ELASTOMERIC COMPOSITION AND PROCESS FOR ITS PREPARATION

Abstract

The invention concerns the field of polymer chemistry and relates to an elastomeric composition and a method for the production thereof.

The object of the present invention is the specification of an elastomeric compound that has a high tensile strength and high hardness, and the specification of a production method that is cost-efficient and easy to carry out.

The object is attained by an elastomeric composition that contains at least one base elastomer, at least one hydrophilic polymer, and at least one inorganic salt. The object is furthermore attained by a method for producing an elastomeric composition in which at least one rubber, at least one hydrophilic polymer and at least one inorganic salt are mixed and subsequently vulcanized, the elastomeric composition is then at least partially brought into contact with water, and afterwards the water is at least partially removed from the elastomeric composition.

The elastomeric composition according to the invention can, for example, be used in vehicles and machines as a seal, grommet, disc, coupling or membrane.

Claims

1. An elastomeric composition, at least containing at least one base elastomer, at least one hydrophilic polymer and at least one inorganic salt, wherein auxiliary materials can be present.

2. The elastomeric composition according to claim 1 in which the base elastomer is a vulcanized natural rubber, acrylonitrile-butadiene rubber (NBR), carboxylated NBR (XNBR), hydrogenated NBR (HNBR), epichlorohydrin-ethylene oxide rubber (GECO), acrylic rubber (ACM), ethylene-propylene diene-monomer rubber (EPDM), chloroprene rubber (CR), butadiene rubber (BR), styrene-butadiene rubber (SBR), polyurethane rubber (PU), fluorinated rubber (FKM) and/or silicone rubber (VMQ).

3. The elastomeric composition according to claim 1 in which the hydrophilic polymer is an alkylene oxide copolymer, a poly(ethylene oxide-co-alkylene oxide) copolymer, a poly(ethylene oxide-alkylene oxide) copolymer, sodium polyacrylate, polyvinyl alcohol, polyacrylic acid, polyacrylamide, carboxymethyl cellulose, poly(acrylic acid-co-acrylamide), poly(hydroxyethyl methacrylate), ethylene oxide-propylene oxide-allyl glycidyl ether, a polycaprolactone-b-poly(ethylene oxide) copolymer, a poly(styrene-ethylene oxide) block copolymer, poly(epichlorohydrin-co-ethylene oxide), poly(ethylene-co-propylene oxide), polyether polyol, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, a poly(phosphazene)-poly(ethylene oxide) copolymer, a polylactide-block-poly(ethylene oxide) copolymer, poly(ethylene oxide)-block-poly(amino acid), propylene glycol-ethylene glycol polycondensate, poly(ethylene oxide-co-propylene oxide-co-butylene oxide) and/or a resin.

4. The elastomeric composition according to claim 3 in which the resin is thermoplastic polymer resin, epoxy resin, polyester resin, polyurethane resin, polyacrylate resin, melamine resin, phenol-formaldehyde resin, polyacrylonitrile resin, polyaspartic resin, polyurea resin, polyvinyl butyral resin, urea-formaldehyde resin, ebonite resin, cyanoacrylate resin and/or vinyl ester resin

5. The elastomeric composition according to claim 1 in which the hydrophilic polymer is present at 30-60 phr.

6. The elastomeric composition according to claim 1 in which the inorganic salt is calcium sulfate (CaSO.sub.4), calcium sulfate dihydrate (Ca[SO.sub.4].2H.sub.2O), calcium sulfate hemihydrate (Ca[SO.sub.4].½H.sub.2O), calcium hydrogen phosphate (CaHPO.sub.4) and/or calcium hydrogen phosphate dihydrate (CaHPO.sub.4.2H.sub.2O).

7. The elastomeric composition according to claim 1 in which the inorganic salt is present at 30-50 phr.

8. The elastomeric composition according to claim 1 in which crosslinkers, compatibilizers, activators, accelerators, retardants, antioxidants, plasticizers and/or antiozonants are present as auxiliary materials.

9. The elastomeric composition according to claim 8 in which sulfur, peroxides and/or amines are present at 0.5-6 phr as crosslinkers.

10. The elastomeric composition according to claim 8 in which polyglycol, methacrylate and/or dialkyl diether glutarate are present at 10-30 phr as compatibilizers.

11. The elastomeric composition according to claim 1 in which additional crosslinking sites from unsaturated compounds with or without functional groups and/or saturated compounds with functional groups are present.

12. The elastomeric composition according to claim 11 in which the functional groups are carboxyl groups, hydroxyl groups or amino groups.

13. A method for producing an elastomeric composition in which at least one rubber, at least one hydrophilic polymer and at least one inorganic salt are mixed and subsequently vulcanized, the elastomeric composition is then at least partially brought into contact with water, and afterwards the water is at least partially removed from the elastomeric composition.

14. The method according to claim 13 in which natural rubber, acrylonitrile-butadiene rubber (NBR), carboxylated NBR (XNBR), hydrogenated NBR (HNBR), epichlorohydrin-ethylene oxide rubber (GECO), acrylic rubber, ethylene-propylene-diene monomer rubber (EPDM), chloroprene rubber (CR), butadiene rubber (BR), styrene-butadiene rubber (SBR), polyurethane rubber (PU), fluorinated rubber and/or silicone rubber is used as rubber.

15. The method according to claim 13 in which sodium polyacrylate, polyvinyl alcohol, polyacrylic acid, polyacrylamide, carboxymethyl cellulose, poly(acrylic acid-co-acrylamide), poly(hydroxyethyl methacrylate), ethylene oxide-propylene oxide-allyl glycidyl ether (GEPO) and/or a resin is used as hydrophilic polymer.

16. The method according to claim 13 in which calcium sulfate (CaSO.sub.4), calcium sulfate dihydrate (Ca[SO.sub.4].2H.sub.2O), calcium sulfate hemihydrate (Ca[SO.sub.4].½H.sub.2O), calcium hydrogen phosphate (CaHPO.sub.4) and/or calcium hydrogen phosphate dihydrate (CaHPO.sub.4.2H.sub.2O) is used as inorganic salt.

17. The method according to claim 13 in which auxiliary materials are added before the vulcanization.

18. The method according to claim 13 in which the rubber, the hydrophilic polymer and the inorganic salt are mixed homogeneously and subsequently vulcanized for 6-20 minutes at temperatures of 140° C.-180° C.

19. The method according to claim 13 in which the elastomeric composition is fully brought into contact with water.

20. The method according to claim 13 in which the elastomeric composition is brought into contact with water for 2-6 hours.

21. The method according to claim 13 in which the elastomeric composition is brought into contact with deionized or distilled water.

22. The method according to claim 13 in which the absorbed water is removed from the elastomeric composition for 3-4 h at 50° C.-60° C., or for 24-48 h at room temperature.

23. The method according to claim 13 in which, after the removal of the absorbed water, the elastomeric composition is subjected to a heat treatment at 160° C. to 220° C.

Description

EXEMPLARY EMBODIMENT 1

[0065] An elastomeric composition was produced in that the rubber, the hydrophilic polymer and the inorganic salt were mixed in a two-roll mixer for 15 min at 60° C. according to Table 1.

TABLE-US-00001 TABLE 1 Constituent Selection Phr Rubber Epichlorohydrin-ethylene oxide rubber 50 (Hydrin T3108) - (GECO) Hydrophilic Ethylene oxide-propylene oxide-allyl 50 polymer glycidyl ether (Zeospan 8030) (GEPO) Inorganic Calcium sulfate (CaSO.sub.4) 50 salt Activator Zinc oxide 3 Accelerator Stearic acid 2 Accelerator Tetramethylthiuram disulfide 2.5 (TMTD) Accelerator Mercaptobenzothiazole (MBT) 1 Crosslinker Sulfur 1

[0066] The activator, accelerator and crosslinker were subsequently added to the mixture, and the mixture was then vulcanized in a hot press for 10 min at 160° C. and afterwards cooled for 60 min to room temperature (22° C.). The sample produced in this manner was then fully immersed in distilled water and, after 2 h, removed again from the distilled water. The water-treated elastomeric composition was then dried for 48 h at room temperature.

[0067] The results of the subsequently performed mechanical analysis of the unfilled composition, as well as the CaSO.sub.4-filled elastomeric composition and the water-treated, CaSO.sub.4-filled elastomeric composition are shown in Table 2.

TABLE-US-00002 TABLE 2 Elastic Tensile Elongation modulus strength at break at 60° C. Hardness Sample (MPa) (%) (MPa) A GECO-GEPO without 2.16 180 7 45 CaSO.sub.4 GECO-GEPO with 2.75 260 9 51 CaSO.sub.4, without water treatment GECO-GEPO with 4.52 272 57 78 CaSO.sub.4, with water treatment after 2 hours

[0068] The results show significantly improved mechanical properties, in particular the tensile strength and hardness of the elastomeric composition reinforced with the inorganic salt following the water treatment.

[0069] Using XRD analyses, it was verified that the amorphous CaSO.sub.4 crystals are converted into crystalline CaSO.sub.4 crystals by means of the water treatment of the elastomeric composition. Transmission electron microscopy showed the formation of nanoscale and highly developed salt crystals after the water treatment. The plate-shaped morphology of the CaSO.sub.4 crystals was converted to nanorods and nanoneedles.

EXEMPLARY EMBODIMENT 2

[0070] The elastomeric composition reinforced by the water treatment according to Exemplary Embodiment 1 was subjected to a heat treatment for 60 minutes at a temperature of 200° C. and then cooled for 3 h at room temperature (22° C.). Dynamic mechanical analyses and strength tests were subsequently performed on the elastomeric composition. The results of the analyses are listed in Table 3 and show that the original morphological state of the inorganic salt was restored as a result of the heat treatment of the reinforced elastomeric composition.

TABLE-US-00003 TABLE 3 Elastic modulus at Hardness Sample 60° C. (MPa) A GECO-GEPO-CaSO.sub.4 without water 9 51 treatment GECO-GEPO-CaSO.sub.4 after 2 h water 57 78 treatment GECO-GEPO-CaSO.sub.4 after 2 h water 10 53 treatment, drying and heat treatment for 1 h at 200° C.