Method for producing cellulosic resin composite

Abstract

To provide a method for producing a cellulosic resin composite which has excellent hardness and impact resistance, and also has excellent workability at the same time.SOLUTION: A method for producing a cellulosic resin composite includes: a string-processing step of string-processing a nonwoven fabric including a cellulose fiber and a thermoplastic resin fiber to obtain a paper string; a cutting step of cutting the paper string to obtain paper string pellets; and a kneading step of kneading the paper string pellets and thermoplastic resin, where the content of the cellulose fiber is 30 mass% or more relative to the total amount of the nonwoven fabric.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a cellulose resin composite.

Background Art

[0002] Conventionally, molded articles and sheets have been discarded as household waste after being used up and disposed of by incineration or landfill. In recent years, due to the increasing environmental awareness, alternatives using materials with low environmental impact, such as products using cellulose fibers, which are plant-derived resources, have attracted attention, and composites obtained by kneading pulverized pulp or waste paper with thermoplastic resins have been developed.

[0003] For example, Patent Document 1 aims to provide a thermoplastic resin composition having higher strength and a method for producing the same while using conventionally used plant fibers as a reinforcing material for the resin. A thermoplastic resin composition containing a predetermined thermoplastic resin, a predetermined plant fiber, and a predetermined binder, and adjusting the content of the binder with respect to the content of the plant fiber within a predetermined range is disclosed. Further, Patent Document 2 discloses a predetermined microcrystalline cellulose fiber-containing sheet, a pulverized product thereof, and a resin composition for the purpose of providing a microcrystalline cellulose fiber-containing sheet excellent in production efficiency when pulverizing or compositing. Furthermore, Patent Document 3 aims to provide a cellulose fiber-containing molded article or the like that can improve moldability in vacuum forming or vacuum pressure forming even when containing cellulose fibers, and can express a unique texture and a soft texture with a matte finish on the surface. A method for producing a cellulose fiber-containing molded article having a predetermined kneading step, a predetermined pelletizing step, a predetermined sheeting step, a step of forming a predetermined cellulose fiber-containing multilayer structure, and a step of forming a predetermined matte finish is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] However, although the techniques described in Patent Documents 1 to 3 all improve the hardness and the like of the composite by mixing resin and cellulose fibers to produce a composite, it is hard to say that the impact resistance is sufficient. Further, although the composite and the like described in Patent Document 2 perform a pulverization treatment on cellulose fibers in order to improve the kneadability between the cellulose fibers and the resin, since the pulverization treatment generally requires a long time, it cannot be said that the production efficiency is sufficient.

[0006] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a cellulose resin composite excellent in hardness and impact resistance and at the same time excellent in production efficiency (hereinafter, also simply referred to as "workability"). [Means for Solving the Problems]

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by the following configuration, and have completed the present invention.

[0008] That is, the present invention is as follows. [1] A twisting step of twisting a nonwoven fabric containing cellulose fibers and thermoplastic resin fibers to obtain a paper string, A cutting step of cutting the paper string to obtain paper string pellets, A kneading step of kneading the paper string pellets and a thermoplastic resin, and A method for producing a cellulose resin composite, wherein the content of the cellulose fibers is 30% by mass or more based on the total amount of the nonwoven fabric. [2] The content of the cellulose fiber in the non-woven fabric is 50% by mass or more based on the total amount of the non-woven fabric. The method for producing the cellulose resin composite according to [1]. [3] The non-woven fabric has a strength in the flow direction of 0.2 kN / m or more and a thickness of 150 μm or less. The method for producing the cellulose resin composite according to [1] or [2]. [4] The average fiber length of the cellulose fiber is 0.9 mm or more and 1.2 mm or less. The method for producing the cellulose resin composite according to any one of [1] to [3]. [5] The basis weight of the non-woven fabric is 35 g / m 2 or more. The method for producing the cellulose resin composite according to any one of [1] to [4]. [6] The cut length of the paper string pellet is 3 mm or more and 15 mm or less. The method for producing the cellulose resin composite according to any one of [1] to [5]. [7] The content of the cellulose fiber in the cellulose resin composite is 10% by mass or more and 30% by mass or less based on the total amount of the cellulose resin composite. The method for producing the cellulose resin composite according to any one of [1] to [6]. [8] In the kneading step, a kneaded product is obtained by kneading with a kneader. The difference between the outlet temperature of the kneaded product discharged from the kneader and the melting point of the thermoplastic resin is 25°C or more and 60°C or less. The method for producing the cellulose resin composite according to any one of [1] to [7]. [9] In the kneading step, a kneaded product is obtained by kneading with a twin-screw kneader having two screws. The discharge rate, which is the ratio of the discharge amount (kg / hr) of the kneaded product to the rotation speed (rpm) of the screw of the twin-screw kneader, is 1.50 kg / rotation or more and 4.50 kg / rotation or less. The method for producing a cellulose resin composite according to any one of [1] to [8].

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a method for producing a cellulose resin composite that is excellent in hardness and impact resistance and at the same time excellent in workability.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention (hereinafter also referred to as "the present embodiment") will be described. Note that the present embodiment is an exemplification for explaining the present invention, and the present invention is not limited only to the present embodiment.

[0012] 1. Method for producing a cellulose resin composite The method for producing a cellulose resin composite of the present embodiment includes a stringing step of stringing a nonwoven fabric containing cellulose fibers and thermoplastic resin fibers to obtain a paper string, a cutting step of cutting the paper string to obtain paper string pellets, and a kneading step of kneading the paper string pellets and a thermoplastic resin. The content of the cellulose fibers is 30% by mass or more based on the total amount of the nonwoven fabric. Further, the method for producing a cellulose resin composite of the present embodiment may include other steps as long as the effects of the present invention are not inhibited. Hereinafter, the specific configuration of the method for producing a cellulose resin composite will be described, but the present invention is not particularly limited thereby.

[0013] 1.1. Stringing step The stringing process is a process of stringing a non-woven fabric containing cellulose fibers and thermoplastic resin fibers to obtain paper strings. In this embodiment, the method for obtaining paper strings is not particularly limited. For example, a method of forming a paper string, which is a single braided cord, by crossing two or more ribbon-shaped fragments of the non-woven fabric inside and outside while spirally winding them clockwise and counterclockwise respectively, or a method of forming a paper string by twisting the ribbon-shaped fragment by passing it through a rotating thin nozzle can be mentioned.

[0014] Stringing is preferably performed such that the density of the paper string pellets obtained through the stringing process and subsequent processes is 0.05 g / m 3 or more and 0.15 g / m 3 or less, more preferably 0.07 g / m 3 or more and 0.12 g / m 3 or less, and even more preferably 0.09 g / m 3 or more and 0.12 g / m 3 or less. Thereby, the contact area during kneading with the thermoplastic resin can be increased, and the workability tends to be excellent. Also, due to more sufficient kneading, the hardness and impact resistance of the cellulose resin composite tend to be improved. The density of the above-mentioned paper string pellets is defined as the mass when the paper string pellets are filled in a container having a certain volume (1000 cc), and is the mass per unit volume.

[0015] Stringing is preferably performed such that the cross-sectional area of the paper string pellets obtained through the stringing process and subsequent processes is 15 mm 2 or more and 30 mm 2 or less, more preferably 17 mm 2 or more and 27 mm 2 or less, and even more preferably 19 mm 2 or more and 25 mm 2It is more preferable to perform as follows. By doing so, there is a tendency for the workability to be further excellent, and by performing more sufficient kneading, the hardness and impact resistance also tend to be further improved. The cross-sectional area of the above paper string pellets is the cross-sectional area approximated by assuming the cross-section when the paper string is cut to obtain the paper string pellets as an ellipse. The cross-sectional area is obtained by measuring the major axis a and minor axis b of the cross-section and using the formula of major axis a × minor axis b × pi. Measure the cross-sectional area for 10 or more paper string pellets, and use the average value as the cross-sectional area of the paper string pellets.

[0016] 1.1.1. Non-woven fabric The non-woven fabric of this embodiment contains cellulose fibers and thermoplastic resin fibers, and may contain other components as long as the effects of the present invention are not inhibited. As for the manufacturing method of the non-woven fabric, a conventionally well-known method can be used and is not particularly limited. For example, the wet method, the dry method, and the spunbond method can be mentioned. The wet method is not particularly limited, but for example, the method described in the examples described later can be used. Each component in the non-woven fabric will be described in detail below.

[0017] 1.1.1.1. Cellulose fibers The cellulose fibers are not particularly limited, and examples include fibers derived from wood pulp and non-wood pulp. The pulp fibers derived from wood pulp are not particularly limited, and examples include pulp fibers derived from coniferous trees such as the Pinaceae and the Cupressaceae, and pulp fibers derived from broad-leaved trees such as the Fagaceae, the Betulaceae, the Aceraceae, the Salicaceae, and the Myrtaceae of Eucalyptus. Those derived from non-wood pulp are not particularly limited, and examples include pulp fibers derived from rice straw, sugarcane, and rush.

[0018] Further, the cellulose fibers of this embodiment may be regenerated cellulose fibers. The regenerated cellulose fibers are fibers obtained by dissolving pulp fibers or the like once by a chemical reaction and then spinning them again. They are not particularly limited, and examples include rayon, polynosic, cupra, and lyocell.

[0019] 1.1.1.2. Average fiber length The average fiber length of the cellulose fibers of the present embodiment is preferably 0.9 mm or more and 1.2 mm or less. When the average fiber length of the cellulose fibers is 0.9 mm or more, the hardness and impact resistance tend to be excellent. When the average fiber length of the cellulose fibers is 1.2 mm or less, the workability tends to be excellent.

[0020] The average fiber length of the cellulose fibers can be adjusted according to the selection of pulp type and the degree of beating treatment during raw material preparation. Also, the average fiber length of the cellulose fibers can be measured as the length-weighted average fiber length, for example, in accordance with JIS P 8226-2:2011.

[0021] The content of the cellulose fibers in the nonwoven fabric is 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total amount of the nonwoven fabric. The upper limit value of the content of the cellulose fibers in the nonwoven fabric is not particularly limited, and may be 95% by mass, 90% by mass, 85% by mass, or 80% by mass. When the content of the cellulose fibers in the nonwoven fabric is 30% by mass or more based on the total amount of the nonwoven fabric, paper breakage is less likely to occur when processing the nonwoven fabric into paper strings, and the processability is further excellent.

[0022] 1.1.1.3. Thermoplastic resin fibers As the thermoplastic resin constituting the thermoplastic resin fiber, conventionally known ones can be used and are not particularly limited. For example, polyethylene resin, polypropylene resin, polyvinyl acetate resin, polyurethane resin, and polyester resin can be mentioned. Among them, from the viewpoint of workability, at least one of polyethylene resin and polypropylene resin is preferable. Also, from the viewpoint of environmental compatibility, among polyester resins, at least one of biomass resin and biodegradable resin is preferable. The biodegradable resin is not particularly limited, and examples include polylactic acid, polybutyl succinate, and polyhydroxyalkanoate. The thermoplastic resin may be used alone or in combination of two or more.

[0023] The content of the thermoplastic resin fiber in the nonwoven fabric is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, and even more preferably 30% by mass or less. The lower limit of the content of the thermoplastic resin fiber in the nonwoven fabric is not particularly limited, and it may be 5% by mass, 10% by mass, 15% by mass, or 20% by mass. When the content of the thermoplastic resin fiber in the nonwoven fabric is 70% by mass or less with respect to the total amount of the nonwoven fabric, the strength of the nonwoven fabric is increased, and when processing the nonwoven fabric into paper strings, paper breakage is less likely to occur, and the processability is further excellent.

[0024] 1.1.1.4. Strength The nonwoven fabric of this embodiment preferably has a strength in the flow direction of 0.2 kN / m or more, more preferably 0.4 kN / m or more, still more preferably 0.6 kN / m or more, even more preferably 0.8 kN / m or more, and particularly preferably 1.0 kN / m or more. When the strength of the nonwoven fabric of this embodiment in the flow direction is 0.2 kN / m or more, it tends to have excellent workability. Here, the strength in the flow direction means the tensile strength in the flow direction of the machine, and the specific measurement method is as described in the examples. The upper limit of the strength in the flow direction is not particularly limited, and for example, it may be 3.0 kN / m, 2.5 kN / m, 2.0 kN / m, or 1.5 kN / m.

[0025] 1.1.1.5. Thickness The nonwoven fabric of this embodiment preferably has a thickness of 150 μm or less, more preferably 140 μm or less, still more preferably 130 μm or less, and even more preferably 120 μm or less. The lower limit of the thickness is not particularly limited, and for example, it may be 90 μm, 100 μm, or 110 μm. When the thickness of the nonwoven fabric of this embodiment is 150 μm or less, it tends to improve the stability of raw material input during kneading, and thereby improve workability.

[0026] 1.1.1.6. Basis weight The basis weight of the nonwoven fabric of this embodiment is preferably 35 g / m 2 or more, more preferably 40 g / m 2 or more, still more preferably 45 g / m 2 or more, and even more preferably 50 g / m 2 or more. When the basis weight of the nonwoven fabric of this embodiment is 35 g / m 2 or more, the resulting cellulose resin composite tends to have excellent hardness. The upper limit of the basis weight of the nonwoven fabric is not particularly limited, and for example, it may be 80 / m 2 or 70 g / m 2 or 60 g / m 2 or less.

[0027] 1.2. Cutting process The cutting process of this embodiment is a process of cutting the paper string of this embodiment to obtain paper string pellets. As a method for cutting the paper string, a conventionally known method can be used and is not particularly limited. For example, cutting by guillotine, cutting by rotary, and cutting by cutter can be mentioned. Here, the paper string pellet means a thing obtained by cutting the paper string into at least two or more pieces.

[0028] The cutting process of this embodiment is preferably performed so that the cut length of the paper string pellet is 3 mm or more and 15 mm or less, preferably 4 mm or more and 12 mm or less, and preferably 5 mm or more and 10 mm or less. When the cut length of the paper string pellet is 3 mm or more, it is possible to prevent the adhesion between the cut surfaces during kneading and the workability tends to be excellent. When it is performed so as to be 15 mm or less, it is possible to prevent the raw material input into the kneader from becoming uneven and the workability tends to be excellent.

[0029] 1.3. Kneading process The kneading process of this embodiment is a process of kneading the paper string pellet and the thermoplastic resin. Further, in the kneading process, other components other than the paper string pellet and the thermoplastic resin may be kneaded as long as the effects of the present invention are not inhibited.

[0030] 1.3.1. Thermoplastic resin As the thermoplastic resin to be kneaded with the paper string pellets, the same resin as that constituting the thermoplastic resin fibers used for producing the nonwoven fabric can be used. That is, as the thermoplastic resin, a conventionally known one can be used and is not particularly limited. For example, polyethylene resin, polypropylene resin, polyvinyl acetate resin, polyurethane resin, polyamide resin, and polyester resin can be mentioned. Among them, from the viewpoint of workability, at least one of polyethylene resin and polypropylene resin is preferable. Also, from the viewpoint of environmental compatibility, among the polyester resins, at least one of biomass resin and biodegradable resin is preferable. The biodegradable resin is not particularly limited, and examples include polylactic acid, polybutyl succinate, and polyhydroxyalkanoate. The thermoplastic resin may be used alone or in combination of two or more.

[0031] The thermoplastic resin may be different from the thermoplastic resin constituting the thermoplastic resin fibers, but it is preferably of the same kind. Thereby, the time required for kneading the nonwoven fabric and the thermoplastic resin can be shortened, the workability is excellent, and at the same time, it can be kneaded more uniformly, and the hardness and impact resistance of the obtained cellulose resin composite tend to be excellent.

[0032] 1.3.2. Mixing ratio The mixing ratio of the paper string pellets and the thermoplastic resin in the kneading process is preferably such that the content of cellulose fibers in the cellulose resin composite is 15% by mass or more and 45% by mass or less, more preferably such that the content is 20% by mass or more and 40% by mass or less, and even more preferably such that the content is 25% by mass or more and 35% by mass or less.

[0033] 1.3.3. Other components Other components used in the kneading process are not particularly limited, and examples thereof include compatibilizers and modifiers. The compatibilizer is not particularly limited, and for example, those that improve the compatibility between the cellulose fiber and the thermoplastic resin can be used, and modified polyolefins and modified celluloses can be mentioned. The modified polyolefin is not particularly limited, and for example, those composed of a polypropylene segment and an anhydrous carboxylic acid segment can be mentioned. The modifier is not particularly limited, and for example, amorphous or low-crystalline α-olefin copolymers can be mentioned.

[0034] 1.3.4 Kneader The kneading treatment is not particularly limited, and for example, one or more types can be selected and used from a single-screw or multi-screw kneader with two or more axes, multi-screw kneading extruder, mixing roll, kneader, roll mill, Banbury mixer, screw press, disperser, etc. Among these, it is preferable to use a multi-screw kneader with two or more axes. Two or more multi-screw kneaders with two or more axes may be used in parallel or in series.

[0035] 1.3.5 Kneading Temperature The kneading temperature in the kneading process may be appropriately set according to the type of thermoplastic resin from the viewpoints of hardness and impact resistance. For example, when the thermoplastic resin is a polypropylene resin, the kneading temperature is preferably 130°C or higher and 220°C or lower, more preferably 130°C or higher and 200°C or lower, and even more preferably 130°C or higher and 190°C or lower.

[0036] In the kneading process, due to frictional heat during the kneading of the thermoplastic resin and the cellulose fiber, the temperature of the actual kneaded product tends to be higher than the set kneading temperature. In the case of a multi-screw kneader with two or more screws, the temperature of the kneaded product at the outlet of the kneader is measured, and the difference between the outlet temperature of the kneaded product discharged from the kneader and the melting point of the thermoplastic resin is preferably 25°C or more and 60°C or less, more preferably 25 or more and 55°C or less, still more preferably 25 or more and 45°C or less, and particularly preferably 25 or more and 35°C or less. By adjusting the kneading temperature of the kneader in this way, a cellulose resin composite excellent in hardness and impact resistance can be provided.

[0037] In addition, when a plurality of thermoplastic resins are used in this embodiment, the melting point of the thermoplastic resin is the melting point of the thermoplastic resin having the highest composition ratio among the thermoplastic resins constituting the cellulose fiber resin composite of this embodiment. The temperature of the kneaded product at the outlet of the kneader can be measured with a measuring instrument such as a thermocouple method or a radiation thermometer.

[0038] 1.3.6 Discharge rate The discharge rate in a multi-screw kneader is defined as shown in Equation (1) by dividing the discharge amount (kg / hr) of the kneaded product per hour in the kneader by the rotational speed (rpm) of the cylinder of the multi-screw kneader. Discharge rate (kg / revolution) = Discharge amount (kg / hr) × 60 / Rotational speed of cylinder (rpm) (Equation 1) From the viewpoint of suppressing thermal degradation and further improving hardness and impact resistance, the discharge rate is preferably 1.50 to 4.50 kg / revolution, more preferably 2.00 to 4.50 kg / revolution, still more preferably 2.50 to 4.50 kg / revolution, and particularly preferably 3.00 to 4.50 kg / revolution. The discharge rate can be adjusted by independently or in combination adjusting the discharge amount of the multi-screw kneader and the rotational speed of the multi-screw kneader.

Examples

[0039] Hereinafter, the cellulose resin composite according to this embodiment will be described more specifically using examples and comparative examples. However, the present invention is not limited by the following examples in any way.

[0040] 1. Production of non-woven fabric <Example 1> First, a non-woven fabric was produced by the wet method. Specifically, first, cellulose fibers (softwood bleached kraft pulp) adjusted to an average fiber length of 0.85 mm with a single disk refiner and 0.6 dtx × 5 mm manufactured by Daiwa Boseki Co., Ltd. as thermoplastic resin fibers were mixed as fiber raw materials so that the mass ratio was 70:30. Next, after dispersing the fiber raw materials in water so that the concentration in water became 0.1% by mass, wet papermaking was performed with an inclined wire type paper making machine, dried at a dryer temperature of 140 °C, and a basis weight of 35 g / m 2 , and a non-woven fabric with a thickness of 125 μm was produced.

[0041] <Other examples and comparative examples> Non-woven fabrics of each example and each comparative example were produced under the same conditions as in Example 1 except that the average fiber length of the cellulose fibers, the content of the cellulose fibers, the content of the thermoplastic resin fibers, and other conditions were changed as shown in Table 1.

[0042]

Table 1

[0043] In Table 1, "average fiber length of cellulose fibers", "basis weight", "density", and "tensile strength (MD)" respectively mean the basis weight of the non-woven fabric, the thickness, and the tensile strength in the machine direction (MD). Also, calendering means that thickness adjustment was performed with a calender device of metal-metal rolls, wet paper press treatment means that when manufacturing the non-woven fabric, the line pressure when squeezing the wet paper and the pressure of pressing the wet paper against the dryer surface were increased to adjust the thickness, and pulverization means that pulverization was performed into a fibrous cotton shape with a conventionally known dry pulverizer.

[0044] Details of each component shown in Table 1 are as follows. · Cellulose fiber: NBKP (needle - leaf tree - derived pulp fiber) · Polyolefin fiber: 0.6 dtx × 5 mm, manufactured by Yamato Boshoku Corporation

[0045] In Table 1, basis weight, thickness, and tensile strength (MD) were measured by the following methods. <Average fiber length of cellulose fiber> In accordance with JIS P8226:2011, the length - weighted average fiber length of cellulose fibers in the examples and comparative examples was measured using the "L&W Fiber Tester PLus" (trade name) manufactured by ABB. <Basis weight> In accordance with JIS P8124:2011, the basis weight of the non - woven fabrics in the examples and comparative examples was measured. <Thickness> In accordance with JIS P8118:2014, the thickness of the non - woven fabrics in the examples and comparative examples was measured. <Tensile strength (MD)> In accordance with JIS P8113:2006, the longitudinal tensile strength of the non - woven fabrics in the examples and comparative examples was measured using the universal testing machine "Strograph E3 - S" (trade name) manufactured by Toyo Seiki Seisakusho.

[0046] 2. Preparation and evaluation of paper string pellets (1) Preparation of paper string pellets The non - woven fabrics of each example and each comparative example were prepared as wound - up materials slit into ribbons with a paper width of 65 mm, processed into paper strings by a string - making machine, and then cut with a guillotine to produce paper string pellets with a length of 5 mm.

[0047] (2) Evaluation of paper string pellets <String - making workability> When the non - woven fabrics of each example and each comparative example were made into strings and cut to produce paper string pellets, the workability was evaluated according to the following evaluation criteria by the confirmation work of a skilled person in the art. The evaluation results are shown in Table 1. Practically, those with a score of "2" or more are usable. [Evaluation criteria] "3": It is possible to process a paper string with a length of 1000 m without cutting it, and it is possible to produce paper string pellets of a certain size. "2": When processing a paper string with a length of 1000 m, the processing speed can be reduced for stringing processing. When cutting into paper string pellets, the twist may partially return. "1": When processing a paper string with a length of 1000 m, even if the processing speed is reduced in the stringing process, the paper will be cut several times. Even if it can be processed, the twist is not sufficient.

[0048] <Raw material input stability> The input stability when the paper string pellets produced by stringing and cutting the non-woven fabrics of each example and each comparative example are put into a twin-screw kneader together with thermoplastic resin pellets was evaluated according to the following evaluation criteria by the confirmation work of skilled persons in the art. The results are shown in Table 1. Practically, those with "2" or more are usable. [Evaluation criteria] "4": Compared with the case of dry-ground fiber cotton, the supply of raw materials to the twin-screw kneader is stable, the workability is good, and the kneading is also stable. "3": Compared with the case of dry-ground fiber cotton, by adjusting the processing speed in the twin-screw kneader, the supply of raw materials to the twin-screw kneader becomes stable. "2": Compared with the case of dry-ground fiber cotton, the supply of raw materials to the twin-screw kneader is unstable, but if the supply speed of raw materials to the kneader is slowed down, kneading can be carried out. "1": Compared with the case of dry-ground fiber cotton, the supply of raw materials to the twin-screw kneader is unstable and the kneading is unstable.

[0049] In the examples, both the stringing workability and the raw material input stability were 2 or more, and the workability was excellent. On the other hand, in the comparative examples, at least one of the stringing workability and the raw material input stability included 1.

[0050] 3. Preparation and evaluation of cellulose resin composites The cellulose resin composites of each example and each comparative example were prepared and evaluated under the following conditions. (1) Preparation of Cellulose Resin Composite Paper string pellets, polypropylene resin, compatibilizer, and modifier were compounded in the following formulation. Using a twin-screw kneader "TEM-26SX-15 / 2V" (trade name, manufactured by Shibaura Machine Co., Ltd.), they were kneaded under the conditions of discharge rate, kneading temperature, and cylinder rotation speed shown in Table 1 to prepare a cellulose resin composite with a pellet cut length of 3 mm. <Formulation> Paper string pellets: In the cellulose resin composite, they were compounded so that the cellulose fiber content was 30% by mass. Polypropylene resin: Polypropylene "Novatec PP BC03B" (melting point: 165°C) manufactured by Japan Polypropylene Corporation. It was compounded to be 86 parts by mass together with the paper string pellets. Compatibilizer: 3 parts by mass of "Maricon" (trade name) manufactured by Osaka Gas Chemical Co., Ltd. Modifier: 11 parts by mass of "Tufmer XM5070" (trade name) manufactured by Mitsui Chemicals, Inc.

[0051] The descriptions related to the twin-screw kneader shown in Table 1 are as follows. · "Set temperature": The twin-screw kneader can control the temperature in 6 zones from the raw material inlet to the outlet. This is the average value of the temperature setting values of these 6 zones. · "Kneaded material temperature": The measured value of the temperature of the kneaded material immediately after the outlet of the twin-screw kneader. · "Temperature difference": The temperature difference between the kneaded material temperature and the temperature of the thermoplastic resin.

[0052] (2) Evaluation of Cellulose Resin Composite (Hardness, Impact Resistance) In Table 1, "flexural modulus" and "Charpy strength" respectively represent the flexural modulus and Charpy impact strength of the cellulose resin composite, and thereby, the hardness and impact resistance of the cellulose resin composite were evaluated respectively. The flexural modulus and Charpy impact strength were measured by the following methods. <Flexural modulus> In accordance with JIS K7171:2016, the flexural modulus of the cellulose resin composites in the examples and comparative examples was measured using a Tensilon universal testing machine "RTI-1310" (trade name) manufactured by A&D Company, Limited. <Charpy impact strength> In accordance with JIS K-7111-1 and -2, the Charpy impact strength of the cellulose resin composites of the examples and comparative examples was measured using "Impact Tester IT" (trade name) manufactured by Toyo Seiki Co., Ltd.

[0053] According to the comparison between each example and each comparative example, it was found that the manufacturing method of the cellulose resin composite includes a fibrillation step, and the cellulose fiber content is 30% by mass or more based on the total amount of the nonwoven fabric, so that it is excellent in hardness and impact resistance, and at the same time excellent in workability. According to the comparison between Examples 1 and 3 to 6, it was found that from the balance of workability, hardness, and impact resistance, the average fiber length of the cellulose fibers is preferably 0.90 to 1.20 mm. According to the comparison between Examples 4, 7, and 8, it was found that by reducing the thickness of the nonwoven fabric, the workability can be improved. According to the comparison between Examples 4 and 9 to 12, it was found that by increasing the basis weight of the cellulose resin composite, the hardness can be improved. According to the comparison between Examples 4 and 13 to 15, it was found that by adjusting the difference between the outlet temperature of the kneaded product discharged from the kneader and the melting point of the thermoplastic resin to be 25°C or more and 60°C or less, a cellulose resin composite excellent in hardness and impact resistance can be provided. According to the comparison between Examples 4 and 16 to 20, it was found that by adjusting the discharge rate, which is the ratio of the discharge amount (kg / hr) of the kneaded product to the rotation speed (rpm) of the screw of the twin-screw kneader, to be 1.50 kg / rotation or more and 4.50 kg / rotation or less, a cellulose resin composite excellent in hardness and impact resistance can be provided.

Industrial Applicability

[0054] The cellulose resin composite obtained by the present invention can be used in the production of synthetic paper, sheets, etc. as an alternative to glass-reinforced resins and carbon fiber resins, and thus has industrial applicability in such fields.

Claims

1. A stringing step of stringing a nonwoven fabric containing cellulose fibers and thermoplastic resin fibers to obtain paper strings, A cutting step of cutting the paper strings to obtain paper string pellets, A kneading step of kneading the paper string pellets and a thermoplastic resin, and includes, The content of the cellulose fibers is 30% by mass or more based on the total amount of the nonwoven fabric, A method for producing a cellulose resin composite.

2. The content of the cellulose fibers in the nonwoven fabric is 50% by mass or more based on the total amount of the nonwoven fabric, The method for producing a cellulose resin composite according to Claim 1.

3. The nonwoven fabric has a strength in the flow direction of 0.2 kN / m or more and a thickness of 150 μm or less, The method for producing a cellulose resin composite according to Claim 1 or 2.

4. The average fiber length of the cellulose fibers is 0.9 mm or more and 1.2 mm or less, The method for producing a cellulose resin composite according to Claim 1 or 2.

5. The basis weight of the nonwoven fabric is 35 g / m ２ or more. The method for producing a cellulose resin composite according to Claim 1 or 2.

6. The cut length of the paper string pellets is 3 mm or more and 15 mm or less, The method for producing a cellulose resin composite according to Claim 1 or 2.

7. The content of the cellulose fibers in the cellulose resin composite is 10% by mass or more and 30% by mass or less based on the total amount of the cellulose resin composite, The method for producing a cellulose resin composite according to Claim 1 or 2.

8. In the kneading step, a kneaded product is obtained by kneading with a kneader, The difference between the outlet temperature of the kneaded product discharged from the kneader and the melting point of the thermoplastic resin is 25°C or more and 60°C or less, The method for producing a cellulose resin composite according to Claim 1 or 2.

9. In the kneading step, a kneaded product is obtained by kneading with a twin-screw kneader having two screws, The discharge rate, which is the ratio of the discharge amount (kg / hr) of the kneaded product to the rotation speed (rpm) of the screw of the twin-screw kneader, is 1.50 kg / rotation or more and 4.50 kg / rotation or less, The method for producing a cellulose resin composite according to Claim 1 or 2.

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