Coating for applicators in electrosurgery

Abstract

A method of applying at least one coating of at least one electrically insulating polymer to an applicator for currents, especially HF currents in surgery, the coating is produced by electrophoretic deposition from a suspension of the polymer in at least one organic solvent, wherein the applicators thus coated are especially clamps, pairs of tweezers or pairs of scissors which are used in the bipolar application technique of HF surgery. Polymers used are especially thermoplastic polymers, such as thermoplastic fluoropolymers, and more particularly polychlorotrifluoroethylene (PCTFE) or ethylene chlorotrifluoroethylene (ECTFE).

Claims

1. A method of preparing an applicator for use in electrosurgery, comprising applying at least one coating of at least one electrically insulating polymer to the applicator, resulting in a polymer coating, wherein the applicator is selected from the group consisting of a clamp, a pair of tweezers and a pair of scissors, further wherein the coating is produced partially or entirely by electrophoretic deposition from a suspension of the polymer in at least one organic solvent, wherein the polymer coating has an electrical breakdown resistance of at least 500 V/mm.

2. The method of claim 1, characterized in that the polymer is a transparent polymer.

3. The method of claim 1, characterized in that the polymer is a colored polymer, wherein the polymer is colored by the addition of color pigments.

4. The method of claim 1, characterized in that the polymer is a polyamide or a polyaryl ether ketone.

5. The method of claim 1, characterized in that the polymer is a fluoropolymer.

6. The method of claim 5, characterized in that the fluoropolymer is polytetrafluoroethylene (PTFE) or more particularly polychlorotrifluoroethylene (PCTFE) or ethylene chlorotrifluoro-ethylene (ECTFE).

7. The method of claim 1, characterized in that the polymer coating obtained has a thickness between 5 m and 500 m.

8. The method of claim 1, characterized in that the polymer coating has a thickness between 5 m and 100 m.

9. The method of claim 1, characterized in that the electrical breakdown resistance is between 3 kV/mm and 150 kV/mm.

10. The method of claim 1, characterized in that the polymer coating is produced at a voltage between 0.2 kV and 4 kV.

11. The method of claim 1, characterized in that the electrophoretic deposition is effected over a period between 5 s and 10 min.

12. The method of claim 1, characterized in that the polymer coating obtained by electrophoretic deposition is subjected to an aftertreatment by melting.

13. The method of claim 12, characterized in that the aftertreatment is effected at a temperature of at maximum 20% above the melting temperature of the polymer.

14. The method of claim 13, characterized in that the aftertreatment is effected over a period of less than 1 hour.

15. A method of preparing an applicator for use in electrosurgery, comprising (a) degreasing the uncoated applicator, wherein the uncoated applicator is selected from the group consisting of a clamp, a pair of tweezers and a pair of scissors; (b) rinsing the applicator with a solvent and drying the applicator which has been degreased; (c) applying a primer layer by electrophoretic deposition; (d) applying a coloring layer by electrophoretic deposition; (e) applying at least one electrically insulating polymer to the applicator, resulting in a polymer coating, wherein the coating is produced partially or entirely by electrophoretic deposition from a suspension of the polymer in at least one organic solvent, wherein the polymer coating has an electrical breakdown resistance of at least 500 V/mm; (f) repeating the preceding steps (c)-(e) electrophoretic application of the polymer coating at least once; (g) treating the polymer coating obtained with at least one solvent; and (h) thermally treating the applicator coated with the polymer for drying and optionally for aftertreatrnent of the polymer coating obtained by melting.

Description

EXAMPLES

(1) For performance of the electrophoretic deposition, a vessel to accommodate the suspension of the electrically insulating polymer to be deposited and a high-voltage source which delivers an output voltage of up to about 4 kV were provided. Also provided was a stirrer for stirring the suspension during the electrophoretic deposition. Finally, a counterelectrode was present, which was connected as the anode during the deposition operation.

(2) Applicators to be coated for HF surgery that were used in the examples were pairs of tweezers for the bipolar technique, called bipolar tweezers. These pairs of tweezers were connected as the cathode during the electrophoretic deposition.

(3) In the pairs of tweezers, the corners were rounded off on all surface regions that were to be provided with the polymer coating, in order in this way to achieve better coating quality with preferably homogeneous layer thickness. In addition, the corresponding surfaces of the pairs of tweezers were blasted with glass beads, in order in this way to provide very fine, clean surfaces for the polymer coating.

(4) The electrically insulating polymer used was the thermoplastic fluoropolymer Halar ECTFE from Solvay Solexis, specifically the Halar 6014 product. This is a transparent ethylene chlorotrifluoroethylene copolymer (ECTFE), in which the ethylene and chlorotrifluoroethylene units are in 1:1 alternation in the copolymer. The average particle size of Halar 6014 is 80 m (ASTM D 1921-63; Method C). The melting temperature is 225 C.

(5) In addition, variants of the Halar polymer colored using dry pigments were produced, specifically a blue-colored Halar, a yellow-colored Halar and a black-colored Halar. The blue and black colors were achieved by means of PTFE pigments, the yellow color by means of a nickel titanium yellow dry pigment.

(6) Also used in the examples was a primer, namely the Halar Primer 6514, which is likewise an ethylene chlorotrifluoroethylene copolymer. This copolymer is a black powder having an average particle size of 80 m. The melting temperature of this copolymer is likewise 225 C.

(7) The polymers mentioned (transparent ECTFE, colored ECTFE, ECTFE primer) were used to produce suspensions for the electrophoretic deposition using the organic solvent n-heptane. This involved providing both suspensions that contained a dispersant, namely sodium dodecylsulfate (SDS), and those that were free of dispersants.

(8) In all the examples, the procedure was as follows:

(9) First of all, the coated pairs of tweezers were degreased, using an anodic hot degreasing operation. The operating temperature was between 80 C. and 100 C. It was possible for the degreasing to take place either in an alkaline medium (for example sodium hydroxide solution or potassium hydroxide solution) or in an acidic medium (for example phosphoric acid).

(10) Then the pairs of tweezers thus degreased were rinsed with a suitable medium, for example with water (ultrapure water) or alternatively with an alcohol, especially ethanol, or with an alkane, especially n-hexane. This rinsing process was effected at room temperature.

(11) Then the corresponding polymer layers (transparent ECTFE, colored ECTFE and/or ECTFE primer) were applied by electrophoretic deposition, performing electrophoretic deposition with a voltage of 2 kV over a period of 10 seconds in the corresponding experiments. With the corresponding process parameters, it was successively possible to apply either several layers of the same material or layers of different materials one on top of another to the applicator surface.

(12) The concentration of the polymer particles to be deposited in the suspension was 100 g/L.

(13) Then the layers obtained were rinsed with an organic solvent, for example an alcohol, especially ethanol, or an alkane, especially n-hexane. This rinsing operation was generally effected at room temperature.

(14) Then the coatings obtained were dried first at temperatures in the range between 60 C. and 80 C. and subsequently thermally aftertreated with at least partial melting of the polymer. This was effected at an operating temperature between about 250 C. and 270 C.

(15) In the case of electrophoretic deposition of several layers one on top of another, the subsequent steps (rinsing, drying, and melting) were conducted after each deposition step.

(16) According to the examples, with the given process parameters, with single deposition of the electrophoretic coating (2 kV over 10 s), polymer layers with the following thickness were formed:

(17) TABLE-US-00001 Transparent Halar 80 m Blue-colored Halar 80 m Yellow-colored Halar 60 m Black-colored Halar 40 m Halar primer 80 m

(18) The layer thickness was determined by gravimetric means, by determining the mass of the polymer coating deposited (before and after the electrophoretic deposition). Assuming a homogeneous layer thickness, this mass was used to calculate the corresponding value for this layer thickness.

(19) By multiple execution of the deposition method detailed, coatings with a total layer thickness of about 200 m were provided. This involved layering either the same polymers one on top of another or different polymers, i.e., for example, a layer sequence of primer beneath layers of transparent or colored ECTFE.

(20) All polymer coatings which were obtained in the examples according to the invention had a breakdown resistance of 5 kV based on the layer thickness of 200 m. These coatings were stable even under multiple application of a sterilization method in an autoclave, as typically employed in medical technology for the sterilization of bipolar applicators.