Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-06-14
2002-10-22
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S436000, C524S504000, C524S522000, C525S078000, C525S221000, C525S329700, C525S386000, C525S387000, C526S318000, C526S318250
Reexamination Certificate
active
06469095
ABSTRACT:
The invention relates to thermoplastic molding compositions comprising
A) from 10 to 90% by weight of at least one thermoplastic polymer,
B) from 1 to 20% by weight of a polyethylene which contains carboxyl groups and has a mean molecular weight M
n
(number average) of from 24,000 to 100,000 g/mol,
C) from 5 to 60% by weight of a halogen-free flame retardant
D) from 0 to 70% by weight of other additives and processing aids,
where the total of the percentages by weight of components A) to D) is 100%.
The invention also relates to the use of the novel molding compositions to produce fibers, films and shaped articles, and to the shaped articles of any type thus obtainable.
Ethylene copolymers carrying functional groups of various types are known as impact-modifiers for thermoplastics: for polyesters, from U.S. Pat. No. 4,879,328, DE-A-26 22 876 and EP-A 174 343, for example; for polyamides, from DE-A-26 22 973, for example.
DE-A 42 16 042 discloses low-molecular-weight polyethylene waxes which contain carboxyl groups and which improve the flame retardancy of unreinforced polyamides through specific preparation processes.
Such low-molecular-weight polyethylene additives, however, always continue to show dripping of flaming material, which for many applications is not acceptable.
Flame-retardant polyester molding compositions which, inter alia, contain ethylene copolymers are known from U.S. Pat. No. 5,021,495, where these molding compositions contain a halogen-containing flame retardant and an antimony synergist.
Halogen-containing flame-retardant thermoplastics are, besides other disadvantages, toxicologically questionable, and are increasingly being replaced by halogen-free flame-retardant thermoplastics.
Important requirements for such flame-retardant systems are in particular a light intrinsic color, adequate high-temperature stability during incorporation in the thermoplastics and retention of effectiveness when fibrous fillers are added (wicking effect of glass fibers, which adversely affects the flame-retardant properties).
Besides red phosphorus, there are mainly four other particular examples of halogen-free flame retardants.
1. Inorganic flame retardants based on hydroxides or carbonates, in particular those of magnesium, which must be employed in large amounts to have sufficient effect;
2. Nitrogen-containing flame retardants, such as melamine cyanurate, which mostly show adequate flame retardancy only in unreinforced thermoplastics;
3. Phosphorus compounds, such as triphenylphosphine oxide as flame retardant, which in many thermoplastics have an undesirable plasticizing side-effect;
4. Ammonium polyphosphates or melamine phosphate, which have inadequate thermal stability above 200° C.
It is an object of the present invention to provide a halogen-free flame-retardant combination for thermoplastics which shows adequate crust formation and charring in the presence of a flame, and prevents dripping of flaming material.
We have found that this object is achieved by means of the molding compositions defined at the outset. Preferred embodiments are seen in the subclaims.
Surprisingly, the addition of the ethylene copolymers according to the invention, in particular low-molecular-weight copolymers, in combination with halogen-free flame retardants, gives a synergistic flame-retardant effect. Thermoplastics containing glass fiber, in particular, show no dripping of flaming material when the combination according to the invention is used.
By means of the combination with ethylene copolymers, the amount of halogen-free flame retardant required to achieve the flammability materials classification V-O according to UL 94 can be drastically reduced, thus improving processibility and mechanical properties.
The novel molding compositions contain, as component A), from 10 to 90% by weight, preferably from 20 to 85% 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 seen with thermoplastics of any type. A list of suitable thermoplastics is found, for example, in Kunststoff-Taschenbuch (ed. Saechtling), 1989 edition, which also gives reference sources. Processes for preparing such thermoplastics are known per se to the person skilled in the art. Some preferred plastics types are described in greater detail below.
1. Polycarbonates and Polyesters
Suitable polycarbonates (often also termed aromatic polyesters) are known per se. They are obtainable, for example, by interfacial polycondensation corresponding to the processes of DE-B-1 300 266 or by reaction of diphenyl carbonate with bisphenols, as in the process of DE-A-14 95 730. The preferred bisphenol is 2,2-di(4-hydroxyphenyl)propane, referred to generally, and also below, as bisphenol A.
In place of bisphenol A, other aromatic dihydroxy compounds can also be used, in particular 2,2-di(4-hydroxyphenyl)pentane, 2,6-dihydroxynapthalene, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfite, 4,4′-dihydroxydiphenylmethane, 1,1-di(4-hydroxyphenyl)ethane or 4,4-dihydroxydiphenyl, and mixtures of these.
Particularly preferred polycarbonates are those based on bisphenol A or bisphenol A together with up to 30 mol % of the abovementioned aromatic dihydroxy compounds.
The relative viscosity of these polycarbonates is generally in the range from 1.1 to 1.5, in particular from 1.28 to 1.4 (measured at 25° C. in a 0.5% strength by weight solution in dichloromethane).
Suitable polyesters are likewise known per se and described in the literature. They contain, in their main chain, an aromatic ring which derives from an aromatic dicarboxylic acid. The aromatic ring may also be substituted, eg. with halogen, such as chlorine and bromine, or with C
1
-C
4
-alkyl, such as methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl or tert-butyl.
The polyesters may be prepared by reaction of aromatic dicarboxylic acids, their esters or other ester-forming derivatives thereof with aliphatic dihydroxy compounds, in a manner known per se.
Preferred dicarboxylic acids are naphthalenedicarboxylic acid, terephthalic acid and isophthalic acid or mixtures of these. Up to 10 mol % of the aromatic dicarboxylic acids can be replaced by aliphatic or cycloaliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and cyclohexanedicarboxylic acids.
Of the aliphatic dihydroxy compounds, preference is given to diols having from 2 to 6 carbon atoms, in particular 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol and neopentyl glycol or mixtures of these.
Particularly preferred polyesters are polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Of these, polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate are particularly preferred.
The viscosity number of the polyesters is generally in the range from 60 to 200 ml/g (measured in a 0.5% strength by weight solution in a mixture of phenol and o-dichlorobenzene (weight ratio 1:1) at 25° C.).
2. Vinylaromatic Polymers
The molecular weight of these polymers, which are known per se and are commercially available, is generally in the range from 1500 to 2,000,000, preferably in the range from 70,000 to 1,000,000.
Vinylaromatic polymers which may be mentioned merely as examples here are those made from styrene, chlorostyrene, &agr;-methylstyrene and p-methylstyrene; comonomers, such as (meth)acrylonitrile or (meth)acrylates, may also be involved in the construction in subordinate proportions (preferably not more than 20% by weight, in particular not more than 8% by weight). Particularly preferred vinylaromatic polymers are polystyrene and impact-modified polystyrene. Mixtures of these may, of course, also be employed. They are preferably prepared by the process described in EP-A-302 485.
Preferred ASA polymers are built up from a soft or rubbery phase of a graft polymer of:
A
1
from 50 to 90% by weight of a graft base, based on
A
11
Deckers Andreas
Gareiss Brigitte
Klatt Martin
Weber Wilhelm
BASF - Aktiengesellschaft
Keil & Weinkauf
Szekely Peter
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