Production method of BOPP (biaxially-oriented polypropylene) pre-coating film without primer

Abstract

The invention discloses a production method of a primer-free BOPP (biaxially-oriented polypropylene) precoating film, the BOPP precoating film comprises a base layer, a functional layer and a hot melt adhesive layer which are sequentially arranged from bottom to top, the base layer is made of homo-polypropylene, the functional layer is made of MLLDPE (metallocene linear low density polyethylene), and the hot melt adhesive layer is made of EVA (ethylene-vinyl acetate) hot melt adhesive. The MLLDPE and the EVA have good compatibility, and after the MLLDPE and the PP material are co-extruded and stretched to form a film, the film forming property is good, and the film thickness uniformity is good.

Description

Technical Field

[0001] The invention relates to the technical field of BOPP films, in particular to a method for producing a primer-free BOPP pre-coating film. Background Art

[0002] Pre-coated film is a flexible packaging material used for printed products. It is first coated on the film by the pre-coated film processing factory according to the specifications and format, and then rewound for the user to choose, and then laminated with the printed matter. Pre-coated film is usually composed of a base layer, a primer layer and a hot melt adhesive layer, but the primer coating requires a corona pre-treatment device, an ozone exhaust device, a coating drying device, etc. The equipment investment cost is high, the floor space is large, the production speed is greatly affected by the drying speed of the primer, and the production efficiency is low. Summary of the invention

[0003] In view of the above-mentioned defects of the prior art, an object of the present invention is to provide a method for producing a primer-free BOPP pre-coating film.

[0004] To solve the above problems, the technical solution of the present invention is: a method for producing a primer-free BOPP pre-coating film, wherein the BOPP pre-coating film comprises a base layer, a functional layer and a hot melt adhesive layer arranged in sequence from bottom to top, wherein the base layer is homopolymer polypropylene, the functional layer is MLLDPE, and the hot melt adhesive layer is EVA hot melt adhesive; The production method comprises the following steps: (1) The base layer and the functional layer raw materials are fed into respective extruders for mixing and plasticizing, and the molten melts are fed into the die heads respectively. After the melts are merged in the die heads, they pass through the flat die head opening to form a molten sheet. The sheet is then attached to a chilled roller by an air knife to form an unshaped sheet. The sheet is then shaped into a cast sheet after being cooled in a water bath. The cast sheet is then passed through a longitudinal stretching machine and a transverse stretching machine to form a film. (2) Compounding a layer of hot melt adhesive on the surface of the functional layer, and then cooling and shaping to obtain a primer-free BOPP pre-coated film; (3) Testing the film bonding strength, including: (31) The primer-free BOPP pre-coated film is laminated with a paper printed product to prepare a composite sample; (32) Cut the composite sample into 10 strips with a length of 200 mm and a width of 15 mm; (33) Pre-peel off the film and paper print by 50 mm along the length direction of each sample; (34) All the splines are placed on an automatic conveying device, which includes a lifting platform, a placing rack and a pushing mechanism. The placing rack includes a plurality of partitions distributed up and down, and a spline is placed on each partition. After the pushing mechanism pushes a spline forward onto the tensile tester, the lifting platform drives the placing rack to rise by the distance of a partition. (35) The tensile tester is equipped with a manipulator, which transfers the specimen to the fixture and fixes it. The test speed of the tensile tester is 300 mm / min. (36) The maximum load when each film strip is completely peeled off from the paper print is the bonding strength, and the test results are taken as the arithmetic mean.

[0005] Furthermore, the automatic conveying device also includes a frame, a bracket is fixed on the top of the frame, and the pushing mechanism includes a pushing cylinder fixed on the top of the bracket and a pushing plate fixed on the end of the piston rod at the front end of the pushing cylinder, and the pushing plate is located behind the partition.

[0006] Furthermore, a lifting drive device is installed in the frame, and a lifting platform is connected to the upper end of the lifting drive device. The placement frame is placed on the top of the lifting platform. The partition is provided with a groove for placing the spline, and the front and rear ends of the groove are open.

[0007] The beneficial effects of the present invention are: MLLDPE has good compatibility with EVA, and after being co-extruded and stretched with PP material to form a film, the film-forming property is good and the film thickness uniformity is good; the primer-free BOPP pre-coated film needs to be tested for bonding strength, and the automatic conveying device can convey the specimens one by one, without the need for manual conveying of the specimens one by one, which can save test time and improve test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic structural diagram of the primer-free BOPP pre-coating film of the present invention; Figure 2 It is a schematic structural diagram of the conveying device of the present invention.

[0009] As shown in the figure: 100 - base layer, 200 - functional layer, 300 - hot melt adhesive layer, 1 - lifting platform, 2 - placement rack, 21 - partition, 3 - frame, 4 - bracket, 5 - push cylinder, 6 - push plate, 7 - lifting drive device. Implementation

[0010] In order to more intuitively and completely understand the technical solution of the present invention, a non-limiting feature description is now provided in conjunction with the accompanying drawings of the present invention as follows: like Figure 1 , Figure 2As shown, the production method of the primer-free BOPP pre-coating film, the BOPP pre-coating film comprises a base layer 100, a functional layer 200 and a hot melt adhesive layer 300 arranged in sequence from bottom to top, the base layer 100 is homopolymer polypropylene, the functional layer 200 is MLLDPE, and the hot melt adhesive layer 300 is EVA hot melt adhesive; The production method comprises the following steps: (1) The raw materials of the base layer 100 and the functional layer 200 are fed into respective extruders for mixing and plasticizing, and the molten melts are fed into the die heads respectively. After the melts are merged in the die heads, they pass through the flat die head opening to form molten sheets. Then, an air knife is used to attach the sheets to a chilled roller to quench them to form unshaped sheets. After cooling in a water bath, the sheets are shaped to form cast sheets. The cast sheets are then passed through a longitudinal stretching machine and a transverse stretching machine to draw the sheets into thin films. (2) Compounding a hot melt adhesive layer 300 on the surface of the functional layer 200, and then cooling and shaping to obtain a primer-free BOPP pre-coated film; (3) Testing the film bonding strength, including: (31) The primer-free BOPP pre-coated film is laminated with a paper printed product to prepare a composite sample; (32) Cut the composite sample into 10 strips with a length of 200 mm and a width of 15 mm; (33) Pre-peel off the film and paper print by 50 mm along the length direction of each sample; (34) All the splines are placed on an automatic conveying device, which includes a lifting platform 1, a placement rack 2 and a pushing mechanism. The placement rack 2 includes a plurality of partitions 21 distributed up and down, and a spline is placed on each partition 21. After the pushing mechanism pushes a spline forward onto the tensile tester, the lifting platform 1 drives the placement rack 2 to rise by the distance of a partition 21; (35) The tensile tester is equipped with a manipulator, which transfers the specimen to the fixture and fixes it. The test speed of the tensile tester is 300 mm / min. (36) The maximum load when each film strip is completely peeled off from the paper print is the bonding strength, and the test results are taken as the arithmetic mean.

[0011] like Figure 2As shown, the automatic conveying device also includes a frame 3, a bracket 4 is fixed on the top of the frame 3, and the pushing mechanism includes a pushing cylinder 5 fixed on the top of the bracket 4 and a pushing plate 6 fixed on the end of the piston rod at the front end of the pushing cylinder 5, and the pushing plate 6 is located behind the partition 21. A lifting drive device 7 is installed in the frame 3, and a lifting platform 1 is connected to the upper end of the lifting drive device 7. The placement frame 2 is placed on the top of the lifting platform 1. The partition 21 has a groove for placing the spline, and the front and rear ends of the groove are open. When the pushing cylinder 5 is working, it can control the pushing plate 6 to move forward, and the pushing plate 6 moves into the partition 21 and pushes the spline in the partition 21 forward.

[0012] MLLDPE has good compatibility with EVA, and after co-extrusion and stretching with PP material, it has good film-forming properties and good uniformity of film thickness; primer-free BOPP pre-coated film needs to be tested for bonding strength. The automatic conveying device can convey the specimens one by one, without the need for manual conveying of the specimens one by one, which can save test time and improve test efficiency.

Claims

1. A method for producing a primer-free BOPP pre-coating film, wherein the BOPP pre-coating film comprises a base layer, a functional layer and a hot melt adhesive layer arranged in sequence from bottom to top, and is characterized in that: The base layer is homopolymer polypropylene, the functional layer is MLLDPE, and the hot melt adhesive layer is EVA hot melt adhesive; The production method comprises the following steps: (1) The base layer and the functional layer raw materials are fed into respective extruders for mixing and plasticizing, and the molten melts are fed into the die heads respectively. After the melts are merged in the die heads, they pass through the flat die head opening to form a molten sheet. The sheet is then attached to a chilled roller by an air knife to form an unshaped sheet. The sheet is then shaped into a cast sheet after being cooled in a water bath. The cast sheet is then passed through a longitudinal stretching machine and a transverse stretching machine to form a film. (2) Compounding a layer of hot melt adhesive on the surface of the functional layer, and then cooling and shaping to obtain a primer-free BOPP pre-coated film; (3) Testing the film bonding strength, including: (31) The primer-free BOPP pre-coated film is laminated with a paper printed product to prepare a composite sample; (32) Cut the composite sample into 10 strips with a length of 200 mm and a width of 15 mm; (33) Pre-peel off the film and paper print by 50 mm along the length direction of each sample; (34) All the splines are placed on an automatic conveying device, which includes a lifting platform, a placing rack and a pushing mechanism. The placing rack includes a plurality of partitions distributed up and down, and a spline is placed on each partition. After the pushing mechanism pushes a spline forward onto the tensile tester, the lifting platform drives the placing rack to rise by the distance of a partition. (35) The tensile tester is equipped with a manipulator, which transfers the specimen to the fixture and fixes it. The test speed of the tensile tester is 300 mm / min. (36) The maximum load when each film strip is completely peeled off from the paper print is the bonding strength, and the test results are taken as the arithmetic mean.

2. The method for producing a primer-free BOPP pre-coating film according to claim 1, characterized in that: The automatic conveying device also includes a frame, a bracket is fixed on the top of the frame, and the pushing mechanism includes a pushing cylinder fixed on the top of the bracket and a pushing plate fixed on the end of the piston rod at the front end of the pushing cylinder, and the pushing plate is located behind the partition.

3. The method for producing a primer-free BOPP pre-coating film according to claim 2, characterized in that: A lifting drive device is installed in the frame, and a lifting platform is connected to the upper end of the lifting drive device. The placement frame is placed on the top of the lifting platform. The partition is provided with a groove for placing the spline, and the front and rear ends of the groove are both open.

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