MAKING ADHESIVE SILICONE SUBSTANCES ADHERE TO FLUOROPOLYMER FILMS USING A CORONA TREATMENT

Abstract

Method for manufacturing an adhesive film wherein one entire face of a fluoropolymer film is activated with a plasma, an adhesive silicone substance is immediately applied to the entire activated face, and the applied silicone substance is cross-linked.

Claims

1. A method for the production of an adhesive film wherein one entire side of a fluoropolymer film is activated with a plasma, a silicone adhesive substance is immediately applied to the entire activated side, and the applied silicone adhesive substance is crosslinked.

2. The method as claimed in claim 1, wherein the fluoropolymer film is activated by plasma discharge.

3. The method as claimed in claim 1, wherein the silicone adhesive substance is crosslinked by the effect of temperature, electron beams, ultraviolet radiation or moisture.

4. The method as claimed in claim 1, wherein the plasma treatment takes place at less than 300 C.

5. The method as claimed in claim 1, wherein the silicone adhesive substance is applied by spreading.

6. The method as claimed in claim 1, wherein the thermal crosslinking is carried out at temperatures of less than 300 C.

7. The as claimed in claim 1, wherein a process gas selected from the group consisting of air, nitrogen, carbon dioxide and mixtures thereof is used for plasma treatment.

8. The method as claimed in claim 1, wherein PTFE (polytetrafluoroethylene), ETFE (poly(co-tetrafluoroethylene)), FEP (poly(tetrafluoroethylene-co-hexafluoropropylene)), PVF (polyvinyl fluoride), PCTFE (polychlorotrifluoroethylene), ECTFE (poly(ethylene-co-chlorotrifluoroethylene)), PVDF (poly(1,1-difluoroethene)), PFA (perfluoroalkoxy polymers) or mixtures of two or more of the above-mentioned fluoropolymers are used as fluoropolymers.

9. The method as claimed in claim 8, wherein the fluoropolymers are mixed with further polymers selected from the group consisting of polyethylene terephthalate (PET), polyamide, polyurethane, polyoxymethylene, polyvinylchloride (PVC), polyethylene naphthalate (PEN), ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), polyamide (PA), sulfone (PES), polyimide (PI), polyarylene sulfide, polyarylene oxide, and combinations thereof.

10. A method for the production of fiber composite materials, wherein one inner surface of a mold is lined with an adhesive film produced as claimed in claim 1, a composite material is produced on the lined inner surface of the fiber composite material, and the produced fiber composite material is detached from the masked inner surface of the mold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The invention is described by means of an example with figures. The figures are as follows:

[0072] FIG. 1 is a schematic diagram of a process sequence for the production of an adhesive tape according to the invention, and

[0073] FIG. 2 is a schematic diagram of a T peel test.

[0074] ETFE film that was provided in strip form and in an indeterminate length is used as the fluoropolymer film 1. The fluoropolymer film 1 is subjected to a filamentous corona treatment. In this case, the filamentous corona discharge is produced using a device from the firm Vetaphone. Air, nitrogen or carbon dioxide is used as a process gas 3. The process gas 3 is blown in the area of the corona discharge onto a surface of the fluoropolymer film 1 according to FIG. 1. The fluoropolymer film 1 is moved through a corona discharge filled with the process gas 3 at a speed of 50 m/min. The dose of the discharge is changed in multiple tests, and tests are also conducted with a dose of 100 Wmin/m.sup.2.

[0075] The process gas 3 used is air in one test, nitrogen in a second test, and carbon dioxide in a third test. After activation of the fluoropolymer film surface by the filamentous corona discharge 2, the activated surface 4 is provided with a two-component silicone adhesive substance 5 in a second method step. The adhesive substance Dow Corning 7657 with Syl-Off 4000 as a second component is used as the silicone adhesive substance 5. According to the section on application of the silicone adhesive substance 5 to the surface of the fluoropolymer film 1, a spreading bar 6 is provided above the fluoropolymer film 1 that distributes the silicone adhesive substance 5 onto a layer with a thickness of 50 g/m.sup.2. This gives rise to a silicone adhesive substance layer thickness of less than 100 m.

[0076] A silicone adhesive substance layer 5a is then crosslinked by thermal heating, and for this purpose, the silicone adhesive substance layer 5a applied to the fluoropolymer film 1 is heat-treated at 100 C. for 2 min. Here, the fluoropolymer film 1 serves as a carrier film for the crosslinked silicone adhesive substance layer 5a, and together with said layer, forms an adhesive tape 7.

[0077] The following Table 1 shows peel forces for various process gases at a dose of 100 Wmin/m.sup.2. The peel forces are also referred to as separating forces.

Peel Force after Spreading and Crosslinking on Treated Film:

[0078] Complete Cohesive Failure of all Samples

TABLE-US-00001 TABLE 1 N.sub.2 + Ar Dose/gas Air [N/cm] N.sub.2 [N/cm] CO.sub.2 [N/cm] [N/cm] 66 Wmin/m.sup.2 100 Wmin/m.sup.2 7.27 (0.16) 7.17 (0.03) 7.25 (0.11) 150 Wmin/m.sup.2

[0079] The peel forces are determined using a so-called T peel test according to FIG. 2. In this case, the adhesive tape 7 is glued onto a chemically etched polyester film 8, wherein the silicone adhesive substance layer 5a of the adhesive tape 7 is glued onto the polyester film 8. The polyester used here is PET. The test piece produced in this manner is then stored for 3 days at room temperature. The polyester film 8 and the fluoropolymer film 1 are then peeled off each other in opposite directions, resulting in an approximately T-shaped configuration of the adhesive tape during the peeling process according to FIG. 2, and the polyester film 8 and the fluoropolymer film 1 are pulled apart using a T peel machine that is set to a constant speed and measures the force required to maintain this constant speed.

[0080] The results are shown in Table 1. It can be seen that the strongest force is generated in use of air as a process gas, the second-strongest force is generated in use of carbon dioxide as a process gas, and the weakest separating force is generated in use of nitrogen as a process gas.

[0081] It is significant in all three of the tests that all three samples cohesively fail, i.e., in all three samples, the adhesive tape 7 separates when the silicone adhesive substance layer 5a fails. The result in particular is that an increase in separating force by means of an improvement, for example by changing the corona treatment, cannot have any additional effect. The separating force cannot be increased in this manner, because failure takes place inside the silicone adhesive substance layer 5a before any such increase can occur.

LIST OF REFERENCE NOS

[0082] 1. Fluoropolymer film [0083] 2. Corona discharge [0084] 3. Process gas [0085] 4. Activated surface [0086] 5. Silicone adhesive substance [0087] 5a. Silicone adhesive substance layer [0088] 6. Spreading bar [0089] 7. Adhesive tape [0090] 8. Polyester film