Classifications

• • 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
  • B27N1/003—Pretreatment of moulding material for reducing formaldehyde gas emission
• • 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
• • 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
  • B27N3/06—Making particle boards or fibreboards, with preformed covering layers, the particles or fibres being compressed with the layers to a board in one single pressing operation

Definitions

• This invention relates to board of lignocellulose- conta ning material m the form of particles or fibers such as particle board and fiberboard.
• the invention also relates to a method of manufacturing such board.
• Board of this type is manufactured by disintegrating the lignocellulose-contaming material to particles or fibers. This disintegrated material is then dried, glued and formed to a mac. Thereby glueing can be performed prior to or after the drying. The finished board is then produced by final drying of the mat by hot pressing for hardening the glue so that a finished board is formed.
• Particle board is made of material, whicn is disintegrated to coarse particles while fiberboard is made of material, which is disintegrated by defibe ⁇ ng, i.e. to more or less exposed fibers.
• the strength of the board is determined by the binding of the particles or fibers to each other.
• the strength of dry-formed glued board is determined by the glue addition, m that the hardened glue binds the particles or fibers togetner.
• glue As binding agent at the manufacture of glued board normally urea-formaldehyde glue is used, which is admixed to tne disintegrated material.
• the amount of glue can be up to 6% or more.
• the glue is relatively expensive, and, therefore, it is desired to minimize the glue addition.
• the present invention renders it possible to improve the strength of the aforesaid types of board.
• the glue addition can be reduced while maintaining the strength of the board.
• the lignm at least m the surface layer of the particles or fibers is modified chemically prior to the final drying, so that an increase m binding reactivity is obtained by introducing hydrophilic groups, and so that the softening temperature of the lignm is lowered.
• the chemical modification of the lignm can be brought about by chemicals, for example sulpnonation or ozone treatment, or some other way.
• the chips are disintegrated by defibermg a defibermg apparatus in one or more steps. After the disintegration, glueing, drying, forming and hot pressing are carried out. Alternatively, drying can take place prior to glueing. At hot pressing, a temperature of 100-115°C is tried to be obtained at the centre of the board for glueing systems based on urea-formaldehyde.
• chemicals reacting with the lignm are a ⁇ ded to the material before the hot pressing.
• the cnemical treatment modifies the lignm chemically so that an increased binding reactivity is obtained by the introduction of hydrophilic groups.
• the softening temperature of the lignm also is lowered at the same time.
• chemicals known per se can be mentioned Na 2 S0 3 and NaHSO,.
• the chemicals can be added after the final defibermg of the material, during or prior to the defibermg.
• the chemicals can be added in direct connection to the defibermg m a d sc refiner, for example in the inlet, the centre or further outward to the periphery of the discs.
• the chemicals should be added immediately before or ⁇ urmg the second or last defibermg step.
• Other chemical dosing points can be m the blow line after the refiner, m connection with the drying or at the preheating before the defibermg.
• the raw material m the form of chips is disintegrated to particles.
• the particles are dried, glued and formed to a web, which is hot pressed to a finished board.
• hardenable glue based on urea-formaldehyde normally is used.
• Chemicals reacting with the lignm are added also in this case prior to the hot pressing.
• the chemical treatment has the same object and can be the same as at the manufacture of fiberboard.
• the chemicals can be added after the final disintegration of the material, during or before the disintegration, preferably immediately before the disintegration, so that the chemical reaction in the lignin takes place during the disintegration and subsequent drying.
• the chemical treatment preferably sulphonation, has the object to chemically modify the lignin at least in the surface layer of the particles or fibers, partly by introducing hydrophilic groups so that an increased binding reactivity is obtained in the lignin, and partly by lowering the softening temperature of the lignin.
• the chemically modified surface layer should have a thickness of about l ⁇ m where the lowering of the softening temperature shall be at least 10°C.
• the lignin should be so sulphonated that a sulphur distribution over the entire cross-section of the particles or fibers is obtained, but where the sulphur content is concentrated to a surface layer of the particles or fibers.
• the sulphur content in a 2 ⁇ m thick surface layer should be at least 50% higher than the average sulphur content in the remaining parts of the particles or fibers.
• the sulphur content in a l ⁇ m thick surface layer should be at least twice as high as the average sulphur content in the remaining parts of the particles or fibers.
• the temperature is increased above the hardening temperature of the glue in the entire board in order to ensure throughhardening of the board.
• the lowest temperature in the board at hot pressing thus, must exceed the hardening temperature required.
• the softening temperature of the lignin in the surface layer of the particles or fibers shall be lowered to a temperature below the lowest temperature in the board at hot pressing.
• the soft lignin layer in the surface of the particles or fibers is pressed out in the point of contact with adjacent particles or fibers, whereby the size of the contact surfaces increases, the glue is utilized more effectively and improved strength properties are obtained, especially in transverse direction of the board.
• the increase m binding reactivity of the lignm by the introduction of hydrophilic groups further implies, that the lignm can form hydrogen bindings more easily. Thereby the binding forces per surface unit increase, and the strength of the board is increased additionally.
• the chemicals should be added at or after the disintegration of the material.
• the dosing of chemicals, the reaction time and temperature conditions must be accurately controlled.
• the modification of the lignm is acnieved at lower dosmgs, and large parts of the interior of the particles or fibers will be unaffected by the sulphonation, so that these parts remain stiff and dimensional stable, which is of a ⁇ vantage for the strength of the board.
• the lignocellulosic material in the form of particles or fibers is partially sulphonated so that the organically combined sulphur exceeds the native sulphur content of the lignocellulose material but is lower than 0.4%.
• the combined sulphur content is 0.04-0.2%.
• the sulphur is substantially combined with the lignm of the lignocellulose material in the form of sulphonic acid groups.
• Raw material in the form of chips from European beech was preheated to 175°C, and an Na 2 S0 3 solution was added. Thereafter disintegration of the material was carried out in a defibering apparatus.
• the charged amount of sulphite (Na 2 S0 3 ) corresponded to 10 kg/ton chips (2.5 kg sulphur/ton chips) .
• a reference charge without chemical addition was also made.
• the softening temperature of the lignin in the reference charge was about 125°C, while the lignin softening temperature of the charge treated with chemical was lowered to about 100°C in the surface layer of the fiber material.
• a urea-formaldehyde glue (UF-glue) was added.
• the charged amount for material treated with sulphite was corresponded by 8% UF- glue, counted on dry fiber material and for the reference material 13% UF-glue, counted on dry fiber material.
• the two material charges were dried to a dry matter content of about 90% and dry-formed to mats.
• These fiber mats were pre- pressed with a pressure of 1.5 MPa and hot pressed to board for 6 minutes at 170°C.
• the temperature at the centre of the board at the end of hot pressing was measured to be between 115 and 120°C, i.e. lower than the softening temperature of the lignin in the reference charge but higher than the softening temperature of the lignin in the charge treated with sulphite.
• Raw material in the form of chips from spruce was preheated to 170°C, and an Na 2 S0 3 solution was added.
• the material was thereafter defibered m a defibermg apparatus.
• the charged amount of sulphite corresponded to 15 and, respectively,
• the softening temperature of the lignm in the reference charge was about 125°C, while the lignm softening temperature of the charge treated with chemical was lowered to below 100°C m the surface layer of the fiber material.
• the fiber material was dried to a dry matter content of about 90% and dryformed to mats. These mats were pre-pressed with a pressure of 1.5 MPa and hot pressed to board for 6 minutes at 170°C. The temperature at the centre of the board at the end of hot pressing was measured to be between 115 and 120°C, i.e. lower than the softening temperature of the lignm m the reference charge but higher than the softening temperature of the lignm in the charge treated with sulphite.
• the result shows a substantial difference between the properties of the board treated with chemical and of the reference board.
• the strengths show the effect of increased binding reactivity and increased binding area, which verifies the technical effect of the invention.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Paper (AREA)
• Charge And Discharge Circuits For Batteries Or The Like (AREA)
• Laminated Bodies (AREA)

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Cited By (2)

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Citations (2)

• 1993
  • 1993-05-19 SE SE9301735A patent/SE502663C2/sv not_active IP Right Cessation
• 1994
  • 1994-02-21 TW TW083101453A patent/TW261567B/zh active
  • 1994-02-22 IL IL10873994A patent/IL108739A0/xx unknown
  • 1994-02-23 ZA ZA941236A patent/ZA941236B/xx unknown
  • 1994-03-01 JP JP6525304A patent/JPH08510186A/ja active Pending
  • 1994-03-01 NZ NZ263890A patent/NZ263890A/en unknown
  • 1994-03-01 BR BR9406538A patent/BR9406538A/pt not_active Application Discontinuation
  • 1994-03-01 EP EP94912717A patent/EP0699121A1/en not_active Ceased
  • 1994-03-01 HU HU9503248A patent/HUT78030A/hu unknown
  • 1994-03-01 CA CA002162396A patent/CA2162396A1/en not_active Abandoned
  • 1994-03-01 SK SK1436-95A patent/SK143695A3/sk unknown
  • 1994-03-01 CN CN94192126A patent/CN1123533A/zh active Pending
  • 1994-03-01 KR KR1019950704796A patent/KR960701731A/ko not_active Application Discontinuation
  • 1994-03-01 PL PL94311658A patent/PL174283B1/pl unknown
  • 1994-03-01 WO PCT/SE1994/000164 patent/WO1994026487A1/en not_active Application Discontinuation
  • 1994-03-01 CZ CZ952994A patent/CZ299495A3/cs unknown
  • 1994-03-01 AU AU65145/94A patent/AU677651B2/en not_active Ceased
  • 1994-04-26 HR HR9301735-8A patent/HRP940269A2/xx not_active Application Discontinuation
• 1995
  • 1995-11-17 NO NO954661A patent/NO954661D0/no unknown
  • 1995-11-17 FI FI955571A patent/FI955571A0/fi unknown

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