Expandable vinylaromatic polymers and process for their preparation

• US 20040242713A1
• Filed: 03/02/2004
• Published: 12/02/2004
• Est. Priority Date: 10/18/2001
• Status: Active Grant

• Current Assignee: Polimeri Europa SPA (Eni Petroleum Company Incorporated)
• Original Assignee: Polimeri Europa SPA (Eni Petroleum Company Incorporated)
• Inventors: Casalini, Alessandro, Ghidoni, Dario, Lanfredi, Roberto, Frigerio, Gilberto
• Granted Patent: US 7,279,504 B2
• Time in Patent Office: Days
• US Class Current: 521/50
• CPC Class Codes: C08J 2201/03 Extrusion of the foamable blend
• CPC Class Codes: C08J 2325/06 Polystyrene
• CPC Class Codes: C08J 9/0066 Use of inorganic compounding ingredients
• CPC Class Codes: C08J 9/16 Making expandable particles
• CPC Class Codes: C08J 9/20 by suspension polymerisation in the presence of the blowing agent

Abstract

Expandable vinylaromatic polymers which comprise: a) a matrix obtained by polymerizing 50-100% by weight of one or more vinylaromatic monomers and 0.50% by weight of a copolymerizable monomer; b) 1-10% by weight, calculated with respect to the polymer (a), of an expanding agent englobed in the polymeric matrix; c) 0.05-25% by weight, calculated with respect to the polymer (a), of an inorganic filler homogeneously distributed in the polymeric matrix with a substantially spherical granulometry, an average diameter ranging from 0.01 to 100 μm, a refraction index higher than 1.6 and a white index, as defined in “Colour Index” (third edition published by the Society of Dyers and Colourists, 1982), equal to or lower than 22.

Claims

1. Expandable vinylaromatic polymers which comprise:

a) a matrix obtained by polymerizing 50-100% by weight of one or more vinylaromatic monomers and 0.50% by weight of a copolymerizable monomer;

b) 1-10% by weight, calculated with respect to the polymer (a), of an expanding agent englobed in the polymeric matrix;

c) 0.05-25% by weight, calculated with respect to the polymer (a), of an inorganic filler homogeneously distributed in the polymeric matrix with a substantially spherical granulometry, an average diameter ranging from 0.01 to 100 μ

m, a refraction index higher than 1.6 and a white index, as defined in “

Colour Index”

(third edition published by The Society of Dyers and Colourists,

     1982), equal to or lower than 22.

2. The polymers according to claim 1, wherein the vinylaromatic monomer is selected from those corresponding to the following general formula:

3. The polymers according to claim 1, wherein the vinylaromatic monomers having general formula (I) are used in a mixture, of up to 50% by weight, with other copolymerizable monomers selected from (meth)acrylic acid, C₁-C₄ alkyl esters of (meth)acrylic acid, amides and nitrites of (meth)acrylic acid, butadiene, ethyl-ene, divinylbenzene, maleic anhydride.

4. The polymers according to claim 3, wherein the copolymerizable monomers are acrylonitrile and methyl-methacrylate.

5. The polymers according to claim 1 wherein the inorganic filler has a refraction index ranging from 1.6 to 3 and a white index ranging from 21 to 5, extremes included.

6. The polymers according to claim 1 wherein the inorganic filler is present in concentrations ranging from 0.5 to 8%-by weight and with a granulometry ranging from 0.1 to 50 μ

m.

8. Expanded articles obtained with the expandable vinylaromatic polymers according to claim 1 having a density ranging from 5 to 50 g/l and a thermal conductivity ranging from 25 to 50 mW/mK, generally even over 10% lower with respect to that of equivalent non-filled expanded materials.

9. A process for preparing expandable vinylaromatic polymers which comprises polymerizing in aqueous suspension one or more vinylaromatic monomers, optionally together with at least one polymerizable comonomer in a quantity of up to 50% by weight, in the presence of an inorganic filler with a substantially spherical granulometry, an average diameter ranging from 0.01 to 100 μ

m, a refraction index higher than 1.6 and a white index, as defined in “

Colour Index”

(third edition published by The Society of Dyers and Colourists,

     1982), equal to or lower than 22, and an expanding agent added before, during or after the end of the polymerization.

10. The process according to claim 9, wherein, at the end of the polymerization, substantially spherical beads of polymer are obtained, with an average diameter ranging from 0.2 to 2 mm inside which the inorganic additive is homogeneously dispersed.

13. The process according to claim 9 wherein the expanding agents are added during the polymerization phase and are selected from the group consisting of an aliphatic hydrocarbon a cycloaliphatic hydrocarbon containing from 3 to 6 carbon atoms;

a halogenated derivative of aliphatic hydrocarbons containing from 1 to 3 carbon atoms;

carbon dioxide;

water; and

mixtures thereof.

14. The process according to claim 9 wherein the polymerization in suspension takes place through a solution of vinylaromatic polymer in the monomer, or mixture of monomers, wherein the concentration of polymer ranges from 1 to 30% by weight.

16. The process according to claim 9 wherein the expandable beads produced are pretreated by means of methods generally applied to beads produced with conventional processes and which consists essentially of:

a) coating the beads with a liquid antistatic agent such as amines, tertiary ethoxylated alkylamines, ethylene oxide-propylene oxide copolymers;

b) applying the coating to the beads thus treated, said coating consisting essentially of a mixture of mono-, di- and trimesters of glycerin with fatty acids and of metallic stearates.

17. The process according to claim 9 wherein the inorganic filler is also added in the coating together with the mixture of esters.

11. The process according to claim wherein during the polymerization flame-retardant agents are added in a quantity ranging from 0.1 to 8% by weight, with respect to the weight of the resulting polymer.

7. The polymers according to claim 11 wherein the inorganic filler is titanium dioxide or barium sulfate.

12. The process according to claim 11, wherein the flame-retardant agents are brominated aliphatic, cycloaliphatic, or aromatic compounds.

15. A process for preparing in mass and in continuous, expandable vinylaromatic polymers, which comprises the following steps in series:

feeding a vinylaromatic polymer, as described above, to an extruder, together with an inorganic filler, having a substantially spherical granulometry, an average diameter ranging from 0.01 to 100 μ

m, a refraction index higher than 1.6 and a white index, as defined in “

Colour Index”

(third edition published by The Society of Dyers and Colourists,

     1982), equal to or lower than 22;

heating the vinylaromatic polymer to a temperature higher than the relative melting point;

injecting the expanding agent and possible additives, into the molten polymer, before extrusion through a die; and

forming beads, optionally expandable, through a die, in a substantially spherical form with an average diameter ranging from 0.2 to 2 mm.

18. The process according to claim 18, wherein said metallic stearates are selected from the group consisting of zinc stearate and magnesium stearate.