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

Abstract

The present application relates to the technical field of nylon packaging film, and particularly relates 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 a water-based mixed solution on the surface of the BOPA film layer, a corona surface is arranged on the BOPA film layer, and the coating layer is connected with the corona surface; the water-based mixed solution is composed of a water-based matt polyurethane dispersion solution, a water-based acrylic emulsion, a crosslinking agent and water in a mass ratio of 75-85:25-30:1.0-1.5:75-100. The film has high light transmittance, high haze and low gloss, has good matt effect, has good effects in terms of scratch resistance, water boiling resistance, steam boiling resistance and oxygen barrier, can prolong the shelf life of the packaging content, has wide application prospects in high-end product packaging, such as food packaging, high-end gift boxes, daily necessities, cosmetics and medicine packaging and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nylon packaging film, in particular to a high-temperature-resistant and high-barrier BOPA matt film and a preparation method thereof. BACKGROUND

[0002] BOPA film is the third largest packaging material after BOPP and BOPET film, and is increasingly used in food packaging materials. Most of the packaging materials are transparent BOPA film. However, with the improvement of living standards, people are no longer limited to single transparent packaging, but pursue visual diversity. The matt film can make the printed color lifelike, the appearance quiet and elegant, and the hand feeling comfortable, and is more and more favored by people. In addition, due to the pursuit of food color, aroma and taste, barrier packaging is also paid more and more attention. It not only can preserve the aroma, but also can prevent oxygen from entering to avoid the content from deteriorating, thereby prolonging the shelf life.

[0003] The current BOPA matt film on the market is obtained by modifying a master batch through three-layer co-extrusion. For example, the patent document with the publication number CN111909413A, which is a BOPA matt film composed of a surface layer, a core layer and a matt layer, adds 98.5~100%(wt) of matt material and 0~1.5%(wt) of slip agent in the matt layer, and then obtains the BOPA matt film through three-layer co-extrusion and double stretching. Although the glossiness (matt surface) of the BOPA matt film prepared by the method is less than 10%, the haze can only reach about 52%, and the matt material is not conducive to dispersion. In addition, the matt film does not have high barrier performance. SUMMARY

[0004] In order to solve the problems of low haze, poor dispersion of matt material and no high barrier performance of the existing BOPA matt film mentioned in the background, the present application provides a high-temperature-resistant and high-barrier BOPA matt film, which comprises a BOPA film layer and a coating layer. The coating layer is formed by coating a water-based mixture on the surface of the BOPA film layer. The BOPA film layer is provided with a corona surface, and the coating layer is connected with the corona surface.

[0005] The water-based mixture is composed of a water-based matt polyurethane dispersion, a water-based acrylic emulsion, a crosslinking agent and water in a mass ratio of 75~85:25~30:1.0~1.5:75~100.

[0006] The water-based matt polyurethane dispersion is prepared from polyether polyol, polyester polyol and isocyanate; and the water-based acrylic emulsion is prepared by polymerization of methyl methacrylate, styrene, itaconic acid and n-butyl acrylate.

[0007] Further, the preparation method of the water-based matte polyurethane dispersion is:

[0008] In a reaction kettle, polyether polyol, polyester polyol and isocyanate are added and reacted at 80-85℃, then hydrophilic chain extender DMBA and castor oil are added, stirred uniformly, then 1.4-butanediol chain extender is added, continue to stir, dilute with acetone, constant temperature reaction, when the NCO content is 3.15-3.25, stop the reaction, obtain the prepolymer, cool to 20-30℃, add neutralizer TEA and stir to disperse, then deionized water, stir to emulsify, finally remove acetone under the conditions of 45-55℃ and vacuum degree (absolute pressure) of 0.02-0.1 MPa, to obtain the water-based matte polyurethane dispersion;

[0009] 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.

[0010] 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.

[0011] Further, on the basis of the above scheme, the polyether polyol includes one or more of polyoxyethylene ether monol, polyoxypropylene diol, polyoxypropylene triol, polytetrahydrofuran diol, polyoxyethylene ether diol; the polyester polyol includes one or more of polyphthalic acid-1,6-hexanediol polyester diol, polyneopentyl glycol polyester diol, polyneopentyl glycol hexanediol polyester diol; the isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate or dicyclohexyl methane diisocyanate.

[0012] Further, on the basis of the above scheme, the preparation method of the water-based acrylic emulsion is as follows:

[0013] Methyl methacrylate, styrene, n-butyl acrylate and itaconic acid, part of OP-10, part of sodium dodecyl sulfate and part of water are added into a pre-emulsification kettle, emulsified for 30-40 min to obtain an emulsion without stratification; then the remaining water, the remaining OP-10 are added into a polymerization kettle, heated to 78-80℃, and ammonium persulfate initiator is added to initiate reaction for 20-30 min, and the initiator is dropped for 3-4 h; then the polymerization kettle is heated to 85-90℃, and kept for 1-2 h, then cooled to 45-50℃, and a pH regulator is added to adjust the pH value of the reaction system to 6-7, to obtain a water-based acrylic emulsion.

[0014] Further to the above scheme, 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.

[0015] 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.

[0016] Further to the above scheme, the crosslinking agent is one of hexamethyl melamine type crosslinking agent or trimethylol melamine type crosslinking agent.

[0017] Further to the above scheme, the BOPA film layer is prepared by corona treatment on the surface of polyamide resin after three-layer co-extrusion and transverse and longitudinal stretching and setting; the polyamide resin is one or more of nylon 6, nylon 6,6, copolymer of nylon 6 and nylon 6,6, nylon 612, nylon 610, nylon 12, nylon 1212 or poly-m-xylylene adipamide.

[0018] Further to the above scheme, flaky magnesium oxide powder is added to the corona surface, and the addition amount is 0.05%-0.1% of the mass of the polyamide resin.

[0019] The purpose of the technical scheme is that the oxide film is sheet-shaped, has a large aspect ratio, can be evenly spread on the surface of the film, and is stacked in a staggered manner layer by layer, so that oxygen needs to pass through a curved path and cannot directly pass through, so that the oxygen is not easy to pass through the film, thereby making the film have excellent barrier properties; in addition, after the sheet-shaped magnesium oxide is subjected to high-temperature cooking, the aqueous mixture will crosslink with the magnesium oxide, thereby improving the adhesion of the coating layer to the film, and after crosslinking, a network structure is formed, so that oxygen cannot pass through, thereby improving the oxygen barrier property.

[0020] Preferably, the sheet-shaped magnesium oxide powder has a transverse size of 300-400 nm and a thickness of 30-40 nm.

[0021] The purpose of limiting the size range of the sheet-shaped magnesium oxide powder is to avoid excessively large size affecting the dispersion performance of the sheet-shaped magnesium oxide powder, and excessively small size easily reducing the oxygen barrier property.

[0022] On the basis of the above scheme, 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.

[0023] The application also provides a preparation method of the high-temperature-resistant and high-barrier BOPA matt film.

[0024] Step a: the water-based matte polyurethane dispersion liquid, the water-based acrylic emulsion, water, and the crosslinking agent are weighed according to the proportion, stirred uniformly, and then the crosslinking agent is continuously stirred, and then the water-based mixture is obtained by standing;

[0025] Step b: the polyamide resin is subjected to three-layer co-extrusion, then is subjected to transverse and longitudinal stretching and setting, and then is subjected to corona treatment on the surface to make the corona value of the surface be greater than or equal to 52 dyn / cm, thereby obtaining the BOPA film.

[0026] Step c: the BOPA film obtained in step b is subjected to coating by passing through the anilox roller with the water-based mixture obtained in step a at a vehicle speed of 180-220 m / min, and is subjected to drying at 110-120 ℃, thereby forming the coating layer.

[0027] Step d: after drying, the BOPA matt film is placed in a constant-temperature room at 45-50 ℃ for aging for 72-96 h, thereby obtaining the high-temperature-resistant and high-barrier BOPA matt film.

[0028] Compared with the prior art, the high-temperature-resistant and high-barrier BOPA matt film and the preparation method thereof have the following advantages:

[0029] 1、 through specific coating layer formula and specific proportion, the coating layer is firmly combined with BOPA film, the prepared BOPA matt film has excellent matt performance, shows good performance in terms of scratch resistance and temperature resistance, and the film has excellent barrier property, and the barrier property is more excellent after high-temperature cooking;

[0030] 2、The water-based acrylic emulsion used in the coating liquid has excellent high transparency, low gloss and water and high temperature resistance, and has good adhesion to the film, and the water-based matt polyurethane dispersion liquid is matched in proportion, the advantages and disadvantages are complementary, the adhesion of the water-based matt polyurethane dispersion liquid to the film is improved, and the obtained water-based mixed liquid has excellent high temperature resistance and excellent matt performance.

[0031] 3、The water-based matt polyurethane dispersion liquid is used in the component of the coating slurry, without additional filler, micro-wax powder and inorganic silicon dioxide;The polyester polyol is formed by esterification reaction, has more ester bonds in the molecule, the molecular chain is relatively tight, and the intermolecular force is relatively strong;The polyether polyol is formed by acetal reaction, has more functional groups such as epoxy group and hydroxyl group in the molecule, and the molecular chains are relatively loose, the coating liquid of the application utilizes the structural difference between polyester polyol and polyether polyol, and after mixing and polymerization, the compatibility is poor, neither completely compatible nor completely incompatible, so that the final product has good matt performance.

[0032] 4、The coating layer obtained under specific proportion conditions, due to the addition of crosslinking agent, the crosslinking density of the water-based mixed liquid is improved after drying, so that the coating layer does not return to stickiness and can maintain good flexibility;In addition, by controlling the addition amount of crosslinking agent, the crosslinking agent is prevented from excessive reaction with water-based polyurethane, so that the coating layer is excessively crosslinked and becomes too hard, which not only easily causes the film to be torn when stretched horizontally, but also makes the printing firmness and composite peeling strength low. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0034] Figure 1 The layer structure schematic diagram of the high-temperature-resistant and high-barrier BOPA matt film of embodiment 1 provided by the present application.

[0035] Reference signs:

[0036] Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] This 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 aqueous acrylic emulsion in the following examples and comparative examples were all prepared using this method.

[0040] The preparation method of the aqueous matte polyurethane dispersion is as follows:

[0041] In a reaction vessel, polytetrahydrofuran glycol, poly(neopentyl phthalate) polyester glycol, and toluene diisocyanate were added. The temperature was gradually raised to 80°C and maintained at 80°C–85°C for 3 hours. Then, hydrophilic chain extender DMBA and castor oil were added under stirring, and the mixture was stirred at 80°C for 2 hours. Then, 1,4-butanediol chain extender was added, and the mixture was stirred at 85°C for 2 hours. Acetone was added for dilution, and the mixture was kept at a constant temperature for 4 hours. The NCO content was then tested. When the NCO content was 3.20, the reaction was stopped to obtain a prepolymer. The temperature was lowered to 25°C, neutralizing agent TEA was added, and the mixture was stirred and dispersed. Then, deionized water was added again, and the mixture was stirred and emulsified. Finally, acetone was removed under conditions of 45–55°C and a vacuum degree (absolute pressure) of 0.02–0.1 MPa to obtain an aqueous matte polyurethane dispersion.

[0042] The mass ratio of polytetrahydrofuran diol, polypentyl phthalate polyester diol, toluene diisocyanate, hydrophilic chain extender DMBA, castor oil, 1,4-butanediol, and neutralizing agent TEA is 30.0:30.0:25.2:2.7:1.65:2.35:1.10.

[0043] The preparation method of the water-based acrylic emulsion is as follows:

[0044] The raw materials including methyl methacrylate, styrene, n-butyl acrylate and itaconic acid, one half of OP-10 and two thirds of sodium dodecyl sulfate, two thirds of water are added into a pre-emulsification kettle, emulsified for 30-40 min to obtain an emulsion without stratification; then the remaining water, the remaining OP-10 are added into a polymerization kettle, heated to 78-80℃, and ammonium persulfate initiator is added to initiate reaction for 20-30 min, and the initiator is dropped for 3-4 h; then the polymerization kettle is heated to 85-90℃ and kept for 1-2 h, and then cooled to 45-50℃, and a pH regulator is added to adjust the pH value of the reaction system to 6-7, thereby obtaining the water-based acrylic emulsion.

[0045] The mass ratio of the methyl methacrylate, styrene, n-butyl acrylate, itaconic acid, OP-10, sodium dodecyl sulfate, ammonium persulfate initiator and water is 6.0:1.0:18.0:21.0:0.92:0.46:0.322:120.

[0046] In order to fully illustrate the beneficial effects of the present application, the following examples and comparative examples are provided:

[0047] Example 1

[0048] The polyamide resin is stretched and shaped in the transverse and longitudinal directions after being co-extruded in three layers by flow casting, and then the surface of the polyamide resin is subjected to corona treatment, so that the corona value of the surface is ≥52 dyn / cm, thereby obtaining a BOPA film containing a corona surface; the powder of flaky magnesium oxide powder is added to the corona surface layer; the transverse size of the flaky magnesium oxide powder is 300 nm, and the thickness is 40 nm, wherein the polyamide resin is nylon 6;

[0049] Then, the BOPA film is quickly passed through a screen roller dipped with a water-based mixed solution composed of water-based matte polyurethane dispersion, water-based acrylic emulsion, crosslinking agent and water in a mass ratio of 75:25:1.0:75 on an offline coating machine, and is subjected to compression coating and gluing, and the vehicle speed is 200 m / min; then, the BOPA film is dried in an oven at 110℃ to form a coating layer, and after drying, the BOPA film is placed in a constant temperature room at 50℃ for 72 h of curing, and after curing, a high-temperature-resistant and high-barrier BOPA matt film is obtained, wherein the thickness of the coating layer 20 is 1 μm, and the thickness of the BOPA film layer 10 is 15 μm.

[0050] The coating layer is connected with the corona surface; and the addition amount of the flaky magnesium oxide powder in the corona surface layer is 0.05% of the mass of the polyamide resin.

[0051] The crosslinking agent is one of hexamethyl melamine type crosslinking agent or trimethylol melamine type crosslinking agent.

[0052] Example 2

[0053] Example 2 differs from Example 1 in that the aqueous mixture is composed of an aqueous matte type polyurethane dispersion, an aqueous acrylic emulsion, a crosslinking agent and water in a mass ratio of 85:30:1.5:100; the addition amount of the flaky magnesium oxide powder in 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 in Example 1.

[0054] Example 3

[0055] Example 3 differs from Example 1 in that the flaky magnesium oxide powder has a lateral dimension of 400 nm and a thickness of 30 nm; the addition amount of the flaky magnesium oxide powder in 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 in Example 1.

[0056] Example 4

[0057] Example 4 differs from Example 1 in that the addition amount of the flaky magnesium oxide powder in 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 in Example 1.

[0058] Example 5

[0059] Example 5 differs from Example 1 in that the aqueous mixture is composed of an aqueous matte type polyurethane dispersion, an aqueous acrylic emulsion, a crosslinking agent and water in a mass ratio of 80:28:1.25:85; the addition amount of the flaky magnesium oxide powder in 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 in Example 1.

[0060] Comparative Example 1

[0061] This comparative example differs from Example 1 in 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:

[0062] A BOPA film is obtained by flow casting a three-layer co-extrusion of a nylon 6 resin, followed by transverse and longitudinal stretching and setting, and then performing corona treatment on the surface of the BOPA film to make the corona value of the surface of the BOPA film ≥52 dyn / cm, thereby obtaining a BOPA film containing a corona surface, and the thickness of the BOPA film is 15 μm.

[0063] Comparative Example 2

[0064] This comparative example differs from Example 1 in that no coating layer is prepared. The preparation method of this comparative example comprises the following steps:

[0065] The BOPA film with thickness of 15 μm is obtained by corona treatment on the surface of the BOPA film obtained by flow casting three-layer co-extrusion and then transverse and longitudinal stretching setting, the corona value of the surface of the film is ≥52 dyn / cm, the film contains a corona surface layer, the sheet-shaped magnesium oxide powder is added in the corona surface layer, the transverse size of the sheet-shaped magnesium oxide powder is 300 nm, and the thickness is 40 nm.

[0066] Comparative Example 3

[0067] The difference between the present comparative example and Example 1 is that the water-based mixture in the coating layer does not contain water-based acrylic emulsion.

[0068] The water-based mixture is composed of water-based matte polyurethane dispersion, crosslinking agent and water in a mass ratio of 75:1.0:75, the remaining components and operation steps are the same as those in Example 1.

[0069] Comparative Example 4

[0070] The difference between the present comparative example and Example 1 is that the water-based mixture in the coating layer does not contain water-based matte polyurethane dispersion.

[0071] The water-based mixture is composed of water-based acrylic emulsion, crosslinking agent and water in a mass ratio of 25:1.0:75, the remaining components and operation steps are the same as those in Example 1.

[0072] Comparative Example 5

[0073] The difference between the present comparative example and Example 1 is that the amount of water-based matte polyurethane dispersion added in the coating layer is too much.

[0074] The water-based mixture is composed of water-based matte polyurethane dispersion, water-based acrylic emulsion, crosslinking agent and water in a mass ratio of 100:25:1.0:75, the remaining components and operation steps are the same as those in Example 1.

[0075] Comparative Example 6

[0076] The difference between the present comparative example and Example 1 is that the amount of water-based acrylic emulsion added in the coating layer is too much.

[0077] The water-based mixture is composed of water-based matte polyurethane dispersion, water-based acrylic emulsion, crosslinking agent and water in a mass ratio of 75:45:1.0:75, the remaining components and operation steps are the same as those in Example 1.

[0078] Comparative Example 7

[0079] The comparative example is different from example 1 in that the amount of flaky magnesium oxide powder added in the coating is too much, the amount of magnesium oxide added in the corona surface layer is 0.50% of the mass of the polyamide resin, and the remaining components and operating steps are the same as in example 1.

[0080] Performance test:

[0081] I. Light transmittance and haze test

[0082] Test according to "GB 2410-1980 Test method for light transmittance and haze of transparent plastics".

[0083] II. Gloss test

[0084] Test according to "GB / T 8807-1988 Test method for specular gloss of plastics".

[0085] III. Scratch and abrasion resistance test

[0086] Cut the sample into a size that can be fastened with a clamp, and make the test surface (coating surface) horizontal. The sample surface must be flat, free of bubbles and impurities, etc. Set up the abrasion tester LT803 (Dongguan Longtian Instrument and Equipment Co., Ltd.), set the speed range to 30 times / min, and the travel range to 0-50 mm. Adjust the weight and material position to the appropriate position, set the weight to 500 g, set the number of abrasions to 2000 times, and the speed to 20 times / min. Press the switch to start the test. After the test is completed, observe the abrasion of the coating surface. If there is scratching, mark it with "X". If there is no change in appearance, mark it with "O".

[0087] IV. Water boiling and steaming resistance performance evaluation

[0088] Pre-coat the BOPA matt film prepared above with PE film by using two-component polyurethane water boiling composite glue, and the composite glue amount is 2.0 g / m 2 Then, after aging in a 45℃ oven for 48 h, a BOPA / PE composite film is obtained, in which the coating layer is on the outside as the outer surface. After bag making, test the water boiling at 100℃ for 30 min, and observe whether the coating layer delaminates or falls off, etc. If there is delamination or falling off, mark it with "X". If there is no change in appearance, mark it with "O".

[0089] Pre-coat the BOPA matt film prepared above with CPP film by using two-component polyurethane steaming composite glue, and the composite glue amount is 3.0 g / m2. Then, after aging in a 45℃ oven for 72 h, a BOPA / CPP composite film is obtained, in which the coating layer is on the outside as the outer surface. After bag making, test the steaming at 125℃ for 40 min, and observe whether the coating layer delaminates or falls off, etc. If there is delamination or falling off, mark it with "X". If there is no change in appearance, mark it with "O".

[0090] V. Oxygen transmission rate test

[0091] Test according to ASTM F1927-2007 "Standard Test Methods for Determining the Oxygen Transmissibility, Permeability, and Fugitivity of Barrier Materials Using a Coulometric Oxygen Sensor at Controlled Relative Humidity"; test at 23°C 50% RH, before and after steaming (125°C for 40 min) of the oxygen transmission rate.

[0092] Test results

[0093] The pre-coated films prepared from the examples and comparative examples were subjected to the performance tests 1 to 5 described above, and the results are shown in the following table:

[0094] Table 1 Performance test table of examples and comparative examples

[0095]

[0096] From the above data, it can be seen that, compared with Comparative Examples 1-7, Examples 1-5 have higher light transmittance, high haze and low gloss, good extinction effect, and good effects in terms of scratch resistance, water resistance and steaming resistance; at the same time, compared with the comparative examples, the oxygen transmission rate is reduced, especially the oxygen transmission rate after steaming is significantly reduced, indicating that the barrier performance of Examples 1-5 is more excellent.

[0097] Comparative Example 1 is a pure BOPA film with high transparency and high light transmittance, and has no extinction effect; Comparative Example 2 has flaky magnesium oxide added to the corona surface of the BOPA film, which can reduce the oxygen transmission rate to a certain extent, but still does not have an extinction effect; Comparative Example 3 uses a water-based matte polyurethane dispersion alone, which has a general extinction effect, and the coating film itself is relatively soft, and cannot meet the requirements of scratch resistance and temperature resistance; Comparative Example 4 uses a water-based acrylic emulsion alone, which not only does not have an extinction effect, but also has poor scratch resistance and temperature resistance, and the oxygen transmission rate does not decrease significantly after steaming; Comparative Example 5 uses a water-based matte polyurethane dispersion and a water-based acrylic emulsion, but the content of the water-based acrylic emulsion is too low, resulting in a general extinction effect of the pre-coated film, and the coating film resin is too soft, which cannot meet the requirements of scratch resistance, high temperature resistance and adhesion, so that the oxygen transmission rate does not change after steaming due to the peeling of the coating; Comparative Example 6 uses a water-based matte polyurethane dispersion and a water-based acrylic emulsion, but the content of the water-based acrylic emulsion is too high, resulting in a general extinction effect and low haze; Comparative Example 7 has too much magnesium oxide added to the corona layer, which can enhance the barrier performance of the film itself, but will affect the light transmittance and haze of the BOPA film itself, and the extinction effect is general.

[0098] In conclusion, the BOPA matt film provided by the application enriches the single appearance of traditional packaging, eliminates the reflection on the film surface, makes the printed color lifelike and the touch comfortable, and has excellent barrier properties, and the barrier properties are even better after high-temperature cooking, thereby prolonging the shelf life of the packaging content, and having a good application prospect in high-end product packaging, such as food packaging, high-end gift boxes, daily necessities (cosmetics), medicine packaging, etc.

[0099] Those skilled in the art can know that when the technical parameters of the application change in the following ranges, the same or similar technical effects as the above-mentioned embodiments can be expected:

[0100] In specific implementation, the polyether polyol includes one or more of polyoxyethylene ether monol, polyoxypropylene diol, polyoxypropylene triol, polytetrahydrofuran diol, and polyoxyethylene ether diol; the polyester polyol includes one or more of poly-1,6-hexanediol phthalate polyester diol, neopentyl glycol phthalate polyester diol, and neopentyl glycol phthalate hexanediol polyester diol; and the isocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, or dicyclohexyl methane diisocyanate.

[0101] Although the terms such as aqueous matte polyurethane dispersion, aqueous acrylic emulsion, BOPA matt film, coating layer, and flaky magnesium oxide powder are used more frequently in the present application, the possibility of using other terms is not excluded. The use of these terms is only for the convenience of describing and explaining the essence of the application; any interpretation as an additional limitation is contrary to the spirit of the application.

[0102] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A high temperature resistant, high barrier, matt BOPA film, characterized in that: The BOPA film layer and the coating layer are formed on the surface of the BOPA film layer by coating the aqueous mixture, and the corona surface is arranged on the BOPA film layer, and the coating layer is connected with the corona surface. The aqueous mixture is composed of an aqueous matt 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 aqueous matt polyurethane dispersion is prepared from polyether polyol, polyester polyol and isocyanate; the aqueous acrylic emulsion is prepared by polymerization of methyl methacrylate, styrene, itaconic acid and n-butyl acrylate. The preparation method of the aqueous matt polyurethane dispersion is as follows: In a reaction kettle, polyether polyol, polyester polyol and isocyanate are added and reacted at 80-85 DEG C, then hydrophilic chain extender DMBA and castor oil are added, stirred uniformly, then 1.4-butanediol chain extender is added, continuously stirred, diluted with acetone, and the reaction is stopped when the NCO content is 3.15-3.25, the temperature is lowered to 20-30 DEG C, neutralizing agent TEA is added and stirred and dispersed, then deionized water is added, stirred and emulsified, and finally acetone is removed under the conditions of 45-55 DEG C and absolute pressure of 0.02-0.1 MPa to obtain the aqueous matt polyurethane dispersion. The mass ratio of the polyether polyol, the polyester polyol, the isocyanate, the hydrophilic chain extender DMBA, the castor oil, the 1.4-butanediol chain extender and the neutralizing agent 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. 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 into a pre-emulsification kettle, emulsified for 30-40 min to obtain an emulsion without stratification; then the remaining water, the remaining OP-10 are added into a polymerization kettle, heated to 78-80 DEG C, and ammonium persulfate initiator is added to initiate the reaction for 20-30 min, the initiator is dropped in 3-4 h; then the polymerization kettle is heated to 85-90 DEG C, and the reaction is kept for 1-2 h, then the temperature is lowered to 45-50 DEG C, and a pH regulator is added to adjust the pH value of the reaction system to 6-7 to obtain the aqueous acrylic emulsion.

2. The high temperature resistant, high barrier, matte BOPA film of claim 1, wherein: The polyether polyol includes one or more of polyoxypropylene glycol, polyoxypropylene triol, polytetrahydrofuran diol and polyoxyethylene ether diol; the polyester polyol includes one or more of polyphthalic acid-1,6-hexanediol polyester diol, polyneopentyl glycol phthalate diol and polyneopentyl glycol hexanediol phthalate diol; and the isocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate and dicyclohexyl methane diisocyanate.

3. The high temperature resistant, high barrier, matte BOPA film of claim 1, wherein: 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.

4. The high temperature resistant, high barrier, matte BOPA film of claim 1, wherein: The crosslinking agent is one of hexamethyl melamine type crosslinking agent or trimethylol melamine type crosslinking agent.

5. The high temperature resistant, high barrier, matte BOPA film of claim 1, wherein: The BOPA film layer is prepared by corona treatment on the surface of the polyamide resin after three-layer co-extrusion and horizontal and vertical stretching setting; the polyamide resin is one or more of nylon 6, nylon 6,6, copolymer of nylon 6 and nylon 6,6, nylon 612, nylon 610, nylon 12, nylon 1212 or poly-m-xylylene adipamide.

6. The high temperature resistant, high barrier, matte BOPA film of claim 1, wherein: The flaky magnesium oxide powder is added to the corona surface, and the addition amount is 0.05%~0.1% of the mass of the polyamide resin.

7. The high temperature resistant, high barrier, matte BOPA film of claim 1, wherein: The thickness of the coating layer is 1.0~1.5μm, and the thickness of the BOPA film layer is 15~25μm.

8. A process for the preparation of a high temperature resistant, high barrier, matt BOPA film according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: Step a, the water-based matte polyurethane dispersion and the water-based acrylic emulsion are weighed according to the proportion, water is added, and stirring is uniform, finally the crosslinking agent is added and stirring is continued, then standing is obtained, and the water-based mixture is obtained; Step b, the polyamide resin is subjected to three-layer co-extrusion and horizontal and vertical stretching setting, and then the surface of the polyamide resin is subjected to corona treatment to make the corona value of the surface of the polyamide resin ≥52dyn / cm, and the BOPA film is obtained; Step c, the surface of the corona of the BOPA film obtained in step b is coated by the anilox roller with the water-based mixture prepared in step a at a vehicle speed of 180~220m / min, and drying is performed at 110~120℃ to form a coating layer; Step d, after drying, the BOPA mat film with high temperature resistance and high barrier property is obtained by placing in a constant temperature room at 45~50℃ for 72~96h.

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