Expansion system for flexible insulation foams

Abstract

A flexible material for thermal and acoustical insulation comprising an expanded polymer (blend) based on at least one elastomer, wherein expansion is achieved by decomposition of a mixture of at least two chemical blowing agents, comprising the exothermic chemical blowing agent 4,4-Oxybis(benzenesulfonyl hydrazide) (OBSH) and at least one endothermic blowing agent.

Claims

1. A material having a closed cell structure prepared from a polymeric mixture, comprising: a) 40.0 wt % to 10.0 wt % of at least one elastomer or a blend of an elastomer and a thermoplastic polymer, of which at least 25 wt % is at least one sulphur and/or metal oxide crosslinkable polymer and b) 5 to 40 wt % of a blowing agent mixture comprising 70 to 95 wt % of 4,4-oxybis(benzenesulfonyl hydrazide) and 5 to 30 wt % of at least one endothermic blowing agent, where the amounts of 4,4-oxybis(benzenesulfonyl hydrazide) and the at least one endothermic blowing agent sum up to 100 wt. %, wherein the material having a closed cell structure has a vacuum water absorption of <5.0% according to ASTM D 1056.

2. The material according to claim 1, wherein the at least one elastomer or the blend of an elastomer and a thermoplastic polymer comprises at least 80 phr of acrylonitrile butadiene rubber, polychloroprene, ethylene propylene diene rubber, butyl rubber including chlorinated and brominated butyl rubber, butadiene rubber, styrene butadiene rubber, polyvinyl chloride including its co- and terpolymers, polyethylene including its co- and terpolymers, chlorinated polyethylene, or a combination thereof.

3. The material according to claim 1, wherein the at least one endothermic blowing agent of the blowing agent mixture is a carbonate or hydrogen carbonate.

4. The material according to claim 1, wherein both the 4,4-oxybis(benzenesulfonyl hydrazide) and the at least one endothermic blowing agent have a median particle size of 1 to 20 m according to ISO 13320:2009.

5. The material according to claim 1, wherein the 4,4-oxybis(benzenesulfonyl hydrazide) and the at least one endothermic blowing agent are coated or surface-modified.

6. The material according to claim 5, wherein the 4,4-oxybis(benzenesulfonyl hydrazide) and the at least one endothermic blowing agent are coated with fatty acids and/or metal salts of fatty acids and/or surface-modified by silanization.

7. The material according to claim 1, wherein the polymeric mixture further comprises at least 60 phr of at least one inorganic filler.

8. The material according to claim 7, wherein the at least one inorganic filler comprises a metal.

9. The material according to claim 1, wherein the polymeric mixture further comprises at least 15 phr of at least one plasticizer.

10. The material according to claim 1, wherein the polymeric mixture further comprises at least one flame retardant.

11. A material according to claim 1, having a density of 70 kg/m.sup.3 according to DIN EN ISO 845.

12. The material according to claim 11, having a vacuum water absorption of <2.5% according to ASTM D 1056.

13. The material according to claim 11, having a water vapor transmission (WVT) value of 3.000 according to EN 13469 or EN 12086.

14. A thermal and/or acoustical insulation material comprising the material according to claim 11.

15. A process for manufacturing a closed cell crosslinked and expanded flexible material having a density of 70 kg/m.sup.3, according to DIN EN ISO 845, comprising: 1) providing a polymeric component which is at least one elastomer or a blend of an elastomer and a thermoplastic polymer, wherein at least 25 wt % of the polymeric component is at least one sulphur and/or metal oxide crosslinkable polymer and the polymeric component is free of any blowing agent mixture and any crosslinking system; 2) then adding a crosslinking system and a blowing agent mixture comprising 70 to 95 wt % of 4,4-oxybis(benzenesulfonyl hydrazide) and 5 to 30 wt % of at least one endothermic blowing agent, wherein the 4,4-oxybis(benzenesulfonyl hydrazide) and the at least one endothermic blowing agent sum up to 100 wt. %, to the mixture of polymeric components in a mixing step to obtain a second mixture, wherein the second mixture comprises 40.0 wt % to 10.0 wt % of the polymeric component and 5 to 40 wt % of the blowing agent mixture; and 3) subsequently extruding and finally expanding and crosslinking the second mixture to obtain a crosslinked and expanded flexible material having a closed cell structure that has a vacuum water absorption of <5.0% according to ASTM D 1056.

16. The process of claim 15, wherein the crosslinking system comprises a peroxide, a triallylcyanurate, a triallylisocyanurate, a phenylmaleimide, a thiadiazole, a fatty acid amide, a hydrosilylation agent, a radiation activator, a sulphur system, a bisphenolic compound a metal oxide, or a combination thereof.

17. The process of claim 15, wherein the crosslinked and expanded flexible material having a closed cell structure has a water vapor transmission (WVT) value of 3.000 according to EN 13469 or EN 12086.

18. The material of claim 7, wherein the at least one inorganic filler is an inorganic filler that releases water and/or carbon dioxide and/or carbon monoxide at temperatures above 180 C.

19. The material of claim 7, wherein the at least one inorganic filler is aluminium hydroxide, magnesium hydroxide, huntite, hydromagnesite, or a combination thereof.

20. The material of claim 1, wherein the polymeric mixture further comprises an organohalogen compound, an (organo)phosphorous compound, or a combination thereof.

Description

EXAMPLES

(1) In the following examples and comparative examples a four step manufacturing process is used: first of all mixing of the components of the polymeric mixture (without blowing agents and crosslinking system), afterwards addition of the crosslinking system and blowing agent mixture in a second mixing step, subsequently extrusion (shaping) and finally expansion and crosslinking. Instead of two mixing steps, the material can also be cooled down in the mixer or on a mill and the crosslinking system and blowing agent mixture can be added within the first mixing step.

(2) Extrusion was performed on a strip feeded single screw vacuum extruder providing unexpanded sheets and tubes. Those were crosslinked and expanded simultaneously in a hot air oven cascade of five ovens to sheets of 25 mm wall thickness and tubes of 25 mm wall thickness and 22 mm inner diameter. Table 1 lists the raw materials used for the polymeric mixture. Table 2 gives an overview about the make-up of some exemplary polymeric mixtures and Table 3 comprises some technical properties of the foamed and crosslinked material.

(3) TABLE-US-00001 TABLE 1 Raw materials Chemical Name Trade Name Supplier Acrylonitrile butadiene rubber (NBR) Europrene N 2860 Polimeri Europe, Italy Ethylene propylene diene rubber (EPDM) KEP650 Kumho Polychem, Korea Ethylene vinyl acetate (EVA) Levapren 400 Arlanxeo, Germany Chlorinated Polyethylene (CPE) Elaslen 401AY Showa Denko, Japan Diphenyl cresyl phosphate (DPK) Disflamoll DPK Lanxess, Germany Paraffin oil (PO) Sunpar 2280 Sunoco Europe, Denmark Carbon black (CB) Corax N550 Evonik Industries, Germany Aluminium hydroxide (ATH) AluMill F280 Europe Minerals, Netherlands Huntite/hydromagnesite mixture (HH) Securoc C10 Ankerport, Netherlands Antimony trioxide (ATX) Triox Produits Chimiques de Lucette, France Azodicarbonamide (ADC) Unicell D 300 K Tramaco, Germany Decabromodiphenyl ether (Deca-BDE) Saytex 102 E Albemarle, France 4,4-Oxybis (benzenesulfonylhydrazide) (OBSH) Tracel OBSH 160 NER Tramaco, Germany Sodium bicarbonate (SB) Bicar Solvay, France

(4) TABLE-US-00002 TABLE 2 Make-up of exemplary polymeric mixtures 1* 2* 3* 4* 5 6 7 Acrylonitrile butadiene 85.0 85.0 85.0 85.0 85.0 rubber (NBR) Ethylene propylene 80.0 80.0 diene rubber (EPDM) Ethylene vinyl acetate 15.0 15.0 15.0 15.0 15.0 (EVA) Chlorinated 20.0 20.0 Polyethylene (CPE) Diphenyl cresyl 75.0 75.0 75.0 75.0 75.0 phosphate (DPK) Paraffin oil (PO) 45.0 45.0 Carbon black (CB) 10.0 10.0 10.0 15.0 10.0 10.0 15.0 Aluminium hydroxide 200.0 200.0 200.0 150.0 200.0 200.0 150.0 (ATH) Huntite/hydromagnesite 50.0 50.0 50.0 50.0 50.0 50.0 50.0 mixture (HH) Antimony trioxide 10.0 10.0 (ATX) Azodicarbonamide 60.0 55.0 (ADC) Decabromodiphenyl 70.0 70.0 ether (Deca-BDE) 4,4-Oxybis 130.0 80.0 110.0 95.0 90.0 (benzenesulfonyl- hydrazide) (OBSH) Sodium bicarbonate 50.0 20.0 35.0 30.0 (SB) Additives, crosslinking 30.0 30.0 30.0 25.0 25.0 25.0 20.0 agents, etc. (AD) 525.0 595.0 595.0 520.0 590.0 590.0 580.0 *comparative examples

(5) Table 3 presents the density (according to DIN EN ISO 845), thermal conductivity at 0 C. (according to DIN EN ISO 8497/DIN EN 12667), water vapour absorption (according to ASTM D 1056) and water vapour transmission (WVT, according to EN 13469/EN 12086) of comparative examples 1 to 4 and innovative examples 5 to 7.

(6) It clearly shows that the right balance between OBSH and endothermic blowing agent (e.g. sodium bicarbonate) can significantly improve the technical properties of the resulting foam, while the sole use of OBSH or a higher share of endothermic blowing agent has the opposite effect, especially regarding WVT.

(7) Beside the listed technical properties, an increase in compression deflection (according to ASTM D 1056) for the innovative examples 5 to 7 could be observed, too, although such samples have the lowest densities.

(8) TABLE-US-00003 TABLE 3 Technical properties Thermal Water vapor Density conductivity absorption Material [kg/m.sup.3] [W/(m*K)] @ 0 C. [%] WVT 1* 62 0.0385 2.8 3200 2* 60 0.0392 7.0 800 3* 68 0.0412 6.2 400 4* 60 0.0390 2.2 4600 5 49 0.0349 1.7 6200 6 53 0.0362 2.2 5400 7 53 0.0355 1.3 7300