CN108559292B

CN108559292B - Wood-plastic composite product with PET sandwich structure

Info

Publication number: CN108559292B
Application number: CN201810371020.8A
Authority: CN
Inventors: 欧荣贤; 王清文; 易欣; 孙理超; 郭垂根; 吴江伟; 谭伟
Original assignee: South China Agricultural University
Current assignee: Guangdong Haipeng Bamboo Fiber New Material Technology Co.,Ltd.
Priority date: 2018-04-24
Filing date: 2018-04-24
Publication date: 2021-01-26
Anticipated expiration: 2038-04-24
Also published as: CN108559292A

Abstract

The invention provides a wood-plastic composite product with a PET sandwich structure. The invention belongs to the field of composite materials, relates to a PET (polyethylene terephthalate) wood-plastic composite product, and particularly relates to a wood-plastic composite product with a PET sandwich structure, wherein the product consists of a wood-plastic composite section and accessories, the wood-plastic composite section is prepared by an extrusion process, the wood-plastic composite section also comprises at least one foamed PET sandwich synchronously prepared by the extrusion process, and the periphery of the foamed PET sandwich is coated by the wood-plastic composite; the wood-plastic composite material section bar is connected with accessories, and the accessories comprise one or more of connecting pieces, handles, locking pieces, sliding rails, glass, sealing pieces and buffering pieces. The product has high strength, light weight, water resistance and deformation resistance, and is suitable for use in humid environment.

Description

Wood-plastic composite product with PET sandwich structure

Technical Field

The invention belongs to the field of composite materials, relates to a PET (polyethylene terephthalate) wood-plastic composite material product, and particularly relates to a wood-plastic composite material product with a PET sandwich structure.

Background

The wood-plastic material is prepared from thermoplastic plastics and wood fiber, bamboo fiber or crop fiber, can fully utilize recycled plastics and agricultural and forestry wastes, and has good ecological benefit and economic benefit. The waste wood-plastic composite material can be produced again after being crushed, so that a recycling utilization mode is formed, and the requirements of developing recycling economy and building a conservation-oriented society are met. The utilization of the wood-plastic composite material can be finally realized only by manufacturing the wood-plastic composite material into products with different functions, and the existing wood-plastic composite material is widely used for manufacturing floors, railings, wall panels and building templates. Products such as wood-plastic shutters, wood-plastic glass windows and the like are also manufactured by the wood-plastic composite material, so that the water-resistant, corrosion-resistant and easy-to-form characteristics of the wood-plastic composite material are effectively utilized, and the advantages of the wood-plastic composite material are highlighted. However, the wood-plastic composite material has high density, and the impact resistance and the heat insulation performance are inferior to those of wood, and further improvement is needed; especially, when the material is used for constructional engineering, the material has higher requirements on heat insulation, sound insulation, noise reduction and mechanical properties, and the performance of the wood-plastic composite material product in the aspects is worthy of further improvement. Although the density of the foamed wood-plastic composite material and the product prepared by foaming the wood-plastic composite material by the process in the prior art is reduced, and the heat insulation, heat preservation, sound insulation and noise reduction performances can be improved to a certain extent, the screw holding force is reduced after the wood-plastic composite material is foamed, so that loose or damage is easy to occur at the position where loose leaves or connecting pieces are installed, and the wood-plastic composite material product with excellent performance is not easy to manufacture.

In addition, the method of adding the solid wood core in the wood-plastic composite material through glue application and the method of adding the solid wood core through co-extrusion have certain requirements on the shape and the water content of the solid wood core material, and the condition that the solid wood is damaged and broken at the joint of the solid wood is difficult to avoid because the length of the solid wood material is limited. The solid wood material is a heterogeneous material, the characteristic of anisotropy is obvious, and the defects of using a solid wood core need to be overcome in the development of wood-plastic composite material products. PET, polyethylene terephthalate, has good mechanical strength, temperature resistance, abrasion resistance, good barrier properties, low water absorption and good toughness, and is the most productive and least expensive of the thermoplastic polyesters. The PET polyester foam material has the characteristics of light weight, high specific strength, high rigidity, excellent electrical insulation property and heat and sound insulation performance. At present, PVC/PP/PE and other resins are often used for producing the wood-plastic composite material, but because the properties of resin matrixes such as deformation resistance, impact strength, scratch resistance and the like have certain difference compared with PET, if the wood-plastic composite material and products can be prepared by the foamed PET polyester foam material, the wood-plastic composite material can obtain more excellent properties, but because the melting temperature of PET is up to 250 ℃, the wood-plastic composite material and products with good properties are difficult to process and obtain in the manufacturing process of the wood-plastic composite material in the prior art, and the production and application of the PET wood-plastic composite material are limited.

Disclosure of Invention

The invention aims to overcome the defects of the background technology and provide a wood-plastic composite product with a PET sandwich structure, which has good mechanical property, heat insulation, sound insulation and noise reduction effects.

In order to achieve the purpose of the invention, the wood-plastic composite material consists of a wood-plastic composite material section and accessories, wherein the wood-plastic composite material section is prepared by an extrusion process, the wood-plastic composite material section also comprises at least one foamed PET sandwich synchronously prepared by the extrusion process, and the periphery of the foamed PET sandwich is coated by the wood-plastic composite material; the wood-plastic composite material section bar is connected with accessories, and the accessories comprise one or more of connecting pieces, handles, locking pieces, sliding rails, glass, sealing pieces and buffering pieces.

Preferably, the cross section of the foamed PET sandwich is one of a rectangle, a rounded rectangle or a regular hexagon, the number of the foamed PET sandwich is at least three, and the foamed PET sandwich is evenly distributed on the cross section of the wood-plastic composite material section along the width direction; after the wood-plastic composite section is formed through an extrusion process, performing routing machining on the surface of the wood-plastic composite section by using a computer machining center to obtain an embedding opening, wherein the embedding opening penetrates or semi-penetrates the wood-plastic composite section, a mirror or glass is embedded in the embedding opening, and the mirror or the glass is sealed in the wood-plastic composite section through a sealing element; the engraving and milling processing is carried out in the middle of the cross section width direction of the wood-plastic composite material section, and the foamed PET sandwich at two ends is not damaged at least.

Preferably, the formula of the wood-plastic composite material section bar comprises PET resin, wood powder, a coupling agent, a foaming agent, a nucleating agent, a plasticizer and sodium carboxymethyl cellulose, wherein: the weight percentage of the wood powder is 45-65%; the weight percentage of the PET resin is 15-39%; the weight percentage of the foaming agent is 4-8%; the weight percentage of the coupling agent is 1.5-4%.

Preferably, the plasticizer is one or more of dioctyl phthalate, acrylic acid and dibutyl phthalate; the foaming agent is a composite foaming agent of azodicarbonamide, bicarbonate and citric acid, wherein the weight of the azodicarbonamide is 2-3% of that of the PET wood-plastic composite material.

Preferably, the coupling agent is one or more of isocyanate, modified aminosilane and vinyl silane; the wood flour is one or more of spruce wood flour, poplar wood flour, pine wood flour, straw powder, sugarcane residue powder, rice hull powder and peanut hull powder.

Preferably, the nucleating agent is selected from one or more of talcum powder, calcium carbonate, nano montmorillonite, titanium dioxide and silicon dioxide; the PET wood-plastic composite material optionally further comprises a foaming auxiliary agent, a mildew preventive or a flame retardant.

Preferably, the foaming auxiliary agent is selected from one or more of nano zinc oxide, zinc carbonate, citric acid, zinc acetate and glycerol.

Preferably, the wood flour is modified wood flour, and the preparation method comprises the following steps:

A. taking wood powder with the particle size of 170-190 microns, carrying out heat treatment drying at 95-105 ℃, extracting with acetone, and drying for later use;

B. and (3) adding water to dilute the thermosetting phenolic resin, adding the wood powder obtained in the step (A), wherein the weight of the wood powder is 0.5-1 time of that of the thermosetting phenolic resin, performing ultrasonic treatment in an ultrasonic cleaner at room temperature for 25-35 min, then performing centrifugal filtration at a centrifugal rotation speed of 1000-1300 r/min for 3-5 min, and performing heat treatment on the centrifuged filtrate at 125-130 ℃ for 0.5-1 h to obtain the modified wood powder.

Preferably, the extrusion process is completed through PET wood-plastic composite extrusion equipment, the PET wood-plastic composite extrusion equipment is provided with control equipment, main extrusion equipment, auxiliary extrusion equipment and a die head for connecting the main extrusion equipment and the auxiliary extrusion equipment together, and the main extrusion equipment is provided with power equipment, a transmission shaft, a machine barrel, a heating device, a feed hopper, a bracket and a platform base; the power equipment is positioned on the platform base, a screw is arranged in the machine barrel, one end of the transmission shaft is connected with the screw, the other end of the transmission shaft is fixedly connected with the power equipment, and the heating device is wrapped on the periphery of the machine barrel; the power equipment is positioned at one end of the main extrusion equipment, which is provided with a transmission shaft, the other end of the main extrusion equipment is sequentially provided with a mixing section, a melting section, a homopolymerization section, a foaming agent injection section, a foaming section and a mixed cooling section, a die head is connected outside the mixed cooling section of the main extrusion equipment, and the feed hopper is positioned at the mixing section of the main extrusion equipment;

the auxiliary extrusion equipment is provided with a power machine, a transmission rod, a threaded inner rod, a reaction cylinder, a heating device, an auxiliary material inlet hopper and a support, the auxiliary extrusion equipment is fixed on the ground through the support, the power machine is connected with the threaded inner rod through the transmission rod, the reaction cylinder wrapping the threaded inner rod is arranged outside the threaded inner rod, the heating device is arranged outside the reaction cylinder, and the auxiliary material inlet hopper is positioned on the upper portion, close to one end of the power machine, of the reaction cylinder; the auxiliary extrusion equipment is connected with the side surface of the die head, and auxiliary materials processed by the auxiliary extrusion equipment are converged into the die head; the main extrusion equipment is also provided with a foaming agent feeding hole, and the foaming agent feeding hole is positioned in a foaming agent injection section of the main extrusion equipment; injecting the blowing agent and the plasticizer into the blowing agent feed port.

Preferably, the heating device comprises an upper arc-shaped heating sheet and a lower arc-shaped heating sheet, and the upper arc-shaped heating sheet and the lower arc-shaped heating sheet are fixedly connected with the machine barrel or the reaction barrel through connecting pieces; the heating device is at least provided with a heating socket and a temperature detecting hole, and a heating power supply device is arranged at the heating socket and is electrically connected with the control equipment; and a temperature detector is arranged at the temperature probing hole and transmits a temperature signal to the control equipment.

Preferably, the extrusion processing can be carried out discontinuously by the main extrusion device, and the auxiliary extrusion device is not interrupted during the discontinuous extrusion processing of the main extrusion device; during the discontinuous period of the extrusion processing of the main extrusion device, the material extruded by the auxiliary extrusion device seals the end of the wood-plastic composite product with the PET sandwich structure due to the fluidity of the fluid.

Preferably, the die head is provided with a main input end, an auxiliary input port and an output end, and the main input end is connected with the mixing and cooling section of the main extrusion equipment; the main input end of the die head is provided with an interface boss, the interface boss comprises an annular base body and an annular convex part, the annular base body and the annular convex part are integrally connected, the annular base body is connected with a machine barrel, the annular convex part is connected with a conical structure, a PET channel is arranged in the conical structure in a hollow mode, a flow groove and a contraction surface are arranged outside the conical structure, a die head shell capable of being tightly combined is sleeved outside the conical structure, the die head shell is hollow in the interior and provided with an inner wall capable of being obliquely reduced towards the direction of an output end, at least part of positions between the flow groove and the die head shell are not in contact with each other, the contraction surface and the die head shell are not in contact with each other, and a WPC channel is formed; the WPC channel forms a wrapping at least in part of the position outside the PET channel; the die head shell is provided with the auxiliary input port, and the auxiliary input port is communicated with the launder to form an auxiliary material channel.

Preferably, the tapered structure comprises a plurality of nested cones, and at least a first cone and a second cone; the second taper body is provided with a second flow groove and a second contraction surface, at least part of the second flow groove is not in mutual contact with the first taper body, the second contraction surface is not in mutual contact with the first taper body, and a second WPC channel is formed among the second flow groove, the second contraction surface and the inner wall of the first taper body; the number of the auxiliary extrusion devices is at least two; the number of the auxiliary input ports on the die head shell is at least two, and at least one auxiliary input port is communicated with the first cone and the second flow groove to form a second auxiliary material channel.

Compared with the prior art, the density of the wood-plastic composite material product with the PET sandwich structure is reduced, the mechanical property of screw holding force is improved, the macroscopic mechanical property and the buffering property are better, the durability is improved in the using process, the service life of the product is prolonged, the appearance performance is improved, the raw material cost and the manufacturing cost are reduced, the material is easier to process and modify on the whole, and the designability of the product is enhanced. The wood-plastic composite product with the PET sandwich structure has light weight and high strength, improves the comprehensive mechanical property, realizes the excellent use of inferior materials, increases the added value of products and widens the application of the wood-plastic composite in the fields of building engineering and building parts.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

FIG. 1 is a schematic structural diagram of a wood-plastic composite product with a PET sandwich structure in the invention;

FIG. 2 is an overall schematic diagram of the PET wood-plastic composite material extrusion device in the invention;

FIG. 3 is a schematic side view of the PET wood-plastic composite extrusion device of the present invention;

FIG. 4 is a schematic perspective view of a PET wood-plastic composite extrusion apparatus;

FIG. 5 is a schematic disassembly diagram of a die head in the PET wood-plastic composite extrusion device;

FIG. 6 is an overall schematic view of a PET wood-plastic composite extrusion apparatus;

FIG. 7 is a schematic drawing showing the mold head disassembled in an apparatus embodying the present invention;

fig. 8 is a schematic disassembled view of the die head in the apparatus of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1:

the wood-plastic composite product with the PET sandwich structure comprises a wood-plastic composite section and accessories, wherein the wood-plastic composite section is prepared by an extrusion process, the wood-plastic composite section also comprises at least one foamed PET sandwich synchronously prepared by the extrusion process, and the periphery of the foamed PET sandwich is coated by the wood-plastic composite; the wood-plastic composite material section bar is connected with accessories, and the accessories comprise one or more of connecting pieces, handles, locking pieces, sliding rails, glass, sealing pieces and buffering pieces.

The section shape of the foaming PET sandwich is one of a rectangle, a rounded rectangle or a regular hexagon, the number of the foaming PET sandwich is at least three, and the foaming PET sandwich is evenly distributed on the cross section of the wood-plastic composite material section along the width direction; after the wood-plastic composite section is formed through an extrusion process, performing routing machining on the surface of the wood-plastic composite section by using a computer machining center to obtain an embedding opening, wherein the embedding opening penetrates or semi-penetrates the wood-plastic composite section, a mirror or glass is embedded in the embedding opening, and the mirror or the glass is sealed in the wood-plastic composite section through a sealing element; the engraving and milling processing is carried out in the middle of the cross section width direction of the wood-plastic composite material section, and the foamed PET sandwich at two ends is not damaged at least.

The formula of the wood-plastic composite material section comprises PET resin, wood powder, a coupling agent, a foaming agent, a nucleating agent, a plasticizer and sodium carboxymethyl cellulose, wherein: the weight percentage of the wood powder is 45-65%; the weight percentage of the PET resin is 15-39%; the weight percentage of the foaming agent is 4-8%; the weight percentage of the coupling agent is 1.5-4%.

Example 2:

modified wood flour was prepared as follows: taking straw powder with the particle size of 170-190 microns, carrying out heat treatment drying at 100 ℃, extracting with acetone, and drying for later use; diluting thermosetting phenolic resin with water, adding the wood powder, performing ultrasonic treatment in an ultrasonic cleaner at room temperature for 30min, centrifuging at a rotation speed of 1200 r/min for 5min, and performing heat treatment on the centrifuged filtrate at 128 ℃ for 45min to obtain the modified wood powder, wherein the weight of the wood powder is 0.8 times of that of the thermosetting phenolic resin. Taking three parts of the obtained modified wood powder, respectively heating to 250 ℃, 350 ℃ and 600 ℃ in a high-purity nitrogen atmosphere of 100mL/min, and preserving the heat for 30min for pyrolysis, wherein the carbon residue rates are detected to be 85.9%, 78.3% and 64.1% respectively.

Modified wood flour was prepared as follows: taking poplar powder with the particle size of 170-190 microns, carrying out heat treatment drying at 105 ℃, extracting with acetone, and drying for later use; diluting thermosetting phenolic resin with water, adding the wood powder, performing ultrasonic treatment in an ultrasonic cleaner at room temperature for 30min, centrifuging at a rotation speed of 1200 r/min for 5min, and performing heat treatment on the centrifuged filtrate at 128 ℃ for 45min to obtain the modified wood powder, wherein the weight of the wood powder is 0.8 times of that of the thermosetting phenolic resin. Taking three parts of the obtained modified wood powder, respectively heating to 250 ℃, 350 ℃ and 600 ℃ in a high-purity nitrogen atmosphere of 100mL/min, and carrying out pyrolysis for 30min, wherein the carbon residue rates are detected to be 87.5%, 76.1% and 63.5% respectively.

Example 3:

referring to fig. 1, fig. 2, fig. 3 and fig. 4, in the wood-plastic composite product with a PET sandwich structure according to the present embodiment, the extrusion process is completed by a PET wood-plastic composite extrusion device, the PET wood-plastic composite extrusion device includes a control device 1, a main extrusion device 2, an auxiliary extrusion device 3, and a die head 4 connecting the main extrusion device 2 and the auxiliary extrusion device 3 together, the main extrusion device 2 includes a power device 21, a transmission shaft 22, a cylinder 23, a heating device 24, a feeding hopper 25, a bracket 27 and a platform base 28; the power device 21 is positioned on the platform base 28, a screw is arranged in the machine barrel 23, one end of the transmission shaft 22 is connected with the screw, the other end of the transmission shaft is fixedly connected with the power device 21, and the heating device 24 is wrapped on the periphery of the machine barrel 23; the power equipment 21 is positioned at one end of the main extrusion equipment 2, which is provided with the transmission shaft 22, the other end of the main extrusion equipment 2 is sequentially provided with a mixing section, a melting section, a homopolymerization section, a foaming agent injection section, a foaming section and a mixing cooling section, the mixing cooling section of the main extrusion equipment 2 is externally connected with a die head 4, and the feed hopper 25 is positioned at the mixing section of the main extrusion equipment 2;

the auxiliary extrusion equipment 3 is provided with a power machine 31, a transmission rod 32, a threaded inner rod, a reaction cylinder 33, a heating device 24, an auxiliary material inlet hopper 34 and a support 27, the auxiliary extrusion equipment 3 is fixed on the ground through the support 27, the power machine 31 is connected with the threaded inner rod through the transmission rod 32, the threaded inner rod is externally provided with the reaction cylinder 33 wrapping the threaded inner rod, the reaction cylinder 33 is externally provided with the heating device 24, and the auxiliary material inlet hopper 34 is positioned on the upper part of the reaction cylinder 33, which is close to one end of the power machine 31; the auxiliary extrusion device 3 is connected with the side surface of the die head 4, and auxiliary materials processed by the auxiliary extrusion device 3 are gathered into the die head 4. It should be noted that, the foamed PET wood-plastic composite material with a sandwich structure can be manufactured by using the main extruder and the auxiliary extruder of the embodiment in combination, and a multi-layer structure can be generated, and different materials can be added at different layers to achieve multiple effects of the composite material. For example, recycled plastic can be used as a substrate in the innermost layer, a reinforcing material can be used for improving the strength stability of the middle layer, and pigment is added in the outer layer, so that the cost can be reduced and the appearance is attractive.

The heating device 24 comprises an upper arc-shaped heating piece 24A and a lower arc-shaped heating piece 24B, and the upper arc-shaped heating piece 24A and the lower arc-shaped heating piece 24B are fixedly connected with the machine barrel 23 or the reaction barrel 33 through a connecting piece 24C; the heating device 24 at least has a heating socket 241 and a temperature probe hole 242, a heating power supply 243 is arranged at the heating socket 241, and the heating power supply 243 is electrically connected with the control device 1; a temperature detector 244 is provided at the temperature detection opening 242, and the temperature detector 244 transmits a temperature signal to the control device 1. It should be noted that, the heating device structure provided by this embodiment can be tightly connected with the barrel of the extruder, and the heating speed is fast and uniform.

Referring to fig. 4, a wood-plastic composite product with a PET sandwich structure according to an embodiment of the present invention is different from the foregoing embodiment in that the control device 1 at least includes a first control box 11 and a second control box 12, the first control box 11 controls heating temperatures of the power device 21 of the main extrusion device 2 and the heating device 24 on the main extrusion device 2, and the second control box 12 controls heating temperatures of the power machine 31 of the auxiliary extrusion device 3 and the heating device 24 on the auxiliary extrusion device 3; the side surfaces of the outer walls of the first control box 11 and the second control box 12 are respectively provided with a transmission port 111 and an aviation plug 112, the outsides of the first control box 11 and the second control box 12 are respectively provided with a temperature display, a temperature control button, a power display, a power control switch and a control switch of power equipment, and the temperature display and the temperature control button are in one-to-one correspondence with the aviation plug. It should be noted that, the control device provided by this embodiment can avoid the leakage of the electric wire, and realize the neat and well-controlled function. In addition, the running and heating conditions of the power equipment and the heating device can be accurately controlled by arranging a plurality of displays and control buttons.

Example 4:

referring to fig. 1, fig. 2, fig. 3, fig. 5 and fig. 6, a wood-plastic composite product with a PET sandwich structure according to an embodiment of the present invention is different from the foregoing embodiments in that the platform base 28 is stepped, the power device 21 is fixed at a higher position of the stepped platform base 28 by a screw or a welding method, and other parts of the main extrusion device 2 are fixed at a lower position of the stepped platform base 28 by a bracket 27; the power device 21 is an electric motor or a hydraulic motor. It should be noted that, the platform base with such a structure can stably fix the main extruder to enhance the safety of the main extruder.

Example 5:

referring to fig. 4, fig. 6, fig. 7 and fig. 8, in another wood-plastic composite product with a PET sandwich structure according to an embodiment of the present invention, the die head 4 has a main input end 4a, an auxiliary input end 4b and an output end 4c, and the main input end 4a is connected to the mixing and cooling section of the main extrusion device 2; the main input end 4a of the die head 4 has an interface boss 41, the interface boss 41 includes an annular base 411 and an annular protrusion 412, the annular base 411 is integrally connected with the annular protrusion 412, the annular base 411 is connected with the cylinder 23, the annular convex part 412 is connected with the conical structure 42, the conical structure 42 is internally hollow and is provided with a PET channel 421, the outer part of the conical structure is provided with a flow groove 422 and a contraction surface 423, the conical structure 42 is externally sleeved with a die shell 43 which can be tightly combined, the interior of the die shell 43 is hollow, the inner wall 431 with the inclination decreasing towards the output end 4c is arranged, at least a portion of the flow channels 422 and the die housing 43 are not in contact with each other, the converging surface 423 and the die housing 43 are not in contact with each other, WPC channel 424 is formed between the flow slot 422, constriction 423 and inner wall 431 of die housing 43; the WPC channel 424 forms a wrap at least in a partial position outside the PET channel 421; the die head shell 43 is provided with the auxiliary input port 4b, and the auxiliary input port 4b is communicated with the flow groove 422 to form an auxiliary material channel 432. It should be noted that the die head structure provided by the present embodiment is unique, and the main extruder and the auxiliary extruder can be simply and quickly connected together by using the die head. The channel 424 is a flow channel of an auxiliary extruder, the extruded substance passes through the PET channel 421 first, and then passes through the channel 424, and the substance coming out of the channel 424 can cover the substance coming out of the PET channel 421 to form a two-layer structure.

Wherein the tapered structure 42 comprises a plurality of nested cones, and comprises at least a first cone 42a and a second cone 42 b; second runner 425 and second converging surface 426 are formed on second conical body 42b, at least a portion of second runner 425 and first conical body 42a are not in contact with each other, second converging surface 426 and first conical body 42a are not in contact with each other, and second WPC channel 427 is formed between second runner 425, second converging surface 426 and the inner wall of first conical body 42 a; the number of the auxiliary extrusion devices 3 is at least two; at least two auxiliary inlets 4b are provided on the die housing 43, and at least one of the auxiliary inlets 4b is communicated with the first cone 42a and the second runner 425 to form a second auxiliary material channel 433. It should be noted that another auxiliary extruder can be connected to the entire runner through the second runner 425 and the second WPC channel 427 of this embodiment, so as to realize layer-by-layer cladding of the composite material.

Referring to fig. 4, an embodiment of the present invention provides a wood-plastic composite product with a PET sandwich structure. The PET wood-plastic composite extrusion equipment is different from any one of the embodiment 4 and the embodiment 5 in that a die body 45 is arranged on one side of the die head shell 43 close to the output end 4c, the die body 45 is tightly combined with the die head shell 43, and a coating channel 451 is arranged between the die head body 45 and the conical structure 42; a hollow spindle-shaped die tongue body 46 is arranged in the PET channel 421, and a part of the outer side wall of the spindle-shaped die tongue body 46 is tightly connected with the inner wall of the conical structure 42; a die lip body 47 is embedded in the die opening body 45, and a coating layer channel 48 is arranged between the die lip body 47 and the spindle-shaped die tongue body 46 as well as between the die opening body 45; a hollow groove-shaped structure 49 is arranged at the output end 4c of the die head 4, and the hollow groove-shaped structure 49 is connected with the die opening body 45 and limits the position of the die lip body 47; the die tongue body 46 and the die lip body 47 can be replaced according to the requirement. It should be noted that the structure provided in this embodiment realizes a process of merging substances from the main extruder and the auxiliary extruder into a whole and performing cooling molding.

Referring to fig. 8, an embodiment of the present invention provides a wood-plastic composite product with a PET sandwich structure. The extrusion equipment for the PET wood-plastic composite material is different from any one of the embodiment 5 and the embodiment 6 in that the hollow first conical body 42a is connected with the die head shell 43, the end part of the first conical body 42a is provided with a circular ring-shaped bulge 428, and the circular ring-shaped bulge 428 is connected with the circular ring-shaped convex part 412; a hole c is arranged between the middle position of the inclined surface of the first conical body 42a and the inclined surface of the die head shell 43; connected with the first taper body 42a is a hollow second taper body 42b, the slope of the second taper body 42b is gentler than that of the first taper body 42a, the end part of the second taper body 42b is provided with a circular ring shaped recess, and a pore canal d is arranged between the middle upper position of the slope of the second taper body 42b and the slope of the first taper body 42 a; the spindle-shaped die tongue body 46 is provided inside the second taper body 42 b; the inner wall of the second taper 42b near the output end 4c has a gradually widened slope, and the spindle die tongue 46 has a long side end and a short side end, and the gradually widened slope is in close contact with the long side end of the spindle die tongue 46. The duct c and the duct d are runners of the auxiliary extruder.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A preparation method of a wood-plastic composite product with a PET sandwich structure is characterized by comprising the following steps: the wood-plastic composite material is composed of a wood-plastic composite material section and accessories, wherein the wood-plastic composite material section is prepared through an extrusion process, the wood-plastic composite material section also comprises at least one foamed PET sandwich synchronously prepared through the extrusion process, and the periphery of the foamed PET sandwich is coated by the wood-plastic composite material; the wood-plastic composite material section bar is connected with accessories, and the accessories comprise one or more of connecting pieces, handles, locking pieces, sliding rails, glass, sealing pieces and buffering pieces;

the formula of the wood-plastic composite material section comprises PET resin, wood powder, a coupling agent, a foaming agent, a nucleating agent, a plasticizer and sodium carboxymethyl cellulose, wherein: the weight percentage of the wood powder is 45-65%; the weight percentage of the PET resin is 15-39%; the weight percentage of the foaming agent is 4-8%; the weight percentage of the coupling agent is 1.5-4%;

the wood powder is modified wood powder, and the preparation method comprises the following steps:

B. adding water to dilute thermosetting phenolic resin, adding the wood powder obtained in the step A, wherein the weight of the wood powder is 0.5-1 time of that of the thermosetting phenolic resin, performing ultrasonic treatment in an ultrasonic cleaner at room temperature for 25-35 min, performing centrifugal filtration at a centrifugal rotation speed of 1000-1300 r/min for 3-5 min, and performing heat treatment on the centrifuged filtrate at 125-130 ℃ for 0.5-1 h to obtain modified wood powder;

the extrusion process is completed through PET wood-plastic composite extrusion equipment, the PET wood-plastic composite extrusion equipment is provided with control equipment, main extrusion equipment, auxiliary extrusion equipment and a die head for connecting the main extrusion equipment and the auxiliary extrusion equipment together, and the main extrusion equipment is provided with power equipment, a transmission shaft, a machine barrel, a heating device, a feed hopper, a support and a platform base; the power equipment is positioned on the platform base, a screw is arranged in the machine barrel, one end of the transmission shaft is connected with the screw, the other end of the transmission shaft is fixedly connected with the power equipment, and the heating device is wrapped on the periphery of the machine barrel; the power equipment is positioned at one end of the main extrusion equipment, which is provided with a transmission shaft, the other end of the main extrusion equipment is sequentially provided with a mixing section, a melting section, a homopolymerization section, a foaming agent injection section, a foaming section and a mixed cooling section, a die head is connected outside the mixed cooling section of the main extrusion equipment, and the feed hopper is positioned at the mixing section of the main extrusion equipment; the auxiliary extrusion equipment is provided with a power machine, a transmission rod, a threaded inner rod, a reaction cylinder, a heating device, an auxiliary material inlet hopper and a support, the auxiliary extrusion equipment is fixed on the ground through the support, the power machine is connected with the threaded inner rod through the transmission rod, the reaction cylinder wrapping the threaded inner rod is arranged outside the threaded inner rod, the heating device is arranged outside the reaction cylinder, and the auxiliary material inlet hopper is positioned on the upper portion, close to one end of the power machine, of the reaction cylinder; the auxiliary extrusion equipment is connected with the side surface of the die head, and auxiliary materials processed by the auxiliary extrusion equipment are converged into the die head; the main extrusion equipment is also provided with a foaming agent feeding hole, and the foaming agent feeding hole is positioned in a foaming agent injection section of the main extrusion equipment; injecting the blowing agent and the plasticizer into the blowing agent feed port;

the heating device comprises an upper arc-shaped heating sheet and a lower arc-shaped heating sheet, and the upper arc-shaped heating sheet and the lower arc-shaped heating sheet are fixedly connected with the machine barrel or the reaction barrel through connecting pieces; the heating device is at least provided with a heating socket and a temperature detecting hole, and a heating power supply device is arranged at the heating socket and is electrically connected with the control equipment; a temperature detector is arranged at the temperature detecting hole and transmits a temperature signal to the control equipment;

the main extrusion equipment can perform extrusion processing discontinuously, and the auxiliary extrusion equipment is not interrupted during the discontinuous extrusion processing of the main extrusion equipment; during the discontinuous period of the extrusion processing of the main extrusion equipment, the end of the wood-plastic composite product with the PET sandwich structure is closed by the material extruded by the auxiliary extrusion equipment due to the fluidity of the fluid;

the die head is provided with a main input end, an auxiliary input port and an output end, and the main input end is connected with the mixed cooling section of the main extrusion equipment; the main input end of the die head is provided with an interface boss, the interface boss comprises an annular base body and an annular convex part, the annular base body and the annular convex part are integrally connected, the annular base body is connected with a machine barrel, the annular convex part is connected with a conical structure, a PET channel is arranged in the conical structure in a hollow mode, a flow groove and a contraction surface are arranged outside the conical structure, a die head shell capable of being tightly combined is sleeved outside the conical structure, the die head shell is hollow in the interior and provided with an inner wall capable of being obliquely reduced towards the direction of an output end, at least part of positions between the flow groove and the die head shell are not in contact with each other, the contraction surface and the die head shell are not in contact with each other, and a WPC channel is formed; the WPC channel forms a wrapping at least in part of the position outside the PET channel; the die head shell is provided with the auxiliary input port, and the auxiliary input port is communicated with the launder to form an auxiliary material channel;

the conical structure comprises a plurality of nested shapes and at least comprises a first conical shape and a second conical shape; the second taper body is provided with a second flow groove and a second contraction surface, at least part of the second flow groove is not in mutual contact with the first taper body, the second contraction surface is not in mutual contact with the first taper body, and a second WPC channel is formed among the second flow groove, the second contraction surface and the inner wall of the first taper body; the number of the auxiliary extrusion devices is at least two; the number of the auxiliary input ports on the die head shell is at least two, and at least one auxiliary input port is communicated with the first cone and the second flow groove to form a second auxiliary material channel.

2. The method for preparing a wood-plastic composite product with a PET sandwich structure according to claim 1, wherein the cross-sectional shape of the foamed PET sandwich is one of rectangle, rounded rectangle or regular hexagon, the number of the foamed PET sandwich is at least three, and the foamed PET sandwich is evenly distributed on the cross section of the wood-plastic composite profile along the width direction; after the wood-plastic composite section is formed through an extrusion process, performing routing machining on the surface of the wood-plastic composite section by using a computer machining center to obtain an embedding opening, wherein the embedding opening penetrates or semi-penetrates the wood-plastic composite section, a mirror or glass is embedded in the embedding opening, and the mirror or the glass is sealed in the wood-plastic composite section through a sealing element; the engraving and milling processing is carried out in the middle of the cross section width direction of the wood-plastic composite material section, and the foamed PET sandwich at two ends is not damaged at least.

3. The preparation method of the wood-plastic composite product with the PET sandwich structure according to claim 1, characterized in that: the plasticizer is one or more of dioctyl phthalate, acrylic acid and dibutyl phthalate;

the foaming agent is a composite foaming agent of azodicarbonamide, bicarbonate and citric acid, wherein the weight of the azodicarbonamide is 2-3% of that of the PET wood-plastic composite material;

the coupling agent is one or more of isocyanate, modified aminosilane and vinyl silane;

the wood powder is one or more of spruce wood powder, poplar wood powder and pine wood powder;

the nucleating agent is selected from one or more of talcum powder, calcium carbonate, nano montmorillonite, titanium dioxide and silicon dioxide;

the PET wood-plastic composite material optionally further comprises a foaming auxiliary agent, a mildew preventive or a flame retardant;

the foaming auxiliary agent is selected from one or more of nano zinc oxide, zinc carbonate, citric acid, zinc acetate and glycerol.