JP3185992B2 - belt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance belt having excellent tensile strength, dimensional stability, and fatigue resistance used for power transmission, transportation, and the like. It relates to a belt provided in a layer.

[0002]

2. Description of the Related Art Generally, a belt is formed by laminating a tensile member such as fiber and a polymer elastic member such as rubber. As the tensile member constituting the belt, conventionally, for example, polyester fiber, polyvinyl alcohol (hereinafter abbreviated as PVA) fiber, glass fiber, metal fiber, and liquid crystal fiber such as aramid or wholly aromatic polyester are used. ing. However, with recent social progress,
The demand for higher performance of belts is becoming more stringent, and conventional belts are not always used satisfactorily.

That is, conventional polyester fibers and PV
The strength and Young's modulus of fiber A are unsatisfactory for increasing the tension of a high-performance belt, and the dimensional stability at high temperatures is poor. Glass fibers are susceptible to the effects of moisture, and have the drawback that when they absorb water during use, the tensile strength drops sharply, and when they are repeatedly bent on a pulley, the fibers themselves cause structural destruction, resulting in a decrease in strength and ultimately a belt. However, there is a problem that the so-called bending fatigue property is inferior, that is, fracture occurs. Further, the metal fiber has a drawback that rust is generated by water absorption, and also has a problem that the bending fatigue property is inferior similarly to the glass fiber. Liquid crystalline polymer fibers such as aramid fibers and wholly aromatic polyester fibers have strength,
It has a high Young's modulus and excellent dimensional stability at high temperatures. Therefore, the use of the fiber as a tensile member for a high-performance belt is described, for example, in Japanese Patent Application Laid-Open No. 63-57941, using a wholly aromatic polyester fiber. No. 8335 proposes to use a mixture of aramid fiber and glass fiber or metal fiber. In other words, liquid crystalline polymer fibers have high strength, high Young's modulus, and high dimensional stability, and also have excellent bending fatigue properties as compared with glass fibers and metal fibers, making them ideal materials for belt tensile members. When the ratio is small, the liquid crystal polymer fiber has extremely excellent bending fatigue properties.

However, with the advancement of society, there is a strong need for compact equipment and space-saving equipment, and belts used for power transmission or transportation in compact equipment or equipment have been developed. The distortion rate must be large. That is, since the belt repeatedly undergoes bending with a large distortion rate, bending fatigue under the condition of a large distortion rate is important. However, it has been found that the conventional liquid crystalline polymer fiber has a significantly deteriorated bending fatigue property when the strain rate is large.

On the other hand, in the case of a flexible polymer, ultra-high molecular weight polyethylene is used as a dilute solution, gel-spinning and ultra-stretching, whereby the molecular chains are highly oriented and crystallized in the fiber axis direction, thereby providing high strength and high Young's strength. The rate of fiber is getting.
Also in the case of PVA, which is also a flexible polymer, by gel-spinning and highly stretching PVA with high degree of polymerization,
High strength and high Young's modulus fibers are obtained. Further, in the case of polyacrylonitrile, similarly, fibers having high strength and high Young's modulus are obtained by devising each of the polymer, spinning method and drawing method. However, fibers obtained from ultra-high-molecular-weight polyethylene have low heat resistance and low adhesiveness to the elastic polymer. In addition, high polymerization degree PVA fiber and high performance polyacrylonitrile fiber are as strong as liquid crystal polymer fiber,
It does not have a Young's modulus, and has a problem that the tensile strength of the belt is inferior to the liquid crystalline polymer fiber in terms of strength and dimensional stability.

[0006]

Accordingly, the present invention is applicable to belts used in compact equipment,
An object of the present invention is to obtain a high-performance belt that can be used at a high tension or at a high temperature and that has excellent durability against repeated bending fatigue with a large strain rate.

[0007]

That is, the present invention relates to a method for producing a tensile body, wherein the tensile body is composed of a plurality of layers, at least one of which is 20 g / g.
and d. a synthetic fiber of a liquid crystalline polymer having a strength of at least d and a Young's modulus of at least 400 g / d, and at least another layer of a flexible polymer having a strength of at least 15 g / d and a Young's modulus of at least 250 g / d. A belt made of fiber. ". In the present invention, it is important that the tensile member is formed into a multi-layer structure, and the tensile member layer that withstands tension and the tensile member layer that withstands bending fatigue are separated and shared.

[0008] The tensile strength layer that can withstand tension has a strength of 20 g /
d and a Young's modulus of 400 g / d, it is necessary to use a synthetic fiber of a liquid crystalline polymer, which makes it difficult to stretch even when a high tension is applied to the belt. Can be hardly cut and broken. If the strength is less than 20 g＼d or the Young's modulus is less than 400 g / d, the high-performance belt aimed at by the present invention cannot be obtained. Examples of the synthetic fibers of the liquid crystalline polymer according to the present invention include, for example, aramid fibers commercially available under the trade names Kevlar, Twaron, and Technora, and wholly aromatic polyester fibers commercially available under the trade name Vectran. These liquid crystalline fibers also have excellent high-temperature performance, and are also effective in maintaining excellent performance even when the belt is exposed to high temperatures. Although it depends on the purpose of use of the belt, when it is used at an extremely high tension, for example, Kevlar 49 having a high Young's modulus is preferable. When the fibers absorb water due to humidity and cause a dimensional change, a wholly aromatic polyester fiber that does not substantially absorb water than a wholly aromatic polyamide (aramid) fiber that easily absorbs water, such as Vectran, is preferred.

Tensile strength is 15 g for the tensile body layer that can withstand flex fatigue.
/ D or more, and it is necessary to use a synthetic fiber of a flexible polymer having a Young's modulus of 250 g / d or more. 15g / d strength
If it is less than 250 g / d or the Young's modulus is less than 250 g / d, the high performance belt aimed at by the present invention cannot be obtained. Since liquid crystalline polymer fibers are inferior in bending fatigue at a large strain rate, it is important to use flexible polymer synthetic fibers to overcome this problem. It is not clear why flexible polymer fibers have better large strain bending fatigue properties than liquid crystalline polymer fibers, but in liquid crystalline polymers the orientation and crystallization of molecules in the fiber axis direction is extremely high, but in the vertical direction. The molecular force is weak and the molecular weight is relatively low, so few tie molecules penetrate between the crystals, whereas in the case of high-strength fibers made of flexible polymers, the molecules are oriented in the fiber axis direction. As it crystallizes and has a high molecular weight, one molecular chain is incorporated not only in one crystal but also in another crystal, and there are many molecules connecting the crystals, that is, tie molecules. It is speculated that they may endure.

The synthetic fiber of the flexible polymer of the present invention is not particularly limited as long as it has a strength of 15 g / d or more and a Young's modulus of 250 g / d or more. Performance polyacrylonitrile-based fibers are exemplified, but high-polymerization degree PVA-based fibers are most preferable in view of the overall performance of strength, Young's modulus, heat resistance, and adhesiveness with the integrated polymer elastic body. In particular, high polymerization degree PVA-based fibers having a viscosity average polymerization degree of 3,000 or more can have strength and Young's modulus comparable to liquid crystal polymer fibers by devising spinning and drawing methods, and have an affinity with a polymer elastic material. It is particularly preferable because it has excellent adhesiveness, has a free shrinkage at 200 ° C. of several percent or less, and has a characteristic that flex fatigue under large strain is remarkably superior to liquid crystal polymer fibers. .

The synthetic fibers of the liquid crystalline polymer and the synthetic fibers of the flexible polymer are each appropriately twisted by a conventional method to form a cord, treated with an adhesive to form a tensile body, and arranged in a multilayer in a belt. Then, the belt is manufactured by integrally molding with the elastic polymer.

When a belt is actually used, for example, on a pulley, the belt is bent. In this case, within the same belt cross-section, it can be divided into three zones: a zone subjected to stretching, a zone subject to compression, and a neutral zone subject to neither. Depending on the actual use condition of the belt, the stress received in the belt may be subjected to only elongation in one zone and only compression in another zone. In a belt in such a use state, when a tensile member made of a synthetic fiber of a liquid crystalline polymer having a high strength and a high Young's modulus is arranged in a zone subjected to tensile stress and a neutral zone, the elongation during actual use is small and the dimensional stability is excellent. It is preferred. On the other hand, it is preferable to dispose a tensile member made of a synthetic fiber of a flexible polymer having excellent bending fatigue properties in the zone subjected to compressive stress, because the tensile member exhibits high resistance to compression. Also, depending on the actual use condition of the belt, within the same belt cross section, a certain pulley receives extension stress,
On another pulley, a zone may be divided into a zone which receives compressive stress and repeatedly undergoes expansion and compression and a neutral zone. In this case, it is preferable to arrange a tensile member made of synthetic fiber of liquid crystalline polymer in the neutral zone, and to arrange a tensile member made of synthetic fiber of flexible polymer in the zone which is subjected to repeated stretching and compression. .

In the present invention, another fiber such as a metal fiber may be mixedly arranged in the tensile body made of synthetic fiber of a liquid crystalline polymer, as long as the object of the present invention is not impaired.
Similarly, in a tensile body made of a synthetic fiber of a flexible polymer, even if other fibers such as a synthetic fiber of a liquid crystalline polymer or a metal fiber are mixed and disposed in a range that does not deteriorate the bending fatigue for the purpose of improving tensile strength. I do not care.

Depending on the purpose of use of the belt, not only one layer but also a plurality of layers of synthetic fibers of liquid crystalline polymer may be laminated. Not only the layers but also a plurality of layers may be laminated. In particular, in the case of a tensile body made of a synthetic fiber of a flexible polymer, it is often convenient to arrange a tensile body made of a synthetic fiber of a liquid crystalline polymer in at least two layers above and below the neutral zone. Further, it is also possible to add and laminate a tensile member made of a fiber other than a synthetic fiber of a liquid crystal polymer or a flexible polymer.

As described above, according to the present invention, in a tensile member of a belt, a tensile member made of a synthetic fiber of a liquid crystalline polymer having an ultra-high strength and an ultra-high Young's modulus is used for a zone sharing tensile strength.
For the zone that is susceptible to bending fatigue, use a tensile member made of synthetic fiber of a flexible polymer with higher strength and higher Young's modulus than ordinary fibers that are resistant to compression fatigue, and even in resistance to tension,
Further, the present invention provides an excellent high-performance belt with respect to bending fatigue having a large strain rate.

The strength and Young's modulus of the fiber according to the present invention are measured by measuring a 50-3000 denier multifilament yarn with substantially no twist (about 80 T / m) using JI.
According to SL-1013, test length 20cm, tensile speed 5
Instron 4301 manufactured by Instron was used under the conditions of 0% / min and an initial load of 50 mg / d, and the chuck was performed using a grip having a large grip for a cord. Denier was cut to 30 cm under a load of 100 mg / d, and determined by a gravimetric method.

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Kevlar 29 which is a solution liquid crystalline wholly aromatic polyamide fiber was used as one tensile member of the belt. This 1500d / 1000f filament yarn has a strength of 22.5 g / d and a Young's modulus of 520 g.
/ D. 230 t / m to this filament yarn
Under twist (Z twist), three ply yarns and over twist (S twist), 1500 d / 1 × 3, 230 × 230 t /
m raw codes were obtained. This was subjected to RFL dipping to obtain a dip code.

On the other hand, for the other tensile member of the belt, PVA having a viscosity average degree of polymerization of 8000 was dissolved in dimethyl sulfoxide, wet-spun into a 3 ° C. methanol bath, and wet stretched.
After extraction and drying, the resultant was subjected to dry heat stretching to obtain a high polymerization degree PVA fiber of 1500 dr / 400f. The strength of this PVA fiber is 2
1.1 g / d and Young's modulus were 450 g / d. This filament yarn is twisted and R
FL processing was performed to obtain a dip code.

The Kevlar 29 dip cords are arranged in a single layer, and the high polymerization degree PVA fiber dip cords are arranged in a single layer, embedded in rubber and vulcanized to form a belt comprising a two-layer tensile body. Was prepared.

The resulting belt had excellent tensile strength and low elongation. The belt is placed on a 25 mm diameter pulley with the cord layer of high polymerization degree PVA fiber on the pulley side.
The bending fatigue test was performed 500,000 times at 5 ° C. After the fatigue test, the belt was disassembled to measure the strength retention of Kevlar and high polymerization degree PVA fibers. As a result, the Kevlar on the extension side is 95
%, And the high polymerization degree PVA fiber on the compression side showed excellent retention of 52% even after 500,000 times, and was excellent.

The flexural fatigue test was performed 30,000 times at 100 ° C. in the same manner, and the strength retention was measured.
8%, and the high polymerization degree PVA fiber was 63%.

Comparative Example 1 A belt was produced in the same manner as in Example 1 except that two layers of the same Kevlar were used in place of the high polymerization degree PVA fiber of Example 1 as a tensile member of the belt. The obtained belt was subjected to 500,000 bending tests at 25 ° C. and 30,000 bending tests at 100 ° C. in the same manner as in Example 1, and the strength retention was measured. The strength retention of the Kevlar on the extension side was 90% or more as in Example 1, but the strength retention of the Kevlar on the side of the pulley that received compression was 8% after 500,000 times at 25 ° C and 100 ° C. After 30,000 times, 21% was significantly damaged.

Example 2: Vectran HT, a wholly aromatic polyester fiber having a liquid crystalline property, as a belt tensile member
(High-strength type) was used. This 1500d / 300f
Has a strength of 27.5 g / d and a Young's modulus of 620 g / d. 20 to this filament yarn
A 0-t / m Z twist was applied, two strands were twisted, and the upper twist was S-twisted to obtain a raw cord of 1500 d / 1 × 2 and 200 × 200 t / m. This was subjected to RFL dipping to obtain a dip code.

On the other hand, as the other tensile member of the belt, PVA having a viscosity average polymerization degree of 17000 was dissolved in dimethyl sulfoxide, wet-spun in a methanol bath at 0 ° C.
After extraction and drying, the resultant was subjected to dry heat drawing to obtain 1500 d / 400 f high polymerization degree PVA fiber. The strength of this PVA fiber is 2
4.1 g / d and Young's modulus were 550 g / d. This filament yarn was subjected to twisting and RFL treatment in the same manner as Vectran HT to obtain a dip cord.

One layer of Vectran HT cord was placed at the center, and two layers of dip cords of high polymerization degree PVA fiber were placed above and below, thereby producing a belt having three layers of tensile members.
This belt was excellent in tensile strength, elongation, dimensional stability at the time of moisture absorption and high temperature, and further, flex fatigue.

[0027]

According to the conventional belt, when the tensile strength is large, the bending fatigue property is poor and the correlation is inverse. However, in the present invention, the high strength and high Young's modulus liquid crystalline polymer synthetic fiber is applied to the zone where the tensile strength is required. In the zone where bending fatigue is required under compressive stress, synthetic fiber of flexible polymer with high strength and high Young's modulus is used as the tensile body in the zone where bending fatigue is required.
The above problem was solved by so-called hybrid of the tensile member, and a high-performance belt was obtained. Therefore, the belt of the present invention is a flat belt for power transmission and conveyance, a V belt,
It can be effectively used for toothed belts, profiled belts and the like.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16G 1/08 F16G 1/10 F16G 1/28 F16G 5/06 F16G 5/08

Claims (3)

(57) [Claims] The tensile body is composed of multiple layers, at least one of which is composed of synthetic fibers of a liquid crystalline polymer having a strength of at least 20 g / d and a Young's modulus of at least 400 g / d, and at least one other at least 15 g. / D or more and 250g /
A belt comprising a synthetic fiber of a flexible polymer having a Young's modulus of d or more. 2. The belt according to claim 1, wherein a tension member made of synthetic fiber of liquid crystalline polymer is disposed in a neutral zone of the belt, and the tension member made of synthetic fiber of flexible polymer is compressed by the belt. A belt, which is arranged in a zone subjected to stress. 3. The belt according to claim 1, wherein the flexible polymer has a viscosity average degree of polymerization of 3,000.
A belt comprising the above polyvinyl alcohol.