Tack free surface cures of polymers by organic peroxides in the presence of air

a technology of organic peroxide and polymer, which is applied in the field of organic peroxide free surface cure of polymers in the presence of air, can solve the problems of laborious surface coating technique, adverse effects of elemental sulfur on the final physical properties of cured elastomers, etc., and achieves the reduction or no surface tack, the effect of increasing the efficiency of free radical cure and reducing the efficiency of free radical initiators

Inactive Publication Date: 2004-09-16
ARKEMA INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0213] The invention contemplates that polysulfide polymers may be used in place of or in admixture with the other compounds (B) in equal quantities to those previously specified for those compounds. Since an excess of polysulfide polymer is not contemplated as detrimental to the practice of the invention, it is also contemplated that they may be preblended with the compound(s) (A) and optionally with the free radical initiator(s) to form masterbatches, either solid or liquid. The polysulfide polymers may also be preblended into the polymer to be cured and and the compound(s) (A) and also the free radical initiator(s) blended in simultaneously or subsequently at the option of the operator. Use of the polysulfide polymers in combination with the other sulfur accelerators contemplated by the invention permits reduction of the amount of sulfur accelerator required by the invention.
[0215] Certain crosslinkable elastomer compositions which are highly filled with oil and / or carbon black (commonly referred to as highly extended elastomer formulations) are normally cured using sulfur vulcanization rather than free radical initiators. Free radical cure is more difficult because the radicals generated lack specificity and react with the filler and oil as well as the elastomer. This reduces efficiency of the free radical initiator.
[0216] It has been found that the use of chlorinated polyethylene and / or chlorosulfonated polyethylene as supplemental ingredients to all the compositions of the various composition aspects of the invention surprisingly increases free radical cure efficiency in highly extended elastomer formulations and allows free radical cure of the systems with reduced or no surface tack. The amount of chlorinated and / or chlorosulfonated polyethylene as supplemental ingredients in the: compositions of the first composition aspect of the invention may be from about 1% to about 50% by weight, preferably 15% to 40% by weight and more preferably from 20% to 35% by weight.

Problems solved by technology

We have found, however, that the use of elemental sulfur adversely affects the final physical properties of the cured elastomer to the point where they are more typical of sulfur cure than peroxide cure.
This surface coating technique is labor intensive as it must be removed and disposed of after the crosslinking reaction step is completed.

Method used

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  • Tack free surface cures of polymers by organic peroxides in the presence of air
  • Tack free surface cures of polymers by organic peroxides in the presence of air
  • Tack free surface cures of polymers by organic peroxides in the presence of air

Examples

Experimental program
Comparison scheme
Effect test

example 1

Evaluation of Prior Art Compositions for Crosslinking EPM in the Presence of Air and their Effect on Surface Tack and Level of Crosslinking

[0219] In the example, various known co-curing agents, e.g., unsaturated monomeric crosslinking coagents, elemental sulfur, or sulfur donor compounds, were evaluated in a cure with an organic peroxide. The elastomer used in this example was an ethylene propylene copolymer (EPM) marketed by Exxon, VISTALON.RTM. 504. Prior art (U.S. Pat. No. 4,983,685) claims that use of high levels (2.5 to 20 parts) of specific sulfur containing compounds with or without optional unsaturated monomers can be used to crosslink elastomers with peroxide in the presence of air and produce a non-tacky surface. Other references employ sulfur. In this example, low levels of sulfur or sulfur donor compounds were evaluated alone or with some monomeric coagents. The data in Table 1 shows these formulations produced a sticky surface, but also provided a crosslinked product wi...

example 2

Compounding of Prior Art Peroxide Formulations Versus Novel Peroxide Formulations for Crosslinking fully Saturated (no Double Bonds within the Polymer Chains) Elastomers

[0225] The novel peroxide formulation provides good physical properties associated with a conventional peroxide cure, plus an unexpected non-tacky surface when crosslinking in the presence of air.

[0226] In this example, 40% assay dicumyl peroxide dispersed on clay, was used to crosslink EPM (polyethylene propylene copolymer) VISTALON.RTM. 707 (Exxon). Table 2, run #1, dicumyl peroxide blended with SR 206 (ethylene glycol dimethacrylate) was evaluated for crosslinking in the MDR, % compression set and in hot air cure for surface tack. Note: prior art (U.S. Pat. No. 4,983,685) used SR 206 as an optional monomeric coagent in their examples. This peroxide and coagent blend produced a good cure (M.sub.H) and % compression set, with a very sticky surface upon hot air cure at 400.degree. F. Addition of Sulfads.RTM. (98% dip...

example 3

Novel Peroxide-Additive Compositions Produce Solid or Foamed Crosslinked Elastomer in Hot Air, with Outstanding Physical Properties, e.g. Percent Compression set, while also Producing a non Tacky Surface when Curing in the Presence of Air

[0234] The elastomer used in this example was Uniroyal.RTM. X3378 EPDM containing 4% dicyclopentadiene as the tenmonomer. Peroximon DC 40KEP (40% dicumyl peroxide on clay) was used as the peroxide crosslinking agent. In this example the levels of Sulfads.RTM. 98% dipentamethylene thiuram tetra sulfide), VULTAC.RTM. 5 (75% alkyl phenol disulfide polymer) and Durax.RTM. (98% N-cyclohexyl-2-benzothiazolesulfenamnide) were varied, keeping the peroxide and HVA-2 coagent constant (Table 3, runs #2 to #6).

[0235] Note: adding 0.5 parts (phr) Sulfads is equivalent to 0.49 parts of dipentamethylene thiuram tetra sulfide, per 100 parts of rubber. Referring to runs #2, #3 and #4, unexpectedly, excellent compression set and a tack free surface were found when us...

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Abstract

Compositions are disclosed which comprise mixtures of at least one compound selected from silicone elastomers, bis-, tri- or higher polymaleimides and / or bis-, tri- or higher polyciraconimides, and at least one compound selected from p-phenylene-diamine based antiozonants, sulfur compounds capable of accelerating sulfur vulcanization of polymers capable of being crosslinked by sulfur and polysulfide polymers which when compounded into polymers curable by free radical initiators in the presence of free radical initiators permit substantially tack free surface cure of the polymers by decomposition of the free radical initiator in the presence of molecular oxygen. Compositions containing the above ingredients and at least one free radical initiator, curable compositions containing the combination and processes for making and using the compositions are also disclosed.

Description

[0001] This application claims priority from provisional application 60 / 164,488 filed Nov. 9, 1999.[0002] This invention relates to compositions of matter classified in the art of chemistry as bis-, tri- and higher poly-maleimides, as bis-, tri-and higher poly-citraconimides, as silicone elastomers, as p-phenylenediamine based antiozonants and as sulfur containing organic compounds which are accelerators for the sulfur curing (crosslinking) of polymers which are curable / crosslinkable by sulfur and also sulfur compounds which are polysulfide polymers. The invention also relates to compositions containing them, to processes for their use and to the products produced by such processes.[0003] Polymers and copolymers crosslinked with free radical initiators; organic peroxides and / or azo initiators, are known to have superior properties, particularly to polymers crosslinked by sulfur cure. These properties include high heat ageing resistance, low compression set, decreased staining of met...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C08F8/00C08F114/00C08K5/00C08K5/3415
CPCC08K5/3415C08K5/0025
Inventor NOVITS, MICHAEL F.PALYS, LEONARD H.GULLO, GARY J.
Owner ARKEMA INC
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