DISPERSION ADHESIVES

Abstract

The invention relates to the use of aqueous dispersion adhesives on the basis of a mixture of aqueous polyurethane or polyurethane-urea dispersions for bonding foam substrates according to the spray coagulation method.

Claims

1. The use of an aqueous dispersion containing a mixture of A) an aqueous polyurethane or polyurethane-urea dispersion containing I. a polymer A) formed from I(i). at least one difunctional aliphatic polyester polyol having a molecular weight of 400 to 5000 g/mol, I(ii). at least one mixture of hexamethylene diisocyanate (HDI) and 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), and I(iii). at least one mixture of two or more aminic chain extenders, wherein at least one compound bears an ionic group, and the polymer A) after drying is semicrystalline or crystalline with a glass transition at a glass transition temperature Tg of between −65° C. and −40° C., and B) an aqueous polyurethane or polyurethane-urea dispersion which differs from A) and contains II. a polymer B) formed from II(i). at least one difunctional aromatic polyester polyol having a molecular weight of 400 to 5000 g/mol, II(ii). at least one difunctional polyol component having a molecular weight of 62 to 399, II(iii). at least one aliphatic diisocyanate and II(iv). at least one aminic chain extender having an ionic group, wherein the polymer B) after drying is amorphous with a glass transition at a glass transition temperature Tg of between −15° C. and +10° C.; and wherein the mixture contains 34.8% to 90.2% by weight of polymer A) and 9.8% to 65.2% by weight of polymer B), based on a sum total of polymers A) and B), for the adhesive bonding of foam substrates by the spray coagulation process.

2. The use of an aqueous dispersion as claimed in claim 1, wherein the mixture contains 44.4% to 87.8% by weight of polymer A) and 12.2% to 55.6% by weight of polymer B).

3. The use of an aqueous dispersion as claimed in claim 1, wherein the mixture contains 54.5% to 81.9% by weight of polymer A) and 18.1% to 45.5% by weight of polymer B).

4. The use of an aqueous dispersion as claimed in claim 1, wherein an HDI:IPDI molar ratio is between 9:1 and 1:9.

5. The use of an aqueous dispersion as claimed in claim 1, wherein an HDI:IPDI molar ratio is between 3:1 and 1:3.

6. The use of an aqueous dispersion as claimed in claim 1, wherein component A) I(iii). is a mixture of diethanolamine and a sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid.

7. The use of an aqueous dispersion as claimed in claim 1, wherein component B) II(i). is a polyester polyol based on o-phthalic acid, o-phthalic anhydride and butane-1,4-diol or hexane-1,6-diol.

8. The use of the aqueous dispersions as claimed in claim 1 for the production of adhesive compositions.

9. A process for preparing the aqueous dispersions as claimed in claim 1, wherein the aqueous polyurethane or polyurethane-urea dispersions of polymers A) and B) are mixed with each other.

10. (canceled)

Description

EXAMPLES

[0095] The invention will be elucidated in more detail below on the basis of the examples. The following methods and test methods were used here:

A) Spray Coagulation Process:

[0096] A standard spray gun for two-component dispersion adhesives, namely the PILOT III 2K from Walther Pilot, is used for application. The adhesive and the coagulant CaCl.sub.2) (3% by weight solution in water) are conveyed separately into the spray gun, mixed in the spray jet and the adhesive is coagulated. As the mixing does not take place until in the spray jet, no pot life needs to be taken into account. A ratio of 86% by weight adhesive dispersion and 14% by weight CaCl.sub.2) solution was chosen.

[0097] The precise settings of the spray gun are known in principle to the person skilled in the art and can be tailored to the specific case without undue burden and determined by simple preliminary experiments. The quantitative ratios and the application weight can be determined by reweighing the reservoir vessel and the substrates.

[0098] The following settings were used: [0099] a.) Adhesive component: conveying pressure 1.3 bar [0100] b.) Coagulation component: conveying pressure 0.3 bar [0101] c.) Atomizer air pressure: 2.8 bar [0102] d.) Bore diameter (nozzle) for adhesive component: 1.0 mm [0103] e.) Bore diameter (nozzle) for coagulant component: 0.4 mm [0104] f.) Application weights: 130-150 g/m.sup.2 (wet)

B) Determination of the Initial Strength:

[0105] As test material, ST 5540 (1) PU foam test specimens from STN Schaumstoff-Technik-Nürnberg GmbH having the dimensions 10×5×3 cm and a foam density of 40 kg/m.sup.3 are used (see FIG. 1). For assessment of the initial strength, immediately after application of the adhesive to the upper side (2) of the foam bodies (1) by the spray coagulation process (application rate 130-150 g/m.sup.2 wet), the test specimens are folded (4) in the middle with a wooden rod (3) (D=7 mm round wood or 7×7 mm rectangle) and fed by means of the test apparatus (5) through 2 steel rolls (6) (diameter 40 mm, length 64 mm) the tangential spacing (7) of which was previously set to 10 mm using a threaded spindle (8). The initial strength is sufficient if the test specimen or the bond seam (9) does not come undone despite the restoring forces present in the test specimen.

C) Determination of the Open Time

[0106] As test material, Recticel T 20120 polyether foam bodies from Recticel having the dimensions 10×5×3 cm and a foam density of 20 kg/m.sup.3 are used. To assess the open time, the test specimens are folded in the middle and joined together with light palm pressure immediately, every 60 seconds, or if necessary at time intervals to be defined, after the application of adhesive by means of the spray coagulation process (application rate 130-150 g/m.sup.2 wet). The end of the open time is indicated by the strength no longer sufficing and the test specimen opening as a result of the restoring forces arising.

D) Ascertainment of the Hardness of the Bond Seam:

[0107] The bond seam of the test specimen produced under B) was assessed in direct comparison with reference samples sensorially by means of touch after 24 h of storage at room temperature. The reference samples were produced using commercially available polychloroprene latices (Covestro Deutschland AG) having differing Shore A hardness. The bond seam of the test specimen formed from Dispercoll® C 84 (Shore A hardness of the pure, dried polymer=88) was taken as a reference for a hard bond seam, the bond seam of the test specimen formed from Dispercoll® C 74 (Shore A hardness of the pure, dried polymer=55) was taken as a reference for a bond seam of intermediate hardness and the bond seam of the test specimen formed from Dispercoll® C 2372 (Shore A hardness of the pure, dried polymer=40) was taken as a reference for a soft bond seam.

E) Ascertainment of the Glass Transition Temperatures, Melting Temperatures and Enthalpies of Fusion by Means of DSC:

[0108] The glass transition temperatures and also melting temperatures and enthalpies of fusion were determined by means of differential scanning calorimetry (DSC) using a Pyris Diamond DSC calorimeter from Perkin-Elmer. To this end, a film was produced by knife coating the dispersion onto a glass sheet at a 100 μm wet film thickness, flashed off for 2 hours, and then this film together with the glass sheet is dried in a dry box for 3 days at room temperature and 0% relative room humidity. Then, using 10 mg of sample material from this film, the DSC curve was recorded with the following measurement conditions: Rapid cooling to the starting temperature −100° C., then commencement of three heatings from −100° C. to +150° C. at a heating rate of 20 K/min and a cooling rate of 320 K/min under a helium atmosphere and with cooling with liquid nitrogen. The glass transition temperature corresponds to the temperature at half the height of the glass transition, with the third heating being assessed. For determination of the melting temperatures and enthalpies of fusion, the first heating was assessed.

F) Feedstocks:

[0109] Polyester I: polyester diol formed from butane-1,4-diol and adipic acid having an OH number=50

[0110] Polyester II: polyester diol formed from hexane-1,6-diol and phthalic anhydride having an OH number=56 [0111] Desmodur® H: hexamethylene 1,6-diisocyanate (Covestro Deutschland AG, Leverkusen/Germany) [0112] Desmodur® I: isophorone diisocyanate (Covestro Deutschland AG, Leverkusen/Germany)

Example 1 (According to the Invention)

Preparation of an Aqueous Polyurethane or Polyurethane-Urea Dispersion Containing Polymer A):

[0113] 450 g of polyester I are dewatered for 1 hour at 110° C. and 15 mbar. At 80° C., 30.11 g of Desmodur® H and then 20.14 g of Desmodur® I are added. The mixture is stirred at 80 to 90° C. until a constant isocyanate content of 1.15% has been reached. The reaction mixture is dissolved in 750 g of acetone and cooled to 48° C. Into the homogeneous solution is added a solution of 5.95 g of the sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid and 2.57 g of diethanolamine in 65 g of water with vigorous stirring. After 30 minutes, the mixture is dispersed by addition of 700 g of water. Distillative removal of the acetone affords an aqueous polyurethane-polyurea dispersion having a solids content of 40.0% by weight.

[0114] The polymer present is semicrystalline after drying with a glass transition at a glass transition temperature Tg of −54° C., a melting temperature of 48° C. and an enthalpy of fusion of 50.4 J/g.

Example 2 (According to the Invention)

Preparation of an Aqueous Polyurethane or Polyurethane-Urea Dispersion Containing Polymer B):

[0115] 1215 g of polyester II are dewatered for 1 hour at 110° C. and 15 mbar. At 80° C., 4.6 g of hexane-1,6-diol and 179.0 g of Desmodur® H are added and the mixture is stirred at 90° C. until a constant isocyanate content of 2.28% has been reached. The reaction mixture is dissolved in 2490 g of acetone and cooled to 48° C. Into the homogeneous solution is added a solution of 31.9 g of the sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid in 300 g of water with vigorous stirring. After 30 minutes, the mixture is dispersed by addition of 1150 g of water. Distillative removal of the acetone affords an aqueous polyurethane-polyurea dispersion having a solids content of 50.0% by weight.

[0116] The polymer present is amorphous after drying (does not have a melting peak in DSC) and has a glass transition at a glass transition temperature Tg of −1.5° C.

Example 3 (Comparison)

[0117] Use of the dispersion from example 1 (containing 100% polymer A). As can be seen from the table, while the initial strength is good, an excessively hard bond seam is obtained and the open time, at one minute, is insufficient.

Example 4 (Comparison)