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US 5,911,940 AGranted
Dual cure process of producing crosslinked polyolefinic foams with enhanced physical properties
AssigneeThe Dow Chemical Company
InventorsKim L. Walton, Seema V. Karande
Life of this patent
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Abstract
Foamed articles having enhanced tensile, elastic recovery, and creep and fatigue resistance properties are prepared using a dual cure system. This system comprises a heat or radiation-activated first stage cure (which follows or coincides with foaming) followed by a moisture-activated second stage cure. Heat-activated curing systems include peroxide, sulfur, etc., and radiation-activated cure systems include electron beam, gamma-ray, etc. Moisture-activated systems include silane, sulfonyl chloride, and the like.
Claims20
A dual cure process for producing a shaped, polyolefinic foamed article, the process comprising the steps of:
- A. compounding and simultaneously or subsequently shaping a composition consisting essentially of at least one olefinic polymer, selected from the group consisting of homogeneously branched linear or substantially linear ethylene copolymers, ethylene/vinyl acetate (EVA), ethylene/methacrylate, ethylene/acrylic acid (EAA), and diene containing polymers, bearing pendent, moisture-activated crosslinking functionality with at least one foaming agent and, optionally, at least one other component selected from the group consisting of curing agent, filler, foaming agent activator, free radical crosslinking coagent, sulfur crosslinking promotor, pigment, foam nucleator, antioxidant, process aid, ultraviolet light absorber, and flame retardant, to form a shaped, substantially uncrosslinked, foamed article precursor;
- B. performing a first stage cure on the precursor of Step A in such a manner that most of the pendent, moisture-activated crosslinking functionality remains unreacted;
- C. simultaneously with or subsequently to the first stage cure of Step B, foaming the precursor of Step A to form a shaped, partially cured, foamed article;
- and
- D. performing a second stage, post-foaming moisture-activated cure of the pendent crosslinking functionality of the shaped, partially cured, foamed article of Step C, to obtain a shaped foamed article having a gel level of at least 90% determined according to ASTM D-2765-84.
2 more elements
A dual cure process for producing a shaped, polyolefinic foamed article, the process comprising the steps of:
- A. compounding under nongrafting conditions (i) at least one olefinic polymer, (ii) at least one moisture-activated, crosslinking functionality capable of being grafted to the olefinic polymer to form an olefinic polymer with pendent, moisture-activated crosslinking functionality, (iii) at least one free radical initiator, (iv) at least one foaming agent, and optionally (v) at least one curing agent to form a substantially homogeneous, uncrosslinked foamed article precursor;
- B. shaping the precursor of Step A under grafting conditions such that the free radical initiator is activated and a shaped, substantially uncrosslinked olefinic polymer with pendent, moisture-activated crosslinking functionality is formed;
- C. simultaneously with Step B, performing a first stage cure of the olefinic polymer with pendent, moisture-activated crosslinking functionality in such a manner that most of the pendent, moisture-activated crosslinking functionality remains unreacted;
- D. simultaneously with the first stage cure of Step C, foaming the precursor of Step A to form a partially cured, foamed article;
- and
- E. performing a second stage, post-foaming moisture-activated cure of the pendent crosslinking functionality of the partially cured, foamed article of Step D, to obtain a shaped foamed article having a gel level of at least 90% determined according to ASTM D-2765-84.
3 more elements
A dual cure process for producing a shaped, polyolefinic foamed article, the process comprising the steps of:
- A. compounding under nongrafting conditions (i) at least one olefinic polymer, (ii) at least one moisture-activated, crosslinking functionality capable of being grafted to the olefinic polymer to form an olefinic polymer with pendent, moisture-activated crosslinking functionality, (iii) at least one free radical initiator, (iv) at least one foaming agent, and optionally (v) at least one curing agent to form a substantially homogeneous, uncrosslinked foamed article precursor;
- B. shaping the precursor of Step A under grafting conditions such that the free radical initiator is activated and a shaped, substantially uncrosslinked olefinic polymer with pendent, moisture-activated crosslinking functionality is formed;
- C. simultaneously with or subsequent to Step B, performing a first stage cure of the olefinic polymer with pendent, moisture-activated crosslinking functionality in such a manner that most of the pendent, moisture-activated crosslinking functionality remains unreacted;
- D. simultaneously with or subsequently to the first stage cure of Step C, foaming the precursor of Step A to form a partially cured, foamed article;
- and
- E. performing a second stage, post-foaming moisture-activated cure of the pendent crosslinking functionality of the partially cured, foamed article of Step D, to obtain a shaped foamed article having a gel level of at least 90% determined according to ASTM D-2765-84,
- wherein the at least one olefinic polymer includes at least one ethylene/propylene/diene terpolymer rubber.
4 more elements
Dependencies are inferred from the claim text.