Transparent high-barrier coating film and preparation method thereof

Abstract

The invention belongs to the technical field of coating films, and particularly relates to a transparent high-barrier coating film and a preparation method thereof.The transparent high-barrier coating film comprises a base film, the surface of the base film is sequentially coated with a bottom coating and a coating layer through a reverse kiss coating technology, and the coating layer is prepared by coating transparent high-barrier coating liquid; the transparent high-barrier coating liquid comprises the following components in parts by mass: 6-10 parts of amino modified PVA resin, 0.4-0.6 part of a coupling agent, 0.1-0.3 part of a filling agent, 60-90 parts of deionized water and 25-50 parts of an alcohol mixed solvent. The coating film prepared by the invention has high oxygen resistance and high water resistance, can be applied to water boiling (cooking) and high-humidity environments, is free of pollution in the production process, and is environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of coating films, in particular to a transparent high-barrier coating film and a preparation method thereof. Background Art

[0002] Oxygen in the environment can cause food to oxidize and deteriorate, and the active ingredients of medicines to degrade. External moisture can cause bacteria to grow in food, causing mildew, and affecting the effectiveness and stability of medicines. The separation of products inside the package also leads to product quality defects, affecting use. In order to ensure the original ingredients, quality and shelf life of the products, higher requirements are placed on the barrier properties of packaging. Especially for products containing special ingredients or requiring special processing technology, such as oil-containing, pre-made, fried, high-sugar, dried, aromatic, boiled, steamed, special medicines, etc., the barrier properties of packaging materials are particularly critical.

[0003] In order to improve the barrier properties of plastic packaging, high barrier properties are often achieved by coating polyvinylidene chloride (PVDC) on a plastic base film to obtain a coating film (commonly known as K film) or coating polyvinyl alcohol (PVA) latex on a plastic base film to obtain a PVA coating film. However, the barrier properties of PVA coating films drop sharply when exposed to boiling (steaming) or high humidity environments, and cannot meet the application requirements of boiling (steaming) or high humidity environments; although PVDC is resistant to boiling and suitable for high humidity environments, its production process may produce harmful byproducts, which are potentially harmful to the environment, and discarded PVDC coating film packaging materials are difficult to recycle and degrade, and will produce harmful gases such as dioxins and hydrogen chloride after burning, causing long-term pollution to the environment.

[0004] Therefore, there is an urgent need for a transparent high-barrier coating film and a preparation method thereof to solve the above problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a transparent high-barrier coating film and a preparation method thereof. The transparent high-barrier coating film has the advantages of high barrier performance, easy recycling and adaptability to special needs.

[0006] In order to achieve one of the purposes of the present invention, the present invention adopts the following technical solutions:

[0007] A transparent high-barrier coating film, comprising a base film, a base coating layer and a coating layer are sequentially coated on the surface of the base film by a reverse kiss coating process, the coating layer is prepared by coating with a transparent high-barrier coating liquid, the transparent high-barrier coating liquid comprises 6-10 parts by weight of amino-modified PVA resin, 0.4-0.6 parts by weight of coupling agent, 0.1-0.3 parts by weight of filler, 60-90 parts by weight of deionized water and 25-50 parts by weight of an alcohol mixed solvent. The deionized water consists of first deionized water, second deionized water and third deionized water.

[0008] The grade of the amino-modified PVA resin is 5003 produced by SEKISUI Company.

[0009] Preferably, the preparation method of the transparent high barrier coating liquid is:

[0010] S1, taking 0.1-0.3 parts by weight of a filler, adding first deionized water to prepare a first solution of 5 wt %;

[0011] S2, taking 0.4-0.6 parts by weight of coupling agent, adding second deionized water to prepare a second solution of 5 wt%;

[0012] S3, add the third deionized water and 6-10 parts by mass of the amino-modified PVA resin to the reactor and stir until the amino-modified PVA resin is completely dissolved, and the sum of the parts by mass of the first deionized water, the second deionized water and the third deionized water is 60-90 parts by mass;

[0013] S4. Set the heating temperature of the reactor, add the first solution and the second solution into the reactor in sequence and stir, then add 25-50 parts by mass of an alcohol mixed solvent, stir, cool naturally, and filter to form a transparent high-barrier coating liquid.

[0014] Preferably, in step S3, first add the third deionized water to the reactor, start stirring, the idling speed of the stirrer is 4000R / min, and the stirring speed is set to 40% of the idling speed; then add the amino-modified PVA resin to the reactor, and the stirring speed is set to 60% of the idling speed.

[0015] Preferably, in step S3, after the amino-modified PVA resin is completely dissolved, the heating temperature of the reactor is set to 95-98° C., the stirring speed is adjusted to 80% of the idling speed, and stirring is continued for 2 hours.

[0016] Preferably, in step S4, the heating temperature of the reactor is 60°C; after the first solution and the second solution are added into the reactor, the temperature is maintained at 60°C and the stirring speed is 80% for 30 minutes, then the stirring speed is reduced to 60% of the idling speed, an alcohol mixed solvent is added, and the stirring is carried out for 10 minutes; and the naturally cooled coating liquid is filtered through a 100-mesh filter.

[0017] Preferably, the coupling agent is 1,2,3,4-butanetetracarboxylic acid (BTCA); the filler is nano-spherical silica (SiO 2 ); the alcohol mixed solvent is prepared by mixing ethanol and isopropanol in a mass ratio of 1:1.

[0018] Preferably, the base film is one of HDPE, BOPP, PET and PA.

[0019] Preferably, the primer layer is prepared by coating the primer on the base film through a reverse kiss coating process; the brand of the primer is EA3250 produced by Beijing Gaomeng Company.

[0020] In order to achieve the second object of the present invention, the present invention provides a method for preparing a transparent high-barrier coating film, which specifically comprises the following steps:

[0021] S1. preparing a transparent high barrier coating liquid;

[0022] S2. A reverse kiss coating process is adopted to first apply a primer on the base film to obtain a primer coating, and then a transparent high-barrier coating liquid is applied online on the primer coating after drying in an oven to obtain a coating layer, and then the transparent high-barrier coating film is obtained by drying, winding and aging in sequence.

[0023] Preferably, the reverse kiss coating process is a reverse kiss coating process using a coater with a double coating head, wherein the first group of coating heads uses a 200-line anilox roller to coat the primer EA3250, which is then dried in an oven and then connected to the second group of coating heads using a 150-line anilox roller to coat the transparent high-barrier aqueous coating liquid; in step S2, the aging temperature is 45°C and the aging time is 48 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The coating film prepared by the present invention has high oxygen and water barrier properties, which meets the application requirements of the coating film in boiling (steaming) and high humidity environments. The production process is pollution-free and environmentally friendly, and packaging waste is easy to recycle. The coating production process is simple and convenient to operate.

[0026] (2) The amino group and hydroxyl group in the amino-modified PVA of the present invention react chemically with the carboxyl group in the coupling agent 1,2,3,4-butanetetracarboxylic acid (BTCA) to form amide bonds and ester bonds. The amide group, carbonyl group, hydroxyl group and polar functional groups are staggered on the molecular chain, so that the prepared coating liquid has a strong and stable interwoven network structure, which increases the bonding force between the materials. Nano-spherical silica (SiO 2 ) has a large specific surface area and excellent dispersibility. Under the bridge effect of the coupling agent 1,2,3,4-butanetetracarboxylic acid (BTCA), it produces a strong cross-linking effect with the amino-modified PVA molecules, filling the pores in the coating, making the coating denser and making it more difficult for gas molecules to pass through. In addition, the nano-spherical silica (SiO 2 ) has waterproof and anti-seepage properties, thereby improving the water resistance of the coating and increasing the barrier properties of the coating. In addition, nano-scale spherical silica (SiO 2) Due to its special structure, it has good dispersibility in water medium, can prevent the emulsion from stratification and precipitation, and can produce tiny flocs, which thickens the emulsion and improves the coating's resistance to water boiling (steaming), high humidity resistance, adhesion, and coating strength. Adding an appropriate proportion of alcohol mixed solvents to the ratio can adjust the viscosity of the coating liquid and eliminate bubbles, so that the coating process can be better leveled, the coating liquid can be better combined with the substrate, and the adhesion and appearance quality of the coating can be improved.

[0027] (3) The present invention uses Beijing Gaomeng New Material EA3250 primer during coating to increase the adhesion between the transparent high-barrier water-based coating and the base film. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a structural diagram of the coating film of the present invention;

[0029] Figure 2 It is a flow chart of the coating film production process of the present invention.

[0030] The meanings of the symbols in the figure are as follows:

[0031] 1- base film, 2- primer layer, 3- coating layer. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0033] A transparent high-barrier coating film comprises a base film 1, a primer layer 2 and a coating layer 3 are sequentially coated on the surface of the base film 1 by a reverse kiss coating process, the coating layer 3 is prepared by coating with a transparent high-barrier coating liquid, and the transparent high-barrier coating liquid comprises 6-10 parts by weight of an amino-modified PVA resin, 0.4-0.6 parts by weight of a coupling agent, 0.1-0.3 parts by weight of a filler, 60-90 parts by weight of deionized water and 25-50 parts by weight of an alcohol mixed solvent.

[0034] Example 1

[0035] according to Figure 1 As shown, a transparent high-barrier coating film comprises a base film 1, a primer layer 2 and a coating layer 3 connected in sequence, the coating layer 3 is prepared by coating with a transparent high-barrier coating liquid, the base film 1 is made of HDPE, BOPP, PET and PA respectively, and the preparation method of the transparent high-barrier coating liquid is as follows:

[0036] S1, 0.2 kg of nano-spherical silicon dioxide (SiO 2) was prepared into a 5 wt% dispersed aqueous solution by mechanical stirring with deionized water.

[0037] S2. 0.5 kg of coupling agent 1,2,3,4-butanetetracarboxylic acid (BTCA) was prepared into a 5 wt % aqueous solution with deionized water under mechanical stirring.

[0038] S3. Add 70 kg of deionized water into the reactor and start stirring (the idling speed of the stirrer is 4000 R / min, and the stirring speed is set to 40%).

[0039] S4. Quickly add 8 kg of amino-modified PVA 5003 resin into the reactor and adjust the speed to 60%.

[0040] S5. After continuous stirring for 1 hour, check whether the amino-modified PVA5003 resin is completely dissolved. If not, continue stirring until it is completely dissolved. If it is completely dissolved, proceed to the next step.

[0041] S6. Set the heating temperature of the reactor to 95-98°C, adjust the stirring speed to 80%, and continue stirring for 2 hours.

[0042] S7, set the heating temperature of the reactor to 60°C, and when the actual heating temperature reaches 60°C, add 5wt% of nano-spherical silica (SiO 2 ) dispersed aqueous solution and 5 wt% 1,2,3,4-butanetetracarboxylic acid (BTCA) aqueous solution were stirred at 60°C and 80% stirring speed for 30 min.

[0043] S8. Reduce the stirring speed to 60%, add 30 kg of alcohol mixed solvent, stir for 10 minutes, stop stirring and heating, and cool naturally to form a transparent high-barrier coating liquid.

[0044] When the transparent high-barrier aqueous coating liquid is naturally cooled to room temperature, it is filtered through a 100-mesh filter and placed in a sealed container for later use.

[0045] A method for preparing a transparent high-barrier coating film is as follows:

[0046] according to Figure 2 As shown, a reverse kiss coating process is used on the surface of the base film 1 using a coater with a double coating head. The primer EA3250 is coated with a 200-line anilox roller in the first group of coating heads. After oven drying, a transparent high-barrier coating liquid is coated with a 150-line anilox roller in the second group of coating heads. After oven drying, the film is rolled up and aged in a 45°C curing room for 48 hours to obtain a transparent high-barrier coating film.

[0047] Comparative Example 1

[0048] Conventional PVA coated film, the coating liquid used is PVA-203 produced by Kuraray, and the other preparation processes are the same as those in Example 1.

[0049] The performance tests were conducted on the coating films prepared using different base films 1 in Example 1 and the coating films prepared in Comparative Example 1. The results are shown in Table 1 below:

[0050] Table 1 Comparison of water vapor permeability and oxygen permeability of coatings of different materials

[0051]

[0052] It can be seen from Table 1 that the barrier properties of the coating films prepared using different materials in Example 1 are better than the barrier properties of the coating films prepared in Comparative Example 1, and meet the boiling (steaming) conditions; in addition, the coating liquid used for the transparent high-barrier coating film of the present invention has good environmental friendliness, avoiding the potential environmental risks of the currently popular PVDC coated K film.

[0053] Table 2 Comparison of coating thickness and square meter solid weight of different materials

[0054]

[0055] It can be seen from Table 2 that the solid weight per square meter of the transparent high barrier coating film prepared in Example 1 is 0.35-0.4 g / m 2 The thickness of the coating after drying is 0.5-0.7 μm, which are lower than the square meter solid weight of the coating film prepared in Comparative Example 1 and the thickness of the coating after drying. Therefore, the coating film prepared by the present invention is not only light in weight, but also has a thinner coating (barrier layer), reduces costs and has better barrier properties.

[0056] The coating film of Example 1 was compounded with CPP to obtain a composite film, and then the common PVDC coating film was compounded with CPP to obtain a composite film. The properties of the two composite films were tested, as shown in Table 3 below:

[0057] Table 3 Comparison of properties of different material coatings after compounding with CPP

[0058]

[0059] It can be seen from Table 3 that the transparent high barrier coating film and CPP composite have great advantages in barrier performance, transparency and environmental protection compared with the ordinary PVDC coating film and CPP composite.

Claims

1. A transparent high barrier coating film, characterized in that: The coating film comprises a base film (1), the surface of the base film (1) is coated with a primer layer (2) and a coating layer (3) in sequence by a reverse kiss coating process, the coating layer (3) is prepared by coating with a transparent high-barrier coating liquid, the transparent high-barrier coating liquid comprises 6-10 parts by weight of an amino-modified PVA resin, 0.4-0.6 parts by weight of a coupling agent, 0.1-0.3 parts by weight of a filler, 60-90 parts by weight of deionized water and 25-50 parts by weight of an alcohol mixed solvent.

2. A transparent high barrier coating film according to claim 1, characterized in that: The preparation method of the transparent high-barrier coating liquid is: S1, taking 0.1-0.3 parts by weight of a filler, adding first deionized water to prepare a first solution of 5 wt %; S2, taking 0.4-0.6 parts by weight of coupling agent, adding second deionized water to prepare a second solution of 5 wt%; S3, add the third deionized water and 6-10 parts by mass of the amino-modified PVA resin to the reactor and stir until the amino-modified PVA resin is completely dissolved, and the sum of the parts by mass of the first deionized water, the second deionized water and the third deionized water is 60-90 parts by mass; S4. Set the heating temperature of the reactor, add the first solution and the second solution into the reactor in sequence and stir, then add 25-50 parts by weight of an alcohol mixed solvent, stir, cool naturally, and filter to obtain a transparent high-barrier coating liquid.

3. A transparent high barrier coating film according to claim 2, characterized in that: In step S3, first add the third deionized water to the reactor, start stirring, the idling speed of the stirrer is 4000R / min, and the stirring speed is set to 40% of the idling speed; then add amino-modified PVA resin to the reactor, and the stirring speed is set to 60% of the idling speed.

4. A transparent high barrier coating film according to claim 3, characterized in that: In step S3, after the amino-modified PVA resin is completely dissolved, the heating temperature of the reactor is set to 95-98° C., the stirring speed is adjusted to 80% of the idling speed, and stirring is continued for 2 hours.

5. The transparent high barrier coating film according to claim 3, characterized in that: In step S4, the heating temperature of the reactor is 60°C; after adding the first solution and the second solution into the reactor, the stirring speed is maintained at 60°C and 80% of the idling speed for 30 minutes, and then the stirring speed is reduced to 60% of the idling speed, and an alcohol mixed solvent is added and stirred for 10 minutes; and the naturally cooled coating liquid is filtered through a 100-mesh filter.

6. A transparent high barrier coating film according to claim 1 or 2, characterized in that: The coupling agent is 1,2,3,4-butanetetracarboxylic acid; the filler is nano-scale spherical silica; and the alcohol mixed solvent is prepared by mixing ethanol and isopropanol in a mass ratio of 1:

1.

7. The transparent high barrier coating film according to claim 1, characterized in that: The base film (1) is one of HDPE, BOPP, PET and PA.

8. The transparent high barrier coating film according to claim 1, characterized in that: The primer layer (2) is prepared by coating the primer on the base film (1) through a reverse kiss coating process.

9. A method for preparing a transparent high barrier coating film according to any one of claims 1 to 8, characterized in that: The specific steps include: S1. preparing a transparent high barrier coating liquid; S2. A reverse kiss coating process is adopted to first apply a primer on the base film (1) to obtain a primer layer (2). After drying in an oven, a transparent high-barrier coating liquid is applied online on the primer layer (2) to obtain a coating layer (3). The transparent high-barrier coating film is then obtained by drying, winding and aging in sequence.

10. The method for preparing a transparent high-barrier coating film according to claim 9, characterized in that: The reverse kiss coating process is a reverse kiss coating process using a coater with double coating heads, wherein the first group of coating heads uses a 200-line anilox roller to coat the primer EA3250, and after oven drying, the second group of coating heads uses a 150-line anilox roller to coat the transparent high-barrier water-based coating liquid; in step S2, the aging temperature is 45°C and the aging time is 48 hours.

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