Polyurethane sealing element and preparation method thereof

Abstract

The invention particularly relates to a polyurethane sealing element and a preparation method thereof. The polyurethane sealing element is prepared from the following raw materials in parts by weight: 40 to 70 parts of polyurethane prepolymer, 5 to 20 parts of chain extender, 10 to 30 parts of filler, 4 to 8 parts of aromatic polyamide fiber, 4 to 8 parts of maleic anhydride grafted POE (Polyolefin Elastomer), 3 to 6 parts of silane coupling agent, 2 to 5 parts of nitrile rubber and 1 to 5 parts of additive. The aromatic polyamide fiber, the maleic anhydride grafted POE, the silane coupling agent, the filler, the nitrile rubber and other raw materials are added into a polyurethane prepolymer system, the polyurethane prepolymer is subjected to chain extension by adopting the chain extender, and the raw materials are mutually matched and have a synergistic effect; the prepared polyurethane sealing element has good wear resistance, oil resistance, mechanical property and low compression set. The preparation method of the polyurethane sealing element is high in production efficiency, convenient to operate and control, stable in process and beneficial to industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of seals, and particularly relates to a polyurethane seal and a preparation method thereof. Background Art

[0002] At present, in the fields of automobiles, aviation, petrochemical industry, chemical fiber textile, machinery, metallurgy and mining, etc., seals are often required for sealing. In the prior art, seals made of polyurethane materials have been widely used. Polyurethane elastomer materials are usually prepared by polymerization reaction of raw materials such as polyols, isocyanates, and additives, and have advantages such as better mechanical strength, elasticity, and oil resistance. However, with the continuous development of technology and the continuous improvement of operating conditions, the working speed, system temperature, and working pressure of equipment using seals, such as hydraulic cylinders, also increase accordingly, which puts higher requirements on the comprehensive performance of seals. However, existing polyurethane seals still often have problems such as poor wear resistance and mechanical properties, and poor compression set performance, and are difficult to be applied to some high - requirement scenarios in the fields of automobiles, aviation, petrochemical industry, etc. Therefore, it is of great practical significance to provide a polyurethane seal with good wear resistance, oil resistance, and mechanical properties, extend the service life of the seal, and provide the reliability of equipment use. Summary of the Invention

[0003] The purpose of the present invention is to provide a polyurethane seal and a preparation method thereof to solve the above - mentioned deficiencies of the prior art. The polyurethane seal has good wear resistance, oil resistance, mechanical properties, and low compression set, can effectively reduce friction loss and wear in sealing occasions, has a wide range of applications, and good durability; the preparation method of the polyurethane seal has high production efficiency, convenient operation control, stable process, and is conducive to industrial production.

[0004] The purpose of the present invention is achieved by the following technical solutions: A polyurethane seal, comprising the following raw materials in parts by weight: 40 - 70 parts of polyurethane prepolymer, 5 - 20 parts of chain extender, 10 - 30 parts of filler, 4 - 8 parts of aromatic polyamide fiber, 4 - 8 parts of maleic anhydride - grafted POE, 3 - 6 parts of silane coupling agent, 2 - 5 parts of nitrile rubber, and 1 - 5 parts of additive; The preparation method of the polyurethane prepolymer comprises the following steps: React polyether polyol, polyester polyol with isocyanate, and the molar ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyether polyol and polyester polyol is 2.1 - 2.3 to obtain a polyurethane prepolymer.

[0005] Further, the isocyanate includes at least one of toluene diisocyanate and diphenylmethane diisocyanate. Preferably, the isocyanate is composed of toluene diisocyanate and diphenylmethane diisocyanate in a weight ratio of 7 - 8:2 - 3.

[0006] Further, the polyether polyol is at least one of polytetrahydrofuran ether diol and polypropylene glycol, and the polyester polyol is at least one of polybutylene adipate diol and polycarbonate diol.

[0007] Further, the weight ratio of the polytetrahydrofuran ether diol to the polybutylene adipate diol is 3 - 4:1 - 2:1 - 2.

[0008] Further, the molecular weight of the polytetrahydrofuran ether diol is 1000 - 2000, the molecular weight of the polypropylene glycol is 800 - 2500, and the molecular weight of the polybutylene adipate diol is 1000 - 1500.

[0009] Further, the chain extender includes at least one of 1,4 - butanediol and 3,3'-dichloro - 4,4'-diaminodiphenylmethane (MOCA). Preferably, the chain extender is composed of 1,4 - butanediol and 3,3'-dichloro - 4,4'-diaminodiphenylmethane in a weight ratio of 4 - 6:1 - 2.

[0010] Further, the filler is at least one of nano - calcium carbonate, carbon black, and nano - silica. Further, each part of the filler includes the following raw materials in parts by weight: 8 - 12 parts of nano - calcium carbonate, 4 - 7 parts of carbon black, and 3 - 6 parts of nano - silica. In the present invention, by compounding nano - calcium carbonate, carbon black, and nano - silica and cooperating with a silane coupling agent to achieve interface strengthening, it helps to improve the wear resistance, oil resistance, and mechanical properties of the polyurethane seal.

[0011] Further, the silane coupling agent is at least one of γ - mercaptopropyltrimethoxysilane, γ - mercaptopropyltriethoxysilane, and bis - [γ - (triethoxysilyl)propyl]tetrasulfide.

[0012] Further, each part of the auxiliary agent includes the following raw materials in parts by weight: 0.5 - 2 parts of lubricant, 0.5 - 1.5 parts of antioxidant, and 0.5 - 1.5 parts of light stabilizer.

[0013] Further, the lubricant is at least one of zinc stearate, calcium stearate, and ethylene bisstearamide.

[0014] Further, the antioxidant is a hindered phenol antioxidant and a phosphite. The hindered phenol antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant BHT, and antioxidant 1098. The phosphite is selected from at least one of antioxidant 168 and antioxidant 626.

[0015] Further, the light stabilizer is a benzotriazole light stabilizer. The light stabilizer is at least one of 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, 2'-hydroxy-5'-tert-octylphenyl benzotriazole, 2-(2H-benzotriazol-2-yl)-4-methylphenol, and 2'-hydroxy-5'-tert-octylphenyl benzotriazole.

[0016] The polyurethane seal of the present invention is prepared by compounding raw materials such as aromatic polyamide fiber, maleic anhydride grafted POE, silane coupling agent, filler, nitrile rubber, etc. with polyurethane prepolymer, and using a chain extender to extend the polyurethane prepolymer. Each raw material can achieve good coordination and synergy, so that the prepared polyurethane seal has good wear resistance, oil resistance, mechanical properties, and low compression set. It can effectively reduce friction loss and wear in the sealing occasions of reciprocating motion or rotary motion, and can be applied to the sealing applications in humid and oil seal environments. It has a wide application range and a long product service life.

[0017] The present invention also provides a preparation method of the above-mentioned polyurethane seal, which includes the following steps:

[0018] (1) Take the raw materials for forming the polyurethane prepolymer in proportion, carry out a prepolymerization reaction to obtain the polyurethane prepolymer.

[0019] (2) Put the polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and auxiliary agent into a disperser in proportion, and carry out a mixing reaction at a temperature of 65-75°C to obtain material A.

[0020] (3) Inject material A into a mold, then put the mold filled with material A into a curing furnace for a curing reaction. After material A is completely cured, take it out of the mold to obtain a preliminary seal.

[0021] (4) Carry out turning processing on the preliminary seal after demolding to obtain the required size and shape.

[0022] (5) Carry out post-treatment on the preliminary seal after turning processing. The post-treatment steps include deburring, polishing, and cleaning to obtain the polyurethane seal.

[0023] Further, in step (1), polyether polyol and polyester polyol are taken to react with isocyanate, and the reaction is carried out for 2.5-3.5 h under the protection of a nitrogen atmosphere at 85-90°C, and then vacuum degassing is carried out until no bubbles escape to obtain the polyurethane prepolymer. The polyether polyol and polyester polyol are preheated and dehydrated.

[0024] Further, in step (2), the polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and auxiliary agent are proportionally placed in a high-speed disperser and mixed at a temperature of 65 - 75°C for 8 - 15 min at a rotation speed of 1400 - 1800 rpm to obtain material A;

[0025] Further, in step (2), the aromatic polyamide fiber is pre-treated with plasma at a treatment power of 100 - 200 W and a treatment time of 20 - 30 min. By adopting the above treatment, active groups are generated on the surface of the aromatic polyamide fiber, and covalent bonds are formed with the silane coupling agent during the mixing reaction process, which helps to improve the wettability and adhesion between the aromatic polyamide fiber and the matrix.

[0026] Further, in step (3), the mold is heated to 90 - 105°C, and material A is injected. It is cured for 40 - 80 min under the conditions of a pressure of 6 - 10 MPa and a temperature of 105 - 115°C, and then the temperature is raised to 120 - 130°C and the pressure is reduced to 2 - 3 MPa, and it is cured for 60 - 120 min.

[0027] By selecting and adjusting the dosage of the raw materials for the polyurethane seal and controlling the process parameters of each step of the preparation method of the polyurethane seal, in which a gradient curing process is adopted for the polyurethane prepolymer system, first high-pressure treatment is carried out, and then pressure reduction and temperature increase treatment are carried out, the internal defects of the seal can be reduced, and it helps to promote the orderly arrangement of molecular chains, improving the oil resistance and mechanical properties.

[0028] The beneficial effects of the present invention are as follows: The polyurethane seal of the present invention adds raw materials such as aromatic polyamide fiber, maleic anhydride grafted POE, silane coupling agent, filler, and nitrile rubber to the polyurethane prepolymer system, and uses a chain extender to extend the polyurethane prepolymer. Each raw material cooperates with each other and acts synergistically, so that the prepared polyurethane seal has good wear resistance, oil resistance, mechanical properties, and low compression set, and can effectively reduce friction loss and wear in the sealing occasions of reciprocating motion or rotary motion, with a wide application range and good durability. The preparation method of the polyurethane seal has high production efficiency, convenient operation control, stable process, and is conducive to industrial production. Detailed Embodiments

[0029] For the convenience of understanding by those skilled in the art, the present invention will be further described below in conjunction with embodiments. The content mentioned in the embodiments does not limit the present invention.

[0030] In some embodiments of the present invention, a polyurethane sealant comprises the following raw materials in parts by weight: 40 - 70 parts of polyurethane prepolymer, 5 - 20 parts of chain extender, 10 - 30 parts of filler, 4 - 8 parts of aromatic polyamide fiber, 4 - 8 parts of maleic anhydride grafted POE, 3 - 6 parts of silane coupling agent, 2 - 5 parts of nitrile rubber, and 1 - 5 parts of auxiliary agent; The preparation method of the polyurethane prepolymer comprises the following steps: reacting polyether polyol, polyester polyol with isocyanate, and the molar ratio of the isocyanate groups in the isocyanate to the hydroxyl groups in the polyether polyol and polyester polyol is 2.1 - 2.3 to obtain the polyurethane prepolymer.

[0031] In some embodiments of the present invention, a polyurethane sealant comprises the following raw materials in parts by weight: 55 - 65 parts of polyurethane prepolymer, 12 - 18 parts of chain extender, 15 - 20 parts of filler, 4 - 8 parts of aromatic polyamide fiber, 4 - 8 parts of maleic anhydride grafted POE, 3 - 6 parts of silane coupling agent, and 1 - 5 parts of auxiliary agent; The preparation method of the polyurethane prepolymer comprises the following steps: reacting polyether polyol, polyester polyol with isocyanate, and the molar ratio of the isocyanate groups in the isocyanate to the hydroxyl groups in the polyether polyol and polyester polyol is 2.1 - 2.3 to obtain the polyurethane prepolymer.

[0032] In some embodiments of the present invention, the isocyanate includes at least one of toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). Preferably, the isocyanate is composed of toluene diisocyanate and diphenylmethane diisocyanate in a weight ratio of 7 - 8:2 - 3.

[0033] In some embodiments of the present invention, the polyether polyol is at least one of polytetrahydrofuran ether diol and polypropylene oxide diol, and the polyester polyol is at least one of polybutylene adipate diol and polycarbonate diol.

[0034] In some embodiments of the present invention, the polyether polyol is composed of polytetrahydrofuran ether diol and polypropylene oxide diol in a weight ratio of 2 - 3:1, and the weight ratio of the polyether polyol to the polyester polyol is 3 - 4:1 - 2.

[0035] In some embodiments of the present invention, the molecular weight of the polytetrahydrofuran ether diol is 1000 - 2000, the molecular weight of the polypropylene oxide diol is 800 - 2500, and the molecular weight of the polybutylene adipate diol is 1000 - 1500.

[0036] In some embodiments of the present invention, the chain extender includes at least one of 1,4-butanediol and 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA). Preferably, the chain extender is composed of 1,4-butanediol and 3,3'-dichloro-4,4'-diaminodiphenylmethane in a weight ratio of 4-6:1-2.

[0037] In some embodiments of the present invention, the filler is at least one of nano calcium carbonate, carbon black, and nano silica. Further, each part of the filler includes the following raw materials in parts by weight: 8-12 parts of nano calcium carbonate, 4-7 parts of carbon black, and 3-6 parts of nano silica. By compounding nano calcium carbonate, carbon black, and nano silica and cooperating with a silane coupling agent in the present invention, interface strengthening is achieved, which helps to improve the wear resistance, oil resistance, and mechanical properties of the polyurethane seal.

[0038] In some embodiments of the present invention, the silane coupling agent is at least one of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and bis-[γ-(triethoxysilyl)propyl]tetrasulfide.

[0039] Further, each part of the auxiliary agent includes the following raw materials in parts by weight: 0.5-2 parts of lubricant, 0.5-1.5 parts of antioxidant, and 0.5-1.5 parts of light stabilizer.

[0040] In some embodiments of the present invention, the lubricant is at least one of zinc stearate, calcium stearate, and ethylene bisstearamide.

[0041] In some embodiments of the present invention, the antioxidant is a hindered phenol antioxidant and a phosphite; the hindered phenol antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant BHT, and antioxidant 1098; the phosphite is selected from at least one of antioxidant 168 and antioxidant 626.

[0042] In some embodiments of the present invention, the light stabilizer is a benzotriazole light stabilizer. The light stabilizer is at least one of 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, 2'-hydroxy-5'-tert-octylphenylbenzotriazole, 2-(2H-benzotriazol-2-yl)-4-methylphenol, and 2'-hydroxy-5'-tert-octylphenylbenzotriazole.

[0043] The present invention also provides a method for preparing a polyurethane seal, which includes the following steps:

[0044] (1) Take the raw materials for forming the polyurethane prepolymer in proportion and carry out a prepolymerization reaction to obtain a polyurethane prepolymer;

[0045] (2) Weigh the polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and additives proportionally and place them in a high-speed disperser. Mix them at a temperature of 65 - 75°C for 8 - 15 minutes at a rotational speed of 1400 - 1800 rpm to obtain Material A in the disperser.

[0046] (3) Inject Material A into the mold, and then place the mold filled with Material A into a curing furnace for curing reaction. After Material A is completely cured, take it out of the mold to obtain the initial product of the seal.

[0047] (4) Perform turning on the initial product of the seal after demolding to obtain the required size and shape.

[0048] (5) Perform post-treatment on the initial product of the seal after turning. The post-treatment steps include deburring, polishing, and cleaning to obtain the polyurethane seal.

[0049] In some embodiments of the present invention, in step (1), polyether polyol, polyester polyol, and isocyanate are reacted under the protection of a nitrogen atmosphere at 85 - 90°C for 2.5 - 3.5 hours, and then vacuum degassed until no bubbles escape to obtain the polyurethane prepolymer. The polyether polyol and polyester polyol are pre-treated by heating and dehydration.

[0050] In some embodiments of the present invention, the aromatic polyamide fiber is pre-treated with plasma before use. The treatment power is 100 - 200 W, and the treatment time is 20 - 30 minutes. The aromatic polyamide fiber is poly(m-phenylene isophthalamide) fiber (aramid 1313).

[0051] In some embodiments of the present invention, in step (3), the mold is heated to 90 - 105°C, Material A is injected, and it is cured for 40 - 80 minutes under the conditions of a pressure of 6 - 10 MPa and a temperature of 105 - 115°C, and then the temperature is raised to 120 - 130°C and the pressure is reduced to 2 - 3 MPa, and it is cured for 60 - 120 minutes.

[0052] Example 1

[0053] In this embodiment, a polyurethane sealant comprises the following raw materials in parts by weight: 60 parts of polyurethane prepolymer, 15 parts of chain extender, 20 parts of filler, 6 parts of aromatic polyamide fiber, 6 parts of maleic anhydride grafted POE, 4 parts of silane coupling agent, 3 parts of nitrile rubber, and 2.8 parts of auxiliary agent; The preparation method of the polyurethane prepolymer comprises the following steps: reacting polyether polyol, polyester polyol with isocyanate, and the molar ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyether polyol and polyester polyol is 2.1 to obtain the polyurethane prepolymer.

[0054] Further, the aromatic polyamide fiber is poly(m-phenylene isophthalamide) fiber, which is pre-treated by plasma with a treatment power of 200 W and a treatment time of 25 min. The poly(m-phenylene isophthalamide) fiber uses Teijin meta-aramid natural white staple fiber. The maleic anhydride grafted POE uses Dow AMPLIFY GR209 maleic anhydride grafted POE. The nitrile rubber uses Zeon nitrile rubber DN3350.

[0055] Further, the isocyanate is composed of toluene diisocyanate and diphenylmethane diisocyanate in a weight ratio of 4:1.

[0056] Further, the polyether polyol is composed of polytetrahydrofuran ether glycol and polyoxypropylene glycol in a weight ratio of 2.5:1, and the polyester polyol is poly(butylene adipate) glycol. The weight ratio of the polyether polyol to the poly(butylene adipate) glycol is 3.5:1.5. The polytetrahydrofuran ether glycol uses Jiangsu Haolong Chemical Industry PTMG1000, the polyoxypropylene glycol uses Jiangsu Maoheng Chemical Industry PPG2000, and the poly(butylene adipate) glycol uses Jiangsu Haolong Chemical Industry PBA 1000.

[0057] Further, the chain extender is composed of 1,4-butanediol and 3,3'-dichloro-4,4'-diaminodiphenylmethane in a weight ratio of 5:1.5.

[0058] Further, each part of the filler comprises the following raw materials in parts by weight: 10 parts of nano calcium carbonate, 6 parts of carbon black, and 4 parts of nano silica. The carbon black uses N330. The particle sizes of the nano calcium carbonate and nano silica are 30 - 50 nm.

[0059] Further, the silane coupling agent is composed of γ-mercaptopropyltrimethoxysilane and bis-[γ-(triethoxysilyl)propyl]tetrasulfide in a weight ratio of 1:1.

[0060] Further, each part of the auxiliary agent comprises the following raw materials in parts by weight: 1 part of lubricant, 1 part of antioxidant, and 0.8 part of light stabilizer.

[0061] Further, the lubricant is zinc stearate. The hindered phenol antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1. The light stabilizer is 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol.

[0062] In this embodiment, the preparation method of the polyurethane seal includes the following steps:

[0063] (1) Take the raw materials for forming the polyurethane prepolymer in proportion, carry out a prepolymerization reaction to obtain a polyurethane prepolymer;

[0064] (2) Put the polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and auxiliary agent in proportion into a disperser, mix at 70 °C for 12 min, and the rotation speed is 1500 rpm to obtain Material A;

[0065] (3) Inject Material A into the mold, then put the mold filled with Material A into a curing furnace for a curing reaction. After Material A is completely cured, take it out of the mold to obtain a preliminary seal;

[0066] (4) Carry out turning processing on the preliminary seal after demolding to obtain the required size and shape;

[0067] (5) Carry out post-treatment on the preliminary seal after turning processing. The post-treatment steps include deburring, polishing, and cleaning to obtain a polyurethane seal.

[0068] Further, in step (1), take polyether polyol, polyester polyol and isocyanate to react, react for 3 h under the protection of nitrogen atmosphere at 86 °C, and then carry out vacuum degassing until no bubbles escape to obtain a polyurethane prepolymer. The polyether polyol and polyester polyol are pre-treated by heating and dehydration.

[0069] Further, in step (3), heat the mold to 95 °C, inject Material A, cure at a pressure of 8 MPa and a temperature of 105 °C for 60 min, then raise the temperature to 125 °C and reduce the pressure to 2.5 Mpa, and cure for 100 min.

[0070] Example 2

[0071] In this embodiment, a polyurethane sealant comprises raw materials in the following parts by weight: 55 parts of polyurethane prepolymer, 12 parts of chain extender, 16 parts of filler, 5 parts of aromatic polyamide fiber, 4 parts of maleic anhydride grafted POE, 4 parts of silane coupling agent, 2.5 parts of nitrile rubber, and 2 parts of auxiliary agent. The preparation method of the polyurethane prepolymer comprises the following steps: taking polyether polyol, polyester polyol and isocyanate to react, and the molar ratio of the isocyanate groups in the isocyanate to the hydroxyl groups in the polyether polyol and the polyester polyol is 2.1 to obtain the polyurethane prepolymer.

[0072] Further, the isocyanate is composed of toluene diisocyanate and diphenylmethane diisocyanate in a weight ratio of 3:1.

[0073] Further, the polyether polyol is composed of polytetrahydrofuran ether diol and polypropylene oxide diol in a weight ratio of 2:1, and the polyester polyol is polybutylene adipate diol. The weight ratio of the polyether polyol to the polybutylene adipate diol is 3:1.

[0074] Further, the chain extender is composed of 1,4-butanediol and 3,3'-dichloro-4,4'-diaminodiphenylmethane in a weight ratio of 4:1.

[0075] Further, each part of the filler comprises raw materials in the following parts by weight: 9 parts of nano calcium carbonate, 4 parts of carbon black, and 3 parts of nano silicon dioxide.

[0076] Further, the silane coupling agent is bis-[γ-(triethoxysilyl)propyl]tetrasulfide.

[0077] Further, each part of the auxiliary agent comprises raw materials in the following parts by weight: 0.8 part of lubricant, 0.6 part of antioxidant, and 0.6 part of light stabilizer. The carbon black is N330; the particle sizes of the nano calcium carbonate and the nano silicon dioxide are 30 - 50 nm.

[0078] Further, the lubricant is zinc stearate. The hindered phenol antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1. The light stabilizer is 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol.

[0079] In this embodiment, the preparation method of the polyurethane sealant comprises the following steps:

[0080] (1) Taking the raw materials for forming the polyurethane prepolymer in proportion and carrying out a prepolymerization reaction to obtain the polyurethane prepolymer;

[0081] (2) Weigh out polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and additives proportionally and place them in a dispersing machine. Mix them at 70 °C for 10 min at a rotation speed of 1500 rpm to obtain Material A;

[0082] (3) Inject Material A into a mold. Then, place the mold filled with Material A into a curing furnace for curing reaction. After Material A is completely cured, take it out of the mold to obtain the initial product of the seal;

[0083] (4) Perform turning on the initial product of the seal after demolding to obtain the required size and shape;

[0084] (5) Perform post-treatment on the initial product of the seal after turning. The post-treatment steps include deburring, polishing, and cleaning to obtain the polyurethane seal.

[0085] Further, in step (1), take polyether polyol, polyester polyol and isocyanate to react. React under the protection of nitrogen atmosphere at 86 °C for 3 h, and then perform vacuum degassing until no bubbles escape to obtain the polyurethane prepolymer. The polyether polyol and polyester polyol are pre-treated by heating and dehydration.

[0086] Further, in step (2), weigh out polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, and additives proportionally and place them in a high-speed dispersing machine. Mix them at 65 °C for 15 min at a rotation speed of 1400 rpm to obtain Material A;

[0087] Further, in step (3), heat the mold to 100 °C, inject Material A, cure it at a pressure of 9 MPa and a temperature of 110 °C for 50 min, then raise the temperature to 120 °C and reduce the pressure to 2 MPa and cure for 100 min.

[0088] The remaining content of this example is the same as that of Example 1.

[0089] Example 3

[0090] In this example, a polyurethane seal includes the following raw materials in parts by weight: 65 parts of polyurethane prepolymer, 16 parts of chain extender, 18 parts of filler, 7 parts of aromatic polyamide fiber, 6 parts of maleic anhydride grafted POE, 5 parts of silane coupling agent, 3.5 parts of nitrile rubber, and 3 parts of additives; the preparation method of the polyurethane prepolymer includes the following steps: take polyether polyol, polyester polyol and isocyanate to react, and the molar ratio of the isocyanate groups in the isocyanate to the hydroxyl groups in the polyether polyol and polyester polyol is 2.1 to obtain the polyurethane prepolymer.

[0091] Further, the isocyanate is composed of toluene diisocyanate and diphenylmethane diisocyanate in a weight ratio of 3:1.

[0092] Further, the polyether polyol is composed of polytetrahydrofuran ether diol and polyoxypropylene diol in a weight ratio of 2.5:1, and the polyester polyol is polybutylene adipate diol. The weight ratio of the polyether polyol to the polybutylene adipate diol is 3.5:1.5.

[0093] Further, the chain extender is composed of 1,4-butanediol and 3,3'-dichloro-4,4'-diaminodiphenylmethane in a weight ratio of 4:1.

[0094] Further, each portion of the filler comprises the following raw materials in parts by weight: 10 parts of nano calcium carbonate, 4 parts of carbon black, and 4 parts of nano silica.

[0095] Further, the silane coupling agent is composed of γ-mercaptopropyltrimethoxysilane and bis-[γ-(triethoxysilyl)propyl]tetrasulfide in a weight ratio of 1.5:1.

[0096] Further, each portion of the auxiliary agent comprises the following raw materials in parts by weight: 1.2 parts of lubricant, 1 part of antioxidant, and 0.8 part of light stabilizer.

[0097] Further, the silane coupling agent is γ-mercaptopropyltrimethoxysilane.

[0098] Further, the lubricant is zinc stearate. The hindered phenol antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1. The light stabilizer is 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol.

[0099] In this embodiment, the preparation method of the polyurethane sealant comprises the following steps:

[0100] (1) Take the raw materials for forming the polyurethane prepolymer in proportion and carry out a prepolymerization reaction to obtain the polyurethane prepolymer;

[0101] (2) Place the polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and auxiliary agent in a disperser according to the proportion, mix at 75°C for 8 min at a rotation speed of 1500 rpm to obtain material A;

[0102] (3) Inject material A into the mold, then place the mold filled with material A into a curing furnace for a curing reaction. After material A is completely cured, take it out of the mold to obtain the initial product of the sealant;

[0103] (4) Perform turning on the initial product of the seal after demolding to obtain the required size and shape;

[0104] (5) Perform post-treatment on the initial product of the seal after turning. The post-treatment steps include deburring, polishing, and cleaning to obtain a polyurethane seal.

[0105] Further, in step (1), polyether polyol, polyester polyol, and isocyanate are reacted. The reaction is carried out for 3 h under the protection of a nitrogen atmosphere at 86 °C, and then vacuum degassing is carried out until no bubbles escape to obtain a polyurethane prepolymer. The polyether polyol and polyester polyol are pre-treated by heating and dehydration.

[0106] Further, in step (3), the mold is heated to 95 °C, and material A is injected. It is cured for 60 min under the conditions of a pressure of 8 MPa and a temperature of 105 °C, then the temperature is raised to 125 °C, and the pressure is reduced to 2.5 Mpa and cured for 100 min.

[0107] The remaining content of this embodiment is the same as that of Embodiment 1.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Embodiment 1 is that in this comparative example, a polyurethane seal includes the following raw materials in parts by weight: 66 parts of polyurethane prepolymer, 15 parts of chain extender, 20 parts of filler, 6 parts of maleic anhydride grafted POE, 4 parts of silane coupling agent, 3 parts of nitrile rubber, and 2.8 parts of auxiliary agent; the preparation method of the polyurethane prepolymer includes the following steps: Take polyether polyol, polyester polyol, and isocyanate to react. The molar ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyether polyol and polyester polyol is 2.1 to obtain a polyurethane prepolymer. That is, this comparative example does not contain aromatic polyamide fiber and is replaced with an equal amount of polyurethane prepolymer.

[0110] The remaining content of this comparative example is the same as that of Embodiment 1 and will not be elaborated here.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Embodiment 1 is that in this comparative example, a polyurethane seal includes the following raw materials in parts by weight: 66 parts of polyurethane prepolymer, 15 parts of chain extender, 20 parts of filler, 6 parts of aromatic polyamide fiber, 4 parts of silane coupling agent, 3 parts of nitrile rubber, and 2.8 parts of auxiliary agent; the preparation method of the polyurethane prepolymer includes the following steps: Take polyether polyol, polyester polyol, and isocyanate to react. The molar ratio of the isocyanate group in the isocyanate to the hydroxyl group in the polyether polyol and polyester polyol is 2.1 to obtain a polyurethane prepolymer. That is, this comparative example does not contain maleic anhydride grafted POE and is replaced with an equal amount of polyurethane prepolymer.

[0113] The polyurethane seals prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the test results are shown in Table 1 below:

[0114]

[0115]

[0116] The abrasion loss of the present invention was tested with reference to ASTM D4060 using a Taber abrasion tester at a rotational speed of 60 r / min. The tear strength was tested with reference to GB / T 529-2008. The tensile strength was tested with reference to GB / T 528-2009. The elongation at break was tested according to GB / T 13477.8-2017. The oil resistance test was carried out by testing the volume change of IRM903 oil. Before the test, the polyurethane seal was placed in IRM903 oil for 72 h at a temperature of 70 °C and tested with reference to ASTM D471. The compression set performance test was carried out with reference to GB / T7759.1-2015.

[0117] In summary, for the polyurethane seal of the present invention, by adding raw materials such as aromatic polyamide fiber, maleic anhydride grafted POE, silane coupling agent, filler, chain extender, and nitrile rubber into the polyurethane prepolymer system, the raw materials cooperate with each other and act synergistically, so that the prepared polyurethane seal has good abrasion resistance, tear strength, tensile strength, oil resistance, and low compression set, can effectively reduce friction loss and wear in the sealing occasions of reciprocating motion or rotary motion, has a wide application range, and good durability.

[0118] The above specific embodiments further illustrate the technical solutions and beneficial effects of the present invention, rather than limiting the implementation mode. For those skilled in the art, any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A polyurethane seal, characterized in that: The invention comprises the following raw materials in parts by weight: 40-70 parts of polyurethane prepolymer, 5-20 parts of chain extender, 10-30 parts of filler, 4-8 parts of aromatic polyamide fiber, 4-8 parts of maleic anhydride grafted POE, 3-6 parts of silane coupling agent, 2-5 parts of nitrile rubber and 1-5 parts of auxiliary agent. The preparation method of the polyurethane prepolymer comprises the following steps: taking polyether polyol and polyester polyol to react with isocyanate, wherein the molar ratio of isocyanate group in the isocyanate to hydroxyl group in polyether polyol and polyester polyol is 2.1-2.3, so as to obtain the polyurethane prepolymer.

2. The polyurethane seal according to claim 1, characterized in that: The isocyanate is at least one of toluene diisocyanate and diphenylmethane diisocyanate.

3. The polyurethane seal according to claim 1, characterized in that: The polyether polyol is at least one of polytetramethylene glycol and polyoxypropylene glycol, and the polyester polyol is at least one of polybutylene adipate glycol and polycarbonate glycol.

4. The polyurethane seal according to claim 1, characterized in that: The chain extender is at least one of 1,4-butanediol and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

5. The polyurethane seal according to claim 1, characterized in that: The filler is at least one of nano calcium carbonate, carbon black and nano silicon dioxide.

6. The polyurethane seal according to claim 1, characterized in that: Each portion of the filler comprises the following raw materials in parts by weight: 8-12 parts of nano calcium carbonate, 4-7 parts of carbon black, and 3-6 parts of nano silicon dioxide.

7. The polyurethane seal according to claim 1, characterized in that: Each part of the auxiliary agent comprises the following raw materials in parts by weight: 0.5-2 parts of lubricant, 0.5-1.5 parts of antioxidant, and 0.5-1.5 parts of light stabilizer.

8. A method for preparing a polyurethane seal according to any one of claims 1 to 7, characterized in that: The steps include: (1) taking raw materials constituting a polyurethane prepolymer in proportion, carrying out a prepolymerization reaction, and obtaining a polyurethane prepolymer; (2) placing polyurethane prepolymer, chain extender, maleic anhydride grafted POE, aromatic polyamide fiber, filler, silane coupling agent, nitrile rubber, and additives in a disperser according to proportion, mixing and reacting at a temperature of 65-75° C. to obtain material A; (3) injecting material A into the mold, and then placing the mold with material A poured into a curing furnace to perform a curing reaction. After material A is completely cured, taking it out of the mold to obtain a preliminary seal; (4) Turning the demolded seal product to obtain the required size and shape; (5) performing post-processing on the initial seal product after turning, wherein the post-processing steps include deburring, grinding and cleaning to obtain a polyurethane seal.

9. The method for preparing a polyurethane seal according to claim 8, characterized in that: In step (1), polyether polyol and polyester polyol are reacted with isocyanate at 85-90° C. under nitrogen atmosphere for 2.5-3.5 hours, and then vacuum degassing is performed to obtain a polyurethane prepolymer.

10. The method for preparing a polyurethane seal according to claim 8, characterized in that: In step (3), the mold is heated to 90-105°C, material A is injected, and cured for 40-80 minutes at a pressure of 6-10 MPa and a temperature of 105-115°C, then the temperature is raised to 120-130°C, the pressure is reduced to 2-3 MPa, and the curing is continued for 60-120 minutes.

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