Water-swellable polyurethane elastomer and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane elastomer production, in particular to a water-swelling polyurethane elastomer and a preparation method thereof. The water-swelling polyurethane elastomer is prepared from a component A and a component B in a mass ratio of 100: (4-30) through reaction, wherein the component A is a prepolymer obtained by reaction of polyether polyol X and isocyanate, the functionality is 2.5-4, and the-NCO content is 3-5wt.%; and the component B is a curing agent component. The high-molecular-weight high-activity polyether polyol with the functionality of 2.5-4 is adopted as a raw material, the polyether polyol is low in potassium ion content, the polymerization reaction activity is moderate during prepolymer synthesis, the operation tolerance is high, production is convenient, and the defects that a traditional water-swelling polyurethane elastomer uses polyethylene glycol with the high potassium ion content as the raw material, and the production cost is low are overcome. And when the prepolymer is synthesized, the gel can be easily polymerized in a kettle.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane elastomer production, in particular to a water-swellable polyurethane elastomer and a preparation method thereof. Background Art

[0002] Water-swelling elastomer is an elastomer with the dual functions of elastic sealing and water swelling. It is a new type of functional polymer material. It has the performance of rapid water absorption while maintaining the high elasticity of rubber. It is mainly used in water-stopping materials, sealing materials, waterproof projects such as above-ground buildings and underground pipelines in civil engineering. The water absorption mechanism is to use the large number of hydrogen bonds inherent in the polyurethane material itself to physically adsorb water. The polyether molecules in the elastomer are connected to the hard segment through chemical cross-linking. After being soaked in water, they will not precipitate. Even if they are soaked in flowing water for a long time or repeatedly, their expansion rate and mass loss can remain basically unchanged. After the elastomer is dried, the overall structure of the material does not change much, and it has good reusability. As a static compression material used for a long time, the chemical chain structure is relatively stable and the mechanical properties retention rate is good.

[0003] Generally, water-swellable polyurethane elastomers are prepared by reacting difunctional polyethylene glycol, polypropylene glycol with isocyanate, adding chain extenders, crosslinkers, and catalysts. They have relatively low hardness, low tensile strength, elongation at break of 400-1000%, and water swelling rate of about 300%. The molecular weight of polyethylene glycol is generally around 4000. To further improve the performance of the elastomer, different crosslinkers, fillers, resins, plasticizers, hydrolysis stabilizers, etc. need to be added during the synthesis of the prepolymer or during the chain extension process. The viscosity is high during operation and it is inconvenient to use. In addition, there is no potassium removal step in conventional products, and the potassium ion content of the product is high. When synthesizing the prepolymer, it is very easy to cause gelling due to excessive activity. Therefore, it has great limitations in the field of prepolymer synthesis.

[0004] Chinese patent CN 116535629 A discloses a water-swelling elastomer and a preparation method thereof, wherein a polyester-type water-swelling elastomer is synthesized using polyacids and / or anhydrides, polyols and a crosslinking agent, and a specially synthesized crosslinking agent, trimethylolpropane trimalate and trimethylolpropane triitaconate, is used to increase the degree of crosslinking. The process is complicated, and the ester group in the polyester is easily hydrolyzed. Although the obtained elastomer has a high tensile strength, the water swelling rate is less than 400%.

[0005] Chinese patent CN 110527058 A discloses a method for synthesizing a water-swellable material. Liquid rubber, bentonite, antioxidant, white carbon black, chain extender and hydrophilic chain extender are added to a special prepolymer before vulcanization. The tensile strength is less than 15 MPa, the hardness is less than Shore A55, and the mass loss rate before and after water absorption is not disclosed. The added liquid rubber has poor compatibility, little chemical crosslinking, and poor stability. When the material absorbs water and expands or the material structure changes due to temperature, it is easy to cause changes in physical properties and material precipitation.

[0006] Chinese patent CN 115651594 A discloses a fast-curing two-component polyurethane water-swellable sealant and a preparation method thereof, wherein a first polyether polyol, a chain extender and a catalyst are mixed as a curing agent component, a water scavenger and a tackifier are added as component A, a second polyether polyol, an antioxidant, an isocyanate and a second epoxy resin are mixed and reacted as component B, and components A and B are stirred and mixed at room temperature to obtain an elastomer. The method adjusts the material's adhesion, mechanical properties and water-swelling properties by adding an appropriate amount of epoxy resin. The elastomer obtained has a high water-swelling ratio, but its hardness is lower than that of traditional water-swelling polyurethane elastomers, generally less than Shore A50. Summary of the invention

[0007] In view of the above deficiencies in the prior art, the object of the present invention is to provide a water-swellable polyurethane elastomer, which overcomes the problems of low hardness, low mechanical properties and low water absorption performance of water-swellable polyurethane elastomer prepared from traditional polyethers, and improves the mechanical properties of the elastomer from the main raw material end through the reasonable design of the main polyether structure and formulation process, and an elastomer with a high water absorption expansion rate and low mass loss can be obtained without adding a hydrophilic chain extender and a hydrolysis stabilizer.

[0008] Another object of the present invention is to provide a method for preparing a water-swellable polyurethane elastomer, which has high operating tolerance and is easy to produce, and overcomes the disadvantage that a conventional water-swellable polyurethane elastomer uses polyethylene glycol with a high potassium ion content as a raw material, which easily leads to gelling during the synthesis of the prepolymer.

[0009] The present invention is achieved by adopting the following technical solutions: The water-swellable polyurethane elastomer is prepared by reacting component A and component B at a mass ratio of 100:(4-30); component A is a prepolymer obtained by reacting polyether polyol X and isocyanate, with a functionality of 2.5-4 and a -NCO content of 3-5wt.%; component B is a curing agent component; The polyether polyol X is a high molecular weight and high activity polyether, with a functionality of 2.5-4, a hydroxyl value of 9.8-13.2 mgKOH / g, and a number average molecular weight of 10500-23000 g / mol.

[0010] The polyether polyol X is obtained by ring-opening polymerization of polyether polyol Y as an initiator and alkylene oxide under the action of a bimetallic catalyst; the content of ethylene oxide (EO) in the polyether polyol X is 70-90wt.%.

[0011] Preferably, the mass ratio of the initiator to the alkylene oxide in the polyether polyol X is 1:(8-14), and the alkylene oxide is a mixture of propylene oxide and ethylene oxide in a mass ratio of 1:(3-6).

[0012] The initiator of the polyether polyol Y is 2 to 4 2 to 6-official small molecule initiators, the catalyst is KOH or phosphazene catalyst, and the ethylene oxide content of the polyether polyol Y is 70 to 90 wt.%.

[0013] The small molecule initiator is two or more of diethylene glycol, propylene glycol, glycerol, trimethylolpropane, trihydroxyethyl isocyanurate, pentaerythritol, sorbitol and mannitol.

[0014] The mass ratio of the polyether polyol X to the isocyanate is (5-15):1.

[0015] The isocyanate is one or more of toluene diisocyanate (TDI), dicyclohexylmethane diisocyanate (HMDI), 1,4-cyclohexane diisocyanate (CHDI), and 2,2,4-trimethylhexane diisocyanate (TMHDI).

[0016] The curing agent is one or more of 1,4-butanediol (BDO), ethylene glycol (EG), neopentyl glycol (NPG), and methyl propanediol (MPD).

[0017] The method for preparing the water-swellable polyurethane elastomer comprises the following steps: (1) Add two or more small molecule initiators and KOH or phosphazene catalyst into a reactor, replace with nitrogen to reduce the oxygen content in the reactor to less than 50 ppm, slowly add uniformly mixed propylene oxide and ethylene oxide after dehydration, add water, phosphoric acid, magnesium silicate, aluminum silicate after the reaction is completed, stir, dehydrate, filter, and obtain intermediate polyether polyol Y; add polyether polyol Y and bimetallic catalyst into a pressure-resistant reactor, mix, replace with nitrogen to reduce the oxygen content in the reactor to less than 50 ppm, add propylene oxide after dehydration for initiation, and slowly add uniformly mixed propylene oxide and ethylene oxide after the initiation is successful, and complete the reaction to obtain polyether polyol X; (2) placing polyether polyol X in a reaction kettle, adding isocyanate after dehydration, and reacting at 70-90°C for 1-2 hours, taking samples for testing, and when the -NCO content reaches 3-5wt.%, cooling and discharging the material, sealing and storing the prepolymer; (3) The curing agent and the prepolymer are mixed evenly in a mass ratio of (4-30):100, poured into a vulcanizer mold, vulcanized at 100-120°C for 1-2 hours, aged at 80°C for 24 hours after demolding, and aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0018] The amount of water added is 3.5% of the mass of polyether polyol Y; the amount of phosphoric acid added is 0.65% of the mass of polyether polyol Y; the amount of magnesium silicate added is 0.1% of the mass of polyether polyol Y; the amount of aluminum silicate added is 0.05% of the mass of polyether polyol Y; the amount of bimetallic catalyst used is 30-80ppm of the total mass of raw materials of the polyether polyol X reaction system; and the amount of propylene oxide added for initiation is 8%-20% of the mass of the initiator.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The water-swellable polyurethane elastomer of the present invention adopts a high molecular weight and high activity polyether polyol with 2.5-4 functionalities as a raw material. The polyether polyol has a low potassium ion content, moderate polymerization reaction activity when synthesizing a prepolymer, high operation tolerance, and convenient production. It overcomes the disadvantage that the conventional water-swellable polyurethane elastomer uses polyethylene glycol with a high potassium ion content as a raw material, which easily leads to gelling when synthesizing a prepolymer.

[0020] (2) The water-swellable polyurethane elastomer of the present invention overcomes the problem of low water absorption and mechanical properties of water-swellable polyurethane elastomer prepared by traditional PEG polyether. Through the reasonable design of the main polyether structure and formulation process, 2.5-4 functional polyether is synthesized using 2-6 functional initiators, the mechanical properties of the material are improved by internal cross-linking, and the water absorption performance is improved by using alcohol chain extenders. An elastomer with high water absorption expansion rate and low mass loss can be obtained without adding hydrophilic chain extenders and hydrolysis stabilizers. The mass loss rate is less than 1.5%, the water absorption expansion rate is higher than 400%, the hardness is greater than Shore A 60, the tear strength is greater than 20kN / m, the tensile strength is greater than 5MPa, and the glass transition temperature T g Water-swellable polyurethane elastomer below -55°C, with performance degradation of less than 95% after 30 repeated water absorptions. DETAILED DESCRIPTION

[0021] In order to make the purpose and technical solution of the present invention more clear, the present invention is further described in detail.

[0022] The raw materials used in the examples and comparative examples are conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples and comparative examples are conventional methods in the art unless otherwise specified.

[0023] TDI, Yantai Juli Isocyanate Co., Ltd.; HMDI, Mitsubishi Chemical Chemical Materials (Shanghai) Co., Ltd.; CHDI, Wanhua Chemical Group Co., Ltd.; TMHDI, Covestro AG; Phosphazene catalyst, Jinan Quansheng Chemical Co., Ltd.; Bimetallic catalyst, Jiangsu Bader Polyurethane Co., Ltd.; PEG20000, Shanghai Dongda Chemical Co., Ltd. (functionality 2, number average molecular weight 20000 g / mol, solid at room temperature).

[0024] Example 1 The preparation method of the water-swellable polyurethane elastomer comprises the following steps: (1) Preparation of polyether polyol Polyol-1: 130 g of pentaerythritol, 14 g of glycerol, 14 g of sorbitol and 6.45 g of KOH were added to a pressure-resistant reactor, and the reaction mixture was replaced with nitrogen three times. After the oxygen content in the reactor was lower than 50 ppm, the reaction mixture was heated to 110°C for dehydration for 1 h. 400 g of PO and 1600 g of EO were slowly added at 115°C and the reaction temperature was controlled at 115°C and the pressure was controlled at 0.1 MPa. After the reaction was completed, the internal pressure was maintained at 115°C for 2 h, and the unreacted monomers were removed by vacuum. The reaction mixture was cooled to 80°C, and 75 g of water, 14 g of 75% phosphoric acid, 2.1 g of magnesium silicate and 1 g of aluminum silicate were added. The mixture was stirred for 1 h, heated to 110°C, dehydrated for 2 h and filtered to obtain the intermediate polyether polyol 1.

[0025] 184g of polyether polyol 1 and 0.1g of bimetallic catalyst were added into a pressure reactor and mixed. The mixture was replaced with nitrogen three times to reduce the oxygen content in the reactor to less than 50ppm. The mixture was heated to 130°C and dehydrated at a vacuum degree of -0.09MPa for 1h. 35g of PO was added at 130°C for initiation. After successful initiation, 160g of PO and 1428g of EO were slowly added. After the reaction was completed, the internal pressure was maintained at 2h and unreacted monomers and small molecular products were removed in vacuo to obtain polyether polyol Polyol-1 with a hydroxyl value of 13.2 mgKOH / g.

[0026] (2) Place 300g Polyol-1 in a reactor, heat to 110°C for dehydration for 1h, cool to 80°C, add 34.56g TDI and react for 1h. Take samples for testing. When the -NCO content reaches 3wt.%, cool down, discharge the material, and seal and store to obtain prepolymer 1.

[0027] (3) 100 g of prepolymer 1 and 4.14 g of BDO were mixed evenly at 90°C, poured into a vulcanizer mold, vulcanized at 100°C for 2 h, and aged at 80°C for 24 h after demolding. The water-swellable polyurethane elastomer was obtained by aging at room temperature for one week.

[0028] Example 2 The preparation method of the water-swellable polyurethane elastomer comprises the following steps: (1) Preparation of polyether polyol Polyol 2: 20 g of diethylene glycol, 20 g of pentaerythritol, 80 g of trimethylolpropane, 15 g of mannitol and 4.35 g of KOH were added to a pressure reactor, and the reaction mixture was replaced with nitrogen three times to reduce the oxygen content in the reactor to less than 50 ppm. The reaction mixture was heated to 110°C for dehydration for 1 h, and 380 g of PO and 1590 g of EO were slowly added at 115°C. The reaction temperature was controlled at 115°C and the pressure was controlled at 0.25 MPa. After the reaction was completed, the internal pressure was maintained at 2 h, and the unreacted monomers were removed by vacuum. The reaction mixture was cooled to 80°C, and 75 g of water, 14 g of 75% phosphoric acid, 2.1 g of magnesium silicate and 1 g of aluminum silicate were added. The mixture was stirred for 1 h, heated to 110°C for dehydration for 2 h, and filtered to obtain the intermediate polyether polyol 2.

[0029] 180g of polyether polyol 2 and 0.1g of bimetallic catalyst were added into a pressure reactor and mixed. The mixture was replaced with nitrogen three times to reduce the oxygen content in the reactor to less than 50ppm. The mixture was heated to 130°C and dehydrated at a vacuum degree of -0.09MPa for 1h. 35g of PO was added at 130°C for initiation. After successful initiation, 170g of PO and 1530g of EO were slowly added. After the reaction was completed, the internal pressure was maintained at 2h and unreacted monomers and small molecular products were removed in vacuo to obtain polyether polyol Polyol 2 with a hydroxyl value of 11 mgKOH / g.

[0030] (2) 300 g Polyol-2 was placed in a reactor, heated to 110°C for dehydration for 1 h, cooled to 70°C, nitrogen was added, and 26.1 g CHDI solid was reacted for 1.5 h. Samples were taken for testing. When the -NCO content reached 4 wt.%, the temperature was lowered, the material was discharged, and the prepolymer 2 was obtained after being sealed and stored.

[0031] (3) 4.95 g of neopentyl glycol was heated to melt and quickly mixed with 100 g of prepolymer 2, and poured into a vulcanizer mold. The mixture was vulcanized at 120°C for 1 h. After demolding, the mixture was aged at 80°C for 24 h. The mixture was aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0032] Example 3 The preparation method of the water-swellable polyurethane elastomer comprises the following steps: Preparation of polyether polyol Polyol-3: 80g propylene glycol, 40g pentaerythritol, 30g trihydroxyethyl isocyanurate, 5g sorbitol, 3g KOH, and 0.05g phosphazene catalyst were added to a pressure-resistant reactor, and nitrogen was replaced three times. After the oxygen content in the reactor was lower than 50ppm, the temperature was raised to 110°C for dehydration for 1h, and 400g PO and 1650g EO were slowly added at 115°C. The reaction temperature was controlled at 115°C and the pressure was controlled at 0.2MPa. After the reaction was completed, the internal pressure was maintained for 2h, and the unreacted monomers were removed by vacuum, and the temperature was lowered to 80°C. 77g water, 14g 75% phosphoric acid, 2.2g magnesium silicate, and 1.1g aluminum silicate were added, stirred for 1h, and then heated to 110°C for dehydration for 2h, and filtered to obtain the intermediate polyether polyol 3.

[0033] 180g of polyether polyol 3 and 0.1g of bimetallic catalyst were added into a pressure reactor and mixed. The mixture was replaced with nitrogen three times to reduce the oxygen content in the reactor to less than 50ppm. The mixture was heated to 130°C and dehydrated at a vacuum degree of -0.09MPa for 1h. 30g of PO was added at 130°C for initiation. After successful initiation, 210g of PO and 950g of EO were slowly added. After the reaction was completed, the internal pressure was maintained for 2h, and unreacted monomers and small molecular products were removed in vacuo to obtain polyether polyol Polyol-3 with a hydroxyl value of 12 mgKOH / g.

[0034] (2) Place 300g Polyol-3 in a reactor, heat to 110°C for dehydration for 1h, cool to 75°C, add 39g MHDI and react for 2h. Take samples for testing. When the -NCO content reaches 4.5wt.%, cool down, discharge, and seal to obtain prepolymer 3.

[0035] (3) 100 g of prepolymer 3 and 4.815 g of ethylene glycol were mixed evenly at 90°C, poured into a vulcanizer mold, vulcanized at 100°C for 1 hour, and aged at 80°C for 24 hours after demolding. The water-swellable polyurethane elastomer was obtained by aging at room temperature for one week.

[0036] Example 4 The preparation method of the water-swellable polyurethane elastomer comprises the following steps: (1) Preparation of polyether polyol Polyol 4: 80 g of pentaerythritol, 40 g of trimethylolpropane, 10 g of sorbitol and 0.2 g of phosphazene catalyst were added to a pressure-resistant reactor, and the reaction mixture was replaced with nitrogen three times to reduce the oxygen content in the reactor to less than 50 ppm. The reaction mixture was heated to 110°C for dehydration for 1 h, and 360 g of PO and 1580 g of EO were slowly added at 120°C. The reaction temperature was controlled at 120°C and the pressure was controlled at 0.15 MPa. After the reaction was completed, the internal pressure was maintained at 120°C for 2 h, and the unreacted monomers were removed by vacuum. The reaction mixture was cooled to 80°C, and 75 g of water, 14 g of 75% phosphoric acid, 2.1 g of magnesium silicate and 1 g of aluminum silicate were added. The mixture was stirred for 1 h, heated to 110°C for dehydration for 2 h, and filtered to obtain the intermediate polyether polyol 4.

[0037] 180g of polyether polyol 4 and 0.1g of bimetallic catalyst were added into a pressure-resistant reactor and mixed. The mixture was replaced with nitrogen three times to reduce the oxygen content in the reactor to less than 50ppm. The mixture was then heated to 130°C and dehydrated at a vacuum degree of -0.09MPa for 1h. 30g of PO was added at 130°C for initiation. After successful initiation, 170g of PO and 1530g of EO were slowly added. After the reaction was completed, the internal pressure was maintained at 2h and unreacted monomers and small molecular products were removed in vacuo to obtain polyether polyol Polyol 4 with a hydroxyl value of 9.8mgKOH / g.

[0038] (2) Place 300g Polyol-4 in a reactor, heat to 110°C for dehydration for 1h, cool to 80°C, add 20.37g TMHDI and 24g HMDI, and react for 2h. Take samples for testing. When the -NCO content reaches 5wt.%, cool down, discharge, and seal to obtain prepolymer 4.

[0039] (3) 100 g of prepolymer 4 was mixed evenly with 5.35 g of methyl propylene glycol and 2 g of ethylene glycol at 80°C, poured into a vulcanizer mold, vulcanized at 100°C for 2 h, aged at 80°C for 24 h after demolding, and aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0040] Comparative Example 1 The difference from Example 1 is that Polyol-1 is replaced by Polyol-5 of the same mass, the isocyanate and the chain extender are the same, MDPA hydrophilic chain extender is added, and TMP cross-linking agent is added.

[0041] (1) Preparation of polyether polyol Polyol-5: Add 2000g PEG20000 into a reactor, replace with nitrogen three times to make the oxygen content in the reactor lower than 50ppm, then heat to 85°C, add 70g water, 13g 75% phosphoric acid, 2g magnesium silicate, and 1g aluminum silicate, stir for 1h, then heat to 110°C, dehydrate for 2h, and filter to obtain polyether polyol Polyol-5.

[0042] (2) 300 g Polyol-5 was placed in a reactor, heated to 110°C for dehydration for 1 h, cooled to 80°C, and 52.64 g HMDI was added for reaction for 2 h. Samples were taken for testing. When the -NCO content reached 4 wt.%, the temperature was lowered, the material was discharged, and the prepolymer 5 was obtained after sealing.

[0043] (3) 100 g of prepolymer 5 was quickly mixed with 4.14 g of BDO, 3 g of TMP and 1 g of MDPA, poured into a vulcanizer mold, vulcanized at 100 °C for 2 h, aged at 80 °C for 24 h after demolding, and aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0044] Comparative Example 2 The difference from Example 1 is that Polyol-1 is replaced by Polyol-5 of the same mass, the isocyanate and the chain extender are the same, and no hydrophilic chain extender and cross-linking agent are added.

[0045] (1) Place 300g Polyol-1 in a reactor, heat to 110°C for dehydration for 1h, cool to 70°C, add 41.33g HMDI and react for 2h. Take samples for testing. When the -NCO content reaches 4wt.%, cool down, discharge the material, and seal and store to obtain prepolymer 6.

[0046] (2) 100 g of the prepolymer 6 and 16.5 g of heated and melted MOCA were quickly mixed and uniformly poured into a vulcanizer mold, vulcanized at 120° C. for 2 h, aged at 80° C. for 24 h after demolding, and aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0047] Comparative Example 3 The difference from Example 2 is that PPDI is used as isocyanate, MCDEA is used as chain extender, and TIPA, a cross-linking agent, and DMBA, a hydrophilic chain extender, are added.

[0048] (1) Place 300g Polyol-2 in a reactor, heat to 110℃ for dehydration for 1h, cool to 80℃, add 23.78g PPDI solid under nitrogen protection and react for 1h. Take samples for testing. When the -NCO content reaches 4wt.%, cool down, discharge, and seal to obtain prepolymer 7.

[0049] (2) 10.24 g of heated and melted MCDEA, 5 g of TIPA, 2 g of DMBA and 100 g of prepolymer 7 were quickly stirred and uniformly poured into a vulcanizer mold. The mixture was vulcanized at 100°C for 1 h. After demolding, the mixture was aged at 80°C for 24 h and then aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0050] Comparative Example 4 The difference from Example 2 is that liquid rubber is added before vulcanization.

[0051] (1) Place 300g Polyol-2 in a reactor, heat to 110℃ for dehydration for 1h, cool to 70℃, add 26.1g CHDI solid under nitrogen protection and stir for 1h. Take samples for testing. When the -NCO content reaches 4wt.%, cool down, discharge, and seal to obtain prepolymer 8.

[0052] (2) 4.95 g of neopentyl glycol was heated to melt and quickly mixed with 100 g of prepolymer 8 and 3 g of liquid rubber, and poured into a vulcanizer mold. The mixture was vulcanized at 120°C for 1 h. After demolding, the mixture was aged at 80°C for 24 h. The mixture was aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

[0053] Comparative Example 5 The difference from Example 1 is that Polyol-1 is replaced with PEG20000 of the same mass; (1) Place 300 g of melted PEG20000 in a reactor, heat to 110 °C for dehydration for 1 h, cool to 80 °C, add 52.64 g of HMDI and react for 2 h. During the reaction, the reactor polymerizes and the reaction is terminated.

[0054] The performance tests were performed on the water-swellable polyurethane elastomers prepared in Examples 1 to 4 and Comparative Examples 1 to 4, respectively, and the test methods were as follows: The volume expansion rate is calculated according to the following formula: V=(v2-v1) / v1×100%,wherein v1 represents the volume before water absorption, and v2 represents the volume of the water-swellable polyurethane elastomer after water absorption.

[0055] The water-swellable polyurethane elastomer was dried in an oven at 80°C for 8 hours and then the mass loss rate was measured. The mass loss rate was calculated according to the following formula: M = (m1-m2) / m1*100%, wherein m1 represents the mass of the elastomer before absorbing water, and m2 represents the mass after absorbing water and drying.

[0056] The vulcanization was carried out using a QLB-D400×400 flat vulcanizer, the hardness was tested using a Shore A rubber hardness tester in accordance with GB / T531.1-2008, and the tensile strength, tear strength and elongation at break were tested using an AI7000S universal material tensile machine produced by Gaotie Technology Co., Ltd. in accordance with GB / T528-2008 and GB / T529-2008. The glass transition temperature T was measured using differential scanning calorimetry GB / T19466.2-2004. g .

[0057] The test data of polyether polyol Polyol-1~5 are shown in Table 1: Table 1 Test data of polyether polyols

[0058] The test results of Examples 1-4 and Comparative Examples 1-4 are shown in Table 2: Table 2 Test results of Examples 1-4 and Comparative Examples 1-4

[0059] The test results of Examples 1-4 and Comparative Examples 1-4 after repeated water absorption 30 times are shown in Table 3.

[0060] Table 3 Test results of Examples 1-4 and Comparative Examples 1-4 after repeated water absorption 30 times

[0061] As can be seen from Table 2, compared with the conventional 2-functional PEG polyether after potassium removal in Comparative Example 1-2, the water-swellable polyurethane elastomer obtained in Example 1-4 has high hardness, good water absorption performance and low mass loss rate during the curing stage; Comparative Example 3 adds a cross-linking agent and a hydrophilic chain extender compared with Examples 1-4, and the obtained elastomer has high hardness, but low elongation at break and volume expansion rate. This is because the elastomer prepared by using 2.5-4-functional polyether polyols, the introduction of internal cross-linking during the synthesis of polyether, the multi-functionality combination to improve the mechanical properties, and the use of alcohol chain extenders to improve the water absorption performance, so that the elastomer with high water absorption expansion rate and low mass loss can be obtained without adding a hydrophilic chain extender and a hydrolysis stabilizer; Comparative Example 5 uses PEG20000 without potassium removal, and the reaction is terminated in the process of preparing the prepolymer.

[0062] It can be seen from Table 3 that after repeated water absorption, the mechanical properties and water absorption expansion rate of the elastomers of Examples 1-4 decrease slightly, and the mass loss is extremely low compared with Comparative Example 4. No liquid rubber needs to be introduced during the synthesis process to avoid the water absorption and expansion of the polyurethane elastomer material and the filler. There is little chemical crosslinking and poor stability. When the water absorption and expansion or the material structure changes due to temperature, it is easy to cause changes in physical properties and material precipitation.

Claims

1. A water-swellable polyurethane elastomer, characterized in that: It is prepared by reacting component A and component B at a mass ratio of 100:(4~30); component A is a prepolymer obtained by reacting polyether polyol X and isocyanate, with a functionality of 2.5~4 and a -NCO content of 3~5wt.%; component B is a curing agent component; The polyether polyol X is a high molecular weight and high activity polyether, with a functionality of 2.5-4, a hydroxyl value of 9.8-13.2 mgKOH / g, and a number average molecular weight of 10500-23000 g / mol.

2. The water-swellable polyurethane elastomer according to claim 1, characterized in that: The polyether polyol X is obtained by ring-opening polymerization of polyether polyol Y as an initiator and alkylene oxide under the action of a bimetallic catalyst; the ethylene oxide content of the polyether polyol X is 70-90wt.%.

3. The water-swellable polyurethane elastomer according to claim 2, characterized in that: The initiator of the polyether polyol Y is 2 to 4 2 to 6-official small molecule initiators, the catalyst is KOH or phosphazene catalyst, and the ethylene oxide content of the polyether polyol Y is 70 to 90 wt.%.

4. The water-swellable polyurethane elastomer according to claim 2, characterized in that: The mass ratio of the initiator to the alkylene oxide in the polyether polyol X is 1:(8-14), and the alkylene oxide is a mixture of propylene oxide and ethylene oxide in a mass ratio of 1:(3-6).

5. The water-swellable polyurethane elastomer according to claim 3, characterized in that: The small molecule initiator is two or more of diethylene glycol, propylene glycol, glycerol, trimethylolpropane, trihydroxyethyl isocyanurate, pentaerythritol, sorbitol and mannitol.

6. The water-swellable polyurethane elastomer according to claim 1, characterized in that: The mass ratio of the polyether polyol X to the isocyanate is (5-15):

1.

7. The water-swellable polyurethane elastomer according to claim 1, characterized in that: The isocyanate is one or more of toluene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, and 2,2,4-trimethylhexane diisocyanate.

8. The water-swellable polyurethane elastomer according to claim 1, characterized in that: The curing agent is one or more of 1,4-butanediol, ethylene glycol, neopentyl glycol and methyl propylene glycol.

9. A method for preparing the water-swellable polyurethane elastomer according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Add two or more small molecule initiators and KOH or phosphazene catalyst into a reactor, replace with nitrogen to reduce the oxygen content in the reactor to less than 50 ppm, slowly add uniformly mixed propylene oxide and ethylene oxide after dehydration, add water, phosphoric acid, magnesium silicate, aluminum silicate after the reaction is completed, stir, dehydrate, filter, and obtain intermediate polyether polyol Y; add polyether polyol Y and bimetallic catalyst into a pressure-resistant reactor, mix, replace with nitrogen to reduce the oxygen content in the reactor to less than 50 ppm, add propylene oxide after dehydration for initiation, and slowly add uniformly mixed propylene oxide and ethylene oxide after the initiation is successful, and complete the reaction to obtain polyether polyol X; (2) placing polyether polyol X in a reaction kettle, adding isocyanate after dehydration, and reacting at 70-90°C for 1-2 hours, taking samples for testing, and when the -NCO content reaches 3-5wt.%, cooling and discharging the material, sealing and storing the prepolymer; (3) The curing agent and the prepolymer are mixed evenly in a mass ratio of (4-30):100, poured into a vulcanizer mold, vulcanized at 100-120°C for 1-2 hours, aged at 80°C for 24 hours after demolding, and aged at room temperature for one week to obtain a water-swellable polyurethane elastomer.

10. The method for preparing a water-swellable polyurethane elastomer according to claim 9, characterized in that: The amount of water added is 3.5% of the mass of polyether polyol Y; the amount of phosphoric acid added is 0.65% of the mass of polyether polyol Y; the amount of magnesium silicate added is 0.1% of the mass of polyether polyol Y; the amount of aluminum silicate added is 0.05% of the mass of polyether polyol Y; the amount of bimetallic catalyst used is 30-80ppm of the total mass of raw materials of the polyether polyol X reaction system; and the amount of propylene oxide added for initiation is 8%-20% of the mass of the initiator.

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