High-strength self-lubricating polyurethane piston seal body, and method for manufacturing the same.

Abstract

The present invention relates to the field of polymeric materials, and to a high-strength, self-lubricating polyurethane piston seal body and a method for making the same. In particular, the present invention relates to a composition that can be used to make the piston seal body, a piston seal body made from the composition, and a method for preparing the piston seal body. The piston seal body of the present invention can be used as a concrete piston seal body for a concrete pumping device.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly to a composition for producing a piston seal body, a piston seal body produced from the composition, and a method for producing a piston seal body. The piston seal body can be used as a concrete piston seal body for a concrete pump device.

Background Art

[0002] A piston is an important core component of a concrete pump device (for example, a pump truck, a drag pump, and a truck-mounted pump), which plays a role in filling gaps and pushing concrete during concrete delivery. Since the delivered concrete has a hard medium, complex components, high pump pressure, and high requirements for sealing performance, the piston needs to have excellent mechanical strength and wear resistance. Currently, pistons have a short service life, frequent replacements, and high operating costs.

[0003] Existing piston seal bodies mainly include two materials, rubber materials or polyurethane materials. Rubber pistons are formed mainly of nitrile rubber by adding reinforcing agents, anti-aging agents, vulcanizing agents, etc., mixing them, and subjecting them to high-temperature compression. Patent Document 1 uses nitrile rubber as the main material for producing a piston for a concrete pump truck. Here, the main raw materials include nitrile rubber, ethyl acetate, polyisocyanate, etc., and a fiber reinforcing material is added during the production process. However, since the pump still has low strength and low hardness with a maximum hardness of 85A and a maximum tensile strength of 36 MPa, it cannot meet the market demand.

[0004] Patent Document 2 relates to a portable pump mechanism for injecting construction materials or water with a pump, and Patent Document 3 relates to the vehicle structure of a concrete pump truck; neither of these relates to a method for manufacturing piston material. Patent Document 4 relates to a method for manufacturing foamed polyurethane material, but its tensile strength is low at approximately 2 MPa, making it unsuitable for manufacturing polyurethane material for piston heads. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Chinese Patent Application No. CN201310234970.3 [Patent Document 2] U.S. Patent No. 10,415,556 [Patent Document 3] U.S. Patent Application Publication No. 2010 / 0264635 [Patent Document 4] German Patent Application Publication No. 102005008242 [Overview of the Initiative] [Means for solving the problem]

[0006] One of the objectives of the present invention is to provide a high-strength, self-lubricating polyurethane piston that solves the problems of existing polyurethane pistons, which have low strength and high wear resistance. By adding a specially treated filler to the polymerization system, the strength and wear resistance of the piston are improved, thereby extending its service life and reducing the frequency of replacement.

[0007] In one embodiment, the present application provides a composition for producing a piston seal comprising the following components: 100 parts by weight of a polyurethane prepolymer, 10 to 20 parts by weight of a chain extender, 5 to 10 parts by weight of surface-silylated ultra-high molecular weight polyethylene powder, 1 to 1.5 parts by weight of an antioxidant, 1 to 2 parts by weight of surface-silylated alumina powder, and 1 to 3 parts by weight of molybdenum disulfide or sodium polytetrafluoroethylene powder.

[0008] In the present invention, "prepolymer" refers to a substance formed by the prepolymerization of monomers, which can be used when it is difficult to completely polymerize monomers into a polymer in one step, or when voids and cracks should be avoided during polymer processing and molding. The present invention uses a polyurethane prepolymer as the main material for producing a piston seal.

[0009] "Polyurethane" is a general term for polymers that contain a certain amount of carbamate groups in their molecules. Polyurethanes can be prepared by the interaction of mono- or polyorganoisocyanates (e.g., toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI)) with polyol compounds (e.g., polyether polyols or polyester polyols), and the resulting polymer backbone contains multiple repeating carbamate groups. Polyurethane prepolymers are reactive semi-finished products obtained by reacting polyorganoisocyanates and polyols in controlled ratios.

[0010] In certain embodiments, the polyurethane prepolymer is of the polyether type.

[0011] In certain embodiments, the polyurethane prepolymer is selected from either or both of the LF M2050 model and the LF M2032 model.

[0012] In certain embodiments, the polyurethane prepolymer has the following characteristics: Free MDI content: less than 0.1 wt%, for example, 0.01 wt% to 0.02 wt%, 0.02 wt% to 0.03 wt%, 0.03 wt% to 0.04 wt%, 0.04 wt% to 0.05 wt%, 0.05 wt% to 0.06 wt%, 0.06 wt% to 0.07 wt%, 0.07 wt% to 0.08 wt%, or 0.08 wt% to 0.09 wt%; Isocyanate (-NCO) content: 3.0% to 5.0%, for example, 3.0% to 3.5%, 3.5% to 4.0%, 4.0% to 4.5%, or 4.5% to 5.0%; Viscosity: 120 to 500 cps, for example, 120 to 150 cps, 150 to 200 cps, 200 to 300 cps, 300 to 400 cps, or 400 to 500 cps. It has one or more of the following.

[0013] In the present invention, "chain extender" refers to a substance that reacts with functional groups on a linear polymer chain to extend the molecular chain and increase the molecular weight, and is commonly used to improve the mechanical and processing properties of polyurethane, polyester products, and the like. In certain embodiments, the chain extender used is an alcohol chain extender, such as an aromatic alcohol chain extender such as 1,4-bis(2-hydroxyethoxy)benzene (HQEE: 1,4-bis(2-hydroxyethoxy)benzene). In certain embodiments, the chain extender used is an amine chain extender, such as a diamine chain extender such as 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0014] The present invention enhances the mechanical strength of polyurethane by adding fillers such as specially modified ultra-high molecular weight polyethylene powder and alumina powder to a polyurethane substrate, and reduces the coefficient of friction by adding molybdenum disulfide or specially treated polytetrafluoroethylene as self-lubricating particles to the inside of the piston.

[0015] In certain embodiments, the ultra-high molecular weight polyethylene powder used in the present invention has a particle size of 30 to 50 μm, for example, 30 to 35 μm, 35 to 40 μm, 40 to 45 μm or 45 to 50 μm.

[0016] In certain embodiments, the ultra-high molecular weight polyethylene powder used in the present invention has a molecular weight (e.g., viscosity average molecular weight) of from 4,000,000 to 5,000,000, for example, from 4,000,000 to 4,500,000 or from 4,500,000 to 5,000,000.

[0017] In certain embodiments, the alumina powder used in the present invention has a particle size of from 3000 to 5000 mesh, for example, from 3000 to 4000 mesh or from 4000 to 5000 mesh.

[0018] In certain embodiments, the antioxidant used in the present invention is a hindered phenol antioxidant, for example, antioxidant 1010.

[0019] In certain embodiments, the polytetrafluoroethylene sodium powder is a polytetrafluoroethylene powder treated with naphthalene sodium.

[0020] In some embodiments, the polytetrafluoroethylene sodium powder has a particle size of 3 to 20 μm, for example, 3 to 5 μm, 5 to 10 μm, 10 to 15 μm or 15 to 20 μm.

[0021] In certain embodiments, the composition comprises from 10 to 11, 11 to 12, 12 to 13, 13 to 14, 14 to 15, 15 to 16, 16 to 17, 17 to 18, 18 to 19 or 19 to 20 parts by weight of a chain extender.

[0022] In some embodiments, the composition comprises from 5 to 6, 6 to 7, 7 to 8, 8 to 9 or 9 to 10 parts by weight of a surface silylated ultra-high molecular weight polyethylene powder.

[0023] In some embodiments, the composition comprises 1 to 1.2, 1.2 to 1.3, 1.3 to 1.4 or 1.4 to 1.5 parts by weight of an antioxidant.

[0024] In some embodiments, the composition comprises 1 to 1.2, 1.2 to 1.5 or 1.5 to 2 parts by weight of surface-silylated alumina powder.

[0025] In some embodiments, the composition comprises 1 to 2 or 2 to 3 parts by weight of molybdenum disulfide or sodium polytetrafluoroethylene powder.

[0026] The surface-silylated ultra-high molecular weight polyethylene powder used in the present invention is Step 1: a step of oxidizing the ultra-high molecular weight polyethylene powder; and Step 2: a step of reacting the oxidized ultra-high molecular weight polyethylene powder with a silane coupling agent and may be produced by a method including the above steps.

[0027] The oxidation treatment in Step 1 may be carried out in a solution containing potassium permanganate and nitric acid. In certain embodiments, the solution is a mixed solution of a saturated aqueous potassium permanganate solution and an aqueous nitric acid solution (for example, a 50% to 60% aqueous nitric acid solution). In certain embodiments, the oxidation treatment includes the steps of introducing the ultra-high molecular weight polyethylene powder into a solution containing potassium permanganate and nitric acid (for example, a mixed solution of a saturated aqueous potassium permanganate solution and a 50% aqueous nitric acid solution), heating (for example, heating to 80 to 90 °C) and stirring (for example, stirring for 30 to 40 minutes), then filtering it to obtain a powder, and then repeatedly washing the powder with deionized water, filtering it, and drying it in an oven.

[0028] In step 2, common silane coupling agents, such as silane coupling agent KH540, silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570, may be used in the silylation reaction. In a particular embodiment, the silane coupling agent used is silane coupling agent KH550. The weight of the silane coupling agent used may be 0.1% to 1% (e.g., 0.3% or 0.6%) of the weight of the ultra-high molecular weight polyethylene powder.

[0029] The silylation reaction may be carried out under conditions of stirring (e.g., at a speed of 1500 to 2000 rpm) and heating (e.g., 70 to 80°C). In certain embodiments, the silylation process is carried out in a high-speed mixer.

[0030] In a particular embodiment, the silylation reaction includes the steps of introducing oxidized ultra-high molecular weight polyethylene powder into a high-speed mixer adjusted to a speed of 1500 rpm and a temperature of 70°C, and performing a coupling treatment by dropwise adding 0.3% or 0.6% by weight of the powder of the silane coupling agent KH550.

[0031] According to the present invention, the sodium naphthalene treatment may include the steps of adding polytetrafluoroethylene powder to a sodium naphthalene treatment solution in which the powder is completely immersed, stirring the solution for 10 to 15 minutes, filtering the solution, and washing it several times with tetrahydrofuran and deionized water until the odor of the sodium naphthalene treatment solution is gone. In certain embodiments, the sodium naphthalene treatment further includes placing the sodium polytetrafluoroethylene powder in an oven to dry it (for example, drying it at 100 to 110°C for 100 to 150 hours), grinding it, and dispersing it.

[0032] In the present invention, the sodium naphthalene treatment solution is a solution obtained by dissolving equimolar amounts of sodium and naphthalene in an active ether, such as tetrahydrofuran, or by complexing them therein.

[0033] In certain embodiments, the sodium naphthalene treatment solution is prepared by the following method: Under the protection of a nitrogen atmosphere, naphthalene is weighed and added to an activated ether (e.g., tetrahydrofuran). Once the naphthalene is completely dissolved, sodium is added, and the mixture is thoroughly stirred until the sodium dissolves, producing the sodium naphthalene treatment solution. In certain embodiments, the weight of naphthalene is 120 to 150 g (e.g., 128 g). In certain embodiments, the weight of sodium is 20 to 25 g (e.g., 23 g). In certain embodiments, the volume of activated ether (e.g., tetrahydrofuran) is 1 L.

[0034] The surface-silylated alumina powder used in the present invention may be prepared by a method comprising the step of reacting alumina powder with a silane coupling agent under conditions of stirring (e.g., at a speed of 2000 to 3000 rpm) and heating (e.g., 70 to 80°C). In certain embodiments, the step is carried out in a high-speed mixer. The silylation reaction may use common silane coupling agents, such as silane coupling agent KH540, silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570. In certain embodiments, the silane coupling agent used is silane coupling agent KH550. The weight of the silane coupling agent used may be 1% to 5%, for example, 2%, of the weight of the alumina powder.

[0035] In a particular embodiment, the steps include introducing alumina powder into a high-speed mixer adjusted to a speed of 2000 rpm and a temperature of 70°C, and performing a coupling process by dropping 2% by weight of the coupling agent KH550 onto the powder.

[0036] In one embodiment, the present application provides the use of any of the above compositions for producing a piston seal body. In a particular embodiment, the piston seal body is a concrete piston seal body.

[0037] In one embodiment, the present application provides a piston seal body manufactured by injection molding any of the above compositions. In a particular embodiment, the piston seal body is a concrete piston seal body.

[0038] This application further provides a method for producing a piston seal body of the present invention, comprising injection molding any of the above compositions.

[0039] In a particular embodiment, the method is a) A step of weighing out parts by weight each of polyurethane prepolymer, chain extender, surface silylated ultra-high molecular weight polyethylene powder, molybdenum disulfide or sodium polytetrafluoroethylene powder, surface silylated alumina powder, and antioxidant, b) A step of introducing a polyurethane prepolymer, surface-silylated ultra-high molecular weight polyethylene powder, molybdenum disulfide or sodium polytetrafluoroethylene powder, and surface-silylated alumina powder into tank A of an injection molding machine, mixing them uniformly, and stirring them at a low speed of 650 rpm to 950 rpm (e.g., 700 rpm) while controlling the temperature to 80 to 100°C (e.g., 90°C), c) Adding the chain extender to tank B of the injection molding machine and controlling the temperature to 110 to 120°C (e.g., 115°C) until the chain extender is completely dissolved, then adding the antioxidant while stirring at a high speed of 1500 to 2500 rpm (e.g., 1600 rpm), d) The steps of cleaning the mold's depressions, spraying the mold with a release agent, and preheating it in an oven at 110 to 130°C (for example, 120°C), e) Mixing the liquids in tank A and tank B in a controlled ratio by an injection molding machine while reducing pressure, stirring at a high speed of 2000 to 3500 rpm while maintaining the temperature at 100 to 120°C, and then injecting the mixture into a mold; f) Place the mold in the oven to bake at 100 to 120°C for 16 to 20 hours, and after removing the mold, perform the demolding step. g) The step of mechanically processing the demolded unfinished product to obtain the piston seal body of the present invention. Includes.

[0040] In certain embodiments, surface-silylated ultra-high molecular weight polyethylene powder, polytetrafluoroethylene sodium powder, and / or surface-silylated alumina powder are prepared by the method described above.

[0041] The piston seal body of the present invention can be used as a high-strength, self-lubricating piston seal body that has excellent wear resistance and a low coefficient of friction, as well as high mechanical strength, thereby significantly extending the service life of the piston. In a particular embodiment, the piston seal body has the following features: Tensile strength: ≥60 MPa; Elongation at break: ≥550%; Tear strength: ≧115kN / m; Shore hardness: 96-98HA; Akron wear: ≤0.025cm 3 ; Service life: Over 550 hours (more than 50% improvement over the service life of pure polyurethane concrete pistons) It has one or more of the following.

[0042] Methods commonly used in the art are used to test the performance of the piston seal. Typical test criteria are shown below.

[0043] [Table 1]

[0044] Furthermore, this application also provides a piston equipped with the piston seal body of the present invention. In certain embodiments, the piston is a concrete piston.

[0045] Furthermore, this application also provides a delivery cylinder equipped with the piston seal body or piston of the present invention.

[0046] Furthermore, this application also provides concrete pumping devices (e.g., pump trucks, drag pumps, truck-mounted pumps) equipped with the piston seal body, piston, or delivery cylinder of the present invention.

[0047] Figures 1 and 2 illustrate the structure of the concrete piston seal body of the present invention. Figure 1 is a cross-sectional view, and Figure 2 is a schematic partial view of the cross-section of Figure 1.

[0048] In the drawings, the numbers refer to the following: 1. Angle of the inner ring of the lip opening of the concrete piston relative to the horizontal plane. 2. Angle of the lip opening of the concrete piston relative to the horizontal plane, 3. Angle of inclination of the lip opening of the concrete piston outward relative to the vertical direction. 4. Side friction surfaces of concrete pistons, 5. Lubricating oil reservoir groove of concrete piston, 6. Schematic diagram of ultra-high molecular weight polyethylene powder 、 Schematic diagram of 7-polytetrafluoroethylene powder, and 8. Schematic diagram of alumina powder .

[0049] In a particular embodiment, the concrete piston seal body of the present invention has the following main dimensions: Angle of the inner ring of the lip opening relative to the horizontal plane: 40-45°, Angle of the lip opening relative to the horizontal plane: 3-10°, Angle of outward inclination of the lip opening relative to the vertical: 15-25°, Width of the side friction surface: 10-15mm, Depth of lubricating oil reservoir groove: 3-5 mm.

[0050] The piston seal body described above is equipped with a special oil-retaining groove that provides even better lubrication. [Effects of the Invention]

[0051] The piston seal body of the present invention has the following advantageous effects: 1. The piston seal body of the present invention is provided with a simple manufacturing process that is low-cost and provides stable quality; 2. With respect to the piston seal body of the present invention, a special filler processing process is employed, as a result in the ultra-high molecular weight polyethylene powder, polytetrafluoroethylene powder, and alumina powder being firmly bound to and uniformly dispersed on the polyurethane substrate; 3. The particles that enhance friction reduction in the piston seal body of the present invention are uniformly dispersed, thereby improving wear resistance; 4. The piston seal body of the present invention has excellent mechanical properties and can meet the operating conditions for concrete extrusion under high pressure; 5. The piston seal body of the present invention can achieve self-lubrication in components such as the seal lip opening, the contact surface with the cylinder, and the contact surface with concrete, thereby reducing the coefficient of friction and wear loss; 6. The self-lubricating particles inside the piston seal body of the present invention are uniformly dispersed, and continue to provide a self-lubricating effect on the new friction surface. It has one or more of the following. [Brief explanation of the drawing]

[0052] [Figure 1] This is a cross-sectional view of the piston seal body of the present invention. The numbers in the drawing refer to: 1 - angle of the inner ring of the piston lip opening relative to the horizontal plane, 2 - angle of the piston lip opening relative to the horizontal plane, 3 - angle of the outward inclination of the piston lip opening relative to the vertical direction, 4 - side friction surface of the concrete piston, 5 - lubricating oil reservoir groove of the piston. [Figure 2]This is a schematic diagram of a section of the cross-section shown in Figure 1. The numbers in the drawings refer to: 6 - schematic diagram of ultra-high molecular weight polyethylene powder, 7 - schematic diagram of polytetrafluoroethylene powder, and 8 - schematic diagram of alumina powder. [Modes for carrying out the invention]

[0053] Embodiments of the present invention are described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered to limit the scope of the invention. Examples in which no specific conditions are specified are carried out under conventional conditions or conditions recommended by the manufacturer. All reagents or equipment used that are not indicated with the manufacturer are commercially available conventional products. [Examples]

[0054] Example 1 (1) 2500 g of ultra-high molecular weight polyethylene powder was added to a mixed solution of saturated potassium permanganate and 50% nitric acid, heated to 80°C and stirred for 30 minutes, then filtered to obtain powder. The powder was then repeatedly washed with deionized water, filtered, and oven-dried. The powder was then placed in a high-speed mixer adjusted to a speed of 1500 rpm and a temperature of 70°C, and 7.5 g of coupling agent KH550 was added dropwise to perform the coupling treatment; (2) 750 g of polytetrafluoroethylene powder was placed in a sodium naphthalene solution to completely immerse it, then stirred, the powder was repeatedly washed with tetrahydrofuran, filtered, and then placed in an oven to dry for 150 hours, after which it was ground and dispersed; (3) 250 g of alumina powder was placed in a high-speed mixer adjusted to a speed of 2000 rpm and a temperature of 70°C, and 5 g of the coupling agent KH550 was added dropwise to perform the coupling treatment; (4) 25,000 g of prepolymer was added to tank A of the injection molding machine, the temperature was controlled to 90°C, and the surface-treated ultra-high molecular weight polyethylene powder, polytetrafluoroethylene powder, and alumina powder were uniformly mixed to form the prepolymer, which was then stirred at a low speed of 700 rpm; (5) 3750g of chain extender was placed in tank B of the injection molding machine, the temperature was controlled to 115°C, and once the chain extender was completely dissolved, 250g of antioxidant was added and the mixture was stirred at a speed of 1600 rpm; (6) Clean the indentation in the mold, spray the mold with a release agent, and preheat the mold in an oven at 120°C; (7) The liquids in tanks A and B were mixed, the pressure was reduced, the temperature was controlled to 120°C, and the mixture was stirred at a high speed of 2500 rpm before being injected into the mold's cavity. (8) Place the mold in a 120°C oven for 16 hours, then remove it and demold it; (9) The demolded, unfinished products were mechanically processed to produce high-strength, self-lubricating polyurethane pistons.

[0055] Example 2 (1) 1250 g of ultra-high molecular weight polyethylene powder was added to a mixed solution of saturated potassium permanganate and 50% nitric acid, heated to 80°C and stirred for 30 minutes, then filtered to obtain powder. The powder was repeatedly washed with deionized water, filtered, and oven-dried. The powder was then placed in a high-speed mixer adjusted to a speed of 1500 rpm and a temperature of 70°C, and 7.5 g of coupling agent KH550 was added dropwise to perform the coupling treatment; (2) 500 g of polytetrafluoroethylene powder was placed in a sodium naphthalene solution to completely immerse it, then stirred, the powder was repeatedly washed with tetrahydrofuran, filtered, and then placed in an oven to dry for 150 hours, after which it was ground and dispersed; (3) 250 g of alumina powder was placed in a high-speed mixer adjusted to a speed of 2000 rpm and a temperature of 70°C, and 5 g of the coupling agent KH550 was added dropwise to perform the coupling treatment; (4) 25,000 g of prepolymer was added to tank A of the injection molding machine, the temperature was controlled to 90°C, and the surface-treated ultra-high molecular weight polyethylene powder, polytetrafluoroethylene powder, and alumina powder were uniformly mixed to form the prepolymer, which was then stirred at a low speed of 700 rpm; (5) 3750g of chain extender was placed in tank B of the injection molding machine, the temperature was controlled to 115°C, and once the chain extender was completely dissolved, 250g of antioxidant was added and the mixture was stirred at a high speed of 1600rpm; (6) Clean the indentation in the mold, spray the mold with a release agent, and preheat the mold in an oven at 120°C; (7) The liquids in tanks A and B were mixed, the pressure was reduced, the temperature was controlled to 120°C, and the mixture was stirred at a high speed of 2500 rpm before being injected into the mold's cavity. (8) Place the mold in a 120°C oven for 16 hours, then remove it and demold it; (9) The demolded, unfinished products were mechanically processed to produce high-strength, self-lubricating polyurethane pistons.

[0056] Comparative Example 1 (1) 25,000 g of prepolymer was added to tank A of the injection molding machine, stirred at a low speed of 700 rpm, and the temperature was controlled to 90°C; (2) 3750g of chain extender was added to tank B of the injection molding machine, the temperature was controlled to 115°C, and once the chain extender was completely dissolved, it was stirred at a high speed of 1600 rpm; (3) Clean the indentations in the mold, spray a release agent evenly into the mold, and preheat the mold in an oven at 120°C; (4) The liquids in tank A and tank B were mixed, the pressure was reduced, the temperature was controlled to 120°C, and after stirring at a high speed of 2500 rpm, the liquid was injected into the depressions of the mold; (5) Place the mold in a 120°C oven for 16 hours, then remove it and demold it; (6) The demolded unfinished products were mechanically processed to produce high-strength, self-lubricating polyurethane pistons.

[0057] The mechanical performance, wear resistance, and service life of the concrete piston seal bodies prepared in Example 1, Example 2, and Comparative Example 1 were tested. The results are shown in Table 1.

[0058] [Table 2]

[0059] While specific embodiments of the present invention have been described in detail, those skilled in the art will understand that, in view of the entirety of the disclosed teachings, many modifications and variations can be made to the details, each of which falls within the scope of the protection of the present invention. The complete scope of the present invention is provided by the appended claims and any equivalent thereof.

Claims

1. A composition for producing a piston seal body, comprising the following components: 100 parts by weight of a polyurethane prepolymer, 10 to 20 parts by weight of a chain extender, 5 to 10 parts by weight of surface-silylated ultra-high molecular weight polyethylene powder, 1 to 1.5 parts by weight of an antioxidant, 1 to 2 parts by weight of surface-silylated alumina powder, and 1 to 3 parts by weight of molybdenum disulfide or sodium polytetrafluoroethylene powder.

2. The composition according to claim 1, wherein the polyurethane prepolymer is of the polyether type.

3. The polyurethane prepolymer has the following characteristics: (1) Free MDI content: less than 0.1 wt%; (2) Isocyanate (-NCO) content: 3.0% to 5.0%; (3) Viscosity: 120 to 500 cps The composition according to claim 1, having one or more of the above.

4. The aforementioned surface-silylated ultra-high molecular weight polyethylene powder is Step 1: The step of oxidizing the ultra-high molecular weight polyethylene powder, Step 2: The oxidized ultra-high molecular weight polyethylene powder is reacted with a silane coupling agent. The composition according to claim 1, which is prepared by a method comprising the following:

5. The composition according to claim 4, wherein the oxidation treatment in step 1 is carried out in a solution containing potassium permanganate and nitric acid.

6. The composition according to claim 5, wherein the solution is a mixed solution of saturated potassium permanganate aqueous solution and nitric acid aqueous solution.

7. The composition according to claim 4, wherein step 1 comprises adding the ultra-high molecular weight polyethylene powder to a solution containing potassium permanganate and nitric acid, heating and stirring, filtering the solution to obtain a powder, and then repeatedly washing the powder with deionized water, filtering it, and oven drying it.

8. The composition according to claim 4, wherein the weight of the silane coupling agent is 0.1% to 1% of the weight of the ultra-high molecular weight polyethylene powder.

9. The composition according to claim 1, wherein the polytetrafluoroethylene sodium powder is polytetrafluoroethylene powder treated with naphthalene sodium.

10. The aforementioned polytetrafluoroethylene powder is The steps include adding polytetrafluoroethylene powder to a sodium naphthalene treatment solution in which it is completely immersed, The step of stirring for 10 to 15 minutes, The filtering step, The composition according to claim 9, wherein the polytetrafluoroethylene sodium powder treated with the naphthalene sodium treatment solution is treated several times with tetrahydrofuran and deionized water until the odor of the naphthalene sodium treatment solution is gone.

11. The composition according to claim 10, wherein the naphthalene sodium treatment further comprises placing the polytetrafluoroethylene sodium powder in an oven for drying, then grinding and dispersing it.

12. The composition according to claim 1, wherein the surface-silylated alumina powder is prepared by a method comprising the step of reacting alumina powder with a silane coupling agent under stirring and heating conditions.

13. The composition according to claim 12, wherein the weight of the silane coupling agent is 1% to 5% of the weight of the alumina powder.

14. The following features: (1) The chain extender is an alcohol chain extender or an amine chain extender; (2) The surface-silylated ultra-high molecular weight polyethylene powder has a particle size of 30 to 50 μm; (3) The surface-silylated ultra-high molecular weight polyethylene powder has a molecular weight of 4,000,000 to 5,000,000; (4) The alumina powder has a particle size of 3,000 to 5,000 mesh; (5) The antioxidant is a hindered phenol antioxidant; (6) The polytetrafluoroethylene sodium powder has a particle size of 3 to 20 μm. The composition according to claim 1, having one or more of the above.

15. Use of the composition according to any one of claims 1 to 14 for manufacturing a piston seal body.

16. The use according to claim 15, wherein the piston seal body is a concrete piston seal body.

17. A piston seal body manufactured by injection molding the composition described in any one of claims 1 to 14.

18. The piston seal body according to claim 17, wherein the piston seal body is a concrete piston seal body.

19. The piston seal body has the following features: Tensile strength: ≥60 MPa; Elongation at break: ≥ 550%; Tear strength: ≧115kN / m; Shore hardness: 96-98HA; Akron wear: ≤0.025 cm³ A piston seal body according to claim 17, having one or more of the above.

20. A method for producing a piston seal body, comprising injection molding a composition according to any one of claims 1 to 14.

21. The method described above is: a) A step of weighing out parts by weight each of the polyurethane prepolymer, chain extender, surface silylated ultra-high molecular weight polyethylene powder, molybdenum disulfide or sodium polytetrafluoroethylene powder, surface silylated alumina powder, and antioxidant, b) The polyurethane prepolymer, the surface-silylated ultra-high molecular weight polyethylene powder, the molybdenum disulfide or the sodium polytetrafluoroethylene powder, and the surface-silylated alumina powder are introduced into tank A of the injection molding machine, mixed uniformly, and stirred at a low speed of 650 rpm to 950 rpm while controlling the temperature to 80 to 100°C. c) The chain extender is introduced into the tank B of the injection molding machine, the temperature is controlled to 110 to 120°C, and once the chain extender has completely dissolved, the antioxidant is added while stirring at a high speed of 1500 to 2500 rpm. d) The steps of cleaning the mold's depressions, spraying a release agent onto the mold, and preheating it in an oven at 110 to 130°C, e) Mixing the liquids in tanks A and B in a ratio controlled by the injection molding machine while reducing the pressure, stirring at a high speed of 2000 to 3500 rpm while maintaining the temperature at 100 to 120°C, and then injecting the liquid into the mold; f) The step of placing the mold in an oven to heat at 100 to 120°C for 16 to 20 hours, and after removing it, demolding the mold, g) The step of mechanically processing the demolded unfinished product to obtain the piston seal body. The method according to claim 20, including the method described in claim 20.

22. A piston comprising the piston seal body described in claim 17.

23. The piston according to claim 22, wherein the piston is a concrete piston.

24. A delivery cylinder comprising the piston described in Claim 22.

25. A concrete pump device comprising the delivery cylinder described in Claim 24.

26. The concrete pumping device according to claim 25, wherein it is a pump truck, a drag pump, or a truck-mounted pump.

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