Novel cross-linking agent, fluororubber as well as preparation method and application of fluororubber

Abstract

The invention provides a novel cross-linking agent, fluororubber and a preparation method and application thereof, and belongs to the technical field of chemical production. According to the invention, p-hydroxystyrene and perfluoropolyether allyl ether are copolymerized to synthesize a macromolecular cross-linking agent with a poly-p-hydroxystyrene structure, and the prepared macromolecular cross-linking agent is applied to cross-linking of fluororubber for the first time, so that the compatibility of the macromolecular cross-linking agent in the fluororubber is remarkably improved; compared with bisphenol AF, the bisphenol AF crosslinking agent with the structure can effectively increase the elongation at break of fluororubber, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical production, and in particular relates to a novel cross-linking agent, fluororubber, and a preparation method and application thereof. Background Art

[0002] Fluororubber, due to the presence of fluorine atoms in its main or side chains, possesses excellent heat and chemical resistance, as well as superior mechanical strength and thermal stability. It is widely used in the automotive and machinery industries. However, fluororubber based on a diphenol-based vulcanization system suffers from low elongation at break. Commonly used fillers such as carbon black, calcium silicate, and diatomaceous earth only provide reinforcement and reduce elongation at break. Currently, the elongation at break of fluororubber based on this system is only 180-200%.

[0003] Bisphenol AF / benzyltriphenylphosphonium chloride (BPP) is a common and effective curing agent system for bisphenol fluororubber. However, as a small molecule, bisphenol AF easily accumulates in fluororubber, resulting in concentrated crosslinking points and low efficiency in fluororubber products, which in turn leads to poor product performance.

[0004] To improve the elongation at break of fluororubber compounds, three existing methods exist: 1. Adding silica for reinforcement. However, silica has limited compatibility and easily migrates to the rubber surface, causing roller sticking and affecting compression set performance. This approach is unsuitable for cylinder head gaskets and O-rings, which require high compression set, limiting its application. 2. Using a binary bisphenol vulcanization system with a ternary bisphenol vulcanization system for raw rubber can lead to compatibility issues, resulting in surface delamination, and the addition of ternary bisphenols can reduce the rubber's compression set performance. 3. Patent application CN117050443A mentions a composite additive made of magnesium oxide, calcium hydroxide, and organosiloxane, which can increase the elongation at break of binary bisphenol fluororubber to approximately 280%. However, the preparation process is cumbersome and unsuitable for industrial production. Patents such as CN202211325898.0 propose dechlorinated bisphenol AF salts, which, while offering relatively balanced and reliable performance, are costly (bisphenol AF is expensive) and offer insufficient resistance to strong acids, resulting in vulcanized rubber elongation at break ranging from 200-250%. For example, Daikin Industries JP Special Table 2004-526047 (publication number JP2004526047A) and patent CN202410680328.6 explore fluorine-free aromatic polyphenol compounds as crosslinking agents. While these have contributed to cost reduction and compression set optimization, their poor compatibility with fluororubber, uneven dispersion, low crosslinking efficiency, and significantly degraded mechanical properties (especially elongation at break) (often less than 150%) have limited their practical application. Patent CN115850886B discloses a high-performance fluororubber compound, in which a crosslinker is introduced into the fluororubber via a carbon nanotube-loaded crosslinker. However, the elongation at break of sealing parts prepared using the fluororubber compound is low and needs to be further improved.

[0005] Therefore, developing a new cross-linking agent to improve the elongation at break of fluororubber is of great significance and far-reaching impact. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a new cross-linking agent and its preparation method and application.

[0007] The present invention provides a cross-linking agent, the structure of which is shown in Formula I:

[0008]

[0009] Wherein, Rf is a K-type or Y-type perfluoropolyether chain with a molecular weight of 500-2000 g / mol, and x and y are each independently selected from integers of 1-40.

[0010] Furthermore, the cross-linking agent is prepared using 4-acetoxystyrene, perfluoropolyether allyl ether, initiator and hydrazine hydrate as raw materials, wherein the molar ratio of 4-acetoxystyrene, perfluoropolyether allyl ether, initiator and hydrazine hydrate is 1:0.1~0.5:0.005~0.05:1~4, preferably 1:0.1~0.2:0.01:1~1.5.

[0011] Furthermore, the perfluoropolyether allyl ether is a K-type perfluoropolyether allyl ether or a Y-type perfluoropolyether allyl ether; the initiator is selected from one of ammonium persulfate, potassium persulfate, benzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate, preferably azobisisobutyronitrile.

[0012] "K-type perfluoropolyether chain" refers to a series of branched polymers formed by polymerization of hexafluoropropylene oxide (HFPO) under the catalysis of cesium fluoride (CsF), with the structural formula: CF3CF2CF2O[CF(CF3)CF2O]nCF(CF3)COF.

[0013] "Y-type perfluoropolyether chain" refers to a polymer formed by photooxidation of hexafluoropropylene (HFP) under the action of ultraviolet light, and its structural formula is: CF3O(C3F6O)m(CF2O)nCF3.

[0014] The present invention also provides a method for preparing the above-mentioned cross-linking agent, which comprises the following steps:

[0015] (1) reacting 4-acetoxystyrene, perfluoropolyether allyl ether and an initiator;

[0016] (2) adding a solvent for precipitation and drying to obtain a precipitate;

[0017] (3) The precipitate is reacted with hydrazine hydrate and dried to obtain a cross-linking agent.

[0018] Furthermore, in step (1), the solvent of the reaction is selected from one of 1,2-dichloroethane, acetonitrile, tetrahydrofuran, toluene, and 1,4-dioxane; the reaction temperature is 50-100° C., and the reaction time is 10-15 h;

[0019] In step (2), the solvent is an organic solvent; the drying temperature is 50 to 70° C., and the drying time is 10 to 15 hours;

[0020] In step (3), the reaction solvent is tetrahydrofuran; the reaction temperature is 10-40° C., and the reaction time is 10-15 h; and the drying temperature is 50-70° C., and the drying time is 10-15 h.

[0021] The present invention also provides a fluororubber, which is prepared from raw materials in the following weight ratio: 100 parts of fluororubber raw rubber, 20-30 parts of carbon black, 1-5 parts of internal release agent, 5-15 parts of acid absorber, 1-5 parts of the above-mentioned crosslinking agent, and 0.1-2 parts of accelerator.

[0022] Furthermore, it is prepared from raw materials in the following weight ratio: 100 parts of fluororubber raw rubber, 25 parts of carbon black, 3 parts of internal release agent, 10 parts of acid absorber, 2 parts of the above crosslinking agent, and 1 part of accelerator.

[0023] Furthermore, the fluororubber raw rubber is 26M;

[0024] The carbon black is carbon black N990;

[0025] The internal release agent is HT290;

[0026] The acid absorbents are magnesium oxide and calcium hydroxide;

[0027] The accelerator is benzyltriphenylphosphonium chloride.

[0028] The present invention also provides a method for preparing the above-mentioned fluororubber, which comprises the following steps: mixing fluororubber raw rubber, carbon black, internal mold release agent and acid absorber and kneading them, then adding the above-mentioned crosslinking agent and accelerator and continuing to mix and knead them to obtain fluororubber.

[0029] Furthermore, the banburying temperature is 80-120° C., and the time is 1-10 minutes.

[0030] The present invention also provides uses of the cross-linking agent and the fluororubber in preparing aerospace materials and automobile manufacturing materials.

[0031] The present invention has achieved the following beneficial effects:

[0032] The present invention utilizes p-hydroxystyrene and perfluoropolyether allyl ether to copolymerize to synthesize a macromolecular crosslinking agent having a poly(p-hydroxystyrene) structure. The present invention also applies the prepared macromolecular crosslinking agent to the crosslinking of fluororubber for the first time, significantly increasing its compatibility in fluororubber, thereby successfully vulcanizing bisphenol fluororubber. Compared with bisphenol AF, this structure can effectively increase the elongation at break of fluororubber as a crosslinking agent, and has good application prospects.

[0033] Compared with the high-performance fluororubber compound disclosed in patent CN115850886B, the elongation at break of the fluororubber sample prepared by the new cross-linking agent in the present application can reach 253% to 317%, while in patent CN115850886B, the elongation at break of the sealing parts prepared by using the fluororubber compound is between 182% and 201%. The elongation at break of the fluororubber sample in the present application is significantly better.

[0034] Obviously, based on the above contents of the present invention, according to common technical knowledge and customary means in this field, without departing from the above basic technical ideas of the present invention, other various forms of modifications, replacements or changes can be made.

[0035] The following is a further detailed description of the present invention through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the infrared spectrum of the new cross-linking agent I.

[0037] Figure 2 This is the infrared spectrum of the new cross-linking agent II.

[0038] Figure 3 This is the infrared spectrum of the new cross-linker III.

[0039] Figure 4 This is the infrared spectrum of the new cross-linker IV. DETAILED DESCRIPTION

[0040] The raw materials and equipment used in the present invention are all known products and are obtained by purchasing commercially available products.

[0041] The "room temperature" in the present invention means 25±5°C.

[0042] The preparation route of the novel cross-linking agent of the present invention is as follows:

[0043]

[0044] Example 1. Synthesis of Novel Cross-linking Agent I

[0045] To a round-bottom flask, add 4-acetoxystyrene (10 g, 61.7 mmol), K-type perfluoropolyether allyl ether (500 g / mol, 3.1 g, 6.17 mmol), azobisisobutyronitrile (0.1 g, 0.62 mmol) and a stirring bar in sequence, introduce nitrogen to replace the system three times, add 100 mL of tetrahydrofuran to the system, and then control the temperature to 70°C under stirring to react for 12 hours. After the reaction is completed, pour the system into petroleum ether to precipitate the reaction product, and vacuum dry it at 60°C for 12 hours to obtain a white solid. After dissolving the obtained white solid in tetrahydrofuran, add hydrazine hydrate (85%, 3.7 mL, 61.7 mmol), react at room temperature for 12 hours, and then reversely precipitate the reaction system into water for filtration. Dry it in a vacuum oven at 60°C for 12 hours to obtain a new crosslinker I (11 g, yield 84%). The infrared spectrum of the new crosslinker I is shown as follows: Figure 1 shown.

[0046] Example 2: Synthesis of Novel Crosslinking Agent II

[0047] To a round-bottom flask, add 4-acetoxystyrene (10 g, 61.7 mmol), K-type perfluoropolyether allyl ether (500 g / mol, 6.2 g, 12.34 mmol), azobisisobutyronitrile (0.1 g, 0.62 mmol) and a stirring bar in sequence, introduce nitrogen to replace the system three times, add 100 mL of tetrahydrofuran to the system, and then control the temperature to 70 ° C under stirring to react for 12 hours. After the reaction is completed, pour the system into petroleum ether to precipitate the reaction product, and vacuum dry it at 60 ° C for 12 hours to obtain a white solid. After dissolving the obtained white solid in tetrahydrofuran, add hydrazine hydrate (85%, 3.7 mL, 61.7 mmol), react at room temperature for 12 hours, and then reversely precipitate the reaction system into water for filtration. Dry it in a vacuum oven at 60 ° C for 12 hours to obtain a new crosslinker II (13.1 g, yield 81%). The infrared spectrum of the new crosslinker II is shown as follows: Figure 2 shown.

[0048] Example 3: Synthesis of Novel Crosslinking Agent III

[0049] To a round-bottom flask, add 4-acetoxystyrene (10 g, 61.7 mmol), K-type perfluoropolyether allyl ether (1200 g / mol, 7.4 g, 6.17 mmol), azobisisobutyronitrile (0.1 g, 0.62 mmol) and a stirring bar in sequence, introduce nitrogen to replace the system three times, add 100 mL of tetrahydrofuran to the system, and then control the temperature to 70°C under stirring to react for 12 hours. After the reaction is completed, pour the system into petroleum ether to precipitate the reaction product, and vacuum dry it at 60°C for 12 hours to obtain a white solid. After dissolving the obtained white solid in tetrahydrofuran, add hydrazine hydrate (85%, 3.7 mL, 61.7 mmol), react at room temperature for 12 hours, and then reversely precipitate the reaction system into water for filtration. Dry it in a vacuum oven at 60°C for 12 hours to obtain a new crosslinker III (14.8 g, yield 85%). The infrared spectrum of the new crosslinker III is shown as follows: Figure 3 shown.

[0050] Example 4: Synthesis of Novel Crosslinking Agent IV

[0051] To a round-bottom flask, add 4-acetoxystyrene (10 g, 61.7 mmol), K-type perfluoropolyether allyl ether (1200 g / mol, 14.8 g, 12.34 mmol), azobisisobutyronitrile (0.1 g, 0.62 mmol) and a stirring bar in sequence, introduce nitrogen to replace the system three times, add 100 mL of tetrahydrofuran to the system, and then control the temperature to 70°C under stirring to react for 12 hours. After the reaction is completed, pour the system into petroleum ether to precipitate the reaction product, and vacuum dry it at 60°C for 12 hours to obtain a white solid. After dissolving the obtained white solid in tetrahydrofuran, add hydrazine hydrate (85%, 3.7 mL, 61.7 mmol), react at room temperature for 12 hours, and then reversely precipitate the reaction system into water for filtration. Dry it in a vacuum oven at 60°C for 12 hours to obtain a new crosslinker IV (19.8 g, yield 80%). The infrared spectrum of the new crosslinker IV is shown as follows: Figure 4 shown.

[0052] Example 5. Preparation of Fluororubber Mixtures I-IV

[0053] First, 100 parts of 26M are plasticized in a mixing chamber at a temperature of 80°C for 1.5 minutes; then, 25 parts of carbon black N990, 3 parts of internal release agent HT290, 5 parts of acid absorber magnesium oxide and 5 parts of calcium hydroxide are added in sequence, and the temperature is raised to 100°C and the mixing is continued for 5 minutes; when the temperature rises to 120°C, the material is discharged, and after being thinned three times on an open mill, 2 parts of a new crosslinking agent I and 1 part of an accelerator benzyltriphenylphosphonium chloride are added and mixed evenly, and at the same time, the open mill roller is used for shearing, and about 8 triangular packages are made and then thinned, and the fluororubber compound I with high elongation is obtained after being produced.

[0054] With reference to the above preparation method, the only difference is that the new cross-linking agent I is replaced by new cross-linking agents II to IV, respectively, to prepare fluororubber compounds II to IV.

[0055] The following is a control sample preparation.

[0056] Comparative Example 1: Preparation of Bisphenol AF Fluororubber Compound

[0057] The preparation method of Reference Example 5 was used, except that the new cross-linking agent I was replaced with bisphenol AF to prepare a bisphenol AF fluororubber compound (denoted as Control Sample I).

[0058] The beneficial effects of the present invention are demonstrated by experimental examples below.

[0059] Experimental Example 1: Testing the Mechanical Properties of Fluororubber Compounds

[0060] 1. Experimental methods

[0061] The hardness test of fluororubber compound after vulcanization is carried out in accordance with GB / T 531.1-2008 standard; the mechanical properties are tested in accordance with GB / T 528-2009 standard; and the compression set test is carried out in accordance with GB / T7759.1-2015 standard.

[0062] 2. Experimental results

[0063] The mechanical properties of the synthesized new crosslinking agents I-IV acting on fluororubber samples are compared as shown in the following table:

[0064]

[0065] It can be seen from the above table that the elongation at break of the fluororubber added with the new crosslinking agents I-IV (253%-317%) is significantly improved compared with the control sample I (191%), and its good comprehensive mechanical properties such as tensile strength, hardness, 100% elongation, and compression permanent deformation are guaranteed.

[0066] Therefore, compared with the fluororubber prepared by the same amount of bisphenol AF, the fluororubber prepared by the new macromolecular crosslinking agent has better elongation at break while ensuring good comprehensive properties such as tensile strength, hardness and 100% elongation.

[0067] In summary, the present invention provides a novel crosslinking agent, fluororubber, and preparation methods and applications thereof. The present invention utilizes p-hydroxystyrene and perfluoropolyether allyl ether to copolymerize to synthesize a macromolecular crosslinking agent having a poly(p-hydroxystyrene) structure. The present invention also applies the prepared macromolecular crosslinking agent to the crosslinking of fluororubber for the first time, significantly increasing its compatibility with the fluororubber, thereby enabling the successful vulcanization of bisphenol fluororubber. Compared with bisphenol AF, this structure as a crosslinking agent can effectively increase the elongation at break of fluororubber, showing promising application prospects.

Claims

1. A cross-linking agent, characterized in that The structure of the cross-linking agent is shown in Formula I: Wherein, Rf is a K-type or Y-type perfluoropolyether chain with a molecular weight of 500-2000 g / mol, and x and y are each independently selected from integers of 1-40.

2. The cross-linking agent according to claim 1, characterized in that The crosslinking agent is prepared using 4-acetoxystyrene, perfluoropolyether allyl ether, an initiator and hydrazine hydrate as raw materials, wherein the molar ratio of 4-acetoxystyrene, perfluoropolyether allyl ether, initiator and hydrazine hydrate is 1:0.1-0.5:0.005-0.05:1-4, preferably 1:0.1-0.2:0.01:1-1.

5.

3. The method according to claim 2, characterized in that The perfluoropolyether allyl ether is K-type perfluoropolyether allyl ether or Y-type perfluoropolyether allyl ether; the initiator is selected from one of ammonium persulfate, potassium persulfate, benzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate, preferably azobisisobutyronitrile.

4. A method for preparing the cross-linking agent according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: (1) reacting 4-acetoxystyrene, perfluoropolyether allyl ether and an initiator; (2) adding a solvent for precipitation and drying to obtain a precipitate; (3) The precipitate is reacted with hydrazine hydrate and dried to obtain a cross-linking agent.

5. The method according to claim 4, characterized in that In step (1), the reaction solvent is selected from one of 1,2-dichloroethane, acetonitrile, tetrahydrofuran, toluene, and 1,4-dioxane; the reaction temperature is 50-100° C., and the reaction time is 10-15 h; In step (2), the solvent is an organic solvent; the drying temperature is 50 to 70° C., and the drying time is 10 to 15 hours; In step (3), the reaction solvent is tetrahydrofuran; the reaction temperature is 10-40° C., and the reaction time is 10-15 h; and the drying temperature is 50-70° C., and the drying time is 10-15 h.

6. A fluororubber, characterized in that: The invention is prepared from raw materials in the following weight ratio: 100 parts of fluororubber raw rubber, 20 to 30 parts of carbon black, 1 to 5 parts of internal mold release agent, 5 to 15 parts of acid absorbent, 1 to 5 parts of the crosslinking agent according to any one of claims 1 to 3, and 0.1 to 2 parts of accelerator.

7. The fluororubber according to claim 6, characterized in that The invention is prepared from raw materials in the following weight ratio: 100 parts of fluororubber raw rubber, 25 parts of carbon black, 3 parts of internal mold release agent, 10 parts of acid absorber, 2 parts of the crosslinking agent according to claim 1 or 2, and 1 part of accelerator.

8. The fluororubber according to claim 7, characterized in that The fluororubber raw rubber is 26M; The carbon black is carbon black N990; The internal release agent is HT290; The acid absorbents are magnesium oxide and calcium hydroxide; The accelerator is benzyltriphenylphosphonium chloride.

9. A method for preparing the fluororubber according to any one of claims 6 to 8, characterized in that: The method comprises the following steps: mixing and kneading fluororubber raw rubber, carbon black, an internal mold release agent and an acid absorber, and then adding the crosslinking agent and accelerator according to claim 1 or 2 and continuing to mix and knead to obtain fluororubber.

10. Use of the cross-linking agent according to any one of claims 1 to 3 and the fluororubber according to any one of claims 6 to 8 in the preparation of aerospace materials and automobile manufacturing materials.

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