JPH02150529A - Toothed belt - Google Patents

Abstract

PURPOSE:To improve characteristics such as durability, fatigue-resistance and so on of a toothed belt by using a special core-sheath compound fiber as a fiber forming covering cloth for reinforcing the tooth surface of a toothed belt. CONSTITUTION:Covering cloth for reinforcing the tooth surface of a toothed belt has weft and warp formed by a core-sheath compound fiber composed of the core component, the principal component of which is polyester composed of ethylene terephthalate and the sheath component, the principal component of which is polyamide wrapping the periphery of the core component. The core-sheath compound fiber is such that the percentage of the polyester core component is 30 - 90wt%, the strength is 7.5g/d or more, the elongation is 20% or less, the initial tensile resistance is 60g/d or more, and hot-air shrinkage percentage is 7% or less. Accordingly, the covering cloth has high modulus and dimensional stability, and is remarkably improved in heat resistance adhesive property and fatigue-resistance after it is subjected to and high temperature hysteresis. Thus, the toothed belt is extremely excellent in durability and can withstand severe conditions.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a toothed belt, and more specifically, the fibers forming the covering fabric that reinforces the tooth surfaces of the toothed belt are made of special fibers to improve durability. This invention relates to a toothed belt with improved characteristics such as durability and fatigue resistance.

[Prior Art] Toothed belts for power transmission in various machines, automobiles, office equipment, etc. have conventionally been provided with a reinforcing fiber fabric on the outermost layer of the tooth surface, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-147142.
The method described in the above publication is known, in which a rubber member in which at least ceramic whiskers are dispersed and blended is impregnated and adhered to a fiber member as a cover layer, and this cover layer is adhered to the surface of the belt with the rubber member exposed. and
Polyamide fibers are used as the fiber member.

[Problems to be Solved by the Invention] In the case of the above-mentioned prior art, a rubber member containing ceramic whiskers is attached to a cover fabric made of polyamide fibers, and the use of this rubber member improves the survival rate of the fabric. However, in the case of toothed belts that rotate at high temperatures and high speeds, such as automobile timing belts, the modulus and dimensional stability are poor, and the toothed belt stretches to its full extent, making the meshing with the toothed pulley unstable. However, it has not yet been put into practical use.

An object of the present invention is to improve the covering fabric that reinforces the tooth surface of the toothed belt, to improve the modulus and dimensional stability of the covering fabric, and to improve the durability and fatigue resistance of the toothed belt. .

In addition, a fabric made of polyester fiber is generally used as a covering fabric to reinforce the tooth surface of a toothed belt, but in the case of the polyester fiber fabric, although it is excellent in high strength and high elastic modulus, The problem has been that it deteriorates due to heat and its strength decreases, and that it also loses its adhesion to rubber and is easily peeled off.

Another object of the present invention is to take advantage of the advantages of the polyester fibers, such as high strength, high modulus of elasticity, and good dimensional stability. To provide a toothed belt whose tooth surfaces are coated with a fabric having excellent properties.

[Means and effects for solving the problems] The structure of the present invention is as follows: (1) A belt body made of rubber or elastic resin in which a tensile material is embedded, and a tooth surface on one side of the belt body. , in a toothed belt in which the surface of the tooth surface is covered with a fabric, the fabric covered on the surface of the tooth surface is woven in a direction substantially parallel to the length direction of the belt and/or in a direction perpendicular to the weft. It is a core-sheath type conjugate fiber consisting of a core component whose main component is polyester whose warp is made of ethylene terephthalate, and a sheath component whose main component is polyamide around the core component. The ratio of the core component is 30 to 90% by weight, the strength of the composite fiber is 7.5 C)/d or more, the elongation is 20% or less, the initial tensile resistance is 600/d or more, and the dry heat shrinkage rate is 7. % or less.

(2) The toothed fabric according to (1) above, characterized in that the core-sheath composite fiber false-twisted yarn made of polyester and polyamide is false-twisted is used as the weft to form a fabric. belt.

(3) In (1) above, a core-sheath composite fiber-covered elastic yarn in which a core-sheath composite fiber made of polyester and polyamide is covered around the elastic yarn is used as a weft to form a fabric. Toothed bell 1~.

It is in.

The composite fiber used as the reinforcing cord for the toothed belt according to the present invention has a high modulus close to that of polyester, heat resistance in rubber, and peeling durability of the polymer at the core-sheath composite interface, which were not achieved with conventional technology. , the specified birefringence, density, and DSC melting peak temperature of the polyester and polyamide fiber portions forming the core and sheath, respectively, and parameters consisting of a combination of high initial tensile resistance and low terminal modulus of the polyester core component fibers. It will be done.

In order to obtain a composite fiber strength of 7.5 o/d or more, the core component polyethylene terephthalate fiber has an intrinsic viscosity (η) of 0.
．． It has a high viscosity of 7 or more, preferably 0.8 or more.

Similar to the polyester core component, the polyamide sheath component polymer also requires a high degree of polymerization in order to obtain a high-strength conjugate fiber, and the relative viscosity of the sulfuric acid is 2.8 or more, preferably 3.0 or more.

Copper salts and other organic and inorganic compounds are added to the polyamide sheath component as thermal oxidative deterioration inhibitors. In particular, 30 to 500 pl) m of copper salts such as iodized steel, copper acetate, copper chloride, and copper stearate, and 0.0 m of alkali metal halides such as potassium iodide, sodium iodide, and potassium bromide.
It is preferable to contain 0.01 to 0.5% by weight and/or 0.01 to 0.1% by weight of an organic or inorganic phosphorus compound.

The ratio of the polyester core component of the composite fiber is 30 to 90
Weight%. If the polyester component is less than 30% by weight, a composite fiber that can effectively utilize the modulus and dimensional stability of the polyester component cannot be obtained, and a preferred reinforcing cord for a toothed belt cannot be obtained.

On the other hand, if the polyester core component accounts for 90% by weight or more, when the composite fiber is used as a reinforcing cord for a toothed belt and the cord is used as a tensile member of the toothed belt, the adhesion to rubber is poor. However, it is not possible to improve the heat resistance of reinforcing cords for toothed belts in rubber.

In the composite fiber, both the polyester core component and the polyamide sheath component are highly oriented and crystallized, and the polyester core component has a birefringence of 160X10' to 190X10.
It is desirable to keep it within the range of -3, 160X
If it is less than 10', the strength of the composite fiber may not be 7.5 a/d or more, and the initial tensile resistance may not be 6C1/d or more. Moreover, if it exceeds 190×10 −3 , dimensional stability and fatigue resistance may not be improved.

On the other hand, the birefringence of the polyamide sheath component is 50x10-3 or more, usually 55x10-3 or more, which is highly oriented. If the birefringence is less than 50×10′, it is difficult to obtain a composite fiber having high strength and high initial tensile resistance.

The birefringence of the core-sheath composite 1ef can be measured as follows. That is, the sheath portion is directly measured using a transmission interference microscope, and the core portion is measured using a transmission interference microscope after dissolving the polyamide sheath component in formic acid, sulfuric acid, fluorinated alcohol, or the like.

The density of the polyester core component is 1.395 CI/cm" or more, and the polyamide sheath component is 1.14 C1/α3 or more, and it is desirable that they are highly crystallized. By fabricating the cloth with a density of each of the above specific values or more, it is possible to The fiber has excellent dimensional stability and fatigue resistance, and when used as a reinforcing cord for a toothed belt, and when this cord is used as a tensile body of a toothed belt, the heat resistance in the rubber of the tensile body is remarkable. Improved.

The density of the polyester core component can be determined by dissolving and removing the polyamide sheath component with formic acid, sulfuric acid, fluorinated alcohol, etc., and the density of the polyamide sheath component can be calculated from the density of the composite fiber and the density of the polyester core. can.

The peak temperature of the DSC melting curve showing the characteristics of the crystal structure of the polyester core component in the composite m-fiber is 247 ° C.
The temperature is preferably 248° C. or higher. The higher the peak temperature, the larger the crystals and/or the more complete the crystals, which corresponds to the more stable the fiber structure. The melting peak temperature of the polyester core component fiber is 247
If the temperature is less than 0.degree. C., the desired modulus, dimensional stability, and fatigue resistance may not be obtained.

Another characteristic reflecting the fiber structure of the composite fiber is that the polyester core component fiber has a high initial tensile resistance of 90 o/d or more and a low terminal modulus of 20 g/d or less. Polyester IIAH with high initial tensile resistance and low terminal modulus
The characteristics of this belt are that there is little loss in strength during the toothed belt processing process and improved fatigue resistance. The terminal modulus is determined by 2.0% from the cutting elongation on the SS curve in a fiber tensile test.
The stress increment between the point on the curve subtracted by 4% and the cutting point is 2.4
It is the value (Q/d) divided by X1σ2, and the conditions of the tensile test are according to JIs-LI O'l 7.

The composite fiber characterized by the above has a high strength of 7°50/d or more, an initial tensile resistance of 6C1/d or more, and an elongation of 20% or less.

More preferable composite fiber properties are strength El/d or higher, initial tensile resistance surface 70q/d or higher, and elongation of 8 to 16%.
This is achieved by a suitable combination of the above conditions.

The composite fiber is manufactured by the novel method shown below.

In order to obtain the polymer physical properties of the polyester core component described above, a polymer consisting essentially of polyethylene terephthalate and having an intrinsic viscosity (η) of 0.75 or more, usually 0.85 or more is used. In addition, in order to obtain fibers with excellent heat resistance,
It is important to spin polymers with low carboxyl end group concentrations. For example, by adopting low temperature polymerization method, polymerization process,
Alternatively, a technique such as adding a sequestering agent during the spinning process is applied, and examples of the sequestering agent include oxabrins, epoxies, carbodiimides, ethylene carbonate, oxalic acid esters, malonic acid varnish, chills, and the like.

The polyamide sheath component polymer has a sulfuric acid relative viscosity of 2°8 or more,
Usually, a polymer with a high polymerization degree of 3.0 or more is used.

It is preferable to use two Ex1-Ruder type spinning machines for melt spinning the polymer. The polyester and polyamide polymers melted by each extruder are introduced into a composite spinning pack, and spun into a composite fiber with polyester in the core and polyamide in the sheath through a composite spinning nozzle.

The spinning speed is 1500 m/min or more, preferably 2000 m/min.
The speed should be at least 1/min. Immediately below the spinneret, a temperature of 200°C or higher, preferably 260°C, is applied for a distance of 10cm or more and within 1m.
A heated atmosphere above ℃ is created by providing a heat insulating cylinder, a heating cylinder, etc. After passing through the above heating atmosphere, the spun yarn is quenched and solidified with cold air, and then, after being applied with an oil agent, it is taken off by a take-off roll that controls the spinning speed. Control of the heating atmosphere directly below the spinneret is important in order to maintain spinnability during high-speed spinning. The bowed undrawn yarn is usually continuously drawn without being wound up. The birefringence of the undrawn yarn sampled on the take-up roll for the purpose of grasping the physical properties of the undrawn yarn before stretching is 20×10-3 or more in the polyamide sheath, preferably 30×10-3 or more, and 20×10 in the polyester core. ' or more, preferably 30×10 −3 or more, and is highly oriented.

Adoption of high-speed spinning has the effect of improving the modulus, dimensional stability, and fatigue resistance of the composite IL fiber, but surprisingly, the durability of the core-sheath composite interface is significantly improved.

Unlike the conventional low-speed spinning method, in which a polyamide component that has undergone moisture absorption and crystallization is combined with an amorphous polyester component, in the high-speed spinning method, oriented crystallization progresses in both the polyamide component and the polyester component. It is thought that the following factors contribute to the durability of the composite interface: the fact that the fiber is in the same state as before, and the stretching ratio after spinning is small.

Next, the undrawn yarn is continuously heated to 180°C or higher, preferably 2°C.
It is hot stretched at a temperature of 00°C or higher.

The stretching is carried out in two or more stages, usually three or more stages, and the stretching ratio is in the range of 1.4 to 3.5 times. The use of such high-temperature thermal stretching according to the present invention also contributes to improving the composite interface durability. The stretching temperature in the third stage of the stretching is low, for example 160
If the temperature is below 180°C, interfacial delamination between the polyester core component and the polyamide sheath component may occur during toothed belt processing and when the toothed belt is used at high speeds.

The ratio of the core component in the core-sheath type composite fiber consisting of a core component mainly composed of polyester made of ethylene terephthalate and a sheath component mainly composed of polyamide surrounding the core component is 30 to 90% by weight, Strength is 7.50/d
Above, elongation is 20% or less, initial tensile resistance is 60q/
When covering the surface of the tooth surface of a toothed belt with a fabric made of a composite fiber having a dry heat shrinkage rate of 7% or more, the composite fiber is in a state where elastic threads such as polyurethane fibers are stretched. The composite fiber-covered elastic yarn is then wrapped around the elastic yarn to form a composite fiber-covered elastic yarn, and the composite mN-covered elastic yarn, that is, the elastic yarn is woven in the longitudinal direction of the toothed belt, that is, as a weft, to obtain a fabric. Although the fabric may use conventionally known fibers such as nylon 66 filament as the weft, it is preferable to use the composite fibers used for the weft. When weaving the above-mentioned fabric, the composite fibers may be false-twisted and used in a stretchable state without being wound around the elastic threads.

The fabric using the above-mentioned elastic yarn is coated with an adhesive such as resorcinol, formalin, or latex, and then heat-treated. This heat treatment is performed while applying a constant tension to the weft yarns so that the stretchable yarns, which are the weft yarns, do not stretch.

A fabric treated with an adhesive using the stretchable yarn is wound around a cylindrical mold having a tooth shape on the outer circumferential surface with the stretch direction along the circumferential surface, and a tensile cord is wound spirally thereon,
Furthermore, after wrapping an unvulcanized rubber sheet of a certain thickness around it, the rubber is press-fitted into the tooth profile of the cylindrical mold by external pressure and heating using the Seitai molding method, and a fabric using elastic thread is molded. It is molded into a shape that follows the tooth profile and vulcanized.

[Example 1 and 2] Comparative Examples 1 to 4 Intrinsic viscosity (η) 1.05, carboxyl end group concentration 10
．． 5eQ/10”Q polyethylene terephthalate (
PET) and 0.02% by weight of iodized steel and 0.02% by weight of potassium iodide.
1 wt.
) were each melted using a 40φ Ktruder-type spinning machine, introduced into a composite spinning pack, and spun from a core/sheath composite spinneret into a composite yarn of polyethylene terephthalate in the core and polyamide in the sheath.

The proportions of the core and sheath components were varied as shown in Table 1.

The cap used had a hole diameter of 0.4 ψ and a number of holes of 45. Polyethylene terephthalate and polyamide were melted at a temperature of 295°C and 290°C, respectively, and the spinning pack temperature was set at 300°C for spinning. A 15 c#l heating cylinder was attached directly below the mouthpiece, and the cylinder was heated to an atmospheric temperature of 290°C. The ambient temperature is the ambient temperature measured at a position 10 cm below the mouth surface and 1 ctn away from the outermost thread. There is a length of 400 mm under the heating cylinder.
# Attach a circular chimney and keep the temperature at 25°C from around the yarn.
The yarn was cooled by blowing cold air at a rate of 40 m/min at right angles to the yarn. After applying an oil agent, the yarn speed was controlled with a take-up roll rotating at the speed shown in Table 1, and then the yarn was drawn continuously without being wound up. The film was stretched in three stages using five pairs of Nelson type rolls, then subjected to a relaxation heat treatment with 3% relaxation, and then wound up. The stretching conditions are: take-up roll temperature of 60°C, first stretching roll temperature of 120°C, second stretching roll temperature of 190°C, and third stretching roll temperature of 225°C.
The tension adjustment roll after stretching was not heated, the first stage stretching ratio was 70% of the total stretching ratio, and the remaining stretching ratio was divided into two stages. The spinning speed, total draw ratio, etc. were varied to produce yarn, and the discharge amount was varied in accordance with the spinning speed and draw ratio so that the fineness of the drawn yarn was about 250 denier. (Examples 1 and 2) Comparative example 1, 2). Two of the obtained drawn yarns were combined into a 500 denier yarn.

The spinning conditions, the obtained drawn yarn properties, and the fiber structure parameters were determined using polyethylene terephthalate (PET) fiber (5
00-96-702G> (Comparative Example 3) and Nylon 66
A comparative test was conducted on the fiber (42068) (Comparative Example 4).

Each condition and fiber properties are as shown in Table 1.

(Hereinafter, blank space) After heating each of the five types of fibers shown in Table 1 above,
Operon thread (polyurethane elastic thread made by DuPont Azuma > 1
40D was stretched 3.5 times and wound to obtain an elastic yarn. The number of windings was set so that the number of windings was 200 times/m when the stretched operon thread was unwound.

The above-mentioned elastic yarn is used as the warp, and nylon 6 is used as the warp.
Weaving was carried out using 6 210D filaments. The weave structure is 2/2 twill weave, and the weave density in the relaxed state is 15 warp.
The fabric had 150 lines and 15 lines with 0 lines and 15 CIR and 1 weft. Resorcin, formalin, and latex were applied to the fabric and heat-treated. The dip liquid contained an adhesive component consisting of 20% resorcinol, formalin, and latex, and was adjusted so that about 4% of the adhesive component adhered to the cord. Heat treatment is 2
It was treated at 25°C for 80 seconds. Next, the obtained fabric is wrapped so that the wefts are aligned in the direction of the tooth surface of the cylindrical mold, and an unvulcanized rubber sheet is wound on top of it (usually a high A tensile material such as a strong nylon cord is arranged, but in order to evaluate the fabric itself, this tensile material was excluded.) Rubber is pressurized and heated from the outside to fit into the tooth profile of a cylindrical mold, and then vulcanized. did. The obtained toothed cylindrical body was cut into a width of 4 CII in the weft direction to create a toothed belt. Regarding the weft in the obtained toothed belt,
Its physical properties were measured. The results were as shown in Table 2.

(The following is a blank space) In the toothed belt according to the present invention, the reinforcing fibers used as the warp of the fabric on which the surface of the tooth surface is covered are composed of a core component mainly composed of polyester and a sheath component mainly composed of polyamide. A new reinforcing material with special properties consisting of This shows that it is a high-strength reinforcing material with significantly improved heat resistance, adhesion resistance, and fatigue resistance.
The modulus and dimensional stability are significantly improved compared to reinforcing materials made of

[Effects of the Invention] In the toothed belt according to the present invention, the warp of the fabric coated on the tooth surface has a modulus and dimensional stability equal to or higher than that of polyester, heat resistance in rubber, Adhesion properties, especially heat-resistant adhesion properties after being subjected to high-temperature history, and fatigue resistance are significantly improved. Therefore, the toothed belt according to the present invention has extremely excellent durability and can withstand severe conditions.

Claims (3)

[Claims] (1) A toothed belt having a belt body made of rubber or elastic resin with a tensile material embedded therein, a tooth surface on one side of the belt body, and the surface of the tooth surface covered with a fabric, A core component whose main component is polyester, the weft threads substantially parallel to the length direction of the belt of fabric coated on the surface of the tooth surface and/or the warp threads woven in a direction perpendicular to the weft threads, are made of ethylene terephthalate; It is a core-sheath type composite fiber consisting of a sheath component mainly composed of polyamide surrounding the core component, and the proportion of the polyester core component in the core-sheath type composite fiber is 30 to 90% by weight, and A toothed belt characterized by being formed of fibers having a strength of 7.5 g/d or more, an elongation of 20% or less, an initial tensile resistance of 60 g/d or more, and a dry heat shrinkage rate of 7% or less. . (2) Claim (1) states that a fabric is formed by using a core-sheath composite fiber false-twisted yarn, which is a core-sheath composite fiber made of polyester and polyamide, as a weft. Features a toothed belt. (3) In claim (1), a core-sheath composite fiber-covered elastic yarn in which a core-sheath composite fiber made of polyester and polyamide is covered around an elastic yarn is used as a weft to form a fabric. A toothed belt characterized by: