Food-grade printing ink containing plant-based resin capable of contacting food and preparation method of food-grade printing ink

Abstract

The invention relates to the technical field of printing ink, in particular to food-grade printing ink containing plant-based resin capable of making contact with food and a preparation method thereof.The food-grade printing ink is prepared from, by weight, 50-60 parts of plant-based resin capable of making contact with food, 5-6 parts of soybean oil, 2-4 parts of modified nano-montmorillonite, 0.1-0.5 part of demulsifying agent, 15-20 parts of pigment, 3-5 parts of cerate and 0.5-2 parts of anti-skinning agent; 0.5-2 parts of a drying agent; the food-contactable plant-based resin comprises at least one of rosin resin and dammar resin. According to the food-grade printing ink containing the plant-based resin capable of being contacted with the food, through matching of the raw materials, the problems that plant-based resin printing ink is poor in durability and insufficient in mechanical property are solved, the mechanical property and adhesive force of the food-grade printing ink are improved, and the food-grade printing ink can be firmly and permanently attached to a printing stock.

Description

Technical Field

[0001] This application relates to the field of ink technology, specifically to a food-grade ink containing a food-contact plant-based resin and its preparation method. Background Technology

[0002] The most critical concern in food packaging today is safety risk. Traditional petroleum-based inks typically contain mineral oil saturated hydrocarbons, mineral oil aromatic hydrocarbons, photoinitiators, plasticizers, and other components. These substances can easily migrate from the outer layer of packaging into the food, posing a health hazard, especially in foods with high fat content. With increasingly stringent global regulations and media coverage of packaging safety incidents, consumer concerns about food contaminated by packaging are growing daily.

[0003] Plant-based resins use natural, renewable plant resources as raw materials. Their chemical structure itself does not contain harmful substances like those found in petroleum-based resins, greatly reducing the potential risk of toxic substance migration and providing consumers with a safer choice.

[0004] However, most plant-based resins are highly hydrophilic, causing the resulting inks to easily dissolve, spread, or peel off in humid environments or when in contact with oils, affecting the clarity and durability of printed patterns. Furthermore, the resulting films are prone to brittleness and insufficient flexibility, making them susceptible to wear when packaging is bent or rubbed. Therefore, improving the durability and mechanical properties of inks containing plant-based resins is a pressing issue in this field. Summary of the Invention

[0005] This application aims to overcome at least one of the defects of the prior art and provide a food-grade ink containing a food-contact plant-based resin and its preparation method. By combining raw materials, the application improves the problems of poor durability and insufficient mechanical properties of plant-based resin inks, and enhances the mechanical properties and adhesion of food-grade inks, enabling them to adhere firmly and persistently to the substrate.

[0006] In a first aspect, embodiments of this application provide a food-grade ink containing a food-contactable plant-based resin, achieved through the following technical solution: A food-grade ink containing a food-contact plant-based resin comprises the following raw materials in parts by weight: The ingredients include 50-60 parts of food-contact plant-based resin, 5-6 parts of soybean oil, 2-4 parts of modified nano-montmorillonite, 0.1-0.5 parts of deemulsifier, 15-20 parts of pigment, 3-5 parts of wax paste, 0.5-2 parts of anti-skinning agent, and 0.5-2 parts of desiccant.

[0007] The food-contact plant-based resin includes at least one of rosin resin and dammar resin.

[0008] The food-grade ink containing a food-contact plant-based resin according to the embodiments of this application has at least the following beneficial effects: The soybean oil of this application can penetrate between resin molecular chains, reduce intermolecular forces, thereby improving the flexibility and extensibility of the ink film, and improving the leveling and adhesion of the ink during the printing process. Soybean oil can be blended with plant-based resins to serve as a carrier for pigments, helping pigments to be evenly dispersed and firmly adhered to the substrate, resulting in inks with bright colors, good color development, and good gloss.

[0009] The modified nano-montmorillonite of this application is completely non-toxic, can form a good bond with plant-based resins, improve the density of the coating film, and can improve the adhesion, abrasion resistance and mechanical properties of the ink layer, while improving the oxidation resistance and corrosion resistance of food-grade inks.

[0010] The deemulsifier of this application can improve the situation of poor ink transfer caused by excessive emulsification, reduce the water absorption value of ink, quickly achieve water-ink balance, improve the ink's antiemulsification ability, effectively control the expansion of printing dots, and reduce the drawbacks such as poor fluidity, poor transferability, plate piling, oiliness, and dirtiness caused by severe emulsification.

[0011] The wax paste of this application can enhance the abrasion resistance, smoothness, and post-printing texture of inks.

[0012] The food-grade ink containing food-contact plant-based resin of this application improves the problems of poor durability and insufficient mechanical properties of plant-based resin inks by combining raw materials, thereby improving the mechanical properties and adhesion of food-grade inks, enabling them to adhere firmly and persistently to the substrate.

[0013] According to some embodiments of this application, the food-contact plant-based resin is a mixture of rosin resin and dammar resin in a weight ratio of (1-2):1.

[0014] According to some embodiments of this application, the preparation method of the modified nano-montmorillonite includes the following steps: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of (8-9):1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 70-80℃ and magnetically stirred at a constant temperature for 5-8 hours. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0015] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0016] S3. Add the pretreated graphene from step S2 to ethanol and disperse it by ultrasonication. Add the organosilicon-modified nano-montmorillonite prepared in step S1. Stir rapidly at 25-35℃ to allow it to react fully. Centrifuge, wash several times with anhydrous ethanol, vacuum dry, and grind to obtain modified nano-montmorillonite.

[0017] The food-grade ink of this application uses modified nano-montmorillonite as a filler. Due to its large specific surface area and high adsorption capacity, nanomaterials can enhance the mechanical properties of the ink layer. Montmorillonite exhibits oleophobicity due to the large number of inorganic ions between its layers, which is not conducive to its dispersion in the ink matrix. The use of organosilicon modification changes the interlayer of montmorillonite from hydrophilic to oleophilic, reduces its surface energy, and increases the interlayer spacing of montmorillonite, thereby increasing the dispersion of nano-montmorillonite in the resin matrix and improving the elasticity, wear resistance, and corrosion resistance of the ink layer. After acidification, the surface of graphene will oxidize to carboxyl groups, which combine with the organosilicon-modified nano-montmorillonite, reducing the problem of graphene agglomeration. The layered structure of graphene allows for more thorough mixing between the filler and the resin, improving the hardness and abrasion resistance of the ink layer.

[0018] Furthermore, the mass ratio of the nano-montmorillonite, the anhydrous ethanol, and the γ-aminopropyltriethoxysilane is 1:(8-10):(0.1-0.2).

[0019] According to some embodiments of this application, the preparation of the demulsifier includes the following steps: 10-15 parts by weight of propylene oxide and 6-9 parts by weight of polyethylene glycol are ground and mixed, then 2-4 parts by weight of sodium gluconate, 1-2 parts by weight of lactic acid and 2-4 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly, and then heated to 75-88°C and kept warm for 1-4 hours to obtain the demulsifier.

[0020] This application prepares an antiemulsifier using the above-mentioned scheme. Propylene oxide forms hydrophobic segments through ring-opening polymerization, polyethylene glycol provides hydrophilic segments and molecular structure, and titanate is introduced as an anchoring group at the chain end. The resulting antiemulsifier has excellent antiemulsification properties, can change the interfacial tension between oil and water, and achieve rapid water separation. By binding the titanate group to the pigment surface, the pigment surface can be passivated, its hydrophilicity can be reduced, and emulsification can be further reduced. It can not only improve compatibility, but also reduce viscosity and promote dispersion.

[0021] According to some embodiments of this application, the anti-skinning agent includes at least one selected from methyl ethyl ketone oxime, butyraldehyde oxime, and cyclohexanone oxime. The anti-skinning agent of this application has good co-solubility with plant-based resins and natural pigments, increases the fluidity of the ink, and prevents the ink from forming a skin after drying.

[0022] According to some embodiments of this application, the pigment includes at least one selected from natural plant carbon black, carmine, chlorophyll, caramel color, purple cabbage red, anthocyanin, and curcumin. The pigments of this application are natural and environmentally friendly, and have good miscibility with plant-based resins, which can maintain the dispersion of pigment particles in the ink system, thus improving ink preservation and color saturation during printing.

[0023] According to some embodiments of this application, the wax paste includes at least one of polyethylene wax, microcrystalline wax, paraffin wax, or polytetrafluoroethylene wax.

[0024] According to some embodiments of this application, the desiccant includes at least one of cobalt isooctanoate, manganese isooctanoate, zirconium isooctanoate, cobalt naphthenate, manganese naphthenate, zirconium naphthenate, cobalt 2-ethylhexanoate, manganese 2-ethylhexanoate, and zinc 2-ethylhexanoate.

[0025] Secondly, this application provides a method for preparing a food-grade ink containing a food-contact plant-based resin, which is achieved through the following technical solution.

[0026] A method for preparing a food-grade ink containing a food-contact plant-based resin includes the following steps: (1) Add soybean oil to the reactor according to the weight, heat and stir in an inert gas atmosphere, and when the temperature rises to 220-230℃, add food-grade plant-based resin and keep warm for 30-60 minutes.

[0027] (2) Add modified nano montmorillonite, deemulsifier, wax paste, anti-skinning agent and desiccant, stir at 500 r / min for 10-15 minutes, and lower the temperature to 150℃.

[0028] (3) Add pigment and stir at 1000r / min for 30-60min. After ball milling and grinding, obtain food-grade ink containing food-contact plant-based resin.

[0029] According to some embodiments of this application, the inert gas in step (1) includes at least one of nitrogen, helium, neon, and argon.

[0030] According to some embodiments of this application, the rotational speed of the ball mill in step (3) is 200-300 r / min.

[0031] According to some embodiments of this application, the grinding in step (3) is three-roll mill grinding.

[0032] According to some embodiments of the present invention, the particle size of the powder after grinding in step (3) does not exceed 5 μm.

[0033] The method for preparing food-grade ink containing food-contact plant-based resin according to the embodiments of this application has at least the following beneficial effects: The preparation method of this application is simple, does not require harsh production conditions and equipment, the manufacturing process is pollution-free, there is no emission of toxic substances, it does not harm the health of operators, ensures the safety of production, has good economic benefits, and is suitable for industrial production. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, a further detailed description will be provided below in conjunction with specific embodiments. The embodiments described herein are merely some examples of this application and should not be construed as limiting the scope of protection of this application. Example 1

[0035] Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 5 parts of soybean oil to the reactor according to the weight, heat and stir in a nitrogen atmosphere, and when the temperature rises to 225°C, add 55 parts of food-grade plant-based resin and keep warm for 45 minutes.

[0036] (2) Add 3 parts of modified nano-montmorillonite, 0.3 parts of deemulsifier, 4 parts of polyethylene wax, 1 part of methyl ethyl ketone oxime, and 1 part of cobalt isooctanoate. Stir at 500 r / min for 12 minutes and reduce the temperature to 150℃.

[0037] (3) Add 18 parts of natural plant carbon black, stir at 1000 r / min for 45 min, and then grind the powder with a ball mill at 250 r / min and a three-roll mill to make the particle size not exceed 5 μm, thus obtaining food-grade ink containing plant-based resin that can be in contact with food.

[0038] The food-contact plant-based resin is made by mixing rosin resin and dammar resin in a weight ratio of 1.5:1.

[0039] Preparation of modified nano-montmorillonite: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of 8.5:1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 75℃ and magnetically stirred at a constant temperature for 7h. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0040] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0041] S3. The graphene pretreated in step S2 is added to ethanol and ultrasonically dispersed. The organosilicon-modified nano-montmorillonite prepared in step S1 is added. The mixture is stirred rapidly at 30°C to allow it to react fully. After centrifugation, the mixture is washed several times with anhydrous ethanol and then vacuum dried. The modified nano-montmorillonite is then ground to obtain the modified nano-montmorillonite.

[0042] The mass ratio of nano-montmorillonite, the anhydrous ethanol, and the γ-aminopropyltriethoxysilane is 1:9:0.15.

[0043] Preparation of demulsifier: 12 parts by weight of propylene oxide and 7 parts by weight of polyethylene glycol are ground and mixed, then 3 parts by weight of sodium gluconate, 1.5 parts by weight of lactic acid and 3 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly. The mixture is heated to 80°C and kept warm for 3 hours to obtain the demulsifier. Example 2

[0044] Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 6 parts of soybean oil to the reactor according to the weight, heat and stir in a helium atmosphere, and when the temperature rises to 220°C, add 60 parts of food-grade plant-based resin and keep warm for 30 minutes.

[0045] (2) Add 4 parts of modified nano-montmorillonite, 0.1 parts of deemulsifier, 5 parts of microcrystalline wax, 0.5 parts of cyclohexanone oxime, and 2 parts of manganese naphthenate. Stir at 500 r / min for 10 minutes and reduce the temperature to 150℃.

[0046] (3) Add 20 parts of anthocyanin, stir at 1000 r / min for 30 min, and then grind the powder with a ball mill at 300 r / min and a three-roll mill to make the powder particle size not exceed 5 μm, so as to obtain food-grade ink containing plant-based resin that can be in contact with food.

[0047] Among them, the food-contact plant-based resin is made by mixing rosin resin and dammar resin in a weight ratio of 1:1.

[0048] Preparation of modified nano-montmorillonite: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water in a mass ratio of 9:1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 70℃ and magnetically stirred at a constant temperature for 8 hours. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0049] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0050] S3. The graphene pretreated in step S2 is added to ethanol and ultrasonically dispersed. The organosilicon-modified nano-montmorillonite prepared in step S1 is added. The mixture is stirred rapidly at 25°C to allow it to react fully. After centrifugation, the mixture is washed several times with anhydrous ethanol and then vacuum dried. The modified nano-montmorillonite is then ground to obtain the modified nano-montmorillonite.

[0051] The mass ratio of nano-montmorillonite, anhydrous ethanol, and γ-aminopropyltriethoxysilane is 1:10:0.1.

[0052] Preparation of demulsifier: 15 parts by weight of propylene oxide and 6 parts by weight of polyethylene glycol are ground and mixed, then 4 parts by weight of sodium gluconate, 1 part by weight of lactic acid and 4 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly. The mixture is heated to 75°C and kept warm for 4 hours to obtain the demulsifier. Example 3

[0053] Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 5 parts of soybean oil to the reactor according to the weight, heat and stir in a nitrogen atmosphere, and when the temperature rises to 230°C, add 50 parts of food-grade plant-based resin and keep warm for 60 minutes.

[0054] (2) Add 2 parts of modified nano montmorillonite, 0.5 parts of deemulsifier, 3 parts of polytetrafluoroethylene wax, 2 parts of butyraldehyde oxime, and 0.5 parts of zinc 2-ethylhexanoate. Stir at 500 r / min for 15 minutes and reduce the temperature to 150℃.

[0055] (3) Add 15 parts of carmine red, stir at 1000 r / min for 60 min, and then grind the powder with a ball mill at 200 r / min and a three-roll mill to make the powder particle size not exceed 5 μm, so as to obtain food-grade ink containing plant-based resin that can be in contact with food.

[0056] Among them, the food-contact plant-based resin is a mixture of rosin resin and dammar resin in a weight ratio of 2:1.

[0057] Preparation of modified nano-montmorillonite: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of 8:1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 80℃ and magnetically stirred at a constant temperature for 5 hours. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0058] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0059] S3. The graphene pretreated in step S2 is added to ethanol and ultrasonically dispersed. The organosilicon-modified nano-montmorillonite prepared in step S1 is added. The mixture is stirred rapidly at 35°C to allow it to react fully. After centrifugation, the mixture is washed several times with anhydrous ethanol and then vacuum dried. The modified nano-montmorillonite is then ground to obtain the modified nano-montmorillonite.

[0060] The mass ratio of nano-montmorillonite, anhydrous ethanol, and γ-aminopropyltriethoxysilane is 1:8:0.2.

[0061] Preparation of demulsifier: 10 parts by weight of propylene oxide and 9 parts by weight of polyethylene glycol are ground and mixed, then 2 parts by weight of sodium gluconate, 2 parts by weight of lactic acid and 2 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly. The mixture is heated to 88°C and kept warm for 1 hour to obtain the demulsifier. Example 4

[0062] Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 6 parts of soybean oil to the reactor according to the weight, heat and stir in a nitrogen atmosphere, and when the temperature rises to 226°C, add 55 parts of food-grade plant-based resin and keep warm for 50 minutes.

[0063] (2) Add 3 parts of modified nano-montmorillonite, 0.4 parts of deemulsifier, 4 parts of paraffin, 1.5 parts of methyl ethyl ketone oxime, and 1 part of zirconium isooctanoate. Stir at 500 r / min for 14 minutes and reduce the temperature to 150℃.

[0064] (3) Add 18 parts of purple cabbage red, stir at 1000 r / min for 40 min, and then grind the powder with a ball mill at 240 r / min and a three-roll mill to make the powder particle size not exceed 5 μm, thus obtaining food-grade ink containing food-contact plant-based resin.

[0065] The food-contact plant-based resin is made by mixing rosin resin and dammar resin in a weight ratio of 1.5:1.

[0066] Preparation of modified nano-montmorillonite: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of 8:1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 75℃ and magnetically stirred at a constant temperature for 6 hours. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0067] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0068] S3. The graphene pretreated in step S2 is added to ethanol and ultrasonically dispersed. The organosilicon-modified nano-montmorillonite prepared in step S1 is added. The mixture is stirred rapidly at 30°C to allow it to react fully. After centrifugation, the mixture is washed several times with anhydrous ethanol and then vacuum dried. The modified nano-montmorillonite is then ground to obtain the modified nano-montmorillonite.

[0069] The mass ratio of nano-montmorillonite, anhydrous ethanol, and γ-aminopropyltriethoxysilane is 1:9:0.2.

[0070] Preparation of demulsifier: 11 parts by weight of propylene oxide and 8 parts by weight of polyethylene glycol are ground and mixed, then 3 parts by weight of sodium gluconate, 1 part by weight of lactic acid and 3 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly. The mixture is heated to 82°C and kept warm for 2 hours to obtain the demulsifier.

[0071] Comparative Example 1 Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 5 parts of soybean oil to the reactor according to the weight, heat and stir in a nitrogen atmosphere, and when the temperature rises to 225°C, add 55 parts of food-grade plant-based resin and keep warm for 45 minutes.

[0072] (2) Add 3 parts of nano-montmorillonite, 0.3 parts of deemulsifier, 4 parts of polyethylene wax, 1 part of methyl ethyl ketone oxime, and 1 part of cobalt isooctanoate. Stir at 500 r / min for 12 minutes and reduce the temperature to 150℃.

[0073] (3) Add 18 parts of natural plant carbon black, stir at 1000 r / min for 45 min, and then grind the powder with a ball mill at 250 r / min and a three-roll mill to make the particle size not exceed 5 μm, thus obtaining food-grade ink containing plant-based resin that can be in contact with food.

[0074] The food-contact plant-based resin is made by mixing rosin resin and dammar resin in a weight ratio of 1.5:1.

[0075] Preparation of demulsifier: 12 parts by weight of propylene oxide and 7 parts by weight of polyethylene glycol are ground and mixed, then 3 parts by weight of sodium gluconate, 1.5 parts by weight of lactic acid and 3 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly. The mixture is heated to 80°C and kept warm for 3 hours to obtain the demulsifier.

[0076] Comparative Example 2 Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 5 parts of soybean oil to the reactor according to the weight, heat and stir in a nitrogen atmosphere, and when the temperature rises to 225°C, add 55 parts of food-grade plant-based resin and keep warm for 45 minutes.

[0077] (2) Add 3 parts of modified nano-montmorillonite, 0.3 parts of deemulsifier, 4 parts of polyethylene wax, 1 part of methyl ethyl ketone oxime, and 1 part of cobalt isooctanoate. Stir at 500 r / min for 12 minutes and reduce the temperature to 150℃.

[0078] (3) Add 18 parts of natural plant carbon black, stir at 1000 r / min for 45 min, and then grind the powder with a ball mill at 250 r / min and a three-roll mill to make the particle size not exceed 5 μm, thus obtaining food-grade ink containing plant-based resin that can be in contact with food.

[0079] The food-contact plant-based resin is made by mixing rosin resin and dammar resin in a weight ratio of 1.5:1.

[0080] Preparation of modified nano-montmorillonite: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of 8.5:1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 75℃ and magnetically stirred at a constant temperature for 7h. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0081] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0082] S3. The graphene pretreated in step S2 is added to ethanol and ultrasonically dispersed. The organosilicon-modified nano-montmorillonite prepared in step S1 is added. The mixture is stirred rapidly at 30°C to allow it to react fully. After centrifugation, the mixture is washed several times with anhydrous ethanol and then vacuum dried. The modified nano-montmorillonite is then ground to obtain the modified nano-montmorillonite.

[0083] The mass ratio of nano-montmorillonite, the anhydrous ethanol, and the γ-aminopropyltriethoxysilane is 1:9:0.15.

[0084] Preparation of demulsifier: 12 parts by weight of propylene oxide and 7 parts by weight of polyethylene glycol are ground and mixed, then 3 parts by weight of sodium gluconate and 1.5 parts by weight of lactic acid are added and ground and mixed evenly. The mixture is heated to 80°C and kept warm for 3 hours to obtain the demulsifier.

[0085] Comparative Example 3 Preparation of food-grade inks containing food-contact plant-based resins: (1) Add 5 parts of soybean oil to the reactor according to the weight, heat and stir in a nitrogen atmosphere, and when the temperature rises to 225°C, add 55 parts of food-grade plant-based resin and keep warm for 45 minutes.

[0086] (2) Add 3 parts of modified nano-montmorillonite, 0.3 parts of deemulsifier, 1 part of methyl ethyl ketone oxime, and 1 part of cobalt isooctanoate. Stir at 500 r / min for 12 minutes and reduce the temperature to 150℃.

[0087] (3) Add 18 parts of natural plant carbon black, stir at 1000 r / min for 45 min, and then grind the powder with a ball mill at 250 r / min and a three-roll mill to make the particle size not exceed 5 μm, thus obtaining food-grade ink containing plant-based resin that can be in contact with food.

[0088] The food-contact plant-based resin is made by mixing rosin resin and dammar resin in a weight ratio of 1.5:1.

[0089] Preparation of modified nano-montmorillonite: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of 8.5:1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 75℃ and magnetically stirred at a constant temperature for 7h. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained.

[0090] S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground.

[0091] S3. The graphene pretreated in step S2 is added to ethanol and ultrasonically dispersed. The organosilicon-modified nano-montmorillonite prepared in step S1 is added. The mixture is stirred rapidly at 30°C to allow it to react fully. After centrifugation, the mixture is washed several times with anhydrous ethanol and then vacuum dried. The modified nano-montmorillonite is then ground to obtain the modified nano-montmorillonite.

[0092] The mass ratio of nano-montmorillonite, the anhydrous ethanol, and the γ-aminopropyltriethoxysilane is 1:9:0.15.

[0093] Preparation of demulsifier: 12 parts by weight of propylene oxide and 7 parts by weight of polyethylene glycol are ground and mixed, then 3 parts by weight of sodium gluconate, 1.5 parts by weight of lactic acid and 3 parts by weight of isopropyl tris(dioctyl pyrophosphate) titanate are added and ground and mixed evenly. The mixture is heated to 80°C and kept warm for 3 hours to obtain the demulsifier.

[0094] Experimental Example The food-grade inks containing food-contact plant-based resins prepared in Examples 1-4 and Comparative Examples 1-3 were printed onto food packaging paper using offset printing. The relevant properties of the inks and printed materials were tested using the following methods: Colors are tested according to GB / T 13217.1-2020 (requirement ≥ level 4).

[0095] The viscosity was tested according to GB / T 18723-2002 (requirements 7.0-16.0).

[0096] The adhesion strength was tested according to the standard GB / T 13217.1-2009 (requirement ≥95%).

[0097] The test method for abrasion resistance is as follows: a friction tester with a left-right swinging motion, and the test conditions are 4 psi / 50 cycles. The evaluation criteria for abrasion resistance are divided into 5 levels, from poorest to best.

[0098] Performance test data are shown in Table 1 below: Table 1

[0099] As can be seen from Table 1, the food-grade inks containing food-contact plant-based resins in Examples 1-4 of this application have good performance in various aspects. Under the specific ratio of raw materials, the color, viscosity, adhesion and abrasion resistance of the prepared inks can all reach a high level.

[0100] In Comparative Example 1, the modified nano-montmorillonite was replaced with ordinary nano-montmorillonite in the preparation raw materials, while the rest were the same as in Example 1. The food-grade ink containing food-contact plant-based resin prepared in Comparative Example 1 showed significantly worse adhesion and abrasion resistance. This indicates that the food-grade ink of this application uses modified nano-montmorillonite as a filler. Due to its large specific surface area and high adsorption capacity, nanomaterials can enhance the mechanical properties of the ink layer. The oleophobicity of montmorillonite due to the large number of inorganic ions between its layers is not conducive to its dispersion in the ink matrix. The use of organosilicon modification changes the interlayer of montmorillonite from hydrophilic to oleophilic, reducing its surface energy and increasing the interlayer spacing of montmorillonite, thereby increasing the dispersion of nano-montmorillonite in the resin matrix and improving the elasticity, abrasion resistance, and corrosion resistance of the ink layer. After acidification, the surface of graphene will oxidize to carboxyl groups, which combine with the organosilicon-modified nano-montmorillonite, reducing the problem of graphene agglomeration. The layered structure of graphene allows for more thorough mixing between the filler and the resin, improving the hardness and abrasion resistance of the ink layer.

[0101] The raw materials for preparing the demulsifier in Comparative Example 2 did not contain isopropyltris(dioctylpyrophosphate)titanate, and were otherwise identical to those in Example 1. The food-grade ink containing food-contact plant-based resin prepared in Comparative Example 2 showed significantly worse color and viscosity. This indicates that in the demulsifier preparation scheme of this application, propylene oxide forms hydrophobic segments through ring-opening polymerization, polyethylene glycol provides hydrophilic segments and molecular structure, and titanate is introduced as an anchoring group at the chain end. The resulting demulsifier has excellent demulsification properties, can change the interfacial tension between oil and water, achieve rapid water separation, and passivate the pigment surface by binding the titanate groups to the pigment surface, reducing its hydrophilicity and further reducing emulsification. It not only improves compatibility but also reduces viscosity and promotes dispersion.

[0102] The raw materials used in Comparative Example 3 did not contain polyethylene wax, and all other materials were the same as in Example 1. The food-grade ink containing food-contact plant-based resin prepared in Comparative Example 3 showed significantly worse color and abrasion resistance, indicating that the wax paste of this application can enhance the abrasion resistance, smoothness, and texture of the ink after printing.

[0103] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions or alterations can be made to these embodiments without departing from the principles and spirit of this application, and the technical solutions resulting from such changes, modifications, substitutions or alterations will all fall within the protection scope of this application.

Claims

1. A food-grade ink containing a food-contact plant-based resin, characterized in that, The preparation materials include the following parts by weight: 50-60 parts of food-contact plant-based resin, 5-6 parts of soybean oil, 2-4 parts of modified nano-montmorillonite, 0.1-0.5 parts of deemulsifier, 15-20 parts of pigment, 3-5 parts of wax paste, 0.5-2 parts of anti-skinning agent, and 0.5-2 parts of desiccant. The food-contact plant-based resin includes at least one of rosin resin and damar resin.

2. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The food-contact plant-based resin is a mixture of rosin resin and dammar resin in a weight ratio of (1-2):

1.

3. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The preparation method of the modified nano-montmorillonite includes the following steps: S1. Nano-montmorillonite was ultrasonically dispersed in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of (8-9):1, and γ-aminopropyltriethoxysilane was added under stirring. The temperature was raised to 70-80℃ and magnetically stirred at a constant temperature for 5-8 hours. After centrifugation, washing and drying, organosilicon-modified nano-montmorillonite was obtained. S2. Graphene pretreatment: Graphene was ultrasonically dispersed in a mixed solution of sulfuric acid and nitric acid, and then refluxed at 80°C for 4 hours. After the reaction was completed, it was dried and ground. S3. Add the pretreated graphene from step S2 to ethanol and disperse it by ultrasonication. Add the organosilicon-modified nano-montmorillonite prepared in step S1. Stir rapidly at 25-35℃ to allow it to react fully. Centrifuge, wash several times with anhydrous ethanol, vacuum dry, and grind to obtain modified nano-montmorillonite.

4. The food-grade ink containing a food-contact plant-based resin according to claim 3, characterized in that, The mass ratio of the nano-montmorillonite, the anhydrous ethanol, and the γ-aminopropyltriethoxysilane is 1:(8-10):(0.1-0.2).

5. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The preparation of the demulsifier includes the following steps: Grind and mix 10-15 parts of propylene oxide with 6-9 parts of polyethylene glycol according to the weight ratio. Then add 2-4 parts of sodium gluconate, 1-2 parts of lactic acid, and 2-4 parts of isopropyl tris(dioctyl pyrophosphoryloxy)titanate and continue grinding and mixing until uniform. Heat to 75-88℃ and keep warm for 1-4 hours to obtain the demulsifier.

6. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The anti-skinning agent includes at least one of methyl ethyl ketone oxime, butyraldehyde oxime, and cyclohexanone oxime.

7. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The pigments include at least one of the following: natural plant carbon black, carmine, chlorophyll, caramel color, purple cabbage red, anthocyanin, and curcumin.

8. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The wax paste includes at least one of polyethylene wax, microcrystalline wax, paraffin wax, or polytetrafluoroethylene wax.

9. The food-grade ink containing a food-contact plant-based resin according to claim 1, characterized in that, The desiccant includes at least one of cobalt isooctanoate, manganese isooctanoate, zirconium isooctanoate, cobalt naphthenate, manganese naphthenate, zirconium naphthenate, cobalt 2-ethylhexanoate, manganese 2-ethylhexanoate, and zinc 2-ethylhexanoate.

10. A method for preparing a food-grade ink containing a food-contact plant-based resin as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Add soybean oil to the reactor according to the weight parts, heat and stir in an inert gas atmosphere, and when the temperature rises to 220-230℃, add food-grade plant-based resin and keep warm for 30-60 minutes. (2) Add modified nano-montmorillonite, deemulsifier, wax paste, anti-skinning agent and desiccant, stir at 500 r / min for 10-15 minutes, and reduce the temperature to 150℃; (3) Add pigment and stir at 1000r / min for 30-60min. After ball milling and grinding, obtain food-grade ink containing food-contact plant-based resin.

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