NON-IONIC HYDROPHYLIZED CROSS-LINKER DISPERSION CONTAINING THERMOLATENTLY BOUND URETHANE/UREA GROUPS

Abstract

The present invention relates to a process for preparing at least one blocked polyisocyanate, comprising the following steps: (A) reacting at least one polyisocyanate with at least one thermally cleavable blocking agent to obtain at least one partially blocked polyisocyanate, (B) reacting the at least one partially blocked polyisocyanate from step (A) with at least one non-ionic hydrophilizing agent to obtain an intermediate product, and (C) reacting the intermediate product obtained in step (B) with at least one thermally cleavable blocking agent to obtain the at least one blocked polyisocyanate. The invention further relates to the use of the blocked polyisocyanate for producing coating agents, adhesives, sealants or elastomers, to corresponding coating agents, adhesives, sealants or elastomers, and to substrates that are provided with coatings obtained using the at least one blocked polyisocyanate according to the invention.

Claims

1. A process for preparing at least one blocked polyisocyanate, comprising the following steps: (A) reacting at least one polyisocyanate with at least one thermally eliminatable blocking agent in order to obtain at least one partly blocked polyisocyanate, (B) reacting the at least one partly blocked polyisocyanate from step (A) with at least one nonionic hydrophilizing agent in order to obtain an intermediate, (C) reacting the intermediate obtained in step (B) with at least one thermally eliminatable blocking agent in order to obtain the at least one blocked polyisocyanate.

2. The process as claimed in claim 1, further comprising: (D) dispersing the at least one blocked polyisocyanate obtained in step (C) in water.

3. The process as claimed in claim 1, wherein the polyisocyanates used are the compounds of relatively high molecular weight that have isocyanurate, urethane, allophanate, biuret, iminooxadiazinetrione, oxadiazinetrione and/or uretdione groups and are based on aliphatic and/or cycloaliphatic diisocyanates.

4. The process as claimed in claim 3, wherein the compounds of relatively high molecular weight that have biuret, iminooxadiazinedione, isocyanurate and/or uretdione groups comprise hexamethylenediamine diisocyanate, isophorone diisocyanate, 4,4′-diisocyanatodicyclohexylmethane, or a combination thereof.

5. The process as claimed in claim 4, wherein the at least one thermally eliminatable blocking agent used in step (A) is selected from the group consisting of 1H-pyrazoles, lactams, phenols, ketoximes, amines, triazoles, esters containing deprotonatable groups or mixtures thereof and/or mixtures with other blocking agents.

6. The process as claimed in claim 1, wherein the at least one thermally eliminatable blocking agent used in step (A) is selected from the group consisting of 1H-pyrazoles, lactams, phenols, ketoximes, amines, triazoles, esters containing deprotonatable groups or mixtures thereof and/or mixtures with other blocking agents.

7. The process as claimed in claim 1, wherein the at least one thermally eliminatable blocking agent used in step (A) and the at least one thermally eliminatable blocking agent used in step (C) are identical.

8. The process as claimed in claim 1, wherein the at least one nonionic hydrophilizing agent is at least one polyoxyalkylene ether containing at least one hydroxyl or amino group.

9. The process as claimed in claim 2, wherein the blocked polyisocyanate in aqueous dispersion has an average particle size of 10 to 400 nm determined in each case by means of laser correlation spectroscopy after dilution of the sample with demineralized water.

10. A blocked polyisocyanate obtained by a process as claimed in claim 1.

11. A polyisocyanate at least partly blocked by at least one thermally eliminatable blocking agent and hydrophilized with at least one nonionic hydrophilizing agent, having a zeta potential of 0 to −15 V.

12. The polyisocyanate as claimed in claim 11, having an acid number below 30 mg KOH/g.

13. The use of the blocked polyisocyanate as claimed in claim 10 for production of coating compositions, adhesives, sealants or elastomers.

14. A coating composition, adhesive, sealant or elastomer comprising at least one blocked polyisocyanate obtained by a process as claimed in claim 1.

15. A substrate provided with a coatings obtained using the at least one blocked polyisocyanate obtained by a process as claimed in claim 1.

Description

EXAMPLES

[0106] Chemicals Used: [0107] Desmodur® Ultra N 3300 isocyanurate based on hexamethylenediamine diisocyanate, Covestro Deutschland AG, Leverkusen, DE

[0108] The further chemicals were purchased from Sigma-Aldrich Chemie GmbH, Taufkirchen, DE.

[0109] Unless stated otherwise, all percentages are percent by weight (% by weight).

[0110] Unless stated otherwise, all analytical measurements were conducted at a temperature of 23° C.

[0111] The viscosities reported were determined by means of rotary viscometry to DIN 53019-2008 at 23° C. with a rotary viscometer from Anton Paar Germany GmbH, Ostfildern, DE.

[0112] NCO contents, unless explicitly stated otherwise, were determined by volumetric means to DIN-EN ISO 11909-2007.

[0113] The reported particle sizes were determined by means of laser correlation spectroscopy (instrument: Malvern Zetasizer 1000, Malvern Inst. Limited) after dilution of the sample with demineralized water.

[0114] The solids contents were ascertained by heating a weighed sample to 120° C. At constant weight, the solids content was calculated by reweighing the sample.

[0115] The check for free NCO groups was conducted by means of IR spectroscopy (band at 2260 cm.sup.−1).

[0116] As a storage test, 250 ml of the dispersion in each case was dispensed and stored both at room temperature and at 40° C. There was a visual check as to whether sediment had formed. Samples with sediment were assessed as being unstable.

[0117] The zeta potential is determined by diluting a small amount of the sample significantly with 1 mmolar potassium chloride solution and homogenizing by stirring. The pH of 8.0 is established using dilute hydrochloric acid or sodium hydroxide solution. The zeta potential is then determined in the “ZetaSizer 3000HSA” (Malvern Instruments, Herrenberg, Germany) at 23° C.

[0118] Acid number is determined to DIN EN ISO 2114—June 2002.

Comparative Example 1

[0119] A standard stirred apparatus was initially charged with 234 g of Desmodur Ultra N 3300 and heated at 40° C. Subsequently, 110.5 g of 3,5-dimethylpyrazole (DMP) was added in portions to the melt such that the temperature did not exceed 75° C. The mixture was stirred at 80° C. until the theoretical isocyanate content went below about 0.59% by weight. Subsequently, 49.5 g of methoxy polyethylene glycol having a number-average molar mass of 750 g/mol was added, and the mixture was stirred at 80° C. until no isocyanate groups were detectable any longer by IR spectroscopy. Then 591 g of deionized water was added with vigorous stirring, with stirring at 40° C. for a further 180 minutes.

[0120] The resultant dispersion had the following properties:

TABLE-US-00001 Solids content: about 39.5% by weight pH: about 5.8 Viscosity about 10 mPa .Math. s Average particle size (LCS): 369 nm

[0121] The dispersion formed two phases overnight and was therefore unusable for further tests.

Comparative Example 2

[0122] A standard stirred apparatus was initially charged with 234 g of Desmodur Ultra N 3300 and heated at 40° C. Subsequently, 49.5 g of methoxy polyethylene glycol having a number-average molar mass of 750 g/mol was added, and the mixture was stirred at 80° C. until the theoretical isocyanate content went below about 16.8% by weight. Subsequently, 110.5 g of 3,5-dimethylpyrazole (DMP) was added in portions to the melt such that the temperature did not exceed 80° C. The mixture was stirred at 80° C. until it was no longer possible to detect any isocyanate groups by IR spectroscopy. Then 591 g of deionized water was added with vigorous stirring, with stirring at 40° C. for a further 180 minutes.

[0123] The resultant dispersion had the following properties:

TABLE-US-00002 Solids content: about 39.8% by weight pH: about 5.6 Viscosity about 10 mPa .Math. s Average particle size (LCS): 343 nm

[0124] The dispersion formed two phases overnight and was therefore unusable for further tests.

Example 3: DMP as Blocking Agent

[0125] A standard stirred apparatus was initially charged with 234 g of Desmodur Ultra N 3300 and heated at 40° C. Subsequently, 58.2 g of 3,5-dimethylpyrazole (DMP) was added in portions to the melt such that the temperature did not exceed 80° C. Then 49.5 g of methoxy polyethylene glycol having a number-average molar mass of 750 g/mol was added, and the mixture was stirred at 80° C. until the theoretical isocyanate content went below about 6.46% by weight. Subsequently, 52.2 g of 3,5-dimethylpyrazole (DMP) was added in portions to the melt such that the temperature did not exceed 80° C. The mixture was stirred at 80° C. until it was no longer possible to detect any isocyanate groups by IR spectroscopy. Then 591 g of deionized water was added with vigorous stirring, with stirring at 40° C. for a further 180 minutes.

[0126] The resultant dispersion had the following properties:

TABLE-US-00003 Solids content: about 39.0% by weight pH: about 5.9 Viscosity about 10 mPa .Math. s Average particle size (LCS): 129 nm Zeta potential: −11.9 V Acid number: <0.2 mg KOH/g

[0127] The dispersion was storage-stable at room temperature and at 40° C. for at least 4 weeks. No phase separation formed within this period of time.

Example 4: Methyl Ethyl Ketoxime as Blocking Agent

[0128] A standard stirred apparatus was initially charged with 234 g of Desmodur Ultra N 3300 and heated at 40° C. Subsequently, 51.3 g of methyl ethyl ketoxime was added gradually to the melt such that the temperature did not exceed 80° C. Then 61.2 g of methoxy polyethylene glycol having a number-average molar mass of 750 g/mol was added, and the mixture was stirred at 80° C. until the theoretical isocyanate content went below about 6.41% by weight. Subsequently, 47.3 g of methyl ethyl ketoxime was added gradually to the melt such that the temperature did not exceed 80° C. The mixture was stirred at 80° C. until it was no longer possible to detect any isocyanate groups by IR spectroscopy. Then 520 g of deionized water was added with vigorous stirring, with stirring at 40° C. for a further 180 minutes; about a further 100 g of water was used here for dilution.

[0129] The resultant dispersion had the following properties:

TABLE-US-00004 Solids content: about 34.4% pH: about 5.7 Viscosity: about 30 mPa .Math. s Average particle size (LCS): 47 nm

[0130] The dispersion was storage-stable at room temperature and at 40° C. for at least 4 weeks. No phase separation formed within this period of time.

Example 5: Caprolactam as Blocking Agent

[0131] A standard stirred apparatus was initially charged with 234 g of Desmodur Ultra N 3300 and heated at 40° C. Subsequently, 68.3 g of caprolactam was added to the melt such that the temperature did not exceed 80° C. Then 51.9 g of methoxy polyethylene glycol having a number-average molar mass of 750 g/mol was added, and the mixture was stirred at 80° C. until the theoretical isocyanate content went below about 6.26% by weight. Subsequently, 61.5 g of caprolactam was added to the melt such that the temperature did not exceed 80° C. The mixture was stirred at 80° C. it was no longer possible to detect any isocyanate groups by IR spectroscopy. Then 624 g of deionized water was added with vigorous stirring, with stirring at 40° C. for a further 180 minutes.

[0132] The resultant dispersion had the following properties:

TABLE-US-00005 Solids content: about 39% by weight pH: about 5.8 Viscosity: about 20 mPa .Math. s Average particle size (LCS): 92 nm

[0133] The dispersion was storage-stable at room temperature and at 40° C. for at least 4 weeks. No phase separation formed within this period of time.