CAR GLAZING

Description

[0001] The present invention relates to a motor vehicle glazing, in particular a glass roof, comprising a window, a thermoplastic elastomer seal and possibly a metal insert overmolded by the thermoplastic elastomer seal.

[0002] In the industrial field of automotive glazing (also commonly referred to as automotive glazing by misuse of language), the term "encapsulation" refers to a process or step of overmolding a polymeric material around the perimeter of a window. An encapsulation composition containing the polymeric material or precursors of the polymeric material is injected in a more or less viscous fluid state into a mold forming a sealed cavity around the edge of the window. After the composition has hardened, by cooling or crosslinking, the mold is opened and removed, leaving a profiled bead at the periphery of the window in contact with the edge and with at least one of the two faces of the window.

[0003] The hardened polymer that forms the profiled bead is often an elastomer capable of acting as a seal between the glazing and the bodywork.

[0004] The most commonly used elastomers as encapsulating materials for the manufacture of automotive glass roofs are polyurethanes obtained by reaction injection molding (RIM). reaction injection molding ) . Precursors, monomers or oligomers, generally polyols and polyisocyanates, are injected into the mold where they react to form a crosslinked three-dimensional network. Two types of polyisocyanates are used in RIM encapsulation compositions: aromatic polyisocyanates and aliphatic polyisocyanates. Aromatic polyisocyanates are known to be more reactive and effectively reduce production cycles. They are also less expensive and have better solvent resistance. FR 2 856 003 A1 discloses a glazing with PU-RIM encapsulation.

[0005] Polyurethanes, however, have the disadvantage of being sensitive to UV aging, which can cause color fading, cracking, or brittleness on exposed surfaces.

[0006] Several solutions have been put forward to improve the UV resistance of polyurethanes, including the development of specific catalysts, the optimization of stoichiometry between the reactants or the addition of UV stabilizers.

[0007] The present invention proposes an alternative solution to the use of polyurethanes in order to solve this problem of sensitivity to UV. It has indeed demonstrated that the use of certain thermoplastic polymers and in particular thermoplastic elastomers (TPE) for the encapsulation of automotive vehicle glazing constitutes a very interesting alternative to thermoset elastomers obtained by RIM with regard to UV resistance.

[0008] Furthermore, the use of TPE has other interesting advantages: automotive window seals made from TPE are recyclable, which is not the case for RIM polyurethane seals; and the use of TPE eliminates the problems associated with the use of reactive and toxic volatile monomers such as isocyanates.

[0009] The present invention therefore relates to a motor vehicle glazing comprising a window, a thermoplastic elastomer seal and optionally a metal insert overmolded by the thermoplastic elastomer seal, said seal comprising a PP / TPE compound comprising from 38 to 80% by weight, preferably from 40 to 75% by weight and in particular from 45 to 70% by weight of polypropylene (PP).

[0010] The seal may generally comprise up to 5% by weight, preferably less than 3% or even less than 1% by weight, of a coupling agent such as a functional alkoxysilane. In a particular embodiment, the seal is free of functional alkoxysilane.

[0011] The pane to be encapsulated may be a mineral glass pane or a plastic pane. It may consist of a single sheet of glass or plastic or a laminated pane formed of two or more sheets of glass or plastic, bonded to each other by means of what is conventionally called a lamination interlayer, generally consisting of poly(vinyl butyral) (PVB) or poly(ethylene-vinyl acetate) copolymer (EVA).

[0012] The glass sheet(s) and the lamination interlayer may be colored, the glass as a whole however retaining a certain transparency, with a light transmission (TL) which is preferably between 10 and 50%, in particular between 15 and 40%.

[0013] In a preferred embodiment of the method of the invention, the glass is a laminated glass made up of two sheets of mineral glass bonded to each other by means of a lamination interlayer.

[0014] The glazing according to the invention is preferably a glazed roof, such glazing being particularly exposed to UV. The dimensions of the glass are preferably such that its perimeter is at least equal to 1.0 m, preferably between 1.0 and 8.0 m, in particular between 1.3 and 4.5 m, ideally between 1.5 and 4.0 m.

[0015] The glazing according to the invention may comprise one or more metal inserts overmolded by the thermoplastic elastomer seal. The metal inserts may act as mechanical reinforcements and / or supports. Such metal inserts, particularly large ones, are necessary for complex automotive glazing such as glass roofs, in particular glass sunroofs. Automotive glazing may also comprise other parts, partially or completely incorporated into the encapsulation, such as centering pins or side brackets.

[0016] The metal insert preferably has fairly large dimensions, for example a length close to one of the dimensions of the window, for example a length between 10 cm and 1.5 m, in particular between 15 cm and 1.2 m.

[0017] The surface of the overmolded metal insert, and therefore in contact with the thermoplastic elastomer seal, may be a contact surface of less than 10 cm 2< . However, it is preferably a contact surface of several tens of square centimeters, or even several hundreds of square centimeters, in particular between 10 cm 2< and 1000 cm 2< .

[0018] The term "thermoplastic elastomer (TPE)" refers to heterogeneous polymer materials comprising rigid (or hard) domains and flexible (or soft) domains. These materials behave like elastomers in a limited temperature range encompassing room temperature, and adopt, at temperatures above the softening temperature of the rigid domains, plastic behavior and can therefore be processed as thermoplastic polymers.

[0019] Thermoplastic elastomers are known and their nomenclature and classification is defined in ISO 18064.

[0020] The thermoplastic elastomers used for the process according to the invention are preferably chosen from the group consisting of the following polymers: unvulcanized ethylene-propylene-diene monomer (EPDM) rubber, partially vulcanized ethylene-propylene-diene monomer (EPDM) rubber, and styrenic thermoplastic elastomers (TPE-S) such as poly(styrene-b-butadiene-b-styrene) (SBS) block copolymers, poly(styrene-b-(ethylene-butylene)-b-styrene) (SEBS) block copolymers, and poly(styrene-b-(ethylene-propylene)-b-styrene) (SEPS) block copolymers.

[0021] When these TPEs are mixed with polypropylene, the resulting TPE / PP compound also exhibits thermoplastic elastomer properties, i.e. elastic behavior within a certain temperature range encompassing room temperature (20°C) and thermoplastic behavior beyond this temperature range.

[0022] Polypropylene also advantageously increases the Shore A hardness of the resulting seals.

[0023] The glazing according to the invention has very good resistance to UV radiation such that the color variation ΔE*, measured according to the ISO 11664 standard, is less than 1 after aging for 1000 hours using a weather-o-meter (WoM) for 1000 hours under the conditions defined by the SAE J1960 standard. Thus, another subject of the present invention relates to the use of an encapsulation seal comprising a PP / TPE compound comprising from 38 to 80% by weight, preferably from 40 to 75% by weight and in particular from 45 to 70% by weight of PP, to improve the resistance to UV radiation of a motor vehicle glazing.

[0024] The present application also relates to a method for manufacturing a motor vehicle glazing comprising a window, an elastomer seal and possibly a metal insert overmolded by the elastomer seal, comprising inserting the edge of a window and possibly a metal insert into an encapsulation mold forming a sealed cavity around the edge of the window, filling the sealed cavity containing the edge of the window and possibly the metal insert, by injecting an encapsulation composition comprising a polypropylene (PP) / thermoplastic elastomer (TPE) compound in the molten state, cooling the encapsulation composition so as to form an elastomer seal in which the metal insert is integrated, demolding the elastomer seal in which the metal insert is integrated, the process being characterized in that said PP / TPE compound comprises from 38 to 80% by weight, preferably from 40 to 75% by weight and in particular from 45 to 70% by weight of polypropylene (PP).

[0025] The encapsulation composition used in the automotive glazing according to the invention may comprise, in addition to the TPE / PP compound, one or more additives whose main function is to reduce the viscosity of the hot encapsulation composition, to promote the adhesion of the composition to the glass, to reduce the costs of the final material obtained, and / or to increase the physical or chemical stability of the final material obtained.

[0026] In order to promote adhesion of the seal to the glass, the encapsulating composition may generally comprise up to 5% by weight, preferably less than 3% or even less than 1% by weight, relative to the total weight of the encapsulating composition, of a coupling agent such as a functional alkoxysilane. In a particular embodiment, the seal is free of functional alkoxysilane.

[0027] Cost-reducing additives are, for example, mineral fillers such as chalk, kaolin, talc, zinc oxide and carbon black. They may be present in an amount typically between 1 and 15%, preferably between 2 and 10% by weight, based on the total weight of the encapsulating composition. The presence of such mineral fillers increases the Shore A hardness of the formed seals.

[0028] Oils, preferably mineral oils, serve as processing aids and make it possible to reduce the glass transition temperature and to fluidify the hot encapsulation composition. They are present, for example, in an amount of 10 to 50%, preferably 20 to 45% by weight, based on the total weight of the encapsulation composition. Their presence has little effect on the hardness of the final joint.

[0029] And finally, anti-oxidant or anti-UV stabilizing agents may also be present in small quantities, generally less than 1% by weight.

[0030] The total amount of such additives should, however, not exceed an upper limit of approximately 30 to 35% by weight and the encapsulation composition preferably comprises between 35 and 65% by weight, preferably between 45% and 60% by weight, and in particular between 50 and 57% by weight of PP / TPE compound, relative to the total weight of the encapsulation composition.

[0031] Ready-to-use encapsulation compositions containing PP / TPE compound and additives (mineral oils / mineral fillers / stabilizing agents) are available on the market from TEKNOR APEX, EXXON, KRAIBURG, MCPP, MULTIBASE.

[0032] The encapsulating composition is preferably injected at a temperature between 170°C and 260°C, in particular between 170°C and 220°C, under a pressure between 15 bars and 120 bars, preferably between 15 bars and 80 bars.

[0033] The "curing" of the encapsulating composition is carried out by simple cooling, active or passive, preferably active, of the mold and the encapsulating material. In other words, the curing step does not include a heating step for the chemical crosslinking of the encapsulating composition.

[0034] The seal is preferably demolded before it has cooled completely to room temperature, for example at a temperature between 40 and 120°C.

[0035] Overmolded metal inserts can be made of any metallic material. They are preferably made of steel. They can optionally be covered with an organic or mineral surface coating, such as a layer of cataphoretic paint, which effectively protects them against corrosion.

[0036] The present invention is illustrated by the following non-limiting examples. Examples

[0037] An automotive glazing according to the invention (example 1) obtained by encapsulation of a mineral glass pane using a TPE comprising a PP / TPE compound comprises from 38 to 80% by weight of PP and two comparative automotive glazings (examples 2 and 3) obtained by encapsulation of a mineral glass pane using a RIM encapsulation composition comprising on the one hand aromatic polyisocyanates (example 2) and on the other hand aliphatic polyisocyanates (example 3).

[0038] These three glazings were subjected to an accelerated aging cycle using a weather-o-meter (WoM) for 1000 hours according to the conditions defined by the SAE J1960 standard. Each of the encapsulation compositions comprising an identical quantity of carbon black filler, the encapsulation seals obtained all have a deep black tint before aging. In order to determine the effect of UV aging on the encapsulation seals, the ΔE* values ​​were calculated from L*a*b* color measurements according to ISO 11664, under illuminant D65, observer at 2°, carried out at the seal before and after aging. The color fastness was also evaluated on a gray scale as defined by the EN 20105-A02: 1994 standard, the index 5 corresponding to the deep black tint of the seals before aging. The results are presented in the following table. Sample Encapsulation material ΔE* Grayscale Ex1 PP / TPE compound < 1 4-5 Ex2 Aromatic PU-RIM > 8 2 Ex3 Aliphatic PU-RIM < 2 3

[0039] The glazings of Comparative Examples 2 and 3 show significant degradation of their color after aging as shown by the high ΔE* values ​​and / or the low scores on the gray scale. In contrast, the glazing of Example 1 according to the present invention is only slightly affected by UV aging.

Claims

1. Glazing for motor vehicles comprising a window glass and a thermoplastic elastomer seal, characterized in that said seal comprising a PP / TPE compound comprises from 38 to 80 wt%, preferably from 40 to 75 wt% and in particular from 45 to 70 wt% of polypropylene (PP).

2. The glazing as claimed in claim 1, characterized in that it comprises a metal insert, at least one locating pin or at least one side bracket overmolded by the thermoplastic elastomer seal.

3. The glazing as claimed in one of claims 1 or 2, characterized in that the TPE is selected from - unvulcanized ethylene-propylene-diene monomer (EPDM) rubber, - partially vulcanized ethylene-propylene-diene monomer (EPDM) rubber, and - styrene thermoplastic elastomers (TPE-S) such as poly(styrene-b-butadiene-b-styrene) block copolymers (SBS), poly(styrene-b-(ethylene-butylene)-b-styrene) block copolymers (SEBS) and poly(styrene-b-(ethylene-propylene) -b-styrene) block copolymers (SEPS).

4. The glazing as claimed in one of claims 1 to 3, characterized in that the seal comprises up to 5 wt%, preferably less than 3 wt% or even less than 1 wt% of a coupling agent.

5. The glazing as claimed in one of claims 1 to 4, characterized in that the seal is free from functional alkoxysilane.

6. A method for manufacturing glazing for motor vehicles comprising a window glass, an elastomer seal and a metal insert overmolded by the elastomer seal, comprising - inserting the edge of a window glass and of a metal insert in an encapsulation mold forming a hermetic cavity around the edge of the window glass, - filling the hermetic cavity containing the edge of the window glass and the metal insert, by injecting an encapsulating composition comprising a polypropylene (PP) / thermoplastic elastomer (TPE) compound in the molten state, - cooling the encapsulating composition so as to form an elastomer seal in which the metal insert is incorporated, - mold release of the elastomer seal in which the metal insert is incorporated, the method being characterized in that said PP / TPE compound comprises from 38 to 80 wt%, preferably from 40 to 75 wt% and in particular from 45 to 70 wt% of polypropylene (PP), and in that the metal insert is covered with a polypropylene coating on all of its surface that may come into contact with the encapsulating composition.

7. The method as claimed in claim 6, characterized in that the encapsulating composition comprises up to 5 wt%, preferably less than 3 wt% or even less than 1 wt% of a coupling agent.

8. The method as claimed in one of claims 6 or 7, characterized in that the seal is free from functional alkoxysilane.

9. The method as claimed in one of claims 6 to 8, characterized in that the encapsulating composition additionally contains mineral fillers such as chalk, kaolin, talc, zinc oxide and carbon black, application aids such as oils, preferably mineral oils, or antioxidant or anti-UV stabilizers.

10. The method as claimed in one of claims 6 to 9, characterized in that the encapsulating composition comprises between 35 and 65 wt%, preferably between 45 wt% and 60 wt%, in particular between 50 and 57 wt% of PP / TPE compound, relative to the total weight of the encapsulating composition.