EP2922448A1

EP2922448A1 - Polycarbonate cooking accessory having a surface provided with an organo-mineral sol-gel coating

Info

Publication number: EP2922448A1
Application number: EP13792934.5A
Authority: EP
Inventors: Laurent Blond; Bérangère Toury; Krystelle LIONTI; Philippe Miele; Aurélien DUBANCHET
Original assignee: SEB SA; Centre National de la Recherche Scientifique CNRS; Universite Claude Bernard Lyon 1 UCBL
Current assignee: SEB SA; Centre National de la Recherche Scientifique CNRS; Universite Claude Bernard Lyon 1 UCBL
Priority date: 2012-11-21
Filing date: 2013-11-21
Publication date: 2015-09-30
Also published as: WO2014079947A1; FR2998153B1; CN104883940A; FR2998153A1

Abstract

The present invention concerns a cooking accessory, in particular intended for use in a steam cooking device, said cooking accessory comprising a polycarbonate support having at least one inner surface intended to be in direct or indirect contact with food. According to the invention, the inner surface of the support is covered by a dense organo-mineral sol-gel coating in the form of a continuous film of a material comprising a matrix formed from at least one metal polyalkoxylate, the accessory having been subjected to firing at a temperature of less than or equal to 135°C. The present invention also concerns a method for applying such a protective coating to at least the inner surface of such a polycarbonate support.

Description

Polycarbonate cooking accessory having a surface provided with an organo-mineral sol-gel coating.

The present invention generally relates to a cooking accessory especially for use in a steam cooking device, this cooking accessory comprising a polycarbonate support having at least one inner surface intended to be in direct or indirect contact with foods coated with a protective coating. The present invention also relates to a process for applying such a protective coating to at least the inner surface of a support such as polycarbonate.

The target area is primarily that of cooking accessories for steam cooking devices (including vats, grates and lid of steam cookers), and by extension cooking appliances or accessories used at temperatures that could generate heat. steam (in particular multicooker lids, or bowls, steam baskets or lids for heated food preparation apparatus such as, for example, heating robots, or blenders or heating mixers).

These accessories generally consist of a polycarbonate support (PC). Indeed, this polymer has many good properties of transparency, lightness, impact resistance, and a good price / quality ratio, but it also has major drawbacks: in a hot and humid environment, the PC tends to cause a release of bisphenol A, whose contact with food is to be avoided. In addition, polycarbonate tends to scratch and stain easily.

The object of the present invention is to provide a protective coating of polycarbonate which overcomes these disadvantages in a sustainable manner with an easily industrializable and inexpensive process.

This object is achieved with a cooking accessory especially for use in a steam cooking device, said cooking accessory comprising a polycarbonate support having at least one inner surface intended to be in direct or indirect contact with food,

characterized in that a sol-gel coating covers said surface of the support, said sol-gel coating being a dense organo-mineral hybrid coating in the form of a continuous film of a material comprising a matrix formed from at least one metal polyalkoxylate, and

in that said accessory has been subjected to baking at a temperature equal to or lower than 135 ° C, preferably between 20 ° C and 135 ° C, and better still between 100 ° C and 135 ° C, and even better between 120 ° C ° C and 135 ° C.

The sol-gel coating of the accessory according to the invention is a protective and retaining coating, which furthermore has high physical (in particular hydrophobicity) and mechanical (especially scratch resistance) properties. In addition, such a coating is transparent.

Advantageously, the metal polyalkoxylate may be chosen from polyalkoxysilanes.

Preferably, the polyalkoxysilane can be obtained from tetraethoxysilane (TEOS) and / or methyltriethoxysilane (MTES).

More preferably, the sol-gel coating according to the invention can be a polyalkoxysilane can be obtained from tetraethoxysilane (TEOS) and glycidoxypropyltriethoxysilane, or from tetraethoxysilane (TEOS) and the mixture of triethoxyoctylsilane, 1H, 1H , 2H, 2H-perfluoroctyltriethoxysilane and glycidoxypropyltriethoxysilane.

The added glycidoxypropyltriethoxysilane alone improves the flexibility and flexibility of the sol-gel coating.

Moreover, the mixture of triethoxyoctylsilane, 1H, 1H, 2H, 2H-perfluoroctyl-triethoxysilane and glycidoxypropyltriethoxysilane makes it possible to increase the hydrophobicity of the sol-gel coating.

Advantageously, the sol-gel coating according to the invention may furthermore comprise at least one colloidal metal oxide, which is preferably finely dispersed in the matrix of the coating. This metal oxide is generally in the form of aggregates, whose size is less than one micron, or even 300 or 400 nm. The presence of colloidal metal oxide in the matrix of the sol-gel coating according to the invention makes it possible to obtain a film having a good cohesion of the film.

As colloidal metal oxides that may be used in the sol-gel coating according to the invention, mention may notably be made of silica, alumina, cerium oxide, zinc oxide, vanadium oxide and the like. zirconium oxide.

Advantageously, colloidal silica is used, preferably at least 20% by weight, more preferably between 30% and 50% by weight, and more preferably around 40% by weight relative to the total weight of the sol-gel coating. . Such a percentage of colloidal silica has the effect of improving the mechanical performance of the sol-gel coating formed (especially in terms of Young's modulus and adhesion to the polycarbonate support).

Advantageously, the sol-gel coating according to the invention may further comprise at least one silicone oil, to promote the spreading of the soil on the support before densification.

As silicone oils that may be used in the sol-gel coating according to the invention, phenyl silicones, methyl-phenyl silicones and methyl silicones. Preferably, the silicone oil used in the context of the food grade.

Preferably, the sol-gel coating film has a thickness of between 2 and 3 μm. Such a thickness is sufficient for the coating to be protective. This is facilitated by the absence of pigments in the coating.

The accessory according to the invention may be a lid, a cooking support, a full-bottomed cooking vessel, a juice recovery tank, a steam cooking bowl with perforated bottom, removable or not, a removable perforated bowl bottom. Steam cooking, a side wall of steam cooking bowl with removable bottom. In the case of a baking bowl sidewall accessory, the polycarbonate support is not only partially covered by the sol-gel coating, while in the case of a removable bottom type of cooking bowl accessory, the support will be completely covered.

The present invention also relates to a process for applying a hybrid organic-mineral sol-gel coating to at least one surface of a polycarbonate support of a cooking accessory, in particular intended for use in a steam cooking device. said method comprising the steps of:

i) optionally, a treatment of said inner surface;

ii) preparing a sol-gel composition comprising:

The preparation of an aqueous composition A comprising at least one colloidal metal oxide, a solvent comprising at least one alcohol, and optionally at least one silicone oil;

The preparation of an acid solution B comprising at least one precursor of metal alkoxide type;

• mixing the solution B of metal alkoxide with the aqueous composition A to obtain a sol-gel composition SG, iii) application on said inner surface of at least one layer of said sol-gel composition SG obtained at the end of step ii); then

iv) baking said accessory thus coated resulting from step iii) at a temperature of less than or equal to 135 ° C., preferably between 20 ° C. and 135 ° C., and better still between 100 ° C. and 135 ° C., and even more better between

120 ° C and 135 ° C.

The cooking accessory comprising a polycarbonate support is as defined above.

The surface of the support, intended to be coated with a sol-gel coating, may, prior to its application, be subjected to a surface treatment in order to promote the adhesion of the coating on the support. Such a treatment may advantageously consist of a physical surface treatment of the plasma or corona type, which has the advantage of promoting the spreading of the reinforcing soil and of reinforcing the adhesion of the sol-gel coating to the support (in particular by activation of the surface) . Such a treatment may also consist of a surface treatment by chemical means (in particular by creating covalent bonds), for example by immersion in a piranha solution (mixture of H ₂ O ₂ and H ₂ SO ₄ ).

With regard to step ii) of preparing a sol-gel composition, this comprises the step of preparing an aqueous composition A comprising at least one colloidal metal oxide, a solvent comprising at least one alcohol, and optionally at least one silicone oil.

The silicone oil and the colloidal metal oxide are as defined above.

The purpose of the presence of an alcohol-based solvent is to improve the compatibility of the aqueous composition A with the solution B of metal alkoxide. The aqueous composition A of the invention is preferably used as a solvent for isopropanol.

Step ii of preparing a sol-gel composition also comprises the step of preparing an acid solution B comprising at least one precursor of metal alkoxide type.

A metal alkoxide selected from the group consisting of:

the precursors corresponding to the general formula M ₁ (OR ₁ ) _n , the precursors corresponding to the general formula M ₂ (OR ₂ ) _(n- ₁₎ R ₂ ', and

the precursors corresponding to the general formula M ₃ (OR ₃ ) _(n- 2> R _{3 '} 2, with:

R ₁ , R ₂ , R ₃ or R ₃ 'denoting an alkyl group, R ₂ ' denoting an alkyl or phenyl group, n being an integer corresponding to the maximum valence of the metals M ₁ , M ₂ or M ₃ , M ₁ M ₂ or M ₃ denoting a metal chosen from Si, Zr, Ti, Sn, Al, Ce, V, Nb, Hf, Mg or Ln,

Advantageously, the metal alkoxide of solution B is an alkoxysilane.

As alkoxysilanes that may be used in solution B of the process of the invention, mention may especially be made of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and dimethyldimethoxysilane, and mixtures thereof, the preferred alkoxysilanes being TEOS and more particularly the MTES, which leads to a polyalkoxylate giving the sol-gel coating interesting properties and in particular excellent resistance in the dishwasher.

Advantageously, during the preparation of the acid solution B based on TEOS:

· Either glycidoxypropyltriethoxysilane as a complementary sol-gel precursor to improve the flexibility and flexibility of the sol-gel coating, • or a mixture of triethoxyoctylsilane, 1H, 1H, 2H, 2H-perfluoroctyltriethoxysilane and glycidoxypropyltriethoxysilane to improve the hydrophobicity.

Alternatively, one could use the MTES instead of the TEOS.

The metal alkoxide precursor of solution B is mixed with an organic, inorganic, Lewis acid.

As acids that can be used for mixing with the metal alkoxide precursor, mention may be made especially of acetic acid, citric acid, ethyl acetoacetate, hydrochloric acid, formic acid, and the like. itaconic acid and nitric acid.

The preferred acids according to the invention are organic acids, and more particularly acetic acid and itaconic acid.

After the preparation of the aqueous composition A and that of the precursor solution B, they are mixed together to form a sol-gel SG composition. The hydrolysis and condensation reactions start then. Step iii) of applying the sol-gel composition to the support in Polycarbonate is preferably carried out at least 24 hours after mixing of solution B with composition A, to ensure that at least one hydrolysis is complete.

This application iii) can advantageously be carried out by dipping / drawing or by spraying. In the case of a baking bowl sidewall accessory, the polycarbonate support is only partially covered by the sol-gel coating: the application iii) may advantageously be carried out by spraying (or "spray-coating ").

On the other hand, in the case of an accessory of the removable bottom type of cooking bowl, the support will be completely covered: the application iii) may advantageously be carried out by spraying (or "spray-coating") or by dip-pulling ( or "dip-coating").

The following examples illustrate the invention without, however, limiting its scope.

In the examples, unless otherwise indicated, all amounts are given in grams.

EXAMPLES

Products Aqueous Composition A

Colloidal metal oxide

colloidal silica in the form of 30% aqueous solution of silica, sold by Grace Davison under the trade name Ludox AS30,

colloidal silica in the form of 20% aqueous solution of silica, sold by the company STARK under the trade name LEVASIL 200 E.

Solvent: isopropanol,

Silicone oil: Food grade non-reactive methylated silicone oil marketed by the company under the trade name "BYK306" and having a viscosity of 300 cSt.

Solution B

Sol-gel precursors

- methyltriethoxysilane (MTES)

tetraethoxysilane (TEOS)

Sol-gel complementary precursors to improve

1 hydrophobicity

triethoxyoctylsilane,

1H, 1H, 2H, 2H-perfluoroctyl-triethoxysilane

Sol-gel complementary precursor to improve the flexibility and flexibility of the coating

glycidoxypropyltriethoxysilane.

Acid: acetic acid. Adhesion tests:

To evaluate the adhesion of the sol-gel coating to the PC support, the adhesion energy G (in J / m ² ) of the sol-gel coating films on the PC support was quantified by the DCB method (in English "double cantilever beam"). This technique consists in determining the fracture energy G (or adhesion energy) between a film and its substrate by breaking a specimen glued with a coated substrate on one side and a bare substrate on the other. Values of G less than 2 J / m ² are characteristic of a purely mechanical grip of the coating on the substrate, while values between 2 and 4 J / m ^{2 indicate} the existence of covalent bonds at the interface.

Hydrophobicity: measurement of the contact angle of a drop of water on the pavement with an Easydrop type of KRUSS goniometer. Dishwasher resistance

A dishwasher resistance test is carried out using dishwashing detergent marketed by SUN under the name "SUN All-One" (registered trade mark), in particular in the form of tablets, and observing which is the state of the coating deposited on the support after a given number of washing cycles.

"Food"

This is a global migration test with an analysis of migrats, made according to standard NF EN 1186-1, for materials intended to be in contact with aqueous products, acids, alcohol and fat. This global migration test consists of immersing a sample of coated PC in a simulating liquid and measuring the amount of material released in the simulant at the end of the test.

According to standard NF EN 1186-1, for materials intended to be in contact with aqueous products, 5 simulating liquids are used: 3% acetic acid (1 h at 100 ° C.), 95% ethanol (3 h at 60 ° C. ), 10% ethanol (1 h at 100 ° C.), isooctane (1 h at 60 ° C.) and olive oil (1 h at 100 ° C.).

For each test, a coating surface of 1 dm ² is contacted with 100 mL of simulating liquid (time and temperature are specified above for each simulant). A quantification of the material (in mg of migrât per dm of analyzed material) having migrated in the simulating liquids is then carried out for each test. .Evaluation of scratch resistance

Using a diamond tip 200 micrometers in diameter, a progressive load is applied to the coating, increasing the applied force from 0 to 2 Newtons. The trace of the scratch is then observed by optical microscope. The delamination value retained for the coating corresponds to the force for which there is a clear break of the film to polycarbonate. The rate settings for load increase and tip travel speed are kept constant for all tests.

EXAMPLE 1 (according to the invention): preparation of a first sol-gel SGI composition according to the invention (without silicone oil or silane-type complementary sol-gel precursor)

A first SGI sol-gel composition was produced according to the invention, the composition of which is given in Table 1 below:

Table 1:

To make this composition SG1, the silanes and the acid were mixed on one side (mixture B), the colloidal silica and the isopropanol of the other (mixture A), then the mixture B was poured into the mixture A, according to the method of the invention.

The hydrolysis and condensation reactions start at least 24 hours before any deposit to ensure that the hydrolysis at least is complete. The gelation comes after 2 weeks.

Then, the soil thus obtained is applied to a polycarbonate support (previously treated by plasma or not) by dipping / drawing ("dip-coating"). This method consists in soaking the substrate in a tank containing the soil to be deposited and then removing it in a controlled manner.

A sol-gel coating film is formed upon removal of the substrate from the vessel. ). After deposition, the coating is annealed in a resistive oven at a temperature of 120 ° C or 135 ° C.

The holding in the dishwasher of the coated PC support is good: after 50 wash cycles, the coating has no significant degradation observable to the naked eye.

EXAMPLE 2 (according to the invention): preparation of a second sol-gel composition SG2 according to the invention (without silicone oil and with a silane-type complementary sol-gel precursor)

A second sol-gel composition SG2 according to the invention was produced, the composition of which is given in Table 2 below:

Table 2:

To produce this composition SG2, the procedure was the same as in Example 1: the silanes and the acid were mixed on one side (mixture B), the colloidal silica and the isopropanol on the other side (mixture A), and then the mixture B was poured into the mixture A according to the process of the invention.

The hydrolysis and condensation reactions start at least 24 hours before any deposit to ensure that the hydrolysis at least is complete. Gelling occurs after a longer period than for Example 1.

Then, the soil thus obtained is applied to a polycarbonate support (previously treated by plasma or not) by dipping / drawing ("dip-coating").

A sol-gel coating film is formed upon removal of the substrate from the vessel. After deposition, the coating is annealed in a resistive oven at a temperature of 120 ° C or 135 ° C. EXAMPLE 3 (according to the invention): preparation of a second sol-gel composition SG2 according to the invention (with silicone oil and with two silane spreading additives)

A third sol-gel composition SG3 according to the invention was made, the composition of which is given in Table 3 below: Table 3:

To produce this composition SG3, the procedure was as in Examples 1 and 2: the silanes and the acid were mixed on one side (mixture B), the colloidal silica and the isopropanol on the other side (mixture A), and then the mixture B was poured into the mixture A according to the process of the invention.

A sol-gel coating film is formed upon removal of the substrate from the vessel. After deposition, the coating is annealed in a resistive oven at a temperature of 120 ° C or 135 ° C. EXAMPLE 4 (comparative): preparation of a sol-gel coating based on glycidoxypropyltriethoxysilane

A fourth sol-gel SG4 composition was made using as sol-gel precursors a mixture of GPTES (glycidoxypropyltriethoxysilane) and APTES (3-aminopropyltriethoxysilane).

If, for the preparation of the mixture B (silanes + acid), acetic acid (acid authorized in industry) is used, the resulting soil gels very quickly, drastically reducing the possible time of application of the soil.

It is preferable to use acetic acid rather than nitric acid as taught in US patent application US 2009/162631 relating to a sol-gel coating obtained from a mixture of 3-glycidoxypropyltriethoxysilane and the 3-aminopropyltriethoxysilane in an acid medium (nitric acid).

Indeed, unlike acetic acid, nitric acid is an oxidizer that is difficult to use in industry. In addition, it is dangerous to handle.

For a viable industrialization, it is necessary that the stability of the ground is the greatest possible. To increase the gel time (and thus the possibility of shaping), it was necessary to remove the aminosilane APTES from the sol-gel composition, thus leading to the systems described in the examples according to the invention 1 to 3.

Results of tests performed

The properties of the various coatings obtained by applying each of the sol-gel compositions of Examples 1 to 3 on a polycarbonate (PC) support, as well as those of a bare PC support (Comparative Example 5) are summarized in Table 4 below.

This table shows in particular that the physical and mechanical characteristics (in particular the resistance to scratching) when the PC support is coated with a sol-gel coating according to the invention.

With regard to the food, the results of Table 4 show that the sol-gel coatings according to the invention are comparable to a new bare PC support (overall migration below the allowable limit) and significantly better than a substrate. Aged PC. Indeed, it is reported that under certain aging conditions (temperature, humidity and / or UV), the PC deteriorates and releases compounds such as bisphenol A.

The coating is therefore precisely intended to protect the PC from premature aging.

Claims

A cooking accessory, in particular for use in a steam cooking device, said cooking accessory comprising a polycarbonate support having at least one inner surface intended to be in direct or indirect contact with foodstuffs,

in that said accessory has been baked at a temperature of 135 ° C or lower.

The cooking accessory according to claim 1, wherein the metal polyalkoxylate is a polyalkoxysilane.

3. Cooking accessory according to claim 2, wherein the polyalkoxysilane is obtained from tetraethoxysilane (TEOS) and / or methyltriethoxysilane (MTES).

4. Cooking accessory according to claim 3, wherein the polyalkoxysilane is obtained from tetraethoxysilane (TEOS) and glycidoxypropyltriethoxysilane.

Cooking accessory according to claim 3, wherein the polyalkoxysilane is obtained from tetraethoxysilane (TEOS) and the mixture of triethoxyoctylsilane, 1H, 1H, 2H, 2H-perfluoroctyltriethoxysilane, and glycidoxypropyltriethoxysilane.

The cooking accessory according to any one of claims 1 to 5, wherein the sol-gel coating further comprises at least one colloidal metal oxide dispersed in said matrix.

The cooking accessory according to claim 6, wherein the colloidal metal oxide is selected from the group consisting of silica, alumina, cerium oxide, zinc oxide, vanadium oxide and the like. zirconium oxide.

8. Cooking accessory according to claim 7, wherein the colloidal metal oxide is colloidal silica, preferably present in an amount of at least 20% by weight and better still between 30 and 50% by weight relative to the total weight of the sol-gel coating.

9. Cooking accessory according to any one of claims 1 to 8, wherein the sol-gel coating comprises at least one silicone oil.

10. Accessory according to claim 9, wherein the silicone oil is chosen from phenyl silicones, methyl-phenyl silicones and methyl silicones.

An accessory according to claim 10, wherein the silicone oil is food grade.

Cooking accessory according to any one of claims 1 to 11, which is a lid, a cooking support, a full-bottom cooking vessel, a juice collector, a removable perforated bottom steam cooking bowl or no, a removable perforated bottom of steam cooking bowl, a side wall of steam cooking bowl with removable bottom.

13. A method for applying a hybrid organic-inorganic sol-gel coating on at least one surface of a polycarbonate support of a cooking accessory, in particular for use in a steam cooking device, said method comprising the steps following:

i) optionally, a surface treatment of said surface;

ii) preparing a sol-gel composition comprising: The preparation of an aqueous composition A comprising at least one colloidal metal oxide, a solvent comprising at least one alcohol, and optionally at least one silicone oil;

• mixing of the solution B of metal alkoxide with the aqueous composition A to obtain a sol-gel composition SG), iii) application on said face of at least one layer of said sol-gel composition SG obtained at the end of step ii); then

iv) baking said accessory thus coated resulting from step iii) at a temperature of less than or equal to 135 ° C.

The method of claim 13, wherein the surface treatment of said surface is a plasma surface treatment.

The method of claim 13 or 14, wherein the metal alkoxide precursor is tetraethoxysilane (TEOS) and / or methyltriethoxysilane (MTES).

16. A process according to any one of claims 13 to 15, in which, during the preparation of the acid solution B based on TEOS, glycidoxypropyltriethoxysilane is used.

17. A process according to any one of claims 13 to 15, in which, during the preparation of the acid solution B based on TEOS, a mixture of triethoxyoctylsilane, 1H, 1H, 2H, 2H-perfluoroctyltriethoxysilane is used. and glycidoxypropyltriethoxysilane.

18. A method according to any one of claims 13 to 17, wherein the application iii) of the sol-gel composition is carried out by dipping / drawing or spraying.

19. A method according to any one of claims 13 to 18, wherein the application iii) of the sol-gel composition is carried out at least 24 hours after mixing the solution B with the composition A.