CA1101625A - Method of binding lignocellulosic materials - Google Patents
Method of binding lignocellulosic materialsInfo
- Publication number
- CA1101625A CA1101625A CA313,614A CA313614A CA1101625A CA 1101625 A CA1101625 A CA 1101625A CA 313614 A CA313614 A CA 313614A CA 1101625 A CA1101625 A CA 1101625A
- Authority
- CA
- Canada
- Prior art keywords
- liquor
- mat
- spent sulfite
- lignocellulosic materials
- sulfite 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
Links
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
- 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
- C08L97/00—Compositions of lignin-containing materials
- C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
Abstract
TITLE
METHOD OF BINDING LIGNOCELLULOSIC MATERIALS
INVENTORS
Kuo-Cheng Shen David P.C. Fung Louis Calve ABSTRACT OF THE DISCLOSURE
A low cost method of binding lignocellulosic materials utilizing ammonium based spent sulfite liquor alone as the binder. Hot pressing a mat comprising ligno-cellulosic material and ammonium spent sulfite liquor at a temperature above 170°C decomposes the spent sulfite liquor. The decomposition products subsequently condense and polymerize in the presence of lignocellulosic materials to produce a composite product. An exterior grade board can be produced under certain operating conditions. Utilizing the lower molecular weight fraction of the liquor provides a more efficient binder.
METHOD OF BINDING LIGNOCELLULOSIC MATERIALS
INVENTORS
Kuo-Cheng Shen David P.C. Fung Louis Calve ABSTRACT OF THE DISCLOSURE
A low cost method of binding lignocellulosic materials utilizing ammonium based spent sulfite liquor alone as the binder. Hot pressing a mat comprising ligno-cellulosic material and ammonium spent sulfite liquor at a temperature above 170°C decomposes the spent sulfite liquor. The decomposition products subsequently condense and polymerize in the presence of lignocellulosic materials to produce a composite product. An exterior grade board can be produced under certain operating conditions. Utilizing the lower molecular weight fraction of the liquor provides a more efficient binder.
Description
D:~6~5 BACKGROUND ~F THE INV~N~ION
This in~ention relates to a method of bi.nding lignocellulosic materials utilizing amm~nium based spent sulfite liquor as the thermosetting adhesive binder.
The most commonly used adhesive binders for binding wood products are urea-formaldehyde and phenol~
formaldehyde, with the more expensive phenol-formaldehyde being used for exterior grade products. Using these conven-tional binders, the cost of the binder itself accounts ~ -for a large portion of the total material cost of the wood ,~
product..
There have been numerous proposals for utilizing spent sulfite liquor, the by-product of the ~;
sulfite pulping process, as an adhesive binder. In United -;
States Patent 2,822,358 to Hearon, Lackey and Martin, there ~ :
is described a process of chemical modification of ammonium ~ :
based spent sulftie liquor by heat under controlled conditions.
The converted liquor is proposed for a variety of water ?i) soluble products including adhesives, dispersants and surface active agents. United States Patent 3,141,873 to Go5s involves heat treating of ammonium based spent sulfite ;
liquor and reacting the treated liquor with a crosslinking agent such as acetone or formaldehyde to produce a thermo-settiny binder for making cellulo.sic board. United States Patent 2,786,008 to Henschler describes a method of mixing a~ oIlium based spent sulfite liquor with pheno]. formaldehyde resin and used the resulting mixkure as adhesive for fiber-~oard and plywood. ~ost of the prior proposals involve '~v extensive chemical modification of the spent sulfite liquox , ~1--!
6~ ~
before use as a binder ~nd the cost fo~ produciny these modified binders is not significantly lower -than conventional adhesives. Moreover, few of these modified binders can produce ex~erior grade products.
In United States Patent No. ~,193,814 by K.C. Shen, is described a composition in which spent sulfite liquor is treated with sulfuric acid. Although an exterior grade product can be produced by this method at costs less than conventional adhesives the acid treatment complicates the system. In the acid treated spent sulfite liquor it is believed that the sulfuric acid generates ; free lignosulfonic acid. Under the heat and pressur~ of the hot pressing o~eration, the lignosulfonic acid condenses and polymerizes into an insoluble state similar to the condensation reaction of conventlonal thermosetting resin binders.
SUMMARY OF THE II~VENTION
It has been found that ammonium based spent sulfite liquor has a relatively low decomposition temperature ~o and that lignosulfonic acid can be freed without the use of acid as required by spent sulfite liquor of othex bases, such as calcium, sodium, and magnesium.
It has been further found that ammonium based spent sulfite liquor can be u.sed directly as a thermosettiny binder for lignocellulosic material. Hot-pressing of a mixture of lignocellulosic materials and ammorl;um spent sulfite liquor at a temperature of 170C, or higher, provides an in-situ reaction in which the ammonium spent sulfite liquor initiall~ decomposes to free lignosulfonic acid, ammonia gas, and other organic material. These decomposition ~2~
'. ~
products su~sequently condense and p~l~me~iæe in the .. presence of the lignocellulosic materials to p~oduce a composite product.
. It has also been found that a fractionated ammonium based spent sulfite liquor containing a greatex proportion of low molecular weight materials provides a '' more efficient binder as compared with an unfractionated ~; liquor. It is believed that low molecular materials ; . other than lignosulfonic acid also play a role in the binding system.
:~ .
DESCRIPTION OF THE PREF:E~RRED EMBODIMENTS ::
, In accordance with the present invention, the i,,:~ .
lignocellulosic materials to be bonded are mixed with at least 2%, by weight, ammonium based spent sulfite liquor solids. The ammonium spent sulite liquor may be in the form ~.
of a concentrated liquor or in the form of a spray dried :~
powder as with conventional adhesive binders. The resulting mixture is formed into a mat, and the mat hot pressed at a temperature of 170C or higher for a time sufficient to consolidate the mat.
Hot pressing of the mat at.a temperature of 170C or higher effects two staqes v .chemical ~eaction irl situ. Firstly, the ammonium based spent sulfite liauor is .:
decomposed to produce free lignosulfonic acid, sulfur dioxide, ammonia gas and other organic material. In the second s~age, the decomposition products condense and pol,ymerize in the presence of the lignocell-ulosic materials to pxoduce a composite product.
Pref~xably -the ammonium spent sulfite liquor is ractionated to provide a highe.r proportion o low molecular weight materials~ ~mprovement in binder efici.ency, particularly required press time t is obtained i~ the racti,on 3- ' 6;2~;
r utilized has ~ molecular ~ei~ht less th~n 30,000. Thi~
provides a retained portion of approxima-tely 70~ of the unfractionated liquor. Preferably the molecular weight is about 10,000, or less, which provides a retained portion of about 30 to 50~ of the unfractionated portion. As the maximum molecular weight of the retained fraction is lowered, binder ef~iciency is impro~ed further, but a smaller portion of liquor is utilized.
Conventional presses in Canada normally provide a maximum press temperature of about 210C. When using unfractionated ammonium based spent sulfite liquor as binder, a press temperature of 2]0C is suitable for producing interior grade products but does not provide an exterior grade (waterproof) product with reasonable press times. In order to obtain an exterior grade product either higher press temperature or a post-curing treatment is required. The post-curing treatment involves subjecting the hot-pressed mat to an elevated temperature for a time to further cure the binder. Hot pressing the mat at a temperature of 230C or higher allows making an exterior grade product without subsequent heat treatment or long press times. The use of fractionated liquor makes it possible to make exterior yrade products without high press temperatu-es or prolonged press times.
EX~PLE 1 An ammonium based spent sulfite liquor of 50~ solids was obtained from a Canadian sulfite mill. This liquor was spra~-dried into powdered form. Before use the powder was baîl-milled to give fine particles (90% by weight passed 200 mesh iyler screen). Poplar waEers containing ., ,~, _ 6~5 ~bout 3~ moisture content obta~ned from a wafexboaxd plant was blended with 4% by weight ammonium based spent sulfite liquor powder and hot-pressed at 232C for a period of 8 and 12 minutes to produce boards 11 mm (7/16 in.) thick and having a density of about 641 kg/m (40 pcf). These boards were tested according to Canadian Standard CSA 0188 (75) and the results are summarized in Table 1.
The results indicated that these boards would pass the CSA 0188 (75) requirements for exterior grade waferboard.
Table 1 _ Press time MOR Torgue (psi) (in-lb) _ Dry Wet Dry Wet 8 min. 2820 1130 54 13 12 min. 2760 1250 52 16 _ :
Poplar waferboards were made under similar conditions as in Example 1 but hot-pressed at a lower press temperature of 210C for ~arious times of 16, 14, 10, 8, 6 and 4 minutes. After hot-pressing, some of the boards were post-cured in an oven for a period of 2 and 4 hours at temperatures of 177C.
In this example, when the press temperature was kept at 210C instead of 232C, and combined with a short press ti.me a follow--up pos-t curing treatment was necessary to obtain boards of exterior grade. Table 2 - shows the results of post-curing effect on board properties.
3~ 5 Table 2 _._ . . . .
Press Press Post-cured MOR Torque Time Temp At 177C (psi) (in--lb) Min. C Time Hour Dry Wet Dry Wet .- . _ _ _ _ , 210 2 2~80 1320 42 14 6 210 ~ 2540 1200 45 24 210 0 28~0 0 80 ~
This example illustrates that similar results can be produced with ammonium based spent sulfite liquor from ! ' both softwood and hardwood sulfite pulping process.
Poplar waferboards were made under similar conditions as in Example 2. Ammonia based spent sulfite liquors from softwood species and hardwood species were used as binders for making those boards in Table 3. Both liquors had a solids content of 40%. The pH values for the softwood and hardwood liquors were 4.3 and 2.0 respectively. The liquor was applied to the wafers by spraying at a rate of 4% by weight of liquor solid to wafers. After spraying, the wafers were air dried to a moisture contenk of about 3.0~ before forr~ing mat and hot~pressed.
:
I'able 3 Press Time ~OR Torque At 210C (psi) (in-lb) Min. Dry ~et Dry Wet ~Softwoo~ I 12 2082 1 0* ~ 5~l ~ o*
14 _ 2260 1~10 72 5 Hardwood 12 2710 1010 69 6 * Specimens desintegrated during the 2 hours boiling treatment.
Ammonium based spent sulfite liquor was -:
separated into low and high molecular weight fractions by means of ultrafiltration. Each of these fraction cons~ituted about 50% by weight of the original liquor.
The high molecular weigh-t fraction was the retentate which was retained by membranes having a molecular weight cut of 10,000. The low molecular weiyht fraction was the permeate which passed through the membranes. Waferboard 11 mm thick was made with 4% solids content of fractionated and unfractionated liquor hot pressed at 210 C for 8 minutes.
Table 4 compares the properties O.e waferboards made with ammonium based spent liquors (MH~-SSL) o different molecular weight ranges. The results show that the low molecular weight fraction is more efficient than the unfractionated original liquor.
.. ..
l ;
.~ `
ii25 Table 4 Molecular MOR Torque : Weight Range of NH4-SSL (psi) (.in.lb) Dry Wet Dry Wet _ ~ _ _ , ~,~
: Unfractionated SSL 2370 0 50 0 Low Molecular Weight SSL 2790 1430 65 14 (50% of Unfractionated High Molecu~ar Weight SSL 1000 0 50 0 (50~ of Unfractionated ~ ~ _ ~,
This in~ention relates to a method of bi.nding lignocellulosic materials utilizing amm~nium based spent sulfite liquor as the thermosetting adhesive binder.
The most commonly used adhesive binders for binding wood products are urea-formaldehyde and phenol~
formaldehyde, with the more expensive phenol-formaldehyde being used for exterior grade products. Using these conven-tional binders, the cost of the binder itself accounts ~ -for a large portion of the total material cost of the wood ,~
product..
There have been numerous proposals for utilizing spent sulfite liquor, the by-product of the ~;
sulfite pulping process, as an adhesive binder. In United -;
States Patent 2,822,358 to Hearon, Lackey and Martin, there ~ :
is described a process of chemical modification of ammonium ~ :
based spent sulftie liquor by heat under controlled conditions.
The converted liquor is proposed for a variety of water ?i) soluble products including adhesives, dispersants and surface active agents. United States Patent 3,141,873 to Go5s involves heat treating of ammonium based spent sulfite ;
liquor and reacting the treated liquor with a crosslinking agent such as acetone or formaldehyde to produce a thermo-settiny binder for making cellulo.sic board. United States Patent 2,786,008 to Henschler describes a method of mixing a~ oIlium based spent sulfite liquor with pheno]. formaldehyde resin and used the resulting mixkure as adhesive for fiber-~oard and plywood. ~ost of the prior proposals involve '~v extensive chemical modification of the spent sulfite liquox , ~1--!
6~ ~
before use as a binder ~nd the cost fo~ produciny these modified binders is not significantly lower -than conventional adhesives. Moreover, few of these modified binders can produce ex~erior grade products.
In United States Patent No. ~,193,814 by K.C. Shen, is described a composition in which spent sulfite liquor is treated with sulfuric acid. Although an exterior grade product can be produced by this method at costs less than conventional adhesives the acid treatment complicates the system. In the acid treated spent sulfite liquor it is believed that the sulfuric acid generates ; free lignosulfonic acid. Under the heat and pressur~ of the hot pressing o~eration, the lignosulfonic acid condenses and polymerizes into an insoluble state similar to the condensation reaction of conventlonal thermosetting resin binders.
SUMMARY OF THE II~VENTION
It has been found that ammonium based spent sulfite liquor has a relatively low decomposition temperature ~o and that lignosulfonic acid can be freed without the use of acid as required by spent sulfite liquor of othex bases, such as calcium, sodium, and magnesium.
It has been further found that ammonium based spent sulfite liquor can be u.sed directly as a thermosettiny binder for lignocellulosic material. Hot-pressing of a mixture of lignocellulosic materials and ammorl;um spent sulfite liquor at a temperature of 170C, or higher, provides an in-situ reaction in which the ammonium spent sulfite liquor initiall~ decomposes to free lignosulfonic acid, ammonia gas, and other organic material. These decomposition ~2~
'. ~
products su~sequently condense and p~l~me~iæe in the .. presence of the lignocellulosic materials to p~oduce a composite product.
. It has also been found that a fractionated ammonium based spent sulfite liquor containing a greatex proportion of low molecular weight materials provides a '' more efficient binder as compared with an unfractionated ~; liquor. It is believed that low molecular materials ; . other than lignosulfonic acid also play a role in the binding system.
:~ .
DESCRIPTION OF THE PREF:E~RRED EMBODIMENTS ::
, In accordance with the present invention, the i,,:~ .
lignocellulosic materials to be bonded are mixed with at least 2%, by weight, ammonium based spent sulfite liquor solids. The ammonium spent sulite liquor may be in the form ~.
of a concentrated liquor or in the form of a spray dried :~
powder as with conventional adhesive binders. The resulting mixture is formed into a mat, and the mat hot pressed at a temperature of 170C or higher for a time sufficient to consolidate the mat.
Hot pressing of the mat at.a temperature of 170C or higher effects two staqes v .chemical ~eaction irl situ. Firstly, the ammonium based spent sulfite liauor is .:
decomposed to produce free lignosulfonic acid, sulfur dioxide, ammonia gas and other organic material. In the second s~age, the decomposition products condense and pol,ymerize in the presence of the lignocell-ulosic materials to pxoduce a composite product.
Pref~xably -the ammonium spent sulfite liquor is ractionated to provide a highe.r proportion o low molecular weight materials~ ~mprovement in binder efici.ency, particularly required press time t is obtained i~ the racti,on 3- ' 6;2~;
r utilized has ~ molecular ~ei~ht less th~n 30,000. Thi~
provides a retained portion of approxima-tely 70~ of the unfractionated liquor. Preferably the molecular weight is about 10,000, or less, which provides a retained portion of about 30 to 50~ of the unfractionated portion. As the maximum molecular weight of the retained fraction is lowered, binder ef~iciency is impro~ed further, but a smaller portion of liquor is utilized.
Conventional presses in Canada normally provide a maximum press temperature of about 210C. When using unfractionated ammonium based spent sulfite liquor as binder, a press temperature of 2]0C is suitable for producing interior grade products but does not provide an exterior grade (waterproof) product with reasonable press times. In order to obtain an exterior grade product either higher press temperature or a post-curing treatment is required. The post-curing treatment involves subjecting the hot-pressed mat to an elevated temperature for a time to further cure the binder. Hot pressing the mat at a temperature of 230C or higher allows making an exterior grade product without subsequent heat treatment or long press times. The use of fractionated liquor makes it possible to make exterior yrade products without high press temperatu-es or prolonged press times.
EX~PLE 1 An ammonium based spent sulfite liquor of 50~ solids was obtained from a Canadian sulfite mill. This liquor was spra~-dried into powdered form. Before use the powder was baîl-milled to give fine particles (90% by weight passed 200 mesh iyler screen). Poplar waEers containing ., ,~, _ 6~5 ~bout 3~ moisture content obta~ned from a wafexboaxd plant was blended with 4% by weight ammonium based spent sulfite liquor powder and hot-pressed at 232C for a period of 8 and 12 minutes to produce boards 11 mm (7/16 in.) thick and having a density of about 641 kg/m (40 pcf). These boards were tested according to Canadian Standard CSA 0188 (75) and the results are summarized in Table 1.
The results indicated that these boards would pass the CSA 0188 (75) requirements for exterior grade waferboard.
Table 1 _ Press time MOR Torgue (psi) (in-lb) _ Dry Wet Dry Wet 8 min. 2820 1130 54 13 12 min. 2760 1250 52 16 _ :
Poplar waferboards were made under similar conditions as in Example 1 but hot-pressed at a lower press temperature of 210C for ~arious times of 16, 14, 10, 8, 6 and 4 minutes. After hot-pressing, some of the boards were post-cured in an oven for a period of 2 and 4 hours at temperatures of 177C.
In this example, when the press temperature was kept at 210C instead of 232C, and combined with a short press ti.me a follow--up pos-t curing treatment was necessary to obtain boards of exterior grade. Table 2 - shows the results of post-curing effect on board properties.
3~ 5 Table 2 _._ . . . .
Press Press Post-cured MOR Torque Time Temp At 177C (psi) (in--lb) Min. C Time Hour Dry Wet Dry Wet .- . _ _ _ _ , 210 2 2~80 1320 42 14 6 210 ~ 2540 1200 45 24 210 0 28~0 0 80 ~
This example illustrates that similar results can be produced with ammonium based spent sulfite liquor from ! ' both softwood and hardwood sulfite pulping process.
Poplar waferboards were made under similar conditions as in Example 2. Ammonia based spent sulfite liquors from softwood species and hardwood species were used as binders for making those boards in Table 3. Both liquors had a solids content of 40%. The pH values for the softwood and hardwood liquors were 4.3 and 2.0 respectively. The liquor was applied to the wafers by spraying at a rate of 4% by weight of liquor solid to wafers. After spraying, the wafers were air dried to a moisture contenk of about 3.0~ before forr~ing mat and hot~pressed.
:
I'able 3 Press Time ~OR Torque At 210C (psi) (in-lb) Min. Dry ~et Dry Wet ~Softwoo~ I 12 2082 1 0* ~ 5~l ~ o*
14 _ 2260 1~10 72 5 Hardwood 12 2710 1010 69 6 * Specimens desintegrated during the 2 hours boiling treatment.
Ammonium based spent sulfite liquor was -:
separated into low and high molecular weight fractions by means of ultrafiltration. Each of these fraction cons~ituted about 50% by weight of the original liquor.
The high molecular weigh-t fraction was the retentate which was retained by membranes having a molecular weight cut of 10,000. The low molecular weiyht fraction was the permeate which passed through the membranes. Waferboard 11 mm thick was made with 4% solids content of fractionated and unfractionated liquor hot pressed at 210 C for 8 minutes.
Table 4 compares the properties O.e waferboards made with ammonium based spent liquors (MH~-SSL) o different molecular weight ranges. The results show that the low molecular weight fraction is more efficient than the unfractionated original liquor.
.. ..
l ;
.~ `
ii25 Table 4 Molecular MOR Torque : Weight Range of NH4-SSL (psi) (.in.lb) Dry Wet Dry Wet _ ~ _ _ , ~,~
: Unfractionated SSL 2370 0 50 0 Low Molecular Weight SSL 2790 1430 65 14 (50% of Unfractionated High Molecu~ar Weight SSL 1000 0 50 0 (50~ of Unfractionated ~ ~ _ ~,
Claims (7)
- CLAIMS:
l. A method for binding lignocellulosic materials which comprises; forming a mixture of the lignocellulosic materials and at least 2%, by weight, ammonium based spent sulfite liquor solids, forming a mat with the mixture and hot pressing the mat at a temperature of 170°C, or higher, for a time sufficient to consolidate the mat. - 2. The method of claim 1 wherein the mat is hot-pressed at 210°C, or higher.
- 3. The method of claim 1 wherein the hot-pressed mat is subjected to an elevated temperature for a period of time to further cure the mat.
- 4. The method of claim l wherein the mat is hot-pressed at 230°C, or higher.
- 5. The method of claim l wherein the ammonium based spent sulfite liquor is fractionated to provide an increased concentration of the low molecular weight materials.
- 6. The method of claim 5 wherein the fractionated liquor has a molecular weight less than 30,000.
- 7. The method of claim 6 wherein the fractionated liquor has a molecular weight of about 10,000, or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA313,614A CA1101625A (en) | 1978-10-17 | 1978-10-17 | Method of binding lignocellulosic materials |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA313,614A CA1101625A (en) | 1978-10-17 | 1978-10-17 | Method of binding lignocellulosic materials |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1101625A true CA1101625A (en) | 1981-05-26 |
Family
ID=4112623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA313,614A Expired CA1101625A (en) | 1978-10-17 | 1978-10-17 | Method of binding lignocellulosic materials |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1101625A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4564649A (en) * | 1984-04-16 | 1986-01-14 | H. B. Fuller Company | Polyvinyl alcohol and lignin sulfonate containing adhesive |
| US4608111A (en) * | 1984-04-16 | 1986-08-26 | H. B. Fuller Company | Bonding method employing an adhesive which contains in an aqueous base an effective amount of a polyvinyl alcohol and a lignin sulfonate |
-
1978
- 1978-10-17 CA CA313,614A patent/CA1101625A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4564649A (en) * | 1984-04-16 | 1986-01-14 | H. B. Fuller Company | Polyvinyl alcohol and lignin sulfonate containing adhesive |
| US4608111A (en) * | 1984-04-16 | 1986-08-26 | H. B. Fuller Company | Bonding method employing an adhesive which contains in an aqueous base an effective amount of a polyvinyl alcohol and a lignin sulfonate |
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| MKEX | Expiry |