Biomass-based food-grade water-based gloss oil as well as preparation method and application thereof

Abstract

The invention discloses biomass-based food-grade water-based gloss oil as well as a preparation method and application thereof. The biomass-based food-grade water-based gloss oil comprises the following preparation raw materials in percentage by weight: 15-25% of macromolecular natural resin; 3%-15% of small molecule natural resin; 2%-5% of vegetable fat; 1%-3% of inorganic filler; 10%-18% of a low-boiling-point cosolvent; 1%-3% of a high-boiling-point cosolvent; 0.3%-0.6% of a metal ion cross-linking agent; 0.1%-0.3% of a defoaming agent; and the balance of water. The biomass-based food-grade water-based gloss oil disclosed by the invention has the advantages of high solid content, low viscosity, high drying speed, good film-forming property, no plastic, no fluorine, degradability and the like, and a uniform and compact film formed by coating a paper product with the biomass-based food-grade water-based gloss oil can endow the paper product with high glossiness and excellent wear resistance and waterproof and oil-proof properties; raw paper recycling and re-pulping are not affected, and the method is suitable for large-scale industrial application.

Description

TECHNICAL FIELD

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

[0002] Food packaging is an important part of food commodities, which can effectively prevent food from being damaged by biological, chemical and physical factors during the flow process. With the enhancement of people's environmental protection consciousness, the food packaging industry is undergoing green transformation, and "using paper instead of plastic" has become an important development trend in the field of disposable food packaging. At present, the disposable food packaging used in the food industry is mainly coated paper (made by coating polyethylene, polyethylene terephthalate plastic film on the surface of paper through coating / film coating process), which has the advantages of good waterproof and oil-proof effect, high surface gloss and good wear resistance, etc. However, the existence of plastic film not only hinders the recycling of coated paper, but also has the problem of difficult degradation. Plastic film is easy to form microplastics in the natural environment, polluting soil and water, and posing a potential threat to the ecological system and human health.

[0003] In recent years, paper products made by surface printing / coating treatment of paper with water-based resin gloss oil (such as water-based acrylic resin gloss oil and water-based polyurethane gloss oil) have developed rapidly, and their recyclability is significantly improved compared with coated paper (the resin layer of paper products coated with water-based resin gloss oil can be dispersed in the pulping system, thereby improving the recycling rate of paper fibers). However, although the existing water-based resin gloss oil does not affect the pulping characteristics of paper, it is still essentially a non-biodegradable petroleum-based polymer material, which is also easy to form microplastics in the natural environment. In addition, there may be trace amounts of un-polymerized monomers (such as acrylamide) and organic peroxide initiators in the existing water-based resin gloss oil, which have a long-term contact with food and have a migration risk, which can cause cumulative harm to consumers' health.

[0004] Therefore, it is of great significance to develop a water-based gloss oil that is plastic-free, biodegradable, and does not affect the recycling of raw paper. SUMMARY

[0005] The present application relates to the technical field of food packaging, in particular to a biomass-based food-grade water-based gloss oil and a preparation method and application thereof.

[0006] The technical solution adopted by the present application is as follows:

[0007] A biomass-based food-grade water-based gloss oil, which comprises the following preparation raw materials by weight percentage:

[0008] Macromolecular natural resin: 15% to 25%;

[0009] Small molecule natural resin: 3% to 15%;

[0010] Vegetable oil: 2% to 5%;

[0011] Inorganic filler: 1% to 3%;

[0012] Low boiling point co-solvent: 10% to 18%;

[0013] High boiling point co-solvent: 1% to 3%;

[0014] Metal ion crosslinking agent: 0.3% to 0.6%;

[0015] Defoaming agent: 0.1% to 0.3%;

[0016] Water: balance.

[0017] Preferably, the macromolecular natural resin is at least one of dammar resin, frankincense resin, orris root, sandarac resin, copal, gum kino.

[0018] Preferably, the macromolecular natural resin has a number average molecular weight greater than 500.

[0019] Preferably, the small molecule natural resin is at least one of rosin, benzoin resin, or Peru balsam.

[0020] Preferably, the small molecule natural resin has a number average molecular weight less than 500.

[0021] Preferably, the vegetable oil is at least one of soybean oil, linseed oil, cottonseed oil, or tung oil.

[0022] Preferably, the inorganic filler is at least one of kaolin, diatomite, talc powder, or mica powder.

[0023] Preferably, the inorganic filler has a particle size less than 10 μm.

[0024] Preferably, the low boiling point co-solvent is a mixture of an alcohol co-solvent having a boiling point less than 100°C and a basic co-solvent.

[0025] Preferably, the low boiling point co-solvent has a weight ratio of the alcohol co-solvent having a boiling point less than 100°C to the basic co-solvent of 4 to 5:1.

[0026] Preferably, the alcohol co-solvent having a boiling point less than 100°C is at least one of ethanol or isopropyl alcohol.

[0027] Preferably, the basic co-solvent is at least one of aqueous ammonia or triethylamine.

[0028] Preferably, the aqueous ammonia has a concentration of 23% to 28% by weight.

[0029] Preferably, the high-boiling point co-solvent is a co-solvent with a primary amine group and a boiling point higher than 100°C.

[0030] Further preferably, the high-boiling point co-solvent is at least one of 1,5-pentanediamine, ethanolamine, n-octylamine, lysine, polyetheramine D230, polyetheramine D400, and 2-amino-2-methyl-1-propanol.

[0031] Preferably, the metal ion crosslinking agent is at least one of calcium hydroxide, ferric chloride, magnesium chloride, and calcium chloride.

[0032] Preferably, the defoaming agent is at least one of polydimethylsiloxane, n-octanol, and high-carbon alcohol fatty acid ester.

[0033] A preparation method of the biomass-based food-grade aqueous gloss oil as described above comprises the following steps:

[0034] 1) Dissolve the macromolecular natural resin, the vegetable fat, the inorganic filler, the low-boiling point co-solvent, and the high-boiling point co-solvent in water by heating and stirring, and then perform high-speed dispersion emulsification under vacuum (the vacuum operation can remove most of the low-boiling point co-solvent, gradually reduce the solubility of the macromolecular natural resin, adjust the extended molecular chain structure of the macromolecular natural resin to a curled structure, generate an emulsion system, and thus effectively reduce the viscosity of the system);

[0035] 2) Dissolve the small-molecule natural resin in the emulsion by heating and stirring (remove the residual low-boiling point co-solvent and part of the high-boiling point co-solvent, and combine the small-molecule natural resin with the macromolecular natural resin through hydrophobic interaction under the action of the solvent), then disperse the metal ion crosslinking agent in the emulsion at high speed to perform crosslinking treatment, add a defoaming agent to perform defoaming treatment, and filter to obtain the filtrate, thereby obtaining the biomass-based food-grade aqueous gloss oil.

[0036] Preferably, the heating and stirring in step 1) is performed at a temperature of 40°C to 50°C and a stirring rate of 300 r / min to 500 r / min, and the heating and stirring time is 1 h to 2 h.

[0037] Preferably, the vacuum operation in step 1) comprises the following steps: first, vacuumize to a vacuum degree of -0.03 MPa to -0.05 MPa and maintain for 0.5 h to 1 h, then vacuumize to a vacuum degree of -0.08 MPa to -0.10 MPa and maintain for 0.5 h to 1 h, and finally vacuumize to a pH value of the system of 7.5 to 8.0 (the step-by-step treatment can avoid the macromolecular natural resin from forming particles with excessively large particle sizes and precipitating).

[0038] Preferably, the high-speed dispersion emulsification of step 1) is carried out at a temperature of 70-80 DEG C and a stirring speed of 1500-2000 r / min, and the high-speed dispersion emulsification is carried out for 1-2 h.

[0039] Preferably, the heating stirring of step 2) is carried out at a temperature of 40-70 DEG C and a stirring speed of 500-800 r / min, and the heating stirring is carried out for 0.3-0.5 h.

[0040] Preferably, the cross-linking treatment of step 2) is carried out at a temperature of 25-50 DEG C and a stirring speed of 1500-2000 r / min, and the cross-linking treatment is carried out for 0.3-0.5 h.

[0041] Preferably, the defoaming treatment of step 2) is carried out at a temperature of 25-30 DEG C and a stirring speed of 100-200 r / min until the bubbles are completely eliminated.

[0042] A food packaging, which comprises a paper substrate and a varnish coating layer, wherein the varnish coating layer is made of the biomass-based food-grade water-based varnish.

[0043] The biomass-based food-grade water-based varnish has the advantages of high solid content, low viscosity, fast drying speed, good film-forming property, no plastic, no fluorine and degradability, and the uniform and dense film formed by coating the biomass-based food-grade water-based varnish on paper products can impart high gloss, excellent wear resistance and water / oil resistance to the paper products, and does not affect the recycling of the original paper, and is suitable for large-scale industrial application.

[0044] Specifically,

[0045] 1) The present application optimizes the performance of natural resin system by innovative process, as follows: first, the macromolecular natural resin is completely dissolved to form a uniform solution by the synergistic effect of low-boiling-point cosolvent and high-boiling-point cosolvent, then the low-boiling-point cosolvent is removed by vacuum extraction, this process not only effectively reduces the viscosity of the system, but also induces the macromolecular chain to transform from the stretched state to the coiled conformation by gradually reducing the solubility of the macromolecular natural resin, significantly weakening the hydrogen bonding and van der Waals force between molecules, further reducing the viscosity of the system, then introducing small molecule natural resin, the molecular weight of small molecule natural resin is relatively low (partly containing carboxyl functional group), which exhibits excellent solubility, under the synergistic effect of residual low-boiling-point cosolvent and high-boiling-point cosolvent, small molecule natural resin can be efficiently dissolved and embedded between macromolecular natural resin molecules, wrapped outside the coiled structure of macromolecular natural resin, constructing a core-shell structure with dense inside and loose outside, the gradual neutralization and consumption of high-boiling-point cosolvent further increases the coiling degree of macromolecular natural resin, making the system viscosity continuously decrease, finally forming a high solid content and low viscosity system with low water content, which significantly improves the drying rate of water-based gloss oil, at the same time, the high solid content provides a basis for the close connection between resin molecules, under the action of metal ion crosslinking agent, the biomass-based food-grade water-based gloss oil of the present application can form a continuous and dense high-gloss coating through dynamic covalent bond combination;

[0046] 2) During the structure regulation process of gradually emulsifying the macromolecular natural resin in the present application, vegetable oil will also be embedded between resin molecules, which improves the film-forming property of water-based gloss oil and the flexibility of coating as a natural plasticizer, the continuous phase structure of macromolecular natural resin and small molecule natural resin is similar to rigid-flexible continuous structure, the rigid macromolecular natural resin can impart excellent wear resistance and scratch resistance to the coating, the flexible small molecule natural resin has low glass transition temperature and strong peristalsis, which helps the full activity of intermolecular and the formation of dynamic covalent bond crosslinking, so as to form a dense coating;

[0047] 3) The macromolecular natural resin and small molecule natural resin in the present application have a large number of aldehyde and ketone structures, which can form dynamic imine bond with the primary amine groups contained in the amine compounds in the high-boiling-point cosolvent, and the carboxyl groups of the resin can form dynamic coordination bond with metal ions, such dynamic covalent bond crosslinking points can act as energy dissipation points to improve the flexibility of the coating, secondly, the dynamic imine bond and dynamic coordination bond are reversible at high temperature, so the coating can realize self-repairing after damage, prolonging the service life of the coating and maintaining the surface smoothness and gloss of the coating through automatic repair of scratches, in addition, under the external composting environment (pH value, humidity, temperature, light or enzyme catalysis), the dynamic covalent bond can be reversibly broken, thereby accelerating the degradation of the material. DETAILED DESCRIPTION

[0048] The application will be further explained and described in connection with specific embodiments.

[0049] Example 1

[0050] A biomass-based food-grade water-based gloss oil is prepared from the raw materials shown in the following table:

[0051] Table 1 Composition of raw materials for preparing biomass-based food-grade water-based gloss oil

[0052]

[0053]

[0054] The preparation method of the biomass-based food-grade water-based gloss oil is as follows:

[0055] 1) The sandarac resin, soybean oil, kaolin, ethanol, ammonia water and 1,5-pentanediamine are heated and stirred to dissolve in deionized water, the heating and stirring is carried out at a temperature of 50℃ and a stirring rate of 300r / min, the heating and stirring time is 2h, then high-speed dispersion emulsification is carried out under vacuum, the vacuum operation is as follows: first vacuum to a vacuum degree of-0.05MPa and keep for 0.5h, then vacuum to a vacuum degree of-0.09MPa and keep for 1h, then vacuum to a pH value of 8 of the system, the high-speed dispersion emulsification is carried out at a temperature of 70℃ and a stirring rate of 2000r / min, the high-speed dispersion emulsification time is 2h, to obtain an emulsion;

[0056] 2) The rosin is heated and stirred to dissolve in the emulsion, the heating and stirring is carried out at a temperature of 70℃ and a stirring rate of 800r / min, the heating and stirring time is 0.5h, then cooled to 50℃, then the ferric chloride (prepared into a 2wt% ferric chloride aqueous solution for use) is high-speed dispersed in the emulsion for crosslinking treatment, the crosslinking treatment is carried out at a temperature of 50℃ and a stirring rate of 2000r / min, the crosslinking treatment time is 0.5h, then cooled to 30℃, then add n-octanol for defoaming treatment, the defoaming treatment is carried out at a temperature of 30℃ and a stirring rate of 200r / min, the defoaming treatment time is 1h, filter the filtrate to obtain the biomass-based food-grade water-based gloss oil.

[0057] A food packaging is prepared by the following method:

[0058] The biomass-based food-grade water-based gloss oil of the present embodiment is printed on food-grade white cardboard with a grammage of 270g / m 2 at a speed of 150m / min by using a flexographic printing machine, the coating amount of the water-based gloss oil is 3g / m 2 (the dry printing amount is 0.8g / m 2 ), then dried to obtain the food packaging.

[0059] Example 2

[0060] A biomass-based food-grade water-based gloss oil is prepared from the following raw materials:

[0061] Table 2 Composition of raw materials for preparing biomass-based food-grade water-based gloss oil

[0062]

[0063]

[0064] The preparation method of the biomass-based food-grade water-based gloss oil is as follows:

[0065] 1) Heat and stir dammar resin, flaxseed oil, talc, isopropyl alcohol, ammonia water, and 2-amino-2-methyl-1-propanol to dissolve in deionized water. Heat and stir at a temperature of 40°C and a stirring rate of 500 r / min. The heat and stirring time is 1.5 h. Then perform high-speed dispersion emulsification under vacuum. The vacuum operation is as follows: first, vacuum to a vacuum degree of -0.03 MPa and maintain for 1 h, then vacuum to a vacuum degree of -0.08 MPa and maintain for 1 h, and then vacuum to a pH value of 7.5 of the system. High-speed dispersion emulsification is performed at a temperature of 75°C and a stirring rate of 2000 r / min. The high-speed dispersion emulsification time is 1.5 h, to obtain an emulsion.

[0066] 2) Heat and stir Peruvian balsam to dissolve in the emulsion. Heat and stir at a temperature of 70°C and a stirring rate of 500 r / min. The heat and stirring time is 0.5 h. Then cool to 40°C. Then high-speed disperse magnesium chloride (prepared into a 1 wt% magnesium chloride aqueous solution for use) in the emulsion to perform crosslinking treatment. Crosslinking treatment is performed at a temperature of 40°C and a stirring rate of 2000 r / min. The crosslinking treatment time is 0.5 h. Then cool to 30°C. Then add polydimethylsiloxane to perform defoaming treatment. Defoaming treatment is performed at a temperature of 30°C and a stirring rate of 200 r / min. The defoaming treatment time is 1 h. Filter to obtain a filtrate, to obtain a biomass-based food-grade water-based gloss oil.

[0067] A food packaging is prepared by the following method:

[0068] A flexographic printing machine is used to print the biomass-based food-grade water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 300 g / m 2 at a speed of 150 m / min. The coating amount of the water-based gloss oil is 5 g / m 2 (the dry printing amount is 1.3 g / m 2 ). Then dry to obtain a food packaging.

[0069] Example 3

[0070] A biomass-based food-grade water-based gloss oil is prepared from the following raw materials:

[0071] Table 3 Composition of raw materials for preparing biomass-based food-grade water-based gloss oil

[0072]

[0073]

[0074] The preparation method of the biomass-based food-grade water-based gloss oil is as follows:

[0075] 1) Heat and stir dammar resin, gurjun balsam, cottonseed oil, mica powder, ethanol, triethylamine, and polyetheramine D230 to dissolve in deionized water. Heat and stirring is performed at a temperature of 50°C and a stirring rate of 500 r / min. The heat and stirring time is 2 h. High-speed dispersion emulsification is then performed under vacuum. The vacuum operation is as follows: first, vacuum to a vacuum degree of -0.04 MPa and maintain for 1 h, then vacuum to a vacuum degree of -0.10 MPa and maintain for 0.5 h, and then vacuum to a pH value of 8 of the system. High-speed dispersion emulsification is performed at a temperature of 80°C and a stirring rate of 2000 r / min. The high-speed dispersion emulsification time is 1 h, to obtain an emulsion.

[0076] 2) Heat and stir rosin to dissolve in the emulsion. Heat and stirring is performed at a temperature of 70°C and a stirring rate of 500 r / min. The heat and stirring time is 0.5 h. Then, cool to 40°C. Then, disperse ferric chloride (prepared into a 2 wt% ferric chloride aqueous solution for use) in the emulsion at high speed to perform crosslinking treatment. Crosslinking treatment is performed at a temperature of 40°C and a stirring rate of 2000 r / min. The crosslinking treatment time is 0.5 h. Then, cool to 30°C. Then, add n-octanol to perform defoaming treatment. Defoaming treatment is performed at a temperature of 30°C and a stirring rate of 100 r / min. The defoaming treatment time is 1 h. Filter to obtain a filtrate, to obtain a biomass-based food-grade water-based gloss oil.

[0077] A food packaging is prepared by the following method:

[0078] A flexographic printing machine is used to print the biomass-based food-grade water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 150 g / m 2 at a speed of 150 m / min. The coating amount of the water-based gloss oil is 4 g / m 2 (the dry printing amount is 1.5 g / m 2 ). Then, dry to obtain a food packaging.

[0079] Example 4

[0080] A biomass-based food-grade aqueous gloss oil was prepared using the raw materials shown in the following table:

[0081] Table 4 Composition of raw materials for preparing biomass-based food-grade aqueous gloss oil

[0082]

[0083]

[0084] The preparation method of the biomass-based food-grade aqueous gloss oil described above is as follows:

[0085] 1) The frankincense resin, linseed oil, talc, isopropyl alcohol, triethylamine, and 2-amino-2-methyl-1-propanol were heated and stirred to dissolve in deionized water. The heating and stirring was performed at a temperature of 50°C and a stirring rate of 500 r / min. The heating and stirring time was 2 h. Then, high-speed dispersion emulsification was performed under vacuum. The vacuum operation was as follows: first, vacuum was applied to a vacuum degree of -0.04 MPa and maintained for 1 h, then vacuum was applied to a vacuum degree of -0.09 MPa and maintained for 1 h, and then the pH value of the system was adjusted to 8. The high-speed dispersion emulsification was performed at a temperature of 80°C and a stirring rate of 2000 r / min. The high-speed dispersion emulsification time was 1 h, and an emulsion was obtained.

[0086] 2) The benzoin resin and Peruvian balsam were heated and stirred to dissolve in the emulsion. The heating and stirring was performed at a temperature of 70°C and a stirring rate of 500 r / min. The heating and stirring time was 0.3 h. Then, the temperature was lowered to 40°C. Calcium chloride (prepared as a 2 wt% calcium chloride aqueous solution) was then high-speed dispersed in the emulsion for crosslinking treatment. The crosslinking treatment was performed at a temperature of 40°C and a stirring rate of 2000 r / min. The crosslinking treatment time was 0.3 h. Then, the temperature was lowered to 25°C. High-carbon alcohol fatty acid ester was then added for defoaming treatment. The defoaming treatment was performed at a temperature of 25°C and a stirring rate of 100 r / min. The defoaming treatment time was 1 h. The filtrate was obtained by filtration, and a biomass-based food-grade aqueous gloss oil was obtained.

[0087] A food packaging was prepared using the following method:

[0088] The biomass-based food-grade aqueous gloss oil of the present example was printed on a food-grade white cardboard with a grammage of 78 g / m 2 at a speed of 150 m / min using a flexographic printing machine. The coating amount of the aqueous gloss oil was 6 g / m 2 (the dry printing amount was 0.9 g / m 2 ). Then, drying was performed, and a food packaging was obtained.

[0089] Comparative Example 1:

[0090] A water-based varnish is prepared in the same manner as in Example 1 except that ferric chloride is not added during preparation.

[0091] A food packaging, the preparation method of which is as follows:

[0092] The flexographic printing machine is used at a speed of 150m / min on a grammage of 270g / m 2 The water-based varnish of this comparative example is printed on food-grade white cardboard, and the coating amount of the water-based varnish is 4g / m 2 (Printing dry weight is 1.1g / m 2 ), and then dried to obtain food packaging. Comparative Example 2:

[0093] A water-based varnish is prepared in the same manner as in Example 1, except that the high-speed dispersion and emulsification in step 1) is carried out under normal pressure (without vacuuming).

[0094] Note: The viscosity of the water-based varnish in this comparative example is too high to be printed on a machine, so food packaging cannot be obtained.

[0095] Comparative Example 3:

[0096] A water-based varnish is prepared in the same manner as in Example 1 except that rosin is not added (rosin is replaced by an equal weight of deionized water).

[0097] A food packaging, the preparation method of which is as follows:

[0098] The flexographic printing machine is used at a speed of 140m / min on a grammage of 270g / m 2 The water-based varnish of this comparative example is printed on food-grade white cardboard, and the coating amount of the water-based varnish is 5g / m 2 (Printing dry weight is 1g / m 2 ), and then dried to obtain food packaging.

[0099] Comparative Example 4:

[0100] A water-based varnish is prepared in the same manner as in Example 1 except that no sandarac resin is added (the sandarac resin is replaced by an equal weight of deionized water).

[0101] A food packaging, the preparation method of which is as follows:

[0102] The flexographic printing machine is used at a speed of 120m / min on a grammage of 270g / m 2 The water-based varnish of this comparative example is printed on food-grade white cardboard, and the coating amount of the water-based varnish is 6g / m 2 (Printing dry weight is 0.9g / m 2A food packaging was obtained by printing the water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 270 g / m2using a flexographic printing machine at a speed of 170 m / min, the coating amount of the water-based gloss oil being 5 g / m2(printing dry amount being 2 g / m2), followed by drying.

[0103] A water-based gloss oil, which was completely identical to that of Example 1 except that the amount of sandarac resin was adjusted from "20%" to "30%" and the amount of rosin was adjusted from "15%" to "20%" (adaptively reducing the amount of deionized water) during preparation.

[0104] Note: The viscosity of the water-based gloss oil of the present comparative example was too high to be printed on a machine, and thus a food packaging was not obtained.

[0105] Comparative Example 6:

[0106] A water-based gloss oil, which was completely identical to that of Example 1 except that the amount of sandarac resin was adjusted from "20%" to "30%" (adaptively reducing the amount of deionized water) during preparation.

[0107] A food packaging was obtained by printing the water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 270 g / m2using a flexographic printing machine at a speed of 170 m / min, the coating amount of the water-based gloss oil being 5 g / m2(printing dry amount being 2 g / m2), followed by drying.

[0108] A food packaging was obtained by printing the water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 270 g / m2using a flexographic printing machine at a speed of 170 m / min, the coating amount of the water-based gloss oil being 5 g / m2(printing dry amount being 2 g / m2), followed by drying. 2 2 2 A food packaging was obtained by printing the water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 270 g / m2using a flexographic printing machine at a speed of 170 m / min, the coating amount of the water-based gloss oil being 5 g / m2(printing dry amount being 2 g / m2), followed by drying.

[0109] Comparative Example 7:

[0110] A water-based gloss oil, which was completely identical to that of Example 1 except that the amount of rosin was adjusted from "15%" to "20%" (adaptively reducing the amount of deionized water) during preparation.

[0111] A food packaging was obtained by printing the water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 270 g / m2using a flexographic printing machine at a speed of 170 m / min, the coating amount of the water-based gloss oil being 5 g / m2(printing dry amount being 2 g / m2), followed by drying.

[0112] A food packaging was obtained by printing the water-based gloss oil of the present example on a food-grade white cardboard with a grammage of 270 g / m2using a flexographic printing machine at a speed of 170 m / min, the coating amount of the water-based gloss oil being 5 g / m2(printing dry amount being 2 g / m2), followed by drying. 2 2 2 Performance test:

[0113] 1) The biobased content, degradation rate, and viscosity test results of the biomass-based food-grade water-based gloss oil of Examples 1 to 4 and the water-based gloss oil of Comparative Examples 1 to 7 are shown in the following table.

[0114] Table 5 Biobased content, degradation rate, and viscosity test results of water-based gloss oil

[0115] Test item Biobased content (%) Degradation rate (%) Viscosity (mPa-s) Example 1 100 92.2 68～75 Example 2 99.5 91.3 32～44 Example 3 99.3 93.6 70～76 Example 4 99.0 94.1 43～54 Comparative Example 1 100 93.1 65～75 Comparative Example 2 100 93.5 > 1000, difficult to print on Comparative Example 3 100 95.4 <20 Comparative Example 4 100 94.8 <20 Comparative Example 5 100 91.6 > 600, difficult to print on Comparative Example 6 100 91.9 90～120 Comparative Example 7 100 92.0 86～100 ​​​​

[0116] Note:

[0117] Bio-based content: tested in accordance with “ASTM D6866-24”.

[0118] Degradation rate: the water-based gloss oil was dried into a film, and then tested in accordance with “ISO 14855-1:2012 Determination of the aerobic biodegradation of plastic materials under controlled composting conditions - Method A: Method for the determination of the amount of carbon dioxide in the presence of oxygen - Part 1: General method” under the environment with the temperature of 25℃±5℃, the test end time of the water-based gloss oil of Examples 1-4 and Comparative Examples 1-7 were 260 days, 251 days, 255 days, 263 days, 267 days, 270 days, 263 days, 260 days, 258 days, 266 days and 259 days, respectively.

[0119] Viscosity: tested in accordance with “GB / T 265-1988 Determination of kinematic viscosity and dynamic viscosity of petroleum products - Test methods and calculation methods”.

[0120] From Table 5, it can be seen that:

[0121] a) The biomass-based food-grade water-based gloss oil of Examples 1-4 is safe, environmentally friendly, degradable and low in viscosity.

[0122] b) The viscosity of the water-based gloss oil of Comparative Example 2 is greatly increased compared with the biomass-based food-grade water-based gloss oil of Example 1, because: during the preparation of the water-based gloss oil, vacuum operation is not used to remove low-boiling-point cosolvents, and the molecular chains of the macromolecular natural resin are in an extended state, so the viscosity is large and the flowability is poor.

[0123] c) The viscosity of the water-based gloss oil of Comparative Example 5 is greatly increased compared with the biomass-based food-grade water-based gloss oil of Example 1, because: the content of macromolecular natural resin and small molecular natural resin in the water-based gloss oil is too high.

[0124] 2) The performance test results of the food packaging of Examples 1-4, Comparative Example 1, Comparative Example 3, Comparative Example 4, Comparative Example 6 and Comparative Example 7 are shown in the following table:

[0125] Table 6 Performance test results of food packaging

[0126]

[0127]

[0128] Note:

[0129] Glossiness: tested in accordance with “GB / T 8941-2013 Determination of specular glossiness of paper and paperboard”.

[0130] Abrasion resistance: using an abrasion resistance tester, load 4LB weight, use A4 paper friction to test the abrasion resistance, record the friction times when the varnish falls off.

[0131] Oil resistance grade: using the Oil Kit Test TAPPI test method (TAPPI 559 oil resistance grade test) to test the oil resistance grade of the food packaging (the oil resistance grade of the original white cardboard is 6).

[0132] Hot oil resistance performance: pour hot olive oil at 85℃ evenly on the food packaging, and observe whether there is oil leakage at the bottom and surface.

[0133] From Table 6, it can be seen that:

[0134] a) The food packaging of Examples 1-4 has high gloss, good abrasion resistance, high oil resistance grade, and excellent hot oil resistance performance, which shows that the biomass-based food-grade water-based varnish of the application can indeed form a uniform and dense film on the paper product, thereby imparting high gloss and excellent abrasion resistance and water and oil resistance to the paper product;

[0135] b) Compared with the food packaging of Example 1, the gloss, abrasion resistance, and oil resistance of the food packaging of Comparative Example 1 are all decreased, which is because the water-based varnish lacks the crosslinking effect of the metal ion crosslinking agent, the density and mechanical strength of the formed coating are decreased, thereby affecting the gloss, abrasion resistance, and oil resistance;

[0136] c) Compared with the food packaging of Example 1, the gloss, abrasion resistance, and oil resistance of the food packaging of Comparative Examples 3 and 4 are all decreased, which is because the water-based varnish lacks macromolecular natural resin or small molecular natural resin, the rigid-flexible continuous structure cannot be formed in the system, and the solid content of the water-based varnish is reduced, the density and mechanical strength of the formed coating are decreased, thereby affecting the gloss, abrasion resistance, and oil resistance;

[0137] d) Compared with the food packaging of Example 1, the gloss, abrasion resistance, and oil resistance of the food packaging of Comparative Examples 6 and 7 are all decreased, which is because the content of macromolecular natural resin or small molecular natural resin in the water-based varnish is too high, the solubility of the system is decreased, the viscosity of the water-based varnish is increased, the formed coating is rough, and the density and mechanical strength of the coating are decreased, thereby affecting the gloss, abrasion resistance, and oil resistance,

[0138] In summary, the biomass-based food-grade water-based varnish of the application has the advantages of high solid content, low viscosity, fast drying speed, good film-forming property, no plastic, no fluorine, and biodegradability. The uniform and dense film formed by coating the biomass-based food-grade water-based varnish on the paper product can impart high gloss and excellent abrasion resistance and water and oil resistance to the paper product.

[0139] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A biomass-based food-grade water-based varnish, characterized in that: The preparation comprises the following raw materials in weight percentage: Macromolecular natural resin: 15% to 25%; Small molecule natural resin: 3% to 15%; Vegetable oils: 2% to 5%; Inorganic filler: 1% to 3%; Low boiling point cosolvent: 10% to 18%; High boiling point cosolvent: 1% to 3%; Metal ion crosslinker: 0.3% to 0.6%; Defoaming agent: 0.1% to 0.3%; Water: Balance.

2. The biomass-based food-grade water-based varnish according to claim 1, characterized in that: The macromolecular natural resin is at least one of dammar resin, frankincense resin, lithospermum officinale, sandarac resin, cobalt gum, and balsam of guyun.

3. The biomass-based food-grade water-based varnish according to claim 1, characterized in that: The small molecule natural resin is at least one of rosin, benzoin resin and Peruvian balsam.

4. The biomass-based food-grade water-based varnish according to any one of claims 1 to 3, characterized in that: The vegetable oil is at least one of soybean oil, linseed oil, cottonseed oil and tung oil.

5. The biomass-based food-grade water-based varnish according to any one of claims 1 to 3, characterized in that: The inorganic filler is at least one of kaolin, diatomaceous earth, talc powder and mica powder.

6. The biomass-based food-grade water-based varnish according to any one of claims 1 to 3, characterized in that: The low-boiling-point cosolvent is a mixture of an alcohol cosolvent with a boiling point lower than 100° C. and an alkaline cosolvent; the high-boiling-point cosolvent is a cosolvent with a primary amine group with a boiling point higher than 100° C.

7. The biomass-based food-grade water-based varnish according to any one of claims 1 to 3, characterized in that: The metal ion cross-linking agent is at least one of calcium hydroxide, ferric chloride, magnesium chloride and calcium chloride.

8. The biomass-based food-grade water-based varnish according to any one of claims 1 to 3, characterized in that: The defoaming agent is at least one of polydimethylsiloxane, n-octanol, and higher alcohol fatty acid ester.

9. A method for preparing a biomass-based food-grade water-based varnish according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) dissolving a macromolecular natural resin, vegetable oil, inorganic filler, a low-boiling point cosolvent, and a high-boiling point cosolvent in water by heating and stirring, and then performing high-speed dispersion and emulsification under vacuum conditions to obtain an emulsion; 2) The small molecule natural resin is heated and stirred to be dissolved in the emulsion, and then the metal ion crosslinking agent is dispersed in the emulsion at a high speed for crosslinking treatment, and then a defoaming agent is added for defoaming treatment, and the filtrate is filtered to obtain the biomass-based food-grade water-based varnish.

10. A food packaging, characterized in that: The composition comprises a paper substrate and a varnish coating; the varnish coating is made of the biomass-based food-grade water-based varnish according to any one of claims 1 to 8.

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