A high-barrier multifunctional recyclable water-based coating composition for industrial packaging bags and a preparation method thereof

Abstract

The present application relates to the field of water-based coatings, and discloses a high-barrier multifunctional recyclable water-based coating composition for industrial packaging bags and a preparation method thereof. The coating composition comprises an aqueous acrylic copolymer emulsion, a styrene-butadiene emulsion, an aqueous polyurethane dispersion, a functional monomer, a barrier enhancement component, an additive, a cross-linking agent and deionized water; the functional monomer is composed of SMA, BA, HEMA and IBOMA in a weight ratio of (1-3): (7-10): (1-3): (0.5-2); the barrier enhancement component is composed of modified bentonite, nano-silicon dioxide and fumed silica in a weight ratio of (3-5): (1-3): (0.5-2). The coating composition of the present application has excellent barrier, water-repellent and mechanical properties, and can be efficiently separated from a paper substrate under alkaline or hot water conditions, thereby realizing the recycling of the paper substrate.

Description

Technical Field

[0001] The present application relates to the field of water-based coatings, and more specifically, to a high-barrier multifunctional recyclable water-based coating composition for industrial packaging bags and a preparation method thereof. Background Art

[0002] Industrial packaging bags are widely used in the chemical, food and other industries, which place strict requirements on the barrier, waterproof and durability of packaging bags. At present, although traditional coating materials such as polyethylene (PE) laminating and polyvinylidene chloride (PVDC) have certain barrier properties, they are not recyclable and have poor environmental performance. At the same time, existing water-based coating materials often have defects such as insufficient barrier properties or poor mechanical properties, which cannot meet the high requirements of industrial packaging.

[0003] For example, the Chinese patent with publication number CN117222524A discloses a high barrier polyethylene film for packaging, which comprises an outer layer for barrier coating made of an outer layer composition, wherein the outer layer composition comprises a catalytically generated polyethylene component AO, which is an ethylene copolymer. The Chinese patent with publication number CN117777793A discloses a high barrier modified PVA / acrylic composite coating liquid, which is prepared from an aqueous acrylic emulsion, a PVA resin, a low molecular weight hydroxyl-containing polyolefin and other additives. The Chinese patent with publication number CN108129926A discloses a barrier coating and its preparation method and application, which is prepared from a styrene-butadiene emulsion, a polyvinylidene chloride emulsion (PVDC), an ethylene-vinyl acetate copolymer and an additive, and the barrier coating is applied to the surface of cardboard to obtain coated paper. A Chinese patent with publication number CN110318291A discloses a water-based barrier coating for coating paper, which includes component A and component B. Component A includes: polyvinyl alcohol, quick-drying agent, plasticizer, bactericide, defoamer; component B includes: modified amine curing agent, isopropyl alcohol. The coating can be used for paper coating and the production of high-barrier paper. Although the above barrier coating has certain barrier properties, it has problems such as non-recyclability and poor environmental performance.

[0004] For example, the Chinese patent with publication number CN112409874A discloses an environmentally friendly barrier coating composition, which is composed of environmentally friendly water-based acrylic resin, pigment, nanocellulose aqueous dispersion, additives and deionized water. Although the coating has certain environmental recyclability, its barrier performance and mechanical properties are not significantly improved compared with commercially available products.

[0005] Therefore, in view of the strict requirements of industrial packaging bags on barrier properties, waterproofness and durability, as well as the problems existing in current coating materials, it is of great significance to develop a barrier coating with good barrier properties, mechanical properties, recyclability and environmental protection. Summary of the invention

[0006] In order to solve the above-mentioned problems existing in the prior art, the present invention provides an aqueous coating composition with high barrier properties, which adopts an optimized combination of multifunctional monomers and combines barrier enhancing components and functional additives to significantly improve the comprehensive performance of the coating while supporting environmentally friendly separation from the paper substrate.

[0007] In order to achieve the above invention objectives, this application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a high-barrier multifunctional recyclable water-based coating composition, comprising the following components in parts by mass:

[0009] 60-70 parts of aqueous acrylic copolymer emulsion;

[0010] Styrene-butadiene emulsion (SBR) 10-12 parts;

[0011] 10-12 parts of waterborne polyurethane dispersion;

[0012] 9.5-18 parts of functional monomer;

[0013] 4.5-10 parts of barrier enhancement component;

[0014] 1.5-3 parts of additives;

[0015] 1-2 parts of cross-linking agent;

[0016] 15-38 parts of deionized water;

[0017] The functional monomers are composed of octadecyl methacrylate (SMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA) and isobornyl methacrylate (IBOMA) in a weight ratio of (1-3): (7-10): (1-3): (0.5-2);

[0018] The barrier enhancement component is composed of modified bentonite, nano silicon dioxide and fumed silicon dioxide in a weight ratio of (3-5): (1-3): (0.5-2).

[0019] Preferably, the amount of deionized water can be adjusted according to actual needs, which is intended to adjust the viscosity of the coating solution to 150-200 mPa·s to meet the requirements of gravure coating or roller coating processes. For example, the amount of deionized water is preferably 18-30 parts.

[0020] Preferably, in the functional monomers, the weight ratio of octadecyl methacrylate, butyl acrylate, hydroxyethyl methacrylate and isobornyl methacrylate is 2:8:2:1.

[0021] Preferably, in the barrier enhancement component, the weight ratio of modified bentonite, nano-silicon dioxide and fumed silica is 4:2:1.

[0022] Preferably, the auxiliary agent, by weight, includes:

[0023] 0.5-1 part of interface wetting agent;

[0024] 0.5-1 part of chemical corrosion resistance additive;

[0025] Flexibility enhancing agent 0.5-1 part

[0026] Preferably, the interface wetting aid is an ethoxy silane coupling agent.

[0027] Preferably, the chemical corrosion resistance additive is PTFE powder.

[0028] Preferably, the flexibility enhancing agent is dibutyl phthalate (DBP).

[0029] Preferably, the crosslinking agent is polyepichlorohydrin.

[0030] In a second aspect, the present application provides a method for preparing the high-barrier multifunctional recyclable aqueous coating composition described in the first aspect, comprising the following steps:

[0031] S1, dispersing modified bentonite, nano-silicon dioxide and fumed silica in deionized water, and treating with ultrasound for 20-30 minutes to prepare a nano-dispersion liquid;

[0032] S2, mixing the aqueous acrylic copolymer emulsion and the aqueous polyurethane dispersion under stirring conditions, and controlling the temperature to be 50-60° C.;

[0033] S3, slowly add styrene-butadiene emulsion and functional monomer, and stir for 15-20 minutes;

[0034] S4, adding the nano-dispersion liquid of step S1, and continuing stirring for 10-15 minutes;

[0035] S5, add crosslinking agent and auxiliary agent, mix well, and adjust the viscosity to 150-200 mPa·s;

[0036] S6, after filtering, the high-barrier multifunctional recyclable aqueous coating composition is obtained.

[0037] In the third aspect, the present application provides the use of the high-barrier multifunctional recyclable aqueous coating composition described in the first aspect in the preparation of industrial packaging bags, wherein the coating process adopts gravure coating or roller coating process, the coating amount is 12-15g / m², and the drying conditions are 60-80°C.

[0038] In a fourth aspect, the present application provides an industrial packaging bag having a surface coated with the high barrier multifunctional recyclable aqueous coating composition described in the first aspect, which has the following properties:

[0039] (1) Water vapor transmission rate (MVTR): <3 g / m²·day;

[0040] (2) Water contact angle: ≥90°;

[0041] (3) The peeling force between the coating and the paper substrate is ≥5N / 25mm;

[0042] (4) The separation rate of the coating from the paper substrate in an alkaline or hot water environment is ≥95%.

[0043] In summary, this application has the following beneficial effects:

[0044] 1. Synergistic effect of functional monomers: The four functional monomers (SMA, BA, HEMA, IBOMA) used in the present invention have a synergistic effect, which can significantly improve the barrier, waterproof and mechanical properties of the coating.

[0045] 2. "Brick wall effect" of barrier enhancement components: Through the synergistic effect of modified bentonite, nano-silica and fumed silica, a multi-layer "brick wall effect" is formed, which significantly reduces the water vapor transmission rate (MVTR) and gives the coating excellent barrier properties.

[0046] 3. Excellent waterproof and mechanical properties: Functional monomers SMA and IBOMA provide excellent hydrophobic properties, with a water contact angle greater than 90°; the synergistic effect of BA and DBP significantly improves flexibility and crack resistance, meeting the needs of dynamic environments of industrial packaging bags.

[0047] 4. Environmentally friendly and recyclable: The coating can be efficiently separated from the paper substrate under alkaline (pH 10-12) or hot water conditions, with a separation rate of over 95%, supporting environmentally friendly recycling.

[0048] 5. Organic-inorganic synergistic enhancement: The present invention combines the respective advantages of organic and inorganic materials through the combination of functional monomers and barrier enhancement components, achieving a comprehensive improvement in barrier properties, waterproof properties, environmental recyclability, and mechanical properties. DETAILED DESCRIPTION

[0049] The technical scheme and effects of the present application are further described in detail below in combination with the embodiments and comparative examples. It should be understood that the specific embodiments described herein are only used to explain the invention, rather than to limit the invention.

[0050] It is worth noting that the raw materials used in this embodiment and comparative examples, unless otherwise specified, are commercially available:

[0051]

[0052] It is worth noting that the performance tests related to the following embodiments and comparative examples, unless otherwise specified, are all existing methods:

[0053] (1) Barrier performance test: According to ISO 15106-3:2015 standard, test MVTR at 38°C and 90% RH;

[0054] (2) Waterproof performance test: Test water contact angle according to ASTM D7334-08;

[0055] (3) Adhesion test: Adhesion was tested according to ASTM D3359 (0B: Most of the coating peeled off in the cutting area; 1B: Large pieces of coating peeled off at the edge of the cut, and some grids peeled off completely, with a peeled area of ​​35%-65%; 2B: The edge of the cut peeled off, large pieces peeled off as a whole, and even some grids peeled off as a whole, with a peeled area of ​​15%-35%; 3B: There was peeling at the edge of the cut and the intersection, with a peeled area of ​​5%-15%; 4B: Small pieces peeled off at the intersection of the cut, and the actual damage in the grid area did not exceed 5%; 5B: The edge of the cut was completely smooth, and there was no peeling at the edge of the grid);

[0056] (4) Flexibility test: tensile strength and elongation at break were tested according to ASTM D882;

[0057] (5) Environmental separation test:

[0058] ①Test purpose:

[0059] Verify the ability of the coating to separate from the paper substrate in an alkaline environment, measure the damage rate of the paper substrate fibers, and evaluate the environmentally friendly and recyclable performance of the coating.

[0060] ②Test conditions:

[0061] Soaking solution: 0.001 mol / L NaOH solution, pH 11;

[0062] Soaking temperature: 50℃;

[0063] Soaking time: 30 minutes;

[0064] Soaking solution volume: 200mL.

[0065] ③Test steps:

[0066] Take a 10 cm × 10 cm sample of coated paper substrate and record the initial mass m0 (unit: g).

[0067] The sample was completely immersed in the alkaline solution and kept in a constant temperature water bath at 50°C for 30 minutes.

[0068] After immersion, the samples were removed and rinsed with deionized water to remove the residual coating.

[0069] Use filter paper to absorb the surface moisture and record the mass m1 (unit: g) of the paper substrate after drying.

[0070] The damage of fibers on the surface of the paper substrate was observed using an optical microscope (100× magnification).

[0071] ④Data calculation

[0072] Coating separation rate (%) = [(m0-m1) / m0] × 100%;

[0073] m0: total mass of initial sample (coating + paper substrate), unit: g;

[0074] m1: mass of paper substrate after soaking, unit: g.

[0075] Fiber damage rate (%) = (damage area / total area) × 100%;

[0076] The lesion area and total area were determined by microscopic observation.

[0077] ⑤Judgment criteria

[0078] Coating separation rate: ≥95% is qualified; <95% indicates insufficient separation performance.

[0079] Fiber damage rate: ≤5% is excellent; 5%-10% is good; ≥10% is unqualified.

[0080] Examples 1-3

[0081] Examples 1-3 disclose a coating composition, the raw materials and amounts used in its preparation are shown in the following table:

[0082]

[0083] The difference between Examples 1, 2 and 3 is that the dosage of each substance is different.

[0084] The preparation method of the coating composition comprises the following steps:

[0085] S1. Modified bentonite, nano-silica and fumed silica were dispersed in deionized water and treated with ultrasound (40 kHz, 25 min) to prepare nano-dispersion;

[0086] S2. At 50° C., the aqueous acrylic copolymer emulsion and the aqueous polyurethane dispersion were mixed and stirred evenly;

[0087] S3. Slowly add SBR and functional monomers (SMA, BA, HEMA, IBOMA) and continue stirring for 15 minutes;

[0088] S4. Slowly add the nano-dispersion of step S1 to the mixture and keep stirring for 10 minutes to ensure uniform dispersion;

[0089] S5. Add additives and cross-linking agent, mix well, adjust viscosity to 180 mPa·s, filter and set aside.

[0090] The coating composition obtained in the above embodiment was tested, and the results are as follows:

[0091]

[0092] Embodiment 4-5

[0093] Example 4-5 discloses a coating composition, which differs from Example 2 only in that the proportions of SMA, BA, HEMA, and IBOMA in the functional monomers are different, as shown in the following table:

[0094]

[0095] The coating composition obtained in the above embodiment was tested, and the results are as follows:

[0096]

[0097] It can be seen from the test results that compared with Examples 4 and 5, the coating composition prepared in Example 2 has better barrier properties, water resistance, adhesion and flexibility. It can be seen that among the functional monomers, the optimal weight ratio of octadecyl methacrylate, butyl acrylate, hydroxyethyl methacrylate and isobornyl methacrylate is 2:8:2:1.

[0098] Embodiment 6-7

[0099] Example 6-7 discloses a coating composition, which differs from Example 2 only in that the ratios of modified bentonite, nano-silicon dioxide and fumed silica in the barrier enhancement component are different, as shown in the following table:

[0100]

[0101] The coating composition obtained in the above embodiment was tested, and the results are as follows:

[0102]

[0103] From the test results, it can be seen that compared with Examples 6 and 7, the coating composition prepared in Example 2 has better barrier properties. It can be seen that in the barrier enhancement component, the optimal weight ratio of modified bentonite, nano-silica and fumed silica is 4:2:1.

[0104] Comparative Examples 1-5

[0105] Comparative Examples 1-5 disclose a composition, which differs from Example 1 only in that the usage of the functional monomer is different, as shown in the following table:

[0106]

[0107] The coating composition obtained in the above comparative example was tested, and the results were as follows:

[0108]

[0109] From the test results, it can be seen that the MVTR value of Example 1 is significantly lower than that of all comparative examples, indicating that the synergistic effect of the functional monomer and the barrier enhancement component significantly improves the barrier performance. The barrier performance of Comparative Example 2 (using only SMA), Comparative Example 3 (using only BA), Comparative Example 4 (using only HEMA) and Comparative Example 5 (using only IBOMA) is better than that of Comparative Example 1 without monomer, but is still significantly lower than that of the optimized combination examples.

[0110] The water contact angles of Example 1 are all greater than 90°, indicating that the coating has excellent hydrophobic properties. Comparative Example 2 (using only SMA), Comparative Example 3 (using only BA), Comparative Example 4 (using only HEMA) and Comparative Example 5 (using only IBOMA) provide certain hydrophobic properties, which are better than Comparative Example 1 without monomers, but are significantly lower than the examples of the optimized combination.

[0111] The adhesion of Example 1 reaches 5B level (no peeling), while the adhesion of the comparative example can only reach 3B-4B.

[0112] The tensile strength and elongation at break of Example 1 are significantly better than those of the comparative example, indicating that the optimized combination of functional monomers has an important contribution to enhancing flexibility and mechanical properties.

[0113] Comparative Examples 6-11

[0114] Comparative Examples 6-11 disclose a composition, which differs from Example 1 only in that the usage of the functional monomer is different, as shown in the following table:

[0115]

[0116] The coating composition obtained in the above comparative example was tested, and the results were as follows:

[0117]

[0118] From the test results, it can be seen that by comparing Comparative Example 1 with Example 1, it can be seen that after adding the functional monomer in the present application, the various properties of the coating composition are significantly improved.

[0119] By comparing Comparative Examples 2-9 with Example 1, it can be seen that the coating compositions prepared by using only any one, two or three of SMA, BA, HEMA and IBOMA still have obvious differences in various properties compared with Example 1 (four functional monomers are used in combination).

[0120] By comparing Comparative Examples 10-11 with Example 1, it can be seen that although the two comparative examples simultaneously use four monomers, namely, SMA, BA, HEMA and IBOMA, the performance effect of Example 1 cannot be achieved due to the ratio reasons.

[0121] This shows that the quaternary functional monomers (SMA, BA, HEMA, IBOMA) used in the present invention are not simply superimposed, but are carefully screened and proportion-optimized to achieve the synergy of multiple molecular forces and the complementarity of structural characteristics at the microscopic level. Specifically:

[0122] The long-chain hydrophobic side chain structure of SMA can form a low-polarity region in the molecular network after the coating is cured, reducing the surface free energy, thereby improving the waterproofness and hydrophobic interface properties of the coating.

[0123] As a flexible monomer, BA's longer flexible butyl side chain gives the polymer chain greater segment mobility, thereby improving the elongation at break and tensile strength. While maintaining flexibility, BA can also form a moderately compatible microphase structure with SMA and other monomers, providing a stable matrix for uniformly distributed nanoparticles.

[0124] HEMA contains hydroxyl functional groups, which can form hydrogen bonds or chemical crosslinks with crosslinkers or other reactive groups during the curing process of the coating. This interaction strengthens the internal network structure of the coating and significantly improves adhesion and durability, thereby maintaining stable performance under conditions of high-speed coating or frequent bending of packaging bags.

[0125] IBOMA has a rigid structural unit, and its benzene ring structure can introduce moderate rigid micro-regions into the polymer network, improving the coating's resistance to mechanical stress and deformation recovery. In the presence of IBOMA, the entire system achieves a good balance between mechanical properties and flexibility.

[0126] In summary, the components of SMA, BA, HEMA, and IBOMA have synergistic effects, which can significantly improve the barrier, water resistance, and mechanical properties of the coating. Moreover, when the four monomers are compounded in the ratio of (1-3): (7-10): (1-3): (0.5-2), they not only have the excellent hydrophobicity and rigidity stability brought by SMA and IBOMA, but also have the flexibility provided by BA and the adhesion enhancement effect of HEMA, thus achieving a comprehensive improvement in water resistance, high toughness, and excellent adhesion at the microscopic level; if any monomer ratio deviates from this ratio range, this delicate balance will be broken, resulting in a decrease in water resistance, mechanical properties, or adhesion.

[0127] Comparative Examples 12-15

[0128] Comparative Examples 12-15 disclose a composition, which differs from Example 1 only in that the use of the barrier enhancement component is different, as shown in the following table:

[0129]

[0130] The coating composition obtained in the above embodiment was tested, and the results are as follows:

[0131]

[0132] Comparative Examples 16-20

[0133] Comparative Examples 16-20 disclose a composition, which differs from Example 1 only in that the use of the barrier enhancement component is different, as shown in the following table:

[0134]

[0135] The coating composition obtained in the above embodiment was tested, and the results are as follows:

[0136]

[0137] From the test results, it can be seen by comparing Comparative Example 12 with Example 1 that after adding the barrier enhancing component in the present application, the barrier property, water resistance and adhesion of the coating composition are significantly improved.

[0138] By comparing Comparative Examples 13-18 with Example 1, it can be seen that the barrier properties, water resistance and adhesion of the coating composition prepared by using only any one or two of modified bentonite, nano-silicon dioxide and fumed silica are still significantly different from those of Example 1 (three barrier enhancement components are used in combination). This shows that the modified bentonite, nano-silicon dioxide and fumed silica have a synergistic effect and can significantly improve the barrier properties, water resistance and adhesion of the coating.

[0139] By comparing Comparative Examples 19-20 with Example 1, it can be seen that although the two comparative examples simultaneously use three barrier enhancement components, namely modified bentonite, nano-silicon dioxide and fumed silica, the performance effect of Example 1 cannot be achieved due to the ratio.

[0140] In terms of barrier enhancement components, the present invention simultaneously selects modified bentonite, nano-silicon dioxide and fumed silica to construct a "ternary synergistic barrier structure" in a ratio of (3-5): (1-3): (0.5-2).

[0141] Among them, for modified bentonite, the organically modified bentonite flakes can form highly ordered, "brick wall"-like micro-nano structures in the coating. These flakes can effectively extend the penetration path of water vapor and gas molecules, thereby reducing MVTR.

[0142] For nano-silica, nano-silica fillers with a particle size of about 200 nm are dispersed in the polymer matrix. On the one hand, they fill micropores to reduce water vapor channels; on the other hand, their surface hydroxyl groups can form hydrogen bonds with the hydroxyl groups of HEMA, improving the overall compatibility and dispersion stability, making the coating structure denser.

[0143] For fumed silica, fumed silica particles with a particle size of about 50 nm have a higher specific surface area and can be embedded in tiny gaps in the polymer network, further reducing the free volume. When nano and ultrafine fumed particles are properly compounded, a layered nano protective barrier can be constructed to improve the density and uniformity of the coating.

[0144] Furthermore, by combining the test results of Examples 1, 2, 6, 7 and Comparative Examples 12-20, it can be seen that when the three barrier enhancement components are used in a ratio of (3-5): (1-3): (0.5-2), the barrier effect is the best, and the optimal ratio is 4:2:1. If any component is missing or its ratio is changed, it is impossible to take into account the barrier property, dispersion stability and adhesion at the same time. Therefore, only a specific ratio (i.e., the ratio disclosed in the present invention) can achieve a comprehensive balance between significantly reduced water vapor transmission rate (<3 g / m²·day) and good mechanical properties.

[0145] Comparative Examples 21-23

[0146] Comparative Examples 21-23 disclose a composition, which differs from Example 1 only in that the use of the auxiliary agent is different, as shown in the following table:

[0147]

[0148] The coating composition obtained in the above embodiment was tested, and the results are as follows:

[0149]

[0150] It can be seen from the test results that for tensile strength, Example 1 (20.3 MPa): the synergistic effect of functional monomers (such as BA and HEMA) and flexibility enhancing additives (DBP) significantly improves the tensile strength, which is far better than all comparative examples; Comparative Example 21 (12.5 MPa): the lack of flexibility enhancing components leads to a significant decrease in tensile strength; Comparative Example 22 (15.5 MPa): the flexibility enhancing components are partially involved, and the tensile strength is improved; Comparative Example 23 (13.0 MPa): the proportion of flexibility additives is insufficient, and the tensile strength is slightly higher than that of Comparative Example 21, but lower than that of Comparative Example 22.

[0151] For the elongation at break, Example 1 (141%): the optimized proportion of functional monomers and the flexibility additives provide excellent ductility; Comparative Example 21 (80%): the lack of flexible components leads to a significant decrease in the elongation at break; Comparative Example 22 (130%): the flexibility enhancing additive significantly improves the ductility, which is close to the level of the embodiment; Comparative Example 23 (85%): the proportion of flexible components is insufficient, and the ductility is significantly weaker than that of Comparative Example 22.

[0152] For chemical corrosion resistance, in Example 1, DBP improves the flexibility of the coating, reduces the generation of cracks caused by mechanical stress, and thus indirectly enhances the chemical stability; PTFE powder forms a low surface energy protective layer on the surface of the coating, reducing the erosion of the coating by alkaline solution. The combined use of DBP and PTFE powder significantly improves the chemical resistance. Comparative Example 21 has no DBP and PTFE powder, and the coating completely fails under the dual effects of mechanical stress and chemical erosion. Comparative Example 22 only has DBP to provide flexibility enhancement, which reduces the generation of mechanical cracks, but lacks the chemical protection of PTFE powder, resulting in insufficient chemical resistance. Comparative Example 23 only has PTFE powder to provide a chemical protection layer. Although chemical erosion is reduced, mechanical cracks are prone to local failure of the coating due to the lack of a flexible additive. It can be seen that the synergistic effect of DBP and PTFE powder is the key to improving the comprehensive performance of the coating, and the balance of mechanical properties and chemical stability is achieved by optimizing the ratio. The addition of DBP and PTFE powder significantly enhances the flexibility and chemical corrosion resistance of the coating, especially effectively reducing the possibility of coating failure under dynamic conditions.

[0153] Comparative Examples 24-28

[0154] They were prepared by the methods described in the examples in CN117222524A, CN117777793A, CN108129926A, CN110318291A and CN112409874A respectively.

[0155]

[0156] From the test results, it can be seen that for barrier performance, the MVTR value of Example 1 is 2.9 g / m²·day, which is lower than 3.2-3.7 g / m²·day of the related art (Comparative Examples 24-28), indicating that Example 1 of this case has better barrier performance than the related art.

[0157] As for the hydrophobic property, the water contact angle of Example 1 is 94°, while the water contact angle of the related art (Comparative Examples 24-28) is only 80-88°, indicating that Example 1 of the present case has better hydrophobicity than the related art.

[0158] As for adhesion, the adhesion of Example 1 reaches 5B grade (no peeling), while the related art (Comparative Examples 24-28) can only reach 4B grade.

[0159] As for mechanical properties, the tensile strength and elongation at break of Example 1 are significantly better than those of the related art (Comparative Examples 24-28).

[0160] As for environmentally friendly and recyclable performance, the coating separation rate of Example 1 can reach 96.3%, and the fiber damage rate is less than 5%. Under the same conditions, the coating separation rate of the related art (Comparative Examples 24-28) is only 89-94%, and the fiber damage rate is ≥5%. It can be seen that the coating of the present invention can be efficiently separated from the paper substrate under alkaline conditions (pH about 10-12). The reason for this may be that under alkaline conditions, functional groups such as SMA undergo slight swelling or dissociation reactions, which significantly reduces the interfacial bonding force between the coating and the paper-based fibers. This weakening of the interface layer is achieved through molecular design, that is, it ensures strong bonding under normal conditions, but reversible release under specific conditions. In addition, the paper fiber itself is subject to very low chemical erosion, because the coating design ensures that it does not require extremely corrosive solutions when it is peeled off, only low-concentration alkali solutions and moderate temperatures are required. This makes the separation process have little effect on the fiber structure (damage rate <5%), which is significantly better than the barrier coating in the prior art.

[0161] In summary, the solution of the present application (Example 1) achieves high separation rate (≥95%) and low fiber damage rate (<5%) under harsh conditions through a combination of specific functional monomers, barrier enhancement components and alkaline or hot water separation design, while maintaining excellent barrier and mechanical properties. In contrast, the prior art (Comparative Examples 24-28) often does not have comprehensive optimization with the same or similar effects.

[0162] It can be seen from the above embodiments and comparative examples that the coating composition of the present application is based on an aqueous acrylic copolymer emulsion, supplemented with a styrene-butadiene emulsion (SBR) and an aqueous polyurethane dispersion, and the multi-layer synergistic barrier effect of the coating is achieved by introducing functional monomers (octadecyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, isobornyl methacrylate) and barrier enhancement components (modified bentonite, nano-silica and fumed silica). In addition, the addition of flexibility enhancement additives, interface wetting additives and chemical corrosion resistance additives significantly improves the flexibility, moisture resistance and chemical corrosion resistance of the coating. Experiments show that the water vapor permeability (MVTR) of the coating composition is less than 3 g / m²·day, the water contact angle is higher than 90°, the adhesion reaches the 5B standard, and the separation rate of the coating and the paper substrate exceeds 95% under alkaline or hot water conditions. The present invention provides a coating solution with excellent performance, environmental protection and recyclability through a synergistic design, which is widely used in industrial packaging fields such as chemicals and food.

[0163] This application uses functional monomers composed of octadecyl methacrylate (SMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA) and isobornyl methacrylate (IBOMA), which significantly improve the hydrophobicity, moisture resistance and adhesion of the coating through synergistic effects.

[0164] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A high barrier multifunctional recyclable water-based coating composition, characterized in that: By mass, it includes the following components: 60-70 parts of aqueous acrylic copolymer emulsion; 10-12 parts of styrene-butadiene emulsion; 10-12 parts of waterborne polyurethane dispersion; 9.5-18 parts of functional monomer; 4.5-10 parts of barrier enhancement component; 1.5-3 parts of additives; 1-2 parts of cross-linking agent; 15-38 parts of deionized water; The functional monomers are composed of octadecyl methacrylate SMA, butyl acrylate BA, hydroxyethyl methacrylate HEMA and isobornyl methacrylate IBOMA in a weight ratio of (1-3): (7-10): (1-3): (0.5-2); The barrier enhancement component is composed of modified bentonite, nano silicon dioxide and fumed silicon dioxide in a weight ratio of (3-5): (1-3): (0.5-2); The auxiliary agent, by weight, includes: 0.5-1 part of interface wetting agent; 0.5-1 part of chemical corrosion resistance additive; 0.5-1 part of flexibility enhancing agent; The chemical corrosion resistant additive is PTFE powder; The flexibility enhancing auxiliary agent is dibutyl phthalate DBP.

2. The high barrier multifunctional recyclable water-based coating composition according to claim 1, characterized in that: In the functional monomers, the weight ratio of octadecyl methacrylate, butyl acrylate, hydroxyethyl methacrylate and isobornyl methacrylate is 2:8:2:

1.

3. The high barrier multifunctional recyclable water-based coating composition according to claim 1, characterized in that: In the barrier enhancement component, the weight ratio of modified bentonite, nano silicon dioxide and fumed silicon dioxide is 4:2:

1.

4. The method for preparing the high-barrier multifunctional recyclable water-based coating composition according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, dispersing modified bentonite, nano-silicon dioxide and fumed silica in deionized water, and treating with ultrasound for 20-30 minutes to prepare a nano-dispersion liquid; S2, mixing the aqueous acrylic copolymer emulsion and the aqueous polyurethane dispersion under stirring conditions, and controlling the temperature to be 50-60° C.; S3, slowly add styrene-butadiene emulsion and functional monomer, and stir for 15-20 minutes; S4, adding the nano-dispersion liquid of step S1, and continuing stirring for 10-15 minutes; S5, add crosslinking agent and auxiliary agent, mix well, and adjust the viscosity to 150-200 mPa·s; S6, after filtering, the high-barrier multifunctional recyclable aqueous coating composition is obtained.

5. Use of the high barrier multifunctional recyclable water-based coating composition according to any one of claims 1 to 3 in the preparation of industrial packaging bags, characterized in that: The coating process adopts gravure coating or roller coating technology, the coating amount is 12-15g / m², and the drying condition is 60-80℃.

6. An industrial packaging bag whose surface is coated with the high-barrier multifunctional recyclable water-based coating composition according to any one of claims 1 to 3.

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