Fire-resistant thermoplastic composition

Abstract

A fire-resistant thermoplastic composition includes at least one ethylene polymer and/or a copolymer of ethylene and another organic compound, an inorganic loading material capable of releasing oxhydryle ions, an alkoxysilane acting as a coupling agent between the polymer or copolymer and the inorganic loading material, and a plasticizer.The alkoxysilane is an aminoalkyl-alkoxysilane, and the polymer or copolymer is non reticulated.

Description

The present invention relates to a fire-resistant thermoplastic composition, comprising at least one ethylene polymer and/or a copolymer of ethylene and of another organic compound, an inorganic loading material capable of releasing oxhydryl ions, an alkoxysilane acting as a coupling agent between the polymer or copolymer and the inorganic load, and a plasticizer.

Published French patent application FR-A-2 141 918 has already proposed such a composition, in which the alkoxysilane is an alkyl lower-alkoxysilane, an alcenyl-alkoxysilane, or an alcyne-alkoxysilane, especially a vinylsilane. That document also proposed substituting an aminosilane for the alkoxysilane, However, these compositions do not give very good results unless the polymer or copolymer is reticulated and one uses vinylsilane as a coupling agent.

The object of the present invention is to obtain a fire-resistant thermoplastic composition which does not require reticulation of the polymer or copolymer, and which still has good mechanical properties after aging and in the presence of oil.

The composition according to the invention is characterized by its alkoxysilane being an aminoalkyl-alkoxysilane and by a nonreticulated polymer or copolymer.

Preferably it has at least one of the following characteristics:

the aminoalkyl-alkoxysilane is gamma-aminopropyl-triethoxysilane; the proportion of amino alkyl-alkoxysilane is between 0.5% and 5% by weight of the polymer or copolymer; the copolymer is a copolymer of ethylene and vinyl acetate; the copolymer is a copolymer of ethylene and ethyl acrylate or butyl acrylate; the copolymer of ethylene is grafted with carboxyl groups; the inorganic loading material is aluminum trihydrate, kaolin, silica, calcium carbonate, or talc; the proportion of inorganic loading material is between 50% and 20% by weight of the polymer or copolymer; and the plasticizer is triphenylphosphate, in the amount of 1% to 10%, by weight, of the polymer or copolymer.

What follows describes, by way of example, two thermoplastic compositions according to the invention and their mechanical properties after and before aging, either in air or in the presence of oil.

EXAMPLE 1

The composition comprises by weight:

______________________________________Copolymer of ethylene or of 100 partsvinyl acetateAluminum Trihydrate Al(OH).sub.3 190 partsGamma-aminopropyl-triethoxysilane 125 partsAntioxidant 1 part(1, 2-dihydro-2, 2, 4-trimethyl-quinolene)Triphenylphosphate 3 parts______________________________________

The mechanical properties of this composition, as well as of an identical composition without the gamma-aminopropyl-triethoxysilane, are the following before and after aging:

______________________________________ Without Silane With Silane______________________________________Resistance to breaking 83.2 131Rr (in bars)Lengthening after 92 180breakage Ar (%)After 10 days of Rr -55% +16%aging at 100.degree. C. Ar +82% -7%After 7 days Rr +8.5%at 135% Ar -20%After 4 hours at 70.degree. C. Rr -25% -25%in the presence of oil Ar +215% +14%"ASTM n.degree. 2"Index of 39threshold oxygen______________________________________

EXAMPLE 2

The composition comprises by weight:

______________________________________Copolymer of ethylene and of 100 partsvinyl acetate grafted withcarboxyl groupsAluminum Trihydrate Al(OH).sub.3 170 partsSilica 30 partsGamma-aminopropyl-triethoxysilane 2.5 partsAntioxidant 1 part(1, 2-dihydro-2, 2, 4-trimethyl-quinolene)Triphenylphosphate 3 parts______________________________________

The mechanical properties, as well as those of an analogous composition, without the gamma-aminopropyl-triethoxysilane, are the following, before and after aging:

______________________________________ Without Silane With Silane______________________________________Resistance to 83 130breaking Rr (in bars)Lengthening at 52 150breakage Ar (%)After aging 10 days Rr brittle +23%at 100.degree. C. Ar unusable -13%After 4 hours at 70.degree. C. Rr -22%in the presence of oil Ar +35%"ASTM n.degree. 2"______________________________________

The invention is especially relevant to the manufacture of casing for electrical cables, such as the cables for telephone exchange.

Claims

1. A fire-resistant thermoplastic composition, comprising at least one ethylene polymer and/or a copolymer of ethylene and another organic compound, an inorganic loading material capable of releasing oxhydryl ions, an alkoxysilane acting as a coupling agent between the polymer or copolymer and the inorganic loading material, and a plasticizer, characterized by the alkoxysilane being an aminoalkyl-alkoxysilane, and by the polymer or copolymer being nonreticulated.

2. A composition according to claim 1, characterized by the aminoalkyl-alkoxysilane being gamma-aminopropyl-triethoxysilane.

3. A composition according to claim 1 or 2, characterized by the proportion of aminoalkyl-alkoxysilane being between 0.5% and 5% by weight of the polymer or copolymer.

4. A composition according to claim 1, characterized by the copolymer being a copolymer of ethylene and vinyl acetate.

5. A composition according to claim 1 characterized by the copolymer being a copolymer of ethylene and ethyl or butyl acrylate.

6. A composition according to claim 4 or 5, characterized by the copolymer being grafted with carboxyl groups.

7. A composition according to one of claims 1, 4, or 5, characterized by the inorganic loading material being selected from the group consisting of aluminum trihydrate, kaolin, silica, calium carbonate, and talc.

8. A composition according to one of claims 1, 4, or 5, characterized by the proportion of the inorganic charge material being between 50% and 200% by weight of the amount of polymer or copolymer.

9. A composition according to one of claims 1, 4, or 5, characterized by the plasticizer being triphenylphosphate, in a proportion of between 1% and 10% by weight of the polymer or copolymer.