WO2020054342A1

WO2020054342A1 - Method for producing rubber composition

Info

Publication number: WO2020054342A1
Application number: PCT/JP2019/032792
Authority: WO
Inventors: 隼人加藤; 康太郎伊藤; 芽衣 ▲高▼木; 喜威山田
Original assignee: 日本製紙株式会社
Priority date: 2018-09-14
Filing date: 2019-08-22
Publication date: 2020-03-19
Also published as: JPWO2020054342A1; JP6915170B2

Abstract

Provided is a method for producing a rubber composition, the method including a mixing step for mixing a modified cellulose nanofiber dispersion and a rubber component-containing latex, by using a static in-line fluid mixer.

Description

Method for producing rubber composition

<< The present invention relates to a method for producing a rubber composition containing modified cellulose nanofibers.

Cellulose nanofibers (CNFs) are expected to be used as reinforcing fibers in rubber compositions. For example, Patent Document 1 describes a rubber composition in which cellulose nanofibers are dispersed.

Generally, in order to uniformly disperse cellulose nanofibers in a rubber composition, dispersion is performed by applying a shearing force with a stirring blade or the like using a homogenizer, a propeller-type stirring device, a rotary stirring device, or the like.

JP 2006-206864 A

However, when a natural rubber latex and a cellulose nanofiber dispersion were mixed using a homogenizer equipped with a high-speed rotating stirring blade, the latex sometimes aggregated due to the shearing force of the stirring blade. In addition, coagulated dirt of latex adheres to the inside of the homogenizer, and the operation of the homogenizer must be stopped periodically to remove the dirt, resulting in a problem in continuous operability.

分散 In addition, the dispersibility of cellulose nanofibers in a rubber composition containing cellulose nanofibers and a rubber component affects physical properties of a molded article or the like made from this rubber composition. Therefore, it is required to further improve the dispersibility of the cellulose nanofiber in the rubber composition.

Therefore, an object of the present invention is to provide a production method which is excellent in dispersibility and continuous operability and can obtain a high-strength rubber composition.

者 The present inventors have conducted intensive studies to achieve such an object, and as a result, have found that it is extremely effective to use a specific mixing device, and have completed the present invention.

The present invention provides the following.
(1) A method for producing a rubber composition containing modified cellulose nanofibers, comprising a mixing step of mixing a modified cellulose nanofiber dispersion and a latex containing a rubber component using an in-line static fluid mixing device. A method for producing a rubber composition.
(2) The method for producing a rubber composition according to (1), wherein the modified cellulose nanofiber contains oxidized cellulose nanofiber.
(3) The method for producing a rubber composition according to (1) or (2), wherein the in-line static fluid mixing device is a static mixer.
(4) The method for producing a rubber composition according to (1) or (2), wherein the in-line static fluid mixing device is an OHR mixer.

According to the present invention, it is possible to provide a production method which is excellent in dispersibility and continuous operability and can obtain a high-strength rubber composition.

Hereinafter, the present invention will be described in detail. In the present invention, “to” includes an end value. That is, “X to Y” includes the values X and Y at both ends.

ゴム The method for producing a rubber composition of the present invention includes a mixing step of mixing a modified cellulose nanofiber dispersion and a latex containing a rubber component using an inline static fluid mixing device.

(Modified cellulose nanofiber)
In the present invention, modified cellulose nanofibers (CNF) are fine fibers made from modified cellulose as a raw material. The fiber diameter of the modified cellulose nanofiber is not particularly limited, but is about 3 to 500 nm. The average fiber diameter and average fiber length of the modified cellulose nanofibers are obtained from observation of each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). It can be obtained by averaging the fiber diameter and fiber length. The modified cellulose nanofiber can be obtained by defibrating modified cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by an oxidation treatment and a defibration treatment.

The average aspect ratio of the modified cellulose nanofiber used in the present invention is usually 50 or more. The upper limit is not particularly limited, but is usually 1,000 or less. The average aspect ratio can be calculated by the following equation:
Aspect ratio = average fiber length / average fiber diameter

Modified cellulose is obtained by modifying cellulose contained in a cellulose raw material. The cellulose raw material may contain cellulose, and is not particularly limited. For example, plants (for example, wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (conifer unbleached kraft pulp (NUKP), Softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), bleached kraft pulp (BKP), softwood unbleached sulphite pulp (NUSP), softwood bleached sulphite pulp (NBSP) Thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (eg, ascidians), algae, microorganisms (eg, acetic acid bacteria (acetobacter)), microorganism products, etc. Examples of the cellulose raw material include: Or a combination of two or more types. Properly plant or microbial origin cellulosic material (e.g., cellulosic fibers), more preferably a cellulose material of plant origin (e.g., cellulose fibers).

数 The number average fiber diameter of the cellulose raw material is not particularly limited, but it is about 30 to 60 μm for softwood kraft pulp, which is a common pulp, and about 10 to 30 μm for hardwood kraft pulp. In the case of other pulp, those having undergone general purification are about 50 μm. For example, in the case of purifying a chip or the like having a size of several centimeters, it is preferable to perform a mechanical treatment with a disintegrator such as a refiner or a beater to adjust the diameter to about 50 μm.

Cellulose has three hydroxyl groups per glucose unit and can be modified in various ways. Examples of the modification (generally, chemical modification) include esterification such as oxidation, etherification, and phosphate esterification, silane coupling, fluorination, and cationization. Among them, oxidation (carboxylation), etherification (carboxymethylation and the like), cationization and esterification are preferred, and oxidation (carboxylation) and carboxymethylation are more preferred.

(Denaturation)
(Oxidation)
In the present invention, when oxidized (carboxylated) cellulose is used as the modified cellulose, oxidized cellulose (also referred to as carboxylated cellulose) can be obtained by oxidizing (carboxylated) the above-mentioned cellulose raw material by a known method. . Although not particularly limited, it is preferable to adjust the amount of the carboxyl group to 0.6 to 2.0 mmol / g with respect to the absolute dry mass of the modified cellulose nanofiber during the oxidation. It is more preferable to adjust the concentration to be 1.0 mmol / g to 2.0 mmol / g.

As an example of the oxidation (carboxylation) method, a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide or a mixture thereof. Methods can be mentioned. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and the cellulose fiber having an aldehyde group and a carboxyl group (—COOH) or a carboxylate group (—COO ⁻ ) on the surface. Can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

N-oxyl compound means a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes a desired oxidation reaction. For example, 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivative (eg, 4-hydroxy TEMPO) can be mentioned.

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalyst amount capable of oxidizing cellulose as a raw material. For example, the amount is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.05 to 0.5 mmol, based on 1 g of absolutely dried cellulose. Further, the amount is preferably about 0.1 to 4 mmol / L with respect to the reaction system.

Bromide is a compound containing bromine, and examples thereof include an alkali metal bromide that can be dissociated and ionized in water. Further, iodide is a compound containing iodine, and examples thereof include alkali metal 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, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol, based on 1 g of absolutely dried cellulose.

As the oxidizing agent, known agents can be used, and for example, halogen, hypohalous acid, halogenous acid, perhalic acid or salts thereof, halogen oxide, peroxide and the like can be used. Among them, sodium hypochlorite which is inexpensive and has a low environmental load is preferable. The amount of the oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol, based on 1 g of absolutely dried cellulose. Further, for example, 1 to 40 mol is preferable for 1 mol of the N-oxyl compound.

酸化 The oxidation of cellulose 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. Since a carboxyl group is generated in the cellulose as the reaction proceeds, a decrease in the pH of the reaction solution is observed. In order for the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous solution of sodium hydroxide 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 of its easy handling and the fact that side reactions hardly occur.

The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of the oxidation, and is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours.

酸化 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 of the oxidized cellulose can be reduced without being inhibited by the salt produced as a by-product in the first-stage reaction. Can be well oxidized.

As another example of the oxidation (carboxylation) method, there can be mentioned a method of oxidizing by bringing a gas containing ozone into contact with a cellulose raw material. By this oxidation reaction, at least the hydroxyl groups at the 2- and 6-positions of the glucopyranose ring are oxidized, and the cellulose chain is decomposed. The ozone concentration in the gas containing ozone is preferably from 50 to 250 g / m ³ , more preferably from 50 to 220 g / m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, more preferably 5 to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. The ozone treatment temperature is preferably 0 to 50 ° C, more preferably 20 to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the conditions of 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 may be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the additional oxidation treatment may be performed by immersing the cellulose raw material in the solution.

量 The amount of carboxyl groups in oxidized cellulose can be adjusted by controlling the reaction conditions such as the amount of the oxidizing agent added and the reaction time.

(Carboxymethylation)
In the present invention, when carboxymethylated cellulose is used as the modified cellulose, the carboxymethylated cellulose may be obtained by subjecting the above-mentioned cellulose raw material to carboxymethylation by a known method, or using a commercially available product. Is also good. In any case, it is preferable that the degree of carboxymethyl group substitution per anhydroglucose unit of cellulose is 0.01 to 0.50. An example of a method for producing such carboxymethylated cellulose includes the following method. Cellulose is used as the starting material, and 3 to 20 times by mass of water and / or lower alcohol as a solvent, specifically, water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary A single medium such as butanol or a mixed medium of two or more kinds is used. When the lower alcohol is mixed, the mixing ratio of the lower alcohol is 60 to 95% by mass. As the mercerizing agent, 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, is used per anhydroglucose residue of the starting material. The starting material, the solvent and the mercerizing agent are mixed, and the mercerizing treatment is performed 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 a molar amount of 0.05 to 10.0 times per glucose residue, and the reaction temperature is 30 to 90 ° C, preferably 40 to 80 ° C, and the reaction time is 30 minutes to 10 hours, preferably 1 hour. The etherification reaction is performed for ４4 hours.

In the present specification, `` carboxymethylated cellulose '', which is one type of modified cellulose used for preparing cellulose nanofibers, is one in which at least a part of the fibrous shape is maintained even when dispersed in water. Say. Therefore, it is distinguished from carboxymethyl cellulose which is a kind of water-soluble polymer. When the aqueous dispersion of “carboxymethylated cellulose” is observed with an electron microscope, a fibrous substance can be observed. On the other hand, even when an aqueous dispersion of carboxymethyl cellulose, which is a kind of water-soluble polymer, is observed, no fibrous substance is observed. In addition, when "carboxymethylated cellulose" is measured by X-ray diffraction, a peak of cellulose type I crystal can be observed, but no cellulose type I crystal is observed in carboxymethyl cellulose as a water-soluble polymer.

(Cationization)
As the modified cellulose, cellulose obtained by further cationizing the carboxylated cellulose can be used. The cation-modified cellulose is obtained by adding a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride or its halohydrin type to the carboxylated cellulose raw material, and an alkali hydroxide as a catalyst. It can be obtained by reacting a metal (such as sodium hydroxide and potassium hydroxide) in the presence of water or an alcohol having 1 to 4 carbon atoms.

カチオン The degree of cation substitution per glucose unit is preferably from 0.02 to 0.50. By introducing a cation substituent into cellulose, the celluloses repel each other electrically. For this reason, the cellulose into which the cation substituent is introduced can be easily nano-defibrated. If the degree of cation substitution per glucose unit is smaller than 0.02, nanofibrillation cannot be sufficiently performed. On the other hand, if the degree of cation substitution per glucose unit is greater than 0.50, the swelling or dissolution may result in the inability to obtain a nanofiber. In order to perform defibration efficiently, the cation-modified cellulose raw material obtained above is preferably washed. The degree of cation substitution can be adjusted by the addition amount of the cationizing agent to be reacted and the composition ratio of water or an alcohol having 1 to 4 carbon atoms.

(Esterification)
Esterified cellulose can be used as the modified cellulose. The cellulose is obtained by a method of mixing a powder or an aqueous solution of the phosphoric acid compound A with the aforementioned cellulose raw material, or a method of adding an aqueous solution of the phosphoric acid compound A to a slurry of the cellulose raw material.

(4) Examples of the phosphoric acid compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among these, compounds having a phosphate group are preferable because they are low-cost, easy to handle, and can improve the defibration efficiency by introducing a phosphate group into cellulose of the pulp fiber. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, potassium phosphite, sodium hypophosphite, potassium hypophosphite , Sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate , Ammonium pyrophosphate, ammonium metaphosphate and the like. These can be used alone or in combination of two or more. Among them, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of phosphate group introduction, easy defibration in the following defibration step, and easy industrial application. Are more preferred. Particularly, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferable. In addition, the phosphoric acid-based compound A is preferably used as an aqueous solution because the uniformity of the reaction is increased and the efficiency of introducing a phosphate group is increased. The pH of the aqueous solution of the phosphoric acid-based compound A is preferably 7 or less from the viewpoint of increasing the efficiency of introducing a phosphate group, but is preferably from 3 to 7 from the viewpoint of suppressing the hydrolysis of pulp fibers.

The following method can be mentioned as an example of the method for producing phosphate esterified cellulose. A phosphoric acid compound A is added to a dispersion of a cellulose raw material having a solid content of 0.1 to 10% by mass while stirring to introduce a phosphate group into the cellulose. When the cellulose raw material is 100 parts by mass, the amount of the phosphoric acid compound A to be added is preferably 0.2 to 500 parts by mass, more preferably 1 to 400 parts by mass, as the amount of phosphorus element. When the ratio of the phosphoric acid compound A is equal to or more than the lower limit, the yield of fine fibrous cellulose can be further improved. However, if the ratio exceeds the upper limit, the effect of improving the yield will level off, which is not preferable in terms of cost.

At this time, in addition to the cellulose raw material and the phosphoric acid-based compound A, other powders or aqueous solutions of the compound B may be mixed. The compound B is not particularly limited, but a nitrogen-containing compound showing basicity is preferable. As used herein, "basic" is defined as the aqueous solution exhibiting a pink to red color in the presence of the phenolphthalein indicator, or the pH of the aqueous solution being greater than 7. The nitrogen-containing compound exhibiting basicity used in the present invention is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. Examples include, but are not limited to, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Of these, urea which is easy to handle at low cost is preferable. The amount of compound B to be added is preferably 2 to 1000 parts by mass, more preferably 100 to 700 parts by mass, based on 100 parts by mass of the solid content of the cellulose raw material. The reaction temperature is preferably from 0 to 95 ° C, more preferably from 30 to 90 ° C. Although the reaction time is not particularly limited, it is about 1-600 minutes, more preferably 30-480 minutes. When the conditions of the esterification reaction are within these ranges, it is possible to prevent cellulose from being excessively esterified and being easily dissolved, and the yield of phosphorylated esterified cellulose is improved. After dehydrating the obtained phosphated cellulose suspension, it is preferable to perform a heat treatment at 100 to 170 ° C. from the viewpoint of suppressing hydrolysis of cellulose. Further, it is preferable to heat at 130 ° C. or lower, preferably 110 ° C. or lower while water is contained in the heat treatment, remove the water, and heat-treat at 100 to 170 ° C.

(4) The phosphoric acid-esterified cellulose preferably has a phosphate group substitution degree per glucose unit of 0.001 to 0.40. By introducing a phosphate group substituent into cellulose, the celluloses repel each other electrically. For this reason, the cellulose into which the phosphate group has been introduced can be easily nanofibrillated. If the degree of substitution of the phosphate group per glucose unit is less than 0.001, nanofibrillation cannot be sufficiently performed. On the other hand, if the degree of substitution of the phosphate group per glucose unit is more than 0.40, it may swell or dissolve, and thus may not be obtained as a nanofiber. In order to carry out the defibration efficiently, it is preferable to wash the phosphoric acid-esterified cellulose raw material obtained above by boiling and then washing with cold water.

(Defibrillation)
In the present invention, the device for defibrating is not particularly limited, but a high-speed rotation type, a colloid mill type, a high pressure type, a roll mill type, applying a strong shearing force to the aqueous dispersion using an apparatus such as an ultrasonic type. Is preferred. In particular, for efficient defibration, it is preferable to use a wet high-pressure or ultra-high-pressure homogenizer capable of applying a pressure of 50 MPa or more to the aqueous dispersion and applying a strong shearing force. The pressure is more preferably at least 100 MPa, even more preferably at least 140 MPa. Prior to the defibration / dispersion treatment with a high-pressure homogenizer, the above-mentioned CNF can be subjected to a pretreatment, if necessary, using a known mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer. It is. The number of processes (passes) in the defibrating device may be one, two or more, and preferably two or more.

In the dispersion treatment, the modified cellulose is usually dispersed in a solvent. The solvent is not particularly limited as long as the modified cellulose can be dispersed, and examples thereof include water, an organic solvent (eg, a hydrophilic organic solvent such as methanol), and a mixed solvent thereof. Since the cellulose raw material is hydrophilic, the solvent is preferably water.

変性 The solid content concentration of the modified cellulose in the dispersion is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more. This makes the liquid amount appropriate for the amount of the cellulose fiber raw material, which is efficient. The upper limit is usually 10% by mass or less, preferably 6% by mass or less. Thereby, fluidity can be maintained.

予備 Prior to the defibrating or dispersing treatment, a preliminary treatment may be performed if necessary. The preliminary treatment may be performed using a mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.

If the modified cellulose nanofiber obtained through the defibration step is in the form of a salt, it may be used as it is, or may be used as the acid form by an acid treatment using a mineral acid or a method using a cation exchange resin. Is also good. Further, hydrophobicity may be imparted by a method using a cationic additive.

において In the present invention, the modified cellulose nanofiber is subjected to a mixing step in a state of a dispersion liquid dispersed in a dispersion medium. Examples of the dispersion medium include water and an organic solvent, and a mixture thereof may be used. The concentration of the modified cellulose nanofiber dispersion used in the mixing step may be 0.1 to 5% (w / v) when the dispersion medium is water, and the dispersion medium may be water and an organic solvent such as alcohol. , It may be 0.1 to 20% (w / v).

The modified cellulose nanofibers may be a combination of two or more modified cellulose nanofibers. In the present invention, from the viewpoint of the reinforcing effect of rubber, it is preferable to include oxidized cellulose nanofibers that are completely nanodispersed and have a high aspect ratio.

(Rubber component)
The rubber component is a raw material of rubber and refers to a material which is crosslinked to form rubber. The rubber component includes a rubber component for natural rubber and a rubber component for synthetic rubber. Examples of the rubber component for natural rubber include natural rubber (NR) in a narrow sense without chemical modification; chemically modified natural rubber such as chlorinated natural rubber, chlorosulfonated natural rubber, and epoxidized natural rubber; hydrogenated natural rubber Rubber; deproteinized natural rubber. Examples of rubber components for synthetic rubber include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber, and styrene-isoprene copolymer. Diene rubbers such as coalesced rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber; butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydrid Non-diene rubbers such as rubber (CO, ECO), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (U), and chlorosulfonated polyethylene (CSM). Among them, NBR, NR, SBR, chloroprene rubber and BR are preferred. The rubber component may be used alone or in combination of two or more.

において In the present invention, the rubber component is subjected to a mixing step as a latex (dispersion liquid) dispersed in a dispersion medium. Examples of the dispersion medium include water and an organic solvent, and a mixture thereof may be used. The content ratio of the rubber component in the latex is preferably 10 to 80%, more preferably 20 to 70%.

(Mixing process)
In the present invention, the modified cellulose nanofiber dispersion and the latex containing the rubber component are mixed using an in-line static fluid mixing device.

(Inline static fluid mixing device)
In the mixing step of the present invention, an in-line static fluid mixing device is used. Examples of the in-line static fluid mixing device include a static mixer, an OHR mixer, and an MSE static mixer. The static mixer, the OHR mixer and the It is more preferable to use

A static mixer is a fluid mixer in which a right-handed spiral element and a left-handed spiral element are alternately arranged in a pipe such that one end is perpendicular to the other end. Device.

The OHR mixer is a fluid mixing device that enhances cavitation in a fluid by providing a plurality of protrusions on a peripheral wall surface of a pipe to promote mixing and stirring.

The MSE static mixer is a fluid mixing device in which a stack of mixing elements having a large number of small through holes and a large through hole in the center is disposed in a pipe, or such a mixing element is installed in a pipe and used. It is a fluid mixing device.

ため In the present invention, since an in-line (continuous) mixing apparatus is used, the production efficiency can be increased as compared with a batch type. Further, space saving can be achieved as compared with the case where the stirring tank is used. In addition, since a stationary mixing device is used, energy can be saved, and latex agglomeration due to shearing force such as rotation of the stirring blade can be suppressed. Further, since the aggregation of the latex is suppressed, the frequency of removing the aggregated dirt is reduced, and as a result, the continuous operability is excellent.

Note that one inline static fluid mixing apparatus may be used alone, or a plurality of inline static fluid mixing apparatuses may be used in combination.

は The number of treatments (passes) in the in-line static fluid mixing device may be one, or two or more, and preferably two or more.

In the method for producing a rubber composition according to the present invention, the rubber component is contained so that the modified cellulose nanofiber is contained in an amount of 0.5 to 30 parts by mass on a solid basis based on 100 parts by mass of the rubber component in the latex. The modified latex and the modified cellulose nanofiber dispersion are mixed.

製造 The production method of the present invention may include a step of adding one or more optional components depending on the use of the obtained rubber composition and the like. Optional components include, for example, reinforcing agents (eg, carbon black, silica, etc.), silane coupling agents, cross-linking agents, vulcanization accelerators, vulcanization accelerators (eg, zinc oxide, stearic acid), oils, and curing. Examples include compounding agents that can be used in the rubber industry, such as resins, waxes, antioxidants, and coloring agents. Among these, a vulcanization accelerator and a vulcanization accelerator are preferable. The content of the optional component may be appropriately determined according to the type of the optional component, and is not particularly limited.

場合 When the rubber composition is an unvulcanized rubber composition or a final product, it preferably contains a crosslinking agent. Examples of the crosslinking agent include sulfur, sulfur halide, organic peroxide, quinone dioximes, organic polyamine compounds, and alkylphenol resins having a methylol group. Of these, sulfur is preferred. The content of the crosslinking agent is preferably at least 1.0 part by mass, more preferably at least 1.5 parts by mass, even more preferably at least 1.7 parts by mass based on 100 parts by mass of the rubber component. The upper limit is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less.

{Examples of the vulcanization accelerator include Nt-butyl-2-benzothiazolesulfenamide and N-oxydiethylene-2-benzothiazolylsulfenamide. The content of the vulcanization accelerator is preferably 0.1 part by mass, more preferably 0.3 part by mass or more, even more preferably 0.4 part by mass or more based on 100 parts by mass of the rubber component. The upper limit is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less.

用途 The use of the rubber composition obtained by the production method of the present invention is not particularly limited as long as it is a composition for obtaining a rubber as a final product. That is, it may be an intermediate (master batch) for rubber production, an unvulcanized rubber composition containing a vulcanizing agent, or rubber as a final product. The use of the final product is not particularly limited. For example, transportation equipment such as automobiles, trains, ships, and airplanes; electric appliances such as personal computers, televisions, telephones, and watches; mobile communication equipment such as mobile phones; Equipment, video playback equipment, printing equipment, copying equipment, sports equipment, etc .; building materials; office equipment such as stationery, containers, containers and the like. Other than these, application to members using rubber or flexible plastic is possible, and application to tires is preferable. Examples of the tire include pneumatic tires for passenger cars, trucks, buses, heavy vehicles, and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, when the method of measuring / calculating each numerical value in each example is not particularly described, it is measured / calculated by the method described in the specification.

(Method of measuring the degree of dispersion)
In Examples and Comparative Examples, a CNF dispersion index was calculated for a mixture of natural rubber latex and an aqueous CNF dispersion as described below, and the degree of dispersion was evaluated according to the following criteria.
To 1 g of a mixture of the CNF aqueous dispersion and the natural rubber latex obtained in the examples and comparative examples, 2 drops of ink drops (manufactured by Kuretake Co., Ltd., solid content: 10%) were dripped, and a vortex mixer (manufactured by IUCHI, device name: (Automatic Lab-mixer HM-10H) was rotated for 1 minute with the rotation speed scale set to the maximum. Next, the mixture containing the ink droplets was sandwiched between two glass plates so that the film thickness became 0.15 mm, and the magnification was measured using an optical microscope (Digital Microscope KH-8700 (manufactured by Hilox Corporation)). Observed at 100x.

In the above observation, the major axis of the aggregate existing in the range of 3 mm × 2.3 mm was measured, and the observed aggregate was determined to be oversized: 150 μm or more, large: 100 μm or more and less than 150 μm, medium: 50 μm or more and less than 100 μm, and small: The particles were classified into 20 μm or more and less than 50 μm, the number of classified aggregates was counted, and the CNF dispersion index was calculated by the following equation.

CNF dispersion index = (extra large number × 512 + large number × 64 + medium number × 8 + small number × 1) ÷ 2 × CNF concentration coefficient The CNF concentration coefficient is shown in Table 1.

(Evaluation standard of dispersion degree)
：: CNF dispersion index is less than 1600 Δ: CNF dispersion index is 1600 or more and less than 6400 ×: CNF dispersion index is 6400 or more The evaluation results of the degree of dispersion are shown in Table 2.

(Production Example 1)
5.00 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from conifers is 39 mg (0.05 mmol per 1 g of absolute dry cellulose) of TEMPO (Sigma Aldrich) and 514 mg of sodium bromide (absolute dry) (1.0 mmol per 1 g of cellulose) was added to 500 mL of an aqueous solution, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system so that the amount of sodium hypochlorite became 6.0 mmol / g, and an oxidation reaction was started. During the reaction, the pH in the system decreased, but the pH was adjusted to 10 by sequentially adding a 3M aqueous sodium hydroxide solution. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). At this time, the pulp yield was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This was adjusted to 1.0% (w / v) with water, and treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain an aqueous dispersion of oxidized cellulose nanofibers. The obtained oxidized cellulose nanofiber had an average fiber diameter of 3 nm and an aspect ratio of 250.

(Method for measuring carboxyl group content)
60 mL of a 0.5% by mass carboxylated cellulose slurry (aqueous dispersion) was prepared, and a 0.1 M aqueous hydrochloric acid solution was added to adjust the pH to 2.5. The electrical conductivity was measured until and the amount of sodium hydroxide consumed in the neutralization step of the weak acid with a gradual change in electrical conductivity was calculated using the following equation:
Carboxyl group content [mmol / g carboxylated cellulose] = a [mL] × 0.05 / carboxylated cellulose mass [g]

(Example 1)
A 1% aqueous dispersion of the oxidized CNF obtained in Production Example 1 above based on 100 parts by mass of the absolute dry solid content of natural rubber latex (trade name: HA latex, Retex Co., solid content concentration: 61.5% by mass) And a static mixer (2 units of 3 / 8-N30-232-F manufactured by NORITAKE CO., LIMITED) connected as an in-line type static fluid mixing device, and a processing flow rate of 10 .9 L / min) to obtain a mixture. The mixture was dried in a heating oven at 70 ° C. for 15 hours to obtain a master batch. After the mixture was obtained, the inside of the static mixer was visually checked, and the degree of contamination by latex aggregates was examined. Staining by latex agglomerates was not observed, which was a good result.

With respect to the masterbatch obtained by the above method, zinc oxide and stearic acid were mixed at 6% by mass and 0.5% by mass with respect to the rubber component in the masterbatch, respectively, and were mixed with an open roll (Kansai Roll Co., Ltd.). A kneaded material was obtained by kneading at 30 ° C. for 10 minutes. To this kneaded material, sulfur and a vulcanization accelerator (BBS, Nt-butyl-2-benzothiazolesulfenamide) were added in an amount of 3.5% by mass and 0.7% by mass, respectively, based on the rubber component in the kneaded material. %, And kneaded at 30 ° C. for 10 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.) to obtain a sheet of an unvulcanized rubber composition. The obtained unvulcanized rubber composition sheet was placed in a mold and press-vulcanized at 150 ° C. for 15 minutes to obtain a vulcanized rubber sheet (vulcanized rubber composition) having a thickness of 2 mm. The obtained vulcanized rubber sheet is cut into a test piece having a predetermined shape, and according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-How to determine tensile properties”, a sheet having a tensile strength of 50% strain ( M50), stress at 100% strain (M100), and stress at 300% strain (M300), and breaking strength were measured. The results are shown in Table 2. As the numerical values of the tensile stress and the breaking strength are larger, the vulcanized rubber composition is satisfactorily reinforced and the mechanical strength is excellent.

(Example 2)
A mixture was obtained in the same manner as in Example 1 except that the treatment by the static mixer was performed in three passes. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

(Example 3)
A mixture was obtained in the same manner as in Example 1, except that the treatment by the static mixer was changed to 10-pass treatment. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

(Example 4)
A mixture was obtained in the same manner as in Example 1, except that 10 passes were performed using an OHR mixer (MX-F8, manufactured by OHR Fluid Engineering Laboratory Co., Ltd., processing flow rate: 3.9 L / min) instead of the static mixer. Was. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

(Example 5)
A mixture was obtained in the same manner as in Example 1, except that 10 passes were performed using an OHR mixer (MX-F8, manufactured by OHR Fluid Engineering Laboratory Co., Ltd., processing flow rate: 6.7 L / min) instead of the static mixer. Was. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

(Comparative Example 1)
A mixture was obtained in the same manner as in Example 1, except that Cavitron (CD1000, manufactured by Eurotech Co., Ltd., processing flow rate: 10.9 L / min), which was an inline emulsifying and dispersing machine, was used instead of the static mixer. After the mixture was obtained, the inside of the Cavitron was visually checked, and the degree of contamination by latex aggregates was examined. Staining by latex agglomerates was observed, which was a bad result. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

(Comparative Example 2)
A mixture was obtained in the same manner as in Comparative Example 1 except that the treatment with the Cavitron was performed in three passes. After the mixture was obtained, the inside of the Cavitron was visually checked, and the degree of contamination by latex aggregates was examined. Many stains due to latex aggregates were observed, which was a very bad result. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

(Comparative Example 3)
Example 2 A natural rubber latex and a 1% aqueous solution of CNF oxide were respectively introduced into a same pipe using a pump at a processing flow rate of 10.9 L / min without using a static mixer, and were passed through the same pipes. A mixture was obtained in the same manner as in Example 1. A masterbatch and a vulcanized rubber sheet were obtained in the same manner as in Example 1 except that this mixture was used, and the tensile strength and the breaking strength were measured. The results are shown in Table 2.

As can be seen from Table 2, according to the method for producing a rubber composition including a mixing step of mixing a modified CNF dispersion and a latex containing a rubber component using a static mixer or an OHR mixer that is an in-line static fluid mixing device. No contamination in the mixer was observed, the degree of dispersion of CNF was high, and the obtained vulcanized rubber sheet was excellent in tensile strength and breaking strength.

Claims

A method for producing a rubber composition containing modified cellulose nanofibers,
A method for producing a rubber composition, comprising a mixing step of mixing a modified cellulose nanofiber dispersion and a latex containing a rubber component using an inline static fluid mixing device.
方法 The method for producing a rubber composition according to claim 1, wherein the modified cellulose nanofibers include oxidized cellulose nanofibers.
3. The method for producing a rubber composition according to claim 1, wherein the in-line static fluid mixing device is a static mixer.
3. The method for producing a rubber composition according to claim 1, wherein the in-line static fluid mixing device is an OHR mixer.