JP6762075B2 - Rubber reinforcement cord - Google Patents

Description

The present invention relates to an aramid fiber cord for rubber reinforcement, and more particularly to a rubber reinforcing cord having excellent wear-fatigue resistance between threads.

Reinforcing fiber cords are embedded in rubber products such as rubber hoses, transmission belts, conveyor belts, and tires. As a reinforcing fiber cord, an aramid fiber cord having a property of high strength and low elongation is widely known. Aramid fiber cord has high strength, high elastic modulus, high heat resistance, flame retardancy, chemical resistance, etc. Therefore, as industrial materials, rubber reinforcements such as rubber hoses, tires, conveyor belts, and ropes , Widely used for fish nets, etc.

Aramid fiber cords for rubber reinforcement are made by arranging a plurality of raw yarns to form twisted yarns, which are then immersed in a solution of resorcin, formalin, and rubber latex (hereinafter referred to as RFL) to impart adhesiveness to rubber. It has been put into practical use, and it is well known that the bending fatigue resistance of rubber products is improved by using a rubber reinforcing cord.

However, when a rubber hose using an aramid fiber cord for rubber reinforcement is repeatedly subjected to a pulsating load of high temperature and high pressure, the filaments of the aramid fibers rub against each other and are damaged, resulting in fluffing of the filaments. Be done.

As a method for improving fluffing, Patent Document 1 describes a treated cord material obtained by impregnating an aramid fiber with a pretreatment agent containing an epoxy resin or an isocyanate resin as a main component to prepare a cord material, and impregnating this cord material with an RFL solution. A reinforcing fiber cord made by aligning and twisting the epoxies is disclosed. As a means for eliminating fluffing of the cord, a method of immersing the belt in an aqueous solution such as vinyl acetate and then drying it is also disclosed.

Patent Document 2 discloses that the frictional force between fibers is reduced when aramid fibers treated with an RFL agent solution are used. However, since the techniques disclosed in Patent Documents 1 and 2 are methods for post-treating the aramid fiber cord, they are not a method for fundamentally solving the abrasion between filaments and the occurrence of fluffing during running. ..

Further, Patent Document 3 discloses that an oil agent or the like may be attached to the fiber cord in order to reduce friction between the fiber filaments constituting the fiber cord, but the quality level is satisfactory. It did not reach.

Japanese Unexamined Patent Publication No. 6-057568 Japanese Unexamined Patent Publication No. 7-229068 Japanese Unexamined Patent Publication No. 6-286426

An object of the present invention is to provide a fiber cord for rubber reinforcement, which eliminates fluffing of the cord due to the filaments of the aramid fiber rubbing against each other and damaging each other, and has excellent wear fatigue resistance between the yarns.

As a result of diligent studies to achieve the above problems, the present inventors have made a cord material in which an oil agent is adhered to the surface of the aramid fiber, and the cord materials are aligned and twisted to optimize the twist coefficient. As a result, we have succeeded in obtaining a fiber cord having excellent wear and fatigue resistance between threads, and have completed the present invention.

That is, the present invention is as follows.

1) dioleyl adipate aramid fiber multifilament oil agent single yarn fineness was attached is filament number is present 400-1500 in 1.1~1.5dtex containing more than 50 wt%, the following formula (1 A rubber reinforcing cord having excellent wear-fatigue resistance between yarns, characterized in that a single twist is applied so that the twist coefficient defined in) is 1.0 to 1.4.
K: Cord twist coefficient
T: Number of twists of cord (times / 10 cm)
D: Fineness of aramid fiber (dtex)

2) The amount of oil adhered is 0.3 to 1.5% by mass with respect to the fiber mass when the water content of the aramid fiber is converted to 0% by mass. Excellent rubber reinforcement cord.

According to the present invention, it is possible to provide a rubber reinforcing cord having excellent wear-fatigue resistance between threads by applying an appropriate twist to the aramid fiber to which the oil agent is attached.

It is explanatory drawing explaining the abrasion fatigue resistance test method.

The aramid fiber to which the oil agent is attached, which is the cord material in the present invention, can be easily obtained by applying the oil agent to the ordinary aramid fiber by a known method.
In the present invention, the water content (R) refers to a value obtained by the following formula.
R = {(m _{1 −} m ₂ ) / m ₂ } × 100
R: Moisture content [%]
m ₁ : Mass at the time of sample collection [g]
m ₂ : Absolute dry mass of sample [g]

In the present invention, the aramid fiber is a fiber having at least one divalent aromatic group which may be usually substituted in the repeating unit of the polymer forming the fiber, and may be a fiber having at least one amide bond. However, there is no particular limitation, and it may be a known one called a total aromatic polyamide fiber or an aramid fiber. In the above, the "optionally substituted divalent aromatic group" means a divalent aromatic group which may have the same or different one or more substituents.

The aramid fiber includes a para-based aramid fiber and a meta-based aramid fiber, and the present invention is particularly effective and preferable for the para-based aramid fiber having excellent tensile strength. Examples of the para-aramid fiber include polyparaphenylene terephthalamide fiber (Dupont, USA, manufactured by Toray DuPont Co., Ltd., trade name "Kevlar" (registered trademark)), copolyparaphenylene-3,4'-oxydi. Examples thereof include phenylene terephthalamide fiber (manufactured by Teijin Limited, trade name "Technora" (registered trademark)). Examples of the meta-aramid fiber include polymetaphenylene terephthalamide fiber (manufactured by DuPont in the United States, trade name "NOMEX" (registered trademark)) and the like. Among these aramid fibers, polyparaphenylene terephthalamide fiber having excellent cut resistance is desirable.

The best way to add oil to aramid fibers is to dissolve polyparaphenylene terephthalamide (PPTA) in concentrated sulfuric acid to make a viscous solution of 18-20% by mass, which is then discharged from the spun cap and slightly After spinning in the air for a while, the fibers are spun into water, the fibers coagulated in the spinning bath are neutralized with an aqueous solution of sodium hydroxide, and then the oil agent is added to the PPTA fibers dried to a moisture content of 15% by mass or less. It is to give and penetrate into the fiber. The application temperature is not particularly limited, and may be applied in a temperature range of about 5 to 90 ° C.

The oil agent is preferably adhered in an amount of 0.3 to 1.5% by mass, preferably 0.4 to 1.2% by mass, based on the fiber mass in which the water content of the PPTA fiber is converted to 0%.

As the oil agent, any general oil agent that can be used for aramid fibers can be used without particular limitation. For example, fatty acid ester, polyether such as polyoxyethylene polyoxypropylene copolymer or derivative, mineral oil, etc. Can be mentioned.

Among them, fatty acid ester-based oils containing at least 50% by mass of fatty acid esters in the oils have less loss of oil residue and fibrils in the twisting process and have a high affinity for PPTA fibers, so that the yarn-thread friction coefficient Is preferably used because it can uniformly lower.

Examples of the fatty acid ester include an ester of a saturated or unsaturated fatty acid having 10 to 22 carbon atoms and an alcohol, and an ester of a saturated or unsaturated alcohol having 12 to 18 carbon atoms and a monobasic acid and / or a polybasic acid. Can be mentioned.

Among the above oils, unsaturated fatty acid ester-based oils containing unsaturated fatty acids or unsaturated alcohols as main components and containing at least 50% by mass of the unsaturated fatty acids are the threads. It is preferable because it is excellent in abrasion and fatigue resistance of the yarn. More preferred as unsaturated fatty acid esters are esters of unsaturated alcohols and dibasic acids. Examples of the dibasic acid include adipic acid, azelaic acid, sebacic acid and the like. Particularly preferred is an ester of oleyl alcohol and adipic acid (oleyl adipate).

The method of applying the oil agent to the aramid fiber is not particularly limited, and any conventionally known method may be adopted. For example, a dipping refueling method, a spray refueling method, a roller refueling method, a guide refueling method using a measuring pump, etc. It is applied to the aramid fiber by the method of.

The aramid fiber cord material obtained by the above method is twisted in a specific range. As the twist coefficient at this time, it is necessary to apply one-sided twist so that the twist coefficient defined by the following general formula (1) is 1.0 to 1.4 .

K: Cord twist coefficient
T: Number of twists of cord (times / 10 cm)
D: Fineness of aramid fiber (dtex)

By adding twisting, the force applied to each single yarn as the cord material is dispersed and frictional fatigue is improved, but if the twist coefficient is less than 1.0, the binding of the single yarn is weak and single yarn breakage occurs. It becomes easier to do. On the other hand, when the twist coefficient exceeds 4.0, the twisted cord is firmly restrained, so that the rigidity of the cord itself increases and the frictional resistance increases .

Filament number constituting the aramid fiber cord of the present invention is a 4 00-1500 present, even more preferably present 500-1200. If the number of filaments is too small, the force applied to the filament single yarn will be concentrated. On the contrary, if the number of filaments is too large, the filament single yarns will overlap and the effect of oil permeation per filament single yarn will be exhibited. It disappears. Single filament fineness of the fiber constituting the fiber cord is 1.1 to 1.5 dtex. When the fineness of the single yarn is less than 1.0 dtex, the strength of the single yarn itself decreases .

The rubber reinforcing cord of the present invention can be made into a fiber cord by using this as a lower twist cord, further bundling two or more cords, and adding an upper twist. Adhesive treatment and heat treatment are preferred for use in rubber reinforcement applications. The adhesive treatment may be performed once or twice or more. The adhesive treatment may be performed on the lower twisted cord or the upper twisted cord.

As the adhesive, an epoxy-based adhesive, a blocked isocyanate-based adhesive, resorcin, formalin, rubber latex (RFL), or the like can be used in combination or alone. The type of adhesive varies depending on the application such as belts, tires and hoses, and chlorophenol compounds may be added if necessary. Rubber latex includes vinylpyridine-styrene-butadiene copolymer rubber latex, styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, chloroprene rubber latex, chlorosulfonated polyethylene rubber latex, acrylate rubber latex and natural rubber. Examples thereof include latex, and examples of the resorcin-formaldehyde initial condensate include a novolac-type condensate obtained by condensing resorcin-formaldehyde under an acid catalyst or an alkali catalyst. The adhesive may be mixed with one or more compounds selected from a blocked polyisocyanate compound, an ethyleneimine compound, a reaction product of polyisocyanate and ethyleneimine, and the like.

Rubbers that use rubber reinforcement cords include acrylic rubber, acrylonitrile-butadiene rubber, hydride acrylonitrile-butadiene rubber, isoprene rubber, urethane rubber, ethylene-propylene rubber, chloroprene rubber, silicone rubber, styrene-butadiene rubber, and polysulfide rubber. , Natural rubber, butadiene rubber, fluororubber and the like.

In the rubber reinforcing cord of the present invention, since the aramid fiber to which the oil agent is applied is properly twisted, it is excellent in abrasion fatigue resistance between threads and is excellent in adhesiveness to rubber. Therefore, for example, a rubber hose. Demonstrates excellent performance when applied to tire cords, power transmission belts, and reinforcement cords for transport belts.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Further, in the following examples and the like, "mass%" is abbreviated as "%" unless otherwise specified.

[Thread-thread wear fatigue resistance evaluation]
It was evaluated by the wear fatigue test method shown in FIG. Under the upper thread fixed with a load of 1 g / d, the lower thread with a load of 1 g / d is reciprocated under the conditions of a stroke length of 5 cm and a reciprocating speed of 55 times / minute, and the worn part is 1 The number of times until the upper thread concentrated on the point was cut was counted. The measurement was carried out 5 times and the average value was calculated.

(Examples 1 to 8 and Comparative Examples 1 to 2)
Polyparaphenylene terephthalamide (PPTA) fiber (1,000 filaments, single yarn fineness 1.1 dtex) obtained by a known method is added with 50 as a main component of the fatty acid ester or EOPO copolymer shown in Table 1. A fatty acid ester-based oil or a polyether-based oil containing% or more was adhered to the fiber at a moisture content of 0% by 1.0%, and then wound on a bobbin in a winding step.
Using one multifilament of the obtained PPTA fiber, the cord was twisted at the number of twists shown in Table 1. The obtained cord was tested for abrasion fatigue by the above method.

(Examples 9 to 10)
A fatty acid ester system containing 50% or more of the fatty acid ester shown in Table 1 as a main component in polyparaphenylene terephthalamide (PPTA) fiber (666 filaments, single yarn fineness 1.7 dtex) obtained by a known method. After 1.0% of the oil agent was attached to the fiber when the moisture content was converted to 0%, it was wound around the bobbin in the winding step.
Using one multifilament of the obtained PPTA fiber, the cord was twisted at the number of twists shown in Table 1. The obtained cord was tested for abrasion fatigue by the above method.

Table 1 summarizes the thread-thread wear fatigue resistance evaluation results of the cords obtained in Examples and Comparative Examples. Examples 1 to 5 and 7 to 10 are reference examples.

From Table 1, the fiber cords obtained by twisting an aramid fiber material to which a fatty acid ester-based oil agent is attached have the same filament single yarn fineness and the number of filaments, but different twist coefficients (Examples 1 to 4 : all reference examples). ) And Comparative Examples 1 and 2), it was found that there was a correlation between the twist coefficient and the yarn-thread wear fatigue property, and that the thread-thread wear fatigue property had a maximum value. From the evaluation results of the fiber cords having different types of oil agents (Examples 5 to 8 : Examples 5, 7 and 8 are reference examples ), the oil agent containing an unsaturated fatty acid ester as a main component showed the best results. Further, when the number of filaments constituting the fiber cord was large (the single yarn fineness was small), the yarn-yarn wear fatigue resistance was improved.

The rubber reinforcing cord of the present invention is useful for reinforcing rubber products such as rubber hoses, transmission belts, conveyor belts, and tires.

Claims (2)

The dioleyl adipate aramid fiber multifilament single yarn fineness of the oil agent was deposited containing more than 50 wt% is filament number is present 400 to 1500 in 1.1～1.5Dtex, the following general formula (1) A rubber reinforcing cord having excellent wear-fatigue resistance between yarns, characterized in that one-sided twist is applied so that the defined twist coefficient is 1.0 to 1.4.
K: Cord twist coefficient
T: Number of twists of cord (times / 10 cm)
D: Fineness of aramid fiber (dtex)
Adhesion amount of oil is, the fiber mass when converted to moisture content of aramid fibers to 0% by weight, excellent abrasion fatigue among yarns of claim 1, wherein from 0.3 to 1.5 mass% Rubber reinforcement cord.