Flame-proof moulding compounds

Details Flame-proof moulding compounds Flame-proof moulding compounds

1999-04-14

2003-03-25

Szekely, Peter (Department: 1714)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S148000, C524S151000, C524S230000, C524S311000

Reexamination Certificate

active

06538054

ABSTRACT:

The invention relates to thermoplastic molding compositions comprising
A) from 30 to 96% by weight of a polyester
B) from 1 to 30% by weight of melamine cyanurate
C) from 1 to 30% by weight of at least one phosphorus-containing flame retardant
D) from 0.01 to 5% by weight of at least one ester or amide derived from a saturated or unsaturated aliphatic carboxylic acid having from 10 to 40 carbon atoms and a saturated aliphatic alcohol or amine having from 2 to 40 carbon atoms
E) from 0 to 60% by weight of other additives and processing aids
where the total of the percentages by weight of components A) to E) is 100%.
The invention also relates to the use of the novel molding compositions to produce fibers, films or shaped articles, and to the shaped articles of any type thus obtained.
The market shows increasing interest in halogen-free flame-retardant polyesters. Important requirements of the flame retardant are: pale intrinsic color, sufficient thermal stability for incorporation in thermoplastics, and its efficacy in reinforced and non-reinforced polymers (wicking effect of glass fibers).
In addition, the UL 94 flammability test should also be passed at the V-0 level.
In principle, besides halogen-containing systems, four halogen-free FR systems are used in thermoplastics:
Inorganic flame retardants which must be employed in large amounts to be effective.
Nitrogen-containing FR systems, such as melamine cyanurate, which has limited efficacy in thermoplastics, eg. polyamide. In reinforced polyamide, it is effective only in combination with shortened glass fibers. In polyesters, melamine cyanurate is not effective.
Phosphorus-containing FR systems, which are generally not effective in polyesters.
Phosphorus
itrogen-containing FR systems, eg. ammonium polyphosphates or melamine phosphates, which have insufficient thermal stability for thermoplastics processed above 200° C.
JP-A 03/281 652 discloses polyalkylene terephthalates containing melamine cyanurate and glass fibers and also a phosphorus-containing flame retardant. These molding compositions contain phosphoric acid derivatives, such as phosphoric acid esters (valence state +5), which tend to “bloom” when subjected to thermal stress.
These disadvantages are also apparent for the combination of melamine cyanurate with resorcinol bis(diphenylphosphate) disclosed in JP-A 05/070 671.
It is an object of the present invention to provide flame-retardant polyester molding compositions which achieve the UL 94 classification V-0 and pass the glowing wire test. In doing so, mold deposit should be minimized, ie. “blooming” of the flame retardants should be substantially prevented. Furthermore, the mechanical properties should be maintained as far as possible.
We have found that this object is achieved by means of the thermoplastic molding compositions defined at the outset. Preferred embodiments are given in the subclaims.
The novel molding compositions comprise, as component (A), from 30 to 96%, preferably from 40 to 93%, and in particular from 50 to 85%, of a thermoplastic polyester.
Polyesters which are used are generally based on aromatic dicarboxylic acids and an aliphatic or aromatic dihydroxy compound.
A first group of preferred polyesters consists of polyalkylene terephthalates having from 2 to 10 carbon atoms in the alcohol moiety.
Polyalkylene terephthalates of this type are known per se and are described in the literature. They contain, in their main chain, an aromatic ring which derives from the aromatic dicarboxylic acid. The aromatic ring may also be substituted, for example with halogen, such as chlorine or bromine, or with C
1
-C
4
-alkyl, such as methyl, ethyl, isopropyl or n-propyl, n-butyl, isobutyl or tert-butyl
These polyalkylene terephthalates can be prepared by reaction of aromatic dicarboxylic acids, their esters or other ester-forming derivatives with aliphatic dihydroxy compounds, in a manner known per se.
Preferred dicarboxylic acids are, for example, 2,6-naphthalenedicarboxylic acid, terephthalic acid and isophthalic acid or mixtures of these. Up to 30 mol %, preferably not more than 10 mol %, of the aromatic dicarboxylic acids may be replaced by aliphatic or cycloaliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and cyclohexanedicarboxylic acids.
Preferred aliphatic dihydroxy compounds are diols with from 2 to 6 carbon atoms, in particular 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethylanol and neopentyl glycol, and mixtures of these.
Particularly preferred polyesters (A) are, for example, polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Of these, especial preference is given to polyethylene terephthalate and polybutylene terephthalate or mixtures of these.
The viscosity number of the polyesters (A) is generally in the range from 70 to 220, preferably from 80 to 160 (measured in a 0.5% strength by weight solution in a mixture of phenol and o-dichlorobenzene (weight ratio 1:1) at 25° C.
Particular preference is given to polyesters whose content of carboxyl end groups is up to 100 mval/kg, preferably up to 50 mval/kg, and especially up to 40 mval/kg of polyester. Polyesters of this type may be prepared, for example, by the process of DE-A-44 01 055. The content of carboxyl end groups is generally determined by titration methods (eg. potentiometry).
Particularly preferred molding compositions contain, as component A), a mixture of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). he proportion of the polyethylene terephthalate in the mixture is preferably up to 50% by weight, in particular from 10 to 30% by weight, based on 100% by weight of A).
Novel molding compositions of this type have very good flame retardance and improved mechanical properties.
It is moreover advantageous to use recycled PET materials (also termed scrap PET) in a mixture with polyalkylene terephthalates, such as PBT.
For the purposes of the invention, recycled materials are generally:
1) Post-industrial recycled materials: these are production wastes from polycondensation or processing, eg. injection-molding sprues, start-up material from injection molding or extrusion or edge cuts from extruded sheets or films.
2) Post-consumer recycled materials: these are plastic items which are collected and reprocessed after use by the final consumer. The items which, in terms of quantity, predominate by a wide margin are blow-molded PET bottles for mineral water, soft drinks and juices.
Both types of recycled material may be in the form either of regrind or of pellets. In the latter case, the raw recycled materials, after separation and cleaning, are melted in an extruder and pelletized. This usually makes the material easier to handle, more free-flowing and easier to meter out for further processing steps.
The recycled materials used may be either pelletized or in the form of regrind; the maximum edge length should be 6 mm, preferably below 5 mm.
Because polyesters can be cleaved by hydrolysis during processing (by traces of moisture), it is advisable to predry the recycled material. The residual moisture content after drying is preferably from 0.01 to 0.7%, in particular from 0.2 to 0.6%.
A further group which may be mentioned is that of the fully aromatic polyesters derived from aromatic dicarboxylic acids and aromatic dihydroxy compounds.
Suitable aromatic dicarboxylic acids are the compounds described above in relation to polyalkylene terephthalates. Preference is given to mixtures of from 5 to 100 mol % of isophthalic acid and from 0 to 95 mol % of terephthalic acid, in particular mixtures of from about 80 to about 50% of terephthalic acid with about 20 to about 50% of isophthalic acid.
where Z is alkylene or cycloalkylene having up to 8 carbon atoms, arylene having up to 12 carbon atoms, carbonyl, sulfonyl, an oxygen or sulfur atom, or a chemical bond, and where m is from 0 to 2. Compounds I may also carry C
1
-C
6
-alkyl or -alkoxy and fluorine, chlorine or bromine a

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