Polyurethane shock pad with low dynamic and static stiffness ratio and preparation method thereof

Abstract

The invention discloses a low-dynamic-static-stiffness-ratio polyurethane shock pad and a preparation method thereof, and relates to the technical field of polyurethane elastomers. The invention discloses a polyurethane shock pad with a low dynamic-static stiffness ratio. The polyurethane shock pad is prepared by mixing a component A, a component B and a component C, the component A comprises modified polyether glycol, blocked polyfunctional isocyanate, a catalyst, a plasticizer and an anti-aging agent; the component B is prepared from blocked polyfunctional isocyanate, diphenylmethane diisocyanate, modified polyether glycol and melamine; and the component C is a mixture of graphene oxide and bis (aminopropyl) polydimethylsiloxane. The component B is pre-polymerized in advance, so that the molecular structure of polyurethane is regular, and the prepared shock pad has better mechanical strength; through modification of polyether glycol and introduction of organic silicon, the shock pad keeps good elasticity at low temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane elastomers, and specifically to a polyurethane damping pad with a low dynamic-static stiffness ratio and a preparation method thereof. Background Technique

[0002] In modern life, people's main means of travel are cars and high-speed rails. However, during the traveling process, vibrations generated by road conditions and component movements will affect the riding comfort and also interfere with the test results of precision instruments. To solve these problems, damping pads, as the most common damping tools, are widely used.

[0003] Polyurethane materials have the advantages of high elasticity, wear resistance, high strength, etc., and have a damping and shock-absorbing effect. They are commonly used materials for damping pads. Patent CN112457467A discloses a high-damping thermoplastic polyurethane elastomer and a preparation method thereof. The raw materials include polyester-based diol, isocyanate, chain extender, etc. The obtained polyurethane elastomer has good damping performance and a simple preparation process. However, the product is a thermoplastic product, and its performance will be affected under normal temperature or low temperature conditions, reducing the service life.

[0004] Therefore, we propose a polyurethane damping pad with a low dynamic-static stiffness ratio and a preparation method thereof to solve the problems raised in the above background technique. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyurethane damping pad with a low dynamic-static stiffness ratio and a preparation method thereof to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A polyurethane damping pad with a low dynamic-static stiffness ratio is prepared by mixing component A, component B, and component C in a mass ratio of 10:(5 - 10):(0.1 - 0.3);

[0007] Component A includes the following mass components: modified polyether diol: 80 - 90 parts, blocked polyfunctional isocyanate: 2 - 10 parts, catalyst: 0.2 - 1 part, plasticizer: 2 - 6 parts, anti-aging agent: 2 - 5.8 parts;

[0008] Component B includes the following mass components: blocked polyfunctional isocyanate: 25 - 45 parts, diphenylmethane diisocyanate: 5 - 15 parts, modified polyether diol: 25 - 35 parts, melamine: 15 - 25 parts;

[0009] Component C is a mixture of graphene oxide / diaminopropyl polydimethylsiloxane;

[0010] Furthermore, the modified polyether diol is obtained by the addition of hydrogen-containing organosilicon and polyether diol;

[0011] The closed polyfunctional isocyanate is prepared by reacting a modified polyether diol with hexamethylene diisocyanate and toluene diisocyanate, and then end-capping with pentaerythritol.

[0012] A method for preparing a polyurethane shock pad with a low dynamic-static stiffness ratio includes the following steps:

[0013] Step (1): Mix a modified polyether diol, a plasticizer, and a closed polyfunctional isocyanate, perform dehydration treatment, and after cooling to room temperature, add a catalyst and an anti-aging agent, and stir evenly to obtain Component A;

[0014] Step (2): Dehydrate the modified polyether diol, and after cooling to room temperature, mix it with a closed polyfunctional isocyanate and diphenylmethane diisocyanate, stir and react, and then add melamine to obtain Component B;

[0015] Step (3): Mix bis(aminopropyl)polydimethylsiloxane, graphene oxide, and tetrahydrofuran, stir evenly, and then add a condensing agent and stir evenly to obtain Component C;

[0016] Step (4): Preheat the mold to 35-45 °C, then mix Component A, Component B, and Component C, inject them into the mold, and cure to obtain a polyurethane shock pad with a low dynamic-static stiffness ratio.

[0017] Further, in step (1), the mass ratio of the modified polyether diol, the closed polyfunctional isocyanate, the catalyst, the plasticizer, and the anti-aging agent is (80-90):(2-10):(0.2-1):(2-6):(2-5.8);

[0018] In step (2), the mass ratio of the closed polyfunctional isocyanate, diphenylmethane diisocyanate, modified polyether diol, and melamine is (25-45):(5-15):(25-35):(15-25);

[0019] In step (3), the ratio of bis(aminopropyl)polydimethylsiloxane to tetrahydrofuran is (0.5-1) g:(1-3) mL;

[0020] The molar ratio of bis(aminopropyl)polydimethylsiloxane to the condensing agent is 1:(10-60);

[0021] The mass ratio of bis(aminopropyl)polydimethylsiloxane to graphene oxide is 10:(0.01-0.5);

[0022] In step (4), the mass ratio of Component A, Component B, and Component C is 10:(5-10):(0.1-0.3).

[0023] Further, in steps (1) and (2), the process conditions for dehydration treatment are as follows: temperature 110 - 120°C, pressure 0.098 - 0.12 MPa, and time 1 - 2 h.

[0024] Further, in step (4), the process conditions for curing are as follows: temperature 20 - 60°C, and time 2 - 20 h.

[0025] Further, in step (1), the plasticizer is one or a mixture of more than one of dioctyl terephthalate, bis(isononyl) 1,2 - cyclohexanedicarboxylate, tributyl acetylcitrate, and trioctyl trimellitate;

[0026] The catalyst is one or a mixture of more than one of tetramethylethylenediamine, triethylenediamine, lead isooctanoate, and dibutyltin dilaurate;

[0027] The anti - aging agent is one or a mixture of two of UV - 531 and UV - 01.

[0028] Further, in step (3), the condensing agent is a mixture of 1-(3 - dimethylaminopropyl)-3 - ethylcarbodiimide and N - hydroxysuccinimide, and the molar ratio is 1:1.

[0029] In the above - mentioned technical solution, by pre - polymerizing component B in advance, part of the heat is released. When curing is carried out later, the heat release is relatively gentle, making the polyurethane molecular structure regular, and the prepared shock - absorbing pad has better mechanical strength; using blocked polyfunctional isocyanate in component B increases the chemical cross - linking points, making the cross - linked polyurethane have a stronger hard - segment structure and a longer hard - segment relaxation time, thereby reducing the loss and lowering the dynamic - static stiffness ratio of polyurethane. Moreover, the blocked polyfunctional isocyanate and diphenylmethane diisocyanate act synergistically to further reduce the dynamic - static stiffness ratio.

[0030] Further, the blocked polyfunctional isocyanate is prepared by the following process:

[0031] S1: Dehydrate the modified polyether diol, and after cooling to room temperature, add hexamethylene diisocyanate, toluene diisocyanate, and dibutyltin dilaurate, heat up for reaction, and then cool down to 30 - 50°C to obtain an isocyanate prepolymer;

[0032] S2: Mix the isocyanate prepolymer, toluene, and dibutyltin dilaurate, stir evenly, and then dropwise add a mixed solution of pentaerythritol and toluene, and stir evenly to obtain the blocked polyfunctional isocyanate.

[0033] Further, in step S1, the molar ratio of the modified polyether diol, hexamethylene diisocyanate, and toluene diisocyanate is 0.8:(1.5 - 2.2):(1.3 - 1.9);

[0034] The mass ratio of the modified polyether diol to dibutyltin dilaurate is 1:(0.05 - 0.1).

[0035] Furthermore, in step S2, the mass ratio of the isocyanate prepolymer, toluene and dibutyltin dilaurate is 1:(2 - 4):(0.05 - 0.1);

[0036] The mass ratio of the isocyanate prepolymer to the mixed solution is 1:(5 - 9);

[0037] The mass ratio of pentaerythritol to toluene is (2 - 4):(3 - 5).

[0038] Furthermore, in step S1, the process conditions for the dehydration treatment are: temperature 110 - 120°C, pressure 0.098 - 0.12 MPa, time 1 - 2 h;

[0039] In step S1, the process conditions for the temperature - rising reaction are: temperature 70 - 80°C, time 3 - 4 h.

[0040] Furthermore, the dropping rate of the mixed solution is 5 - 10 drops / min.

[0041] In the above - mentioned technical solution, by modifying the modified polyether diol in component A and introducing silicone, the silicone can still rotate freely at low temperatures, having good low - temperature resistance, and enhancing the low - temperature resistance of the shock - absorbing pad; at the same time, using the blocked polyfunctional isocyanate as a cross - linker, when reacting with the modified polyether diol, it expands outwards to form small and evenly distributed micropores; since the polyfunctional isocyanate has strong reaction activity and is very easy to react with other substances containing active hydrogen, in order to improve stability, pentaerythritol is used to block it; and the remaining pentaerythritol can undergo an esterification reaction with melamine at high temperatures to form a non - flammable three - dimensional spatial structure, increasing the flame - retardant property of the material to a certain extent.

[0042] In component C, the amino group of the diaminopropyl polydimethylsiloxane reacts with the carboxyl group in graphene oxide to generate an amide bond, and then a condensing agent promotes the condensation reaction. The ammonia gas generated during the condensation reaction enables the polyurethane elastomer to form a porous structure. Acting synergistically with the blocked polyfunctional isocyanate, it can improve the pore density and structure, making their distribution more uniform, enhancing the elasticity and toughness of the polyurethane elastomer, thereby reducing the dynamic - to - static stiffness ratio; and graphene oxide can form a block copolymer with polyurethane, enhancing the mechanical strength of the shock - absorbing pad and extending its service life.

[0043] Furthermore, the modified polyether diol is prepared by the following process:

[0044] Allyl glycidyl ether, ethylene glycol and propylene oxide are mixed to obtain a mixture, and then sodium methoxide is added. Under the protection of a nitrogen atmosphere, a heating reaction is carried out to obtain a polyether diol containing allyl; the polyether diol containing allyl is mixed with polymethylhydrogensiloxane, and then chloroplatinic acid is added. Under the protection of a nitrogen atmosphere, a heating reaction is carried out to obtain a modified polyether diol.

[0045] Further, the molar ratio of allyl glycidyl ether, ethylene glycol and propylene oxide is (1 - 3):1:(2 - 6);

[0046] The mass ratio of the mixture to sodium methoxide is 10:(0.015 - 0.025);

[0047] The molar ratio of allyl glycidyl ether to polymethylhydrogensiloxane is (0.5 - 1.5):1;

[0048] The mass ratio of allyl glycidyl ether to chloroplatinic acid is 1:(3×10 -6 ~5×10 -6 ).

[0049] Further, the process conditions for the first heating reaction are: temperature 100 - 120 °C, pressure 200 - 400 kPa.

[0050] Further, the process conditions for the second heating reaction are: temperature 100 - 120 °C, pressure 100 - 500 kPa.

[0051] Compared with the prior art, the beneficial effects of the present invention are:

[0052] 1. By pre - polymerizing the B component in advance, part of the heat is released. When curing, the heat release is relatively gentle, making the polyurethane molecular structure regular, and the damping pad prepared has good mechanical strength; a blocked polyfunctional isocyanate is used in the B component to increase chemical cross - linking points, making the cross - linked polyurethane have a stronger hard - segment structure and a longer hard - segment relaxation time, thereby reducing losses and lowering the dynamic - static stiffness ratio of polyurethane. Moreover, the synergistic effect of the blocked polyfunctional isocyanate and diphenylmethane diisocyanate further reduces the dynamic - static stiffness ratio.

[0053] 2. By modifying the modified polyether diol in Component A and introducing silicone, the silicone can still rotate freely at low temperatures, having good low-temperature resistance and enhancing the low-temperature resistance of the shock pad. At the same time, using blocked polyfunctional isocyanate as a crosslinking agent, when reacting with the modified polyether diol, it expands outwards to form fine and evenly distributed micropores. Since the polyfunctional isocyanate has strong reactivity and easily reacts with other substances containing active hydrogen, in order to improve its stability, pentaerythritol is used to block it. And the remaining pentaerythritol can undergo an esterification reaction with melamine at high temperatures to form a non-flammable three-dimensional spatial structure, increasing the flame retardancy of the material to a certain extent.

[0054] 3. In Component C, the amino group of diaminopropyl polydimethylsiloxane reacts with the carboxyl group in graphene oxide to form an amide bond. Then, a condensing agent is used to promote the condensation reaction. The ammonia gas generated during the condensation reaction enables the polyurethane elastomer to form a porous structure. Acting synergistically with the blocked polyfunctional isocyanate, it can improve the pore density and structure, making their distribution more uniform, enhancing the elasticity and toughness of the polyurethane elastomer, and thus reducing the dynamic-static stiffness ratio. And graphene oxide can form a block copolymer with polyurethane, which can enhance the mechanical strength of the shock pad and extend its service life. Specific Embodiments

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] In the following specific embodiments,

[0057] The plasticizer is dioctyl terephthalate, CAS No. 6422-86-2, sourced from Jinan Kaichuang Chemical Co., Ltd.

[0058] The catalyst is tetramethylethylenediamine, CAS No. 110-18-9, sourced from Jinan Hongwang Chemical Co., Ltd.

[0059] The anti-aging agent is UV-531, CAS No. 1843-05-6, sourced from Dongguan Xingyuan Chemical Co., Ltd.

[0060] Diphenylmethane diisocyanate, CAS No. 101-68-8, sourced from Shandong Yinglang Chemical Co., Ltd.

[0061] Diaminopropyl polydimethylsiloxane, CAS No. 106214-84-0, sourced from Jining Tangyi Chemical Co., Ltd.

[0062] Graphene oxide, 2000 mesh, sourced from Bohan Mineral Products Co., Ltd., Lingshou County;

[0063] Allyl glycidyl ether, CAS No. 106 - 92 - 3, sourced from Wuhan Jiyesheng Chemical Co., Ltd.;

[0064] Ethylene glycol, CAS No. 107 - 21 - 1, sourced from Jinan Kaijun Chemical Co., Ltd.;

[0065] Propylene oxide, CAS No. 75 - 56 - 9, sourced from Shandong Rongsheng New Materials Co., Ltd.;

[0066] Sodium methoxide, CAS No. 124 - 41 - 4, sourced from Shandong Yuanjin New Materials;

[0067] Polymethylhydrosiloxane, CAS No. 63148 - 57 - 2, sourced from Jiangsu Runfeng Synthetic Technology Co., Ltd.;

[0068] Tetrahydrofuran, CAS No. 109 - 99 - 9, sourced from Shandong Jinhe Chemical Co., Ltd.;

[0069] Chloroplatinic acid, CAS No. 16941 - 12 - 1, sourced from Shandong Shengcang Chemical Technology Co., Ltd.;

[0070] Hexamethylene diisocyanate, CAS No. 822 - 06 - 0, sourced from Wuhan Jixin Yibang Biotechnology Co., Ltd.;

[0071] Toluene diisocyanate, CAS No. 26471 - 62 - 5, sourced from Jiangsu Bost Chemical Technology Co., Ltd.;

[0072] Dibutyltin dilaurate, CAS No. 77 - 58 - 7, sourced from Jinan Jingyu Chemical Co., Ltd.;

[0073] Toluene, CAS No. 108 - 88 - 3, sourced from Merck reagent;

[0074] Pentaerythritol, CAS No. 115 - 77 - 5, sourced from Merck reagent;

[0075] Prepare a condensing agent: Mix 1-(3 - dimethylaminopropyl)-3 - ethylcarbodiimide and N - hydroxysuccinimide in a molar ratio of 1:1 to obtain the condensing agent;

[0076] 1-(3 - dimethylaminopropyl)-3 - ethylcarbodiimide, CAS No. 1892 - 57 - 5, sourced from Henan Wokasi Biotechnology Co., Ltd.;

[0077] N - hydroxysuccinimide, CAS No. 6066 - 82 - 6, sourced from Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0078] Example 1: A preparation method of a polyurethane shock pad with a low dynamic-static stiffness ratio, comprising the following steps:

[0079] (1) Preparation of modified polyether diol:

[0080] Mix allyl glycidyl ether, ethylene glycol, and propylene oxide in a molar ratio of 3:1:6 to obtain a mixture. Then add sodium methoxide and heat the reaction under a nitrogen atmosphere to obtain a polyether diol containing allyl groups. Mix the polyether diol containing allyl groups with polymethylhydrosiloxane, and then add chloroplatinic acid and heat the reaction under a nitrogen atmosphere to obtain a modified polyether diol. The mass ratio of the mixture to sodium methoxide is 10:0.025; the molar ratio of allyl glycidyl ether to polymethylhydrosiloxane is 1.5:1; the mass ratio of allyl glycidyl ether to chloroplatinic acid is 1:5×10 -6 ; The process conditions for the first heating reaction are: temperature 120 °C, pressure 400 kPa; the process conditions for the second heating reaction are: temperature 120 °C, pressure 500 kPa;

[0081] (2) Preparation of blocked polyfunctional isocyanate:

[0082] S1: Dehydrate the modified polyether diol, cool it to room temperature, then add hexamethylene diisocyanate, toluene diisocyanate, and dibutyltin dilaurate, and raise the temperature to 80 °C for reaction for 4 h, and then cool it to 50 °C to obtain an isocyanate prepolymer; S2: Mix the isocyanate prepolymer, toluene, and dibutyltin dilaurate, stir evenly, and then dropwise add a mixed solution of pentaerythritol and toluene at a rate of 10 drops / min, and stir evenly to obtain a blocked polyfunctional isocyanate; in step S1, the molar ratio of the modified polyether diol, hexamethylene diisocyanate, and toluene diisocyanate is 0.8:2.2:1.9; the mass ratio of the modified polyether diol to dibutyltin dilaurate is 1:0.1; in step S2, the mass ratio of the isocyanate prepolymer, toluene, and dibutyltin dilaurate is 1:4:0.1; the mass ratio of the isocyanate prepolymer to the mixed solution is 1:9; the mass ratio of pentaerythritol to toluene is 4:5; in step S1, the process conditions for dehydration treatment are: temperature 120 °C, pressure 0.12 MPa, time 2 h;

[0083] (3) Preparation of polyurethane shock pad:

[0084] Step (1): Mix the modified polyether diol, plasticizer, and blocked polyfunctional isocyanate, conduct dehydration treatment, and after cooling to room temperature, add a catalyst and an anti-aging agent, and stir evenly to obtain Component A; Step (2): Conduct dehydration treatment on the modified polyether diol, and after cooling to room temperature, mix it with the blocked polyfunctional isocyanate and diphenylmethane diisocyanate, stir and react, and then add melamine to obtain Component B; Step (3): Mix bis(aminopropyl)polydimethylsiloxane, graphene oxide, and tetrahydrofuran, stir evenly, and then add a condensing agent and stir evenly to obtain Component C; Step (4): Preheat the mold to 45°C, then mix Component A, Component B, and Component C in a mass ratio of 10:10:0.3, inject them into the mold, and cure to obtain a polyurethane shock-absorbing pad with a low dynamic-to-static stiffness ratio; In Step (1), the mass ratio of the modified polyether diol, blocked polyfunctional isocyanate, catalyst, plasticizer, and anti-aging agent is 90:2:0.2:2:5.8; In Step (2), the mass ratio of the blocked polyfunctional isocyanate, diphenylmethane diisocyanate, modified polyether diol, and melamine is 45:5:25:25; In Step (3), the ratio of bis(aminopropyl)polydimethylsiloxane to tetrahydrofuran is 1 g:3 mL; the molar ratio of bis(aminopropyl)polydimethylsiloxane to the condensing agent is 1:60; the mass ratio of bis(aminopropyl)polydimethylsiloxane to graphene oxide is 10:0.5; In Steps (1) and (2), the process conditions for dehydration treatment are: temperature 120°C, pressure 0.12 MPa, time 2 h; the process conditions for curing are: temperature 60°C, time 20 h.

[0085] Example 2: A preparation method of a polyurethane shock-absorbing pad with a low dynamic-to-static stiffness ratio, comprising the following steps:

[0086] (1) Preparation of the modified polyether diol:

[0087] Mix allyl glycidyl ether, ethylene glycol, and propylene oxide in a molar ratio of 2:1:4 to obtain a mixture, then add sodium methoxide, and under the protection of a nitrogen atmosphere, heat and react to obtain a polyether diol containing allyl; Mix the polyether diol containing allyl with polymethylhydrosiloxane, and then add chloroplatinic acid, and under the protection of a nitrogen atmosphere, heat and react to obtain the modified polyether diol; The mass ratio of the mixture to sodium methoxide is 10:0.010; the molar ratio of allyl glycidyl ether to polymethylhydrosiloxane is 1.0:1; the mass ratio of allyl glycidyl ether to chloroplatinic acid is 1:4×10 -6 ; The process conditions for the first heating reaction are: temperature 110°C, pressure 300 kPa; the process conditions for the second heating reaction are: temperature 110°C, pressure 300 kPa;

[0088] (2) Preparation of the blocked polyfunctional isocyanate:

[0089] S1: Dehydrate the modified polyether diol. After cooling to room temperature, add hexamethylene diisocyanate, toluene diisocyanate and dibutyltin dilaurate, heat up to 75 °C and react for 3.5 h, then cool down to 40 °C to obtain an isocyanate prepolymer; S2: Mix the isocyanate prepolymer, toluene and dibutyltin dilaurate, stir evenly, and then dropwise add a mixed solution of pentaerythritol and toluene at a rate of 7 drops / min, stir evenly to obtain a blocked polyfunctional isocyanate; In step S1, the molar ratio of the modified polyether diol, hexamethylene diisocyanate and toluene diisocyanate is 0.8:1.9:1.6; the mass ratio of the modified polyether diol and dibutyltin dilaurate is 1:0.08; In step S2, the mass ratio of the isocyanate prepolymer, toluene and dibutyltin dilaurate is 1:3:0.08; the mass ratio of the isocyanate prepolymer and the mixed solution is 1:7; the mass ratio of pentaerythritol and toluene is 3:4; In step S1, the process conditions for dehydration treatment are: temperature 115 °C, pressure 0.010 MPa, time 1.5 h;

[0090] (3) Preparation of polyurethane shock pad:

[0091] Step (1): Mix the modified polyether diol, plasticizer and blocked polyfunctional isocyanate, dehydrate, and after cooling to room temperature, add a catalyst and an anti-aging agent, stir evenly to obtain component A; Step (2): Dehydrate the modified polyether diol, and after cooling to room temperature, mix it with the blocked polyfunctional isocyanate and diphenylmethane diisocyanate, stir and react, and then add melamine to obtain component B; Step (3): Mix bis(aminopropyl)polydimethylsiloxane, graphene oxide and tetrahydrofuran, stir evenly, and then add a condensing agent, stir evenly to obtain component C; Step (4): Preheat the mold to 40 °C, and then mix component A, component B and component C in a mass ratio of 10:7:0.2, inject into the mold, and cure to obtain a polyurethane shock pad with a low dynamic-static stiffness ratio; In step (1), the mass ratio of the modified polyether diol, blocked polyfunctional isocyanate, catalyst, plasticizer and anti-aging agent is 85:6:0.6:4:4.4; In step (2), the mass ratio of the blocked polyfunctional isocyanate, diphenylmethane diisocyanate, modified polyether diol and melamine is 35:10:35:20; In step (3), the ratio of bis(aminopropyl)polydimethylsiloxane and tetrahydrofuran is 0.7 g:2 mL; the molar ratio of bis(aminopropyl)polydimethylsiloxane and the condensing agent is 1:35; the mass ratio of bis(aminopropyl)polydimethylsiloxane and graphene oxide is 10:0.3; In steps (1) and (2), the process conditions for dehydration treatment are: temperature 115 °C, pressure 0.010 MPa, time 1.5 h; the process conditions for curing are: temperature 40 °C, time 12 h.

[0092] Example 3: A preparation method of a polyurethane shock pad with a low dynamic-static stiffness ratio, comprising the following steps:

[0093] (1) Preparation of modified polyether diol:

[0094] Allyl glycidyl ether, ethylene glycol and propylene oxide are mixed in a molar ratio of 1:1:2 to obtain a mixture, and then sodium methoxide is added. Under the protection of a nitrogen atmosphere, heating reaction is carried out to obtain a polyether diol containing allyl; the polyether diol containing allyl is mixed with polymethylhydrogensiloxane, and then chloroplatinic acid is added. Under the protection of a nitrogen atmosphere, heating reaction is carried out to obtain a modified polyether diol; the mass ratio of the mixture to sodium methoxide is 10:0.015; the molar ratio of allyl glycidyl ether to polymethylhydrogensiloxane is 0.5:1; the mass ratio of allyl glycidyl ether to chloroplatinic acid is 1:3×10 -6 ; The process conditions for the first heating reaction are: temperature 100°C, pressure 200 kPa; the process conditions for the second heating reaction are: temperature 100°C, pressure 100 kPa;

[0095] (2) Preparation of blocked polyfunctional isocyanate:

[0096] S1: The modified polyether diol is dehydrated, cooled to room temperature, and then hexamethylene diisocyanate, toluene diisocyanate and dibutyltin dilaurate are added, and the temperature is raised to 70°C for reaction for 3 h, and then cooled to 30°C to obtain an isocyanate prepolymer; S2: The isocyanate prepolymer, toluene and dibutyltin dilaurate are mixed and stirred evenly, and then a mixed solution of pentaerythritol and toluene is added dropwise at a rate of 5 drops / min, and stirred evenly to obtain a blocked polyfunctional isocyanate; in step S1, the molar ratio of the modified polyether diol, hexamethylene diisocyanate and toluene diisocyanate is 0.8:1.5:1.3; the mass ratio of the modified polyether diol to dibutyltin dilaurate is 1:0.05; in step S2, the mass ratio of the isocyanate prepolymer, toluene and dibutyltin dilaurate is 1:2:0.05; the mass ratio of the isocyanate prepolymer to the mixed solution is 1:5; the mass ratio of pentaerythritol to toluene is 2:3; in step S1, the process conditions for dehydration treatment are: temperature 110°C, pressure 0.098 MPa, time 1 h;

[0097] (3) Preparation of polyurethane shock pad:

[0098] Step (1): Mix the modified polyether diol, plasticizer and blocked polyfunctional isocyanate, conduct dehydration treatment, and after cooling to room temperature, add a catalyst and an anti-aging agent, and stir evenly to obtain Component A; Step (2): Conduct dehydration treatment on the modified polyether diol, and after cooling to room temperature, mix it with the blocked polyfunctional isocyanate and diphenylmethane diisocyanate, stir and react, and then add melamine to obtain Component B; Step (3): Mix bis(aminopropyl)polydimethylsiloxane, graphene oxide and tetrahydrofuran, stir evenly, and then add a condensing agent and stir evenly to obtain Component C; Step (4): Preheat the mold to 35°C, and then mix Component A, Component B and Component C in a mass ratio of 10:5:0.1, inject them into the mold, and cure to obtain a polyurethane shock pad with a low dynamic-to-static stiffness ratio; In Step (1), the mass ratio of the modified polyether diol, blocked polyfunctional isocyanate, catalyst, plasticizer and anti-aging agent is 80:10:1:6:3; In Step (2), the mass ratio of the blocked polyfunctional isocyanate, diphenylmethane diisocyanate, modified polyether diol and melamine is 25:15:35:25; In Step (3), the ratio of bis(aminopropyl)polydimethylsiloxane to tetrahydrofuran is 0.5 g:1 mL; The molar ratio of bis(aminopropyl)polydimethylsiloxane to the condensing agent is 1:10; The mass ratio of bis(aminopropyl)polydimethylsiloxane to graphene oxide is 10:0.01; In Steps (1) and (2), the process conditions for dehydration treatment are: temperature 110°C, pressure 0.098 MPa, time 1 h; The process conditions for curing are: temperature 20°C, time 2 h.

[0099] Comparative Example 1: Taking Example 1 as a comparison, the polyether diol is not modified, and the other conditions remain unchanged.

[0100] Comparative Example 2: Taking Example 1 as a comparison, Component C is not added during preparation, and the other conditions remain unchanged.

[0101] Comparative Example 3: Taking Example 1 as a comparison, the blocked polyfunctional isocyanate is replaced with diphenylmethane diisocyanate, and the other conditions remain unchanged.

[0102] Comparative Example 4: Taking Example 1 as a comparison, the polyether diol is not modified and Component C is not added at the same time, and the other conditions remain unchanged.

[0103] Experiment: Take the polyurethane shock pads obtained in Examples 1 to 3 and Comparative Examples 1 to 4, and test their various performances;

[0104] Dynamic-to-static stiffness ratio: The static stiffness is detected according to the method in Appendix A of TB3395.1, the dynamic stiffness is detected according to the method in Appendix B of TB3395.1, and the dynamic-to-static stiffness ratio = dynamic stiffness / static stiffness;

[0105] Tensile strength: Detected with reference to the method of GB / T10654-2001.

[0106] Cold resistance test: Place it in an environment of -20°C and test its dynamic-static stiffness ratio;

[0107] The following table shows the dynamic-static stiffness ratio, tensile strength, and cold resistance test data of the polyurethane shock pads

[0108] Dynamic and static stiffness ratio Tensile strength / MPa Dynamic and static stiffness ratio at low temperature Example 1 1.15 4.4 1.22 Example 2 1.19 4.0 1.27 Example 3 1.24 3.7 1.32 Comparative example 1 1.16 4.2 1.40 Comparative example 2 1.27 3.4 1.36 Comparative example 3 1.32 3.0 1.41 Comparative example 4 1.36 2.8 1.45

[0109] Based on the data in the above table, the following conclusions can be clearly obtained:

[0110] The polyurethane shock pads obtained in Examples 1 to 3 are compared with the polyurethane shock pads obtained in Comparative Examples 1 to 4. The test results show that

[0111] Compared with Example 1, in Comparative Example 1, the polyether diol is not modified, and the dynamic-static stiffness ratio of the shock pad increases significantly at low temperatures. The reason is that the Si-O bond can still rotate freely at low temperatures, having good low-temperature resistance, which can effectively enhance the low-temperature resistance of the shock pad, so that the change in the dynamic-static stiffness ratio at low temperatures is smaller than that at room temperature;

[0112] Compared with Example 1, in Comparative Example 2, component C is not added during preparation. The tensile strength of the shock pad decreases significantly, and the dynamic-static stiffness ratio also increases. The reason is that the amino group of the diaminopropyl polydimethylsiloxane undergoes a condensation reaction with graphene oxide, and the generated ammonia gas can make the polyurethane elastomer form a porous structure, which synergistically acts with the blocked polyfunctional isocyanate to improve the pore density and structure, making its distribution more uniform, enhancing the elasticity and toughness of the polyurethane elastomer, and thus reducing the dynamic-static stiffness ratio; and graphene oxide can form a block copolymer with polyurethane, which can enhance the mechanical strength of the shock pad;

[0113] Compared with Example 1, in Comparative Example 4, the blocked polyfunctional isocyanate is replaced by diphenylmethane diisocyanate, and its dynamic-static stiffness ratio increases. The reason is that the polyfunctional isocyanate can increase the crosslinking points, making the crosslinked polyurethane have a stronger hard segment structure and a longer hard segment relaxation time, reducing the dynamic-static stiffness ratio of the polyurethane;

[0114] Compared with Example 1, in Comparative Example 4, neither the polyether diol is modified nor component C is added. The dynamic-static stiffness ratios at both room temperature and low temperature increase significantly, and the tensile strength also decreases. This shows that the preparation process of the shock pad and the setting of its used components in the present invention can reduce its dynamic-static stiffness ratio and enhance its mechanical properties at the same time.

[0115] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A polyurethane shock-absorbing pad with low dynamic-static stiffness ratio, characterized in that: The component A, the component B and the component C are mixed in a mass ratio of 10: (5-10): (0.1-0.3); The component A comprises the following components by weight: 80-90 parts of modified polyether diol, 2-10 parts of blocked multifunctional isocyanate, 0.2-1 parts of catalyst, 2-6 parts of plasticizer, and 2-5.8 parts of anti-aging agent; The B component includes the following components by weight: 25-45 parts of blocked multifunctional isocyanate, 5-15 parts of diphenylmethane diisocyanate, 25-35 parts of modified polyether diol, and 15-25 parts of melamine; The C component is a graphene oxide / bisaminopropyl polydimethylsiloxane mixture; The modified polyether diol is obtained by adding hydrogen-containing organic silicon to polyether diol.

2. The low dynamic-static stiffness ratio polyurethane shock-absorbing pad according to claim 1, characterized in that: The blocked multifunctional isocyanate is prepared by reacting modified polyether diol with hexamethylene diisocyanate and toluene diisocyanate, and then blocking with pentaerythritol.

3. A method for preparing a polyurethane shock-absorbing pad with a low dynamic-static stiffness ratio, characterized in that: The following steps are involved: Step (1): mixing a modified polyether diol, a plasticizer and a blocked multifunctional isocyanate, dehydrating the mixture, cooling the mixture to room temperature, adding a catalyst and an anti-aging agent, and stirring the mixture to obtain component A; Step (2): dehydrating the modified polyether diol, cooling it to room temperature, mixing it with blocked multifunctional isocyanate and diphenylmethane diisocyanate, stirring for reaction, and then adding melamine to obtain component B; Step (3): mixing bisaminopropyl polydimethylsiloxane, graphene oxide and tetrahydrofuran, stirring evenly, then adding a condensing agent, stirring evenly, to obtain component C; Step (4): preheat the mold to 35-45° C., then mix component A, component B and component C, inject them into the mold, and solidify them to obtain a polyurethane shock-absorbing pad with a low dynamic-static stiffness ratio.

4. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 3, characterized in that: The blocked multifunctional isocyanate is prepared by the following process: S1: Dehydrating the modified polyether diol, cooling it to room temperature, adding hexamethylene diisocyanate, toluene diisocyanate and dibutyltin dilaurate, heating it for reaction, and then cooling it to 30-50° C. to obtain an isocyanate prepolymer; S2: Mix the isocyanate prepolymer, toluene and dibutyltin dilaurate, stir evenly, then dropwise add a mixed solution of pentaerythritol and toluene, stir evenly, and obtain a blocked multifunctional isocyanate.

5. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 3, characterized in that: The preparation process of the modified polyether diol is as follows: Allyl glycidyl ether, ethylene glycol and propylene oxide are mixed to obtain a mixture, sodium methoxide is added, and the mixture is heated to react under the protection of a nitrogen atmosphere to obtain a polyether diol containing an allyl group; the polyether diol containing an allyl group is mixed with polymethyl hydrogen siloxane, chloroplatinic acid is added, and the mixture is heated to react under the protection of a nitrogen atmosphere to obtain a modified polyether diol.

6. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 4, characterized in that: In step S1, the molar ratio of modified polyether diol, hexamethylene diisocyanate and toluene diisocyanate is 0.8:(1.5-2.2):(1.3-1.9); The mass ratio of the modified polyether diol to dibutyltin dilaurate is 1:(0.05-0.1).

7. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 4, characterized in that: In step S2, the mass ratio of isocyanate prepolymer, toluene and dibutyltin dilaurate is 1:(2-4):(0.05-0.1); The mass ratio of the isocyanate prepolymer to the mixed solution is 1:(5-9); The mass ratio of pentaerythritol to toluene is (2-4):(3-5).

8. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 3, characterized in that: In step (4), the curing process conditions are: temperature 20-60° C., time 2-20 h.

9. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 3, characterized in that: In step (1) and step (2), the process conditions for the dehydration treatment are: temperature 110-120° C., pressure 0.098-0.12 MPa, and time 1-2 h.

10. The method for preparing a polyurethane shock-absorbing pad with low dynamic-static stiffness ratio according to claim 3, characterized in that: In step (3), the ratio of bisaminopropyl polydimethylsiloxane to tetrahydrofuran is (0.5-1) g: (1-3) mL; The molar ratio of bisaminopropyl polydimethylsiloxane to the condensing agent is 1:(10-60); The mass ratio of bisaminopropyl polydimethylsiloxane to graphene oxide is 10:(0.01-0.5).