Flexible board paper cup and printing process thereof

Abstract

The invention discloses a flexographic paper cup and a printing process thereof, and relates to the technical field of flexographic printing gloss oil, the paper cup takes food-grade paper as a base material, a lamination layer is obtained after lamination material treatment, printing treatment is carried out through a flexible printing machine, then water-based UV curing gloss oil treatment is carried out on the surface of the printed paper, and the printing process of the flexographic paper cup is completed. And finally, the treated paper is subjected to die cutting to form fan-shaped pieces, then the fan-shaped pieces are formed into paper cups, and the flexible board paper cups are obtained. The lamination material is prepared from the following raw materials in parts by weight: 25 to 35 parts of PLA, 25 to 31 parts of hydroxyl-containing castor oil-based functional polyamide, 15 to 22 parts of nano clay, 8 to 12 parts of a silane coupling agent, 1 to 3 parts of an antioxidant and 2 to 3 parts of a toughening agent. According to the flexible printing process for the paper cup, the printing effect can be remarkably improved, and the paper cup has the characteristics that the bonding strength of gloss oil, printing ink and a laminating material is high, and the friction resistance is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible printing varnish technology, in particular to a flexible paper cup and a printing process thereof. BACKGROUND

[0002] With the rapid development of China's economy and the steady improvement of people's living standards, people's health consciousness is also constantly strengthened, and paper product tableware with no odor, good image, degradable and no pollution has entered Chinese families in large quantities, and its market is growing rapidly and expanding. However, paper product tableware, while being convenient to use, can also cause certain food safety hazards.

[0003] At present, paper product tableware is often printed by flexographic printing, offset printing and gravure printing, and usually uses environmentally friendly inks such as water-based inks and UV curing inks, among which UV curing inks are internationally recognized as environmentally friendly inks. UV curing inks have the advantages of less volatile solvent, fast curing rate, high production efficiency, no pollution and energy saving. Paper product tableware such as paper cups and paper bowls are often stacked together when sold, and the ink on the surface of the paper cup or paper bowl will more or less come into contact with another paper cup or paper bowl. Therefore, a layer of varnish is usually applied during printing to prevent ink from smearing onto another paper cup and to ensure cleanliness and hygiene.

[0004] However, the interfacial adhesion between the varnish coating and the polyethylene (PE) or polylactic acid (PLA) film substrate is insufficient, and especially under the conditions of simulated logistics transportation shock or high temperature, the varnish layer is prone to scratches, peeling and other phenomena, which seriously affects the use effect and food safety of the printed paper cup. Therefore, improving the interfacial adhesion, wear resistance, heat resistance and food-grade compliance between the varnish, ink and film has become a key problem that needs to be solved in the paper product tableware industry. SUMMARY

[0005] In order to improve the quality of paper cup flexible printing and enhance the bonding strength and friction resistance of varnish, ink and film material, the present application provides a flexible paper cup and a printing process thereof.

[0006] The flexible paper cup provided by the present application adopts the following technical solution:

[0007] A flexible paper cup, the paper cup uses food-grade paper as a substrate, is treated with a film material to obtain a film layer, is printed by a flexible printing machine, is treated with water-based UV curing varnish on the surface of the printed paper, and is then cut into a fan-shaped piece and formed into a paper cup, thereby obtaining a flexible paper cup.

[0008] The said film material is composed of the following raw materials in parts by weight: 25-35 parts of PLA, 25-31 parts of hydroxyl-containing castor oil-based functional polyamide, 15-22 parts of nano clay, 8-12 parts of silane coupling agent, 1-3 parts of antioxidant, 2-3 parts of toughening agent.

[0009] Preferably, the raw materials of the aqueous UV curing gloss oil include, in percentage by mass: 8-10% of free radical photoinitiator, 2-3% of cationic photoinitiator, 21.5-24.5% of epoxy acrylate, 21.5-23.5% of aliphatic polyurethane acrylate resin, 10-14% of rosin-based epoxy soybean oil acrylate, 10-13% of trimethylolpropane triacrylate, 6.5-8.5% of dipropylene glycol diacrylate, 10-13% of 1,6-hexanediol diacrylate, 0.5-1.5% of defoaming agent, 0.5-1% of leveling agent, 1-1.5% of wetting agent, 2-3% of antioxidant.

[0010] Preferably, the rosin-based epoxy soybean oil acrylate is prepared from the following raw materials in parts by weight: 30-40 parts of rosin, 10-20 parts of acrylic acid, 5-15 parts of 4-tert-butyl benzoic acid, 0.5-1 part of catalyst, 0.1-0.5 part of polymerization inhibitor, 50-60 parts of epoxy soybean oil.

[0011] Preferably, the method for preparing the rosin-based epoxy soybean oil acrylate comprises the following steps:

[0012] After the rosin, acrylic acid, 4-tert-butyl benzoic acid, catalyst and polymerization inhibitor are mixed and stirred uniformly, a mixed solution is obtained; under a nitrogen environment, the mixed solution is added dropwise to the epoxy soybean oil at a temperature of 80-90°C, and after the dropwise addition is completed, the temperature is maintained at 80-90°C for 1-2 hours; then the temperature is raised to 110-120°C and the reaction is carried out for 3-4 hours; after the reaction is completed, the product is washed several times, water is removed, and the product is dried in a vacuum drying oven to obtain the rosin-based epoxy soybean oil acrylate.

[0013] Preferably, the free radical photoinitiator is IRGACURE 819; and the cationic photoinitiator is Omnicat 550.

[0014] Preferably, the hydroxyl-containing castor oil-based functional polyamide is prepared from the following raw materials in parts by weight: 10-15 parts of butyl ester side group-containing polyamide monomer, 3.8-5.7 parts of 3,6-dioxa-1,8-dithiol, 0.1-0.2 parts of azobisisobutyronitrile, 18-30 parts of tetrahydrofuran.

[0015] Preferably, the butyl ester side group-containing polyamide monomer is prepared from the following raw materials in parts by weight: 34-51 parts of hydroxyl side group-containing polyamide monomer, 14-28 parts of butyric anhydride, 0.3-0.6 parts of 4-dimethylaminopyridine, 36-70 parts of tetrahydrofuran.

[0016] Preferably, the hydroxyl side group containing polyamide monomer is prepared from the following raw materials by weight: 9-15 parts of 1,3-diamino-2-propanol, 62-94 parts of methyl ricinoleate, 27-57 parts of tetrahydrofuran, and 0.3-0.5 parts of sodium methoxide solution.

[0017] Preferably, the preparation method of the hydroxyl-containing ricinoleic acid-based functional polyamide comprises the following steps:

[0018] The butyrate side group containing polyamide monomer, 3,6-dioxane-1,8-dithiol, azobisisobutyronitrile and tetrahydrofuran are mixed and stirred uniformly, and then reacted at 55-63℃ for 24-30h under nitrogen environment. After the reaction is completed, the reaction solution is diluted with tetrahydrofuran and precipitated with methanol for several times, and then the precipitate is dried under vacuum at 40-50℃ to obtain the hydroxyl-containing ricinoleic acid-based functional polyamide.

[0019] The preparation method of the butyrate side group containing polyamide monomer comprises the following steps:

[0020] The hydroxyl side group containing polyamide monomer, butyric anhydride, 4-dimethylamino pyridine and tetrahydrofuran are mixed and stirred uniformly, and then reacted at 58-63℃ for 24-30h. Then, deionized water and tetrahydrofuran are injected to quench the unreacted anhydride. Then, the reaction solution is poured into dichloromethane, washed with sodium bicarbonate and sodium chloride aqueous solution, dried with anhydrous magnesium sulfate and evaporated to obtain the butyrate side group containing polyamide monomer.

[0021] The preparation method of the hydroxyl side group containing polyamide monomer comprises the following steps:

[0022] The 1,3-diamino-2-propanol, methyl ricinoleate and tetrahydrofuran are mixed and stirred uniformly, heated to 55-63℃ under nitrogen environment, and then sodium methoxide solution is added. After 24-30h of reaction, the tetrahydrofuran is removed by rotary evaporation, and then methanol is added for recrystallization several times to obtain the hydroxyl side group containing polyamide monomer.

[0023] Preferably, the antioxidant is a mixture of rosemary antioxidant and hydrotalcite, and the mass ratio of the rosemary antioxidant to the hydrotalcite is 1:2-4.

[0024] The printing process of the flexible version paper cup provided in the present application adopts the following technical solution:

[0025] The printing process of the flexible version paper cup comprises the following steps:

[0026] S1. Cut the food-grade paper into appropriate size, and remove the dust and impurities on the surface;

[0027] S2. The lamination material is heated to a molten state and uniformly coated on the surface of the paper through the lamination head to obtain a lamination layer; the thickness of the lamination layer is controlled to be 20-30 g / m 2 ;

[0028] S3. A flexographic printing machine is used to perform printing on the lamination layer, and after printing, a hot air drying device is used for drying;

[0029] S4. The water-based UV curing gloss oil is uniformly coated on the surface of the printed paper, and a UV curing machine is used for curing treatment; the thickness of the water-based UV curing gloss oil is controlled to be 1-4 g / m 2 ;

[0030] S5. The cured paper is die-cut into fan-shaped pieces, and then edge curling and bonding are performed on a forming machine to form a paper cup.

[0031] In summary, the present application has at least one of the following beneficial technical effects:

[0032] 1. The present application provides a hydroxyl-containing castor oil-based functional polyamide. The hydroxyl group is introduced into the main chain of the castor oil-based polyamide, and the hydroxyl group has high chemical activity, can form hydrogen bonds or chemical bonds with polar groups (such as hydroxyl, carboxyl, amino, etc.) in the water-based gloss oil and ink, and the chemical action can significantly enhance the interfacial bonding force between the lamination material and the gloss oil and ink, thereby improving the adhesion and enhancing the wear resistance; and when the hydroxyl-containing castor oil-based polyamide is used in combination with nanoclay, silane coupling agent and toughening agent, the hydroxyl group can have a synergistic effect with these components, enhancing the dispersibility of nanoclay in the PLA matrix, thereby improving the interfacial compatibility of the entire system, and the nanoclay can significantly improve the mechanical properties, thermal stability and barrier properties of the lamination material.

[0033] 2.The application utilizes 4-vinylbenzoic acid, rosin and acrylic acid to react with epoxy soybean oil to synthesize a high-performance rosin epoxy soybean oil acrylate containing a benzene ring and a high bio-based content; the rosin-based epoxy soybean oil acrylate contains rich polar groups (such as hydroxyl groups, carboxyl groups, epoxy groups and the like), which can form hydrogen bonds or chemical bonds with the polar groups on the surface of the paper cup coating material and ink, effectively enhancing the chemical bonding force between the glazing oil and the coating material and ink, improving the adhesion and wear resistance; and the glazing oil provided by the application has the characteristics of free radical photocuring and cationic photocuring, high curing degree, less residual active monomer and photoinitiator, excellent adhesion and abrasion resistance. In summary, the water-based UV glazing oil provided by the application has the characteristics of high gloss, can make the surface of the printed paper cup smoother and brighter, improve the visual effect of the printed pattern, and enhance the adhesion between the glazing oil and the ink and coating, thereby preventing the ink from falling off or blurring during printing and ensuring the clarity and color brightness of the printed pattern; and has good high-temperature stability and chemical stability, effectively prolonging the service life of the paper cup. DETAILED DESCRIPTION

[0034] The application will be further described in detail below in combination with examples.

[0035] The chemical reagents used in the preparation examples, examples and comparative examples provided by the application are all commercially available goods, and the brands and manufacturers thereof are as follows.

[0036] Epoxy soybean oil, Shanghai Macklin Biochemical Science and Technology Co., Ltd., E808876;

[0037] Rosin, Shanghai Macklin Biochemical Science and Technology Co., Ltd., C832364;

[0038] Methyl ricinoleate, Shanghai Macklin Biochemical Science and Technology Co., Ltd., M101313;

[0039] Nanoclay, Sigma-Aldrich (Shanghai) Trading Co., Ltd.;

[0040] PLA, Shanghai Macklin Biochemical Science and Technology Co., Ltd., P742431;

[0041] IRGACURE 819, Hubei Yiling Biological Technology Co., Ltd.;

[0042] Omnicat 550, Shanghai Yanze Chemical Co., Ltd.;

[0043] Rosemary antioxidant, Shandong Xinxiong Biological Technology Co., Ltd.;

[0044] Hydrotalcite, Chengdu Makaher Chemical Co., Ltd.;

[0045] Epoxy acrylate, Hubei Xinmingtai Chemical Co., Ltd.

[0046] Aliphatic polyurethane acrylate, Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0047] Flowing agent BYK-320, Shanghai Nazhong New Chemical Material Co., Ltd.

[0048] Wetting agent BYK-306, Shanghai Nazhong New Chemical Material Co., Ltd.

[0049] Defoaming agent DS8000, Zhengzhou Junlei Chemical Product Co., Ltd.

[0050] Preparation of rosin-based epoxy soybean oil acrylate

[0051] Preparation Example 1.1

[0052] 30 g of rosin, 10 g of acrylic acid, 5 g of 4-tert-butyl benzoic acid, 0.5 g of triphenylphosphine with a mass fraction of 1.5%, and 0.1 g of hydroquinone were mixed and stirred uniformly to obtain a mixed solution; under a nitrogen environment, the mixed solution was added dropwise to 50 g of epoxy soybean oil at 80°C, and after the dropwise addition was completed, the temperature was maintained at 80°C for 1 h; then the temperature was raised to 110°C, and the reaction was carried out for 3 h; after the reaction was completed, the product was washed with a 10% mass fraction sodium chloride hot water solution for 3 times, then dehydrated with magnesium sulfate, and placed in a vacuum drying oven for drying, to obtain rosin-based epoxy soybean oil acrylate.

[0053] Preparation Example 1.2

[0054] 35 g of rosin, 15 g of acrylic acid, 10 g of 4-tert-butyl benzoic acid, 0.75 g of triphenylphosphine with a mass fraction of 1.5%, and 0.3 g of hydroquinone were mixed and stirred uniformly to obtain a mixed solution; under a nitrogen environment, the mixed solution was added dropwise to 55 g of epoxy soybean oil at 85°C, and after the dropwise addition was completed, the temperature was maintained at 85°C for 1.5 h; then the temperature was raised to 115°C, and the reaction was carried out for 3.5 h; after the reaction was completed, the product was washed with a 10% mass fraction sodium chloride hot water solution for 4 times, then dehydrated with magnesium sulfate, and placed in a vacuum drying oven for drying, to obtain rosin-based epoxy soybean oil acrylate.

[0055] Preparation Example 1.3

[0056] Mixing 40 g of rosin, 20 g of acrylic acid, 15 g of 4-tert-butyl benzoic acid, 1 g of triphenylphosphine with a mass fraction of 1.5%, and 0.5 g of hydroquinone, stirring to obtain a mixed solution; under a nitrogen environment, heating to 90°C, and adding the mixed solution dropwise into 60 g of epoxy soybean oil, and after the dropwise addition is completed, keeping the temperature at 90°C for 2 h; then heating to 120°C and reacting for 4 h; after the reaction is completed, washing the product with a 10% mass fraction sodium chloride hot water solution for 3 times, and then dehydrating with magnesium sulfate, and drying in a vacuum drying oven, to obtain rosin-based epoxy soybean oil acrylate.

[0057] Preparation of hydroxyl-containing castor oil-based functional polyamide

[0058] Preparation Example 2.1

[0059] S1. Mix 9 g of 1,3-diamino-2-propanol, 62 g of methyl ricinoleate, and 27 g of tetrahydrofuran, stir to obtain a mixed solution, and then heat to 55°C under a nitrogen environment, and then add 0.3 g of 5 mol / L sodium methoxide solution, and after 24 h of reaction, remove the tetrahydrofuran by rotary evaporation, and then recrystallize twice with methanol to obtain a polyamide monomer with hydroxyl side groups;

[0060] S2. Mix 34 g of the polyamide monomer with hydroxyl side groups prepared in S1, 14 g of butyric anhydride, 0.3 g of 4-dimethylaminopyridine, and 36 g of tetrahydrofuran, stir to obtain a mixed solution, and then react at 58°C for 24 h; then inject 10 g of deionized water and 35 g of tetrahydrofuran to quench the unreacted anhydride, and then pour the reaction solution into dichloromethane, wash with sodium bicarbonate and sodium chloride aqueous solution, and then dry with anhydrous magnesium sulfate and evaporate the solvent to obtain a polyamide monomer with butyl ester side groups;

[0061] S3. Mix 10 g of the polyamide monomer with butyl ester side groups, 3.8 g of 3,6-dioxo-1,8-dithiol, 0.1 g of azobisisobutyronitrile, and 18 g of tetrahydrofuran, stir to obtain a mixed solution, and then react at 55°C for 24 h under a nitrogen environment, and then dilute with tetrahydrofuran and precipitate twice with methanol after the reaction is completed, and then dry the precipitate at 40°C under vacuum to obtain a hydroxyl-containing castor oil-based functional polyamide.

[0062] Preparation Example 2.2

[0063] S1. Mix 12 g of 1,3-diamino-2-propanol, 78 g of methyl ricinoleate, and 42 g of tetrahydrofuran, stir to obtain a mixed solution, and then heat to 60°C under a nitrogen environment, and then add 0.45 g of 5 mol / L sodium methoxide solution, and after 27 h of reaction, remove the tetrahydrofuran by rotary evaporation, and then recrystallize three times with methanol to obtain a polyamide monomer with hydroxyl side groups;

[0064] S2. Mix 42.5 g of the polyamide monomer with hydroxyl side groups prepared in S1, 21 g of butyric anhydride, 0.45 g of 4-dimethylaminopyridine and 53 g of tetrahydrofuran, stir uniformly, then react at 60°C for 27 h; then inject 15 g of deionized water and 45 g of tetrahydrofuran to quench the unreacted anhydride, pour the reaction solution into dichloromethane, wash with sodium bicarbonate and sodium chloride aqueous solution, and then dry with anhydrous magnesium sulfate and evaporate the solvent to obtain a polyamide monomer with butyric ester side groups;

[0065] S3. Mix 12.5 g of the polyamide monomer with butyric ester side groups, 4.8 g of 3,6-diox-1,8-dithiol, 0.15 g of azobisisobutyronitrile, 24 g of tetrahydrofuran, stir uniformly, react at 60°C for 27 h under nitrogen, dilute with tetrahydrofuran after the reaction is completed, precipitate 3 times with methanol, and then dry the precipitate at 45°C under vacuum to obtain a ricin oil-based functional polyamide with hydroxyl groups.

[0066] Preparation Example 2.3

[0067] S1. Mix 15 g of 1,3-diamino-2-propanol, 94 g of methyl ricinoleate and 57 g of tetrahydrofuran, stir uniformly, heat to 63°C under nitrogen, add 0.5 g of 5 mol / L sodium methoxide solution, react for 30 h, remove tetrahydrofuran by rotary evaporation, then recrystallize 4 times with methanol to obtain a polyamide monomer with hydroxyl side groups;

[0068] S2. Mix 51 g of the polyamide monomer with hydroxyl side groups prepared in S1, 28 g of butyric anhydride, 0.6 g of 4-dimethylaminopyridine and 70 g of tetrahydrofuran, stir uniformly, then react at 63°C for 30 h; then inject 20 g of deionized water and 55 g of tetrahydrofuran to quench the unreacted anhydride, pour the reaction solution into dichloromethane, wash with sodium bicarbonate and sodium chloride aqueous solution, and then dry with anhydrous magnesium sulfate and evaporate the solvent to obtain a polyamide monomer with butyric ester side groups;

[0069] S3. Mix 15 g of the polyamide monomer with butyric ester side groups, 5.7 g of 3,6-diox-1,8-dithiol, 0.2 g of azobisisobutyronitrile, 30 g of tetrahydrofuran, stir uniformly, react at 63°C for 30 h under nitrogen, dilute with tetrahydrofuran after the reaction is completed, precipitate 4 times with methanol, and then dry the precipitate at 50°C under vacuum to obtain a ricin oil-based functional polyamide with hydroxyl groups.

[0070] Example 1

[0071] S1. Cut the food-grade paper into appropriate size, remove dust and impurities on the surface;

[0072] S2. The coating material is heated to a molten state and uniformly coated on the paper surface through the coating head to obtain a coating layer; the thickness of the coating layer is controlled to be 20 g / m 2 ;

[0073] S3. The flexible printing machine and UV curing ink are used to perform printing on the coating layer, and the printed paper is dried and cured through the UV curing machine;

[0074] S4. The water-based UV curing varnish is uniformly coated on the surface of the printed paper, and the curing treatment is performed through the UV curing machine; the thickness of the water-based UV curing varnish is controlled to be 1 g / m 2 ;

[0075] S5. The cured paper is die-cut into fan-shaped pieces, and then the edge is curled and bonded on the forming machine to form a paper cup;

[0076] The preparation method of the coating material comprises the following steps:

[0077] 25 g of PLA, 25 g of the hydroxyl-containing castor oil-based functional polyamide prepared in Preparation Example 2.1, 15 g of nano-clay, 8 g of silane coupling agent KH550, 1 g of antioxidant, and 2 g of toughening agent polycaprolactone are added into a high-speed mixer and mixed at 50℃ and 200 rpm for 5 min, and then added into a twin-screw extruder, melted and extruded, and then drawn out from the outlet of the die. The melting extrusion temperature of the twin-screw extruder is 150℃. After cooling, the particles are obtained.

[0078] The preparation method of the water-based UV curing varnish comprises the following steps:

[0079] The free radical photoinitiator 8%, the cationic photoinitiator 2%, the epoxy acrylate 22%, the aliphatic polyurethane acrylate resin 20.5%, the rosin-based epoxy soybean oil acrylate prepared in Preparation Example 1.1 10%, the trimethylolpropane triacrylate 13%, the dipropylene glycol diacrylate 6.5%, the 1,6-hexanediol diacrylate 13%, the defoaming agent DS8000 0.5%, the leveling agent BYK-320 1%, the wetting agent BYK-306 1%, and the antioxidant 2.5% are uniformly mixed according to the mass percentage to obtain the water-based UV curing varnish.

[0080] The antioxidant is a mixture of rosemary antioxidant and hydrotalcite; the mass ratio of the rosemary antioxidant to the hydrotalcite is 1:2.

[0081] Example 2

[0082] S1. The food-grade paper is cut into a suitable size, and the dust and impurities on the surface are removed;

[0083] S2. The cast film material is heated to a molten state and uniformly coated on the surface of the paper through the cast film head to obtain a cast film layer; the thickness of the cast film layer is controlled to be 25 g / m 2 ;

[0084] S3. A flexographic printing machine and UV curing ink are used to perform printing on the cast film layer, and after printing, a UV curing machine is used for drying and curing;

[0085] S4. The water-based UV curing varnish is uniformly coated on the surface of the printed paper, and a UV curing machine is used for curing treatment; the thickness of the water-based UV curing varnish is controlled to be 2.5 g / m 2 ;

[0086] S5. The cured paper is die-cut into fan-shaped pieces, and then edge-welding and bonding are performed on a forming machine to form a paper cup;

[0087] The preparation method of the cast film material comprises the following steps:

[0088] 25 g of PLA, 25 g of the hydroxyl-containing castor oil-based functional polyamide prepared in Preparation Example 2.1, 15 g of nano-clay, 8 g of silane coupling agent KH550, 1 g of antioxidant, and 2 g of toughening agent polycaprolactone are added into a high-speed mixer and mixed at 50℃ and 200 rpm for 5 min, and then added into a twin-screw extruder, melted and extruded, and then drawn out from the outlet of the die; the melting extrusion temperature of the twin-screw extruder is 150℃, and after cooling, the particles are obtained by cutting to obtain the cast film material;

[0089] The preparation method of the water-based UV curing varnish comprises the following steps:

[0090] The free radical photoinitiator 8%, the cationic photoinitiator 2%, the epoxy acrylate 22%, the aliphatic polyurethane acrylate resin 20.5%, the rosin-based epoxy soybean oil acrylate prepared in Preparation Example 1.1 10%, the trimethylolpropane triacrylate 13%, the dipropylene glycol diacrylate 6.5%, the 1,6-hexanediol diacrylate 13%, the defoaming agent DS8000 0.5%, the leveling agent BYK-320 1%, the wetting agent BYK-306 1%, and the antioxidant 2.5% are uniformly mixed according to the mass percentage to obtain the water-based UV curing varnish;

[0091] The antioxidant is a mixture of rosemary antioxidant and hydrotalcite; the mass ratio of the rosemary antioxidant to the hydrotalcite is 1:2.

[0092] Example 3

[0093] S1. The food-grade paper is cut into a suitable size, and the dust and impurities on the surface are removed;

[0094] S2. Heat the coating material to a molten state, uniformly coat on the surface of the paper through the coating head to obtain a coating layer; control the thickness of the coating layer to be 30 g / m 2 ;

[0095] S3. Use a flexographic printing machine and UV curing ink to perform printing on the coating layer, and after printing, dry and cure through a UV curing machine;

[0096] S4. Uniformly coat water-based UV curing varnish on the surface of the printed paper, and perform curing treatment through a UV curing machine; control the thickness of the water-based UV curing varnish to be 4 g / m 2 ;

[0097] S5. Die cut the cured paper into fan-shaped pieces, and then perform edge curling and bonding on a forming machine to form a paper cup;

[0098] The preparation method of the coating material comprises the following steps:

[0099] Add 25 g of PLA, 25 g of the hydroxyl-containing castor oil-based functional polyamide prepared in Preparation Example 2.1, 15 g of nanoclay, 8 g of silane coupling agent KH550, 1 g of antioxidant, and 2 g of toughening agent polycaprolactone into a high-speed mixer, mix at 50℃ and 200 rpm for 5 min, and then add into a twin-screw extruder. After melt extrusion, the melt extrusion temperature of the twin-screw extruder is 150℃, and the coating material is obtained after cooling and granulation;

[0100] The preparation method of the water-based UV curing varnish comprises the following steps:

[0101] Mix 8% of free radical photoinitiator, 2% of cationic photoinitiator, 22% of epoxy acrylate, 20.5% of aliphatic polyurethane acrylate, 10% of rosin-based epoxy soybean oil acrylate prepared in Preparation Example 1.1, 13% of trimethylolpropane triacrylate, 6.5% of dipropylene glycol diacrylate, 13% of 1,6-hexanediol diacrylate, 0.5% of defoaming agent DS8000, 1% of leveling agent BYK-320, 1% of wetting agent BYK-306, and 2.5% of antioxidant according to the mass percentage to obtain the water-based UV curing varnish;

[0102] The antioxidant is a mixture of rosemary antioxidant and hydrotalcite; the mass ratio of the rosemary antioxidant to the hydrotalcite is 1:2.

[0103] Example 4

[0104] S1. Cut the food-grade paper into a suitable size, and remove dust and impurities on the surface;

[0105] S2. The coating material is heated to a molten state and uniformly coated on the surface of the paper through the coating head to obtain a coating layer; the thickness of the coating layer is controlled to be 20 g / m 2 ;

[0106] S3. The coating layer is printed using a flexographic printing machine and UV curing ink, and dried and cured through a UV curing machine after printing;

[0107] S4. The printed paper is uniformly coated with water-based UV curing varnish, and cured through a UV curing machine; the thickness of the water-based UV curing varnish is controlled to be 1 g / m 2 ;

[0108] S5. The cured paper is die-cut into fan-shaped pieces, and then edge-rolled and bonded on a forming machine to form a paper cup;

[0109] The preparation method of the coating material comprises the following steps:

[0110] 30 g of PLA, 28 g of hydroxyl-containing castor oil-based functional polyamide prepared by Preparation Example 2.1, 18.5 g of nanoclay, 10 g of silane coupling agent KH550, 2 g of antioxidant, and 2.5 g of toughening agent polycaprolactone are added to a high-speed mixer and mixed at 55℃ and 250 rpm for 8 min, and then added to a twin-screw extruder. After melt extrusion, it is drawn out from the outlet of the die. The melt extrusion temperature of the twin-screw extruder is 180℃. After cooling, the granules are obtained.

[0111] The preparation method of the water-based UV curing varnish comprises the following steps:

[0112] The free radical photoinitiator 9%, the cationic photoinitiator 2.5%, the epoxy acrylate 21%, the aliphatic polyurethane acrylate resin 20%, the rosin-based epoxy soybean oil acrylate prepared by Preparation Example 1.1 12%, the trimethylolpropane triacrylate 11.5%, the dipropylene glycol diacrylate 7.5%, the 1,6-hexanediol diacrylate 11.5%, the defoaming agent DS8000 1%, the leveling agent BYK-320 0.5%, the wetting agent BYK-306 1.5%, and the antioxidant 2% are uniformly mixed to obtain the water-based UV curing varnish.

[0113] The antioxidant is a mixture of rosemary antioxidant and hydrotalcite; the mass ratio of the rosemary antioxidant to the hydrotalcite is 1:2.

[0114] Example 5

[0115] S1. The food-grade paper is cut to a suitable size, and the dust and impurities on the surface are removed;

[0116] S2. Heat the coating material to a molten state and apply it evenly to the paper surface through a coating head to obtain a coating layer; control the thickness of the coating layer to be 20 g / m. 2 ;

[0117] S3. Print the coating layer using a flexographic printing press and UV-curable ink, and then dry and cure it using a UV curing machine;

[0118] S4. Apply the water-based UV-curable varnish evenly to the surface of the printed paper and cure it using a UV curing machine; control the thickness of the water-based UV-curable varnish to be 1 g / m. 2 ;

[0119] S5. The cured paper is die-cut into fan-shaped pieces, and then rolled and glued on a forming machine to form paper cups;

[0120] The preparation method of the coating material includes the following steps:

[0121] 35g PLA, 31g hydroxyl-containing castor oil-based functional polyamide prepared in Preparation Example 2.1, 22g nano clay, 12g silane coupling agent KH550, 3g antioxidant, and 3g toughening agent polycaprolactone were added to a high-speed mixer and mixed at 60°C and 300rpm for 10min. Then, the mixture was fed into a twin-screw extruder and melt-extruded from the die outlet. The melt extrusion temperature of the twin-screw extruder was 200°C. After cooling, the mixture was pelletized to obtain the coating material.

[0122] The preparation method of the water-based UV-curable varnish includes the following steps:

[0123] By weight percentage, 10% of free radical photoinitiator, 3% of cationic photoinitiator, 19% of epoxy acrylate, 19.5% of aliphatic polyurethane acrylic resin, 14% of rosin-based epoxy soybean oil acrylate prepared in Preparation Example 1.1, 10% of trimethylolpropane triacrylate, 8.5% of dipropylene glycol diacrylate, 10% of 1,6-hexanediol diacrylate, 1.5% of defoamer DS8000, 0.5% of leveling agent BYK-320, 1% of wetting agent BYK-306, and 3% of antioxidant are mixed evenly to obtain a water-based UV-curable varnish.

[0124] The antioxidant is a mixture of rosemary antioxidant and hydrotalcite; the mass ratio of the rosemary antioxidant to hydrotalcite is 1:2.

[0125] Example 6

[0126] The difference between Example 6 and Example 1 is that the hydroxyl-containing castor oil-based functional polyamide used in Example 6 was prepared from Preparation Example 2.2.

[0127] Example 7

[0128] Example 7 differs from Example 1 in that the hydroxyl group-containing castor oil-based functional polyamide employed in Example 7 is prepared by Preparation Example 2.3.

[0129] Example 8

[0130] Example 8 differs from Example 1 in that an equal amount of epoxy acrylate is employed in place of the rosin-based epoxy soybean oil acrylate in Example 8.

[0131] Example 9

[0132] Example 9 differs from Example 1 in that the rosin-based epoxy soybean oil acrylate employed in Example 9 is prepared by Preparation Example 1.2.

[0133] Example 10

[0134] Example 10 differs from Example 1 in that the rosin-based epoxy soybean oil acrylate employed in Example 10 is prepared by Preparation Example 1.3.

[0135] Example 11

[0136] Example 11 differs from Example 1 in that the mass ratio of rosemary antioxidant and hydrotalcite employed in Example 11 is 1:3.

[0137] Example 12

[0138] Example 12 differs from Example 1 in that the mass ratio of rosemary antioxidant and hydrotalcite employed in Example 12 is 1:4.

[0139] Example 13

[0140] Example 13 differs from Example 1 in that the mass ratio of rosemary antioxidant and hydrotalcite employed in Example 13 is 1:1.

[0141] Example 14

[0142] Example 14 differs from Example 1 in that the mass ratio of rosemary antioxidant and hydrotalcite employed in Example 14 is 1:5.

[0143] Comparative Example 1

[0144] Comparative Example 1 differs from Example 1 in that an equal amount of polyamide resin is employed in place of the hydroxyl group-containing castor oil-based functional polyamide in Comparative Example 1.

[0145] Comparative Example 2

[0146] Comparative Example 2 differs from Example 1 in that the flexible paper cup in Comparative Example 2 is not subjected to water-based UV curing gloss oil treatment

[0147] Performance detection test

[0148] I. Binding strength: the binding strength of the flexible paper cups obtained from Examples 1-14 and Comparative Examples 1-2 was detected by GB / T 7706-2008 “Letterpress Decorated Printings”, and the results are shown in Table 1.

[0149] II. Rubbing resistance: the rubbing resistance of the flexible paper cups obtained from Examples 1-14 and Comparative Examples 1-2 was detected by GB / T 7706-2008 “Letterpress Decorated Printings”, and the results are shown in Table 1.

[0150] The specific detection results are as follows:

[0151] Table 1 Performance detection results

[0152]

[0153]

[0154] As can be seen from the detection results in Table 1, the flexible paper cup and the printing process provided by the present application have high binding strength and strong rubbing resistance.

[0155] The specific embodiments are merely an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and the modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A flexographic paper cup characterized by: The paper cup is based on food-grade paper, which is treated by a coating material to obtain a coating layer, printed by a flexible printing machine, treated by water-based UV curing varnish on the printed paper surface, and finally cut into a fan-shaped piece and formed into a paper cup, namely a flexible version paper cup. The coating material is composed of the following raw materials in parts by weight: 25-35 parts of PLA, 25-31 parts of a hydroxyl-containing castor oil-based functional polyamide, 15-22 parts of nano clay, 8-12 parts of a silane coupling agent, 1-3 parts of an antioxidant, and 2-3 parts of a toughening agent.

2. The flexible paper cup according to claim 1, wherein: The water-based UV curing varnish raw material includes, by mass percentage: 8-10% of a free radical photoinitiator, 2-3% of a cationic photoinitiator, 21.5-24.5% of epoxy acrylate, 21.5-23.5% of aliphatic polyurethane acrylate, 10-14% of rosin-based epoxy soybean oil acrylate, 10-13% of trimethylolpropane triacrylate, 6.5-8.5% of dipropylene glycol diacrylate, 10-13% of 1,6-hexanediol diacrylate, 0.5-1.5% of a defoaming agent, 0.5-1% of a leveling agent, 1-1.5% of a wetting agent, and 2-3% of an antioxidant.

3. A flexible paper cup according to claim 2, wherein: The rosin-based epoxy soybean oil acrylate is prepared from the following raw materials in parts by weight: 30-40 parts of rosin, 10-20 parts of acrylic acid, 5-15 parts of 4-tert-butyl benzoic acid, 0.5-1 part of a catalyst, and 0.1-0.5 part of a polymerization inhibitor, and 50-60 parts of epoxy soybean oil.

4. A flexible paper cup according to claim 3, wherein: The preparation method of the rosin-based epoxy soybean oil acrylate comprises the following steps: The rosin, acrylic acid, 4-tert-butyl benzoic acid, catalyst, and polymerization inhibitor are mixed and stirred uniformly to obtain a mixed solution; under a nitrogen environment, the mixed solution is added dropwise to the epoxy soybean oil at 80-90°C, and after the dropwise addition is completed, the mixture is kept at 80-90°C for 1-2 hours; then the temperature is raised to 110-120°C and the reaction is carried out for 3-4 hours; after the reaction is completed, the product is washed several times, water is removed, and the product is dried in a vacuum drying oven to obtain the rosin-based epoxy soybean oil acrylate.

5. The flexible paper cup of claim 2, wherein: The free radical photoinitiator is IRGACURE 819, and the cationic photoinitiator is Omnicat 550.

6. A flexible sheet paper cup and its printing process as claimed in claim 1 wherein: The hydroxyl-containing castor oil-based functional polyamide is prepared from the following raw materials in parts by weight: 10-15 parts of a butyl ester side group-containing polyamide monomer, 3.8-5.7 parts of 3,6-dioxa-1,8-dithiol, 0.1-0.2 parts of azobisisobutyronitrile, and 18-30 parts of tetrahydrofuran.

7. A flexible paper cup according to claim 6, wherein: The butyl ester side group-containing polyamide monomer is prepared from the following raw materials in parts by weight: 34-51 parts of a hydroxyl side group-containing polyamide monomer, 14-28 parts of butyric anhydride, 0.3-0.6 parts of 4-dimethylamino pyridine, and 36-70 parts of tetrahydrofuran. The hydroxyl side group-containing polyamide monomer is prepared from the following raw materials in parts by weight: 9-15 parts of 1,3-diamino-2-propanol, 62-94 parts of methyl ricinoleate, 27-57 parts of tetrahydrofuran, and 0.3-0.5 parts of sodium methoxide solution.

8. The flexible paper cup of claim 6, wherein: The preparation method of the hydroxyl-containing castor oil-based functional polyamide comprises the following steps: The butyl ester side group containing polyamide monomer, 3, 6-dioxane-1, 8-dithiol, azobisisobutyronitrile and tetrahydrofuran are mixed and stirred uniformly, and then reacted at 55-63℃ for 24-30h under nitrogen atmosphere, after the reaction is completed, the reaction solution is diluted with tetrahydrofuran and precipitated with methanol for several times, and then the precipitate is dried at 40-50℃ under vacuum, thereby obtaining the ricin oil group functional polyamide containing hydroxyl groups; The preparation method of the butyl ester side group containing polyamide monomer comprises the following steps: The hydroxyl side group containing polyamide monomer, butyric anhydride, 4-dimethylamino pyridine and tetrahydrofuran are mixed and stirred uniformly, and then reacted at 58-63℃ for 24-30h, then deionized water and tetrahydrofuran are injected to quench the unreacted anhydride, then the reaction solution is poured into dichloromethane, washed with sodium bicarbonate and sodium chloride aqueous solution, and then dried with anhydrous magnesium sulfate and evaporated to obtain the butyl ester side group containing polyamide monomer; The preparation method of the hydroxyl side group containing polyamide monomer comprises the following steps: The 1, 3-diamino-2-propanol, ricin oil acid methyl ester and tetrahydrofuran are mixed and stirred uniformly, heated to 55-63℃ under nitrogen atmosphere, and then sodium methoxide solution is added, reacted for 24-30h, then the tetrahydrofuran is removed by rotary evaporation, and then recrystallized with methanol for several times to obtain the hydroxyl side group containing polyamide monomer.

9. The flexible paper cup according to claim 1 or 2, wherein: The antioxidant is a mixture of rosemary antioxidant and hydrotalcite, and the mass ratio of the rosemary antioxidant to the hydrotalcite is 1:2-4.

10. A process for printing of flexible paper cups as claimed in any one of claims 1 to 9, wherein: The method comprises the following steps: S1. cutting food grade paper into appropriate size, removing dust and impurities on the surface; S2. The coating material is heated to a molten state and uniformly coated on the paper surface through the curtain coating head to obtain a coating layer; the thickness of the coating layer is controlled to be 20-30 g / m 2 ; S3. using a flexographic printing machine to print on the laminated layer, and then drying by a hot air drying device; S4. uniformly coating the water-based UV curing varnish on the surface of the printed paper, and then curing by a UV curing machine; The thickness of the water-based UV curing gloss oil is controlled to be 1-4 g / m 2 ; S5. cutting the cured paper into fan-shaped pieces, and then performing edge curling and bonding on a forming machine to form a paper cup.

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