Reactive polyurethane hot melt adhesives containing fillers

Abstract

The present invention relates to a reactive polyurethane (PUR) hot-melt adhesive, in particular a moisture cross-linking 1K-PUR hot-melt adhesive, wherein the PUR adhesive contains neutralized hollow glass spheres as fillers. The invention also relates to the use of said adhesive for adhesively bonding substrates.

Claims

1. A reactive polyurethane-based hot-melt adhesive composition containing, based on the total weight of the adhesive composition, from 1 to <30 wt. % of at least one solid particulate filler, wherein the at least one filler comprises neutralized hollow glass spheres, the hollow glass spheres, as a 5 wt. % dispersion in water at 20° C., having a pH of 6 to 9.

2. The hot-melt adhesive composition according to claim 1, containing, based on the total weight of the adhesive composition, from 1 to <10 wt. % of neutralized hollow glass spheres.

3. The hot-melt adhesive composition according to claim 1, containing, based on the total weight of the adhesive composition, from 2 to 6 wt. % of neutralized hollow glass spheres.

4. The hot-melt adhesive composition according to claim 1, wherein the hollow glass spheres, as a 5 wt. % dispersion in water at 20° C., have a pH of from 6 to 8.

5. The hot-melt adhesive composition according to claim 1, wherein the hollow glass spheres, as a 5 wt. % dispersion in water at 20° C., have a pH of from 6.5 to 7.5.

6. The hot-melt adhesive composition according to claim 1, wherein the at least one filler has an average particle size d.sub.50 of from 5 to 50 μm.

7. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive composition contains at least one NCO-terminated polyurethane prepolymer.

8. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive composition contains at least one NCO-terminated polyurethane prepolymer in an amount of from 20 to 95 wt. % based on the total weight of the hot-melt adhesive composition.

9. The hot-melt adhesive composition according to claim 1, comprising an MDI-terminated polyurethane prepolymer reaction product of a polyester polyol mixture and MDI.

10. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive is a moisture-curing 1K polyurethane hot-melt adhesive.

11. The hot-melt adhesive composition according to claim 1, wherein the composition further contains at least one thermoplastic polyester in an amount of from 3 to 35 wt. %, based on the total weight of the hot-melt adhesive composition.

12. The hot-melt adhesive composition according to claim 1, wherein the composition further contains at least one thermoplastic polyester, in an amount of from 5 to 25 wt. %, based on the total weight of the hot-melt adhesive composition.

13. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive composition: (a) has a viscosity of from 2,000 to 60,000 mPas determined according to DIN EN ISO 2555:2000-01 (Brookfield viscometer RV DV-II, spindle no. 27, 130° C.; 5 rpm); and/or (b) has an NCO-content of from 0.25 to 4 wt. %; and/or (c) has a density of ≤1.5 g/cm.sub.3.

14. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive composition has a density of 0.9 to 1.1 g/cm.sup.3.

15. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive composition has an increase in viscosity after 16 h at 130° C. of no more than 400%.

16. The hot-melt adhesive composition according to claim 1, wherein the hot-melt adhesive composition has an increase in viscosity after 16 h at 130° C. of no more than 250%.

17. The hot-melt adhesive composition according to claim 1, wherein: (a) the composition further contains one or more additives selected from tackifying resin, tackifier, adhesion promoter, crosslinking agent, viscosity regulator, pigment, plasticizer, stabilizer, catalyst, wax or antioxidant; and/or (b) the composition is substantially free of organic solvent.

18. Cured reaction products of the hot-melt adhesive composition according to claim 1 for adhesively bonding two or more substrates.

19. A substrate bonded to cured reaction products of the hot-melt adhesive composition according to claim 1.

20. A reactive polyurethane-based hot-melt adhesive composition comprising, based on the total weight of the adhesive composition, from 1 to <30 wt. % of neutralized hollow glass spheres, wherein the hollow glass spheres, as a 5 wt. % dispersion in water at 20° C., have a pH of less than 9.0.

Description

EXAMPLES

Example 1 (According to the Invention)

(1) In a heated and stirred tank reactor, a reactive hot-melt adhesive composition having free isocyanate groups was prepared from the following components:

(2) TABLE-US-00001 Polyester 1 (of adipic acid and hexanediol-1,6, OH number 10 wt. % 30) Polyester 2 (of dodecanedioic acid and hexanediol-1,6, OH 30 wt. % number 30) Polyester 3 (of phthalic acid, isophthalic acid and neopentyl 38 wt. % glycol, OH number 30) Thermoplastic polyurethane (TPU, Pearlbond ® 501,  5 wt. % Lubrizol) Hollow glass spheres (neutralized, 3M Glass Bubbles  5 wt. % iM30K-N) 4,4′-MDI (diphenylmethane diisocyanate) 12 wt. %

(3) In addition, the polyesters 1-3 were melted at 130° C. and then, together with the TPU and the hollow glass spheres, filled into the heatable stirred tank reactor and dehydrated to a moisture content of <200 ppm under vacuum at 130° C., the melt being visually checked for homogeneity. The reaction vessel was then aerated with nitrogen and the calculated amount of 4,4′-MDI was added while the stirrer was stationary and at 120-130 ° C. This was then stirred at 100 rpm, a vacuum was applied and the temperature was kept at 120-130° C. The reaction time was 30 minutes. The reaction was then terminated, the degassed product immediately decanted into a moisture-tight sealable container and the NCO content (NCO content according to EN ISO 11909:2007-05), density and viscosity (according to DIN EN ISO 2555:2000-01 using a Brookfield viscometer RV DV-II, spindle no. 27, 130° C., 5 rpm) were determined. The density was 1.05 g/cm.sup.3. The viscosity increased by 200% over 16 h at 130° C.

(4) The pH of the hollow glass spheres (5 wt. % in demineralized water) at 20° C. was 7.0 (determined according to EN ISO 10523:2012-04).

Example 2 (Comparative Example)

(5) In a heated and stirred tank reactor, a reactive hot-melt adhesive composition having free isocyanate groups was prepared from the following components:

(6) TABLE-US-00002 Polyester 1 (adipic acid and hexanediol-1,6, OH number 30) 10 wt. % Polyester 2 (dodecanedioic acid and hexanediol-1,6, OH 30 wt. % number 30) Polyester 3 (phthalic acid, isophthalic acid and neopentyl 38 wt. % glycol, OH number 30) Thermoplastic polyurethane (TPU, Pearlbond ® 501,  5 wt. % Lubrizol) Hollow glass spheres (non-neutralized, 3M Glass Bubbles  5 wt. % VS 5500) 4,4′-MDI (diphenylmethane diisocyanate) 12 wt. %

(7) The composition was prepared as described in Example 1. The density of the product was 1.07 g/cm.sup.3. The viscosity significantly increased at 130° C. and the product was already gelled and unusable after 1.5 h (increase >500%).

(8) The pH of the hollow glass spheres (5 wt. % in demineralized water) at 20° C. was 9.5 (determined according to EN ISO 10523:2012-04).

Example 3 (Comparative Example)

(9) In a heated and stirred tank reactor, a reactive hot-melt adhesive composition having free isocyanate groups was prepared from the following components:

(10) TABLE-US-00003 Polyester 1 (adipic acid and hexanediol-1,6, OH number 30) 11 wt. % Polyester 2 (dodecanedioic acid and hexanediol-1,6, OH 32 wt. % number 30) Polyester 3 (phthalic acid, isophthalic acid and neopentyl 40 wt. % glycol, OH number 30) Thermoplastic polyurethane (TPU, Pearlbond ® 501, Lubrizol)  5 wt. % 4,4′-MDI (diphenylmethane diisocyanate) 12 wt. %

(11) The composition was prepared as described in Example 1. The density of the product was 1.20 g/cm.sup.3. The viscosity increased by 210% over 16 h at 130° C.

Example 4 (Comparative Example)

(12) In a heated and stirred tank reactor, a reactive hot-melt adhesive composition having free isocyanate groups was prepared from the following components:

(13) TABLE-US-00004 Polyester 1 (adipic acid and hexanediol-1,6, OH number 30) 10 wt. % Polyester 2 (dodecanedioic acid and hexanediol-1,6, OH 32 wt. % number 30) Polyester 3 (phthalic acid, isophthalic acid and neopentyl 40 wt. % glycol, OH number 30) Thermoplastic polyurethane (TPU, Pearlbond ® 501, Lubrizol)  5 wt. % Polymer microcapsules (Expancell DU80, Akzo Nobel)  1 wt. % 4,4′-MDI (diphenylmethane diisocyanate) 12 wt. %

(14) The composition was prepared as described in Example 1. The density of the product was 1.08 g/cm.sup.3. The viscosity significantly increased at 130° C. and the product was already gelled and unusable after 1.5 h (viscosity no longer measurable).

Example 5 (Comparative Example)

(15) In a heated and stirred tank reactor, a reactive hot-melt adhesive composition having free isocyanate groups was prepared from the following components:

(16) TABLE-US-00005 Polyester 1 (adipic acid and hexanediol-1,6, OH number   10 wt. % 30) Polyester 2 (dodecanedioic acid and hexanediol-1,6, OH   30 wt. % number 30) Polyester 3 (phthalic acid, isophthalic acid and neopentyl 37.95 wt. % glycol, OH number 30) Thermoplastic polyurethane (TPU, Pearlbond ® 501,    5 wt. % Lubrizol) Hollow glass spheres (non-neutralized, 3M Glass Bubbles    5 wt. % K20) Phosphorous acid (H.sub.3PO.sub.3)  0.05 wt. % 4,4′-MDI (diphenylmethane diisocyanate)   12 wt. %

(17) The composition was prepared as described in Example 1. The density of the product was 1.07 g/cm.sup.3. The viscosity significantly increased at 130° C. and the product was already gelled and unusable after 2 h (increase >500%). The addition of acids therefore does not provide sufficient stabilization.