Waterproof, heat-sealable wrapping paper and its surface treatment process

Abstract

The application relates to the technical field of packaging paper, and particularly discloses waterproof and heat-sealable packaging paper and a surface treatment process thereof, the surface treatment process of the waterproof and heat-sealable packaging paper comprises the following treatment process: step one, polylactic acid is dissolved in chloroform solvent to prepare a polylactic acid solution with a concentration of 2-3.5 wt%, then the polylactic acid solution is coated on one side of white cardboard, and the white cardboard is dried to obtain polylactic acid modified white cardboard; step two, the polylactic acid modified white cardboard is immersed in an aniline solution, then an ammonium persulfate aqueous solution is added, and the polylactic acid modified white cardboard is placed in an ice water bath for 1-2.5 hours; after the reaction is completed, the polylactic acid modified white cardboard is washed with deionized water and dried at room temperature; then the polylactic acid modified white cardboard is immersed in a polyethylene glycol aqueous solution for 3-4.5 hours, and the polylactic acid modified white cardboard is dried to obtain packaging paper. The packaging paper prepared in the application has the advantages of waterproofness.

Description

Technical Field

[0001] This invention relates to the field of packaging paper technology, and in particular to a waterproof, heat-sealable packaging paper and its surface treatment process. Background Technology

[0002] Packaging paper is a general term for a type of paper mainly used for packaging purposes. It typically possesses high strength and toughness, is pressure-resistant and fold-resistant, and has simpler quality requirements than paper used for cultural printing. There are many sub-types of packaging paper, each with different properties and uses; for example, there are oil-proof packaging paper, moisture-proof packaging paper, and rust-proof paper.

[0003] Chinese invention patent CN108589402B discloses a wood grain packaging paper, which includes a base paper layer, a wood grain layer coated on the surface of the base paper layer, and a varnish layer coated on the wood grain layer. The wood grain layer is formed by curing wood grain paint.

[0004] In the aforementioned related technologies, as people's living standards improve, the uses of packaging paper are becoming more and more widespread. Therefore, packaging paper needs to have other uses in addition to meeting basic requirements. A waterproof and heat-sealable packaging paper is particularly important. Thus, developing a heat-sealable waterproof packaging paper has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] To improve the waterproof performance of packaging paper, this application provides a waterproof, heat-sealable packaging paper and its surface treatment process.

[0006] This application provides a surface treatment process for waterproof and heat-sealable packaging paper, which adopts the following technical solution:

[0007] A surface treatment process for waterproof, heat-sealable packaging paper includes the following processing steps:

[0008] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a polylactic acid solution with a concentration of 2-3.5 wt%. Then coat the solution onto one side of white cardboard and dry it to obtain polylactic acid modified white cardboard.

[0009] Step two: Immerse polylactic acid-modified white cardboard in an aniline solution, then add an ammonium persulfate aqueous solution and place in an ice-water bath for 1-2.5 hours. After the reaction is complete, wash with deionized water and air dry at room temperature. Then immerse in a polyethylene glycol aqueous solution for modification for 3-4.5 hours, and dry to obtain packaging paper.

[0010] By adopting the above technical solution, a polylactic acid (PLA) film is first coated on the surface of white cardboard. PLA has advantages such as biodegradability, safety and hygiene, and low price. Some functional groups of PLA are insoluble in water, giving it a certain degree of hydrophobicity. PLA has good permeability to organic gases, water vapor, and CO2. Then, polyaniline particles are generated on the surface of the PLA film. The hydrogen atoms of −NH2 in the aniline monomer can form hydrogen bonds with the oxygen atoms of C=O in PLA. Therefore, the aniline monomer is adsorbed on the surface of PLA, and polyaniline particles are generated on the surface of PLA film. Polyaniline has good heat resistance and strength. The combination of PLA and polyaniline can achieve good heat-sealing strength.

[0011] Next, the surface-grown polyaniline is immersed in a polyethylene glycol solution. Polyethylene glycol contains hydrophilic -OH groups and large hydrophobic groups. Since the -OH groups can be linked to the amine groups in polyaniline by hydrogen bonds, the hydrophobic groups of polyethylene glycol extend to the outside of the polyaniline chain, which greatly reduces the surface energy of polyaniline and makes polyaniline exhibit superhydrophobicity. Therefore, a superhydrophobic layer is formed on the surface of white cardboard.

[0012] Optionally, the concentration of aniline in the aniline solution is 0.1-0.3 mol / L.

[0013] By adopting the above technical solution, the concentration of aniline monomer increases, the polymerization rate of aniline increases, and polyaniline particles are generated in situ on the surface of polylactic acid film, achieving good heat-sealing performance.

[0014] Optionally, the solvent for the aniline solution is an aqueous solution of citric acid.

[0015] By adopting the above technical solution, citric acid can be doped into the polyaniline molecular chain during the aniline polymerization process, giving polyaniline hydrophobic properties.

[0016] Optionally, the concentration of citric acid in the citric acid aqueous solution is 0.8-1.5 mol / L.

[0017] By adopting the above technical solution, citric acid is incorporated into polyaniline molecules, giving polyaniline certain hydrophobic properties. When combined with polyethylene glycol, it can achieve superhydrophobicity and improve the waterproofness of white cardboard.

[0018] Optionally, the concentration of the polyethylene glycol is 1.5-3 wt%.

[0019] By adopting the above technical solution, the hydroxyl groups of polyethylene glycol are bonded to the molecular chain of polyaniline through hydrogen bonds, so that the hydrophobic groups of polyethylene glycol extend to the outer layer of the polyaniline molecule, forming a hydrophobic layer.

[0020] Optionally, the polyethylene glycol has a molecular weight of one of 9,000 Daltons, 10,000 Daltons, and 12,000 Daltons.

[0021] By adopting the above technical solution, high molecular weight polyethylene glycol has a longer hydrophobic chain and better hydrophobicity. Polyethylene glycol hydrophobically modifies polyaniline, and the hydrophobic chain extends to the outer layer of the polyaniline molecule, thereby improving the waterproof performance of white cardboard.

[0022] Optionally, the concentration of ammonium persulfate in the aqueous solution is 0.2-0.5 mol / L.

[0023] By adopting the above technical solution, aniline is polymerized in situ on the surface of polylactic acid film under the action of ammonium persulfate initiator to generate polyaniline particles.

[0024] Secondly, this application provides a waterproof and heat-sealable packaging paper, which is obtained by surface treatment process of any of the waterproof and heat-sealable packaging papers described above.

[0025] By adopting the above technical solution, the packaging paper prepared by surface treatment of white cardboard has good waterproof and heat-sealing properties.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. Since this application uses polylactic acid to generate polyaniline particles, the hydrogen atom of −NH2 in the aniline monomer can form a hydrogen bond with the oxygen atom of C=O in the polylactic acid. Therefore, the aniline monomer is adsorbed on the polylactic acid surface, and polyaniline particles are generated on the polylactic acid film surface. Polyaniline has good heat resistance and strength. The combination of polylactic acid and polyaniline can achieve good heat sealing strength.

[0028] 2. This application uses polyethylene glycol to immerse the surface-grown polyaniline in a polyethylene glycol solution. Polyethylene glycol contains hydrophilic -OH groups and large hydrophobic groups. Since -OH groups can be linked to the amine groups in polyaniline by hydrogen bonds, the hydrophobic groups of polyethylene glycol extend to the outside of the polyaniline chain, which greatly reduces the surface energy of polyaniline and makes polyaniline exhibit superhydrophobicity. Therefore, a superhydrophobic layer is formed on the surface of white cardboard. Detailed Implementation

[0029] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0030] Raw material sources for the examples and comparative examples: The raw materials for the examples and comparative examples are all commercially available. Example

[0031] Example 1

[0032] A surface treatment process for waterproof, heat-sealable packaging paper includes the following processing steps:

[0033] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a 3wt% polylactic acid solution. Then, coat the solution onto one side of white cardboard using a coating machine. Place the solution in a vacuum drying oven at 60°C for 24 hours. After drying, polylactic acid modified white cardboard is obtained.

[0034] Step two: Immerse the white cardboard obtained in step one in a 0.2 mol / L aniline solution, then add a 0.35 mol / L ammonium persulfate aqueous solution and place it in an ice-water bath for 2 hours. After the reaction is complete, wash with deionized water, air dry at room temperature, and then immerse in a 2 wt% polyethylene glycol aqueous solution for 4 hours for modification. The molecular weight of polyethylene glycol is 12000 Daltons. Place it in a vacuum drying oven at 40°C for 6 hours to dry, and obtain the packaging paper.

[0035] Example 2

[0036] A surface treatment process for waterproof, heat-sealable packaging paper includes the following processing steps:

[0037] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a 2wt% polylactic acid solution. Then, coat the solution onto one side of white cardboard using a coating machine. Place the solution in a vacuum drying oven at 60°C for 24 hours. After drying, polylactic acid modified white cardboard is obtained.

[0038] Step two: Immerse the white cardboard obtained in step one in a 0.1 mol / L aniline solution, then add a 0.2 mol / L ammonium persulfate aqueous solution and place it in an ice-water bath for 1 hour. After the reaction is complete, wash with deionized water, air dry at room temperature, and then immerse in a 1.5 wt% polyethylene glycol aqueous solution for 3 hours for modification. The polyethylene glycol has a molecular weight of 10,000 Daltons. Place it in a vacuum drying oven at 40°C for 6 hours to dry, and obtain the packaging paper.

[0039] Example 3

[0040] A surface treatment process for waterproof, heat-sealable packaging paper includes the following processing steps:

[0041] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a polylactic acid solution with a concentration of 3.5 wt%. Then, coat the solution onto one side of white cardboard using a coating machine. Place the solution in a vacuum drying oven at 60°C for 24 hours. After drying, polylactic acid modified white cardboard is obtained.

[0042] Step two: Immerse the white cardboard obtained in step one in a 0.3 mol / L aniline solution, then add a 0.5 mol / L ammonium persulfate aqueous solution and place it in an ice-water bath for 2.5 h. After the reaction is complete, wash with deionized water, air dry at room temperature, and then immerse in a 3 wt% polyethylene glycol aqueous solution for modification for 4.5 h. The polyethylene glycol has a molecular weight of 9000 Daltons. Place it in a vacuum drying oven at 40°C for 6 h to dry, and obtain the packaging paper.

[0043] Example 4

[0044] A surface treatment process for waterproof, heat-sealable packaging paper, which differs from Example 2 in that the concentration of aniline is 0.09 mol / L.

[0045] Example 5

[0046] A surface treatment process for waterproof, heat-sealable packaging paper differs from Example 3 in that the concentration of aniline is 0.35 mol / L.

[0047] Example 6

[0048] A surface treatment process for waterproof and heat-sealable packaging paper, wherein the solvent for the aniline solution in this embodiment is an aqueous solution of citric acid with a concentration of 0.7 mol / L.

[0049] Example 7

[0050] A surface treatment process for waterproof, heat-sealable packaging paper, wherein the solvent for the aniline solution in this embodiment is an aqueous solution of citric acid with a concentration of 1.6 mol / L.

[0051] Example 8

[0052] A surface treatment process for waterproof, heat-sealable packaging paper, which differs from Example 3 in that the molecular weight of the polyethylene glycol is 8000 Daltons.

[0053] Example 9

[0054] A surface treatment process for waterproof, heat-sealable packaging paper, which differs from Example 1 in that the molecular weight of the polyethylene glycol is 15,000 Daltons.

[0055] Comparative Example 1

[0056] A surface treatment process for waterproof, heat-sealable packaging paper, differing from Example 1 in that the raw materials do not include polyaniline, and includes the following processing steps:

[0057] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a 3wt% polylactic acid solution. Then, coat the solution onto one side of white cardboard using a coating machine. Place the solution in a vacuum drying oven at 60°C for 24 hours. After drying, polylactic acid modified white cardboard is obtained.

[0058] Step two: The polylactic acid-modified white cardboard is then immersed in a 2wt% polyethylene glycol aqueous solution for 4 hours. The polyethylene glycol has a molecular weight of 12,000 Daltons. The cardboard is then placed in a vacuum drying oven at 40°C for 6 hours to dry, thus obtaining the packaging paper.

[0059] Comparative Example 2

[0060] A surface treatment process for waterproof, heat-sealable packaging paper, differing from Example 1 in that the raw materials do not include polyethylene glycol, and includes the following processing steps:

[0061] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a 3wt% polylactic acid solution. Then, coat the solution onto one side of white cardboard using a coating machine. Place the solution in a vacuum drying oven at 60°C for 24 hours. After drying, polylactic acid modified white cardboard is obtained.

[0062] Step two: Immerse the white cardboard obtained in step one in a 0.2 mol / L aniline solution, then add a 0.35 mol / L ammonium persulfate aqueous solution and place it in an ice-water bath for 2 hours. After the reaction is complete, wash with deionized water and air dry at room temperature to obtain the packaging paper.

[0063] Comparative Example 3

[0064] A surface treatment process for waterproof, heat-sealable packaging paper, differing from Example 1 in that the raw materials do not include polyaniline and polyethylene glycol, and includes the following processing steps:

[0065] Step 1: Dissolve polylactic acid in chloroform solvent to prepare a 3wt% polylactic acid solution. Then, coat the solution onto one side of white cardboard using a coating machine. Place the cardboard in a vacuum drying oven at 60°C for 24 hours. After drying, the packaging paper is obtained.

[0066] The packaging paper obtained in Examples 1-9 and Comparative Examples 1-3 was used as the test samples.

[0067] 1. Heat Seal Strength Test: The packaging paper is heated and sealed on a pulse sealing machine. A strip of packaging paper with the same width as the sample for tensile strength testing is selected. The heat sealing temperature is 200 ℃, the heat sealing pressure is 200 N, and the heat sealing time is 0.5 s. The heat-sealed sample is placed in an artificial climate chamber (23 ℃, 50% relative humidity) for 24 h. The maximum tensile force when the packaging paper strip is pulled open is measured on a universal testing machine according to the tensile strength test method. The heat seal strength is determined by the ratio between the maximum tensile force and the heat-sealed area. The measurement is repeated 3 times, and the average value is taken.

[0068] 2. Waterproofing test: The adhesion of each sample after immersion in water and the water resistance of the outer layer within 30 minutes were tested. Each sample was tested 3 times, and the average value of the results was taken.

[0069] Table 1 Performance Test Results

[0070] Adhesion Outer layer water resistance Heat seal strength (KN / m2) Example 1 0.91 impermeable 1.84 Example 2 0.89 impermeable 1.7 Example 3 0.90 impermeable 1.8 Example 4 0.81 impermeable 1.5 Example 5 0.83 impermeable 1.6 Example 6 0.76 impermeable 1.51 Example 7 0.73 impermeable 1.58 Example 8 0.60 impermeable 1.8 Example 9 0.72 impermeable 1.82 Comparative Example 1 0.67 permeable 1.2 Comparative Example 2 0.57 permeable 1.6 Comparative Example 3 0.51 permeable 1.1

[0071] As can be seen from Examples 1-3 and Comparative Examples 1-3 and Table 1, the performance of Examples 1-3 is better than that of Comparative Examples 1-3. This application greatly improves the heat-sealing performance of packaging paper by in-situ polymerization of polyaniline particles on the surface of polylactic acid film, and further improves the waterproof performance of packaging paper by introducing polyethylene glycol on the surface of polyaniline particles, thus obtaining packaging paper with waterproof and heat-sealing properties.

[0072] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A surface treatment process for waterproof, heat-sealable packaging paper, characterized in that: The following processing techniques are included: Step 1: Dissolve polylactic acid in chloroform solvent to prepare a polylactic acid solution with a concentration of 2-3.5 wt%, then coat it onto one side of white cardboard and dry it to obtain polylactic acid modified white cardboard. Step 2: Immerse polylactic acid modified white cardboard in aniline solution, then add ammonium persulfate aqueous solution and place in an ice-water bath for 1-2.5 hours. After the reaction is complete, wash with deionized water, air dry at room temperature, then immerse in polyethylene glycol aqueous solution for 3-4.5 hours for modification, and dry to obtain packaging paper.

2. The surface treatment process for waterproof, heat-sealable packaging paper according to claim 1, characterized in that: The concentration of aniline in the aniline solution is 0.1-0.3 mol / L.

3. The surface treatment process for waterproof, heat-sealable packaging paper according to claim 1, characterized in that: The solvent for the aniline solution is an aqueous solution of citric acid.

4. The surface treatment process for waterproof, heat-sealable packaging paper according to claim 3, characterized in that: The concentration of citric acid in the citric acid aqueous solution is 0.8-1.5 mol / L.

5. The surface treatment process for waterproof, heat-sealable packaging paper according to claim 1, characterized in that: The concentration of the polyethylene glycol is 1.5-3 wt%.

6. The surface treatment process for waterproof, heat-sealable packaging paper according to claim 5, characterized in that: The polyethylene glycol has a molecular weight of one of 9,000 Daltons, 10,000 Daltons, and 12,000 Daltons.

7. The surface treatment process for waterproof, heat-sealable packaging paper according to claim 1, characterized in that: The concentration of ammonium persulfate in the aqueous solution is 0.2-0.5 mol / L.

8. A waterproof, heat-sealable packaging paper, obtained by surface treatment process as described in any one of claims 1-7.