JPS6222487Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a conveyor belt, particularly a conveyor belt with excellent flame retardancy. Flame-retardant conveyor belts are widely used, for example, for transporting coal and the like out of mines. As a typical example of this type of conveyor belt, as shown in the cross-sectional view of FIG. A front cover rubber layer 3' and a back cover rubber layer 4' having a predetermined thickness are integrated in a laminated manner on both the front and back surfaces of the belt, which are embedded in parallel. One way to make this type of conveyor belt flame retardant is to add a flame retardant to the cover layer with halogenated polymers, such as chlorinated polymers such as chloroprene and PVC, or broadly speaking, polymers such as SBR, BR, NBR, EPDM, and IIR. Belts are known in which flame retardant properties are improved by adding organic compounds containing halogens and phosphorus, and inorganic compounds such as antimony trioxide and aluminum hydroxide. Generally speaking, flame retardancy test methods are as follows:
The flame test specified in JIS K 6324 is the main part of the test, but based on the experience of fire accidents in mines in recent years, the performance that flame-retardant conveyor belts should have is determined by the flame test when the conveyor belt and drive pulley slip. The ignition resistance of these materials is becoming increasingly important. In other words, intensive slip friction between the drive pulley and the back cover rubber layer of the belt causes rapid heat generation at the contact area, which ignites lubricating oil or coal dust from the belt body or conveyor system, causing an explosion. It also becomes. As a method for evaluating the ignition resistance due to slip between the drive pulley and the conveyor belt, a drum friction test is specified in Australian standards (AS1334.11), Canadian standards (FRL269), etc. In addition, standardization under JIS is also being considered domestically. In order to pass the drum friction test of the above standards, the main raw materials for the belt cover layer have traditionally been limited to chloroprene and vinyl chloride resin, but even when these polymers are used, the back cover rubber layer There are significant restrictions on the thickness of the canvas and the number of layers of tensile canvas. However, even if the thickness of the back cover rubber layer is 2.0 mm and the number of canvas layers is 4 plies, it will fail if the thickness of the back cover rubber layer is 1.5 mm.
The current situation is that even 2.0 mm is unstable and will fail if the number of layers of canvas is 5 plies. On the other hand, when general-purpose polymers such as SBR and BR are used as the main raw material for the cover layer, the back cover rubber layer softens and becomes sticky due to the frictional resistance when the conveyor belt and drive pulley slip, causing intense heat generation. If a canvas made of a tensile material such as 6-nylon, 66-nylon, polyester fiber, etc. is used, a part of the back cover layer may peel off and become damaged due to heat generation, causing the canvas to melt and make the belt even more sticky. Even if it passes the above-mentioned standards, it has more restrictions in terms of belt structure than a belt cover layer whose main raw materials are chloroprene or vinyl chloride resin, and there are still problems in its practical application. ing. From the above-mentioned viewpoint, the present invention significantly reduces the frictional resistance when the drive pulley and conveyor belt slip, thereby reducing heat generation, eliminating the risk of fire even if a slip accident occurs, and further improving the cover. This provides a flame-retardant conveyor belt that can be designed without restricting the polymer of the rubber layer and the belt structure, and maintains the orientation of short fiber groups made of organic, inorganic, or metal fibers in the same direction in the rubber or synthetic resin layer. The short fiber group is arranged and covered with a reinforcing layer embedded in the cover layer on the back side of the belt while maintaining the directionality perpendicular to the plane of the belt. A specific example of the combustible conveyor belt will be described in detail with reference to the accompanying drawings. Figure 2 shows a cross section of the conveyor belt 1 of this invention.A plurality of canvas tensile members 2 are embedded in the belt longitudinal direction approximately at the center of the belt 1, and on both the front and back sides of the belt. The structure in which the front cover layer 3 and the back cover layer 4, each made of rubber or synthetic resin such as vinyl chloride or urethane and having a predetermined thickness are integrated in a laminated manner, is similar to the structure of a conventional conveyor belt. . In the conveyor belt 1 of this invention, short fibers 6 are included in the rubber or synthetic resin layer 5 in the back cover layer 4.
A reinforcing layer 7 in which groups of short fibers are embedded while maintaining orientation in the same direction is placed and covered with a cover layer on the back side of the belt while maintaining orientation perpendicular to the plane of the belt, and fixed by vulcanization. . At this time, the short fiber group 6 is previously subjected to an adhesive treatment and embedded in the rubber or synthetic resin layer 5 made of the same material as the back cover layer 4 or a different material. Note that the short fibers 6 have an aspect ratio (length/
Thickness) 10 to 10,000, preferably 50 to 1,000 short fibers, organic fibers such as aromatic polyamide, aliphatic polyamide, polyester, vinylidene chloride, inorganic fibers such as glass fiber, carbon fiber, ceramic fiber, or 1 to 100 parts by weight, preferably 10 to 50 parts by weight of metal fibers such as stainless steel fibers and alumina fibers are mixed into 100 parts by weight of rubber. Here, when the aspect ratio is less than 10, the short fibers become powdery and the heat resistance effect on flame retardation is small, and when the aspect ratio is more than 10,000, the short fibers are too long and it becomes difficult to orient them vertically in the rubber layer. On the other hand, if the amount of short fibers mixed is less than 1, the effect will be small, and if it is more than 100, it will not become rubbery, so it is desirable to use it within the above range. Note that the entire back cover layer 4 may be formed with a reinforcing layer 7 made of the rubber or synthetic resin and short fibers (see FIG. 3), and the tensile body 2 is not limited to the canvas shown in the figure. You can also replace it with a steel cord instead of the one with a steel cord. Next, more detailed examples will be described in order to disclose the flame retardant effect of the conveyor belt according to this invention. Example Aromatic polyamide was added to the back cover layer of an unvulcanized belt made of 4 plies of tensile canvas, with a front cover thickness of 3.0 mm and a back cover thickness of 1.0 mm, in the blending ratio shown in Table 1 below. A reinforcing layer containing 30 parts by weight of short fibers per 100 parts by weight of rubber was attached in such a way that the short fibers maintained their orientation perpendicular to the belt plane.
Vulcanized and fixed for minutes, the total thickness of this belt is 150 mm wide
A sample with a size of 1.5 m and a length of 1.5 m was taken, and a drum friction test was conducted according to the test method of Canadian standard FRL269. The results are shown in Table 2 below.

【table】

[Table] The samples shown as comparative examples in Table 2 are the same rubber-based compositions that do not contain any short fibers. As is clear from the above drum friction test results, a belt in which a reinforcing layer in which short fibers, which constitute the main part of this invention, are oriented perpendicularly to the belt plane is attached to the back side of the belt, does not contain any short fibers at all. It has been demonstrated that the calorific value is much lower than that of a belt that does not contain any contaminants, and that it has excellent flame retardancy. As described above, the flame-retardant conveyor belt of this invention has a reinforcing layer in which a group of short fibers are embedded in a rubber or synthetic resin layer while maintaining orientation in the same direction. By maintaining the orientation perpendicular to the belt plane and covering it, the frictional resistance when the drive pulley and conveyor belt slip is reduced, reducing the amount of heat generated.
It possesses excellent ignition resistance, and flame-retardant conveyor belts can be manufactured without restricting the cover rubber polymer and belt structure. Furthermore, by embedding and oriented the short fibers in a direction perpendicular to the plane of the belt, wear and tear on the back surface of the belt due to digging up of the short fibers can be suppressed even during long-term use.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional conveyor belt, FIG. 2 is a cross-sectional view of a conveyor belt according to this invention, and FIG. 3 is a view corresponding to FIG. 2 showing another embodiment. In the figure, 1 is a conveyor belt, 2 is a tensile material, 3 is a front cover layer, 4 is a back cover layer, 5 is a rubber or resin layer, 6 is a short fiber, and 7 is a reinforcing layer.

Claims (1)

[Scope of utility model registration request] In a conveyor belt that has a tensile material embedded approximately in the center and cover layers on both the front and back sides of the belt, a reinforcing layer in which short fiber groups are embedded in the rubber or synthetic resin layer while maintaining the same orientation is used. A flame-retardant conveyor belt, characterized in that the short fiber group is arranged and coated on a cover layer on the back side of the belt while maintaining directionality perpendicular to the plane of the belt.