An oil-proof paint, a preparation method and application thereof

Abstract

The application belongs to the field of paint, and particularly discloses an oil-proof paint, a preparation method and application thereof. The application adds starch, beta-cyclodextrin and oleic acid amide into the oil-proof paint system, so that the barrier property of the film layer of the oil-proof paint is improved, and the prepared paper-based oil-proof coating has excellent oil-proof effect.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and specifically to an oil-proof coating and a preparation method and application thereof. Background Art

[0002] With increasing environmental awareness, food packaging is trending towards reducing or even eliminating the use of environmentally polluting materials such as pure plastic. Instead, the use of paper-based materials, such as plant cellulose, as new food packaging materials has become a major development direction. However, due to the high surface energy of paper-based materials, which contain a large number of hydroxyl groups, they easily absorb liquids. Furthermore, the porous structure of paper allows liquids to penetrate the paper through capillary action. Consequently, ordinary paper packaging materials cannot prevent wetting by grease and lack oil-proof properties. Therefore, paper packaging materials must undergo oil-proof treatment to meet the requirements of food packaging.

[0003] Oil-proofing treatments generally include laminating and coating. Laminating involves applying a thin plastic film to the surface of a paper substrate. Plastics are generally incompatible with most liquids, thus providing an oil-proofing effect. However, this laminating treatment only reduces the amount of plastic used and does not fundamentally address the pollution problem caused by the slow degradation of plastics. Oil-proof coatings involve applying a layer of oil-proofing chemicals to the surface of the paper substrate. These chemicals reduce the surface tension of the paper, preventing it from wetting with grease. This not only offers oil-proof properties but also offers the advantages of being easily biodegradable and recyclable. Because fluorine has the strongest electronegativity, the fluorocarbon polymers it forms possess strong stability and extremely low surface energy. Therefore, fluorine-containing oil-proofing additives are commonly used in current oil-proofing coatings. However, fluorine-containing groups, like other halogens, are highly bioaccumulative and difficult to degrade. Long-term contact with food, in particular, can pose a health risk to humans. Therefore, efforts are underway to develop fluorine-free coatings that achieve effective oil-proofing without causing harm. Summary of the Invention

[0004] In response to the problems of fluorine-containing and poor oil-proof effects in the above-mentioned prior art oil-proof coatings, the present invention will provide a fluorine-free and excellent oil-proof oil-proof coating as well as a preparation method and application thereof.

[0005] To achieve the above objectives, the following technical solutions are specifically included:

[0006] An oil-proof paint comprises the following components in percentage by weight: 25-35% waterborne polymer resin, 2-10% starch, 1.5-3% beta-cyclodextrin, 0.5-1.5% oleamide, 1-5% polyvinyl alcohol, 6-10% wax, 1-5% emulsifier, 0.1-2% polyol, and the balance water.

[0007] The invention adds starch, beta-cyclodextrin and oleamide to the oil-proof coating system, which can improve the barrier property of the film layer of the oil-proof coating, so that the prepared paper-based oil-proof coating has excellent oil-proof effect.

[0008] Preferably, the water-based polymer resin includes at least one of a water-based polyurethane resin and a water-based acrylic resin.

[0009] Preferably, the water-based acrylic resin includes at least one of a water-dispersible, water-soluble or water-stable acrylic resin and an aqueous dispersion or emulsion thereof.

[0010] Preferably, the acrylic resin includes at least one of acrylic acid-acrylate copolymer, ethylene-acrylic acid polymer, and styrene / acrylate copolymer.

[0011] Waterborne polymer resins are water-dispersible, water-soluble or water-stable polymer resins that have good film-forming properties and are environmentally friendly and easily degradable.

[0012] The mass percentage of the waterborne polymer resin can be 25%, 27%, 29%, 31%, 33%, 35%, etc., as well as specific values ​​within the above value ranges.

[0013] Preferably, the mass ratio of the aqueous polymer resin to starch is (25-33):(2-10).

[0014] Water-based polymer resin and starch both have good barrier properties after film formation. When the two are compounded in a certain proportion, they have a synergistic effect, especially under the above-mentioned ratio, they have a better oil-proof effect.

[0015] Preferably, the starch includes at least one of unmodified starch and modified starch, and the modified starch includes at least one of oxidatively modified starch, oxidatively esterified starch, and acid-degraded modified starch.

[0016] Modified starch has been modified to change the content of its hydroxyl groups and the types of other groups, which can reduce the liquid absorption effect to a certain extent, and thus better cooperate with the water-based polymer resin to improve the oil-proof effect of the oil-proof coating.

[0017] The mass percentage of β-cyclodextrin can be 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9%, 3.0%, etc., as well as specific point values ​​between the above point value ranges.

[0018] The cyclic structure of β-cyclodextrin can encapsulate various molecules, improve the mutual binding effect between starch and water-based polymer resin, and thus improve the oil-proof effect of oil-proof coatings.

[0019] The mass percentage of β-cyclodextrin can be 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, etc., as well as specific values ​​between the above value ranges.

[0020] Starch and β-cyclodextrin have relatively poor compatibility and dispersibility with the matrix resin, and both are susceptible to deterioration (e.g., mildew). Oleamide not only serves as a compatibilizer and lubricant for starch and β-cyclodextrin with the matrix resin, promoting the coordination of the various components in the oil-proof coating, but also, after being formed into a film, can migrate to the surface, providing a protective barrier, preventing the deterioration of starch and β-cyclodextrin and enhancing the oil-proofing effectiveness of the oil-proof coating film. Therefore, the ratio of the total mass of starch and β-cyclodextrin to the mass of oleamide is related to the oil-proofing effect and prevention of coating deterioration. The inventors of the present invention have discovered that a ratio of the total mass of starch and β-cyclodextrin to the mass of oleamide of (4.5-8):1 exhibits superior coating deterioration and oil-proofing effectiveness.

[0021] Polyvinyl alcohol has a good film-forming effect, improves the density and barrier properties of the coating after film formation, and its mass percentage can be 1%, 2%, 3%, 4%, 5%, etc., as well as specific point values ​​between the above point value ranges.

[0022] Preferably, the wax comprises at least one of palm wax, candelilla wax, microcrystalline wax, petroleum wax and paraffin wax.

[0023] Preferably, the emulsifier includes at least one of Tween emulsifiers, Span emulsifiers, palmitic acid, and sodium dodecylbenzenesulfonate.

[0024] Preferably, the polyol includes at least one of ethylene glycol, glycerol, butanol, and pentanol.

[0025] The present invention also provides a method for preparing the oil-proof coating, comprising the following steps:

[0026] (1) uniformly mixing an emulsifier, water, starch, β-cyclodextrin, and an aqueous polymer resin to obtain a first mixture;

[0027] (2) uniformly mixing oleamide, polyvinyl alcohol, wax, and polyol to obtain a second mixture;

[0028] (3) adding the second mixture to the first mixture and homogenizing the mixture under stirring to obtain the oil-proof coating.

[0029] Preferably, the mixing temperature in step (1) is 40-80°C.

[0030] Preferably, the mixing temperature in step (2) is 60-90°C.

[0031] Preferably, in step (3), the stirring rate is 500-1000 rpm.

[0032] The present invention also provides an application of an oil-proof coating in food packaging paper. The oil-proof coating can be applied to food packaging paper by conventional coating methods, such as spraying, roller coating, dipping, etc. The obtained oil-proof coating has good water and conventional grease barrier functions, meeting the current oil-proof and water-proof performance requirements in the food packaging field.

[0033] Compared with the prior art, the present invention has the following beneficial effects: by adding starch, β-cyclodextrin and oleamide to the oil-proof coating system, the barrier properties of the film layer of the oil-proof coating can be improved, so that the prepared paper-based oil-proof coating has excellent oil-proof effect. DETAILED DESCRIPTION

[0034] To better illustrate the objectives, technical solutions, and advantages of the present invention, the present invention will be further described below with reference to specific examples. The experimental methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available unless otherwise specified.

[0035] Examples 1-10 and Comparative Examples 1-4

[0036] A method for preparing an oil-proof coating comprises the following steps:

[0037] (1) According to the formula in Tables 1 and 2, an emulsifier, water, starch, β-cyclodextrin, and an aqueous polymer resin were mixed at 65° C. to obtain a first mixture;

[0038] (2) According to the formula in Tables 1 and 2, oleamide, polyvinyl alcohol, vegetable wax, and polyol were mixed at 80° C. to obtain a second mixture;

[0039] (3) Add the second mixture to the first mixture and homogenize at 500-1000 rpm to obtain the oil-proof coating.

[0040] The water-based polymer resin is acrylic acid-acrylate copolymer, the starch is unmodified tapioca starch or modified starch; the plant wax is palm wax; the emulsifier is Span-80, and the polyol is glycerol.

[0041] Table 1

[0042]

[0043] Table 2

[0044]

[0045]

[0046] The oil-proof coatings prepared in the above examples and comparative examples were applied at a coating amount of 5 g / m 2 The coating was applied to food-grade white cardboard and dried at 60°C for 5 minutes. The contact angle of the surface with water was tested, and the oil resistance of the oil-proof coating-coated paper was determined using the TAPPI 559cm-02 "Grease Resistance Test for Paper and Paperboard" test method. The oil resistance is graded from 1 to 12, with grade 1 being the worst and grade 12 being the best. The test results are shown in Table 3.

[0047] Table 3

[0048]

[0049]

[0050] It can be seen from the above examples that the oil-proof coating of the present invention has excellent liquid (water and oil) barrier properties, a water contact angle ≥130°, and an oil-proof performance grade ≥8.

[0051] It can be seen from Example 1 and Comparative Examples 1-4 that the starch, β-cyclodextrin and oleamide in the system can significantly improve the oil-proof effect of the oil-proof coating.

[0052] As can be seen from Examples 1 and 8-10, the use of oxidized modified starch, oxidized esterified starch, and acetate starch can further reduce the hydrophilicity and lipophilicity of the oil-proof coating and improve the barrier properties of the oil-proof coating. In particular, the use of oxidized esterified starch can achieve an oil-proof grade of 12, which is the most effective in improving the barrier properties.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An oil-proof coating, characterized in that: The invention comprises the following components in percentage by weight: 25-33% aqueous polymer resin, 2-10% starch, 1.5-3% beta-cyclodextrin, 0.5-1.5% oleamide, 1-5% polyvinyl alcohol, 6-10% wax, 1-5% emulsifier, 0.1-2% polyol, and the balance water; the starch comprises at least one of unmodified starch and modified starch; and the aqueous polymer resin is an acrylic acid-acrylate copolymer.

2. The oil-proof coating according to claim 1, characterized in that The modified starch includes at least one of oxidatively modified starch and acid-degraded modified starch.

3. The oil-proof coating according to claim 1, characterized in that The modified starch includes oxidized esterified starch.

4. The oil-proof coating according to claim 1, wherein The mass ratio of the total mass of the starch and β-cyclodextrin to the mass of oleamide is (4.5-8):

1.

5. The oil-proof paint according to claim 1, wherein The wax includes at least one of palm wax, candelilla wax, microcrystalline wax, petroleum wax and paraffin wax; the emulsifier includes at least one of Tween emulsifier, Span emulsifier, palmitic acid and sodium dodecylbenzene sulfonate.

6. The oil-proof paint according to claim 1, characterized in that The polyol includes at least one of ethylene glycol, glycerol, butanol, and pentanol.

7. A method for preparing the oil-proof coating according to any one of claims 1 to 6, characterized in that: The steps include: (1) uniformly mixing an emulsifier, water, starch, β-cyclodextrin, and an aqueous polymer resin to obtain a first mixture; (2) uniformly mixing oleamide, polyvinyl alcohol, wax, and polyol to obtain a second mixture; (3) Adding the second mixture to the first mixture and homogenizing the mixture under stirring to obtain the oil-proof coating.

8. Use of the oil-proof coating according to any one of claims 1 to 6 in food packaging paper.

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