JP6484583B2 - Boot member and pin slide type vehicle disc brake using the boot member - Google Patents

Description

  The present invention relates to a boot member and a pin slide type vehicle disc brake using the boot member.

  Conventionally, in a pin slide type disc brake, a pin boot is provided so as to cover a sliding shaft portion exposed from a caliper bracket or a caliper body of a pin member. The pin boot includes a bellows portion that covers the sliding shaft portion of the pin member, a base end attachment portion that is attached to either the caliper bracket or the caliper body, and a tip attachment portion that is attached to the outer periphery of the pin member. (For example, refer to Patent Documents 1 and 2.)

  The pin boot protects the sliding shaft portion from muddy water or the like by covering the exposed sliding shaft portion of the pin member. The pin boot has at least one end attached to either the caliper bracket or the caliper body, and the bellows portion expands and contracts following the movement of the caliper body relative to the caliper bracket.

  In recent years, cellulose nanofibers obtained by defusing natural cellulose fibers into nanosizes have attracted attention. Natural cellulose fiber is biomass that uses pulp such as wood as a raw material, and it is expected to reduce the environmental load by effectively using this.

  Then, the manufacturing method of the rubber composition using at least one of an oxidized cellulose fiber and a cellulose nanofiber is proposed (refer patent document 3).

JP 2006-275129 A JP 2011-208769 A Japanese Patent Laying-Open No. 2015-98576

  An object of the present invention is to provide a boot member that reduces environmental load and is excellent in fatigue characteristics, and a pin slide type vehicle disk brake using the boot member.

[Application Example 1]
The boot member according to this application example is
A cylindrical boot member used for a pin slide type vehicle disc brake ,
The boot member has a first attachment portion attached to the caliper bracket fixed to the vehicle body, and a second attachment portion attached to a pin member attached to the caliper body or the caliper bracket movable over the previous SL caliper bracket An elastic bellows part connecting the first attachment part and the second attachment part ,
The boot member is composed of a rubber composition containing 5 to 20 parts by mass of at least one of oxidized cellulose fiber and cellulose nanofiber with respect to 100 parts by mass of rubber.
Rubber, includes a scan styrene-Butajiengo-time,
The oxidized cellulose fiber has an average fiber diameter of 10 μm to 30 μm,
Cellulose nanofibers, the average value of the fiber diameter Ri 1nm~200nm der,
The rubber composition has a tensile strength in a tensile test according to JIS K6251 of 15 MPa or more and a breaking elongation of 420% or more.
The rubber composition, the maximum tear strength in the tear test conforming to JIS K6252 is characterized der Rukoto than 40N / mm.

  According to the boot member according to this application example, it is possible to reduce the environmental load by including at least one of the oxidized cellulose fiber and the cellulose nanofiber, and it is excellent in fatigue characteristics.

[Application Example 2]
In the boot member according to this application example,
The rubber may further include ethylene / propylene rubber .

[Application Example 3 ]
The pin slide type vehicle disc brake according to this application example is
The boot member;
It said caliper bracket fixed to the vehicle body,
It said caliper body is movable relative to said caliper bracket,
And said pin member attached to one of said caliper bracket and said caliper body,
Including
The pin member supports the other one of the caliper bracket and the caliper body so as to be movable along the axial direction of the pin member,
The boot member covers an outer periphery of the pin member between the caliper bracket and the caliper body.

  According to the pin slide type vehicle disc brake according to this application example, the boot member includes at least one of the oxidized cellulose fiber and the cellulose nanofiber, thereby reducing the environmental load. Moreover, according to the pin slide type vehicle disc brake according to this application example, the sliding member of the pin member can be reliably protected for a long period of time because the boot member has excellent fatigue characteristics.

It is a partial cross section top view of the pin slide type vehicle disc brake concerning one embodiment. It is a partial cross section top view which shows the pin boot shown in FIG. 1, and a pin member. It is a partial cross section top view of the disc brake for pin slide type vehicles concerning other embodiments. FIG. 4 is an explanatory view showing a state in which the pin boot on the action part side of the pin slide type vehicle disc brake shown in FIG. 3 is contracted and the pin boot on the reaction part side is extended. It is a figure which shows typically the dispersion | distribution process in the manufacturing method of the rubber composition which concerns on one Embodiment. It is a figure which shows typically the dispersion | distribution process in the manufacturing method of the rubber composition which concerns on one Embodiment. It is a figure which shows typically the dispersion | distribution process in the manufacturing method of the rubber composition which concerns on one Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

The boot member according to the present embodiment is a cylindrical boot member used for a pin slide type vehicle disc brake, and the boot member includes a first attachment portion attached to a caliper bracket fixed to a vehicle body, a second attachment portion attached to a pin member attached to the caliper body or the caliper bracket movable with respect to serial caliper bracket, and a telescopic bellows portion connecting the first mounting portion and the second mounting portion wherein the boot member, 100 parts by mass of the rubber hand, consists of at least one 5 parts by mass to a rubber composition containing 20 parts by weight of oxidized cellulose fibers and the cellulose nanofibers, rubber comprises a scan styrene-Butajiengo arm, Oxidized cellulose fibers have an average fiber diameter of 10 μm to 30 μm, and cellulose nanofibers are fibers Average value 1nm~200nm der of is, the rubber composition has a tensile strength in a tensile test according to JIS K6251 is at 420% or more and breaking elongation than 15 MPa, the rubber composition, the JIS K6252 maximum tear strength in compliance with tear test, characterized in der Rukoto than 40N / mm.

  Further, the pin slide type vehicle disc brake according to the present embodiment includes the boot member, a caliper bracket fixed to a vehicle body, a caliper body movable with respect to the caliper bracket, the caliper bracket, and the caliper body. A pin member attached to one of the pins, and the pin member supports the other one of the caliper bracket and the caliper body movably along the axial direction of the pin member, and the boot member is The outer periphery of the pin member is covered between the caliper bracket and the caliper body.

1. Pin Slide Type Vehicle Disc Brake FIG. 1 is a plan view showing a part of a pin slide type vehicle disc brake 1 according to an embodiment in cross section. FIG. 2 is a plan view showing a part of the pin boot 6 and the pin member 5 shown in FIG. In the following description, the pin slide type vehicle disc brake 1 is simply referred to as a disc brake 1.

  A disc brake 1 shown in FIG. 1 includes pin boots 6 and 6 as an example of a boot member, a caliper bracket 3 fixed to a vehicle body (not shown), a caliper body 4 movable with respect to the caliper bracket 3, a caliper bracket 3, Pin members 5 and 5 attached to either one of the caliper bodies 4. In the present embodiment, the pin member 5 is attached to the caliper body 4.

  The caliper bracket 3 is fixed to a vehicle body (not shown) with a fixing bolt, for example, at one side portion of the disk rotor 2 that rotates in the direction of arrow A when the vehicle moves forward. The pair of caliper supports projecting in the direction of the action portion 4a while sandwiching the disc rotor turn-in side and the turn-out side of the bridge portion 4c of the caliper body 4 across the outside of the disc rotor 2 at both ends of the caliper bracket 3 Arms 3d and 3d are extended. The guide hole 3f formed in each caliper support arm 3d opens to the action portion 4a side, and a boot groove 3g into which the pin boot 6 is fitted is formed in the opening. The boot groove 3g is an annular groove provided in the opening of the guide hole 3f.

  The caliper body 4 includes an action portion 4a and a reaction portion 4d that are arranged opposite to each side of the disc rotor 2, and a bridge portion 4c that connects the caliper support arms 3d and 3d across the outer periphery of the disc rotor 2 and connects them. Become.

The action part 4a is provided with action part side mounting arms 4f and 4f protruding to both sides, a cylinder hole in which a piston (not shown) is accommodated, and a hydraulic chamber defined at the bottom of the cylinder hole. A through-hole through which the mounting bolt 5d is inserted is formed in the distal end side of each action portion side mounting arm 4f in a direction parallel to the rotation axis of the disc rotor 2.

  The reaction portion 4b has a reaction force claw (not shown) at a position facing the piston, and a pair of friction pads 10 and 10 are disposed to face each other with the disc rotor 2 interposed therebetween.

  As shown in FIG. 2, each pin member 5 includes a sliding shaft portion 5a on the distal end side that slides in the guide hole 3f, and a fixed shaft on the proximal end side that has a larger diameter than the sliding shaft portion 5a. Part 5b. The guide hole 3f is a bag-like hole that accommodates the pin member 5 in a slidable manner. The fixed shaft portion 5b abuts against the action portion side mounting arm 4f and gradually decreases in diameter toward the sliding shaft portion 5a, and a female screw hole opened on the action portion side mounting arm 4f side is formed on the central axis. Is formed. The fixed shaft portion 5b is provided with a fitting groove 5c that is an annular groove. Further, a bush 13 (FIG. 1) for preventing the pin member 5 from falling is fitted on the outer periphery of the tip end portion of the sliding shaft portion 5a.

  The pin member 5 is fixed to the action portion side mounting arm 4f by the mounting bolt 5d in a state where the sliding shaft portion 5a is inserted into the guide hole 3f and the fixed shaft portion 5b is in contact with the action portion side attachment arm 4f. . When a hydraulic pressure is generated in a hydraulic chamber (not shown), the sliding shaft portion 5a of the pin member 5 slides on the inner surface of the guide hole 3f, so that the caliper bracket 3 moves along the axial direction of the pin member 5. The caliper body 4 moves forward and backward.

2. The boot member includes a first attachment portion attached to the first object, a second attachment portion attached to the second object, and an elastic bellows that connects the first attachment portion and the second attachment portion. A cylindrical boot member provided with a portion. Here, the pin boot 6 attached to the caliper bracket 3 will be described as a boot member. In the following description, the pin boot 6 (7) will be described as a boot member.

  Each pin boot 6 is formed into a cylindrical shape by a rubber composition. The rubber composition will be described later.

  As shown in FIG. 2, the pin boot 6 includes a base end attachment portion 6b as a first attachment portion attached to the caliper bracket 3 that is the first object, and a second attachment attached to the pin member 5 that is the second object. A distal end attachment portion 6c as an attachment portion, and a telescopic bellows portion 6a that connects the distal end attachment portion 6c and the proximal end attachment portion 6b are provided. More specifically, the base end attaching portion 6b is attached to the boot groove 3g of the caliper support arm 3d, and the tip attaching portion 6c is attached to the fitting groove 5c of the pin member 5.

  The base end mounting portion 6b is a ring-shaped convex portion protruding from the outer peripheral surface of the base end, and enters the fitting groove 5c of the guide hole 3f to prevent the pin member 5 from coming off in the axial direction. The tip mounting portion 6c has an inner diameter slightly smaller than the outer shape of the fitting groove 5c, and enters the fitting groove 5c to prevent the pin member 5 from coming off in the axial direction.

  The pin boot 6 is an exposed portion of the pin member 5, that is, a portion protruding from the guide hole 3f and covers the fitting groove 5c. And since the bellows part 6a can be expanded-contracted, the pin boot 6 can cover the exposed part of the pin member 5 reliably, while the caliper bracket 3 and the caliper body 4 relatively move forward and backward.

  The boot member is not limited to the pin brake 6 for the disc brake, but may be a boot used for a disc brake boot-like dust seal, a boot used for a negative pressure booster, a ball joint boot, a dust boot for a vehicle shock absorber, or the like.

3. Other Embodiments FIG. 3 is a partial cross-sectional plan view of a pin slide type vehicle disc brake 1a according to another embodiment, and FIG. 4 is an action portion of the pin slide type vehicle disc brake 1a shown in FIG. It is explanatory drawing which shows the state which the pin boot 6 by the side of 4a contracted, and the pin boot 7 by the side of the reaction part extended. In the following description, parts / portions that are substantially the same as those in the above embodiment are given the same reference numerals, and redundant description is omitted.

  In the pin slide type disc brake 1a for a vehicle, a pair of action part side mounting arms 4f and 4f are provided on a disk introduction side and a delivery side of the action part 4a, and a disk introduction side and a delivery side of the reaction part 4b. A pair of reaction portion side mounting arms 4g, 4g are provided in a protruding manner. Each action portion side mounting arm 4f is formed with a pin insertion hole 4h through which the pin member 5 is inserted, and each reaction portion side mounting arm 4g is formed with a female screw hole 4i on which the pin member 5 is screwed. .

  Guide holes 3f are formed in the caliper support arms 3d on the outer side of the disk so as to be coaxial with the pin insertion holes 4h and the female screw holes 4i of the caliper body 4, and the pin member 5 is inserted into the guide hole 3f in the disk axial direction. Is slidably inserted.

  In this way, the caliper body 4 is supported by the caliper bracket 3 fixed to the vehicle body so as to be movable in a direction parallel to the rotational axis of the disc rotor 2 via the pair of pin members 5 and 5.

  The pin member 5 includes a guide sleeve 11 and a connecting pin 12, and the guide sleeve 11 is inserted into the guide hole 3f so as to be slidable in the disk axial direction, and the connecting pin 12 is inserted into the guide sleeve 11.

  Each guide sleeve 11 is formed with the same length as the distance between the action part side attachment arm 4f and the reaction part side attachment arm 4g, and both ends of the guide sleeve 11 are sandwiched between the attachment arms 4f and 4g. Both ends of the guide sleeve 11 protruding from the guide hole 3f are covered with the pin boot 6 on the action part 4a side and the pin boot 7 on the reaction part 4b side, respectively, and the guide hole 11 slides on the guide hole 3f when the guide sleeve 11 slides on the guide hole 3f. Dirty water, dust, etc. are prevented from entering the inside of 3f.

  The pin boots 6 on the side of each working part 4a are formed in a cylindrical shape with a rubber composition, and include a telescopic bellows part 6a, a base end attaching part 6b and a tip attaching part 6c at both ends of the bellows part 6a. I have. The base end attachment portion 6b is attached to the boot groove 3g formed at the action portion side end portion of the caliper support arm 3d, and the tip attachment portion 6c is an annular shape formed at the end portion of the guide sleeve 11 on the action portion 4a side. Is fitted in the fitting groove 11a. The pin boot 7 on each reaction portion 4b side has basically the same configuration as the pin boot 6 on the reaction portion 4b side. Thus, two pin boots 6 and 7 may be used for each pin member 5.

4). Rubber composition The pin boots 6 and 7 are made of a rubber composition containing 0.1 to 60 parts by mass of at least one of oxidized cellulose fiber and cellulose nanofiber with respect to 100 parts by mass of rubber. Here, “parts by mass” indicates “phr” unless otherwise specified, and “phr” indicates “parts”.
This is an abbreviation for “per hundred of resin or rubber”, and represents the percentage of external additives such as additives to rubber.

  The rubber composition is a rubber composition in which at least one of defibrated oxidized cellulose fiber and cellulose nanofiber is dispersed. The rubber composition may further contain carbon black.

When the rubber composition is employed in, for example, a pin boot of a disc brake, it can reduce environmental burden and can be excellent in fatigue characteristics by including at least one of oxidized cellulose fiber and cellulose nanofiber.

  The rubber composition may have a tensile strength of 15 MPa or more in a tensile test based on JIS K6251. Since the pin boot uses a rubber composition having a high tensile strength, cracks are not easily generated even when the disk brake is repeatedly expanded and contracted. The rubber composition can have a tensile strength of 15 MPa or more and 30 MPa or less in the same test, and can further have a tensile strength of 16 MPa or more and 25 MPa or less.

  The rubber composition may have a maximum tear strength of 40 N / mm or more in a tear test according to JIS K6252. The test method will be described later. The maximum tear strength is obtained by measuring the maximum tear force (N) obtained by conducting a tear test and dividing the measurement result by the thickness of the test piece of 1 mm. Since the pin boot uses a rubber composition having a high maximum tear strength, cracks are not easily generated even when the disk brake is repeatedly expanded and contracted. The rubber composition can have a maximum tear strength of 40 N / mm or more and 70 N / mm or less in the same test, and a maximum tear strength of 40 N / mm or more and 60 N / mm or less.

  The rubber composition has a large number of times until the test piece breaks in a fatigue test (described later in Examples). That is, the rubber composition is excellent in fatigue life at high temperature, and a pin boot excellent in heat resistance and fatigue durability can be obtained.

  In addition, the rubber composition has at least one of oxidized cellulose fibers and cellulose nanofibers defibrated to rubber and has a diameter of at least one of oxidized cellulose fibers and cellulose nanofibers having a diameter of 0.1 mm or more. It is preferable not to have an aggregate of 1 mm or more. The aggregate containing at least one of the oxidized cellulose fiber and the cellulose nanofiber is a mass in which these fibers are gathered together. The aggregate of the oxidized cellulose fiber, the aggregate of the cellulose nanofiber, and the oxidized cellulose fiber and the cellulose It contains aggregates composed of nanofibers.

  According to the rubber composition in the present embodiment, it does not have an aggregate and is reinforced by dispersing in a state where at least one of oxidized cellulose fiber and cellulose nanofiber is defibrated, and has rigidity, strength, and low linear expansion. Excellent coefficient and fatigue resistance. However, it is difficult to prove that aggregates of cellulose nanofibers are not present in the rubber composition. When only the cellulose nanofiber is contained in the rubber composition, the aggregate can be confirmed by observation with an optical microscope (see Patent Document 4). Since the same dispersion process is used in this embodiment, the rubber composition does not have an aggregate of 0.1 mm or more of cellulose nanofibers.

  The rubber, the oxidized cellulose fiber, and the cellulose nanofiber constituting the rubber composition will be described later.

5. Method for Producing Rubber Composition A method for producing a rubber composition used for pin boots comprises a mixing step of mixing an aqueous solution containing at least one of oxidized cellulose fibers and cellulose nanofibers and rubber latex to obtain a first mixture, The method includes a drying step of drying the first mixture to obtain a second mixture, and a dispersion step of thinning the second mixture with an open roll to obtain a rubber composition.

5-1. Raw material First, the raw material used for a mixing process is demonstrated.

5-1-1. Aqueous solution The aqueous solution includes an aqueous solution containing oxidized cellulose fibers, an aqueous solution containing cellulose nanofibers, and an aqueous solution containing oxidized cellulose fibers and cellulose nanofibers.

  The aqueous solution containing oxidized cellulose fibers can be produced, for example, by an oxidation process in which natural cellulose fibers are oxidized to obtain oxidized cellulose fibers.

  The aqueous solution containing cellulose nanofibers can be obtained, for example, by a production method including an oxidation step of oxidizing natural cellulose fibers to obtain oxidized cellulose fibers, and a refining step of refining oxidized cellulose fibers.

  The aqueous solution containing oxidized cellulose fibers and cellulose nanofibers can be obtained by mixing an aqueous solution containing oxidized cellulose fibers and an aqueous solution containing cellulose nanofibers.

  Here, natural cellulose fibers include, for example, wood pulp, cotton-based pulp, bacterial cellulose and the like. More specifically, examples of the wood pulp include coniferous pulp, hardwood pulp, and the like. Examples of the cotton pulp include cotton linter and cotton lint. Non-wood pulp includes Mention may be made of straw pulp, bagasse pulp and the like. At least one of these natural cellulose fibers can be used.

  Natural cellulose fibers have a structure composed of cellulose microfibril bundles and lignin and hemicellulose filling them. That is, it is presumed that the cellulose microfibril and / or the cellulose microfibril bundle has a structure in which hemicellulose covers and further this is covered with lignin. Cellulose microfibrils and / or cellulose microfibril bundles are firmly bonded by lignin to form plant fibers. Therefore, it is preferable that lignin in the plant fiber is removed in advance from the viewpoint that aggregation of the cellulose fiber in the plant fiber can be prevented. Specifically, the lignin content in the plant fiber-containing material is usually about 40% by mass or less, preferably about 10% by mass or less. Further, the lower limit of the lignin removal rate is not particularly limited, and it is preferably as close to 0% by mass. The lignin content can be measured by the Klason method.

  As the cellulose microfibril, a cellulose microfibril having a width of about 4 nm exists as a minimum unit, and this can be called a single cellulose nanofiber. In the present invention, the “cellulose nanofiber” is a material obtained by unraveling natural cellulose fibers and / or oxidized cellulose fibers to the nanosize level. In particular, the average value of the fiber diameters can be 1 nm to 200 nm, and further 1 nm. Can be ˜150 nm, in particular cellulose microfibrils and / or cellulose microfibril bundles of 1 nm to 100 nm. That is, the cellulose nanofiber can include a single cellulose nanofiber alone or a bundle of a plurality of single cellulose nanofibers.

  The aspect ratio (fiber length / fiber diameter) of the cellulose nanofiber can be an average value of 10 to 1000, more preferably 10 to 500, and particularly preferably 100 to 350.

In addition, the average value of the fiber diameter and fiber length of a cellulose nanofiber is an arithmetic average value measured about at least 50 or more of the cellulose nanofiber within the visual field of an electron microscope.

  First, an oxidation process adds water with respect to the natural cellulose fiber used as a raw material, processes with a mixer etc., and prepares the slurry which disperse | distributed the natural cellulose fiber in water.

  Next, natural cellulose fibers are oxidized in water using an N-oxyl compound as an oxidation catalyst to obtain oxidized cellulose fibers. Examples of N-oxyl compounds that can be used as an oxidation catalyst for cellulose include 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (hereinafter also referred to as TEMPO), 4-acetamide-TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO, etc. can be used.

  After the oxidation step, for example, a purification step of repeating washing with water and filtration can be carried out to remove impurities other than oxidized cellulose fibers contained in the slurry, such as unreacted oxidant and various by-products. The solvent containing the oxidized cellulose fiber is, for example, in a state of being impregnated with water. At this stage, the oxidized cellulose fiber is not defibrated up to the unit of cellulose nanofiber. As the solvent, water can be used. For example, in addition to water, organic solvents (alcohols, ethers, ketones, etc.) soluble in water can be used depending on the purpose.

  Oxidized cellulose fiber has a carboxyl group by modifying a part of the hydroxyl group of cellulose nanofiber with a substituent having a carboxyl group.

  The average value of the fiber diameter of the oxidized cellulose fiber can be 10 μm to 30 μm. In addition, the average value of the fiber diameter of an oxidized cellulose fiber is an arithmetic average value measured about at least 50 or more of the oxidized cellulose fiber in the visual field of an electron microscope.

  The oxidized cellulose fiber can be a bundle of cellulose microfibrils. The oxidized cellulose fiber does not need to be fibrillated to the unit of cellulose nanofiber in the mixing step and the drying step described later. Oxidized cellulose fibers can be fibrillated into cellulose nanofibers in the refinement process.

  In the micronization step, the oxidized cellulose fiber can be stirred in a solvent such as water, and cellulose nanofibers can be obtained.

  In the miniaturization step, the solvent as the dispersion medium can be water. Moreover, as a solvent other than water, water-soluble organic solvents such as alcohols, ethers, and ketones can be used alone or in combination.

  The agitation treatment in the miniaturization process includes, for example, a disaggregator, a beater, a low pressure homogenizer, a high pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short axis extruder, a twin screw extruder, an ultrasonic agitator, and a home juicer mixer. Etc. can be used.

  Moreover, solid content concentration of the solvent containing the oxidized cellulose fiber in the refining treatment can be, for example, 50% by mass or less. When this solid content concentration exceeds 50% by mass, high energy is required for dispersion.

An aqueous solution containing cellulose nanofibers can be obtained by the refinement process. The aqueous solution containing cellulose nanofibers can be a colorless, transparent or translucent suspension. In the suspension, cellulose nanofibers, which are fibers oxidized and defibrated and refined, are dispersed in water. That is, in this aqueous solution, the cellulose nanofibers can be obtained by weakening the strong cohesive force between the microfibrils (hydrogen bonding between the surfaces) by introducing carboxyl groups in the oxidation process, and further through the refinement process. And by adjusting the conditions of the oxidation step, the carboxyl group content, polarity, average fiber diameter, average fiber length, average aspect ratio, etc. can be controlled.

  The aqueous solution thus obtained can contain 0.1% by mass to 10% by mass of cellulose nanofibers. Moreover, for example, it can be an aqueous solution diluted to a solid content of 1% by mass of cellulose nanofibers. Furthermore, the aqueous solution can have a light transmittance of 40% or more, a light transmittance of 60% or more, and particularly 80% or more. The transmittance of the aqueous solution can be measured as the transmittance at a wavelength of 660 nm using an ultraviolet-visible spectrophotometer.

5-1-2. Rubber latex As the rubber latex, a natural rubber latex solution and a synthetic rubber latex solution can be used.

  The natural rubber latex solution is a natural product produced by the metabolic action of plants, and a natural rubber / water system in which the dispersion solvent is water can be used. Synthetic rubber latex solutions include, for example, styrene / butadiene rubber, butadiene rubber, methyl methacrylate-butadiene rubber, 2-vinylpyridine-styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, silicone rubber, fluorine rubber, etc. Can be produced by emulsion polymerization.

  The rubber latex has a large number of fine rubber particles dispersed in a dispersion solvent.

5-1-3. Carbon black Carbon black of various grades using various raw materials can be used. The carbon black can be 10 nm to 500 nm, and the average particle size can be 100 nm or more and 300 nm or less. The average particle diameter of carbon black can be obtained by observing by imaging with a scanning electron microscope and measuring 2000 or more particle diameters of basic constituent particles and arithmetically averaging them.

  As such carbon black, for example, reinforcing carbon black such as SAF, ISAF, HAF, SRF, T, GPF, FT, and MT can be used. By using carbon black having a relatively large particle size, the rubber composition is reinforced with oxidized cellulose fibers and cellulose nanofibers in which rubber components in the gaps formed between the carbon blacks are dispersed while maintaining the flexibility of the rubber composition. be able to. As the carbon black, MT grade carbon black can be used.

5-1-4. Rubber Rubber is a solid rubber other than the rubber latex described above, natural rubber (NR), epoxidized natural rubber (ENR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR ), Ethylene / propylene rubber (EPR, EPDM), butyl rubber (IIR), chlorobutyl rubber (CIIR), acrylic rubber (ACM), silicone rubber (Q), fluororubber (FKM), butadiene rubber (BR), epoxidized butadiene Rubbers such as rubber (EBR), epichlorohydrin rubber (CO, CEO), urethane rubber (U), polysulfide rubber (T), and mixtures thereof can be used. In particular, ethylene / propylene rubber or styrene / butadiene rubber is preferred as the rubber for pin boots used in disc brakes. For example, a rubber having a low polarity such as ethylene / propylene rubber (EPDM) has a relatively high kneading temperature (for example, 50% in the case of EPDM).
When the temperature is set to ˜150 ° C., free radicals are generated, so that oxidized cellulose fibers and cellulose nanofibers can be dispersed. EPDM (ethylene / propylene / diene / copolymer), EPM (ethylene / propylene copolymer) and the like can be used as the ethylene / pyropyrene rubber, and EPDM is preferred. The rubber is usually used after being crosslinked and does not contain a thermoplastic elastomer.

  The reason why the solid rubber is blended in addition to the rubber latex is that the entire rubber component of the pin boot is produced from the rubber latex because it has too much moisture and is not practical in terms of processing. The solid rubber component may be the same type as the rubber used in the rubber latex, or may be a rubber that is compatible with the rubber component of the rubber latex.

5-2. Each manufacturing process FIGS. 5-7 is a figure which shows typically the manufacturing method of the rubber composition which concerns on one Embodiment.

5-2-1. Mixing step In the mixing step, an aqueous solution containing at least one of oxidized cellulose fibers and cellulose nanofibers and rubber latex are mixed to obtain a first mixture. As the mixing step, for example, a roll kneading method using a roll kneading device, a stirring operation using a propeller type stirring device, a homogenizer, a rotary stirring device, and an electromagnetic stirring device, or a manual stirring operation can be used. In particular, a roll kneading method can be used for the mixing step.

  As the roll kneading apparatus used for the roll kneading method, for example, an open roll can be used. Moreover, the roll kneading apparatus used for the roll kneading method can use, for example, two rolls or three rolls.

  The mixture of the aqueous solution and the rubber latex is gradually introduced into a roll kneading apparatus in which the distance between the rolls is set to a predetermined interval. The distance between the rolls can be set to such a distance that the mixture of the aqueous solution and the rubber latex is wound around the rolls, and the mixture does not fall between the rolls. The mixture charged in the roll kneader is gradually increased in viscosity by being kneaded. When the viscosity of the mixture becomes high, the mixture can be taken out from the roll kneading apparatus, and the distance between the rolls can be set to be further narrowed, and then fed again into the roll kneading apparatus. This step can be performed multiple times.

  By performing the mixing step, it can be expected that at least one of the oxidized cellulose fiber and the cellulose nanofiber enters the rubber fine particles while passing between the rolls. In particular, by using the roll kneading method, the reinforcing effect by the fibers can be further improved as compared with other stirring operations.

  The 1st mixture obtained at a mixing process is 0.1 mass part-60 mass parts at least one of an oxidized cellulose fiber and a cellulose nanofiber with respect to 100 mass parts of rubber solid components by the mass ratio after a drying process. Can be included. When at least one of the oxidized cellulose fiber and the cellulose nanofiber is 0.1 part by mass or more, a reinforcing effect is obtained, and if it is 60 parts by mass or less, processing after the drying step is possible.

5-2-2. Drying step The drying step is a step of obtaining the second mixture by drying the first mixture obtained in the mixing step. For example, since the first mixture contains moisture, a general method for removing water can be adopted. For example, a known drying method such as natural drying, oven drying, freeze drying, spray drying, or pulse combustion can be employed for the drying process.

  The drying step can be performed at a temperature at which the rubber, oxidized cellulose fiber, and cellulose nanofiber are not thermally decomposed, and can be dried by heating at 100 ° C., for example.

  The second mixture includes a rubber component and at least one of oxidized cellulose fiber and cellulose nanofiber. A 2nd mixture can contain 0.1-60 mass parts of at least one of an oxidized cellulose fiber and a cellulose nanofiber with respect to 100 mass parts of rubber | gum, for example. Furthermore, the second mixture can contain 1 part by mass to 50 parts by mass of at least one of the oxidized cellulose fiber and the cellulose nanofiber, and particularly can contain 5 parts by mass to 40 parts by mass. When at least one of oxidized cellulose fibers and cellulose nanofibers is contained in an amount of 0.1 parts by mass or more in the second mixture, a reinforcing effect of the rubber composition can be obtained, and at least one of oxidized cellulose fibers and cellulose nanofibers in the solvent. If it contains 60 mass parts or less, it can process easily.

5-2-3. Dispersing Step In the dispersing step, a rubber composition can be obtained by thinly passing the second mixture containing at least one of oxidized cellulose fibers and cellulose nanofibers with an open roll.

  First, before thinning, as shown in FIG. 5, the second mixture 130 wound around the first roll 110 can be masticated, and the molecular chains of rubber in the second mixture can be appropriately adjusted. To produce free radicals. The free radicals of the rubber generated by mastication are likely to be combined with at least one of oxidized cellulose fibers and cellulose nanofibers.

  Next, as shown in FIG. 6, a kneading step is performed in which a compounding agent 180 is appropriately added to the bank 134 of the second mixture 130 wound around the first roll 110 and kneaded to obtain an intermediate mixture. it can. Here, the compounding agent 180 includes a reinforcing agent containing carbon black, solid rubber other than rubber latex, and further includes, for example, a crosslinking agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization retarder, a softening agent, a plasticizer, Curing agents, reinforcing agents, fillers, anti-aging agents, colorants, acid acceptors and the like can be included. These compounding agents can be added to the rubber at an appropriate time during the mixing process.

  The step of obtaining the intermediate mixture 136 (FIG. 7) by the steps of FIGS. 5 and 6 is not limited to the open roll method, and for example, a closed kneading method or a multi-screw extrusion kneading method can also be used.

  The intermediate mixture 136 (FIG. 7) is obtained by combining oxidized cellulose fibers and cellulose with respect to 100 parts by mass of rubber in which the rubber solid component in the rubber latex in the mixing step and the rubber component in the compounding agent 180 added in the dispersing step are combined. At least one of the nanofibers may include 0.1 to 60 parts by mass. By adding rubber in the dispersion step, the load of the drying step can be reduced by using a small amount of rubber latex in the mixing step. Therefore, the rubber component added in the dispersing step is preferably more than the rubber solid component in the rubber latex, and can be, for example, 50 mass% to 99 mass% in the rubber component in the intermediate mixture 136.

Further, as shown in FIG. 7, thinning can be performed. The thinning step can be a step of obtaining an uncrosslinked rubber composition 150 by thinning at 0 ° C. to 50 ° C. using an open roll 100 having a roll interval of 0.5 mm or less. In this step, the roll interval d between the first roll 110 and the second roll 120 is set to, for example, 0.5 mm or less, more preferably 0 mm to 0.5 mm, and the intermediate mixture obtained in FIG. 136 can be put into the open roll 100 and thinning can be performed once to several times. For example, the thinning can be performed about 1 to 10 times. When the surface speed of the first roll 110 is V1, and the surface speed of the second roll 120 is V2, the ratio of the surface speeds (V1 / V2) in thinness is 1.05 to 3.00. And can be 1.05-1.2. By using such a surface velocity ratio, a desired shear force can be obtained.

  The rubber composition 150 pushed out between the narrow rolls as described above is greatly deformed as shown in FIG. 7 due to the restoring force due to the elasticity of the rubber, and at that time, at least one of the oxidized cellulose fiber and the cellulose nanofiber moves greatly together with the rubber. To do. The rubber composition 150 obtained through thinning is rolled with a roll and dispensed into a sheet having a predetermined thickness, for example, 100 μm to 500 μm.

  In this thinning process, in order to obtain as high a shearing force as possible, the roll temperature can be set to, for example, 0 ° C. to 50 ° C., and further set to a relatively low temperature of 5 ° C. to 30 ° C. be able to. The measured temperature of the rubber composition can also be adjusted to 0 ° C. to 50 ° C., and further adjusted to 5 ° C. to 30 ° C.

  By adjusting to such a temperature range, it is possible to defibrate at least one of oxidized cellulose fiber and cellulose nanofiber using the elasticity of rubber, and disperse the defibrated cellulose nanofiber in the rubber composition. it can.

  Due to the high shearing force in this thinning process, a high shearing force acts on the rubber, and at least one of the aggregated oxidized cellulose fibers and cellulose nanofibers is separated from each other so as to be pulled out one by one into the rubber molecules. , Dispersed in rubber. In particular, since rubber has elasticity and viscosity, at least one of oxidized cellulose fiber and cellulose nanofiber can be defibrated and dispersed. And the rubber composition 150 excellent in the dispersibility and dispersion stability (at least one of an oxidized cellulose fiber and a cellulose nanofiber is hard to re-aggregate) of at least one of an oxidized cellulose fiber and a cellulose nanofiber can be obtained.

  More specifically, when rubber and at least one of oxidized cellulose fiber and cellulose nanofiber are mixed with an open roll, rubber having viscosity penetrates into at least one of oxidized cellulose fiber and cellulose nanofiber. When the surface of at least one of the oxidized cellulose fiber and the cellulose nanofiber is moderately high by, for example, oxidation treatment, it can be easily bonded to a rubber molecule. Next, when a strong shearing force was applied to the rubber, at least one of the oxidized cellulose fiber and the cellulose nanofiber moved with the movement of the rubber molecules, and further aggregated by the restoring force of the rubber due to elasticity after shearing. At least one of the oxidized cellulose fiber and the cellulose nanofiber is separated and dispersed in the rubber. In particular, the open roll method is preferable because it can measure and manage not only the roll temperature but also the actual temperature of the mixture.

5-2-4. Coagulation step A coagulation step of coagulating the rubber latex in the first mixture can be further included between the mixing step and the drying step.

  Since the first mixture obtained in the mixing step in 5-2-1 contains a large amount of moisture as it is, it takes a long time to remove moisture in the drying step in 5-2-2. . Therefore, in the coagulation step, a predetermined amount of a known coagulant that coagulates rubber latex is added to the first mixture that is an aqueous solution, and the mixture is stirred and mixed. The rubber component in the first mixture is solidified by the coagulant. The coagulation step can include dehydration and washing for the coagulum. Dehydration and washing can be repeated multiple times.

  The dehydration in this step only needs to remove water to the extent that the drying time in the drying step can be shortened, and separates the solidified rubber component and moisture to some extent. Dehydration can be performed using, for example, a general rotary dehydrator (centrifugation), a rubber film roll, a press machine, or the like. Moreover, the washing | cleaning in this process can be performed with water, for example.

  As the coagulant, a known latex coagulant can be appropriately employed depending on the type of rubber latex in the first mixture. As the coagulant, for example, a known acid or salt can be used, and the polymer flocculant may be used in place of or together with the salt. Examples of the acid used for the coagulant include formic acid, acetic acid, propionic acid, citric acid, oxalic acid, sulfuric acid, hydrochloric acid, and carbonic acid. As a salt used for the coagulant, for example, sodium chloride, aluminum sulfate, calcium nitrate and the like can be used. As the polymer flocculant, any of anionic, cationic and nonionic polymer flocculants can be used.

  Since a large amount of water can be removed from the first mixture in the coagulation process, the heating time of the drying process performed after the coagulation process can be shortened, and the working efficiency is improved.

5-2-5. Molding process of pin boot The kneaded rubber composition is molded by a rubber molding process generally employed using a mold having a desired pin boot shape. Examples of the molding process include press molding, extrusion molding, and injection molding. In the molding step, the rubber component of the rubber composition containing a crosslinking agent is crosslinked. As the cross-linking agent, for example, a known cross-linking agent applied to rubber appropriately selected according to the use can be used.

  When the pin boot thus obtained is used for a disc brake, the environmental impact can be reduced by the pin boot including at least one of oxidized cellulose fiber and cellulose nanofiber. In addition, according to such a disc brake, the pin boots are excellent in fatigue characteristics, so that the sliding shaft portion of the pin member can be reliably protected for a long period of time.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(1) Preparation of sample (1-1) Examples 1-4
Obtaining an aqueous solution:
Cellulose nanofibers were obtained in the same manner as in the method disclosed in Production Example 1 of JP2013-18918A.

  Specifically, after sufficiently stirring bleached kraft pulp of softwood with ion-exchanged water, TEMPO 1.25% by mass, sodium bromide 12.5% by mass, sodium hypochlorite 28.4% with respect to 100 g of pulp mass. Mass% was added in this order at 20 ° C. Sodium hydroxide was added dropwise to maintain the pH at 10.5, and an oxidation reaction was performed. After the oxidation reaction was performed for 120 minutes, dropping was stopped to obtain an aqueous solution containing 10% by mass of TEMPO-oxidized oxidized cellulose fiber. The oxidized cellulose fiber had a fiber diameter of 10 μm to 30 μm and a fiber length of 1 mm to 5 mm, which were the same as those of the original pulp.

Furthermore, the oxidized cellulose fiber was sufficiently washed with ion-exchanged water and then dehydrated. Thereafter, the oxidized cellulose fiber was adjusted to a solid content of 1% by mass with ion-exchanged water and refined using a high-pressure homogenizer to obtain an aqueous dispersion containing 1% by mass of cellulose nanofibers. The average fiber diameter of the cellulose nanofiber was 3.3 nm, and the average aspect ratio was 225.

Mixing process:
Styrene-butadiene rubber (hereinafter referred to as “SBR”) latex (manufactured by JSR 0561: aqueous dispersion with a solid content of 69% by mass, 10.3 pH, viscosity 440 (mPa · s) ), Surface tension 32 (mN / m), average particle size 700 (nm), Tg-63 ° C.), and mixed at a rotational speed of 10,000 rpm using a juicer mixer.

  After mixing by the mixer, the mixture was passed through a three roll (M-50) manufactured by EXAKT having a nip of 10 μm at a rotation speed of 200 rpm to perform additional mixing to obtain a first mixture.

Drying process:
The first mixture was heat-dried in an oven set at 50 ° C. for 4 days to obtain a second mixture. The blending ratio in the second mixture after drying was SBR solid content of 100 phr and cellulose nanofibers of 60 phr.

Dispersion process:
The second mixture was masticated at a roll interval of 1.5 mm, and SBR, EPDM and carbon black, which are solid rubbers, were added and kneaded to obtain a mixture having the composition shown in Table 1. Further, this mixture was put into an open roll having a roll gap of 0.3 mm, and thinned at 10 to 30 ° C. to obtain a rubber composition sample. At this time, the surface speed ratio of the two rolls was set to 1.1. Thinning was repeated 5 times. In addition, the compounding quantity in Table 1 and Table 2 is a mass part (phr).

Vulcanization process:
A sheet obtained by adding 8 parts by mass of peroxide as a cross-linking agent to a rubber composition sample obtained through thinning and compression-molding the sheet at 170 ° C. for 10 minutes, and forming a sheet-like cross-linked rubber composition sample having a thickness of 1 mm Got.

(1-2) Comparative Examples 1 and 2
In Comparative Examples 1 and 2, each raw material was put into an open roll having a roll gap of 1.5 mm and kneaded so as to have the composition shown in Table 2, and further 8 parts by mass of peroxide was added as a crosslinking agent. The sheet was compression molded at 170 ° C. for 10 minutes to obtain a sheet-like crosslinked rubber composition sample having a thickness of 1 mm.

In Tables 1 and 2,
“SBR” is a blended amount of 1503, specific gravity 0.93, Mooney viscosity 52 (ML _{1 + 4} (100 ° C.)) manufactured by JSR, in addition to the solid content of the SBR latex.
“EPDM” is EP24 manufactured by JSR, specific gravity 0.87, Mooney viscosity 42 (ML _{1 + 4} (100 ° C.)),
"MT carbon" is carbon black of MT grade (average particle diameter and DBP oil absorption are manufacturer's published values) with an average particle diameter of 200 nm and DBP oil absorption of 25 ml / 100 g.
“Cellulose” was an oxidized cellulose nanofiber having an average fiber diameter of 3.3 nm and an average aspect ratio of 225 obtained in the above step.

(2) Basic characteristic test The rubber hardness (Hs (JIS A)) of the rubber composition sample was measured based on the JIS K6253 test.

  About the rubber composition sample, the tensile strength (TS (MPa)) and the elongation at break (Eb (%)) are test pieces punched into a JIS No. 6 dumbbell shape using a tensile tester manufactured by Shimadzu Corporation. , Measured at 23 ± 2 ° C. under a tensile speed of 500 mm / min based on JIS K6251.

(3) Tear test A rubber composition sample was punched into an angle-shaped test piece without incision in JIS K6252, and a tear test was performed in accordance with JIS K6252 at a pulling speed of 500 mm / min using an autograph AG-X manufactured by Shimadzu Corporation. The tear strength (Tr (N / mm)) was calculated by measuring the maximum tearing force (N) and dividing the measurement result by the test piece thickness of 1 mm.

(4) Fatigue life test About the rubber composition sample, as a fatigue life (indicated as "fatigue (2 N / mm)" in Tables 3 and 4), the test sample was 10 mm x 4 mm wide x 1 mm thick (the long side was Punched into a strip-shaped test piece in a row direction), a 1 mm depth incision was made with a razor blade in the width direction from the center of the long side of the test piece, and the test piece was tested using a TMA / SS6100 testing machine manufactured by SII. The short side of both ends is held by a chuck, and a fatigue test is performed by repeatedly applying a tensile load (1 N / mm to 2 N / mm) under the condition of a frequency of 1 Hz in an air atmosphere at 120 ° C., and the test piece breaks. The number of times until it was measured.

(5) Durability Test A pin boot was prepared from a rubber composition sample and attached to a pin slide type disc brake as shown in FIG. 1, and the braking operation was repeated 1 million times at an atmospheric temperature of 150 ° C. The appearance of the pin boot after the test was inspected, and the durability was evaluated as “X” when the crack occurred and “◯” when the crack did not occur. In addition, a normal durability test is about 200,000 times to 500,000 times.

  From the results of Tables 3 and 4, the rubber compositions of Examples 1 to 4 were reinforced with cellulose nanofibers, and the tensile strength was the same or higher than the samples of Comparative Examples 1 and 2. In addition, the rubber compositions of Examples 1 to 4 showed higher values of maximum tear strength and tear fatigue life than the samples of Comparative Examples 1 and 2.

  Further, from the results of Tables 3 and 4, it was found that the pin boots of Examples 1 to 4 were superior in heat resistance and durability as compared with the pin boots of Comparative Examples 1 and 2.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  DESCRIPTION OF SYMBOLS 1,1a ... Disc brake, 2 ... Disc rotor, 3 ... Caliper bracket, 3d ... Caliper support arm, 3f ... Guide hole, 3g ... Boot groove, 4 ... Caliper body, 4a ... Action part, 4b ... Reaction part, 4c ... Bridge part, 4f ... Action part side mounting arm, 4g ... Reaction part side mounting arm, 4h ... Pin insertion hole, 4i ... Female screw hole, 5 ... Pin member, 5a ... Sliding shaft part, 5b ... Fixed shaft part, 5c ... Fitting groove, 5d ... mounting bolt, 6 ... pin boot, 6a ... bellows part, 6b ... proximal end attaching part, 6c ... tip attaching part, 7 ... pin boot, 10 ... friction pad, 11 ... guide sleeve, 11a ... fitting groove , 12 ... connecting pin, 13 ... bush, 100 ... open roll, 110 ... first roll, 120 ... second roll, 130 ... second mixture, 134 ... bank, 136 ... intermediate mixture, 150 ... rubber composition 180 ... formulations, V1, V2 ... rotational speed, d ... roll distance

Claims (3)

A cylindrical boot member used for a pin slide type vehicle disc brake ,
The boot member has a first attachment portion attached to the caliper bracket fixed to the vehicle body, and a second attachment portion attached to a pin member attached to the caliper body or the caliper bracket movable over the previous SL caliper bracket An elastic bellows part connecting the first attachment part and the second attachment part ,
The boot member is composed of a rubber composition containing 5 to 20 parts by mass of at least one of oxidized cellulose fiber and cellulose nanofiber with respect to 100 parts by mass of rubber.
Rubber, includes a scan styrene-Butajiengo-time,
The oxidized cellulose fiber has an average fiber diameter of 10 μm to 30 μm,
Cellulose nanofibers, the average value of the fiber diameter Ri 1nm~200nm der,
The rubber composition has a tensile strength in a tensile test according to JIS K6251 of 15 MPa or more and a breaking elongation of 420% or more.
The rubber composition Ru der maximum tear strength is 40N / mm or more at the tear test according to JIS K6252, boot member. In claim 1,
The rubber member further includes an ethylene / propylene rubber . The boot member according to claim 1 or 2 ,
It said caliper bracket fixed to the vehicle body,
It said caliper body is movable relative to said caliper bracket,
And said pin member attached to one of said caliper bracket and said caliper body,
Including
The pin member supports the other one of the caliper bracket and the caliper body so as to be movable along the axial direction of the pin member,
The boot member is a pin slide type vehicle disc brake that covers an outer periphery of the pin member between the caliper bracket and the caliper body.

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