JPH02150528A - Cord for reinforcing power transmission belt and power transmission belt - Google Patents

Abstract

PURPOSE:To improve characteristics of a reinforcing cord and a power transmission belt where the cord is buried by using a special core-sheath compound fiber as a fiber forming a power transmission belt reinforcing cord. CONSTITUTION:A power transmission belt reinforcing cord is formed by a core-sheath compound fiber composed of core component, the principal component of which is polyester composed of ethylene terephthalate and a sheath component, the principal component of which is polyamide wrapping the periphery of the above core component. The core-sheath compound fiber is such that the percentage of polyester 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 the hot air shrinkage percentage is 70% or less. Accordingly, the reinforcing cord has high modulus and dimensional stability, and a power transmission belt where the reinforcing cord is buried is remarkably improved in heat-resistance adhesive property and fatigue-resistance after it is subjected to treatment of rubber heat resistance and high temperature hysteresis of a cord buried in the belt, so that the durability of the belt can be remarkably improved.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a cord for reinforcing power transmission belts, and more specifically, a cord for reinforcing power transmission belts. The present invention relates to a cord for reinforcing a transmission belt, and is particularly characterized by the characteristics of the composite fiber.

The present invention also relates to a power transmission belt, such as a timing belt or a belt, in which the power transmission belt reinforcing cord described above is embedded in rubber as a tensile member.

[Prior Art] Polyester fibers, typically polyethylene terephthalate fibers, have the characteristics of high strength and high elastic modulus, and are used as reinforcing cords for power transmission belts. but,
In the case of the power transmission belt, the cord made of polyester fibers deteriorates due to the heat accumulated during driving, resulting in a decrease in strength, loss of adhesion to the rubber, and peeling. As a means to improve the adhesion between polyester fibers and rubber, composite fibers containing polyester as a core component and polyamide as a sheath component are disclosed, for example, in JP-A-49-85315 and JP-B-Sho 62-42061.
It is stated in the No.

[Problem to be solved by the invention] The above-mentioned Japanese Patent Application Laid-Open No. 49-85315 and Japanese Patent Publication No. 62-4
The fiber with a core-sheath composite structure proposed by the method of Publication No. 2061 is intended to have improved adhesion to rubber by the polyamide component of the sheath, and to maintain modulus and dimensional stability by the polyester component of the core. there were. Although adhesion is certainly improved sufficiently by this method, the modulus and dimensional stability decrease as the nylon component of the sheath increases, and it is difficult to sufficiently maintain the modulus and dimensional stability of polyester fibers. On the other hand, it was not possible to fully utilize the heat resistance and fatigue resistance of nylon in rubber.

In addition, ordinary polyesters such as polyethylene terephthalate and ordinary polyamides such as nylon 6 and nylon 66 have poor compatibility with each other, so when manufactured using normal manufacturing methods, the interface between the two polymers in the core-sheath composite structure It was not possible to obtain a material that was easily peeled off and had sufficient durability for practical use.

Additionally, polyester fibers generally have poor heat resistance in rubber. That is, at high temperatures, the ester bonds of polyester fibers are broken due to the action of moisture and amine compounds in the rubber, causing a decrease in strength. It also has poor adhesion to rubber, especially when repeatedly exposed to high-temperature atmospheres for long periods of time, and the adhesion to rubber decreases significantly, making it difficult to use power transmission belt reinforcing cords made of such polyester fibers in power transmission belts. High strength, which is a characteristic of polyester fibers,
Although the high modulus performance is effective, when the power transmission belt is driven, the power transmission belt becomes heated, the polyester fiber deteriorates due to heat, and its strength decreases, and the adhesive force with rubber decreases. It had drawbacks. When produced using a normal yarn spinning method, the core-sheath composite structure was prone to peeling and fracture at the interface between both polymers, and did not have sufficient durability for practical use. In particular, the polymer interface is destroyed by the repeated stretching and compression fatigue experienced during the drawing process, power transmission belt processing process such as twisting, dipping, belt vulcanization process, and belt driving, making it impossible to obtain the performance expected of the original core-sheath composite fiber. Ta.

By overcoming the above problems, the present invention provides reinforcement for power transmission belts that have excellent adhesion to rubber, high modulus and dimensional stability close to those of polyester, and improved heat resistance and fatigue resistance in rubber. It is an object of the present invention to provide a cord for reinforcing a power transmission belt suitable for use in applications, and a power transmission belt reinforced with the cord. In particular, it has high modulus, improved dimensional stability, and improved heat resistance in rubber (hereinafter referred to as heat resistance in rubber) that could not be achieved with conventional technology.
It is also an object of the present invention to provide a power transmission belt reinforcing cord that has sufficient durability against peeling of the bolimar at the core-sheath composite interface, and a power transmission belt reinforced with the cord.

[Means and effects for solving the problems] The present invention has the following features: (1) A cord for reinforcing a power transmission belt, in which the fibers forming the cord have a core component of polyester containing ethylene terephthalate as a main component; It is a core-sheath type composite fiber consisting of a core component and a sheath component mainly composed of polyamide, and the proportion of the core component made of polyester in the composite fiber is 30 to 90% by weight, and the strength of the composite fiber is 1. A cord for reinforcing a power transmission belt, characterized in that: is 7°50/d or more, elongation is 20% or less, initial tensile resistance is 600/d or more, and dry heat shrinkage is 7% or less.

(2) In the power transmission belt reinforcing cord of (1) above, the power transmission belt reinforcing cord is characterized in that the terminal modulus of the composite fiber is 20 g/d or less and the initial tensile resistance is 9C1/d or more. .

(3) In the power transmission belt reinforcing cord of (1) above, the polyester forming the core component of the composite fiber has an intrinsic viscosity (η) of 0.8 or more and a birefringence of 160X10' to 19
0X10-3, density 1.395g/ca+” or more, D
The peak temperature of the melting curve measured by SC is 247°C or higher, and the relative sulfuric acid viscosity (η
r) is 2.8 or more, birefringence is 50X10-3 or more, density is 1°140q/cI113 or more, and both the core component and sheath component have a highly oriented and highly crystalline fiber structure. Cord for belt reinforcement.

(4) In the power transmission belt, the treated cord obtained by deep-treating the power transmission belt reinforcing cord described in (1) above and having a layer of resorcinol, formalin, or latex formed on the surface is used as a tensile material in rubber. The power transmission bell 1 is characterized by being embedded in the bell.

The composite fiber used as the cord for reinforcing the power transmission 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. determined by the specified birefringence, density, and DSC melting peak temperature of the polyester and polyamide fiber portions forming the core and sheath, respectively, and by parameters consisting of a combination of high initial tensile resistance and low terminal modulus of the polyester core component fibers. be able to.

In order to obtain a composite fiber strength of 7.5 cx/d or more, the core component polyethylene terephthalate fiber has a high intrinsic viscosity (η) of 0.7 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 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, copper salts such as iodized steel, copper acetate, copper chloride, and copper stearate are used as copper at 30 to 5 ooppm, and alkali metal halides such as potassium iodide, sodium iodide, and potassium bromide are added at 0.0 ooppm.
It is preferable to contain 1 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 Il miscellaneous is 30 to 9
It is 0% by weight. If the polyester component is less than 30% by weight, it is not possible to effectively utilize the modulus and dimensional stability of the polyester component to form a vine composite fiber, and it is not possible to obtain a preferred cord for reinforcing a power transmission belt.

On the other hand, if the polyester core component accounts for 90% by weight or more, when the composite m* is used as a cord for reinforcing a power transmission belt and the cord is used as a tensile member of a power transmission belt, the adhesion to rubber is poor. However, it has not been possible to improve the heat resistance of power transmission belt reinforcing cords 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 160X 10-3 to 190X10.
It is desirable to keep it within the range of 160X
If it is less than 10', the strength of the composite fiber is 7.5 CI/d or more,
The initial tensile resistance may not exceed 60 g/d. Moreover, if it exceeds 190 x 10', dimensional stability and fatigue resistance may not be improved.

On the other hand, the birefringence of the polyamide sheath component is 50x1()-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 fiber can be measured in the following manner. 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, etc.

The density of the polyester core component is 1.3950/cm3 or more, and the polyamide sheath component is 1.140q/cm3 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, composite II In addition to having excellent dimensional stability and fatigue resistance, when this cord is used as a power transmission belt reinforcement cord and is used as a tensile member of a power transmission belt, the heat resistance in the rubber of the tensile member is significantly improved. be done.

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

The peak temperature of the DSC melting curve showing the characteristics of the crystal structure of the polyester core component in the composite 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 C]/d or more and a low terminal modulus of 20 g/d or less. The characteristics of polyester fibers, which have a high initial tensile resistance surface and a low terminal modulus, are that there is little loss in strength during the power transmission belt processing process.
Fatigue resistance is improved. The terminal modulus is 2.4 from the cutting elongation on the SS curve in the fiber tensile test.
%The stress increment between the point on the curve and the cutting point is 2.4X
It is the value divided by 10' (g/d), and the conditions of the tensile test are in accordance with JIS-L1017.

Composite fibers characterized by the above are 7゜5 g/d
It has a high strength of 60 o/d or more, an initial tensile resistance of 60 o/d or more, and an elongation of 20% or less.

More preferable composite fiber properties are a strength of 8 g/d or more, an initial tensile resistance of 70 a/d or more, and an elongation of 8 to 16%, which can be achieved by appropriately combining 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, techniques such as adding a capping agent during the spinning process are applied, and examples of the capping agent include oxazolines, epoxies, carbodiimides, ethylene carbonate, oxalic acid esters, malonic acid esters, and the like.

The polyamide sheath component polymer has a sulfuric acid relative viscosity of 2°8 or more,
Usually, a highly polymerized polymer having a polymerization ratio of 3.0 or more is used.

It is preferable to use two extruder 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 a take-up roll for the purpose of understanding the physical properties of the undrawn yarn before stretching is 20X10-3 or more for the polyamide sheath, preferably 30X10-3 or more, and 20X10 for the polyester core. -3 or more, preferably 30X10-3 or more, highly oriented.

The adoption of high-speed spinning improves the modulus, dimensional stability, and
This brings about the effect of improving fatigue resistance, but surprisingly, the durability of the core-sheath composite interface is significantly improved. Unlike the conventional low-speed spinning method, in which a highly hygroscopic and crystallized polyamide component is combined with an amorphous polyester component, in the high-speed spinning method, the polyamide component,
It is thought that the fact that both the polyester components are in a state where oriented crystallization progresses, and that the stretching ratio after spinning is small can contribute to the durability of the composite interface.

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 stretching is low, for example 160
When stretched below 180°C, interfacial delamination between the polyester core component and polyamide sheath component may occur during power transmission belt processing and when the power transmission belt is used at high speeds. .

[Example] Example-1 and 2) Comparative Examples 1 to 4 Intrinsic viscosity (η) 1.05, carboxyl end group concentration 10
．． Bo IJ of 5eq/106o Ethylene terephthalate (PET) and iodide steel 0.02% by weight and potassium iodide 0
．． 66/6T containing 1% by weight (80:20 weight ratio)
Copolyamide (relative viscosity of sulfuric acid, ηr3.2) or hexamethylene adipamide (N66: relative viscosity of sulfuric acid, ηr3.3) is melted in a 40φ xtruder-type spinning machine, guided into a composite spinning pack, and core-sheath composite spinning is carried out. It was spun from a spinneret into a composite yarn with polyethylene terephthalate in the core and polyamide in the sheath.

The proportions of the core component and sheath component were varied as shown in Table 1. The cap used had a hole diameter of 0.4#φ and 90 holes. Polymer temperatures were as follows: polyethylene terephthalate was melted at 295°C, polyamide was melted at 290°C, and spinning pack humidity was set at 300°C. A 15 cm heating cylinder was attached directly below the mouthpiece, and the atmosphere inside the cylinder was heated to 290°C. The ambient temperature is the ambient temperature measured at a position 10 cm below the mouth surface and 1 cm away from the outermost thread. An annular chimney with a length of 400 m is installed under the heating cylinder, and the temperature is 40 m from the circumference of the yarn at 25°C.
/ minute of cold air was blown perpendicularly to the yarn to cool it. Then, after applying an oil agent, the yarn speed was controlled with a bow-cutting 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 were a take-up roll temperature of 60°C, a first stretching roll temperature of 120°C, a second stretching roll temperature of 190°C, a third stretching roll temperature of 225°C, and a tension adjustment roll after stretching that was not heated. The first stage stretching ratio was 70% of the total stretching ratio, and the remainder was divided into two stages for stretching. The yarn was produced by changing the spinning speed, total drawing ratio, etc., but the fineness of the drawn yarn was about 50.
The discharge amount was varied in accordance with the spinning speed and the stretching ratio so as to obtain 0 denier (Example 1.2) Comparative Example 1.2).

Two of the obtained drawn yarns were combined into a 1000 denier yarn.

The spinning conditions, the obtained drawn yarn properties, and the fiber structure parameters were determined using polyethylene terephthalate (PET) fiber (1
000-192-702G) (Comparative Example 3) and Nylon 6611i fiber (840136-1781) (Comparative Example 4)
A comparative test was conducted on the following. Each condition and fiber properties are as shown in Table 1.

(The following is a blank space) Using each of the fibers shown in Table 1 above, these fibers were twisted and twisted in opposite directions at a rate of 25T/10cal to obtain a 2000/2 raw cord. This raw cord was applied with an adhesive and heat-treated in a conventional manner using a dipping machine manufactured by Ritzler to obtain a dipped cord.

The dip liquid contained an adhesive component consisting of 20% resorcinol, formalin, and latex, and was adjusted so that about 3% of the adhesive component adhered to the cord. Heat treatment is 225℃ and 80℃
The process was performed while stretching the cord so that the intermediate elongation of the dip cord was about 5%. Nylon 66 in Comparative Example 4 was stretched under the same heat treatment conditions so that the intermediate elongation was approximately 9%. Also, PE in Comparative Example 3
For T, two-bath adhesion treatment is performed using a conventional method, and heat treatment is performed at 240°C.
, for 120 seconds, and was stretched so that the intermediate elongation was approximately 5%.

A test piece was made by embedding the thus obtained dipped cord in rubber in the same manner as when it is used as a tensile member for a power transmission belt, and the heat resistance, adhesion, fatigue resistance, etc. in the rubber were evaluated. The results were as shown in Table 2.

The power transmission belt reinforcing cord according to the present invention has a modulus and dimensional stability equal to or higher than conventional polyester fiber cords, and has higher heat resistance in rubber and heat resistance than conventional polyester fiber cords. This shows that it is a high-strength cord with significantly improved adhesion and fatigue resistance.

Furthermore, the power transmission belt reinforcing cord according to the present invention includes:
This is a power transmission belt reinforcing cord with significantly improved modulus and dimensional stability compared to conventional nylon fiber cords.

(The following is a blank space) [Effects of the invention] The power transmission belt reinforcing cord according to the present invention has a modulus equal to or higher than that of conventional polyester and improved dimensional stability, and has a reinforcing cord made of conventional polyester. Compared to a power transmission belt in which a cord is embedded, the power transmission belt according to the present invention has the rubber heat resistance and adhesive properties of the cord embedded in the belt, especially heat resistant adhesive property after high temperature history, and fatigue resistance. As a result, the power transmission belt has extremely good durability against repeated fatigue.

Claims (4)

[Claims] (1) In a cord for reinforcing a power transmission belt, the fibers forming the cord consist of a core component made of polyester whose main component is ethylene terephthalate, and a sheath component whose main component is polyamide surrounding the core component. type composite fiber, the ratio of the core component made of the polyester in the composite fiber is 30 to 90% by weight, the strength of the composite fiber is 7.5 g/d or more, the elongation is 20% or less, and the initial tensile resistance is A cord for reinforcing a power transmission belt, characterized by a strength of 60 g/d or more and a dry heat shrinkage rate of 7% or less. (2) The power transmission belt reinforcing cord according to claim (1), wherein the composite fiber has a terminal modulus of 20 g/d or less and an initial tensile resistance of 90 g/d or more. Cord for belt reinforcement. (3) In the cord for reinforcing a power transmission belt according to claim (1), the polyester forming the core component of the composite fiber has an intrinsic viscosity (η) of 0.8 or more and a birefringence of 160.
×10^-^3 ~ 190 × 10^-^3, density is 1.3
95g/cm^3 or more, the peak temperature of the melting curve measured by DSC is 247℃ or more, the sulfuric acid relative viscosity (ηr) of the polyamide forming the sheath component is 2.8 or more, and the birefringence is 50 x 10^- ^3 or more, density 1.140g/cm^
3 or more, both the core component and the sheath component are highly oriented,
A power transmission belt reinforcing cord characterized by having a highly crystalline fiber structure. (4) In the power transmission belt, Claim No. 1
It is characterized by being embedded in rubber as a tensile material by using a treated cord obtained by dipping the power transmission belt reinforcing cord described in item 2 and forming a layer of resorcinol/formalin/latex on the surface thereof. Power transmission belt.