JP2017008157A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition that maintains the excellent strength even at high temperatures as well as that has an excellent stretch-ability, and to provide a process for producing the rubber composition.SOLUTION: A rubber composition contains a rubber, a fine cellulose fiber or modified material thereof, and a plasticizer, in which the fine cellulose fiber has an average fiber diameter of 0.1 nm or more and 200 nm or less, and the cellulose constituting the fine cellulose fiber has a carboxylic group. A process for producing the rubber composition comprises the steps of: mixing the plasticizer and a dispersion of the fine cellulose fiber or modified material thereof, and removing a portion of the solvent to obtain a mixture of the fine cellulose fiber or modified material thereof, and plasticizer; and mixing the mixture obtained in the previous step and the rubber.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition. More specifically, the present invention relates to a rubber composition that can be suitably used as a machine tool part, a home appliance part, an automobile part, and the like, and a method for producing the rubber composition.

  Although rubber compositions are widely used for industrial applications, the use conditions of molded products using rubber compositions are becoming more severe, and the development of high-performance rubber materials is an urgent need.

  For example, Patent Document 1 includes 5 to 50 parts by weight of carbon black, 5 to 60 parts by weight of graphite having an average particle diameter of 5 μm or less, and 5 to 50 parts by weight of conductive carbon other than these with respect to 100 parts by weight of nitrile rubber. A nitrile rubber composition is disclosed, which has been shown to satisfy the muddy water resistance and sealing properties required for oil seals for rolling bearings of automobiles and the like and to achieve low torque. .

  In Patent Document 2, a rubber component containing a hydrogenated nitrile rubber having an iodine value of 11 mg / 100 mg or less and a short fiber blended with the rubber component are formed, and the short fiber is a nitrile group. A toothed belt made of rubber that has been surface-treated with an adhesive treatment containing a copolymer containing an oil is disclosed, and it is used in an internal combustion engine such as an automobile or as a drive / power transmission belt for an oil pump to improve oil resistance. It has been shown that the belt life can be improved.

  On the other hand, Patent Document 3 utilizes the surface oxidation reaction of cellulose by an N-oxyl compound, has a number average fiber diameter of 2 to 150 nm, and some hydroxyl groups of cellulose are oxidized to carboxyl groups or aldehyde groups. In addition, fine cellulose fibers having cellulose I-type crystal structure and usable as various functional additives and structural materials are disclosed.

JP 2012-97213 A JP 2012-197857 A JP 2008-001728 A

  However, further improvement is required as a rubber composition to be applied to various uses. That is, it is desired to develop a rubber composition that not only exhibits good mechanical strength at normal temperature, but also does not decrease in strength at high temperatures and has excellent stretchability.

  The present invention relates to a rubber composition that maintains excellent strength even at high temperatures and also has excellent stretchability, and a method for producing the rubber composition.

  The present inventors have found that by blending specific cellulose fibers with rubber together with a plasticizer, the strength is high not only at room temperature but also at high temperature and the tensile strength can be improved without degrading workability. The present invention has been completed.

The present invention relates to the following [1] to [2].
[1] A rubber composition comprising rubber, fine cellulose fibers or a modified product thereof, and a plasticizer, wherein the fine cellulose fibers have an average fiber diameter of 0.1 nm to 200 nm, and the fine cellulose fibers A rubber composition in which the cellulose constituting the resin has a carboxy group.
[2] The method for producing a rubber composition according to the above [1], comprising the following steps (I) and (II).
Step (I): A step of mixing a plasticizer and a dispersion of fine cellulose fibers or a modified product thereof, and then removing a part of the solvent to obtain a mixture of fine cellulose fibers or a modified product / plasticizer thereof ( II): Step of mixing the mixture obtained in the step (I) with rubber

  The rubber composition of the present invention exhibits not only good mechanical strength at normal temperature, but also has excellent effects that the strength does not decrease even at high temperatures and is excellent in stretchability.

  Conventionally, rubber compositions have been widely used for applications requiring rubber elasticity, and attempts have been made to blend cellulose fibers for the purpose of improving mechanical strength. However, since the dispersibility is not sufficient, blending of a plasticizer has been studied. However, since the strength at high temperature becomes too low by compounding the plasticizer, a further rubber composition that maintains the strength at high temperature is required. Further, higher stretchability is required from the viewpoint of application to uses requiring rubber elasticity. Therefore, as a result of the study by the present inventors, surprisingly, when a plasticizer and a specific fine cellulose fiber were blended with rubber, it became excellent not only at room temperature but also at high temperature, and stretched. It has been found that the performance is also improved. The detailed reason is unknown, but by blending fine cellulose fibers with a specific fiber diameter together with a plasticizer, it is possible to disperse well even in a highly hydrophobic rubber and is relatively resistant to heat. It is presumed that the strength of the rubber composition in the high temperature region can be improved by uniformly dispersing the cellulose fibers in the rubber. Moreover, it is estimated that a plasticizer interrupts between the rubber | gum molecule | numerators, prevents the approach between molecule | numerators, and a micro cellulose fiber coexists there, and it is estimated that a stretching property improves by a synergistic effect with a cellulose fiber. In this specification, “strength at high temperature” is “storage elastic modulus at 100 ° C.” described later, and “strength at normal temperature (mechanical strength)” is “storage elastic modulus at 20 ° C.” described later. Means the property evaluated by

(Rubber composition)
The rubber composition of the present invention contains rubber, fine cellulose fibers or a modified product thereof, and a plasticizer.

[Rubber]
The rubber used in the present invention is not particularly limited, but diene rubber is preferable from the viewpoint of reinforcement. Diene rubbers include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butyl rubber (IIR), butadiene-acrylonitrile copolymer rubber (NBR). ), Chloroprene rubber (CR) and modified rubber. Examples of the modified rubber include epoxidized natural rubber, hydrogenated natural rubber, hydrogenated butadiene-acrylonitrile copolymer rubber (HNBR), and the like. Among these, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (from the viewpoint of achieving both good processability and high impact resilience of the rubber composition ( 1 type or 2 types or more selected from SBR), chloroprene rubber (CR) and modified rubber are preferable, and selected from natural rubber (NR), styrene-butadiene copolymer rubber (SBR), chloroprene rubber (CR) and modified rubber. One type or two or more types are more preferable. The diene rubbers can be used alone or in combination of two or more.

[Fine cellulose fiber or modified product thereof]
Examples of the fine cellulose fiber or modified product thereof used in the present invention include a known fine cellulose fiber and a fine cellulose fiber modified product in which a modifying group is introduced into the fine cellulose fiber. In the present specification, the introduction of the modifying group into the fine cellulose fiber means a state in which the modifying group is bonded to the carboxy group on the surface of the fine cellulose fiber by an ionic bond and / or an amide bond. . More specifically, when the carboxy group of the fine cellulose fiber is deprotonated, the amine having the modifying group is ionically bonded, or the carbon atom of the amide group is covalently bonded to the cellulose skeleton of the fine cellulose fiber, and the nitrogen atom The modification group is covalently bonded directly or via a linking group.

<Fine cellulose fiber>
(Average fiber diameter)
The fine cellulose fiber in the present invention has an average fiber diameter of 0.1 nm or more and 200 nm or less, but from the viewpoint of producing a fine cellulose fiber modified product having a uniform fiber diameter, the average fiber diameter is preferably 0.2 nm or more, More preferably, it is 0.5 nm or more, More preferably, it is 0.8 nm or more, More preferably, it is 1 nm or more. Further, from the viewpoint of sufficiently improving the mechanical strength when it is contained in a rubber to form a rubber composition (also referred to as a composite material) and improving the strength at high temperature, it is preferably 100 nm or less, more preferably 50 nm or less. More preferably, it is 20 nm or less, More preferably, it is 10 nm or less, More preferably, it is 5 nm or less. In addition, in this specification, the average fiber diameter of a cellulose fiber can be measured using an atomic force microscope (AFM), and is specifically measured by the method as described in the below-mentioned Example. In general, the smallest unit of cellulose nanofibers prepared from higher plants is a 6 × 6 molecular chain packed in a nearly square shape, so the height analyzed by AFM images is regarded as the fiber width. Can do.

(Carboxy group content)
The carboxy group content of the fine cellulose fiber is preferably 0.1 mmol / g or more, more preferably 0.4 mmol / g or more, still more preferably 0.6 mmol / g or more, from the viewpoint of stable refinement and modification group introduction. More preferably, it is 0.8 mmol / g or more. Moreover, from a viewpoint of improving handleability, Preferably it is 3 mmol / g or less, More preferably, it is 2 mmol / g or less, More preferably, it is 1.8 mmol / g or less. In the fine cellulose fiber used in the present invention, a fine cellulose fiber having a carboxy group content outside this range may be unintentionally contained as an impurity. The “carboxy group content” means the total amount of carboxy groups in the cellulose constituting the fine cellulose fiber, and is specifically measured by the method described in Examples described later.

(Average aspect ratio)
The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is preferably 10 or more, more preferably 20 or more, from the viewpoint of sufficiently improving the mechanical strength when contained in rubber to form a composite material. Preferably it is 50 or more, More preferably, it is 100 or more. Moreover, from a viewpoint of suppressing the mechanical strength fall accompanying the dispersibility fall in a rubber composition, Preferably it is 1000 or less, More preferably, it is 500 or less, More preferably, it is 400 or less, More preferably, it is 350 or less. Fine cellulose fibers having an average aspect ratio in the above range are excellent in dispersibility in rubber when blended with rubber, and have a high mechanical strength and are difficult to brittlely break. In the present specification, the average aspect ratio is obtained by calculating back the aspect ratio of the cellulose fiber by the following formula (1) from the relationship between the concentration of the cellulose fiber in the dispersion and the specific viscosity of the dispersion with respect to water. In addition, following formula (1) is The Theory of Polymer Dynamics, M. DOI and D.D. F. EDWARDS, CLARENDON PRESS · OXFORD, 1986 , P312 viscosity rigid-rod molecules according to equation (8.138), the relationship wherein the _{^{Lb 2 × ρ = M / N}} A, L is the fiber length, b is fiber width (cellulose fiber cross section is a square), [rho is the cellulose fiber concentration (kg / m 3), ^M is the molecular weight, the N _a are those derived from the representative of Avogadro's number]. Moreover, in said viscosity formula (8.138), let a rigid rod-shaped molecule | numerator be a cellulose fiber. In the following formula (1), η _SP is the specific viscosity, π is the circumference, ln is the natural logarithm, P is the aspect ratio (L / b), γ = 0.8, ρ _S is the density of the dispersion medium (kg / m ³ ), ρ ₀ represents the density of the cellulose crystals (kg / m ³ ), and C represents the mass concentration of the cellulose (C = ρ / ρ _S ).

(Crystallinity)
The crystallinity of the fine cellulose fibers is preferably 30% or more, more preferably 35% or more, and still more preferably 40% or more, from the viewpoint of improving the mechanical strength when contained in a rubber to form a composite material. More preferably, it is 45% or more. Moreover, from a viewpoint of improving reaction efficiency, Preferably it is 95% or less, More preferably, it is 90% or less, More preferably, it is 85% or less, More preferably, it is 80% or less. In the present specification, the crystallinity of cellulose is the cellulose I-type crystallinity calculated by the Segal method from the diffraction intensity value by the X-ray diffraction method, and is defined by the following calculation formula (A).
Cellulose type I crystallinity (%) = [(I22.6-I18.5) /I22.6] × 100 (A)
[Wherein I22.6 is the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ = 22.6 °) in X-ray diffraction, and I18.5 is the amorphous portion (diffraction angle 2θ = 18.5 °). Shows the diffraction intensity of
Cellulose type I is a crystalline form of natural cellulose, and cellulose type I crystallinity means the proportion of the total amount of crystal region in the whole cellulose.

<Modified product of fine cellulose fiber (fine cellulose fiber composite)>
The modified product of fine cellulose fiber used in the present invention is one in which a modifying group is bonded to the surface of the fine cellulose fiber, which is selected from, for example, carboxy groups already present on the surface of the fine cellulose fiber. Thus, it can be obtained by ion-bonding and / or amide-bonding an amine having a modifying group. In addition, in this specification, the modified product of a fine cellulose fiber may be described as a fine cellulose fiber composite.

(Amine having a modifying group)
The amine having a modifying group may be any amine as long as it has a modifying group to be described later. In the case of ionic bonding, any of primary amine, secondary amine, and tertiary amine may be used. Therefore, a primary amine or a secondary amine is preferable, and a primary amine is more preferable. In the case of an amide bond, either a primary amine or a secondary amine may be used, but a primary amine is preferable from the viewpoint of reactivity.

  As the modifying group in the present invention, a hydrocarbon group, an ethylene oxide / propylene oxide (EO / PO) copolymer part, or the like can be used from the viewpoint of improving the strength at high temperature. These may be introduced into the fine cellulose fiber alone or in combination of two or more.

  Examples of the hydrocarbon group include a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, and an aromatic hydrocarbon group. From the viewpoint, a chain saturated hydrocarbon group, a cyclic saturated hydrocarbon group, and an aromatic hydrocarbon group are preferable.

  The chain saturated hydrocarbon group may be linear or branched. The number of carbon atoms of the chain saturated hydrocarbon group is preferably 1 or more, more preferably 3 or more, still more preferably 5 or more, still more preferably 10 or more, and more preferably 15 or more from the viewpoint of maintaining strength at high temperatures and stretchability. Further preferred. Further, from the same viewpoint, 30 or less is preferable, 24 or less is more preferable, and 18 or less is more preferable.

  Specific examples of the chain saturated hydrocarbon group include, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group, isobutyl group, pentyl group, tert-pentyl group, Examples include isopentyl group, hexyl group, isohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, octadecyl group, docosyl group, octacosanyl group, etc. From the viewpoint of maintaining the strength and stretchability, preferably propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group, isobutyl group, pentyl group, tert-pentyl group, isopentyl group, hexyl group, isohexyl Group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, Sil group, dodecyl group, tridecyl group, tetradecyl group, octadecyl group, docosyl group, octacosanyl group, more preferably propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group, isobutyl group, pentyl group Tert-pentyl group, isopentyl group, hexyl group, isohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, octadecyl group. These may be introduced alone or two or more of them may be introduced in an arbitrary ratio.

  The chain unsaturated hydrocarbon group may be linear or branched. The number of carbon atoms of the chain unsaturated hydrocarbon group is preferably 1 or more, more preferably 2 or more, and still more preferably 3 or more from the viewpoint of handleability. Moreover, from a viewpoint of availability, 30 or less are preferable, 18 or less are more preferable, 12 or less are still more preferable, and 8 or less are still more preferable.

  Specific examples of the chain unsaturated hydrocarbon group include, for example, ethylene group, propylene group, butene group, isobutene group, isoprene group, pentene group, hexene group, heptene group, octene group, nonene group, decene group, dodecene group. , Tridecene group, tetradecene group and octadecene group, and from the viewpoint of affinity with rubber, preferably ethylene group, propylene group, butene group, isobutene group, isoprene group, pentene group, hexene group, heptene group, octene group , Nonene group, decene group and dodecene group, more preferably hexene group, heptene group, octene group, nonene group, decene group and dodecene group. These may be introduced alone or two or more of them may be introduced in an arbitrary ratio.

  From the viewpoint of handleability, the number of carbon atoms of the cyclic saturated hydrocarbon group is preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more. Moreover, from a viewpoint of availability, 20 or less is preferable, 16 or less is more preferable, 12 or less is further more preferable, and 8 or less is still more preferable.

  Specific examples of the cyclic saturated hydrocarbon group include, for example, a cyclopropane group, a cyclobutyl group, a cyclopentane group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cyclododecyl group, and a cyclotridecyl group. , Cyclotetradecyl group, cyclooctadecyl group, etc., from the viewpoint of affinity with rubber, preferably cyclopropane group, cyclobutyl group, cyclopentane group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, A cyclodecyl group and a cyclododecyl group, more preferably a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and a cyclododecyl group. These may be introduced alone or two or more of them may be introduced in an arbitrary ratio.

  The aromatic hydrocarbon group is selected from the group consisting of an aryl group and an aralkyl group, for example. The aryl group and aralkyl group may be substituted or unsubstituted on the aromatic ring itself.

  The total number of carbon atoms of the aryl group may be 6 or more, and from the viewpoint of affinity with rubber, it is preferably 24 or less, more preferably 20 or less, still more preferably 14 or less, still more preferably 12 or less, still more preferably 10 or less.

  The total number of carbon atoms of the aralkyl group is 7 or more, preferably 8 or more from the viewpoint of affinity with rubber, and from the same viewpoint, preferably 24 or less, more preferably 20 or less, still more preferably. 14 or less, more preferably 13 or less, and still more preferably 11 or less.

  Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a biphenyl group, a triphenyl group, a terphenyl group, and a group in which these groups are substituted with a substituent described later. One kind alone or two or more kinds may be introduced in an arbitrary ratio. Among these, from the viewpoint of affinity with rubber, a phenyl group, a biphenyl group, and a terphenyl group are preferable, and a phenyl group is more preferable.

  As an aralkyl group, for example, a benzyl group, a phenethyl group, a phenylpropyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, and an aromatic group of these groups are substituted with a substituent described later. Group etc. are mentioned, These may be introduce | transduced individually by 1 type or 2 types or more, respectively. Among these, from the viewpoint of affinity with rubber, benzyl group, phenethyl group, phenylpropyl group, phenylpentyl group, phenylhexyl group, phenylheptyl group are preferable, benzyl group, phenethyl group, phenylpropyl group, phenylpentyl group, A phenylhexyl group is more preferable, and a benzyl group, a phenethyl group, a phenylpropyl group, and a phenylpentyl group are more preferable.

  The amine having a hydrocarbon group can be prepared according to a known method. Commercially available products may be used. Examples of amines having a chain saturated hydrocarbon group include propylamine, isopropylamine, butylamine, sec-butylamine, tert-butylamine, isobutylamine, pentylamine, and tert-pentylamine. , Isopentylamine, hexylamine, isohexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, dodecylamine, tridecylamine, tetradecylamine, octadecylamine, docosylamine, octacosanylamine Can do. Examples of the amine having a chain unsaturated hydrocarbon group include ethyleneamine, propyleneamine, buteneamine, isobuteneamine, isopreneamine, penteneamine, hexeneamine, hepteneamine, octeneamine, nonenamine, deceneamine, and dodecenamine. As the amine having a cyclic saturated hydrocarbon group, cyclopropanamine, cyclobutylamine, cyclopentaneamine, cyclohexylamine, cycloheptylamine, cyclooctylamine, cyclononylamine, cyclodecylamine, and cyclododecylamine can be used. . Examples of the amine having an aromatic hydrocarbon group include aniline, 4-biphenylylamine, diphenylamine, 2-aminonaphthalene, p-terphenylamine, 2-aminoanthracene, 2-aminoanthraquinone, benzylamine, phenethylamine, 3 -Phenylpropylamine, 5-phenylpentylamine, 6-phenylhexylamine, 7-phenylheptylamine, 8-phenyloctylamine can be used.

  The average bond amount (mmol / g) of hydrocarbon groups in the fine cellulose fiber composite is the same as that of the fine cellulose fibers for chain saturated hydrocarbon groups, chain unsaturated hydrocarbon groups, and cyclic saturated hydrocarbon groups. On the other hand, since the control of the bonding amount of the hydrocarbon group is easy, it is preferably 0.001 mmol / g or more, more preferably 0.005 mmol / g or more, and still more preferably 0.01 mmol / g or more. Moreover, from a reactive viewpoint, Preferably it is 3 mmol / g or less, More preferably, it is 2 mmol / g or less, More preferably, it is 1 mmol / g or less. For the aromatic hydrocarbon group, the average bond amount of the hydrocarbon group is preferably 0.1 mmol / g or more, more preferably from the viewpoint of obtaining a rubber composition having excellent mechanical strength when blended with rubber. Is 0.2 mmol / g or more, more preferably 0.5 mmol / g or more, more preferably 0.7 mmol / g or more, still more preferably 0.9 mmol / g or more, still more preferably 1.0 mmol / g or more. Moreover, from a reactive viewpoint, Preferably it is 3 mmol / g or less, More preferably, it is 2 mmol / g or less, More preferably, it is 1.5 mmol / g or less. Here, even when a hydrocarbon group selected from a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, and a cyclic saturated hydrocarbon group and an aromatic hydrocarbon group are simultaneously introduced. The average bond amount is preferably within the above range.

  The introduction rate of the hydrocarbon group is preferably from the viewpoint of the mechanical strength of the resulting rubber composition for the chain saturated hydrocarbon group, the chain unsaturated hydrocarbon group, and the cyclic saturated hydrocarbon group. 10% or more, more preferably 30% or more, still more preferably 50% or more, still more preferably 60% or more, still more preferably 70% or more. From the viewpoint of reactivity, it is preferably 99% or less, more preferably 97%. % Or less, more preferably 95% or less, and still more preferably 90% or less. For the aromatic hydrocarbon group, the introduction rate of the hydrocarbon group is preferably 10% or more, more preferably 30% or more, from the viewpoint of obtaining a rubber composition having excellent mechanical strength when blended with rubber. More preferably, it is 50% or more, more preferably 60% or more, further preferably 70% or more, more preferably 80% or more. From the viewpoint of reactivity, it is preferably 99% or less, more preferably 97% or less, Preferably it is 95% or less, More preferably, it is 90% or less. Here, when a hydrocarbon group selected from a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, and a cyclic saturated hydrocarbon group and an aromatic hydrocarbon group are introduced simultaneously, In a range where the sum of the rates does not exceed 100% of the upper limit, it is preferably within the above range.

  The EO / PO copolymerization part means a structure in which ethylene oxide (EO) and propylene oxide (PO) are polymerized randomly or in a block form. For example, when an amine having an EO / PO copolymer part is represented by the formula (i) described later, ethylene oxide (EO) and propylene oxide (PO) have a random or block chain structure. Is an amine having a structure represented by the following formula (ii), (EO) a (PO) b, (EO) c (PO) d, (EO) e (PO) f are linked. You don't have to.

  The PO content (mol%) in the EO / PO copolymerization part is preferably 1 mol% or more, more preferably 5 mol% or more, and still more preferably 7 from the viewpoint of obtaining a rubber composition having excellent mechanical strength. From the same viewpoint, it is preferably 100 mol% or less, more preferably 90 mol% or less, still more preferably 85 mol% or less, still more preferably 75 mol% or less, from the same viewpoint. More preferably, it is 60 mol% or less, More preferably, it is 50 mol% or less, More preferably, it is 40 mol% or less, More preferably, it is 30 mol% or less. The PO content of 100 mol% means that the EO / PO copolymer part is composed only of PO, and in the present invention, the PO polymer part may be introduced.

  The molecular weight of the EO / PO copolymerization part is preferably 500 or more, more preferably 1,000 or more, still more preferably 1,500 or more, from the viewpoint of obtaining a rubber composition having excellent mechanical strength. , Preferably 10,000 or less, more preferably 7,000 or less, still more preferably 5,000 or less, still more preferably 4,000 or less, still more preferably 3,500 or less, and even more preferably 2,500 or less. . For example, in the case of an amine having a structure represented by the formula (ii) described later, the total molecular weight of (EO) a (PO) b + (EO) c (PO) d + (EO) e (PO) f is And the molecular weight of the EO / PO copolymer part. The PO content (mol%) in the EO / PO copolymerization part and the molecular weight of the EO / PO copolymerization part can be calculated from the average number of moles added when the amine is produced.

  The EO / PO copolymer part and the amine are preferably bonded directly or via a linking group. As the linking group, a hydrocarbon group is preferable, and an alkylene group having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms is used. For example, an ethylene group and a propylene group are preferable.

  Examples of the amine having such an EO / PO copolymer part include the following formula (i):

[Wherein, R ₁ represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, —CH ₂ CH (CH ₃ ) NH ₂ group, or a group represented by the following formula (ii): EO and PO are present in a random or block form, a is a positive number indicating the average added mole number of EO, and b is a positive number indicating the average added mole number of PO.
The compound represented by these is mentioned.

Formula (ii):

[In the formula, n is 0 or 1, R ₂ represents a phenyl group, a hydrogen atom, or a linear or branched alkyl group having 1 to 3 carbon atoms, and EO and PO are present in a random or block form. , C and e represent the average number of added moles of EO, independently a number from 0 to 50, and d and f represent the average number of moles added of PO, independently from 1 to 50]

  In the formula (i), a represents the average added mole number of EO, and from the viewpoint of obtaining a rubber composition excellent in mechanical strength, it is preferably 11 or more, more preferably 15 or more, still more preferably 20 or more, and further preferably 25. From the same viewpoint, it is preferably 100 or less, more preferably 70 or less, still more preferably 60 or less, still more preferably 50 or less, and still more preferably 40 or less.

  In formula (i), b represents the average added mole number of PO, and from the viewpoint of obtaining a rubber composition excellent in mechanical strength, it is preferably 1 or more, more preferably 2 or more, and further preferably 3 or more. From the viewpoint, it is preferably 50 or less, more preferably 40 or less, still more preferably 30 or less, still more preferably 25 or less, still more preferably 20 or less, still more preferably 15 or less, still more preferably 10 or less.

  The PO content (mol%) in the EO / PO copolymer part is calculated from the above a and b when the amine is represented by the formula (i). When the amine is represented by the formula (i) and the formula (ii), the formula: (b + d + f) × 100 / (a + b + c + d + e + f). A preferred range is as described above.

R ₁ in formula (i) represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a —CH ₂ CH (CH ₃ ) NH ₂ group, or a group represented by the formula (ii). As shown, a hydrogen atom is preferable from the viewpoint of obtaining a rubber composition having excellent mechanical strength. The linear or branched alkyl group having 1 to 6 carbon atoms is preferably a methyl group, an ethyl group, an iso or normal propyl group.

In addition, when R ₁ in formula (i) is a group represented by formula (ii), the linear or branched alkyl group having 1 to 3 carbon atoms of R ₂ in formula (ii) is preferably A methyl group and an ethyl group. When R ₂ is a methyl group or an ethyl group, n is preferably 1, and when R ₂ is a hydrogen atom, n is preferably 0. Moreover, as c and e in Formula (ii), 10-30 are preferable independently, and as d and f, 5-25 are preferable independently.

  The amine having an EO / PO copolymer moiety represented by the formula (i) can be prepared according to a known method. For example, a desired amount of ethylene oxide or propylene oxide may be added to propylene glycol alkyl ether, and then the hydroxyl terminal may be aminated. If necessary, the terminal can be made into a hydrogen atom by cleaving the alkyl ether with an acid. For these production methods, reference can be made to JP-A-3-181448.

  Commercially available products are also preferably used, and specific examples include Jeffamine M-2070, Jeffamine M-2005, Jeffamine M-1000, Surfamine B200, Surfamine L100, Surfamine L200, Surfamine L200, Surfamine L200, Surfamine L200, Surfamine L200, Surfamine L200, Surfamine L200, SurfLamine L200, SurfX. -501, XTJ-506, XTJ-507, XTJ-508; M3000 manufactured by BASF, Jeffamine ED-900, Jeffamine ED-2003, Jeffamine D-2000, Jeffamine D-4000, XTJ-510, Jeffine T-3000, Jeffamine T-5000, XTJ-502, XTJ-509, X J-510 and the like. These may be used alone or in combination of two or more.

  The average binding amount (mmol / g) of the EO / PO copolymer part in the fine cellulose fiber composite is preferably 0.01 mmol / g or more, more preferably 0.00, from the viewpoint of obtaining a rubber composition having excellent mechanical strength. 05 mmol / g or more, more preferably 0.1 mmol / g or more, more preferably 0.3 mmol / g or more, more preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more. Moreover, from a reactive viewpoint, Preferably it is 3 mmol / g or less, More preferably, it is 2 mmol / g or less, More preferably, it is 1.5 mmol / g or less.

  The introduction ratio of the EO / PO copolymer part in the fine cellulose fiber composite is preferably 10% or more, more preferably 20% or more, and still more preferably 30%, from the viewpoint of obtaining a rubber composition having excellent mechanical strength. Above, more preferably 40% or more, more preferably 50% or more, more preferably 60% or more, more preferably 70% or more, more preferably 80% or more, from the viewpoint of obtaining a rubber composition having excellent mechanical strength Therefore, it is preferably 95% or less.

  The modifying group may have a substituent. For example, it is preferable that the total number of carbon atoms of the hydrocarbon group including the substituent is within the above range. Examples of the substituent include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, an isopentyloxy group, and a hexyloxy group. C1-C6 alkoxy group; methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, isopropoxycarbonyl group, butoxycarbonyl group, isobutoxycarbonyl group, sec-butoxycarbonyl group, tert-butoxycarbonyl group, pentyloxycarbonyl Group, an alkoxy-carbonyl group having 1 to 6 carbon atoms of an alkoxy group such as isopentyloxycarbonyl group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; 1 carbon atom such as an acetyl group or a propionyl group ~ 6 Sill group; an aralkyl group; an aralkyloxy group; an alkylamino group having 1 to 6 carbon atoms; the carbon number of the alkyl group have dialkylamino group having 1 to 6. In addition, the above-described hydrocarbon group itself may be bonded as a substituent.

  In the present specification, the average bonding amount of the modifying group can be adjusted by the amount of amine added, the type of amine, the reaction temperature, the reaction time, the solvent, and the like. The average binding amount (mmol / g) and introduction rate (%) of the modifying group in the fine cellulose fiber composite are the amount and ratio of the modifying group introduced into the carboxy group on the surface of the fine cellulose fiber, It can be calculated by measuring the carboxy group content of fine cellulose fibers according to a known method (for example, titration, IR measurement, etc.).

<Method for producing fine cellulose fiber composite>
The fine cellulose fiber composite can be produced according to a known method without particular limitation as long as a modifying group can be introduced into the fine cellulose fiber. For example, a reaction for introducing a modifying group into fine cellulose fibers prepared in advance may be performed, or a reaction for introducing a modifying group may be performed when preparing fine cellulose fibers. In addition, a fine cellulose fiber can be manufactured by a well-known method, for example, the method of Unexamined-Japanese-Patent No. 2011-140632.

The following two modes may be mentioned depending on the mode of introduction of the modifying group into the fine cellulose fiber. That is, there are an embodiment (embodiment A) in which the modifying group is bonded to the fine cellulose fiber by ionic bond and an embodiment (embodiment B) in which the modifying group is bonded to the fine cellulose fiber by amide bond.
[Aspect A]
Step (1): Oxidation of natural cellulose fibers in the presence of an N-oxyl compound to obtain carboxy group-containing cellulose fibers Step (2A): Carboxy group-containing cellulose fibers obtained in step (1), and modifying groups A step of mixing with an amine having [Aspect B]
Step (1): Natural cellulose fiber is oxidized in the presence of an N-oxyl compound to obtain a carboxy group-containing cellulose fiber Step (2B): Carboxy group-containing cellulose fiber obtained in step (1) and a modifying group The step of amidation reaction with an amine having the following: As the preferred production method, the step (2A or 2B) is performed after the step (1) is followed by a finer step, which will be described later, to obtain a carboxy group-containing fine cellulose fiber. Examples include a method of performing (first manufacturing mode) and a method of performing step (2A or 2B) after step (1) and then performing a miniaturization step (second manufacturing mode).

  Hereinafter, based on the 1st manufacture form of aspect A, the manufacturing method of a fine cellulose fiber composite is demonstrated.

[Step (1)]
Step (1) is a step of oxidizing a natural cellulose fiber in the presence of an N-oxyl compound to obtain a carboxy group-containing cellulose fiber.

  In the step (1), first, a slurry in which natural cellulose fibers are dispersed in water is prepared. The slurry is about 10 to 1000 times as much water (mass basis) as the raw material natural cellulose fiber (absolute drying basis: mass of natural cellulose fiber after being heated and dried at 150 ° C. for 30 minutes), It is obtained by processing with a mixer or the like. Examples of natural cellulose fibers include wood pulp such as softwood pulp and hardwood pulp; cotton pulp such as cotton linter and cotton lint; non-wood pulp such as straw pulp and bagasse pulp; bacterial cellulose and the like. These 1 type can be used individually or in combination of 2 or more types. The natural cellulose fiber may be subjected to a treatment for increasing the surface area such as beating. Further, the cellulose I type crystallinity of the commercially available pulp is usually 80% or more.

(Oxidation process)
Next, the natural cellulose fiber is oxidized in the presence of an N-oxyl compound to obtain a carboxy group-containing cellulose fiber (hereinafter sometimes simply referred to as “oxidation treatment”).

  As the N-oxyl compound, one or more heterocyclic N-oxyl compounds selected from piperidine oxyl compounds having 1 or 2 carbon atoms, pyrrolidine oxyl compounds, imidazoline oxyl compounds, and azaadamantane compounds are preferable. . Among these, piperidineoxyl compounds having an alkyl group having 1 or 2 carbon atoms are preferable from the viewpoint of reactivity, and 2,2,6,6-tetraalkylpiperidine-1-oxyl (TEMPO), 4-hydroxy- 2,2,6,6-tetraalkylpiperidine-1-oxyl, 4-alkoxy-2,2,6,6-tetraalkylpiperidine-1-oxyl, 4-benzoyloxy-2,2,6,6-tetra Di-tert-alkylnitroxyl compounds such as alkylpiperidine-1-oxyl and 4-amino-2,2,6,6-tetraalkylpiperidine-1-oxyl, 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4 -Phosphonoxy-TEMPO etc. are mentioned. Among these piperidine oxyl compounds, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4- Methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl is preferred, and 2,2,6,6 tetramethylpiperidine-1-oxyl (TEMPO) is more preferred.

  The amount of the N-oxyl compound may be a catalytic amount, and is preferably 0.001 to 10% by mass, more preferably 0.01 to 9% by mass, and still more preferably based on natural cellulose fiber (absolute dry basis). Is 0.1 to 8% by mass, more preferably 0.5 to 5% by mass.

  An oxidizing agent can be used in the oxidation treatment of natural cellulose fibers. As the oxidizing agent, from the viewpoint of solubility and reaction rate when the solvent is adjusted to an alkaline region, oxygen or air, peroxides; halogens, hypohalous acids, halous acids, perhalogen acids and their alkali metals Salt or alkaline earth metal salt; halogen oxide, nitrogen oxide and the like. Among these, alkali metal hypohalites are preferable, and specific examples include sodium hypochlorite and sodium hypobromite. The amount of the oxidizing agent used may be selected according to the degree of carboxy group substitution (oxidation degree) of the natural cellulose fiber, and the oxidation reaction yield varies depending on the reaction conditions. Preferably it is the range used as about 1-100 mass% with respect to a cellulose fiber (absolute dry reference | standard).

  In order to perform the oxidation reaction more efficiently, bromides such as sodium bromide and potassium bromide and iodides such as sodium iodide and potassium iodide can be used as a co-catalyst. The amount of the promoter is not particularly limited as long as it is an effective amount that can exhibit its function.

  The reaction temperature in the oxidation treatment is preferably 50 ° C. or lower, more preferably 40 ° C. or lower, further preferably 20 ° C. or lower, from the viewpoint of reaction selectivity and side reaction suppression, and the lower limit thereof is preferably −5. It is above ℃.

  Further, the pH of the reaction system is preferably matched to the nature of the oxidizing agent. For example, when sodium hypochlorite is used as the oxidizing agent, the pH of the reaction system is preferably on the alkali side, preferably pH 7 to 13, A pH of 10 to 13 is more preferred. The reaction time is preferably 1 to 240 minutes.

  By performing the oxidation treatment, a carboxy group-containing cellulose fiber having a carboxy group content of preferably 0.1 mmol / g or more is obtained.

(Purification process)
The carboxy group-containing cellulose fiber obtained by the oxidation reaction contains an N-oxyl compound such as TEMPO or a by-product salt used as a catalyst. The next step may be carried out as it is, but purification can also be carried out to obtain a highly purified carboxy group-containing cellulose fiber. As the purification method, an optimum method can be employed depending on the type of solvent in the oxidation reaction, the degree of oxidation of the product, and the degree of purification. For example, reprecipitation using water as a good solvent, methanol, ethanol, acetone, etc. as a poor solvent, extraction of TEMPO into a solvent that is phase-separated from water such as hexane, purification by ion exchange of salts, dialysis, etc. Can be mentioned.

(Miniaturization process)
In the first production mode, after the purification step, a step of refining the carboxy group-containing cellulose fiber obtained in the step (1) is performed. In the refinement process, it is preferable to perform the refinement process by dispersing the carboxy group-containing cellulose fiber that has undergone the purification process in a solvent. By carrying out this refinement step, fine cellulose fibers having an average fiber diameter in the above range can be obtained.

  The solvent as the dispersion medium is water, alcohol having 1 to 6 carbon atoms such as methanol, ethanol and propanol, preferably 1 to 3 carbon atoms; ketone having 3 to 6 carbon atoms such as acetone, methyl ethyl ketone and methyl isobutyl ketone. 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 groups having 2 to 5 carbon atoms; Examples include alkyl ethers; polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and diesters of succinic acid and triethylene glycol monomethyl ether. These can be used alone or in admixture of two or more, but from the viewpoint of the operability of the micronization treatment, water, alcohol having 1 to 6 carbon atoms, ketone having 3 to 6 carbon atoms, carbon number 2 Polar solvents such as -5 lower alkyl ethers, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, succinic acid methyltriglycol diester are preferable, and water is more preferable from the viewpoint of reducing environmental burden. The amount of the solvent used is not particularly limited as long as it is an effective amount capable of dispersing the carboxy group-containing cellulose fiber, but is preferably 1 to 500 times by mass, more preferably 2 to 200 times with respect to the carboxy group-containing cellulose fiber. It is more preferable to use mass times.

  Moreover, a well-known disperser is used suitably as an apparatus used by refinement | miniaturization processing. For example, a disaggregator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short screw extruder, a twin screw extruder, an ultrasonic stirrer, a domestic juicer mixer, and the like can be used. Further, the solid content concentration of the reactant fiber in the refinement treatment is preferably 50% by mass or less.

  As the form of the carboxy group-containing fine cellulose fiber obtained after the refining process, the solid content concentration is adjusted as required (sustainedly colorless transparent or opaque liquid), or dried powder (however, Or a powder form in which fine cellulose fibers are aggregated, and does not mean cellulose particles). In the case of a suspension, only water may be used as a dispersion medium, and a mixed solvent of water and other organic solvents (for example, alcohols such as ethanol), surfactants, acids, bases, etc. May be used.

  By such oxidation treatment and refinement treatment of natural cellulose fiber, the hydroxyl group at the C6 position of the cellulose structural unit is selectively oxidized to a carboxy group via an aldehyde group, and the carboxy group content is preferably 0.8. Cellulose fibers comprising 1 mmol / g or more of cellulose and having an average fiber diameter of 0.1 nm or more and 200 nm or less, preferably having a crystallinity of 30% or more can be obtained. Here, the said carboxy-group containing fine cellulose fiber has a cellulose I type crystal structure. This means that the carboxy group-containing fine cellulose fiber used in the present invention is a fiber obtained by surface-oxidizing and refining a naturally-derived cellulose solid raw material having an I-type crystal structure. In step (1), after the natural cellulose fiber is oxidized, an acid (for example, hydrochloric acid) can be further reacted to adjust the carboxy group content, and the reaction can be performed before or after the refining treatment. You may go to either of them.

[Step (2A)]
In the first production mode, the step (2A) is a step of obtaining a fine cellulose fiber composite by mixing the carboxy group-containing fine cellulose fiber obtained through the above-mentioned finening step and an amine having a modifying group. is there. Specifically, the carboxy group-containing fine cellulose fiber and an amine having a modifying group are mixed in a solvent.

  Examples of the amine having a modifying group used in the step (2A) include those described above in the fine cellulose fiber composite.

  The amount of amine used can be determined by the amount of the desired amine salt bound in the fine cellulose fiber composite, but from the viewpoint of reactivity, with respect to 1 mol of carboxy group contained in the carboxy group-containing fine cellulose fiber, The amine group is preferably 0.01 mol or more, more preferably 0.1 mol or more, still more preferably 0.5 mol or more. From the viewpoint of product purity, it is preferably 50 mol or less, more preferably 20 mol or less, still more preferably 10 mol. Use the following amounts. In addition, you may use for the reaction of the quantity of amine contained in the said range at once, or you may divide | segment and use for reaction. When the amine is a monoamine, the above amine group and amine are the same.

  As the solvent, it is preferable to select a solvent in which the amine to be used is dissolved. For example, ethanol, isopropanol (IPA), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N, N-dimethylacetamide, tetrahydrofuran (THF), diester of succinic acid and triethylene glycol monomethyl ether, acetone, methyl ethyl ketone (MEK), acetonitrile, dichloromethane, chloroform, toluene, acetic acid, water, etc., and one of these may be used alone or in combination of two or more Can be used in combination. Among these polar solvents, diester of succinic acid and triethylene glycol monomethyl ether, ethanol, DMF, and water are preferable.

  The temperature during mixing is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, and still more preferably 10 ° C. or higher, from the viewpoint of amine reactivity. Moreover, from a viewpoint of coloring of a composite, Preferably it is 50 degrees C or less, More preferably, it is 40 degrees C or less, More preferably, it is 30 degrees C or less. The mixing time can be appropriately set according to the type of amine and solvent used, but from the viewpoint of amine reactivity, it is preferably 0.01 hours or longer, more preferably 0.1 hours or longer, and even more preferably 1 It is more than time, Preferably it is 48 hours or less, More preferably, it is 24 hours or less.

  After the salt formation, an appropriate post-treatment may be performed in order to remove unreacted amine and the like. As the post-treatment method, for example, filtration, centrifugation, dialysis and the like can be used.

  Moreover, about the manufacturing method of aspect B, since a process (1) can be performed similarly to aspect A, it describes below about the process (2B) in a 1st manufacturing form. For example, it can manufacture by the method as described in Unexamined-Japanese-Patent No. 2013-151661.

[Step (2B)]
In the first production mode, in the step (2B), a carboxy group-containing fine cellulose fiber obtained through the above-mentioned finening step and an amine having a modifying group are amidated to obtain a fine cellulose fiber composite. It is a process. As the mixing method, there is no particular problem as long as the raw material reacts. Specifically, the raw material is mixed in the presence of a condensing agent, and the carboxy group contained in the carboxy group-containing fine cellulose fiber and Then, the amino group of the amine having a modifying group is subjected to a condensation reaction to form an amide bond.

  Examples of the amine having a modifying group used in the step (2B) include those described above in the fine cellulose fiber composite.

  In the step (2B), a carboxy group-containing fine cellulose fiber and an amine having a modifying group are amidated in the presence of a condensing agent.

  From the viewpoint of reactivity, the amount of the amine used is preferably 0.1 mol or more, more preferably 0.5 mol or more, with respect to 1 mol of the carboxy group contained in the carboxy group-containing fine cellulose fiber. From the viewpoint of product purity, the amount used is preferably 50 mol or less, more preferably 20 mol or less, still more preferably 10 mol or less. In addition, you may use for the reaction of the quantity of amine contained in the said range at once, or you may divide | segment and use for reaction.

  Examples of the condensing agent include, but are not limited to, condensing agents described in Synthetic Chemical Series Peptide Synthesis (Maruzensha) P116, or Tetrahedron, 57, 1551 (2001). For example, 4- (4,6- And dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholinium chloride (hereinafter sometimes referred to as “DMT-MM”).

  In the above-mentioned amidation reaction, the solvent in the above-mentioned refinement step is mentioned, and it is preferable to select a solvent in which the amine to be used is dissolved.

  The reaction time and reaction temperature in the amidation reaction can be appropriately selected according to the type of amine and solvent to be used, but from the viewpoint of the reaction rate, preferably 1 to 24 hours, more preferably 10 to 20 hours. It is. The reaction temperature is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, and further preferably 10 ° C. or higher from the viewpoint of reactivity. Moreover, from a viewpoint of coloring of a composite, Preferably it is 200 degrees C or less, More preferably, it is 80 degrees C or less, More preferably, it is 30 degrees C or less.

  After the reaction, in order to remove unreacted amine, condensing agent and the like, post-treatment may be appropriately performed. As the post-treatment method, for example, filtration, centrifugation, dialysis and the like can be used.

  Note that, in any of the aspects A and B, in the second manufacturing mode, the steps described above are performed in the order of the step (1), the step (2A) or the step (2B), and the miniaturization step. The same method as in the first manufacturing mode can be used.

  Moreover, the fine cellulose fiber composite obtained by combining aspect A and aspect B may be sufficient, ie, the fine cellulose fiber composite which has the modification group connected through the ionic bond and the modification group connected through the amide bond It may be a body. In this case, either step (2A) or step (2B) may be performed first.

  Thus, a fine cellulose fiber composite in which the modifying group is linked to the fine cellulose fiber via an ionic bond and / or an amide bond can be obtained. In the present invention, from the viewpoint of the balance between strength and elasticity of the resulting rubber composition, a fine cellulose fiber composite in which modifying groups are connected via an amide bond is preferable.

  The obtained fine cellulose fiber composite can be used in the state of the dispersion after the above-mentioned post-treatment, or by removing the solvent from the dispersion by a drying treatment or the like, A fine cellulose fiber composite can be obtained and used. Here, “powder” is a powder in which fine cellulose fiber composites are aggregated, and does not mean cellulose particles.

  Examples of the powdered fine cellulose fiber composite include, for example, a dried product obtained by directly drying the dispersion of the fine cellulose fiber composite; a powder obtained by pulverizing the dried product by mechanical processing; and a dispersion of the fine cellulose fiber composite. Examples include those obtained by pulverizing a liquid by a known spray drying method; those obtained by pulverizing a dispersion of the fine cellulose fiber composite by a known freeze drying method, and the like. The spray drying method is a method in which a dispersion of the fine cellulose fiber composite is sprayed in the air and dried.

  The fine cellulose fiber composite preferably has an average fiber diameter of 0.1 nm or more, more preferably 0.2 nm or more, and still more preferably 0.5 nm, from the viewpoint of improving the strength of the resulting rubber composition at high temperature. More preferably, it is 0.8 nm or more, more preferably 1 nm or more. Further, from the viewpoint of strength at high temperature and normal temperature of the obtained rubber composition, it is preferably 200 nm or less, more preferably 100 nm or less, still more preferably 50 nm or less, still more preferably 20 nm or less, and even more preferably 10 nm or less. .

  In addition, since the crystallinity does not fall by reaction of a process (2A) or a process (2B), a fine cellulose fiber composite has a crystallinity degree comparable as the crystallinity degree of the said fine cellulose fiber. Is preferred.

  The fine cellulose fiber composite contained in the rubber composition of the present invention includes a hydrocarbon group and / or an EO / PO copolymer part in the fine cellulose fiber having an average fiber diameter of 0.1 nm to 200 nm as described above. Are linked via an ionic bond and / or an amide bond, and those having an average fiber diameter of 0.1 nm to 200 nm are preferred.

[Plasticizer]
It does not specifically limit as a plasticizer, The plasticizer used for a general rubber composition is mentioned. For example, phthalic acid derivatives, isophthalic acid derivatives, tetrahydrophthalic acid derivatives, adipic acid derivatives, azelaic acid derivatives, sebacic acid derivatives, dodecane-2-acid derivatives, maleic acid derivatives, fumaric acid derivatives, trimellitic acid derivatives, pyromellitic acid Derivatives, citric acid derivatives, itaconic acid derivatives, oleic acid derivatives, ricinoleic acid derivatives, stearic acid derivatives, sulfonic acid derivatives, phosphoric acid derivatives, glutaric acid derivatives, glycol derivatives, glycerin derivatives, paraffin derivatives, polyester derivatives, epoxy derivatives, poly And ether derivatives. Preferred examples include polyether ester plasticizers, phthalate ester plasticizers, adipate ester plasticizers, trimellitic ester plasticizers, sebacic ester plasticizers, and phosphate ester plasticizers. Specific examples include di2-ethylhexyl sebacate, di- (2-ethylhexyl) adipate, tricresyl phosphate, di- (2-ethylhexyl) phthalate, and the like. Only one kind of plasticizer may be used, or a plurality of kinds may be used in combination.

  The content of each component in the rubber composition of the present invention is as follows.

  The rubber content in the rubber composition of the present invention is preferably 30% by mass or more, more preferably 45% by mass or more, and further preferably 55% by mass or more, from the viewpoint of moldability of the composition. From the viewpoint of containing a cellulose fiber composite or a plasticizer, it is preferably 80% by mass or less, more preferably 75% by mass or less.

  The content of fine cellulose fibers or a modified product thereof in the rubber composition of the present invention is preferably 1 part by mass with respect to 100 parts by mass of rubber from the viewpoint of improving the mechanical strength and stretchability of the resulting composition. Above, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, from the viewpoint of operability during production, preferably 20 parts by mass or less, more preferably 15 parts by mass. Hereinafter, it is more preferably 12 parts by mass or less. In addition, content of the fine cellulose fiber here is content of the fine cellulose fiber in which the modification group is not introduce | transduced.

  When the rubber composition of the present invention contains a modified product of fine cellulose fibers, the content (converted amount) of fine cellulose fibers is 100 parts by weight of rubber, and the mechanical strength and expansion / contraction of the resulting composition. From the viewpoint of improving the properties, preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and from the viewpoint of operability during production, Is 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

  The content of fine cellulose fibers or a modified product thereof in the rubber composition of the present invention is preferably 1% by mass or more, more preferably 2% by mass from the viewpoint of improving the mechanical strength and stretchability of the resulting composition. Or more, more preferably 3% by mass or more, further preferably 4% by mass or more, further preferably 5% by mass or more, and from the viewpoint of operability during production, preferably 15% by mass or less, more preferably 10% by mass. Hereinafter, it is more preferably 8% by mass or less.

  The content of the plasticizer in the rubber composition of the present invention is preferably 1 mass with respect to 100 parts by mass of rubber from the viewpoint of improving the strength and moldability of the resulting composition at high and normal temperatures. Part or more, more preferably 3 parts by weight or more, more preferably 5 parts by weight or more, more preferably 8 parts by weight or more, preferably from the viewpoint of containing a fine cellulose fiber composite and maintaining mechanical strength. 50 parts by mass or less, more preferably 40 parts by mass or less, further preferably 35 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 25 parts by mass or less, still more preferably 20 parts by mass or less, and further preferably 15 parts by mass. Or less.

  The content of the plasticizer in the rubber composition of the present invention is preferably 1% by mass or more, and more preferably 3% by mass from the viewpoint of improving strength at high temperature and normal temperature of the resulting composition and moldability. % Or more, more preferably 5% by mass or more, from the viewpoint of containing a fine cellulose fiber composite and maintaining mechanical strength, preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably. It is 35% by mass or less, more preferably 30% by mass or less, further preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and further preferably 10% by mass or less.

[Additive]
In the rubber composition of the present invention, a reinforcing filler, a vulcanizing agent, a vulcanization accelerator, a vulcanization retarder, an aging agent, and the like, which are usually used in the rubber industry, as long as the object of the present invention is not impaired. Various conventional additives for tires such as inhibitor, process oil, vegetable oil and fat, scorch inhibitor, zinc white, stearic acid, magnesium oxide, wax, etc. be able to.

  As the reinforcing filler, carbon black, silica or the like is preferably used. As the carbon black, for example, channel black; SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF Furnace black such as N-234; Thermal black such as FT and MT; Acetylene black and the like. Carbon black may be composed of a single species or a plurality of species.

  Examples of the vulcanizing agent include sulfur, sulfur compounds, oximes, nitroso compounds, polyamines, organic peroxides, and the like. Only one kind of vulcanizing agent may be used, or a plurality of kinds may be used in combination.

  Examples of the vulcanization accelerator include guanidine, aldehyde-amine, aldehyde-ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, xanthate, and the like. Only one kind of vulcanization accelerator may be used, or a plurality of kinds may be used in combination.

  Examples of the vulcanization retarder include aromatic organic acids such as salicylic acid, phthalic anhydride, benzoic acid, N-nitrosodiphenylamine, N-nitroso-2,2,4-trimethyl-1,2-dihydroquinone, N- And nitroso compounds such as nitrosophenyl-β-naphthylamine. Only one kind of vulcanization retarder may be used, or a plurality of kinds may be used in combination.

  Examples of the anti-aging agent include amine-based, quinoline-based, hydroquinone derivatives, monophenol-based, polyphenol-based, thiobisphenol-based, hindered phenol-based, and phosphite-based compounds. Only one kind of anti-aging agent may be used, or a plurality of kinds may be used in combination.

  Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Only one kind of process oil may be used, or a plurality of kinds may be used in combination.

  Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, fallen raw oil, wax, rosin, and pine oil. Only one kind of vegetable oil may be used, or a plurality of kinds may be used in combination.

The rubber composition of the present invention can be prepared without particular limitation as long as it contains rubber, the fine cellulose fiber or a modified product thereof, and a plasticizer. However, when cellulose fiber is directly mixed with rubber, Because it is easy to agglomerate, the dispersibility of cellulose fibers is improved by dispersing fine cellulose fibers or a modified product thereof in a plasticizer that is highly miscible with rubber and then mixing with rubber. It is considered that a rubber composition having improved maintenance and stretchability can be obtained. Therefore, this invention also provides the manufacturing method containing the following process (I) and (II) as a manufacturing method of the rubber composition of this invention.
Step (I): A step of mixing a plasticizer and a dispersion of fine cellulose fibers or a modified product thereof, and then removing a part of the solvent to obtain a mixture of fine cellulose fibers or a modified product / plasticizer thereof ( II): Step of mixing the mixture obtained in the step (I) with rubber

  The mixing mass ratio of the plasticizer and the fine cellulose fiber or the modified product thereof in the step (I) is preferably 1 to 200 parts by mass of the fine cellulose fiber or the modified product with respect to 100 parts by mass of the plasticizer. It is more preferable to mix -100 mass parts.

  As a mixing method, a mixing method using a homogenizer is preferable from the viewpoint of promoting dispersion by applying a high shear force and pressure, but a method using a propeller type stirring device, a rotary stirring device, an electromagnetic stirring device, or the like can also be used.

  The mixing temperature is preferably 10 ° C to 50 ° C, more preferably 15 ° C to 30 ° C, from the viewpoint of handling.

  The resulting mixture is then dried and a portion of the solvent is removed to obtain a fine cellulose fiber or its modified / plasticizer mixture. Drying does not need to be performed until the solvent is completely removed, and may contain a solvent as long as the object of the present invention is not impaired. As a drying method, a method of removing the solvent by a water squeeze roll and then drying in a heating oven, a method of drying by a shock wave by pulse combustion, a freeze drying method, a spray drying method, a vacuum drying method, or the like can be employed.

  In step (II), the mixture (fine cellulose fiber or a modified product / plasticizer thereof) obtained in step (I) is mixed with rubber. The temperature in that case is 10-300 degreeC normally, Preferably it is 20-200 degreeC. The same method as the mixing method in the step (I) can be used as the mixing method in the step (II). In the step (II), the above-mentioned additive is dispersed in advance in the mixture obtained in the step (I) and then mixed with rubber.

  The rubber composition of the present invention can be used after being kneaded by a known method in addition to the above method to be a composition, vulcanized or crosslinked. For example, it can be kneaded using a kneader such as an open kneader such as a roll or a closed kneader such as a Banbury mixer, vulcanized after molding, and applied to various rubber products.

  The rubber composition of the present invention has good processability and good strength at high temperatures, and also has excellent stretchability, so that it can be used in various applications such as household goods, home appliance parts, and automobile parts. However, it can be suitably used for automobile applications.

  Hereinafter, the present invention will be specifically described with reference to examples. Note that this example is merely illustrative of the present invention and is not meant to be limiting. The parts in the examples are parts by mass unless otherwise specified. “Normal pressure” indicates 101.3 kPa, and “normal temperature” indicates 25 ° C.

[Average fiber diameter of fine cellulose fiber]
Water is added to fine cellulose fibers to prepare a dispersion having a concentration of 0.0001% by mass, and the dispersion is dropped onto mica (mica) and dried, and an atomic force microscope ( Using AFM, Nanoscope III Tapping mode AFM, manufactured by Digital Instrument, and using Probe Probe (NCH) manufactured by Nanosensors, the fiber height of the cellulose fiber in the observed sample is measured. In that case, in the microscope image which can confirm this cellulose fiber, five or more fine cellulose fibers are extracted, and an average fiber diameter is calculated from those fiber heights.

[Carboxy group content of fine cellulose fiber and fine cellulose fiber composite]
Take a fine cellulose fiber or a fine cellulose fiber composite with a dry mass of 0.5 g in a 100 mL beaker, add ion-exchanged water or a mixed solvent of methanol / water = 2/1 to make a total of 55 mL, and 0.01M sodium chloride aqueous solution there 5 mL is added to prepare a dispersion, and the dispersion is stirred until the fine cellulose fiber or fine cellulose fiber composite is sufficiently dispersed. 0.1M hydrochloric acid was added to this dispersion to adjust the pH to 2.5-3, and 0.05M sodium hydroxide aqueous solution was added using an automatic titrator (trade name “AUT-50” manufactured by Toa DKK Corporation). The solution is dropped into the dispersion under the condition of a waiting time of 60 seconds, and the conductivity and pH values are measured every minute, and the measurement is continued until the pH is about 11 to obtain a conductivity curve. From this conductivity curve, the sodium hydroxide titration amount is obtained, and the carboxy group content of the fine cellulose fiber or fine cellulose fiber composite is calculated by the following formula.
Carboxy group content (mmol / g) = sodium hydroxide titration × sodium hydroxide aqueous solution concentration (0.05 M) / mass of cellulose fiber (0.5 g)

Preparation Example 1 of Fine Cellulose Fiber (Dispersion of carboxy group-containing fine cellulose fiber (long fiber) obtained by allowing N-oxyl compound to act on natural cellulose)
Conifer bleached kraft pulp (Fletcher Challenge Canada, trade name “Machenzie”, CSF 650 ml) was used as natural cellulose fiber. As TEMPO, a commercially available product (ALDRICH, Free radical, 98% by mass) was used. As sodium hypochlorite, a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.) was used. A commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.) was used as sodium bromide.

  First, 100 g of bleached kraft pulp fiber of coniferous trees was sufficiently stirred with 9900 g of ion-exchanged water, and then TEMPO 1.25 mass%, sodium bromide 12.5 mass%, sodium hypochlorite 28 with respect to 100 g of the pulp mass. .4% by weight was added in this order. Using a pH stud, 0.5 M sodium hydroxide was added dropwise to maintain the pH at 10.5. After carrying out the reaction for 120 minutes (20 ° C.), dropping of sodium hydroxide was stopped to obtain oxidized pulp. The oxidized pulp obtained using ion-exchanged water was sufficiently washed and then dehydrated. Thereafter, 3.9 g of oxidized pulp and 296.1 g of ion-exchanged water were refined twice at 245 MPa using a high-pressure homogenizer (manufactured by Sugino Machine Co., Ltd., Starburst Lab HJP-2 5005), and carboxy group-containing fine cellulose fibers A dispersion (solid content concentration 1.3% by mass) was obtained. This fine cellulose fiber had an average fiber diameter of 3.3 nm and a carboxy group content of 1.4 mmol / g.

Preparation Example 2 of Fine Cellulose Fiber (Carboxy Group-Containing Fine Cellulose Fiber Dispersion Obtained by Acid Type Treatment)
Add 4088.75 g of the carboxy group-containing fine cellulose fiber dispersion obtained in Preparation Example 1 of fine cellulose fibers (solid content concentration: 1.3% by mass) and 4085 g of ion-exchanged water to a beaker to obtain a 0.5% by mass aqueous solution, The mixture was stirred with a mechanical stirrer at room temperature (25 ° C.) for 30 minutes. Subsequently, 245 g of 1M hydrochloric acid aqueous solution was added and reacted at room temperature for 1 hour. After completion of the reaction, the solution was reprecipitated with acetone, filtered, and then washed with acetone / ion exchange water to remove hydrochloric acid and salts. Finally, acetone was added and filtered to obtain an acetone-containing acid-type cellulose fiber dispersion (solid content concentration: 5.0% by mass) in which carboxy group-containing fine cellulose fibers were swollen in acetone. After completion of the reaction, the mixture was filtered, and then washed with ion exchange water to remove hydrochloric acid and salts. After solvent substitution with acetone, the solvent substitution with dimethylformamide (DMF) was performed to obtain a DMF-containing acid-type cellulose fiber dispersion (solid content concentration 5.0% by mass) in a state where the carboxy group-containing fine cellulose fibers were swollen. This fine cellulose fiber had an average fiber diameter of 3.3 nm and a carboxy group content of 1.4 mmol / g.

Production Examples 1 to 4 of an amine having an EO / PO copolymer part (EOPO amine)
132 g (1 mol) of propylene glycol tertiary butyl ether was charged into a 1 L autoclave, heated to 75 ° C., added with 1.2 g of flaky potassium hydroxide, and stirred until dissolved. Next, after reacting the amounts of ethylene oxide (EO) and propylene oxide (PO) shown in Table 1 at 110 ° C. and 0.34 MPa, Magnesol 30/40 (magnesium silicate, manufactured by Dallas Group) 7.14 g The resulting product was neutralized at 95 ° C., and 0.16 g of ditertiary butyl-p-cresol was added to and mixed with the resulting product, followed by filtration to obtain a polyether as an EO / PO copolymer. Obtained.

On the other hand, a polyether (8.) obtained in a 1.250 mL tubular reaction vessel filled with a catalyst of nickel oxide / copper oxide / chromium oxide (molar ratio: 75/23/2) (Wako Pure Chemical Industries, Ltd.). 4 mL / min), ammonia (12.6 mL / min), and hydrogen (0.8 mL / min) were supplied. The container temperature was maintained at 190 ° C. and the pressure was maintained at 14 MPa. The crude effluent from the vessel was distilled off at 70 ° C. and 3.5 mmHg for 30 minutes. 200 g of the obtained aminated polyether and 93.6 g of 15% hydrochloric acid aqueous solution were charged into a flask, and the reaction mixture was heated at 100 ° C. for 3.75 hours to cleave tertiary butyl ether with an acid. The product was neutralized with 144 g of a 15% aqueous potassium hydroxide solution. Next, the neutralized product was distilled off under reduced pressure at 112 ° C. for 1 hour and filtered to obtain a monoamine (EOPO amine) having an EO / PO copolymer part represented by the above formula (i). In the obtained monoamine, the EO / PO copolymer part and the amine are directly bonded, and R ₁ in the formula (i) is a hydrogen atom.

The molecular weight of the amine copolymerization part is, for example, in the case of the amine of Production Example 1,
44 [EO molecular weight (44.03) × EO addition moles (1)] + 522 [PO molecular weight (58.04) × PO addition moles (9)] + 58.04 [PO partial molecular weight in starting material (propylene glycol) )] = 624
Was rounded to 600.

Production Example 1 of Fine Cellulose Fiber Composite (Examples 1-4, 7-9)
A beaker equipped with a magnetic stirrer and a stirrer was charged with 35 g of carboxy group-containing fine cellulose fiber dispersion (solid content concentration 5.0% by mass) obtained in Preparation Example 2 of fine cellulose fibers. Subsequently, 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4, which is a condensing agent, corresponds to the amount of amine group shown in Table 2 for the types of amines shown in Table 2. -Methylmorpholinium chloride (DMT-MM) in an amount corresponding to 2.2 to 4 mol with respect to 1 mol of carboxy groups of fine cellulose fibers, and N-methylmorpholine (NMM) with respect to 1 mol of carboxy groups of fine cellulose fibers. An amount corresponding to 1.2 to 3 mol was charged and dissolved in 300 g of DMF, and the reaction solution was reacted at room temperature (25 ° C.) for 14 hours. After completion of the reaction, filtration, washing with ion-exchanged water, removing DMT-MM salt, washing with acetone and solvent substitution, the types of amines shown in Table 2 are linked to fine cellulose fibers via amide bonds. A fine cellulose fiber composite was obtained. In addition, amines other than EOPO amine (C3 amine: propylamine, C12 amine: dodecylamine, C18 amine: octadecylamine) were purchased and used.

Production Example 2 of Fine Cellulose Fiber Composite (Example 5)
A beaker equipped with a magnetic stirrer and a stirrer was charged with 35 g of carboxy group-containing fine cellulose fiber dispersion (solid content concentration 5.0% by mass) obtained in Preparation Example 2 of fine cellulose fibers. Subsequently, an amine of the type shown in Table 2 was charged in an amount corresponding to the amine group amount shown in Table 2, dissolved in 300 g of ion-exchanged water, and the reaction solution was reacted at room temperature (25 ° C.) for 14 hours. After completion of the reaction, the mixture is filtered, washed with ion-exchanged water, washed with acetone, and solvent-replaced to obtain a fine cellulose fiber composite in which amines of the types shown in Table 2 are linked to fine cellulose fibers via ionic bonds. It was.

Production Example 3 of Fine Cellulose Fiber Composite (Example 10)
<Phenyl group modification by amide bond>
A beaker equipped with a magnetic stirrer and a stirrer was charged with 35 g of carboxy group-containing fine cellulose fiber dispersion (solid content concentration 5.0% by mass) obtained in Preparation Example 2 of fine cellulose fibers. Subsequently, aniline is an amount corresponding to the amount of amine groups shown in Table 2, DMT-MM as a condensing agent is an amount corresponding to 2.5 mol with respect to 1 mol of carboxy groups of the fine cellulose fiber, and NMM is carboxy of the fine cellulose fiber. An amount corresponding to 1.4 mol was charged per 1 mol of the group, dissolved in 300 g of DMF, and the reaction solution was reacted at room temperature (25 ° C.) for 14 hours. After completion of the reaction, the mixture is filtered, washed with ion-exchanged water, DMT-MM salt is removed, washed with acetone, and solvent substitution is performed. Fine cellulose fiber composites in which phenyl groups are connected to fine cellulose fibers via amide bonds Got the body.
<Modification of EO / PO copolymer part by ionic bond>
An amount of EOPO amine shown in Table 2 corresponding to the amine group amount shown in Table 2 was charged into 10 g of the obtained fine cellulose fiber composite dispersion (solid content concentration 5.0% by mass), and in 100 g of ion-exchanged water. The reaction solution was reacted at room temperature (25 ° C.) for 14 hours. After completion of the reaction, the mixture is filtered, washed with ion-exchanged water, washed with acetone, and solvent-substituted, so that the fine cellulose fiber has a phenyl group via an amide bond and an EO / PO copolymer part via an ionic bond. A linked fine cellulose fiber composite was obtained.

Examples 1 to 10 and Comparative Example 1
<Production of a mixture of a plasticizer and fine cellulose fibers or a modified product thereof>
To the dispersion of the fine cellulose fiber composite produced in Production Examples 1 to 3 of the fine cellulose fiber composite or the dispersion of the fine cellulose fiber produced in Preparation Example 2 of the fine cellulose fiber, a plasticizer (Dibasic Sebacate 2 -Ethylhexyl, manufactured by Taoka Chemical Co., Ltd.) was added so as to have the blending amount shown in Table 2, and stirred for 2 minutes with an ultrasonic homogenizer (US-300E, manufactured by Nippon Seiki Seisakusho Co., Ltd.). , Starburst Lab HJP-2 5005) was subjected to fine treatment at 100 MPa for 2 passes and 150 MPa for 1 pass (25 ° C.). The homogeneous mixture was poured into a glass petri dish and vacuum-dried at 40 ° C. for 2 days to produce a mixture of a plasticizer and fine cellulose fibers or a modified product thereof.

<Preparation of rubber composition>
To 100 parts by mass of the rubber component, a mixture of the plasticizer and fine cellulose fiber obtained as described above or a modified product thereof mixed with the additives shown in Table 2 according to the formulation of Table 2 is added, A rubber composition was prepared by kneading using an ordinary Banbury mixer.

In addition, the raw material in Table 2 is as follows.
[Rubber]
Chloroprene rubber: Denka Chloroprene DCR-36, natural rubber (NR) manufactured by Denki Kagaku Kogyo Co., Ltd .: RSS # 3, manufactured by Takehara Rubber Co., Ltd. [plasticizer]
Plasticizer: Di-2-ethylhexyl sebacate, DOS, manufactured by Taoka Chemical Co., Ltd. [Additives]
Zinc flower: Zinc oxide, Zinc flower No. 3, Stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd .: Industrial stearic acid, Magnesium oxide manufactured by Kao Co., Ltd .: Kyowa Mag 150, Kyowa Chemical Industry Co., Ltd. wax: Microcrystalline wax, Seiko Chemical Co., Ltd. Agent: Antigen 6C, Sulfur manufactured by Sumitomo Chemical Co., Ltd .: Vulcanizing agent, 5% oil-treated sulfur, Noxeller TS manufactured by Hosoi Chemical Co., Ltd .: Vulcanization accelerator, Sunseller DM-G manufactured by Ouchi Shinsei Chemical Co., Ltd .: Vulcanization accelerator Sanshin Chemical Industries, Ltd. Vulcanization retarder: Retarder CTP, Toray Fine Chemicals

About the obtained rubber composition, vulcanized rubber was produced by the following methods, respectively, and evaluated according to the methods of Test Examples 1 and 2 below. The results are shown in Table 2.
(Preparation of Vulcanized Rubber) Each rubber composition was filled in a 20 cm × 20 cm mold and heated at 150 ° C. for 30 minutes to prepare a vulcanized rubber.

Test example 1 (storage modulus)
Using a dynamic viscoelastic device (trade name “DMS6100” manufactured by SII), a strip-shaped sample having a width of 5 mm and a length of 20 mm was subjected to a frequency of 1 Hz in a nitrogen atmosphere at a frequency of 1 Hz for 1 minute. The temperature was increased at a rate of 2 ° C. and measured in the tensile mode. The storage elastic modulus (E ′) was 100 ° C. and 20 ° C. The larger the value of the storage elastic modulus, the better the mechanical strength. The numerical value at 20 ° C is preferably 70 MPa or more, and the mechanical strength is excellent, and the value at 100 ° C is preferably 8.2 MPa or more. In some cases, the strength at high temperature is maintained.

Test Example 2 (Elongation at break)
Using a tensile and compression tester (manufactured by SHIMADZU, trade name “Autograph AGS-X”), the molded body was measured by a tensile elongation test at break according to JIS K7113. A sample punched with a No. 2 dumbbell was set at a fulcrum distance of 80 mm and measured at a crosshead speed of 10 mm / min. When the elongation at break is 50% or more, the stretchability is excellent, and the higher the value, the better the stretchability.

  As is clear from the results shown in Table 2, the rubber compositions obtained in the examples have higher storage elastic modulus at 20 ° C. and 100 ° C. than the rubber compositions of the comparative examples, and maintain the strength even at high temperatures. I understand that Also, it can be seen that the elongation at break is high and the stretchability is excellent.

  The rubber composition of the present invention can be suitably used as machine tool parts, home appliance parts, automobile parts and the like.

Claims (5)

  A rubber composition comprising rubber, fine cellulose fibers or a modified product thereof, and a plasticizer, wherein the fine cellulose fibers have an average fiber diameter of 0.1 nm or more and 200 nm or less, and constitute the fine cellulose fibers A rubber composition in which cellulose has a carboxy group.   The rubber composition according to claim 1, wherein the modified product of the fine cellulose fiber is obtained by introducing a hydrocarbon group or an ethylene oxide / propylene oxide (EO / PO) copolymer part into a carboxy group of the fine cellulose fiber.   The rubber composition according to claim 2, wherein the introduction of the hydrocarbon group or the ethylene oxide / propylene oxide (EO / PO) copolymerized part is via an amide bond and / or an ionic bond.   The rubber composition according to any one of claims 1 to 3, wherein a content of the fine cellulose fiber or a modified product thereof is 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber. The manufacturing method of the rubber composition in any one of Claims 1-4 which has following process (I) and (II).
Step (I): A step of mixing a plasticizer and a dispersion of fine cellulose fibers or a modified product thereof, and then removing a part of the solvent to obtain a mixture of fine cellulose fibers or a modified product / plasticizer thereof ( II): Step of mixing the mixture obtained in the step (I) with rubber