Highly waterproof water-based gloss oil as well as preparation method and application thereof

Abstract

The invention particularly relates to high-waterproofness water-based gloss oil as well as a preparation method and application thereof. The water-based gloss oil is prepared from 65%-75% of organic silicon modified acrylic emulsion, 5%-15% of epoxy ester prepolymer, 2%-6% of wax emulsion, 1%-3% of a coalescing agent, 0.1%-0.5% of a defoaming agent, 0.1%-0.3% of a wetting leveling agent, 0-1% of a neutralizing agent and the balance of deionized water. The obtained water-based gloss oil has good water resistance and wear resistance, is strong in adhesive force with a paper packaging material, completely takes water as a dispersion medium, and meets the requirements of environmental regulations. The prepared water-based gloss oil has good waterproofness and mechanical durability, the surface of a coating has a certain matte effect, and meanwhile, the water-based gloss oil has a certain short-distance fresh-keeping function when being applied to paper packaging bags.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-based gloss oil, in particular to a high-waterproof water-based gloss oil and a preparation method and application thereof. BACKGROUND

[0002] With the increasing global environmental awareness and the widespread implementation of the "plastic limit order" policy, paper packaging materials have been vigorously developed due to their environmental advantages such as recyclability and biodegradability. Paper packaging bags, honeycomb express bags, food packaging bags and other products are used to replace traditional plastic bags and have become one of the most common items in logistics, retail and daily life. However, due to the hydrophilicity and porous structure of paper packaging materials, they are prone to strength reduction, deformation or damage in a humid environment or after being exposed to water, which severely limits their applicability. Therefore, how to improve the waterproofness of paper packaging materials has become a key problem to be solved in the industry.

[0003] In the production process of paper packaging materials, gloss oil is an important part of surface treatment. By coating a layer of gloss oil on the surface of the product, a protective film can be formed to effectively isolate the direct contact between water and the paper substrate, thereby making up for the poor water resistance of paper packaging materials. Currently, the waterproof gloss oil for paper products on the market is divided into solvent-based gloss oil, water-based gloss oil and UV gloss oil. Among them, solvent-based gloss oil uses ester, ketone and other organic solvents. Although this type of product has good film forming performance, fast drying speed and high water resistance, it releases a large amount of VOC during production, which can easily harm the environment and human body, and is difficult to meet the development requirements of environmental regulations. Water-based gloss oil uses water as the dispersion medium, and the common film-forming materials include acrylic emulsion, polyurethane emulsion, styrene-acrylic acid copolymer, etc. This type of material is non-toxic and does not contain VOC, and has good advantages in terms of environmental protection. However, it has obvious shortcomings in terms of adhesion to paper packaging materials, waterproofness and wear resistance.

[0004] In the present application, a high-waterproof water-based gloss oil is proposed, but the comprehensive balance between the adhesion of the coating film to the paper packaging material, the waterproofness and the mechanical properties needs to be overcome. SUMMARY

[0005] Therefore, the present application aims to overcome the problems in the prior art and provide a high-waterproof water-based gloss oil and a preparation method and application thereof. The water-based gloss oil prepared by the present application has good waterproofness and mechanical durability, and the coating surface has a certain matte effect. When applied to paper packaging bags, it has a certain short-term preservation function.

[0006] To achieve the above technical purpose, achieve the above technical effect, the present application is realized by the following technical solutions: The application provides a high-waterproof water-based gloss oil, which comprises the following raw materials in percentage by mass: silicone-modified acrylic emulsion 65-75%, epoxy ester prepolymer 5-15%, wax emulsion 2-6%, film-forming aid 1-3%, defoaming agent 0.1-0.5%, wetting and leveling agent 0.1-0.3%, neutralizing agent 0-1%, and the rest is deionized water.

[0007] Further, the wax emulsion is an emulsion formed by at least one of PE wax, PTFE wax, paraffin wax and silicone wax and an emulsifying agent under the action of high shear force, and the solid content is 30%.

[0008] Further, the film-forming aid is dipropylene glycol methyl ether or propylene glycol phenyl ether.

[0009] Further, the defoaming agent is BYK-093 or DF85.

[0010] Further, the wetting and leveling agent is polyether-modified silicone.

[0011] Further, the neutralizing agent is ammonia water or aminomethyl propanol.

[0012] Further, the preparation method of the epoxy ester prepolymer comprises the following steps: placing epoxy resin E20, linoleic acid, a catalyst and hypophosphorous acid in a reaction kettle, heating to 125-130 DEG C under a nitrogen atmosphere, constant temperature reaction for 2-2.5 h, then continuously increasing the temperature to 190-200 DEG C, and keeping warm for 1.5-2 h, stopping the reaction when the acid value in the system is reduced to 5-10 mg KOH / g, and adding propylene glycol butyl ether when the temperature is reduced to below 130 DEG C and slowly stirring; continuously cooling to 60-70 DEG C, adding dimethyl ethanolamine dropwise and continuously stirring for 20-30 min, then adding deionized water under high-speed stirring to obtain a milky white dispersion, thereby obtaining the epoxy ester prepolymer.

[0013] Further, the mass ratio of the epoxy resin E20 and the linoleic acid is 100:35-45, the catalyst is 0.2-0.5% of the mass of the epoxy resin E20, the hypophosphorous acid is 0.1-0.3% of the mass of the epoxy resin E20, the dimethyl ethanolamine is 6-10% of the mass of the epoxy resin E20, and the propylene glycol butyl ether is 20-30% of the mass of the epoxy resin E20. The solid content of the epoxy ester prepolymer is 45-50%.

[0014] Further, the silicone-modified acrylic emulsion comprises component A and component B, wherein the component A comprises hard monomer 15-25 parts, emulsifier A 1-1.5 parts and deionized water 13-16 parts. Component B includes 35-45 parts of soft monomer, 4-8 parts of functional monomer, 3-8 parts of glycidyl methacrylate, 5-8 parts of siloxane monomer, 0.2-0.6 parts of initiator, 0.5-1.5 parts of emulsifier BA, and 35-40 parts of deionized water.

[0015] Furthermore, the soft monomer is butyl acrylate, the hard monomer is at least one of methyl methacrylate, isobornyl methacrylate, and ethylene tert-carbonate, and the functional monomer is at least one of acrylic acid, methacrylic acid, and hydroxyethyl methacrylate.

[0016] Furthermore, the siloxane monomer is γ-methacryloxypropyltrimethoxysilane or vinyltrimethoxysilane.

[0017] Furthermore, emulsifier A and emulsifier B are at least one or a combination of two of reactive emulsifiers and nonionic emulsifiers. The reactive emulsifier is selected from alkyl allyl polyether sulfonate CO-436 or sodium allyl hydroxypropanesulfonate, and the nonionic emulsifier is selected from at least one of OP-10, AEO-7, XP-70, and AEO-9.

[0018] Furthermore, the initiator is ammonium persulfate or potassium persulfate.

[0019] Furthermore, the pH adjuster is ammonia water or aminomethylpropanol.

[0020] In this invention, the preparation method of the organosilicon-modified acrylic emulsion includes the following steps: Step A1: Add emulsifier B and deionized water from component B to a pre-emulsification tank. Under stirring conditions, add soft monomer, functional monomer, glycidyl methacrylate and half of the siloxane monomer in sequence and mix evenly to obtain a pre-emulsion. Prepare an initiator solution with 5-10 parts of deionized water solvent for later use. Step A2: Add the hard monomer, emulsifier A and deionized water from component A to a reaction vessel under a nitrogen atmosphere and stir. Heat to 75-80℃, add 1 / 3 of the initiator solution, and keep warm for 20-30 minutes to obtain the seed emulsion. Step A3: Raise the temperature to 80-85℃, and then add the pre-emulsion obtained in step A1 and the remaining initiator solution dropwise to the seed emulsion, controlling the dropwise addition rate to 2.5-3.5h. After the addition is completed, keep warm for 20-30min. Step A4: Add the remaining siloxane monomer dropwise, keep warm for 1-1.5 hours, cool the reactor to below 40°C, filter to remove the gel, and add a pH adjuster while stirring slowly to obtain the organosilicon-modified acrylic emulsion.

[0021] Furthermore, in step A4, a pH adjuster is added to adjust the pH of the emulsion to 7.5-8.5.

[0022] In this invention, the structure obtained by seed emulsion polymerization of the organosilicon-modified acrylic emulsion prepared by the above method can easily form a mechanical anchoring effect on the porous fibers of paper packaging materials, and introduce epoxy groups on the acrylic resin chain segments to form chemical crosslinks, which can significantly improve the water resistance and mechanical strength of the coating film. Furthermore, the hydrophobicity is improved by introducing siloxane monomer copolymerization, thereby forming a crosslinked, hydrophobic, and tough three-dimensional network structure after film formation.

[0023] The present invention also provides a method for preparing the above-mentioned highly waterproof water-based varnish, comprising the following steps: adding an organosilicon-modified acrylic emulsion into a dispersion vessel, slowly adding an epoxy ester prepolymer under stirring conditions and mixing evenly, then sequentially adding a wax emulsion, a film-forming aid, a wetting and leveling agent and a defoamer, and after complete dispersion, adding deionized water, and finally adjusting the pH of the system to 7.5-8.5 with a neutralizing agent, filtering to remove gel and impurities, and then discharging to obtain the highly waterproof water-based varnish.

[0024] Furthermore, this invention applies the highly waterproof water-based varnish prepared above to paper packaging materials, specifically by printing the water-based varnish onto the surface of the paper packaging material, with a coating amount of 1-20 g / m². 2 Then, the water-based varnish is cured into a film by infrared and hot air drying.

[0025] Furthermore, the invention includes a second printing of waterproof varnish on the edges of the paper packaging material where folding is required and at the paper cut edges (cut edges). In this invention, the second printing of waterproof varnish strengthens the paper packaging material to prevent water seepage in blind spots caused by cracking of the surface waterproof varnish at the edges after folding, and also avoids water seepage blind spots at the cut edges of the paper packaging material.

[0026] Compared with existing technologies, the beneficial effects of this invention are as follows: The highly waterproof water-based varnish of this invention effectively improves the waterproofness of the coating film through the combined action of silicone-modified acrylic emulsion, epoxy ester prepolymer, and wax emulsion. Furthermore, the epoxy ester prepolymer and silicone acrylic emulsion together exhibit good adhesion to paper substrates, while simultaneously improving the weather resistance of the coating film, making it suitable for use in various environments. The chemical cross-linking structure formed by the combined action of the components endows the coated film with excellent mechanical properties and durability. Moreover, this highly waterproof water-based varnish uses water as the dispersion medium, has low VOC content, and complies with environmental regulations. Furthermore, the water-based varnish prepared by this invention not only possesses excellent waterproof and mechanical durability properties, but also has a certain matte finish on the coating surface, and when applied to paper packaging bags, it provides a certain short-distance preservation function.

[0027] This invention involves secondary printing of waterproof varnish on the edges and cuts of paper packaging materials where folding is required. This ensures that all paper fiber cross-sections are completely covered and not exposed to air, thus completely blocking the capillary penetration channels of moisture and resulting in paper packaging products with excellent waterproof performance. Attached Figure Description

[0028] Figure 1 This is a temperature change curve of the sample bag prepared in Example 1 after it was placed into an ice pack.

[0029] Figure 2 This is a temperature change curve of an unvarnished kraft paper bag (blank group) after being filled with an ice pack. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments; those skilled in the art can also use other alternative methods to implement the invention for some well-known technologies.

[0031] Example 1 This embodiment provides a highly waterproof water-based varnish, comprising the following raw materials by weight percentage: 75% silicone-modified acrylic emulsion, 10% epoxy ester prepolymer, 6% wax emulsion, 1% film-forming aid, 0.3% defoamer, 0.2% wetting and leveling agent, 0.5% neutralizer, and the remainder being deionized water.

[0032] Furthermore, the wax emulsion is an emulsion formed by PTFE wax and emulsifier (composed of Span80 and OP-6 in a mass ratio of 1:2, with a dosage of 10%) under high-speed shear force (130℃, 1000 r / min, 30min), with a solid content of 30%.

[0033] Furthermore, the film-forming aid is propylene glycol phenyl ether.

[0034] Furthermore, the defoamer is BYK-093.

[0035] Furthermore, the wetting and leveling agent is Greesol A04PA.

[0036] Furthermore, the neutralizing agent is aminomethylpropanol.

[0037] Furthermore, the preparation method of the epoxy ester prepolymer includes the following steps: epoxy resin E20, linoleic acid, catalyst and hypophosphoric acid are placed in a reaction vessel, heated to 130°C under a nitrogen atmosphere, and reacted at a constant temperature for 2 hours. Then, the temperature is further increased to 195°C and held for 2 hours. When the acid value in the system decreases to 5-10 mg KOH / g, the reaction is stopped. When the temperature drops below 130°C, propylene glycol butyl ether is added and stirred slowly. The temperature is further cooled to 60°C, dimethyl ethanolamine is added dropwise and stirred for 30 minutes. Then, deionized water is added under high-speed stirring to obtain a milky white dispersion, which is the epoxy ester prepolymer.

[0038] Furthermore, the mass ratio of epoxy resin E20 to linoleic acid is 100:40, the catalyst is 0.3% of the mass of epoxy resin E20, the hypophosphite is 0.2% of the mass of epoxy resin E20, the dimethylethanolamine is 8% of the mass of epoxy resin E20, and the propylene glycol butyl ether is 25% of the mass of epoxy resin E20. The solid content of the epoxy ester prepolymer is 48%.

[0039] Furthermore, the silicone-modified acrylic emulsion includes component A and component B, wherein component A includes 20 parts of hard monomer, 1.2 parts of emulsifier A, and 14 parts of deionized water; Component B includes 40 parts of soft monomer, 6 parts of functional monomer, 5 parts of glycidyl methacrylate, 8 parts of siloxane monomer, 0.4 parts of initiator, 1 part of emulsifier B, and 38 parts of deionized water.

[0040] Furthermore, the soft monomer is butyl acrylate, the hard monomer is ethylene tert-carbonate, and the functional monomer is hydroxyethyl methacrylate.

[0041] Furthermore, the siloxane monomer is γ-methacryloxypropyltrimethoxysilane.

[0042] Furthermore, the emulsifiers A and B are compounded from alkyl allyl polyether sulfonate CO-436 and AEO-9 in a mass ratio of 1:1.

[0043] Furthermore, the initiator is ammonium persulfate.

[0044] Furthermore, the pH adjuster is aminomethylpropanol.

[0045] In this invention, the preparation method of the organosilicon-modified acrylic emulsion includes the following steps: Step A1: Add emulsifier B and deionized water from component B to a pre-emulsification tank. Under stirring conditions, add soft monomer, functional monomer, glycidyl methacrylate and half of the siloxane monomer in sequence and mix evenly to obtain a pre-emulsion. Prepare an initiator solution with 5 parts of deionized water solvent for later use. Step A2: Add the hard monomer, emulsifier A and deionized water from component A to a reaction vessel under nitrogen atmosphere and stir. Heat to 80°C, add 1 / 3 of the initiator solution, and keep warm for 30 minutes to obtain seed emulsion. Step A3: Raise the temperature to 85°C, and then add the pre-emulsion obtained in step A1 and the remaining initiator solution dropwise to the seed emulsion, controlling the dropwise addition rate to 3h. After the addition is completed, keep warm for 30min. Step A4: Add the remaining siloxane monomer dropwise, keep warm for 1 hour, cool the reactor to below 40°C, filter to remove the gel, and add a pH adjuster while stirring slowly to obtain the organosilicon-modified acrylic emulsion.

[0046] Furthermore, in step A4, a pH adjuster is added to adjust the pH of the emulsion to 8.

[0047] In this embodiment, the preparation method of the above-mentioned highly waterproof water-based varnish includes the following steps: adding silicone-modified acrylic emulsion into a dispersion vessel, slowly adding epoxy ester prepolymer under stirring conditions and mixing evenly, then sequentially adding wax emulsion, film-forming aid, wetting and leveling agent and defoamer, adding deionized water after complete dispersion, finally adjusting the pH of the system to 8 with a neutralizing agent, filtering to remove gel and impurities, and then discharging to obtain the highly waterproof water-based varnish.

[0048] Example 2 This embodiment provides a highly waterproof water-based varnish, comprising the following raw materials by weight percentage: 73% silicone-modified acrylic emulsion, 14% epoxy ester prepolymer, 5% wax emulsion, 2.5% film-forming aid, 0.4% defoamer, 0.25% wetting and leveling agent, 0.6% neutralizer, and the remainder being deionized water.

[0049] Furthermore, the wax emulsion is an emulsion formed by PTFE wax and emulsifier (composed of Span80 and OP-6 in a mass ratio of 1:2, with a dosage of 10%) under high-speed shear force (130℃, 1000 r / min, 30min), with a solid content of 30%.

[0050] Furthermore, the film-forming aid is dipropylene glycol methyl ether.

[0051] Furthermore, the defoamer is BYK-093.

[0052] Furthermore, the wetting and leveling agent is Greesol A04PA.

[0053] Furthermore, the neutralizing agent is aminomethylpropanol.

[0054] Furthermore, the preparation method of the epoxy ester prepolymer includes the following steps: epoxy resin E20, linoleic acid, catalyst and hypophosphoric acid are placed in a reaction vessel, heated to 125°C under a nitrogen atmosphere, and reacted at a constant temperature for 2.5 h. Then the temperature is further increased to 195°C and held for 2 h. When the acid value in the system decreases to 5-10 mg KOH / g, the reaction is stopped. When the temperature drops below 130°C, propylene glycol butyl ether is added and stirred slowly. The temperature is further cooled to 65°C, dimethyl ethanolamine is added dropwise and stirred for 25 min. Then deionized water is added under high-speed stirring to obtain a milky white dispersion, which is the epoxy ester prepolymer.

[0055] Furthermore, the mass ratio of epoxy resin E20 to linoleic acid is 100:38, the catalyst is 0.3% of the mass of epoxy resin E20, the hypophosphite is 0.15% of the mass of epoxy resin E20, the dimethylethanolamine is 9% of the mass of epoxy resin E20, and the propylene glycol butyl ether is 26% of the mass of epoxy resin E20. The solid content of the epoxy ester prepolymer is 50%.

[0056] Furthermore, the silicone-modified acrylic emulsion includes component A and component B, wherein component A includes 18 parts of hard monomer, 1 part of emulsifier A, and 15 parts of deionized water; Component B includes 38 parts of soft monomer, 6 parts of functional monomer, 6 parts of glycidyl methacrylate, 7 parts of siloxane monomer, 0.3 parts of initiator, 1.2 parts of emulsifier B, and 36 parts of deionized water.

[0057] Furthermore, the soft monomer is butyl acrylate, the hard monomer is isobornyl methacrylate, and the functional monomer is a compound of methacrylic acid and hydroxyethyl methacrylate in a mass ratio of 1:5.

[0058] Furthermore, the siloxane monomer is γ-methacryloxypropyltrimethoxysilane.

[0059] Furthermore, the emulsifiers A and B are compounded from alkyl allyl polyether sulfonate CO-436 and XP-70 in a mass ratio of 1:1.

[0060] Furthermore, the initiator is potassium persulfate.

[0061] Furthermore, the pH adjuster is aminomethylpropanol.

[0062] In this invention, the preparation method of the organosilicon-modified acrylic emulsion includes the following steps: Step A1: Add emulsifier B and deionized water from component B to a pre-emulsification tank. Under stirring conditions, add soft monomer, functional monomer, glycidyl methacrylate and half of the siloxane monomer in sequence and mix evenly to obtain a pre-emulsion. Prepare an initiator solution with 10 parts of deionized water solvent for later use. Step A2: Add the hard monomer, emulsifier A and deionized water from component A to a reaction vessel under a nitrogen atmosphere and stir. Heat to 75°C, add 1 / 3 of the initiator solution, and keep warm for 30 minutes to obtain the seed emulsion. Step A3: Raise the temperature to 80℃, and then add the pre-emulsion obtained in step A1 and the remaining initiator solution dropwise to the seed emulsion, controlling the dropwise addition rate at 3.5h. After the addition is completed, keep warm for 30min. Step A4: Add the remaining siloxane monomer dropwise, keep warm for 1.5 hours, cool the reactor to below 40°C, filter to remove the gel, and add a pH adjuster while stirring slowly to obtain the organosilicon-modified acrylic emulsion.

[0063] Furthermore, in step A4, a pH adjuster is added to adjust the pH of the emulsion to 8.

[0064] In this embodiment, the preparation method of the above-mentioned highly waterproof water-based varnish includes the following steps: adding silicone-modified acrylic emulsion into a dispersion vessel, slowly adding epoxy ester prepolymer under stirring conditions and mixing evenly, then sequentially adding wax emulsion, film-forming aid, wetting and leveling agent and defoamer, adding deionized water after complete dispersion, finally adjusting the pH of the system to 8 with a neutralizing agent, filtering to remove gel and impurities, and then discharging to obtain the highly waterproof water-based varnish.

[0065] Example 3 This embodiment provides a highly waterproof water-based varnish, comprising the following raw materials by weight percentage: 73% silicone-modified acrylic emulsion, 14% epoxy ester prepolymer, 5% wax emulsion, 2.5% film-forming aid, 0.4% defoamer, 0.25% wetting and leveling agent, 0.6% neutralizer, and the remainder being deionized water.

[0066] Furthermore, the wax emulsion is an emulsion formed by PTFE wax and emulsifier (composed of Span80 and OP-6 in a mass ratio of 1:2, with a dosage of 10%) under high-speed shear force (130℃, 1000 r / min, 30min), with a solid content of 30%.

[0067] Furthermore, the film-forming aid is dipropylene glycol methyl ether.

[0068] Furthermore, the defoamer is BYK-093.

[0069] Furthermore, the wetting and leveling agent is Greesol A04PA.

[0070] Furthermore, the neutralizing agent is aminomethylpropanol.

[0071] Furthermore, the preparation method of the epoxy ester prepolymer includes the following steps: epoxy resin E20, linoleic acid, catalyst and hypophosphoric acid are placed in a reaction vessel, heated to 125°C under a nitrogen atmosphere, and reacted at a constant temperature for 2.5 h. Then the temperature is further increased to 195°C and held for 2 h. When the acid value in the system decreases to 5-10 mg KOH / g, the reaction is stopped. When the temperature drops below 130°C, propylene glycol butyl ether is added and stirred slowly. The temperature is further cooled to 65°C, dimethyl ethanolamine is added dropwise and stirred for 25 min. Then deionized water is added under high-speed stirring to obtain a milky white dispersion, which is the epoxy ester prepolymer.

[0072] Furthermore, the mass ratio of epoxy resin E20 to linoleic acid is 100:38, the catalyst is 0.3% of the mass of epoxy resin E20, the hypophosphite is 0.15% of the mass of epoxy resin E20, the dimethylethanolamine is 9% of the mass of epoxy resin E20, and the propylene glycol butyl ether is 26% of the mass of epoxy resin E20. The solid content of the epoxy ester prepolymer is 50%.

[0073] Furthermore, the silicone-modified acrylic emulsion includes component A and component B, wherein component A includes 18 parts of hard monomer, 1 part of emulsifier A, and 15 parts of deionized water; Component B includes 38 parts of soft monomer, 6 parts of functional monomer, 6 parts of glycidyl methacrylate, 7 parts of siloxane monomer, 0.3 parts of initiator, 1.2 parts of emulsifier B, and 36 parts of deionized water.

[0074] Furthermore, the soft monomer is butyl acrylate, the hard monomer is isobornyl methacrylate, and the functional monomer is a compound of methacrylic acid and hydroxyethyl methacrylate in a mass ratio of 1:5.

[0075] Furthermore, the siloxane monomer is γ-methacryloxypropyltrimethoxysilane.

[0076] Furthermore, the emulsifiers A and B are compounded from alkyl allyl polyether sulfonate CO-436 and XP-70 in a mass ratio of 1:1.

[0077] Furthermore, the initiator is potassium persulfate.

[0078] Furthermore, the pH adjuster is aminomethylpropanol.

[0079] In this invention, the preparation method of the organosilicon-modified acrylic emulsion includes the following steps: Step A1: Add emulsifier B and deionized water from component B to a pre-emulsification tank. Under stirring conditions, add soft monomer, functional monomer, glycidyl methacrylate and half of the siloxane monomer in sequence and mix evenly to obtain a pre-emulsion. Prepare an initiator solution with 10 parts of deionized water solvent for later use. Step A2: Add the hard monomer, emulsifier A and deionized water from component A to a reaction vessel under a nitrogen atmosphere and stir. Heat to 75°C, add 1 / 3 of the initiator solution, and keep warm for 30 minutes to obtain the seed emulsion. Step A3: Raise the temperature to 80℃, and then add the pre-emulsion obtained in step A1 and the remaining initiator solution dropwise to the seed emulsion, controlling the dropwise addition rate at 3.5h. After the addition is completed, keep warm for 30min. Step A4: Add the remaining siloxane monomer dropwise, keep warm for 1.5 hours, cool the reactor to below 40°C, filter to remove the gel, and add a pH adjuster while stirring slowly to obtain the organosilicon-modified acrylic emulsion.

[0080] Furthermore, in step A4, a pH adjuster is added to adjust the pH of the emulsion to 8.

[0081] In this embodiment, the preparation method of the above-mentioned highly waterproof water-based varnish includes the following steps: adding silicone-modified acrylic emulsion into a dispersion vessel, slowly adding epoxy ester prepolymer under stirring conditions and mixing evenly, then sequentially adding wax emulsion, film-forming aid, wetting and leveling agent and defoamer, adding deionized water after complete dispersion, finally adjusting the pH of the system to 8 with a neutralizing agent, filtering to remove gel and impurities, and then discharging to obtain the highly waterproof water-based varnish.

[0082] Comparative Example 1 The difference between this comparative example and Example 1 is that the epoxy ester prepolymer in Example 1 was not added in this comparative example, and the remaining components were adjusted in proportion.

[0083] Comparative Example 2 The difference between this comparative example and Example 1 is that the silicone-modified acrylic emulsion in this comparative example includes component A and component B, wherein component A includes 25 parts of hard monomer, 1.2 parts of emulsifier A, and 14 parts of deionized water; Component B includes 38 parts of soft monomer, 8 parts of functional monomer, 8 parts of glycidyl methacrylate, 0.4 parts of initiator, 1 part of emulsifier B, and 38 parts of deionized water.

[0084] Furthermore, the soft monomer is butyl acrylate, the hard monomer is ethylene tert-carbonate, and the functional monomer is hydroxyethyl methacrylate.

[0085] Furthermore, the siloxane monomer is γ-methacryloxypropyltrimethoxysilane.

[0086] Furthermore, the emulsifiers A and B are compounded from alkyl allyl polyether sulfonate CO-436 and AEO-9 in a mass ratio of 1:1.

[0087] Furthermore, the initiator is ammonium persulfate.

[0088] Furthermore, the pH adjuster is aminomethylpropanol.

[0089] Comparative Example 3 The difference between this comparative example and Example 1 is that this comparative example uses 1.5 parts of polyethylene wax powder instead of the wax emulsion in Example 1.

[0090] Performance testing: A layer of the highly waterproof water-based varnish prepared in Examples 1-3 and Comparative Examples 1-3 was printed onto the surface of kraft paper (80G stretch kraft paper, Dongguan Hehe Paper Industry Co., Ltd.) using a screen printing machine, with a coating weight of 7.5 g / m². 2 The samples were dried using infrared / hot air (80-110℃ in six sections, with a dwell time of 4 minutes) to obtain the test samples. Unvarnished kraft paper served as the blank group. Water resistance, tensile strength, tear strength, and burst strength were tested on both the blank group and the test samples. The results are shown in the table below.

[0091] Among them, the waterproof performance is tested by the static water contact angle, which is measured by a static contact angle measuring instrument.

[0092] Tensile strength was tested according to GB / T12914-2008. The sample size was 160*15mm, and each group contained 10 samples. The average value was taken.

[0093] Tear resistance was tested according to GB / T455-2002. The sample size was 60*50mm, and each group contained 5 samples. The average value was taken.

[0094] Bursting strength was tested according to GB / T454-2022, with 5 samples in each group and the average value was taken.

[0095] In addition, the gloss of the coating was tested using GB / T 9754-2007 at a test angle of 60°.

[0096]

[0097] As shown in the table above, the water-based varnishes prepared in Examples 1-3 of this invention, when used for varnishing kraft paper, result in products with high waterproof and mechanical properties. The static water contact angle is greater than 98°, and only a slight decay occurs after 300 seconds, indicating good waterproof performance. Furthermore, compared to the blank group and Comparative Examples 1-3, it can be seen that this invention, through the synergistic effect of silicone-modified acrylic emulsion and epoxy ester prepolymer to form a stable cross-linked network, makes the coating film denser, thereby significantly improving the tensile strength, tear resistance, and burst strength of the kraft paper product. Simultaneously, the silicone modification and wax emulsion impart low surface energy and high hydrophobicity to the coating film, significantly enhancing its waterproof performance. Moreover, regarding the gloss of the water-based varnish coating, the gloss of the water-based varnishes prepared in Examples 1-3 of this application is around 8-9 GU, indicating a certain degree of matte effect.

[0098] In addition, a sample bag obtained by printing the water-based varnish of Example 1 onto the inner and outer surfaces of a food-grade paper packaging bag was tested at 25°C and 32% humidity. Two 600mL ice packs were then placed inside the sample bag and sealed. Simultaneously, a 24-hour temperature test was conducted using an internal temperature sensor, and the resulting temperature change curve is shown below. Figure 1 As shown.

[0099] Depend on Figure 1 It can be seen that when the ice pack was first placed inside, the temperature inside the sample bag gradually decreased from an initial 22.8℃ to below 3℃; subsequently, for a continuous period of 19 hours, the temperature inside the sample bag remained within the range of 10℃; and for 24 hours, the temperature inside the sample bag remained within the range of 20℃. And from... Figure 2 It was found that the internal temperature of the sample bag without the water-based varnish coating was above 20°C after 18 hours. This indicates that the sample bag prepared in Example 1 can provide a certain degree of short-distance preservation. This is mainly because the water-based varnish coating gives the sample bag a certain barrier property, greatly reducing moisture / water penetration.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A highly waterproof water-based varnish, characterized in that: The raw materials include the following percentages by weight: 65-75% silicone-modified acrylic emulsion, 5-15% epoxy ester prepolymer, 2-6% wax emulsion, 1-3% film-forming aid, 0.1-0.5% defoamer, 0.1-0.3% wetting and leveling agent, 0-1% neutralizer, and the remainder is deionized water.

2. The highly waterproof water-based varnish according to claim 1, characterized in that: The wax emulsion is an emulsion formed by at least one of PE wax, PTFE wax, paraffin wax, and silicone wax with an emulsifier under high-speed shear force.

3. The highly waterproof water-based varnish according to claim 1, characterized in that: The film-forming aid is dipropylene glycol methyl ether or propylene glycol phenyl ether.

4. The highly waterproof water-based varnish according to claim 1, characterized in that: The preparation method of the epoxy ester prepolymer includes the following steps: epoxy resin E20, linoleic acid, catalyst and hypophosphoric acid are placed in a reaction vessel and heated to 125-130℃ under a nitrogen atmosphere, and reacted at a constant temperature for 2-2.5h. Then the temperature is further increased to 190-200℃ and kept at that temperature for 1.5-2h. When the acid value in the system decreases to 5-10mg KOH / g, the reaction is stopped. When the temperature drops below 130℃, propylene glycol butyl ether is added and stirred slowly. The temperature is further cooled to 60-70℃, dimethyl ethanolamine is added dropwise and stirred for 20-30min. Then deionized water is added under high-speed stirring to obtain a milky white dispersion, which is the epoxy ester prepolymer.

5. The highly waterproof water-based varnish according to claim 4, characterized in that: The mass ratio of epoxy resin E20 to linoleic acid is 100:35-45, the catalyst is 0.2-0.5% of the mass of epoxy resin E20, the hypophosphite is 0.1-0.3% of the mass of epoxy resin E20, the dimethylethanolamine is 6-10% of the mass of epoxy resin E20, and the propylene glycol butyl ether is 20-30% of the mass of epoxy resin E20.

6. The highly waterproof water-based varnish according to claim 1, characterized in that: The silicone-modified acrylic emulsion comprises component A and component B. Component A comprises 15-25 parts of hard monomer, 1-1.5 parts of emulsifier A, and 13-16 parts of deionized water. Component B comprises 35-45 parts of soft monomer, 4-8 parts of functional monomer, 3-8 parts of glycidyl methacrylate, 5-8 parts of siloxane monomer, 0.2-0.6 parts of initiator, 0.5-1.5 parts of emulsifier BA, and 35-40 parts of deionized water.

7. The highly waterproof water-based varnish according to claim 6, characterized in that: The soft monomer is butyl acrylate, the hard monomer is at least one of methyl methacrylate, isobornyl methacrylate, and ethylene tert-carbonate, and the functional monomer is at least one of acrylic acid, methacrylic acid, and hydroxyethyl methacrylate.

8. The method for preparing a highly waterproof water-based varnish according to any one of claims 1-7, characterized in that: The silicone-modified acrylic emulsion is added to a dispersion vessel. Under stirring conditions, epoxy ester prepolymer is slowly added and mixed evenly. Then, wax emulsion, film-forming aid, wetting and leveling agent and defoamer are added in sequence. After complete dispersion, deionized water is added. Finally, the pH of the system is adjusted to 7.5-8.5 with a neutralizing agent. After filtering to remove gel and impurities, the product can be discharged to obtain the highly waterproof water-based varnish.

9. The application of the highly waterproof water-based varnish as described in any one of claims 1-8 in paper packaging materials, characterized in that: Water-based varnish is printed onto the surface of paper packaging materials, with a coating amount of 1-20 g / m². 2 Then, the water-based varnish is cured into a film by infrared and hot air drying.

10. The application of the highly waterproof water-based varnish according to claim 9 in paper packaging materials, characterized in that: This also includes applying a second layer of waterproof varnish to the edges and cuts of the paper packaging material where folding is required.

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