Heat sealing cover paper and manufacturing method thereof

Abstract

The invention discloses heat-sealing cover paper and a manufacturing method thereof, the heat-sealing cover paper is composed of paper forming a cover body and water-based paint respectively coated on the front surface and the back surface of the paper, the water-based paint is dried and calendered, the paper is stretchable paper, and the water-based paint is prepared from inorganic filler, water-based resin, a dispersing agent and water. The defects that a paper base material is rough and porous in surface, poor in printing performance, poor in flexibility, prone to being bent and curled in different environments after being die-cut into paper pieces and the like are successfully overcome, layering is avoided after a cup opening is torn off after sealing, and aluminum-plastic composite paper on the market can be perfectly replaced for use.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and relates to cover paper for heat-sealed paper cups / barrels, and in particular to a heat-sealed cover paper and a manufacturing method thereof. Background Art

[0002] At present, the sealing caps used in cup / barrel packaging products, such as instant noodle barrels, Oreo mini paper barrels, etc., are all made of aluminum-plastic-paper composite caps. They are beautifully printed and have good flatness. When the cup mouth and the cover paper are torn open after sealing, there is no obvious stratification damage, so they are widely used in the sealing of various cups and barrels. However, this leads to a complex structure of the material, using a large amount of plastic and aluminum layers. Under the current conditions, it is difficult to recycle resources, which does not conform to the concept of low-carbon environmental protection and sustainable development. Therefore, using paper as a substitute is a very good choice, and it is very important to develop a packaging material that replaces paper.

[0003] There is no doubt that paper-based materials are environmentally friendly and sustainable, but the defects of paper fibers themselves also restrict their application to a certain extent. Due to the material characteristics of paper fibers themselves, changes in environmental temperature and humidity cause changes in the moisture content of the fibers. When the air humidity is high, the moisture content of the paper is relatively high, the fibers appear to be relaxed, and the flatness of a single piece of paper is relatively good. When the air humidity is low, the paper will lose water and its moisture content will decrease, and the fibers will shrink, resulting in obvious deformation. After being die-cut into sheets, the flatness is difficult to control, which has a greater impact on the application as a single-piece sealing cover paper. Moreover, when the normal moisture content of the paper is 5-7%, it is obviously harder, and it will show obvious warping deformation when sealing with a paper cup, resulting in a decrease in sealing quality. Therefore, the key to the application of sealing cover paper is to invent a paper with good weather resistance and a certain degree of softness, which is not easy to delaminate after the cup mouth is torn open after sealing. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a heat-sealed cover paper which is weather-resistant, meets the requirements of sealing softness and is not prone to delamination after being torn, so as to overcome the defects of the prior art.

[0005] A heat-sealed cover paper, characterized in that it is composed of paper forming a cover body and a water-based coating respectively coated on the front and back sides of the paper and dried and calendered, the paper is stretchable paper, and the water-based coating is prepared from an inorganic filler, a water-based resin, a dispersant and water.

[0006] Preferably, the paper is a stretchable paper with a transverse elongation greater than 7%, a longitudinal length greater than 4%, and a paper weight of 50 to 100 gsm.

[0007] Preferably, the inorganic filler is calcium carbonate solution and / or calcined kaolin, and the solid content of the calcium carbonate solution is 78%.

[0008] Preferably, the weight proportion of calcium carbonate particles in the calcium carbonate solution having a particle size less than 2 um is greater than 98%.

[0009] Preferably, the aqueous resin is an ethylene and vinyl acetate copolymer emulsion.

[0010] Preferably, the water-based coating is divided into a first water-based coating applied on the front side of the paper and a second water-based coating applied on the back side of the paper, the inorganic filler in the first water-based coating is a mixture of a calcium carbonate solution with a solid content of 78% and calcined kaolin, and the inorganic filler in the second water-based coating is a calcium carbonate solution with a solid content of 78%.

[0011] Preferably,

[0012] The first water-based coating comprises the following substances in parts by mass:

[0013] 7-12 parts of calcined kaolin,

[0014] 40-65 parts of calcium carbonate solution,

[0015] 25-45 parts of water-based resin,

[0016] Defoaming agent 0.1-2 parts,

[0017] Dispersant 0.2-2 parts,

[0018] 3-7 parts water;

[0019] The secondary coating comprises the following substances in parts by weight:

[0020] 80-85 parts of calcium carbonate solution,

[0021] 13-18 parts of water-based resin,

[0022] Defoaming agent 0.1-2 parts,

[0023] Dispersant 0.2-2 parts,

[0024] 3-7 parts water.

[0025] In addition, the present invention also provides a method for preparing heat-sealed cover paper, the steps of which are:

[0026] Take the paper and use a scraper coater to apply the first water-based coating on the front of the paper. After two coatings, the coating amount is 30g / m 2 After drying, drying and cooling, the second water-based coating is applied to the back of the paper. After one coating, the coating amount is 15g / m 2 Dry weight, drying, cooling; then calendering treatment by the calendering device in the coating equipment, the pressure is 0.5 atmosphere pressure; finally winding.

[0027] By adopting the above technical scheme, the present invention applies water-based coating and calendering treatment on the front and back sides of the stretch paper with a transverse elongation rate of more than 7%, a longitudinal length rate of more than 4%, and a paper weight of 50-100gsm, respectively. It not only successfully solves the shortcomings of the paper substrate such as rough and porous surface, poor printing performance, poor flexibility, and easy bending and curling under different environments after die-cutting into paper sheets, but also no delamination occurs after the cup mouth is torn open after sealing, and can perfectly replace the aluminum-plastic composite paper on the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the heat-sealed paper cover of the present invention after being heat-sealed on the mouth of a paper cup;

[0029] Figure 2 A schematic diagram of tearing off a heat-sealed paper cover from a sealed paper cup. DETAILED DESCRIPTION

[0030] Example 1

[0031] Prepare the first water-based coating: take 8 parts of calcined kaolin, 50 parts of calcium carbonate solution with a solid content of 78%, 30 parts of water-based resin, 0.15 parts of defoaming agent, 0.5 parts of dispersant, and 11 parts of water, and mix and stir.

[0032] Prepare the second water-based coating: take 82 parts of calcium carbonate solution with a solid content of 78%, 14 parts of water-based resin, 0.15 parts of defoamer, 0.5 parts of dispersant, and 3 parts of water, and mix and stir the calcium carbonate solution.

[0033] In the above selected calcium carbonate solution, the weight proportion of calcium carbonate particles with a particle size less than 2 um is greater than 98%.

[0034] The water-based resin is an ethylene-vinyl acetate copolymer emulsion. In this embodiment, Wacker's CA 5800. The dispersant used is Raybo 61 from the BYK series.

[0035] The production steps are: take 80g / m 2 The stretchable white kraft paper with a transverse elongation of more than 7% and a longitudinal elongation of more than 4% and a width of 730 mm is coated on the front side by a blade coater, and the first water-based coating is applied twice with a coating amount of about 30 g / m2 of dry weight each time, dried, and cooled; the second water-based coating is then applied to the back side with a coating amount of about 15 g / m2 of dry weight, dried, cooled, and then calendered by a calendering device in the coating equipment at a pressure of 0.5 atmospheres, and rolled up to obtain the heat-sealed cover paper of this embodiment.

[0036] Example 2

[0037] Prepare the first water-based coating: take 10 parts of calcined kaolin, 43 parts of calcium carbonate solution with a solid content of 78%, 40 parts of water-based resin, 0.15 parts of defoaming agent, 0.5 parts of dispersant, and 7 parts of water, and mix and stir.

[0038] Prepare the second water-based coating: take 80 parts of calcium carbonate solution with a solid content of 78%, 15 parts of water-based resin, 0.15 parts of defoaming agent, 0.5 parts of dispersant, and 5 parts of water, and mix and stir.

[0039] In the above selected calcium carbonate solution, the weight proportion of calcium carbonate particles with a particle size less than 2 um is greater than 98%.

[0040] The water-based resin is an ethylene-vinyl acetate copolymer emulsion. In this embodiment, Wacker's CA 5370. The dispersant used is Raybo 61 from the BYK series.

[0041] The production steps are: take 80g / m 2 The stretchable white kraft paper with a transverse elongation of more than 7% and a longitudinal elongation of more than 4% and a width of 730 mm is coated on the front side by a blade coater. After two coatings, the coating amount is about 30 g / m2 dry weight each time, and the paper is dried and cooled. Then, the second water-based coating is coated on the back side. After one coating, the coating amount is about 15 g / m2 dry weight. The paper is dried and cooled. The paper is then calendered by a calendering device in the coating equipment at a pressure of 0.5 atmospheres and rolled up to obtain the heat-sealed cover paper of this embodiment.

[0042] Example 3

[0043] Prepare the first water-based coating: take 7 parts of calcined kaolin, 60 parts of calcium carbonate solution with a solid content of 78%, 30 parts of water-based resin, 0.15 parts of defoaming agent, 0.5 parts of dispersant, and 3 parts of water, and mix and stir.

[0044] Prepare the second water-based coating: take 85 parts of calcium carbonate solution with a solid content of 78%, 10 parts of water-based resin, 0.15 parts of defoaming agent, 0.5 parts of dispersant, and 5 parts of water, and mix and stir.

[0045] In the above selected calcium carbonate solution, the weight proportion of calcium carbonate particles with a particle size less than 2 um is greater than 98%.

[0046] The water-based resin is an ethylene-vinyl acetate copolymer emulsion. In this embodiment, Wacker's CA 5800. The dispersant used is Raybo 61 from the BYK series.

[0047] The production steps are: take 90g / m 2The stretchable white kraft paper with a transverse elongation of more than 7% and a longitudinal elongation of more than 4% and a width of 730 mm is coated on the front side by a blade coater, and the first water-based coating is applied twice with a coating amount of about 30 g / m2 of dry weight each time, dried, and cooled; the second water-based coating is then applied to the back side with a coating amount of about 15 g / m2 of dry weight, dried, cooled, and then calendered by a calendering device in the coating equipment at a pressure of 0.5 atmospheres, and rolled up to obtain the heat-sealed cover paper of this embodiment.

[0048]

Performance test

[0049] 1. Printing performance test

[0050] The heat-sealed flap paper obtained in the above embodiments is smooth and delicate when observed with the naked eye. After being printed on a machine, it is observed with the naked eye that the pattern is printed beautifully and the printing effect is good.

[0051] 2. Weather resistance test

[0052] The heat-sealed cover papers prepared in Example 1, Example 2 and Example 3 were cut into 3 sheets using a 100 cm2 original sheet sampler to form heat-sealed paper covers, which were placed in a constant temperature and humidity chamber with set constant temperature and humidity chamber parameters for 2 hours (h) respectively, and the deformation of each heat-sealed paper cover was observed and measured.

[0053] The constant temperature and humidity chamber parameters set in sequence are:

[0054] High temperature and low humidity (temperature 80°C, humidity 20% RH);

[0055] High temperature and high humidity (temperature 80°C, humidity 70% RH);

[0056] Low temperature and low humidity (temperature 23°C, humidity 20% RH);

[0057] Low temperature and high humidity (temperature 23°C, humidity 70% RH).

[0058] The observations and measurements are as follows:

[0059]

[0060]

[0061] From the results, it can be seen that the warping degree of the above heat-sealed paper covers is less than 8MM, the deformation is small, and it can meet the requirements of single-chip machine.

[0062] 3. Sealing and tearing cup mouth test

[0063] The heat-sealed paper covers and paper cups in the above weather resistance test were sealed using a milk tea sealing device, with the sealing temperature set to 135° C. and the sealing time set to 0.4 s.

[0064] After sealing, the sealing effect is as follows Figure 1 As shown, after visual inspection, each heat-sealed paper cover is adhered to the mouth of the paper cup.

[0065] Tear the seal by hand through the tearing mouth of the heat-sealed paper cover (such as Figure 2 Observe the edge of the paper cup and the heat-sealed area of ​​the paper sheet, and there is obvious fiber damage, but none of the paper sheets show delamination, which indicates that the seal is firmly adhered and will not delaminate when the cup mouth is torn open.

[0066] It can be seen from the above detailed introduction that the present invention not only successfully solves the shortcomings of the paper substrate, such as rough and porous surface, poor printing performance, poor flexibility, easy bending and curling in different environments after die-cutting into paper sheets, but also no delamination occurs after the cup mouth is torn open after sealing, and can perfectly replace the aluminum-plastic composite paper on the market.

Claims

1. A heat-sealed cover paper, characterized in that: The cover is formed by paper, which is coated on the front and back of the paper and then dried and calendered. The paper is stretchable paper, and the water-based paint is prepared from inorganic fillers, water-based resin, dispersant and water.

2. The heat-sealed lidding paper according to claim 1, characterized in that: The paper is a stretchable paper with a transverse elongation greater than 7%, a longitudinal length greater than 4%, and a paper weight of 50 to 100 gsm.

3. The heat-sealed lidding paper according to claim 1, characterized in that: The non-polar filler is calcium carbonate solution and / or calcined kaolin, and the solid content of the calcium carbonate solution is 78%.

4. The heat-sealed cover paper according to claim 3, characterized in that: The calcium carbonate particles in the calcium carbonate solution have a particle size less than 2 μm, accounting for more than 98% by weight.

5. The heat-sealed lidding paper according to claim 1, characterized in that: The water-based resin is an ethylene-vinyl acetate copolymer emulsion.

6. The heat-sealed lidding paper according to claim 1, characterized in that: The water-based coating is divided into a first water-based coating applied on the front side of the paper and a second water-based coating applied on the back side of the paper. The inorganic filler in the first water-based coating is a mixture of calcium carbonate solution and calcined kaolin, and the inorganic filler in the second water-based coating is calcium carbonate solution.

7. The heat-sealed lidding paper according to claim 6, characterized in that: The first water-based coating comprises the following substances in parts by mass: 7-12 parts of calcined kaolin, 40-65 parts of calcium carbonate solution, 25-45 parts of water-based resin, Defoaming agent 0.1-2 parts, Dispersant 0.2-2 parts, 3-7 parts water; The secondary coating comprises the following substances in parts by weight: 80-85 parts of calcium carbonate solution, 13-18 parts of water-based resin, Defoaming agent 0.1-2 parts, Dispersant 0.2-2 parts, 3-7 parts water.

8. A method for preparing the heat-sealed lidding paper according to claim 7, comprising the steps of: Take the paper and use a scraper coater to apply the first water-based coating on the front of the paper. After two coatings, the coating amount is 30g / m 2 After drying, drying and cooling, the second water-based coating is applied to the back of the paper. After one coating, the coating amount is 15g / m 2 Dry weight, drying, cooling; then calendering treatment by the calendering device in the coating equipment, the pressure is 0.5 atmosphere pressure; finally winding.

9. The method for preparing the heat-sealed cover paper according to claim 8, characterized in that: The paper is a stretchable white kraft paper with a transverse elongation greater than 7%, a longitudinal length greater than 4%, and a paper weight of 50-100gsm.

10. The method for preparing the heat-sealed cover paper according to claim 9, characterized in that: The water-based resin is an ethylene-vinyl acetate copolymer emulsion.

Images