Note: Descriptions are shown in the official language in which they were submitted.
2158636 '~
FAST CURE AMD PRE--CURE ~ I ~ CRDSS-LINKED PHENOL-FCRMALDEHYDE
ADHESIVES AMD MF~ nfi OF M~XING SAME
Field of Invention
S m e pr~ t inNention relates to a new and useful fast
curing thermosetting adhesive comprised of cross-linked bLnary phenol-
formaldehyde and lignin and additionally, an adhesive ~hich can be
rend=rel "Fear~alrc" resistant, as well as the mRthods of preparing
same. ~he fast curing and "pra-cure" resistant adhesive may be used in
the preparation of nE~nufactured lignocellulosic Fl~xhJcts such as b~ards
and panels employing ~--~t, wood chips, wood wafers and the like.
Backgxound of Invention
Phenol-formaldehyde (PF) adhesive resins have long been
used as th~rmn~etting binders in the ~ a~Lian of manufactured boards
or panels. NhmY~nOU6 attempts have been made to develop suitable
substitute adhesives, which utilize wood waste, in order to not only
meet growlng envi~u.~ U~ s~ but to also red~ce the de ~ ~ ~e
upon petroleum hased constituents, the av~ hility and cost of which
is increasLngly uncertain.
These att~Fts have included efforts to develop suitable
adhesive binders by using PF to cro6s-link other possible adhesive
constituents, including one or ~ re waste pr~duK ts of wccd ~ ~Yssing.
Uhfortunately, to date thRse efforts have n~t with only limited
s~c~s .
21S8636
Ihe ~ e of w~od waste Frxr~ s which have been
successfully cross-linked is limlted, and the m~x~ds used to produce
these adhesive binders have been slow and lakorious, often rlc~ulrLng
~u~leatment of the waste product constituent. Furthermore, the cure
time and adhesion characteristics of th~se adhesive binders have been
such that widespread use or aoc~an ~ of these sub6titutes by the
manufactured b~ard in~ustry has not cxxlunn3d. For example, it is
often the case that the adhesive binder must be used under acidic
conditions. However, board and panel manufactI~rs prefer to operate
in an alkaline envil~a~nent, since less wear and tear is encountered by
pGIduLtion e~ m~nt.
Ih U.S. Patent No. 2,786,008 j~l on Mbrch 19, 1957 -
Herschler, an adhesive binder consisting of Fhenol-formaldehyde (PF)
and ammonium b~sed spent sulFhite liquor (NHlSSL) is ~i~rlosed. In
addition to p~oducing an acidic adhesive which is slow curing, the
methcd ~i~clo~e~ by Herschler is laborious and tiDY~Ionsuming, as it is
ne~;s~ry to make the alk21ine PF "acid tolerant" in order to avoid
precipitation of the PF resin upon mixing of same with the acidic spent
sulphite liquor.
Anokher example of using PF to cro6s-link a wood waste
product is that disclosed in U.S. Patent no. 4,113,675 i~sued on
September 12, 1978 - Clar~e et al., wherein methylolated lignin was
cro6s-linked by an acid catalyzed low molecular weiqht PF resin. It
was c~6~~d that kraft lignin was itself not sufficiently reactive to
215863~ --
under significant cross-li ~ with PF, and that it was thus nçQ~s~ry
to pre-react the lignin with a methylolating agent, such as
formaldehyde, so as to intlxx~ooe methylol group6 to the lignin
molecule. M~reover, it was indicated that in order to achieve
S satisfactory cross-lin ~ on curing, the pH of the binder must be
acidic. Finally, the adhesive disclosed in Clar~e et al. was fcund to
be relatively slow curing.
In Can~dian patent 1,214,293 i~e~ on Nove~ber 18, 1986 -
Calve et al., an adhesive oonsisting of am~nium based spent sulphite
liquor (N~ r ) cross-linlc~ ~y a camr~rcial PF is ~ ~. It was
fa~ that while PF normally precipitates when in acidic solutian with
N~I,S5L, a useful adhesive could ~e obtain~ if the ~I,S~PF were
n~int~ in dispersion thr~ rigorous stirring or agitatical.
h~ain, acidic co~2ditions, of pH 3 to 7, were required to E~vide
acceptable m~ulus of rupture (M~R) test results on wafer~oard and
particle~oard manufactured with the adhesive.
In U. S . patent 4 ,127, 544 issued on N~vember 28, 1978
Allan, a p~oaess for the partial su ~ titlltion of a~nonium
ligno6ulfonate for phenol in aIkaline phenolic-aldehyde resin adhesives
is described. However, the N~S5L is first pre-reacted with phenol at
a temperature range of 150-300'C under autogencus F~ re prior to
cxYI~nsation with formaldehyde under alkaline oonditions. Ihe reaction
at high temperature and pressNre is exFensive. Also, no w~od adhesive
bond test data were provided.
2158636
In U.S. patent 4,324,747 i~ql on April 13, 1982 - S ~
et al, a resin where an alkaline phenol-formaldehyde resin is simply
muxed wqth a kraft pulping liquor and use to bond waferboard is
disclosed. m e phenolic resin is ~u~ 3l by refluxing phenol and
forr~l~P~yde in the F~T~I~X~C of zinc acetate or heating at lower
ten~x~ature m the presence of calcium oxide. No reference to
ad~u~LL~ of molecular weight disdl-~bution of the phenolic resin or
example of addition of a~ium salt is provided. mis type of resin
is slow a~ring and not "pre~c" resistant.
Ib be aoceptAhle for ir~ial use, a new ~ive mllst
meet certain criteria. For example, it must be available as a s~ray
dried p~der or stable l;~ ; be qui~k setting if it is employed as a
core adhesive for thiclc m~lti-layer panels where the resin is far fmm
the heating s~ce, or be "pr~e" resistant if it is ~lo~ed for
bonding a ~nolayer panel or the faoe of a multi-layer panel. If the
resin c ~res ~L~L-~rely while the mat is r~~ting on a ho~t caul plate
before pressing or at first contact with the press platens before
sufficient pressure is applied to c~olidate the mat, a poor bond will
ensue.
In the aforer~ntioned examples and el~e~re, it has not
been suggested or conten~lated that the PF ~ ent of the adhesive be
modified or ~peci~lly constituteld to ~k~e the cross-linking of the
wo~d waste product ocsponent of the adhesive.
21536~
While a tw~ oomponcnt or '~binary PF" resin, oomprised of a
ni~lme of high average molecular weight PF and low average molecular
weight PF comp~lk~-~s, has long been used in the manufacture of board,
heretofore, the low ~le2~1~r weight PF has been added to enhance resin
flaw wqth nu~Lunum d~y-out. Its unique reactivity to produce a quick
set~i~ng resin when used in oombination with w~od waste, especially
polydi~e~e lignin, has not been ~e~x~ ized and its use in oo~bination
with wxx~d waste product not contemplated.
~or example, in U.S. patent no. 4,269,949 issued on May 26,
1981 - Hickson et al, there is ~i~clofiPd a binary PF resin oomprised of
a n~ re of high and low molecular weight resins, particularly
suitable for use in hardboard applications, ow m g to the nuruu~lm dry-
cut ~xhihited by the adhesive.
In U.S. patent no. 4,433,120 issued on February 21, 1984 -
Chiu, it was der~x~Lla ed that a liquid binary PF resin having low
viscosity and law surfa oe tension could be used for efficient spray
application as fine droplets in waferboard n~nufacture. m e liquid
binary PF resLn has limited F~e-clLre resistance d~e to the E~ oce of
the slawer curing low molecular weight phenolic resin which is however
not sufficient for a surface resin. Although thle liquid bin~ry PF
resin exhibited some pre-cure resistance, this resin is relatively
expensive to produce, and displayed only limited Ere-cure resistanoe.
It is also difficult to spray-dry without advancing the resin and
reducing its Ere-cure resistance.
215863 6
In a reoent study Stephens and Kutscha (Wbod and Fiber
Science, 19(4), 1987, pp. 353-361) fractionated a phenol-formaldehyde
resin Lnto a high and low molecular weight resin by ultrafiltration and
clD~YIngd the adhesive ~u~e~Lies of each fraction to the unfractionated
PF resin. They found that: "the high ~ lecular weight resin fracticn
performed nearly as well as the unfractionated resin". m e ~les~x~e of
low molecular weight penol-formalde~yde only slighkly imQrove the
characteristic of the PF resin, and is not essential to the ~YL~5S.
Sln~m~ry of T~vention
an the c~nlLLc~ to previous findings, it has been fcund
that a mixture of a bLnary PF and a polydisFY~is lignin, shows an
ur~oq?ecte~ high adhesive reactivity.
While in previo~s w~r~, different types of phenolic resin
were required, for example, with kraft or sulphite lignin which have
different ~ lecular weight distribution, in ac~L~ ~ with this
invention results better than previous were cl*ained with a binary PF
resin cross-linker for the lignin and inde ~ ~ ly of the lignin
origin. While high molecular weight PF resin could be used alone as
adhesive, with a w w d waste product such as lignin, the FQI#~nce of
b~th high and low molecular weight phenolic resin is needed to pr~xhb3e
a fast c~ring adhesive cnmrosition an~ a s ~ weather resi~L~i~e
joint. The use of high or low molecular weight PF alcne with a wxxxl
waste ~ e such as lig m n, results in a we3k bond, while a h~l~nce
oomposition of high molecular weig~t PF, low molecular weig~t P~ and
- 2158636
lignin has been found to result in an ~hp~ive with curing and strength
~uu~e~Lies similar to a fast curing cr~E~rcial phenolic resin. Both
high and low molecular weight PF cross-link the lignln which is itself
a mixture of high and low molecul ~ weight particles. m e small
S phenolic molecules are also kelieved to link the high molecular weight
lignin polymer as the resin is cured while the large phenolic mol ~ lles
link the smaller lignin mol~les. Ihis sy~3m can also be used under
acidic conditions, as a water solution or disFersion.
It has also been fo md that the lig m n, as ~ell as their
uses as a water dispersion, lmpnoves the f~il;ty of ~u-ay drying of
the phRnolic sy~tem resulting in a higher yield. This is re~arded as
impo~ L since a resin which spray drys m~re o~cily can ~e pr~Y~ at
a higher rate, increasing ErodLL*ivity.
In aoco~u~e with yet another ~pect of thiC inventicn,
the incogp3nsive resin can also ke made to exhibit im~rov3d FrT~1~Ire
resistance which is i~cuL~.~ when used as a liquid or spray-dried
powder face adhesive for three-layer ccmposite Fr~ch~*s, such as
wafer~x~rd.
This was achieved by simple n~cu~g a phenol-formaldehyde
resin (one which could ~e used as core adhQsive for a 3-layer panel,
for e~uy?le), a relatively large quantity of a lignin and an ammonium
2S salt. m e use of ammonium spent sulphite liquor is preferred as li~nin
source as it already crnt~ins the ammonium salt corpcn~ft. If kraft,
2158636
steam hydrolysed, organic extract, SSL of other cooking base
or glucose was employed, the resin flow and pre-cure
resistance is capable of being controlled by addition of
ammonium hydroxide and ammonium salt such as ammonium
sulphate, ammonium p-tolenesulfonic acid or ammonium
chloride. The use of low molecular weight lignin is often
preferable as it will help to control the flow of the resin.
Upon addition of sodium hydroxide or a strong base other
than ammonium hydroxide, the resin was found to lose some of
its pre-cure resistance. Although the presence of a lignin
is much preferred, it was also found possible to slightly
improve the pre-cure resistance of a phenolic resin by
adding directly to it an ammonium salt. The use of a binary
PF resin is preferred for pre-cure resistance in the
presence of lignin and ammonium salt.
As indicated above, the present invention
contemplates using binary PF to cross-link wood waste lignin
in order to provide a novel quick-curing thermosetting
adhesive. By employing a binary PF, it is not necessary to
include the additional step of pretreating (by
methylolation) lignin as was the case in Clarke et al
(supra.). Furthermore, contrary to the results indicated in
Canadian Patent 1,214,293, it has been found that sodium
based spent sulphite liquor (NaSSL) can be employed as an
adhesive component where binary PF is utilized.
Importantly, satisfactory results are obtainable where the
adhesive is employed under alkaline, as well as acidic,
conditions. Not only is the adhesive of the present
invention relatively simple to produce, but it is also
quick-curing, easy to spray-dry and demonstrates improved
adhesion characteristics.
21~863~
An adhesive having the foregoing quick or fast
curing qualities is produced by reacting preferably by
mixing the binary PF in solution with lignin which
advantageously, can be obtained from wood, pulp, waste, such
as that produced in the sulphite, kraft, organic extract or
steam hydrolysed pulping process (of course mixing the
various ingredients by powder to powder blending is also
possible). As previously noted, the binary PF consists of a
mixture of high average molecular weight PF (high MW PF) and
low average molecular weight PF (low MW PF). As indicated
herein, binary PF has been found to be an effective cross-
linker for the aforementioned lignins to produce a quick-
curing adhesive having improved adhesion characteristics.
Preferably, either the low MW PF is mixed with the
lignin prior to mixing with the high MM PF, or, the high MW
PF and the low MW PF are mixed concurrently with the lignin.
The adhesive system can be used as an
alkaline water (aqueous) solution (pH 9-11) by simple
mixing of the alkaline binary PF with the lignin copolymer
and slight addition of a base such as sodium hydroxide if
required to increase the resin solubility or by utilization
of a binary PF having a concentration of low MW PF, for
example, 85% low MM PF and 15% high MM PF. Excessive
addition of sodium hydroxide will result in advancing the
resin particularly during spray-drying, and reducing its
adhesive properties. As well, the pH of the solution can be
lowered to disperse the adhesive (pH 3-9), or the adhesive
may be separated from the solution, or spray-dried. Slight
21586~
f
lmprovement in lig m nrPF reactivity has b~en o~tl~roed if the ligninr
PF mixture is heated at low temperat~re (for ex~ngple 2 hours at 50 C),
prior to spray-drying.
The ~ h~ ratio of the high MW PF to the low MW PF can be
fram 1:1 to 9:1, and is preferably in the area of 7:3, but where an
acid water solution is prefe ~ , the ratio can be 1:9 to 1:4,
preferably 15:85.
Ihe average molecular weight of the high MW PF is
preferably from 1,200 to 10,000, and the average molex~llAr weight of
the low MW PF is from 200 to 1,200. me weight ratio of binary PF to
lignin may be from 9:1 to 1:9, preferably 80:20.
me weight ratio of the binary PF to li3nin can range fr~
9:1 to 1:9 and is preferably 85:15 for the pr~tion of a quic3c
s~tting adhesive.
me rendering of the adhesive "~:ure" resistant
co~plates the adrlition of an an~ ium salt to a PF resin to pr~vide
a novel ~~e resistant then~et~ adhesive. I~is type of
a~esive is primarily inter~ed for use as a face adh~ive for three
layer wafeLL~a~3s. Employing a binary PF for this type of re~in is
preferred. A face or a core PF resin (preferably core PF as m~re PF
2S could bP rP~l~l with lignin) ~ tly used for the ma~mfacture of
waferboard can be used. The amcunt of lignin an~/or ammonium salt, and
2158636
the choi oe of PF copolymer will determine the rate of curing of ,'h~
adhesive and its Fh~ re resistance. AS before, the adhesive can be
transformed into a useful adhesive powder by spray drying and is
generally employed under alkaline conditions.
Tb produce the "Fn~ Lre" resistant adhesive, as before, a
PF in solution (and which preferably a binary PF) is mixed with a
lignin which advan~ ly is in waste form and L~WVel~3~ f m m one of
the different pulping ~ Y~ S, and an am~onium salt. As previously
noted, the ammcnium salt may consist for example of am~Lnium
lignosulfonate, a ~ nium s~ hAte, ammLnium p-toluenesulfonic acid or
annonium chloride.
m e ammonium salts are generally acidic and wqll cause
precipitation of the alkaline phenolic r~sin up~n mixing. m is may ke
prevented by crr~llr~ent slight addition of ammonium h~nxxide. Again
excessive addition of ~Ln~ ~ base cther than ammonium hydroxide such as
sodium hydroxide will r~duce the flow and Fcl~clrre resistance of the
resin. me oontent of amr~ni~n salt (salt other th_n an~ni~n spent
sulphite liquor) in the resin mix~e may vary fmm 1 to 3096 ~sed on
the total dry ~~ight of the resin mix~e and is prefer~bly 2-696.
In the case of NH,SSL, the salt being also the lignin
co~olyn~r, the PF to ~,S5L weiqht ratio can vary fr~ 8:2 to 1:9 and
is preferably 70:30. ~e preferred weight ratio is also 70:30 for
lignin sa~rces other than ~,S5L su~h as for e~nnple, sodimn or calcium
2158636
based ~CT~ or steam hydr~lysed lig m n. If a ~Ll~ ~ly alkaline kraft
lignin is being used, it has been found that by rlqxrrLng part of the
sodium salt oontent of the kraft lig m n by precipitation of the lig m n
in acidic solution and w~L~ng with a dilute acid water solution, may
be preferable, in order to avoid formation of excess of sodium
hydroxide in the final resin mixture. It is also po~ihle to formulate
a phenolic resin with less sodium hydroxide to acYxnml~date this
copolymer.
As for the quick setting adhesive, the pH of the resin
solution can be lowered to disperse the adhesive (pH 3-9) but it is
preferably used as a water solution (pH 9-11). m e resin may be spray
dried into a stable pcw~er or used as a liquid.
An impo~ ~ aspect of these findings is that the lignin as
well as most ammonium salts are inexpensive in co~pariscn to phenol-
form21dehyde. Also i~ L is the i~ se in the quantity of
material reoovered if spray-dried into stable pawder per hour employing
existing ~irm~nt, a further reduction in the adhQsive prodh~tion
006t.
A further a~lLaye of this finding is that the lignin and
ammonium salt in a ocmposite panel, during thermLsetting, will react
with any free for~ Phyde present in the resin formulation and thus
act as a formaldehyde scavenger.
2158636
.,
Brief Descripkion of Drawl~g
Figure 1 iS a graphic ~ ntation of the relationship
between the ~e~ La~ yield and particle size of ths ~h~ive in
pow~er form ob*ained after spray drying, and the ~e~ w .~Yye of binary
PF and/or N~CT present in the ~hF~;ve mixture before spray drying.
It should bs noted that the 100% N~LSSL and PF were sprayed as a water
soluticn while all the PF-Nn~SSL mixture were spray~dried as a
dispersion at a pH of 5Ø It should be added that similar high yield
(89% po~der recovery based on initial resin dry weight) ob~ained using
a resin containing kraft lignLn (27%)-(N~ 30~(3%)-PF(70%). m e resin
was spray dried as a water solution at a pH of 9.8.
Detailed Descri~tion of Preferred EhtxxL~cnts
~n the followlng, the L_ U ~d of ~u~ ~Lng the ~h~ives of
the invention are described. As well, test results including
~csf~;~"~l~s of the a~P~ion cheQ~}cteristics of various adhesive
formLlaticns are set forth.
m e Binary PF Re!sins
m ere are several examples in the literature of methcd of
preparation of binary PF resins (Ex. U.S. Pat. 3,180,784; 3,267,188;
3,S91,535; 3,927,140; 4,269,949; 4,345,054; 4,433,120). As a~ K~y
mentioned, the unique reactivity of binary phenolic resLn to F~xx~x3e a
quick setting resin when used in combinatiom with lignLn has not be~n
reoognized. m e intent is not to show how to produce a binary PF since
this art has already been described in the literature, but to provide
2158636 ~-
e~les of bir~3ry resin f~lations ~ic~ ~~uld be used to
d~x~ L ~Le their unique reactivity when emplcyed with wood waste
products such as lignin or ccxd~l ming lignin.
EXample of ~ ation of a BLnary PF ~in
For the ~Le~ Lion of high MW resm P~formalde~le (167
g) was SU~ K~3~ in water (378 g) and heated at 9~ for 30 n~inrtes.
m e ~ e was then ccoled to 25 C and phenol (210 g) was added
followed by slow additicn of sodium hydroxide (62.5 g at 50 pe~cent
solid). m e temperature of the reaction was raised to 90~C in a 60
minutes period and held until the resin reached a (Er~x~kfield)
visooeity of 50 cps (visoosity ne##~i~ed at 25~C). Ihe resin was cooled
to 75~C and held at this tL~r~L~e until a vqscosity of 300 c~s was
ci*ained. At this point the resin was cooled to room temperature and
10 g of scdium hydro~ide was added. m e resin had a weight average
molecular weight (M~) of 4,000 and a number average moleaular weight
of 1314 as mE##~LD?d by gel permeation chrom~o~ hy (polyethylene
glycol calibration).
For the ~pa~Lion of the low MW resin: P-formaldehyde
(148 g) was suspended in water (220 C) and heated at 95~C for 30
minutes. me mixture was then cooled to 25C and phenol (210 g) was
added followed by slow addition of sodium hydrcxide (30.8 g at 50
~e~ .b solid). m e t~.~ re was raised to 6~C and held at this
temperature until a E~obkfield viscosity of 35 cps was ob*~ined. At
215863~ '-
this point the resin was cooled to room temperature and scc~.n~
hydroxide (25 g) was added.
Ob~iously the ~ c~Lion of a binary PF is not restricted
to these examples. For example, a high ~ lecular weiqht PF could ke
obtained by a using a gradient temperature starting at 60 C and
increasing to reflux and the order of addition of the varicus
ingredients may be ~ ~e~. Alkaline catalyst other than sodium
hydroxide may be employed.
It is also po6sihl~ to produce a binary phenolic resin in
a single ~u~oess instead of s~a1~ely producing the low and high
mole~llAr weight cco~ ~ and nu~cLng- Far example, an A~Xy~YC
solution of phenol, for~AldPhyde and a catalyst such as sodium
hydroxide can be treated at a temperature of about 95~C and for a tIme
sufficient to produoe the hiqh mol~lAr weight PF cYxexx~3nt.
Following cooling, additional phRnol, formaldehyde and catalyst is
added to this cYx$x>nent and heated within a tem~erature range from
about 40~C to about 6~C for a time sufficient to ~ ~ e the lcw
molecular weight PF comp~nent of the binary PF. It is also possible to
reverse the two process step6 by producing the low MW PF c~lx~3n~-
prior to the high MW PF ccmponcnt.
Mixing of Binary PF and r;gnin
An adhesive solution may be prepared by first adding the
low MW PF to the lignLn, and then adding the high MW PF to the ni~lrre
2158636
of low MW PF and lignin, or the low MW PF and high MW PF may be added
concurrcntly to the lignin. P~k~ng high MW PF directly to the lignin
may result in precipitation. Following r(*K~=inq the binary PF and
lign m preferably by nuuuLng, the pH of the solution may b adjusted by
adding hydrochloric acid or sodium hydroxide. C~ um adhesive
p4V~ ies for N~lSSL as the lignin CC~u~ were obtained when mixed
with a weig~t ratio of 30% low MW PF to 70% high MW PF and at a pH of
3 to 10.5.
It is also po~cihle to add the lignLn during the single
~ ss pro~ n of the high and low MW PF previously described with
the lignin during the first or seoond stage of the binary PF
prcduotion, or bath. m e cross-linking reaction b~tween the lignin and
binary PF is ac~elerated with the application of heat and thus it is
pn~;hle to effeot cross-linking when an aqueous solution of the binary
PF and lignin is spray dried to create a dry adhesive pcw~er.
Mixing of PF, Lignin Ccpolymer and Ammonium Salt
A pre-cure resistant adhesive solution is prepaled hy
mixing ammonia, preferably amm~nium salt, and more preferably an
ammonium acid salt with lignin and then ad~ing the PF resin while
stirring vigorously. A~dition of the ammonium acid salt directly to PF
will cause its precipitation into a gummy mass rendering it difficult
to work with. m e n~rbure of PF, lignin and amm~nium salt can be used
as an alkaline solution by ad~usting to pH 9-11 with an~ m ium
21S8636
17
ide. m e ErT!1alre resistance can be ad~usted by varying the
solid weight ratio of PF, lignin and salt.
The single ~L~ess technique of producing bin~ry PF with or
S wit~out the addition of lignin thereto as above described c~n also
ad~ 3e~l~1y be modified if it is desired that the then~x~tiLng
resin also exhibit Fol~alro r~istanoe. For example, ammonia,
preferably in the form of an ammLnia salt can be added with the seoond
stage addition of phenol, formaldehyde and catalyst ~ c~y for the
p~xx~;on of the low molecular weight ccDçxYK3nt in the binary PF.
, the temperature gradients, quantities of addition and
sequerco of addition of ~he ingredients can also vary and deperx~mg
upon the intcn~cd end use or ~a~l~ristics of the adhesive (face or
core ~plic~tions and if it is to be made pre-cure resistant or not).
lS
Example 1
In this example, the adhesive ~*~Lies of NH~5LrPF
adhesives having either a high ~le~ r weight or a low m~leaular
weight PF cc~xxKent are cc~FYred wi~h a resin prepared by mixing in a
1 to 1 weiqht ratio a binary PF resin and N~SSL with the re5ult~ being
set forth in T'able 1.
215g63~
'D
:~
E
z
I u~ O
Ll I .. .. ~ .
;
~ O O ~n o ~
0
J IOD Gg ~ 1~ -- O
o
'- O O O O O O O
g
O O ~ ' '
-- ~ O O O O -- _
U7
Z ~ ~ ~ O
-
E~ I' ~ O
D V~D ~ V
D
C U~
--I ~ U C C~
~ C~. t.J E ~
L V
O , _ ~,
_~ . 5
U ~ ~ -- ~ V V
J _ ~ _
~ ~ O ~ o V
~ o u- o u~ e
o
U -- _ "~
L C~ ~ _
C ~ I _ ~
o ~I O ~ O
.0 U
215863G
As the results in lable 1 indicate, the A~esive cc~dLuLin~
the binary PF yielded a better quality wafer~oard in comparison to an
adhesive having either only a low dV~y~ ~ lecular weight or high
average ~ lecular weight PF CXA~ K~I~. Both wet and dry MoR (modulus
of rupture), and M~E (mcdulus of elasticity) results were superior for
the binary PF-N~SSL adhesive under b~th acid and alkaline conditions
and exhibited oo~çaratively higher IB (internal bond ~L~ ~ U~) vall~c.
Tbrsion shear test results also confirm the superiority of the binary
PF-N~LS~L adhesive under b~th acid and alkaline oonditions. Tbrsion
shear test results also oonfirm the superiority of the binary PF-
N~lS~L adhesive. Of par~ia~l~r note is that satisfactory adhesion
characteristics are noked for the binary PF-N~LSSL adhesive under both
A~i~ic and alkaline conditions-
Example 2
In the following e~ample, an A~e~ -L of the relative
efficacy of a commercial PF resin (not a binary PF) and a binary PF
resin as a cro6s-linker for methylolated kraft lignin (MKL) was made
with the results set forth in lable 2. As indicated by the superior
M~R and IB values, under b~th acid and alkaline conditions MKL was
cross-lined with the binary PF to prcvide an adhesive yieldLng a
waferboard having prlperties superior to waferboard prepared when a
cc~n~rcial PF was used as MKL cross-linker.
2158636
TABLE 2
Comparison Between a Co~mercial PF and Experimental Binary
Phenolic Resin a5 Crosslinker for Methylolated Kraft Lignin
(MXl)1,2
Board Properties
MOR
Resin Type pH Dry Wet IB
........... (Mpa)
Co~mercial PF-MXl 11 4.B 0
9.5 16.1 8.6 0.28
3.0 23.5 11.4 0.30
Binary PF-MXL3 10.5 25.6 13.1 0.46
5.0 27.0 16.1 0.~2
1 Waferboards pressed 5 min. at 210~C
2 Resin containing 50~ PF solid by weight
3 Binary PF-MKL3 resin formulated from the single two
stage process
215863~ ~
21
Fxam~le 3
Test results as set forth in Table 3 indicate that an
N~S5LrPF adhesive having acceptable adhesion characteristics is
ci*~L~Y~d where the weight ratio of high average ~ lecular weight PF to
low average m~lecular weight PF is ke*~en 1:1 and 4:1, with optimal
results being ci*lLLn3d where the weight ratio is 7:3. As also
indicated by the results of Table 3, the pe~ w Laye yield of adhesive
cl~ 3d upon spray drying is ~ where high MW PF mol ~ ~lAr
weight PF is present in y~ea~ quantity, with accept~ble results be m g
cL~zLi~3d for binary PF having at least 70% high MW PF.
, 215~636
~able 3
0ptimi2ation of PF molecular weight dist~rit~ with relation
to SSL (50~) - PF (50%) adhesive properties' and spray-drying
yie~
PF MOR SPRAY-D~tlNG
- (MPa) ----- (%)
0 100 280 22.1 0 0
600 26.5 7.0 0
850 25.1 9.8 13
1300 25.5 14.0 76
~350 27.1 12.3 82
100 0 1590 16.9 0 90
; Waferboard of 11.1 mm thickness press 4 minutes at 210qC.
2 Spray dried with a laboratory spray-dryer nBowen EE 1031) at 165~~ inle~
9~ outlet temperature.
' Molecular weight ~eterm m ed by size exclusion ch~ Lography (SEC) relati~e
to poly (ethylene glycol) stand3l~s.
215863~ -
Fx~m~le 4
In this example, a quick curing adhesive consisting by
weight of 15% lignin of various origin and 85% binary PF resin
(ccmprised of a 1:1 by weight mixture of high and low average molecular
weight PF) was prepared. As indicated by the test results as
summarized in Table 4, the binary PF resin effectively cross-linked
each of the various lignin copolymers identified in Table 4 to produce
an adhesive having adhesion characteristics cso}~Lrable to a c~J~u~ ia
PF adhesive.
(: 2l586~6 '~
Table 4
Effect of li~ ~e on binary PF (85%) - lignin (15%1 adhesive
~u~ ies for ~,~ous waferboards
RE~IN RE~
CYCLE --MPa--
Kraft Ligmn 10.3 3 28.0 13.7
Steam Hydrolyzed
Lignin 9.5' 3 29.5 14.7
N~C~ 8.5 4 28.9 14.2
NaSSL 9.0 4 26.2 13.6
Commercial PF 3 28.8 14.8
~ Panel 11.1 mm thickness press 3 minutes at 210-C with 2.0~ resLn.
' Li~-PF resLn heated 2 hours at 50 C prior to spray drying.
21~8636
Fx~le 5
A further a ~ age of u~ ;ng a binary PF resin to
croes-link a lignin copolymer such as N~l~CT is that ~ ~Y~3~ yields may
be ob*auned u~on spray drying. As graphically illustrated Ln Figure 1,
S the yield on spray drying an N~LssLrbinary PF di~ rsion was greatest
for a dispersion consisting of 50% ky weight N~LssL and 50% by weight
binary PF. m is is imp~ L as it indicates that more kilogram per
hour of a lignin-phenolic resin can be pr~Y~x~l in a commercial spray
dryer, in comparison to spray dryLng of PF without lign m . m is
0 L~tS~ a higher prodbcti~n rate and impoiL~IL saving for a resi;n
powder prDducsr.
m e followLng examples illustrate the ~uY~Lies of pre-
cure resistant ~h~ives ob*dined from a mixture of a PF, a lignLn and
an ammcnium salt. m e PF may be a s~rfa oe phenolic resin or a faster
curing core phenolic resin. T~e core phenolic resin prodbces a faster
curLng pre-cure resistant PF-lignin adhesive.
EXample 6
In a ~ill, a waferboard ~at may rest on a caul plate at 140
- 150 C for a few minutes before being transferred into the pre~s. In
the p~ess, the mat may then rest on the hot press platen few seoands
before pre~s closing to target panel thichless. If the resin is not
pr~re resistant and cures prematurely, a poor band will result. One
n~.U~d to ~differentiate be~een a face and ~re resin is th~3 s~ce
cure test. Ihe test imrolved placing 0.75 g of resin an a hot platen
~ 215863~
26
set at a tempera~re of 150' and sE~read back and forth until hardened
and cannot be spread furt~r. A fast core resin will generally have a
short str~ke cure of 15-25 seconds, which co~qxl~es to 35-45 seoonds for
a face pre~e resistant adhesive.
As sh~ in Table 5, a resin made frc~ ~I,S~iL (30%) and P~
(70%) had a str~e cure test of 42 se~, if an~nium sulF~ate salt
was added, longer stroke c~re test cauld be d~Air~l. It was also
po;sihle to ~tain a resin with stroke cure test ~ ~ arable to a
commercial face r~sin (3S - 45 seconds) fram kraft lignin (27%), (N~),
S~l (3%) and a ~ ~ ial PF (70%). Similar results were also ci~lL~ed
with lign m other than kraft or N~S5L, such as N~.~CT. or o,~ku~olv
lignin.
215~63fi ' '
Table S
Effect of lignin and ammonium sulphate additives on
5stroke cure test of ccmmercial core phenolic resin powder
(sprayed at 200'C inlet and 90'C outlet)
PF.l pFbl Kraft' N~LSSL (N~L)~30, Stroke Cure
Tbst at 15C~C
(%) (%) (%) (%) (%) (sec. )
100 0 0 0 0 24
0 100 0 0 0 26
0 0 30 0 42
67 0 0 30 3 62
0 67 0 30 3 38
0 30 0 0 22
27 0 0 3 40
94 o 0 0 6 36
1 PF. and PFb are core PF resin
2 Kraft lignin precipitated and washed to remove the free inorganic
salts
2~5~636
28
FxamPle 7
In okher methods to test the resi ~ of an adhesive to
"F~ alre", the caul plate was heated m an oven at 200 C and then
pl~e~ on the waferboard mat (wafers blended with the adhesive being
tested) for five munutes under 25 kg weight. Ihe mat was ~ n pressed
in a normal manner. The panels were then tested for inberral band
~LL~ ~ U~ (IB). For the Erercmre resistant adhesives, it w3s found the
hot caul plate treatment had no adverse effects on IB. m e tL~t~ re
of the 1.6 mm thick metal caul plate at exit fru~ the oven was cb6erved
to be l9~C. At ccntact w~ith the wood furnish, the caul plate cooled
off gradually to aE~IxKLmately 80 C w~ithin the 5 munute ~LeaL
me results set forth in Table 6 below are for wafe~Lcau~
with the mat treated with a h~t caul plate prior to pressing. m e hot
caul plate treatment had an adverse effect on IB and fa oe failure for
the sample bonded with the cx~ rcial core PF and also the binary PF
copolymer. No ad~erse effect was noticed for the panels bonded w~ith
N~LSSL-PF and kraft-PF-(N~L)~3o, resins as IB and fa oe failure test
results were similar to those cl*lL~ned wqth panels bonded with the
cc~Yercial face PF control.
2 1 ~8636
Table 6
Effect of caul plate heat treatment of mat~
5prior to pressing on ~ ical ~lopt~ies of
three layer wafertlxmls' bonded with
ocmmercial and experiment21 resins
Fa oe Resin' Density IB Face'
Failure
(kg/h~) (MPa) (%)
Commercial Fa oe PF 675 .467 8
P~ Cro6slinker 664 .390 42
N~LSSL (30%)-P~(70%) 652 .450 8
Kraft (27%)-F~(70%)- 650 .509 8
(N~ (3%)
CX~ rcial Cbre PF 648 .179 100
~ Caul plate heated in an oven at 200'C then placed on top of
wafelL~al~ mat 5 minutes ~ r 55 kg weight
' Panel pressed 4 minutes at 220 C with 2.0% resLn
' Sample ~ nation (failure at surfa oe layers during test m g of
12 IB samples
The core wafers were bcnded with a cx~ ial core PF for all the
panels
S Experimental resin cnrro6~A of high Mw PF (70%) and low M~ PF
(30%) resins
