Expandable vinyl aromatic composition containing functionalized ethylene-vinyl acetate copolymer

Patent metadata

Field	Value
Publication number	US-10920033-B2
Application number	US-201716314047-A
Country	US
Kind code	B2
Filing date	Jul 28, 2017
Priority date	Jul 29, 2016
Publication date	Feb 16, 2021
Grant date	Feb 16, 2021

Abstract

The present invention relates to polymeric compositions that can be used for producing packaging with dynamic cushioning, with a pleasant touch, with reduced abrasive power, in which the expanded particles constituting the packaging adhere well to one another and do not come detached during use. Said compositions comprise: a) from 70% to 90% by weight of a vinyl aromatic polymer and/or copolymer, calculated with respect to (a)+(b); b) from 10% to 30% by weight of an ethylene-vinyl acetate copolymer (EVA) containing a percentage that ranges from 10% to 30% by weight of vinyl acetate, calculated with respect to (a)+(b); c) from 3 to 10 parts by weight of a blowing agent, calculated on 100 parts of component a) added to component b); said copolymer (b) being distributed in the polymer (a) in the form of particles having an average volumetric diameter ranging from 1 nm to 2000 nm. The compositions described and claimed do not include styrene-butadiene or styrene-isoprene block copolymers, hydrogenated or non-hydrogenated; thermoplastic polyurethanes, polystyrene-butadiene grafted polymers or styrene core-shell polymers.

First claim

The invention claimed is:

1. Expandable polymeric composition comprising:
a) from 70% to 90% by weight of a vinyl aromatic polymer and/or vinyl aromatic copolymer, calculated with respect to (a)+(b);
b) from 10% to 30% by weight of an ethylene-vinyl acetate copolymer (EVA) containing a percentage that ranges from 10% to 30% by weight of vinyl acetate, calculated with respect to (a)+(b);
c) from 3 to 10 parts by weight of a blowing agent, calculated on 100 parts of component a) added to component b);

said ethylene-vinyl acetate copolymer (EVA) being distributed in said vinyl aromatic polymer and/or said vinyl aromatic copolymer in the form of particles having an average volumetric diameter ranging from 1 nm to 2000 nm; and with the proviso that said expandable polymeric composition does not contain a hydrogenated or non-hydrogenated, styrene-butadiene or styrene-isoprene block copolymer, a thermoplastic polyurethane, a polystyrene-butadiene grafted polymer or a styrene core-shell polymer.

2. Polymeric composition according to claim 1 in which the particles of said ethylene-vinyl acetate copolymer (EVA) have an average volumetric diameter ranging from 100 nm to 1000 nm.

3. Polymeric composition according to claim 1 wherein the amount of said vinyl aromatic polymer and/or said vinyl aromatic copolymer ranges from 80% to 90% by weight, calculated with respect to (a)+(b).

4. Polymeric composition according to claim 1 wherein the weight-average molecular weight of said vinyl aromatic polymer ranges from 130 kDa to 250 kDa.

5. Polymeric composition according to claim 1 wherein the amount of said ethylene-vinyl acetate copolymer (EVA) ranges from 10% to 25% by weight.

6. Polymeric composition according to claim 1 in which the content of vinyl acetate comonomer (VA) in said ethylene-vinyl acetate copolymer (EVA) ranges from 14% to 30% by weight.

7. Polymeric composition according to claim 1 wherein said vinyl aromatic polymer and/or said vinyl aromatic copolymer is obtained from a vinyl aromatic monomer of formula (I)

alone, from a mixture including said vinyl aromatic monomer of formula (I) or from a mixture including said vinyl aromatic monomer of formula (I) and copolymerizable vinyl monomers in which said copolymerizable vinyl monomers are present in an amount up to 35% by weight based on the weight of the mixture; in which R is a hydrogen or a methyl group; n is zero or an integer that varies from 1 to 3; Y is selected from a halogen; a chloromethyl; an alkyl group or an alkoxy group having from 1 to 3 carbon atoms.

8. Polymeric composition according to claim 7 , wherein said vinyl aromatic monomer of formula (I) is selected from styrene, α-methylstyrene, methylstyrene, ethyl-styrene, vinyltoluene isomers, ethylstyrene isomers, propylstyrene isomers, chloro styrene isomers, methylchlorostyrene isomers, methoxystyrene isomers, acetoxystyrene isomers, hydroxystyrene isomers, of methylhydroxystyrene isomers, and mixtures thereof.

9. Polymeric composition according to claim 7 wherein said copolymerizable vinyl monomers are selected from (meth)acrylic acid, maleic anhydride, alkyl esters of (meth)acrylic acid having 1 to 18 carbon atoms, amides and nitriles of (meth)acrylic acid.

10. A continuous mass process for preparing the polymeric composition according to claim 1 , comprising the following steps:
1. providing said vinyl aromatic polymer and/or said vinyl aromatic copolymer in a form of granules;
2. heating said vinyl aromatic polymer and/or said vinyl aromatic copolymer to a temperature above its melting point together with said ethylene-vinyl acetate copolymer (EVA), functionalized with polar groups so as to form a polymeric composition in the molten state;
3. then incorporating said blowing agent into said polymeric composition in the molten state.

11. Expanded beads that contain the polymeric composition according to claim 1 .

12. Packaging comprising the beads according to claim 11 .

13. Packaging comprising the polymeric composition according to claim 1 .

14. A continuous mass process for preparing the polymeric composition according to claim 1 , comprising the following steps:
1. providing said vinyl aromatic polymer and/or said vinyl aromatic copolymer in a molten state,
2. adding said ethylene-vinyl acetate copolymer (EVA), functionalized with polar groups,
3. and then incorporating said blowing agent to form a polymer composition.

Assignees

• Versalis Spa

Inventors

• Cuder Giovanni
• Comba Stefano
• Longo Aldo

Classifications

• C08J9/14 Primary

  organic · CPC title

• C08F263/04

  on to polymers of vinyl acetate · CPC title

• C08F255/02

  on to polymers of olefins having two or three carbon atoms · CPC title

• C08F212/08

  Styrene · CPC title

• C08J9/16

  Making expandable particles · CPC title