FR2868065A1 - Reinforcing of glass-ceramic or glass plate useful as cooktop plate comprises fixing layer(s) comprising (co)polymer(s) which is resistant to high temperature onto part(s) of the surface of at least one of two main sides - Google Patents

Abstract

A glass-ceramic or glass plate, having two approximately parallel main sides, is reinforced by fixing layer(s) comprising (co)polymer(s) which is resistant to high temperature onto part(s) of the surface of at least one of the two main sides.

Description

2868065 1

  The subject of the present invention is: a method of reinforcing plates, made of glass-ceramic or glass; as well as - plates of this type, reinforced.

  The method of the invention is a method of treating the plates in question which improves the mechanical properties of said plates.

  This type of ceramic glass or glass (glass or tempered glass) plates is more and more used today, especially as a heating plate, more particularly a hob, and a firewall plate.

  The fragility of such plates, all the more critical as the dimensions of their main faces increase, poses a problem, both during their manufacture, storage, transportation and use ... To obtain stronger plates it has been proposed: to intervene in the implementation of the method of their manufacture: for example, by making them from an intrinsically stronger material (ss-quartz) and / or by implementing said manufacturing process while ensuring the absence of any defect and / or making them more consistent thicknesses; and / or - adding steps to said method: for example, polishing the plates obtained to eliminate any scratching on their main faces or texturing of the rear face of said plates to generate, using rollers, pins .

  Moreover, without reference to the technical problem of the fragility of these plates, it has been described more or less transparent, with colored coating (paint) secured to their lower face; said coating thus being intended to be seen through their thickness. Such plates, decorated on their underside, have in particular been described in patent documents EP-A-277 075, EP-A-1 267 593, EP-A-861 014, US-A-2002/0 084 263, US Pat. A-2002/0169 864, FR-A-2 838 429 and are also described in a co-pending patent application filed by the Applicant on the same day as the present application: the application FR 04 03123.

  On 13.07.2004 2868065 2 In such a context, said Applicant is currently proposing a new process for reinforcing glass-ceramic or glass plates, a new process that is particularly advantageous in that it allows, on the one hand, the effective strengthening of the plates. as existing to date; and secondly, an effective reinforcement of non-valued plates to date by their intrinsic fragility because of their small thickness and / or their poor quality.

  Said new method constitutes the first object of the present invention; reinforced plates (valued, according to the invention, because of said reinforcement) is the second.

  The reinforcement method of the invention aims to reinforce: - plates (having two substantially parallel main faces): that is to say solid elements which have two substantially parallel main faces (of a smaller thickness compared to the surface of said main faces); - in a glass-ceramic or glass: the constituent material of the plates in question may be glass-ceramic or glass. The term glass is generic. It corresponds to glass and tempered glass (chemically or thermally toughened).

  Said reinforcing process comprises the joining of at least one layer comprising at least one high temperature resistant (co) polymer to at least a portion of the surface of at least one of said two main faces of the plate in question.

  One of said two faces (said two faces) may be affected (s), in whole or in part. It is understood that the intensity of the reinforcement obtained is related to the area of intervention of the layer (s) of reinforcement.

  The plates can be reinforced on their two main faces but advantageously they are only on one of said two faces, very generally that intended to constitute, during the use of said plates, their lower face (or face or face of the below).

  The reinforcement method of the invention therefore involves, in a completely original way, as a reinforcing layer (reinforcement underlayer most often), at least one layer comprising at least one (co) resistant polymer at high temperature. It has in fact been discovered, quite unexpectedly, that such at least one layer comprising at least one high temperature resistant (co) polymer is capable of reinforcing the plate to which it is secured, is able to strengthen said plate until its degradation. Quite unexpectedly, layers of this type have proved effective, as reinforcement, and remain so as long as they are not completely degraded.

  According to the invention, therefore, the use of said at least one layer comprising at least one (co) polymer resistant to high temperature as mechanical reinforcement of the plates in question. This is a new use, not suggested by the use according to the prior art of such layers, as a decorative coating.

  Said at least one reinforcing layer is based on a polymeric organic binder, copolymer, a mixture of at least two polymers, at least two copolymers, at least one polymer and at least one high-strength copolymer temperature, i. e. having a degradation temperature greater than 400 C (generally between 400 and 500 C). Said binder is capable of withstanding or resisting by undergoing physical changes (crosslinking, or even pyrolysis: see below). This resistance to high temperatures is required for the reinforcing layer insofar as it is intended that the reinforcing effect is exerted during the use of the plates, under more or less severe temperature conditions.

  Said at least one reinforcing layer according to the invention obviously comprises said at least one (co) polymer resistant to high temperature in a significant amount, effective as to the desired reinforcing action. It is in fact based on said at least one (co) polymer resistant to high temperature.

  Said at least one reinforcing layer is generally essentially composed of said at least one high temperature resistant (co) polymer, whether or not containing mineral fillers (see below). However, it can not be ruled out that at least one other high-temperature-resistant (co) polymer (able to exert the desired effect and exert it, subjected to high temperatures) should be mixed with at least one other compound, for example a setting aid (diluent type), to disappear. The intervention, temporary or otherwise, of such another compound, by its nature and / or its quality, must not significantly impair the desired effect.

  The nature of said at least one layer comprising at least one (co) polymer resistant to high temperature is further specified in the present text, in no way limiting.

  With regard to the operation of joining said at least one layer to the glass-ceramic or to the constituent glass of the plate to be reinforced, it does not really pose any particular problem. It generally comprises the deposition of said at least one layer, optionally followed by a heat treatment of said at least one deposited layer.

  The deposit may be implemented by any suitable technique, adapted in particular to the viscosity of said at least one layer.

  It may include a brush deposit, a squeegee deposit, a spray deposit, an electrostatic deposit, a dip deposit, a curtain deposit or a silkscreen deposit. Said at least one layer is advantageously deposited by a squeegee deposit or by screen printing. It is very advantageously deposited by screen printing.

  The deposit is advantageously used to deposit a single layer.

  The possible heat treatment may be used to ensure drying of the at least one deposited layer, or even a real heat treatment thereof. Such heat treatment is capable of physically transforming said at least one deposited layer. Such a physical transformation can be performed before any use of the plate in question or may result from the use of said plate. In any case, it must not cancel the reinforcement effect provided, destroying said at least one deposited layer.

  The nature of said at least one layer comprising at least one (co) polymer resistant to high temperature is now specified, in no way limiting.

  Said at least one layer, advantageously said layer, is advantageously based on a polyimide, polyamide, polyfluorinated and / or polysiloxane resin. Said resin may be based on a single resin of one of the above types, a mixture of several resins of one of the above types, a resin mixture of at least two of the above types. - above. It is advantageously a polyimide or polysiloxane resin, very advantageously a crosslinkable polysiloxane resin.

  Polysiloxane resins are particularly preferred, in that they are colorless and therefore capable of being colored, of the desired color (i.e. containing fillers conferring them of said desired color); and in that they exist, crosslinkable, and therefore likely to be suitable, as a reinforcing layer: in the state; physically transformed: reticulated; - even more physically transformed: pyrolyzed.

  Indeed, said resins, pyrolyzed, are not completely consumed but retain their framework based on silicon. They evolve from the organic to the mineral and retain, in any case, a mineral skeleton capable of exerting the desired strengthening action.

  Polysiloxane resins recommended for the purposes of the invention advantageously have, in their formula, phenyl, methyl, ethyl, propyl and vinyl units, very advantageously phenyl and / or methyl units. They are preferably chosen from: - polydimethylsiloxanes, - polydiphenylsiloxanes, - phenylmethylsiloxane polymers, and - dimethylsiloxane-diphenylsiloxane copolymers.

  Whatever their exact nature, they are crosslinkable generally by the presence of SiOH groups and / or SiOMe in their formula. Such groups generally intervene up to 1 to 6% by weight of their total mass.

  The said crosslinkable polysiloxane resins generally have a weight-average molecular weight (Mw) of between 2,000 and 300,000 Daltons.

  In no way limiting, it can be indicated that Dow Corning 804, 805, 806, 808, 840, 249, 409 HS and 418 HS resins, Rhodorsil 6405 and 6406 from Rhodia, Triplus from General Electric Silicone and SILRES 604 from Wacker Chemie GmbH , used alone or as a mixture, are perfectly suitable.

  In general, it is recalled here that the resins, suitable for the purposes of the invention, are resistant to high temperatures, in the state or physically transformed. They are thus well suited to withstand heating by induction, if they occur under a hob associated with such a heating mode; they are likely to be suitable (in particular, the polysiloxane resins seen above) to resist radiant or halogen heating, if they occur under a hob associated with such another heating mode.

  Said at least one layer, used as reinforcement in the sense of the invention, advantageously contains an effective amount of mineral fillers, to ensure its cohesion and / or coloring. It is not excluded that such a layer intervene, free of mineral charges, especially if its thickness remains low. However, such mineral fillers generally intervene to at least mechanically strengthen said at least one layer (reinforcement). They contribute to the cohesion of said layer, to its attachment to the plate, to fight against the appearance and propagation of cracks within it. For such purposes, at least a fraction of said mineral fillers advantageously has a lamellar structure.

  For coloring purposes, coloring pigments can be specifically used. Fillers, ensuring the cohesion of said at least one layer, can also be used for the coloration ... The coloring effects are, in the context of the present invention, incidental.

  The technical effect of said at least one layer comprising at least one (co) polymer resistant to high temperature, currently highlighted is that of mechanical strengthening of the plate.

  The effective amount of mineral fillers, advantageously occurring within the reinforcing layer of the invention (monolayer or multilayer, advantageously monolayer) generally corresponds to a volume ratio of 10 to 60%, more generally at a volume ratio of 15 to 30%. % (said volume ratios are based on the total volume of the charges and the layer in question).

  Said at least one reinforcing layer of the invention generally has a thickness of between 1 and 100 μm, advantageously between 5 and 50 μm.

  Surprisingly, the presence of such layers, as thin, has been found to significantly strengthen glass plates or glass-ceramic. This is shown in the examples below.

  With regard to the color stability of such colored reinforcing layers, the teaching of the co-pending patent application FR 04 03123 is again cited here. Said color stability is acquired if the resin, more particularly silicone, intervening (or the intervening resins in mixture) are (virtually) free (s) precursor (s) of material (s) carbon (s).

  We now come to the second subject of the present invention, plates not interesting per se according to the prior art, because of their intrinsic fragility, valued according to the invention because of the original reinforcement associated with them.

  New reinforced plates of the invention consist of: - glass-ceramic or glass plates, comprising a base substrate, glass-ceramic or glass, in the form of a plate having two substantially parallel main faces, and at least one layer comprising at least one (co) polymer resistant to high temperature or a porous silica-based mineral matrix, secured to at least one of said two faces, advantageously to one of said two faces; said base substrate having a thickness of less than 4 mm. Glass-ceramic or glass plates of the prior art (base substrates), which are too fragile because of their small thickness (less than 4 mm), are reinforced by said at least one layer comprising at least one (co) high temperature resistant polymer (as deposited or crosslinked) or by said silica-based porous inorganic matrix (obtained by pyrolysis of such at least one layer of silicone resin type); - Glass-ceramic or glass plates, comprising a base substrate, glass-ceramic or glass, in the form of a plate having two substantially parallel main faces, and at least one layer comprising at least one (co) resistant polymer at high temperature or a porous silica-based mineral matrix, secured to at least one of said two faces, advantageously to one of said two faces; said base substrate having a modulus of rupture less than 100 MPa; with unacceptable mechanical properties, 13.07.2004 with reference to their use. Glass-ceramic or glass plates of the prior art (base substrates), which are too fragile because of their poor mechanical properties (MOR less than 100 MPa), are reinforced by said at least one layer comprising at least one ( co) polymer resistant to high temperature (as deposited or crosslinked) or by said porous mineral matrix based on silica (obtained by pyrolysis of such at least one layer of silicone resin type).

  It can not be excluded to involve in the structure of new plates of the invention (reinforced plates), on one side, at least one layer comprising at least one (co) polymer resistant to high temperature and on the other side a porous mineral matrix based on silica or on each of said two faces, at least one layer of (co) polymer (s) resistant to high temperature of different nature.

  Those skilled in the art have already grasped the whole point of the present invention which, in particular, allows the valuation of non-performing plates to date.

  The invention is illustrated, in no way limiting, by the examples below.

  The mechanical strength of the plates, reinforced or not, is evaluated by the conventional measurement of the modulus of rupture (MOR). This measurement is carried out on 32 mm diameter disc-shaped plate samples, the thickness of which is reduced to 2.1 mm, by grinding and polishing.

  The samples are based on a three-point support. In the case of reinforced samples, their coated side constitutes their underside. The load is applied on their upper side. The contact is provided by a 1.79 mm diameter ball. The descent speed of the contact point is 0.3 mm / min. The MOR is calculated with the assumption of a Poisson's ratio of 0.2.

Example 1

  A crosslinkable polysiloxane resin is prepared by mixing Dow Corning 249 silicone polymer and 10 g of Dow Corning 840 silicone solution until a homogeneous mixture is obtained.

  In said homogeneous mixture, 7.46 g of mica muscovite, 13.2004 referenced Mica-mu, CMMP (Counter of Minerals and Raw Materials) and 3.73 g of TiO2 RL60 from Cerdec were introduced. The charged (white) polysiloxane resin obtained is again thoroughly mixed.

  It is applied to the squeegee in a wet film of 60 am thickness on a 4 mm thick Keroidite glass ceramic plate (on one of the main faces of said plate).

  The coated glass ceramic plate is fired at 200 ° C. for 45 minutes and then at 300 ° C. for 45 minutes. The applied resin is then crosslinked.

  The modulus of rupture of this reinforced plate is measured as well as that of the reference Keralite plate. The results are shown in Table I below.

Example 2

  The polysiloxane resin mixture of Example 1 is prepared according to the same procedure. It is this time loaded with 8 g of Merck Iriodine 24 mica. The homogeneous mixture obtained (red) is applied in the same way on the same type of plate (Keratite thick 4 mm). The coated ceramic hob is fired according to the same heating schedule.

  The modulus of rupture of this plate is measured and appears in Table I below.

Table I

  Test Plate Breaking Module: MOR (MPa) Reference Plate 221 34 Plate of Example 1 288 41 Plate of Example 2 270 91 The plates of Examples 1 and 2 were reinforced.

  They also show good adhesion of the reinforcing coating to the glass-ceramic and a good cohesion of the coating 30 itself, in line with the intended application.

  Aged at 400 C (conditions of use as hotplates associated with induction heating), said plates remain reinforced.

  Their coating is also stable in color.

Example 3

  A white coating composition is prepared in the following manner: 40 g of Dow Corning 249 silicone polymer granules are dissolved in 18 g of Exxon Solvesso 100 solvent from Exxon Mobil Chemical. This dissolution is carried out with stirring at 80 ° C.

  After cooling, 29.1 g of 325 mesh muscovite mica (CMMP: Counter of Minerals and Raw Materials) and 14.6 g of TiO2 RL628 (Ferro Colors France S.A.) are added to the solution and mixed until homogenization. This composition is applied by screen printing (fabric: 90 threads / cm) on transparent glass ceramic substrates (Eurokera) and polymerized (crosslinked) for 1 hour at 250 ° C. for a dry film thickness of about 15 microns.

  The rupture modulus of these reinforced plates (as well as after thermal aging at 400 and 510 C (that is with their pyrolyzed coating)) is measured and compared to that of the reference plate ( uncoated). The results are given in Table II below.

Table II

  Test plate Fracture modulus: MOR (MPa) Uncoated substrate (14 samples) 208 71 Substrate with white coating (8 samples) 243 68 Substrate with aged white coating 400 C / 15 h 271 54 (5 samples) Substrate with aged white coating 510 C / 9 h 259 66 (6 samples) 2868065 11 The coated plates have been reinforced and remain so, even when aged under severe conditions. Such plates are ideally suited for use as hobs associated with induction heaters and heaters with radiant or halogen electrical elements.

  It is also emphasized the good adhesion of the reinforcing coating to the plate, the good cohesion of said coating and the very slight color change of said coating.

2868065 12

Claims (11)

  1. A process for reinforcing a plate, having two substantially parallel main faces, in a glass-ceramic or a glass, characterized in that it comprises the joining of at least one layer comprising at least one high-resistant (co) polymer. temperature at least a portion of the area of at least one of said two main faces.   2. Reinforcing method according to claim 1, characterized in that it comprises said attachment to one of said two faces.   3. A reinforcing method according to claim 1 or 2, characterized in that said joining comprises the deposition of said at least one layer comprising at least one (co) polymer resistant to high temperature, optionally followed by a heat treatment of said least one layer deposited.   4. Reinforcing method according to claim 3, characterized in that said deposition is carried out by brush deposition, squeegee deposition, spraying, electrostatic deposition, dipping, curtain deposition, screen printing, advantageously by screen printing.   5. Reinforcement method according to any one of claims 1 to 4, characterized in that said at least one layer is based on a polyimide resin, polyamide, polyfluorinated and / or polysiloxane; advantageously a polyimide or polysiloxane resin; very advantageously a crosslinkable polysiloxane resin.   6. Reinforcement method according to any one of claims 1 to 5, characterized in that said at least one layer contains an effective amount of mineral fillers, to ensure cohesion and / or coloring.   7. Reinforcement method according to claim 6, characterized in that at least a fraction of said mineral fillers has a lamellar structure.   8. The reinforcing method according to claim 6 or 7, characterized in that said effective amount corresponds to a volume ratio of between 10 and 60%, advantageously between 15 and 30%.   9. Reinforcement method according to any one of claims 1 to 8, characterized in that said at least one layer has a thickness of between 1 and 100 μm, advantageously between 5 and 50 μm.   A glass ceramic or glass plate, comprising a glass ceramic or glass base substrate, in the form of a plate having two substantially parallel main faces, and at least one layer comprising at least one (co) polymer resistant to high temperature or a porous silica-based mineral matrix, secured to at least one of said two faces, advantageously to one of said two faces, characterized in that said base substrate, made of glass-ceramic or glass, has a thickness less than 4 mm.   Glass-ceramic or glass-ceramic plate, comprising a base substrate, made of glass-ceramic or glass, in the form of a plate having two substantially parallel main faces, and at least one layer comprising at least one (co) polymer resistant to high temperature or a silica-based porous mineral matrix, secured to at least one of said two faces, advantageously to one of said two faces, characterized in that said glass-ceramic or glass base substrate has a rupture modulus (MOR) less than 100 MPa.