Fluoride-free oil-proof paper containing bio-based composite coating and preparation method of fluoride-free oil-proof paper

Abstract

The invention discloses fluoride-free oil-proof paper containing a bio-based composite coating and a preparation method thereof.The method comprises the following steps that 1, natural polymer carboxylic acid sodium salt, chitosan, natural clay and deionized water are mixed and stirred to be uniform at the temperature of 35-65 DEG C, and a mixed solution is obtained; 2, paper is soaked in a calcium chloride solution until the paper is completely soaked, then drying is conducted, and pretreated paper is obtained; and step 3, uniformly coating the surface of the pretreated paper with the mixed solution, and then drying to obtain the fluoride-free oil-proof paper containing the bio-based composite coating. The preparation method is simple and easy to operate, and the prepared fluoride-free oil-proof paper has the advantages of being excellent in oil-proof performance, low in price and biodegradable.

Description

Technical Field

[0001] The invention relates to packaging paper, in particular to fluorine-free oil-proof paper containing a bio-based composite coating and a preparation method thereof. Background Art

[0002] Paper packaging has the advantages of a wide range of raw material sources, green environmental protection, safety and hygiene, easy processing and easy degradation and recycling. It has received widespread attention in the field of food packaging and has considerable potential for sustainable development. However, the paper packaging material itself has weak barrier properties against substances such as air, water and grease. In order to improve the barrier properties and enhance the oil-proof performance of paper, it is usually necessary to use oil-proof agent modification.

[0003] Traditional greaseproof paper is mainly divided into coated paper and fluorine-containing greaseproof paper. Among them: fluorine-containing greaseproof paper combines fluorine-containing compounds with paper to reduce the surface energy of paper to achieve the purpose of blocking moisture and grease; coated paper is developed after fluorine-containing greaseproof paper. It uses paper as the base material and usually adopts coating technology to cover the surface of the base material with a layer of plastic film to form waterproof and oil-proof coated paper.

[0004] Although coated paper and fluorinated oil-proof paper both have good oil-proof properties, with the ban on plastics and the prohibition of perfluorooctane sulfonate (PFOS) chemicals, the use of these two types of oil-proof paper has been restricted. Therefore, there is an urgent need for a more environmentally friendly oil-proof agent to replace traditional oil-proof paper for use as paper food packaging material.

[0005] Bio-based polymers have the advantages of being green, environmentally friendly, non-toxic and biodegradable, and have become a hot research direction in the field of food packaging. It is of great significance to use biopolymers as the main raw material to prepare environmentally friendly paper oil-proof agents. However, there is still a lack of oil-proof paper that is biodegradable, low-priced and high-performance. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a fluorine-free oil-proof paper containing a bio-based composite coating and a preparation method thereof. Not only is the preparation method simple and easy to operate, but the prepared fluorine-free oil-proof paper also has the advantages of excellent oil-proof performance, low price and biodegradability.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing fluorine-free oil-proof paper containing a bio-based composite coating comprises the following steps:

[0009] Step 1, mixing natural polymer carboxylic acid sodium salt, chitosan, natural clay and deionized water, stirring at 35-65° C. to obtain a mixed solution;

[0010] Step 2, immersing the paper in a calcium chloride solution until it is thoroughly soaked, and then drying to obtain pretreated paper;

[0011] Step 3: evenly coating the mixed solution on the pretreated paper surface, and then drying to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

[0012] Furthermore, in the mixed solution of step 1, natural polymer carboxylic acid sodium salt accounts for 0.5wt% to 3.5wt%, chitosan accounts for 0.5wt% to 3.5wt%, natural clay accounts for 0.2wt% to 1wt%, and the remainder is deionized water.

[0013] Furthermore, the natural polymer carboxylic acid sodium salt in step 1 is at least one of sodium carboxymethyl starch, sodium carboxymethyl cellulose or sodium alginate.

[0014] Furthermore, the natural clay in step 1 is at least one of kaolinite, montmorillonite or illite.

[0015] Furthermore, the mass fraction of the calcium chloride solution in step 2 is 1% to 2%.

[0016] Furthermore, the drying temperature in step 2 is 50-60°C.

[0017] Furthermore, the coating amount of the mixed solution on the pretreated paper surface in step 3 is 2 to 8 g / m 2 .

[0018] Furthermore, the drying in step 3 is performed in an oven at 85 to 105° C. for 5 to 15 minutes.

[0019] A fluorine-free oil-proof paper containing a bio-based composite coating, with an oil-proof grade of not less than grade 3.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] On the one hand, the hydrogen bonding reaction between chitosan and the -OH of natural polymer carboxylic acid sodium salt enhances the interaction between substances, and the -NH2 +- and the electrostatic interaction between -COO- of natural polymer carboxylic acid sodium salt, make chitosan and natural polymer carboxylic acid sodium salt highly biocompatible, thus forming a dense and stable coating; on the other hand, using natural clay as a filler, the oil barrier performance of paper is enhanced, and the negatively charged natural clay and cationic chitosan form a stable and harmonious blend to improve compatibility, increasing the density and stability of the coating; on the other hand, the calcium ions of natural polymer carboxylic acid sodium salt and calcium chloride are cross-linked, making the oil-proof coating more closely combined with the paper; therefore, even at a low coating amount, fluorine-free oil-proof paper can achieve excellent oil-proof performance. In addition, the dense and stable coating on the surface of the paper also gives the fluorine-free oil-proof paper low air permeability and good mechanical properties, which is very suitable for use as packaging paper.

[0022] The invention not only has a simple preparation process, is easy to operate, and is suitable for large-scale production, but also has low-cost raw materials and is environmentally friendly. The prepared fluorine-free oil-proof paper does not contain fluorine and is easy to degrade, which solves the pollution problem caused by existing fluorine-containing packaging paper and has good application prospects in the fields of disposable tableware and food packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : A schematic structural diagram of the fluorine-free oil-proof paper containing a bio-based composite coating prepared by the present invention;

[0024] Figure 2 : Actual photo of fluorine-free oil-proof paper containing bio-based composite coating prepared by the present invention. DETAILED DESCRIPTION

[0025] The specific contents of the present invention are further explained in detail below in conjunction with embodiments.

[0026] Example 1

[0027] Step 1, 0.5wt% sodium carboxymethyl starch, 3.5wt% chitosan, 0.4wt% kaolinite and 95.6wt% deionized water were mixed, and stirred at 55°C to obtain a mixed solution;

[0028] Step 2, immersing the paper in a 1.5% by mass calcium chloride solution until it is soaked, and drying at 50° C. to obtain pretreated paper;

[0029] Step 3: 8g / m 2 The mixed solution was evenly coated on the pretreated paper surface with a coating amount of , and then dried in an oven at 100°C for 5 minutes to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

[0030] Example 2

[0031] Step 1, 1.0wt% sodium carboxymethyl cellulose, 1.5wt% chitosan, 0.2wt% kaolinite and 97.3wt% deionized water were mixed, and stirred at 65°C to obtain a mixed solution;

[0032] Step 2, immersing the paper in a 1% by mass calcium chloride solution until it is soaked, and drying at 55° C. to obtain pretreated paper;

[0033] Step 3: 6g / m 2 The mixed solution was evenly coated on the pretreated paper surface with a coating amount of , and then dried in an oven at 105°C for 5 minutes to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

[0034] Example 3

[0035] Step 1, 3.5wt% sodium alginate, 0.5wt% chitosan, 1.0wt% montmorillonite and 95wt% deionized water were mixed, and stirred at 45°C to obtain a mixed solution;

[0036] Step 2, immersing the paper in a 1.5% by mass calcium chloride solution until it is soaked, and drying at 60° C. to obtain pretreated paper;

[0037] Step 3: 4g / m 2 The mixed solution was evenly coated on the pretreated paper surface with a coating amount of , and then dried in an oven at 85°C for 15 minutes to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

[0038] Example 4

[0039] Step 1, 1.5wt% sodium carboxymethyl starch, 1.0wt% chitosan, 0.2wt% montmorillonite and 97.3wt% deionized water were mixed, and stirred at 60°C to obtain a mixed solution;

[0040] Step 2, immersing the paper in a 2% by mass calcium chloride solution until it is soaked, and drying at 50° C. to obtain pretreated paper;

[0041] Step 3: 6g / m 2 The mixed solution was evenly coated on the pretreated paper surface with a coating amount of , and then dried in an oven at 100°C for 10 minutes to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

[0042] Example 5

[0043] Step 1, 2.0 wt% sodium carboxymethyl cellulose, 2.0 wt% chitosan, 0.6 wt% illite and 95.4 wt% deionized water are mixed, and stirred at 35° C. to obtain a mixed solution;

[0044] Step 2, immersing the paper in a 1% by mass calcium chloride solution until it is soaked, and drying at 60° C. to obtain pretreated paper;

[0045] Step 3: 2g / m 2 The mixed solution was evenly coated on the pretreated paper surface with a coating amount of , and then dried in an oven at 90°C for 8 minutes to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

[0046] According to the national standard, the tensile strength, tear strength and air permeability of the fluorine-free oil-proof paper containing the bio-based composite coating prepared in Examples 1 to 5 were tested respectively, wherein: the tensile strength was measured by a tensile strength tester according to GB / T12914-2008; the air permeability was measured by an air permeability tester according to GB / T458-2008; the tear strength was measured by a tear strength tester according to GB / T455-2002; the oil-proof grade was measured according to TAPPI T 559cm-12, a test standard widely used in the current oil-proof paper and paperboard industry; at the same time, for the convenience of comparison, ordinary paper was used as a control group, and the tensile strength, tear strength, air permeability and oil-proof grade were tested respectively. The results of the above four tests are shown in Table 1. It can be seen from Table 1 that the fluorine-free oil-proof paper containing the bio-based composite coating prepared in Examples 1 to 5 has good oil-proof performance, mechanical properties and low air permeability, and is therefore very suitable for use as food packaging paper.

[0047] Table 1 Tensile strength, tear strength, air permeability and oil resistance grade of ordinary paper and fluorine-free oil-proof paper prepared in Examples 1 to 5

[0048] Test items Example 1 Example 2 Example 3 Example 4 Example 5 Comparison Example Oil resistance grade 3 5 7 12 10 0 Air permeability (μm / Pa·S) 5.592 0.064 0.042 0.0098 0.094 53.5 Tensile strength(N) 34.8 37.4 39.3 43.1 38.3 36.0 Tear strength(mN) 1153.3 1172.8 1314.9 1420.0 1360.8 662.9

Claims

1. A method for preparing fluorine-free oil-proof paper containing a bio-based composite coating, characterized in that: The steps include: Step 1, mixing natural polymer carboxylic acid sodium salt, chitosan, natural clay and deionized water, stirring at 35-65° C. to obtain a mixed solution; Step 2, immersing the paper in a calcium chloride solution until it is soaked, and then drying to obtain pretreated paper; Step 3: evenly coating the mixed solution on the pretreated paper surface, and then drying to obtain fluorine-free oil-proof paper containing a bio-based composite coating.

2. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: In the mixed solution of step 1, natural polymer carboxylic acid sodium salt accounts for 0.5wt% to 3.5wt%, chitosan accounts for 0.5wt% to 3.5wt%, natural clay accounts for 0.2wt% to 1wt%, and the balance is deionized water.

3. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: The natural polymer carboxylic acid sodium salt in step 1 is at least one of sodium carboxymethyl starch, sodium carboxymethyl cellulose or sodium alginate.

4. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: The natural clay in step 1 is at least one of kaolinite, montmorillonite or illite.

5. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: The mass fraction of the calcium chloride solution in step 2 is 1% to 2%.

6. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: The drying temperature in step 2 is 50-60°C.

7. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: The coating amount of the mixed solution on the pretreated paper surface in step 3 is 2 to 8 g / m 2 .

8. The method for preparing fluorine-free oil-proof paper containing a bio-based composite coating according to claim 1, characterized in that: The drying in step 3 is performed in an oven at 85 to 105° C. for 5 to 15 minutes.

9. A fluorine-free oil-proof paper containing a bio-based composite coating prepared by the method according to any one of claims 1 to 8, characterized in that: The oil resistance level is not less than level 3.

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