Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1994-08-17
1995-12-19
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524101, 524493, C08K 534
Patent
active
054768870
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This application is a 371 of PCT/92/105,558 filed Dec. 14, 1992.
This invention relates to certain flame retardant polyamides and more particularly to such polyamides where the polyamides are copolymers of polyamide 6.6.
The use of melamine and melamine derivatives such as melamine cyanurate as flame retardant agents for polyamides has been known for many years (U.S. Pat. No. 3,660,344 and U.S. Pat. Re. No. 30,402). In the case of polyamide 6.6, which is specifically used for its better thermal aging properties, versus polyamide 6, this has not been achieved with melamine because its volatility creates a large amount of melamine white mold deposition. Additionally, blooming of melamine from molded pieces under various simulated use condition has been noted previously (U.S. Pat. No. 4,525,505) as a reason why this art has not been practiced commercially. The volatility of melamine and its tendency to sublime at typical polyamide 6.6 molding temperatures (270.degree. C.-290.degree. C.) has generally rendered melamine-containing polyamide 6.6 compositions unattractive from a commercial point of view. The alternative to melamine has been the use of melamine derivatives or its condensation products such as melamine cyanurate; but, although these have presented solutions to the melamine blooming tissues, they have proved difficult to scale-up to typical commercial processes without some loss of flammability control.
The object of the invention is to provide unreinforced flame retardant polyamide molding compositions which have melamine as the flame retardant and which consistently meet the UL94 V-0 criteria at all the specified thicknesses according to standards described for commercial acceptability based on statistical representation whilst at the same time rain,zing any blooming of melamine during the molding process without reducing the thermal resistance properties of the polyamides.
SUMMARY OF THE INVENTION
The present invention provides a flame retardant polyamide composition consisting essentially of: a filler is added to the aforesaid composition. Further provided is a shaped article formed from the aforesaid unfilled or filled polyamide compositions.
DETAILED DESCRIPTION OF THE INVENTION
The object of the present invention has been accomplished by combining a polyamide having a melting point of below about 250.degree. C. with melamine whereby the resulting composition contains 10-20% by weight of melamine.
Specifically, the melting point of polyamide 6.6 (m.p.=about 260.degree. C.) is lowered to a temperature below about 250.degree. C., preferably below about 245.degree. C., and most preferably in the range of about 230.degree. C.-245.degree. C. This is accomplished by copolymerizing polyamide 6.6 with another monomer copolymerizable with it and which provides a copolymer melting point in the ranges stated above. Additional benefits in terms of long term aging are realized by the addition of a small amount of a heat stabilizer, preferably copper iodide. Other additives well known to those in the polyamide processing and molding art can be used as desired.
Suitable polyamides include those described in U.S. Pat. Nos. 2,071,250, 2,071,250, 2,130,523, 2,130,948, 2,24 1,322, 2,312,966, 2,512,606, and 3,393,210. These polyamides are well known in the art and embrace those semi-crystalline and amorphous polymers having a molecular weight of at least 5,000 and commonly referred to as nylons.
The polyamide can be produced by condensation of equimolar amounts of a saturated dicarboxylic acid containing from 4-12 condensation of equimolar amounts of a saturated dicarboxylic acid containing from 4 to 12 carbon atoms with a diamine, in which the diamine contains from 4 to 14 carbon atoms. Excess diamine can be employed to provide an excess of amine end groups over carboxy end groups in the polyamide.
Examples of polyamides include copolymers of polyhexamethylene adipamide (66 nylon), which melt below 250.degree. C., polyhexamethylene azelaamide (69 nylon), polyhexamethylene sebac
REFERENCES:
patent: 4001177 (1977-01-01), Tsutsumi et al.
patent: 4360616 (1982-11-01), Pagilagan
E. I. du Pont de Nemours & Company
Foelak Morton
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