JP3122197B2 - Polyurethane composition for power transmission belt and power transmission belt using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane composition used for a polyurethane belt and a power transmission belt containing the same as a main component.

[0002]

2. Description of the Related Art Conventionally, toothed belts for high-load transmission have been used for driving large-sized processing machines such as machine tools and molding machines. Conventionally, a toothed belt having a structure in which a glass fiber core body as a tensile member is buried in rubber and the tooth surface is reinforced with a nylon woven fabric has been used. However, in recent years, there has been an increasing demand for toothed belts that can be used under even higher load conditions. In response to this, a polyurethane resin having a strength higher than that of rubber is used, and a core of aramid fiber is contained in the polyurethane resin belt body. Attempts have been made to cope with high-load conditions by embedding the steel and further reinforcing the teeth with a woven or nonwoven fabric.

In such a polyurethane belt, there are demands for lowering the friction coefficient μ, lowering the noise, lowering the bending fatigue resistance, and the like. For the purpose of reducing the μ and the noise, it is conventionally known to add an aliphatic amide, an aromatic amide, Teflon (registered trademark) or paraffin to a lubricant as a composition of a belt. Further, Japanese Unexamined Utility Model Publication No. 57-194946 proposes that a lubricant such as graphite, Teflon (registered trademark), resin powder, paraffin, molybdenum disulfide, wood wax or the like be mixed into polyurethane. . Further, Japanese Patent Application Laid-Open No. 3-346 discloses that a timing belt is composed of a composition obtained by adding a fatty alcohol ester to a polyurethane elastic body.

On the other hand, in order to increase the bending fatigue resistance of the belt, it is known that the ratio of the number of moles of the active hydrogen groups of the crosslinking agent to the number of isocyanate groups of the polyurethane polymer is set to around 1.

[0005]

However, in the above-mentioned conventional technology, it is difficult to simultaneously achieve a reduction in μ and noise and an increase in bending fatigue resistance, and only one of them achieves the object. Can not.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve a polyurethane composition for a power transmission belt so as to reduce the μ of the polyurethane power transmission belt, reduce noise, and bend fatigue resistance. And to increase the sexuality at once.

[0007]

In order to achieve this object, according to the invention of claim 1, a polyurethane composition for a power transmission belt comprises a higher fatty acid having 13 or more carbon atoms and a higher fatty acid having 8 carbon atoms.
A mixture of more liquid and powdery higher fatty acid esters composed of a higher alcohol and additives, urethane
Of a cross-linking agent for isocyanate groups
The ratio of the number of moles of active hydrogen groups is set to 0.97 to 1.1.

According to a second aspect of the present invention, the power transmission belt is a belt containing the polyurethane composition of the first aspect as a main component.

[0009]

According to the above construction, in the invention of claim 1 or 2, since the polyurethane composition for the power transmission belt has as an additive a mixture of liquid and powdery higher fatty acid esters, the higher fatty acid ester Precipitation (bloom or bleed) can reduce μ and maintain it.

Also, urethane prepolymer isocyanate
Since the ratio of the number of moles of the active hydrogen groups of the cross-linking agent to the salt groups is 0.97 to 1.1, the cross-linked structure, that is, the branched structure of the polymer is reduced, and the linear structure is strengthened. In addition, since the powdery solid low-μ additive is dispersed in the composition, even if cracks occur, they are prevented from growing, and these can increase the bending fatigue resistance.

Further, since the higher fatty acid ester as an additive is partly liquid, low noise can be ensured by this liquid one. Therefore, by the above synergistic action, it is possible to simultaneously reduce the μ and the noise of the polyurethane transmission belt and increase the bending fatigue resistance.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a toothed belt B for high-load transmission according to one embodiment of the present invention. This belt B has basically the same configuration as a conventional toothed belt, and has an inner surface with a constant pitch. A belt body 1 made of a polyurethane composition having tooth portions 2, 2,... Is embedded along a bottom of each tooth portion 2 of the belt body 1 with a core body 3 made of aramid fiber as a tensile member. I have. Further, a reinforcing material layer 4 made of a woven fabric, a knitted fabric, a nonwoven fabric, or the like is formed on each tooth portion 2.

The feature of the present invention lies in the polyurethane composition constituting the belt body 1. That is, the polyurethane composition has a mixture of a liquid or powdery higher fatty acid ester composed of a higher fatty acid having 13 or more carbon atoms and a higher alcohol having 8 or more carbon atoms as an additive, and a urethane prepolymer. No shishi
The ratio of the number of moles of active hydrogen groups of the crosslinking agent to the number of anate groups is set to 0.97 to 1.1.

Accordingly, in this embodiment, since the polyurethane composition of the belt body 1 uses a mixture of liquid and powdery higher fatty acid esters as an additive, the higher fatty acid ester is precipitated by bloom or bleed. , The belt B can be reduced and maintained.

The urethane prepolymer isocyanate
Since the ratio of the number of moles of the active hydrogen groups of the crosslinking agent to the salt groups is 0.97 to 1.1, the crosslinked structure of the polymer, that is, the branched structure is reduced, and the linear structure is strengthened. Since the solid low-μ additive is dispersed in the composition, even if cracks occur, they are prevented from progressing, and the synergistic effect thereof can increase the bending fatigue resistance.

Further, since the higher fatty acid ester as an additive is partly liquid, low noise can be ensured by this liquid one. In addition, since the liquid higher fatty acid ester has an extremely low viscosity, the holding power as an intervening layer interposed between the polyurethane and the pulley is weak. For this reason, in a toothed belt that performs meshing transmission, by increasing the amount of the powdered higher fatty acid ester added, it is possible to add viscosity to the intervening layer and increase the holding force,
Effective for reducing noise.

The present inventor made a plurality of test specimens with various additives of the polyurethane composition, and performed evaluation tests on the low μ property and the low μ retention property. The test apparatus is as shown in FIG. 2. A test piece T as a belt is hung on a pulley P made of S-45C having a pulley diameter of 19.54 mm, and a 1.6 kgf weight W is suspended at one end of the pulley P. Was measured at a peripheral speed of 1.84 m / sec, and the results in Table 1 below were obtained.

[0018]

[Table 1]

Regarding the bending fatigue resistance, four types of test pieces T1 to T4 were prepared, and the gripping interval of the test pieces T1 to T4 was set to 7 using a dematcher bending test apparatus with a 2 mm notch.
The test was performed so that the distance from 5 mm to 60 mm when bent. Table 2 shows the results.

[0020]

[Table 2]

FIG. 3 shows a test device for noise measurement. This test apparatus is provided with drive and driven pulleys P1 and P2 composed of 28T pulleys arranged vertically, and test pieces TA to TC composed of three kinds of belts between both pulleys P1 and P2.
And a lower driven pulley P2 is loaded with a load of 160 kgf downward, and the upper drive pulley P1 is
Driven pulley P2 when rotated at 1000 rpm
The noise at a position 300 mm laterally on the axis of rotation was measured with a microphone. Test pieces TA to TC are 15 mm wide, 10
It is a 0T S14M type belt. The background noise is 62dB
And the equivalent noise level was corrected by the audibility correction (A).
Table 3 shows the results.

[0022]

[Table 3]

From these results, it can be seen that the belt of the present invention has a low μ.
It can be seen that all of the properties, low noise and bending fatigue resistance can be satisfied.

Although the above embodiment is applied to a toothed belt, the present invention can be applied to other transmission belts.

[0025]

As described above, according to the first or second aspect of the present invention, as a polyurethane composition for a power transmission belt,
A mixture of a liquid or powdery higher fatty acid ester composed of a higher fatty acid having 13 or more carbon atoms and a higher alcohol having 8 or more carbon atoms, as an additive, a urethane prepolymer
The ratio of the number of moles of the active hydrogen groups of the crosslinking agent to the isocyanate groups of-
A power transmission belt composition that satisfies all of low noise and bending fatigue resistance can be obtained.
, Low noise, and increased bending fatigue resistance can be achieved.

[Brief description of the drawings]

FIG. 1 is a partial front view of a toothed belt according to an embodiment of the present invention.

FIG. 2 is a schematic view of an apparatus for evaluating and testing the low μ property of a belt and its holding property.

FIG. 3 is a schematic view of an apparatus for evaluating and testing low noise of a belt.

[Explanation of symbols]

 B Toothed belt 1 Belt body 2 Tooth

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-68348 (JP, A) JP-A-3-346 (JP, A) JP-A-51-50351 (JP, A) JP-A 50-1983 76165 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F16G 1/00-5/20 C08K 3/00-13/08 C08L 1/00-101/16

Claims (2)

(57) [Claims] 1. A higher fatty acid having 13 or more carbon atoms and 8 higher carbon atoms.
A mixture of liquid and powdery higher fatty acid esters composed of the above higher alcohols is used as an additive to crosslink the urethane prepolymer to isocyanate groups.
A polyurethane composition for a power transmission belt, wherein the ratio of the number of moles of active hydrogen groups of the agent is 0.97 to 1.1. 2. A power transmission belt comprising the polyurethane composition according to claim 1 as a main component.