High-temperature-resistant and high-barrier BOPA matt film and preparation method thereof

Abstract

The invention relates to the technical field of nylon packaging films, in particular to a high-temperature-resistant and high-barrier BOPA matt film and a preparation method thereof. The film comprises a BOPA film layer and a coating layer, the coating layer is formed by coating the surface of the BOPA film layer with an aqueous mixed solution, a corona surface is arranged on the BOPA film layer, and the coating layer is connected with the corona surface; the water-based mixed liquid is prepared from a water-based matte polyurethane dispersion liquid, a water-based acrylic emulsion, a cross-linking agent and water according to the mass ratio of (75 to 85) to (25 to 30) to (1.0 to 1.5) to (75 to 100). The film has the advantages of high light transmittance, high haze, low glossiness and good extinction effect, has very good effects in the aspects of scratch resistance, water boiling resistance, steaming and boiling resistance and oxygen passing prevention, can prolong the shelf life of packaged contents, and has very good application prospects in high-grade product packages such as food packages, high-grade gift boxes, daily necessities, cosmetics and medicine packages and the like. Wide application prospects are realized.

Description

Technical Field

[0001] The invention relates to the technical field of nylon packaging films, and in particular to a high-temperature-resistant and high-barrier BOPA matte film and a preparation method thereof. Background Art

[0002] BOPA film is the third largest packaging material after BOPP and BOPET films. It is increasingly used in food packaging. Most of the packaging materials are transparent BOPA film. However, with the improvement of living standards, people are not limited to the singleness of transparent packaging, but pursue visual diversity. Matt film can make the printing color realistic, the appearance is quiet and elegant, and the hand feel is comfortable. It is becoming more and more popular. Due to people's pursuit of the color, fragrance and taste of food, barrier packaging is also receiving more and more attention. It can not only preserve the fragrance, but also prevent oxygen from entering, avoid the deterioration of the contents, and thus extend the shelf life.

[0003] The current BOPA matte film on the market is obtained by three-layer co-extrusion through masterbatch modification. For example, the patent document "Scratch-resistant and high-temperature resistant matte BOPA pre-coated film and its preparation method" with publication number CN111909413A is a BOPA matte film composed of a surface layer, a core layer and a matte layer. The BOPA matte film is obtained by adding 98.5~100% (wt) of matte material and 0~1.5% (wt) of lubricant to the matte layer, and then co-extruding and biaxially stretching the three-layer BOPA matte film. Although the gloss (matte surface) of the BOPA matte film obtained by this method is less than 10%, the haze can only reach about 52%, and there is still a problem that the matte material is not conducive to dispersion, and the matte film does not have high barrier properties. Summary of the invention

[0004] In order to solve the problems mentioned in the above background technology that the existing BOPA matte film has low haze, the matte material is not conducive to dispersion and does not have high barrier performance, the present invention provides a high temperature resistant and high barrier BOPA matte film, comprising a BOPA film layer and a coating layer, wherein the coating layer is formed by coating an aqueous mixed liquid on the surface of the BOPA film layer, and a corona surface is provided on the BOPA film layer, and the coating layer is connected to the corona surface; The aqueous mixed liquid is composed of an aqueous matte polyurethane dispersion, an aqueous acrylic emulsion, a crosslinking agent and water in a mass ratio of 75-85:25-30:1.0-1.5:75-100; The water-based matte polyurethane dispersion is prepared from polyether polyol, polyester polyol and isocyanate; the water-based acrylic emulsion is prepared by polymerization of methyl methacrylate, styrene, itaconic acid and n-butyl acrylate.

[0005] On the basis of the above scheme, further, the preparation method of the aqueous matte polyurethane dispersion is: In a reactor, add polyether polyol, polyester polyol and isocyanate, react at 80℃~85℃, then add hydrophilic chain extender DMBA and castor oil, stir evenly, add 1.4-butanediol chain extender, continue stirring, add acetone to dilute, react at constant temperature, stop the reaction when the NCO content is 3.15~3.25, obtain prepolymer, cool to 20℃~30℃, add neutralizer TEA and stir to disperse, then deionize water again, stir to emulsify, finally remove acetone at 45~55℃ and vacuum (absolute pressure) of 0.02~0.1MPa to obtain water-based matte polyurethane dispersion; Wherein, the mass ratio of the polyether polyol: polyester polyol: isocyanate: hydrophilic chain extender DMBA: castor oil: 1.4-butanediol chain extender: neutralizer TEA is 27.0~32.0: 27.0~32.0: 23.5~25.5: 2.65~2.75: 1.60~1.70: 2.30~2.40: 1.05~1.15.

[0006] Preferably, the mass ratio of the polyether polyol: polyester polyol: isocyanate: hydrophilic chain extender DMBA: castor oil: 1.4-butanediol chain extender: neutralizer TEA is 30.0: 30.0: 25.2: 2.7: 1.65: 2.35: 1.10.

[0007] On the basis of the above scheme, further, the polyether polyol includes one or more of polyoxyethylene ether monool, polyoxypropylene diol, polyoxypropylene triol, polytetramethylene furan diol, and polyoxyethylene ether diol; the polyester polyol includes one or more of polyphthalic acid-1,6-hexanediol polyester diol, polyphthalic acid neopentyl glycol polyester diol, and polyphthalic acid neopentyl glycol hexanediol polyester diol; the isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, or dicyclohexylmethane diisocyanate.

[0008] On the basis of the above scheme, further, the preparation method of the aqueous acrylic emulsion is as follows: Methyl methacrylate, styrene, n-butyl acrylate and itaconic acid, part of OP-10, part of sodium dodecyl sulfate and part of water are added to a pre-emulsification kettle, emulsified for 30-40 minutes to obtain a non-stratified emulsion; then the remaining water and the remaining OP-10 are added to the polymerization kettle, the temperature is raised to 78-80°C, ammonium persulfate initiator is added to react for 20-30 minutes, and the initiator is controlled to drip within 3-4 hours; then the polymerization kettle is heated to 85-90°C, the temperature is kept for reaction for 1-2 hours, then the temperature is lowered to 45-50°C, a pH adjuster is added to adjust the pH value of the reaction system to 6-7, and a water-based acrylic emulsion is obtained.

[0009] On the basis of the above scheme, further, the mass ratio of methyl methacrylate: styrene: n-butyl acrylate: itaconic acid: OP-10: sodium dodecyl sulfate: ammonium persulfate initiator: water is 5.95~6.05: 0.95~1.05: 17.5~18.5: 20.7~21.2: 0.90~0.95: 0.45~0.47: 0.319~0.324: 115~125.

[0010] Preferably, the mass ratio of methyl methacrylate: styrene: n-butyl acrylate: itaconic acid: OP-10: sodium dodecyl sulfate: ammonium persulfate initiator: water is 6.0: 1.0: 18.0: 21.0: 0.92: 0.46: 0.322: 120.

[0011] On the basis of the above scheme, further, the cross-linking agent is one of a hexamethylmelamine type cross-linking agent or a trimethylolmelamine type cross-linking agent.

[0012] On the basis of the above scheme, further, the BOPA film layer is made of polyamide resin through three-layer co-extrusion, transverse and longitudinal stretching and shaping, and then corona treatment on the surface; the polyamide resin is one or more of nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 612, nylon 610, nylon 12, nylon 1212 or poly-m-xylene hexamide.

[0013] On the basis of the above solution, further, flaky magnesium oxide powder is added to the corona surface, and the added amount is 0.05% to 0.1% of the mass of the polyamide resin.

[0014] The purpose of adopting the above technical scheme is that the oxide film is flaky, has a large aspect ratio, can be evenly spread on the surface of the film, and is staggered and superimposed layer by layer. When oxygen passes through, it needs to pass through a curved path instead of directly passing through, making it difficult for oxygen to pass through the film, thereby giving the film excellent barrier properties; in addition, after the flaky magnesium oxide is boiled at high temperature, the aqueous mixture will undergo a cross-linking reaction with the magnesium oxide, which not only improves the adhesion of the coating to the film, but also forms an interpenetrating network structure after cross-linking, making it even more difficult for oxygen to pass through, thereby improving the oxygen barrier properties.

[0015] Preferably, the flaky magnesium oxide powder has a lateral dimension of 300-400 nm and a thickness of 30-40 nm.

[0016] The above technical solution is used to limit the size range of the flaky magnesium oxide powder, in order to avoid the size being too large, which affects the dispersibility of the flaky magnesium oxide powder; if the size is too small, the oxygen barrier performance is easily reduced.

[0017] On the basis of the above solution, further, the thickness of the coating layer is 1.0-1.5 μm, and the thickness of the BOPA film layer is 15-25 μm.

[0018] The present invention also provides a method for preparing the high temperature resistant and high barrier BOPA matte film as described above, comprising the following steps: Step a, weighing a water-based matte polyurethane dispersion and a water-based acrylic emulsion in proportion, adding water, stirring evenly, and finally adding a cross-linking agent, continuing to stir, and then standing to obtain an aqueous mixed solution; Step b, after the polyamide resin is subjected to three-layer co-extrusion and then stretched horizontally and longitudinally to be shaped, a corona treatment is performed on the surface thereof so that the corona value of the surface is ≥52dyn / cm, thereby obtaining a BOPA film; Step c, coating the corona surface of the BOPA film obtained in step b through an anilox roller with the aqueous mixture obtained in step a at a speed of 180-220 m / min, and drying at 110-120° C. to form a coating; Step d: After drying, the film is placed in a constant temperature chamber at 45-50° C. for aging for 72-96 hours to obtain a high temperature resistant and high barrier BOPA matte film.

[0019] Compared with the prior art, the high temperature resistant and high barrier BOPA matte film and the preparation method thereof provided by the present invention have the following advantages: 1. Through a specific coating layer formula and a specific ratio, the coating layer is firmly combined with the BOPA film. The obtained BOPA matte film has excellent matte performance, and shows good performance in scratch resistance and temperature resistance. At the same time, the film has excellent barrier properties, and the barrier properties are even better after high-temperature cooking; 2. The aqueous acrylic emulsion used in the coating liquid of the present invention has excellent high transparency, low gloss, water resistance and high temperature resistance, and has good adhesion to the film. It is mixed with the aqueous matte polyurethane dispersion in proportion to achieve complementary advantages and disadvantages, improve the adhesion of the aqueous matte polyurethane dispersion to the film, and the obtained aqueous mixed liquid has excellent high temperature resistance, excellent extinction performance, etc.; 3. The coating slurry of the present invention uses a water-based matte polyurethane dispersion without external fillers, micro wax powder, inorganic silica, etc.; the polyester polyol used is formed by esterification reaction, contains more ester bonds in the molecule, the molecular chain is relatively tight, and the intermolecular force is also strong; the polyether polyol used is formed by acetal reaction, contains more epoxy groups, hydroxyl groups and other functional groups in the molecule, and the molecular chains are relatively loose. The coating liquid of the present invention utilizes the difference in molecular structure of polyester polyol and polyether polyol. After mixed polymerization, the compatibility is poor, which is neither completely compatible nor completely incompatible, so that the final product has good matting performance; 4. The coating layer obtained under specific proportion conditions of the present invention has a higher crosslinking density after drying due to the addition of a crosslinking agent, so that the coating does not stick again and can maintain good flexibility; in addition, the present invention also controls the amount of crosslinking agent added to avoid excessive reaction of the crosslinking agent with the water-based polyurethane, which makes the coating excessively crosslinked and becomes too hard, which not only easily causes the film to be torn during transverse stretching, but also causes low printing fastness and composite peeling strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a schematic diagram of the layer structure of the high temperature resistant and high barrier BOPA matte film of Example 1 provided by the present invention.

[0022] Reference numerals: DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0025] The present invention provides an example of a method for preparing an aqueous matte polyurethane dispersion and an aqueous acrylic emulsion. The aqueous matte polyurethane dispersion and the aqueous acrylic emulsion in the following embodiments and comparative examples are all prepared by this method.

[0026] The preparation method of the aqueous matte polyurethane dispersion is as follows: In the reactor, add polytetrahydrofuran diol, poly(neopentyl phthalate) polyester diol and toluene diisocyanate, gradually heat to 80°C, keep at 80°C~85°C for 3h, then add hydrophilic chain extender DMBA and castor oil under stirring, and stir at 80°C for 2h, then add 1.4-butanediol chain extender, continue stirring at 85°C for 2h, add acetone to dilute, and test the NCO content after constant temperature reaction for 4h. When the NCO content is 3.20, stop the reaction to obtain the prepolymer, cool to 25°C, add neutralizer TEA and stir to disperse, then deionize water again, stir to emulsify, and finally remove acetone at 45~55°C and vacuum (absolute pressure) of 0.02~0.1MPa to obtain a water-based matte polyurethane dispersion; The mass ratio of polytetrahydrofuran diol: poly(neopentyl phthalate) polyester diol: toluene diisocyanate: hydrophilic chain extender DMBA: castor oil: 1.4-butanediol: neutralizer TEA is 30.0:30.0:25.2:2.7:1.65:2.35:1.10.

[0027] The preparation method of the aqueous acrylic emulsion is as follows: The raw materials including methyl methacrylate, styrene, n-butyl acrylate and itaconic acid, half of OP-10, two-thirds of sodium dodecyl sulfate and two-thirds of water are added to a pre-emulsification kettle, and emulsified for 30-40 minutes to obtain an emulsion without stratification; then the remaining water and the remaining OP-10 are added to the polymerization kettle, the temperature is raised to 78-80°C, and ammonium persulfate initiator is added to react for 20-30 minutes, and the initiator is controlled to drip within 3-4 hours; then the polymerization kettle is heated to 85-90°C and kept warm for reaction for 1-2 hours, and the temperature is lowered to 45-50°C, and a pH adjuster is added to adjust the pH value of the reaction system to between 6 and 7, so as to obtain a water-based acrylic emulsion.

[0028] Wherein, the mass ratio of methyl methacrylate: styrene: n-butyl acrylate: itaconic acid: OP-10: sodium dodecyl sulfate: ammonium persulfate initiator: water is 6.0: 1.0: 18.0: 21.0: 0.92: 0.46: 0.322: 120.

[0029] In order to fully illustrate the beneficial effects of the present invention, the present invention provides the following embodiments and comparative examples: Example 1 The polyamide resin is subjected to three-layer co-extrusion by casting, and then stretched horizontally and vertically to be shaped, and then corona treatment is performed on the surface of the polyamide resin to make the corona value of the surface ≥52dyn / cm, so as to obtain a BOPA film with a corona surface; the corona surface layer is added with flaky magnesium oxide powder; the flaky magnesium oxide powder has a lateral size of 300nm and a thickness of 40nm, wherein the polyamide resin used is nylon 6; Then, the film was quickly passed through an anilox roller dipped with an aqueous mixed solution consisting of an aqueous matte polyurethane dispersion, an aqueous acrylic emulsion, a crosslinking agent and water in a mass ratio of 75:25:1.0:75 on an offline coating machine for lamination and gluing at a speed of 200 m / min; then, the film was dried in an oven at 110° C. to form a coating, and after drying, the film was placed in a constant temperature chamber at 50° C. for aging for 72 hours, and after aging, a high-temperature resistant and high-barrier BOPA matte film was obtained, wherein the coating layer 20 had a thickness of 1 μm, and the BOPA film layer 10 had a thickness of 15 μm; The coating layer is connected to the corona surface; the amount of flaky magnesium oxide powder added to the corona surface layer is 0.05% of the mass of the polyamide resin; The crosslinking agent is one of a hexamethylmelamine type crosslinking agent and a trimethylolmelamine type crosslinking agent.

[0030] Example 2 The difference between Example 2 and Example 1 is that the aqueous mixed liquid is composed of an aqueous matte polyurethane dispersion, an aqueous acrylic emulsion, a cross-linking agent and water in a mass ratio of 85:30:1.5:100; the amount of flaky magnesium oxide powder added to the corona surface layer is 0.10% of the mass of the polyamide resin; and the remaining components and operating steps are the same as those in Example 1.

[0031] Example 3 The difference between Example 3 and Example 1 is that the lateral size of the flaky magnesium oxide powder is 400 nm and the thickness is 30 nm; the amount of flaky magnesium oxide powder added to the corona surface layer is 0.10% of the mass of the polyamide resin; and the remaining components and operating steps are the same as those in Example 1.

[0032] Example 4 The difference between Example 4 and Example 1 is that the added amount of flaky magnesium oxide powder in the corona surface layer is 0.10% of the mass of the polyamide resin, and the other components and operating steps are the same as those in Example 1.

[0033] Example 5 The difference between Example 5 and Example 1 is that the aqueous mixed liquid is composed of an aqueous matte polyurethane dispersion, an aqueous acrylic emulsion, a cross-linking agent and water in a mass ratio of 80:28:1.25:85; the amount of flaky magnesium oxide powder added to the corona surface layer is 0.10% of the mass of the polyamide resin; and the remaining components and operating steps are the same as those in Example 1.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that no coating layer is prepared and no flaky magnesium oxide powder is added to the corona surface. The preparation method of this comparative example comprises the following steps: After the nylon 6 resin is cast through three-layer co-extrusion and then stretched in the transverse and longitudinal directions to be shaped, the surface of the obtained BOPA film is corona treated to make the surface corona value ≥52dyn / cm, thereby obtaining a BOPA film with a corona surface and a thickness of 15μm.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that no coating layer is prepared. The preparation method of this comparative example comprises the following steps: After nylon 6 resin is subjected to three-layer co-extrusion by casting and then stretched in the transverse and longitudinal directions for finalizing, the surface of the obtained BOPA film is subjected to corona treatment so that the corona value of the surface is ≥52dyn / cm, thereby obtaining a BOPA film containing a corona surface with a thickness of 15μm; flaky magnesium oxide powder is added to the corona surface layer; the flaky magnesium oxide powder has a transverse size of 300nm and a thickness of 40nm.

[0036] Comparative Example 3 The difference between this comparative example and Example 1 is that the aqueous mixed liquid in the coating does not contain aqueous acrylic emulsion.

[0037] The aqueous mixed liquid is composed of an aqueous matte polyurethane dispersion, a crosslinking agent and water in a mass ratio of 75:1.0:75, and the remaining components and operating steps are the same as those in Example 1.

[0038] Comparative Example 4 The difference between this comparative example and Example 1 is that the aqueous mixed liquid in the coating does not contain an aqueous matte polyurethane dispersion.

[0039] The aqueous mixed liquid is composed of aqueous acrylic emulsion, crosslinking agent and water in a mass ratio of 25:1.0:75, and the remaining components and operating steps are the same as those in Example 1.

[0040] Comparative Example 5 The difference between this comparative example and Example 1 is that the amount of the aqueous matte polyurethane dispersion added to the coating is relatively large.

[0041] The aqueous mixed liquid is composed of aqueous matte polyurethane dispersion, aqueous acrylic emulsion, crosslinking agent and water in a mass ratio of 100:25:1.0:75, and the remaining components and operating steps are the same as those in Example 1.

[0042] Comparative Example 6 The difference between this comparative example and Example 1 is that the amount of water-based acrylic emulsion added to the coating is relatively large.

[0043] The aqueous mixed liquid is composed of an aqueous matte polyurethane dispersion, an aqueous acrylic emulsion, a crosslinking agent and water in a mass ratio of 75:45:1.0:75, and the remaining components and operating steps are the same as those in Example 1.

[0044] Comparative Example 7 The difference between this comparative example and Example 1 is that the amount of flaky magnesium oxide powder added in the coating is relatively large, the amount of magnesium oxide added in the corona surface layer is 0.50% of the mass of the polyamide resin, and the other components and operating steps are the same as those in Example 1.

[0045] Performance Test: 1. Transmittance and haze test Tested according to GB 2410-1980 Test method for light transmittance and haze of transparent plastics.

[0046] 2. Glossiness test The test is carried out according to "GB / T 8807-1988 Test method for mirror gloss of plastics".

[0047] 3. Scratch and abrasion resistance test Fasten the cut samples with clamps, making the test surface (coating surface) horizontal. The sample surface must be flat, free of bubbles and impurities, etc. Set up the friction tester LT803 (Dongguan Longtian Instrument Equipment Co., Ltd.), set the speed range to 30 times / min, and the stroke range to 0-50mm. Adjust the weight and material position to the appropriate position, the weight is 500g, set the number of friction times to 2000 times, adjust the speed to 20 times / min, press the switch to start the test, and after the test, observe the wear of the coating surface. Scratches are indicated by "×", and no changes in appearance are indicated by "O".

[0048] 4. Evaluation of water boiling resistance and steaming resistance The BOPA matte film pre-coated above was composited with the PE film by boiling the composite glue with two-component polyurethane water, and the composite glue amount was 2.0g / m 2 , and then aged in an oven at 45°C for 48 hours to obtain a BOPA / PE composite film, in which the coating layer is laminated on the outside as the outer surface. After bag making, a 100°C, 30-min boiling test is performed to observe whether the coating layer is delaminated or detached. If so, it is indicated by "×", and if the appearance is intact and unchanged, it is indicated by "O".

[0049] The BOPA matte film and CPP film prepared above were compounded by using two-component polyurethane steam-cooking composite glue, with the composite glue amount being 3.0g / m2, and then aged in a 45°C oven for 72h to obtain a BOPA / CPP composite film, in which the coating layer was compounded on the outside as the outer surface. After bag making, a 125°C, 40min cooking test was performed to observe whether the coating layer was delaminated or detached, and if so, it was indicated by "×", and if the appearance was intact and unchanged, it was indicated by "O".

[0050] 5. Oxygen Transmission Rate Test The test was conducted according to ASTM F1927-2007 Test Method for Oxygen Transmission Rate, Permeability and Penetration Through Barrier Materials at Controlled Relative Humidity Using an Electricity Detector; the oxygen transmission rate was tested before and after steaming (125℃ steaming for 40min) at 23℃50%RH.

[0051] Test Results The pre-coated films prepared in the examples and comparative examples were subjected to the above-mentioned performance tests one to five, and the results are shown in the following table: Table 1 Performance test table of embodiments and comparative examples

[0052] It can be seen from the above data that, compared with Comparative Examples 1 to 7, Examples 1 to 5 have higher light transmittance, higher haze and lower gloss, better matting effect, and better scratch resistance, water resistance and boiling resistance. At the same time, compared with the comparative example, the oxygen permeability is reduced, especially the oxygen permeability after boiling is significantly reduced, indicating that the barrier properties of Examples 1 to 5 are more excellent.

[0053] Comparative Example 1 is a pure BOPA film, which has high transparency and high light transmittance, and has no matting effect. In Comparative Example 2, flake magnesium oxide is added to the corona surface of the BOPA film, which can reduce the oxygen permeability to a certain extent, but still has no matting effect. Comparative Example 3 uses a water-based matte polyurethane dispersion alone, which performs generally in matting, and its coating itself is relatively soft, and does not meet the requirements in terms of scratch resistance and temperature resistance. Comparative Example 4 uses a water-based acrylic emulsion alone, which not only does not have matting, but also has poor scratch resistance and temperature resistance, and the oxygen permeability does not decrease significantly after cooking. Although Comparative Example 5 uses a water-based matte polyurethane dispersion, it has a good performance in terms of matting. Ester dispersion and water-based acrylic emulsion, but due to the low content of water-based acrylic emulsion, the matting effect of the pre-coated film is average, and the coating resin is soft, and the scratch resistance and high temperature resistance do not meet the requirements, and the adhesion is not good, so the oxygen permeability does not change after cooking due to the shedding of the coating; although comparative example 6 uses water-based matte polyurethane dispersion and water-based acrylic emulsion, due to the high content of water-based acrylic emulsion, the matting performance is average and the haze is low; the amount of magnesium oxide added in the corona layer of comparative example 7 is too much, although it can enhance the barrier properties of the film itself, it will affect the transmittance and haze of the BOPA film itself, and the matting effect is average.

[0054] In summary, the BOPA matte film provided by the present invention enriches the singleness of the transparent appearance of traditional packaging, eliminates the reflection on the surface of the film, makes the printed color realistic and comfortable to the touch, and at the same time, the film also has excellent barrier properties, and the barrier properties are even better after high-temperature cooking, which prolongs the shelf life of the package contents. It has a good application prospect in high-end product packaging, such as food packaging, high-end gift boxes, daily necessities (cosmetics), and pharmaceutical packaging.

[0055] Those skilled in the art will appreciate that when the technical parameters of the present invention vary within the following ranges, the same or similar technical effects as those of the above embodiments can be expected: In specific implementation, the polyether polyol includes one or more of polyoxyethylene ether monool, polyoxypropylene diol, polyoxypropylene triol, polytetramethylene glycol, and polyoxyethylene ether diol; the polyester polyol includes one or more of polyphthalic acid-1,6-hexanediol polyester diol, polyphthalic acid neopentyl glycol polyester diol, and polyphthalic acid neopentyl glycol hexanediol polyester diol; the isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, or dicyclohexylmethane diisocyanate.

[0056] Although the terms such as water-based matte polyurethane dispersion, water-based acrylic emulsion, BOPA matte film, coating layer and flaky magnesium oxide powder are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only for the purpose of more conveniently describing and explaining the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high temperature resistant and high barrier BOPA matte film, characterized by: It comprises a BOPA film layer and a coating layer, wherein the coating layer is formed by coating an aqueous mixed liquid on the surface of the BOPA film layer, a corona surface is arranged on the BOPA film layer, and the coating layer is connected to the corona surface; The aqueous mixed liquid is composed of an aqueous matte polyurethane dispersion, an aqueous acrylic emulsion, a crosslinking agent and water in a mass ratio of 75-85:25-30:1.0-1.5:75-100; The water-based matte polyurethane dispersion is prepared from polyether polyol, polyester polyol and isocyanate; the water-based acrylic emulsion is prepared by polymerization of methyl methacrylate, styrene, itaconic acid and n-butyl acrylate.

2. The high temperature resistant and high barrier BOPA matte film according to claim 1, characterized in that: The preparation method of the aqueous matte polyurethane dispersion is: In a reactor, add polyether polyol, polyester polyol and isocyanate, react at 80℃~85℃, then add hydrophilic chain extender DMBA and castor oil, stir evenly, add 1.4-butanediol chain extender, continue stirring, add acetone to dilute, react at constant temperature, stop the reaction when the NCO content is 3.15~3.25, obtain prepolymer, cool to 20℃~30℃, add neutralizer TEA and stir to disperse, then deionize water again, stir to emulsify, finally remove acetone at 45~55℃ and vacuum (absolute pressure) of 0.02~0.1MPa to obtain water-based matte polyurethane dispersion; Wherein, the mass ratio of the polyether polyol: polyester polyol: isocyanate: hydrophilic chain extender DMBA: castor oil: 1.4-butanediol chain extender: neutralizer TEA is 27.0~32.0: 27.0~32.0: 23.5~25.5: 2.65~2.75: 1.60~1.70: 2.30~2.40: 1.05~1.

15.

3. The high temperature resistant and high barrier BOPA matte film according to claim 2, characterized in that: The polyether polyol includes one or more of polyoxyethylene ether monool, polyoxypropylene diol, polyoxypropylene triol, polytetramethylene furan diol, and polyoxyethylene ether diol; the polyester polyol includes one or more of polyphthalic acid-1,6-hexanediol polyester diol, polyphthalic acid neopentyl glycol polyester diol, and polyphthalic acid neopentyl glycol hexanediol polyester diol; the isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, or dicyclohexylmethane diisocyanate.

4. The high temperature resistant and high barrier BOPA matte film according to claim 1, characterized in that: The preparation method of the aqueous acrylic emulsion is as follows: Methyl methacrylate, styrene, n-butyl acrylate and itaconic acid, part of OP-10, part of sodium dodecyl sulfate and part of water are added to a pre-emulsification kettle, emulsified for 30-40 minutes to obtain a non-stratified emulsion; then the remaining water and the remaining OP-10 are added to the polymerization kettle, the temperature is raised to 78-80°C, ammonium persulfate initiator is added to react for 20-30 minutes, and the initiator is controlled to drip within 3-4 hours; then the polymerization kettle is heated to 85-90°C, the temperature is kept for reaction for 1-2 hours, then the temperature is lowered to 45-50°C, a pH adjuster is added to adjust the pH value of the reaction system to 6-7, and a water-based acrylic emulsion is obtained.

5. The high temperature resistant and high barrier BOPA matte film according to claim 4, characterized in that: The mass ratio of the methyl methacrylate: styrene: n-butyl acrylate: itaconic acid: OP-10: sodium dodecyl sulfate: ammonium persulfate initiator: water is 5.95-6.05: 0.95-1.05: 17.5-18.5: 20.7-21.2: 0.90-0.95: 0.45-0.47: 0.319-0.324: 115-125.

6. The high temperature resistant and high barrier BOPA matte film according to claim 1, characterized in that: The crosslinking agent is one of a hexamethylmelamine type crosslinking agent and a trimethylolmelamine type crosslinking agent.

7. The high temperature resistant and high barrier BOPA matte film according to claim 1, characterized in that: The BOPA film layer is made of polyamide resin through three-layer co-extrusion, transverse and longitudinal stretching and shaping, and then corona treatment on the surface; the polyamide resin is one or more of nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 612, nylon 610, nylon 12, nylon 1212 or poly-m-xylene hexamide.

8. The high temperature resistant and high barrier BOPA matte film according to claim 1, characterized in that: The corona surface is added with flaky magnesium oxide powder, and the added amount is 0.05% to 0.1% of the mass of the polyamide resin.

9. The high temperature resistant and high barrier BOPA matte film according to claim 1, characterized in that: The coating layer has a thickness of 1.0-1.5 μm, and the BOPA film layer has a thickness of 15-25 μm.

10. A method for preparing a high temperature resistant and high barrier BOPA matte film according to any one of claims 1 to 9, characterized in that: The steps include: Step a, weighing a water-based matte polyurethane dispersion and a water-based acrylic emulsion in proportion, adding water, stirring evenly, and finally adding a cross-linking agent, continuing to stir, and then standing to obtain an aqueous mixed solution; Step b, after the polyamide resin is subjected to three-layer co-extrusion and then stretched horizontally and longitudinally to be shaped, a corona treatment is performed on the surface thereof so that the corona value of the surface is ≥52dyn / cm, thereby obtaining a BOPA film; Step c, coating the corona surface of the BOPA film obtained in step b through an anilox roller with the aqueous mixture obtained in step a at a speed of 180-220 m / min, and drying at 110-120° C. to form a coating; Step d: After drying, the film is placed in a constant temperature chamber at 45-50° C. for aging for 72-96 hours to obtain a high temperature resistant and high barrier BOPA matte film.

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