A mixed coating liquid and fluorine-free oil-proof barrier paper and preparation method thereof

Abstract

The present invention relates to the field of food packaging, and in particular to a mixed coating liquid and a fluorine-free oil-proof barrier paper and a preparation method thereof, which are prepared by uniformly mixing the following raw materials in percentage by mass: component A: 1-5% silica gel; component B: 1-5% methylhydrogensiloxane / polysiloxane; component C: 5-15% styrene; component D: 3-10% acrylic acid; component E: 5-20% butyl acrylate; component F: 20-70% water; the sum of the mass percentages of the above components is 100%. At the same time, a fluorine-free oil-proof barrier paper is provided, which is formed by coating a mixed coating liquid on at least one surface of a paper substrate. This scheme completely excludes the use of fluoride-containing materials, realizes green packaging product materials that are harmless to the human body, and conforms to the concept of environmental protection and health. At the same time, through a specific silicon nano-modified material mixed coating liquid, this scheme reaches the oil-proof level of 6 and above (up to 12) required by the market, effectively preventing grease penetration and keeping the outer surface of the package clean.

Description

Technical Field

[0001] The invention relates to the field of food packaging, in particular to a mixed coating liquid and a fluorine-free oil-proof barrier paper and a preparation method thereof. Background Art

[0002] In the field of food packaging, as people pay more and more attention to food safety and hygiene, how to effectively prevent the penetration of oily foods during the packaging process has become a key technical challenge that needs to be solved urgently. Traditionally, in order to solve this problem, the food packaging industry has widely used fluoride-containing oil-proof paper. This type of paper can resist the penetration of oil to a certain extent and keep the outside of the package clean by coating it with a special coating containing fluoride.

[0003] However, as scientific research deepens, the potential health risks of fluoride are gradually exposed. Studies in many countries have shown that long-term contact or ingestion of fluoride-containing substances may cause chronic damage to the human body and affect health. Therefore, many countries and regions have begun to restrict or prohibit the use of fluoride in food packaging materials to protect the health rights and interests of consumers.

[0004] In this context, it is particularly important to develop a green packaging material that can effectively prevent oil penetration and does not contain fluoride that is harmful to the human body. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a mixed coating liquid and a fluorine-free oil-proof barrier paper and a preparation method thereof, which completely eliminates the use of fluoride-containing materials, realizes green packaging product materials that are harmless to the human body, and conforms to the concept of environmental protection and health. At the same time, through the specific silicon nano-modified material mixed coating liquid, this solution achieves the oil-proof level of 6 and above (the highest is 12) required by the market, effectively preventing grease penetration and keeping the outer surface of the packaging clean.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a mixed coating liquid is prepared by uniformly mixing the following raw materials in percentage by mass:

[0007] Component A: silica gel 1-5%;

[0008] Component B: methyl hydrogen siloxane / polysiloxane 1-5%;

[0009] Component C: styrene 5-15%;

[0010] Component D: acrylic acid 3-10%;

[0011] Component E: butyl acrylate 5-20%;

[0012] Component F: water 20-70%;

[0013] The sum of the mass percentages of the above components is 100%.

[0014] As another technical solution, a fluorine-free oil-proof barrier paper is also provided, which is formed by coating a mixed coating liquid of the above-mentioned silicon nano-modified substance on at least one surface of a paper substrate.

[0015] Furthermore, the paper substrate is kraft paper.

[0016] As another technical solution, a method for preparing fluorine-free oil-proof barrier paper is also provided, comprising the following steps:

[0017] Step 1, preparing a coating liquid: according to the formula ratio, silica gel, methyl hydrogen siloxane / polysiloxane, styrene, acrylic acid, butyl acrylate, and water are evenly mixed to prepare a mixed coating liquid;

[0018] Step 2, substrate preparation: choose ordinary kraft paper as the substrate;

[0019] Step 3, coating operation: using a coating device to evenly coat the mixed coating liquid on the surface of the kraft paper;

[0020] Step 4, drying and curing: After coating is completed, the coated paper is sent to a drying equipment for drying and curing.

[0021] Step 5, post-processing: the dried and cured coated paper is subjected to post-processing operations such as cutting and winding to become a finished product of fluorine-free oil-proof barrier paper.

[0022] Furthermore, in step 1, the viscosity of the mixed coating liquid after mixing and stirring is 27-30 seconds, and the viscosity is the viscosity measured by a British 2# Zahn cup at 25°C.

[0023] Further, in step 3, the coating equipment has two sets of anilox rollers with 250 lines per inch.

[0024] As another technical solution, another method for preparing fluorine-free oil-proof barrier paper is also provided, comprising the following steps:

[0025] Step 1, prepare coating liquid and printing ink: Prepare coating liquid: according to the formula ratio, mix silica gel, methyl hydrogen siloxane / polysiloxane, styrene, acrylic acid, butyl acrylate and water evenly to prepare a mixed coating liquid; and prepare the required printing ink;

[0026] Step 2, substrate preparation: prepare ordinary kraft paper as the substrate for coating and printing;

[0027] Step 3, coating and printing: firstly print the pattern, and then immediately coat the oil-proof mixed liquid on the pattern surface;

[0028] Step 4, drying and curing: After coating, drying and curing treatment is carried out to fix the oil-proof coating and printed pattern on the surface of kraft paper.

[0029] Step 5, post-processing: cutting, winding and other post-processing operations are performed to produce fluorine-free oil-proof barrier paper.

[0030] This solution completely eliminates the use of fluorinated materials, realizes green packaging product materials that are harmless to the human body, and is in line with the concept of environmental protection and health. At the same time, through the specific silicon nano-modified material mixed coating liquid, this solution achieves the oil-proof level 6 and above (up to level 12) required by the market, effectively preventing grease penetration and keeping the outer surface of the packaging clean. In addition, in this application, two processes are provided: one is a separate coating on a printing machine or a coating machine; the other is simultaneous with surface pattern printing. The latter significantly saves production time and improves overall production efficiency. The solution is not only suitable for the production of fluorine-free oil-proof barrier paper, but also can produce fluorine-free oil-proof barrier printing semi-finished products to meet the diverse needs of different customers. DETAILED DESCRIPTION

[0031] The present invention relates to a mixed coating liquid, which is prepared by uniformly mixing the following raw materials in percentage by mass:

[0032] Component A: silica gel 1-5%;

[0033] Component B: methyl hydrogen siloxane / polysiloxane 1-5%;

[0034] Component C: styrene 5-15%;

[0035] Component D: acrylic acid 3-10%;

[0036] Component E: butyl acrylate 5-20%;

[0037] Component F: water 20-70%;

[0038] The sum of the mass percentages of the above components is 100%.

[0039] The specific analysis according to its components is as follows:

[0040] Silica gel (1-5%) Function: Silica gel has good film-forming properties and water resistance, and can form a continuous, smooth coating on the substrate. This coating helps to block the penetration of grease and improve the oil-proof performance of the packaging paper. Its advantages: Silica gel is non-toxic, odorless, has good chemical stability, is safe for contact with food, and meets the requirements of food packaging materials.

[0041] Methylhydrogensiloxane / polysiloxane (1-5%) Role: Methylhydrogensiloxane / polysiloxane has excellent cross-linking properties and can react with other components to form a stable three-dimensional network structure. This structure can further enhance the mechanical strength and oil resistance of the coating. Its advantage is that it can enhance the durability and oil resistance of the coating while maintaining the flexibility and processability of the coating.

[0042] Styrene (5-15%) Role: Styrene is an important monomer for synthetic polymers and can copolymerize with other components to form high molecular compounds. In the coating, the presence of styrene helps to improve the hardness and wear resistance of the coating, making it more durable. Its advantages are: improving the hardness and wear resistance of the coating and reducing coating damage caused by friction and scratches.

[0043] Acrylic acid (3-10%) Role: Acrylic acid and its derivatives are important raw materials for synthetic resins, with good adhesion and film-forming properties. In the coating, acrylic acid can closely bond with the substrate and form a continuous, elastic coating film. Advantages: Enhance the adhesion between the coating and the substrate, improve the overall performance of the coating, and make it more solid and durable.

[0044] Butyl acrylate (5-20%) Role: Butyl acrylate is a soft monomer that can give the coating good flexibility and low temperature resistance. In the coating, it copolymerizes with hard monomers such as acrylic acid to form a polymer with appropriate softness and hardness. Advantages: Improve the flexibility and low temperature resistance of the coating, making it adaptable to the use requirements in different environments.

[0045] Water (20-70%) Role: Water is a solvent used to evenly disperse other components and form a coatable mixture. During the coating process, water gradually evaporates, leaving a solid coating formed by other components. Advantages: Environmentally friendly, low cost, easy to control the concentration and coating amount of the coating solution, and helps reduce the emission of harmful substances.

[0046] The first process implementation method (single coating):

[0047] A method for preparing fluorine-free oil-proof barrier paper comprises the following steps:

[0048] Step 1, prepare the coating liquid: according to the formula ratio, mix the silica gel, methyl hydrogen siloxane / polysiloxane, styrene, acrylic acid, butyl acrylate and water raw materials evenly to make a coating mixture. This mixture should have good stability and coating performance.

[0049] Step 2, substrate preparation: Select suitable ordinary kraft paper as the substrate, and ensure that its surface smoothness and water absorption meet the coating requirements.

[0050] Step 3, coating operation: Use a special coating device (anilox roller coater, and the anilox roller coater has two sets of 250 lines per inch anilox rollers) to evenly coat the mixed liquid on the surface of kraft paper. By controlling the coating amount (about 8 grams per square meter) and the number of coating layers, the desired oil-proof effect and coating thickness can be achieved.

[0051] Step 4, drying and curing: After coating, the coated paper is sent to the drying equipment for drying and curing. During this process, the water in the mixed liquid gradually evaporates, and the remaining organic matter forms a stable three-dimensional network structure through cross-linking reaction and is fixed on the surface of kraft paper.

[0052] Step 5, post-processing: the dried and cured coated paper is subjected to post-processing operations such as cutting and winding to become a finished product of fluorine-free oil-proof barrier paper.

[0053] The following is a specific embodiment for the first process:

[0054] Step 1, prepare the coating liquid: formula ratio: 3% silica gel, 2% methyl hydrogen siloxane / polysiloxane, 10% styrene, 6% acrylic acid, 15% butyl acrylate, 64% water. Mixing conditions: at room temperature, use a high-speed mixer to stir at a speed of about 1000 rpm for 30 minutes until the mixture is uniform and free of bubbles.

[0055] Step 2, substrate preparation: You can choose ordinary kraft paper of different gram weights (40-80g / ㎡), and remove dust from the kraft paper to ensure that its surface is clean and free of impurities.

[0056] Step 3, coating operation: use an anilox roller coater with two sets of anilox rollers and an anilox roller line count of 250 lines / inch. By adjusting the gap between the anilox roller and the substrate, ensure that the coating amount is about 8 grams / square meter. In addition, the coating machine runs at a speed of 50 meters / minute.

[0057] Step 4, drying and curing: The paper is transported by the conveyor belt and stays in the drying oven for about 2 minutes to ensure that the coating is completely dried and cured. In addition, the temperature of the hot air drying oven is set at 110-130°C.

[0058] Step 5, post-processing: according to customer requirements, use an automatic cutter to cut the dried coated paper into specified sizes. The cut coated paper is rolled up and packaged for shipment.

[0059] The second process implementation method (surface pattern printing at the same time):

[0060] The following steps are included:

[0061] Step 1, prepare coating liquid and printing ink: prepare the oil-proof coating liquid according to the formula ratio and prepare the required printing ink.

[0062] Step 2, substrate preparation: prepare ordinary kraft paper as the substrate for coating and printing.

[0063] Step 3, synchronous coating and printing: On the printing machine, the pattern is printed first, and then the oil-proof mixed liquid is immediately coated on the pattern surface. This synchronous operation can complete pattern printing and oil-proof coating in one process, greatly improving production efficiency.

[0064] Step 4, drying and curing: After coating, drying and curing treatment is carried out to fix the oil-proof coating and printed pattern on the surface of kraft paper.

[0065] Step 5, post-processing: the same post-processing operations such as cutting and winding are performed to obtain a fluorine-free oil-proof barrier printing semi-finished product.

[0066] The following is a specific embodiment for the second process:

[0067] Step 1, coating liquid and ink preparation:

[0068] Prepare 3% silica gel, 2% methylhydrogensiloxane / polysiloxane, 10% styrene, 6% acrylic acid, 15% butyl acrylate, and 64% water. Accurately weigh each component according to this ratio and stir at about 1000 rpm at room temperature for 15 minutes using a high-speed stirrer until the mixture is uniform and free of bubbles.

[0069] At the same time, according to the color and effect requirements of the design pattern, choose the corresponding type of flexographic printing ink. The ink needs to be stirred evenly in advance and adjusted to the appropriate viscosity range.

[0070] Step 2, equipment and substrate preparation:

[0071] A multifunctional flexographic printing press is used, which is equipped with independent coating unit and printing unit, and the two can run precisely synchronously. Ordinary kraft paper of different gram weights (40-80g / ㎡) can be selected, and dust removal is carried out to ensure that the paper surface is clean and free of impurities.

[0072] Step 3, simultaneous coating and printing:

[0073] First install the designed printing plate roller and adjust the printing pressure to ensure clear patterns and rich colors. The ink is evenly transferred to the anilox roller through the ink fountain, and then transferred from the anilox roller to the printing plate roller. In addition, the printing speed is set to 80 meters / minute to ensure the printing quality and coordinate with the subsequent coating process.

[0074] Step 4, coating operation:

[0075] When the printed pattern is not completely dry (after the ink is initially dry but still maintains a certain degree of viscosity), immediately start the coating unit for oil-proof coating. At the same time, by adjusting the gap of the coating unit and the pressure of the coating roller, ensure that the oil-proof coating amount reaches about 7.0-9.0g / ㎡. At the same time, monitor the coating uniformity to avoid the situation where the coating is too thick or too thin.

[0076] Step 5: Drying and curing

[0077] Since coating and printing are carried out simultaneously, the drying process needs to take into account the curing requirements of both layers (printing layer and oil-proof layer). The temperature of the hot air drying oven can be set to 110°C-130°C, and the paper stays in the drying oven for about 2.5-3 seconds. By adjusting the conveyor belt speed and the drying oven temperature, it is ensured that both layers can be fully dried and cured without adhesion or blistering.

[0078] Step 6, post-processing:

[0079] After drying and curing, the paper is cut into specified sizes by an automatic cutter and rolled and packaged using automated equipment. During the packaging process, attention should be paid to moisture-proof and dust-proof measures to ensure product quality.

[0080] In order to prove that the finished fluorine-free oil-proof barrier paper produced by the first process does not contain fluoride, we sent the finished fluorine-free oil-proof barrier paper produced by the first process for inspection.

[0081] Test report number: CANEC24013260701

[0082] Sample name: Lianxing Brown Cow Fluorine-free Coated Paper

[0083] Test method: Refer to IEC 62321-3-2:2020 method

[0084] Test results: The test results of perfluorinated and polyfluorinated alkyl compounds (in terms of fluorine) were ND (not detected, < MDL), which is far below the limit of 50 mg / kg set by the customer, proving that there is no fluoride residue in the product. Therefore, the fluorine-free oil-proof kraft paper prepared by the process of this application completely eliminates the use of fluoride-containing materials, avoids the potential harm of fluoride in traditional oil-proof paper to human health, and conforms to modern environmental protection and health concepts.

[0085] At the same time, in order to prove that the fluorine-free oil-proof barrier paper product made by the first process can achieve the oil-proof barrier function, we made the fluorine-free oil-proof barrier paper product made by the first process into food packaging bags and sent the food packaging bags for inspection;

[0086] Test report number: QGWT20240055365

[0087] Sample name: Fluorine-free oil-proof brown cattle bag (TY-04)

[0088] Test basis: GB / T 22805.2-2008 "Determination of fat resistance of paper and paperboard Part 2: Surface repulsion method"

[0089] Test results: The fat resistance value is 10 (maximum value is 11), indicating that the product performs well in the fat resistance test and can effectively block grease penetration. Through the specific silicon nano-modified material mixed coating liquid, the fluorine-free oil-proof kraft paper prepared reaches the oil-proof level 6 and above required by the market, effectively preventing grease penetration and keeping the outer surface of the packaging clean.

[0090] The above implementation modes are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing fluorine-free oil-proof barrier paper, characterized in that: The following steps are included: Step 1, prepare the coating solution: Silica gel, methyl hydrogen siloxane / polysiloxane, styrene, acrylic acid, butyl acrylate and water are uniformly mixed according to the following mass percentages to prepare a mixed coating liquid: Wherein component A: silica gel 1-5%; Component B: methyl hydrogen siloxane / polysiloxane 1-5%; Component C: styrene 5-15%; Component D: acrylic acid 3-10%; Component E: butyl acrylate 5-20%; Component F: water 20-70%; The sum of the mass percentages of the above components is 100%; Step 2, substrate preparation: choose ordinary kraft paper as the substrate; Step 3, coating operation: using a coating device to evenly coat the mixed coating liquid on the surface of the kraft paper; Step 4, drying and curing: After coating is completed, the coated paper is sent to a drying device for drying and curing; Step 5, post-processing: the dried and cured coated paper is cut and rolled up for post-processing to become a fluorine-free oil-proof barrier paper product.

2. The method for preparing a fluorine-free oil-proof barrier paper according to claim 1, characterized in that: In step 1, the viscosity of the mixed coating liquid after mixing and stirring is 27-30 seconds, and the viscosity is the viscosity measured by a British No. 2 Zahn cup at 25°C.

3. The method for preparing a fluorine-free oil-proof barrier paper according to claim 2, characterized in that: In step 3, the coating equipment has two sets of 250 lines per inch anilox rollers.

4. The method for preparing a fluorine-free oil-proof barrier paper according to claim 1, characterized in that: The following steps are included: Step 1, prepare coating liquid and printing ink: Prepare the coating liquid: Mix silica gel, methyl hydrogen siloxane / polysiloxane, styrene, acrylic acid, butyl acrylate, and water in the following mass percentages to make a mixed coating liquid: Wherein component A: silica gel 1-5%; Component B: methyl hydrogen siloxane / polysiloxane 1-5%; Component C: styrene 5-15%; Component D: acrylic acid 3-10%; Component E: butyl acrylate 5-20%; Component F: water 20-70%; The sum of the mass percentages of the above components is 100%; And prepare the required printing ink; Step 2, substrate preparation: prepare ordinary kraft paper as the substrate for coating and printing; Step 3, coating and printing: firstly print the pattern, and then immediately coat the oil-proof mixed liquid on the pattern surface; Step 4, drying and curing: After coating, drying and curing treatment is performed to fix the oil-proof coating and printed pattern on the surface of kraft paper; Step 5, post-processing: cutting and winding post-processing operations are performed to produce fluorine-free oil-proof barrier paper.