Note: Descriptions are shown in the official language in which they were submitted.
2~J~118
FIRE R15TARI~NTS t~l~ PRODU~TS PRODUCED T~EREWITH
~ACKGROUND OF T~E ~NVENTION
.
M~ny di~rer~nt compo~ltlone ~ave long been used ~n
~re~tment o~ wood.and other cellulo~lc materlals to provlds a
degrfle ot ~ir~ ret~rdan~ properti~ to such material~. SUCh
prope~le~ mo~ ~ommonly have beQn ob~a~ned ~1) by depo~ltlng
on the ~u~facQ o~ an artlcle ~elthe~ An artlcle or manu~aoture
or cellulo~ic p~rticle~ rrom whlch ~ manu~aatured ~rtlcle i~
to be for~ad) ~ CoA~i~g compri~ing el~her (a~ A composltlon
aontAlnlng a ~lnely divl~ed ~oll~ ~ateri~l havlng ~lre
retaxdnn~ pro.~p~rtie~, or (b~ ~n intume~cen~ compo~lt~on whlch~
on expocure to the hlgh temperaturee or burnlng, d~oompoee~
pyrolytlcally to f orm a protactlve, ln~ula~ing ohar layer on
the coat~ ar~lcle, or ~Z) by 1mpregnatlng ~uch ~ater~le wlt~
~luid compo~ltlon capab~e o~ penet~ting the lnteretlce~ of
~olid wood or other celluloslc ~at~rial to be t~eated an~ whlch
ao~pos:itlon, and/or one or more decomposltion product~ thereo~
whlch, on exposure to wood pyroly~le temperaturee, reacte wlth
*ood beoro pyroly~ls ~o ~orm, primarlly, carbon ~nd water ~ln
~h~ ~or~ o~ Am~
.
Typlcal of s~rface coatlng type composltlon are those
aomprieing ~ire re~a~dant oolld mater1al~ ln preclpltated or
other~lse ~inely dlvlded for~, ~uch ~6~ caJ carbonate~ and
: ~lc~rbonatea oP aodium, potas~lum or AmmonlumJ dlammoni~m
~; pho~pha~e, o~ p~rticulate metalllc element~ euch a~ ~lumlnum
~to~8el U.S. P~ten~ ~o. 4,0~6~540 whlch alBo provides an
::extensl~a de~crlptlon o~ prlor art rire retardants). 8uch
~aterlal~ m~y be applled, ln the ~orm o~ ~olld powd~re, or
pa~te~ oX sucpenslon~ ~o the eurfacee oS wood artl~ to be
~:tr~ated~ ~or ~amplQ a~ shown ln Handa Qt Al. U.S. Pstent No.
3/811~992. Suc~ prlor art compo~ltlons euitable ~or the
:llmlted purpoee o~ 6urace tr~atment Or flbrous celluloBlc
m~teriAlB or 0~ woo~'~ partlcle~ for the manufact~re of
2 2 ~ 1 8
~i'~"~board and ~imll-~r material6 al60 lnclude lonic complexe6
o~ nitrogen, phoQphoru~, oxygen and AlUminU~ togethe~ ~lth A
boria ~cid compound and urea ~Stossel U.S. Pa~ent ~,076,540):
a u ~'J~ llu ~ 1~ ~J U ' ~ ). w l L l l W d ~ e~ L ~ U~ U L c~ ~ d ~
~uch ~e tho~e o~ an~onla, al~all metal3 ~d ~lknllne ~arth
metale, ~o~ example borax ~60dlum tetraborate, Na2B407 . lO
~2) ~Dietrlch et A~, U.S. Patent ~o. 4~ 404). Al~o in thi~
~ategory o~ rlre re~ardant composltions ls Schaa~ et ~l- U. S.
Patenl;' .~o. 3, 955, 987 whlch ls directed to a temporary
lntu~e~aen~ ccating ln elther dr~ powder form or in the ror~
o~ an aqUeou~ ~spension contalning mohoammon~um pho~phato
and/or diammoniu~ phosphate as a flreproofing agent, urea
and/or dlcyan~la~lde (cyanoguanidlne) a~ a ga~ for~ing ag~nt
to promote lhtume6cence, a polyol ~uch as mono~ or
tripentaerythritol, ~tarch, or .~uga~s such as ~noeltol~
dextro~o or eucrose as pro~oter~ o~ lnltlal, low te~per~ture
lntume~cence, and tltanlu~ dioxide a~ A heat-re~lecting ~gent.
By rea~on o~ the ~olld physlcal state o~ BUC~ compo~i~ion~ or . .
componen~3 thereo~, they cannot be lmp~egnated lnto solld wood ~ ~
and henae are useful o~ly for sur~ace trea~ment o~ wood ~ ::
artiale~ or o~ pa~tlcles o~ wood and other celluloslc materlal~
u~d ln the man~act~re o~ o~her artlale~. All coatl~g~ are :~
de~igned to for~ lnsulat~ng barriers and do no~ pro~ote ~ ..
ca~alytla dehydratlon o~ the wood ~ubstance.
5ur~ace coatlng ~ire re~ardant~ may be in the ~or~ o~
~ re~ln ~nd al~o may contaln A boron compoun~. ~uch
compo~lt~on~ lnclude, for example, t~ose contalnlng A
pho~phoric acld~dicyan~iamlde-formaldeh~de re~ln, 6uc~ ag ~ ~ :
dlsclo~ed ln SurdyX u. s. Pa~ent NO. 3,874,990, ~he~eln the
reein component 1~ us~d together with An Alkallne bora~e ~u~h
~9 ~ m~xtu~e o~ borax and bo~lc acid ~or sodlum polyborate) and
a blndlng resln 6uch a~ a urea- or melamlne-formaldehyde reeln.
Othex example~ lnolude: boric acid ester ~e~lnsi imp~egnated ~;
into paxtiole board and then hydrolyzed to depo~lt boric acid
or boron oxlde withln ~he wood prod~c~ (ShO~ et ~l, U. ~
Patent No. 4,076,871); urea-formaldehyde and boric acld or
sodium phospha~e, ammonlum bromide, or an ammonium salt sUch ~ ~-
as th~ pho~phate, 6ul~ate, or sulfamate urea, borax, a
. .
.
:
...., .. . ~,
202~118
poly~lnyl Alcohol and a poly}~ydric al~oholJ urea and one ~r
~ore o~ boxic ~cid, borax and ammonlum phosphate: borla ~cid
an~ urea, thloure~ or ~lcyandlamideJ urea-rormaldehyde re~ln
and borax polyvihyl chlorl~e or polyethylene with borate~ or
boron oxlde; and the above-described ionla complex-boxia ~old-
urea aomposltion# (contalnlng at lea~ 23~ urea) whlc~ al~o can
be ~pplied in ~qu~ou9 re~ln form (ro~ A ~ore det~lled
d~scription o~ Buoh composltlong Bee Stos~el U.S. P~tent ~o.
4,07~,540~ polymer~ ~uch a~ melamine, dlcyandlaml~e~ ~nhydrou~
bo~x~ boxax deoahydrate (or borlc acld), ammonium
polyphq~phate and ~onoammonlum phosphate -- ~or additlon to a
pla~tia ma~erial durin~ manufacture thereo~ (Schml~mann et al.
U, S. Patent No. ~,43~,028): ~unega U. s. Patent ~o. 3,832,316
And Juneqa Canadian Patent No. 917,334, directed to rlre
retnrd~n~e contalning dlcyandlaml~e, melamine, form~ldehy~e And
pho~phori¢ ~cld wherein a minor portion o~ the phosphoric ~cid
may be eu~itu~ed wlth another ~cld, such as borl¢ ~c~ and
Han~a et Al. U. S. Patent No. 3,811,~92 whlch di~clo~e~
pxetreatlng plywood wlth a ~illcate materlal ~uoh ~ so~lum
~lllcat~ or alkoxysllanol polymers with a dellquescent materlal
~Uch Ae ammon~um bromlde ~which inhibit~ the low temper~ture
rlashing te~den~y Or the ~lllaon compounds)~ then ~oat~ng the
pretrea~Q~ plywood wlth a fire retardant ln the $ox~ of A~
~queou~ pas~e compri~ing 20-35% of a urea compound ~u~h ~
thioureA, dimethyl thlourea or monomethlyolmel~mlne, and 10-20
~ or'an a~monlum hallde wlth optlonal a~ounte o~ an or~no-
phosphoru~ or orga~ sul~ur compound gener~ting ~ ~lxe
retar~ing vapor a~ a pyrolysis tempe~ature over about ~o~ ~og.
C, for example trlcresyl phosphate, glycerine phosphate,
guanidine phosphate or ammonlu~ ~ul~amate, a metal hallde ~u~h
~B zlnc chlorlde, a sulfate such ns ammonl~ 6ul~ate, and A
we~k a~ld eu¢h a~ borlc acld or a weak acld compound ~uoh A~
ammonlum b~ate or ammonium phosphate, an antimony oompound
su~h a~ ~ntlmony trioxlde or antimony tr~chlorlde, a ~ul~oxlde
~nd ~orm~ldehyde.
When u~ed as sur~ace coating~, re~lnou~ and paste-llke
materials, alone or together wlth other compo~itlon component~,
~er~e the ~e retardant functlon by formlng, on the sur~aco
: .
2 ~ 1 8
~ the ~ated wood #rticls or wo~d partiClQ~ ~ro~ whi~ an
nr~icle i~ to be ~o~ed, an insulatlng carbonlzed coatl~,
whlch, in ~ome ca~e~, ~ay be ~oamed to ln~rea~e the in~ulation
prop~rtle~. Upon sub~ectlng larg~ ~r~as o~ ~uch coatod
materials to carbonizing temp~ratures (such that tha heat
ene~gy 1~ not conducted away~, the untreated wood under the
coating p~roly~, cracXs form in th~ coatlng ~rom which
vol~tlllz~d ga~eB iB6Ue and ~urn. U~der prolonged exposure to
such conditlon~, the entlre mass o~ the wood ~ay be oonsumed.
superlor resistance to burnlng o~ wood produc'c~ 1B
obtained by ~mp~ëgnatlng the wood mass wi~h a flr~ reta~dant
materi~l. However, lt ls difflcul~ or lmpos~i~le to impregnate
d~ns~ ~olld wood with flre retardant composlt~on~ in vlsoous
re~lnou~ ~orm. So~e euch composltlons, havlng a su~floiently
low vl6ao~1ty, lend themSQlve~ to at least a llm~ted degree o~
per~e~tlon ln~o relat~vely porous wood, par~icle board ~nd
elmilAr porou~ celluloslc product~. Even ~n ~uc~ oA~e~,
l~pregnat~on and c~rlng Or the resln ordlnarlly 1~ very tlme
~on~uming and requ~ res extended times at h~gh temperature8~
e.g. upwardly of 180~ - 30~F, whlch can lmpalr wood ~trength
p~operties. For example, the above-mentioned Handa et al. U.S.
Patent ~o. 3,811,992 show~ the need for A 15 hour perlod for
per~eatlng n 4 mm thlck wood panel.~t amblent temperature,
~ollowed by an e~evated temperature ~reatmen~ ln an eleatrla
drle~. 'rhe Above-descrlbed Short et al. U. S. Patent No~
4,076,871, dis~loses, as a necessary ~tep ~or t~eatlng 1/4 lnch
thlck h~rdboard panels, ~iln heating panel~ coated wlth the
borate-cont~lnlng resln for l-l/2 to 2 hour~ at 150C to 165C
(302F to 329F) ln order to cause the resln to penetrate ~nto
the bo~rd.
Prior art ~lre reta~dant~ suita~le ror ~mpr~gnatlon o~
8011d wood artlcle~ lnalude, for example: ~oldstein U. S.
P~t~nt No. 2,917,403 directed to a oomposltlon contalning
d~cyandlam~de ahd pho~phorlc acld7 Goldsteln U. S, Patent No.
3,159,S03 wh~reln ~uch ~ compo~itlon addltlonally cont~ins A
emall ~ount o~ ~ormaidehyde, and Steez U, S. Patent No.
4,174,22~ whioh ~ BClose~ a ~ wa~er-solu~le compo~ltion
co~prislng a~monlum hitrate~ ammon~um polyphosphate, urea (over
.'
202~1 18
30 w~ight perc~nt) and, optlonal~y, a b~s~ ~uoh a~ nodlu~
hydroxld~, And mola~seE), eugar ox ~tarch to ~ld ln the
ret~rdation o~ PlAmlng and af~erglow. Such compo~1~lone whlo}
al~o ~on~ln ~oron ar~ ex~mplirie~ by: J..ewcl~lermwong U. S.
P~tent No. 4,725,3~2 whereln the ~ire retardant compositlon
contain~ borlo acld tln the ~oxm o~ the anhydrlde~, ~2b3
pho~phorua pentoxi~e and ammonla; and Goett6che ~t al. U. S.
Patent No. 4~461~721 whloh provides a wood pre~ervative ~and
rlame-prooring) composltlon con~alnlng a boria acld ~alt
water-so.luble Amlne such ~g monoethanolamlne, water ~nd sodium
polybcr~te (or ~ mlxtur~ Or borla naid ~nq borax~.
~ n ~ddi~ion to fire retardant actlon per ~e~ ~lro
retardant aompositlons must posses~ other ~mportant proper~les
rOr thelr general acceptablllty and applloation. For ~xample~
acaeptable flre rethrdants must not ~elease or promo~e
produotion o~ dangerou~ amounts o~ po~s~nou~ ga6e~ or ~ume~ on
burnlng. ~s exQ~plifled ln 6everal o~ the above-aescrlbod
~ent~ ~or ~xample, Surdyk U.S. Paten~ No. 3,874,~9~ ny
prior ar~ ~lr~ ~etardan~s, especially tho~e havlng a re~ln aa
the e~ec~i~e lngxedien~ conta'ln formaldehyde or othor
materlAl ~ormlng ~ormaldehyde a~ A hlgh tempera~ure reaction
produat. Foxmaldehyde ~s con~idered a carclnogen~ and products
containlns or releasing Eubstantial amounts o~ formal~Qhyde
durlng proce~sing or on eXpo6Ure to high, pre-pyrolyG~
temperatUro~ poee slgnlfieant health hazards .
Composltion~ comprlslng~ ~ as the e~rectlve Slre
reta~d~nt, oo~pound~ ~avlng a hlgh deg~ee o~ amblent
te~perature solubillty in water are qulckly leached out o~
impregnated wood product~ on exposure to weathering conditlon~
80 ~re not aultable ~or treating woo~ A~tlcle~ lnt~nded ~or
prolo~ged exteri.or and underground con~tructlon appllaatlons.
~xa~plQs o~ water-~oluble materialg which have been used ~n
rire reta~dant compositions lnclude phosphorl~ acid, ~monlum
6alt5 ~uah a~ ammonium phosphates, ammon~um ~hloride or
a~onium BUl~at~ and eoluble metal 6alt~ such as ~hloridea o~
zinc, sodium or magneslum. (see, ~or example, Handa et al.
U.S. Patent No. 3,811`~92 -- metal hall~es sueh as zlna
ohlorlde. al~ ~lkall metal eillcates suoh a~ 60dlum ~lllcates
: ~
, "
sc~lttmann ~.S. Patent No. 4,438,02a -- boraxl Gottcche et ~?
U.~. P~tont No. 4,461,721 -- eo~lum tetrabor~te~ ~ietrich ~.S.
Patent No. 4~801,404 -- alkall metal and alkallne earth ~etal
~lte). Metal-contalnlng compositions~ especi~lly tho~o
contulning ~lkali ~et~l~ and alkallne earth metals (e.g. ~
dl~lo8ed in the Dletrich paten~ and in 6urdyk U.S. Patent ~o.
3,874~990), are glowing accelerators~ that is, they pro~ote
wood cot~bustion by glowing, and .accord~ngly~ com~o~ltlon~
cont~lning ~ub~tantial amounts o~ 6uch materials ~re
unde~irabl~ ~omponent~ of fire ~etardan~ co~po~itlon~. ~u¢h
~ire ~et~rdan~ material~ have t:h~ f~rther ob~ectionablo
~e~tUres Or caus~ng 6mo~y burnlng and possible production o~
toxla ~ume~, ~uch ob~ectionable results also nro produced on
combu~tlon o~ wood treated wlth flre r~tardant~ oontalnlng
bro~ine, ~or example, as ln the composltlons ~l~clo~Qd ln the
HAnda U.S. P~tent No. 3, B 11,9g 2 . . ~ n o t h e r 8 e rl oU~
shor~coming o~ many prlor art ~ire retardan~ compo~ltions 1B
~heir h~gh degree of hygroscop~c~ty. In genera~ ln dryln~
prlor a~t ~ire retardant-~reated wood products~ th~ ~oi~ture
Gontent is reduced to under abou~ 10% o~ the product welght.
~he composltlon o~ the ~reated produc~ ~hould ~e su~h that lt
does not ~bsorb ~urther substan~lal amounts Or water in exce~
oP ~hat which would exceed the flber saturatlon o~ the wood
product -it~elf. Accordlng~y, fire-retardant composltlon~
should be ~reo o~ hygroscoplc lngredient~ ~hlch would ~au~
such exoessl~Q water ab~orptlon.
It la ~nown to the p~lor art ~hat flre retardan~
compo~itlons shouid be essentlally non-hygroscoplc or o~ lo~
h~gro~coplcity, in order to ~void undue molsture absorption ~y
treated wood products. For example, Obe~ley U. S. Pa~ent No.
4,373~010 teaahes tha~ use o~ hygroscoplc material~ ~s ~ire
retar~ante or a~ components oS such col~o~lt10n~ should be
avolded to prevent bloomlng of thè wood. ~loomln~ result~ ~om
water absorption ~y wood to an extent to ~orm llquids allowing
ealt9 to mlgrate ~o ~nd deposlt 6alt crystals on ~th~ wood
~r~ace. Thl~ interferes wlth or prevents painting or othex
~urface treatment Or the wood prod~ct. Hlgh water Content 0~
treated produat~ contal~i~g wate~-soluble acid~ or aoid-~orning
. ................................................. :
, . :
- 2020118
compounds al~o prov~des ~he co~ditlon~ ~or corroslve attAck o~
me~al~ ln contAct wi~h such products ~nd, as discu~sed in more
etail below, ~o~ acid hydrolysls o~ the wood ~ellulose.
Hygro~o~pic mate~lal~ may be pre~ent a~ origin~l
~o~p~n~nt~ ot th~ ~ire ret~rdant or they may be ~orme~ ~
reaation pro~uc~ during preparatlon o~ the ~i~e retardant
oo~posltion, for example, on heat~ng o~ the composit~on to
~ol~bl~i.z~ the ~ire retardant component, or during d~ying
the ~re~t~d ~ood pro~ucts at elevated temperatures.
Plre retardant compositiona compri~lng or contalnin~
sub~tantial amouhtg ~p ~uch hygroscoplc materlals are not
~ene~ally use~ul and are to be avolded ln many or mo~t
perm~n~nt wood-tr~atlng applloations.
. ~yg~oeaopic materials which have been used in ~ire
~etardantn promlnently lnclude, ~or example~ urea -- whiah in
very hygrosoopl¢ ~for example, th'e Oberley ~.D. Patent ~o.
4,373~010 mentlons that urea ~hould be held under about 15~ ln
o~r to avold lt~ strong hy~roscoplc aatlon) ~ al~call pletal
~lt~ auch aB sodlum chloride, 60dium ~ul~ate1 other met~l
ualt~ ~uch ae magnesium ohlorlde, ~nd ~mmonium sul~a~ate.
~x~mple~ o~ prlor Art flre retardant composltlons comprloing
such hygroscoplo materials lnclude those descrlbea ln: Handa
et ~1. U. S. Patent No. 3,811,992 (except as hygroscopl~i~y 1
reduced by addlng formaldehyde): Surdyk U. ~. Patent No.
874,990~ Schaar et al. u. ~. Paten~ No. 3,955,987J Stos~e~ U.S.
P~ton~ No. 4,0~6,540 and Schmlttmann U. S. Paten~ No.
4,~38,02a.
A~ lllu~trated by certain of the ~bove descrlbed prlor
a~t patont~, phosphoric acid~and~its 6alts~ such as ammonlum
phoGphatec~ are very eommon constltuents of pr~or art ~ire
ratardant~. The term "phosphorlc acidl~ re~erq to
orthopho~phorlc acld, ~3P04 and corresponding ~`hydrated
compouhds ~uoh as 2~l3P04.H20, which i~ the oxy Aold 0
pho~phoru~ mo~ commonly avallable and used, and to Which
re~erence usually i~ ~ad~ when such ~erm 1B used~ alt~ough the
te~m pho~phorl~ acld also-may be used to include Any or all o~
the other oxy aclds o.~ phosphorus ~uch as: H3P03 (phosphorous
acld)J H4P207 (pyrophosphoric ~cid) : H4P205 (pyrophosphorouq
:
- ` - 2 ~ . 8
~cid)~ ~3P~2 (hypophosphorlc acld)~ ~4P26 aAd HPO3
(mQt~pho~phori~ ~Cid9~, ~he polyphosphoric acld~ an~ m~xture~
O~ the ~bo~e, Orthophosphorlo acld, ~13P~4~ i~ a triba~lc ao~d,
h~lng ~ pKl o~ about 2 in aqueous ~olutlons acaordlngly, it
i~ ~ e~ron~ açi~. A~ i~ well ~nown, the t~rm pK re~ern to the
negatlve logarithm o~ the dissocla~lon con~tant, X~ o~ a
pa~tlcula~ ~hemical compound to whl~ch reference ls ~de. PXA
and pK~ conveniently are us~d, respeo~ively, a~ ~e~sUrs~ o~
acld or ba~e strength. Aold o~ base strcngth deareasee ~ pK~
or PXB increase~.
A s~rQng.acld, ~uch a~ p~losphorlc ~cld~ i~ a deslrable
in~dient of rirO ~etardant oo~position~ in Prder to reao~
wlth wood a~ or below pyrolysis tempe~atu~e~ to ~or~ Xeaction
product~ ~uch a~ water, ammonia ~nd non-co~bu6tlble c~bon --
r~kher than combustible carbon containing tar and ga~e~ which
result ln heat generatl~n ~nd flame ~pread. ~owe~er,
phosph~ria ~ per se~ ls no~ a good ~lre re~ardant beoause
It ~orm~ pyrophosphate~ at co~bustion te~peratures ~nd such
ao~pound~ ha~e no slgni~icant ~ire ~etardant a~tlon in
~ccordanoe wl~h u~ual test standards, ~oreover, use o~ the
highly aol~la phosphorlc acld per se woul.d pose a ~anu~act~rln~
Pnd handling sa~ety ha~ard. ~he alXali metal phosphate~ and
slkaline ea~th metal pho~phates nr~ not effe~tlve ~re
retardant~ because ~ln addltlon to the above-de3crlbed
artexglow o~eo~ WhlCh they promote) they retain a
~ubsta~ti411y neutral pll on heatin~ ~nd cannot ~erve as
c~talytlc qehydratlng agents to form carbon and wa~er -- A
common theory of thl~ mo~e or rlre retardancy. on the o~her
hand~ ammonlu~ ~ho6phates are acldlo and have qood flre
~etardAnce propertles, Rolyphospha~es, o~ hlgh a~ldlty and
good r~re retardance, are ~ormed under the hlgh energy
condltlons prevaillng at combustlon temperatures. HoWe~Qr~
th~e desira~1~ properties tend to be 105t and the~les~ ~iro
retardan~ pyrophosphates tend to be formed under ~he~e
oonditlo~s. Ammonlum phosphates release ~mmonla whlch redu~eo
the rate Or rormatlon oe~`the non-fire ~etardant pyrophoop~a~ee
and thereby incxea~e~ ~he time ~uring ~hlch the deslrable
~lr~ retardan~e properties o~ polyphospha~e~ ~an b~ exerted.
', .: . ` .. ' ' ', " ', ,: ~ ,
2 ~
The value o~ using, as comp~nent~ -o~ fire xet~dant
co~positlonn, ~ ma~erlal such as phosphorla ac~d, whlch, und~r
Ambie~t conditione, exhiblt~ high aci~ity, un~ortunately ha~
~lll other accompanying 6erlou~ disadvallt~ge~. Fo~ ex~mule,
it long h~ been known tl~at ~ire-re~ardant composit~on~ or hig~
Aai~i~y ~n~ hygro~coplclty are corroglve to metals in con~act
With the treated wood produat~. In general, t~le mo~e acl~la
the ~ire retardant compo~itlon, ~he grea~er le the corr~lon
probl~m. ~cldic anion5 used in fire retardan~ compos~tion~
g~n~all~ are selected ~rom the followlng group: hallde, e.g.
bromlde or chiorldeJ sulfate: nitrate: phosphate, and bora~e -
- in de~cendlng order o~ acldity, Strongly aaidia and
hy~ro~copic composltlons have the ~urther disadvantage Oe
~erloualy affec~ing the strength propertles o~ wood prod~ct~
due to aaid hydrolysi~ o~ the w.ood cellulose ln pxolong~d
contact wlth such ~ire ret~rdant composl~ion~. Thi~ e~e~t
only recently ha~ ~een re~ognlzed and treated a9 a ~rlous
proble~ by regulatory ~gencie~, the construction ~ndustry, an~
the ~nsuranae bu6iness. ~s a ~esult~ the use o~ ~lre rotardant
co~po~itlon~ ca~lng dangerous strength los~ due to th~lr
s~rong~y acldlc nature has been rest~icted or banned ~n Be~e~a
~t~ts~.
Examples o~ highly acldla prlor ar~ 1re retardant
compo~1tlons include those dlsclo3ed in Handa et al. U.S~
P~ten~ No. 3~ 992l Schaar U.S. Patent No. 3,955,9~7~ S~ossel
U.S. Patent ~o. 4,076,540, and steez V.~. Pa~en~ ~. 4,174,223.
The compoeltlon~ o~ U.s. Patent 4,373,~1~, sold by Hic~son Ltd.
under the trademar~ "DRIC0~,1' comprise aq~eous solutlon~ cr
~ retardan~ compositions wlth whl¢h s~lld wood i~ ea~lly
l~p~egnated and aont~ln'lng, by wei~ht o~ the composlti~n prior
to reac~lon, from 60 to 90% ~preferably abou~ 70%) o~
dlcyandiamlde plus phosphoric acld -- whlch are reac~ed to ~orm
guanylurea pho~ph~te (''GUP~ and ~rom lO ~o 40% (pre~er~ly
about 30~) o~ borlc acid. Thls comblnation o~ lngredlent~ nC~B
~yne~gl~tlcally, the ~eaotion product, "DP~," exhibl~lng a
~reater reduction o~ fire weight loss as compared to the
~ndivldual components o~ the mixture. Such compositions a~e
belle~ed to be the only commerci~lly prodaoe~ ~ire retaxdant
, r ,
lo 2~ 18
p~c~uct~ for pre~aure ~reatlng o~ wood Which currently are
allowad unr~ loted marketing ln ~11 6tate~ of the Unl~ed
StntR~. ~hi~ is d~e in part to the les~er de~radatlon o~ wood
by acid hydroly~i~ than other prlor art commercially avalla~lo
~ire retard~nt~. ~lowever, such co~positlon~ cont~in reactlon
produat~, sU~ a~ guanylu~ea pho~phate, Which are hlghly ~CidlC
under hlgh ~m~ien~ temperature and humldit~ conditlon8 and
there~ore re~ul~ in At least a moderate degree o~ Acld
hydroly~ nd corre~pondlng wood ~txength lo~ d~r~ng ~lln
drylng and/or with prolonged exposure to high moi~uxe
conditlon~. ~onsequently, there is a compelllng ne~d rO~ rire
retArdant ~ ~ ffsltlons which do not have the eerio~
~hortco~ing~ of those based upon a phosphorlc acld-ammonlum
phoepha~e ey~t~m.
Due to the very lo~ Acldlty o~ boric acid, lt~ u~e ln
A ~ire retardant composltlon would be pre~erable to str~nge~
acld~ euch a8 phosphorlc acld, especl~lly unde~ hygro~copla
aondltlon~, ln order to reduce metal con~act corroslon and the
wood-degradlng e~fects o~ ~cld hydrolysl~. ~owever, a~ al~
desorl~ed in U.S. Paten~ No. 4,373~010, borl~ acld alon~ ha6
l~ttle Pi~e ~etardant ef~eot over a wide range o~ borlc a~ld
lmpregnant, for example, over a range from 0.5% ~o 2.5% borc~n
ret~lned ln wood, for example as resul~lng rom ~reatment under
atmo~ph~r~a pres~ure with ~n aqueous 601utlon contalning 1~%
by welght Or boria aold.
E~ectivene~ o~ a fire re~ardant Composition
lncrea~ed~ up to a polnt o~ maxlmum ef~e¢~lvenes~ ~th~
~hre~hold value~ wlth lncreaslng amount o~ the compo81tlon
whlch ~ lmpregnated into a treated wood artlcle. There~ore,
lt ie de~ixabl~ to be able to provide hlgh concentr~tions O~
~he eP~ecti~e ~ire retardant ~aterials ln aqueous 601utlon~ ror
treatln~ wood products, especially hlgh den~ity woods.
However~ ln view o~ the limited low (e.g. amblent) temperatu~e
solubilitie~ o~ many ~uch materials, such as ~oric acid, lt 1~
dl~fi~lt or lmposelble to attain a deslred or effective level
O~ retained f~re ret~rdan~ during lmpregna~ion Or wood
produ¢t~. S~c~ problems were par~ially overcome ~ the
com~o~ltlon~ of Oberley U.S. Patent No. 4,313,010 wh~reln the
11 2~
low tempera~uro ~olubilitle~ of both boric acid ~nd ~UP ~re
inareaBe~ ~ubstantlally W~en those mate.rlal~ are pXe~ent
'cogeth-3r ~n ~ wn,ter eol~ltion. Y~r example, ln n 25C w~te~
~olutlon, ~olu~ y o~ a 70~ GUP-30~ boria ~cld mlxtu~e la
1~%~ comparQd to 601ubllitles o~ 9~ ~or GUP and S% ~o~ borl~
~¢ld in Beparate water ~olutions a~ the ~ame ~emperature. That
pa~ent also ~how~ that guanylurea ~ho~pha~e tGUP) ha~ ~omewh~t
better rlre retardant p~ope~tles at hlqher borlc acid
conce~trptlons ~e.g. over about 1.24~ retalne~ boron oontent
in ~redt~d wood), And ~hat the reactlon product ~ormed ~ln
prepara~lon or, Gyp/borlc acld composition~ ha~ a ~ynergi~tlc
Or~ec~ o~ Slxe welght-loss.
~ hu~, in accordance with the ~bove-described prior art~
the use o~ borla aold as the 601e or ma~or componen~ Or ~lre
xetnr~an~ compo~ltion~, ror example, ln plac~ o~ phoephorlo
~cld~ would be aon~ldered ineffectlve due to lts low Acldl~y
an~ ~ire ro~ardancy, as well as lts llml~ced low temperA~ure
BOlUb~ y -- even a~ those propertie~ are enhanced ~y the
phoephoru~-based compo~ltion~ o~ Oberley U.S. P~tent No.
4,373,010.
SUM~ARY OF THE INVENTIOtJ
The ob~ects o~ thl~ lnventlon lnclude the pro~ on o~
lmproYed borla acld flre retardant composltlon~, me~hod~ for
mA~lng the same~ and wood and other cellulo~lc products ~re~ted
wl~h su~h aompoBlt~ on~ ~ When ~uch ~omposltlona are
inoorporat~d in water ~olutlon, a ma~or por~lon o~ the ~olute
pha~e comprises borlc acld and a minor portlon comprlees
materlAls lnc~ea~lng the water solublllty o~ borlc acld and lt8
~ire r~tardanc~. Such composltlons are es~entially free o~ or
¢ontain only controlled, low amounts o~ 6trong mlneral aclds
or ~cld ualt~, are ~ubstantially non~hygroscopic or o~
controlled, low hy~roscoplalty. Solld wood and other
~ullul~ pr~aucts lmpregna~ea wl~n ~ucn compo~lt~iOn~ ~re
ess~ntlall~ non-corrosive to ~uxtaposed metals and the ~trength
propertie~ o~ the impregnated products are sub~tantially
una~ ted by acid hyd~o~l`ysis.
:: :
'~ 2 ~ .1 8
PETAILED ~ESCRIPTION OF T~ INVENTION
Cont~y to the teachlng~ o~ the prlor a~t, a~ above
de~arlbed~ I now have ~ound ~hat there can ~e produce~ A
compo~lt1oll ror ~roating wood an~ ~t2ler c~lluloalc pro~u~t~ -
- ~or example, but wlthout llmltation -~hereto, pape~,
a~rdboar~ cotton, ~ute and he~p -- ~such ~e.lluloslc prod~t~
~enerally being referred to hereln a~ Wood or wood produots~,
and compri~ing an aqueous solution, produced at amblent or only
~lightly elevated temperatures, ln which the 601ute (that i~,
t~e ahar~ed materlale, excludlng water) contains borlc BCid
ln hmount~ upwardly o~ 40~, preferably at lea~t 45~, and
e~pe~ially ~t lea~t 50~, by welght o~ the 601ute, ~oge~her ~t~
minor proportlons o~. ~orl~ ~cld ~olublllzers and cert~ln Water
noluble, n~rogen-contalnlng ~ynergls~s which enhanae
e~feotivenes~ as a ~ire retardan~. In additlon to excellen~
rlre r~tardancy, 6uch composltions also have lo~ ~etal
oorro~lvlty ~nd ~re wlthout ~lgnificant hydrolytio degradatlon
o~ the treated wood product~.
~ ha ~er~ ~'borlc ~cid" oommonly i~ used ln r~erenco to
one or ~nothe~ o~ ~everal compounds whlch dif~er ~ro~ one
~no~h~r by the amount of chemical wate.r content o~ the
mDound~ Reprt~.~s~nt~t.lv~ nml~nlln~ 1n~ R~n~l)J ~hnrlr.
e-c~ b2 ~m6~tu~0~ aci~ ~ H2~4V7 ~ce~cra~orlC aala1 1 ~2c73
~b~iq oxl~ ~r bo~i~ aT~hy~rlde) and m~xtu~e~ the~eo~, ana lt
is to b~ under~tood that 5UC~ compounds may be refe~red to
he~eln as bo~ic acld unless otherwise lndicated ln a par~lcular
cont~xt, ~(OH)3, the compound most ~enerally ~eferred to by
thc te~m borlc acld, 1~ a very weak ~onob~sia acld which tend~
to torm pol~meric ~truckures in mixed 60lution-q with borates`.
~s a~o~ 1ndicated, borlc acld solublllty in cold water (20C)
19 about S parts per 100, 1ncreasing to about 40 parts/10~ at
100C. Borlc oxlde, ~23' is ~lightly les~ ~oluble tabout 1.1
p~rt per 100 ln water 601ution at 0C and hbout 16 part~/100
at 100C) a~d~ With water, ~orm~ B(OH)3. ``
The comparatlvely low amblent temperature water
solubility or borlc aald 15 0~ advantage ln ~orio acid-baaed
~ire retardants in that ~od treated with such compositions can
be used ior certAln outdoor appllcat~on~, ~uch a~ ~empora~y
2 ~ 2~
13
construotlon~ whll~ re~ainin~ fire retar~ancy longQ~ ~han
co~po~ition~ co~taining mor~ solubl~ l~gr~diento a~ ~bov~
descri~ed .
A~ previous~y descrlbed, borlc acid is the l~a~t acldic
o~ the acld anlon~ commonly ~ound ln Sire rQtardant
compo~itlon~, belng Or nearly neutral pH in aqueou~ ~olution
at ambi~nt temperature~. The ba~lc equill~rium con~tant, P~A~
~or boric a~id, B(OH)3, 1~ ln the range o~ about 7 to about g
depending upon the par~lcular etrueture and molar concentration
in wat~x Bolutlon~ u~ borlc aaid 19 a very ~Iweak~ 8¢1~ a~
~ompared, ~o~ exampls to phosphorio acid and the oth~r "~trong"
~Ine~a~ Acldc above-descrlbed as commonly used ln prlor art
rir~ retar~n~ compo~itions.
It 1~ belleved that th~ relatlve lneectlvene~ o~
~orl~ acld alone a~ a rlre re~ardant i~ due to the ~ormation
o~ boxo~ oxlde, ~23~ whlch ls non-~lre retardan~ -- but ~ B
~trong glow lnhlbltor . ~lthough a flre retardant compositlon
ba~d on sm~onlum phosp~ate ls a good flre retar~ant ~eaau~e
o~ the slo~ los~ o~ ammonla, a comblnatlon o~ boria a~id and
ammonla 1~ not. At elevated temp~ratures, e.g. abav~ about
250~-300C., at which wood beglns to pyrolyze at a rapid ~a~e,
Aoidity oS ~orlc acid increases, approachlng that o~ phosphorla
aold, BO that lt can ~eact wlt~ ammonla to produce transien~
acldia ammonlum salts, such as ammonlum tetrabo~ates, which,
a~ ~ire retardants, are About a~ effective as are ~mmoniu~
pho~phatc~. However, these reactlon products arQ the~ally
un~table even at hlyh amblen~ tempera~ures, and at mo~e
e~evated tempera~ure~ substan~lally all of the a~monia ln an
lmpregnated wood product is lost quickly by ~olatlllzatlon,
leav~ng ~orlc acld whlch, A'~ wood pyroly~ls temp~rature~, ~orm~
th~ non-~lre retardant ~23~ However, I hav~ dlscovered
th~t a GUperior flre retardan~ c~mposition ¢an be ~ad~ by
providlng, in comblnatlon with boric acid and water, a material
whlch eubstantlally lncrease~ the low temperature wa~er
~olublllty OP borla acl~ln aqueous solutlon, and a non~aoldlc
nltrogen-con~alning materlal which is no~ 6ub~eat to ~he above-
de~oribed chortcomlng~ Or an ammonla-boric acld 6y~tem an~
wh~ch, wi~h boria acld, provldes a BynerqlStla e~Pec~ ln
2~2~18
14
en~ancing ~i~e retardancy o~ ood pro~uc~ treated wl~h E~uch
composition~. ,
~ Use~ul nitrogen-containing ~ynergists inaluds ~uch
wa~er ~oluble~ nltrogen-contalnlng ~ompounds a~ semloarbazlde~
guanidine~ c~anamlde, dlcyandlamide, urea and guanylurea.
M~14mine~ ~iuret ~nd oxamlde also are useful ~ynerg~ st~ ~Ut
they ha~ low wa~er ~olubllity at ~he oomparatlvely low
~emperature~ normally used ~or produc~ion of the compo~itlon~
o~ thi~ l~entlon. I~ ~uch ma~erlAls are ~sed as the ~ole
synergi~t(~1~ their ~olubility can be lncreas~d by U~Q o~ ~n
approprl~te .~dltional ~olubilizln~ agen~. ~or example,
~olubilization o~ one mol o~ melamine can be obtained wlth uBe
o~ ~out l/2 ~ol o~ ~o~m~ldehyde. E~or my purpo3e~ the~e
~ergist materials are not adequate solvents ror bor~c acld~
bu~ in aomblnation ~ith borla ~cld they provlde ox¢ellent
impro~emen~ ln ~l~e retardancy as compared to ~uc2l material~
or borl~ aold 310ne.
I ~elieve that the 5ynerglstlc ~ction o~ ~ese
nl~rogen-contalnlng materials 1~ due malnly to th~ protectlon
Which they ~o~d ~g~ln~t the formatlon o~ non-flre retardant
boron oxlde durin~ h~atlng And burnlng o~ wood treat~d wlth
BUah compo~ition~. At Wood combu~tlon temperaturoo, the
nitrogen-contalnlng 6ynerglsts decompose, provldinq
oon~inuoue ~upply of ~mmonia ~hich~ together with ~uaaeB~ive
pr~duced inter~odiate reactlon produete~ reac~ wlth the now
aoidia boric acid~ rormlng hlghly aaidlc borate~ and adduct~
and ~it~ the production o~ steam (along with carbon ~rom the
wood cellulo~e)~ T~e lnvolved ca~alyt~c de~ydratlon reaotlon~
~etard thQ ~ltlmate ~ormatlon o~ non-~re retardan~ ~23 (and
pyropho~pha~,. ir t~e I co~pos~tion contaln~ pho~phorus
compounds) ~or a tlme sufflcient to allow the Buppre~sion o~
co~bu~tlon. In ~cco~dance wlth thi~ ~nderstan~ing, there may
be ¢onsldered~ for example, a composit~on cont~ining~
aicyandia~lae t"dlcy") as the synergist. At pyrolyele
temper~ture~ the "dicy" hydrolyze~ to g~anylurea~ the
guanylurea react~ wit~ ~orio acld to form tho oorre~pondlng
acldi~ borate: the bora~e ls hydrolyzed to gua~idlno bora~e
and ammonia~ the guanldlne borate i~ fur~her hydrolyzed to
.~ ,.
15 2~ 18 ~: ~
uro~-borlc ncid a~uct ~nd ~d~i~ional ~ monl~ th~ adduc~
~urther hydrolyz~s to tranSien~ ammoniU~ boratQ whloh
ultlmately lea~ to the formation o~ boron oxide.
Such ~yetems there~ore provide ~ire retardar
compo~i~.lons which are essentially non-acldlc at xoom
tempernture -- hence they do not ~esult ln ~cld hydrolysl~ o~
lmpregnated wood -- but, on hea~lng to wood co~bu~tion
t~mpe~tuxe~, ~hey become ~trongly acidla and hence Are good
rire r~ rdAnt4.
BS~ective ~olubllizlng agents ~or the boria ~cld
~nclude s~rongl~basic non-al~all metal, non-alkaline earth
~etal nitrogen-contalnlng compounds, for example, those having
a p~ value under About 5, pre~erably under 4, ~the PXB value
~or ~mmonla ln aqueou~ solutlon a.~ 25C 19 4.75) ~uch aB:
ammonla~ basio amines, lncluding primary, secondary and
tertlaFy ~l~ylamlne~ and alXanolamine~ (amlno ~lcohol~) ~uch
a~ ~ono, dl- and trlethyla~lnes; mono~ and
trlpropylamines~ mono-, dl- and triethanolamines, and mono~
dl- an~ trlpropano- l~mine~, and addltion compounds such A~
hexamethylenetet~amine and those formed by reactlon .Or
~ormaldeh~de (for exa~ple, when u6ed a~ a 6olubll1zer ror
certai~ ~ynerglsts~ as aforesald) and amines suah as urea or
mel~mlne, o~ dlcyandiamlde u~ea as ~.ynerglsts. s~ltable borla
ACi~ eol~llizere also include sub~tar.tlally pH-neutr~l or
weakly ~aeic nl~ogen-containing compound~ ~pK Or about 5 or
gr~ater)~ ~or example: h~drazine; hydroxylamlne, ammonlum
ca~bonate~ and ammonium carbamate. Another type o~ eui~iable
~olublllzer inolude~ alcoho~ 6uch as the lo~er ~ater ~ioluble)
~ia~uratea ~ono~ydric alcohols fiuoh as methanol, ethanol,
n-p~opa~ol, lsopropanol, and lbutyl and amyl al~ohol9~ and
polyoi8, $noluding dlhydrlc alcohols sucll as ethylen~ glyc~l
~nd propyl~ne gl~col, trlhydrlc alcohols suoh aB gly¢erol
tglycexine), hlghe~ polyhydric alCohOls, for example, ~an~itol
an~ eo~bito~, and the monosaccharldesi and disaccharide~
Pre~er~ed ~onoh~dric alcohols are methanol and et~anol,
~8p~ 11y ~ethanol, I.n the polyhydric ~l~ohol c~tegory,
glycerol 18 pre~erred. In the category o~ sugars, ~ucro~e i8
pre~erre~ ough, ln dllute 601utlon.~, 6ugar~ are rea~i?y
,
2 ~ 8
16
lmprognated int:o wood product~, w~en t~le product~ a~ ~r~d,
thQy tend to ha~e a somewhat stlck~ su~ace. ~here~ore ~uch
~olubllizers ~re no~ preferred fo~ ~om~ appllcatlon~.
Solubillz~lon o~ boric acld ls promot~d by it~
reaction with ths lower alcohols and pol~hy~roxy compound~ auch
a~ the'trihydrlç alcohol, glycerol, and the monosaocharlde~ And
dls~ocharld~, Alone or mixed wlth flmmonia, to ~orm equlllbFlum
bor~te ester~ ~nd ~omplexes whlch e~ectlvely lnorea~e th~ rate
And ~xt~nt o~ eolu~lon o~ boric acid.
In the cas~ o~ GolubllizerB which can react to form
reelnou~ materlal~, for example borate ester~ or ~ormaldehyde
r~act~on p~d~t~ uch solublllzer~ requlred ~or e~eati~
borlc a~ld solu~llization a~e limited ~o an amount su~iclentl~
~mall ae to avoid the rormatlon or ~uoh quantltle~ o~ vlB~ous
ro~lnoun materials a9 would lnterfere wlth the lmpre~nation o~
wood produ¢t~ or glve rlse to the need for hlgh temporature
~uring o~ ~he ~reated product6. Un~ike t~e ammonia-~orl~ a~id
~yatem, the compounds ~ormed Ag reac~lon product~ o~ borla ~cl~
wl~h the contemplated borlc ac~d solublllzers do not comple~ely
vola~ e or preclpltate under a~blent con~itlons. A~ter
drying o~ wood produc~s lmpregnated wl~h 6uah oomposi~lon~
~o~e ~ thes~ reaction products ~emaln ln the wood.
Some o~ the contempla~ed n~trogen-contalnlng
BolUbill~er~ ~or example, the al~cylamines, BlSo may s~rve a
oyn~r~lstla ~unction ln the composltlon~ of thle inven~lon~
Suoh aotion depends upon the partlcular organla ra~loa~ and tho
natu~e of the chemical bond lnvolved. Depending up~n ~uch
~ctor~, ~IB ~rell a~ the decompo~ltion X~te and the coTnbuBtlblo
carbon conten~ o~ s~ch materlals, such materlals may ten~ to
promo~e ~lame ~preadlng.upon exposure to burnlng ~emperature~.
~n general, the larger the organlc radlc~l, the more rUel ~t
~dds ~n~ e mor~ combustible 1~ 19. However, the latter
c~aracterl~tic is not contraindicative o~ use o~ ~uh
mate~lnls in my fire retar~ant co~posltlons, where, ~or
QxAmple, the ~mount required ~or solubilizatlon 1~ r~latlvely
~m~ d th~, ~yner~lst~la e~e~t ls pronouneed. In suoh a~RA,
2 ~ 1 8
17
the adv~Ages gained ln borla aold ~olubilization an~
~ynerglet1c e~a~ on ~lre retardance may outweigh the ~la~
~preading potentia~ of ~Uch ma~erlals.
Mono- and ~lammonlum phosphate~ and guanylurea
phoBphate al~o Ar~ use~ul ~ borl~ Aal~ ~olubll1ze~, and the~e
~terial~ Al~o have the des1rable characterl~tic o~ Acting,
with boric Acld~ a~ ~ynerglsts in effec~ on fire ret~anay.
Phosphorl~ acld, ln llmlted amoun~, also can serve a role a~
a euppiemental ~lre retardant ln the compo~itlon~ o~ the
lnventl~n. ~owever~ ln view of ths 6trongly acld n~tu~o o~
~uCh material~ they.must be used in small quantltles or they
Will cau80 unacceptable ac~d hydroly~i~ and correspondln~
~reng~h lo~s oP treated wood products. ~hus, ~uch materlal~
arQ 11mite~ ln comblned amount to les~ than about 20~,
pre~er~bly 1~ th~ 15 or 16~ by welght o~ the solute ~hArge
mAteriAl~ excluding water).
When phosphorus compounds are added to the ~ormulat~on~
~he borl~ ac1d content can be recluced by An Amoun~ abou~ equal
to th~ pho6phorlc a¢id equlvalent ln the phosphorus aompo~nd.
The co~po~ltion~ o~ the invention are most e~fectlve when the
mo~ar ratlo o~ N to ~ or ~P ls from abou~ ~.5:1 to about 2
pre~erably about 0.8:1 to 1.5:1, depend~ng on the degree o~
s~nerglsm ot tho nltrogen-con~alnlng synergis~ compound.
Tho ¢ompo~itlon~ o~ the inven~lon can be prepared ln
the ra~ o~ a dry powder mlxture o~ those componen~o whlc~ ar0
Or solld ~orm at ambion~ tempor~tur~s. I~ ~mmoni~ 1~ ln~ludod
ln the oomposltlon, t~e dr~ formulatlon may lnclu~e ammonlum
carbonate. o~her components, ln 11quld ~orm at amblent
tempe~atur~ may be added when formlng an aqueous ~ire
returdant solutlon. AqUeous ~olution~, containlng the
conte~plated solublli~er~ and comblned solublllzer/synerglats~
can be prepared at falrly low tempera~ures and aonta~nin~
large~ 8mounts of borlo acid th~n he~eto~ore ha~e beQn
employed. Thus, it 1~ possible to pr~pare suoh eolutlon~
~ontainlng borlo aoid ln~amounts upwardly Or 5% to about lS or
20~ by welght o~ the .solution and whereln the bori~ acid
comprl~eo o~er 40 to ~s~ to about 70% by welght o~ the oharge
materl~ he aapaclty of woods to absorb wa~er and such
r,~
r 18
treating solutions varies greatly, for example by increasing
wood weight ~rom under 100~ to over 200%. Thus, the
concentration o~ boric acid in the treating solutions o~ this
invention correspondingly may vary over a wide range. In such
context, solutions for use directly in treating most wood
product~, ~or example those capable of about 150~ weight
increase on treatment, may contain boric acid in amount rrom
about 5 to about 9 or 10 weight percent o~ the solution and
whereln the boric acid comprises, by weight percent o~ the
charge materials, ~rom about 45%, especially at least S0%, to
about 65~, and particularly about 60%.
Preparation o~ aqueous solutions o~ the contemplated
~ire retardsnt compositions can be carried out by adding the
component chemicals to water at a temperature ~rom close to
0C, ospecially about 20C., to about 100C. At the lower end
o~ this range, solution of boric acid may rsquire use of
solubillzer~ o~ greater solubilization capacity and/or in
greater amounts than required at higher temperatures. The
hlgher end of such range is not necessary and is not preferred
in preparation o~ compositions containing materials, such as
ammonla, having high rates of volatilization at such elevated
temperaturos. A practical processing temperature range between
about 30C. and 60C., especially about 30C. to about 45C.,
18 preferred. A preferred method is to add the boric acid and
solublllzer~s) to water and agitate the mixture until the boric
acid i~ dissolved, and then add the synergist(s) ~ollowed by
any remaining water and other ingredients, and then allowing
the solution to cool to ambient temperature. In an alternate
mothod all o~ the chemicals can be added, for example, to about
20C to 45C water, and agitated until the chemicals are
dlssolved. Such aqueous solutions may be prepared with solute
¢ontents suitable ~or use directly as wood treating
compositions, or they may be prepared in the form o~ more
concentrated solutions which may be diluted with ~urther
amounts o~ water, a8 desired.
~ he ~actor ultimately determining the amount of
solubillzer to be used in making a fire retardant treating
solution in accordance with this invention is the amount of
, ,
,
19
boric acid (and ~ynergist) to be introduced in~o a particular
wood product to be treated. ThiS depends upon the degree o~
~ire retardance desired for the wood product and the solution
absorption capability of the wood product at a particular
treating temperature. Once such ~actors are known, the
required amount o~ solubilizer can be determ~ned in terms o~
the corresponding required concentration Or boric acid in the
treating solution and, in turn, the solubilization capacity of
a particular selected solu~ilizer and the temperature to be
used in making the fire retardant treating solution. Factors
affecting solubilization capacity, hence selection and amount
o~ a particular solubilizer, include, for example, it~ basicity
and rate and extent o~ reaction with boric acid and with other
ingredients o~ the composition, for example by formation of
addition compounds, borate esters or complexes, or the ability
to increase the acid strength and availability Or borlc acid
~or reaction. Other known chemical and physical
characteristics of the solubillzer, such as volatllity,
lgnition temperature, and flame spreading or inhibiting
tendency, al80 are to be considered in selecting and
determining the amount of particula~ solubilizers.
A practical advantage o~ the pre~erred, solubllizer-
contalning compositions of this invention and the ~ethod o~
preparing aqueous solutions of those compositions is that the
solutions can be made at the above-described pre~erred,
compsrat$vely low temperatures in the range of about 20C. or
30C. to about 45C. Such processihg requires less energy than
do temperatures in the higher portion of the broad temperature
range, and at the lower temperatures there is less los~ of any
volatile proces~ materials. Moreover, such solutions can be
s~ored and handled at ambient temperatures without
precipitation o~ sdlute components. Storage of aqueous
olutions Or the compositions o~ the invention normally is at
temperature~ well above ~reezing, in order to avoid
precipitation o~ dissolved compounds. ~owever, these
compositions have the further advantage that, if ~rozen, they
can be reheated and the solute redissolved without reducing the
e~fectlve flre retardancy o~ the compositions. Nevertheless,
..,
2 o 2 ~
~uch ~dditlon~l ~tep~ ar~ costly and normall~ should b~
A~oid~3d.
~ lng into account the foregoing ~actor~, I h~e ~ou~d
~h~t the ~mount o~ ~olublllzers requlr~d ln prepa~ing
oompo~ltlen~ ln the lower port~ons Or t~e proce~lng
temp~xatu~e range may be a~ little a~ about 8~ to ~ou~ 30%,
And pre~e~Ably ~rom abou~ 10% to about 20~ by welght o~ the
ahArge matQrialB.
Where volatilizat1on o~ pxocess materlal~ 19 not ot
conc~n, an~ abeorptlon capaclty o~ wood ~o be treated 1~ hlgh,
aompo~itlon~ having relatively low borlc acld con~ent~ in the
aq~eoue tre~ting ~olu~lon6 can be made by carrylng ou~ the
pro~e~e ~t tempera~ures upwardly of about 50C., without the
uee o~ boria acid solublllzers. u$e o~ a solublllzer also ~an
be omltted under certai~, llmited conditions, for example where
hlgh borlc A¢l~ concentratlons are not needed, or where llmlted
ab~orptlon capaolty o~ a partlcul,ar ~oo~ product pr~clude~
impregnAtion o~ large amount~ or flre retardant, or where the
corresponding borlc acld concentratlon o~ the treatlng solution
~ ~uf~iciently lo~ to avold precipitatlon under amblont
otorn~e ~nd handling temperatures, or where the praqtical and
economlc erPe~ts o~ either reheating ~o resolubilize
pre~ipltAted 801ute, or o~ etorlng and handling o~ the solutlon
~t ~lQ~ated tempera~ures to prevent preclpltatlon may be
~oa~lble.
~ ho guan~it~ o~ synerglst(s) will depend Upon ~he
degree o~ fl~e xeta~d~ncy requlred and the partl~ula~
~ynergl~t~, or comblned 6olubilizer/synerg6t~s) whlch are
~elected, Th~ required amount o~ ~uch materlals gen~rally may
r~nge from about 25 to about 40~, preferably ~rom 30 to 3~% ~y
welght o~ the (non-aqueous) charge materlal~, except that urea
1~ re~ric~e~ ln maxl~um amount to about 15 to 17% ~n~o~r
llmit unde~lrable hygroscoplclty o~ ~he composltlons. Amount~
o~ u~a up to such maximum llml~ are useful, not only tO aid
ln ~o~ubllizatlon of b~rlc acld, bu~ also ~by vir~ue or ite
0trong hygro~cop~lty) to serve to keep treated wood produat~
rro~ ~ompletely drying. ~ut by retalning a s~all amoun~ o~ w~ter
ln the pro~uot~.
~ ' .
. .
2~2~
W21er~ the f~ire retardant: oomposltlon ¢ontainn
ce~ponen~ whlcll acts both as a solublllze~ ~nd a~ a ~yne~gl~t~
auah ~ultiple functions mus~ be conside~ed in determinln~ e
to~al amountEI ~ such componerl~e zlnd other Golubilizers and
~ynergi~ required to obtaln a desired ~egree o~ ~lxe
~e~ardancy. In such cases~ ~he total Amoun~ o~ ~uch materlal~
~ogether wi~h non-so~ubll~lng ~ynerglst(s~ may range~ rO~
example, ~rom about 15% to about 3~%; and pre~era~ly S~om ~bout
20% to.Abou~ 30~ o~ the welght of the charge material~.
In one embodiment o~ the lnventlon, water, borio acid~
~içyAn~ia~lde (-eyne~glst) and urea (~erving as a ~om~ine~
oelubllize~ and con~rolled water retentlon agent), wlthin
welg~t rangee o~ each functlonal compound type a~ above
de60ribed~ are he~ed with agitatlon a~ a ~emperature betwe~n
30C and 60C~ pre~erably at a~ou~ 45C. When maximum solut~on
0~ borlc acld 1~ Achieved~ monoethanolamlne ~solu~lllzer)
added ~ollowed by ammonlum hydroxlde ~solubillzer). When all
component~ are dlssolved, the ~olutlon ls aooled to roo~
temperature. The re6pective proportlon.~ oS oha~ge materi~ls
~e~ui~ed~ Wit~l~ the range3 Or each materi~l, in preparing thi~
and o~her compoeitlon~ in accordance with thl~ invention
~e~dily can bo determined experimentally in llght o~ ~e
prln~lple~ and example~ hereln taught and provlded.
~ ori~ ~Cid is an ef~ectlve bloclde. However~
~ddltlonal blocides and other materlal~ may ~c added ~o the
compoeltions o~ the lnventlon, but such additive~ ~houla not
~a~erlally a~eo~ the non-reslnous, non-hygroscoplc and low
acidlty nature o~ the composi~ions or thelr flre ret~rdant
prop~tie~ ~nd ~hould not con~rl~ute o~hcr un~e~lrable
characterlstic~, such ~ as p~roduction oS no~iou~ ~ume~
a~terglow, eto. on hlgh temperature exposure o~ the ~reated
wood produats.
Aqueous ~olutlon~ of the flre retardant co~po6it~0n~
Or thiq ~nventlon can ~e used to treat wood produc~ ~y ~ny one
o~ the varlou~ technlques whleh are ~ell know~ 1~ the ~
~x~mple~ oP ~uch ~ethod~ lnclude d.ipping, soaking and Va~um
or ~acuum-pre~Rure lmpregnatlon. ~he partlcular ~echnique u6Qd
will be determined Py such fac~ors as the ~pecle~ o~ wood belng
:: '
22
treated~ the thickness of the wmPd prQdU~ b~ degr~R Q~ ~lr~
retardancy required and the intended end use o~ the treated
wood product. The treating method and conditions to be
employed also are factors to be considered in determining the
solute composition and component concentrations o~ the agueous
treating solution.
After treatment o~ a wood product, it therea~ter ~ay
be dried ln a conventional manner at am~ient temperature.
Alternatively, drying may be accelerated by heating the
product, ror example, in a kiln to a temperature o~ ~rom about
40C to about 65C, for a time sufficient to reduce the wood
mol~ture content to about 10 to 20 percent, normally around
10~. Because the fire retardant compositions o~ the invention
are essentially non-re~inous, an extended, high temperature
~e.g. 65C or greater) curing cycle i8 not required.
There~ore, wood strength is not impaired.
The following ~urther examples will illustrate the
invention.
Example 1
A 12.5~ aqueous treating solution i8 prepared ~rom
Cl.84 gm. tl mole) boric acid, 11.22 gm. (0.18 mole)
monoothanolamine, 11.22 gm. ammonium hydroxide ~3.25 gm. - 0.19
mol- NH3), 18.02 gm. (0.30 mole) urea, 6.15 gm. ~0.08 mole)
dlcyandia~ide, and 669.39 gm. (37.1 mole~) water. Hal~ Or the
water 1~ heated to 45C and, while agitating, the boric acid,
urea and dicyandiamide are added. When about ~aximum
~olubility is achieved, the ethanolamine and ammonium hydroxide
are added and agitation is continued until all o~ the
components are in solution. The remainder o~ the water is
added and the solution ~s cooled to room temperature.
A composition in accordance with Example 1 was prepared
ln ~u~ic~ent amount tolaccommodate the immersion therein and
impregnation therewith of four ponderosa pine fire tube
specimen~ having dimensions of 3/8 inch x 3/4 inch x 40 inches.
The specimens were submersed in a treating cylinder designed
for pressure impregnation and a vacuum o~ about 30 inches o~
Hg was applied ~or 30 minutes, followed by a pressure
impregnation period o~ 3 hours at about 150 psi. ~he pressure
.,.: ~ ~ . .: . .. . . . ; . . ., . . . . . . . ., . . -
2020118
23
then waa r~ a~ed ;~nd t~ ipecimen3 r~mc~ved ~ro~ he cyl~n~r
An~ ~llowed to alr dry ~or one day an~ ~hen oven ~ried at ~bout
50¢ un~ n e~uilibrlum molsturq content Or about ~ to lo~
wa~ reA~hed. O~her compositions, ldentifled a~ Example~ ~, 3
And 4 in ~a~le 1 below, were ~milarly prepared and u~d to
~mllarly ~reat ~ddltional slmllar wood 6ample~. Th~ ammonia
ln the ~ormulatlons o~ Examples 1-3 is volatile and 1~ r~movo~
e~en~lally oompletely ~rom the wood during drying.
. The thu~-~reated speclmen~, as well a~ ~i~ilAr
untreat~d ~ood oontrol 6amples, and ~imllar sample~ treated
onl~ Wl~h ~orlc.a~ld, monoethanolamine or urea, were eub~ectea
to ~l~e tube test6.1n accordance wlth the proce~re oS AS~
E69-50~ ~o~ordin~ to thl~ standard, ~lre tube welgh~ 10B~
under 30% i~ con~idered acceptable fir~ r~tardanc~. The
~peci~en~ were oven-drled and equilibrated to a ~oi~ture
content o~ about 5% and placed ln a metalllc ~ube havin~ vent
holeq. The bottom end~ of the ~pecl~ens were positione~ a
d~etance o~ one ~nch from the top o~ a burner and a callbrsted
~lAme then wa~ applle~ to the bottom o~ the eamples. The
burnor was ad~u~ted to provlde a ~lame height o~ 11 inche~ and
a temperature at the top o~ the ~ire ~ube (in the ab6~nce o~
a ~ample) oP 175C to 180C. ~he 6amples, were 6u~pe~ded ove~
the ~lame ~or a perlod o~ 4 minute~. In caso o~ the untrsated
e~mple~ and each ot the samples treated w1th boric acld,
monoethanolamine or ~rea, b~rning oont~nued after the pllot
~l~me wa~ ~emoved. In eac~ case, the wel~ht o~ the non-
con~um~d po~tion o~ the 6ample was 6~btracted ~rom th~ orlglnal
wel~h~ to det~ine ~elght loss. Such data are glven ln ~abl~
1 ~h~eln ~ormulatlon percentages are by weight o~ charga
~at~ial~
24 2~ l8
~ le 1
~xample~ F~re ~UbQ
~Formulatlon~ ~$~;,~c;tlvq c~mi~L Wt. Loss
ln ~- pBraQn~) pcf % B % P ~ ~+p 9
. ~
A . U~ltre~t~d o o O o 8 5
~. Monou~hanolamln~ 5 0 0 0 90
C: . Uretl 5 o o o 8 ~ . ; . . .
D. H3so3 only 4 . o 2 . 50 0 2 . 50 65
2.7 1.68 0 1.68 68
1.6 1.~0 0 1.00 70 ,
E~ RICONb, io96 5.5 1.03 2.13 3.16 21
GUPCJt30% H3B03 4.G 0.86 1.78 2.64 ~8
1. 57.3 H ~0
10.4 ~S3n~3 7.1 2.a3 ~ 2.83 21
e~h~nol~mlr~e 5 . a 2 . 32 0 2 . 32 25
10.4 NH40l~ 5.0 2.00 0 2.00 27
~299c ~J~3)
16. 7 Ut,ea
~.~ Dlcyandian~ide
2. 58.1 H BO
1.7 ~ 0
~2~% N~ ~
10.3 HMT~U 6.~ 2.3~ 0.70 3.06 ~ 21
11.5 Urea 4.8 1.83 0.54 ~.37 26 ~ ~,
5.7 D~ayandiamide
12.7 759~ ~3P04 : :
3 . 50. 0 H 1~0
10 . O Ni~40
~29% NH )
15.0 Ur3a 5.9 2.05 0.54 ~.S9 20
10.0 llM~rA 5.0 1.73 0.46 ~.19 25
lS . 0 ~;UP
4. 4~.0 H3B0 i . .
41-1 N B~ 7'1H2 9,1 2.40 0 2.40 27
8.5 U2ea~. j. 5,.7~ 1.50 0 1.50 SB .
8 . 4 Dicy~ndlamide
~cP - pound~/cu. ft. ~ -
b'lD~ICON'I ~ a trademark of Hlck~on, 1td. ``~
~GUP - guanylurea phosphate
dHMTA ~ hexamethylenetetramlne
. ................................................ - ~
... ~
; :: .
, ,,
2~?.011 8
The boron and phosphoru~ r~tention~ o~ T~bl~ 1 are ; ~ -
convert~d ~o borlc acid [B(OH3) ~ and phosphoric a~ld tH3poJ~
equivalent~, !py weight percent, in Table 2 whereln the ratios
o~ welght percent~ge~ o~ thos~ compound3 as well ~ t~e
~lm~ lar ratlo~ or elemental boron and phosphorus al~o
giv~n. ~
~~ble 2 : -:
Weiqh~ Peroe~t~ ~ ht B.~~ -
~orlc Phosphorlc Bo~la Acld/
D 1~.3 . O
9 .6 0 ~
g.l O -- --
E 5.g 6.7 0.88 0.4~ :
~.9 5.6 0.8~ 0.48
16.2 0 - ~
13.3 0 - _
11 . 4 0 ~ --
2 13.5 2.2 6.14 3-37
10.5 1.7 6.18 3-3~
3 . 11.7 1.7 6.88 3.80
9.Y 1.4 7.07 3.76
4 13.7 0 - ~ ::
8.~; 0
From the data o~ Table 1~ it caTl be ~een tha~, uced
alone~ ~elt~ler monoethanolamlne nor urea ~Example~ ~ ~nd C)
howe~ any Bignlplcant fire retardan~ e~e¢t. Boric aold ;
~lone (Example ~) ~ad very llttle ~uch e~eo~, but~ when
pro~ent t~gother with the, ,other co~ponents Or the Examplo 1
mixture~ a dra6tlc and unexpected 6ynerglstia e~feat
hieved. These ~ata also include the results ~t preparatlon~
trcatment and fire tube testinq, es above-described~ O~ a ~;:
~imllar wood sample ~Example E) treated wlth a oompoeltion
RICON~) in accordance wlth Oberley U.S. Patent No.
4,373,~ ro~ suc~ comparative da~a lt le ~een that the .:
rl~e ~etardancy o~ the wood ~reated wlth the phosphoruu-~xee
202~118
~G
AmE~ mpo~itic~n 19 about equal t~ ~:hat oE the ~ample
tre~ted with. the hig}~ phosphorus, rel;~tively hi~hly aaldic
~A40Ut pH 3.~) D~ICON compositlon. ~s above-de~ribed,
aompo~tlone ~uch aA that u~ed ln Ex~mple ~ ha~e tha ~urther
tage ovRr acidic phosphorus-containing ~omposltlon~ ~uch
~ th~lt o~ Ex~mple E, o~ being nearly neutral t~l le ln tne
rAngo o~ ~bout 6 . 5 t:o about 6. 9) and hl3nce rree or ha~mtul
~ood degr~ation by acld hydrolyoi~.
Exampleo 2 and 3 o~ Table 1 r~rther illu~tr~e the
co~posi~ion~ o~ ~he in~ehtion. These compositlonn cont~in
hlgh percentagQ~ (respectively 5~.1% and 50~) o~ boric aold
~ogether wlth other boric ao.id ~olubillzer~ (a~monla and
hexamQthylenet~tramlne) and ~upplemental sGlubll~zera~
~ynargl~n ~phoop~oric acld ln Ex~mple 2 and gu~nylu~e~
pho~phate ln Example 3 -- bo~h or whic~ compounds are li~i~ed
to 15% or less ln order to avold high aaidity o~ the
co~po~ltlon~ oth ~xamples 2 and 3 ohow excellent flre
reta~danc~, ~B ln the oa~e Or Example 1, rlre tube welght
100H io ln ~he range o~ 20 - 27~, a~ compared ~o a weight locs
o~ ~5% ror untreated wood ~Example A) and ~5-7~ rOr borl¢
~cld ~lone.
In Example 1 o~ ~able l, the amount o~ the
mono~thanola~lne 601ubilizer ls~determlne~ an a ~unction Or
the mlnimum amount at whlch, ln the pree~nce of the
~ynergi~, ur~a and dlcyan~lAmide~ t)~e deslred Amount o~
~orla aci~ can be dls6elved in wa~er a~ the predeterminedl
prAc~lcally low te~perature, wlthout th~ ~ddltion o~ ~o ~uch
monoethanolamln~ ~hat unaccepta~le flame spreadin~ would occur
upon oxpo~ure to w~od ~ombu~ion tempera~ures. The a~ount o~
~onoethanolamlne ~equired for ~uch purpose can be reducQd, ~nd
1~B contrlbution to flame sp~eading decreased, by uelng~ in
con~unction wi~h the amine, a 6econd ~olubilizeYl ~uch
ammonlum hydroxide, WhlCh adds no ~el ~alue to th~
composltion. Slmllar consl~eratlons o~n easl.ly be applled by
tho~e eXllled ln the~art to select others Or the ~e~aribed
~olu~illzers and ~yne~gists and to balance the re~peatlve
~mountu Or each ln accordanc~ ~lth the prlnciple~ o~ the
inventlon as set ~orth herein,
,:
2~20~8
2 1
For ~ccepl;able fire retard~ncy~ an ~mount o~ flre
retnrdAn~ ~Ateriall ~u~cient to exert ~ectlve ~lre
r-al;nrd~ncy on burnlng o~ a wood ar~icle, mu~ b~ lmpr~gna~e~
in1:o ~nd retalned wit~lln the wood. on the other h~nd, wlth
too l~rgo a quantity o~ flre reta~an~ lmprognated w~d
produo~ wlll ~ecome e~nbrlt~led an~ o~ ~uch lncrea~ed d~nsi~y
A~ to noc~B~ita~e redeslgn for the inten~ed ~ppl~tion. In
~lew o~ this latter facto~, ~etalned fire retardant m~erials
ohoui~ be ~ept under an amoun~ wlllch would Blgni~lc~ntly
ombrittle the wo~d product . Tl-e Amount o~ f lre rotArd~nt
materlAl ne~ded ~o achleve acceptable ~lre retArdanay le
dependent upon ~actor~ ~ùch a~ woo~ ep~cle~ and den~ y, An~
condl~n~ o~ ~anuSacturing a woo~ art1cle~ s~ch a~ plywood-
For exa~ple, ~uc~ ~etention using an effic~ent flre ret~r~ant
varleo fro~ a~ lit~le as Z.s~3.0 pound3 per oubio ~oot ror
Dou~la~ f~r lun~er 'co reten~lons as hlgh a~ 6 poun~ per CUbiC
~oot ~or Southern yellow plne plywood. For sf~ective rir~
re~ar~anco~ the amoun~ or e~fectlv~ ~lre retsrdant shoul~ be
allgh~ly greater than the thre~hold level ~etermlned to
provi~e ~uo~ adequate fi~e xetardancy. Thus~ ~rom ExampleB
2-3 ~ T~ble l, it wlll be eeen that~ wl~h ~se o~ the
composition~ o~ ~hl~ inven~lon, adequ~te flre r~tardancy
~b~lo~ 3~ ~ire tube wetght loss) 1~ achleved at retention~
le~ han 6 pound~ per cu~lc root Or tho pondero~a plne
e~mple~. Thi~ rèsult i5 ob~alned Wlth Concentration~ o~
retalned boron ln t2~e range o~ 2% o~ 1eB9~ Furthe~ such
xe~ s ~r~ obtalne~ with only very little pho~phoru~ ~0.46~
to 0.70% as ln Examples 2 and 3) or no phosphorus ~Example l~
With A ~ire ~etardance equivalent to that o~ ~h~ mo~t
e~fe~ti~e pr.ior aXt ~ompositions represented ,by Example E~
con~ining AbOU~ the ~Ame amount o~ retalned ~ire retArd~
~4.6 pounds per cublc foot) and over l~ Or phosph~oru~.
~ .~ also shown ln ~able 2, the be~ And nearest
comp~rnble prlor art ~lre retardant composl~ion ~I~DR~CON~
ExA~pln E~ ha~ a B:P~wei~ht xatlo les~ than ~ hexeas the
aompoeition~ o~ ~he ln~entlon as ~hown in Table 1 hav~ A~ B:P
welght r~tio over 3:1, l.e. over 6 time~ grea~er. Si~larly,
nn t.h~ wa~ht. ~ar~nt ~e r~t~ln~r.l ~ira r~t~r~nt, in
- 202~ 18
:
termB 0~ equlv~lent borlc ~oid and phosphorl¢ aaid, the boric
~cld/phocphorl~ ~cid ratlo, ~or the phocp~loric acid-con~Ainirlg
Ex~mploa 2 ~Ind 3, 1~ about 7-~ tim~ ~rca'cer than that ~or
Ex~mpl~ E .
~ ExAmple 4 o~ Table 1 Contain~ borax ~ well ~ bori¢
ac1d~ At ~n ac:ceptable level o~ retained ~ire retardAnt ~ rc~
x~mple~ 5.7 pounds per oublc ~oot ~g ~hown ~or ~h6~ ~e~;:ond
te~ compo~ltion o~ Example 4 ), t~e ~1re r~tardancy o~ ~uch
<~ompoeitione i8 ~uch less (5896 fire tube welgh~ 10~9) 'chan the
pre~ex~ed compo~it1on~ o~ thls inventlon. Thie latte~ te~t ~ ~ :
illu~trate~ th~ dl~advantage of the use o~ metal ~alt~ ~uch
bor~x ln ~ire retardant composltlons d~le to tho nction o~
~uch oal~ ln reducing thelr e~ectivenes~ k~y deactl~r~ting
boric ~cid a~ a fl~:e ~etardan~, on a mol-~or-mol ba~i~. Whilo
a sodium-cont~lnlng ~ormula~clon 6uch as tha~ o~ ~xample 4 can
provide rea~onable flre retardancy an~ uatis~ctorlly low
~yg~o~coplcity and aoldlty, ~lre re~ardancy equal to th~t o~ ~:
the p~ePerred compo~ltions o~ this invention ls poss$ble only
l~.the A~ount o~ ~lre retardan~ 1~ inc~eased to A level ~t
whloh the l~pregnated wood becomes unacceptably den~e a~d
brittle -- AS DhOWIl in ~he firs~ o~ ~he ~wo test co~po~itlons
4~ Ex~m~le 4. Although fire retardant per~ormance o~ ~uch
~o~po~itions ~an be lmproved by lncreasln~ the amount o~
dlayandlamlae and~or Urea~ hlgher than optlmum retentiona
stlll ~re requlre~
~ n ~ddition to the described technlcal advAntage~
o~ the compos~tlons o~ this lmrention A9 compared to ~'~RICON~
t~pQ ~ire r~tard~nts, the new compoSit~ons ~lso ~re
~ubntantlally less cos~ly~th'an the ~'DRIC~N~I oompo~ition~
.
; ' ~ ' '~'
.. ~;,, .
,: -. -.
'
