Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/20—Compounding polymers with additives, e.g. colouring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/17—Amines; Quaternary ammonium compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
  • C08K5/41—Compounds containing sulfur bound to oxygen
  • C08K5/42—Sulfonic acids; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/02—Cellulose; Modified cellulose
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
  • C08L101/12—Compositions of unspecified macromolecular compounds characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity
  • C08L101/14—Compositions of unspecified macromolecular compounds characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity the macromolecular compounds being water soluble or water swellable, e.g. aqueous gels
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L21/00—Compositions of unspecified rubbers

Definitions

• the present invention relates to a rubber composition and a method for producing the same.
• Rubber compositions containing a rubber component and cellulose-based fibers are known to have excellent mechanical strength.
• Patent Document 1 describes that a rubber composition containing a rubber component, an inorganic filler, a plasticizer, and powdered cellulose having predetermined physical properties in a predetermined blend ratio has excellent moldability, mechanical properties, etc.
• Rubber compositions containing rubber components and cellulose-based fibers are expected to be used in a variety of fields, and further improvements in strength are required.
• the present invention aims to improve a rubber composition containing a rubber component and cellulose fibers, and to provide a method for producing such a rubber composition with good strength.
• the present invention provides the following [1] to [11].
• Component A a rubber component
• Component B a cellulose-based filler
• Component C a water-soluble polymer
• a rubber composition comprising: [2] The rubber composition according to [1], wherein component B contains fine cellulose fibers.
• component B contains cellulose nanofibers or cellulose microfibrils.
• Component D The rubber composition according to any one of [1] to [4], further comprising a crosslinkable compound having a thiosulfate group or an ⁇ , ⁇ -unsaturated carbonyl group and an amino group.
• Component D is A compound in which a thiosulfate group and an amino group are linked by an alkyl group, or The rubber composition according to [5] or [6], which contains at least a compound in which an ⁇ , ⁇ -unsaturated carbonyl group and an amino group are linked to an aromatic ring through a divalent group containing an amide bond.
• the present invention provides a rubber composition containing a rubber component and cellulose fibers that exhibits strength, particularly good dynamic viscoelasticity, and an efficient method for producing the same.
• the rubber composition contains the following Components A to C, and preferably further contains Component D.
• Component A is a rubber component.
• the rubber component include synthetic rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM), fluororubber (FKM), epichlorohydrin rubber (CO, ECO), urethane rubber (U), silicone rubber (Q), halogenated butyl rubber, and polysulfide rubber, but are not particularly limited thereto.
• synthetic rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene
• thermoplastic elastomers such as polystyrene-based thermoplastic elastomers, polypropylene-based thermoplastic elastomers, polydiene-based thermoplastic elastomers, chlorine-based thermoplastic elastomers, and engineering plastics-based elastomers can also be used.
• Natural rubber (NR) is more preferred as component A.
• the vulcanization of rubber components is generally carried out using a vulcanization system that combines sulfur or a sulfur-donating compound with various general-purpose vulcanization accelerators such as sulfenamides and thiuram compounds. Organic peroxide crosslinking is also possible.
• organic peroxides examples include commonly used compounds such as tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 1,3-di(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropylcarbonate, and n-butyl-4,4-di(tert-butylperoxy)valerate.
• tert-butyl peroxide dicumyl peroxid
• a polyfunctional unsaturated compound such as triallyl isocyanurate, triallyl cyanurate, triallyl trimellitate, trimethylolpropane trimethacrylate, or N,N'-m-phenylene bismaleimide in combination.
• Component B is a cellulose-based filler.
• the cellulose-based filler may be any filler derived from a cellulose raw material, and examples of the filler include pulp fiber, powdered cellulose, and fine cellulose fiber.
• the cellulose raw material is usually wood, and may be any of broadleaf trees, softleaf trees, or a combination of two or more of these.
• broad-leaved trees include plants of the genus Beech (e.g., beech), linden (e.g., linden), birch (e.g., birch, beech), poplar (e.g., poplar), Eucalyptus (e.g., eucalyptus), Acacia (e.g., acacia), Quercus (e.g., oak, phillyraeoides, quercus serrata, oak), maple (e.g., maple), Kalopanax (e.g., Asiatic ash), Elm (e.g., elm), Paulownia (e.g., Paulownia), Magnolia (e.g., magnolia), Salix (e.g., willow), A
• Coniferous trees include, for example, trees of the genus Cedar (e.g., Japanese cedar), the genus Picea (e.g., Picea jezoensis), the genus Larch (e.g., Larch, Western larch, Tamarack), the genus Pinus (e.g., Pinus thunbergii, Pinus sieboldii, Pinus radiata, Eastern white pine), the genus Abies (e.g., Abies sachalinensis, Abies monadelpha, Western fir), the genus Taxus (e.g., Taxus cuspidatum), the genus Arborvitae (e.g., Juniperus japonicus, Yellow cedar (Hibara cypress)), the genus Picea (e.g., Abies japonica, Abies serrata, Examples of suitable plants include plants of the genus Picea (e.g., Picea abies, Sitka s
• pulp fibers include, but are not limited to, unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), thermomechanical pulp (TMP), linter pulp, recycled pulp, waste paper, etc.), non-wood pulp, and combinations of two or more selected from these.
• NUKP unbleached softwood kraft pulp
• NKP bleached softwood kraft pulp
• LKP unbleached hardwood kraft pulp
• LKP bleached hardwood kraft pulp
• NUSP unbleached softwood sulfite pulp
• NBSP bleached softwood sulfite pulp
• TMP thermomechanical pulp
• linter pulp recycled pulp, waste paper, etc.
• the average fiber diameter of the pulp fibers is not particularly limited, but is usually 60 ⁇ m or less, preferably 50 ⁇ m or less, more preferably 30 ⁇ m or less, or 20 ⁇ m or less, and even more preferably 10 ⁇ m or less.
• the average fiber diameter of softwood kraft pulp is about 30 to 60 ⁇ m, that of hardwood kraft pulp is about 10 to 30 ⁇ m, and that of other pulps (those that have undergone general refining) is about 50 ⁇ m (e.g., 40 to 60 ⁇ m).
• a process to adjust the average fiber diameter may be carried out, such as mechanical processing using a disintegrator such as a refiner or beater.
• Powdered cellulose is cellulose in a powdered form derived from a cellulose raw material.
• methods for producing it include Method 1: a method in which pulp is subjected to acid hydrolysis treatment with an acid (e.g., an inorganic acid (specifically, for example, a mineral acid such as hydrochloric acid, sulfuric acid, or nitric acid) and then subjected to treatment such as pulverization; Method 2: a method in which pulp is subjected to mechanical pulverization without being subjected to acid hydrolysis treatment, and Method 1 is preferred. Powdered cellulose with few impurities can be obtained by Method 1.
• an acid e.g., an inorganic acid (specifically, for example, a mineral acid such as hydrochloric acid, sulfuric acid, or nitric acid)
• Method 2 a method in which pulp is subjected to mechanical pulverization without being subjected to acid hydrolysis treatment, and Method 1 is preferred.
• Powdered cellulose with few impurities
• the average particle size of powdered cellulose is preferably 1 ⁇ m or more, and more preferably 3 ⁇ m or more.
• the average particle size is preferably 70 ⁇ m or less, more preferably 50 ⁇ m or less, even more preferably 25 ⁇ m or less or less than 15 ⁇ m, and even more preferably 11 ⁇ m or less. Therefore, the average particle size of powdered cellulose is preferably 1 to 70 ⁇ m, more preferably 1 to 50 ⁇ m, 1 to 25 ⁇ m, or 1 to 15 ⁇ m, and even more preferably 1 to 11 ⁇ m.
• the average particle size is the value at which the volume accumulation distribution is 50% when the particle size distribution is expressed as an accumulation distribution using the laser scattering method as the measurement principle.
• the degree of polymerization (average degree of polymerization) of the powdered cellulose is preferably 100 or more, more preferably 200 or more.
• the upper limit is preferably 1400 or less, more preferably 1000 or less, even more preferably 500 or less, and even more preferably 400 or less. Therefore, the degree of polymerization of the powdered cellulose is preferably 100 to 1400, more preferably 100 to 1000 or 100 to 500, even more preferably 100 to 500, 100 to 400 or 200 to 500, and even more preferably 100 to 400 or 200 to 400.
• the degree of polymerization can be determined by a viscosity measurement method using copper ethylenediamine described in the 16th revised Japanese Pharmacopoeia Manual, Crystalline Cellulose Verification Test (2).
• the apparent density of powdered cellulose is preferably 0.1 to 0.6 g/ml, more preferably 0.1 to 0.45 g/ml, even more preferably 0.15 to 0.45 g/ml, and particularly preferably 0.2 to 0.4 g/ml.
• the apparent density can be calculated by placing 10 g of sample into a 100 ml graduated cylinder, tapping the bottom of the cylinder until the height of the sample stops decreasing (manually for approximately 10 minutes), reading the scale on the flattened surface, and dividing by the mass of the sample.
• the cellulose type I crystallinity of powdered cellulose is preferably 70-90%, more preferably 80-90%.
• the cellulose type I crystallinity can be calculated by subjecting a sample to X-ray diffraction measurement, measuring and comparing the intensity of the (200) peak at around 22.6° and the valley between (200) and (110) (around 18.5°).
• the crystallinity can be adjusted by the type of cellulose raw material and the manufacturing method. Powdered cellulose manufactured through acid hydrolysis treatment (for example, by method (1)) tends to have a high degree of crystallinity, while powdered cellulose manufactured without such treatment (for example, by method (2)) tends to have a low degree of crystallinity.
• the fine cellulose fiber is a fine fibrous cellulose derived from a cellulose raw material.
• the fine fibrous cellulose is, for example, a dispersion liquid (1 wt%) of fine cellulose fiber, which has a light transmittance of 1 to 99% obtained at an optical path length of 1 cm/660 nm using a visible spectroscopic analyzer (UV-1800, manufactured by Shimadzu Corporation).
• Methods for producing fine cellulose fiber include a method of defibrating pulp and a method of chemically modifying the pulp before or after defibration (usually before defibration) as necessary.
• Fine cellulose fiber having a fiber diameter of the nano-order is called cellulose nanofiber
• fine cellulose fiber having a fiber diameter of the micron order is called cellulose microfibril.
• the size of the fine cellulose fiber can be adjusted by the conditions of the micronization treatment and chemical modification treatment. Incidentally, the above-mentioned powdered cellulose does not become dispersed even when stirred in a solvent such as water, but rather settles, so the light transmittance of the dispersion cannot be measured and it can be clearly distinguished from fine cellulose fibers.
• cellulose nanofiber refers to cellulose fiber having a fiber diameter on the nano-order, which is prepared through a micronization process.
• the average fiber diameter (length-weighted average fiber diameter) of CNF is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less.
• the lower limit is not particularly limited, but is usually 1 nm or more, preferably 2 nm or more. Therefore, the average fiber diameter (length-weighted average fiber diameter) of CNF is usually 1 to 500 nm or 2 to 500 nm, preferably 2 to 300 nm or 2 to 100 nm, more preferably 2 to 50 nm or 3 to 30 nm.
• the average fiber length (length-weighted average fiber length) is usually 50 to 2000 nm, preferably 100 to 1000 nm.
• the aspect ratio of CNF is usually 10 or more, preferably 50 or more.
• the upper limit is not particularly limited, but is usually 1000 or less.
• the average fiber diameter and average fiber length of fine cellulose fibers can be determined using a fractionator manufactured by Valmet Co., Ltd. When a fractionator is used, the length-weighted fiber width and the length-weighted average fiber length can be determined, respectively.
• cellulose microfibrils (microfibrillated cellulose, MFC) refer to cellulose fibers having a fiber diameter on the micron order that are prepared through a pulverization process.
• the average fiber diameter (average fiber width) of MFC is usually 500 nm or more, preferably 1 ⁇ m or more, and more preferably 3 ⁇ m or more. This allows it to exhibit higher water retention than unfibrillated cellulose fibers, and even a small amount can provide higher strength and yield improvement effects compared to finely defibrated CNF.
• the upper limit of the average fiber diameter is preferably 60 ⁇ m or less, more preferably 40 ⁇ m or less, even more preferably 30 ⁇ m or less, and even more preferably 20 ⁇ m or less, but there is no particular limit.
• the average fiber length is usually 10 ⁇ m or more, 20 ⁇ m or more, or 40 ⁇ m or more, preferably 200 ⁇ m or more, 300 ⁇ m or more, or 400 ⁇ m or more, more preferably 500 ⁇ m or more, or 550 ⁇ m or more, and even more preferably 600 ⁇ m or more, 700 ⁇ m or more, or 800 ⁇ m or more.
• the upper limit is not particularly limited, but is usually 3,000 ⁇ m or less, preferably 2,500 ⁇ m or less, more preferably 2,000 ⁇ m or less, even more preferably 1,500 ⁇ m or less, 1,400 ⁇ m or less, or 1,300 ⁇ m or less.
• the aspect ratio of the MFC is preferably 3 or more, more preferably 5 or more, even more preferably 7 or more, and may be 10 or more, 20 or more, or 30 or more.
• the upper limit of the aspect ratio is not particularly limited, but is preferably 1,000 or less, more preferably 100 or less, and even more preferably 80 or less.
• the fine cellulose fibers may be modified fine cellulose fibers or unmodified fine cellulose fibers.
• Modified fine cellulose fibers refer to fine cellulose fibers (e.g., cellulose nanofibers, cellulose microfibrils) in which at least one of the three hydroxyl groups contained in the glucose unit has been chemically modified (hereinafter simply referred to as "modified").
• the chemical modification treatment sufficiently refines the cellulose fibers, and cellulose nanofibers with uniform average fiber length and average fiber diameter can be obtained by defibration. Therefore, when compounded with a rubber component, a sufficient reinforcing effect can be exhibited. From this viewpoint, modified cellulose fibers are preferred.
• modifications include oxidation, etherification, esterification such as phosphate esterification, silane coupling, fluorination, cationization, etc.
• oxidation carboxylation
• etherification e.g., benzylation
• cationization e.g., benzylation
• esterification e.g., benzylation
• the oxidized fine cellulose fibers usually have a structure in which at least one of the carbon atoms having a primary hydroxyl group contained in the glucopyranose unit constituting the cellulose molecular chain (for example, a carbon atom having a primary hydroxyl group at the C6 position) is oxidized.
• the amount of carboxyl groups in the oxidized cellulose fibers and oxidized cellulose nanofibers is preferably 0.5 mmol/g or more, more preferably 0.8 mmol/g or more, and even more preferably 1.0 mmol/g or more, based on the bone dry mass.
• the upper limit of the amount is preferably 3.0 mmol/g or less, more preferably 2.5 mmol/g or less, and even more preferably 2.0 mmol/g or less.
• the amount of carboxyl groups 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 amount of carboxyl groups can be adjusted by controlling the conditions when oxidizing the cellulose fibers (for example, the amount of oxidizing agent added, the reaction time). In addition, the amount of carboxylate groups and aldehyde groups can also be adjusted by controlling these conditions.
• the oxidation method is not particularly limited, but an example is a method in which a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a bromide, iodide, or a mixture thereof.
• the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to generate at least one group selected from the group consisting of an aldehyde group, a carboxy group (-COOH), and a carboxylate group ( -COO- ).
• the concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by mass or less.
• N-oxyl compound refers to a compound capable of generating a nitroxy radical.
• nitroxyl radicals include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and its derivatives (e.g., 4-hydroxyTEMPO).
• TEMPO 2,2,6,6-tetramethylpiperidine 1-oxyl
• Any compound that promotes the target oxidation reaction can be used as the N-oxyl compound.
• the amount of the N-oxyl compound used so long as it is a catalytic amount capable of oxidizing the raw cellulose.
• the amount is preferably 0.01 mmol or more, more preferably 0.02 mmol or more, per 1 g of bone-dry cellulose raw material.
• the upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less.
• 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, per 1 g of bone-dry cellulose raw material.
• the amount of the N-oxyl compound used in the reaction system is usually 0.1 to 4 mmol/L.
• Bromides are compounds that contain bromine, such as bromides of alkali metals that can dissociate and ionize in water.
• Iodides are compounds that contain iodine, such as iodides of alkali metals.
• 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 even more preferably 0.5 to 5 mmol, per 1 g of bone-dry cellulose raw material.
• the oxidizing agent may be any known oxidizing agent, such as halogen, hypohalous acid, hypohalous acid, perhalogen acid or their salts, halogen oxides, or peroxides.
• hypohalous acid or its salts are preferred because they are inexpensive and have a low environmental impact
• hypochlorous acid or its salts are more preferred
• sodium hypochlorite is preferred.
• the appropriate amount of oxidizing agent to be used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and even more preferably 3 to 10 mmol, per 1 gram of bone-dry cellulose raw material.
• 1 to 40 mol is preferred per 1 mol of N-oxyl compound.
• the reaction temperature is preferably 4 to 40°C, but may also be around 15 to 30°C, i.e. room temperature.
• carboxyl groups are generated in the cellulose, causing a decrease in the pH of the reaction solution.
• an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at around 8 to 12, or 10 to 11. Water is preferred as the reaction medium, as it is easy to handle and unlikely to cause side reactions.
• the reaction time for the oxidation reaction can be set appropriately according to the degree of oxidation progress, and is usually about 0.5 to 6 hours, for example, about 0.5 to 4 hours.
• the oxidation reaction may be carried out in two stages.
• the oxidized cellulose obtained by filtration after the completion of the first stage reaction can be oxidized again under the same or different reaction conditions, allowing efficient oxidation without reaction inhibition by table salt, which is a by-product of the first stage reaction.
• Another example of the carboxylation (oxidation) method is a method of oxidizing the cellulose raw material by contacting it with an ozone-containing gas (ozone oxidation).
• This oxidation reaction oxidizes at least the hydroxyl groups at the 2- and 6-positions of the glucopyranose ring, and decomposes the cellulose chain.
• the ozone concentration in the ozone-containing gas is preferably 50 to 250 g/m 3 , more preferably 50 to 220 g/m 3.
• the amount of ozone added is preferably 0.1 to 30 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass of the solid content of the cellulose raw material.
• 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, and preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, the cellulose raw material can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is good.
• a further oxidation treatment may be carried out using an oxidizing agent.
• the oxidizing agent used in the further oxidation treatment is not particularly limited, but examples include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid.
• the procedure for the further oxidation treatment may include, for example, dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the oxidized cellulose in the solution.
• Acid-type oxidized cellulose and desalination - Oxidized cellulose contains carboxy groups as a result of oxidation, but may contain more acid-type carboxy groups (-COOH) than salt-type carboxy groups (e.g., -COO-, -COONa), or may contain more salt-type carboxy groups than acid-type carboxy groups.
• the amount of salt-type carboxy groups and acid-type carboxy groups can be adjusted by desalting treatment. By desalting treatment, salt-type carboxy groups can be converted to acid-type carboxy groups.
• oxidized cellulose (which has been desalted) is called acid-type oxidized cellulose, and oxidized cellulose (which has not been desalted, as described below) is called salt-type oxidized cellulose.
• Salt-type oxidized cellulose usually contains mainly salt-type carboxy groups.
• acid-type oxidized cellulose contains many acid-type carboxy groups, and the proportion of acid-type carboxy groups in the carboxy groups is preferably 40% or more, more preferably 60% or more, and even more preferably 85% or more.
• Acid-type oxidized cellulose can exhibit a superior reinforcing effect together with component C.
• the proportion of acid-type carboxy groups can be calculated by the following procedure.
• the timing of desalting may be after oxidation, and may be either before or after defibration, but is usually after oxidation and before defibration.
• Desalting is usually performed by replacing salts (e.g., sodium salts) contained in salt-type oxidized cellulose with protons.
• Examples of desalting methods include a method of adjusting the system to be acidic, and a method of contacting oxidized cellulose with a cation exchange resin.
• the pH of the system is preferably adjusted to 2 to 6, more preferably 2 to 5, and even more preferably 2.3 to 5.
• an acid e.g., inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, sulfurous acid, nitrous acid, and phosphoric acid; organic acids such as acetic acid, lactic acid, oxalic acid, citric acid, and formic acid
• a washing treatment may be performed as appropriate.
• the cation exchange resin either a strongly acidic ion exchange resin or a weakly acidic ion exchange resin can be used as long as the counter ion is H + .
• the ratio of the oxidized cellulose and the cation exchange resin when they are contacted is not particularly limited, and a person skilled in the art can set it appropriately from the viewpoint of efficient proton replacement.
• the cation exchange resin after contact can be recovered by a conventional method such as suction filtration.
• etherification examples include carboxyalkylation, methylation, ethylation, cyanoethylation, hydroxyethylation, hydroxypropylation, ethylhydroxyethylation, and hydroxypropylmethylation, with carboxyalkylation being preferred and carboxymethylation being more preferred.
• Carboxyalkylated cellulose fibers usually have a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom bearing a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is carboxymethylated.
• the degree of carboxyalkyl substitution (preferably the degree of carboxymethyl substitution (CM-DS)) per anhydrous glucose unit of the carboxyalkylated cellulose is preferably 0.01 or more, 0.02 or more, or 0.05 or more, more preferably 0.10 or more, even more preferably 0.15 or more, even more preferably 0.20 or more, and particularly preferably 0.25 or more. This ensures a degree of substitution that can be achieved by chemical modification.
• the upper limit of the degree of substitution is preferably 0.50 or less, more preferably 0.45 or less, 0.40 or less, or 0.35 or less. This makes it difficult for the cellulose fiber to dissolve in water, and allows the fiber form to be maintained in water. Therefore, the degree of carboxyalkyl substitution is preferably 0.01 to 0.50, more preferably 0.01 to 0.45, even more preferably 0.02 to 0.40, 0.10 to 0.35, or 0.20 to 0.30.
• the degree of substitution for example, the degree of carboxymethyl substitution, can be measured by the following method. Approximately 2.0 g of carboxymethylated cellulose (bone dry) is weighed out and placed in a 300 mL Erlenmeyer flask with a stopper. 100 mL of a solution of 1,000 mL of methanol and 100 mL of concentrated nitric acid is added, and the mixture is shaken for 3 hours to convert the salt-type carboxymethylated cellulose (hereinafter also referred to as "salt-type carboxymethylated cellulose”) to the acid-type carboxymethylated cellulose (hereinafter also referred to as "acid-type carboxymethylated cellulose").
• CM -DS degree of carboxymethyl substitution
• A [(100 x F - ( 0.1 N H2SO4 (mL)) x F') x 0.1] / (bone dry mass (g) of acid-type carboxymethyl cellulose)
• CM-DS 0.162 ⁇ A/(1-0.058 ⁇ A)
• F' Factor of 0.1N H2SO4
• F Factor of 0.1N NaOH
• the degree of carboxyalkyl substitution can be adjusted by controlling the reaction conditions, such as the amount of carboxyalkylating agent added to the reaction, the amount of mercerizing agent, and the composition ratio of water and organic solvent.
• carboxyalkylation method is to mercerize the cellulosic raw material as the starting material (bottom raw material) and then etherify it. Carboxymethylation will be explained below as an example.
• Carboxymethylated cellulose can be produced by starting with unmodified cellulose fibers (cellulose raw material: e.g., pulp), carrying out a mercerization treatment, and then carrying out an etherification reaction. This reaction is usually carried out in the presence of a solvent.
• a solvent for example, water, lower alcohols (e.g., methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tertiary butanol) can be used alone or in a mixture of two or more. When lower alcohols are mixed, the mixing ratio of the lower alcohol is preferably 60 to 95% by mass.
• the amount of the solvent is about three times the amount of the cellulose raw material, calculated by mass. The upper limit of this amount is not particularly limited, but is 20 times or less.
• the amount of the solvent is preferably 3 to 20 times the amount of the cellulose raw material, calculated by mass.
• mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
• the amount of mercerizing agent used, in molar terms is preferably 0.5 times or more per anhydrous glucose residue of the starting material, more preferably 1.0 times or more, and even more preferably 1.5 times or more. The upper limit of this amount is usually 20 times or less, preferably 10 times or less, and even more preferably 5 times or less.
• the amount of mercerizing agent used, in molar terms is preferably 0.5 to 20 times, more preferably 1.0 to 10 times, and even more preferably 1.5 to 5 times.
• the reaction temperature for mercerization is usually 0°C or higher, preferably 10°C or higher.
• the upper limit is usually 70°C or lower, preferably 60°C or lower.
• the reaction temperature is usually 0 to 70°C, preferably 10 to 60°C.
• the reaction time for mercerization is usually 15 minutes or more, preferably 30 minutes or more.
• the upper limit is usually 8 hours or less, preferably 7 hours or less.
• 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.
• the carboxymethylating agent include monochloroacetic acid or a salt thereof (e.g., a metal salt such as a sodium salt).
• the amount of the carboxymethylating agent added is, in molar terms, 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 or less, preferably 5 times or less, and more preferably 3 times or less.
• the amount of the carboxymethylating agent added is, in molar terms, preferably 0.05 to 10.0 times, more preferably 0.5 to 5 times, and even more preferably 0.8 to 3 times.
• the reaction temperature is usually 30°C or higher, preferably 40°C or higher.
• the upper limit is usually 90°C or lower, preferably 80°C or lower.
• 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.
• the upper limit is usually 10 hours or less, preferably 4 hours or less.
• the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours.
• the reaction liquid may be stirred as necessary.
• the carboxyalkylated cellulose fiber maintains at least a part of its fibrous shape even when dispersed in water (is water-insoluble).
• the carboxyalkylated cellulose fiber is distinguished from carboxymethylcellulose (e.g., component C described later), which is a type of water-soluble polymer that dissolves in water and imparts viscosity.
• carboxymethylcellulose e.g., component C described later
• a fibrous substance can be observed.
• an aqueous dispersion of carboxymethylcellulose which is a type of water-soluble polymer, is observed, no fibrous substance is observed.
• anion-modified cellulose fiber has crystallinity, and when measured by X-ray diffraction, a peak of cellulose type I crystals can be observed, but when carboxymethylcellulose powder, which is a water-soluble polymer, is similarly measured, cellulose type I crystals are usually not observed.
• Carboxyalkylated cellulose may contain more acid-type carboxy groups than salt-type carboxy groups, or may contain more salt-type carboxy groups than acid-type carboxy groups.
• the amount of salt-type carboxy groups and acid-type carboxy groups can be adjusted by desalting treatment. By desalting treatment, salt-type carboxy groups can be converted to acid-type carboxy groups.
• carboxyalkylated cellulose (which has been desalted) is called acid-type carboxyalkylated cellulose
• carboxyalkylated cellulose which has not been desalted, as described below) is called salt-type carboxyalkylated cellulose.
• Salt-type carboxyalkylated cellulose usually mainly has salt-type carboxy groups (-COO-).
• acid-type carboxyalkylated cellulose has many acid-type carboxy groups, and the ratio of the amount of acid-type carboxy groups to the amount of carboxy groups in acid-type carboxyalkylated cellulose is preferably 40% or more, more preferably 60% or more, and even more preferably 85% or more. It is presumed that acid-type carboxyalkylated cellulose is superior in reinforcing effect with component C.
• the method for calculating the ratio of acid-type carboxy groups is as described above.
• the timing of desalting is usually after carboxyalkylation, preferably after etherification and before fibrillation.
• the desalting method may be a method of contacting carboxyalkylated cellulose with a cation exchange resin.
• the cation exchange resin either a strong acid ion exchange resin or a weak acid ion exchange resin can be used as long as the counter ion is H + .
• the ratio of the two when contacting carboxyalkylated cellulose with a cation exchange resin is not particularly limited, and a person skilled in the art can appropriately set it from the viewpoint of efficient proton replacement.
• the ratio can be adjusted so that the pH of the aqueous dispersion after addition of the cation exchange resin is preferably 2 to 6, more preferably 2 to 5, relative to the carboxyalkylated cellulose aqueous dispersion.
• the cation exchange resin after contact may be recovered by a conventional method such as suction filtration.
• esterification (phosphate esterification) A first example of an esterified cellulose fiber is phosphorylated cellulose, which usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is phosphorylated.
• the degree of substitution of phosphoric acid-based groups per glucose unit in phosphoric acid esterified CNF is preferably 0.001 or more and less than 0.40.
• the degree of phosphoric acid substitution can be measured by the following method. A slurry of phosphoric acid esterified CNF with a solid content of 0.2 mass% is prepared. A strongly acidic ion exchange resin is added to the slurry in an amount of 1/10 by volume, and the slurry is shaken for 1 hour, and then poured onto a mesh with an opening of 90 ⁇ m to separate the resin and the slurry, thereby obtaining hydrogen-type phosphoric acid esterified CNF.
• the degree of phosphate group substitution can be adjusted by controlling the reaction conditions, such as the amount of the compound containing a phosphate group added and the amount of the basic compound added if necessary.
• An example of a phosphorylation method is to react a compound having a phosphate group with unmodified cellulose fibers (phosphorylation).
• Examples of the phosphorylation method include mixing a powder or an aqueous solution of a compound having a phosphate group with a cellulosic raw material (e.g., a suspension (solids concentration of about 0.1 to 10% by mass)) and adding an aqueous solution of a compound having a phosphate group to an aqueous dispersion of the cellulosic raw material, with the latter being preferred.
• a cellulosic raw material e.g., a suspension (solids concentration of about 0.1 to 10% by mass)
• an aqueous solution of a compound having a phosphate group to an aqueous dispersion of the cellulosic raw material, with the latter being preferred.
• the pH of the aqueous solution of the compound having a phosphate group is preferably 7 or less from the viewpoint of
• Examples of compounds having a phosphate group include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, esters and salts thereof. These compounds are low cost and easy to handle, and can be introduced into cellulose to improve defibration efficiency.
• compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, 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, and ammonium metaphosphate.
• Compounds having a phosphate group can be used alone or in combination of two or more.
• the amount of the compound having a phosphate group added to the cellulose raw material is preferably 0.1 to 500 parts by mass, more preferably 1 to 400 parts by mass, and even more preferably 2 to 200 parts by mass, in terms of phosphorus element, per 100 parts by mass of the solid content of the cellulose raw material. This makes it possible to efficiently obtain a yield that corresponds to the amount of the compound having a phosphate group used.
• 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.
• a basic compound e.g., a compound having an amino group that shows basicity, such as urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, or hexamethylenediamine
• a basic compound e.g., a compound having an amino group that shows basicity, such as urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, or hexamethylenediamine
• the suspension obtained after esterification is dehydrated as necessary, and preferably subjected to a heat treatment after dehydration.
• This can suppress hydrolysis of the cellulose raw material.
• the heating temperature is preferably 100 to 170°C, and while water is contained during the heat treatment, it is more preferable to heat at 130°C or less (preferably 110°C or less), remove the water, and then heat treat at 100 to 170°C. After boiling, it is preferable to perform a washing treatment such as washing with cold water. This allows efficient defibration. Washing may be performed by adding water and then dehydrating (for example, filtration), and may be repeated two or more times. Washing is preferably performed until the electrical conductivity of the filtrate decreases.
• the electrical conductivity is preferably 200 or less, more preferably 150 or less, and even more preferably 120 or less.
• a neutralization treatment may be performed as necessary.
• the neutralization treatment can be performed by adding an alkali (for example, sodium hydroxide). Washing may be performed again after neutralization.
• a second example of a method for producing an esterified cellulose fiber is a phosphite-esterified cellulose fiber.
• Phosphite-esterified cellulose fiber usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is phosphorylated.
• the degree of substitution of the phosphite group per glucose unit in the phosphite esterified cellulose fiber (hereinafter simply referred to as the "degree of phosphite substitution”) is preferably 0.001 to 0.60.
• the degree of substitution of the phosphite group can be measured by the same method as that for measuring the degree of phosphate group substitution.
• the degree of phosphite group substitution can be adjusted by controlling reaction conditions such as the amount of phosphorous acid or a salt thereof added, the amount of an alkali metal ion-containing substance used as necessary, and urea or a derivative thereof added.
• An example of a method for phosphite esterification is to react unmodified cellulose fibers with phosphorous acid or a metal salt thereof (preferably sodium hydrogen phosphite) to introduce an ester group of phosphorous acid.
• phosphorous acid or a metal salt thereof preferably sodium hydrogen phosphite
• Examples of phosphorous acid and its metal salts include phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid, and combinations of two or more selected from these, with sodium hydrogen phosphite being preferred. This allows alkali metal ions to be introduced into the cellulose fibers.
• phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium
• the amount of phosphorous acid or its metal salts added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and even more preferably 300 to 1,500 g per kg of unmodified cellulose fibers.
• an alkali metal ion-containing material e.g., hydroxide, metal sulfate, metal nitrate, metal chloride, metal phosphate, metal carbonate
• hydroxide, metal sulfate, metal nitrate, metal chloride, metal phosphate, metal carbonate may be further added to the reaction system.
• Urea or a derivative thereof may also be added to the reaction system. This allows carbamate groups to also be introduced into the cellulose fibers.
• urea and urea derivatives include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and combinations of two or more selected from these, with urea being preferred.
• the amount of urea and urea derivatives added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, and even more preferably 0.5 to 10 mol per mol of phosphorous acid or its metal salt.
• the reaction temperature is preferably 100 to 200°C, more preferably 100 to 180°C, and even more preferably 100 to 170°C.
• the reaction time is usually about 10 to 180 minutes, more preferably 30 to 120 minutes. It is preferable to wash the phosphite esterified cellulose fiber before defibrating it.
• the degree of substitution of phosphite groups per glucose unit is preferably 0.01 or more and less than 0.23.
• a third example of the method for producing an esterified cellulose fiber is a sulfated cellulose fiber.
• Cellulose sulfate usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is phosphorylated.
• the amount of sulfate groups per glucose unit in sulfated cellulose fibers is preferably 0.1 to 3.0 mmol/g.
• the degree of cationic substitution per glucose unit is 0.50 or less, swelling or dissolution can be suppressed, and a situation in which it becomes impossible to obtain nanofibers can be prevented.
• the amount of sulfate groups per glucose unit can be measured by the following method.
• An aqueous dispersion of sulfated CNF is subjected to solvent replacement with ethanol and then t-butanol, and then freeze-dried.
• 15 ml of ethanol and 5 ml of water are added to 200 mg of the obtained sample, and the mixture is stirred for 30 minutes.
• 10 ml of 0.5 N aqueous sodium hydroxide solution is added, and the mixture is stirred at 70°C for 30 minutes and further stirred at 30°C for 24 hours.
• Amount of sulfate group [mmol/g sample] (5-(0.1 ⁇ titer of hydrochloric acid [ml] ⁇ 2))/0.2.
• the amount of sulfate groups can be adjusted by controlling the reaction conditions, such as the amount of sulfate compound added to the reaction.
• One example of a method for sulfate esterification is to react unmodified cellulose fibers with a sulfate compound to introduce sulfate groups derived from the sulfate compound into the cellulose to produce sulfated cellulose.
• sulfate compounds include sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, and esters or salts of these. Of these, it is preferable to use sulfamic acid, since it has low solubility in cellulose and low acidity.
• the amount of sulfamic acid used can be adjusted appropriately taking into account the amount of anion groups introduced into the cellulose chain.
• the amount is preferably 0.01 to 50 mol, more preferably 0.1 to 3.0 mol, per 1 mol of glucose units in the cellulose molecule.
• the esterified cellulose may contain more acid-type carboxy groups than salt-type carboxy groups, or may contain more salt-type carboxy groups than acid-type carboxy groups.
• esterified cellulose those that have not been subjected to a desalting treatment and those that have been subjected to a desalting treatment are called salt-type esterified cellulose and acid-type esterified cellulose, respectively.
• Salt-type esterified cellulose mainly has salt-type carboxy groups. It is presumed that acid-type esterified cellulose has a superior reinforcing effect due to the component C.
• the counter cation of the salt-type carboxy group and the preparation method thereof are as explained in the explanation of oxidized cellulose.
• -Cationization- Cationic cellulose usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at C6 constituting the glucopyranose unit) is cationized, and usually contains cations such as ammonium, phosphonium, and sulfonium, or a group having such a cation, in the molecule.
• the degree of cationic substitution per glucose unit in cationized cellulose is preferably 0.02 to 0.50.
• the degree of cationic substitution per glucose unit can be measured by the following method.
• the degree of cationic substitution can be adjusted by changing reaction conditions such as the amount of cationizing agent added to the reaction and the composition ratio of water or alcohol with 1 to 4 carbon atoms.
• An example of a method for cationization is to react unmodified cellulose fibers with a cationization agent (e.g., glycidyl trimethylammonium chloride, 3-chloro-2-hydroxypropyl trialkylammonium hydride or a halohydrin type thereof) and an alkali metal hydroxide catalyst (e.g., sodium hydroxide, potassium hydroxide) in the presence of water and/or an alcohol having 1 to 4 carbon atoms.
• a cationization agent e.g., glycidyl trimethylammonium chloride, 3-chloro-2-hydroxypropyl trialkylammonium hydride or a halohydrin type thereof
• an alkali metal hydroxide catalyst e.g., sodium hydroxide, potassium hydroxide
• the amount of the cationizing agent is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, based on 100 parts by mass of the cellulose raw material.
• the upper limit of the amount is usually 800 parts by mass or less, preferably 500 parts by mass or less.
• catalysts that may be used as necessary during cationization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
• the amount of catalyst is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the cellulose raw material.
• the upper limit of the amount is usually 7 parts by mass or less, preferably 3 parts by mass or less.
• Base-type cationized cellulose fiber The cationized cellulose fibers after cationization are preferably converted to base-type cationized cellulose or base-type cationized cellulose nanofibers by desalting.
• the salt in the cationized cellulose can be converted to a base by desalting.
• cationized cellulose (nanofibers) that have been desalted are referred to as base-type cationized cellulose (nanofibers) or cationized cellulose (nanofibers) (base type).
• Desalting may be performed at any time before (cationized cellulose) or after (cationized cellulose nanofibers) defibration, which will be described later. Desalting means that the salt (e.g. Cl - ) contained in the cationized cellulose (salt type) and the cationized cellulose nanofiber (salt type) is replaced with a base to make it a base type.
• a method of contacting the cationized cellulose or cationized cellulose nanofibers with an anion exchange resin can be mentioned.
• the anion exchange resin either a strong basic ion exchange resin or a weak basic ion exchange resin can be used as long as the counter ion is OH- .
• the ratio of the two when the modified cellulose is contacted with the anion exchange resin is not particularly limited, and a person skilled in the art can set it appropriately from the viewpoint of efficiently performing cation replacement.
• the ratio can be adjusted so that the pH of the aqueous dispersion after the addition of the anion exchange resin to the cationized cellulose nanofiber aqueous dispersion is preferably 8 to 13, more preferably 9 to 13.
• the anion exchange resin after contact can be recovered by a conventional method such as suction filtration.
• the pulverization is usually carried out by a mechanical treatment.
• the mechanical treatment preferably beating or defibration
• the mechanical treatment is usually carried out in a wet manner (i.e., in the form of an aqueous dispersion of cellulose fibers).
• Examples of the apparatus used for the mechanical treatment include a refiner (e.g., a disk type, a conical type, a cylinder type), a high-speed defibrator, a shear type agitator, a colloid mill, a high-pressure jet disperser, a beater, a PFI mill, a kneader, a disperser, a high-speed defibrator (top finer), a high-pressure or ultra-high-pressure homogenizer, a grinder (a stone-type grinder), a ball mill, a vibration mill, a bead mill, a single-screw, twin-screw or multi-screw kneader/extruder, a homomixer under high-speed rotation, a refiner, a defibrator, a friction grinder, a high-shear defibrator, and a high-shear defibrator.
• a refiner
• the device examples include a device capable of imparting a mechanical defibration force, such as a defibrator, a disperger, or a homogenizer (e.g., a microfluidizer), of which a device capable of imparting a wet defibration force is preferred, and a high-speed disintegrator or a refining device is more preferred, but there are no particular limitations on the device.
• a device capable of imparting a mechanical defibration force such as a defibrator, a disperger, or a homogenizer (e.g., a microfluidizer), of which a device capable of imparting a wet defibration force is preferred, and a high-speed disintegrator or a refining device is more preferred, but there are no particular limitations on the device.
• a device capable of imparting a mechanical defibration force such as a defibrator, a disperger, or
• an aqueous dispersion of cellulose fibers is usually prepared.
• the solids concentration of the modified cellulose in the aqueous dispersion is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more.
• the upper limit of the concentration is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less.
• pH adjustment e.g., 7 or less, 6 or less, 5 or less
• a pretreatment such as dry grinding (e.g., grinding after drying) may be performed prior to preparing the aqueous dispersion.
• a pretreatment such as dry grinding (e.g., grinding after drying)
• the apparatus used for dry grinding include, but are not limited to, impact mills such as hammer mills and pin mills, media mills such as ball mills and tower mills, and jet mills.
• a posttreatment may be performed after defibration.
• posttreatment examples include, but are not limited to, drying (e.g., freeze drying, spray drying, tray drying, drum drying, belt drying, thin spreading on a glass plate or the like and drying, fluidized bed drying, microwave drying, heated fan reduced pressure drying, reduced pressure (degassing) drying), redispersion in water (dispersion apparatus is not limited), and grinding (e.g., grinding using equipment such as a cutter mill, hammer mill, pin mill, or jet mill).
• drying e.g., freeze drying, spray drying, tray drying, drum drying, belt drying, thin spreading on a glass plate or the like and drying, fluidized bed drying, microwave drying, heated fan reduced pressure drying, reduced pressure (degassing) drying), redispersion in water (dispersion apparatus is not limited
• grinding e.g., grinding using equipment such as a cutter mill, hammer mill, pin mill, or jet mill.
• the fine cellulose fibers may be in the form of an aqueous dispersion obtained after production, or may be subjected to post-treatment as necessary.
• post-treatment include drying (e.g., freeze drying, spray drying, tray drying, drum drying, belt drying, thin spreading on a glass plate or the like and drying, fluidized bed drying, microwave drying, and heated fan type reduced pressure drying), redispersion in water (dispersion device is not limited), and pulverization (e.g., pulverization using equipment such as a cutter mill, hammer mill, impact mill, airflow mill, roller mill, and vibration mill), but are not particularly limited thereto.
• the fine cellulose fibers preferably have the following physical properties.
• the BET specific surface area of the fine cellulose fibers is preferably 25 m2 /g or more, more preferably 50 m2 /g or more, and even more preferably 100 m2 /g or more.
• the BET specific surface area can be measured by substituting t-BuOH in the aqueous dispersion and then freeze-drying the sample according to the nitrogen gas adsorption method (JIS Z 8830) using a BET specific surface area meter.
• the crystallinity of cellulose type I in fine cellulose fibers is usually 50% or more, preferably 60% or more.
• the upper limit is not particularly limited, but it is practically considered to be about 90%.
• the crystallinity of cellulose can be controlled by the degree of chemical modification.
• the crystallinity of cellulose type I can be calculated by measuring and comparing the intensity of the (200) peak near 22.6° and the valley (near 18.5°) between (200) and (110) by X-ray diffraction measurement.
• fine cellulose fibers contain type II crystals, it is preferable to separate the peaks (near 12.3°, 20.2°, and 21.9°) due to type II crystals and then calculate the intensity of type I crystals.
• the viscosity of the water dispersion is low. This allows the material to have good handleability despite being fibrillated.
• the B-type viscosity (25°C, 60 rpm) of a water dispersion having a solid content of 1% by mass is usually 6,000 mPa ⁇ s or less or 5,000 mPa ⁇ s or less, preferably 4,500 mPa ⁇ s or less, more preferably 4,000 mPa ⁇ s or less.
• the lower limit is preferably 10 mPa ⁇ s or more, more preferably 20 mPa ⁇ s or more, even more preferably 50 mPa ⁇ s or more, 100 mPa or more, 500 mPa or more, 1,000 mPa or more, or 2,000 mPa or more.
• the B-type viscosity (25°C, 6 rpm) of an aqueous dispersion with a solid content of 1% by mass is usually 25,000 mPa ⁇ s or less or 20,000 mPa ⁇ s or less, preferably 18,000 mPa ⁇ s or less, more preferably 15,000 mPa ⁇ s or less.
• the lower limit is preferably 100 mPa ⁇ s or more, more preferably 500 mPa ⁇ s or more, and even more preferably 1,000 mPa ⁇ s or more, 2,00 mPa or more, 3,000 mPa or more, 4,000 mPa or more, or 5,000 mPa or more.
• the B-type viscosity can be measured, for example, by the following method.
• dilution is performed as necessary, and the mixture is stirred with a homodisper (e.g., 3000 rpm, 5 min), and then the viscosity is measured (the viscosity is measured after rotating at 6 or 60 rpm for 3 minutes).
• a homodisper e.g., 3000 rpm, 5 min
• the transparency of a CNF aqueous dispersion having a solid content of 1.0% by mass is usually 40% or more, preferably 50% or more, and more preferably 60% or more. There is no particular upper limit, and it may be 100% or less.
• the transparency of a MFC aqueous dispersion having a solid content of 1.0% by mass is usually 1% or more, preferably 5% or more.
• the upper limit is 50% or less.
• the transparency can be measured as the transmittance of 660 nm light using a visible light photometer.
• the degree of anionization is usually 2.50 meq/g or less, preferably 2.30 meq/g or less, more preferably 2.0 meq/g or less, and even more preferably 1.50 meq/g or less. This is thought to make the chemical modification more uniform throughout the cellulose than cellulose fibers with a higher degree of anionization, and it is thought that the effects specific to chemically modified cellulose fibers, such as water retention, can be obtained more stably.
• the lower limit is usually 0.06 meq/g or more, preferably 0.10 meq/g or more, more preferably 0.30 meq/g or more, but is not particularly limited.
• the degree of anionization is the equivalent of anion per unit mass of modified cellulose microfibril, and can be calculated from the equivalent of diallyldimethylammonium chloride (DADMAC) required to neutralize the anionic groups in unit mass of modified cellulose microfibril.
• DADMAC diallyldimethylammonium chloride
• the water retention capacity is preferably 10 or more, more preferably 15 or more, even more preferably 20 or more, and even more preferably 30 or more.
• the upper limit is thought to be about 200 or less in reality, but is not particularly limited.
• the water retention capacity corresponds to the mass of water in the sediment relative to the mass of the solid content of the fibers in the sediment, and is the ratio of the water content to the solid content in the precipitated gel, measured and calculated by centrifuging a 0.3 mass% aqueous dispersion of the fibers at 25,000 G.
• Water retention capacity (B+C-0.003 ⁇ A)/(0.003 ⁇ A-C)
• Water retention can be measured or calculated for fibers that have been fibrillated, but cannot usually be measured for fibers that have not been fibrillated or defibrated, or for cellulose nanofibers that have been defibrated down to single microfibrils.
• cellulose fibers that have not been fibrillated or defibrated are centrifuged under the above conditions, a dense sediment cannot be formed, making it difficult to separate the sediment from the aqueous phase.
• cellulose nanofibers are centrifuged under the above conditions, there is usually very little sedimentation.
• the fibrillation rate (Fibrillation %) is preferably 1.0% or more, more preferably 1.2% or more, and even more preferably 1.5% or more. This allows confirmation that fibrillation is sufficient.
• the fibrillation rate can be adjusted depending on the type of cellulose-based raw material used.
• the fibrillation rate can be determined by an image analysis type fiber analyzer such as a fractionator manufactured by Valmet Co., Ltd.
• the electrical conductivity of the aqueous dispersion (solid content concentration 1.0% by mass) is preferably 500 mS/m or less, more preferably 300 mS/m or less, even more preferably 200 mS/m or less, even more preferably 100 mS/m or less, and particularly preferably 70 mS/m or less.
• the lower limit is preferably 5 mS/m or more, more preferably 10 mS/m or more.
• the electrical conductivity can be measured by preparing 200 g of an aqueous dispersion of cellulose microfibrils having a solid content concentration of 1.0% by mass and using an electrical conductivity meter (HORIBA ES-71 type).
• Component C is a water-soluble polymer.
• the water-soluble polymer include cellulose derivatives (e.g., carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or ethyl cellulose or salts thereof (e.g., sodium salts)), xanthan gum, Xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, potato starch, kudzu flour, cationic starch, phosphorylated starch, corn starch, gum arabic, locust bean gum, gellan gum, polydextrose, Pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein Dissolved matter, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate
• CMC refers to a compound having a structure in which the hydroxyl groups in the glucose residues that make up cellulose are replaced with carboxymethyl ether groups.
• examples of the salt include metal salts such as sodium salts.
• the CMC may have the following physical properties and shape, and among them, it is preferable that the CMC satisfies a predetermined viscosity.
• the B-type viscosity (25°C, 30 rpm) of a 1% by mass aqueous solution of CMC is usually 20 mPa ⁇ s or more, preferably 25 mPa ⁇ s or more, and more preferably 30 mPa ⁇ s or more.
• the upper limit is usually 500 or less, preferably 400 or less, more preferably 300 or less, and even more preferably 250 or less.
• the water-soluble polymer is CMC
• CMC was weighed into a 1000 mL glass beaker and dispersed in 900 mL of distilled water to prepare an aqueous dispersion with a solid content of 1% (w/v).
• the aqueous dispersion was stirred at 600 rpm for 3 hours at 25°C using a stirrer. Thereafter, the viscosity after 3 minutes was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.) in accordance with the method of JIS-Z-8803 with a No. 1 rotor at a rotation speed of 30 rpm.
• degree of carboxymethyl substitution The degree of carboxymethyl substitution per anhydrous glucose unit of CMC is usually 0.45 or more, preferably 0.6 or more. This allows it to exhibit sufficient water solubility.
• the upper limit is usually 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less.
• the degree of substitution of carboxymethyl groups can be calculated by the same measurement method as the degree of substitution of carboxymethylated cellulose described above.
• the degree of carboxymethyl substitution can be adjusted by controlling the reaction conditions such as the amount of etherification agent and mercerization agent reacted during production.
• -Amount of acid type carboxyl group- CMC may have an acid type carboxy group, and the amount of the acid type carboxy group is usually 20.00 mmol/g or less, preferably 15.00 mmol/g or less, more preferably 3.00 mmol/g or less.
• the lower limit may be 0, or may be, for example, 1.15 mmol/g or more.
• the amount of the acid type carboxy group can be adjusted by adjusting the pH of a 1% by mass aqueous solution of CMC to an acidic range.
• the amount of acid carboxyl groups in CMC is calculated by: preparing CMCx (g) as an aqueous solution; measuring the electrical conductivity of the aqueous solution; and dropping a sodium hydroxide aqueous solution of a predetermined concentration y (N).
• the amount of sodium hydroxide aqueous solution a (mL) consumed in the neutralization step of the acid carboxyl groups, which is a weak acid with a gradual change in electrical conductivity, is calculated using the formula (A).
• Amount of acid-type carboxyl group [mmol/g] a [mL] ⁇ y [N]/mass of CMC x [g] (A)
• the amount of acid-type carboxyl groups in CMC can be measured by the following method. 100 mL of ion-exchanged water is added to 0.1 g of CMC to prepare an aqueous solution, and a 0.1 N aqueous sodium hydroxide solution is added dropwise at a rate of 0.5 mL/min while measuring the electrical conductivity. A titration curve is then created by plotting the electrical conductivity against the amount of added sodium hydroxide solution.
• a first asymptote is created by the least squares method from the points in the range where the electrical conductivity changes slowly
• a second asymptote is created by the least squares method from the points in the range where the electrical conductivity changes rapidly
• the amount of added sodium hydroxide solution at the intersection of the first asymptote and the second asymptote is taken as the amount of sodium hydroxide solution a (mL) consumed in the neutralization step of the acid-type carboxyl groups.
• the amount of acid-type carboxyl groups is calculated from the mass (g) of CMC used in the titration, the concentration of sodium hydroxide (N), and the amount of sodium hydroxide solution a (mL) according to formula (A).
• the electrical conductivity the value obtained from the electrical conductivity meter may be used as is, or a corrected electrical conductivity may be obtained by multiplying the value obtained from the electrical conductivity meter by a coefficient calculated from the following formula (B), and the first asymptote and the second asymptote may be obtained using this corrected electrical conductivity.
• (Coefficient) (V 0 (mL) + v (mL)) / V 0 (mL)...
• V 0 represents the amount of the aqueous solution of carboxymethyl cellulose or a salt thereof before the addition of the aqueous sodium hydroxide solution
• v represents the amount of the aqueous sodium hydroxide solution added at each electrical conductivity value.
• the pH (25° C.) of a 1% by mass aqueous solution of CMC may be in the neutral range (eg, pH 6.8 to 7.2) or in the acidic range (eg, pH 4.0 or more and less than 6.8).
• the maximum particle size of CMC is usually less than 50 ⁇ m, preferably less than 45 ⁇ m. This can suppress the generation of undissolved matter in the aqueous solution of CMC.
• the lower limit is not particularly limited as long as it exceeds 0.
• the maximum particle size of CMC before granulation is in the above range.
• the maximum particle size is the cumulative 100% volume particle size measured by a laser diffraction/scattering particle size distribution analyzer using methanol as a dispersant.
• the average particle size of CMC is usually 30 ⁇ m or less, preferably 20 ⁇ m or less, and more preferably 15 ⁇ m or less.
• the lower limit is usually 12 ⁇ m or more.
• the average particle size is the cumulative 50% volume particle size measured with a laser diffraction/scattering particle size distribution analyzer using methanol as a dispersion medium.
• the method for producing CMC may be any method that involves carboxymethylation of a cellulose raw material, and an example is as follows.
• -Carboxymethylation- Carboxymethylation can be performed on a cellulose raw material (e.g., pulp such as dissolving pulp, linter, regenerated cellulose, crystalline cellulose) as a starting raw material (starting raw material), and for example, a method of mercerizing the cellulose raw material and then etherifying it can be mentioned.
• the molar ratio of the mercerizing agent to the etherifying agent is preferably 2.00 or more. This allows the etherification after mercerization to proceed sufficiently, and the remaining etherifying agent (e.g., monochloroacetic acid) can be suppressed.
• the upper limit is preferably 2.45 or less.
• CMC is a water-soluble polymer, and preferably exhibits water solubility by expressing an appropriate viscosity, and therefore does not have a fibrous shape in water, which is different from the method for producing carboxymethylated fine cellulose fibers as component B, which maintain a fibrous shape even in water after being defibrated.
• the pH of a 1% by weight aqueous solution of CMC obtained through carboxylation is usually in the neutral range, but the pH may be adjusted to an acidic range as necessary.
• An example of a method for adjusting to an acidic range is a method of adding an acid (e.g., acetic acid). The adjustment may be performed in the presence of a solvent (dispersion medium).
• the solvent include alcohols such as methanol, water, and mixtures thereof, and preferably methanol or a mixture of methanol and water.
• the solvent can be removed by dehydration treatment such as filtration and drying.
• Carboxymethylcellulose or a salt thereof which has a neutral pH (pH 6.8 to 7.2) when made into an aqueous solution with a solid content of 1% by mass, can be converted into carboxymethylcellulose or a salt thereof of this embodiment, which has a pH in the acidic range (pH 4.0 or more and less than 6.8) when made into an aqueous solution with a solid content of 1% by mass, by, for example, adding an acid.
• pulverization or further granulation may be performed as necessary (pulverized product, granulated product).
• the pulverization is usually a mechanical pulverization performed using a machine.
• the pulverization method of carboxymethylcellulose or its salt includes, for example, a dry pulverization method in which the carboxymethylcellulose or its salt is treated in a powder state, and a wet pulverization method in which the carboxymethylcellulose or its salt is treated in a dispersed or dissolved state in a liquid, and either of these is preferred.
• Examples of pulverization devices that can be used for mechanical pulverization include, for example, a cutter mill, a hammer mill, an impact mill, an airflow mill, a roller mill, and a vibration mill, and may be either a dry pulverizer or a wet pulverizer.
• classification process In the production of CMC, a classification process may be performed as necessary.
• classification means a process of sieving particles to be classified into those having a certain particle size or more and those having a size or less based on the particle size (preferably the maximum particle size). Classification means.
• Classification is preferably performed based on whether the maximum particle size is less than 50 ⁇ m or 50 ⁇ m or more. This makes it possible to selectively collect carboxymethylcellulose or its salts with a maximum particle size of less than 50 ⁇ m.
• the timing of the classification is not particularly limited, and it may be performed during the pulverization process or after the pulverization process is completed.
• a known method can be used, for example, a method using a dry classifier or a wet classifier.
• dry classifiers include a cyclone classifier, a DS separator, a turbo classifier, a microseparator, and an air separator.
• wet classifiers include a liquid cyclone type classifier, a centrifugal settler, and a hydrosilator. Of these, a dry classifier is preferred, and a cyclone classifier is more preferred.
• Component D is a crosslinkable compound.
• the storage modulus (E′) of the rubber composition can be further improved.
• the cross-linking compound has a thiosulfate group or an ⁇ , ⁇ -unsaturated carbonyl group and an amino group.
• the thiosulfate group may be in the acid form (-SSO 3 H) or in the salt form (-SSO 3 - ).
• examples of the counter cation include alkali metals such as sodium, lithium, calcium, and cesium, and quaternary ammonium salts such as N(R 6 ) 4 - (wherein R 6 may be the same or different and is a hydrogen atom, or an organic group such as an alkyl group or an ammonium group; the same applies hereinafter).
• R1 and R2 each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxy group, or a hydrocarbon group, and R1 and R2 may be linked together.
• R1 or R2 is a hydrogen atom, and more preferably, both are hydrogen atoms.
• R3 is a counter ion, and examples of such counter ions include alkali metals such as sodium, lithium, calcium, and cesium, and quaternary ammonium salts such as N( R6 ) 4- .
• R 4 and R 5 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. It is preferable that at least one of R 4 and R 5 is a hydrogen atom, and it is more preferable that both are hydrogen atoms (—NH 2 ).
• Examples of the spacer linking the thiosulfate group or ⁇ , ⁇ -unsaturated carbonyl group to the amino group include an alkyl group and a divalent group containing an aromatic ring and an amide bond.
• the spacer linking the thiosulfate group to the amino group is preferably an alkyl group, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably an alkyl group having 2 to 5 carbon atoms.
• the spacer linking the ⁇ , ⁇ -unsaturated carbonyl group to the amino group is preferably a divalent group containing an aromatic ring and an amide bond.
• crosslinkable Compounds S-(3-aminopropyl)thiosulfuric acid and (2Z)-4-[(4-aminophenyl)amino]-4-oxo-2-butenoic acid (e.g., sodium salt) are preferred, the structural formulas of which are shown in the following formulas (3) and (4), respectively.
• Component D may be a single crosslinkable compound or a combination of two or more crosslinkable compounds.
• a crosslinking compound containing a thiosulfate group it is preferable to include the compound of formula (3).
• the reason why the compound of formula (3) is more preferable is unclear, but is as follows. Since the crosslinking compound of component D mainly reacts with the OH group in the cellulose structure of component B as a crosslinking point, it is presumed that the compound of formula (3), which has relatively little steric hindrance, can be used with component B having a variety of structures and is more likely to react with the above-mentioned crosslinking point.
• the rubber composition may further contain one or more optional components according to the requirements of the application of the rubber composition.
• the optional components include compounding agents that can be used in the rubber industry, such as reinforcing agents (e.g., silica, carbon black), fillers other than cellulose fillers (e.g., calcium carbonate, clay), silane coupling agents, crosslinking agents, vulcanization accelerators, vulcanization accelerator assistants (e.g., zinc oxide, stearic acid), oils, cured resins, waxes, antioxidants, colorants, and foaming agents. Among these, vulcanization accelerators and vulcanization accelerator assistants are preferred.
• the content of the optional components may be appropriately determined according to conditions such as the type of the optional components, and is not particularly limited.
• crosslinking agents include sulfur compounds such as sulfur halides, peroxides (peroxides, for example, organic peroxides such as dicumyl peroxide, bis( ⁇ , ⁇ -dimethylbenzyl) peroxide, cumene peroxide, cumyl peroxide, and dicumyl peroxide), quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups.
• sulfur and peroxides are preferred, and sulfur is more preferred.
• vulcanization accelerators include guanidines such as diphenylguanidine (DPG), thiazoles such as di-2-benzothiazolyl disulfide (MBTS) and 2-mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N-tert-butyl-2-benzothiazolyl sulfenamide (BBS), N-oxydiethylene-2-benzothiazolyl sulfenamide (OBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide.
• DPG diphenylguanidine
• thiazoles such as di-2-benzothiazolyl disulfide (MBTS) and 2-mercaptobenzothiazole (MBT)
• CBS N-cyclohexyl-2-benzothiazolyl sulfenamide
• BBS N-tert-butyl-2
• vulcanization accelerators include sulfenamide-based accelerators such as (DZ), thiourea-based accelerators such as ethylenethiourea (EU), diethylthiourea (EUR), and trimethylthiourea (TMU), thiuram-based accelerators such as tetramethylthiuram monosulfide (TMTM) and tetramethylthiuram disulfide (TMTD), thiocarbamic acid-based accelerators such as zinc dimethyldithiocarbamate (ZnMDC) and zinc di-n-butyldithiocarbamate (ZnBDC), and xanthogenate-based accelerators such as zinc isopropylxanthogenate (ZIX). These may be used alone or in combination of two or more.
• sulfenamide-based accelerators such as (DZ)
• thiourea-based accelerators such as ethylenethiourea (EU), diethylthiourea (EUR), and
• the content of Component B is usually 0.5 parts by mass or more, preferably 1 part by mass or more, and more preferably 1.5 parts by mass or more, relative to 100 parts by mass of Component A.
• the upper limit is usually 50 parts by mass or less or 40 parts by mass or less, preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Therefore, the content of Component B is usually 0.5 to 50 parts by mass, 0.5 to 50 parts by mass, preferably 1 to 50 parts by mass or 1 to 30 parts by mass, and more preferably 1.5 to 30 parts by mass or 1.5 to 25 parts by mass, relative to 100 parts by mass of Component A.
• the content of Component C is usually 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, relative to 100 parts by mass of Component A.
• the upper limit is usually 5 parts by mass or less, preferably 4 parts by mass or less, and more preferably 3 parts by mass or less. Therefore, the content of Component C is usually 0.05 to 5 parts by mass, preferably 0.1 to 4 parts by mass, and more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of Component A.
• the content of component C is usually 0.5 parts by mass or more, preferably 2.5 parts by mass or more, and more preferably 5 parts by mass or more, relative to 100 parts by mass of component B.
• the upper limit is usually 25 parts by mass or less, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. Therefore, the content of component C is usually 0.5 to 25 parts by mass, preferably 2.5 to 20 parts by mass, and more preferably 5 to 10 parts by mass, relative to 100 parts by mass of component B. This improves the dispersibility of the fine cellulose fibers in the latex.
• the content of Component D is usually 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, relative to 100 parts by mass of Component A.
• the upper limit is usually 10 parts by mass or less, preferably 8 parts by mass or less, and more preferably 5 parts by mass or less. Therefore, the content of Component C is usually 0.05 to 10 parts by mass, preferably 0.1 to 8 parts by mass, and more preferably 0.5 to 5 parts by mass, relative to 100 parts by mass of Component A.
• the content of the crosslinking agent is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of Component A.
• 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.
• the content of the vulcanization accelerator is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more, per 100 parts by mass of component A.
• the upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.
• the method for producing the rubber composition may, for example, include a method including a step of kneading Components A to C to obtain a mixture, and a step of drying the mixture.
• components A to C are kneaded (primary kneading not including a vulcanizing agent) to obtain a mixture.
• the amounts of each component are as described above.
• Component D and optional components may be added as necessary when, simultaneously with, during, or after the mixing of components A to C, but the crosslinking agent and granulation accelerator are preferably added after the mixing and kneading of components A to C.
• components A to C to be mixed is not particularly limited. Examples include solids of each component, dispersions dispersed in a dispersion medium (latex in the case of component A), and solutions dissolved in a solvent. Examples of dispersion mediums and solvents (hereinafter collectively referred to as "liquids") include water and organic solvents, with water being preferred. The amount of liquid is preferably 10 to 1,000 parts by mass per 100 parts by mass of rubber solids (the total amount when two or more rubber components are used). The dispersions and solutions may contain a dispersant as necessary.
• the primary kneading can be carried out using known devices such as a homomixer, homogenizer, or propeller agitator.
• a homomixer homogenizer
• propeller agitator There are no limitations on the mixing temperature, but room temperature (20 to 30°C) is preferred.
• the mixing time can also be adjusted as appropriate.
• the solid content concentration of the mixture obtained in the mixing step is usually 3% by mass or more, preferably 4% by mass or more, more preferably 5% by mass or more, 6% by mass or more, or 7% by mass or more. This allows a film with a large thickness to be formed in the drying step, so that the heat transmitted to components B and C can be reduced, thereby suppressing the progress of thermal denaturation and suppressing the decrease in dispersibility after drying.
• the upper limit is usually 70% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less, 40% by mass or less, or 30% by mass or less. This suppresses the increase in viscosity of the mixture and allows the drying process to be carried out smoothly.
• the solid content concentration is usually 3 to 70% by mass, preferably 4 to 60% by mass, more preferably 5 to 50% by mass, 6 to 40% by mass, or 7 to 30% by mass.
• the solid content concentration of the mixture can be adjusted by the solid content concentrations of each of components A to C (component D added as necessary) and the amount of solvent added as necessary.
• the treatment time is preferably 1 to 24 hours. By setting the heating temperature or heating time under the above conditions, damage to the rubber component can be suppressed.
• the mixture after drying may be in an absolutely dry state or may contain residual solvent.
• the drying method is not limited to the above methods, and any conventionally known method for removing the solvent may be appropriately selected.
• the form of component B to be subjected to the primary kneading is not particularly limited.
• Examples include an aqueous dispersion of a cellulose-based filler, a dry solid of the aqueous dispersion, and a wet solid of the aqueous dispersion.
• concentration of the cellulose-based filler in the aqueous dispersion may be 0.1 to 5% (w/v) when the dispersion medium is water, and may be 0.1 to 20% (w/v) when the dispersion medium contains water and an organic solvent such as alcohol.
• the wet solid is a solid having an intermediate form between the aqueous dispersion and the dry solid.
• the amount of the dispersion medium in the wet solid obtained by dehydrating the aqueous dispersion by a conventional method is preferably 5 to 15% by mass based on the total amount of solids.
• the amount of the dispersion medium in the wet solid can be appropriately adjusted by adding liquid or further drying.
• the primary kneading may be carried out using a kneader according to a known method.
• kneading machines include open kneaders such as two-roll and three-roll kneaders, intermeshing Banbury mixers, tangential Banbury mixers, pressure kneaders, homodispersers, and super mixers.
• the primary kneading may be a multi-stage process. For example, a combination of kneading with a closed kneader in the first stage and then re-kneading with an open kneader may be used.
• the processing time for the primary kneading is usually about 3 to 20 minutes, and the time required for uniform kneading can be appropriately selected.
• the temperature for the primary kneading may be about room temperature (e.g., about 15 to 30°C), but it may be heated to a somewhat higher temperature.
• the upper limit of the temperature is usually 150°C or less, preferably 140°C or less, and more preferably 130°C or less.
• the lower limit of the temperature is 15°C or more, preferably 20°C or more, and more preferably 30°C or more.
• the temperature for the primary kneading is preferably 15 to 150°C, more preferably 20 to 140°C, and even more preferably 30 to 130°C.
• the drying step the mixture obtained in the mixing step is dried. Drying can be performed using a drying device such as an oven or a drum dryer, and it is preferable to use a drum dryer.
• the temperature condition during drying is usually 70°C or higher, preferably 80°C or higher, more preferably 90°C or higher, 100°C or higher, or 110°C or higher. This allows the drying process to proceed efficiently.
• the upper limit is usually 150°C or lower, preferably 140°C or lower, more preferably 135°C or lower. This makes it possible to suppress cellulose denaturation due to heat, and to avoid a decrease in mechanical properties after molding of the resulting dried body.
• the drying process can be efficiently proceeded and a decrease in mechanical properties can be avoided.
• the temperature during drying means the temperature of the drum surface when drum drying is performed using a drum dryer.
• the treatment time varies depending on the conditions such as temperature and drying equipment, but is usually 0.01 to 24 hours.
• the obtained dried product may be used as a master batch as it is, or after further kneading (for example, kneading with a kneader such as a roll kneader) as necessary.
• any additives such as a rubber component, a crosslinking agent, a vulcanization aid, etc. may be added to these master batches, kneaded again (secondary kneading), and used as a final product (vulcanized rubber, crosslinked rubber).
• molding may be performed as necessary.
• molding methods include metal molding, injection molding, extrusion molding, blow molding, and foam molding. Appropriate equipment can be selected depending on the shape, application, and molding method of the final product.
• finishing treatment Before the kneaded material is made into a final product, it may be subjected to a finishing treatment as necessary.
• finishing treatments include polishing, surface treatment, lip finishing, lip cutting, and chlorine treatment. Only one of these treatments may be performed, or two or more may be combined.
• the use of the rubber composition is not particularly limited as long as it is a composition for obtaining a rubber product 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 a rubber product as a final product.
• the uses of the final products are not particularly limited, and examples include transportation equipment such as automobiles, trains, ships, and airplanes (e.g., tires, anti-vibration rubber); electrical appliances such as personal computers, televisions, telephones, and watches; mobile communication devices such as mobile phones; portable music players, video players, printing equipment, copying equipment, and sporting goods; building materials (e.g., seismic isolation rubber); office equipment such as stationery; containers; and other applications.
• transportation equipment such as automobiles, trains, ships, and airplanes (e.g., tires, anti-vibration rubber); electrical appliances such as personal computers, televisions, telephones, and watches; mobile communication devices such as mobile phones; portable music players, video players, printing equipment, copying equipment, and sporting goods; building materials (e.g., seismic isolation rubber); office equipment such as stationery; containers; and other applications.
• the products can also be applied to components that use rubber or flexible plastics.
• the oxidized pulp (solid content 3.1%) obtained in the above process was adjusted to 3.0% (w/v) with water and treated three times with an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain a TEMPO-oxidized CNF dispersion.
• the average fiber diameter of the obtained TEMPO-oxidized CNF was 3 nm, and the aspect ratio was 150.
• the amount of carboxyl groups was 1.45 mmol/g
• the solid content during production was 3.12%
• the concentration at the time of analysis was 1.0%
• the pH was 7.22
• the transparency was 93.4%
• the B-type viscosity (60 rpm, 6 rpm) was 2160 mPa ⁇ s and 13930 mPa ⁇ s, respectively.
• Aspect ratio average fiber length/average fiber diameter
• viscosity A CNF dispersion with a solid content of 1.0 mass% was prepared (after fibrillation (e.g., defibration), the dispersion was left to stand for at least one day, and then stirred with a homodisper (e.g., 3,000 rpm, 5 min)). The viscosity after 3 minutes at a rotation speed of 60 rpm and after 3 minutes at a rotation speed of 6 rpm were measured using a B-type viscometer (manufactured by Eiko Seiki Co., Ltd.) at 25°C.
• a homodisper e.g., 3,000 rpm, 5 min
• CM-DS carboxymethyl substitution degree
• CM-DS carboxymethyl substitution degree
• Table 1 shows the viscosity and CM-DS of each CMC.
• CM-DS carboxymethyl substitution degree
• Dynamic Viscoelasticity Dynamic Viscoelasticity Dynamic properties were measured according to JIS K6394:2017 "Vulcanized rubber and thermoplastic rubber - Determination of dynamic properties - General guidelines”. That is, using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science, DMA7100), the elastic modulus (E') at 23°C and the loss tangent (tan ⁇ ) at 60°C were measured under normal temperature control (temperature range: 18-110°C), measurement mode: tension, and DMA frequency: 10 Hz.
• DMA7100 Dynamic Viscoelasticity measuring device
• the storage modulus E' (23°C) and tan ⁇ (60°C) of Comparative Examples 2 and 4 (blank) were 7.0 MPa ⁇ s, 0.060, and 7.6 MPa ⁇ s, 0.040, respectively.
• the rubber compositions of Comparative Examples 1 and 3 (using the CMC of Comparative Manufacturing Example 1) had no difference in dynamic viscoelasticity from Comparative Examples 2 and 4 (no CMC added).
• the rubber compositions of Examples 1 to 10 had better dynamic viscoelasticity than the Comparative Examples, and their static tensile strength was equal to or greater than that of the Comparative Examples without any decrease. Focusing on the 100% intermediate stress (M100) of the static tensile strength, Examples 1 to 5 (sulfur crosslinked) tended to show a high M100 when using a CMC with low viscosity and/or high CM-DS (Table 2).
• Examples 11 and 12 Rubber compositions were obtained in the same manner as in Examples 5 and 10 (both of which used CMC5 of Production Example 6), except that the amount of CMC was changed to 4 phr.
• Example 13 Example 5
• S-(3-aminopropyl)thiosulfuric acid (Sumilink (registered trademark) 100, manufactured by Sumitomo Chemical Co., Ltd., abbreviated as SL100) was added in the amount shown in Table 3 during rubber kneading, and the amount of CMC added was changed to the amount shown in Table 3, to obtain a rubber composition.

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