A VACUUM INSULATING GLAZING

Abstract

The present invention refers to a Vacuum Insulating Glazing (VIG) able to provide excellent thermal insulation to the transparent components of curtain walling systems in buildings and to cabinets for domestic or commercial refrigerators, and to a process for its manufacture.

Claims

1: A vacuum insulating glazing comprising: two glass panes facing one another, and spaced apart from one another by one or more pillars so as to create a void volume therebetween; a non-evaporable getter system placed within said volume; and a polymer-based sealing edge sealing off said volume in order to define a closed space in between said glass panes, wherein said sealing edge is obtained by curing of a sealant composition comprising: (a) a curable thermosetting non-halogenated polyepoxide resin comprising in average at least two epoxy groups per molecule; (b) an aromatic diamine curing agent in amount sufficient to provide from 0.5 to 2.0 equivalents of amine N—H per equivalent of epoxy groups in the epoxy resin; and (c) an inorganic dryer in amount ranging between 5% and 25% by weight with respect to the total weight of said sealant composition.

2: The vacuum insulating glazing of claim 1, wherein said aromatic diamine curing agent amount provides from 0.5 to 1.0 equivalents of amine N—H per equivalent of epoxy groups in said epoxy resin.

3: The vacuum insulating glazing of claim 1, wherein said inorganic dryer is selected from the group consisting of oxides, preferably CaO, hygroscopic salts such as perchlorate dryers, preferably Mg(ClO.sub.4).sub.2, and reversible dryers, such as zeolites and active carbon or a mixture thereof.

4: The vacuum insulating glazing of claim 1, wherein said sealant composition further comprises one or more passive fillers.

5: The vacuum insulating glazing of claim 4, wherein said passive filler is selected from the group consisting of poly(vinyl alcohol), polyimides, SiO.sub.2, TiO.sub.2, glass beads, glass fibers, metal or glass ribbons, and metal or glass wires.

6: The vacuum insulating glazing of claim 1, wherein said non-halogenated polyepoxide resin is a phenol-formaldehyde resin.

7: The vacuum insulating glazing of claim 6, wherein said phenol-formaldehyde resin has the following formula (I): ##STR00002## wherein n is an integer comprised between 0 and 8.

8: The vacuum insulating glazing of claim 1, wherein said aromatic diamine curing agent comprises sulphonated and/or phenol groups.

9: The vacuum insulating glazing of claim 1, wherein said aromatic diamine curing agent is 4,4′-diamino-diphenyl sulphone.

10: The vacuum insulating glazing of claim 1, wherein said sealant composition has a glass transition temperature T.sub.g, as determined by differential scanning calorimetry (DSC) measurements according to ISO 11357-2:2013, higher than 100° C.

11: The vacuum insulating glazing of claim 1, wherein said non-evaporable getter system comprises a Zr alloy having a N.sub.2 absorption capacity by ASTM absorption test at room temperature ≥1 cctorr/g.

12: The vacuum insulating glazing of claim 11, wherein said Zr alloy is selected from the group consisting of ZrTiV, ZrTiVAl, ZrVAI, ZrVFe and ZrVFeMn-RE alloys, wherein RE is one or more rare earth elements, optionally sintered in mixtures further comprising Zr powders.

13: The vacuum insulating glazing of claim 1, wherein said non-evaporable getter system comprises a powder getter distributed on at least one side of a metal strip.

14: A window or facade comprising the vacuum insulating glazing as defined in claim 1.

15: A cabinet for domestic or commercial refrigerators comprising the vacuum insulating glazing as defined in claim 1.

16: A process for manufacturing a vacuum insulating glazing of claim 1, the process comprising the steps of: i) providing a top and a bottom glass pane, and preparing said bottom glass pane by the following steps a to c in any order: a. positioning of pillars; b. positioning of a non-evaporable getter system on the glass surface or in a dedicated space, and optionally gluing said getter; and c. depositing a sealant composition comprising: 1) a curable thermosetting non-halogenated polyepoxide resin comprising in average at least two epoxy groups per molecule; 2) an aromatic diamine curing agent in amount sufficient to provide from 0.5 to 2.0 equivalents of amine N—H per equivalent of epoxy groups in the epoxy resin; and 3)) an inorganic dryer in amount ranging between 5% and 25% by weight with respect to the total weight of said sealant composition; ii) pairing said top glass pane on said bottom glass pane; iii) curing said sealant composition, thus forming a VIG chamber; iv) pumping out said VIG chamber; v) activating said getter; and vi) sealing an evacuation hole.

17: The process according to claim 16, wherein said step i) c. is carried out by positioning pre-formed laminated strips of said sealant composition or by deposition of said sealant composition from pre-filled syringes.

18: The process according to claim 16, wherein said curing step iii) of the sealant composition is carried out by heating and optionally also by UV curing.

19: The process according to claim 16, wherein said getter activating step v) is carried out by radio-frequency (RF) heating in a temperature range of 300° C.-600° C.

20: The process according to claim 20, where said steps ii) and iii) of pairing said glass panes and curing said sealant composition are performed in a large evacuated chamber enclosing the entire VIG.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0019] The characteristics and advantages of the vacuum insulating glazing and of the process for its manufacture according to the present invention, will be clearly illustrated in the following exemplary and not limiting description of their embodiments, also with reference to the attached figures wherein:

[0020] FIG. 1 shows schematically a preferred embodiment of the present vacuum insulating glazing and the main components thereof;

[0021] FIG. 2 is a sketch of the VIG preferential design with a getter full frame of four strips and equal sealing edge widths;

[0022] FIGS. 3a, 3b and 3c show alternative VIG designs with only two getter strips and different sealing edge widths.

DETAILED DESCRIPTION OF THE INVENTION

[0023] As said above, the aim of the present invention is to provide an improved Vacuum Insulating Glazing (herein also indicated as “VIG”) first of all from the point of view of the thermal insulation and energetic efficiency.

[0024] Now the Applicant has developed a novel device based on the Vacuum Insulating Glass technology, which is able to provide an excellent thermal insulation and barrier to gas permeability thanks to an innovative system involving the use of both a getter and a special sealant composition.

[0025] With particular reference to FIG. 1, a preferred embodiment of a vacuum insulating glazing 1 according to the present invention is illustrated, wherein two glass panes 2 and 2′ facing one another are spaced apart from one another by a plurality of pillars 3, 3′, 3″ . . . , so as to create a void volume 4 therebetween. Pillars 3, 3′, 3″ . . . have to be placed in between the glass panes 2 and 2′ to maintain them at a predetermined distance imposed by the pillar's height. Preferably pillars are equally distributed over the whole glass surface; their number may vary depending on how large is the surface and can be easily established by any person with ordinary skills in the art.

[0026] According to a particular embodiment of the present invention, the glass panes 2 and 2′ in the present VIG device are tempered glasses, with at least one of the surfaces covered by a low emissivity layer facing to the inner volume 4 of the VIG. The lateral size of the glass panes 2 and 2′ are typically comprised between 0.25 and 3 m, with the thickness of the pillars 3, 3′, 3″ . . . ranging from 0.1 to 0.6 mm.

[0027] To seal off the void volume 4, in the present VIG device, a polymer-based sealant 6 is deposited on the edges of the glass panes so as to define an inner, closed space between the glass panes 2 and 2′. After curing, taking into account the typical size details of the present VIG, a corresponding preferred width of the sealing edge along the VIG perimeter is comprised between 5 and 35 mm.

[0028] The sealing edge 6 in the present VIG device is obtained by deposition and curing of a sealant composition comprising: [0029] (a) a curable thermosetting non-halogenated polyepoxide resin comprising in average at least two epoxy groups per molecule; [0030] (b) an aromatic diamine curing agent in amount sufficient to provide from 0.5 to 2.0 equivalents of amine N—H per equivalent of epoxy groups in the epoxy resin, preferably from 0.5 to 1.0 equivalents; and [0031] (c) an inorganic dryer in amount ranging between 5% and 25% by weight with respect to the total weight of said sealant composition.

[0032] According to a preferred embodiment of the present invention, the non-halogenated polyepoxide resin in the present sealant composition is a phenol-formaldehyde resin or polyphenol diglycidyl ethers also known as Novolac resins, and more preferably it has the following formula (I):

##STR00001##

wherein n is an integer comprised in the range between 0 and 8.

[0033] As the curing agent, the aromatic diamine in the present sealant composition preferably comprises sulphonated and/or phenol groups, and more preferably is 4,4′-diamino-diphenylsulphone.

[0034] The present sealant composition as above described has preferably a glass transition temperature higher than 100° C. and more preferably higher than 150° C. as determined by differential scanning calorimetry (DSC) measurements according to ISO 11357-2:2013.

[0035] As disclosed by the European patent application publication No 2576950, the present sealant composition can be used in combination with other sealant elements suitable to reduce even more the permeation gas load, essentially working on geometrical factors: it can be possible to add a peripheral impermeable frame (such as a metallic or glassy or ceramic U shaped profile clamping the assembly) glued with the present sealant composition on the outer VIG edge or at least on a portion of it. In such configuration, the permeation can be reduced and even when the width of the sealant should be considerably lowered for aesthetical or technical reasons.

[0036] According to the present invention, a non-evaporable getter system, indicated in FIG. 1 as 5 and 5′, is placed within the void volume 4, created between the glass panes 2 and 2′.

[0037] In a particular embodiment of this invention, the non-evaporable getter is a Zr alloy having a N.sub.2 absorption capacity 1 cctorr/g measured by ASTM absorption test at room temperature. As a Zr alloy of possible use in the getter of this invention, an alloy selected from the group consisting of ZrTiV, ZrTiVAl, ZrVAI, ZrVFe, and ZrVFeMn-RE, wherein RE is one or more rare earth elements, optionally sintered in mixtures comprising Zr powders. Even though, pills, such as a getter alloy like TiVFeAlSi, can be usefully be selected and used, preferred according to this invention are powder getters laminated on metal strips or coated on metal tapes, the getter being deposited on one side or on both sides of the metal support. Typically, the metal support for the getter is 5-20 mm large and 0.05-0.3 mm thick, with an amount of active getter material loaded on the support ranging for instance between 10 and 30 mg/cm.

[0038] FIG. 1 shows also the presence of an evacuation hole 7 in at least one of the glass panes 2 or 2″, that is required by the most common manufacturing processes of VIGs devices.

[0039] The simplest VIG configuration according to the present invention is reported in FIG. 2 with the maximum amount of getter and consisting in four getter strips positioned in a full second frame close to the sealant.

[0040] In FIGS. 3a to 3c alternative designs of a VIG according to the present invention are shown, with a lower number of getter strips contained in them with respect to the design in FIG. 2. These alternative designs have two strips on two different edges in order to simplify the activation process. By reducing the number of strips, we lose the symmetry that can result in asymmetric total edge widths (FIG. 3a) or in asymmetric sealant widths (FIGS. 3b and 3c). Designs of FIGS. 3b and 3c are equivalent and they differ in the location of getter strips, on the short edges for design of FIG. 3b and on the long edges for design of FIG. 3c.

[0041] In the case of asymmetric sealant widths, the deposition process could be carried out by choosing a sealant curb equivalent to the narrow sealant deposit and by using multiples of that curb to produce the wide sealant deposits.

[0042] The inorganic dryer in the present sealant composition can be selected from irreversible dryers, such as CaO, other oxides, perchlorate dryers, and hygroscopic salts or from reversible dryers, such as zeolites or active carbon or a mixture thereof.

[0043] According to a particular embodiment of this invention the present sealant composition further comprises one or more passive fillers, that may be organic or inorganic fillers, such as poly(vinyl alcohol) (PVOH), polyimides, SiO.sub.2, TiO.sub.2, glass beads, glass fibers that may be either chopped or in strain form, metal or glass ribbons, and metal or glass wires.

[0044] In the following Table 1, exemplary weight percentages of the components in the present sealant composition are described.

TABLE-US-00001 TABLE 1 exemplary composition of the polymer-based sealant Additive Composition size Range Component Function (μm) % [w/w] Phenol-formaldehyde resin (Nevolac) Matrix — 75 ÷ 60  4,4′-diaminodiphenyl sulfone (Dapsone) Curing <63 25 ÷ 40 Agent (% eq/eq: 0.5 ÷ 1) Reversible: Zeolites e.g. LTA-Na, FAU 13X; Dryer <10 5 ÷ 30 Irreversible: e.g. CaO Organic: e.g. PVOH Passive <10 0 ÷ 50 Inorganic: e.g. SiO.sub.2, glass beads, TiO.sub.2 Filler

[0045] In addition, subject of this invention is a process for manufacturing a vacuum insulating glazing comprising the steps of: [0046] i) providing a top and a bottom glass pane, and preparing said bottom glass pane by the following steps a to c in any order, not necessarily in the order they are reported below: [0047] a. positioning of pillars; [0048] b. positioning of a non-evaporable getter system on the glass surface (e.g. in the case of getter strips) or in a dedicated space (e.g. drilled hole for getter pills) and optionally glue the getter in order to avoid its movement during the pairing operation; [0049] c. depositing a sealant composition as described above; [0050] ii) pairing the top glass pane on the bottom glass pane; [0051] iii) curing the sealant preferably by heating and optionally also by UV curing; [0052] iv) pumping out the VIG chamber preferentially under baking to improve vacuum conditions; [0053] v) activating the getter, preferentially by radio-frequency (RF) heating in a temperature range of 300° C.-600° C. [0054] vi) sealing of the evacuation hole.

[0055] The sealant deposition can be carried out by means of traditional deposition techniques, e.g. needle dispensing by deposition of the sealant composition from pre-filled syringes, or by positioning pre-formed laminated strips of the sealant composition.

[0056] According to an aspect of the present invention, the curing step iii) is carried out at about 200° C. for 1 hour.

[0057] In another aspect of the present invention the curing step iii) is carried out at about 170° C. for 1 hour.

[0058] In a particular embodiment of the present manufacturing process, the steps i) and ii) above may be performed in a large evacuated chamber enclosing the entire VIG, without the need for a subsequent pumping out.

[0059] Advantages of the present invention are linked to the high energy efficiency and thermal insulation obtained thanks to the present vacuum insulating glazing with both a getter and the above described sealing edge. The present VIG device has shown high barrier properties towards atmospheric gases and moisture too thanks to the presence of a dryer comprised in the sealant composition, not separated from it in the inner volume 4 of the VIG device. The present sealant compositions have been tested as illustrated in the following experimental part, and found that they are able to yield vacuum grade under any of the aging protocols tested, while the comparison compositions fail, especially for longer time aging.

[0060] Moreover, the presence of the dryer in the sealant formulation allows reaching the same high efficiency with a lower amount of getter or alternatively with the use even in conditions of a not fully-activated getter according to the temperature limits imposed by the VIG production process.

[0061] Further advantages of the present VIG device are its mechanical properties too: the present VIG device, and in particular its sealing edge, is in fact able to accommodate the large stress due to the pressure difference between the inner volume 4 and external atmosphere. It is also able to accommodate the different thermal dilation between inner and outer glass panes, as well as to sustain, at the end of the manufacturing process, outgassing procedures at temperatures higher than 100° C., but below the sealant T.sub.g, to remove the gases and moisture from the inner volume of the VIG device. High yield stress and adhesion strength on glass surfaces (>7 MPa) of the present devices are shown in the following experimental part following lap-shear tests, in comparison with devices comprising different sealant compositions.

[0062] Furthermore, as regards to the present process for manufacturing the vacuum insulating glazing, advantages are shown by the present sealant edge in particular in that it has a curing temperature below 250° C. and a glass transition temperature higher than 100° C. Moreover, it was observed that no gaseous species is released during polymerization.

[0063] Finally, a further important advantage of the present invention is that the process for the manufacture of the present VIG device is simple and cost-effective.

Experimental Part

[0064] Some representative VIG samples, subjected to different aging protocols (see Table 2), have been tested in terms of pressure evolution which ultimately affects the thermal properties.

TABLE-US-00002 TABLE 1 Aging protocols. Temperature (° C.)/ Aging Protocols Time (days) Relative Humidity (%) A 1 25°/90% B 15 25°/90% C 30 25°/90%

[0065] A VIG size of 300 mm×300 mm has been chosen with sealing edge width of 1 cm and a vacuum gap of 0.25 mm.

[0066] Sealant Samples A, B and C with formulations of the present invention are reported in Table 2. Comparative sealant compositions 1, 2, 3, 4 and 5, wherein other resins have been used as sealants have been considered for comparison; they are also listed in the same Table 3 below. All these polymer-based sealants were tested after the above reported aging protocols and results have been reported in Table 3. All the tests were carried out with a fully-activated getter in the form of ZrVAI alloy laminated on both sides of 0.1 mm thick nickel-plated iron 8 mm-wide strips. For each VIG sample, four getter strips were used as illustrated in FIG. 2.

TABLE-US-00003 TABLE 2 Compositions of sealant sample investigated in the test examples Component Composition % (w/w) Sample A Phenol-formaldehyde resin 67.5 4,4′ diaminodiphenyl sulphone 22.5 calcium oxide 10 Sample B Phenol-formaldehyde resin 67.5 4,4′ diaminodiphenyl sulphone 22.5 Zeolites LTA 10 Sample C Phenol-formaldehyde resin 62.8 4,4′ diaminodiphenyl sulphone 20.9 calcium oxide 9.3 silicon dioxide 7 Comparative 1 Phenol-formaldehyde resin 75 4,4′ diaminodiphenyl sulphone 25 Comparative 2 Bisphenol F 73.75 4,4′ diaminodiphenyl sulphone 26.25 Comparative 3 Polysulfide 100 Comparative 4 ethylene-octene copolymer 50.5 calcium oxide 33 Silicon dioxide 16.5 Comparative 5 polydimethylsiloxane 100

[0067] The measurements on the samples illustrated above were carried out by monitoring the total pressure evolution by spinning rotor gauge (SRG). Despite the fact SRGs are considered high accuracy transfer standard for high vacuum pressure measurements, they need a gas-dependent calibration factor, that at the moment is not known being the permeants mixture unknown [see for instance NIST Special Publication 250-93 “NIST Calibration Services for Spinning Rotor Gauge Calibrations” by Robert F. Berg and James A. Fedchak and the handbook from MKS at https://www.mksinst.com/f/srg-3-spinning-rotor-vacuum-gauge-system]. For this reason, the results are reported in the following Table 4 in comparative terms of vacuum grade quality: [0068] + means high vacuum, i.e. pressure 10.sup.−3 mbar; [0069] ≈ means medium pressure, i.e. in the range from 5.Math.10.sup.−3 mbar to 10.sup.−3 mbar, and [0070] − means low vacuum range, i.e. pressure 5.Math.10.sup.−3 mbar.

TABLE-US-00004 TABLE 3 Vacuum grade results for different polymer-based sealants undergoing different aging protocols. Vacuum Grade Sealant Aging Protocol A Aging Protocol B Aging Protocol C Sample A + + + Sample B + + + Sample C + + + Comparative 1 + ≈ − Comparative 2 + + ≈ Comparative 3 + ≈ − Comparative 4 ≈ − − Comparative 5 − − −

[0071] The results obtained show the excellence of the present sealant compositions over the comparison ones, the latter not being able to reach a high vacuum grade under all aging conditions tested, especially for longer times (aging protocol C). On the contrary, the sealant compositions of the invention are able to maintain high or medium vacuum grade even for longer times. In particular those of the present compositions comprising one or more oxide dryers show a high vacuum grade under any aging protocols.

[0072] All Samples and Comparative samples have been tested for their mechanical properties by lap-shear tests. Results are summarized in the following Table.

[0073] Data are collected based on ISO 4587:2013 “Adhesives—Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies”

TABLE-US-00005 TABLE 5 Lap shear tests for different polymer-based sealant compositions. Sealant Adhesion strength (MPa) Sample A >7 Sample B >7 Sample C >7 Comparative 1 ≈2.4 Comparative 2 ≈4 Comparative 3 ≈1.2 Comparative 4 ≈1.5 Comparative 5 ≈2

[0074] These results confirm high yield stress and adhesion strength (>7 MPa) on glass surfaces, showing that the present sealant compositions fulfil the mechanical requirements for a VIG application.

[0075] The present invention has been described above with reference to its preferred embodiments, but further embodiments may exist, all comprised in a same inventive core, as defined by the scope of the attached claims.