Ultralow-temperature pure carbon dioxide gas explosion resistant fluororubber and preparation method thereof

Abstract

The invention discloses ultralow-temperature pure carbon dioxide gas explosion resistant fluororubber and a preparation method thereof. The fluororubber is prepared from the following components in parts by weight: 100 parts of raw fluororubber, 10 to 30 parts of acetylene carbon black, 15 to 25 parts of semi-reinforcing carbon black, 3 to 10 parts of triallyl isocyanurate, 2 to 5 parts of 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexane, 10 to 15 parts of kaolin, 5 to 8 parts of barium sulfate and 1 part of processing aid. Through the synergistic effect of the compound filler of the low-temperature fluororubber raw rubber, the flaky kaolin and the barium sulfate and the specific peroxide vulcanization system, the material still keeps good elasticity at-55 DEG C, and the gas explosion resistance of the material in a high-pressure pure carbon dioxide environment is remarkably improved. Tests show that the volume change rate of the material is less than 9% after the material is aged in 20MPa pure CO2, the gas explosion failure pressure is greater than or equal to 35MPa, and the technical problem that the existing fluororubber is easy to bubble, embrittle and leak under the working condition of cryogenic CO2 is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rubber technology, and particularly relates to a fluororubber with super-low-temperature resistance to pure carbon dioxide gas explosion and a preparation method thereof. BACKGROUND

[0002] In the fields of liquefied carbon dioxide storage and transportation, supercritical carbon dioxide extraction and transportation, and carbon dioxide geological storage, the sealing material not only needs to withstand high-pressure, high-purity carbon dioxide medium, but also often faces the service environment of extreme low temperature (such as -40 DEG C to -60 DEG C). Fluororubber (FKM) is one of the preferred materials in such harsh working conditions due to its excellent high-temperature resistance, oil resistance and chemical medium resistance.

[0003] The existing fluororubber formula still has significant defects when coping with the dual harsh conditions of "high-pressure pure carbon dioxide" and "super-low temperature": high-pressure carbon dioxide (especially in the supercritical state) has a relatively high solubility and permeability in fluororubber. In the process of rapid pressure relief, the supersaturated dissolved CO2 is easy to precipitate sharply, resulting in "gas explosion" phenomenon, which causes the internal bubble, delamination and even overall explosion failure of the sealing element, and seriously threatens the system safety; the glass transition temperature of general fluororubber is relatively high, and the chain segment movement ability decreases at super-low temperature, the material tends to be hard and brittle, and the elasticity and flexibility are greatly reduced. This leads to stress cracking in low-temperature dynamic sealing, and the assembly gap change caused by temperature fluctuation cannot be effectively compensated, resulting in sealing leakage.

[0004] In order to improve the medium resistance, the amount of filler is often increased to reduce gas permeability, but this will further worsen the low-temperature performance and compression permanent deformation of the rubber. Although the conventional peroxide vulcanization system can provide good thermal stability, it still has deficiencies in improving the density of the crosslinked network to resist gas dissolution and permeation, and the targeted improvement of "anti-explosion" performance is limited.

[0005] Therefore, it is urgent to develop a fluororubber formula with excellent super-low-temperature elasticity and excellent resistance to high-pressure pure carbon dioxide permeation and anti-explosion performance to meet the urgent needs of modern industry for high-reliability sealing under extreme working conditions. SUMMARY

[0006] In order to overcome the defects of the prior art, the present application provides a fluororubber with super-low-temperature resistance to pure carbon dioxide gas explosion, which comprises the following raw materials in parts by weight:

[0007] 100 parts of main material, 10-30 parts of acetylene carbon black, 15-25 parts of semi-reinforcing carbon black, 3-10 parts of 60%-70% triallyl isocyanurate, 2-5 parts of 45%-50% 2,5-di-methyl-2,5-di(tert-butyl peroxy)hexane, 10-15 parts of kaolin, 5-8 parts of barium sulfate, and 1 part of processing aid.

[0008] On the basis of the above technical scheme, the fluorine rubber comprises the following raw materials in parts by weight:

[0009] 100 parts of main material, 10 parts of acetylene carbon black, 25 parts of semi-reinforcing carbon black, 3 parts of triallyl isocyanurate of 60% to 70%, 2 parts of 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane of 45% to 50%, 10 parts of kaolin, 8 parts of barium sulfate and 1 part of processing aid.

[0010] Further, the fluorine rubber comprises the following raw materials: 100 parts of main material, 30 parts of acetylene carbon black, 15 parts of semi-reinforcing carbon black, 10 parts of triallyl isocyanurate of 60% to 70%, 5 parts of 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane of 45% to 50%, 15 parts of kaolin, 5 parts of barium sulfate and 1 part of processing aid.

[0011] A preparation method of the fluorine rubber resistant to pure carbon dioxide gas explosion at ultra-low temperature comprises the following steps:

[0012] Mixing: after plasticizing the fluorine rubber raw rubber, all the reinforcing fillers, processing aids and vulcanization systems are sequentially added and uniformly mixed on an open mill to obtain a mixed rubber;

[0013] Vulcanization forming: the mixed rubber is formed by mold pressing in a flat vulcanization machine;

[0014] Post-processing: the formed rubber is heat-treated in an oven to complete the final vulcanization.

[0015] Compared with the prior art, the present application mainly has the following beneficial effects:

[0016] 1. The compound system of kaolin (sheet-shaped) and barium sulfate (granular) forms a unique “labyrinth” physical barrier structure in the fluorine rubber matrix. This structure can effectively prolong the diffusion path of carbon dioxide molecules, greatly reduce the dissolution rate and saturated dissolution amount of CO2 under high pressure. As the test data shows, the volume expansion rate (about 8%) of the material of the present application is much lower than that of the comparative sample (22.3%) without using the compound system, and its failure critical pressure (≥35 MPa) is increased by more than 50% compared with the comparative sample in the “gas explosion” simulation test, which fundamentally solves the failure risk of sealing element bubbling, delamination and even explosion in the high-pressure pure carbon dioxide environment.

[0017] 2. By selecting low-temperature fluorine rubber raw rubber and cooperating with a specific reinforcing system, the material of the present application still maintains good flexibility at an extreme low temperature of-55℃. Its brittle temperature is lower than-58℃, and the low-temperature retraction (TR10) is lower than-42℃, which ensures that the sealing material will not lose the following property due to brittleness at deep cold working conditions, effectively compensates for the change of assembly gap caused by temperature fluctuation, and maintains the long-term sealing effectiveness. DETAILED DESCRIPTION

[0018] The application is further described below in connection with the detailed description. The raw materials used in the formulations are obtained from commercial sources, and all parts are by weight unless otherwise specified.

[0019] Example 1

[0020] The formulation includes:

[0021] Fluororubber raw rubber: 100 parts, acetylene black: 10 parts, semi-reinforcing carbon black: 25 parts, triallyl isocyanurate (content 65%): 3 parts, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane (content 50%): 2 parts, kaolin (flaky, 1250 mesh): 10 parts, barium sulfate (precipitation method): 8 parts, processing aid (low molecular weight silicone): 1 part.

[0022] The preparation method is specifically as follows:

[0023] The fluororubber raw rubber is plasticized on an open mill at low temperature and thin pass;

[0024] Acetylene black, semi-reinforcing carbon black, kaolin, barium sulfate, and processing aid are sequentially added and fully mixed and uniform; triallyl isocyanurate and peroxide vulcanizing agent are added, and the triangle bag is quickly thin-passed for 6-8 times to ensure uniform dispersion before being discharged; after the mixed rubber is stored at room temperature for 24 hours, it is molded into a sheet in a flat vulcanizing machine at 175°C and 15 MPa;

[0025] The vulcanized rubber is subjected to secondary vulcanization in an oven at 230°C for 8 hours.

[0026] Example 2

[0027] The formulation includes:

[0028] Fluororubber raw rubber: 100 parts, acetylene black: 30 parts, semi-reinforcing carbon black: 15 parts, triallyl isocyanurate (content 70%): 10 parts, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane (content 45%): 5 parts, kaolin (flaky, 800 mesh): 15 parts, barium sulfate: 5 parts, processing aid: 1 part.

[0029] The preparation method is the same as in Example 1.

[0030] Comparative Example 1

[0031] The formulation is basically the same as in Example 1, but kaolin and barium sulfate are removed and replaced with an equal amount of semi-reinforcing carbon black.

[0032] Comparative Example 2

[0033] The formulation is basically the same as in Example 1, but an equal number of general-purpose fluororubber raw rubber (Tg≈ -20℃) is used instead of low-temperature raw rubber.

[0034] Comparative Example 3

[0035] Fluororubber formulations using the traditional bisphenol AF vulcanization system were used as a control for commercially available ordinary products.

[0036] The vulcanizates from the above examples and comparative examples were prepared into standard samples, and their ultra-low temperature performance (-55℃) and CO2 explosion resistance were tested. The results are shown in the table below:

[0037]

[0038] Based on the above data, this invention achieves the following effects through the synergistic design of low-temperature fluororubber raw rubber, specific reinforcing fillers, and a highly efficient peroxide vulcanization system:

[0039] 1. Excellent cryogenic elasticity: As shown in the examples, the brittle temperature is below -55°C and the cryogenic shrinkage (TR10) is below -42°C, ensuring sealing reliability in a cryogenic CO2 environment.

[0040] 2. Excellent resistance to CO2 penetration and explosion: The flake and granular compound system of kaolin and barium sulfate played a key role (Comparative Example 1 and Comparative Example 1). They not only improved the physical barrier properties of the cross-linked network, but also significantly reduced the dissolution and penetration of CO2 (the volume expansion rate was only about 1 / 3 of that of Comparative Example 1).

[0041] The applicant declares that, based on the above embodiments, those skilled in the art can combine the specific content values ​​of a certain component in the above embodiments with the technical solutions in the invention content section to generate new numerical ranges, which are also within the scope of this invention. To keep the specification concise, this application will not list these numerical ranges.

Claims

1. A fluororubber resistant to ultra-low temperature pure carbon dioxide gas explosion, characterized in that, By weight, it includes the following raw materials: The main ingredients are 100 parts, acetylene black is 10-30 parts, semi-reinforcing carbon black is 15-25 parts, triallyl isocyanurate (60%-70%) is 3-10 parts, 2-5 parts 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (45%-50%) is 10-15 parts, barium sulfate is 5-8 parts, and processing aids are 1 part.

2. The fluororubber resistant to ultra-low temperature pure carbon dioxide gas explosion according to claim 1, characterized in that, By weight, it includes the following raw materials: The main material consists of 100 parts, 10 parts, 25 parts, semi-reinforcing carbon black, 3 parts, 60%~70% triallyl isocyanurate, 2 parts, 45%~50% 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 10 parts, 8 parts, and 1 part, processing aid.

3. The fluororubber resistant to ultra-low temperature pure carbon dioxide gas explosion according to claim 1, characterized in that, By weight, it includes the following raw materials: The main ingredients are 100 parts, acetylene black is 30 parts, semi-reinforcing carbon black is 15 parts, 60%~70% triallyl isocyanurate is 10 parts, 45%~50% 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane is 5 parts, kaolin is 15 parts, barium sulfate is 5 parts, and processing aids are 1 part.

4. The method for preparing fluororubber according to claim 3, characterized in that, Includes the following steps: Mixing: After plasticizing the raw fluororubber, all reinforcing fillers, processing aids and vulcanization system are added in sequence and mixed evenly on a two-roll mill to obtain the compound. Vulcanization molding: The compounded rubber is molded in a flat vulcanizing machine; Post-processing: The molded rubber compound is placed in an oven for heat treatment to complete the final vulcanization.

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