Preparation method of PGA@PLA@PBAT composite film

Abstract

The application discloses a preparation method of PGA@PLA@PBAT composite film, which comprises the following steps: (1) mixing PLA, PGA and a compatibilizer in a high-speed mixer according to a mass ratio of 70-88:10-30:0-2, and then melt blending in a double-screw extruder to obtain PGA@PLA particles by extruding and granulating; and (2) melt blending PBAT, the PGA@PLA particles prepared in the step (1), a lubricant and an opening agent in a double-screw extruder according to a proportion, and then performing film blowing after extruding and granulating to obtain the PGA@PLA@PBAT composite film. The PGA@PLA@PBAT composite film prepared by the method has high barrier property and excellent mechanical property.

Description

Technical Field

[0001] This invention relates to the field of biodegradable plastic films, and more specifically to a method for preparing a PGA@PLA@PBAT composite film. Background Technology

[0002] Developing new biodegradable plastics that meet usage requirements is one of the important ways to reduce plastic pollution at its source and achieve green and sustainable development in the plastics industry. Polybutylene terephthalate (PBAT) is a 100% biodegradable resin that has been widely used in fields such as mulch films and film bag packaging. However, compared with traditional non-degradable films such as polyethylene (PE) and polypropylene (PP), PBAT films have lower tensile strength and modulus, and their barrier properties against O2 and H2O are also relatively poor.

[0003] Polyglycolic acid (PGA) is a biodegradable polyester with high tensile strength, modulus, and barrier properties. Melt blending PGA with PBAT or PLA@PBAT blends can effectively improve the tensile and barrier properties of PBAT without affecting its biodegradability. For example, patent CN113025015A uses ADR as a compatibilizer to melt blend PGA and PBAT and then blow-mold to obtain a low-permeability and high-water-blocking film product. However, because the melting point of PGA (220-240℃) is much higher than that of PBAT (120-140℃), it is difficult to directly melt-blend the two. Patent CN114031760A introduces a diol containing hydrophobic groups into the PBAT chain segments through copolymerization, and then blow-molds it to obtain a biodegradable film with hydrophobic and water-blocking properties.

[0004] In addition, Ji Eun et al. (C. Ji Eun, et al. Influence of Modified Poly(Glycolicacid) on the Physical and Mechanical Properties of PLA / PBAT / mPGA Multi-phase Blends. J. Polym. Environ., 2024.) prepared a biodegradable blend by using mPGA with epoxy groups as a compatibilizer, melt-blending PGA with PBAT / PLA (polylactic acid) in a small internal mixer and then molding it into sheets. The oxygen and water vapor barrier properties of the sheets with added mPGA were improved, but the elongation at break decreased significantly.

[0005] Because the melting point of PGA (220-240℃) is much higher than that of PBAT (120-140℃), it is difficult to uniformly disperse PGA in PBAT or PLA@PBAT continuous phase through simple melt blending (PBAT's maximum processing temperature is usually 190-200℃), thereby improving the mechanical and barrier properties of PBAT films. Summary of the Invention

[0006] To address the goal of improving the mechanical and barrier properties of PBAT by adding PGA, this invention provides a method for preparing a biodegradable PGA@PLA@PBAT composite film with high barrier properties and excellent mechanical properties through gradient melt blending.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a PGA@PLA@PBAT composite film includes the following steps:

[0009] (1) PLA (polylactic acid), PGA (polyglycolic acid) and compatibilizer are premixed in a high-speed mixer at a mass ratio of 70-88%:10-30%:0-2%, then melt-blended in a twin-screw extruder, and extruded and granulated to obtain PGA@PLA particles;

[0010] (2) PBAT (poly(di ...(di((di((i((i((i((i((i((i((i((i((i( -(["[[(i("I(I(I(I((I((I(["I(I(I(I(I(I(I(["I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(I(["I(I(I(I(I(I(I(I(I(I(I(I

[0011] The mass percentage of each component in the composite film is as follows: PBAT 40-68%, PGA@PLA particles 30%-50%, lubricant 0.1-0.5%, and opening agent 0.1-0.5%.

[0012] Preferably, the PLA has a melt flow rate of 3-5 g / 10 min (190 °C, 2.16 kg).

[0013] Preferably, the intrinsic viscosity of the PGA is 1.0-1.5 dL / g, the melting point is 220-240℃, and the crystallinity is 40-50%.

[0014] Preferably, the compatibilizer is an epoxy-functionalized copolymer, ADR.

[0015] Preferably, the PBAT has a melt flow rate of 2-10 g / 10 min (190 °C, 2.16 kg) and a terminal carboxyl content of 1-30 mol / ton.

[0016] Preferably, the lubricant is one or more of stearic acid, butyl stearate, and glyceryl stearate.

[0017] Preferably, the opening agent is one or more of oleamide, erucamide, and ethylene bis-stearamide.

[0018] Preferably, in step (1), the temperature of the high-speed mixer is 60-80℃, the speed is 200-500rpm, and the mixing time is 10-20min.

[0019] Preferably, in step (1), the twin-screw extruder is a parallel co-rotating twin-screw extruder with a screw length-to-diameter ratio greater than 20:1 and not exceeding 56:1; the temperature of the first to tenth sections of the twin-screw extruder is 180-240℃; the die temperature is 220-240℃; and the rotation speed is controlled at 150-300rpm.

[0020] Preferably, in step (1), the granulation is carried out by air-cooled pelletizing to obtain PGA@PLA particles.

[0021] Preferably, in step (2), the twin-screw extruder is a parallel co-rotating twin-screw extruder with a screw length-to-diameter ratio greater than 20:1 and not exceeding 56:1; the temperature of the first to tenth sections of the twin-screw extruder is 150-190℃; the die temperature is 150-170℃; and the rotation speed is controlled at 150-300rpm.

[0022] Preferably, in step (2), the granulation is carried out by air-cooled pelletizing to obtain PGA@PLA@PBAT particles.

[0023] Preferably, in step (2), the temperature of the blown film extruder in sections one to four is 160-180℃, the blow-up ratio (die diameter: film bubble diameter) is 1:2-4, and the blown film stretching ratio is 1.0-2.0.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) The present invention uses gradient melt blending to prepare PGA@PLA@PBAT composite material. First, PGA is uniformly dispersed in PLA with a slightly lower melting point (160-175℃) by a twin-screw extruder, and then the prepared PGA@PLA is uniformly dispersed in PBAT with a relatively low melting point.

[0026] (2) In this invention, ADR is pre-added to the PGA / PLA blend system, which can increase the interfacial compatibility between the two and achieve good dispersion of PGA in PLA, and also increase the interfacial compatibility of PLA / PBAT and achieve good dispersion of PLA (containing PGA dispersed phase) in PBAT.

[0027] (2) Compared with direct melt blending, the present invention effectively solves the problem of difficult processing of PBAT and PGA due to the large difference in melting point by gradient melt blending. Composite film with good barrier properties and mechanical properties can be prepared by using conventional PBAT blown film process.

[0028] (3) The gradient melt blending method of the present invention is applicable to all polymer systems that are difficult to process due to large differences in melting points, and has the advantages of wide applicability and simple implementation.

[0029] (4) The process of this invention is simple, easy to operate, and suitable for large-scale production. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0031] The raw materials used in this invention are as follows:

[0032] PLA: Melt flow rate is 4.2 g / 10 min (190℃, 2.16 kg);

[0033] PBAT: Melt flow rate is 6.4 g / 10 min (190℃, 2.16 kg), and terminal carboxyl content is 13 mol / ton;

[0034] ADR-4468: Molecular weight is 7250, epoxy resin equivalent is 310 g / mol;

[0035] PGA: intrinsic viscosity is 1.2 dL / g, melting point is 220-240℃, and crystallinity is 43%.

[0036] The remaining additives are commercially available processing aids.

[0037] Example 1

[0038] The PGA@PLA particles comprise 89% PLA, 10% PGA, and 81% ADR-446 by weight percentage.

[0039] The composite film comprises, by weight percentage, 69.3% PBAT, 30% PLA / PGA / ADR particles, 0.5% stearic acid (lubricant), and 0.2% erucamide (opening agent).

[0040] Preparation of PGA@PLA granules: PLA, PGA, and ADR-4468 were weighed according to the formula and directly added to a 5L high-speed mixer (LN-G5L, Guangdong Lina Industrial Co., Ltd.). The mixture was mixed at 80℃ and 300rpm for 15min. Then, the mixture was added to a parallel co-rotating twin-screw extruder (φ20, L / D=36, Nanjing Juli Chemical Machinery Co., Ltd.) for mixing, plasticizing, and extrusion. After stretching and air cooling, PGA@PLA granules were obtained. The temperatures of each section of the extruder were as follows: the temperatures of sections one to ten were 180, 185, 190, 200, 220, 240, 220, 200, 195, and 190℃, respectively, and the die temperature was 200℃. The rotation speed was 200rpm.

[0041] Preparation of PGA@PLA@PBAT composite material: PABT and PGA@PLA granules, lubricant, and opening agent were weighed according to the formula and added to a parallel co-rotating twin-screw extruder (φ20, L / D=36, Nanjing Juli Chemical Machinery Co., Ltd.) for mixing, plasticizing, and extrusion. After stretching and air cooling, the extruder pellets were obtained. The extruder temperatures were as follows: the temperatures of sections one to ten were 160, 165, 170, 170, 180, 180, 170, 160, 155, and 150℃ respectively, and the die temperature was 160℃. The rotation speed was 200 rpm.

[0042] Preparation of PGA@PLA@PBAT composite film: The obtained granules were directly blown into a PGA@PLA@PBAT composite film using a blown film extruder (XH-430B, Xihua Testing Instruments Co., Ltd.). The temperatures of the first to fourth stages of the blown film extruder were 160, 170, 165, and 160℃ respectively, the blow-up ratio (die diameter: bubble diameter) was 1:3, the blown film stretch ratio was 1.2, and the film thickness was 40μm.

[0043] The obtained films were subjected to tensile property tests according to GB / T1040.3-2006 to obtain data such as tensile strength and elongation at break. Water vapor and oxygen barrier properties were measured according to ASTM 3985. The results are shown in Tables 1 and 2.

[0044] Example 2

[0045] The procedure was the same as in Example 1, except that the mass percentage content of PLA and PGA in the PGA@PLA particles was changed to 79% PLA and 20% PGA. The film performance testing was also the same as in Example 1. The results are shown in Tables 1 and 2.

[0046] Example 3

[0047] The procedure was the same as in Example 1, except that the mass percentage content of PLA and PGA in the PGA@PLA particles was changed to 69% PLA and 30% PGA. The film performance testing was also the same as in Example 1. The results are shown in Tables 1 and 2.

[0048] Example 4

[0049] The procedure is the same as in Example 1, except that the mass percentage content of PLA and PGA in the PGA@PLA particles is changed to 59% PLA and 40% PGA. The film performance testing is also the same as in Example 1. The results are shown in Tables 1 and 2.

[0050] Example 5

[0051] The procedure was the same as in Example 1, except that the mass percentage content of PLA and PGA in the PGA@PLA particles was changed to 49% PLA and 50% PGA. The film performance testing was also the same as in Example 1. The results are shown in Tables 1 and 2.

[0052] Example 6

[0053] Other aspects are the same as in Example 1, but ADR-4468 is not added, meaning the PGA@PLA particles contain 89.9% PLA and 10.1% PGA. Thin film performance testing is also the same as in Example 1. Results are shown in Tables 1 and 2.

[0054] Compare with Example 1

[0055] The composite film, by mass percentage, comprises 69.3% PBAT, 26.7% PLA, 3% PGA, 0.3% ADR-4468, 0.5% stearic acid (lubricant), and 0.2% erucamide (opening agent). PABT, PLA, PGA, compatibilizer, lubricant, and opening agent are weighed out according to the specified proportions and added to a 5L high-speed mixer. The mixture is then blended for 15 minutes at 80°C and 300 rpm. The mixture is then fed into a parallel co-rotating twin-screw extruder for compounding, plasticizing, and extrusion. After stretching and air cooling, the extruder pellets are obtained. The extruder temperatures for each section are: sections one through ten are 180, 185, 190, 200, 220, 240, 220, 200, 195, and 190°C respectively; the die temperature is 200°C; and the rotation speed is 200 rpm.

[0056] The obtained granules were directly blown into PBAT / PGA / PLA composite films using a blown film extruder. The temperatures of the first to fourth stages of the blown film extruder were 190, 220, 210, and 200°C, respectively. The blow-up ratio (die diameter: bubble diameter) was 1:3, and the blown film stretch ratio was 1.2. The film performance was tested in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0057] Compare with Example 2

[0058] Other parameters were the same as in Comparative Example 1, but PLA and PGA were omitted. The composite film contained 98.6% PBAT, 0.4% ADR-4468, 0.7% stearic acid (lubricant), and 0.3% erucamide (opening agent). Film performance testing was also performed as in Example 1. Results are shown in Tables 1 and 2.

[0059] Table 1 Mechanical properties of composite films

[0060]

[0061] Table 1 Barrier properties of composite films

[0062] <![CDATA[O2 transmittance]]> <![CDATA[H2O transmittance]]> <![CDATA[g / m 2 ·24h]]> <![CDATA[g / m 2 ·24h]]> Example 1 805 578 Example 2 765 562 Example 3 726 547 Example 4 679 522 Example 5 607 474 Example 6 894 607 Compare with Example 1 914 614 Compare with Example 2 1337 623

Claims

1. A method for preparing a PGA@PLA@PBAT composite film, characterized in that: The preparation method includes the following steps: (1) PLA, PGA and compatibilizer are premixed in a high-speed mixer at a mass ratio of 70-88%:10-30%:0-2%, then melt-blended in a twin-screw extruder, and extruded and granulated to obtain PGA@PLA particles; PLA and PGA refer to polylactic acid and polyglycolic acid, respectively. (2) PBAT, PGA@PLA particles prepared in step (1), lubricant and opening agent are melt-blended in a twin-screw extruder in proportion, extruded and granulated and blown into film to obtain PGA@PLA@PBAT composite film; PBAT refers to poly(adipate-butylene terephthalate); The mass percentage of each component in the composite film is as follows: PBAT 40-68%, PGA@PLA particles 30%-50%, lubricant 0.1-0.5%, opening agent 0.1-0.5%, and the sum of the mass percentages of each component is 100%.

2. The preparation method according to claim 1, characterized in that: The melt flow rate of the PLA is 3-5 g / 10min (190 g / min). o C, 2.16 kg).

3. The preparation method according to claim 1, characterized in that: The intrinsic viscosity of the PGA is 1.0-1.5 dL / g, and the melting point is 220-240°C. o C, with a crystallinity of 40-50%.

4. The preparation method according to claim 1, characterized in that: The compatibilizer is an epoxy-functionalized copolymer, ADR.

5. The preparation method according to claim 1, characterized in that: The melt flow rate of the PBAT is 2-10 g / 10 min (190 o C, 2.16 kg), with a terminal carboxyl group content of 1-30 mol / ton.

6. The preparation method according to claim 1, characterized in that: The lubricant is one or more of stearic acid, butyl stearate, and glyceryl stearate; the opening agent is one or more of oleamide, erucamide, and ethylene bis-stearamide.

7. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the high-speed mixer is 60-80°C. o C, the rotation speed is 200-500 rpm, and the mixing time is 10-20 min.

8. The preparation method according to claim 1, characterized in that: In step (1), the twin-screw extruder is a parallel co-rotating twin-screw extruder with a screw length-to-diameter ratio greater than 20:1 and not exceeding 56:1; the temperature of the first to tenth stages of the twin-screw extruder is 180-240°C. o C; Die head temperature is 220-240℃ o C; The engine speed should be controlled between 150-300 rpm.

9. The preparation method according to claim 1, characterized in that: In step (2), the twin-screw extruder is a parallel co-rotating twin-screw extruder with a screw length-to-diameter ratio greater than 20:1 and not exceeding 56:1; the temperature of the first to tenth stages of the twin-screw extruder is 150-190°C. o C; Die head temperature is 150-170°C o C; The engine speed should be controlled between 150-300 rpm.

10. The preparation method according to claim 1, characterized in that: In step (2), the temperature of the blown film extruder used for blown film extrusion is 160-180°C in sections one to four. o C, the blow-up ratio is 1:2-4, and the blown film stretch ratio is 1.0-2.0.

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