CA2159165C - Intumescent silicone rubber composition - Google Patents
Intumescent silicone rubber composition Download PDFInfo
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- CA2159165C CA2159165C CA 2159165 CA2159165A CA2159165C CA 2159165 C CA2159165 C CA 2159165C CA 2159165 CA2159165 CA 2159165 CA 2159165 A CA2159165 A CA 2159165A CA 2159165 C CA2159165 C CA 2159165C
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- 239000000203 mixture Substances 0.000 title claims abstract description 119
- 229920002379 silicone rubber Polymers 0.000 title claims abstract description 16
- 239000004945 silicone rubber Substances 0.000 title abstract description 4
- 229910052910 alkali metal silicate Inorganic materials 0.000 claims abstract description 11
- 239000011230 binding agent Substances 0.000 claims abstract description 11
- 239000000463 material Substances 0.000 claims abstract description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 26
- 239000010439 graphite Substances 0.000 claims description 26
- 229910002804 graphite Inorganic materials 0.000 claims description 26
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 13
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 10
- 239000004115 Sodium Silicate Substances 0.000 claims description 9
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 9
- 150000002009 diols Chemical class 0.000 claims description 8
- 239000004205 dimethyl polysiloxane Substances 0.000 claims description 7
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 claims description 7
- -1 polydimethylsiloxane Polymers 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 6
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 claims description 4
- 229920001971 elastomer Polymers 0.000 claims description 4
- 239000000806 elastomer Substances 0.000 claims description 3
- 239000010445 mica Substances 0.000 claims description 3
- 229910052618 mica group Inorganic materials 0.000 claims description 3
- 239000010455 vermiculite Substances 0.000 claims description 3
- 229910052902 vermiculite Inorganic materials 0.000 claims description 3
- 235000019354 vermiculite Nutrition 0.000 claims description 3
- GDVKFRBCXAPAQJ-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O GDVKFRBCXAPAQJ-UHFFFAOYSA-A 0.000 claims description 2
- 229910001701 hydrotalcite Inorganic materials 0.000 claims description 2
- 229960001545 hydrotalcite Drugs 0.000 claims description 2
- 239000010451 perlite Substances 0.000 claims description 2
- 235000019362 perlite Nutrition 0.000 claims description 2
- 239000007770 graphite material Substances 0.000 claims 6
- 238000010438 heat treatment Methods 0.000 claims 2
- 239000002131 composite material Substances 0.000 claims 1
- 229910052914 metal silicate Inorganic materials 0.000 claims 1
- 238000009472 formulation Methods 0.000 description 33
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- 239000003513 alkali Substances 0.000 description 4
- 229920001296 polysiloxane Polymers 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 239000002585 base Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 150000004760 silicates Chemical class 0.000 description 3
- 230000003628 erosive effect Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 229920000915 polyvinyl chloride Polymers 0.000 description 2
- 239000004800 polyvinyl chloride Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 241000134426 Ceratopogonidae Species 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical class [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910021626 Tin(II) chloride Inorganic materials 0.000 description 1
- UKLDJPRMSDWDSL-UHFFFAOYSA-L [dibutyl(dodecanoyloxy)stannyl] dodecanoate Chemical compound CCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCC UKLDJPRMSDWDSL-UHFFFAOYSA-L 0.000 description 1
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical class O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 1
- 229910021538 borax Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000012975 dibutyltin dilaurate Substances 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000011067 equilibration Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000013008 moisture curing Methods 0.000 description 1
- 125000005375 organosiloxane group Chemical group 0.000 description 1
- 125000005646 oximino group Chemical group 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- 238000004073 vulcanization Methods 0.000 description 1
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- Compositions Of Macromolecular Compounds (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Sealing Material Composition (AREA)
Abstract
An intumescent silicone rubber composition is provided having an expandable intumescent material present in the composition by up to 20% by weight, a polyorganosiloxane oil present in an amount from about 10% to about 40% by weight of the composition, a hydrated alkali metal silicate present in an amount: of up to 80% by weight of the composition and a silicone elastomer binder present in an amount from about 4%
to about 30% by weight of the composition. The result is a very effective and relatively inexpensive composition which when used as firestop material around combustible pipe, such as PVC or ABS, readily meets the test criteria set forth under ASTM Standard E-814.
to about 30% by weight of the composition. The result is a very effective and relatively inexpensive composition which when used as firestop material around combustible pipe, such as PVC or ABS, readily meets the test criteria set forth under ASTM Standard E-814.
Description
_219165 INTUMESCENT SILICONE RUBBER COMPOSITION
The present invention relates to an intumescent composition and more particularly relates to a intumescent composition useful as a fire stop material which includes a polyorganosiloxane oil compound.
The present invention is useful to seal combustible pipes passing through fire separations when exposed to fire conditions. As the pipe softens and collapses, the rubber 7.0 based compositions (in the form of a collar) must rapidly intumescE~ to fill the void and prevent the spread of the fire to the unexposed side of the fire separation. Typically, the intumesce:nt composition is encased within a metal collar so that the intumescence is directed towards the pipe. The expanded composition must also resist the effects of erosion due to the turbulence and positive pressure of the fire for the duration of the rating of the assembly, typically a one or two hour period.
20 Generally speaking, the phenomenon of intumescence using silicone rubber matrices is already known and has been set forth in the prior art. A typical reference is U.S. Patent No. 5,047,449 issued to Pastureau, September 10, 1991, for a fire protection material. The patentee provides a intumescent composition which includes a silicone elastomer (RTV-121) a reinforcing charge of a metal oxide, borax and an insulative charge of mica or vermiculite.
U.S. Patent No. 5,262,454, issued to Leroux et al., 30 November 16, 1993, teaches a flame resistant polyorganosiloxane compound containing hollow glass balls and intumescent compound. The composition indicated in the disclosure includes the use of a relatively high percentage of hollow glass balls containing a non-combustible gas.
'~1~9165 Further prior art in this area of technology includes European Patent Application 508751-A2, which teaches the use of a sodium silicate and expandable graphite in an aqueous system with a polyvinyl alcohol binder.
To effectively meet fire, temperature and hose stream requirements of ASTM Standard E-814, the release and amplitude of the intumescence must be controlled and limited. The use of a silicone binder has been generally considered advantageous in view of the fact that there is no production of toxic pyrolysis products in the case of fire.
Further prior art related to this art is Japanese Patent publications JP 0415169 and JP 04145178. These references generally refer to the combination of sodium silicate and foamed o:r sponge-like graphite powders for use in heat resistant coatings. Silicone and aluminum phosphate compounds have also been set forth as suitable binders for use in :intumesce:nt compositions.
2 ~0 Having regard to the intumescent compositions that have been previously set forth in the prior art, there exists a need for an intumescent composition which when used as firestop material around combustible pipe, such as PVC or ABS, readily meets the test criteria set forth under ASTM Standard E-814.
An _'Lntumescent composition comprising: an expandable intumescent material other than a hydrated alkali metal silicate for expanding the composition being present in an 30 amount up to 20% by weight of said composition; a poly-organosiloxane oil compound present in an amount from about 10~
to about 40o by weight of the composition; a hydrated alkali metal silicate present in an amount of up to 80~ by weight of the compcrsition; and a silicone elastomer binder present in an amount from about 4~ to about 30%, by weight of the composition.
The composition of the invention was prepared by incorporating the intumescent materials into the silicone binder and more specifically the silicone elastomer base, by means of a planetary type mixer with vacuum capability, the latter being well known to those skilled in the art.
1. 0 The silicone elastomer, as an example, was prepared by polyconde:nsation of polydimethylsiloxane diol with a moisture cure crop>slinker, such as methyl oximino silane, and further with the trace addition of a catalyst which is typically a tin salt, an example of which is dibutyl tin dilaurate. A poly-dimethyls~iloxane diol, preferably with a viscosity of 50 to 80 Pa.s (50,000 to 80,000 cps) at 25°C, was blended with a non-reactive polydimethylsiloxane oil terminally end-blocked with methyl groups, preferably having a viscosity of 1 Pa.s (1,000 20 cps) at 25°C. The oil enables relatively higher charges of alkali metal silicate to be accommodated and additionally softens -the elastomer resulting in a greater free volume expansion of the composition at 250°C.
Generally speaking, the hydrated alkali metal silicate, preferably sodium silicate, should be in the form of a powder rather than a granular form so that the intumesced composition has a homogeneous foam structure. The silica to alkali weight ratio may be between about 2.00 and about 3.75:1.
As has been well recognized in this art, intumesced sodium silicate is resistant to erosion and eventually hardens under furnace or fire conditions. The refractoriness of the char that results once the product has been exposed to fire or ~l~~lf 5 furnace c:onditions, also increase with the increase of the silica to alkali ratio. For the purposes of illustration, BRITESIL~ C24 with an intermediate silica to alkali weight ratio of 2.4:1 was used.
In a preferred form, the expandable intumescent material comprises expandable graphite having a rate of volume expansion of 80:1 and ASBURY CARBONS # 3335 was used.
to Reference will now be made to the accompanying drawings illustrating preferred embodiments, and in which:
Figure 1 is a graphical representation of the effect of the fraction percentage of oil in the composition and its accompanying effect on the free volume expansion of the product.
Having just thus generally described the invention, reference will now be made to specific examples to further 20 illustrate the invention so that a greater understanding can be obtained.
Table 1 tabulates the results of test of various compositions in terms of their resulting free volume expansion at 250°C. The free volume expansion ratio is calculated by dividing 'the final volume of the intumesced composition after thirty minutes of exposure to 250°C in a muffle furnace with 3~0 subsequent equilibration to ambient temperature as compared to the initial volume, i.e.
FREE VOLUME EXPANSION RATIO = FINAL VOLUME (23°C) INITIAL VOLUME (23°C) ~~~9~~~
s (~ O 07 ~ N N stV
N ~
m ~ N N V
N
N N ~ ~ ~ M ~L
I
01 O N N ~ ~ ~ N
N
N N '~t~ ~ M
S c00r N N V O ~ O
N
M N r N N ~ N V
N
O OD
M ~ N N ~ V f~
N c00~ N N ~ N
r- 07 a O N
~ O~ N N V ~ p O
O Z
J z ~n ooC
Z
- a CD F- a x S (D OyN N V ~ ~ CO
- W W
.
CL
O
S ~ ~ J p~ O
N N V V O N
O N st 7 W
c00 ~ O a0 ~ td N
N ~f C
N
t00~ N N ~ ~ V '3 M ~ ~ N N ~ ~ M N
Q O O t0 O 00 ' O N .- O> N N V ~ . N
N N ~ N N V ~ .. CO
O .
M
00 ~ . ~ N N ~ N O
- i N
I
O .
O O ~ N N ~ V N
N
L
O
Z ~ M
d1 N N ~ 'M M I
tC ptm p = ~ ~ c ~
a a m ~
~
0 o d c O ~ ~
r tn _N .Yd f/iO L t U m '~v ~ - I
0 0 - _ L j o ~E ~ o D D O Viin U tLU Q C7 C7 N
~1~9165 A comparison of the formulations 0191, 0183 and 0202 illustrates that at 250 ° C the absence of graphite or a decrease in the level of sodium silicate from 195 to 98 parts does not result in any substantial difference in free volume expansion from 2.5 to 2.7.
A decrease in the silicate content in formulation 0202 produces ~an unacceptably weak and friable char at temperatures greater than 250°C. The absence of graphite in formulation l0 0183 results in unacceptable shrinkage of the intumescent product at temperatures higher than about 250°C.
Comparing formulations 0191, 0491, 0492, 1181 and 1361 shows that by increasing the siloxane oil versus the diol content and keeping the sodium silicate/ graphite quantities constant, a marked increase in free volume expansion at 250°C
can be realized i.e. from 2.0 to 10Ø
For the purposes of closing a 50 mm polyvinyl chloride 2o pipe under ASTM Standard E-814, manufacturers typically prescribe a single nominal 6.4 mm thick intumescent strip 50 mm in width to be wrapped around the pipe contained within a metal collar. A calculated valume expansion of about 200%, i.e. a free volume expansion ratio of 3, would just seal the opening. A volume expansion of at least 300 to 400% is more desirable so as to provide not only a safety factor but also a firmer intumesced matrix in a constrained environment such as a metal collar. Formulation 0491 with a free volume expansion ratio of 4.8 (380%) is generally preferred to fulfil 30 this requirement.
Formulation 0762 shows that by increasing the silicate content, i~hus the strength of the char, while maintaining the oil to dio~l ratio in formulation 0491, a comparable free volume ~1~916~
expansion of 4.9 can be realized. At temperatures greater than 250 ° C, the strength of the char is superior to that of formula-tion 0491. Unfortunately, the high silicate content of formulation 0762 renders the composition difficult to mix with a standard planetary mixer and may produce temperatures that could cause premature gelling.
Formulation 0481 produced a non-vulcanizing, non-tacky putty formulation while maintaining the siloxane, sodium silicate and graphite contents constant in formulation 0491.
The putty material was found to slough off at elevated temperatures and in direct flame source. It was believed that vulcanization of the siloxane base is required for the product to intumesce.
Figure 1 shows a graphical representation of the relationship between the silicone base, in terms of the percentage oil content and the free volume expansion based on formulations 0191, 0491, 0492, 1181 and 1361. In addition, Table 2 illustrates the free volume expansion for various formulations, the contents of which are tabulated in Table 1 for temperatures from 250°C to 575°C as the composition intumesces in stages and at direct exposure at 575°C.
The addition of formulation 0201 in Table 1 illustrates that with the removal of the oil and replacement with a lower viscosity diol (20 Pa.s), a free volume expansion of only 1.8 can be achieved. Formulation 1081 shows that the replacement of the silicate in formulation 0491 with a non-intumescent 3n filler, an example of which is chalk or limestone, results in the expansion ratio dropping from 4.8 to 1.7.
It wall be readily appreciated that an important feature of the present invention is that the composition provides a ~1~9165 firm char matrix regardless of whether it intumesces slowly or in stager when shielded from the flame source or rapidly when in directs contact with the flame source. Formulation 0491 is the most desirable composition in this regard.
Basead on the information in Table 2, desirable features in the final intumesced product are achieved by those formulations having an oil content greater than about 20.8% by weight and more desirably 30.2% by weight.
Formula % Oil FREE VOLUME EXPANSION RATIO
250°C -~ 575°C 575°C (direct) 1361 4.7 2.0 -> 3.8priable char)3.6 (rtgld char) t. 0 0191 20.8 2.7 -~ 4.2(iriabie 3.4 (rigid char) char) 0491 30.2 4.8 -~ 4.3(rigid char)4.2 (rigid char) 1181 35.9 10.0 --~5.0(rigid char)6.1 (rigid char) 1265 33.3 9.7 ~ 1.5(rlgid~char)less than -~ starting volume 1311 30.2 7.7 -~ 17.0(tr(able 13.4 (friable char) char) 1362 27.7 4.8 -~ 9.7(tr(able 9.4 (triabia char) char) 1364 30.2 9.0 -~ 7.0(rlgld char)6.7 (rigid char) 1401 30.2 9.1 ~ 14.9(weak char) 10.3 (weak char) 1711 22.8 3.8 -->5.4(rigid char)5.7 (rigid char) 2201 24.2 4.2 -->3.7(rigid char)2.1 (rigid char) 2062 11.4 5.4 -~ (weak char) > 5.4 (weak > char) 5.4 Table 2 further shows the influence of the graphite in the 0491 formulation. Formulation 1265 is identical to 0491 but without the graphite present and thus has a slightly higher percentage of oil. The absence of the graphite results in a 9.7 free 'volume expansion at 250°C which clearly exceeds that of 0491. It would appear therefore that the graphite is actually holding back the expansion of the silicate in 0491.
Its presence is necessary, however, to prevent a large shrink-back at higher temperatures. Formulation 1311 is identical to 0491 excE:pt that Asbury #3393 graphite is substituted for #3335. Asbury #3393 has a rate of volume expansion of 145:1 versus 80:1 for #3335. With the substitution of Asbury #3393 the free volume expansion at 250°C increases from 4.8 to 7.7, indicating that a higher expansion graphite may be warranted in formu:Lation 0491. However, we find that at elevated temperatures the expansion of the #3393 graphite exceeds that of the si:Licate and a friable char is produced. If the amount of #3335 graphite is doubled from the 9% in 0491, i.e. 1362, a friable product is also produced.
2 ~0 Formulations 1364 and 1401 increase the oil versus diol content in 0491 to that in 1181, in order to accommodate more C24 (about 47% by weight). As with formulation 0762 these compositions were difficult to mix but they expanded as much as formulation 1181 which had only 36.9% by weight of C24.
Formulation 1401 substituted #3393 graphite for #3335 and produced ~~ very weak char at 575°C, in relation to formulation 1311 which produced a friable char. It would appear therefore that the supper limit for the graphite is about 17% by weight 30 with a rage of volume expansion of no less than 80:1 and 9% by weight with a graphite having a rate of volume expansion of not greater than 145:1. It would appear therefore that the upper limit for the graphite will be roughly 17% by weight with a ~1~J~6~
rate of 'volume expansion of no less than 80:1 and no greater than 145:1.
Experiments have been done with two silicates having silica to alkali ratios above and below the Britesil~ C24, i.e.
2 and 3.:22 in hydrated and anhydrous forms. These silicates were directly substituted for C24 in the 0491 formulation. In hydrated form both these silicates intumesced in much the same way as the C24, with the 3.22 silicate having an even greater :~0 free volume expansion at 250°C. Both intumesced products, however, formed slightly weaker chars at 575°C than the C 24.
The anhydrous forms produced a 'punky' intumesced product at 250°C which became friable even when directly heated at 575°C.
BRITESIL~' C24 does not have an anhydrous equivalent. The silicate must therefore be hydrated (preferably about 18.5%
moisture content) to produce the desired product.
Formulation 1711 increased the C24 level to the maximum it could be wetted out. At 60% by weight, the composition was 2;o able to vulcanize but produced a product with poor rubber-like properties. The free volume expansion ratio at 250°C was 3.8 which i:: consistent with the data for an intumescent composition having 22.8% oil content. The free volume expansion ratio of 5.4 to 5.7 at 575°C regardless of whether it was heated directly or in stages, indicates that the expandable graphite has less of an influence on the char dimensions at high fill levels of C24. This is borne out by formulation 2201 where the graphite was not present and the char dimE~nsions at 575°C were superior to those found with 30 formulation 1265 with 40.5% parts by weight of C24.
Formulation 2062 produced a composition with 80 % by weight of hydrated granular sodium silicate Britesil~ ft24. The formulation had an oil content of 11.4% by weight and produced i i 11.
an intumescable product which had a very weak and porous char at 575°C.
Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
The expandable intumescent material is selected from the group of vermiculite, perlite, mica, expandable graphite, wermlandite, thamasite and hydrotalcite".
The present invention relates to an intumescent composition and more particularly relates to a intumescent composition useful as a fire stop material which includes a polyorganosiloxane oil compound.
The present invention is useful to seal combustible pipes passing through fire separations when exposed to fire conditions. As the pipe softens and collapses, the rubber 7.0 based compositions (in the form of a collar) must rapidly intumescE~ to fill the void and prevent the spread of the fire to the unexposed side of the fire separation. Typically, the intumesce:nt composition is encased within a metal collar so that the intumescence is directed towards the pipe. The expanded composition must also resist the effects of erosion due to the turbulence and positive pressure of the fire for the duration of the rating of the assembly, typically a one or two hour period.
20 Generally speaking, the phenomenon of intumescence using silicone rubber matrices is already known and has been set forth in the prior art. A typical reference is U.S. Patent No. 5,047,449 issued to Pastureau, September 10, 1991, for a fire protection material. The patentee provides a intumescent composition which includes a silicone elastomer (RTV-121) a reinforcing charge of a metal oxide, borax and an insulative charge of mica or vermiculite.
U.S. Patent No. 5,262,454, issued to Leroux et al., 30 November 16, 1993, teaches a flame resistant polyorganosiloxane compound containing hollow glass balls and intumescent compound. The composition indicated in the disclosure includes the use of a relatively high percentage of hollow glass balls containing a non-combustible gas.
'~1~9165 Further prior art in this area of technology includes European Patent Application 508751-A2, which teaches the use of a sodium silicate and expandable graphite in an aqueous system with a polyvinyl alcohol binder.
To effectively meet fire, temperature and hose stream requirements of ASTM Standard E-814, the release and amplitude of the intumescence must be controlled and limited. The use of a silicone binder has been generally considered advantageous in view of the fact that there is no production of toxic pyrolysis products in the case of fire.
Further prior art related to this art is Japanese Patent publications JP 0415169 and JP 04145178. These references generally refer to the combination of sodium silicate and foamed o:r sponge-like graphite powders for use in heat resistant coatings. Silicone and aluminum phosphate compounds have also been set forth as suitable binders for use in :intumesce:nt compositions.
2 ~0 Having regard to the intumescent compositions that have been previously set forth in the prior art, there exists a need for an intumescent composition which when used as firestop material around combustible pipe, such as PVC or ABS, readily meets the test criteria set forth under ASTM Standard E-814.
An _'Lntumescent composition comprising: an expandable intumescent material other than a hydrated alkali metal silicate for expanding the composition being present in an 30 amount up to 20% by weight of said composition; a poly-organosiloxane oil compound present in an amount from about 10~
to about 40o by weight of the composition; a hydrated alkali metal silicate present in an amount of up to 80~ by weight of the compcrsition; and a silicone elastomer binder present in an amount from about 4~ to about 30%, by weight of the composition.
The composition of the invention was prepared by incorporating the intumescent materials into the silicone binder and more specifically the silicone elastomer base, by means of a planetary type mixer with vacuum capability, the latter being well known to those skilled in the art.
1. 0 The silicone elastomer, as an example, was prepared by polyconde:nsation of polydimethylsiloxane diol with a moisture cure crop>slinker, such as methyl oximino silane, and further with the trace addition of a catalyst which is typically a tin salt, an example of which is dibutyl tin dilaurate. A poly-dimethyls~iloxane diol, preferably with a viscosity of 50 to 80 Pa.s (50,000 to 80,000 cps) at 25°C, was blended with a non-reactive polydimethylsiloxane oil terminally end-blocked with methyl groups, preferably having a viscosity of 1 Pa.s (1,000 20 cps) at 25°C. The oil enables relatively higher charges of alkali metal silicate to be accommodated and additionally softens -the elastomer resulting in a greater free volume expansion of the composition at 250°C.
Generally speaking, the hydrated alkali metal silicate, preferably sodium silicate, should be in the form of a powder rather than a granular form so that the intumesced composition has a homogeneous foam structure. The silica to alkali weight ratio may be between about 2.00 and about 3.75:1.
As has been well recognized in this art, intumesced sodium silicate is resistant to erosion and eventually hardens under furnace or fire conditions. The refractoriness of the char that results once the product has been exposed to fire or ~l~~lf 5 furnace c:onditions, also increase with the increase of the silica to alkali ratio. For the purposes of illustration, BRITESIL~ C24 with an intermediate silica to alkali weight ratio of 2.4:1 was used.
In a preferred form, the expandable intumescent material comprises expandable graphite having a rate of volume expansion of 80:1 and ASBURY CARBONS # 3335 was used.
to Reference will now be made to the accompanying drawings illustrating preferred embodiments, and in which:
Figure 1 is a graphical representation of the effect of the fraction percentage of oil in the composition and its accompanying effect on the free volume expansion of the product.
Having just thus generally described the invention, reference will now be made to specific examples to further 20 illustrate the invention so that a greater understanding can be obtained.
Table 1 tabulates the results of test of various compositions in terms of their resulting free volume expansion at 250°C. The free volume expansion ratio is calculated by dividing 'the final volume of the intumesced composition after thirty minutes of exposure to 250°C in a muffle furnace with 3~0 subsequent equilibration to ambient temperature as compared to the initial volume, i.e.
FREE VOLUME EXPANSION RATIO = FINAL VOLUME (23°C) INITIAL VOLUME (23°C) ~~~9~~~
s (~ O 07 ~ N N stV
N ~
m ~ N N V
N
N N ~ ~ ~ M ~L
I
01 O N N ~ ~ ~ N
N
N N '~t~ ~ M
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~1~9165 A comparison of the formulations 0191, 0183 and 0202 illustrates that at 250 ° C the absence of graphite or a decrease in the level of sodium silicate from 195 to 98 parts does not result in any substantial difference in free volume expansion from 2.5 to 2.7.
A decrease in the silicate content in formulation 0202 produces ~an unacceptably weak and friable char at temperatures greater than 250°C. The absence of graphite in formulation l0 0183 results in unacceptable shrinkage of the intumescent product at temperatures higher than about 250°C.
Comparing formulations 0191, 0491, 0492, 1181 and 1361 shows that by increasing the siloxane oil versus the diol content and keeping the sodium silicate/ graphite quantities constant, a marked increase in free volume expansion at 250°C
can be realized i.e. from 2.0 to 10Ø
For the purposes of closing a 50 mm polyvinyl chloride 2o pipe under ASTM Standard E-814, manufacturers typically prescribe a single nominal 6.4 mm thick intumescent strip 50 mm in width to be wrapped around the pipe contained within a metal collar. A calculated valume expansion of about 200%, i.e. a free volume expansion ratio of 3, would just seal the opening. A volume expansion of at least 300 to 400% is more desirable so as to provide not only a safety factor but also a firmer intumesced matrix in a constrained environment such as a metal collar. Formulation 0491 with a free volume expansion ratio of 4.8 (380%) is generally preferred to fulfil 30 this requirement.
Formulation 0762 shows that by increasing the silicate content, i~hus the strength of the char, while maintaining the oil to dio~l ratio in formulation 0491, a comparable free volume ~1~916~
expansion of 4.9 can be realized. At temperatures greater than 250 ° C, the strength of the char is superior to that of formula-tion 0491. Unfortunately, the high silicate content of formulation 0762 renders the composition difficult to mix with a standard planetary mixer and may produce temperatures that could cause premature gelling.
Formulation 0481 produced a non-vulcanizing, non-tacky putty formulation while maintaining the siloxane, sodium silicate and graphite contents constant in formulation 0491.
The putty material was found to slough off at elevated temperatures and in direct flame source. It was believed that vulcanization of the siloxane base is required for the product to intumesce.
Figure 1 shows a graphical representation of the relationship between the silicone base, in terms of the percentage oil content and the free volume expansion based on formulations 0191, 0491, 0492, 1181 and 1361. In addition, Table 2 illustrates the free volume expansion for various formulations, the contents of which are tabulated in Table 1 for temperatures from 250°C to 575°C as the composition intumesces in stages and at direct exposure at 575°C.
The addition of formulation 0201 in Table 1 illustrates that with the removal of the oil and replacement with a lower viscosity diol (20 Pa.s), a free volume expansion of only 1.8 can be achieved. Formulation 1081 shows that the replacement of the silicate in formulation 0491 with a non-intumescent 3n filler, an example of which is chalk or limestone, results in the expansion ratio dropping from 4.8 to 1.7.
It wall be readily appreciated that an important feature of the present invention is that the composition provides a ~1~9165 firm char matrix regardless of whether it intumesces slowly or in stager when shielded from the flame source or rapidly when in directs contact with the flame source. Formulation 0491 is the most desirable composition in this regard.
Basead on the information in Table 2, desirable features in the final intumesced product are achieved by those formulations having an oil content greater than about 20.8% by weight and more desirably 30.2% by weight.
Formula % Oil FREE VOLUME EXPANSION RATIO
250°C -~ 575°C 575°C (direct) 1361 4.7 2.0 -> 3.8priable char)3.6 (rtgld char) t. 0 0191 20.8 2.7 -~ 4.2(iriabie 3.4 (rigid char) char) 0491 30.2 4.8 -~ 4.3(rigid char)4.2 (rigid char) 1181 35.9 10.0 --~5.0(rigid char)6.1 (rigid char) 1265 33.3 9.7 ~ 1.5(rlgid~char)less than -~ starting volume 1311 30.2 7.7 -~ 17.0(tr(able 13.4 (friable char) char) 1362 27.7 4.8 -~ 9.7(tr(able 9.4 (triabia char) char) 1364 30.2 9.0 -~ 7.0(rlgld char)6.7 (rigid char) 1401 30.2 9.1 ~ 14.9(weak char) 10.3 (weak char) 1711 22.8 3.8 -->5.4(rigid char)5.7 (rigid char) 2201 24.2 4.2 -->3.7(rigid char)2.1 (rigid char) 2062 11.4 5.4 -~ (weak char) > 5.4 (weak > char) 5.4 Table 2 further shows the influence of the graphite in the 0491 formulation. Formulation 1265 is identical to 0491 but without the graphite present and thus has a slightly higher percentage of oil. The absence of the graphite results in a 9.7 free 'volume expansion at 250°C which clearly exceeds that of 0491. It would appear therefore that the graphite is actually holding back the expansion of the silicate in 0491.
Its presence is necessary, however, to prevent a large shrink-back at higher temperatures. Formulation 1311 is identical to 0491 excE:pt that Asbury #3393 graphite is substituted for #3335. Asbury #3393 has a rate of volume expansion of 145:1 versus 80:1 for #3335. With the substitution of Asbury #3393 the free volume expansion at 250°C increases from 4.8 to 7.7, indicating that a higher expansion graphite may be warranted in formu:Lation 0491. However, we find that at elevated temperatures the expansion of the #3393 graphite exceeds that of the si:Licate and a friable char is produced. If the amount of #3335 graphite is doubled from the 9% in 0491, i.e. 1362, a friable product is also produced.
2 ~0 Formulations 1364 and 1401 increase the oil versus diol content in 0491 to that in 1181, in order to accommodate more C24 (about 47% by weight). As with formulation 0762 these compositions were difficult to mix but they expanded as much as formulation 1181 which had only 36.9% by weight of C24.
Formulation 1401 substituted #3393 graphite for #3335 and produced ~~ very weak char at 575°C, in relation to formulation 1311 which produced a friable char. It would appear therefore that the supper limit for the graphite is about 17% by weight 30 with a rage of volume expansion of no less than 80:1 and 9% by weight with a graphite having a rate of volume expansion of not greater than 145:1. It would appear therefore that the upper limit for the graphite will be roughly 17% by weight with a ~1~J~6~
rate of 'volume expansion of no less than 80:1 and no greater than 145:1.
Experiments have been done with two silicates having silica to alkali ratios above and below the Britesil~ C24, i.e.
2 and 3.:22 in hydrated and anhydrous forms. These silicates were directly substituted for C24 in the 0491 formulation. In hydrated form both these silicates intumesced in much the same way as the C24, with the 3.22 silicate having an even greater :~0 free volume expansion at 250°C. Both intumesced products, however, formed slightly weaker chars at 575°C than the C 24.
The anhydrous forms produced a 'punky' intumesced product at 250°C which became friable even when directly heated at 575°C.
BRITESIL~' C24 does not have an anhydrous equivalent. The silicate must therefore be hydrated (preferably about 18.5%
moisture content) to produce the desired product.
Formulation 1711 increased the C24 level to the maximum it could be wetted out. At 60% by weight, the composition was 2;o able to vulcanize but produced a product with poor rubber-like properties. The free volume expansion ratio at 250°C was 3.8 which i:: consistent with the data for an intumescent composition having 22.8% oil content. The free volume expansion ratio of 5.4 to 5.7 at 575°C regardless of whether it was heated directly or in stages, indicates that the expandable graphite has less of an influence on the char dimensions at high fill levels of C24. This is borne out by formulation 2201 where the graphite was not present and the char dimE~nsions at 575°C were superior to those found with 30 formulation 1265 with 40.5% parts by weight of C24.
Formulation 2062 produced a composition with 80 % by weight of hydrated granular sodium silicate Britesil~ ft24. The formulation had an oil content of 11.4% by weight and produced i i 11.
an intumescable product which had a very weak and porous char at 575°C.
Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
The expandable intumescent material is selected from the group of vermiculite, perlite, mica, expandable graphite, wermlandite, thamasite and hydrotalcite".
Claims (25)
1. An intumescent composition comprising:
an expandable intumescent graphite material for expanding said composition being present in an amount up to 20%
by weight of said composition;
a polyorganosiloxane oil compound present in an amount from about 10% to about 40% by weight of said composition;
a hydrated alkali metal silicate present in an amount of up to 80% by weight of said composition; and a silicone elastomer binder present in an amount from about 4% to about 30%, by weight of said composition.
an expandable intumescent graphite material for expanding said composition being present in an amount up to 20%
by weight of said composition;
a polyorganosiloxane oil compound present in an amount from about 10% to about 40% by weight of said composition;
a hydrated alkali metal silicate present in an amount of up to 80% by weight of said composition; and a silicone elastomer binder present in an amount from about 4% to about 30%, by weight of said composition.
2. The composition as set forth in claim 1, wherein said polyorganosiloxane oil comprises polydimethylsiloxane oil.
3. The composition as set forth in claim 1, wherein said silicone elastomer binder comprises polydimethylsiloxane diol.
4. The composition as set forth in claim 1, wherein said expandable intumescent material is selected from the group comprising vermiculite, perlite, mica, expandable graphite wermlandite, thanmasite, and hydrotalcite.
5. The composition as set forth in claim 1, wherein said graphite material has a rate of volume expansion of between about 80:1 and about 145:1.
6. The composition as set forth in claim 5, wherein said expandable graphite material is present in said composition in an amount of about 5 to 17% by weight of said composition.
7. The composition as set forth in claim 6, wherein said expandable graphite material is present in said composition in an amount of 9% by weight of said composition.
8. The composition as set forth in claim 1, wherein said polyorganosiloxane oil is present in an amount of about 20 to 35%
by weight of said composition.
by weight of said composition.
9. The composition as set forth in claim 1, wherein said hydrated alkali metal silicate is present in an amount of 36 to 47% by weight of said composition.
10. The composition as set forth in claim 9, wherein said hydrated alkali metal silicate has a moisture content of about 18.5%.
11. The composition as set forth in claim 9, wherein said hydrated alkali metal silicate comprises a sodium silicate.
12. The composition as set forth in claim 1, wherein said polyorganosiloxane oil comprises an end blocked trimethyl siloxane oil.
13. The composition as set forth in claim 1 wherein said silicone elastomer binder comprises polydimethylsiloxane diol.
14. An intumescent fire stop composition comprising:
a hydrated metal silicate expandable intumescent in an amount up to 80% by weight of said composition, said silicate being subject to shrink-back at temperatures above 500°C;
a second expandable intumescent, not subject to shrink-back, in an amount up to 20% by weight of said composition and sufficient to prevent shrink-back;
a silicone elastomer in an effective binding amount from about 4 to about 30% by weight of said composition; and a polyorganosiloxane oil softener in an amount from about 10 to about 40% by weight of said composition, with higher amounts of oil softener being used with higher amounts of silicate.
a hydrated metal silicate expandable intumescent in an amount up to 80% by weight of said composition, said silicate being subject to shrink-back at temperatures above 500°C;
a second expandable intumescent, not subject to shrink-back, in an amount up to 20% by weight of said composition and sufficient to prevent shrink-back;
a silicone elastomer in an effective binding amount from about 4 to about 30% by weight of said composition; and a polyorganosiloxane oil softener in an amount from about 10 to about 40% by weight of said composition, with higher amounts of oil softener being used with higher amounts of silicate.
15. The composition as set forth in claim 14, wherein said hydrated alkali metal silicate expandable intumescent is in an amount ranging from about 22 up to about 60% by weight of said composition.
16. The composition as set forth in claim 14, wherein said second expandable intumescent comprises graphite.
17. The composition as set forth in claim 16, wherein said second expandable intumescent is in an amount within the range of about 5 up to about 17% by weight of said composition.
18. The composition as set forth in claim 14, wherein said silicone elastomer is present in an amount from about 8 to about 30% by weight.
19. The composition as set forth in claim 14, wherein said polyorganosiloxane oil softener is in an amount from about
20 to about 40% by weight of said composition.
20. The composition as set forth in claim 18, wherein said polyorganosiloxane oil softener is selected to soften the elastomer and permit the desired expansion.
20. The composition as set forth in claim 18, wherein said polyorganosiloxane oil softener is selected to soften the elastomer and permit the desired expansion.
21. An intumescent composition which expands and forms a composite char on heating, comprising:
an expandable intumescent graphite material being present in an amount up to 20% by weight of said composition;
a polyorganosiloxane oil compound present in an amount from about l0% to about 40% by weight of said composition:
a hydrated alkali metal silicate present in an amount of up to 80% by weight of said composition;
a silicone elastomer binder present in an amount from about 4% to about 30% by weight of said composition; and a sufficient amount of said oil being present to soften said elastomer and accommodate the expansion, said intumescent graphite material being present in an amount effective to reduce shrink-back due to the silicate on heating to form char.
an expandable intumescent graphite material being present in an amount up to 20% by weight of said composition;
a polyorganosiloxane oil compound present in an amount from about l0% to about 40% by weight of said composition:
a hydrated alkali metal silicate present in an amount of up to 80% by weight of said composition;
a silicone elastomer binder present in an amount from about 4% to about 30% by weight of said composition; and a sufficient amount of said oil being present to soften said elastomer and accommodate the expansion, said intumescent graphite material being present in an amount effective to reduce shrink-back due to the silicate on heating to form char.
22. The composition as set forth in claim 21, wherein said polyorganosiloxane oil comprises polydimethylsiloxane oil.
23. The composition as set forth in claim 21, wherein said silicone elastomer binder comprises polydimethylsiloxane diol.
24. The composition as set forth in claim 21, wherein said graphite has a rate of volume expansion of between about 80:1 and about 145:1.
25. The composition as set forth in claim 24, wherein said expandable graphite is present in said composition in an amount of about 5 to 17% by weight of said composition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/328,283 US5508321A (en) | 1994-06-15 | 1994-10-05 | Intumescent silicone rubber composition |
| US08/328,283 | 1994-10-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2159165A1 CA2159165A1 (en) | 1996-04-06 |
| CA2159165C true CA2159165C (en) | 2003-05-13 |
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ID=23280327
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2159165 Expired - Lifetime CA2159165C (en) | 1994-10-05 | 1995-09-26 | Intumescent silicone rubber composition |
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| Country | Link |
|---|---|
| CA (1) | CA2159165C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016153993A1 (en) * | 2015-03-20 | 2016-09-29 | Kongsberg Actuation Systems Ii, Inc. | Flame resistant hose assembly and method therefore |
-
1995
- 1995-09-26 CA CA 2159165 patent/CA2159165C/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016153993A1 (en) * | 2015-03-20 | 2016-09-29 | Kongsberg Actuation Systems Ii, Inc. | Flame resistant hose assembly and method therefore |
| US10190706B2 (en) | 2015-03-20 | 2019-01-29 | Kongsberg Actuation System II, Inc. | Flame resistant hose assembly and method therefore |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2159165A1 (en) | 1996-04-06 |
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