Scorch-retardant composition

a technology of corrosion-retardant composition and composition, applied in the field of corrosion-retardant composition, can solve the problems of inhomogeneity or surface roughness premature crosslinking (scorching), and imperfections of the final product, and achieve the effect of improving the plasticity of the material

Inactive Publication Date: 2004-10-07
ARKEMA INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a scorch-retardant composition that prevents premature crosslinking (scorching) during the preparatory phase of thermoplastic and elastomeric materials. The invention uses a specific family of nitroxides that do not negatively impact the crosslinking time and final crosslinking density. The nitroxides used in the invention have at least one unsaturation that is reactive towards free-radical addition. The invention also includes a scorch-retardant crosslinking composition and a crosslinkable composition that includes a thermoplastic polymer or elastomeric polymer that may be crosslinked by means of a peroxide or an azo compound, a nitroxide, and a free-radical initiator.

Problems solved by technology

Premature crosslinking (scorching) during the preparatory phase is a major difficulty in the use of peroxides and azo compounds in crosslinking (curing) applications of elastomeric and / or thermoplastic materials.
The presence of these gel particles leads to imperfections (inhomogeneity or surface roughness) of the final product.
Excessive scorching reduces the plastic properties of the material, such that the said material can no longer be converted, leading to loss of the entire batch.
In addition, excessive scorching may lead to the total stoppage of the extrusion operation.
The drawbacks of this approach are the low production efficiency due to a long curing time and the high energy costs.
However, the use of the additives of the art cited above to increase the scorch-resistance time has a harmful effect on the curing time and / or on the final crosslinking density.
It leads to a reduction in the production efficiency and / or properties of the final product.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 2

Not in Accordance With the Invention

[0054] Example 1 was repeated without the use of 2,2,6,6-tetramethylpiperi-dyloxy. The results are given in Table 1. The comparison of Examples 1 and 2 shows that the higher scorch time with TEMPO is accompanied by a large decrease in the crosslinking density and a slight increase in the crosslinking time.

example 3

[0055] The process is performed as described in Example 1, except that the 3 g of 2,2,6,6-tetramethylpiperidyloxy are replaced with 4.4 g of NT1 (2,2,6,6-tetramethyl-4-piperidyloxy methacrylate) so as to carry out a comparison for an equivalent concentration of nitroxide function.

[0056] The comparison of the results with those obtained in the preceding examples shows unambiguously that this nitroxide makes it possible to increase the scorch time while at the same time increasing the crosslinking density.

1 TABLE 1 Maximum Scorch Crosslinking torque at time at time at 180.degree. C. 145.degree. C. 180.degree. C. (M.sub.H) (T.sub.s5) (T.sub.90) Additive (N.m) (min:s) (min:s) Example 1 TEMPO 1.21 19:00 7:10 Example 2 -- 1.95 8:40 6:50 Example 3 NT1 2.42 14:10 6:20 Example 4 -- 5.94 2:50 5:21 Example 5 OH-TEMPO 5.14 16:19 5:39 Example 6 NT1 6.14 15:47 4:12

example 4

Not in Accordance With the Invention

[0057] 318 g of compound EPDM DIN 7863 (containing 100 g of ethylene-propylene-diene terpolymer and 218 g of fillers) were conditioned in a Banbury-type mixer with a volume of 350 cm.sup.3 at 50.degree. C. for 5 minutes at a speed of 50 revolutions / min. 8 g of Luperox F40ED (40% di(tert-butylperoxyisopropyl)benzene and 60% inert fillers) were added and mixed with the compound for 5 minutes at 50.degree. C. at a speed of 50 revolutions / min.

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Abstract

The present invention relates to the prevention of scorching before crosslinking of a thermoplastic and / or elastomeric composition with peroxides or azo compounds. This is achieved by using a family of specific nitroxides as additive.

Description

[0001] (i) Field of the Invention[0002] The present invention relates to the prevention of scorching before crosslinking of a thermoplastic and / or elastomeric composition with peroxides or azo compounds.[0003] (ii) Description of Related Art[0004] Premature crosslinking (scorching) during the preparatory phase is a major difficulty in the use of peroxides and azo compounds in crosslinking (curing) applications of elastomeric and / or thermoplastic materials. The preparatory phase consists in general in blending the constituents and optionally extruding them at temperatures that are often high. The operating conditions of this preparatory phase quite often lead to decomposition of the peroxide or azo initiator, thus inducing the crosslinking reaction with formation of gel particles in the bulk of the blend. The presence of these gel particles leads to imperfections (inhomogeneity or surface roughness) of the final product. Excessive scorching reduces the plastic properties of the mater...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C08K5/32C08K5/3412C08K5/3415C08K5/3435
CPCC08K5/32C08K5/3412C08K5/3415C08K5/3435C08L21/00
InventorDEBAUD, FABIENDEFRANCISCI, ALFREDOGUERRET, OLIVIERKERVENNAL, JACQUES
OwnerARKEMA INC