PROCESS FOR PRODUCTION OF A NON-PNEUMATIC TIRE

Abstract

One aspect of this invention involves a process for producing a non-pneumatic tire comprising a structure and a shear band, said process comprising providing a structure comprising a thermoplastic material having a surface intended to be brought into contact with a shear band; pretreating the surface of the structure to obtain a pretreated surface; providing an atmospheric pressure plasma generated from a gas mixture; depositing a plasma polymerized coating layer from the atmospheric pressure plasma on the pretreated surface to produce a structure with a coated surface comprising a plasma polymerized coating layer; providing a shear band with a layer of rubber material and contacting the coated surface of the structure with said layer of rubber material; and co-vulcanizing the coated surface of the structure with the layer of rubber material of the shear band.

Claims

1. A process for the production of a non-pneumatic tire comprising a structure and a shear band, wherein the process comprises the steps of: providing a structure having a surface intended to be put in contact with a shear band wherein the structure comprises a thermoplastic material; pretreating the surface of the structure to obtain a pretreated surface; providing an atmospheric pressure plasma generated from a gas mixture; depositing a plasma polymerized coating layer from the atmospheric pressure plasma on the pretreated surface to produce a structure with a coated surface comprising a plasma polymerized coating layer; providing a shear band with a layer of rubber material and contacting the coated surface of the structure with said layer of rubber material; and co-vulcanizing the coated surface of the structure with the layer of rubber material of the shear band.

2. The process of claim 1, wherein the surface intended to be put in contact with a shear band comprises one or more plates, or one or more strips or a combination thereof, so that the surface intended to be put in contact with a shear band is at least partially plane or annular.

3. The process according to claim 1, wherein the thermoplastic material is one or more selected from thermoplastic elastomers, polyamides, polyesters, polyketones, polyurethanes, and polyaramids.

4. The process according to claim 1, wherein the thermoplastic material comprises at least one polyester-based thermoplastic elastomer having one or more of: a Shore D Hardness (3 s) ranging from 30 to 85 as determined by ISO 868; a tensile modulus of at least 200 MPa as determined by ISO 527-1/-2; a melt flow rate ranging from 1 to 50 g/10 min as determined by ISO 1133 (230° C.-2.16 kg).

5. The process of claim 1, wherein the step of pretreating includes a sub-step of roughening the surface.

6. The process of claim 1, wherein the step of pretreating includes a sub-step of roughening the surface followed by one or more sub-steps selected from solvent cleaning and air plasma activation.

7. The process of claim 1, wherein the step of pretreating includes a sub-step of air plasma activation and the step of depositing a plasma polymerized coating layer from the atmospheric pressure plasma is performed at most 30 min after performing the sub-step of air plasma activation.

8. The process of claim 1, wherein the step of depositing a plasma polymerized coating layer from the atmospheric pressure plasma is performed using an atmospheric pressure plasma system comprising a nozzle, with one or more of: a nozzle displacement velocity ranging from 1 to 20 m/min; a nozzle offset ranging from 1 to 10 mm; a gap between the nozzle and the pretreated surface ranging from 0.1 to 5 mm; a number of plasma coating passes ranging from 1 to 5.

9. The process of claim 1, wherein the step of depositing a plasma polymerized coating layer from the atmospheric pressure plasma is performed using an atmospheric pressure plasma system comprising a nozzle comprising a cylindrical body having a longitudinal axis and a bottom end, the body comprising a conical inlet coaxial with the longitudinal axis for receiving a plasma, a radial inlet for receiving a precursor material, a core outlet coaxial with the longitudinal axis for receiving plasma from the conical inlet and a toroidal outlet for receiving the precursor material from the radial inlet, wherein an inner sidewall of the toroidal outlet extends only a part of the way to the bottom end of the nozzle, and an outer sidewall of the toroidal outlet extends to the bottom end of the nozzle.

10. The process according to claim 1, wherein the gas mixture comprises a carrier gas and a precursor comprising one or more sulfur-containing compounds.

11. The process according to claim 1, wherein the structure is made of a composite material comprising a thermoplastic material and one or more fillers, and wherein the composite material comprises at least 30 weight percent of thermoplastic material based on the total weight of the composite material.

12. The process according to claim 1, wherein the structure comprises a surface layer made of the thermoplastic material or of a composite material comprising the thermoplastic material wherein the surface layer is the surface intended to be put in contact with a shear band.

13. The process according to claim 1, wherein the rubber material comprises one or more diene-based elastomers selected from a styrene butadiene rubber, a polybutadiene rubber, a natural rubber, a synthetic polyisoprene rubber or combinations thereof.

14. The process according to claim 1, wherein the rubber material is a rubber composition comprising at least 25 weight percent of natural rubber, based on the total weight of the rubber composition.

15. A process for the production of a non-pneumatic tire comprising a structure and a shear band, wherein the process comprises the steps of: providing a structure with a surface intended to be put in contact with the shear band wherein the structure comprises a thermoplastic material; pretreating the surface of the structure to obtain a pretreated surface wherein the step of pretreating comprises a sub-step of roughening the surface and an optional sub-step of cleaning the surface; providing an atmospheric pressure plasma generated from a gas mixture; wherein the gas mixture comprises a carrier gas and a precursor comprising one or more sulfur-containing compounds and an optional alkyne; depositing a plasma polymerized coating layer from the atmospheric pressure plasma on the pretreated surface to produce a structure with a coated surface comprising a plasma polymerized coating layer; providing a shear band with a layer of rubber material comprising a diene-based elastomer and contacting the coated surface of the structure with said layer of rubber material; and co-vulcanizing the coated surface of the structure with the layer of rubber material of the shear band at a temperature of at least 120° C. and for a time of at least 20 minutes.

16. The process of claim 15, wherein the substep of cleaning the surface is performed with a polar solvent.

17. The process according to claim 15, wherein the structure comprises one or more annular strips forming one or more outer cylinders, the one or more outer cylinders being connected to an inner cylinder through a connecting structure comprising a plurality of connecting reinforcement members, and wherein the outside surface of one or more outer cylinders in the tire radial direction is the surface intended to be put in contact with the shear band.

18. The process according to claim 15, wherein the process is devoid of a step of application of a polyisocyanate adhesive.

19. A process for the co-vulcanization of (i) a structure comprising a plate or a strip comprising a thermoplastic material with (ii) a rubber material, wherein the process comprises the steps of: providing a structure comprising a plate or a strip with a surface intended to be submitted to co-vulcanization; wherein the plate or the strip comprises a thermoplastic material that is selected from one or more of thermoplastic elastomers, polyamides, polyesters, polyketones, polyurethanes, and polyaramids; pretreating the surface of the plate or the strip to obtain a pretreated surface, wherein the step of pretreating comprises a sub-step of roughening the surface or a sub-step of air plasma activation or a combination of those; providing an atmospheric pressure plasma generated from a gas mixture, wherein the gas mixture comprises a carrier gas and a precursor comprising one or more sulfur-containing compounds and optionally an alkyne; depositing a plasma polymerized coating layer from the atmospheric pressure plasma on the pretreated surface to produce a plate or a strip with a coated surface comprising a plasma polymerized coating layer; providing a rubber material comprising a diene-based elastomer and contacting a layer of said rubber material with the coated surface of the plate or the strip; and performing a co-vulcanization of the plate or the strip with the rubber material at a temperature of at least 120° C. and for a time of at least 20 min.

20. The process according to claim 19, wherein the rubber material is a part of a tire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0118] FIG. 1 is a schematic illustration of an atmospheric pressure plasma system

[0119] FIG. 2 is a schematic representation of a plasma nozzle

[0120] FIG. 3 is a partial perspective view of a non-pneumatic tire according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0121] In one embodiment of the invention, a process for the co-vulcanization of i) a structure, e.g. a connecting structure, comprising a plate or a strip made of thermoplastic material, or comprising a thermoplastic material, with ii) a rubber material, is provided, wherein the process comprises the steps of:

[0122] providing a structure comprising a plate or a strip with a surface intended to be submitted to co-vulcanization, wherein the plate or the strip comprises a thermoplastic material;

[0123] pretreating the surface of the plate or the strip to obtain a pretreated surface;

[0124] providing an atmospheric pressure plasma generated from a gas mixture;

[0125] depositing a plasma polymerized coating layer from the atmospheric pressure plasma on the pretreated surface to produce a strip or a plate with a coated surface comprising a plasma polymerized coating layer;

[0126] providing a rubber material and depositing a layer of said rubber material on the coated surface of the plate or the strip (or in other words contacting a layer of said rubber material with the coated surface); and

[0127] performing a co-vulcanization of the plate or the strip with the rubber material.

[0128] For example, said structure, or member, comprising the plate or the strip made of or comprising a thermoplastic material is a part of a tire such as a non-pneumatic tire or is part of a tire assembly. For example, the structure comprising the plate or strip holds one or more tire sensors. It is possible, that the plate or strip is integrally formed with a sensor housing to hold a sensor.

[0129] For example, the process according to the present disclosure is a process for the co-vulcanization of a plate or a strip comprising thermoplastic material with a rubber material for the production of a tire, for example, for the production of a non-pneumatic tire.

[0130] An example of a non-pneumatic tire is provided in EP3238957 which is incorporated herein by reference. This document shows an example of a shear band suitable for use in the present process such as a shear band comprising a three-dimensional spacer structure, wherein the three-dimensional spacer structure comprises or is formed from a first and second layer of material, each layer of material having first reinforcement members which extend in a first and direction, and second reinforcement members which extend in a second direction, wherein each layer of material is connected by a plurality of connecting reinforcement members which extend in a third direction. The three-dimensional spacer structure is positioned between at least a first and a second layer of rubber material. In the present disclosure, one of the layers of rubber of a shear band is fixed to the structure of the non-pneumatic tire by co-vulcanization.

[0131] Thus, in particular, a process for the production of a non-pneumatic tire comprising a structure and a shear band is provided, wherein the process comprises the steps of:

[0132] providing a structure having a surface intended to be put or brought into contact with (or to be connected to) a shear band wherein the structure comprises a thermoplastic material;

[0133] pretreating the surface of the structure to obtain a pretreated surface;

[0134] providing an atmospheric pressure plasma generated from a gas mixture;

[0135] depositing a plasma polymerized coating layer from the atmospheric pressure plasma on the pretreated surface to produce a structure with a coated surface comprising a plasma polymerized coating layer;

[0136] providing a shear band with a layer of rubber material and contacting the coated surface of the structure with said layer of rubber material; and

[0137] co-vulcanizing the treated surface of the coated surface of the structure with the layer of rubber material of the shear band.

[0138] In an embodiment, the layer of rubber material has a thickness ranging from 0.3 to 3.0 mm.

[0139] For example, the structure comprises a connecting structure, one or more plates, one or more strips, or any combination thereof.

[0140] A non-limiting embodiment of a non-pneumatic tire according to the present disclosure is illustrated in FIG. 3. The non-pneumatic tire 29 comprises a structure and a shear band 39. In the illustrated example, the structure is comprising a hub 31 (or inner cylinder 31), a connecting structure 33 that comprises a plurality of connecting reinforcement (or reinforced) members or 35 (such as spokes) having a radially outer end 37 forming a surface that is in contact with the shear band 39 and particular to a layer 41 of rubber material of the shear band 39. In this example, the connecting structure 33 connects the hub 31 with the shear band 39.

[0141] In an embodiment not illustrated, the connecting structure comprises connecting reinforcement (or reinforced) members comprising at their radially outer end one or more plates, or one or more strips, or a combination thereof, so that the surface intended to be brought into contact with a shear band is at least partially plane or annular.

[0142] In another embodiment not illustrated, the structure comprises one or more annular strips forming one or more outer cylinders, the one or more outer cylinders being connected to an inner cylinder (or hub) through a connecting structure comprising a plurality of connecting reinforcement members (such as spokes), and wherein the outside surface of one or more outer cylinders in the tire radial direction is the surface intended to be brought into contact with a shear band.

[0143] For example, the structure comprises a thermoplastic material or is made of a thermoplastic material. In an embodiment, the connecting structure or the plate or the strip is comprising a thermoplastic material or is made of a thermoplastic material. For example, the structure is made of a composite material comprising a thermoplastic material and one or more fillers. For example, the connecting structure or the plate or the strip is made of a composite material comprising a thermoplastic material and one or more fillers. Fillers may be selected from talc mineral filler, wollastonite, calcium carbonate, silica, carbon black, graphite, graphene, carbon nanotubes, poly-paraphenylene terephthalamide fibers (i.e., Kevlar fibers); polyester fibers, hybrid fibers, carbon fibers, polyamide fibers, polyethylene terephthalate fibers, glass fibers, bamboo fibers, flax fibers and hemp fibers.

[0144] For example, the composite material comprises at least 30 weight percent of thermoplastic material, based on the total weight of the composite material, for example, at least 40 weight percent, for example, at least 50 weight percent, for example, at least 60 weight percent, for example, at least 70 weight percent, or for example, at least 80 weight percent.

[0145] In an embodiment, the composite material comprises from 30 weight percent to 95 weight percent of thermoplastic material, based on the total weight of the composite material, for example from 40 weight percent to 90 weight percent, for example from 50 weight percent to 80 weight percent.

[0146] The structure or the connecting structure or the strip or the plate further can further comprise one or more non-thermoplastic reinforcements selected from wires, metal cords and fabric cords.

[0147] In an embodiment, the structure or the connecting structure comprising a plate or strip holds one or more tire sensors. Thus, it may connect the sensor to the shear band or rubber layer, e.g. of the tire.

[0148] The structure or the connecting structure or the strip or the plate may comprise a surface layer made of the thermoplastic material or of a composite material comprising the thermoplastic material, wherein the surface layer is the surface intended to be brought into contact with a shear band. For example, the surface layer has a thickness of at least 0.5 mm, for example at least 1.0 mm, for example, at least 1.5 mm, or for example, at least 2 mm.

[0149] In an embodiment, the structure, the plate or the strip or the connecting structure comprises a thermoplastic material or is made of a thermoplastic material, wherein the thermoplastic material is one or more selected from thermoplastic elastomers, polyamides, polyesters, polyketones, polyurethanes, and polyaramids. With preference, the thermoplastic material has a tensile modulus of at least 200 MPa as determined by ISO 527-1/-2, for example of at least 250 MPa; and/or a Shore D Hardness (3s) ranging from 30 to 85 as determined by ISO 868; for example ranging from 40 to 75; for example ranging from 45 to 70 or ranging from 50 to 65.

[0150] The thermoplastic material may be or comprise one or more thermoplastic elastomers selected from polyester-based thermoplastic elastomers (TPC/TPE), polyamide-based thermoplastic elastomers (TPA), polyolefin-based thermoplastic elastomers (TPO), and polystyrene-based thermoplastic elastomers (TPS). For example, the thermoplastic material is or comprises one or more polyester-based thermoplastic elastomers.

[0151] In another embodiment, the structure or the plate or the strip or the connecting structure comprises a polyester-based thermoplastic elastomer or is made of a polyester-based thermoplastic elastomer wherein, preferably, the polyester-based thermoplastic elastomer has a Shore D Hardness (3 s) ranging from 30 to 85 as determined by ISO 868, for example, ranging from 40 to 75, for example, ranging from 45 to 70 or ranging from 50 to 65. In addition or alternatively, the polyester-based thermoplastic elastomer has a tensile modulus of at least 200 MPa as determined by ISO 527-1/-2; for example, of at least 250 MPa. In addition or alternatively, the polyester-based thermoplastic elastomer has a melt flow rate ranging from 1 to 50 g/10 min as determined by ISO 1133 (230° C.-2.16 kg) or for example, from 2 to 25 g /10 min or from 3 to 15 g/10 min.

[0152] Examples of suitable thermoplastic materials comprise commercially available by DSM products as sold under the trade name Arnitel™ EM630, Arnitel™ PM581, Arnitel™ EM460, Arnitel™ PL581, Arnitel™ PL461, Arnitel™ ID2060 HT; or by DuPont De Nemours as sold under the trade name Hytrel™ 6356.

[0153] Before the deposition of the plasma polymerized coating layer, the surface of the structure, the strip, the plate or the connecting structure is preferably subject to a pretreatment step to obtain a pretreated surface.

[0154] The step of pretreating may include one or more sub-steps selected from roughening the surface; cleaning the surface; and air plasma activation of the surface.

[0155] It is preferred that the step of pretreating includes at least a sub-step of roughening the surface. The pretreated surface has preferably a roughness average parameter Ra ranging from 0.2 micrometers to 50.0 micrometers, or from 0.5 micrometers to 20.0 micrometers, or from 1.0 micrometers to 10.0 micrometers.

[0156] The sub-step of roughening the surface, when present, is preferably carried out with sand paper. For example, a sub-step of polishing the surface with a polishing machine is performed before the sub-step of roughening. If present, the sub-step of cleaning the surface is performed with a solvent, preferably a polar solvent. The solvent or the polar solvent may be selected from methyl ethyl ketone (MEK), acetone, isopropanol (IPA), toluene or any mixture thereof. If present, the sub-step of cleaning the surface is performed after the sub-step of roughening the surface.

[0157] If a sub-step of air plasma activation of the surface is carried out, the pretreated surface becomes hydrophilic, and hydrophilic groups are created (such as alcohols, aldehydes, acids, ketones, etc.) that favor the chemical bonding of the plasma polymerized coating layer to the thermoplastic material.

[0158] If present, the sub-step of air plasma activation of the surface can be carried out with an atmospheric pressure plasma system comprising a nozzle. For example, the nozzle displacement velocity is ranging from 1 to 20 m/min, for example, ranging from 1.5 to 10 m/min or ranging from 2 to 5 m/min. For example, the nozzle offset is ranging from 1 to 10 mm; for example, ranging from 1.5 mm to 8 mm or ranging from 2 mm to 5 mm. For example, the gap or gap width between the nozzle and the surface is ranging from 0.1 mm to 5 mm, from 0.5 mm to 4 mm, or from 0.7 mm to 3 mm. The number of plasma coating passes may range from 1 to 5, or from 1 to 3. If present, the sub-step of air plasma activation is preferably performed after the sub-step of roughening the surface; and more preferably after the sub-step of cleaning the surface.

[0159] In an embodiment, the step of pretreating includes a sub-step of air plasma activation and the step of depositing a plasma polymerized coating layer from the atmospheric pressure plasma is carried out at most 30 minutes, with preference at most 20 minutes, after having carried out the sub-step of air plasma activation.

[0160] Referring to FIG. 1, in an example of an atmospheric pressure air plasma (APAP) system 1, polymerizable material in the form of a monomer or of a precursor comprising one or more sulfur-containing compounds and an optional alkyne in a feedstock vessel 3 may be supplied in a metering tube using a mass flow controller (not shown) and vaporized and mixed with a carrier gas in mixing chamber 5. The carrier gas may be supplied from a carrier gas feedstock vessel 7 and introduced through a meter into the mixing chamber 5. This mixture may be introduced into an atmospheric pressure air plasma apparatus containing a plasma of ionized gas. The ionized gas may come from or supplied by an ionization gas feedstock vessel 9, preferably through a metering device.

[0161] Gradients of monomers may be developed where an additional feedstock vessel (not shown) holding other monomers feeds through a supply line to the monomer feedstock vessel to incrementally adjust the ratio or ratios of the monomers in the feedstock. Other monomers may be fed through a supply line to a metering device that may be adjusted incrementally or step-wise based on the ratio or ratios of monomers.

[0162] Suitable ionization gases of the atmospheric pressure air plasma system may include but are not limited to, noble gases, oxygen, nitrogen, hydrogen, carbon dioxide, or combinations thereof. The ionization gas may also be a nitrous oxide, which may allow the obtaining of a highly oxidizing plasma without the use of oxygen or air. Suitable carrier gases include any of the noble gases including helium, argon, xenon, and neon. Also, suitable as carrier gas are nitrogen, carbon dioxide, nitrous oxide, carbon monoxide, or air. In a preferred example, the carrier gas can be argon and/or air.

[0163] For example, the one or more sulfur-containing compounds are selected from elemental sulfur, carbon disulfide, carbonyl sulfide, thiophene, dimethyl sulfide, diethyl sulfide, methyl ethyl sulfide, dimethyldisulfide, diethyldisulfide, methyl ethyl disulfide, diphenyldisulfide, chloromethyl methyl sulfide, thiobenzophenone, 1,3,5-trithiane, thioformaldehyde and any mixture thereof. With preference, the sulfur-containing compound is selected from elemental sulfur, carbon disulfide and any mixture thereof.

[0164] In an embodiment, the precursor further comprises an alkyne; with preference, the alkyne is one or more C.sub.2 to C.sub.10 alkynes selected from acetylene, propyne, 1-butyne, 2-butyne, 1-pentyne, 2-pentyne, 3-methylbut-1-yne, 1-hexyne, 2-hexyne, 3-hexyne, 3,3-dimethylbut-1-yne, 1-heptyne and isomers, 1-octyne and isomers, 1-nonyne and isomers, and 1-decyne and isomers. With preference, the alkyne is or comprises acetylene.

[0165] In one embodiment, the sulfur-containing compound and alkyne are present in a volume ratio sulfur-containing compound/alkyne in a range of from 0.1 to 10. In one embodiment, the sulfur-containing compound and alkyne are present in a volume ratio sulfur-containing compound/alkyne in a range of from 0.8 to 3.

[0166] In one embodiment, the sulfur-containing compound and alkyne are present in a volume ratio (sulfur-containing compound+alkyne)/carrier gas in a range of from 0.001 to 0.2. In one embodiment, the sulfur-containing compound and alkyne are present in a volume ratio (sulfur-containing compound+alkyne)/carrier gas in a range of from 0.005 to 0.15.

[0167] The plasma generator may be any suitable plasma generation device as known in the art to generate atmospheric pressure plasmas, such as atmospheric pressure plasma jet, atmospheric pressure microwave glow discharge, atmospheric pressure glow discharge, and atmospheric dielectric barrier discharge. In one embodiment, the plasma generator is of the dielectric barrier discharge type. The dielectric barrier discharge apparatus generally includes two electrodes with a dielectric-insulating layer disposed between the electrodes and operates at about atmospheric pressures. For instance, a dielectric barrier discharge apparatus does not provide one single plasma discharge but instead provides a series of short-lived, self-terminating arcs, which on a long-timescale (greater than a microsecond), appears as a stable, continuous, and homogeneous plasma. The dielectric layer serves to ensure termination of the arc.

[0168] As known in the art, by atmospheric pressure plasma, it is meant that the pressure of the plasma is (essentially) equal to or slightly above the ambient pressure of the surroundings.

[0169] In an embodiment, the step of depositing a plasma polymerized coating layer from the atmospheric pressure plasma is carried out by using an atmospheric pressure plasma system comprising a specific nozzle as described in EP2326153 which is hereby incorporated by reference. The use of said nozzle may improve the adhesion performance between the thermoplastic material and the rubber material by delaying mixing of the monomer with the carrier gas when producing and applying the plasma polymerized coating layer.

[0170] Reference is made to FIG. 2 for further description of the nozzle 11. The nozzle 11 comprises a cylindrical body 15 having a longitudinal axis and a bottom end, the body comprising a conical inlet 17 coaxial with the longitudinal axis for receiving a plasma 13, a radial inlet 19 for receiving gas mixture 21, a core outlet 23 coaxial with the longitudinal axis for receiving plasma 13 from the conical inlet 17 and a toroidal outlet 25 for receiving the gas mixture 21 from the radial inlet 19, wherein an inner sidewall of the toroidal outlet 25 extends only a part of the way to the bottom end of the nozzle 11 (i.e. does not extend all the way to the bottom end of the nozzle 11), and an outer sidewall of the toroidal outlet 25 extends to the bottom end of the nozzle 11.

[0171] For example, the nozzle 11 or the body 15 is constructed of a ceramic material. In particular, a ceramic nozzle 11 is less prone to abrasion by the plasma 13 than a metallic nozzle. For example, an axially inner end of the toroidal outlet is closed. For example, the radial inlet 19 has a cylindrical shape. The radial inlet 19 may be oriented perpendicularly or at least substantially perpendicularly to the longitudinal axis. For example, the radial inlet 19 extends through the cylindrical body to the toroidal outlet 25. The outer sidewall of the toroidal outlet 25 may extend a first distance in the direction of the longitudinal axis from an axially inner end of the toroidal outlet 25 to the bottom end of the nozzle 11, wherein the inner sidewall of the toroidal outlet 25 extends over a second distance in the direction of the longitudinal axis, and wherein the second distance is smaller than the first distance. With preference, the second distance is in a range of from 40% to 90% of the first distance or more preferably, in a range of from 50% to 70% of the first distance. For example, the bottom end of the nozzle 11 and the bottom end of the outer sidewall of the toroidal outlet 25 are flush. For example, the inner sidewall of the toroidal outlet 25 extends over the second distance from the axially inner end of the toroidal outlet 25 towards the bottom end of the nozzle 11. For example, the nozzle 11 allows at least a partial mixing of the plasma and the precursor within the nozzle 11 or before deposition of a plasma polymerized coating layer onto the surface of the substrate 27.

[0172] In an embodiment, the process uses the specific nozzle 11 as defined above and comprises the step of transporting the precursor through the radial inlet 19 and the toroidal outlet 25 by a carrier gas, preferably by transporting the precursor as a mist (i.e. a gas mixture 21) through the radial inlet 19 and the toroidal outlet 25 by a carrier gas. For example, a release of the precursor at the toroidal outlet 25 provides a shield around the plasma at the core outlet, the shield preferably extending at least partially axially into the toroidal outlet 25.

[0173] It is understood that the system operates in a highly turbulent hydrodynamic regime. The plasma is swirling out of a nozzle. By using the above described nozzle 11, small amounts of precursor diluted in a carrier gas are preferably sufficient to deposit high quality, functional coatings (less oxidized polymers) on a substrate 27.

[0174] The precursor may be introduced either as a vapor or a mist. Vapor may be carried away simply by bubbling the carrier gas in a low boiling point precursor. A mist may allow the introduction of complex blends as well as the use of a much broader range of compounds, such as high molecular weight compounds like oligomers, polymers, or high boiling liquids, etc. Best results have been achieved when the viscosity of the liquid to be nebulized (pure precursor or blend of different precursors) is no more than 1.0-1.5 centiPoise (viscosity of water at 25° C. is 1.0).

[0175] Plasma polymerizing a mist of precursor allows a mild deposition of coatings that are not over-crosslinked and that still contain substantial amounts of fragile reactive functionalities (such as C═C double bonds, other saturations depending on the precursor used, etc.) that may otherwise have been destroyed in a plasma polymerization of a vapor. Nevertheless, the person skilled in the art may use the above nozzle or any nozzle suitable for deposition of a plasma polymerized coating layer.

[0176] The atmospheric pressure plasma system deposes the plasma polymerized coating layer on the pretreated surface wherein the plasma polymerized coating layer comprises an adhesively effective amount of polymerized or partially polymerized sulfur-containing compound. By adhesively effective amount, it is meant that the coated surface will show increased adhesion to a cured rubber compound compared to a noncoated surface, as measured by a standard Peel Resistance of Adhesives test (T-Peel Test) described in ASTM D1876-08 (2015).

[0177] Thermal heating of the coated surface varies according to the gap between nozzle and surface to be coated as well as the torch scan velocity (the smaller the gap and/or the lower the torch scan velocity, the higher the temperature of the surface). Also, the gap between the nozzle and the surface to be treated has an impact on gas dynamics. A smaller gap results in a higher velocity of the gases escaping the surroundings of the nozzle. These effects have an influence on the quality of the bonding of the plasma coating to the surface to be coated. The gap is preferably ranging from 0.1 mm to 5 mm, from 0.5mm to 4 mm or from 0.7 mm to 3 mm.

[0178] The gases from the exit of the nozzle may form a spray pattern with an outer penumbra having mostly ionized gas whereas closer to the center of the spray pattern, there may be an area of higher concentration of coating material. The nozzle offset is the distance between 2 line-scans of the torch; i.e., at the end of a line scan, the torch displaces of the offset value before starting another line scan until the whole area of the sample has been scanned. Accordingly, the nozzle offset, i.e., the distance between two line-scans of the nozzle, is also a parameter that will affect the coating quality and efficiency. The nozzle offset is preferably ranging from 1 to 10 mm, from 1.5 mm to 8 mm or from 2 mm to 5 mm.

[0179] To obtain the desired thickness of the plasma coating, the plasma nozzle displacement velocity, and the number of plasma coating passes can be taken into account. The plasma nozzle displacement velocity is the line scan speed of the nozzle above the surface to be coated. It is preferably at least 1 m/min. It is preferably at most 20 m/min, at most 10 m/min, at most 8 m/min, or preferably at most 6 m/minute. It may be preferably within a range of 1 to 20 m/min, 1.5 to 10 m/min or 2 to 5 m/min.

[0180] The number of plasma coating passes will provide a variation of the thickness of the plasma polymerized coating layer and the homogeneity of the coating. A higher number of plasma coating passes results in higher coating homogeneity but increases the thickness of the coating. The preferred number of plasma coating passes is at most 3 plasma coating passes, and preferably at most 2 plasma coating passes. For example, the number of plasma coating passes may range from 1 to 5 or for example from 1 to 3. In an embodiment, the plasma polymerized coating layer is deposited in a single plasma coating pass.

[0181] The precursor carrier gas flow rate is another variable that may be adjusted to improve the coating operation. It is the flow of precursor carrier gas that is used to push the nebulized or vaporized precursor into the nozzle. An optimum flow rate is the minimum flow of precursor carrier gas that provides the best results. The precursor carrier flow rate is preferably ranging from 0.1 and 10 standard liters per minute (SLM) as the measure for gas at standard conditions for temperature and pressure defined at a temperature of 273.15 K (0° C., 32° F.) and an absolute pressure of 1 atm (1.013 bar), more preferably from 0.1 and 5 SLM, and even more preferably from 0.2 and 4 SLM.

[0182] The flow rate of the gas mixture into the plasma treatment system to obtain a desired adhesively effective amount of polymerized or partially polymerized sulfur-containing compound onto the surface will depend on the desired gas velocity (e.g., in cm/s) passing perpendicular to a characteristic internal cross-sectional area of the plasma treatment system. The necessary flow rate may be determined by one skilled in the art without undue experimentation.

[0183] A rubber composition to be contacted with the coated surface of the structure preferably includes one or more rubbers or elastomers containing olefinic unsaturation. The phrases “rubber or elastomer containing olefinic unsaturation” or “diene-based elastomer” are intended to include both natural rubber and its various raw and reclaimed forms as well as various synthetic rubbers. In the present disclosure, the terms “rubber” and “elastomer” may be used interchangeably, unless otherwise described. The terms “rubber composition,” “compounded rubber” and “rubber compound” are used interchangeably to refer to rubber which has been blended or mixed with various ingredients and materials and such terms are well known to those having skill in the rubber mixing or rubber compounding art. Representative synthetic polymers are the homopolymerization products of butadiene and its homologues and derivatives, for example, methylbutadiene, dimethylbutadiene and pentadiene as well as copolymers such as those formed from butadiene or its homologues or derivatives with other unsaturated monomers. Among the latter are acetylenes, for example, vinyl acetylene; olefins, for example, isobutylene, which copolymerizes with isoprene to form butyl rubber; vinyl compounds, for example, acrylic acid, acrylonitrile (which polymerizes with butadiene to form nitrile butadiene rubber (NBR)), methacrylic acid and styrene (the latter compound polymerizing with butadiene to form styrene-butadiene rubber (SBR)), as well as vinyl esters and various unsaturated aldehydes, ketones and ethers, e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Specific examples of synthetic rubbers include neoprene (polychloroprene), polybutadiene (including cis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene), butyl rubber, halobutyl rubber such as chlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadiene rubber, copolymers of 1,3-butadiene or isoprene with monomers such as styrene, acrylonitrile and methyl methacrylate, as well as ethylene/propylene terpolymers, also known as ethylene/propylene/diene monomer (EPDM), and in particular, ethylene/propylene/dicyclopentadiene terpolymers. Additional examples of rubbers which may be used include alkoxy-silyl end functionalized solution polymerized polymers (SBR, PBR, IBR and SIBR), silicon-coupled and tin-coupled star-branched polymers. The preferred rubbers or elastomers utilized herein are one or more of polyisoprene (natural or synthetic), polybutadiene and SBR.

[0184] In an example, the rubber composition to be contacted with the coated surface may include at least one of methylene donors and methylene acceptors.

[0185] In one embodiment, the methylene donor is an N-substituted oxymethylmelamine, of the general formula:

##STR00001##

wherein X is hydrogen or an alkyl having from 1 to 8 carbon atoms, R1, R2, R3, R4 and R5 are individually selected from the group consisting of hydrogen, an alkyl having from 1 to 8 carbon atoms, the group —CH.sub.2OX or their condensation products. Specific methylene donors include hexakis-(methoxymethyl)melamine, N,N′,N″-trimethyl/N,N′,N″-trimethylolmelamine, hexamethylolmelamine, N,N′,N″-dimethylolmelamine, N-methylolmelamine, N,N′-dimethylolmelamine, N,N′,N″-tris(methoxymethyl)melamine, N,N′N″-tributyl-N,N′,N″-trimethylol-melamine, hexamethoxymethylmelamine, and hex aethoxymethylmelamine. In one embodiment, the N-substituted oxymethylmelamine is hexamethoxymethylmelamine. The N-methylol derivatives of melamine are prepared by known processes.

[0186] The amount of N-substituted oxymethylmelamine in the rubber composition may vary. In one embodiment, the amount of N-substituted oxymethylmelamine ranges from 0.5 phr to 4 phr. In another embodiment, the amount of N-substituted oxymethylmelamine ranges from 1 phr to 3 phr. The N-substituted oxymethylmelamine may be added as the free compound, or dispersed on a carrier medium such as silica.

[0187] In one embodiment, the rubber composition includes a methylene acceptor. The term “methylene acceptor” is known to those skilled in the art and is used to describe the reactant to which a methylene donor reacts to form what is believed to be a methylol monomer. The condensation of the methylol monomer by the formation of a methylene bridge produces the resin. The initial reaction that contributes the moiety that later forms into the methylene bridge is the methylene donor wherein the other reactant is the methylene acceptor. Representative compounds which may be used as a methylene acceptor include but are not limited to resorcinol, resorcinolic derivatives, monohydric phenols and their derivatives, dihydric phenols and their derivatives, polyhydric phenols and their derivatives, unmodified phenol novolak resins, modified phenol novolak resin, resorcinol novolak resins and mixtures thereof. Examples of methylene acceptors include but are not limited to those disclosed in U.S. Pat. Nos. 6,605,670; 6,541,551; 6,472,457; 5,945,500; 5,936,056; 5,688,871; 5,665,799; 5,504,127; 5,405,897; 5,244,725; 5,206,289; 5,194,513; 5,030,692; 4,889,481; 4,605,696; 4,436,853; and 4,092,455. The teachings of U.S. Pat. Nos. 6,605,670; 6,541,551; 6,472,457; 5,945,500; 5,936,056; 5,688,871; 5,665,799; 5,504,127; 5,405,897; 5,244,725; 5,206,289; 5,194,513; 5,030,692; 4,889,481; 4,605,696; 4,436,853; and 4,092,455 are incorporated by reference herein. Examples of modified phenol novolak resins include but are not limited to cashew nut oil-modified phenol novolak resin, tall oil-modified phenol novolak resin and alkyl modified phenol novolak resin. In one embodiment, the methylene acceptor is resorcinol.

[0188] Other examples of methylene acceptors include activated phenols by ring substitution and a cashew nut oil-modified novolak-type phenolic resin. Representative examples of activated phenols by ring substitution include resorcinol, cresols, t-butyl phenols, isopropyl phenols, ethyl phenols and mixtures thereof. Cashew nut oil modified novolak-type phenolic resins are commercially available from Schenectady Chemicals Inc. under the designation SP6700. The modification rate of oil based on total novolak-type phenolic resin may range from 10 to 50 percent. For the production of the novolak-type phenolic resin modified with cashew nut oil, various processes may be used. For example, phenols such as phenol, cresol and resorcinol may be reacted with aldehydes such as formaldehyde, paraformaldehyde and benzaldehyde using acid catalysts. Examples of acid catalysts include oxalic acid, hydrochloric acid, sulfuric acid and p-toluenesulfonic acid. After the catalytic reaction, the resin is modified with the oil.

[0189] The amount of methylene acceptor in the rubber composition may vary. In one embodiment, the amount of methylene acceptor, if used, ranges from 0.5 phr to 5 phr. In another embodiment, the amount of methylene acceptor, if used, ranges from 1 phr to 3 phr. In one embodiment, the rubber composition excludes a methylene acceptor. In one embodiment, the rubber composition excludes resorcinol (is free of resorcinol).

[0190] In an embodiment, the rubber composition is suitable for wire coating and/or comprises at least 25 weight percent of natural rubber based on the total weight of the rubber composition or for example, at least 40 weight percent or at least 50 weight percent. In another embodiment, the rubber composition comprises from 0.1 phr to 5 phr of a cobalt salt, and more preferably from 0.2 phr to 2 phr of a cobalt salt. This content may be of particular interest if used in wire coating compounds as it may amongst others improve the adhesion of the compound to a ply or shear band component including wires. The cobalt compound will typically be a cobalt salt of a fatty acid or a cobalt salt of an aliphatic or alicyclic carboxylic acid containing from 6 to 30 carbon atoms. Some representative examples of cobalt compounds which may be used include the cobalt salts, cobalt naphthanate, cobalt linoleate, cobalt stearate, cobalt oleate, cobalt acetate, cobalt neodecanoate, cobalt tallate, cobalt resinate, cobalt acetonate, or in situ salts prepared from cobalt hydroxide and an organic acid such as naphthenic acid, stearic acid, oleic acid, acetic acid, linoleic acid and the like. Additional cobalt compounds which may be used are known under the tradename Manoband™ C. Manoband™ C is a cobalt complex of an organic acid containing boron manufactured by Manchem Company. Manoband™ C is described in British Patent No. 972,804, which is incorporated by reference in its entirety.

[0191] In one embodiment, the addition of carbon black comprises about 1 to 200 parts by weight of diene rubber (phr). In another embodiment, from about 10 to about 100 phr of carbon black is used. Several commercially available carbon blacks may be used. Included in, but not limited to, the list of carbon blacks are those known under the ASTM designations N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550 and N582.

[0192] Silica, if used, may be used in an amount of 5 to 200 phr, preferably 5 to 100 phr, often with a silica coupling agent. Representative silicas may be, for example, hydrated amorphous silicas.

[0193] In one embodiment, the rubber composition may contain sulfur containing organosilicon compounds or silanes. Examples of suitable sulfur containing organosilicon compounds are of the formula:

Z-Alk-S.sub.n-Alk-Z   I

in which Z is selected from the group consisting of

##STR00002##

where R.sup.1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl; R.sup.2 is an alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8. In one embodiment, the sulfur containing organosilicon compounds are the 3,3′-bis(trimethoxy or triethoxy silylpropyl) polysulfides. In one embodiment, the sulfur containing organosilicon compounds are 3,3′-bis(triethoxysilylpropyl) disulfide and/or 3,3′-bis(triethoxysilylpropyl) tetrasulfide. Therefore, as to formula I, Z may be

##STR00003##

where R.sup.2 is an alkoxy of 2 to 4 carbon atoms, alternatively 2 carbon atoms; Alk is a divalent hydrocarbon of 2 to 4 carbon atoms, alternatively with 3 carbon atoms; and n is an integer of from 2 to 5, alternatively 2 or 4. In another embodiment, suitable sulfur containing organosilicon compounds include compounds disclosed in U.S. Pat. No. 6,608,125. In one embodiment, the sulfur containing organosilicon compounds includes 3-(octanoylthio)-1-propyltriethoxysilane, CH.sub.3(CH.sub.2).sub.6C(═O)—S—CH.sub.2CH.sub.2CH.sub.2Si(OCH.sub.2CH.sub.3).sub.3, which is available commercially as NXT™ from Momentive Performance Materials. In another embodiment, suitable sulfur containing organosilicon compounds include those disclosed in U.S. Patent Application Publication No. 2003/0130535. In one embodiment, the sulfur containing organosilicon compound is Si-363 from Degussa. The amount of the sulfur containing organosilicon compound in a rubber composition may vary depending on the level of other additives that are used. Generally speaking, the amount of the compound may range from 0.5 phr to 20 phr. In one embodiment, the amount will range from 1 phr to 10 phr.

[0194] Processing aids may be present and can include, for example, aromatic, naphthenic, and/or paraffinic processing oils. Typical amounts of tackifying resins, such as phenolic tackifiers, range from 1 phr to 3 phr.

[0195] The rubber compound may contain various conventional rubber additives. Typical amounts of antioxidants comprise about 1 phr to about 5 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine, polymerized 1,2-dihydro-2,2,4-trimethylquinoline and others, such as, for example, those disclosed in the Vanderbilt Rubber Handbook (1990), pages 343-362. Typical amounts of antiozonants comprise about 1 to about 5 phr. Representative antiozonants may be, for example, those disclosed in the Vanderbilt Rubber Handbook (1990), pages 363-367. Typical amounts of fatty acids, if used, which can include stearic acid comprise about 0.5 phr to about 3 phr. Typical amounts of waxes comprise about 1 phr to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers comprise about 0.1 phr to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.

[0196] In an embodiment of the present invention, the amount of zinc oxide may be relatively high as mentioned herein above.

[0197] It is readily understood by those having skill in the art that the rubber compositions used in tire components would be compounded by processes generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents and reinforcing materials such as, carbon black. As known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.

[0198] The vulcanization is conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents include insoluble sulfur, elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. In one embodiment, the sulfur vulcanizing agent is elemental sulfur. In one embodiment, sulfur vulcanizing agents are used in an amount ranging from about 0.5 phr to about 8 phr. In another embodiment, about 3 phr to about 5 phr of sulfur vulcanizing agents are used.

[0199] Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. In one embodiment, a single accelerator system may be used, i.e., primary accelerator. Conventionally, a primary accelerator is used in amounts ranging from about 0.5 phr to about 2.5 phr. In another embodiment, combinations of two or more accelerators may be used, including a primary accelerator which is generally used in the larger amount (0.5 phr to 2.0 phr), and a secondary accelerator which is generally used in smaller amounts (0.05 phr to 0.50 phr) to activate and to improve the properties of the vulcanizate. Combinations of these accelerators have been known to produce a synergistic effect of the final properties and are somewhat better than those produced by the use of either accelerator alone. Also, delayed action accelerators may be used which are not affected by normal processing temperatures but produce satisfactory cures at ordinary vulcanization temperatures. Suitable types of accelerators that may be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. In one embodiment, the primary accelerator is a sulfenamide. In another embodiment, if a second accelerator is used, the secondary accelerator may be a guanidine, dithiocarbamate, thiuram, or a second sulfenamide. In one embodiment of this invention, the vulcanization (i.e. the co-vulcanization) is conducted at a temperature of at least 120° C. and/or for a time of at least 20 minutes.

[0200] A process in accordance with an embodiment of the invention, is further described with reference to the following examples.

EXAMPLE 1

[0201] In this example, the effect of treating a strip of thermoplastic material with an atmospheric plasma generated by a dielectric barrier discharge is illustrated. The atmospheric pressure plasma system used had a nozzle as described in EP2326153. A series of experiments exposing panels of thermoplastic material to plasma was performed. The plasma equipment was purchased from Plasmatreat GmbH, and consists of a portable plasma torch and plasma generator that is run at its maximum power.

[0202] The panel's size was 6 inches long and 1.5 inches wide, with a thickness of 1.5 mm. For each sample, a layer of wire coating rubber of a thickness of about 3 mm was sandwiched between 2 coated panels. A band of Mylar was placed between the two panels at one end to create an unbounded portion. The samples were put in mold for a cure at 155° C. for 25 minutes at a pressure of 13 bar.

[0203] Each cured sample was then tested for adhesion to determine the average peel force. The method used was described in ASTM D1876-08 (2015) with the difference that the panels were 1.5 inches wide and 6 inches long but bounded over about 4.5 inches of their length. Thus, the unbounded ends were over about 1.5 inches of the panel's length. The test specimens were cuts from the centre portion of the panels to have a width of 1 inch.

[0204] The tests were performed using the following commercially available polyester-based thermoplastic elastomers: EM630 having a melting temperature of 212 ° C. as determined by ISO 11357-1/-3, a Durometer Shore D hardness of 60 as determined by ISO 868, a tensile modulus of 280 MPa as determined by ISO 527-1/-2 and a melt flow rate (MFR) 4 g/10 min as determined by ISO 1133 (230° C.-2.16 kg); and HYTREL 6356 having a melting temperature of 210 ° C. as determined by ISO 11357-1/-3, a tensile modulus of 280 MPa as determined by ISO 527-1/-2 and a melt flow rate (MFR) 8.5 g/10 min as determined by ISO 1133 (230° C.-2.16 kg).

Fixed Parameters

[0205] For all experiments, the current was 8.4 A and the voltage was 287 V. The carrier gas was argon with a gas flow of 3 bar. The precursor was carbon disulfide (CS.sub.2) and the precursor flow was 1 ml/min. The plasma frequency was 20 kHz. No acetylene precursor was used. The offset was set at 2 mm, the nozzle velocity was 2 m/min, and each of the samples was subjected to two plasma coating passes. The substrate temperature ranged from about 50° C. to about 100° C. In any case, these experiments are summarized in Table 1.

TABLE-US-00001 TABLE 1 Experiments Carried Out with Plasma Treatment/Coating Prec. Pretreatment Carrier Average with Gas Flow Peel Exp Substrate Sandpaper (SLM) Gap Force S01 2xEM630 plates P400 (manual).sup.  2 1.0 mm 200 N S02 2xEM630 plates P400 (manual).sup.  4 1.0 mm 250 N S03 2xEM630 plates P400 (manual).sup.  1 1.0 mm 300 N S04 2xEM630 plates P400 (manual).sup.  2 1.0 mm 250 N S05 2xEM630 plates P400 (manual).sup.1 2 1.7 mm 300 N S06 2x black Hytrel P400 (manual).sup.1 2 1.7 mm 275 N plates S07 2x black Hytrel P400 (manual).sup.1 2 1.7 mm 240 N plates S08 2x black Hytrel P400 (manual).sup.1 2 2.0 mm 525 N plates .sup.1After being mechanically polished.

[0206] Comparative experiments were performed wherein the surface was only pre-treated by roughening without plasma treatment/coating.

TABLE-US-00002 TABLE 2 Experiments carried out without plasma treatment/coating PRETREATMENT Average Peel Exp. Substrate with sand paper Force (N) CS01 2xEM630 plates sand paper P320   20 N (automatic) CS02 2xPM581 plates sand paper P320   15 N (automatic) CS03 2xHytrel plates sand paper P320 10-15 N (automatic)

[0207] Based on a comparison of the results according to Tables 1 and 2, an improvement of the adhesion for samples treated with a plasma coating is observed, as demonstrated by the higher average peel force (at least 200 N) in the samples treated with plasma. Without using plasma, the average peel force is at most 20 N.

[0208] Other comparative experiments were performed using panels of PM581 and standard adhesive. The adhesion trials were less effective.

[0209] The disclosure has been described with reference to preferred embodiments. Potential modifications and alterations will occur to others upon a reading and understanding of this description. It is to be understood that all such modifications and alterations are included in the scope of the disclosure as set forth in the appended claims, or the equivalents thereof.

[0210] While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.