Abstract:
A hose comprising a core layer, an elastomeric friction layer overlaying the core layer, at least one reinforcement layer overlaying the friction layer, and a cover layer overlaying the at least one reinforcement layer, wherein the core layer is comprised of a blend of two different non-plasticized polyamides.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of co-pending Ser. No. 60/486,520, fully incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The disclosed invention relates to refrigerant hoses for use in automotive and industrial air conditioners.  
       BACKGROUND OF THE INVENTION  
       [0003]     The automotive industry uses hoses for transporting refrigerants. The hoses generally have a three-layer laminar construction consisting of an innermost layer, an outermost cover layer located radially outwardly of the inner tube, and a reinforcing fiber layer interposed between the innermost layer and the outermost layer. Generally, the inner and outer layers are formed of rubber. The reinforcing fiber layer usually is a mesh structure formed by braided organic yarn such as polyester fiber, rayon fiber, or nylon fiber. The outer cover typically is formed of ethylene propylene diene rubber (EPDM) or chloroprene rubber (CR). Adhesion layers be may employed between the layers.  
         [0004]     The known multi-layered rubber hoses discussed above have a high degree of flexibility. Because of this property of the rubber materials, rubber hoses can be handled with ease. However, rubber materials generally tend to have high gas permeability. Attempt to improve resistance of conventional rubber hoses to refrigerant permeation by incorporating polyamide layers such as nylon 6 or nylon 66 as an inner layer.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is directed to a hose comprising a core layer, an elastomeric friction layer overlaying the core layer, at least one reinforcement layer overlaying the friction layer, and a cover layer overlaying the at least one reinforcement layer, wherein the core layer is comprised of a blend of two different non-plasticized polyamides with flexibility and ultra low permeation.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The invention will be described by way of example and with reference to the accompanying drawings in which:  
         [0007]      FIG. 1  is a perspective view of a hose in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0008]     The refrigerant hose  10  of the present invention is illustrated in  FIG. 1 . The hose  10  has a core layer  12 , relative to the radial direction of the hose and the longitudinal hose axis. The core layer  12  is formed from a blend a polyamides. Over the core layer  12  is an elastomeric friction layer  18 , over which is a reinforcing layer  20 , and overall, a cover layer  22 .  
         [0009]     The core layer  12 , as noted, is formed from a blend of two polyamides. Both polyamides are non-plasticized polyamides. Suitable polyamides for use in the core layer  12  include nylon 6 and a copolymer of nylon 6 and nylon 66. In one embodiment, the inner core comprises a blend nylon 6 and a copolymer of nylon 6 and nylon 66 with a weight ratio of nylon 6 to copolymer of nylon 6 and nylon 66 of from about 1 to about 3. In another embodiment, the inner core comprises a blend nylon 6 and copolymer of nylon 6 and nylon 66 with a weight ratio of nylon 6 to copolymer of nylon 6 and nylon 66 of from about 1.5 to about 2.5. Suitable nylon 6 is available from DuPont as FN727. Suitable copolymer of nylon 6 and nylon 66 is available from Atofina. The polyamides may be blended using any of the thermoplastic blending methods as are known in the art, including but not limited to extrusion. The core layer  12  may be extruded from preblended polyamides, or formed directly by extrusion of a mixture of polyamide pellets.  
         [0010]     Layer  18  is an elastomeric friction layer between the outermost core layer  16  and the reinforcing layer  20  and provides flexibility to the hose  10 . The elastomer selected for this layer should meet those characteristics. For adhesion to the adjacent polyamide layer  16 , the elastomeric layer  18  may be extruded onto the core layer  12 . The layer may also be applied in the form of a sheet either spirally wrapped or butt seamed. These methods of applying such layers are known in the art, and variations thereof are contemplated herein.  
         [0011]     The elastomeric friction layer  18  comprises a base polymer selected from polyisoprene, polybutadiene, copolymers of butadiene and acrylonitrile, copolymers of butadiene and styrene, polychloroprene, polybutadiene, ethylene propylene copolymers, EPDM&#39;s such as ethylene propylene norbornene terpolymers, ethylene propylene-1,4-hexadiene terpolymers, ethylene propylene dicyclopentadiene terpolymers and the like. In one embodiment, the base stock for the friction layer is EPDM.  
         [0012]     The base polymer in the friction layer  18  must have an adhesive system and a peroxide or sulfur curative. The adhesive systems useful are the conventionally known resorcinol, phenolic, or maleinized polybutadiene based adhesive systems. The resorcinol component may be added to the elastomer in the nonproductive mix, or preformed adhesive resins may be added during the productive mix. The amount of adhesive system utilized in the elastomeric friction layer can range from 1 to 10 parts by weight based on 100 parts of base stock polymer. The peroxide or sulfur curatives useful in the friction layer  18  are those that are normally used in such base stocks. The peroxide or sulfur curatives useful in the elastomeric friction layer are those that are normally used in such base stocks. For example peroxides such as dicumyl peroxide, [α,α′-bis(t-butylperoxide)diisopropylbenzene], benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, and n-butyl 4,4-bis(t-butylperoxy)valerate. From 1 to about 10 parts of peroxide or sulfur are utilized based on 100 parts of base polymer.  
         [0013]     The reinforcing layer  20  may be a fiber layer as commonly used as a reinforcing layer for hoses. The layer  20  may be formed by braiding, spiraling, knitting, or helical knitting of yarn. The yarn may be selected from conventional hose reinforcing yarns such as glass, steel, cotton, polyester, or aramid fibers, or a blend of any of these fibers.  
         [0014]     The cover layer  22  is selected from known cover layer materials, including but not limited to nitrile-butadiene rubber (NBR), chlorosulfonated polyethylene rubber (CSM), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-IIR), epichlorohydrine rubber (CHR, CHC), acrylic rubber (ACM), chloroprene rubber (CR), ethylene-acrylic elastomer (AEM) and the like. In one embodiment, the base stock for the cover layer is AEM.  
         [0015]     As discussed above, the hose  10  having core  12  has a low permeation rate with refrigerants. The hose  10  has a permeation rate of less than 0.5 g/m/day, preferably 0.15 to 0.5 g/m/day. A hose with a permeation rate of less than 0.5 is considered an ultra low permeation hose.  
       EXAMPLE  
       [0016]     A hose  10  was built in accordance with the present invention, having a core with a polyamide blend, an EPDM friction layer, an aramid reinforcement, and an AEM cover. The core  12  was formed by extruding a 2 to 1 weight ratio of nylon 6 and nylon 6, 66. The core  12  had a gauge of about 0.3-0.4 mm.  
                                                 TABLE 1                                   polyamide 1 1     polyamide 2 2     blend                                    Tensile Strength, MPa    38    70   28       % Elongation at Break   337   368   243       Permeation Rate*, g/m/day   —   —   0.23                 *measured with R134A refrigerant, 10 days at 90° C.              1 FN727, a nylon 6, obtained from DuPont              2 non-plasticized copolymer of nylon 6 and nylon 66 obtained from Atofina             
 
         [0017]     The hose was tested for 10 days at 90° C. following Volkswagen Specification TL 823 16 to determine the permeation rate. The permeation rate was 0.23 μm/day, and the exemplary hose is a low permeation hose.  
         [0018]     Variations in the present invention are possible in light of the description of it provided herein.  
         [0019]     While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.