FR3147568A1 - Silane-based adhesion primer deposited by atmospheric pressure plasma - Google Patents

Abstract

The invention relates to a method of adhesion between a polyamide substrate and a layer of thermoplastic elastomer, by means of an adhesion primer based on an amino silane deposited by atmospheric pressure plasma. It also relates to an article, such as a guide rail intended to guide the movement of a movable window of a vehicle, comprising a polyamide substrate, a layer of thermoplastic elastomer adhering to the substrate by means of an adhesion primer based on an amino silane, characterized in that the adhesion is obtained by such a method. Another subject of the invention is a glazing comprising such a guide rail, a movable window received in the guide rail, and optionally an element on which the guide rail is fixed.

Description

Silane-based adhesion primer deposited by atmospheric pressure plasma

The invention relates to a method of adhesion between a polyamide substrate and a layer of thermoplastic elastomer, by means of an adhesion primer based on an amino silane deposited by atmospheric pressure plasma. It also relates to an article, such as a guide rail intended to guide the movement of a movable window of a vehicle, comprising a polyamide substrate, a layer of thermoplastic elastomer adhering to the substrate by means of an adhesion primer based on an amino silane, characterized in that the adhesion is obtained by such a method. Another subject of the invention is a glazing comprising such a guide rail, a movable window received in the guide rail, and optionally an element on which the guide rail is fixed.

Thermoplastic elastomers, also called thermoplastic rubbers, are materials that combine the elastic properties of elastomers with thermoplastic properties. Due to their chemical resistance, flexibility and ability to recover after application of a load, these materials are used in many applications, particularly in the automotive field.

For some of these applications, the thermoplastic elastomer is deposited via an injection molding step, on a rigid substrate, such as a polyamide substrate. However, to obtain good adhesion properties between the flexible material and the rigid substrate, a simple cleaning, stripping or etching step is not sufficient, and a more significant modification of the substrate surface is necessary.

There are several techniques to address this problem, and one of them consists of applying a coating to the surface of the substrate, in particular by depositing a liquid solution containing an adhesive, typically based on isocyanate.

Although good adhesion performance can be achieved with this method, it faces several limitations:

- the deposition of the liquid solution requires a drying step which lengthens the implementation time of the process;

- obtaining a coating that is uniform in thickness and surface area is difficult to achieve;

- the deposition of the thermoplastic elastomer after drying of the liquid solution must not be too late, due to the sensitivity of the isocyanate-based coating to external conditions, such as cold and humidity;

- legislation is becoming increasingly strict regarding the use of isocyanates, which are toxic.

There therefore remains a real need to provide a process that overcomes the above limitations, while maintaining good adhesion performance between the rigid substrate, typically polyamide, and the thermoplastic elastomer.

In this context, the inventors have developed a method in which a silane-based adhesion primer is deposited on a polyamide substrate by atmospheric pressure plasma, before the deposition of a layer of thermoplastic elastomer. Surprisingly, to obtain good adhesion performances, advantageously at least equivalent to those obtained with an isocyanate-based primer deposited by liquid means, the silane must comprise at least one (O) _n Si unit, where n is 1, 2, or 3, and at least one amine. Conversely, silanes lacking one and/or the other of these characteristics do not allow good adhesion between the polyamide and the thermoplastic elastomer. This is particularly the case for (3-glycidyloxypropyl)trimethoxysilane, which nevertheless comprises an epoxy, a chemical function often found in the adhesion primers commonly used.

Atmospheric pressure plasma also has the advantage of being less expensive and simpler to implement than low pressure (or “vacuum”) plasma.

This invention is particularly applicable in the automotive field. In particular, the guide rails, which allow the movement of a movable window of a vehicle to be guided when it is opened, are generally formed by the adhesion between a polyamide support and a strip of thermoplastic elastomer.

Thus, the present invention relates to a method of adhesion between a polyamide substrate and a layer of thermoplastic elastomer, comprising:

a) the deposition of an adhesion primer on a surface of the polyamide substrate by an atmospheric pressure plasma comprising a silane, and

b) the deposition of a layer of thermoplastic elastomer on the adhesion primer,

characterized in that said silane comprises at least one (O) _n Si unit, where n is 1, 2, or 3, and at least one amine.

In some embodiments, the silane is of formula (I):

in which:

- n is 1, 2, or 3 (preferably 2 or 3, better still n is 3),

- each R ¹ , identical or different, represents a hydrocarbon group having 1 to 12 carbon atoms, optionally comprising one or more (for example, one or two) heteroatoms,

- each R ² , identical or different, represents a hydrocarbon group having 1 to 12 carbon atoms, and

- R ³ represents a hydrocarbon group having 1 to 12 carbon atoms, comprising one or more (for example, one, two or three) groups selected from -NH ₂ and -NH-, and optionally one or more (for example, one, two or three) additional heteroatoms.

In some embodiments, n is 3, each R ¹ , the same or different, is C1-C12 alkyl, and R ³ is of the formula -R ⁴ -NH ₂ where R ⁴ is C1-C12 alkylene or C1-C12 heteroalkylene.

Preferably, the silane is (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane or a mixture thereof.

In some embodiments, the thermoplastic elastomer is a blend of polypropylene and a polystyrene-b-poly(ethylene-butylene)-b-polystyrene copolymer, or a blend of polypropylene and ethylene-propylene-diene rubber.

In some embodiments, the substrate is polyamide 6 or polyamide 6-6, and optionally includes glass beads or fibers.

In some embodiments, the plasma is a plasma of _N2 , _O2 , air, argon, helium, or a combination thereof, preferably an air or _N2 plasma, more preferably an air plasma.

In some embodiments, the plasma power is between 600 W and 1500 W, preferably between 650 W and 1200 W.

In some embodiments, the plasma comprising said silane is ejected by a torch moving at a speed of 20 to 600 mm/sec, for example 20 to 100 mm/sec, in step a). In such an embodiment, 1 to 10 track passes, for example 3 to 7 track passes, may be implemented.

The projection distance between the torch and the surface of the substrate is advantageously between 1 cm and 10 cm, for example between 1.5 cm and 4 cm, in step a).

In some embodiments, the silane is introduced into the plasma at a flow rate of between 10 and 300 µL/min.

In some embodiments, the thermoplastic elastomer is deposited, in step b), by injection overmolding.

Another object of the present invention is an article, such as a guide rail for guiding the movement of a movable window of a vehicle, comprising:

- a polyamide substrate and

- a layer of thermoplastic elastomer adhering to the substrate by means of an adhesion primer based on a silane comprising at least one (O) _n Si unit, where n is 1, 2, or 3, and at least one amine,

characterized in that the adhesion by means of said primer is obtained by the process as defined in the present application.

Another object of the present invention is a glazing comprising a guide rail as defined above, a movable pane received in the guide rail, and optionally an element on which the guide rail is fixed.

FIGURES

: Movement pattern of a plasma device during step a) of the adhesion method, in a particular embodiment of the invention.

: Exploded view of a guide rail and a movable window, in a particular embodiment of the invention.

: Schematic cross-sectional representation of a guide rail, in a particular embodiment of the invention.

: Exploded view of a glazing, in a particular embodiment of the invention.

: Schematic cross-sectional representation of a glazing, in a particular embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

The groups referred to in the present application with a prefix C _x -C _y , where x and y are integers, have from x to y carbon atoms. If, for example, the term C ₁ -C ₆ is used, this means that the corresponding group may comprise from 1 to 6 carbon atoms, in particular 1, 2, 3, 4, 5 or 6 carbon atoms.

By "aliphatic" is meant a non-aromatic, saturated or unsaturated, linear or branched acyclic hydrocarbon group. In a particular embodiment, an aliphatic group is an alkyl or alkenyl group.

By “alkyl” is meant a saturated aliphatic group, preferably having from 1 to 12 carbon atoms. Examples of C1-C12 alkyl include, in particular, methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl.

By “alkenyl” is meant an unsaturated aliphatic group, comprising at least one carbon-carbon double bond, preferably having from 2 to 12 carbon atoms. Examples of C2-C12 alkenyl are in particular, ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl.

By "alicyclic" is meant a non-aromatic, saturated or unsaturated, cyclic (mono- or polycyclic) hydrocarbon group. In a particular embodiment, an alicyclic group is a cycloalkyl group.

By "cycloalkyl" is meant a saturated alicyclic group, preferably having from 3 to 12 carbon atoms. Examples of C3-C12 cycloalkyl include, in particular, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, or cyclododecyl.

By “aryl” is meant an aromatic hydrocarbon group (mono- or polycyclic), preferably having 6 to 12 carbon atoms. An example of C6-C12 aryl is phenyl.

By "alkylene" is meant a saturated, linear or branched, divalent hydrocarbon group, preferably having from 1 to 12 carbon atoms. Examples of alkylene include methylene (-CH ₂ -), ethylene (-(CH ₂ ) ₂ -), propylene (-(CH ₂ ) ₃ -), butylene (-(CH ₂ ) ₄ -), pentylene (-(CH ₂ ) ₅ -), or hexylene (-(CH ₂ ) ₆ -).

A "heteroalkylene" group is an alkylene group containing one or more heteroatoms.

By "a group comprising at least one heteroatom" is meant a group interrupted by, or comprising at one and/or the other of its ends, at least one heteroatom.

In this application, the expression “at least one” may be used equivalently to “one or more”.

In this application, a range defined with the expression "between (X) and (Y)" includes the lower (X) and upper (Y) limits, and is equivalent to "from (X) to (Y)".

The method according to the invention is a simple and effective method which makes it possible to obtain good adhesion between a polyamide substrate and a layer of thermoplastic elastomer. It is based on the deposition on the substrate of a silane-based adhesion primer by atmospheric pressure plasma, which silane comprises at least one (O) _n Si unit, where n is 1, 2, or 3 and at least one amine.

In step a) of the method according to the invention, an adhesion primer is deposited on a surface of the polyamide substrate by an atmospheric pressure plasma comprising a silane, said silane comprising at least one (O) _n Si unit, where n is 1, 2, or 3 and at least one amine. This type of deposition may be called plasma-enhanced chemical vapor deposition (or PE-CVD).

By "silane" is meant an organic compound comprising one or more silicon atoms. The silane used in the process of the invention is such that at least one silicon atom forms a (O) _n Si unit, where n is 1, 2, or 3. The oxygen(s) of the (O) _n Si unit are typically linked to a hydrocarbon group, forming in this case a (RO) _n Si- unit where n is 1, 2, or 3 and each R, identical to or different from each other, represents a hydrocarbon group. The silane further comprises at least one amine (for example one or two amines), said at least one amine being in particular chosen from an -NH ₂ group and an -NH- group. Preferably the silane comprises an -NH ₂ group, and optionally one or more (for example, one, two, three or four, preferably only one) -NH- groups.

Preferably, said silane comprises an (O) _n Si unit, where n is 1, 2, or 3, an NH ₂ group and optionally one or more (e.g., one, two, three or four, preferably only one) -NH- groups. More preferably, said silane comprises an (O) ₃ Si unit and an NH ₂ group.

Said at least one (O) _n Si unit, where n is 1, 2, or 3, and said at least one amine are typically linked together by a hydrocarbon group.

Said silane generally has between 3 and 70 carbon atoms. Said silane generally has a molar mass of between 100 and 600 g/mol, for example between 150 and 500 g/mol.

Preferably n is 2 or 3, better still n is 3.

In a particular embodiment, said silane is of formula (I):

in which:

- n is 1, 2, or 3 (preferably 2 or 3, better still n is 3),

- each R ¹ , identical or different, represents a hydrocarbon group having 1 to 12 carbon atoms, optionally comprising one or more (for example, one or two) heteroatoms,

- each R ² , identical or different, represents a hydrocarbon group having 1 to 12 carbon atoms, and

- R ³ represents a hydrocarbon group having 1 to 12 carbon atoms, comprising one or more (for example, one, two or three) groups selected from -NH ₂ and -NH-, and optionally one or more additional heteroatoms.

When n is 1, 2 or 3, the compound of formula (I) can be represented respectively as follows:

A hydrocarbon group can be linear or branched, cyclic or acyclic, saturated or unsaturated, aliphatic or aromatic.

In a particular embodiment, each R ¹ , identical or different, represents a C1-C12 aliphatic group, a C3-C12 alicyclic group or a C6-C12 aryl. In a more particular embodiment, each R ¹ , identical or different, represents a C1-C12 alkyl, a C2-C12 alkenyl, a C3-C12 cycloalkyl or a C6-C12 aryl.

In a particular embodiment, R ¹ is a C1-C12 alkyl, optionally comprising one or more oxygens.

Preferably, each R ¹ , identical or different (preferably identical), represents a C1-C12 alkyl. More preferably, each R ¹ , identical or different (preferably identical), represents a C1-C6 alkyl, for example a methyl or an ethyl.

When present (i.e. if n is 1 or 2), each R ² , identical or different, may represent a C1-C12 aliphatic group, a C3-C12 alicyclic group or a C6-C12 aryl. More particularly, each R ² , identical or different, may represent a C1-C12 alkyl, a C2-C12 alkenyl, a C3-C12 cycloalkyl or a C6-C12 aryl. Preferably, each R ^{2 , identical or different, represents a C1-C12 alkyl. More preferably, each R 2 ,} identical or different, represents a C1-C6 alkyl, for example a methyl or an ethyl.

In a particular embodiment, R ³ represents an alkyl having 1 to 12 carbon atoms, comprising one or more (for example, one, two or three) groups selected from -NH ₂ and -NH-, and optionally one or more (for example, one, two or three) additional heteroatoms (selected in particular from oxygen and sulfur).

In a preferred embodiment, R ³ is a group of formula -R ⁴ -NH ₂ , in which R ⁴ represents a divalent hydrocarbon group having 1 to 12 carbon atoms, optionally comprising one or more heteroatoms.

In a particular embodiment, R ⁴ represents a divalent hydrocarbon group having 1 to 12 carbon atoms, optionally comprising one or more (for example, one, two, three or four) heteroatoms selected from oxygen, nitrogen and sulfur.

Preferably, R ⁴ is a C1-C12 alkylene or a C1-C12 heteroalkylene. In this embodiment, the C1-C12 heteroalkylene may comprise, for example, one, two, three or four heterotoms, in particular one, two, three or four nitrogen atoms.

More preferably, R ⁴ is a C1-C6 alkylene, for example a propylene (ie -CH ₂ -CH ₂ -CH ₂ -).

In a preferred embodiment, n is 3, each R ¹ , identical or different, is a C1-C12 alkyl, and R ³ is of formula -R ⁴ -NH ₂ where R ⁴ is a C1-C12 alkylene or a C1-C12 heteroalkylene.

Preferably, said silane is (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane or a mixture thereof.

By “polyamide” is meant a condensation product of one or more amino acids, of condensation of one or more lactams, or of condensation of one or more polyacids (e.g. diacids) with one or more polyamines (e.g. diamines).

Examples of amino acids include aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid or a salt thereof.

Examples of lactams include β,β-dimethylpropriolactam, α,α-dimethylpropriolactam, amylolactam, capryllactam, caprolactam or lauryllactam.

Examples of diacids include isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, 1,4 cyclohexyldicarboxylic acid, or a salt thereof.

Examples of diamines include aliphatic diamines or aryl diamines. More specific examples include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine, methyl pentamethylenediamine, bis(aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, dodecamethylenediamine, metaxylyenediamine, bis-p-aminocyclohexylmethane and trimethylhexamethylenediamine or a salt thereof.

The polyamide can be a homopolyamide or a copolyamide.

Examples of homopolyamides include polyamide 6 (also called polycaprolactam, denoted PA 6) or polyamide 6-6 (i.e. polymer of adipic acid and hexamethylenediamine, denoted PA 6-6).

Examples of copolyamides include copolymers of caprolactam and lauryllactam (PA 6/12), copolymers of caprolactam, adipic acid and hexamethylenediamine (PA 6/6-6), copolymers of caprolactam, lauryllactam, adipic acid and hexamethylenediamine (PA 6/12/6-6), copolymers of caprolactam, lauryllactam, amino-11-undecanoic acid, azelaic acid and hexamethylenediamine (PA 6/6-9/11/12), copolymers of caprolactam, lauryllactam, amino-11-undecanoic acid, adipic acid and hexamethylenediamine (PA 6/6-6/11/12), copolymers of lauryllactam, azelaic acid and hexamethylenediamine (PA 6-9/12).

In a particular embodiment, the polyamide is a polyamide 6 or a polyamide 6-6.

Preferably, the polyamide is a polyamide 6.

The substrate may further comprise fillers such as reinforcing beads or fibers, including glass beads, glass fibers, carbon fibers, or poly(p-phenylene terephthalamide) (Kevlar®) fibers. These fillers are typically homogeneously dispersed in the polyamide. For example, the substrate may comprise between 5% and 60% (e.g., between 20% and 50%, between 30% and 50%, between 35% and 45%, or between 38% and 42%) by weight of fillers (e.g., glass beads or fibers), relative to the total weight of the substrate.

In a preferred embodiment, the substrate is polyamide 6 or polyamide 6-6 (preferably polyamide 6), and comprises glass fibers, typically between 30% and 50% by weight relative to the total weight of the substrate.

The plasma used in the method of the invention is an atmospheric pressure plasma. Atmospheric pressure plasma, as opposed to low pressure plasma, refers to a plasma well known to those skilled in the art, which is implemented at a pressure of the order of atmospheric pressure. This pressure may typically be 1000 ± 400 mbar, preferably 1000 ± 200 mbar, or even 1000 ± 100 mbar.

Plasma is formed from a gas, subjected to an electrical discharge. Devices suitable for forming a plasma at atmospheric pressure are well known to those skilled in the art. Generally, such a device comprises a chamber comprising a pair of electrodes and opening onto a nozzle. In such a device, the gas passes through the pair of electrodes, which generate the electrical discharge, and the plasma initiated at these electrodes is ejected by the nozzle. The device is typically a plasma torch.

In a particular embodiment, the plasma is a plasma of a gas selected from _N2 , _O2 , air, argon, helium and a combination thereof. In some embodiments, said gas is selected from the aforementioned gases and further comprises dihydrogen, in a content less than or equal to 5% by volume.

Preferably the plasma is air or _N2 plasma, more preferably air plasma.

The plasma power is advantageously between 600 W and 1500 W, for example between 600 W and 1300 W, preferably between 650 W and 1200 W, or even between 700 W and 1200 W.

The flow rate of the gas used to form the plasma can, for example, be between 10 and 100 L/min, preferably between 30 and 50 L/min, or even between 35 and 45 L/min.

The silane is preferably introduced into the plasma by spraying. Advantageously, when the plasma is ejected by a nozzle, the silane is introduced into the plasma after its ejection by the nozzle. Said silane is generally introduced into the plasma, continuously, as the latter is applied to the surface of the substrate. The flow rate at which the silane is introduced into the plasma may for example be between 10 µL/min and 300 µL/min, preferably between 50 µL/min and 250 µL/min, or even between 150 µL and 250 µL/min. It will be preferable to use an inert gas, such as N ₂ or argon, to introduce, by spraying, said silane into the plasma.

Preferably, the silane is introduced into the plasma in the form of an undiluted liquid. By “undiluted liquid” is meant a liquid consisting essentially of the silane (i.e., typically comprising at least 90%, or even at least 95%, or even at least 98%, by weight of said silane relative to the total weight of the liquid).

In some embodiments, the plasma comprising said silane is ejected by a device (typically a torch) moving at a speed of 20 to 600 mm/sec, for example 20 to 100 mm/sec (or even 20 to 50 mm/sec) or 50 to 400 mm/sec (or even 100 to 400 mm/sec). In such an embodiment, 1 to 10 track passes, for example 3 to 7 track passes, can be implemented. When several track passes are implemented, the movement of the device is advantageously carried out according to a pattern substantially identical to the previous one. The pattern determined by the movement of the device is not limiting.

The projection distance between the device (typically a torch) and the surface of the substrate is advantageously between 1 cm and 10 cm, for example between 1.5 cm and 4 cm. As explained above, the device (for example, a torch) generally comprises a nozzle (or any other type of equivalent orifice), and the projection distance then corresponds to the distance between the nozzle through which the plasma is ejected and the surface of the substrate subjected to the plasma.

The thickness of the adhesion primer layer is generally between 10 nm and 100 µm, more particularly between 1 µm and 50 µm. The thickness of the polyamide substrate is generally between 1 and 20 mm, for example between 1 and 10 mm, or even between 2 and 6 mm. The thickness of the thermoplastic elastomer layer is generally between 1 and 20 mm, for example between 1 and 10 mm, or even between 2 and 6 mm.

In a particular embodiment, the polyamide substrate has a width of between 5 and 20 mm (e.g. between 8 and 20 mm) and a length of between 200 and 600 mm. In a particular embodiment, the polyamide substrate has a total surface area of between 20 and 500 cm ² .

In some embodiments, the substrate comprises two faces (preferably each having a surface area of between 10 and 150 cm ² ). In such an embodiment, the adhesion primer is advantageously deposited on a single face, and preferably covers, after its deposition, at least 70%, or even at least 80%, or even at least 90%, or even at least 95% of said single face.

Alternatively, the adhesion primer can be deposited on both sides, and preferably covers, after its deposit, at least 70%, or even at least 80%, or even at least 90%, or even at least 95% of each side.

In the method according to the invention, step b) comprises the deposition of a layer of thermoplastic elastomer on the adhesion primer.

By “thermoplastic elastomer” (or “TPE”) is meant a copolymer (typically, block) or blend of polymers, which combines the elastic properties of an elastomer with a thermoplastic character. The thermoplastic elastomer is generally a copolymer (typically, block), a blend of polymers, or a combination thereof, typically based on one or more elastomers and one or more thermoplastic polymers. Thermoplastic elastomers are a category of materials well known to those skilled in the art.

In a particular embodiment, the thermoplastic elastomer is a block copolymer. In such an embodiment, the copolymer preferably comprises at least one thermoplastic block selected from a polyurethane block, a polystyrene block, a polyester block, a poly(methyl methacrylate) block and a polyamide block, and at least one elastomer block selected from a polyether block, a polybutadiene block, a polyisoprene block, a polyethylene block, a poly(ethylene-propylene) block, and a poly(ethylene-butylene) block.

In a more particular embodiment, the thermoplastic elastomer is a block copolymer of polyurethane and polybutadiene, polyurethane and polyether, polyester and polybutadiene, polyester and polyether, polyamide and polybutadiene, polyamide and polyether, polystyrene and polybutadiene, polystyrene and polyisoprene, polystyrene and poly(ethylene-butylene), polystyrene and poly(ethylene-propylene), polystyrene and poly(ethylene-ethylene/propylene), or a combination thereof.

Particular examples of TPEs include: polystyrene-b-polybutadiene-b-polystyrene (SBS), polystyrene-b-polyisoprene-b-polystyrene (SIS), polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS), polystyrene-b-poly(ethylene-propylene)-b-polystyrene (SEPS), polystyrene-b-poly(ethylene-ethylene/propylene)-b-polystyrene (SEEPS), poly(methyl methacrylate)-b-polybutadiene-b-polystyrene (MBS), or a mixture thereof.

In another particular embodiment, the thermoplastic elastomer is a blend of polymers. Examples of such TPEs include a blend based on polypropylene and a polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS) copolymer, or a blend based on polypropylene and rubber (such as ethylene-propylene-diene rubber (EPDM) where the diene may include ethylidene norbornene (ENB), styrene-butadiene rubber (SBR), or butadiene-acrylonitrile rubber (NBR), preferably rubber (EPDM). The rubber may be vulcanized or not.

In a particular embodiment, the thermoplastic elastomer is a blend based on polypropylene and a polystyrene-b-poly(ethylene-butylene)-b-polystyrene copolymer, or a blend based on polypropylene and ethylene-propylene-diene rubber.

Preferably, the thermoplastic elastomer is deposited by injection overmolding. In such a mode, the thermoplastic elastomer is typically inserted into a hot press, generally in the form of granules, beads or pellets, to be heated, prior to its deposition on the adhesion primer. The temperature to which the thermoplastic elastomer is heated is a temperature sufficient for the latter to melt. Preferably, the temperature to which the thermoplastic elastomer is heated prior to its deposition is between 180°C and 260°C, for example between 200 and 250°C, or even between 210°C and 230°C. Once heated, the thermoplastic elastomer is deposited on the adhesion primer. In injection overmolding, a mold is used to define the shape of the layer of thermoplastic elastomer deposited on the adhesion primer.

Preferably, the thermoplastic elastomer covers at least 90%, or even at least 95%, and more preferably at least 98% of the surface area of the adhesion primer. In some embodiments, the thermoplastic elastomer covers 100% of the surface area of the adhesion primer.

The method according to the invention makes it possible to obtain excellent adhesion between the polyamide substrate and the thermoplastic elastomer layer. Advantageously, the peel force, obtained by a peel test with a peel angle of 90° and a speed of 100 mm/min, at 23°C and 50% relative humidity, is at least 30 N/cm, for example between 30 N/cm and 50 N/cm, with preferably a cohesion rate of at least 20%, or at least 30%, or even at least 50% and better still at least 70%.

The present invention also relates to an article comprising:

- a polyamide substrate and

- a layer of thermoplastic elastomer adhering to the substrate by means of an adhesion primer based on a silane comprising at least one (O) _n Si unit where n is 1, 2, or 3, and at least one amine,

characterized in that the adhesion by means of the primer is obtained by the process as defined in the present application.

It is understood that the definitions and methods described above for the process (e.g. polyamide, silane, thermoplastic elastomer, plasma conditions, dimensions) also apply to the article according to the invention.

The article according to the invention may, for example, be an article used in the automotive field.

Such an article may in particular be a filling insert, a fixing insert (e.g. a filling insert or fixing for the bodywork), and/or a positioning insert (e.g. a pin). More particularly, the article may be a guide rail intended to guide the movement of a window of a vehicle.

There shows an example (exploded view) of a guide rail 1 configured to guide the movement of a movable window 3 of a vehicle, in a direction indicated by a double arrow on the .

There shows a cross-section of an example of a guide rail 1. The cross-section of the guide rail 1 has a general U-shape. The guide rail 1 comprises a polyamide substrate 4, which constitutes an external portion of the guide rail 1, and a thermoplastic elastomer layer 6, which constitutes an internal portion of the guide rail 1. The substrate 4 acts as a rigid support and surrounds the thermoplastic elastomer layer 6, which is flexible. The thermoplastic elastomer layer 6 adheres to the substrate 4 by means of a layer 5 (dotted in the figure) of adhesion primer based on a silane comprising at least one (O) _n Si unit (where n is 1, 2, or 3) and at least one amine, and the adhesion by means of the primer is obtained by the method as defined in the present application. The inner surface 6 ₁ of the thermoplastic elastomer layer 6 delimits a housing configured to receive an edge of a movable window and guide its movement. The outer surface 4 ₁ of the substrate 4 is configured to be fixed to an element of a vehicle, such as a bodywork element or a fixed window (eg a quarter window). The outer surface 4 ₁ of the substrate 4 may in particular define a housing configured to receive an edge of a fixed window.

Another object of the present invention is a glazing comprising a guide rail as defined above, a movable window received in the guide rail, and optionally an element on which the guide rail is fixed. Said element may be a bodywork element of a vehicle, or a fixed window, such as a quarter window. Preferably, said element is a fixed window, such as a quarter window.

There shows an example (exploded view) of glazing 10, which comprises a guide rail 1 and a movable pane 3 received in the guide rail 1, in which the guide rail 1 is fixed to an element 2 which is a fixed pane. The guide rail may in particular be as described above for the .

There shows a cross section of an exemplary glazing 10 comprising a guide rail 1 as described above for the , a movable window 3 whose edge is received in the housing defined by the internal surface 6 ₁ of the thermoplastic elastomer layer 6 of the guide rail 1, and in which the guide rail 1 is fixed to an element 2 which is a fixed window. More particularly, the external surface 4 ₁ of the substrate 4 of the guide rail 1 defines a housing which receives the edge of the fixed window.

EXAMPLES

General procedure

The substrate (denoted “PA” hereinafter) tested here is made of polyamide 6 and contains 40% glass fibers for reinforcement. The sample is cut according to the following dimensions: 15 cm*4 cm and has a thickness of 4 mm.

The thermoplastic elastomer (hereinafter referred to as “TPE”) comes in the form of pellets of approximately 3 mm in diameter. The PA substrate and the TPE are stored overnight at 80°C to remove any moisture.

Just before plasma functionalization, the PA substrates are cleaned with MEK solvent (methyl ethyl ketone = butanone CAS 78-93-3). The PA substrates are then fixed with an aluminum adhesive on a glass sheet under the plasma torch to be functionalized. The silane is nebulized by a carrier gas (here nitrogen) and is sprayed just under the nozzle of the torch from which the plasma is ejected (so-called PE-CVD technique).

The torch is moved in a pattern shown on the , to functionalize one face of the substrate. A complete movement along this pattern is called “a track”, and can be performed one or more times.

The thickness of the adhesion primer layer is approximately 10-20 µm.

Several conditions were tested in the following range:

- plasma power: from 650 W to 1200 W,

-the distance between the torch and the PA substrate: between 1.9 cm and 3.9 cm,

-the number of tracks: from 1 to 10,

-speed: from 20 to 100 mm/s,

- plasma gas: air or pure nitrogen,

-the flow rate of the silane in the range of 0 to 300 µL/min.

Silane is sprayed in liquid form (purity: 99%), and is stored in the refrigerator.

TPE pellets are embedded in a manual hot press and heated to 220°C. A mold is prepared to mold the TPE strip on the PA (TPE strip size: 15 cm * 4 cm and 3 mm thickness). The TPE is then injected into the mold. The typical time from functionalization to molding varies between 2 and 3 h. The samples are stored at 50% relative humidity (“RH”), 23°C and then subjected to the peel test (peel angle = 90°; speed = 100 mm/min; T = 23 °C and RH = 50%). The time from sample preparation to peel test is 7 days. The cohesion rate is assessed visually.

Peel test results

Plasma + silane APTES Power (W) Silane flow rate (µl/min) Distance (cm) Tracks Gas Speed (mm/sec) Peel force (N/cm) % Cohesion 650-1200 200 1.9-2.9 4-5 air 20-100 37-40 60-90

Plasma + silane APTMS Power (W) Silane flow rate (µl/min) Distance (cm) Tracks Gas Speed (mm/sec) Peel force (N/cm) % Cohesion 650-1200 200 2.9-3.9 4-5 air or N ₂ 20-100 33-42 40-91

Comparative examples:

Treatment Peel force (N/cm) % Cohesion Isocyanate primer ¹ 40 90% Without treatment ² <5 0% Plasma only ³ <5 0% Silane only ⁴ (silanes tested: TEOS, HMDS, APTMS, APTES, GPTMS) <5 0% Plasma + silane TEOS ⁵ <5 0% Plasma + silane GPTMS ⁶ <10 0% Plasma + silane HDMS ⁷ <20 0%

1 - Application of an isocyanate primer (62% (m/m) of Köratac GM 503 -Kommerling; 5% (m/m) of Köracur TH 240 - Kommerling; 33% (m/m) of MEK) on the PA, then drying at 80°C for 30 minutes, then deposition of the TPE.

2 - PA-TPE adhesion without treatment (i.e. only washing of PA with MEK before deposition of TPE).

3 - The plasma jet is applied to the PA (activation at 900 W, 5 tracks, 100 mm/s, air plasma, distance=1.6 cm) but without silane, then deposition of the TPE.

4 - a solution of 0.3 mL of silane (TEOS, HMDS, APTMS, APTES, or GPTMS) diluted in 1 mL of HCl (0.1M) and 9 mL of isopropanol is stirred at room temperature for 1 hour to allow hydrolysis of the silane, and wet-deposited on the PA, without plasma, then deposition of the TPE.

5 - General procedure described above in which the silane used is TEOS (Plasma power: 700-1200 W, silane flow rate: 200µL/min, projection distance: 2.9 cm, number of tracks: 5, plasma gas: air, displacement speed: 20-100 mm/sec).

6 - General procedure described above in which the silane used is GPTMS (Plasma power: 700-1200 W, silane flow rate: 200µL/min, projection distance: 2.9 cm, number of tracks: 5, plasma gas: air, displacement speed: 20-100 mm/sec).

7 - General procedure described above in which the silane used is HDMS (Plasma power: 650-1200 W, silane flow rate: 200µL/min, projection distance: 2.9 cm, number of tracks: 5-10, plasma gas: air, displacement speed: 100 mm/sec).

The results in Tables 1-3 show that:

- the presence of an (O) _n Si unit (precisely here (O) ₃ Si) and an amine in the silane is crucial to obtain good adhesion properties. It is noted in fact that a silane comprising only the (O) _n Si unit (TEOS, GPTMS) or a silane comprising only an amine (HMDS) does not allow good results to be obtained;

- the peeling forces obtained with the plasma comprising a silane comprising at least one (O) _n Si unit and at least one amine are equivalent, and sometimes better, than those obtained by application of the isocyanate primer (Table 1 vs. Table 3 “isocyanate primer”). Very satisfactory cohesion rates, often equivalent to those obtained by application of the isocyanate primer, have also been achieved.

- whatever the conditions (power, flow rate, nature of the gas, etc.) that were applied, good adhesion performances were achieved, which demonstrates the flexibility of the system (Table 1).

Claims (15)

Method of adhesion between a polyamide substrate and a layer of thermoplastic elastomer, comprising:
(a) the deposition of an adhesion primer on a surface of the polyamide substrate by an atmospheric pressure plasma comprising a silane, and
b) depositing a layer of thermoplastic elastomer on the adhesion primer,
characterized in that said silane comprises at least one (O) _n Si unit, where n is 1, 2, or 3, and at least one amine. A method according to claim 1, wherein the silane is of formula (I):

in which:
- n is 1, 2, or 3,
- each R ¹ , identical or different, represents a hydrocarbon group having 1 to 12 carbon atoms, optionally comprising one or more heteroatoms,
- each R ² , identical or different, represents a hydrocarbon group having 1 to 12 carbon atoms, and
- R ³ represents a hydrocarbon group having 1 to 12 carbon atoms, comprising one or more groups chosen from -NH ₂ and -NH-, and optionally one or more additional heteroatoms. A method according to claim 2, wherein n is 3, each R ¹ , identical or different, is a C1-C12 alkyl, and R ³ is of the formula -R ⁴ -NH ₂ where R ⁴ is a C1-C12 alkylene or a C1-C12 heteroalkylene. A method according to claim 2 or 3, wherein the silane is (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane or a mixture thereof. Method according to one of claims 1 to 4, in which the thermoplastic elastomer is a mixture based on polypropylene and a polystyrene-b-poly(ethylene-butylene)-b-polystyrene copolymer, or a mixture based on polypropylene and ethylene-propylene-diene rubber. Method according to one of claims 1 to 5, in which the substrate is made of polyamide 6 or polyamide 6-6, and optionally comprises glass beads or fibers. A method according to one of claims 1 to 6, wherein the plasma is a plasma of N ₂ , O ₂ , air, argon, helium, or a combination thereof, preferably an air or N ₂ plasma, more preferably an air plasma. Method according to one of claims 1 to 7, in which the power of the plasma is between 600 W and 1500 W, preferably between 650 W and 1200 W. A method according to any one of claims 1 to 8, wherein the plasma comprising said silane is ejected by a torch moving at a speed of 20 to 600 mm/sec, for example 20 to 100 mm/sec, in step a). A method according to claim 9, wherein 1 to 10 track passes, for example 3 to 7 track passes are implemented in step a). A method according to claim 9 or 10, wherein the projection distance between the torch and the surface of the substrate is between 1 cm and 10 cm, for example between 1.5 cm and 4 cm, in step a). Method according to one of claims 1 to 11, in which the silane is introduced into the plasma at a flow rate of between 10 and 300 µL/min. Method according to one of claims 1 to 12, in which the thermoplastic elastomer is deposited, in step b), by injection overmolding. Article, such as a guide rail (1) intended to guide the movement of a movable window (3) of a vehicle, comprising:
- a polyamide substrate (4) and
- a layer of thermoplastic elastomer (6) adhering to the substrate by means of an adhesion primer (5) based on a silane comprising at least one (O) _n Si unit, where n is 1, 2, or 3, and at least one amine,
characterized in that the adhesion by means of said primer (5) is obtained by the method as defined in one of claims 1 to 13. Glazing (10) comprising a guide rail (1) as defined in claim 14, a movable pane (3) received in the guide rail (1), and optionally an element (2), such as a fixed pane, on which the guide rail (1) is fixed.