Preparation method of polyglycolic acid with low yellowness value and obtained polyglycolic acid

Abstract

The invention discloses a preparation method of polyglycolic acid with a low yellowness value and the obtained polyglycolic acid. The preparation method of the low-yellowness-value polyglycolic acid comprises the step of carrying out mixed reaction on components including glycolide and a reaction aid, the mixed reaction adopts an at least four-stage gradient heating mode; the temperature of the second section is increased by 0-9 DEG C, preferably 5-9 DEG C, compared with that of the first section; the temperature of the last section is 1-5 DEG C higher than that of the previous adjacent section, preferably 2-5 DEG C; the temperature of the latter section of the other adjacent sections is increased by 16-40 DEG C compared with the temperature of the former adjacent section, and preferably, the temperature is increased by 16-35 DEG C. According to the method, a specific gradient heating process is adopted, so that side reactions such as depolymerization reaction, aromatization reaction and monomer cracking reaction in the reaction process can be reduced, and the yellowness value of a polyglycolic acid product is reduced, and the hue of the product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyglycolic acid preparation, and in particular to a preparation method of polyglycolic acid with a low yellowness value and the obtained polyglycolic acid. Background Art

[0002] Polyglycolic acid (PGA) is a biodegradable polymer with excellent gas barrier properties, good machining performance, and outstanding biodegradability. It is widely used in medical materials (surgical sutures and drug sustained-release capsules), packaging materials (bottle linings), membrane materials (ground membranes), and engineering plastics (petroleum field).

[0003] The synthesis of PGA is generally obtained by the ring-opening polymerization of glycolide. Depending on the process and formula, the yellowness value of the obtained PGA is different. Some downstream products have higher requirements on the yellowness value of raw materials, such as medical materials and packaging materials. In the prior art, taking patent CN112469763A as an example, the yellowness value of the polyglycolic acid prepared therein is 40-90, which is difficult to meet the needs of specific products.

[0004] Therefore, there is an urgent need for a process for preparing polyglycolic acid with a low yellowness value. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for preparing polyglycolic acid with a low yellowness value and the obtained polyglycolic acid. The present invention adopts a specific gradient temperature increase process, so that each reaction section such as the active center generation section, the reaction initiation section, the deep polymerization section, and the reaction equilibrium section are carried out within a preferred temperature range, which can reduce the occurrence of side reactions such as depolymerization reaction, aromatization reaction, and monomer cracking reaction during the reaction process, which is manifested in the reduction of the yellowness value of the polyglycolic acid product and the improvement of the product hue.

[0006] One of the purposes of the present invention is to provide a method for preparing polyglycolic acid with a low yellowness value, comprising the steps of mixing components including glycolide and a reaction aid; the mixing reaction adopts at least 4-stage gradient temperature increase; the temperature of the second stage is increased by 0-9°C than that of the first stage, preferably by 5-9°C; the temperature of the last stage is increased by 1-5°C than that of the previous adjacent stage, preferably by 2-5°C; the temperature of the latter stage of other adjacent stages is increased by 16-40°C than that of the previous adjacent stage, preferably by 16-35°C.

[0007] In a preferred embodiment of the present invention,

[0008] The mixed reaction adopts a 4-9 stage gradient temperature increase method, preferably a 5-9 stage gradient temperature increase method, for example, a 5-stage, 6-stage, 7-stage, 8-stage, 9-stage gradient temperature increase method; and / or,

[0009] The residence time of each temperature stage is 0-60 minutes, preferably 0-30 minutes, and more preferably 2-30 minutes.

[0010] In a preferred embodiment of the present invention,

[0011] The mixing reaction is carried out at 100-240°C, preferably at 120-240°C; preferably,

[0012] The temperature range of the first section is between 125-155°C; the temperature range of the last section is between 225-235°C.

[0013] In a preferred embodiment of the present invention,

[0014] The mixing reaction is carried out in at least one of a static mixer, an extruder, a horizontal twin-shaft reactor, and a twin-rotor reactor, preferably in a static mixer, and the static mixer is a conventional static mixer in the art.

[0015] In a preferred embodiment of the present invention,

[0016] The glycolide is in a molten state; preferably, the molten glycolide enters the reactor at a temperature range of 80-155°C; more preferably,

[0017] The acid value of the glycolide is 0.1-50 mol / t, preferably 0.2-25 mol / t; and / or the water content of the glycolide is 10-1000 ppm, preferably 20-500 ppm.

[0018] In a preferred embodiment of the present invention,

[0019] The reaction aids include catalysts and initiators.

[0020] In a preferred embodiment of the present invention,

[0021] The catalyst is selected from at least one of stannous octoate, tetraphenyltin, tetrabutyl stannate, stannous chloride, stannous chloride dihydrate, stannous chloride, stannous acetylacetonate, tin lactate, tin ethoxide, zinc oxide, zinc acetylacetonate, diethylzinc, zinc acetate dihydrate, ferric lactate, and antimony trioxide; and / or,

[0022] Based on the total weight of glycolide and the reaction aid being 100%, the amount of the catalyst used is 0.0005%-0.05%, preferably 0.001%-0.03%.

[0023] In a preferred embodiment of the present invention,

[0024] The initiator contains at least one hydroxyl group, preferably at least one of water and fatty alcohol, more preferably at least one of water, methanol, ethanol, propanol, butanol, pentanol, decanol, dodecanol, tetradecanol, and hexadecanol; and / or,

[0025] Based on the total weight of glycolide and the reaction aid being 100%, the amount of the initiator is 0-1%, preferably 0-0.5%, and more preferably 0.05-0.5%.

[0026] The present invention may also include other conventional reaction aids, such as antioxidants, etc. The antioxidant is at least one of phosphate compounds, phosphite compounds, hindered phenols, etc., and the amount used is also a conventional amount. Those skilled in the art can add it according to actual conditions.

[0027] In a preferred embodiment of the present invention,

[0028] The preparation method further comprises the step of devolatilizing the glycolide-polyglycolic acid mixture obtained after the reaction; preferably, the devolatilization is carried out at an absolute pressure of ≤400 Pa, and / or a temperature of 225-240° C., and / or a time of 2-60 minutes.

[0029] The preparation method of the low yellowness value polyglycolic acid of the present invention can adopt the following specific technical scheme:

[0030] (1) Molten glycolide and an auxiliary agent are respectively introduced into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture; the static mixer adopts at least 4-stage gradient temperature increase; the temperature range of the first stage is between 125-155°C; the temperature range of the last stage is between 225-235°C; the temperature of the second stage is 0-9°C higher than that of the first stage; the temperature of the last stage is 1-5°C higher than that of the previous adjacent stage; the temperature of the latter stage of other adjacent stages is between 16-40°C higher than that of the previous adjacent stage.

[0031] (2) The glycolide-polyglycolic acid mixture enters a devolatilizer to remove unreacted glycolide to obtain polyglycolic acid with a low yellowness value.

[0032] The second object of the present invention is to provide polyglycolic acid obtained by the preparation method of the first object of the present invention.

[0033] In a preferred embodiment of the present invention,

[0034] The yellowness value of the polyglycolic acid is less than 40.

[0035] Beneficial effects of the present invention:

[0036] The present invention takes into account that the glycolide ring-opening polymerization reaction includes multiple stages, including an active center generation stage, a reaction initiation stage, a deep polymerization stage, a reaction equilibrium stage, etc. Therefore, by adopting a specific gradient temperature increase process, it is strived to make each stage within a preferred temperature range, which can reduce the occurrence of side reactions such as depolymerization reaction, aromatization reaction, monomer cracking reaction, etc. during the reaction process, which is manifested in a reduction in the yellowness value of the polyglycolic acid product and an improvement in the product hue. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0038] The raw materials used in the examples are all conventional commercially available raw materials.

[0039] Determination of the yellowness value of polyglycolic acid: The yellowness index of polyglycolic acid was measured by using the American HunterLab Scan XE yellowness index instrument. The polyglycolic acid particles were poured into a cylindrical container made of quartz glass and the yellowness value was measured by the reflection method.

[0040] [Example 1]

[0041] Molten glycolide with an acid value of 1 mol / t, a water content of 300 ppm and a temperature of 100°C, a catalyst stannous octoate and an initiator n-butanol are respectively put into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The static mixer adopts a 7-stage gradient heating method, which is 130°C, 135°C, 155°C, 185°C, 205°C, 225°C, and 227°C; the temperature residence time of each stage is 5 minutes, 5 minutes, 10 minutes, 20 minutes, 40 minutes, 20 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.002% and the initiator content is 0.5%. The glycolide-polyglycolic acid mixture enters a roll-type devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 100 Pa, the temperature is 230°C, and the time is 20 minutes to obtain polyglycolic acid with a yellowness value of 35.

[0042] [Example 2]

[0043] Molten glycolide with an acid value of 10 mol / t, a water content of 100 ppm and a temperature of 100°C, a catalyst diethyl zinc and an initiator dodecanol are respectively put into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The static mixer adopts an 8-stage gradient heating method, which is 126°C, 135°C, 155°C, 174°C, 190°C, 206°C, 225°C, and 230°C; the temperature residence time of each stage is 5 minutes, 5 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 5 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.02% and the initiator content is 0.1%. The glycolide-polyglycolic acid mixture enters a roll devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 400 Pa, the temperature is 232°C, and the time is 10 minutes to obtain polyglycolic acid with a yellowness value of 30.

[0044] [Example 3]

[0045] Molten glycolide with an acid value of 2 mol / t, a water content of 190 ppm and a temperature of 100°C, a catalyst stannous octoate and an initiator water are respectively put into a horizontal biaxial reactor for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The horizontal biaxial reactor adopts a 5-stage gradient heating method, which is 140°C, 145°C, 180°C, 220°C, and 225°C; the temperature residence time of each stage is 5 minutes, 5 minutes, 15 minutes, 40 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.006% and the initiator content is 0.8%. The glycolide-polyglycolic acid mixture enters a roll-type devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 50Pa, the temperature is 228°C, and the time is 8 minutes to obtain polyglycolic acid with a yellowness value of 32.

[0046] [Example 4]

[0047] Molten glycolide with an acid value of 4 mol / t, a water content of 250 ppm and a temperature of 100°C, a catalyst of stannous chloride and an initiator of decanol were respectively put into a double-rotor reactor for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The double-rotor reactor adopts a 9-stage gradient heating method, which is 125, 126, 142, 158, 174, 190, 206, 222, and 227°C respectively; the temperature residence time of each stage is 5 minutes, 5 minutes, 5 minutes, 5 minutes, 5 minutes, 10 minutes, 15 minutes, 10 minutes, and 5 minutes respectively. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.008% and the initiator content is 0.25%. The glycolide-polyglycolic acid mixture enters a roll-type devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 20 Pa, the temperature is 232°C, and the time is 5 minutes to obtain polyglycolic acid with a yellowness value of 38.

[0048] [Comparative Example 1]

[0049] Molten glycolide with an acid value of 10 mol / t, a water content of 100 ppm and a temperature of 100°C is mixed and polymerized with a catalyst, diethyl zinc, and an initiator, dodecanol, in a static mixer to obtain a glycolide-polyglycolic acid mixture. Each section of the static mixer adopts a fixed temperature of 225°C and a reaction time of 70 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.02% and the initiator content is 0.1%. The glycolide-polyglycolic acid mixture enters a roll devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 400 Pa, the temperature is 232°C, and the time is 10 minutes to obtain polyglycolic acid with a yellowness value of 60.

[0050] [Comparative Example 2] (The temperature of the second stage is 10°C higher than that of the first stage)

[0051] Molten glycolide with an acid value of 1 mol / t, a water content of 300 ppm and a temperature of 100°C, a catalyst stannous octoate and an initiator n-butanol are respectively put into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The static mixer adopts a 7-stage gradient heating method, which is 130°C, 140°C, 160°C, 185°C, 205°C, 225°C, and 227°C; the temperature residence time of each stage is 5 minutes, 5 minutes, 10 minutes, 20 minutes, 40 minutes, 20 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.002% and the initiator content is 0.5%. The glycolide-polyglycolic acid mixture enters a roll devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 100 Pa, the temperature is 230°C, and the time is 20 minutes to obtain polyglycolic acid with a yellowness value of 44.

[0052] [Comparative Example 3] (The temperature of the last section is 10°C higher than that of the previous adjacent section)

[0053] Molten glycolide with an acid value of 1 mol / t, a water content of 300 ppm and a temperature of 100°C, a catalyst stannous octoate and an initiator n-butanol are respectively put into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The static mixer adopts a 7-stage gradient heating method, which is 130°C, 135°C, 155°C, 185°C, 205°C, 225°C, and 235°C; the temperature residence time of each stage is 5 minutes, 5 minutes, 10 minutes, 20 minutes, 40 minutes, 20 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.002% and the initiator content is 0.5%. The glycolide-polyglycolic acid mixture enters a roll-type devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 100Pa, the temperature is 230°C, and the time is 20 minutes to obtain polyglycolic acid with a yellowness value of 48.

[0054] [Comparative Example 4] (The temperature of the next adjacent section is lower than that of the previous adjacent section by less than 16°C)

[0055] Molten glycolide with an acid value of 1 mol / t, a water content of 300 ppm and a temperature of 100°C, a catalyst stannous octoate and an initiator n-butanol are respectively put into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The static mixer adopts a 9-stage gradient heating method, which is 130°C, 135°C, 150°C, 165°C, 180°C, 195°C, 210°C, 225°C, and 227°C; the temperature residence time of each stage is 5 minutes, 5 minutes, 10 minutes, 10 minutes, 10 minutes, 40 minutes, 10 minutes, 10 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.002% and the initiator content is 0.5%. The glycolide-polyglycolic acid mixture enters a roll devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 100 Pa, the temperature is 230° C., and the time is 20 minutes to obtain polyglycolic acid with a yellowness value of 46.

[0056] [Comparative Example 5] (The temperature of the next section of the other adjacent sections is higher than that of the previous adjacent section by more than 40°C)

[0057] Molten glycolide with an acid value of 1 mol / t, a water content of 300 ppm and a temperature of 100°C, a catalyst stannous octoate and an initiator n-butanol are respectively put into a static mixer for mixing and polymerization reaction to obtain a glycolide-polyglycolic acid mixture. The static mixer adopts a 5-stage gradient heating method, which is 130°C, 135°C, 180°C, 225°C, and 227°C; the temperature residence time of each stage is 5 minutes, 15 minutes, 30 minutes, 50 minutes, and 5 minutes. Based on the total weight of glycolide, catalyst and initiator as 100%, the catalyst content is 0.002% and the initiator content is 0.5%. The glycolide-polyglycolic acid mixture enters a roll-type devolatilizer to remove unreacted glycolide. The devolatilizer pressure is 100Pa, the temperature is 230°C, and the time is 20 minutes to obtain polyglycolic acid with a yellowness value of 51.

[0058] It can be seen from Example 2 and Comparative Example 1 that, under the same reaction raw materials, total reaction time and devolatilization conditions, since Comparative Example 1 adopts a fixed temperature for the polymerization reaction, compared with the multi-stage gradient temperature increase reaction of Example 2, the yellowness value of the polyglycolic acid obtained in Comparative Example 1 is significantly worse.

[0059] It can be seen from Example 1 and Comparative Example 2 that, under the same reaction raw materials, reaction time and devolatilization conditions, since the temperature of the second stage of the multi-stage gradient temperature increase reaction in Comparative Example 2 is 10°C higher than that of the first stage, which is not within the range of 0-9°C of the present application, the yellowness value of the obtained polyglycolic acid is significantly higher than that of Example 1.

[0060] It can be seen from Example 1 and Comparative Example 3 that, under the same reaction raw materials, reaction time and devolatilization conditions, since the temperature of the last stage of the multi-stage gradient temperature increase reaction in Comparative Example 3 is 10°C higher than that of the previous adjacent stage, which is not within the range of 1-5°C of the present application, the yellowness value of the obtained polyglycolic acid is also significantly higher than that of Example 1.

[0061] It can be seen from Example 1 and Comparative Examples 4-5 that, under the same reaction raw materials, total reaction time and devolatilization conditions, since the temperature of the other adjacent sections of the multi-stage gradient temperature increase reaction in Comparative Example 4 is lower than 16°C higher than the temperature of the previous adjacent section, and the temperature of the other adjacent sections of the multi-stage gradient temperature increase reaction in Comparative Example 5 is higher than 40°C higher than the temperature of the previous adjacent section, both are not within the range of 16-40°C of the present application, and therefore the yellowness value of the obtained polyglycolic acid is also significantly higher than that of Example 1.

[0062] It can be seen that in the present invention, only when the gradient heating method satisfies that the temperature of the second section is 0-9°C higher than that of the first section, the temperature of the last section is 1-5°C higher than that of the previous adjacent section, and the temperature of the latter section of other adjacent sections is 16-40°C higher than that of the previous adjacent section, can the occurrence of side reactions such as depolymerization reaction, aromatization reaction, monomer cracking reaction, etc. during the reaction process be effectively reduced, which is manifested in the reduction of the yellowness value of the polyglycolic acid product and the improvement of the product hue. Preferably, the yellowness value of the obtained polyglycolic acid is made to be below 40.

[0063] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0064] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0065] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0066] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0067] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0068] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A method for preparing low yellowness polyglycolic acid, comprising the steps of mixing components including glycolide and a reaction aid; the mixing reaction adopts at least 4-stage gradient temperature increase; the temperature of the second stage is 0-9°C higher than that of the first stage, preferably 5-9°C higher; the temperature of the last stage is 1-5°C higher than that of the previous adjacent stage, preferably 2-5°C higher; the temperature of the latter stage of other adjacent stages is 16-40°C higher than that of the previous adjacent stage, preferably 16-35°C higher.

2. The preparation method according to claim 1, characterized in that: The mixed reaction adopts a 4-9 stage gradient temperature increase method, preferably a 5-9 stage gradient temperature increase method; and / or, The residence time of each temperature section is 0-60 minutes, preferably 0-30 minutes.

3. The preparation method according to claim 1 or 2, characterized in that: The mixing reaction is carried out at 100-240°C; preferably, The temperature range of the first section is between 125-155°C; the temperature range of the last section is between 225-235°C.

4. The preparation method according to claim 1, characterized in that: The mixing reaction is carried out in at least one of a static mixer, an extruder, a horizontal twin-shaft reactor, and a twin-rotor reactor, preferably in a static mixer.

5. The preparation method according to claim 1, characterized in that: The glycolide is in a molten state; preferably, the molten glycolide enters the reactor at a temperature range of 80-155°C; more preferably, The acid value of the glycolide is 0.1-50 mol / t, preferably 0.2-25 mol / t; and / or the water content of the glycolide is 10-1000 ppm, preferably 20-500 ppm.

6. The preparation method according to claim 1, characterized in that: The reaction aids include catalysts and initiators.

7. The preparation method according to claim 6, characterized in that: The catalyst is selected from at least one of stannous octoate, tetraphenyltin, tetrabutyl stannate, stannous chloride, stannous chloride dihydrate, stannous chloride, stannous acetylacetonate, tin lactate, tin ethoxide, zinc oxide, zinc acetylacetonate, diethylzinc, zinc acetate dihydrate, ferric lactate, and antimony trioxide; and / or, Based on the total weight of glycolide and the reaction aid being 100%, the amount of the catalyst used is 0.0005%-0.05%, preferably 0.001%-0.03%.

8. The preparation method according to claim 6, characterized in that: The initiator contains at least one hydroxyl group, preferably at least one of water and fatty alcohol, more preferably at least one of water, methanol, ethanol, propanol, butanol, pentanol, decanol, dodecanol, tetradecanol, and hexadecanol; and / or, Based on the total weight of glycolide and the reaction aid being 100%, the amount of the initiator is 0-1%, preferably 0-0.5%.

9. The preparation method according to claim 1, characterized in that: The method further comprises the step of devolatilizing the glycolide-polyglycolic acid mixture obtained after the reaction; preferably, the devolatilization is carried out at an absolute pressure of ≤400 Pa, and / or a temperature of 225-240° C., and / or a time of 2-60 minutes.

10. Polyglycolic acid obtained by the preparation method according to any one of claims 1 to 9.

11. The polyglycolic acid according to claim 10, characterized in that: The yellowness value of the polyglycolic acid is less than 40.