A high temperature resistant flame retardant rubber compound for conveyor belts and a method for preparing the same

Abstract

The application provides a high-temperature-resistant and flame-retardant rubber mixture for a conveying belt, which is prepared from the following raw materials in parts by weight: ethylene-propylene-diene rubber 70-85 parts, ethylene-propylene-terpolymer rubber 15-30 parts, active agent 6-10 parts, carbon black 45-55 parts, anti-aging agent 4-8 parts, peroxide crosslinking agent 3-5 parts, crosslinking auxiliary agent 2-4 parts, solid plasticizer 5-10 parts, liquid plasticizer 10-16 parts, bromine-based flame retardant 15-20 parts, inorganic flame retardant 5-15 parts, and flame-retardant synergist 4-8 parts; the application also provides a preparation method of the high-temperature-resistant and flame-retardant rubber mixture for the conveying belt; and the application solves the technical problems of short service life and poor flame-retardant performance of the existing high-temperature-resistant conveying belt made of ethylene-propylene-diene rubber or ethylene-propylene-terpolymer rubber, and belongs to the technical field of rubber products.

Description

Technical Field

[0001] This invention belongs to the technical field of rubber products and relates to a high-temperature resistant and flame-retardant rubber compound for conveyor belts and its preparation method. Background Technology

[0002] In industries such as steel, coking, and cement, conveyor belts are commonly used to transport materials. When the material temperature is high and sometimes red-hot or even flammable, the conveyor belt is required to have high temperature resistance and flame retardant properties to ensure production safety.

[0003] Currently, many rubber materials in the industry meet the T4 level of GB / T 20021-2017 "Canvas Core Heat-Resistant Conveyor Belts" in terms of high-temperature resistance. Among them, EPDM (ethylene propylene diene monomer) and EPDM (ethylene propylene diene monomer) are the two most commonly used materials. These are mainly produced by batch mixing of EPDM or EPDM, reinforcing systems, plasticizing systems, and protective systems to form a rubber mixture, which is then vulcanized to produce the finished conveyor belt. However, high-temperature resistant conveyor belts made of EPDM tend to soften, become sticky, and lose wear resistance after a period of use, while high-temperature resistant conveyor belts made of EPDM tend to harden, become brittle, and crack easily after a period of use, thus affecting their service life.

[0004] Furthermore, the chemical industry standard HG / T 4732-2014 "Scorch-resistant Conveyor Belts" only specifies the high-temperature resistance and scorch resistance of conveyor belts, without making any requirements for flame retardant performance. Therefore, most people currently use scorch resistance to measure the flame retardant performance of rubber materials used in conveyor belts, and there is little research on its flame retardant performance. As a result, the flame retardant performance of existing high-temperature resistant conveyor belts made of EPDM or EPDM is not outstanding.

[0005] Therefore, existing high-temperature resistant conveyor belts made of ethylene propylene diene monomer (EPDM) or ethylene propylene diene monomer (EPDM) rubber have technical problems such as short service life and poor flame retardant properties. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is to provide a high-temperature resistant and flame-retardant rubber compound for conveyor belts and its preparation method.

[0007] This invention provides a high-temperature resistant and flame-retardant rubber compound for conveyor belts, which is composed of the following raw materials in parts by weight: 70-85 parts of ethylene propylene diene monomer (EPDM) rubber, 15-30 parts of ethylene propylene diene monomer (EPDM) rubber, 6-10 parts of activator, 45-55 parts of carbon black, 4-8 parts of antioxidant, 3-5 parts of peroxide crosslinking agent, 2-4 parts of crosslinking aid, 5-10 parts of solid plasticizer, 10-16 parts of liquid plasticizer, 15-20 parts of brominated flame retardant, 5-15 parts of inorganic flame retardant, and 4-8 parts of flame retardant synergist.

[0008] Preferably, the Mooney viscosity value [ML(1+4)100℃] of the ethylene propylene diene monomer (EPDM) rubber is 40-50, and the ethylene content is below 60%; the Mooney viscosity value [ML(1+4)100℃] of the ethylene propylene diene monomer (EPDM) rubber is 45-60, and the ethylene content is below 65%, with the third monomer being ethyleneide norbornene at a content of 0.5-2.5%; the total weight parts of the ethylene propylene diene monomer (EPDM) rubber and the ethylene propylene diene monomer (EPDM) rubber are 100 parts.

[0009] Preferably, the activator is composed of 99.7% indirect zinc oxide, light magnesium oxide and stearic acid.

[0010] Preferably, the carbon black is any one or a combination of at least two of N330, N326, N220, and N234; the antioxidant is any one or a combination of at least two of antioxidant 445, antioxidant MB, antioxidant NBC, and antioxidant RD.

[0011] Preferably, the solid plasticizer is an alkylphenol resin, and the liquid plasticizer is a metallocene polyalphaolefin or a mixture of metallocene polyalphaolefin and paraffin oil.

[0012] Preferably, the bromine-based flame retardant is an environmentally friendly bromine-based flame retardant with a melting point above 330℃; the inorganic flame retardant is zinc borate; and the flame retardant synergist is antimony trioxide.

[0013] The method for preparing the high-temperature resistant and flame-retardant rubber compound for conveyor belts according to any one of the above-mentioned methods includes the following steps:

[0014] (1) Weigh the ethylene propylene diene monomer (EPDM) rubber and ethylene propylene diene monomer (EPDM) rubber according to their weight, and put them into a mixer for mixing to obtain mixture A;

[0015] (2) Weigh out the activator, antioxidant and solid plasticizer by weight, and put them into the internal mixer to mix with mixture A to obtain mixture B;

[0016] (3) Weigh half the weight of carbon black, bromine flame retardant, inorganic flame retardant and flame retardant synergist respectively, and put them into a mixer to mix with mixture B to obtain mixture C.

[0017] (4) Weigh the remaining 1 / 2 weight of carbon black and liquid plasticizer separately, and put them into the internal mixer to mix with mixture C. Then heat up to discharge the material, and extrude it into sheets using a twin-screw extruder or open mill. Cool to room temperature and let stand to obtain mixture D.

[0018] (5) Weigh the peroxide crosslinking agent and crosslinking aid separately according to their weight, and put the mixture D, peroxide crosslinking agent and crosslinking aid into the internal mixer for mixing to finally obtain the rubber mixture.

[0019] Preferably, in step (1), the speed of the internal mixer is 40 r / min, the initial temperature is 60-80℃, and the mixing time is 30s; in step (2), the mixing time is 30s; and in step (3), the mixing time is 60s.

[0020] Preferably, in step (4), the mixing time is 60-90s, the temperature is raised to 120-145℃ for discharge, and the standing time is 6-8h.

[0021] Preferably, in step (5), the temperature of the internal mixer is 40-60℃, the rotation speed is 20r / min, the mixing time is 90-120s, and the temperature of the internal mixer chamber is below 100℃.

[0022] The beneficial effects of this invention are as follows: This invention provides a high-temperature resistant flame-retardant rubber compound for conveyor belts and its preparation method. By using a combination of ethylene propylene diene monomer (EPDM) and ethylene propylene diene monomer (EPDM), it solves the problems of EPDM becoming soft, sticky, and unwear-resistant after aging, and EPDM becoming hard, brittle, and prone to cracking after aging. Through reasonable proportioning, the cross-linking and degradation of the molecular chains in the vulcanized rubber compound are maintained in a balanced state when subjected to high temperatures, improving the heat resistance of the rubber compound and extending the service life of the conveyor belt made from it. Furthermore, by using a high-melting-point environmentally friendly bromine-based flame retardant... The synergistic effect of using bromodiphenyl ethane with the inorganic flame retardant zinc borate and the flame retardant synergist antimony trioxide significantly improves the flame retardant properties of the rubber compound, while simultaneously addressing the shortcomings of conventional flame retardants, such as easy aging and short service life due to their low decomposition temperature. By employing high-viscosity, high-flash-point polyalphaolefin alone or in combination with high-flash-point paraffin oil as a liquid plasticizer, the compatibility between the liquid plasticizer and ethylene propylene rubber is improved, thereby enhancing the high-temperature resistance of the rubber compound. Conveyor belts made from the high-temperature flame-retardant rubber compound of this invention, as the cover rubber, simultaneously meet the high-temperature resistance requirements of GB / T 20021-2017 "Canvas Core Heat-Resistant Conveyor Belts" T4 level and the flame-retardant performance requirements of GB / T 10822-2014 "General Purpose Fabric Core Flame-Retardant Conveyor Belts" K2 level. Detailed Implementation

[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0024] This invention provides a high-temperature resistant and flame-retardant rubber compound for conveyor belts. To verify the reliability of the invention's effectiveness, the invention is described below in conjunction with Examples 1-4, and compared with Comparative Examples 1-4, as shown in Table 1.

[0025] Table 1. Raw materials and weights (parts by mass) of the rubber mixtures of Examples 1-4 and Comparative Examples 1-4

[0026]

[0027] Among them, the content of the third monomer ethylene-bis(norbornene) in EPDM rubber A is 1.8%, the content of the third monomer ethylene-bis(norbornene) in EPDM rubber B is 2.3%, and the other raw materials are conventional commercial products.

[0028] This invention provides a method for preparing high-temperature resistant and flame-retardant rubber mixtures for conveyor belts according to the raw materials and weights of Examples 1-4 and Comparative Examples 1-4 in Table 1, comprising the following steps:

[0029] (1) Weigh the binary ethylene propylene rubber and the ternary ethylene propylene rubber according to Table 1, and put them into a mixer with a speed of 40 r / min. Mix them at an initial temperature of 60-80℃ for 30s to obtain mixture A.

[0030] (2) Weigh the activator, antioxidant and solid plasticizer according to Table 1, and put them into the internal mixer to mix with mixture A for 30s to obtain mixture B;

[0031] (3) Weigh half the weight of carbon black, bromine flame retardant (chlorine flame retardant added in Comparative Example 3), inorganic flame retardant and flame retardant synergist according to Table 1, and put them into a mixer to mix with mixture B for 60s to obtain mixture C.

[0032] (4) Weigh the remaining 1 / 2 weight of carbon black and liquid plasticizer according to Table 1, and put them into the internal mixer to mix with mixture C for 60-90s. Then heat to 120-145℃ to discharge the material, and extrude it into sheets using a twin-screw extruder or open mill. Cool to room temperature and let stand for 6-8h to obtain mixture D.

[0033] (5) Weigh the peroxide crosslinking agent and crosslinking aid according to Table 1. Then, control the temperature of the internal mixer at 40-60℃ and the speed at 20r / min. Add the mixture D, peroxide crosslinking agent and crosslinking aid to the internal mixer for mixing. Mix for 90-120s. During the mixing process, control the temperature of the mixing chamber below 100℃. Finally, obtain the rubber mixtures prepared according to the raw materials and weights of Examples 1-4 and Comparative Examples 1-4 in Table 1.

[0034] The rubber mixtures obtained in Examples 1-4 and Comparative Examples 1-4 were subjected to heat resistance, flame retardancy, and abrasion resistance tests, respectively.

[0035] Heat resistance test:

[0036] The heat resistance of rubber compounds is determined by testing the change in hardness and the change in elongation at break before and after aging. The greater the increase in hardness and the greater the change in elongation at break before and after aging, the worse the heat resistance of the rubber compound.

[0037] (1) Aging conditions: 180 degrees Celsius for 168 hours.

[0038] (2) Hardness change: In accordance with GB / T 531-1999 "Rust pocket hardness tester indentation hardness test method", the initial hardness and hardness after aging of each rubber mixture were measured and the hardness change was calculated. The results are shown in Table 2.

[0039] (3) Change rate of elongation at break: In accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber", the initial elongation at break and the elongation at break after aging of each rubber mixture were measured, and the change rate of elongation at break was calculated. The results are shown in Table 2. During the test, the specimens were cut into dumbbell II type specimens.

[0040] Table 2 Results of heat resistance test

[0041]

[0042] As shown in Table 2, the changes in hardness and elongation at break of the high-temperature resistant flame-retardant rubber mixtures prepared in Examples 1-4 were significantly lower than those in Comparative Examples 1, 2, and 4. This indicates that the high-temperature resistant flame-retardant rubber mixtures prepared in this application have excellent heat resistance. This is because, on the one hand, the combination of binary ethylene propylene diene monomer (EPDM) rubber and ternary ethylene propylene diene monomer (EPDM) rubber, through reasonable proportioning, maintains a balance between the crosslinking and degradation of molecular chains in the vulcanized rubber mixture when subjected to high temperatures, thereby improving the heat resistance of the rubber mixture. On the other hand, the combination of high-viscosity, high-flash-point polyalphaolefin and high-flash-point paraffin oil as liquid plasticizers improves the compatibility between the liquid plasticizer and EPDM rubber, thus improving the high-temperature resistance of the rubber mixture.

[0043] Flame retardant performance test:

[0044] The flame retardant properties of the rubber compound were determined by burning the sample with an alcohol torch and recording the burning time. The shorter the burning time, the better the flame retardant properties. Specifically, the test was conducted in accordance with the provisions of GB / T 3685-2017 "Laboratory-scale Test Method for Combustion Characteristics of Conveyor Belts". The results are shown in Table 3.

[0045] Table 3 Flame retardant performance test results

[0046] Example 1 Example 2 Example 3 Example 4 Comparative Example 3 Comparative Example 4 Burning time / s 5.5 4.5 5 6 7 7

[0047] As shown in Table 3, the burning time of the high-temperature resistant flame-retardant rubber mixtures prepared in Examples 1-4 was significantly lower than that in Comparative Examples 3 and 4. This indicates that the high-temperature resistant flame-retardant rubber mixtures prepared in this application have excellent flame retardancy. This is because, on the one hand, the high-melting-point environmentally friendly bromine-based flame retardant decabromodiphenyl ethane is used in combination with the inorganic flame retardant zinc borate and the flame retardant synergist antimony trioxide, resulting in a synergistic effect that significantly improves the flame retardant performance of the rubber mixture. On the other hand, the combination of high-viscosity, high-flash-point polyalphaolefin and high-flash-point paraffin oil improves the high-temperature resistance of the rubber mixture, thereby enhancing its flame retardancy.

[0048] Abrasion resistance test:

[0049] According to GB / T 9867-2008 "Determination of abrasion resistance of vulcanized rubber or thermoplastic rubber (rotary roller abrasion tester method)", the abrasion amount of each rubber mixture was measured, and the results are shown in Table 4.

[0050] Table 4. Abrasion resistance test results

[0051]

[0052] As shown in Table 4, the wear amount of the high-temperature resistant flame-retardant rubber mixtures prepared in Examples 1-4 is significantly lower than that in Comparative Examples 1-4. This indicates that the high-temperature resistant flame-retardant rubber mixtures prepared in this application have excellent wear resistance, which is determined by the raw material composition and preparation method of this application.

[0053] The conveyor belt made of the high-temperature resistant and flame-retardant rubber compound of the present invention as the cover rubber can simultaneously meet the high-temperature performance requirements of GB / T20021-2017 "Canvas Core Heat-Resistant Conveyor Belts" T4 level and the flame-retardant performance requirements of GB / T10822-2014 "General Purpose Fabric Core Flame-Retardant Conveyor Belts" K2 level, and is suitable for conveying materials with temperatures of 180-400℃ in industries such as steel, coking, and cement.

[0054] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A high-temperature resistant and flame-retardant rubber compound for conveyor belts, characterized in that, It is composed of the following raw materials in parts by weight: 70-85 parts of ethylene propylene diene monomer (EPDM) rubber, 15-30 parts of ethylene propylene diene monomer (EPDM) rubber, 6-10 parts of activator, 45-55 parts of carbon black, 4-8 parts of antioxidant, 3-5 parts of peroxide crosslinking agent, 2-4 parts of crosslinking aid, 5-10 parts of solid plasticizer, 10-16 parts of liquid plasticizer, 15-20 parts of brominated flame retardant, 5-15 parts of inorganic flame retardant, and 4-8 parts of flame retardant synergist. The Mooney viscosity value [ML(1+4)100℃] of the binary ethylene propylene diene monomer (EPDM) rubber is 40-50, and the ethylene content is below 60%; the Mooney viscosity value [ML(1+4)100℃] of the ternary ethylene propylene diene monomer (EPDM) rubber is 45-60, and the ethylene content is below 65%, with the third monomer being ethyleneide norbornene at a content of 0.5-2.5%; the total weight parts of the binary and ternary ethylene propylene diene monomer (EPDM) rubbers are 100 parts. The liquid plasticizer is a mixture of metallocene polyalphaolefin and paraffin oil, with a mass ratio of metallocene polyalphaolefin to paraffin oil of 2:1-5:1 or 5:

3. The activator consists of 99.7% indirect zinc oxide, light magnesium oxide, and stearic acid; The preparation method of the high-temperature resistant and flame-retardant rubber compound for conveyor belts includes the following steps: (1) Weigh the binary ethylene propylene rubber and the ternary ethylene propylene rubber according to their weight, and put them into a mixer for mixing to obtain mixture A; (2) Weigh out the activator, antioxidant and solid plasticizer by weight, and put them into the internal mixer to mix with mixture A to obtain mixture B; (3) Weigh half the weight of carbon black, bromine flame retardant, inorganic flame retardant and flame retardant synergist respectively, and put them into a mixer to mix with mixture B to obtain mixture C; (4) Weigh the remaining 1 / 2 weight of carbon black and liquid plasticizer separately, and put them into the internal mixer to mix with mixture C. Then heat up to discharge the material, and extrude it into sheets using a twin-screw extruder or open mill. Cool to room temperature and let stand to obtain mixture D. (5) Weigh the peroxide crosslinking agent and crosslinking aid separately according to their weight, and put the mixture D, peroxide crosslinking agent and crosslinking aid into the internal mixer for mixing to finally obtain the rubber mixture.

2. The high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in claim 1, characterized in that, The carbon black is any one or a combination of at least two of N330, N326, N220, and N234; the antioxidant is any one or a combination of at least two of antioxidant 445, antioxidant MB, antioxidant NBC, and antioxidant RD.

3. The high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in claim 1, characterized in that, The solid plasticizer is an alkylphenol resin.

4. The high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in claim 1, characterized in that, The bromine-based flame retardant is an environmentally friendly bromine-based flame retardant with a melting point above 330℃; the inorganic flame retardant is zinc borate; and the flame retardant synergist is antimony trioxide.

5. The method for preparing a high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Weigh the binary ethylene propylene rubber and the ternary ethylene propylene rubber according to their weight, and put them into a mixer for mixing to obtain mixture A; (2) Weigh out the activator, antioxidant and solid plasticizer by weight, and put them into the internal mixer to mix with mixture A to obtain mixture B; (3) Weigh half the weight of carbon black, bromine flame retardant, inorganic flame retardant and flame retardant synergist respectively, and put them into a mixer to mix with mixture B to obtain mixture C; (4) Weigh the remaining 1 / 2 weight of carbon black and liquid plasticizer separately, and put them into the internal mixer to mix with mixture C. Then heat up to discharge the material, and extrude it into sheets using a twin-screw extruder or open mill. Cool to room temperature and let stand to obtain mixture D. (5) Weigh the peroxide crosslinking agent and crosslinking aid separately according to their weight, and put the mixture D, peroxide crosslinking agent and crosslinking aid into the internal mixer for mixing to finally obtain the rubber mixture.

6. The method for preparing the high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in claim 5, characterized in that, In step (1), the speed of the internal mixer is 40 r / min, the initial temperature is 60-80℃, and the mixing time is 30s; in step (2), the mixing time is 30s; in step (3), the mixing time is 60s.

7. The method for preparing the high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in claim 5, characterized in that, In step (4), the mixing time is 60-90s, the temperature is raised to 120-145℃ for discharge, and the settling time is 6-8h.

8. The method for preparing the high-temperature resistant and flame-retardant rubber compound for conveyor belts as described in claim 5, characterized in that, In step (5), the internal mixer temperature is 40-60℃, the rotation speed is 20r / min, the mixing time is 90-120s, and the internal mixing chamber temperature is below 100℃.

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