Note: Descriptions are shown in the official language in which they were submitted.
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B-STAGED RESlN IMPREGNATED FIBER MAT PLYWOOD GLUE
Field of th~lnvention
The invention is directed to a process for making col.lpo~;le wood products using a
5 B-staged resin, such as a B-staged, phPnQli~ resole resin~ .re~lated fiber mat as a
glueline.
eround of the Invention
~ wood co~ u~;t~ or lamin~, re~ fiber mats have been
used to provide fiber reinforcing layers. Typically, the fibers are h"~ gnaled with a
10 resin and then allowed to fully cure. A s~p~ . resin is then used to adhere the
folei.-g layer to other layers, such as veneer in plywood or LVL. ~ -
The fiber mat is made of any suitable fiber such as glass fibers, mineral wool, andcarbon fibers. Blended fibers have also been used, such as the wlllbination of ~lass fibers
and mineral wool. Fiber mats usually are made co,..l~e.~ally by a wet-laid process, which
15 is carried out on ~ ~ paper or asbestos making machinery. De3~ Jfions ofthe wet-
laid process may be found in a number of U.S. patents, ;.~ -\g U.S. Patent Nos.
2,906,660; 3,012,929; 3,050,427; 3,103,461; 3,228,825; 3,760,458; 3,766,003;
3,838,99S; 3,905,067; and 4,129,674.
The known wet-laid process for making glass fiber mats eG.nt,.;~s first ~,,,u..g an
20 ~ slurly of short-length glass fibers (--,f, .-~d to in the art as "white water") under
agitation 1n a mLlcing tanlS then feeding the slur~y through a mo~nng screen on which the
fibers enmesh th~n~h~s into a freshly p~p&~d wet glass fiber mat, while water isseparated lhc3 ~.,..~
~ .
Afterthe mat is formed, abinder material is used to hold the fiber mat tog~l. r. The
25 binder ~ l is l~ll,~ll~ i,llp.~lated directly into the fiber mat and set or cured to
provide the desired integrity. Thc glass mats may then be used as layers in chingl~s and
other co.,.i~Gs:le wood p~du.ls to provide s~.cn~ll.. Such composite wood products
include plywood, e~..r~ed lumber, LVL, and hardboard.
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Typically, an adhesive is applied to the glass mat and/or the wood veneer at the time
a comp~,site wood product is made. U.S. Patent 4,533,589, for inStqnce, describes a
composite material ~.I paled by hllyre~ at least one layer of ,e;n~o,c~;...e.-t fibers
with a first resin, coating the su~f - ~s of at least one layer of wood veneer with a second
5 resin, stq~ing the resin illlyle~wted .,,..~.ceme.,l fiber layer with the resin coated wood
veneer and bonding the layers together under app-ùplia~e heat and p..,i,;.u[e cor~ tiorle
U.S. Patent 4,61~,936 desc.il,~s a veneer lqminqte structure CGlllpliS;llg, a sheet of
y~ucessod material sandwiched bel~.~en two sheets of wood veneer. Resin is inte.yosed
be~een the sheets of the sandwich to firmly bond the sheets together.
Cûv~ cn~ ûf India Speçifi~Atil~n Nû. 139,241 des~,~;l.fs c~.,.pu3;te l~m.~ s
rt,;.~rced with glass wool or rovings i...~ ed with resins. The wool or rovings is
i~n~ ted with the resin to form a mat and then allowed to dry and cure. The mat is
then glued to other layers in the compGs;le such as wood veneers. Go. ~,. .,."c-.l of India
Spev;fi~ -~;on No. 139,241 des~;l)~s cûlllyoa;le lqminates wh~ layers are formed from
15 wood veneer, glass fiber, fabric, paper, and the like, by i...yregn~ 8 the fiber with a resin
and curing. The layers are then glued togethe~ to form a co..lpGs;le.
Wood adhesives used to prepare wood composites often include urea-formaldehyde
resins or phenol-formaldehyde resins. Usually, the resin is plep~,d under heated qlkqline
ct)n~ ions by reacting phenol and formaldehyde, for ~", ple, in specific F/P mole ratios
20 to produce ph~n- liC polymers having the desired moleclllqr weight dial,il,--lion. The
cooked resins are then used either in neat forrn or more usually are rnixed with various
r~ df a, fillers and otner additives before being applied to the wood sub;,l~ales by
a~a~ing~ curtain coatin~ foam extrusion, roll coating or other l~ hods After theapplicatiûn of the adhesive to the wooden substrates, e.g. pa.li~,les or veneer, the
25 s.-~3 ~ales are pressed in a hot press typically using high ~.~,e and elc~dted
te~,.pw~lu~ es to cure the ph~nolic resin. The .. ; ~ .. time to cure the resin depen~1s,
inter alia, on the press te~e.~l~re, wood oi;,lu,e cont~nt, t_ickness of the pressed
construc~ion, adhesive ro.... ~t;~in and the adhesive resin's mQlec~lsr weight distribution.
The typical wood composite or l- ninstç, made by .- .pQs;i~g glass rnats bel~ ~e.-
30 veneer layers using a fluid resin-based adhesive to form the glue line, is ~iffic~lt to
~,.a.,.~r, ~ when the veneer has a high l~o~1u~ content or is of poor quality~ e.g. rough
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stock, thick or thin veneer. This is particularly a problem in plywood and LVL
msn~lf~cture It is ~ller~ore desired to provide a way for gluing a wood composite
r~d with a glass mat which can be used for all types of veneer, not just good, low
,l,oi~lule stock.
S SC~
Applicants have d;scoie.~d that a resin i~l?leg~lated fiber mat p(tpa~'e~ by
ilnpn ~lating a fiber mat with a B~ ,e -~'e resin which is then dried to advance the resin
to the B-stage can be used as the glue line in p~epOIillg a co...po~;le wood product.
Applicants fu~ther discov~,.,,d that the use of a fiber mat prepared in this manner as the
10 glue line provides for a thicker c~ allowing for a reductiQn of the thicicness of the
veneer or allowing for a reduction in the number of veneer layers used to make a given
product Ih;~ L ~es5
The present invention thus is d;,~ ed to a method for making a cola~.Gs;le wood
product comrncing the steps of (a) il.lp.eg,.A~h~p at least one fiber mat with a B-
15 ~ hl~ resin; (b) drying and a~lv~ c..~g the resin of the i,ll~ nat~ mat to a B-stage;
(c) placing the B-staged, resin-hll~.~.5n~ mat b~ n at least one facing set of aplurality of wood veneers to form an ,q-c~mbly; and (d) con~oli~qtin~ the assembly
under heat and ~ to form the C~ ~;t wood plu-luc~, and to a cG.IlpGs;le wood
product made by the mPth~d
20 D~tailed De~cnption of the Tnventjoll
The present ..l~ iol~ is a process for making cG...I,os;le wood l,r~,d~ s, such as
pl~.ood, e~gineered lumber, laminated veneer lumber (LVL), hal-ll,oa~d and other wood
Ia~nates. A~c4nli.lg to the ~ ol~, a fiber mat is illlyl~ ated with a B-ststg~ le resin
~ (i e an -A-stage resin). The resin which illlpl e~tes the mat is then advanced to a B-
2S stage. A B-staged resin-;.,.p.e~led mat is then placed beh._en at least one facing se
of aph~ of woodveneers and the ~cc~ ~.bly is concr~lid~t~d under al plic~1 ;on of heat
and pl.,s;~ue to bond the wood veneers tog~the~.
The B-staged resin-illlplc~led mat thus fim~tif)nc as a glueLne for the wood
c~ e and, after final cunng, the mat imparts added a~ h to the final product. The
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added ~ from the glass mat is a benefit for m. ny products such as plywood, but in
particular for products such as LVL which require good flexural s~len~,lh. It has been
found that the B-staged resin-,...~,.egr~ed mat also acts as a gap filler during the bonding
process and e~ PS many of the veneer problems coll-,llonly q-c~o~iqted with poor5 veneer quality such as rough stock and uneven sizes. Further, it has been observed that
the B-staged, resin-in-pre~.aled mat relaxes the need to dry high moisture content veneer
to much lower l..o;~lu-e levels in order to reduce the in~ nce of blows that areencountered when trying to reduce the press c,vcle time. This reduced need for drying
should lead to lower volatile orgqnic cG...pounds (VOCs) Pmic~ionc from the dryer and
10 also lower energy costs. The use of the B-staged, resin~ .yre~ ed mat ~ .;.ni7~s the
need for using low moisture content veneer while p~: ...;lI;-.g fast press c,vcles.
In addition, in the m~n~.r~ dllg of plywood, LVL, or other lqminqtes~ a large
pc; ce.ltage of the total cost of the composite wood product is associated with the wood
actually used to make the veneer The use of resin-.,..yrepllated fiber mats of the
15 u~.e~lt~on as a glue line has reduced the amount of wood nf~eccy- y to prepare a co.nyGs;le
wood product of a given thickness. In order to attain the high MOR and MOE values
desired in a norrnal lz~ ed wood cGlllpGs;le construction, the surface veneer must be
~o--,yl~sed to a high density This co-..~sa;on reduces the Ill-rL l~r.cS of the raw wood
stock during forrnation ofthe l~ ed wood co.npo..;l.,. The use of resin-;...p~ ed
20 fiber mats accord...g to the invention, to bond the surface veneers at the front and back
side of a lqrninqte wood compGs;le, however, decreases the arnount of co".yre;~;on
needed during the pr~-g cycle to maintain the sarne MOE and MOR values. Thus, the
use of~these resin-..llyre~laled fiber mats aUows for a reductil~n of the thickness of
individual veneers used to make the product, (or a redllction of the number of veneers
25 used~ without loss of strength for the wood CO--~ e product having a desired 1~ c,
thereby decl~lg the cost of the pr~.,l.
An rl~itinrL~ benefit to the present ;n~e.l~;on is that no ~ditio~ql resin adhesives are
necessz~y b~t~.ee~ the B-staged, resin-;...~,re~,aled fiber rnat and the veneer and
,.~ly, none is applied. Astrong glue line ~h.~1 opposing veneer layers is achieved
30 with only the B-staged resin-;,."~,~g,.~l~d fiber mat. ~lthough it is conl~ ~-plaled that
more than one glass mat may be used b~ oppos.ng veneer layers, only one B-staged
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resin ~~..~)~lated fiber mat is generally ~ d per glue line and pl~f~abl~ only one mat
is used_ -
The fiber mat may be made from any suitable fibers such as glass fibers, mineral wool,~sbestos, boron, aramid, metal, or carbon fibers or synthetic or natural fibers such as
5 cotton. The fiber mat may also be made from a co..~h;~ ;on of fibers such as glass fibers
and mind wool. Preferably the fiber mat is made from glass fibers. The fibers used to
make the fiber mat may also be in any suitable form such as random or nondirectional
fibers, directional fibers, woven fibers and the like. Preferably the fibers are random or
nondireclional. More preferably the fiber mat is p~ ,ared from chopped glass. Fiber
10 mat9 are avail&ble con~ lly and may be made usin~ any suitable proce9s such a9 wet-
laid p~v~e~s de ~ in U.S. Patent Nos. 2,906,660; 3,012,929; 3,050,427; 3,103,461;
3,~8,825; 3,760,458; 3,766,003; 3,838,995; 3,905,067; and 4,129,674. For example,
glass fibers may be slurried into an nqueous mer~ n. and then dewatered on a
fol...~ ed surface to form a mat.
Generally, the fiber mat should be thick enough to hold enough adhesive for a suitable
glue line but thin enou h so glue is not wasted. The th;r~np~s of the mat is chosen based
on a~ ;lity and the thickness of the desued end product and mats would gen~,. ally be
in the range of 1/16 to 1/4 inch. Co..... -~ c;~ fiber mats are typically about 1/8 inch thick
and are suitable for most Al pli~l;nnc
In accordance with the ~ tion, the fiber mat is i.ll~ ~d with a B-sta,~ ~ble resin
using any suitable techr~ique, for example by using a s~ ade. or by dipping the mat into
a vat of resin. The rcsin must saturate the fiber mat, to provide s~ ient resin
Ih~v~ n n~l the mat so th-at when the mat and veneer are consolidated and heated, the resin
flaws into gaps in the veneer"~e.ut~dtes the surface of the veneer, and provides a strong
bond ~ n the veneer and the fibcr mat. Generally, thc resin is applied to achieve
about 10 to 4v g of dry gluc pcr squarc foot. Dry gluc is the solids part of the gluc with
thc liquid .~ ...o.cd.
The resin-il"~,.eg..aled mat is then heated for a ~ . r"~ period oftime to advance
thc resin to a B-stage. ~Pating may bc ~rc~ pl;che~ by passirlg thc resin-hnpreg~ ted
30 mat through a drying oven where thc mat is dried and the resin is advanced to a B-stagc.
Typical drying te.,~s are in the rangc of about 100 to 180~F, more typically about
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140~F. Typical drying times are in the range of about 30 to 90 minlltPs, typically about
1 hour. ~igher or lower te~llpe. a~ul ~,s and shorter or longer times may be used provided
the resin is advanced only to a B-stage.
An A-stage resin is a resin in a liquid state. Generally, resins used in adhesives that
5 are applied as glue lines are A-stage resins. The viscosity of the resin may be mo~ifi~d by
the use of various PYtpn~l~prs and other additives to make an adhesive. An A-stage resin,
and an adhesive based on an A-stage resin, will flow into the cracks and imperfections of
the wood ~ul~ al~s or veneer and make coating of the veneer easier. The flowability of
the A-stage resin can be ~d;. ~e~d by adjusting the ViscGs;~y and solids content of the resin.
10A B-stage resin is a resin that has heen partially cured but remains tht.~-loplastic, that
is, it will flow when rehP~ted Thus, in the present invention, an A stage (liquid) resin is
impreg~ ed into the fiber mat and then cured to a B-stage. When the B-stage resin-
impregnated fiber mat is used as a glue line in a veneer assembly, and pressed under heat
and ples~ , the B-staged resin will soften and flow into the wood of the veneer to
15 provide a good bond b~ ,n the wood and the fiber mat. Resins that have heen cured
beyond a B-stage will not flow when reheated and thus are ~1. ..,.OS~,l A~er consolid?tion
of the ~ecPmhly in the present ill~ lJon, the B-staged resin has been a~ ced to a
,l resin The temperature and time a resin ,~,~ir~.s to achieve a B-stage dependson the A-stage resin char~ tirc
20The A-stage (B-stageable) resin may be a phenol-formaldehyde resole resin, a
w ~,u~ol-formaldehyde resin, a phenoh~,sorcinol-for n~ phyde resin, a ~ f urea-
rO. ~ nkyde resin, a mdamine-formaldehyde resin, and other similar resins which can be
~JcC~r~ y B-staged. Pl~,f~,.~l~ the resin is a B- ,,ea}'~ phenol-formaldehyde resole
res~L The resin ma~r be prepared in any suitable manner well known to those skilled in the
25art A typical resin may have about 43% solids, a vlscosily of 800-1000 cp, 6% NaO~
a pH about 11.5-12 and a F:P mole ratio of about 2.2. However, these characteristics
may be altered depPn~ing on, for P- ~-..ple, the method of Arplir ~ n of the resin to the
fiber mat, orthe -n~ content ofthe wood veneer. For example, when illlpiCg~
the fiber mat by dipping, the resin is diluted to about 20% solids to make dipping easier.
30Typically, an A-stage phenol-formaldehyde resole resin is p~,p~ed using a two-part
reaction ~he.~ formaldehyde and phenol are reacted in the ~.eienc~ of a catalyst and
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then ~ ;tionql form~ hyde and catalyst are added before the reaction mixture is fully
cooked.~Acid reaction contiitionc may be initially employed, if desired, to react phenol
with ru~ e'-yde; but the reaction medium preferably is converted llltimqtPIy to allcaline
co~ ions by adding a basic catalyst.
More sperifi~qlly, an alkaline catalyzed phenol-formaldehyde resin suitable for
ill,yl~ e a glass mat can be ~)lep~ed by first c~ 9 formaldehyde and phenol at
an initial formaldehyde to phenol mole ratio b~,h.~n about 0.1:1 to 2.5:1, more y,~,f~,ably
bcl~een about 0.7:1 to 1.5:1, in an Dq~eo~C reaction media and in the p,~sel-ce of an
effective catalytic amount of a basic catalyst. The p,.,~,l.,d catalyst to phenol mole ratio
at the initiqtion ofthe reaction is b~,L~ n about 0.1:1 and 0.5:1, more usually be~
about 0.15:1 and 0.25:1. The l~?ction te.~?c~alu~c is p,t;~l~bly il~c.~sed to bet-..,en
about 70 to 105~C, more usually be~ ,., about 80 to 100~C to promote the reaction.
This l~?ction generally takes b~ ., about 10 minutes and two hours and is comple~e
after the e"oll,~,."l ofthe reaction has ~.l,s:~A
~ itiQnsl forrnqldehyde then is added to provide a ~ nl~lqtive formaldehyde to
phenol mole ratio of about 1.5:1 to 2.5:1, pr~fe.~.bly about 2.0:1 to 2.2:1. S~ nt
o--' catalyst also is added to catalyze the reaction of the ad~lition~l formaldehyde
with residual phenol and other methylolated species. Pl~.ably the, Itlitionql catalyst is
added in an amount to provide a ~m~l,qvtive catalyst to phenol mole ratio b~,t~ about
0.5:1 and 1:1, more usually b~ about 0.6:1 and 0.9:1. The r~ ;"g phenol-
formaldehyde resin is then cooked at a tempera~ure of b~ ,n about 70 to 90~C until the
resin (at about 43 % solids) attams a v~ of about 500-1000 cps (Broo'~PY). Afterthe resin is cooled, prefer. bly to about room t~,,"~,~,.al~lre, it is then ready to be used in
prep~ring the resin-"llplcgnaled glass mat. Other pr~ s for making an A-stage (B-
stageable) resin are well u.ld~ ood by those skilled in the art.
~ ,
~ Additives typically used in p,cp~,ng adhesive c~.~.rGs;~;o~t for bond;~g wood
composites may be added to the resin prior to ap~ n to the glass mat, for example
fire retarda~s, ~ n~ . s, fillers, and the lilce. It is within the sl~ll of the art to
add appr~pl~le additives as required for particular adhesive qu~litips
To prepare the laminated wood composite, a B-staged resin-;",pre~5l,ated fiber mat
is placed between at least one facing set of a plurality of wood veneers. A plurality of
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wood veneers is the number of veneers suitable for p, epa,h~g a wood product of desired
th:~~n~cs A plurality in~l~ldes as-few as two veneers having a single fiber mat b.,l~ee n
the veneers as the glueline. Plywood typically has anywhere from 3 to 15 veneers (plies).
A~er a fiber mat is placed between the layers of veneer, the a~sembly is con~o~; hqted
5 under heat and pressure to form the wood composite product. The t~ p~alllre and
~,~ u~ used to bond the veneers depends on many factors such as the IIIOi~Ul'e content
ofthe wood, the number of veneer layers, and the like. Typical press te.lllJc.a~ures range
~ about 275 and 350~F at press ~,~ b~._en about 150 and 200 psi. Typical
pressing times range between 2 to 20 mi~n~te~ and depend on panel thickness, and the
10 temperature and pl~s~ e used to consolidate the veneer.
A resin iu~ ~ted fiber mat which is used as a glueline prepaled in accordance with
the present invention provides e~cçll~rlt wood failure and press time results.
The "I~ ~n will be further descnbed by ~ ce to the following examples. These
15 examples should not be con~llued in any way as limiting the u~e.l ion to an~ "g less
than that which is ~ os~l or which could have been obvious to anyone skilled in the art.
r~
A two by one foot sheet of glass mat having a thickness of 1/8 inch was m~ple~edwith a B~ 2.2:1 F/P mole ratio phel~olic resin by dipping the glass mat in a vat of
20 resin, allowing the resin to saturate the glass mat, and then removing excess resin from the
surface; The resin-;mp~gnq~Pd fiber mat was dried in an oven at 140~F for one hour to
advance dle resinto aB-stage. The ul~ ,g~ed glass was then used as the gl~lelin~s for
pre?a,;ng 3-ply plywood. A sandwich assc~ ly was p.~pa,~d with a single mat
k~sed ~l~ each ofthe opposing veneer layers. The veneer had a 12% I.loi;.lule
2S Cont~nt The ~ss~ -..hl~ was pressed at 315~F for three mim~tes The re.,ulli"g plywood
was cut into strips and the mod~ c of rupture (MOR) and the ml~dvl~lc of elasl;~(MOE) values were nl~asu.~d. The MOR in.,,~ased by 20% and the MOE L~c,e~ed by
11 % over a control 3-ply ~ssç-..bly made without the glass mat using the same resin in
a ~1~ dafd glue mix.
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In a ~1,s~~ r ~ ..1 veneer layers were prepared with shims (about ltl0 inch
plywoo~ strips that provide gaps to Ci nlllqt~ roughne~c of veneer) to compare bord;~g
of veneer layers using a resin-h"~ ~led glass mat as a glue line in ac~d~ ce with the
present invention and using a slu~d~.l glue line wilhou~ a glass mat. When three ply
5 pl~ od was prepared with the shims-mo~lified veneer layers, the glass mat glue line was
better able to handle deviation of the shims than was the standard glue line.
Data from 3-ply l .~ cd Using Glass Mat
With Glass Without Glas~
MOR (psi) 21500 16200
MOE (psi) 2434000 2041000
10 F.Yqrr~ple 2
A 2.2 F/P mole ratio A-stage phenol-formaldehyde resin and a glass mat pre~ ,d
from chopped glass were ob~ d The glass mat was impregnated with the resin by
dipping the mat into the resin and then removing excess resin. The resin "..preg.lated
glass mats were then dried in an oven at 140~F for 60 m;nl~tP~ The 1.~.... .1 levels
lS averaged about 20 glft2 of dry glue per glue line.
In preparing wood billets, the resin coated glass mats were used only for bondi..g the
outer most wood layers to the ass~.llul~. The other glue lines in the billet were provided
by applying a co~ nnql fluid (A stage) ph~nolic resole resin-based adhesive to the
veneer sked directly using a standart ~.e~den
Four sds of billets were prepared: Billds ~;tho~ glass mat (control billets), billds
h4ne sheet of glass mat bonding one face sheet to the ~ bly~ billds vith two sheds
of glass m. t bonding both facing sheets to the a~~ , and fnally a billet vith t vo sheets
of glass mat with extra caustic added to the resin used to i...~ ,a~e the glass mat.
The billets were then tested for MOR, MOE, and short span bPn~ing ~lexural
25 strength was examined on an Instron machine using 24 x 3 sq. in. samples with a span of
23 inches. A short span test was carriet out with S x 2 sq. in. samples with a span of 4
mches.
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Conditions for the Billet Studies
~ - Pre~s Speed Shd~y
- Veneer 1/8" ~iclc southern yellow pine 12" x 24"
Face/Back Moisture Content 12.4%
Core Moisture Content 6-8%
Panel C~ ~tiv.................... 7-ply, 7/8" thick 12" x 24"
Glue Spreads 31-32 g/R2, 73 MDGL Equivalent
Lay-up .2 Wlets pcr condition
Open Asserïlbly Time 20 minute~
Prepless 4 minute~ at 150 psi
10 Clos~d Assembly Time ~'~,,lj~ ' '
~Iot P~s~ 315~F, 175 psi, I PPO
Time in Hot Pres9 15 minute~
Hot Stack 2 ~ours
Te~t MORJMOE: 3 samples per billd
Short Spsn 8endmg Test: 3 sample~ per billct
Properties of Billet
Cor~lition Thiclcness Short MOR MOE
inches Span psi psi psi
( ~ about ( ' about ( l about ( ' about
13%) 5-/~) 12%) 10-/o)
Control 0.711 621 15400 2194000
~wo Sheets of Glass 0.756 647 14700 2088000
Two Sheets of Glass, high caustic 0.726 619 16100 2126000
,, . _
One Sheet of Glass 0.740 679 13600 1933000
The short span test is de~;~.ed to isolate the stress to the glue line and was used to
evaluate the effect a resin~ egnated glass mat had on the bor,~ ,g co,..~)arcd with the
bonding achieved with a normal glue line using a sl~da,d resin glue mix. The data
in~ te that using the glass mat in the panel did not have a deL~ e.ltal effect on the
- 10-
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bonding since there was no loss of ~ nglh obs~. ved in the panels made with the glass
mat. MeE and MOR values were ~co~ &able to the control.
A .li~. . ~nce in thirl~n~c~ of the billets was observed. The billets with the glass mat
were thicker than those without a glass mat by an amount larger than can be attributed to
5 the thirlrnPcc of the glass mat, possibly due to a higher level of wood adhesive
;OIl in samples made without the glass mat. The higher amount of water in the
glue in these samples provides better p1qctiri~tion of the adhesive in the wood and hence
higher col.,ple~;,;on. The billet made with the glass mat with added caustic was the
thinnPst of the billets co.~ ;ng glass, though thicker than the control. Again, this may
10 possibly have resulted because the caustic increased the pl~ctit~-i7~tiQn of the wood.
Since the billets made with glass mat .~lai,led a greater amount of their original
~h;~.L ~-~ 5S after ~ ing while still having co,--pa,able physical pro~ ies to that of the
control billets, the use of glass mats may allow for a reduction in the i'~ npss of ea~h
veneer and/or a reduction of the number of pliés n~cç5s-~ y to make a conlposite woo. a
l5 product of a desired thi(L-nPcc and ~ ngl}l.
It will be apparent to those skil1ed in the art that various mo~ifir?tions and variations
can be made in the ~ os~;ol-s and methods of the present ;n~e.l~ion without depa. Iing
from the spirit or scope of the i..~_nlion. Thus, it is intPn~led that the present i,.~_.,lion
cover the modific~tionc and variations of this invention provided they come within the
20 scope of the appended clairns and their equivalents.
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