Fire resistant glazing unit
The present invention relates to a fire resistant glazing unit ( 10 ), and in particular to novel curable gelling compositions which may form a fire-resistant hydrogel interlayer ( 3 ) between the glass panes ( 1 ) of the glazing unit ( 10 ). The gelling compositions of the invention comprise 5-40% w/w of a curable hydrogel-forming component (typically an acidic vinyl monomer such as acrylic acid or its metal salt); 20-60% w/w of one or more salts (e.g. magnesium salts); 40-90% w/w of an aqueous vehicle; and the gelling compositions have an acidic p H between p H 1 and 7. Such gelling compositions, when cured to form a hydrogel interlayer, provide excellent fire-resistant properties and also an excellent radiation barrier in the event of a fire.
1. A gelling composition for forming a fire-resistant hydrogel interlayer within a glazing unit, the gelling composition obtained by mixing together:
5-40% w/w of a curable hydrogel-forming component;
20-60% w/w of one or more salts; and
an aqueous vehicle;
wherein the sum total of % w/w of all ingredients mixed together to obtain the gelling composition, including any further ingredients, is 100% w/w;
characterised in that:
the composition has a pH between 3 and 6.8; and
the one or more salt(s) comprise monovalent or divalent metal cations or a combination thereof;
the curable hydrogel-forming component comprises:
a polymerisable hydrophilic monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamide-2-phenylpropanesulfonic acid, 2-acrylamide-2-methyl-propanesulfonic acid, vinyl phosphoric acid, (meth)acrylate of ethylene oxide-modified phosphoric acid, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropylmethacrylamide, N,N-dimethylaminopropylacrylamide; or
a polymerisable hydrophilic monomer defined by Formula (I):
wherein R 1 is H, or (1-2C)alkyl;
R 2 is selected from OH, OR 3 , NH 2 , NHR 3 , and NR 3 R 4 ; and
R 3 and R 4 are independently (1-2C)alkyl;
or a salt thereof.
2. The gelling composition as claimed in claim 1 , wherein the gelling composition is a curable gelling composition, which can be cured to form a polyelectrolyte hydrogel.
3. The gelling composition as claimed in claim 1 , wherein the pH of the gelling composition is between 4 and 5.5.
4. The gelling composition as claimed in claim 1 , wherein the gelling composition further comprises 0.02-0.08% w/w cross-linking agent.
5. The gelling composition as claimed in claim 1 , wherein the one or more salts constitute 35-52% w/w of the gelling composition.
6. The gelling composition as claimed in claim 1 , wherein the one or more salt(s) comprise magnesium sulphate.
7. The gelling composition as claimed in claim 1 , wherein the one or more salt(s) comprise magnesium acetate.
8. The gelling composition as claimed in claim 1 , wherein the one or more salts are or include one or more metal salts including magnesium sulphate, magnesium oxide, and magnesium acetate.
9. The gelling composition as claimed in claim 8 , wherein the gelling composition comprises:
5-35% w/w MgSO 4 .7H 2 O;
0-3% w/w MgO;
5-35% w/w Mg(OAc) 2 .4H 2 O.
10. The gelling composition as claimed in claim 1 , wherein the gelling composition comprises 6-15% w/w hydrogel-forming component.
11. The gelling composition as claimed in claim 1 wherein the hydrogel-forming component is acrylic acid.
12. The gelling composition as claimed in claim 1 , wherein the gelling composition comprises:
6-16% w/w acrylic acid;
20-60% w/w of one or more salts, including:
5-35% w/w (of composition as a whole) MgSO 4 .7H 2 O;
0-3% w/w (of composition as a whole) MgO;
5-35% w/w (of composition as a whole) Mg(OAc) 2 .4H 2 O;
water;
0.02-0.08% w/w cross-linking agent;
0.001-0.05% w/w photoinitiator; and
wherein the composition has a pH between 4 and 6.
13. A process for forming a glazing unit, the process comprising:
(i) providing a first and a second transparent pane;
(ii) partially assembling the glazing unit such that the first and second transparent panes are spaced apart from one another and a sealing means holds the first and second panes in position; wherein;
the sealing means comprises an opening; and
the first and second panes and the sealing means together define an internal space;
(iii) delivering a gelling composition as claimed in claim 1 into the internal space through the opening in the sealing means;
(iv) closing the opening in the sealing means to provide a sealed internal space; and
(v) curing the gelling composition to provide a hydrogel gel interlayer within the internal space;
wherein the gel is bonded to the inner surfaces of the first and/or second transparent panes by either coating at least one of the internal surfaces of the first and/or second panes with a coupling agent prior to step (iii) or incorporating the coupling agent into the gelling composition.
14. A glazing unit comprising a first transparent pane and a second transparent pane with an interlayer disposed therebetween, wherein the interlayer is a hydrogel formed by curing the gelling composition as claimed in claim 1 .
15. The gelling composition of claim 1 , wherein the one or more salts constitute 30-60% w/w of the gelling composition.
16. The gelling composition of claim 1 , wherein the monovalent and divalent metal cations are selected from the group consisting of Na + , K + , Li + , Mg 2+ , Ca 2+ , and Zn 2+ .
17. The gelling composition of claim 1 , wherein the curable hydrogel-forming component comprises a hydrophilic polymerisable monomer that is a vinyl-containing monomer that polymerises to form a polyelectrolyte having pendant ionisable groups.
18. The gelling composition of claim 1 , wherein the hydrogel-forming component comprises a polymerisable hydrophilic monomer, wherein the polymerisable monomer is an acrylate or alkylacrylate monomer of Formula (I):
wherein R 1 is H or (1-2C)alkyl;
R 2 is selected from OH, OR 3 , NH 2 , NHR 3 , and NR 3 R 4 ; and
R 3 and R 4 are independently (1-2C)alkyl;
or a salt thereof.
19. The gelling composition of claim 18 , wherein the hydrogel-forming component is acrylic acid.
20. The gelling composition of claim 1 , wherein the curable hydrogel-forming component comprises an acrylate or alkylacrylate monomer of Formula (I):
wherein R 1 is H or (1-2C)alkyl;
R 2 is selected from OH, OR 3 , NH 2 , NHR 3 , and NR 3 R 4 ; and
R 3 and R 4 are independently (1-2C)alkyl;
or a salt thereof;
the composition has a pH between 4 and 5.5; and
the one or more salt(s) comprise divalent metal cations.
21. The gelling composition of claim 1 , wherein the gelling composition is a transparent solution.
22. The gelling composition of claim 1 , wherein the pH is between 3 and 6.
23. The gelling composition of claim 1 , wherein the gelling composition comprises an initiator that is a photoinitiator.
24. The gelling composition of claim 1 , wherein an initiator is present within the gelling composition, and the initiator comprises 0.001-0.05% w/w of the total gelling composition.
25. The gelling composition of claim 1 , wherein the one or more salts comprise a mixture of metal salts.
26. The gelling composition of claim 1 , wherein the one or more salts comprise divalent cations.