Production method of biaxially oriented polylactic acid film

Abstract

The invention discloses a production method of a biaxially oriented polylactic acid film, and belongs to the technical field of polylactic acid films, polylactic acid is used as a raw material and is subjected to blending modification with diacetyl epoxy soybean glyceryl oleate, the biaxially oriented polylactic acid film is produced through sapium sebiferum and an anti-blocking agent, and the product has good biocompatibility and degradation performance and is environmentally friendly; high light transmittance, low haze, good surface glossiness and excellent printing performance are realized; good heat sealing performance is achieved, and direct heat sealing can be achieved without gluing; the processing performance is excellent, and the folding form stability and the kink retentivity are good. The bio-based degradable polylactic acid film produced by the production method of the biaxially oriented polylactic acid film has excellent air permeability and moisture permeability, is very suitable for breathing packaging, prolongs the refreshing time of flowers and foods, and can effectively meet the requirements of downstream customers on simple printing and bag making.

Description

Technical Field

[0001] The invention belongs to the technical field of polylactic acid films, and in particular relates to a production method of a biaxially stretched polylactic acid film. Background Art

[0002] PLA has good barrier properties and transparency, but its low thermal stability and inherent brittleness limit its application. At the same time, the excellent performance of PLA is related to its crystal structure, morphology and crystallinity, and its molding method will affect the crystallization behavior, which in turn affects the performance of PLA film products. Zhu Ziwei introduced the compatibilizer Joncry4468 to toughen and modify PLA with polyamide 11 (PA11), and prepared PLA / PA11 / Joncry4468 (mass ratio of 78.4 / 20 / 1.6) cast film by extrusion and unidirectional and bidirectional stretching. Chen Zhiping et al. used 1%~3.5% of a specific structure ester quaternary ammonium salt (the ester group and long-chain alkyl contained make the ester quaternary ammonium salt have good compatibility with PLA) and 96.5%~99% PLA as raw materials, and obtained an antistatic BOPLA film with good optical properties by blending the prepared antistatic masterbatch with PLA. Li et al.

[27] modified PLA with 3% pyromellitic anhydride (PMDA) and 3% pentaerythritol glycidyl ether (PGE) to produce long-chain branched PLA (LCB-PLA), and compared the physical properties of LCB-PLA and pure PLA films after biaxial stretching. The above production methods are complex and costly. Therefore, those skilled in the art are in urgent need of developing a production method for biaxially stretched polylactic acid film to meet the existing market demand and performance requirements. Summary of the invention

[0003] The purpose of the present invention is to provide a method for producing a biaxially oriented polylactic acid film in view of the existing problems.

[0004] A method for producing a biaxially stretched polylactic acid film comprises the following steps: using an extruder to uniformly mix modified polylactic acid, Chinese tallow fat and an anti-blocking agent in a mass ratio of 100:10-15:0.3-0.5; drying the pellets obtained by extrusion granulation at 55-60°C for 2-4 hours; forming a cast sheet according to a melt extrusion process; and then performing a longitudinal stretching stage, a transverse stretching stage, and then heat-setting and rolling at 120-140°C to obtain the film.

[0005] Furthermore, the modified polylactic acid is obtained by first mixing diacetyl epoxy soybean glyceride and polylactic acid in a mass ratio of 1-2:11-13 in a high-speed mixer, melt blending in a twin-screw extruder, extruding, water cooling, air drying and then pelletizing, with a screw speed of 100-150 r / min and a temperature of 175°C-190°C.

[0006] Furthermore, the longitudinal stretching stage includes: preheating section 50~60°C, slow stretching section 60~65°C, heat treatment section 50~55°C, stretching ratio 2.5~3, and stretching rate 60~80% / s.

[0007] Furthermore, the transverse stretching stage includes: preheating section 65~70°C, slow stretching section 75~80°C, heat treatment section 130~135°C, stretching ratio 2.5~3, and stretching rate 60~80% / s.

[0008] Resin, a white solid, is obtained from the mesocarp of the fruit of Sapium sebiferum, a deciduous tree of the Euphorbiaceae family.

[0009] Furthermore, the temperatures of zones 1 to 5 of the melt extrusion process are respectively set to 145-150°C, 170-175°C, 190-195°C, 195-200°C, and 200°C, and the die temperature is 175-180°C.

[0010] Furthermore, the opening agent is palmitamide. Beneficial effects of the present invention:

[0011] Using polylactic acid as raw material and diacetyl epoxy soybean glyceride for blending and modification, biaxially oriented polylactic acid film is produced by using tallow fat and anti-blocking agent. The product has good biocompatibility and degradation performance, and is environmentally friendly; high light transmittance, low haze, good surface gloss, and excellent printing performance; it has good heat sealing performance and can be directly heat-sealed without gluing; it has excellent processing performance and has good folding shape stability and kink retention. The bio-based and degradable polylactic acid film produced by the production method of biaxially oriented polylactic acid film has excellent air permeability and moisture permeability, and is very suitable for use in breathing packaging, extending the shelf life of flowers and food, and can also effectively meet the needs of downstream customers for simple printing and bag making. DETAILED DESCRIPTION

[0012] The present invention is described below with specific examples, but is not intended to be limiting of the present invention. Example 1

[0013] Yongjian Machinery SY-00 biaxially oriented film production line has 2 preheating zones, 3 stretching zones, and 1 heat treatment zone. Each zone is 2m long, with a speed of 100m / min. Lingke Chemical Tallow Oil; Mailun Daily Chemical Palm Kernel Oil Amide DEA6501.

[0014] A method for producing a biaxially stretched polylactic acid film comprises the following steps: first, preparing modified polylactic acid by mixing diacetyl epoxy soybean glyceride and polylactic acid in a mass ratio of 1.5:12 in a high-speed mixer, then melting and blending in a twin-screw extruder, extruding, water cooling, air drying, and then pelletizing, wherein the screw speed is 120r / min and the temperature is 180°C; second, uniformly mixing the modified polylactic acid, Chinese tallow fat, and an anti-blocking agent in a mass ratio of 100:12:0.4 using an extruder, drying the pellets obtained by extruding and granulating at 58°C for 3h, and then granulating according to a melt extrusion process. The product was then quenched at 50°C to form a casting sheet. The temperatures of zones 1 to 5 in the melt extrusion process were set to 148°C, 173°C, 193°C, 198°C, and 200°C, respectively, and the die temperature was 178°C; the product was subjected to a longitudinal stretching stage and a transverse stretching stage, and then heat-set and rolled at 120-140°C. In the longitudinal stretching stage, the preheating section was 55°C, the slow-drawing section was 63°C, the heat treatment section was 53°C, the stretching ratio was 2.8, and the stretching rate was 70% / s; in the transverse stretching stage, the preheating section was 68°C, the slow-drawing section was 78°C, the heat treatment section was 132°C, the stretching ratio was 2.8, and the stretching rate was 60-80% / s.

[0015] Products: Roll length 6000m, paper tube specification (inches) 3; no wrinkles; no uneven winding on the end surface; no pitting, fish eyes, bubbles, pin points; no impurity pollution, oil stains, different colors, frosting; no warping, axial misalignment; no chrysanthemum shape on the end surface; no wrinkles, ribs, stripes, or end surface scratches. Example 2

[0016] Yongjian Machinery SY-00 biaxially oriented film production line has 2 preheating zones, 3 stretching zones, and 1 heat treatment zone. Each zone is 2m long, the speed is 100m / min, 789 chemical tallow fat; Mailun daily chemical 6501 palm kernel oil amide DEA.

[0017] A method for producing a biaxially stretched polylactic acid film comprises the following steps: first, preparing a modified polylactic acid by mixing diacetyl epoxy soybean glyceride and polylactic acid in a mass ratio of 1:11 in a high-speed mixer, then melting and blending the mixture in a twin-screw extruder, extruding, water cooling, air drying, and then pelletizing the mixture, wherein the screw speed is 100 r / min and the temperature is 175°C to 190°C; second, uniformly mixing the modified polylactic acid, Chinese tallow fat, and an anti-blocking agent in a mass ratio of 100:10:0.3 using an extruder, drying the pellets obtained after extrusion and granulation at 55-60°C for 2-4 hours, and then quenching the pellets at 55°C according to a melt extrusion process. The casting sheet is formed by rapid cooling, and the temperatures of zones 1 to 5 of the melt extrusion process are respectively set to 145°C, 170-175°C, 190-195°C, 195-200°C, and 200°C, and the head temperature is 175-180°C; it is then subjected to a longitudinal stretching stage and a transverse stretching stage and then heat-set and rolled at 120-140°C. The longitudinal stretching stage: preheating section 50°C, slow drawing section 60°C, heat treatment section 50°C, stretching ratio 2.5, stretching rate 60% / s; transverse stretching stage: preheating section 65°C, slow drawing section 75°C, heat treatment section 130°C, stretching ratio 2.5, stretching rate 60-80% / s.

[0018] Products: Roll length 6000m, paper tube specification (inches) 3; no wrinkles; no uneven winding on the end surface; no pitting, fish eyes, bubbles, pin points; no impurity pollution, oil stains, different colors, frosting; no warping, axial misalignment; no chrysanthemum shape on the end surface; no wrinkles, ribs, stripes, or end surface scratches. Example 3

[0019] Yongjian Machinery SY-00 biaxially oriented film production line has 2 preheating zones, 3 stretching zones, and 1 heat treatment zone. Each zone is 2m long, the speed is 100m / min, 789 chemical tallow fat; Mailun daily chemical 6501 palm kernel oil amide DEA.

[0020] A method for producing a biaxially stretched polylactic acid film comprises the following steps: first, preparing a modified polylactic acid by mixing diacetyl epoxy soybean glyceride and polylactic acid in a mass ratio of 2:13 in a high-speed mixer, then melting and blending in a twin-screw extruder, extruding, water cooling, air drying, and then pelletizing, wherein the screw speed is 150r / min and the temperature is 190°C; second, uniformly mixing the modified polylactic acid, Chinese tallow fat, and an anti-blocking agent in a mass ratio of 100:15:0.5 using an extruder, drying the pellets obtained by extrusion granulation at 55-60°C for 2-4h, and then melting and extruding the pellets according to the melt extrusion method. The extrusion process is then quenched at 50°C to form a cast sheet. The temperatures of zones 1 to 5 in the melt extrusion process are set to 150°C, 175°C, 195°C, 200°C, and 200°C, respectively, and the head temperature is 180°C; after the longitudinal stretching stage and the transverse stretching stage, the film is heat-set and rolled at 120~140°C. The longitudinal stretching stage: preheating section 60°C, slow drawing section 65°C, heat treatment section 55°C, stretching ratio 3, stretching rate 80% / s; transverse stretching stage: preheating section 70°C, slow drawing section 80°C, heat treatment section 135°C, stretching ratio 3, stretching rate 60~80% / s.

[0021] Products: Roll length 6000m, paper tube specification (inches) 3; no wrinkles; no uneven winding on the end surface; no pitting, fish eyes, bubbles, pin points; no impurity pollution, oil stains, different colors, frosting; no warping, axial misalignment; no chrysanthemum shape on the end surface; no wrinkles, ribs, stripes, or end surface scratches.

[0022] Products: Roll length 6000m, paper tube specification (inches) 3; no wrinkles; no uneven winding on the end surface; no pitting, fish eyes, bubbles, pin points; no impurity pollution, oil stains, different colors, frosting; no warping, axial misalignment; no chrysanthemum shape on the end surface; no wrinkles, ribs, stripes, or end surface scratches.

[0023]

[0024] Note: Tensile strength and nominal tensile strain are in accordance with GB / T1040.3-2006. The sample type is type 2, a long strip of 150mm long and 151mm wide, with a distance of 100mm between fixtures and a test speed of 100mm / min. Heat shrinkage is in accordance with GB / T12027-2004. The measurement conditions are 100℃ and 10min. Haze transmittance is in accordance with GB / T2410-2008. Friction coefficient is in accordance with GB / T10006-2021. Wetting tension is in accordance with GB / T14216-2008. Heat sealing strength: The sample is tested using an A4 sampling plate, and 5 samples are taken evenly across the entire width of the film. During the test, the sample is folded in half and the two ends are aligned for heat sealing. Heat sealing temperature is 85℃, heat sealing pressure is 135kpa, and heat sealing time is 2S. The test is carried out in accordance with GB / T1040.3-2006. The sample adopts type 2, a long strip of 150mm in length and 15mm±0.1mm in width. The sample is clamped on the two clamps of the test machine with the heat-sealed part as the center line. The distance between the clamps is 100mm, and the test speed is 100mm / min. Calculation of results Take 2 strips from each sample to test its heat-sealing strength. The result is the arithmetic mean of 10 measurements, expressed in N / 15mm. The moisture permeability is tested in accordance with GB / T1037. The oxygen permeability is tested in accordance with GB / T1038.

Claims

1. A method for producing a biaxially oriented polylactic acid film, characterized in that: The method comprises using an extruder to uniformly mix modified polylactic acid, Chinese tallow fat and an anti-blocking agent in a mass ratio of 100:10-15:0.3-0.5, drying the pellets obtained by extrusion granulation at 55-60°C for 2-4 hours, forming a cast sheet according to a melt extrusion process, and then performing a longitudinal stretching stage, a transverse stretching stage, and then heat-setting and rolling at 120-140°C to obtain the cast sheet.

2. The method for producing a biaxially oriented polylactic acid film according to claim 1, characterized in that: The modified polylactic acid is prepared by mixing diacetyl epoxy soybean glyceride and polylactic acid in a mass ratio of 1-2:11-13 in a high-speed mixer, and then melt blending in a twin-screw extruder, extruding, water cooling, air drying, and then pelletizing. The screw speed is 100-150 r / min and the temperature is 175° C.-190° C.

3. The method for producing a biaxially oriented polylactic acid film according to claim 1, characterized in that: The longitudinal stretching stage includes: preheating section 50-60°C, slow stretching section 60-65°C, heat treatment section 50-55°C, stretching ratio 2.5-3, and stretching rate 60-80% / s.

4. The method for producing a biaxially oriented polylactic acid film according to claim 1, characterized in that: The transverse stretching stage includes: preheating section 65-70°C, slow stretching section 75-80°C, heat treatment section 130-135°C, stretching ratio 2.5-3, and stretching rate 60-80% / s.

5. The method for producing a biaxially oriented polylactic acid film according to claim 1, characterized in that: The temperatures of zones 1 to 5 of the melt extrusion process are respectively set to 145-150°C, 170-175°C, 190-195°C, 195-200°C, and 200°C, and the die head temperature is 175-180°C.

6. The method for producing a biaxially oriented polylactic acid film according to claim 1, characterized in that: The opening agent is palmitamide.

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