Expanded polystyrene made using D-limonene as a plasticizer
Disclosed is a process for production of expanded polystyrene using D-limonene as a plasticizer, which allows reducing the amount of pentane in the process, yet allows generating beads with similar cell size as if greater quantities of pentane had been used. Pentane is an organic solvent with toxicity associated with organic solvents.
1. A process of forming expanded polystyrene beads having internal cells of a size typically generated by including a larger amount of pentane in the formulation, comprising:
heating a mixture of styrene, demineralized water, brominated flame retardant chemicals, a peroxide first polymerization initiator, paraffin, tricalcium phosphate (TCP), a surfactant, an extender and D-limonene to a first polymerization temperature;
adding 3-8% by weight pentane and a second polymerization initiator to the mixture and heating to a second polymerization temperature to form EPS beads having cells as large as if about 25% more pentane was used than the amount of pentane which actually was used.
2. The process of claim 1 wherein the brominated compounds are decabromodiphenyl oxide, phenoxy tetrabromnobisphenol A, or tetrabromobisphenol A bis(allyl ether), hexabromocyclododecane, and brominated polymer.
3. The process of claim 1 wherein the tricalcium phosphate (TCP) is in the form of fine particles.
4. The process of claim 1 wherein the extender is dodecylbenzenesulfonate or a persulfate salt.
5. The process of claim 4 wherein the persulfate salt is ammonium or potassium persulfate.
6. The process of claim 1 wherein the surfactant is a combination of a molecular colloid and an inorganic alkali metal salt.
7. The process of claim 6 wherein the molecular colloid is polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) and the inorganic alkali metal salt is Mg 2 P 2 O 7 , Ca 3 (PO 4 ) 2 or another alkali metal salt including salts of sulfates, chlorides, carbonates or hydrogencarbonates.
8. The process of claim 1 wherein the peroxide is dibenzoyl peroxide, hydrogen peroxide 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, or hydrogen peroxide.
9. The process of claim 1 wherein the second polymerization initiator is tert-butyl perbenzoate, tert-butyl peroxy-2-ethylhexanoate, t-butyl ethylhexylmonoperoxycarbonate or t-amyl ethylhexylmonoperoxycarbonate.
10. The process of claim 1 further including melting the beads produced by the process of claim 1 inside a mold to form objects in the shape of the mold.
11. The process of claim 10 wherein the melting of the beads is with steam.