Fluororubber recovery system of open mill and fluororubber recovery method

Abstract

The invention provides a fluororubber recovery system of an open mill and a fluororubber recovery method, and belongs to the field of fluoroelastomer processing, the fluororubber recovery system specifically comprises an open mill and a roller built-in cooler, to-be-recovered fluororubber is cooled and preliminarily crushed; the constant temperature system is used for controlling the refrigerant temperature and the refrigerant flow rate of the cooler; the low-temperature freezing and crushing system is used for performing low-temperature freezing and crushing on the primarily crushed fluororubber to obtain fluororubber particles; the screening system is used for screening the crushed fluororubber particles conforming to the preset size; the washing system is used for washing the additive powder released by removing the fluororubber particles in the freezing and crushing process; and the high-gradient magnetic field separator is used for removing ferromagnetic particles generated in the freezing and crushing process from the cleaned fluororubber particles by adopting a high-gradient magnetic field so as to obtain recycled fluororubber particles. By means of the treatment scheme, the fluororubber particles are efficiently recycled, and the performance of rubber products is not affected.

Description

Technical Field

[0001] The invention relates to the field of fluoroelastomer processing, and in particular to a system for recycling fluororubber using an open mill and a method for recycling fluororubber. Background Art

[0002] Fluororubber, especially perfluoroether rubber, has a low yield, which can generate a large amount of waste in the process of producing fluororubber products. Considering the high cost of producing fluororubber products and expensive raw materials, manufacturers are forced to reprocess and reuse the waste generated in production to obtain the maximum economic benefits. How to treat the waste generated by primary vulcanization or secondary vulcanization in production so that it can be reused in the process cycle has become a major problem.

[0003] Even if the existing equipment is used to crush and recycle the waste generated during the production process, due to the large elasticity of fluororubber during the crushing and recycling process, it cannot be crushed to the target particle size, resulting in the performance of the prepared rubber products being reduced once the recycled fluororubber is added to the raw materials. Summary of the invention

[0004] Therefore, in order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a system and a method for recovering fluororubber by an open mill, which can efficiently recover fluororubber particles without affecting the performance of rubber products.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a system for recycling fluororubber by an open mill, comprising: an open mill, a roller with a built-in cooler for cooling the fluororubber to be recycled and performing preliminary crushing; the fluororubber is at least one of a binary or ternary fluororubber containing vinylidene fluoride and a perfluoroether rubber; a constant temperature system for controlling the refrigerant temperature and refrigerant flow rate of the cooler; a low-temperature freezing and crushing system for performing low-temperature freezing and crushing on the fluororubber after preliminary crushing to obtain fluororubber particles; a screening system for screening the fluororubber particles that meet the predetermined size after crushing, and continuing to convey the fluororubber particles that do not meet the predetermined size to the low-temperature A freezing and crushing system; a washing system for washing the fluororubber particles during the freezing and crushing process to remove the additive powder released; a high-gradient magnetic field separator for removing the ferromagnetic particles generated during the freezing and crushing process from the washed fluororubber particles using a high-gradient magnetic field to obtain recovered fluororubber particles, wherein the cooler includes a rotary joint connecting the refrigerant and the roller, a chamber through which the refrigerant flows, a refrigerant inlet pipe, and a refrigerant outlet pipe; the rotary joint is installed at one end of the roller, and the rotary joint adopts a one-way flow type; the refrigerant inlet pipe located on the central axis of the chamber extends deep into the other end of the roller and is stationary relative to the rotation of the roller.

[0006] In one of the embodiments, fins or baffles are installed on the outside of the refrigerant inlet pipe.

[0007] In one embodiment, the refrigerant temperature of the cooler is -50°C to 80°C. The refrigerant is water or an aqueous solution at 10°C to 80°C, or an ethylene glycol aqueous solution or an organic refrigerant at -50°C to 50°C.

[0008] In one embodiment, the speed ratio of adjacent rollers in the mixing mill is 1-1.5, the speed of the rollers is 1-30 rpm, and the spacing between adjacent rollers is 1-6 mm.

[0009] In one embodiment, the mixing mill is placed in a nitrogen or dry air environment box, and the dew point temperature of the gas in the environment box is lower than -40°C.

[0010] In one embodiment, the washing medium in the washing system is deionized water.

[0011] In one embodiment, the fluororubber is waste material generated by primary vulcanization and / or waste material generated by secondary vulcanization.

[0012] In one of the embodiments, in the low-temperature freezing and pulverizing system, the time for secondary cooling and freezing the pre-cooled fluororubber using liquid refrigerant is 5 to 25 minutes.

[0013] In one embodiment, the magnetic induction intensity of the high gradient magnetic field separator is not less than 1200 GS within a range of 100 mm from the magnet surface.

[0014] A method for recovering fluororubber comprises: cooling and preliminarily crushing the fluororubber to be recovered in an open mill; the fluororubber is at least one of binary or ternary fluororubber containing vinylidene fluoride and perfluoroether rubber, and the preliminarily crushed fluororubber is subjected to low-temperature freezing and crushing to obtain fluororubber particles; screening the crushed fluororubber particles that meet a predetermined size, and continuing to cryogenically freeze and crush the fluororubber particles that do not reach the predetermined size; removing additive powder released from the fluororubber particles during the washing and freezing and crushing process; and removing ferromagnetic particles generated during the freezing and crushing process from the washed fluororubber particles using a high gradient magnetic field to obtain recovered fluororubber particles.

[0015] Compared with the prior art, the advantages of the present invention are: using an open mill to perform cold crushing of rubber for preliminary crushing of rubber, and further reducing the particle size of fluororubber by low-temperature freezing crushing during the preliminary crushing, thereby increasing the specific surface area of ​​fluororubber particles, thereby increasing the interaction force between the recycled fluororubber particles and the rubber matrix, improving the rubber interface compatibility, and ensuring the performance of rubber products. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 is a scanning electron microscope image of fluororubber particles recovered in an embodiment of the present invention; Figure 2 It is a comparison chart of the tensile strength of the products made of fluororubber recycled in the embodiments of the present invention and other control examples. DETAILED DESCRIPTION

[0018] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0019] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0020] It should be noted that various aspects of the embodiments within the scope of protection of the present invention are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0021] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0022] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0023] An embodiment of the present application provides a system for recycling fluororubber using an open mill, comprising an open mill, a constant temperature system, a low-temperature freezing and crushing system, a screening system, a washing system, and a high-gradient magnetic field separator.

[0024] The open mill has a roller with a built-in cooler, which is used to cool the fluororubber to be recycled and perform preliminary crushing; the fluororubber is at least one of binary or ternary fluororubber containing vinylidene fluoride and perfluoroether rubber.

[0025] The temperature outside the open mill is 10℃ to 15℃ higher than the temperature of the inner wall. The open mill can adjust the roller temperature, roller speed and distance between rollers.

[0026] When mixing rubber using an open rubber mixing mill (referred to as an open mixing mill), the rubber passing through the gap between the rollers is subjected to high tensile and high shear forces, causing heat and deformation. This is because the rubber deforms after receiving mechanical energy, and part of the energy is accumulated as elastic energy of the rubber, and the remaining part is used as viscosity, which is converted into heat energy and becomes loss energy. Based on the relationship between the plasticizing behavior in the open mixing mill and the rubber temperature and viscosity caused by heat, a curve is drawn, and the rubber temperature can be divided from low to high into four areas: low temperature zone, hard low temperature zone, soft high temperature zone starting from the high viscosity zone, and low viscosity zone.

[0027] The cold rubber crushing technology of the open mill can achieve the purpose of preliminary crushing of rubber, and the efficiency of liquid nitrogen low-temperature freezing crushing can be improved after preliminary crushing. However, during the cold rubber crushing process of the open mill, the rubber temperature must be in the low temperature zone or hard low temperature zone, so as to remove the heat energy released during the crushing process in time and prevent the rubber from heating up and bonding.

[0028] The cooler includes a rotary joint connecting the refrigerant and the roller, a chamber through which the refrigerant flows, a refrigerant inlet pipe, and a refrigerant outlet pipe.

[0029] A rotary joint is installed at one end of the roller of the mixing mill, and the rotary joint adopts a one-way flow type.

[0030] The refrigerant inlet pipe is located at the central axis of the chamber and extends into the other end of the roller and is stationary relative to the rotation of the roller.

[0031] The refrigerant discharge pipe can be arranged in contact with the tube wall of the roller, or can be arranged similarly to the refrigerant introduction pipe.

[0032] Constant temperature system, used to control the refrigerant temperature and refrigerant flow rate of the cooler.

[0033] The low-temperature freezing and pulverizing system is used to perform low-temperature freezing and pulverizing on the fluororubber after preliminary pulverization to obtain fluororubber particles.

[0034] The cryogenic freezing and crushing system can place rubber of a certain particle size in a refrigerating medium and freeze it below the glass transition temperature. At this time, the rubber molecular chain is in a frozen state, and the vulcanized rubber changes from an elastic material to a brittle material. The cryogenic freezing and crushing system can adopt a two-stage crushing method of normal temperature and freezing, or directly freeze and crush at one time. The refrigeration methods include liquid nitrogen refrigeration, air circulation turbine refrigeration, and liquefied natural gas cold energy refrigeration. The liquid refrigeration medium can be any one of liquid nitrogen, LNG or liquid carbon dioxide.

[0035] When the low-temperature freezing pulverization system adopts the two-stage pulverization method of normal temperature and freezing, the normal temperature of the fluororubber can be directly cooled by the cooler of the open mill, or it can be cooled by additional cooling equipment after the fluororubber is pulverized in the open mill. The normal temperature here can be 0~20℃.

[0036] The screening system is used to screen the fluororubber particles that meet the predetermined size after crushing, and the fluororubber particles that do not reach the predetermined size are continuously conveyed to the low-temperature freezing crushing system.

[0037] For example, rubber particles that have passed through a 30-mesh screen (0.6 mm) are crushed with liquid nitrogen at low temperature, and rubber particles that have passed through a 100-mesh screen (0.15 mm) are recycled. After crushing, fluororubber particles that meet the predetermined size are transported to the washing system for washing.

[0038] The washing system is used to wash the fluororubber particles to remove the additive powder released during the freezing and crushing process. During the low-temperature freezing and crushing process, solid additives such as white carbon black (silicon dioxide), titanium dioxide (titanium dioxide), carbon black and other powders will separate from the fluororubber, thereby generating free impurities. In order to effectively remove impurities such as additive powders, the surface property differences (hydrophobic properties) and density differences between the fluororubber powder and the additive powder in the water phase can be used for screening. Therefore, during the washing process, based on the differences in additive powders, the low-temperature fluororubber waste can be reheated and the impurities can be separated.

[0039] The high gradient magnetic field separator is used to remove the ferromagnetic particles generated in the freezing and crushing process from the cleaned fluororubber particles by using a high gradient magnetic field to obtain recovered fluororubber particles.

[0040] 1) The magnetic medium of the high gradient magnetic separator can be made of ferrite stainless steel with high magnetization strength, which has good corrosion resistance. The smaller the cross-sectional area of ​​the magnetic medium, the higher the magnetic field gradient.

[0041] 2) High gradient magnetic separators can remove ferromagnetic particles ranging from a few microns to hundreds of microns. The magnetic separator can generate a 1T magnetic field and a 100T / cm magnetic field gradient.

[0042] 3) High gradient magnetic separators have low energy consumption, simple operation, no secondary pollution, low cost and high separation efficiency.

[0043] like Figure 1 As shown, the recovered fluororubber is uniform at a scale of 100 μm (125 mesh), indicating that the particle size can be controlled within the range of 100 μm (125 mesh).

[0044] The fluororubber recovery method corresponding to the system includes: Step 1, cooling the fluororubber to be recovered in an open mill and preliminarily crushing it; the fluororubber is at least one of a binary or ternary fluororubber containing vinylidene fluoride and a perfluoroether rubber, Step 2, subjecting the preliminarily crushed fluororubber to low-temperature freezing and crushing to obtain fluororubber particles; Step 3, screening the fluororubber particles that meet the predetermined size after crushing, and continuing to cryogenically crush the fluororubber particles that do not reach the predetermined size; Step 4, washing the fluororubber particles to remove the additive powder released during the freezing and crushing process; Step 5, using a high gradient magnetic field to remove the ferromagnetic particles generated during the freezing and crushing process from the cleaned fluororubber particles to obtain recovered fluororubber particles.

[0045] The above method uses an open mill to perform preliminary crushing of the rubber with cold crushed rubber, and further reduces the particle size of the fluororubber by low-temperature freezing crushing during the preliminary crushing, thereby increasing the specific surface area of ​​the fluororubber particles, thereby increasing the interaction force between the recovered fluororubber particles and the rubber matrix, improving the rubber interface compatibility, and ensuring the performance of the rubber product.

[0046] In one embodiment, fins or baffles are installed outside the refrigerant introduction pipe to enhance heat exchange.

[0047] In one embodiment, the refrigerant temperature of the cooler is -50°C to 80°C, and the refrigerant is water or an aqueous solution at 10°C to 80°C, or an ethylene glycol aqueous solution at -50°C to 50°C or an organic refrigerant.

[0048] In one embodiment, the rotation speed ratio of adjacent rollers in the mixing mill is 1-1.5, the rotation speed of the rollers is 1-30 rpm, and the spacing between adjacent rollers is 1-6 mm.

[0049] The open mixing mill is generally equipped with at least two rollers, the front and rear rollers. The speed ratio of adjacent rollers refers to the ratio of the speeds of the front and rear rollers. The speed of the front roller is faster than that of the rear roller, so that the rubber raw materials can be better mixed and refined. Whether it is the front roller or the rear roller, the speed of the roller is within 1~30 rpm. When the speed ratio f>1, increasing the roller linear speed, increasing the speed ratio, and reducing the roller distance can effectively increase the speed gradient, increase the shear efficiency, and improve the cold rubber crushing effect. When the speed ratio is determined, the appropriate value can be selected according to the type of processed material, and it will not change during the rubber crushing process.

[0050] In one embodiment, the mixing mill is placed in a nitrogen or dry air environment box, and the dew point temperature of the gas in the environment box is lower than -40°C.

[0051] In one embodiment, the washing medium in the washing system is deionized water.

[0052] In one embodiment, the fluororubber is waste material generated by primary vulcanization and / or waste material generated by secondary vulcanization. The waste material generated by primary vulcanization may include burrs, scraps and unqualified semi-products generated during the molding process; the waste material generated by secondary vulcanization may include unqualified products after secondary vulcanization. In one embodiment, the recycled waste material is classified and recycled according to different types and colors.

[0053] In one embodiment, in the low-temperature freezing and pulverizing system, the time for secondary cooling and freezing the pre-cooled fluororubber using liquid refrigerant is 5 to 25 minutes.

[0054] In one embodiment, the magnetic induction intensity of the high gradient magnetic field separator within a range of 100 mm from the magnet surface is not less than 1200 GS.

[0055] In one embodiment, a near-parallel magnetic field is made of permanent magnetic material, and the magnetic induction intensity is not less than 1200GS within a range of 100mm from the magnet surface. A magnetic collecting device such as a filter or a magnetic separation frame composed of magnetizable materials is placed in the inner space of the near-parallel magnetic field to remove ferromagnetic impurities. When a super-strong magnetic separation device is made using permanent magnetic material as a magnetic source, the selection of permanent magnetic material and the design of the magnetic circuit are two important links that restrict and promote each other.

[0056] Example 1 A system for recycling fluororubber using cold rubber crushing technology using an open mill comprises an open mill, a constant temperature system, a liquid nitrogen low-temperature pulverizer, a screening system, a washing system and a high-gradient magnetic field separator.

[0057] The open mill with built-in cooler can adjust the roller temperature, roller speed and roller spacing. The roller size is 150 mm in diameter and 320 mm in length, with a speed ratio of 1:1.4, a speed of 0-28 rpm, and a roller spacing of 0-6 mm. The refrigerant is a 45% (v / v) ethylene glycol aqueous solution, and the temperature is controlled at -30℃~30℃.

[0058] The cooler includes a rotary joint connecting the refrigerant and the roller, a chamber through which the refrigerant flows, a refrigerant inlet pipe, and a refrigerant outlet pipe. The rotary joint connecting the refrigerant and the roller adopts a one-way flow type: the rotary joint is installed at one end of the roller, and the refrigerant fluid is introduced and discharged at this end at the same time. The refrigerant inlet pipe located at the center axis of the chamber goes deep into the other end of the roller and is stationary relative to the rotation of the roller.

[0059] Fins or baffles are installed on the outside of the refrigerant inlet pipe.

[0060] The mixing mill is placed in a nitrogen environment box with a gas dew point temperature of -60°C to prevent condensation of water on the low-temperature roller surface from interfering with the thin-through mixing process.

[0061] Liquid nitrogen low-temperature pulverizer, pass liquid nitrogen to cool the pulverizer cavity, add fluororubber of a certain mesh size, continue to pass liquid nitrogen, then start pulverizing for 10s~20s, stop for 2 minutes, and then pulverize for another 10s~20s.

[0062] The rubber powder screened by the high-gradient magnetic field separator passes through the high-gradient magnetic field from top to bottom. The magnetic separation system is designed with a size of 300 mm long × 300 mm wide × 900 mm high. The powder enters the magnetic field area composed of meshed wire mesh from the upper "round to square structure" channel, and the outside is a permanent magnet and yoke iron. The lower "square to round structure" channel is responsible for material collection and distribution, and the system combines high-frequency ultrasonic vibration to prevent material blockage.

[0063] In the FKM production process, the flash and defective products generated by primary and secondary vulcanization account for about 6% of the total input material.

[0064] Take 1000 g of black flash, place the open mill in a nitrogen environment box, the gas dew point temperature in the environment box is -60℃, the roller surface temperature is controlled to -30℃, the roller speed ratio is 1:1.4, the speed is 10 rpm, and the roller spacing is 2 mm. Cold crush the rubber 4 times, sieve with a 30-mesh screen (0.6 mm), and continue to cold crush the large particles that have not been sieved until all pass the 30-mesh screen. After drying and cooling, it weighs about 869 g.

[0065] The dried and cooled powdered rubber was sieved through a 100-mesh sieve (0.15 mm) by a liquid nitrogen low-temperature pulverizer, and 725 g of the product was obtained after drying.

[0066] 200 g of the recycled material sieved through 100 mesh was weighed, 400 g of the new mixed rubber was added, the mixture was thinly mixed, and the mixture was compression molded to prepare a rubber product.

[0067] Example 2 Take 1000 g of black flash, place the open mill in a nitrogen environment box, the gas dew point temperature in the environment box is -60℃, the roller surface temperature is controlled to -30℃, the roller speed ratio is 1:1.4, the speed is 10 rpm, and the roller spacing is 2 mm. Cold crush the rubber 4 times, sieve with a 30-mesh screen (0.6 mm), and continue to cold crush the large particles that have not been sieved until all pass through the 30-mesh screen. After drying and cooling, weigh about 858 g.

[0068] The dried and cooled powdered rubber was sieved through a 60-mesh sieve (0.25 mm) by a liquid nitrogen low-temperature pulverizer, and 732 g of the product was obtained after drying.

[0069] 200 g of the recycled material sieved through 60 mesh was weighed, 400 g of the new mixed rubber was added, the mixture was thinly mixed, and the mixture was compression molded to prepare a rubber product.

[0070] Embodiment 3: Take 1000 g of black flash, place the open mill in a nitrogen environment box, the gas dew point temperature in the environment box is -60℃, the roller surface temperature is controlled to -30℃, the roller speed ratio is 1:1.4, the speed is 10 rpm, and the roller spacing is 2 mm. Cold crush the rubber 4 times, sieve with a 30-mesh screen (0.6 mm), and continue to cold crush the large particles that have not been sieved until all pass the 30-mesh screen. After drying and cooling, weigh about 854 g.

[0071] The dried and cooled powdered rubber was crushed by liquid nitrogen low-temperature mill, sieved through 30-100 mesh (0.25 mm), and 729 g of product was obtained after drying.

[0072] 200 g of 30-100 mesh sieved recycled material and 400 g of new mixed rubber were added, mixed and molded to prepare rubber products.

[0073] Embodiment 4: Take 1000 g of black flash, place the open mill in a nitrogen environment box, the gas dew point temperature in the environment box is -60℃, the roller surface temperature is controlled to -30℃, the roller speed ratio is 1:1.4, the speed is 10 rpm, and the roller spacing is 2 mm. Cold crush the rubber 4 times, sieve with a 30-mesh screen (0.6 mm), and continue to cold crush the large particles that have not been sieved until all pass the 30-mesh screen. After drying and cooling, it weighs about 862 g.

[0074] The dried and cooled powdered rubber was sieved through a 100-mesh sieve (0.15 mm) by a liquid nitrogen low-temperature pulverizer, and 721 g of the product was obtained after drying.

[0075] Only 400 g of 100-mesh sieved recycled material and 200 g of new mixed rubber were added, mixed and molded to prepare rubber products.

[0076] Comparative Example 1: 600 g of new rubber compound was added, thinly mixed, and compression molded to prepare a rubber product.

[0077] like Figure 2 As shown in the figure, the tensile strength comparison of the product made of the fluororubber recycled in the embodiment and other control examples is shown. According to the figure, it can be seen that the particle size of the fluororubber is further reduced by low-temperature freezing and crushing after recycling and preliminary crushing, and the specific surface area of ​​the fluororubber particles is increased, thereby increasing the interaction force between the recycled fluororubber particles and the rubber matrix, improving the rubber interface compatibility, and ensuring the performance of the rubber product.

[0078] When 33.3% of the recycled material sieved through 100 mesh was added (Example 1), the tensile strength was basically the same as that of the new mixed rubber (Comparative Example 1), but when 66.6% of the recycled material sieved through 100 mesh was added (Example 4), the performance difference was quite large.

[0079] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be included in the protection scope of the present application.

Claims

1. A system for recycling fluororubber using an open mill, characterized in that: include: The open mill has a roller with a built-in cooler, which is used to cool the fluororubber to be recycled and perform preliminary crushing; the fluororubber is at least one of a binary or ternary fluororubber containing vinylidene fluoride and a perfluoroether rubber. A constant temperature system for controlling the refrigerant temperature and refrigerant flow rate of the cooler; The low-temperature freezing and crushing system is used to perform low-temperature freezing and crushing on the fluororubber after preliminary crushing to obtain fluororubber particles; A screening system, used for screening the fluororubber particles that meet the predetermined size after being crushed, and continuously conveying the fluororubber particles that do not reach the predetermined size to the low-temperature freezing crushing system; A washing system, used for washing the fluororubber particles to remove the additive powder released during the freezing and crushing process; A high gradient magnetic field separator is used to remove ferromagnetic particles generated in the freezing and crushing process from the cleaned fluororubber particles using a high gradient magnetic field to obtain recovered fluororubber particles. Wherein, the cooler comprises a rotary joint connecting the refrigerant and the roller, a chamber through which the refrigerant flows, a refrigerant inlet pipe and a refrigerant outlet pipe; The rotary joint is installed at one end of the roller, and the rotary joint adopts a one-way flow type; The refrigerant introduction pipe located at the central axis of the chamber penetrates into the other end of the roller and is stationary relative to the rotation of the roller.

2. The system according to claim 1, characterized in that Fins or baffles are installed outside the refrigerant introduction pipe.

3. The system according to claim 1, characterized in that The refrigerant temperature of the cooler is -50℃~80℃. The refrigerant is water or an aqueous solution at 10°C to 80°C, or an ethylene glycol aqueous solution or an organic refrigerant at -50°C to 50°C.

4. The system according to claim 1, characterized in that The speed ratio of adjacent rollers in the mixing mill is 1~1.5, the speed of the rollers is 1~30 rpm, and the spacing between adjacent rollers is 1~6 mm.

5. The system according to claim 1, characterized in that The mixing mill is placed in a nitrogen or dry air environment box, and the dew point temperature of the gas in the environment box is lower than -40°C.

6. The system according to claim 1, characterized in that The washing medium in the washing system is deionized water.

7. The system according to claim 1, characterized in that The fluororubber is waste material generated by primary vulcanization and / or waste material generated by secondary vulcanization.

8. The system according to claim 1, characterized in that In the low-temperature freezing and pulverizing system, the liquid refrigerant is used to perform secondary cooling and freezing on the pre-cooled fluororubber for 5 to 25 minutes.

9. The system according to claim 1, characterized in that The magnetic induction intensity of the high gradient magnetic field separator within 100mm from the magnet surface is not less than 1200GS.

10. A method for recovering fluororubber, characterized in that: include: The fluororubber to be recovered is cooled in an open mill and preliminarily crushed; the fluororubber is at least one of a binary or ternary fluororubber containing vinylidene fluoride and a perfluoroether rubber. The fluororubber after preliminary crushing is subjected to low temperature freezing and crushing to obtain fluororubber particles; Screening the fluororubber particles that meet the predetermined size after crushing, and continuing to cryogenically crush the fluororubber particles that do not meet the predetermined size; The additive powder released from the fluororubber particles during washing, freezing and crushing; A high gradient magnetic field is used to remove the ferromagnetic particles generated in the freezing and crushing process from the cleaned fluororubber particles to obtain recovered fluororubber particles.

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