Kneading method of cellulose-containing resin and cellulose-containing resin molded body

Abstract

To provide a kneading method of cellulose-containing resin, the method curbing discoloration of a cellulose-containing resin composition, and a cellulose-containing molded body high in whiteness.SOLUTION: A kneading method of kneading a resin composition containing thermoplastic resin and cellulose is a kneading method of cellulose-containing resin by kneading the resin composition under an inert gas atmosphere. A cellulose-containing molded body is manufactured by a manufacturing method including the kneading method of cellulose-containing resin.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for kneading a cellulose-containing resin and a molded product of a cellulose-containing resin. [Background technology]

[0002] Conventionally, in plastics containing a resin component and a reinforcing material, inorganic minerals, for example, inorganic fillers such as calcium and talc, are used as reinforcing materials. In recent years, as carbon neutrality (effectively zero greenhouse gas emissions) is being promoted as a national policy, efforts are being made to reduce CO2 emissions by changing part or all of the inorganic minerals to cellulose and kneading them with resin. In addition, by changing the inorganic minerals to cellulose, the molded plastic can be made lighter, and the handleability of the plastic product can be improved. For example, Patent Document 1 below describes an apparatus for kneading resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 027615 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since cellulose undergoes thermal degradation when heated, the whiteness of the resin composition is reduced by heating during kneading of the resin and cellulose, and therefore the resulting resin molded product needs to be colored in limited colors before use. The present invention has been made in consideration of the above circumstances, and aims to provide a method for kneading a cellulose-containing resin that can suppress discoloration due to heating when kneading a thermoplastic resin and cellulose, and a cellulose-containing resin molded body with high whiteness. [Means for solving the problem]

[0005] As a result of intensive research to solve the above problems, the present inventors have conceived the following invention and found that the above problems can be solved. [1] A method for kneading a resin composition containing a thermoplastic resin and cellulose, comprising kneading the resin composition under an inert gas atmosphere. [2] The method for kneading a cellulose-containing resin according to [1], wherein the inert gas atmosphere is carried out by supplying an inert gas to an apparatus for kneading the resin composition. [3] The method for kneading a cellulose-containing resin according to [2], wherein the inert gas atmosphere is achieved by supplying the inert gas and then sealing an apparatus for kneading the resin composition. [4] The method for kneading a cellulose-containing resin according to [1] or [2], wherein the inert gas is nitrogen gas. [5] The method for kneading a cellulose-containing resin according to [1] or [2], wherein the cellulose is contained in a resin composition in an amount of 10% by mass to 40% by mass. [6] The method for kneading a cellulose-containing resin according to [1] or [2], wherein the cellulose is a microfiber having an average fiber length of 5 μm or more and 100 μm or less and an average fiber diameter of 0.5 μm or more and 50 μm or less. [7] The method for kneading a cellulose-containing resin according to [1] or [2], wherein the thermoplastic resin is a biodegradable resin. [8] A method for producing a cellulose-containing resin molded body, comprising molding pellets from a resin composition kneaded by the cellulose-containing resin kneading method described in claim 1 or 2, and molding the pellets under an inert gas atmosphere. [9] A cellulose-containing resin molded body produced by a production method including the cellulose-containing resin kneading method described in [1] or [2]. Effect of the Invention

[0006] According to the present invention, discoloration caused by heating during kneading of a resin composition can be suppressed, and a cellulose-containing resin molded product having high whiteness can be provided. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a twin-screw kneading system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The method for kneading a cellulose-containing resin and a cellulose-containing resin molded product (hereinafter, simply referred to as a "resin molded product") according to the present invention will be described below with reference to the accompanying drawings.

[0009] The method for kneading a cellulose-containing resin according to the present embodiment is carried out by kneading a resin composition containing a thermoplastic resin and cellulose under an inert gas atmosphere.

[0010] [Resin composition] First, a resin composition used in the method for kneading a cellulose-containing resin according to the present embodiment will be described. The resin composition according to the present embodiment contains a thermoplastic resin and cellulose.

[0011] (thermoplastic resin) As the thermoplastic resin, various resins can be used depending on the type of the target molded body.Specifically, for example, thermoplastic resins such as polyethylene, polypropylene, polymethyl methacrylate, polyamide, polycarbonate, amorphous polyolefin, polyetherimide, polyethylene terephthalate, polyether ether ketone, ABS resin, polyphenylene sulfide, polyamideimide, etc., and composite materials thereof can be used.

[0012] Examples of biodegradable resins include aliphatic polyesters such as polylactic acid, polycaprolactone, polybutylene succinate, and polybutylene succinate adipate, aromatic aliphatic polyesters such as polybutylene adipate terephthalate, polyvinyl alcohol resins, polyhydroxyalkanoates, etc. By using a biodegradable thermoplastic resin, even if the produced resin molded body is disposed of in the ground, most of it is naturally decomposed into harmless water and carbon dioxide by microorganisms present in the ground, making it possible to make a material with excellent environmental friendliness.

[0013] In addition, by using a thermoplastic resin having a low melting point, the temperature during kneading can be lowered, so that discoloration of the resin composition itself can be reduced.In addition, by using a thermoplastic resin having a high melting point, the degree of discoloration caused by kneading in an air atmosphere and an inert gas atmosphere is significantly different from that in the case of a low temperature, so that the effect of the present invention can be more effectively exhibited.

[0014] (cellulose) The cellulose used in the present invention is not particularly limited, but cellulose microfiber can be used. The cellulose microfiber can be obtained, for example, by subjecting a plant raw material to a fiberization treatment and then subjecting the resulting cellulose fiber to a fiber defibration treatment. Examples of the plant raw material include wood, bamboo, hemp, cotton, paper, cloth, jute, kenaf, beet, agricultural products, and agricultural waste, and preferably wood. These plant raw materials can be used alone or in combination of two or more types.

[0015] Examples of the fiberization process include chemical processes, mechanical processes, etc. Examples of the chemical processes include the Kraft process, the sulfate process, the sulfite process, etc. Examples of the mechanical processes include grinding, etc. The type of cellulose fiber obtained varies depending on the type of plant raw material, and for example, when wood is used as the plant raw material, examples of the cellulose fiber include pulp, etc. More specifically, examples of the cellulose fiber include chemical pulp, semi-chemical pulp, chemi-ground pulp, chemi-mechanical pulp, mechanical pulp, refiner mechanical pulp, thermo-mechanical pulp, chemi-thermomechanical pulp, groundwood pulp, etc.

[0016] The average fiber length of the cellulose microfiber is, for example, 5 μm or more, preferably 10 μm or more, and for example, 100 μm or less, preferably 50 μm or less. The average fiber diameter of the cellulose microfiber is, for example, 0.5 μm or more, preferably 1.0 μm or more, and for example, 50 μm or less, preferably 30 μm or less. The average fiber length and the average fiber diameter can be measured by a digital microscope. For example, the fiber length and the fiber diameter of 30 cellulose microfibers are measured, and the average value can be calculated.

[0017] In the resin composition, the content of cellulose is not particularly limited and can be set appropriately depending on the purpose and application, but can be, for example, within the following ranges. The content of cellulose is preferably 10% by mass or more, more preferably 20% by mass or more, based on the total amount of the resin composition. Also, it is preferably 40% by mass or less, more preferably 30% by mass or less. By setting the content of cellulose within the above range, discoloration of the produced resin molded body can be suppressed and the strength can be maintained.

[0018] In the present embodiment, the use of cellulose can replace inorganic minerals that impart strength to conventional resin materials, and can impart strength to the resin molded body to be manufactured. In addition, the use of cellulose makes it possible to make a plant-derived material with excellent environmental resistance.

[0019] (Additives) The additives added to the cellulose-containing resin composition used in the present invention are not particularly limited as long as they can impart a predetermined function to the resulting resin molded body. Examples of additives include inorganic particles or precursors thereof such as organometallic complexes and metal alkoxides, inorganic fillers or modified compounds thereof such as carbon fibers and glass fibers, compatibilizers for promoting alloying of various resins, surfactants, dyes, nanocarbons, antistatic agents, flame retardant materials, phenolic, phosphorus, or sulfur additives for suppressing oxidation and thermal degradation of cellulose, etc. The concentration of the additive in the resin composition can be appropriately selected in consideration of the type of additive used and the function of the desired resin molded body, and is not particularly limited, but is preferably equal to or less than the saturated solubility.

[0020] [Mixing system] Next, an example of an apparatus for carrying out the method for kneading a cellulose-containing resin of the present invention will be described below. Fig. 1 is a schematic diagram of a twin-screw kneading system.

[0021] The twin-screw kneading system 100 shown in Figure 1 comprises a raw material supply section 110 that measures the raw materials, namely resin, cellulose, and additives, and supplies a predetermined amount of raw materials, a kneading and molding section 120 that kneads and molds the raw materials supplied from the raw material supply section 110, a cutting section 130 that cuts the resin molded body molded in the kneading and molding section 120, and a storage section 140 that stores the resin molded body cut by the cutting section 130.

[0022] The raw material supply section 110 includes a cellulose tank 1 and a resin tank 2 for storing the thermoplastic resin, cellulose, and additives, which are the raw materials of the cellulose-containing resin, respectively, and a plurality of additive tanks 3 for storing a plurality of types of additives, respectively. The raw material supply section 110 includes weight measuring machines 4 and 5 for measuring the weight of the cellulose and thermoplastic resin to be supplied to the kneading and molding section 120. The raw material supply section 110 also includes a weighing mixer 6 for weighing and mixing the materials stored in each of the additive tanks 3. Furthermore, the mixture of additives mixed in the weighing mixer 6 is weighed by a weighing machine 7 and supplied to the kneading and molding section 120.

[0023] The kneading and molding section 120 kneads and molds the raw materials supplied from the raw material supply section 110. The kneading and molding section 120 includes a forced feeder 8, and the cellulose, thermoplastic resin, and additives supplied from the raw material supply section 110 are premixed in the forced feeder 8 to form a cellulose-containing resin material. A nitrogen gas supply pipe 12, one end of which is connected to a nitrogen cylinder 9, is connected to a cellulose supply pipe 11 that supplies cellulose from the weight measuring device 4 to the forced feeder 8. The nitrogen gas supplied from the nitrogen cylinder 9 pressure-feeds the cellulose-containing resin material in the forced feeder 8 to the twin-screw kneader 10, and the forced feeder 8 and the twin-screw kneader 10 can be placed under a nitrogen atmosphere.

[0024] After the cellulose-containing resin material in the forced feeder 8 is pressure-fed into the twin-screw kneader 10, nitrogen gas is fed into the twin-screw kneader 10 for a while, and when the inside of the twin-screw kneader 10 is under a nitrogen gas atmosphere, the inlet and the outlet side (downstream side) of the twin-screw kneader 10 are also closed to seal the inside of the twin-screw kneader 10 under a nitrogen atmosphere. The cellulose-containing resin material fed into the twin-screw kneader 10 is plasticized as a thermoplastic resin on the upstream side of the twin-screw kneader 10 by rotating two screws (not shown) in the twin-screw kneader 10 to form a molten resin. The molten cellulose-containing resin material is kneaded by the rotation of the screws. At this time, since the inside of the twin-screw kneader 10 is under a nitrogen atmosphere, discoloration of the cellulose-containing resin material can be suppressed even if heating is performed to melt the thermoplastic resin.

[0025] The twin-screw kneader 10 is provided on the downstream side with an open vent 13 and a vacuum vent 14 for returning the inside of the twin-screw kneader 10 to normal pressure. When the kneading of the cellulose-containing resin material is completed, the gas inside the twin-screw kneader 10 can be released by opening the open vent 13. Furthermore, the pressure inside the twin-screw kneader 10 can be reliably returned to normal pressure by sucking with the vacuum vent 14.

[0026] The molten resin is extruded from the tip of the downstream side of the twin-screw kneader 10 to be molded into pellets of a desired shape. For example, an extrusion die for the shape of the pellets to be formed is provided on the downstream side (tip) of the twin-screw kneader 10, and a screw is advanced by a moving means provided on the upstream side (rear end) of the twin-screw kneader 10, and the molten resin having a predetermined shape is extruded from the extrusion die.

[0027] The molten resin extruded by the twin-screw kneader 10 in the kneading and molding section 120 is cooled when sent to the cutting section 130, and a hardened resin body is produced. The hardened resin body produced is cut in the cutting section 130 to form pellets of a predetermined size. The cutting section 130 is equipped with a pelletizer 15, and the hardened resin body is cut by the pelletizer 15.

[0028] The pellets cut in the cutting section 130 are transferred to the storage section 140 and stored in the product tank 18 provided in the storage section 140. The storage section 140 includes a blower 16, a cyclone 17, and the product tank 18. The pellets cut by the pelletizer 15 are pressurized by air blown by the blower 16 and transported to the cyclone 17. The pellets are separated into air and pellets in the cyclone 17, and the pellets fall downward to be stored in the product tank 18.

[0029] According to the twin-screw kneading system 100, the atmosphere inside the twin-screw kneader 10 when kneading the cellulose-containing resin with the twin-screw kneader 10 can be a nitrogen atmosphere, so that discoloration caused by heating the cellulose can be suppressed. In addition, by suppressing discoloration, strength deterioration can be suppressed. Therefore, the pellets formed can provide a product with high whiteness and high strength.

[0030] In addition, in Fig. 1, an example is described in which a twin-screw kneading system 100 equipped with a twin-screw kneader 10 is used, but the kneading method for the cellulose-containing resin is not limited to the twin-screw kneader. For example, it can be performed using a single-screw kneader using one screw.

[0031] In addition, the method of creating a nitrogen atmosphere inside the kneader (twin-screw kneader 10) is not limited to sealing the inside of the kneader and creating a nitrogen atmosphere. The inside of the kneader can also be left open and kneaded while supplying nitrogen gas to create a nitrogen atmosphere.

[0032] The pellets produced using the twin-screw kneading system 100 shown in Fig. 1 are sent to a molding device (not shown) to produce a resin molded body. In the molding process of the pellets, the pellets are heated and melted to be molded, so this molding process is also preferably performed under an inert gas atmosphere. As the inert gas, an inert gas described later can be used.

[0033] The method of molding the pellets is not particularly limited, and may be injection molding, blow molding (hollow molding, blow molding), extrusion molding, vacuum molding, compression molding, or the like. For example, when molding by injection molding, an apparatus equipped with an injection device and a mold is used. The pellets produced by the twin-screw kneading system are fed into the injection device, where they are heated and melted. A screw is also provided in the injection device, and the molten resin is extruded by the screw and supplied in a fixed amount to the mold. The molten resin supplied to the mold is cooled in the mold, and the molten resin solidifies to form a resin molded body.

[0034] Heating is performed in the injection device to melt the pellets, but discoloration due to thermal deterioration of cellulose can be suppressed by making the atmosphere in the injection device an inert gas atmosphere. The method of making the atmosphere in the injection device an inert gas atmosphere can be the same as the case of making the atmosphere in the twin-screw kneader 10 an inert gas atmosphere, in which the resin is melted and supplied while supplying an inert gas into the injection device, or by supplying an inert gas into the injection device and sealing it.

[0035] In addition, when molding by blow molding, for example, cylindrical pellets are molded, the cylindrical pellets are placed in a metal mold, and while heating and melting the cylindrical pellets in the metal mold, an inert gas is supplied into the cylindrical pellets, thereby forming a resin molded body by blow molding.

[0036] In the above, a method for producing pellets using the twin-screw kneading system 100 and then molding the produced pellets has been described. However, in the case of injection molding, extrusion molding, or the like, a mold may be placed downstream of the twin-screw kneader 10 of the twin-screw kneading system 100, and the molten resin kneaded by the twin-screw kneader 10 may be processed and molded without producing pellets.

[0037] (inert gas) In the twin-screw kneading system 100 shown in Fig. 1, nitrogen is used as the inert gas used when kneading and molding the resin composition under an inert gas atmosphere, but the inert gas is not limited to nitrogen and may be a rare gas such as helium, neon, argon, krypton, xenon, or radon, or carbon dioxide gas. Among these, nitrogen gas is preferable from the viewpoint of cost.

[0038] (Cellulose-containing resin molding) The resin molded product produced by the production method including the method for kneading the cellulose-containing resin of this embodiment can be used for the same applications as conventional ones depending on the type of thermoplastic resin, etc. For example, resin molded articles using polypropylene, a composition of polycarbonate and ABS resin, or a composition of polyester and ABS resin as the thermoplastic resin can be effectively used in automotive applications such as automobile bumpers, instrument panels, door trims, fan covers, heater housings, ducts, etc. Furthermore, resin molded articles using polypropylene can be effectively used in applications such as tray containers. EXAMPLES

[0039] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0040] (Test Example 1 [Reference Test Example]) A heating test was conducted using cellulose to confirm the color change of cellulose due to heating. 20 g of cellulose microfiber (hereinafter also referred to as "CMF") was weighed into an Erlenmeyer flask (500 ml) and heated in a dryer (internal dimensions: 450 × 480 × 450 mm, internal volume: 97 L, temperature control accuracy: ±1 °C). The heating temperatures were 130 °C, 160 °C, 190 °C, and 220 °C, and the temperatures were maintained for 5 minutes, 10 minutes, and 15 minutes after reaching each temperature. The gas atmosphere in the dryer was air atmosphere, open air atmosphere, or air atmosphere sealed atmosphere. The nitrogen atmosphere was nitrogen supply atmosphere in which nitrogen gas was supplied at 1 L / min (50 L / kg min for CMF) or 4 L / min (200 L / kg min for CMF), and nitrogen sealed atmosphere in which nitrogen gas was supplied and then sealed. The CMFs used in the test are shown below. The evaluation was performed by the weight loss rate, visual observation, and color measurement test. The evaluation methods are shown below. The results are shown in Table 1.

[0041] (Cellulose microfiber) -Manufactured by Rettenmaier Japan Co., Ltd., Product number: ARBOCEL FD 600 / 30, Moisture content: 9.16%, (Fiber length: 30 μm, Fiber diameter: 18 μm, Fiber density: 200-260 (catalog value))

[0042] (Evaluation method) <Weight reduction rate> The weight loss of CMF before and after heating was measured. Weight loss (g) / weight of CMF before heating (g) x 100 The weight loss rate was calculated by the following. Visual Observation The color of the CMF after heating was visually confirmed. <Color measurement test> In order to examine the degree of discoloration of the CMF in the Erlenmeyer flask, the following color measurement test was carried out on the CMF after heating. The color measurement test was carried out using the following equipment under the following conditions. Measuring equipment: Spectroscopic whiteness and color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd.) Model: PF700R Measurement wavelength: 400nm~700nm, output at 10nm intervals Light source: Pulsed xenon lamp Table color system: L Sample preparation: 5 ml of dioctyl phthalate (DOP) was added to 2.5 g of CMF on a glass plate, mixed with a spatula until it became a paste, and placed in a cylindrical glass cell (diameter 35 mm, height 15 mm, thickness 2 mm), and then measured using the PF700R.

[0043] [Table 1]

[0044] As shown in Table 1, by heating in a nitrogen atmosphere, color change was suppressed more than in an air atmosphere. Furthermore, even in a nitrogen atmosphere, color change was suppressed most when the container was sealed during heating, and color change was suppressed even more when the nitrogen supply flow rate was low.

[0045] (Test Example 2) The resin and CMF were kneaded by supplying nitrogen gas to the kneader when kneading the resin and CMF. A twin-screw kneader was used, and before the materials were fed into the twin-screw kneader, nitrogen was flowed into the kneader to thoroughly replace the atmosphere inside the kneader with nitrogen. After the atmosphere inside the kneader was thoroughly replaced with nitrogen, 70 parts by weight of the resin and 30 parts by weight of cellulose microfiber (CMF) were weighed and fed into the kneader, and the resin and CMF were kneaded at the heating temperature and heating time in Table 2 while supplying the nitrogen flow rate shown in Table 2. The screw rotation speed of the kneader was 200 rpm.

[0046] As a comparative example, the same materials as in Examples 1-6 were used, and the resin and CMF were kneaded under atmospheric pressure without supplying nitrogen gas. The materials used in the test are shown below. (resin) [Example 1, Comparative Example 1] BiO PBS (Bio Polybutylene Succinate), biodegradable, manufactured by Mitsubishi Chemical Corporation, resin part number: ZM9B02 [Example 2, Comparative Example 2] PBAT (Polybutylene Adipate Terephthalate), biodegradable, manufactured by Zhuhai Kingfa Biomaterial Co., Ltd., resin part number: A400 [Example 3, Comparative Example 3] PHA (Polyhydroxyalkanoate), biodegradable, manufactured by TianAn Biologic Materials Co., Ltd, resin part number: Y1000P [Example 4, Comparative Example 4] ·PLA (polylactic acid), biodegradable, made by Zhejiang Haicheng Biomaterial Co., Ltd., resin product number: REVODE290 [Example 5, Comparative Example 5] LDPE (low density polyethylene), petroleum-based, manufactured by Tosoh Corporation, resin part number: Petrothene 175 [Example 6, Comparative Example 6] PP (polypropylene), petroleum-based, manufactured by SunAllomer Co., Ltd., resin part number: VB370A (Cellulose microfiber) [Examples 1 to 6, Comparative Examples 1 to 6] -Manufactured by Rettenmaier Japan Co., Ltd., Product number: ARBOCEL FD 600 / 30, Moisture content: 9.16%, (Fiber length: 30 μm, Fiber diameter: 18 μm, Fiber density: 200-260 (catalog value))

[0047] (evaluation) <Color measurement test> The resin composition of the kneaded resin and cellulose fiber was poured into a mold (30×30×6 mm) to produce a cellulose-containing resin molded body. The degree of discoloration of the cellulose-containing resin molded body was measured by a color measurement test in the same manner as in Test Example 1. The results of Examples 1-6 are shown in Table 2, and the results of Comparative Examples 1-6 are shown in Table 3.

[0048] [Table 2]

[0049] [Table 3]

[0050] As shown in Tables 2 and 3, comparing the respective Examples and Comparative Examples, discoloration due to heating could be suppressed by kneading the resin and CMF under a nitrogen atmosphere while flowing nitrogen.

[0051] (Test Example 3) The kneader used for kneading the resin and CMF and the method for creating a nitrogen atmosphere were changed to knead the resin and CMF. When kneading was performed while supplying nitrogen, the inside of the kneader was replaced with nitrogen in the same manner as in Test Example 2, and kneading was performed while supplying nitrogen at 15 L / min. When kneading was performed under a sealed nitrogen atmosphere, nitrogen was supplied at 15 L / min, and after the inside of the kneader was sufficiently replaced with nitrogen, the kneader was sealed and kneading was performed. The kneading time was 12 minutes in all cases. For the evaluation, a cellulose-containing resin molded product was produced in the same manner as in Test Example 2, and a color measurement test was carried out to evaluate it. The results are shown in Table 4.

[0052] The materials used in Test Example 3 are shown below. (resin) [Examples 7 and 8, Comparative Example 7] PP (polypropylene), manufactured by Prime Polymer Co., Ltd., resin part number: F113G LLDPE (linear low-density polyethylene), manufactured by Tosoh Corporation, resin part number: Nipolon Z (TZ421)

[0053] [Table 4]

[0054] As shown in Table 4, kneading in a nitrogen atmosphere was able to suppress color change due to heating more than kneading in an air atmosphere. In addition, by creating a nitrogen atmosphere inside the kneader and kneading in an airtight state, color change could be further suppressed.

[0055] (Test Example 4) Additives were added when mixing the resin and CMF, and the resin and CMF were mixed using an actual twin-screw mixer system (twin-screw mixer) shown in Figure 1. Mixing was performed while replacing the atmosphere inside the mixer with nitrogen and supplying nitrogen from four points at 12.5 L / min. The mixing time was 12 minutes. The evaluation was performed by carrying out a color measurement test in the same manner as in Test Example 2. The test conditions and results are shown in Table 5.

[0056] The materials used in Test Example 4 are shown below. (resin) PP (polypropylene), manufactured by Prime Polymer Co., Ltd., resin part number: JU708UG (Additives) [Comparative Example 9, Example 10] Compatibilizer, manufactured by Osaka Gas Chemicals Co., Ltd., product name: Maricon J1000MB, blending amount: 1% by weight Calcium stearate, Dainichi Chemical Industry Co., Ltd., product name: Daiwax C-40P, blending amount: 1% by weight [Example 11] Compatibilizer, Mitsubishi Chemical Corporation, product name: Diacarna 30M, blending amount: 1% by weight Calcium stearate, Dainichi Chemical Industry Co., Ltd., product name: Daiwax C-40P, blending amount: 1% by weight Phenolic antioxidant, manufactured by Adeka Corporation, product name: Adeka STAB AO-60, blending amount: 0.3% by weight Phosphorus-based antioxidant, manufactured by Adeka Corporation, product name: Adeka STAB 2112, blending amount: 0.3% by weight

[0057] [Table 5]

[0058] As shown in Table 5, the addition of additives could further suppress the color change due to heating. [Industrial Applicability]

[0059] By kneading cellulose and resin using the method for kneading a cellulose-containing resin of the present invention, discoloration due to heating can be suppressed. Therefore, the method can be applied to uncolored plastic products or to colored plastic products of various colors. [Explanation of symbols]

[0060] 1 Cellulose tank 2 Resin tank 3 Additive tank 4, 5, 7 Weighing machine 6 Measuring mixer 8 Forced feed machine 9 Nitrogen Cylinder 10 Twin-shaft kneader 11 Cellulose supply pipe 12 Nitrogen gas supply pipe 13 Open Vent 14 Vacuum Vent 15 Pelletizer 16 Blower 17. Cyclone 18 Product Tank 100 Twin-screw mixing system 110 Raw material supply department 120 Kneading and molding section 130 Cutting section 140 Storage unit

Claims

1. A method for kneading a resin composition containing a thermoplastic resin and cellulose, comprising the steps of: A method for kneading a cellulose-containing resin, comprising kneading the resin composition under an inert gas atmosphere.

2. The method for kneading a cellulose-containing resin according to claim 1 , wherein the inert gas atmosphere is provided by supplying an inert gas to an apparatus for kneading the resin composition.

3. The method for kneading a cellulose-containing resin according to claim 2 , wherein the inert gas atmosphere is achieved by supplying the inert gas and then sealing an apparatus for kneading the resin composition.

4. 3. The method for kneading a cellulose-containing resin according to claim 1, wherein the inert gas is nitrogen gas.

5. The method for kneading a cellulose-containing resin according to claim 1 or 2, wherein the cellulose is contained in a resin composition in an amount of 10% by mass to 40% by mass.

6. 3. The method for kneading a cellulose-containing resin according to claim 1, wherein the cellulose is a microfiber having an average fiber length of 5 μm or more and 100 μm or less and an average fiber diameter of 0.5 μm or more and 50 μm or less.

7. 3. The method for kneading a cellulose-containing resin according to claim 1, wherein the thermoplastic resin is a biodegradable resin.

8. A resin composition kneaded by the method for kneading a cellulose-containing resin according to claim 1 or 2 is molded into pellets, The pellets are molded in an inert gas atmosphere to produce a cellulose-containing resin molded article.

9. A cellulose-containing resin molded product produced by a production method including the method for kneading a cellulose-containing resin according to claim 1 or 2.

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