Monomodal foamed polymeric compositions containing clay nucleating agents are described. The clays are preferably sepiolite, palygorskite/attapulgite, or combinations thereof. Also described are processes for forming the foamed compositions.
1. A foamable polymer composition comprising a polymeric matrix having at least one sepiolite-type clay dispersed therein, the polymeric matrix comprising at least one of i) a thermoplastic polymer and ii) a thermoset polymer;
wherein, when the polymeric matrix comprises i) a thermoplastic polymer, then the blowing agent used to form the composition into a foam is free of water;
at least one selected from the group consisting of nekoite, okenite, faujasite and hillebrandite; and
at least one blowing agent dispersed in the polymeric matrix.
2. The foamable polymer composition according to claim 1 , further comprising at least one additive agent dispersed in the polymeric matrix, wherein the additive agent is selected from the group consisting of flame retardants, secondary nucleating agents, blowing agents, dyes, pigments, lubricants, antistatic agents, biocides, aging modifiers, heat stabilizers, antioxidants, ultraviolet stabilizers, coupling agents, fillers, acid scavengers, preservatives, plasticizers, impact modifiers, chain extenders, graphite, graphene, hydrophilic agents, and combinations thereof.
3. The foamable polymer composition according to claim 2 , wherein the flame retardant additive is a halogenated compound, including polymeric halogenated additives.
4. The foamable polymer composition according to claim 3 , wherein the halogenated compound is a bromine-containing compound.
5. The foamable polymer composition according to claim 2 , wherein the flame retardant additive is a phosphorus compound and is selected from the group consisting of organophosphorus-sulfur compounds, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, phosphines, phosphonium salts, phosphorus-sulfur compounds, and combinations thereof.
6. The foamable polymer composition according to claim 1 , wherein the at least one sepiolite-type clay is from about 0.01% to about 5% by weight of the polymeric matrix.
7. The foamable polymer composition according to claim 1 , wherein the at least one blowing agent includes CO 2 .
8. The foamable polymer composition of claim 1 , wherein the sepiolite-type clay is attapulgite.
9. The polymer foam composition according to claim 2 , wherein the at least one additive agent includes a secondary nucleating agent selected from the group consisting of talc, wollastonite, zeolite, diatomaceous earth, a molecular sieve material, and combinations thereof.
10. The foamable polymer composition of claim 2 , wherein the flame retardant additive is selected from the group consisting of halogenated compounds, halogen-free compounds, phosphorus compounds, nitrogen-based compounds, polymeric halogenated additives, and combinations thereof.
11. The foamable polymer composition according to claim 4 , wherein the halogenated bromine-containing compound is selected from the group consisting of tris(tribromoneopentyl)phosphate, tetrabromobisphenol A bis (2,3-dibromopropyl ether), hexabromocyclododecane (HBCD), and mixtures thereof.
12. The foamable polymer composition according to claim 1 , wherein the thermoplastic polymer is selected from the group consisting of polystyrene, polyethylene, polypropylene, ethylene vinyl acetate, maleic anhydride grafted polymers, polyethylene terephthalate, poly(methyl methacrylate), polyamide, thermoplastic polyesters, polycarbonate, styrene butadiene copolymers, acrylonitrile butadiene styrene, styrene acrylonitrile, styrene block copolymers, ethylene methyl acrylate copolymers, polyacrylonitriles, polyurethanes, polyvinyl chloride, polyvinyl alcohol, melamine formaldehyde, urea formaldehyde, polymethyiene urea, natural rubber, synthetic rubber, elastomers, biodegradable polymers, and mixtures thereof.
13. The foamable polymer composition according to claim 1 , wherein the sepiolite-type clays are pre-wetted with water.
14. The foamable polymer composition according to claim 1 , wherein the thermoset polymer is selected from the group consisting of unsaturated polyesters, polyurethanes, amino resins, alkyl resins, phenolic resins, epoxy resins, isocyanate resins, isocyanurate resins, polysiloxane resins, and mixtures thereof.
15. The foamable polymer composition according to claim 2 , wherein the additive agents includes alkyl sulfonate.
16. A method of forming a monomodal polymeric foam, the method comprising:
incorporating sepiolite-type clay particles into a polymer matrix comprising at least one of i) a thermoplastic polymer and ii) a thermoset polymer;
introducing at least one blowing agent into the polymer matrix;
introducing at least one selected from the group consisting of nekoite, okenite, faujasite and hiliebrandite into the polymer matrix; and
processing the polymer matrix with the sepiolite-type clay particles and at least one blowing agent, to thereby produce the monomodal polymeric foam;
wherein when the polymeric matrix comprises i) a thermoplastic polymer, then the at least one blowing agent is free of water.
17. The method according to claim 16 , wherein the sepiolite-type clay particles are pre-wetted with water.