A polyurethane primer for coating high-barrier plastic films and a preparation method thereof

Abstract

The application discloses a polyurethane primer for coating high-barrier plastic film and a preparation method thereof. The polyurethane primer comprises a main agent, a curing agent and a solvent, and the weight ratio of the main agent, the curing agent and the solvent is 20:2-6:50-120. The main agent is prepared from isocyanate monomer, polycaprolactone polyol, self-made polyester polyol, epoxy resin, functional additive, functional filler and solvent. The curing agent is a multifunctional isocyanate curing agent or a commercially available L-75 curing agent. The polyurethane primer can solve the problems of poor adhesion between barrier materials and base films, poor high-temperature resistance and poor medium corrosion resistance of existing PVDC, PVA, nanocellulose and other high-barrier coating films.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyurethane primers, in particular to a polyurethane primer for high-barrier plastic film coating and a preparation method thereof. BACKGROUND

[0002] With the increasing urgency of plastic recycling demand in countries around the world, the demand for single packaging has also increased in recent years. In order to maintain the barrier properties of traditional metal composite film or evaporated metal composite film, high-barrier plastic film in single material packaging or plastic-plastic composite packaging is a cost-effective solution verified by the market.

[0003] Currently, high-barrier plastic film is mainly achieved by coating high-barrier emulsion on general substrates such as polyester film PET, nylon film PA, biaxially oriented polypropylene film OPP, etc. Commonly used high-barrier emulsion includes polyvinylidene chloride PVDC emulsion, polyvinyl alcohol PVA emulsion, nanocellulose emulsion, etc. If the above high-barrier emulsion is directly coated on the surface of the plastic film material by a coating machine, and then prepared into single material packaging or composite film packaging bag with other plastic films, after hot canning, pasteurization, high-temperature retort sterilization, or long-term storage at harsh storage temperatures with certain acidity, alkalinity, corrosion or high and low temperatures, the high-barrier coating layer is prone to separate from the substrate film, thereby affecting the packaging performance of the entire packaging product.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a polyurethane primer for high-barrier plastic film coating and a preparation method, which can improve the adhesion, temperature resistance and moisture and gas resistance of the high-barrier coating on the plastic film material, thereby solving the above technical problems existing in the prior art.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A polyurethane primer for high-barrier plastic film coating, comprising:

[0008] The weight ratio of the main agent, the curing agent and the diluent solvent is 20:2-6:50-120; wherein,

[0009] The main agent is made of isocyanate monomer, polycaprolactone polyol, self-made polyester polyol, epoxy resin, functional additive, silane coupling agent, chain extender, fumed silica, functional filler and solvent;

[0010] The curing agent uses a multifunctional isocyanate curing agent or a commercially available L-75 curing agent.

[0011] Preferably, in the main agent of the polyurethane primer, the amount of each raw material is as follows in parts by weight:

[0012]

[0013] Preferably, in the main agent of the polyurethane primer, the self-made polyester polyol is a polyester polyol with a molecular weight of 500-3000 and an acid value of less than 1 mgKOH / g, which is synthesized from adipic acid, terephthalic acid, hexanediol, 1,4-butanediol, neopentyl glycol, and diethylene glycol.

[0014] Preferably, in the main agent of the polyurethane primer, the isocyanate monomer is one or two of toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate.

[0015] Preferably, in the main agent of the polyurethane primer, the polycaprolactone has a molecular weight of 400-4000 and a functionality of 2-3.

[0016] Preferably, in the main agent of the polyurethane primer, the epoxy resin is one or a mixture of two of commercially available epoxy resins E44 and E51.

[0017] Preferably, in the main agent of the polyurethane primer, the functional auxiliary includes, in parts by weight, 0.000005-0.00001 parts of a catalyst and 0.0003-1.99999 parts of a yellowing-resistant auxiliary.

[0018] The functional filler includes, in parts by weight, 2.99999-9.99999 parts of food-grade paraffin and 0.000005-0.00001 parts of inorganic metal ions.

[0019] The solvent is one or a mixture of two of ethyl acetate, methyl acetate, acetone, and butanone.

[0020] Preferably, in the curing agent of the polyurethane primer, the multifunctional isocyanate curing agent is an isocyanate curing agent with an NCO content of 8-15% and a solid content of 50-80%, which is made from toluene diisocyanate, diphenyl diisocyanate, trimethylolpropane, 1,4-butanediol, a trifunctional polyether polyol with a molecular weight of less than 1000, and ethyl acetate.

[0021] A method for preparing the polyurethane primer for coating high-barrier plastic films according to the present application, comprising the following steps:

[0022] Preparation of the main agent: take each raw material according to the main agent formula described in the application, add the isocyanate monomer in the main agent raw material, 10-20 parts of the solvent, polycaprolactone polyol and self-made polyester polyol into the reaction kettle, and react at 60-70 DEG C for 1-2h; add the functional auxiliary agent, heat to 80-90 DEG C, and keep the temperature for 2-4h; add the remaining solvent, epoxy resin, silane coupling agent and fumed silica, keep the temperature at 70-80 DEG C for 1h, and finally add the functional filler and chain extender, stir for 0.5h, and then discharge, so that the main agent is prepared;

[0023] The main agent, the curing agent and the solvent are configured into a working solution with a solid content of 5-20% according to the weight ratio of 20:2-6:50-120, so that the polyurethane primer for high-barrier plastic film coating is obtained.

[0024] Compared with the prior art, the polyurethane primer for high-barrier plastic film coating and the preparation method have the beneficial effects including:

[0025] The polyurethane primer can be coated on the plastic film material to form a 0.5-1.5 mu m polyurethane primer layer, which facilitates the subsequent coating of the high-barrier functional liquid, and can improve the adhesion, temperature resistance and moisture and gas resistance of the high-barrier coating on the plastic film material, thereby solving the problems of poor adhesion of the barrier material to the substrate film, poor high-temperature resistance and poor medium corrosion resistance of the existing PVDC, PVA and nanocellulose high-barrier coating film. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the application will be described clearly and completely in combination with the specific contents of the application; obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments, which do not constitute a limitation on the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0027] First, the terms that can be used in this paper are described as follows:

[0028] The term "and / or" means either one or both, for example, X and / or Y means three cases including "X" or "Y" and "X and Y".

[0029] The terms "comprising", "containing", "including", "having" or any other similar semantic descriptions should be interpreted to be non-exclusive inclusion. For example, the inclusion of a technical feature element (such as raw materials, components, ingredients, carriers, dosage forms, materials, sizes, parts, components, mechanisms, devices, steps, processes, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or articles, etc.) should be interpreted as not only including the explicitly listed technical feature element, but also including other technical feature elements not explicitly listed but known in the art.

[0030] The term "consisting of" means excluding any technical feature element not explicitly listed. If this term is used in a claim, the term will make the claim closed such that it contains no technical feature element other than those explicitly listed, except for conventional impurities associated therewith. If the term is only present in a certain clause of the claim, it only limits the elements explicitly listed in that clause, and the elements recited in other clauses are not excluded from the overall claim.

[0031] The term "mass parts" is used to represent the mass ratio relationship between multiple components. For example, if it is described that X component is x mass parts and Y component is y mass parts, it means that the mass ratio of X component to Y component is x:y. 1 mass part can represent any mass, for example, 1 mass part can represent 1 kg or 3.1415926 kg, etc. The sum of the mass parts of all components does not necessarily equal 100 parts, and can be greater than, less than, or equal to 100 parts. Unless otherwise specified, the parts, proportions, and percentages described herein are by mass.

[0032] When a concentration, temperature, pressure, size, or other parameter is expressed as a numerical range, the numerical range should be understood to specifically disclose all ranges formed from any pair of an upper limit value, a lower limit value, and a preferred value within the numerical range, regardless of whether the range is explicitly recited; for example, if the numerical range "2-8" is recited, the numerical range should be interpreted to include ranges such as "2-7", "2-6", "5-7", "3-4 and 6-7", "3-5 and 7", "2 and 5-7", etc. Unless otherwise specified, the numerical ranges recited herein include both the end values and all integers and fractions within the numerical range.

[0033] A polyurethane primer for coating a high-barrier plastic film and a method for preparing the same are provided. The contents not described in detail in the embodiments of the present application are the prior art known to those skilled in the art. In the embodiments of the present application, unless otherwise specified, the conditions are performed according to the conventional conditions in the art or the conditions recommended by the manufacturer. In the embodiments of the present application, unless otherwise specified, the reagents or instruments used are conventional products that can be commercially available.

[0034] The application provides a polyurethane primer for coating high-barrier plastic film, which comprises the following components:

[0035] The main agent, the curing agent and the solvent are mixed uniformly in a weight ratio of 20:2-6:50-120.

[0036] The main agent is made of isocyanate monomer, polycaprolactone polyol, self-made polyester polyol, epoxy resin, functional additive, silane coupling agent, chain extender, fumed silica, functional filler and solvent.

[0037] The curing agent is L-75 curing agent or self-made multi-functional isocyanate curing agent with fast reaction.

[0038] Further, the isocyanate monomer used in the main agent is one or two of toluene diisocyanate, diphenyl methane diisocyanate and isophorone diisocyanate.

[0039] Further, the polycaprolactone used in the main agent has a molecular weight of 400-4000 and a functionality of 2-3. The addition of the polycaprolactone can improve the hydrolysis resistance of the primer.

[0040] Further, the epoxy resin used in the main agent is commercially available epoxy resin E44 or epoxy resin E51 or a mixture of the two, and the addition of the epoxy resin can increase the heat resistance and scratch resistance of the primer.

[0041] Further, the self-made polyester polyol used in the main agent is synthesized by using raw materials including adipic acid, terephthalic acid, hexanediol, 1,4-butanediol, neopentyl glycol and diethylene glycol, and has a molecular weight of 500-3000 and an acid value of <1 mgKOH / g.

[0042] Further, the functional additive used in the main agent includes, in terms of weight parts, 0.000005-0.00001 parts of catalyst and 0.0003-1.99999 parts of yellowing-resistant additive.

[0043] The functional filler includes, in terms of weight parts, 2.99999-9.99999 parts of food-grade paraffin and 0.000005-0.00001 parts of inorganic metal ion.

[0044] Further, the functional filler used in the main agent includes fumed silica, food-grade paraffin and inorganic metal ion.

[0045] Further, the solvent used is one or a mixture of two of ethyl acetate, methyl acetate, acetone and butanone.

[0046] The ratio of each raw material in the main agent is shown in Table 1 below:

[0047] No. Raw material Amount (by weight) 1 Isocyanate monomer 3～10 2 Polycaprolactone polyol 10～20 3 Self-made polyester polyol 20～50 4 Epoxy resin 3～10 5 Functional additive 0.000305～5 6 Silane coupling agent 0.1～5 Chain extender 0.1～5 Fumed silica 1～3 7 Functional filler 3～10 8 Solvent 20～50

[0048] Further, the main raw materials of the self-made multifunctional isocyanate curing agent used in the curing agent described above are toluene diisocyanate, diphenyl diisocyanate, trimethylolpropane, 1,4-butanediol, trifunctional polyether polyol with a molecular weight less than 1000, and ethyl acetate; the NCO content of the self-made multifunctional isocyanate curing agent is 8-15%, and the solid content is 50-80%.

[0049] The present application also provides a preparation method of the polyurethane primer for high-barrier plastic film coating.

[0050] Preparation of the main agent of the primer:

[0051] According to the raw materials and amounts in the formula table, the isocyanate monomer, 10-20 parts by weight of solvent, polycaprolactone polyol, and self-made polyester polyol are added to a reaction kettle, and reacted at 60-70°C for 1-2h; functional additives (i.e., catalyst and yellowing-resistant additives) are added, and the temperature is raised to 80-90°C for 2-4h of heat preservation reaction; the remaining solvent, the formula amount of epoxy resin, silane coupling agent, and fumed silica are added, and the temperature is maintained at 70-80°C for 1h of reaction; finally, functional fillers (including food-grade paraffin and inorganic metal ions) and chain extenders are added, and the material is discharged after stirring for 0.5h, thereby obtaining the main agent.

[0052] Preparation method of the primer: the main agent A, curing agent B, and solvent ethyl acetate are configured in a weight ratio of 20:2-6:50-120 to obtain a working solution with a solid content of 5-20%, thereby obtaining the polyurethane primer for high-barrier plastic film coating.

[0053] As can be seen from the above, the polyurethane primer of the present application can be coated on the plastic film material to form a polyurethane primer layer with a thickness of 0.5-1.5μm, which facilitates the subsequent coating of high-barrier functional liquid. The polyurethane primer can improve the adhesion, temperature resistance, and moisture and gas resistance of the high-barrier coating on the plastic film material, thereby solving the problems of poor adhesion between the barrier material and the substrate film, poor high-temperature resistance, and poor medium corrosion resistance of the existing PVDC, PVA, and nanocellulose high-barrier coating film.

[0054] In order to more clearly show the technical solutions provided by the present application and the technical effects produced thereby, the polyurethane primer for high-barrier plastic film coating and the preparation method thereof provided by the present application are described in detail below with specific examples.

[0055] Examples 1, 2, and Comparative Example

[0056] The amount of each raw material of the main agent of Examples 1, 2 and Comparative Examples is shown in Table 2 below

[0057] The preparation method of each example is as follows: the polyurethane primer for high-barrier plastic film coating is synthesized according to the following steps:

[0058] The main agent is prepared according to the requirements of the following Table 2 formulation: the isocyanate monomer, part of the solvent, polycaprolactone polyol, and self-made polyester polyol are added to the reaction kettle and reacted at 60-70°C for 1-2h; functional additives (including catalyst and yellowing-resistant additives) are added, the temperature is raised to 80-90°C, and the reaction is kept for 2-4h; the remaining solvent, epoxy resin, silane coupling agent, and fumed silica additives required by the formulation are added, and the temperature is kept at 70-80°C for 1h; finally, functional fillers (including food-grade paraffin and inorganic metal ions) and chain extenders and other remaining components are added, and the mixture is stirred for 0.5h before discharging, thereby obtaining the required main agent.

[0059] Table 2 below is the main agent A of two examples and one comparative example prepared according to the above process.

[0060] Table 2 is the feeding formulation table of Examples 1, 2 and Comparative Examples

[0061]

[0062]

[0063] The main agent of each example and comparative example above is mixed with commercially available L-75 polyurethane curing agent and self-made multifunctional isocyanate curing agent, and dilution solvent (ethyl acetate) to prepare the coating primer, and the specific matching ratio is shown in the following table:

[0064] Table 3 is the formulation table of the primer working solution prepared by mixing the main agent of Examples 1, 2 and Comparative Examples with different curing agents

[0065]

[0066] According to the matching ratio of Table 3, the main agent A, curing agent B, and solvent ethyl acetate are mixed uniformly in a glue mixing barrel, and then poured into the primer glue tank of the coating machine. According to the normal K film (PVDC coating) production process, the substrate film material is polyester PET film material-12μm, and the machine equipment parameters during normal production are used to produce different working liquids of K film. After curing is completed, the moisture and oxygen permeability of the K film and the adhesion of the K coating are tested, and the specific test results are shown in Table 4 below:

[0067]

[0068] From the test results in Table 4, it can be seen that:

[0069] The coating without primer has poor adhesion and is easy to fall off after curing.

[0070] The primer 1 to 4 are working solutions of the primer prepared by different combinations of the main agent and the curing agent according to the requirements of the present application, and the oxygen and water vapor permeability of the K film prepared by the working solutions are obviously improved, reaching the test standard of high barrier film material.

[0071] The primer 5 to 6 are working solutions of the primer prepared by different combinations of the main agent and the curing agent according to the comparative examples, and the oxygen and water vapor permeability is improved compared with the film material without primer, but cannot reach the requirements of high barrier film material, and the adhesion is also not as good as the primer prepared by the examples.

[0072] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any change or replacement easily thought by the skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. The information disclosed in the background section of the present application is only intended to deepen the understanding of the general background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes the prior art known by the skilled in the art.

Claims

1. A polyurethane primer for coating of high barrier plastic films, characterized in that, The application relates to a polyurethane primer for high-barrier plastic film coating. The primer, the curing agent and the solvent are in a weight ratio of 20:2-6:50-120. The primer is prepared from isocyanate monomers, polycaprolactone polyols, self-made polyester polyols, epoxy resins, functional additives, silane coupling agents, chain extenders, fumed silica, functional fillers and solvents. The curing agent is a multifunctional isocyanate curing agent. In the primer, the dosages of the raw materials are as follows: isocyanate monomers 3-10 parts, polycaprolactone polyols 10-20 parts, self-made polyester polyols 20-50 parts, epoxy resins 3-10 parts, functional additives 0.000305-2 parts, silane coupling agents 0.1-5 parts, chain extenders 0.1-5 parts, fumed silica 1-3 parts, functional fillers 3-10 parts and solvents 20-50 parts. In the primer, the self-made polyester polyols are polyester polyols with a molecular weight of 500-3000 and an acid value less than 1 mgKOH / g, which are synthesized from adipic acid, terephthalic acid, hexanediol, 1,4-butanediol, neopentyl glycol and diethylene glycol. In the primer, the isocyanate monomers are one or two of toluene diisocyanate, diphenyl methane diisocyanate and isophorone diisocyanate. In the primer, the epoxy resins are one or a mixture of two of commercially available epoxy resins E44 and E51. In the primer, the functional additives include, by weight, 0.000005-0.00001 parts of a catalyst and 0.0003-1.99999 parts of a yellowing-resistant additive. In the functional fillers, by weight, 2.99999-9.99999 parts of food-grade paraffin and 0.000005-0.00001 parts of inorganic metal ions are included. In the solvents, one or a mixture of two of ethyl acetate, methyl acetate, acetone and butanone is used. In the curing agent, the multifunctional isocyanate curing agent is an isocyanate curing agent with an NCO content of 8-15% and a solid content of 50-80%, which is prepared from toluene diisocyanate, diphenyl diisocyanate, trimethylolpropane, 1,4-butanediol, a trifunctional polyether polyol with a molecular weight less than 1000 and ethyl acetate.

6. A preparation method of the polyurethane primer for high-barrier plastic film coating according to any one of claims 1-5, comprising the following steps: Preparation of the primer: according to the primer formula in any one of claims 1-5, the raw materials are taken, the isocyanate monomers, 10-20 parts of solvents, polycaprolactone polyols and self-made polyester polyols in the primer raw materials are added into a reaction kettle, and reaction is carried out at 60-70 DEG C for 1-2 h; the functional additives are added, the temperature is raised to 80-90 DEG C, and reaction is carried out at the temperature for 2-4 h; the remaining solvents, epoxy resins, silane coupling agents and fumed silica are added, and reaction is carried out at 70-80 DEG C for 1 h; finally, the functional fillers and the chain extenders are added, and after stirring for 0.5 h, the product is discharged, and the primer is prepared. ​ ​ 2. The polyurethane primer for coating a high barrier plastic film according to claim 1, characterized by, ​ 3. The polyurethane primer for coating a high barrier plastic film according to claim 1, characterized by, ​ 4. The polyurethane primer for coating a high barrier plastic film according to claim 1, characterized by, ​ ​ ​ 5. The polyurethane primer for coating high-barrier plastic films according to claim 1, characterized by, ​ ​ ​ The main agent, the curing agent and the solvent are mixed in a weight ratio of 20:2-6:50-120 to form a working solution with a solid content of 5-20%, which is a polyurethane primer for high-barrier plastic film coating.

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