JP2020007548A - Rubber composition - Google Patents

Abstract

To provide a rubber composition excellent in dynamic magnification and static spring constant.SOLUTION: There is provided a rubber composition containing at least a rubber, a filler which is carbon black or silica, and powdery cellulose having average particle diameter of 20 μm to 50 μm, and satisfying at least one of following conditions (A) to (B). (A) a relational expression of y<0.011x+0.67 is satisfied wherein total blend number of the filler and the powdery cellulose contained in the rubber composition is x and dynamic magnification of the rubber composition is y. (B) a relational expression of Ks>4.543x+135.86 is satisfied, wherein total blend number of the filler and the powdery cellulose contained in the rubber composition is x and static spring constant of the rubber composition is Ks.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rubber composition suitable for reducing noise and vibration of mechanical parts.

  BACKGROUND ART Rubber compositions are widely used in industry, and rubber members are used for the purpose of reducing noise and vibration of mechanical parts such as vehicle parts and the like. Various studies have been made on improving the performance of a rubber member (composition) called a vibration damping rubber suitable for such purpose.

  As such an anti-vibration rubber composition, there has been proposed a method of performing a surface treatment of calcium carbonate to be mixed with rubber in order to improve anti-vibration characteristics (dynamic magnification) (for example, see Patent Document 1). According to this method, it is disclosed that the vibration proof property can be improved or adjusted with other physical properties.

  Further, a rubber composition containing a composite zinc white and a bismaleimide compound in a diene rubber has been proposed in order to reduce dynamic magnification and improve heat resistance (for example, see Patent Document 2).

JP 2015-160826 A JP 2012-077080 A

  However, in the method of Patent Literature 1, surface-treated calcium carbonate is used in order to enhance vibration isolation characteristics. Therefore, when the surface treatment of calcium carbonate is not performed uniformly, there is a concern that the expected effect cannot be obtained. Further, since there are many processing steps, it is economically undesirable.

  In the rubber composition of Patent Document 2, composite zinc white (zinc oxide) is used. Zinc oxide has a large specific surface area and is easily aggregated. Therefore, the composite zinc white is difficult to be uniformly dispersed in the rubber composition, and there is a concern that the expected effect cannot be obtained.

By the way, one of the other performances required of the rubber for vibration isolation is a static spring constant which is an index of strength for supporting the object in a static state. It is known that the static spring constant tends to increase as the rubber hardness increases. Therefore, when supporting a heavier object, or when it is desired to support the vibration-proof rubber having a small size even under the same load, it is necessary to increase the static spring constant, so that the hardness of the rubber is required to be increased.
However, in general, when the static spring constant is increased, the dynamic magnification, which is an index of the vibration isolation characteristics, deteriorates. Therefore, there is a demand for a material that does not increase the dynamic magnification while increasing the static spring constant, and there is still room for improvement in the inventions of Patent Documents 1 and 2 from the viewpoint of the static spring constant.

  Accordingly, an object of the present invention is to provide a rubber composition having excellent dynamic magnification and static spring constant.

The present inventors have conducted intensive studies on the above problems, and as a result, have at least a rubber, a filler that is carbon black or silica, and at least a powdered cellulose, a dynamic magnification or a static spring constant, and a blend of the filler and the powdered cellulose. It has been found that the above problem can be solved by satisfying at least one of the relational expressions set by the number of copies and the present invention, and the present invention has been completed.
That is, the present inventors provide the following [1] to [6].
[1] A rubber composition that contains at least a filler material that is rubber, carbon black or silica, and powdered cellulose having an average particle diameter of 20 μm to 50 μm, and satisfies at least one of the following conditions (A) and (B).
(A) When the total number of the filler and the powdered cellulose contained in the rubber composition is x and the dynamic magnification of the rubber composition is y, the relational expression of y <0.011x + 0.67 is obtained. To meet.
(B) The relationship of Ks> 4.543x + 135.86, where x is the total number of the filler and the powdered cellulose contained in the rubber composition, and Ks is the static spring constant of the rubber composition. Satisfy the formula.
[2] The rubber composition according to [1], further satisfying the following condition (C).
(C) The dynamic magnification y and the static spring constant Ks of the rubber composition satisfy a relational expression of Ks / y ≧ 300.
[3] The rubber composition according to the above [1] or [2], wherein the amount of the powdered cellulose contained in the rubber composition is in the range of 1 to 50 parts by weight based on the rubber solid content.
[4] The rubber composition according to any one of the above [1] to [3], wherein the filler contained in the rubber composition is in a range of 20 to 120 parts by weight based on a rubber solid content.
[5] The rubber composition according to any one of [1] to [4], wherein the rubber is a natural rubber.
[6] A rubber composition for vibration isolation using the rubber composition according to any one of [1] to [5].

  According to the present invention, a rubber composition having excellent dynamic magnification and static spring constant can be provided.

FIG. 1 shows the rubbers of Examples and Comparative Examples when the total number x of carbon black and powdered cellulose contained in the rubber composition is plotted on the horizontal axis, and the dynamic magnification y of the rubber composition is plotted on the vertical axis. 3 is a graph showing the relationship between x and y in a composition. FIG. 2 shows an example and a comparative example in which the horizontal axis represents the total number x of carbon black and powdered cellulose contained in the rubber composition and the vertical axis represents the static spring constant Ks of the rubber composition. 4 is a graph showing the relationship between x and Ks in the rubber composition of FIG.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Unless otherwise specified, the description “AA to BB%” indicates “AA% or more and BB% or less”.

The present invention is a rubber composition that contains at least one of rubber, a filler that is carbon black or silica, and powdered cellulose having an average particle diameter of 20 μm to 50 μm, and satisfies at least one of the following conditions (A) and (B). .
(A) When the total number of fillers and powdered cellulose contained in the rubber composition is x, and the dynamic magnification of the rubber composition is y, the relational expression y <0.011x + 0.67 is satisfied. .
(B) When the total number of fillers and powdered cellulose contained in the rubber composition is x and the static spring constant of the rubber composition is Ks, the relational expression of Ks> 4.543x + 135.86 is obtained. To meet.

<Rubber>
The rubber composition of the present invention contains rubber.

  Examples of the rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene / butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), and ethylene. Propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM), fluoro rubber (FKM), epichlorohydrin rubber (CO, ECO), urethane rubber (U), silicone rubber (Q), synthetic rubber such as halogenated butyl rubber and polysulfide rubber, and the like, but are not particularly limited. Further, thermoplastic elastomers such as polystyrene-based thermoplastic elastomer, polypropylene-based thermoplastic elastomer, polydiene-based thermoplastic elastomer, chlorine-based thermoplastic elastomer, and engineering plastics-based elastomer can also be used.

  As the rubber, natural rubber (NR) or ethylene propylene diene rubber (EPDM) is preferable. By using natural rubber and the powdered cellulose described below, a rubber composition having a low environmental load can be obtained.

  Further, vulcanization of these rubbers is generally performed by a vulcanization system using a combination of sulfur or a sulfur-donating compound, and various general-purpose vulcanization accelerators such as sulfenamide compounds and thiuram compounds. . Organic peroxide crosslinking is also possible. Examples of the organic peroxide include tertiary butyl peroxide, dicumyl peroxide, tertiary butyl cumyl peroxide, 1,1-di (tertiary butylperoxy) -3,3,5-trimethylcyclohexane, , 5-Dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3,1,3-di (tert-butyl) Peroxyisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tertiary butyl peroxybenzoate, tertiary butyl peroxyisopropyl carbonate, n-butyl-4,4-di A commonly used compound such as tributyl peroxy) valerate is used. In the case of organic peroxide crosslinking, polyfunctional unsaturated compounds such as triallyl isocyanurate, triallyl cyanurate, triallyl trimellitate, trimethylolpropane trimethacrylate, N, N'-m-phenylenebis It is preferable to use a maleimide in combination.

<Filling material>
It is important that the rubber composition of the present invention contains a filler that is carbon black or silica.

In the present invention, the silica is not particularly limited, and examples thereof include natural silica and synthetic silica (precipitated silica, dry silica, wet silica). As silica, for example, silica used as a filler in tires may be used. By treating the surface of silica with a silane coupling agent, the affinity for various rubbers is improved. Therefore, when using silica as a filler, it is preferable to treat with a silane coupling agent.
The silane coupling agent is not particularly limited and includes, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis ( 2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4- Trimethod (Silylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethyl Thiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-to Silane coupling agent having a sulfide group such as methoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide A silane coupling agent having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyltriethoxysilane, vinyltriethoxysilane Silane coupling agents having a vinyl group such as methoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- ( Silane coupling agents having an amino group such as 2-aminoethyl) aminopropyltriethoxysilane and 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycidoxypropyltriethoxysilane, γ-glycidoxy Silane coupling agents having a glycidoxy group such as propyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxy Silane coupling agent having a nitro group such as silane; silane having a chloro group such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane Coupling agent, and the like. These may be used alone or in combination of two or more.

  In the present invention, the carbon black refers to carbon fine particles having a diameter of about 3 to 500 nm, which are manufactured by industrially controlling the quality. In addition, carbon blacks include those having a property of being compatible with rubber by controlling a functional group on the particle surface.

<Powdered cellulose>
The powdery cellulose is not particularly limited as long as it has an average particle diameter of 20 to 50 μm. Powdered cellulose is obtained by pulverizing cellulose raw materials such as pulp that has been subjected to acid hydrolysis with a mineral acid (ie, inorganic acid) such as hydrochloric acid, sulfuric acid, or nitric acid, or mechanically processing cellulose raw materials such as pulp that is not subjected to acid hydrolysis. It can be obtained by grinding.
The powdery cellulose used in the rubber composition of the present invention is preferably powdery cellulose having a small amount of impurities obtained by pulverizing a cellulose raw material such as pulp that has been subjected to an acid hydrolysis treatment.

  The average particle size of the powdered cellulose is 20 μm or more, preferably 23 μm or more, and more preferably 25 μm or more. The average particle size is 50 μm or less, preferably 42 μm or less, and more preferably 35 μm or less.

  When the average particle diameter is large, the roughness of the rubber composition becomes conspicuous, and the appearance deteriorates. In addition, it is difficult to uniformly mix the powdered cellulose with the rubber or the filler, so that the effect of the present invention tends to be hardly obtained. On the other hand, when the average particle size is small, the rubber or filler and the powdered cellulose can be uniformly mixed, but the dynamic magnification and the static spring constant of the rubber produced from the rubber composition tend to be inferior.

  In the present specification, the average particle diameter is a value measured by a laser scattering method when the particle size distribution is represented as a cumulative distribution and the cumulative distribution is 50%.

  The average degree of polymerization of the powdered cellulose is preferably 150 or more and 4800 or less, more preferably 600 or more and 4500 or less, still more preferably 1000 or more and 4000 or less, still more preferably 1250 or more and 3500 or less, and particularly preferably 1400 or more and 3500 or less. It is. If the average degree of polymerization is too low, the static spring constant may be poor. On the other hand, if the average polymerization degree is too high, the effect of the present invention may not be obtained due to an increase in the load during kneading.

The average degree of polymerization can be measured by a known method, and in this specification, a value calculated by the following method is used. The average polymerization degree of 350 or less is a method using the confirmation test (3) of crystalline cellulose in the 14th revision Japanese Pharmacopoeia. In the average polymerization degree 350 than the range, with a fully automated viscosity pulp Polymer measurement system RPV-1 (manufactured by Rheotek), measures the intrinsic viscosity, _{"VISCOSITY MEASUREMENTS OF CELLULOSE / SO 2 -AMINE} DIMETHYLSULFOXIDE SOLUTION " [I] = 0.909 x DP ^0.85 (Equation (2) in the literature) described in (Isokai et al., 1989).

The crystallinity of the powdered cellulose is preferably from 70 to 90%, more preferably from 80 to 90%. If the crystallinity is low, the time required for heating and vulcanizing becomes long, so that the workability tends to deteriorate. When the crystallinity is 80% or more, the effect on the vulcanization rate is hardly confirmed, so that it is more preferable.
The degree of crystallinity of the powdered cellulose changes depending on the manufacturing method, in addition to the type of pulp used as a raw material. For example, powdery cellulose having a high degree of crystallinity can be obtained by using an acid hydrolysis-treated cellulose raw material. On the other hand, powdered cellulose produced by only mechanical treatment without performing acid hydrolysis treatment tends to have low crystallinity.

In the present specification, the crystallinity of powdered cellulose is a value obtained by measuring X-ray diffraction of a sample. The crystallinity can be determined by the method of Segal et al. (L. Segal, JJ Greeny, et al., Text. Res. J., 29, 786, 1959), and the method of Kamide et al. (K. Kamide et al, Polymer). J., 17, 909, 1985), and the diffraction pattern on the 002 plane is determined using the diffraction intensity of 2θ = 4 ° to 32 ° in the diffraction pattern obtained from the X-ray diffraction measurement as a baseline. From the intensity and the diffraction intensity of the amorphous portion at 2θ = 18.5 °, it is calculated by the following equation.
Xc = (I _002C -Ia) / I _002C × 100
Xc: Crystallinity of cellulose (%)
I _002C : 2θ = 22.6 °, diffraction intensity of 002 plane Ia: 2θ = 18.5 °, diffraction intensity of amorphous portion

  The apparent specific gravity of the powdered cellulose is preferably 0.15 g / mL or more, more preferably 0.18 g / mL or more, still more preferably 0.20 g / mL or more, and even more preferably 0.30 g. / ML or more. The apparent specific gravity of the powdered cellulose is preferably 0.60 g / mL or less, more preferably 0.50 g / mL or less, still more preferably 0.45 g / mL or less, and still more preferably 0.35 g. / ML or less. If the apparent specific gravity is small, the powder is bulky, and the dispersibility in the components of the rubber composition (eg, rubber, carbon black, etc.) tends to decrease. On the other hand, when the apparent specific gravity is large, the powder has low bulk and is compact, so that the dispersibility in the components of the rubber composition (eg, rubber, carbon black, etc.) is good, but the average particle diameter of the powder is high. , The effect of the present invention tends to decrease.

  In this specification, the apparent specific gravity was calculated by putting 10 g of a sample in a 100-ml measuring cylinder, and continuing to tap the bottom of the measuring cylinder until the height of the sample did not decrease, and then reading the scale of the flattened surface. Value.

The angle of repose of the powdered cellulose is preferably 45 ° or more, more preferably 48 ° or more. The angle of repose of the powdered cellulose is preferably 60 ° or less, more preferably 58 ° or less, and further preferably 56 ° or less. If the angle of repose is large, the powder fluidity tends to be poor, which may be unfavorable in work. On the other hand, if the angle of repose is small, the powder fluidity is good and the workability is improved, but there is a tendency for powder flutter to occur.
In the present specification, the angle of repose is a value of Angle Response measured using a powder tester (PT-N type, manufactured by Hosokawa Micron Corporation).

  As a method for producing powdered cellulose, for example, a production method comprising a preparation step of a cellulose raw material, an acid hydrolysis reaction step, a neutralization / washing / liquid removal step, a drying step, a pulverization step, a classification step, or A method of performing mechanical pulverization without performing acid hydrolysis treatment is exemplified.

  More specifically, the following method may be mentioned as a method for producing powdered cellulose. First, a dispersion having a pulp concentration of 3 to 10% by weight (in terms of solid content) adjusted to an acid concentration of 0.1 to 2.0 N is subjected to acid hydrolysis at a temperature of 80 to 100 ° C. for 30 minutes to 3 hours. Perform processing. Next, in the dehydration step, the pulp subjected to the acid hydrolysis treatment and the waste acid are subjected to solid-liquid separation, and the pulp subjected to the acid hydrolysis treatment is neutralized by adding an alkali agent and washed. Then, it is dried with a dryer to obtain powdered cellulose. After drying, it may be mechanically pulverized / classified by using a pulverizer or a classifier to obtain powdered cellulose. Further, for energy saving and the like, the moisture concentration before drying may be adjusted using a dehydrator before drying.

  When the fluid pulp from the pulp bleaching process is used as a raw material, a predetermined amount is added to the reaction tank after concentration by a dehydrator (eg, screw press, belt filter) in order to increase the concentration before being charged into the hydrolysis reaction tank. May be input. When a dry sheet of pulp is used as a raw material, the pulp may be loosened with a crusher (eg, a roll crusher) or the like and then charged into a reaction tank.

  Examples of the cellulose raw material of the powdered cellulose include hardwood-derived pulp, softwood-derived pulp, and non-wood pulp. Examples of the pulping method include a sulfite cooking method, a kraft cooking method, a soda quinone cooking method, and an organosolve cooking method. The form of the cellulose raw material is not particularly limited, and it can be used in the form of a slurry or a sheet.

  The acid concentration in the oxidative hydrolysis treatment of the cellulose raw material is not particularly limited, but is usually about 0.1 to 2.0 N. When the acid concentration of the acid hydrolysis treatment is lower than 0.1 N, the depolymerization of cellulose by acid can be suppressed, so that the decrease in the average degree of polymerization of the powdered cellulose can be reduced. Can be very difficult to do. On the other hand, when the acid concentration is higher than 2.0 N, the depolymerization of the cellulose proceeds, the control of the average particle size of the powdered cellulose becomes easy, and the powder flowability is improved, but the average polymerization degree is lowered. , Mechanical properties tend to decrease.

  As a device for drying the pulp after the reaction and the neutralization, a known device can be appropriately selected as needed. For example, various devices as described below can be used. Inclined fluidized bed dryer rocking flow dryer (Aichi Electric Co., Ltd.), vacuum heating dryer rocking dryer (Aichi Electric Co., Ltd.), vacuum dryer high speed vacuum dryer (Earth Technica Co., Ltd.), shelf type draft dryer TRAY DRYER FOR FOODS (Okada Seiko Co., Ltd.), Spray dryer Spray dryer (Okawara Kakoki Co., Ltd.), Vibration / fluid dryer Vibro / Flow dryer (Fuji Powder Co., Ltd.), Fluidized bed dryer Flow dryer (Fuji Powder Co., Ltd.) Company), fluid bed dryer Midget Dryer (Dalton Co., Ltd.), agitated indirect heating dryer CD dryer (Kurimoto Iron Works Co., Ltd.), indirect heating liquid dryer CD dryer (Nishimura Iron Works Co., Ltd.), Drum dryer (Fuji Koki Co., Ltd.), rotary dryer Fujiko machine Co., Ltd.).

Examples of the pulverizer include cutting mills: mesh mill (manufactured by Horai Co., Ltd.), Atoms (manufactured by Yamamoto Hyakuma Seisakusho), knife mill (manufactured by Palman), cutter mill (manufactured by Tokyo Atomizer Manufacturing Co., Ltd.), CS Cutter (Mitsui Mining Co., Ltd.), rotary cutter mill (Nara Machinery Co., Ltd.), pulp crusher (Zuiko Co., Ltd.), shredder (Shinko Pantech Co., Ltd.), etc., hammer mill: jaw crusher (stock) Hakin Crusher (manufactured by Makino Sangyo Co., Ltd.), Impact mills: Pulverizer (manufactured by Hosokawa Micron Co., Ltd.), Fine Impact Mill (manufactured by Hosokawa Micron Co., Ltd.), Super Micron Mill (manufactured by Hosokawa Micron Co., Ltd.), Inomaizer (hosokawa micron) Co., Ltd.), Phi Mill (manufactured by Nippon Pneumatic Industries, Ltd.), CUM type centrifugal mill (manufactured by Mitsui Mining Co., Ltd.), Ixeded Mill (manufactured by Makino Sangyo Co., Ltd.), Ultraplex (manufactured by Makino Sangyo Co., Ltd.) Coroplex (Makino Sangyo Co., Ltd.), Sample Mill (Seisin Co., Ltd.), Bantam Mill (Seisin Co., Ltd.), Atomizer (Seisin Co., Ltd.), Tornado Mill (Nikkiso Co., Ltd.), Near Mill (stock) Co., Ltd.), HT type pulverizer (Horai Co., Ltd.), free pulverizer (Nara Machinery Co., Ltd.), New Cosmomizer (Nara Machinery Co., Ltd.), gather mill (Nishimura Machinery Co., Ltd.) ), Spar Powder Mill (Nishimura Machinery Co., Ltd.), Blade Mill (Nissin Engineer) Co., Ltd.), Super Rotor (Nissin Engineering Co., Ltd.), Npa Crusher (Misho Industry Co., Ltd.), Wheelie Crusher (Miki Co., Ltd.), Pulp Crusher (Zuiko Co., Ltd.), Jacobson Fine crusher (Shinko Pantech Co., Ltd.), Universal Mill (Tokuju Kousaku Co., Ltd.), Air flow mill: CGS type jet mill (Mitsui Mining Co., Ltd.), Micron Jet (Hosokawa Micron Co., Ltd.), Counter Jet Mill (manufactured by Hosokawa Micron Co., Ltd.), cross jet mill (manufactured by Kurimoto Iron Works, Ltd.), supersonic jet mill (manufactured by Nippon Pneumatic Industries, Ltd.), current jet (manufactured by Nisshin Engineering Co., Ltd.), jet mill (san Sho Industry Co., Ltd.), Ebara Jet Micronizer (Manufactured by EBARA CORPORATION), Ebara Toriad Jet (manufactured by EBARA CORPORATION), selenium mirror (manufactured by Masuyuki Sangyo Co., Ltd.), New Microsic Mat (manufactured by Masuno Seisakusho), Kryptron (Kawasaki Heavy Industries, Ltd.) Vertical Roller Mill: Vertical Roller Mill (Shinion Co., Ltd.), Vertical Roller Mill (Schaeffler Japan Co., Ltd.), Roller Mill (Kotobuki Giken Kogyo Co., Ltd.), VX Mill (Kurimoto Tekko Co., Ltd.) Place), KVM vertical mill (Earth Technica Co., Ltd.), IS mill (IHI Plant Engineering Co., Ltd.), and turbo mill (Freund Sangyo Co., Ltd.).
Among these, tornado mill (manufactured by Nikkiso Co., Ltd.), blade mill (manufactured by Nisshin Engineering Co., Ltd.), free crusher (manufactured by Nara Machinery Co., Ltd.), turbo mill (manufactured by Freund Sangyo Co., Ltd.) ) Is preferably used.

  For the purpose of imparting functionality or improving functionality, powdered cellulose is mixed with a raw material of powdered cellulose and another organic component and / or an inorganic component by one kind alone or in an arbitrary ratio of two or more kinds. It is also possible to grind. In addition, chemical treatment can be performed as long as the average degree of polymerization of natural cellulose used as a raw material is not significantly impaired.

<Rubber composition>
In the rubber composition of the present invention, the amount of the powdered cellulose contained in the rubber composition is preferably in the range of 1 to 50 parts by weight based on the solid content of the rubber.

  In the rubber composition of the present invention, the filler contained in the rubber composition is preferably in the range of 20 to 120 parts by weight, more preferably 45 to 120 parts by weight, based on the solid content of rubber. More preferably, it is in the range of 45 to 100 parts by weight, even more preferably in the range of 45 to 90 parts by weight.

  In the rubber composition of the present invention, in addition to the rubber and the compounding components (pulverized cellulose, filler), other various rubber compounding agents, for example, other fillers such as clay and calcium carbonate; silane coupling Agent; activator; oil; zinc white; stearic acid; softener; antioxidant; retarder; dispersing aid; processing aid; additives such as compatibilizers; vulcanizing agents such as sulfur and vulcanization accelerators; Can also be appropriately blended, and the blending amount can be used within a range that does not impair the effects of the present invention.

  Examples of the vulcanization accelerator include guanidines such as diphenylguanidine (DPG), thiazoles such as di-2-benzothiazolyl disulfide (MBTS) and 2-mercaptobenzothiazole (MBT), and N-cyclohexyl-2. -Benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N-oxydiethylene-2-benzothiazolylsulfenamide (OBS), N, N- Sulfenamides such as dicyclohexyl-2-benzothiazolylsulfenamide (DZ), thiurams such as tetramethylthiuram monosulfide (TMTM) and tetramethylthiuram disulfide (TMTD), zinc dimethyldithiocarbamate (ZnMDC), -N-butyldithi Thiocarbamates systems such as zinc carbamate (ZnBDC), vulcanization accelerator xanthate system such as isopropyl xanthate, zinc (Zix) and the like.

  Fillers such as carbon black, silica, and powdered cellulose, and various additives are mixed with the above rubber by using a Banbury mixer, a pressure kneader, a closed kneader such as an intermix, or an open roll. A method in which a filler is appropriately compounded while kneading is used.

  The rubber composition of the present invention obtained in this way has a total compounding number of fillers such as carbon black, silica and powdered cellulose contained in the rubber composition of x, a dynamic magnification of y, and a static spring. When the constant is Ks, at least one of a relational expression of y <0.011x + 0.67 and a relational expression of Ks> 4.543x + 135.86 is satisfied.

  In this specification, the dynamic magnification and the static spring constant are values obtained by the following method.

(Static spring constant (Ks))
Each rubber composition is press-formed while being vulcanized to prepare a vulcanized rubber sample having a columnar shape (diameter: 50 mm, height: 25 mm). A test piece is produced by bonding a pair of cylindrical fittings (diameter 60 mm, thickness 6 mm) to the upper and lower surfaces of the vulcanized rubber sample using an adhesive. After compressing the produced test piece 7 mm twice in the axial direction of the cylinder, 1.5 mm and 3.5 mm deflection loads were measured from the load deflection curve when the strain was restored, and the static spring was determined from these values. Calculate the constant (Ks) (N / mm).

(Dynamic spring constant (Kd))
The test piece used for measuring the static spring constant (Ks) is compressed by 2.5 mm in the cylinder axis direction. A constant displacement harmonic compression vibration having an amplitude of 0.05 mm is applied from the lower side at a frequency of 100 Hz and a dynamic load is detected by an upper load cell around the position compressed by 2.5 mm from the lower side, and in accordance with JIS-K 6394. The dynamic spring constant (Kd) (N / mm) is calculated.

(Dynamic magnification: Kd / Ks)
The dynamic magnification is calculated from the following equation based on the calculated dynamic spring constant and static spring constant.
(Dynamic magnification) = (Dynamic spring constant (Kd)) / (Static spring constant (Ks))

  Since the rubber composition of the present invention satisfies the above relational expression, the excellent effects of the present invention can be obtained. The condition (B) satisfies the relational expression Ks> 4.543x + 135.86, and more preferably satisfies the relational relation Ks> 4.543x + 140.

The rubber composition of the present invention preferably satisfies the condition (C).
(C) The dynamic magnification y and the static spring constant Ks of the rubber composition satisfy the relational expression of Ks / y ≧ 300.

  The rubber composition of the present invention preferably satisfies the conditions (B) and (C), and more preferably satisfies all of the conditions (A) to (C).

The rubber composition of the present invention is relatively excellent in dynamic magnification (indicating a low value) even when the static spring constant is set high (that is, the hardness of rubber is high). Therefore, the rubber composition of the present invention can exhibit excellent performance as a rubber composition for vibration isolation.
Examples of such a vibration damping rubber composition include an engine mount, a liquid seal engine mount, a body mount, a cap mount, a member mount, a muffler mount, a cab mount, a differential mount, a strut mount, a strut bar cushion, a stabilizer bush, and a suspension. Bush, tension rod bush, lower ring bush, arm bush, sliding bush, damper pulley, torsional damper, chain damper, handle damper, center bearing support, steering rubber coupling, bump strapper, FF engine roll stopper, muffler hanger, bumper rubber , Bumper guard, helper rubber, spring seat, shock absorber, air spring, clutch rubber, radio Anti-vibration rubber for automobiles such as tar supporters; anti-vibration rubber for railway vehicles; anti-vibration rubber for industrial machinery; anti-vibration rubber for construction; anti-vibration rubber for anti-vibration rubber bearings; anti-vibration rubber for computer hard disks Dampers for general home appliances such as washing machines and washing machines; Suitable for applications such as building damping walls, damping (damping) devices such as damping dampers and seismic isolation devices in the building and housing fields Can be used. In addition, tire tread, sidewall, shoulder, inner liner, bead filler, carcass, belt, hose, sealant, oil seal, float, rubber ball, tennis ball, rubber plate, rubber tile boots, shoe sole, string protection It can also be suitably used as an agent, a sports shoe, a sponge product, a rubber sealing material, and the like.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples. In addition, the measuring method of a physical property value etc. is the measuring method described above, unless otherwise described.

(Production Example 1: Preparation of powdered cellulose)
The hardwood-derived pulp was reacted at 95 ° C. for 2 hours under conditions where the pulp concentration was adjusted to 5.5% and the hydrochloric acid concentration was adjusted to 0.15N. After the reaction was completed, the reaction mixture was neutralized with sodium hydroxide, sufficiently washed with water, and then dried by blowing air at a temperature of 60 ° C. for about 1 day. The dried sample was mechanically pulverized using a hammer mill (AP-S type, manufactured by Hosokawa Micron Corp.), and powdered cellulose 1 (average particle diameter 30.2 μm, average degree of polymerization 1950, crystallinity 85. 3%, an apparent specific gravity of 0.33 g / mL, and a repose angle of 53.8 °).

(Production Example 2)
The hardwood-derived pulp was reacted at 95 ° C. for 2 hours under conditions where the pulp concentration was adjusted to 5.5% and the hydrochloric acid concentration was adjusted to 1.10 N. After the reaction was completed, the reaction mixture was neutralized with sodium hydroxide, sufficiently washed with water, and then dried by blowing air at a temperature of 60 ° C. for about 1 day. The dried sample was mechanically pulverized using a hammer mill (AP-S type, manufactured by Hosokawa Micron Corp.) to obtain a powdered cellulose 2 (average particle diameter 25.9 μm, average degree of polymerization 1536, degree of crystallinity 86. 9%, an apparent specific gravity of 0.50 g / mL, and a repose angle of 50.7 °).

<Preparation of rubber composition>
(Example 1)
5 parts by mass of the powdered cellulose 1 obtained in Production Example 1 and 60 parts by mass of FT-grade carbon black (FT black, trade name “Asahi Thermal”, manufactured by Asahi Carbon Co., Ltd.) were mixed with natural rubber (trade name “RSS # 3”). ") 100 parts by mass. 5 parts by mass of zinc white, 1 part by mass of stearic acid, 1.5 parts by mass of vulcanization accelerator CBS (N-cyclohexyl-2-benzothiazolylsulfenamide), and 2 parts by mass of sulfur with respect to 100 parts by mass of natural rubber Was further added and kneaded with two rolls to obtain an unvulcanized rubber. This sample was press-vulcanized at 150 ° C. to obtain a vulcanized rubber.

(Example 2)
A vulcanized rubber was obtained in the same manner as in Example 1 except that the amount of the powdered cellulose 1 was changed to 10 parts by mass.

(Example 3)
A vulcanized rubber was obtained in the same manner as in Example 1 except that the amount of the powdered cellulose 1 was changed to 15 mass.

(Comparative Example 1)
A vulcanized rubber was obtained in the same manner as in Example 1 except that powdered cellulose was not blended and 65 parts by mass of FT grade carbon black was blended.

(Comparative Example 2)
A vulcanized rubber was obtained in the same manner as in Example 1 except that powdered cellulose was not blended and 75 parts by mass of FT grade carbon black was blended.

(Comparative Example 3)
A vulcanized rubber was obtained in the same manner as in Example 1 except that powdered cellulose was not blended and FT-grade carbon black was blended in an amount of 80 parts by mass.

<Dynamic magnification>
The dynamic magnification was determined from the ratio (Kd / Ks) by obtaining the dynamic spring constant (Kd) and the static spring constant (Ks) by the method described above. The measurement results are shown in Table 1 together with the results of the formulation, the static spring constant (Ks), and the satisfaction / non-satisfaction of the conditions (A) to (C).

  For the rubber compositions used in Examples and Comparative Examples, the total number of parts x of carbon black and powdered cellulose was plotted on the horizontal axis, and in FIG. 1, the dynamic magnification y of Examples 2-3 and Comparative Examples 1-3 was calculated. On the vertical axis, the static spring constants Ks of Examples 1 to 3 and Comparative Examples 1 to 3 are plotted on the vertical axis, and approximate expressions of the respective comparative examples are calculated (software used: Excel 2016) and described. .

(Example 4)
A vulcanized rubber was obtained in the same manner as in Example 1 except that 20 parts by mass of FT-grade carbon black was blended.

(Example 5)
A vulcanized rubber was obtained in the same manner as in Example 2 except that 40 parts by mass of FT-grade carbon black was blended.

(Example 6)
A vulcanized rubber was obtained in the same manner as in Example 5 except that the powdered cellulose 2 obtained in Production Example 2 was blended instead of the powdered cellulose 1 obtained in Production Example 1.

(Example 7)
A vulcanized rubber was obtained in the same manner as in Example 2 except that 80 parts by mass of FT-grade carbon black was blended.

(Example 8)
A vulcanized rubber was obtained in the same manner as in Example 2 except that 80 parts by mass of FEF class carbon black (FEF black, trade name "Asahi # 60UG") was used instead of the FT class carbon black.

(Example 9)
Instead of FT grade carbon black, 40 parts by mass of wet silica (trade name "Nipsil AQ", manufactured by Tosoh Silica Co., Ltd.) and 3.2 parts by mass of silane coupling agent (trade name "Cabras 4," manufactured by Osaka Soda Co., Ltd.) A vulcanized rubber was obtained in the same manner as in Example 2 except that was blended.

(Example 10)
A vulcanized rubber was obtained in the same manner as in Example 8, except that EPDM (trade name "JSR EP21", manufactured by JSR Corporation) was used instead of natural rubber, and 50 parts by mass of FEF grade carbon black was blended.

(Comparative Example 4)
A vulcanized rubber was obtained in the same manner as in Example 1 except that 40 parts by mass of FT grade carbon black was compounded without mixing powdered cellulose 1.

(Comparative Example 5)
A vulcanized rubber was obtained in the same manner as in Example 1 except that powdered cellulose 1 was not blended, and 80 parts by mass of FEF grade carbon black was blended.

(Comparative Example 6)
Instead of FT grade carbon black, 50 parts by mass of wet silica (trade name "Nipsil AQ", manufactured by Tosoh Silica) and 4 parts by mass of silane coupling agent (trade name "Cabras 4," manufactured by Osaka Soda Co., Ltd.) Except that, a vulcanized rubber was obtained in the same manner as in Comparative Example 4.

(Comparative Example 7)
A vulcanized rubber was obtained in the same manner as in Comparative Example 5 except that EPDM (trade name "JSR EP21", manufactured by JSR) was used instead of natural rubber, and 60 parts by mass of FEF grade carbon black was blended. .

  Table 2 shows the formulation of Examples 4 to 10 and Comparative Examples 4 to 7, static spring constant (Ks), dynamic magnification, and results of satisfaction / non-satisfaction of the conditions (A) to (C).

Claims (6)

A rubber composition, which comprises at least a filler that is rubber, carbon black or silica, and powdered cellulose having an average particle diameter of 20 μm to 50 μm, and satisfies at least one of the following conditions (A) and (B).
(A) When the total number of the filler and the powdered cellulose contained in the rubber composition is x and the dynamic magnification of the rubber composition is y, the relational expression of y <0.011x + 0.67 is obtained. To meet.
(B) The relationship of Ks> 4.543x + 135.86, where x is the total number of the filler and the powdered cellulose contained in the rubber composition, and Ks is the static spring constant of the rubber composition. Satisfy the formula. The rubber composition according to claim 1, further satisfying the following condition (C).
(C) The dynamic magnification y and the static spring constant Ks of the rubber composition satisfy a relational expression of Ks / y ≧ 300.   The rubber composition according to claim 1, wherein the powdery cellulose contained in the rubber composition is in a range of 1 to 50 parts by weight based on a rubber solid content.   The rubber composition according to any one of claims 1 to 3, wherein the filler contained in the rubber composition is in a range of 20 to 120 parts by weight based on a rubber solid content.   The rubber composition according to any one of claims 1 to 4, wherein the rubber is a natural rubber.   A rubber composition for vibration isolation using the rubber composition according to any one of claims 1 to 5.

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