Initiator for glycolide polymerization, method for preparing polyglycolic acid and obtained polyglycolic acid

Abstract

The invention discloses an initiator for glycolide polymerization, a method for preparing polyglycolic acid and the obtained polyglycolic acid, and relates to the technical field of polyglycolic acid preparation, the initiator for glycolide polymerization comprises one or a mixture of polyaliphatic alkane diacid polyol esters; the structural formula of the polyaliphatic alkane diacid polyol ester comprises a structural unit derived from C3-C6 aliphatic polyol and a structural unit derived from C8-C12 diacid. According to the invention, the polyaliphatic alkane diacid polyol ester is used as an initiator for glycolide polymerization, and the polyaliphatic alkane diacid polyol ester in the polymerized polyglycolic acid can be used as a soft core to play roles in dissipating stress, preventing microcrack growth and the like, so that an in-situ enhancement role is played, the mechanical property of the PGA is improved, and the influence on the degradation property of the PGA is small.

Description

Technical Field

[0001] This invention relates to the field of polyglycolic acid preparation technology, and more specifically, to an initiator for glycolide polymerization, a method for preparing polyglycolic acid, and the resulting polyglycolic acid. Background Technology

[0002] Polyglycolic acid (PGA) is a thermoplastic polymer with good biodegradability and biocompatibility. It can be processed through extrusion, injection molding, spinning, blow molding, etc., and the resulting products are used in many fields such as absorbable surgical sutures, tissue engineering scaffolds, drug delivery carriers, barrier materials, and temporary plugging balls. Some applications have high requirements for the mechanical properties of PGA, requiring reinforcement modification.

[0003] Taking Chinese patent document CN114075377A as an example, the flexural modulus of PGA is improved by introducing polyurethane and isocyanate compounds into PGA through a co-extrusion process. However, this method affects the biodegradability of the material. At the same time, the processing can easily lead to thermal degradation and yellowing of PGA, which affects product quality. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an initiator for glycolide polymerization, a method for preparing polyglycolic acid (PGA), and the resulting PGA. This invention uses polyglycerol sebacate (or polyglycerol sebacate) as the initiator for glycolide polymerization, which provides in-situ reinforcement after polymerization, improving the mechanical properties of PGA, and has minimal impact on the degradation performance of PGA.

[0005] One of the objectives of this invention is to provide an initiator for the polymerization of glycolide.

[0006] The initiator for glycolide polymerization described in this invention includes one or a mixture of polyaliphatic alkyl diacid polyol esters.

[0007] The structural formula of the polyaliphatic alkyl diacid polyol ester includes structural units derived from aliphatic polyols of C3 to C6 and structural units derived from diacids of C8 to C12.

[0008] In a preferred embodiment of the present invention:

[0009] The C3-C6 aliphatic polyols are at least one selected from glycerol, pentaerythritol, xylitol, mannitol, and sorbitol; and / or,

[0010] The C8-C12 diacid is at least one of octanoic acid, azelaic acid, sebacic acid, undecanoic acid, and dodecanoic acid.

[0011] In a preferred embodiment of the present invention:

[0012] The initiator includes one or a mixture of polyglycerol sebate; preferably,

[0013] The poly(diglyceride sebacic acid) ester has a structural formula comprising structural units derived from glycerol and structural units derived from sebacic acid; preferably:

[0014]

[0015] Where R is OH, At least one of them, n is 1 to 15, preferably 1 to 10; and / or,

[0016] The initiator includes one or a mixture of pentaerythritol polyoctanoate; preferably,

[0017] The structural formula of the polypentaerythritol octanoate includes structural units derived from pentaerythritol and structural units derived from octanoic acid; preferably:

[0018]

[0019] Where R1 and R2 can be the same or different, and are independently OH, One of them, where n is 1 to 15, preferably 1 to 10; and / or,

[0020] The initiator comprises one or a mixture of polysorbate dodecanoate; preferably,

[0021] The structural formula of the poly(sorbitol dodecanoate) ester includes structural units derived from sorbitol and structural units derived from dodecanoate; preferably:

[0022]

[0023] Among them, R1, R2, R3, and R4 can be the same or different, and each independently represents OH, One of them, where n is 1 to 15, preferably 1 to 10.

[0024] The initiator of this invention is a prepolymer with a low degree of reactivity. It does not achieve the typical three-dimensional network structure of polymers and can be considered a linear structure with branched chains. Furthermore, it avoids the problem of polymers with three-dimensional network structures being insoluble in glycolide. The initiator with the structure described above is more suitable for glycolide polymerization.

[0025] In a preferred embodiment of the present invention:

[0026] The initiator has a molecular weight of 250-8000, preferably 250-5500; and / or,

[0027] The molar ratio of the structural units derived from C3 to C6 aliphatic polyols to the structural units derived from C8 to C12 diacids is (0.4-1.5):1, preferably (0.7-1.4):1.

[0028] A second objective of this invention is to provide a method for preparing an initiator for glycolide polymerization as described in one objective of this invention.

[0029] The method for preparing the initiator for glycolide polymerization according to the present invention includes melt polycondensation of components including C8-C12 diacids and C3-C6 aliphatic polyols; preferably,

[0030] The initiator is prepared by a polycondensation reaction comprising thoroughly mixing a C8-C12 diacid and a C3-C6 aliphatic polyol, heating and melting them, and then raising the temperature to the reaction temperature.

[0031] In a preferred embodiment of the present invention:

[0032] The molar ratio of the C3-C6 aliphatic polyol to the C8-C12 diacid is (0.4-1.5):1, preferably (0.7-1.4):1; and / or,

[0033] The heating and melting temperature is 120–160°C, preferably 130–150°C; and / or

[0034] The polycondensation reaction temperature is 140–180°C, preferably 150–170°C; more preferably,

[0035] The heating is a slow heating, and the specific heating rate can be adjusted by those skilled in the art.

[0036] The polycondensation reaction includes a reaction under normal pressure followed by a reaction under negative pressure; more preferably,

[0037] The atmospheric pressure reaction time is 0.5 to 3 hours; and / or the negative pressure reaction time is 0.1 to 3 hours; and / or the negative pressure reaction pressure is 0.5 to 10 kPa.

[0038] It should be noted that the preparation method of the initiator of the present invention is based on the above parameters, assuming that the reaction is complete. Therefore, the molar ratio of the structural units derived from C3-C6 aliphatic polyols and the structural units derived from C8-C12 diacids in the obtained initiator is equivalent to the theoretical molar ratio, and its molar ratio range is equivalent to the molar ratio range of C3-C6 aliphatic polyols and C8-C12 diacids during the initiator preparation.

[0039] The third objective of this invention is to provide a method for preparing polyglycolic acid.

[0040] The method for preparing polyglycolic acid according to the present invention comprises a polymerization reaction of components including glycolide, an initiator and a catalyst to obtain the polyglycolic acid; the initiator is selected from one or a mixture of polyglycerol sebacate prepared according to any one of claims 1 to 3 or according to any one of claims 4 to 5.

[0041] In a preferred embodiment of the present invention:

[0042] The acid value of the glycolide is 0.1–30 mol / t, preferably 0.2–20 mol / t, and / or the water content is 10–400 ppm, preferably 20–300 ppm; and / or,

[0043] The catalyst is at least one of stannous octoate, tetrabutyl stannate, stannous chloride, stannous chloride dihydrate, stannous chloride, and stannous acetylacetonate.

[0044] In a preferred embodiment of the present invention:

[0045] The mass ratio of the glycolide to the initiator is (100-1000):1, preferably (300-800):1; and / or,

[0046] The mass ratio of glycolide to catalyst is (1000-100000):1, preferably (3000-50000):1.

[0047] In a preferred embodiment of the present invention:

[0048] The polymerization reaction is carried out at a temperature of 140–240°C, preferably 180–230°C, and / or for a reaction time of 10–150 minutes, preferably 20–120 minutes.

[0049] The fourth objective of this invention is to provide a polyglycolic acid prepared by the method described in the third objective of this invention.

[0050] In a preferred embodiment of the present invention:

[0051] The polyglycolic acid has a tensile strength of 100-160 MPa and / or an elongation at break ≥20%, and / or a flexural strength of 180-240 MPa, and / or a notched impact strength ≥5 kJ / m. 2 .

[0052] This invention uses polyaliphatic alkyl diacid polyol ester as an initiator for glycolide polymerization. After polymerization, the polyaliphatic alkyl diacid polyol ester in polyglycolic acid can act as a soft core to dissipate stress and prevent microcrack growth, thereby playing an in-situ reinforcement role, improving the mechanical properties of PGA, and having little impact on the degradation performance of PGA. Detailed Implementation

[0053] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0054] The raw materials used in the embodiments and comparative examples of this invention are all commercially available products, and the glycolide was purchased from Beijing Inokai Reagent Co., Ltd.

[0055] Injection Molding and Mechanical Property Testing: PGA specimens with a length of 25.0 mm, a width of 4.0 mm, and a thickness of 2.0 mm were prepared using an injection molding machine. Tensile tests and three-point bending tests were performed on the prepared polyglycolic acid using a universal tensile testing machine at a test rate of 5 mm / min.

[0056]

Example 1

[0057] Preparation of initiators:

[0058] 20.2 g of 1,10-sebacic acid and 13.8 g of glycerol were mixed and heated to 140 °C, then slowly increased to 170 °C and reacted under normal pressure for 2 h, followed by reaction under negative pressure (5 kPa) for 2 h to obtain the initiator polysaccharide glycerol. The structure of the initiator is as follows: Where the group R is OH, At least one of them, the number-average molecular weight is 2000 and the average degree of polymerization n is 3 as measured by GPC.

[0059]

Example 2

[0060] Preparation of initiators:

[0061] 20.2 g of 1,10-sebacic acid and 10.1 g of glycerol were mixed and heated to 130 °C, then slowly heated to 150 °C and reacted at normal pressure for 3 h, followed by reaction under negative pressure (0.5 kPa) for 3 h to obtain the initiator polysaccharide glycerol. The structure of the initiator is as follows: Where the group R is OH, At least one of them, the number-average molecular weight is 8000 and the average degree of polymerization n is 14 as measured by GPC.

[0062]

Example 3

[0063] Preparation of initiators:

[0064] 20.2 g of 1,10-sebacic acid and 6.44 g of glycerol were mixed and heated to 150 °C, then slowly heated to 160 °C and reacted under normal pressure for 1 h, followed by reaction under negative pressure (2 kPa) for 1 h to obtain the initiator polysaccharide glycerol. The structure of the initiator is as follows: Where the group R is OH, At least one of them, the number-average molecular weight is 5000 and the average degree of polymerization n is 9 as measured by GPC.

[0065]

Example 4

[0066] Preparation of initiators:

[0067] 17.4 g of octanoic acid and 8.17 g of pentaerythritol were mixed and heated to 120 °C, then slowly heated to 160 °C and reacted under normal pressure for 3 h, followed by reaction under negative pressure (1 kPa) for 2 h to obtain the initiator polypentaerythritol octanoate. The structure of the initiator is as follows: Where R1 and R2 are OH, One of them, measured by GPC, has a number-average molecular weight of 4000 and an average degree of polymerization n of 9.

[0068]

Example 5

[0069] Preparation of initiators:

[0070] 23.0 g of dodecanoic acid and 7.29 g of sorbitol were mixed and heated to 150 °C, then slowly heated to 160 °C and reacted at normal pressure for 1.5 h, followed by reaction under negative pressure (0.5 kPa) for 2 h to obtain the initiator poly(sorbitol dodecanoic acid). The structure of the initiator is as follows: Where R1, R2, R3, and R4 are OH, One of them, measured by GPC, has a number-average molecular weight of 6000 and an average degree of polymerization n of 10.

[0071]

Example 6

[0072] Polymerization was carried out in glycolide with an acid value of 5 mol / t and a water content of 100 ppm, using the initiator and catalyst prepared in Example 1. The mass ratio of glycolide to initiator was 400:1. The catalyst was stannous octoate, and the mass ratio of glycolide to catalyst was 1000:1. The polymerization temperature was 220℃, and the reaction time was 12 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid obtained had a tensile strength of 110 MPa, an elongation at break of 24%, a flexural strength of 200 MPa, and a notched impact strength of 5.5 kJ / m. 2 .

[0073]

Example 7

[0074] Polymerization was carried out in glycolide with an acid value of 0.1 mol / t and a water content of 10 ppm, using the initiator and catalyst prepared in Example 1. The mass ratio of glycolide to initiator was 100:1. The catalyst was tetrabutyl stannate, and the mass ratio of glycolide to catalyst was 3000:1. The polymerization temperature was 140℃, and the reaction time was 150 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid was found to have a tensile strength of 125 MPa, an elongation at break of 29%, a flexural strength of 205 MPa, and a notched impact strength of 6.9 kJ / m. 2 .

[0075]

Example 8

[0076] Polymerization was carried out in glycolide with an acid value of 12 mol / t and a water content of 210 ppm, using the initiator and catalyst prepared in Example 2. The mass ratio of glycolide to initiator was 300:1. The catalyst was stannous chloride dihydrate, and the mass ratio of glycolide to catalyst was 50000:1. The polymerization temperature was 190℃, and the reaction time was 120 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid was found to have a tensile strength of 138 MPa, an elongation at break of 26%, a flexural strength of 225 MPa, and a notched impact strength of 7.4 kJ / m. 2 .

[0077]

Example 9

[0078] Polymerization was carried out in glycolide with an acid value of 1.2 mol / t and a water content of 50 ppm, using the initiator and catalyst prepared in Example 2. The mass ratio of glycolide to initiator was 600:1. The catalyst was tin chloride, and the mass ratio of glycolide to catalyst was 8000:1. The polymerization temperature was 230℃, and the reaction time was 10 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid was found to have a tensile strength of 160 MPa, an elongation at break of 20%, a flexural strength of 230 MPa, and a notched impact strength of 6.5 kJ / m. 2 .

[0079]

Example 10

[0080] Polymerization was carried out in glycolide with an acid value of 30 mol / t and a water content of 400 ppm, using the initiator and catalyst prepared in Example 3. The mass ratio of glycolide to initiator was 700:1. The catalyst was stannous octoate, and the mass ratio of glycolide to catalyst was 20000:1. The polymerization temperature was 200℃, and the reaction time was 100 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid was found to have a tensile strength of 100 MPa, an elongation at break of 32%, a flexural strength of 180 MPa, and a notched impact strength of 5.0 kJ / m. 2 .

[0081]

Example 11

[0082] Polymerization was carried out in glycolide with an acid value of 22 mol / t and a water content of 280 ppm, using the initiator and catalyst prepared in Example 4. The mass ratio of glycolide to initiator was 1000:1. The catalyst was stannous acetylacetone, and the mass ratio of glycolide to catalyst was 100000:1. The polymerization temperature was 240℃, and the reaction time was 15 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid was found to have a tensile strength of 105 MPa, an elongation at break of 35%, a flexural strength of 195 MPa, and a notched impact strength of 6.1 kJ / m. 2 .

[0083]

Example 12

[0084] Polymerization was carried out in glycolide with an acid value of 0.8 mol / t and a water content of 60 ppm, using the initiator and catalyst prepared in Example 5. The mass ratio of glycolide to initiator was 800:1. The catalyst was stannous octoate, and the mass ratio of glycolide to catalyst was 50000:1. The polymerization temperature was 210℃, and the reaction time was 20 minutes. Based on the above injection molding and mechanical property tests, the high-strength polyglycolic acid was found to have a tensile strength of 150 MPa, an elongation at break of 28%, a flexural strength of 240 MPa, and a notched impact strength of 5.8 kJ / m. 2 .

[0085] Comparative Example 1

[0086] Polymerization was carried out in glycolide with an acid value of 5 mol / t and a water content of 100 ppm by adding an initiator and a catalyst. The initiator was lauryl alcohol, and the mass ratio of glycolide to initiator was 400:1. The catalyst was stannous octoate, and the mass ratio of glycolide to catalyst was 1000:1. The polymerization temperature was 220℃, and the reaction time was 12 minutes. Based on the above injection molding and mechanical property tests, the tensile strength of polyglycolic acid was obtained as 90 MPa, the elongation at break was 13%, the flexural strength was 150 MPa, and the notched impact strength was ≥2.1 kJ / m. 2 .

[0087] The test results from Example 4 and Comparative Example 1 show that the polyglycolic acid obtained by using lauryl alcohol as a conventional initiator in the polymerization of glycolide in Comparative Example 1 has inferior mechanical properties compared to that obtained by using polyglycerol sebacic acid as an initiator. Specifically, it exhibits lower tensile strength, lower elongation at break, lower flexural strength, and lower notched impact strength. This difference in performance is significantly related to the initiator. In polymerization reactions using polyglycerol sebacic acid as an initiator, branched polyglycolic acid can be obtained, and this structure plays a crucial role in improving its mechanical properties.

Claims

1. An initiator for glycolide polymerization, comprising one or a mixture of polyaliphatic alkyl diacid polyol esters; The structural formula of the polyaliphatic alkyl diacid polyol ester includes structural units derived from aliphatic polyols of C3 to C6 and structural units derived from diacids of C8 to C12.

2. The initiator according to claim 1, characterized in that: The C3-C6 aliphatic polyols are at least one selected from glycerol, pentaerythritol, xylitol, mannitol, and sorbitol; and / or, The C8-C12 diacid is at least one of octanoic acid, azelaic acid, sebacic acid, undecanoic acid, and dodecanoic acid.

3. The initiator according to claim 1 or 2, characterized in that: The initiator includes one or a mixture of polyglycerol sebate; preferably, The poly(diglyceride sebacic acid) ester has a structural formula comprising structural units derived from glycerol and structural units derived from sebacic acid; preferably: Where R is OH, At least one of them, n is 1 to 15, preferably 1 to 10; and / or, The initiator includes one or a mixture of pentaerythritol polyoctanoate; preferably, The structural formula of the polypentaerythritol octanoate includes structural units derived from pentaerythritol and structural units derived from octanoic acid; preferably: Where R1 and R2 can be the same or different, and are independently OH, One of them, where n is 1 to 15, preferably 1 to 10; and / or, The initiator comprises one or a mixture of polysorbate dodecanoate; preferably, The structural formula of the poly(sorbitol dodecanoate) ester includes structural units derived from sorbitol and structural units derived from dodecanoate; preferably: Among them, R1, R2, R3, and R4 can be the same or different, and each independently represents OH, One of them, where n is 1 to 15, preferably 1 to 10.

4. The initiator according to claim 1 or 2, characterized in that: The initiator has a molecular weight of 250-8000, preferably 250-5500; and / or, The molar ratio of the structural units derived from C3 to C6 aliphatic polyols to the structural units derived from C8 to C12 diacids is (0.4-1.5):1, preferably (0.7-1.4):

1.

5. A method for preparing an initiator for glycolide polymerization according to any one of claims 1 to 4, comprising obtaining it by melt polycondensation of components including a C8-C12 diacid and a C3-C6 aliphatic polyol; preferably, The initiator is prepared by a polycondensation reaction comprising thoroughly mixing a C8-C12 diacid and a C3-C6 aliphatic polyol, heating and melting them, and then raising the temperature to the reaction temperature.

6. The method according to claim 5, characterized in that: The molar ratio of the C3-C6 aliphatic polyol to the C8-C12 diacid is (0.4-1.5):1, preferably (0.7-1.4):1; and / or, The heating and melting temperature is 120–160°C, preferably 130–150°C; and / or The polycondensation reaction temperature is 140–180°C, preferably 150–170°C; more preferably, The polycondensation reaction includes a reaction under normal pressure followed by a reaction under negative pressure; more preferably, The atmospheric pressure reaction time is 0.5 to 3 hours; and / or the negative pressure reaction time is 0.1 to 3 hours; and / or the negative pressure reaction pressure is 0.5 to 10 kPa.

7. A method for preparing polyglycolic acid, comprising: The polyglycolic acid is prepared by polymerization of components including glycolide, an initiator and a catalyst; the initiator is selected from one or a mixture of polyglycerol sebacate prepared according to any one of claims 1 to 4 or according to any one of claims 5 to 6.

8. The method according to claim 7, characterized in that: The acid value of the glycolide is 0.1–30 mol / t, preferably 0.2–20 mol / t, and / or the water content is 10–400 ppm, preferably 20–300 ppm; and / or, The catalyst is at least one of stannous octoate, tetrabutyl stannate, stannous chloride, stannous chloride dihydrate, stannous chloride, and stannous acetylacetonate.

9. The method according to claim 7, characterized in that: The mass ratio of the glycolide to the initiator is (100-1000):1, preferably (300-800):1; and / or, The mass ratio of glycolide to catalyst is (1000-100000):1, preferably (3000-50000):

1.

10. The method according to claim 7, characterized in that: The polymerization reaction is carried out at a temperature of 140–240°C, preferably 180–230°C, and / or for a reaction time of 10–150 minutes, preferably 20–120 minutes.

11. A polyglycolic acid prepared by the method according to any one of claims 7-10.

12. The polyglycolic acid according to claim 11, characterized in that: The polyglycolic acid has a tensile strength of 100-160 MPa and / or an elongation at break ≥20%, and / or a flexural strength of 180-240 MPa, and / or a notched impact strength ≥5 kJ / m. 2 .

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