JP6153694B1 - Method for producing rubber composition - Google Patents

Abstract

The present invention provides a method for producing a rubber composition containing cellulose nanofibers having a higher dispersibility of cellulose nanofibers and improved tensile strength at a relatively high solid content concentration. Let it be an issue. A method for producing a rubber composition containing cellulose nanofibers, comprising a step of mixing a dry solid containing cellulose nanofibers and an aqueous dispersion containing a rubber component, Solve the problem.

Description

  The present invention relates to a method for producing a rubber composition.

  In recent years, a technique called cellulose nanofiber, which improves various strengths in a rubber composition, such as tensile strength, has been known by incorporating into a rubber composition a material produced by finely pulverizing plant fibers to the nano level. .

  For example, Patent Document 1 discloses a rubber / short fiber masterbatch obtained by stirring and mixing cellulose short fibers having an average diameter of less than 0.5 μm and rubber latex. According to this document, a short fiber having an average fiber diameter of less than 0.5 μm is preliminarily fibrillated in water, and this is mixed with a rubber latex and dried to uniformly distribute the short fiber in the rubber. It is said that by using this rubber / short fiber master batch, a rubber composition having a balance between rubber reinforcement and fatigue resistance can be obtained.

  However, in this method, since the solid content concentration of the cellulose nanofiber aqueous dispersion is as low as several percent or less, if this is added to the rubber latex, the solid content concentration of the whole mixed solution is lowered and is difficult to handle.

  On the other hand, solids obtained by drying cellulose nanofibers dispersed in water are known. However, once dried cellulose nanofibers are not sufficiently redispersed even if they are dispersed again in water. In addition to freeze-drying, critical point drying, substitution after drying with organic solvents, and other methods for redispersing dried solids of cellulose nanofibers in water, drying is performed after mixing with water-soluble polymers. Although a method (Patent Document 2) has been proposed, Patent Document 2 does not describe inclusion in a rubber composition.

JP 2006-206864 A International Publication No. 2015/107995

  Therefore, an object of the present invention is to provide a method for producing a rubber composition having a sufficiently improved reinforcing property by containing cellulose nanofibers at a relatively high solid content concentration.

The present invention provides the following.
(1) A method for producing a rubber composition containing cellulose nanofibers,
The manufacturing method of a rubber composition including the process of mixing the dry solid substance containing a cellulose nanofiber, and the aqueous dispersion containing a rubber component.
(2) The method for producing a rubber composition according to (1), further comprising a step of removing the dispersion medium from the dispersion of cellulose nanofibers to prepare the dry solid.
(3) Manufacture of the rubber composition as described in (1) in which the dry solid substance containing the said cellulose nanofiber contains 5-50 weight% of water-soluble polymer with respect to the absolutely dry solid content of a cellulose nanofiber. Method.
(4) The dry solid containing the cellulose nanofiber is obtained by removing the dispersion medium from the dispersion containing the cellulose nanofiber and the water-soluble polymer with a drum dryer. (1) or (3) The manufacturing method of the rubber composition of description.
(5) The dry solid containing the cellulose nanofiber is obtained by adjusting the pH of the dispersion containing the cellulose nanofiber and the water-soluble polymer to 9 to 11, and then removing the dispersion medium (1 ), (3) or (4). The method for producing a rubber composition according to any one of (4).
(6) The manufacturing method of the rubber composition as described in (2) in which the dispersion liquid of the said cellulose nanofiber contains 5 to 50 weight% of water-soluble polymer with respect to the absolutely dry solid content of a cellulose nanofiber.
(7) The dispersion of the cellulose nanofiber contains a water-soluble polymer, and in the adjusting step, the dispersion medium is removed from the dispersion containing the cellulose nanofiber and the water-soluble polymer by a drum dryer. ) Or the method for producing a rubber composition according to (6).
(8) The dispersion liquid of the cellulose nanofiber contains a water-soluble polymer, and after adjusting the pH of the dispersion liquid containing the cellulose nanofiber and the water-soluble polymer to 9 to 11 in the preparation step, The method for producing a rubber composition according to any one of (2), (6), and (7), wherein
(9) The cellulose nanofiber according to any one of (1) to (8), wherein the cellulose nanofiber has a carboxyl group amount of 0.6 to 2.0 mmol / g with respect to the absolute dry weight of the cellulose nanofiber. Of producing a rubber composition.
(10) The rubber composition according to any one of (1) to (8), wherein the cellulose nanofiber has a degree of carboxymethyl substitution of 0.01 to 0.50 per glucose unit of the cellulose nanofiber. Production method.
(11) The production of the rubber composition according to any one of (1) to (8), wherein the cellulose nanofiber has a cation substitution degree of 0.01 to 0.40 per glucose unit of the cellulose nanofiber. Method.
(12) The method for producing a rubber composition according to any one of (3) to (11), wherein the water-soluble polymer is carboxymethylcellulose or a salt thereof.

  ADVANTAGE OF THE INVENTION According to this invention, the dispersibility of a cellulose nanofiber can be improved and the method of manufacturing the rubber composition in which the tensile strength was improved in a comparatively high solid content concentration can be provided.

In the present invention, “X to Y” includes X and Y which are the end values. “X or Y” means either X or Y, or both.
<Cellulose nanofiber>
In the present invention, the cellulose nanofiber is a fine fiber having an average fiber diameter of about 4 to 500 nm and an average aspect ratio of 100 or more, and can be obtained by fibrillating an unmodified or chemically modified cellulose raw material.

The average fiber diameter and average fiber length of cellulose nanofibers can be obtained by averaging the fiber diameter and fiber length obtained from the results of observing each fiber using a field emission scanning electron microscope (FE-SEM). it can. Also, the aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length / average fiber diameter In the present invention, there is no particular limitation as to whether the cellulose raw material is unmodified or chemically modified. Examples of chemical modification methods include oxidation, etherification, Phosphorylation, esterification, silane coupling, fluorination, cationization and the like can be performed, but from the viewpoint of affinity with rubber, it is preferably chemically modified, and among them, an N-oxyl compound is used. More preferably, it is any of oxidation, carboxymethylation, and cationization.
<Cellulose raw material>
In the present invention, the cellulose raw material may be a plant (for example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (coniferous unbleached kraft pulp (NUKP), coniferous bleached kraft pulp (NBKP), broadleaf tree not yet). Bleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP) thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (for example, Squirrels), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), microbial products, etc. are known, and any of them can be used in the present invention, preferably cellulose fibers derived from plants or microorganisms More preferably, it is a cellulose fiber derived from a plant.

The fiber diameter of the cellulose fiber raw material used in the present invention is not particularly limited, and the number average fiber diameter is 1 μm to 1 mm. What has undergone general purification is about 50 μm. For example, when a chip or the like having a size of several centimeters is refined, it is preferable to perform a mechanical treatment with a disintegrator such as a refiner or a beater to make it about 50 μm. The cellulose raw material dispersion is preferably water.
<Oxidation>
In the present invention, the oxidation of the cellulose raw material can be performed using a known method, and is not particularly limited, but the amount of the carboxyl group is 0.6 mmol / g to 2.0 mmol with respect to the absolute dry weight of the cellulose nanofiber. It is preferable to adjust to / g.

  As an example, oxidized cellulose is obtained by oxidizing cellulose in water in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide or a mixture thereof. Can do. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and a cellulose fiber having an aldehyde group and a carboxyl group or a carboxylate group on the surface can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by weight or less. The N-oxyl compound refers to a compound that can generate a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction.

  The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize cellulose as a raw material. For example, 0.01 to 10 mmol is preferable, 0.01 to 1 mmol is more preferable, and 0.05 to 0.5 mmol is more preferable with respect to 1 g of absolutely dry cellulose. Moreover, about 0.1-4 mmol / L is preferable with respect to the reaction system. Bromide is a compound containing bromine, examples of which include alkali metal bromides that can dissociate and ionize in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of absolutely dry cellulose.

  As the oxidizing agent, known ones can be used, and for example, halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide and the like can be used. Of these, sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact. The appropriate amount of the oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, further preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. . For example, 1-40 mol is preferable with respect to 1 mol of N-oxyl compounds.

  The cellulose oxidation process allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40 ° C, and may be room temperature of about 15 to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose, so that the pH of the reaction solution is reduced. In order to advance the oxidation reaction efficiently, an alkaline solution such as an aqueous sodium hydroxide solution is added to maintain the pH of the reaction solution at about 8 to 12, preferably about 10 to 11. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions. The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours. The oxidation reaction may be performed in two stages. 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 generated as a by-product in the first-stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing by contacting a gas containing ozone and a cellulose raw material. By this oxidation reaction, at least the hydroxyl groups at the 2nd and 6th positions of the glucopyranose ring are oxidized and the cellulose chain is decomposed. Ozone concentration in the ozone containing gas is preferably 50 to 250 g / ^{m 3,} more preferably 50~220g / ^{m 3.} The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by weight and more preferably 5 to 30 parts by weight when the solid content of the cellulose raw material is 100 parts by weight. The ozone treatment temperature is preferably 0 to 50 ° C, and more preferably 20 to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the conditions for the ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved. After the ozone treatment, an additional oxidation treatment may be performed 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, persulfuric acid, and peracetic acid. For example, these oxidizing agents can be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and a cellulose raw material can be immersed in the solution for additional oxidation treatment.

The amount of the carboxyl group, carboxylate group, and aldehyde group of the cellulose fiber can be adjusted by controlling the amount of the oxidizing agent added and the reaction time. The carboxyl group content is measured, for example, by preparing 60 ml of a 0.5 wt% slurry (aqueous dispersion) of oxidized cellulose, adding 0.1 M hydrochloric acid aqueous solution to pH 2.5, and then adding 0.05 N sodium hydroxide. The electrical conductivity was measured by dropping the aqueous solution until the pH reached 11, and the amount was calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid where the change in electrical conductivity was slow, using the following formula: can do:
Amount of carboxyl group [mmol / g oxidized cellulose or cellulose nanofiber] = a [ml] × 0.05 / oxidized cellulose weight [g].

<Carboxymethylation>
In the present invention, the carboxymethylation of the cellulose raw material can be performed using a known method, and is not particularly limited. However, the substitution degree of carboxymethyl group per anhydroglucose unit of cellulose is 0.01 to 0.50. It is preferable to adjust to. As an example, the following production method can be mentioned, but it may be synthesized by a conventionally known method or a commercially available product may be used. Cellulose is used as a starting material, and 3 to 20 times by weight of water or lower alcohol or both are used as a solvent. Specifically, as the lower alcohol, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol or the like alone or a mixed medium of two or more kinds is used. In addition, the mixing ratio of the lower alcohol when used as a mixed solvent is 60 to 95% by weight. As the mercerizing agent, 0.5 to 20 times moles of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide is used per anhydroglucose residue of the bottoming material. A bottoming raw material, a solvent, and a mercerizing agent are mixed and subjected to mercerization treatment at a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times mol per glucose residue, a reaction temperature of 30 to 90 ° C., preferably 40 to 80 ° C., and a reaction time of 30 minutes to 10 hours, preferably 1 hour. Perform etherification reaction for ~ 4 hours.

As a measuring method of the carboxymethyl substitution degree per glucose unit, it can obtain by the following method, for example. That is, 1) About 2.0 g of carboxymethylated cellulose fiber (absolutely dry) is precisely weighed and put into a 300 mL conical stoppered Erlenmeyer flask. 2) Add 100 mL of a solution of 100 mL of special concentrated nitric acid to 1000 mL of nitric acid methanol and shake for 3 hours to convert the carboxymethyl cellulose salt (CM cellulose) into hydrogenated CM cellulose. 3) Weigh accurately 1.5 to 2.0 g of hydrogenated CM-modified cellulose (absolutely dry) and put into a 300 mL conical flask with a stopper. 4) Wet the hydrogenated CM cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1N H ₂ SO ₄ using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by the following formula:
A = [(100 × F ′ − (0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry weight of hydrogenated CM-modified cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralizing 1 g of hydrogenated CM-modified cellulose
F ′: Factor of 0.1 N H ₂ SO ₄ F: Factor of 0.1 N NaOH <Cationization>
In the present invention, the cationization of the cellulose raw material can be performed using a known method. By cationization, for example, ammonium, phosphonium, sulfonium, groups having these ammonium, phosphonium or sulfonium can be present in the cellulose molecule, but groups having ammonium are preferred, and groups containing quaternary ammonium are particularly preferred. The specific cationization method is not particularly limited, but as an example, a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2hydroxypropyltrialkylammonium hydride or a halohydrin type thereof is used as a cellulose raw material and a catalyst. Cation-modified with a group containing quaternary ammonium by reacting certain alkali metal hydroxides (sodium hydroxide, potassium hydroxide, etc.) in the presence of water or alcohols having 1 to 4 carbon atoms, or both Cellulose can be obtained. In this method, the degree of cation substitution per glucose unit of the cation-modified cellulose obtained is controlled by controlling the addition amount of the cationizing agent to be reacted, the composition ratio of water and an alcohol having 1 to 4 carbon atoms. Can be adjusted. The degree of substitution herein refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. In other words, it is defined as “a value obtained by dividing the number of moles of the introduced substituent by the total number of moles of 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 substitution of the cellulose fiber of the present invention is 3 (minimum value is 0).

  In the present invention, the degree of cation substitution per glucose unit of cationized cellulose is preferably 0.01 to 0.40. By introducing a cationic substituent into cellulose, the celluloses repel each other electrically. For this reason, the cellulose which introduce | transduced the cation substituent can be nano-defibrated easily. In addition, when the cation substitution degree per glucose unit is smaller than 0.01, nano-defibration cannot be sufficiently performed. On the other hand, if the degree of cation substitution per glucose unit is larger than 0.40, the fiber form cannot be maintained because it swells or dissolves and may not be obtained as a nanofiber. The degree of cation substitution per glucose unit is calculated by the following equation after measuring the nitrogen content with a total nitrogen analyzer TN-10 (Mitsubishi Chemical Corporation) after drying the sample (cation-modified cellulose). can do. The degree of substitution referred to here represents the average value of the number of moles of substituents per mole of anhydroglucose unit.

Degree of cation substitution = (162 × N) / (1-151.6 × N)
N: Nitrogen content <defibration>
In the present invention, an apparatus for defibrating is not particularly limited, but a strong shearing force is applied to the aqueous dispersion using an apparatus such as a high-speed rotation type, a colloid mill type, a high pressure type, a roll mill type, or an ultrasonic type. Is preferred. In particular, for efficient defibration, it is preferable to use a wet high-pressure or ultrahigh-pressure homogenizer that can apply a pressure of 50 MPa or more to the aqueous dispersion and can apply a strong shearing force. The pressure is more preferably 100 MPa or more, and further preferably 140 MPa or more. In addition, prior to defibration and dispersion treatment with a high-pressure homogenizer, if necessary, the cellulose nanofibers are pretreated using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer. Is also possible.

  In the case of defibration by the above treatment, the solid content concentration as the cellulose fiber raw material is 0.1 wt% or more, preferably 0.2 wt% or more, particularly 0.3 wt% or more, and 10 wt% or less, particularly 6 It is preferable that it is below wt%. When the solid content concentration is too low, the amount of liquid is too large with respect to the amount of the cellulose fiber raw material to be processed, resulting in poor efficiency, and when the solid content concentration is too high, the fluidity is deteriorated.

<Water-soluble polymer>
In the present invention, the water-soluble polymer refers to a polymer compound that dissolves in water, such as cellulose derivatives (carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean. Gum, Alginic acid, Alginate, Pullulan, Starch, Hard starch, Scrap flour, Positive starch, Phosphorylated starch, Corn starch, Arabic gum, Locust bean gum, Gellan gum, Gellan gum, Polydextrose, Pectin, Chitin, Water-soluble chitin, Chitosan, Casein , Albumin, soy protein lysate, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyvinyl pyrrolidone, polyvinyl acetate, polyamino , Polylactic acid, polymalic acid, polyglycerin, latex, rosin sizing agent, petroleum resin sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide , Hydrophilic cross-linked polymers, polyacrylates, starch polyacrylic acid copolymers, tamarind gum, gellan gum, pectin, guar gum and colloidal silica and mixtures of one or more thereof. Among these, it is preferable from the point of affinity to use carboxymethylcellulose or its salt. Carboxymethyl cellulose as a water-soluble polymer is different from cellulose nanofibers into which a carboxymethyl group has been introduced.

<Dry solid>
In the present invention, the dry solid refers to a solid obtained by removing the dispersion medium from a dispersion of cellulose nanofibers. In the present invention, the dry solid refers to a completely dry or wet state, and refers to a solid medium having a dispersion medium of 12% by weight or less. Specifically, the dry solid substance which consists of a cellulose nanofiber or this and a dispersion medium below this amount, or the dry solid substance which consists of a cellulose nanofiber and a water-soluble polymer or these and a dispersion medium below this amount is mentioned. Examples of the dispersion medium include water and aqueous organic solvents, but water is preferable. Removing the dispersion medium means removing the dispersion medium by dehydrating (dedispersing medium) or drying the dispersion.

  In the present invention, a solid or liquid water-soluble polymer may be dissolved or dispersed in the aqueous dispersion. Moreover, after adjusting the pH of the dispersion to 9 to 11, a dry solid having good affinity between the rubber composition and the cellulose nanofiber can be obtained by dehydration or drying. In the present invention, the dispersion of cellulose nanofibers refers to a liquid in which cellulose nanofibers are dispersed in a dispersion medium.

  In the present invention, the blending amount of the water-soluble polymer in the dry solid containing the cellulose nanofiber and the water-soluble polymer is 5 to 50% by weight with respect to the absolutely dry solid content of the cellulose nanofiber. preferable. If it is less than 5% by weight, the effect of sufficient redispersibility is hardly exhibited. On the other hand, when it exceeds 50% by weight, problems such as a decrease in viscosity characteristics and dispersion stability, which are characteristics of cellulose nanofibers, may occur. Also, it is not clear why dry solids containing cellulose nanofibers and water-soluble polymers have high affinity (dispersibility) with the rubber component, but when mixing the rubber component and cellulose nanofibers, Molecules dissolve in the rubber component and the viscosity increases. As a result, it is presumed that cellulose nanofibers can be uniformly dispersed in the rubber component by applying a high shear stress during stirring.

  As a method for dehydrating or drying the dispersion or the mixed solution, any conventionally known method may be used, and examples thereof include spray drying, pressing, air drying, hot air drying, and vacuum drying. Examples of the drying apparatus specifically used in the method of the present invention are as follows. That is, continuous tunnel dryer, band dryer, vertical dryer, vertical turbo dryer, multi-stage disk dryer, aeration dryer, rotary dryer, air dryer, spray dryer dryer, spray dryer , Cylindrical dryers, drum dryers, screw conveyor dryers, rotary dryers with heating tubes, vibration transport dryers, batch-type box dryers, aeration dryers, vacuum box dryers, stirring dryers, etc. These drying apparatuses can be used alone or in combination of two or more. Among these, it is preferable to use a drum drying apparatus from the viewpoint of energy efficiency because the heat energy is uniformly supplied directly to an object to be dried. The drum drying apparatus is also preferable in that it can immediately collect a dried product without applying heat more than necessary.

<Rubber component>
The rubber component is a raw material of rubber and is crosslinked to become rubber. Although there are a rubber component for natural rubber and a rubber component for synthetic rubber, either one may be used in the present invention, or both may be combined. For convenience, rubber components for natural rubber and the like are referred to as “natural rubber polymers” and the like.

  Natural rubber (NR) polymer is a natural rubber polymer in a narrow sense without chemical modification; natural rubber polymer chemically modified such as chlorinated natural rubber polymer, chlorosulfonated natural rubber polymer, epoxidized natural rubber polymer; Rubber polymer; deproteinized natural rubber polymer. Examples of synthetic rubber polymers include butadiene rubber (BR) polymer, styrene-butadiene copolymer rubber (SBR) polymer, isoprene rubber (IR) polymer, acrylonitrile-butadiene rubber (NBR) polymer, chloroprene rubber polymer, styrene-isoprene copolymer. Diene 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 (ACM) polymer, epichlorohydrin rubber (CO, ECO) polymer, fluoro rubber (FKM) polymer, silicone rubber (Q) polymer, urethane rubber (U) polymer, chlorosulfonated polyethylene Down (CSM) non-diene-based rubber polymers such as polymers. These rubber polymers may be used alone or in combination. Among these, diene rubber is preferable. These may be used alone or in combination of two or more.

  In the present invention, the rubber component is preferably used as an aqueous dispersion (latex) of the rubber component. Here, the aqueous dispersion (latex) containing the rubber component is a system (emulsion) in which fine particles of the rubber component are stably dispersed in the aqueous solution, and the solid content concentration of the rubber component is usually 30 to 70. %. Moreover, it is preferable that pH of the aqueous dispersion of a rubber component is 7-12.

  When a dry solid containing the cellulose nanofiber and the water-soluble polymer is mixed with the rubber component, the weight ratio of the cellulose nanofiber is 1 to 50% by weight with respect to the absolutely dry solid content of the rubber component. Is preferred. When the ratio is less than 1% by weight, a sufficient tensile strength improvement effect is not exhibited when a crosslinked rubber composition is obtained. On the other hand, when the ratio exceeds 50% by weight, the processability of the rubber composition decreases.

  The lower limit of the total solid concentration of the mixture obtained in this step is preferably 20% by weight or more, more preferably 30% by weight or more, and further preferably 40% by weight or more. Further, the upper limit of the concentration is preferably 100% by weight or less, more preferably 90% by weight or less, and further preferably 80% by weight or less. The production method of the present invention prepares a mixture having a high solid content concentration by subjecting a dry solid obtained by removing a dispersion medium from a dispersion containing cellulose nanofibers, which has not been studied in the past, to mixing with a rubber component. To do. For this reason, the manufacturing method of this invention is excellent in work efficiency and productivity. Also, by dispersing at a high solid content concentration, sufficient shear stress is applied to the cellulose nanofibers, and redispersibility is improved to produce a rubber composition with excellent mechanical strength with high work efficiency and productivity. Achieved that.

<Rubber composition>
The rubber composition of the present invention is produced by removing water or the like derived from latex or dry solid from a mixture of the rubber component and the dry solid. When the dry solid contains a dispersion medium other than water, the water and the dispersion medium are removed from the mixture of the rubber component and the dry solid. In the present invention, water or a dispersion medium is also referred to as a “liquid medium”. The method for removing the liquid medium is not particularly limited, and the mixture may be dried as it is in an oven, or may be dehydrated or dried after coagulation. At this time, the pH may be adjusted to 2-6.

  In the present invention, the rubber composition and other necessary rubbers and compounding agents are mixed by a conventionally known method using, for example, a rubber kneader or the like, and crosslinked by a conventionally known method (when sulfur is used, “ Vulcanization)). In the present invention, the rubber composition includes a composition before crosslinking and a crosslinked composition. The composition before crosslinking is referred to as “uncrosslinked rubber composition”, and the composition after crosslinking is also referred to as “crosslinked rubber composition”. Say.

  In the rubber composition of the present invention, in addition to the components described above, other compounding agents conventionally used in the rubber industry include, for example, reinforcing agents, silane coupling agents, vulcanizing agents, stearic acid, vulcanization accelerators, Vulcanization accelerators, oils, curing resins, waxes, anti-aging agents, and the like can be added.

  As the reinforcing agent, any of those used in tire applications can be suitably used, but it is particularly preferable to use at least one of carbon black and silica.

  The use of the vulcanized rubber composition of the present invention is not particularly limited, but is suitable for tires due to its characteristics. For example, it can be used as a pneumatic tire for passenger cars, trucks, buses, heavy vehicles and the like.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these.
<Manufacture of oxidized cellulose nanofiber>
Add 500 g of bleached unbeaten kraft pulp (whiteness 85%) derived from coniferous trees (absolutely dry) to 500 ml of an aqueous solution in which 780 mg of TEMPO (Sigma Aldrich) and 75.5 g of sodium bromide are dissolved, until the pulp is uniformly dispersed Stir. An aqueous sodium hypochlorite solution was added to the reaction system to 6.0 mmol / g to initiate the oxidation reaction. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous 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 no longer changed. The reaction mixture was filtered through a glass filter to separate the pulp, and the pulp was sufficiently 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. The oxidized pulp obtained in the above step was adjusted to 1.0% (w / v) with water and treated three times with an ultrahigh pressure homogenizer (20 ° C., 150 MPa) to obtain a cellulose nanofiber dispersion. The obtained fiber had an average fiber diameter of 4 nm and an aspect ratio of 150.

<Production of carboxymethylated cellulose nanofiber>
In a stirrer capable of mixing pulp, 200 g of dry pulp (NBKP (conifer bleached kraft pulp), manufactured by Nippon Paper Industries Co., Ltd.) and 111 g of sodium hydroxide by dry weight are added, and the pulp solid content is 20% (w / v Water was added so that Thereafter, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (in terms of active ingredient) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and stirred for 1 hour. Thereafter, the reaction product was taken out, neutralized and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. Thereafter, the carboxymethylated pulp was made into 1% (w / v) solid content with water, and fibrillated by treating with a high pressure homogenizer 5 times at 20 ° C. and a pressure of 150 MPa to obtain carboxymethylated cellulose fibers. The obtained fiber had an average fiber diameter of 50 nm and an aspect ratio of 120.

<Manufacture of cationized cellulose nanofiber>
Add pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd.) in dry weight of 200g and sodium hydroxide in dry weight of 24g to pulper that can stir the pulp, and add water so that the pulp solid concentration is 15%. It was. Then, after stirring for 30 minutes at 30 ° C., 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 cation-modified cellulose having a cation substitution degree of 0.05 per glucose unit. Thereafter, the cation-modified pulp was treated at a solid concentration of 1% (w / v) and treated twice with a high-pressure homogenizer at 20 ° C. and a pressure of 140 MPa. The obtained fiber had an average fiber diameter of 50 nm and an aspect ratio of 120.

<Example 1>
Carboxymethylcellulose (trade name: F350HC-4) was added to the 0.7% by weight aqueous dispersion of the above oxidized cellulose nanofibers in an amount of 30% by weight with respect to the cellulose nanofibers, and the mixture was added at 60 with a TK homomixer (12,000 rpm). Stir for minutes. To this aqueous dispersion, 0.5% by weight of an aqueous sodium hydroxide solution was added to adjust the pH to 9, and then a vapor pressure of 0.5 MPa. G, and dried with a drum dryer D0405 (Katsuragi Industry Co., Ltd.) with a drum rotation speed of 2 rpm to obtain a mixed dry solid of cellulose nanofibers and carboxymethylcellulose having a water content of 5% by weight. 100 g of rubber latex (trade name: HA latex, Residex, solid content concentration: 65% by weight) is mixed with 5% by weight of the above-mentioned mixed dry solid in a dry dry equivalent, and TK homomixer (8000 rpm) ) For 60 minutes to obtain a mixture. The mixture had a very high total solids concentration of 68.25% by weight. This mixture was dried in a heating oven at 70 ° C. for 10 hours to obtain a master batch.

  For the master batch obtained by the above method, zinc oxide and stearic acid are mixed in an amount of 6% by weight and 0.5% by weight, respectively, with respect to the rubber component in the master batch. A kneaded material was obtained by kneading at 30 ° C. for 10 minutes. Sulfur and a vulcanization accelerator (BBS, Nt-butyl-2-benzothiazole sulfenamide) were added to the kneaded product at 3.5 wt% and 0.7 wt%, respectively, with respect to the rubber component in the kneaded product. % And using an open roll (manufactured by Kansai Roll Co., Ltd.), kneading at 30 ° C. for 10 minutes to obtain a sheet of an unvulcanized rubber composition. The obtained unvulcanized rubber composition sheet was sandwiched between molds and press vulcanized at 150 ° C. for 10 minutes to obtain a vulcanized rubber sheet having a thickness of 2 mm. The obtained vulcanized rubber sheet was cut into a test piece having a predetermined shape, and according to JIS K6251 “vulcanized rubber and thermoplastic rubber—how to obtain tensile properties”, indicating tensile strength, at 100% strain, The stress at 300% strain and the breaking strength were measured. The larger each value, the better the vulcanized rubber composition is reinforced and the better the mechanical strength.

In this example, a vulcanized rubber composition was produced using a mixture having a total solid content of 68.25% by weight, which was very high, and the cellulose nanofibers were well dispersed in the rubber matrix. As shown, excellent mechanical properties were obtained.
<Example 2>
It carried out similarly to Example 1 except having changed the cellulose nanofiber into the carboxymethylated cellulose nanofiber manufactured by said method.
<Example 3>
It carried out similarly to Example 1 except having changed the cellulose nanofiber into the cationized cellulose nanofiber manufactured by said method.
<Example 4>
When the aqueous dispersion of cellulose nanofibers was dried, the same procedure as in Example 1 was carried out except that the cellulose nanofibers were dried alone without mixing carboxymethylcellulose.

<Comparative Example 1>
In Example 1, when obtaining a masterbatch, it carried out like Example 1 except not using the mixed dry solid substance of a cellulose nanofiber and carboxymethylcellulose.
<Comparative example 2>
In Example 1, when obtaining a master batch, instead of using a dried cellulose nanofiber solid material, an undried cellulose nanofiber aqueous dispersion (solid content concentration: 1.0% by weight) was used. 1 was performed. The amount of cellulose nanofibers relative to the rubber component was the same as in Example 1.
<Comparative Example 3>
In Example 2, when obtaining a masterbatch, instead of using a dried cellulose nanofiber solid material, an undried cellulose nanofiber aqueous dispersion (solid content concentration: 1.0% by weight) was used except that Performed in the same manner as 2. The amount of cellulose nanofibers relative to the rubber component was the same as in Example 2.
<Comparative example 4>
In Example 3, when obtaining a masterbatch, instead of using a dried cellulose nanofiber solid material, an undried cellulose nanofiber aqueous dispersion (solid content concentration: 1.0% by weight) was used. This was carried out in the same manner as in 3. The amount of cellulose nanofibers relative to the rubber component was the same as in Example 3.

上記の結果から、セルロースナノファイバーと水溶性高分子の混合乾燥固形物を用いた実施例１〜３およびセルロースナノファイバーの乾燥固形物を用いた実施例４では、セルロースナノファイバーを用いなかった比較例１、未乾燥のセルロースナノファイバー水分散液を用いた比較例２〜４に比べ、１００％、３００％ひずみ時における応力、破断強度が明らかに大きいことから、加硫ゴム組成物が良好に補強されており、機械強度に優れることが分かる。これは、ゴム成分とセルロースナノファイバーの混合物において固形分濃度が高いため、撹拌時に十分なずり応力（せん断応力）が発生して、セルロースナノファイバーの分散性を高めたためと推察される。さらに本発明は、固形分濃度の高い混合物から加硫ゴム組成物を得ることができるため生産性及び作業性に優れていることも明らかである。

From the above results, in Examples 1 to 3 using a mixed dry solid of cellulose nanofibers and a water-soluble polymer and in Example 4 using a dry solid of cellulose nanofibers, comparison was made without using cellulose nanofibers. Compared to Example 1 and Comparative Examples 2 to 4 using an undried cellulose nanofiber aqueous dispersion, the stress at 100% and 300% strain and the breaking strength are clearly large, so that the vulcanized rubber composition is excellent. It can be seen that it is reinforced and has excellent mechanical strength. This is presumably because the mixture of the rubber component and the cellulose nanofiber has a high solid content concentration, so that a sufficient shear stress (shear stress) is generated at the time of stirring and the dispersibility of the cellulose nanofiber is increased. Furthermore, since the vulcanized rubber composition can be obtained from the mixture having a high solid content concentration, the present invention is clearly excellent in productivity and workability.

Claims (15)

A method for producing a rubber composition containing cellulose nanofibers,
The manufacturing method of a rubber composition including the process of mixing the dry solid substance containing a cellulose nanofiber, and the aqueous dispersion containing a rubber component.   The manufacturing method of the rubber composition of Claim 1 which further includes the process of removing a dispersion medium from the dispersion liquid of a cellulose nanofiber, and preparing the said dry solid substance.   The manufacturing method of the rubber composition of Claim 1 in which the dry solid containing the said cellulose nanofiber contains 5-50 weight% of water-soluble polymer with respect to the absolutely dry solid content of a cellulose nanofiber.   The rubber composition according to claim 1 or 3, wherein the dry solid containing the cellulose nanofibers is obtained by removing a dispersion medium from a dispersion containing cellulose nanofibers and a water-soluble polymer with a drum dryer. Manufacturing method.   The dry solid containing the cellulose nanofibers is obtained by removing the dispersion medium after adjusting the pH of the dispersion containing the cellulose nanofibers and the water-soluble polymer to 9-11. Or the manufacturing method of the rubber composition as described in any one of 4.   The manufacturing method of the rubber composition of Claim 2 in which the dispersion liquid of the said cellulose nanofiber contains 5-50 weight% of water-soluble polymer with respect to the absolutely dry solid content of a cellulose nanofiber.   The dispersion of the cellulose nanofiber contains a water-soluble polymer, and in the adjusting step, the dispersion medium is removed from the dispersion containing the cellulose nanofiber and the water-soluble polymer by a drum dryer. The manufacturing method of the rubber composition as described in above.   The dispersion liquid of the cellulose nanofiber contains a water-soluble polymer, and after the pH of the dispersion liquid containing the cellulose nanofiber and the water-soluble polymer is adjusted to 9 to 11 in the preparation step, the dispersion medium is removed. The manufacturing method of the rubber composition as described in any one of Claim 2, 6, or 7. The manufacturing method of the rubber composition of Claim 1 or 2 with which the said cellulose nanofiber has the amount of carboxyl groups of 0.6-2.0 mmol / g with respect to the absolute dry weight of a cellulose nanofiber. The manufacturing method of the rubber composition of Claim 1 or 2 with which the said cellulose nanofiber has 0.01-0.50 carboxymethyl substitution degree per glucose unit of a cellulose nanofiber. The manufacturing method of the rubber composition of Claim 1 or 2 with which the said cellulose nanofiber has a cation substitution degree of 0.01-0.40 per glucose unit of a cellulose nanofiber. The rubber composition according to any one of claims 3 to 8, wherein the cellulose nanofiber has a carboxyl group amount of 0.6 to 2.0 mmol / g with respect to the dry weight of the cellulose nanofiber. Production method. The manufacturing method of the rubber composition as described in any one of Claims 3-8 in which the said cellulose nanofiber has 0.01-0.50 carboxymethyl substitution degree per glucose unit of a cellulose nanofiber. The method for producing a rubber composition according to any one of claims 3 to 8, wherein the cellulose nanofiber has a cation substitution degree of 0.01 to 0.40 per glucose unit of the cellulose nanofiber. The method for producing a rubber composition according to any one of claims 3 to 8 , and 12 to 14 , wherein the water-soluble polymer is carboxymethyl cellulose or a salt thereof.