CA1153294A - Manufacture of plywood comprising methylolated kraft lignin solids - Google Patents
Manufacture of plywood comprising methylolated kraft lignin solidsInfo
- Publication number
- CA1153294A CA1153294A CA000344464A CA344464A CA1153294A CA 1153294 A CA1153294 A CA 1153294A CA 000344464 A CA000344464 A CA 000344464A CA 344464 A CA344464 A CA 344464A CA 1153294 A CA1153294 A CA 1153294A
- Authority
- CA
- Canada
- Prior art keywords
- plies
- organic solids
- liquid form
- kraft lignin
- mkl
- 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
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B21/00—Layered products comprising a layer of wood, e.g. wood board, veneer, wood particle board
- B32B21/13—Layered products comprising a layer of wood, e.g. wood board, veneer, wood particle board all layers being exclusively wood
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/04—Interconnection of layers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G16/00—Condensation polymers of aldehydes or ketones with monomers not provided for in the groups C08G4/00 - C08G14/00
- C08G16/02—Condensation polymers of aldehydes or ketones with monomers not provided for in the groups C08G4/00 - C08G14/00 of aldehydes
- C08G16/0293—Condensation polymers of aldehydes or ketones with monomers not provided for in the groups C08G4/00 - C08G14/00 of aldehydes with natural products, oils, bitumens, residues
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
- C09J161/04—Condensation polymers of aldehydes or ketones with phenols only
- C09J161/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
- C09J5/06—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers involving heating of the applied adhesive
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2607/00—Walls, panels
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
- C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
- C08L2666/26—Natural polymers, natural resins or derivatives thereof according to C08L1/00 - C08L5/00, C08L89/00, C08L93/00, C08L97/00 or C08L99/00
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Materials Engineering (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Veneer Processing And Manufacture Of Plywood (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of bonding wood plies to form plywood panels is disclosed. The method utilizes resins produced from wood chemicals rather than solely utilizing a resin from non renewable petrochemical sources. In the method a water soluble phenol formaldehyde resole resin in liquid form having a pH of at least about 9 is applied to at least one bonding surface between the plies. Methylolated kraft lignin organic solids in a liquid form having a pH of at least about 10 is applied to at least one bonding surface between the plies, wherein the methylolated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to at least one bonding surface. The plies are sandwiched to-gether and subjected to pressure and heat simultaneously to bond the plies together to form plywood panels.
A method of bonding wood plies to form plywood panels is disclosed. The method utilizes resins produced from wood chemicals rather than solely utilizing a resin from non renewable petrochemical sources. In the method a water soluble phenol formaldehyde resole resin in liquid form having a pH of at least about 9 is applied to at least one bonding surface between the plies. Methylolated kraft lignin organic solids in a liquid form having a pH of at least about 10 is applied to at least one bonding surface between the plies, wherein the methylolated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to at least one bonding surface. The plies are sandwiched to-gether and subjected to pressure and heat simultaneously to bond the plies together to form plywood panels.
Description
~S3Z~4 METHOD ~F BONDING WOO~ PLIES TO ~RM PLYWOOD PANELS
This invention relates to plywood and more particu-larly to a method of bonding wood plies to form plywood panels utili:zing phenol formaldehyde and lignin formaldehyde, referred to as methylolated kraft lignin (MKL~.
The most common bonding agent used in the preparation of exterior grade plywood is phenol formaldehyde resin (herein-after referred to as PF). This resin is derived from non renewable petrochemical sources, and is day by day be-GOming more expensive. Resins produced from wood chemicals have been considered as a replacement for PF and other petro-chemical resins However, no satisfactory resin has yet been produced from wood chemicals which has the same bonding properties as PF resins at the same low resin solids content used in PF
bonding of plywood.
In plywood, the bonding is dependent on two criteria, 1~ controlled wetting and penetration of the wood by the ad-hesive, and 2) the development of sufficient strength in the adhesive after curing. Adhesive penetration is largely influenced by the molecular weight of the resin and the association of resin molecules. If the effective size of the resin molecule is too small, it is rapidly absorbed by the capillary structure of the wood, producing an adhesive starved joint. If the resin mole-cular size is too large, penetration of the resin into the wood is retarded, resulting in a shallou, weak bond. After hot press-ing the plywood assembly, the strength of the cured adhesive must exceed the strength of the wood itself. When this condition is not fulfilled failure of the adhesive joint occurs in the glue line instead of in the wood.
Many attempts have been made with kraft or soda black liquor to form adhesives as substitutes for PF resin. In general, the adhesives produced by these attempts have been limited because in order to obtain the same adhesive properties as ob-11~32~
tained with PF it has been necessary to use large quantities ofthe lignin derivsd materials which reduces the advantages of this type of adhesive. Attempts have been made to modify kraft lignin with PF to cause cross linking of the lignin molecules. Clarke and Dolenko in U.S. Patent 4,113,675 combined ~KL with a liquid PF resin in the pH range of 4 - 7. The resulting dispersion was used as a wet adhesive for plywood. In this adhesive MKL acted both as an extender and as a source of resin solids. However, it was found that to achieve a satisfactory bond in plywood required nearly twice as much lignin containing adhesive as compared to the level of PF resin normally used.
In another example, Herrick et al, in U.S. Patent 3,454,508, describe a thermosetting phenolic resin in which an alcohol soluble polymethylol phenol was condensed with an acid precipitated alkali lignin in a fugitive base such as ammonia.
In another example, Ball et al in U.S. Patent 3,185,654 suggested a phenolic resin in which an A stage resole was reacted in methanol with an alkali lignin. Neither Herrick nor Ball showed sufficient crosslinking between free methylol groups of the resole and hydroxyl groups in the lignin. These methods failed to produce satisfactory bonds in plywood.
Marton et al in the publication entitled "Lignin Structure and Reactions", Advances in Chemistry Series 59, American Chemical Society, Washington, D.C., Pages 125 - 144, (1966) reported a method of improving the reactivity o~ kraft ~ lignin by introducing methylol groups into the lignin structure via an alkali catalyzed condensation with formaldehyde. Abe in a publication of Hokkaido Forest Product Institute ~o. 55 (1970) also extensively examined the mechanism of the lignin formalde-hyde reaction in alkaline media, and prepared plywood adhesivesbased on the co-condensation of lignin with phenol and formalde-hyde. Both these adhesives gave poo:r water resistance and wet llS;~
strength properties in the bonded product. Enkvist, in U.S.
Patent 3,864,291 describes a process for manufacture of an ad-hesive in which kraft or soda black liquor was methylolated with formaldehyde in the presence of alkali and subsequently condensed with phenol or cresol formaldehyde. However, plywood panels glued with this adhesive showed unsatisfactory wet strength after boil-ing.
One purpose of the present invention is to provide a method of bonding wood plies to form plywood panels. The adhesive used for this bonding replaces a portion of the more commonly used PF resin adhesives and provides glue bond properties that meet the requirements of CSA standards for plywood. CSA 0151 (1974) lays down the minimum glue bond requirements for plywood panels. Glue bond is measured by wood failure tests. The ad-hesive is applied in either a one step or a two step application.
In the present invention, methylolated kraft lignin (MXL) is prepared from black liquor first by methylolation wherein formaldehyde is added to strong black liquor, followed by the addition of acid to the methylolated liquor. Suspension, dilution and filtration of the precipitate produces a filter cake of MKL
solids. An aqueous alkaline solution of the MKL organic solids is then prepared from the filter cake, The composltion of an adhesive mix is gener~lly expressed in terms of percentage by weight of the total adhesive solids in the mix In the case of PF the total adhesive solids ` comprisesthe resin solids which is the portion of the adhesive taking part in the condensation of the adhesive during the curing step. In the present text the term "organic solids" is used throughout, especially in association with ~IKL. In a simple system such as PF, organic solids and resin solids mean the same thing, however, in the case of MKL the organic solids may include other organic matter coprecipitated with the MKL.
li53;~4 Plywood is made in a variety of different constructions wlth varying numbers and types of plies The bonding surfaces of the pli.es refer to all the surfaces of the plies except the exter-ior surfaces of the two outer plies. In the present application the outer plies in a sheet o~ plywood are referred to as face plies, and the inside plies are referred to as inner plies.
Although only a three-ply panel with a single in~er ply is de-scribed herein, it will be apparent to th~ e skilled in the art that plywood panels with any desirable number of plies may be made by the process of the present invention.
The present invention provides a method of bonding wood plies to form plywood panels comprising the steps of, applying water soluble PF resole resin in liquid form to at least one bond-ing surface between the plies, wherein the PF resole resin in liquid form has a pH of at least about 9, applying MKL organic solids in liquid form to the at least one bonding s~r~ace between the plies, wherein the MKL organic solids in liquid form have a pH of at least about 10, and wherein the MKL organic solids are up to about 60% by weight of the total PF resole resin and MKL
organic solids applied to the at least one bonding surface between the plies, sandwiching the plies together, and subjecting the plies to pressure and heat simultaneously to bond the plies together to form plywood panels, In one method of bonding wood plies referred to as the one-step method, water soluble PF resole resin in liquid form having a pH of at least about 9 is mixed with MKL organic solids in liquid form, having a pH of at least about 10 such that the NKL
organic solids are up to about 30% b~ weight of the total PF resole resin and MKL organic solids, applying the mixture to at least one bonding surface between the plies, sandwiching the plies together, and subjecting the plies to pressure and heat simultaneously to bond the plies together to form plywood panels, In another method referred to as the two-step method 11S3;~4 a first layer of water soluble PF resole resin in liquid form is applied to insLde surfaces of two face plies, and both sur-faces of at least one inner ply, wherein the PF resole resin in liquid form has a pH of at least about 9, a second layer is applied of ~L organic solids in liquid form to both surfaces of the inner ply, wherein the MKL organic solids in liquid form - have a pH of at least about 10, and wherein the MKL organic solids are up to about 60% by weight of the total PF resole resin and MKL organic solids supplied to the surfaces of the plies. A
layup is then made by sandwiching the inner ply between the two face plies and the layup is subjected to pressure and heat simul-taneously to bond the plies together to form plywood panels. In one variation of the two-step method, the first layer is a mix-ture of PF and MKL, wherein the weight ratio of MKL to PF is up to about 30 to 70, that is the mixture should not contain more than about 30 parts MKL. In another variation of the two step method, the second layer is a mixture of MKL and PF in any pro-portion. Any combination of these variations may be used so as to give the ratio of total MKL to total PF required in the finished product. In the two step method, up to about 18 hours may pass between the application of the first layer and the application of the second layer, In one embodlment the first layer is applied by spraying, and the second layer is applied by roll spr0ading.
In preferred embodiments, the water soluble PF resole resin in liquid form has a resin solids content range by weight of from about ~5 - 40%. The MKL organic solids in liquid form has an organic solids content preferably in the range of from about 15 - 35% by weight, and the solution contains an alkali metal base such as NaOH or sodium carbonate, In the case of NaOH, the ratio of NaOH to ~KL organic solids is preferably in the range of about 0.15 - 0.30 to 1 by weight, The invention will now be described in more detail, MKL organic solids in liquid form are made by mixing filter cake, 115;~2~?~
prepared in the manner described, with water and an alkali metal base such as sodium hydroxide The MKL organic solids in liquid form has a pH of at least about 10, preferably in the range of 11 - 13. The sodium hydroxide mixed with this MKL
organic solids in liquid form is in the ratio of NaOH to MKL in the range of about 0.15 - 0.30 by weight. The PF resol~ resin may be a commercially available resin with a pH of at least about 9 when in liquid form. Preferably the range is about 11 to 13.
The MKL organic solids in liquid form has an organic solids con-tent range of from about 15 - 35 percent by weight, and the PF
resole resin in liquid form has a resin solids content range by weight of from about 15 - 40 percent. In a preferred embodiment and to form a plywood meeting CSA standards, it is preferable that the ratio of MKL to PF should be not greater than about 30 to 70.
The MKL/PF adhesive mixture is applied to at least one of the bonding surfaces between the plies by any suitable method, such as spraying, curtain coating, or roll spreading. In one embodiment when making a three-ply panel, the mixture is applied to both surfaces of the inner ply. The plies are then sandwiched together~
and in that form subjected to pressure and heat simultaneously so that the plies bond together toform plywood panels In the two-step process, a PF resole resin adhesive ~n liquid form is first prepared as in the one-step process. The PF resole resin in liquid form has a pH of at least about 9, and in a preferred embodiment the resin solid content range is from - about 15 - 40 percent by weight of the liquid adhesive mixture A first layer of the PF resole resin in liquid form is applied to the inside surfaces of the face plies and to both surfaces of one or more inner plies The coating may be applied by any suitable method such as spraying, curtain coating or roll spreading It has been found that the PF resole resin in liquid form may be applied to the plies several hours in advance of the application of the second layer. In fact, tests have shown that about 18 1153~4 hours may elapse between the f~rst and second layer application of adhesive.
The first layer may comprise 100% P~ or may contain MKL in the weight ratio of up to about 30 to 70, MKL to PF. The mixture should not contain more than about 30 parts MKL to 70 parts PF.
The second layer may comprise a 100% MKL organic solids in liquid form, having a pH of at least about 10. Pre-ferably the organic solids in the liquid form has a content range of about 15 - 35 percent by weight. Alternatively, the second layer may be a prepared mixture of PF resole resin in liquid form having a pH of at least about 9 and MKL organic solids in liquid form having a pH of at least about 10. Any proportion of PF may be added to the MKL, depending only on the ratio of P~ to MKL
desired in the final plywood product. The second layer is only applied to the surfaces of the inner plies such that there is always a first layer between the second layer and the surface of the wood. There should not be a second layer which is predomi-nately MKL dir~ctly adjacent to the wood surface. The plies are then sandwiched together between the two face plies, and are sub~ected to pressure and heat simultaneously to bond the plies together to form the plywood panels. Excellent plywood bonds were obtained with formulations wherein the MKL organic solids were up to between about 40 to 60 percent by weight of the total PF and MKL organic solids applied to the surfaces of the plies, ; with assembly times as long as about 50 minutes. The second layer may be applied by any suitable method such as spraying, curtain coating, or roll spreading. Durlng adhesive mixing the necessary extenders for application may be included.
The MKL adhesive mix is prepared from MKL resin and water J and includes preferably an alkali such as sodium hydroxide to give an alkaline mix. The alkaline aqueous solution of MKL
~1532~4 organic solids in liquid form has a pH of at least about 10. A
preferred embodiment provides a pH in the range of about 11 - 13.
The MKL organic solids in liquid form have an organic solid con-tent range of from about 15 - 35 percent by weight. If the mix is to be sprayed onto the plies, then the organic solids content is generally in the lower level to avoid plugging of the sprays.
However, in some cases it is preferred to apply the MKL organic solids in liquid form by roll spreader in which case a higher organic solids content in the mix may be used. Plywo~d bonded wi$h adhesives according to the two-step process wherein MKL
organic solids range up to about 60% of the total organic solids applied to the plywood exhibited similar behaviour to panels bonded with 100~ PF resole resin adhesive. This was determined after tests for accelerated aging for one boil/dry/boil cycle, in accordance with CSA Standard 0151 - 1974 for Canadian soft-wood plywood.
EXAMPLE: 1 MKL organic solids were prepared by stirring an alka-line solution of kraft lignin with formaldehyde at room tempera-ture for 72 hours.
ConstituentsParts by total solution wei~ht for 22,4%
resin sollds Kraft lignin (95% total solids~ 0.4~ ash) 2328 Formaldehyde (37%) 1646 Sodium hydroxide (flake) 398 Water 5450 A series o~ plywood adhesive mixes was prepared inwhich a portion of the water soluble PF resole resin (35. lZ resin solids) was replaced by an equivalent amount of MKL organic solids.
The MKL/PF adhesives were formed with initial viscosity maintained in the range of 1.0 - 3.0 Pa.s by reducing the amount of extender added with increasing proportion of MKL replacement. All other additives were held constant.
11532~(~
Parts by total solution weight for 21.0 - 21.2%
resiD sollds Formulation (MKL/PF) 20/80 40/60 60/4080/20 Constituents _ PF Resin 3728 2796 1864 932 Extender 750 650 - 600 300 Wheat flour 160 150 150 150 Soda ash 150 150 150 150 Water 1479 1069 603 400 3-ply 5/16" Douglas fir plywood panels were manufactured by a single stage application of the MKL/PF formulation Qn both surfaces of the inner ply using a roll spreader as follows:
Adhesive spread 56 lb/MDGL
Press temperature 177C (350F) Press time 9 minutes (2 panels per opening) Pressure 1380 kPa (200 psi) Closed Assembly time 10 minutes, 30 minutes 8 panels per condition Sample chips were tested after one boil/dry/boil cycle (CSA 0151-1974 -1~53294 _ ~
O h ~ C~ U~
h a. CS~
O s~ ~-,, ~r tD
q U~ U~
O a~ h ~' ~i _I _~
~1 ~3 O h ~ ~ u) IC~
Ct tD ~q t` ~ t--l O h Cl. _I ~1 _I
~ e OD ~ ~
_ X h ~rl ~ t~ It~
O h C~. ~ tD
1~
.
_ 10 --115~z~4 Table 1 shows that up to 20% of the PF resole resin solids in an adhesive mix could be replaced by MKL while still achieving satisfactory plywood bond quality. Beyond this re-placement level, wood failure showed an inverse dependence on the degree of MKL substitution. The shear strength of plywood ad- -hesive joints bonded with MKL/PF adhesives were acceptable even at 60% MKL substitution.
EXAMPLE: 2 . . .
A plywood adhesive mix was prepared in uhich 20~ of the PF resole resin solids were replaced by an equivalent amount of organic solids derived from MKL. The caustic and extender con-tent in this formulation was maintained at the same level as the control glue mix.
A series of 3-ply 5/16" Douglas fir plywood panels was manufactured by a single stage application of the adhesive mixture using a roll spreader OD both surfaces of the inner ply, as follows:
Glue Spread 56 lb/MDGL
Closed Assembly Time 0, 10, 20, 30 minutes Press Temperature 149C (300F); 166~C (330F) Press Time 4, 4~ minutes (2 panels per opening) ~ Pressure 1,380 kPa (200 psi) ;~ 20 8 panels per condition Sample chips were tested after vacuum pressure treatment. Bond quality data is summarized in Table 2.
The plywood panels bonded with PF resole resins modified with 20% MKL give an average wood failure in excess of 80~ as re-quired by CSA 0151 over the complete range of pressing conditions tested. , liS3Z~
_ ~ ~15 ~ 8 ~
~O P~ _ ~ 0 l ~ _I 1~
N. W _~ S .
1~3 ~ 3 t~ N
~ O E-~ ~,e co 15) ~ N ~O ~
~: . S el~ ~O
' ~ ~ __ _ ' _ ~ ~ W CS~ G
.
: - 12 -MKL organic solids were prepared by reacting formalde-hyde with strong black liquor at 120 - 130F (49 - 54C) for 12 hours. This mixture was then acidified with concentrated H2S04 to pH 5. The precipitated MKL was collected by filtration and washed.
Analysis % Total solids 59.4 of moist filter cake % Ash 8.5 % Lignin (sPectrophotometric) 79.2 % Organics (100~ - % ash) 91.5 An aqueous solution of PF resole resin (16.7% resin s~lids) for spray application was prepared by diluting 4 parts of the standard PF mixed glue (20,9% resin solids) with one part water.
Constituents ofParts by total solution weight Standard PF Gluefor 20.9% resin solids Resin 4660 ; Primary Extender750 Wheat Flour 150 Soda Ash 150 Water 1990 Two formulations of alkaline aqueous solutions of MKL organic :20 solids were prepared, one having 20~ of the MKL organic solids ~: rsplaced with PF ~, Parts by total solution wei~ht for 20.9~ organic solids For~ulation (MKL/PF) 80/20 100/0 Constituents .
PF Resin 932 Primary Extender 600 600 Wheat Flour 150 150 Soda Ash 150 150 Sodium hydroxide (flake)336 419 Water 3260 3538 The adhesive solutions were applied to the plies in two stages as follows: first, all four wood surfaces in a 3-ply construction namely the inside surfaces of the two face plies, ~lS3Z~4 and both surfaces of the inner ply were sprayed with PF solution and allowed to stand open for 60 minutes in order to achieve pene-tration of the PF into the wood, and secondly the MKL solution was applied to the core using a roll spreader.
Control MXL/PF (Overall) 40/60 6.0/40 0/100 Formulation MKL/PF (to inner ply surfaces)80/20100/080/20 100/0 0/100 PF to all bonding surfaces lb/MSGL17.6 21.2 8.8 14.0 --MKL/PF to inner ply surfaces lb/MDGL28.4 22.9 42.7 34.4 56.0 PROCESSING CONDITIONS
This invention relates to plywood and more particu-larly to a method of bonding wood plies to form plywood panels utili:zing phenol formaldehyde and lignin formaldehyde, referred to as methylolated kraft lignin (MKL~.
The most common bonding agent used in the preparation of exterior grade plywood is phenol formaldehyde resin (herein-after referred to as PF). This resin is derived from non renewable petrochemical sources, and is day by day be-GOming more expensive. Resins produced from wood chemicals have been considered as a replacement for PF and other petro-chemical resins However, no satisfactory resin has yet been produced from wood chemicals which has the same bonding properties as PF resins at the same low resin solids content used in PF
bonding of plywood.
In plywood, the bonding is dependent on two criteria, 1~ controlled wetting and penetration of the wood by the ad-hesive, and 2) the development of sufficient strength in the adhesive after curing. Adhesive penetration is largely influenced by the molecular weight of the resin and the association of resin molecules. If the effective size of the resin molecule is too small, it is rapidly absorbed by the capillary structure of the wood, producing an adhesive starved joint. If the resin mole-cular size is too large, penetration of the resin into the wood is retarded, resulting in a shallou, weak bond. After hot press-ing the plywood assembly, the strength of the cured adhesive must exceed the strength of the wood itself. When this condition is not fulfilled failure of the adhesive joint occurs in the glue line instead of in the wood.
Many attempts have been made with kraft or soda black liquor to form adhesives as substitutes for PF resin. In general, the adhesives produced by these attempts have been limited because in order to obtain the same adhesive properties as ob-11~32~
tained with PF it has been necessary to use large quantities ofthe lignin derivsd materials which reduces the advantages of this type of adhesive. Attempts have been made to modify kraft lignin with PF to cause cross linking of the lignin molecules. Clarke and Dolenko in U.S. Patent 4,113,675 combined ~KL with a liquid PF resin in the pH range of 4 - 7. The resulting dispersion was used as a wet adhesive for plywood. In this adhesive MKL acted both as an extender and as a source of resin solids. However, it was found that to achieve a satisfactory bond in plywood required nearly twice as much lignin containing adhesive as compared to the level of PF resin normally used.
In another example, Herrick et al, in U.S. Patent 3,454,508, describe a thermosetting phenolic resin in which an alcohol soluble polymethylol phenol was condensed with an acid precipitated alkali lignin in a fugitive base such as ammonia.
In another example, Ball et al in U.S. Patent 3,185,654 suggested a phenolic resin in which an A stage resole was reacted in methanol with an alkali lignin. Neither Herrick nor Ball showed sufficient crosslinking between free methylol groups of the resole and hydroxyl groups in the lignin. These methods failed to produce satisfactory bonds in plywood.
Marton et al in the publication entitled "Lignin Structure and Reactions", Advances in Chemistry Series 59, American Chemical Society, Washington, D.C., Pages 125 - 144, (1966) reported a method of improving the reactivity o~ kraft ~ lignin by introducing methylol groups into the lignin structure via an alkali catalyzed condensation with formaldehyde. Abe in a publication of Hokkaido Forest Product Institute ~o. 55 (1970) also extensively examined the mechanism of the lignin formalde-hyde reaction in alkaline media, and prepared plywood adhesivesbased on the co-condensation of lignin with phenol and formalde-hyde. Both these adhesives gave poo:r water resistance and wet llS;~
strength properties in the bonded product. Enkvist, in U.S.
Patent 3,864,291 describes a process for manufacture of an ad-hesive in which kraft or soda black liquor was methylolated with formaldehyde in the presence of alkali and subsequently condensed with phenol or cresol formaldehyde. However, plywood panels glued with this adhesive showed unsatisfactory wet strength after boil-ing.
One purpose of the present invention is to provide a method of bonding wood plies to form plywood panels. The adhesive used for this bonding replaces a portion of the more commonly used PF resin adhesives and provides glue bond properties that meet the requirements of CSA standards for plywood. CSA 0151 (1974) lays down the minimum glue bond requirements for plywood panels. Glue bond is measured by wood failure tests. The ad-hesive is applied in either a one step or a two step application.
In the present invention, methylolated kraft lignin (MXL) is prepared from black liquor first by methylolation wherein formaldehyde is added to strong black liquor, followed by the addition of acid to the methylolated liquor. Suspension, dilution and filtration of the precipitate produces a filter cake of MKL
solids. An aqueous alkaline solution of the MKL organic solids is then prepared from the filter cake, The composltion of an adhesive mix is gener~lly expressed in terms of percentage by weight of the total adhesive solids in the mix In the case of PF the total adhesive solids ` comprisesthe resin solids which is the portion of the adhesive taking part in the condensation of the adhesive during the curing step. In the present text the term "organic solids" is used throughout, especially in association with ~IKL. In a simple system such as PF, organic solids and resin solids mean the same thing, however, in the case of MKL the organic solids may include other organic matter coprecipitated with the MKL.
li53;~4 Plywood is made in a variety of different constructions wlth varying numbers and types of plies The bonding surfaces of the pli.es refer to all the surfaces of the plies except the exter-ior surfaces of the two outer plies. In the present application the outer plies in a sheet o~ plywood are referred to as face plies, and the inside plies are referred to as inner plies.
Although only a three-ply panel with a single in~er ply is de-scribed herein, it will be apparent to th~ e skilled in the art that plywood panels with any desirable number of plies may be made by the process of the present invention.
The present invention provides a method of bonding wood plies to form plywood panels comprising the steps of, applying water soluble PF resole resin in liquid form to at least one bond-ing surface between the plies, wherein the PF resole resin in liquid form has a pH of at least about 9, applying MKL organic solids in liquid form to the at least one bonding s~r~ace between the plies, wherein the MKL organic solids in liquid form have a pH of at least about 10, and wherein the MKL organic solids are up to about 60% by weight of the total PF resole resin and MKL
organic solids applied to the at least one bonding surface between the plies, sandwiching the plies together, and subjecting the plies to pressure and heat simultaneously to bond the plies together to form plywood panels, In one method of bonding wood plies referred to as the one-step method, water soluble PF resole resin in liquid form having a pH of at least about 9 is mixed with MKL organic solids in liquid form, having a pH of at least about 10 such that the NKL
organic solids are up to about 30% b~ weight of the total PF resole resin and MKL organic solids, applying the mixture to at least one bonding surface between the plies, sandwiching the plies together, and subjecting the plies to pressure and heat simultaneously to bond the plies together to form plywood panels, In another method referred to as the two-step method 11S3;~4 a first layer of water soluble PF resole resin in liquid form is applied to insLde surfaces of two face plies, and both sur-faces of at least one inner ply, wherein the PF resole resin in liquid form has a pH of at least about 9, a second layer is applied of ~L organic solids in liquid form to both surfaces of the inner ply, wherein the MKL organic solids in liquid form - have a pH of at least about 10, and wherein the MKL organic solids are up to about 60% by weight of the total PF resole resin and MKL organic solids supplied to the surfaces of the plies. A
layup is then made by sandwiching the inner ply between the two face plies and the layup is subjected to pressure and heat simul-taneously to bond the plies together to form plywood panels. In one variation of the two-step method, the first layer is a mix-ture of PF and MKL, wherein the weight ratio of MKL to PF is up to about 30 to 70, that is the mixture should not contain more than about 30 parts MKL. In another variation of the two step method, the second layer is a mixture of MKL and PF in any pro-portion. Any combination of these variations may be used so as to give the ratio of total MKL to total PF required in the finished product. In the two step method, up to about 18 hours may pass between the application of the first layer and the application of the second layer, In one embodlment the first layer is applied by spraying, and the second layer is applied by roll spr0ading.
In preferred embodiments, the water soluble PF resole resin in liquid form has a resin solids content range by weight of from about ~5 - 40%. The MKL organic solids in liquid form has an organic solids content preferably in the range of from about 15 - 35% by weight, and the solution contains an alkali metal base such as NaOH or sodium carbonate, In the case of NaOH, the ratio of NaOH to ~KL organic solids is preferably in the range of about 0.15 - 0.30 to 1 by weight, The invention will now be described in more detail, MKL organic solids in liquid form are made by mixing filter cake, 115;~2~?~
prepared in the manner described, with water and an alkali metal base such as sodium hydroxide The MKL organic solids in liquid form has a pH of at least about 10, preferably in the range of 11 - 13. The sodium hydroxide mixed with this MKL
organic solids in liquid form is in the ratio of NaOH to MKL in the range of about 0.15 - 0.30 by weight. The PF resol~ resin may be a commercially available resin with a pH of at least about 9 when in liquid form. Preferably the range is about 11 to 13.
The MKL organic solids in liquid form has an organic solids con-tent range of from about 15 - 35 percent by weight, and the PF
resole resin in liquid form has a resin solids content range by weight of from about 15 - 40 percent. In a preferred embodiment and to form a plywood meeting CSA standards, it is preferable that the ratio of MKL to PF should be not greater than about 30 to 70.
The MKL/PF adhesive mixture is applied to at least one of the bonding surfaces between the plies by any suitable method, such as spraying, curtain coating, or roll spreading. In one embodiment when making a three-ply panel, the mixture is applied to both surfaces of the inner ply. The plies are then sandwiched together~
and in that form subjected to pressure and heat simultaneously so that the plies bond together toform plywood panels In the two-step process, a PF resole resin adhesive ~n liquid form is first prepared as in the one-step process. The PF resole resin in liquid form has a pH of at least about 9, and in a preferred embodiment the resin solid content range is from - about 15 - 40 percent by weight of the liquid adhesive mixture A first layer of the PF resole resin in liquid form is applied to the inside surfaces of the face plies and to both surfaces of one or more inner plies The coating may be applied by any suitable method such as spraying, curtain coating or roll spreading It has been found that the PF resole resin in liquid form may be applied to the plies several hours in advance of the application of the second layer. In fact, tests have shown that about 18 1153~4 hours may elapse between the f~rst and second layer application of adhesive.
The first layer may comprise 100% P~ or may contain MKL in the weight ratio of up to about 30 to 70, MKL to PF. The mixture should not contain more than about 30 parts MKL to 70 parts PF.
The second layer may comprise a 100% MKL organic solids in liquid form, having a pH of at least about 10. Pre-ferably the organic solids in the liquid form has a content range of about 15 - 35 percent by weight. Alternatively, the second layer may be a prepared mixture of PF resole resin in liquid form having a pH of at least about 9 and MKL organic solids in liquid form having a pH of at least about 10. Any proportion of PF may be added to the MKL, depending only on the ratio of P~ to MKL
desired in the final plywood product. The second layer is only applied to the surfaces of the inner plies such that there is always a first layer between the second layer and the surface of the wood. There should not be a second layer which is predomi-nately MKL dir~ctly adjacent to the wood surface. The plies are then sandwiched together between the two face plies, and are sub~ected to pressure and heat simultaneously to bond the plies together to form the plywood panels. Excellent plywood bonds were obtained with formulations wherein the MKL organic solids were up to between about 40 to 60 percent by weight of the total PF and MKL organic solids applied to the surfaces of the plies, ; with assembly times as long as about 50 minutes. The second layer may be applied by any suitable method such as spraying, curtain coating, or roll spreading. Durlng adhesive mixing the necessary extenders for application may be included.
The MKL adhesive mix is prepared from MKL resin and water J and includes preferably an alkali such as sodium hydroxide to give an alkaline mix. The alkaline aqueous solution of MKL
~1532~4 organic solids in liquid form has a pH of at least about 10. A
preferred embodiment provides a pH in the range of about 11 - 13.
The MKL organic solids in liquid form have an organic solid con-tent range of from about 15 - 35 percent by weight. If the mix is to be sprayed onto the plies, then the organic solids content is generally in the lower level to avoid plugging of the sprays.
However, in some cases it is preferred to apply the MKL organic solids in liquid form by roll spreader in which case a higher organic solids content in the mix may be used. Plywo~d bonded wi$h adhesives according to the two-step process wherein MKL
organic solids range up to about 60% of the total organic solids applied to the plywood exhibited similar behaviour to panels bonded with 100~ PF resole resin adhesive. This was determined after tests for accelerated aging for one boil/dry/boil cycle, in accordance with CSA Standard 0151 - 1974 for Canadian soft-wood plywood.
EXAMPLE: 1 MKL organic solids were prepared by stirring an alka-line solution of kraft lignin with formaldehyde at room tempera-ture for 72 hours.
ConstituentsParts by total solution wei~ht for 22,4%
resin sollds Kraft lignin (95% total solids~ 0.4~ ash) 2328 Formaldehyde (37%) 1646 Sodium hydroxide (flake) 398 Water 5450 A series o~ plywood adhesive mixes was prepared inwhich a portion of the water soluble PF resole resin (35. lZ resin solids) was replaced by an equivalent amount of MKL organic solids.
The MKL/PF adhesives were formed with initial viscosity maintained in the range of 1.0 - 3.0 Pa.s by reducing the amount of extender added with increasing proportion of MKL replacement. All other additives were held constant.
11532~(~
Parts by total solution weight for 21.0 - 21.2%
resiD sollds Formulation (MKL/PF) 20/80 40/60 60/4080/20 Constituents _ PF Resin 3728 2796 1864 932 Extender 750 650 - 600 300 Wheat flour 160 150 150 150 Soda ash 150 150 150 150 Water 1479 1069 603 400 3-ply 5/16" Douglas fir plywood panels were manufactured by a single stage application of the MKL/PF formulation Qn both surfaces of the inner ply using a roll spreader as follows:
Adhesive spread 56 lb/MDGL
Press temperature 177C (350F) Press time 9 minutes (2 panels per opening) Pressure 1380 kPa (200 psi) Closed Assembly time 10 minutes, 30 minutes 8 panels per condition Sample chips were tested after one boil/dry/boil cycle (CSA 0151-1974 -1~53294 _ ~
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_ 10 --115~z~4 Table 1 shows that up to 20% of the PF resole resin solids in an adhesive mix could be replaced by MKL while still achieving satisfactory plywood bond quality. Beyond this re-placement level, wood failure showed an inverse dependence on the degree of MKL substitution. The shear strength of plywood ad- -hesive joints bonded with MKL/PF adhesives were acceptable even at 60% MKL substitution.
EXAMPLE: 2 . . .
A plywood adhesive mix was prepared in uhich 20~ of the PF resole resin solids were replaced by an equivalent amount of organic solids derived from MKL. The caustic and extender con-tent in this formulation was maintained at the same level as the control glue mix.
A series of 3-ply 5/16" Douglas fir plywood panels was manufactured by a single stage application of the adhesive mixture using a roll spreader OD both surfaces of the inner ply, as follows:
Glue Spread 56 lb/MDGL
Closed Assembly Time 0, 10, 20, 30 minutes Press Temperature 149C (300F); 166~C (330F) Press Time 4, 4~ minutes (2 panels per opening) ~ Pressure 1,380 kPa (200 psi) ;~ 20 8 panels per condition Sample chips were tested after vacuum pressure treatment. Bond quality data is summarized in Table 2.
The plywood panels bonded with PF resole resins modified with 20% MKL give an average wood failure in excess of 80~ as re-quired by CSA 0151 over the complete range of pressing conditions tested. , liS3Z~
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: - 12 -MKL organic solids were prepared by reacting formalde-hyde with strong black liquor at 120 - 130F (49 - 54C) for 12 hours. This mixture was then acidified with concentrated H2S04 to pH 5. The precipitated MKL was collected by filtration and washed.
Analysis % Total solids 59.4 of moist filter cake % Ash 8.5 % Lignin (sPectrophotometric) 79.2 % Organics (100~ - % ash) 91.5 An aqueous solution of PF resole resin (16.7% resin s~lids) for spray application was prepared by diluting 4 parts of the standard PF mixed glue (20,9% resin solids) with one part water.
Constituents ofParts by total solution weight Standard PF Gluefor 20.9% resin solids Resin 4660 ; Primary Extender750 Wheat Flour 150 Soda Ash 150 Water 1990 Two formulations of alkaline aqueous solutions of MKL organic :20 solids were prepared, one having 20~ of the MKL organic solids ~: rsplaced with PF ~, Parts by total solution wei~ht for 20.9~ organic solids For~ulation (MKL/PF) 80/20 100/0 Constituents .
PF Resin 932 Primary Extender 600 600 Wheat Flour 150 150 Soda Ash 150 150 Sodium hydroxide (flake)336 419 Water 3260 3538 The adhesive solutions were applied to the plies in two stages as follows: first, all four wood surfaces in a 3-ply construction namely the inside surfaces of the two face plies, ~lS3Z~4 and both surfaces of the inner ply were sprayed with PF solution and allowed to stand open for 60 minutes in order to achieve pene-tration of the PF into the wood, and secondly the MKL solution was applied to the core using a roll spreader.
Control MXL/PF (Overall) 40/60 6.0/40 0/100 Formulation MKL/PF (to inner ply surfaces)80/20100/080/20 100/0 0/100 PF to all bonding surfaces lb/MSGL17.6 21.2 8.8 14.0 --MKL/PF to inner ply surfaces lb/MDGL28.4 22.9 42.7 34.4 56.0 PROCESSING CONDITIONS
2 Step Adhesive System Control Press temperature 177C (350F) 149C (300F) Press time (2 panels per opening) 9 minutes 4~ minutes Pressure 1380 kPa (200 psi) 1380 kPa (200 psi) Open assembly time 60 minutes (PF treated plies) ---Closed assembly time 0, 10,20,30 minutes 0,10,20,30 minutes 8 panels per condition Samples were tested a~ter one cycle o~ the boil/dry/boll condl-tionlng treatment (CSA 0161 - lg74), ~ .
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, llS~Z94 The two step adhesive application showed a considerable improvement over the conventional one step application system.
(Compare Table 3 with Table 1) E~cellent plywood bonds were obtained with both the 80/20, and 100/0 MKL/PF formulations at the total replacement level of 40% MKL solids.
EXAMPLE: 4 Example 3 was repeated using the 80/20 MKL/PF formu-lation for application to the inner ply. Plies sprayed with PF
resole resin mixed adhesive were allowed to stand open at room temperature for 18 hours prior to application of the MKL/PF ad-hesive to the inner ply. The results are shown in Table 4.
., MKL/PF (Overall) 40/60 60/40 MKL/PF to ; inner ply 80/20 80/20 Closed Assembly Shear Shear Time Strength Strength Minutes % WF psi % WF psi 89 11~ 80 128 . _ Average 87 110 79 121 Mixed PF resole resin solutions may be sprayed onto the plies several hours in advance of application of the MKL/PF solution to the inner ply. This method of adhesive application allows - replacement of between 40 - 60% of the PF solids in the total adhesive mix, while ~till maintaining plywood bond quality.
EXAMPLE: 5 Example 3 was repeated with 80/20 and 100/0 ~L/PF
formulations applied to the inner ply. The overall ratios were 115~Z~4 40/60 and 60/40 MKL/PF and the results were compared with a 100% PF control. Table 5 shows the results.
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, llS~Z94 The two step adhesive application showed a considerable improvement over the conventional one step application system.
(Compare Table 3 with Table 1) E~cellent plywood bonds were obtained with both the 80/20, and 100/0 MKL/PF formulations at the total replacement level of 40% MKL solids.
EXAMPLE: 4 Example 3 was repeated using the 80/20 MKL/PF formu-lation for application to the inner ply. Plies sprayed with PF
resole resin mixed adhesive were allowed to stand open at room temperature for 18 hours prior to application of the MKL/PF ad-hesive to the inner ply. The results are shown in Table 4.
., MKL/PF (Overall) 40/60 60/40 MKL/PF to ; inner ply 80/20 80/20 Closed Assembly Shear Shear Time Strength Strength Minutes % WF psi % WF psi 89 11~ 80 128 . _ Average 87 110 79 121 Mixed PF resole resin solutions may be sprayed onto the plies several hours in advance of application of the MKL/PF solution to the inner ply. This method of adhesive application allows - replacement of between 40 - 60% of the PF solids in the total adhesive mix, while ~till maintaining plywood bond quality.
EXAMPLE: 5 Example 3 was repeated with 80/20 and 100/0 ~L/PF
formulations applied to the inner ply. The overall ratios were 115~Z~4 40/60 and 60/40 MKL/PF and the results were compared with a 100% PF control. Table 5 shows the results.
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l~S3Z~4 The two step adhesive application system produced superior plywood bonds with both the 80/20 and 100/0 MKL/PF
formulations, at an overall replacement level of 40 and 60% PF
resole resin solids.
In a further series of tests the closed assembly time was extended to 50 minutes, excellent results were obtained as shown in Table 6.
MKL/PF _ (Overall) 60/40 MKL/PF
to inner ply 80/20 100/0 Closed Assembly Shear Shear Time Strength Strength Minutes % WF psi% WF psi EXAMPLE: 6 Plywood panels were manufactured using the two step adhesive application system described in Example 3, so that 70%
and 80% respectively of the PF resole resin solids were replaced by MKL. Analysis of MKL
% Total solids 61.8 of moist filter cake ~ % Ash 8.5 : % Organics (100% - % ash)91.5 Preparation of MKL Mixed Adhesives -Formulation (MKL/PF - 100/0) Parts by total solution weight for 20.5% organic solids Constituents Primary Extender 600 Wheat flour 150 Soda Ash 150 Sodium hydroxide (flake)419 Water 3686 ilS32~?4 MKL and PF were applied to the plies as a two step system (as described in Example 3) MKL/PF (Overall) 70/30 80/20 Formulation MKL/PF ~to inner ply) 100/0 100/0 PF to lnnerply surfaces lb/MSGL 10.5 7.0 PF to core lb/MDGL 40.1 45.8 Processing Conditions Press temperature 177C -(350F) Press time (2 panels per opening) 9 minutes Pressure 1390 kPa (200 psi) Open assembly time 60 minutes (PF treated plies) Closed assembly time 0,10,20,30,50 minutes 8 panels per condition Samples were tested after one cycle of the boil/dry/
boil conditioning treatment (CSA 0151-1974) MKL/PF (Overall) 70/30 80/20 MXL/PF
To inner ply 100/0 100/0 Closed Assembly Shear Shear Time Strength Strength : Minutes % WF psi % WF psi _ : 20 79 128 68 128 119 66 la7 126 73 130 ~ -_ Average 178 123 69 124 The results in Table 7 show that when 70% or more of the PF resole resin solids were replaced with MKL, the wood failure fell below the CSA specification of 80
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l~S3Z~4 The two step adhesive application system produced superior plywood bonds with both the 80/20 and 100/0 MKL/PF
formulations, at an overall replacement level of 40 and 60% PF
resole resin solids.
In a further series of tests the closed assembly time was extended to 50 minutes, excellent results were obtained as shown in Table 6.
MKL/PF _ (Overall) 60/40 MKL/PF
to inner ply 80/20 100/0 Closed Assembly Shear Shear Time Strength Strength Minutes % WF psi% WF psi EXAMPLE: 6 Plywood panels were manufactured using the two step adhesive application system described in Example 3, so that 70%
and 80% respectively of the PF resole resin solids were replaced by MKL. Analysis of MKL
% Total solids 61.8 of moist filter cake ~ % Ash 8.5 : % Organics (100% - % ash)91.5 Preparation of MKL Mixed Adhesives -Formulation (MKL/PF - 100/0) Parts by total solution weight for 20.5% organic solids Constituents Primary Extender 600 Wheat flour 150 Soda Ash 150 Sodium hydroxide (flake)419 Water 3686 ilS32~?4 MKL and PF were applied to the plies as a two step system (as described in Example 3) MKL/PF (Overall) 70/30 80/20 Formulation MKL/PF ~to inner ply) 100/0 100/0 PF to lnnerply surfaces lb/MSGL 10.5 7.0 PF to core lb/MDGL 40.1 45.8 Processing Conditions Press temperature 177C -(350F) Press time (2 panels per opening) 9 minutes Pressure 1390 kPa (200 psi) Open assembly time 60 minutes (PF treated plies) Closed assembly time 0,10,20,30,50 minutes 8 panels per condition Samples were tested after one cycle of the boil/dry/
boil conditioning treatment (CSA 0151-1974) MKL/PF (Overall) 70/30 80/20 MXL/PF
To inner ply 100/0 100/0 Closed Assembly Shear Shear Time Strength Strength : Minutes % WF psi % WF psi _ : 20 79 128 68 128 119 66 la7 126 73 130 ~ -_ Average 178 123 69 124 The results in Table 7 show that when 70% or more of the PF resole resin solids were replaced with MKL, the wood failure fell below the CSA specification of 80
Claims (3)
1. A method of bonding wood plies to form plywood panels comprising the steps of:
applying water soluble phenol formaldehyde resole resin in liquid form to at least one bonding surface between the plies, wherein the phenol formaldehyde resole resin in liquid form has a pH of at least about 9, applying methylolated kraft lignin organic solids in a liquid form to the at least one bonding surface between the plies, wherein the methylolated kraft lignin organic solids in liquid form have a pH of at least about 10, and wherein the methylolated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylo-lated kraft lignin organic solids applied to the at least one bonding surface between the plies, sandwiching the plies together, and subjecting the plies to pressure and heat simul-taneously to bond the plies together to form plywood panels.
applying water soluble phenol formaldehyde resole resin in liquid form to at least one bonding surface between the plies, wherein the phenol formaldehyde resole resin in liquid form has a pH of at least about 9, applying methylolated kraft lignin organic solids in a liquid form to the at least one bonding surface between the plies, wherein the methylolated kraft lignin organic solids in liquid form have a pH of at least about 10, and wherein the methylolated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylo-lated kraft lignin organic solids applied to the at least one bonding surface between the plies, sandwiching the plies together, and subjecting the plies to pressure and heat simul-taneously to bond the plies together to form plywood panels.
2. A method of bonding wood plies to form plywood panels comprising the steps of:
applying a first layer of water soluble phenol formalde-hyde resole resin in liquid form to inside surfaces of two face plies and both surfaces of at least one inner ply, wherein the phenol formaldehyde resole resin in liquid form has a pH of at least about 9, applying a second layer of methylolated kraft lignin organic solids in liquid form to both surfaces of the inner ply, wherein the methylolated kraft lignin organic solids in liquid form have a pH of at least about 10, and wherein the methylo-lated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to the surfaces of the plies, sandwiching the inner ply between the two face plies, and subjecting the plies to pressure and heat simul-taneously to bond the plies together to form plywood panels.
3. A method of bonding wood plies to form plywood panels comprising the steps of:
applying a first layer of water soluble phenol formaldehyde resole resin in liquid form to inside surfaces of two face plies and both surfaces of at least one inner ply, wherein the phenol formaldehyde resole resin in liquid form has a pH of at least about 9, applying a second layer of a mixture of water soluble phenol formaldehyde resole resin in liquid form having a pH of at least 9 and methylolated kraft lignin organic solids in liquid form having a pH of at least about 10 to both surfaces of the inner ply, wherein the methylolated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to the surfaces of the plies, sandwiching the inner ply between the two face plies, and subjecting the plies to pressure and heat simultaneously to bond the plies together to form plywood panels.
4. The method according to claim 2 or claim 3 wherein up to about 18 hours may pass between the application of the first layer and the application of the second layer.
5. The method according to claim 2 or claim 3 wherein the methylolated kraft lignin organic solids are up to about 40% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to the surfaces of the plies.
6. The method according to claim 2 or claim 3 wherein the phenol formaldehyde resole resin in liquid form has a resin solids content range by weight of from about 15 - 40%.
7. The method according to claim 2 or claim 3 wherein an alkali metal base is present with the methylolated kraft lignin organic solids in liquid form.
8. The method according to claim 2 or claim 3 wherein NaOH is present with the methylolated kraft lignin organic solids in liquid form, with the ratio of NaOH to methylolated kraft lignin organic solids in the ratio of about 0.15 - 0.30 to 1 by weight.
9. The method according to claim 2 or claim 3 wherein the methylolated kraft lignin organic solids in liquid form has an organic solids content range of from about 15 - 35%
by weight.
10. Plywood panels made by the process of claim 2 or
applying a first layer of water soluble phenol formalde-hyde resole resin in liquid form to inside surfaces of two face plies and both surfaces of at least one inner ply, wherein the phenol formaldehyde resole resin in liquid form has a pH of at least about 9, applying a second layer of methylolated kraft lignin organic solids in liquid form to both surfaces of the inner ply, wherein the methylolated kraft lignin organic solids in liquid form have a pH of at least about 10, and wherein the methylo-lated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to the surfaces of the plies, sandwiching the inner ply between the two face plies, and subjecting the plies to pressure and heat simul-taneously to bond the plies together to form plywood panels.
3. A method of bonding wood plies to form plywood panels comprising the steps of:
applying a first layer of water soluble phenol formaldehyde resole resin in liquid form to inside surfaces of two face plies and both surfaces of at least one inner ply, wherein the phenol formaldehyde resole resin in liquid form has a pH of at least about 9, applying a second layer of a mixture of water soluble phenol formaldehyde resole resin in liquid form having a pH of at least 9 and methylolated kraft lignin organic solids in liquid form having a pH of at least about 10 to both surfaces of the inner ply, wherein the methylolated kraft lignin organic solids are up to about 60% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to the surfaces of the plies, sandwiching the inner ply between the two face plies, and subjecting the plies to pressure and heat simultaneously to bond the plies together to form plywood panels.
4. The method according to claim 2 or claim 3 wherein up to about 18 hours may pass between the application of the first layer and the application of the second layer.
5. The method according to claim 2 or claim 3 wherein the methylolated kraft lignin organic solids are up to about 40% by weight of the total phenol formaldehyde resole resin and methylolated kraft lignin organic solids applied to the surfaces of the plies.
6. The method according to claim 2 or claim 3 wherein the phenol formaldehyde resole resin in liquid form has a resin solids content range by weight of from about 15 - 40%.
7. The method according to claim 2 or claim 3 wherein an alkali metal base is present with the methylolated kraft lignin organic solids in liquid form.
8. The method according to claim 2 or claim 3 wherein NaOH is present with the methylolated kraft lignin organic solids in liquid form, with the ratio of NaOH to methylolated kraft lignin organic solids in the ratio of about 0.15 - 0.30 to 1 by weight.
9. The method according to claim 2 or claim 3 wherein the methylolated kraft lignin organic solids in liquid form has an organic solids content range of from about 15 - 35%
by weight.
10. Plywood panels made by the process of claim 2 or
claim 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000344464A CA1153294A (en) | 1980-01-28 | 1980-01-28 | Manufacture of plywood comprising methylolated kraft lignin solids |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000344464A CA1153294A (en) | 1980-01-28 | 1980-01-28 | Manufacture of plywood comprising methylolated kraft lignin solids |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1153294A true CA1153294A (en) | 1983-09-06 |
Family
ID=4116119
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000344464A Expired CA1153294A (en) | 1980-01-28 | 1980-01-28 | Manufacture of plywood comprising methylolated kraft lignin solids |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1153294A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4001376A1 (en) * | 2020-11-13 | 2022-05-25 | Wilsonart LLC | Multi-part lignin-based resin system for decorative laminates |
-
1980
- 1980-01-28 CA CA000344464A patent/CA1153294A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4001376A1 (en) * | 2020-11-13 | 2022-05-25 | Wilsonart LLC | Multi-part lignin-based resin system for decorative laminates |
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