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CN-122011693-A - Environment-friendly packaging plastic film and preparation method thereof

CN122011693ACN 122011693 ACN122011693 ACN 122011693ACN-122011693-A

Abstract

The invention relates to the technical field of polymer material processing, and discloses an environment-friendly packaging plastic film and a preparation method thereof, the film is prepared from PBAT, polylactic acid, epoxidized soybean oil, anhydrous citric acid micropowder, pentaerythritol stearate, zinc stearate and polymerized carbodiimide. And adding anhydrous citric acid in a delayed manner, and controlling in-situ branching reaction to be carried out in a controlled rheological environment by matching with reverse temperature gradient setting of the middle and rear sections of the extruder to construct a uniformly distributed crosslinked network. Pentaerythritol stearate provides steric hindrance by utilizing a star-shaped long-chain structure, and inhibits the regular folding of polylactic acid in a cooling section. And the later stage is independently injected with the polymerized carbodiimide, so as to quench unreacted free carboxyl in the system in situ and eliminate the catalytic degradation effect of the acid end group on the polyester main chain. The invention effectively locks plasticizer molecules, reduces migration and separation rate, reduces gel defects on the surface of the film, and improves processing stability and longitudinal tearing strength of the film.

Inventors

  • HUANG ZHIJIAN
  • Wei Hanze
  • WEI JINHAI

Assignees

  • 广州图彩塑胶制品有限公司

Dates

Publication Date
20260512
Application Date
20260225

Claims (10)

  1. 1. The environment-friendly packaging plastic film is characterized by being prepared from the following raw materials in parts by weight: 60.0-80.0 parts of polybutylene terephthalate-adipate; 10.0-30.0 parts of polylactic acid; 5.0-12.0 parts of epoxidized soybean oil; 1.0 to 3.0 parts of anhydrous citric acid micro powder; 0.5-1.5 parts of pentaerythritol stearate; 0.1-0.5 part of zinc stearate; 0.3-1.0 part of polymerized carbodiimide.
  2. 2. The environmentally friendly packaging plastic film according to claim 1, wherein the polybutylene terephthalate-adipate has a melt index of 2.0-5.0g/10min and the polylactic acid has a melt index of 4.0-12.0g/10min.
  3. 3. The environment-friendly packaging plastic film according to claim 1, wherein the epoxy value of the epoxy soybean oil is 6.0% -6.4%, the anhydrous citric acid micro powder is sieved by a 100-200 mesh sieve, and the mass fraction of the effective carbodiimide groups of the polymerized carbodiimide is 8.0% -12.0%.
  4. 4. A method for preparing an environment-friendly packaging plastic film, which is applied to the environment-friendly packaging plastic film as claimed in any one of claims 1 to 3, and comprises the following steps: mixing polybutylene terephthalate-adipic acid and polylactic acid, placing the mixture in a drying device for continuous drying, and placing anhydrous citric acid micropowder and zinc stearate in a mixing device for normal-temperature premixing to obtain premixed powder; adding the dried polybutylene terephthalate-adipic acid butanediol ester, the polylactic acid and pentaerythritol stearate into a main feeding port of a double-screw extruder through main feeding equipment, and simultaneously injecting liquid epoxidized soybean oil into a machine barrel zone 2 of the double-screw extruder through liquid injection equipment to form a mixed material in the machine barrel zone 1 to the machine barrel zone 3 of the double-screw extruder; Pressing the premixed powder into a cylinder 4 zone of the double-screw extruder through lateral feeding equipment, and carrying out melt blending with the mixed material; Starting a machine barrel cooling system of the double-screw extruder, and controlling the temperatures of a machine barrel zone 5, a machine barrel zone 6 and a machine barrel zone 7 of the double-screw extruder to decrease in sequence so that the mixed material stays in the machine barrel zone 5 to the machine barrel zone 7 of the double-screw extruder; Injecting the heated melted polymeric carbodiimide into the barrel zone 8 of the twin screw extruder by a melt pumping device as the mixture enters the barrel zone 8 of the twin screw extruder; Starting a vacuum exhaust system in a machine barrel 9 zone of the double-screw extruder, extruding a melt strip of the mixed material through an extrusion die head of the double-screw extruder through a machine barrel 10 zone of the double-screw extruder, and granulating and centrifugally dehydrating the melt strip to obtain modified biodegradable master batches; And adding the modified biodegradable master batch into film blowing equipment for blow molding, and rolling to obtain the environment-friendly packaging plastic film.
  5. 5. The method for producing an environment-friendly packaging plastic film according to claim 4, wherein the drying equipment is a dehumidifying dryer, the mixing equipment is a high-speed mixer, and the continuous drying temperature is controlled to be 70-85 ℃ and the continuous drying time is 3.0-6.0 hours in the step of continuously drying the polybutylene terephthalate and the polylactic acid in the dehumidifying dryer after mixing.
  6. 6. The method for preparing an environment-friendly packaging plastic film according to claim 4, wherein the main feeding equipment is a main weightless type feeding scale, the double-screw extruder is a homodromous double-screw extruder, and the liquid injection equipment is a liquid metering pump; The length-diameter ratio of the homodromous double-screw extruder is 40-48, the temperature of a machine barrel 1 region to a machine barrel 3 region of the homodromous double-screw extruder is 160-180 ℃, and the screw rotating speed of the homodromous double-screw extruder is 200-300rpm; the lateral feeding device is a lateral forced feeder, and the temperature of a machine barrel 4 region of the double-screw extruder is set to be 160-170 ℃.
  7. 7. The method for producing an environment-friendly packaging plastic film according to claim 4, wherein the temperature of the 5 th zone of the barrel of the twin-screw extruder is set to 150-160 ℃, the temperature of the 6 th zone of the barrel of the twin-screw extruder is set to 145-155 ℃, and the temperature of the 7 th zone of the barrel of the twin-screw extruder is set to 140-150 ℃; Controlling the average residence time of the mixed material in a barrel 5 zone to a barrel 7 zone of the double-screw extruder to be 30-75 seconds.
  8. 8. The method for producing an environmentally friendly packaging plastic film according to claim 4, wherein the melt pumping device is a high pressure melt gear pump, and the barrel zone 8 temperature of the twin screw extruder is set to 150-160 ℃.
  9. 9. The method according to claim 4, wherein the temperatures of the barrel 9 region of the twin-screw extruder, the barrel 10 region of the twin-screw extruder and the extrusion die of the twin-screw extruder are set to 155-165 ℃, and the vacuum degree of the vacuum evacuation system is controlled to be-0.06 to-0.09 MPa.
  10. 10. The method for producing an environment-friendly packaging plastic film according to claim 4, wherein the film blowing device is a single screw film blowing machine, the die temperatures of each region of the single screw film blowing machine and the single screw film blowing machine are set to 140-165 ℃, the inflation ratio of the single screw film blowing machine is set to 2.0-4.0, and the traction ratio of the single screw film blowing machine is set to 3.0-6.0.

Description

Environment-friendly packaging plastic film and preparation method thereof Technical Field The invention relates to the technical field of polymer material processing, in particular to an environment-friendly packaging plastic film and a preparation method thereof. Background At present, biodegradable matrix resins represented by polybutylene terephthalate-adipate and polylactic acid are widely used in the field of environmental-friendly packaging plastic films. In order to improve the flexibility of the film, it is generally necessary to add a plasticizer to the resin matrix. Because most of the plasticizers and the polyester macromolecules are simply and physically mixed, small molecular plasticizers are easy to migrate and separate out to the surface in the storage and use processes of the film, and the comprehensive performance and the service life of the film are affected. In order to limit the migration of plasticizers, some of the prior art have incorporated crosslinking agents to modify the polyester system. However, in conventional continuous melt extrusion processes, the rate of the crosslinking reaction is often difficult to control effectively, and local crosslinking is too fast to result in the formation of macromolecular gel clusters in the polyester matrix. These clusters, after film formation, can appear as gel defects on the film surface, which not only reduce the apparent mass of the packaging film, but also can act as sources of structural stress concentrations, resulting in a decrease in the longitudinal right-angle tear strength of the film. In addition, acidic substances such as free carboxyl groups which are not completely reacted generally remain in the crosslinking system introduced due to processing time limitations. When the modified master batch enters a single-screw film blowing machine for secondary high-temperature processing, the residual acidic substances catalyze the polyester main chain to generate hydrolysis and thermal degradation chain breakage. The acidolysis degradation of the matrix resin can cause abnormal fluctuation of the melt flow rate, so that the processing stability of the film forming process is poor, and the defective rate is increased. Disclosure of Invention Aiming at the defects of the prior art, the invention provides an environment-friendly packaging plastic film and a preparation method thereof, which solve the problems that the plasticizer is easy to migrate and separate out in the processing and using processes of the biodegradable packaging film, the gel defect density on the film surface is high, and the matrix resin is easy to be acidolyzed and degraded in the secondary processing process. In order to achieve the above purpose, the invention is realized by the following technical scheme: The invention provides an environment-friendly packaging plastic film which is prepared from the following raw materials, by weight, 60.0-80.0 parts of polybutylene terephthalate-adipate, 10.0-30.0 parts of polylactic acid, 5.0-12.0 parts of epoxidized soybean oil, 1.0-3.0 parts of anhydrous citric acid micro powder, 0.5-1.5 parts of pentaerythritol stearate, 0.1-0.5 parts of zinc stearate and 0.3-1.0 part of polymerized carbodiimide. By adopting the technical scheme, the flexibility of the film can be improved by adopting the polybutylene terephthalate-adipic acid and the polylactic acid as the biodegradable matrix and the epoxidized soybean oil as the plasticizer. In the system, anhydrous citric acid micropowder is used as a polyfunctional crosslinking agent, and reacts with epoxy soybean oil containing multiple epoxy groups and active groups at the ends of polyester macromolecules in situ in the process of melt extrusion. The reaction mechanism is that carboxyl in anhydrous citric acid and epoxy group in epoxy soybean oil are subjected to ring-opening addition reaction to produce esterified product containing hydroxyl, and the esterified product is further combined with hydroxyl or carboxyl at the chain end of poly (butylene terephthalate-adipate) or poly (lactic acid) to construct a branched network structure with certain crosslinking degree inside the matrix. The branched network limits free epoxidized soybean oil molecules in a polyester macromolecule gap through physical entanglement and chemical anchoring, so that the migration resistance of the plasticizer to the surface of the film is increased, and the migration rate of the plasticizer is further reduced. Meanwhile, pentaerythritol stearate contains four long chains of stearate with a star structure, and can provide steric hindrance at a blending phase interface. The steric hindrance can interfere regular folding of the polylactic acid chain segment in the extrusion cooling process, delay the crystallization kinetics process, prevent supercooling crystallization of materials in a low temperature region of an extruder, and maintain the melt rheological property required in an in-situ network constructio