CN115592763B - Manufacturing method of formaldehyde-free medium-high density fiberboard - Google Patents
Manufacturing method of formaldehyde-free medium-high density fiberboard Download PDFInfo
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- CN115592763B CN115592763B CN202211275156.1A CN202211275156A CN115592763B CN 115592763 B CN115592763 B CN 115592763B CN 202211275156 A CN202211275156 A CN 202211275156A CN 115592763 B CN115592763 B CN 115592763B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N1/00—Pretreatment of moulding material
- B27N1/02—Mixing the material with binding agent
- B27N1/0209—Methods, e.g. characterised by the composition of the agent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
- B27N3/04—Manufacture of substantially flat articles, e.g. boards, from particles or fibres from fibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
- B27N3/08—Moulding or pressing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
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Abstract
The invention is suitable for the technical field of fiber boards, and provides a method for manufacturing formaldehyde-free medium-high density fiber boards, which mainly comprises the steps of manufacturing formaldehyde-free adhesives, manufacturing waterproof agents, raw material treatment, application of the waterproof agents, blending addition of the formaldehyde-free adhesives, primary application of the formaldehyde-free adhesives, drying wood fibers, secondary application of the formaldehyde-free adhesives, paving wood fibers, manufacturing the formaldehyde-free medium-high density fiber boards, wherein the blending addition step of the formaldehyde-free adhesives is that the formaldehyde-free adhesives are conveyed to a glue storage tank of a production workshop, filtered by a filter screen, enter a glue mixing box from a gear metering pump according to 12% -16% of application amount, and are uniformly stirred; meanwhile, 6% -8% of isocyanate adhesive, release agent and a proper amount of water are added into the glue mixing box. Therefore, the invention solves the problems that the MDI glue blocks the conveying pipeline, adheres to equipment and the like; solves the problem that the curing time of the isocyanate adhesive (MDI) added into wood fiber is short; can reach the level of normal large-scale production.
Description
Technical Field
The invention relates to the technical field of fiber boards, in particular to a method for manufacturing formaldehyde-free medium-high density fiber boards with zero formaldehyde addition.
Background
At present, adhesives adopted by fiber boards sold in domestic markets are mainly urea-formaldehyde resin adhesives, phenolic resin adhesives and melamine modified urea-formaldehyde resin adhesives, namely, so-called trialdehyde resin adhesives. During the production and use of these adhesives, formaldehyde, a gas harmful to the environment and human health, is released. Formaldehyde can produce toxic effects on systems such as eyes, nose, breath, nerves and the like of people, not only causes human diseases, but also causes environmental pollution, and has been listed in a class of carcinogen list by the world health organization, so that an environment-friendly formaldehyde-free fiberboard is needed to improve the quality of life and health.
With the rapid development of construction and furniture repair industry, the living standard of people is increasingly improved, the safety consciousness and the environmental protection consciousness of people are enhanced, and the formaldehyde pollution hazard problem of furniture and finishing materials is more and more paid attention to. Solves the problem of formaldehyde pollution hazard, and researches and develops the environment-friendly formaldehyde-free fiber board which is a necessary way for future survival and development of the artificial board industry.
In order to promote the upgrading of the traditional artificial board industry and realize the green sustainable development, on the basis of the traditional fiber board product, the research and development of the green environment-friendly formaldehyde-free fiber board is also a long-term development requirement of enterprises. The primary problem of industrial research and development of formaldehyde-free fiber board is that: firstly, the problem that the prior domestic isocyanate adhesive (MDI) and wood fiber are mixed and dried to block a conveying pipeline and adhere to a hot pressing plate is solved; secondly, the problem that the curing time of adding the isocyanate adhesive (MDI) into wood fiber is short is solved; thirdly, the problem that the formaldehyde-free fiber board cannot be produced in a normal large scale by adopting isocyanate adhesive (MDI) is solved, and the research and development and industrialization work of the domestic formaldehyde-free density board are directly influenced by the effective solution of the problems.
In view of the above, it is apparent that the prior art has drawbacks in practical use, and thus needs to be improved.
Disclosure of Invention
Aiming at the defects, the invention aims to provide a manufacturing method of formaldehyde-free medium-high density fiberboard with zero formaldehyde addition, which solves the problems of blockage of a conveying pipeline, adhesion equipment and the like caused by MDI glue; solves the problem that the curing time of the isocyanate adhesive (MDI) added into wood fiber is short; can reach the level of normal large-scale production.
In order to achieve the above purpose, the invention provides a method for manufacturing formaldehyde-free medium-high density fiberboard, which is characterized by comprising the steps of manufacturing formaldehyde-free adhesive, manufacturing waterproof agent, raw material treatment, waterproof agent application, preparation and addition of formaldehyde-free adhesive, primary application of formaldehyde-free adhesive, drying wood fiber, secondary application of formaldehyde-free adhesive, paving wood fiber and manufacturing formaldehyde-free medium-high density fiberboard, wherein the formaldehyde-free adhesive is manufactured by aqueous polymer polyvinyl alcohol (PVA), polyvinyl acetate emulsion, polyacrylate emulsion and additives;
the preparation and addition steps of the formaldehyde-free adhesive are that the formaldehyde-free adhesive is conveyed to a glue storage tank of a production workshop through a stainless steel centrifugal pump, filtered through a 25-mesh filter screen, and enters a glue mixing box from a gear metering pump according to the application amount of 12% -16% of the absolute dry fiber amount, and is uniformly stirred; at the same time, adding isocyanate adhesive (MDI), release agent and water with the application amount of 6-8% of the absolute dry fiber amount into a glue mixing box.
According to the method for manufacturing the formaldehyde-free medium-high density fiberboard with zero formaldehyde addition, the method comprises the following steps of:
1) Filtering and screening water-soluble polymer compound powdery sodium carboxymethyl starch (CMS-Na) with a 120-mesh filter screen;
2) Putting 20 parts of screened sodium carboxymethyl starch into a reaction kettle, simultaneously injecting 2 parts of ethanol with the purity of 80% and 50 parts of water into the reaction kettle, stirring while adding, heating the water to 45 ℃ after uniform mixing, preserving heat and stirring for 30min until the sodium carboxymethyl starch is completely dissolved, and cooling to 40 ℃;
3) Adding buffer 1 part NH 4 CL, keeping the temperature and stirring for 10min;
4) Adding a proper amount of 0.1mol/L HCL to adjust the pH value of the mixed solution to 7.5-8.0;
5) 15 parts of polyvinyl acetate emulsion with the solid content of 50% and 15 parts of polyacrylate emulsion with the solid content of 45% are respectively put into a reaction kettle, stirred while being added, and stirred and mixed for 1h at the temperature of 40 ℃;
6) Adding 0.3 part of preservative 2-methyl-4-isothiazolin-3-one (MIT), and stirring and mixing for 10min at 40 ℃;
7) 10 parts of rice hull powder which is a natural organic filler and is filtered by a 100-mesh filter screen is taken and put into a reaction kettle, and stirring is carried out while adding, and heat preservation and stirring are carried out for 30min;
8) Buffer NaHCO 3 Preparing 10% solution by using water, adding a proper amount of water into a reaction kettle, adjusting the pH value of the mixed solution to 7-8, and uniformly stirring to obtain milky viscous liquid-formaldehyde-free adhesive;
9) The solid content is more than 45%; the viscosity is measured to be 20 to 40 seconds at 25 ℃; pH value: 7-8, after primary filtration by a 25-mesh filter screen, conveying the filter screen to a glue storage tank for storage by a conveying pump.
According to the method for manufacturing formaldehyde-free medium-high density fiberboard, the steps of manufacturing the waterproof agent are as follows:
1) Sequentially adding 2.4-2.6 parts of water-soluble emulsifier T-80, 3.6-3.8 parts of OP-10, 0.6-0.8 part of sodium dodecyl sulfate and 50 parts of water into a No. 1 reaction kettle, heating to 80 ℃ to completely dissolve, and uniformly stirring;
2) Sequentially adding 2.4-2.6 parts of lipophilic emulsifier S-80, 2.3-2.5 parts of anti-foaming agent polypropylene glycol PPG2000, and 38-40 parts of 58# paraffin into a No. 2 reaction kettle, heating to 90 ℃ to completely melt, uniformly stirring, and preserving heat for 15min at 90 ℃;
3) Sequentially adding 5-6 parts of polydimethylsiloxane and 0.4-0.6 part of nonionic surfactant glyceryl monostearate into a No. 2 reaction kettle, stirring while adding, and preserving heat at 90 ℃ for 15min to react to form emulsion;
4) Adding 30% of the water solution which is uniformly stirred in the No. 1 reaction kettle into the No. 2 reaction kettle, stirring while adding, and preserving the temperature for 15min at 90 ℃ to form water-in-oil emulsion; continuously adding 30% of the aqueous solution, stirring while adding, and maintaining the temperature at 90 ℃ for 25min to form an oil-in-water emulsion; adding the rest water solution, stirring while adding, maintaining at 90deg.C for 15min, cooling to room temperature, filtering, and transferring to storage tank by stainless steel transfer pump.
According to the method for manufacturing the formaldehyde-free medium-high density fiberboard, raw materials are processed, namely, three residues of agriculture and forestry and secondary small firewood materials are subjected to mechanical cutting, wind washing and screening, enter a pre-cooking cylinder for first cooking softening under the steam pressure of 7.5-8.0 bar, are extruded by a high-efficiency wear-resistant conical plug screw device, filter out water contained in the raw materials, loose firewood materials enter a cooking cylinder for second cooking softening under the steam pressure of 7.3-7.8 bar, the height of the cooking material level is controlled to be 1.5-2.0 m, then the raw materials are quantitatively conveyed by a stainless steel variable screw pitch double-line discharging screw, belt type screw steam discharging feeding is carried out, and the loose firewood materials are ground into fine and uniform wood fibers.
According to the method for manufacturing the formaldehyde-free medium-high density fiberboard, the waterproofing agent is applied through the steps of filtering the waterproofing agent to isolate 1.2% -1.6% of the added amount of the fiber, and spraying the waterproofing agent from a V-shaped precise nozzle to wood fiber in a hot mill grinding chamber through a check valve by a high-pressure metering gear pump under the condition of being 7.5bar higher than the pressure of the hot mill grinding chamber so as to mix the waterproofing agent with the wood fiber.
According to the method for manufacturing the formaldehyde-free added formaldehyde-free medium-high density fiberboard, the formaldehyde-free adhesive is sequentially applied in the steps that wood fibers attached with waterproof agents pass through a glue spraying pipe at a speed of 28-32 m/s along a spraying pipeline through an electric control flow valve under the action of high-pressure steam, the prepared formaldehyde-free adhesive is precisely metered and weighed, a 30-mesh precise filter cylinder is used for filtering, an additive amount which is 80% of the total adhesive is formed into a 60-degree angle with the glue spraying pipe along the flow direction of the wood fibers through a high-pressure screw pump, and the wood fibers are sprayed into the glue spraying pipe in a fan-shaped fine mist form through three precise V-shaped nozzles which are 75 degrees each other, so that the cross section of the whole glue spraying pipe is sealed.
According to the method for manufacturing formaldehyde-free medium-high density fiberboard, the wood fiber is dried by uniformly mixing the wood fiber impregnated with waterproof agent with formaldehyde-free adhesive in a glue spraying blowing pipe and a glue mixer for the second time before drying, the inlet temperature of a drying pipeline is 110-140 ℃, the outlet temperature is 45-70 ℃, and the water content of the dried wood fiber is 6-13%.
According to the manufacturing method of the formaldehyde-free added formaldehyde-free medium-high density fiberboard, the formaldehyde-free adhesive is secondarily applied, wood fibers adhered with the formaldehyde-free adhesive are dried at a high speed through a glue spraying blowing pipe under the action of high-pressure steam, then are subjected to solid-gas separation through a cyclone separator, are weighed and measured by a weighing belt, fall into a fiber glue mixer to form vortex-shaped fiber flow under the pneumatic conveying condition, and the formaldehyde-free adhesive is sprayed onto the fiber flow from one end of the glue mixer in a conical fine mist form through 4 precise nozzles which are 90 degrees under the action of a high-pressure screw pump, and are secondarily and fully mixed with the wood fibers under the action of vortex.
According to the manufacturing method of the formaldehyde-free medium-high density fiberboard, the step of wood fiber pavement is that wood fibers attached with formaldehyde-free adhesives enter a fiber separation and then enter a pavement machine for mechanical pavement by an air-assisted system, and the wood fibers are preformed by prepressing and are divided by trimming.
According to the method for manufacturing the formaldehyde-free medium-high density fiberboard, the steps of manufacturing the formaldehyde-free medium-high density fiberboard are that the blank after being divided at the same edge enters a hot press, and the formaldehyde-free medium-high density fiberboard is manufactured after 3-10 min under the temperature of 150-180 ℃ and the pressure of 220-250 Bar.
The invention aims to provide a method for manufacturing formaldehyde-free medium-high density fiberboard, which has the following technical innovation and beneficial effects;
1. the isocyanate adhesive (MDI) modification technology is adopted, so that the moisture curing performance (curing in water reaction) of the isocyanate adhesive (MDI) and the bonding property to metal materials are improved. Mixing the new formaldehyde-free adhesive with isocyanate adhesive (MDI) to wrap the MDI glue particles with the new formaldehyde-free glue particles. The non-binding property of the novel formaldehyde-free adhesive to the metal material makes up the defect of strong binding property of the isocyanate adhesive (MDI) to the metal material, and solves the problems of the MDI adhesive that the conveying pipeline is blocked, the equipment is adhered and the like.
2. The fan-shaped fine mist application mode of the glue spraying blowing pipe before wood fiber drying and the cone-shaped fine mist application mode of the glue mixer after wood fiber drying are adopted, so that the wood fiber and the adhesive are fully and uniformly mixed, the mechanical property and the internal bonding strength of the product are improved, and the using amount of the adhesive is saved.
3. The waterproof agent is sprayed onto wood fibers in a grinding chamber of the thermal mill through a precise nozzle by a high-pressure metering pump, uniformly permeates into the wood fibers under the high-speed running of a grinding disc of the thermal mill, and is fully and uniformly mixed with the wood fibers, so that the optimal waterproof effect is achieved, and the water absorption expansion rate of the product is reduced.
4. The novel formaldehyde-free adhesive and isocyanate adhesive (MDI) compounding technology is adopted, so that the isocyanate adhesive (MDI) adhesive particles are wrapped by the novel formaldehyde-free adhesive particles, the curing time of the isocyanate adhesive (MDI) is improved, the production hot-press curing period is adjusted according to the proportion, the problem that the curing time of the isocyanate adhesive (MDI) in wood fibers is short is solved, the formaldehyde-free characteristic of the isocyanate adhesive (MDI) is fully reserved, and the formaldehyde-free characteristic of the board is endowed.
5. The experiment develops a new technology for mass production of the formaldehyde-free fiber board, solves the problem that the formaldehyde-free board cannot be produced in a normal scale by adopting isocyanate adhesive (MDI), and realizes the industrialized revolution of the formaldehyde-free fiber board.
Drawings
FIG. 1 is a first page of inspection report of national artificial board and wood and bamboo product quality supervision and inspection center;
FIG. 2 is a second page of inspection report of the national manmade board and wood and bamboo product quality supervision and inspection center;
Fig. 3 is a third page of inspection report of the national inspection center for quality supervision and inspection of artificial boards and wood-bamboo products.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1: making 9mm, density of 810Kg/m 3 The formaldehyde-free medium-high density fiberboard comprises the following steps;
preparing an aldehyde-free adhesive, preparing a waterproof agent, treating raw materials, applying the waterproof agent, preparing and adding the aldehyde-free adhesive, applying the aldehyde-free adhesive once, drying wood fibers, applying the aldehyde-free adhesive twice, paving the wood fibers, and preparing the aldehyde-free medium-high density fiberboard.
1. Preparation of aldehyde-free adhesive
1) Filtering and screening water-soluble polymer compound powdery sodium carboxymethyl starch (CMS-Na) with a 120-mesh filter screen;
2) Putting 20 parts of screened sodium carboxymethyl starch into a reaction kettle, simultaneously injecting 2 parts of ethanol with the purity of 80% and 50 parts of water into the reaction kettle, stirring while adding, heating the water to 45 ℃ after uniform mixing, preserving heat and stirring for 30min until the sodium carboxymethyl starch is completely dissolved, and cooling to 40 ℃;
3) Adding buffer 1 part NH 4 CL, keeping the temperature and stirring for 10min;
4) Adding a proper amount of 0.1mol/L HCL to adjust the pH value of the mixed solution to 7.5-8.0;
5) 15 parts of polyvinyl acetate emulsion with the solid content of 50% and 15 parts of polyacrylate emulsion with the solid content of 45% are respectively put into a reaction kettle, stirred while being added, and stirred and mixed for 1h at the temperature of 40 ℃;
6) Adding 0.3 part of preservative 2-methyl-4-isothiazolin-3-one (MIT), and stirring and mixing for 10min at 40 ℃;
7) 10 parts of rice hull powder which is a natural organic filler and is filtered by a 100-mesh filter screen is taken and put into a reaction kettle, and stirring is carried out while adding, and heat preservation and stirring are carried out for 30min;
8) Buffer NaHCO 3 Preparing 10% solution by using water, adding a proper amount of water into a reaction kettle, adjusting the pH value of the mixed solution to 7-8, and uniformly stirring to obtain milky viscous liquid-formaldehyde-free adhesive;
9) The solid content is more than 45%; the viscosity is measured to be 20 to 40 seconds at 25 ℃; pH value: 7-8, after primary filtration by a 25-mesh filter screen, conveying the filter screen to a glue storage tank for storage by a conveying pump.
The formaldehyde-free adhesive prepared by the process used in the step does not contain formaldehyde and other pollutants, is environment-friendly, pollution-free, good in water resistance and heat resistance and ageing resistance, realizes industrialized production, fundamentally solves the problem of formaldehyde pollution of fiber boards, and is an ideal adhesive for replacing urea-formaldehyde resin adhesive.
2. Preparation of waterproofing agent
1) Firstly, sequentially adding 2.52 parts of water-soluble emulsifier T-80, 3.72 parts of OP-10, 0.72 part of sodium dodecyl sulfate and 50 parts of water into a No. 1 reaction kettle, heating to 80 ℃ to completely dissolve, and uniformly stirring;
2) Sequentially adding 2.64 parts of lipophilic emulsifier S-80, 2.4 parts of anti-foaming agent polypropylene glycol PPG2000, and 38 parts of 58# paraffin into a No. 2 reaction kettle, heating to 90 ℃ to completely melt, uniformly stirring, and preserving heat at 90 ℃ for 15min;
3) Adding 6 parts of polydimethylsiloxane and 0.5 part of nonionic surfactant glyceryl monostearate in sequence in a No. 2 reaction kettle, stirring while adding, and preserving heat at 90 ℃ for 15min to react to form emulsion;
4) Slowly adding 30% of the water solution uniformly stirred in the No. 1 reaction kettle into the No. 2 reaction kettle, stirring while adding, and preserving the temperature at 90 ℃ for 15min to form water-in-oil emulsion; continuously slowly adding 30% of the water solution, stirring while adding, and maintaining the temperature at 90 ℃ for 25min to form an oil-in-water emulsion; slowly adding the rest aqueous solution, stirring while adding, maintaining at 90deg.C for 15min, cooling to room temperature to obtain stable emulsion waterproof agent (solid content > 50%), primarily filtering with 25 mesh filter screen, and transferring to storage tank by stainless steel.
3. Raw material treatment
The three residues in agriculture and forestry and the secondary small firewood material are subjected to mechanical cutting, wind washing and screening, enter a pre-cooking cylinder for first cooking softening under the steam pressure of 7.6bar, are extruded by a high-efficiency wear-resistant conical plug screw device, filter out water contained in the water, loosen firewood material, effectively reduce the grinding power consumption of a thermal mill, enter the cooking cylinder for second cooking softening under the steam pressure of 7.3bar, control the cooking material level height to be 1.5m, then quantitatively control and convey the material by a stainless steel variable screw pitch double-line discharging screw, discharge steam and supply the material by a belt screw, and return the steam to the cooking cylinder to ensure the steam pressure balance of the system, so that the feeding is smooth. The loose firewood after cooking enters a high-temperature high-pressure precise thermal mill through a belt type spiral, and is stirred into a millstone working area running at high speed to be ground into fine and uniform wood fibers under the action of a movable millstone stirring fluted disc. The screening value of the wood fiber (which does not pass through a sieve pore with phi 0.8 mm) is less than or equal to 1.7 percent.
4. Application of waterproofing agents
In the sizing process of the aldehyde-free fiberboard manufacture, the waterproofing agent is filtered to isolate the addition amount of 1.2% of the fibers, and is sprayed onto the wood fibers in a grinding chamber of a thermal mill from a V-shaped precise nozzle under the condition that the pressure of the grinding chamber of the thermal mill is 7.5bar higher than that of a check valve by a high-pressure metering gear pump to be quickly mixed with the wood fibers. The screening value of the wood fiber (which does not pass through a sieve pore with phi 0.8 mm) is less than or equal to 1.7 percent. Even grinding is carried out at a high speed by a millstone of a thermal mill, the waterproof agent is evenly permeated into wood fibers and is fully and evenly mixed with the wood fibers, so that the wood fibers achieve the optimal waterproof effect.
5. Formulation and addition of aldehyde-free adhesives
The formaldehyde-free adhesive prepared from water-based high polymer polyvinyl alcohol (PVA), polyvinyl acetate emulsion, polyacrylate emulsion and additives is conveyed to a glue storage tank of a production workshop through a stainless steel centrifugal pump, filtered through a 25-mesh filter screen, enters a glue mixing box from a gear metering pump according to the application amount of 12% of absolute dry fibers, and is uniformly stirred; at the same time, adding isocyanate adhesive (MDI) with the application amount of 6 percent of the absolute dry fiber amount, a release agent and a proper amount of water into a glue mixing box. The addition of the release agent is helpful to solve the problem of sticking the plate during hot pressing of the plate blank, and a proper amount of water is added to ensure the viscosity of the adhesive required by production; the prepared formaldehyde-free adhesive mixed solution is stirred uniformly at room temperature and then enters a production application system, and the application way adopts a mode of primary application of the formaldehyde-free adhesive and secondary application of the formaldehyde-free adhesive.
6. One-time application of aldehyde-free adhesive
Under the action of high-pressure steam, wood fibers attached with the waterproof agent enter a spraying pipeline through an electric control flow valve and pass through a glue spraying blowing pipe at a speed of 30 m/s. The prepared formaldehyde-free adhesive is precisely metered and weighed, and after being filtered by a 30-mesh precise filter cylinder, the prepared formaldehyde-free adhesive is sprayed into a glue spraying blowing pipe in a fan-shaped fine mist mode through three precise V-shaped nozzles which are 75 degrees each other by a 60-degree angle formed between the flow direction of wood fibers and the glue spraying blowing pipe by a high-pressure screw pump according to the additive amount of 80% of the total adhesive, so that the formaldehyde-free adhesive can be uniformly adhered to all wood fibers adhered with a waterproof agent through the glue spraying blowing pipe. Through the diffusion effect of the venturi tube of the glue spraying and blowing tube, the wood fiber and the aldehyde-free adhesive are ensured to be fully mixed.
7. Drying of wood fibres
The waterproofing agent is sprayed onto wood fiber in the grinding chamber of the thermal mill from a precise nozzle in a conical fine mist shape by a high-pressure double-gear metering pump after being filtered, and is uniformly infiltrated into the wood fiber under the high-speed running of the grinding disc of the thermal mill, and is fully and uniformly mixed with the wood fiber, so that the wood fiber achieves the optimal waterproof effect. And uniformly mixing the wood fiber impregnated with the waterproof agent with the formaldehyde-free adhesive in a glue spraying blowing pipe before drying and in a glue mixer after drying. The inlet temperature of the drying pipeline is 120 ℃, the outlet temperature is 60 ℃, and the moisture content of the dried wood fiber is 6.9%.
8. Secondary application of aldehyde-free adhesive
Wood fiber adhered with the formaldehyde-free adhesive enters a drying system for drying at high speed through a glue spraying blowing pipe under the action of high-pressure steam. Then the fiber glue is subjected to high-efficiency solid-gas separation by a cyclone separator, and falls into a fiber glue mixer after being weighed by a weighing belt, and the fiber glue mixer is in vortex-shaped fiber flow under the pneumatic conveying condition. The formaldehyde-free adhesive is sprayed onto fiber flow from one end of a glue mixer in a conical fine mist form through 4 precise nozzles which are 90 degrees each other under the action of a high-pressure screw pump in an adding amount which is 20% of the total amount of the adhesive, and is fully mixed with wood fibers for the second time under the action of vortex. The adhesive secondary application technology ensures that wood fibers and the adhesive are fully mixed, and saves the adhesive.
9. Wood fiber pavement
Wood fiber attached with the formaldehyde-free adhesive enters a fiber sorting system, enters a paving machine for mechanical paving, is preformed by prepressing, is divided by edges, and enters a hot press, wherein the paving speed of the wood fiber is 258mm/s.
10. Manufacturing formaldehyde-free medium-high density fiberboard
And (3) under the conditions of the hot pressing temperature of the plate blank of 160 ℃ and the pressure of 245Bar, 196s are carried out to prepare the formaldehyde-free medium-high density fiberboard.
The formaldehyde-free medium-high density fiberboard with the thickness of 9mm manufactured by the method is detected by a national artificial board and wood-bamboo product quality supervision and inspection center: density of 810Kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the Deviation of density in board: +1.2% -1.2%; the water content is 6.9%; the water absorption expansion rate is 7.2%; the internal bonding strength is 1.85MPa; static bending strength is 28.9MPa; formaldehyde release amount: is not detected (limit of detection: 0.005 mg/m) 3 ) See fig. 1 to 3 in detail.
The physical and mechanical performance indexes of the formaldehyde-free fiber board manufactured by the method exceed the national standard requirements of the Medium Density fiber board (GB/T11718-2009) and the standard formaldehyde release amount requirements of the industry community of the formaldehyde-free artificial board and products thereof (T/CNFPIA 3002-2018), thereby realizing the research, development and industrial production of the formaldehyde-free fiber board.
Example 2: 15mm of the product is produced, and the density is 870Kg/m 3 Aldehyde-free medium-high density fiberboard
1. Preparation of aldehyde-free adhesive
Step one, the step of manufacturing the formaldehyde-free adhesive is that,
1) Filtering and screening water-soluble polymer compound powdery sodium carboxymethyl starch (CMS-Na) with a 120-mesh filter screen;
2) Putting 20 parts of screened sodium carboxymethyl starch into a reaction kettle, simultaneously injecting 2 parts of ethanol with the purity of 80% and 50 parts of water into the reaction kettle, stirring while adding, heating the water to 45 ℃ after uniform mixing, preserving heat and stirring for 30min until the sodium carboxymethyl starch is completely dissolved, and cooling to 40 ℃;
3) Adding buffer 1 part NH 4 CL, keeping the temperature and stirring for 10min;
4) Adding a proper amount of 0.1mol/L HCL to adjust the pH value of the mixed solution to 7.5-8.0;
5) 15 parts of polyvinyl acetate emulsion with the solid content of 50% and 15 parts of polyacrylate emulsion with the solid content of 45% are respectively put into a reaction kettle, stirred while being added, and stirred and mixed for 1h at the temperature of 40 ℃;
6) Adding 0.3 part of preservative 2-methyl-4-isothiazolin-3-one (MIT), and stirring and mixing for 10min at 40 ℃;
7) 10 parts of rice hull powder which is a natural organic filler and is filtered by a 100-mesh filter screen is taken and put into a reaction kettle, and stirring is carried out while adding, and heat preservation and stirring are carried out for 30min;
8) Buffer NaHCO 3 Preparing 10% solution by using water, adding a proper amount of water into a reaction kettle, adjusting the pH value of the mixed solution to 7-8, and uniformly stirring to obtain milky viscous liquid-formaldehyde-free adhesive;
9) The solid content is more than 45%; the viscosity is measured to be 20 to 40 seconds at 25 ℃; pH value: 7-8, after primary filtration by a 25-mesh filter screen, conveying the filter screen to a glue storage tank for storage by a conveying pump.
2. Preparation of waterproofing agent
1) Firstly, sequentially adding 2.60 parts of water-soluble emulsifier T-80, 3.78 parts of OP-10, 0.8 part of sodium dodecyl sulfate and 50 parts of water into a No. 1 reaction kettle, heating to 80 ℃ to completely dissolve, and uniformly stirring;
2) Sequentially adding 2.70 parts of lipophilic emulsifier S-80, 2.5 parts of anti-foaming agent polypropylene glycol PPG2000, and 40 parts of 58# paraffin into a No. 2 reaction kettle, heating to 90 ℃ to completely melt, uniformly stirring, and preserving heat at 90 ℃ for 15min;
3) Adding 6 parts of polydimethylsiloxane and 0.6 part of nonionic surfactant glyceryl monostearate in sequence in a No. 2 reaction kettle, stirring while adding, and preserving heat at 90 ℃ for 15min to react to form emulsion;
4) Slowly adding 30% of the water solution uniformly stirred in the No. 1 reaction kettle into the No. 2 reaction kettle, stirring while adding, and preserving the temperature at 90 ℃ for 15min to form water-in-oil emulsion; continuously slowly adding 30% of the water solution, stirring while adding, and maintaining the temperature at 90 ℃ for 25min to form an oil-in-water emulsion; slowly adding the rest aqueous solution, stirring while adding, maintaining at 90deg.C for 15min, cooling to room temperature to obtain stable emulsion waterproof agent (solid content > 50%), primarily filtering with 25 mesh filter screen, and transferring to storage tank by stainless steel.
3. Raw material treatment
The three residues in agriculture and forestry and the secondary small firewood material are subjected to mechanical cutting, wind washing and screening, enter a pre-cooking cylinder for first cooking softening under the steam pressure of 7.8bar, are extruded by a high-efficiency wear-resistant conical plug screw device, filter out water contained in the water, loosen firewood material, effectively reduce the grinding power consumption of a thermal mill, enter the cooking cylinder for second cooking softening under the steam pressure of 7.5bar, control the height of the cooking material level to be 1.8m, then quantitatively control and convey the material level by a stainless steel variable screw pitch double-line discharging screw, discharge steam and supply the material in a belt type screw, and return the steam to the cooking cylinder to ensure the steam pressure balance of the system, so that the material is smoothly fed. The loose firewood after cooking enters a high-temperature high-pressure precise thermal mill through a belt type spiral, and is stirred into a millstone working area running at high speed to be ground into fine and uniform wood fibers under the action of a movable millstone stirring fluted disc. The screening value of the wood fiber (which does not pass through a sieve pore with phi 0.8 mm) is less than or equal to 1.7 percent.
4. Application of waterproofing agents
The waterproofing agent is applied in the sizing process of aldehyde-free fiber board manufacture, the waterproofing agent is filtered to ensure that the adding amount of 1.2 percent of absolute dry fiber is sprayed onto wood fiber in a hot mill grinding chamber from a V-shaped precise nozzle under the condition that the pressure of the high-pressure metering gear pump is 7.5bar higher than the grinding chamber pressure of the hot mill through a one-way valve, and the waterproofing agent is quickly mixed with the wood fiber. The screening value of the wood fiber (which does not pass through a sieve pore with phi 0.8 mm) is less than or equal to 1.7 percent. Even grinding is carried out at a high speed by a millstone of a thermal mill, the waterproof agent is evenly permeated into wood fibers and is fully and evenly mixed with the wood fibers, so that the wood fibers achieve the optimal waterproof effect.
5. Formulation and addition of aldehyde-free adhesives
The formaldehyde-free adhesive prepared from water-based high polymer polyvinyl alcohol (PVA), polyvinyl acetate emulsion, polyacrylate emulsion and additives is conveyed to a glue storage tank of a production workshop through a stainless steel centrifugal pump, filtered through a 25-mesh filter screen, enters a glue mixing box from a gear metering pump according to the application amount of 14% of absolute dry fibers, and is uniformly stirred; at the same time, adding isocyanate adhesive (MDI) with the application amount of 7 percent of the absolute dry fiber amount, a release agent and a proper amount of water into a glue mixing box. The addition of the release agent is helpful to solve the problem of sticking the plate during hot pressing of the plate blank, and a proper amount of water is added to ensure the viscosity of the adhesive required by production; the prepared formaldehyde-free adhesive mixed solution is stirred uniformly at room temperature and then enters a production application system, and the application way adopts a mode of primary application of the formaldehyde-free adhesive and secondary application of the formaldehyde-free adhesive.
6. One-time application of aldehyde-free adhesive
Under the action of high-pressure steam, wood fibers attached with the waterproof agent enter a spraying pipeline through an electric control flow valve and pass through a glue spraying blowing pipe at a speed of 28 m/s. The prepared formaldehyde-free adhesive is precisely metered and weighed, and after being filtered by a 30-mesh precise filter cylinder, the prepared formaldehyde-free adhesive is sprayed into a glue spraying blowing pipe in a fan-shaped fine mist mode through three precise V-shaped nozzles which are 75 degrees each other by a 60-degree angle formed between the flow direction of wood fibers and the glue spraying blowing pipe by a high-pressure screw pump according to the additive amount of 80% of the total adhesive, so that the formaldehyde-free adhesive can be uniformly adhered to all wood fibers adhered with a waterproof agent through the glue spraying blowing pipe. Through the diffusion effect of the venturi tube of the glue spraying and blowing tube, the wood fiber and the aldehyde-free adhesive are ensured to be fully mixed.
7. Drying of wood fibres
The waterproofing agent is sprayed onto wood fiber in the grinding chamber of the thermal mill from a precise nozzle in a conical fine mist shape by a high-pressure double-gear metering pump after being filtered, and is uniformly infiltrated into the wood fiber under the high-speed running of the grinding disc of the thermal mill, and is fully and uniformly mixed with the wood fiber, so that the wood fiber achieves the optimal waterproof effect. And uniformly mixing the wood fiber impregnated with the waterproof agent with the formaldehyde-free adhesive in a glue spraying blowing pipe before drying and in a glue mixer after drying. The inlet temperature of the drying pipeline is 122 ℃, the outlet temperature is 65 ℃, and the moisture content of the dried wood fiber is 6.8%.
8. Secondary application of aldehyde-free adhesive
Wood fiber adhered with the formaldehyde-free adhesive enters a drying system for drying at high speed through a glue spraying blowing pipe under the action of high-pressure steam. Then the fiber glue is subjected to high-efficiency solid-gas separation by a cyclone separator, and falls into a fiber glue mixer after being weighed by a weighing belt, and the fiber glue mixer is in vortex-shaped fiber flow under the pneumatic conveying condition. The formaldehyde-free adhesive is sprayed onto fiber flow from one end of a glue mixer in a conical fine mist form through 4 precise nozzles which are 90 degrees each other under the action of a high-pressure screw pump in an adding amount which is 20% of the total amount of the adhesive, and is fully mixed with wood fibers for the second time under the action of vortex. The adhesive secondary application technology ensures that wood fibers and the adhesive are fully mixed, and saves the adhesive.
9. Wood fiber pavement
Wood fiber attached with the formaldehyde-free adhesive enters a fiber sorting system and then enters a paving machine for mechanical paving through an air-assisted system, and is preformed in a prepressing mode, cut at the same edge and paved at the speed of 195mm/s.
10. Manufacturing formaldehyde-free medium-high density fiberboard
Then the fiber board is put into a hot press and is made into the formaldehyde-free medium-high density fiber board after 272s under the temperature of 180 ℃ and the pressure of 245 Bar.
The fiberboard inspection data obtained in this example are shown in the following table:
| project | Data | Standard of | Determination of |
| Density (g/cm) 3 ) | 0.87 | ≥0.65 | Qualified product |
| Moisture content (%) | 6.5 | 3～13 | Qualified product |
| Expansion ratio of water absorption thickness (%) | 5.2 | 12.0 | Qualified product |
| Internal bond Strength (Mpa) | 0.69 | 0.45 | Qualified product |
| Static bending strength (Mpa) | 27.5 | 24.0 | Qualified product |
| Formaldehyde emission (detection by perforation extraction method) | Not detect | —— | —— |
Example 3: 15mm of density is produced850Kg/m 3 Aldehyde-free medium-high density fiberboard
1. Preparation of aldehyde-free adhesive
1) Filtering and screening water-soluble polymer compound powdery sodium carboxymethyl starch (CMS-Na) with a 120-mesh filter screen;
2) Putting 20 parts of screened sodium carboxymethyl starch into a reaction kettle, simultaneously injecting 2 parts of ethanol with the purity of 80% and 50 parts of water into the reaction kettle, stirring while adding, heating the water to 45 ℃ after uniform mixing, preserving heat and stirring for 30min until the sodium carboxymethyl starch is completely dissolved, and cooling to 40 ℃;
3) Adding buffer 1 part NH 4 CL, keeping the temperature and stirring for 10min;
4) Adding a proper amount of 0.1mol/L HCL to adjust the pH value of the mixed solution to 7.5-8.0;
5) 15 parts of polyvinyl acetate emulsion with the solid content of 50% and 15 parts of polyacrylate emulsion with the solid content of 45% are respectively put into a reaction kettle, stirred while being added, and stirred and mixed for 1h at the temperature of 40 ℃;
6) Adding 0.3 part of preservative 2-methyl-4-isothiazolin-3-one (MIT), and stirring and mixing for 10min at 40 ℃;
7) 10 parts of rice hull powder which is a natural organic filler and is filtered by a 100-mesh filter screen is taken and put into a reaction kettle, and stirring is carried out while adding, and heat preservation and stirring are carried out for 30min;
8) Buffer NaHCO 3 Preparing 10% solution by using water, adding a proper amount of water into a reaction kettle, adjusting the pH value of the mixed solution to 7-8, and uniformly stirring to obtain milky viscous liquid-formaldehyde-free adhesive;
9) The solid content is more than 45%; the viscosity is measured to be 20 to 40 seconds at 25 ℃; pH value: 7-8, after primary filtration by a 25-mesh filter screen, conveying the filter screen to a glue storage tank for storage by a conveying pump.
2. Preparation of waterproofing agent
1) Firstly, sequentially adding 2.40 parts of a water-soluble emulsifier T-80, 3.60 parts of OP-10, 0.60 part of sodium dodecyl sulfate and 50 parts of water into a No. 1 reaction kettle, heating to 80 ℃ to completely dissolve, and uniformly stirring;
2) Sequentially adding 2.4 parts of lipophilic emulsifier S-80, 2.30 parts of anti-foaming agent polypropylene glycol PPG2000, and 38 parts of 58# paraffin into a No. 2 reaction kettle, heating to 90 ℃ to completely melt, uniformly stirring, and preserving heat at 90 ℃ for 15min;
3) Sequentially adding 5 parts of polydimethylsiloxane and 0.40 part of nonionic surfactant glyceryl monostearate into a No. 2 reaction kettle, stirring while adding, and preserving heat at 90 ℃ for 15min to react to form emulsion;
4) Slowly adding 30% of the water solution uniformly stirred in the No. 1 reaction kettle into the No. 2 reaction kettle, stirring while adding, and preserving the temperature at 90 ℃ for 15min to form water-in-oil emulsion; continuously slowly adding 30% of the water solution, stirring while adding, and maintaining the temperature at 90 ℃ for 25min to form an oil-in-water emulsion; slowly adding the rest aqueous solution, stirring while adding, maintaining at 90deg.C for 15min, cooling to room temperature to obtain stable emulsion waterproof agent (solid content > 50%), primarily filtering with 25 mesh filter screen, and transferring to storage tank by stainless steel.
3. Three-residue and sub-small firewood cooking
The three residues in agriculture and forestry and the secondary small firewood material are subjected to mechanical cutting, wind washing and screening, enter a pre-cooking cylinder for first cooking softening under the steam pressure of 7.5bar, are extruded by a high-efficiency wear-resistant conical plug screw device, filter out water contained in the water, loosen firewood material, effectively reduce the grinding power consumption of a thermal mill, enter the cooking cylinder for second cooking softening under the steam pressure of 7.8bar, control the cooking material level height to 2.0m, and then quantitatively control and convey the material by a stainless steel variable screw pitch double-line discharging screw, discharge steam and supply the material by a belt screw, and return the steam to the cooking cylinder to ensure the steam pressure balance of the system, so that the feeding is smooth. The loose firewood after cooking enters a high-temperature high-pressure precise thermal mill through a belt type spiral, and is stirred into a millstone working area running at high speed to be ground into fine and uniform wood fibers under the action of a movable millstone stirring fluted disc. The screening value of wood fiber (which does not pass through a sieve pore with phi 0.8 mm) is less than or equal to 1.7 percent
4. Application of waterproofing agents
The waterproofing agent is filtered to be added in an amount of 1.2% of absolute dry fiber, and is sprayed onto wood fiber in a grinding chamber of a thermal mill from a V-shaped precise nozzle by a high-pressure metering gear pump under the condition that the pressure of the grinding chamber of the thermal mill is 7.5bar higher than the pressure of the grinding chamber of the thermal mill, and is quickly mixed with the wood fiber. The screening value of the wood fiber (which does not pass through a sieve pore with phi 0.8 mm) is less than or equal to 1.7 percent. Even grinding is carried out at a high speed by a millstone of a thermal mill, the waterproof agent is evenly permeated into wood fibers and is fully and evenly mixed with the wood fibers, so that the wood fibers achieve the optimal waterproof effect.
5. Formulation and addition of aldehyde-free adhesives
The formaldehyde-free adhesive prepared from water-based high polymer polyvinyl alcohol (PVA), polyvinyl acetate emulsion, polyacrylate emulsion and additives is conveyed to a glue storage tank of a production workshop through a stainless steel centrifugal pump, filtered through a 25-mesh filter screen, enters a glue mixing box from a gear metering pump according to the application amount of 12% of absolute dry fiber amount, and is uniformly stirred; at the same time, adding isocyanate adhesive (MDI) with the application amount of 6 percent of the absolute dry fiber amount, a release agent and a proper amount of water into a glue mixing box. The addition of the release agent is helpful to solve the problem of sticking the plate during hot pressing of the plate blank, and a proper amount of water is added to ensure the viscosity of the adhesive required by production; the prepared formaldehyde-free adhesive mixed solution is stirred uniformly at room temperature and then enters a production application system, and the application way adopts a mode of primary application of the formaldehyde-free adhesive and secondary application of the formaldehyde-free adhesive.
6. One-time application of aldehyde-free adhesive
Under the action of high-pressure steam, wood fibers attached with the waterproof agent enter a spraying pipeline through an electric control flow valve and pass through a glue spraying blowing pipe at the speed of 32 m/s. The prepared formaldehyde-free adhesive is precisely metered and weighed, and after being filtered by a 30-mesh precise filter cylinder, the prepared formaldehyde-free adhesive is sprayed into a glue spraying blowing pipe in a fan-shaped fine mist mode through three precise V-shaped nozzles which are 75 degrees each other by a 60-degree angle formed between the flow direction of wood fibers and the glue spraying blowing pipe by a high-pressure screw pump according to the additive amount of 80% of the total adhesive, so that the formaldehyde-free adhesive can be uniformly adhered to all wood fibers adhered with a waterproof agent through the glue spraying blowing pipe. Through the diffusion effect of the venturi tube of the glue spraying and blowing tube, the wood fiber and the aldehyde-free adhesive are ensured to be fully mixed.
7. Drying of wood fibres
The waterproofing agent is sprayed onto wood fiber in the grinding chamber of the thermal mill from a precise nozzle in a conical fine mist shape by a high-pressure double-gear metering pump after being filtered, and is uniformly infiltrated into the wood fiber under the high-speed running of the grinding disc of the thermal mill, and is fully and uniformly mixed with the wood fiber, so that the wood fiber achieves the optimal waterproof effect. And uniformly mixing the wood fiber impregnated with the waterproof agent with the formaldehyde-free adhesive in a glue spraying blowing pipe before drying and in a glue mixer after drying. The inlet temperature of the drying pipeline is 136 ℃, the outlet temperature is 50 ℃, and the moisture content of the dried wood fiber is 6.5%.
8. Secondary application of aldehyde-free adhesive
Wood fiber adhered with the formaldehyde-free adhesive enters a drying system for drying at high speed through a glue spraying blowing pipe under the action of high-pressure steam. Then the fiber glue is subjected to high-efficiency solid-gas separation by a cyclone separator, and falls into a fiber glue mixer after being weighed by a weighing belt, and the fiber glue mixer is in vortex-shaped fiber flow under the pneumatic conveying condition. The formaldehyde-free adhesive is sprayed onto fiber flow from one end of a glue mixer in a conical fine mist form through 4 precise nozzles which are 90 degrees each other under the action of a high-pressure screw pump in an adding amount which is 20% of the total amount of the adhesive, and is fully mixed with wood fibers for the second time under the action of vortex. The adhesive secondary application technology ensures that wood fibers and the adhesive are fully mixed, and saves the adhesive.
9. Wood fiber pavement
Wood fiber attached with the formaldehyde-free adhesive enters a fiber sorting system and then enters a paving machine for mechanical paving through an air-assisted system, and is subjected to prepressing forming, trimming and cutting, wherein the paving speed of the wood fiber is 200mm/s.
10. Manufacturing formaldehyde-free medium-high density fiberboard
Then the fiber board is put into a hot press, and the aldehyde-free medium-high density fiber board is manufactured after the hot pressing temperature of the board blank is 180 ℃ and the hot pressing pressure is 245Bar and the hot pressing time is 290 s.
The fiberboard inspection data obtained in this example are shown in the following table:
The technical innovation and beneficial effects of the invention are as follows;
1. the isocyanate adhesive (MDI) modification technology is adopted, so that the moisture curing performance (curing in water reaction) of the isocyanate adhesive (MDI) and the bonding property to metal materials are improved. Mixing the new formaldehyde-free adhesive with isocyanate adhesive (MDI) to wrap the MDI glue particles with the new formaldehyde-free glue particles. The non-binding property of the novel formaldehyde-free adhesive to the metal material makes up the defect of strong binding property of the isocyanate adhesive (MDI) to the metal material, and solves the problems of the MDI adhesive that the conveying pipeline is blocked, the equipment is adhered and the like.
2. The fan-shaped fine mist application mode of the glue spraying blowing pipe before wood fiber drying and the cone-shaped fine mist application mode of the glue mixer after wood fiber drying are adopted, so that the wood fiber and the adhesive are fully and uniformly mixed, the mechanical property and the internal bonding strength of the product are improved, and the using amount of the adhesive is saved.
3. The waterproof agent is sprayed onto wood fibers in a grinding chamber of the thermal mill through a precise nozzle by a high-pressure metering pump, uniformly permeates into the wood fibers under the high-speed running of a grinding disc of the thermal mill, and is fully and uniformly mixed with the wood fibers, so that the optimal waterproof effect is achieved, and the water absorption expansion rate of the product is reduced.
4. The novel formaldehyde-free adhesive and isocyanate adhesive (MDI) compounding technology is adopted, so that the isocyanate adhesive (MDI) adhesive particles are wrapped by the novel formaldehyde-free adhesive particles, the curing time of the isocyanate adhesive (MDI) is improved, the production hot-press curing period is adjusted according to the proportion, the problem that the curing time of the isocyanate adhesive (MDI) in wood fibers is short is solved, the formaldehyde-free characteristic of the isocyanate adhesive (MDI) is fully reserved, and the formaldehyde-free characteristic of the board is endowed.
5. The experiment develops a new technology for mass production of the formaldehyde-free fiber board, solves the problem that the formaldehyde-free board cannot be produced in a normal scale by adopting isocyanate adhesive (MDI), and realizes the industrialized revolution of the formaldehyde-free fiber board.
Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention, as will be apparent to those skilled in the art, without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. The manufacturing method of the formaldehyde-free added formaldehyde-free medium-high density fiberboard is characterized by comprising the steps of manufacturing a formaldehyde-free adhesive, manufacturing a waterproof agent, processing raw materials, applying the waterproof agent, preparing and adding the formaldehyde-free adhesive, applying the formaldehyde-free adhesive once, drying wood fibers, applying the formaldehyde-free adhesive twice, paving the wood fibers, and manufacturing the formaldehyde-free medium-high density fiberboard, wherein the formaldehyde-free adhesive is manufactured by aqueous high polymer polyvinyl alcohol (PVA), polyvinyl acetate emulsion, polyacrylate emulsion and additives;
The preparation and addition steps of the formaldehyde-free adhesive are that the formaldehyde-free adhesive is conveyed to a glue storage tank of a production workshop through a stainless steel centrifugal pump, filtered through a 25-mesh filter screen, and enters a glue mixing box from a gear metering pump according to the application amount of 12% -16% of the absolute dry fiber amount, and is uniformly stirred; meanwhile, adding isocyanate adhesive (MDI), a release agent and water, wherein the application amount of the isocyanate adhesive is 6-8% of the absolute dry fiber amount, into a glue mixing box;
the preparation method of the formaldehyde-free adhesive comprises the following steps:
1) Filtering and screening water-soluble polymer compound powdery sodium carboxymethyl starch (CMS-Na) with a 120-mesh filter screen;
2) Putting 20 parts of screened sodium carboxymethyl starch into a reaction kettle, simultaneously injecting 2 parts of ethanol with the purity of 80% and 50 parts of water into the reaction kettle, stirring while adding, heating the water to 45 ℃ after uniform mixing, preserving heat and stirring for 30min until the sodium carboxymethyl starch is completely dissolved, and cooling to 40 ℃;
3) Adding buffer 1 part NH 4 CL, keeping the temperature and stirring for 10min;
4) Adding a proper amount of 0.1mol/L HCL to adjust the pH value of the mixed solution to 7.5-8.0;
5) 15 parts of polyvinyl acetate emulsion with the solid content of 50% and 15 parts of polyacrylate emulsion with the solid content of 45% are respectively put into a reaction kettle, stirred while being added, and stirred and mixed for 1h at the temperature of 40 ℃;
6) Adding 0.3 part of preservative 2-methyl-4-isothiazolin-3-one (MIT), and stirring and mixing for 10min at 40 ℃;
7) 10 parts of rice hull powder which is a natural organic filler and is filtered by a 100-mesh filter screen is taken and put into a reaction kettle, and stirring is carried out while adding, and heat preservation and stirring are carried out for 30min;
8) Buffer NaHCO 3 Preparing 10% solution by using water, adding a proper amount of water into a reaction kettle, adjusting the pH value of the mixed solution to 7-8, and uniformly stirring to obtain milky viscous liquid-formaldehyde-free adhesive;
9) The solid content is more than 45%; the viscosity is measured to be 20 to 40 seconds at 25 ℃; pH value: 7-8, after primary filtration by a 25-mesh filter screen, conveying the filter screen to a glue storage tank for storage by a conveying pump.
2. The method for producing formaldehyde-free medium-high density fiberboard according to claim 1, wherein the step of producing the waterproofing agent comprises:
1) Sequentially adding 2.4-2.6 parts of water-soluble emulsifier T-80, 3.6-3.8 parts of OP-10, 0.6-0.8 part of sodium dodecyl sulfate and 50 parts of water into a No. 1 reaction kettle, heating to 80 ℃ to completely dissolve, and uniformly stirring;
2) Sequentially adding 2.4-2.6 parts of lipophilic emulsifier S-80, 2.3-2.5 parts of anti-foaming agent polypropylene glycol PPG2000, and 38-40 parts of 58# paraffin into a No. 2 reaction kettle, heating to 90 ℃ to completely melt, uniformly stirring, and preserving heat for 15min at 90 ℃;
3) Sequentially adding 5-6 parts of polydimethylsiloxane and 0.4-0.6 part of nonionic surfactant glyceryl monostearate into a No. 2 reaction kettle, stirring while adding, and preserving heat at 90 ℃ for 15min to react to form emulsion;
4) Adding 30% of the water solution which is uniformly stirred in the No. 1 reaction kettle into the No. 2 reaction kettle, stirring while adding, and preserving the temperature for 15min at 90 ℃ to form water-in-oil emulsion; continuously adding 30% of the aqueous solution, stirring while adding, and maintaining the temperature at 90 ℃ for 25min to form an oil-in-water emulsion; adding the rest water solution, stirring while adding, maintaining at 90deg.C for 15min, cooling to room temperature, filtering, and transferring to storage tank by stainless steel transfer pump.
3. The method for manufacturing formaldehyde-free medium-high density fiberboard according to claim 2, wherein the raw materials are processed by mechanically cutting, wind washing and screening three residues of agriculture and forestry and secondary small firewood materials, then entering a pre-cooking cylinder for first cooking softening under the steam pressure of 7.5-8.0 bar, then extruding by a high-efficiency wear-resistant conical plug screw device, filtering out water contained in the raw materials, loosening firewood materials, then entering a cooking cylinder for second cooking softening under the steam pressure of 7.3-7.8 bar, controlling the height of the cooking material level to be 1.5-2.0 m, then quantitatively controlling and conveying the raw materials by a stainless steel variable screw pitch double-line discharging screw, and grinding the loose firewood materials into fine and uniform wood fibers.
4. The method for producing formaldehyde-free medium-high density fiberboard according to claim 3, wherein the waterproofing agent is applied by filtering the waterproofing agent to isolate 1.2% -1.6% of the fiber, and spraying the waterproofing agent from a V-shaped precise nozzle to the wood fiber in the grinding chamber of the thermal mill to mix with the wood fiber by a high-pressure metering gear pump through a check valve at a pressure 7.5bar higher than the pressure in the grinding chamber of the thermal mill.
5. The method for manufacturing formaldehyde-free medium-high density fiberboard according to claim 4, wherein the formaldehyde-free adhesive is sequentially applied, wood fiber attached with waterproof agent passes through the glue spraying blowing pipe at a speed of 28-32 m/s along the glue spraying pipe through an electric control flow valve under the action of high-pressure steam, the prepared formaldehyde-free adhesive is precisely metered and weighed, after being filtered by a 30-mesh precise filter cylinder, the wood fiber is sprayed into the glue spraying blowing pipe in a fan-shaped fine mist manner through three precise V-shaped nozzles which are 75 degrees each other at an angle of 60 degrees along the wood fiber flow direction by a high-pressure screw pump according to the addition amount of 80 percent of the total adhesive, and the cross section of the whole glue spraying blowing pipe is sealed.
6. The method for manufacturing formaldehyde-free medium-high density fiberboard according to claim 5, wherein the step of drying the wood fiber is that the wood fiber impregnated with the waterproof agent is uniformly mixed with formaldehyde-free adhesive in a glue spraying blowing pipe and in a glue mixer for the second time before drying, the inlet temperature of a drying pipeline is 110-140 ℃, the outlet temperature is 45-70 ℃, and the water content of the dried wood fiber is 6-13%.
7. The method for manufacturing formaldehyde-free medium-high density fiberboard is characterized in that formaldehyde-free adhesive is secondarily applied, wood fiber adhered with the formaldehyde-free adhesive is dried by a high-pressure steam through a glue blowing pipe at a high speed, then is subjected to solid-gas separation through a cyclone separator, is weighed and measured by a weighing belt and falls into a fiber glue mixer, and is subjected to vortex-shaped fiber flow under the pneumatic conveying condition, the formaldehyde-free adhesive is sprayed onto the fiber flow from one end of the glue mixer in a conical fine mist form through 4 precise nozzles which are 90 degrees under the action of a high-pressure screw pump, and is secondarily and fully mixed with the wood fiber under the vortex action.
8. The method for manufacturing formaldehyde-free medium-high density fiberboard according to claim 7, wherein the step of wood fiber paving is that wood fibers with formaldehyde-free adhesive are subjected to fiber sorting, then are subjected to mechanical paving by an air-assisted system, and subjected to prepressing forming and trimming and cutting.
9. The method for manufacturing the formaldehyde-free medium-high density fiberboard is characterized in that the step of manufacturing the formaldehyde-free medium-high density fiberboard is that a blank plate after being divided by the trimming is put into a hot press, and the formaldehyde-free medium-high density fiberboard is manufactured by 3-10 min under the temperature of 150-180 ℃ and the pressure of 220-250 Bar.
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