Composite material for the protection of H2O sensitive devices based on surface functionalized nanozeolites dispersed in a polymeric matrix

Abstract

A sensitive device is described including an edge of the sensitive device and a composite material sealing the edge of the sensitive device. The composite material includes a homogeneous dispersion of superficially functionalized nanozeolites in a polymerizable compound. The nanozeolites contain surface modifying organic groups belonging to the same chemical class of at least one functional group of the polymerizable compound.

Claims

1. A sensitive device comprising: an edge of the sensitive device; a composite material sealing the edge of the sensitive device, the composite material comprising: a homogeneous dispersion of superficially functionalized nanozeolites in a polymerizable compound, wherein said nanozeolites contain surface modifying organic groups belonging to the same chemical class of at least one functional group of the polymerizable compound, said composite material capable of being a barrier against H.sub.2O, wherein functionalization on the superficially modified nanozeolites consists of phenyl groups.

2. The sensitive device according to claim 1, wherein the sensitive device is a photovoltaic cell.

3. The sensitive device according to claim 1, wherein the sensitive device is an organic light emitting diode (OLED) screen.

4. The sensitive device according to claim 1, wherein the sensitive device is a micro-electromechanical device.

5. The sensitive device according to claim 1, wherein the sensitive device is an energy storage device.

6. The sensitive device according to claim 5, wherein the sensitive device is a lithium battery.

7. The sensitive device according to claim 1 wherein the surface modifying organic group of the nanozeolites is the same as at least one functional group of the polymerizable compound.

8. The sensitive device according to claim 1, wherein said polymerizable compound is an organic resin, an epoxy resin, or an acrylic resin.

9. The sensitive device according to claim 1, wherein said polymerizable compound is a novolac resin.

10. The sensitive device according to claim 1, wherein said surface modified nanozeolites are one or more of Linde Type A (LTA), Faujasite (FAU), Linde Type L (LTL), Mordentite (MOR), and Gismondine (GIS) zeolites.

11. The sensitive device according to claim 8, wherein the polymerizable compound is a single component resin.

12. The sensitive device according to claim 11, wherein said single component resin is a bisphenol and epichlorohydrin (DGEBA) based resin.

13. A sensitive device comprising: an edge of the sensitive device; a composite material sealing the edge of the sensitive device, the composite material comprising: a homogeneous dispersion of superficially functionalized nanozeolites in a polymerizable compound, wherein said nanozeolites contain surface modifying organic groups belonging to the same chemical class of at least one functional group of the polymerizable compound, said composite material capable of being a barrier against H.sub.2O, wherein functionalization on the superficially modified nanozeolites comprises a pentafluorophenyl group.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The accompanying drawing, which is incorporated into and constitutes a part of this specification, illustrates one or more embodiments of the present disclosure and, together with the description of the example embodiments, serves to explain the principles and implementations of the disclosure.

(2) FIG. 1 shows a comparison of the barrier properties between composite material of the present invention and prior art.

DETAILED DESCRIPTION OF THE INVENTION

(3) The invention will be further described by means of FIG. 1, showing a comparison of the barrier properties between a composite material according to the present invention and a composite material of the prior art.

(4) In fact, when the use of nanozeolites as reactive species is foreseen, a suitable solution to the above-described problem of achieving a homogeneous dispersion is to functionalize their surface with organic groups in order to reduce their tendency to aggregate and to obtain an unexpected improvement of the barrier properties of the final composite material with respect to a composite material containing non-functionalized or not-suitably functionalized nanozeolites.

(5) Organic functional groups that can be covalently bonded on the surface of the nanozeolites or connected (still by a covalent bond) to the main chain of a polymerizable material can be classified basing on its chemical class: for example, in the following description of the invention, this classification will considered aliphatic groups such as alkyl-, alkenyl- (e.g. vinyl-) or alkynyl-, aromatic groups as phenyl- or benzyl-. Moreover, functional groups can be classified as amino-, imino-, acrylic- and methacryl-, epoxidic-, isocianate- etc. groups.

(6) The inventors have found out that, once the polymerizable composition of the preferred sealing resin has been chosen, only some types of functionalization of the nanozeolites can ensure, subsequent to the consolidation step, levels of H.sub.2O penetration that are compatible with the maintenance of inner concentrations of the gaseous species lower than the critical value for time comparable to the desired life of the sensitive device. Thus special chemical formulations have been found, which comprise precursors of polymeric matrices and also nanometric zeolites superficially functionalized that are to be considered particularly advantageous.

(7) With regard to the characteristic of the polymeric compounds to be used as barrier composite material according to the present invention, the preferred ones exhibit a permeability lower than 10 g mm m.sup.?2 day.sup.?1 at 25? C. and 60% relative humidity. Concerning the formulation of the dispensable material of the present invention, epoxy resins are particularly suitable as precursors of the polymeric matrix, with particular reference to single component formulations, acrylic (to obtain, for example, polymethylmethacrylate PMMA), urethane (polyurethane PU), olefins (polyethylene PE or HDPE, polypropylene PP, Ethylene propylene rubber EPR) and styrene (polystyrene PS) polymers, as well as isobutylene/isoprene based copolymers (known as butyl rubbers BR). Among epoxy resins, Bisphenol A and epichlorhydrin based resins, known under the acronym DGEBA (Diglycidyl Ether of Bisphenol A), novolak resins and cycloaliphatic resins are particularly advantageous.

(8) Concerning nanometric zeolites that have proved to be suitable to be used as reactive species to be inserted into the polymeric matrix there are surface modified Linde Type A (LTA), Linde Type L (LTL), Faujasite (FAU), Mordenite (MOR) or Gismondine (GIS) zeolites.

(9) With regard to the specific type of their functionalization, the inventors have found that better results can be obtained with particular reference to aromatic groups such as phenyl groups (POD) or pentafluorphenyl groups (PFOD), or organic groups such as vinyl groups (VN), allyl groups (ALL), amino groups (AMP), glycidoxy groups (GTO) methacrilic groups (MCR) or other aliphatic groups (as for example iso-butyl groups OD).

(10) Possible suitable additives present inside the dispensable composition are cationic photoinitiators, plasticizing additives, additives providing flexibility, reactive diluents, consolidating/cross-linking agents and adhesion promoters.

(11) The inventors have found out that barrier properties depend on the composition containing a dispensable material and nanozeolites and mainly can be distinguished in different cases according to different surface functionalization of the nanozeolites: a. not organically functionalized; b. functionalized by organic groups belonging to different chemical classes with respect to those which are contained in the polymerizable compound; c. functionalized by organic groups belonging to the same chemical class but not identical to those which are contained in the polymerizable compound; or d. functionalized by organic groups belonging to the same chemical class and identical to at least one of those which are contained in the polymerizable compound.
Moreover, in the case d), the identical organic groups present on the surface of the nanozeolites and in the polymerizable compound may be polymerizable groups or not.

(12) The relationship between the particular case among the above reported ones and the barrier properties can be evaluated considering different parameters, as for example the lag time or the breakthrough time. These physical properties are described and studied in the article Reactive barrier membranes: some theoretical observations regarding the time lag and breakthrough curves by A. Siegel published on the Journal of Membrane Science, vol. 229 pp. 33-41 in the 2004. These properties can be also related to the effective sorption capacity of the nanozeolites in the polymeric matrix as an effect of the reduced amount of their sorption performance as compared to when they are in the powder form and not incorporated in a matrix.

(13) The inventors have found that the use of functionalized nanozeolites can give better results with respect to both non surface-functionalized nanozeolites and to unloaded polymeric materials. By way of example, FIG. 1 shows a formulation that has been found particularly advantageous. This composition provides for the homogeneous dispersion of nanometric zeolites LTA 4A functionalized with aromatic groups POD within a DGEBA based epoxy resin that can be obtained through mechanical stirring. Nanozeolites were previously thermally activated. The obtained composite material has been compared to the case in which not-functionalized LTA 4A nanozeolites have been loaded in the same polymeric material.

(14) The permeation front, a parameter which characterized the barrier properties of a given material, has been evaluated using a glass-to-glass configuration where the sealant composition was previously deposited to completely fill the space between the two glasses. This parameter is defined as the length of the barrier material deposit in glass-to-glass configuration corresponding to a specific critical H.sub.2O concentration, that can be different in relation to the final device of interest. Therefore it can be monitored with any analytical techniques able to measure the local amount of H.sub.2O in the polymeric material.

(15) The performance as barrier material for different composite materials can be evaluated by comparing the different times after which the same penetration front has been observed: the relative time, referred to best performing material, have been reported. This parameter, in fact, is evaluated for a chosen H.sub.2O amount but it can be considered as a general property by the assumption that the penetration rate of water is constant in the material (i.e. does not change in function of the water concentration in the polymer).

(16) Table 1 shows some experimental data obtained by comparing the behavior of different composite barriers in terms of the relative time to have the same penetration front. The nanozeolite dispersion in a polymeric matrix (evaluable as the standard deviation in the normal distribution that fits the size spectrum of the agglomerated dispersed phase) does not change meaningfully with their specific functionalization. This is not the case for the barrier properties, that are strongly affected by the specific nature of the functionalization group. Therefore the difference in the barrier performance is not related to the uniformity of the inorganic particle dispersion in the final matrix.

(17) Using, for example, PMMA as polymeric material containing the same weight percent content of active species, not-functionalized nanozeolites (none case) or not-suitably functionalized (POD case) give the same effect on the barrier property of the final material whereas best results have been obtained with crosslinkable identical functional groups in the polymeric material and on the zeolite surface (MCR case). In particular in the reported example it can be observed that PMMAOD or PMMAMCR compositions, because of the longer time to have the same penetration front with respect to the PMMAPOD or PMMAnone, can not only protect a sensitive element for longer lasting time (from about 25 to 100%), but also can be used as protective coating or sealing perimetral deposits with reduced dimensions with respect to the comparative compositions, with obvious advantage in manufacturing and technological development.

(18) In Table 2 other experimental data characterizing the barrier properties of composite materials have been reported, considering different concentration of active species and different kind of adhesive resin, as for example the acrylic resin (for example the Epotek og-603 sold by Epotek Technologies Inc.), a DGBEA-based epoxy glue (Epotek OG-142-17 by Epotek Technologies Inc.) or a cold-setting resin based on two fluid DGBEA-based epoxy components (Epofix by the Struers Inc.).

(19) In a second aspect thereof the invention resides in a method for the use of the compositions of the invention during the encapsulating process of H.sub.2O sensitive devices, in order to protect them from the permeation of this contaminant by means of composite sorbers formed of nanozeolites superficially functionalized with organic groups inside a polymeric matrix.

(20) The inventors have found out that deposition techniques particularly suitable for the compositions of the present invention are serigraphy (screen-printing), micro-dispensing (e.g. using a syringe), spin-coating, spray-coating, doctor blade technique, ink-jet, one-drop process. The deposition process may be so configured to result in a deposit along the edge only of the sensitive device or in an at least partial but preferably complete covering of the element or surface particularly sensible to the presence of moisture in the device.

(21) The consolidation process is carried out after having suitably positioned the two surfaces desired to be coupled. Among the possible processes, UV radiation, thermal consolidation or a combination thereof have proved to be suitable for the present invention. As thermal consolidation, it can be also considered the room temperature curing of a bi-component mixture of precursor organic compounds or the solvent evaporation whenever the precursor is a solution containing the active species and the organic compounds.

(22) In a third aspect the invention consists in a sensitive device wherein the barrier composition of the invention is used for its protection from external contamination, with main reference to moisture and oxygen.

(23) Generally, the present invention is advantageous when it is necessary that the concentration of H.sub.2O inside the sensitive device does not exceed a critical value during the normal operation of the device. This critical value is related to the type of sensitive device, and among the devices requiring a very small water concentration there are the OLEDs, which typically require concentrations of 10 ppm or lower, whereas solar cells may withstand up to 5000 ppm before irreversible deterioration phenomena are generated. Photovoltaic cells (CIS-CIGS cells, CdTe cells, a-Si cells, OSC, DSSC), OLED displays, micro-electromechanical devices (MEMS or MOEMS), Light Emission Diodes (LED) and energy storage devices (with particular reference to lithium batteries and lithium air batteries) are among the sensitive devices that mostly benefit from the application of the method of the invention.

(24) The composition of the invention, after its consolidation treatment, can act as the perimetric sealant material of the sensitive device, as perimetral barrier deposit coupled along an outer sealant material of the device or as a barrier layer coating the surface of the structural and/or functional elements of the device that are sensitive to the external environment contaminations. As a limit case, the barrier layer can be used as a filler material that completely fills the encapsulated volume in the sensitive device.

(25) The invention will be further described with reference to the following examples.

Example 1

(26) 7.74 grams of LTA 4A-POD previously activated through a thermal process at 240? C. under vacuum have been added to 31.36 grams of an Epo-tek OG 142-17 resin (single component commercial epoxy resin based on epichlorhydrin and bisphenol A), viscosity 300-500 cPa s, Tg 54? C. The composition (DGBEAepoxyPOD) has been thus pre-dispersed by means of simple mechanical stirring and subsequently made homogeneous using a so called 3 roll mill mixer. All the operations previously described have been carried out inside a chamber under dry nitrogen atmosphere (generally referred to as glove box).

(27) A second composition (DGBEAepoxynone) has been prepared similarly to the procedure above described, using 3.66 grams of non-organically functionalized LTA-4A and 14.50 grams of resin.

(28) Glass-to-glass configurations (one for each composition) have been prepared under a moisture protected atmosphere by depositing 0.22 grams of dispensable material onto a surface of (2.54?6.00) cm.sup.2 in order to achieve a thickness of 300 ?m, followed by UV curing (300 sec, 100 mW/cm2, ?=250-400 nm).

(29) The kinetic penetration level of H.sub.2O under an exposure condition of each sample at 85? C. and with 85% relative humidity is set forth in the graph of FIG. 1 in the form of a solid line 1 for the composition containing the surface modified zeolites and in the form of the broken line 2 for the non-functionalized case. In table 2 have been reported the relative times to have the same penetration front in the compared samples.

Example 2

(30) 230.8 grams of PMMA (Aldrich, MW 120000) were previously dissolved in 800 ml of Toluene anhydrous 99% (Aldrich). A clear viscous PMMA/Toluene suspension has been obtained under reflux heating at 80? C. for 30 minutes and mechanical stirring.

(31) The composition PMMAnone prepared adding 1.90 grams of LTA 4A (previously activated 450? C. under vacuum) to 30.05 grams of PMMA/Toluene solution has been thus pre-dispersed by means of simple mechanical stirring and subsequently made homogeneous using a so-called 3 roll mill mixer. All the operations were carried out in glove box.

(32) The glass to glass configurations were performed in glove box depositing the composite over a glass substrate 2.54?6.00?0.015 cm, and gently heated to 50? C. for 10 minutes to consolidate the film, then a cover glass was applied and the glass to glass sample were dried under vacuum at 80? C. for 6 hours until constant weight of the system was achieved.

(33) Similarly, surface modified nanozeolite containing compositions have been prepared using respectively: a) PMMAPOD composition: 1.91 grams of LTA-4A POD (previously activated through a thermal process at 240? C.) in 31.32 grams of PMMA/Toluene solution; b) PMMAOD composition: 1.90 grams of LTA-4A OD previously activated through a thermal process at 170? C. in 31.50 grams of PMMA/Toluene solution; or c) PMMAMCR composition: 1.79 grams of LTA-4A MCR previously activated through a thermal process at 180? C. in 29.9 grams of PMMA/Toluene solution.

(34) Glass-to-glass configurations using these compositions have been obtained following the same procedure described for the PMMAnone composition.

(35) In Table 1 the relative times to have the same penetration front (testing conditions 85? C. and 85% relative humidity) in the compared samples have been reported.

Example 3

(36) 1.50 grams of LTA 4A-POD previously activated through a thermal process at 240? C. under vacuum have been added to 28.00 grams of an Epo-tek OG-603 resin (single component acrylic resin), viscosity 300-500 cPa s, Tg 54? C. The composition acrylicPOD has been thus pre-dispersed by means of simple mechanical stirring and subsequently made homogeneous using a so-called 3 roll mill mixer. All the operations previously described have been carried out inside a glove-box.

(37) A second composition (acrylicMCR) has been prepared similarly to the procedure as above described, using 1.05 grams of LTA-4A MCR and 20.03 grams of resin.

(38) Glass-to-glass configurations (one for each composition) have been prepared under a moisture protected atmosphere by depositing 0.49 grams of dispensable material onto a surface of (2.54?6.00) cm.sup.2 followed by UV curing (10 sec, 100 mW/cm2, ?=250-400 nm).

(39) The kinetic penetration levels of H.sub.2O under an exposure condition of the sample at 85? C. and with 85% relative humidity have been evaluated and in table 2 have been reported the relative times to have the same penetration front in the compared samples.

Example 4

(40) 0.42 grams of LTA 4A activated through a thermal process at 450? C. under vacuum have been added to a mix of 1.60 grams of Epofix base, 0.07 grams of Epofix hardener (commercial available bicomponent DGEBA epoxy resin) and 0.1 grams of (3-glycidoxypropyl)trimethoxysilane (ABCR). The composition (cold setting epoxynone) has been thus pre-dispersed by means of simple mechanical stirring and subsequently made homogeneous using a so-called 3 roll mill mixer. All the operations were carried out in glove box.

(41) Similarly, a second composition (cold setting resinGTO) has been obtained by adding 0.42 grams of GTO (pre-activated through a thermal process at 175? C. under vacuum) to a mix of 1.60 grams of Epofix base, 0.07 grams of Epofix hardener and 0.1 g of ABCR.

(42) Finally a third composition (cold setting resinPOD) has been obtained, with the same procedure, adding, 0.42 grams of (POD pre-activated through a thermal process at 240? C. under vacuum) to a mix of 1.60 grams of Epofix base, 0.07 grams of Epofix hardener and 0.1 grams of ABCR.

(43) In order to achieve the glass to glass configuration for each composition, they were performed in glove depositing the glue over a glass substrate 2.54?6.00?0.015 cm and covered with another glass slide. The resins were cured at 80? C. for 1 hour.

(44) The kinetic penetration levels of H.sub.2O under an exposure condition of the sample at 85? C. and with 85% relative humidity have been evaluated and in table 2 have been reported the relative times to have the same penetration front in the compared samples.

(45) TABLE-US-00001 TABLE 1 Relative Time Nanozeolite to have the same Nanozeolite Polymer functionalization w/w % penetration front dispersion PMMA none 20% 0.55 12% PMMA POD 20% 0.57 13% PMMA OD 20% 0.70 10% PMMA MCR 20% 1.00 10%

(46) TABLE-US-00002 TABLE 2 Relative Time Nanozeolite to have the same Resin functionalization w/w % penetration front acrylic POD 5% 0.75 acrylic MCR 5% 1.00 DGEBA-epoxy none 20% 0.81 DGEBA-epoxy POD 20% 1.00 cold-setting epoxy none 20% 0.68 cold-setting epoxy POD 20% 0.95 cold-setting epoxy GTO 20% 1.00