JP6944451B2 - Masterbatch manufacturing method - Google Patents

Description

The present invention relates to a method for producing a masterbatch containing a rubber component and a cellulosic fiber.

Rubber compositions containing rubber and cellulosic fibers are known to have excellent mechanical strength. For example, Patent Document 1 describes a master batch of rubber / short fibers obtained by stirring and mixing cellulose short fibers having an average fiber diameter of less than 0.5 μm and rubber latex. According to the document, a rubber in which short fibers having an average fiber diameter of less than 0.5 μm are uniformly dispersed in rubber by mixing and drying a dispersion liquid in which short fibers are fibrillated in water and rubber latex. It is said that a rubber composition having an excellent balance between rubber reinforcing property and fatigue resistance can be produced from a master batch of short fibers. However, in general, rubber and cellulosic fibers have low compatibility, so that sufficient strength of the rubber composition has not been obtained. Therefore, it has been studied to use a coupling agent to improve compatibility and to introduce a long-chain alkyl group into a cellulose fiber (for example, Patent Documents 2 and 3). However, there is a problem that the reagents used for these are expensive. Further, the above method has a problem that the reaction rate is low and a sufficient strength improving effect cannot be obtained.

Japanese Unexamined Patent Publication No. 2006-206864 Japanese Unexamined Patent Publication No. 2009-191198 Japanese Unexamined Patent Publication No. 2014-125607

An object of the present invention is to provide a masterbatch containing a rubber component and a cellulosic fiber, which provides a rubber composition having excellent mechanical properties.

The inventor has found that the compatibility between the rubber component and the cellulosic fiber can be improved by heating the mixture, and completed the present invention. That is, the following invention solves the above-mentioned problems.
(1) (a) a step of obtaining a mixture containing a rubber component and a cellulosic fiber, and (b) a step of heating the mixture at 100 to 300 ° C. for 5 to 600 minutes.
Masterbatch manufacturing method.
(2) The step (a) is carried out using the dispersion liquid or solution of the rubber component or the dispersion liquid of the cellulosic fiber.
The production method according to (1), further comprising a step of removing the dispersion medium or solvent before the step (b).
(3) The production method according to (1) or (2), wherein the cellulosic fiber is a chemically modified cellulosic fiber.
(4) The production method according to any one of (1) to (3), wherein the length-weighted average fiber length of the cellulosic fiber is 50 to 2000 nm, and the length-weighted average fiber diameter is 2 to 500 nm.
(5) The rubber component includes an acrylonitrile-butadiene rubber (NBR) polymer, a natural rubber (NR) polymer, a styrene-butadiene rubber (SBR) polymer, or a chloroprene rubber (CR) polymer (1) to (4). The manufacturing method according to any one of.
(6) A method for producing an uncrosslinked rubber composition, which comprises a step of preparing a masterbatch by the method according to (1) to (5) above, and a step of mixing a crosslinking agent with the masterbatch.
(7) A method for producing a rubber composition, which comprises a step of cross-linking the uncrosslinked rubber composition according to (6) above.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a masterbatch containing a rubber component and a cellulosic fiber, which provides a rubber composition having excellent mechanical properties.

Hereinafter, the present invention will be described in detail. In the present invention, "X to Y" includes its fractional values, that is, X and Y.

1. 1. Method for Producing Masterbatch In the method for producing a masterbatch of the present invention, (a) a step of obtaining a mixture containing a rubber component and a cellulosic fiber, and (b) heating the mixture at 100 to 300 ° C. for 5 to 600 minutes. Including the process. Generally, the definition of a masterbatch is diverse, but in the present invention, a masterbatch is a composition containing a rubber component and a cellulosic fiber but not a cross-linking agent. The rubber composition refers to an uncrosslinked rubber composition containing a masterbatch and a crosslinking agent, or a crosslinked rubber composition obtained by crosslinking the uncrosslinked rubber composition.

(1) Step (a)
In this step, the rubber component and the cellulosic fiber are mixed. Mixing can be carried out using a known device such as a homomixer, a homogenizer, or a propeller stirrer. The mixing temperature is not limited, but room temperature (20 to 30 ° C.) is preferable. The mixing time may also be adjusted as appropriate.

The mixing ratio in this step is adjusted so that the ratio of the rubber composition described later can be achieved. For example, the cellulosic fiber is set to 0.1 to 100 parts by weight with respect to 100 parts by weight of the rubber component. Is preferable.

1) Rubber component A rubber component is a raw material for rubber that is crosslinked to form rubber. There are a rubber component for natural rubber and a rubber component for synthetic rubber, but in the present invention, either of them may be used, or both may be combined. For convenience, a rubber component for natural rubber or the like is referred to as a "natural rubber polymer" or the like.
Natural rubber (NR) polymers include natural rubber polymers in the narrow sense that are not chemically modified; chemically modified natural rubber polymers such as chlorinated natural rubber polymers, chlorosulfonated natural rubber polymers, and epoxidized natural rubber polymers; hydrogenated natural Rubber polymer; Examples thereof include deproteinized natural rubber polymer. Examples of the synthetic rubber polymer include butadiene rubber (BR) polymer, styrene-butadiene copolymer rubber (SBR) polymer, isoprene rubber (IR) polymer, acrylonitrile-butadiene rubber (NBR) polymer, chloroprene rubber (CR) polymer, and styrene. Diene-based rubber polymers such as -isoprene copolymer rubber polymer, styrene-isoprene-butadiene copolymer rubber polymer, isoprene-butadiene copolymer rubber polymer; butyl rubber (IIR) polymer, ethylene-propylene rubber (EPM, EPDM) polymer , Acrylic rubber (ACM) polymer, epichlorohydrin rubber (CO, ECO) polymer, fluororubber (FKM) polymer, silicone rubber (Q) polymer, urethane rubber (U) polymer, chlorosulfonated polyethylene (CSM) polymer, etc. Examples include non-diene rubber polymers. Only one kind of these rubber polymers may be used, or a plurality of kinds thereof may be used in combination. Among these, NBR polymer, NR polymer, SBR polymer, and chloroprene rubber (CR) polymer are particularly preferable.

The rubber component may be used for mixing as it is, or may be used for mixing as a dispersion liquid (latex) in which the rubber component is dispersed in a dispersion medium or a solution dissolved in a solvent. Examples of the dispersion medium and the solvent (hereinafter, collectively referred to as “liquid medium”) include water and an organic solvent. The amount of the liquid medium is preferably 10 to 1000 parts by weight with respect to 100 parts by weight of the rubber component.

2) Cellulose-based fiber As the cellulosic fiber, a cellulosic fiber having a fiber diameter on the order of micron or a cellulose nanofiber having a fiber diameter on the nano-order obtained by chemically modifying the cellulosic fiber as necessary and then defibrating the fiber is used. can.

Cellulose fibers are not particularly limited, and examples thereof include those derived from plants, animals (for example, ascidians), algae, microorganisms (for example, acetobacter), and microbial products. Plant-derived materials include, for example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleached kraft pulp (NBKP), broadleaf unbleached kraft pulp (NBKP). LUKP), broadleaf bleached kraft pulp (LBKP), conifer unbleached sulphite pulp (NUSP), conifer bleached sulphite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, used paper, etc.). The cellulose raw material used in the present invention may be any one or a combination of these, but is preferably a cellulosic fiber derived from a plant or a microorganism, and more preferably a cellulose fiber derived from a plant.

The average fiber diameter of the cellulose fibers is not particularly limited, but is about 30 to 60 μm in the case of softwood kraft pulp, which is a general pulp, and about 10 to 30 μm in the case of hardwood kraft pulp. In the case of other pulps, the average fiber diameter after undergoing general purification is about 50 μm. For example, when a raw material obtained by purifying a chip or the like having a size of several cm is used, it is preferable to perform mechanical treatment with a dissociator such as a refiner or a beater to adjust the average fiber diameter to about 50 μm.

The average fiber diameter of the cellulose nanofibers is usually about 2 to 500 nm in terms of the length-weighted average fiber diameter, but is preferably 2 to 50 nm. The average fiber length is preferably 50 to 2000 nm in terms of length-weighted average fiber length. Atomic force microscope (AFM) or transmission electron microscope (TEM) is used for the length-weighted average fiber diameter and the length-weighted average fiber length (hereinafter, also simply referred to as "average fiber diameter" and "average fiber length"). It is obtained by observing each fiber. The average aspect ratio of cellulose nanofibers is usually 10 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following formula.
Average aspect ratio = average fiber length / average fiber diameter The following describes a method for producing cellulose nanofibers. For convenience, cellulose fibers, which are raw materials for cellulose nanofibers, are also referred to as "cellulose raw materials".

[Degeneration]
The cellulose raw material has three hydroxyl groups per glucose unit and can be subjected to various chemical denaturations. In the present invention, both a chemically modified cellulose raw material and a non-chemically modified cellulose raw material can be used. However, when a chemically modified cellulose raw material is used, the finer fibers are sufficiently refined to obtain cellulose nanofibers having a uniform fiber length and fiber diameter, so that a sufficient reinforcing effect is exhibited when composited with rubber. obtain. Therefore, a chemically modified cellulose raw material is preferable. Examples of chemical denaturation include oxidation, etherification, phosphorylation, esterification, silane coupling, fluorination, and cationization. Of these, oxidation (carboxylation), etherification, cationization, and esterification are preferable, and these will be described below.

[Oxidation]
The amount of carboxyl groups in the oxidized cellulose or cellulose nanofibers obtained by this treatment is preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, still more preferably 1. It is 0 mmol / g or more. The upper limit of the amount is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, still more preferably 2.0 mmol / g or less. Therefore, the amount is preferably 0.5 to 3.0 mmol / g, more preferably 0.8 to 2.5 mmol / g, and even more preferably 1.0 to 2.0 mmol / g.

The oxidation method is not particularly limited, but as an example, the cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromide, iodide and a mixture thereof. There is a way to do it. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of cellulose is selectively oxidized to generate a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by weight or less.

The N-oxyl compound is a compound capable of generating a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it is a compound that promotes the desired oxidation reaction. The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 mmol or more is preferable, and 0.02 mmol or more is more preferable with respect to 1 g of cellulose that has been completely dried. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and even more preferably 0.02 to 0.5 mmol with respect to 1 g of the dry cellulose.

The bromide is a compound containing bromine, and examples thereof include alkali metals bromide that can be dissociated and ionized in water, such as sodium bromide. Further, the iodide is a compound containing iodine, and examples thereof include an alkali metal iodide. The amount of bromide or iodide used can be selected within the range in which the oxidation reaction can be promoted. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, based on 1 g of dry cellulose. The upper limit of the amount is preferably 100 mmol or less, more preferably 10 mmol or less, and further preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, still more preferably 0.5 to 5 mmol, relative to 1 g of dry cellulose.

The oxidizing agent is not particularly limited, and examples thereof include halogens, hypohalogenic acids, subhalogenic acids, perhalogenic acids, salts thereof, halogen oxides, and peroxides. Among them, hypochlorous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable because it is inexpensive and has a small environmental load. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, still more preferably 3 mmol or more, based on 1 g of the dry cellulose. The upper limit of the amount is preferably 500 mmol or less, more preferably 50 mmol or less, still more preferably 25 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, further preferably 1 to 25 mmol, and particularly preferably 3 to 10 mmol with respect to 1 g of the dry cellulose. When an N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more with respect to 1 mol of the N-oxyl compound, and the upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C. or higher, more preferably 15 ° C. or higher. The upper limit of the temperature is preferably 40 ° C. or lower, more preferably 30 ° C. or lower. Therefore, the reaction temperature is preferably 4 to 40 ° C, and may be about 15 to 30 ° C, that is, room temperature. The pH of the reaction solution is preferably 8 or more, more preferably 10 or more. The upper limit of pH is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11. Usually, the pH of the reaction solution tends to decrease because a carboxyl group is generated in the cellulose as the oxidation reaction progresses. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution in the above range. Water is preferable as the reaction medium for oxidation because it is easy to handle and side reactions are unlikely to occur.

The reaction time in oxidation can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours or more, and the upper limit thereof is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in oxidation is usually about 0.5 to 6 hours, for example, about 0.5 to 4 hours. Oxidation may be carried out in two or more steps. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt produced as a by-product in the first-stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is ozonolysis. By this oxidation reaction, the hydroxyl groups at at least the 2nd and 6th positions of the glucopyranose ring constituting the cellulose are oxidized, and the cellulose chain is decomposed. Ozone treatment is usually carried out by bringing a gas containing ozone into contact with a cellulose raw material. The ozone concentration in the gas ^{is preferably 50 g / m 3} or more. The upper limit is ^{preferably 250 g / m 3} or less, and ^{more preferably 220 g / m 3} or less. Therefore, the ozone concentration in the gas is preferably 50 to 250 g / ^{m 3,} more preferably 50~220g / ^{m 3.} The amount of ozone added is preferably 0.1 part by weight or more, and more preferably 5% by weight or more, based on 100% by weight of the solid content of the cellulose raw material. The upper limit of the amount of ozone added is usually 30% by weight or less. Therefore, the amount of ozone added is preferably 0.1 to 30% by weight, more preferably 5 to 30% by weight, based on 100% by weight of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0 ° C. or higher, preferably 20 ° C. or higher, and the upper limit is usually 50 ° C. or lower. Therefore, the ozone treatment temperature is preferably 0 to 50 ° C, more preferably 20 to 50 ° C. The ozone treatment time is usually 1 minute or more, preferably 30 minutes or more, and the upper limit is usually 360 minutes or less. Therefore, the ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes. When the ozone treatment conditions are within the above ranges, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of the oxidized cellulose becomes good.

The ozone-treated cellulose may be further subjected to an additional oxidation treatment using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfate, and peracetic acid. Examples of the method of the additional oxidation treatment include a method of dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the oxidizing agent solution. The amount of carboxyl group, carboxylate group, and aldehyde group contained in the cellulose oxide nanofiber can be adjusted by controlling the oxidation conditions such as the amount of the oxidizing agent added and the reaction time.

An example of a method for measuring the amount of carboxyl groups will be described below. Prepare 60 mL of a 0.5 wt% slurry (aqueous dispersion) of cellulose oxide, add a 0.1 M hydrochloric acid aqueous solution to adjust the pH to 2.5, and then add a 0.05 N sodium hydroxide aqueous solution to bring the pH to 11. Measure the electrical conductivity until it becomes. It can be calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of a weak acid in which the change in electrical conductivity is gradual, using the following formula.
Carboxyl group amount [mmol / g cellulose oxide or cellulose nanofiber] = a [mL] x 0.05 / cellulose oxide weight [g]

[Aetherization]
As etherification, carboxymethyl (ether), methyl (ether), ethyl (ether), cyanoethyl (ether), hydroxyethyl (ether), hydroxypropyl (ether), ethyl hydroxyethyl (ether) And hydroxypropylmethyl (ether) conversion. The method of carboxymethylation will be described below as an example.

The degree of carboxymethyl substitution per anhydrous glucose unit in the carboxymethylated cellulose or cellulose nanofiber obtained by carboxymethylation is preferably 0.01 or more, more preferably 0.05 or more, and preferably 0.10 or more. More preferred. The upper limit of the degree of substitution is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less. Therefore, the degree of carboxymethyl group substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and even more preferably 0.10 to 0.30.

The carboxymethylation method is not particularly limited, and examples thereof include a method in which a cellulose raw material as a bottoming raw material is marcelled and then etherified. A solvent is usually used for the reaction. Examples of the solvent include water, alcohol (for example, lower alcohol) and a mixed solvent thereof. Examples of the lower alcohol include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutanol, and tertiary butanol. The mixing ratio of the lower alcohol in the mixed solvent is usually 60% by weight or more or 95% by weight or less, preferably 60 to 95% by weight. The amount of solvent is usually 3 times by weight with respect to the cellulose raw material. The upper limit of the amount is not particularly limited, but is 20 times by weight. Therefore, the amount of the solvent is preferably 3 to 20 times by weight.

Mercerization is usually carried out by mixing a bottoming material and a mercerizing agent. Examples of the mercerizing agent include alkali metals hydroxide such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent used is preferably 0.5 times mol or more, more preferably 1.0 mol or more, and further preferably 1.5 times mol or more per anhydrous glucose residue of the bottoming material. The upper limit of the amount is usually 20 times or less, preferably 10 times or less, more preferably 5 times or less, and therefore, the amount of the mercerizing agent used is preferably 0.5 to 20 times by mole, 1.0. 10-fold molars are more preferred, and 1.5-5-fold moles are even more preferred.

The reaction temperature for mercerization is usually 0 ° C. or higher, preferably 10 ° C. or higher, and the upper limit is usually 70 ° C. or lower, preferably 60 ° C. or lower. Therefore, the reaction temperature is usually 0 to 70 ° C, preferably 10 to 60 ° C. The reaction time is usually 15 minutes or longer, preferably 30 minutes or longer. The upper limit of the time is usually 8 hours or less, preferably 7 hours or less. Therefore, the reaction time is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

The etherification reaction is usually carried out by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate. The amount of the carboxymethylating agent added is usually preferably 0.05 times by mole or more, more preferably 0.5 times by mole or more, and further preferably 0.8 times by mole or more per glucose residue of the cellulose raw material. The upper limit of the amount is usually 10.0 times mol or less, preferably 5 times or less, more preferably 3 times mol or less, and therefore the amount is preferably 0.05 to 10.0 times mol, and more. It is preferably 0.5 to 5, and more preferably 0.8 to 3 times the molar amount. The reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. Therefore, the reaction temperature is usually 30 to 90 ° C, preferably 40 to 80 ° C. The reaction time is usually 30 minutes or more, preferably 1 hour or more, and the upper limit thereof is usually 10 hours or less, preferably 4 hours or less. Therefore, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. If necessary, the reaction solution may be stirred during the carboxymethylation reaction.

The degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose nanofibers is measured, for example, by the following method. That is, 1) Approximately 2.0 g of carboxymethylated cellulose (absolutely dried) is precisely weighed and placed in an Erlenmeyer flask with a 300 mL stopper. 2) Add 100 mL of a solution prepared by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol nitrate, and shake for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethylated cellulose. 3) Weigh 1.5 to 2.0 g of hydrogen-type carboxymethylated cellulose (absolutely dry) and put it in an Erlenmeyer flask with a 300 mL stopper. 4) Wet hydrogen-type carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. 5) Using phenolphthalein as an indicator, back titrate excess NaOH with _{0.1 N H 2} SO _4. 6) Calculate the degree of carboxymethyl substitution (DS) by the following formula:
A = [(100 x F'-(0.1 N H ₂ SO ₄ ) (mL) x F) x 0.1] / (absolute dry mass (g) of hydrogen-type carboxymethylated cellulose)
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required to neutralize 1 g of hydrogen-type carboxymethylated cellulose
F: 0.1N H ₂ SO ₄ factor F': 0.1N NaOH factor

[Cationation]
The cationized cellulose nanofiber obtained by cationization may contain a cation such as ammonium, phosphonium, or sulfonium, or a group having the cation in the molecule. The cationized cellulose nanofibers preferably contain a group having ammonium, and more preferably contain a group having quaternary ammonium.

The cationization method is not particularly limited, and examples thereof include a method in which a cationizing agent and a catalyst are reacted with a cellulose raw material in the presence of water or alcohol. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrite (eg, 3-chloro-2-hydroxypropyltrimethylammonium hydrate), and halohydrin forms thereof. By using any of these, cationized cellulose having a group containing quaternary ammonium can be obtained. Examples of the catalyst include alkali metals hydroxide such as sodium hydroxide and potassium hydroxide. Examples of the alcohol include alcohols having 1 to 4 carbon atoms. The amount of the cationizing agent is preferably 5% by weight or more, more preferably 10% by weight or more, based on 100% by weight of the cellulose raw material. The upper limit of the amount is usually 800% by weight or less, preferably 500% by weight or less. The amount of the catalyst is preferably 0.5% by weight or more, more preferably 1% by weight or more, based on 100% by weight of the cellulose fibers. The upper limit of the amount is usually 7% by weight or less, preferably 3% by weight or less. The amount of alcohol is preferably 50% by weight or more, more preferably 100% by weight or more, based on 100% by weight of the cellulose fibers. The upper limit of the amount is usually 50,000% by weight or less, preferably 500% by weight or less.

The reaction temperature during cationization is usually 10 ° C. or higher, preferably 30 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. The reaction time is usually 10 minutes or more, preferably 30 minutes or more, and the upper limit is usually 10 hours or less, preferably 5 hours or less. If necessary, the reaction solution may be stirred during the cationization reaction.

The degree of cation substitution per glucose unit of cationized cellulose can be adjusted by the amount of cationizing agent added and the composition ratio of water or alcohol. The degree of cation substitution indicates the number of introduced substituents per unit structure (glucopyranose ring) constituting cellulose. That is, the degree of cation substitution is defined as "the value obtained by dividing the number of moles of the introduced substituent by the total number of moles of the hydroxyl groups of the glucopyranose ring". Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of cation substitution is 3 (minimum value is 0).

The degree of cation substitution per glucose unit of the cationized cellulose nanofiber is preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more. The upper limit of the degree of substitution is preferably 0.40 or less, more preferably 0.30 or less, and even more preferably 0.20 or less. Therefore, the degree of cation substitution is preferably 0.01 to 0.40, more preferably 0.02 to 0.30, and even more preferably 0.03 to 0.20. By introducing a cationic substituent into cellulose, the celluloses are electrically repelled from each other. Therefore, cellulose into which a cation substituent has been introduced can be easily nano-defibrated. When the degree of cation substitution per glucose unit is 0.01 or more, nano-defibration can be sufficiently performed. On the other hand, when the degree of cation substitution per glucose unit is 0.40 or less, swelling or dissolution can be suppressed, whereby the fiber morphology can be maintained, and a situation that cannot be obtained as nanofibers can be prevented. be able to.

An example of a method for measuring the degree of cation substitution per glucose unit will be described below. After the sample (cationized cellulose) is dried, the nitrogen content is measured with a total nitrogen analyzer TN-10 (manufactured by Mitsubishi Chemical Corporation). For example, when 3-chloro-2-hydroxypropyltrimethylammonium chloride is used as the cationizing agent, the degree of cationization is calculated by the following formula. The degree of cation substitution referred to here is an average value of the number of moles of substituents per mole of anhydrous glucose unit.
Cation degree of substitution = (162 × N) / (1-116 × N)
N: Nitrogen content per 1 g of cationized cellulose (mol)

[Esterification]
The method of esterification is not particularly limited, and examples thereof include a method of reacting a cellulosic raw material with compound A, which will be described later. Examples of the method for reacting the compound A with the cellulosic raw material include a method of mixing the powder or the aqueous solution of the compound A with the cellulosic raw material, a method of adding the aqueous solution of the compound A to the slurry of the cellulosic raw material, and the like. Of these, a method of mixing an aqueous solution of compound A with a cellulosic raw material or a slurry thereof is preferable because the uniformity of the reaction is enhanced and the esterification efficiency is increased.

Examples of the compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. Compound A may be in the form of a salt. Among the above, a phosphoric acid-based compound is preferable because it is low in cost, easy to handle, and the phosphoric acid group can be introduced into the cellulose of the pulp fiber to improve the defibration efficiency. The phosphoric acid-based compound may be a compound having a phosphoric acid group, for example, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, diphosphate. Examples thereof include potassium hydrogen hydrogen, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate and the like. .. The phosphoric acid-based compound used may be one or a combination of two or more of these. Of these, from the viewpoints of high efficiency of introducing a phosphoric acid group, easy defibration in the defibration process, and easy industrial application, phosphoric acid, sodium phosphate salt of phosphoric acid, potassium salt of phosphoric acid, and phosphoric acid Ammonium salt is preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. In addition, it is preferable to use an aqueous solution of a phosphoric acid-based compound for esterification because the uniformity of the reaction is enhanced and the efficiency of introducing a phosphoric acid group is increased. The pH of the aqueous solution of the phosphoric acid-based compound is preferably 7 or less from the viewpoint of increasing the efficiency of introducing the phosphoric acid group, and more preferably 3 to 7 from the viewpoint of suppressing the hydrolysis of the pulp fiber.

Examples of the esterification method include the following methods. Compound A is added to a suspension of a cellulosic raw material (for example, a solid content concentration of 0.1 to 10% by weight) with stirring to introduce a phosphoric acid group into cellulose. When the compound A is a phosphoric acid-based compound, the amount of the compound A added is preferably 0.2 parts by weight or more, more preferably 1 part by weight or more, as the amount of phosphorus element with respect to 100 parts by weight of the cellulosic raw material. Thereby, the yield of the fine fibrous cellulose can be further improved. The upper limit of the amount is preferably 500 parts by weight or less, more preferably 400 parts by weight or less. As a result, a yield commensurate with the amount of compound A used can be efficiently obtained. Therefore, 0.2 to 500 parts by weight is preferable, and 1 to 400 parts by weight is more preferable.

When the compound A is reacted with the cellulosic raw material, the compound B may be further added to the reaction system. Examples of the method of adding the compound B to the reaction system include a method of adding the compound B to the slurry of the cellulosic raw material, an aqueous solution of the compound A, or a method of adding the compound B to the slurry of the cellulosic raw material and the compound A. Compound B is not particularly limited, but is preferably basic, and a nitrogen-containing compound exhibiting basicity is more preferable. "Exhibiting basicity" usually means that the aqueous solution of Compound B exhibits a pink to red color in the presence of a phenolphthalein indicator, or that the pH of the aqueous solution of Compound B is greater than 7. The nitrogen-containing compound exhibiting basicity is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned. Of these, urea is preferable because it is low in cost and easy to handle. The amount of compound B added is preferably 2 to 1000 parts by weight, more preferably 100 to 700 parts by weight. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. When the conditions of the esterification reaction are within any of these ranges, it is possible to prevent the cellulose from being excessively esterified and easily dissolved, and it is possible to improve the yield of the phosphate esterified cellulose. ..

After reacting compound A with a cellulosic raw material, an esterified cellulose suspension is usually obtained. The esterified cellulose suspension is dehydrated as needed. It is preferable to perform heat treatment after dehydration. As a result, hydrolysis of the cellulosic raw material can be suppressed. The heating temperature is preferably 100 to 170 ° C., and is heated at 130 ° C. or lower (more preferably 110 ° C. or lower) while water is contained during the heat treatment, and after removing the water, it is heated at 100 to 170 ° C. It is more preferable to process.

In phosphoric acid esterified cellulose, a phosphate group substituent is introduced into the cellulose raw material, and the celluloses electrically repel each other. Therefore, the phosphate esterified cellulose can be easily nano-defibrated. The amount of the phosphoric acid group introduced is preferably 0.1 to 3.5 mmol / g, more preferably 0.2 to 3.0 mmol / g, and 0.4 to 2.5 mmol / g per 1 g (mass) of cellulose. g is more preferable, and 0.6 to 2.3 mmol / g is particularly preferable. By setting the amount of the phosphoric acid group introduced within the above range, nanofibering of the cellulose raw material can be facilitated and the stability of the cellulose nanofibers can be enhanced. Further, by setting the amount of the phosphoric acid group introduced within the above range, the viscosity of the cellulose nanofiber slurry can be adjusted within an appropriate range.

[Defibration]
The defibration of the cellulose raw material may be carried out before or after the chemical modification of the cellulose raw material. The defibration treatment may be performed once or a plurality of times. In the case of multiple times, the timing of each defibration may be any time.

The device used for defibration is not particularly limited, and examples thereof include high-speed rotary type, colloid mill type, high pressure type, roll mill type, ultrasonic type and the like, and a high pressure or ultrahigh pressure homogenizer is preferable, and a wet high pressure type is preferable. Alternatively, an ultrahigh pressure homogenizer is more preferable. The apparatus preferably can apply a strong shearing force to the cellulose raw material or modified cellulose (usually a dispersion). The pressure that can be applied by the device is preferably 50 MPa or more, more preferably 100 MPa or more, and even more preferably 140 MPa or more. The apparatus is preferably a wet high-pressure or ultra-high pressure homogenizer capable of applying the above pressure to a cellulose raw material or modified cellulose (usually a dispersion) and applying a strong shearing force. As a result, defibration can be performed efficiently.

When defibration is performed on a dispersion of a cellulose raw material, the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3. Weight% or more. As a result, the amount of the liquid becomes appropriate with respect to the amount of the cellulose fiber raw material, and the efficiency becomes high. The upper limit of the concentration is usually 10% by weight or less, preferably 6% by weight or less. This makes it possible to maintain liquidity.

Pre-treatment may be performed, if necessary, prior to defibration (preferably defibration with a high-pressure homogenizer) or, if necessary, a dispersion treatment before defibration. The pretreatment may be performed using a mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.

[Form of cellulosic fibers to be mixed]
The form of the cellulosic fiber mixed with the rubber component is not particularly limited. For example, a dispersion in which cellulosic fibers are dispersed in a dispersion medium, a dry solid of the dispersion, and a wet solid of the dispersion may be mixed. The concentration of cellulosic fibers in the dispersion can be 0.1 to 5% (w / v) when the dispersion medium is water. When the dispersion medium contains an organic solvent such as alcohol in addition to water, the concentration can be 0.1 to 20% (w / v). The wet solid is a solid in an intermediate mode between the dispersion and the dry solid. The amount of the dispersion medium in the wet solid obtained by dehydrating the dispersion liquid by a usual method is preferably 5 to 15% by weight based on the cellulosic fibers, but the dispersion is dispersed by adding a liquid medium or further drying. The amount of medium can be adjusted as appropriate.

Further, a mixed solution of a cellulosic fiber and a water-soluble polymer solution, a dry solid of the mixed solution, a wet solid of the mixed solution, and the like can be used. The amount of the liquid medium in the mixture and the dry solid may be in the above range. Examples of the water-soluble polymer include cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucane, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, purulan, starch, shavings, and waste. Powder, Positive Starch, Phosphorescent Starch, Corn Starch, Arabian Gum, Locust Bean Gum, Gellan Gum, Gellan Gum, Polydextrose, Pectin, Chitin, Water Soluble Chitin, Chitosan, Casein, Albumin, Soy Protein Dissolved, Peptone, Polyvinyl Alcohol, Poly Acrylamide, sodium polyacrylate, polyvinylpyrrolidone, vinylacetate, polyamino acid, polylactic acid, polyaronic acid, polyglycerin, latex, rosin-based sizing agent, petroleum resin-based sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin , Polyamide polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide, hydrophilic cross-linked polymer, polyacrylic acid salt, starch polyacrylic acid copolymer, tamarind gum, gellan gum, pectin, guar gum, and colloidal silica, and these. Examples include a mixture of. Among these, from the viewpoint of solubility, it is preferable to use carboxymethyl cellulose and a salt thereof.

The dry solid and the wet solid can be prepared by drying a dispersion of cellulosic fibers or a mixed solution of cellulosic fibers and a water-soluble polymer. The drying method is not particularly limited, and examples thereof include spray drying, squeezing, air drying, hot air drying, and vacuum drying. Examples of the drying device include a continuous tunnel drying device, a band drying device, a vertical drying device, a vertical turbo drying device, a multi-stage disk drying device, an aeration drying device, a rotary drying device, an air flow drying device, and a spray dryer drying device. , Spray drying device, Cylindrical drying device, Drum drying device, Screw conveyor drying device, Rotating drying device with heating tube, Vibration transport drying device, etc. Examples include a stirring and drying device. These drying devices may be used alone or in combination of two or more. The drum drying device is preferable because it can uniformly supply heat energy directly to the object to be dried, so that it is highly energy efficient and can immediately recover the dried product without applying heat more than necessary.

3) Other compounding agents In this step (a), other compounding agents may be mixed in addition to the rubber component and the cellulosic fiber. Other compounding agents include sulfenamide (Nt-butyl-2-benzothiazole sulfenamide, etc.), vulcanization accelerators such as zinc oxide and stearic acid, vulcanization accelerator aids, carbon black, silica and the like. Reinforcing agents, silane coupling agents, oils, hardened resins, waxes, anti-aging agents, vulcanizing agents, colorants, pH adjusters, etc. that can be used in the field of rubber.

4) Filtering When cellulose nanofibers are used as cellulosic fibers, foreign substances such as undefibrated fibers may be present in the cellulose nanofibers due to insufficient defibration. If the rubber composition contains foreign matter, the rubber composition is likely to break from the foreign matter or the like as a starting point, and the strength may decrease. Therefore, as the cellulosic fiber in the step (a), the dispersion obtained by filtering the cellulose nanofiber dispersion or the cellulose nanofiber isolated from the dispersion may be used. Hereinafter, the filtration treatment of the cellulose nanofiber dispersion liquid will be described.

In the present invention, it is preferable to perform pressure filtration or vacuum filtration of the cellulose nanofiber dispersion liquid with a filtration differential pressure of 0.01 MPa or more. The cellulose nanofiber concentration in the cellulose nanofiber dispersion to be filtered is 0.1 to 5% by weight, preferably 0.2 to 4% by weight, and more preferably 0.5 to 3% by weight. By performing filtration with the filtration differential pressure, a sufficient amount of filtration treatment can be performed even if the concentration and viscosity of the cellulose nanofiber dispersion liquid are high. The filtration differential pressure is preferably 0.01 to 10 MPa. If the difference is less than 0.01 MPa, a sufficient filtration treatment amount cannot be obtained, and a considerable dilution is required to obtain the filtration treatment amount, which is not appropriate in consideration of the subsequent steps. Examples of the apparatus used for filtration include a nutche type, a candle type, a leaf disc type, a drum type, a filter press type, a belt filter type and the like.

The amount of filtration treatment ^{is preferably 10 L / m 2} or more per hour, and more preferably 100 L / m ² or more. Examples of the filtration method include auxiliary agent filtration using a filtration auxiliary agent and filter medium filtration using a porous filter medium. In the present invention, an appropriate method can be selected, and the above two filtration methods may be used in combination. In this case, the order of the filtration methods can be arbitrarily selected. When two or more filtration steps are further carried out, any one of the filtration steps may be carried out at the filtration differential pressure, but all the filtration steps may be carried out at the filtration differential pressure. Hereinafter, the filtration aid and the filter medium will be described in detail.

(I) Filtration Auxiliary Auxiliary agent filtration using a filtration aid is preferable because clogging of the filter medium caused by the filtration treatment can be easily eliminated by removing the filtration layer formed by the filtration aid. Therefore, continuous filtration processing can be performed. The filtration aid is preferably particles having an average particle size of 150 μm or less, more preferably 1 to 150 μm, further preferably 10 to 75 μm, and even more preferably 15 to 45 μm. Granules of 25 to 45 μm are particularly preferred. If the average particle size is smaller than this, the filtration rate will decrease, and if the particle size is larger than this, foreign matter cannot be captured and the effect of the filtration process cannot be obtained. As will be described later, the filtration aid may be rod-shaped like powdered cellulose when it is substantially spherical such as diatomaceous earth, but in either case, the average particle size can be measured with a laser diffraction measuring device according to JIS Z8825-1. ..

Filtration using a filtration aid can be performed by either precoat filtration in which a layer of the filtration aid is formed on the filter medium, or body feed filtration in which the filtration aid and the cellulose nanofiber dispersion are mixed in advance and filtered. It is good, but it is more preferable to combine both of them because the processing amount is improved and the quality of the filtrate is improved. Further, the auxiliary agent may be filtered in multiple stages by changing the type of the auxiliary agent. When two or more filtration steps are carried out using a filtration aid, it is sufficient that any one of the filtration steps is carried out at the filtration differential pressure, but all the filtration steps are carried out at the filtration differential pressure. May be good. As the filtration aid, either an inorganic compound or an organic compound may be used, but a granular one is preferable. Preferred examples include diatomaceous earth, powdered cellulose, pearlite, activated carbon and the like. Hereinafter, diatomaceous earth and powdered cellulose will be described in detail as examples.

(Ii) Diatomaceous earth Diatomaceous earth is a soft rock or soil mainly composed of diatom shells, which is mainly composed of silica, but also contains alumina, iron oxide, alkali metal oxides, etc. in addition to silica. May be good. Further, it is preferable that the cake is porous, has a high porosity, and has a cake bulk density of ^{about 0.2 to 0.45 g / cm 3.} Among the diatomaceous earths, calcined products and flux-fired products are preferable, and freshwater diatomaceous earth is preferable, but other diatomaceous earths can also be used. Specific examples of such diatomaceous earth include Celite (registered trademark) manufactured by Celite and Yori Ceratom (registered trademark) manufactured by Eagle Pitcher Minerals.

(Iii) Powdered Cellulose Powdered cellulose is rod-axis particles made of microcrystalline cellulose obtained by removing a non-crystalline portion of wood pulp by acid hydrolysis treatment, and then pulverizing and sieving. The degree of polymerization of cellulose in powdered cellulose is preferably about 100 to 500, the degree of crystallinity of powdered cellulose by X-ray diffraction is preferably 70 to 90%, and the volume average particle diameter by a laser diffraction type particle size distribution measuring device. Is preferably 100 μm or less, and more preferably 50 μm or less. When the volume average particle size is 100 μm or less, a cellulose nanofiber dispersion having excellent fluidity can be obtained. The powdered cellulose used in the present invention has, for example, a rod-shaped shaft and a constant particle size produced by a method of purifying, drying, pulverizing, and sieving an undecomposed residue obtained after acid hydrolysis of selected pulp. Examples thereof include crystalline cellulose powder having a distribution, KC Flock (registered trademark) manufactured by Nippon Paper Industries, Ltd., Theoras (registered trademark) manufactured by Asahi Kasei Chemicals Co., Ltd., and Abyssel (registered trademark) manufactured by FMC.

(Iv) Filter media The filter media is made by sintering filters, membranes, filter cloths, and metal powders made of materials such as metal fibers, cellulose, polypropylene, polyester, nylon, glass, cotton, polytetrafluoroethylene, and polyphenylene sulfide. Examples thereof include a filter and a slit-shaped filter. Of these, a metal filter or a membrane filter is particularly preferable.

The preferable average pore size of the filter medium is not particularly limited when used in combination with the above-mentioned filtration aid, and known ones can be used. On the other hand, when filtering only with the filter medium without using the above-mentioned filtration aid, the average pore size of the filter medium is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm, and further preferably 1 to 30 μm. If the average pore size is smaller than this, a sufficient filtration rate cannot be obtained, and if it is larger than this, the filtration aid cannot be captured and the filtration effect becomes difficult to obtain.

(V) Evaluation of dispersibility The dispersibility of the cellulose nanofiber dispersion liquid after filtration is preferably evaluated by the following method.
1) After adding a surface tension adjusting agent to the dispersion liquid of the cellulose nanofibers, the film is thinned.
2) A pair of polarizing plates are arranged on both sides of the thin film so that their polarization axes are orthogonal to each other.
3) Irradiate light from one polarizing plate side and acquire a transmitted image from the other polarizing plate side.
4) The foreign matter area is specified by image analysis of the image, and the foreign matter area ratio per 1 g of the absolute dry weight of the cellulose nanofibers is calculated.
Details of the method are described in Japanese Patent Application No. 2016-044675, the contents of which are incorporated in the present invention.
The filtered cellulose nanofiber dispersion liquid preferably has a foreign matter area ratio of 25% or less in the evaluation method.

(2) Step (b)
In this step, the mixture is heated under the condition of 100-300 ° C. for 5-600 minutes. This heat treatment improves the compatibility between the cellulosic fiber and the rubber component. The mechanism by which the compatibility is improved is not limited, but it is presumed that the surface of the cellulosic fiber is modified by heating to become hydrophobic. In the present invention, compatibility is synonymous with affinity. If the temperature is less than 100 ° C, this effect is not sufficiently exhibited, and if it exceeds 300 ° C, the rubber component and the like deteriorate. From this viewpoint, the lower limit of the heating temperature is preferably 105 ° C. or higher, more preferably 110 ° C. or higher, and even more preferably 120 ° C. or higher. The lower limit of the heating temperature is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. Similarly, if the heating time is less than 5 minutes, this effect is not sufficiently exhibited, and if it exceeds 600 minutes, the rubber component and the like deteriorate. From this viewpoint, the heating time is preferably 5 to 300 minutes, more preferably 10 to 120 minutes, still more preferably 15 to 70 minutes.

The heat treatment can be performed using a known device such as a ventilation oven. The heating atmosphere may be in the presence or absence of oxygen. Further, the pressure of the heating atmosphere is preferably under normal pressure (1 atm).

(3) Drying Step As described above, the step (a) is carried out using a dispersion in which the rubber component is dispersed in a dispersion medium, a solution in which the rubber component is dissolved in a solvent, a dispersion in which cellulosic fibers are dispersed in a dispersion medium, or the like. can. In this case, since the liquid medium is present in the mixture, it is preferable to remove it before the step (b). Specifically, it is preferable to dry the mixture to remove the liquid medium. The drying temperature is preferably 50 to 80 ° C. The drying time may be adjusted as appropriate. The mixture after drying may be in an absolutely dry state, but may contain a liquid medium of 10% by weight or less based on the total amount of the rubber component and the cellulosic fiber. Further, the method for removing the liquid medium other than the above is not particularly limited, and a conventionally known method can be used. For example, a method of coagulating the mixture by adding an acid or a salt, dehydrating, washing and drying can be mentioned.

2. Method for Producing Rubber Composition An uncrosslinked rubber composition (crosslinkable rubber composition) can be produced by adding a crosslinking agent to the masterbatch produced by the above method and kneading the masterbatch. Kneading is a step of uniformly dispersing a cross-linking agent and other compounding agents in a masterbatch. The kneading may be carried out as known, and can be carried out by using, for example, a Banbury mixer, a kneader, an open roll or the like. Examples of the cross-linking agent include sulfur and peroxide. The blending amount of the cross-linking agent may be adjusted as appropriate. Other compounding agents include sulfenamide (Nt-butyl-2-benzothiazole sulfenamide, etc.), vulcanization accelerators such as zinc oxide and stearic acid, vulcanization accelerator aids, carbon black, silica and the like. Reinforcing agents, silane coupling agents, oils, hardened resins, waxes, anti-aging agents, vulcanizing agents, colorants, pH adjusters, etc. that can be used in the field of rubber. Other formulations can also be added to the masterbatch.

Further, it is also possible to add a rubber component together with a cross-linking agent to the master batch and knead the master batch to obtain a rubber composition in which the cellulosic fiber concentration is diluted.

The kneading temperature may be about room temperature (about 15 to 30 ° C.), but may be heated to a high temperature so that the rubber component does not undergo a cross-linking reaction. For example, the upper limit of the temperature is 140 ° C. or lower, more preferably 100 ° C. The lower limit of the temperature is 15 ° C. or higher, preferably 20 ° C. or higher. Therefore, the kneading temperature is preferably about 15 to 140 ° C, more preferably about 20 to 100 ° C.

After the mixing is completed, molding may be performed if necessary. Examples of the molding apparatus include mold molding, injection molding, extrusion molding, hollow molding, foam molding and the like, which may be appropriately selected according to the shape, application and molding method of the final product.

Regarding cross-linking, the temperature is not particularly limited as long as the cross-linking reaction proceeds, but in general, the uncross-linked rubber composition obtained by kneading is heated for cross-linking (vulcanization when sulfur is contained). Also referred to as), a crosslinked rubber composition is obtained. The heating temperature is preferably 140 ° C. or higher, preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. Therefore, the heating temperature is preferably about 140 to 200 ° C, more preferably about 140 to 180 ° C. For cross-linking, for example, a vulcanizer that performs mold vulcanization, can vulcanization, continuous vulcanization, and the like can be used. The rubber composition of the present invention tends to undergo a cross-linking reaction more rapidly than the composition containing no cellulose nanofibers. The reason for this is not limited, but it is presumed that functional groups such as carboxyl groups in the cellulose nanofibers promote the cross-linking reaction.

If necessary, a finishing treatment may be performed after the cross-linking and before the final product. Examples of the finishing treatment include polishing, surface treatment, lip finishing, lip cutting, chlorine treatment, and the like, and only one of these treatments may be performed, or a combination of two or more of these treatments may be performed.

3. 3. Masterbatch and Rubber Composition The masterbatch of the present invention provides a rubber composition having excellent mechanical properties because it has excellent adhesion between cellulosic fibers and rubber components. The content of the cellulosic fiber in the rubber composition is preferably 0.1 to 100 parts by weight with respect to 100 parts by weight of the rubber component. From the viewpoint of improving the tensile strength, the content is more preferably 1 part by weight or more, further preferably 2 parts by weight or more, still more preferably 3 parts by weight or more with respect to 100 parts by weight of the rubber component. The upper limit of the amount is more preferably 50 parts by weight or less, further preferably 40 parts by weight or less, and further preferably 30 parts by weight or less. With this amount, workability in the manufacturing process can be maintained.

The use of the rubber composition of the present invention is not particularly limited, and for example, transportation equipment such as automobiles, trains, ships, and airplanes; electrical appliances such as personal computers, televisions, telephones, and watches; mobile communication equipment such as mobile phones. Etc .; AV equipment such as portable music playback equipment and video playback equipment; printing equipment; copying equipment; sports equipment; building materials; office equipment such as stationery; packaging equipment such as containers and containers. Other than these, it can be applied to members using rubber or flexible plastic, and is preferably applied to tires. Examples of tires include pneumatic tires for passenger cars, trucks, buses, heavy vehicles, and the like.

<Example 1>
[Manufacture of cellulose oxide nanofibers]
5.00 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from coniferous trees, 39 mg (0.05 mmol with respect to 1 g of absolute dry cellulose) of TEMPO (manufactured by Sigma Aldrich) and 514 mg of sodium bromide (absolutely dry). It was added to 500 mL of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of absolute dry cellulose, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that the sodium hypochlorite content was 5.5 mmol / g, and the oxidation reaction was started at room temperature. Although the pH in the system decreased during the reaction, a 3M aqueous sodium hydroxide solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90% by weight, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. Water was added to the reaction mixture to adjust the concentration to 1.1% by mass (w / v), and the mixture was treated with an ultra-high pressure homogenizer (20 ° C., 150 MPa) three times to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 3 nm and the aspect ratio was 250.

[Manufacturing of masterbatch]
1) Mixing and drying steps 636 g of an aqueous dispersion having a solid content concentration of 1.1% (w / v) (1.1% by weight) of the cellulose oxide nanofibers obtained as described above and acrylonitrile-butadiene rubber polymer latex as a rubber component. (Product name: Nipol511A, manufactured by Nippon Zeon Co., Ltd., solid content concentration 46% by weight) Mix 76 g so that the weight ratio of the rubber component and the cellulose nanofibers is 100:20, and use a TK homomixer (8000 rpm). The mixture was stirred for 10 minutes. The aqueous suspension was dried overnight in a heating oven at 70 ° C. to give a dried product.

2) Heating step This dried product was heated at 120 ° C. for 30 minutes in an oven to produce a masterbatch.

3) Vulcanization and molding process 1.2 g of sulfur (3.5% by weight based on rubber component) and 0.25 g of vulcanization accelerator (N-oxydiethylene-2-benzothiazolyl sulphenamide) in the master batch. (0.7% by weight based on rubber component), 2.1 g zinc oxide (6% by weight based on rubber component), 0.18 g stearic acid (0.5% by weight based on rubber component), and open roll (Kansai) Using Roll Co., Ltd.), the mixture was kneaded at 30 ° C. for 10 minutes to obtain a sheet of an uncrosslinked rubber composition.

This sheet was sandwiched between dies and press-crosslinked at 160 ° C. for 15 minutes to obtain a sheet of a crosslinked rubber composition having a thickness of about 2 mm. This is cut into a test piece having a predetermined shape, and according to JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to obtain tensile properties", the tensile characteristics, which is one of the reinforcing properties, is 50% strain and 100% strain. The stress at time and at break was measured, respectively. The larger each value is, the better the crosslinked rubber composition (vulcanized rubber composition) is reinforced, indicating that the mechanical strength of the rubber is excellent.

<Example 2>
A rubber composition was produced and evaluated in the same manner as in Example 1 except that the heating time in the heating step was 60 minutes.

<Example 3>
A rubber composition was produced and evaluated in the same manner as in Example 1 except that the heating temperature in the heating step was set to 150 ° C.

<Example 4>
A rubber composition was produced and evaluated in the same manner as in Example 1 except that the heating temperature in the heating step was 150 ° C. and the heating time was 60 minutes.

<Example 5>
A rubber composition was produced and evaluated in the same manner as in Example 1 except that the heating temperature in the heating step was 180 ° C. and the heating time was 30 minutes.

<Example 6>
A rubber composition was produced and evaluated in the same manner as in Example 1 except that the cationized CNF prepared as follows was used instead of the TEMPO oxidized CNF.

[Manufacture of cationized cellulose nanofibers]
To a pulper capable of stirring pulp, 200 g of pulp (NBKP, manufactured by Nippon Paper Industries, Ltd.) by dry weight and 24 g of sodium hydroxide by dry weight are added, and water is added so that the pulp solid concentration becomes 15% by weight. rice field. Then, after stirring at 30 ° C. for 30 minutes, the temperature was raised to 70 ° C., and 200 g (in terms of active ingredient) of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added as a cationizing agent. After reacting for 1 hour, the reaction product was taken out, neutralized and washed to obtain a cationically modified cellulose having a degree of cation substitution of 0.05 per glucose unit. Then, the cation-modified pulp was adjusted to a solid concentration of 1% by weight (w / v), and treated twice with a high-pressure homogenizer at a pressure of 20 ° C. and 140 MPa. The average fiber diameter of the obtained fibers was 25 nm, and the aspect ratio was 50.

<Example 7>
A rubber composition was produced and evaluated in the same manner as in Example 6 except that the heating time was changed to 60 minutes.
<Example 8>
A rubber composition was produced and evaluated in the same manner as in Example 6 except that the heating temperature was changed to 150 ° C.
<Example 9>
A rubber composition was produced and evaluated in the same manner as in Example 6 except that the heating temperature was changed to 150 ° C. and the heating time was changed to 60 minutes.

<Example 10>
A rubber composition was produced in the same manner as in Example 1 except that natural rubber (trade name HA-LATEX, manufactured by Reditex Co., Ltd., solid content concentration 61.7% by weight) was used instead of the acrylonitrile butadiene rubber polymer. evaluated.
<Example 11>
A rubber composition was produced in the same manner as in Example 3 except that natural rubber (trade name HA-LATEX, manufactured by Reditex Co., Ltd., solid content concentration 61.7% by weight) was used instead of the acrylonitrile butadiene rubber polymer. evaluated.

<Example 12>
A rubber composition was produced and evaluated in the same manner as in Example 11 except that TEMPO-oxidized CNF prepared as follows was used.

[Manufacture of cellulose oxide nanofibers]
5.00 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from coniferous trees, 39 mg (0.05 mmol per 1 g of absolute dry cellulose) and 514 mg of sodium bromide (absolutely dry). It was added to 500 mL of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that the sodium hypochlorite content was 3.5 mmol / g, and the oxidation reaction was started at room temperature. Although the pH in the system decreased during the reaction, a 3M aqueous sodium hydroxide solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change. The mixture after the reaction was filtered through a glass filter to separate pulp, and the separated pulp was thoroughly washed with water to obtain oxidized pulp (oxidized (carboxylated) cellulose). The pulp yield at this time was 91% by weight, the time required for the oxidation reaction was 80 minutes, and the amount of carboxyl groups was 1.0 mmol / g. This was adjusted to 1.0% by weight (w / v) with water, treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa), and oxidized (carboxylated) cellulose nanofiber dispersion liquid (1.0% by weight). (W / v)) was obtained. The average fiber diameter was 3 nm and the aspect ratio was 270.

<Example 13>
A rubber composition was produced and evaluated in the same manner as in Example 11 except that the carboxymethylated CNF prepared as follows was used.

[Manufacture of carboxymethylated cellulose nanofibers]
In a stirrer capable of mixing pulp, 200 g of pulp (NBKP (coniferous bleached kraft pulp), manufactured by Nippon Paper Industries) by dry mass and 111 g of sodium hydroxide by dry mass (2.25 per anhydrous glucose residue of starting material). (Double mol) was added, and water was added so that the pulp solid content was 20% by weight. Then, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (in terms of active ingredient, 1.5 times by mole per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and the mixture was stirred for 1 hour. Then, the reaction product was taken out, neutralized and washed to obtain a carboxylmethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. Water was added to this to make the solid content concentration 1% by weight, and the carboxymethylated cellulose nanofibers (1% by weight (w / v)) were defibrated by treating with a high-pressure homogenizer at a pressure of 20 ° C. and 150 MPa five times. Obtained. The average fiber diameter was 15 nm and the aspect ratio was 50.

<Example 14>
A rubber composition was produced and evaluated in the same manner as in Example 11 except that the phosphoric acid esterified CNF prepared as follows was used.

[Manufacture of Phosphate Esterified Cellulose Nanofibers]
6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate are dissolved in 19.62 g of water to obtain an aqueous solution of a phosphoric acid compound (hereinafter referred to as "phosphorylation reagent"). rice field. Water was added to unbleached softwood kraft pulp (NUKP, water content 80% by weight, Canadian standard drainage (CSF) 580 mL as measured according to JIS P8121) to a concentration of 4% by weight. Then, using a double disc refiner, the irregular CSF (similar to JIS P8121 except that the plain weave was 80 mesh and the pulp sampling amount was 0.3 g) was beaten to 200 mL and the average fiber length was 0.66 mm. The cellulose suspension thus obtained was diluted to 0.3% by weight, and a pulp sheet (thickness 200 μm) having a water content of 90% by weight and a solid content (absolute dry mass) of 3 g was obtained by a papermaking method. This pulp sheet is immersed in 31.2 g of the phosphorylation reagent (80 parts by weight of phosphorus element with respect to 100 parts by weight of dried pulp) and heated in a blower dryer (Yamato Scientific Co., Ltd. DKM400) at 105 ° C. for 1 hour. Further, heat treatment was performed at 150 ° C. for 30 minutes to introduce a phosphoric acid group into the cellulose fibers. Next, 500 mL of ion-exchanged water was added to a pulp sheet in which a phosphate group was introduced into cellulose fibers, and the pulp sheet was stirred and washed, and then dehydrated. The dehydrated sheet was diluted with 300 mL of ion-exchanged water, and 5 mL of a 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a cellulose suspension having a pH of 12 to 13. Then, this cellulose suspension was dehydrated, and 500 mL of ion-exchanged water was added for washing. This dehydration washing was repeated twice more. Ion-exchanged water was added to the sheet obtained after washing and dehydration, and the mixture was stirred to obtain a 0.5% by weight cellulose suspension. This cellulose suspension is defibrated for 30 minutes under the condition of 21500 rpm using a defibration treatment device (Clearmix-2.2S manufactured by M-Technique) to defibrate cellulose (phosphate ester). Cellulose-forming nanofibers) suspension was obtained. When the cellulose contained in the defibrated cellulose suspension was observed with a transmission electron microscope, it was confirmed that fine fibrous cellulose having a width of about 4 nm was contained. In addition, it was confirmed by X-ray diffraction that cellulose maintained cellulose type I crystals. Further, by measuring the infrared absorption spectrum by FT-IR, absorption ^{based on a phosphate group was observed at 1230 to 1290 cm-1,} and the addition of a phosphate group was confirmed. The amount of phosphoric acid group introduced at this time was 1.4 mmol / g per 1 g (weight) of fine fibrous cellulose.

<Example 15>
A rubber composition was produced and evaluated in the same manner as in Example 11 except that the weight ratio of the rubber component to the cellulose nanofibers was 100: 5.

<Example 16>
A rubber composition was prepared in the same manner as in Example 3 except that chloroprene rubber polymer latex (Showa Denko 571, solid content concentration 50.6% by weight) was used instead of acrylonitrile-butadiene rubber polymer latex as the rubber component. Manufactured and evaluated.

<Example 17>
A rubber composition similar to Example 3 except that styrene-butadiene rubber polymer latex (Nippon Zeon Corporation Nipol LX110, solid content concentration 40.5% by weight) was used instead of acrylonitrile-butadiene rubber polymer latex as the rubber component. Was manufactured and evaluated.

<Comparative example 1>
A rubber composition was produced and evaluated in the same manner as in Example 1 except that the heating step was not carried out.

<Comparative example 2>
A fiber-free rubber composition was produced and evaluated in the same manner as in Example 1 except that the cellulose oxide nanofibers were not used.

<Comparative example 3>
A fiber-free rubber composition was produced and evaluated in the same manner as in Comparative Example 2 except that the heating step was not carried out.
<Comparative example 4>
A rubber composition was produced and evaluated in the same manner as in Example 6 except that the heating step was not carried out.
<Comparative example 5>
A rubber composition was produced and evaluated in the same manner as in Example 10 except that the heating step was not carried out.
<Comparative Examples 6-9>
A rubber composition was produced and evaluated in the same manner as in Examples 12 to 15 except that the heating step was not carried out.

<Comparative Example 10>
A fiber-free rubber composition was produced and evaluated in the same manner as in Example 10 except that the cellulose oxide nanofibers were not used and the heating step was not carried out.
<Comparative Example 11>
A rubber composition was produced and evaluated in the same manner as in Example 16 except that the heating step was not carried out.
<Comparative Example 12>
A fiber-free rubber composition was produced and evaluated in the same manner as in Example 16 except that the cellulose oxide nanofibers were not used and the heating step was not carried out.

<Comparative Example 13>
A rubber composition was produced and evaluated in the same manner as in Example 17 except that the heating step was not carried out.
<Comparative Example 14>
A fiber-free rubber composition was produced and evaluated in the same manner as in Example 17 except that the cellulose oxide nanofibers were not used and the heating step was not carried out.
These results are shown in Table 1.

The rubber composition produced from the masterbatch of the present invention obtained through the heating step has excellent mechanical properties. It is presumed that this is because the surface of the cellulose nanofibers became hydrophobic and the compatibility with rubber was improved.

Claims (9)

It comprises (a) a step of obtaining a mixture containing a rubber component and a cellulosic fiber, and (b) a step of heating the mixture at 120 to 300 ° C. for 15 to 600 minutes.
Masterbatch manufacturing method. The step (a) is carried out using the dispersion liquid or solution of the rubber component or the dispersion liquid of the cellulosic fiber.
A step of removing the dispersion medium or solvent is further included before the step (b).
The manufacturing method according to claim 1. The production method according to claim 1 or 2, wherein the cellulosic fiber is a chemically modified cellulosic fiber. The production method according to any one of claims 1 to 3, wherein the length-weighted average fiber length of the cellulosic fiber is 50 to 2000 nm, and the length-weighted average fiber diameter is 2 to 500 nm. The invention according to any one of claims 1 to 4, wherein the rubber component comprises an acrylonitrile-butadiene rubber (NBR) polymer, a natural rubber (NR) polymer, a styrene-butadiene rubber (SBR) polymer, or a chloroprene rubber (CR) polymer. Manufacturing method. The production method according to any one of claims 1 to 5, wherein the temperature is 150 to 300 ° C. The production method according to any one of claims 1 to 6, wherein the time is 30 to 600 minutes. A method for producing an uncrosslinked rubber composition, which comprises a step of preparing a masterbatch by the method according to claims 1 to 7 and a step of mixing a crosslinking agent with the masterbatch. A method for producing a rubber composition, which comprises the step of cross-linking the uncrosslinked rubber composition according to claim 8.