METHOD FOR ENCAPSULATING GLAZING IN POLYCARBONATE PROVIDED WITH AN ANTI-SCRATCH COATING

Abstract

The present invention relates to a process for encapsulating a polycarbonate glazing comprising, on at least one of its faces, a silicone-based abrasion-resistant hardcoat, said process comprising the following successive steps: (a) the treatment of a region of the face of the glazing bearing the silicone-based hardcoat by atmospheric plasma with a plasma nozzle, the distance between the end of the plasma nozzle and the surface of the glazing being at most equal to 7 mm, (b) the application, to said region treated by atmospheric plasma, of a primer composition comprising one or more adhesion promoters selected from diisocyanates, polyisocyanates and chlorinated polyolefins, in solution or suspension in an organic or aqueous solvent, (c) the evaporation of the solvent so as to form a dry primer layer, and (d) the overmolding of a thermoplastic polymer over the region covered by the dry primer layer.

Claims

1. A process for encapsulating a polycarbonate glazing comprising, on at least one of its faces, a silicone-based abrasion-resistant hardcoat, said process comprising: (a) treating a region of the face of the glazing bearing the silicone-based hardcoat by atmospheric plasma with a plasma nozzle having a power of between 100 voltamperes and 1000 voltamperes, wherein a distance between the end of the plasma nozzle and the surface of the glazing is at most equal to 7 mm, thereby obtaining a region treated by atmospheric plasma, (b) applying, to the region treated by atmospheric plasma, a primer composition comprising at least one adhesion promoter selected from the group consisting of diisocyanates, polyisocyanates, and chlorinated polyolefins, in solution or suspension in an organic or aqueous solvent, (c) evaporating the solvent, thereby forming a dry primer layer, and (d) overmolding a thermoplastic polymer over the region covered by the dry primer layer.

2. The process as claimed in claim 1, wherein the rate of relative movement of the plasma nozzle with respect to the glazing is between 2 and 4 m/minute.

3. The process as claimed in claim 1, wherein the distance between the end of the plasma nozzle and the surface of the glazing is less than 6 mm.

4. The process as claimed in claim 1, wherein the plasma nozzle operates with a carrier gas.

5. The process as claimed in claim 1, wherein the adhesion promoter is at least one selected from the group consisting of isophorone diisocyanate (IPDI), 4,4-diphenylmethane diisocyanate (MDI) and maleic anhydride-grafted chlorinated polyolefin.

6. The process as claimed in claim 5, wherein the primer composition essentially consists of the at least one adhesion promoter selected from the group consisting of diisocyanates, polyisocyanates and chlorinated polyolefins, in solution or suspension in an organic or aqueous solvent.

7. The process as claimed in claim 1, wherein the thermoplastic polymer is selected from the group consisting of styrenic thermoplastic elastomers (TPE-S), vulcanized olefinic thermoplastic elastomers (TPE-V), poly(vinyl chloride), thermoplastic polyurethanes (TPU), poly(methyl methacrylate) (PMMA), polycarbonates (PC), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends and polypropylene (PP).

8. The process as claimed in claim 1, wherein the thermoplastic polymer is an elastomer.

9. The process as claimed in claim 4, wherein the plasma nozzle operates with filtered air as the carrier gas at a pressure of between 3 and 4 bar.

10. The process as claimed in claim 1, wherein the thermoplastic polymer is a thermoplastic elastomer or a poly(vinyl chloride).

11. The process as claimed in claim 1, wherein the surface energy of the region before treatment by atmospheric plasma is less than 30 mN/m.

12. The process as claimed in claim 1, wherein the surface energy of the region after treatment by atmospheric plasma is at least 45 mN/m.

13. The process as claimed in claim 1, wherein a peel strength of the thermoplastic polymer overmolded over the region covered by the dry primer layer is capable of storage for 14 days at 70 C. and at 95% relative humidity, then two hours at 20 C., while maintaining a peel strength of at least 10 N/cm.

14. The process as claimed in claim 1, wherein the silicone-based hardcoat has not been subjected to mechanical abrasion.

15. The process as claimed in claim 1, wherein the plasma nozzle is a rotatable nozzle having a cone angle of between 10 and 30.

16. The process as claimed in claim 1, wherein the treating of the region of the face of the glazing bearing the silicone-based hardcoat by atmospheric plasma comprises passing the plasma nozzle over the same region of the substrate more than once.

17. The process as claimed in claim 1, wherein the treating of the region of the face of the glazing bearing the silicone-based hardcoat by atmospheric plasma comprises passing the plasma nozzle over the same region of the substrate over each point of the glazing at most one time.

18. The process as claimed in claim 1, wherein a thickness of the primer composition applied to the region treated by atmospheric plasma, prior to evaporating the solvent, is less than 300 m.

19. The process as claimed in claim 1, wherein the dry primer layer has a thickness of less than 30 m.

20. The process as claimed in claim 1, wherein a content of filler, if present, in the thermoplastic polymer is less than 5%.

21. The process as claimed in claim 3, wherein the distance between the end of the plasma nozzle and the surface of the glazing is at most equal to 5 mm.

22. The process as claimed in claim 21, wherein the distance between the end of the plasma nozzle and the surface of the glazing is between 2 mm and 4 mm.

Description

EXAMPLE

[0072] Samples of polycarbonate glazing covered with a silicone-based hardcoat (Basecoat Silfort SHP 470+AS4700, Momentive) are passed under an Openair (Plasmatreat) plasma torch with a rotatable nozzle (diameter of 22 mm, exit angle of 14, outward inclination) having an output power of 500 voltamperes.

[0073] The plasma torch operates with filtered air under a pressure of between 3 and 4 bar. The plasma torch is fixed and the edge of the samples is made to travel in front of the end of the torch at a speed of 2 m/minute.

[0074] The edge of each sample undergoes a single pass under the plasma torch. The distances between the surface of the glazing and the end of the nozzle are indicated in table 1. The axis of the torch is normal relative to the plane of the glazing.

[0075] After a single pass of the sample under the plasma torch, the surface energy (wettability) of the treated region is measured in accordance with the ISO 8296 standard with an ethanol-based test solution. The values obtained are indicated in table 1.

[0076] Each of the primer compositions below is then applied to the plasma-treated region:

IPDI CPO-w: Isophorone diisocyanate+chlorinated polyolefin in water (LOCTITE TP661 (Henkel))
CPO-s: Chlorinated polyolefin in a xylene/ethylbenzene mixture (KORATAC GM510 (Kmmerling))
CPO-w: Chlorinated polyolefin in water (HARDLEN EW5515 (Toyobo))
IPDI-w: Isophorone diisocyanate in water (WITCOBOND 434-27 (Baxenden))
IPDI-s: Isophorone diisocyanate in an n-butyl acetate/ethyl acetate/butanone mixture (SIKA 209N (Sika))
IPDI-MDI-s: Isophorone diisocyanate and 4,4-diphenylmethane diisocyanate in an ethyl acetate/butanone mixture (SIKA 209D (Sika))

[0077] The application is carried out using a foam material impregnated with the primer composition.

[0078] The solvent is left to evaporate at ambient temperature, the edge of the samples of glazing is introduced into an encapsulation mold and is overmolded either with a TPE-V (Sarlink 4775B42, from Teknor Apex Co.) or with a plasticized PVC (APEX 1523F3, from Teknor Apex Co.).

[0079] No preheating of the glazing is carried out between the priming step and the encapsulation.

[0080] After encapsulation, the samples are stored for 7 days at 23 C. and 50% relative humidity, then are subjected to the following accelerated aging conditions: 14 days at 70 C. and at 95% relative humidity, then two hours at 20 C.

[0081] The quality of the adhesive contact is evaluated by a 90 peel test (pull rate of 100 mm/min). The peel strength in N/cm and the percentage of adhesive or cohesive failure in accordance with the ASTM-D413 standard are measured.

[0082] Table 1 shows all of the results obtained.

[0083] The comparative samples without plasma treatment were simply cleaned with isopropanol.

TABLE-US-00001 TABLE 1 Peel strength and type of failure (cohesive or adhesive) of the adhesive contact as a function of the distance between nozzle and surface and of the primer composition used Distance between torch Peel strength and surface of Surface after accelerated the hardcoat energy Encapsulation aging test (mm) (mN/m) Priming polymer (N/cm) Type of failure 2 >60 IPDI + CPO.sub.w TPE-V >70 100% CF* 2 >60 CPO.sub.s TPE-V >65 100% CF 2 >60 CPO.sub.w TPE-V >70 100% CF 2 >60 IPDI.sub.w PVC >50 45% CF/55% AF 2 >60 IPDI.sub.s PVC >75 100 CF 2 >60 IPDI + MDI.sub.s PVC >30 100 AF** 4 54 IPDI + CPO.sub.w TPE-V >30 40% CF/60% AF 4 54 CPO.sub.s TPE-V >20 30% CF/70% AF 4 54 CPO.sub.w TPE-V >30 40% CF/60% AF 4 54 IPDI.sub.w PVC >10 100% AF 4 54 IPDI.sub.s PVC >40 70% CF/30% AF 4 54 IPDI + MDI.sub.s PVC >10 100% AF 8 36 IPDI + CPO.sub.w TPE-V 0 100% AF 4 36 CPO.sub.s TPE-V 0 100% AF 8 36 CPO.sub.w TPE-V 0 100% AF 8 36 IPDI.sub.w PVC 0 100% AF 8 36 IPDI.sub.s PVC >20 100% AF 8 36 IPDI + MDI.sub.s PVC 0 100% AF Without plasma <30 IPDI + CPO.sub.w TPE-V 0 100% AF Without plasma <30 CPO.sub.s TPE-V 0 100% AF Without plasma <30 CPO.sub.w TPE-V 0 100% AF Without plasma <30 IPDI.sub.w PVC 0 100% AF Without plasma <30 IPDI.sub.s PVC >10 100% AF Without plasma <30 IPDI + MDI.sub.s PVC 0 100% AF *CF = cohesive failure **AF = adhesive failure

[0084] It is observed that in the samples according to the invention where the is distance between the nozzle and the surface of the hardcoat is 2 and 4 mm, all the peel strength values are greater than 10 mN/m.

[0085] On the contrary, for the samples that have not undergone any plasma treatment or that have undergone a plasma treatment with a torch/substrate distance of 8 mm, the peel strength is insufficient in the vast majority of cases.

[0086] It is furthermore observed that the peel strength is higher for the samples treated at a distance of 2 mm than for those treated at a distance of 4 mm.

[0087] The surface energy of the samples after plasma treatment is even greater when the nozzle/surface distance is small.