JP3070613B2 - Aramid fiber cord and toothed belt using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aramid fiber cord with improved bending fatigue resistance and improved fraying of a cord, and a toothed belt using the same.

[Prior art] Unlike a flat belt or a V-belt, a toothed belt has the advantages of being able to reliably transmit without slipping, and having advantages such as not requiring lubrication compared to the reliable transmission of a gear or a chain. In recent years, demand has increased rapidly. In particular, the advance is remarkable in the transmission drive of an overhead camshaft (OHC) of an automobile.

However, in the case of the OHC drive, since the toothed belt is used under a high load and with multiple axes, the belt receives bending fatigue and is elongated. When the toothed belt used under such severe conditions is stretched by about 0.1% or more, the engagement with the pulley becomes poor, and the jumping phenomenon tends to occur. The tendency of the toothed belt to behave is influenced by the properties of the cord, that is, elongation and bending fatigue.

By the way, an aramid fiber cord having high strength and small elongation is used today as one of the cords of the toothed belt. For example, Japanese Patent Application Laid-Open No. 54-135954 discloses the use of a toothed belt for cords having a twist coefficient of aramid fiber of 1.4 to 2.6 and a thickness of 300 to 500 d.

In addition, recently, as an aramid fiber cord that becomes a core wire, several yarns are aligned and turned into a twisted yarn, a flexible RFL treatment with good adhesion as a film, and a rubber glue is applied and overcoated. Is being developed. This is intended to improve both the flex fatigue of the belt and the fraying of the cord.

[Problem to be Solved by the Invention] In such an aramid fiber cord, the surface of the cord is
Since the RFL solution treatment and the overcoat treatment were performed sequentially, the fraying of the cord was improved. However, when the toothed belt using the cords was run for a long time under a high-load condition at a high temperature, the filaments of the aramid fiber rubbed against each other, causing fibrillation of the filaments. This has been found to cause a reduction in the strength retention of the toothed belt and promote bending fatigue.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. An aramid fiber cord which prevents the fibrillation of filaments, improves the bending fatigue of the belt, and eliminates the fraying of the cord, and a toothed cord using the same. Its main purpose is to provide belts.

[Means for Solving the Problems] That is, a feature of the present invention is an aramid fiber cord used as a core wire of a toothed belt, and the cord is pre-treated with a filament group constituting a raw yarn. An aramid fiber cord coated with a rubber latex as an agent is attached by impregnating and attaching at least two or more such yarns, and then twisted and then impregnated with a resorcinol-formalin-rubber latex liquid and attached, and further coated with a rubber layer. It is in.

Further, in a toothed belt including a plurality of tooth portions arranged along the belt length direction and a back rubber in which a core wire is embedded, a pre-treatment is performed on a filament group constituting an original yarn of aramid fiber as the core wire. A rubber latex is impregnated and adhered as an agent, and at least two or more such yarns are aligned and twisted, and then a resorcinol-formalin-rubber latex liquid is impregnated and adhered, and the rubber layer is further covered. The toothed belt used.

The rubber latex used as the pretreatment agent is at least one latex selected from chlorosulfonated polyethylene, alkylated chlorosulfonated polyethylene, hydrogenated nitrile rubber, and epichlorohydrin.

FIG. 1 is a sectional perspective view of a toothed belt according to the present invention. A toothed belt 1 has a back rubber 4 in which a plurality of tooth rubbers 2 and a core wire 3 made of aramid fiber cord are embedded along the belt longitudinal direction. A cover canvas 5 is adhered to the surface of the tooth rubber 2.

The tooth rubber 2 and the back rubber 4 are chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene (ACSM) or acrylonitrile-butadiene rubber. Butadiene rubber (referred to as hydrogenated nitrile rubber and expressed as H-NBR) is a rubber with improved heat deterioration resistance.

Magnesium oxide-aluminum oxide solid solution is added to the chlorosulfonated polyethylene rubber to improve heat resistance.
The aluminum oxide solid solution is generally represented by Mg _0.7 Al _0.3 O _1.15 , and a specific example thereof is KW-20 manufactured by Kyowa Chemical Industry Co., Ltd.
00 and KW-2100.

The amount of the acid acceptor added was chlorosulfonated polyethylene.
The amount is 1 to 50 parts by weight, preferably 4 to 20 parts by weight based on 100 parts by weight. In this case, if the magnesium oxide-aluminum oxide solid solution is less than 1 part by weight, hydrogen chloride generated during crosslinking must be sufficiently removed. Therefore, a crosslinked point of the chlorosulfonated polyethylene is reduced and a predetermined vulcanizate cannot be obtained, resulting in a toothed belt which lacks heat resistance and easily generates cracks at an early stage. On the other hand, if it exceeds 50 parts by weight,
The Mooney viscosity becomes extremely high, causing processing problems.
Therefore, the rubber composition used for the toothed belt of the present invention is:
In order to improve the belt life and satisfy the workability, it is most preferable to add a magnesium oxide-aluminum oxide solid solution to the chlorosulfonated polyethylene within the above range.

The alkylated chlorosulfonated polyethylene rubber was obtained by chlorosulfonating a low-density polyethylene having a linear molecular structure so that the chlorine content was in the range of 15 to 45 wt% and the sulfur content was in the range of 0.5 to 2.5 wt%. Chlorosulfonated polyethylene rubber compositions are used. Since this rubber has an alkyl side chain, the crystallinity of polyethylene in the main chain is reduced, and the rubber has rubber-like properties. Also, since crystallization hardly occurs even in a low temperature region (-10 ° C or lower),
Maintains rubber elasticity and has cold resistance.

As the cover canvas 5, a plain woven fabric, a twill woven fabric, a satin woven fabric, or the like having elasticity in a weft direction (belt longitudinal direction) can be used. Above all, in the case of plain woven canvas, the weft 5a and the warp 5b are alternately vertically crossed and laminated, so that the weft 5a and the warp 5b
Are formed continuously in the weft and meridian directions. On the other hand, when twill weave and satin weave are used, wefts and warps form intersections in a wave shape every plural number, and there are fewer wave-shaped intersections than ordinary plain weave canvas, and rubber is not only between yarns but also at intersections. It is preferable to penetrate the belt sufficiently into the gap and use it in the belt corrugated portion because it is possible to avoid direct contact between the warp and the weft in the belt flexibility and improve the belt life.

Then, the cover canvas 5 is first made of a weft yarn constituting a woven fabric.
The surfaces of 5a and 5b are coated with an adhesive layer made of a cured product of an RFL solution, an isocyanate solution or an epoxy solution.

The cover canvas is made of polyamide fiber, polyester fiber, aromatic polyester fiber or the like.

Further, in the aramid fiber cord which is the core wire 3, 1
100 to 6 denier aromatic polyamide filaments
200200 converged raw yarns are impregnated with an aqueous solution of a rubber latex having excellent heat resistance, such as a chlorosulfonated polyethylene, an alkylated chlorosulfonated polyethylene, a hydrogenated nitrile rubber, or an aqueous latex of epichlorohydrin. Dry and pre-treat for ~ 10 minutes. The above-mentioned solidified rubber latex sufficiently intervenes in the gaps between the filament groups constituting the raw yarn, and prevents fibrillation due to rubbing of the filaments when the filaments are converged.

The pre-processed yarn has 2 to 5 yarns and a twist coefficient of 2.5.
Twisted in the range of ~ 3.5, followed by RFL treatment and overcoat treatment.

The RFL solution used here is a mixture of a latex of an initial condensate of resorcinol and formalin, and in this case, the molar ratio of resorcinol to formalin is preferably 1: 0.5 to 3 in order to increase the adhesive force. .

In addition, the initial condensate of resorcinol and formalin is mixed with latex such that the resin content is 2 to 30 parts by weight based on 100 parts by weight of the rubber component of the latex,
The total solids concentration is adjusted to 5-40%.

The latex is a styrene-butadiene-vinylpyridine terpolymer, chlorosulfonated polyethylene,
Hydrogenated nitrile rubber, epichlorohydrin, natural rubber,
Latex such as SBR, chloroprene rubber and olefin-vinyl ester copolymer.

The rubber paste used in the overcoat treatment is a rubber composition having excellent adhesion to the backing rubber, for example, chlorosulfonated polyethylene, alkylated chlorosulfonated polyethylene or hydrogenated nitrile rubber rubber composition, isocyanate, methyl ethyl ketone, and toluene. And the like.

The aramid fiber associated with the core wire 3 is a polyamide fiber having an aromatic ring in the main chain of the molecular structure, for example, trade names such as Conex, Nomex, Kevlar, and Technora.

[Action] In the present invention, since the solidified rubber latex is attached to the gaps between the filament groups of the aramid fiber raw yarn,
Even if the filaments are converged and in contact with each other, fibrillation due to rubbing of the filaments does not occur. The toothed belt using the cords hardly causes a decrease in tension during running, and is excellent in bending fatigue resistance. Further, the core wire exposed on the belt end face is less likely to be frayed because the filaments are bonded to each other by the rubber latex.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1] A 1500 denier raw yarn in which a plurality of filament groups were converged as a core wire was impregnated with a pretreatment liquid consisting of a 5% aqueous solution of a hydrogenated nitrile rubber latex or a 5% aqueous solution of a chlorosulfonated polyethylene latex, After drying at 80 ° C for 5 minutes, the yarns are drawn and aligned twice twice / 10c
m, and then impregnated with the RFL solution shown in Table 1, dried at 140 ° C. for 4 minutes, baked at 210 ° C. for 40 seconds, and further impregnated with the rubber paste shown in Table 2. rear,
It was dried at 160 ° C. for 50 seconds, baked at 200 ° C. for 50 seconds, and overcoated to obtain an aramid fiber cord.

On the other hand, the cover canvas uses 6.6 nylon wooly-processed yarn for the warp and uses industrial 6.6 nylon for the warp. The thickness on the belt cross section is 0.25 mm and 0.30 mm. Of twill weave, which has been subjected to an adhesive treatment matching the tooth rubber.

For the tooth rubber and the back rubber, a rubber composition composed mainly of hydrogenated nitrile rubber and chlorosulfonated polyethylene rubber shown in Table 3 was used.

Using the above materials, a toothed belt was manufactured by a conventional press-fitting method. The obtained belt is an STPD tooth form having a tooth pitch of 8 mm, and has 99 teeth and a belt width of 19.1 mm.

Then, the obtained core wire was examined for fraying property, the adhesive strength between the core wire and the backing rubber of the belt before running, and the pulling force of the core wire. Table 4 shows the results. The belt was run by a biaxial running test, and the relationship between the running time and the retention rate (%) of the belt tensile strength was determined. The result is shown in FIG.

In the biaxial running test, a driving pulley (teeth portion 21), one driven pulley (42 teeth), and a tension pulley (52 mm in diameter) between both pulleys. The running conditions were an ambient temperature of 120 ° C., a rotational speed of the driving pulley of 72,000 rpm, a load of 5 horsepower, and an initial tension of 15 kgf.

As described above, the belts No. 3 and No. 4 have good balance in the fraying property of the cord, the adhesive strength between the cord and the backing rubber, the pulling force of the cord and the retention rate of the belt tensile strength with respect to the running time. The belt No. 4 is particularly excellent. The belt No. 2 has a good retention of the belt tensile strength, but is inferior in the looseness of the cord and the adhesive strength between the cord and the backing rubber.

From this, it is understood that the core wire in which the aramid fiber original yarn was pre-treated with latex in advance has excellent fraying properties, and the belt using the same has excellent durability.

[Effects] As described above, in the aramid fiber cord used as the core wire of the toothed belt of the present invention and the toothed belt using the same, the solidified rubber latex penetrates into the gaps between the filament groups of the aramid fiber raw yarn, Due to the adhesion, fibrillation due to rubbing of filaments is prevented, thereby improving the bending fatigue property of the belt, and the core wire is RFL treated and overcoated, and the filament bundle is well bound. Therefore, it is possible to prevent the core wire from fraying.

[Brief description of the drawings]

FIG. 1 is a cross-sectional perspective view of a toothed belt according to the present invention, and FIG. 2 is a graph showing the relationship between the running time of the toothed belt and the retention rate of belt tensile strength. 1 ... toothed belt 2 ... tooth rubber 3 ... core wire 4 ... back rubber 5 ... cover canvas

 ──────────────────────────────────────────────────続 き Continuing on the front page Judge, Susumu Funaki, Judge Judge Yoshihiro Ikeda Judge, Minoru Torii (56) References JP-A-56-105135 (JP, A) JP-A-63-74632 (JP, A) Showa 63-62651 (JP, U) Actually open Showa 62-151396 (JP, U)

Claims (4)

(57) [Claims] An aramid fiber cord used as a core wire of a toothed belt, wherein the cord is impregnated with a rubber latex as a pretreatment agent and adheres to a group of filaments constituting a raw yarn of aramid fiber. An aramid fiber cord, wherein at least two or more yarns are aligned and twisted, and subsequently, a resorcin-formalin-rubber latex liquid is impregnated and adhered thereto, and further covered with a rubber layer. 2. The aramid fiber cord according to claim 1, wherein the pretreatment agent is a latex selected from chlorosulfonated polyethylene, alkylated chlorosulfonated polyethylene, hydrogenated nitrile rubber and epichlorohydrin. 3. In a toothed belt comprising a plurality of teeth arranged along a belt length direction and a backing rubber having a core wire embedded therein, a filament group constituting an aramid fiber raw yarn as the core wire. , A rubber latex was impregnated as a pretreatment agent and adhered, and at least two such yarns were aligned and twisted, followed by impregnating and adhering a resorcinol-formalin-rubber latex liquid, and further covered with a rubber layer. A toothed belt characterized by using a belt. 4. The toothed belt according to claim 3, wherein the pretreatment agent is a latex selected from chlorosulfonated polyethylene, alkylated chlorosulfonated polyethylene, hydrogenated nitrile rubber and epichlorohydrin.