JP6743388B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire having a reinforcing fiber cord using fibroin fiber containing a polypeptide derived from a natural spider silk protein.

Synthetic fibers such as nylon and polyester derived from petroleum resources are widely used for fiber cords for reinforcing rubber products such as pneumatic tires. However, synthetic fibers remain as environmental pollutants without being decomposed even when buried in soil at the time of disposal. Further, when incinerated, harmful gas is generated, which also causes environmental pollution. Therefore, as an environmental protection measure, it is desired to use a material derived from a resource other than petroleum for the reinforcing fiber cord.

As a fiber derived from a resource other than petroleum that can be used as a reinforcing fiber cord, rayon fiber made from wood has been known for a long time. However, since rayon fiber uses wood as a raw material, it has a problem of contributing to environmental damage. Furthermore, since toxic substances such as carbon disulfide are used in the manufacturing process, it is necessary to strictly control the manufacturing process so that the carbon disulfide does not cause environmental pollution.

In terms of tire performance, high-roof vehicles such as minivans are on the increase in recent years, and demands for steering stability of tires are becoming stricter. Furthermore, with the spread of hybrid cars, tire strength (plunger strength) and steering The requirements for stability are becoming more stringent.

Fibers derived from non-petroleum resources other than rayon fibers include silk obtained from domestic silkworms and wild silkworms, silk-like threads obtained from arachnids (spiders), silkworms derived from silkworms, silkworms, wild silkworms, or spiders. Although manufactured silk-like yarns and the like can be mentioned (see Patent Document 1, etc.), a pneumatic tire having these silk-like yarns as fiber cords for tire reinforcement cannot obtain sufficient tire strength and steering stability. There's a problem.

On the other hand, Patent Document 1 describes a method for producing a fibroin fiber containing a polypeptide derived from a natural spider silk protein having excellent strength and toughness, but the tire strength and steering stability are not sufficient.

Japanese Patent No. 3938386

It is an object of the present invention to provide a pneumatic tire having a reinforcing fiber cord derived from a resource other than petroleum and further having excellent tire strength and steering stability.

The present invention is composed of fibroin fibers containing a polypeptide derived from a natural spider silk protein, has a tensile modulus of 8 GPa or more, a toughness of 138 MJ/m ³ or more, and a breaking strength of 0.35 GPa or more. , A pneumatic tire having a reinforcing fiber cord having an elongation at break of 10% or more.

It is preferable to have the reinforcing fiber cord as a carcass cord.

According to the pneumatic tire having the reinforcing fiber cord of the present invention, which is composed of the fibroin fiber containing the polypeptide derived from the natural spider silk protein and has the predetermined physical properties, the fiber derived from the resource other than petroleum is used as the reinforcing fiber cord. It is possible to provide a pneumatic tire having excellent tire strength and steering stability regardless of using.

The pneumatic tire of the present invention is characterized by comprising fibroin fibers containing a polypeptide derived from a natural spider silk protein and having a reinforcing fiber cord having predetermined physical properties.

Fibroin Fiber A fibroin fiber containing a polypeptide derived from a natural spider silk protein according to the present invention contains a polypeptide derived from a natural spider silk protein as a main component. In addition, the main component in this specification means containing 80 mass% or more, more preferably containing 90 mass% or more, and still more preferably containing 95 mass% or more. The fibroin fiber may contain components other than the polypeptide derived from the natural spider silk protein as long as the effect of the present invention is not impaired.

The fibroin fiber containing the polypeptide derived from the natural spider silk protein of the present invention is obtained by spinning a polypeptide produced using a host transformed with a gene encoding the polypeptide derived from the natural spider silk protein. It can be produced by stretching. For example, a fiber manufactured by the manufacturing method described in Japanese Patent No. 5540166 can be used.

The polypeptide derived from the natural spider silk protein is a polypeptide containing a variant, analog or derivative of the natural spider silk protein, and may be derived from the natural spider silk protein, Not limited.

Further, from the viewpoint of excellent toughness, the polypeptide is preferably a polypeptide derived from a large vesicular lacquer silk protein produced in the large bottle-shaped line of a spider. Examples of the large votiver guideline proteins include large bottle-shaped line spidroins MaSp1 and MaSp2 derived from Nephila clavipes, and ADF3 and ADF4 derived from Araneus diadematus. Among them, a polypeptide derived from ADF3, which is one of the two major dragline proteins of the Japanese spider, Araneus diadematus, is preferable because of its basically high elongation and toughness and easy synthesis. The polypeptide derived from the large vesicle guideline protein includes variants, analogs or derivatives of the large vesicle guideline protein.

The polypeptide derived from the natural spider silk protein can be produced using a host transformed with an expression vector incorporating a gene encoding the polypeptide. The method for preparing the gene is not particularly limited, and examples thereof include a method of amplifying a gene encoding a natural spider silk protein from a spider-derived cell by polymerase chain reaction (PCR) or the like, or a method of chemically synthesizing the gene. .. The method for chemically synthesizing the gene is not particularly limited, and for example, based on the amino acid sequence information of the natural spider silk protein obtained from the NCBI web database or the like, an automatically synthesized oligonucleotide is linked by PCR or the like to synthesize the gene. be able to. At this time, in order to facilitate purification and confirmation of the protein, a gene encoding a protein having an amino acid sequence obtained by adding an amino acid sequence comprising a start codon and a His10 tag to the N-terminal of the above amino acid sequence may be synthesized. .. As the expression vector, a plasmid, phage, virus or the like that can express a protein from a DNA sequence can be used. The plasmid type expression vector is not particularly limited as long as it can express a target gene in a host cell and can amplify itself. For example, when Escherichia coli Rosetta (DE3) is used as a host, pET22b(+) plasmid vector, pCold plasmid vector or the like can be used. Among them, it is preferable to use the pET22b(+) plasmid vector from the viewpoint of protein productivity. As the host, for example, animal cells, plant cells, microorganisms and the like can be used, and it is preferable to use microorganisms as the host for production in terms of production efficiency and simplicity.

The polypeptide produced by the above-mentioned production method can be made into a spinning solution in which a soluble solvent is added to adjust the viscosity so that it can be spun, and can be made into an unextended yarn by wet spinning.

The solvent is not particularly limited as long as it is a solvent capable of dissolving the polypeptide, and for example, when the polypeptide is derived from the spider Spider, as an example, hexafluoroisopropanol (HFIP), hexafluoroacetone (HFA), formic acid, An aqueous solution containing urea, guanidine, sodium dodecyl sulfate (SDS), lithium bromide, calcium chloride, lithium thiocyanate, etc. is used as a solvent, and an appropriate amount is added to obtain a spinning solution having a solution viscosity of 100 to 10,000 cP (centipoise).

By performing wet spinning for the spinning, the solvent in which the polypeptide is dissolved can be removed (also referred to as desolvation), and an undrawn yarn can be obtained. The coagulating liquid used for the wet spinning may be any solution as long as it can remove the solvent. When the solvent is HFIP, the coagulating liquid is preferably a lower alcohol having 1 to 5 carbon atoms such as methanol, ethanol or 2-propanol, or acetone. Here, the temperature of the coagulating liquid is preferably 0 to 30° C. because spinning is stable.

An unstretched yarn is obtained by extruding the spinning solution into a coagulating solution. In the case of a syringe pump having a nozzle with a diameter of 0.1 to 0.6 mm, the extrusion speed is preferably 0.2 to 2.4 ml/h per hole, and 0.6 to 2.2 ml/h, because spinning is stable. h is more preferable. Further, since the solvent can be efficiently removed, the length of the coagulating liquid tank is preferably 200 to 500 mm, the take-up speed of the undrawn yarn is preferably 1 to 3 m/min, and the residence time is preferably 0.01 to 0.15 min. .. Stretching (pre-stretching) may be carried out in the coagulating liquid, but in consideration of evaporation of the lower alcohol, it is preferable to keep the coagulating liquid at a low temperature and take it out in the state of undrawn yarn.

By drawing the undrawn yarn, a fibroin fiber containing a polypeptide derived from a natural spider silk protein is obtained. Although the stretching method is not particularly limited, it is preferable to stretch by the multi-stage stretching described in Japanese Patent No. 5540166, since a fibroin fiber excellent in tensile modulus, toughness, breaking strength and elongation at break can be obtained.

The fibroin fiber is preferably 1500 to 9000 dtex, more preferably 1500 to 5000 dtex, from the viewpoint of ensuring the necessary cord strength and not being too thick and heavy.

Reinforcing Fiber Cord The reinforcing fiber cord according to the present invention is a cord composed of fibroin fiber containing a polypeptide derived from the natural spider silk protein.

Examples of the cord include a single twist cord obtained by twisting only the fibroin fiber according to the present invention, and a composite twist cord obtained by twisting the fibroin fiber and a different fiber cord. Among them, a single twist cord obtained by twisting only the fibroin fibers is preferable because the effect of the present invention can be further obtained. The method of twisting the cord is not particularly limited, and the conventional method of twisting the organic fiber cord may be appropriately adopted.

The reinforcing fiber cord according to the present invention has a predetermined tensile modulus, toughness, breaking strength and elongation at break. The tensile modulus, breaking strength and elongation at break of the reinforcing fiber cord in the present specification are the breaking strength and tensile strength of the fiber measured with a tensile tester under the conditions of a temperature of 25° C. and a relative humidity of 60%. Elastic modulus and elongation at break, and toughness is a value calculated by the following equation.
Toughness=[E/(r ² ×π×L)×1000] (unit: MJ/m ³ ).
(In the formula, E is the breaking energy (unit: J), r is the radius of the fiber (unit: mm), π is the circular constant, and L is the distance between the grippers at the time of tensile test measurement: 20 mm. )

The tensile elastic modulus of the reinforcing fiber cord is 8 GPa or more, preferably 14 GPa or more. When the tensile elastic modulus of the reinforcing fiber cord is less than 8 GPa, steering stability tends to be insufficient. Moreover, the upper limit of the tensile elastic modulus is not particularly limited.

Toughness of the reinforcing fiber cord is a 138MJ / m ³ or more, preferably 170 mJ / m ³ or more, more preferably 240 mJ / m ³ or more, more preferably 260 mJ / m ³ or more. When the toughness is less than 138 MJ/m ³ , the tire strength tends to be insufficient. The upper limit of toughness is not particularly limited.

The breaking strength of the reinforcing fiber cord is 0.35 GPa or more, preferably 0.40 GPa or more, and more preferably 0.59 GPa or more. If the breaking strength is less than 0.35 GPa, the tire strength tends to be insufficient. Moreover, the upper limit of the breaking strength is not particularly limited.

The elongation at break of the reinforcing fiber cord is 10% or more, preferably 12% or more. If the elongation at break is less than 10%, sufficient tire strength and steering stability may not be secured. Moreover, the upper limit of the elongation at break is not particularly limited.

The reinforcing fiber cord according to the present invention is a reinforcing cord used in a pneumatic tire, and can be used as a reinforcing cord such as a carcass cord, a chafer cord, and a band cord in which an organic fiber cord has been conventionally used. .. Further, it may be used as a breaker cord or a bead wire which has conventionally been made of a steel cord. Among them, it is preferable to use the carcass cord, which has a great influence on the tire strength and the steering stability, from the viewpoint that the effect of the present invention can be more exerted.

The pneumatic tire of the present invention can be manufactured by an ordinary method using a reinforcing fiber cord composed of a predetermined fibroin fiber containing a polypeptide derived from the natural spider silk protein. That is, a predetermined tire member is molded by topping the reinforcing fiber cord with a rubber composition for cord topping, and is bonded together with another tire member on a tire molding machine, and molded by a usual method. The pneumatic tire of the present invention can be manufactured by forming an unvulcanized tire and heating and pressurizing the unvulcanized tire in a vulcanizer.

The rubber composition for cord topping is not particularly limited, and a conventional rubber composition for cord topping can be used. Among them, it is preferable to use a rubber composition for cord topping containing 3 parts by mass or more of sulfur with respect to 100 parts by mass of the rubber component, because the adhesive property between the reinforcing fiber cord and the rubber composition is excellent. ..

The pneumatic tire of the present invention, which is composed of a fibroin fiber containing a polypeptide derived from a natural spider silk protein and has a reinforcing fiber cord showing predetermined physical properties, is excellent in tire strength and steering stability, and therefore for a passenger car. It can be suitably used for tires, truck bus tires, light truck tires, motorcycle tires, and the like.

The present invention will be described based on examples, but the present invention is not limited to the examples.

The fibers used in Examples and Comparative Examples are shown below.
Spider fiber fibroin fiber: 840 dtex/2f, fiber containing 95% by mass of ADF3-derived polypeptide derived from N. spider 66 Nylon fiber: 840 dtex/2f
PET (polyethylene terephthalate) fiber: 840 dtex/2f
Aramid fiber: 840dtex/2f
Rayon fiber: 840dtex/2f
Silk thread fibroin fiber: 840dtex/2f

The following evaluation was performed on each of the above fibers. The results are shown in Table 1.

Examples and Comparative Examples A cord was produced by twisting the fibers shown in Table 1 with an upper twist number of 20 turns/10 cm and a lower twist number of 20 turns/10 cm. A test tire (size: 195/65R15) was produced using the obtained cord as a carcass cord. As the tire members other than the carcass cord, in all the examples and comparative examples, members formed of a general cord and a rubber composition having a general composition were used in a unified manner. The following evaluation was performed about the obtained tire. The results are shown in Table 1.

<Measurement of physical properties of cord>
Under the conditions of a temperature of 25° C. and a relative humidity of 60%, a tensile tester (AUTOGRAPH AGS-5kNX manufactured by Shimadzu Corporation) was used to measure the tensile elastic modulus, the breaking strength, and the elongation at break, according to the following formulas. The toughness was calculated.
Toughness=[E/(r ² ×π×L)×1000] (unit: MJ/m ³ ).
(In the formula, E is the breaking energy (unit: J), r is the radius of the fiber (unit: mm), π is the circular constant, and L is the distance between the grippers at the time of tensile test measurement: 20 mm. )

<Raw material biomass>
When each fiber raw material was made into biomass, "○" was given, and when it was not made into biomass, "X" was given.

<Environmental load during manufacturing>
The environmental load in each fiber manufacturing process was evaluated according to the following criteria.
Low: Environmentally hazardous substances are not produced in the manufacturing process High: Environmentally hazardous substances are produced in the manufacturing process

<Tire strength>
Each test tire was assembled on a 15×6 JJ aluminum wheel rim, and a plunger destructive test according to JIS D4230 was performed under the condition of being filled with an internal pressure of 300 kPa (plunger diameter 38 mm, pushing speed 50.0 m). /S). The breaking energy at that time was compared by an index with Example 1 being 100. The larger the value, the better the tire strength.

<Steering stability>
Each test tire was assembled on a 15 x 6JJ aluminum wheel rim, filled with an internal pressure of 210kPa (same for front and rear), and mounted on four wheels of a domestic FF vehicle with a displacement of 2000cc, and one driver was on the test course. Sensory evaluation was performed by driving. The index was evaluated with the index of Example 1 being 100. The larger the value, the better the steering stability.

From the results in Table 1, according to the pneumatic tire using the reinforcing fiber cord made of the predetermined fibroin fiber containing the polypeptide derived from the natural spider silk protein, the fiber derived from a resource other than petroleum is used as the reinforcing fiber cord. It can be seen that the tire has excellent tire strength and steering stability despite being used.

Claims (3)

A pneumatic tire having a reinforcing fiber cord topped with a rubber composition for cord topping,
The reinforcing fiber cord is composed of fibroin fiber containing a polypeptide derived from a natural spider silk protein,
A pneumatic tire having a tensile modulus of 8 GPa or more, a toughness of 300 MJ/m ³ or more, a breaking strength of 0.35 GPa or more, and an elongation at break of 10% or more. The pneumatic tire according to claim 1, wherein the reinforcing fiber cord is a carcass cord. The pneumatic tire according to claim 1 or 2, wherein the rubber composition for cord topping contains 3 parts by mass or more of sulfur with respect to 100 parts by mass of a rubber component.