Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-03-02
2002-11-05
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S516000, C428S520000, C524S504000, C525S066000, C525S09200D
Reexamination Certificate
active
06475582
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to multi-layer tubing made from polyamide and polyolefin materials.
BACKGROUND OF THE INVENTION
Polyamides such as nylon-11 and nylon-12 have been used as a material for automobile fuel lines because of their excellent gasoline resistance, low oxygen and hydrocarbon permeability, high impact resistance, and good flexibility at low temperatures, as well as good zinc chloride (road salt) resistance. Nylon-12 also exhibits high strength under creep, and stress crack resistance, which is particularly important in fuel lines. Nylon-6 has also been tested for fuel lines, but it suffers from stress cracking when it comes into contact with galvanized parts or is exposed to road salt solution.
Since polyamides are expensive, many attempts have been made to find a less expensive material that also meets the stringent requirements for fuel line applications, e.g., low permeability to gasoline, ozone, auto-oxidized gas, and methanol/gasoline. The use of multi-layer tubing to achieve a combination of moisture barrier, oxygen barrier and low hydrocarbon permeation rate is disclosed, for example, in U.S. Pat. No. 5,507,320. A laminated hose is described that consists of an inner layer of a fluorocarbon elastomer backed by a thin layer of Teflon polymer. These layers are then reinforced by an elastomeric tie layer, a reinforcing layer and an elastomeric cover.
U.S. Pat. No. 3,553,042 discloses extrusion coating a layer of polyamide or polyolefin onto a metal-encased cable bundle to form a loose fitting tube. The tube is subsequently stretched while heating to orient and constrict the insulating sheath. One or more such sheathed cables can in turn be sheathed in polyvinyl chloride. The process is used to make insulated cable for electrical connections.
JP 9314767 discloses products useful for window frame and machine parts made by co-extrusion molding, e.g., a polypropylene base, an ethylene/butene-1 copolymer middle layer, and a poly(methyl methacrylate) outer layer. The product has good heat, moisture, and weather resistance.
However, there is still a need for a material that is less expensive than nylon but still has a desirable mechanical property balance that is comparable to nylon mono-layer tubing.
SUMMARY OF THE INVENTION
The multi-layer, co-extruded tubing of this invention comprises:
(1) an inner layer comprising a polyamide selected from the group consisting of (a) nylon-6, (b) nylon-11, (c) a nylon-6
ylon-6,6 copolymer, (d) a nylon-6
ylon-12 copolymer, and (e) nylon-12,
(2) a middle layer comprising:
(a) greater than 1% but not greater than 15% of a graft copolymer comprising a polyolefin backbone to which is grafted a polymerized monomer selected from the group consisting of (i) an &agr;,&bgr;-unsaturated aliphatic carboxylic acid or drivatives thereof and (ii) an &agr;,&bgr;-unsaturated alicyclic carboxylic acid or derivatives thereof,
(b) about 15% to about 40% of a broad molecular weight distribution propylene polymer material,
(c) about 20% to about 40% of a graft copolymer comprising a backbone of propylene polymer material to which are grafted polymerized monomers selected from the group consisting of (i) methyl methyacrylate and methyl acrylate, and (ii) methyl methacrylate and methacrylic acid, and
(d) about 20% to about 50% of an olefin copolymer rubber, wherein (a)+(b)+(c)+(d)=100% by weight, and
(3) an outer layer comprising:
(a) about 25% to about 45% of a broad molecular weight distribution propylene polymer material.
(b) about 25% to about 45% of a graft copolymer comprising a backbone of propylene polymer material to which are grafted polymerized monomers selected from the group consisting of (i) methyl methacrylate and methyl acrylate, and (ii) methyl methacrylate and methacrylic acid, and
(c) about 20% to about 50% of an olefin copolymer rubber,
wherein (a)+(b)+(c)=100% by weight.
The multi-layer, co-extruded tubing of this invention is suitable for fuel systems, high pressure tubing, and other tubing for automotive applications. The tubing has good flexibilty and toughness, even at temperatures as low as −40° C., good tensile strength for burst strength at high pressure, good weatherability and environmental stress cracking resistance, good moisture barrier properties and hydrocarbon resistance, and good zinc chloride resistance.
DETAILED DESCRIPTION OF THE INVENTION
The inner layer of the multi-layer tubing of this invention comprises a polyamide selected from the group consisting of (a) nylon-6, (b) nylon-11, (c) a nylon-6
ylon-6,6 copolymer, (d) a nylon-6
ylon-12 copolymer, and (e) nylon-12.
Methods for making these polyamides are well known and all are commercially available. Basically they can be obtained by polymerizing a monoamino-monocarboxylic acid or a lactam thereof having at least two carbon atoms between the amine and carboxylic acid group, or by polymerizing substantially equimolecular proportions of a diamine that contains at least two carbon atoms between the amine groups and a dicarboxylic acid; or by polymerizing a monoaminocarboxylic acid or a lactam thereof as defined above, together with substantially equimolecular proportions of a diamine and dicarboxylic acid. The dicarboxylic acid may be used in the form of a functional derivative thereof for example, an ester or acid chloride. Nylon-6 is polycaprolactam, nylon-6,6 is polyhexamethylene adipamide made from hexamethylenediamine and adipic acid, nylon 11 is polyundecanolactam, and nylon-12 is polydodecanolactam.
The polyamide provides good gasoline resistance, high strength for high bursting pressure, and low oxygen permeability.
Component (a) of middle layer (2) of the multi-layer tubing of this invention is a graft copolymer comprising a polyolefin backbone to which is grafted a polymerized monomer selected from the group consisting of (i) an &agr;,&bgr;-unsaturated aliphatic carboxylic acid or a derivative thereof and (ii) an &agr;,&bgr;-unsaturated alicyclic carboxylic acid or a derivative thereof Suitable polymerizable monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, endocyclo(2,2,1)-5-heptene-2,3-carboxylic acid and cis4-cyclohexene-1,2-carboxylic acid and anhydrides, esters, amides, and imides thereof Polypropylenes modified with various amounts of maleic anhydride or maleic acid are preferred and are available commercially, for example, from Uniroyal Chemical Corporation and Aristech Chemicals. The grafted polypropylenes generally contain about 0.5% to about 10% of maleic acid or maleic anhydride, based on the total weight of the modified polymer.
The graft copolymer is used in an amount of greater than 1% but not greater than 15%, preferably not greater than 10%, based on the total weight of the composition used for making layer (2).
Component (b) of middle layer (2) is a broad molecular weight distribution propylene polymer material (BMWD PP). The BMWD PP typically has a M
w
/M
n
of about 5 to about 60, preferably about 5 to about 40; a melt flow rate of about 0.5 to about 50, preferably about 1 to about 30 g/10 min, and xylene insolubles at 25° C. of greater than or equal to 94%, preferably greater than or equal to 96%, and most preferably greater than or equal to 98%. The propylene polymer material having a broad molecular weight distribution can be a homopolymer of propylene or an ethylene/propylene rubber impact-modified homopolymer of propylene, wherein the propylene homopolymer has a broad molecular weight distribution.
The BMWD PP can be prepared by sequential polymerization in at least two stages, in the presence of a Ziegler-Natta catalyst supported on magnesium halide in active form. The polymerization process occurs in separate and consecutive stages, and in each stage polymerization takes place in the presence of the polymer and the catalyst from the preceding stage.
The polymerization process can be carried out in a batch or in a continuous mode according to known techniques, operating in liquid phase in the presence or not of an ine
DeNicola, Jr. Anthony J.
Haylock John C.
Phan Tam T. M.
Basell Poliolefine Italia S.p.A.
Hon Sow-Fun
Pyon Harold
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