WO2019054481A1 - Rubber composition and transmission belt using same - Google Patents

Abstract

A rubber composition containing a rubber component and natural spider silk fibroin short fibers and/or artificial spider silk fibroin short fibers derived therefrom dispersed in the rubber component.

Description

Rubber composition and transmission belt using the same

The present invention relates to a rubber composition and a transmission belt using the same.

The dynamic friction coefficient of the surface is adjusted by forming the pulley contact portion of the transmission belt with a rubber composition in which short fibers are dispersed. For example, Patent Document 1 discloses a V-ribbed belt in which a compressed rubber layer at a pulley contact portion is formed of a rubber composition in which nylon short fibers are dispersed in a rubber component.

Further, Patent Document 2 discloses that rubber is reinforced using an artificial spider silk fibroin fiber of a pseudo-natural fiber containing a polypeptide as a main component.

JP, 2006-349002, A Patent No. 5540154 gazette

The present invention is a rubber composition comprising a rubber component, and natural spider silk fibroin short fibers dispersed in the rubber component and / or artificial spider silk fibroin short fibers derived therefrom.

The present invention is a power transmission belt in which a pulley contact portion of a belt main body is formed by the rubber composition of the present invention.

It is a perspective view of a part of V belt. It is a perspective view of a part of V ribbed belt. It is a perspective view of a part of toothed belt. It is explanatory drawing which shows the measuring method of a dynamic friction coefficient. It is a graph which shows the relationship of the sliding time and dynamic friction coefficient of Example 3 and Comparative Example 1.

Hereinafter, the embodiment will be described in detail.

The rubber composition according to the embodiment includes various rubber components containing natural spider silk fibroin staple fibers and / or artificial spider silk fibroin staple fibers derived therefrom (hereinafter simply referred to as "spider silk fibroin staple fibers") and a crosslinking agent. The uncrosslinked rubber composition into which the above rubber composition is compounded and kneaded is heated and pressurized to form a crosslinked rubber composition in which the rubber component is crosslinked by the crosslinking agent. The rubber composition according to this embodiment contains a rubber component and spider yarn fibroin short fibers dispersed in the rubber component.

According to the rubber composition according to the embodiment, the spider fiber fibroin short fiber containing the polypeptide as the main component is dispersed in the rubber component, whereby the high water absorption function of the spider fiber fibroin short fiber is expressed, and as a result, It is possible to obtain excellent surface dynamic friction coefficient return performance when moisture intervenes.

Here, as the rubber component, for example, ethylene propylene diene monomer (hereinafter referred to as "EPDM"), ethylene-α-olefin elastomer such as ethylene propylene copolymer (EPM), chloroprene rubber (CR), styrene butadiene rubber (SBR) And natural rubber (NR). The rubber component preferably contains one or more of these, more preferably contains an ethylene-α-olefin elastomer, and still more preferably contains EPDM.

The spider silk fibroin constituting the spider silk fibroin short fiber preferably contains a spider silk polypeptide selected from the group consisting of natural spider silk proteins and artificial spider silk proteins derived from natural spider silk proteins.

Natural spider silk proteins include, for example, large nasogastric silkworm silk proteins, weft silk proteins, and vesicle glandular proteins. The large threading yarn has a repeated region consisting of a crystalline region and an amorphous region (also referred to as "amorphous region"), and therefore has high stress and elasticity. The weft has a feature that it does not have a crystalline region and has a repeated region consisting of an amorphous region. The weft yarn is inferior in stress as compared with the large discharge tube dragline yarn, but has high stretchability.

The large nasogastric silkworm silk protein is produced in a large spider line and is characterized by excellent toughness. Examples of the large nasogastric silkworm silk proteins include the major ampullate spidroins MaSp1 and MaSp2 derived from Nephila clavipes, and the ADF3 and ADF4 derived from the giant spider spider (Araneus diadematus). ADF3 is one of the two major large nasogastric silkworm silk proteins. The artificial spider silk proteins may be polypeptides derived from these large intestinal canal silk proteins. Artificial spider silk proteins derived from ADF3 are relatively easy to synthesize and have excellent properties in terms of strength and elongation and toughness.

The weft protein is produced in the flagelliform gland of the spider. As the weft protein, for example, flagelliform silk protein derived from Nephila clavipes and the like can be mentioned.

The artificial spider silk protein may be a recombinant spider silk protein. Examples of recombinant spider silk proteins include mutants, analogues, derivatives and the like of natural spider silk proteins. A preferred example of such an artificial spider silk protein is a recombinant spider silk protein (also referred to as "a polypeptide derived from the large nasogastric silkworm dragline protein").

Examples of the polypeptide derived from the large nasogastric silkworm silk protein include proteins including a domain sequence represented by the formula 1: [(A) n motif-REP] m. Here, in the formula 1, the (A) n motif indicates an amino acid sequence mainly comprising an alanine residue, and n is preferably 2 or more, more preferably 4 or more, further preferably 8 or more, still more preferably It is an integer of 10 or more, preferably 20 or less, more preferably 16 or less. The ratio of the number of alanine residues to the total number of amino acid residues in the (A) n motif may be 40% or more, preferably 60% or more, and more preferably 70% or more. % Or more is more preferable, 90% or more is still more preferable, and 100% (meaning it is composed of only alanine residues) may be used. REP represents an amino acid sequence composed of 2 or more and 200 or less amino acid residues. m represents an integer of 2 or more and 300 or less. The plurality of (A) n motifs may be identical to each other or different from each other. The plurality of REPs may be identical amino acid sequences to each other or different amino acid sequences. Specific examples of the polypeptide derived from the large nasogastric silkworm silk protein include proteins containing the amino acid sequences shown by SEQ ID NO: 1 and SEQ ID NO: 4 in the sequence listing.

The artificial spider silk protein may be a protein derived from the weft protein. As a protein derived from the weft protein, for example, a protein comprising a domain sequence represented by Formula 2: [REP2] o (wherein, in Formula 2, REP2 is composed of Gly-Pro-Gly-Gly-X An amino acid sequence is shown, X is one amino acid selected from the group consisting of alanine (Ala), serine (Ser), tyrosine (Tyr), valine (Val), o represents an integer of 8 or more and 300 or less.) Etc. Specific examples of the protein derived from the weft protein include a protein comprising the amino acid sequence shown by SEQ ID NO: 2 in the sequence listing. The amino acid sequence shown by SEQ ID NO: 2 is from the N-terminus corresponding to the repeat part and motif of the partial sequence (NCBI accession number: AAF36090, GI: 7106224) of the flagellar silk protein of American jellium spider obtained from the NCBI database The amino acid sequence from residues 1220 to 1659 (referred to as the PR1 sequence) and a partial sequence of the flagella-like silk protein of the American spider spider obtained from the NCBI database (NCBI accession numbers: AAC38847, GI: 2833649) The C-terminal amino acid sequence from residue C 816 to residue 907 is joined, and the amino acid sequence (tag sequence and hinge sequence) shown in SEQ ID NO: 3 is added to the N terminus of the joined sequence It is

The artificial spider silk protein expresses the nucleic acid by, for example, a host transformed with an expression vector having a nucleic acid sequence encoding the protein and one or more regulatory sequences operably linked to the nucleic acid sequence. It can be produced by

The method for producing the nucleic acid encoding the artificial spider silk protein is not particularly limited. For example, the nucleic acid can be produced by a method of amplification and cloning by polymerase chain reaction (PCR) or the like or a method of chemical synthesis using a gene encoding a natural structural protein. The chemical synthesis method of the nucleic acid is not particularly limited, and, for example, AKTA oligopilot plus 10/100 (manufactured by GE Healthcare Japan) based on the amino acid sequence information of the structural protein obtained from the NCBI web database etc. The gene can be chemically synthesized by a method of ligating the oligonucleotide synthesized at step S by PCR or the like. At this time, in order to facilitate purification and / or confirmation of the protein, a nucleic acid encoding a protein consisting of an amino acid sequence obtained by adding an amino acid sequence consisting of a start codon and a His tag to the N terminus of the above amino acid sequence is synthesized It is also good.

The regulatory sequence is a sequence that controls the expression of a recombinant protein in a host (for example, a promoter, an enhancer, a ribosome binding sequence, a transcription termination sequence, etc.), and can be appropriately selected depending on the type of host. As a promoter, an inducible promoter which functions in a host cell and is capable of inducing expression of a target protein may be used. An inducible promoter is a promoter that can control transcription due to the presence of an inducer (expression inducer), the absence of a repressor molecule, or physical factors such as temperature, osmotic pressure or an increase or decrease in pH value.

The type of expression vector can be appropriately selected according to the type of host, such as a plasmid vector, a virus vector, a cosmid vector, a fosmid vector, an artificial chromosome vector and the like. As the expression vector, a vector capable of autonomous replication in a host cell or capable of being integrated into the host chromosome and containing a promoter at a position capable of transcribing a nucleic acid encoding a target protein is suitably used.

As a host, any of eukaryotes such as prokaryotes, yeasts, filamentous fungi, insect cells, animal cells and plant cells can be suitably used.

Preferred examples of prokaryotic hosts include, for example, microorganisms belonging to the genus Escherichia, Brevibacillus, Serratia, Bacillus, Microbacterium, Microbacterium, Brevibacterium, Corynebacterium, Pseudomonas, etc. . Examples of microorganisms belonging to the genus Escherichia include, for example, Escherichia coli and the like. Examples of the microorganism belonging to the genus Brevibacillus include Brevibacillus agri and the like. Examples of the microorganism belonging to the genus Serratia include Serratia liquofaciens and the like. Examples of the microorganism belonging to the genus Bacillus include, for example, Bacillus subtilis. Examples of the microorganism belonging to the genus Microbacterium include, for example, Microbacterium ammoniafilum and the like. Examples of the microorganism belonging to the genus Brevibacterium include Brevibacterium divaricatam and the like. Examples of microorganisms belonging to the genus Corynebacterium include Corynebacterium ammoniagenes and the like. Examples of microorganisms belonging to the genus Pseudomonas include, for example, Pseudomonas putida.

When a prokaryote is used as a host, examples of vectors for introducing a nucleic acid encoding a target protein include pBTrp2 (manufactured by Boehringer Mannheim), pGEX (manufactured by Pharmacia), pUC18, pBluescriptII, pSupex, pET22b, pCold, pUB110, pNCO2 (disclosed in JP-A-2002-238569) and the like can be mentioned.

Eukaryotic hosts include, for example, yeast and filamentous fungi (molds and the like). As a yeast, the yeast which belongs to Saccharomyces genus, Pichia genus, Schizosaccharomyces genus etc. is mentioned, for example. Examples of filamentous fungi include filamentous fungi belonging to the genus Aspergillus, Penicillium, Trichoderma, and the like.

When a eukaryote is used as a host, examples of vectors into which a nucleic acid encoding a target protein is introduced include YEP13 (ATCC37115), YEp24 (ATCC37051), and the like. As a method of introducing the expression vector into the host cell, any method can be used as long as it is a method of introducing DNA into the host cell. For example, a method using calcium ion [Proc. Natl. Acad. Sci. USA, 69, 2110 (1972)], electroporation method, spheroplast method, protoplast method, lithium acetate method, competent method and the like.

As a method for expressing a nucleic acid by a host transformed with an expression vector, for example, in addition to a direct expression method, a secretory production and a fusion protein expression method, etc. according to the method described in Molecular Cloning 2nd Edition, etc. Can be mentioned.

The artificial spider silk protein can be produced, for example, by culturing a host transformed with an expression vector in a culture medium, producing and accumulating the protein in the culture medium, and collecting the protein from the culture medium. The method of culturing the host in a culture medium can be carried out according to a method usually used for culturing the host.

When the host is a prokaryote such as E. coli or a eukaryote such as yeast, the culture medium contains a carbon source which can be used by the host, a nitrogen source, inorganic salts and the like, and the culture of the host can be performed efficiently. As long as the medium can be used, either a natural medium or a synthetic medium may be used.

The carbon source may be any as long as the above-mentioned transformed microorganism can assimilate, for example, glucose, fructose, sucrose and molasses containing these; carbohydrates such as starch and starch hydrolysate; acetic acid and propionic acid etc Organic acids; and alcohols such as ethanol and propanol. Nitrogen sources include, for example, inorganic acids such as ammonia, ammonium chloride, ammonium sulfate, ammonium acetate, ammonium phosphate, ammonium salts of organic acids, other nitrogen-containing compounds, peptone, meat extract, yeast extract, corn steep liquor, casein Examples thereof include hydrolysates, soybean meal and soybean meal hydrolysates, various fermented cells, and digests thereof. Examples of the inorganic salts include potassium monophosphate, potassium monobasic, magnesium phosphate, magnesium sulfate, sodium chloride, ferrous sulfate, manganese sulfate, copper sulfate, calcium carbonate and the like.

The culture of a prokaryote such as E. coli or a eukaryote such as yeast can be performed under aerobic conditions such as shake culture and submerged aeration culture, for example. The culture temperature is, for example, 15 ° C. or more and 40 ° C. or less. The culture time is usually 16 hours or more and 7 days or less. The pH of the culture medium during culture is preferably maintained at 3.0 or more and 9.0 or less. The pH of the culture medium can be adjusted using an inorganic acid, an organic acid, an alkaline solution, urea, calcium carbonate, ammonia or the like.

In addition, during culture, antibiotics such as ampicillin and tetracycline may be added to the culture medium as needed. When a microorganism transformed with an expression vector using an inducible promoter as a promoter is cultured, an inducer may be added to the medium as needed. For example, when culturing a microorganism transformed with an expression vector using a lac promoter, isopropyl-β-D-thiogalactopyranoside or the like may be added to the medium, and transformation is carried out with an expression vector using a trp promoter. When culturing the microorganism, indole acrylic acid or the like may be added to the medium.

Isolation and purification of the expressed artificial spider silk protein can be performed by a commonly used method. For example, when an artificial spider silk protein is expressed in a dissolved state in cells, after completion of culture, host cells are recovered by centrifugation, suspended in an aqueous buffer, and then sonicated, French press, Manton A cell-free extract can be obtained by disrupting host cells with a Gaulin homogenizer, Dyno-Mil, etc., and a purified preparation can be obtained from the supernatant obtained by centrifuging the cell-free extract. In order to obtain a purified preparation from the supernatant, methods usually used for isolation and purification of proteins, that is, solvent extraction method, salting out method with ammonium sulfate etc, desalting method, precipitation method with organic solvent, diethylaminoethyl ( Anion exchange chromatography method using a resin such as DEAE) -Sepharose, DIAION HPA-75 (manufactured by Mitsubishi Kasei Corp.), a cation exchange chromatography method using a resin such as S-Sepharose FF (manufactured by Pharmacia), Hydrophobic chromatography method using resin such as butyl sepharose or phenyl sepharose, gel filtration method using molecular sieve, affinity chromatography method, chromatofocusing method, electrophoresis method such as isoelectric focusing, etc. alone or in combination You can do it.

Also, when an artificial spider silk protein forms an insoluble form in cells and is expressed, the host cell is similarly recovered and then disrupted and centrifuged to recover an insoluble form of the protein as a precipitated fraction. be able to. The recovered insoluble form of protein can be solubilized with a protein denaturant. After the operation, a purified preparation of artificial spider silk protein can be obtained by the same isolation and purification method as described above. When the artificial spider silk protein is secreted extracellularly, the protein can be recovered from the culture supernatant. That is, a culture supernatant is obtained by treating the culture according to a technique such as centrifugation, and a purified preparation can be obtained from the culture supernatant by using the same isolation and purification method as described above.

The protein raw material fiber of spider silk fibroin short fiber is obtained by spinning the above-mentioned natural spider silk protein and / or artificial spider silk protein, and contains these as a main component. The protein raw material fiber can be produced by a known spinning method. That is, for example, when producing a protein raw material fiber containing spider silk fibroin as a main component, first, spider silk fibroin produced according to the method described above is dimethylsulfoxide (DMSO), N, N-dimethylformamide (DMF) ), And added to a solvent such as hexafluoroisopronol (HFIP) together with an inorganic salt as a dissolution accelerator to dissolve to prepare a dope solution, and then, using this dope solution, wet spinning, dry spinning, dry / wet By spinning by a known spinning method such as formula spinning, a target protein raw material fiber can be obtained. Spider silk fibroin short fibers can be produced by cutting this protein raw material fiber into a predetermined fiber length.

The fineness of the filament of the spider silk fibroin short fiber is preferably 5 dtex or more and 15 dtex or less from the viewpoint of obtaining the excellent return performance of the dynamic friction coefficient of the surface when water intervenes. The fiber length of the spider silk fibroin short fiber is preferably 0.10 mm or more and 6.0 mm or less, more preferably 0.30 mm or more, from the viewpoint of obtaining an excellent return performance of the dynamic friction coefficient of the surface when water intervenes. It is 0 mm or less.

The content of spider silk fibroin short fibers in the rubber composition according to the embodiment is preferably 1 part by mass with respect to 100 parts by mass of the rubber component from the viewpoint of obtaining the excellent performance of restoring the surface dynamic friction coefficient when water intervenes. The amount is not less than 45 parts by mass and more preferably not less than 5 parts by mass and not more than 30 parts by mass.

The spider silk fibroin short fibers are preferably disposed so as to project from the surface of the rubber composition according to the embodiment, from the viewpoint of obtaining the excellent return performance of the dynamic friction coefficient of the surface when water intervenes. The protruding length of the spider silk fibroin short fiber is preferably 0.010 mm or more and 5.0 mm or less, and more preferably 0.050 mm or more and 5.0 mm or less. The protruding length of this spider silk fibroin short fiber is determined as an arithmetic average of 50 or more and 100 or less measured by observation with a scanning electron microscope (SEM) or the like.

In order to impart adhesiveness to the rubber component, the spider silk fibroin short fiber is subjected to an RFL adhesion treatment which is heated after being immersed in an aqueous resorcin / formalin / latex solution (hereinafter referred to as “RFL aqueous solution”) and / or a rubber paste It may be subjected to a rubber paste adhesion process of dipping and drying.

Crosslinking agents include sulfur and organic peroxides. As the crosslinking agent, sulfur may be used alone, an organic peroxide may be used alone, or both of them may be used in combination. In the case of sulfur, the blending amount of the crosslinking agent is, for example, 0.5 parts by mass or more and 4.0 parts by mass or less with respect to 100 parts by mass of the rubber component, and in the case of organic peroxide, with respect to 100 parts by mass of the rubber component For example, 0.5 parts by mass or more and 8 parts by mass or less.

The rubber composition according to the embodiment may contain, as another rubber compound, for example, a reinforcing material such as carbon black, a softener, a processing aid, a vulcanization accelerator, a vulcanization accelerator and the like. .

As carbon black as a reinforcing material, for example, furnace blacks such as FEF, HAF, SAF, ISAF, N-339, N-351, MAF, SRF, GPF, ECF, N-234; thermal blacks such as FT, MT, etc. Can be mentioned. The reinforcing material preferably contains one or more of these. The content of the reinforcing material in the rubber composition according to the embodiment is, for example, 60 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component. The carbon black preferably contains both FEF and HAF. In this case, the content of FEF in the rubber composition according to the embodiment is, for example, 30 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the rubber component. The content of HAF in the rubber composition according to the embodiment is, for example, 30 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the rubber component. The content of HAF is preferably higher than the content of FEF.

Examples of softeners include mineral oil-based softeners such as paraffinic oil, castor oil, cottonseed oil, linseed oil, rapeseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, dropped green oil, wax, rosin, pine oil, etc. Vegetable oil-based softeners and petroleum-based softeners. The softener preferably contains one or more of these. The content of the softener in the rubber composition according to the embodiment is, for example, 10 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber component.

Examples of processing aids include stearic acid, polyethylene wax, metal salts of fatty acids, and the like. The processing aid preferably contains one or more of these. The content of the processing aid in the rubber composition according to the embodiment is, for example, 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of the rubber component.

Examples of the vulcanization acceleration auxiliary include metal oxides such as zinc oxide (zinc white) and magnesium oxide, metal carbonates, fatty acids and derivatives thereof. The vulcanization accelerating coagent preferably contains one or more of these. The content of the vulcanization acceleration aid in the rubber composition according to the embodiment is, for example, 3 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the rubber component.

Examples of vulcanization accelerators include sulfenamide vulcanization accelerators, thiuram vulcanization accelerators, dithiocarbamate vulcanization accelerators, and thiazole vulcanization accelerators. The vulcanization accelerator preferably contains one or more of these. The content of the vulcanization accelerator in the rubber composition according to the embodiment is, for example, 2 parts by mass or more and 6 parts by mass or less with respect to 100 parts by mass of the rubber component. The vulcanization accelerator preferably includes three types of a sulfenamide vulcanization accelerator, a thiuram vulcanization accelerator, a dithiocarbamate vulcanization accelerator, and a thiazole vulcanization accelerator.

The rubber composition according to the embodiment contains short fibers of natural fibers such as cotton other than spider silk fibroin short fibers, short fibers of synthetic fibers such as nylon short fibers, aramid short fibers, and polyester short fibers. It is also good.

By the way, for example, in the field of transmission belt, when water intervenes between the transmission belt and the pulley, the coefficient of dynamic friction decreases at the pulley contact portion formed of the rubber composition of the transmission belt, which causes slip or abnormal noise There is a problem of causing the occurrence. From such a thing, the rubber composition according to the embodiment has an excellent ability to restore the dynamic friction coefficient of the surface when moisture intervenes, so it is suitable as a material for forming the pulley contact portion of the belt main body of the transmission belt. It can be used.

For example, in a V-belt B as shown in FIG. 1A, a rubber belt is formed by an adhesive rubber layer 11 in which a core 14 is embedded, a compression rubber layer 12 on the inner peripheral side, and an extension rubber layer 13 on the outer peripheral side. It is preferable that the main body 10 be configured, and the compressed rubber layer 12 in contact with the pulley among them be formed of the rubber composition according to the embodiment.

In the V-ribbed belt B as shown in FIG. 1B, the belt body 10 made of rubber is formed by the adhesive rubber layer 11 in which the core 14 is embedded, the compression rubber layer 12 on the inner peripheral side, and the extension rubber layer 13 on the outer peripheral side. It is preferable that the compression rubber layer 12 in contact with the rib pulley and / or the stretch rubber layer 13 in contact with the idler pulley be formed of the rubber composition according to the embodiment.

When the compression rubber layer 12 of the V-ribbed belt B is formed of the rubber composition according to the embodiment, the spider silk fibroin short fibers are disposed so as to be oriented in the belt width direction from the viewpoint of enhancing the bending fatigue resistance. Is preferred. Further, from the viewpoint of enhancing the abrasion resistance of the compression rubber layer 11 constituting the pulley contact portion, it is preferable that the spider fiber fibroin short fibers be disposed so as to protrude from the surface of the V rib 15 of the compression rubber layer 11.

In the toothed belt B as shown in FIG. 2, the back rubber layer 15 in which the core wire 14 is embedded and the tooth rubber portion 16 constitute the belt body 10 made of rubber, and the back rubber in contact with the idler pulley among them. The layer 15 is preferably formed of the rubber composition according to the embodiment.

In addition, the rubber composition which concerns on embodiment is not limited to a transmission belt, For example, it can use also for rubber products, such as a tire and a hose.

(Rubber composition)
The rubber compositions of the following Examples 1 to 4 and Comparative Examples 1 to 2 were prepared. Each configuration is shown in Table 1.

Example 1
35 parts by mass of carbon black as a reinforcing material, FEF (manufactured by SEAT SO Tokai Carbon Co., Ltd.) and HAF (manufactured by SEAST 3 Tokai Carbon Co., Ltd.) 40 based on 100 parts by mass of rubber component EPDM (manufactured by EP 123 JSR) as a rubber component Parts by mass, Softener process oil (Sumper 2280 Nippon Sun Oil Co., Ltd.) 14 parts by mass, Processing aid Stearic acid (Stearic acid S50 made by Shin Nippon Rika Co., Ltd.) 1 part by mass, Vulcanization accelerating aid Zinc oxide (Zinc oxide 3 types of white water chemical company 5 parts by mass, sulfur of a vulcanizing agent (Seimio OT Nippon Drip Ind. Co., Ltd. 1.67 parts by mass), sulfenamide vulcanization accelerator (Noccellar MSA-G Ouchi emerging chemical company) A mixture of 1.2 parts by mass of a thiuram vulcanization accelerator, a dithiocarbamate vulcanization accelerator, and a thiazole vulcanization accelerator (Sunseller EM-2 manufactured by Sanshin Chemical Industry Co., Ltd.) Uncrosslinked rubber compounded with 2.8 parts by mass and 20 parts by mass of artificial spider silk fibroin staple fiber (made by Spiber, fineness: 7.8 dtex, fiber length: 1.0 mm, no adhesion treatment, sequence number 4 in the array table) The rubber composition obtained by crosslinking the composition is referred to as Example 1.

<Examples 2 to 4>
The rubber composition of Example 1 was the same except that the blending amount of the artificial spider silk fibroin short fiber was 25 parts by mass, 30 parts by mass and 45 parts by mass with respect to 100 parts by mass of the rubber component. It was 2 to 4.

Comparative Example 1
25 parts by mass per 100 parts by mass of a rubber component of nylon 6,6 short fibers (Deona, Asahi Kasei Co., Ltd. Fineness: 6.7 dtex, fiber length: 1.0 mm, with RFL adhesion treatment) instead of artificial spider silk fibroin short fibers A rubber composition having the same configuration as that of Example 1 except that it was compounded was taken as Comparative Example 1.

Comparative Example 2
A rubber composition having the same structure as that of Example 1 except that the artificial spider silk fibroin short fiber was not blended was taken as Comparative Example 2.

(Test method)
<Elongation at cutting>
For each of Examples 1 to 4 and Comparative Examples 1 and 2, a tensile test was performed based on JIS K6251: 2010 to measure elongation at break.

<Dynamic friction coefficient>
For each of Examples 1 to 4 and Comparative Examples 1 to 2, as shown in FIG. 3, a rectangular parallelepiped test piece S having a square end face of 5 mm is prepared, and one end face thereof is fixed to the fixture 21. At the same time, after bringing the other end face into contact with the disk-shaped friction partner 22, place the weight 23 on the fixture 21 and press the test piece S against the friction partner 22 at a pressure of 59 kPa. The friction counter member 22 was rotated for 16 minutes so that the velocity at the contact position of the piece S was 0.15 m / sec. In addition, 40 μl of water W was dropped onto the friction partner 22 three minutes after the start of rotation. And the time-dependent change of the dynamic friction coefficient of the test piece S at this time was observed, and time (DELTA) t required for the return from a WET state to a DRY state was calculated | required. The dynamic friction coefficient of the test piece S was calculated from the pressing force of the test piece S against the friction partner material 21 and the friction force of the test specimen S detected in the friction partner material 22.

(Test results)
The results of elongation at break of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1. According to this, it is understood that the elongation at the time of cutting decreases as the content of the artificial spider silk fibroin short fiber increases. Further, it can be seen that it is more difficult to reduce the elongation at the time of cutting when the artificial spider silk fibroin short fiber is contained than when the nylon short fiber is contained.

Table 1 shows the results of the time Δt required to return from the WET state to the DRY state in each of Examples 1 to 4 and Comparative Examples 1 and 2. Further, FIG. 4 shows the relationship between the sliding time and the dynamic friction coefficient in Example 3 and Comparative Examples 1 and 2. According to these, in Examples 1 to 4 in which the artificial spider silk fibroin short fiber is contained, the comparisons with Comparative Example 1 in which the nylon 6, 6 short fiber is contained and Comparative Example 2 in which the artificial spider silk fibroin short fiber is not contained Then, it is understood that the return time to the DRY state is short, that is, the return performance of the dynamic friction coefficient of the surface when water intervenes is excellent. It is considered that this is because the water absorption capacity of the artificial spider silk fibroin short fiber is excellent and the water absorption capacity and the water absorption speed thereof are very high.

The present invention is useful in the technical fields of rubber compositions and transmission belts using the same.

B V-belt, V-ribbed belt, toothed belt S test piece W water 10 belt main body 11 adhesive rubber layer 12 compression rubber layer 13 stretch rubber layer 14 core wire 15 back rubber layer 16 tooth rubber portion 21 fixture 22 friction counter member 23 weight

Claims (10)

1. A rubber composition comprising a rubber component, and natural spider silk fibroin short fibers dispersed in the rubber component and / or artificial spider silk fibroin short fibers derived therefrom.
2. In the rubber composition according to claim 1,
   The rubber composition wherein the spider silk fibroin constituting the natural spider silk fibroin short fiber and / or the artificial spider silk fibroin short fiber derived therefrom is a protein comprising the amino acid sequence shown in SEQ ID NO: 4.
3. The rubber composition according to claim 1 or 2
   The rubber composition wherein the fineness of the filament of the natural spider silk fibroin short fiber and / or the artificial spider silk fibroin short fiber derived therefrom is 5 dtex or more and 15 dtex or less.
4. In the rubber composition according to any one of claims 1 to 3,
   The rubber composition wherein the fiber length of the natural spider silk fibroin short fiber and / or the artificial spider silk fibroin short fiber derived therefrom is 0.10 mm or more and 6.0 mm or less.
5. In the rubber composition according to any one of claims 1 to 4,
   The rubber composition wherein the content of the natural spider silk fibroin short fiber and / or the artificial spider silk fibroin short fiber derived therefrom is 1 part by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the rubber component.
6. The rubber composition according to any one of claims 1 to 5,
   The rubber composition in which the natural spider silk fibroin short fibers and / or the artificial spider silk fibroin short fibers derived therefrom are arranged to protrude from the surface.
7. The rubber composition according to any one of claims 1 to 6,
   A rubber composition, wherein the rubber component comprises an ethylene-α-olefin elastomer.
8. The rubber composition according to any one of claims 1 to 7,
   A rubber composition further containing carbon black FEF and HAF.
9. In the rubber composition according to claim 8,
   The rubber composition in which content of the said HAF is more than content of the said FEF.
10. A power transmission belt having a pulley contact portion of a belt main body formed of the rubber composition according to any one of claims 1 to 9.

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