Preparation method of polylactic acid bio-based polyester ether polyol

Abstract

The present invention belongs to the technical field of polyester ether polyols, and specifically relates to a method for preparing polylactic acid bio-based polyester ether polyols. The method for preparing polylactic acid bio-based polyester ether polyols comprises the following steps: firstly dispersing lactic acid in a small molecule alcohol to carry out lactic acid dehydration and self-polymerization, and then using the obtained polylactic acid and small molecule alcohol as raw materials, carrying out an esterification reaction under the action of a small molecule alcohol mixed esterification catalyst to obtain an intermediate; finally, adding a high-functionality alcohol initiator, bio-oil, and an alkaline catalyst to the intermediate, and carrying out a polymerization reaction with an epoxy olefin to obtain polylactic acid bio-based polyester ether polyols. The polylactic acid bio-based polyester ether polyols of the present invention have the characteristics of low hydroxyl value, low viscosity, and good compatibility, and the polyurethane foam prepared therefrom has good mechanical properties, is green and degradable, and is environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester ether polyols, and particularly relates to a method for preparing polylactic acid bio-based polyester ether polyols. Background Art

[0002] At present, with the increasing scarcity of petrochemical resources, bio-based polyurethane foam materials have become a hot topic of research, and various bio-based alternative products have gradually been discovered. For example, vegetable oil, cashew nut shell oil, corn straw and other bio-based renewable raw materials are used to synthesize polyols or isocyanates as the main raw materials for polyurethane materials, which are then subjected to various chemical modifications and foaming to obtain various types of polyurethane foam materials.

[0003] Among them, polylactic acid (PLA) is a good biodegradable material with good mechanical properties, compatibility, and physical properties, and has good biodegradability. After use, it can be completely degraded by microorganisms in nature, and finally generates carbon dioxide and water, which does not pollute the environment. It is a recognized environmentally friendly material. However, the existing bio-based polyether polyols or bio-based polyester polyols synthesized with polylactic acid as raw materials are difficult to achieve the indicators of low hydroxyl value and low viscosity at the same time, and have poor compatibility with polyurethane foaming agents, which greatly limits their application in degradable polyurethane products. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing polylactic acid bio-based polyester ether polyol, which has the characteristics of low hydroxyl value, low viscosity and good compatibility, and the polyurethane foam prepared therefrom has good mechanical properties, is green and degradable, and is environmentally friendly.

[0005] The preparation method of the polylactic acid bio-based polyester ether polyol of the present invention comprises the following steps: firstly dispersing lactic acid in a small molecule alcohol to carry out lactic acid dehydration self-polymerization; then using the obtained polylactic acid and the small molecule alcohol as raw materials, carrying out an esterification reaction under the action of a small molecule alcohol mixed esterification catalyst to obtain an intermediate; finally, adding a high-functionality alcohol initiator, bio-oil, and an alkaline catalyst to the intermediate, carrying out a polymerization reaction with an olefin oxide, and obtaining the polylactic acid bio-based polyester ether polyol.

[0006] Preferably, the method for preparing the polylactic acid bio-based polyester ether polyol comprises the following steps:

[0007] (1) Lactic acid and a small molecule alcohol are placed in a reaction kettle, and lactic acid is dehydrated and self-polymerized at 70-80° C. for 2-3 hours, and then a small molecule alcohol mixed esterification catalyst is added, and the temperature is first raised to 120-130° C. for esterification reaction for 5-6 hours, and then the temperature is further raised to 160-190° C., and negative pressure dehydration is performed at a pressure lower than -0.09 MPa for 3-4 hours to obtain an intermediate;

[0008] (2) Cooling the intermediate to 80-100° C., adding a high-functionality alcohol initiator, bio-oil, and an alkaline catalyst and mixing them evenly, pre-dripping the epoxy olefin, and then heating the mixture to 110-120° C., and continuing to feed the epoxy olefin. After the feeding is completed, the polymerization reaction is continued for 2-3 hours to obtain polylactic acid bio-based polyester ether polyol.

[0009] In the present invention, the lactic acid is dispersed in a small molecule alcohol for dehydration and self-polymerization, which can avoid excessive viscosity after the lactic acid self-polymerization, which is not conducive to stirring. The obtained polylactic acid is an oligomer polylactic acid synthesized by dehydration and polycondensation of lactic acid.

[0010] In the present invention, the small molecule alcohol is one or more of diethylene glycol, propylene glycol, glycerol, butylene glycol, and ethylene glycol.

[0011] In the present invention, the esterification catalyst is one or more of p-toluenesulfonic acid, tetrabutyl titanate, stannous octoate, stannous chloride dihydrate, and dibutyltin laurate; the added amount of the esterification catalyst is 0.05-0.1% of the total mass of lactic acid and small molecule alcohol.

[0012] In the present invention, the mass ratio of the small molecule alcohol to lactic acid is 0.5:(1-20).

[0013] In the present invention, in the small molecule alcohol mixed esterification catalyst, the mass ratio of the small molecule alcohol to the esterification catalyst is 1:(0.05-0.1).

[0014] In the present invention, the high-functionality alcohol initiator is one or both of sucrose and sorbitol; the mass ratio of the high-functionality alcohol initiator to lactic acid is (0.3-1):1.

[0015] In the present invention, the bio-oil is one or more of palm oil, soybean oil, epoxidized soybean oil, castor oil, cottonseed oil, and corn oil; the mass ratio of the bio-oil to lactic acid is (0.3-1):1.

[0016] In the present invention, the epoxy olefin is one or both of propylene oxide and ethylene oxide; the amount of epoxy olefin added is determined by calculating the designed hydroxyl value of the target product polyester ether polyol.

[0017] In the present invention, the alkaline catalyst is one or more of potassium hydroxide, sodium hydroxide, dimethylamine, triethylamine, N,N-dimethylbenzylamine, and N,N-dimethylaniline; the amount of the alkaline catalyst added is 0.1-1% of the total mass of the intermediate, high-functionality alcohol initiator, bio-oil, and epoxy olefin.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention first disperses lactic acid in a small molecule alcohol to carry out lactic acid dehydration and self-polymerization, then uses the obtained polylactic acid and the small molecule alcohol as raw materials to synthesize a polylactic acid ester compound, and then carries out polymerization reaction with a high-functionality alcohol initiator, bio-oil and epoxy olefin. The prepared polyester ether polyol has a hydroxyl value of 300-400 mgKOH / g and a viscosity of 3000-7000 mPa·s at 25° C., and has the characteristics of low hydroxyl value, low viscosity and good compatibility, and the polyurethane foam prepared therefrom has good mechanical properties;

[0020] (2) The polylactic acid used in the present invention is widely available and is green and degradable. The synthesized polyester ether polyol can be completely degraded, and the obtained products are environmentally friendly. DETAILED DESCRIPTION

[0021] The present invention is further described below with reference to the examples. The raw materials used in the examples, unless otherwise specified, are all commercially available conventional raw materials; the process methods used in the examples, unless otherwise specified, are all conventional methods in the art.

[0022] Example 1

[0023] Polylactic acid bio-based polyester ether polyol A was prepared as follows:

[0024] (1) Add 425g of lactic acid and 76g of propylene glycol to a reactor, close the reactor and test for leakage and replace, then heat to 70°C under a nitrogen atmosphere, and bubbling nitrogen under a negative pressure of -0.09 MPa to perform lactic acid dehydration and self-polymerization for 3h; then dissolve 0.5g of stannous octoate esterification catalyst in 5g of diethylene glycol, draw into the reactor, stir and heat to 120°C, heat to the set temperature and react for 6 hours, during which water is intermittently discharged to maintain the pressure in the reactor <0.4 MPa; after the pressure in the reactor is stable, continue to heat to 160°C for negative pressure dehydration reaction, and bubbling nitrogen under a pressure of -0.09 MPa for 4h to obtain an intermediate;

[0025] (2) The intermediate was cooled to 100°C, and a mixture of 240g sucrose, 10g alkaline catalyst triethylamine and 360g palm oil was drawn in. After stirring evenly, the temperature was controlled at 85°C, and propylene oxide was pre-dripped. The pre-dripping mass was 180g. After the pre-dripping was completed, the temperature was raised to 120°C, and propylene oxide was continued to be fed. The mass was 153g. After the feeding was completed, the internal pressure was maintained for 2h. After the internal pressure was completed, the negative pressure was pumped to -0.09Mpa. After degassing and bubbling for half an hour, the temperature was lowered to about 80°C, and the material was discharged to obtain polylactic acid bio-based polyester ether polyol A with a hydroxyl value of 305mgKOH / g and a viscosity of 3256mPa·s at 25°C.

[0026] Example 2

[0027] Polylactic acid bio-based polyester ether polyol B was prepared as follows:

[0028] (1) Add 635g of polylactic acid and 106g of diethylene glycol to a reactor, close the reactor and test for leakage and replace, then heat to 80°C under nitrogen atmosphere, and bubbling nitrogen under negative pressure of -0.09 MPa to carry out lactic acid dehydration and self-polymerization for 2h; then dissolve 0.3g of p-toluenesulfonic acid esterification catalyst in 5g of glycerol, draw into the reactor, stir and heat to 130°C, heat to the set temperature and react for 5 hours, during which water is intermittently discharged to maintain the pressure in the reactor <0.4 MPa; after the pressure in the reactor is stable, continue to heat to 190°C for negative pressure dehydration reaction, and bubbling nitrogen under pressure of -0.09 MPa for 3h to obtain an intermediate;

[0029] (2) The intermediate was cooled to 80°C, and a mixture of 325g sucrose, 12g alkaline catalyst N,N-dimethylbenzylamine and 380g soybean oil was drawn in. After stirring evenly, the temperature was controlled at 85°C, and propylene oxide was pre-dripped with a mass of 280g. After the pre-dripping was completed, the temperature was raised to 110°C, and propylene oxide was continued to be fed with a mass of 140g. After the feeding was completed, the internal pressure was maintained for 3h. After the internal pressure was completed, the negative pressure was pumped to -0.09Mpa. After degassing and bubbling for half an hour, the temperature was lowered to about 80°C, and the material was discharged to obtain polylactic acid bio-based polyester ether polyol B with a hydroxyl value of 345mgKOH / g and a viscosity of 5567mPa·s at 25°C.

[0030] Comparative Example 1

[0031] Polyether polyol B1 was prepared as follows:

[0032] 325 g of sucrose, 50 g of solid sorbitol, 80 g of diethylene glycol, 255 g of palm oil and 12 g of fatty amine catalyst were added to the reaction kettle. After the kettle was closed for leak testing and replacement, the temperature was raised to 105°C under negative pressure. After reaching the temperature, 787 g of propylene oxide was dripped into the kettle. At the same time, the nitrogen atmosphere pressure in the kettle was maintained at 0.13±0.02 MPa. After the dripping of propylene oxide was completed, the reaction was kept warm for 3 hours until the pressure in the kettle no longer decreased. After bubbling and stripping of monomers for 2 hours, the temperature was lowered to 80°C and the material was discharged to obtain polyether polyol B1 with a hydroxyl value of 405 mgKOH / g and a viscosity of 5830 mPa·s at 25°C.

[0033] Comparative Example 2

[0034] Polyether polyol B2 was prepared as follows:

[0035] 325 g of sucrose, 165 g of diethylene glycol and 11.4 g of DMA catalyst were added to the reactor. After the reactor was closed for leak testing and replacement, the temperature was raised to 105°C under negative pressure. After reaching the temperature, 913 g of propylene oxide was dripped into the reactor. At the same time, the nitrogen atmosphere pressure in the reactor was maintained at 0.13±0.02 MPa. After the dripping of propylene oxide was completed, the reaction was kept warm for 3 hours until the pressure in the reactor no longer decreased. After bubbling and stripping of monomers for 2 hours, the temperature was lowered to 80°C, and the material was discharged to obtain polyether polyol B2 with a hydroxyl value of 440 mgKOH / g and a viscosity of 3460 mPa·s at 25°C.

[0036] The product indicators of the polyols prepared in Example 1-2 and Comparative Example 1-2 are shown in Table 1.

[0037] Table 1

[0038] index Hydroxyl value (mgKOH / g) Viscosity (mPa.s) Bio-based content (%) Cyclopentane miscibility (g / 100g) Example 1 305 3256 75.2 82 Example 2 345 5567 75.8 68 Comparative Example 1 405 5830 47.1 55 Comparative Example 2 440 3460 34.6 15

[0039] As can be seen from Table 1, the bio-based polyester ether synthesized by using polylactic acid as an initiator in the present invention has a large molecular weight, a low hydroxyl value, a medium viscosity, and a bio-based content of more than 75%, which greatly reduces petroleum resources and oxidized olefin resources. After being used to synthesize polyurethane, the product is degradable and polymeric, which is environmentally friendly; at the same time, the bio-based polyester ether has better miscibility with the polyurethane foam blowing agent.

[0040] The polyols of Example 1-2 and Comparative Example 1-2 were used to prepare polyurethane foams. The raw material composition and performance test results are shown in Table 2. The raw material amounts are expressed in parts by mass.

[0041] Table 2

[0042]

[0043] As can be seen from Table 2, due to the change of the initiator, the increase of the molecular weight and the decrease of the hydroxyl value index, the activity of the polyester ether polyol of the present invention is lower than that of the polyether polyols commonly used in the current market (Comparative Examples 1-2), and it is easier to adjust and apply the downstream combined polyether formula, and the physical properties are also better than those of conventional polyether products.

Claims

1. A method for preparing polylactic acid bio-based polyester ether polyol, Features: First, lactic acid is dispersed in a small molecule alcohol to carry out lactic acid dehydration self-polymerization, and then the obtained polylactic acid and small molecule alcohol are used as raw materials to carry out esterification reaction under the action of a small molecule alcohol mixed esterification catalyst to obtain an intermediate; finally, a high-functionality alcohol initiator, bio-oil, and an alkaline catalyst are added to the intermediate to carry out polymerization reaction with epoxy olefins to obtain polylactic acid bio-based polyester ether polyol; in: The small molecule alcohol is one or more of diethylene glycol, propylene glycol, glycerol, butylene glycol, and ethylene glycol; The mass ratio of the small molecule alcohol to lactic acid is 0.5:(1-20); In the small molecule alcohol mixed esterification catalyst, the mass ratio of the small molecule alcohol to the esterification catalyst is 1:(0.05-0.1); The high-functionality alcohol initiator is one or both of sucrose and sorbitol; the mass ratio of the high-functionality alcohol initiator to lactic acid is (0.3-1):1; The bio-oil is one or more of palm oil, soybean oil, epoxidized soybean oil, castor oil, cottonseed oil, and corn oil; the mass ratio of the bio-oil to lactic acid is (0.3-1):

1.

2. The method for preparing polylactic acid bio-based polyester ether polyol according to claim 1, Features: The following steps are involved: (1) Lactic acid and a small molecule alcohol are placed in a reaction kettle, and lactic acid is dehydrated and self-polymerized at 70-80° C. for 2-3 hours, and then a small molecule alcohol mixed esterification catalyst is added, and the temperature is first raised to 120-130° C. for esterification reaction for 5-6 hours, and then the temperature is further raised to 160-190° C., and negative pressure dehydration is performed at a pressure lower than -0.09 MPa for 3-4 hours to obtain an intermediate; (2) Cooling the intermediate to 80-100° C., adding a high-functionality alcohol initiator, bio-oil, and an alkaline catalyst and mixing them evenly, pre-dripping the epoxy olefin, and then heating the mixture to 110-120° C., and continuing to feed the epoxy olefin. After the feeding is completed, the polymerization reaction is continued for 2-3 hours to obtain polylactic acid bio-based polyester ether polyol.

3. The method for preparing polylactic acid bio-based polyester ether polyol according to claim 1, Features: The esterification catalyst is one or more of p-toluenesulfonic acid, tetrabutyl titanate, stannous octoate, stannous chloride dihydrate, and dibutyltin laurate; the added amount of the esterification catalyst is 0.05-0.1% of the total mass of lactic acid and small molecule alcohol.

4. The method for preparing polylactic acid bio-based polyester ether polyol according to claim 1, Features: The olefin oxide is one or both of propylene oxide and ethylene oxide.

5. The method for preparing polylactic acid bio-based polyester ether polyol according to claim 1, Features: The alkaline catalyst is one or more of potassium hydroxide, sodium hydroxide, dimethylamine, triethylamine, N,N-dimethylbenzylamine and N,N-dimethylaniline; the amount of the alkaline catalyst added is 0.1-1% of the total mass of the intermediate, high-functionality alcohol initiator, bio-oil and epoxy olefin.

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