Inflatable stopper

Abstract

The invention relates to a non-crosslinked natural rubber latex composition for an inflatable stopper comprising a homogeneous mixture of: a) natural rubber latex; b) a surfactant; c) an amine based chemical antiozonant; d) possibly ammonia and preferably e) single or double wall electrically conductive nanotubes. The invention furthermore relates to an ozone resistant inflatable stopper comprising non-crosslinked natural rubber latex and fiber reinforcement, the rubber having an ozone resistance according to ISO 1431/1 at 50 pphm concentration ozone at 23±2° C., for the time frame of 48 hours, atmospheric humidity of 55% and strain static exposure of 20% and preferably a surface resistivity lower than 100 GΩ according to DIN EN 60079-32-2 and DVGW G 5621-3 (VP) measured at 1000 V and a maximum relative humidity of 30%.

Claims

1. A low surface resistivity inflatable stopper comprising non-crosslinked natural rubber latex and fiber reinforcement, the rubber having a surface resistivity lower than 100 GΩ according to DIN EN 60079-32-2 and DVGW G 5621-3 (VP), wherein the stopper comprises a rubber latex base layer and a secondary layer with fiber reinforcement and a non-crosslinked natural rubber latex which adheres to the fibers and the base layer, at least one rubber latex layer having a surface resistivity according to DIN EN 60079-32-2 and DVGW G-5621-3 (VP) of not exceeding 100 GΩ.

2. The inflatable stopper of claim 1, wherein the rubber latex comprises as antistatic ingredient, carbon nanotubes having a diameter ranging from 1-100 nm, and a length of 0.1-100 μm.

3. The inflatable stopper of claim 2, wherein the carbon nanotubes have a diameter ranging from 1-50 nm.

4. The inflatable stopper of claim 2, wherein the carbon nanotubes have a diameter ranging from 4-20 nm.

5. The inflatable stopper of claim 2, wherein the carbon nanotubes have a length of 0.1-10 μm.

6. The inflatable stopper of claim 2, wherein the aspect ratio of the length over the diameter of the carbon nanotubes is about 10 or more.

7. The inflatable stopper of claim 2, wherein the aspect ratio of the length over the diameter of the carbon nanotubes is about 30 or more.

8. The inflatable stopper of claim 2, wherein the aspect ratio of the length over the diameter of the carbon nanotubes is about 50 or more.

9. The inflatable stopper of claim 2, wherein the aspect ratio of the length over the diameter of the carbon nanotubes is about 1000 or less.

10. The inflatable stopper of claim 2, wherein the aspect ratio of the length over the diameter of the carbon nanotubes is about 300 or less.

Description

EXAMPLES

Example 1; Formulation A

(1) 6 mL Flexzone® 4 L was mixed with 3 mL Carbowet® 138 Surfactant to provide MIX 1. A second mixture was provided by diluting 7.5 mL modified acrylic polymeric emulsion surfactant (K-STAT® 1300) with 15 mL ammonia (MIX 2). Thereafter, MIX 1 was added to 500 mL DX 7349/1 non-crosslinked natural rubber latex and the mixture was homogenized during 3 minutes. Thereafter, MIX 2 was added to 500 mL DX 7349/1 non-crosslinked natural rubber latex and the mixture was homogenized for 3 minutes.

Example 2; Formulation B

(2) 6 mL Uvasorb K289 was mixed with 6 mL ammonia (MIX 1). Furthermore, 6 mL Flexzone® 4 L was mixed with 3 mL Carbowet® 138 Surfactant (MIX 2). Also, 7.5 mL modified acrylic polymeric emulsion surfactant (K-STAT® 1300) was mixed with 15 mL ammonia (MIX 3). Next, to 500 mL DX 7349/1 natural rubber latex MIX 2 was added, and the resulting mixture was homogenized for 3 minutes. To the resulting natural rubber latex mixture MIX 1 was added, and mixed for 3 minutes. As the last step, MIX 3 was added, and mixed for 3 minutes.

(3) Test strips were prepared from the latex composition, and the strips were tested according ISO 1431/1 (50 pphm ozone); both test strips were in conformity with the test; no cracks were visible.

(4) Further formulations were prepared as above but without antiozonant. The result was not in conformity with the standard ISO 1431/1 as it was severely cracked.

Example 3; Formulation C

(5) A mixture I (MIX 1) was made consisting of 1 gram ICH CC VS coloring pigment and 500 gram natural rubber (latex). A mixture 2 (MIX 2) was made consisting of 5 gram Carbowet 138 surfactant and 0.5 gram Nanocyl NC7000 nanotubes. MIX 2 preferably is kept for a period of time of 6 hours or longer, and for a preferred period of 48 hours in order to set and to create a homogenous gel. Subsequently a mixture 2A (MIX 2A) was made whereby 5 gram Flexzone 4L was mixed with MIX 2. After mixing, MIX 2B was diluted with demineralized water in a 50/50 ratio. The obtained MIX 2B was added to 500 gr MIX 1, being the natural rubber (latex). MIX 2A contains specific weight quantities of the various ingredients whereby the final weight percentages of the various ingredients are determined by evaporation of water and some of the ingredients, if any.

(6) Test strips were prepared from formulation C, and the strips were tested according to ISO 1431/1 (50 pphm ozone) and DIN EN 60079-32-2/DVGW G 5621-3 (VP).

(7) The test strips were in conformity with the ozone resistance test, and furthermore, the surface resistivity did not exceed 100 GΩ measured at 1000 V and maximum 30% relative humidity.

(8) The ozone improvement has been demonstrated according to standard ISO 1431/1. The latter specifies procedures intended for use in estimating the resistance of vulcanized or thermoplastic rubbers to cracking when exposed, under static or dynamic tensile strain, to air containing a definite concentration of ozone and at a definite temperature in circumstances that exclude the effects of direct light.

(9) The low surface resistivity has been demonstrated according to standard DIN60079-32-2 and DVGW G 5621-3 (VP). Both specify test methods, test procedures and test requirements concerning the equipment, product and process properties necessary to avoid ignition and electrostatic shock hazards arising from static electricity.