METHOD FOR PRODUCING POLYURETHANE HARD FOAM COMPOSITE ELEMENTS USING MANNICH POLYOLS

Abstract

The present disclosure relates to a method for producing rigid polyurethane foam composite elements, including at least one outer layer and a rigid polyurethane foam layer, by mixing (a) polyisocyanates with (b) compounds having at least two hydrogen atoms reactive with isocyanate groups, (c) optionally flame retardant(s), (d) blowing agent, (e) catalyst, and (f) optionally auxiliaries and adjuvants to form a reaction mixture, applying the reaction mixture to the outer layer, and curing it to form the rigid polyurethane foam. The present disclosure further relates to a rigid polyurethane foam composite element obtainable by such a method.

Claims

1. A method for producing rigid polyurethane foam composite elements, comprising at least one outer layer and a rigid polyurethane foam layer, by mixing (a) polyisocyanates with (b) compounds having at least two hydrogen atoms reactive with isocyanate groups, (c) optionally flame retardant(s), (d) blowing agent, (e) catalyst, and (f) optionally auxiliaries and adjuvants to form a reaction mixture, applying the reaction mixture to the outer layer, and curing it to form the rigid polyurethane foam, where component (b) comprises at least one polyether alcohol (b1), prepared by alkoxylation of a starter or of a starter mixture having an average functionality of 4 to 8 and a hydroxyl number of 300 to 600 mg KOH/g, at least one aromatic Mannich condensate (b2), which may have been alkoxylated, preparable by reaction of an aromatic compound which on an aromatic ring carries at least one hydroxyl group and/or at least one group —NHR, where R is any organic radical or is hydrogen, one or more aldehydes and/or ketones, and one or more primary or secondary amines, at least one aromatic polyester polyol (b3), and optionally chain extenders and/or crosslinking agents, the fraction of aromatic Mannich condensate being greater than 5 wt % to less than 20 wt %, based on the total weight of component (b).

2. The method according to claim 1, wherein the compounds (b) having at least two hydrogen atoms reactive with isocyanate groups comprise chain extenders and/or crosslinking agents (b4).

3. The method according to claim 1 or claim 2, wherein the compounds (b) having at least two hydrogen atoms reactive with isocyanate groups comprise at least one polyether alcohol (b5) having a functionality of 2 to 4 and a hydroxyl number in the range from 100 to less than 300 mg KOH/g.

4. The method according to any of claims 1 to 3, wherein the compounds (b) having at least two hydrogen atoms reactive with isocyanate groups comprise 20 to 60 wt % of one or more polyether alcohols (b1), greater than 5 to less than 20 wt % of one or more aromatic Mannich condensates in alkoxylated or unalkoxylated form (b2), 20 to 60 wt % of an aromatic polyester polyol (b3), and 0 to 15 wt % of chain extenders and/or crosslinking agents (b4) and 0 to 15 wt % of polyether alcohol (b5), based in each case on the total weight of components (b1) to (b5).

5. The method according to any of claims 1 to 4, wherein the hydroxyl number of the compounds (b) having at least two hydrogen atoms reactive with isocyanate groups is 150 to 350 mg KOH/g.

6. The method according to any of claims 1 to 5, wherein the aromatic Mannich condensate (b2) is 1,2-propoxylated and has an OH number of 200 to 650 mg KOH/g.

7. The method according to any of claims 1 to 6, wherein the aromatic polyester polyol (b3) is obtained by esterification of dicarboxylic acids or derivatives thereof, selected from the group consisting of phthalic acid, phthalic acid derivatives, isophthalic acid, isophthalic acid derivatives, terephthalic acid, terephthalic acid derivatives, or mixtures thereof, at least one dialcohol, and at least one fatty acid.

8. The method according to any of claims 1 to 7, wherein the polyester alcohol (b3) has an OH functionality of greater than 2 to less than 4 and a hydroxyl number of 200 to 400 mg KOH/g.

9. The method according to any of claims 1 to 8, wherein the polyisocyanates (a) comprise one or more isocyanates selected from the group consisting of 2,2′-MDI, 2,4′-MDI, 4,4′-MDI and oligomers of MDI.

10. The method according to any of claims 1 to 9, wherein the isocyanate index on mixing of components (a) to (f) is 160 to 230.

11. The method according to any of claims 1 to 10, wherein the catalyst (e) comprises a metal carboxylate or ammonium carboxylate.

12. The method according to any of claims 1 to 11, wherein the blowing agent (d) comprises at least one aliphatic or cycloaliphatic hydrocarbon having 4 to 8 carbon atoms.

13. The method according to any of claims 1 to 12, wherein the rigid polyurethane foam composite element is produced continuously by the double belt process.

14. The method according to any of claims 1 to 13, wherein the rigid polyurethane foam composite element has a thickness of 30 to 100 mm.

15. A rigid polyurethane foam composite element obtainable by a method according to any of claims 1 to 12.

Description

EXAMPLES

Starting Materials:

[0095] Polyether polyol 1: Polyether alcohol with a hydroxyl number of 490 mg KOH/g and an average functionality of 4.3, prepared by propoxylation of a mixture of sucrose and glycerol as starters.

[0096] Polyether polyol 2: Polyether polyol with a hydroxyl number of 188 mg KOH/g and a functionality of 2.0, prepared by ethoxylation of ethylene glycol as starter.

[0097] Polyether polyol 3: Polyether polyol with a hydroxyl number of 605 mg KOH/g and a functionality of 3.0, prepared by ethoxylation of trimethylolpropane as starter.

[0098] Polyester polyol 1: Product of esterification of terephthalic acid, diethylene glycol, oleic acid, and a trimethylolpropane ethoxylated to a hydroxyl number of 600 mg KOH/g, the product having a hydroxyl number of 245 mg KOH/g and a functionality of 2.5.

[0099] Polyester polyol 2: Product of esterification of terephthalic acid, diethylene glycol, oleic acid, and a glycerol ethoxylated to a hydroxyl number of 530 mg KOH/g, the product having a hydroxyl number of 245 mg KOH/g and a functionality of 2.5.

[0100] Mannich polyol 1: Desmophen® M530 from Covestro: Propoxylated Mannich condensate synthesized from bisphenol A, formaldehyde, and diethanolamine, having a hydroxyl number of 530 mg KOH/g and an average functionality of 3.0.

[0101] Mannich polyol 2: Rokopol® RF 151 from PCC Rokita: Propoxylated Mannich condensate synthesized from nonylphenol, formaldehyde, and diethanolamine, having a hydroxyl number of 450 mg KOH/g.

[0102] TCPP: Tris(2-chloroisopropyl) phosphate

[0103] TEP: Triethyl phosphate

[0104] Niax® L 6635: Silicone-containing foam stabilizer from Momentive

[0105] Catalyst A: Trimerization catalyst consisting of 47 wt % of potassium acetate in solution in monoethylene glycol

[0106] Catalyst B: Dimethylcyclohexylamine

[0107] Pentane S 80/20: Mixture of 80 wt % n-pentane and 20 wt % isopentane.

[0108] Lupranat® M50: Polymeric methylenediphenyl diisocyanate (PMDI), with a viscosity of around 500 mPa*s at 25° C.

[0109] In the production of the rigid polyurethane foam composite elements 50 mm, 100 mm, and 170 mm thick in the double belt process, the polyol components shown in table 1 and conditioned to 20±1° C. were reacted with Lupranat® M50, which was likewise conditioned at 20±1° C. The amount of Lupranat® M50 was always selected such that all of the rigid foams produced had an isocyanate index of 200±10.

[0110] For producing the composite elements, the lower outer layer used was an aluminum foil with a thickness of 0.05 mm, heated to 35±2° C., and an aluminum sheet with slight profiling, 0.5 mm thick and heated to 37±1° C. The temperature of the double belt was always 50±1° C.

[0111] To produce the composite elements 50 mm thick, the amount of catalyst B and water was selected such that the gel time of the reaction mixture was exactly 25 seconds and the contact time of the reaction mixture with the upper belt was exactly 20 seconds, and the foam had an overall density of 36.5±1 g/l.

[0112] To produce the composite elements 100 mm thick, the amount of catalyst B and water was selected such that the gel time of the reaction mixture was exactly 30 seconds and the contact time of the reaction mixture with the upper belt was exactly 24 seconds, and the foam likewise had an overall density of 36.5±1 g/l.

[0113] To produce the composite elements 170 mm thick, the amount of catalyst B and water was selected such that the gel time of the reaction mixture was exactly 35 seconds and the contact time of the reaction mixture with the upper belt was exactly 29 seconds, and the foam had an overall density of 36.5±1 g/l.

[0114] Based on components a) to f), all formats were processed with a pentane S 80/20 fraction of 1.8 wt %.

TABLE-US-00001 TABLE 1 Comparative Inventive Comparative Inventive Comparative Inventive example 1 example 1 example 2 example 2 example 3 example 3 Polyether 28.2 28.2 28.2 28.2 24.5 24.5 polyol 1 [parts by wt.] Polyether 5.5 5.5 5.5 5.5 polyol 2 [parts by wt.] Polyether 5.5 5.5 polyol 3 [parts by wt.] Polyester 38.3 28.3 polyol 1 [parts by wt.] Polyester 38.3 28.3 38.5 28.5 polyol 2 [parts by wt.] Mannich 10.0 10.0 polyol 1 [parts by wt.] Mannich 10.0 polyol 2 [parts by wt.] TCPP 24.5 24.5 24.5 24.5 24.0 24.0 [parts by wt.] TEP 3.5 3.5 [parts by wt.] Niax L6635 2.5 2.5 2.5 2.5 2.5 2.5 [parts by wt.] Catalyst A 1.0 1.0 1.0 1.0 1.0 1.0 [parts by wt.] Pentane S 1.8 1.8 1.8 1.8 1.8 1.8 80/20 Element 50 50 100 100 170 170 thickness [mm]

[0115] For all of the inventive and comparative examples, samples with a length of 2.0 m and a width of 1.25 m were taken. The properties described below were determined on these samples.

[0116] These properties were determined as follows:

Determination of Transverse Tensile Strength:

[0117] Further test specimens with dimensions of 100 mm×100 mm×sandwich thickness (50 mm, 100 mm, 170 mm) were taken from the samples, using a band saw. The test specimens were taken at identical locations distributed over the width of the element (left, center, right), and the transverse tensile strength of the foam, or the adhesion to the outer layer, was determined in accordance with the sandwich standard DIN EN ISO 14509-A.1 according to EN 1607.

Determination of Compressive Strength:

[0118] Further test specimens with dimensions of 100 mm×100 mm×sandwich thickness (50 mm, 100 mm, 170 mm) were taken from the samples, using a band saw. The test specimens were taken at identical locations distributed over the width of the element (left, center, right), and the compressive strength of the foam was determined in accordance with the sandwich standard DIN EN ISO 14509-A.2 according to EN 826.

Assessment of Foam Surface after Removal of the Lower Outer Layers:

[0119] Following mechanical removal of the aluminum foil and of the aluminum sheets, to which the liquid reaction mixture is applied directly in the double belt process (lower outer layer), the foam surfaces were assessed visually and rated, with rating 1 denoting the best foam surface and rating 5 denoting the poorest foam surface:

TABLE-US-00002 Aluminum foil Profiled sheet Rating 1 Visually flawless (velvet Visually flawless (velvet skin) skin) Rating 2 Small areas lacking Small areas lacking conformity conformity Rating 3 Void depth: <0.2 cm Void depth: <0.2 cm Rating 4 Void depth: 0.3-0.6 cm Void depth: 0.3-0.6 cm Rating 5 Void depth: >0.6 cm Void depth: >0.6 cm

TABLE-US-00003 TABLE 2 Comparative Inventive Comparative Inventive Comparative Inventive example 1 example 1 example 2 example 2 example 3 example 3 Overall density 36.2 35.8 36.1 36.4 37.1 36.3 [g/l] Pressure 0.115 0.147 0.118 0.161 0.121 0.157 [N/mm.sup.2] Tensile 0.09 0.17 0.13 0.17 0.08 0.12 [N/mm.sup.2] Sheet surface 6 4 2 1 1 1 Foil surface 5 3 2 2 1 1

[0120] The results in table 2 show that the tensile strengths of the foams produced in accordance with the inventive examples are much higher than those of the corresponding comparative examples. Additionally, the foams from all inventive examples exhibit significantly better compressive strength in comparison to the foams from all comparative examples.

[0121] Furthermore, the surface quality with respect to both outer layers (aluminum foil and profiled sheet) is significantly improved in the foam from inventive example 1 relative to the foam from comparative example 1. Relative to the foam from comparative example 2, as well, the foam from inventive example 2 displays qualitative advantages at the interface with the profile sheet. From experience, surface defects between foam surfaces and the outer layer running at the bottom in the double belt process occur with particular frequency during the production of relatively thin sandwich elements. The polyol components of the invention, described by way of example using inventive examples 1, 2, and 3, therefore make it possible to achieve not only improved foam mechanics but also a significant improvement in foam quality, especially in the case of processing to form rigid foam composite elements having thicknesses ≤100 mm.