AQUEOUS ADHESIVE DISPERSION CONTAINING POLYURETHANES AND ETHOXYLATED FATTY ALCOHOLS

Abstract

Described are aqueous adhesive dispersions comprising dispersed polyurethanes and also ethoxylated fatty alcohols as emulsifiers. The polyurethanes are constructed from certain organic diisocyanates, dihydroxy compounds selected from certain polyester diols and polyether diols, and compounds having groups reactive toward isocyanate groups and having at least one ionic group. The adhesive dispersions can be used as laminating adhesives, for example for composite film lamination or for the lamination of rigid moldings with flexible decorative foils.

Claims

1. An aqueous adhesive dispersion, comprising: a) at least one dispersed polyurethane constructed from a1) at least one organic diisocyanate, selected from diisocyanatcs of the formula: X(NCO).sub.2, where X is a noncyclic aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms, an aromatic hydrocarbon radical having 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms, a2) at least one dihydroxy compound selected from the group consisting of a polyester diol and a polyether diol, the polyester diol being formed from at least one aliphatic dicarboxylic acid and at least one alkanediol, and the polyether diol being selected from the group consisting of a polypropylene oxide and a polytetrahydrofuran, a3) at least one compound having at least one group reactive toward isocyanate groups, and additionally carrying at least one ionic group or one group which can be converted into an ionic group, and a4) optionally at least one further compound different from a1) to a3); and b) at least one nonionic emulsifier comprising an ethoxylated fatty alcohol.

2. The aqueous adhesive dispersion according to claim 1, wherein the dihydroxy compound a2) has a number-average molar weight of 500 to 5000 g/mol and comprises no ionic group or group which can be converted into an ionic group.

3. The aqueous dispersion according to claim 1, comprising: 30 to 55 weight % of the polyurethane a), based on the aqueous adhesive dispersion; and, 0.5 to 2 weight % of the nonionic emulsifier b), based on a total amount of solids.

4. The aqueous dispersion according to claim 1, wherein the diisocyanate a1) is selected from the group consisting of hexamethylene diisocyanate, 1-isocyanato-3,5,5 -trimethyl-5-isocyanatomethylcyclohexane, 2,6-diisocyanatotoluene, 2,4-diisocyanatotoluene, tetramethylxylylene diisocyanate, and a mixture thereof.

5. The aqueous dispersion according to claim 1, wherein the dihydroxy compound a2) is selected from the group consisting of an adipic acid-butanediol polyester and an adipic acid-hexanediol polyester.

6. The aqueous dispersion according to claim 1, wherein the compound a3) is selected from the group consisting of a dihydroxycarboxylic acid, diaminocarboxylic acid and a diaminosulfonic acid.

7. The aqueous dispersion according to claim 1, wherein the ethoxylated fatty alcohol b) is a C16 to C18 fatty alcohol with a degree of ethoxylation of 8 to 50.

8. The aqueous dispersion according to claim 1, wherein: the polyurethane a) is constructed from a1) at least one organic diisocyanate selected from the group consisting of hexamethylene diisocyanate, 1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane, 2,6-diisocyanatotoluene, 2,4-diisocyanatotoluene, tetramethylxylylene diisocyanate, and a mixture thereof, a2) at least one dihydroxy compound selected from the group consisting of adipic acid-butanediol polyester and adipic acid-hexanediol polyester, a3) at least one compound having at least one group reactive toward isocyanate groups, and additionally carrying at least one ionic group or one group which can be converted into an ionic group, selected from the group consisting of a diaminocarboxylic acid and a diaminosulfonic acid, a4) optionally the at least one further compound different from a1) to a3); and the aqueous adhesive dispersion comprises: b) from 0.5 to 2 weight %, based on the total amount of solids, of at least one nonionic emulsifier which is a C16 to C18 fatty alcohol with a degree of ethoxylation of 8 to 50.

9. A laminating adhesive, comprising aqueous adhesive dispersion of claim 1.

Description

EXAMPLES

Example 1

[0074] Aqueous dispersion comprising [0075] (a) 40 parts by weight of polyurethane, formed from [0076] 4 parts by weight of diisocyanatotoluene (2,4- or 2,6-diisocyanatotoluene) [0077] 4 parts by weight of hexamethylene diisocyanate [0078] 87 parts by weight of adipic acid/butanediol polyester with molecular weight Mn of 2400 [0079] 5 parts by weight of the sodium salt of ethylenediaminemonopropionic acid [0080] (b) 1 weight % (based on polyurethane) of Lutensol® AT 18 (C16-18 fatty alcohol, ethoxylated with 18 units of ethylene oxide)

Example 2

[0081] Aqueous dispersion comprising [0082] (a) 40 parts by weight of polyurethane, formed from [0083] 4 parts by weight of diisocyanatotoluene (2,4- or 2,6-diisocyanatotoluene) [0084] 4 parts by weight of hexamethylene diisocyanate [0085] 87 parts by weight of adipic acid/butanediol polyester with molecular weight Mn of 2400 [0086] 5 parts by weight of the sodium salt of ethylenediaminemonopropionic acid [0087] (b) 1 weight % (based on polyurethane) of Lutensol® AT 25 (C16-18 fatty alcohol, ethoxylated with 25 units of ethylene oxide)

Example 3 (Comparative; No Additive)

[0088] Aqueous dispersion comprising [0089] 40 parts by weight of polyurethane, formed from [0090] 4 parts by weight of diisocyanatotoluene (2,4- or 2,6-diisocyanatotoluene) [0091] 4 parts by weight of hexamethylene diisocyanate [0092] 87 parts by weight of adipic acid/butanediol polyester with molecular weight Mn of 2400 [0093] 5 parts by weight of the sodium salt of ethylenediaminemonopropionic acid

Example 4 (Comparative)

[0094] Aqueous dispersion comprising [0095] (a) 40 parts by weight of polyurethane, formed from [0096] 4 parts by weight of diisocyanatotoluene (2,4- or 2,6-diisocyanatotoluene) [0097] 4 parts by weight of hexamethylene diisocyanate [0098] 87 parts by weight of adipic acid/butanediol polyester with molecular weight Mn of 2400 [0099] 5 parts by weight of the sodium salt of ethylenediaminemonopropionic acid [0100] (b) 1 weight % (based on polyurethane) of Pluronic® PE 6800 (nonionic ethylene oxide/propylene oxide (80:20) block copolymer; Mw 1750)

Example 5 (Comparative)

[0101] Aqueous dispersion comprising [0102] (a) 40 parts by weight of polyurethane, formed from [0103] 4 parts by weight of diisocyanatotoluene (2,4- or 2,6-diisocyanatotoluene) [0104] 4 parts by weight of hexamethylene diisocyanate [0105] 87 parts by weight of adipic acid/butanediol polyester with molecular weight Mn of 2400 [0106] 5 parts by weight of the sodium salt of ethylenediaminemonopropionic acid [0107] (b) 1 weight % (based on polyurethane) of Pluronic® PE 10500 (nonionic ethylene oxide/propylene oxide (50:60) block copolymer; Mw 3250)

[0108] Measurements

[0109] Shear Stability Test

[0110] A sample of the dispersion for testing is subjected to shearing at 10 000 rpm for 10 minutes using a disperser disk. The LT before and after shearing is measured. Shear instability is manifested in a drop in LT (formation of microcoagulum). The smaller the drop, the more stable the dispersion is with respect to shearing.

[0111] LT

[0112] Light transmittance; variable for determining particle sizes in disperse systems. The polymer dispersion here is diluted to 0.01% solids content, and the light transmittance is measured in % in comparison to pure water.

[0113] Foam Development Test

[0114] A determination is made of the rise in the amount of foam (increase in foam volume, in %) during the shear stability test.

[0115] Electrolyte Stability Test

[0116] One drop of the dispersion under investigation is allowed to drop into a calcium chloride solution of defined concentration, and the mixture is shaken. If the drop dissolves in the solution, without visible coagulum formation, this concentration of calcium chloride is deemed to be compatible. The higher the maximum compatible calcium chloride concentration, the more electrolyte-stable the dispersion.

Examples:

[0117] PUD: Polyester polyurethane dispersion consisting of TDI/HDI/adipic acid butanediol/PUD salt

[0118] (Luphen D 200 A)

TABLE-US-00001 Additive Shear Electrolyte Foam (1 weight %, stability stability develop- solid on (% LT [g/l ment solid) drop) CaCl.sub.2] [%] Example 1 Lutensol ® AT 18 2 0.4 100 Example 2 Lutensol ® AT 25 2 0.4 100 Example 3 — 30 0.01 80 (comparative) Example 4 Pluronic ® 1 0.03 150 (comparative) PE6800 Example 5 Pluronic ® 2 0.03 150 (comparative) PE10500

[0119] The addition of the Lutensol® additives in examples 1 and 2 does not cause any change in the adhesive properties relative to example 3. The relevant adhesive properties are application-specific, and in the case of the laminating applications include peel strengths, which are determined at room temperature or at 90° C. immediately after the production of the laminate, and also 24 hours after production of the laminate.