Bio-based fluoride-free oil-proof agent for food packaging paper

Abstract

The invention discloses a bio-based fluoride-free oil-proof agent for food packaging paper, which is prepared from the following raw materials in parts by weight: 30 to 50 parts of modified low-viscosity starch, 5 to 15 parts of reinforced polymer emulsion, 10 to 30 parts of 10wt% polyvinyl alcohol aqueous solution, 3 to 20 parts of 3wt% nano cellulose aqueous solution, 0.5 to 2 parts of plasticizer and 0.01 to 0.3 part of preservative. The invention has the advantages of environment-friendly raw materials, fluoride-free property, high-efficiency oil-proof property and the like.

Description

Technical Field

[0001] The invention relates to the technical field of oil-proofing agent production, and in particular to a bio-based fluorine-free oil-proofing agent for food packaging paper. Background Art

[0002] With the continuous development of society and the continuous improvement of people's material living standards, the application of oil-proof paper is becoming more and more extensive, and the demand is also increasing. At present, almost all food-grade oil-proof papers on the market use fluoride as an oil-proof agent. The surface of fluorine atoms contains more negative charges, and the atomic volume is larger, which can form a dense thin layer with low surface energy, reducing the interaction between fibers and liquids. Applying a layer of fluorine-containing oil-proof agent on the surface of paper can give the paper good oil-proof properties. However, scientists have proven that fluoride is carcinogenic to the body.

[0003] Since 2016, the U.S. Food and Drug Administration (FDA) has announced a ban on the use of three perfluorinated compounds in food packaging materials. On June 14, 2017, the European Union published (EU) 2017 / 1000 in its official gazette, adding a new restriction clause on perfluorooctanoic acid (PFOA) in Annex XVII of the REACH Regulation, item 68, and officially included PFOA and its salts and related substances in the REACH Regulation restriction list. Since 2019, the EU has comprehensively restricted the entry of fluorinated paper products into the market. Therefore, it is of great significance to innovate and develop fluorine-free oil-proof coatings and develop a fluorine-free oil-proof paper.

[0004] Fluorine-free oil repellent fundamentally eliminates the harm caused by fluorine-containing oil repellent or coating to the environment or organisms, and is more in line with people's pursuit of green environmental protection. However, fluorine-free oil repellent has the problems of high viscosity, inconvenient operation, poor oil repellent effect and high price.

[0005] Patent CN113931005A discloses a method for preparing food oil-proof packaging. The method uses paraffin as a raw material, adds an emulsifier and an emulsifier, and obtains a uniform and stable fluorine-free oil-proof agent through high-speed dispersion emulsification and high-pressure homogenization. The oil-proof agent is applied to the surface of paper, and then dried to obtain oil-proof paper with resistance to oil penetration. However, the poor mechanical properties and degradation ability limit the application of the oil-proof paper.

[0006] Patent CN110258184A discloses a method of preparing a biopolymer coating from amorphous modified starch and chitosan, which is then applied to the surface of paper and dried to produce food greaseproof paper. The greaseproof paper has good green safety and high biodegradability, but chitosan is expensive and has a low concentration, which limits its application in greaseproof paper.

[0007] Patent CN 118621615 A discloses that after coating and sizing with a coating containing sodium alginate and carboxymethyl cellulose, the mechanical properties and barrier properties of the base paper can be enhanced; applying a polydimethylsiloxane solution to the sized dry paper can improve the oil resistance and barrier properties of the paper. However, both sodium alginate and carboxymethyl cellulose have the problem of high viscosity, and sodium alginate is expensive, requiring two-layer coating, and the complex process limits its application in greaseproof paper. Summary of the Invention

[0008] The purpose of the present invention is to provide a bio-based fluorine-free oil-proof agent for food packaging paper, which has the advantages of environmentally friendly raw materials, fluorine-free, and high-efficiency oil prevention.

[0009] The technical solution adopted by the present invention to solve its technical problems is: A bio-based fluorine-free oil-proof agent for food packaging paper, calculated by weight, the raw material composition of the bio-based fluorine-free oil-proof agent is: 30 parts to 50 parts of modified low-viscosity starch, 5 parts to 15 parts of enhanced polymer emulsion, 10 parts to 30 parts of 10wt% aqueous polyvinyl alcohol solution, 3 parts to 20 parts of 3wt% aqueous nanocellulose solution, 0.5 parts to 2 parts of plasticizer, and 0.01 parts to 0.3 parts of preservative.

[0010] The preparation method of the modified low-viscosity starch is: Mix low-viscosity starch and water to form a mixed solution with a mass concentration of 20-30%, add α-amylase, and carry out enzymatic hydrolysis at 40°C - 60°C for 10 min - 1 h, and then heat up to 90°C - 95°C and keep warm for 0.5 h - 1 h for gelatinization and inactivation treatment.

[0011] The low-viscosity starch is one or several of cationic starch, anionic starch or amphoteric starch.

[0012] The dosage of α-amylase is 0.1% - 1% of the absolute dry mass of low-viscosity starch.

[0013] The raw materials of the enhanced polymer emulsion are calculated by mass, and the composition is as follows: 30 - 40 parts of acrylamide, 5 - 10 parts of methacryloyloxyethyl trimethyl ammonium chloride, 3 - 5 parts of itaconic acid, 5 - 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1 - 0.5 parts of nanocellulose, 3 - 5 parts of sodium methallylsulfonate, 3 - 5 parts of initiator, 5 - 10 parts of crosslinking agent N,N-dimethylacrylamide, 3 - 5 parts of ethylenediaminetetraacetic acid; 1 - 3 parts of 98% sulfuric acid, 1 - 3 parts of sodium sulfite, 1 - 3 parts of defoaming agent (polydimethylsiloxane, Nanjing Gold Key Biotechnology Co., Ltd.), 1 - 3 parts of sodium dodecyl sulfonate (SDS), and add water to adjust the solid content to 15wt% - 25wt%; the initiator is ammonium persulfate.

[0014] The preparation method of the enhanced polymer emulsion is as follows: (1) Pre-emulsification Add acrylamide, methylacryloyloxyethyl trimethyl ammonium chloride, itaconic acid, 2-acrylamido-2-methylpropane sulfonic acid, nanocellulose, sodium methallyl sulfonate, ethylenediaminetetraacetic acid, 98% sulfuric acid, sodium sulfite, and sodium dodecyl sulfonate into the reaction kettle, add 30%-50% of the total water consumption, and stir at high speed (500-1000 rpm) for 30 minutes to form a pre-emulsion; (2) Seed preparation Under stirring conditions, take 10%-30% of the total weight of the pre-emulsion, heat it to 40-50°C, slowly dropwise add the remaining water. After the addition is complete, add 20%-30% of the total weight of the initiator, raise the temperature to 60-70°C, and react for 1-2 hours to form a stable seed latex; (3) Main polymerization stage Add the remaining pre-emulsion, crosslinking agent N,N-dimethylacrylamide and the remaining initiator, control the temperature at 70-85°C, and continuously stir for 4-6 hours; (4) Post-treatment Cool down to 40°C, add NaOH to neutralize to pH 7-8, and control the viscosity at 1000-3000 Pa*s.

[0015] The diameter of the nanocellulose is less than 50 nm, and the length is less than 1000 nm.

[0016] The plasticizer is one or more of glycerol, triethyl citrate, and epoxy soybean oil.

[0017] The preservative is selected from one or more of sodium benzoate, potassium benzoate, sodium sorbate, potassium sorbate, sodium propionate, calcium propionate, and natamycin.

[0018] The degree of polymerization of the polyvinyl alcohol is 1700-1800 (polyvinyl alcohol 1788, 1799).

[0019] After sizing by coating with a coating of modified low-viscosity starch, polyvinyl alcohol, enhanced polymer emulsion, and nanocellulose, the mechanical properties and barrier properties of the base paper can be enhanced; the oil resistance and barrier properties of the paper can be improved. Moreover, the system has a low viscosity, low raw material cost, simple process, and can expand the application of greaseproof paper in food packaging.

[0020] The present invention uses bio-based low-viscosity starch as the main body. Polyvinyl alcohol can improve the film densification, thereby enhancing the oil-proof performance. In coordination with low-molecular-weight reinforcing polymers, which are prepared together with nanocellulose due to the presence of active groups such as hydroxyl and amino groups, an interpenetrating network structure can be formed, which can promote hydrogen bonding and electrostatic adsorption with starch, polyvinyl alcohol, and fibers, thus increasing the binding force between fibers, enhancing the strength of the film, and blocking the penetration of grease. Nanocellulose forms a three-dimensional network structure in the oil-proof system, which can improve the stability of the system and form a dense barrier layer on the surface of the oil-proof paper, further enhancing the grease barrier property of the oil-proof paper. Starch, polyvinyl alcohol, and nanocellulose all have oil-proof effects, and their synergistic effect has a synergistic effect, which can improve the barrier property of the film, reduce the coating amount, and nanocellulose also has the effect of stabilizing the system.

[0021] Using the present invention as an oil-proof agent for paper, it does not contain chemical substances harmful to the human body, meets the food hygiene standards, and meets the requirements of food packaging paper.

[0022] The beneficial effects of the present invention are as follows: (1) The bio-based fluorine-free oil-proof agent of the present invention not only has the advantages of environmentally friendly raw materials, fluorine-free, and high-efficiency oil-proof.

[0023] (2) The present invention also has the characteristics of high bio-based content, low viscosity, and low dosage, with strong process operability, providing an efficient and environmentally friendly solution for fluorine-free oil-proof.

[0024] (3) The raw material cost is low, and it is coated once with a low process cost. Therefore, it has broad application prospects and market potential in the field of fluorine-free oil-proof technology. Specific embodiments

[0025] The following are specific examples to further illustrate the technical solutions of the present invention.

[0026] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the following examples are conventional methods in the art unless otherwise specified.

[0027] The 10wt% polyvinyl alcohol (model 1788) used in the examples: Dilute polyvinyl alcohol with water to a concentration of 10wt%, heat it to 95°C, stir and keep it warm for 1h, and then cool it to room temperature for standby. The diameter of the nanocellulose used in the examples is below 50nm, and the length is below 1000nm.

[0028] Example 1: Preparation of reinforcing polymer emulsion Enhance the polymer emulsion formulation. The raw materials are composed by weight parts as follows: acrylamide (AM) 30 parts, methyl acryloyloxyethyl trimethyl ammonium chloride (DMC) 5 parts, itaconic acid 5 parts, 2-acrylamido-2-methylpropanesulfonic acid 5 parts, nanocellulose 0.5 parts, sodium methallylsulfonate 3 parts, initiator ammonium persulfate 3 parts, crosslinking agent N,N-dimethylacrylamide 5 parts, ethylenediaminetetraacetic acid (EDTA) 3 parts; 98% sulfuric acid 1 part, sodium sulfite 3 parts, defoaming agent (polydimethylsiloxane) 1 part, sodium dodecyl sulfonate (SDS) 3 parts, and water is added to adjust the solid content of the system to 15 wt%.

[0029] The preparation steps of the enhanced polymer are as follows: (1) Pre-emulsification Add acrylamide, methyl acryloyloxyethyl trimethyl ammonium chloride, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, nanocellulose, sodium methallylsulfonate, ethylenediaminetetraacetic acid, 98% sulfuric acid, sodium sulfite, and sodium dodecyl sulfonate (emulsifier) into the reaction kettle, add 30% of the total water consumption of water, stir at high speed (500 rpm) for 30 minutes to form a pre-emulsion; (2) Seed preparation Under stirring conditions, take 10% of the total weight of the pre-emulsion, heat it to 4°C, slowly dropwise add the remaining water. After the dropping is completed, add 20% of the total weight of the initiator, raise the temperature to 60°C, and react for 2 hours to form a stable seed latex; (3) Main polymerization stage Add the remaining pre-emulsion, crosslinking agent N,N-dimethylacrylamide and the remaining initiator, control the temperature at 70°C, and continuously stir for 6 hours; (4) Post-treatment Cool down to 40°C, add NaOH to neutralize to pH 7, and control the viscosity at about 1000 Pa*s.

[0030] Example 2: Preparation of enhanced polymer emulsion Enhance the polymer emulsion formulation. The raw materials are composed by weight parts as follows: acrylamide (AM) 40 parts, methyl acryloyloxyethyl trimethyl ammonium chloride (DMC) 10 parts, itaconic acid 3 parts, 2-acrylamido-2-methylpropanesulfonic acid 10 parts, nanocellulose 0.1 parts, sodium methallylsulfonate 5 parts, initiator ammonium persulfate 5 parts, crosslinking agent N,N-dimethylacrylamide 10 parts, ethylenediaminetetraacetic acid (EDTA) 5 parts; 98% sulfuric acid 3 parts, sodium sulfite 1 part, defoaming agent (polydimethylsiloxane) 3 parts, sodium dodecyl sulfonate (SDS) 1 part, and water is added to adjust the solid content of the system to 25 wt%.

[0031] The preparation steps of the enhanced polymer are as follows: (1) Pre-emulsification Add acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, nanocellulose, sodium methallylsulfonate, ethylenediaminetetraacetic acid, sulfuric acid with a concentration of 98%, sodium sulfite, and sodium dodecyl sulfonate (emulsifier) into the reaction kettle. Add 50% of the total water consumption, and stir at high speed (1000 rpm) for 30 minutes to form a pre-emulsion; (2) Seed preparation Under stirring conditions, take 30% of the total weight of the pre-emulsion, heat it to 50 °C, slowly add the remaining water drop by drop. After the addition is complete, add 30% of the total weight of the initiator, raise the temperature to 70 °C, and react for 1 hour to form a stable seed latex; (3) Main polymerization stage Add the remaining pre-emulsion, crosslinking agent N,N-dimethylacrylamide and the remaining initiator, control the temperature at 85 °C, and continuously stir for 4 hours; (4) Post-treatment Cool down to 40 °C, add NaOH to neutralize to pH 8, and control the viscosity at about 3000 Pa*s.

[0032] Example 3: Preparation of enhanced polymer emulsion The ratio of the enhanced polymer emulsion, and the raw materials are composed of the following parts by weight: acrylamide (AM) 35 parts, methacryloyloxyethyl trimethyl ammonium chloride (DMC) 7 parts, itaconic acid 4 parts, 2-acrylamido-2-methylpropanesulfonic acid 8 parts, nanocellulose 0.3 parts, sodium methallylsulfonate 4 parts, initiator ammonium persulfate 4 parts, crosslinking agent N,N-dimethylacrylamide 7 parts, ethylenediaminetetraacetic acid (EDTA) 4 parts; 98% sulfuric acid 2 parts, sodium sulfite 2 parts, defoaming agent (polydimethylsiloxane) 2 parts, sodium dodecyl sulfonate (SDS) 2 parts, and add water to adjust the solid content of the system to 20 wt%.

[0033] The preparation steps of the enhanced polymer are as follows: (1) Pre-emulsification Add acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, nanocellulose, sodium methallylsulfonate, ethylenediaminetetraacetic acid, sulfuric acid with a concentration of 98%, sodium sulfite, and sodium dodecyl sulfonate (emulsifier) into the reaction kettle. Add 40% of the total water consumption, and stir at high speed (800 rpm) for 30 minutes to form a pre-emulsion; (2) Seed preparation Under stirring conditions, take 20% of the total weight of the pre-emulsion, heat it to 45 °C, slowly add the remaining water drop by drop. After the addition is complete, add 25% of the total weight of the initiator, raise the temperature to 65 °C, and react for 1.5 hours to form a stable seed latex; (3) Main polymerization stage Add the remaining pre-emulsion, crosslinking agent N,N-dimethylacrylamide and the remaining initiator, control the temperature at 80 °C, and continuously stir for 5 hours; (4)Post-treatment Cool down to 40 °C, add NaOH to neutralize to pH 7, and control the viscosity at 2000 Pa*s.

[0034] Example 4: A bio-based fluorine-free oil-proof agent for food packaging paper: By weight, add 30 parts of modified low-viscosity starch, 10 parts of 20 wt% enhanced polymer emulsion (prepared in Example 3), 10 parts of 10 wt% polyvinyl alcohol (model 1788), 5 parts of 3 wt% aqueous nanocellulose solution. Heat up to 85 °C, and under this temperature, stir for 1 h. Then cool down to 60 °C, add 1 part of plasticizer glycerol and 0.05 part of preservative sodium benzoate, stir evenly and mix. Cool down to room temperature to obtain the oil-proof agent.

[0035] Preparation of modified low-viscosity starch: Prepare oxidized corn starch with water to a concentration of 20 wt%, add ɑ-amylase (Henan Wanbang Chemical Technology Co., Ltd.), the dosage of ɑ-amylase is 0.5% (relative to the absolute dry starch amount), enzymolyze at 60 °C for 30 min, and heat up to 95 °C, keep warm for 1 h for gelatinization and inactivation treatment to obtain.

[0036] Example 5: A bio-based fluorine-free oil-proof agent for food packaging paper: By weight, add 45 parts of modified low-viscosity starch, 15 parts of 25 wt% enhanced polymer emulsion (prepared in Example 2), 20 parts of 10 wt% polyvinyl alcohol (model 1788), 3 parts of 3 wt% aqueous nanocellulose solution. Heat up to 85 °C, and under this temperature, stir for 1 h. Then cool down to 60 °C, add 2 parts of plasticizer epoxidized soybean oil and 0.01 part of preservative potassium sorbate, stir evenly and mix. Cool down to room temperature to obtain the oil-proof agent.

[0037] Preparation of modified low-viscosity starch: Prepare oxidized corn starch with water to a concentration of 30 wt%, add ɑ-amylase (Henan Wanbang Chemical Technology Co., Ltd.), the dosage of ɑ-amylase is 0.1% (relative to the absolute dry starch amount), enzymolyze at 40 °C for 60 min, and heat up to 90 °C, keep warm for 1 h for gelatinization and inactivation treatment to obtain.

[0038] Example 6: A bio-based fluorine-free oil-proofing agent for food packaging paper: By weight, add 50 parts of modified low-viscosity starch, 5 parts of 20wt% enhanced polymer emulsion (prepared in Example 3), 30 parts of 10wt% polyvinyl alcohol (model 1788), 20 parts of 3wt% nano-cellulose aqueous solution. Heat up to 85°C, stir for 1h at this temperature, cool down to 60°C, add 0.5 part of plasticizer triethyl citrate and 0.3 part of preservative sodium propionate, stir evenly and mix, then cool down to room temperature to obtain the oil-proofing agent.

[0039] Preparation of modified low-viscosity starch: Prepare oxidized corn starch with water to a concentration of 25wt%, add ɑ-amylase (Henan Wanbang Chemical Technology Co., Ltd.), the dosage of ɑ-amylase is 1% (relative to the absolute dry starch amount), enzymolyze at 50°C for 10min, and heat up to 95°C, keep warm for 0.5h for gelatinization and inactivation treatment to obtain.

[0040] Example 7: The difference from Example 4 is that cationic starch replaces oxidized corn starch.

[0041] Example 8: The difference from Example 4 is that polyvinyl alcohol is replaced with model 1799 instead of 1788.

[0042] Comparative Example 1: The difference from Example 4 is that the enhanced polymer emulsion is not added, and other operations are the same as Example 4.

[0043] Comparative Example 2: The difference from Example 4 is that polyvinyl alcohol is not added, and other operations are the same as Example 4.

[0044] Comparative Example 3: The difference from Example 4 is that the nano-cellulose aqueous solution is not added, and other operations are the same as Example 4.

[0045] Evaluation of high-temperature oil resistance: Drop salad oil at 105°C on the oil-resistant paper, wipe it off after 15 seconds. Then visually observe the oil-resistant paper and evaluate the high-temperature oil resistance according to the following criteria: ◯: No spots; ◯-: There are spots; ▲: The trace of the oil drop remains circular; ×: The oil leaks.

[0046] The data of each example and comparative example are as follows in the table: 。

[0047] The above-described embodiments are only a preferred solution of the present invention and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions described in the claims.

Claims

1. A bio-based fluorine-free oil-proofing agent for food packaging paper, characterized in that, By weight parts, the raw material composition of the bio-based fluorine-free oil-proof agent is as follows: 30 parts to 50 parts of modified low-viscosity starch, 5 parts to 15 parts of enhanced polymer emulsion, 10 parts to 30 parts of 10wt% aqueous solution of polyvinyl alcohol, 3 parts to 20 parts of 3wt% aqueous solution of nanocellulose, 0.5 parts to 2 parts of plasticizer, and 0.01 parts to 0.3 parts of preservative.

2. The bio-based fluorine-free oil repellent according to claim 1, wherein The preparation method of the modified low-viscosity starch is as follows: Mix low-viscosity starch and water to form a mixed solution with a mass concentration of 20 - 30%, add α-amylase, and carry out enzymatic hydrolysis at 40°C - 60°C for 10 min - 1 h, then raise the temperature to 90°C - 95°C and keep warm for 0.5 h - 1 h for gelatinization and inactivation treatment.

3. The bio-based fluorine-free oil repellent according to claim 2, wherein The low-viscosity starch is one or several of cationic starch, anionic starch or amphoteric starch.

4. The bio-based fluorine-free oil repellent according to claim 2, characterized in that, The dosage of α-amylase is 0.1% - 1% of the absolute dry mass of low-viscosity starch.

5. The bio-based fluorine-free oil repellent according to claim 1, characterized in that, By mass parts, the raw materials of the enhanced polymer emulsion are composed as follows: 30 - 40 parts of acrylamide, 5 - 10 parts of methacryloyloxyethyltrimethylammonium chloride, 3 - 5 parts of itaconic acid, 5 - 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1 - 0.5 parts of nanocellulose, 3 - 5 parts of sodium methallylsulfonate, 3 - 5 parts of initiator, 5 - 10 parts of crosslinking agent N,N-dimethylacrylamide, 3 - 5 parts of ethylenediaminetetraacetic acid; 1 - 3 parts of 98% sulfuric acid, 1 - 3 parts of sodium sulfite, 1 - 3 parts of defoamer, 1 - 3 parts of sodium dodecylsulfonate, and add water to adjust the solid content to 15wt% - 25wt%; the initiator is ammonium persulfate.

6. The bio-based fluorine-free oil repellent according to claim 5, wherein The preparation method of the enhanced polymer emulsion is as follows: (1) Pre-emulsification Add acrylamide, methacryloyloxyethyltrimethylammonium chloride, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, nanocellulose, sodium methallylsulfonate, ethylenediaminetetraacetic acid, 98% sulfuric acid, sodium sulfite, and sodium dodecylsulfonate into the reaction kettle, add water accounting for 30% - 50% of the total water consumption, and stir at high speed for 30 minutes to form a pre-emulsion; (2) Seed preparation Under stirring conditions, take 10% - 30% of the total weight of the pre-emulsion, heat it to 40 - 50°C, slowly drop the remaining water, after dropping, add 20% - 30% of the total weight of the initiator, raise the temperature to 60 - 70°C, and react for 1 - 2 hours to form a stable seed latex; (3) Main polymerization stage Add the remaining pre-emulsion, crosslinking agent N,N-dimethylacrylamide and the remaining initiator, control the temperature at 70 - 85°C, and continuously stir for 4 - 6 hours; (4) Post-treatment Cool down to 40°C, add NaOH to neutralize to pH 7 - 8, and control the viscosity at 1000 - 3000 Pa*s.

7. The bio-based fluorine-free oil repellent according to claim 1 or 2 or 5, characterized in that, The diameter of the nanocellulose is below 50 nm and the length is below 1000 nm.

8. The bio-based fluorine-free oil repellent according to claim 1 or 2 or 5, characterized in that, The plasticizer is one or several of glycerol, triethyl citrate, and epoxidized soybean oil.

9. The bio-based fluorine-free oil repellent according to claim 1 or 2 or 5, characterized in that, The preservative is selected from one or several of sodium benzoate, potassium benzoate, sodium sorbate, potassium sorbate, sodium propionate, calcium propionate, and natamycin.

10. The bio-based fluorine-free oil repellent according to claim 1 or 2 or 5, characterized in that, The degree of polymerization of the polyvinyl alcohol is 1700 - 1800.