High-barrier water-based paint for flexible package as well as preparation method and application of high-barrier water-based paint

Abstract

The invention discloses a high-barrier water-based paint for flexible packaging, and a preparation method and application thereof. The high-barrier water-based paint comprises two types of polyurethane resin, wherein one type of polyurethane resin is polyolefin type polyurethane which is a polyurethane dispersion formed by polymerizing polyolefin polyol and polyisocyanate; and the other one is hydroxyl-containing crystalline polyurethane which is a medium-high hydroxyl / high-crystalline polyurethane dispersion formed by polymerizing polyester polyol and polyisocyanate. The high-barrier water-based paint disclosed by the invention has excellent oxygen barrier property, moisture barrier property, adhesive force, flexibility, wettability, chemical resistance, steaming and boiling resistance and the like, and can be used for high-barrier flexible packaging of base materials such as paper and films.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of waterborne coatings, and particularly relates to a high-barrier coating with excellent high-barrier properties, which can be used in fields such as film-based and paper-based flexible packaging, a preparation method and an application thereof. Background Art

[0002] With the development of social economy, plastic pollution has become increasingly serious, causing serious harm to human society and the ecological environment. One of the biggest sources of plastic pollution is the packaging industry, and plastic packaging accounts for 25%-40% of the total plastic consumption. Moreover, the scale of the Chinese plastic market is still growing rapidly, and it will reach 70 billion US dollars by 2025. Among plastic packaging, composite flexible packaging has become one of the fastest-growing varieties in plastic packaging due to its good comprehensive performance and cost performance. However, since composite flexible packaging concentrates the characteristics of different materials on a 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 promised in the environmental program report to achieve 100% reusable, recyclable or compostable plastic packaging by 2025. Government signatories cooperate with industries and other stakeholders to achieve a 70% plastic packaging recycling rate by 2025. More than 180 global brand owners have joined the Circular Economy for Flexible Packaging (CEFLEX) and are committed to achieving the circular use of all flexible packaging by 2025. Among the solutions for making flexible packaging recyclable, single-material recyclability is widely regarded as the mainstream form of future sustainable packaging in the industry, and more than 80% of the surveyed flexible packaging enterprises have or are developing "single-material" flexible packaging products. However, the biggest problem with single-material flexible packaging is the poor barrier property, which cannot meet the requirements of some application fields with a longer shelf life. Therefore, it is necessary to develop a high-barrier coating that can be used for flexible packaging, which can not only meet the requirements of oxygen and moisture barrier, but also does not affect the recycling of flexible packaging.

[0004] Patent CN102333803B introduces a polyurethane dispersion and a manufacturing method thereof. The polyurethane dispersion has both sealing properties and gas barrier properties and can be used as a tackifying coating agent for lamination with aluminized film to prepare 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 combination with a coating layer, which increases the cost and process difficulty of packaging and cannot meet the requirements of retort resistance.

[0005] Patent CN 102533092A introduces a polyurethane coating film-forming substance, a polyurethane coating and an application thereof. The polyurethane coating is mainly used for the topcoat of wooden furniture and is coated on the surface of wooden furniture or the primer of wooden furniture, which can effectively reduce the release of formaldehyde in acid-curing coatings or substrates. However, this coating is only applicable to the field of wooden furniture coatings to reduce formaldehyde release, and its barrier performance cannot meet the requirements in the field of flexible packaging.

[0006] Patent CN 105585726A introduces a high-barrier polyester film, which is characterized in that the high-barrier polyester film is composed of a base film and a high-barrier resin coating applied and cured on one or both sides of the base film. The base film is a biaxially oriented polyester film prepared from polyethylene terephthalate, and the high-barrier resin coating is a coating solution mainly composed of PVDC. This high-barrier polyester film has excellent oxygen and water vapor barrier effects, but the thermal degradation temperature of PVDC is lower than the melting temperature of the film, which affects the recycling of the film. Therefore, materials containing PVDC can only be incinerated, but this also produces toxic gases and harms the environment.

[0007] Patent CN 116396604A introduces an aqueous polyurethane high-barrier resin for food packaging and its preparation method. The modified aqueous polyurethane dispersion is a polyurethane prepolymer modified by a promoter and methacrylic acid oligomer ester, and has excellent heat resistance, adhesion, environmental protection performance and solvent resistance. The main application of this resin is as a binder for food packaging, and its barrier performance refers to water resistance, but its water vapor and oxygen barrier performances are poor and it cannot be applied to the barrier layer of single-material flexible packaging.

[0008] Patent CN 114316692A discloses an oxygen high-barrier coating, a preparation method and a coating method. The oxygen high-barrier coating therein is obtained by compounding an acrylate high-oxygen barrier coating and shellac. Although the oxygen barrier property of this coating is relatively good, due to the rich hydroxyl and carboxyl groups in shellac, the barrier property will decrease extremely in a humid environment, and the heat resistance of shellac makes it inapplicable to retort packaging.

[0009] Patent CN 115895357A discloses a degradable high-barrier film coating solution, its preparation method and application. The degradable high-barrier film coating solution is composed of the following components in mass percentage: 8%-10% polyvinyl alcohol, 0.5%-8% tetraethyl orthosilicate, 0%-2% urea, 0%-12% ethanol, and the balance is water. This coating solution uses the active silanol groups of the hydrolysis product and the hydroxyl groups of PVA to condense and crosslink during the drying process, improving the barrier performance of the coating. Although the oxygen barrier property is particularly excellent, due to the high content of hydroxyl groups in PVA, it has strong water absorption, and the oxygen barrier property will decrease sharply in a humid environment, and its moisture barrier and retort resistance performances are relatively poor.

[0010] At present, it is very difficult for current aqueous high-barrier coatings to balance oxygen barrier, moisture barrier and retort resistance performances, and they cannot help flexible packaging achieve recyclability through a single material. With the increasing attention of humans to environmental issues and the increasingly stringent governance policies of various countries on plastic pollution problems, the recyclability of single-material flexible packaging is inevitably the future development trend. Therefore, there is an urgent need for a high-barrier coating solution that can replace the original barrier layer and does not affect the recycling of flexible packaging. Summary of the Invention

[0011] The present invention provides a preparation method of a polyurethane high-barrier coating to solve the problems existing in the prior art. This coating has excellent oxygen and moisture barrier properties, excellent adhesion and wettability on films, and also has excellent flexibility, chemical resistance, and retort resistance, etc. It can achieve excellent barrier performance at a low coating amount, realize the simplification of flexible packaging, and ultimately achieve the recycling of flexible packaging.

[0012] Another object of the present invention is to provide a preparation method of this high-barrier waterborne coating for flexible packaging.

[0013] Still another object of the present invention is to provide the application of this high-barrier waterborne coating for flexible packaging.

[0014] In order to achieve the above-mentioned invention objects, the present invention provides the following technical solutions:

[0015] A high-barrier waterborne coating for flexible packaging, comprising components with the following mass percentages:

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

[0017] The first polyurethane dispersion 5 - 45%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., preferably 10 - 30%;

[0018] The second polyurethane dispersion 25 - 70%, such as 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., preferably 30 - 60%;

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

[0020] pH regulator 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] Defoamer 0.1 - 0.7%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, etc., preferably 0.2 - 0.6%;

[0022] Wetting agent 5 - 30%, such as 5%, 10%, 15%, 20%, 25%, 30%, etc., preferably 10 - 25%;

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

[0024] The first crosslinking agent is 20-80%, such as 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] Among them, the mass ratio of component A to component B is (5-20):1, such as 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 the present invention, the first polyurethane dispersion is a polyolefin-based polyurethane, a polyurethane dispersion formed by polymerizing polyolefin polyols and polyisocyanates; the second polyurethane dispersion is a hydroxyl-containing crystalline polyurethane, a medium-high hydroxyl / high crystalline polyurethane dispersion formed by polymerizing 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., preferably 10-40%; the weight-average molecular weight Mw = 5000-20000 g / mol, such as 5000 g / mol, 10000 g / mol, 15000 g / mol, 20000 g / mol, etc., preferably 5000-15000 g / mol; the glass transition temperature Tg = -60-(-10) °C, such as -60 °C, -55 °C, -50 °C, -45 °C, -40 °C, -35 °C, -30 °C, -25 °C, -20 °C, -15 °C, -10 °C, etc., preferably -40-(-120) °C; and it can be miscible with alcohol in any proportion.

[0029] In some preferred embodiments, the polyolefin polyol is a polyhydroxy olefin oligomer having 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 (such as 2, 3, 4, etc.); preferably any one or more of hydroxyl-terminated polybutadiene polyols, hydroxyl-terminated polybutadiene-acrylonitrile polyols, hydroxyl-terminated hydrogenated polybutadiene polyols, hydroxyl-terminated styrene-butadiene liquid rubbers, polyisoprene polyols, and polyolefin polyols having a number average molecular weight of 500 to 5,000 and a functionality of 2 to 3.

[0030] In some more preferred embodiments, the first polyurethane dispersion is one of 1876, 0225, and TAKELAC of Mitsui Chemicals TM WPB 341, or more than one of them, but not limited thereto.

[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 to 2.5 wt% (based on the solid content), such as 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 to 2%; the crystallization temperature is 15°C to 50°C, such as 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, etc., preferably 20°C to 40°C; the solid content is 20 to 50 wt%, such as 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, etc., preferably 30 to 40%; the weight average molecular weight Mw = 5,000 to 20,000 g / mol, such as 5,000 g / mol, 10,000 g / mol, 15,000 g / mol, 20,000 g / mol, etc., preferably Mw = 10,000 to 20,000 g / mol; and it can be miscible with alcohol in any proportion.

[0032] In some preferred embodiments, the second polyurethane dispersion is one of 6512, 6526, 4288, and one of U 2757 of Covestro, or more than one of them, but not limited thereto.

[0033] In some specific embodiments, the first crosslinking agent is an epoxy silane coupling agent crosslinking agent, among which commonly used ones include 3-glycidoxypropyltrimethoxysilane Z-6040, 3-glycidoxypropyltrimethoxysilane Z6041, 3-glycidoxypropylmethyldiethoxysilane Z6042, etc. of Dow Corning Corporation, but not limited thereto.

[0034] In some specific embodiments, the second crosslinking agent is a polycarbodiimide crosslinking agent, among which commonly used ones include XL-701, XL-702, XL-732, XL-755, preferably XL-702, XL-732, etc., but not limited thereto.

[0035] In some specific embodiments, the pH regulator includes one or more of alkanolamines, ammonia water, caustic alkalis, etc. Among them, commonly used ones include one or more of N-methylethanolamine (MMAE), dimethylethanolamine (DMEA), diethanolamine, triethylamine, triethanolamine, ammonia water, sodium hydroxide; preferably ammonia water, sodium hydroxide, methylethanolamine (DMEA), etc.

[0036] In some specific embodiments, the defoaming agent is one or more of polysiloxane defoaming agents and / or polyether polysiloxane defoaming agents, preferably BYK-024, Foamex1488, but not limited thereto.

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

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

[0039] On the other hand, the preparation method of the aforementioned high-barrier waterborne coating for flexible packaging is as follows:

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

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

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

[0043] On the other hand, the high-barrier waterborne coating of the present invention or the high-barrier waterborne coating for flexible packaging prepared by the method can be mainly used for high-barrier flexible packaging such as paper-based and film-based, replacing the original barrier layer, realizing the simplification of flexible packaging, and ultimately enabling the recyclability of flexible packaging.

[0044] Specifically, for the application, the high-barrier waterborne coating of the present invention is roll-coated on a film substrate, with a dry film thickness of 0.8 - 1.2 μm, baked at 80 °C for 30 s and taken off the production line; cured at 40 °C for 48 h, and then the properties such as adhesion and barrier property are tested.

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

[0046] (1) In the present invention, the soft segment of the first aqueous polyurethane dispersion is selected as polyolefin polyol. Such soft segments can well increase the rotational freedom of the polymer chain, make the main chain of the polyurethane polymer become soft, be easy to wet the surface of the substrate, and enhance the adhesion between interfaces. Secondly, the main chain of the polyolefin polyol is similar or identical to the main chain structure of the polyolefin substrate. According to the principle of similar compatibility and the adhesion mechanism, it is easy to wet and level on the polyolefin surface, and then form a firm adhesion, so that the polyurethane can generate a firm adhesion and bonding with the polyolefin substrate by means of chemical bonds, etc. Thirdly, the polyhydroxyolefin oligomer has the properties of polymers such as natural rubber and polyolefin, with strong hydrophobicity, excellent hydrolysis resistance, water resistance, electrical insulation, acid and alkali resistance, flexibility and aging resistance, making the polyurethane have excellent chemical resistance, adhesion and good flexibility.

[0047] (2) The second aqueous polyurethane selected in the present invention is a hydroxyl-containing crystalline polyurethane. The soft segment of the second aqueous polyurethane is polyester polyol or polyether polyol, its molecular structure is regular, the arrangement between molecules is relatively dense, and the space for molecular movement is small, so it is relatively easy to crystallize. Secondly, the hydrogen bonds of the polyester and polyether polyols themselves make the intermolecular binding force between them stronger. Therefore, it is more difficult for molecules such as water molecules and oxygen molecules to pass through, and it has relatively good barrier properties.

[0048] (3) An epoxy-based polysiloxane crosslinking agent is added to the formula of the present invention. The silicon-oxygen bond is easy to form a bridge and hydrogen bond with the substrate surface, which can further improve the adhesion of the coating on the film substrate. The epoxy group can react with the hydroxyl group of the second hydroxyl PUD, reduce the hydroxyl content, improve the water resistance while increasing the crosslinking density of the coating, and thus reduce the water vapor and oxygen transmission rates of the coating.

[0049] (4) In the formulation of the present invention, a polycarbodiimide crosslinking agent is added, which undergoes a crosslinking reaction with the carboxyl groups in the polyurethane during the baking film-forming process, further improving the crosslinking degree of the barrier coating during the film-forming process, making the intermolecular structure denser, and further enhancing 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, improving the retort resistance of the barrier coating. Detailed implementation manners

[0050] To better understand the technical solution of the present invention, the content of the present invention will be further elaborated below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0051] Performance test methods:

[0052] 1. Preparation of test samples

[0053] The substrate is a 12-micron PET film. A high-barrier waterborne coating is applied to the corona-treated surface, and the coating amount is 1 g / m 2 , baked at 80 °C for 30 s, and cured at 40 °C for 48 h. Then, it is laminated with the PET film through an adhesive to prepare a single-layer PET film with a PET-high-barrier film-adhesive-PET structure.

[0054] 2. Oxygen transmission rate:

[0055] Using an oxygen transmission rate measuring device (OX-TRAN, Mocon), the oxygen transmission rate of the test sample is measured at 23 °C and 0% RH according to Method B (isobaric method) of JIS K7126 (2000). The measurement is carried out three times, and the average value is taken.

[0056] 3. Water vapor transmission rate:

[0057] Using a water vapor transmission rate measuring device (Permatran, manufactured by Mocon), the water vapor transmission rate of the test sample is measured at 40 °C and 90% RH according to Method B (infrared sensor method) of JlSK7129 (2000). The measurement is carried out three times, and the average value is taken.

[0058] 4. Adhesion:

[0059] The substrate is a 12-micron PET film. A high-barrier waterborne coating is applied to the corona-treated surface, and the coating amount is 1 g / m 2 , baked at 80 °C for 30 s, and cured at 40 °C for 24 h. The barrier coating on the surface of the PET film is adhered with 3M tape, and the adhesion is rated according to the amount of coating peeling. 5B represents the worst adhesion and complete peeling; 5A represents the best adhesion and no peeling at all.

[0060] 5. Flexibility:

[0061] The base material is a 12-micron PET film, and a high-barrier waterborne coating is applied on the corona-treated surface with a coating amount of 1 g / m 2 , baked at 80°C for 30 s, and cured at 40°C for 24 h. The cured film is repeatedly folded 5 times along a certain line, and it is observed whether cracks appear in the paint film. If cracks appear, it is regarded as Failed; if not, it is regarded as Pass.

[0062] 6. Retort test:

[0063] The prepared single-material PET film is cooked in hot water at 90°C for 30 min, and the oxygen transmission rate and water vapor transmission rate of the film after cooking are measured. The oxygen transmission rate and water vapor transmission rate of the uncooked film are compared to judge the quality of the retort resistance performance.

[0064] Example 1

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

[0066] Table 1

[0067]

[0068] It is characterized in that the ratio of component A to component B is 100:20.

[0069] The specific preparation steps are as follows:

[0070] (1) Add 30 g 1876, 30 g 6512, 14.6 g deionized water, 0.1 g ammonia water, 0.3 g BYK-024, and 25 g ethanol into the paint mixing tank in sequence, stir evenly to obtain component A;

[0071] (2) Add 6 g Z-6040 and 14 g XL-702 into another paint mixing tank, stir evenly to obtain component B;

[0072] (3) Mix component A and component B to obtain the final waterborne high-barrier coating solution.

[0073] Example 2

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

[0075] Table 2

[0076]

[0077] It is characterized in that the ratio of component A to component B is 100:15.

[0078] The specific preparation steps are as follows:

[0079] (1) Add 20 g 0225, 40 g 6526, 24.6 g of deionized water, 0.1 g of sodium hydroxide, 0.3 g of BYK-024, and 15 g of isopropanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0080] (2) Add 6 g of Z-6041, 9 g XL-702 into another paint mixing tank, and stir evenly to obtain Component B;

[0081] (3) Mix Component A and Component B to obtain the final waterborne high-barrier coating solution.

[0082] Example 3

[0083] The raw material components required in the preparation process of a high-barrier waterborne coating are shown in Table 3 as follows:

[0084] Table 3

[0085]

[0086] It is characterized in that the ratio of Component A to Component B is 100:10.

[0087] The specific preparation steps are as follows:

[0088] (1) Add 10 g of TAKELAC TM WPB 341, 60 g 4288, 19.6 g of deionized water, 0.1 g of DMEA, 0.3 g Foamex1488, 10 g of isopropanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0089] (2) Add 6 g of Z-6042, 4 g XL-732 into another paint mixing tank, and stir evenly to obtain Component B;

[0090] (3) Mix Component A and Component B to obtain the final waterborne high-barrier coating solution.

[0091] Example 4

[0092] The raw material components required in the preparation process of a high-barrier waterborne coating are shown in Table 4 as follows:

[0093] Table 4

[0094]

[0095] It is characterized in that the ratio of Component A to Component B is 100:10.

[0096] The specific preparation steps are as follows:

[0097] (1) Add 15 g 1876, 50 g U 2757, 14.6 g deionized water, 0.1 g ammonia water, 0.3 g BYK-024, and 20 g isopropanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0098] (2) Add 5 g Z-6040 and 5 g XL-755 into another paint mixing tank, and stir evenly to obtain Component B;

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

[0100] Example 5

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

[0102] Table 5

[0103]

[0104]

[0105] It is characterized in that the ratio of Component A to Component B is 100:6.6.

[0106] The specific preparation steps are as follows:

[0107] (1) Add 25 g TAKELAC TM WPB 341, 45 g 6512, 14.6 g deionized water, 0.1 g sodium hydroxide, 0.3 g BYK-024, and 15 g ethanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0108] (2) Add 4.6 g Z-6041 and 2 g XL-732 into another paint mixing tank, and stir evenly to obtain Component B;

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

[0110] Comparative Example 1

[0111] The substrate is a 12-micron PET film without the high-barrier water-based coating layer of the present invention, and its oxygen transmission rate is tested to be 115 g / m 2 ·24 h, and the water vapor transmission rate is 58 ml / m 2 ·24 h·Mpa.

[0112] Comparative Example 2

[0113] Without using the first polyurethane dispersion, replace it with an equal amount of deionized water, and only use the second polyurethane dispersion. The rest is the same as in Example 4.

[0114] The specific preparation steps are as follows:

[0115] (1) Add 50 g U 2757, 29.6 g of deionized water, 0.1 g of ammonia water, 0.3 g of BYK-024, and 20 g of isopropanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0116] (2) Add 5 g of Z-6040, 5 g XL-755 into another paint mixing tank, and stir evenly to obtain Component B;

[0117] (3) Mix Component A and Component B to obtain the final aqueous high-barrier coating solution.

[0118] Comparative Example 3

[0119] Without using the second polyurethane dispersion, replace it with an equal amount of deionized water, and only use the first polyurethane dispersion. The rest is the same as in Example 4.

[0120] The specific preparation steps are as follows:

[0121] (1) Add 15 g 1876, 64.6 g of deionized water, 0.1 g of ammonia water, 0.3 g of BYK-024, and 20 g of isopropanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0122] (2) Add 5 g of Z-6040, 5 g XL-755 into another paint mixing tank, and stir evenly to obtain Component B;

[0123] (3) Mix Component A and Component B to obtain the final aqueous high-barrier coating solution.

[0124] Comparative Example 4

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

[0126] The specific preparation steps are as follows:

[0127] (1) Add 15 g 1876, 15 g U 2757, 49.6 g of deionized water, 0.1 g of ammonia water, 0.3 g of BYK-024, and 20 g of isopropanol into the paint mixing tank in sequence, and stir evenly to obtain Component A;

[0128] (2) Add 5 g of Z-6040 and 5 g of XL-755 to another paint mixing tank, stir evenly to obtain Component B;

[0129] (3) Mix Component A and Component B to obtain the final waterborne high-barrier coating solution.

[0130] Comparative Example 5

[0131] Do not use the first crosslinking agent, replace it with an equal amount of deionized water, and use only the second crosslinking agent. The rest is the same as in Example 4.

[0132] The specific preparation steps are as follows:

[0133] (1) Add 15 g of 1876, 50 g of U 2757, 14.6 g of deionized water, 0.1 g of ammonia water, 0.3 g of BYK-024, and 20 g of isopropanol to the paint mixing tank in sequence, stir evenly to obtain Component A;

[0134] (2) Add 5 g of deionized water and 5 g of XL-755 to another paint mixing tank, stir evenly to obtain Component B;

[0135] (3) Mix Component A and Component B to obtain the final waterborne high-barrier coating solution.

[0136] Comparative Example 6

[0137] Do not use 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) Add 15 g of 1876, 50 g of U 2757, 14.6 g of deionized water, 0.1 g of ammonia water, 0.3 g of BYK-024, and 20 g of isopropanol to the paint mixing tank in sequence, stir evenly to obtain Component A;

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

[0141] (3) Mix Component A and Component B to obtain the final waterborne high-barrier coating solution.

[0142] Performance test, the 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 retort resistance compared with Comparative Examples 1-6.

[0147] According to the above specific implementation of the present invention, the obtained high-barrier waterborne coating has excellent oxygen barrier and moisture barrier properties, excellent adhesion and wettability on the film, and also has excellent flexibility, chemical resistance and retort resistance, etc. It can achieve excellent barrier properties at low coating amounts.

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

Claims

1. A high-barrier waterborne coating for flexible packaging, characterized in that, Comprising components with the following mass percentages: Component A: Based on the mass of Component A Component B: Based on the mass of Component B The first crosslinking agent: 20 - 80%, preferably 30 - 70%; The second crosslinking agent: 20 - 80%, preferably 30 - 70%; Wherein, the mass ratio of Component A to Component B is (5 - 20):1, preferably (5 - 15):

1.

2. The high-barrier waterborne coating for flexible packaging according to claim 1, characterized in that, 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%, preferably 10 - 40 wt%; the molecular weight Mw = 5000 - 20000 g / mol, preferably 5000 - 15000 g / mol; the glass transition temperature Tg = -60 to -10 °C, preferably -40 to -20 °C; and it can be miscible with alcohol in any proportion.

3. The high-barrier waterborne coating for flexible packaging according to claim 2, characterized in that, The polyolefin polyol is a polyhydroxy olefin oligomer with a number average molecular weight of 500 - 15000 g / mol and a functionality of at least 2; preferably, any one or more of hydroxyl-terminated polybutadiene polyols, hydroxyl-terminated polybutadiene-acrylonitrile polyols, hydroxyl-terminated hydrogenated polybutadiene polyols, hydroxyl-terminated styrene-butadiene liquid rubber, polyisoprene polyols, and polyolefin polyols with a number average molecular weight of 500 - 5000 g / mol and a functionality of 2 - 3.

4. The high-barrier waterborne coating for flexible packaging according to any one of claims 1 to 3, characterized in that, The first polyurethane dispersion is selected from Wanhua Chemical 1876, 0225, TAKELAC of Mitsui Chemicals TM one or more of WPB 341.

5. The high-barrier waterborne coating for flexible packaging according to claim 1, characterized in that, The soft segment of the second polyurethane dispersion is a hydroxyl-containing polyester polyol; preferably, the hydroxyl content of the second polyurethane dispersion is 0.5 - 2.5 wt%, the crystallization temperature is 15 °C - 50 °C, the solid content is 30 - 50 wt%, the molecular weight Mw = 10000 - 20000 g / mol, and it can be miscible with alcohol in any proportion.

6. The high-barrier waterborne coating for flexible packaging according to claim 1 or 5, characterized in that, The second polyurethane dispersion described above is selected from Wanhua Chemical 6512, 6526, 4288, Covestro one or more of U 2757.

7. The high-barrier waterborne coating for flexible packaging according to any one of claims 1 to 6, characterized in that, The first crosslinking agent is an epoxy silane coupling agent crosslinking agent, preferably at least any one of 3-glycidoxypropyltrimethoxysilane Z-6040, 3-glycidoxypropyltrimethoxysilane Z6041, and 3-glycidoxypropylmethyldiethoxysilane Z6042 from Dow Corning; and / or The second crosslinking agent described is a polycarbodiimide crosslinking agent, preferably Stahl XL-701, XL-702, XL-732, at least any one of XL-755.

8. The high-barrier waterborne coating for flexible packaging according to any one of claims 1 to 7, characterized in that, The pH regulator is selected from one or more of alkanolamines, ammonia water, and caustic alkalis; preferably one or more of N-methylethanolamine (MMAE), dimethylethanolamine (DMEA), diethanolamine, triethylamine, triethanolamine, ammonia water, and sodium hydroxide; and / or The defoamer is selected from one or more of polysiloxane defoamers and / or polyether silicone defoamers, preferably one or more of BYK-024, Foamex1488; The wetting agent is small molecule alcohols, preferably one or more of ethanol and isopropanol.

9. A method for preparing the high-barrier waterborne coating for flexible packaging according to any one of claims 1 to 8, characterized in that, Including the following steps: (1) Add the first polyurethane dispersion, the second polyurethane dispersion, water, pH regulator, defoamer, and wetting agent into a paint mixing tank, stir evenly to obtain Component A; (2) Add the first crosslinking agent and the second crosslinking agent into another paint mixing tank, stir evenly to obtain Component B; (3) Mix Components A and B to obtain the final high-barrier waterborne coating.

10. Application of the high-barrier waterborne coating for flexible packaging according to any one of claims 1 to 8 or the high-barrier waterborne coating for flexible packaging prepared by the preparation method according to claim 9 in the field of high-barrier flexible packaging, especially as a high-barrier coating for film-based and paper-based flexible packaging fields.

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