Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1986-07-10
1988-08-30
Short, Patricia
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428375, 525444, B32B 2706, B32B 2736
Patent
active
047676680
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrical wire and cable having insulation or jacketing materials based on polytetramethylene terephthalate (PTMT) polymers.
PTMT polymers are well known and have many useful properties. However, their tendency to embrittle at elevated temperatures, especially in presence of flame retardants, and their susceptibility to solvent stress crazing renders them unsuitable for a number of applications, e.g. as wire insulation.
British Pat. No. 1,603,910 discloses that the susceptibility of PTMT polymers to embrittlement in the presence of flame retardants is greatly reduced by blending the PTMT polymer with certain additional polymers which have solubility parameters within .+-.1.5 of the solubility parameter of the PTMT polymer. Examples of polymers that may be blended with the PTMT polymer are block copolymers having crystallizable hard blocks having repeating units of the general formula ##STR1## in which p is at least 2 and is preferably 4, and in which Ar represents an unsubstituted or substituted aryl group, and having amorphous soft blocks having repeating units of the general formula ##STR2## in which p and Ar are preferably as defined above and n has a value sufficient to give the repeating unit a molecular weight of about 600 to 3000, e.g. n, which may vary throughout the polymer, preferably has a value of from 6 to 40. Preferred polymers are copolymers having poly(tetramethylene terephthalate) hard blocks and soft blocks based on poly(polytetramethylene oxide terephthalate). The addition of these block copolymers has also been found to improve the solvent resistance of the blends to a number of solvents, e.g. acetone and methyl ethyl ketone, the improvement in solvent resistance presumably being due to the presence of the soft blocks (since the hard blocks are the same as the PTMT polymer).
However, although compositions disclosed therein are suitable for applications in a number of environments, it is difficult using such compositions to form wire or cable insulation that is resistant to more agressive solvents such as trichloroethane or petrol.
According to the present invention, there is provided an electrical wire or cable having a layer of insulation or jacketing material which comprises an intimate mixture of: tetramethylene terephthalate units; and polyester (1), of a block copolymer in which one of the blocks comprises repeating units of the general formula: ##STR3## in which p is an integer of at least 2 and Ar represents an unsubstituted or substituted aryl group, and the other of the blocks comprises a polyalkylene ether; the block copolymer having a flex modulus of at least 69 MPa (10,000 p.s.i.) preferably at least 138 MPa (20,000 p.s.i.)
The flex modulus values referred to herein are measured by the method of ASTM 6790-71.
The present invention is based on our observation that, for a given ratio of block copolymer (2) to polyester (1), the resistance of the blend to solvent stress crazing increases with the hardness of the block copolymer (2), i.e. increases with the proportion of tetramethylene terephthalate hard blocks in the block copolymer (2). This is particularly surprising in view of the fact that it is only the presence of the soft blocks that distinguishes the block copolymer (2) from the polyester (1). Also, it has been observed that if the insulation or jacketing material contains less than 40% by weight of the block copolymer (2) based on the weight of the copolymer (1), the susceptibility of the insulation or jacketing material to solvent stress crazing becomes highly sensitive to relatively small changes in the extrusion conditions, with the result that the possibility of unacceptable solvent resistance is increased when the wire or cable is manufactured.
In the polyester (1), at least 70 mole %, preferably at least 80 mole %, particularly at least 90 mole %, especially 100 mole %, of the repeating units are tetramethylene terephthalate units.
Preferred copolymers (2) are those described above, and especially those having polytetramethylene terepht
REFERENCES:
patent: 3907926 (1975-09-01), Brown et al.
patent: 4013613 (1977-03-01), Abolins et al.
patent: 4097446 (1978-06-01), Abolins et al.
patent: 4125571 (1978-11-01), Scott et al.
patent: 4140670 (1979-02-01), Charles et al.
patent: 4219628 (1980-08-01), Weemes et al.
patent: 4327198 (1982-04-01), Weemes et al.
patent: 4332855 (1982-06-01), Zingheim
patent: 4369282 (1983-01-01), Campbell
patent: 4467057 (1984-08-01), Dieck et al.
Smith Timothy S.
Thornley David W. M.
Burkard Herbert G.
Raychem Limited
Rice Edith A.
Short Patricia
LandOfFree
Electric wire and cable does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electric wire and cable, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electric wire and cable will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2087749