A method for producing a liquid crystal polyarylate conveyor belt and a cover layer thereof

Abstract

The application provides a liquid crystal polyarylate conveying belt and a preparation method of a cover layer thereof, the conveying belt comprising a liquid crystal polyarylate fabric belt core and a cover layer fixed to the surface of the belt core through an interlayer adhesive, the belt core taking liquid crystal polyarylate fibers as warp yarns and nylon filaments as weft yarns; the cover layer comprises the following components in parts by mass: synthetic rubber 55-70 parts, natural rubber 30-40 parts, thermoplastic polyurethane elastomer 5-15 parts, chopped fibers 2-6 parts, reinforcing agent 5-8 parts, nano clay 0.5-0.8 parts, smoke suppressant 2-4 parts, and flame retardant 5-10 parts; the chopped fibers contain liquid crystal polyarylate fibers and are modified by using a sodium salt of a monoalkyl ether phosphate or potassium dodecyl phosphate. The belt core has high tensile strength, and the tensile strength is improved by adding modified chopped fibers of liquid crystal polyarylate fibers in the cover layer material, so that the overall tensile strength of the conveying belt is further improved, and the conveying belt has a good market prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of mining transfer equipment, specifically relating to a liquid crystal polyarylate conveyor belt and a method for preparing its covering layer. Background Technology

[0002] In my country's coal mines, flame-retardant conveyor belts are generally made of fabric core or steel cord core. Compared to steel cord core conveyor belts, fabric core flame-retardant conveyor belts are lighter, have lower production costs, are easier to maintain and replace, have relatively easier joints, and are safer to use. However, because the core is made of fabric fibers such as nylon, cotton, and polyaramid, its strength is relatively low, making it difficult to adapt to working conditions requiring high tensile strength. While steel cord core flame-retardant conveyor belts have higher tensile strength, they are heavy and sometimes prone to longitudinal tearing. Furthermore, they cannot be broken when ignited, which can easily lead to the spread of fire along the conveyor belt. Therefore, fabric core flame-retardant conveyor belts have a clear advantage in general applications. If the tensile strength of fabric core flame-retardant conveyor belts can be further improved, they may be able to further replace steel cord core flame-retardant conveyor belts. Traditional conveyor belts with ordinary rubber as the cover layer and cotton fiber fabric core are characterized by low strength, poor durability, high energy consumption during transportation, and significant production pollution. With the development of high-performance fiber materials, high-strength and high-modulus fiber materials such as aramid, LCP fiber, and ultra-high molecular weight polyethylene have begun to be applied to fabric core flame-retardant conveyor belts. Among them, liquid crystal polyarylate fiber, which is lighter, stronger, has less shrinkage, and better durability, has shown excellent performance in fabric core flame-retardant conveyor belts. However, due to the large steric hindrance effect between the amide bonds in polyarylate fiber, it is difficult to form hydrogen bonds with other materials, resulting in poor fiber surface activity. This makes it difficult for the belt core made of polyarylate fiber material to bond with the cover layer.

[0003] Patent application number CN2025100669837 discloses a polyaryl woven solid flame-retardant conveyor belt and its manufacturing method. The method involves impregnating and plasticizing a polyaryl woven solid core in a core-impregnating rubber compound to obtain a plasticized core. A cover layer is then dynamically vulcanized and bonded to the plasticized core under heat to obtain the polyaryl woven solid flame-retardant conveyor belt. The polyaryl woven solid core of this design uses polyaryl fiber for its stress lines, resulting in high strength, a thin belt body, and light weight; the finished belt weighs approximately 50% of a steel cord conveyor belt of equivalent strength. Overall, the tensile strength of this polyaryl woven solid flame-retardant conveyor belt still has room for improvement to be applicable to more demanding operating scenarios.

[0004] If the tensile strength of the cover layer can be increased to a certain extent, then the overall tensile strength of the fabric core flame-retardant conveyor belt can also be increased, making up for the lack of tensile strength of the fabric core. Summary of the Invention

[0005] The purpose of this invention is to provide a liquid crystal polyarylate conveyor belt and a method for preparing a cover material containing liquid crystal polyarylate chopped fibers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A liquid crystal polyaryl ester conveyor belt includes a liquid crystal polyaryl ester fabric core and a cover layer fixed to the surface of the core by an interlayer adhesive. The liquid crystal polyaryl ester fabric core uses liquid crystal polyaryl ester fibers as warp yarns and nylon filaments as weft yarns. The cover layer rubber material, by weight, contains the following components: 55-70 parts synthetic rubber, 30-40 parts natural rubber, 5-15 parts thermoplastic polyurethane elastomer, 2-6 parts chopped fiber, 5-8 parts silica, 0.5-0.8 parts nano-ceramic, 2-4 parts smoke suppressant, and 5-10 parts flame retardant. The chopped fiber contains liquid crystal polyaryl ester fibers and is modified with sodium monoalkyl ether phosphate or potassium dodecyl phosphate.

[0008] Preferably, the smoke suppressant includes molybdate smoke suppressant or zinc borate, and the reinforcing agent includes carbon black or silica.

[0009] Preferably, the flame retardant is a compound of aluminum hydroxide and decabromodiphenyl ether, wherein the proportion of decabromodiphenyl ether in the flame retardant is 2-4%.

[0010] Preferably, the length of the chopped fiber is 1-5 mm.

[0011] Preferably, the chopped fibers are made from recycled waste liquid crystal polyarylate ropes, and the content of liquid crystal polyarylate fibers in the waste liquid crystal polyarylate ropes is not less than 60%.

[0012] Preferably, the ratio of synthetic rubber to natural rubber is 6:4±0.2.

[0013] Preferably, the synthetic rubber includes styrene-butadiene rubber and / or cis-butadiene rubber.

[0014] A method for preparing a cover layer material for a liquid crystal polyarylate conveyor belt, characterized by comprising the following steps:

[0015] S1. Preparation of chopped fibers: Discarded liquid crystal polyarylate ropes are cut into segments and soaked in a neutral detergent solution at 50-80℃ for 20-40 minutes. During soaking, the discarded liquid crystal polyarylate ropes are rubbed and brushed to further remove impurities. They are then removed, cleaned, and dried. The pre-cleaned discarded liquid crystal polyarylate ropes are then immersed in 0.5-2 mol / L dilute sulfuric acid or dilute hydrochloric acid under ultrasonic conditions for 10-20 minutes to further clean them. Wash and increase the surface roughness of the waste liquid crystal polyarylate rope fibers, then rinse and dry; inspect the washed waste liquid crystal polyarylate rope, cut off any parts with residual impurities, then cut the waste liquid crystal polyarylate rope to obtain short fibers with a length of 1-5mm, and thoroughly knead and disperse the short fibers; put the short fibers into a mesh bag, soak in a modifier solution at a temperature of 50-70℃ for 2-5 minutes, take them out and let them drain naturally, then dry them at 80-85℃ for 2 hours before use;

[0016] S2. The natural rubber is first plasticized, and then synthetic rubber and thermoplastic polyurethane elastomer are added and mixed evenly.

[0017] S3. Add chopped fibers, reinforcing agents, and nano-ceramic;

[0018] S4. Add flame retardants and smoke suppressants.

[0019] Preferably, in S1, the modifier solution is a 2-4% (w / w) aqueous solution of sodium monoalkyl ether phosphate or potassium dodecyl phosphate.

[0020] Preferably, in step S3, the nano-ceramic and the chopped fibers obtained in step S1 are premixed and sprayed with a silane coupling agent, the amount of which is 0.5%-1% of the mass of the chopped fibers obtained in step S1; then the treated chopped fibers are mixed with 1 / 4-1 / 3 of the rubber compound obtained in step S2, followed by the addition of a reinforcing agent, and then the remaining rubber compound is added in 1-3 steps for mixing.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The core uses liquid crystal polyaramid fiber as warp yarn and nylon filament as weft yarn, balancing tensile strength and cost control;

[0023] 2. In the coating material, the wear resistance and aging resistance of the coating material are improved by adding thermoplastic polyurethane elastomer;

[0024] 3. By adding modified short-cut fibers containing liquid crystal polyarylate fibers, the tensile strength and durability of the coating layer are enhanced, and it is also less prone to longitudinal tearing;

[0025] 4. Due to the high cost of liquid crystal polyarylate fiber, the cost of the core is reduced by using nylon filament as the weft yarn, and the cost of the cover layer is reduced by using recycled materials to prepare chopped fibers.

[0026] 5. By compounding aluminum hydroxide with decabromodiphenyl ether as a flame retardant, dual flame retardancy in both the gas phase and condensed phase is achieved, and zinc borate and other substances are further used to achieve both smoke suppression and flame retardant effects.

[0027] 6. The combination of a high-tensile-strength belt core and a high-tensile-strength cover layer further improves the overall tensile strength of the liquid crystal polyarylate conveyor belt. Detailed Implementation

[0028] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the present invention are all commercially available.

[0029] Example 1

[0030] A liquid crystal polyaryl ester conveyor belt includes a liquid crystal polyaryl ester fabric belt core and a covering layer fixed to the surface of the belt core by an interlayer adhesive. The liquid crystal polyaryl ester fabric belt core uses liquid crystal polyaryl ester fibers as warp yarns and nylon filaments as weft yarns. The covering layer material, by weight, contains the following components: 60 parts butadiene rubber, 40 parts natural rubber, 8 parts thermoplastic polyurethane elastomer, 2-6 parts chopped strand fiber, 5 parts silica, 0.8 parts nano-ceramic clay, 3 parts zinc borate, 6 parts aluminum hydroxide, and 0.2 parts decabromodiphenyl ether.

[0031] The chopped fibers contain liquid crystal polyarylate fibers and are modified with sodium monoalkyl ether phosphate or potassium dodecyl phosphate. Industrial-grade sodium monoalkyl ether phosphate or potassium dodecyl phosphate costs no more than 40 yuan / kg, resulting in low cost. In this embodiment, a cheaper 45% content potassium dodecyl phosphate is used.

[0032] The length of the chopped fibers is 1-5 mm.

[0033] The chopped fibers are made from recycled, discarded liquid crystal polyaryl ester ropes, wherein the liquid crystal polyaryl ester fiber content in the discarded ropes is not less than 60%. In this embodiment, a ship mooring liquid crystal polyaryl ester rope that was scrapped after 4 years of use is used, and its liquid crystal polyaryl ester fiber content is 100%, with a single filament diameter of 60μm.

[0034] A method for preparing a cover layer rubber material, characterized by comprising the following steps:

[0035] S1. Preparation of chopped fibers: Discarded liquid crystal polyarylate ropes are cut into segments and soaked in a neutral detergent solution at 50-80℃ for 20-40 minutes. During soaking, the discarded liquid crystal polyarylate ropes are rubbed and brushed to further remove impurities. They are then removed, cleaned, and dried. The pre-cleaned discarded liquid crystal polyarylate ropes are then immersed in 1.5 mol / L dilute sulfuric acid and subjected to ultrasonic treatment at 28-33 kHz for 15 minutes to further... The waste liquid crystal polyarylate ropes were cleaned and the surface roughness of the fibers was increased. Then, they were rinsed and dried. The cleaned waste liquid crystal polyarylate ropes were inspected, and any parts with residual impurities were cut off. The waste liquid crystal polyarylate ropes were then cut into short fibers of about 3 mm in length, and the short fibers were thoroughly rubbed and broken up. The short fibers were put into a mesh bag and soaked in a modifier solution at a temperature of 50-70℃ for 2-5 minutes. They were then taken out and allowed to drain naturally, and then dried at 80-85℃ for 2 hours before use.

[0036] S2. The natural rubber is first plasticized, and then synthetic rubber and thermoplastic polyurethane elastomer are added and mixed evenly.

[0037] S3. Add short-cut fibers, silica, and nano-ceramic; in synergy with reinforcing agents, nano-ceramic can toughen plastic materials to a certain extent.

[0038] S4. Add flame retardants and smoke suppressants;

[0039] When the rubber compound is mixed in an internal mixer, the speed of the internal mixer is 40-60 RPM and the discharge temperature is about 140℃. When processing the conveyor belt, a sulfur vulcanization system can be used in S3 and S4, with 2 parts sulfur and 1 part accelerator CZ / DM gradually added to the rubber compound. Before vulcanization, the rubber compound is combined with the fabric core that has been pre-impregnated with interlayer adhesive (rubber paste) using a calender, so that the rubber compound covers the fabric core from both the top and bottom. Then, vulcanization is carried out on a flat vulcanizing machine at 142-145℃, high pressure (such as 15MPa), and 1-3 minutes / mm (total thickness).

[0040] In S1, the modifier solution is a 2-4% mass concentration aqueous solution of sodium monoalkyl ether phosphate or potassium dodecyl phosphate.

[0041] In step S3, nano-ceramic and the chopped fibers obtained in step S1 are premixed and sprayed with a silane coupling agent. The addition of the silane coupling agent can prevent or reduce the agglomeration of the chopped fibers during processing, which helps to achieve uniform distribution of the chopped fibers in the rubber system and improve the tensile strength of the composite material. During production, the chopped fibers can be sprayed with the silane coupling agent first and then stirred at high speed, and then mixed with the nano-ceramic. When mixing into the rubber compound, 1 / 3 of the rubber compound is first mixed with the treated short fibers, then silica is added, and the remaining rubber compound is added in two batches for mixing. In this embodiment, the silane coupling agent used is KH-590, and the amount is 0.5% of the mass of the chopped fibers obtained in step S1. Generally speaking, adding more silane coupling agent (such as 1%-2% of the mass of the chopped fibers) can achieve a more thorough dispersion effect on the chopped fibers, but excessive use of silane coupling agent in combination with potassium dodecyl phosphate may have an adverse effect on the tensile strength of the material.

[0042] Below, we used the ratio of silane coupling agent to potassium dodecyl phosphate as a variable, with the modifier (potassium dodecyl phosphate aqueous solution) concentration gradients of 0%, 1%, 2%, 3%, and 4%, and the silane coupling agent (KH-590) dosage (percentage of chopped fiber weight) gradients of 0.0%, 0.3%, 0.5%, 0.8%, and 1%. The tensile strength (unit: MPa) of the prepared capping material was tested according to the MT147-95 industry standard. The measurement results are as follows:

[0043]

[0044] It is evident that the synergistic effect is optimal when the potassium dodecyl phosphate concentration is around 3% and the KH-590 dosage is around 0.8-1% (higher dosages do not yield significant gains), resulting in higher tensile strength of the coating material. Furthermore, using the method of impregnating with the modified solution followed by natural drainage may lead to reduced interfacial compatibility due to excessive residue on the fiber surface when using a modified solution of 4% or higher, thereby decreasing the bonding effect between the chopped fibers and the rubber.

[0045] Comparative Example 1

[0046] Similar to Example 1, the difference lies in the use of novel liquid crystal polyarylate chopped fibers (monofilament diameter 60 μm) under conditions of 3% potassium dodecyl phosphate aqueous solution concentration and 0.8% KH-590 weight of chopped fibers; the average tensile strength of the covering material was 25.6. During long-term use, the surface structure of the liquid crystal polyarylate rope experiences wear, and natural erosion from prolonged exposure to sunlight and wind and rain causes surface erosion (long-term use may lead to internal defects such as cracks, but when made into chopped fibers, these defects have little adverse effect and may even have a positive effect on the bonding between the chopped fibers and rubber). Compared to the increased surface roughness of the liquid crystal polyarylate fibers caused by acid washing, the effect of natural erosion on the fiber surface may be more conducive to the reaction between the modifier and the fiber surface, promoting better bonding between the fiber and rubber.

[0047] Comparative Example 2

[0048] Similar to Example 1, the difference lies in that, under the conditions of 3% potassium dodecyl phosphate aqueous solution concentration and 0.8% KH-590 by weight of chopped fibers, the liquid crystal polyarylate chopped fibers were replaced with nylon chopped fibers of the same specification. The average tensile strength of the capping layer material was 17.3. It is evident that, due to the high modulus and other properties of the liquid crystal polyarylate chopped fibers, they have a good effect on improving the tensile strength of the capping layer material.

[0049] Comparative Example 3

[0050] Similar to Example 1, the difference lies in that, under the conditions of a 3% potassium dodecyl phosphate aqueous solution concentration and KH-590 dosage of 0.8% of the chopped fiber weight, no chopped fibers were added. The average tensile strength of the capping layer material was 15.2. It is evident that the addition of chopped fibers significantly improves the tensile strength of the capping layer material.

[0051] Overall, improving the tensile strength of conveyor belts by enhancing the tensile strength of the cover material is feasible and has good market prospects.

[0052] The above embodiments are preferred implementations of the present invention and are used to illustrate the present invention. However, the present invention is not limited to the specific details of the above embodiments. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A liquid crystalline polyarylate conveyor belt, characterized by, The application relates to a liquid crystal polyarylate fabric belt core and a covering layer fixed to the surface of the belt core through an interlayer adhesive, wherein the liquid crystal polyarylate fabric belt core takes liquid crystal polyarylate fibers as warp yarns and nylon filaments as weft yarns; the covering layer contains the following components in parts by mass: synthetic rubber 55-70 parts, natural rubber 30-40 parts, thermoplastic polyurethane elastomer 5-15 parts, chopped fibers 2-6 parts, reinforcing agent 5-8 parts, nano clay 0.5-0.8 parts, smoke suppressant 2-4 parts and flame retardant 5-10 parts; the chopped fibers contain liquid crystal polyarylate fibers and are modified by sodium salt of monoalkyl ether phosphate or potassium salt of dodecyl phosphate.

2. The liquid crystalline polyarylate conveyor belt according to claim 1, wherein The smoke suppressant comprises molybdate or zinc borate, and the reinforcing agent comprises carbon black or white carbon black.

3. The liquid crystalline polyarylate conveyor belt according to claim 1, wherein The flame retardant is compounded with aluminum hydroxide and decabromodiphenyl ether, wherein the proportion of decabromodiphenyl ether in the flame retardant is 2-4%.

4. The liquid crystalline polyarylate conveyor belt according to claim 1, wherein The length of the chopped fibers is 1-5 mm.

5. The liquid crystalline polyarylate conveyor belt according to claim 4, wherein The chopped fibers are made of recycled scrap liquid crystal polyarylate ropes, and the content of the liquid crystal polyarylate fibers in the scrap liquid crystal polyarylate ropes is not less than 60%.

6. The liquid crystalline polyarylate conveyor belt according to claim 1, wherein The use ratio of the synthetic rubber to the natural rubber is 6:4+ / -0.

2.

7. The liquid crystalline polyarylate conveyor belt according to claim 6, wherein The synthetic rubber comprises styrene-butadiene rubber and / or cis-butadiene rubber.

8. A method of producing the cover material of the liquid crystalline polyarylate conveyor belt according to claim 1, characterized by, The application comprises the following steps: S1. Preparation of chopped fibers: the scrap liquid crystal polyarylate ropes are cut and separated, soaked in 50-80 DEG C neutral detergent for 20-40 min, and rubbed and washed during the soaking process to make the impurities on the scrap liquid crystal polyarylate ropes fall off, then the scrap liquid crystal polyarylate ropes are taken out, washed and dried; the preliminarily washed scrap liquid crystal polyarylate ropes are immersed in 0.5-2 mol / L dilute sulfuric acid or dilute hydrochloric acid, and the scrap liquid crystal polyarylate ropes are soaked in an ultrasonic environment for 10-20 min to further clean the scrap liquid crystal polyarylate ropes and increase the fiber surface roughness of the scrap liquid crystal polyarylate ropes, then the scrap liquid crystal polyarylate ropes are washed and dried; the cleaned scrap liquid crystal polyarylate ropes are detected, and the parts with residual impurities are cut off, then the scrap liquid crystal polyarylate ropes are sheared to obtain chopped fibers with a length of 1-5 mm, and the chopped fibers are fully rubbed and scattered; the chopped fibers are put into a mesh bag, soaked in a modifier solution at a temperature of 50-70 DEG C for 2-5 min, taken out and naturally drained, and then dried at 80-85 DEG C for 2 h; S2. The natural rubber is first plasticized, and then the synthetic rubber and the thermoplastic polyurethane elastomer are added and uniformly mixed; S3. The chopped fibers, the reinforcing agent and the nano clay are added; S4. The flame retardant and the smoke suppressant are added.

9. The method of claim 8, wherein the coating rubber material is prepared by mixing the base rubber material and the coating rubber material in a ratio of 1 : 1 to 1 :

10. In S1, the modifier solution is a 2-4% mass concentration aqueous solution of sodium salt of monoalkyl ether phosphate or potassium salt of dodecyl phosphate.

10. The method of claim 8, wherein the coating rubber material is prepared by mixing the base rubber material and the coating rubber material. In S3, the nano clay and the chopped fibers obtained in S1 are premixed and sprayed with a silane coupling agent, and the amount of the silane coupling agent accounts for 0.5%-1% of the mass of the chopped fibers obtained in S1; then the treated chopped fibers are mixed with 1 / 4-1 / 3 of the rubber material obtained in S2, and then the reinforcing agent is added, and the remaining rubber material is added in 1-3 steps.

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