JP7391821B2 - Molding parts and their uses - Google Patents

Description

The present invention relates to a molding member used for manufacturing crosslinked molded products such as tires and belts, and uses thereof.

In recent years, against the backdrop of social demands for energy conservation and downsizing, the ambient temperature around the engine compartment of automobiles has risen compared to before, and with this rise in ambient temperature, the operating environment temperature of power transmission belts has also increased. It's here. Traditionally, the main polymers used for power transmission belts (particularly V-ribbed belts) have been natural rubber, styrene-butadiene rubber, chloroprene rubber, etc., but as the demand for improved heat resistance and materials that do not contain environmentally hazardous substances increases, , ethylene-α-olefin elastomer was adopted, and organic peroxides came to be used as crosslinking agents for this polymer.

As one method for manufacturing the V-ribbed belt, Japanese Patent Laid-Open No. 2009-119846 (Patent Document 1) discloses that a process is performed on the outer peripheral surface of a bladder (flexible jacket) attached to a cylindrical forming drum (inner mold). , the members constituting the belt (core wire, rubber sheet, etc.) are wound in order to form an unvulcanized belt sleeve, the inner mold with the belt sleeve attached is placed inside the outer mold, and the outer mold is heated. A method is disclosed in which a bladder is expanded while pressing an unvulcanized sleeve against an outer mold having groove-like markings corresponding to the rib portions on the inner circumferential surface to form rib portions.

In this manufacturing process, when the bladder is deflated and returned to its original state after vulcanization, the outer diameter of the bladder becomes smaller than the inner diameter of the vulcanized belt sleeve, so the bladder and vulcanized belt It becomes possible to release the mold from the sleeve. When the releasability of the bladder decreases, the workability, especially the workability of an automated production line, decreases significantly. Furthermore, since the bladder is repeatedly used to vulcanize the belt sleeve, damage and deterioration in mold releasability due to deterioration over time during repeated use pose problems.

Conventionally, butyl rubber, which has excellent heat resistance and low gas permeability, has been used as the rubber material used for the bladder. A tire manufacturing bladder is disclosed that is made by vulcanizing a rubber composition containing a rubber component including a resin and butyl rubber.

However, when a rubber composition containing an organic peroxide as a crosslinking agent is used in the rubber layer of the belt sleeve, the butyl rubber is attacked by radicals generated by decomposition of the organic peroxide, causing a decomposition reaction. In particular, if a rubber layer made of a rubber composition containing an organic peroxide comes into direct contact with a bladder made of butyl rubber, the butyl rubber of the bladder will be damaged. Therefore, compared to belt sleeves made of conventional sulfur-crosslinked rubber compositions, the curing and deterioration of the surface of the bladder that comes into close contact with the rubber layer of the belt sleeve is significant, and the usable number of repetitions is shortened.

Therefore, as a bladder that does not use butyl rubber, Japanese Patent Application Laid-Open No. 2010-221506 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2011-161767 (Patent Document 4) disclose bladders for tire manufacturing that use silicone rubber or fluororubber. Disclosed.

However, when silicone rubber is used, although it has excellent mold release properties, it has poor hydrolysis resistance and tear resistance (tear crack resistance), resulting in a shortened service life. Furthermore, the use of fluororubber increases the lifespan, but it is difficult to use due to cost considerations since it is an expensive material.

Therefore, as an example of improving conventional butyl rubber using ethylene-α-olefin elastomer, which is an inexpensive material, Japanese Patent Publication No. 2018-513248 (Patent Document 5) describes an ethylene-propylene-diene ternary copolymer. Manufacture of tires formed from a rubber composition comprising 20 to 50 parts by weight of a copolymer of ethylene, C _3-23 α-olefin and polyene monomer, such as EPDM, and 50 to 80 parts by weight of a butyl-type rubber, such as butyl rubber. A bladder for use is disclosed. Furthermore, JP-A-2012-232517 (Patent Document 6) discloses that butyl rubber and ethylene-α-olefin elastomer are used as a vulcanization molding member (jacket) for a power transmission belt at a ratio of 10/90 to 60% (former/latter). /40 (mass ratio) of a rubber composition is disclosed.

Japanese Patent Application Publication No. 2009-119846 Japanese Patent Application Publication No. 10-130441 Japanese Patent Application Publication No. 2010-221506 Japanese Patent Application Publication No. 2011-161767 Special table 2018-513248 publication Japanese Patent Application Publication No. 2012-232517

However, in recent years, as ethylene-α-olefin elastomer has been adopted as the rubber component of power transmission belts, and the crosslinking temperature has become higher, it has become necessary to increase the durability of molded parts such as bladders by changing the rubber components that make up the bladder. A high degree of heat resistance has also become necessary. For this purpose, as in the molding members of Patent Documents 5 and 6, if butyl rubber is included, sufficient heat resistance cannot be obtained, so a rubber component that takes heat resistance into consideration is required.

In addition, as mentioned above, when butyl rubber or silicone rubber is repeatedly used as a bladder for producing a power transmission belt from an unvulcanized sleeve formed from a rubber composition containing an organic peroxide, the mechanical properties of the bladder ( (tear resistance, etc.) decreased, resulting in a decrease in durability life, and in the resulting belt, the mold releasability decreased.

Furthermore, regarding the durability life of the bladder, even if the tear resistance is improved, the life may be reached due to permanent deformation (permanent deformation). Specifically, in forming a power transmission belt, a molded body is produced by spinning a core wire with tension applied to the outer circumference of the bladder, so that the bladder to which the molded body is attached is tightened by the core wire. In this state, when the bladder is expanded in the cross-linking process, the core wires are bitten into the bladder. Therefore, when the bladder is used repeatedly in the cross-linking process, traces of the core wires are gradually transferred to the outer circumferential surface of the bladder (the shape of the core wires changes). (forms unevenness along the surface) and cannot return. When cross-linking molding is performed using a bladder with cord traces formed on the outer circumferential surface, the cord traces are also transferred to the inner circumferential surface of the molded product (the surface in contact with the bladder). Since the inner circumferential surface of the molded body is the back surface of the power transmission belt, the appearance of the back surface of the power transmission belt is poor. In this specification, such deformation in which traces of the core wire are formed and cannot be recovered is referred to as permanent deformation (permanent distortion). In other words, even if the bladder is used repeatedly and the outer circumferential surface of the bladder is permanently deformed to the extent that traces of the core wire are transferred to the inner circumferential surface (back surface of the power transmission belt) of the molded product to be cross-linked, Endurance life.

Therefore, an object of the present invention is to provide a molding member that has excellent heat resistance and can improve durability such as permanent deformation resistance, and uses thereof.

As a result of intensive studies to achieve the above-mentioned object, the present inventors have developed a molding member for producing a crosslinked molded product using a soft material with a primary particle diameter of 40 nm or more that is combined with an ethylene-α-olefin elastomer in a specific ratio. It has been discovered that by forming a crosslinked rubber composition of carbon, hard carbon with a primary particle diameter of less than 40 nm, and an organic peroxide, it has excellent heat resistance and can improve durability such as permanent deformation resistance. , completed the invention.

That is, the molding member of the present invention is a molding member for producing a crosslinked molded product by crosslinking the uncrosslinked body while in contact with the uncrosslinked body, and comprises a rubber component, carbon black, and an organic polymer. It is formed of a crosslinked rubber composition containing an oxide, the rubber component contains an ethylene-α-olefin elastomer, and the carbon black is hard carbon with a primary particle diameter of less than 40 nm and soft carbon with a primary particle diameter of 40 nm or more. , the proportion of the hard carbon is 5 to 45 parts by mass with respect to 100 parts of the rubber component, and the proportion of the soft carbon is 40 to 95 parts by mass with respect to 100 parts of the rubber component. be. The proportion of the soft carbon may be more than 100 parts by mass and not more than 230 parts by mass based on 100 parts by mass of the hard carbon. The proportion of the carbon black may be 60 to 130 parts by mass based on 100 parts by mass of the rubber component. The hard carbon may have a BET specific surface area of 70 to 140 m ² /g. The soft carbon may have a BET specific surface area of 25 to 60 m ² /g. The ethylene content of the ethylene-α-olefin elastomer may be 50 to 70% by weight, and the diene content may be 0.4 to 5% by weight. The proportion of the organic peroxide may be 2 to 8 parts by weight based on 100 parts by weight of the rubber component. The compression set of the molding member according to JIS K 6262 may be 5 to 20%. The elongation at break of the molding member according to JIS K 6251 may be 100 to 500%. The molding member may be a bladder for manufacturing a power transmission belt. The uncrosslinked body may contain an organic peroxide.

The present invention also includes a method for producing a crosslinked molded body by crosslinking the uncrosslinked body while the molding member is in contact with the uncrosslinked body. In this method, the uncrosslinked body may be crosslinked by deforming the molding member.

In the present invention, a molding member for producing a crosslinked molded article is composed of an ethylene-α-olefin elastomer, soft carbon with a primary particle size of 40 nm or more and hard carbon with a primary particle size of less than 40 nm, which are combined in a specific ratio, and an organic Because it is made of a crosslinked rubber composition combined with peroxide, it has excellent heat resistance and has a long lifespan.For example, it can be used as a bladder for manufacturing power transmission belts. You can improve. In particular, regarding durability, the durability life due to tear cracking can be improved, and the durability life due to permanent deformation can be improved. In addition, even if it is repeatedly used as a molding member for producing a crosslinked molded product from an uncrosslinked product made of a rubber composition containing an organic peroxide, the mechanical properties (tear properties, etc.) of the molding member deteriorate. It is possible to suppress deterioration of mold releasability from the resulting crosslinked molded product.

FIG. 1 is a schematic perspective view (a) showing an example of an inner mold of a belt forming apparatus for manufacturing a V-ribbed belt, and a partially enlarged schematic cross-sectional view (b) thereof. FIG. 2 is a schematic perspective view (a) of a state in which a belt sleeve is attached to the inner mold of FIG. 1, and a partially enlarged schematic cross-sectional view (b) thereof. FIG. 3 is a schematic perspective view (a) showing a process of inserting the inner mold with the belt sleeve shown in FIG. 2 into the outer mold, and a partially enlarged schematic sectional view (b ). FIG. 4 is a schematic perspective view (a) of the belt forming apparatus in which the inner mold is inserted into the outer mold of FIG. 3 in a state where the bladder is inflated, and a partially enlarged schematic cross-sectional view (b) thereof. FIG. 5 is a schematic perspective view (a) showing a step of removing the inner mold from the belt forming apparatus shown in FIG. 4, and a partially enlarged schematic sectional view (b) showing a state in which the inner mold is removed from the belt forming apparatus. FIG. 6 is a schematic cross-sectional view showing an example of a V-ribbed belt.

[Method for manufacturing crosslinked molded body]
The molding member of the present invention is used to produce a crosslinked molded article by crosslinking the uncrosslinked body while in contact with the uncrosslinked body. The crosslinked molded body may be any crosslinked molded body made of rubber or the like, and examples thereof include tires, belts, and the like. Among these, belts are preferred as crosslinked molded bodies manufactured using the molding member of the present invention, and power transmission belts (power transmission belts) are particularly preferred. Examples of transmission belts include flat belts; friction transmission belts such as wrapped V-belts, low-edge V-belts, raw-edge cogged V-belts, and V-ribbed belts; interlocking transmission belts such as toothed belts and double-sided toothed belts; V-belts such as V-ribbed belts are commonly used. Below, a method for manufacturing a V-ribbed belt using the molding member of the present invention as a bladder, which is a flexible jacket for manufacturing a V-ribbed belt, will be described.

(belt forming device)
A V-ribbed belt can be manufactured by a belt forming apparatus that includes an outer mold and an inner mold that can be inserted into and removed from the hollow part of the outer mold. FIG. 1 is a schematic perspective view (a) showing an example of an inner die of a belt forming apparatus for manufacturing a V-ribbed belt, and an enlarged schematic cross-sectional view (b) of an upper portion thereof. FIG. 3 is a diagram of a belt forming apparatus in which the inner mold and the outer mold are combined, and in detail, a schematic perspective view (a ) and a partially enlarged schematic sectional view (b) showing a state in which the inner mold is inserted into the outer mold.

As shown in FIG. 1, the shape of the inner mold 1, which is a mold, is columnar or cylindrical. At both longitudinal ends (both upper and lower ends) of the inner mold 1, an upper end flange 22a and a lower end flange 22b, which are disc-shaped and project in the outer circumferential direction, are formed. In this example, the upper end flange 22a is formed to have a larger diameter than the lower end flange 22b, and is formed to have a larger diameter than the outer diameter of a bladder 5, which will be described later, mounted on the inner mold 1.

A cylindrical bladder 5, which is a molding member of the present invention, is attached to the outer peripheral surface of the inner mold 1. Specifically, by fitting the inner mold 1 into the cylindrical interior of the flexible bladder 5, The outer peripheral surface of the inner mold 1 is in contact with the inner peripheral surface of the cylindrical bladder 5. As will be described later, the material of the bladder 5 is made of a crosslinked rubber composition that is stretchable and airtight. The bladder 5 is attached so that the entire circumferences of both longitudinal end surfaces (upper end surface and lower end surface) are in close contact with the upper end flange 22a and the lower end flange 22b, respectively. Therefore, the space between the outer circumferential surface of the inner mold 1 and the inner circumferential surface of the bladder 5 is sealed by flanges at both upper and lower ends.

Furthermore, the inner mold 1 includes an upper end flange 22a and a fluid supply path 23 passing through the inner mold 1. The fluid supply path 23 has an opening at the upper end located above the upper end flange 22a, passes through the upper end flange 22a, and further curves through the inner mold 1 to reach the inner circumferential surface of the bladder 5. It extends and forms an opening at the boundary between the outer circumferential surface of the inner mold 1 and the inner circumferential surface of the bladder 5 . In the inner mold 1, fluid such as air can be supplied between the outer peripheral surface of the inner mold 1 and the inner peripheral surface of the bladder 5 through the fluid supply path 23. When fluid is supplied through the fluid supply path 23 in this way, since the outer circumferential surface of the inner mold 1 and the inner circumferential surface of the bladder 5 are sealed at both upper and lower ends, the bladder 5 is moved outward as the fluid flows in. is expanded to. Furthermore, when fluid is not being supplied from the fluid supply path 23, the bladder 5 is in close contact with the outer peripheral surface of the inner mold 1.

As shown in FIG. 3, the outer mold 6 has a cylindrical shape into which the inner mold 1 can be inserted, and as shown in FIG. A molding convex portion 45 is formed on the surface. The molding convex portion 45 is formed as a mold shape (inverted shape) corresponding to the intended rib portion, and protrudes over the entire inner peripheral surface of the outer mold 6. A large number of them are formed in parallel at predetermined constant intervals in a direction perpendicular to the circumferential direction of the inner peripheral surface.

The V-ribbed belt is manufactured using this belt forming apparatus, and the specific steps include a forming process of forming an uncrosslinked belt precursor, a crosslinking process of crosslinking the uncrosslinked belt precursor, and a crosslinking process of forming the crosslinked belt precursor ( It is obtained through a finishing process to produce a V-ribbed belt from a belt sleeve).

(molding process)
The molding process is a process of forming an uncrosslinked belt precursor 4 using an inner mold 1 equipped with a bladder 5 on its outer peripheral surface.

FIG. 2 shows the state of the belt forming apparatus in the forming process. Specifically, FIG. b). As shown in FIG. 2, the uncrosslinked belt precursor 4 is formed as a laminate of a core wire 2 spirally wound around the outer peripheral surface of the bladder 5 and a precursor sheet 3 wound around the outer peripheral surface of the bladder 5. In the embodiment shown in FIG. 2, two types of precursor sheets 3 including at least an uncrosslinked rubber sheet are used: a sheet 3a for forming a stretch layer on the outer peripheral surface of the bladder 5 from the inner peripheral side; A laminated material consisting of the core wire 2 forming the core and the uncrosslinked rubber sheet 3b for forming the compressed layer is wound and laminated in this order to form the uncrosslinked belt precursor 4. As the sheet 3a for forming the stretch layer, a cloth or an uncrosslinked rubber sheet is used. In addition, when forming a core layer in which the core (core wire) is embedded in an adhesive rubber layer, an adhesive rubber layer for embedding the core (core wire) is formed between the sheets 3a and 3b. An uncrosslinked rubber sheet may also be provided, and the layer structure is not limited to the above.

(Crosslinking process)
The crosslinking process is performed by compression molding (molding) the uncrosslinked belt precursor 4 into a desired shape corresponding to the shape of the mold, thereby carrying out a crosslinking reaction of the rubber components constituting each rubber layer. This is a step of bonding and integrating the laminated materials constituting the uncrosslinked belt precursor 4 to form a belt sleeve (crosslinked belt precursor) 4A (FIG. 5(b) to be described later). In this crosslinking step, the uncrosslinked belt precursor 4 is crosslinked and the rib portions 7 are formed to obtain the belt sleeve 4A. Therefore, in the crosslinking step, the compressed rubber layer is molded at the same time as the crosslinking.

FIG. 3 shows a preparatory step for subjecting the uncrosslinked belt precursor to a crosslinking process, as detailed above. FIG. 4 shows the state of the belt forming apparatus in the crosslinking process, and in detail, a schematic perspective view (a) of the belt forming apparatus in which the inner mold is inserted into the outer mold shown in FIG. It is a partially enlarged schematic sectional view (b).

Specifically, in order to subject the uncrosslinked belt precursor to the crosslinking process, as shown in FIG. inserted into. Inside the outer mold 6, a heating/cooling jacket 35 is formed as a sealed hollow part over the entire circumference, and above the outer peripheral wall 6a of the outer mold 6, a heating medium such as steam is provided. A heat medium supply port 36 is formed, and a coolant supply port 37 for supplying a cooling medium such as cooling water is formed below the outer peripheral wall 6a.

In the crosslinking process, as shown in FIG. 4, a heating medium is supplied from the heating medium supply port 36 to heat the outer mold 6 using the heating/cooling jacket 35, and a fluid such as air is supplied from the fluid supply path 23 to the inner mold. 1 and the inner periphery of the bladder 5, and as shown in FIG. Then, the uncrosslinked belt precursor 4 that is wrapped around the outer peripheral surface of the bladder 5 is pressed against the inner peripheral surface of the outer mold 6, and the uncrosslinked belt precursor 4 is heated between the bladder 5 and the outer mold 6. Apply pressure. At this time, the uncrosslinked belt precursor 4 is pressed against the inner peripheral surface of the outer mold 6 and pressurized, so that the outer peripheral surface of the uncrosslinked belt precursor 4 is applied to the recess between the molding convex parts 45 of the outer mold 6. Since it is press-fitted, the rib portion 7 can be formed on the outer peripheral surface. The heating temperature is, for example, 120 to 180° C., the molding pressure is, for example, 0.5 to 1.5 MPa, and the heating time is, for example, 15 to 30 minutes. Through this step, the uncrosslinked belt precursor 4 is crosslinked to obtain a belt sleeve 4A.

(Finishing process)
In the finishing step, a V-ribbed belt is manufactured from the belt sleeve 4A obtained in the crosslinking step. FIG. 5 shows the belt forming apparatus in the finishing process, and is a schematic perspective view (a) showing the process of removing the inner mold from the belt forming apparatus in the state shown in FIG. It is a partially enlarged schematic sectional view (b) showing a state.

In the crosslinking step, after the belt sleeve 4A is crosslinked and heating is stopped, the supply of fluid from the fluid supply path 23 is stopped, thereby contracting the bladder 5 and returning it to the state before expansion, and further closing the refrigerant supply port. A cooling medium is supplied from 37 to cool the outer mold 6. When the bladder 5 contracts to its original state, the outer diameter of the bladder 5 becomes smaller than the inner diameter of the cross-linked belt sleeve 4A, so as shown in FIG. The inner mold 1 can be pulled out from the outer mold 6 while leaving the portion 4A on the inner periphery of the outer mold 6.

After extracting the inner mold 1 from the outer mold 6 and removing the belt sleeve 4A having a plurality of ribs on the outer periphery from the outer mold 6, the belt sleeve 4A is cut into rounds in the longitudinal direction of the belt at a predetermined width using a cutter. , the belt is separated one by one and the inner and outer circumferential sides are turned over (inverted) to create a V-ribbed belt.

In this manner, in manufacturing a V-ribbed belt, the bladder as a forming member is heated and expanded and contracted to be deformed and used to form the rib portion. The molding member of the present invention can improve durability even in applications where heating and deformation are repeated. Therefore, the molding member of the present invention can be preferably used in applications in which it is heated for crosslinking and is deformed in crosslinking molding (especially in bladders).

[Molding parts]
The molding member typified by the aforementioned bladder is formed of a crosslinked rubber composition containing a rubber component, carbon black, and an organic peroxide.

(rubber component)
The rubber component includes an ethylene-α-olefin elastomer. Ethylene-α-olefin elastomer does not contain a double bond in its main chain, so it has excellent heat resistance and is preferred as a material for molding members that are repeatedly heated. In particular, in the crosslinking step using a molding member such as the bladder, the uncrosslinked body and the molding member come into contact. When the uncrosslinked rubber composition contains an organic peroxide, if the rubber component constituting the molding member is attacked by radicals generated by the decomposition of the organic peroxide and decomposes, softening and deteriorating, the molding member will deteriorate. The mechanical strength (particularly tearing properties) of the uncrosslinked body decreases, and the releasability of the uncrosslinked body from the crosslinked molded body (such as a belt sleeve) decreases. In the present invention, by using as a rubber component an ethylene-α-olefin elastomer that is not decomposed by attack by radicals generated by decomposition of an organic peroxide, it is possible to suppress softening and deterioration of the molding member.

The ethylene-α-olefin elastomer may contain ethylene units and α-olefin units as constituent units, and may further contain diene units. Ethylene-α-olefin elastomers include ethylene-α-olefin copolymer rubber, ethylene-α-olefin-diene terpolymer rubber, and the like.

Examples of the α-olefin for forming the α-olefin unit include linear α-C _3-12 olefins such as propylene, butene, pentene, methylpentene, hexene, and octene. Among these α-olefins, α-C _3-4 olefins such as propylene (especially propylene) are preferred.

As the diene monomer for forming the diene unit, a non-conjugated diene monomer is usually used. Examples of the non-conjugated diene monomer include dicyclopentadiene, methylenenorbornene, ethylidenenorbornene, 1,4-hexadiene, and cyclooctadiene. Among these diene monomers, ethylidene norbornene and 1,4-hexadiene (especially ethylidene norbornene) are preferred.

Representative ethylene-α-olefin elastomers include, for example, ethylene-propylene copolymer (EPM) and ethylene-propylene-diene terpolymer (EPDM).

These ethylene-α-olefin elastomers can be used alone or in combination of two or more. Among these, ethylene-α-olefin-diene terpolymer rubber is preferred, and ethylene-propylene-diene terpolymer (EPDM) is particularly preferred, since it has excellent crosslinking efficiency using diene units.

In the ethylene-propylene-diene terpolymer, the ratio (mass ratio) of ethylene and propylene is former/latter = 35/65 to 90/10, preferably 40/60 to 80/20, more preferably 45 /55 to 70/30, most preferably 50/50 to 60/40.

The ethylene content of the ethylene-α-olefin elastomer (especially ethylene-α-olefin-diene terpolymer rubber such as EPDM) may be 30% by mass or more (for example, 30 to 80% by mass), preferably The amount is 50 to 70% by weight, more preferably 52 to 65% by weight, more preferably 53 to 60% by weight, and most preferably 54 to 58% by weight. If the ethylene content is too low, there is a risk that heat resistance will decrease.

In the present application, the ethylene content means the mass proportion of ethylene units in all units constituting the ethylene-α-olefin elastomer, and can be measured by a conventional method, but may also be a monomer ratio.

The diene content of the ethylene-α-olefin elastomer (especially ethylene-α-olefin-diene terpolymer rubber such as EPDM) may be 10% by mass or less (for example, 0.1 to 10% by mass), Preferably 0.3 to 8% by weight, more preferably 0.4 to 7% by weight (eg 0.4 to 5% by weight), more preferably 0.5 to 6% by weight, most preferably 1 to 5% by weight. It is. In the present invention, heat resistance is improved by using a rubber component that does not have double bonds in the main chain, but by suppressing double bonds due to diene units introduced as side chains to a small amount, high It can ensure good heat resistance. If the diene content is too high, there is a risk that high heat resistance cannot be ensured.

In this application, the diene content means the mass proportion of diene monomer units in all units constituting the ethylene-α-olefin elastomer, and can be measured by a conventional method, but may also be a monomer ratio.

The Mooney viscosity [ML (1 + 4) 125 ° C.] of the unvulcanized ethylene-α-olefin elastomer may be 80 or less, and the Vm of the rubber composition can be adjusted and the dispersibility of carbon black can be improved. For example, it is 10-80, preferably 20-70, more preferably 30-60, and most preferably 35-50. If the Mooney viscosity is too high, there is a risk that the fluidity of the rubber composition will decrease and the processability during kneading will decrease.

In this application, Mooney viscosity can be measured by a method according to JIS K 6300-1 (2013), and the test conditions are: using an L-shaped rotor, test temperature 125 ° C, preheating 1 minute, rotor operating time 4 minutes. It is.

The proportion of the ethylene-α-olefin elastomer in the rubber component may be 50% by mass or more, but preferably exceeds 90% by mass, more preferably 95% by mass or more, more preferably 99% by mass or more, and 100% by mass. % is most preferred. If the proportion of the ethylene-α-olefin elastomer in the rubber component is too small, there is a risk that the heat resistance will decrease.

The rubber component may further contain other rubber components. Other rubber components include, for example, diene rubber [natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (nitrile rubber), hydrogenated nitrile rubber, etc.], chlorosulfonated Examples include polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber.

The rubber component may contain these other rubber components in a proportion such that the proportion of the ethylene-α-olefin elastomer falls within the above range, as long as the effects of the present invention are not impaired. It does not substantially contain butyl rubber as other rubber components, since it can improve the properties and tear resistance.

The proportion of butyl rubber in the rubber component may be less than 10% by mass, preferably 5% by mass or less, more preferably 1% by mass or less, more preferably 0.1% by mass or less, and most preferably 0% by mass. .

(Carbon black)
The rubber composition forming the molding member can improve the durability of the molding member by further containing carbon black in addition to the above-mentioned rubber components.

Carbon black is generally classified into several grades based on differences in primary particle diameter, iodine adsorption amount, BET specific surface area, etc. Carbon black with a small primary particle size has a high reinforcing effect on rubber, while carbon black with a large primary particle size has a low reinforcing effect on rubber.

Regarding the classification of carbon black, ASTM classifies it into N0** to N9** based on the amount of iodine adsorbed, but the conventional classification based on the performance of the rubber product in which it is compounded (SAF, HAF, GPF, etc.) ) are also used. N110 (SAF), N220 (ISAF), N330 (HAF), etc., which have small primary particle diameters, are called hard carbons, while N550 (FEF), N660 (GPF), N762 (SRF), etc., which have large primary particle diameters, are soft carbons. It is sometimes called. There is a close relationship between the amount of iodine adsorbed and the primary particle size, and the smaller the primary particle size, the larger the amount of iodine adsorbed. Taking the SEAST (registered trademark) series manufactured by Tokai Carbon Co., Ltd. as an example, the iodine adsorption amount and average primary particle diameter are summarized and the relationships are as shown in Table 1.

In this application, carbon black contained in a rubber composition is not classified by raw material, but carbon black with a primary particle size of 40 nm or more is referred to as soft carbon, and carbon black with a primary particle size of less than 40 nm is referred to as hard carbon. .

In the present application, the primary particle diameter of carbon black can be measured on a number basis using, for example, a transmission electron microscope.

In the present invention, permanent deformation resistance can be improved by combining hard carbon with a primary particle diameter of less than 40 nm and soft carbon with a primary particle diameter of 40 nm or more in a specific ratio.

The primary particle size of hard carbon may be less than 40 nm (for example, 15 to 35 nm), but the maximum primary particle size may be, for example, 38 nm or less, preferably 35 nm or less, and more preferably 30 nm or less. If the maximum primary particle size of hard carbon is too large, there is a risk that tear resistance will decrease. The minimum primary particle diameter may be, for example, 5 nm or more, preferably 8 nm or more, and more preferably 10 nm or more. If the minimum primary particle diameter of hard carbon is too small, there is a risk that it will be difficult to prepare the hard carbon itself.

The average primary particle diameter of hard carbon is, for example, about 10 to 35 nm, preferably 15 to 33 nm, more preferably 20 to 32 nm (especially 25 to 30 nm). If the average primary particle diameter of the hard carbon is too small, it may be difficult to prepare the hard carbon itself, and if it is too large, the tear resistance may decrease.

The BET specific surface area of hard carbon is, for example, 60 to 160 m ² /g, preferably 65 to 150 m ² /g, more preferably 70 to 140 m ² /g, more preferably 75 to 130 m 2 /g, and most preferably 75 to 130 m ² /g. It is 100m ² /g. If the BET specific surface area is too small, there is a risk that the rubber composition will be difficult to stretch, and if it is too large, the hardness of the rubber composition may become too high.

In addition, in this application, the BET specific surface area means the specific surface area measured using nitrogen gas by the BET method.

The iodine adsorption amount of hard carbon may be 60 g/kg or more, for example, 60 to 150 g/kg, preferably 65 to 130 g/kg, more preferably 70 to 100 g/kg, and most preferably 75 to 90 g/kg. be. If the amount of iodine adsorbed is too small, there is a risk that the tear resistance will decrease, and if it is too large, there is a risk that it will be difficult to prepare the hard carbon itself.

In the present application, the amount of iodine adsorbed by carbon black can be measured in accordance with the standard test method of ASTM D1510-17.

The proportion of hard carbon is 5 to 45 parts by mass (especially 10 to 40 parts by mass), preferably 20 to 38 parts by mass, more preferably 23 to 37 parts by mass, and most preferably It is 25 to 35 parts by mass. If the proportion of hard carbon is too small, the tear resistance will decrease, and if it is too large, the permanent deformation resistance will decrease.

The primary particle size of soft carbon may be 40 nm or more (for example, 40 to 100 nm), but the maximum primary particle size may be, for example, 300 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. If the maximum primary particle size of the soft carbon is too large, the reinforcing properties of the carbon black may be reduced and the tear resistance may be reduced.

The average primary particle diameter of soft carbon is, for example, 45 to 100 nm, preferably 50 to 90 nm, more preferably 53 to 80 nm, more preferably 55 to 70 nm, most preferably 60 to 65 nm. If the average primary particle diameter of the soft carbon is too small, there is a risk that the permanent deformation resistance will be reduced, and if it is too large, the reinforcing properties of the carbon black will be reduced, and the tear resistance may be reduced.

The BET specific surface area of soft carbon is, for example, 10 to 60 m ² /g (for example, 25 to 60 m ² /g), preferably 15 to 55 m ² /g, more preferably 20 to 50 m 2 /g, and more preferably 22 to 40 m ² /g. ² /g, most preferably 23-30 m ² /g. If the BET specific surface area is too small, there is a risk that the reinforcing properties of carbon black will be reduced and the tear resistance will be reduced, and if it is too large, there is a risk that the permanent deformation resistance will be reduced.

The iodine adsorption amount of the soft carbon may be less than 60 g/kg, for example, 10 g/kg or more and less than 60 g/kg, preferably 15 to 50 g/kg, more preferably 18 to 40 g/kg, and most preferably 20 to 30 g. /kg. If the amount of iodine adsorbed is too small, there is a risk that the reinforcing properties of carbon black will be reduced and the tear resistance will be reduced, and if it is too large, there is a risk that the permanent deformation resistance will be reduced.

The proportion of soft carbon is 40 to 95 parts by mass (especially 50 to 90 parts by mass), preferably 52 to 80 parts by mass, more preferably 53 to 70 parts by mass, and most preferably It is 55 to 65 parts by mass. If the proportion of soft carbon is too small, the permanent deformation resistance will decrease, and if it is too large, the tear resistance will decrease.

The mass proportion of soft carbon may be larger than that of hard carbon, for example, more than 100 parts by mass and less than 300 parts by mass (for example, more than 100 parts by mass and not more than 230 parts by mass) with respect to 100 parts by mass of hard carbon. For example, the amount may be 110 to 300 parts by weight, preferably 120 to 250 parts by weight, more preferably 130 to 230 parts by weight, more preferably 150 to 220 parts by weight, and most preferably 180 to 210 parts by weight. If the proportion of soft carbon is too small, there is a risk that the permanent deformation resistance will decrease, and if it is too large, there is a possibility that the tear resistance will decrease.

The total proportion of carbon black can be selected from a range of about 60 to 130 parts by mass, for example 60 to 120 parts by mass, preferably 65 to 115 parts by mass, more preferably 65 to 110 parts by mass, based on 100 parts by mass of the rubber component. , more preferably 70 to 105 parts by weight, most preferably 80 to 100 parts by weight. If the total proportion of carbon black is too small, there is a risk that the rubber composition will be too soft and the durability will be reduced, whereas if it is too large, the rubber composition will be too hard and there is a risk that the durability will be reduced.

(organic peroxide)
When the rubber composition forming the molding member further contains an organic peroxide in addition to the rubber component and carbon black, the durability of the molding member can be improved.

As the organic peroxide, conventional components such as diacyl peroxide (dilauroyl peroxide, dibenzoyl peroxide, etc.), peroxyketal [1,1-di(t-butylperoxy)cyclohexane, 2,2 -di(t-butylperoxy)butane, etc.], alkyl peroxy esters (t-butylperoxybenzoate, etc.), dialkyl peroxides [di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,1,1-di(t-butylperoxy)-3,3,5- trimethylcyclohexane, 1,3-bis(2-t-butylperoxyisopropyl)benzene, 2,5-di-methyl-2,5-di(benzoylperoxy)hexane, etc.), dialkyl peroxide (dicumyl peroxide, etc.) oxide, t-butylcumyl peroxide, etc.), peroxycarbonate (t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethyl-hexyl carbonate, t-amylperoxy-2-ethyl-hexyl carbonate, etc.) Examples include.

These organic peroxides can be used alone or in combination of two or more. Among these, peroxides having a dialkyl group are preferred, and dialkyl peroxides such as dicumyl peroxide are more preferred.

The proportion of the organic peroxide is, for example, 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, more preferably 2 to 8 parts by weight, and more preferably 3 to 7.0 parts by weight, based on 100 parts by weight of the rubber component. 5 parts by weight, most preferably 5 to 7 parts by weight. If the proportion of organic peroxide is too small, the rubber composition may be too soft and the durability may be reduced; if it is too large, the rubber composition may be too hard and the durability may be reduced.

(other ingredients)
In addition to the rubber component, carbon black, and organic peroxide, the rubber composition forming the molding member may further contain additives that are conventionally blended into rubber as other components.

Examples of additives include other crosslinking agents or vulcanizing agents (inorganic peroxides, sulfur-based vulcanizing agents, etc.), co-crosslinking agents (bismaleimides, etc.), vulcanization aids or vulcanization accelerators (thiuram, etc.) vulcanization retarders, reinforcing agents (silica, clay, calcium carbonate, talc, mica, short fibers, etc.), metal oxides (zinc oxide, magnesium oxide, calcium oxide, barium oxide, iron oxide, (copper, titanium oxide, aluminum oxide, etc.), softeners (oils such as paraffin oil and naphthenic oil, etc.), processing agents or processing aids (stearic acid, metal stearate, wax, paraffin, fatty acid amide, etc.) , silane coupling agents, anti-aging agents (antioxidants, heat anti-aging agents, flex cracking inhibitors, anti-ozonation agents, etc.), colorants, tackifiers, stabilizers (ultraviolet absorbers, heat stabilizers, etc.) ), flame retardants, antistatic agents, etc. These additives can be used alone or in combination of two or more. Note that the metal oxide may act as a crosslinking agent.

The total proportion of customary additives is, for example, 5 to 50 parts by weight, preferably 10 to 30 parts by weight, more preferably 15 to 25 parts by weight, based on 100 parts by weight of the rubber component.

(Characteristics of molding parts)
The molding member of the present invention has high resistance to permanent deformation. Therefore, the compression set of the molding member of the present invention may be 20% or less, for example, 5 to 20%, preferably 8 to 17%, more preferably 9 to 15%, more preferably 10 to 14%. , most preferably 11-13%. If the compression set is too small, there is a risk that the rubber composition will be too hard and the durability will be reduced, whereas if it is too large, there is a risk that the permanent deformation resistance will be reduced.

In the present application, the compression set can be measured by compressing at 120° C. for 24 hours in accordance with JIS K 6262, and more specifically, it can be measured by the method described in the Examples below.

The hardness (JIS A) of the molding member of the present invention is, for example, 75 to 90°, preferably 78 to 88°, more preferably 80 to 87°, more preferably 81 to 85°, and most preferably 82 to 84°. It is. If the hardness is too high, there is a risk that it will be too hard and the durability will be reduced; if the hardness is too low, there is a risk that it will be too soft and the durability will be reduced.

In addition, in this application, hardness (JIS A) is determined according to the durometer hardness test (Type A) specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - How to determine hardness). Means the measured value Hs (JIS A).

The tensile strength of the molding member of the present invention is, for example, 10 to 30 MPa, more preferably 15 to 25 MPa, more preferably 17 to 20 MPa, and most preferably 18 to 19 MPa. If the tensile strength is too low, there is a risk that it will be too soft and the durability will be reduced; if the tensile strength is too large, it will be too hard and there is a risk that the durability will be reduced.

The elongation at break of the molding member of the present invention is, for example, 100 to 500%, preferably 120 to 300%, more preferably 130 to 250%, more preferably 140 to 170%, and most preferably 150 to 160%. . If the elongation at break is too small, there is a risk that it will be too hard and the durability will be reduced, whereas if it is too large, there is a risk that it will be too soft and the durability will be reduced.

In addition, in this application, tensile strength and elongation at break can be measured based on JIS K 6251 (2010), and in detail, can be measured by the method described in the Examples described later.

[Crosslinked molded body]
Examples of crosslinked molded products obtained using the molding member of the present invention include tires, belts, etc., as described above. As described above, the crosslinked molded product is preferably a crosslinked molded product produced by heating and deforming the molding member of the present invention. A diagram (a cross-sectional view in a direction perpendicular to the belt longitudinal direction) is shown in FIG.

As shown in FIG. 6, the V-ribbed belt 50 includes a core layer 53 including a core wire 52, and compressed rubber that is provided on the inner circumferential side of the core layer 53 and constitutes a V-rib portion 51a that is a pulley contact portion. It is composed of a layer 51 and a stretch layer 54 provided on the outer peripheral side of the core layer. A plurality of grooves having a V-shaped cross section extending in the longitudinal direction of the belt are formed in the compressed rubber layer 51, and a plurality of ribs (V rib portions 51a) having a V-shaped cross section (inverted trapezoid) are formed between the grooves. The two inclined surfaces (surfaces) of this rib form a friction transmission surface, which contacts the pulley and transmits power (friction transmission). The stretch layer may be formed of a rubber composition, or may be formed of a fabric (reinforced fabric) such as a woven fabric. Further, a surface layer may be provided on the surface of the V rib portion.

The crosslinked molded product is preferably a crosslinked molded product (for example, a belt sleeve of a V-ribbed belt) whose surface that contacts the molding member is formed of a rubber composition containing an organic peroxide. In the case of a V-ribbed belt, the surface that comes into contact with the molding member may be a rubber composition or fabric (or a fabric containing a rubber composition) forming the stretch layer.

The rubber composition containing an organic peroxide may be a rubber composition containing an ethylene-α-olefin elastomer and an organic peroxide. As the ethylene-α-olefin elastomer and organic peroxide, the ethylene-α-olefin elastomer and organic peroxide described as materials for forming the molding member can be used. The ratio of the organic peroxide to the rubber component is also the same as that of the organic peroxide for forming the molding member. The molding member of the present invention can improve durability even when used for manufacturing a crosslinked molded product formed from a crosslinked rubber composition containing an organic peroxide.

The present invention will be explained in more detail below based on Examples, but the present invention is not limited by these Examples. In addition, details of the raw materials used in the examples are shown below.

[material]
EPDM1: "EPT3070" manufactured by Mitsui Chemicals, Inc., Mooney viscosity (125°C) ≒ 47, ethylene content 58% by mass, diene content 4.7% by mass
EPDM2: "EPT2060M" manufactured by Mitsui Chemicals, Inc., Mooney viscosity (125°C) ≒ 40, ethylene content 55% by mass, diene content 2.3% by mass
Butyl rubber: “Butyl268” manufactured by JSR Corporation, Mooney viscosity (125°C) ≒ 51
Hard carbon 1: “SEAST 3” manufactured by Tokai Carbon Co., Ltd., average particle diameter 28 nm, BET specific surface area 79 m ² /g
Hard carbon 2: “SEAST 6” manufactured by Tokai Carbon Co., Ltd., average particle diameter 22 nm, BET specific surface area 119 m ² /g
Soft carbon 1: “SEAST V” manufactured by Tokai Carbon Co., Ltd., average particle diameter 62 nm, BET specific surface area 27 m ² /g
Soft carbon 2: “SEAST S” manufactured by Tokai Carbon Co., Ltd., average particle diameter 66 nm, BET specific surface area 27 m ² /g
Zinc oxide: “Zinc oxide type 2” manufactured by Hakusui Tech Co., Ltd.
Stearic acid: “Tsubaki Beads Stearic Acid” manufactured by NOF Corporation
Softener: “NS-90” manufactured by Idemitsu Kosan Co., Ltd. (paraffin-based process oil)
Anti-aging agent: diphenylamine-based anti-aging agent, “Nocrac AD-F” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Organic peroxide: “Percmil D” manufactured by NOF Corporation
Resin crosslinking agent: Schenectady Chem. “SP-1055” (alkylphenol/formaldehyde resin)
Crosslinking aid: “PM-40” manufactured by Denka Co., Ltd.
Nylon short fiber: “66 nylon” manufactured by Asahi Kasei Corporation
Hydrous silica: “Ultrasil VN3” manufactured by Evonik Industries AG, BET specific surface area 180 m ² /g
Resorcinol/formaldehyde condensate: Solution containing 2.6 parts by mass of resorcin, 1.4 parts by mass of 37% formalin, 17.2 parts by mass of vinylpyridine-styrene-butadiene copolymer latex, and 78.8 parts by mass of water Acceleration of vulcanization Agent: “Noxeler (registered trademark) DM” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Hexamethoxymethylolmelamine: “PP-1890S” manufactured by Power Plast
Sulfur: Manufactured by Bigen Kagaku Co., Ltd. Core wire: 1,000 denier polyethylene terephthalate fibers twisted in a 2 x 3 configuration with a final twist coefficient of 3.0 and a final twist coefficient of 3.0, with a total denier of 6,000. Twisted cord with adhesive treatment, core wire diameter 1.0mm.

[Preparation of bladder]
Rubber compositions for bladders having the formulations shown in Tables 2 and 3 were kneaded with a Banbury mixer and rolled to a predetermined thickness with a calendar roll. A rolled sheet having a thickness of 3 mm and a surface length of 630 mm was wrapped around a cylindrical mold, covered with a jacket, and heated at 170° C. for 20 minutes to perform crosslinking molding. A cylindrical bladder was obtained by cooling and demolding. By setting a cylindrical bladder on the outer periphery of the inner mold of the belt forming device and fixing the flange tightly around the entire circumference of both ends of the opening of the bladder, the distance between the outer periphery of the inner mold and the inner periphery of the bladder is at both the upper and lower ends. sealed in.

[Physical properties of rubber composition for bladder]
1) Measurement of hardness Uncrosslinked rubber sheets of the rubber compositions shown in Tables 2 and 3 were pressed and heated using a press for 30 minutes (temperature 170°C, surface pressure 2.0 MPa), and crosslinked rubber sheets ( 100 mm x 100 mm x 2 mm thickness) was produced. In accordance with JIS K 6253 (2012), a laminate of three crosslinked rubber sheets was used as a sample, and the hardness was measured using a durometer type A hardness tester.

2) Measurement of tensile properties (tensile strength, elongation at break) According to JIS K 6251 (2010), a dumbbell-shaped No. 3 test piece taken from the above-mentioned crosslinked rubber sheet in the anti-grain direction was pulled at room temperature. A tensile test was conducted at a speed of 500 mm/min, and the tensile strength (MPa) and elongation rate (%) at the time the test piece broke were calculated. As the tensile tester, "Autograph AG-5000A" manufactured by Shimadzu Corporation was used. When used as a bladder, the elongation at break of the rubber composition should be 100% or more in order to prevent breakage and cracking even when expanded by cross-linking.

3) Measurement of compression set According to JIS K 6262 (2013), the rubber composition was rolled into a sheet, put into a mold and cross-linked at a temperature of 165°C for 30 minutes, with a diameter of about 29 mm and a thickness of about 12 mm. A cylindrical sample with a diameter of .5 mm was prepared. The obtained sample was compressed under the test conditions of a compression ratio of approximately 10% (spacer thickness 11.25 mm), a test temperature of 120°C, and a test time of 24 hours, and the thickness of the sample before and after compression was measured. Distortion was calculated. In detail, the thickness of the sample before compression is h0 (mm), the thickness of the sample after compression is h1 (mm), the thickness of the spacer is hS (mm), and the compression set: CS (%) is as follows. It was calculated using the formula.

CS=[(h0-h1)/(h0-hS)]×100

4) Measurement of tear properties (tear strength) A sample was punched out from the above crosslinked rubber sheet in a crescent shape according to JIS K 6252 (2015), and a cut of 1.00 ± 0.05 mm was made in the center of the depression. A tear test was conducted at a tensile speed of 500 mm/min, and the tear strength when the test piece broke was measured. As the tensile tester, "Autograph AG-5000A" manufactured by Shimadzu Corporation was used. In addition, in the accelerated aging test, a method A AA-2 forced circulation heat aging tester (cross wind type) was used.

The measurement results are shown in Tables 5 and 6.

[Bladder performance evaluation]
Using the manufacturing equipment shown in Figures 1 to 5, the production (crosslinking molding) of belt sleeves, which are the precursors of V-ribbed belts, was carried out using bladders manufactured with the rubber compositions of Examples 1 to 11 and Comparative Examples 1 to 6. We repeatedly verified the durability life under permanent deformation of the bladder.

(Belt sleeve used for verification)

The stretch layer including the contact surface with the bladder was a stretch rubber layer, and the core layer was a belt sleeve in which the core wire was embedded in the adhesive rubber layer.

Rubber Composition 1 was used for the stretchable rubber layer, Rubber Composition 2 was used for the compression rubber layer, and Rubber Composition 3 was used for the adhesive rubber layer. Each rubber composition was kneaded with a Banbury mixer, and then kneaded with a calendar roll to a predetermined thickness. An uncrosslinked rubber sheet for forming a stretched rubber layer, an uncrosslinked rubber sheet for forming a compressed rubber layer, and an uncrosslinked rubber sheet for an adhesive rubber layer were prepared by rolling.

Next, an uncrosslinked rubber sheet for forming a stretchable rubber layer is wrapped around the outermost periphery of the cylindrical inner mold with the bladder attached, a core wire forming the core is spun in a spiral shape around the outer periphery, and the adhesive rubber An uncrosslinked rubber sheet for forming a layer and an uncrosslinked rubber sheet for forming a compressed rubber layer were wound in this order to form an uncrosslinked molded body.

Further, a cylindrical outer mold having a plurality of ribs carved on the inner peripheral surface is used, and an inner mold in which the uncrosslinked molded body is formed is placed concentrically within this outer mold. Thereafter, the bladder is expanded toward the inner peripheral surface (rib mold) of the outer mold, and the outer peripheral side (compressed rubber layer) of the uncrosslinked molded body is press-fitted into the rib mold, heated at 180°C for 20 minutes, and crosslinked. did. After removing the inner mold from the outer mold, the belt sleeve having a plurality of ribs on the outer periphery was removed from the outer mold.

This belt sleeve production (cross-linking molding) is repeated until traces of the core wires are transferred to the inner peripheral surface (back surface of the power transmission belt) of the cross-linked molded body, and the back surface of the power transmission belt is judged to have a poor appearance. The durability life is determined by deformation, and the number of uses until the durability life is reached is compared and verified. Regarding the number of uses, the quality was judged based on the following criteria. Note that ◯ and △ are practical passing levels.

○: 180 times or more △: 120 times or more, less than 180 times ×: less than 120 times.

The comparative verification results are shown in Tables 5 and 6.

As is clear from the results in Table 5, two types of carbon black (hard carbon and soft carbon) are blended, and the ratio of soft carbon is higher than that of hard carbon, and the amount of hard carbon blended is 10 to 100 parts by mass per 100 parts by mass of the rubber component. 40 parts by mass, the blended amount of soft carbon is 50 to 90 parts by mass, and the total amount of carbon black is 60 to 130 parts by mass. ) was 120 times or more (judgment △ or more), and the durability life of the bladder was at an effective level.

In particular, in Examples 1 to 5, 7, and 9 to 10, in which the blending amount is in the range of 25 to 40 parts by mass of hard carbon and 50 to 80 parts by mass with respect to 100 parts by mass of the rubber component, the durability of the bladder was The lifespan (number of uses until the end of life due to permanent deformation) was 180 times or more (judgment ○).

Example 11 has a blend within the above range, but the blending ratio of hard carbon to soft carbon is small (hard carbon: soft carbon = 100:240), and the durable life of the bladder is 145, probably because it lacks reinforcing effect. times (judgment △), which was slightly shorter.

In Example 6, the hard carbon content was 10 parts by mass, which was less than the above range, and the durability life of the bladder was slightly shortened to 130 cycles (judgment Δ), probably because the reinforcing effect was lacking.

In Example 8, the amount of soft carbon was 90 parts by mass, which was higher than the above range, and the durability life of the bladder was slightly shortened to 170 cycles (judgment Δ), probably because the reinforcing effect was lacking.

Among Examples 1 to 5, 7, and 9 to 10, Example 2 had the best balance. That is, among Examples 1 to 3 in which the proportion of organic peroxide was changed, the bladder life of Example 2, in which 6 parts by mass of organic peroxide was blended with 100 parts by mass of the rubber component, was the longest. In contrast to Example 1, Example 4, which used EPDM with a lower diene content, had substantially the same results as Example 1. In addition, Example 5, in which the types of hard carbon and soft carbon were changed from Example 1, had almost the same results as Example 1, but Example 1 had a slightly longer bladder life. . Furthermore, Examples 7 and 9 to 10, in which the blending amounts of hard carbon and soft carbon were changed from Example 1, had almost the same results as Example 1, but Example 1 had slightly higher bladder content. had a long lifespan.

Comparative Example 1 is an example in which two types of carbon black are blended, but the proportion of soft carbon is smaller than that of hard carbon. Compared to the bladder of the example, the compression set as a physical property of the rubber composition was large, and the durability life of the bladder was 110 times (judgment: ×), which was inferior.

Comparative Example 2 is an example in which two types of carbon black were blended and the proportion of soft carbon was higher than that of hard carbon, but the proportion of soft carbon was too large (over 90 parts by mass). The total amount of carbon black was 140 parts by mass, which was excessive, and the compression set was also large, and the durability life of the bladder was 63 times (judgment: ×), which resulted in the end of its life early.

Comparative Example 3 is an example in which two types of carbon black are blended and the proportion of soft carbon is higher than that of hard carbon, but the proportion of hard carbon and soft carbon is too high (over 40 parts by mass and over 90 parts by mass). It is. The total amount of carbon black was 150 parts by mass, which was excessive, and the compression set was also large, and the durability life of the bladder was 68 times (judgment: ×), which was the end of its life at an early stage.

Comparative Example 4 is an example in which only one type of carbon black (hard carbon) is used, and although the tensile strength is increased due to the reinforcing effect, the permanent deformation (compression set) is increased. As a result of this balance, the durable life of the bladder was 60 times (judgment: ×), which was the end of its life early.

Comparative Example 5 is an example in which only one type of carbon black (soft carbon) is used, and although the permanent deformation (compression set) is reduced, the tensile strength is reduced due to lack of reinforcing effect. As a result of this balance, the durability of the bladder was 115 times (judgment: x), which was not acceptable.

Comparative Example 6 is an example in which butyl rubber was used as the rubber component, but the compression set was extremely large, and the durability life of the bladder was 60 times (judgment: ×), which was the end of the life at an early stage.

The molding member of the present invention can be used as a molding member for manufacturing crosslinked bodies such as tires and belts, and in particular, jackets and bladders (flexible jackets) for manufacturing power transmission belts such as V-ribbed belts. It is useful as a molding member (particularly a bladder).

1... Inner mold 4... Uncrosslinked belt precursor 5... Bladder 6... Outer mold

Claims (12)

A molding member for producing a crosslinked molded article by crosslinking the uncrosslinked body while in contact with the uncrosslinked body,
It is formed from a crosslinked rubber composition containing a rubber component, carbon black and an organic peroxide,
The rubber component includes an ethylene-α-olefin elastomer,
The carbon black includes hard carbon with a primary particle diameter of 5 nm or more and less than 40 nm and soft carbon with a primary particle diameter of 40 nm or more and 300 nm or less ,
The ratio of the hard carbon is 5 parts by mass or more and less than 28 parts by mass with respect to 100 parts by mass of the rubber component, and the ratio of the soft carbon is 40 to 95 parts by mass with respect to 100 parts by mass of the rubber component. A certain molding member. The molding member according to claim 1, wherein the proportion of the soft carbon is 150 to 230 parts by mass based on 100 parts by mass of the hard carbon. The molding member according to claim 1 or 2, wherein the proportion of the carbon black is 60 to 120 parts by mass based on 100 parts by mass of the rubber component. The molding member according to any one of claims 1 to 3, wherein the hard carbon has a BET specific surface area of 70 to 140 m ² /g, and the soft carbon has a BET specific surface area of 25 to 60 m ² /g. . The molding member according to any one of claims 1 to 4, wherein the ethylene content of the ethylene-α-olefin elastomer is 50 to 70% by mass and the diene content is 0.4 to 5% by mass. The molding member according to any one of claims 1 to 5, wherein the proportion of the organic peroxide is 2 to 8 parts by mass based on 100 parts by mass of the rubber component. The molding member according to any one of claims 1 to 6, which has a compression set of 5 to 20% according to JIS K 6262. The molding member according to any one of claims 1 to 7, which has an elongation at break of 100 to 500% according to JIS K 6251. The molding member according to any one of claims 1 to 8, which is a bladder for manufacturing a power transmission belt. The molding member according to any one of claims 1 to 9, wherein the uncrosslinked body contains an organic peroxide. A method for producing a crosslinked molded body by crosslinking the uncrosslinked body while the molding member according to any one of claims 1 to 10 is in contact with the uncrosslinked body. 12. The method according to claim 11, wherein the uncrosslinked body is crosslinked by deforming the molding member.

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