CA1129761A - Process for preparing wood chip boards - Google Patents
Process for preparing wood chip boardsInfo
- Publication number
- CA1129761A CA1129761A CA337,180A CA337180A CA1129761A CA 1129761 A CA1129761 A CA 1129761A CA 337180 A CA337180 A CA 337180A CA 1129761 A CA1129761 A CA 1129761A
- Authority
- CA
- Canada
- Prior art keywords
- weight
- glue
- chip
- chip material
- liquor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L97/00—Compositions of lignin-containing materials
- C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
-
- 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
- B27N1/006—Pretreatment of moulding material for increasing resistance to swelling by humidity
-
- 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
- B27N3/002—Manufacture of substantially flat articles, e.g. boards, from particles or fibres characterised by the type of binder
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
- C08L61/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Medicinal Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Health & Medical Sciences (AREA)
- Forests & Forestry (AREA)
- Materials Engineering (AREA)
- Dry Formation Of Fiberboard And The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides in a process for prepar-ing a wood chip board in which the wood raw material is subjected to a cutting operation and to a subsequent drying step so as to achieve a moisture content of less than 4% by weight, whereafter the wood chip material is glued with an aqueous liquor of an amino-plast and then the glued chip material thus obtained is compressed under heat, the improvement in which the glueing is effected with a liquor having a solid resin content in the range between 20 and 35% by weight, the amount of glue used containing less than 6% by weight of solid resinbased on the total chip material weight cal-culated as absolutely dry material.
The present invention provides in a process for prepar-ing a wood chip board in which the wood raw material is subjected to a cutting operation and to a subsequent drying step so as to achieve a moisture content of less than 4% by weight, whereafter the wood chip material is glued with an aqueous liquor of an amino-plast and then the glued chip material thus obtained is compressed under heat, the improvement in which the glueing is effected with a liquor having a solid resin content in the range between 20 and 35% by weight, the amount of glue used containing less than 6% by weight of solid resinbased on the total chip material weight cal-culated as absolutely dry material.
Description
97~l The present invention rela-tes to a proccss ~or prepar-ing wood chip boards in which the raw wood material is subjected to a cutting operation and a subsequent drying step so as to achieve a moisture content o~ less than 4%, preferably less than
2%, whereafter it is glued (sized) with an aqueous liquor (bath) of an aminoplast and then the glued (sized) chip material thus obtained is compressed under pressure and heat to give the boards.
The mechanical properties of wood chip boards are depen-dent to a substantial extent on the aminoplast glue used for bond-ing of the chip material. Generally, an increase of the amount ofthe glue used for the bonding of the chip material is accompanied with an increase of the strength. It is clear that the glue repre-sents a substantial cost factor in the preparation of wood chip boards, so that efforts are being made to use as small an amount of glue as possible. A urther reason for keeping the amount of glue as low as possible is that the formaldehyde contained in aminoplast resin ma~ cause undesired environmental problems.
However, with the conventional process mentioned above such is restricted by the decrease in the strength of the boards accom-panying a decrease in the amount of glue.
Heretofore the optimum procedure has been the use of aglue liquor having a solid resin content of about 50% by weight and the use of several features in the mixing apparatus for glue-ing the chip material, i.e. to achieve as high a number of glue-ing point as possible on the chip material, which points also determine the strength of the boards. With processes of the above type for preparing so called "normal boards", i.e. boards having a specific gravity of more than 650 kg/m when the usual chip material is used and in which the chip material is glued substan-tially all over (on all sides), it has been possible to achievedthe properties laid down in norm rules with a content of solid resin of about 8 to 9% by weiyht, calculated on basis of absolutely dry ~a.d.) chip material.
The presen-t invention pxovides a process of -the type mentioned above by which a further improved utili~a-tion of the glue for glueing the chip ma-terial may be obtained, in which pro-cess for achieving a required strength of the boards with a pre-determined chip material a lower amount of solid resin is suffic-ient than has been possible heretofore. The process of the present inven-tion may be effected with conventional devices without a substantial change of the procedure and without a sub stantial change of the period of time required for the process.
According to the present invention there is provided in a process for preparing a wood chip board in which the wood raw material is subjected to a cutting operation and to a subsequent drying step so as to achieve a moisture content of less than 4 by weight whereafter the wood chip material is glued with an aqueous liquor of an aminoplast and then the glued chip material thus obtained is compressed under heat, the improvement in which the glueing is effected with a liquor having solld resin content in the range between 20 and 35% by weight the amount of glue used containing less than 6% by weight of solid resin based on the total chip material weight calculated as absolu-tely dry material.
Thus in accordance with the present invention the glue-ing step is carried out with a liquor having a so:Lid res:Ln content of between 20 and 35% by weight, preferably between 22 and 30% by weight and the amount of glue used contains less than 6% by weight, preferably between 3 and 5% by weight of solid resin, calculated on basis of the whole a.d. chip material.
In the process of the present invention wood chip boards are obtained with use of a relatively small amount of glue, the mechanical values of the boards corresponding to the norm require-ments. In the process of the present invention also the problem frequently important in the conventional processes of the type ~9~6~
mentioned above, i.e. that the fine chips present in the chip material ta~e up very much more glue than the coarser chips due to the greater surface thereof, based on the weight, may be counteracted.
Because of the generally good distribu-tion of the glue on the surface of the chip material obtainable by the process of the present invention the glue is very well utilized so that boards having very good mechanical properties may be obtained with a relatively small amount of the glue. The fact that the process ~-of the present invention allows the improvement of the glue absorp-tion of the coarse portion of the chip material in the glueing step to the debit of the fine portion of the chip material repre-sents a very important effect.
A comparative test resulted e.g. in the Eact that in cJlueing chip material with 55% by weicJht of a glue llquor usiny ~ by weight of solid resin, calculated on basis of a.d. chip material, the greatest chip fraction (residue on a 2 ~m sieve) had a content of solid resin of 2.0% by weight, based on a.d.
chip, and the smallest chip fraction (passing a 0.25 mm sieve) had a content of solid resin of 9.9% by weight, based on a.d.
chip material. In case of glueing the same chip material with 25% by weight of a glue liquor using again 4% by weight oE solid resin, calculated on basis of a.d. chip material, glueings of 2.9 and 7.9% respectively by weight of solid resin, calculated on basis of a.d. chip material have been obtained for the above mentioned chip fractions. Accordingly, the ratio of glueing of the fraction of the largest chips to glueing of the smallest chips has been reduced from about 1:5 to somewhat more than 1:2.5.
As mentioned above the glueing step of the process of the invention is carried out preferably with a liquor, the solid resin content of which is in the range of 22 to 30~ by weight, as in such a way both the required uniform glueing of the chip mass 7 IEi~
and the requirements with respect to the moisture content oE the chip mass made by the compressing step may be satisfied.
In the glue dis-tributlon obtained by the process of -the presen~ invention it is also desirable to keep the mois.ure con-tent of the glued chip material to be subjected to the compressing step below 12% by weight which may be achieved by selection of the concentration of the glue liquor, as the concentration of -the glue liquor determines also the amount of wa-ter applied onto the chip material in the glueing step.
In the practice the addition of a thickening agent to the glue liquor has proved to be advantageous as thereby an undesired penetration of the glue into the chip material may be counteracted without any disadvantageous hindrance of the distri-bution of the glue. Examples of useful thickening agents are especially cellulose derivatives, e.g. methyl cellulose, ethyl cellulose and carboxymethyl cellulose. These compounds react neutrally with respect to the curing of the glue. -Such as in case of the conventional process of the type mentioned above also according to the process of the invention a paraffin emulsion or molten paraffin may be added for rendering the chip boards hydrophobic. Furthermore, according to the pro-cess of the invention agents for rendering the chip board flame-retardant or fungicides may be applied onto the chip material during the glueing step, e.g. by adding such agents to the glue liquor.
The present invention will be further illustrated by way of the following Examples.
Example 1 The glueing degree obtained by glueing a mixture of wood chips containing chips of different sizes with use of glue liquors of different concentrations on basis of highly diluteable urea-formaldehyde glue was tested. The mixture of wood chips was pre-~2~7~
pared from hardwood and coniferous wood an~ had a chip size distribution in accordance with the following sieve analysls:
> 2.0 mm 7.8% 0.25 - 0.5 mm 22.8~
1.0 - 2.0 mm 25.8% < 0.25 mm 9.1%
0.5 ~ 1.0 mm 3~.5%
Glue liquors containing 55 and 25% by weight of solid resin were used. Amounts of these liquors were applied onto the chips such that the glueing for each liquor concentration was 4%
by weight of solid resin, based on a.d. chip material. The glue-ing was carried out in a glueing mixer with addition of air bymeans of a nozzle for dispensing two components. After the glue-ing step the chips were fractionated in order of their size by a sleve analysis and the glueing degree was established by deter-mination of the nitrogen content. The obtained values are reported in the following Table.
T a b l e Nitrogen content chip fraction 5S% by weight of25% by weight liquor of liquor 20~ 2.0 mm 0.56% 0.78%
1.0 - 2.0 mm 0.65% 0.90 0.5 - 1.0 mm 0.98% 1.11%
0.25 - 0.5 mm 1.54% 1.33%
c 0.25 mm 2.52% 2.063%
.
In each case the values of the nitrogen content refer to dry chipmaterial. Itcan beseen howit ispossible toachieve acon-siderable proportionation of the glue distribution on coarse and fine chip fractions by use of the highly diluted glue liquors of the present invention.
Exam~
A chip material was used for the preparation of chip ~Z917~
boards which was obtained in a conventional r~anner hy cuttiny down of 20% by weight trunk woocl, 25% by weigh-t chopping pieces and 55~ by weight waste material of sawmills (mainly sawdust) and con-sisted with respect to the wood types, of G5% by weight coniferous wood and 35% by weight beech and other hardwood. The chip mixture thus prepared was separated by means of adequate screening devices into a coarse portion for the middle layer and a fine portion for the cover layer. The fine portion had a moisture content of 3.5%
by weight before the glueing step and the coarse portion and a moisture content of 1% by weight. The chips -thus prepared were glued with a glue liquor having a solid resin content of 35% by weight and containing furthermore the required amounts of curing and buffering substances as well as a paraffin emulsion. The amount of glue was selected such that the chip material or the cover layer had a glueing deyree of 6.56 by weight of -tlle solid resin and the chip material for the middle layer had a glueing degree of 5.S% by weight of the solid resin, both calculated on basis of a.d. chip material. The moisture of the glued chip was 13.1~ by weight in case of the fine portion and 10% by weight in case of the coarse portion. The glued chip material was scattered to give a three-layer fleece and compressed in a press having sevexal floors under pressure and heat during a compressing period of 14 sec/mm raw thickness to give a chip board having a thick-ness of 19 mm and a specific gravity of 685 kg/m3. The thus obtained chip board prepared mainly from waste wood satisfied the requirements of DIN 68763.
Example 3 Chip material as it is used for preparing chip boards and which has been dried -to a moisture content of 1.5% was glued in a glueing mixer with a glue liquor containing in addition to the usual amounts of curing and buffering substances and a paraffin emulsion in an amount corresponding to an addition of 0.8% by weight of solid paraffin 29% by weight of solid resin (calculated on basis of a.d. chip material). The supply o:E chip material and glue liquor was adjusted such that a glueing degree of 4.8% by weight of solid resin, based on a.d. chip material was obtained. The glued chip material was scattered to give a fleece which had a moisture content of 10.8% by weiyht after the scatter-ing station. It was compressed in a press having one floor to give a chip board. The temperature of the heating plate was 200C
the pressure was maximally 30 bar and the compressing time 3.15 min. A chip board having a raw thickness of 23.5 mm and a speci-fic gravit~ of 670 kg/m3 was obtained. The strength values of this board satisfied the re~uirements of DIN 68763.
Example 4 Chip material obtained by usual treatment of (:runk wood in cutting devices and consisting of 90% by weight conifero~ls wood and 10% by weight light hardwood with a small amount of finest particles was dried in a rotary nozzle dryer to a moisture content of less than 1% by weight. This chip material was pro-vided first of all with molten paraffin in an amount of 0.8~, based on a.d. chip material, and then glued with a glue liquor containing 22% by weight of solid resin. In addition the glue liquor contained 2% by weight of ammonium chloride, calculated on basis of solid resin. A glueing degree of 3.5% by weight, of solid resin, calculated onbasis of a.d. chipmaterial wasadjusted.
The moisture content of the gluedchips, measuredafter thescattering device wasll.5% by weight. From this chipmaterial, achip boardhav-ing a thickness of 18 mm and a specific gravity of 700 kg/m3 was prepared in a press having one floor. The properties of the board satisfied the requirements of DIN 68763.
Example 5 A raw mater al consisting of about 50~ by weight trunk wood and 50~ by weight waste wood (saw dust, chopping pieces) was cut, dried to a moisture conten-t of about 1% by weight and the chip materiai was separated into a fine portion and a coarse por-tion. The fine portion and the coarse portion were glued separ-ately with aqueous liquors of a commercial urea-formaldehyde--glue.
For glueing the fine portion a liquor containing 24.9% by weight of solid resin was used, which contained additionally 0.1go by weight of ammonium chloride (based on solid resin), a paraffin emulsion as hydrophobic agent and 2% by weight of a hydroxyethyl cellulose as thickening agent (based on solid resin). The addi-tion of the thickening agent resulted in a viscosity of the highly diluted glue liquor of 105 mPa.s. The amount of the glue liquor was selected such that a glueing of 4.2% by weight of solid resin, calculated on basis of a.d. fine portion of the chip material was obtained. The moisture content of the glued chips was l~go by weiyht. A glue liquor COntaininCJ 33.1% by weight of solid resin with an addition of 1.6g6 by weight of ammonium chloride (calcu-lated on basis of solid resin), a paraffin emulsion and 1% by weight (based on solid resin) of the above mentioned thickening agent was used for glueing the coarse portion of the chip material.
The viscosi~y of the highly diluted glue liquor was 100 mPa.s due to the addition of the thickening agent. The amount of this liquor was selected such that a glueing degree o ~.2% by weight of solid resin, calculated on basis of a.d. coarse portion, was obtained. The moisture content of the glued chips was 8go. Then the two glued chip fractions were scattered in separated scatter-ing devices to give a three-layer chip fleece the fine chip por-tion forming the cover layers and the coarse chip portion forming the middle layer. The chip fleece was compressed in a heating press under pressure and heat with 15 sec/mm raw thickness to a 19 mm chip board having a specific gravity of 68~ kg/m3. The strength values of this board satisfied very well the requirement of DIN 68763. A comparative board prepared under the same condi-~2~7~L
tions, however, with use of glue liquors without any thickening agent also sa-tisfied the requirements of DIN 6~763, but the strength values were lower by about 15%.
g .
The mechanical properties of wood chip boards are depen-dent to a substantial extent on the aminoplast glue used for bond-ing of the chip material. Generally, an increase of the amount ofthe glue used for the bonding of the chip material is accompanied with an increase of the strength. It is clear that the glue repre-sents a substantial cost factor in the preparation of wood chip boards, so that efforts are being made to use as small an amount of glue as possible. A urther reason for keeping the amount of glue as low as possible is that the formaldehyde contained in aminoplast resin ma~ cause undesired environmental problems.
However, with the conventional process mentioned above such is restricted by the decrease in the strength of the boards accom-panying a decrease in the amount of glue.
Heretofore the optimum procedure has been the use of aglue liquor having a solid resin content of about 50% by weight and the use of several features in the mixing apparatus for glue-ing the chip material, i.e. to achieve as high a number of glue-ing point as possible on the chip material, which points also determine the strength of the boards. With processes of the above type for preparing so called "normal boards", i.e. boards having a specific gravity of more than 650 kg/m when the usual chip material is used and in which the chip material is glued substan-tially all over (on all sides), it has been possible to achievedthe properties laid down in norm rules with a content of solid resin of about 8 to 9% by weiyht, calculated on basis of absolutely dry ~a.d.) chip material.
The presen-t invention pxovides a process of -the type mentioned above by which a further improved utili~a-tion of the glue for glueing the chip ma-terial may be obtained, in which pro-cess for achieving a required strength of the boards with a pre-determined chip material a lower amount of solid resin is suffic-ient than has been possible heretofore. The process of the present inven-tion may be effected with conventional devices without a substantial change of the procedure and without a sub stantial change of the period of time required for the process.
According to the present invention there is provided in a process for preparing a wood chip board in which the wood raw material is subjected to a cutting operation and to a subsequent drying step so as to achieve a moisture content of less than 4 by weight whereafter the wood chip material is glued with an aqueous liquor of an aminoplast and then the glued chip material thus obtained is compressed under heat, the improvement in which the glueing is effected with a liquor having solld resin content in the range between 20 and 35% by weight the amount of glue used containing less than 6% by weight of solid resin based on the total chip material weight calculated as absolu-tely dry material.
Thus in accordance with the present invention the glue-ing step is carried out with a liquor having a so:Lid res:Ln content of between 20 and 35% by weight, preferably between 22 and 30% by weight and the amount of glue used contains less than 6% by weight, preferably between 3 and 5% by weight of solid resin, calculated on basis of the whole a.d. chip material.
In the process of the present invention wood chip boards are obtained with use of a relatively small amount of glue, the mechanical values of the boards corresponding to the norm require-ments. In the process of the present invention also the problem frequently important in the conventional processes of the type ~9~6~
mentioned above, i.e. that the fine chips present in the chip material ta~e up very much more glue than the coarser chips due to the greater surface thereof, based on the weight, may be counteracted.
Because of the generally good distribu-tion of the glue on the surface of the chip material obtainable by the process of the present invention the glue is very well utilized so that boards having very good mechanical properties may be obtained with a relatively small amount of the glue. The fact that the process ~-of the present invention allows the improvement of the glue absorp-tion of the coarse portion of the chip material in the glueing step to the debit of the fine portion of the chip material repre-sents a very important effect.
A comparative test resulted e.g. in the Eact that in cJlueing chip material with 55% by weicJht of a glue llquor usiny ~ by weight of solid resin, calculated on basis of a.d. chip material, the greatest chip fraction (residue on a 2 ~m sieve) had a content of solid resin of 2.0% by weight, based on a.d.
chip, and the smallest chip fraction (passing a 0.25 mm sieve) had a content of solid resin of 9.9% by weight, based on a.d.
chip material. In case of glueing the same chip material with 25% by weight of a glue liquor using again 4% by weight oE solid resin, calculated on basis of a.d. chip material, glueings of 2.9 and 7.9% respectively by weight of solid resin, calculated on basis of a.d. chip material have been obtained for the above mentioned chip fractions. Accordingly, the ratio of glueing of the fraction of the largest chips to glueing of the smallest chips has been reduced from about 1:5 to somewhat more than 1:2.5.
As mentioned above the glueing step of the process of the invention is carried out preferably with a liquor, the solid resin content of which is in the range of 22 to 30~ by weight, as in such a way both the required uniform glueing of the chip mass 7 IEi~
and the requirements with respect to the moisture content oE the chip mass made by the compressing step may be satisfied.
In the glue dis-tributlon obtained by the process of -the presen~ invention it is also desirable to keep the mois.ure con-tent of the glued chip material to be subjected to the compressing step below 12% by weight which may be achieved by selection of the concentration of the glue liquor, as the concentration of -the glue liquor determines also the amount of wa-ter applied onto the chip material in the glueing step.
In the practice the addition of a thickening agent to the glue liquor has proved to be advantageous as thereby an undesired penetration of the glue into the chip material may be counteracted without any disadvantageous hindrance of the distri-bution of the glue. Examples of useful thickening agents are especially cellulose derivatives, e.g. methyl cellulose, ethyl cellulose and carboxymethyl cellulose. These compounds react neutrally with respect to the curing of the glue. -Such as in case of the conventional process of the type mentioned above also according to the process of the invention a paraffin emulsion or molten paraffin may be added for rendering the chip boards hydrophobic. Furthermore, according to the pro-cess of the invention agents for rendering the chip board flame-retardant or fungicides may be applied onto the chip material during the glueing step, e.g. by adding such agents to the glue liquor.
The present invention will be further illustrated by way of the following Examples.
Example 1 The glueing degree obtained by glueing a mixture of wood chips containing chips of different sizes with use of glue liquors of different concentrations on basis of highly diluteable urea-formaldehyde glue was tested. The mixture of wood chips was pre-~2~7~
pared from hardwood and coniferous wood an~ had a chip size distribution in accordance with the following sieve analysls:
> 2.0 mm 7.8% 0.25 - 0.5 mm 22.8~
1.0 - 2.0 mm 25.8% < 0.25 mm 9.1%
0.5 ~ 1.0 mm 3~.5%
Glue liquors containing 55 and 25% by weight of solid resin were used. Amounts of these liquors were applied onto the chips such that the glueing for each liquor concentration was 4%
by weight of solid resin, based on a.d. chip material. The glue-ing was carried out in a glueing mixer with addition of air bymeans of a nozzle for dispensing two components. After the glue-ing step the chips were fractionated in order of their size by a sleve analysis and the glueing degree was established by deter-mination of the nitrogen content. The obtained values are reported in the following Table.
T a b l e Nitrogen content chip fraction 5S% by weight of25% by weight liquor of liquor 20~ 2.0 mm 0.56% 0.78%
1.0 - 2.0 mm 0.65% 0.90 0.5 - 1.0 mm 0.98% 1.11%
0.25 - 0.5 mm 1.54% 1.33%
c 0.25 mm 2.52% 2.063%
.
In each case the values of the nitrogen content refer to dry chipmaterial. Itcan beseen howit ispossible toachieve acon-siderable proportionation of the glue distribution on coarse and fine chip fractions by use of the highly diluted glue liquors of the present invention.
Exam~
A chip material was used for the preparation of chip ~Z917~
boards which was obtained in a conventional r~anner hy cuttiny down of 20% by weight trunk woocl, 25% by weigh-t chopping pieces and 55~ by weight waste material of sawmills (mainly sawdust) and con-sisted with respect to the wood types, of G5% by weight coniferous wood and 35% by weight beech and other hardwood. The chip mixture thus prepared was separated by means of adequate screening devices into a coarse portion for the middle layer and a fine portion for the cover layer. The fine portion had a moisture content of 3.5%
by weight before the glueing step and the coarse portion and a moisture content of 1% by weight. The chips -thus prepared were glued with a glue liquor having a solid resin content of 35% by weight and containing furthermore the required amounts of curing and buffering substances as well as a paraffin emulsion. The amount of glue was selected such that the chip material or the cover layer had a glueing deyree of 6.56 by weight of -tlle solid resin and the chip material for the middle layer had a glueing degree of 5.S% by weight of the solid resin, both calculated on basis of a.d. chip material. The moisture of the glued chip was 13.1~ by weight in case of the fine portion and 10% by weight in case of the coarse portion. The glued chip material was scattered to give a three-layer fleece and compressed in a press having sevexal floors under pressure and heat during a compressing period of 14 sec/mm raw thickness to give a chip board having a thick-ness of 19 mm and a specific gravity of 685 kg/m3. The thus obtained chip board prepared mainly from waste wood satisfied the requirements of DIN 68763.
Example 3 Chip material as it is used for preparing chip boards and which has been dried -to a moisture content of 1.5% was glued in a glueing mixer with a glue liquor containing in addition to the usual amounts of curing and buffering substances and a paraffin emulsion in an amount corresponding to an addition of 0.8% by weight of solid paraffin 29% by weight of solid resin (calculated on basis of a.d. chip material). The supply o:E chip material and glue liquor was adjusted such that a glueing degree of 4.8% by weight of solid resin, based on a.d. chip material was obtained. The glued chip material was scattered to give a fleece which had a moisture content of 10.8% by weiyht after the scatter-ing station. It was compressed in a press having one floor to give a chip board. The temperature of the heating plate was 200C
the pressure was maximally 30 bar and the compressing time 3.15 min. A chip board having a raw thickness of 23.5 mm and a speci-fic gravit~ of 670 kg/m3 was obtained. The strength values of this board satisfied the re~uirements of DIN 68763.
Example 4 Chip material obtained by usual treatment of (:runk wood in cutting devices and consisting of 90% by weight conifero~ls wood and 10% by weight light hardwood with a small amount of finest particles was dried in a rotary nozzle dryer to a moisture content of less than 1% by weight. This chip material was pro-vided first of all with molten paraffin in an amount of 0.8~, based on a.d. chip material, and then glued with a glue liquor containing 22% by weight of solid resin. In addition the glue liquor contained 2% by weight of ammonium chloride, calculated on basis of solid resin. A glueing degree of 3.5% by weight, of solid resin, calculated onbasis of a.d. chipmaterial wasadjusted.
The moisture content of the gluedchips, measuredafter thescattering device wasll.5% by weight. From this chipmaterial, achip boardhav-ing a thickness of 18 mm and a specific gravity of 700 kg/m3 was prepared in a press having one floor. The properties of the board satisfied the requirements of DIN 68763.
Example 5 A raw mater al consisting of about 50~ by weight trunk wood and 50~ by weight waste wood (saw dust, chopping pieces) was cut, dried to a moisture conten-t of about 1% by weight and the chip materiai was separated into a fine portion and a coarse por-tion. The fine portion and the coarse portion were glued separ-ately with aqueous liquors of a commercial urea-formaldehyde--glue.
For glueing the fine portion a liquor containing 24.9% by weight of solid resin was used, which contained additionally 0.1go by weight of ammonium chloride (based on solid resin), a paraffin emulsion as hydrophobic agent and 2% by weight of a hydroxyethyl cellulose as thickening agent (based on solid resin). The addi-tion of the thickening agent resulted in a viscosity of the highly diluted glue liquor of 105 mPa.s. The amount of the glue liquor was selected such that a glueing of 4.2% by weight of solid resin, calculated on basis of a.d. fine portion of the chip material was obtained. The moisture content of the glued chips was l~go by weiyht. A glue liquor COntaininCJ 33.1% by weight of solid resin with an addition of 1.6g6 by weight of ammonium chloride (calcu-lated on basis of solid resin), a paraffin emulsion and 1% by weight (based on solid resin) of the above mentioned thickening agent was used for glueing the coarse portion of the chip material.
The viscosi~y of the highly diluted glue liquor was 100 mPa.s due to the addition of the thickening agent. The amount of this liquor was selected such that a glueing degree o ~.2% by weight of solid resin, calculated on basis of a.d. coarse portion, was obtained. The moisture content of the glued chips was 8go. Then the two glued chip fractions were scattered in separated scatter-ing devices to give a three-layer chip fleece the fine chip por-tion forming the cover layers and the coarse chip portion forming the middle layer. The chip fleece was compressed in a heating press under pressure and heat with 15 sec/mm raw thickness to a 19 mm chip board having a specific gravity of 68~ kg/m3. The strength values of this board satisfied very well the requirement of DIN 68763. A comparative board prepared under the same condi-~2~7~L
tions, however, with use of glue liquors without any thickening agent also sa-tisfied the requirements of DIN 6~763, but the strength values were lower by about 15%.
g .
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for preparing a wood chip board in which the wood raw material is subjected to a cutting operation and to a subsequent drying step so as to achieve a moisture con-tent of less than 4% by weight whereafter the wood chip material is glued with an aqueous liquor of an aminoplast and then the glued chip material thus obtained is compressed under heat, the improvement in which the glueing is effected with a liquor having solid resin content in the range between 20 and 35% by weight, the amount of glue used containing less than 6% by weight of solid resin based on the total chip material weight calculated as absolutely dry material.
2. A process as claimed in claim 1 in which the glue has a solid resin content of from 22 to 30% by weight.
3. A process as claimed in claim 2 in which the glue is used in an amount of between 3 and 5% of solid resin based on the total chip material.
4. A process as claimed in claim 1, 2 or 3 in which the cut and dried chip material has a moisture content of less than 2% by weight.
5. A process as claimed in claim 1, 2 or 3 in which the moisture content of the glued chip material is below 12%
by selecting the amount of water applied onto the chip material together with the glue liquor.
by selecting the amount of water applied onto the chip material together with the glue liquor.
6. The process of claim 1 in which a thickening agent is added to the glue liquor.
7. A process as claimed in claim 6 in which the thick-ening agent is a cellulose derivative.
8. A process as claimed in claim 7 in which the thick-ening agent is selected from methyl cellulose, ethyl cellulose and carboxymethyl cellulose.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT738978A AT357334B (en) | 1978-10-13 | 1978-10-13 | METHOD FOR PRODUCING WOOD CHIPBOARDS |
| ATA7389/78 | 1978-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129761A true CA1129761A (en) | 1982-08-17 |
Family
ID=3595580
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA337,180A Expired CA1129761A (en) | 1978-10-13 | 1979-10-09 | Process for preparing wood chip boards |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0010537B1 (en) |
| JP (1) | JPS5553549A (en) |
| AT (1) | AT357334B (en) |
| CA (1) | CA1129761A (en) |
| DE (1) | DE2962211D1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3063263D1 (en) * | 1979-04-23 | 1983-07-07 | Oesterr Hiag Werke Ag | Wood chip board and process for its production |
| JPS59201807A (en) * | 1983-04-30 | 1984-11-15 | アイン・エンジニアリング株式会社 | Method of molding woody resin board material |
| JPS6036104A (en) * | 1983-08-10 | 1985-02-25 | Sadao Nishibori | Molding of composite formed board |
| JPS6073808A (en) * | 1983-09-30 | 1985-04-26 | Sadao Nishibori | Method of molding woody synthetic molded item |
| JPS6143504A (en) * | 1984-08-08 | 1986-03-03 | Ain Eng Kk | Ligneous synthetic plate |
| JPS6143503A (en) * | 1984-08-08 | 1986-03-03 | Ain Eng Kk | Molding method of ligneous synthetic molded article |
| US5882564A (en) * | 1996-06-24 | 1999-03-16 | Andersen Corporation | Resin and wood fiber composite profile extrusion method |
| CN110228118B (en) * | 2019-05-27 | 2021-01-15 | 蚌埠学院 | Manufacturing process of environment-friendly wooden door |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2122817B2 (en) * | 1971-05-08 | 1978-05-24 | Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V., 8000 Muenchen | Process for the production of chipboard |
| FI311773A (en) * | 1973-10-08 | 1975-04-09 | Keskuslaboratorio | |
| DE2536539A1 (en) * | 1975-08-16 | 1977-02-17 | Siempelkamp Gmbh & Co | Wood chip board having predetermined moisture content - formed by hot pressing in two stages in which temp is program controlled |
| DE2553459A1 (en) * | 1975-11-28 | 1977-06-23 | Basf Ag | PROCESS FOR MANUFACTURING WOOD-BASED MATERIALS |
-
1978
- 1978-10-13 AT AT738978A patent/AT357334B/en not_active IP Right Cessation
-
1979
- 1979-10-09 CA CA337,180A patent/CA1129761A/en not_active Expired
- 1979-10-09 EP EP19790890041 patent/EP0010537B1/en not_active Expired
- 1979-10-09 DE DE7979890041T patent/DE2962211D1/en not_active Expired
- 1979-10-11 JP JP13236279A patent/JPS5553549A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0010537A1 (en) | 1980-04-30 |
| JPS5553549A (en) | 1980-04-19 |
| ATA738978A (en) | 1979-11-15 |
| AT357334B (en) | 1980-07-10 |
| DE2962211D1 (en) | 1982-03-25 |
| EP0010537B1 (en) | 1982-02-24 |
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