JPH0425882B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a tire tube for two-wheeled vehicles that is mainly composed of a thermoplastic polyurethane elastomer and has excellent blocking resistance. (Prior art) Butyl rubber has traditionally been mainly used for tire tubes for motorcycles, bicycles, etc., but butyl rubber has low strength and poor abrasion resistance, making it prone to punctures, and moreover, it is susceptible to ozone in the atmosphere. The problem is that the material deteriorates over time. Therefore, in recent years, tubes made of thermoplastic polyurethane elastomer, which have many excellent properties such as elasticity, flexibility, abrasion resistance, aging resistance, and mechanical strength, have been proposed in place of such butyl rubber tubes. (JP-A-54-122507, JP-A-56-39805) However, as is well known, thermoplastic polyurethane elastomers tend to block at relatively low temperatures below 60°C, so they are difficult to block during tube molding. Even if a tire is left flat in direct sunlight for a long time, the inner surfaces of the tube may block against each other, and in extreme cases, there is a risk that they will fuse together and lose their function as a tire tube. (Problems to be Solved by the Invention) The present invention solves the problems seen in the conventional tubes made of thermoplastic polyurethane elastomer as described above, and its purpose is to It has excellent elasticity, flexibility, abrasion resistance, aging resistance, and mechanical strength, as well as excellent blocking resistance without sacrificing properties such as joint workability and puncture repairability, which are essential for motorcycle tire tubes. An object of the present invention is to provide an improved tire tube for a two-wheeled vehicle. (Means for Solving the Problems) As a specific means for improving the blocking resistance of thermoplastic polyurethane elastomer tubes, the present inventors have proposed a method in which an anti-blocking agent such as starch fine particles is attached to the inner surface of the tube. As a result of intensive study on methods of laminating various synthetic resins on the inner surface of the tube, we found that laminating a modified thermoplastic polyurethane elastomer containing a specific synthetic resin on the inner surface of the tube would only improve blocking resistance. The present invention was completed based on the conclusion that this is the best method in that it can simultaneously satisfy the performance requirements unique to motorcycle tire tubes, such as tire jointing and puncture repair. That is, the present invention provides polyolefin resins, polyester resins, polyamide resins, acrylic resins, polyvinyl chloride resins, and ethylene-vinyl resins that can be blended with the thermoplastic polyurethane elastomer on the inner surface of a tube made of a thermoplastic polyurethane elastomer. Contains at least 80% by weight of at least one synthetic resin selected from alcohol resins, polycarbonate resins, and acrylic modified vinylidene fluoride resins, and JISZ1515
A motorcycle tire tube characterized in that a layer made of a modified thermoplastic polyurethane elastomer with a blocking resistance of 60°C or higher measured according to This is related. In the present invention, the thermoplastic polyurethane elastomer constituting the tube body is a thermoplastic rubber-like elastic polymer containing a urethane group in its molecular structure whose main raw materials are bifunctional polyol, diisocyanate, and glycol. It is a general term for thermoplastic polyurethane elastomers such as adipate ester, polyether, caprolactone ester, and polycarbonate ester types, which are distinguished depending on the type of raw materials such as the polyols used. includes, but
Among these, polyether-based thermoplastic polyurethane elastomers are preferred, as they have excellent water resistance and weather resistance, and have relatively low permanent elongation. The thermoplastic polyurethane elastomer may contain other additives such as polyolefin, polyvinyl chloride, polyester, etc., within a range that does not significantly impair its properties such as elasticity, flexibility, abrasion resistance, aging resistance, and mechanical strength. There is no problem even if less than 5% by weight of resin such as polyamide or acrylic is added. On the other hand, the modified thermoplastic polyurethane elastomer used in the present invention is laminated on the inner surface of the tube made of the thermoplastic polyurethane elastomer constituting the tube body, thereby improving the seaming processability that is essential for a motorcycle tire tube. , a polyolefin resin that can be blended with the thermoplastic polyurethane elastomer because it must be able to improve blocking resistance without impairing properties such as puncture repairability;
At least one synthetic resin selected from polyester resins, polyamide resins, acrylic resins, polyvinyl chloride resins, ethylene-vinyl alcohol resins, polycarbonate resins, and acrylic-modified vinylidene fluoride resins up to 80% by weight It must be a modified thermoplastic polyurethane elastomer with a blocking resistance of 60°C or higher as measured in accordance with JIS Z1515. In the present invention, the effect achieved by configuring the resin laminated on the inner surface of the tube with a modified thermoplastic polyurethane elastomer obtained by blending a thermoplastic polyurethane elastomer with the above-mentioned synthetic resin is the anti-blocking layer laminated on the inner surface of the tube. Compared to a case where the thermoplastic polyurethane elastomer is composed of a single synthetic resin, it has excellent thermal adhesion with the thermoplastic polyurethane elastomer body, that is, it has excellent interlayer strength after lamination, and it is also easy to join tubes and repair punctures. That is, the motorcycle tire tube according to the present invention is manufactured by cutting a material tube into a predetermined length using a method such as extrusion molding, attaching pulp rubber seats, and then joining both ends of the material tube to form a ring shape. However, the tubes are usually joined by butting the cross sections of both ends of the heat-cut tubes, so if a layer of different resin is involved, the strength of the joint will weaken, leading to punctures and bursts. In addition to this, there is also the problem that sufficient adhesive strength cannot be obtained when repairing punctures. Therefore, if the blend ratio of the synthetic resin to the thermoplastic polyurethane elastomer exceeds 80% by weight, the interlaminar strength between the thermoplastic polyurethane elastomer and the main body will be weak, and it will be susceptible to harsh conditions such as impact, twisting, compression, and bending that are characteristic of motorcycle tire tubes. Not only will it not be able to withstand the conditions of use, but the joint strength during the tube joining process will be insufficient, making it more likely to cause punctures and bursts, and it will also be difficult to repair punctures, leading to other inconvenient problems. Among the synthetic resins used in the present invention, the polyolefin resin may be any resin as long as it can be blended with the thermoplastic polyurethane elastomer, but it is usually made by copolymerizing ethylene with other vinyl monomers, such as ethylene- These include vinyl acetate copolymer resin, ethylene/ethyl acrylate copolymer resin, ethylene/methyl methacrylate copolymer resin, and ethylene/acrylic acid ester/maleic anhydride ternary copolymer resin. Examples of polyester resins include poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene terephthalate/isophthalate), and poly(ethylene glycol/cyclohexanedimethanol/terephthalate), among which the melting point is high. Isophthalic acid, part of the dicarboxylic acid component or diol component is added to the same level as the plastic polyurethane elastomer.
Copolyester resins modified with adipic acid, sebacic acid, cyclohexanedimethanol, neopentyl glycol, etc. are suitable. Furthermore, in the present invention, in addition to the above synthetic resins, polycapramide (nylon-6), polyundecaneamide (nylon-11), polylauryllactam (nylon-12), polyhexamethylene adipamide (nylon-6.6), poly Polyamide resins such as hexamethylene dodecamide (nylon-6.12),
Acrylic resins such as polymethyl methacrylate and polyacrylonitrile, polyvinyl chloride resins, polyvinyl chloride resins such as polyvinyl chloride-vinylidene chloride copolymer resins, ethylene content 20 to 50 mol%
Ethylene-vinyl alcohol resin with a saponification degree of 95% or more, polycarbonate resin, and vinylidene fluoride polymer, polymethyl methacrylate,
A synthetic resin such as an acrylic modified vinylidene fluoride resin blended with polyethyl methacrylate, polymethyl acrylate, etc. can be used. In the present invention, the thermoplastic polyurethane elastomer to be blended with these synthetic resins is preferably the same as the thermoplastic polyurethane elastomer constituting the tube body because it has excellent thermal adhesive properties, but a different type may also be used. Needless to say. It is also essential that the modified thermoplastic polyurethane elastomer used in the tire tube of the present invention has a degree of blocking resistance of 60°C or higher. The reason for this is that in cases where a process of pressing with pinch rolls is required during take-up and winding during the tube forming process, it is necessary at least to prevent blocking between the inner surfaces of the tube caused by the pressing. It is necessary to have a blocking resistance of 60℃ or higher, and when transporting or storing the tube, the tube must be degassed, flattened, and left in that state for a long period of time. To prevent blocking,
The degree of blocking resistance must be 60℃ or higher, and furthermore, blocking in the event of a puncture is caused by a combination of heat stored in the wheel rim and radiant heat coming from the ground, rather than by heat directly applied to the tube from the outside temperature. This is based on the knowledge that in order to solve this type of blocking problem, the degree of blocking resistance must be at least 60°C, preferably at least 80°C. Therefore, if a modified thermoplastic polyurethane elastomer having a degree of blocking resistance lower than 60° C. is laminated on the inner surface of the tube, a sufficient effect in improving the blocking resistance cannot be exhibited. In the present invention, with regard to the thickness of the modified thermoplastic polyurethane elastomer laminated on the inner surface of the tube, if the thickness is too thin, the effect of improving blocking resistance due to expansion and contraction of the tube will be insufficient; If the resin is too thick, the elasticity and flexibility will deteriorate and the riding feeling of the motorcycle tire tube will be poor.The thickness varies depending on the type and amount of resin added, but Generally 0.3 to 50%, preferably 1 to 50%
The thickness ratio is 30%. In addition, coextrusion is the most preferable method for laminating such modified thermoplastic polyurethane elastomer on the inner surface of the tube made of thermoplastic polyurethane elastomer, and in this case, appropriate adhesiveness is required between the two resins to improve adhesiveness. A resin may also be used. Additionally, appropriate additives such as lubricants, ultraviolet absorbers, antioxidants, colorants, etc. may be added to the thermoplastic polyurethane elastomer and modified thermoplastic polyurethane elastomer constituting the tire tube of the present invention, if necessary. do not have. (Examples) Hereinafter, in order to make it easier to understand the tire tube for two-wheeled vehicles of the present invention, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 4, Comparative Examples 1 to 2 The difunctional polyol component was polytetramethylene glycol, the diisocyanate component was 4.4' diphenylmethane diisocyanate, and the glycol component was
1.4 A polyether-based thermoplastic polyurethane elastomer raw material (Elastan E385 manufactured by Nippon Elastran Co., Ltd.) made of butanediol was put into the first extruder (screw diameter 50φ) and the second extruder (screw diameter 25φ). A modified thermoplastic polyurethane elastomer raw material prepared by blending 70% by weight of the same thermoplastic polyurethane elastomer with 30% by weight of various synthetic resins shown in Table 1 was supplied and melt-kneaded, respectively, and the total extrusion amount was about 15 Kg/hr. A layer 540 made of thermoplastic polyurethane elastomer with a fold diameter of 20 mm and a thickness of 20 mm is formed by introducing the two layers into a circular die having the same die and joining them inside the die, and then taking it off at a speed of about 6 m/min. A two-layer tube was prepared in which the layer made of modified thermoplastic polyurethane elastomer was 60 microns thick. For comparison, we used the same thermoplastic polyurethane elastomer raw material as above to measure the thickness.
A tube with a folded diameter of 28 mm was fabricated from only 600 micron thermoplastic polyurethane elastomer.
(Comparative Example 2) The tubes obtained in these Examples and Comparative Examples were subjected to a blocking test under direct sunlight in summer (temperature 35°C) by applying a static load of approximately 5 kg/cm ² to the tubes. It is shown in Table 1. As can be seen from the same table, tubes in which a modified thermoplastic polyurethane elastomer having a degree of blocking resistance within the range of the present invention was laminated on the inner surface of a thermoplastic polyurethane elastomer exhibited no blocking at all and were extremely suitable as tire tubes for two-wheeled vehicles.

[Table] Examples 5 to 9, Comparative Examples 3 to 4 Modified thermoplastic polyurethane elastomers were prepared in the same manner as in Example 2, except that the blend ratio of thermoplastic polyurethane elastomer and ethylene ethyl acrylate copolymer resin was varied. Folding diameter 28
A two-layer tube with a thickness of 540 μm for the layer made of thermoplastic polyurethane elastomer and 60 μm for the layer made of modified thermoplastic polyurethane elastomer was prepared. The tubes obtained in these examples and comparative examples were subjected to the same blocking test as in the above examples, and the interlaminar strength between the thermoplastic polyurethane elastomer and the modified thermoplastic polyurethane elastomer of the tube body, the joint processability of the tube,
Table 2 shows the results of a comprehensive evaluation of suitability as a tire tube for two-wheeled vehicles, including puncture repairability. From the same table, modified thermoplastic polyurethane elastomers whose blend ratio of thermoplastic polyurethane elastomer and ethylene ethyl acrylate copolymer resin and blocking resistance are within the range of the present invention show no blocking at all, and are suitable for use as motorcycle tire tubes. However, in the case where the degree of blocking resistance was outside the range of the present invention (Comparative Example 3), the effect of improving the blocking resistance was insufficient, and The one with a blend ratio outside the range of the present invention (Comparative Example 4) has a weak interlaminar strength with the thermoplastic polyurethane elastomer of the tube body, and is also inferior in bonding strength when joining the tubes together. However, it was difficult to use it as a tire tube for two-wheeled vehicles.

[Table] (Note)

[Table] Examples 10 to 13, Comparative Examples 5 to 6 Modified thermoplastic polyurethane elastomers were prepared in the same manner as in Example 3, except that the blend ratio of thermoplastic polyurethane elastomer and cyclohexanedimethanol-modified polyester copolymer resin was varied. A two-layer tube with a fold diameter of 20 mm and a thickness of 540 microns for the layer made of thermoplastic polyurethane elastomer and 60 microns for the layer made of modified thermoplastic polyurethane elastomer was prepared. The tubes obtained in these Examples and Comparative Examples were comprehensively evaluated for their suitability as tire tubes for two-wheeled vehicles through blocking tests, etc., as in the previous Examples, and the results are shown in Table 3. From the same table, modified thermoplastic polyurethane elastomers with a blend ratio of thermoplastic polyurethane elastomer and cyclohexanedimethanol-modified polyester copolymer resin and blocking resistance within the range of the present invention show no blocking at all, and motorcycle tires. It had excellent properties such as moldability and durability as a tube, but the blocking resistance was outside the range of the present invention (Comparative Example 5), and the effect of improving the blocking resistance was insufficient. In addition, the blend ratio outside the range of the present invention (Comparative Example 6) has weak interlaminar strength with the thermoplastic polyurethane elastomer of the tube body, and also has poor bonding strength when joining the tubes. Overall, it was difficult to use it as a tire tube for two-wheeled vehicles.

[Table] (Effects of the Invention) The tire tube of the present invention as described above solves the blocking resistance problem seen in conventional tubes made only of thermoplastic polyurethane elastomer.
It has properties that are essential for motorcycle tire tubes, such as the excellent elasticity, flexibility, abrasion resistance, aging resistance, and mechanical strength unique to thermoplastic polyurethane elastomers, as well as tube joint workability and puncture repairability. It was resolved without any damage. In addition, since the tire tube of the present invention is mainly composed of thermoplastic polyurethane elastomer, it not only has stronger resistance to puncture bursts than conventional butyl rubber tubes, but also has excellent cold resistance and ozone resistance. Since it far exceeds butyl rubber in these respects, it has a high industrial value as it not only significantly extends the useful life of the tube, but also allows for weight reduction and cost reduction by making the tube thinner.

Claims (1)

[Claims] 1. On the inner surface of the tube made of thermoplastic polyurethane elastomer, polyolefin resin, polyester resin, polyamide resin, acrylic resin, polyvinyl chloride resin, ethylene-vinyl alcohol resin, which can be blended with the thermoplastic polyurethane elastomer, From a modified thermoplastic polyurethane elastomer containing up to 80% by weight of at least one synthetic resin selected from polycarbonate resins and acrylic modified vinylidene fluoride resins, and having a blocking resistance of 60°C or higher as measured in accordance with JIS Z1515. The layer is coated with a thickness ratio of 0.3 to 50% of the total thickness of the tube.
Or a motorcycle tire tube characterized by being laminated.