STORAGE-STABLE POLYURETHANE CASTING COMPOUND FOR EMBEDDING HOLLOW FIBRES IN THE PRODUCTION OF FILTER ELEMENTS

Abstract

Disclosed are polyurethane encapsulating compounds for embedding hollow fibers of filter elements, obtainable by mixing a polyol component (A) and an isocyanate component (B), including at least one aromatic isocyanate, to give a reaction mixture and reacting the mixture to completion to give the polyurethane encapsulating compound. The polyol component (A) includes at least one fatty-acid-based polyol (a1) having a hydroxyl number of greater than 50 to less than 500 mg KOH/g and a functionality of from 2-6, and at least one bismuth catalyst (a2), obtainable by mixing a bismuth carboxylate (a2-1) with an amine compound (a2-11) having at least one tertiary nitrogen atom and at least one isocyanate-reactive hydrogen atom. The molar ratio of bismuth to amine compound (a2-11) is 1:0.5-1:50. Also disclosed are methods for producing filter elements using the polyurethane encapsulating compounds and to uses of the polyurethane encapsulating compounds for the embedding of hollow fibers.

Claims

1. A polyurethane encapsulating compound for embedding hollow fibers of filter elements, obtainable by mixing a polyol component (A) and an isocyanate component (B), comprising at least one aromatic isocyanate, to give a reaction mixture and reacting the mixture to completion to give the polyurethane encapsulating compound, wherein the polyol component (A) comprises (a1) at least one fatty-acid-based polyol having a hydroxyl number of greater than 50 to less than 500 mg KOH/g and a functionality of from 2 to 6 and (a2) at least one bismuth catalyst, obtainable by mixing a bismuth carboxylate (a2-1) with an amine compound (a2-11) having at least one tertiary nitrogen atom and at least one isocyanate-reactive hydrogen atom, wherein the molar ratio of bismuth to the amine compound (a2-11) is 1:0.5 to 1:50.

2. The polyurethane encapsulating compound according to claim 1, wherein the amine compound (a2-11) has at least three isocyanate-reactive hydrogen atoms.

3. The polyurethane encapsulating compound according to claim 1, wherein the amine compound (a2-11) is an alkoxylated amine having a hydroxyl number of from 500 to 1200 mg KOH/g and having 3 to 6 hydrogen atoms that are reactive toward isocyanate groups.

4. The polyurethane encapsulating compound according to claim 3, wherein the amine compound (a2-11) is a diamine-started propylene oxide having a nominal functionality of from 3 to 6 and a hydroxyl number of from 500 to 900 mg KOH/g.

5. The polyurethane encapsulating compound according to claim 1, wherein the fat-based polyol (a1) comprises castor oil or the alkoxylation product of castor oil.

6. The polyurethane encapsulating compound according to claim 1, wherein the polyol component (A) comprises at least one, at least difunctional, polyol (a3) which has a functionality of from 2 to 8 and a hydroxyl number of from 600 to 1350 mg KOH/g and does not have a tertiary nitrogen atom.

7. The polyurethane encapsulating compound according to claim 1, wherein the proportion of the fatty-acid-based polyol (a1) is 60 to 98% by weight, the proportion the proportion of the bismuth catalyst (a2) is 0.001 to 1.0% by weight and the proportion of the polyol (a3) is 0 to 25% by weight, based in each case on the total weight of components (a1) to (a3).

8. The polyurethane encapsulating compound according to claim 1, wherein the isocyanate component (B) comprises prepolymers of isomers and/or homologs of diphenylmethane diisocyanate.

9. A method for producing filter elements in which a bundle of hollow fibers is embedded and cured at their end in a polyurethane encapsulating compound according to claim 1.

10. The method according to claim 9, wherein the filter element is a filter element for use in medicine.

11. The method according to claim 10, wherein the filter element is a dialysis filter element.

12. The method according to claim 9, wherein the filter element is a water filter element.

13. The use of a polyurethane encapsulating compound according to claim 1 for the partial embedding of hollow fibers.

Description

EXAMPLE E5

[0080] A 250 ml four-neck flask with thermometer, stirrer, condenser and nitrogen feed was initially charged with 75.00 g of Cat 3 and heated to 60° C. 44.23 g of molten Poly 6 was then added slowly to the catalyst while stirring. At the end of addition, the mixture was stirred further for an additional 15 minutes and 30 g of CE 3 were added. The mixture was then decanted and used for further experiments. These reaction products likewise displayed good storage stability and constant reactivity, as the appended example 6 shows:

TABLE-US-00004 TABLE 3 E6 Poly 1 94.90 Poly 2 5.00 Cat from example E5 0.10 Iso 1 X Mixing ratio 100:X 69.2 Gel time [mm:ss]  1 d 06:21 14 d 06:18 90 d 06:12