Bio-based hydrophilic polyurethane water-swellable elastomer and preparation method thereof

Abstract

The invention belongs to the field of polyurethane materials, and particularly relates to a preparation method of a bio-based hydrophilic polyurethane water-swelling elastomer, which comprises the following steps: step 1, uniformly mixing isocyanate, bio-based polycaprolactone polyol, polylactic acid polyol, a catalyst, polyethylene glycol and water, and reacting at room temperature to obtain a reaction solution; and step 2, foaming and curing the reaction liquid to obtain the bio-based hydrophilic polyurethane water-swelling elastic material. The hydrophilic polyurethane expansion elastomer prepared by the preparation method disclosed by the invention has better hydrophilicity and stable water expansion performance, also has better mechanical properties and better application prospects; the bio-based hydrophilic polyurethane water-swellable elastomer prepared by the method disclosed by the invention is low in preparation cost, suitable for large-scale batch production and beneficial to application of the bio-based hydrophilic polyurethane water-swellable elastomer.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane materials, and in particular relates to a bio-based hydrophilic polyurethane water-swellable elastomer and a preparation method thereof. Background Art

[0002] Hydrophilic materials can be divided into two categories: water-swelling materials and water-non-swelling materials. Water-non-swelling materials will not expand in volume after absorbing water, and are mainly used in furniture and clothing. Water-swelling materials will expand to several to dozens of times their original volume after absorbing water, and their applications are more extensive, with good application prospects in the fields of waterproofing, water conservancy projects, and marine aquaculture.

[0003] Existing methods for preparing water-swellable materials include physical mixing, grafting polymerization and chemical synthesis. Among them, the grafting polymerization method is to graft specific monomers onto the main chain of the polymer to form side chains with specific functions, thereby giving the material the property of swelling when exposed to water. This method can prepare water-swellable materials with stable structure and controllable performance, but the control of the grafting reaction is relatively complicated, requiring precise control of reaction conditions and monomer ratios, which is difficult. The physical mixing method usually involves mixing a variety of raw materials such as rubber, activator, antioxidant, reinforcing agent and filler in a certain proportion, and preparing water-swellable materials by mechanical mixing or hot pressing. This method is simple to operate and suitable for large-scale production. However, physical mixing may lead to uneven material properties, especially in terms of expansion properties and mechanical strength. The chemical synthesis method involves the synthesis of multiple chemical substances, such as the reaction of polyether polyurethane prepolymer and end-capping agent HEMA, and preparing double-bond-terminated polyurethane water-swellable materials by adding catalysts and heating. This method can accurately control the molecular structure of polyurethane water-swellable materials, thereby obtaining materials with specific expansion properties, with good results.

[0004] At present, in the preparation process of hydrophilic polyurethane water-swellable materials, polyols and isocyanates containing hydrophilic ethylene ether segments (-CH2-CH2-O-) are used as raw materials, and the ethylene ether segments in the polyether segments are often required to be controlled within a certain ratio range to make them have a certain degree of hydrophilicity and ion resistance. For example, a document prepared a hydrophilic polyurethane foam with a water absorption time of less than 30s by mixing different contents of ethylene oxide in a polyether polyol, but the hydrophilicity and water swelling properties of the polyurethane elastomer prepared by this method were not excellent enough, which limited its application range. Summary of the invention

[0005] In order to solve the problems of the existing polyurethane water-swellable elastomer having insufficient hydrophilicity and swelling performance, the present invention provides a bio-based hydrophilic polyurethane water-swellable elastomer and a preparation method thereof.

[0006] The preparation method of the bio-based hydrophilic polyurethane water-swellable elastomer comprises the following steps:

[0007] Step 1: uniformly mix isocyanate, bio-based polycaprolactone polyol, polylactic acid polyol, catalyst, polyethylene glycol and water, and react at room temperature to obtain a reaction solution;

[0008] Step 2: foaming and aging the reaction solution to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0009] In step 1, the structural formula of the bio-based polycaprolactone polyol is as follows:

[0010]

[0011] Among them, R is O and One of; m is 3-15, n is 3-15;

[0012] The structural formula of the polylactic acid polyol is as follows:

[0013]

[0014] Among them, a is 3-20 and b is 3-20.

[0015] Furthermore, the isocyanate in step 1 is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

[0016] Furthermore, in step 1, the mass ratio of the bio-based polycaprolactone polyol to the polylactic acid polyol and the polyethylene glycol is 100:(50-70):(50-80).

[0017] Furthermore, in step 1, the ratio of the total mass of the bio-based polycaprolactone polyol, polylactic acid polyol and polyethylene glycol to the mass of the isocyanate is 100:(35-45).

[0018] Furthermore, in step one, the mass ratio of the catalyst, water and polylactic acid polyol is 1:(20-50):(200-300).

[0019] Furthermore, the catalyst in step 1 is one of an organic tin catalyst and an amine catalyst.

[0020] Furthermore, the polyethylene glycol in step 1 is selected from one or more of polyethylene glycol 500, polyethylene glycol 1000, and polyethylene glycol 2000.

[0021] Furthermore, the polylactic acid polyol is prepared by the following method:

[0022] Step (1), mixing zinc salt, organic ammonium salt and bis(ethylene carbonate) ether and heating to react to obtain an in-situ catalyst;

[0023] Step (2), adding the purified LA monomer to the in-situ catalyst to react and obtain a product.

[0024] The invention also provides a bio-based hydrophilic polyurethane water-swellable elastomer.

[0025] The bio-based hydrophilic polyurethane water-swellable elastomer is prepared by the method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer as described in any one of the above items.

[0026] The beneficial effects brought by the present invention are as follows:

[0027] (1) The method of the present invention uses bio-based polycaprolactone polyol and polylactic acid polyol with hydrophilic flexible segments in combination with polyethylene glycol in a certain proportion, so that the prepared polyurethane water-swellable elastomer has excellent hydrophilicity and water absorption and swelling properties, and has good application prospects;

[0028] (2) In the process of preparing the bio-based hydrophilic polyurethane water-swellable elastomer, the present invention adds polyethylene glycol and introduces polyethylene glycol segments into the polyurethane water-swellable elastomer, thereby providing a suitable cross-linking length. In addition, due to the introduction of different segments, the cohesive energy is increased and the intermolecular force is enhanced, so that the prepared polyurethane water-swellable elastomer has better mechanical properties.

[0029] (3) The bio-based polycaprolactone polyol and polylactic acid polyol prepared by the method of the present invention have low cost, and the cost of using them to prepare polyurethane water-swellable elastomers is low; and the preparation method provided by the present invention is simple and easy to operate, has low requirements on equipment, is conducive to further reducing the preparation cost, is suitable for large-scale batch production, and is conducive to the application of the prepared bio-based hydrophilic polyurethane water-swellable elastomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention provides a flow chart of the preparation method of the bio-based hydrophilic polyurethane water-swellable elastomer. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings, but they should not be construed as limiting the applicable scope of the present invention.

[0032] The polyethylene glycol 1000, polyethylene glycol 2000 and polyethylene glycol 500 used in the examples and comparative examples of the present invention are produced by Shanghai MacLean Biochemical Technology Co., Ltd.; the δ-CL monomers used are all δ-caprolactone of biological origin.

[0033] The structural formula of the bio-based polycaprolactone polyol of the present invention is as follows:

[0034]

[0035] Among them, R is O and One of the following; m is 3-15, n is 3-15.

[0036] Optionally, the preparation methods of the bio-based polycaprolactone polyol A, bio-based polycaprolactone polyol B and bio-based polycaprolactone polyol C used in the examples and comparative examples of the present invention are:

[0037] Step 1, mixing zinc salt, organic ammonium salt and initiator, heating to 180° C. and reacting for 4 hours to obtain an in-situ catalyst;

[0038] Step 2, first adding calcium oxide to remove moisture in the δ-CL monomer, and then purifying the δ-CL monomer to obtain a purified δ-CL monomer;

[0039] Step 3, adding the purified δ-CL monomer to the in-situ catalyst and reacting at 170° C. for 1.5 h to obtain a product;

[0040] Step 4: adding methanol for precipitation, and obtaining bio-based polycaprolactone polyol after separation.

[0041] The selection of zinc salt, organic ammonium salt and initiator added in the process of preparing bio-based polycaprolactone polyol A, bio-based polycaprolactone polyol B and bio-based polycaprolactone polyol C is shown in Table 1, and the addition ratio of each raw material is shown in Table 2.

[0042] Table 1

[0043]

[0044] Table 2

[0045]

[0046] See also Figure 1 , a method for preparing a bio-based hydrophilic polyurethane water-swellable elastomer, characterized in that it comprises the following steps:

[0047] Step 1: uniformly mix isocyanate, bio-based polycaprolactone polyol, polylactic acid polyol, catalyst, polyethylene glycol and water, and react at room temperature to obtain a reaction solution;

[0048] Step 2: foaming and aging the reaction solution to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0049] In step 1, the structural formula of the bio-based polycaprolactone polyol is as follows:

[0050]

[0051] Among them, R is O and One of; m is 3-15, n is 3-15;

[0052] The structural formula of the polylactic acid polyol is as follows:

[0053]

[0054] Among them, a is 3-20 and b is 3-20.

[0055] The method of the present invention uses bio-based polycaprolactone polyol, polylactic acid polyol and polyethylene glycol with hydrophilic flexible chain segments in a certain proportion during the preparation of the polyurethane water-swellable elastomer, so that the prepared polyurethane water-swellable elastomer has excellent hydrophilicity and water absorption and swelling properties, and also has good mechanical properties.

[0056] Example 1

[0057] 1. Preparation of polylactic acid polyol

[0058] Step (1), adding zinc chloride, dimethylaminopyridine and bis(ethylene carbonate) ether in a mass ratio of 1:30:40, mixing zinc chloride, dimethylaminopyridine and bis(ethylene carbonate) ether, heating to 200° C. and reacting for 2 hours to obtain an in-situ catalyst;

[0059] Step (2), taking the purified LA monomer at a mass ratio of bis(ethylene carbonate) ether to LA monomer of 1:45, adding it to the above-mentioned in-situ catalyst and reacting it at 160° C. for 1.5 hours to obtain a product;

[0060] Step (3), adding methanol for precipitation, and obtaining polylactic acid polyol after separation.

[0061] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0062] Step 1: evenly mix toluene diisocyanate, the above-mentioned bio-based polycaprolactone polyol A, the above-mentioned polylactic acid polyol, dibutyltin dilaurate, polyethylene glycol 1000 and water, and react at room temperature to obtain a reaction solution, wherein the mass ratio of the added bio-based polycaprolactone polyol A to the polylactic acid polyol and polyethylene glycol 1000 is 20:12:13, the total mass ratio of the added bio-based polycaprolactone polyol A, polylactic acid polyol and polyethylene glycol 1000 to the mass ratio of isocyanate is 5:2, and the mass ratio of the added dibutyltin dilaurate, water and polylactic acid polyol is 1:35:250;

[0063] Step 2: The reaction solution is foamed at room temperature and 50 bar for 3 minutes, and then aged for 24 hours to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0064] Example 2

[0065] 1. Preparation of polylactic acid polyol

[0066] Step (1), zinc bromide, tetrabutylammonium chloride and bis(ethylene carbonate) ether are added in a mass ratio of 1:10:30, and then heated to 180° C. for reaction for 3 hours to obtain an in-situ catalyst;

[0067] Step (2), taking the purified LA monomer at a mass ratio of bis(ethylene carbonate) ether to LA monomer of 1:30, adding it to the above-mentioned in-situ catalyst and reacting it at 130° C. for 2 hours to obtain a product;

[0068] Step (3), adding ethanol for precipitation, and obtaining polylactic acid polyol after separation.

[0069] 2. Preparation of polyurethane elastomer

[0070] Step 1, mix isophorone diisocyanate, the above-mentioned bio-based polycaprolactone polyol B, the above-mentioned polylactic acid polyol, stannous octoate, polyethylene glycol 2000 and water evenly, react at room temperature to obtain a reaction solution, the mass ratio of the added bio-based polycaprolactone polyol B to the polylactic acid polyol and polyethylene glycol 2000 is 2:1:1, the mass ratio of the added bio-based polycaprolactone polyol B, polylactic acid polyol and polyethylene glycol 2000 to the mass ratio of isocyanate is 20:7, and the mass ratio of the added stannous octoate, water and polylactic acid polyol is 1:20:200;

[0071] Step 2: foaming the reaction solution at room temperature and 10 bar for 5 minutes, and then aging for 24 hours to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0072] Example 3

[0073] 1. Preparation of polylactic acid polyol

[0074] Step (1), zinc acetate, tetrabutylammonium bromide and bis(ethylene carbonate) ether are added in a mass ratio of 1:50:50, and then heated to 220° C. for reaction for 1 hour to obtain an in-situ catalyst;

[0075] Step (2), taking the purified LA monomer at a mass ratio of bis(ethylene carbonate) ether to LA monomer of 1:60, adding it to the above-mentioned in-situ catalyst and reacting it at 180° C. for 1 hour to obtain a product;

[0076] Step (3), adding methanol for precipitation, and obtaining polylactic acid polyol after separation.

[0077] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0078] Step 1: Evenly mix diphenylmethane diisocyanate, the bio-based polycaprolactone polyol C, the polylactic acid polyol, N,N-dimethylcyclohexylamine, polyethylene glycol 500 and water, and react at room temperature to obtain a reaction solution, wherein the mass ratio of the added bio-based polycaprolactone polyol C to the polylactic acid polyol and polyethylene glycol 500 is 10:7:8, the mass ratio of the added bio-based polycaprolactone polyol C, polylactic acid polyol and polyethylene glycol 500 to the mass ratio of isocyanate is 20:9, and the mass ratio of the added N,N-dimethylcyclohexylamine, water and polylactic acid polyol is 1:50:300;

[0079] Step 2: The reaction solution is foamed at room temperature and 100 bar for 5 minutes, and then aged for 24 hours to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0080] Example 4

[0081] 1. Preparation of polylactic acid polyol

[0082] Step (1), zinc chloride, tetrabutylammonium iodide and bis(ethylene carbonate) ether are mixed in a mass ratio of 1:10:50, and then heated to 200° C. for reaction for 2 hours to obtain an in-situ catalyst;

[0083] Step (2), taking the purified LA monomer at a mass ratio of bis(ethylene carbonate) ether to LA monomer of 1:45, adding it to the above-mentioned in-situ catalyst and reacting at 150° C. for 2 hours to obtain a product;

[0084] Step (3), adding ethanol for precipitation, and obtaining polylactic acid polyol after separation.

[0085] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0086] Step 1, take hexamethylene diisocyanate, bio-based polycaprolactone polyol B, the above-mentioned polylactic acid polyol, bis(2-dimethylaminoethyl) ether, polyethylene glycol 1000 and water, mix them evenly, react at room temperature to obtain a reaction solution, the mass ratio of the added bio-based polycaprolactone polyol B and polylactic acid polyol, polyethylene glycol 1000 is 5:3:4, the mass ratio of the added bio-based polycaprolactone polyol B, polylactic acid polyol and polyethylene glycol 1000 to the mass ratio of isocyanate is 5:2, and the mass ratio of the added bis(2-dimethylaminoethyl) ether, water and polylactic acid polyol is 1:50:200;

[0087] Step 2: The reaction solution is foamed at room temperature and 50 bar for 3 minutes, and then aged for 24 hours to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0088] Comparative Example 1

[0089] 1. Preparation of polylactic acid polyol

[0090] The preparation of polylactic acid polyol is the same as that in Example 1.

[0091] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0092] The polycaprolactone polyol used in step 1 of this comparative example is brand 2302, and the manufacturer is Hunan Juren New Materials Co., Ltd.; other technical features are the same as those in Example 1.

[0093] Comparative Example 2

[0094] Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0095] The polylactic acid polyol used in step 1 of this comparative example is PLA220B, and the manufacturer is Shenzhen Guanghua Weiye Co., Ltd.; other technical features are the same as those in Example 1.

[0096] Comparative Example 3

[0097] 1. Preparation of polylactic acid polyol

[0098] The preparation of polylactic acid polyol is the same as that in Example 1.

[0099] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0100] The mass ratio of the bio-based polycaprolactone polyol, polylactic acid polyol and polyethylene glycol 1000 described in step 1 of this comparative example is 1:1:1; other technical features are the same as those in Example 1.

[0101] Comparative Example 4

[0102] 1. Preparation of polylactic acid polyol

[0103] The preparation of polylactic acid polyol is the same as that in Example 1.

[0104] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0105] The mass ratio of the bio-based polycaprolactone polyol, polylactic acid polyol and polyethylene glycol 1000 in step 1 of this comparative example is 10:4:5; other technical features are the same as those in Example 1.

[0106] Comparative Example 5

[0107] 1. Preparation of polylactic acid polyol

[0108] The preparation of polylactic acid polyol is the same as that in Example 1.

[0109] 2. Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0110] Step 1: evenly mix toluene diisocyanate, the above-mentioned polylactic acid polyol, dibutyltin dilaurate, polyethylene glycol 1000 and water, and react at room temperature to obtain a reaction solution, wherein the mass ratio of the added polylactic acid polyol and polyethylene glycol 1000 is 12:33, the mass ratio of the added polylactic acid polyol and polyethylene glycol 1000 to the mass of isocyanate is 5:2, and the mass ratio of the added dibutyltin dilaurate, water and polylactic acid polyol is 1:35:250;

[0111] Step 2: The reaction solution is foamed at room temperature and 50 bar for 5 minutes, and then aged for 24 hours to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0112] Comparative Example 6

[0113] Preparation of Bio-based Hydrophilic Polyurethane Water-Swellable Elastomer

[0114] Step 1: evenly mix toluene diisocyanate, the above-mentioned bio-based polycaprolactone polyol A, dibutyltin dilaurate, polyethylene glycol 1000 and water, and react at room temperature to obtain a reaction solution, wherein the mass ratio of the added bio-based polycaprolactone polyol and polyethylene glycol 1000 is 20:33, the mass ratio of the added bio-based polycaprolactone polyol A and polyethylene glycol 1000 to the mass ratio of isocyanate is 5:2, and the mass ratio of the added dibutyltin dilaurate, water and bio-based polycaprolactone polyol is 1:35:250;

[0115] Step 2: The reaction solution is foamed at room temperature and 50 bar for 5 minutes, and then aged for 24 hours to obtain the bio-based hydrophilic polyurethane water-swellable elastomer.

[0116] The hydrophilicity and water swelling properties of the polyurethane elastomers prepared in the examples and comparative examples were tested. The test results are shown in Table 1.

[0117] Among them, the water absorption rate and water absorption expansion rate are tested according to GB / T 1034-2008 standard;

[0118] The tensile strength and elongation at break are tested according to GB / T6344-2008 standard.

[0119] Table 1

[0120] Water absorption (%) Water absorption expansion rate (%) Tensile strength(Kpa) Elongation at break (%) Example 1 857 233 85 150 Example 2 959 245 80 140 Example 3 879 249 89 156 Example 4 948 257 92 163 Comparative Example 1 912 206 87 143 Comparative Example 2 903 228 95 159 Comparative Example 3 953 209 92 163 Comparative Example 4 951 202 76 133 Comparative Example 5 818 184 86 139 Comparative Example 6 809 195 64 123

[0121] It can be seen from the above test results that the bio-based hydrophilic polyurethane water-swellable elastomer prepared by the method of the present invention has good hydrophilicity and water absorption and swelling properties. In Comparative Examples 1 and 2, the existing polycaprolactone polyol or polylactic acid polyol is used to prepare the bio-based hydrophilic polyurethane water-swellable elastomer. Since it contains fewer ethylene ether segments and a single type of segments or groups, the prepared polyurethane elastomer has relatively poor water absorption and swelling properties; in Comparative Example 3, a bio-based hydrophilic polycaprolactone polyol with a small content is used to prepare the bio-based hydrophilic polyurethane water-swellable elastomer, and a large amount of polyethylene glycol is added. Since the ethylene ether segments are reduced and the segments contained are less flexible, the prepared polyurethane elastomer has relatively poor water absorption and swelling properties; in Comparative Example 4, a small content of polylactic acid is used to prepare the bio-based hydrophilic polyurethane water-swellable elastomer. The bio-based hydrophilic polyurethane water-swellable elastomer is prepared using bio-based polycaprolactone polyol, but due to its less rigid groups, its tensile properties and elongation at break are relatively poor; in Comparative Example 5, the bio-based hydrophilic polyurethane water-swellable elastomer is not prepared using bio-based polycaprolactone polyol, and the flexible ethylene ether segments are less, so the hydrophilicity and water swelling properties of the prepared polyurethane elastomer are relatively poor; in Comparative Example 6, the bio-based hydrophilic polyurethane water-swellable elastomer is not prepared using polylactic acid polyol, and due to its less rigid groups and flexible ethylene ether segments, the water swelling properties, tensile strength and elongation at break of the prepared polyurethane elastomer are relatively poor.

[0122] In addition, the bio-based hydrophilic polyurethane water-swellable elastomer prepared by the method of the present invention has a low cost. The cost of the polyurethane elastomer prepared by the existing reported technology for preparing petroleum-based polycaprolactone polyol is 26 to 35 yuan / kg, while the cost of the bio-based hydrophilic polyurethane water-swellable elastomer available on the market is 30 to 35 yuan / kg. The cost of the hydrophilic bio-based polyurethane prepared by the method of the present invention is 20 to 30 yuan / kg, which can effectively reduce the preparation cost of the bio-based hydrophilic polyurethane water-swellable elastomer.

Claims

1. A method for preparing a bio-based hydrophilic polyurethane water-swellable elastomer, characterized in that: The following steps are involved: Step 1: uniformly mix isocyanate, bio-based polycaprolactone polyol, polylactic acid polyol, catalyst, polyethylene glycol and water, and react at room temperature to obtain a reaction solution; Step 2: foaming and aging the reaction solution to obtain the bio-based hydrophilic polyurethane water-swellable elastomer. In step 1, the structural formula of the bio-based polycaprolactone polyol is as follows: Among them, R is O and One of; m is 3-15, n is 3-15; The structural formula of the polylactic acid polyol is as follows: Among them, a is 3-20 and b is 3-20.

2. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The isocyanate in step 1 is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

3. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The mass ratio of the bio-based polycaprolactone polyol to the polylactic acid polyol and the polyethylene glycol in step 1 is 100:(50-70):(50-80).

4. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The mass ratio of the total mass of the bio-based polycaprolactone polyol, polylactic acid polyol and polyethylene glycol to the mass of the isocyanate in step 1 is 100:(35-45).

5. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The mass ratio of the catalyst, water and polylactic acid polyol in step 1 is 1:(20-50):(200-300).

6. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The catalyst in step 1 is one of an organic tin catalyst and an amine catalyst.

7. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The polyethylene glycol in step 1 is selected from one or more of polyethylene glycol 500, polyethylene glycol 1000, and polyethylene glycol 2000.

8. The method for preparing the bio-based hydrophilic polyurethane water-swellable elastomer according to claim 1, characterized in that: The polylactic acid polyol is prepared by the following method: Step (1), mixing zinc salt, organic ammonium salt and bis(ethylene carbonate) ether and heating to react to obtain an in-situ catalyst; Step (2), adding the purified LA monomer to the in-situ catalyst to react and obtain a product.

9. A bio-based hydrophilic polyurethane water-swellable elastomer, characterized in that: The bio-based hydrophilic polyurethane water-swellable elastomer is prepared by the preparation method of the bio-based hydrophilic polyurethane water-swellable elastomer according to any one of claims 1 to 8.

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