Method for producing thermoplastic resin composition

Abstract

To provide a method for producing a thermoplastic resin composition in which cellulose fibers contained in an aqueous dispersion can be blended with a resin by the method different from conventional ones.SOLUTION: Provided is a method for producing a thermoplastic resin composition which forms a polyolefin resin as a continuous phase and comprises a fibrous composite dispersed in the continuous phase. The fibrous composite comprises cellulose fibers and a copolymer having an acid-modified group, the cellulose fibers being bonded to the copolymer, and the acid-modified group being an anhydrous carboxyl group and / or a carboxyl group derived from an anhydrous carboxyl group. The cellulose fibers and the copolymer are bonded through an ester bond formed between the acid-modified group and a hydroxy group present in a cellulose constituting the cellulose fibers. The thermoplastic resin composition can be obtained by a kneading step in which the polyolefin resin, the aqueous dispersion containing the cellulose fibers, and the copolymer are made to coexist and then are kneaded.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a thermoplastic resin composition, and more particularly to a method for producing a thermoplastic resin composition containing cellulosic fibers. [Background technology]

[0002] In recent years, cellulose fibers have been used in aqueous applications to control viscoelasticity as thickeners, etc. On the other hand, in composite material applications, for example, cellulose fibers have been proven to be excellent reinforcing materials for resins for some time, but the reality is that they have not yet been put to practical use. The technologies of Patent Documents 1 to 3 listed below are known to suggest the usefulness of cellulose fibers in composite material applications. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-148629 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-176052 [Patent Document 3] Japanese Patent Application Publication No. 2019-189792 Summary of the Invention [Problem to be solved by the invention]

[0004] Cellulose fibers are generally handled in an aqueous dispersion, but increasing the solids concentration above 60% by mass can be difficult. This solids concentration decreases as the degree of defibration of the cellulose fibers in the aqueous dispersion increases, and in products generally referred to as nanocellulose, the solids concentration does not reach 15% by mass. In other words, cellulose is handled in a state where it coexists with far more water than the target components. This is believed to be because cellulose, a polysaccharide, has a high number of hydroxyl groups derived from sugar chains, making it highly hydrophilic. For example, as mentioned above, blending with resins is difficult if there is more water than the target components. Even if blending is possible, removing the water requires a significant amount of energy. On the other hand, cellulose fibers have the property that, as the amount of water removed from an aqueous dispersion increases, the cellulose gradually aggregates and solidifies through hydrogen bonding. While this property is extremely useful in paper production, it is impossible to form a dispersion in the absence of water. Therefore, there are problems with cellulose fibers: they cannot be dispersed in a non-hydrophilic environment, and they cannot be dispersed in resins. Cellulose fibers must be handled in the presence of water, and they aggregate when the dispersant is removed. This makes them difficult to handle, and therefore there are many applications and uses for which their practical use is hindered.

[0005] In this regard, the above-mentioned Patent Document 1 discloses a technology (e.g., [Claim 1]) for chemically modifying some of the hydroxyl groups in the cellulose that constitutes the nanocellulose with alkanoyl groups having an alicyclic hydrocarbon group, with the aim of providing a novel modified nanocellulose and a resin composition containing the same (

[0011] ). The above-mentioned Patent Document 2 aims to provide a fiber-reinforced resin composition in which highly dispersible fibers are suitably combined, and a method for producing the same (

[0007] ). It discloses a fiber-reinforced resin composition ([Claim 1], etc.) that contains (A) chemically modified cellulose nanofibers and (B) a thermoplastic resin, in which the ratio R of the SP value of (A) to the SP value of (B) is 0.87 to 1.88, and the crystallinity of (A) is 42.7% or more. This disclosure mentions (

[0012] ) that the introduction of alkanoyl groups such as acetyl groups (i.e., chemically modifying the hydroxyl groups) blocks the hydroxyl groups of cellulose molecules, thereby suppressing the hydrogen bonding strength of the cellulose molecules. The above-mentioned Patent Document 3 discloses a modified cellulose nanofiber (e.g., [Claim 1]) that has a cellulose nanofiber, a polycarboxylic acid bonded to the cellulose molecules, and a polyvalent metal salt of a fatty acid having 8 to 24 carbon atoms that is chelate-bonded to carboxy groups of the polycarboxylic acid other than the carboxy group bonded to the cellulose molecule, with the aim of providing a modified cellulose nanofiber that can be kneaded with a thermoplastic resin in a dry powder state and has good compatibility and dispersibility in the thermoplastic resin (

[0009] ).

[0006] The techniques described in Patent Documents 1 to 3 all solve the above problems by chemically modifying hydroxy groups derived from sugar chains. These techniques make it possible to handle cellulose fibers in a non-aqueous system, thereby solving the problems associated with resin blending. However, for example, Patent Document 1 raises concerns about the need to use a special alicyclic compound as a chemical modifying agent, and Patent Document 2 raises concerns about the large amount of organic solvent used during production, requiring a total of 750 mL of organic solvent (Patent Document 1

[0445] ) for 5 g of plant fiber solids. Furthermore, the technology of Patent Document 3 uses a chelate bond via a metal salt, which is less stable than chemical modification using a covalent bond, and there are concerns about the long-term stability, hydrolysis resistance, and resistance to catalytic decomposition due to metal ions of products obtained using the modified cellulose.

[0007] The techniques described in Patent Documents 1 to 3 all solve the above problems by chemically modifying hydroxy groups derived from sugar chains. These techniques make it possible to handle cellulose fibers in a non-aqueous system, thereby solving the problems associated with resin blending. Thus, from the viewpoint of making it possible to handle cellulose fibers in a non-aqueous system, various methods are currently being considered, but it remains unclear which technologies and solutions are appropriate and practical, and in order to have more options for the future, more different options are required.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a method for producing a thermoplastic resin composition that can incorporate cellulosic fibers contained in an aqueous dispersion into a resin by a method different from conventional methods. [Means for solving the problem]

[0009] That is, the present invention includes the following. [1] A method for producing a thermoplastic resin composition comprising a polyolefin resin as a continuous phase and a fibrous composite dispersed in the continuous phase, The fibrous composite is formed by bonding cellulosic fibers and a copolymer having an acid-modified group, the acid-modified group is a carboxy anhydride group and / or a carboxy group derived from a carboxy anhydride group, the cellulosic fiber and the copolymer are bonded by an ester bond between a hydroxy group of cellulose constituting the cellulosic fiber and the acid-modified group, A method for producing a thermoplastic resin composition, comprising a kneading step of bringing the polyolefin resin, the aqueous dispersion containing the cellulosic fibers, and the copolymer into coexistence and kneading them together. [2] The method for producing a thermoplastic resin composition according to the above [1], wherein the kneading is carried out at 100°C or higher. [3] The method for producing a thermoplastic resin composition according to the above [1] or [2], further comprising a pre-kneading step of kneading the copolymer at 100°C or higher before the kneading step. [4] The method for producing a thermoplastic resin composition according to the above [3], wherein the preliminary kneading step and the kneading step are carried out continuously in the same kneader. [5] The method for producing a thermoplastic resin composition according to any one of [1] to [4] above, wherein the copolymer has an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-octene copolymer, or a styrene-ethylene / butylene-styrene copolymer as a backbone. [6] A method for producing a thermoplastic resin composition according to any one of [1] to [5] above, wherein the copolymer has structural units derived from at least two types of monomers differing in the number of carbon atoms by two or more. [7] The method for producing a thermoplastic resin composition according to any one of [1] to [6] above, wherein the number of the acid-modified groups is five or more. [Effects of the Invention]

[0010] According to the method for producing a thermoplastic resin composition of the present invention, cellulosic fibers contained in an aqueous dispersion can be blended with a resin by a method different from conventional methods. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph comparing the trends of Experimental Examples 1 to 7 with the trends of Experimental Examples 1, 8, and 9 based on the correlation between flexural modulus and Charpy impact strength. DETAILED DESCRIPTION OF THE INVENTION

[0012] The matters set forth herein are for illustrative purposes only and are intended to provide an illustrative description of the embodiments of the present invention, with the aim of providing what is believed to be the most effective and easily understandable explanation of the principles and conceptual features of the present invention. In this respect, it is not intended to show structural details of the present invention beyond the extent necessary for a fundamental understanding of the present invention, and the description, taken together with the drawings, will make clear to those skilled in the art how some aspects of the present invention may be actually embodied. In this specification, unless otherwise specified, the expression "XX to YY" means "XX or higher and YY or lower." Furthermore, "normal temperature" means 25°C, and "normal pressure" means 1013.25 hPa.

[0013] [1] Method for producing thermoplastic resin composition The method for producing a thermoplastic resin composition of the present invention is a method for producing a thermoplastic resin composition having a polyolefin-based resin as a continuous phase and a fibrous composite dispersed in the continuous phase, The fibrous composite is formed by bonding cellulosic fibers and a copolymer having an acid-modified group, the acid-modified group is a carboxy anhydride group and / or a carboxy group derived from a carboxy anhydride group, the cellulosic fiber and the copolymer are bonded by an ester bond between a hydroxy group of cellulose constituting the cellulosic fiber and the acid-modified group, The method is characterized by comprising a kneading step in which the polyolefin resin, the aqueous dispersion containing the cellulosic fibers, and the copolymer are allowed to coexist and then kneaded together.

[0014] (1) Thermoplastic resin composition The "thermoplastic resin composition" has a polyolefin resin as a continuous phase and comprises fibrous composites dispersed within the continuous phase.

[0015] (2) Fibrous composite The "fibrous composite" is a component that forms a dispersed phase in a thermoplastic resin composition. The fibrous composite is formed by bonding cellulosic fibers and a copolymer having an acid-modified group. The acid-modified group is a carboxy anhydride group and / or a carboxy group derived from a carboxy anhydride group. In the fibrous composite, the cellulosic fiber and the copolymer are bonded together by an ester bond between a hydroxy group of the cellulose constituting the cellulosic fiber and an acid-modified group of the copolymer.

[0016] (3) Cellulose fibers The term "cellulosic fiber" as used herein refers to a fibrous material primarily composed of cellulose. In this specification, cellulosic fiber will be referred to as follows, as necessary. That is, cellulosic fiber contained in an aqueous dispersion, which is a raw material for a fibrous composite, will also be referred to as "aqueous cellulosic fiber." That is, aqueous cellulosic fiber requires the coexistence of water to inhibit aggregation, and the aqueous cellulosic fiber exists as a dispersoid in the aqueous dispersion. Furthermore, cellulosic fiber incorporated into a fibrous composite and ester-bonded to a copolymer will also be referred to as "intra-composite cellulosic fiber." When the term "aqueous cellulosic fiber" and "intra-composite cellulosic fiber" are used interchangeably, they will also be referred to simply as "cellulosic fiber."

[0017] The maximum length of such cellulosic fibers is usually 1000 μm or less, and can be 500 μm or less, 250 μm or less, or even 100 μm or less. There is no lower limit, and a single cellulose is usually 1 nm or more, 3 nm or more, 5 nm or more, or even 10 nm or more. These upper and lower limits can be appropriately combined. Therefore, for example, the maximum length can be 1 nm to 1000 μm, 3 nm to 500 μm, 5 nm to 250 μm, or 10 nm to 100 μm.

[0018] Specifically, cellulosic fibers include plant-derived fibers, pulp, cellulose microfibrils, cellulose nanofibers (hereinafter also referred to simply as "CNF"), lignocellulose (fibrous lignocellulose), etc. These may be used alone or in combination of two or more. Therefore, for example, CNF (fiber width 3 to 100 nm, aspect ratio 10 or more, length 100 μm or less) according to ISO / TS 20477:2017 is included.

[0019] The origin of the cellulosic fiber is not limited, and examples thereof include cellulosic fiber obtained from plants, cellulosic fiber produced by microorganisms (bacterial cellulose), etc. These may be used alone or in combination of two or more. Of these, the cellulosic fibers obtained from plants may be those obtained primarily from plants, or they may be those re-obtained (secondarily obtained, or more multiple times obtained, etc.) from articles formed using the cellulosic fibers obtained primarily.

[0020] The primary source of acquisition is not limited to, but may be a tree, a plant, or other plants such as bamboo or algae. The tree may be any of tall trees, shrubs, subshrubs, conifers, broad-leaved trees, evergreen trees, deciduous trees, vines, etc. The part of the tree is not limited to, and may be, for example, xylem, roots, leaves, bark, etc. The plant may be annual, biennial, perennial, erect, creeping, vine, etc. The part of the plant is not limited to, and may be, for example, stems, roots, leaves, etc. These may be used alone or in combination of two or more. Examples of reclaimed materials include cloth, woven fabric, knitted fabric, paper, etc. These may be used alone or in combination of two or more.

[0021] The plant-derived fibers may be obtained by fiberizing plants in any manner, including, for example, plant-derived fibers obtained by pulping, plant-derived fibers obtained by retting, plant-derived fibers obtained by microbial decomposition, plant-derived fibers obtained by enzymatic decomposition, etc. These may be used alone or in combination of two or more.

[0022] Among the above, the plant-derived fibers (i.e., pulp) fiberized by pulping may be mechanically treated pulp (mechanical pulp (MP), groundwood pulp (GP), refiner ground pulp (RGP), thermomechanical pulp (TMP), etc.), chemically treated pulp (chemical pulp (CP), kraft pulp (KP), sulfite pulp (SP), soda pulp (AP), etc.), pulp treated to have properties of both of these (chemical ground pulp (CGP), semi-chemical pulp (SCP), etc.), or recycled pulp. Furthermore, it may be fiber pulp or dissolving pulp (DP). These may be used alone or in combination of two or more.

[0023] As mentioned above, the source of the pulp is not limited, and it may be wood pulp or non-wood pulp. Examples of wood pulp include softwood pulp (N pulp) and hardwood pulp (L pulp). These may be used alone or in combination of two or more. Examples of non-wood pulp include linter pulp, rag pulp, linen pulp, bagasse pulp, bamboo pulp, kenaf pulp, esparto pulp, hemp pulp, and straw pulp. These may be used alone or in combination of two or more.

[0024] Furthermore, there are no limitations on whether the pulp is bleached or not. Examples include bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), bleached hardwood sulfite pulp (LBSP), unbleached hardwood sulfite pulp (LUSP), bleached softwood sulfite pulp (NBSP), unbleached softwood sulfite pulp (NUSP), etc. These may be used alone or in combination of two or more. Furthermore, there are no limitations on whether the pulp has been beaten. That is, it may be beaten pulp or unbeaten pulp. In the case of beaten pulp, it may be beaten pulp that has undergone a loose beating process or a sticky beating process. These may be used alone or in combination of two or more. In the case of beaten pulp, there are no limitations on the degree of beating and freeness (Canadian Freeness Standard [CFS]), etc.

[0025] Among the above, dissolving pulp (DP) can be selected from the viewpoints of odor reduction and heat resistance. Dissolving pulp has a high cellulose content, and therefore a lower content of lignin, which is thermally decomposed in a lower temperature heating environment, compared to non-dissolving pulp. Therefore, the use of dissolving pulp can reduce odor compared to when not using dissolving pulp.

[0026] Here, the odor refers to an odor generated by the decomposition of components constituting cellulosic fibers. For example, a molded body obtained from a resin for molding (thermoplastic resin composition) containing cellulosic fibers undergoes heating (heating to a temperature at which the resin can flow) during the process of incorporating the cellulosic fibers into the resin for molding, the process of molding the obtained resin for molding, etc. As a result, components constituting the cellulosic fibers, such as lignin, may be thermally decomposed, causing the obtained molded body to emit an odor. In contrast, when DP pulp is used as the cellulosic fiber, the amount of low-temperature decomposition components (such as lignin) contained in the DP pulp is small, or the DP pulp is substantially free of low-temperature decomposition components, so that no odor is generated even after the heating, or even if an odor is generated, the odor can be reduced.

[0027] Furthermore, by using dissolving pulp, it is possible to obtain better heat resistance than when no dissolving pulp is used. Excellent heat resistance includes, for example, a reduced temperature dependence of mechanical strength. That is, as described above, in molded bodies obtained from resins for molded bodies containing cellulosic fibers, lignin and the like are decomposed. Therefore, the mechanical strength of the resulting molded body may be strongly temperature-dependent. Specifically, the rate at which the flexural modulus decreases with increasing temperature may be increased. In contrast, when DP pulp is used as the cellulosic fiber, the amount of low-temperature decomposition components (lignin, etc.) contained in the DP pulp is small or substantially absent, so the rate at which the flexural modulus decreases even after the above-mentioned heating can be reduced compared to the former.

[0028] As mentioned above, cellulosic fibers are fibrous materials primarily composed of cellulose. The percentage of cellulose contained in the cellulosic fibers is not limited, but can be, for example, 40% by mass or more, assuming that the entire cellulosic fiber is 100% by mass. When the cellulosic fibers contain 40% by mass or more of cellulose, the effects of cellulose can be effectively obtained. This percentage is preferably 50% by mass or more, and more preferably 60% by mass or more. Alternatively, this percentage may be 100% by mass. The cellulose content in cellulosic fibers is calculated from the alkali-decomposed insoluble matter. Specifically, the sample is immersed in a 17.5% NaOH aqueous solution for two hours, followed by adding an equal volume of water to the NaOH solution and boiling for one hour. The dried residue (dried at 80°C or less) is used as the cellulose. If the sample contains lignin, the lignin is decomposed and removed by chlorination, and the cellulose content is then measured. Specifically, the sample is immersed in a solution containing sodium chlorite and acetic acid in a mass ratio of 5:1, heated to 80°C for one hour, and filtered to obtain a residue. The same procedure is repeated four times to measure the cellulose content of the residue from which the lignin has been removed.

[0029] However, since the number of cellulosic fibers contained in a thermoplastic resin composition and the number of cellulosic fibers constituting a fibrous composite are large, and as a result, it is sufficient that these are contained in the thermoplastic resin composition, there is no practical meaning in specifying the cellulose content of each cellulosic fiber. Similarly, when using cellulosic fibers derived from plants, the cellulose content varies depending on the source (type, part, etc.) of acquisition, and also depending on the degree of purification, there are some fibers with a high cellulose content and some with a low cellulose content, and these can be used in combination, so as a result, it is sufficient that a fibrous composite is formed in the thermoplastic resin composition, and there is no practical meaning in specifying the average value. The cellulosic fibers may or may not contain hemicellulose, lignin, and components derived therefrom.

[0030] The form of the cellulosic fiber is not limited other than being fibrous, but specifically, it is preferable that the aspect ratio is 4 or more. An aspect ratio of 4 or more makes it easier to maintain the form within the thermoplastic resin composition, particularly the form of the fibrous composite, in a fibrous form. The aspect ratio is more preferably 5 or more, and more preferably 6 or more. The aspect ratio is usually 10,000 or less. The aspect ratio can be determined by measuring the maximum length and the minimum length of the cellulosic fiber using an optical microscope or an electron microscope and calculating the ratio between them. However, since the number of cellulosic fibers contained in a thermoplastic resin composition and the number of cellulosic fibers constituting a fibrous composite are large, and as a result, it is sufficient for these fibers to be contained in the thermoplastic resin composition, there is no substantial meaning in specifying the aspect ratio of each of the cellulosic fibers. Similarly, when using plant-derived cellulosic fibers, the aspect ratio varies depending on the source (type, part, etc.) of acquisition, and also depending on the processing process, some fibers have a large aspect ratio and some have a small aspect ratio, and these can be used in combination, so as a result, it is sufficient for a fibrous composite to be formed in the thermoplastic resin composition, and there is no substantial meaning in specifying the average aspect ratio.

[0031] The content of cellulosic fibers in the aqueous dispersion is not limited, but when the total amount of the aqueous dispersion is taken as 100% by mass, the lower limit can be 1% by mass or more, and can be 3% by mass or more, 5% by mass or more, 7% by mass or more, 9% by mass or more, 11% by mass or more, or 12% by mass or more. On the other hand, the upper limit can be, for example, 90% by mass or less, 60% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 17% by mass or less. These upper and lower limits can be appropriately combined. Therefore, for example, the content can be 3 to 90% by mass, 5 to 60% by mass, 7 to 40% by mass, 9 to 30% by mass, 11 to 20% by mass, or 12 to 17% by mass.

[0032] (4) Copolymer The "copolymer" is a polymer having acid-modified groups before the kneading step, and a polymer in which the acid-modified groups have been consumed in the formation of ester bonds after the kneading step. Furthermore, as described above, the copolymer is a polymer having structural units derived from two or more types of monomers. In this specification, the copolymer will be described as follows, as necessary. That is, the copolymer before the kneading step will also be called a "pre-copolymer," and the copolymer after the kneading step will also be called a "post-copolymer." When describing content common to these, they will also be called a "copolymer." That is, the pre-copolymer is a copolymer having an acid-modified group, and the post-copolymer is a copolymer in which the acid-modified group has been consumed in the formation of an ester bond.

[0033] The acid-modified group of the copolymer is a group capable of functioning as an acid, and in the present invention, is at least one of a carboxy anhydride group and a carboxy group derived from a carboxy anhydride group. Of these, the former is a carboxy anhydride group having a closed ring structure. On the other hand, the latter is a carboxy group formed by ring-opening a carboxy anhydride group. Therefore, the latter has a structure in which two carboxy groups are adjacent to each other (i.e., an open-ring structure). Hereinafter, the latter is also referred to as a "dicarboxy group."

[0034] The copolymer (post-copolymer) exists as part of the fibrous composite in the thermoplastic resin composition, and as described above, is ester-bonded to the cellulosic fiber (cellulosic fiber in the composite) in the fibrous composite. That is, the acid-modified group of the pre-copolymer is ester-bonded to the hydroxy group of the cellulose. Therefore, in the fibrous composite, the acid-modified group of the pre-copolymer is consumed by the ester bond, and the post-copolymer has, in addition to the ester bond with the cellulosic fiber, a single carboxy group that is the remainder of the acid-modified group.

[0035] The pre-copolymer contains acid-modified groups, which allow hydroxyl groups in cellulose to form ester bonds with the acid-modified groups. Specifically, by using carboxyl anhydride groups and / or dicarboxyl groups as acid-modified groups, high reactivity can be imparted to the pre-copolymer. In other words, the acid-modified groups can function as effective reaction sites within the pre-copolymer. Furthermore, instead of conventional methods of binding low-molecular-weight compounds to the hydroxyl groups in cellulose to inhibit hydrogen bonding in cellulose, the polymer copolymer is modified into cellulose. Therefore, even if the modification involves a small number of ester bonds, the hydroxyl groups in cellulose can be extensively inhibited by the copolymer. This effectively inhibits the hydrophilicity of cellulose.

[0036] A carboxy anhydride group originally contains two carboxy groups, which form a ring closure to form the carboxy anhydride group. On the other hand, a dicarboxy group is composed of two adjacent carboxy groups and is not ring-closed. That is, both a carboxy anhydride group and a dicarboxy group contain two carboxy groups, but at least one of these two carboxy groups is ester-linked to a hydroxy group in cellulose. That is, when a hydroxy group in cellulose is ester-linked to a carboxy anhydride group, only one of the two carboxy groups in the carboxy anhydride group is ester-linked, while the other carboxy group can remain as a carboxy group. Similarly, when a hydroxy group in cellulose is ester-linked to a dicarboxy group, only one of the two carboxy groups in the dicarboxy group is ester-linked, while the other carboxy group can remain as a carboxy group. In either case, the remaining carboxy group may also be ester-linked to another hydroxy group in cellulose.

[0037] The presence of acid-modified groups in the pre-copolymer allows the copolymer to be efficiently modified into cellulosic fibers, and the deterioration and decomposition of the cellulosic fibers during modification can be suppressed. However, the inventors' studies have shown that, when comparing acid-modified groups in the form of dicarboxy groups with acid-modified groups in the form of carboxy anhydride groups, dicarboxy groups have lower reactivity and are less likely to form ester bonds. The inventors' studies have also shown that, under normal circumstances, the equilibrium state between carboxy anhydride groups and dicarboxy groups is biased toward the side where dicarboxy groups are more abundant. That is, under normal circumstances, the acid-modified groups in the pre-copolymer are more likely to exist as dicarboxy groups. This can be confirmed using infrared absorption spectroscopy, as described below. Therefore, it is preferable to ring-close the dicarboxy groups to increase the presence probability of carboxy anhydride groups (represented as [-CO-O-OC-]), and then use a pre-copolymer with a high presence probability of carboxy anhydride groups.

[0038] Furthermore, in this method, the target thermoplastic resin composition is kneaded after allowing the three components, i.e., the polyolefin resin, the aqueous dispersion containing cellulosic fibers, and the copolymer, to coexist. Alternatively, the cellulosic fibers and the copolymer may be ester-bonded in advance, i.e., a fibrous composite may be formed in advance, and the fibrous composite may then be kneaded with the polyolefin resin to obtain the target thermoplastic resin composition. If the latter method is selected, the problem of the equilibrium between the carboxy anhydride groups and the dicarboxy groups becomes apparent. That is, it becomes necessary to heat-treat the acid-modified groups in the pre-copolymer to increase the probability of the presence of carboxy anhydride groups before reacting with the cellulosic fibers. Furthermore, since the cellulosic fibers used are difficult to react in their aqueous dispersion form, they must be converted into non-aqueous cellulosic fibers before being reacted. Thus, the inventors' investigations have revealed that if a fibrous composite is first obtained, the formation of the fibrous composite requires a large amount of pretreatment.

[0039] In this regard, in the method for producing a thermoplastic resin composition of the present invention, as described above, a pre-copolymer with a high probability of dicarboxy groups is used directly in the kneading process. While the formation of a fibrous composite requires extensive pretreatment, the present method allows for the extremely easy production of the target thermoplastic resin composition. The mechanism behind this difference is currently unclear. However, it is believed that the presence of a polyolefin resin as a matrix during the reaction contributes to this. That is, kneading with a polyolefin resin typically requires a molten environment for the polyolefin resin. The inventors have found that such a high-temperature environment increases the probability of dicarboxy groups being ring-closed to form carboxy anhydride groups. Therefore, in a melt-kneading environment with a polyolefin resin, dicarboxy groups are more likely to be converted to carboxy anhydride groups, which facilitates the reaction of the cellulosic fiber with the copolymer to form a fibrous composite. The formed fibrous composite is likely to be incorporated into the coexisting polyolefin resin, maintaining an environment conducive to the formation of a new fibrous composite.

[0040] As described above, the carboxy anhydride group can be expressed as [-CO-O-OC-] and has a cyclic acid anhydride skeleton formed by dehydrating one molecule of HO from two carboxy groups. The carboxy anhydride group is also referred to as an acid anhydride group, a carboxylic acid anhydride group, a dicarboxylic acid anhydride group, etc. Whether the acid-modified group in the copolymer is a carboxy anhydride group or a dicarboxy group can be determined by infrared absorption spectroscopy. Specifically, when a carboxy anhydride group is present, a peak due to C=O of the carboxy anhydride group is detected at 1790 cm -1 and 1850cm -1 On the other hand, when a dicarboxy group is present, a peak due to C=O is observed at 1700-1720 cm -1 If both of these are present, all of the above peaks are allowed. The reactivity of the pre-copolymer was confirmed by the peak at 1790 cm due to the carboxyanhydride group. -1and the peak height of 1700–1720 cm due to the dicarboxyl group. -1 The peak height is equal to or equal to 1790 cm -1 It is believed that the effect can be improved further when the peak height of

[0041] The acid-modified group may be derived from any monomer or compound. For example, it can be introduced into the copolymer using a structure derived from maleic acid, itaconic acid, succinic acid, glutaric acid, adipic acid, citraconic acid, tetrahydrophthalic acid, butenylsuccinic acid, or an acid anhydride thereof (i.e., maleic anhydride, itaconic anhydride, succinic anhydride, glutaric anhydride, adipic acid anhydride, citraconic anhydride, tetrahydrophthalic anhydride, butenylsuccinic anhydride, etc.). These may be used alone or in combination of two or more. Among these, structures derived from maleic acid and / or maleic anhydride are preferred. Note that a carboxy anhydride group can form a dicarboxy group by hydrolysis. Similarly, a dicarboxy group can form a carboxy anhydride group by dehydration condensation.

[0042] In this method, an acid-modified group is used as the reactive group. However, instead of the carboxy anhydride group and the dicarboxy group, for example, a carboxy group (-COOH, non-adjacent carboxy group), an epoxy group {-CO (a three-membered ring structure consisting of two carbon atoms and one oxygen atom)}, an isocyanate group (-NCO), an oxazoline group (-CHNO), etc. may also be used. However, the carboxyl group (-COOH) has a problem of lower reactivity than the ring-closed carboxyl anhydride group. Furthermore, although epoxy groups, isocyanate groups, oxazoline groups, and the like have excellent reactivity, they are deactivated when reacting with water in the system (e.g., water coexisting with cellulose), and thereafter, they become unable to react with the hydroxyl groups of cellulose. In this regard, even if a carboxy anhydride group reacts with water in the reaction system to become a dicarboxy group, it can be dehydrated again in the system to return to a carboxy anhydride group, and therefore the carboxy anhydride group and the dicarboxy group can ultimately be deactivated by reacting with a hydroxy group in cellulose, thereby enabling cellulose to be modified more efficiently than by using reactive groups other than acid-modified groups.

[0043] Furthermore, the use of a copolymer makes it easier to obtain bulkiness in the polymer itself than the use of a homopolymer, and therefore the hydrophilicity of cellulose can be more effectively inhibited. In this specification, a "copolymer having an acid-modified group" means that the main chain is a copolymer. Therefore, for example, modified polyethylene or modified polypropylene (maleic acid-modified PE or maleic acid-modified PP) has a main chain of polyethylene or polypropylene, and is not a copolymer, and therefore is not included in the "copolymer" referred to in this application. On the other hand, for example, a modified ethylene propylene copolymer is included in the "copolymer" referred to in this application because its main chain is a copolymer of ethylene and propylene. Similarly, for example, a modified ethylene butene copolymer is included in the "copolymer" referred to in this application because its main chain is a copolymer of ethylene and butene.

[0044] Furthermore, the use of a copolymer allows the melting point of the polymer itself to be kept lower than that of a homopolymer, and therefore allows the copolymer to react with cellulose at a lower temperature than when a homopolymer is used as the main chain. Furthermore, the use of a copolymer can provide greater flexibility to the main chain than the use of a homopolymer. Therefore, compared to the use of a homopolymer as the main chain, there are more opportunities for the hydroxyl groups of cellulose to react with the acid-modified groups of the copolymer. That is, the reactivity between cellulose and the copolymer can be improved. From the same perspective, it is preferable that the copolymer has a side chain and that the acid-modified group is contained in the side chain, rather than that the acid-modified group be contained in the main chain of the copolymer.

[0045] Furthermore, the use of a copolymer can provide greater elastomer properties than the use of a homopolymer. This can prevent the cellulosic fibers from becoming fracture origins within the thermoplastic resin composition. That is, within the fibrous composite, the cellulosic fibers are surrounded by an elastic copolymer. Therefore, within the thermoplastic resin composition, the elastic copolymer is present in the gaps between the polyolefin resin matrix and the cellulosic fibers. This is thought to prevent the formation of the above-mentioned fracture origins.

[0046] More specifically, for example, when unmodified cellulosic fibers (in which hydroxyl groups derived from cellulose have been inhibited by other means) are added to a substance to be added (such as a resin), the substance to be added forms a matrix within which the unmodified cellulosic fibers are dispersed. In this case, the interface between the substance to be added and the unmodified cellulosic fibers is prone to dissociation due to the difference in their material properties, and this can become the starting point for fracture. In contrast, in copolymer-modified cellulosic fibers (i.e., fibrous composites), the cellulosic fibers are at least partially coated with the copolymer, so that the copolymer is present at the interface between the object to be added and the cellulosic fibers, and furthermore, by exhibiting elastic properties at the interface, it is possible to prevent the above-mentioned cellulosic fibers from becoming the origin of fracture. Therefore, by using the copolymer as the main chain of the copolymer having acid-modified groups, it is possible to prevent the cellulosic fibers from becoming the origin of fracture in the object to which the copolymer is added.

[0047] The structure of the copolymer skeleton (the main chain of the copolymer excluding the side chains) is not limited, and various structures can be used. Specific examples include olefin copolymers, styrene copolymers, etc. These may be used alone or in combination of two or more. The olefin copolymer includes an olefin elastomer (olefin thermoplastic elastomer), and the styrene copolymer includes a styrene elastomer (styrene thermoplastic elastomer).

[0048] Examples of olefin copolymers include polymeric compounds obtained by copolymerizing two or more olefins as monomers. The copolymers may be random copolymers, block copolymers, copolymers of other types, hydrogenated copolymers thereof, or mixtures thereof.

[0049] Examples of the olefin include ethylene, propylene, and α-olefins having 4 to 8 carbon atoms. Examples of the α-olefins having 4 to 8 carbon atoms include butene (1-butene, etc.), pentene (3-methyl-1-butene, 1-pentene, etc.), hexene (3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, etc.), and octene (1-octene, etc.). These may be used alone or in combination of two or more.

[0050] Among these, the olefin copolymer is preferably a copolymer of ethylene and another α-olefin. That is, for example, a copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms, or a copolymer of propylene and an α-olefin having 4 to 8 carbon atoms, etc. These may be used alone or in combination of two or more.

[0051] Among the above, examples of copolymers of ethylene and α-olefins having 3 to 8 carbon atoms include ethylene-propylene copolymer (EPR), ethylene-butene copolymer (EBR), ethylene-pentene copolymer, and ethylene-octene copolymer (EOR). Examples of copolymers of propylene and α-olefins having 4 to 8 carbon atoms include propylene-butene copolymer (PBR), propylene-pentene copolymer, and propylene-octene copolymer (POR). These may be used alone or in combination of two or more. Among these, copolymers of ethylene and an α-olefin having 3 to 8 carbon atoms are preferred. That is, EPR, EBR and EOR are preferred, and EBR and / or EOR are more preferred.

[0052] The styrene copolymer may be a polymer compound obtained by copolymerizing a styrene compound with another monomer, and may be a random copolymer, a block copolymer, a copolymer of another type, a hydrogenated product thereof, or a mixture thereof.

[0053] Examples of styrene-based compounds include styrene and its derivatives. These may be used alone or in combination of two or more. Among these, examples of styrene derivatives include alkylstyrenes such as α-methylstyrene, p-methylstyrene, and pt-butylstyrene, p-methoxystyrene, and vinylnaphthalene. These may be used alone or in combination of two or more.

[0054] Examples of monomers other than styrene-based compounds include conjugated diene compounds, olefins, etc. Among these, examples of conjugated diene compounds include butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene, etc. These may be used alone or in combination of two or more. On the other hand, the olefins that can be used are those described above.

[0055] Therefore, examples of styrene copolymers include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene / butylene-styrene copolymer (SEBS, i.e., hydrogenated SBS copolymer), and styrene-ethylene / propylene-styrene copolymer (SEPS). These may be used alone or in combination of two or more. Among these, SEBS is preferred.

[0056] As described above, various options are available for the skeleton of the copolymer having an acid-modified group, but from the viewpoint of obtaining higher elastomeric properties, it is preferable to adopt a skeleton having structural units derived from at least two types of monomers differing in the number of carbon atoms by two or more. That is, for example, in the case of an olefin-based copolymer, among EPR, EBR, EOR, PBR, POR, etc., EBR, EOR, and POR are preferred. Furthermore, in the case of a styrene-based copolymer, any of the above-mentioned copolymers is also preferred. Furthermore, the skeleton of the copolymer having an acid-modifiable group is preferably linear rather than branched, from the viewpoints that it is easier to align with cellulose and that the crystallinity of the cellulose is less likely to be inhibited. By being linear, the hydrophilicity of cellulose can be inhibited more effectively.

[0057] The copolymer may have one or more acid-modified groups, and the number is not limited, but because the copolymer is a polymer compound, having multiple acid-modified groups will result in higher reactivity than having only one acid-modified group. Furthermore, when actually forming ester bonds with cellulosic fibers, having ester bonds at multiple locations is preferable to having only one ester bond, from the viewpoint of being able to more firmly modify the cellulosic fibers with the copolymer.

[0058] As mentioned above, the number of acid-modified groups contained in the copolymer (in the present invention, when the acid-modified group is a carboxy anhydride group, this means the number of carboxy anhydride groups; when the acid-modified group is a dicarboxy group, this means the number calculated as one set of two carboxy groups constituting the dicarboxy group) is not limited, but is preferably 2 or more, more preferably 3 or more, more preferably 4 or more, and more preferably 5 or more. On the other hand, the number of acid-modified groups does not need to be excessively large, and is usually 50 or less, preferably 30 or less, more preferably 20 or less, more preferably 12 or less, and can be 11 or less. These upper and lower limits can be appropriately combined, for example, 1 to 50, 2 to 30, 3 to 20, 4 to 12, or 5 to 11. The acid-modified group may be contained in the main part within the copolymer backbone (for example, when maleic anhydride is used as a monomer), or may be contained in a grafted side chain to the copolymer backbone, or may be both.

[0059] The copolymer may not necessarily have any functional groups other than the acid-modified group, but may have other functional groups. In this case, examples of such other functional groups include a carboxyl group (-COOH), an epoxy group (-CO (a three-membered ring structure consisting of two carbon atoms and one oxygen atom)), an oxazoline group (-CHNO), and an isocyanate group (-NCO). These may be used alone or in combination of two or more.

[0060] The molecular weight of the copolymer having an acid-modifying group is not limited, but the mass-average molecular weight can be 30,000 or more, 50,000 or more, or even 70,000 or more. By making the mass-average molecular weight of the copolymer 30,000 or more, it is possible to impart sufficient bulkiness to the cellulosic fiber, and to more effectively inhibit the hydrophilicity of cellulose. On the other hand, the upper limit of the mass average molecular weight is not limited, but is usually 1,000,000 or less, and can be 500,000 or less, 300,000 or less, or 200,000 or less. The mass average molecular weight of the copolymer may exceed 1,000,000, but an excessively large molecular weight makes the copolymer itself difficult to handle, so it is preferably 1,000,000 or less. These upper and lower limits can be appropriately combined, and can be, for example, 30,000 to 1,000,000, 30,000 to 500,000, 50,000 to 300,000, or 70,000 to 200,000. The mass average molecular weight is measured by the GPC method (converted to standard polystyrene).

[0061] Although the properties of the copolymer having an acid-modified group are not limited, for example, the MFR (230°C / 2.16 kg) of the copolymer having an acid-modified group can be 10 g / 10 min or less. By having the copolymer have an MFR of 10 g / 10 min or less, higher elastomer properties can be obtained. This MFR can be further reduced to 7 g / 10 min or less, or even 5 g / 10 min or less. While the lower limit is not limited, it can be 0.5 g / 10 min or more, or even 1.0 g / 10 min or more. The MFR (230°C / 2.16 kg) of the copolymer is a value based on ISO 1133. The density of the copolymer with acid-modified groups is 0.90 g / cm 3 or less, and further 0.89 g / cm 3 The lower limit of the density is not limited, but it can be 0.85 g / cm 3 These MFR and density can be adjusted by the molecular weight and modification amount of the copolymer. The density of the copolymer is a value based on ISO1183.

[0062] (5) Polyolefin resin The polyolefin resin is a component that forms a continuous phase in the thermoplastic resin composition. The type of polyolefin resin is not limited, but examples thereof include thermoplastic polyolefin resins and thermoplastic polyolefin elastomers. These may be used alone or in combination of two or more.

[0063] The type of olefin constituting the above-mentioned thermoplastic polyolefin resin and thermoplastic polyolefin elastomer is not limited, and examples include ethylene, propylene, olefins having 4 carbon atoms (1-butene, etc.), olefins having 5 carbon atoms (3-methyl-1-butene, 1-pentene, etc.), olefins having 6 carbon atoms (3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, etc.), olefins having 8 carbon atoms (1-octene, etc.), etc. These may be used alone or in combination of two or more. Therefore, examples of polyolefins include polyethylene, polyethylene-based copolymers, polypropylene, polypropylene-based copolymers, polybutene, polybutene-based copolymers, etc. These polymers may be used alone or in combination of two or more. Furthermore, when two or more types are used, this includes both pellets made of mixed resins and pellet mixtures.

[0064] Among the above, polyethylene includes ethylene homopolymers and copolymers of ethylene and olefins having 3 or more carbon atoms. Examples of the latter include ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, and ethylene-octene copolymers. Copolymers of ethylene and other olefins may be random copolymers or block copolymers. In addition, copolymers of propylene and other olefins contain ethylene-derived structural units in an amount of 50% or more of the total number of structural units.

[0065] In addition, as polyethylene, plant-derived polyethylene (hereinafter simply referred to as "plant-derived PE") with a bio-based carbon content of 80% or more according to ISO16620-2 can be used. This bio-based carbon content is the percentage of the total carbon content. 14 This is the plant-derived carbon content (bio-based carbon content) calculated based on the proportion of C. When using plant-derived PE, a bio-based carbon content of 80% or more (or 100%) is preferred, with plant-derived PE of 85% or more, or even 90% or more being acceptable. In addition to ISO 16620-2, values ​​measured in accordance with ASTM D6866 can also be used for the bio-based carbon content. Generally, the values ​​measured in accordance with these standards are essentially the same.

[0066] Plant-derived polyethylene is a polymer whose main backbone is a structure (methylene chain) of linked methylene groups (-CH2-). The methylene chain is a structural unit derived specifically from ethylene. Plant-derived PE also includes ethylene homopolymers and copolymers of ethylene and other olefins. These may be used alone or in combination of two or more. When the plant-derived PE is a copolymer, non-ethylene-derived units (units derived from other olefins) preferably account for 50% or less (more preferably 30% or less, and even more preferably 10% or less) of the total number of constituent units. This is because a lower proportion of non-ethylene-derived units allows for a higher bio-based carbon content. In other words, plant-derived PE that has a low proportion of non-ethylene-derived units (for example, 10% or less) and is essentially an ethylene homopolymer is preferred.

[0067] Examples of other olefins include olefins having 3 carbon atoms (propylene), olefins having 4 carbon atoms (1-butene, etc.), olefins having 5 carbon atoms (3-methyl-1-butene, 1-pentene, etc.), olefins having 6 carbon atoms (3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, etc.), olefins having 8 carbon atoms (1-octene, etc.), etc. These may be used alone or in combination of two or more.

[0068] The properties of plant-derived PE are not limited, but include a density of 0.942 g / cm 3Preferably, the plant-derived PE is a high-density polyethylene of 35 g / 10 min or less. The MFR (230°C / 2.16 kg) of the plant-derived PE is preferably 35 g / 10 min or less, and can be 20 g / 10 min or less, or even 15 g / 10 min or less. While there are no lower limits, from the viewpoint of ease of melt-kneading, it is preferably 2 g / 10 min or more, and can be 3 g / 10 min or more. The MFR (230°C / 2.16 kg) of the plant-derived PE is a value measured in accordance with ISO 1133 or ASTM D1238. The values ​​according to these standards are usually substantially the same.

[0069] As mentioned above, the density of plant-derived PE is 0.942 g / cm 3 or more is preferable, and the density is 0.950 g / cm 3 The upper limit of the density is not limited, but it is 0.954 g / cm 3 The density of polyethylene is preferably a value measured in accordance with the standards of ISO 1183 or ASTM D792. The values ​​according to these standards are usually substantially the same. The compatibility of the above-mentioned MFR and density can be adjusted by adjusting the linearity, branching amount, molecular weight, etc. of the polyethylene.

[0070] Among the above, polypropylene includes propylene homopolymers and copolymers of propylene with other olefins. Examples of the latter include propylene-ethylene copolymers, propylene-butene copolymers, propylene-hexene copolymers, and propylene-octene copolymers. Furthermore, copolymers of propylene with other olefins may be random copolymers or block copolymers. Among these, propylene-ethylene copolymers can be used due to their excellent elastomeric properties. Propylene-ethylene copolymers are block copolymer polypropylenes with ethylene blocks as the dispersed phase. That is, they are polypropylene resins with a homopolypropylene continuous phase and a dispersed phase containing polyethylene within this continuous phase. Copolymer polypropylenes with ethylene blocks as the dispersed phase are also known as impact copolymers, polypropylene impact copolymers, heterophasic polypropylenes, and heterophasic block polypropylenes. Furthermore, copolymers of propylene with other olefins have more than 50% of their total structural units derived from propylene.

[0071] The properties of the polyolefin resin are not limited. For example, in the case of polypropylene, the density is 0.85 to 0.95 g / cm. 3 (Furthermore, the density is 0.88 to 0.92 g / cm 3 ) can be used. The MFR (230°C / 2.16 kg) can be, for example, 15 g / 10 min or more. When the MFR of polypropylene is 15 g / 10 min or more (usually 100 g / 10 min or less), excellent impact resistance can be obtained. This MFR can further be 20 g / 10 min or more, or 25 g / 10 min or more. There is no upper limit, but from the viewpoint of ease of kneading, it can be 80 g / 10 min or less, or 50 g / 10 min or less. The MFR (230°C / 2.16 kg) of polyolefin is measured in accordance with ISO 1133. The compatibility of MFR and density can be adjusted by the linearity, branching amount, molecular weight, etc. of the polyolefin.

[0072] The thermoplastic composition produced by the method of the present invention may contain components other than the polyolefin resin, aqueous dispersion, and copolymer, as long as the functions and effects of the components are maintained. Examples of other components include various additives such as flame retardants, flame retardant auxiliaries, fillers, colorants, antibacterial agents, and antistatic agents.

[0073] (6) Composition of each ingredient The cellulosic fiber and the copolymer may be used in any quantitative ratio, but the copolymer can be used in a range of 0.001 to 500 parts by mass per 100 parts by mass of the cellulosic fiber. It can be 0.005 parts by mass or more, 0.01 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, 5 parts by mass or more, or 7 parts by mass or more. On the other hand, it can be 250 parts by mass or less, 150 parts by mass or less, 100 parts by mass or less, 80 parts by mass or less, or 50 parts by mass or less. These upper and lower limits can be appropriately combined. Therefore, for example, it can be 0.005 to 250 parts by mass, 0.01 to 250 parts by mass, 0.5 to 150 parts by mass, 1 to 100 parts by mass, 5 to 80 parts by mass, or 7 to 50 parts by mass.

[0074] Furthermore, when the total of the polyolefin resin, cellulosic fiber, and copolymer is taken as 100% by mass, the total blend ratio of the cellulosic fiber and copolymer is not limited, but the lower limit can be 0.0001% by mass or more, and can be 0.001% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.07% by mass or more. On the other hand, the upper limit can be, for example, 50% by mass or less, and can be 10% by mass or less, 5% by mass or less, 1% by mass or less, or 0.5% by mass or less. These upper and lower limits can be appropriately combined. Therefore, for example, the range can be 0.0001 to 50% by mass, 0.001 to 10% by mass, 0.01 to 5% by mass, 0.05 to 1% by mass, or 0.07 to 0.5% by mass.

[0075] (7) Kneading process The kneading step is a step in which the polyolefin resin, the aqueous dispersion, and the copolymer (pre-copolymer) are allowed to coexist and then kneaded together. The coexistence of the three components is sufficient as long as the three components ultimately coexist. Therefore, for example, when kneading is performed using an extruder, the three components may be added simultaneously and kneaded, or one or two of the three components may be added and kneading may begin first. More specifically, a first component of the three components is added to the extruder to begin kneading, a second component is added to the extruder by a side feed to create an environment in which the first and second components are kneaded, and then a third component is added to the extruder by a side feed to create an environment in which the third component is kneaded with the kneaded product of the first and second components. Note that when two of the three components are first kneaded together and kneaded, and then the remaining component is added and kneaded, the two components kneaded first may react.

[0076] Among these various methods of adding, as mentioned above, from the viewpoint of promoting the ring closure of the dicarboxyl groups, it is preferable to first add the copolymer out of the three components to the kneading apparatus and start kneading (this is called pre-kneading). By pre-kneading only the copolymer, the probability that the acid-modified groups possessed by the copolymer exist as carboxy anhydride groups can be increased, and a copolymer with higher reactivity can be formed. The proportion of carboxy anhydride groups in the copolymer ring-closed by such pre-kneading is not limited. For example, in the infrared absorption spectrum measured by the above-mentioned method, the proportion of carboxy anhydride groups at 1790 cm due to C=O of the carboxy anhydride groups can be increased. -1 The peak height observed in the range of 1700 to 1720 cm is due to the C=O of the dicarboxyl group. -1 The peak height of the copolymer may be equal to or greater than that observed in the

[0077] The pre-kneading temperature in the pre-kneading is not limited, but can be, for example, 100°C or higher, further 120°C, 140°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, or 185°C or higher. On the other hand, the upper limit of the pre-kneading temperature is not limited, and it may be any temperature at which the copolymer does not change or decompose, but can be, for example, 300°C or lower, further 270°C or lower, 235°C or lower, 220°C or lower, 210°C or lower, 205°C or lower, or 200°C or lower. These upper and lower limits can be appropriately combined. Therefore, for example, the temperature can be 100 to 300°C, 120 to 270°C, 140 to 235°C, 160 to 220°C, 170 to 210°C, 180 to 205°C, or 185 to 200°C.

[0078] Pre-mixing and mixing may be carried out in any manner, and any apparatus may be used. For example, a kneader, extruder, kneader, mixer (high-speed fluid mixer, paddle mixer, ribbon mixer, etc.), etc. may be used. These may be used alone or in combination of two or more. When two or more types are used, they may be operated continuously or batchwise (batchwise). Furthermore, the raw materials may be mixed all at once, or may be added and mixed in multiple batches (multi-stage blending). Furthermore, when these apparatuses have screws, they may be single-shaft, twin-shaft, or multi-shaft, with twin-shaft being preferred.

[0079] The kneading conditions are not limited as long as the three components can be kneaded by softening the polyolefin resin and copolymer, but from the viewpoint of suppressing decomposition and deterioration of the components constituting the cellulosic fiber (cellulose, lignin, hemicellulose, etc.), the kneading temperature can be 220°C or lower, 215°C or lower, 210°C or lower, 205°C or lower, 200°C or lower, or 195°C or lower. As described above, the lower limit of the kneading temperature can be set to 100°C or higher, and can further be set to 150°C or higher, 170°C or higher, 175°C or higher, 180°C or higher, or 185°C or higher. These upper and lower limits can be appropriately combined. Therefore, the temperature can be, for example, 100 to 220°C, 150 to 215°C, 170 to 210°C, 175 to 205°C, 180 to 200°C, or 85 to 195°C.

[0080] As described above, in the kneading step, the pre-kneading temperature when pre-kneading the copolymer may be different from the kneading temperature in the subsequent kneading step, but can be the same temperature. This is preferable from the viewpoint of production efficiency. Furthermore, the pre-kneading device when pre-kneading the copolymer may be different from the kneading device in the subsequent kneading step, but can be the same. In other words, pre-kneading and kneading can be carried out continuously in one kneading device. This is preferable from the viewpoint of production efficiency.

[0081] The production of a thermoplastic resin composition can be comprised of a pre-mixing step, a mixing step, etc., but other steps may also be included. Examples of other steps include a purification step for purifying cellulosic fibers. The purification step is a step for purifying cellulosic fibers, and can be, for example, a step for increasing the cellulose concentration or a step for increasing the degree of beating. The purification step is preferably carried out before the mixing step. [Example]

[0082] The present invention will be specifically described below with reference to examples. [1]Each raw material component Cellulose fiber: refiner pulp (commercially available pulp further defibrated), solid content 11.3% by mass Copolymer (mEBR): Maleic acid modified ethylene-butene copolymer (mEBR) / Copolymer backbone: Ethylene-butene copolymer, Mass average molecular weight: 100,000, Type of carboxylic anhydride group: Derived from maleic anhydride, Number of acid-modified groups per molecule: 10 Homopolymer (mPP): Maleic acid-modified polypropylene homopolymer (mPP) / Homopolymer skeleton: Polypropylene homopolymer, Mass average molecular weight: 70,000, Type of carboxylic anhydride group: Derived from maleic anhydride, Number of acid-modified groups per molecule: 65 Polyolefin resin: Propylene block copolymer, manufactured by Japan Polypropylene, product name "Novatec BC6", MFR 2.7g / 10min, melting point 163℃

[0083] [2] Preparation of thermoplastic resin composition and molded article for evaluation Each of the raw materials in [1] above was fed into a twin-screw kneading extruder (manufactured by Technovel Co., Ltd., model "KZW15TW-30 / 45MG-NH", screw diameter 15 mm, L / D=45) so as to obtain the blending ratios of Experimental Examples 2 to 7 shown in Table 1, and kneaded at an extrusion rate of 0.6 kg / hour and a screw rotation speed of 200 rpm to obtain each of the thermoplastic resin compositions of Experimental Examples 2 to 7. Thereafter, each of the thermoplastic resin compositions was injected from the twin-screw kneading extruder into a mold to obtain each of the molded articles for evaluation of Experimental Examples 2 to 7.

[0084] [3] Manufacturing of evaluation molded bodies for comparison (1) Evaluation molded body made only of polyolefin resin Only the copolymer (mEBR) [1] above was fed into a twin-screw kneading extruder (manufactured by Technovel Co., Ltd., model "KZW15TW-30 / 45MG-NH", screw diameter 15 mm, L / D = 45) and kneaded at an extrusion rate of 0.6 kg / hour and a screw rotation speed of 200 rpm. The mixture was then injected from the twin-screw kneading extruder into a mold, and a molded article for evaluation in Experimental Example 1 was obtained.

[0085] (2) Evaluation molded body using homopolymer (mPP) The cellulosic fiber used was a microfibrillated fiber (microfibrous cellulose) with a solids concentration of 14.4% by mass and a product name of "Celish KY110N" (manufactured by Daicel Miraize Co., Ltd.), which was mixed with a water-soluble nonionic compound (NMP: N-methyl-2-pyrrolidone) in the following apparatus to obtain a powder (non-aqueous cellulosic fiber). This cellulosic fiber was then mixed with the homopolymer (mPP) of [1] above in the following apparatus to obtain a fibrous composite (i.e., a fibrous composite in which the hydroxyl groups of the cellulosic fiber and the acid-modified groups of the mPP are ester-bonded).

[0086] Specifically, the homopolymer and cellulosic fiber were placed in the reactor of the following apparatus, and the reactor was vacuum-distilled at 0.030 MPa while the stirrer was rotating at 20 Hz and heated to 120°C. After substantially all of the water contained in the raw materials had been distilled, the apparatus was stopped and the reaction product (fibrous composite) was removed from the reactor. The reaction product was a powder with a soft texture and a moisture content of 0 (zero). The ratio of the homopolymer to the cellulosic fibers in the fibrous composite was 1:10 (homopolymer:cellulosic fibers).

[0087] Apparatus used: An apparatus was prepared that had one reaction vessel and could perform mixing, kneading, and vacuum distillation individually or simultaneously within the reaction vessel. The apparatus was designed to perform the mixing and kneading operations by mixing the contents of the reaction vessel using a three-pronged stirrer (motor performance: 0.75 kW, 4P, 200 V, 60 Hz, 39 A, 1800 rpm / min) and heating the reaction vessel to a maximum of approximately 300°C using a heater jacket wrapped around the reaction vessel. Furthermore, the apparatus was designed to perform the distillation operation by reducing the pressure inside the reaction vessel to a maximum of approximately 0.1 MPa using a connected vacuum pump and heating the reaction vessel to a maximum of approximately 80°C using a heater jacket wrapped around the reaction vessel.

[0088] The obtained fibrous composite (homopolymer:cellulosic fiber = 1:10) was fed into a twin-screw kneading extruder (manufactured by Technovel Co., Ltd., model "KZW15TW-30 / 45MG-NH", screw diameter 15 mm, L / D = 45) so as to obtain the blending ratios of Experimental Examples 8 to 9 shown in Table 1, and kneaded at an extrusion rate of 0.6 kg / hour and a screw rotation speed of 200 rpm to obtain the thermoplastic resin compositions of Experimental Examples 8 to 9. Thereafter, each thermoplastic resin composition was injected from the twin-screw kneading extruder into a mold to obtain molded articles for evaluation of Experimental Examples 8 to 9.

[0089] [4] Evaluation of molded products for evaluation (1) Measurement of bending modulus Using each of the evaluation molded articles of Experimental Examples 1 to 9 obtained in [2] and [3] above, a tensile test was carried out in accordance with ISO 527-1. The results are shown in Table 1 under the column "Flexural modulus." [Test conditions] Testing equipment: Autograph 50kN (Shimadzu Corporation, model "AGS-X") Test temperature: 23℃ Specimen shape: ISO multipurpose specimen Tensile speed (elastic modulus measurement): 1 mm / min Drying conditions: Vacuum drying at 23°C for 24 hours or more

[0090] (2) Charpy impact strength measurement A Charpy impact strength test (based on ISO 179) was carried out using each of the evaluation molded articles of Experimental Examples 1 to 9 obtained in [2] and [3] above. Test pieces with a notch (Type A) were used, and the test was carried out by the edgewise test method at a test temperature of 23°C. The results are shown in the "Charpy impact strength" column in Table 1.

[0091] [Table 1]

[0092] [5] Consideration (1) Figure 1 shows a graph comparing the trends of Experimental Examples 1 to 7 with those of Experimental Examples 1, 8, and 9 based on the results of Table 1. In Experimental Examples 8 and 9, a homopolymer was used instead of a copolymer, and a fibrous composite was formed by first ester-bonding a cellulosic fiber and a homopolymer, and then the fibrous composite was blended with a polyolefin resin. On the other hand, Experimental Examples 2 to 7 are examples produced according to the production method of the present invention. Comparing these two groups, it can be seen that the graphs of Experimental Examples 1, 8, and 9 show a more rapid drop in Charpy impact strength than the graphs of Experimental Examples 1 to 7. In particular, it can be seen that Experimental Examples 5 to 7 maintain Charpy impact strength that is approximately twice as high as Experimental Examples 8 and 9.

[0093] The present invention is not limited to the specific examples described above, and various modifications can be made within the scope of the present invention depending on the purpose and application.

[0094] The foregoing examples are for illustrative purposes only and are not to be construed as limiting the invention. While the invention has been described with reference to exemplary embodiments, it is understood that the language used in describing and illustrating the invention is descriptive and exemplary, rather than limiting. As detailed herein, changes may be made within the purview of the appended claims without departing from the scope or spirit of the invention in its form. While the description of the invention has referred to specific structures, materials, and examples, it is not intended that the invention be limited to the disclosure set forth herein; rather, the invention is intended to cover all functionally equivalent structures, methods, and uses within the scope of the appended claims.

Claims

1. A method for producing a thermoplastic resin composition comprising a polyolefin resin as a continuous phase and a fibrous composite dispersed in the continuous phase, comprising: The fibrous composite is formed by bonding cellulosic fibers and a copolymer having an acid-modified group, the acid-modified group is a carboxy anhydride group and / or a carboxy group derived from a carboxy anhydride group, the cellulosic fiber and the copolymer are bonded by an ester bond between a hydroxy group of cellulose constituting the cellulosic fiber and the acid-modified group, A method for producing a thermoplastic resin composition, comprising a kneading step of bringing the polyolefin resin, the aqueous dispersion containing the cellulosic fibers, and the copolymer into coexistence and kneading them together.

2. The method for producing a thermoplastic resin composition according to claim 1 , wherein the kneading is carried out at 100° C. or higher.

3. The method for producing a thermoplastic resin composition according to claim 1 or 2, further comprising a pre-kneading step of kneading the copolymer at 100°C or higher before the kneading step.

4. The method for producing a thermoplastic resin composition according to claim 3, wherein the preliminary kneading step and the kneading step are carried out continuously in the same kneader.

5. 3. The method for producing a thermoplastic resin composition according to claim 1, wherein the copolymer has a skeleton of an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-octene copolymer, or a styrene-ethylene / butylene-styrene copolymer.

6. The method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the copolymer has structural units derived from at least two types of monomers that differ in the number of carbon atoms by two or more.

7. The method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the number of the acid-modifiable groups is five or more.

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