Chemical corrosion resistant KPET double coating film, preparation method and application

Abstract

The invention discloses a chemical corrosion resistant KPET double coating film, a preparation method and an application, and belongs to the technical field of coating films. The preparation method of the chemical corrosion resistant KPET double coating film comprises the following steps: S1 performs corona treatment on a KPET substrate to obtain a pre-treated KPET substrate; S2 places the pre-treated KPET substrate on a coating machine, and applies a coating agent to both sides of the pre-treated KPET substrate by means of a roller and a spraying method on the coating machine; S3 smoothes the coated KPET substrate with a smoothing roller, dries, inspects and packages, and obtains a chemical corrosion resistant KPET double coating film. The double coating film prepared by the invention has good oxygen barrier, moisture barrier and chemical corrosion resistance effects.

Description

Technical Field

[0001] The invention relates to the technical field of coating films, and in particular to a chemical corrosion resistant KPET double coating film, a preparation method and application thereof. Background Art

[0002] Polyethylene terephthalate (PET) film is widely used in packaging, printing, advertising and other industries because of its advantages such as lightness, transparency, moisture resistance and oxidation resistance, good air tightness, toughness, folding resistance and smooth surface. However, PET film has low surface free energy, and it is difficult to print, spray and adhere directly on its surface. It is necessary to modify the surface of the film product according to actual needs. Water-based coatings are the first choice of coating raw materials because of their low environmental pollution and simple processing. However, water-based polyurethane also has the disadvantages of poor film toughness and low adhesion.

[0003] Polyvinylidene chloride (PVDC) emulsion is a water-soluble polymer coating that is non-toxic, odorless, safe and reliable, with high oxygen and moisture barrier properties. It also has excellent oil resistance, corrosion resistance, taste retention and printing properties. Its high barrier properties can be used for coating substrates such as cellophane, plastic, and cardboard for food and drug packaging. It can also be widely used in construction and industrial anti-corrosion coatings.

[0004] The Chinese invention patent (application number: 202311265526.8) discloses a core-shell PVDC emulsion with high barrier and adhesion modified by organic silicon and its preparation method. The PVDC emulsion is copolymerized by weight percentage of 43-46% vinylidene chloride, 4-8% acrylate monomer, 1-4% polysiloxane, 0.1-3% functional monomer, 0.4-4% emulsifier, 0.1-0.9% redox compound initiator, 0.05-0.35% ph regulator, and 45-55% deionized water. Although the PVDC emulsion prepared by the invention has good adhesion to the substrate and also has certain oxygen barrier properties, the invention still has some disadvantages, such as poor corrosion resistance and no moisture barrier properties, which is subject to certain restrictions when used. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the present invention provides a chemical corrosion resistant KPET double coating film, a preparation method and an application thereof.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for preparing a chemical corrosion resistant KPET double coating film comprises the following steps:

[0008] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 4-8KW, and the speed of the corona machine is 80-120m / min;

[0009] S2, coating: placing the pretreated KPET substrate on a coating machine, and coating the pretreated KPET substrate on both sides with the coating agent by means of a roller and spray on the coating machine; the coating amount of the coating agent in S2 is 1.8-2.8 g / m 2 ;

[0010] S3, drying: the coated KPET substrate is smoothed by a smoothing roller, dried, inspected and packaged to obtain a chemical corrosion resistant KPET double coating film.

[0011] Polyvinylidene chloride is a copolymer with vinylidene chloride monomer as the main component. Due to its symmetrical molecular structure and high crystallinity, oxygen molecules and water molecules are difficult to move in PVDC molecules. In addition, chlorine atoms are hydrophobic and will not form hydrogen bonds. Therefore, it has excellent oxygen and moisture barrier properties. The presence of chlorine atoms in its structure can also make the coating anti-mildew and anti-fouling properties, and it can also be used specifically in incense tablets.

[0012] The coating agent is prepared as follows: 20-40 parts by weight of polyvinylidene chloride emulsion, 8-15 parts by weight of modified acrylic emulsion, 1-3 parts by weight of surfactant, 0.5-2 parts by weight of defoamer, and 1-3 parts by weight of anti-blocking agent.

[0013] The surfactant includes at least one of sodium dodecylbenzene sulfonate, sodium lignin sulfonate, and polyethylene glycol octylphenyl ether; the defoamer is at least one of tributyl phosphate, polyoxypropylene glycerol ether, and ether defoamers; and the anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0014] Although PVDC has good chemical resistance, the oxygen barrier, water barrier and chemical corrosion resistance of PVDC coating may decrease due to environmental factors (such as temperature and humidity changes) during long-term use. Therefore, polyfluorosilicone is added in the preparation process of PVDC emulsion. Polyfluorosilicone can form a more stable protective layer and waterproof layer on the surface of the coating, which can significantly improve the chemical corrosion resistance, oxygen barrier and moisture barrier of KPET double coating.

[0015] Polyfluorosilicone molecules contain unique Si-O bonds, which make them highly chemically stable. Adding polyfluorosilicone to the KPET double coating can form a dense protective layer on the coating surface, effectively preventing chemical substances from corroding the PVDC coating. In addition, polyfluorosilicone has a low surface energy, making the coating surface less likely to be contaminated, further improving the coating's chemical corrosion resistance.

[0016] The fluorine atoms in the molecular structure of polyfluorosilicone have strong electron-attracting ability, which makes the oxygen atoms in the molecule highly active. Adding polyfluorosilicone to the KPET double coating helps to increase the activity of oxygen atoms in the coating, thereby enhancing the coating's barrier properties to oxygen. In addition, the dense layer formed by polyfluorosilicone molecules on the surface of the coating can effectively reduce the penetration of oxygen molecules, further improving the coating's oxygen barrier properties.

[0017] Polyfluorosilicone molecules have good hydrophobicity and can form a waterproof layer on the surface of the KPET double coating. This waterproof layer can effectively prevent the penetration of water molecules and improve the moisture barrier performance of the coating. At the same time, the dispersion of polyfluorosilicone molecules in the coating helps to improve the density of the coating and further reduce the penetration of water molecules.

[0018] Polyfluorosilicone molecules have good interfacial activity, which can improve the interfacial compatibility between PVDC and KPET substrates and enhance the adhesion of the coating. In addition, the dense layer formed by polyfluorosilicone molecules on the surface of the coating helps to improve the smoothness of the coating surface and reduce the friction coefficient, thereby improving the appearance quality of the packaging product.

[0019] In summary, adding polyfluorosilicone in the preparation process of polyvinylidene chloride emulsion can effectively improve the chemical corrosion resistance, oxygen barrier and moisture barrier properties of KPET double coating, mainly due to the special properties of polyfluorosilicone molecular structure and the dense protective layer formed on the surface of the coating. This will help to improve the shelf life and safety of incense tablets.

[0020] The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps:

[0021] M1: 50-60 parts by weight of water and 1-2 parts by weight of emulsifier are mixed and stirred evenly, 0.5-2 parts by weight of acrylic monomer, 0.3-0.8 parts by weight of acrylic acid and 3-4 parts by weight of vinylidene chloride monomer are added, and stirred at 50-60°C and 100-300 rpm for 10-30 minutes, and then 0.2-0.5 parts by weight of initiator are added, and the reaction is continued for 10-30 minutes to obtain a seed solution;

[0022] M2, under stirring conditions at 40-55°C and 100-300rpm, 1-2 parts by weight of emulsifier, 0.1-0.4 parts by weight of initiator, 2-4 parts by weight of water, 1-3 parts by weight of acrylic monomer, 0.5-2 parts by weight of acrylic acid, 40-60 parts by weight of vinylidene chloride monomer and 0.5-2 parts by weight of polyfluorosiloxane are added dropwise to the above seed solution at 1-3mL / min, and stirring is continued for 50-100min to obtain a mixed emulsion;

[0023] M3, under stirring conditions at 40-55°C and 100-300rpm, add 0.3-0.8 parts by weight of emulsifier, 0.1-0.5 parts by weight of initiator, 1-4 parts by weight of water, 3-8 parts by weight of acrylic monomer, 2-4 parts by weight of acrylic acid, 12-20 parts by weight of vinylidene chloride monomer and 3-6 parts by weight of polyfluorosilicone to the above mixed emulsion at a rate of 1-3mL / min, continue stirring for 30-60min, and then place at 80-90°C for reaction for 1-4h to obtain polyvinylidene chloride emulsion.

[0024] The initiator is any one of sodium bisulfite, azobisisobutyronitrile, di-tert-butyl peroxide, and benzoyl peroxide; the emulsifier is any one of sorbitan monooleate, Tween80, monoglycerol fatty acid glyceride, sodium lignin sulfonate, and sodium p-styrene sulfonate; and the acrylic acid ester monomer is any one of hydroxyethyl methacrylate phosphate, methyl acrylate, isooctyl acrylate, ethyl methacrylate, and butyl methacrylate.

[0025] The preparation method of the polyfluorosilicone is as follows: 1,1, dimethyl 1,2-siloxane methacrylic acid and concentrated sulfuric acid are mixed, cyclohexane and hydroquinone are added, heated and stirred to obtain an acrylate siloxane compound; N-(3-triethoxysilylpropyl) perfluorooctaneamide and xylene are stirred and mixed uniformly to obtain an N-(3-triethoxysilylpropyl) perfluorooctaneamide solution;

[0026] The above-mentioned acrylic ester siloxane compound and xylene are mixed, trifluoromethanesulfonic acid and water are added under heating and stirring conditions, heated to react, and all the above-mentioned N-(3-triethoxysilylpropyl)perfluorooctylamide solution is added dropwise. After the addition is completed, the reaction is continued by keeping the temperature, filtering, and removing the solvent by reduced pressure distillation to obtain polyfluorosilicone.

[0027] Reaction mechanism: First, with 1,1, dimethyl 1,2-siloxane and methacrylic acid as the main raw materials, under acidic conditions (concentrated sulfuric acid as a catalyst), 1,1, dimethyl 1,2-siloxane is ring-opened to form an active intermediate of siloxane; the ring-opened siloxane intermediate undergoes an esterification reaction with methacrylic acid to generate acrylate siloxane compounds, and hydroquinone is used as an inhibitor to prevent acrylate from polymerizing at high temperatures.

[0028] Secondly, under nitrogen protection, acrylate siloxane compounds are mixed with trifluoromethanesulfonic acid and water. Trifluoromethanesulfonic acid is used as a catalyst to promote the polymerization reaction of siloxane. Then N-(3-triethoxysilylpropyl) perfluorooctylamide solution is added to react with the growing siloxane chain to introduce perfluoroalkyl side chains.

[0029] Sodium bicarbonate is added to neutralize the remaining acid, and then solid impurities are removed by filtration, and the solvent is removed by distillation under reduced pressure to obtain polyfluorosilicone.

[0030] Preferably, the preparation method of the polyfluorosilicone is as follows:

[0031] 50-70 parts by weight of 1,1, dimethyl 1,2-siloxane, 30-50 parts by weight of methacrylic acid, and 2-5 parts by weight of 70-90wt% concentrated sulfuric acid are mixed, 80-120 parts by weight of cyclohexane and 0.05-0.2 parts by weight of hydroquinone are added, and the mixture is stirred at 110-140°C and 300-500rpm for 3-5h, cooled to room temperature, filtered, and purified to obtain an acrylate siloxane compound; 10-30 parts by weight of N-(3-triethoxysilylpropyl)perfluorooctaneamide and 50-150 parts by weight of xylene are stirred and mixed uniformly to obtain an N-(3-triethoxysilylpropyl)perfluorooctaneamide solution;

[0032] Under nitrogen protection, 3-8 parts by weight of the above-mentioned acrylate siloxane compound and 10-20 parts by weight of xylene are mixed, 0.03-0.1 parts by weight of trifluoromethanesulfonic acid and 1-3 parts by weight of water are added at 80-90° C. and 400-800 rpm, stirring is continued for 1-4 hours, and then placed at 120-140° C. for reaction for 1-3 hours, and all of the above-mentioned N-(3-triethoxysilylpropyl)perfluorooctylamide solution is added dropwise at a speed of 1-3 mL / min. After the addition is completed, the reaction is continued by keeping the temperature for 3-6 hours, 3-6 parts by weight of sodium bicarbonate are added, stirring is continued for 15-26 hours, filtering, and removing the solvent by reduced pressure distillation to obtain polyfluorosilicone.

[0033] The chemical corrosion resistant KPET double coating film is obtained by adopting any one of the above preparation methods.

[0034] The chemical corrosion resistant KPET double coating film is used in incense tablets.

[0035] Beneficial effects of the invention: The chemical corrosion resistant KPET double coating film provided by the invention is a coating agent prepared by taking polyvinylidene chloride emulsion and modified acrylic emulsion as main raw materials, water as solvent, and simultaneously combining surfactant, defoaming agent and anti-adhesion agent, and finally coating on a KPET substrate to prepare a chemical corrosion resistant KPET double coating film. The double coating film does not contain organic solvents, has no VOC emissions, is low in cost, is simple in operation method, is not easy to generate bubbles during the coating process, has good filling effect, and has good oxygen barrier, moisture barrier and chemical corrosion resistance effects during long-term use. DETAILED DESCRIPTION

[0036] The above content of the present invention is further described in detail below in conjunction with specific implementation modes, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments.

[0037] Introduction of some raw materials in this application:

[0038] The KPET substrate was purchased from Shijiazhuang Dajia New Material Technology Co., Ltd., with the brand name DJ-KPET-11.

[0039] The modified acrylic emulsion was purchased from Shandong Suihua Biotechnology Co., Ltd., model: AR-2888W.

[0040] The polyether-modified polydimethylsiloxane was purchased from Jining Fangyu Chemical Co., Ltd. with the brand name TY-813.

[0041] Commercially available polyvinylidene chloride emulsion was purchased from Shanghai Qiaowei Chemical Technology Co., Ltd., brand: A736.

[0042] Example 1: A method for preparing a chemically resistant KPET double coating film, comprising the following steps:

[0043] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to increase the surface tension of the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 6KW, and the speed of the corona machine is 100m / min;

[0044] S2. Coating: Place the pretreated KPET substrate on the coating machine, and evenly coat the coating agent on both sides of the KPET substrate by means of the roller and spray on the coating machine. The coating amount of the coating agent is 2g / m 2 ;

[0045] S3, drying: After the KPET substrate coated with the coating agent is smoothed by a smoothing roller, it is introduced into an oven by a traction roller for drying, inspection, and packaging to obtain a chemical corrosion resistant KPET double coating film.

[0046] The coating agent is prepared as follows: 30 parts by weight of polyvinylidene chloride emulsion, 10 parts by weight of modified acrylic emulsion, 2 parts by weight of surfactant, 1 part by weight of defoamer, and 2 parts by weight of anti-blocking agent.

[0047] The surfactant is sodium dodecylbenzene sulfonate.

[0048] The defoaming agent is tributyl phosphate.

[0049] The anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0050] The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps:

[0051] M1: 55 parts by weight of water and 1.5 parts by weight of sorbitan monooleate were mixed and stirred evenly, 1 part by weight of hydroxyethyl methacrylate phosphate, 0.5 parts by weight of acrylic acid and 3.5 parts by weight of vinylidene chloride monomer were added, and stirred at 55°C and 200 rpm for 20 minutes, and then 0.4 parts by weight of azobisisobutyronitrile were added, and the reaction was continued for 20 minutes to obtain a seed solution;

[0052] M2, under stirring conditions at 45°C and 200rpm, 1.5 parts by weight of sorbitan monooleate, 0.3 parts by weight of azobisisobutyronitrile, 2.5 parts by weight of water, 2 parts by weight of hydroxyethyl methacrylate phosphate, 1 part by weight of acrylic acid, 50 parts by weight of vinylidene chloride monomer and 1 part by weight of polyfluorosiloxane were added dropwise to the above seed solution at 2mL / min, and stirring was continued for 70min to obtain a mixed emulsion;

[0053] M3, under stirring conditions at 45°C and 200 rpm, 0.5 parts by weight of sorbitan monooleate, 0.3 parts by weight of azobisisobutyronitrile, 2.5 parts by weight of water, 5 parts by weight of hydroxyethyl methacrylate phosphate, 2.5 parts by weight of acrylic acid, 16.5 parts by weight of vinylidene chloride monomer and 4 parts by weight of polyfluorosilicone were added dropwise to the above mixed emulsion at a rate of 2 mL / min, and stirring was continued for 40 minutes. The mixture was then placed at 85°C for reaction for 2 hours to obtain a polyvinylidene chloride emulsion.

[0054] The preparation method of the polyfluorosilicone is as follows:

[0055] 60 parts by weight of 1,1, dimethyl 1,2-siloxane, 40 parts by weight of methacrylic acid, and 3 parts by weight of 80wt% concentrated sulfuric acid were mixed, 100 parts by weight of cyclohexane and 0.1 parts by weight of hydroquinone were added, and the mixture was stirred at 120°C and 400rpm for 4h, cooled to room temperature, filtered, and purified to obtain an acrylate siloxane compound; 20 parts by weight of N-(3-triethoxysilylpropyl)perfluorooctaneamide and 100 parts by weight of xylene were stirred and mixed uniformly to obtain an N-(3-triethoxysilylpropyl)perfluorooctaneamide solution;

[0056] Under nitrogen protection, 5 parts by weight of the above-mentioned acrylate siloxane compound and 15 parts by weight of xylene were mixed, 0.05 parts by weight of trifluoromethanesulfonic acid and 1.5 parts by weight of water were added at 85°C and 600rpm, stirring was continued for 2 hours, and then the mixture was placed at 130°C for reaction for 2 hours. All of the above-mentioned N-(3-triethoxysilylpropyl)perfluorooctylamide solution was added dropwise at a rate of 2mL / min. After the addition was completed, the reaction was continued by keeping the temperature for 4 hours, 4 parts by weight of sodium bicarbonate were added, stirring was continued for 18 hours, filtration was performed, and the solvent was removed by distillation under reduced pressure to obtain polyfluorosilicone.

[0057] Example 2: A method for preparing a chemically resistant KPET double coating film, comprising the following steps:

[0058] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to increase the surface tension of the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 4KW, and the speed of the corona machine is 80m / min;

[0059] S2. Coating: Place the pretreated KPET substrate on the coating machine, and evenly coat the coating agent on both sides of the KPET substrate by means of the roller and spray on the coating machine. The coating amount of the coating agent is 1.8 g / m 2 ;

[0060] S3, drying: After the KPET substrate coated with the coating agent is smoothed by a smoothing roller, it is introduced into an oven by a traction roller for drying, inspection, and packaging to obtain a chemical corrosion resistant KPET double coating film.

[0061] The coating agent is prepared as follows: 30 parts by weight of polyvinylidene chloride emulsion, 10 parts by weight of modified acrylic emulsion, 2 parts by weight of surfactant, 1 part by weight of defoamer, and 2 parts by weight of anti-blocking agent.

[0062] The surfactant is sodium dodecylbenzene sulfonate.

[0063] The defoaming agent is tributyl phosphate.

[0064] The anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0065] The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps:

[0066] M1: 50 parts by weight of water and 1 part by weight of sorbitan monooleate were mixed and stirred evenly, 0.5 parts by weight of hydroxyethyl methacrylate phosphate, 0.3 parts by weight of acrylic acid and 3 parts by weight of vinylidene chloride monomer were added, and the mixture was stirred at 50°C and 100 rpm for 10 min, and then 0.2 parts by weight of azobisisobutyronitrile was added, and the reaction was continued for 10 min to obtain a seed solution;

[0067] M2, under stirring conditions at 40°C and 100 rpm, 1 part by weight of sorbitan monooleate, 0.1 part by weight of azobisisobutyronitrile, 2 parts by weight of water, 1 part by weight of hydroxyethyl methacrylate phosphate, 0.5 part by weight of acrylic acid, 40 parts by weight of vinylidene chloride monomer and 0.5 part by weight of polyfluorosiloxane were added dropwise to the above seed solution at 1 mL / min, and stirring was continued for 50 min to obtain a mixed emulsion;

[0068] M3 was added dropwise at 1 mL / min to the mixed emulsion at 40°C and 100 rpm under stirring conditions: 0.3 parts by weight of sorbitan monooleate, 0.1 parts by weight of azobisisobutyronitrile, 1 part by weight of water, 3 parts by weight of hydroxyethyl methacrylate phosphate, 2 parts by weight of acrylic acid, 12 parts by weight of vinylidene chloride monomer and 3 parts by weight of polyfluorosilicone. The mixture was stirred for 30 min and then placed at 80°C for reaction for 1 h to obtain a polyvinylidene chloride emulsion.

[0069] The preparation method of the polyfluorosilicone is as follows:

[0070] 50 parts by weight of 1,1, dimethyl 1,2-siloxane, 30 parts by weight of methacrylic acid, and 2 parts by weight of 70wt% concentrated sulfuric acid were mixed, 80 parts by weight of cyclohexane and 0.05 parts by weight of hydroquinone were added, and the mixture was stirred at 110°C and 300rpm for 3h, cooled to room temperature, filtered, and purified to obtain an acrylate siloxane compound; 10 parts by weight of N-(3-triethoxysilylpropyl)perfluorooctaneamide and 50 parts by weight of xylene were stirred and mixed uniformly to obtain an N-(3-triethoxysilylpropyl)perfluorooctaneamide solution;

[0071] Under nitrogen protection, 3 parts by weight of the above-mentioned acrylate siloxane compound and 10 parts by weight of xylene were mixed, 0.03 parts by weight of trifluoromethanesulfonic acid and 1 part by weight of water were added at 80°C and 400rpm, stirring was continued for 1 hour, and then the mixture was placed at 120°C for reaction for 1 hour, and all the above-mentioned N-(3-triethoxysilylpropyl)perfluorooctylamide solution was added dropwise at a rate of 1 mL / min. After the addition was completed, the reaction was continued by keeping the temperature for 3 hours, 4 parts by weight of sodium bicarbonate were added, stirring was continued for 15 hours, filtration was performed, and the solvent was removed by distillation under reduced pressure to obtain polyfluorosilicone.

[0072] Example 3: A method for preparing a chemically resistant KPET double coating film, comprising the following steps:

[0073] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to increase the surface tension of the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 8KW, and the speed of the corona machine is 120m / min;

[0074] S2. Coating: Place the pretreated KPET substrate on the coating machine, and evenly coat the coating agent on both sides of the KPET substrate by means of the roller and spray on the coating machine. The coating amount of the coating agent is 2.8g / m 2 ;

[0075] S3, drying: After the KPET substrate coated with the coating agent is smoothed by a smoothing roller, it is introduced into an oven by a traction roller for drying, inspection, and packaging to obtain a chemical corrosion resistant KPET double coating film.

[0076] The coating agent is prepared as follows: 30 parts by weight of polyvinylidene chloride emulsion, 10 parts by weight of modified acrylic emulsion, 2 parts by weight of surfactant, 1 part by weight of defoamer, and 2 parts by weight of anti-blocking agent.

[0077] The surfactant is sodium dodecylbenzene sulfonate.

[0078] The defoaming agent is tributyl phosphate.

[0079] The anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0080] The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps:

[0081] M1: 60 parts by weight of water and 2 parts by weight of sorbitan monooleate were mixed and stirred evenly, 2 parts by weight of hydroxyethyl methacrylate phosphate, 0.8 parts by weight of acrylic acid and 4 parts by weight of vinylidene chloride monomer were added, and the mixture was stirred at 60°C and 300 rpm for 30 min, and then 0.5 parts by weight of azobisisobutyronitrile was added, and the reaction was continued for 30 min to obtain a seed solution;

[0082] M2, under stirring conditions at 55°C and 300rpm, 2 parts by weight of sorbitan monooleate, 0.4 parts by weight of azobisisobutyronitrile, 4 parts by weight of water, 3 parts by weight of hydroxyethyl methacrylate phosphate, 2 parts by weight of acrylic acid, 60 parts by weight of vinylidene chloride monomer and 2 parts by weight of polyfluorosiloxane were added dropwise to the above seed solution at 3mL / min, and stirring was continued for 100min to obtain a mixed emulsion;

[0083] M3 was added dropwise at 3 mL / min to the mixed emulsion at 55°C and 300 rpm under stirring conditions: 0.8 parts by weight of sorbitan monooleate, 0.5 parts by weight of azobisisobutyronitrile, 4 parts by weight of water, 8 parts by weight of hydroxyethyl methacrylate phosphate, 4 parts by weight of acrylic acid, 20 parts by weight of vinylidene chloride monomer and 6 parts by weight of polyfluorosilicone. The mixture was stirred for 60 min and then reacted at 90°C for 4 h to obtain a polyvinylidene chloride emulsion.

[0084] The preparation method of the polyfluorosilicone is as follows:

[0085] 70 parts by weight of 1,1, dimethyl 1,2-siloxane, 50 parts by weight of methacrylic acid, and 5 parts by weight of 90 wt% concentrated sulfuric acid were mixed, 120 parts by weight of cyclohexane and 0.2 parts by weight of hydroquinone were added, and the mixture was stirred at 140° C. and 500 rpm for 5 hours, cooled to room temperature, filtered, and purified to obtain an acrylate siloxane compound; 30 parts by weight of N-(3-triethoxysilylpropyl)perfluorooctaneamide and 150 parts by weight of xylene were stirred and mixed uniformly to obtain an N-(3-triethoxysilylpropyl)perfluorooctaneamide solution;

[0086] Under nitrogen protection, 8 parts by weight of the above-mentioned acrylate siloxane compound and 20 parts by weight of xylene were mixed, 0.1 parts by weight of trifluoromethanesulfonic acid and 3 parts by weight of water were added at 90°C and 800rpm, stirring was continued for 4 hours, and then placed at 140°C for reaction for 3 hours, and all of the above-mentioned N-(3-triethoxysilylpropyl)perfluorooctylamide solution was added dropwise at a rate of 3mL / min. After the addition was completed, the reaction was continued to be kept warm for 6 hours, 4 parts by weight of sodium bicarbonate were added, stirring was continued for 26 hours, filtered, and the solvent was distilled off under reduced pressure to obtain polyfluorosilicone.

[0087] Comparative Example 1: A method for preparing a chemically resistant KPET double coating film, comprising the following steps:

[0088] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to increase the surface tension of the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 6KW, and the speed of the corona machine is 100m / min;

[0089] S2. Coating: Place the pretreated KPET substrate on the coating machine, and evenly coat the coating agent on both sides of the KPET substrate by means of the roller and spray on the coating machine. The coating amount of the coating agent is 2g / m 2 ;

[0090] S3, drying: After the KPET substrate coated with the coating agent is smoothed by a smoothing roller, it is introduced into an oven by a traction roller for drying, inspection, and packaging to obtain a chemical corrosion resistant KPET double coating film.

[0091] The coating agent is prepared as follows: 30 parts by weight of polyvinylidene chloride emulsion, 10 parts by weight of modified acrylic emulsion, 2 parts by weight of surfactant, 1 part by weight of defoamer, and 2 parts by weight of anti-blocking agent.

[0092] The surfactant is sodium dodecylbenzene sulfonate.

[0093] The defoaming agent is tributyl phosphate.

[0094] The anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0095] The polyvinylidene chloride emulsion is commercially available.

[0096] Comparative Example 2: A method for preparing a chemically resistant KPET double coating film, comprising the following steps:

[0097] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to increase the surface tension of the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 6KW, and the speed of the corona machine is 100m / min;

[0098] S2. Coating: Place the pretreated KPET substrate on the coating machine, and evenly coat the coating agent on both sides of the KPET substrate by means of the roller and spray on the coating machine. The coating amount of the coating agent is 2g / m 2 ;

[0099] S3, drying: After the KPET substrate coated with the coating agent is smoothed by a smoothing roller, it is introduced into an oven by a traction roller for drying, inspection, and packaging to obtain a chemical corrosion resistant KPET double coating film.

[0100] The coating agent is prepared as follows: 30 parts by weight of polyvinylidene chloride emulsion, 10 parts by weight of modified acrylic emulsion, 2 parts by weight of surfactant, 1 part by weight of defoamer, and 2 parts by weight of anti-blocking agent.

[0101] The surfactant is sodium dodecylbenzene sulfonate.

[0102] The defoaming agent is tributyl phosphate.

[0103] The anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0104] The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps:

[0105] M1: 55 parts by weight of water and 1.5 parts by weight of sorbitan monooleate were mixed and stirred evenly, 1 part by weight of hydroxyethyl methacrylate phosphate, 0.5 parts by weight of acrylic acid and 3.5 parts by weight of vinylidene chloride monomer were added, and stirred at 55°C and 200 rpm for 20 minutes, and then 0.4 parts by weight of azobisisobutyronitrile were added, and the reaction was continued for 20 minutes to obtain a seed solution;

[0106] M2, under stirring conditions at 45°C and 200rpm, 1.5 parts by weight of sorbitan monooleate, 0.3 parts by weight of azobisisobutyronitrile, 2.5 parts by weight of water, 2 parts by weight of hydroxyethyl methacrylate phosphate, 1 part by weight of acrylic acid, and 50 parts by weight of vinylidene chloride monomer were added dropwise to the above seed solution at 2mL / min, and stirring was continued for 70min to obtain a mixed emulsion;

[0107] M3, under stirring conditions at 45°C and 200 rpm, 0.5 parts by weight of sorbitan monooleate, 0.3 parts by weight of azobisisobutyronitrile, 2.5 parts by weight of water, 5 parts by weight of hydroxyethyl methacrylate phosphate, 2.5 parts by weight of acrylic acid, and 16.5 parts by weight of vinylidene chloride monomer were added dropwise to the above mixed emulsion at a rate of 2 mL / min, and stirring was continued for 40 minutes. The mixture was then placed at 85°C for reaction for 2 hours to obtain a polyvinylidene chloride emulsion.

[0108] Comparative Example 3: A method for preparing a chemically resistant KPET double coating film, comprising the following steps:

[0109] S1. Pretreatment of KPET substrate: performing corona treatment on the KPET substrate to increase the surface tension of the KPET substrate to obtain a pretreated KPET substrate; the power of the corona machine is 6KW, and the speed of the corona machine is 100m / min;

[0110] S2. Coating: Place the pretreated KPET substrate on the coating machine, and evenly coat the coating agent on both sides of the KPET substrate by means of the roller and spray on the coating machine. The coating amount of the coating agent is 2g / m 2 ;

[0111] S3, drying: After the KPET substrate coated with the coating agent is smoothed by a smoothing roller, it is introduced into an oven by a traction roller for drying, inspection, and packaging to obtain a chemical corrosion resistant KPET double coating film.

[0112] The coating agent is prepared as follows: 30 parts by weight of polyvinylidene chloride emulsion, 10 parts by weight of modified acrylic emulsion, 2 parts by weight of surfactant, 1 part by weight of defoamer, and 2 parts by weight of anti-blocking agent.

[0113] The surfactant is sodium dodecylbenzene sulfonate.

[0114] The defoaming agent is tributyl phosphate.

[0115] The anti-adhesion agent is polyether-modified polydimethylsiloxane.

[0116] The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps:

[0117] M1: 55 parts by weight of water and 1.5 parts by weight of sorbitan monooleate were mixed and stirred evenly, 1 part by weight of hydroxyethyl methacrylate phosphate, 0.5 parts by weight of acrylic acid and 3.5 parts by weight of vinylidene chloride monomer were added, and stirred at 55°C and 200 rpm for 20 minutes, and then 0.4 parts by weight of azobisisobutyronitrile were added, and the reaction was continued for 20 minutes to obtain a seed solution;

[0118] M2, under stirring conditions at 45°C and 200rpm, 1.5 parts by weight of sorbitan monooleate, 0.3 parts by weight of azobisisobutyronitrile, 2.5 parts by weight of water, 2 parts by weight of hydroxyethyl methacrylate phosphate, 1 part by weight of acrylic acid, 50 parts by weight of vinylidene chloride monomer and 1 part by weight of N-(3-triethoxysilylpropyl)perfluorooctylamide were added dropwise to the above seed solution at 2mL / min, and stirring was continued for 70min to obtain a mixed emulsion;

[0119] M3 was added dropwise at 2 mL / min to the mixed emulsion at 45°C and 200 rpm under stirring conditions: 0.5 parts by weight of sorbitan monooleate, 0.3 parts by weight of azobisisobutyronitrile, 2.5 parts by weight of water, 5 parts by weight of hydroxyethyl methacrylate phosphate, 2.5 parts by weight of acrylic acid, 16.5 parts by weight of vinylidene chloride monomer and 4 parts by weight of N-(3-triethoxysilylpropyl)perfluorooctylamide. The mixture was stirred for 40 min and then reacted at 85°C for 2 h to obtain a polyvinylidene chloride emulsion.

[0120] Test Example 1: Chemical corrosion resistance test: Acid resistance test: Refer to the acid resistance test standard in HG / T4759-2014 "Waterborne Epoxy Resin Anticorrosive Coatings" for testing. The chemical corrosion resistant KPET double coating prepared above was immersed in a 20wt% sulfuric acid aqueous solution to observe the time when the sample appeared blistering, obvious discoloration, softening, wrinkling, rusting, peeling and other coating pathological phenomena. When the corrosion area of ​​the sample coating is greater than 30% of the test area, the coating is considered to have failed. There are 3 samples in each group. The results are shown in Table 1.

[0121] Alkali resistance test: refer to the alkali resistance test standard in HG / T4759-2014 "Waterborne Epoxy Resin Anticorrosive Coatings" for testing. The chemical corrosion resistant KPET double coating prepared above was immersed in a 20wt% sodium hydroxide aqueous solution to observe the time when the sample showed blistering, obvious discoloration, softening, wrinkling, rusting, peeling and other coating pathological phenomena. When the corrosion area of ​​the sample coating is greater than 30% of the test area, the coating is considered to have failed. There are 3 samples in each group. The results are shown in Table 1.

[0122] Table 1 Chemical corrosion resistance test

[0123] Acid resistance (d) Alkali resistance (d) Example 1 66 69 Example 2 63 65 Example 3 64 67 Comparative Example 1 30 35 Comparative Example 2 40 43 Comparative Example 3 53 57

[0124] Test Example 2: Moisture barrier and oxygen barrier test: The water vapor permeability performance of Example 1 and Comparative Examples 1-3 was tested with reference to the second method electrolytic analysis method in the national standard YBB00092003-2015 "Water vapor permeability determination method", and the gas permeability performance of Example 1 and Comparative Examples 1-3 was tested with reference to the first method pressure difference method in the national standard YBB00082003-2015 "Gas permeability determination method". Each group was tested 3 times and the average value was taken. The results are shown in Table 2.

[0125] Table 2 Chemical corrosion resistance test

[0126] <![CDATA[Water vapor transmission rate (cm 3 / ㎡·24h·0.1MPa)]]> <![CDATA[Oxygen transmission rate (cm 3 / ㎡·24h·0.1MPa) <!-- 8 -->]]> Example 1 0.08 0.11 Comparative Example 1 1.32 1.91 Comparative Example 2 0.81 1.14 Comparative Example 3 0.45 0.58

[0127] From the above results, it can be seen that the chemical corrosion resistant KPET double coating film prepared by the present invention not only has good chemical corrosion resistance, but also has good moisture and oxygen barrier effects, thereby improving the service life of incense tablets. From the above results, it can be seen that adding polyfluorosilicone during the preparation of PVDC emulsion can form a more stable protective layer and waterproof layer on the surface of the coating film, which can significantly improve the chemical corrosion resistance, oxygen barrier and moisture barrier properties of the KPET double coating film.

[0128] Polyfluorosilicone molecules contain unique Si-O bonds, which make them highly chemically stable. Adding polyfluorosilicone to the KPET double coating can form a dense protective layer on the coating surface, effectively preventing chemical substances from corroding the PVDC coating. In addition, polyfluorosilicone has a low surface energy, making the coating surface less likely to be contaminated, further improving the coating's chemical corrosion resistance.

[0129] The fluorine atoms in the molecular structure of polyfluorosilicone have strong electron-attracting ability, which makes the oxygen atoms in the molecule highly active. Adding polyfluorosilicone to the KPET double coating helps to increase the activity of oxygen atoms in the coating, thereby enhancing the coating's barrier properties to oxygen. In addition, the dense layer formed by polyfluorosilicone molecules on the surface of the coating can effectively reduce the penetration of oxygen molecules, further improving the coating's oxygen barrier properties.

[0130] Polyfluorosilicone molecules have good hydrophobicity and can form a waterproof layer on the surface of the KPET double coating. This waterproof layer can effectively prevent the penetration of water molecules and improve the moisture barrier performance of the coating. At the same time, the dispersion of polyfluorosilicone molecules in the coating helps to improve the density of the coating and further reduce the penetration of water molecules.

[0131] Polyfluorosilicone molecules have good interfacial activity, which can improve the interfacial compatibility between PVDC and KPET substrates and enhance the adhesion of the coating. In addition, the dense layer formed by polyfluorosilicone molecules on the surface of the coating helps to improve the smoothness of the coating surface and reduce the friction coefficient, thereby improving the appearance quality of the packaging product.

[0132] In summary, adding polyfluorosilicone in the preparation process of polyvinylidene chloride emulsion can effectively improve the chemical corrosion resistance, oxygen barrier and moisture barrier properties of KPET double coating, mainly due to the special properties of polyfluorosilicone molecular structure and the dense protective layer formed on the surface of the coating. This will help to improve the shelf life and safety of incense tablets.

Claims

1. A method for preparing a chemical corrosion resistant KPET double coating film, characterized in that: The steps include: S1. KPET substrate pretreatment: performing corona treatment on the KPET substrate to obtain a pretreated KPET substrate; S2, coating: placing the pretreated KPET substrate on a coating machine, and coating the pretreated KPET substrate on both sides with the coating agent by means of a roller and spray on the coating machine; S3, drying: smoothing the coated KPET substrate with a smoothing roller, drying, inspecting, and packaging to obtain a chemical corrosion resistant KPET double coating film; The coating agent is prepared as follows: 20-40 parts by weight of polyvinylidene chloride emulsion, 8-15 parts by weight of modified acrylic emulsion, 1-3 parts by weight of surfactant, 0.5-2 parts by weight of defoamer, and 1-3 parts by weight of anti-adhesion agent; The preparation method of the polyvinylidene chloride emulsion is as follows, comprising the following steps: M1: 50-60 parts by weight of water and 1-2 parts by weight of emulsifier are mixed and stirred evenly, 0.5-2 parts by weight of acrylic monomer, 0.3-0.8 parts by weight of acrylic acid and 3-4 parts by weight of vinylidene chloride monomer are added, and stirred at 50-60°C and 100-300 rpm for 10-30 minutes, and then 0.2-0.5 parts by weight of initiator are added, and the reaction is continued for 10-30 minutes to obtain a seed solution; M2, under stirring conditions at 40-55°C and 100-300rpm, 1-2 parts by weight of emulsifier, 0.1-0.4 parts by weight of initiator, 2-4 parts by weight of water, 1-3 parts by weight of acrylate monomer, 0.5-2 parts by weight of acrylic acid, 40-60 parts by weight of vinylidene chloride monomer and 0.5-2 parts by weight of polyfluorosiloxane are added dropwise to the above seed solution at 1-3mL / min, and stirring is continued for 50-100min to obtain a mixed emulsion; M3, under stirring conditions at 40-55°C and 100-300rpm, 0.3-0.8 parts by weight of emulsifier, 0.1-0.5 parts by weight of initiator, 1-4 parts by weight of water, 3-8 parts by weight of acrylic monomer, 2-4 parts by weight of acrylic acid, 12-20 parts by weight of vinylidene chloride monomer and 3-6 parts by weight of polyfluorosilicone are added dropwise to the mixed emulsion at 1-3mL / min, stirring is continued for 30-60min, and then placed at 80-90°C for reaction for 1-4h to obtain polyvinylidene chloride emulsion; The preparation method of the polyfluorosilicone is as follows: 50-70 parts by weight of 1,1-dimethyl-1,2-siloxane, 30-50 parts by weight of methacrylic acid, and 2-5 parts by weight of 70-90wt% concentrated sulfuric acid are mixed, 80-120 parts by weight of cyclohexane and 0.05-0.2 parts by weight of hydroquinone are added, and the mixture is stirred at 110-140°C and 300-500rpm for 3-5h, cooled to room temperature, filtered, and purified to obtain an acrylate siloxane compound; 10-30 parts by weight of N-(3-triethoxysilylpropyl)perfluorooctaneamide and 50-150 parts by weight of xylene are stirred and mixed uniformly to obtain an N-(3-triethoxysilylpropyl)perfluorooctaneamide solution; Under nitrogen protection, 3-8 parts by weight of the above-mentioned acrylate siloxane compound and 10-20 parts by weight of xylene are mixed, 0.03-0.1 parts by weight of trifluoromethanesulfonic acid and 1-3 parts by weight of water are added at 80-90° C. and 400-800 rpm, stirring is continued for 1-4 hours, and then placed at 120-140° C. for reaction for 1-3 hours, and all of the above-mentioned N-(3-triethoxysilylpropyl)perfluorooctylamide solution is added dropwise at a speed of 1-3 mL / min. After the addition is completed, the reaction is continued by keeping the temperature for 3-6 hours, 3-6 parts by weight of sodium bicarbonate are added, stirring is continued for 15-26 hours, filtering, and removing the solvent by reduced pressure distillation to obtain polyfluorosilicone.

2. The method for preparing the chemical corrosion resistant KPET double coating film according to claim 1, characterized in that: The coating amount of the coating agent in S2 is 1.8-2.8 g / m 2 .

3. The method for preparing the chemical corrosion resistant KPET double coating film according to claim 1, characterized in that: The surfactant includes at least one of sodium dodecylbenzene sulfonate, sodium lignin sulfonate, and polyethylene glycol octylphenyl ether; the defoamer is at least one of tributyl phosphate, polyoxypropylene glycerol ether, and ether defoamers; and the anti-adhesion agent is polyether-modified polydimethylsiloxane.

4. The method for preparing the chemical corrosion resistant KPET double coating film according to claim 1, characterized in that: The initiator is any one of sodium bisulfite, azobisisobutyronitrile, di-tert-butyl peroxide, and benzoyl peroxide; the emulsifier is any one of sorbitan monooleate, Tween80, monoglycerol fatty acid glyceride, sodium lignin sulfonate, and sodium p-styrene sulfonate; and the acrylic acid ester monomer is any one of hydroxyethyl methacrylate phosphate, methyl acrylate, isooctyl acrylate, ethyl methacrylate, and butyl methacrylate.

5. A chemical corrosion resistant KPET double coating film, characterized in that: The method is adopted as claimed in any one of claims 1 to 4.

6. Application of the chemical corrosion resistant KPET double coating as claimed in claim 5 in incense tablets.