JP2000001570A - Rubber composition and conveyor belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber compsn. which is excellent in heat resistance and in adhesion to steel cords under heat. SOLUTION: Based on 100 pts.wt. rubber blend contg. at least one rubber selected from among natural rubbers, styrene-butadiene copolymer rubbers (SBR), and butadiene rubbers (BR), this compsn. contains 1-10 pts.wt. cobalt salt of an org. acid, 0.5-10 pts.wt. sulfur, and 0.5-10 pts.wt. lead oxide and further contains a formaldehyde generator, a formaldehyde acceptor, silica, and a vulcanization accelerator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having excellent heat-resistant adhesion to a steel cord, and a conveyor belt including the steel cord using the rubber composition.

[0002]

2. Description of the Related Art Conventionally, rubber industrial products such as conveyor belts, hoses, and automobile tires often include steel cords or the like inside in order to improve mechanical properties such as strength. In a rubber industrial product including such a steel cord, the strength, life, and the like are greatly influenced by the adhesion between the rubber composition and a metal linear material such as a steel cord. Adhesion is a very important issue.

[0003] Steel cord conveyor belts containing a steel cord inside are used in various parts of the world.
Conveyor belts used in the tropics, conveyor belts for transporting high-temperature goods, and the like are exposed to high temperatures. Therefore, a steel cord conveyor belt used in such a high temperature environment is required to maintain high adhesion between the steel cord and the rubber composition even at a high temperature.

[0004] In general, the following two types of rubber compositions have been proposed in order to obtain rubber compositions having excellent adhesion to steel cords. The first rubber composition is a so-called RHS rubber composition containing resorcinol, hexamethylenetetramine and silica, and the second rubber composition is a rubber composition containing a metal salt, particularly a cobalt salt. is there.

Among the above rubber compositions, the second rubber composition is widely used.
No. 3737, Japanese Patent Application Laid-Open No. 59-22338 and the like disclose a rubber using a vulcanization accelerator such as a sulfenamide type and an adhesion promoter such as sulfur and cobalt naphthenate, cobalt stearate or cobalt neodecanoate. A composition is disclosed.

However, such a rubber composition uses only an organic acid cobalt salt as an adhesion promoter,
A conveyor belt having such a composition has excellent adhesiveness to a steel cord at a temperature close to room temperature (hereinafter, also simply referred to as adhesiveness), but has an adhesive property to a steel cord after being exposed to a high temperature. (Hereinafter simply referred to as heat-resistant adhesiveness) is not always sufficient.

[0007]

DISCLOSURE OF THE INVENTION In view of the above, the present invention has been made in view of the above circumstances, and provides a rubber composition having excellent heat resistance and excellent heat resistance adhesion to a steel cord, and a high-temperature environment using the rubber composition. It is intended to provide a conveyor belt having a long life even under the belt.

[0008]

Means for Solving the Problems The rubber composition of the present invention comprises:
Natural rubber, styrene-butadiene copolymer rubber (SBR)
And butadiene rubber (BR) with respect to 100 parts by weight of a rubber mixture containing at least one selected from the group consisting of:
1 to 10 parts by weight of organic acid cobalt salt and 0.5 to 1 part of sulfur
0 parts by weight, and containing 0.5 to 10 parts by weight of lead oxide,
Further, it is characterized by containing a formaldehyde generator, a formaldehyde receptor, silica and a vulcanization accelerator. The conveyor belt of the present invention is characterized in that the rubber composition and a plated steel cord are vulcanized and bonded. Hereinafter, the present invention will be described in detail.

[0009] The rubber composition of the present invention contains a rubber mixture containing at least one of natural rubber, styrene-butadiene copolymer rubber (SBR) and butadiene rubber (BR).

The rubber mixture may be a mixture of the above rubber alone or a combination of two or more of the above rubbers. Further, these rubbers may be further compounded with other rubbers. Examples of the rubber that can be compounded include polyisoprene rubber (IR). The combination of these rubbers is not particularly limited, but among them, a combination of natural rubber and SBR is preferred. Examples of the rubber mixture comprising the above natural rubber and SBR include those containing 10 to 40% by weight of natural rubber and 60 to 90% by weight of styrene-butadiene copolymer rubber (SBR).

The rubber composition of the present invention comprises 1 to 10 parts by weight of an organic acid cobalt salt and 0.5 to 5 parts by weight of sulfur based on 100 parts by weight of a rubber mixture containing at least one of the above rubbers.
-10 parts by weight and 0.5 to 10 parts by weight of lead oxide,
Further, it contains a formaldehyde generator, a formaldehyde receptor, silica and a vulcanization accelerator.

The organic acid cobalt salt is not particularly limited, but is preferably cobalt naphthenate, cobalt stearate, cobalt neodecanoate, or the like from the viewpoint that a rubber composition having excellent adhesion can be obtained. More preferred.

The above-mentioned organic acid cobalt salt is usually obtained by a method of heating and melting an organic acid and cobalt oxide. When the organic acid cobalt salt is less than 1 part by weight, the rubber composition is inferior in adhesiveness, and when it exceeds 10 parts by weight, the rubber composition has excellent initial adhesiveness after vulcanization, Since the heat resistance is poor and the aging is accelerated, it is limited to the above range. More preferably, it is 3 to 8 parts by weight.

If the sulfur content is less than 0.5 part by weight, the strength of the rubber composition itself is weakened, and the rubber composition is easily broken.
If the amount is more than 10 parts by weight, the rubber composition is inferior in adhesiveness, so that it is limited to the above range. More preferably, 1.
0 to 7 parts by weight.

[0015] The above-mentioned lead oxide also has functions as a vulcanization accelerator and a vulcanization aid, but by combining a formaldehyde generator and a formaldehyde receptor, the heat resistance is excellent. The lead oxide is not particularly limited,
From the point that it can be a rubber composition excellent in adhesion,
PbO, Pb ₂ O _{3 and the} like are preferable, and PbO is more preferable. When the lead oxide is less than 0.5 parts by weight, the heat-resistant adhesiveness is inferior, and when it exceeds 10 parts by weight, the adhesiveness becomes slightly inferior, especially in the heat-resistant adhesiveness. Limited to range. More preferably, 1.0
６6 parts by weight.

Examples of the above-mentioned formaldehyde generator include hexamethylenetetramine and hexamethoxymethylmelamine. Of these, hexamethylenetetramine is preferred. The amount of the formaldehyde generator to be added is preferably 0.5 to 5 parts by weight based on 100 parts by weight of the rubber mixture.

Examples of the above-mentioned formaldehyde receptor include resorcinol, m-aminophenol and the like. Of these, resorcin is preferred. The amount of the formaldehyde receptor to be added is preferably 1 to 10 parts by weight based on 100 parts by weight of the rubber mixture. At the time of heating such as vulcanization, an adhesive is formed between the formaldehyde generator and the formaldehyde receptor, so that the adhesiveness to the steel cord is improved. In addition, since the formed adhesive does not deteriorate by heat, the rubber composition containing the adhesive has excellent heat-resistant adhesiveness.

The above silica is obtained by combining a formaldehyde generator and a formaldehyde receptor.
The adhesion is improved. Examples of the silica include hydrous silicic acid and silicic anhydride. The amount of the silica is 5 to 3 parts by weight based on 100 parts by weight of the rubber mixture.
0 parts by weight is preferred.

Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators and thiazole vulcanization accelerators. As the vulcanization accelerator, two or more of the above sulfenamide vulcanization accelerators and the above thiazole vulcanization accelerators may be used in combination, and the above sulfenamide vulcanization accelerator or the above thiazole vulcanization accelerator may be used. A sulfur accelerator and another vulcanization accelerator may be used in combination, and the sulfenamide-based vulcanization accelerator and the thiazole-based vulcanization accelerator may be used in combination of two or more. The addition amount of the vulcanization accelerator is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the rubber mixture, from the viewpoint of maintaining excellent adhesiveness.

[0020] The rubber composition of the present invention, in addition to the above rubber,
Fillers, softeners, anti-aging agents, processability improvers, flame retardants,
It may contain zinc oxide, stearic acid and the like. The use of the rubber composition is not particularly limited. For example, the rubber composition can be used for rubber industrial products such as conveyor belts, hoses and automobile tires containing steel cords therein.

The rubber composition of the present invention has excellent heat resistance as well as excellent heat resistance and adhesiveness.
The mechanical properties do not deteriorate even after long-term use in a high-temperature environment, and the adhesive strength to the steel cord does not decrease.

The conveyor belt of the present invention is obtained by bonding the above rubber composition and a plated steel cord by vulcanization. Examples of the plating material include zinc, nickel, brass, and the like. Of these, zinc is preferred. FIG. 1 is a cross-sectional view schematically showing a conveyor belt of the present invention using the above rubber composition.

This conveyor belt 1 usually has a steel cord 2 buried in a substantially planar shape at the center, an adhesive rubber 5 for covering the steel cord 2 from above and below, and a cover rubber 3 for covering from above and below the steel cord 2. It consists of. The steel cord 2 is usually plated with zinc or the like.

The method for producing the conveyor belt of the present invention is not particularly limited, and a commonly used method or the like can be employed. For example, first, after kneading the raw materials using a Banbury mixer, a kneader mixer, a roll, etc.,
Using a calender or the like, an adhesive rubber made of the above rubber composition formed into a sheet is produced.

Next, a steel cord is sandwiched between the two bonding rubbers, and further, a cover rubber is stuck up and down, and then vulcanization is performed using a vulcanizing press to integrate the two. .

The conveyor belt of the present invention has excellent heat-resistant adhesion to steel cord, does not deteriorate in mechanical properties even when used for a long time in a high-temperature environment, and has a long life as a conveyor belt.

[0027]

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

Examples 1 to 5 and Comparative Examples 1 to 3 Each raw material was blended so as to have the composition shown in Table 1 below, kneaded with a Banbury mixer, and a 3.5 mm thick adhesive rubber was used. Was prepared. Next, a zinc-plated steel cord having a diameter of 6.3 mm is sandwiched between the two bonding rubbers, and a cover rubber having a thickness of 9.0 mm is adhered up and down. A sample for evaluation containing a steel cord was prepared by partial vulcanization.

[0029]Evaluation method  (1) Measurement of pull-out strength of steel cord before heat treatment From the sample for evaluation described above, JIS K 6369
According to the method, the steel cord drawn in the shape shown in Fig. 2
A test piece 4 for a test was prepared. In addition, the length (l
_Two) Is 100 ± 2 mm.

Next, the prepared test piece 4 is placed in a standard room at 23 ± 2 ° C. for 3 hours or more, and then the test piece 4 is correctly attached to the grip with a distance between the grips of 250 mm or more, and pulled. The steel cord was pulled at a speed of 100 ± 10 mm / min, and the maximum tensile force until the steel cord was pulled out was measured. The results are shown in Table 1 below.

(2) Measurement of pull-out strength after heat treatment From the sample for evaluation, a strip having a shape close to the shape of a test piece was prepared according to the method described in JIS K6369, and a spacer was used with a vulcanizing press. 145 ± 5 ℃, 1 ±
After heating and pressurizing for 150 ± 1 minute under the condition of 0.3 MPa, the sample was allowed to cool to room temperature, and then a test piece 4 having the shape shown in FIG. 2 was produced. Then, using this test piece 4,
The maximum tensile force was measured by the same test method as in (1). The results are shown in Table 1 below.

[0032]

[Table 1]

As is clear from the results shown in Table 1 above, the steel cord conveyor belt using the rubber composition according to the above example has a high pulling strength before the heat treatment and, in particular, after the heat treatment. Has high pull-out strength and excellent heat resistance.

[0034]

As described above, the rubber composition of the present invention has excellent heat resistance as well as excellent heat resistance adhesion to a steel belt.

Further, the conveyor belt of the present invention is as described above, and has excellent heat resistance and also excellent heat resistance adhesion between the rubber composition and the steel belt. Therefore, it is possible to provide a conveyor belt having a long service life in which the mechanical characteristics are not deteriorated even in a high temperature environment.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a conveyor belt of the present invention.

FIG. 2 is a conceptual diagram schematically showing a test piece for performing a pull-out test of a steel cord on a conveyor belt.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conveyor belt 2 Steel cord 3 Rubber 4 Test piece 5 Rubber for bonding

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/36 C08K 3/36 5/09 5/09 C08L 9/00 C08L 9/00 9/06 9 / 06 // C08J 5/04 CEQ C08J 5/04 CEQ F-term (reference) 3F024 AA07 AA11 CA02 CA04 CA08 CB03 CB10 CB13 4F072 AA03 AB11 AD02 AE01 AE02 AE06 AE14 AF02 AF05 AG02 AH25 AL01 4F213 AA13A AAB AB18 AG16 WA04 WA15 WA53 WA87 WB01 WB11 WK01 WK03 4J002 AC031 AC081 DA047 DE158 DJ019 EG046 EJ019 EN069 EU189 EV279 EV329 GM01

Claims (2)

[Claims] 1. A rubber mixture 100 containing at least one selected from the group consisting of natural rubber, styrene-butadiene copolymer rubber (SBR) and butadiene rubber (BR).
1 to 10 parts by weight of an organic acid cobalt salt, 0.5 to 10 parts by weight of sulfur, and 0.5 to 10 parts by weight of lead oxide
A rubber composition, which contains parts by weight and further contains a formaldehyde generator, a formaldehyde receptor, silica and a vulcanization accelerator. 2. A conveyor belt comprising the rubber composition according to claim 1 and a plated steel cord bonded by vulcanization.