the present invention relates to a fireproof seal consisting of an elastomer , vulcanizing agents , a softening agent with a relatively high aromatic content for compatibility to provide softness , a flame retardant plasticizer , fillers for both flame retardant and mechanical properties , and an alkali metal silicate intumescent . if a sponge fireproof material is desired , a combination of blowing agents such as azocarbonamide and benzenesulfonyl hydrazide is incorporated to generate the sponge during processing . in addition , calcium sodium metaphosphate can be added to improve green strength if necessary . the uniqueness of this invention lies in the use of an alkali metal silicate , e . g ., hydrated sodium silicate , as the intumescent in combination with a softening oil , particularly , a naphthenic oil . this combination provides the excellent fire and hose stream resistance performance and the compressibility required in the construction industry . ingredients used to produce compressible fireproof seals of the invention as will be shown in the following examples are listed and described in table i . table i______________________________________ingredient supplier description______________________________________neoprene whv - 100 dupont flame retardant poly - chloroprene rubber having a mooney viscosity in the medium - high range . butachlor mh - 30 a . schulman flame retardant poly - chloroprene rubber having mooney viscosity in the high range . wingstay 100 goodyear antioxidant consisting of mixed diaryl p - phenylenediamine . mag - paste gold elastochem 55 % highly active magne - sium oxide dispersed in an organic binder . vulcanizing agent . iron oxide u . s . steel iron oxide by - products of steel blast furnaces . colorant . antimony oxide harwick flame retardant . elasto - o - cal 8ons elastochem a drying agent contain - ing 80 % calcium oxide in an organic binder . struktrol wb - 222 struktrol high molecular weight fatty acid esters used as a processing aid . petrolatum sr - 172 c . p . hall petroleum semi - solid wax of the aliphatic hydrocarbon class . release agent . chlorowax 65 occidental a liquid chlorinated chemical paraffin with approx - imately 65 % chlorine content . secondary plasticizer and flame retardant . ultraflex wax petrolite processing aid wax . solem h - 36 solem hydrated aluminum oxide industries with a medium particle size of 25 microns . flame retardant and filler . cab - o - sil m5 cabot cab - o - sil is silica produced through flame hydrolysis of silicon tetrachloride at about 1100 ° c . filler to enhance physical properties . ecp ( azo )- 72 elastochem a blowing agent disper - sion of celogen az199 , celogen az130 , celogen ot , and sunthene 4240 in 5 , 10 , 5 and 7 . 78 parts by weight ratios respectively . sunthene 4240 sun oil softening agent refined from napthenic crude oil containing 46 . 7 % aromatics . pbetu - 75 elastochem a 75 % by weight disper - sion of ethylene thio - urea in a polymeric binder . used as an accelerator for neoprene rubber . mbts uniroyal 2 , 2 &# 39 ; dibenzothiazyl chemical disulfide . used as a retardantsulfur c . p . hall a find grind rubber makers sulfur . vulcan - izing agent . elast - o - zinc elastochem an 88 % active zinc oxide paste , utilizing high purity , activation grade french process zinc oxide . vulcanizing agent . expantrol 4 3m hydrated sodium silicate containing boron . intum - escent when heated______________________________________ the ingredients are mixed on conventional rubber processing equipment . this equipment includes rubber mill , banbury , or intermix compounding . after mixing , the mill base is slabbed , cooled , and allowed to age a minimum of 24 hours . alternatively , the mill base is cut into strips , festooned , cooled , and aged . after aging , the mill base is extruded or molded into the desired shape and vulcanized in a hot air oven , or in a salt bath , or in a heated press . instead of extruding or molding , the mill base can be calendered or pressed and cut to the desired shape . a sponge is obtained by incorporating blowing agents . to demonstrate the utility of this invention the following examples were prepared . in the examples , phr means parts per hundred weight rubber . ______________________________________ingredient phr______________________________________neoprene whv - 100 70 . 0butachlor mh - 30 30 . 0wingstay 100 2 . 00mag - paste gold 7 . 27iron oxide 8 . 00antimony oxide 5 . 00elasto - o - cal 8ons 7 . 00struktrol wb - 222 2 . 50petrolatum sr - 172 3 . 00chlorowax 65 15 . 0ultraflex wax 3 . 00solem h - 36 25 . 0cab - o - sil m5 6 . 96ecp ( azo )- 72 13 . 9sunthene 4240 27 . 4pbetu - 75 4 . 00mbts 1 . 00sulfur 1 . 00elasto - o - zinc 5 . 68expantrol 4 150______________________________________ the ingredients were compounded on a 2 - roll rubber mill . the mill base was cut into strips and the strips fed into an extruder . the extrudate was continuously sponged and vulcanized in a hot air oven . ______________________________________sponge density : 50 . 7 #/ cubic ft ( 812 kg / m . sup . 3 ) expansion : 226 % compression - deflection @ 10 % deflection : 2 . 77 psi ( 19 . 1 kpa )@ 25 % deflection : 6 . 73 psi ( 46 . 4 kpa )@ 33 - 1 / 3 % deflection : 10 . 7 psi ( 73 . 8 kpa )@ 50 % deflection : 31 . 0 psi ( 214 kpa ) ______________________________________ ______________________________________ingredient phr______________________________________neoprene whv - 100 70 . 0butachlor mh - 30 30 . 0wingstay 100 2 . 00mag - paste gold 7 . 27iron oxide 8 . 00antimony oxide 5 . 00elast - o - cal 8ons 7 . 00struktrol wb - 22 2 . 50petrolatum sr - 172 3 . 00chlorowax 65 15 . 0ultraflex wax 3 . 00solem h - 36 25 . 0cab - o - sil m5 2 . 50celogen az130 6 . 66celogen az199 3 . 33sunthene 4240 32 . 8pbetu - 75 5 . 33mbts 1 . 00sulfur 1 . 00elasto - o - zinc 5 . 68expantrol 4 150______________________________________ the ingredients were compounded on a 2 - roll rubber mill . the mill base was hot pressed at 65 ° c . into the desired thickness , cut to size , and sponged and vulcanized in a hot air over . ______________________________________sponge density 43 . 9 #/ cubic ft ( 703 kg / m . sup . 3 ) sponge expansion : 157 % compression - deflection @ 10 % deflection : 3 . 94 psi ( 27 . 2 kpa )@ 25 % deflection : 10 . 8 psi ( 74 . 5 kpa )@ 33 - 1 / 3 % deflection : 16 . 4 psi ( 113 kpa )@ 50 % deflection : 35 . 7 psi ( 245 kpa ) fire test : 5 . 4 hrgreen strength ( r . t . ): 4 . 97 psi ( 34 . 3 kpa ) ______________________________________ ______________________________________ingredients phr______________________________________neoprene whv - 100 70 . 0butachlor mh - 30 30 . 0wingstay 100 2 . 00mag - paste gold 7 . 27iron oxide 8 . 00antimony oxide 5 . 00elasto - o - cal 8ons 7 . 00struktrol wbk - 222 2 . 50petrolatum sr - 172 3 . 00chlorowax 65 15 . 0solem h - 36 25 . 0cab - o - sil m5 7 . 50ecp ( azo )- 72 27 . 8sunthene 4240 17 . 8pbetu - 75 5 . 33sulfur 1 . 00elast - o - zinc 5 . 68expantrol 4 150______________________________________ the ingredients were compounded on a 2 - roll rubber mill . the mill base was hot pressed at 65 ° c . into the desired thickness , cut to size , and sponged and vulcanized in a molten salt bath . ______________________________________sponge density : 41 . 8 # cubic ft ( 670 kg / m . sup . 3 ) sponge expansion : 162 % compression - deflection :@ 10 % deflection : 4 . 6 psi ( 32 kpa )@ 25 % deflection : 9 . 6 psi ( 66 kpa )@ 33 - 1 / 3 % deflection : 13 . 9 psi ( 95 . 8 kpa )@ 50 % deflection : 46 . 8 psi ( 323 kpa ) fire test : 4 . 7 hrs . ______________________________________ ______________________________________ingredients phr______________________________________neoprene whv - 100 70 . 0butachlor mh - 30 30 . 0wingstay 100 2 . 00mag - paste gold 7 . 27iron oxide 8 . 00antimony oxide 5 . 00elast - o - cal 8ons 7 . 00struktrol wb - 222 2 . 50petrolatum sr - 172 3 . 00chlorowax 65 15 . 0ultraflex wax 3 . 00solem h - 36 25 . 0calcium sodium metaphosphate fiber 15 . 0cab - o - sil m5 5 . 00celogen ot 8 . 33celogen az130 11 . 1celogen az199 5 . 56sunthene 4240 20 . 3pbetu - 75 5 . 33mbts 1 . 00sulfur 1 . 00elast - o - zinc 5 . 68expantrol 4 150______________________________________ the ingredients were compounded on a 2 - roll rubber mill . the mill base was hot pressed at 65 ° c . to the desired thickness , cut to size , and sponged and vulcanized in a hot air oven . ______________________________________sponge density : 48 . 6 #/ cubic ft ( 779 kg / m . sup . 3 ) sponge expansion 107 % compression - deflection :@ 10 % deflection 5 . 90 psi ( 40 . 7 kpa )@ 25 % deflection 12 . 3 psi ( 84 . 8 kpa )@ 33 - 1 / 3 % deflection 17 . 1 psi ( 118 kpa )@ 50 % deflection 49 . 3 psi ( 340 kpa ) fire test : 3 . 00 hrs . green strength ( r . t . ): 9 . 48 psi ( 65 . 4 kpa ) ______________________________________ calcium sodium metaphosphate fiber , obtained from monsanto corp ., improved the green strength without detriment to sponge softness . when wolastinite fibers were incorporated in the composition , sponge softness decreased considerably . although not essential in the composition , the addition of calcium sodium metaphosphate fiber provides greater latitude in processing the sponge . the ingredients listed in the previous examples can also be molded into a cellular fireproof seal . by removing the blowing agents , noncellular fireproof seals are obtained . in preferred compositions , the plasticizer concentration is modified . in the following example the plasticizer content was lowered , the blowing agents removed to produce a noncellular part , and although not necessary , the drying agent and processing aid removed . example 5 ______________________________________ingredients phr______________________________________neoprene whv - 100 70 . 0butachlor mh - 130 30 . 0wingstay 100 2 . 00mag - paste gold 7 . 27iron oxide 8 . 00antimony oxide 5 . 00chlorowax 65 15 . 0ultraflex wax 3 . 00solem h - 36 25 . 0cab - o - sil m5 6 . 96sunthene 4240 10 . 0pbetu - 75 4 . 00mbts 1 . 00sulfur 1 . 00elast - o - zinc 5 . 68expantrol 4 150______________________________________ the ingredients were compounded on a 2 - roll rubber mill . mill base was molded for 10 min . at 149 ° c . into sheets 6 . 4 mm × 30 . 5 cm × 30 . 5 cm , or for 5 min . at 165 ° c . into tubes 1 . 6 cm id × 2 . 3 cm od × 32 . 4 cm . ______________________________________properties :* density 76 . 8 #/ cubic ft ( 1230 kpa ) char density 13 . 1 #/ cubic ft ( 210 kpa ) expansion 316 % tensile strength 360 psi ( 2180 kpa ) ultimate elongation 457 % shore a hardness 60 . 0fire test & gt ; 2 . 0 hrs . ______________________________________ * the fire test was run on molded tubes . all other tests were on specimens taken from molded sheets . comparative examples were run utilizing the teachings of examples 1 , 2 and 6 of u . s . pat . no . 4 , 266 , 039 ( hons - olivier , et al ). additional comparative examples were run by substituting vermiculite for the alkali metal silicate in the examples of this invention . in either situation , the resulting compressible fireproof seal could not pass the astm e - 814 fire test . the preferred intumescent of the present invention is a composition comprising a mixture of alkali metal silicate , represented by the formula m 2 o : xsio 2 in which m is alkali metal ; at least one oxy boron compound ; and water ; in which x ( weight ratio of silica to alkali metal oxide ) ranges from about 1 . 5 to about 4 , the molar ratio of boron to m is between about 0 . 2 and about 0 . 9 , and the water comprises about 5 to 15 weight percent of the total composition . examples of useful alkali metal silicates are sodium silicate , lithium silicate and potassium silicate ; sodium silicate being preferred . a mixture of alkali metal silicates can be used . thus m may stand for an admixture of alkali metals in silicate form . for purposes of this description , the term &# 34 ; oxy boron &# 34 ; or &# 34 ; borate &# 34 ; means any compound having a radical which contains boron and oxygen , such as the metaborate , tetraborate , perborate , or polyborate radicals . examples of suitable oxy boron compounds are : boric acid and borate salts of group i and ii elements , including naturally occurring borate compounds , such as borax and colemanite . by group i and ii elements , it is meant all elements in groups ia , ib , iia and iib of the periodic table of elements . some additional examples of suitable borates are calcium metaborate , magnesium borate , and zinc borate . the temperature at which expansion or intumescence begins with these silicate compositions can be controlled as needed for the application . generally , the lower the concentration of water the higher is the temperature of intumescence . there is preferably about 5 to 10 weight percent water in the composition . also , if a higher intumescence activation temperature is required , this can be accomplished by adding calcium hydroxide to the basic formulation . if a lower activation temperature is needed , borax can be used in place of boric acid as the oxy boron compound . for cases in which the borate is the salt of an alkali metal ( e . g ., borax or sodium borate ) the alkali metal originating from the oxy boron compound will become part of the composition , and this alkali metal is included in calculating the ratio x stated above between the silica and alkali metal . the amount of the preferred intumescent when a cellular , compressible fireproof seal is desired should be between 130 phr and 200 phr and preferably between 140 phr and 180 phr . when a noncellular compressible fireproof seal is desired , the amount of preferred intumescent should be between 100 phr and 200 phr and preferably between 130 phr and 170 phr . furthermore , according to the teaching of this invention a preferred softening agent is napthenic oil . the amount of this preferred softening agent when a cellular compressible fireproof seal is desired should be between 25 phr and 45 phr and preferably between 30 phr and 40 phr . when a noncellular compressible fireproof seal is desired the amount of napthenic oil should be between 5 phr and 30 phr and preferably between 15 phr and 20 phr . various omissions , modifications and changes to the principles described herein may be made by one skilled in the art without departing from the true scope and spirit of the invention which is indicated by the following claims . for example , a useful filler in place of hydrated aluminum oxide or silica could be clay .