Abstract:
A rubber composition includes acrylonitrile butadiene,polychloroprene and polyoctanamer. The rubber composition is particularly useful in making the tubular portion of reinforced rubber base which has brass-coated metal braiding therearound. By using this rubber composition, the process of manufacturing reinforced rubber hose is enhanced because the compound is easily mixed, the need of process aids is minimized, and the freezing temperature necessary to crystallize the rubber is reduced.

Description:
FIELD OF THE INVENTION 
     The present invention relates to rubber compositions, hoses fabricated using the rubber compositions, and methods of fabricating hoses using the rubber compositions. More particularly, the present invention relates to rubber compositions usable for various purposes, reinforced hoses made of the rubber compositions, and to methods of manufacturing reinforced hoses using the rubber compositions. 
     BACKGROUND OF THE INVENTION 
     A variety of rubber products such as hoses, belts rubber rolls and molded goods are widely used for many purposes. With rubber goods, there is continuing need to improve performance by, for example, improving low temperature flexibility, maintaining physical properties when the goods are exposed to heat, and improving oil resistance and ozone resistance. These considerations are of special importance with hydraulic fluid transfer hoses. In that such hoses are used for a multitude of applications, they are produced in great quantities. Accordingly, there is a need to decrease the cost of the rubber compound component of such hoses, as well as to improve the processibility of the rubber compound in both mixing and hose manufacturing steps. As always, it is also desirable to decrease the amount of scrap generated by the manufacturing process. 
     While accomplishing these ends, it is an important consideration to improve adhesion to metal substrates, such as brass coated wire substrates, which are used for reinforcement. Such an improvement can occur by omitting adhesion promoters from the compound formulation so as to avoid problems in both processing and in the finished product. In addition, there are problems introduced by using processing aids such as waxes and oils which normally interfere with adhesion between the rubber and metal. By minimizing the use of process aids, adhesion between the rubber and metal. By minimizing the use of process aids, adhesion problems can be reduced and the cost of manufacture decreases. In producing hose which has braided wire reinforcement, it is necessary to expose the rubber tubular portion to freezing temperatures. By lowering the freezing temperature, refrigeration costs are reduced. Moreover, with reinforced hose, the tubular portion of the hose which is manufactured from a rubber composition must stiffen prior to braiding. Accordingly, if the tube stiffens more quickly, there is improved dimensional stability during storage prior to braiding so that braiding can be performed more quickly after the rubber tubing has been produced. This lowers inventory and storage costs. 
     In view of the aforementioned considerations, there is a need for improvements in rubber compounds, which lead to improved hose performance at lower costs. While these considerations are of specific importance relative to hydraulic fluid hose, they are also of considerable importance with respect to other rubber and rubber based products. 
     SUMMARY OF THE INVENTION 
     In view of these features and other features, the present invention is directed to novel compositions for a rubber compound comprising the first component selected from the group consisting of the acrylonitrile butadiene, chlorinated polyethylene, chlorosulfanated polyethylene, and polychloroprene. A second component is selected from a group not duplicating the first component, and consisting of polychloroprene, acrylonitrile butadiene, and chlorosulfonated polyethylene. A third component is selected from the group consisting of polyoctanamer, isoprene, polybutadiene, and styrene butadiens. The composition has more of the first component than the second component or the third component. 
     In a more specific and preferable aspect of the invention, the first component is acrylonitrile butadiene, the second component is polychloroprene, and the third component is polyoctanamer. 
     In another aspect of the invention, a hose structure is provided which includes a metal substrate, preferably made of brass coated metal wire, to which the aforedescribed novel rubber compositions are bonded. 
     In still a further aspect of the invention, the reinforced hose is made according to a method in which a tube is formed of the novel rubber compositions and the brass coated wire is then braided upon the tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a section of reinforced rubber hose, shown partially in elevation and partially broken away, configured in accordance with the principles of the present invention; and 
     FIG. 2 is a schematic diagram illustrating the manufacture of the reinforced rubber hose of FIG. 1, according to the methods of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, there is shown a reinforced hose  10  configured in accordance with the principles of the present invention. The reinforced hose  10  has a specific use as a hose for transferring pressurized hydraulic fluid and includes a tubular rubber portion  12  surrounded by a braided metal wire reinforcing layer  14 . The braided metal wire layer  14  is preferably made of brass coated steel wire  15  to which the outer cylindrical surface  16  of the tubular portion  12  adheres. 
     Referring now to FIG. 2, the hose  10  is manufactured by an arrangement in which a rubber compound  17  with reinforcing carbon black (or clay or silica) as well as additives are mixed in a mixer  20  which is connected to an extruder  22 . The extruder  22  produces the tubular portion  12  of the reinforced hose  10 . After it emerges from the extruder  22 , the tubular portion  12  is retained in a freezer  26  to crystallize the rubber of which the tubular portion  12  is comprised and is thereafter passed through a braider  28  which braids the brass coated wire  15  around the tubular portion to form the reinforcing layer  14 . 
     It is desirable with reinforced hose, such as the reinforced hose  10 , to improve low temperature flexibility of the hose, to retain the physical properties of the hose when the hose is exposed to heat and to have good oil resistance and good ozone resistance. It is also desirable to decrease both the cost of the rubber compound  17  used to make the tubular portion  10  and the cost of the overall product. These cost reductions result from improving the processibility of the rubber in both the mixing step for the rubber constituents and during the manufacturing step in which the rubber compound  17  is extruded as a tube  12  and reinforced with the brass coated braiding  14 . Decreases in costs also occur by reducing the scrap product rate which also reduces environmental impact of these products since a high scrap rate is indicative of inefficiencies increases production amounts of chemicals as well as the amount of product which must be disposed of before it is used. By utilizing the rubber compounds of the present invention, all of these concerns are addressed. 
     In accordance with the preferred embodiments of the present invention, the material forming the rubber compound  17  which is placed in the mixer  20  includes a combination of acrylonitrile butadiene, polychloroprene and polyoctanamer. This preferable mixture results in a rubber which has improved low temperature flexibility, retention of physical properties with heat exposure, and good oil resistance as well as good ozone resistance. 
     By utilizing the mixture of acrylonitrile butadiene, polychloroprene and polyoctanamer to provide the rubber compound of the tube  12 , there is improved adhesion to the brass coated wire substrate  14  which improved adhesion allows for the omission of adhesion promoters from the compound formula. Omitting adhesion promoters is beneficial because adhesion promoters cause their own problems both in processing rubber compositions to make the finished product and in the performance of the finished product. Moreover, the preferred rubber formulation allows for the omission of process aids such as waxes, oils, and the like, which normally interfere with the adhesion of the rubber surface  16  to the brass coated wire braid  14 . 
     It has also been found that the preferred formulation does not require a freezing temperature as low as that currently used during the braiding process in order to achieve necessary dimensional stability. Accordingly, there is faster production and lower refrigeration costs which result in a lower product cost. Moreover, there is an improvement in the extrusion process because the preferred formulation crystallizes more rapidly and thus stiffens more quickly upon exiting the extruder  22 , which gives improved dimensional stability during storage prior to braiding. 
     By using acrylonitrile butadiene, polychloroprene and polyoctanamer to formulate the rubber compound, process aids that are normally used in rubber compounds are not necessary. The polyoctanamer is a preferred softener and is exemplary of materials which add thermoplastic properties to the compound. In addition, polyoctanamer provides all of the advantages of the processing aids. Acrylonitrile butadiene and polychloroprene are both high viscosity compounds which are softened by the addition of polyoctanamer, which significantly improves the ease at which the compounds can be mixed. In addition, polyoctanamer also works to improve low temperature flexibility. Moreover, polyoctanamer adds significantly to the uncured hardness of the compound, which decreases the amount of scrap at both the extruder  22  and the braider  28 . 
     The use of acrylonitrile butadiene provides resistance to oil and other non-polar fluids which are transferred in the hose  10  while the acrylonitrile component provides good low temperature flexibility with adequate heat resistance. Preferably, the acrylonitrile butadiene used in a preferred formulation has medium acrylonitrile content, for example, 28% with a 55 Mooney viscosity. Moreover, acrylonitrile butadiene serves to lower material cost over compounds prepared using only polychloroprene. 
     By using polychloroprene, two significant properties are provided for the formulation. First, the crystallization rate of polychloroprene is such that when the uncured compound is subjected to the freezing action in the freezer  26  prior to applying the wire braid  14  to the tube surface  16 , the tubular portion  12  stiffens faster than if the rubber compound were comprised of acrylonitrile butadiene alone. The second benefit of including polychloroprene is improvement in adhesion between the tube surface  16  and the surface of the wire  15 . The brass coated wire substrate  14  utilized in the hydraulic hose  10  provides an opportunity for the formation of cuprous sulfide which bonds with the points of unsaturation in the rubber, which points are readily available from polychloroprene. Moreover, the added adhesion enhances significantly the performance of the hose  10  in both field and laboratory settings. 
     The mixture includes a composition for the rubber compound wherein the first component is about 70 to about 90 parts per hundred rubber hydrocarbon by weight (phr), the second component is about 15 to about 20 phr, and the third component is about 2 to about 10 phr. In the preferred embodiment, the acrylonitrile butadiene is about 77.0 phr, the polychloroprene is about 18 phr, and the polyoctanamer is about 5 phr. These three components comprise the rubber composition. To this rubber composition is added a hydrocarbon resin, phthalate plasticizer and reinforcing carbon black. The amount of reinforcing carbon black is in the range of about 50 to about 150 phr by weight, which carbon black is mixed with the rubber compounds. To this mixture is added a metal oxide such as zinc oxide, sulfur in the form of elemental sulfur, and anti-oxidant such as octylated diphenylamine, a retarder such as phthalic anhydride, and a fatty acid such as stearic acid. A vulcanizing aid such as 2-(4-Morpholinothio)-benzothiazole is also added to the mixture. 
     The resulting rubber material has durometer hardness in a range of about 75 to about 95 pts shore A, a tensile strength in the range of about 1500 psi to about 2400 psi, and a percent elongation in the range of about 100 to 300 percent. Preferably, the rubber has a durometer hardness of about 85 pts shore A, tensile strength of about 1900 psi, and an elongation of about 150 percent. 
     EXAMPLES 
     The following is a preferable list of components of the composition in parts per hundred rubber hydrocarbon by weight (phr): 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
               
               
                   
                          phr 
                   
               
               
                   
                 (parts per hundred 
               
               
                   
                 rubber hydrocarbon 
               
               
                 Ingredient 
                 by weight) 
                 Description 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Krynac 28E55 
                  77.0 
                 Acrylonitrile butadiene 
               
               
                 Baypren 210 
                 18.0 
                 Polychloroprene 
               
               
                 Vestenamer 8012 
                 5.0 
                 Polyoctanamer 
               
               
                 LX 2600 Resin 
                 3.0 
                 Hydrocarbon resin 
               
               
                 Palatinol 711-P 
                 14.0 
                 Phthalate plasticizer 
               
               
                 N650 and/or N762 
                 110.0 
                 Reinforcing carbon black 
               
               
                 Antioxidant S 
                 0.90 
                 Octylated diphenylamine 
               
               
                 Retarder AK 
                 0.50 
                 Phthalic anhydride 
               
               
                 Stearic acid 
                 0.90 
                 fatty acid 
               
               
                 Vulkacit and/or MOZ 
                 1.30 
                 2-(4-Morpholinothio)- 
               
               
                   
                   
                 benzothiazole 
               
               
                 Zinc oxide 
                 4.25 
                 metal oxide 
               
               
                 Sulfur 
                 2.30 
                 elemental sulfur 
               
               
                   
               
             
          
         
       
     
     Method parameters 
     The aforementioned components are placed in mixer, such as a Shaw K5 mixer or a similar internal type of mixer and mixed for about 3 to about 10 minutes, preferably about 5 minutes, at a drop temperature in the range of about 300° F., and preferably about 330° F. 
     After being extruded, the tubular portion  12  is exposed to freezing in the freezer  26  at a temperature in the range of about 0° F., with a preferred temperature of about −120° F. 
     Alternative Ingredients for the Preferred Formulation: 
     
       
         
               
               
             
           
               
                   
               
               
                 Preferred Formula Components 
                       Alternatives 
               
               
                   
               
             
             
               
                 Acrylonitrile butadiene 
                     Chlorinated polyethylene, 
               
               
                   
                 Chlorosulfonated polyethylene, 
               
               
                   
                 Polychloroprene - about 70 to about 
               
               
                   
                 90 phr 
               
               
                 Polychloroprene 
                 acrylonitrile butadiene, chlorosulfonated 
               
               
                   
                 polyethylene - about 15 to about 25 phr 
               
               
                 Polyoctanamer 
                 Isoprene, Polybutadiene, Styrene 
               
               
                   
                 butadiene - about 2 to about 10 phr 
               
               
                 Hydrocarbon resin 
                 Mineral rubber, High styrene resin 
               
               
                 Phthalate plasticizer 
                 Ester or polyester plasticizers 
               
               
                 Carbon black 
                 Clay, Silica - about 50 to about 150 phr 
               
               
                 Octylated diphenylamine 
                 Diryl p-phenylenediamine, 
               
               
                   
                 Diphenyl-p-phenylenediamine 
               
               
                 Phthalic anhydride 
                 Salicyclic acid, Nitroso diphenylamine 
               
               
                 Stearicacid 
                 Oleic acid, Linoleic acid 
               
               
                 2-(4-Morpholinothio)- 
                 N-isopropyl-2-benzothiazyl-sulfenamide 
               
               
                 benzothiazole 
               
               
                 Zinc oxide 
                 Magnesium oxide, Calcium oxide 
               
               
                 Elemental sulfur 
                 Sulfur donors 
               
               
                   
               
             
          
         
       
     
     The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples. 
     From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.