A dry composite process for easy-tear film

Abstract

The invention discloses a dry-process composite process for easy-tear films, belonging to the technical field of easy-tear film preparation. The process comprises the following steps: polyurethane glue, a curing agent and ethyl acetate are mixed in proportion to prepare an adhesive; a modified PE film is coated with the adhesive and placed in a drying oven for drying; an aluminum foil is pressed onto the side of the modified PE film coated with the adhesive; an adhesive is coated on the side of the aluminum foil facing away from the modified PE film, the film is dried in the drying oven, and a CPP film is pressed onto the film. The film is aged at 45-48°C for 36 hours to obtain the easy-tear film. The raw materials of the modified PE film include PE resin, polyimide resin and modified nano-boron nitride. The prepared easy-tear film has high peel strength and low solvent residue, meeting the use requirements of the easy-tear film. The polyimide resin is beneficial for improving the high-temperature resistance and dimensional stability of the modified PE film, thereby facilitating improved tearing performance and high-temperature cooking resistance of the easy-tear film.

Description

Technical Field

[0001] The invention belongs to the technical field of easy-tear film preparation, and particularly relates to a dry-process composite process for easy-tear films. Background Art

[0002] Easy-tear film is a packaging film that can be easily torn. After the general plastic packaging is heat-sealed at the seal, it takes a lot of force to open the packaging. The easy-tear film is tightly sealed, and the tearing edge is smooth and neat after opening, which is conducive to enhancing the consumer experience. In addition, due to its good light-shielding, moisture-proof, airtight and barrier properties, easy-tear film has been widely used in the packaging of food and medicine.

[0003] Easy-tear films are generally prepared by solvent-free lamination or dry lamination. The solvent-free lamination process is widely used in food composite packaging bags due to its lack of solvent residue, no volatile solvent emissions, low energy consumption, low cost and high safety performance during the production of food packaging bags. However, when used for lamination of substrates with high requirements for medium resistance, low-temperature or high-temperature sterilization, aluminum foil and various types of composite film substrates, the peel strength of the laminated film is not high. Food and other packaging also require high-temperature steaming and sterilization, and the composite film is prone to wrinkling. Dry lamination is a lamination process that uses adhesives to bond plastic films or other film substrates to produce composite flexible packaging materials. It can be applied to the lamination of easy-tear films containing aluminum foil materials. Solvent-containing adhesives need to be dried first during the lamination process. However, for film materials with poor high-temperature resistance such as PE, the temperature of the solvent during the drying process will cause uneven distribution of the film's mechanical properties, making the tearability of the easy-tear film worse and unable to meet the use requirements of the easy-tear film. Summary of the Invention

[0004] The object of the present invention is to provide a dry lamination process for easy-tear films to solve the problems in the background technology.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A dry lamination process for an easy-tear film comprises the following steps:

[0007] Step 1: Preparation of modified PE film:

[0008] 1) Pyromellitic acid and 3,5-diaminotrifluorotoluene are added to a flask, and then glacial acetic acid is added and refluxed at 115° C. for 24-26 hours. The temperature of the reaction system is lowered to room temperature, and the reaction product is transferred to a flask containing methanol to precipitate a solid, which is filtered and washed with methanol 3-5 times. Finally, the solid is vacuum dried at 80° C. for 20-24 hours to obtain a rigid diamine monomer.

[0009] Furthermore, the usage ratio of pyromellitic acid, 3,5-diaminotrifluorotoluene and glacial acetic acid is 25 g:36 g:600 mL.

[0010] 2) Add a rigid diamine monomer, pyromellitic acid, triphenyl phosphite, pyridine, anhydrous calcium chloride and N-methylpyrrolidone to a flask, react under nitrogen protection at 100° C. for 8-9 hours, cool the temperature of the reaction system to room temperature, transfer the reaction product to a flask containing methanol, stir and disperse, filter, wash the filter cake with methanol 3-5 times, and vacuum dry to obtain a polyimide resin.

[0011] Furthermore, the usage ratio of the rigid diamine monomer, pyromellitic acid, triphenyl phosphite, pyridine, anhydrous calcium chloride and N-methylpyrrolidone is 14 g: 6 g: 40 mL: 40 mL: 6 g: 240 mL.

[0012] 3) PE resin and polyimide resin with a number average molecular weight of 80,000 are chopped and dissolved in N,N-dimethylacetamide, and then modified nano-boron nitride is added and mixed uniformly to obtain a polymer dispersion; the polymer dispersion is filtered and a modified PE film is prepared by a casting method, which is then rolled up and set aside.

[0013] Furthermore, the usage ratio of PE resin, polyimide resin, N,N-dimethylacetamide and modified nano-boron nitride is 8g:2-3g:190g:0.05-0.1g.

[0014] Furthermore, the modified nano boron nitride is prepared by the following steps:

[0015] The silane coupling agent KH550 was added to a 95% by mass ethanol solution and hydrolyzed for 30 min, and then nano-boron nitride was added and ultrasonically dispersed for 30 min. The mixture was filtered, and the filter residue was washed with anhydrous ethanol for 2-3 times and dried at 100-110°C for 2 hours to obtain modified nano-boron nitride.

[0016] Step 2: Evenly mix the polyurethane glue, curing agent, and ethyl acetate in a ratio of 36-58 g: 7-9 g: 32-57 g to prepare an adhesive for later use.

[0017] Step 3: Use CPP film as the inner layer of the easy-tear film, aluminum foil as the middle layer of the easy-tear film, and modified PE film as the outer layer of the easy-tear film; first, coat the modified PE film with adhesive using a concave roller and place it in a drying oven to dry; then press the aluminum foil onto the adhesive-coated side of the modified PE film using a composite roller; then use a concave roller to coat the adhesive on the side of the aluminum foil away from the modified PE film; after drying in the drying oven, press the CPP film using a composite roller and age at 45-48°C for 36 hours to prepare an easy-tear film.

[0018] Beneficial effects of the present invention:

[0019] The easy-tear film produced by the dry lamination process exhibits high peel strength between the inner and outer layers and the middle layer, and low solvent residue, meeting the requirements for easy-tear film use. The outer layer of the easy-tear film is a modified PE film, in which the added modified nano-boron nitride is treated with a silane coupling agent, which facilitates uniform distribution in the polymer dispersion and improves the thermal conductivity of the modified PE film, thereby shortening the drying time of the adhesive during dry lamination and improving the production efficiency of the easy-tear film. The modified PE film is produced by a cast film method, and the added polyimide resin contains a large amount of trifluoromethyl groups, which has excellent thermal stability. The rigid amide bonds help increase the rigidity of the molecular chain, thereby improving the high-temperature resistance and dimensional stability of the modified PE film, thereby improving the tearability and high-temperature cooking resistance of the easy-tear film. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Example 1

[0022] Preparation of modified PE film, including the following steps:

[0023] Step 1: Add 25 kg of pyromellitic acid and 36 kg of 3,5-diaminotrifluorotoluene into a flask, then add 600 L of glacial acetic acid and reflux at 115 ° C for 24 hours. The temperature of the reaction system is lowered to room temperature, and the reaction product is transferred to a flask filled with methanol to precipitate the solid. Filter it, wash it with methanol three times, and finally vacuum dry it at 80 ° C for 20 hours to obtain a rigid diamine monomer.

[0024] Step 2: Add 14 kg of rigid diamine monomer, 6 kg of pyromellitic acid, 40 L of triphenyl phosphite, 40 L of pyridine, 6 kg of anhydrous calcium chloride and 240 L of N-methylpyrrolidone into a flask, react under nitrogen protection at 100 ° C for 8 hours, reduce the temperature of the reaction system to room temperature, transfer the reaction product into a flask containing methanol, stir and disperse, filter, wash the filter cake with methanol 3 times, and vacuum dry to obtain a polyimide resin.

[0025] Step 3: Add silane coupling agent KH550 to a 95% by mass ethanol solution and hydrolyze for 30 min, then add nano-boron nitride and ultrasonically disperse for 30 min, filter, wash the filter residue twice with anhydrous ethanol, and dry at 100°C for 2 h to obtain modified nano-boron nitride; 8 kg of PE resin with a number average molecular weight of 80,000 and 2 kg of polyimide resin are chopped and dissolved with 190 kg of N,N-dimethylacetamide, and then 50 g of modified nano-boron nitride is added and mixed evenly to obtain a polymer dispersion; after filtering the polymer dispersion, a modified PE film is prepared by a casting method, rolled up, and set aside.

[0026] Example 2

[0027] Preparation of modified PE film, including the following steps:

[0028] Step 1: 25 kg of pyromellitic acid and 36 kg of 3,5-diaminotrifluorotoluene were added to a flask, and then 600 L of glacial acetic acid was added and refluxed at 115 ° C for 25 hours. The temperature of the reaction system was lowered to room temperature, and the reaction product was transferred to a flask containing methanol to precipitate the solid. The solid was filtered and washed with methanol 4 times. Finally, it was vacuum dried at 80 ° C for 22 hours to obtain a rigid diamine monomer.

[0029] Step 2: Add 14 kg of rigid diamine monomer, 6 kg of pyromellitic acid, 40 L of triphenyl phosphite, 40 L of pyridine, 6 kg of anhydrous calcium chloride and 240 L of N-methylpyrrolidone to a flask, react under nitrogen protection at 100 ° C for 8.5 hours, reduce the temperature of the reaction system to room temperature, transfer the reaction product to a flask containing methanol, stir and disperse, filter, wash the filter cake with methanol 4 times, and vacuum dry to obtain a polyimide resin.

[0030] Step 3: Add silane coupling agent KH550 to a 95% by mass ethanol solution and hydrolyze it for 30 minutes, then add nano-boron nitride and ultrasonically disperse it for 30 minutes, filter, wash the filter residue twice with anhydrous ethanol, and dry it at 105°C for 2 hours to obtain modified nano-boron nitride; 8 kg of PE resin with a number average molecular weight of 80,000 and 2.5 kg of polyimide resin are chopped and dissolved with 190 kg of N,N-dimethylacetamide, and then 80 g of modified nano-boron nitride is added and mixed evenly to obtain a polymer dispersion; after filtering the polymer dispersion, a modified PE film is prepared by a casting method, rolled up, and set aside.

[0031] Example 3

[0032] Preparation of modified PE film, including the following steps:

[0033] Step 1: Add 25 kg of pyromellitic acid and 36 kg of 3,5-diaminotrifluorotoluene into a flask, then add 600 L of glacial acetic acid and reflux at 115 ° C for 26 hours. The temperature of the reaction system is lowered to room temperature, and the reaction product is transferred to a flask containing methanol to precipitate the solid. Filter it, wash it with methanol 5 times, and finally vacuum dry it at 80 ° C for 24 hours to obtain a rigid diamine monomer.

[0034] Step 2: Add 14 kg of rigid diamine monomer, 6 kg of pyromellitic acid, 40 L of triphenyl phosphite, 40 L of pyridine, 6 kg of anhydrous calcium chloride and 240 L of N-methylpyrrolidone into a flask, react under nitrogen protection at 100 ° C for 9 hours, reduce the temperature of the reaction system to room temperature, transfer the reaction product into a flask containing methanol, stir and disperse, filter, wash the filter cake with methanol 5 times, and vacuum dry to obtain a polyimide resin.

[0035] Step 3: Add silane coupling agent KH550 to a 95% by mass ethanol solution and hydrolyze for 30 min, then add nano-boron nitride and ultrasonically disperse for 30 min, filter, wash the filter residue with anhydrous ethanol three times, and dry it at 100-110°C for 2 hours to obtain modified nano-boron nitride; chop 8 kg of PE resin with a number average molecular weight of 80,000 and 3 kg of polyimide resin and dissolve them in 190 kg of N,N-dimethylacetamide, then add 100 g of modified nano-boron nitride and mix evenly to obtain a polymer dispersion; filter the polymer dispersion and prepare a modified PE film by a casting method, which is rolled up and set aside.

[0036] Example 4

[0037] The dry composite preparation of the easy-tear film includes the following steps:

[0038] Step 1: Isocyanate curing agent: 360g of polyurethane glue, 70g of isocyanate curing agent and 320g of ethyl acetate are mixed evenly according to the usage ratio to prepare an adhesive for later use.

[0039] Step 2: Using CPP film as the inner layer of the easy-tear film, aluminum foil as the middle layer of the easy-tear film, and the modified PE film prepared in Example 1 as the outer layer of the easy-tear film; setting the drying tunnel temperature of the dry laminator to 66±6°C, first, coating the modified PE film with an adhesive using a concave roller and then placing it in the drying tunnel to dry, then pressing the aluminum foil onto the adhesive-coated side of the modified PE film using a composite roller, and then using a concave roller to apply adhesive to the side of the aluminum foil away from the modified PE film. After drying in the drying tunnel, the CPP film is pressed again using a composite roller and aged at 45°C for 36 hours to obtain an easy-tear film.

[0040] The easy-tear film is cut and hot-pressed into packaging bags, and then steamed at 121°C for 40 min. The outer layer of the packaging bag does not wrinkle and the size of the packaging bag is stable.

[0041] Example 5

[0042] The dry composite preparation of the easy-tear film includes the following steps:

[0043] Step 1: Isocyanate curing agent: Evenly mix 420 g of polyurethane glue, 80 g of isocyanate curing agent and 400 g of ethyl acetate according to the usage ratio to prepare an adhesive for later use.

[0044] Step 2: Using CPP film as the inner layer of the easy-tear film, aluminum foil as the middle layer of the easy-tear film, and the modified PE film prepared in Example 2 as the outer layer of the easy-tear film; setting the drying tunnel temperature of the dry laminator to 66±6°C, first, the modified PE film is coated with an adhesive with a concave roller and then placed in the drying tunnel to dry, and then the aluminum foil is pressed onto the adhesive-coated side of the modified PE film through a composite roller, and then the adhesive is coated on the side of the aluminum foil away from the modified PE film with a concave roller. After drying in the drying tunnel, the CPP film is pressed again with a composite roller and aged at 46°C for 36 hours to obtain an easy-tear film.

[0045] The easy-tear film is cut and hot-pressed into packaging bags, and then steamed at 121°C for 40 min. The outer layer of the packaging bag does not wrinkle and the size of the packaging bag is stable.

[0046] Example 6

[0047] The dry composite preparation of the easy-tear film includes the following steps:

[0048] Step 1: Isocyanate curing agent: 580g of polyurethane glue, 90g of isocyanate curing agent and 570g of ethyl acetate are mixed evenly according to the usage ratio to prepare an adhesive for later use.

[0049] Step 2: Using CPP film as the inner layer of the easy-tear film, aluminum foil as the middle layer of the easy-tear film, and the modified PE film prepared in Example 2 as the outer layer of the easy-tear film; setting the drying tunnel temperature of the dry laminator to 66±6°C, first, the modified PE film is coated with an adhesive with a concave roller and then placed in the drying tunnel to dry, and then the aluminum foil is pressed onto the adhesive-coated side of the modified PE film through a composite roller, and then the adhesive is coated on the side of the aluminum foil away from the modified PE film with a concave roller. After drying in the drying tunnel, the CPP film is pressed again with a composite roller and aged at 48°C for 36 hours to obtain an easy-tear film.

[0050] The easy-tear film is cut and hot-pressed into packaging bags, and then steamed at 121°C for 40 min. The outer layer of the packaging bag does not wrinkle and the size of the packaging bag is stable.

[0051] Comparative Example 1: Based on Example 6, a commercially available PE film was used as the outer layer, and all other steps remained unchanged to prepare an easy-tear film. The easy-tear film was cut and hot-pressed into a packaging bag. The bag was then steamed at 121°C for 40 min. The outer layer of the bag wrinkled, and the bag shrank slightly.

[0052] Comparative Example 2: Based on Example 3, a modified PE film was prepared without adding modified nano-boron nitride, and then an easy-tear film was prepared according to the method of Example 6. The easy-tear film was cut and hot-pressed into packaging bags. After steaming at 121°C for 40 minutes, the outer layer of the packaging bag did not wrinkle and the packaging bag was dimensionally stable.

[0053] Comparative Example 3: Based on Example 3, a modified PE film was prepared without adding polyimide resin, and then an easy-tear film was prepared according to the method of Example 6. The easy-tear film was cut and hot-pressed into a packaging bag, which was then steamed at 121°C for 40 min. The outer layer of the packaging bag was wrinkled and the packaging bag was slightly shrunk.

[0054] Performance tests were conducted on Examples 4-6 and Comparative Examples 1-3. First, the linear tear properties of the easy-tear films produced in each group were tested. Twenty specimens measuring 220 mm x 40 mm were prepared for each group, labeled N1-N2. A 20 mm tear was cut in the middle of the short side of each specimen. The specimens were torn along the tear at a speed of 500 mm / min using a tear strength testing device. The distance L between the final tear position and the centerline of the tear was measured (half of the tear was measured for each specimen). A value of L ≤ 6 mm was considered acceptable, and L > 6 mm was considered unacceptable. The results are shown in Table 1.

[0055] Table 1

[0056]

[0057]

[0058] As can be seen from Table 1, the easy-tear films prepared in Examples 4 to 6 all passed the straight-line tearing test, and the pass rates of Comparative Examples 1 and 3 were below 50%.

[0059] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A dry lamination process for an easy-tear film, characterized in that: The steps include: Step 1: Mix polyurethane glue, curing agent and ethyl acetate in a ratio of 36-58g: 7-9g: 32-57g to prepare an adhesive for later use; Step 2: After coating the modified PE film with adhesive, place it in a drying oven to dry, and then press aluminum foil onto the adhesive-coated side of the modified PE film; apply adhesive to the side of the aluminum foil away from the modified PE film, dry it in a drying oven, and then press CPP film onto it. After aging at 45-48°C for 36 hours, an easy-to-tear film is obtained. The raw materials of the modified PE film include PE resin, polyimide resin and modified nano-boron nitride; the polyimide resin is prepared by the following steps: Add rigid diamine monomer, pyromellitic acid, triphenyl phosphite, pyridine, anhydrous calcium chloride and N-methylpyrrolidone into a flask, react at 100°C under nitrogen protection for 8-9 hours, cool, and disperse the reaction product with methanol, filter, wash and dry to obtain a polyimide resin; The rigid diamine monomer is prepared by the following steps: Pyromellitic acid and 3,5-diaminobenzotrifluoride are added to a flask, followed by glacial acetic acid, which is refluxed at 115°C for 24-26 hours. The temperature is then lowered, and the reaction product is transferred to a flask containing methanol to precipitate a solid, which is then filtered, washed, and vacuum-dried at 80°C for 20-24 hours to obtain a rigid diamine monomer. The modified nano boron nitride is prepared by the following steps: The silane coupling agent KH550 was added to a 95% by mass ethanol solution and hydrolyzed for 30 minutes. Then, nano-boron nitride was added and ultrasonically dispersed for 30 minutes. The mixture was filtered, and the filter residue was washed with anhydrous ethanol for 2-3 times and dried at 100-110°C for 2 hours to obtain modified nano-boron nitride.

2. The dry lamination process for an easy-tear film according to claim 1, characterized in that: The usage ratio of the rigid diamine monomer, pyromellitic acid, triphenyl phosphite, pyridine, anhydrous calcium chloride and N-methylpyrrolidone is 14 g: 6 g: 40 mL: 40 mL: 6 g: 240 mL.

3. The dry lamination process for an easy-tear film according to claim 1, characterized in that: The usage ratio of the pyromellitic acid, 3,5-diaminotrifluorotoluene and glacial acetic acid is 25 g:36 g:600 mL.

4. The dry lamination process for an easy-tear film according to claim 1, characterized in that: The modified PE film is prepared by the following steps: PE resin and polyimide resin are chopped and dissolved with N,N-dimethylacetamide, and then modified nano-boron nitride is added and mixed evenly to obtain a polymer dispersion; the polymer dispersion is filtered and then a modified PE film is prepared by a casting method.

5. The dry lamination process for an easy-tear film according to claim 4, characterized in that: The usage ratio of the PE resin, the polyimide resin, the N,N-dimethylacetamide and the modified nano-boron nitride is 8g: 2-3g: 190g: 0.05-0.1g.

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