Polylactic acid polyol, and preparation method and application thereof

Abstract

The application discloses polylactic acid polyol as well as a preparation method and application thereof, and the preparation method comprises the following steps: preparing an in-situ catalyst by heating reaction of a zinc salt, an organic ammonium salt and bis(ethylene carbonate) ether; the anion of the organic ammonium salt is selected from any one of bromide, chloride and iodide; and a lactide monomer is added to obtain polylactic acid polyol through a polymerization reaction. The polylactic acid polyol prepared by the application has a flexible chain segment, can provide better flexibility, and can be applied to preparation of polyurethane materials.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a polylactic acid polyol, its preparation method, and its application. Background Technology

[0002] Polylactic acid (PLA), also known as polylactide, is a widely used bio-based chemical derived from the fermentation of starches (such as rice and corn) or from kitchen waste and cellulose. PLA polyols, prepared by the ring-opening polymerization of lactic acid, exhibit excellent biocompatibility and biodegradability, and can ultimately be completely degraded into CO2 and H2O, meeting the needs of sustainable development.

[0003] Currently, most methods for preparing polylactic acid polyols involve using different alcohols as initiators and lactide as the main raw material through ring-opening polymerization of lactide under the action of a catalyst. For example, CN109265660 A and CN109293901A report the preparation of polylactic acid polyols using lactide monomers and other substances as raw materials, and catalyzed by metal catalysts such as magnesium and neodymium through catalytic ring-opening polymerization of lactones. However, these methods suffer from limitations in application in the biopharmaceutical, packaging, and microelectronics fields due to the difficulty in removing harmful metals, the low reactivity and yield of the catalytic systems used, and the high equipment requirements, resulting in high cost and lower safety of the final products.

[0004] Furthermore, polylactic acid (PLA) polyols with flexible segments can be used to prepare flexible materials, which can broaden the application scenarios of PLA polyols. However, the existing PLA polyols are relatively few in variety and their flexibility is not excellent enough, which limits their application to some extent. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a polylactic acid polyol, its preparation method, and its applications. This polylactic acid polyol has low preparation cost, high safety, and good flexibility.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] On one hand, the present invention provides a method for preparing polylactic acid polyol, comprising the following steps:

[0008] Step 1: An in-situ catalyst is prepared by heating zinc salt, organic ammonium salt, and bis(ethylene carbonate) ether; the anion of the organic ammonium salt is selected from any one of bromide ion, chloride ion, and iodide ion.

[0009] Step 2: Add lactide monomer and polymerize to obtain polylactic acid polyol.

[0010] In the technical solution of the present invention, the in-situ catalyst obtained by ring opening of bis(ethylene carbonate) ether can initiate the polymerization reaction of lactide.

[0011] In a preferred embodiment, the zinc salt is selected from at least one of zinc chloride and zinc bromide; the organic ammonium salt is selected from at least one of tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium iodide.

[0012] In the technical solution of this invention, the structural formula of the bis(ethylene carbonate) ether is:

[0013]

[0014] Preferably, the mass ratio of the zinc salt, the organic ammonium salt, and the bis(ethylene carbonate) ether is 1:10-50:30-50.

[0015] Preferably, in step 1, the temperature of the heating reaction is 180–220°C, and the heating reaction time is 1–3 hours.

[0016] In the technical solution of the present invention, the heating reaction will generate gas and needs to be carried out in a pressure-resistant device; the pressure-resistant device can withstand a pressure ≥1MPa.

[0017] In a preferred embodiment, the mass ratio of bis(ethylene carbonate) ether in step 1 to lactide monomer in step 2 is 1:30-60.

[0018] Preferably, in step 2, the polymerization reaction is carried out at a temperature of 130–180°C for 1–2 hours.

[0019] In some specific embodiments, step 2 further includes adding a precipitant to separate and obtain the polylactic acid polyol, specifically: adding a precipitant, removing the solvent, and drying; the precipitant is selected from either methanol or ethanol.

[0020] In another aspect, the present invention provides polylactic acid polyols obtained by the above preparation method.

[0021] In the technical solution of the present invention, the general structural formula of the polylactic acid polyol is shown in formula (1):

[0022]

[0023] In equation (1), m is 3 to 20, n is 3 to 20, and X is a halogen atom.

[0024] In the technical solution of the present invention, the halogen atom is selected from any one of bromine, chlorine and iodine.

[0025] In another aspect, the present invention provides the application of the above-mentioned polylactic acid polyol in the preparation of polyurethane materials.

[0026] In another aspect, the present invention provides a polyurethane material prepared from the above-mentioned polylactic acid polyol, the preparation comprising the following steps:

[0027] The polylactic acid polyol and polyisocyanate were reacted under the action of a catalyst to obtain the polyurethane material.

[0028] In a preferred embodiment, the polyisocyanate is selected from at least one of toluene diisocyanate and diphenylmethane diisocyanate;

[0029] Preferably, the catalyst is a tin catalyst, specifically including dibutyltin dilaurate, stannous octoate, stannous chloride, and stannous lactate octoate, etc.

[0030] Preferably, the reaction is carried out at room temperature for 1 to 2 hours;

[0031] Preferably, the mass ratio of polylactic acid polyol to polyisocyanate is 28-65:100;

[0032] In some specific embodiments, a foaming agent is added to the reaction; the foaming agent is water.

[0033] The beneficial effects of this invention are as follows:

[0034] To address the technical problems of high cost, low safety, poor flexibility, and complex preparation methods in the preparation of polylactic acid polyols, which hinder their widespread application, this invention uses a highly catalytically active catalytic system and initiator to prepare polylactic acid polyols with specific structures.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The polylactic acid polyol provided by the present invention has ether bonds in its chain segments, making the molecular chain easy to rotate. Furthermore, the molecular structure contains two hydroxyl groups, which can provide a suitable degree of crosslinking and improve the flexibility of the materials prepared using it, thus having good application prospects.

[0037] (2) The polylactic acid polyol provided by the present invention has a high catalytic activity and also has the advantages of being non-toxic, safe and low cost. It can improve the yield, reduce the preparation cost, expand its application range and enable large-scale production.

[0038] (3) The polylactic acid polyol provided by the present invention contains both polylactic acid long chain segments of suitable length and halogenated short branches, which can improve its compatibility with other systems; the polylactic acid chain segments of suitable length can enhance the tensile strength of the prepared polylactic acid polyol, which is beneficial to obtaining better mechanical properties; in addition, the polylactic acid chain segments are biodegradable, and the polyol structure helps it to decompose further in the environment, so the prepared polylactic acid polyol has good environmental protection.

[0039] (4) The polyurethane material prepared by the above polylactic acid polyol has a low indentation hardness and high softness as a biological material or encapsulation material, which improves user comfort and cushioning capacity. Detailed Implementation

[0040] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0041] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0042] Example 1

[0043] In this embodiment, a polylactic acid polyol was prepared using the following method:

[0044] Step 1: Mix 0.5g of bis(ethylene carbonate) ether, 0.01g of zinc chloride, and 0.3g of tetrabutylammonium chloride, and react them in a container at 200℃ and 1MPa pressure for 1h to obtain an in-situ catalyst;

[0045] Step 2: Add 18g of purified lactide (LA) monomer to the above in-situ catalyst and react at 160℃ for 1h;

[0046] Step 3: After the reaction is complete, methanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0047] After characterization, the structural formula of the polylactic acid polyol prepared in this embodiment is as follows:

[0048]

[0049] Example 2

[0050] In this embodiment, a polylactic acid polyol was prepared using the following method:

[0051] Step 1: Mix 0.4g of bis(ethylene carbonate) ether, 0.01g of zinc bromide and 0.1g of tetrabutylammonium bromide, and react them in a container at 200℃ and 1MPa pressure for 1.5h to obtain an in-situ catalyst;

[0052] Step 2: Add 18g of LA monomer to the above in-situ catalyst and react at 180℃ for 1h;

[0053] Step 3: After the reaction is complete, methanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0054] After characterization, the structural formula of the polylactic acid polyol prepared in this embodiment is as follows:

[0055]

[0056] Example 3

[0057] In this embodiment, a polylactic acid polyol was prepared using the following method:

[0058] Step 1: Mix 0.3g of bis(ethylene carbonate) ether, 0.01g of zinc chloride, and 0.3g of tetrabutylammonium chloride, and react them in a container at 200℃ and 1MPa pressure for 1.5h to obtain an in-situ catalyst;

[0059] Step 2: Add 16.2 g of LA monomer to the above in-situ catalyst and react at 130 °C for 2 h;

[0060] Step 3: After the reaction is complete, methanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0061] After characterization, the structural formula of the polylactic acid polyol prepared in this embodiment is as follows:

[0062]

[0063] Example 4

[0064] In this embodiment, a polylactic acid polyol was prepared using the following method:

[0065] Step 1: Mix 0.5g of bis(ethylene carbonate) ether, 0.01g of zinc chloride, and 0.5g of tetrabutylammonium iodide, and react them in a container at 200℃ and a pressure of 1MPa for 1h to obtain an in-situ catalyst;

[0066] Step 2: Add 18g of LA monomer to the above in-situ catalyst and react at 160℃ for 2h;

[0067] Step 3: After the reaction is complete, methanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0068] After characterization, the structural formula of the polylactic acid polyol prepared in this embodiment is as follows:

[0069]

[0070] Example 5

[0071] In this embodiment, a polylactic acid polyol was prepared using the following method:

[0072] Step 1: Mix 0.5g of bis(ethylene carbonate) ether, 0.01g of zinc bromide and 0.1g of tetrabutylammonium bromide, and react them in a container at 210℃ and 1MPa pressure for 1h to obtain an in-situ catalyst;

[0073] Step 2: Add 18g of LA monomer to the above in-situ catalyst and react at 160℃ for 1h;

[0074] Step 3: After the reaction is complete, ethanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0075] After characterization, the structural formula of the polylactic acid polyol prepared in this embodiment is as follows:

[0076]

[0077] Example 6

[0078] In this embodiment, a polylactic acid polyol was prepared using the following method:

[0079] Step 1: Mix 0.5g of bis(ethylene carbonate) ether, 0.01g of zinc bromide and 0.5g of tetrabutylammonium iodide, and react in a container at 220℃ and 1MPa pressure for 2h to obtain an in-situ catalyst;

[0080] Step 2: Add 15g of LA monomer to the above in-situ catalyst and react at 160℃ for 1h;

[0081] Step 3: After the reaction is complete, methanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0082] After characterization, the structural formula of the polylactic acid polyol prepared in this embodiment is as follows:

[0083]

[0084] Comparative Example 1

[0085] This comparative example prepared a polylactic acid polyol, which was prepared in the same way as in Example 1, except that the bis(vinyl carbonate) ether added in step 1 was replaced with 0.5g of ethylene glycol diglycidyl ether.

[0086] Comparative Example 2

[0087] This comparative example prepared a polylactic acid polyol using the same preparation method as in Example 1, except that the LA monomer was replaced with butyrolactone.

[0088] Comparative Example 3

[0089] In this comparative example, a polylactic acid polyol was prepared using the following method:

[0090] Step 1: Mix 0.5g of bis(ethylene carbonate) ether, 0.005g of zinc chloride and 0.3g of tetrabutylammonium chloride, and react them in a container at 200℃ and 1MPa pressure for 1h to obtain an in-situ catalyst;

[0091] Step 2: Add 18g of purified LA monomer to the above in-situ catalyst and react at 160℃ for 1h;

[0092] Step 3: After the reaction is complete, methanol is added to the reaction system to precipitate the polylactic acid polyol. After removing the solvent, the polylactic acid polyol is dried under vacuum at 40°C for 48 hours.

[0093] Application Examples

[0094] The polylactic acid polyols prepared in the above examples and comparative examples were reacted with toluene diisocyanate (TDI) to prepare polyurethane materials. The preparation process is as follows:

[0095] 10g of toluene diisocyanate (TDI), 6g of polylactic acid polyol, 0.2g of dibutyltin dilaurate and 0.8g of water were mixed evenly and reacted at room temperature for 1.5h to obtain a reaction solution; the reaction solution was foamed and cured at normal pressure for 24h to obtain the polyurethane sponge material.

[0096] The catalytic activity (higher yield within the same time frame) of the catalytic system in the preparation of polylactic acid polyols in the above examples and comparative examples, as well as the preparation yield of polylactic acid polyols, were tested. The flexibility of the prepared polyurethane materials was also tested, and the test results are shown in Table 1. The flexibility of the polyurethane materials can be characterized by measuring the indentation hardness, which was tested according to GB10807-2006 standard.

[0097] Table 1

[0098] Test Items Yield TOF value Indentation hardness Example 1 85.3％ <![CDATA[3034h -1 ]]> 1.53 Example 2 71.2％ <![CDATA[2543h -1 ]]> 1.55 Example 3 57.8％ <![CDATA[1026h -1 ]]> 1.50 Example 4 98.0％ <![CDATA[3485h -1 ]]> 1.52 Example 5 72.1％ <![CDATA[2464h -1 ]]> 1.48 Example 6 69.8％ <![CDATA[3357h -1 ]]> 1.46 Comparative Example 1 10.1％ <![CDATA[359h -1 ]]> 1.58 Comparative Example 2 13.7％ <![CDATA[487h -1 ]]> 1.65 Comparative Example 3 38.7％ <![CDATA[1375h -1 ]]> 1.67

[0099] As can be seen from the test results in Table 1, replacing bis(ethylene carbonate) ether with ethylene glycol diglycidyl ether in Comparative Example 1 and replacing the LA monomer with butyrolactone in Comparative Example 2 resulted in lower catalytic activity and lower preparation yield in the catalytic systems of Comparative Example 1 and Comparative Example 2. Furthermore, due to the shorter molecular chains of the polylactic acid polyols prepared, the polyurethane materials prepared using them had poor flexibility. The polylactic acid polyol prepared in Comparative Example 3 had a reduced catalyst content, a higher degree of polymerization, a longer chain length, and relatively poor chain segment flexibility. The polylactic acid polyol prepared using it had relatively higher indentation hardness.

[0100] In summary, the preparation method provided by this invention exhibits high catalytic activity and a high yield. Furthermore, the polylactic acid polyol provided in the embodiments of this invention possesses flexible segments, which can provide suitable crosslinking when used to prepare polyurethane materials. The resulting polyurethane materials have low indentation hardness and good flexibility. In addition, the production cost of existing polylactic acid polyols is 50–70 yuan / kg, while the production cost of the polylactic acid polyol of this invention is 40–60 yuan / kg. It can be seen that the method of this invention significantly reduces the preparation cost of polylactic acid polyols.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a polylactic acid polyol, characterized by, The preparation method comprises the following steps: Step 1, preparing an in-situ catalyst by heating reaction of a zinc salt, an organic ammonium salt and bis(ethylene carbonate) ether; Step 2, adding lactide monomers to obtain the polylactic acid polyol by polymerization reaction; The zinc salt is at least one selected from zinc chloride and zinc bromide; the organic ammonium salt is at least one selected from tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium iodide compound; The mass ratio of the zinc salt, the organic ammonium salt and bis(ethylene carbonate) ether is 1:10-50:30-50; The mass ratio of bis(ethylene carbonate) ether in step 1 to lactide monomers in step 2 is 1:30-60.

2. The production method according to claim 1, characterized by, In step 1, the heating reaction is carried out at a temperature of 180-220 ℃ for 1-3 h.

3. The production method according to claim 1, characterized by, In step 2, the polymerization reaction is carried out at a temperature of 130-180 ℃ for 1-2 h.

4. The polylactic acid polyol prepared by the preparation method in any one of claims 1-3.

5. Application of the polylactic acid polyol in claim 4 in preparation of a polyurethane material.

6. A polyurethane material prepared from the polylactic acid polyol of claim 4, characterized by, The preparation comprises the following steps: The polylactic acid polyol and polyisocyanate are reacted under the action of a catalyst to obtain the polyurethane material.

7. The polyurethane material according to claim 6, characterized in that The polyisocyanate is at least one selected from toluene diisocyanate and diphenylmethane diisocyanate.

8. The polyurethane material of claim 6, wherein, The catalyst is a tin catalyst.

9. The polyurethane material according to claim 6, characterized in that, The reaction is carried out for 1-2 h.

10. The polyurethane material of claim 6, wherein, The mass ratio of the polylactic acid polyol to polyisocyanate is 28-65:100.

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