METHOD FOR PRODUCING AN ARTICLE COMPRISING AN ANTI-STATIC COATING, AND ARTICLE COMPRISING SUCH A COATING

Abstract

An article including a substrate including a ceramic and/or a polymer, and an anti-static coating present on at least part of a surface of the substrate. The anti-static coating is a cross-linked inorganic organic hybrid coating including at least one epoxy functional group, wherein the coating further includes an ammonium salt and/or phosphoric acid, wherein the anti-static coating has a surface resistivity of at most 10.sup.10/cm as measured by means of a multimeter with spot-like electrodes, and wherein the cross-linked inorganic organic hybrid coating includes silicon and/or titanium. Also, a method for producing such an article.

Claims

1-15. (canceled)

16. An article comprising a substrate and an anti-static coating present on at least part of a surface of the substrate, wherein the substrate comprises a ceramic and/or a polymer, wherein the anti-static coating is a cross-linked inorganic organic hybrid coating comprising at least one epoxy functional group R.sup.1, wherein the cross-linked inorganic organic hybrid coating comprises an ammonium compound and phosphoric acid, the anti-static coating has a surface resistivity of at most 10.sup.10/cm as measured by means of a multimeter with spot-like electrodes, and the cross-linked inorganic organic hybrid coating comprises silicon and/or titanium.

17. The article according to claim 16, wherein the ammonium compound is a trialkyl ammonium group, optionally bonded to a silane compound.

18. The article according to claim 16, wherein the anti-static coating has a surface resistivity of at most 10.sup.9/cm, as measured by means of a multimeter with spot-like electrodes.

19. The article according to claim 16, wherein the coating has an optical transmittance in the visible light of at least 90%, preferably at least 95%.

20. The article according to claim 18, wherein the coating has a luminous absorption of less than 5%, preferably less than 2%.

21. The article according to claim 16, wherein the cross-linked inorganic organic hybrid coating comprises carbon-silicon bonds and/or carbon-titanium bonds, when the coating comprises silicon and/or titanium, respectively.

22. The article according to claim 16, wherein the substrate comprises a ceramic, wherein the ceramic is a hybrid composition of a ceramic and a biosourced compound.

23. The article according to claim 16, wherein the substrate comprises a polymer, wherein the polymer is polyurethane, preferably thermoplastic polyurethane.

24. The article according to claim 16, wherein the article is a watch component.

25. A method (10) for producing an article comprising a substrate and an anti-static coating present on at least part of a surface of the substrate, wherein the substrate comprises a ceramic and/or a polymer, the method comprising: providing a substrate (1) comprising a ceramic and/or a polymer, providing a first compound according to formula (I) (3) and a second compound according to formula (II) (4) ##STR00003## wherein M is silicon or titanium, R.sup.1 is an epoxy functional group, R.sup.5 is a cross-linkable functional group, R.sup.2, R.sup.3, R.sup.4, R.sup.6, R.sup.7, and R.sup.8 are each independently from each other H, a C.sub.1-C.sub.20 alkyl, a C.sub.3-C.sub.10 aryl, C.sub.2-C.sub.20 alkenyl, C.sub.4-C.sub.20 alkylaryl, or C.sub.4-C.sub.20 arylalkyl, hydrolysing (5) the first compound and the second compound in the presence of water, condensing (6) the hydrolysed first compound and the hydrolysed second compound, thereby obtaining a pre-polymer comprising R.sup.1 and R.sup.5 as functional groups, adding (7) an ammonium compound and phosphoric acid to the pre-polymer, applying (8) the pre-polymer comprising the ammonium compound and/or phosphoric acid to at least part of a surface of the substrate, and inducing cross-linking (9) of the cross-linkable functional group R.sup.5 by exposing the pre-polymer comprising the ammonium compound and/or phosphoric acid to one or more of a temperature up to 250 C., UV radiation or IR radiation, thereby obtaining an article comprising a substrate and an anti-static coating covering at least part of a surface of the substrate, wherein the anti-static coating is a cross-linked inorganic organic hybrid coating comprising at least one functional group R.sup.1, and that the anti-static coating has a surface resistivity of at most 10.sup.10/cm as measured by means of a multimeter with spot-like electrodes.

26. The method according to claim 25, wherein the ammonium compound is a trialkyl ammonium group, optionally bonded to a silane compound.

27. The method (10) according to claim 25, wherein R.sup.5 is a functional group selected from the group consisting of an epoxy, a (meth)acrylate, an ester, a mercapto, a vinyl, and a (meth)acrylated urethane.

28. The method according to claim 25, wherein the cross-linking is performed at a temperature between 50 C. and 200 C., preferably between 100 C. and 175 C.

29. Use of an article according to claim 16 in a watch.

30. Use of a method according to claim 25, for obtaining an anti-static watch component.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0061] Aspects of the invention will now be described in more detail with reference to the appended drawings, wherein same reference numerals illustrate same features and wherein:

[0062] FIG. 1 schematically represents the steps of a method according to the present disclosure,

[0063] FIG. 2 shows a ceramic plate comprising an anti-static coating according to the invention,

[0064] FIG. 3 shows a ceramic watch case comprising an anti-static coating according to the invention,

[0065] FIGS. 4A and 4B show the (anti-)static behaviour of an untreated and a treated ceramic plate, respectively,

[0066] FIG. 5 shows a TPU watch bracelet comprising an anti-static coating according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0067] FIG. 1 schematically shows the steps of a method according to the present disclosure. The method 10 comprises the step of providing a substrate 1. Advantageously, the substrate comprises or substantially consists of a ceramic and/or a polymer.

[0068] Advantageously, the substrate comprises a ceramic or a combination of ceramics. A particularly suited ceramic is a bioceramic. A bioceramic is, in the light of the present disclosure, a hybrid composition of a ceramic material or compound and a biosourced material. For example, the biosourced material can be sourced from castor-plant oil.

[0069] Alternatively or additionally, and advantageously, the substrate comprises a polymer or a combination of polymers, including copolymers. Non-limiting examples of polymers and copolymers include polyurethane, such as thermoplastic polyurethane (TPU), polyethylene, polypropylene, polyester (e.g. PBT or PET), polyamide (e.g. PA6, PA6-6), polyimide, polyamide-imide, polystyrene, polytetrafluoroethylene (PTFE), polymethyl methacrylate, polycarbonate, and methacrylate acrylonitrile butadiene styrene (MABS).

[0070] Optionally, the substrate can comprise further additives. Such additives can be additives known in the art, such as fillers or flame-retardants.

[0071] The method further comprises the provision of a first compound 3 according to formula (I), wherein formula (I) is as described hereinabove.

[0072] Advantageously, R.sup.1 comprises or substantially consists of an epoxy functional group (i.e. an oxirane functional group). For example, R.sup.1 can be an alpha-epoxy or 1,2-epoxy, which comprises a three-member ring structure.

[0073] Advantageously, C.sub.1-C.sub.20 alkyl includes alkyl functional groups comprising between 1 and 20 carbon atoms in the chain. Advantageously, the C.sub.1-C.sub.20 alkyl is C.sub.1-C.sub.12 alkyl, preferably C.sub.1-C.sub.10 alkyl, such as C.sub.1-C.sub.8 alkyl, C.sub.1-C.sub.6 alkyl, or C.sub.1-C.sub.4 alkyl.

[0074] Advantageously, C.sub.3-C.sub.10 aryl includes aryl functional groups comprising between 3 and 10 carbon atoms in the chain. For example, R.sup.1 can comprise a phenyl functional group, or can be C.sub.3-C.sub.20 alkyl phenyl.

[0075] Advantageously, C.sub.2-C.sub.20 alkenyl includes alkenyl functional groups comprising between 2 and 20 carbon atoms in the chain. Advantageously, the C.sub.2-C.sub.20 alkenyl is C.sub.2-C.sub.12 alkenyl, preferably C.sub.2-C.sub.10 alkenyl, such as C.sub.2-C.sub.8 alkenyl, C.sub.2-C.sub.6 alkyl, or C.sub.2-C.sub.4 alkenyl.

[0076] The method further comprises the provision of a second compound 4 according to formula (II), wherein formula (II) is as described hereinabove.

[0077] Advantageously, the first compound and the second compound are hydrolysed 5 as explained hereinabove. Advantageously, the hydrolysed first compound and the hydrolysed second compound are condensed 6 as explained hereinabove, thereby obtaining a pre-polymer.

[0078] The method further comprises adding an ammonium compound and/or phosphoric acid 7 to the pre-polymer. Advantageously, the ammonium compound is as described hereinabove. Advantageously, the ammonium compound and/or phosphoric acid is (are) added to the pre-polymer in an amount as described hereinabove.

[0079] Optionally, further components or substances can be added to the pre-polymer. For example, a surfactant can be added to the pre-polymer. Advantageously, when a surfactant is added, it is added in an amount between 0.5% and 30% by weight, based on the total weight of the pre-polymer comprising the ammonium compound and/or phosphoric acid.

[0080] Advantageously, the pre-polymer comprising the ammonium compound and/or phosphoric acid is applied 8 to at least a part of a surface of the substrate as explained hereinabove. Various application methods known in the art can be used. A preferred method comprises immersing the substrate into the pre-polymer, thereby contacting (the part of) the surface of the substrate to which the pre-polymer is to be applied with the pre-polymer. The substrate can be immersed in the pre-polymer by means of dipping the substrate in the pre-polymer.

[0081] The method further comprises cross-linking 9 of the pre-polymer, thereby obtaining an anti-static coating on the substrate. The cross-linking 9 is advantageously performed as described above.

[0082] Optionally, the substrate can be pre-treated 2 prior to applying 8 the pre-polymer to at least a part of a surface of the substrate (so-called pre-treatment). Suitable examples of pre-treatments include cleaning at least (a part of) the surface of the substrate (a so-called pre-cleaning). The pre-cleaning can be performed by methods known in the art. Non-limiting examples include grinding and polishing, chemical cleaning, ultrasonic cleaning, sandblasting, plasma treating at atmospheric pressure or at reduced pressure, corona treating (air plasma), and an alkaline treatment.

[0083] Advantageously, the anti-static coating is an inorganic organic hybrid coating. Advantageously, the anti-static coating is a cross-linked inorganic organic hybrid coating. Advantageously, the anti-static coating is bonded to the surface of the substrate by means of polar interaction(s).

[0084] Advantageously, the cross-linked inorganic organic hybrid coating comprises one or more of silicon, titanium, zirconium, aluminium, iron, or boron, preferably silicon and/or titanium.

[0085] Advantageously, the cross-linked inorganic organic hybrid coating further comprises carbon-silicon bonds.

[0086] Advantageously, the coating has a thickness between 1 m and 20 m, preferably between 1.2 m and 10 m, such as between 1.5 m and 5 m. As will be understood, the optimal coating thickness depends, amongst others, on the substrate, in particular its composition and shape, on the required saturation and transparency of the coating, and on the intended use of the article.

EXAMPLES

Example 1

[0087] A ceramic plate and a watch case in ceramic were provided as substrates.

[0088] A pre-polymer was prepared. A trimethyl ammonium compound covalently bonded to a silane compound, and phosphoric acid were added to the pre-polymer in an amount so that the pre-polymer comprising the trimetyl ammonium and phosphoric acid comprised 30% by weight of the trimethyl ammonium compound and phosphoric acid.

[0089] The pre-polymer comprising the trimethyl ammonium compound and phosphoric acid was applied to the ceramic substrates by immersing the ceramic substrates into the pre-polymer at a rate of 100 mm/min. After removing the ceramic substrates from the pre-polymer, the pre-polymer present on the ceramic was cross-linked by thermally curing the substrate at 95 C. for 1 hour.

[0090] FIG. 2 shows the flat ceramic substrate after cross-linking. FIG. 3 shows the watch case after cross-linking. It is clear that the anti-static coating homogeneously covers the surfaces.

[0091] The anti-static properties were tested by charging the surface by intensive rubbing the surface with a textile tissue, directly followed by positioning the rubbed surface over a tray comprising ashes. The distance between the rubbed surface and the tray was between 3 and 5 cm. The same test was also performed on the reference ceramic substrate without any anti-static treatment.

[0092] FIG. 4A shows that the reference ceramic substrate attracted a significant amount of ashes, indicating a clear static attraction. FIG. 4B shows that the ceramic substrate with the anti-static coating of the invention did not attract any ashes, clearly demonstrating the anti-static properties. Similar results were obtained on the ceramic watch case.

[0093] The adhesion of the ceramic samples was tested according to ASTM 3359-95A, and showed an adhesion of 100% (no delamination noticed).

Example 2

[0094] A watch bracelet in thermoplastic polyurethane (TPU) was provided as substrate.

[0095] The pre-polymer of example 1 was applied to the TPU bracelet by immersing the bracelet into the pre-polymer at a rate of 100 mm/min. After removing the TPU bracelet from the pre-polymer, the pre-polymer present on the bracelet was cross-linked by thermally curing the substrate at 95 C. for 1 hour.

[0096] FIG. 5 shows the TPU bracelet after cross-linking. It is clear that the anti-static coating homogeneously covers the surfaces.

[0097] The anti-static properties were tested as described for Example 1. The TPU with the anti-static coating of the invention did not attract any ashes, clearly demonstrating the anti-static properties, while the reference TPU, without any anti-static treatment, attracted a significant amount of ashes.

[0098] The adhesion of the treated TPU bracelet was tested according to ASTM 3359-95A, and showed an adhesion of 100% (no delamination noticed).

Nomenclature

[0099] 1. provision of a substrate [0100] 2. optional pre-treatment of the substrate [0101] 3. provision of a first compound [0102] 4. provision of a second compound [0103] 5. hydrolysis [0104] 6. condensation [0105] 7. adding an ammonium compound and/or phosphoric acid [0106] 8. applying to the substrate [0107] 9. cross-linking [0108] 10. method