阅读说明：本技术 一种无氟防水防油食品级涂料及其制备方法 (Fluorine-free waterproof oil-proof food-grade coating and preparation method thereof ) 是由 陈挺 朱华杨 谭康梅 孙小玲 于 2020-06-09 设计创作，主要内容包括：本发明公开了一种无氟防水防油食品级涂料及其制备方法,该涂料由以下组分和质量百分比制成：改性聚乙烯醇3％-5％、棕榈蜡5％-15％、乳化剂1.5％-6.5％、复配水性聚合物树脂25％-35％、甘油0.5％-1.5％和去离子水37％-65％。该涂料具有良好的防水防油特性,应用在纸张后具备理想的防水防油性能,改善纸质材料防油防水性能的不足,能够替代淋膜纸,尤其是取代防水防油剂中的含氟聚合物,而且该涂料是无氟共聚物,环保、易于自然降解,解决含氟涂料危害健康、淋膜纸难以回收、影响环境的问题,同时解决食品安全隐患问题,有利于普及推广应用。(The invention discloses a fluorine-free waterproof oil-proof food-grade coating and a preparation method thereof, wherein the coating is prepared from the following components in percentage by mass: 3-5% of modified polyvinyl alcohol, 5-15% of palm wax, 1.5-6.5% of emulsifier, 25-35% of compound aqueous polymer resin, 0.5-1.5% of glycerol and 37-65% of deionized water. The coating has good waterproof and oilproof properties, has ideal waterproof and oilproof performance after being applied to paper, improves the deficiency of the oilproof and waterproof performance of paper materials, can replace laminating paper, especially replaces fluorine-containing polymers in waterproof and oilproof agents, is fluorine-free copolymer, is environment-friendly and easy to naturally degrade, solves the problems that the fluorine-containing coating is harmful to health, the laminating paper is difficult to recover and the environment is influenced, solves the problem of potential safety hazard of food, and is favorable for popularization and application.)

1. The fluorine-free waterproof oil-proof food-grade coating is characterized by being prepared from the following components in percentage by mass:

3% -5% of modified polyvinyl alcohol;

5% -15% of palm wax;

1.5 to 6.5 percent of emulsifier;

25-35% of compound waterborne polymer resin;

0.5% -1.5% of glycerin;

37-65% of deionized water.

2. The coating according to claim 1, wherein the modified polyvinyl alcohol is prepared by water-resistant modification of polyvinyl alcohol with the polymerization degree of 1700-1800.

3. The coating of claim 2, wherein the modified polyvinyl alcohol is prepared by a water-resistant modification reaction of polyvinyl alcohol with citric acid and glutamic acid.

4. The coating of claim 1, 2 or 3, wherein the carnauba wax is a food grade natural vegetable wax.

5. The coating of claim 1, 2 or 3, wherein the built aqueous polymer resin is prepared by compounding an aqueous polyurethane resin and a polyacrylate.

6. The coating according to claim 5, wherein the compounding ratio of the aqueous polyurethane resin to the polyacrylate is 0.3-2.

7. A process for preparing the fluorine-free water and oil repellent food-grade coating according to any one of claims 1 to 6, which comprises the following steps:

a. adding a proper amount of emulsifier into deionized water, and heating to obtain a mixed solution;

b. adding palm wax into the mixed solution, continuously heating and raising the temperature, and stirring and emulsifying at a high speed to obtain emulsion;

c. heating the emulsion, slowly adding the modified polyvinyl alcohol into the emulsion, adding glycerol after the modified polyvinyl alcohol is completely dissolved, and uniformly stirring;

d. and adding the compound water-based polymer resin into the emulsion, and stirring to obtain the fluorine-free waterproof oil-proof food-grade coating.

8. The method of claim 7, wherein the heating in step a is to 90 ℃, the heating in step b is to 100 ℃ to 120 ℃, the stirring time in step c is 1h, and the stirring in step d is performed at room temperature.

9. The method according to claim 7, wherein the stirring speed in step b is 1500r/min to 2000 r/min.

10. The method according to claim 7, wherein the emulsification time in step b is 30-45 min.

Technical Field

The invention belongs to the field of food packaging and coatings, and particularly relates to a waterproof and oilproof food-grade coating coated on paper food packaging and a preparation method thereof.

Background

With the rapid development of economy and the enhancement of environmental awareness, paper packaging is becoming the largest packaging material used in the fields of catering, food packaging and the like. Paper packaging must be water, oil and barrier resistant because of the contact with oily, greasy or aqueous foods.

In order to obtain the waterproof and oil-proof effects, most of the current food packaging paper is coated with a thin polyethylene plastic layer by spraying to form a continuous and compact organic polymer film, so that oil and water cannot pass through a protective layer, and the waterproof and oil-proof purposes are achieved. The high-end is also packaged by adopting silicone oil paper, the silicone oil paper has a three-layer structure, the first layer is base paper, the second layer is a laminating film, and the third layer is silicone oil. Some of the polymers contain bisphenol A, harmful substances can be released when the polymers contact high-temperature food, and the polymer materials cannot be degraded in the nature, so that the recycling difficulty is high, the recycling cost is high, and the problem of environmental pollution exists.

Except for film coating, a very small amount of waterproof and oil-proof agent is added in the paper making process or a layer of coating with waterproof and oil-proof performance is coated on the surface of paper at present, so that the surface tension of the paper is reduced, the waterproof and oil-proof performance can be endowed to a paper base material, and the cyclic utilization of the paper product is not influenced. Although the waterproof and oilproof effects are excellent, the waterproof and oilproof agent is usually a polymer containing perfluoroalkyl groups, has the defects of strong bioaccumulation and difficult degradation, particularly has strong toxicity to human bodies after being contacted with food for a long time, is difficult to recycle, is easy to pollute the environment, and has extremely limited application range.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a fluorine-free copolymer for water and oil proofing of paper and a preparation method of a coating thereof, aiming at the defects in the prior art, the fluorine-free copolymer is synthesized, so that the fluorine-free copolymer can be prepared into emulsion, has ideal water and oil proofing performance after being applied to paper, can replace coated paper, and solves the problems that the fluorine-containing coating is harmful to health, the coated paper is difficult to recycle and the environment is influenced.

The purpose of the invention is realized by adopting the following technical scheme:

the fluorine-free waterproof and oilproof food-grade coating is uniformly coated on the surface of common paper, has excellent waterproof and oilproof performance and meets the requirement of food packaging. The coating provided by the invention is prepared from the following components in percentage by mass:

3% -5% of modified polyvinyl alcohol;

5% -15% of palm wax;

1.5 to 6.5 percent of emulsifier;

25-35% of compound waterborne polymer resin;

0.5% -1.5% of glycerin;

37-65% of deionized water.

Further, the modified polyvinyl alcohol is prepared by performing water-resistant modification on polyvinyl alcohol with the polymerization degree of 1700-1800, and the preferable scheme is as follows: the modified polyvinyl alcohol is prepared by carrying out water-resistant modification reaction on polyvinyl alcohol, citric acid and glutamic acid.

Further, the palm wax is food-grade natural plant wax.

Further, the compound waterborne polymer resin is prepared by compounding waterborne polyurethane resin and polyacrylate.

Further, the compounding ratio of the waterborne polyurethane resin to the polyacrylate is 0.3-2.

A preparation method of a fluorine-free waterproof oil-proof food-grade coating comprises the following steps:

a. adding a proper amount of emulsifier into deionized water, and heating to obtain a mixed solution;

b. adding palm wax into the mixed solution, continuously heating and raising the temperature, and stirring and emulsifying at a high speed to obtain emulsion;

c. heating the emulsion, slowly adding the modified polyvinyl alcohol into the emulsion, adding glycerol after the modified polyvinyl alcohol is completely dissolved, and uniformly stirring;

d. and adding the compound water-based polymer resin into the emulsion, and stirring to obtain the fluorine-free waterproof oil-proof food-grade coating.

Further, heating to 90 ℃ in step a, heating to 100-120 ℃ in step b (optimally, heating the emulsion to boiling), stirring for 1h in step c, and stirring at room temperature in step d.

Further, the stirring speed in the step b is 1500r/min-2000 r/min.

Further, the emulsifying time in the step b is 30-45 min.

The invention has the following beneficial effects:

1. the polyethylene film can be used as food packaging paper after being coated on the surface of paper, and compared with the film coated food packaging paper, the problem of white pollution caused by long-term retention of the film in the nature due to non-recovery is solved, and the polyethylene film is not required to be treated by spending a large amount of time and energy in the recovery and reutilization process, so that the cost is saved, and the benefit is greatly improved.

2. The polyvinyl alcohol is a degradable material, the palm wax is natural plant wax, no toxic or side effect is caused, the environment is protected, and the coated food packaging paper has the advantages of being environment-friendly and superior in food safety.

3. The coating resin is water-based emulsion, does not contain organic solvent, is environment-friendly and nontoxic, and can form good luster. Strong, abrasion resistant and water resistant films.

4. According to the coated food packaging paper disclosed by the invention, both the PVA and the palm wax have oil resistance, and the PVA and the palm wax are combined to form a compact film, so that the permeation of water can be prevented, and the use requirements on water resistance and oil resistance can be met; the heat resistance is good, the coated paper is made into paper cups and paper bowls which are respectively filled with hot water and hot oil at the temperature of 95 ℃ and are placed for 0.5h, and no water seepage or oil leakage occurs.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention relates to a fluorine-free waterproof and oil-proof food-grade coating which is prepared from the following components in percentage by mass: 3-5% of modified polyvinyl alcohol, 5-15% of palm wax, 1.5-6.5% of emulsifier, 25-35% of compound aqueous polymer resin, 0.5-1.5% of glycerol and 37-65% of deionized water. The modified polyvinyl alcohol is prepared by carrying out water-resistant modification on polyvinyl alcohol with the polymerization degree of 1700-1800, and the preferable scheme is as follows: the modified polyvinyl alcohol is prepared by carrying out water-resistant modification reaction on polyvinyl alcohol, citric acid and glutamic acid; the compound waterborne polymer resin is prepared by compounding waterborne polyurethane resin and polyacrylate; the compounding ratio of the aqueous polyurethane resin to the polyacrylate is 0.3-2.

As shown in figure 1, the preparation method of the fluorine-free water-proof oil-proof food-grade coating comprises the following steps:

s100, adding a proper amount of emulsifier into deionized water, and heating to obtain a mixed solution; wherein the temperature is raised to 90 ℃.

S200, adding palm wax into the mixed solution, continuously heating, raising the temperature, and stirring at a high speed for emulsification to obtain emulsion; wherein the temperature is increased to 100-120 ℃ (the optimal scheme is that the emulsion is heated to boiling), the stirring speed is 1500-2000 r/min, and the emulsifying time is 30-45 min.

S300, heating the emulsion, slowly adding modified polyvinyl alcohol into the emulsion, adding glycerol after the modified polyvinyl alcohol is completely dissolved, and uniformly stirring; wherein the stirring time is 1 h.

S400, adding the compound waterborne polymer resin into the emulsion, and stirring to obtain the fluorine-free waterproof and oilproof food-grade coating, wherein the stirring is carried out at room temperature.

The coating disclosed by the invention has good waterproof and oilproof properties, has ideal waterproof and oilproof performance after being applied to paper, overcomes the defect of the oil-proof and waterproof performance of a paper material, can replace the coated paper, particularly replace the fluoropolymer in a waterproof and oilproof agent, is a fluorine-free copolymer, is environment-friendly and easy to naturally degrade, solves the problems that the fluorine-containing coating is harmful to health, the coated paper is difficult to recover and the environment is influenced, solves the problem of potential safety hazard of food, and is beneficial to popularization and application.

The fluorine-free water-proof oil-proof food-grade coating and the preparation method thereof are further illustrated by the following examples.