WO2018074471A1

WO2018074471A1 - Plied cord, production method therefor, transmission belt, and method for using same

Info

Publication number: WO2018074471A1
Application number: PCT/JP2017/037532
Authority: WO
Inventors: 拓也友田
Original assignee: 三ツ星ベルト株式会社
Priority date: 2016-10-20
Filing date: 2017-10-17
Publication date: 2018-04-26

Abstract

The present invention relates to a plied cord comprising three or four first twist yarns containing para-aramid fibers, wherein: the para-aramid fibers have an average size of 1000–1250 dtex, a tensile elasticity of 55–70 GPa and a tensile strength of 2800–3500 MPa; and for the plied cord, the number of first twists when the number of the first twist yarns is three is 33–40 twists/10 cm and the number of first twists when the number of the first twist yarns is four is 42–52 twists/10 cm, the second twist direction is the opposite direction from the first twist, and the ratio of the second twist coefficient to the first twist coefficient is 0.25–1.

Description

Various twisted cords, manufacturing method thereof, transmission belt and usage method thereof

The present invention relates to various twisted cords used for a tensile body of a transmission belt (particularly a V-ribbed belt), a manufacturing method thereof, a transmission belt, and a usage method thereof.

The core wire forming the V-ribbed belt tensile body is required to have high tensile strength and bending fatigue resistance, and an aramid core wire has been used particularly for high load applications. In general, an aramid core wire is manufactured by first twisting a fiber bundle and then twisting several twisted fiber bundles. However, the above characteristics required for an aramid core wire have a contradictory relationship that when the number of twists of the core wire is increased to improve the bending fatigue resistance, the tensile strength is decreased. In addition, in order to meet the demands of high load transmission, V-ribbed belts for driving automotive accessories with para-aramid cords (cords made of twisted yarns of para-aramid fibers) as tensile bodies have been on the market for a long time. With the advent of engines equipped with ISG (Integrated Starter Generator), demands for belt strength and bending fatigue resistance are increasing.

On the other hand, para-aramid fibers used for high-load power transmission include para-aramid fibers of single repeating units represented by Kevler (registered trademark) and Twaron (registered trademark). Regarding fatigue, Technora (registered trademark), which is a copolymerized para-aramid fiber containing a plurality of types of repeating units, is more excellent and has been awarded. However, copolymerized para-aramid fibers containing a plurality of types of repeating units have problems of cost and supply stability, and it has been desired to improve bending fatigue resistance even with para-aramid fibers having a single repeating unit.

In addition, if the core wire is rung-twisted (the twist direction of the lower and upper twists is the same), the bending fatigue resistance will be improved, but if it is rung-twisted, it will pop out under high tension conditions (the core wire is the belt). (Phenomenon popping out from the side surface) This phenomenon is presumed to be caused by the non-straightness of the core wire due to the untwisting torque of the Lang twist, and the twists in which the untwisting torque is offset by the lower twist and the upper twist (twist direction of the lower twist and the upper twist) On the other hand, it is known that pop-out hardly occurs. Therefore, in order to prevent the core wire from twisting itself, the twist direction of the lower twist and the upper twist is reversed, and the twist coefficient of the lower twist (lower twist coefficient) and the twist coefficient of the upper twist (upper twist coefficient) It was common to make them substantially the same.

On the other hand, Japanese Patent No. 4694616 (Patent Document 1) discloses a first twist multiplier and a first twist multiplier as load sharing cords of a multi-V ribbed belt having a good balance between load sharing performance and bending fatigue resistance. A plurality of yarns having a first twist corresponding to one twist direction, and a second twist corresponding to a second twist multiplier in a direction opposite to the first twist direction, the second twist multiplier A cord is disclosed in which the ratio of the first twist multiplier to is greater than about 1.5. In the example of this document, a ratio of the first twist multiplier corresponding to the lower twist to the second twist multiplier corresponding to the upper twist is 2.5 (that is, the second twist) using the 1000 denier para-aramid fiber as the base yarn. A cord having a twist multiplier / first twist multiplier = 0.4) is manufactured.

In Japanese Patent No. 5750561 (Patent Document 2), as a core wire of a transmission belt excellent in bending fatigue resistance, a para-aramid fiber bundle having a fineness of 1000 to 1250 dtex and a twist coefficient of 1200 to 1350 are unidirectional. The four lower twisted yarns were composed of various twisted yarns having a total fineness of 4000 to 5000 dtex, in which the four lower twisted yarns were twisted in the opposite direction to the lower twist with a twist coefficient of 900 to 1100. A core wire is disclosed. This document describes that the ratio of the upper twist coefficient to the lower twist coefficient (upper twist coefficient / lower twist coefficient) in the various twisted yarns constituting the core wire is 0.5 to 1. In the examples, the upper twist coefficient Various twisted cords having a number of 14.3 to 17.5, a number of lower twists of 38.1 to 42.9, and an upper twist coefficient / lower twist coefficient = 0.67 to 0.92 are manufactured.

However, even these twisted cords did not sufficiently satisfy the bending fatigue resistance in the engine application with ISG. Furthermore, these patent documents do not describe pop-out resistance.

Japanese Patent No. 4694616 Japanese Patent No. 5750561

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-strand cord capable of simultaneously improving the tensile strength, bending fatigue resistance and pop-out resistance of a transmission belt (particularly a V-ribbed belt) having a para-aramid core as a tensile body, and its manufacture. It is an object of the present invention to provide a method, a transmission belt provided with the twisted cord as a tensile body, and a method of using the transmission belt.

As a result of earnest studies to achieve the above-mentioned problems, the present inventor prepared a plurality of underwound yarns having a specific underwound coefficient by using a high elongation type para-aramid fiber, and further a twist coefficient of the underwound When the twisted cords obtained by twisting the lower twisted yarn so that the ratio of the twist coefficient of the upper twist to the predetermined range is used as the tensile body of the V-ribbed belt, the tensile strength and bending resistance of the transmission belt such as the V-ribbed belt The present inventors have found that fatigue and pop-out resistance can be improved at a high level simultaneously.

That is, the plied cords of the present invention are plied cords including three lower twisted yarns containing para-aramid fibers, the para-aramid fibers having an average fineness of 1000 to 1250 dtex, a tensile modulus of 55 to 70 GPa and a tensile strength. The twisted cord has a twist of 33 to 40 times / 10 cm, the direction of the upper twist is opposite to that of the lower twist, and the upper twist with respect to the lower twist factor is 2800 to 3500 MPa. The ratio of the coefficients is 0.25-1. The number of upper twists of the twisted cords is preferably about 10 to 15 times / 10 cm. The ratio of the upper twist coefficient to the lower twist coefficient of the twisted cords may be about 0.5 to 0.75.

The plied cords of the present invention are laid cords comprising four lower twisted yarns containing para-aramid fibers, the para-aramid fibers having an average fineness of 1000 to 1250 dtex, a tensile modulus of 55 to 70 GPa and a tensile strength. The twisted cord has a twist number of 42 to 52 times / 10 cm, the upper twist direction is opposite to the lower twist, and the upper twist relative to the lower twist coefficient is 2800 to 3500 MPa. The ratio of the coefficients is 0.25-1. The number of upper twists of the twisted cords is preferably about 5 to 15 times / 10 cm. The ratio of the upper twist coefficient to the lower twist coefficient of the twisted cords may be about 0.33 to 0.66.

In the two types of twisted cords, the average diameter of the twisted cords is preferably about 0.7 to 0.9 mm. The para-aramid fiber may be a polyparaphenylene terephthalamide fiber.

The present invention includes a twisting process in which a para-aramid fiber is twisted in one direction to obtain a twisted yarn, and three or four of the twisted yarns obtained in the twisting process are aligned to reverse the twisted direction. Also included is a method for producing the above-mentioned twisted cords, which includes an upper twisting step in which the twisted cords are twisted to obtain the twisted cords.

The present invention also includes a transmission belt including a tensile body formed of the plied cords. In the transmission belt of the present invention, the tensile body may be a core wire, and the average pitch of the core wire is preferably about 0.8 to 1.05 mm. The power transmission belt of the present invention may further include a compressed rubber layer formed of a rubber composition containing a rubber component. The rubber component may be an ethylene-α-olefin elastomer. The transmission belt is preferably a V-ribbed belt.

The present invention includes a method of using the transmission belt to drive an ISG-equipped engine.

In the present invention, 3 to 4 (preferably 3) twisted yarns having a specific twisting factor are prepared using a high elongation type para-aramid fiber, and an upper twisting factor corresponding to the twisting factor of the twisting is further prepared. Since the twisted cords obtained by twisting the lower twisted yarn so that the ratio of the twisting coefficients is within a certain range are used as the tensile body of the transmission belt (particularly V-ribbed belt), the tensile strength, flexural fatigue resistance and Pop-out resistance can be improved at a high level at the same time.

FIG. 1 is a schematic cross-sectional view in the belt width direction showing an example of a V-ribbed belt of the present invention. FIG. 2 is a schematic view for explaining a method for evaluating the bending fatigue resistance of the V-ribbed belts obtained in the examples and comparative examples.

[Various twisted cords]
The twisted cords of the present invention are prepared by twisting para-aramid fiber (aromatic polyamide fiber) in one direction to form a twisted yarn (cord), and arranging 3 to 4 (preferably 3) twisted yarns. The twisted cords are twisted cords that are twisted in the opposite direction, and can be used as a tensile body of a transmission belt (particularly a V-ribbed belt). In the present invention, by making the lower twist and the upper twist in opposite directions, the untwisting torque is offset between the lower twist and the upper twist, and the pop-out resistance can be improved. In addition, it is preferable to use three twisted yarns from the viewpoints of excellent balance of tensile strength, bending fatigue resistance, pop-out resistance, economy and the like of the transmission belt and high improvement in pop-out resistance.

The base yarn of the lower twist yarn is usually a para-aramid multifilament yarn containing para-aramid fibers. Furthermore, the para-type aramid multifilament yarn only needs to contain a monofilament yarn of para-type aramid fibers, and may contain monofilament yarns of other fibers (such as polyester fibers) if necessary. The ratio of the para-type aramid fiber is 50% by mass or more (particularly 80 to 100% by mass) with respect to the whole monofilament yarn (multifilament yarn), and usually all monofilament yarns are composed of para-type aramid fiber.

The para-aramid fiber as the raw yarn is a copolymer para-aramid fiber containing a plurality of types of repeating units (for example, a copolymer aramid fiber of polyparaphenylene terephthalamide and 3,4'-oxydiphenylene terephthalamide). Teijin Limited's “Technora” etc.) may be used, but para-aramid fibers (for example, polypara-arabic) having a single repeating unit are excellent in terms of economy and availability and the effects of the present invention are remarkably exhibited. Preference is given to Teijin's "Twaron" and Toray DuPont's "Kevlar", which are phenylene terephthalamide fibers.

The tensile elastic modulus of the para-aramid fiber as the raw yarn is 55 to 70 GPa, preferably 58 to 68 GPa, more preferably about 60 to 65 GPa. If the tensile elastic modulus is too small, the belt stretches at a high load. On the other hand, if the tensile elastic modulus is too large, it becomes difficult to balance the tensile strength, the bending fatigue resistance, and the pop-out resistance. Bending fatigue resistance decreases. In addition, in this specification and a claim, a tensile elasticity modulus is measured by the method of measuring a load-elongation curve by the method as described in JIS L1013 (2010), and calculating | requiring the average inclination of the area | region of a load of 1000 MPa or less.

The tensile strength of the para-aramid fiber as the raw yarn is 2800 to 3500 MPa, preferably 2850 to 3400 MPa (for example, 2900 to 3300 MPa), and more preferably about 3000 to 3200 MPa. If the tensile strength is too small, it becomes difficult to balance the tensile strength, the bending fatigue resistance and the pop-out resistance, and the belt tensile strength is particularly lowered. In the present specification and claims, the tensile strength is measured by the method described in JIS L1013 (2010). In addition, as described in the standard, in measuring the tensile strength of a non-twisted multifilament, the measurement is performed by applying 8 twists per 10 cm.

As a para-aramid fiber of a single repeating unit having such mechanical properties, as a high elongation type para-aramid fiber, for example, “Twaron 2100” manufactured by Teijin Ltd. or “Toray DuPont” manufactured by “Toray DuPont” Commercial products such as “Kevlar 119” can be used. In the present invention, high tensile strength and tensile elastic modulus can be imparted to the V-ribbed belt by preparing plied cords using a high elongation type para-aramid fiber.

The average fineness of the para-aramid fiber as the raw yarn is 1000 to 1250 dtex, preferably about 1050 to 1200 dtex, and more preferably about 1080 to 1150 dtex. If the fineness is too small, the belt tensile strength is lowered. Conversely, if the fineness is too large, the bending fatigue resistance is lowered.

The number of twists of the twisted cords (number of twists) can be selected according to the number of twisted yarns. In the case of various twisted cords including three lower twisted yarns, the number of lower twists is 33 to 40 times / 10 cm, preferably 35 to 39.5 times / 10 cm from the viewpoint of imparting excellent bending fatigue resistance and tensile strength. (For example, 36 to 39.3 times / 10 cm), more preferably about 37 to 39 times / 10 cm (especially 38 to 38.5 times / 10 cm). On the other hand, in the case of various twisted cords including four lower twisted yarns, the number of lower twists is 42 to 52 times / 10 cm, preferably 42.5 to 51. 5 in terms of imparting excellent bending fatigue resistance and tensile strength. It is about 8/10 cm (for example, 43 to 51.5 times / 10 cm), more preferably about 46.1 to 51 times / 10 cm (particularly 46.5 to 50.5 times / 10 cm). If the number of lower twists is too small, the bending fatigue resistance decreases, and if it is too large, the tensile strength decreases.

The number of upper twists (upper twist) of various twisted cords can be selected from a range of about 5 to 20 times / 10 cm (especially 5 to 19 times / 10 cm) depending on the number of lower twisted yarns. In particular, in various twisted cords including three lower twisted yarns, the number of upper twists is, for example, 10 to 19 times / 10 cm (for example, 10 to 15 times / 10 cm), preferably 12 to 15 times / 10 cm (for example, 13 to 15 times / 10 cm), more preferably about 14 to 15 times / 10 cm (especially 14.5 to 15 times / 10 cm). On the other hand, in the case of various twisted cords including four lower twisted yarns, the number of upper twists is, for example, 5 to 19 times / 10 cm (for example, 5 to 15 times / 10 cm), preferably 6 to 16 times / 10 cm (for example, 8.2 to 14). 2 times / 10 cm), more preferably about 9-14 times / 10 cm (especially 9.6-12.8 times / 10 cm), and further about 10-12 times / 10 cm. By adjusting the number of upper twists within the above range, it is possible to appropriately maintain the ratio of the twist coefficient (upper twist coefficient) of the upper twist to the twist coefficient (lower twist coefficient) of the lower twist. In particular, in various twisted cords including three lower twisted yarns, the pop-out resistance can be improved to a high degree by increasing the number of upper twists. If the number of upper twists is too small, the pop-out resistance may be lowered. On the other hand, if the number is too large, the tensile strength may be lowered or the bending fatigue resistance may be lowered.

The ratio of the upper twist coefficient to the lower twist coefficient of the various twisted cords (upper twist coefficient / lower twist coefficient) is also in the range of about 0.25 to 1 (for example, 0.3 to 0.8) depending on the number of the lower twist threads. You can choose from. In particular, in various twisted cords including three lower twisted yarns, the coefficient ratio is, for example, about 0.5 to 0.75, preferably about 0.6 to 0.73, and more preferably about 0.65 to 0.7. . On the other hand, in the case of various twisted cords including four lower twisted yarns, the coefficient ratio is, for example, 0.33 to 0.66, preferably 0.35 to 0.6, more preferably 0.36 to 0.55 (particularly 0). .38 to 0.5), and may be 0.45 to 0.53. In the present invention, excellent bending fatigue resistance and pop-out resistance can be imparted by setting the twist direction of the lower twist and the upper twist in opposite directions and adjusting the ratio of the upper twist coefficient to the lower twist coefficient within the above range. In particular, in various twisted cords including three lower twisted yarns, the pop-out resistance can be improved to a high degree by bringing the coefficient ratio close to 1. When the ratio of the upper twist coefficient to the lower twist coefficient is too small, the pop-out resistance is lowered. Conversely, when the ratio is too large, the bending fatigue resistance is lowered. In addition, in this specification and a claim, each twist coefficient of a lower twist coefficient and an upper twist coefficient is calculated based on the following formula | equation.

Twist coefficient (TF) = [twist number (times / m) × √total fineness (tex)] / 960.

The lower twist coefficient and the upper twist coefficient of the various twisted cords are not particularly limited as long as the above-mentioned ratio is satisfied, but the lower twist coefficient is, for example, 4 to 6, preferably 4.5 to 5.5, More preferably, it is about 4.8 to 5.3, and the upper twist coefficient is, for example, about 1.5 to 3.5, preferably 1.8 to 3, and more preferably about 2 to 2.5.

The average diameter (diameter) of the various twisted cords is, for example, about 0.5 to 1.2 mm, preferably 0.6 to 1 mm, and more preferably 0.7 to 0.9 mm (particularly 0.78 to 0.88 mm). It is. In particular, in an ISG-equipped engine, the requirements for belt strength and bending fatigue resistance are severe, and a thicker core wire diameter is preferable to increase belt strength, but if it is too thick, bending fatigue resistance decreases. It is preferable to adjust to the range. If the average diameter of the plied cords is too small, the tensile strength and the tensile modulus of elasticity may be reduced. On the other hand, if the average diameter is too large, the bending fatigue resistance may be reduced.

When the twisted cords are multifilament yarns, the average fineness of the twisted cords may be, for example, about 2000 to 7000 dtex, preferably about 3000 to 6000 dtex, and more preferably about 4000 to 5000 dtex. The multifilament yarn may include, for example, about 1000 to 6000 monofilament yarns, preferably 2000 to 5000 yarns, and more preferably about 2500 to 4500 yarns.

The tensile strength of the plied cords may be, for example, 600 N or more (especially 650 N or more), preferably 600 to 1000 N, more preferably 650 to 900 N (particularly 700 to 800 N). If the tensile strength of the twisted cords is too small, the tensile strength and pop-out resistance of the belt may be reduced. In the present specification and claims, the tensile strength of plied cords is measured by the method described in the examples described later.

The twisted cords of the present invention are prepared by a conventional method in which a para-aramid fiber is first twisted in one direction to obtain a lower twisted yarn, and three or four lower twisted yarns obtained in the lower twisted step are drawn. They can be manufactured through an upper twisting step in which twisted cords are obtained by twisting in the opposite direction to the lower twist.

[Power transmission belt]
The transmission belt of this invention should just contain the tensile body formed with the said twisted cord, and usually contains the said twisted cord as a core wire. Examples of the transmission belt include friction transmission belts such as a V belt and a V-ribbed belt, and meshing transmission belts such as a toothed belt and a double-sided toothed belt. Since the tensile strength, the bending fatigue resistance and the pop-out resistance can be improved at a high level at the same time, the twisted cord of the present invention can be particularly preferably used as a core of a V-ribbed belt for driving an ISG-equipped engine. Hereinafter, the form of the V-ribbed belt will be described.

The form of the V-ribbed belt as an example of the present invention is not particularly limited as long as it has a plurality of V-rib portions extending in parallel with each other along the belt longitudinal direction. For example, the form shown in FIG. The FIG. 1 is a schematic cross-sectional view in the belt width direction showing an example of the V-ribbed belt of the present invention. A V-ribbed belt shown in FIG. 1 has a compression rubber layer 2, an adhesive rubber layer 4 in which a core wire 1 is embedded in the longitudinal direction of the belt, a cover canvas (from the belt lower surface (inner circumferential surface) to the belt upper surface (back surface). Woven fabric, knitted fabric, non-woven fabric, etc.) or a stretched layer 5 made of a rubber composition. A plurality of V-shaped grooves extending in the longitudinal direction of the belt are formed in the compressed rubber layer 2, and a plurality of V-rib portions 3 having a V-shaped cross section (reverse trapezoid) are formed between the grooves (example shown in FIG. 1). 4), and the two inclined surfaces (surfaces) of the V-rib portion 3 form a friction transmission surface and contact the pulley to transmit power (friction transmission).

The V-ribbed belt is not limited to this form, and it is sufficient that at least a part is provided with a compression rubber layer having a transmission surface that can come into contact with the V-rib groove portion (V-groove portion) of the pulley. What is necessary is just to provide the rubber layer and the core wire embed | buried along the belt longitudinal direction between them. In the V-ribbed belt of the present invention, for example, the core wire 1 may be embedded between the stretched layer 5 and the compressed rubber layer 2 without providing the adhesive rubber layer 4. Further, the adhesive rubber layer 4 is provided on either the compressed rubber layer 2 or the stretched layer 5, and the core wire 1 is disposed between the adhesive rubber layer 4 (compressed rubber layer 2 side) and the stretched layer 5, or the adhesive rubber layer 4 It may be embedded between the (extended layer 5 side) and the compressed rubber layer 2.

Note that at least the compressed rubber layer 2 is preferably formed of a rubber composition described in detail below, and the adhesive rubber layer 4 may be formed of a conventional rubber composition used as an adhesive rubber layer. The stretch layer 5 may be formed of a conventional cover canvas or rubber composition used as a stretch layer, and may not be formed of the same rubber composition as the compressed rubber layer 2.

The tensile strength of the V-ribbed belt may be, for example, 6000 N or more (especially 6500 N or more), preferably about 6000 to 9000 N, more preferably about 6500 to 8000 N (particularly 7000 to 7500 N). If the tensile strength is too small, there is a high possibility that the belt will break during traveling. In the present specification and claims, the tensile strength of the V-ribbed belt is measured by the method described in Examples described later.

(Core)
In the adhesive rubber layer 4, a plurality of core wires 1 extend in the belt longitudinal direction and are spaced apart from each other at a predetermined pitch in the belt width direction.

The average pitch of the core wires (the average distance between adjacent core wires) can be appropriately selected according to the core wire diameter and the target belt tensile strength, for example, 0.6 to 2 mm, preferably 0.8 to 1.5 mm, More preferably, it can be selected from a range of about 0.8 to 1.05 mm. Further, the average pitch of the core wires may be selected according to the number of the lower twisted yarns. In particular, in a twisted cord including three lower twisted yarns, the average pitch of the cords is, for example, about 0.7 to 1 mm, preferably about 0.75 to 0.95 mm, and more preferably about 0.8 to 0.9 mm. . On the other hand, in a twisted cord including four lower twisted yarns, the average pitch of the cords is, for example, 0.8 to 1.2 mm, preferably 0.9 to 1.05 mm, and more preferably about 0.9 to 1 mm. . If the core wire pitch is too small, there is a risk that the core wires may run up in the belt manufacturing process, and conversely if too large, the tensile strength and tensile modulus of the belt may be reduced.

The core wire may be either S-twisted or Z-twisted, but it is preferable to alternately arrange S-twisted and Z-twisted to improve the straightness of the belt.

The core wire may be subjected to a conventional adhesion treatment (or surface treatment), such as a resorcin-formalin-latex (RFL) solution or a treatment solution containing an isocyanate compound. Furthermore, the core wire may be covered with a rubber composition containing a rubber component constituting the adhesive rubber layer.

(Rubber composition)
The compressed rubber layer 2, the adhesive rubber layer 4, and the stretch layer 5 may be formed of a rubber composition containing a rubber component. In particular, by forming a compressed rubber layer with a rubber composition, it is possible to provide excellent quietness and power transmission performance, and by using a rubber composition to form a compressed rubber layer or an adhesive rubber layer, an existing method is used. Thus, it is possible to perform an adhesion treatment with a para-aramid core wire.

As the rubber component, a vulcanizable or crosslinkable rubber may be used. For example, a diene rubber (natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (nitrile rubber), Hydrogenated nitrile rubber, etc.), ethylene-α-olefin elastomer, chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber and the like. These rubber components can be used alone or in combination of two or more. Preferred rubber components are ethylene-α-olefin elastomers (ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.), and chloroprene rubber. Further, since it does not contain harmful halogen, has ozone resistance, heat resistance, cold resistance, weather resistance, and can reduce the belt weight, an ethylene-α-olefin elastomer [ethylene-propylene copolymer (EPM), Ethylene-propylene-diene terpolymer (EPDM) etc.] is particularly preferred. When the rubber component contains an ethylene-α-olefin elastomer, the proportion of the ethylene-α-olefin elastomer in the rubber component may be 50% by mass or more (particularly about 80 to 100% by mass) or 100% by mass (ethylene -Α-olefin elastomer only) is particularly preferred.

The rubber composition may further contain short fibers. Examples of the short fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyalkylene arylate fibers (for example, polyethylene terephthalate ( PET) fibers, C _2-4 alkylene C _8-14 arylate fibers such as polyethylene naphthalate (PEN) fibers), vinylon fibers, polyvinyl alcohol fibers, synthetic fibers such as polyparaphenylene benzobisoxazole (PBO) fibers; Examples include natural fibers such as cotton, hemp, and wool; inorganic fibers such as carbon fibers. These short fibers can be used alone or in combination of two or more. In order to improve dispersibility and adhesiveness in the rubber composition, the short fibers may be subjected to a conventional adhesion treatment (or surface treatment) as in the case of the core wire.

The rubber composition may further contain a conventional additive. Examples of conventional additives include vulcanizing agents or crosslinking agents (or crosslinking agent systems) (sulfur vulcanizing agents, etc.), co-crosslinking agents (bismaleimides, etc.), vulcanization aids or vulcanization accelerators ( Thiuram accelerators), vulcanization retarders, metal oxides (zinc oxide, magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), enhancers (for example, carbon black, , Silicon oxide such as hydrous silica), fillers (clay, calcium carbonate, talc, mica, etc.), softeners (for example, oils such as paraffin oil and naphthenic oil), processing agents or processing aids (stearin Acid, stearic acid metal salt, wax, paraffin, fatty acid amide, etc.), anti-aging agent (antioxidant, thermal anti-aging agent, anti-bending agent, anti-ozone degradation agent, etc.), colorant, tackifier , Plasticizers, coupling agents (silane coupling agent, etc.), stabilizers (UV absorbers, heat stabilizers, etc.), flame retardants, antistatic agents and the like. These additives can be used alone or in combination of two or more. The metal oxide may act as a crosslinking agent. In particular, the rubber composition constituting the adhesive rubber layer 4 may contain an adhesion improver (resorcin-formaldehyde cocondensate, amino resin, etc.).

The rubber composition constituting the compressed rubber layer 2, the adhesive rubber layer 4 and the stretch layer 5 may be the same or different from each other. Similarly, the short fibers contained in the compressed rubber layer 2, the adhesive rubber layer 4, and the stretch layer 5 may be the same or different from each other.

(Cover canvas)
The stretch layer 5 may be formed of a cover canvas. The cover canvas can be formed of, for example, a cloth material (preferably a woven cloth) such as a woven cloth, a wide-angle canvas, a knitted cloth, and a non-woven cloth. If necessary, the stretch layer 5 may be subjected to adhesion treatment, for example, treatment with an RFL solution (immersion treatment, etc.), friction for rubbing adhesive rubber into the cloth material, or lamination (coating) of the adhesive rubber and the cloth material. ) And then laminated on the compressed rubber layer and / or the adhesive rubber layer in the above-described form.

[Manufacturing method of V-ribbed belt]
The manufacturing method of the V ribbed belt which is an example of this invention is not restrict | limited in particular, A well-known or usual method is employable. For example, the compressed rubber layer 2, the adhesive rubber layer 4 in which the core wire 1 is embedded, and the stretched layer 5 are each formed by laminating with an unvulcanized rubber composition, and this laminate is formed into a cylindrical shape with a molding die. And then vulcanizing to form a sleeve and cutting the vulcanized sleeve to a predetermined width. More specifically, the V-ribbed belt can be manufactured by the following method.

(First manufacturing method)
First, a stretching layer sheet is wound around a cylindrical mold (mold or mold) having a smooth surface, and a core wire (twisted cord) that forms a core body is spirally spun on the sheet. An adhesive rubber layer sheet and a compressed rubber layer sheet are sequentially wound to prepare a molded body. After that, the molding mold is accommodated in a vulcanizing can with the vulcanization jacket covered from above the molded body, vulcanized under predetermined vulcanization conditions, and then demolded from the molding mold and cylindrical vulcanized. Get a rubber sleeve. Then, the outer surface (compressed rubber layer) of the vulcanized rubber sleeve is polished by a grinding wheel to form a plurality of ribs, and then the vulcanized rubber sleeve is cut in a circumferential direction with a predetermined width using a cutter. Finish in a V-ribbed belt. By reversing the cut belt, a V-ribbed belt provided with a compressed rubber layer having a rib portion on the inner peripheral surface can be obtained.

(Second manufacturing method)
First, a cylindrical inner mold having a flexible jacket attached to the outer peripheral surface is used as the inner mold, and a stretch layer sheet is wound around the flexible jacket on the outer peripheral surface, and a core wire forming a core body is formed on the sheet. Spinning in a spiral shape and winding a compressed rubber layer sheet to produce a laminate. Next, as an outer mold that can be attached to the inner mold, a cylindrical outer mold in which a plurality of rib molds are engraved on the inner peripheral surface is used, and an inner mold in which the laminate is wound is provided in the outer mold. Install concentrically. Thereafter, the flexible jacket is expanded toward the inner peripheral surface (rib type) of the outer mold, and the laminate (compressed rubber layer) is press-fitted into the rib mold and vulcanized. Then, the inner mold is extracted from the outer mold, the vulcanized rubber sleeve having a plurality of ribs is removed from the outer mold, and then the vulcanized rubber sleeve is cut in the circumferential direction with a predetermined width by using a cutter. Finish. In the second manufacturing method, a laminated body including an extension layer, a core body, and a compressed rubber layer can be expanded at a time to be finished into a sleeve (or V-ribbed belt) having a plurality of ribs.

(Third production method)
In connection with the second production method, for example, a method disclosed in Japanese Patent Application Laid-Open No. 2004-82702 (only a compression rubber layer is expanded to form a preform (semi-vulcanized state), A method in which the core body is expanded and pressure-bonded to the preform, and vulcanized and integrated into a V-ribbed belt) may be employed.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the detail of the raw material used in the Example and the evaluation method of the measured evaluation item are shown below.

[material]
Para-aramid fiber of high elongation type single repeating unit: “Twaron (registered trademark) 2100” manufactured by Teijin Limited, tensile elastic modulus 62 GPa, tensile strength 3100 MPa
Para-aramid fiber of standard type single repeating unit: “Twaron (registered trademark) 1014” manufactured by Teijin Limited, tensile elastic modulus 82 GPa, tensile strength 2800 MPa
Pre-dip treatment liquid: Toluene solution containing 10% by mass of polymeric isocyanate Resorcin-formalin-latex (RFL) treatment liquid: 4 parts by mass of a prepolymer of resorcin and formalin (2.6 parts by mass of resorcin, 1.4 parts of formalin) Mixed solution containing 17.2 parts by mass of latex (styrene-butadiene-vinylpyridine copolymer, manufactured by Nippon Zeon Co., Ltd.) and 78.8 parts by mass of water Overcoat treatment liquid: adhesive rubber shown in Table 1 Mixed liquid containing 9.3 parts by mass of rubber composition for layer, 0.7 parts by mass of polymeric isocyanate and 90 parts by mass of toluene EPDM: “IP3640” manufactured by DuPont Dow Elastomer Japan Co., Ltd., Mooney viscosity 40 (100 ° C.)
Carbon HAF: “Seast 3” manufactured by Tokai Carbon Co., Ltd.
Hydrous silica: “Nippil VN3” manufactured by Tosoh Silica Co., Ltd., BET specific surface area 240 m ² / g
Resorcin / formaldehyde condensate: Less than 20% resorcinol, less than 0.1% formalin Anti-aging agent: “Nonflex OD3” manufactured by Seiko Chemical Co., Ltd.
Vulcanization accelerator DM: Di-2-benzothiazolyl disulfide Polyamide short fiber: “66 nylon” manufactured by Asahi Kasei Corporation
Paraffin softener: “Diana Process Oil” manufactured by Idemitsu Kosan Co., Ltd.
Organic peroxide: “Parkadox 14RP” manufactured by Kayaku Akzo Corporation.

Examples 1 to 11 and Comparative Examples 1 to 12
[Production of core wire]
As cores used in Examples 1 to 7 and Comparative Examples 1 to 4, a multifilament (fineness of 1100 dtex) of a para-aramid fiber of a high elongation type single repeating unit is decreased in one direction with the number of twists shown in Table 3. These were twisted together, and four of them were aligned and twisted in the direction opposite to the lower twist with the number of upper twists shown in Table 3 to produce various twisted cords (S twisted, Z twisted) having a total fineness of 4400 dtex. The twisted cords thus obtained were immersed in a pre-dip treatment solution for 10 seconds and then heat treated at 180 ° C. for 4 minutes. Next, the pre-dip-treated various twisted cords were immersed in an RFL treatment solution for 10 seconds and then heat-treated at 230 ° C. for 2 minutes. Furthermore, after the RFL-treated various twisted cords were immersed in an overcoat treatment solution for 3 seconds, heat treatment was performed at 150 ° C. for 4 minutes to obtain a treated cord covered with adhesive rubber. On the other hand, as the cords used in Comparative Examples 5 to 7, treatment cords were prepared in the same manner as in Examples 1 to 7 and Comparative Examples 1 to 4 except that a para-aramid fiber of a standard type single repeating unit was used. did. Further, as the cords used in Examples 8 to 11 and Comparative Examples 8 to 12, multifilaments of para-aramid fibers of high elongation type single repeating units are twisted in one direction with the number of twists shown in Table 4. Examples were prepared except that three wires were aligned and twisted in the direction opposite to the bottom twist with the number of twists shown in Table 4 to produce various twisted cords (S twisted, Z twisted) having a total fineness of 3300 dtex. Treated cords were prepared in the same manner as in 1-7 and Comparative Examples 1-4. The core diameters of the treated cords obtained in Examples 1 to 7 and Comparative Examples 1 to 7 are φ0.82 mm in diameter. The cord diameters of the treated cords obtained in Examples 8 to 11 and Comparative Examples 8 to 12 are as follows. The diameter was 0.72 mm.

[Tensile strength of treated cord]
One of the obtained treated cords was pulled using an autograph (“AGS-J10kN” manufactured by Shimadzu Corporation) at a tensile speed of 50 mm / min, and the strength at break of the treated cord was measured. The tensile strength of the treated cord was evaluated according to the following criteria based on the strength value, and the results are shown in Tables 3 and 4.

○: 650 N or more (high tensile strength)
Δ: 600N to less than 650N (no problem in practical use)
X: Less than 600 N (problematic in practical use).

[Production of V-ribbed belt]
First, a 1-ply (one-ply) cotton canvas with rubber is wound around the outer periphery of a cylindrical molding mold having a smooth surface, and an unaddition formed of the rubber composition shown in Table 1 is formed on the outside of the cotton canvas. A sheet for adhesive rubber layer of sulfur was wound. Next, two treated cords (S twisted, Z twisted) in a state where an S twisted processing cord and a Z twisted processing cord are arranged in parallel at a pitch of 0.95 mm or 0.85 mm from above the adhesive rubber layer sheet. And a non-vulcanized compressed rubber layer formed with the rubber composition shown in Table 2 and an unvulcanized adhesive rubber layer sheet formed with the rubber composition. The sheets were wound in order. The molding mold was placed in a vulcanizing can and vulcanized in a state where a vulcanizing jacket was disposed outside the compressed rubber layer sheet. The cylindrical vulcanized rubber sleeve obtained by vulcanization is taken out from the molding mold, the compressed rubber layer of the vulcanized rubber sleeve is ground simultaneously with a plurality of V-shaped grooves by a grinder, and then the vulcanized rubber sleeve is cut into rings. In this way, a V-ribbed belt having a circumferential length of 1100 mm in which three ribs were formed was obtained by cutting in the circumferential direction with a cutter (the obtained belt is a cross-sectional view in the direction shown in FIG. It was in parallel with the Z-twisted processing cord).

[Belt tensile strength]
The obtained V-ribbed belt was pulled using a universal testing machine ("UH-200kNX" manufactured by Shimadzu Corporation) at a pulling speed of 50 mm / min, and the strength at break of the V-ribbed belt was measured. The tensile strength of the V-ribbed belt was evaluated according to the following criteria based on its strength value, and the results are shown in Tables 3 and 4.

○: 6000 N or more (high tensile strength)
Δ: 5700N or more and less than 6000N (no problem in practical use)
X: Less than 5700 N (practical problem).

[Bending fatigue resistance]
As shown in FIG. 2, the obtained V-ribbed belt is composed of a drive pulley 11 (diameter 120 mm, rotation speed: 4900 rpm), a driven pulley 12 (diameter 120 mm, load: 8.8 kW), an idler pulley 13 (diameter 85 mm) and a tension. It was wound around a pulley 14 (diameter 45 mm, axial load: 60 kgf (constant)) and allowed to run at an ambient temperature of 120 ° C. for 200 hours. Using a universal testing machine ("UH-200kNX" manufactured by Shimadzu Corporation), the belt tensile strength before and after the belt running test was pulled at a tensile speed of 50 mm / min, and the strength at break of the belt was measured. The strength retention was calculated by the following formula. Further, Tables 3 and 4 show the results of evaluating the calculated strength retention ratio based on the following criteria.

Strength retention rate (%) = (Strength after bending test / Strength before bending test) x 100

(Evaluation of strong retention)
○: Strength retention rate is 85% or more (good bending fatigue resistance)
Δ: Strong retention rate of 80% to less than 85% (no problem in practical use)
X: Strength retention is less than 80% (practical problem).

[Pop-out resistance]
In the evaluation of pop-out resistance, it was determined that pop-out occurred when the core wire protruded from the side surface of the belt by 5 mm or more in the high tension test and the over tension test described below. The belt running test conditions of the high tension test and the over tension test are the same as the belt running test conditions in the above-described evaluation of the bending fatigue resistance except for the axial load. The axial load of the high tension test is 82 kgf, and the over tension test The axial load was 104 kgf. Tables 3 and 4 show the results of the high-tensile test and the over-tensile test, which were evaluated according to the following criteria.

○: Pop-out did not occur in both tests (good pop-out resistance)
Δ: Pop-out occurred in the over-tensile test, but no pop-out occurred in the high-tensile test (no problem in practical use)
X: Pop-out occurred in both tests (problematic problems).

[Comprehensive judgment]
Tables 3 and 4 also show the results of evaluation on the following criteria for the results of tensile strength, bending fatigue resistance, and pop-out resistance.

○: In each evaluation item, there is no X judgment, and ○ is two or more items (Achieved simultaneously in a dimension with high tensile strength, flex fatigue resistance, and pop-out resistance)
X: In each evaluation item, even if the individual judgment is one item, x or Δ is two items or more (not simultaneously achieved in a dimension with high tensile strength, bending fatigue resistance, and pop-out resistance)

[Results and discussion]
As is apparent from Table 3, in the case of various twisted cords including four lower twisted yarns, the raw yarn type is a high elongation type, the number of lower twists is in the range of 43 to 50.3 times / 10 cm, and In Examples 1 to 7 in which the ratio of the upper twist coefficient to the twist coefficient is in the range of 0.33 to 0.66, the overall judgment is “◯”, and the tensile strength, the bending fatigue resistance, and the pop-out resistance are high. It has been achieved simultaneously in the dimension, and it can be seen that the performance required for a belt mounted on a recent automobile engine is satisfied.

In Comparative Examples 1 and 3, it is estimated that the reason why the tensile strength is low is that the number of twists is too large. Moreover, in Comparative Examples 2 and 4, it is estimated that the reason why the bending fatigue resistance is low is that the number of twists is too small.

In Examples 1 to 7, since the number of lower twists is maintained in an appropriate range, it is considered that tensile strength and bending fatigue resistance are compatible. In particular, it can be confirmed that in Examples 3 to 5 in which the number of lower twists is 46.7 times / 10 cm, the strength retention (bending fatigue resistance) is relatively high.

Next, when paying attention to the pop-out resistance, pop-out occurs in the over-tensile test and / or the high-tensile test in Example 1 and Comparative Examples 1 and 5, and the determination is “x” or “Δ”. . In these three examples, the values of the ratio of the upper twist coefficient to the lower twist coefficient are relatively small, 0.33, 0.30, and 0.38, respectively, and the upper twist is in a state of being sweeter than the lower twist. For this reason, it is considered that the untwisting torque between the lower twist and the upper twist is not offset, and the straightness of the belt is lowered, leading to the occurrence of pop-out. In addition, regarding Example 1 and Comparative Example 5, pop-out occurs only in the over-tensile test, and it is considered that pop-out does not occur in use under the appropriate tension, and the pop-out resistance is at a level at which there is no problem. Although it is judged that there is an increase in the complexity of the layout and the increase in load fluctuations as in the case of ISG-equipped engines, the configuration of Example 4 is more effective for these strict requirements. .

Further, focusing on the case where the ratio of the upper twist coefficient to the lower twist coefficient is large, in Comparative Example 4, the value of the ratio of the upper twist coefficient to the lower twist coefficient is 0.74. Is. Further, in Example 7, the ratio of the upper twist coefficient to the lower twist coefficient is 0.66, which is a relatively large value, but the determination of the bending fatigue resistance is “Δ”, and the ratio of the upper twist coefficient to the lower twist coefficient When the value of is increased, it is considered that the bending fatigue resistance tends to decrease. From the above, it can be seen that both the resistance to pop-out and the resistance to bending fatigue can be achieved by maintaining the value of the ratio of the upper twist coefficient to the lower twist coefficient within an appropriate range. In particular, in Example 4 in which the ratio of the upper twist coefficient to the lower twist coefficient is 0.49, the strength retention (flexural fatigue resistance) is the highest.

On the other hand, as can be seen from the overall judgments of Comparative Examples 5 to 7 being “x”, when the standard type single repeat unit para-aramid fiber is used as the raw yarn, the tensile strength, Bending fatigue resistance and pop-out resistance cannot be achieved at a high level at the same time. The reason for this can be presumed that even if the ratio of the upper twist coefficient to the number of twists and the lower twist coefficient is adjusted, the tensile strength and the bending fatigue resistance of the raw yarn itself are low.

As is apparent from Table 4, in the case of various twisted cords including three lower twisted yarns, the number of upper twists is in the range of 11.1 to 14.8 times / 10 cm, and the ratio of the upper twist coefficient to the lower twist coefficient is 0. In Examples 8 to 11 in the range of 50 to 0.74, the overall judgment is “◯”, and the tensile strength, the bending fatigue resistance and the pop-out resistance are simultaneously achieved in a high dimension. It can be seen that the performance required for the belt mounted on the automobile engine is satisfied. In the twisted cords including three lower twisted yarns, the number of upper twists and the higher twist coefficient ratio were better than those in the twisted cords including four lower twisted yarns. Furthermore, since the number of twisted yarns is small, it is considered that both the tensile strength and the bending fatigue resistance are achieved by reducing the number of lower twists and narrowing the core wire pitch. In particular, in Example 10 where the number of upper twists is 14.8 times / 10 cm and the number of lower twists is 38.4 times / 10 cm, it is confirmed that the strength retention (flexural fatigue resistance) is the highest. it can.

Although there is no difference in the data under the test conditions of this time, in the case of various twisted cords including three lower twisted yarns, the untwisting torque decreases as the twist coefficient ratio increases (closer to 1). It is considered that the pop-out resistance is also improved as compared with the various twisted cords containing four.

On the other hand, even if the number of upper twists is appropriate, in Comparative Example 8, since the number of lower twists is too large, the pop-out resistance is lowered. In Comparative Example 9, the number of lower twists is too small, so Fatigue decreased. Further, in Comparative Example 10, since the number of upper twists is large and the number of lower twists is too small, the bending fatigue resistance is lowered, and in Comparative Example 11, both the number of upper twists and the number of lower twists are too small, Both bending fatigue resistance and pop-out resistance decreased. Furthermore, in Comparative Example 12, since the number of upper twists and the number of lower twists were both too large, the belt tensile strength decreased.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2016-206182 filed on October 20, 2016 and Japanese Patent Application No. 2017-192971 filed on October 2, 2017, the contents of which are incorporated herein by reference.

The twisted cords of the present invention can be used for tensile bodies of various transmission belts (for example, friction transmission belts such as V-belts and V-ribbed belts, meshing transmission belts such as toothed belts and double-sided toothed belts). , Especially suitable as the core of a V-ribbed belt for driving an ISG-equipped engine, because it can be suitably used as a core of a V-ribbed belt and can simultaneously improve tensile strength, bending fatigue resistance and pop-out resistance at a high level. Available to:

DESCRIPTION OF SYMBOLS 1 ... Core wire 2 ... Compression rubber layer 3 ... V rib part 4 ... Adhesive rubber layer 5 ... Stretch layer

Claims

Various twisted cords including three lower twisted yarns containing para-aramid fibers,
The para-aramid fiber has an average fineness of 1000 to 1250 dtex, a tensile modulus of 55 to 70 GPa and a tensile strength of 2800 to 3500 MPa,
The various twisted cords have a lower twist number of 33 to 40 times / 10 cm, the upper twist direction is opposite to the lower twist, and the ratio of the upper twist coefficient to the lower twist coefficient is 0.25. ~ 1 twisted cords.
The twisted cord according to claim 1, wherein the number of twists of the twisted cord is 10 to 15 times / 10 cm.
The twisted cord according to claim 1 or 2, wherein the ratio of the upper twist coefficient to the lower twist coefficient of the twisted cord is 0.5 to 0.75.
Various twisted cords including four lower twisted yarns containing para-aramid fibers,
The para-aramid fiber has an average fineness of 1000 to 1250 dtex, a tensile modulus of 55 to 70 GPa and a tensile strength of 2800 to 3500 MPa,
In the twisted cords, the number of lower twists of the lower twisted yarn is 42 to 52 times / 10 cm, the direction of the upper twist is opposite to that of the lower twist, and the ratio of the upper twist coefficient to the lower twist coefficient is 0.25. ~ 1 twisted cords.
The twisted cord according to claim 4, wherein the number of upper twists of the twisted cord is 5 to 15 times / 10 cm.
The twisted cord according to claim 4 or 5, wherein the ratio of the upper twist coefficient to the lower twist coefficient of the twisted cord is 0.33 to 0.66.
The twisted cord according to any one of claims 1 to 6, wherein the average diameter of the twisted cord is 0.7 to 0.9 mm.
The stranded cord according to any one of claims 1 to 7, wherein the para-aramid fiber is a polyparaphenylene terephthalamide fiber.
Twist the para-aramid fiber in one direction to obtain a lower twisted yarn, three or four lower twisted yarns obtained in the lower twisted step are aligned and twisted in the opposite direction to the lower twist The method for producing multi-twisted cords according to any one of claims 1 to 8, further comprising an upper twisting step for obtaining a multi-twisted cord.
A transmission belt comprising a tensile body formed of the stranded cords according to any one of claims 1 to 8.
The transmission belt according to claim 10, wherein the tensile body is a core wire, and an average pitch of the core wires is 0.8 to 1.05 mm.
The transmission belt according to claim 10 or 11, further comprising a compression rubber layer formed of a rubber composition containing a rubber component.
The transmission belt according to claim 12, wherein the rubber component is an ethylene-α-olefin elastomer.
A method of using the transmission belt according to any one of claims 10 to 13 to drive an engine equipped with an ISG.