Note: Descriptions are shown in the official language in which they were submitted.
5~
This inven-tion relates to fire re-tardant com-
positions. In one aspect, this invention relates to com-
positions comprising a polyalkylenepolyamine and a four-
component inor~anic salt fire retardant formulation. In
another aspect, this invention relates to a method of
imparting fire retardancy to cellulosic substrates by
treating same with said composi.tions.
Various inoryanic sa].t formulations are well-
known, standardized fire retardants for cellulosic substrates.
However, many of these formulations contain components
which are highly hygroscopic, thus causing such Eormulations
to have limited utility. For example, ammonium sulfate is
a common component in many of these formulations. If
exposed to 81 percent relative humidity at 20C, it will
absorb sufficient water vapor to reach saturation. Wood
treated with an ammonium sulfate formulation and exposed to
similar conditions also reaches saturation, primarily due
to the hygroscopicity of such salts. Consequently, these
formulations, or components -thereof, migrate (leach) to the
surface of the treated substrate and the resulting dripping
not only depletes the salt content of the wood, rendering
it less fire resistant, but also severely disfigures the
surface~ especially if finishedO If the treated substrate
is exposed to running water or rainfall, this leaching is
accelerated.
Strother, in U.S. Patent 3,565,679, teaches
imparting fire retardancy to cellulosic substrates by
treatlng same with a complex of a polyalkylenepolyamine and
a condensation product of phosphorus pentoxide and ammonia.
Brown, et al., in U.S. Patent 4,038,451 teach that com-
:
: ~ ,, ''
, ~
: 18,328-F -1-
'7~i
-- 2
positions comprising polyalkylenepolyamines and a
mixture of mono- and diammonium phosphates can be used
as fire retardants for cellulosic substrates.
According to this invention, a composition
comprising a polyalkyleneopolyamine having a number
average molecular weight of at least l,OOO and a four-
component ~ire retardant formulation consisting o~:
a) ammonium sul~ate,
b) boric acid, and
c) two compnents selected from the group
consisting of zinc halide, alkali metal
dichromate, diammonium phosphate and
alkali metal tetraborate
not only imparts fire retardancy to various cellulosic
substrates, but also demonstrates surprising leach
resistance, even at elevated humidity.
The present invention is also directed to a
method of imparting fire retardancy to a cellulosic
subs-trate comprising treating the substrate with a ~ire
retardant amount of an aqueous solution of any of the
compositions of the present invention described above.
Both branched and linear polyalkylenepolyamines
are useful in this invention. The linear polyalkylene-
polyamines are known compounds consisting of n randomly
joined unites (I, II) and are readily prepared by the
ring-opening polymerization of substituted oxazolines
or similar compounds (III~, ~ollowed optionally by
hydrolysis.
18,328-F
.
. ~
.. . - . . .. , -
: : . . ~ . ', ., :
~. : : - . .
' ' .; ' ., ' .. -, .,. ~ . :~ . .. .
- : . . . .. ..
:: , . . : . .. .
.
76
- 2a -
(I) ~N- (CHR) x-CH2t
C-R'
o
(II) tN- (CHR)X-cH2t
H
(III) ~ O\
R'
( HR) x N
The substituents and subscripts are hereinafter defined.
The ring-opening polymerization is generally conducted
in the presence of a cationic polymerization catalyst
:~ :
t: !
. .
~: .. . - : : -
at a reaction temperature of about 0-200C. Typical
catalys-ts include strony mineral acids, or~anic sulfonic
acids and their es-ters, acidic salts s~ch as ammonium
sulfate, Lewis acids such as aluminum trichloride,
stannous tetrachloride, boron trifluoride, and organic
diazoniumfluoroborates and dialkylsulfates. Thi.s
ring-opening polymerization is further described by Tomalia
et al., J. Polymer_Sc~ence, 4, 2253 (1966); Bassiri et al.,
Polymer Letters, 5, 871 (1967); and Seeliger, Ger. 1,206,585.
The pre-hydrolyæed po.Lymers thereby obtained
are linear, N-acylated polyalkylenepolyamines having a
molecular structure consisting essentially of repeating
units I. These polymers are easily deacylated by acid,
. base or neutral hydrolysis. Hydrolysis is best controlled
under acidic conditions and acid hydrolysis is thus preferred.
The partially deacylated polyalkylenepolyamines have a
molecular structure consisting essentially of the randomly
joined units I and II, illustratively depicted as:
(IV) ~N-(CHR)x-CH2) (N-(CHR) -CH2t
C-R' h H x n-h
O
wherein:
: n is the total`number of units;
:h is the number of acylated units; and
: n-h is the num er of deacylated unitsO
"Deacylated polyalkylenepolyamines" here includes
both:the fully~and partially deacylated polymers.
~ ~ Partlally deacylated polyalXylenepolyamines have at
: : least;~one secondary amine group (-N-) per polymer chain
H
,
:
, : :
18,328-F ~ _3~
. , . . : , -, . : ~ ,: , : .
::- - :: : . . . .
.,
as in IV where n-h is at least 1. Preferably, the
polyalkylenepolyamines here used are at least about
50 percent deacylated (n-h is at least about 50 percent
of n~ and more preferably at 1eas-t about 90 percent
deacylated (n-h is at least abou-t 90 percent of n).
Fully deacylated polyalkylenepolyamines (n-h is ~lbout 100
percent of n) are most preferred.
The branched polyalkylenepolyamines (V) include
those obtained from reacting an alkylenepolyamine (e.g. r
10 - ethylenediamine, 1,2~propylenediamine, diethylenetriamine,
te~raethylenepentamine, etc.) with a difunctional
chain-extending and cross-linking agent (e.g., 1,2
dichloroethane, epichlorohydrin, etc.).
~V) ~CH2CH2-N-CH2cEl2 NH CH2CH2
,CH2
Cll
, 2
HN-CH2C~I2-NH-CH2CH2'-N-CH2CH2-NHt
,C~2
CH2
NH2
::
~15 Of course, acylated polyalkylenepolyamines are not
generated by these preparations and the branched poly-
alkylenepolyamines~are thus without acyl groups, or
in the language of line~ar polyalkylenepolyamines, they
are fully deacylated. Also included within the term
2Q ~ 'Ibranch0d polyalkylenepolyamine" is polyethylenimine,
generally~produced by the polymerization o~ ethylenimine
in~the~presence af an acid catalyst, and the corresponding
po~lypropylenimines. Polyethylenepolyamines, ~specially
the polyethylenimines, are preferred for reasons of commercial
availability.
18/328-F _4_
'- ' : . ': ' ~ :
., .-
-
5~
As regards the other substituents and subscripts
in the above formulae, R is hydro~en or Cl-C3 alkyl, R' is
hydro~-Jcn or alk~l having up to abou-t 18 carbon a-toms or an
inertly-substituted derivative thereof, and x is l or 2.
By "inertly-substituted" is meant that the substituents do
not reduce the polyalkylenepolyamines anti~hygroscopic
properties. Illustrative inert substituents include
halogen, ethylenic unsaturation, ether oxygen, carbonyl
and ester. Exemplary R substituents include hydrogen,
methyl, e-thyl and propyl, and exemplary R' substituents
(alkyl) include methyl, ethyl, propyl, pentyl, cyclohexyl,
- dodecyl, octadecyl, and the various halogenated and
ethylenically unsa-turated derivatives of each. Fully
deacylated polyethylenimines (x is l~ wherein R is hydrogen
are the preferred linear polyalkylenepolyamines. Branched
polyethylenimines are most preferred.
~ Polyalkylenepolyamines having a number average
molecular weight of at least about l,000, as determined
by gel permeation chromatography, are used in the practice
of this invention. Typically these compounds have an
average number molecular weight of at least about 20,000
:
and preferably of about 25,000. Practical considerations~
such as preparation, mechanical application, and the like
are the only limitations upon these compounds' average
: :
maximum molecular weight although convenience prefers a
~ :
maximum of ~out 200,000, and most preferably of about
` 100 ,000 .
Thle four-component Eire retardant formulations
here used consist of:
a) ammonium sulfate,
:
18,328-F ~5- ~
,,, , . .. . . , . _ .. .. ... ., .. ..... , .. ., ... . . . ~ .. ....... . .... . .. ~ . ..
:
'7~
b) boric acid, an(l
c) two components selectecl from -the group consistiny
oE zinc halide, alkali metal dichrornate,
diammonium phosphate and alkali me-tal tetraborate.
Preferred ~inc ha)ides are zinc chloride and zinc bromide
with zinc chloride especially preferred. Preferred
alkali metal dichromates include sodi~l and potassiwm
dichromate with sodium dichromate especially preferred.
Preferred alkali metal tetraborates include sodium and
potassium tetraborate with sodium tetrabora-te especially
preferred. Any suitable formulation of these ma-terials
can be used but preferred formulations consist of ammonium
sulfate, boric acid, zinc chloride and sodium dichromate~
Most preferred formula~iuns consist of, by weight:
a) 32 to about 38 percent ammonium sulfate,
based on nitroyen and sulfur,
b) 23 to about 27 percent boric acid, based
on boron,
c) 32 to about 38 percent zinc chloride, based
on zinc, and
d~ 3 to about 7 percent sodium dichromate.
The respective concen-trations of polyalkylene-
polyamine and fire retardant formulation in the composition
of this invention can vary widely, the exact amounts of
each depending upon the substrate and the degree of both
fire retardancy and hygroscopicity suppression desired.
A polyalkylenepolyamine concentration of at least abou-t
2 weight percent, and preferably of about 5 weight percent~
is generally satis~actory. A maximum polyalkylenepolyamine
concentration o about 50 weight percent, and preferably
'
18,3~8-F -~_
: : . .
5~7~i
oE about ~0 w~.:igh-t percen-t, i.s used for economic reason~.
Of course, the remaininy weigh-t pexcents consist of
the fire retardant formulati.on, i.e., a minlmum of about 50
weiyht percent, and preferably about 80 weiyht pe.rcent, and
a maximum of ab~ut 98 weiyht percent, and preferably about
95 weight percent~ respective].y.
The composi-tion of t:his inven-tion is applied
to a cellulos.ic substrate in any convent.ional manner,
e.g~, spraying, painting, dipping, roll coating, reverse
roll coating~ pressure or vacuum treating, precipitation
on fiber slurries or impregnation. Typically, the
composition is dissolved in an aqueous medium which is
then applied to the cellulosic substrate. Sufficient
composition is generally dissolved to form an aqueous
solution having a concentration of at least about 5 weight
percent, and preferably about 10 weight percent, solids
basis. A maximum aqueous concentration of about 50 weight
percent, and preferably of about 20 weight percent, is
used because of both economics and the composition's
general solubility. The aqueous medium can be water
per se or can be an aqueous solution or dispersion
comprising other materials, such as pigments and sealers.
The dissolved, aqueous composition is generally applied
to the substrat~ in an amount sufficient to either thoroughly :~
wet the surface of the substrate~or thoroughly impregl~ate
the ~ubstrate, depending upon the method of application
and the degree of protection desired. As regards surface
~:
application, on a solids basis, the substrate is usually
: contacted with at least about 0.005 pound (2.3 g.), and
preferaoly of a :out 0.01 pound ~4.5 g.)~ of composition per
''
:
18,328-F -7-
.. .. ... .. _.. _ _~.. _._, ___ _ _ . _.. . . .. ...... ... . .. ...... . . . .. ... ........ . .
~ .
. :
~5~
square foot (0~093 m.2) of substra-te surface. Prac-tical
considerations, such as economy, etc., are the only limita-tions
upon the maximum amount of co~lposition that is con-tacted
with the substrate, although convenience prefers about
O.OS pound (23 g.), and most preferably about 0.03 pound
(13.6 g.), oE composition per square foo-t (0.093 m?) of
substrate surface. Regarding imprec3ncltion of the substrate,
again on a ~olids basis, the su~s-tra-te is usually impregnated
with the composition to at least about 5 weight percent and
preferably to about 10 weiyht percent of the substrate's
untrea-ted weight. Similar -to the surface application,
practical considerations are the only limitations upon the
maximum amount of composition that can be impregnated into
the substrate, although convenience prefers impregnating
with the composition to a maximum of about 70 weight percent,
and most preferably to a maximum of 50 weight percent, of
the substrate's untreated weight. After application, the
treated substrate is normally dried at elevated temperatures
to remove the solvent (water).
"Cellulosic s~strates" include wood, wood
composites, wood-derived products and combinations thereof.
Any cellulosic substrate capable of receiving an application
of an aqueous composition of polyalkylenepolyamine and
ire retardant formulation can be used in the practice
o this invention. Typical examples include: wood,
such as pine, cedar or oak; wood composites, such
as particle and fiberboard and plywood; and wood-derived
products, such as veneer and paper; and combinations
thereof,~such as paper-coated hardboard and particle
board, or veneer-surfaced particle board.
:
18,328-F ~ -8-
.
~5~6
The Eollowing examples ;llus-trate the lnvention.
Each control and example were conducted in duplicate, and
unless o-therwise notecl all parts and percentages are by
weight~
Control A:
Individual componen-ts (which were subsequently
combined in the Eollowing embodiments) were evaluated as
follows:
Three samples each oE PEI 600 (branched
polyethylenimine havin~ a number average molecular weight
of from 40,000 to 60,000),fire-retardant formulation Type D
(described by the American Wood Preservers1 Association
Standard P10-68 as 35 percent zinc chloride, 35 percent
ammonium sulfate, 25 percent boric acid and 5 percent
sodium dichromate), and untreated, air dry, ponderosa
pine wafers were individually exposed to relative humidities
of 66, 75 and 93 percent. The samples were exposed
to equilibrium and subsequently analyzed for moisture
gain (moisture reyain with respect to the treated wafer)
in percent of material weight. The results are hereinafter
tabulated.
Example 1:
PEI 600 and Type D were formulated into a
composition comprising 15 parts by weight PEI 600 and 85
::
~25 parts by weight Type D. Three comparable samples of this
composition~were individually exposed to varying relative
humidlties per Control A and subsequently analyzed for
:: :
~ ~ moisture gain. The results are also hereinafter tabulated~
.
18,328-F -9~
Control B:
Type D was indlvidually diluted to bo-th 10
and 15 percent by weight (solids basis) aqueous solutions
ancl each solu-tion was individually applied by vacuum treat-
ment -to six, oven-dried~ untreated ponderosa pine wa~ers.
The wafers were air driecl for 24 hours and then dried
in a constant temperature oven to less than 1 percent
water con-tent. I'he wafers were then indlviclually e~posed
to -the relative humidities per Control A and sllbsequently
analyzed for mois-ture regain. Again, the resul-ts are
hereinafter tabulated.
Example 2:
, Control B was repeated excep-t that the six,
oven-dried ponderosa pine wafers were individually
treated with 10 and 15 percent by weight, solids basis,
aqueous solutions of the composition o~ Fxample 1. The
results are tabulated below.
18,328-F ~ -10-
~l~S~6
o~ r~
~') ~ 1~ r; ~)
~:1
~t)
~ " 1 ~ o ~ r` r; ~) Ci~ O 3
cn ~ r--l ~r r~ 1 r--l ~1
r-l r-l p h
~n o r~ r- P 4
~r . - -
u~ ~ o ~
~; ~ ~ ~ ~r ~r o
f l~ r~ > rc~
W ~)
~o
_ H t~
u~ cou~ In 1~ ~ ~, h
~Ll ~D . .. . ~
H a ~r~ r~ O O n ~
o~ ~r--l f~
n I I I I I
H ~ rd
~: u~ ,1 o~ r~ ~ o E~
~ Il~) ~ ~ r l
5: i` O ~D Lr) t~ ~ ra h
1~ Ll~ r~ ) r-l r~l r~ rd
~ ~1
r-l e~ ') O C~
E-~ ~J .. .. ~ .,
1~1 ~j Ll~ r~ a) O
~3 ~1 ~
~4 E~ O ' '
Z 1~ rd
H 00In t` ~ ~ O ~
~ a ~ 0 ~
_ o\~ Lt~r--l r--I ~ ~ Ul r4
r~l ~
m In ~
. ~ h
i ~ U~ r-l O ~
~D ~ r~J r-lr-l r-lr-l r~ rd ~J
r~ r
O ~ o ~ U~ r~
1 ~ n ~ co oo (D a
~rr--I r-lr--I r~l Q~ ~ r l
X u~ r--l
3 IJ
~1) cO 1~ 1~ r~l ~1 0
P~ r~ l r--¦ ~ 41
O
~1 r-l -I ~I S-lh
r J .~) O
r ~ O ~ ~ 0
r l O ~ a o ~~ a ~ ~ O r--I rl S l
h ~ O 11) a)
(U 1~1~1 1~1 ¢1 E~l ~ ~ ~r~ U~
~ H 1~ 4 H ~ H-~I r
1 (D r~l ~ r--~ 1 0 ~ r ~ r
O r--I O ~ O r--~ ) r l ~; U
~ QI ~ h
O ~ : 0 X O 3~
C) ~ V ~ C.) ~ r l t`~l ~1 ~ Il'~ W
, :,: : :
18,328-~F ~
: ~ - . : . . :
The results oE Control A demor1strake -that both
PEI 600 and Type D are hygroscopic materials, e.g., at
66 percent relative humidi-ty, PEI 600 absorbed water
vapor to 62 percent of i-ts original clry weight.
!he an-ticipated clata of Example l (and similarl~
of Control B and Example 2) was computed by multiplying
the moisture gain of PEI 600 by O.lS and the moisture
gain of Type D by 0.85, both at the same given humidity,
and-then summing the products. For example, at 66 percent
relative humidity, the calculation is:
PEI 600: 62 x 0.15 = 10
TYPE D : 41 x 0.85 = 34
ANT. PEI 600/TYPE D: 44
The percent difference data was calculated, of course, by
subtracting the actual data from the anticipated data
and dividing the difEerence by the latter, i.e., at
66 percent relative humidity, 44 - l9 - 25, 25 . 44 = 56.8
This Example l data demonstrates the profound and un-
expected effect PEI 600 has on suppressing the hygroscopicity
of Type D.
The Control B data demonstrates that the hygro-
scopicity of Type D is suppressed upon its application
to a wood substrate.
In each ins-tance, the results of Example 2
shows an improved hygroscopicity suppression of Type D
as compared to the reported results of Control B.
,
'
!
1~/328-F -12- ~
::. . - . ,' , , :
