LATENT REACTIVE ADHESIVE PREPARATIONS

Abstract

The invention relates to the use of solid polycarbodiimide resins having a softening temperature of >+30° C. as cross-linking agents for adhesive dispersions polymers. The mixtures from at least one solid polycarbodiimide resin and at least one polymer dispersion are suitable for producing storage stable latent-reactive adhesive dispersions, latent-reactive adhesive layers, self-supporting latent reactive adhesive films or latent-reactive adhesive powders.

Claims

1. A latently reactive, dispersion polymer-based preparation having a minimum film-forming temperature of ≤+23° C. and a glass transition temperature measured by DSC (heating rate 20 K/min) of ≤0° C. that can be crosslinked with carbodiimides and that comprises at least one polycarbodiimide having a glass transition temperature of at least +30° C. and an average functionality of at least 2.

2. The preparation of claim 1, which is an aqueous dispersion.

3. The preparation of claim 1, which is a pulverulent mixture.

4. The preparation of claim 1, which is a film.

5. The preparation of claim 1, wherein the polycarbodiimide has aliphatically or cycloaliphatically attached carbodiimide groups.

6. The preparation of claim 1, wherein the polycarbodiimide has a particle size dv(50)≤70 μm.

7. The preparation of claim 1, wherein the dispersion polymer is a polyurethane polymer or polyurethane-polyurea polymer.

8. The preparation of claim 1, wherein the dispersion polymer is a semicrystalline polyurethane polymer or polyurethane-polyurea polymer.

9. The preparation of claim 1, wherein the dispersion polymer is a polyurethane polymer or polyurethane-polyurea polymer that comprises polycarbonate segments in the polyol component (A).

10-17. (canceled)

18. The preparation of claim 6, wherein the polycarbodiimide has a particle size dv(50)≤20 μm.

19. The preparation of claim 18, wherein the polycarbodiimide has a particle size dv(50)≤3.4 μm.

20. A substrate coated with the preparation of claim 1.

21. The substrate of claim 20, wherein the substrate is coated with a latently reactive film obtained from the preparation of claim 1.

22. The substrate of claim 21, wherein the substrate is bonded by thermally induced curing of the latent-reactive film.

23. An adhesive comprising the preparation of claim 1.

24. The adhesive of claim 23, wherein the adhesive is a dispersion.

25. The adhesive of claim 23, wherein the adhesive is one or more storage-stable, latently reactive adhesive layers.

26. The adhesive of claim 23, wherein the adhesive is a storage-stable, self-supporting latently reactive adhesive film.

27. The adhesive of claim 23, wherein the adhesive is a storage-stable, self-supporting latently reactive adhesive powder.

Description

EXAMPLES

[0151] The present invention is elucidated further by the examples that follow, without being restricted thereto.

[0152] Starting Materials: [0153] Cycloaliphatic polyisocyanate H12MDI: 4,4′-Diisocyanatodicyclohexylmethane, CAS No. 79103-62-1 (Desmodur® W, Covestro Deutschland AG, Leverkusen, Germany) [0154] Carbodiimidization catalyst: 3-Methyl-1-phenyl-2-phospholene-1-oxide; CAS No. 707-61-9 (Sigma-Aldrich Chemie GmbH, Munich, Germany) [0155] Stabaxol® P: Aromatic polycarbodiimide in powder form. Stabaxol® P is used as a hydrolysis stabilizer for thermoplastic polyurethanes (TPU), polyesters (PET), polyamides (PA), etc. Stabaxol® P has a melting point between 60° C. and 90° C. The carbodiimide content is at least 12.5%. (from Lanxess AG, Köln, Germany) [0156] Stabaxol® P100: Polycarbodiimide in powder form. Stabaxol® P is used as a hydrolysis stabilizer inter alia for polyesters (PET), polyamides (PA), etc. Stabaxol® P 100 has a melting point between 100° C. and 120° C. The carbodiimide content is at least 13%. (from Lanxess AG, Köln, Germany) [0157] BorchiGel® A LA: Thickener for aqueous polyacrylate-based coating systems. (Borchers GmbH, Berghausener Str. 100, 40764 Langenfeld, Germany) [0158] BorchiGel® L75N: Polyurethane-based liquid thickener (Borchers GmbH, Berghausener Str. 100, 40764 Langenfeld, Germany) [0159] Lucramul® 1820 liquid: Nonionic dispersant base: Fatty alcohol (C16-C18) ethoxylated (LEVACO Chemicals GmbH, Chempark Leverkusen, 51368 Leverkusen, Germany) [0160] Disperbyk 191: VOC- and solvent-free wetting/dispersing additive for water-based paint systems and adhesives. Suitable for binder-free and binder-containing pigment concentrates. Specially optimized for emulsion systems. (BYK-Chemie GmbH 46483 Wesel) [0161] BYK® 024: VOC-free silicone-containing defoamer for water-based dispersion paints, printing inks and overprint varnishes and also dispersion adhesives. (BYK-Chemie GmbH 46483 Wesel) [0162] PUD 1: Dispercoll® U 2824 XP: Polyester diol-based polyurethane dispersion from Covestro Deutschland AG, 51365 Leverkusen; solids content approx. 40% by weight. The polymer contains approx. 18 mmol of COOH groups/100 g. The polymer has a glass transition temperature of approx. −40° C. The melting point of the crystalline segments in the polyurethane polymer chain is +47° C. [0163] PUD 2: Dispercoll® U XP 2643: Polypropylene glycol-based polyurethane dispersion from Covestro Deutschland AG, 51365 Leverkusen; solids content approx. 40% by weight. The polymer contains approx. 18 mmol of COOH groups/100 g. The polymer has a glass transition temperature of approx. −50° C.

[0164] Formulations:

Example 1

Preparation of a Solid Polycarbodiimide

[0165] A 1 L flat-flange-jointed beaker is charged with 524 g of Desmodur® W, which is reacted with 129 g of dibutylamine over a 2 h period. 3.25 g of 3-methyl-1-phenyl-2-phospholene oxide is then added and the carbodiimidization reaction is initiated by heating the reaction mixture to 180° C. The reaction mixture is held at this temperature for 60 h. The polycarbodiimide resin is then poured onto a metal sheet, causing it to solidify.

[0166] The polycarbodiimide resin has a glass transition temperature of +35° C.

[0167] The solid polycarbodiimide (example 1) was ground to the appropriate particle size dv50<100 μm by grinding in a knife mill or a jet mill (Hosowaka-Alpine model 100 AFG).

TABLE-US-00002 Carbodiimide content Example dv10 dv50 dv90 [meq DCC/g] 1a 15.0 65.8 186   3.0 1b  6.3 20.8 50.9 3.0 1c  1.1  3.4  7.7 3.3 dv values in μm

[0168] 2a and 2b are non-inventive comparative examples. These polycarbodiimide powders are used as hydrolysis stabilizers for polymers comprising polyester segments (polyesters, TPUs, etc.).

TABLE-US-00003 Carbodiimide content Example dv10 dv50 dv90 *[meq DCC/g] 2a Staboxol P 100 21.3  86.9 219 3.2 2b Stabaxol P    15.5 105   357 3.3 dv values in μm

[0169] *For better comparability, the carbodiimide content [meq DCC/g] was calculated from the information in the data sheets.

[00001]$meq\frac{DCC}{g}=\frac{CDI\left[\%\right]}{\frac{40g}{\mathrm{mol}}}\frac{1000\mathrm{mmol}/\mathrm{mol}}{100}$

[0170] Preparation of the Aqueous Formulation Comprising Polycarbodiimide Powder: [0171] Example 3a and 3b: 100 g of polycarbodiimide powder 1a or 1b, 135 g of water, 10 g of Lucramul® 1820 liquid, and 2.6 g of BorchiGel® ALA are added to a beaker and mixed with a dissolver disk at 3000 rpm for 5 min. A pseudoplastic paste forms that can be stirred directly into the polymer dispersion. [0172] Example 4: 100 g of polycarbodiimide lc, 142 g of water, 20 g of Disperbyk® 191, 1.4 g of BYK® 024, and 4 g of BorchiGel® L 75N are added to a beaker and mixed with a dissolver disk at 3000 rpm for 5 min. A viscous paste forms that can be stirred directly into the polymer dispersion. [0173] Example 5 and 6: 100 g of polycarbodiimide example 2a or 2b, 136 g of water, 20 g of Disperbyk® 191, 1.4 g of BYK® 024, and 4 g of BorchiGel® L 75N are added to a beaker and mixed with a dissolver disk at 3000 rpm for 5 min. A viscous paste forms that can be stirred directly into the polymer dispersion.

TABLE-US-00004 Polycarbodiimide Aqueous formulation of powder polycarbodiimide powder 1a Example 3a 1b Example 3b 1c Example 4  2a Example 5  2b Example 6 

[0174] Reactive Polymer Dispersion:

TABLE-US-00005 Aqueous Polymer formulation of Molar ratio: dispersion polycarbodiimide meq Example PUD 1 PUD 2 3a 3b 4 DCC:—COOH  7* 100 — — — — —  8 100 —  7.4 — — 1.4:1    9 100 — 15.1 — — 2.5:1   10 100 — — 14.8 — 2.5:1   11 100 — — 29.6 — 5.0:1   12 100 — — — 10.8 2:1 13 100 — — — 21.6 4:1 14* — 100 — — — — 16 — 100  7.4 — — 1.4:1   17 — 100 15.1 — — 2.5:1   18 — 100 — 14.8 — 2.5:1   19 — 100 — 29.6 — 5.0:1   20 — 100 — — 10.8 2:1 21 — 100 — — 21.6 4:1 All quantities stated in g

[0175] Comparative examples with solid nolycarbodiimide for use as hydrolysis stabilizers

TABLE-US-00006 Polymer Aqueous formulation Molar ratio: meq dispersion polycarbodiimide DCC:—COOH Example PUD 1 5  6  22* 100 22.9 4:1 23* 100 22.9 4:1 All quantities stated in g The examples marked with * are comparative examples

[0176] Results:

[0177] Oscillation Measurements:

[0178] The oscillation measurements are carried out on dried adhesive films. For this purpose, the dispersions example 7*, 10, 11, 14*, 18, and 19 were poured into Teflon dishes such that the adhesive polymers had a layer thickness of approx. 1 mm after drying. After storage for one week at 23° C. and 50% relative humidity, the film samples were investigated in an oscillation rheometer (ARES, TA-Instruments).

[0179] Softening Temperature of the Adhesive Bond:

TABLE-US-00007 Thermal activation 1 min at temperature Example 70° C. 80° C. 90° C. 100° C. 110° C. 120° C.  7* 33 33 33 33 33 33  8 33 37 32 33 29 37  9 40 37 39 36 35 40 10 37 34 42 37 43 46 11 43 41 40 45 52 65 12 53 53 53 56 55 55 13 54 52 53 59 58 57 14* 26 26 26 26 26 26 16 26 24 38 32 29 32 17 29 28 42 38 37 48 18 50 56 67 76 86 115 19 71 82 84 113 107 96 20 50 64 72 101 103 118 21 59 48 105 116 121 124 All numerical values [° C.]

TABLE-US-00008 Thermal activation 5 min at temperature Example 70° C. 80° C. 90° C. 100° C. 110° C. 120° C.  7* 33 33 33 33 33 33  8 39 37 36 39 45 48  9 40 40 42 45 45 51 10 42 45 51 56 104 105 11 44 49 60 69 138 138 12 53 55 55 59 64 63 13 55 66 89 102 127 119 14* 26 26 26 26 26 26 16 39 45 57 57 71 95 17 43 42 58 69 85 105 18 58 67 103 141 140 138 19 111 99 97 128 119 117 20 70 86 86 96 92 106 21 128 139 130 137 135 142 All numerical values [° C.]

[0180] The crosslinking effect of solid polycarbodiimide (examples 2a and 2b and also 3) in the adhesive layers—produced from the polyurethane dispersions PUD 1 and PUD 2—is clear. The softening temperatures of the adhesive bonds increase with rising temperature and with increasing duration of exposure to heat. The increase in the softening temperature is directly due to the polymer crosslinking and thus to the decrease in the flowability of the adhesive polymer at elevated temperature.

[0181] Storage of the adhesive-coated substrates for 1 month at 23° C./50% rel. humidity:

TABLE-US-00009 Thermal activation 5 min at temperature Example 70° C. 80° C. 90° C. 100° C. 110° C. 120° C. 12 53 53 58 61 71 81 13 54 57 66 80 102 128 20 58 65 75 81 86 87 21 134 136 140 142 143 141 All numerical values [° C.]

[0182] Storage of the adhesive-coated substrates for 2 months at 23° C./50% rel. humidity:

TABLE-US-00010 Thermal activation 5 min at temperature Example 70° C. 80° C. 90° C. 100° C. 110° C. 120° C. 12 53 54 57 62 67 86 13 54 59 68 79 99 131 20 38 56 76 77 80 85 21 87 128 137 128 135 131 All numerical values [° C.]

[0183] The stability of the reactive adhesive layer on the substrate is likewise clear. Even after storage of the coated substrates for 2 months, it is possible to produce adhesive bonds in which the softening temperatures are above the softening temperatures of the adhesive polymers without polycarbodiimide crosslinkers (comparative examples 7* and 14*).

[0184] Stability of the Polycarbodiimide Powders in Aqueous Formulation:

[0185] The aqueous polycarbodiimide subspersion example 3 was stored at 23° C. The carbodiimide concentration of the fresh polycarbodiimide suspension and of the polycarbodiimide suspension stored for 1 month or 2 months was determined after dissolving the dried polycarbodiimide resin in xylene.

TABLE-US-00011 Age of the aqueous polycarbodiimide suspension Example 3 Fresh 3.2 1 week 3.3 1 month 3.1 2 months 3.0

[0186] All data in meq DCC/g polycarbodiimide powder.

[0187] The aqueous formulations of the solid polycarbodiimide (example 3) are adequately stable for at least 2 months.

[0188] FIG. 1 shows that the crosslinking of the polymer chains of the dispersion polymer from PUD 1 by the solid polycarbodiimide (example 3b) is clear: [0189] i. Polymer from example 7 (without crosslinker) is G′<G″ over the entire temperature range [0190] ii. Polymer from example 10: G′ increases from 94° C.; G′=G″ at 120° C. [0191] iii. Polymer from example 11: G′ increases from 86° C.; G′=G″ at 105° C.

[0192] FIG. 2 shows that the crosslinking of the polymer chains of the dispersion polymer from PUD 2 by the solid polycarbodiimide (example 3b) is clear: [0193] i. Polymer from example 14 (without crosslinker)=G′<G″ at 100° C. [0194] ii. Polymer from example 18: G′>G″ over the entire temperature range. The separation between G′ and G″ increases with increasing temperature. [0195] iii. Polymer from example 19: G′>G″ over the entire temperature range. The separation between G′ and G″ increases with increasing temperature.

[0196] FIG. 3 shows that the Staboxol® P 100 used as a hydrolysis stabilizer (example 2a) has no crosslinking effect at up to 160° C. The value for G′ is below the value of G″ over the entire temperature range.

[0197] FIG. 4 shows that the Staboxol P used as a hydrolysis stabilizer (example 2b) has no crosslinking effect at up to 160° C. The value for G′ is below the value of G″ over the entire temperature range.