A kind of method for preparing wood plastic composite through heat treated vegetable fibre and plastic blend
Technical field
The present invention relates to the wood and plastic composite preparation method for material, be specifically related to a kind of preparation method by the wood plastic composite that forms through heat treated vegetable fibre and plastic blend.
Background technology
Wood plastic composite (Wood Plastic Composites, be called for short WPC), be the type material that utilizes sponge such as wood powder, bamboo powder, rice husk, straw etc. and macromolecule resin matrix such as PE (polyethylene), PP (polypropylene), PS (polystyrene), PVC (polyvinyl chloride), PET (polyethylene terephthalate), ABS (acrylonitrile-styrene-butadienecopolymer), PA (nylon) etc. to be composited.Wood plastic composite has the advantage of timber and plastics concurrently, it has better water absorption resistance, ageing resistance and anti-warpage properties than traditional timber, and cost is lower than pure timber or plastics, can be widely used in war industry (as gun stock, gun rack etc.), light industry (as furniture, artwork etc.), building industry (as floor, backing plate, various finishing with lines etc.) and timber industry etc.The appearance of wood plastic composite, make the waste and the waste or used plastics of timber be fully utilized, both can improve timber utilization rate effectively, alleviate China's Forest Resources poorness, wood supply contradiction in short supply, can reduce again because the environmental pollution of using plastics to bring.
But also there are some problem demanding prompt solutions in wood plastic composite, interface compatibility as wood powder and plastics is bad, especially the water tolerance of matrix material is not high, easy warpage, dimensional stability is relatively poor, can not satisfy the use needs of some material, as bathroom floor, wrapping material, outdoor architecture finishing material etc., result of use and life-span can be subjected to remarkably influenced.
For wood plastic composite, the method for improving vegetable fibre and Compatibility in Plastics mainly contains the pre-treatment of the modification of vegetable fibre, plastics and adds three kinds of methods of interface modifier.The modification of wood fibre can be adopted the chemical structure that changes the vegetable fibre surface, thereby improve the bonding interface of fiber and matrix resin, as Mierocrystalline cellulose etc. is carried out grafting, the homopolymer of some vinyl monomer on cellulosic surface grafting, can improve wetting property, water-absorbent, cementability of material etc., thereby improve the dispersiveness of fiber in matrix, improve the consistency of fiber and hydrophobic polymer, reach the purpose of the mechanical property that improves matrix material.Pre-treatment to plastics is to change its polarity by introduce polar group on matrix resin, makes the polarity of plastics and xylon close, thereby improves both consistencies, and method commonly used is to handle polymkeric substance with maleic anhydride graft.Interface modifier can reduce the interfacial tension of out-phase storeroom, strengthen interface binding power, thereby raising performance of composites, with more interface modifier be organic coupling agent, its can with polar functional group in the vegetable fibre (mainly be-OH) reacting forms covalent linkage or hydrogen bond, simultaneously, organic coupling agent can pass through the grafting, copolymerization and modification polymeric matrix, thereby produces strong interface bonding or take place crosslinked.All there is this problem of great amount of hydroxy group in the method for improving vegetable fibre and Compatibility in Plastics at wood fibre and proposes.These methods all have certain effect to the solution of hydroxyl problem, but because hydroxyl quantity is huge in the vegetable fibre, it is bad that present technology still can't solve interface compatibility fully, and especially the water tolerance of matrix material is not high, dimensional stability is relatively poor, use easily produces and goes mouldy and problem such as warpage.Moreover in the modification of wood fibre, methods such as pre-treatment, all to use chemical reagent to plastics, increased virtually in the matrix material processing to the problem that influences of environment and composite finished product this in use and discard after environmental issue.Therefore, adopt treatment process non-chemically, solve wood fibre and have this problem of great amount of hydroxy group, will fundamentally provide a kind of new approach for the interface compatibility that solves wood plastic composite and the water tolerance of matrix material.
With regard to the timber heat treatment technics, Ou Zhou France, Finland, these four countries of Germany and Holland adopt high temperature anoxic mode that raw material timber is handled in recent years, with destruction or in conjunction with the hydroxyl in the timber, and then the water absorbability of reduction timber, improve Wood Dimensional Stability and wearing quality, and reached the purpose of corrosion resistant.Yet relevant report is not seen in the processing that the timber heat treatment technics is applied to the wood plastic composite raw material as yet.
Summary of the invention
Purpose of the present invention is exactly that will to overcome the interface compatibility of wood powder and plastics bad, especially the water tolerance of matrix material is not high, easy warpage, the problem that dimensional stability is relatively poor, can destroy the principle of the part of hydroxyl in the vegetable fibre according to thermal treatment, under anoxia condition, vegetable fibre is heat-treated certain hour at 140~350 ℃, carry out the compound novel wood-plastic matrix material that obtains with thermoplastics again, the matrix material of preparation has advantages such as water-intake rate is low, intensity is high, modulus is big, dimensional stability is good.
Purpose of the present invention realizes by following proposal:
1, vegetable fibre is pulverized, 20~120 orders sieve and make the vegetable fibre powder.Place pyrolysis oven through the comminuted plants fiber dust, adopt under the anoxia condition and heat-treat, be prepared into the modified plant fibers powder.Heat treatment time is 0.5~24h, and temperature is 140~350 ℃, and preferred range is 180~250 ℃.
2, modified plant fibers powder and plastics, lubricant, softening agent, stablizer, compatilizer mix under high-speed stirring and make mixture.The rotating speed of stirrer is 1800~8000r/min, mixing time 10~15min.The raw material that is added by weight, each component is: 10~70 parts of modified plant fibers, 20~70 parts in plastics, 0.5~10 part of lubricant, 0~10 part of coupling agent, 1~10 part of compatilizer, 0.5~10 part in softening agent, 0~50 part of reinforcing filler.
3, mixture is reacted in twin screw extruder extrude.The screw rod melt temperature is 150~200 ℃, and the residence time of mixture in screw rod is 5~12min.
4, after the cooling of the material extruded, obtain pellet or the per os mould directly is extruded into goods through the dicing machine pelletizing.
Employing anoxia condition of the present invention is meant a kind of or arbitrary combination between them in secluding air condition, nitrogen protection atmosphere or the high-temperature vapor atmosphere.
Plastics of the present invention are PE (polyethylene), PP (polypropylene), PS (polystyrene), PVC (polyvinyl chloride), PET (polyethylene terephthalate) or ABS (acrylonitrile-styrene-butadienecopolymer), PA (nylon), and the mixture of any one or wherein several arbitrary proportion that comprises the plastics recovery material of above-mentioned plastics variety.
Vegetable fibre powder of the present invention is a kind of or wherein several arbitrary proportion mixture in wood powder, bamboo powder, shell powder, straw powder, litter shell powder, peanut hull meal or the bagasse.
Lubricant of the present invention is polyethylene wax, whiteruss, silicone oil, oleic acid, oleylamide, hard acid amides, quadrol, bis-stearamides, butyl stearate, glyceryl monostearate or N, a kind of or wherein several arbitrary proportion mixture in the two ethylene stearic amides of N-.
Coupling agent of the present invention is titanate coupling agent or silane coupling agent.
Compatilizer of the present invention is a kind of or wherein several arbitrary proportion mixture in maleic anhydride grafted polyethylene, maleic anhydride inoculated polypropylene, ethylene-ethyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), polyolefin elastomer (POE), terpolymer EP rubber (EPDM), styrene-butadiene copolymer (SBS), Hydrogenated SBS multipolymer (SEBS) or the styrene-isoprene block copolymer (SIS).
Softening agent of the present invention is stearic acid or stearates, comprise Zinic stearas (ZnSt), calcium stearate (CaSt), barium stearate etc., diethyl phthalate (DOP), dibutyl maleate, tributyl acetylcitrate (ATBC), oxidic polyethylene, polyurethane plasticizer or Polyurethane Plasticizer, or the mixture of forming by them.
Reinforcing filler of the present invention comprises common used filling additive in the modifying plastics processing, and as lime carbonate, talcum powder, flyash, industrial slag etc., preferable particle size is 5~40 μ m.
Remove above-mentioned describedly, use needs according to complete processing and product, the wood plastic composite of above-mentioned preparation can add some other auxiliary agents man-hour adding, as oxidation inhibitor, and stablizer, whipping agent, fire retardant etc.
Can pass through prepared in twin-screw extruder wood plastic composite pellet earlier among the preparation method of wood plastic composite of the present invention, adopt modes such as injection moulding, mold pressing to carry out the forming process of wood plastic composite then.
Vegetable fibre powder of the present invention after Overheating Treatment, has reduced hydroxyl quantity, has reduced wetting ability, and dimensional stability is improved.The vegetable fibre powder is in heat treatment process, wherein the loss of polysaccharide mainly is a hemicellulose, hemicellulose is unbodied material, form by two or more glycosyls, contain hydrophilic radical on main chain and the side chain, thereby it is one of component of water absorbability maximum in the vegetable fibre, is to make vegetable fibre produce one of important factor of wet swelling, strain cracking.Vegetable fibre is in high-temperature heat treatment process, some polysaccharide in the hemicellulose is cracked into the split product of alditol and some carbohydrate easily, under the effect of heat, polymerization can take place again and generate water-insoluble polymer in these materials, thereby can reduce the water absorbability of vegetable fibre, improve its dimensional stability and rotproofness.Effects such as degraded also can take place in the cellulosic component in the vegetable fibre in heat treatment process, reduce the wetting ability of vegetable fibre.
Vegetable fibre and polyolefinic interface compatibility after the thermal treatment modification of the present invention improves greatly, the wood plastic composite bending strength of making has improved 50%~150% than matrix, tensile strength has improved 20%~100% than matrix, water-absorbent can reduce by 50%~180% than the water-absorbent of unmodified wood fibre-composite polyethylene material, and the manufacture craft of matrix material is simple, pollution-free, the matrix material color and luster is simple and tasteful, antibiont corrodibility is strong, can make different shapes, satisfy the product of different demands, as furniture, bathroom floor, outdoor seat, toy for children, wrapping material, exterior decoration materials etc., range of application is extremely extensive.
Embodiment
Following embodiment further specifies of the present invention, rather than limits the scope of the invention.
Embodiment 1
1,, makes the size wood powder powder of unanimity relatively after sieving with 120 orders with the wood powder of pulverizing.Place pyrolysis oven through the comminuted plants fiber, heat-treat under the condition of employing starvation, heat treatment time is 12h, and temperature is 250 ℃.
2, get modified wood powder powder 60kg, add LDPE 32kg, oleic acid 2kg, 5 parts of maleic anhydride inoculated polypropylenes, 1 part of white oil, under high-speed stirring, mix and make mixture.The rotating speed of stirrer is 1800r/min, mixing time 10min.
3, mixture is reacted in twin screw extruder extrude, the residence time of mixture in screw rod is 12min.Twin screw extruder adopts the PTW-24 of German HAAKE company, and each section of forcing machine temperature is: 145 ℃, 150 ℃, 155 ℃, 155 ℃, 155 ℃, 155 ℃.
After the material cooling of 4, extruding, obtain pellet through the dicing machine pelletizing.Section bar is pressed into the standard batten respectively according to GB GB/T1040-1992, GB/T9340-2000, GB/T1043-1993, tensile strength, flexural strength and the simple beam impact strength of GB/T1034-1998 test compound material and the water-absorbent of matrix material.The tensile strength of matrix material is 35MPa, and flexural strength is 38MPa, and shock strength is 8kJ/m
2, water-intake rate is 0.17%.
Embodiment 2
1,, makes the size bamboo powder of unanimity relatively after sieving with 20 orders with the bamboo powder of pulverizing.Getting bamboo powder 70kg and place the pyrolysis oven that has agitator, thermometer, is under the stirring at low speed of 400r/min at rotating speed, continues to feed high-temperature vapor and heat-treats, and obtains through heat treated modification bamboo powder.Heat treatment time is 1h, and the high-temperature vapor temperature is 340 ℃.
2, get modified wood powder powder 60kg, add HDPE plastics 50kg, oleic acid 2kg, polyethylene wax 5kg, silane coupling agent K5601.5kg, Zinic stearas 1kg, styrene-butadiene copolymer (SBS) 3kg mixes under high-speed stirring and makes mixture.The rotating speed of stirrer is 6000r/min, mixing time 15min.
3, mixture is reacted in twin screw extruder extrude, the residence time of mixture in screw rod is 5min.Twin screw extruder adopts the PTW-24 of German HAAKE company, and each section of forcing machine temperature is: 165 ℃, 170 ℃, 180 ℃, 185 ℃, 185 ℃, 185 ℃.
After the material cooling of 4, extruding, obtain pellet through the dicing machine pelletizing.Respectively according to GB GB/T1040-1992, GB/T9340-2000, GB/T1043-1993, tensile strength, flexural strength and the simple beam impact strength of GB/T1034-1998 test compound material and the water-absorbent of matrix material.The tensile strength of matrix material is 45MPa, and flexural strength is 50MPa, and shock strength is 4.5kJ/m
2, water-intake rate is 0.37%.
Embodiment 3
1,, makes the size wheat straw powder of unanimity relatively after sieving with 60 orders with the wheat straw powder of pulverizing.Getting wheat straw powder 100kg and place the pyrolysis oven that has agitator, thermometer, is under the stirring at low speed of 400r/min at rotating speed, continues to feed nitrogen and heat-treats, and obtains through heat treated modification wheat straw powder.Heat treatment time is 20h, and temperature is 140 ℃.
2, get modification wheat straw powder 60kg, add PS (polystyrene) plastics 30kg, oleic acid 5kg, polyethylene wax 4kg, titanate coupling agent 1.0kg, Zinic stearas 2kg, styrene-butadiene copolymer (SBS) 7kg mixes under high-speed stirring and makes mixture.The rotating speed of stirrer is 8000r/min, mixing time 15min.
3, mixture is reacted in twin screw extruder extrude, the residence time of mixture in screw rod is 5min.Twin screw extruder adopts the PTW-24 of German HAAKE company, and each section of forcing machine temperature is: 155 ℃, 160 ℃, 165 ℃, 165 ℃, 165 ℃, 165 ℃.
After the material cooling of 4, extruding, obtain pellet through the dicing machine pelletizing.Respectively according to GB GB/T1040-1992, GB/T9340-2000, GB/T1043-1993, tensile strength, flexural strength and the simple beam impact strength of GB/T1034-1998 test compound material and the water-absorbent of matrix material.The tensile strength of matrix material is 48MPa, and flexural strength is 55MPa, and shock strength is 4.9kJ/m
2, water-intake rate is 0.32%.