CN109968596B

CN109968596B - Manufacturing method of environment-friendly paper-plastic composite tray

Info

Publication number: CN109968596B
Application number: CN201910217856.7A
Authority: CN
Inventors: 王明贤; 刘思琪; 张海军; 李牧; 李连进
Original assignee: Tianjin University of Commerce
Current assignee: Tianjin University of Commerce
Priority date: 2019-03-21
Filing date: 2019-03-21
Publication date: 2020-11-27
Anticipated expiration: 2039-03-21
Also published as: CN109968596A

Abstract

The invention discloses a manufacturing method of an environment-friendly paper-plastic composite tray, which comprises the following steps: firstly, heating and melting granular PE composite wood-plastic materials to obtain liquid PE composite wood-plastic materials; and step two, directly covering the liquid PE composite wood-plastic material on the outer surface of the paper tray with a preset shape and size, cooling and shaping, and manufacturing to obtain the required paper-plastic composite tray. The manufacturing method of the environment-friendly paper-plastic composite tray disclosed by the invention can fully utilize rice straws, conveniently and reliably prepare the paper-plastic composite tray, ensure that the paper-plastic composite tray has good mechanical properties and good moisture-proof effect, is beneficial to wide application and has great production practice significance.

Description

Manufacturing method of environment-friendly paper-plastic composite tray

Technical Field

The invention relates to the technical field of tray manufacturing, in particular to a manufacturing method of an environment-friendly paper-plastic composite tray.

Background

The tray is the carrier of stacking the goods, can form the unit that does benefit to mechanized loading and unloading and transport with the small-size goods of dispersion, and the collection dress of the goods of being convenient for, stack, transport and transportation. Therefore, the tray has become an indispensable important tool for modern logistics systems. The material used by the tray mainly comprises wood, plastic, metal and the like, goods or products are often stored in the open air, the tray is basically required to be carried for storing the goods, and the tray can not be recycled due to too much stock and recycling. The current commonly used pallets include wooden pallets, plastic pallets, metal pallets, paper pallets and the like.

The wooden tray is the most widely used at present because of low price and firmness, but the wood has the defects of easy damp and mildew, worm damage and incapability of cleaning, and the wooden tray is required to be fumigated and treated without peculiar smell internationally in order to prevent the diffusion of insect pests; the plastic tray has good integrity, is sanitary and clean and is easy to wash and disinfect, but the price is relatively expensive, but the bearing capacity is small, and the plastic tray is easy to age and deform; the metal tray is firm and durable, has easy specification and size change, is mainly used for occasions with higher requirement on the bearing weight of the tray, and has the defects of heavy self-mass, high price, corrosion and rust; the paper tray is usually made of corrugated board or honeycomb board, and features light weight, no need of fumigation and disinfection, no need of inspection and export, no generation of waste, cleanness and sanitation, and is suitable for transportation in food and medicine industry.

At present, the wooden pallet has the greatest advantages of easy processing and low cost, but the wood is consumed by thousands of cubic meters every year, which is a heavy burden for such countries as China with forest resource shortage. Under the background of emphasizing sustainable development in all countries around the world, tray production enterprises should continuously develop and develop new materials and new products of trays, vigorously develop plastic trays, metal trays, paper trays and the like, and reduce the proportion of wooden trays in the total holding capacity as much as possible. Meanwhile, in order to meet international rapid commodity inspection clearance and environmental protection requirements, customers require tray manufacturers to manufacture trays which are high in relative strength, free of peculiar smell, low in cost and capable of being used outdoors, and conveying efficiency is improved to the maximum extent.

Meanwhile, a large amount of waste crop straws such as rice straws, corn straws, wheat straws, reed straws and the like need to be treated in China, so that the development of plant fiber materials is one of effective ways for solving the problems, and the method has good prospects and profound significance to China and enterprises.

Therefore, at present, a technology is urgently needed to be developed, wastes such as straws, rice husks and the like can be fully utilized, a wood-plastic tray material can be conveniently and reliably prepared, the manufacturing and using requirements of the tray are met, and resources of the wastes such as the straws, the rice husks and the like are recycled.

Disclosure of Invention

In view of the above, the present invention provides a method for manufacturing an environment-friendly paper-plastic composite tray, which can make full use of rice straws, conveniently and reliably manufacture the paper-plastic composite tray, ensure that the paper-plastic composite tray has good mechanical properties and good moisture-proof effect, is beneficial to wide application, and has great production practice significance.

Therefore, the invention provides a manufacturing method of an environment-friendly paper-plastic composite tray, which comprises the following steps:

firstly, heating and melting granular PE composite wood-plastic materials to obtain liquid PE composite wood-plastic materials;

and step two, directly covering the liquid PE composite wood-plastic material on the outer surface of the paper tray with a preset shape and size, cooling and shaping, and manufacturing to obtain the required paper-plastic composite tray.

In the first step, the preparation process of the granular PE composite wood-plastic material comprises the following steps:

a) drying the plant fiber at the temperature of 90-100 ℃ to reach a preset water content;

b) fully mixing and stirring the plant fiber, the plastic resin, the coupling agent, the lubricant, the light stabilizer and the colorant according to the preset weight percentage to obtain a stirred mixture;

c) and putting the stirred mixture into an extrusion granulator for extrusion granulation operation to prepare the granular PE composite wood-plastic material.

Wherein, in the step a), the plant fiber is bamboo powder with the particle diameter of 0.15 mm.

Wherein, in the step a), the water content of the plant fiber is dried to 2-4%.

Wherein, in the step b), 30 to 36 weight percent of bamboo powder, 60 to 65 weight percent of plastic resin, 2.0 to 4.0 weight percent of coupling agent, 0.7 to 1.2 weight percent of lubricant, 0.3 to 0.4 weight percent of light stabilizer and 0.01 to 0.03 weight percent of colorant are fully mixed and stirred.

Wherein the plastic resin is polyethylene;

the lubricant is polyethylene wax;

the coupling agent is a silane coupling agent;

the colorant is toner.

Wherein, in the second step, place the paper tray in advance in the mould of predetermineeing shape and size, then through the injection molding machine, pour into the mould with liquid PE composite wood-plastic material for liquid PE composite wood-plastic material is full of the die cavity of whole mould under the effect of pressure, then the cooling is stereotyped again.

Wherein, in the second step, the paper pallet comprises a deck and a plurality of stringers;

the bottom surface of the floor board is bonded with the top surface of the longitudinal beam.

Wherein, the plank is formed by bonding two layers of corrugated boards together up and down;

the longitudinal beam is formed by presetting a plurality of layers of corrugated paper boards to be overlapped and bonded together.

Compared with the prior art, the manufacturing method of the environment-friendly paper-plastic composite tray can make full use of the rice straws, conveniently and reliably prepare the paper-plastic composite tray, ensure that the paper-plastic composite tray has good mechanical property and good moisture-proof effect, is beneficial to wide application and has great production practice significance.

Drawings

Fig. 1 is a flow chart of a manufacturing method of an environment-friendly paper-plastic composite tray provided by the invention.

Fig. 2 is a schematic view of the main production process flow of the corrugated board used in the environment-friendly paper-plastic composite tray provided by the invention.

Detailed Description

In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings and embodiments.

Referring to fig. 1, the invention provides a manufacturing method of an environment-friendly paper-plastic composite tray, which is used for the environment-friendly paper-plastic composite tray. The method specifically comprises the following steps:

firstly, heating and melting granular PE (polyethylene) composite wood-plastic materials to obtain liquid PE (polyethylene) composite wood-plastic materials;

and step two, directly covering the liquid PE (polyethylene) composite wood-plastic material on the outer surface of the paper tray with a preset shape and size, cooling and shaping, and manufacturing to obtain the required paper-plastic composite tray.

In the invention, in a first step, a preparation process of the granular PE (polyethylene) composite wood-plastic material comprises the following steps:

c) and putting the stirred mixture into an extrusion granulator (also called an extrusion granulator) for extrusion granulation operation to prepare the granular PE (polyethylene) composite wood-plastic material.

In the present invention, in step a), the plant fiber is specifically bamboo powder with a particle diameter of 0.15 mm.

In the present invention, in step a), the plant fiber is dried to a moisture content of 2% to 4%, preferably 2%.

It should be noted that the plant fiber is composed of cellulose, hemicellulose, lignin and various extracts, and the mechanical properties of the fiber are different due to the content difference. When the addition amount of the bamboo powder is low, the bending strength and the rigidity of the material are improved along with the increase of the addition amount of the bamboo powder, but the fluidity of the material is reduced, if the weight percentage of the bamboo powder in the total weight of the PE composite wood-plastic material exceeds 36%, a large amount of bamboo powder fibers are gathered in the material to form a special structure, and the fluidity is extremely poor; below 30%, the toughness and strength of the wood-plastic are insufficient. Thus, the weight ranges of the control fibers are: accounting for 30 to 36 percent of the total weight of the PE composite wood-plastic material. The bamboo powder fiber has strong water absorption, and the water content (namely the water content) needs to be strictly controlled to be 2-16% (the water content of the raw material can be properly relaxed). In addition, the composite material with the bamboo powder particle diameter of 0.15mm has the best mechanical property.

In the invention, in the step b), 30 to 36 weight percent of bamboo powder, 60 to 65 weight percent of plastic resin, 2.0 to 4.0 weight percent of coupling agent, 0.7 to 1.2 weight percent of lubricant, 0.3 to 0.4 weight percent of light stabilizer and 0.01 to 0.03 weight percent of colorant are fully mixed and stirred.

In step b), the mixing and stirring can be performed sufficiently by an existing mixer. The specific stirring time can be 20 minutes, the clearance between the stirring blade of the mixer and the wall of the cylinder is less than 0.5 cm, the mixing effect of the raw materials and the auxiliary materials is basically uniform by visual observation, no obvious agglomeration or aggregation occurs, and the time is generally 40 minutes to 1 hour.

In the present invention, in step b), the plastic resin is preferably: polyethylene PE.

The lubricant is preferably: polyethylene wax (PE wax);

the coupling agent is preferably: a silane coupling agent;

the colorant is preferably a toner.

In the present invention, in step c), the extrusion granulator (also referred to as an extrusion granulator) may be an existing single-screw plastic granulator.

In particular implementation, the length-diameter ratio (namely the ratio of the length to the diameter of the screw) of the single-screw plastic granulator is 32: 1.

it should be noted that, for the present invention, the mixed material is placed into a chamber with a length-diameter ratio of 32: 1, in a hopper of the single-screw extruder, the temperature of a machine barrel of the extruder is 160-180 ℃, the rotating speed of a screw is 5-10 r/min, and the wood-plastic material compounded by the bamboo powder and the PE plastic resin as the plant fiber is prepared by adopting a granulating mode and sieving.

The plastics in the wood-plastic material are divided into two types, namely thermosetting plastics and thermoplastic plastics, and the invention adopts Polyethylene (PE) in the thermoplastic plastics. If the plant fiber in the plastic solution has good wettability and uniform distribution, the mechanical property of the wood-plastic material can be improved. For the plastic resin, if the weight percentage of the plastic resin in the total weight of the PE composite wood-plastic material exceeds 65%, the bamboo powder as the plant fiber can float in the melted plastic resin liquid, the stability is poor, the bamboo powder is easy to be unevenly distributed and poor in stability, and the toughness and the strength of the wood-plastic material are insufficient; when the weight content of the plastic resin is less than 60%, the flowability of the wood-plastic material is poor due to too little liquid. Therefore, the addition amount of the plastic resin is controlled to be 60-65% of the total weight of the PE composite wood-plastic material.

In the present invention, it is further noted that the compatibility of the bamboo powder fiber and the plastic is poor, the bamboo powder has strong water absorption and strong polarity, and the plastic has hydrophobicity and is mostly nonpolar, which results in small interfacial adhesion of the two materials, and appropriate various additives are added to improve the surface properties of the bamboo powder and the plastic, so as to improve the interfacial adhesion between the bamboo powder and the plastic and the mechanical properties of the composite material.

In the invention, it should be noted that the coupling agent can generate strong interface bonding between the plastic and the fiber surface, reduce the water absorption of the fiber, and improve the compatibility and dispersibility of the plant fiber and the plastic, thereby improving the mechanical properties of the wood-plastic material. In the invention, when the silane coupling agent is adopted and accounts for less than 2.0 percent of the total weight of the PE composite wood-plastic material, the use effect of the coupling agent is not obvious. With the increase of the content of the additive, the bonding force between the plastic and the fiber can be improved, the dispersibility of the fiber is improved, and the water absorption is reduced; however, when the weight percentage of the PE composite wood-plastic composite material is more than 4.0 percent of the total weight of the PE composite wood-plastic composite material, the dispersion performance of the improved fibers is obviously reduced, the adhesion of the improved fibers and plastics is poor, and mutually exclusive reaction imagination occurs. Therefore, the adding amount of the silane coupling agent is preferably 2.0 to 4.0 percent of the total weight of the PE composite wood-plastic material.

In the invention, the lubricant is used for improving the fluidity of the melt and the surface quality of an extruded product, reducing the intermolecular friction in the plastic resin, improving the melt fluidity, promoting the interface lubrication between the plastic resin and the wood powder, improving the production efficiency and reducing the edge abrasion. If the weight percentage of the lubricant in the total weight of the PE composite wood-plastic material exceeds 1.2%, the finally prepared tray product is easy to deform along with the rise of temperature due to the excessive amount of the lubricant with low melting point, and the rigidity of the tray product is influenced; if the weight percentage of the PE composite wood-plastic composite material is less than 0.7 percent of the total weight of the PE composite wood-plastic composite material, the content is too small, the mutual friction among molecules is difficult to reduce, and the aims of improving the melt fluidity and the interface lubrication between the resin and the filler cannot be fulfilled. Therefore, the adding amount of the lubricant should be controlled to be 0.7-1.2% of the total weight of the PE composite wood-plastic material.

In the invention, the stabilizers are divided into heat stabilizers and light stabilizers, wherein the heat stabilizers have the main functions of preventing thermal degradation during processing and also have the function of preventing the product from aging in the long-term use process, and the service life and the forming time of the tray are generally relatively short, so the heat stabilizers are not adopted; the light stabilizer is used for preventing the degradation caused by the automatic oxidation reaction initiated by the absorption of ultraviolet light energy by the plastic, and the light stabilizer preferably accounts for 0.3 to 0.4 percent of the total weight of the PE composite wood-plastic material.

Specifically, the light stabilizer is light stabilizer 622 (polybutylene succinate), which can be light stabilizer 622 (polybutylene succinate) produced by Beijing Tiangang assistant, Ltd. Or may be a light stabilizer JT-540, suitable for PE and PP plastics, and may be a product of Kyowa Kagaku chemical Co., Ltd.

In the invention, it is noted that, for the invention, the toners used in the wood-plastic pallet material are yellow, red, black, titanium dioxide, etc., which can make the prepared pallet have uniform and stable color and slow decolorization.

In the second step, the paper tray is placed in a mold with a preset shape and size in advance, then the liquid PE (polyethylene) composite wood-plastic material is injected into the mold through an injection molding machine, so that the liquid PE (polyethylene) composite wood-plastic material fills the cavity of the whole mold under the action of pressure, and then the mold is cooled and shaped.

In the present invention, in a specific implementation, in the second step, the paper tray includes a deck 1 and a plurality of longitudinal beams 2 (not limited to three);

the bottom surface of the plank 1 is bonded with the top surface of the longitudinal beam 2.

In the second step, the paving board 1 is formed by bonding two layers of corrugated boards together from top to bottom;

the longitudinal beam 2 is formed by laminating and bonding a plurality of preset corrugated paper boards together.

The paper tray adopting the structure has the advantages of good compression resistance, simple manufacturing process and easiness in wood-plastic covering.

The invention is characterized in that the floor board is formed by bonding two layers of corrugated boards, the thickness of the board is 30mm, the water content of the board is controlled to be 9.5-10%, the bending strength measurement value of the floor board is 342-355 KPa, and the flat-pressing strength measurement value is 265-300 KPa. According to the requirements of ISO 8611-2, part II performance requirements and test selection 2005-02-15 and the national standard GB/T4996-. Pallets illustrating this material and construction can carry 2 tons of goods.

Therefore, the paper-plastic composite tray has good waterproofness on the basis of keeping good mechanical performance. Meanwhile, the environment-friendly tray is low in cost, simple and convenient to process, small in shrinkage rate and even, and has advantages when used as an environment-friendly tray for outdoor and indoor use.

Specifically, the corrugated board is kraft paper, such as 180-shell kraft paper, the thickness of the paper is 0.21mm, the ring crush strength is 1.35kN/m, the ring crush index is 7.52 N.m/g, and the burst index is 2.61 Kpa.m²/g。

Specifically, the preparation process of the corrugated board, as shown in fig. 2, includes the following steps:

the first substep, raw material treatment: cutting rice straws into sections according to the requirements of cooking and pulping, and removing impurity parts which do not contain fibers or contain few fibers in the raw materials so as to improve the quality of paper pulp, wherein the length of the rice straws is preferably between 1.30 and 1.71 mm.

The second substep, the cooking process: selecting a sulfite method to cook the segmented raw material by using a rotary spherical digester (or a vertical digester), adding water which is 3.5 times of the weight of the raw material (namely the rice straw treated in the first substep) into the rotary spherical digester, wherein the adding amount of sodium hydroxide is 11-13% of the weight of the water, and the adding amount of sodium sulfate is 12-15% of the weight of the sodium hydroxide; the temperature of the alkali liquor is 85-90 ℃; after the rotary spherical digester idles for 10 minutes, the temperature is raised for 45 minutes, the steam pressure is 0-0.45 MPa, the temperature is kept for 10-20 minutes, the liquid is discharged for 20-30 minutes, and the steam is discharged for 10 minutes; and (4) requiring 5-8 g/L of residual alkali after cooking, and finally preparing the rice straw pulp. That is, the rice straw pulp is prepared by adopting a sulfite method.

It should be noted that the sulfite method is used, and sulfate pulp is produced by this method. The sulfate pulp adopts the mixed solution of sodium hydroxide and sodium sulfate as a cooking agent. In the course of cooking, the action of the liquor is moderate, and the fibre is not strongly corroded, so that it is strong and tough, and the made paper is good in folding resistance, breaking resistance and tearing strength. The unbleached sulfate pulp of the present invention can be used for manufacturing kraft paper, paper bag paper, kraft box board, general packing paper and board, etc.

The third substep, washing and screening process: in view of the fact that the main component of the pulp, which constitutes the fibers, is cellulose, there are also substances of varying degrees, such as hemicellulose, lignin, resins, pigments, pectin and ash. Among them, cellulose and hemicellulose are essential components required for pulp, and other components are removed. Therefore, the coarse pulp after cooking enters a washing and screening process section, which specifically comprises the following steps: a part of impurity fine bubbles in the rice straw pulp are removed through washing and screening, so that the ratio of organic matters to inorganic matters in the pulp is improved, the viscosity of the pulp is reduced, and the stiffness is reduced; the epidermis membrane of the raw material is decomposed by beating, otherwise, the epidermis fine bubbles are still connected together in a flaky manner and are not easy to separate, so that the brittleness of the paper is increased; the concentration is strengthened, the non-steamed parts, the fiber bundles and non-fibrous impurities are reduced, the drainage performance and the fiber uniformity of the straw pulp are ensured, the dispersibility and the flexibility of the fibers are improved, and the yellowing of the pulp is reduced.

In the concrete implementation, a horizontal belt type four-section countercurrent washing mode can be adopted, and a dilution stirring tank is matched between the sections to provide mixing and diffusion space and time so as to realize high fiber extraction rate and clean pulp washing. The slurry washing net adopts a 30-40 mesh metal net and a sand setting plate, and is matched with a high-pressure flushing pipe to wash the net surface, so that the fiber extraction rate is ensured to reach more than 80%, and the cleanliness is controlled to be 9-13 mg/L.

The fourth substep, beating process: in view of the beating, the mechanical beating method and the hydraulic beating method of the ultrasonic beating machine are mechanical and physical processes, and the fibers are subjected to the action of shearing force in the beating process, so that the shapes and properties of the fibers are changed, the mechanical strength, the physical performance and the colloidal property of paper pulp can be improved, the strength, the bursting strength, the folding resistance, the uniformity, the stiffness and the like of the paper are improved, and the surface roughness and the loose porosity are reduced; the water filtering performance of the paper material on the net is adjusted and controlled through beating to meet the production requirement of a paper machine, so that the paper obtains good forming, and the uniformity and the strength index of the paper are improved.

In the specific implementation, in the papermaking process of the rice straws, a mild pulping process mainly comprising defibering and dispersing is adopted, so that the dispersibility and the uniformity of the fibers are improved. The specific pulping process comprises the following steps: the rice straw paper pulp is firstly subjected to double-disc grinding, then is beaten in series by a fluffer, and finally is washed and screened to obtain refined pulp, wherein the beating degree is controlled to be 36-38 SR, and the humidity is 3.2-3.8 g.

The fifth substep, papermaking process: paper making is generally classified into a wet method using water as a medium and a dry method using air as a medium. At present, a wet papermaking process is mainly adopted, and the wet papermaking comprises three devices, namely fourdrinier papermaking, cylinder papermaking and wire-clamping papermaking. The papermaking process mainly comprises squeezing, drying and press polishing.

The papermaking process includes dewatering paper pulp and consolidating paper web through pressing to raise smoothness and strength of wet paper web, reduce bulk and transfer the wet paper web to dry part; drying to remove water in the wet paper, improving the strength of the paper, increasing the smoothness of the paper and finishing the sizing of the paper; and then calendering is carried out, pressure, shearing force and steam are applied through rolling of a steam roller, and paper fibers are heated and moistened to be more flexible and strengthened, so that the smoothness and the glossiness of the paper are improved, and the transverse uniformity of parameters such as the thickness of the paper is improved.

Through the preparation process of the corrugated board, the produced kraft paper is 180 g of double-sided offset paper which is used as the corrugated board.

It should be noted that, the invention has the advantages that the rice straw is used as the raw material, the raw material is rich, the cost is low, the paper quality completely reaches the national standard of high-strength kraft paper, the waste straw is applied, and the environmental pollution caused by straw burning is reduced; in the whole process flow, the technological conditions provided by strict execution of the cooking, washing and pulping process links are well implemented.

Based on the technical scheme, the pulping and papermaking process of the rice straws comprises the steps of raw material treatment, stewing, washing, screening, pulping and papermaking, wherein the pulping and papermaking process of the rice straws comprises the steps of straw cutting → dust removal → presoaking, stewing in a spherical digester added with sodium hydroxide and sodium sulfate, washing → screening → purifying the stewed coarse pulp, and papermaking by squeezing, drying and calendaring to prepare 150 g of kraft paper. Compared with the common papermaking process, the processes of bleaching and adding the filler are reduced. If the filler is present, the bonding between the fibers is reduced, resulting in a reduction in the tensile strength, folding strength and bursting strength of the paper.

According to the invention, the composite material prepared by mixing the bamboo fibers, the PE waste plastics and the additives is covered on the surface of a paper tray made of a corrugated board mainly produced by the rice straw fibers, so that the composite material has the characteristics of simplicity and convenience in processing, low cost, moisture resistance, corrosion resistance, attractive appearance and the like on the basis of meeting the use mechanical properties, can be matched according to requirements, and is suitable for outdoor use.

It should be noted that, for the invention, the paper produced by rice straw is used to make corrugated paper board, and further the corrugated paper board is used to make paper tray; then, the bamboo fiber and the waste plastic are mixed according to a certain proportion, a proper auxiliary agent is added for stirring, a wood-plastic material with good fluidity is matched, the wood-plastic material is covered on the surface of the paper-made tray, and finally the environment-friendly paper-plastic composite tray is manufactured, so that the transportation requirements of the food and medicine industry are met.

The technical scheme of the invention is further illustrated by the following specific examples.

Examples are given.

In the invention, the wood-plastic material is manufactured by taking bamboo powder and PE plastic resin as base materials, and the specific components according to the weight ratio are shown in the following table 1.

Table 1: the composition ratio (weight ratio:%) of the wood-plastic material is shown schematically.

No	Fiber	Plastic resin	Coupling agent	Lubricant agent	Stabilizer	Coloring agent
							1	31.7	64.9	2.3	0.74	0.34	0.02
2	35.6	61.1	2.2	0.71	0.38	0.01
							3	33.1	61.8	3.6	1.16	0.31	0.03
4	32.9	62.7	2.9	1.09	0.38	0.03
							5	34.7	60.5	3.6	0.82	0.37	0.01
6	30.7	64.1	3.7	1.18	0.31	0.01

The invention relates to an injection molding process of a paper-plastic composite tray, which specifically comprises the steps of directly covering wood-plastic material particles on the surface of a paper tray in a mold through an injection molding machine, mechanically heating, pressurizing and melting the wood-plastic material, filling a liquid wood-plastic solution into a cavity of the whole mold under the action of pressure, and finally cooling and shaping.

In the injection molding process, if the injection molding temperature is too low, the wood-plastic material is not fully melted and the pressure of a machine head is too high, so that the liquid has poor fluidity in a machine barrel and a die and the wood-plastic material is difficult to extrude; the temperature is too high, the wood-plastic material is easy to degrade and burn, and the pressure of the machine head cannot reach the specified standard, so that the extruded material cannot fill the cavity. Therefore, the temperature of the feeding section of the injection molding machine is controlled to be 170-175 ℃, the temperature of the compression section and the homogenization section are controlled to be 170-190 ℃, and the temperature of the machine head and the injection molding opening are controlled to be 170-175 ℃.

In the injection molding process, if the extrusion pressure of an injection molding machine is insufficient, the product has rough surface and low strength; the higher extrusion pressure makes the difference between the internal pressure and the external pressure of the head neck mold large, which is not beneficial to obtaining a uniform and fine structure. The rotation speed of the screw is generally between 12 and 18r/min, and the injection pressure is kept between 200 and 230 MPa.

Compared with the prior art, the environment-friendly paper-plastic composite tray prepared by the invention has the following beneficial technical effects:

1. the method is beneficial to the protection of forest resources, and fumigation, mildew prevention and odor erosion treatment are not needed;

2. the product is clean and sanitary, is not damaged by worms, meets the market requirements of Europe and America, and can be directly used in the industries of food, medicine and the like;

3. the appearance is flat and smooth, no chippings, iron nails and the like exist, and the package of the bearing object can be protected to a greater extent;

4. the paint has the functions of preventing moisture, water and rain, and the like, and can be used outdoors;

5. the device is firm and durable, has low price, is convenient to assemble and disassemble, is free from inspection, is convenient to clear customs, and saves the cost in transportation;

6. compared with the wooden pallet, the paper pallet is 3-5 times lighter and 100% recyclable under the same weight.

In conclusion, compared with the prior art, the manufacturing method of the environment-friendly paper-plastic composite tray provided by the invention can be used for conveniently and reliably preparing the paper-plastic composite tray by fully utilizing the rice straws, ensures that the paper-plastic composite tray has good mechanical properties and good moisture-proof effect, is beneficial to wide application and has great production practice significance.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The manufacturing method of the environment-friendly paper-plastic composite tray is characterized by comprising the following steps of:

secondly, directly covering the liquid PE composite wood-plastic material on the outer surface of a paper tray with a preset shape and size, and then cooling and shaping to obtain the required paper-plastic composite tray;

c) putting the stirred mixture into an extrusion granulator for extrusion granulation operation to obtain granular PE composite wood-plastic material;

in step a), the plant fiber is bamboo powder with the particle diameter of 0.15 mm;

in the step a), drying the water content of the plant fiber to 2% -4%;

in the step b), 30 to 36 weight percent of bamboo powder, 60 to 65 weight percent of plastic resin, 2.0 to 4.0 weight percent of coupling agent, 0.7 to 1.2 weight percent of lubricant, 0.3 to 0.4 weight percent of light stabilizer and 0.01 to 0.03 weight percent of colorant are fully mixed and stirred;

the plastic resin is polyethylene;

the lubricant is polyethylene wax;

the coupling agent is a silane coupling agent;

the colorant is toner;

in a second step, the paper pallet comprises a deck and a plurality of stringers;

the bottom surface of the floor board is bonded with the top surface of the longitudinal beam;

the floor board is formed by bonding two layers of corrugated boards together up and down;

the longitudinal beam is formed by presetting a plurality of layers of corrugated paper boards to be overlapped and bonded together;

the preparation process of the corrugated board comprises the following steps:

the first substep, raw material treatment: cutting rice straws into sections according to the requirements of cooking and grinding, and removing impurity parts which do not contain fibers or contain few fibers in the raw materials, wherein the length of the rice straws is between 1.30 and 1.71 mm;

the second substep, the cooking process: preparing rice straw pulp by adopting a sulfite method according to the rice straw treated in the first substep;

the third substep, washing and screening process: removing a part of impurity fine bubbles in the rice straw pulp by washing and screening, and decomposing a skin membrane of the raw material by beating; the concentration is enhanced, the non-steamed parts, fiber bundles and non-fibrous impurities are reduced, the drainage performance and the fiber uniformity of the rice straw pulp are ensured, the dispersibility and the flexibility of the fibers are improved, and the yellowing of the pulp is reduced;

the fourth substep, beating process: pulping the rice straw pulp, wherein the rice straw pulp is firstly subjected to double-disc grinding, then is subjected to serial beating through a fluffer, and finally is washed and screened to obtain refined pulp, wherein the beating degree is controlled to be 36-38 SR, and the humidity is 3.2-3.8 g;

the fifth substep, papermaking process: dewatering the refined pulp obtained in the fourth substep by pressing and consolidating the paper web, then drying the wet paper web to remove water and simultaneously finishing sizing of the paper web; and then performing calendaring, applying pressure, shearing force and steam through the rolling of a steam roller, heating and wetting paper fibers, and finally preparing the corrugated board.

2. The manufacturing method according to claim 1, wherein in the second step, the paper tray is previously placed in a mold having a predetermined shape and size, and then the liquid PE composite wood plastic material is injected into the mold through an injection molding machine, so that the liquid PE composite wood plastic material fills the cavity of the entire mold under pressure, and then is cooled and set.