Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-06-05
2000-05-09
Niland, Patrick D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
428 369, 428 3692, 524168, 524528, 524538, 524539, 525183, 525185, 525186, C08F 830, C08L 2300, C08L 4700, C08L 7700, C08K 543
Patent
active
060605626
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a thermoplastic composition exhibiting improved properties for the production of containers for fuels, such as fuel oil, petrol, diesel oil or alcohol, and more particularly lines for feeding the fuel tank or feeding the engine with fuel.
The term "fuel" should be understood as comprising the various mixtures of hydrocarbons used as fuel in internal combustion or high-compression engines. Thus, this term in particular encompasses fuel oil, diesel oil and all categories of petrol, as well as mixtures of hydrocarbons and alcohols, or the like.
It is known that compositions comprising polyhexamethyleneadipamide (PA 6.6) or polycaprolactam (PA 6) as thermoplastic polymer matrix are not suitable for the production of fuel lines.
This is because these polymers do not exhibit resistance to saline solutions, such as a zinc chloride (ZnCl.sub.2) solution. Such a resistance is required by car manufacturers and is defined in particular by International Standard SAE 844 for the resistance of fuel lines to saline solutions. In brief, this test consists in determining the resistance of the material to cracking or splitting when the material is immersed in a saline solution, generally of ZnCl.sub.2, with application of a flexural force. This property is generally known under the name of resistance to stress cracking or "ZnCl.sub.2 test". Thus, a pipe made of PA 6.6 or PA 6, immersed in a ZnCl.sub.2 solution and placed under mechanical stress, splits and even bursts in a few minutes.
To overcome this problem, provision has been made to use polyamides obtained from monomers with a higher number of carbon atoms, namely 11 or 12.
These polyamides 11 or 12 exhibit an improved resistance to the ZnCl.sub.2 test but have a limited impact strength at ambient temperature and a high manufacturing cost. In addition, these polymers have a high permeability to hydrocarbons.
Provision has also been made, in U.S. Pat. No. 5,256,460, for a thermoplastic composition comprising a mixture of a thermoplastic copolymer with a polyolefin comprising grafted functional groups. The thermoplastic copolymer is obtained by copolymerization of .epsilon.-caprolactam with amino acid monomers or their lactams comprising at least 9 carbon atoms or a mixture of hexamethylenediamine and dicarboxylic acid monomers comprising at least 9 carbon atoms. The copolyamide obtained by copolymerization of a monomer mixture comprising .epsilon.-caprolactam, hexamethylenediamine and a dimeric acid comprising 36 carbon atoms (PA 6/6.36) is described as preferred copolymer.
This copolymer can also be used as a mixture with polyamide 11 or 12 in proportions by weight of 0.1 to 40% by weight with respect to the composition.
It is also described that the mixture can comprise polyamide 6 in a proportion of 0.1 to 20% by weight and preferably of 1 to 7% by weight with respect to the composition.
These compositions exhibit good resistance to the "ZnCl.sub.2 test". However, certain mechanical properties of the copolymer 6/6.36 are weaker than those of polyamides PA 6 or PA 6.6, for example the bursting strength.
In order to overcome these disadvantages, the Applicant Company provides a composition exhibiting a degree of resistance to the "ZnCl.sub.2 test" of the same order of magnitude as the compositions of U.S. Pat. No. 5,246,460 but with superior mechanical properties.
To this end, the Applicant Company provides a thermoplastic composition comprising a matrix made of thermoplastic polymer and at least one compound which improves the resilience of thermoplastic compositions, characterized in that the matrix is composed of a mixture of at least one first thermoplastic copolymer obtained by copolymerization of .epsilon.-caprolactam with at least one of the monomers chosen from the group comprising: lactam carbon atoms, the ratio by weight of .epsilon.-caprolactam to the hexamethylenediamine and diacid total being between 4 and 9, polymerization of monomers comprising less than 9 carbon atoms. The content by weight of the second polymer or copolymer in
REFERENCES:
patent: 5071924 (1991-12-01), Koch et al.
patent: 5256460 (1993-10-01), Yu
Guaita Cesare
Speroni Franco
Niland Patrick D.
Nyltech Italia
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