JP6832110B2 - 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 a 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 JP-A-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 heats a mixture of a rubber component and a cellulosic fiber and adds a methylene acceptor compound and a methylene donor compound, or a mixture containing a rubber component, a cellulosic fiber, a methylene acceptor compound and a methylene donor compound. The present invention has been completed by finding that the mechanical properties can be improved by heating. That is, the following invention solves the above problems.
(1) A method for producing a masterbatch, which comprises a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound.
(A1) A step of mixing a rubber component and a cellulosic fiber to obtain a mixture,
(B1) The step of heating the mixture obtained in the step (a1) at 100 to 300 ° C. for 5 to 600 minutes, and (c1) the mixture obtained in the step (b1), a methylene acceptor compound and a methylene donor compound. A method of manufacturing a master batch, which comprises the step of mixing with.
(2) A method for producing a masterbatch, which comprises a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound.
(A2) A step of preparing a mixture containing a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound, and (b2) the mixture obtained in the step (a2) of 5 to 600 at 100 to 300 ° C. A method for producing a master batch, which comprises a step of heating for minutes.
(3) The mixture of the step (a1) contains at least a dispersion or solution of the rubber component, or a dispersion medium or solvent derived from the dispersion of the cellulosic fibers.
The production method according to (1), further comprising a step of removing the dispersion or solution of the rubber component or the dispersion medium or solvent derived from the dispersion of the cellulosic fiber before the step (b1).
(4) The mixture of the step (a2) is at least a dispersion or solution of the rubber component, a dispersion of cellulosic fibers, or a dispersion medium or a dispersion derived from a solution or dispersion of a methylene acceptor compound or a methylene donor compound. Contains solvent,
Prior to the step (b2), the dispersion medium or solvent derived from the dispersion or solution of the rubber component, the dispersion of the cellulosic fiber, or the solution or dispersion of the methylene acceptor compound or the methylene donor compound is removed. The production method according to (2), further comprising a step.
(5) The production method according to any one of (1) to (4), wherein the cellulosic fiber is a chemically modified cellulosic fiber.
(6) The production method according to any one of (1) to (5), 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.
(7) The production method according to any one of (1) to (6), wherein the rubber component contains an acrylonitrile-butadiene rubber (NBR) polymer or a natural rubber (NR) polymer.
(8) The production method according to any one of (1) to (7), wherein the methylene acceptor compound is selected from the group consisting of resorcin, a resorcin derivative, a resorcin-based resin, and a combination thereof.
(9) The production method according to any one of (1) to (8), wherein the methylene donor compound is hexamethylenetetramine.
(10) A method for producing a rubber composition, which comprises a step of preparing a masterbatch by the method according to (1) to (9) above, and a step of cross-linking the masterbatch.

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.

In general, the definition of a masterbatch is diverse, but in the present invention, a masterbatch is an uncrosslinked rubber composition or a crosslinkable rubber composition containing a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound. Say. A crosslinked rubber composition is produced by crosslinking the masterbatch. In the present invention, the term "rubber composition" simply means a crosslinked rubber composition.

The present invention is characterized in that it includes a step of heating a mixture of a rubber component and a cellulosic fiber, and includes the following aspects depending on the timing of heating.
First production method: A methylene acceptor compound and a methylene donor compound are added after heating a mixture of a rubber component and a cellulosic fiber.
Second production method: A mixture containing a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound is heated.
Hereinafter, each aspect 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 First Master Batch The method for producing the first master batch of the present invention is a step of (a1) mixing a rubber component and a cellulose-based fiber to obtain a mixture, and (b1) mixing the mixture at 100 to 300 ° C. The step of heating for 5 to 600 minutes and the step of mixing the mixture obtained in the step (c1) (b1) with the methylene acceptor compound and the methylene donor compound are included.

(1) Step (a1)
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 as to achieve the ratio of the rubber composition described later. 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 polymer, and styrene-isoprene. Diene-based rubber polymers such as polymer 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 Non-diene type such as (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 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 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. In the present invention, the dispersion medium and the solvent are also collectively referred to as "liquid medium". Examples of the liquid medium used for the dispersion liquid of the rubber component 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 fibers As the cellulosic fibers, cellulose fibers having a fiber diameter on the order of micron or cellulose nanofibers having a fiber diameter on the nano-order obtained by chemically modifying the cellulose fibers as necessary and then defibrating the fibers are used. it 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, agricultural 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 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, still 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. The iodide is a compound containing iodine, and examples thereof include alkali metals iodide. The amount of bromide or iodide used can be selected within a range that can promote the oxidation reaction. 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, still more 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, hypochlorous acids, hypochlorous acids, perhalonic 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, as the oxidation reaction progresses, carboxyl groups are generated in cellulose, so that the pH of the reaction solution tends to decrease. 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. It 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-based 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 amounts of the carboxyl group, carboxylate group, and aldehyde group contained in the cellulose oxide nanofibers 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), ethylhydroxyethyl (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 carboxymethylated cellulose or cellulose nanofibers 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, and is 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 or more, more preferably 1.0 or more, and even more preferably 1.5 times 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 or less, 1.0. 10-fold molars are more preferred, and 1.5-5-fold molars 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 or more, more preferably 0.5 times or more, and even more preferably 0.8 times 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

[Cation]
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 the cationized cellulose can be adjusted by the amount of the 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 cation substituent into the cellulose, the celluloses electrically repel 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.
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 cellulose-based raw material with compound A, which will be described later. Examples of the method of reacting compound A with a cellulosic raw material include a method of mixing a powder or an aqueous solution of compound A with a cellulosic raw material, a method of adding an aqueous solution of compound A to a slurry of a 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, polyphosphoric 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 kind or a combination of two or more kinds thereof. Of these, from the viewpoints of high efficiency of introducing phosphoric acid groups, easy defibration in the defibration process, and easy industrial application, phosphoric acid, sodium phosphate 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 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 phosphate group into the 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 then heated at 100 to 170 ° C. after removing the water. 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 degree of phosphoric acid group substitution per glucose unit of the phosphate esterified cellulose is preferably 0.001 or more. As a result, sufficient defibration (for example, nano-defibration) can be carried out. The upper limit of the degree of substitution is preferably 0.60. As a result, it is possible to prevent the swelling or dissolution of the phosphate esterified cellulose and prevent the situation where nanofibers cannot be obtained. Therefore, the degree of substitution is preferably 0.001 to 0.60. It is preferable that the phosphoric acid esterified cellulose is subjected to a washing treatment such as washing with cold water after boiling. As a result, defibration can be performed efficiently.

[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 time 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 further 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 the 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 matter is a solid matter having an intermediate aspect between the dispersion liquid and the dry solid matter. 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 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 mixed solution 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, xyloglucan, 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, Polydexstrose, Pectin, Chitin, Water Soluble Chitin, Chitosan, Casein, Albumin, Soy Protein Dissolved, Peptone, Polyvinyl Alcohol, Poly Acrylamide, sodium polyacrylic acid, polyvinylpyrrolidone, vinyl acetate, polyamino acid, polylactic acid, polyapple 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. The 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, pressing, 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., batch type box drying device, aeration drying device, vacuum box drying device, or 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 has high energy efficiency and can immediately recover the dried object without applying heat more than necessary.

3) Other compounding agents In this step (a1), other compounding agents may be mixed in addition to the rubber component and the cellulosic fiber. Other compounding agents include sulfenamide (Nt-butyl-2-benzothiazolesulfenamide, etc.), zinc oxide, stearic acid and other vulcanization accelerators, 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 regulators, etc. that can be used in the field of rubber. The mixture obtained in this step (a1) is subjected to the heating step (b1). As will be described later, the conditions are adjusted so that the cross-linking of the rubber component does not proceed in the heating step, but it is preferable that the cross-linking agent is not mixed in this step from the viewpoint of increasing the degree of freedom of the conditions.

4) Filtration 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 (a1), the dispersion obtained by filtering the cellulose nanofiber dispersion or the cellulose nanofiber isolated from the dispersion may be used. Regarding filtration, the contents described in Japanese Patent Application No. 2016-136722 are incorporated in the present invention.

(2) Step (b1)
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. If the temperature is less than 100 ° C., this effect is not sufficiently exhibited, and if the temperature 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 point of view, the heating time is preferably 5 to 300 minutes, more preferably 10 to 120 minutes, still more preferably 15 to 70 minutes. However, the heating temperature and time of this step are selected so that the cross-linking reaction of the rubber component does not proceed.

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, in the mixture obtained in the step (a1), a dispersion liquid in which the rubber component is dispersed in a dispersion medium, a solution dissolved in a solvent, or a dispersion in which cellulosic fibers are dispersed in a dispersion medium. Since there may be a liquid medium derived from a liquid or the like, it is preferable to remove it before the step (b1). 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.

(4) Step (c1)
In this step, the mixture obtained in step (b1), the methylene acceptor compound and the methylene donor compound (for convenience, the former is referred to as "MA compound", the latter is referred to as "MD compound", and both are collectively referred to as "MA / MD compound". There is) and mix. The methylene acceptor compound (MA compound) is a compound that can accept a methylene group and can form a polymer by mixing with a methylene donor compound and heating. Examples of the methylene acceptor compound include phenol compounds such as phenol, resorcinol, resorcin, and cresol and derivatives thereof, resorcin-based resins, cresol-based resins, and phenol resins. Examples of the phenol resin include a condensate of the above-mentioned phenol compound and its derivative and an aldehyde compound such as formaldehyde and acetaldehyde. The phenol resin can be classified into a novolak resin (acid catalyst) and a resol resin (alkaline catalyst) depending on the catalyst at the time of condensation, and any of them may be used in the present invention. The phenolic resin may be modified with oil or fatty acid. Examples of oils and fatty acids include rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, linoleic acid and the like.

The methylene donor compound (MD compound) is a compound that can donate a methylene group and can form a polymer by mixing with a methylene acceptor compound and heating. Examples of the methylene acceptor compound include hexamethylenetetramine and melamine derivatives. Examples of the melamine derivative include hexamethylol melamine, hexamethoxymethyl melamine, pentamethoxymethyl melamine, pentamethoxymethylol melamine, hexaethoxymethyl melamine, hexaxyl- (methoxymethyl) melamine and the like.

Examples of the combination of the MA compound and the MD compound include a combination of cresol, a cresol derivative or a cresol resin and pentamethoxymethylmelamine, a combination of resorcin, a resorcin derivative or a resorcin resin and hexamethylenetetramine, and a cashew-modified phenol resin and hexa. Examples include a combination with methylenetetramine and a combination of phenol resin and hexamethylenetetramine. Of these, a combination of cresol, cresol derivative or cresol resin and pentamethoxymethylmelamine, or a combination of resorcin, resorcin derivative or resorcin resin and hexamethylenetetramine is preferable.

The content of the MA compound is preferably 1% by weight, more preferably 1.3% by weight or more, still more preferably 1.5% by weight or more, based on 100% by weight of the rubber component. As a result, the effect of improving the tensile strength can be sufficiently exhibited. The upper limit is preferably 50% by weight or less, preferably 20% by weight or less, and even more preferably 10% by weight or less. As a result, workability in the manufacturing process can be maintained. Therefore, the content is preferably 1 to 50% by weight, more preferably 1.3 to 20, and even more preferably 1.5 to 10.

The content of the MD compound is preferably 10% by weight, more preferably 20% by weight or more, still more preferably 25% by weight or more, based on 100% by weight of the MA compound. As a result, the effect of improving the tensile strength can be sufficiently exhibited. The upper limit is preferably 100% by weight or less, preferably 90% by weight or less, and even more preferably 85% by weight or less. As a result, workability in the manufacturing process can be maintained. Therefore, the content is preferably 10 to 100% by weight, more preferably 20 to 90% by weight, still more preferably 25 to 85% by weight.

The method of adding the MA / MD compound to the masterbatch composition is not limited, but it is preferable to add the MA / MD compound without using a solvent. These can be mixed, for example, by kneading the MA / MD compound and the masterbatch composition. The temperature at the time of kneading is preferably 20 to 80 ° C. from the viewpoint that the reaction of the compound does not proceed excessively. Further, a rubber composition can be formed by kneading an additive such as a cross-linking agent into the masterbatch composition and then cross-linking, but it is preferable to add the MA / MD compound in the kneading. 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 may be carried out using, for example, a Banbury mixer, a kneader, an open roll or the like. Examples of the cross-linking agent include sulfur and peroxide. Other compounding agents include sulfenamide (Nt-butyl-2-benzothiazolesulfenamide, etc.), zinc oxide, stearic acid and other vulcanization accelerators, 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 regulators, etc. that can be used in the field of rubber. Other formulations can also be added to the masterbatch. It is also possible to dilute the cellulosic fiber concentration by kneading the masterbatch by adding a rubber component together with a cross-linking agent.

The temperature of the kneading may be about room temperature (about 15 to 30 ° C.), but it may be heated to a high temperature so that the rubber component does not undergo a crosslinking 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.

The heating temperature for crosslinking is not particularly limited as long as the crosslinking reaction proceeds. The lower limit of the heating temperature is preferably 140 ° C. or higher, the upper limit is 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 rapid cross-linking reaction as compared with a composition containing no cellulose nanofibers. The reason for this is not limited, but it is speculated 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 thereof may be performed.

2. 2. Method for Producing Second Master Batch The method for producing the second master batch is a step of preparing a mixture containing (a2) a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound, and (b2) the above. It comprises heating the mixture at 100-300 ° C. for 5-600 minutes.

(1) Step (a2)
In this step, a mixture containing a rubber component, a cellulosic fiber, a methylene acceptor compound (MA compound), and a methylene donor compound (MD compound) is prepared. The rubber component, the cellulosic fiber, the MA / MD compound, and the blending amount thereof are as described in the first production method.
This step can be carried out in the following aspects.
Aspect 1: A mixture of a rubber component and a cellulosic fiber and a MA / MD compound are mixed.
Aspect 2: A mixture of a rubber component and a MA / MD compound and a cellulosic fiber are mixed.
Aspect 3: A mixture of a cellulosic fiber and an MA / MD compound and a rubber component are mixed.
Aspect 4: A mixture of a rubber component and one compound of an MA compound or an MD compound and a mixture of a cellulosic fiber and the other compound are mixed.
Aspect 5: A rubber component, a cellulosic fiber, and a MA / MD compound are mixed.

i) Aspect 1
The mixture of the rubber component and the cellulosic fiber can be prepared in the same manner as in the step (a1) of the first production method. The method of mixing this mixture with the MA / MD compound is not limited. For example, the MA / MD compound dissolved in a solvent or dispersed in a dispersion medium or the MA / MD compound can be added to a mixture of a rubber component containing a liquid medium and a cellulosic fiber without using a solvent. In this case, it is preferable to remove the liquid medium from the mixture before performing step (b2). The concentrations of the MA compound solution or dispersion and the MD compound solution or dispersion are preferably about 5 to 20% by weight, respectively. As the solvent or dispersion medium, a hydrophilic solvent such as water or alcohol is preferable.

ii) Aspect 2
The mixture of the rubber component and the MA / MD compound is prepared by dissolving the rubber component in a dispersion medium or a solution dissolved in a solvent without using the MA / MD compound or the solvent dissolved in the solvent or dispersed in the dispersion medium. It can be prepared by adding a MA / MD compound. The mixture of the mixture and the cellulosic fiber can be prepared in the same manner as in the step (a1) of the first production method. In this case, it is preferable to remove the liquid medium from the mixture before performing step (b2). The concentrations of the MA compound solution and the MD compound solution or dispersion are the same as in Aspect 1.

iii) Aspect 3
A mixture of the cellulosic fiber and the MA / MD compound can be prepared by adding the MA / MD compound dissolved in the solvent or dispersed in the dispersion medium to the cellulosic fiber dispersion or the MA / MD compound without using the solvent. The mixture of the mixture and the rubber component can be prepared in the same manner as in the step (a1) of the first production method. In this case, it is preferable to remove the liquid medium from the mixture before performing step (b2). The concentrations of the solution or dispersion of the MA compound and the solution or dispersion of the MD compound are the same as those in the first aspect.

iv) Aspect 4
For the mixture of the rubber component and the MA compound, the MA compound dissolved in the solvent or dispersed in the dispersion medium or the MA compound is added to the dispersion liquid in which the rubber component is dispersed in the dispersion medium or the solution dissolved in the solvent. Can be prepared by The mixture of the cellulosic fiber and the MD compound can be prepared by adding the MD compound dissolved in the solvent or dispersed in the dispersion medium or the MD compound to the cellulosic fiber dispersion without using the solvent. The two mixtures can be further mixed in the same manner as in the step (a1) of the first production method. The same applies when the MA compound and the MD compound are replaced. It is preferable to remove the liquid medium from the mixture before performing step (b2). The concentrations of the solution or dispersion of the MA compound and the solution or dispersion of the MD compound are the same as those in the first aspect.

v) Aspect 5
In this embodiment, the rubber component, the cellulosic fiber, and the MA / MD compound are mixed at the same time. The mixing is preferably carried out in the presence of a liquid medium. The liquid medium may be derived from a rubber component dispersion or solution, a cellulose nanofiber dispersion, an MA compound solution or dispersion, or an MD compound solution or dispersion.

The mixture obtained in this step can contain the above-mentioned compounding agent. However, from the viewpoint of suppressing the progress of the crosslinking reaction in the heating step, it is preferable that the mixture obtained in this step does not contain a crosslinking agent.

(2) Step (b2)
The step (b2) can be carried out in the same manner as the step (b1) in the first manufacturing method. However, considering the influence of the thermal history on the MA / MD compound, it is preferable to set the temperature in the step (b2) to be lower than the temperature in the step (b1). Specifically, it is preferable to heat at 150 ° C. or lower, and more preferably 120 ° C. or lower.

(3) Kneading and Cross-linking Step The rubber composition can be formed by kneading and cross-linking the master batch obtained in the step (b2). The kneading and cross-linking are as described in the first method.

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.

[Manufacture of cellulose oxide nanofibers]
5.00 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from softwood, 39 mg (0.05 mmol per 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 prepared by dissolving 1.0 mmol) in 1 g of absolute dry cellulose, and 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%, 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 1.0% by weight (w / v), and the mixture was treated three times with an ultrahigh pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 3 nm and the aspect ratio was 250.

1. 1. Example by the first manufacturing method <Example 1-1>
[Mixing step a1]
673.1 g of an aqueous dispersion having a solid content concentration of 1.04% (w / v) of the cellulose oxide nanofibers obtained as described above, and a natural rubber polymer as a rubber component (trade name: HA-LATEX, REDITEX Co., Ltd.) 56.7 g (31.7% solid content concentration) was mixed so that the weight ratio of the rubber component and the cellulose nanofibers was 100:20, and the mixture was stirred with a TK homomixer (8000 rpm) for 10 minutes. The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to give a mixture.

[Heating step b1]
The dried mixture obtained in the mixing step was heated in an oven at 120 ° C. for 30 minutes.

[MA / MD compound mixing step c1]
The natural rubber polymer was dried in a heating oven at 70 ° C. for 19 hours.
To 42 g of the mixture obtained in the heating step, the dried natural rubber polymer, which is 3 times by weight of the natural rubber polymer of the mixture, is added, and 4.9 g of sulfur and a vulcanization accelerator (N-oxydiethylene-2-) are added. Benzothiazolyl vulcan amide) 0.98 g, zinc oxide 8.4 g, stearic acid 0.7 g, resorcin 0.88 g, hexamethylene tetramine 0.56 g were added, and open roll (manufactured by Kansai Roll Co., Ltd.) was used. The mixture was kneaded at 50 ° C. for 20 minutes to obtain a master batch sheet. The weight ratio of the rubber component to the cellulose nanofibers is 100: 5, the weight ratio of the rubber component to resorcin is 100: 0.63, and the weight ratio of resorcin to hexamethylenetetramine is 100: 63.6. It was.

[Crossing (vulcanization) process]
This sheet was sandwiched between dies and press-crosslinked at 150 ° C. for 15 minutes to obtain a sheet of a rubber composition having a thickness of about 2 mm. This was cut into a test piece having a predetermined shape, and the tensile property, which is one of the reinforcing properties, was measured according to JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to obtain the tensile property". The larger each value is, the better the rubber composition is reinforced, indicating that the mechanical strength of the rubber is excellent.

<Example 1-2>
A rubber composition was produced and evaluated in the same manner as in Example 1-1 except that the heating temperature in the heating step was set to 150 ° C.

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

2. 2. Example by the second manufacturing method <Example 2-1>
[Mixing step a2]
673.1 g of an aqueous dispersion having a solid content concentration of 1.04% (w / v) of the cellulose oxide nanofibers obtained as described above, and a natural rubber polymer as a rubber component (trade name: HA-LATEX, REDITEX Co., Ltd.) 56.7 g of the product, solid content concentration 61.7%) was mixed so that the weight ratio of the rubber component and the cellulose nanofibers was 100:20, and 8.75 g of a 10 wt% resorcin aqueous solution and 5.6 g were added. A 10 wt% hexamethylenetetramine aqueous solution was added, and the mixture was stirred with a TK homomixer (8000 rpm) for 10 minutes. The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to give a mixture. The weight ratio of the rubber component to the total amount of resorcin and hexamethylenetetramine was 100: 4.1.

[Heating step b2]
The dried mixture obtained in the mixing step was heated in an oven at 120 ° C. for 30 minutes.

[Crossing (vulcanization) process]
The natural rubber polymer was dried in a heating oven at 70 ° C. for 19 hours.
To 43.4 g of the mixture obtained in the heating step, a dried natural rubber polymer three times by weight of the natural rubber polymer of the mixture was added, and 4.9 g of sulfur and a vulcanization accelerator (N-oxydiethylene-2-) were added. Add 0.98 g of benzothiazolyl vulcan amide), 8.4 g of zinc oxide, and 0.7 g of stearic acid, and knead with open roll (manufactured by Kansai Roll Co., Ltd.) at 50 ° C. for 20 minutes to prepare a master batch sheet. Obtained. The weight ratio of the rubber component to the cellulose nanofibers was 100: 5, the weight ratio of the rubber component to resorcin was 100: 0.63, and the weight ratio of resorcin to hexamethylenetetramine was 100: 63.6.

This sheet was sandwiched between dies and press-crosslinked at 150 ° C. for 15 minutes to obtain a sheet of a rubber composition having a thickness of about 2 mm. This was cut into a test piece having a predetermined shape, and the tensile property, which is one of the reinforcing properties, was measured according to JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to obtain the tensile property". The larger each value is, the better the rubber composition is reinforced, indicating that the mechanical strength of the rubber is excellent.

<Example 2-2>
A rubber composition was produced and evaluated in the same manner as in Example 2-1 except that the heating temperature in the heating step was set to 150 ° C.

<Comparative example 2>
A rubber composition was produced and evaluated in the same manner as in Example 2-1 except that the heating step was not carried out.

<Comparative example 3>
The natural rubber polymer was dried in a heating oven at 70 ° C. for 19 hours. To 140 g of the natural rubber polymer, 4.9 g of sulfur, 0.98 g of a vulcanization accelerator (N-oxydiethylene-2-benzothiazolyl sulphenamide), 8.4 g of zinc oxide, and 0.7 g of stearic acid were added and opened. Using a roll (manufactured by Kansai Roll Co., Ltd.), kneading was performed at 50 ° C. for 20 minutes to obtain a sheet of a master batch for comparison. This sheet was sandwiched between dies and press-crosslinked at 150 ° C. for 15 minutes to obtain a comparative rubber composition sheet having a thickness of about 2 mm, which was evaluated in the same manner as in Example 1-1.

<Comparative example 4>
The solid content concentration of the cellulose oxide nanofibers obtained as described above is 1.04% (w / v) (1% by weight), 673.1 g of the aqueous dispersion, and a natural rubber polymer (trade name: trade name: HA-LATEX) as a rubber component. , Made by Latex Co., Ltd., solid content concentration 61.7%) 56.7 g was mixed so that the weight ratio of the rubber component and the cellulose nanofibers was 100:20, and the mixture was stirred with a TK homomixer (8000 rpm) for 10 minutes. did. The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to give a mixture.
To 42 g of the dried mixture, a dried natural rubber polymer 3% by weight of the natural rubber polymer of the mixture is added, and 4.9 g of sulfur and a vulcanization accelerator (N-oxydiethylene-2-benzothiazolylsul) are added. Add 0.98 g of fenamide), 8.4 g of zinc oxide, and 0.7 g of stearic acid, and knead with an open roll (manufactured by Kansai Roll Co., Ltd.) at 50 ° C. for 20 minutes to combine the rubber component with the cellulose nanofibers. A sheet of a comparative master batch having a weight ratio of 100: 5 was obtained. A rubber composition sheet for comparison was obtained and evaluated in the same manner as in Comparative Example 3.
These results are shown in Table 1.

The rubber composition produced from the masterbatch of the present invention 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. Furthermore, it is considered that the mechanical strength of the rubber composition was further improved by forming a novolak type polymer by the addition condensation reaction of the MA / MD compound, which further enhanced the affinity between the hydrophobized fiber and the rubber component. Be done.

Claims (10)

A method for producing a masterbatch, which comprises a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound.
(A1) A step of mixing a rubber component and a cellulosic fiber to obtain a mixture,
(B1) The step of heating the mixture obtained in the step (a1) at 100 to 300 ° C. for 5 to 600 minutes, and (c1) the mixture obtained in the step (b1), a methylene acceptor compound and a methylene donor compound. look including a step of mixing door,
The cellulosic fiber is carboxylated cellulose or carboxymethylated cellulose.
The methylene acceptor compound is a phenol compound, a derivative thereof, a resorcin-based resin, a cresol-based resin, or a phenol resin.
The methylene donor compound is hexamethylenetetramine or a melamine derivative.
The content of the methylene acceptor compound is 1% by weight or more with respect to 100% by weight of the rubber component.
The content of the methylene donor compound is 10% by weight or more with respect to 100% by weight of the methylene acceptor compound.
How to make a masterbatch. A method for producing a masterbatch, which comprises a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound.
(A2) A step of preparing a mixture containing a rubber component, a cellulosic fiber, a methylene acceptor compound, and a methylene donor compound, and (b2) the mixture obtained in the step (a2) of 5 to 600 at 100 to 300 ° C. the minute heating to process only contains,
The cellulosic fiber is carboxylated cellulose or carboxymethylated cellulose.
The methylene acceptor compound is a phenol compound, a derivative thereof, a resorcin-based resin, a cresol-based resin, or a phenol resin.
The methylene donor compound is hexamethylenetetramine or a melamine derivative.
The content of the methylene acceptor compound is 1% by weight or more with respect to 100% by weight of the rubber component.
The content of the methylene donor compound is 10% by weight or more with respect to 100% by weight of the methylene acceptor compound.
How to make a masterbatch. The mixture of the step (a1) contains at least a dispersion or solution of the rubber component, or a dispersion medium or solvent derived from the dispersion of the cellulosic fibers.
The production method according to claim 1, further comprising a step of removing the dispersion or solution of the rubber component or the dispersion medium or solvent derived from the dispersion of the cellulosic fiber before the step (b1). The mixture of the step (a2) contains at least a dispersion or solution of the rubber component, a dispersion of the cellulosic fibers, or a dispersion medium or solvent derived from a dispersion or solution of a methylene acceptor compound or a methylene donor compound. ,
Prior to the step (b2), the dispersion medium or solvent derived from the dispersion liquid or solution of the rubber component, the dispersion liquid of the cellulosic fiber, or the dispersion liquid or solution of the methylene acceptor compound or the methylene donor compound is removed. The production method according to claim 2, further comprising a step. The content of the methylene acceptor compound is 50% by weight or less with respect to 100% by weight of the rubber component.
The production method according to any one of claims 1 to 4, wherein the content of the methylene donor compound is 100% by weight or less with respect to 100% by weight of the methylene acceptor compound. The production method according to any one of claims 1 to 5, 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 production method according to any one of claims 1 to 6, wherein the rubber component comprises an acrylonitrile-butadiene rubber (NBR) polymer or a natural rubber (NR) polymer. The production method according to any one of claims 1 to 7, wherein the methylene acceptor compound is selected from the group consisting of resorcin, a resorcin derivative, a resorcin-based resin, and a combination thereof. The production method according to any one of claims 1 to 8, wherein the methylene donor compound is hexamethylenetetramine. A method for producing a rubber composition, which comprises a step of preparing a masterbatch by the method according to claims 1 to 9 and a step of cross-linking the masterbatch.