Toughened cyanoacrylate compositions
Curable cyanoacrylate compositions are reported that comprise cyanoacrylate and a thermoplastic polyurethane (TPU) components. Such compositions are toughened cyanoacrylate compositions exhibiting long term viscosity stability when stored for prolonged periods at room temperature (25° C.). TPU components are reported having structural units in which at least one of the structural units has the formula —O—R 1 —O—Ar—O—R 2 —O—, wherein Ar is a C 6 -C 20 aromatic group with at least one aromatic ring; R 1 is a C 2 -C 10 alkyl group; and R 2 is a C 2 -C 10 alkyl group. The thermoplastic polyurethane (TPU) component may be present in the curable cyanoacrylate composition from about 1 wt % to about 40 wt %, for example from about 2 wt % to about 30 wt %, such from about 3 wt % to about 20 wt %, suitably from about 5 wt % to about 10 wt %, based on the total weight of the composition.
1. A curable cyanoacrylate composition comprising:
(i) a cyanoacrylate; and
(ii) a thermoplastic polyurethane (TPU) having a chain formed from structural units;
wherein at least one of the structural units of the chain of the TPU (ii) has the formula:
—O—R 1 —O—Ar—O—R 2 —O—,
wherein:
Ar is a C 6 -C 20 aromatic group with at least one aromatic ring;
R 1 is a C 2 -C 10 alkyl group; and
R 2 is a C 2 -C 10 alkyl group,
and wherein the TPU (ii) is present in the curable cyanoacrylate composition from about 1 wt % to about 40 wt %, based on the total weight of the composition.
2. A curable cyanoacrylate composition as claimed in claim 1 wherein the aromatic group Ar in the structural unit with the formula:
—O—R 1 —O—Ar—O—R 2 —O—
is selected from: benzene, methyl benzene, dimethylbenzene, ethylbenzene, trimethylbenzene, tetramethylbenzene, diethylbenzene, triethylbenzene, naphthalene, methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene, tetraethylbenzene, tetramethylnaphthalene, pentamethylnaphtalene, hexamethylnaphthalene, ethylnaphthalene, diethylnaphthalene, or triethylnaphthalene.
3. A curable cyanoacrylate composition as claimed in claim 1 wherein the aromatic group Ar in the structural unit with the formula:
—O—R 1 —O—Ar—O—R 2 —O—
is a benzene group or a naphthalene group.
4. A curable cyanoacrylate composition according to claim 1 wherein at least one of the alkyl groups R 1 and R 2 in the structural unit with the formula:
—O—R 1 —O—Ar—O—R 2 —O—
is a C 2 alkyl group.
5. A curable cyanoacrylate composition according to claim 1 wherein the alkyl groups R 1 and R 2 in the structural unit with the formula:
—O—R 1 —O—Ar—O—R 2 —O—
are both C 2 alkyl groups.
6. A curable cyanoacrylate composition as claimed in claim 1 wherein the structural unit with the formula:
—O—R 1 —O—Ar—O—R 2 —O—
is formed from hydroquinone bis( 2 -hydroxyethyl) ether (HQEE).
7. A curable cyanoacrylate composition according to claim 1 , wherein the structural unit with the formula:
—O—R 1 —O—Ar—O—R 2 —O—
is present in the TPU (ii) in an amount from about 0.5 wt % to about 50 wt %, based on the total weight of the thermoplastic polyurethane (ii).
8. A curable cyanoacrylate composition as claimed in claim 1 , wherein the TPU (ii) is prepared using a polyol selected from the group consisting of a polyester-polyol, a co-polyester-polyol, a polyether-polyol, a co-polyether-polyol, a polycaprolactone-polyol, and a co-polycaprolactone-polyol.
9. A curable cyanoacrylate composition as claimed in claim 8 , wherein the polyol used in the preparation of the thermoplastic polyurethane (TPU) (ii) is a polyester-polyol or a co-polyester-polyol.
10. A curable cyanoacrylate composition as claimed in claim 9 , wherein the polyol used in the preparation of the TPU (ii) is a co-polyester formed from a dicarboxylic acid and 1,6-hexanediol.
11. A curable cyanoacrylate composition as claimed in claim 10 wherein the polyol used in the preparation of the TPU) (ii) is a linear polyester-polyol formed from a dicarboxylic acid and 1,6-hexanediol, and wherein the linear polyester-polyol has a hydroxyl number of from about 1 to about 60 mg KOH/g, as measured according to ASTM E222.
12. A curable cyanoacrylate composition according to claim 1 wherein the cyanoacrylate (i) is selected from the group consisting of ethyl 2-cyanoacrylate and β-methoxycyanoacrylate.
13. A curable cyanoacrylate composition according to claim 1 wherein the cyanoacrylate (i) is present in an amount of about 50 wt % to about 99 wt % based on the total weight of the cyanoacrylate composition.
14. A curable cyanoacrylate composition according to claim 1 wherein the cyanoacrylate (i) is present in an amount of about 60 wt % to about 90 wt % based on the total weight of the cyanoacrylate composition.
15. A curable cyanoacrylate composition according to claim 1 wherein the TPU (ii) is present in an amount of about 1 wt % to about 40 wt % based on the total weight of the cyanoacrylate composition.
16. A curable cyanoacrylate composition according to claim 1 wherein the TPU (ii) is present in an amount of about 5 wt % to about 20 wt % based on the total weight of the cyanoacrylate composition.
17. A curable cyanoacrylate composition according to claim 1 further comprising a stabiliser in an amount from about 0.0005 wt % to about 5 wt % based on the total weight of the cyanoacrylate composition.
18. A curable cyanoacrylate composition according to claim 17 wherein the stabiliser is selected from BF 3 , SO 2 , or HF.
19. A curable cyanoacrylate composition according to claim 1 further comprising ultra-high molecular weight polyethylene in an amount from about 0.05 wt % to about 5 wt % based on the total weight of the cyanoacrylate composition.
20. A curable cyanoacrylate composition as claimed in claim 1 wherein the viscosity of the uncured composition as measured at 25° C. does not decrease by greater than 5% from the starting viscosity over 30 days of storage at 25° C.
21. A curable cyanoacrylate composition as claimed in claim 1 , wherein the composition further comprises an antioxidant at an amount from about 0.01 wt % to about 1 wt %, by weight based on the total weight of the composition.
22. A curable cyanoacrylate composition as claimed in claim 21 , wherein the antioxidant is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).
23. A method of preparing a curable cyanoacrylate composition that retains a stable viscosity for at least 30 days when stored at 25° C., the viscosity measured at 25° C., wherein the method involves preparing a composition comprising from about 60 wt % to about 90 wt % of a cyanoacrylate with from about 1 wt % to about 40 wt % of a TPU, wherein the percentages are by weight based on the total weight of the composition and wherein the TPU has been prepared from:
a polyol selected from the group consisting of a polyester-polyol, a co-polyester-polyol, a polyether-polyol, a co-polyether-polyol, a polycaprolactone-polyol, and a co-polycaprolactone-polyol; and
an isocyanate compound selected from the group consisting of 1,4-diisocyanatobenzene (PPDI), toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (4,4′-MDI), 2,4′-diphenylmethane diisocyanate (2,4′-MDI), polymethylene poly(phenyl isocyanate) (PMDI), 1,5-naphthalene diisocyanate (NDI), bitolylene diisocyanate (TODI), 1,3-xylene diisocyanate (XDI),p-1,1,4,4-tetramethylxylene diisocyanate (p-TMXI), m-1,1,3,3-tetramethylxylylene diisocyanate (m-TMXDI), 1,6-diisocyanato-2,4,4-trimethylhexane, 1,4-cyclohexane diisocyanate (CHDI), 1,4-cyclohexanebis(methylene isocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), dicyclohexylmethane diisocyanate (H12MDI), and triphenylmethane -4,4′,4″-triisocyanate; and
a chain extender with the formula:
HO—R 1 —O—Ar—O—R 2 —OH,
wherein Ar is a C 6 -C 20 aromatic group with at least one ring,
R 1 is a C 2 -C 10 alkyl group, and
R 2 is a C 2 -C 10 alkyl group.
24. The method according to claim 23 , wherein the TPU has been prepared from a polyol selected from the group consisting of a polyester-polyol, a co-polyester-polyol, a polyether-polyol, a co-polyether-polyol, a polycaprolactone-polyol, and a co-polycaprolactone-polyol, and
an isocyanate compound selected from the group consisting of 1,4-diisocyanatobenzene (PPDI), toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (4,4′-MDI), 2,4′-diphenylmethane diisocyanate (2,4′-MDI), polymethylene poly(phenyl isocyanate) (PMDI), 1,5-naphthalene diisocyanate (NDI), bitolylene diisocyanate (TODI), 1,3-xylene diisocyanate (XDI),p-1,1,4,4-tetramethylxylene diisocyanate (p-TMXI), m-1,1,3,3-tetramethylxylylene diisocyanate (m-TMXDI), 1,6-diisocyanato-2,4,4-trimethylhexane, 1,4-cyclohexane diisocyanate (CHDI), 1,4-cyclohexanebis(methylene isocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), dicyclohexylmethane diisocyanate (H12MDI), and triphenylmethane-4,4′,4″-triisocyanate,
and
a chain extender with the formula:
HO—R 1 —O—Ar—O—R 2 —OH, wherein said chain extender is hydroquinone bis( 2 -hydroxyethyl) ether (HQEE).