Thermoplastic elastomer composition for encapsulation

Abstract

A thermoplastic composition for overmolding of an elastomer on a substrate made of mineral glass includes: (1) from 50 to 70% by weight of at least one thermoplastic elastomer (TPE) chosen from copolymers comprising styrene blocks (TPE-Ss), (b) from 20 to 35% by weight of a polyolefin chosen from propylene homopolymers (PPs), ethylene homopolymers (PEs) and copolymers of propylene and ethylene, and (c) at least 7% by weight of a functional alkoxysilane. The percentages are expressed with respect to the sum of the components (a), (b) and (c).

Claims

1. A process for overmolding by injection molding of a thermoplastic composition over a glazing, the process comprising: (1) heating a thermoplastic composition comprising: (a) from 50 to 68% by weight of at least one thermoplastic elastomer (TPE), which is a copolymer comprising styrene blocks (TPE-Ss); (b) from 20 to 35% by weight of a polyolefin selected from the group consisting of propylene homopolymers (PPs), ethylene homopolymers (PEs), and copolymers of propylene and ethylene; and (c) at least 8% by weight of a functional alkoxysilane, wherein the percentages are with respect to the sum of the components (a), (b) and (c), to a temperature sufficient to obtain a viscosity of less than 1000 Pa.Math.s.sup.1, thereby producing a heated thermoplastic composition; (2) injecting the heated thermoplastic composition into a mold cavity into which is inserted an edge of the glazing, thereby producing a glazing-overmolding assembly; and (3) removing the glazing-overmolding assembly from the mold, wherein apart of the glazing which comes into contact with the thermoplastic composition is devoid of an organic priming layer, and wherein the heated thermoplastic composition comes directly into contact with the glazing.

2. A process for overmolding by extrusion of a thermoplastic composition onto a glazing, the process comprising: (1) heating a thermoplastic composition comprising: (a) from 50 to 68% by weight of a thermoplastic elastomer (TPE), which is a copolymer comprising styrene blocks (TPE-Ss); (b) from 20 to 35% by weight of a polyolefin selected from the group consisting of propylene homopolymers (PPs), ethylene homopolymers (PEs), and copolymers of propylene and ethylene; and (c) at least 8% by weight of a functional alkoxysilane, wherein the percentages are with respect to the sum of the components (a), (b) and (c), in an extruder, up to a temperature sufficient to obtain a viscosity of less than 1000 Pa.Math.s.sup.1, thereby producing a heated thermoplastic composition; and (2) extruding the heated thermoplastic composition in contact with an edge of the glazing, wherein a part of the glazing which comes into contact with the thermoplastic composition is devoid of an organic priming layer, and wherein the heated thermoplastic composition comes directly into contact with the glazing.

3. The process as claimed in claim 1, further comprising heating the overmolded glazing.

4. The process as claimed in claim 1, further comprising: before injecting the heated thermoplastic composition, heating the edge of the glazing to be overmolded.

5. The process as claimed in claim 1, further comprising: physically pretreating a surface of the glazing to be overmolded with a plasma or a corona discharge.

6. The process as claimed in claim 2, further comprising heating the overmolded glazing.

7. The process as claimed in claim 2, further comprising a stage of heating the edge of the glazing before the stage of extruding.

8. The process as claimed in claim 2, further comprising a stage of physical pretreatment of a surface of the glazing to be oveiinolded with a plasma.

9. The process as claimed in claim 1, wherein the thermoplastic composition further comprises from 0.5 to 10% by weight with respect to the sum of (a)+(b)+(c), of an organic polymer grafted with maleic anhydride (MAH).

10. The process as claimed in claim 9, wherein the organic polymer grafted with maleic anhydride is selected from the group consisting of a TPE-S grafted with maleic anhydride and a polyolefin grafted with maleic anhydride.

11. The process as claimed in claim 1, wherein the functional alkoxysilane is at least one selected from the group consisting of an aminosilane, an epoxysilane, a vinylsilane, a mercaptosilane and a (meth)acryloyisilane.

12. The process as claimed in claim 1, wherein the thermoplastic composition is devoid of a volatile organic solvent.

13. The process as claimed in claim 1, wherein the thermoplastic composition comprises: (b) from 22 to 30% by weight of the polyolefin.

14. The process as claimed in claim 1, wherein the thermoplastic composition comprises: (c) from 8 to 20% by weight of the functional alkoxysilane.

15. The process as claimed in claim 1, wherein the thermoplastic composition further comprises from 1 to 5% by weight, with respect to the sum of (a)+(b)+(c), of an organic polymer grafted with maleic anhydride (MAH).

16. The process as claimed in claim 1, wherein the functional alkoxysilane is a mixture of at least two silanes selected from the group consisting of an aminosilane, a vinylsilane and an epoxysilane.

17. The process as claimed in claim 2, wherein the thermoplastic composition further comprises from 0.5 to 10% by weight with respect to the sum of (a)+(b)+(c), of an organic polymer grafted with maleic anhydride (MAH).

18. The process as claimed in claim 17, wherein the organic polymer grafted with maleic anhydride is selected from the group consisting of a TPE-S grafted with maleic anhydride and a polyolefin grafted with maleic anhydride.

19. The process as claimed in claim 2, wherein the functional alkoxysilane is at least one selected from the group consisting of an aminosilane, an epoxysilane, a vinylsilane, a mercaptosilane and a (meth)aciyloylsilane.

20. The process as claimed in claim 2, wherein the thermoplastic composition is devoid of a volatile organic solvent.

21. The process as claimed in claim 2, wherein the thermoplastic composition comprises: (b) from 22 to 30% by weight of the polyolefin.

22. The process as claimed in claim 2, wherein the thermoplastic composition comprises: (c) from 8 to 20% by weight of the functional alkoxysilane.

23. The process as claimed in claim 2, wherein the thermoplastic composition further comprises from 1 to 5% by weight, with respect to the sum of (a)+(b)+(c), of an organic polymer grafted with maleic anhydride (MAH).

24. The process as claimed in claim 2, wherein the functional alkoxysilane is a mixture of at least two silanes selected from the group consisting of an aminosilane, a vinylsilane and an epoxysilane.

25. The process as claimed in claim 1, wherein the thermoplastic composition comprises: (a) from 50 to 65% by weight of the thermoplastic elastomer (TPE); and (c) from 9 to 15% by weight of the functional alkoxysilane.

Description

EXAMPLES

(1) The following thermoplastic blend is prepared on an injection station using volumetric metering devices:

(2) 63 parts by weight of an SBS copolymer,

(3) 25 parts by weight of polypropylene homopolymer,

(4) 5 parts by weight of 3-aminopropyltriethoxysilane,

(5) 5 parts by weight of vinyltrimethoxysilane,

(6) 1 part by weight of polypropylene grafted with maleic anhydride, and

(7) 1 part by weight of SEBS grafted with maleic anhydride.

(8) These ingredients are blended and heated to a temperature from 200 C. to 250 C. (temperature of the screw). The molten material is injected into an overmolding mold into which is inserted a glazing which has not been subjected to any pretreatment. Neither the mold nor the glazing is independently heated.

(9) After approximately one minute, the glazing overmolded with a seal is removed from the mold and stored at a temperature of 23 C. and a relative humidity of 50% for seven days, during which period the reaction of the coupling agents continues.

(10) After storing for seven days, the adhesion of the seal to the glazing is evaluated by means of a 90 peel test (pull rate: 100 mm/minute). The overmolded glazing is subsequently subjected to wet poultice aging (14 days at 70 C., relative humidity 95%, then thermoshock by cooling for 2 hours at 20 C.) and the adhesion test is repeated (example 1).

(11) The above procedure is repeated while implementing the following variants:

Example 2

(12) the glazing is preheated to 80 C. before the stage of overmolding the thermoplastic composition;

Example 3

(13) the region of the glazing intended to come into contact with the thermoplastic composition is subjected to an atmospheric plasma treatment;

Example 4

(14) the overmolded glazing is subjected, after removing from the mold, to a stage of postcuring at 80 C. for an hour;

Example 5

(15) a chemical activation composition, comprising a solution of 2% of N-(3-(trimethoxysilyl)propyl)-1,2-ethanediamine and 2% of 3-trimethoxysilylpropane-1-thiol in isopropanol (Betawipe VP 04604 from Dow Automotive), is applied manually, before the insertion of the glazing into the injection mold;

Example 6

(16) a solution of 2% of N-(3-(trimethoxysilyl)propyl)-1,2-ethylenediamine and 2% of tris(dodecylbenzenesulfonato-O)(propan-2-olato)titanium in a mixture of organic solvents (Sika Aktivator) is applied manually, before the insertion of the glazing into the injection mold.

(17) The type of failure and the peel strength, recorded for examples 1 to 6, before and after the stage of wet poultice aging, are shown in table 1.

(18) TABLE-US-00001 TABLE 1 (examples according to the invention) Before aging After aging Peel strength Peel strength Failure (N/cm) Failure (N/cm) Example 1 adhesive >30 cohesive >35 Example 2 cohesive >40 cohesive >50 Example 3 adhesive >35 cohesive >40 Example 4 cohesive >30 cohesive >40 Example 5 adhesive >40 cohesive >40 Example 6 adhesive >30 cohesive >40

(19) It is observed that the overmolding composition according to the invention gives better results after a period of hot aging. These results indicate that the reaction responsible for the polymer/glass adhesion certainly continues well after removal from the mold, possibly even after the first period of storage at ambient temperature for seven days.

(20) After the aging period, all the failures are of cohesive type (polymer/glass adhesion is greater than the internal cohesion of the polymer material), which is a very difficult result to obtain with adhesion primers.

(21) When examples 1 to 6 above are repeated but using one fifth of the amount of silanes, that is to say one part by weight of 3-aminopropyltriethoxysilane and one part by weight of vinyltrimethoxysilane, the adhesion results presented below in table 2 are obtained.

(22) TABLE-US-00002 TABLE 2 (comparative examples) Before aging Failure Peel strength (N/cm) Comparative example 1 adhesive >5 Comparative example 2 adhesive >20 Comparative example 3 adhesive >10 Comparative example 4 adhesive >20 Comparative example 5 adhesive >5 Comparative example 6 adhesive >5

(23) It is observed that all the failures are of adhesive type and that the peel strengths are inadequate (less than 30 N/cm).