Polymer dispersants and cellulose fiber resin compositions

Abstract

To provide a polymeric dispersant which can effectively disperse cellulose fibers into an olefinic thermoplastic resin that is a hydrophobic medium, and can easily observe its dispersion state.SOLUTION: A polymeric dispersant used to disperse cellulose fibers into an olefinic thermoplastic resin is an A-B block copolymer including a B chain having a structural unit (B-2) derived from fluorescent dye methacrylate represented by a following general formula (1). In the general formula (1), R1 represents CH2CH2, R2 represents an alkylene group having 2 to 18 carbon atoms, R3 to R6 represent a hydrogen atom, and R7 and R8 represent a hydrogen atom.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polymer dispersant and cellulose fiber resin composition to things and is concerned with it.

Background Art

[0002] Cellulose is the basic skeletal substance of all plants and has an accumulation of over one trillion tons on the earth. In addition, since cellulose is a renewable resource through tree planting, its effective utilization is desired. In recent years, it has been studied to use cellulose fiber, which is a biomass material, as a filler to be contained in a dispersed state in a thermoplastic resin. Among them, cellulose nanofiber (CNF, microfibrillated plant fiber) obtained by defibrating cellulose fiber has attracted attention as a lightweight and high-strength material, and various materials using CNF have been developed.

[0003] For example, by containing CNF as a filler in a dispersed state in a matrix such as a resin, a CNF reinforcing material with improved mechanical strength has been developed. Since CNF has a rich hydroxyl group, it is hydrophilic and has a strong polarity. Therefore, CNF has a side that it is inferior in compatibility with an olefin-based thermoplastic resin that is hydrophobic and has a weak polarity. Therefore, it has been studied to improve the compatibility with an olefin-based thermoplastic resin by surface modification of CNF by chemical treatment or introduction of a functional group.

[0004] For example, a fiber-reinforced composite material in which a matrix material is impregnated into a reinforcing material obtained by chemically modifying the hydroxyl group of bacterial cellulose with a functional group such as an acetyl group or a methacryloyl group has been proposed (Patent Document 1). However, in terms of using bacterial cellulose and manufacturing a composite material by impregnating a matrix material, it cannot be said that it is very suitable for industrialization.

[0005] Furthermore, a fiber-reinforced composite material has been proposed in which cellulose fibers, whose hydrophobicity has been enhanced by grafting resins such as polymethyl methacrylate or polystyrene onto their surface, are incorporated into a matrix of polymethyl methacrylate or polystyrene (Patent Document 2). However, the grafted resins such as polymethyl methacrylate are not compatible with olefin-based thermoplastic resins. For this reason, it is uncertain whether a sufficient reinforcing effect can be obtained when using olefin-based thermoplastic resins as the matrix.

[0006] Olefin-based thermoplastic resins such as polyethylene and polypropylene are widely used as aliphatic hydrocarbon resins. Compared to other resins, olefin-based thermoplastic resins are low in density and lightweight. Therefore, if cellulose fibers or CNF can be dispersed in an olefin-based thermoplastic resin in a good dispersion state, lightweight and high-strength composite materials can be obtained. However, as mentioned above, cellulose fibers and the like have many hydroxyl groups and are highly hydrophilic, making it difficult to disperse them in hydrophobic media such as aliphatic hydrocarbon resins. Furthermore, even when CNF is chemically modified to become hydrophobic, it has been difficult to sufficiently improve its dispersibility in olefin-based hydrophobic media.

[0007] In contrast, a cellulose composition has been proposed in which the dispersibility of cellulose fibers and the like in a resin such as polyethylene is enhanced using a polymer dispersant without chemical modification treatment (Patent Document 3). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2007-51266 [Patent Document 2] Patent No. 5188765 [Patent Document 3] Patent No. 5825653 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, cellulose fibers and CNF tend to aggregate significantly even when treated with polymer dispersants, requiring considerable energy and time to disperse them in the resin. Furthermore, the heat generated during mixing and kneading can cause the polymer dispersant adsorbed onto the cellulose fibers to detach. Once the polymer dispersant is removed, the cellulose fibers re-aggregate strongly through hydrogen bonding, making it impossible to disperse them evenly throughout the olefin-based thermoplastic resin matrix. As a result, obtaining a sufficiently reinforced composite material was difficult.

[0010] This invention has been made in view of the problems of the prior art, and its objective is to provide a polymer dispersant that can effectively disperse cellulose fibers in an olefin-based thermoplastic resin, which is a hydrophobic medium, and that allows for easy observation of the dispersion state of cellulose fibers in the thermoplastic resin.

[0011] Furthermore, an object of the present invention is to provide a cellulose fiber resin composition in which cellulose fibers are dispersed in a hydrophobic medium, an olefin-based thermoplastic resin, in a good dispersion state, and in which the dispersion state of the cellulose fibers can be easily observed. Furthermore, an object of the present invention is to provide a method for inspecting a cellulose fiber resin composition that allows for easy observation of the dispersion state of cellulose fibers dispersed in an olefin-based thermoplastic resin. [Means for solving the problem]

[0012] In other words, the present invention provides the following polymer dispersant. [1] A polymeric dispersant used to disperse cellulose fibers in an olefin-based thermoplastic resin, wherein the polymer is a polymer that satisfies the following requirements (1) to (3). [Requirement (1)]: This is an AB block copolymer containing A chain and B chain, with a content of 90% by mass or more of constituent units derived from methacrylic acid monomers. [Requirement (2)]: The A chain has a constituent unit (A-1) derived from at least one selected from the group consisting of alkyl methacrylates having 1 to 18 carbon atoms, t-butylcyclohexyl methacrylate, dicyclopentanyl methacrylate, and dicyclopentenyloxyethyl methacrylate, with a number-average molecular weight of 3,000 to 10,000 and a molecular weight distribution of less than 1.5. [Requirement (3)]: The B chain comprises a constituent unit (B-1) derived from at least one selected from the group consisting of 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, 4-hydroxybutyl methacrylate, and 2,3-hydroxypropyl methacrylate, and a constituent unit (B-2) derived from a fluorescent dye methacrylate represented by the following general formula (1), wherein the content of constituent unit (B-1) is 80 to 99.5% by mass, the content of constituent unit (B-2) is 0.5 to 5% by mass, and the number average molecular weight is 3,000 to 10,000.

[0013] TIFF0007872549000001.tif55170 (In the above general formula (1), R1 represents CH2CH2 or CH2CH2OCH2CH2, R2 represents an alkylene group or cycloalkylene group having 2 to 18 carbon atoms, R3 to R6 independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R7 and R8 independently represent a hydrogen atom or a methyl group)

[0014] [2] The fluorescent dye methacrylate is represented by the polymer dispersant described in [1] above, which is represented by the following formula (1A).

[0015] TIFF0007872549000002.tif53170

[0016] Furthermore, the present invention provides the following cellulose fiber resin composition. [3] An olefinic thermoplastic resin, a cellulose fiber, and the polymer dispersant according to [1] or [2] for dispersing the cellulose fiber in the thermoplastic resin, wherein the content of the cellulose fiber is 1 to 30% by mass, and the content of the polymer dispersant is 10 to 100 parts by mass with respect to 100 parts by mass of the cellulose fiber. A cellulose fiber resin composition.

[0017] Further, according to the present invention, a method for inspecting a cellulose fiber resin composition as shown below is provided. [4] A step of confirming the dispersion state of the cellulose fiber in the cellulose fiber resin composition by fluorescence generated by irradiating the cellulose fiber resin composition with visible light or ultraviolet light, wherein the cellulose fiber resin composition is an olefinic thermoplastic resin, a cellulose fiber, and the polymer dispersant according to [1] or [2] for dispersing the cellulose fiber in the thermoplastic resin. A method for inspecting a cellulose fiber resin composition containing the same.

Advantages of the Invention

[0018] According to the present invention, it is possible to effectively disperse cellulose fibers in an olefinic thermoplastic resin which is a hydrophobic medium, and to provide a polymer dispersant capable of easily observing the dispersion state of cellulose fibers in the thermoplastic resin.

[0019] Further, according to the present invention, it is possible to provide a cellulose fiber resin composition in which cellulose fibers are dispersed in a good dispersion state in an olefinic thermoplastic resin which is a hydrophobic medium, and in which the dispersion state of the cellulose fibers can be easily observed. Furthermore, according to the present invention, it is possible to provide a method for inspecting a cellulose fiber resin composition capable of easily observing the dispersion state of cellulose fibers dispersed in an olefinic thermoplastic resin.

[0020] In the cellulose fiber resin composition of the present invention, the cellulose fibers are dispersed in an olefin-based thermoplastic resin in a good dispersion state, so that the reinforcing effect of the cellulose fibers as a filler is effectively exerted. Therefore, by using the cellulose fiber resin composition of the present invention, a molded product excellent in strength, toughness, etc. can be manufactured. In addition, since the dispersion state of the cellulose fibers can be easily confirmed, the quality inspection accuracy can be improved, and it can also be applied to technical aspects such as elucidating the mechanism of strength improvement. Furthermore, since it emits fluorescence, it is also useful for security applications and anti-counterfeiting applications.

Brief Description of the Drawings

[0021] [Figure 1] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 2] It is a polarized light microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 3] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 4] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 5] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 6] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 7] It is a fluorescence microscope photograph showing the microstructure of the surface of the cellulose fiber resin composition - 1 of Example 1. [Figure 8] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 2. [Figure 9] It is a fluorescence microscope photograph showing the microstructure of the cut surface of the cellulose fiber resin composition - 1 of Example 3. [Modes for carrying out the invention]

[0022] <Polymer dispersant> The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below. It is possible to disperse cellulose fibers in an olefin-based thermoplastic resin by treating cellulose fibers or cellulose nanofibers (hereinafter collectively referred to simply as "cellulose fibers") with a polymer dispersant having a portion that is compatible with the olefin-based thermoplastic resin, which is the dispersion medium. However, if the polymer dispersant does not have high adsorption to the cellulose fibers, the polymer dispersant will detach from the cellulose fibers during kneading and dispersion treatment under high temperature conditions, causing the cellulose fibers to aggregate and resulting in poor dispersibility in the thermoplastic resin. Therefore, in order to strongly adsorb to the cellulose fibers and to prevent detachment from the cellulose fibers even when dispersion treatment is performed under high temperature conditions, it is important that the portion of the polymer dispersant that adsorbs to the cellulose fibers does not have high compatibility (is incompatible) with the thermoplastic resin.

[0023] Thus, based on the assumption that a polymer dispersant needs to have a site that adsorbs to cellulose fibers and a site that exhibits compatibility with thermoplastic resins, the inventors of the present invention have found the configuration of the present invention. That is, one embodiment of the polymer dispersant of the present invention is a polymer dispersant used to disperse cellulose fibers in an olefin-based thermoplastic resin. The polymer dispersant of this embodiment is a polymer that satisfies the following requirements (1) to (3).

[0024] [Requirement (1)]: This is an AB block copolymer containing A chain and B chain, with a content of 90% by mass or more of constituent units derived from methacrylic acid monomers. [Requirement (2)]: Chain A has a constituent unit (A-1) derived from at least one selected from the group consisting of alkyl methacrylates having 1 to 18 carbon atoms, t-butylcyclohexyl methacrylate, dicyclopentanyl methacrylate, and dicyclopentenyloxyethyl methacrylate, with a number-average molecular weight of 3,000 to 10,000 and a molecular weight distribution of less than 1.5. [Requirement (3)]: The B chain has a constituent unit (B-1) derived from at least one selected from the group consisting of 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, 4-hydroxybutyl methacrylate, and 2,3-hydroxypropyl methacrylate, and a constituent unit (B-1) derived from a fluorescent dye methacrylate represented by general formula (1), with a content of constituent unit (B-1) of 80 to 99.5% by mass, a content of constituent unit (B-2) of 0.5 to 5% by mass, and a number-average molecular weight of 3,000 to 10,000.

[0025] TIFF0007872549000003.tif55170 (In the above general formula (1), R1 represents CH2CH2 or CH2CH2OCH2CH2, R2 represents an alkylene group or cycloalkylene group having 2 to 18 carbon atoms, R3 to R6 independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R7 and R8 independently represent a hydrogen atom or a methyl group)

[0026] (Requirement (1)) The polymeric dispersant of this embodiment is an AB block copolymer containing A and B chains, with a content of 90% or more, preferably 100% by mass, of constituent units derived from methacrylic acid monomers. Since the polymeric dispersant of this embodiment is substantially composed only of constituent units derived from methacrylic acid monomers, it can be designed to have a relatively high glass transition temperature. Furthermore, the polymerization method for producing the polymeric dispersant of this embodiment is suitable for using methacrylic acid monomers, and a special block structure can be easily formed. Other monomers besides methacrylic acid monomers can be styrene monomers, acrylate monomers, vinyl alkanoate ester monomers, and vinyl amide monomers. It is preferable that the polymeric dispersant of this embodiment is an AB block copolymer with a content of substantially 100% by mass of constituent units derived from methacrylic acid monomers.

[0027] (Requirement (2)) The AB block copolymer has an A chain, which is a site that is easily compatible with thermoplastic resins, and a B chain, which is a site that adsorbs to cellulose fibers but is not easily compatible with thermoplastic resins. The A chain has a constituent unit (A-1) derived from at least one selected from the group consisting of alkyl methacrylates having 1 to 18 carbon atoms, t-butylcyclohexyl methacrylate, dicyclopentanyl methacrylate, and dicyclopentenyloxyethyl methacrylate. Examples of alkyl methacrylates having 1 to 18 carbon atoms include methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, decyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate. The A chain having constituent unit (A-1) exhibits compatibility with olefin-based thermoplastic resins.

[0028] The number-average molecular weight (Mn) of the A chain is 3,000 to 10,000, preferably 3,500 to 9,500. The number-average molecular weight of the polymer in this specification is the polystyrene-based or polymethyl methacrylate-based value measured by gel permeation chromatography using tetrahydrofuran (THF) or dimethylformamide (DMF) as the developing solvent. If the number-average molecular weight of the A chain is less than 3,000, the compatibility with thermoplastic resins decreases, and it may become difficult to maintain the dispersion stability of cellulose fibers due to steric hindrance. On the other hand, if the number-average molecular weight of the A chain is greater than 10,000, the compatibility with thermoplastic resins decreases, and the properties of the thermoplastic resin may be impaired due to the properties of the AB block copolymer.

[0029] The molecular weight distribution of chain A (weight-average molecular weight (Mw) / number-average molecular weight (Mn), hereinafter also referred to as "PDI") is less than 1.5, preferably 1.05 to 1.3. That is, chain A is a polymer chain with relatively uniform molecular weights. If the molecular weight distribution is broad (the PDI value is too high), it may contain many molecular chains outside the aforementioned number-average molecular weight range, which may reduce compatibility with thermoplastic resins or impair the properties of thermoplastic resins.

[0030] (Requirement (3)) The B chain has a constituent unit (B-1) derived from at least one selected from the group consisting of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, and 2,3-hydroxypropyl methacrylate. Since the B chain is a constituent unit derived from a methacrylic acid monomer having a hydroxyl group, it is a polymer block that can adsorb by hydrogen bonding with the hydroxyl groups of cellulose fibers. The content of constituent unit (B-1) in the B chain is 80 to 99.5% by mass. If the content of constituent unit (B-1) in the B chain is less than 80% by mass, the B chain may become more compatible with thermoplastic resins, and the polymer dispersant may easily detach from the cellulose fibers during heat kneading to disperse the cellulose fibers in the thermoplastic resin.

[0031] The B chain further comprises a constituent unit (B-2) derived from the fluorescent dye methacrylate represented by the following general formula (1).

[0032] TIFF0007872549000004.tif55170 (In the above general formula (1), R1 represents CH2CH2 or CH2CH2OCH2CH2, R2 represents an alkylene group or cycloalkylene group having 2 to 18 carbon atoms, R3 to R6 independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R7 and R8 independently represent a hydrogen atom or a methyl group)

[0033] If the B chain is composed solely of the constituent unit (B-1), adsorption to the cellulose fiber is limited to hydrogen bonding, resulting in insufficient adsorption. Therefore, by using the fluorescent dye methacrylate represented by general formula (1), a fluorescent dye skeleton capable of staining cellulose can be introduced into the AB block copolymer. Staining the cellulose fiber with the fluorescent dye skeleton increases the affinity between the cellulose fiber and the B chain, improving the adsorption of the B chain to the cellulose fiber. Furthermore, by introducing a highly polar fluorescent dye skeleton exhibiting ionic properties, the compatibility of the B chain with thermoplastic resins can be further reduced.

[0034] The fluorescent dye skeleton in general formula (1) is a dye skeleton such as a xanthene dye or rhodamine. More specifically, it is the skeleton of a fluorescent dye such as rhodamine 6G or rhodamine B. Halide ions are usually used as counterions for fluorescent dyes. In contrast, in the structural unit (B-1) introduced into the B chain of the AB block copolymer, which is a polymer dispersant in this embodiment, bis(trifluoromethanesulfonyl)imide (TFSI) ions are used as counterions from the viewpoint of imparting heat resistance and hydrophobicity. Furthermore, by using TFSI ions as counterions, the solubility of the fluorescent dye methacrylate in the organic solvent used during polymerization is improved, and the introduction efficiency of structural unit (B-1) can be improved.

[0035] The fluorescent dye methacrylate is preferably a compound represented by the following formula (1A).

[0036] TIFF0007872549000005.tif53170

[0037] The fluorescent dye skeleton of the compound represented by formula (1A) is rhodamine 6G. Therefore, it is easy to obtain raw materials, synthesize, and purify. Furthermore, since it emits fluorescence by absorbing wavelengths of a specific range, it is suitable for the inspection method of the present invention described later. This fluorescent dye has an absorption maximum wavelength of 526 nm when tetrahydrofuran is used as the solvent. When irradiated with light of a wavelength of 400 to 560 nm, it emits fluorescence at 550 nm, so fluorescence can be efficiently confirmed using a predetermined detection device.

[0038] Fluorescent dyes, specifically methacrylates, can be synthesized by conventionally known methods. For example, a primary amine is introduced by reacting rhodamine 6G with diamines such as ethylenediamine, hexamethylenediamine, and decanediamine in ethanol. After purification, methacryloyloxyethyl isocyanate or methacryloyloxyethoxyethyl isocyanate is reacted to form methacrylate. Subsequently, under hydrochloric acid conditions, ion exchange using lithium bis(trifluoromethanesulfonyl)imide can be performed to obtain the fluorescent dye methacrylate represented by general formula (1).

[0039] The content of constituent unit (B-2) in the B chain is 0.5 to 5% by mass, preferably 1 to 3% by mass. If the content of constituent unit (B-2) in the B chain is less than 0.5% by mass, the adsorption to cellulose fiber will be insufficient. On the other hand, if the content of constituent unit (B-2) in the B chain exceeds 5% by mass, the solubility of the B chain will decrease, and the fluorescence may become too strong. In addition, because the fluorescent dye methacrylate has a large molecular weight, the polymerization rate tends to decrease, and residue may remain.

[0040] The number-average molecular weight (Mn) of the B chain is 3,000 to 10,000, preferably 5,000 to 9,000. The number-average molecular weight of the B chain is the value obtained by subtracting the number-average molecular weight of the A chain from the number-average molecular weight of the entire AB block copolymer. If the number-average molecular weight of the B chain is less than 3,000, the adsorption to cellulose fibers will be insufficient, and the dispersibility of cellulose fibers in the thermoplastic resin will decrease. On the other hand, if the number-average molecular weight of the B chain is greater than 10,000, the portion that does not mix with the thermoplastic resin will become too large, and even if the A chain is present, the AB block copolymer as a whole may not mix well with the thermoplastic resin. It is preferable that the number-average molecular weight of the B chain is approximately the same as, or greater than, the number-average molecular weight of the A chain.

[0041] (Method for manufacturing polymer dispersants) Since polymer dispersants are AB block copolymers, they can be produced by polymerization methods such as living anionic polymerization, living cationic polymerization, and living radical polymerization. Among these, living radical polymerization is preferred because it does not require new equipment or high-purity raw materials, nor does it require special polymerization conditions. Living radical polymerization methods include the nitroxide method using nitroxide compounds; atom transfer radical polymerization utilizing the oxidation-reduction of metal complexes such as copper; reversible addition-cleavage chain transfer polymerization using dithioesters or dithiocarbonates; the TERP method using organotellurium; iodine transfer polymerization using iodine compounds as the starting compound; reversible transfer catalytic polymerization (RTCP method) using organic catalysts; and reversible catalyst-mediated polymerization (RCMP method). Among these, the RTCP method and RCMP method are preferred because they do not require protection of functional groups, can use general-purpose commercially available materials, and allow the production of block copolymers using conventionally known equipment and polymerization conditions. In the RTCP and RCMP methods, it is generally preferable to use methacrylate, which is a tertiary radical, as the monomer, from the viewpoint of living properties and blocking efficiency. Therefore, the RTCP and RCMP methods are suitable as methods for producing the polymer dispersant of this embodiment, which is an AB block copolymer containing 90% by mass or more of constituent units derived from methacrylate monomers.

[0042] Either chain A or chain B may be polymerized first. Of these, polymerizing chain A first is preferable because it makes it easier to improve compatibility with olefin-based thermoplastic resins.

[0043] It is preferable to polymerize the AB block copolymer by solution polymerization. In the case of solution polymerization, the cellulose fiber resin composition may be produced using the solution obtained by polymerization with an organic solvent. Alternatively, the organic solvent in the obtained solution may be evaporated to obtain the solid AB block copolymer, or it may be precipitated in a poor solvent, filtered, and dried to obtain the solid AB block copolymer. Furthermore, after precipitation in a poor solvent, it is also possible to obtain an aqueous paste of the AB block copolymer by filtering and washing with water.

[0044] When volatilizing the organic solvent used during polymerization, it is preferable to use an organic solvent with a low boiling point (for example, 150°C or below). When precipitation occurs in a poor solvent, water is preferred as the poor solvent, and a water-soluble organic solvent is preferred as the organic solvent for polymerization. Glycol-based solvents and amide-based solvents are preferred as organic solvents. Specific examples of organic solvents include propylene glycol monomethyl ether, propylene glycol monopropyl ether, diethylene glycol monobutyl ether, N-methylpyrrolidone, and 3-methoxy-N,N-dimethylpropanamide.

[0045] <Cellulose fiber resin composition> One embodiment of the cellulose fiber resin composition of the present invention contains an olefin-based thermoplastic resin, cellulose fibers, and the aforementioned polymer dispersant for dispersing the cellulose fibers in the thermoplastic resin.

[0046] (thermoplastic resin) As the olefin-based thermoplastic resin (hereinafter also simply referred to as "thermoplastic resin"), conventionally known olefin (polyolefin)-based thermoplastic resins can be used. Polyolefins are usually polymers of unsaturated hydrocarbon monomers and are low-polarity hydrocarbon polymers. Examples of polyolefins include polyethylene, polypropylene, polyisoprene, polyisobutylene, polybutene, polybutadiene, polyhexene, poly-α-olefin, polycycloolefin, and copolymers with random or block structures using the monomers that constitute these. It is also preferable to use biopolyethylene using plant-derived raw materials. Furthermore, polymers containing the monomers that constitute these polyolefins as copolymer components may also be used. Examples include ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, and styrene-butadiene copolymers. Furthermore, chemically modified polyolefins, such as maleic anhydride grafted polypropylene, can be used.

[0047] (Cellulose fiber) Conventional known cellulose fibers can be used as the cellulose fibers. For example, cellulose nanofibers, which are nano-sized fibers with an average fiber diameter of 5 nm to 1,000 μm and an average fiber length of 100 nm to 10,000 μm, can be used, as well as micron-sized cellulose fibers. Alternatively, cellulose fibers can be produced by defibrating pulp, or the produced cellulose fibers can be dispersed directly into a thermoplastic resin. In other words, pulp itself can also be used as the cellulose fiber.

[0048] Examples of pulp (plant fibers) used as raw materials for cellulose fiber include natural cellulose obtained from natural plant materials such as wood, bamboo, hemp, jute, kenaf, cotton, beets, agricultural waste, and cloth; and regenerated cellulose fibers such as paper, rayon, and cellophane. Examples of wood include Sitka spruce, cedar, cypress, eucalyptus, and acacia. Examples of paper include deinked recycled paper, recycled corrugated cardboard, magazines, and copy paper. Lignocellulose, the main component of pulp, is mainly composed of cellulose, hemicellulose, and lignin, and each of these is bonded together to form plant fibers. Pulp can be obtained by mechanically or chemically processing plant fibers containing lignocellulose to remove hemicellulose and lignin and increase the purity of cellulose. Furthermore, the amount of lignin in the obtained pulp can be controlled by bleaching or adjusting the amount of delignin as needed.

[0049] Examples of pulps include chemical pulps obtained by mechanically or chemically processing plant fibers (kraft pulp (KP), sulfite pulp (SP)), semi-chemical pulp (SCP), chemigland pulp (CGP), chemimechanical pulp (CMP), wood pulp (GP), refiner mechanical pulp (RMP), thermomechanical pulp (TWP), and chemothermetic pulp (CTMP); and deinked recycled paper pulp, corrugated cardboard recycled paper pulp, and magazine recycled paper pulp, which are mainly composed of these pulps. Among these, various kraft pulps derived from coniferous trees with high fiber strength (unbleached coniferous kraft pulp (NUKP), oxygen-bleached unbleached coniferous kraft pulp (NOKP), and bleached coniferous kraft pulp (NBKP)) are preferred. The lignin content in the pulp is usually 0 to 40% by mass, preferably 0 to 10% by mass. The lignin content in pulp can be measured by the Klason method.

[0050] As cellulose fibers, cellulose fibers with a micron-sized diameter can be used. Particles, ball-shaped, or cotton-like cellulose fibers with an average fiber diameter of 0.3 to 50 μm, an average fiber length of 5 to 2,000 μm, and an average aspect ratio of 2 to 100 can be used. Such cellulose fibers are readily obtainable industrially and are inexpensive materials that do not require special defibrillation or processing steps like cellulose nanofibers.

[0051] Furthermore, nanocellulose with an average fiber diameter of 4-500 nm can also be used as the cellulose fiber. By using such nanocellulose, it is possible to disperse cellulose that functions as a filler at the nanoscale level in the thermoplastic resin, allowing the high strength and reinforcing effect of the cellulose fiber to be fully realized.

[0052] Nanocellulose can be obtained by breaking down (defibrillating) cellulose-containing materials such as wood pulp to the nanoscale level. In plant cell walls, the smallest unit is a cellulose microfibril (single cellulose nanofiber) with a width of about 4 nm. Nanocellulose is a nanoscale cellulose fiber formed by the aggregation of multiple cellulose microfibrils or cellulose microfibrils.

[0053] Among nanocelluloses, cellulose nanofibers (CNF) are nano-sized fibers obtained by mechanically defibrating cellulose. CNF fibers have a width of approximately 4-500 nm and a length of approximately 1 μm or more. The specific surface area of ​​CNF is 70-300 m². 2 It is preferable that the value be / g, and 70-250m 2 It is even more preferable that it be / g, and 100-200m 2It is particularly preferable that the density is / g. Dispersing CNF with a large specific surface area in a thermoplastic resin increases the contact area with the thermoplastic resin, resulting in a resin composition with improved strength. However, if the specific surface area of ​​the CNF is extremely large, it tends to aggregate in the resin composition, which may slightly reduce the strength of the resin composition. The fiber diameter of the CNF is usually 4 to 500 nm, preferably 4 to 300 nm, and more preferably 4 to 100 nm. The average values ​​of the fiber diameter of the cellulose fiber containing CNF (average fiber diameter, average fiber length, average crystal width, average crystal length) are the average values ​​measured for 50 or more nanocellulose fibers within the field of view of an electron microscope.

[0054] Nanocellulose has a large specific surface area, is lighter than steel, and has high strength. Nanocellulose has lower thermal expansion and less thermal deformation than glass. Preferably, the nanocellulose has cellulose type I crystals and a crystallinity of 50% or more, more preferably 55% or more, and particularly preferably 60% or more. The crystallinity of cellulose type I in nanocellulose is usually 95% or less, preferably 90% or less.

[0055] As the cellulose fiber, surface-treated cellulose fiber may be used. Specifically, cellulose fiber in which the hydroxyl groups on its surface have been chemically modified can be used. More specifically, cellulose fiber that has been esterified, etherified, or carboxylated using organic compounds can be used. Esterified cellulose fiber is an esterified product obtained by reacting the hydroxyl groups of cellulose fiber with an anhydride such as dodecenyl succinic anhydride. Etherified cellulose fiber is an etherified product in which fluoroceine groups, etc., are ether-bonded to the cellulose fiber. Carbochlorinated cellulose fiber is a carboxylated product in which the hydroxyl groups of cellulose fiber are oxidized with TEMPO to form carboxyl groups.

[0056] The cellulose fibers may be in the form of a dry material, a water paste, or a paste containing an organic solvent. In the case of a water paste, the cellulose fibers are less likely to aggregate and have good dispersibility. For example, the cellulose fibers can be dispersed in a thermoplastic resin by melt-mixing a water paste of cellulose fibers with a thermoplastic resin and then removing the water.

[0057] The cellulose fiber content in the cellulose fiber resin composition is 1 to 30% by mass, preferably 5 to 20% by mass, based on the entire resin composition. If the cellulose fiber content is less than 1% by mass, the reinforcing effect of the cellulose fiber may not be achieved. On the other hand, if the cellulose fiber content exceeds 30% by mass, the cellulose fiber may not be sufficiently dispersed, resulting in the formation of lumps or a large amount of aggregates.

[0058] The amount of polymeric dispersant in the cellulose fiber resin composition is 10 to 100 parts by mass, preferably 10 to 50 parts by mass, per 100 parts by mass of cellulose fiber. If the amount of polymeric dispersant is less than 10 parts by mass per 100 parts by mass of cellulose fiber, the dispersant may not function sufficiently. On the other hand, if the amount of polymeric dispersant is more than 100 parts by mass per 100 parts by mass of cellulose fiber, the amount of polymeric dispersant becomes too large, and the polymeric properties of the polymeric dispersant may become apparent, which may degrade the physical properties of the cellulose fiber resin composition.

[0059] (Additives) The cellulose fiber resin composition may further contain various additives. Examples of additives include antioxidants, nucleating agents, light stabilizers, ultraviolet absorbers, lubricants, fluorescent whitening agents, fillers, inorganic fillers, foaming agents, foaming aids, plasticizers, crosslinking agents, compatibilizers, antistatic agents, flame retardants, and pigments.

[0060] (Method for producing cellulose fiber resin composition) After pre-mixing solid cellulose fibers, a polymer dispersant, and a thermoplastic resin using a tumbler mixer or Banbury mixer, the mixture is kneaded using a kneader, multi-screw kneader, or three-roll disperser to disperse the cellulose fibers in the thermoplastic resin and obtain the desired cellulose resin composition. The processing temperature can be set according to the processing temperature of the thermoplastic resin; for example, it can be kneaded at 100-200°C. If the polymer dispersant is solid, it can be used as is. On the other hand, if the polymer dispersant is used in the form of a water paste or solution, it should be thoroughly kneaded while removing water and organic solvents. Since the polymer dispersant is a polymer to which a fluorescent dye is bound, it does not substantially bleed or leach even when kneaded at the above processing temperature. Furthermore, since the fluorescent dye uses bis(trifluoromethanesulfonyl)imide as a counterion, the fluorescent dye does not substantially degrade even when kneaded at the above processing temperature, and it has excellent heat resistance.

[0061] Normally, solid cellulose fibers are aggregated, and dispersing them in thermoplastic resins can require a significant amount of time and energy. Therefore, it is preferable to mechanically grind or beat a water paste, water suspension, or water slurry prepared by immersing pulp in water using a disperser, refiner, high-pressure homogenizer, grinder, single-screw mixer, twin-screw mixer, multi-screw mixer, and bead mill, etc., to convert the pulp into cellulose fibers in an aqueous medium and obtain a cellulose fiber aqueous mixture. When using cellulose fibers in the form of a dry powder, cotton, or ball, etc., the cellulose fibers can be mixed and stirred using a disperser or disperser to break down the shape of the cellulose fibers and disperse them in water to obtain a cellulose fiber aqueous mixture. Furthermore, by dispersing the obtained cellulose fiber aqueous mixture using a disperser, etc., and defibrating the cellulose fibers to the nano level, a nano-sized cellulose fiber aqueous mixture can be obtained.

[0062] A cellulose fiber resin composition can be obtained by kneading a cellulose fiber aqueous mixture, a polymer dispersant, and a thermoplastic resin under heated conditions, dispersing the cellulose fibers while removing water and organic solvents. For example, first, a cellulose fiber aqueous mixture is mixed with preferably powdered thermoplastic resin so that the cellulose fibers make up 10-50% by mass, then filtered to adjust the non-volatile content to 60-80% by mass. Next, a solution of the polymer dispersant is added and dried to obtain a pre-composition containing cellulose fibers, a polymer dispersant, and a thermoplastic resin. Subsequently, the pre-composition is mixed with the thermoplastic resin and, if necessary, a dispersion aid such as urea, and dispersed using a kneader while removing volatile components to obtain the desired cellulose fiber resin composition.

[0063] (Use of cellulose fiber resin composition) By molding the cellulose fiber resin composition using conventionally known molding methods, molded products can be obtained according to their intended purpose. Examples of molding methods include injection molding, extrusion molding, blow molding, pressure molding, rotational molding, and film molding. The cellulose fiber resin composition is useful as a constituent material for, for example, automobiles, home appliances, electronic components, display materials, buildings, containers, films, batteries, trays, etc. Furthermore, since the cellulose fiber resin composition of this embodiment emits fluorescence, it can be used for anti-counterfeiting, security applications, design applications, latent image representation, and the like.

[0064] <Method for testing cellulose fiber resin compositions> The present invention provides a method for inspecting a cellulose fiber resin composition, comprising the step of confirming the dispersion state of cellulose fibers in the cellulose fiber resin composition by irradiating the cellulose fiber resin composition with visible light or ultraviolet light to generate fluorescence. The cellulose fiber resin composition contains an olefin-based thermoplastic resin, cellulose fibers, and the aforementioned polymer dispersant for dispersing cellulose fibers in the thermoplastic resin.

[0065] The aforementioned polymeric dispersant is an AB block copolymer containing a B chain having a constituent unit (B-2) derived from the fluorescent dye methacrylate, and this B chain is a site (polymer block) that adsorbs to cellulose fibers. Since such a polymeric dispersant is adsorbed to cellulose fibers, fluorescence is emitted when the cellulose fiber resin composition is irradiated with visible light or ultraviolet light. By observing the generated fluorescence, it is possible to confirm how the cellulose fibers are dispersed in the thermoplastic resin.

[0066] For example, a molded product, such as a film or pellet made from a cellulose fiber resin composition, is irradiated with visible light or ultraviolet light using a device that emits visible light or ultraviolet light, and the resulting fluorescence is observed. Examples of devices that emit ultraviolet light include light sources that emit ultraviolet light with wavelengths such as 254 nm and 350-400 nm, black lights, mercury lamps, metal halide lamps, and LED lights. It is also preferable to use a handheld device.

[0067] In particular, it is preferable to use a fluorescence microscope as the device for irradiating with ultraviolet light. Fluorescence microscopes are typically equipped with an "excitation filter," which is a fluorescence filter that allows light in a specific wavelength range from the light source to pass through, and an "absorption filter," which transmits the light necessary for observation from the fluorescence emitted from the sample. This allows for the observation of the dispersion, orientation, and distribution of fine cellulose fibers using the microscope. Other devices such as disk fluorescence microscopes, confocal laser scanning fluorescence microscopes, super-resolution microscopes, and scanning X-ray fluorescence microscopes can also be used.

[0068] These devices can be used to observe the dispersion state of cellulose fibers in a cellulose fiber resin composition. Since the fluorescent dye is not contained in the composition as a single molecule but is contained within the polymer's constituent units, it does not bleed out during observation, allowing for clear observation of the cellulose fiber dispersion state. The shape of the cellulose fibers, as well as the degree of dispersion, distribution, and orientation of the cellulose fibers in the thermoplastic resin, can be clearly observed, making it useful for inspecting the reinforcing effect and quality confirmation of cellulose fibers in a composition. Furthermore, the inspection method for cellulose resin compositions of this embodiment contributes to improving the reliability and stabilizing the quality of cellulose fiber compositions as products, and is useful as a method for inspecting the quality of cellulose resin compositions. Moreover, the inspection method for cellulose fiber resin compositions of this embodiment is expected to have great potential for use in the security and anti-counterfeiting fields. [Examples]

[0069] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are based on mass unless otherwise specified.

[0070] <Manufacturing of fluorescent dye methacrylate> (Manufacturing Example 1) 47 parts of rhodamine 6G, 400 parts of ethanol, and ethylenediamine 107.1 were placed in a reaction vessel. After stirring and reacting at room temperature (25°C) for 6 hours, 400 parts of deionized water were added, and the resulting red precipitate was filtered to obtain compound 1. After washing the obtained precipitate, it was vacuum-dried at 40°C for 24 hours to obtain 34.5 parts of pink powder compound 1. The NMR and IR measurements of the obtained compound 1 confirmed that it has the structure represented by the following formula (1-a).

[0071] TIFF0007872549000006.tif59170

[0072] 35.4 parts of the obtained compound 1 and 531 parts of toluene were placed in a reaction vessel, heated to 40°C and stirred to form a suspension. A mixture of 14.2 parts of methacryloyloxyethyl isocyanate and 14.2 parts of toluene was added dropwise over 2 hours, and the mixture was reacted at 40°C for 2 hours. After confirming the disappearance of the isocyanate by measuring IR, the resulting precipitate was filtered to obtain the compound 2 represented by the following formula (1-b). The obtained precipitate was washed with ethyl acetate and dried to obtain 46.0 parts of compound 2 represented by the following formula (1-b).

[0073] TIFF0007872549000007.tif53170

[0074] 46 parts of the obtained compound 2 and 700 parts of ethanol were placed in a reaction vessel, and 300 parts of 3.5% dilute hydrochloric acid were added and the mixture was stirred. A mixture of 27 parts of lithium bis(trifluoromethanesulfonyl)imide and 100 parts of water was gradually added and the mixture was stirred for 2 hours. The resulting solution was added to a large amount of water while stirring. The precipitated red powder was filtered, washed, and dried to obtain 52.9 parts of the fluorescent dye methacrylate (RHM-1). The obtained RHM-1 was measured by NMR and IR, and analyzed by HPLC to confirm that it has the structure represented by the following formula (1A).

[0075] TIFF0007872549000008.tif53170

[0076] (Comparative manufacturing example 1) Fluorescent dye methacrylate (RHM-2) was obtained in the same manner as in Production Example 1 described above, except that lithium bis(trifluoromethanesulfonyl)imide was not used. The NMR and IR of the obtained RHM-2 were measured to confirm that it has the structure represented by the following formula (2).

[0077] TIFF0007872549000009.tif56170

[0078] <Synthesis of polymer dispersants> (Example of synthesis 1) 107.6 parts of 3-methoxy-N,N-dimethylpropanamide (trade name "Equamid M", manufactured by KJ Chemical Co., Ltd.), 1.0 part of iodine, 3.7 parts of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (trade name "V-70", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 0.2 parts of diphenylmethane (DPM), and 48.1 parts of methyl methacrylate (MMA) were placed in a reaction vessel. The mixture was stirred while flowing nitrogen and the temperature was raised to 45°C. Polymerization was carried out for 5 hours to form the A chain. A portion of the reaction solution was sampled, and the solid content, measured using a moisture meter, was 32.8%, indicating a polymerization conversion rate of approximately 100%. The number-average molecular weight (Mn) measured by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as the developing solvent was 3,900, the PDI (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) was 1.28, and the peak-top molecular weight (PT) was 5,700.

[0079] 1.6 parts of V-70 were added to the reaction vessel. A monomer solution consisting of 52.1 parts of 2-hydroxyethyl methacrylate (HEMA) and 1.0 part of RHM-1 was further added, and polymerization was carried out at 40°C for 4 hours to form the B chain, obtaining a polymer solution containing the AB block copolymer. The solid content of the polymer solution was 49.8%, confirming that the target product was obtained almost quantitatively. The Mn of the AB block copolymer was 8,600, the PDI was 1.53, and the PT was 14,000. The Mn of the B chain, calculated by subtracting the Mn of the A chain from the total Mn of the AB block copolymer, was 4,700. The PT of the B chain was 8,300.

[0080] 2,000 parts of an aqueous methanol solution (water / methanol = 1 / 2) were placed in a beaker. Using a high-speed stirrer (disper), the aqueous methanol solution was stirred at 1,500 rpm, and 100 parts of the resulting polymer solution were gradually added to precipitate the solid. After adding all of the polymer solution, the mixture was stirred at 1,500 rpm for 30 minutes to atomize the precipitated solid. The fine particles were filtered under reduced pressure using a Nutsch filter, and then washed three times with 1 L of water to obtain a polymer aqueous paste. The obtained polymer aqueous paste was dried in a 60°C oven for 24 hours to obtain the polymer dispersant FP-1. The solid content of the obtained polymer dispersant FP-1 was 99.7%.

[0081] (Examples of actual synthesis 2-6, comparative synthesis examples 1 and 2) Polymer dispersants FP-2 to FP-6, HFP-1, and HFP-2 were obtained in the same manner as in the previously described experimental synthesis example 1, except for the compositions shown in Tables 1 and 2. The physical properties of the obtained polymer dispersants are shown in Tables 1 and 2. The meaning of the abbreviations in the tables is explained below. • FA512M: Dicyclopentenyloxyethyl methacrylate LMA: Lauryl methacrylate TBCHMA:4-tert-butylcyclohexyl methacrylate • FA513M: Dicyclopentanyl methacrylate HBMA: 4-hydroxybutyl methacrylate HPMA:2-hydroxypropyl methacrylate GLMA: 2,3-hydroxypropyl methacrylate

[0082] TIFF0007872549000010.tif226170

[0083] TIFF0007872549000011.tif252170

[0084] <Production of Cellulose Fiber Resin Composition (1)> (Example 1) 100 parts of bleached coniferous kraft pulp (NBKP, refined, 25% solids) were added to 1,000 parts of ethanol. After stirring with a disperser, the mixture was filtered to obtain a pulp ethanol paste. The obtained paste was dissolved by adding 1,000 parts of ethanol, and then 53.3 parts of polyethylene (product name "Flowbeads HE3040", manufactured by Sumitomo Seika Co., Ltd.) (PE) were added. After stirring, the mixture was filtered to obtain a pulp and PE ethanol paste. To the obtained paste, a solution obtained by dissolving 5 parts of polymer dispersant FP-1 in 100 parts of THF was added. After mixing, the mixture was dried under reduced pressure at 60°C to obtain a pre-mixture with a pulp / FP-1 / PE ratio of 25 / 5 / 53.3 and a pulp content of 30%.

[0085] 83.3 parts of the obtained pre-mixture, 163 parts of PE, and 10.4 parts of urea were placed in a small mixer and mixed to obtain the pre-kneading composition. The pre-kneading composition obtained using a twin-screw extruder was kneaded at 140°C, extruded in strand form, cooled, and cut with a pelletizer to obtain pelletized cellulose fiber resin composition-1.

[0086] (Examples 2 and 3, Comparative Examples 1-3) Pellet-shaped cellulose fiber resin compositions -1 to 3, -1H, and -2H were obtained in the same manner as in Example 1 described above, except that the types of polymer dispersants shown in Table 3 were used. Comparative Example 1 was provided for PE alone (without cellulose fiber or polymer dispersant).

[0087] <Rating> The obtained cellulose fiber resin compositions (PE alone for Comparative Example 1) were injection molded at 160°C to produce dumbbell pieces (dumbbell thickness: 2 mm). Tensile tests were then performed using a tensile testing machine (universal testing machine, manufactured by Shimadzu Corporation) in accordance with ISO 527-1 / -2. Specifically, tensile tests were performed on the prepared dumbbell pieces at a tensile speed of 10 mm / min, and the tensile modulus, tensile strength, and elongation at break were measured and calculated. The results are shown in Table 3.

[0088] TIFF0007872549000012.tif63170

[0089] A portion of a dumbbell made using the cellulose fiber resin composition-1 of Example 1 was cut to a thickness of 20 μm using a microtome. A slide was then prepared on a hot stage and observed and photographed using a disk-scanning fluorescence microscope (product name "IX2-DSU", Olympus Corporation, magnification 290x). The fluorescence microscope image taken is shown in Figure 1. As shown in Figure 1, the polymer dispersant was adsorbed onto the cellulose fibers, causing the cellulose fibers to fluoresce, allowing us to understand the dispersion state (degree of dispersion) of the cellulose fibers in PE. Furthermore, from Figure 1, it was confirmed that the average diameter of the cellulose fibers was nanoscale, and the average length of the cellulose nanofibers was 5-10 μm (actual color photographs allow for a clearer confirmation of the dispersion state and size of the cellulose fibers). In addition, a microscope image taken using a polarizing microscope (product name "BX-53P", Olympus Corporation) is shown in Figure 2. As shown in Figure 2, the dispersion state of the cellulose fibers is not clear in the microscope image without fluorescence emission. As described above, by using the polymer dispersant in the examples, the dispersion state of the cellulose fiber could be clearly confirmed.

[0090] Furthermore, a portion of a dumbbell made using the cellulose fiber resin composition-1 of Example 1 was cut into sections with thicknesses of 40 μm, 60 μm, 80 μm, and 100 μm using a microtome. Slides were then prepared in the same manner as described above and observed and photographed using a disk-scanning fluorescence microscope. The resulting fluorescence microscope images are shown in Figures 3 to 6. In addition, a fluorescence microscope image of the surface of the dumbbell made using the cellulose fiber resin composition-1 of Example 1 is shown in Figure 7. As shown in Figures 3 to 6, by observing test pieces of different thicknesses, information such as the dispersion state of the cellulose fibers and the aggregation of some cellulose fibers can be obtained. Furthermore, as shown in Figure 7, the dispersion state of the cellulose fibers can be confirmed not only by observing the cut surface of the test piece but also by observing the surface. The fluorescent dye used in the cellulose fiber resin composition of this embodiment is bound to the polymer, which is a polymer dispersant, and therefore does not bleed substantially. For this reason, the polymer dispersant and cellulose fiber resin composition of this embodiment are expected to be used, for example, in anti-counterfeiting and security fields.

[0091] Furthermore, portions of dumbbells made using cellulose fiber resin compositions-2 and-3 of Examples 2 and 3, respectively, were cut to a thickness of 20 μm using a microtome. Then, slides were prepared in the same manner as above and observed and photographed using a disk-scanning fluorescence microscope. The fluorescence microscope images taken are shown in Figures 8 and 9. As shown in Table 3, cellulose fiber resin compositions-2 and-3 of Examples 2 and 3 have improved tensile strength compared to cellulose fiber resin composition-1 of Example 1. Furthermore, as shown in Figures 8 and 9, it can be seen that the cellulose fibers in cellulose fiber resin compositions-2 and-3 are finer and more oriented. This is presumed to be the reason for the improved tensile strength of cellulose fiber resin compositions-2 and-3. In particular, as shown in Figure 9, it was confirmed that the cellulose fibers in cellulose fiber resin composition-3 are oriented in a directional manner, which is presumed to be the reason for the improved tensile modulus and tensile strength.

[0092] <Production of Cellulose Fiber Resin Composition (2)> (Example 4) 50.0 parts of cellulose fiber (trade name "ARBOCEL B400", manufactured by Rettenmaier, average fiber diameter 20 μm, average fiber length 900 μm, average aspect ratio 45, cotton-like) and 4950.0 parts of water were placed in a vat. After stirring at 3,000 rpm for 1 hour using a high-speed stirrer, it was filtered to obtain a water paste of cellulose fiber (solid content 32.5%). 153 parts of the obtained water paste were added to 1,530 parts of ethanol, and then a solution prepared by dissolving 5 parts of polymer dispersant FP-4 in 15 parts of THF was further added. After stirring and mixing, it was put into water, and the resulting precipitate was filtered to obtain 54.6 parts of water paste. The solid content of the obtained water paste was 35.0%. The obtained water paste is a dispersion-treated product obtained by treating 100 parts of cellulose fiber with 10 parts of polymer dispersant. 50 parts of the obtained water paste and 88.5 parts of polypropylene (trade name "Novatec PP MA04A", manufactured by Japan Polypropylene Corporation) (PP) were put into a small laboratory kneader and melt-kneaded at 160 °C until the generation of steam ceased. Then, it was dried in a dryer at 110 °C to obtain cellulose fiber resin composition - 4.

[0093] The tensile modulus of the obtained cellulose fiber resin composition - 4 was 2.4 GPa, and the tensile strength was 40.0 MPa. On the other hand, the tensile modulus of PP alone was 1.8 GPa, and the tensile strength was 35.0 MPa. Also, when observed with a fluorescence microscope in the same manner as in Example 1, fluorescence was developed in the same manner as in Example 1, and the dispersion state of the cellulose fiber could be confirmed.

[0094] <Production of CNF> 100 parts of bleached coniferous kraft pulp (NBKP, refined, 25% solids) were mixed with 47,100 parts of water to obtain an aqueous suspension (slurry) with a pulp slurry concentration of 0.75%. The obtained aqueous suspension was mechanically defibrated using a millstone grinder (product name "Super Mascolloider," manufactured by Masuko Sangyo Co., Ltd.) in a total of 8 passes using two types of grinding wheels. Subsequently, it was dewatered using a filter press to obtain 2,350 parts of cellulose nanofiber (CNF-1). The obtained CNF-1 was in a hydrated state and had a solids content of 15.3%. The average diameter of the CNF-1 observed and measured using a microscope was 3-8 nm, and the average length was 5-10 μm.

[0095] <Manufacturing of Cellulose Fiber Resin Composition (3)> (Examples 5 and 6) Cellulose fiber resin compositions 5 and 6 were obtained in the same manner as in Example 4, except that CNF-1 manufactured in place of cellulose fiber was used, and polymer dispersants FP-5 and FP-6 were used in place of polymer dispersants FP-4, respectively. The tensile modulus of cellulose fiber resin composition 5 was 2.9 GPa, and its tensile strength was 2.0 MPa. The tensile modulus of cellulose fiber resin composition 6 was 2.4 GPa, and its tensile strength was 39.0 MPa. Furthermore, when observed with a fluorescence microscope in the same manner as in Example 1, both compositions exhibited fluorescence in the same way as in Example 1, confirming the dispersion state of the cellulose fibers. [Industrial applicability]

[0096] The cellulose fiber resin composition of the present invention contains a lightweight olefin-based thermoplastic resin such as PE or PP as a base resin, and is therefore useful as a constituent material for components used in fields where lightness and high strength are required, such as automobiles, home appliances, electronic components, display materials, buildings, containers, films, batteries, trays, and sporting goods. Furthermore, because it emits fluorescence, it is useful for anti-counterfeiting, security applications, design applications, and latent image representation.

Claims

1. A polymer dispersant used to disperse cellulose fibers in an olefin-based thermoplastic resin, A polymer dispersant that satisfies the following requirements (1) to (3). [Requirement (1)]: This is an A-B block copolymer containing A-chain and B-chain, with a content of 90% by mass or more of constituent units derived from methacrylic acid monomers. [Requirement (2)]: The A chain has a constituent unit (A-1) derived from at least one selected from the group consisting of alkyl methacrylates having 1 to 18 carbon atoms, t-butylcyclohexyl methacrylate, dicyclopentanyl methacrylate, and dicyclopentenyloxyethyl methacrylate, and has a number-average molecular weight of 3,000 to 10,000 and a molecular weight distribution of less than 1.

5. [Requirement (3)]: The B chain comprises a constituent unit (B-1) derived from at least one selected from the group consisting of 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, 4-hydroxybutyl methacrylate, and 2,3-hydroxypropyl methacrylate, and a constituent unit (B-2) derived from a fluorescent dye methacrylate represented by the following general formula (1), wherein the content of constituent unit (B-1) is 80 to 99.5% by mass, the content of constituent unit (B-2) is 0.5 to 5% by mass, and the number average molecular weight is 3,000 to 10,000. (In the general formula (1), R １ represents CH ２ CH ２ or CH ２ CH ２ OCH ２ CH ２ represents, R ２ represents an alkylene group or a cycloalkylene group having 2 to 18 carbon atoms, and R ３ to R ６ each independently represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R ７ and R ８ each independently represents a hydrogen atom or a methyl group)

2. The polymer dispersant according to claim 1, wherein the fluorescent dye methacrylate is represented by the following formula (1A).

3. A polymer dispersant according to claim 1 or 2, comprising an olefin-based thermoplastic resin, cellulose fibers, and the cellulose fibers dispersed in the thermoplastic resin, The cellulose fiber content is 1 to 30% by mass. A cellulose fiber resin composition wherein the content of the polymer dispersant is 10 to 100 parts by mass per 100 parts by mass of the cellulose fiber.

Images