Fireproofed thermoplastic moulding masses

Details Fireproofed thermoplastic moulding masses Fireproofed thermoplastic moulding masses

1998-10-15

2000-07-25

Dawson, Robert

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

524116, 524121, 524415, 524499, 524523, 524525, 524556, 524599, 524601, 524604, 524605, 524606, 524607, 523452, 523506, 528398, C08K 332

Patent

active

060937599

DESCRIPTION:

BRIEF SUMMARY
The invention relates to flame-retardant thermoplastic molding compositions, comprising are as follows: 100%.
The invention also relates to the use of the novel molding compositions for producing fibers, films and moldings, and also to the resultant moldings.
One of the disadvantages of halogen-containing flame-retardant thermoplastics is that they are toxicologically hazardous, and to an increasing extent they are being replaced by halogen-free flame-retardant thermoplastics.
Important requirements for flame-retardant systems of this type are in particular a pale intrinsic color, adequate heat resistance during incorporation into the thermoplastics, and also the retention of efficacy when fibrous fillers are added ("wicking" effect with glass fibers, adversely affecting flame-retardancy).
Besides red phosphorus, there are four other possible halogen-free flame retardants.
1) Inorganic flame retardants based on hydroxides or on carbonates, in particular of magnesium. Large amounts of these have to be used to be sufficiently effective.
2) Nitrogen-containing flame retardants, such as melamine cyanurate. These mostly exhibit adequate flame retardancy only in unreinforced thermoplastics.
3) Phosphorus compounds, such as triphenylphosphine oxide as flame retardant. In many thermoplastics, these have an undesirable plasticizing side-effect.
4) Ammonium polyphosphates or melamine phosphate. These do not have adequate thermal stability above 200.degree. C.
Phosphazenes and their effectiveness as flame-retardants in thermoplastics have been disclosed in U.S. Pat. No. 3,332,905 and in C. W. Allen, Journal of Fire Sciences 11, 1993, p. 320-328.
EP-A 417 839 has disclosed the addition of a phospham of the formula (PN.sub.2 H).sub.x as a flame retardant for thermoplastics. Thermo-gravimetric studies in EP-A 417 839 have shown that (PN.sub.2 H).sub.x is heat-resistant up to 390.degree. C., but has disadvantages in other flame-retardant properties, since there is no crust formation on ignition and this makes it necessary to add an antidrip agent to prevent burning drops, and also an additive to promote carbonization.
It is an object of the present invention to provide a flame retardant for thermoplastics which gives adequate crust formation and carbonization on ignition, and does not give burning drops.
We have found that this object is achieved by means of the molding compositions defined at the outset. Preferred embodiments are given in the subclaims.
Surprisingly, the addition of a highly crosslinked phosphazene gives flame-retardant molding compositions which do not give burning drops and have adequate crust formation and carbonization. This is surprising because highly crosslinked phosphazenes are very thermally stable, i.e. chemically inert, and thus should have poorer effectiveness.
The novel molding compositions comprise, as component A) from 5 to 99% by weight, preferably from 10 to 80% by weight and in particular from 30 to 80% by weight of a thermoplastic polymer.
In principle, the advantageous effect in the novel molding compositions is apparent with thermoplastics of any type. A list of suitable thermoplastics is found, for example, in Kunststoff-Taschenbuch (ed. Saechtling), 1989 edition, in which supply sources are also mentioned. Processes for preparing such thermoplastics or thermosets are known per se to the person skilled in the art. Some preferred plastics types will be described below in somewhat more detail.
Polymers of this type are known per se to the person skilled in the art and are described in the literature.
Very generally, these polymers have at least 50 mol % of recurring --CH.sub.2 O-- units in the main polymer chain.
The homopolymers are generally prepared by polymerizing formaldehyde or trioxane, preferably in the presence of suitable catalysts.
For the purposes of the invention, preference is given to poly-oxymethylene copolymers, in particular those which, besides the recurring --CH.sub.2 O-- units, also have up to 50 mol %, preferably from 0.1 to 20 mol % and in particular from 0.3 t

REFERENCES:
patent: 3332905 (1967-07-01), Teter
patent: 4044104 (1977-08-01), Cremer et al.
patent: 4946885 (1990-08-01), Weil et al.
patent: 5578659 (1996-11-01), Anada et al.
Gmelin's Handbush der Anorganischen Chemie, 8th Ed., System No. 16, Part C, Verlag Chemie, Weinheim/Bergstr, 1965.
Journal of the Chemical Society, M.C. Miller et al., pp. 3233-3236, 1963.
The Use of Phosphazenes as Fire Resistant Materials, Allen, Jr. of Fire Sci., vol. 11, Jul./Aug. 1993, 320-328.

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