CA2020118A1 - Fire retardants and products produced therewith - Google Patents

Abstract

ABSTRACT
Improved fire retardant compositions, methods of making such compositions, and wood and other cellulosic products treated with such compositions which comprise a major amount of boric acid and a minor amount of (a) one or more synergist materials which, with boric acid, enhance the fire retardant properties of treated products as compared to boric acid or the synergist alone, and (b) optionally, one or more solubilizers which increase the water solubility of boric acid. The compositions are of substantially neutral pH and do not cause metal corrosion or acid hydrolysis or treated products.

Description

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 . ................................................. :

, . :

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~

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 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 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 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 , , , 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 :: ' 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 .,.: ~ ~ . .: . .. . . . ; . . ., . . . . . . . ., . . -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 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~

.
; ' ~ ' '~' .. ~;,, .
,: -. -.

'

Claims (32)

1. An improved, water soluble fire retardant composition adapted, in a water solution thereof, for impregnation of solid wood products and other cellulosic material and comprising, by weight percent of the composition charge materials, excluding water solvent, from about 40% to about 70% of boric acid, at least one nitrogen-containing synergist material which is soluble in water at a solution temperature of from over 0°C, to under 100°C, in an amount which, in combination with boric acid, is effective to enhance the fire retardancy of wood products impregnated therewith as compared to that of he synergist material and boric acid alone, and a combined total of not more than about 15% of materials having an acid strength greater than boric acid, such composition, when introduced into wood products, having substantially no effect on hydrolysis of the wood cellulose and corrosion of metals in contact with the wood product.

2. A composition according to claim 1 additionally containing at least one solubilizer which is water soluble in an amount effective to increase water solubility of boric acid in the presence of the synergist material at a temperature within the aforesaid solution temperature range.

3. A composition according to claim 2 wherein the composition is essentially free of materials having an acid strength greater than that of boric acid.

4. A composition according to claim 2 wherein the solution temperature is in the range from about 20°C. to about 65°C. and the composition contains at least about 45% boric acid, is substantially non-resinous and free of alkali metals and alkaline earth metals, and is capable of being dried, after impregnation of an aqueous solution thereof into a wood product, at a temperature under about 65°C.

5. A composition according to claim 4 wherein the boric acid content is from about 50% to about 65%.

6. A composition according to claim 4 wherein the boric acid content is from about 50% to about 60%.

7. A composition according to claim 4 wherein the boric synergist material is selected from the group consisting of semicarbazide, guanidine, cyanamide, dicyandiamide, urea, guanylurea, guanylurea phosphate, monoammonium phosphate and diammonium phosphate, and mixtures thereof, and wherein urea is limited to a maximum amount of about 17% and guanylurea phosphate, monoammonium phosphate and diammonium phosphate are limited in combined amount to less than 20%.

8. A composition according to claim 7 wherein the group of synergist materials additionally includes melamine, biuret and oxamide and mixtures thereof with each other and with other synergists of the group and wherein, when the composition contains such an additional synergist, the composition also contains an amount of a supplemental solubilizer in amount sufficient to dissolve an effective amount of such additional synergist in the water solution.

9. A composition according to claim 8 wherein the amount of urea and the combined amount of the phosphorus-containing materials each is limited to about 15%.

10. A composition according to claim 9 wherein the additional synergist material is melamine and the supplemental solubilizer is formaldehyde.

11. A composition according to claim 7 wherein the solubilizer material is selected from the group consisting of ammonia, basic nitrogen compounds other than ammonia, monohydric alcohols, polyols, and mixtures thereof with or without ammonia.

12. A composition according to claim 11 wherein the basic nitrogen compounds other than ammonia are selected from the group consisting of ammonium carbonate, strongly basic amines having a pKB under about 5, and more weakly basic compounds having a pKB of about 5 or larger,

13. A composition according to claim 12 wherein the basic amines are more strongly basic than ammonia.

14. A composition according to claim 13 wherein the basic amines are selected from the group consisting of primary, secondary and tertiary alkylamines and alkanolamines, and hexamethylenetetramine.

15. A composition according to claim 14 wherein the alkylamines and alkanolamines are selected from the group consisting of ethylamines, propylamines, ethanolamines and propanolamines, and the weakly basic compound are selected from the group consisting of formaldehyde-amine addition compounds, hydrazine, ammonium carbonates and ammonium carbamate, the monohydric alcohol is a saturated alcohol selected from the group consisting of methanol, ethanol, N-propanol, isopropanol, and butyl and amyl alcohols, and the polyol is selected from the group consisting of dihydric alcohols, trihydric alcohols, higher polyhydric alcohols, monosaccharides and disaccharaides.

16. A composition according to claim 15 wherein the saturated monohydric alcohol is methanol, the dihydric alcohol is selected from the group consisting of ethylene glycol and propylene glycol, the trihydric alcohol is glycerol, the higher polyhydric alcohol is selected from the group consisting of mannitol and sorbitol, the monosaccharide is selected from the group consisting of glucose and fructose, and the disaccharide is sucrose.

17. A composition according to claim 9 comprising from an effective amount up to about 25% by weight of a boric acid solubilizer selected from the group consisting of monoethanolamine, hexamethylenetetramine, ammonia, phosphoric acid and guanylurea phosphate, wherein ammonia, phosphoric acid and guanylurea phosphate each is limited in maximum amount to about 15% and the combined amount of phosphoric acid and guanylurea phosphate is limited to about 15%.

18. A composition according to claim 17 wherein the synergist material comprises from an effective amount up to about 10% by weight of dicyandiamide, and from an effective amount up to about 17% by weight of urea as a combined synergist and for retaining a minimum required amount of moisture in a wood product impregnated with a water solution of such composition.

19. A composition according to one of claims 2 and 4 wherein the synergist material is selected from the group consisting of semicarbazide, guanidine, cyanamide, dicyandiamide, urea, guanylurea, guanylurea phosphate, monoammonium phosphate and diammonium phosphate, and mixtures thereof, the solubilizer material is selected from the group consisting of ammonia, basic nitrogen compounds other than ammonia, monohydric alcohols, polyols, and mixtures thereof with or without ammonia, urea is limited to a maximum amount of about 17%, and guanylurea phosphate, monoammonium phosphate and diammonium phosphate are limited in combined amount to less than 20%.

20. A solution for treating solid wood and other cellulosic products to improve the fire resistance thereof, comprising an aqueous solvent and a solute having a composition according to one of claims 1, 2, 3, 4 and 11.

21. A solution concentrate adapted for dilution with water to form a treating solution for solid wood and other cellulosic products to improve the fire resistance thereof, comprising an aqueous solvent and a solute having a composition according to one of claims 1, 2, 3, 4 and 11 and wherein the boric acid comprises from over 10% to about 20%
by weight of the solution.

22. A solution for treating solid wood and other cellulosic products to improve the fire resistance thereof, comprising an aqueous solvent and a solute having a composition according to one of claims 1, 2, 3, 4 and 11 and wherein the boric acid comprises from about 5% to about 15% by weight of the solution.

23. A wood product impregnated with an aqueous solution of a fire retardant

24. A wood product impregnated with an aqueous solution of a fire retardant composition according to one of claims 1, 2, 3, 4 and 11 and dried after impregnation and containing up to about 6 pounds per cubic foot of retained fire retardant.
wherein the weight ratio of retained boron to phosphorus is at least 3 to 1.

25. A wood product impregnated with an aqueous solution of a fire retardant composition according to one of claims 1, 2, 3, 4 and 11 and dried after impregnation and containing up to about 6 pounds per cubic foot of retained fire retardant.
wherein the weight ratio of retained boron to phosphorus is at least 3 to 1 and the product contains, by weight percent, at least about 1.5% of retained boron and from substantially none to less than about 0.75% phosphorus.

26. A method of treating a cellulosic product to impart fire retardency thereto comprising impregnating said article with a fire retardant amount of a composition according to one of claims 1, 2, 3, 4 and 11.

27. A process for forming a treating solution for imparting fire retardance to wood and other cellulosic products comprising forming an initial aqueous solution containing from about 15% to about 20% by weight of boric acid by adding to water, within a reaction temperature range from about 20°C to about 65°C, boric acid and at least one non-acidic boric acid solubilizer which is soluble under such conditions in an amount effective to provide such minimum boric acid content, and at least one synergist material which is soluble under such conditions in an amount effective to provide, with boric acid, a fire retardency greater than that of boric acid or the synergist material alone, agitating the solution until the reactants are substantially fully dissolved, cooling and diluting the solution to a boric acid concentration in the range from about 5% to under 15% by weight of the diluted solution.

28. A process according to claim 27 wherein the reaction temperature range is from about 30°C. to about 45°C.

29. A process according to one of claims 27 and 28 wherein the solute comprises, by weight percent, from about 50% to about 70% boric acid, from about 8% to about 30% of solubilizer, and from about 15% to about 35% of synergist material.

30. A process for making a treating solution for imparting fire retardance to wood and other cellulosic products comprising adding to water boric acid and at least one synergist material and agitating the solution at a reaction temperature in the range from about 50°C to under 100°C, and wherein the boric acid addition is in an amount from about 5% to about 12% by weight of solution and the synergist material addition is in an amount which is soluble at the reaction temperature in an amount at least sufficient to provide, with the boric acid, a fire retardance greater than that of boric acid or the synergist material alone, continuing agitation of the solution until the additions are substantially completely dissolved, and cooling the solution to ambient temperature.

31. A composition according to one of claims 1, 2, 4 and 11 wherein the mol ratio of nitrogen to boron or to boron plus phosphorus is from about 0.5:1 to about 2:1.

32. A composition according to one of claims 1, 2, 4 and 11 wherein the mol ratio of nitrogen to boron or to boron plus phosphorus is from about 0.8:1 to about 1.5:1.