JP7474638B2 - Resin composition - Google Patents

Description

The present invention relates to a resin composition containing an engineering plastic.

In the past, engineering plastics such as polyamide, polycarbonate, and polyacetal have been used to replace metal materials in order to reduce their weight. However, their use has been limited due to problems such as dimensional stability and deterioration of mechanical properties at high temperatures. To solve these problems, inorganic fillers such as glass fiber are currently commonly used in combination with metal materials, but resins containing inorganic fillers are difficult to material recycle or thermally recycle, and the only way to dispose of them is to bury them. In addition, technology that uses cellulose fiber as an environmentally friendly organic filler to replace inorganic fillers has been attracting attention in recent years, but discoloration and deterioration during the molding process of engineering plastics, which generally exceed 250°C, is a major issue.

For example, Patent Document 1 discloses cellulose fine fibers in which acetyl groups are introduced simultaneously with or after defibration of the cellulose in order to impart heat resistance.

JP 2019-6875 A

However, as a result of the investigations conducted by the present inventors, the cellulose fibers of Patent Document 1 contain chemically unstable ester bonds, and therefore are not fully satisfactory in terms of preventing color deterioration of molded articles produced by combining them with resins.

The present invention therefore relates to a resin composition containing engineering plastics and modified cellulose fibers that is excellent at suppressing color deterioration, and a method for producing the same.

The present invention relates to the following [1] and [2].
[1] A resin composition comprising an engineering plastic and a modified cellulose fiber,
The resin composition comprises the modified cellulose fiber having cellulose I type crystals, and at least one of the hydroxyl groups derived from cellulose has a substituent having an aromatic ring bonded to it via an ether bond.
[2] A method for producing a resin composition, comprising a mixing step of mixing an engineering plastic with a modified cellulose fiber,
A method for producing a resin composition, wherein the modified cellulose fiber has cellulose I type crystals, and a substituent having an aromatic ring is bonded to at least one of the hydroxyl groups derived from cellulose via an ether bond.

The molded article obtained using the resin composition of the present invention has an excellent effect of suppressing color deterioration, and the manufacturing method of the present invention makes it possible to manufacture a resin composition having such an effect.

<Resin Composition>
The resin composition of the present invention is a resin composition containing an engineering plastic and a modified cellulose fiber having a specific substituent.

[Engineering plastics]
In the present invention, any engineering plastic can be used without any particular limitation. The engineering plastic may be a crystalline resin or an amorphous resin.

In the case of crystalline resins, from the viewpoint of suppressing color deterioration, the heat distortion temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. The method for measuring the heat distortion temperature of crystalline resins is as described in the examples below.

In the case of amorphous resins, the higher the glass transition temperature, the better from the viewpoint of suppressing color deterioration. Specifically, the glass transition temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. The method for measuring the glass transition temperature is as described in the examples below.

Whether the resin is crystalline or amorphous, from the viewpoint of use as an engineering plastic, the higher the tensile strength at 25°C, the better; specifically, it is preferably 49 MPa or more, more preferably 55 MPa or more, and even more preferably 60 MPa or more. The method for measuring the tensile strength is as described in the examples below.

Whether the resin is crystalline or amorphous, from the viewpoint of exhibiting the coloration suppression effect, the higher the flexural modulus at 25°C, the better; specifically, it is preferably 2 GPa or more, more preferably 2.2 GPa or more, and even more preferably 2.5 GPa or more. The method for measuring the flexural modulus is as described in the examples below.

Specific examples of engineering plastics used in the present invention include polyamide, polybutylene terephthalate, polypropylene terephthalate, polyethylene terephthalate, polycarbonate, polyacetal, modified polyphenylene oxide, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyether sulfone, polysulfone, polyamide imide, polyether imide, polyimide, polyarylate, polyaryl ether nitrile, etc. Although the crystallinity is not generally determined depending on the application and the chemical structure of the resin, examples of crystalline resins in these examples include polyamide, polybutylene terephthalate, polypropylene terephthalate, polyethylene terephthalate, polyacetal, polyphenylene sulfide, polyether ether ketone, and polyaryl ether nitrile, and examples of amorphous resins include polycarbonate, modified polyphenylene oxide, modified polyphenylene ether, polyether sulfone, polysulfone, polyamide imide, polyether imide, polyimide, and polyarylate.

Among these, from the viewpoint of expressing the coloration suppression effect, preferred engineering plastics are polyamide, polybutylene terephthalate, polypropylene terephthalate, polyethylene terephthalate, polycarbonate, polyacetal, modified polyphenylene oxide, and modified polyphenylene ether, more preferred are polyamide, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, and polyacetal, and even more preferred are polyamide, polybutylene terephthalate, polyethylene terephthalate, and polycarbonate. Depending on the type of resin and the application, a photocuring and/or heat curing process can be carried out as appropriate, regardless of the order of the mixing process with the modified cellulose fiber.

In this specification, polyamide is a general term for a polymeric compound formed by amide bonds between monomers. Specific examples of polyamides include polycaproamide (polyamide 6), polyundecane amide (polyamide 11), polydodecane amide (polyamide 12), polytetramethylene adipamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polyundecamethylene adipamide (polyamide 116), polyhexamethylene sebacamide (polyamide 613), polyhexamethylene sebacamide (polyamide 614), polyhexamethylene dodecamide (polyamide 615), polyhexamethylene adipamide (polyamide 116), polyhexamethylene sebacamide (polyamide 616), polyhexamethylene sebacamide (polyamide 617), polyhexamethylene sebacamide (polyamide 618), polyhexamethylene sebacamide (polyamide 619), polyhexamethylene sebacamide (polyamide 620), polyhexamethylene sebacamide (polyamide 621), polyhexamethylene sebacamide (polyamide 622), polyhexamethylene sebacamide (polyamide 623), polyhexamethylene sebacamide (polyamide 624), polyhexamethylene sebacamide (polyamide 625), polyhexamethylene sebacamide (polyamide 626), polyhexamethylene sebacamide (polyamide 627), polyhexamethylene sebacamide (polyamide 628), polyhexamethylene sebacamide (polyamide 629), polyhexamethylene sebacamide (polyamide 630), polyhexamethylene sebacamide (polyamide 631), polyhexamethylene sebacamide (polyamide 632), Examples of such polyamides include methylene terephthalamide (polyamide 6T), polynonamethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), polyundecamethylene terephthalamide (polyamide 11T), polytrimethylhexamethylene terephthalamide (polyamide TMHT), polyundecamethylene hexahydroterephthalamide (polyamide 11T(H)), polyhexamethylene terephthalic/isophthalamide (polyamide 6T/6I), polyhexamethylene isophthalamide (polyamide 6I), and polymetaxylylene adipamide (polyamide MXD6). Such polyamides can be preferably used as the engineering plastics in this specification.

[Modified cellulose fibers]
The modified cellulose fiber used in the present invention has cellulose I type crystals and has a specific substituent, i.e., a substituent having an aromatic ring, bonded to at least one of the hydroxyl groups derived from cellulose via an ether bond. In this specification, a compound for bonding a specific substituent to a hydroxyl group derived from cellulose via an ether bond is referred to as an "etherifying agent".

The specific structure of the modified cellulose fiber used in the present invention can be shown, for example, by the following general formula (Ce):

General formula (Ce):

(In the formula, each R is independently hydrogen, a substituent having an aromatic ring, or a hydrocarbon group which may have an oxygen atom, and at least one R is a substituent having an aromatic ring. m is preferably an integer of 20 or more and 3,000 or less.)

In general formula (Ce), m is preferably an integer of 20 or more, more preferably an integer of 100 or more, from the viewpoint of the mechanical strength of the molded article of the resin composition, while from the viewpoint of availability and cost, it is preferably an integer of 3,000 or less, more preferably an integer of 2,000 or less.

(Substituent Having an Aromatic Ring)
In the modified cellulose fiber used in the present invention, a substituent having an aromatic ring is bonded to at least one of the hydroxyl groups derived from cellulose via an ether bond, which means that at least one of the R in general formula (Ce) is a substituent having an aromatic ring.

The substituent having an aromatic ring is preferably one or more substituents selected from the group consisting of a substituent represented by the following general formula (1), a substituent represented by the following general formula (2), and a substituent represented by the following general formula (3). Among these, from the viewpoint of suppressing discoloration and deterioration of the resin composition, the substituent represented by the following general formula (1) or (2) is more preferable, and the substituent represented by the following general formula (2) is even more preferable.
_-CH2- CH(OH) _-R1 (1)
_-CH2- CH(OH) _-CH2- (OA) _n -O- _R1 (2)
-R ₁ (3)
(In the formulae, R ₁ in general formulas (1) to (3) each independently represents a hydrocarbon group having 6 to 30 carbon atoms and at least one aromatic ring, n in general formula (2) represents a number of 0 to 50, and A represents a linear or branched divalent saturated hydrocarbon group having 1 to 6 carbon atoms.)

R ₁ in the general formulas (1) to (3) is a hydrocarbon group having at least one aromatic ring and having 6 to 30 carbon atoms. From the viewpoint of the mechanical strength of a molded article of the resin composition, the carbon number of R ₁ is preferably 6 or more, and from the viewpoints of reactivity and availability, the carbon number of R 1 is preferably 25 or less, more preferably 20 or less. Specific examples of R ₁ include aryl groups such as a phenyl group, a cresyl group, a methoxyphenyl group, a trityl group, a naphthyl group, a tolyl group, and a xylyl group, and aralkyl groups such as a benzyl group and a phenethyl group.

In general formula (2), n represents the number of moles of alkylene oxide added. n is a number between 0 and 50, but from the viewpoints of availability and cost, it is preferably 0, and from the same viewpoint, it is preferably 40 or less, more preferably 30 or less, even more preferably 20 or less, and even more preferably 15 or less.

In general formula (2), A is a linear or branched divalent saturated hydrocarbon group having 1 to 6 carbon atoms, and forms an oxyalkylene group with an adjacent oxygen atom. The number of carbon atoms in A is 1 to 6, but from the viewpoints of availability and cost, it is preferably 2 or more, and from the same viewpoint, it is preferably 4 or less, and more preferably 3 or less. Specific examples of A include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group, among which an ethylene group and a propylene group are preferred, and an ethylene group is more preferred.

From the viewpoints of availability and cost, the combination of A and n in general formula (2) is preferably one in which A is a linear or branched divalent saturated hydrocarbon group having 2 to 3 carbon atoms and n is a number from 0 to 20, and more preferably one in which A is a linear or branched divalent saturated hydrocarbon group having 2 to 3 carbon atoms and n is a number from 0 to 15.

(Hydrocarbon group which may have an oxygen atom)
In general formula (Ce), all R may be substituents having an aromatic ring, or at least one of the plurality of R may be a substituent having an aromatic ring. In the latter case, it is preferable that the R other than the substituent having an aromatic ring is a hydrogen atom or a hydrocarbon group which may have an oxygen atom.

As such a hydrocarbon group which may have an oxygen atom, one or more kinds of substituents selected from the group consisting of a substituent represented by the following general formula (4), a substituent represented by the following general formula (5), and a substituent represented by the following general formula (6) are preferable.
-CH2 _-CH (OH) _-R2 (4)
_-CH2- CH(OH) _-CH2- (OA) _n -O- _R2 (5)
-R ₃ (6)
(In the formulae, _R2 in general formulae (4) and (5) are each independently hydrogen or a linear, cyclic or branched, saturated or unsaturated alkyl group having 1 to 30 carbon atoms and containing no aromatic ring; n in general formula (5) is a number between 0 and 50, and A is a linear or branched, divalent, saturated hydrocarbon group having 1 to 6 carbon atoms. In addition, in the formulae, _R3 in general formula (6) is a linear, cyclic or branched, saturated or unsaturated alkyl group having 1 to 30 carbon atoms and containing no aromatic ring.)

When _R2 in general formulas (4) and (5) is the alkyl group, the number of carbon atoms of the alkyl group is preferably 1 or more, more preferably 2 or more, from the viewpoint of mechanical strength of a molded article of the resin composition, and is preferably 25 or less, more preferably 20 or less, from the viewpoint of reactivity and availability. Specific examples of _R2 include a methyl group, an ethyl group, an allyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a hexadecyl group, an octadecyl group, an isostearyl group, an oleyl group, an icosyl group, and the like.

In general formula (5), n indicates the number of moles of alkylene oxide added. From the viewpoints of availability and cost, the number of n is preferably 0, and from the viewpoints of the same and the mechanical strength of the molded article of the resulting resin composition, the number of n is preferably 40 or less, more preferably 30 or less, even more preferably 20 or less, even more preferably 15 or less, even more preferably 10 or less, and even more preferably 5 or less.

In general formula (5), A forms an oxyalkylene group with the adjacent oxygen atom. From the viewpoints of availability and cost, the number of carbon atoms in A is preferably 2 or more, and from the same viewpoints, it is preferably 4 or less, more preferably 3 or less. Specific examples of A are the same as A in general formula (2).

From the viewpoints of availability and cost, the combination of A and n in general formula (5) is preferably one in which A is a linear or branched divalent saturated hydrocarbon group having 2 to 3 carbon atoms and n is a number from 0 to 20, and more preferably one in which A is a linear or branched divalent saturated hydrocarbon group having 2 to 3 carbon atoms and n is a number from 0 to 15.

The number of carbon atoms in the alkyl group of _R3 in general formula (6) is preferably 1 or more, more preferably 2 or more, from the viewpoint of the mechanical strength of a molded article of the resin composition, and is preferably 25 or less, more preferably 20 or less, from the viewpoint of reactivity and availability. Specific examples of _R3 include a methyl group, an ethyl group, an allyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a hexadecyl group, an octadecyl group, an isostearyl group, an oleyl group, and an icosyl group.

(Crystallization degree)
The crystallinity of the modified cellulose fiber is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more from the viewpoint of strength expression of the molded body of the resin composition. In addition, from the viewpoint of raw material availability, it is preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, and even more preferably 75% or less. In this specification, the crystallinity of cellulose is the cellulose I type crystallinity calculated from the diffraction intensity value by X-ray diffraction method, and can be measured according to the method described in the examples below. In addition, cellulose I type refers to the crystalline form of natural cellulose, and cellulose I type crystallinity means the proportion of the crystalline region amount in the whole cellulose. The presence or absence of cellulose I type crystal structure can be determined by the presence of a peak at 2θ = 22.6 ° in X-ray diffraction measurement.

(Molar Substitution (MS) of Substituent Having an Aromatic Ring)
In the modified cellulose fiber, the molar amount (molar substitution degree: MS) of the aromatic ring-containing substituent bonded to 1 mole of anhydrous glucose unit of cellulose is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.03 or more, from the viewpoint of dispersibility. On the other hand, from the viewpoint of the mechanical strength of the molded body obtained when the modified cellulose fiber is applied to the resin composition, the MS is preferably 1.5 or less, more preferably 1.3 or less, even more preferably 1.0 or less, and even more preferably 0.8 or less. Here, when the aromatic ring-containing substituent is composed of multiple types of substituents, the MS of the aromatic ring-containing substituent is the sum of the MS of each substituent. In this specification, the anhydrous glucose unit may be abbreviated as "AGU". The AGU is calculated assuming that the cellulose raw material is composed entirely of anhydrous glucose units.

(Molar Substitution (MS) of Hydrocarbon Group Optionally Having Oxygen Atoms)
When a hydrocarbon group which may have an oxygen atom is bonded to the modified cellulose fiber, the molar amount of the hydrocarbon group which may have an oxygen atom bonded to 1 mole of anhydrous glucose unit of cellulose in the modified cellulose fiber (molar substitution degree: MS) is, from the same viewpoint as for the substituent having an aromatic ring, preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.02 or more, preferably 1.5 or less, more preferably 1.3 or less, even more preferably 1.0 or less, and even more preferably 0.8 or less. Here, when the hydrocarbon group which may have an oxygen atom is composed of a plurality of kinds of substituents, the MS of the hydrocarbon group which may have an oxygen atom is the sum of the MS of each substituent.

In this specification, the degree of bonding of the substituents (i.e., the molar substitution (MS)) can be measured according to the method described in the Examples below.

(Average fiber diameter)
The average fiber diameter of the modified cellulose fiber used in the present invention is preferably 5 μm or more, regardless of the type of the substituent. From the viewpoints of handling, availability, and cost, it is more preferably 7 μm or more, even more preferably 10 μm or more, and even more preferably 15 μm or more. In addition, although there is no particular upper limit, from the viewpoint of handling, it is preferably 10,000 μm or less, more preferably 5,000 μm or less, even more preferably 1,000 μm or less, even more preferably 500 μm or less, and even more preferably 100 μm or less.

On the other hand, the modified cellulose fiber used in the present invention may be one that has been subjected to a micronization treatment. In this case, the average fiber diameter of the modified cellulose fiber is in the nano-order regardless of the type of the substituent. The average fiber diameter of the micronized modified cellulose fiber is preferably 1 nm or more, more preferably 3 nm or more, even more preferably 10 nm or more, and even more preferably 20 nm or more from the viewpoints of handling, availability, and cost, and is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, even more preferably 150 nm or less, and even more preferably 120 nm or less from the viewpoints of handling and mechanical strength.
The average fiber diameter of the modified cellulose fiber can be measured according to the method described in the Examples below.

[Method of preparing modified cellulose fibers]
Such modified cellulose fibers can be produced, for example, by mixing and reacting a compound having an aromatic ring as an etherification agent with a cellulose raw material in the presence of a base, as described below in more detail.

(Cellulose raw material)
The cellulose raw material used in the present invention is not particularly limited, and examples thereof include woody plants (coniferous trees and broad-leaved trees), herbaceous plants (plant raw materials of the Gramineae, Malvaceae, and Leguminosae families, and non-woody raw materials of plants of the Palmaceae family), pulps (cotton linter pulp obtained from the fibers surrounding cotton seeds, etc.), papers (newspapers, cardboard, magazines, fine paper, etc.), etc. Among these, woody plants and herbaceous plants are preferred from the viewpoints of availability and cost.

The shape of the cellulose raw material is not particularly limited, but from the viewpoint of ease of handling, fibers, powder, spheres, chips, and flakes are preferred. A mixture of these may also be used.

In addition, from the standpoint of ease of handling, etc., the cellulose raw material can be subjected to at least one pretreatment selected from the biochemical treatment, chemical treatment, and mechanical treatment described in paragraphs 0017 to 0018 of JP 2018-145571 A.

The average fiber diameter of the cellulose raw material is not particularly limited, but from the viewpoint of ease of handling and cost, it is preferably 5 μm or more, more preferably 7 μm or more, even more preferably 10 μm or more, and even more preferably 15 μm or more. In addition, there is no particular upper limit, but from the viewpoint of ease of handling, it is preferably 10,000 μm or less, more preferably 5,000 μm or less, even more preferably 1,000 μm or less, even more preferably 500 μm or less, and even more preferably 100 μm or less. In addition, fine cellulose fibers with a fiber diameter of 1 to 200 nm that have been subjected to a micronization treatment in advance can also be used if necessary.

(Etherification Agent for Bonding Substituents Having an Aromatic Ring)
The cellulose raw material, a base, an etherification agent for bonding a substituent having an aromatic ring, and, if necessary, a solvent are mixed together to carry out an etherification reaction in which the substituent is bonded to at least one of the hydroxyl groups derived from the cellulose.
Examples of preferred etherification agents for bonding a substituent having an aromatic ring include aromatic ring-containing alkylene oxide compounds, aromatic ring-containing glycidyl ether compounds, and aromatic ring-containing organic halogen compounds. Among these, from the viewpoints of availability and reactivity, aromatic ring-containing alkylene oxide compounds and aromatic ring-containing glycidyl ether compounds are more preferred, and aromatic ring-containing glycidyl ether compounds are even more preferred.

[Alkylene oxide compounds containing aromatic rings]
Examples of aromatic ring-containing alkylene oxide compounds include those having a structure represented by the following general formula (1A): By using such an etherifying agent, the substituent represented by general formula (1) can be bonded to cellulose fibers.

(In the formula, R ₁ is a hydrocarbon group having at least one aromatic ring and having 6 to 30 carbon atoms.)
The carbon number and specific examples of the hydrocarbon group of R ₁ in general formula (1A) are the same as the carbon number and specific examples of the hydrocarbon group of R ₁ in general formula (1).

Specific examples of aromatic ring-containing alkylene oxide compounds include styrene oxide and its derivatives. Among these, styrene oxide is preferred from the viewpoints of availability and reactivity.

[Aromatic ring-containing glycidyl ether compounds]
Examples of aromatic ring-containing glycidyl ether compounds include those having a structure represented by the following general formula (2A): By using such an etherifying agent, the substituent represented by general formula (2) can be bonded to the cellulose fibers.

(In the formula, R ₁ is a hydrocarbon group having at least one aromatic ring and having 6 to 30 carbon atoms.)
The carbon number and specific examples of the hydrocarbon group of R ₁ in general formula (2A) are the same as the carbon number and specific examples of the hydrocarbon group of R ₁ in general formula (2).

Specific examples of aromatic ring-containing glycidyl ether compounds include phenyl glycidyl ether, methylphenyl glycidyl ether, methoxyphenyl glycidyl ether, trityl glycidyl ether, benzyl glycidyl ether, and derivatives thereof. Among these, from the viewpoints of availability and reactivity, phenyl glycidyl ether and methylphenyl glycidyl ether are preferred, and phenyl glycidyl ether is more preferred.

[Aromatic ring-containing organohalogen compounds]
Examples of aromatic ring-containing organic halogen compounds include those having a structure represented by the following general formula (3A): By using such an etherifying agent, the substituent represented by general formula (3) can be bonded to the cellulose fibers.
X-R ₁ (3A)
(In the formula, X is a halogen atom, and _R1 is a hydrocarbon group having 6 to 30 carbon atoms and at least one aromatic ring.)
The carbon number and specific examples of the hydrocarbon group of R ₁ in general formula (3A) are the same as the carbon number and specific examples of the hydrocarbon group of R ₁ in general formula (3).

Specific examples of aromatic ring-containing organic halogen compounds include chlorobenzene, benzyl chloride, naphthyl chloride, trityl chloride, and derivatives thereof, as well as compounds in which the chlorine in the above compounds has been replaced with bromine or iodine. Among these, from the viewpoints of availability and reactivity, chlorobenzene, benzyl chloride, and naphthyl chloride are preferred, and chlorobenzene and benzyl chloride are even more preferred.

The amount of these etherification agents can be determined depending on the desired introduction rate of the substituent in the resulting modified cellulose fiber. For example, from the viewpoint of reactivity, the amount of etherification agent per unit of anhydrous glucose unit of the cellulose raw material is preferably 0.02 equivalents or more, more preferably 0.05 equivalents or more, even more preferably 0.1 equivalents or more, even more preferably 0.3 equivalents or more, even more preferably 1.0 equivalents or more, while from the viewpoint of the mechanical strength of the resulting molded body, it is preferably 10.0 equivalents or less, more preferably 8.0 equivalents or less, even more preferably 7.0 equivalents or less, even more preferably 6.0 equivalents or less. Here, when multiple types of etherification agents are used as etherification agents for bonding substituents having aromatic rings, the amount of etherification agent is the total amount of each etherification agent.

(Etherification Agent for Bonding Hydrocarbon Groups Which May Contain an Oxygen Atom)
In the present invention, in addition to the etherification agent (referred to as etherification agent (a)), an etherification agent (referred to as etherification agent (b)) for bonding a hydrocarbon group which may have an oxygen atom may be used in combination. The order in which these etherification agents are mixed with the cellulose raw material and the like is not particularly limited. For example, the etherification agent (a) and the etherification agent (b) may be mixed simultaneously with the cellulose raw material and the like, or the etherification agent (a) may be mixed first and then the etherification agent (b) may be mixed, or the reverse order may be used. In the present invention, from the viewpoint of increasing the molar substitution degree of the substituent having an aromatic ring, it is preferable to mix the etherification agent (b) first and then mix the etherification agent (a).

Etherification agents for bonding hydrocarbon groups that may have oxygen atoms include, for example, alkylene oxide compounds, glycidyl ether compounds, and compounds having halogenated hydrocarbon groups.

[Alkylene oxide compounds]
Examples of alkylene oxide compounds include those having a structure represented by the following general formula (4A): By using such an etherifying agent, the substituent represented by general formula (4) can be bonded to the cellulose fibers.

(In the formula, _R2 is the same as _R2 in the above general formula (4).)
The carbon number and specific examples of the hydrocarbon group of R ₂ in general formula (4A) are the same as the carbon number and specific examples of the hydrocarbon group of R ₂ in general formula (4).

Specific examples of compounds represented by general formula (4A) include ethylene oxide, propylene oxide, butylene oxide, 3,4-epoxy-1-butene, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxy-5-hexene, 1,2-epoxyoctane, 1,2-epoxydecane, 1,2-epoxydodecane, 1,2-epoxytetradecane, and 1,2-epoxyoctadecane.

[Glycidyl ether compounds]
Examples of glycidyl ether compounds include those having a structure represented by the following general formula (5A): By using such an etherifying agent, the substituent represented by general formula (5) can be bonded to the cellulose fibers.

(In the formula, _R2 is the same as _R2 in the above general formula (5).)
The carbon number and specific examples of the hydrocarbon group of R ₂ in general formula (5A) are the same as the carbon number and specific examples of the hydrocarbon group of R ₂ in general formula (5).

Specific examples of such glycidyl ether compounds include glycidol, methyl glycidyl ether, ethyl glycidyl ether, propyl glycidyl ether, isoprenyl glycidyl ether, allyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, dodecyl glycidyl ether, (iso)stearyl glycidyl ether, polyoxyalkylene alkyl ether-added glycidyl ether, etc.

[Compounds containing halogenated hydrocarbon groups]
An example of a compound having a halogenated hydrocarbon group is a compound having a structure represented by the following general formula (6A): By using such an etherifying agent, the substituent represented by general formula (6) can be bonded to the cellulose fiber.
X- _R3 (6A)
(In the formula, X is a halogen atom, and _R3 is the same as _R3 in the above general formula (6).)
The carbon number and specific examples of the hydrocarbon group of R ₃ in general formula (6A) are the same as the carbon number and specific examples of the hydrocarbon group of R ₃ in general formula (6).

Specific examples of compounds represented by general formula (6A) include chloromethane, chloroethane, 1-chloropropane and its isomers, 1-chlorobutane and its isomers, 1-chloropentane and its isomers, 1-chlorohexane and its isomers, 1-chlorohexane and its isomers, 1-chlorodecane and its isomers, 1-chlorododecane and its isomers, 1-chlorohexadecane and its isomers, 1-chlorooctadecane and its isomers, 1-chloroeicosane and its isomers, 1-chlorotriacontane and its isomers, 1-chloro-5-hexene and its isomers, chlorocyclohexane, and the above compounds in which the chlorine has been replaced with bromine or iodine.

The amount of these etherification agents can be determined depending on the desired introduction rate of the substituent in the resulting modified cellulose fiber. For example, from the viewpoint of reactivity, the amount of etherification agent per unit of anhydrous glucose unit of the cellulose raw material is preferably 0.02 equivalents or more, more preferably 0.05 equivalents or more, even more preferably 0.1 equivalents or more, even more preferably 0.3 equivalents or more, even more preferably 1.0 equivalents or more, while from the viewpoint of the mechanical strength of the resulting molded body, it is preferably 10.0 equivalents or less, more preferably 8.0 equivalents or less, even more preferably 7.0 equivalents or less, even more preferably 6.0 equivalents or less. Here, when multiple types of etherification agents are used as etherification agents for bonding hydrocarbon groups that may have oxygen atoms, the amount of etherification agent is the total amount of each etherification agent.

(base)
The etherification agent and the cellulose raw material are preferably mixed in the presence of a base. The base used here is not particularly limited, but from the viewpoint of proceeding with the etherification reaction, one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, primary to tertiary amines, quaternary ammonium salts, imidazole and its derivatives, pyridine and its derivatives, and alkoxides are preferred. Specific examples of these bases include those described in paragraphs 0024 to 0029 of JP 2018-145571 A.

The amount of base is preferably 0.01 equivalents or more, more preferably 0.05 equivalents or more, even more preferably 0.1 equivalents or more, and even more preferably 0.2 equivalents or more, relative to the anhydrous glucose units of the cellulose raw material, from the viewpoint of proceeding with the etherification reaction, and is preferably 10 equivalents or less, more preferably 8 equivalents or less, even more preferably 5 equivalents or less, and even more preferably 3 equivalents or less, from the viewpoint of production costs.

(solvent)
The etherification agent and the cellulose raw material may be mixed in the presence of a solvent, which is not particularly limited and includes, for example, water, isopropanol, t-butanol, dimethylformamide, toluene, methyl isobutyl ketone, acetonitrile, dimethyl sulfoxide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, hexane, 1,4-dioxane, and mixtures thereof.

The amount of the solvent used is not necessarily determined by the type of cellulose raw material or etherification agent, but from the viewpoint of reactivity, it is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 75 parts by mass or more, even more preferably 100 parts by mass or more, and even more preferably 200 parts by mass or more, per 100 parts by mass of cellulose raw material, and from the viewpoint of productivity, it is preferably 10,000 parts by mass or less, more preferably 7,500 parts by mass or less, even more preferably 5,000 parts by mass or less, even more preferably 2,500 parts by mass or less, and even more preferably 1,000 parts by mass or less.

(Etherification reaction)
The etherification reaction between the etherification agent and the cellulose raw material can be carried out by mixing them, preferably in the presence of a base and/or a solvent.

There are no particular limitations on the mixing conditions as long as the cellulose raw material and etherification agent are mixed uniformly and the reaction can proceed sufficiently, and continuous mixing may or may not be performed. When a relatively large reaction vessel is used, appropriate stirring may be performed from the viewpoint of controlling the reaction temperature.

The reaction temperature is not necessarily determined by the type of cellulose raw material and etherification agent and the target introduction rate, but from the viewpoint of improving reactivity, it is preferably 30°C or higher, more preferably 35°C or higher, and even more preferably 40°C or higher, and from the viewpoint of suppressing thermal decomposition, it is preferably 120°C or lower, more preferably 110°C or lower, even more preferably 100°C or lower, even more preferably 90°C or lower, even more preferably 80°C or lower, and even more preferably 70°C or lower.

The reaction time is not necessarily determined by the type of cellulose raw material and etherification agent and the target introduction rate, but from the viewpoint of reactivity, it is preferably 0.1 hours or more, more preferably 0.5 hours or more, even more preferably 1 hour or more, even more preferably 3 hours or more, even more preferably 6 hours or more, even more preferably 10 hours or more, and from the viewpoint of productivity, it is preferably 60 hours or less, more preferably 48 hours or less, even more preferably 36 hours or less.

After the reaction, appropriate post-treatment can be carried out to remove unreacted compounds, bases, etc. For example, the post-treatment can be carried out by neutralizing the unreacted base with an acid (organic acid, inorganic acid, etc.) and then washing with a solvent in which the unreacted compounds and bases dissolve. If desired, further drying (vacuum drying, etc.) can be carried out.

Thus, modified cellulose fibers are obtained that have cellulose type I crystals and have a substituent having an aromatic ring bonded to at least one of the hydroxyl groups derived from cellulose via an ether bond.

(Micronization process)
The modified cellulose fiber in the present invention may be one that has been subjected to a micronization treatment. The micronization treatment can be carried out by a known micronization treatment method. For example, in order to obtain a fine modified cellulose fiber having an average fiber diameter of 1 nm to 500 nm, the fiber can be micronized by treatment using a grinder such as a mass colloider or treatment using a high-pressure homogenizer in a solvent.

The timing of the micronization process is not particularly limited; for example, it may be performed before or after the etherification reaction, or the engineering plastic and the modified cellulose fiber may be mixed and then micronized at the same time.

The solvent used in the micronization process is not particularly limited, but examples thereof include water, methanol, ethanol, propanol, and other alcohols having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms; acetone, methyl ethyl ketone, methyl isobutyl ketone, and other ketones having 3 to 6 carbon atoms; linear or branched saturated or unsaturated hydrocarbons having 1 to 6 carbon atoms; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as methylene chloride and chloroform; lower alkyl ethers having 2 to 5 carbon atoms; polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide, dimethyl sulfoxide, and diesters of succinic acid and triethylene glycol monomethyl ether. The amount of the solvent used is not particularly limited as long as it is an effective amount capable of dispersing the modified cellulose fibers, but it is more preferable to use an amount of the solvent that is preferably 1 mass or more, more preferably 2 mass or more, preferably 500 mass or less, and more preferably 200 mass or less relative to the modified cellulose fibers.

In addition to high-pressure homogenizers, known dispersing machines are also suitable for use in the micronization process. For example, disintegrators, beaters, low-pressure homogenizers, grinders, mass colloiders, cutter mills, ball mills, jet mills, single-screw extruders, twin-screw extruders, ultrasonic agitators, household juicer mixers, etc. may be used. In addition, the solids concentration of the modified cellulose fiber in the micronization process is preferably 50% by mass or less.

By this micronization process, it is possible to produce modified cellulose fibers having an average fiber diameter of the nano-order as specified above.

[Resin composition]
The content of the engineering plastic in the resin composition of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, even more preferably 50% by mass or more, and even more preferably 60% by mass or more, from the viewpoint of obtaining the physical properties of the engineering plastic itself, while from the same viewpoint, it is preferably 99.95% by mass or less, more preferably 99.9% by mass or less, preferably 99.7% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less.

The content of the modified cellulose fiber in the resin composition of the present invention is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, more preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, in terms of heat resistance and mechanical strength of the molded body of the resin composition. On the other hand, from the viewpoint of suppressing coloring deterioration, it is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less. The cellulose fiber amount (equivalent amount) refers to the mass obtained by subtracting the mass of the substituent from the mass of the modified cellulose fiber. The cellulose fiber amount (equivalent amount) in the modified cellulose fiber can be measured by the method described in the examples below.

The content of the modified cellulose fiber in the resin composition of the present invention is preferably 0.06 parts by mass or more, more preferably 0.12 parts by mass or more, even more preferably 0.36 parts by mass or more, even more preferably 0.6 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the engineering plastic, from the viewpoint of heat resistance and mechanical strength of the molded body of the resin composition. On the other hand, from the viewpoint of production cost, it is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 60 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

The resin composition of the present invention may contain additives that are commonly used in the field of the present invention. Examples of such additives include compatibilizers, crystal nucleating agents, inorganic fillers, organic fillers, hydrolysis inhibitors, impact modifiers, flame retardants, antioxidants, lubricants, antistatic agents, antifogging agents, curing agents, dyes, pigments, plasticizers, catalysts, fungicides, defoamers, leveling agents, pigment dispersants, antisettling agents, antisagging agents, thickeners, matting agents, light stabilizers, and ultraviolet absorbers. The content of such additives in the resin composition cannot be generally determined depending on the type of engineering plastic and additive used, but from the viewpoint of the effect of the additives, it is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more, and from the viewpoint of not impairing the physical properties of the resin composition, it is preferably 30% by mass or less, more preferably 15% by mass or less, and even more preferably 5% by mass or less.

<Method of producing resin composition>
The method for producing a resin composition of the present invention is a production method including a mixing step of mixing the engineering plastic with the modified cellulose fiber.

[Mixing process]
The mixing step can be carried out by melt-kneading the above-mentioned components using a known kneader such as an internal kneader, a single-screw or twin-screw extruder, a roll mill, or an open-roll type kneader, or by shearing the components using a solvent casting method or a shearing device such as a high-shear processing machine.

Preferably, this mixing process includes a step of performing a shearing treatment and/or a kneading treatment at 200°C or higher, more preferably 220°C or higher, and even more preferably 250°C or higher. By performing such treatment, this mixing process can be easily carried out.

The engineering plastics and modified cellulose fibers used in the mixing process are the same as those used in the resin composition of the present invention.

The amount of modified cellulose fiber in the mixing step is preferably 0.06 parts by mass or more, more preferably 0.12 parts by mass or more, even more preferably 0.36 parts by mass or more, even more preferably 0.6 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the engineering plastic, from the viewpoint of expressing mechanical properties in the molded article of the resin composition. On the other hand, from the viewpoint of production costs, it is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 60 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

The amount of cellulose fiber (equivalent amount) in the resin composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of engineering plastic, from the viewpoint of expressing mechanical properties in a molded article of the resin composition. On the other hand, from the viewpoint of production costs, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

<Resin Molded Body>
The resin molded article of the present invention can be produced by appropriately using a known molding method such as extrusion molding, injection molding, press molding, cast molding, etc., using the resin composition of the present invention or a resin composition produced by the production method of the present invention. Since the resin composition of the present invention is excellent in suppressing color deterioration during molding, the resin molded article can be suitably used for various applications.

The degree of coloration of the resin molded body can be evaluated by the YI (Yellow Index) value described in the examples below, and the smaller the ΔYI value, the more strongly color deterioration is suppressed.

The applications for which the resin composition and resin molded article of the present invention can be used are not particularly limited, but they can be used for a variety of industrial applications, such as information appliance parts that require high heat resistance, mechanical strength, and durability, packaging materials for information appliance parts, automobile parts, three-dimensional modeling materials, cushioning materials, repair materials, sealing materials, insulation materials, and sound-absorbing materials.

The present invention will be specifically explained below with reference to examples. Note that these examples are merely illustrative of the present invention and do not imply any limitations. Parts in the examples are parts by weight unless otherwise specified. Note that "normal pressure" refers to 101.3 kPa, and "room temperature" refers to 25°C.

[Average fiber diameter of various cellulose fibers]
(1) When the average fiber diameter of the cellulose fibers to be measured is expected to be several nanometers to several hundred nanometers, the average fiber diameter of the cellulose fibers is determined as follows.
A suitable solvent is added to the cellulose fibers to be measured to prepare a dispersion with a concentration of 0.0001% by mass. The dispersion is dropped onto mica and dried to be used as an observation sample, and the fiber height of the cellulose fibers in the observation sample is measured using an atomic force microscope (AFM) (Nanoscope III Tapping mode AFM manufactured by Digital Instrument, Inc., probe is Point Probe (NCH) manufactured by Nanosensors, Inc.). The suitable solvent may be any solvent that swells the cellulose fibers to be measured, and water or ethanol is preferable for cellulose raw materials, and DMF or toluene is preferable for modified cellulose fibers. At that time, 100 or more cellulose fibers are extracted from a microscope image in which the cellulose fibers can be confirmed, and the average fiber diameter is calculated from the fiber height. The average fiber length is calculated from the distance in the fiber direction. The average aspect ratio is calculated from the average fiber length/average fiber diameter, and the standard deviation is also calculated. Generally, the smallest unit of cellulose nanofibers prepared from higher plants is a 6 x 6 molecular chain packed in an approximately square shape, so the height analyzed in an AFM image can be regarded as the width of the fiber.

(2) When the average fiber diameter of the cellulose fibers to be measured is expected to be between several hundred nanometers and several thousand micrometers, the average fiber diameter of the cellulose fibers is determined as follows.
A medium is added to the cellulose fibers to be measured to prepare a dispersion having a content of 0.01% by mass. The dispersion is measured using a wet dispersion type image analysis particle size distribution meter (manufactured by Jusco International, product name: IF-3200) under the following conditions: front lens: 2x, telecentric zoom lens: 1x, image resolution: 0.835 μm/pixel, syringe inner diameter: 6515 μm, spacer thickness: 500 μm, image recognition mode: ghost, threshold: 8, analysis sample amount: 1 mL, sampling: 15%. 100 or more cellulose fibers are measured, and the average ISO fiber diameter and average ISO fiber length are calculated as the average fiber diameter and average fiber length, respectively. The average aspect ratio is calculated from the average fiber length/average fiber diameter, and the standard deviation is also calculated.

[Confirmation of the crystal structure of cellulose fibers]
The crystal structure of cellulose fibers such as cellulose raw materials and modified cellulose fibers is confirmed by measurement under the following conditions using a diffractometer (manufactured by Rigaku Corporation, product name: MiniFlexII).
Measurement pellet preparation conditions: A pressure in the range of 10-20 MPa is applied to the target cellulose fibers using a tablet press to prepare smooth pellets with an area of 320 mm ² × thickness of 1 mm.
X-ray diffraction analysis conditions: step angle 0.01°, scan speed 10°/min, measurement range: diffraction angle 2θ=5 to 40°
X-ray source: Cu/Kα-radiation, tube voltage: 15 kv, tube current: 30 mA
Peak division conditions: After removing background noise, the peaks are fitted with a Gaussian function so that the error between 2θ=13° and 23° is within 5%.
The crystal structure of the modified cellulose fiber is confirmed by measuring it using the above-mentioned diffractometer under the above-mentioned conditions.

The degree of crystallinity of the cellulose type I crystal structure is calculated based on the following formula (A) using the area of the X-ray diffraction peak obtained by the above-mentioned peak division.
Cellulose I type crystallinity (%) = [I _cr / (I _cr + I _am )] × 100 (A)
(In the formula, I _cr represents the area of the diffraction peak of the lattice plane (002 plane) (diffraction angle 2θ=22-23°) in X-ray diffraction, and I _am represents the area of the diffraction peak of the amorphous portion (diffraction angle 2θ=18.5°).)

[MS Measurement]
First, the content (mass%) of the substituent contained in the cellulose fiber to be measured is calculated according to the Zeisel method, which is known as a method for analyzing the average number of moles of alkoxy groups added to cellulose ether, as described in Analytical Chemistry, Vol. 51, No. 13, 2172 (1979), "The 15th Revised Japanese Pharmacopoeia (section on the analysis method of hydroxypropyl cellulose)" and the like. The procedure is as follows.

(i) Add 0.1 g of n-tetradecane to a 200 mL measuring flask and fill up to the mark with hexane to prepare an internal standard solution.
(ii) 70 mg of purified and dried cellulose fiber to be measured and 80 mg of adipic acid are precisely weighed into a 10 mL vial, and 2 mL of hydroiodic acid is added and the vial is then sealed.
(iii) The mixture in the vial is heated in a block heater at 160° C. for 1 hour while being stirred with a stirrer tip.
(iv) After heating, 2 mL of the internal standard solution and 2 mL of diethyl ether are successively poured into the vial, and the mixture is stirred at room temperature for 1 minute.
(v) The upper layer (diethyl ether layer) of the mixture separated into two phases in the vial is analyzed by gas chromatography (Shimadzu Corporation, product name: GC2010Plus).
(vi) Analyze in the same manner as (ii) to (v), except that the cellulose fiber to be measured is changed to 5 mg, 10 mg, or 15 mg of the etherification agent used to modify the fiber, and prepare a calibration curve for the etherification agent.
(vii) Based on the prepared calibration curve and the analysis results of the cellulose fiber to be measured, the substituents contained in the cellulose fiber to be measured are quantified. The analysis conditions are as follows:

Column: Agilent Technologies, product name: DB-5 (12 m, 0.2 mm x 0.33 μm)
Column temperature: 30° C. (10 min hold) → 10° C./min → 300° C. (10 min hold)
Injector temperature: 300°C
Detector temperature: 300°C
Injection amount: 1 μL

Next, the molar substitution (MS) is calculated from the obtained substituent content using the following mathematical formula (B) or (C). When one type of substituent is introduced, the MS is calculated using mathematical formula (B), and when two types of substituents are introduced, the MS is calculated using mathematical formula (C).
Formula (B)
MS=(W/Mw)/((100− _W1 )/162.14)
W: The content (mass%) of the substituent in the cellulose fiber to be measured
Mw: Molecular weight of the etherification agent used (g/mol)

Formula (C)
_MS1 = ( _W1 / _Mw1 )/((100- _W1 - _W2 )/162.14)
_MS2 = ( _W2 / _Mw2 )/((100- _W1 - _W2 )/162.14)
MS ₁ : MS of the first type of substituent
MS ₂ : MS of the second type of substituent
W ₁ : The content (mass%) of the first type of substituent in the cellulose fiber to be measured
_W2 : The content (mass%) of the second type of substituent in the cellulose fiber to be measured
_Mw1 : Molecular weight of the first etherification agent (g/mol)
_Mw2 : Molecular weight of the second etherification agent (g/mol)

[Amount of cellulose fiber in modified cellulose fiber (equivalent amount)]
The cellulose fiber (equivalent amount) in the modified cellulose fiber is calculated by the following formula.
Amount of cellulose fiber (converted amount) (g) = 162 / (162 + molecular weight of etherification agent used (g / mol) × MS) × mass of modified cellulose fiber (g)
When two or more kinds of etherification agents are added, the sum of the products of the molecular weights and MS of the respective etherification agents is calculated to calculate the amount of cellulose fiber (converted amount).

[Production of Molded Product]
The target resin or resin composition is injection molded using an injection molding machine (manufactured by Japan Steel Works, Ltd., product name: J110AD-180H, cylinder temperature setting at six points). The cylinder temperature is set to 280°C from the nozzle tip side to the 5th unit, 250°C for the remaining unit, 45°C below the hopper, and 80°C, to produce a molded product of the desired shape.

[Heat distortion temperature of crystalline resin]
The heat distortion temperature of the crystalline resin is measured as follows.
The resin to be evaluated is injection molded by the method described in [Production of Molded Body] above to prepare a rectangular columnar test piece (125 mm x 13 mm x 6.4 mm). For this rectangular columnar test piece, the deflection temperature under load (DTUL) when deflected 0.254 mm is measured using a heat distortion temperature measuring device (Yasuda Seiki Seisakusho, Full Automatic Heat Distortion Tester/No. 148-HDA6) based on ASTM D648 under the conditions of edgewise, heating rate of 2°C/min, and low load (0.45 MPa), and this is taken as the heat distortion temperature.

[Glass transition temperature of amorphous resin]
The glass transition temperature of the amorphous resin is measured as follows.
Using a differential scanning calorimeter (TA Instruments Japan, DSC Q20), 0.01 to 0.02 g of a sample is weighed into an aluminum pan and heated to 200°C. From that temperature, the sample is cooled to 0°C at a rate of 10°C/min. The sample is then heated at a rate of 10°C/min and the endothermic peak is measured. The glass transition temperature is determined as the temperature at the intersection of an extension of the baseline below the highest endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the apex of the peak.

[Tensile strength of engineering plastics]
The tensile strength of the engineering plastic is measured as follows.
The resin to be evaluated is injection molded by the method described in [Production of Molded Articles] above to prepare a dumbbell-shaped test piece (ISO527, Type 1A). A tensile test is performed on this dumbbell-shaped test piece in accordance with ISO527 using an autograph (Shimadzu Corporation, Autograph Precision Universal Testing Machine, AGS-10kNX) at a tensile speed of 50 mm/min to determine the tensile strength (yield stress).

[Flexural modulus of engineering plastics]
The flexural modulus of an engineering plastic is measured as follows.
The resin to be evaluated is injection molded by the method described in the above [Production of Molded Article] to prepare a rectangular test piece (125 mm x 13 mm x 6.4 mm). A bending test is performed on this rectangular test piece based on ASTM D790 using a Tensilon (Orientec Co., Ltd., Tensilon Universal Testing Machine, RTC-1210A) with a crosshead speed set to 3 mm/min to determine the bending modulus.

<Production of modified cellulose fibers>
Modified Cellulose Fiber Production Example 1
267.1 g of 6.4% by weight aqueous sodium hydroxide solution (NaOH 0.28 equivalents/AGU) was added to 250.0 g of bone-dried bleached coniferous kraft pulp (hereinafter abbreviated as NBKP, manufactured by West Fraser, "Hinton", fibrous, cellulose content 90% by weight, moisture content 5% by weight) and mixed uniformly. Then, 333.8 g of butylene oxide (manufactured by Wako Pure Chemical Industries, Ltd., 3.0 equivalents/AGU) was added as an etherification agent, and the mixture was sealed and stirred at 50 ° C. for 7 hours using a kneader rotating device to carry out a reaction. After the reaction, the mixture was neutralized with acetic acid, and thoroughly washed with ion-exchanged water until the conductivity of the filtrate was 50 μs/cm or less in the measurement of the conductivity using a compact electrical conductivity meter (manufactured by Horiba, Ltd., LAQUAtwin EC-33B), and then thoroughly washed with 5 L of acetone to remove impurities. Next, the fiber was vacuum dried overnight at 70°C to obtain modified cellulose fiber 1 in which 2-hydroxybutyl groups as substituents were bonded to hydroxyl groups derived from cellulose via ether bonds (the degree of substitution (MS) is shown in the table; the same applies below).

Modified Cellulose Fiber Production Example 2
To 4.0 g of the modified cellulose fiber 1 obtained in Production Example 1, 42.3 g of a 6.4 mass% aqueous sodium hydroxide solution (NaOH 2.97 equivalents/AGU) and 0.5 g of Kotamin D2345P (manufactured by Kao Corporation, 0.04 equivalents/AGU) were added and mixed uniformly. Then, 11.2 g of o-methylphenyl glycidyl ether (manufactured by Sigma-Aldrich, 3.0 equivalents/AGU) was added as an etherification agent and sealed. Then, the reaction was carried out in a vial at 70°C for 24 hours. After the reaction, the mixture was washed with acetone, neutralized with acetic acid, and thoroughly washed with ion-exchanged water until the conductivity of the filtrate measured by a compact electrical conductivity meter (manufactured by Horiba, Ltd., LAQUAtwin EC-33B) was 50 μs/cm or less, and then thoroughly washed with 1 L of acetone to remove impurities. Next, the mixture was vacuum dried overnight at 70° C. to obtain modified cellulose fiber 2 in which a substituent having an aromatic ring was bonded to a hydroxyl group derived from cellulose via an ether bond. The average fiber diameter of the modified cellulose fiber 2 was 22 μm.

Modified cellulose fiber production example 3
The same operations as in Example 2 of modified cellulose production were carried out except that the amount of etherification agent (o-methylphenyl glycidyl ether) used was changed to 18.7 g (5.0 equivalents/AGU), thereby obtaining modified cellulose fiber 3 in which a substituent having an aromatic ring is bonded to a hydroxyl group derived from cellulose via an ether bond.

Modified Cellulose Fiber Production Example 4
By carrying out the same operations as in Example 2 of modified cellulose production, except that the type and amount of the etherification agent used was changed to phenyl glycidyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), 17.1 g (5.0 equivalents/AGU), modified cellulose fiber 4 was obtained in which a substituent having an aromatic ring is bonded to a hydroxyl group derived from cellulose via an ether bond.

Modified Cellulose Fiber Production Example 5
To 4.0 g of the modified cellulose fiber 1 obtained in Production Example 1, 4.3 g of a 6.4 mass% aqueous sodium hydroxide solution (NaOH 0.30 equivalents/AGU) and 36 g of 2-propanol were added and mixed uniformly. Then, 3.9 g of lauryl glycidyl ether (manufactured by Tokyo Chemical Industry Co., Ltd., 0.7 equivalents/AGU) was added as an etherification agent and sealed. Then, the reaction was carried out in a vial at 70 ° C. for 24 hours. After the reaction, the fiber was washed with acetone, neutralized with acetic acid, and thoroughly washed with ion-exchanged water until the electrical conductivity of the filtrate measured by a compact electrical conductivity meter (manufactured by Horiba, Ltd., LAQUAtwin EC-33B) was 50 μs/cm or less, and then thoroughly washed with 1 L of acetone to remove impurities. Next, the fiber was vacuum dried overnight at 70 ° C. to obtain modified cellulose fiber 5 in which a dodecyl group as a substituent is bonded to a hydroxyl group derived from cellulose via an ether bond.

Table 2 summarizes the properties of NBKP and the modified cellulose fibers for each of the above manufacturing examples. The amounts of each material that makes up the resin composition in Table 2 are in parts by weight.

<Production of Resin Composition: Polycarbonate>
Examples 1 to 4
The materials shown in Table 2, i.e., polycarbonate as an engineering plastic, modified cellulose fibers 2 to 4, and optionally a compatibilizer, were combined as shown in Table 2 and melt-kneaded at 280°C with a discharge rate of 10 kg/h and a rotation speed of 200 rpm using a twin-screw kneader (manufactured by Japan Steel Works, Ltd., product name: TEX28V (screw diameter 28 mm, L/D = 42)) to obtain a resin composition. The pellets of the obtained resin composition were dehumidified and dried at 120°C for 2 hours or more so that the moisture value was 100 ppm or less.

Comparative Examples 1 to 3
Pellets of the resin composition were obtained in the same manner as in the above examples, except that the cellulose raw material NBKP was used instead of the modified cellulose fiber (Comparative Example 1), modified cellulose fiber 1 was used as the modified cellulose fiber (Comparative Example 2), or modified cellulose fiber 5 was used as the modified cellulose fiber (Comparative Example 3).

<Production of Molded Article: Examples 1 to 4, Comparative Examples 1 to 3>
The obtained resin composition was injection molded by the method described in the above section "Production of Molded Article" to mold a flat test piece (70 mm x 40 mm x 3 mm) to obtain a molded article of the resin composition.

Details of materials, abbreviations, etc. in the examples are as follows:
〔resin〕
PC: Bisphenol A polycarbonate resin (amorphous resin), manufactured by Idemitsu Kosan Co., Ltd., product name: Toughlon A1900

[Compatibilizer]
Modiper CL430-G: NOF Corporation, main chain is polycarbonate, side chain is graft polymer of glycidyl methacrylate-styrene-acrylonitrile copolymer

Test Example 1 <YI (Yellow Index) Value>
The YI value of the flat test piece of each molded body obtained using the resin composition of the Examples and Comparative Examples was measured with a color difference meter (SE2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The ΔYI value was calculated by subtracting the YI of the blank resin from the YI value of the resin composition. A smaller value indicates a better hue and excellent thermal stability. Here, the blank resin refers to a resin or resin composition that does not contain cellulose fibers or modified cellulose fibers.

From Table 2, it can be seen that the ΔYI value in Comparative Example 1, which used unmodified cellulose fiber, i.e., cellulose raw material, was very large, and the molded body in Comparative Example 1 was discolored and deteriorated to a considerable extent. In Comparative Examples 2 and 3, which used modified cellulose fiber outside the scope of the present invention, the ΔYI value was smaller than that of Comparative Example 1, but the degree of discoloration and deterioration of the molded body was large, and the discoloration and deterioration was clearly visible to the naked eye.

On the other hand, in the examples using modified cellulose fibers within the scope of the present invention, the ΔYI value was small, and even when the degree of color deterioration of the molded body was checked with the naked eye, the difference from the blank resin was barely noticeable.

From Example 1 and Comparative Example 3, it was found that, although the number of carbon atoms in the substituent was greater in Comparative Example 3, the ΔYI value was clearly smaller in Example 1, which had a substituent with an aromatic ring. This suggests that the degree of color deterioration in the molded product is greatly affected not by the number of carbon atoms in the substituent in the modified cellulose fiber, but by the structure of the substituent, in particular whether or not it has an aromatic ring.

Modified Cellulose Fiber Production Example 6
The same procedure as in Production Example 2 was carried out, except that the amount of o-methylphenyl glycidyl ether used as the etherifying agent was changed to 18.7 g (Sigma-Aldrich, 5.0 equivalents/AGU), to obtain modified cellulose fiber 6 in which a substituent having an aromatic ring is bonded to a hydroxyl group derived from cellulose via an ether bond.

<Production of Resin Composition: Polybutylene Terephthalate>
Example 5
Each material was melt-kneaded in the amounts shown in Table 6 using a kneader (Labo Plastomill, manufactured by Toyo Seiki Seisakusho) at a rotation speed of 90 rpm and 240° C. for 10 minutes under a nitrogen atmosphere to obtain a resin composition.

Comparative Example 4
A resin composition was obtained in the same manner as in Example 5, except that the cellulose raw material NBKP was used instead of the modified cellulose fiber.

<Production of resin composition: Polyamide 6>
Example 6
A resin composition was obtained in the same manner as in Example 5, except that the resin used was changed to polyamide 6.

Comparative Example 5
A resin composition was obtained in the same manner as in Example 6, except that the cellulose raw material NBKP was used instead of the modified cellulose fiber.
<Production of resin composition: Polyamide 66>

Example 7
A resin composition was obtained in the same manner as in Example 5, except that the resin used was changed to polyamide 66 and the kneading conditions were changed to the temperatures shown in Table 8.

Comparative Example 6
A resin composition was obtained in the same manner as in Example 7, except that the cellulose raw material NBKP was used instead of the modified cellulose fiber.

<Production of Molded Articles: Examples 5 to 7, Comparative Examples 4 to 6>
The obtained resin composition was molded into a sheet having a thickness of 0.4 mm under the following conditions using an auto press molding machine (manufactured by Toyo Seiki Seisakusho) and a 0.4 mm spacer, to obtain a molded article of the resin composition. The pressing conditions were as follows:
The sheets were pressed at 0.5 MPa for 2 minutes at various temperatures (PBT: 250°C, PA6: 240°C, PA66: 280°C) depending on the resin used, and then pressed at 20 MPa for 1 minute without changing the temperature.Then, the sheets were pressed by hand at 10 MPa, 80°C for 1 minute, and then pressed at 15°C for 20 seconds to produce sheets of each resin composition.

Details of materials, abbreviations, etc. in the examples are as follows:
〔resin〕
Polybutylene terephthalate (PBT): DURANEX 700FP (Polyplastics)

Polyamide 6 (PA6): Amilan CM1017 (manufactured by Toray Industries, Inc.)

Polyamide 66 (PA66): Amilan CM3001-N (manufactured by Toray Industries, Inc.)

Test Example 2 <YI (Yellow Index) Value>
The YI value of each of the sheet molded articles obtained using the resin compositions of Examples 5 to 7 and Comparative Examples 4 to 6 was measured in the same manner as in Test Example 1, and the ΔYI value was calculated.

Tables 6 to 8 summarize the properties of modified cellulose fiber 6 and the compositions and results of Examples 5 to 7 and Comparative Examples 4 to 6. The amounts of each material that makes up the resin composition in these tables are in parts by mass.

From Examples 5 to 7 and Comparative Examples 4 to 6, it was confirmed that when the specific modified cellulose fiber of the present invention is applied to engineering plastics other than polycarbonate, the color deterioration suppression effect is achieved similarly to polycarbonate.

The resin composition of the present invention can be used for various industrial applications, such as information appliance parts that require high heat resistance, mechanical strength, and durability, packaging materials for information appliance parts, automobile parts, three-dimensional modeling materials, cushioning materials, repair materials, sealing materials, insulation materials, and sound-absorbing materials.

Claims (10)

A resin composition comprising an engineering plastic and a modified cellulose fiber,
the modified cellulose fiber has cellulose I type crystals, and a substituent having an aromatic ring is bonded to at least one of the hydroxyl groups derived from cellulose via an ether bond ;
The substituent having an aromatic ring is one or more kinds of substituents selected from the group consisting of a substituent represented by the following general formula (1), a substituent represented by the following general formula (2), and a substituent represented by the following general formula (3).
-CH2 _- CH(OH)-R1 ₍ 1)
-CH2 _- CH(OH)-CH2- ₍ OA)n-O-R1 ₍ 2)
-R ₁ (3)
(In the formulae, R ₁ in general formulas (1) to (3) each independently represents a hydrocarbon group having 6 to 30 carbon atoms and at least one aromatic ring, n in general formula (2) represents a number of 0 to 50, and A represents a linear or branched divalent saturated hydrocarbon group having 1 to 6 carbon atoms.) The resin composition according to claim 1, wherein the engineering plastic is a crystalline resin. The resin composition according to claim 2, wherein the engineering plastic has a heat distortion temperature of 100°C or higher. The resin composition according to claim 1, wherein the engineering plastic is an amorphous resin. The resin composition according to claim 4, wherein the glass transition temperature of the engineering plastic is 100°C or higher. The resin composition according to any one of claims 1 to 5, wherein the tensile strength of the engineering plastic at 25°C is 49 MPa or more. The resin composition according to any one of claims 1 to 6, wherein the engineering plastic has a flexural modulus of 2 GPa or more at 25°C. The resin composition according to any one of claims 1 to 7, wherein the engineering plastic is at least one selected from the group consisting of polyamide, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polyacetal, modified polyphenylene oxide, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyether sulfone, polysulfone, polyamide imide, polyether imide, polyimide, polyarylate, and polyaryl ether nitrile. A method for producing a resin composition, comprising a mixing step of mixing an engineering plastic with a modified cellulose fiber,
the modified cellulose fiber has cellulose I type crystals, and a substituent having an aromatic ring is bonded to at least one of the hydroxyl groups derived from cellulose via an ether bond ;
The method for producing a resin composition, wherein the substituent having an aromatic ring is one or more types of substituents selected from the group consisting of a substituent represented by the following general formula (1), a substituent represented by the following general formula (2), and a substituent represented by the following general formula (3):
-CH2 _- CH(OH)-R1 ₍ 1)
-CH2 _- CH(OH)-CH2- ₍ OA)n-O-R1 ₍ 2)
-R ₁ (3)
(In the formulae, R ₁ in general formulas (1) to (3) each independently represents a hydrocarbon group having 6 to 30 carbon atoms and at least one aromatic ring, n in general formula (2) represents a number of 0 to 50, and A represents a linear or branched divalent saturated hydrocarbon group having 1 to 6 carbon atoms.) The method for producing a resin composition according to claim 9 , wherein the mixing step includes a step of performing a shearing treatment and/or a kneading treatment at 200° C. or more.