High-barrier water-based coating for soft packaging, preparation method and application thereof

Abstract

The application discloses a high-barrier water-based paint for soft packaging, a preparation method and application thereof. The high-barrier water-based paint comprises two polyurethane resins, one is a polyolefin type polyurethane, which is a polyurethane dispersion formed by polymerization of a polyolefin type polyol and a polyisocyanate; and the other is a crystalline polyurethane containing a hydroxyl group, which is a medium-high hydroxyl / high-crystalline polyurethane dispersion formed by polymerization of a polyester polyol and a polyisocyanate. The high-barrier water-based paint has excellent oxygen resistance, moisture resistance, adhesion, flexibility, wettability, chemical resistance and cooking resistance, and can be used for high-barrier soft packaging of paper, film and other substrates.

Description

Technical Field

[0001] This invention relates to the field of waterborne coating preparation technology, and in particular to a high-barrier coating with excellent high-barrier properties that can be used in film-based, paper-based flexible packaging and other fields, its preparation method and application. Background Technology

[0002] With the development of society and the economy, plastic pollution has become increasingly serious, causing severe harm to human society and the ecological environment. One of the largest sources of plastic pollution is the packaging industry, with plastic packaging accounting for 25%-40% of total plastic consumption. Moreover, the Chinese plastic market is still growing rapidly, reaching a scale of $70 billion by 2025. Among plastic packaging, composite flexible packaging has become one of the fastest-growing varieties due to its excellent comprehensive performance and cost-effectiveness. However, because composite flexible packaging combines the properties of different materials into a single composite packaging film through printing and lamination, it also increases the difficulty and cost of recycling.

[0003] In response to plastic pollution, the United Nations, in its environmental program report, pledged to achieve 100% reusable, recyclable, or compostable plastic packaging by 2025. Government signatories are collaborating with industry and other stakeholders to achieve a 70% recycling rate for plastic packaging by 2025. More than 180 global brands have joined the Circular Economy in Flexible Packaging (CEFLEX) organization, committed to achieving the recycling of all flexible packaging by 2025. Among the solutions for achieving recyclable flexible packaging, single-material recyclability is widely considered by the industry to be the mainstream form of sustainable packaging in the future, with over 80% of surveyed flexible packaging companies having or developing "single-material" flexible packaging products. However, the biggest problem with single-material flexible packaging is its barrier properties, which do not meet the requirements of some applications with long shelf lives. Therefore, there is a need to develop a high-barrier coating for flexible packaging that can meet the requirements of oxygen and moisture barrier properties without affecting the recycling of flexible packaging.

[0004] Patent CN102333803B describes a polyurethane dispersion and its manufacturing method. This polyurethane dispersion possesses both sealing and gas barrier properties and can be used as a tackifying coating agent for aluminum plating, thereby preparing a gas barrier film. However, although the polyurethane resin mentioned in this patent has certain barrier properties, it cannot meet the requirements of high-barrier packaging and must be used in conjunction with a coating, increasing the cost and process difficulty of packaging, and it cannot meet the requirements for retort resistance.

[0005] Patent CN 102533092A describes a polyurethane coating film-forming material, a polyurethane coating, and its applications. This polyurethane coating is mainly used as a topcoat for wood varnishes, applied to the surface of wood or wood primers, and can effectively reduce the release of formaldehyde from acid-cured coatings or substrates. However, this coating is only suitable for reducing formaldehyde release in the wood varnish field; its barrier properties do not meet the requirements in the flexible packaging field.

[0006] Patent CN 105585726A discloses a high-barrier polyester film, characterized in that the high-barrier polyester film is composed of a base film and a high-barrier resin coating applied and cured to one or both sides of the base film. The base film is a biaxially oriented polyester film made of polyethylene terephthalate, and the high-barrier resin coating is a coating liquid mainly composed of PVDC. This high-barrier polyester film has excellent oxygen and water vapor barrier effects; however, the thermal degradation temperature of PVDC is lower than the melting temperature of the film, thus affecting the film's recyclability. Therefore, materials containing PVDC can only be incinerated, but this also produces toxic gases, posing a threat to the environment.

[0007] Patent CN 116396604A describes a waterborne polyurethane high-barrier resin for food packaging and its preparation method. The modified waterborne polyurethane dispersion is a polyurethane prepolymer modified with an accelerator and methacrylic acid polyester, exhibiting excellent heat resistance, adhesion, environmental performance, and solvent resistance. This resin is primarily used as an adhesive in food packaging, and its barrier properties refer to water resistance; however, its resistance to water vapor and oxygen is poor, making it unsuitable for use as a barrier layer in single-material flexible packaging.

[0008] Patent CN 114316692A discloses an oxygen-barrier coating, its preparation method, and its application method. The oxygen-barrier coating is obtained by combining an acrylic high-oxygen-barrier coating with shellac. Although this coating has good oxygen barrier properties, the barrier properties of shellac, which is rich in hydroxyl and carboxyl groups, decrease significantly in high-humidity environments. Furthermore, shellac's heat resistance prevents its application in retort packaging.

[0009] Patent CN 115895357A discloses a biodegradable high-barrier film coating liquid, its preparation method, and its application. This biodegradable high-barrier film coating liquid is composed of the following components by mass percentage: 8%-10% polyvinyl alcohol, 0.5%-8% tetraethyl orthosilicate, 0-2% urea, 0-12% ethanol, and the balance being water. This coating liquid utilizes the condensation crosslinking of the active silanol groups of the hydrolysis products with the hydroxyl groups of PVA during the drying process, thereby improving the barrier properties of the coating. Although its oxygen barrier properties are particularly excellent, due to the high hydroxyl content of PVA, it has strong water absorption. In humid environments, its oxygen barrier properties decrease sharply, and its moisture barrier properties and resistance to boiling are relatively poor.

[0010] Current water-based high-barrier coatings struggle to simultaneously achieve oxygen barrier, moisture barrier, and retort resistance, hindering the recyclability of flexible packaging from a single material. However, as environmental concerns grow and national policies addressing plastic pollution become increasingly stringent, the recyclability of flexible packaging from a single material is undoubtedly the future trend. Therefore, there is an urgent need for high-barrier coating solutions that can replace existing barrier layers without compromising the recyclability of flexible packaging. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a method for preparing a polyurethane high-barrier coating. This coating has excellent oxygen and moisture barrier properties, excellent adhesion and wettability on films, and also excellent flexibility, chemical resistance, and resistance to boiling. It can achieve excellent barrier performance with low coating amount, realize the standardization of flexible packaging, and ultimately realize the recycling of flexible packaging.

[0012] Another object of the present invention is to provide a method for preparing such a high-barrier water-based coating for flexible packaging.

[0013] Another object of the present invention is to provide the application of such high-barrier water-based coatings for flexible packaging.

[0014] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0015] A high-barrier water-based coating for flexible packaging comprises the following components in weight percentage:

[0016] Component A: Based on the mass of component A

[0017] The first polyurethane dispersion is 5% to 45%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., preferably 10% to 30%;

[0018] The second polyurethane dispersion comprises 25% to 70%, for example, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., preferably 30% to 60%.

[0019] Water content is 5% to 30%, such as 5%, 10%, 15%, 20%, 25%, 30%, etc., preferably 10% to 25%;

[0020] pH adjuster 0.05-0.3%, such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc., preferably 0.05-0.2%;

[0021] The defoamer is 0.1% to 0.7%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, etc., preferably 0.2% to 0.6%.

[0022] The wetting agent is 5% to 30%, such as 5%, 10%, 15%, 20%, 25%, 30%, etc., preferably 10% to 25%;

[0023] Component B: Based on the mass of component B

[0024] The first crosslinking agent is 20-80%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., preferably 30-70%;

[0025] The second crosslinking agent is 20-80%, such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., preferably 30-70%;

[0026] The mass ratio of component A to component B is (5-20):1, for example, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, etc., preferably (5-15):1.

[0027] In this invention, the first polyurethane dispersion is a polyolefin-type polyurethane, which is a polyurethane dispersion polymerized from polyolefin polyols and polyisocyanates; the second polyurethane dispersion is a hydroxyl-containing crystalline polyurethane, which is a medium-high hydroxyl / high crystalline polyurethane dispersion polymerized from polyester polyols and polyisocyanates.

[0028] In some specific embodiments, the soft segment of the first polyurethane dispersion is a polyolefin polyol. Preferably, the solid content of the first polyurethane dispersion is 5-40 wt%, such as 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, etc., more preferably 10-40%; the weight-average molecular weight Mw is 5000-20000 g / mol, for example 5000 g / mol, 1 0000 g / mol, 15000 g / mol, 20000 g / mol, etc., preferably 5000~15000 g / mol; glass transition temperature Tg=-60~(-10)℃, for example -60℃, -55℃, -50℃, -45℃, -40℃, -35℃, -30℃, -25℃, -20℃, -15℃, -10℃, etc., preferably -40~(-120)℃; and it can be miscible with alcohol in an unlimited proportion.

[0029] In some preferred embodiments, the polyolefin polyol is a polyhydroxyolefin oligomer with a number average molecular weight of 500 to 15,000, such as 500, 1,000, 5,000, 10,000, 15,000, etc., and a functionality of at least 2 (e.g., 2, 3, 4, etc.); preferably, any one or more of the following: hydroxyl-terminated polybutadiene polyol, hydroxyl-terminated polybutadiene-acrylonitrile polyol, hydroxyl-terminated hydrogenated polybutadiene polyol, hydroxyl-terminated styrene-butadiene liquid rubber, polyisoprene polyol, and polyolefin polyol with a number average molecular weight of 500 to 5,000 and a functionality of 2 to 3.

[0030] In some preferred embodiments, the first polyurethane dispersion is a product of Wanhua Chemical. 1876 0225. Takelac in Mitsui Chemicals products TM One or more of WPB 341, but not limited to.

[0031] In some specific embodiments, the soft segment of the second polyurethane dispersion is a hydroxyl-containing polyester polyol. Preferably, the hydroxyl content of the second polyurethane dispersion is about 0.5–2.5 wt% (based on solid content), for example, 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.3 wt%, 2.5 wt%, etc., preferably 0.8–2%; the crystallization temperature is 15°C–50°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C. Temperatures range from 20°C to 40°C, preferably 20°C to 40°C; solid content ranges from 20°C to 50°C, for example, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, preferably 30% to 40%; weight-average molecular weight Mw = 5000 to 20000 g / mol, for example, 5000 g / mol, 10000 g / mol, 15000 g / mol, 20000 g / mol, preferably Mw = 10000 to 20000 g / mol; and it is miscible with alcohol in an unlimited proportion.

[0032] In some preferred embodiments, the second polyurethane dispersion is a product of Wanhua Chemical. 6512 6526、 4288, Covestro products One or more of U 2757, but not limited to.

[0033] In some specific implementation schemes, the first crosslinking agent is an epoxy silane coupling agent, among which commonly used ones include Dow Corning's 3-glycidyl etheroxypropyltrimethoxysilane Z-6040, 3-glycidyl etheroxypropyltrimethoxysilane Z6041, and 3-glycidyl etheroxypropylmethyldiethoxysilane Z6042, but are not limited to these.

[0034] In some specific implementation schemes, the second crosslinking agent is a polycarbodiimide crosslinking agent, among which commonly used ones include... XL-701 XL-702 XL-732 XL-755, Preferred XL-702 XL-732, etc., but not limited to these.

[0035] In some specific implementations, the pH adjuster comprises one or more of alkanolamines, ammonia, caustic soda, etc., among which commonly used ones include one or more of N-methylethanolamine (MMAE), dimethylethanolamine (DMEA), diethanolamine, triethylamine, triethanolamine, ammonia, and sodium hydroxide; ammonia, sodium hydroxide, methylethanolamine (DMEA), etc. are preferred.

[0036] In some specific implementations, the defoamer is one or more of polysiloxane defoamers and / or polyether siloxane defoamers, preferably BYK-024. Foamex1488, but not limited to this.

[0037] In some specific embodiments, the wetting agent is one or more small molecule alcohols, preferably ethanol, propanol, isopropanol, etc., but not limited to these.

[0038] In some specific implementation schemes, the water is deionized water.

[0039] On the other hand, the preparation method of the aforementioned high-barrier water-based coating for flexible packaging includes the following steps:

[0040] (1) Add the first polyurethane dispersion, the second polyurethane dispersion, water, pH adjuster, defoamer, and wetting agent to the paint mixing tank and stir evenly to obtain component A;

[0041] (2) Add the first crosslinking agent and the second crosslinking agent to another paint mixing tank and stir evenly to obtain component B;

[0042] (3) Mix components A and B to obtain the final high-barrier water-based coating.

[0043] On the other hand, the high-barrier waterborne coatings described in this invention or the high-barrier waterborne coatings for flexible packaging prepared by the method can be mainly used for high-barrier flexible packaging such as paper-based and film-based packaging, replacing the original barrier layer, realizing the standardization of flexible packaging, and ultimately achieving the recyclability of flexible packaging.

[0044] Specifically, the application involves applying the high-barrier water-based coating of the present invention to a thin film substrate by roller coating, with a dry film thickness of 0.8–1.2 μm, baking conditions of 80°C for 30 seconds, and curing at 40°C for 48 hours to test adhesion, barrier properties, and other performance characteristics.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] (1) In this invention, the soft segment of the first waterborne polyurethane dispersion is selected as a polyolefin polyol. This type of soft segment can effectively increase the rotational freedom of the polymer chain, making the polyurethane polymer backbone softer and easier to wet the substrate surface, thus enhancing the adhesion between interfaces. Secondly, the backbone of the polyolefin polyol is similar or consistent with the backbone structure of the polyolefin substrate. According to the principle of similar compatibility and adhesion mechanism, it is easy to wet and level with the polyolefin surface, thereby forming a strong adhesion. This allows the polyurethane to form a strong adhesion and bond with the polyolefin substrate through chemical bonds and other means. Thirdly, the polyhydroxyolefin oligomer has the properties of natural rubber and polyolefin polymers, such as strong hydrophobicity, excellent hydrolysis resistance, water resistance, electrical insulation, acid and alkali resistance, flexibility and aging resistance. This gives the polyurethane excellent chemical resistance, adhesion and good flexibility.

[0047] (2) The second waterborne polyurethane selected in this invention is a hydroxyl-containing crystalline polyurethane. The soft segment of the second waterborne polyurethane is a polyester polyol or a polyether polyol, which has a regular molecular structure and a relatively dense arrangement between molecules, resulting in less space for molecular movement and thus easier crystallization. Furthermore, the hydrogen bonds inherent in the polyester and polyether polyols strengthen the intermolecular bonding. Therefore, molecules such as water and oxygen have difficulty passing through, exhibiting good barrier properties.

[0048] (3) The formulation of this invention incorporates an epoxy-based polysiloxane crosslinking agent. The silicon-oxygen bonds readily form bridging and hydrogen bonds with the substrate surface, which can further improve the adhesion of the coating to the film substrate. The epoxy groups can react with the hydroxyl groups of the second hydroxyl PUD, reducing the hydroxyl content, improving water resistance, and increasing the crosslinking density of the coating, thereby reducing the water vapor and oxygen permeability of the coating.

[0049] (4) The formulation of this invention incorporates a polycarbodiimide crosslinking agent, which undergoes a crosslinking reaction with the carboxyl groups in the polyurethane during the baking and film-forming process. This further increases the degree of crosslinking of the barrier coating during film formation, making the intermolecular density more compact and thus further improving the oxygen and moisture barrier properties of the coating. In addition, the consumption of carboxyl groups in the resin greatly reduces the water absorption of the formulation, thereby improving the resistance of the barrier coating to boiling. Detailed Implementation

[0050] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0051] Performance testing methods:

[0052] 1. Preparation of test samples

[0053] The substrate is a 12-micron PET film, with a high-barrier water-based coating applied to the corona-treated surface at a coating weight of 1 g / m². 2 The film is baked at 80℃ for 30 seconds and cured at 40℃ for 48 hours. Then, it is laminated with a PET film using an adhesive to prepare a single-material PET film with a PET-high-barrier-adhesive-PET structure.

[0054] 2. Oxygen transmission rate:

[0055] The oxygen permeability of the test sample at 23°C and 0% RH was measured using an oxygen permeability measuring device (OX-TRAN, Mocon) according to Method B (isobaric method) of JIS K 7126 (2000). The test was performed three times, and the average value was taken.

[0056] 3. Water vapor transmission rate:

[0057] The water vapor transmission rate of the test sample at 40°C and 90% RH was determined using a water vapor transmission rate measuring device (Permatran, Mocon) according to Method B (infrared sensor method) of JlSK7129 (2000). Three tests were performed, and the average value was taken.

[0058] 4. Adhesion:

[0059] The substrate is a 12-micron PET film, with a high-barrier water-based coating applied to the corona-treated surface at a coating weight of 1 g / m². 2 Bake at 80℃ for 30 seconds, then cure at 40℃ for 24 hours. Apply the barrier coating to the surface of the PET film using 3M tape, and rate the adhesion based on the amount of coating peeling off. 5B represents the worst adhesion, complete peeling; 5B represents the best adhesion, no peeling at all.

[0060] 5. Flexibility:

[0061] The substrate is a 12-micron PET film, with a high-barrier water-based coating applied to the corona-treated surface at a coating weight of 1 g / m². 2 Bake at 80℃ for 30 seconds, then cure at 40℃ for 24 hours. Fold the cured film repeatedly along a certain line 5 times and observe whether cracks appear in the paint film. If cracks appear, it is considered Failed; if no cracks appear, it is considered Pass.

[0062] 6. Boiling resistance test:

[0063] The prepared single-material PET film was boiled in hot water at 90℃ for 30 minutes. The oxygen permeability and water vapor permeability of the film after boiling were tested. The oxygen permeability and water vapor permeability of the unboiled film were compared to determine the degree of its boiling resistance.

[0064] Example 1

[0065] The raw material components required for the preparation process of a high-barrier water-based coating are shown in Table 1:

[0066] Table 1

[0067]

[0068] Its characteristic is that the ratio of component A to component B is 100:20.

[0069] The specific preparation steps are as follows:

[0070] (1) 30g 1876, 30g 6512, 14.6g deionized water, 0.1g ammonia, 0.3g BYK-024, and 25g ethanol were added sequentially to a paint mixing tank and stirred until homogeneous to obtain component A.

[0071] (2) Add 6g Z-6040 and 14g XL-702 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0072] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0073] Example 2

[0074] The raw material components required for the preparation process of a high-barrier water-based coating are shown in Table 2:

[0075] Table 2

[0076]

[0077] Its characteristic is that the ratio of component A to component B is 100:15.

[0078] The specific preparation steps are as follows:

[0079] (1) Take 20g 0225, 40g 6526, 24.6g deionized water, 0.1g sodium hydroxide, 0.3g BYK-024, and 15g isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0080] (2) Add 6g Z-6041 and 9g XL-702 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0081] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0082] Example 3

[0083] The raw material components required for the preparation process of a high-barrier water-based coating are shown in Table 3:

[0084] Table 3

[0085]

[0086] Its characteristic is that the ratio of component A to component B is 100:10.

[0087] The specific preparation steps are as follows:

[0088] (1) Take 10g of TAKELAC TM WPB 341, 60g 4288, 19.6g deionized water, 0.1g DMEA, 0.3g Foamex 1488 and 10g of isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0089] (2) Add 6g Z-6042 and 4g XL-732 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0090] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0091] Example 4

[0092] The raw material components required for the preparation process of a high-barrier water-based coating are shown in Table 4:

[0093] Table 4

[0094]

[0095] Its characteristic is that the ratio of component A to component B is 100:10.

[0096] The specific preparation steps are as follows:

[0097] (1) 15g 1876, 50g U 2757, 14.6g deionized water, 0.1g ammonia, 0.3g BYK-024, and 20g isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0098] (2) Add 5g Z-6040 and 5g XL-755 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0099] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0100] Example 5

[0101] The raw material components required for the preparation process of a high-barrier water-based coating are shown in Table 5:

[0102] Table 5

[0103]

[0104]

[0105] Its characteristic is that the ratio of component A to component B is 100:6.6.

[0106] The specific preparation steps are as follows:

[0107] (1) Take 25g of TAKELAC TM WPB 341, 45g 6512, 14.6g deionized water, 0.1g sodium hydroxide, 0.3g BYK-024, and 15g ethanol were added sequentially to a paint mixing tank and stirred until homogeneous to obtain component A.

[0108] (2) Add 4.6g Z-6041 and 2g XL-732 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0109] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0110] Comparative Example 1

[0111] The oxygen permeability of a 12-micron PET film without the high-barrier water-based coating layer of this invention was tested to be 115 g / m³. 2 • 24h, water vapor transmission rate is 58ml / m 2 24h MPa.

[0112] Comparative Example 2

[0113] Instead of using the first polyurethane dispersion, it was replaced with an equal amount of deionized water, and only the second polyurethane dispersion was used, with the rest being the same as in Example 4.

[0114] The specific preparation steps are as follows:

[0115] (1) 50g U 2757, 29.6g deionized water, 0.1g ammonia, 0.3g BYK-024, and 20g isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0116] (2) Add 5g Z-6040 and 5g XL-755 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0117] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0118] Comparative Example 3

[0119] Instead of using the second polyurethane dispersion, it was replaced with an equal amount of deionized water. Only the first polyurethane dispersion was used, and the rest was the same as in Example 4.

[0120] The specific preparation steps are as follows:

[0121] (1) 15g 1876 ​​g of deionized water, 64.6 g of ammonia, 0.1 g of BYK-024, and 20 g of isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0122] (2) Add 5g Z-6040 and 5g XL-755 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0123] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0124] Comparative Example 4

[0125] Reduce the amount of the second polyurethane dispersion and replace the reduced amount with an equal amount of deionized water; otherwise, it is the same as in Example 4.

[0126] The specific preparation steps are as follows:

[0127] (1) 15g 1876, 15g U 2757, 49.6g deionized water, 0.1g ammonia, 0.3g BYK-024, and 20g isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0128] (2) Add 5g Z-6040 and 5g XL-755 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0129] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0130] Comparative Example 5

[0131] Instead of using the first crosslinking agent, replace it with an equal amount of deionized water, and use the second crosslinking agent exclusively. The rest is the same as in Example 4.

[0132] The specific preparation steps are as follows:

[0133] (1) 15g 1876, 50g U 2757, 14.6g deionized water, 0.1g ammonia, 0.3g BYK-024, and 20g isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0134] (2) Add 5g of deionized water and 5g of... XL-755 was added to another paint mixing tank and stirred until homogeneous to obtain component B;

[0135] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0136] Comparative Example 6

[0137] Instead of using the second crosslinking agent, replace it with an equal amount of deionized water, and use only the first crosslinking agent, the rest is the same as in Example 4.

[0138] The specific preparation steps are as follows:

[0139] (1) 15g 1876, 50g U 2757, 14.6g deionized water, 0.1g ammonia, 0.3g BYK-024, and 20g isopropanol were added sequentially to the paint mixing tank and stirred until homogeneous to obtain component A.

[0140] (2) Add 5g Z-6040 and 5g deionized water to another paint mixing tank and stir evenly to obtain component B;

[0141] (3) Mix components A and B to obtain the final water-based high-barrier coating liquid.

[0142] Performance test results are shown in Table 5:

[0143] Table 5

[0144]

[0145]

[0146] Conclusion: As can be seen from Table 5, Examples 1-5 have better oxygen barrier, water vapor barrier, adhesion, flexibility and cooking resistance compared with Comparative Examples 1-6.

[0147] According to the specific implementation described above, the high-barrier waterborne coating obtained by the present invention has excellent oxygen and moisture barrier properties, excellent adhesion and wettability on the film, and also has excellent flexibility, chemical resistance and boiling resistance, and can achieve excellent barrier performance with low coating amount.

[0148] The above descriptions are only some examples of the present invention. Due to space limitations, other examples of the present invention cannot be listed one by one. However, any equivalent modifications or changes in proportions made to the above examples within the formula and process specified in the present invention based on the technical principles of the present invention are within the protection scope of the present invention.

Claims

1. A high barrier water-based coating for flexible packaging, characterized by, Components in the following mass percentage: Component A: based on the mass of component A Component B: based on the mass of component B The first crosslinking agent 20-80%; The second crosslinking agent 20-80%; The mass ratio of component A to component B is (5-20):1; The soft segment of the first polyurethane dispersion is a polyolefin-based polyol; The soft segment of the second polyurethane dispersion is a hydroxyl-containing polyester polyol; The first crosslinking agent is an epoxy silane coupling agent crosslinking agent; The second crosslinking agent is a polycarbodiimide crosslinking agent.

2. The high barrier water-based coating for flexible packaging according to claim 1, characterized in that, Components in the following mass percentage: Component A: based on the mass of component A Component B: based on the mass of component B The first crosslinking agent 30-70%; The second crosslinking agent 30-70%; The mass ratio of component A to component B is (5-15):

1.

3. The high barrier water-based coating for flexible packaging according to claim 1 or 2, characterized in that, The solid content of the first polyurethane dispersion is 5-40wt%; the molecular weight Mw=5000-20000g / mol; the glass transition temperature Tg=-60--10℃; and it can be mixed with alcohol in any proportion.

4. The high barrier water-based coating for flexible packaging according to claim 3, characterized in that, The solid content of the first polyurethane dispersion is 10-40wt%; the molecular weight 5000-15000g / mol; the glass transition temperature Tg=-40--20℃.

5. The high barrier water-based coating for flexible packaging according to claim 1 or 2, characterized in that, The polyolefin-based polyol is any one or more of a polyhydroxy olefin oligomer with a number average molecular weight of 500-15000g / mol and a functionality of at least 2.

6. The high barrier water-based coating for flexible packaging according to claim 5, characterized in that, The polyolefin-based polyol is any one or more of a hydroxyl-terminated polybutadiene polyol, a hydroxyl-terminated polybutadiene-acrylonitrile polyol, a hydroxyl-terminated hydrogenated polybutadiene polyol, a hydroxyl-terminated butadiene-styrene liquid rubber, and a polyisoprene polyol, each with a number average molecular weight of 500-5000g / mol and a functionality of 2-3.

7. The high barrier water-based coating for flexible packaging according to claim 3, characterized in that, The first polyurethane dispersion is selected from the group consisting of 1876、 0225, TAKELAC by Mitsui Chemicals TM one or more of WPB 341.

8. The high barrier water-based coating for flexible packaging according to claim 1 or 2, characterized in that, The second polyurethane dispersion has a hydroxyl content of 0.5-2.5wt%, a crystallization temperature of 15-50℃, a solid content of 30-50wt%, a molecular weight Mw=10000-20000g / mol, and can be mixed with alcohol in any proportion.

9. The high barrier water-based coating for flexible packaging according to claim 8, characterized in that, The second polyurethane dispersion is selected from Wanhua Chemical. 6512 6526、 4288, Covestro One or more of U2757.

10. The high barrier water-based coating for flexible packaging according to claim 1 or 2, characterized in that, The first crosslinking agent is at least any one of Dow Corning's 3-glycidyl ether oxypropyl trimethoxysilane Z-6040, 3-glycidyl ether oxypropyl trimethoxysilane Z6041, and 3-glycidyl ether oxypropyl methyldiethoxysilane Z6042; The second crosslinking agent is at least one of Star XL-701, XL-702, XL-732, XL-755.

11. The high barrier water-based coating for flexible packaging according to claim 1 or 2, characterized in that, The pH regulator is selected from one or more of alkanolamine, ammonia, and caustic soda; and / or The defoaming agent is selected from one or more of polysiloxane defoaming agent and / or polyether siloxane defoaming agent; The wetting agent is a small molecule alcohol.

12. The high barrier water-based coating for flexible packaging according to claim 11, characterized in that, The pH regulator is selected from one or more of N-methyl ethanolamine (MMAE), dimethyl ethanolamine (DMEA), diethanolamine, triethylamine, triethanolamine, ammonia, and sodium hydroxide; and / or The defoaming agent is selected from the group consisting of BYK-024, one or more of Foamex 1488; The wetting agent is one or more of ethanol and isopropyl alcohol.

13. Process for the preparation of a high barrier waterborne coating for flexible packaging according to any one of claims 1 to 12, characterized in that, The method comprises the following steps: (1) adding the first polyurethane dispersion, the second polyurethane dispersion, water, the pH regulator, the defoaming agent, and the wetting agent into a paint mixing tank, stirring uniformly to obtain component A; (2) adding the first crosslinking agent and the second crosslinking agent into another paint mixing tank, stirring uniformly to obtain component B; (3) mixing A and B components to obtain the final high-barrier waterborne coating.

14. Use of the high-barrier waterborne coating for flexible packaging according to any one of claims 1 to 12 or prepared according to the method of claim 13 in the field of high-barrier flexible packaging.

15. Use according to claim 14, characterized in that, High-barrier coating for the field of film-based, paper-based flexible packaging.

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