cellulose content is 60% by weight or less.

2. The resin composition according to claim 1, wherein the cellulose content is 10% by weight or more.

3. The resin composition according to claim 1, wherein the cellulose comprises recycled material.

4. The resin composition according to claim 1, wherein the amount of hemicellulose in the cellulose is 10% by weight or less.

5. The resin composition according to claim 1, wherein the cellulose is not chemically modified.

6. The resin composition according to claim 1, wherein the cellulose has an average particle size of 100 μm or less.

7. The viscosity of the thermoplastic resin at 200°C is 1 x 10 ６ The resin composition according to claim 1, having a viscosity of Pa·s or less.

8. The resin composition according to claim 1, wherein the melting temperature of the thermoplastic resin is 200°C or lower.

9. The resin composition according to claim 1, wherein the melt flow rate (MFR) of the thermoplastic resin at a temperature of 230°C and a load of 2.16 kgf is 2.5 g / 10 min or more.

10. The resin composition of claim 1, wherein the thermoplastic resin comprises a polyolefin.

11. The resin composition of claim 1, wherein the thermoplastic resin comprises recycled material.

12. The resin composition according to claim 1, wherein the content of said titanium oxide is 5% by weight or less based on the weight of said resin composition.

13. A molded article obtained by injection molding the resin composition according to any one of claims 1 to 12.

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