MECHANICALLY STRONG TINTED GLASS SUBSTRATE COATED WITH A MINERAL PAINT FOR A MOTOR VEHICLE ROOF
20200189967 · 2020-06-18
Inventors
Cpc classification
C03C17/007
CHEMISTRY; METALLURGY
International classification
Abstract
A temperable tinted glass substrate has at least one of its faces that is partially coated with a layer of mineral paint obtained from an aqueous paint composition based on an alkali metal silicate solution including the mixing of a platy mineral filler with at least one other filler chosen from alumina, boron or germanium, and at least one black mineral pigment.
Claims
1. A temperable tinted glass substrate, at least one of the faces of which is partially coated with a layer of mineral paint obtained from an aqueous paint composition based on an alkali metal silicate solution comprising the mixing of a platy mineral filler with at least one other filler chosen from alumina, boron or germanium, and at least one black mineral pigment.
2. The substrate as claimed in claim 1, wherein a weight ratio between the alkali metal silicate and all of the mineral fillers including the pigment is between 0.05 and 2.
3. The substrate as claimed in claim 2, wherein the weight ratio between the alkali metal silicate and the mineral fillers including the pigment is between 0.1 and 1.
4. The substrate as claimed in claim 1, wherein the platy mineral filler is talc, mica, or clays based on silicate or on aluminosilicate.
5. The substrate as claimed in claim 1, wherein the aqueous mineral paint composition comprises between 10% and 55% by weight of sodium silicate, potassium silicate and/or lithium silicate.
6. The substrate as claimed in claim 1, wherein the mineral paint composition further comprises a dispersant, an anti-foaming agent, a thickener, a stabilizer and/or a curing agent, in amounts of between 0.01% and 5% by weight of the aqueous mineral paint composition.
7. The substrate as claimed in claim 1, which is obtained by drying the aqueous paint composition at a temperature below 250 C.
8. The substrate as claimed in claim 1, wherein the mineral paint layer, measured after drying, has a thickness of at least 1 m.
9. The substrate as claimed in claim 1, wherein a light transmission TLA of the substrate is less than 30%, the TLA being measured on a portion of the substrate having a thickness of 4 mm that is not coated with mineral paint.
10. The substrate as claimed in claim 1, wherein the lightness component L* measured in reflection on a portion of the glazing coated with the mineral paint layer is less than 5.
11. A process for manufacturing a temperable tinted glass substrate, of which at least one portion of one of the faces thereof is coated with a mineral paint, the process comprising: a. applying, to a tinted glass substrate, at least one layer of a paint composition based on a solution of alkali metal silicate in water comprising the mixing of a platy mineral filler with at least one other filler chosen from alumina, boron or germanium, and at least one black mineral pigment, the weight ratio between the alkali metal silicate and all of the mineral fillers including the pigment preferably being between 0.05 and 2, b. drying said layer at a temperature below or equal 250 C.
12. The process as claimed in claim 11, wherein the paint composition is applied to at least one edge of the tinted glass substrate, a light transmission of which under D65 illuminant is less than 30% for a substrate having a thickness of 4 mm, the transmission being measured on a portion of the substrate nt coated with said paint.
13. The process as claimed in claim 11, wherein the step of applying the paint composition is carried out by spray coating, roll coating, laminar flow coating, by digital printing or by screen printing.
14. The process as claimed claim 11, wherein the drying step is carried out at a temperature below 210 C.
15. A motor vehicle roof obtained after thermal tempering of a substrate as claimed in claim 1.
16. The substrate as claimed in claim 3, wherein the weight ratio between the alkali metal silicate and the mineral fillers including the pigment is between 0.1 and 0.3.
17. The substrate as claimed in claim 4, wherein the clays include kaolinite, illite, montmorillonite or sepiolite.
18. The substrate as claimed in claim 5, wherein the aqueous mineral paint composition comprises between 15% and 25% by weight of sodium silicate, potassium silicate and/or lithium silicate.
19. The substrate as claimed in claim 8, wherein the mineral paint layer, measured after drying, has a thickness of at least 5 m.
20. The process as claimed in claim 12, wherein the light transmission is less than 20%.
Description
EXAMPLE 1
[0033] The mineral paint is prepared by mixing, in a mixer with vigorous mechanical stirring, the following amounts: [0034] 63.1 g of water with 0.2 g of thickener (Betolin V30) and with 0.6 g of wetting agent (Tego 740 Evonik) [0035] Addition of 0.1 g of antifoam (Foamex 825) and of 20 g of FeMn black pigment (Black 444 Shepherd) [0036] Addition of 14 g of talc (Jetfine 1A) with 62 g of alumina (CTC20 Almatis) [0037] Addition of 40 g of the potassium silicate solution (K42T Woellner) which is a solution composed of 40% by weight of silicate and of 60% by weight of water.
[0038] The mixing is carried out so as to obtain a pasty paint, that is as homogeneous as possible, with no lumps.
[0039] The weight ratio between the potassium silicate and all of the mineral fillers including alumina, talc and black pigment is 0.17.
[0040] The paint is then passed through a three-roll mill in order to refine the microstructure of the elements of the formulation (in particular the mineral powders) and to complete the homogenization thereof.
[0041] The paint is deposited on a 4 mm thick tinted glass substrate having a TLA of less than 18% with the aid of a film coater then is dried in a drying oven at 200 C. for 20 minutes then cured in a chamber at 760 C. for 180 seconds, before being cooled to 20 C. The thickness of the paint after drying is 30 m and the lightness value L* measured after drying and tempering is less than 5.
[0042] Flexural rupture measurements were carried out on the sample thus obtained, with the aid of a ring-on-tripod apparatus in order to evaluate the weakening thereof.
[0043] The ring-on-tripod flexural test is carried out using an Instron 4400R machine, which can drop a metal part (ring) on a test specimen. The machine is equipped with a 10 kN force sensor. The ring is made of tempered steel with a diameter of 10 mm and is fixed with a torus having a radius of 1 mm at the end of the Instron machine. The Instron machine also comprises a base on which three balls with a radius of 5 mm are adhesively bonded, these balls being positioned at 120 over a circle with a radius of 20 mm, the center of which is coincident with the center of the ring.
[0044] The test specimen is 70 mm70 mm glass with a thickness of 3.85 mm, optionally coated on one of its faces with the paint to be analyzed. The test specimen rests on the three balls of the base and is aligned with the centre of the ring, to within 1 mm. An adhesive film is applied to the uncoated face of the test specimen in order to retain the pieces of the test specimen when it breaks and to verify that the rupture indeed lies at the center of the sample. Once the test specimen is in place, the ring comes into contact with the surface of the test specimen and an increasing force is then applied to the ring until the test specimen breaks. Only the test specimens for which the origin of breakage is under the ring are counted. The breaking stress as a function of the force at break and of the thickness of the test specimen is given by the following formula:
[0045] The results show that the probability of the test specimen tested breaking reaches 50% for a stress of 150 MPa. By way of comparison, the probability of an equivalent glass substrate coated with a 15 m thick enamel layer breaking is 100 MPa.
EXAMPLE 2
[0046] A paint is prepared as in example 1, replacing the potassium silicate solution with a sodium silicate solution comprising 45% by weight of silicate and 55% by weight of water (50/50 weight ratio of a Woellner Betol 39T and Betol mixture).
[0047] The weight ratio between the potassium silicate and all of the mineral fillers including alumina, talc and black pigment is 0.19. The thickness of the layer deposited and the drying and curing heat treatment is identical to that described in example 1.
[0048] The probability of the test specimen tested breaking reaches 50% for a stress of 160 MPa.
EXAMPLE 3
[0049] The same paint as that described in example 1 is deposited so as to form, after drying and curing, a 5 m thick layer.
[0050] The probability of the test specimen tested breaking reaches 50% for a stress of 180 MPa. By way of comparison, the probability of an equivalent glass substrate coated with a 5 m thick enamel layer breaking is 90 MPa, and is 170 MPa for a bare substrate without any layer.
EXAMPLE 4
[0051] The same paint as that described in example 2 is deposited so as to form, after drying and curing, a 5 m thick layer.
The probability of the test specimen tested breaking reaches 50% for a stress of 195 MPa.
EXAMPLE 5
Not in Accordance with the Invention
[0052] A paint is prepared as an example 1, replacing the alumina with copper II oxide (Sigma-Aldrich) in equivalent amounts.
[0053] The thickness of the layer deposited and the drying and curing heat treatment is identical to that described in example 1.
[0054] The probability of the test specimen tested breaking reaches 50% for a stress of 90 MPa.
EXAMPLE 6
Not in Accordance with the Invention
[0055] A paint as prepared as in examples 1 and 5, modifying the amounts of talc and copper oxide: 6 g of talc (Jetfine 1A) are mixed with 68 g copper II oxide. The weight ratio between the silica and all of the mineral fillers remains unchanged.
[0056] The thickness of the layer deposited and the drying and curing heat treatment is identical to that described in example 1.
[0057] The probability of the test specimen tested breaking reaches 50% for a stress of 75 MPa.