Frictional power transmission belt
The present invention relates to a frictional power transmission belt containing an extensible layer to form a belt back surface, a compressive layer formed on one surface of the extensible layer and having a power transmission surface at least a part of which can be in contact with pulleys, and a tension member embedded between the extensible layer and the compressive layer along a belt length direction, in which at least the compressive layer is formed of a rubber composition containing a polymer component, short fibers and a surfactant and in which the short fibers contain at least short fibers of water-absorbing fibers.
1. A frictional power transmission belt comprising:
an extensible layer to form a belt back surface,
a compressive layer formed on one surface of the extensible layer and having a power transmission surface at least a part of which is configured to contact with pulleys, and
a tension member embedded between the extensible layer and the compressive layer along a belt length direction,
wherein at least the compressive layer is formed of a rubber composition comprising a polymer component, short fibers and a surfactant,
wherein the content of the polymer component in the rubber composition is in a range of 45% to 55% by weight, and the polymer component comprises an ethylene-α-olefin elastomer,
wherein the short fibers comprise at least water-absorbing fibers,
wherein the short fibers and the surfactant exist to be exposed out to a surface of at least a part of the power transmission surface, and the surfactant adheres to a surface of at least a part of the exposed short fibers, and
wherein the mean length of the short fibers is 2 mm to 30 mm.
2. The frictional power transmission belt according to claim 1 , wherein the short fibers further comprise reinforcing fibers.
3. The frictional power transmission belt according to claim 2 , wherein the water-absorbing fibers comprise cellulosic fibers, the reinforcing fibers comprise at least one type of fibers selected from polyester fibers and polyamide fibers, and the surfactant comprises a nonionic surfactant.
4. The frictional power transmission belt according to claim 2 , wherein the short fibers comprise the water-absorbing fibers and the reinforcing fibers in a weight ratio of former/latter of from 10/90 to 50/50.
5. The frictional power transmission belt according to claim 1 , wherein the surfactant comprises a polyethylene glycol-type nonionic surfactant having a hydrophile-lipophile-balance (HLB) value of from 8.7 to 17.
6. The frictional power transmission belt according to claim 1 , wherein the surfactant is selected from polyoxyethylene C 10-26 alkyl ethers, alkylphenol-ethylene oxide adducts and polyalcohol C 10-26 fatty acid ester-ethylene oxide adducts, and has a hydrophile-lipophile-balance (HLB) value of from 9 to 15.
7. The frictional power transmission belt according to claim 1 , wherein the surfactant has a melting point of 20° C. or lower and a boiling point of 180° C. or higher.
8. The frictional power transmission belt according to claim 1 , wherein, relative to 100 parts by weight of the polymer component in the rubber composition, a proportion of the surfactant is from 0.1 to 12 parts by weight and a proportion of the water-absorbing fibers is from 1 to 20 parts by weight.
9. The frictional power transmission belt according to claim 1 , wherein a weight ratio of the short fibers of water-absorbing fibers to the surfactant is, as the former/latter, from 15/1 to 0.8/1.