UNVULCANIZED LIQUID OR SOLID SILICONE RUBBER AND METHOD FOR USING LIQUID OR SOLID SILICONE RUBBER IN AN INJECTION METHOD

Abstract

An unvulcanized liquid or solid silicone rubber containing a proportion of a filler material that expands at an increased temperature.

Claims

11. A liquid or solid silicone rubber composition, comprising: a liquid or solid silicone rubber in an unvulcanized state; and a portion of filler material expandable at an elevated temperature.

12. The liquid or solid silicone rubber composition of claim 11, wherein the filler material comprises microspheres.

13. The liquid or solid silicone rubber composition of claim 12, wherein the microspheres have a spherical plastic shell in which a propellant is encapsulated.

14. The liquid or solid silicone rubber composition of claim 13, wherein the spherical plastic shell of the microspheres comprise a material that is in a thermoelastic range at a vulcanization temperature of the liquid or solid silicone rubber and is expandable under the influence of the propellant at the vulcanization temperature.

15. An injection molding method for processing a liquid or solid silicone rubber, comprising: providing a filler material that is expandable under heat; providing a liquid or solid silicone rubber; adding the liquid or solid silicone rubber to the filler material to form a mixture; adding the mixture into a material mold for an injection procedure, the mixture of the liquid or solid silicone rubber and the filler material being expandable under heat; keeping the mixture below a vulcanization temperature and below an expansion temperature of the filler material prior to the injection procedure; and injecting the mixture into a workpiece mold during the injection procedure, filling the workpiece mold with the mixture and heating the mixture to the vulcanization temperature of liquid or solid silicone rubber.

16. The injection molding method of claim 15, wherein the filler material comprises microspheres.

17. The injection molding method of claim 15, wherein the mixture is introduced into the workpiece mold in a low volumetric amount.

18. The injection molding method of claim 17, wherein the workpiece mold is filled between 50 and 90% with the mixture.

19. The injection molding method of claim 16, wherein a vulcanization time and the vulcanization temperature of the liquid or solid silicone rubber are coordinated with an expansion temperature and an expansion time of the microspheres.

20. A method of injection molding a component or workpiece using a liquid or solid silicone rubber composition, comprising: providing a liquid or solid silicone rubber composition having a liquid or solid silicone rubber in an unvulcanized state and a portion of filler material expandable at an elevated temperature; and injection molding a component or workpiece using the liquid or solid silicone rubber composition.

21. The method of injection molding in accordance with claim 20, wherein the portion of filler material comprises microspheres.

22. The method of injection molding in accordance with claim 21, wherein the microspheres have a spherical plastic shell in which a propellant is encapsulated.

23. The method of injection molding in accordance with claim 22, wherein the spherical plastic shell of the microspheres comprise a material that is in a thermoelastic range at a vulcanization temperature of the liquid or solid silicone rubber and is expandable under the influence of the propellant at the vulcanization temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0016] The subject of the invention is likewise an injection molding method for manufacturing components while processing liquid or solid silicone rubber, wherein a filter material expandable under heat, in particular microspheres, is added to the liquid or solid silicone rubber before the injection of the liquid or solid silicone rubber into the workpiece mold, with the mixture of liquid or solid silicone rubber being kept below the vulcanization temperature and below the expansion temperature of the filler material during the injection procedure and with a heating of the mixture to the vulcanization temperature of the silicone rubber taking place after a filling of the workpiece mold. The vulcanization time and the vulcanization temperature are here advantageously coordinated with the expansion temperature and the expansion time of the microspheres. It becomes clear from this that the microspheres do not yet expand in the plasticizing unit of the injection molding machine. The expansion of the microspheres and thus the increase of the pore volume or reduction of the density of the mixture only takes place in the workpiece mold. This has the great advantage, however, that there are in principle no limits to the expansion of the microspheres in the workpiece mold. The volumes of the microspheres can increase by 40 to 50 times in the workpiece mold. Provision is also made to this extent that the mixture of liquid or solid silicone rubber is injected into the workpiece mold in a low volumetric amount, that is the degree of filling of the workpiece mold is approximately at 50 to 90%. The advantage of the described procedure is that damage to the microspheres is almost precluded on the processing in the plasticizing unit. This is in contrast to if the microspheres were already to be introduced into the plasticizing units in an expanded state since there is then a risk that the microspheres are damaged in the expanded state in the plasticizing unit. This does not only apply during the dwell time of the microspheres in the actual plasticizing unit, but in particular also on the passage through the nozzle at the tip of the plasticizing unit into the workpiece mold. For the nozzle has a diameter of approximately 400 m, which hinders the passage of fully expanded microspheres through the nozzle and can lead to damage to the microspheres.

[0017] It is now, however, by all means the case that there is an endeavor to increase the portion of high-volume microspheres in the end product, e.g. in the component or workpiece. For it has been found that the increase of the volume size of the microspheres in the workpiece is accompanied by an improvement in the elasticity, in particular with regard to a smaller pressure deformation residue and a higher impact resilience.

[0018] The improvement in the elasticity is thus only possible in the processing of liquid or solid silicone rubber in the injection molding process when the expansion of the microspheres in the liquid or solid silicone rubber only takes place in the workpiece mold and not already in the plasticizing unit because the mixing in of already expanded microspheres produces an increase in the viscosity of the material and thus in higher shear forces in the processing. To prevent damage to the microspheres in the processing, only a small portion of already expanded microspheres can be worked into the liquid or solid silicone rubber.

[0019] A greater portion of filler material can be mixed into the liquid or solid silicone rubber due to the use of expandable microspheres so that an improvement of the elasticity and a significant reduction of the density can be achieved.

[0020] The subject of the invention is furthermore the use of a liquid or solid silicone rubber, for manufacturing a component or workpiece in an injection molding process. cm 1.-10. (canceled)