Method for manufacturing a plastic-substitute packaging paper with a foamed cushioning layer

Abstract

The application discloses a kind of production methods of plastic-replacing packaging paper with foaming buffer layer, belong to packaging material technical field, comprising the following steps: S1, after coating high-temperature-resistant agent on the surface of base paper, drying high-temperature-resistant base paper is obtained;S2, polybutylene succinate, plasticizer, crosslinking agent, foaming agent, foaming aid, nucleating agent, foaming aid are mixed uniformly, and heated to melt to obtain foaming slurry;S3, double-layer fiber silk formed by foaming slurry and polycaprolactone using three-axis spinning needle head blow molding is sprayed on the surface of high-temperature-resistant base paper to obtain load base paper;S4, two load base papers are compounded into foaming paper;S5, foaming slurry is foamed and solidified after heating to form foaming buffer layer;S6, after coating barrier material on the surface of two high-temperature-resistant base papers, drying barrier layer is formed, and plastic-replacing packaging paper is obtained;The plastic-replacing packaging paper of the application has good protection performance.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and in particular to a method for manufacturing plastic-substitute packaging paper with a foaming buffer layer. Background Art

[0002] In order to prevent fragile or valuable products from being damaged by mechanical loads such as impact and vibration during transportation, it is usually necessary to cushion the products. Currently, common cushioning packaging is made of materials such as foam cotton, bubble film, corrugated cardboard, and honeycomb cardboard. Foam cotton and bubble film have good toughness and elasticity, good cushioning performance, durability, and waterproofness, and can protect the products well. However, foam cotton and bubble film are usually made of difficult-to-degrade materials, and improper abandonment can easily lead to environmental pollution. Corrugated cardboard and honeycomb cardboard both have many cavities inside and have certain cushioning properties. Although the materials used are usually easy to degrade, they have defects such as brittleness, poor resilience, and non-waterproofness, and their durability during use is poor. Therefore, it is necessary to produce a cushioning packaging material with good cushioning performance, durability, waterproofness and easy degradation based on the defects of current cushioning packaging materials.

[0003] Chinese patent publication number CN111572999A discloses a wood fiber foamed packaging paperboard and a preparation method thereof, which comprises the following preparation process: (1) soaking wood fiber in dilute sulfuric acid and then bleaching it with a hydrogen peroxide solution to obtain pretreated wood fiber; (2) adding starch, a cross-linking agent, and sodium hydroxide into water and stirring and gelatinizing them to obtain a slurry of gelatinized starch; (3) adsorbing ammonium bicarbonate onto diatomaceous earth and spraying it with a cross-linked polyvinyl alcohol glue to obtain a foaming aid; (4) adding pretreated wood fiber, inorganic fiber, and a foaming aid to the slurry of gelatinized starch to obtain a paste; (5) applying the paste to the surface of a base paper, sandwiching it between two base papers, rolling it flat, foaming it at high temperature, and cutting it to obtain a wood fiber foamed packaging paperboard.

[0004] The above-mentioned packaging cardboard is obtained by foaming a paste material made of starch, cross-linking agent, wood fiber, inorganic fiber, foaming aid, etc. to form a foaming layer, thereby obtaining a wood fiber foamed packaging cardboard. The packaging cardboard is made of degradable materials and is environmentally friendly. However, the foaming layer is mainly composed of starch, wood fiber, and inorganic fiber, and has certain brittleness and poor elasticity and waterproofness. The packaging cardboard is easily irreversibly deformed or even punctured when hit by external objects, making it difficult to protect the products packaged therein. Therefore, there is still room for improvement. Summary of the Invention

[0005] In view of the technical defects existing in the background technology, the present invention proposes a method for manufacturing plastic-substitute packaging paper with a foaming buffer layer, which solves the above technical problems and meets practical needs. The specific technical solution is as follows:

[0006] A method for manufacturing plastic-substitute packaging paper having a foaming buffer layer comprises the following steps:

[0007] S1. Applying a high-temperature resistant agent on the surface of the base paper, drying the base paper after the high-temperature resistant agent is completely permeated into the base paper to obtain the high-temperature resistant base paper;

[0008] S2, mixing 80%-93% polybutylene succinate, 2%-8% plasticizer, 0.1%-1% cross-linking agent, 1%-5% foaming agent, 1%-3% auxiliary foaming agent, 1%-4% nucleating agent, and 0.2%-1% foaming aid, and heating until melted to obtain a foaming slurry;

[0009] S3, blowing the molten foaming slurry and molten polycaprolactone with high-pressure airflow using a three-axis spinning needle, pulling to form a double-layer fiber filament wrapped with polycaprolactone, and evenly spraying the double-layer fiber filament on one side of the high-temperature resistant base paper to obtain a loaded base paper;

[0010] S4, compounding the two layers of loaded base paper into a paper to be foamed, wherein the paper to be foamed is composed of a high-temperature resistant base paper, a double-layer fiber, and a high-temperature resistant base paper in the thickness direction;

[0011] S5. Heating the foamable paper to be foamed to foam the foaming slurry. After the foaming slurry is foamed and solidified, a foaming buffer layer is formed between the two layers of high-temperature resistant base paper. The two layers of high-temperature resistant base paper and the foaming buffer layer together constitute the middle paper.

[0012] S6. Barrier materials are coated on the surfaces of the two layers of high-temperature resistant base paper of the middle paper and then dried to form a barrier layer. The two barrier layers and the middle paper together constitute the plastic-substitute packaging paper.

[0013] As a further technical solution of the present invention, the base paper is selected from one of wood pulp paper, kraft paper, chicken paper, and coated paper, the gram weight of the base paper is 20-200gsm, and the base paper is formed with a plurality of micropores by mechanical punching, and the high temperature resistant agent is selected from one or more of silicone oil, boric acid solution, and silicate solution.

[0014] As a further technical solution of the present invention, the plasticizer is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

[0015] As a further technical solution of the present invention, the cross-linking agent is selected from one or more of dicumyl peroxide, silane coupling agent, divinylbenzene, and diisocyanate.

[0016] As a further technical solution of the present invention, the foaming agent is 4,4'-oxobisbenzenesulfonylhydrazide, and the auxiliary foaming agent is urea.

[0017] As a further technical solution of the present invention, the nucleating agent is selected from one or more of diphenyl dihydrazide sebacate, 2,2′-methylenebis(4,6-tert-butylphenol)phosphine aluminum salt, dibenzylidene sorbitol, di(p-monomethylbenzylidene) sorbitol, and di(p-chlorosubstituted benzylidene) sorbitol.

[0018] As a further technical solution of the present invention, the foaming aid includes the following components by mass: 40%-60% foam stabilizer, 40%-60% antioxidant; the foam stabilizer is selected from one or more of polyvinyl alcohol, polyacrylic acid, micron-sized silica, micron-sized calcium carbonate, fatty alcohol polyoxyethylene ether, and alkyl glycoside; the antioxidant is selected from one or more of 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl) phosphite, and vitamin E.

[0019] As a further technical solution of the present invention, in step S3, the propulsion speed ratio of the molten foaming slurry and the molten polycaprolactone in the triaxial spinning needle is 1:1 to 4:1, and the pressure of the high-pressure air flow is 1-2 bar.

[0020] As a further technical solution of the present invention, in step S5, the heating temperature for foaming the foaming slurry is 120-150°C.

[0021] As a further technical solution of the present invention, the barrier material is selected from one or more of starch-based barrier materials, cellulose-based barrier materials, and chitosan-based barrier materials.

[0022] The beneficial effects of the present invention are:

[0023] The plastic substitute packaging paper of the present invention is mainly made of degradable materials, which can be degraded into harmless substances in the environment in a relatively short time and is environmentally friendly. The foaming buffer layer is made of a foaming material formed by foaming polybutylene succinate and polycaprolactone as a skeleton, so that the foaming buffer layer has good impact buffering performance, rebound performance and structural stability. The plastic substitute packaging paper can replace the current common plastic material buffering packaging materials; in addition, after the barrier material is coated on the surface of the high-temperature resistant base paper to form a barrier layer, the waterproofness, sealing and toughness of the surface of the high-temperature resistant base paper are improved, thereby improving the overall protective performance of the plastic substitute packaging paper, and can well protect the products packaged therein from damage caused by external objects collision, liquid penetration and other factors. DETAILED DESCRIPTION

[0024] The following describes the implementation of the present invention in conjunction with relevant embodiments. The implementation of the present invention is not limited to the following embodiments, and the present invention relates to relevant necessary components in this technical field and should be regarded as a well-known technology in this technical field, which can be known and mastered by technical personnel in this technical field.

[0025] A method for manufacturing plastic-substitute packaging paper having a foaming buffer layer comprises the following steps:

[0026] S1. Applying a high-temperature resistant agent on the surface of the base paper, drying the base paper after the high-temperature resistant agent is completely permeated into the base paper to obtain the high-temperature resistant base paper;

[0027] S2, mixing 80%-93% polybutylene succinate, 2%-8% plasticizer, 0.1%-1% cross-linking agent, 1%-5% foaming agent, 1%-3% auxiliary foaming agent, 1%-4% nucleating agent, and 0.2%-1% foaming aid, and heating until melted to obtain a foaming slurry;

[0028] S3, blowing the molten foaming slurry and molten polycaprolactone with high-pressure airflow using a three-axis spinning needle, pulling to form a double-layer fiber filament wrapped with polycaprolactone, and evenly spraying the double-layer fiber filament on one side of the high-temperature resistant base paper to obtain a loaded base paper;

[0029] S4, compounding the two layers of loaded base paper into a paper to be foamed, wherein the paper to be foamed is composed of a high-temperature resistant base paper, a double-layer fiber, and a high-temperature resistant base paper in the thickness direction;

[0030] S5. Heating the foamable paper to be foamed to foam the foaming slurry. After the foaming slurry is foamed and solidified, a foaming buffer layer is formed between the two layers of high-temperature resistant base paper. The two layers of high-temperature resistant base paper and the foaming buffer layer together constitute the middle paper.

[0031] S6. Barrier materials are coated on the surfaces of the two layers of high-temperature resistant base paper of the middle paper and then dried to form a barrier layer. The two barrier layers and the middle paper together constitute the plastic-substitute packaging paper.

[0032] The present invention can unwind the base paper roll and process the base paper through an assembly line to obtain plastic-substitute packaging paper. In step S1, after the high-temperature resistant agent is coated on the surface of the base paper and dried, the high-temperature resistant agent can form a protective layer on the outer surface of the base paper, effectively preventing the base paper from being damaged or the performance degradation in a high-temperature environment. The high-temperature resistant agent can also prevent or slow down the oxidation reaction of the base paper at high temperature, and can effectively prevent the base paper from oxidative degradation in a high-temperature environment, maintaining the stability of its structure and performance. After the base paper is coated with the high-temperature resistant agent and dried, the high-temperature resistant base paper is obtained. The high-temperature resistant base paper has good high-temperature resistance, which can avoid damage to the base paper or performance degradation when the foaming paper is subsequently heated for foaming.

[0033] In step S2 of the present application, 85.9% polybutylene succinate, 5% plasticizer, 0.5% crosslinking agent, 3% foaming agent, 2% foaming aid, 3% nucleating agent and 0.6% foaming aid are mixed uniformly and heated to melt to obtain a foaming slurry, the main component of the foaming slurry is polybutylene succinate, wherein the plasticizer is added to reduce the melting temperature and processing performance of polybutylene succinate, so that the above-mentioned materials can be converted into a molten state after being heated to 100-110 DEG C, in order to avoid premature foaming of the foaming slurry, the starting foaming temperature of the foaming agent should be greater than 110 DEG C; polybutylene succinate contains easily hydrolyzed ester groups, which can be easily decomposed and metabolized by various microorganisms in nature or enzymes in plants and animals under conditions such as composting and contact with specific microorganisms, and ultimately decomposed into carbon dioxide and water, polybutylene succinate, as one of the main components of the foaming buffer layer in the plastic-substituted packaging paper of the present application, has the characteristics of easy degradation, which can improve the environmental protection of the plastic-substituted packaging paper.

[0034] In step S3 of the present application, the three-axis spinning needle can simultaneously extrude the molten foaming slurry and the molten polycaprolactone, the foaming slurry is extruded from the center needle, the second layer of needle is wrapped outside the center needle and extrudes polycaprolactone to wrap the outer surface of the foaming slurry, the third layer of needle is wrapped around the second layer of needle and sprays high-pressure gas flow to pull the polycaprolactone to form a double-layer fiber silk, the high-pressure gas flow simultaneously sprays several double-layer fiber silks uniformly on one side of the high-temperature base paper, the melting temperature of polycaprolactone is relatively low, the double-layer fiber silk still has a certain plasticity after being sprayed, and the double-layer fiber silk can be adhered to the surface of the high-temperature base paper through polycaprolactone, the fiber film formed by loading several double-layer fiber silks on one side of the high-temperature base paper obtains a loaded base paper; and polycaprolactone has an ester bond structure, which is easily broken under specific environmental conditions such as enzyme action, microbial degradation and hydrolysis, thereby realizing the degradation of the polymer into carbon dioxide and water, polycaprolactone, as another main component of the foaming buffer layer in the plastic-substituted packaging paper of the present application, has the characteristics of easy degradation, which can improve the environmental protection of the plastic-substituted packaging paper.

[0035] After the above operation, it should be noted that in order to compound the two layers of loaded base paper into a double-layer structure of paper to be foamed, in step S1, two rolls of base paper need to be used to unwind the base paper in parallel with each other and synchronously process it into high-temperature resistant base paper. In step S3, the double-layer fiber filaments are sprayed on the surface of the high-temperature resistant base paper opposite to the other high-temperature resistant base paper. The double-layer fiber filaments are sprayed on the surface of the two layers of high-temperature resistant base paper, thereby obtaining two layers of loaded base paper, and the surface of the loaded base paper carrying the double-layer fiber filaments is opposite to the surface of the other loaded base paper carrying the double-layer fiber filaments; in step S4, while the polycaprolactone in the double-layer fiber filaments is still at a relatively high temperature and has plasticity, the two layers of loaded base paper are compounded into paper to be foamed. A certain pressure can be applied during the compounding process, and the polycaprolactone in the paper to be foamed acts as an adhesive. The compounded paper to be foamed consists of a three-layer structure consisting of high-temperature resistant base paper, double-layer fiber, and high-temperature resistant base paper.

[0036] In step S5 of the present invention, the paper to be foamed is heated to make the foaming slurry in the double-layer fiber filaments become a molten state again, and then the heating is continued to the starting foaming temperature of the foaming agent to make the foaming agent start to foam, so that a polybutylene succinate foam material is formed between the two layers of high-temperature resistant base paper, and the molten polycaprolactone is squeezed by the bubbles formed by the foaming slurry and dispersed in the polybutylene succinate foam material, and adheres to the two layers of high-temperature resistant base paper so that the two layers of high-temperature resistant base paper and the foaming material are fixed. After the foaming of the foaming slurry is completed, the foaming is slowly The temperature is slowly lowered to room temperature to allow the polybutylene succinate foam material and polycaprolactone to solidify to form a foamed buffer layer. The foamed buffer layer uses the foamed material formed by foaming polybutylene succinate as the main structure. The foamed material has a plurality of pores, and polycaprolactone is filled between some of the pores. The pore structure of the foamed buffer layer gives it good impact resistance and cushioning performance. Polycaprolactone has shape memory properties. Polycaprolactone can be regarded as a skeleton in the foamed buffer layer, which can improve the rebound performance and structural stability of the foamed buffer layer.

[0037] In step S6 of the present invention, a barrier material is coated on the surface of the high-temperature resistant base paper and then dried to form a barrier layer that can prevent liquid penetration. The barrier layer can improve the waterproofness, sealing, toughness and other properties of the high-temperature resistant base paper. The high-temperature resistant base paper serves as the surface structure of the plastic substitute packaging paper, and the barrier layer can improve the protective performance of the plastic substitute packaging paper. The plastic substitute packaging paper of the present invention can be used to make cushioning packaging for fragile or valuable products. The high-temperature resistant base paper and the foaming buffer layer are both made of degradable materials, which are environmentally friendly and can replace plastic cushioning packaging materials such as bubble cotton and bubble film. In addition, the foaming buffer layer has good toughness, impact cushioning performance, rebound performance and structural stability, and the high-temperature resistant base paper has good waterproofness, sealing and toughness, so that the plastic substitute packaging paper has good protective performance, which can well protect the products packaged therein from damage due to factors such as collision with external objects and liquid penetration. It can also replace degradable cushioning packaging materials such as corrugated paper and honeycomb paper.

[0038] To sum up, the plastic substitute packaging paper of the present invention is mainly made of degradable materials, which can be degraded into harmless substances in the environment in a relatively short time and is environmentally friendly. The foaming buffer layer is made of a foaming material formed by foaming polybutylene succinate and polycaprolactone as a skeleton, so that the foaming buffer layer has good impact buffering performance, rebound performance and structural stability. The plastic substitute packaging paper can replace the current common plastic material buffering packaging materials; in addition, after the barrier material is coated on the surface of the high-temperature resistant base paper to form a barrier layer, the waterproofness, sealing and toughness of the surface of the high-temperature resistant base paper are improved, thereby improving the overall protective performance of the plastic substitute packaging paper, and can well protect the products packaged therein from damage caused by external objects collision, liquid penetration and other factors.

[0039] As one of the preferred embodiments of the present invention, the base paper is selected from wood pulp paper, kraft paper, chicken paper, and coated paper, and the base paper has a grammage of 20-200 gsm.

[0040] The base paper of the present invention can be selected from different types and weights of paper according to the purpose of the plastic substitute packaging paper. Among them, wood pulp paper is usually made of virgin wood pulp, and has moderate toughness and hardness, and is suitable for making cushioning packaging for packaged food, electronic products, pharmaceutical products and other products; kraft paper and chicken skin paper both have high toughness and moderate hardness, and the plastic substitute packaging paper made from them can well replace plastic cushioning packaging materials such as bubble cotton and bubble film; coated paper has high hardness and moderate toughness, and the plastic substitute packaging paper made from it has high surface hardness, and can well replace corrugated cardboard and honeycomb cardboard to make cardboard-shaped cushioning packaging.

[0041] As one of the preferred embodiments of the present invention, a plurality of micropores are formed in the base paper by mechanical punching.

[0042] After the base paper of the present invention is formed with a number of micropores by mechanical punching, the high-temperature resistant base paper obtained after being coated with a high-temperature resistant agent and dried still has a number of micropores. These micropores discharge excess gas during the foaming process of the foaming slurry, thereby preventing gas from being trapped between the two layers of high-temperature resistant base paper and causing deformation of the middle paper after foaming.

[0043] As one of the preferred embodiments of the present invention, the high temperature resistant agent is selected from one or more of silicone oil, boric acid solution, and silicate solution.

[0044] The high-temperature resistant agent of the present invention is used to improve the high-temperature resistance of the base paper. When the high-temperature resistant agent is coated on the outer surface of the base paper and dried, a protective layer is formed to obtain the high-temperature resistant base paper. The protective layer can effectively prevent the high-temperature resistant base paper from being damaged or the performance is degraded in a high-temperature environment. The protective layer can also be a stable oxide film formed by the high-temperature resistant agent by reacting with oxygen. The oxide film can prevent oxygen from directly contacting the fibers and chemicals in the base paper, thereby preventing the base paper from oxidative degradation in a high-temperature environment.

[0045] As one of the preferred embodiments of the present invention, the plasticizer is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

[0046] The plasticizer of the present invention is mainly used to improve the softness, plasticity and processing performance of polybutylene succinate, and at the same time reduce its melting temperature so that it can be processed and formed at a lower temperature. The plasticizer can also improve the foaming performance of polybutylene succinate, which is beneficial to the formation and expansion of bubbles during the foaming process and obtains a more uniform and finer foaming material, thereby improving the impact resistance and cushioning performance of the buffer foam layer.

[0047] As one of the preferred embodiments of the present invention, the crosslinking agent is selected from one or more of dicumyl peroxide, silane coupling agent, divinylbenzene, and diisocyanate.

[0048] The cross-linking agent of the present invention decomposes and generates free radicals when heated, thereby initiating a cross-linking reaction between polybutylene succinate chains, effectively improving the strength of the polybutylene succinate melt, facilitating the formation of a uniform pore structure during the foaming process, maintaining the stability of the pore structure, and preventing pore rupture, ultimately obtaining a foamed material with good structural stability, and improving the cushioning performance of the foamed cushioning layer.

[0049] As one of the preferred embodiments of the present invention, the foaming agent is 4,4'-oxobisbenzenesulfonylhydrazide, and the auxiliary foaming agent is urea.

[0050] The present invention uses 4,4'-monooxy-bisbenzenesulfonylhydrazine as a foaming agent for polybutylene succinate. The foaming agent is suitable for foaming at normal pressure, and the gas generated during the foaming process is environmentally friendly nitrogen. The foamed material obtained after foaming has a fine and uniform pore structure. Under normal circumstances, 4,4'-monooxy-bisbenzenesulfonylhydrazine requires a temperature above 130° C. to generate gas for foaming. However, after adding urea as a co-foaming agent, the foaming temperature of 4,4'-monooxy-bisbenzenesulfonylhydrazine is reduced to about 120° C., thereby better controlling the melting temperature and foaming temperature of polybutylene succinate.

[0051] As one of the preferred embodiments of the present application, the nucleating agent is selected from one or more of decanedioic acid, diphenyl dihydrazide, 2,2'-methylenebis(4,6-tert-butylphenol) phosphine aluminum salt, dibenzyl sorbitol, di(p-methylbenzyl) sorbitol, di(p-chloro-substituted benzyl) sorbitol.

[0052] The main role of the nucleating agent of the present application is to form tiny bubble nuclei in the foaming process of polybutylene succinate, which are then enlarged in the foaming process to form the final cell structure. The above component as a nucleating agent can effectively improve the nucleation speed of polybutylene succinate and has the effect of refining the nucleation size, which is beneficial to form a stable and uniform cell structure. The above component as a nucleating agent can also improve the flexural modulus, heat distortion temperature and impact strength of the polybutylene succinate foaming material, showing good flexibility and heat resistance.

[0053] As one of the preferred embodiments of the present application, the foaming aid includes the following components by mass: 40%-60% foam stabilizer, 40%-60% antioxidant; the foam stabilizer is selected from one or more of polyvinyl alcohol, polyacrylic acid, micron-sized silicon dioxide, micron-sized calcium carbonate, fatty alcohol polyoxyethylene ether, alkyl glycoside; the antioxidant is selected from one or more of 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl) phosphite, vitamin E.

[0054] In the foaming aid of the present application, the foam stabilizer is used to keep the cell stable during the foaming process of polybutylene succinate, prevent the cells from merging or breaking each other, and thus obtain an ideal cell structure. The foam stabilizer maintains the stability of the cell structure by adsorbing on the cell surface to form a liquid protective film or a solid particle protective layer, reducing the liquid surface activity, etc. The antioxidant is used to improve the oxidation resistance and aging resistance of the polybutylene succinate foaming material, thereby improving the durability of the plastic packaging paper. The antioxidant realizes the oxidation resistance function by interrupting the chain reaction and preventing the further progress of the oxidation process, capturing free radicals generated by the decomposition of hydroperoxide, etc.

[0055] As one of the preferred embodiments of the present application, in step S3, the ratio of the pushing speed of the molten foaming slurry to the molten polycaprolactone in the three-axis spinning needle is 1:1 to 4:1, and the pressure of the high-pressure gas flow is 1-2 bar.

[0056] In step S3 of the present application, the ratio of the pushing speed of the molten foaming slurry and the molten polycaprolactone in the three-axis spinning needle is preferably 3:1. The ratio of the pushing speed can ensure that the double-layer fiber filament structure is stable and has sufficient foaming slurry inside, so that the double-layer fiber filament can be foamed by the foaming slurry to form a foaming buffer layer. Controlling the ratio of the foaming slurry and the polycaprolactone in the double-layer fiber filament can control the foaming ratio, and the performance of the foaming buffer layer can be controlled by the foaming ratio.

[0057] As one of the preferred embodiments of the present application, in step S5, the heating temperature for foaming the foaming slurry is 120-150℃.

[0058] In step S5 of the present application, the foaming slurry is usually heated to 120℃ to start foaming, and then slowly heated to 130℃ to completely foam. It is necessary to observe whether there is insufficient foaming, so as to determine whether it is necessary to increase the temperature to ensure that the foaming slurry is completely foamed.

[0059] As one of the preferred embodiments of the present application, the barrier material is selected from one or more of starch-based barrier material, cellulose-based barrier material, and chitosan-based barrier material.

[0060] In the present application, the barrier material is coated on the surface of the high-temperature-resistant base paper and dried to form a barrier layer. The barrier itself has good water resistance or hydrophobic and oleophobic properties. After the barrier material is coated on the surface of the high-temperature-resistant base paper, the barrier material will fill the pores, cracks and micropores on the surface of the high-temperature-resistant base paper, thereby increasing the density, strength and surface smoothness of the high-temperature-resistant base paper. After the barrier material is dried, a barrier layer that can prevent liquid penetration is formed, so that the plastic packaging paper has good water resistance.

[0061] The above is only a preferred embodiment of the present application. It should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for producing plastic-substitute packaging paper with a foaming buffer layer, characterized in that: The following steps are involved: S1. Applying a high-temperature resistant agent on the surface of the base paper, drying the base paper after the high-temperature resistant agent is completely permeated into the base paper to obtain the high-temperature resistant base paper; S2. Evenly mix 80%-93% of polybutylene succinate, 2%-8% of plasticizer, 0.1%-1% of cross-linking agent, 1%-5% of foaming agent, 1%-3% of urea, 1%-4% of nucleating agent, and 0.2%-1% of foaming aid, and heat until melted to obtain a foaming slurry; The foaming aid comprises the following components by mass: 40%-60% foam stabilizer, 40%-60% antioxidant; S3, blowing the molten foaming slurry and molten polycaprolactone with high-pressure airflow using a three-axis spinning needle, pulling to form a double-layer fiber filament wrapped with polycaprolactone, and evenly spraying the double-layer fiber filament on one side of the high-temperature resistant base paper to obtain a loaded base paper; S4, compounding the two layers of loaded base paper into a paper to be foamed, wherein the paper to be foamed is composed of a high-temperature resistant base paper, a double-layer fiber, and a high-temperature resistant base paper in the thickness direction; S5. Heating the foamable paper to be foamed to foam the foaming slurry. After the foaming slurry is foamed and solidified, a foaming buffer layer is formed between the two layers of high-temperature resistant base paper. The two layers of high-temperature resistant base paper and the foaming buffer layer together constitute the middle paper. S6. Barrier materials are coated on the surfaces of the two layers of high-temperature resistant base paper of the middle paper and then dried to form a barrier layer. The two barrier layers and the middle paper together constitute the plastic-substitute packaging paper.

2. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The base paper is selected from one of wood pulp paper, kraft paper, chicken paper, and coated paper. The base paper has a grammage of 20-200gsm. The base paper is formed with a plurality of micropores by mechanical punching. The high temperature resistant agent is selected from one or more of silicone oil, boric acid solution, and silicate solution.

3. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The plasticizer is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

4. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The crosslinking agent is selected from one or more of dicumyl peroxide, silane coupling agent, divinylbenzene, and diisocyanate.

5. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The foaming agent is 4,4'-oxobisbenzenesulfonylhydrazide.

6. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The nucleating agent is selected from one or more of diphenyl dihydrazide sebacate, 2,2′-methylenebis(4,6-tert-butylphenol)phosphine aluminum salt, dibenzylidene sorbitol, di(p-monomethylbenzylidene) sorbitol, and di(p-chlorosubstituted benzylidene) sorbitol.

7. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The foam stabilizer is selected from one or more of polyvinyl alcohol, polyacrylic acid, micron-sized silicon dioxide, micron-sized calcium carbonate, fatty alcohol polyoxyethylene ether, and alkyl polyglycoside; the antioxidant is selected from one or more of 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl)phosphite, and vitamin E.

8. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: In step S3, the propulsion speed ratio of the molten foaming slurry and the molten polycaprolactone in the triaxial spinning needle is 1:1 to 4:1, and the pressure of the high-pressure air flow is 1-2 bar.

9. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: In step S5, the heating temperature for foaming the foaming slurry is 120-150°C.

10. The method for making plastic-substitute packaging paper with a foaming buffer layer according to claim 1, characterized in that: The barrier material is selected from one or more of starch-based barrier materials, cellulose-based barrier materials, and chitosan-based barrier materials.