Search

EP-4735514-A1 - FLAME RETARDANT POLYMERIC COMPOSITIONS

EP4735514A1EP 4735514 A1EP4735514 A1EP 4735514A1EP-4735514-A1

Abstract

A moisture curable polymeric composition includes 10 wt% to 99 wt% of a silane-functionalized polyolefin based on the total weight of the moisture curable polymeric composition and 1 wt% to 90 wt% of an intumescent flame-retardant mixture based on the total weight of the moisture curable polymeric composition. The intumescent flame-retardant mixture comprises piperazine pyrophosphate and from 15 wt% to 55 wt% of a phosphoric acid compound based on the total weight of the intumescent flame-retardant mixture.

Inventors

  • CHAUDHARY, BHARAT I.
  • TAPPER, Richard, I.

Assignees

  • Dow Global Technologies LLC

Dates

Publication Date
20260506
Application Date
20240626

Claims (11)

  1. CLAIMS What is claimed is 1. A moisture curable polymeric composition comprising: 10 wt% to 99 wt% of a silane-functionalized polyolefin based on the total weight of the moisture curable polymeric composition; and 1 wt% to 90 wt% of an intumescent flame-retardant mixture based on the total weight of the moisture curable polymeric composition, wherein the intumescent flame-retardant mixture comprises piperazine pyrophosphate and from 15 wt% to 55 wt% of a phosphoric acid compound based on the total weight of the intumescent flame-retardant mixture.
  2. 2. The moisture curable polymeric composition of claim 1, wherein the silane functionalized polyolefin is a silane functionalized ethylene-based polymer.
  3. 3. The moisture curable polymeric composition of any one of claims 1 and 2, wherein the polymeric composition comprises 30 wt% or greater of the silane functionalized polyolefin based on a total weight of the moisture curable polymeric composition.
  4. 4. The moisture curable polymeric composition of any one of claims 1-3, wherein the polymeric composition comprises 15 wt% or greater of the intumescent flame-retardant mixture based on a total weight of the moisture curable polymeric composition.
  5. 5. The moisture curable polymeric composition of any one of claims 1-4, wherein the intumescent flame-retardant mixture comprises from 25 wt% to 45 wt% of phosphoric acid compound based on the total weight of the intumescent flame-retardant mixture.
  6. 6. The moisture curable polymeric composition of any one of claims 1-5, wherein the phosphoric acid compound is selected from the group consisting of melamine polyphosphate, ammonium polyphosphate, or combinations thereof.
  7. 7. The moisture curable polymeric composition of any one of claims 1-6, wherein the moisture curable polymeric composition exhibits a density of 1.70 g/cc or less as measured according to ASTM D792.
  8. 8. The moisture curable polymeric composition of any one of claims 1-8, wherein the moisture curable polymeric composition is free of dibutyltin dilaurate and sulfonic acid.
  9. 9. A moisture cured polymeric composition prepared from the moisture curable polymeric composition of any one of claims 1-8, wherein the moisture cured polymeric composition exhibits one or more of the following properties: a peak tensile strength of 4 megapascals or greater as measured according to ASTM D638; a tensile elongation at break of 50% or greater as measured according to ASTM D638; and 175% or less hot creep as measured according to UL 2556 Section 7.9.
  10. 10. A coated conductor, comprising a conductor; and the moisture-cured polymeric composition of claim 9 positioned around the conductor.
  11. 11. The coated conductor of claim 10, wherein the coated conductor passes a UL-2556 Horizontal Burn Test.

Description

FLAME RETARDANT POLYMERIC COMPOSITIONS BACKGROUND Field of the disclosure The present disclosure relates to polymeric compositions, and more specifically to filled flame retardant polymeric compositions. Introduction Jacket and/or insulation layers of wires and cables utilized in structures often must exhibit certain threshold flame retardancy properties. Thermoplastic ethylene-based polymers (also known as polyethylenes) are often utilized as the base polymers in the compositions of such jackets or insulations when incorporating high levels of halogen-free flame retardant (“HFFR”) fillers in such materials, however thermoplastic compositions lack sufficient resistance to flow and deformation when exposed to elevated temperatures. Crosslinked polyolefin compositions are used in a variety of applications where such heat resistance and good mechanical properties are required. The crosslinking of a polyolefin transforms a thermoplastic composition into a thermoset composition which increases its resistance to deformation and flow at elevated temperatures because the polymer chains are linked together, unlike in the case of a thermoplastic composition. There are a variety of methods to crosslink polymeric compositions including vulcanization for peroxide-induced crosslinking, electron beam based crosslinking and moisture-induced crosslinking through the use of silane functionalization. Silane crosslinking of polymeric compositions utilizing silane functionalization of the polymers typically requires use of silanol condensation catalysts such as tin-based dibutyltin dilaurate and/or strong acids such as sulfonic acids. The presence of moisture in such formulations is undesirable as it can lead to premature crosslinking during melt extrusion. Moisture-induced crosslinking of the formulations occurs in a subsequent step after fabrication of the article, through the diffusion of water into the article. Polymeric compositions are typically considered to be crosslinked if they exhibit a gel content of 10 wt% or greater as measured according to ASTM D2765. The level of flame retardancy (if any) required in a moisture-cured polymeric composition will depend on its intended application, with the UL-2556 Horizontal Burn Test being an example in the arena of wire and cable applications. Typically, a flame retardant moisture-cured polymeric composition should exhibit a peak tensile strength of 600 psi (4 megapascals, MPa) or greater, a tensile elongation at break of 50% or greater, hot creep (also known as hot set elongation) < 175% measured according to ICEA Standard T-28-562 and, for horizontal burn applications, should exhibit a char length of 100 mm or less and no dripping or cotton ignition when tested according to the UL-2556 Horizontal Burn Test. Intumescent compounds can be used as halogen-free flame retardant (“HFFR”) fillers in polymeric applications. Intumescent compounds operate by expanding when exposed to heat thereby volume diluting the available polymeric material available for combustion. For example, United States Patent Application Publication number 2003/0088000A1 discloses the use of intumescent compounds with polymeric systems such as polypropylene. Intumescent compounds have not been used in silane crosslinked (moisture curable) systems before possibly because they often contain pentaerythritol (as a charring agent) which can undergo dehydration in the presence of an acid or acid source (such as ammonium polyphosphate, which is a typical component of intumescent compounds) to yield water that in turn would yield premature crosslinking during melt extrusion of compositions containing silane functionalized polymers. Equation 1 of Applied Catalysis A: General 253 (2003) 29–32 depicts the generation of water from acid-catalyzed dehydration of pentaerythritol. In view of the forgoing, it would be surprising to discover a silane crosslinked (moisture curable) polymeric composition including an intumescent flame-retardant mixture which does not crosslink prematurely during melt extrusion and which exhibits the above -noted peak tensile strength, tensile elongation at break and passage of the Horizontal Burn Test. SUMMARY OF THE DISCLOSURE The inventors of the present disclosure have discovered a silane crosslinked (moisture curable) polymeric composition including an intumescent flame-retardant mixture which does not crosslink prematurely during melt extrusion and which exhibits the above-noted peak tensile strength, tensile elongation at break and passage of the Horizontal Burn Test. The present disclosure is the result of using intumescent flame-retardant mixtures comprising piperazine pyrophosphate and a phosphoric acid compound that do not undergo acid catalyzed decomposition to yield problematic water during melt extrusion, the evidence of which would be surface roughness due to premature crosslinking of the silane-functionalized polyolefin. According to a first feature of the disclosure, a moistu