A continuous process for the production of a polyglycolic acid multilayer film and the resulting multilayer film

Abstract

The present application relates to a kind of continuous preparation method of polyglycolic acid multilayer film and the multilayer film obtained.The method includes simultaneously polyglycolic acid and biodegradable polyester respectively and parallel extrusion casting, cooling, then the polyglycolic acid film and biodegradable polyester film obtained are respectively drawn into the same hot pressing unit and are hot-pressed to obtain the multilayer film.The present application can obtain the adhesion with other low-melting biodegradable resin film by controlling the crystallinity of high-melting polyglycolic acid film, with higher peel strength.The method of the present application can be compounded with the biodegradable resin material with large melting point difference, avoiding the partial thermal degradation of adjacent low-melting resin layer due to high temperature caused by high-melting resin in multilayer co-extrusion process.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and more specifically, to a continuous preparation method for a multilayer film of polyglycolic acid, particularly a multilayer film of a blend of a high-melting-point polyglycolic acid film and a low-melting-point biodegradable resin film, as well as the resulting multilayer film and its applications. Background Technology

[0002] As the simplest linear aliphatic polyester, polyglycolic acid (PGA) is a typical highly crystalline polymer with a stable crystal lattice and a high melting point. In recent years, PGA has received widespread attention and application in fields such as medical sutures, drug delivery systems, fracture fixation materials, tissue engineering scaffolds, reinforcing materials, and oil fields due to its excellent biodegradability, rapid degradation rate, good biocompatibility, good bioreabsorption, and high mechanical strength (some indicators comparable to engineering plastics). However, a series of problems, including PGA's high melting point, narrow processing temperature range, high crystallinity, and excessively rapid degradation rate, seriously affect its application in processing and the aforementioned materials.

[0003] Biodegradable polyester resins have been widely used in recent years due to their excellent biodegradability in disposable packaging materials, especially shopping bags, express delivery bags, and agricultural mulch films. Specific examples include polylactic acid (PLA), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), carbon dioxide-based biodegradable plastics (PPC), and dicarboxylic acid diol copolyesters. Summary of the Invention

[0004] One of the technical problems this invention aims to solve is the poor heat-sealing performance and significant difference in melting points between pure polyglycolic acid (PGA) films and biodegradable polyester resin films in existing technologies. This invention provides a continuous preparation method for a composite film of high-melting-point PGA and low-melting-point biodegradable polyester resin. The inventors have discovered that this process can prepare continuous multilayer (≥2 layers) biodegradable composite films. This method can composite biodegradable resin materials with large melting point differences (>15℃), avoiding the partial thermal degradation of the low-melting-point resin layer due to high temperatures when joining a single film in a multilayer co-extrusion process. Under the process conditions of this invention, the resulting biodegradable multilayer film exhibits excellent heat-sealing performance under industrial conditions, expanding the application of biodegradable PGA multilayer films in fields such as barrier packaging films.

[0005] The second technical problem to be solved by the present invention is to provide a continuous method for preparing a multilayer film of polyglycolic acid and biodegradable polyester resin.

[0006] The third technical problem to be solved by the present invention is to provide a polyglycolic acid and biodegradable polyester resin multilayer film product prepared by the continuous preparation method applicable to polyglycolic acid and biodegradable polyester resin multilayer film.

[0007] The fourth technical problem to be solved by the present invention is to provide an application method for multilayer films of polyglycolic acid and biodegradable polyester resin, which corresponds to solving the first or third technical problem.

[0008] To address the aforementioned technical problems, one objective of this invention is to provide a continuous preparation method for polyglycolic acid multilayer films, comprising simultaneously extruding and casting polyglycolic acid and biodegradable polyester in parallel, cooling them, then drawing the resulting polyglycolic acid film and biodegradable polyester film into the same hot pressing unit for hot pressing, and finally drawing out the multilayer film.

[0009] In the continuous preparation method of the present invention, before entering the hot pressing unit, the adhesion between the high melting point polyglycolic acid film and the low melting point biodegradable polyester film is achieved by controlling the crystallinity of the high melting point polyglycolic acid film. The crystallinity of the polyglycolic acid film entering the hot pressing unit is 1-30%, preferably 1-17%.

[0010] The polyglycolic acid can be obtained by ring-opening polymerization of glycolide or condensation polymerization of glycolic acid or methyl glycolate; preferably, the intrinsic viscosity of the polyglycolic acid can be 0.9 to 4 dl / g, and more preferably 0.9 to 2 dl / g.

[0011] The polyglycolic acid resin described herein has a melting temperature range of 200–235°C when tested at a heating / cooling rate of 10 / min.

[0012] The crystallinity of the polyglycolic acid resin is 1-70%.

[0013] The polyglycolic acid has a weight-average molecular weight of 50,000 to 1,000,000 g / mol, preferably 100,000 to 500,000 g / mol.

[0014] The molecular weight distribution index of the polyglycolic acid is 0.5 to 15.0, preferably 1.5 to 3.0.

[0015] The biodegradable polyester is selected from one, two or more blends of polylactic acid (PLA), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), carbon dioxide-based biodegradable plastics (PPC), and dicarboxylic acid diol copolyesters.

[0016] The dicarboxylic acid-diol copolyester is preferably an α,ω-aliphatic diacid or a copolyester containing 2-18 main chain carbon atoms of an aliphatic diacid and at least one aromatic diacid condensed with at least one aliphatic diol.

[0017] The diacid-diol copolyester includes, but is not limited to, one or more of polybutylene terephthalate-co-adipate (PBAT), polyethylene terephthalate-co-adipate, polybutylene terephthalate-co-succinate (PBST), polyethylene terephthalate-co-succinate, polybutylene succinate-adipate (PBSA), and polybutylene succinate (PBS); preferably, the diacid-diol copolyester is one or more of polybutylene terephthalate-co-adipate (PBAT) and polybutylene terephthalate-co-succinate (PBST).

[0018] The biodegradable polyester resin has a melting point of less than or equal to 180°C.

[0019] The biodegradable polyester resin has a melt index of 2-20 g / 10 min, more preferably 2-15 g / 10 min, under test conditions of 190°C and 2.16 kg.

[0020] The difference between the melting point of the biodegradable polyester and the melting point of polyglycolic acid is greater than or equal to 15°C, preferably greater than or equal to 20°C.

[0021] In the continuous preparation method described in this invention, the extrusion casting can be performed using equipment commonly used in the art, preferably a single-screw extruder.

[0022] In the continuous preparation method of the present invention, polyglycolic acid and biodegradable polyester are extruded and cast into films simultaneously in parallel through two or more extruders, and then cooled by cooling rollers.

[0023] In the continuous preparation method of the present invention, the extrusion casting temperature of polyglycolic acid is 200-255°C, and the die temperature is preferably 210-235°C.

[0024] In the continuous preparation method of the present invention, the cooling temperature of the polyglycolic acid film during extrusion casting is 10–60°C, preferably 10–40°C. The polyglycolic acid film obtained by casting is cooled by a cooling roller, the temperature of which is 10–60°C, preferably 10–40°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0025] In the continuous preparation method of the present invention, the crystallinity of the polyglycolic acid film obtained after cooling is 1-30%, preferably 1-17%, and more preferably 9-17%.

[0026] In the continuous preparation method of the present invention, the extrusion casting temperature of the biodegradable polyester is 100-180℃, preferably 120-180℃; the rotation speed is 30-300rpm, preferably 30-200rpm.

[0027] In the continuous preparation method of the present invention, the temperature of the hot pressing unit is 50-200℃, preferably 100-160℃; the hot pressing time is 0.1-5min, preferably 0.1-3min; and the hot pressing pressure is 2-200kPa, preferably 5-100kPa.

[0028] In the continuous preparation method of the present invention, the hot pressing unit adopts a hot pressing roller, which can be a circular roller or a square roller.

[0029] In the continuous preparation method described in this invention, there is no particular limitation on the thickness of the obtained polyglycolic acid film and biodegradable polyester film; the thickness can be the usual thickness or adjusted according to the actual application.

[0030] According to a preferred embodiment of the present invention, the continuous preparation method of the present invention may include the following steps:

[0031] 1) High-melting-point polyglycolic acid is cast into a film in a single-screw extruder. After exiting the film, it is cooled by a cooling roller and then continues to be drawn by a traction roller.

[0032] 2) Simultaneously, biodegradable polyester is cast into a film from another single-screw extruder, and then pulled by traction rollers after passing through the film.

[0033] 3) The obtained biodegradable polyester film and polyglycolic acid film are combined into the same hot pressing unit under traction and hot pressing to obtain a composite multilayer film.

[0034] In step 3), the high-melting-point polyglycolic acid film and the low-melting-point biodegradable polyester film can be laminated in two, three or more layers.

[0035] For example, in a three-layer composite, a high-melting-point polyglycolic acid film and a low-melting-point biodegradable polyester film are laminated in an ABA, BAB, or ABC pattern (A: biodegradable polyester film, B: polyglycolic acid film, C: biodegradable polyester film).

[0036] The second objective of this invention is to provide a polyglycolic acid multilayer film prepared by the continuous preparation method of the aforementioned polyglycolic acid multilayer film.

[0037] The polyglycolic acid multilayer film of this invention is a polyglycolic acid / biodegradable polyester multilayer film product, comprising a high-melting-point polyglycolic acid layer and a low-melting-point biodegradable polyester layer. The multilayer film is a composite film with two or more layers.

[0038] A third objective of this invention is to provide the application of the polyglycolic acid multilayer film in barrier packaging.

[0039] This invention, through the aforementioned method for preparing a continuous polyglycolic acid (PGA) multilayer film, particularly by controlling the crystallinity of the high-melting-point PGA film, enhances the adhesion to other low-melting-point biodegradable polyester films (with a melting point difference of at least 15°C from PGA), resulting in higher peel strength and a degree of novelty. Unlike traditional multilayer co-extrusion casting processes, this method uses separate single-screw extruders to allow PGA and / or biodegradable polyester to flow from their respective nozzles (instead of merging into a single nozzle during multilayer co-extrusion). By controlling the temperature of the high-melting-point PGA cooling roller, a low-crystallinity PGA film is obtained. This film is then laminated with other low-melting-point biodegradable polyester casting films in the same hot-pressing unit to obtain a continuous multilayer biodegradable composite film. This method can use biodegradable resin materials with large melting point differences (>15°C) as raw materials, avoiding the partial thermal degradation of adjacent low-melting-point resin layers caused by high temperatures during multilayer co-extrusion processes. Detailed Implementation

[0040] 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.

[0041] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] The materials and preparation methods used in this invention are briefly described below:

[0043] 1. Polyglycolic acid

[0044] Polyglycolic acid (PGA), also known as polyhydroxyacetic acid, is the simplest linear aliphatic polyester. PGA can be prepared by methods such as glycolic acid melt polycondensation or glycolide ring-opening polymerization. PGA is a typical highly crystalline polymer with a stable crystal lattice and a high melting point. The rapid crystallization rate and high crystallinity of PGA result in high brittleness and high modulus, but low impact strength, making its products extremely prone to breakage and limiting its applications.

[0045] Polyglycolic acid (PGA) possesses excellent biodegradability, allowing it to enter the human circulatory system for in vivo degradation and excretion, as well as degrade in the external environment. Its main applications include medical sutures, drug delivery systems, fracture fixation materials, tissue engineering scaffolds, and reinforcing materials. Through solution spinning and melt spinning, PGA can be processed into surgical sutures, exhibiting high tensile strength that can be maintained for sufficient time, making it suitable for suturing deep tissue wounds.

[0046] 2. Biodegradable polyester

[0047] Biodegradable polyester resins have been widely used in recent years in disposable packaging materials, especially shopping bags, express delivery bags, and agricultural mulch films, due to their good biodegradability. Specifically, they include one or more blends of polylactic acid (PLA), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), carbon dioxide-based biodegradable plastics (PPC), and diacid-diol copolyesters. The diacid-diol copolyester is preferably an α,ω-aliphatic diacid or a copolyester containing 2-18 main chain carbon atoms of an aliphatic diacid and at least one aromatic diacid condensed with at least one aliphatic diol; more preferably, it is one or more of polybutylene terephthalate-co-adipate, polyethylene terephthalate-co-adipate, polyethylene terephthalate-co-succinate, and polybutylene terephthalate-co-succinate.

[0048] 3. Polyglycolic acid blend multilayer film

[0049] 1) High-melting-point polyglycolic acid is cast into a film using a single-screw extruder at temperatures of 200-210-220-220-230℃. The die temperature is set to 230℃. After passing through the die, the film is cooled by a cooling roller and then continued to be drawn under the action of a traction roller. 2) Simultaneously, biodegradable polyester is cast into a film using a separate single-screw extruder. 3) After passing through the die, the biodegradable film is cooled by a cooling roller and then drawn, overlapping with the polyglycolic acid film. Finally, it is hot-pressed by a hot press roller to obtain a composite film.

[0050] All raw materials used in the examples and comparative examples are commercially available.

[0051] Polyglycolic acid (PGA), manufactured by Corbion Purac, has an intrinsic viscosity of 1.0–1.4 dl / g, a melting point of 200–230°C, and a crystallinity of 30–70%.

[0052] Aliphatic aromatic copolyesters, manufactured by BASF (BASF) under the following brand name: FC-1200 is an aliphatic aromatic copolyester PBAT particle with a melting point of 120-140℃.

[0053] Aliphatic aromatic copolyester, PBST particles of aliphatic aromatic copolyester with the grade TS 159 produced by Yizheng Chemical Fiber, have a melting point of 120-140℃.

[0054] Polylactic acid (PLA) particles, grade 4032D, manufactured by NatureWorks, have a melting point of 150–170°C.

[0055] The performance of this invention was determined using the following method:

[0056] Heat seal strength test: The test was conducted according to OB / T 2358-98 standard using an INSTRON 3344 film product testing machine with Bluehill version 2.31 software. The film was cut to Type 2 as per ISO 527-2 standard and placed in a Bluepard BPS-100CB constant temperature and humidity chamber (23℃, 50% relative humidity) at Shanghai Yiheng Scientific Instruments Co., Ltd. for 24 hours. During testing, the initial clamp spacing was 50mm, and the tensile rate was 300mm / min. Centered on the heat-sealed area, the upper film was peeled to the same position, opened 180°, and the two ends of the sample were clamped onto the two clamps of the testing machine, with the lower ends of the sample extending by the same length. Each sample was tested 5 times, and the average value was recorded. The maximum load at which the sample broke was read.

[0057] Thin film crystallinity testing: The crystallization thermodynamic parameters of PGA thin films were determined using a differential scanning calorimeter (DSC) from TA Instruments (USA). Approximately 4-8 mg of PGA thin film sample was added to the DSC sample cell and heated to 250°C at a rate of 10°C / min, held at that temperature for 2 min to eliminate thermal history. Then, the sample was cooled to -50°C at a rate of 10°C / min, and the cooling crystallization DSC spectrum was recorded. The sample was then heated to 250°C again at a rate of 10°C / min, and the crystallization melting DSC spectrum was recorded. Processing the two DSC curves yielded the crystallization thermodynamic parameters of the PGA thin film, including crystallization temperature, melting point, and heat of fusion. Among these, the crystallinity of the PGA thin film (X...)... c Calculate according to the following formula:

[0058]

[0059] In the formula, X c Crystallinity, %; ΔH m The enthalpy of melting is ΔH, J / g. m100 The enthalpy of melting endothermic reaction during complete crystallization of PGA is 191.32 J / g.

[0060] The present invention will be further described below through specific embodiments, but the scope of the invention is not limited to the examples shown.

[0061] Comparative Example 1

[0062] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. The extruder temperatures during the experiment were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 225℃, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20-50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set to 80℃, and the drawing speed was 1.6 m / min. (DSC testing showed that the crystallinity of the obtained PGA film at this time was 37%).

[0063] Meanwhile, PBAT particles were cast using two other Thermo Scientific Haake PolyLab OS single-screw extruders. During the experiment, the screw temperatures of extruder sections 2-11 were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBAT film, it was drawn by a calendering roller at a speed of 1.6 m / min. Next, the cooled PGA film, serving as the inner layer, was pressed together with the upper and lower PBAT films onto a hot press roller at a temperature of 120℃ for 3 minutes under a pressure of 80 kPa, and then wound up by the calendering roller.

[0064]

Example 1

[0065] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 225℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set to 60℃, and the drawing speed was 1.6 m / min. (After DSC testing, the crystallinity of the obtained PGA film at this time was 27%).

[0066] Meanwhile, PBAT particles were cast using two other Thermo Scientific Haake PolyLab OS single-screw extruders. During the experiment, the screw temperatures in sections 2-11 of the extruder were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBAT film, it was drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film (inner layer) was pressed with the upper and lower PBAT films using hot press rollers, with the hot press roller temperature set at 120℃ and maintained at a pressure of 80 kPa for 3 minutes. Finally, it was wound up by calendering rollers.

[0067]

Example 2

[0068] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 225℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set to 60℃, and the drawing speed was 1.6 m / min. (After DSC testing, the crystallinity of the obtained PGA film at this time was 27%).

[0069] Meanwhile, PBAT particles were cast using two other Thermo Scientific Haake PolyLab OS single-screw extruders. During the experiment, the screw temperatures in sections 2-11 of the extruder were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBAT film, it was drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film (inner layer) was pressed with the upper and lower PBAT films using hot press rollers, with the hot press roller temperature set at 180℃ and the pressure at 80 kPa, before being wound up by calendering rollers.

[0070]

Example 3

[0071] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 225℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set at 20℃, and the drawing speed was 1.6 m / min. (After DSC testing, the crystallinity of the obtained PGA film at this time was 13%).

[0072] Meanwhile, PBAT particles were cast using two other Thermo Scientific Haake PolyLab OS single-screw extruders. During the experiment, the screw temperatures in sections 2-11 of the extruder were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBAT film, it was drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film (inner layer) was pressed with the upper and lower PBAT films using hot press rollers at a temperature of 120℃ and a pressure of 80 kPa, followed by winding by calendering rollers.

[0073]

Example 4

[0074] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 220℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set at 20℃, and the drawing speed was 1.6 m / min. (After DSC testing, the crystallinity of the obtained PGA film at this time was 13%).

[0075] Meanwhile, PBST particles were cast using two other Thermo Scientific Haake PolyLab OS single-screw extruders. During the experiment, the screw temperatures in sections 2-11 of the extruder were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBST film, it was drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film (inner layer) was pressed together with the upper and lower PBST films using hot press rollers, with the hot press roller temperature set at 120℃ and maintained at a pressure of 80 kPa for 3 minutes. Finally, it was wound up by calendering rollers.

[0076]

Example 5

[0077] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 220℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set at 20℃, and the drawing speed was 1.6 m / min. (After DSC testing, the crystallinity of the obtained PGA film at this time was 13%).

[0078] Meanwhile, PBST and PBAT particles were cast using a Thermo Scientific Haake PolyLabOS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBAT and PBST films, they were drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film, as the inner layer, was pressed together with the PBST and PBAT films by hot press rollers at a temperature of 120℃ and a pressure of 80, followed by winding by calendering rollers.

[0079]

Example 6

[0080] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 220℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set at 20℃, and the drawing speed was 1.6 m / min. (DSC testing showed that the crystallinity of the obtained PGA film at this time was 13%).

[0081] Meanwhile, PLA / PBAT blend particles with a mass ratio of 20 / 80 were cast using a Thermo SCIENTIFICHAAKE PolyLab OS single-screw extruder. During the experiment, the screw temperatures of extruder sections 2-11 were 150℃, 160℃, 160℃, 170℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PLA / PBAT film, it was drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film (inner layer) was pressed with the PLA / PBAT film using hot press rollers at a temperature of 120℃ and a pressure of 80 kPa, followed by winding by calendering rollers.

[0082]

Example 7

[0083] PGA particles were cast using a Thermo Scientific Haake PolyLab OS single-screw extruder. During the experiment, the screw temperatures in sections 2-11 of the extruder were 200℃, 220℃, 230℃, 230℃, 240℃, 250℃, 250℃, 240℃, 230℃, and 225℃, respectively, with the screw speed set at 200 rpm. During stable operation, the torque ranged from 20% to 50%. The PGA film exiting at 225℃ was cooled by a cooling roller and then drawn by a calendering roller. The cooling roller temperature was set at 40℃, and the drawing speed was 1.6 m / min. (After DSC testing, the crystallinity of the obtained PGA film at this time was 22%).

[0084] Meanwhile, PBST particles were cast using two other Thermo Scientific Haake PolyLab OS single-screw extruders. During the experiment, the screw temperatures of extruder sections 2-11 were 140℃, 150℃, 150℃, 160℃, 170℃, 160℃, 160℃, 150℃, 150℃, and 150℃, respectively, with the screw speed set at 100 rpm. During stable operation, the torque ranged from 10% to 50%. After exiting the PBST film, it was drawn by calendering rollers at a speed of 1.6 m / min. Then, the cooled PGA film (inner layer) was pressed with the upper and lower PBST films using hot press rollers, with the hot press roller temperature set at 120℃ and maintained at a pressure of 80 kPa for 3 minutes, before being wound up by calendering rollers.

[0085]

Example 8

[0086] The PGA films in Examples 1-7 and Comparative Example 1 were heated at a rate of 10 °C / min, and their crystallization thermodynamic parameters were measured using a differential scanning calorimeter (DSC) from TA Instruments, USA. The values ​​are listed in Table 1.

[0087] Table 1. DSC thermal performance data of the inner PGA film in the multilayer film.

[0088]

[0089]

Example 9

[0090] The multilayer films prepared in Examples 1-7 and Comparative Example 1 were first placed in a constant temperature and humidity environment of 23°C and 50%RH for 24 hours for pretreatment. The thermal bonding performance of the samples was measured according to the steps described above, and the values ​​are listed in Table 2.

[0091] Table 2. Thermal strength of specimens from Examples 1-7 and Comparative Example 1

[0092]

Claims

1. A continuous preparation method for a polyglycolic acid (PGA) multilayer film, comprising: simultaneously extruding and casting PGA and biodegradable polyester in parallel, cooling them, and then drawing the resulting PGA film and biodegradable polyester film into the same hot-pressing unit for hot pressing to obtain the multilayer film, wherein the crystallinity of the PGA film is 1-17%, and the melting point of the biodegradable polyester differs from that of the PGA film by at least 15°C. o C, wherein the biodegradable polyester is selected from at least one of polylactic acid, polyhydroxy fatty acid esters, polycaprolactone, carbon dioxide-based biodegradable plastics, and dicarboxylic acid diol copolyesters; and the temperature of the hot pressing unit is 100~160℃.

2. The continuous preparation method according to claim 1, characterized in that: The intrinsic viscosity of the polyglycolic acid is 0.9~4 dl / g; The polyglycolic acid has a melting temperature of 200~235℃ when tested at a heating / cooling rate of 10℃ / min. The crystallinity of the polyglycolic acid is 1-70%; The weight-average molecular weight of the polyglycolic acid is 50,000 to 1,000,000 g / mol; The molecular weight distribution index of the polyglycolic acid is 0.5 to 15.

0.

3. The continuous preparation method according to claim 2, characterized in that: The intrinsic viscosity of the polyglycolic acid is 0.9~2 dl / g; The weight-average molecular weight of the polyglycolic acid is 100,000 to 500,000 g / mol; The molecular weight distribution index of the polyglycolic acid is 1.5 to 3.

0.

4. The continuous preparation method according to claim 1, characterized in that: The dicarboxylic acid diol copolyester is selected from at least one of polybutylene terephthalate-co-adipate, polyethylene terephthalate-co-adipate, polybutylene terephthalate-co-succinate, polyethylene terephthalate-co-succinate, polybutylene succinate-adipate, and polybutylene succinate.

5. The continuous preparation method according to claim 1, characterized in that: Under test conditions of 190°C and 2.16 kg, the melt index of the biodegradable polyester is 2~20 g / 10 min.

6. The continuous preparation method according to claim 5, characterized in that: The melt index of the biodegradable polyester is 2~15 g / 10 min.

7. The continuous preparation method according to claim 1, characterized in that: In the extrusion casting process, the melt extrusion temperature of polyglycolic acid is 200~255℃; The cooling temperature of polyglycolic acid film is 10~60℃.

8. The continuous preparation method according to claim 7, characterized in that: In the extrusion casting process, the die temperature is 210~235℃. o C; The cooling temperature of polyglycolic acid film is 10~40℃.

9. The continuous preparation method according to claim 1, characterized in that: In the extrusion casting process, the melt extrusion temperature of the biodegradable polyester is 100~180℃; the rotation speed is 30~300 rpm.

10. The continuous preparation method according to claim 9, characterized in that: The rotation speed is 30~200 rpm.

11. The continuous preparation method according to claim 1, characterized in that: The hot-pressing time is 0.1~5 min; the hot-pressing pressure is 2~200 kPa; The hot pressing unit uses hot pressing rollers.

12. The continuous preparation method according to claim 11, characterized in that: The hot-pressing time is 0.1~3 min; the hot-pressing pressure is 5~100 kPa; The hot press roller can be a round roller or a square roller.

13. A polyglycolic acid multilayer film obtained by the continuous preparation method according to any one of claims 1 to 12.

14. The use of the polyglycolic acid multilayer film of claim 13 in barrier packaging.

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