CN115872850A - Method for recovering glycolic acid from polyglycolic acid and application thereof - Google Patents
Method for recovering glycolic acid from polyglycolic acid and application thereof Download PDFInfo
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Abstract
The invention discloses a method for recovering glycolic acid from polyglycolic acid and application thereof. The method comprises the following steps: step A, mixing polyglycolic acid, an organic solvent and water; and B, carrying out liquid-liquid separation on the product obtained in the step A to obtain a water phase and an organic solvent phase. According to the method for recovering glycolic acid from polyglycolic acid, the polyglycolic acid, water and an organic solvent are simultaneously hydrolyzed and extracted, the organic solvent is added during the hydrolysis process, so that the glycolic acid obtained by hydrolysis enters the water phase, colored impurities, unhydrolyzed oligomers and the like generated in the hydrolysis process are dissolved in the oil phase of the organic solvent, the glycolic acid can be rapidly separated, the hydrolysis process is promoted to be carried out, the hydrolysis process is relatively thorough, the content of impurities in the obtained glycolic acid is low, the purity of the glycolic acid is high, and the obtained glycolic acid can directly meet the recycling requirement.
Description
Technical Field
The invention relates to a method for recovering glycolic acid from polyglycolic acid and application thereof.
Background
Glycolic acid is the simplest aliphatic hydroxycarboxylic acid of molecular chains, and is used as an important organic synthesis intermediate in the fields of chemical cleaning, welding, sterilization, high polymer materials and the like. Among them, polyglycolic acid obtained by polymerizing glycolic acid monomers has good biodegradability and is widely used in the medical industry, for example, as an operation suture.
However, glycolic acid is relatively active in nature, and is highly susceptible to side reactions such as oxidation and carbonization at the polymerization temperature, resulting in severe yellowing of polyglycolic acid formed by polymerization. None of the conventional processes for synthesizing polyglycolic acid can be carried out by direct polymerization of glycolic acid. Also, polyglycolic acid obtained by direct polymerization of glycolic acid has a low molecular weight, and thus cannot satisfy the demand of practical use. In general, the problems of yellowing and low molecular weight can be solved well by dimerizing glycolic acid to produce glycolide, and further performing ring-opening polymerization using glycolide as a monomer.
In general, the process of preparing glycolide using glycolic acid requires three steps of prepolymerization, depolymerization and purification.
CN111087381A relates to a refining treatment method of glycolide, which mainly solves the problem of high acid value of glycolide crystals obtained by refining treatment, and the refining treatment method of glycolide comprises the steps of stirring and mixing crude glycolide and a solvent in a stirring mode of combining a stirring paddle and a stirring cutter head, and then crystallizing.
CN100999516A relates to a method for purifying glycolide by removing glycolide oligomers, glycolic acid, water and other impurities from crude glycolide to obtain high-yield and high-purity glycolide from the crude glycolide. The method comprises mixing a mixture of glycolide containing a glycolide oligomer, glycolic acid and water with an organic solvent, and can remove glycolic acid and water from crude glycolide, thereby preventing hydrolysis of glycolide and producing high-purity glycolide in high yield.
The two technical schemes are that crude glycolide generated by depolymerization is contacted with an alcohol/ester solvent, and glycolic acid monomers, linear oligomers and colored impurities in the crude glycolide are removed by washing. In addition, in order to improve the utilization rate of the raw material, it is necessary to recycle glycolic acid oligomer in the washing liquid. Therefore, how to efficiently and stably recover glycolic acid monomers from glycolic acid oligomers is a problem to be solved.
Disclosure of Invention
In view of the above problems of the prior art, the present invention provides a method for recovering glycolic acid from polyglycolic acid and its use. In the method, the polyglycolic acid, the organic solvent and the water are simultaneously mixed and reacted, so that colored impurities and some unhydrolyzed oligomers generated in the hydrolysis process can be simultaneously dissolved in the organic solvent, and the glycolic acid in the water phase obtained by liquid-liquid separation can directly meet the recycling requirement.
In a first aspect the present invention provides a process for the recovery of glycolic acid from polyglycolic acid, the process comprising the steps of:
step A, mixing polyglycolic acid, an organic solvent and water;
and B, carrying out liquid-liquid separation on the product obtained in the step A to obtain a water phase and an organic solvent phase.
According to the method for recovering glycolic acid from polyglycolic acid, an organic solvent and water are directly mixed, so that hydrolysis and extraction of polyglycolic acid are simultaneously carried out, glycolic acid obtained by hydrolysis enters an aqueous phase, impurities and unhydrolyzed oligomers generated in the hydrolysis process are dissolved in the organic solvent phase, hydrolysis is promoted, and glycolic acid in the obtained aqueous phase can directly meet the recycling requirement.
According to some embodiments of the method of the present invention, the organic solvent is selected from C 4 Fatty alcohol, C above 4 Aliphatic polyol and C 6 The above fatAlcohol, C 6 The above aliphatic polyhydric alcohols and aliphatic ketones.
According to some embodiments of the method of the present invention, the organic solvent has a solubility in water of < 3g/100mL at ambient temperature.
According to a preferred embodiment of the process of the invention, the organic solvent has a solubility in water of < 0.1g/100mL at ambient temperature.
According to some embodiments of the method of the present invention, the organic solvent is selected from at least one of n-butanol, n-hexanol, n-octanol, n-hexanoic acid and methyl isobutyl ketone.
According to some embodiments of the method of the present invention, the polyglycolic acid is selected from at least one of low molecular weight polyglycolic acid.
According to some embodiments of the method of the present invention, the low molecular weight polyglycolic acid has a number average molecular weight of 400 to 2000.
According to some embodiments of the method of the present invention, the low molecular weight polyglycolic acid has a weight content of > 50% of hexamers or more based on the total weight of the polyglycolic acid.
According to a preferred embodiment of the process according to the invention, the low molecular weight polyglycolic acid has a content of > 70% by weight of hexamers or more based on the total weight of the polyglycolic acid.
According to some embodiments of the method of the present invention, the polyglycolic acid contains colored impurities.
According to some embodiments of the method of the present invention, preferably, the colored impurities are present in an amount of ≦ 10% by weight based on the total weight of the polyglycolic acid.
According to some embodiments of the method of the present invention, the weight ratio of the polyglycolic acid, the organic solvent, and the water is 1:0.01 to 3:0.1 to 10.
According to a preferred embodiment of the method of the present invention, the weight ratio of the polyglycolic acid, the organic solvent, and the water is 1:0.1 to 1:0.3 to 5.
In some embodiments of the method according to the invention, the conditions of the polyglycolic acid, organic solvent, and water mixing process include: the temperature is 70-150 ℃ and the time is 0.1-10 h. For example, in various embodiments of the present invention, the temperature of the mixing process can be 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, and any values and any combination ranges therebetween. The mixing process may be performed for 0.1h, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, and any value and any range of combinations therebetween.
According to a preferred embodiment of the method of the present invention, the temperature of the mixing process of the polyglycolic acid, the organic solvent, and the water is 80 to 140 ℃.
According to some embodiments of the methods of the present invention, in step B, the liquid-liquid separation process is performed at a temperature of 50 ℃ or less.
According to a preferred embodiment of the method of the present invention, in step B, the temperature of the liquid-liquid separation process is less than or equal to 40 ℃.
According to some embodiments of the method of the present invention, step B is followed by: the aqueous phase is concentrated.
According to a preferred embodiment of the process according to the invention, the water content in the aqueous phase after the concentration treatment is less than or equal to 50% by weight.
In a second aspect, the invention provides the use of a process as described above for the recovery of glycolic acid from polyglycolic acid in the production of glycolic acid. Preferably in the production of glycolide. But is not limited thereto.
The invention has the beneficial effects that:
according to the method for recovering the glycolic acid from the polyglycolic acid, water and an organic solvent are hydrolyzed and extracted at the same time, the organic solvent is added at the same time of the hydrolysis process, so that the glycolic acid obtained by hydrolysis enters a water phase, colored impurities, unhydrolyzed oligomers and the like generated in the hydrolysis process are dissolved in an organic solvent oil phase, the glycolic acid can be rapidly separated, the hydrolysis process is promoted, the hydrolysis process is thorough, the content of impurities in the obtained glycolic acid is low, the purity is high, and the obtained glycolic acid can directly meet the recycling requirement.
Detailed Description
In order that the present invention may be more readily understood, the following detailed description of the invention is given by way of example only, and is not intended to limit the scope of the invention.
The test method and the equipment used in the test are as follows:
(1) The HPLC is model 2695 from Waters, and the operating conditions for performing HPLC analysis on the oil phase and the water phase are as follows: the mobile phase is 0.5% phosphoric acid water solution and acetonitrile, the mixture ratio of the two is 95.
(2) The rotary evaporator was a Heizbad Hei-VAP model from heidolph.
(3) The absorbance value is measured by a spectrophotometer, and the model of the spectrophotometer is as follows: shanghai instrument electricity L5S.
The reagents used in the following examples and comparative examples are all commercially available.
[ example 1 ]
The raw material composition in this example is shown in table 1 below:
TABLE 1
30g of the raw materials shown in the table 1, 60g of water and 30g of n-octanol are placed in a 250mL stainless steel reaction kettle, the reaction kettle is sealed, nitrogen is introduced into the reaction kettle to replace air in the reaction kettle for 3 times, and then 0.5MPa nitrogen is injected. Heating a stainless steel reaction kettle to 130 ℃ to carry out hydrolysis reaction for 3h.
After the reaction is finished, stirring the reaction system until the reaction system is cooled to 50 ℃, transferring the reaction liquid into a separating funnel, and standing for layering. After layering, impurities such as colored substances and the like in the reaction system are enriched in the upper oil phase (namely n-octanol), and glycolic acid generated by hydrolysis is enriched in the lower water phase.
HPLC analysis (high performance liquid chromatography) was performed on the oil phase and the aqueous phase, respectively, to obtain compositions of the oil phase and the aqueous phase as shown in Table 2.
And (3) diluting the water-phase product to 5.00 percent of monomer weight according to the monomer content, and testing the absorbance of the product at 390nm to obtain the value of 0.01735.
Separating water phase, vacuum concentrating the separated water phase in a rotary evaporator until glycolic acid content in the water phase reaches 65%, and closing rotary evaporation to obtain recovered glycolic acid water solution.
TABLE 2
[ example 2 ] A method for producing a polycarbonate
The same procedure as in example 1, except that: n-octanol is replaced by n-butanol. And HPLC analysis was performed on the finally separated oil phase and water phase, respectively, to obtain compositions of the oil phase and water phase as shown in table 3.
And (3) diluting the water-phase product to 5.00 percent of monomer weight content according to the monomer content, and testing the absorbance of the product at 390nm to obtain the value of 0.01801.
TABLE 3
[ example 3 ]
The same procedure as in example 1, except that: n-hexanol was used instead of n-octanol. And HPLC analysis was performed on the finally separated oil phase and water phase, respectively, to obtain compositions of the oil phase and water phase as shown in table 4.
And (3) diluting the water-phase product to 5.00 percent of monomer weight content according to the monomer content, and testing the absorbance of the product at 390nm to obtain the value of 0.01769.
TABLE 4
[ example 4 ]
The same procedure as in example 1, except that: n-octanol was replaced with n-hexanoic acid. And HPLC analysis was performed on the finally separated oil phase and water phase, respectively, to obtain compositions of the oil phase and water phase as shown in table 5.
The aqueous phase product was diluted to a monomer content of 5.00% by weight and the absorbance of the product was measured at 390nm to give a value of 0.01881.
TABLE 5
[ example 5 ] A method for producing a polycarbonate
The same procedure as in example 1, except that: methyl isobutyl ketone is used to replace n-octanol. And HPLC analysis was performed on the finally separated oil phase and water phase, respectively, to obtain compositions of the oil phase and water phase as shown in table 6.
The water phase product was diluted to 5.00% by weight monomer content and the absorbance of the product was measured at 390nm to give a value of 0.01806.
TABLE 6
[ example 6 ]
The same procedure as in example 1, except that: a250 mL stainless steel reaction vessel was charged with 30g of the starting material shown in Table 1, 9g of water, and 30g of n-octanol. And HPLC analysis was performed on the finally separated oil phase and water phase, respectively, to obtain compositions of the oil phase and water phase as shown in table 7.
And (3) diluting the water-phase product according to the monomer content until the weight content of the monomer is 5.00%, and testing the absorbance of the product at 390nm to obtain the value of 0.03235.
TABLE 7
[ example 7 ]
The same procedure as in example 1, except that: to a 250mL stainless steel reaction vessel were added 30g of the raw material shown in Table 1, 30g of water, and 30g of n-octanol. And HPLC analysis was performed on the finally separated oil phase and aqueous phase, respectively, to obtain compositions of the oil phase and aqueous phase as shown in Table 8.
The water phase product is diluted to 5.00 percent of monomer content according to the monomer content, and the absorbance of the product is tested at 390nm to obtain the value of 0.02661.
TABLE 8
[ example 8 ]
The same procedure as in example 1, except that: a250 mL stainless steel reaction vessel was charged with 30g of the raw material shown in Table 1, 90g of water, and 30g of n-octanol. And HPLC analysis was performed on the finally separated oil phase and aqueous phase, respectively, to obtain compositions of the oil phase and aqueous phase as shown in Table 9.
And (3) diluting the water-phase product to 5.00 percent of monomer weight according to the monomer content, and testing the absorbance of the product at 390nm to obtain the value of 0.01704.
TABLE 9
[ example 9 ]
The same procedure as in example 1, except that: a250 mL stainless steel reaction vessel was charged with 30g of the raw material shown in Table 1, 150g of water, and 30g of n-octanol. And HPLC analysis was performed on the finally separated oil phase and aqueous phase, respectively, to obtain compositions of the oil phase and aqueous phase as shown in Table 10.
And (3) diluting the water-phase product to 5.00 percent of monomer weight content according to the monomer content, and testing the absorbance of the product at 390nm to obtain the value of 0.01700.
Watch 10
[ example 10 ] A method for producing a polycarbonate
The same procedure as in example 1, except that: to a 250mL stainless steel reaction vessel were added 30g of the raw material shown in Table 1, 30g of water, and 3g of n-octanol. And HPLC analysis was performed on the finally separated oil phase and aqueous phase, respectively, to obtain compositions of the oil phase and aqueous phase as shown in Table 11.
And (3) diluting the water-phase product according to the monomer content until the weight content of the monomer is 5.00%, and testing the absorbance of the product at 390nm to obtain the value of 0.01933.
TABLE 11
[ example 11 ] A method for producing a polycarbonate
The same procedure as in example 1, except that: to a 250mL stainless steel reaction vessel were added 30g of the raw material shown in Table 1, 30g of water, and 15g of n-octanol. And HPLC analysis was performed on the finally separated oil phase and aqueous phase, respectively, to obtain compositions of the oil phase and aqueous phase as shown in table 12.
And (3) diluting the water-phase product according to the monomer content until the weight content of the monomer is 5.00%, and testing the absorbance of the product at 390nm to obtain the value of 0.01910.
TABLE 12
[ example 12 ]
The same procedure as in example 1, except that: the composition of the raw materials in this example is shown in table 15 below:
watch 13
In this example, the procedure was the same as in example 1, and HPLC analysis was performed on the finally separated oil phase and aqueous phase, respectively, to obtain compositions of the oil phase and the aqueous phase as shown in Table 14.
And (3) diluting the water-phase product to 5.00 percent of monomer weight according to the content of the monomer, and testing the absorbance of the product at 390nm to obtain the value of 0.01666.
TABLE 14
Comparative example 1
40g of the raw materials shown in Table 1 and 80g of water were placed in a 250mL stainless steel reaction vessel, the reaction vessel was sealed, and then nitrogen gas was introduced into the reaction vessel to displace 3 MPa of air in the vessel, followed by purging with 0.5MPa of nitrogen gas. Heating a stainless steel reaction kettle to 130 ℃ to carry out hydrolysis reaction for 3h.
After the reaction, the reaction system was stirred until the reaction system was cooled to 50 ℃, and the reaction solution was not layered after the reaction, and the HPLC analysis was performed on the reaction solution to obtain the composition shown in table 15.
The product was diluted to 5.00% by weight monomer content and the absorbance of the product was measured at 390nm to give a value of 0.33582.
Watch 15
Comparative example 2
60g of the product obtained in comparative example 1 was added with 20g of n-octanol, and the mixture was stirred at room temperature for 30min and then layered, and the separated oil phase and water phase were subjected to HPLC analysis, respectively, to obtain compositions of the oil phase and water phase as shown in Table 16.
And (3) diluting the water-phase product according to the monomer content until the weight content of the monomer is 5.00%, and testing the absorbance of the product at 390nm to obtain the value of 0.03557.
TABLE 16
As can be seen from the above examples and comparative examples, the method for recovering glycolic acid from low molecular weight polyglycolic acid provided by the present invention employs a method of simultaneously hydrolyzing and extracting low molecular weight polyglycolic acid, water and an organic solvent, so that glycolic acid obtained by hydrolysis enters an aqueous phase, colored impurities and unhydrolyzed oligomers generated in the hydrolysis process are dissolved in an organic solvent oil phase, glycolic acid can be rapidly separated, and the hydrolysis process is promoted to be relatively thorough, and the obtained glycolic acid has a low impurity content and a high purity.
What has been described above is merely a preferred example of the present invention. It should be noted that other equivalent variations and modifications can be made by those skilled in the art based on the technical teaching provided by the present invention, and the protection scope of the present invention should be considered.
Claims (10)
1. A method for recovering glycolic acid from polyglycolic acid, the method comprising the steps of:
step A, mixing polyglycolic acid, an organic solvent and water;
and B, carrying out liquid-liquid separation on the product obtained in the step A to obtain a water phase and an organic solvent phase.
2. The method according to claim 1, wherein the organic solvent is selected from C 4 Fatty alcohol, C above 4 Aliphatic polyol and C 6 Fatty alcohol, C above 6 The above aliphatic polyhydric alcohols and aliphatic ketones.
3. The method according to claim 1 or 2, wherein the solubility of the organic solvent in water is < 3g/100mL at ambient temperature, preferably < 0.1g/100mL at ambient temperature.
4. The method according to any one of claims 1 to 3, wherein the organic solvent is at least one selected from the group consisting of n-butanol, n-hexanol, n-octanol, n-hexanoic acid, and methyl isobutyl ketone.
5. The process according to any one of claims 1 to 4, wherein the polyglycolic acid is at least one selected from low molecular weight polyglycolic acids, preferably the low molecular weight polyglycolic acid has a number average molecular weight of 400 to 2000, more preferably the low molecular weight polyglycolic acid has a content of hexamers or more of > 50% by weight based on the total weight of the polyglycolic acid, still more preferably the low molecular weight polyglycolic acid has a content of hexamers or more of > 70% by weight based on the total weight of the polyglycolic acid.
6. The method according to any one of claims 1 to 5, characterized in that the polyglycolic acid contains colored impurities, preferably in an amount of 10% by weight or less based on the total weight of the polyglycolic acid.
7. The method according to any one of claims 1 to 6, wherein the weight ratio of the polyglycolic acid to the organic solvent to the water is 1:0.01 to 3: 0.1-10, preferably, the weight ratio of the polyglycolic acid, the organic solvent and the water is 1:0.1 to 1:0.3 to 5.
8. The method according to any one of claims 1 to 7, wherein in step A, the conditions of the polyglycolic acid, the organic solvent, and the water mixing process include: the temperature is 70-150 ℃, the time is 0.1-10 h, and preferably, the temperature of the mixing process of the polyglycolic acid, the organic solvent and the water is 80-140 ℃; and/or the presence of a gas in the gas,
in the step B, the temperature in the liquid-liquid separation process is less than or equal to 50 ℃, and preferably, the temperature in the liquid-liquid separation process is less than or equal to 40 ℃.
9. The method according to any one of claims 1-8, further comprising, after step B: and (3) concentrating the water phase, preferably, the weight content of water in the water phase after the concentration treatment is less than or equal to 50%.
10. Use of a process for the recovery of glycolic acid from polyglycolic acid according to any one of claims 1 to 9 in the production of glycolic acid, preferably glycolide.
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