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EP-3755675-B1 - ACCELERATED PEROXIDE-CURED RESIN COMPOSITIONS HAVING EXTENDED OPEN TIMES

EP3755675B1EP 3755675 B1EP3755675 B1EP 3755675B1EP-3755675-B1

Inventors

  • CROCKER, EVAN

Dates

Publication Date
20260513
Application Date
20190211

Claims (15)

  1. A curable resin composition comprised of: a). at least one curable resin; b). at least one organic peroxide, other than a perketal, which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more; c). at least one perketal which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more; d). at least one salt of at least one metal selected from the group consisting of Li, Al, Mg, Co, Fe, Cu, Zn, Ni, Mn, Cr, Sn, Au, Pd and Pt; e). at least one thiol-functionalized organic compound; and f). at least one free radical trap.
  2. The curable resin composition of claim 1, wherein the at least one thiol-functionalized organic compound includes at least one thiol-functionalized organic compound comprised of two or more thiol functional groups, and preferably includes at least one α-mercaptoacetate or β-mercaptopropionate ester of an alcohol.
  3. The curable resin composition of claim 1, wherein the at least one thiol-functionalized organic compound includes at least one thiol-functionalized organic compound selected from the group consisting of dipentene-dimercaptan; ethylcyclohexyldimercaptan; ethylene-1,2-bis-3-mercaptoacetate; ethylene-1,2-bis-3-mercaptopropionate; 1,2,3-propanetrithiol; 1,2,6-hexanetrithiol; pentaerythritolthiol; pentaerythritol tetramercaptoacetate; pentaerythritol tetramercaptopropionate; trimethylol propane tris(3-mercaptopropionate); 1,1,1-propanetriyl tris(mercaptoacetate)and thiolic derivatives of the formula: R-(R'-CH(OH)-CH 2 -SH) n wherein R is a linear alkyl group having 3-30 carbon atoms, R' is a linear alkylene group having 3-30 carbon atoms and n is an integer of 2-6.
  4. The curable resin composition of any of claims 1-3, wherein the at least one free radical trap includes at least one nitroxide radical, preferably selected from the group consisting of SG-1 free radicals and TEMPO free radicals.
  5. The curable resin composition of any of claims 1-4, wherein the at least one organic peroxide, other than a perketal, includes at least one perester or percarbonate which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more, preferably selected from the group consisting of t-butyl peroxybenzoate, t-amyl peroxybenzoate, t-butyl peroxyacetate, t-amyl peroxyacetate, t-butyl peroxy-3,5,5-trimethylhexanoate, OO-(t-butyl) O-isopropyl monoperoxycarbonate, OO-(t-butyl) O-(2-ethylhexyl) monoperoxycarbonate, OO-(t-amyl) O-(2-ethylhexyl) monoperoxycarbonate, and polyether poly-t-butylperoxy carbonate; and/or wherein the at least one perketal includes at least one perketal selected from the group consisting of 1,1-di(t-amylperoxy)-cyclohexane, 1,1-di(t-butylperoxy)-cyclohexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, ethyl 3,3-di(t-amylperoxy)butyrate and n-butyl 4,4-di(t-butylperoxy)valerate.
  6. The curable resin composition of any of claims 1-5, wherein the at least salt includes at least one transition metal halide, preferably at least one zinc halide.
  7. The curable resin composition of any of claims 1-6, wherein the at least one curable resin includes at least one curable resin selected from the group consisting of alkyd resins, unsaturated polyester resins, vinyl ester resins and (meth)acrylate resins.
  8. A cured resin composition obtained by curing the curable resin composition of any of claims 1-7.
  9. A composite comprised of the cured resin composition of claim 8 and, optionally, at least one reinforcing filler, wherein the composite is preferably in the form of a pultruded article or a cured-in-place pipe.
  10. A method of preparing a cured composition, comprising combining at least one curable resin; at least one organic peroxide, other than a perketal, which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more; at least one perketal which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more; at least one salt of at least one metal selected from the group consisting of Li, Al, Mg, Co, Fe, Cu, Zn, Ni, Mn, Cr, Sn, Au, Pd and Pt; at least one thiol-functionalized organic compound; and at least one free radical trap to form a curable resin composition and heating the curable resin composition.
  11. A system useful as a curing system for a curable resin, wherein the system comprises a first component and a second component and wherein the first component comprises at least one organic peroxide, other than a perketal, which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more; and at least one perketal which is liquid at 25°C and has a ten hour half-life temperature of 80°C or more, and the second component comprises at least one salt of at least one metal selected from the group consisting of Li, Al, Mg, Co, Fe, Cu, Zn, Ni, Mn, Cr, Sn, Au, Pd and Pt and at least one thiol-functionalized organic compound, wherein at least one free radical trap is present in at least one of the first component or the second component.
  12. An impregnated article comprised of at least one matrix of a reinforcing filler which is impregnated with a curable resin composition in accordance with any of claims 1-6.
  13. A method of making a pultruded, fiber-reinforced, resinous article comprising coating continuous fiber strands with a curable resin composition in accordance with any of claims 1-6 to obtain resin-coated continuous fiber strands and pulling the resin-coated continuous glass fiber strands through a shaping zone to provide an elongated structure, the curable resin composition being heated to a temperature effective to initiate curing of the curable resin.
  14. A method of making a cured-in-place pipe, comprising impregnating a liner with a curable resin composition in accordance with any of claims 1-6 to obtain an impregnated liner, placing the impregnated liner material within an existing pipe, and curing the impregnated liner within the existing pipe.
  15. A method of making a resin transfer molded article, comprising impregnating fiber reinforcement in matched mold tooling with a curable resin composition in accordance with any of claims 1-6 to obtain a composite part.

Description

Field of the Invention The present invention pertains to resin compositions which are capable of being cured using peroxides and which have an extended pot life (open time) at ambient (room) temperatures and yet can be quickly cured at higher temperatures, thereby making them particularly suitable for use in composite applications such as pultrusion, cure-in-place pipes, and resin transfer molding. Background of the Invention Composites based on curable thermoset resins such as unsaturated polyester resins and reinforcing fillers such as glass or carbon fibers typically exhibit advantageous mechanical properties such as high strength and rigidity. Curing of the resins in such systems often is achieved by initiation of free radical reactions using peroxides, leading to crosslinking of the curable resin. In at least some end-use applications for such composite systems, it is desirable for the resin to cure rapidly upon heating to an elevated temperature, in order to lower production costs and increase the efficiency of a composite manufacturing operation. Heating a curable resin containing peroxide may cause the peroxide to decompose and generate free radical species, which then initiate curing of the resin, resulting in the hardening of the liquid resin and providing the improved physical properties desirable in a composite system. A composite is considered cured when the physical form and shape of the composite part is fixed at the expected utilization temperature of the composite part. At the same time, however, the curable resin/peroxide/reinforcing filler mixture should desirably have a relatively slow rate of cure at ambient (room) temperature, in order to provide sufficient time for such a mixture to be shaped into a target form. Generally speaking, elevated temperature cures in which organic peroxides are used depend upon the thermal degradation of such organic peroxides to initiate polymerization of curable resins such as unsaturated polyester resins. In order to achieve cure times short enough to ensure reasonable cycle times, peroxides with relatively short half-lives at room temperature are used as primary initiators. Such peroxides generally are selected from peresters which must be stored at sub-ambient (freezing) temperatures due to their instability, such as t-butyl peroxyneodecanoate, or solid peroxydicarbonates such as di(2-ethylhexyl) peroxydicarbonate or di-(4-t-butylcyclohexyl) peroxydicarbonate. While effective, such types of peroxides are not optimal as they either require freezer storage (in the case of the liquid peroxides) which may increase storage costs and safety risks or (in the case of the solid peroxides) require additional effort and costs to disperse into a curable resin and are regulated with respect to storage due to their fire code classification. U.S. Pat. No. 5,310,826 describes accelerator compositions for the free radical polymerization and curing of unsaturated polyesters, wherein complexes of thiolic compounds with metal salts are used as accelerators. The accelerators may also include oxygen-containing compounds and may be used in combination with peroxide initiators. U.S. Pat. No. 5,235,010 teaches accelerator compositions for curing various unsaturated resins which include a complex of a salt of certain metals with an oxygen-containing compound, wherein a thiol compound may also be present. A peroxide initiator may be employed in combination with such complexes. U.S. Pat. Appln. Pub. No. 2011/0250373 discloses the use of nitroxides to control free radical cured resin systems in the production of thermosetting materials, wherein a radical initiator free radical polymerization initiator selected from diacyl peroxides, peresters, peroxydicarbonates and mixtures thereof may be utilized. International Publication No. WO 2008/003496 describes a two-component composition comprising a first component and a second component, wherein the first component is a resin composition comprising an unsaturated polyester resin or vinyl ester resin, a manganese compound and a thiol-containing compound and the second component comprises hydrogen peroxide or an alkyl hydroperoxide. U.S. Pat. Appln. Pub. No. 2009/0065737 discloses resin compositions comprising a thermosetting resin, an organic peroxide, preferably chosen from diacyl peroxides, peroxydicarbonates and peroxyesters, and a nitroxide compound. Summary of the Invention The invention is set out in the appended set of claims. The invention concerns various combinations of room-temperature-stable organic peroxides and various additives useful as initiators for the elevated temperature curing of composite systems based on curable resins such as unsaturated polyester resins. In accordance with aspects of the present invention, processes are provided that require only short cure times at elevated temperatures, while maintaining extended open times at ambient temperatures. In the context of the embodiments addressed here, cure time i