Fluorine-containing polyurethane elastomers for harsh environments and methods for making the same

Abstract

The application belongs to the technical field of polyurethane elastomers, and particularly relates to a fluorine-containing polyurethane elastomer for harsh environments and a preparation method thereof. The elastomer is prepared by adding a chain extender to a fluorine-containing polyurethane prepolymer prepared from a fluorine-containing polyether polyol or a mixture of the fluorine-containing polyether polyol and a non-fluorine-containing polyether polyol and diisocyanate, and then vulcanizing after curing. The preparation method of the fluorine-containing polyether polyol comprises the following steps: polymerizing fluorine-containing phenolic compounds and INOVOL C304 as a composite initiator with propylene oxide under the action of a DMC catalyst to obtain the fluorine-containing polyether polyol; and the fluorine-containing phenolic compounds are one of 3,4,5-trifluorophenol, pentafluorophenol or heptafluoro-2-naphthol. The fluorine-containing polyurethane elastomer has excellent high-temperature resistance, hydrolysis resistance and chemical resistance; and the preparation method is simple and easy to implement, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane elastomer technology, specifically relating to a fluorinated polyurethane elastomer for harsh environments and its preparation method. Background Technology

[0002] Polyurethane elastomers, due to their high elasticity, excellent mechanical strength, and good processing adaptability, are widely used in key fields such as mechanical seals, automotive parts, electronic packaging, and petrochemicals. However, in harsh service environments such as high temperature, humidity, strong corrosion, or long-term outdoor exposure, the performance of traditional polyurethane elastomers is prone to significant degradation: at high temperatures above 120°C, their main chains are prone to thermal oxidation and breakage or cross-linking structure decomposition, leading to loss of elasticity and sudden changes in hardness; in humid or water-immersed environments, ester bonds are easily attacked and broken by water molecules, causing material weight gain, swelling, or even cracking; when exposed to ultraviolet light, ozone, or chemical media for a long time, the molecular chains are prone to oxidative degradation, resulting in a significant decrease in core mechanical properties such as tensile strength and elongation at break.

[0003] Existing modification technologies mostly optimize the weather resistance and heat resistance of polyurethane elastomers by introducing aromatic isocyanates, adding antioxidants, ultraviolet absorbers, or using crosslinking modification. However, these methods cannot fundamentally solve the core problems of easy hydrolysis of ester bonds and insufficient thermal stability of the main chain, and the improvement effect is limited.

[0004] Fluorinated polyurethanes possess significant performance advantages due to the introduction of fluorine. Fluorine atoms have high electronegativity and small atomic radii; their introduction into the polyurethane structure enhances molecular chain stability, thereby improving the overall performance of polyurethane elastomers, such as heat resistance and chemical resistance. Chinese patent CN116262809A discloses a fluorinated polyurethane elastomer, its preparation method, and its applications. It synthesizes fluorinated polyester polyols using fluorinated diacids and diols as raw materials. By controlling the proportion of fluorine in the elastomer, the product's heat resistance and water resistance are optimized. However, it has two core drawbacks: firstly, the preparation process of the fluorinated polyester polyol has high energy consumption; secondly, the product's mechanical properties are insufficient. Under a hardness of 91 (Shore A), the tensile strength is only 28 MPa, which is insufficient to meet the requirements of high-end applications.

[0005] Chinese patent CN117645705A discloses a fluorinated polyurethane elastomer and its preparation method. This technology uses bisphenol AF as a raw material to synthesize bisphenol AF polyether polyol, and then reacts it with isophorone diisocyanate to prepare the fluorinated polyurethane elastomer. However, this technology has obvious limitations: first, it relies on only bisphenol AF-derived polyether polyols; second, the mechanical properties of the product are not good; and third, the preparation process requires the use of multiple polyether polyols, which makes it difficult to control the polyol ratio and involves complicated reaction steps, making it difficult to meet the industry's demand for large-scale production of high-performance polyurethane elastomers.

[0006] Therefore, developing a polyurethane elastomer with excellent high-temperature resistance, hydrolysis resistance, aging resistance, and chemical resistance to broaden its application range in harsh environments has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a fluorinated polyurethane elastomer for harsh environments, exhibiting excellent high-temperature resistance, hydrolysis resistance, and chemical resistance. The invention also provides a simple and easy-to-implement preparation method suitable for large-scale production.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] The fluorinated polyurethane elastomer for harsh environments is prepared by adding a chain extender to the fluorinated polyurethane prepolymer and curing it by vulcanization.

[0010] The diisocyanate is one of toluene-2,4-diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), or terephthalic diisocyanate (PPDI).

[0011] The isocyanate content of the fluorinated polyurethane prepolymer is 4.0-6.8% by mass.

[0012] The chain extender is one of 1,4-butanediol or 4,4'-methylenebis(2-chloroaniline) (MOCA).

[0013] The mass ratio of the chain extender to the fluorinated polyurethane prepolymer is (4.3-14.3):100.

[0014] The method for preparing the fluorinated polyether polyol includes the following steps: using a fluorinated phenolic compound and INOVOLC304 as a composite initiator, polymerizing with propylene oxide under the action of a DMC catalyst to obtain the fluorinated polyether polyol; wherein the fluorinated phenolic compound is one of 3,4,5-trifluorophenol, pentafluorophenol, or heptafluoro-2-naphthol.

[0015] Preferably, the preparation method of the fluorinated polyether polyol includes the following steps:

[0016] Using fluorinated phenolic compounds and INOVOL C304 as composite initiators, the composite initiators and DMC catalysts were added to a high-pressure reactor, purged with nitrogen, heated to 100°C, evacuated to -0.09 MPa, and dehydrated for 2 hours. Then, 7-14% of the total mass of the composite initiator was added to propylene oxide to initiate the polymerization reaction. After successful initiation, propylene oxide was continuously added to the high-pressure reactor by a high-pressure pump to carry out polymerization, thus obtaining fluorinated polyether polyol.

[0017] The fluorinated polyether polyol has a functionality of 2 and a number-average molecular weight of 998-2000 g / mol.

[0018] The amount of DMC catalyst added is 800-1500 ppm of the total mass of the fluorinated polyether polyol.

[0019] The polymerization is carried out at a temperature of 120-145℃.

[0020] The method for preparing fluorinated polyurethane elastomers for harsh environments according to the present invention includes the following steps:

[0021] (1) Fluorinated polyether polyol or a mixture of fluorinated polyether polyol and non-fluorinated polyether polyol is added to a reaction vessel and kept at a constant temperature to prepare a fluorinated polyurethane prepolymer.

[0022] (2) Add a chain extender to the fluorinated polyurethane prepolymer obtained in step (1), and after curing, vulcanize to obtain a fluorinated polyurethane elastomer for harsh environments.

[0023] In step (1), the temperature of the heat preservation reaction is 75-85℃ and the reaction time is 3-5h.

[0024] In step (2), the chain extender is added at a temperature of 60-85℃.

[0025] Preferably, the method for preparing the fluorinated polyurethane elastomer for harsh environments includes the following steps:

[0026] (1) Add fluorinated polyether polyol or a mixture of fluorinated polyether polyol and non-fluorinated polyether polyol into a reaction vessel, turn on the stirrer, add diisocyanate, then seal the vessel with nitrogen, keep the reaction at 75-85℃ for 3-5h, after the reaction is completed, keep the vacuum degree ≤-0.095MPa to remove bubbles, and prepare a fluorinated polyurethane prepolymer with an isocyanate mass content of 4.0-6.8%;

[0027] (2) At 60-85℃, add chain extender to the fluorinated polyurethane prepolymer obtained in step (1), mix evenly and pour into a preheated mold, continue the reaction, open the mold after the reaction is completed, and vulcanize at 100℃ for 16h to obtain fluorinated polyurethane elastomer.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) In the fluorinated phenolic compounds used in this invention, the fluorine atoms are directly bonded to the aromatic ring skeleton. As part of the structural skeleton, they can provide a more uniform and denser protective layer. The high electronegativity of fluorine atoms can make the electron cloud density on the aromatic ring more uniform and stable, which avoids excessive chemical activity caused by excessive concentration of local electrons and reduces the damage of external factors to the electron cloud, thereby enhancing the chemical stability of the entire molecule. As a typical rigid ring structure, the aromatic ring structure can provide a stable "support skeleton" for the molecular chain and improve the rigidity of the polyether polyol. The fluorine atoms and the aromatic ring work together to improve the tolerance of the polyether polyol from multiple dimensions.

[0030] (2) In this invention, fluorinated phenolic compounds and small molecule polyols (INOVOL C304) are used as composite initiators. By utilizing the synergistic activation effect of the two, the bottleneck of low reactivity of traditional fluorinated monomers is effectively overcome. The polymerization of epoxide alkane is directly induced in the DMC catalytic system to prepare fluorinated polyether polyols.

[0031] (3) In this invention, fluorinated polyether polyols are reacted with diisocyanates to generate fluorinated prepolymers. The structural advantages of fluorinated polyether polyols can further improve the comprehensive performance of polyurethane elastomers, achieving a balance between "stability" and "mechanical properties", and ultimately obtaining polyurethane elastomers with excellent high temperature resistance, hydrolysis resistance, aging resistance and chemical resistance, thus broadening their application range.

[0032] (4) In this invention, the preparation of fluorinated polyether polyols adopts DMC catalyst catalysis process. The resulting polyol products have a narrow molecular weight distribution and uniform and stable mechanical properties. No purification treatment is required, and the process meets the requirements of green chemistry. Detailed Implementation

[0033] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0034] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available materials, and the process methods used in the examples and comparative examples are all conventional methods in the art.

[0035] The following is a description of some of the raw materials used in the examples and comparative examples:

[0036] INOVOL C304: Number average molecular weight is 375, Shandong Yinuowei New Materials Co., Ltd.

[0037] 3,4,5-Trifluorophenol: Number average molecular weight 148, Hubei Xinkang Pharmaceutical Chemical Co., Ltd.;

[0038] Pentafluorophenol: Number average molecular weight 184, Hubei Yunmei Technology Co., Ltd.;

[0039] Heptafluoro-2-naphthol, with a number-average molecular weight of 270, is produced by Sichuan Tiancai Fine Chemical Co., Ltd.

[0040] PTMG1000, with a number average molecular weight of 1000, BASF (China) Co., Ltd.

[0041] Perfluoropolyether glycol FD-161: Number average molecular weight is 2000, manufactured by Yuyao Huihong Plastics Factory;

[0042] Bisphenol AF: Number average molecular weight 336, Zhongshan Dixing Chemical Co., Ltd.;

[0043] PPDI: Zhejiang Lishui Youbang New Materials Co., Ltd.;

[0044] TDI: Shandong Yinuowei Polyurethane Co., Ltd.;

[0045] MDI: Wanhua Chemical Group Co., Ltd.

[0046] DMC catalyst: Jiangsu Bade Polyurethane Co., Ltd.

[0047] Example 1

[0048] The preparation method of the fluorinated polyether polyol A includes the following steps:

[0049] 74g of 3,4,5-trifluorophenol, 187.5g of INOVOL C304, and 0.8g of DMC catalyst were added to a high-pressure reactor. After purging with nitrogen three times, the temperature was raised to 100℃, and the pressure was evacuated to -0.09MPa for 2 hours to remove water. Then, the temperature was raised to 125℃, and 19g of propylene oxide was added dropwise to initiate the polymerization reaction. After successful initiation, the pressure was lowered to -0.08MPa, and 719.5g of propylene oxide was slowly added to the high-pressure reactor by a high-pressure pump. The pressure was controlled to be less than 0.30MPa during the polymerization reaction. After the addition was completed, the internal pressure reaction was carried out for 2 hours, followed by monomer removal for 0.5 hours to obtain fluorinated polyether polyol A with a functionality of 2, a hydroxyl value of 112.4mgKOH / g, and a number-average molecular weight of 998g / mol.

[0050] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0051] (1) 79.3g of fluorinated polyether polyol A (moisture content ≤0.05%) was added to the reactor. When the temperature dropped below 60℃, the stirring was turned on and 20.7g of PPDI was added at once. Then the reactor was sealed with nitrogen to maintain a slight positive pressure inside. The reactor was kept at 55℃ for 30min and then the temperature was raised to 80℃ in the first 60min. The temperature was kept for 3.5h and the vacuum degree was kept ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 4.2% was obtained.

[0052] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 60℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 4.3g of 1,4-butanediol to it, mix evenly and pour into a mold at 110℃. Open the mold after 20min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0053] Example 2

[0054] The preparation method of the fluorinated polyether polyol B includes the following steps:

[0055] 92g of pentafluorophenol, 187.5g of INOVOL C304, and 1.56g of DMC catalyst were added to a high-pressure reactor. After purging with nitrogen three times, the temperature was raised to 100℃, and the pressure was evacuated to -0.09MPa for 2 hours to remove water. Then, the temperature was raised to 120℃, and 28g of propylene oxide was added dropwise to initiate the polymerization reaction. After successful initiation, the pressure was lowered to -0.08MPa, and 992.5g of propylene oxide was slowly added to the high-pressure reactor by a high-pressure pump. The pressure was controlled to be less than 0.30MPa during the polymerization reaction. After the addition was completed, the internal pressure reaction was carried out for 2 hours, followed by monomer removal for 0.5 hours to obtain fluorinated polyether polyol B with a functionality of 2, a hydroxyl value of 86.2mgKOH / g, and a number-average molecular weight of 1302g / mol.

[0056] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0057] (1) 66.9g of fluorinated polyether polyol B (moisture content ≤0.05%) and 33.1g of MDI were added to the reactor, the stirring was turned on, the reactor was sealed with nitrogen, and a slight positive pressure was maintained inside the reactor. Then the temperature was raised to 75℃ within the first 60min, and the temperature was maintained for 3h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 6.8% was obtained.

[0058] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 60℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 6.9g of 1,4-butanediol to it, mix evenly and pour into a mold at 110℃. Open the mold after 40min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0059] Example 3

[0060] The preparation method of the fluorinated polyether polyol C includes the following steps:

[0061] 135g of heptafluoro-2-naphthol, 187.5g of INOVOL C304, and 3g of DMC catalyst were added to a high-pressure reactor. After purging with nitrogen three times, the temperature was raised to 100℃, and the pressure was evacuated to -0.09MPa for 2 hours to remove water. Then, the temperature was raised to 145℃, and 45g of propylene oxide was added dropwise to initiate the polymerization reaction. After successful initiation, the pressure was lowered to -0.08MPa, and 1632.5g of propylene oxide was slowly added to the high-pressure reactor by a high-pressure pump. The pressure was controlled to be less than 0.30MPa during the polymerization reaction. After the addition was completed, the internal pressure reaction was carried out for 2 hours, followed by monomer removal for 0.5 hours to obtain fluorinated polyether polyol C with a functionality of 2, a hydroxyl value of 56.1mgKOH / g, and a number-average molecular weight of 2000g / mol.

[0062] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0063] (1) 82.5g of fluorinated polyether polyol C (moisture content ≤0.05%) and 17.5g of TDI were put into the reactor, the stirring was turned on, the reactor was sealed with nitrogen, and a slight positive pressure was maintained inside the reactor. Then the temperature was raised to 85℃ in the first 60min, and the temperature was maintained for 4.5h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 5.0% was obtained.

[0064] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 80℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 14.3g of MOCA to it, mix evenly and pour into a mold at 110℃. Open the mold after 30min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0065] Example 4

[0066] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0067] (1) 40.1g of fluorinated polyether polyol C (moisture content ≤0.05%), 40.1g of PTMG1000 (moisture content ≤0.05%) and 19.8g of TDI were put into the reactor, the stirring was turned on, the reactor was sealed with nitrogen, and a slight positive pressure was maintained inside the reactor. Then the temperature was raised to 85℃ in the first 60min, and the temperature was maintained for 5h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 4.5% was obtained.

[0068] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 85℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 12.9g of MOCA to it, mix evenly and pour into a mold at 110℃. Open the mold after 40min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0069] Example 5

[0070] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0071] (1) 62.7g of fluorinated polyether polyol A (moisture content ≤0.05%), 15.7g of fluorinated polyether polyol C (moisture content ≤0.05%) and 21.6g of TDI were put into the reactor, the stirring was turned on, the reactor was sealed with nitrogen, and a slight positive pressure was maintained inside the reactor. Then the temperature was raised to 85℃ in the first 60min, and the temperature was maintained for 5h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 4.5% was obtained.

[0072] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 80℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 12.9g of MOCA to it, mix evenly and pour into a mold at 110℃. Open the mold after 40min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0073] Comparative Example 1

[0074] The method for preparing the polyether polyol includes the following steps:

[0075] 228g of bisphenol A and 0.2g of DMC catalyst were added to a high-pressure reactor. After purging with nitrogen three times, the temperature was raised to 100℃, and the pressure was evacuated to -0.09MPa for 2 hours to remove water. Then, the temperature was raised to 145℃, and 33g of propylene oxide was added dropwise to initiate the polymerization reaction. After successful initiation, the pressure was lowered to -0.08MPa, and 1739g of propylene oxide was slowly added to the high-pressure reactor by a high-pressure pump. The pressure was controlled to be less than 0.30MPa during the polymerization reaction. After the addition was completed, the internal pressure reaction was carried out for 2 hours, followed by monomer removal for 0.5 hours to obtain a polyether polyol with a functionality of 2, a hydroxyl value of 56.1mgKOH / g, and a number-average molecular weight of 2000g / mol.

[0076] The preparation method of the polyurethane elastomer described in this comparative example is the same as that in Example 3, except that the fluorinated polyether polyol C in step (1) is replaced with the polyether polyol prepared in this comparative example above, and the other steps are the same.

[0077] Comparative Example 2

[0078] The method for preparing the polyurethane elastomer includes the following steps:

[0079] (1) 63.2g of PTMG1000 (moisture content ≤0.05%) and 36.8g of pure MDI were added to the reactor, the stirring was turned on, the reactor was sealed with nitrogen, and a slight positive pressure was maintained inside the reactor. Then the temperature was raised to 75℃ within the first 60min, and the temperature was maintained for 3h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a polyurethane prepolymer with an isocyanate mass content of 7.0% was obtained.

[0080] (2) When using, the temperature of the polyurethane prepolymer is controlled at 60℃. Take 100g of the polyurethane prepolymer obtained in step (1), add 7.1g of 1,4-butanediol to it, mix evenly and pour into a mold at 110℃. Open the mold after 40min and place it in a 100℃ oven for 16h for curing. After curing, the polyurethane elastomer is obtained.

[0081] Comparative Example 3

[0082] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0083] (1) 39.2g of perfluorinated polyether glycol FD-161 (moisture content ≤0.05%), 39.2g of PTMG1000 (moisture content ≤0.05%) and 21.7g of TDI were put into the reactor, the stirring was turned on, the reactor was sealed with nitrogen and a slight positive pressure was maintained inside the reactor, and then the temperature was raised to 85℃ in the first 60min, and the temperature was maintained for 4h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 5.5% was obtained.

[0084] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 85℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 15.7g of MOCA to it, mix evenly and pour into a mold at 110℃. Open the mold after 40min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0085] Comparative Example 4

[0086] The method for preparing the polyether polyol D includes the following steps:

[0087] 336g of bisphenol AF and 1g of DMC catalyst were added to a high-pressure reactor. After nitrogen purging three times, the temperature was raised to 100℃, and the pressure was evacuated to -0.09MPa for 2 hours to remove water. Then, the temperature was raised to 145℃, and 33g of propylene oxide was added dropwise to initiate the polymerization reaction. After successful initiation, the pressure was lowered to -0.08MPa, and 1631g of propylene oxide was slowly added to the high-pressure reactor by a high-pressure pump. The pressure was controlled to be less than 0.30MPa during the polymerization reaction. After the addition was completed, the internal pressure reaction was carried out for 2 hours, followed by monomer removal for 0.5 hours to obtain polyether polyol D with a functionality of 2, a hydroxyl value of 56.1mgKOH / g, and a number-average molecular weight of 2000g / mol.

[0088] The method for preparing the fluorinated polyurethane elastomer includes the following steps:

[0089] (1) 82.5g of polyether polyol D (moisture content ≤0.05%) and 17.5g of TDI were put into the reactor, the stirring was turned on, the reactor was sealed with nitrogen, and a slight positive pressure was maintained inside the reactor. Then the temperature was raised to 85℃ in the first 60min, and the temperature was maintained for 4.5h. The vacuum degree was maintained at ≤-0.095MPa to remove bubbles, and a fluorinated polyurethane prepolymer with an isocyanate mass content of 5.0% was obtained.

[0090] (2) When using, the temperature of the fluorinated polyurethane prepolymer is controlled at 80℃. Take 100g of the fluorinated polyurethane prepolymer obtained in step (1), add 14.3g of MOCA to it, mix evenly and pour into a mold at 110℃. Open the mold after 30min and place it in a 100℃ oven for 16h for curing. After curing, the fluorinated polyurethane elastomer is obtained.

[0091] The polyurethane elastomers prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to performance tests, and the test standards and methods are as follows:

[0092] The mechanical properties of the samples were determined using a UN-7001-LS servo universal tensile testing machine from China High-Speed ​​Railway Testing Instruments Co., Ltd., in accordance with the GB / T 528-2009 standard.

[0093] Shore A hardness was determined according to GB / T 531.1-2008 standard.

[0094] The hydrolysis resistance was tested by constant temperature and humidity hydrolysis resistance method according to QB / T 4671-2014 standard. The test conditions were: test temperature 70℃, relative humidity 95%, continuous hydrolysis treatment for 168h, after which the sample was taken out and placed at room temperature for 2h before mechanical property test, and the hydrolysis performance retention rate before and after treatment was calculated.

[0095] The high-temperature aging test was conducted according to the test method in GB / T 3512-2014. The test conditions were as follows: test temperature 120℃, continuous heat treatment for 168h, after which the sample was taken out and placed at room temperature for 2h before mechanical property testing, and the mechanical property retention rate before and after aging treatment was calculated.

[0096] Chemical resistance testing was conducted according to the test method in GB / T 1690-2010. The samples were treated with alkali resistance and the test conditions were as follows: test temperature 80℃, continuous immersion in NaOH solution with pH=12 for 168h, removal and 2h at room temperature before mechanical property testing, and calculation of the retention rate of mechanical properties before and after chemical treatment.

[0097] The performance test results of Examples 1-5 and Comparative Examples 1-4 are shown in Table 1.

[0098] Table 1 Comparison of performance data of Examples 1-5 and Comparative Examples 1-4

[0099]

[0100] As can be seen from the data in Table 1, the polyurethane elastomers prepared in Examples 1-5 exhibit excellent mechanical properties. Comparative analysis with Comparative Examples 1-3 shows that the fluorinated polyether polyols synthesized in this invention significantly improve the retention rate of hydrolysis resistance, high-temperature aging resistance, and chemical resistance compared to the comparative examples. This is mainly because the initiators used in the fluorinated polyether polyols of this invention are all fluorinated phenolic compounds. Compared to the perfluorinated polyether diol used in Comparative Example 3, the aromatic rings of fluorinated phenolic compounds can significantly improve the rigidity of the elastomer, exhibiting the heat-resistant properties of aromatic rings at the same hardness. The synergistic effect between the aromatic ring and fluorine atoms makes the structural stability and mechanical properties of the elastomer significantly better than those synthesized from chain-like fluorinated polyethers. The introduction of fluorine atoms ensures the stability of the elastomer molecular chain. Compared with the bisphenol A type polyurethane elastomer used in Comparative Example 1, the introduction of fluorine atoms can significantly improve the elastomer's high-temperature aging resistance and chemical resistance. The high electronegativity of fluorine atoms further enhances the stability of the electron cloud density of the benzene ring. The synergistic effect of the two not only provides excellent mechanical properties but also effectively improves the stability of the polymer structure, greatly improving the product's resistance to hydrolysis, high-temperature aging, and chemical resistance.

[0101] A comparison of the experimental data from Example 3 and Comparative Example 4 shows that both polyurethane elastomers were prepared using fluorinated polyether polyols and had consistent initial properties. However, the product using bisphenol AF as an initiator exhibited lower retention rates in hydrolysis, high-temperature aging, and alkali resistance. The core reason for this difference lies in the fact that the fluorine atoms in heptafluoro-2-naphthol are directly bonded to the aromatic ring skeleton, forming a high-density fluorinated surface that prevents the intrusion of OH- ionic corrosive media. At the same time, the high-bond-energy CF skeleton on the benzene ring inherently improves heat resistance, fully demonstrating the efficient synergistic effect between the fluorine atoms and the benzene ring. In contrast, the fluorine atoms in the bisphenol AF structure are not directly connected to the benzene ring but are bridged to the two benzene rings in the form of trifluoromethyl side chains. Although this can stabilize the adjacent C-C bonds and the aromatic ring, the benzene ring itself still faces the risk of oxidation at high temperatures, and the urethane bonds may still hydrolyze in alkaline environments, thus failing to form a true fluorine-aromatic ring synergistic effect.

Claims

1. A fluorinated polyurethane elastomer for use in harsh environments, characterized in that: Fluorinated polyurethane prepolymer is prepared by mixing fluorinated polyether polyol or a mixture of fluorinated polyether polyol and non-fluorinated polyether polyol with diisocyanate. A chain extender is added to the fluorinated polyurethane prepolymer, and the mixture is cured and then vulcanized to obtain the final product. The preparation method of the fluorinated polyether polyol includes the following steps: using a fluorinated phenolic compound and INOVOL C304 as a composite initiator, polymerizing with propylene oxide under the action of DMC catalyst to obtain the fluorinated polyether polyol; wherein the fluorinated phenolic compound is one of 3,4,5-trifluorophenol, pentafluorophenol or heptafluoro-2-naphthol; The diisocyanate mentioned is one of toluene-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, or terephthalic diisocyanate; The isocyanate content of the fluorinated polyurethane prepolymer is 4.0-6.8% by mass.

2. The fluorinated polyurethane elastomer for harsh environments according to claim 1, characterized in that: The chain extender is one of 1,4-butanediol or 4,4'-methylenebis(2-chloroaniline).

3. The fluorinated polyurethane elastomer for harsh environments according to claim 1 or 2, characterized in that: The mass ratio of chain extender to fluorinated polyurethane prepolymer is (4.3-14.3):

100.

4. The fluorinated polyurethane elastomer for harsh environments according to claim 1, characterized in that: The functionality of fluorinated polyether polyols is 2, and the number-average molecular weight is 998-2000 g / mol.

5. The fluorinated polyurethane elastomer for harsh environments according to claim 1, characterized in that: The amount of DMC catalyst added is 800-1500 ppm of the total mass of the fluorinated polyether polyol.

6. The fluorinated polyurethane elastomer for harsh environments according to claim 1, characterized in that: The polymerization is carried out at a temperature of 120-145℃.

7. A method for preparing a fluorinated polyurethane elastomer for harsh environments as described in any one of claims 1-6, characterized in that: Includes the following steps: (1) Fluorinated polyether polyol or a mixture of fluorinated polyether polyol and non-fluorinated polyether polyol is added to a reaction vessel and kept at a constant temperature to prepare a fluorinated polyurethane prepolymer. (2) Add a chain extender to the fluorinated polyurethane prepolymer obtained in step (1), and after curing, vulcanize to obtain a fluorinated polyurethane elastomer for harsh environments.

8. The method for preparing a fluorinated polyurethane elastomer for harsh environments according to claim 7, characterized in that: In step (1), the temperature of the heat preservation reaction is 75-85℃ and the reaction time is 3-5h.

9. The method for preparing a fluorinated polyurethane elastomer for harsh environments according to claim 7, characterized in that: In step (2), the chain extender is added at a temperature of 60-85℃.

Images