GB2223233A - Fuel resistant elastomeric composition - Google Patents

Description

2 2 2? 7, 2 3, 3 1 FUEL RESISTANT ELASTOMERIC COMPOSITION is This

invention relates to the art of synthetic resins and more particularly to a fuel resistant synthetic resin of the acrylonitrile type.

The invention is particularly applicable to a resilient riaterial which is formed into fuel pump isolation members for use with fuel pumps which are submerged in fuel and will be described with particular reference thereto, although it will be appreciated that the invention has broader applications and can be used wherever elastomeric parts having resistance to attack from a broad range of fuel chemicals over a broad temperature range are needed.

In the past, most fuel pumps in automobiles and other internal combustion engine applications were located near the engine outside of the fuel tank. However, with the advent of fuel injection type internal combustion engines, it has become common for fuel pumps to be mounted inside the fuel tank associated with the internal cotibustion engine. This location presents problems.

Automobile fuel tanks are normally located outside of the engine compartment. Noise originating in the fuel tank is easily transmitted to the passenger compartment. Fuel pumps are often a source of vibration and noise. When located in a fuel tank, the fuel. pump should be acoustically insulated.

Automobile fuel tanks are sometimes fabricated from sheet steel. Automobile fuel tanks are sometimes fabricated by blow molding plastic into a thin walled body. In either case, a drum like body is created. When a fuel pump is Mounted within a fuel tank, the drum like characteristic of the fuel tank can accentuate the noise produced by the fuel pump. Fuel pumps should be acoustically isolated from the fuel tank.

Fuel pump insulation and isolation has taken the form of resilient menbers fabricated from various materials resistant to attack from gasoline. Significant problems may result if the resilient member is fabricated from materials which do not have the appropriate fuel resistance. First, the resilient member itself can deteriorate. It can swell, loose elasticity, disintegrate and/or physically fail. Second, the material may "poison" the fuel. If compounds or elements from the resilient member are extracted by the fuel and contaminate fuel injector parts, catalysts in the exhaust catalytic converter or other critical elements, they may cause engine malfunctions and require expensive repair to the automobile in addition to the replacement of the fuel pump isolation members themselves.

The problems of chemical attack on the resilient members and fuel poisoning have been exacerbated by the advent of fuels for use in automobiles other than straight gasoline. Thus, alcohol, both methanol and/or ethanol, are now added to gasoline in many areas. Aromatics and other organic chemicals may be added to gasoline as may kerosene and metbyl tert-butyl ether (also known as 11,TBE). Alcohol is often added to gasoline in cities having significant pollution problems as it is thought to reduce air pollution caused by automobile traffic. The other fuel elements referred to above are added for various reasons in various locations. New fuel additives are constantly being developed and promoted.

As a driver may not know what is being added to the fuel he is purchasing at a filling station, it has become necessary to consider the use of fuel pump isolation members having resistance to all of the above named fuel additives and elements, and others, so that an automobile may be operated with confidence throughout a wide geographic area and over its intended life span. Because so many automobiles are sold, the search for appropriate materials for use in fuel pump isolation nembers has been intensive. Conventional thinking in this area has centered upon fluoroelastomers.

Fluoroelastomers have several drawbacks when considered as a material fbr fuel pump isolation riembers to be immersed in fuel. Fluoroelastomers are very expensive. Fluoroelastomers are difficult to mold into intricate shapes and sometimes require special mold designs.

Fluoroelastomers have poor tear properties at molding or processing temperatures making extraction of a finisbed part from a mold difficult. Fluoroelastomers generally have high -i hardness. This hardness increases in colder temperatures. Fluoroelastomers are very dense. More f lueroela stonier, by weight, is needed to fabricate a given part then is the case with most other elastomeric compositions. Transfer molding of complex fluoroelestomeric parts is difficult.

Fluoroelastomers have been used widely in the fabrication of small gaskets and the like for use in fuel exposed parts in spite of the above referred to difficulties. In many applications these factors are unimportant end in other applications, the fluoroelastomers are simply the best, or only, available choice.

While fluoroelastomers have good high temperature performance, their low temperature performance is severely limited because of the increasing hardness at low tempera- ture and other difficulties.

Arlines are n9W being used as an additive for fuels. Some amines interact with some fluoroelastomers destructively. A fluoroelastomeric part t,ay fail in a fuel containing amines.

Nitriles have also been used in the past in situations involving exposure to gasoline. 0De application was fuel lines. Difficulties were encountered. "Sour gas", that is, gasoline containing hydroperoxides, has an adverse effect on nitrile elastomers. Sour gas can be caused by simply allowing gasoline to age in a given container for a long period of time. This can occur at a filling station or in an automobile gas tank itself. Sour gas has been known to destroy nitrile compositions usee. as fuel lines leading to fuel leaks and other unacceptable conditions. Additionally, conventional nitrile compositions often contained substances which become corrosive to copper when exposed to fuel. This made use of nitrile materials in an immersed environment also containing electricDl components a problem.

one of the modes of failure of elastomeric materials subject to chemical attack is swelling. A part fabricated to have certain dimensions, when immersed in a chemical which attacks it, increases its dirnensions by a significant percentage. Mechanical damage to the part results and mechanical properties are altered. Vitrile elastomer compounds and related compounds are susceptible to swelling when exposed to alcohols now sometimes used in fuels. These problems are discussed in "Status Report, Effects of Gasohol on General Purpose Hycar Witrile Compounds by D. A. Seil; Fuel Resistance and Fuel Permeability of NBR and NBR Blends, J. R. Dunn, R. G. Vara, Elastomerics Magazine, May 1986; and, Compatability of Fuel-Handling Rubbers with Gaso- line/Alcohol Blends, A. Nersasian, Elastomerics Magazine, October 1980 which are incorporated herein by reference.

SUMMARY OF THE INVENTION

The present invention provides an elastomeric composition which can be readily transfer molded or injection molded or processed in other ways into parts which can withstand immersion in fuels of various compositions and maintain good elestomeric characteristics over a wide range of temperatures.

In accordance with the present invention, there is provided a composition for fabricating a fuel resistant elestomeric isolation member comprising an acrylonitrile/butadiene copolymer; pbtlialate plasticizer; fillers selected from the class comprising carbon black, calcium-magnesium carbonate and polytetrafluorethylene; zinc oxide and fatty acid processing aids; and, a catalyst having resistance to degradation when immersed in a variety of fuels and additives.

These ingredients, in accordance with the invention, are present in the following general proportion in parts by weight, basis 100 parts:

ingredient Parts Acrylonitrile/butadiene copolymer 20-40 Plasticizer 19-27 Zinc oxide 0.1-10 Fatty acid 0.01-2.0 Substantially sulfur free carbon black 20-32 Calcium carbonate 10-20 Polytetrafluoretbylene 0.1-20 Sulfur free catalyst or curing agent 0.3-10 Further in accordance with the invention, the acrylonitrile/butadiene copolymer has at least a 45 percent acrylonitrile content.

Still further in accordance with the invention, the fatty acid processing aid is stearic acid having a specific gravity of 0.84 and a 1 percent maximum moisture content.

Yet further in accordance with the invention the plasticizer is a phthal8te plasticizer.

Still further in accordance with the invention the phthalate plasticizer is a butyl benzyl phtbalate plasticizer with a specific gravity of from 1.115 to 1.123 and a refractive index of from 1.535-1.540. - Yet further in accordance with the invention the sulfur free catalyst or curing agent is an organic peroxide catalyst or curing agent.

Yet further in accordance with the invention the organic peroxide catalyst or curing agent is 2,5 dimethyl-2,5 di (t-butyl peroxy hexane) 50 percent active on a mineral carrier.

Still further in accordance with the invention, the composition for fabricating a fuel resistant elastomeric Isolation member comprises, in parts by weight, basis 100 total weight parts:

Ingredient Parts Acrylonitrile/butadiene copolymer about 30.22 (45% acrylonitrile content) Phthalate plasticize about 24.19 Zinc oxide about 1.51 Stearic acid about 0.15 Carbon black about 27.21 Calcium-magnesium carbonate about 15.12 Polytetrafluorethylene about.6 organic peroxide catalyst about 1 The principal object of the present invention is to provide an isolation member having good physical character- istic when immersed in a fuel containing any or all of a variety of fuel additives over a wide temperature range.

-B- It is another object to the present invention to provide a noise and vibration insulation and/or isolation member having a low initial cost when compared to other available materials.

It is still another object to the present invention to provide an insulation and/or isolation member fabricated from an elastomeric composition which is relatively easy to mold into complex shapes.

It is a further object to the present invention to provide an elastomeric insulation and/or isolation ilember which will not "poison" fuel when irunersed in fuel over an extended period of time.

It is yet another object to the present invention to provide an elastomeric composition which will not cause the corrosion of electrical parts immersed in the same body of fuel in which a member fabricated from the composition is immersed.

It is a further object the the present invention to provide a composition which is resistant to attack from a wide variety of fuel materials and fuel additives when totally immersed in such fuel materials and fuel additives.

It is still another object to the present invention to provide an elastomeric. composition which can be injection molded, trafisfer molded, or otherwise fabricated into a part which is resistant to a vide variety of fuels and fuel additives and maintains its mechanical characteristics over 1 normally regions.

It is yet another object of the present invention to provide an elastomeric composition which is capable of being molded into parts which retain elasticity and mechanical properties at temperatures below OF to about 21211F and withstand immersion in a variety of fuels.

These and other features and objects of the present invention will become apparent from the detailed descrip tion of the preferred embodiment which follows.

encountered ambient temperatures in temperate THE PREFERRED EMBODIMENT Insulation and isolation members for fuel pumps and the like are parts of complex shape. These parts are sometimes cylindrical having an overall length of about three inches and a diameter of two 2 inches. The parts way have thick walls containing a number of long holes longitudinally disposed within the thick wall of the device. Other shapes, such as a tapered cylinder having an annular recess in one end, are also common. While the shapes described differ radically in appearance from one another, they share several characteristics. First, the shapes are complex. Second, the shapes present large surface areas including small recesses. Third, the complexity of the shapes are necessary in order for the part to perform its intended function, i.e. to prevent vibration and generation of noise when a fuel pump is operating within a fuel containing tank.

The complexity of the shapes described require complex molding dies and the use of an elastomeric composition capable of being molded into complex shapes.

The composition described below satisfies these criteria and others. The composition comprises a number of ingredients.

The first essential ingredient of the material is an acrylonitrile/butadiene copolymer. Such materials are available in a wide variety of formulations. It has been found to be advantageous to use an scrylonitrile/but,-Idiene copolymer with at least a 45 percent acrylonitrile content. A preferred acrylonitrile/butadiene copolymer is available under the trademark CHEMIGUM 14206 from Goodyear Chemical.

The acrylonitrile/butadiene copolymer will contribute from about 20 to 40 weight parts, basis 100 weight parts. if more than 40 parts are used, the swell characteristic of the composition may suffer.

The next essential ingredient is a phtbalate plasticizer. Numerous phtbalate plasticizers are available and might be usable in this composition. The preferred plasticizer is butyl benzyl pbthalate plasticizer with a specific gravity of 1.115 to 1. 123 and a refractive index of 1.535-1.540. An appropriate plasticizer is available under the trademark SANTICIZER 160 from Nonsanto Chemical Company. The plasticizer will contribute from about 15 to about 45 weight parts.

The next ingredient in the composition is carbon black f iller. It has been found that a semi-reinforcing furnace, low modulus, non-staining carbon black has advantages in the present invention. one advantage is that such carbon black is substantially sulfur free. While sulfur can aid in the curing of elastomeric compositions, it has been found that sulfur in the carbon black can contribute to the poisoning of fuel when used in an elastomeric composition molded into an isolation member for a fuel pump. An appropriate carbon black is available under the trademark FURNEX N762 from Columbian Carbon. While other fillers may be usable, carbon black adds physical strength and decreases absorptivity.

The next ingredient of the composition is dry ground calcium carbonate filler. It has been found that dry ground calcium-magnesium carbonate with a specific gravity of 2.71 and a.005 percent maximum residue on a 325 mesh screen is preferred in the present invention. However, calcium carbonates from other sources and having slightly different characteristics have been used successfully in the inven- tion.

The next ingredient used in the preferred embodiment is ground polytetrafluorethylene. The preferred material is ground to a 350-650 micron particle size range with a specific gravity of 2.1.5 to 2.20. An appropriate material is available under the trademark TEFLON 6C from DuPont Chemical Company. This filler increases tear strength and aids in expelling air in molding. The composition will fulfill its specification without this filler, but process ing will be much more difficult.

The next ingredient of the composition is zinc oxide as a processing aid. French process zinc oxide having a specific gravity of 5.57 and a 0.5 percent maximum residue on a 325 mess screen is preferred. An appropriate zinc oxide is available from Pacific Smelting under the trademark PASCO 524T. The use of zinc oxide improves the tear strength of parts fabricated frorn the composition by acti- vating curing. Improved tear strength allows complex parts to be removed from a mold.

The next ingredient is a fatty acid processing aid. In the preferred embodiment rubber grade stearic acid with a specific gravity of 0.84 and a 1.0 percent maximum moisture content is used. An appropriate stearic acid is available from Harwick Chemical under the designation F1500. The zinc oxide and stearic acid appear to work best together as an aid to polymerization, or curing, when present in a ratio of approximately ten parts zinc oxide to one part stearic acid.

The last essential ingredient is a catalyst added to cure the elastomeric composition. A sulfur free catalyst is preferred. Organic peroxides are used in the" preferred embodiment. Specifically, 2,5-dimethyl-2,5-di(tbutyl peroxy hexane) 50 percent active on a mineral carrier is used. Such an organic peroxide is available under the trademark VAROX DBPH-50 from R. T. Vanderbilt Company.

The ingredients described above are combined in the following proportions in weight parts, basis 100, aind blended together:

Ingredient Acrylonitrilelbutadiene copolymer Phtbalate plasticizer Carbon black Calcium carbonate Polytetrafluorethylene French process zinc oxide Stearic aciJ Organic peroxide catalyst The resulting mixture is thoroughly blended and cated through injection molding, transfer molding or conventional fabrication techniques. The composition processes well, especially when compared to fluoroelastomers, the only other class of elastomers known to have comparable fuel resistance. Additionally, the finished parts fabricated from this composition generally has better tear strength, better low temperature characteristics, a lower durometer and a lower specific gravity than the fluoroelastomers. A lower specific gravity means that it takes less weight of the composition of this invention then of a fluoroelastorier to fabricate the same part. This, coupled with the significant cost advantage per unit weight of the current invention compared to fluoroelastomers, results in a significant savings in cost per part. Additionally, although the material is less expensive, it is superior in vibration and noise isolation and insulation at low temperature to competitive fluoroelastomeric materials.

Parts 30.22 24.19 27.21 15.12 0.60 1.51 0.15 1.0 fabri- other carbon black, 4-1, 1 x>.ne calcium-magnesium polytetrafluore y described above, are present prima- rily as fillers. Other fillers such as clays, fused silica, precipitated silica, ground quartz, ground coal, talc, mica and ground cork have been considered for use in this composition. Bowever, it has been calcium-magnesium carbonate and polytetrafluorethylene contribute to the overall stability of the composition when subject to attack by fuel and fuel additives.

carbonate and found that carbon black, Polytetrafluorethylene also acts as a processing aid. The amount of each filler present may be varied. black may be present in from about 20 to about 35 parts. Calcium carbonate may be present in fror about 8 parts to about 22 parts. Polytetrafluorethylene may be omitted altogether, however, processing will be difficult, or may be present in up to about 2 parts or more.

The addition of french process zinc oxide, stearic acid and an organic peroxide catalyst appear to promote polymerization of the acrylonitrile/butadiene part into an excep- tionally stable fuel pump isolation member which is immune from attack by fuels and fuel additives and substantially sulfur free. The amount of zinc oxide and stearic acid present may be varied to accommodate processing needs. For a part of simple shape, these processing aids may be delet- Thus, carbon ed.

The use Of the plasticized with a phtbalate plasticizer, acrylonitrile/butodiene copolymer as set forth -is- above, results in a finished part having a surprisingly good resistance to fuels containing alcohol and additives. Acrylonitrile/butadiene copolymer having lower concentrations of acrylonitrile have been used in the past but adequate fuel additive resistance has not been achieved. It bas been found that a 45 percent acrylonitrile content improves resistance to attack by fuel additives. Surprisingly, good low temperature characteristics can be maintained in the composition of the preferred embodiment although a 45 percent acrylonitrile content copolymer is used.

COMPARATIVE PROPERTIES OF THE PREFERRED EMBODIMENT A comparison is set forth below showing the improved properties of fuel pump isolation and insulation members made from the elastomeric composition in accordance with the present invention. The comparison is made to a nitrile composition currently accepted by at least one major automobile manufacturer for use in making a fuel pump isolation member and a fluorocarbon composition.

The existing nitrile composition is identified by a code number 5420 and is comprised of the following:

Acrylonitrile/butadiene co polymer having approximately 33 percent acrylonitrile content Dioctyl pbthalate ester plasticizer with a specific gravity of 0.985 French process zinc oxide Stearic acid 34.75 parts 22.86 parts 1.73 parts 0.17 parts 99 percent active recrystallized dicumyl peroxide 0.35 parts Carbon black 23.04 parts Dry ground calcium-magnesium carbonate 17.28 parts Set forth below are the results of testing of these three compounds immersed in various fuel like liquids conventionally used for testing the ability of elostomeric compositions to withstand immersion in fuels. The results of these tests are set forth in three columns. The first column sets forth the results for the previously accepted nitrile composition, 5420; the second column sets forth the results for the composition and part of the preferred embodiment identified by the reference number 5205 and the third column sets forth the results for a fluorocarbon elastomer identified by the code 8102.

The results set forth are the initial Shore hardness characteristics, the tensile strength and the per cent elongation of the compounds. This is followed by results of similar testing done on parts f?'Dricated from the composi- tions and beat aged or immersed in fuel like compositions for a stated period of time. The last entry in each table is the material cost for the composition under test.

Code 5420 5205 INITIAL VALUES 8102 Durometer, Shore A 42 51 58 Tensile Strength, MPa 7.17 9.41 8.82 %Elongation 450% 400% 320% CHANGES Heat Aging-70hrs@1.00C Durometer 49 63 60 Tensile 6.76 10.23 9.06 %Elongation 380% 305% 280% ASTM Fuel C-48hrs@23C Durometer 27 41 60 Tensile 3.68 7.08 7.65 %Elongation 280% 345% 290% Volume +21.3% -0.5% +1.7% ASTM Fuel C 80% Etbanol 20% 48hrs@23C Durometer.18 32 NC Tensile 2.52 5.60 6.46 %Elongation 240% 295% 275% Volume +32.4% +7.2% +3.8% ASTM Fuel C 90% Methanol 10% 45hrs@23C Durometer 16 33 54 Tensile 1.98 5.09 6.11 %Elongation 210% 275% 270% Volume +41.3% +9.3% +6.2% ASTM Fuel C 80% Methanol 20% 48hrs@23C Durometer 16 31 52 Tensile 1.90 5.09 5.46 7-Elongation 200% 280% 260% Volume +48.7% +11.3% +6.9% AS71.1 Fuel C 50% Methanol 50% 48hrs@23C Durometer 18 36 53 Tensile 2.39 5.72 6.49 %Elongation 230% 273% 260% Volume +37.6% +6.4% +6.7% Methanol 100% 48hrs@23C Durometer 32 45 58 Tensile 4.78 7.43 6.93 %Elongation 280% 350% 280% Volume +5.8% -7.8% +2.5% Peroxide Humber Sour Gas 168hrs@60C per AZ5-1 Durometer 34 69 52 Tensile 2.62 5.97 4.22 %Elongation 250% 150% 220% Volume +6.8% -10.1% +8.45% Material Cost ix 1.75X 50X At least one major automobile manufacturer has set a 15 percent maximum swell standard for fuel pump isolation member materials. Therefore the percentage swell is a very important characteristic. It can be seen that the existing nitrile composition, 5420, does not meet this criterion when immersed in ASTM fuel C, fuel C and ethanol or fuel C and methanol. Swell, or percent volume change, is as high as 48.7 percent for a mixture of 80 percent ASTM fuel C and 20 percent methanol. On the other hand, the preferred embodiment of the present invention shows a maximum swell of only 11.3 percent in this same mixture, well within the limit.

When comparing the preferred embodiment of the present invention to the fluorocarbon elastomer, two things stand out. The first is shown in the preceding table as the last line. The fluorocarbon material costs more than 25 times as much as the preferred embodiment of the present invention. The second important characteristic is hardness. After immersion in all of the test fluids, except 90 peroxide number sour gas, the preferred embodiment of the present invention maintained a shore A durometer of betWeen 30 and 45. The fluorocarbon elastomer bad a substantially higher durometer as originally manufactured and after immersion. Higher durometer is a characteristic of fluorocarbon elastomers.

The hardness difference is accentuated by low temperature environments. At temperatures below the freezing point of water, the durometer of fluoroelastomers increase significantly. Such temperatures are often encountered in the operation of automobiles. Parts made from these compounds become very hard and their usefulness as vibration isolators and/or dampers is greatly impaired. On the other hand, the preferred embodiment of the present invention maintains it lower shore A durorneter parameter and its vibration damping characteristics at colder temperatures. Fuel. pump isolation members made in accordance with the preferred embodiment maintain a low Shore hardness at temperatures as cold as 40 below zero Fahrenheit. This makes the material usable over the entire range of ambient temperatures normally encoun- tered in the continental United States or other temperate regions.

Claims (30)

1. A fuel and alcohol resistant, acoustically insulating, ela::tomeric composition retaining its acoustic insulating properties over a temperature range extending from below OOF to about 200'F comprising in parts by weight basis 100 total weight parts:

Parts Acrylonitrile/butadiene copolymer with at least about a 45% acrylonitrile content 20-40 Phthalate plasticizer 15-45 Zinc oxide 0.1-15 Fatty acid 0.01-1.5 A substantially sulfur-free filler selected from the group consisting of carbon black, calcium carbonate, polytetrafluorethylene and combinations thereof 23-63 A substantially sulfur-free catalyst 0.3-10

2. The composition of claim 1 wherein said catalyst is an organic peroxide.

3. The composition of claim 2 wherein said catalyst is 2,5 dimethyl-2, 5di(t-butyl peroxy hexane).

4. The composition of claim. 3 wherein said catalyst is at least 50 per cent active on a mineral carrier.

5. The composition of claim 1 wherein said filler includes poly tetra f luorethylene in weight parts of said total composition 0.1-4.0.

v."

6. The composition of claim 5 wherein said fill comprises in weight parts of said total composition:

Carbon black 20-35 Calcium-magnesium carbonate 8-22 Polytetrafluorethylene 0.1-2.0

7. The composition of claim 6 wherein said filler comprises in weight parts of said total composition:

Carbon black 24-30 Calcium-magnesium carbonate 12-18 Polytetrafluorethylene 0.4-1.0

8. The composition of claim 1 wherein said filler comprises in weight parts of said total composition about:

Carbon black 27 Calcium-magnesium carbonate 15 Polytetrefluorethylene 0.6

9. The composition of claim 1 wherein said copolymer and said plasticizer comprise:

Acrylonitrile/butadiene copolymer 25-35 Phthalate plasticizer 20-30

10. The composition of claim 9 wherein said phthalate plasticizer is butyl benzyl phthalate plasticizer.

er

11. The composition of claim 1 wherein said copolymer and said plasticizer comprise in weight parts of said total composition about:

Acrylonitrilelbutadiene copolymer 30 Phthalate plasticizer 24

12. The composition of claim 11 wherein said phthalate plasticizer is butyl benzyl phthalate plasticizer.

13. The composition of claim 1 wherein said fatty acid is stearic acid and said zinc oxide and stearic acid com- prise about in weight parts of said total composition:

Zinc oxide 1.5 Stearic acid 0.15

14. A fuel and alcohol resistant, acoustically insulat- ing, elastomeric composition retaining its acoustic insulat- ing properties over a temperature range extending from OIF to about 21.2F comprising in parts by weight, basis 100 total weight parts:

An acrylonitrile/butadiene copolymer with at least a 45% acrylonitrile content 20-40 parts A plasticizer 15-35 parts An inorganic polymerization aid and a co-acting fatty acid or fatty acid derivative 0.

1-5 parts A catalyst 0.1-5.0 parts A filler selected from the group consisting of carbon black, calcium carbonate and polytetrafluorethylene 33-53 parts 15. A fuel resistant, acoustically insulating, elastomeric isolation member retaining its acoustic insulat- ing properties over a broad temperature range comprising in parts by weight basis 100 total weight parts:

Acrylonitrilelbutadiene copolymer 20-40 parts Substantially sulfur-free carbon black 22-32 parts Calcium carbonate 10-20 parts Zinc oxide 0.01-10 parts Fatty acid 0.01-5.0 parts Plasticizer 19-29 parts A non-sulfur bearing curing agent 0.3-10 parts Polytetrafluorethylene 0.1-20 parts

16. A fuel resistant, acoustically insulating, elastomeric isolation member retaining its acoustic insulat- ing properties over a broad temperature range fabricated 1 1 1 100 -23from a composition comprising about in parts by weight basis total weight parts:

Acrylonitrilelbutediene copolymer 30.22 parts Substantially sulfur-free carbon black 27.21 parts Calcium carbonate 15.12 parts Zinc oxide 1.51 parts Fatty acid 0.15 parts Plasticizer 24.19 parts A non-sulfur bearing curing agent 1.0 parts Polytetrafluorethylene 0.6 parts

17. The member of claim 16 wherein said curing agent is an organic peroxide.

18. The member of claim 16 wherein said plasticizer is a phthalate plasticizer.

19. The member of claim 16 wherein said fatty acid is stearic acid.

20. The member acrylonitrilelbutadiene acrylonitrile content.

of claim 16 wherein said copolymer has at least about a 45%

21. A fuel and alcohol resistant, acoustically insulating, elastomeric composition retaining its acoustic insulating properties over a temperature range extending from below OOF to about 200OF comprising in parts by weight basis 100 total weight parts:

Parts Acryloni-trile/butadiene copolymer with at least about a 45% acrylonitrile content 20-40 Phthalate plasticizer 15-45 A substantially sulfur-free filler 23-63 A substantially sulfur-free catalyst 03-10

22. The composition of claim 21 wherein sold catalyst is an organic peroxide.

23. The composition of claim 21 wherein said filler is selected from the group consisting of carbon black, calcium carbonate, polytetrafluorethylene and combinations thereof.

24. The composition of claim 23 wherein said filler comprises in weight parts of said total composition:

Carbon black 20-35 Calcium-magnesium carbonate 8-22 Polytetrafluorethylene 0.1-2.0

25. The composition of claim 24 wherein said filler comprises in weight parts of said total composition:

Carbon black 24-30 Calcium-magnesium carbonate 12-18 Polytetrefluorethylene 0.4-1.0

26. The composition of claim 21 wherein said filler comprises in weight parts of said total composition about:

Carbon black

27 Calcium-magnesium carbonate 15 Polytetrafluoretbylene 0.6 27. The composition of claim 21 wherein said copolymer and said plasticizer comprise:

Acrylonitrilelbutediene copolymer 25-35 Phthalate plasticizer 20-30

28. The composition of claim 27 wherein said phthalate plasticizer is butyl benzy 1 pbthalate plasticizer.

1 j.

29. The composition of claim 21 wherein said copolymer and said plasticizer comprise in weight parts of said total composition about:

Acrylonitrilelbutediene copolymer 30 Phthalate plasticizer 24

30. The composition of claim 29 wherein said phthalate plasticizer is butyl benzyl phthalate plasticizer.

Published 1990 at Tbe Patent Office. State House. 66 71 High Holborn, London WCIR4TP.Purther copies maybe obtainedfrom The Patent Office Sales Branch, St Mary Cray. Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent. Con. 187