CN101670607B - Hot-pressing technology for manufacturing board by utilizing crop straws - Google Patents
Hot-pressing technology for manufacturing board by utilizing crop straws Download PDFInfo
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Abstract
The invention relates to hot-pressing technology for manufacturing a board by utilizing crop straws. The hot-pressing process on a board blank comprises a compression stage and a molding stage, wherein a molding temperature set value in the molding stage is lower than a compression temperature set value in the compression stage; and a molding pressure set value in the molding stage is lower than a compression pressure set value in the compression stage. The hot-pressing technology has no technological design of the conventional steam release stage, can solve the problems of board bursting and bubbling in the process of manufacturing the board, save the time, and improve the rate of finished products and processing efficiency.
Description
Technical field:
The present invention relates to the heat pressing process in the manufacturing board by crop straws method, especially relate to the controlled heat pressing process of alternating temperature transformation in a kind of hot pressing.
Background technology:
Scarcity and requirement on environmental protection along with timber resources; the sheet material price that with timber is raw material is more and more expensive; and various countries put into effect a series of laws and regulations that protect forest resources in succession, and the sheet material of therefore seeking new material substitutes certain choosing that the wood-base fibre and particle panel material material becomes the field pattern existence of sheet material city, seeks development.And agricultural crop straw is big with its byproduct as agricultural production, output, and cellulose and lignin content are higher, and become the preferred material that substitutes the wood-base fibre and particle panel material material, so not only can " good and cheap, turn waste into wealth ", and can reduce crop straw burning, reduce deforestation, avoid indoor formaldehyde to pollute, improve people's living standard.Up to the present, the domestic year production capacity of production 23 ten thousand stere agricultural crop straw sheet materials, the external production capacity of producing 200 ten thousand steres in nearly year built up.But, because agricultural crop straw is because of its intrinsic characteristic, for example fiber is short, non-fibrocyte is many, particle is difficult to compression, thermal conductivity factor is lower than factors such as timber, cause the difficulty of processing that the difficulty of processing of crops sheet material is far longer than the wood-base fibre and particle panel material material, not only cost is high but also can only be the flakeboard of low side thereby cause the agricultural crop straw sheet material that processes at present, still can not produce high-quality, high-end middle-high density sheet material.According to present technology, the processing step of making sheet material as raw material with agricultural crop straw generally comprises: the raw material classification, and raw material is just handled, wood shavings preparations (raw material pulverizing), glue mixing is mated formation, hot pressing, pre-treatment and finished product are handled.Wherein, the factor that influences the manufactured goods board quality has a lot, but develops into now, and heat pressing process has become a bottleneck of restriction agricultural crop straw board quality.Referring to Fig. 1, the heat pressing process that adopts roughly can be divided into three phases at present, is respectively slab compression stage A, PMDI (isocyanate glue) reaction cure stage B and low pressure steam discharge stage D.As China Patent No. is that heat pressing process substantially all is to adopt above-mentioned three-phase approach in the processing method of CN200410065859.7, CN200610045348.8, CN200710020632.4, the record of CN200710135199.9 patent.But there are a lot of defectives in this heat pressing process: the one, and the steam discharge time is long, because the thermal conductivity factor of agricultural crop straw is little, no matter be hot pressing or steam discharge, can only be undertaken by water vapour, the steam discharge time is about 1/3rd of whole heat pressing process, thereby causes production efficiency low; The 2nd, slab tends to occur " fried plate " or produces bubbling in the steam discharge process, because the excessive excessive steam that causes of slab sandwich layer moisture content, if exhaust passage is not smooth or velocity of exhaust is too fast, very easily produce this phenomenon, especially more obvious when the higher sheet material of production density, thus cause that product percent of pass descends, cost improves.In present actual production process, people are in order to improve the yield rate of agricultural crop straw sheet material, and often adopting increases resin added in the moisture content that reduces the making sheet raw material.But the sheet material moisture content that adopts this method to produce is low, causes defectives such as the product buckling deformation is serious, hot pressing time length, other physicochemical property difference.Can the key of agricultural crop straw plate production be solve the relation between moisture content, resin added and product quality and the production cost in the agricultural crop straw sheet material production process well; The 3rd, be difficult to overcome the density bottleneck, cause to be difficult to overcome the intensity bottleneck.As mentioned above, because the existence of moisture content and steam discharge problem, cause to produce qualified middle-high density and thick (18mm and more than) agricultural crop straw sheet material, thereby crop stalk sheet material is difficult to break through DENSITY LIMIT causes the sheet material physical and chemical index poor, though make middle-high density sheet material then because cost is too high without any the market competitiveness.Thereby limited the production of middle-high density and thick agricultural crop straw sheet material, caused present agricultural crop straw sheet material can only be used for some low side occasions.
Summary of the invention:
The technical issues that need to address of the present invention are exactly in order to overcome the defective of above-mentioned prior art, heat pressing process step crucial in the agricultural crop straw plate-making method has been carried out new design, thus overcome existing heat pressing process defective, shorten whole process time, reduce cost, improved product quality.
According to a kind of heat pressing process that utilizes manufacturing board by crop straws provided by the invention, the hot pressing that slab is carried out comprises compression stage and formative stage, wherein, forming temperature setting value in formative stage is lower than the compression temperature setting value in compression stage, and the briquetting pressure setting value in formative stage sets value less than the compression pressure in compression stage.
More specifically say also have following technical characterictic according to the heat pressing process of manufacturing board by crop straws that utilizes provided by the invention:
The hot pressing that slab is carried out also comprises the described formative stage temper stage afterwards that is positioned at, wherein, be between forming temperature setting value and the compression temperature setting value in the temperature setting value of temper in the stage, raise once more in the tempering pressure set points of temper in the stage, but be between briquetting pressure setting value and the compression pressure setting value.
The compression temperature that is adopted in described compression stage sets value the heat of the heating platen that makes press to the slab transmission, moisture vaporization in the raw material of slab top layer is transmitted to the slab sandwich layer, thereby heating slab sandwich layer makes the slab core layer temperature reach the required solidification temperature of adhesive; The forming temperature setting value that is adopted in described formative stage makes the heating platen transmission of the heat of slab to press, thereby the slab skin temperature is reduced; The temperature setting value that is adopted in stage in described temper is transmitted the heat of the heating platen of press once more to the slab top layer.
The curve of the briquetting pressure setting value in the described formative stage becomes stepped.
The compression temperature setting value of described compression stage is 170 ℃～240 ℃, and exert pressure for the heating platen of press, make the closed compression of heating platen slab, slab is compressed into the thickness of setting, switches to described formative stage after described slab core layer temperature reaches setting value.
The forming temperature setting value of described formative stage is 80 ℃～160 ℃, after the sandwich layer reaction of described slab is solidified, switches to the described temper stage.
The temperature setting value in described temper stage is 130 ℃～180 ℃, the pressure that imposes on the heating platen of press in this stage raises once more, reach whole pressing cycle technology and set time, sheet material sandwich layer steam pressure and open described press during less than described sheet material internal bond strength, finish whole heat pressing process.
The temperature difference between described forming temperature setting value and the described compression temperature setting value is at 10 ℃-150 ℃.
Based on the thickness of made sheet material, the setting value of a pressing cycle time was by calculating in 10～25 seconds/millimeter.
The compression pressure setting value that puts in described compression stage on the slab is 2.1MPa-4.0MPa.
The briquetting pressure setting value that puts in described formative stage on the slab is 0.5MPa-2.0MPa.
The tempering pressure set points that puts in stage on the slab in described temper is 0.6MPa-2.5MPa.
Before the explanation beneficial effect, the variation that earlier this heat pressing process is changed the heat transfer type that brings describes as principle.
When slab entered press, heating platen just began heat energy is directly passed to slab by the slab top layer.Since the physical characteristic of raw material, the rate of heat addition that these diabatic processes are different according to the thickness needs of slab.In the heat conductive process, because the top layer of slab contacts with metal caul with the press heating platen, so its top layer is heated very soon.Although the very fast temperature that reaches heating platen in plate top layer, the heat-conducting effect of string own is very poor, and the heat of heating platen can not infiltrate the sandwich layer of slab.Therefore the sandwich layer of slab keeps entering the preceding temperature of press.On the other hand, in the process on Fast Heating top layer, because the contained water of raw material itself becomes water vapour and because of the temperature difference between the top layer of heat and the cold sandwich layer, steam moves towards the centre of slab and causes sandwich layer to heat.Quick on the top layer, the abundant heated while, the heating of sandwich layer is hysteresis and limited.
By on learn that the heating of slab sandwich layer mainly is to rely on the moisture that exists in the raw material, the moisture content of raw material is therefore very important to heat pressing process, seems particularly important when particularly producing slab.But the one side that the moisture content in the increase raw material is favourable also has disadvantageous one side.Higher moisture content means when the slab top layer can produce more steam during by Fast Heating, thereby the heat time heating time of sandwich layer has been shortened at this center that just can make steam reach slab quickly, and this is to producing the slab particular importance.But because the top layer of slab is under the high-temperature high-pressure state at this moment, steam can not discharge by the surface of slab, but the edge by slab discharges in the pressures cycle process.Thus, the steam pressure at slab center begins rapidly to rise and reaches a very high pressure.At this moment, if open press, sheet material or layering so, or plate bursting or bubbling.Belong to any situation wherein, made plate all is a scrap.
Therefore, steam the time is to help heat pressing process in beginning, but near pressures cycle when terminal steam be exactly an obstacle to heat pressing process.Common way in the past before press is opened, discharges steam as much as possible.This is by reaching in the terminal adding of pressures cycle one " steam discharges the stage ", and the specific purposes in this stage are before press is opened the steam pressure in the plate to be discharged.In fact, this is by discharging in the sheet material in the press almost all steam pressures, guarantees that press do not open but will keep just enough pressure in this process.This method makes sheet material can discharge water vapour lentamente and helps the edge release of the steam at plate center by sheet material.In present actual production process, the steam discharge stage needs long time usually, and with regard to the wheat stalk plate, the steam discharge stage accounts for about 1/3 of whole pressing cycle at least.In addition,, cause the moisture content in the final products low, influence product quality owing to discharge the stage with the most of steam release in the sheet material at steam.In order to eliminate above-mentioned defective, often the environment health that will spray water or place certain humidity and temperature the sheet material after the hot pressing improves the moisture content of sheet material with this.
Based on above-mentioned discussion, main beneficial effect of the present invention is as follows:
1, the present invention adopts compression stage and formative stage, in this two stages, the temperature and pressure that is adopted is different, at formative stage, make the forming temperature setting value be lower than the compression temperature setting value, cause the temperature that is lower than the slab top layer in the heating platen temperature of this stage press, make of the heating platen transmission of the heat on slab top layer, thereby the slab skin temperature is reduced to press.Therefore, the present invention heats the top layer of slab rapidly at compression stage, makes the water in the slab become steam and mobile to the slab sandwich layer, thereby heat is delivered to sandwich layer, reaches the required solidification temperature of adhesive rapidly.At this moment, switch to formative stage, be lower than the temperature on slab top layer in the heating platen temperature of this stage press, make of the heating platen transmission of the heat on slab top layer to press, thereby the slab skin temperature is reduced, reduced the steam pressure of slab sandwich layer, and the steam pressure that makes the slab sandwich layer is less than the slab internal bond strength.Therefore, the present invention does not have traditional steam and discharges the stage process design, can solve plate bursting and bubbling problem in the board making process, and save time, improves yield rate and working (machining) efficiency.
2, the present invention does not have the steam release stage process design of traditional mask-making technology, be not to discharge slab sandwich layer steam pressure by the discharging steam, therefore, sheet material after the hot pressing still has higher moisture content, thereby overcome the moisture content problem of middle-high density plate, eliminated the restriction that moisture content centering high-density plate and thick plates are brought, process qualified middle-high density plate and/or thick plates when improving finished product sheet material moisture content, make agricultural crop straw sheet material really can substitute middle and high end high-quality wood-base fibre and particle panel material material.
3, the present invention is provided with the temper stage after formative stage, and this stage is similar to the temper in the metal processing, makes the stress distribution of sheet material more even, reduces the distortion of sheet material, can improve finished product accuracy and qualification rate.
4, the present invention adopts compression and moulding and does not have steam and discharge the stage process design, the time that can improve firing rate and reduce whole heat pressing process greatly, can also reduce adhesive use amount, save cost.
Description of drawings:
Fig. 1 is the pressure and temperature of heat pressing process in the prior art and the curvilinear trend figure between the time.
Fig. 2 is pressure and temperature in the heat pressing process of the present invention and the curvilinear trend figure between the time.
Fig. 3 is the structure and the hot conduction orientation schematic diagram of slab in the compression stage of the present invention.
Fig. 4 is the structure and the hot conduction orientation schematic diagram of slab in the formative stage of the present invention.
Fig. 5 is the structure and the hot conduction orientation schematic diagram of temper of the present invention slab in the stage.
The specific embodiment:
Referring to Fig. 2, the heat pressing process that utilizes manufacturing board by crop straws that provides in the present invention, the hot pressing that slab is carried out comprises compression stage and formative stage, wherein, forming temperature setting value in formative stage is lower than the compression temperature setting value in compression stage, and the briquetting pressure setting value in formative stage sets value less than the compression pressure in compression stage.Heat pressing process of the present invention has been abandoned the steam discharge stage in the traditional handicraft, reduces the steam pressure that the slab sandwich layer is assembled by the low temperature moulding stage, has overcome crops and has made suffered density bottleneck and the intensity bottleneck of sheet material as raw material.Solved the low excessively problem that causes board quality to descend of sheet material moisture content after the hot pressing.
The hot pressing that the present invention carries out slab also comprises the described formative stage temper stage afterwards that is positioned at, wherein, be between forming temperature setting value and the compression temperature setting value in the temperature setting value of temper in the stage, raise once more in the tempering pressure set points of temper in the stage, but be between briquetting pressure setting value and the compression pressure setting value.The temper stage is set makes that the stress distribution of sheet material is even, is difficult for deforming.
Wherein, each description of symbols and relevant parameter scope are as follows in the accompanying drawing 2:
The stalk plate density of agricultural crop straw raw material, raw material moisture content, resin added and manufacturing that the time of whole pressing cycle is used according to making sheet, thickness of slab etc. are different and different, a pressing cycle time calculates by the technique initialization value between 10～25 seconds/millimeter according to thickness of slab, and this numerical value is the hot pressing speed of heating platen.
P1 among Fig. 2, P2, P3, P4 are different phase surface pressure setting value (unit pressure setting value) in the pressing cycle, equally the stalk plate density of agricultural crop straw raw material, raw material moisture content, resin added and the manufacturing of using according to making sheet etc. is different and different, wherein, to put on the maximal pressure compression pressure setting value P1 scope on the slab be 2.1～4.0MPa to compression stage.The briquetting pressure setting value P2, the P3 scope that put in described formative stage on the slab are 0.5MPa-2.0MPa.The tempering pressure set points P4 scope that puts in stage on the slab in described temper is 0.6MPa-2.5MPa.Wherein, the curve of the briquetting pressure setting value in the described formative stage becomes stepped, promptly at formative stage a plurality of pressure set points can be set, and makes the pressure reduction progressively that is applied on the sheet material, improves the Forming Quality of sheet material.
T1 among Fig. 2, T2, T3 are the heating platen temperature of different phase press in the pressing cycle, and be temperature required when the heating platen temperature of press is each stage.Wherein, T1 is the heating platen desired temperature of compression stage press, and promptly compression temperature sets value, scope: 170 ℃～240 ℃; T2 is the heating platen desired temperature of formative stage press, i.e. moulding desired temperature, scope: 80 ℃～160 ℃; T3 is the heating platen desired temperature of temper stage pressing cycle press when finishing, i.e. temperature setting value, scope: 130 ℃～180 ℃.
Thereby said here compression temperature setting value is meant to suppressing slab and makes slab top layer Fast Heating and make the moisture vaporization in the material of top layer heat the slab sandwich layer to the sandwich layer transmission, make core layer temperature reach adhesive and be cured required temperature, in compression process, temperature will be controlled within the specific limits.If temperature is too high, then can the carbonization slab, influence board quality.But if temperature is too low, then can prolong the heat time heating time of slab, influence the time of whole heat pressing process.Said forming temperature setting value is meant the temperature in the time of will being lower than high temperature compressed stage, make the heating platen of press and the heat direction of transfer on slab top layer change, sheet material no longer absorbs heat from the heating platen of press, thereby reduce sheet material sandwich layer steam pressure, but the temperature of sandwich layer also to satisfy the adhesive solidification requirement at this moment.Therefore, here said compression temperature setting value is to set according to different material behaviors and adhesive characteristic with the forming temperature setting value, but total thinking is the demand that will guarantee will satisfy in the compression stage temperature compression and heating, to satisfy the heating platen of press and the heat direction of transfer in the slab top layer changes at formative stage, and the steam pressure in the sandwich layer is reduced.In temper stage temperature setting value is the one section transformation temperature that is between forming temperature setting value and the compression temperature setting value.
Each pre-set parameter of the present invention is meant in whole heat pressing process process, the technological requirement parameter in each stage.Might there be error in the actual value of each desired temperature and pressure set points and press, and the size of error depends primarily on the precision of equipment.But must, this error range can't be very big.Each setting value that from press, reads and the setting value basically identical of technological requirement.In the present invention, because the temperature and pressure of heating platen rises or descends and needs the regular hour in the press, even and reach setting value, also can be subjected to the influence of other factors, make setting value fluctuate.Therefore, the alleged setting value among the present invention in compression stage and the formative stage is meant that temperature and pressure reaches certain stable state in this stage, and certain time.Certainly, in order better to reach the purpose of compression and moulding, can set a plurality of setting values sometimes, make the desired temperature of compression stage and the curve of pressure set points become stepped at compression stage.In like manner, also can set a plurality of setting values, make the desired temperature of formative stage and the curve of pressure set points become stepped at formative stage.
Referring to Fig. 3, Fig. 4 and Fig. 5, the arrow among the figure is represented the trend of steam, promptly represents the direction that heat transmits.The present invention is owing to carried out above-mentioned compression temperature setting value and the setting of forming temperature setting value, make in whole heat pressing process process, guarantee that the compression temperature setting value that is adopted makes the heat of the heating platen 9 of press transmit to slab 8 top layers in described compression stage, moisture vaporization in the slab 8 top layer raw materials is transmitted to the slab sandwich layer, thereby heating slab sandwich layer makes the slab core layer temperature reach the required solidification temperature of adhesive; The forming temperature setting value that is adopted in described formative stage makes the heat on slab 8 top layers transmit to the heating platen 9 of press, thereby the slab skin temperature is reduced; The temperature setting value that is adopted in stage in described temper is transmitted the heat of the heating platen 9 of press once more to slab 8 top layers.By the direction of transfer of change heat, thereby sheet material 8 sandwich layer steam pressures are reduced, and need not its thorough discharge in different phase.Therefore, the present invention not only can effectively solve the concentrated problem of steam pressure that exists in the slab sandwich layer, and, make that the sheet material after the hot pressing has higher moisture content, thereby need not to carry out the post-production processing for improving the sheet material moisture content again.The moisture content that this moulding itself is had will will be got well more than the moisture that the later stage adds, and board quality obviously improves.
Whole heat pressing process of the present invention is finished on hot press, specifies each stage of heat pressing process of the present invention below in conjunction with press.
The difference of factors such as the stalk plate density of the agricultural crop straw raw material that described compression stage of the present invention is used according to making sheet, raw material moisture content, resin added and manufacturing, thickness, the technological temperature setting value of the heating platen temperature of control press between 170 ℃～240 ℃, and exert pressure for the heating platen of described press, make the closed compression of heating platen slab, slab is compressed into the thickness of setting, switches to described formative stage after described slab core layer temperature reaches setting value.The compression pressure setting value that the present invention puts in described compression stage on the slab is the technique initialization value between 2.1MPa-4.0MPa.Top layer at this compression stage slab can be heated rapidly in the early stage, its moisture that contains is heated rapidly becomes steam, and the temperature on top layer can be higher than the temperature of sandwich layer, makes steam move to sandwich layer, thereby heat is delivered in the sandwich layer, and sandwich layer is heated.
The difference of factors such as the stalk plate density of the agricultural crop straw raw material that described formative stage of the present invention is used according to making sheet, raw material moisture content, resin added and manufacturing, thickness, control the technological temperature setting value of heating platen temperature between 80 ℃～160 ℃ of described press, this stage imposes on the briquetting pressure setting value of heating platen of described press less than the compression pressure setting value of described compression stage, after the sandwich layer reaction of described slab is solidified, switch to the described temper stage.The briquetting pressure setting value that puts in described formative stage on the slab is the technique initialization value between 0.5MPa～2.0MPa.To reduce the heating platen temperature of press in this low temperature moulding stage, make the heat on slab top layer to the heating platen transmission of press, the steam pressure of slab sandwich layer promptly less than the sheet material internal bond strength, makes steam pressure can not cause damage to sheet material less than the solidification intensity of adhesive.In this stage, the temperature difference between described forming temperature setting value of the present invention and the described compression temperature setting value is at 10 ℃-150 ℃.Preferably at 20 ℃-100 ℃, the heat direction of transfer that is beneficial to so more in the sheet material changes.The temperature fall time that sets value described forming temperature setting value from described compression temperature is 10 seconds-150 seconds, thus the technological requirement of better meeting.
The difference of factors such as the stalk plate density of agricultural crop straw raw material, raw material moisture content, resin added and manufacturing that the described temper stage of the present invention is used according to making sheet, thickness, the technological temperature setting value of the heating platen temperature of control described press when pressing cycle finishes between 130 ℃～180 ℃, selected temperature setting value will be higher than the forming temperature setting value, but is lower than the compression temperature setting value.The pressure that this stage imposes on the heating platen of described press raises once more, reaches whole pressing cycle technology and sets time, sheet material sandwich layer steam pressure and open described press during less than described sheet material internal bond strength, finishes whole heat pressing process.Putting on tempering pressure set points on the slab in stage in described temper is technique initialization value between 0.6MPa-2.5MPa.The described temper stage is similar to the temper in the metal processing, makes that the stress distribution of sheet material is more even, improves the quality of sheet material.Simultaneously, the described later stage in temper stage can raise the heating platen temperature of press, and reaches the compression stage temperature before next pressing cycle begins, thereby fully enhances productivity.
The present invention is applied to above-mentioned heat pressing process in the processing method of utilizing manufacturing board by crop straws, mainly may further comprise the steps:
A, get the raw materials ready, agricultural crop straw is processed processing, prepare required raw material, raw material is evenly mixed with adhesive;
B, paving prefabricating are mated formation mixed raw material, and are pre-pressed into slab;
C, hot pressing making sheet, described heat pressing process adopts above-mentioned heat pressing process, makes the required sheet material of slab typing becoming;
D, post-processed are carried out post-processed to the sheet material after the hot pressing, obtain finished product.
In step a, the moisture content of the raw material of preparation is 7%-17%, and the resin added of adhesive is 2%-20% of an over dry raw material, and wherein adopting the resin added of carbimide (PMDI) adhesive is 2%-8% of over dry raw material.In step c, the moisture content of the sheet material after the hot pressing is 4%-13%.Heat pressing process raw material of the present invention can adopt moisture content any number between 7%-17%, and need not will consider as traditional handicraft the moisture content of raw material, for shortening the steam discharge time moisture content of raw material is controlled at minimum standard.The present invention does not have the design of steam discharge segment process, need not too much to consider the moisture content of raw material, can use different moisture content raw materials, produces the sheet material of different water cut rate.Therefore, the moisture content of the sheet material that the present invention produces is controlled, the requirement of moisture content is produced the sheet material of the corresponding moisture content that is had itself according to product.
Above-mentioned processing method of the present invention is suitable for middle-high density sheet material, especially be fit to the production of agricultural crop straw slab, solved the main problem that exists in the present production process of middle-high density agricultural crop straw slab, making agricultural crop straw produce the middle-high density slab as raw material becomes possibility, and relative cost reduces.
The present invention utilizes the moisture content of the finished product middle-high density sheet material that above-mentioned technology makes 4%-13%, and the density of described sheet material is 600～950Kg/m
3The thickness of described sheet material is 10mm-50mm.Processing method of the present invention goes for the multiple kinds of crops stalk, and is same, also is applicable to the residue of industrial crops.The sheet material that is processed by processing method of the present invention is suitable with the performance of wood-base fibre and particle panel material material, can substitute existing wood-base fibre and particle panel material material fully.
Below in conjunction with above-mentioned heat pressing process and processing method, specifically provide the detailed process that several agricultural crop straws are made into sheet material.
Embodiment 1:
(1) get the raw materials ready:
(place of production: the Chuzhou, Anhui) pulverize through beater grinder, the two screen cloth diameters of pulverizer are respectively 6mm, 6mm to wheat stalk, and the raw material after the pulverizing is removed impurity such as stipes and wheat through pneumatic separation device, and the moisture content that is used for the wheat stalk pulverizing material of making sheet is 12.5%.In mixer, atomizing of carbimide (PMDI) adhesive and wheat stalk are pulverized material evenly mix.Used adhesive is HuntsmanSuprasec5005, and resin added is 3.5% of a wheat stalk pulverizing material oven dry weight.
(2) paving prefabricating:
Make the homogeneous texture wheat stalk plate of 20mm thickness, get 1.2mm sanding surplus, promptly the not sanded board setting thickness of slab of producing through press is 21.2mm, and setting not, the density of sanded board is 820Kg/m
3According to these parameters, the raw material after the applying glue evenly to be mated formation on metal caul, backing plate is handled through the demoulding coating, and surface sprinkling remover thereon, to prevent haftplatte.Then the material base of completing is carried out precompressed, and the material base surface sprinkling remover after precompressed.
(3) hot pressing making sheet:
The press of the material base that presses in advance being sent into two cycling hot pressing systems carries out making sheet.The heat pressing process process is divided into compression, moulding and temper three phases.Basic hot pressing parameters is as follows:
Hot pressing time: 400 seconds, hot pressing speed: 400s/21.2mm=18.9s/mm.
Making sheet pressure set points (surface pressure setting value): the compression pressure setting value P1 in the compression stage is 3.0MPa; It is that 1.5MPa, P3 are 0.6MPa that briquetting pressure setting value in the formative stage is respectively P2; The tempering pressure set points P4 in tempering stage is 1.5MPa.
The heating platen desired temperature of press: wherein the compression temperature of compression stage setting value T1 is 185 ℃; The forming temperature setting value T2 of formative stage is 120 ℃; The temperature setting value T3 in temper stage is 120 ℃-170 ℃, promptly from 120 ℃ of one section temperature that rises to 170 ℃.At this, the temperature difference between the compression temperature setting value T1 of the forming temperature of formative stage setting value T2 and compression stage is 65 ℃.The temperature fall time that sets value described forming temperature setting value from described compression temperature is 45 seconds.
(4) post-processed:
To carry out cutting edge, cooling through the hot-forming sheet material of press, stacking carries out sanding, fixed thick, classification etc. after 48 hours.
According to every performance indications of standard GB/T4897-2003 particieboard national standard test homogeneous wheat stalk plate, its specific performance index is as follows:
Thickness of slab: 20mm; Density: 780Kg/m
3MOR: 24MPa;
The modulus of elasticity in static bending: 2796MPa; Internal bond strength: 0.55MPa;
Surface bonding strength: 1.3MPa; Hold screw power: plate face 1180N, edges of boards 760N2h thickness swelling rate: 3%; Moisture content: 9%; Averag density deviation in the plate :-4%～+ 3%
Embodiment 2:
(1) get the raw materials ready:
Wheat stalk (the place of production: carry out the first time through beater grinder Guannan County, Lianyun Harbour, Jiangsu) and pulverize, the two screen cloth diameters of pulverizer are respectively 8mm, 6mm, raw material after the pulverizing is removed impurity such as stipes and wheat through pneumatic separation device, get the 60% sandwich layer raw material as making sheet wherein.40% of pulverizing material is pulverized through beater grinder (the screen cloth diameter is respectively 3mm, 3mm) again, as the top layer material of making sheet.The moisture content that is used for the top layer material of making sheet is 14.5%, and the moisture content that is used for the core layer material of making sheet is 10%.Top layer material and core layer material are separated applying glue, in mixer, atomizing of carbimide (PMDI) adhesive and top layer expected even the mixing after, again with the even applying glue of core layer material.Used adhesive is Huntsman Suprasec5005, and the top layer resin added is 3.5% of wheat stalk top layer material oven dry weight, and the sandwich layer resin added is 3% of a wheat stalk core layer material over dry total amount.
(2) paving prefabricating:
Make the three-decker wheat stalk plate of 18mm thickness, get 1.2mm sanding surplus, promptly the not sanded board setting thickness of slab of producing through press is 19.2mm, and setting not, the density of sanded board is 780Kg/m
3The top layer material accounts for 35% of the material base gross weight of mating formation, core layer material accounts for 65% of the material base gross weight of mating formation, according to these parameters, divide three layers evenly to mat formation on metal caul the top layer after the applying glue, sandwich layer raw material, the material base operation of mating formation: the top layer material that will account for material base gross weight 17.5% is evenly mated formation on metal caul, the core layer material that will account for material base gross weight 65% is evenly mated formation then, and the top layer material that will account for material base gross weight 17.5% is at last evenly mated formation, and finishes mating formation of material base.Backing plate is handled through the demoulding coating, and surface sprinkling remover thereon, to prevent haftplatte.The material base of completing is carried out precompressed, and the material base surface sprinkling remover after precompressed.
(3) hot pressing making sheet:
The press of the material base that presses in advance being sent into two cycling hot pressing systems carries out making sheet.The heat pressing process process is divided into compression, moulding and temper three phases.Basic hot pressing parameters is as follows:
Hot pressing time: 350 seconds; Hot pressing speed: 350s/19.2mm=18.2s/mm
Making sheet pressure set points (surface pressure setting value): the compression pressure setting value P1 in the compression stage is 2.6MPa; It is that 1.8MPa, P3 are 0.7MPa that briquetting pressure setting value in the formative stage is respectively P2; The tempering pressure set points P4 in tempering stage is 1.0MPa.
The heating platen desired temperature of press: the compression temperature setting value T1 of compression stage is 210 ℃; The forming temperature setting value T2 of formative stage is 110 ℃; The temperature setting value T3 in temper stage is 110 ℃-175 ℃, promptly from 110 ℃ of one section temperature that rises to 175 ℃.At this, the temperature difference between the compression temperature setting value T1 of the forming temperature of formative stage setting value T2 and compression stage is 100 ℃.The temperature fall time that sets value described forming temperature setting value from described compression temperature is 100 seconds.
(4) post-processed:
To carry out cutting edge, cooling through the hot-forming sheet material of press, stacking carries out sanding, fixed thick, classification etc. after 48 hours.
According to every performance indications of standard GB/T4897-2003 particieboard national standard test three-decker wheat stalk plate, its specific performance index is as follows:
Thickness of slab: 18mm; Density: 740Kg/m
3MOR: 21MPa; The modulus of elasticity in static bending: 2647MPa; Internal bond strength: 0.45MPa; Surface bonding strength: 1.4MPa; Hold screw power: plate face 1260N, edges of boards 890N; 2h thickness swelling rate: 3%; Moisture content: 10%; Averag density deviation in the plate :-4%～+ 4%
Embodiment 3:
(1) get the raw materials ready:
(place of production: Harbin, Heilungkiang) carry out the first time through beater grinder and pulverize, the two screen cloth diameters of pulverizer are respectively 10mm, 10mm to maize straw skin, and the raw material after the pulverizing is got the 60% sandwich layer raw material as making sheet wherein.40% of pulverizing material is pulverized through beater grinder (the screen cloth diameter is respectively 3mm, 4mm) again, as the top layer material of making sheet.The moisture content that is used for the top layer material of making sheet is 15.5%, and the moisture content that is used for the core layer material of making sheet is 11%.Top layer material and core layer material are separated applying glue, in mixer, atomizing of carbimide (PMDI) adhesive and top layer expected even the mixing after, again with the even applying glue of core layer material.Used adhesive is Huntsman Suprasec5005, and the top layer resin added is 3% of a top layer material oven dry weight, and the sandwich layer resin added is 2.5% of a core layer material over dry total amount.
(2) paving prefabricating:
Make the three-decker maize straw board of 18mm thickness, get 1.2mm sanding surplus, promptly the not sanded board setting thickness of slab of producing through press is 19.2mm, and setting not, the density of sanded board is 780Kg/m
3The top layer material accounts for 35% of the material base gross weight of mating formation, core layer material accounts for 65% of the material base gross weight of mating formation, according to these parameters, divide three layers evenly to mat formation on metal caul the top layer after the applying glue, sandwich layer raw material, the material base operation of mating formation: the top layer material that will account for material base gross weight 17.5% is evenly mated formation on metal caul, the core layer material that will account for material base gross weight 65% is evenly mated formation then, and the top layer material that will account for material base gross weight 17.5% is at last evenly mated formation, and finishes mating formation of material base.Backing plate is handled through the demoulding coating, and surface sprinkling remover thereon, to prevent haftplatte.The material base of completing is carried out precompressed, and the material base surface sprinkling remover after precompressed.
(3) hot pressing making sheet:
The press of the material base that presses in advance being sent into two cycling hot pressing systems carries out making sheet.The heat pressing process process is divided into compression, moulding and temper three phases.Basic hot pressing parameters is as follows:
Hot pressing time: 330 seconds; Hot pressing speed: 330s/19.2mm=17.2s/mm
Making sheet pressure set points (surface pressure setting value): the compression pressure setting value P1 in the compression stage is 2.6MPa; It is that 1.7MPa, P3 are 0.7MPa that briquetting pressure setting value in the formative stage is respectively P2; The tempering pressure set points P4 in tempering stage is 1.0MPa.
The heating platen desired temperature of press: the compression temperature setting value T1 of compression stage is 190 ℃; The forming temperature setting value T2 of formative stage is 140 ℃; The temperature setting value T3 in temper stage is 140 ℃-180 ℃, promptly from 140 ℃ of one section temperature that rises to 180 ℃.At this, the temperature difference between the compression temperature setting value T1 of the forming temperature of formative stage setting value T2 and compression stage is 50 ℃.The temperature fall time that sets value described forming temperature setting value from described compression temperature is 30 seconds.
(4) post-processed:
To carry out cutting edge, cooling through the hot-forming sheet material of press, stacking carries out sanding, fixed thick, classification etc. after 48 hours.
According to every performance indications of standard GB/T4897-2003 particieboard national standard test three-decker maize straw board, its specific performance index is as follows:
Thickness of slab: 18mm; Density: 738Kg/m
3MOR: 23MPa; The modulus of elasticity in static bending: 3036MPa; Internal bond strength: 0.50MPa; Surface bonding strength: 1.5MPa; Hold screw power: plate face 1140N, edges of boards 886N; 2h thickness swelling rate: 5%; Moisture content: averag density deviation in 11% plate :-5%～+ 6%
Embodiment 4:
(1) get the raw materials ready:
(place of production: Nanhui, Shanghai) pulverize through beater grinder, the two screen cloth diameters of pulverizer are respectively 8mm, 8mm to rice straw, and the raw material after the pulverizing is removed impurity such as stipes and grain through pneumatic separation device, and sieve removes about 10% ash content.The moisture content that is used for the rice straw pulverizing material of making sheet is 13.5%.In mixer, atomizing of carbimide (PMDI) adhesive and rice straw are pulverized material evenly mix.Used adhesive is Huntsman Suprasec5005, and resin added is 4.5% of a rice straw pulverizing material oven dry weight.
(2) paving prefabricating:
Make the homogeneous texture rice straw plate of 18mm thickness, get 1.2mm sanding surplus, promptly the not sanded board setting thickness of slab of producing through press is 19.2mm, and setting not, the density of sanded board is 920Kg/m
3According to these parameters, the raw material after the applying glue evenly to be mated formation on metal caul, backing plate is handled through the demoulding coating, and surface sprinkling remover thereon, to prevent haftplatte.Then the material base of completing is carried out precompressed, and the material base surface sprinkling remover after precompressed.
(3) hot pressing making sheet:
The press of the material base that presses in advance being sent into two cycling hot pressing systems carries out making sheet.The heat pressing process process is divided into compression, moulding and temper three phases.Basic hot pressing parameters is as follows:
Hot pressing time: 365 seconds; Hot pressing speed: 365s/19.2mm=19.0s/mm
Making sheet pressure set points (surface pressure setting value): the compression pressure setting value P1 in the compression stage is 3.2MPa; It is that 2.2MPa, P3 are 0.9MPa that briquetting pressure setting value in the formative stage is respectively P2; The tempering pressure set points P4 in tempering stage is 1.2MPa.
The heating platen desired temperature of press: the compression temperature setting value T1 of compression stage is 200 ℃; The forming temperature setting value T2 of formative stage is 120 ℃; The temperature setting value T3 in temper stage is 120 ℃-175 ℃, promptly from 120 ℃ of one section temperature that rises to 175 ℃.At this, the temperature difference between the compression temperature setting value T1 of the forming temperature of formative stage setting value T2 and compression stage is 80 ℃.The temperature fall time that sets value described forming temperature setting value from described compression temperature is 65 seconds.
(4) post-processed:
To carry out cutting edge, cooling through the hot-forming sheet material of press, stacking carries out sanding, fixed thick, classification etc. after 48 hours.
According to every performance indications of standard GB/T4897-2003 particieboard national standard test homogeneous rice straw plate, its specific performance index is as follows:
Thickness of slab: 18mm; Density: 890Kg/m
3MOR: 23MPa; The modulus of elasticity in static bending: 3145MPa; Internal bond strength: 0.60MPa; Surface bonding strength: 1.1MPa; Hold screw power: plate face 1340N, edges of boards 1060N; 2h thickness swelling rate: 5%; Moisture content: 8%
Averag density deviation in the plate :-5%～+ 5%.
Claims (11)
1. heat pressing process that utilizes manufacturing board by crop straws, it is characterized in that: the hot pressing that slab is carried out comprises compression stage and formative stage, wherein, forming temperature setting value in formative stage is lower than the compression temperature setting value in compression stage, briquetting pressure setting value in formative stage sets value less than the compression pressure in compression stage, the hot pressing that slab is carried out also comprises the described formative stage temper stage afterwards that is positioned at, wherein, be between forming temperature setting value and the compression temperature setting value in the temperature setting value of temper in the stage, raise once more in the tempering pressure set points of temper in the stage, but be between briquetting pressure setting value and the compression pressure setting value.
2. heat pressing process according to claim 1, it is characterized in that: the compression temperature that is adopted in described compression stage sets value the heat of the heating platen that makes press to the slab transmission, moisture vaporization in the raw material of slab top layer is transmitted to the slab sandwich layer, thereby heating slab sandwich layer makes the slab core layer temperature reach the required solidification temperature of adhesive; The forming temperature setting value that is adopted in described formative stage makes the heating platen transmission of the heat of slab to press, thereby the slab skin temperature is reduced; The temperature setting value that is adopted in stage in described temper is transmitted the heat of the heating platen of press once more to the slab top layer.
3. heat pressing process according to claim 1 is characterized in that: the curve of the briquetting pressure setting value in the described formative stage becomes stepped.
4. heat pressing process according to claim 1, it is characterized in that: the compression temperature setting value of described compression stage is 170 ℃～240 ℃, and exert pressure for the heating platen of press, make the closed compression of heating platen slab, slab is compressed into the thickness of setting, switches to described formative stage after described slab core layer temperature reaches setting value.
5. heat pressing process according to claim 1 is characterized in that: the forming temperature setting value of described formative stage is 80 ℃～160 ℃, after the sandwich layer reaction of described slab is solidified, switches to the described temper stage.
6. heat pressing process according to claim 1, it is characterized in that: the temperature setting value in described temper stage is 130 ℃～180 ℃, the pressure that imposes on the heating platen of press in this stage raises once more, reach whole pressing cycle technology and set time, sheet material sandwich layer steam pressure and open press during less than described sheet material internal bond strength, finish whole heat pressing process.
7. heat pressing process according to claim 1 is characterized in that: the temperature difference between described forming temperature setting value and the described compression temperature setting value is at 10 ℃-150 ℃.
8. heat pressing process according to claim 1 is characterized in that: based on the thickness of made sheet material, the setting value of a pressing cycle time was by calculating in 10～25 seconds/millimeter.
9. heat pressing process according to claim 1 is characterized in that: the compression pressure setting value that puts in described compression stage on the slab is 2.1MPa-4.0MPa.
10. heat pressing process according to claim 1 is characterized in that: the briquetting pressure setting value that puts in described formative stage on the slab is 0.5MPa-2.0MPa.
11. heat pressing process according to claim 1 is characterized in that: the tempering pressure set points that puts in the stage on the slab in described temper is 0.6MPa-2.5MPa.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1649706A (en) * | 2002-05-03 | 2005-08-03 | 沈国镇国际有限公司 | Method for making dimensionally stable composite products from lignocellulosic material |
| CN1966225A (en) * | 2006-09-21 | 2007-05-23 | 陳正中 | Plant fiber composite artificial plate and its production process |
| CN101323130A (en) * | 2008-07-11 | 2008-12-17 | 东北林业大学 | Heat pressing production method of polyethylene fiber-plant fibre compound material |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1649706A (en) * | 2002-05-03 | 2005-08-03 | 沈国镇国际有限公司 | Method for making dimensionally stable composite products from lignocellulosic material |
| CN1966225A (en) * | 2006-09-21 | 2007-05-23 | 陳正中 | Plant fiber composite artificial plate and its production process |
| CN101323130A (en) * | 2008-07-11 | 2008-12-17 | 东北林业大学 | Heat pressing production method of polyethylene fiber-plant fibre compound material |
Non-Patent Citations (2)
| Title |
|---|
| JP特开2001-269911A 2001.10.02 |
| JP特开2002-273711A 2002.09.25 |
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