Liquid fluoroelastomer and method of making and use thereof

Abstract

The application relates to the technical field of fluorine materials, and discloses a liquid fluorine elastomer as well as a preparation method and application thereof. The liquid fluorine elastomer is obtained by mixing and reacting a fluorine-containing elastomer solution, magnesium oxide and an alcohol amine; wherein the fluorine-containing elastomer is free of side hydroxyl groups. The preparation method has the characteristics of less by-products, simplicity, controllability, high yield and the like. The high-functionality low-molecular-weight liquid fluorine elastomer of the application contains side hydroxyl groups, and the preferred example can also contain terminal carboxyl groups or terminal hydroxyl groups, has high functionality and good reactivity, and is crosslinked with a polyisocyanate compound to be solidified. The solidified product has excellent mechanical properties and chemical medium resistance, and can be used to prepare special adhesives, sealants and coatings.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorine materials, and in particular to a liquid fluorine elastomer and a preparation method and application thereof. Background Art

[0002] Fluoroelastomers are polymer materials containing fluorine atoms in the backbone or side chains. They exhibit excellent chemical and thermal stability, as well as excellent solvent resistance, and are widely used in a variety of fields, including aerospace, petrochemicals, and automotive. However, traditional fluoroelastomers are solid at room temperature and require the same molding methods as solid rubber, making them difficult to produce as solvent-free adhesives, coatings, and other products. Liquid fluoroelastomers exhibit a certain degree of fluidity and can be cured into desired shapes by adding a suitable curing agent. They can also be cured "in situ," retaining the excellent properties of solid fluoroelastomers, such as high-temperature and chemical resistance. Liquid fluoroelastomers can be divided into two categories: those without reactive functional groups in their chemical structure and those with reactive functional groups, which can be located in side chains or at either end of the molecular chain. "Active" liquid fluoroelastomers with reactive functional groups, particularly those containing two or more, exhibit excellent reactivity and are therefore valuable for a wide range of applications.

[0003] The main methods for synthesizing active liquid fluoroelastomers are monomer polymerization and oxidative degradation. Due to the complex process, difficulty and low yield of the monomer polymerization method, the molecular weight of the obtained product is difficult to control, and the initiators and telogens used in the monomer polymerization method are usually organic compounds with high prices and complex synthesis. Foreign researchers began to study the preparation of liquid fluoroelastomers by oxidative degradation around 1950. After continuous development, oxidative degradation is generally used to prepare liquid fluoroelastomers in modern industrial production. The problem with preparing liquid fluoroelastomers by oxidative degradation is that the actual functionality is low. During the oxidative degradation process, the two ends of the broken chain cannot be completely converted into carboxyl groups. Even if they are all converted into carboxyl groups, their theoretical functionality is 2, the cross-linking reactivity is low, and the mechanical strength is low.

[0004] The preparation of carboxyl-terminated liquid fluoroelastomers by oxidative degradation reveals that fluoroelastomers containing vinylidene fluoride units can undergo dehydrofluorination to form double bonds in an alkaline environment. These double bonds can also undergo addition reactions to introduce reactive groups. Currently, common methods for introducing hydroxyl groups onto double bonds include double bond epoxidation ring-opening reactions and thiol-double bond click reactions. However, epoxidation reagents are mostly peroxides, and the more effective ring-opening reagent, osmium tetroxide, is a highly toxic compound. The commonly used hydroxylation reagent, 2-mercaptoethanol, is also somewhat toxic, posing safety concerns.

[0005] Therefore, there is an urgent need to develop a low molecular weight liquid fluoroelastomer that is highly functional and simple and safe to prepare. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art and to provide a liquid fluoroelastomer and a preparation method and application thereof.

[0007] The present invention enables the liquid fluoroelastomer to have pendant hydroxyl groups, and the terminal groups can also be terminal carboxyl groups or terminal hydroxyl groups. These reactive functional groups have good reactivity and react with crosslinking agents to undergo curing. The cured product has good mechanical properties and stability.

[0008] In order to achieve the above object, the first aspect of the present invention provides a liquid fluoroelastomer, characterized in that the structural formula of the liquid fluoroelastomer is as shown in Formula I:

[0009]

[0010] Wherein, R1 is -NH(CH2) x OH, R2 is a non-reactive terminal group, carboxyl group or hydroxyl group;

[0011] x is 1-6;

[0012] The ratio between m and q is 4-25:1.

[0013] The second aspect of the present invention provides a method for preparing the liquid fluoroelastomer according to the first aspect, wherein the method comprises: mixing a fluoroelastomer solution, magnesium oxide and an alcohol amine and reacting them to obtain the liquid fluoroelastomer;

[0014] Wherein, the fluorine-containing elastomer has no pendant hydroxyl groups.

[0015] The third aspect of the present invention provides a liquid fluoroelastomer prepared according to the method described in the second aspect.

[0016] The fourth aspect of the present invention provides use of the liquid fluoroelastomer according to the first aspect or the third aspect in the preparation of special adhesives, sealants and coatings.

[0017] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0018] (1) The high-functionality, low-molecular-weight liquid fluoroelastomer provided by the present invention introduces hydroxyl groups on the side groups. Compared with the terminal-active liquid fluoroelastomer, both the terminal groups and the side groups are reactive, which makes up for the defect of low functionality of the terminal-active liquid fluoroelastomer. During the cross-linking and curing process, it has more cross-linking sites, high cross-linking reactivity, high cross-linking density, and better mechanical properties after vulcanization.

[0019] (2) This invention is the first to propose a method for preparing a high-functionality liquid fluoroelastomer. The raw material synthesis is relatively simple, and no fluorinated olefin copolymerization method is required. The synthesis process is simple and controllable. During the operation, few reactants are added, and no additional initiators or catalysts are required. Moreover, unreacted raw materials are easily removed.

[0020] (3) The high-functionality liquid fluoroelastomer provided by the present invention is a viscous liquid or semi-solid at room temperature, and can react with carboxyl and hydroxyl crosslinking agents to undergo crosslinking and curing. The cured product has excellent mechanical properties, thermal stability and chemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing the infrared spectrum (FT-IR) test results of the high-functionality, low-molecular-weight liquid fluoroelastomer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] A first aspect of the present invention provides a liquid fluoroelastomer, wherein the structural formula of the liquid fluoroelastomer is as shown in Formula I:

[0024]

[0025] Wherein, R1 is -NH(CH2) x OH, R2 is a non-reactive terminal group, carboxyl group or hydroxyl group;

[0026] x is 1-6;

[0027] The ratio between m and q is 4.36-23.4:1.

[0028] In the present invention, x, m, n, p, r, and q are all integers. In some cases, n, p, and r are not all 0 at the same time, for example, p≠0.

[0029] The liquid fluoroelastomer provided by the present invention partially introduces R1 groups in a specific proportion on the vinylidene fluoride structural unit to achieve the purpose of introducing active groups on the side groups, thereby improving the functionality of the liquid fluoroelastomer and ultimately obtaining a vulcanized product with better mechanical properties.

[0030] In some embodiments of the present invention, x is 2-4, preferably 3.

[0031] In some embodiments of the present invention, the ratio between m and q is 4.36-23.4:1, for example, 4.36, 4.48, 4.66, 4.8, 4.9, 5.16, 8.21, 8.62, 8.84, 11.09, 11.11, 11.42, 12.34, 12.51, 13.18, 14.65, 16.44, 17.49, 19.34, 20.8, 21.6, 23.4, and any value within the range of any two of the above values, preferably 8.84-17.49:1, and more preferably 14.65-17.49:1.

[0032] In some embodiments of the present invention, the functionality of the liquid fluoroelastomer is above 2.5, for example, 2.5, 2.53, 2.58, 2.6, 2.63, 2.67, 2.7, 2.8, 3, 3.3, 3.45, 3.5, 3.54, 3.7, 3.75, 3.9, 4.03, 4.39, 4.6, 5.05, 6.2, and any value within the range of any two of the above values, preferably above 4, or 3.3-6.2.

[0033] In some embodiments of the present invention, the liquid fluoroelastomer is selected from at least one of a side hydroxyl vinylidene fluoride-hexafluoropropylene copolymer, a side hydroxyl-terminated hydroxyl vinylidene fluoride-hexafluoropropylene copolymer, a side hydroxyl-terminated carboxyl vinylidene fluoride-hexafluoropropylene copolymer, a side hydroxyl-terminated hydroxyl vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer and a side hydroxyl-terminated carboxyl vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer.

[0034] The second aspect of the present invention provides a method for preparing the liquid fluoroelastomer according to the first aspect, wherein the method comprises: mixing a fluoroelastomer solution, magnesium oxide and an alcohol amine and reacting them to obtain the liquid fluoroelastomer;

[0035] Wherein, the fluorine-containing elastomer has no pendant hydroxyl groups.

[0036] Alkanolamines are weak bases, eliminating the need for subsequent reactions after dehydrofluorination with alkali. Liquid fluoroelastomers can be directly dehydrofluorinated by the alcoholamines, while the alcoholamines act as nucleophiles to react with double bonds, resulting in a simple and easy-to-use method. Therefore, the present invention introduces hydroxyl groups into a liquid fluoroelastomer with inactive side groups through an addition reaction with an alcoholamine to prepare a hydroxyl-containing liquid fluoroelastomer. Furthermore, by combining oxidative degradation with the introduction of hydroxyl groups into side groups, a liquid fluoroelastomer with active groups on both the side groups and the end groups is prepared.

[0037] In some embodiments of the present invention, the fluorine-containing elastomer is a binary, ternary or multi-component copolymer of vinylidene fluoride, preferably G-101 produced by Daikin Corporation of Japan, a carboxyl-terminated liquid fluorine elastomer or a hydroxyl-terminated liquid fluorine elastomer.

[0038] In some embodiments of the present invention, the solvent in the fluorine-containing elastomer solution is an organic solvent, preferably at least one selected from methyl isobutyl ketone, tetrahydrofuran and acetone.

[0039] In some embodiments of the present invention, the alcoholamine is selected from at least one of ethanolamine, 3-aminopropanol and 4-amino-1-butanol, preferably 3-aminopropanol.

[0040] In some embodiments of the present invention, the molar ratio of the alcoholamine to the vinylidene fluoride structural unit in the fluorine-containing elastomer is 0.5-4:4, preferably 1-3:4, more preferably 1.5-2:4, and most preferably 2:4.

[0041] In some embodiments of the present invention, the reaction time is 3-15 h, preferably 8-12 h;

[0042] In some embodiments of the present invention, the reaction temperature is 20-120°C, preferably 25-116°C, and more preferably 25°C, 60°C or 110°C.

[0043] In some embodiments of the present invention, after the reaction is completed, the system is cooled to room temperature, the inorganic salt and residual alcoholamine are extracted to remove, the solvent is removed by rotary evaporation, and the final product is obtained after drying.

[0044] The third aspect of the present invention provides a liquid fluoroelastomer prepared according to the method described in the second aspect.

[0045] The fourth aspect of the present invention provides use of the liquid fluoroelastomer according to the first aspect or the third aspect in the preparation of special adhesives, sealants and coatings.

[0046] The present invention will be described in detail below through examples.

[0047] In the following examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents and instruments used, if no manufacturer is specified, are commercially available conventional products.

[0048] In each embodiment of the present invention,

[0049] Low molecular weight liquid fluoroelastomer with inactive terminal groups, brand G-101, purchased from Daikin Corporation of Japan;

[0050] Carboxyl-terminated low molecular weight liquid fluoroelastomer, homemade;

[0051] Hydroxyl-terminated low molecular weight liquid fluoroelastomer, homemade;

[0052] Sodium borohydride was purchased from Tianjin Huadong Reagent Factory with CAS number 16940-66-2;

[0053] Iodine, purchased from Fuchen Chemical, CAS No. 109-99-9;

[0054] Hydrochloric acid, purchased from Beijing Chemical Plant, CAS No. 16881-77-9;

[0055] Anhydrous sodium sulfite, purchased from Aladdin, CAS number 7440-05-3;

[0056] Tetrahydrofuran, purchased from Fuchen Chemical, CAS No. 109-99-9;

[0057] HDI trimer curing agent, purchased from Covestro, CAS number 3779-63-3;

[0058] Ethylene glycol, purchased from McLean, CAS number 107-21-1;

[0059] Magnesium oxide, purchased from Maclean, CAS number 1309-48-4;

[0060] Methyl isobutyl ketone, purchased from Maclean, CAS number 108-10-1;

[0061] Ethanolamine, purchased from Maclean, CAS number 141-43-5;

[0062] 3-Aminopropanol, purchased from Maclean, CAS number 156-87-6;

[0063] 4-Amino-1-butanol was purchased from Maclean with CAS number 13325-10-5.

[0064] The low molecular weight fluorine-containing elastomer used in Examples 1-11 is a vinylidene fluoride (VDF)-hexafluoropropylene (HFP) copolymer manufactured by Daikin Corporation of Japan, with a brand name of G-101, a copolymerization composition with a VDF:HFP molar ratio of 80:20, and a number average molecular weight of 6200.

[0065] The low molecular weight fluorinated elastomer used in Examples 12-14 was carboxyl-terminated liquid fluorocarbon elastomer A, which was a vinylidene fluoride (VDF)-hexafluoropropylene (HFP) binary copolymer with a VDF:HFP molar ratio of 78:22, a carboxyl content of 3 wt %, and a number average molecular weight of 2600. It was prepared as follows:

[0066] 100 g of vinylidene fluoride (VDF)-hexafluoropropylene (HFP) copolymer elastomer (M n =296200,M w=335500, copolymer composition VDF:HFP molar ratio of 78:22) and 900g of acetone were mechanically stirred until the solid elastomer was completely dissolved; 32g of KOH and 39.8g of deionized water were weighed in a 100mL beaker to prepare a 45% by mass KOH aqueous solution; 60g of 30% by mass hydrogen peroxide was weighed in another 100mL beaker; the contents of the reactor were cooled to 10°C by a low-temperature coolant circulation pump, and then the hydrogen peroxide was added dropwise over 20 minutes, and the KOH aqueous solution was added dropwise over 30 minutes. After the addition is completed, the reaction is continued at 10°C for 5 hours; the stirring is stopped, the reaction solution is transferred to a 2L beaker, and after standing for 1 hour, the supernatant is transferred to another beaker, and the lower alkali solution is discarded; dilute hydrochloric acid is added to the clear liquid to adjust the pH to 2, and then 3 times the volume of deionized water is added thereto under stirring. The viscous liquid condensed on the bottom and wall of the beaker is the crude product; the crude product is further dissolved in acetone and continued to condense in deionized water. The obtained product is dried in a vacuum oven to constant weight to obtain a refined product, a carboxyl-terminated low molecular weight liquid fluoroelastomer A, as a colorless viscous liquid.

[0067] The low molecular weight fluorinated elastomer used in Examples 15-17 was a carboxyl-terminated liquid fluorocarbon elastomer B, which is a vinylidene fluoride (VDF)-hexafluoropropylene (HFP)-tetrafluoroethylene (TFE) terpolymer having a copolymerization composition of VDF:HFP:TFE in a molar ratio of 43:16:41, a carboxyl content of 4.2 wt %, and a number average molecular weight of 1500. It was prepared as follows:

[0068] 100 g of vinylidene fluoride (VDF)-hexafluoropropylene (HFP)-tetrafluoroethylene (TFE) ternary copolymer elastomer (M n =283300,M w=326100, copolymer composition VDF:HFP:TFE molar ratio = 43:16:41) and 900g of acetone were mechanically stirred until the solid elastomer was completely dissolved; 32g of KOH and 39.8g of deionized water were weighed in a 100mL beaker to prepare a 45% by mass KOH aqueous solution; 60g of 30% by mass hydrogen peroxide was weighed in another 100mL beaker; the contents of the reactor were cooled to 10°C by a low-temperature coolant circulation pump, and then the hydrogen peroxide was added dropwise over 20 minutes, and the KOH was added dropwise over 30 minutes. After the addition is completed, the reaction is continued at 10°C for 5 hours; the stirring is stopped, the reaction solution is transferred to a 2L beaker, and after standing for 1 hour, the upper clear liquid is transferred to another beaker, and the lower alkali solution is discarded; dilute hydrochloric acid is added to the clear liquid to adjust the pH to 2, and then 3 times the volume of deionized water is added thereto under stirring. The viscous liquid condensed on the bottom and wall of the beaker is the crude product; the crude product is further dissolved in acetone and continued to condense in deionized water. The obtained product is dried in a vacuum oven to constant weight to obtain a refined product, a carboxyl-terminated low molecular weight liquid fluoroelastomer B, as a colorless viscous liquid.

[0069] The low molecular weight fluoroelastomer used in Examples 18-20 is a hydroxyl-terminated liquid fluorocarbon elastomer C, which is a vinylidene fluoride (VDF)-hexafluoropropylene (HFP) binary copolymer with a VDF:HFP molar ratio of 78:22 and a number average molecular weight of 2600. It was prepared as follows:

[0070] Weigh 50g of carboxyl-terminated liquid fluorocarbon elastomer A and dissolve it in 215g of tetrahydrofuran. Stir until the solution is completely dissolved into a homogeneous fluorocarbon elastomer solution. Dissolve 12.68g (0.05mol) of iodine in 67g of tetrahydrofuran to prepare an iodine solution. Place a 500mL three-necked flask in an ice-water bath and add 37.8g of tetrahydrofuran and 3.78g (0.1mol) of sodium borohydride. After stirring for 5 minutes, add the fluorocarbon elastomer solution and iodine solution in the order of "gel first, then iodine". The specific operation is as follows: slowly add the prepared fluorocarbon elastomer solution to the reaction flask dropwise for about 1 hour; after stirring for 1 hour, continue to add the iodine solution dropwise for about 1 hour. After continuing to stir and react for 1 hour, heat the system to the reflux temperature of 70°C and reflux for 5 hours. After the reaction is complete, the reaction is terminated, the system is cooled to room temperature, an appropriate amount of dilute hydrochloric acid is added to quench the residual sodium borohydride in the system, and an appropriate amount of sodium sulfite solution is added to remove the residual iodine, and the system is adjusted to neutral. Subsequently, 70-80% of the tetrahydrofuran solvent in the system is removed by rotary evaporation at a temperature of 40°C, a speed of 30 rpm, and a rotary evaporation time of 2 hours. The system is then washed three times with 4-5 volumes of deionized water, and finally dried in a vacuum oven to constant weight to obtain a low molecular weight hydroxyl-terminated fluorocarbon elastomer C as a colorless to light yellow viscous liquid.

[0071] The low molecular weight fluoroelastomer used in Examples 21-23 is a hydroxyl-terminated liquid fluorocarbon elastomer, which is a vinylidene fluoride (VDF)-hexafluoropropylene (HFP)-tetrafluoroethylene (TFE) terpolymer with a copolymer composition of VDF:HFP:TFE in a molar ratio of 43:16:41 and a number average molecular weight of 1500. It was prepared as follows:

[0072] Weigh 50g of carboxyl-terminated liquid fluorocarbon elastomer B and dissolve it in 215g of tetrahydrofuran. Stir until the fluorocarbon elastomer solution is completely dissolved and a homogeneous phase is formed. Dissolve 5.92g of iodine in 67g of tetrahydrofuran to prepare an iodine solution. Place a 500mL three-necked flask in an ice-water bath and add 37.8g of tetrahydrofuran and 5.29g of sodium borohydride. After stirring for 5 minutes, add the fluorocarbon elastomer solution and then the iodine solution in the order of "gel first, then iodine". The specific operation is as follows: slowly add the prepared fluorocarbon elastomer solution dropwise to the reaction flask for about 1 hour; after stirring for 1 hour, continue to add the iodine solution dropwise for about 1 hour. After stirring for another hour, heat the system to reflux temperature of 70°C and reflux for 5 hours. After the reaction is complete, the reaction is terminated, the system is cooled to room temperature, and an appropriate amount of dilute hydrochloric acid is added to quench the residual sodium borohydride in the system. An appropriate amount of sodium sulfite solution is then added to remove the residual iodine, and the system is adjusted to neutral. Subsequently, 70-80% of the tetrahydrofuran solvent in the system is removed by rotary evaporation at a temperature of 40°C, a speed of 30 rpm, and a rotary evaporation time of 2 hours. The system is then washed three times with 4-5 volumes of deionized water, and finally dried in a vacuum oven to constant weight to obtain a low molecular weight hydroxyl-terminated fluorocarbon elastomer D as a colorless to light yellow viscous liquid.

[0073] Example 1

[0074] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0075] To a 250mL three-necked flask, 10g of G-101 and 90g of methyl isobutyl ketone were added and stirred at room temperature to dissolve to form a colorless, transparent solution with a concentration of 10wt%. 0.985g of magnesium oxide and 1.5g of ethanolamine were then added, with the molar ratio of ethanolamine to the vinylidene fluoride structural unit in G-101 being 1:4. The reaction was continued at 110°C for 12 hours, and the reaction was terminated. A small amount of deionized water was added to the reaction solution, and after standing to separate the layers, the supernatant was washed three times. The resulting solution was poured into a rotary evaporator and rotary evaporated at 95°C. When the solvent content of the solution was reduced, it was poured into a 100mL beaker and dried in a vacuum oven to constant weight, resulting in a dark brown, highly functional liquid fluoroelastomer.

[0076] Figure 1 The infrared spectrum (FT-IR) test results of the prepared high-functionality low molecular weight liquid fluoroelastomer are shown in Figure 2. Figure 1It can be seen that the side hydroxyl fluorocarbon oligomer and G-101 are both at 870-890 cm -1 1170~1200cm -1 1390~1400cm -1 The characteristic absorption peaks of fluorinated polymers appeared at 3344 cm, corresponding to the stretching vibration peaks of -CF-, -CF2-, and -CF3 groups. -1 The stretching vibration peak of -OH appears at , indicating that the double bond reacts with amino alcohol to introduce -OH on the side group, proving the synthesis of side hydroxyl fluorocarbon oligomers.

[0077] Example 2

[0078] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0079] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 1, except that the reaction system temperature is 25°C.

[0080] Example 3

[0081] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0082] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 1, except that the reaction system temperature is 60°C.

[0083] Example 4

[0084] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0085] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 1, except that 2.25 g of ethanolamine is added to the reaction, and the molar ratio of ethanolamine to the vinylidene fluoride structural unit in G-101 is 1.5:4.

[0086] Example 5

[0087] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0088] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 1, except that 3 g of ethanolamine is added to the reaction, and the molar ratio of ethanolamine to the vinylidene fluoride structural unit in G-101 is 2:4.

[0089] Example 6

[0090] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0091] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is basically the same as that of Example 1, except that the added alcoholamine is 3-aminopropanol with a mass of 1.87 g, and the molar ratio of 3-aminopropanol to the vinylidene fluoride structural unit in G-101 is 1:4.

[0092] Example 7

[0093] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0094] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 6, except that 2.81 g of 3-aminopropanol is added, and the molar ratio of 3-aminopropanol to the vinylidene fluoride structural unit in G-101 is 1.5:4.

[0095] Example 8

[0096] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0097] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 6, except that 3.75 g of 3-aminopropanol is added, and the molar ratio of 3-aminopropanol to the vinylidene fluoride structural unit in G-101 is 2:4.

[0098] Example 9

[0099] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0100] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is basically the same as that of Example 1, except that the added alcohol amine is 4-amino-1-butanol with a mass of 2.18 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in G-101 is 1:4.

[0101] Example 10

[0102] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0103] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is basically the same as that of Example 9, except that the mass of added 4-amino-1-butanol is 3.28 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in G-101 is 1.5:4.

[0104] Example 11

[0105] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0106] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is substantially the same as that of Example 9, except that 4.36 g of 4-amino-1-butanol is added, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in G-101 is 2:4.

[0107] Example 12

[0108] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0109] To a 250mL three-necked flask, 10g of carboxyl-terminated liquid fluoroelastomer A and 90g of methyl isobutyl ketone were added and stirred at room temperature to dissolve to form a colorless, transparent solution with a concentration of 10wt%. 0.985g of magnesium oxide and 2.13g of 4-amino-1-butanol were then added, with the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in carboxyl-terminated liquid fluoroelastomer A being 1:4. The reaction was continued at 110°C for 12 hours, and the reaction was terminated. A small amount of deionized water was added to the reaction solution, and after standing to separate layers, the supernatant was washed three times. The resulting solution was poured into a rotary evaporator and rotary evaporated at 95°C. When the solvent content of the solution was reduced, it was poured into a 100mL beaker and dried in a vacuum oven to constant weight, resulting in a dark brown, high-functionality, low-molecular-weight liquid fluoroelastomer.

[0110] Example 13

[0111] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0112] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 12, except that the mass of the added 4-amino-1-butanol is 3.2 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer A is 1.5:4.

[0113] Example 14

[0114] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0115] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 12, except that the mass of the added 4-amino-1-butanol is 4.25 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer A is 2:4.

[0116] Example 15

[0117] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0118] To a 250mL three-necked flask, add 10g of carboxyl-terminated liquid fluoroelastomer B and 90g of methyl isobutyl ketone (MIBK). Stir and dissolve at room temperature to form a colorless, transparent solution with a concentration of 10wt%. Then, add 0.985g of magnesium oxide and 1.17g of 4-amino-1-butanol (the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in carboxyl-terminated liquid fluoroelastomer B is 1:4). The reaction is continued at 110°C for 12 hours, and the reaction is terminated. A small amount of deionized water is added to the reaction solution. After standing to separate layers, the supernatant is washed three times. The resulting solution is poured into a rotary evaporator and rotary evaporated at 95°C. When the solvent content is low, the solution is poured into a 100mL beaker and dried in a vacuum oven to constant weight, resulting in a dark brown, high-functionality liquid fluoroelastomer.

[0119] Example 16

[0120] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0121] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 15, except that the mass of the added 4-amino-1-butanol is 1.76 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer B is 1.5:4.

[0122] Example 17

[0123] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0124] The preparation method of the high-functionality, low-molecular-weight liquid fluoroelastomer is basically the same as that of Example 15, except that the mass of the added 4-amino-1-butanol is 2.34 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer B is 2:4.

[0125] Example 18

[0126] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0127] To a 250mL three-necked flask, 10g of hydroxyl-terminated liquid fluoroelastomer C and 90g of methyl isobutyl ketone were added. Stirring and dissolving at room temperature formed a colorless, transparent solution with a concentration of 10wt%. Then, 0.985g of magnesium oxide and 2.13g of 4-amino-1-butanol were added, where the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in carboxyl-terminated liquid fluoroelastomer C was 1:4. The reaction was continued at 110°C for 12 hours, and the reaction was terminated. A small amount of deionized water was added to the reaction solution. After standing and separating the layers, the supernatant was washed three times. The resulting solution was poured into a rotary evaporator and rotary evaporated at 95°C. When the solvent content of the solution was reduced, it was poured into a 100mL beaker and dried in a vacuum oven to constant weight, resulting in a dark brown, high-functionality liquid fluoroelastomer.

[0128] Example 19

[0129] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0130] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 18, except that the mass of the added 4-amino-1-butanol is 3.2 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer C is 1.5:4.

[0131] Example 20

[0132] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0133] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 18, except that the mass of the added 4-amino-1-butanol is 4.25 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer C is 2:4.

[0134] Example 21

[0135] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0136] To a 250mL three-necked flask, 10g of hydroxyl-terminated liquid fluoroelastomer D and 90g of methyl isobutyl ketone were added. Stirring and dissolving at room temperature formed a colorless, transparent solution with a concentration of 10wt%. Then, 0.985g of magnesium oxide and 1.17g of 4-amino-1-butanol were added, where the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in carboxyl-terminated liquid fluoroelastomer D was 1:4. The reaction was continued at 110°C for 12 hours, and the reaction was terminated. A small amount of deionized water was added to the reaction solution. After standing and separating the layers, the supernatant was washed three times. The resulting solution was poured into a rotary evaporator and rotary evaporated at 95°C. When the solvent content of the solution was reduced, it was poured into a 100mL beaker and dried in a vacuum oven to constant weight, resulting in a dark brown, high-functionality liquid fluoroelastomer.

[0137] Example 22

[0138] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0139] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 21, except that the mass of the added 4-amino-1-butanol is 1.76 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer D is 1.5:4.

[0140] Example 23

[0141] This example provides a preparation method for a high-functionality, low-molecular-weight liquid fluoroelastomer.

[0142] The preparation method of the high-functionality liquid fluoroelastomer is basically the same as that of Example 21, except that the mass of the added 4-amino-1-butanol is 2.34 g, and the molar ratio of 4-amino-1-butanol to the vinylidene fluoride structural unit in the carboxyl-terminated liquid fluoroelastomer D is 2:4.

[0143] Comparative Example 1

[0144] G-101 produced by Daikin Corporation of Japan was used as a comparative example.

[0145] Comparative Example 2

[0146] Carboxyl-terminated liquid fluoroelastomer A was used as a comparative example.

[0147] Comparative Example 3

[0148] Carboxyl-terminated liquid fluoroelastomer B was used as a comparative example.

[0149] Comparative Example 4

[0150] The hydroxyl-terminated liquid fluoroelastomer C was used as a comparative example.

[0151] Comparative Example 5

[0152] The hydroxyl-terminated liquid fluoroelastomer D was used as a comparative example.

[0153] Effect Example 1

[0154] Yield:

[0155] Where m1 is the total mass of the reactants before the reaction; m2 is the mass of the products after the reaction.

[0156] Functionality f: f = f1 + f2

[0157] Side group functionality f1: x = m + n + p + r

[0158]

[0159] End group functionality f2:

[0160] (When converting carboxyl-terminated liquid fluoroelastomer to hydroxyl-terminated liquid fluoroelastomer, the functionality does not change)

[0161] Among them, M n is the number average molecular weight of the liquid fluoroelastomer raw material;

[0162] 64 is the molecular weight of the vinylidene fluoride structural unit;

[0163] 100 is the molecular weight of tetrafluoroethylene structural unit;

[0164] 150 is the molecular weight of the hexafluoropropylene structural unit;

[0165] 154 is the molecular weight of the perfluoromethyl vinyl ether structural unit;

[0166] 45 is the molecular weight of -COOH;

[0167] -COOH% is the carboxyl content;

[0168] The specific method for determining -COOH% is as follows: Weigh 0.6g of sample and dissolve it in 30mL of acetone. Prepare and calibrate a KOH-C2H5OH solution as the titrant according to GB / T 601-2016, use bromocresol purple as the indicator, and titrate until the solution changes from yellow to light blue. The carboxyl content is calculated according to the following formula:

[0169] -COOH%=(V×C×45.02) / m

[0170] Where: V-volume of KOH-C2H5OH used for titration, mL;

[0171] Concentration of C-KOH-C2H5OH standard titration solution, mol / L;

[0172] m-mass of the test sample, mg.

[0173] m, n, p, and r are shown in Formula I.

[0174] m / q: H NMR spectrum

[0175] Taking ethanolamine when x=2 as an example, the m / q calculation method is as follows

[0176]

[0177] Among them, ∫3.6~3.65ppm is the integral of -CH2 close to -OH in -NHCH2CH2OH in the side hydroxyl fluorocarbon oligomer, and ∫2.3~3.4ppm is the integral of the -CH2- structure in the main chain of the side hydroxyl fluorocarbon oligomer.

[0178] Table 1

[0179]

[0180]

[0181] It can be seen from the results in Table 1 that after the side groups of the present invention are introduced with hydroxyl groups, the functionality is improved compared with the raw materials, and the yield is above 70%.

[0182] Effect Example 2

[0183] The high-functionality, low-molecular-weight liquid fluoroelastomers of Examples 1-23 and the elastomers of Comparative Examples 1-4 were mixed with a chain extender, 1,4-butanediol, and a curing agent, HDI trimer (wherein the value of n(-NCO) / [n(-COOH)+n(-OH)] is 2, and n is the number of moles), and stirred evenly under an overhead mechanical stirrer. 1% wt of dibutyltin dilaurate was added dropwise, and the mixture was stirred evenly with planetary stirring and degassing for 3 minutes. The mixture was poured into a mold, cured in a hot press at 100°C for 4 hours, and then taken out to obtain a cured product.

[0184] The tensile properties were tested using a universal testing machine from Meters Industrial Systems (China) Co., Ltd. According to the provisions of GB / T528-2009, a type 3 dumbbell specimen standard was selected, the tensile rate was 200 mm / min, and the test environment was room temperature (25±2°C). According to the provisions of GB / T 531.1-2008, the hardness was tested using a Shore A durometer.

[0185] The test results are shown in Table 2.

[0186] Table 2

[0187]

[0188] The results in Table 2 show that after the introduction of hydroxyl groups into the side groups of the present invention, the functionality is improved and the number of cross-linking sites increases, forming a more compact cross-linked network structure after curing. Compared with the raw liquid fluoroelastomer, the tensile strength is improved while the elongation at break does not decrease significantly. The high degree of cross-linking leads to higher hardness.

[0189] Effect Example 3

[0190] The solvent immersion method was used to study the solvent resistance of the cured product, and the quality change rate of the cured product before and after immersion was used to examine whether its solvent resistance was excellent.

[0191] The formula for calculating the mass change rate is:

[0192]

[0193] Wherein, m1 is the mass of the cured product sample before immersion, g;

[0194] m2 is the mass of the cured product sample after immersion, g.

[0195] The mass change rate of the cured product after immersion in strong acid, strong base and polar solvent for 72 hours is shown in Table 3.

[0196] Table 3

[0197]

[0198]

[0199] The results in Table 3 show that the mass change rate does not exceed 15% when the immersion time is as long as 72 hours, and the mass change rate does not exceed 5% in alkaline solvents and polar solvents, indicating that a stable three-dimensional network cross-linked structure is formed after curing, which can resist the attack of external atoms and has excellent solvent resistance.

[0200] Effect Example 4

[0201] The cured products of Examples 5, 8, and 11 were subjected to thermogravimetric tests. 5％ =370-385℃, T 10％ =390-412℃, the residual carbon rate is 30-36.4% at 800℃.

[0202] G101 of Comparative Example 1: T 5％ =318℃, T 10％ =385℃, the residual carbon rate is 0 at 800℃.

[0203] Therefore, the cured products of the embodiments of the present invention have improved thermal stability.

[0204] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A liquid fluoroelastomer, characterized in that The structural formula of the liquid fluoroelastomer is shown in Formula I: Wherein, R1 is -NH(CH2) x OH, R2 is a non-reactive terminal group, carboxyl group or hydroxyl group; x is 1-6; The ratio between m and q is 4-25:1; n, p, and r are not all 0 at the same time.

2. The liquid fluoroelastomer according to claim 1, wherein x is 2-4; and / or, the ratio between m and q is 4.36-23.4:

1.

3. The liquid fluoroelastomer according to claim 1, wherein x is 3; and / or, the ratio between m and q is 8.84-17.49:

1.

4. The liquid fluoroelastomer according to claim 1, wherein The ratio between m and q is 14.65-17.49:

1.

5. The liquid fluoroelastomer according to claim 1 or 2, wherein The functionality of the liquid fluoroelastomer is above 2.

5.

6. The liquid fluoroelastomer according to claim 5, wherein The functionality of the liquid fluoroelastomer is above 4.

7. The liquid fluoroelastomer according to any one of claims 1 to 3, wherein The liquid fluoroelastomer is selected from at least one of a side hydroxyl vinylidene fluoride-hexafluoropropylene copolymer, a side hydroxyl-terminated hydroxyl vinylidene fluoride-hexafluoropropylene copolymer, a side hydroxyl-terminated carboxyl vinylidene fluoride-hexafluoropropylene copolymer, a side hydroxyl-terminated hydroxyl vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer and a side hydroxyl-terminated carboxyl vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer.

8. A method for preparing a liquid fluoroelastomer according to any one of claims 1 to 7, characterized in that: The method comprises: mixing a fluorine-containing elastomer solution, magnesium oxide and an alcohol amine to react to obtain the liquid fluorine elastomer; Wherein, the fluorine-containing elastomer has no pendant hydroxyl groups.

9. The method according to claim 8, wherein The fluorine-containing elastomer is a binary, ternary or multi-component copolymer of vinylidene fluoride; and / or, the solvent in the fluorine-containing elastomer solution is an organic solvent; And / or, the alcoholamine is selected from at least one of ethanolamine, 3-aminopropanol and 4-amino-1-butanol.

10. The method according to claim 8, wherein The fluorine-containing elastomer is G-101 of Daikin Corporation of Japan, carboxyl-terminated liquid fluorine elastomer or hydroxyl-terminated liquid fluorine elastomer; and / or, the solvent in the fluorine-containing elastomer solution is selected from at least one of methyl isobutyl ketone, tetrahydrofuran and acetone; And / or, the alcoholamine is 3-aminopropanol.

11. The method according to claim 8 or 9, wherein: The molar ratio of the alcohol amine to the vinylidene fluoride structural unit in the fluorine-containing elastomer is 0.5-4:

4.

12. The method according to claim 11, wherein The molar ratio of the alcohol amine to the vinylidene fluoride structural unit in the fluorine-containing elastomer is 1-3:

4.

13. The method according to claim 11, wherein The molar ratio of the alcohol amine to the vinylidene fluoride structural unit in the fluorine-containing elastomer is 1.5-2:

4.

14. The method according to claim 11, wherein The molar ratio of the alcohol amine to the vinylidene fluoride structural unit in the fluorine-containing elastomer is 2:

4.

15. The method according to claim 8, wherein The reaction time is 3-15h; and / or, the reaction temperature is 20-120° C.; And / or, after the reaction is completed, the system is cooled to room temperature, the inorganic salt and residual alcoholamine are extracted to remove, the solvent is removed by rotary evaporation, and the final product is obtained after drying.

16. The method according to claim 8, wherein The reaction time is 8-12h; And / or, the reaction temperature is 25-116°C.

17. The method according to claim 8, wherein The reaction temperature is 25°C, 60°C or 110°C.

18. A liquid fluoroelastomer prepared according to the method of any one of claims 8 to 17.

19. Use of the liquid fluoroelastomer according to any one of claims 1 to 7 and 18 in the preparation of special adhesives, sealants and coatings.

Images