Paper-based heat-sealing packaging material for extraction paper

Abstract

The invention discloses a paper-based heat-seal packaging material for extraction paper, and relates to a packaging material, in particular to a paper-based heat-seal packaging material for extraction paper. The problem that when the extraction paper is applied to the paper-based packaging material, the extraction paper is easy to tear off at the extraction paper outlet is solved. According to the method, a pulped fiber material is added into the heat-sealing coating, a surfactant, a dispersing agent, a charge control agent, a thickening agent and other auxiliaries are added, the pH value of the coating is adjusted, and the low shear viscosity of the coating is controlled. Under the condition of high-speed dispersion, the fiber material is uniformly dispersed in the coating by adjusting the adding sequence of each auxiliary agent and other proportioning processes, the prepared coating is coated on the paper surface in a curtain type coating manner, and after drying, the flexibility and tear resistance of the paper surface are improved by a single-surface or double-surface coating of the paper-based heat-sealing material, so that the paper-based heat-sealing material can be applied to the paper-based heat-sealing material. And the longitudinal / transverse tearing strength exceeds 700mN, so that the problem that the paper is easy to tear at a paper taking outlet is effectively solved.

Description

Technical Field

[0001] The invention relates to a packaging material, in particular to a paper-based heat-sealed packaging material for tissue paper. Background Art

[0002] As one of the four major materials in the packaging industry, plastic packaging ranks second in usage, following paper and cardboard packaging materials, accounting for more than 25%. However, the recycling rate of plastics is not high, and they still need to be incinerated or landfilled, which has caused serious and long-term pollution to the environment. More than 8 million tons of plastic waste enters the ocean every year. Plastic waste not only harms marine life, but may also threaten human health. Refractory plastic waste has become a recognized problem in the world, and countries around the world have issued bans and restrictions on plastics.

[0003] Under the guidance of the new plastic restriction policy, new green and environmentally friendly functional packaging materials have been born. Paper packaging materials are used more and more due to their wide sources, renewable, recyclable, and biodegradable waste. Some manufacturers produce packaging materials that can replace traditional plastics by coating the surface of paper with a heat-sealing coating, and realize the application of heat-sealed packaging on the original production line. At present, it is more common to coat one or both sides of the base paper with water-based coatings with heat-sealing properties, including acrylic emulsions, which have good heat-sealing properties and certain barrier properties. By replacing plastic with paper, the pollution to the environment after the packaging materials are discarded can be reduced.

[0004] However, compared with plastic materials, the flexibility and tensile strength of paper-based packaging materials are significantly worse. During the production and application processes, paper packaging is prone to being pulled apart or torn. Xiamen Dingwen New Materials Co., Ltd. has announced a patent for "an improved soft-drawn packaging film with tear protection" (patent application number: 202322668935.4). This patent solves the problem that film packaging (including paper-based packaging) is easily torn and scratched during application by providing an improved soft-drawn packaging film with tear protection. The solution is to adhere a layer of reinforced protective tape to the surrounding side of the easy-tear opening; a limiting portion is provided adjacent to the reinforced protective tape and the easy-tear opening. This method requires the reinforced protective tape to be adhered separately during packaging production. This not only requires the modification of packaging production equipment, but also increases production costs. At the same time, the use of self-adhesive or hot-melt adhesive during pasting makes the recycling process of packaging paper more difficult. Some manufacturers improve the problem of opening tearing by increasing the basis weight of base paper, but the effect is limited. At the same time, the flexibility of paper-based packaging materials will deteriorate with a significant increase in basis weight, affecting the packaging process, and the heat sealing performance will be significantly reduced, which cannot meet the requirements of heat sealing strength. Therefore, it is necessary to develop a paper-based packaging material that is easy to use and low in cost to meet the application requirements of replacing plastic with paper. Summary of the invention

[0005] The present invention provides a paper-based heat-sealed packaging material for tissue paper. The paper is coated on one or both sides to produce a packaging substrate with heat-sealing properties and certain barrier properties. At the same time, by adding fibrous materials to the coating, after drying, the tearing degree of the base paper is improved, thereby improving the problem that the tissue paper after packaging is easily torn at the paper outlet when taking the tissue paper. At the same time, by adjusting the rheological properties of the coating, the uniform distribution of the fiber material in the coating is effectively improved, and the uniformity of the coating is improved.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] (1) Add pulped fiber materials to the heat-seal coating, add surfactants, dispersants, charge regulators, thickeners and other additives, adjust the pH value of the coating, and control the low shear viscosity of the coating. Under high-speed dispersion conditions, by adjusting the order of adding each additive and other batching processes, the fiber material is evenly dispersed in the coating, and the prepared coating is applied to the paper surface by curtain coating. After drying, the single-sided or double-sided coating of the paper-based heat-seal material increases the flexibility and tear resistance of the paper surface, and the longitudinal / lateral tear strength exceeds 700mN.

[0008] (2) The fiber materials used include plant fibers, nanofibers, polyester fibers, polypropylene fibers, polyvinyl alcohol fibers, polyamide fibers, aramid fibers, polyacrylonitrile fibers, polyethylene fibers, carbon fibers, two-component composite fibers, PLA fibers, PLA / PBAT composite fibers, PHA fibers, PBS fibers, etc., or a combination of these fibers. The fibers are processed by beating, cutting, or fibrillation. The length of the processed fibers does not exceed 5 mm, and the beating degree does not exceed 80°SR.

[0009] (3) After the pulping treatment, suitable dispersants, surfactants, hydrophilic modifiers and other additives are added to disperse the fibers, and the dispersion concentration does not exceed 5%. At the same time, a suspension thickener is added to improve the dispersion and suspension properties of the fibers in water. For different fibers, some surfactants or dispersants can be added during pulping to improve the pulping effect.

[0010] (4) The dispersants used for fiber dispersion include one or a combination of dodecyl, sodium sulfate, Tween series, polyethylene glycol, polyethylene oxide, polyacrylic acid, carboxymethyl cellulose, sodium alginate, chitosan derivatives, betaine, styrene-maleic anhydride copolymer, etc.

[0011] (5) The amount of dispersant added to the fiber should not exceed 5%, and the dispersion conditions should be adjusted according to the fiber characteristics. Good fiber dispersion performance can be obtained by adjusting the appropriate zeta potential, pH value, temperature, etc.

[0012] (6) The main components of the heat-seal coating used include one or more of acrylic emulsion, ethylene / vinyl acetate copolymer emulsion, vinyl acetate / ethylene copolymer emulsion, polyurethane emulsion, etc. The ratio of the heat-seal coating component to the fiber is 100:40 to 100:1, the mixed preparation concentration is not higher than 30%, and the low shear viscosity of the coating is not higher than 1000cp.

[0013] (7) The thickener used in the coating is a water-based or water-soluble thickener, such as PVA, CMC, xanthan gum, guar gum, sodium alginate, starch, chitosan, etc., which are commonly used thickeners in water-based coatings, or a combination of several of them.

[0014] (8) The die head of the curtain coating method is a slit type, and the slit width is not more than 0.8 mm. The slit width can be adjusted to obtain different curtain falling speeds, so that the fibers in the wet coating applied to the paper have different longitudinal and transverse orientations. The coating speed is not higher than 1500m / min. Single-sided or double-sided coating is used. The coating amount on each side is not more than 30g / m 2 , paper weight 20~150g / m 2 .

[0015] The fibers in the coating act as reinforcing ribs. The heat-sealing component has excellent bonding properties, which can firmly adhere the fibers to each other and to the surface of the base paper, strengthen the tear resistance of the base paper surface, and improve the surface flexibility, which can effectively solve the problem of easy tearing at the paper outlet. During coating, the orientation of the fibers in the heat-sealing coating can be adjusted by adjusting the curtain speed and the paper width speed, thereby improving the longitudinal and transverse tear resistance. Through the coordination of the dispersant, the fibers are effectively dispersed evenly in the coating, avoiding the problem of fiber entanglement and agglomeration, thereby avoiding the problem of blocking the die head gap. DETAILED DESCRIPTION

[0016] Implementation Method 1

[0017] Select coniferous pulp plant fiber for pulping treatment, the pulping concentration is 2.5%, and the beating is carried out by a Valli beater. Since the coniferous pulp fiber is long, it is initially pulped by cutting, and then the weight is reduced to perform sticky beating to improve the effect of silk brooming. The beating degree is controlled at 45-55°SR, and the fiber length is controlled at 2-3mm. Put the beaten coniferous pulp into the batching tank, adjust the batching tank speed to 300 rpm, add polyethylene oxide (PEO) dispersant, the addition amount is 1-2%, add low foam surfactant, the addition amount is 0.5%, increase the stirring speed to 500 rpm, add xanthan gum, the addition amount is 0.06%, and after adding, reduce the stirring speed to 200 rpm, continue stirring for 50 minutes, test and adjust the fiber zeta potential to -5-15mV, and adjust the pH value to above 6.5. Add the acrylic emulsion stock solution to the fiber dispersion under stirring, adjust the stirring speed to 300 rpm, slowly add the acrylic emulsion, the ratio of acrylic emulsion to fiber is 100:20. Add 0.35% low dynamic surface tension surfactant, 0.1% sodium alginate, 0.8% wax emulsion, adjust the solid content of the heat seal coating to 15%, and the low shear viscosity of the coating to 400cp. Adjust the curtain coating die gap to 0.3mm, the coating speed to 400m / min, the die outlet flow rate to 1.13m / s, and the base paper weight to 25g / m 2 , single-sided coating amount 8g / m 2 , double-sided coating, paper weight 41g / m 2 After drying, the longitudinal tear strength of the paper is 721mN and the transverse tear strength is 750mN.

[0018] Implementation Method 2

[0019] PLA fiber was selected for pulping treatment, with a pulping concentration of 4.5%. A Wally pulper was used for pulping. PLA fiber was relatively difficult to pulp, so a heavy weight cutting method was used for pulping. Tween80 surfactant was added in an amount of 1.5%, the pulping temperature was controlled below 60°C, the pulping degree was controlled at 35-40°SR, and the fiber length was controlled at 3-5mm. The beaten PLA fiber was placed in a batching tank, the speed of the batching tank was adjusted to 350 rpm, CMC was added in an amount of 1.5%, the pH value was adjusted to 7.5-8.0, the stirring speed was increased to 400 rpm, sodium alginate was added in an amount of 0.1%, and the stirring speed was reduced to 200 rpm after addition, and stirring was continued for 80 minutes. The fiber zeta potential was tested and adjusted to -25--30mV. Add vinyl acetate / ethylene copolymer emulsion to the fiber dispersion under stirring, adjust the stirring speed to 300 rpm, slowly add vinyl acetate / ethylene copolymer emulsion, the ratio of vinyl acetate / ethylene copolymer emulsion to PLA fiber is 100:10. Add 0.3% low dynamic surface tension surfactant, adjust the solid content of heat seal coating to 25%, and the low shear viscosity of coating to 600cp. Adjust the curtain coating die gap to 0.35mm, coating speed to 350m / min, die outlet flow rate to 0.63m / s, base paper weight to 35g / m 2 , single-sided coating amount 10g / m 2 , double-sided coating, paper weight 55g / m 2 After drying, the longitudinal tear strength of the paper is 853mN and the transverse tear strength is 972mN.

[0020] Implementation 3

[0021] PBS fiber was selected for pulping treatment, with a pulping concentration of 4.8%. The pulping was carried out using a Wali pulping machine. PBS fiber was relatively hydrophobic and difficult to pulp. The heavy weight cutting method was used for pulping. Tween80 surfactant was added in an amount of 2.0%, chitosan derivative was added in an amount of 0.3%, the pulping temperature was controlled below 60°C, the pulping degree was controlled at 20-40°SR, and the fiber length was controlled at 4-5mm. The beaten PBS fiber was placed in a batching tank, the speed of the batching tank was adjusted to 350 rpm, PVA was added in an amount of 0.5%, the pH value was adjusted to 7.0-7.5, and the stirring speed was reduced to 200 rpm after addition, and stirring was continued for 20 minutes. The fiber zeta potential was tested and adjusted to -35--40mV. The polyurethane emulsion was added to the fiber dispersion under stirring, the stirring speed was adjusted to 300 rpm, and the polyurethane emulsion was slowly added. The ratio of polyurethane emulsion to PBS fiber was 100:25. Add 0.4% low dynamic surface tension surfactant and adjust the solid content of heat seal coating to 17%. Adjust the curtain coating die gap to 0.25mm, coating speed to 250m / min, die outlet flow rate to 1.40m / s, base paper weight to 45g / m 2 , single-sided coating amount 15g / m 2 , single-sided coating, paper weight 60g / m 2 After drying, the longitudinal tear strength of the finished paper is 923mN and the transverse tear strength is 875mN.

Claims

1. A paper-based heat-sealed packaging material for tissue paper, characterized in that: Add pulped fiber materials to the heat-sealing coating, add surfactants, dispersants, charge regulators, thickeners and other additives, adjust the pH value of the coating, control the low shear viscosity of the coating under high-speed dispersion conditions, adjust the order of adding each additive and other batching processes, so that the fiber material is evenly dispersed in the coating, and apply the prepared coating on the paper surface by curtain coating. After drying, the single-sided or double-sided coating of the paper-based heat-sealing material increases the flexibility and tear resistance of the paper surface, and the longitudinal / lateral tear strength exceeds 700mN.

2. A paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: The fiber materials used include plant fibers, nanofibers, polyester fibers, polypropylene fibers, polyvinyl alcohol fibers, polyamide fibers, aramid fibers, polyacrylonitrile fibers, polyethylene fibers, carbon fibers, two-component composite fibers, PLA fibers PLA / PBAT composite fibers, PHA fibers, PBS fibers, etc., or a combination thereof. The fibers are processed by beating, cutting, or fibrillation, and the length of the treated fibers does not exceed 5 mm, and the beating degree does not exceed 80°SR.

3. The paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: After the pulping treatment, suitable dispersants, surfactants, hydrophilic modifiers and other additives are added to disperse the fibers, and the dispersion concentration does not exceed 5%. At the same time, a suspension thickener is added to improve the dispersion and suspension properties of the fibers in water. For different fibers, some surfactants or dispersants can be added during pulping to improve the pulping effect.

4. The paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: The dispersants used for fiber dispersion include one or a combination of dodecyl, sodium sulfate, Tween series, polyethylene glycol, polyethylene oxide, polyacrylic acid, carboxymethyl cellulose, sodium alginate, chitosan derivatives, betaine, styrene-maleic anhydride copolymer, etc.

5. The paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: The amount of dispersant added to the fiber does not exceed 5%, and the dispersion conditions are adjusted according to the fiber characteristics. Good fiber dispersion performance is obtained by adjusting the appropriate zeta potential, pH value, temperature, etc.

6. The paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: The main components of the heat-sealing coating used include one or more composites of acrylic emulsion, ethylene / vinyl acetate copolymer emulsion, vinyl acetate / ethylene copolymer emulsion, polyurethane emulsion, etc. The ratio of the heat-sealing coating component to the fiber is 100:40 to 100:1, the mixed preparation concentration is not higher than 30%, and the low shear viscosity of the coating is not higher than 1000cp.

7. The paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: The thickener used in the coating is a water-based or water-soluble thickener, such as PVA, CMC, xanthan gum, guar gum, sodium alginate, starch, chitosan and other thickeners commonly used in water-based coatings, or a combination of several of them.

8. The paper-based heat-seal packaging material for tissue paper according to claim 1, characterized in that: The die head of curtain coating is slit type, and the gap width is not more than 0.8mm. The gap width can be adjusted to obtain different curtain falling speeds, so that the fibers in the wet coating on the paper have different longitudinal and transverse orientations. The coating speed is not higher than 1500m / min. Single-sided or double-sided coating is adopted. The coating amount on each side is not higher than 30g / m 2 , paper weight 20~150g / m 2 .