INSULATED PIPE CONTAINING POLYURETHANE FOAM WHICH IS FOAMED BY AN ENVIRONMENTALLY FRIENDLY FOAMING AGENT AND HAS A LOW DEGREE OF BRITTLENESS

Abstract

Described herein is a process for producing a pipe insulated with polyurethane foam, where (a) isocyanates are mixed with (b) polyols, (c) blowing agent including at least one aliphatic, halogenated hydrocarbon compound (c1), made up of from 2 to 5 carbon atoms, at least one hydrogen atom and at least one fluorine and/or chlorine atom, where the compound (c1) includes at least one carbon-carbon double bond, (d) catalyst including N,N-dialkylbenzylamine, optionally (e) chain extenders and/or crosslinkers and optionally (f) auxiliaries and additives to give a reaction mixture, the reaction mixture is applied to a pipe for media and is allowed to cure to give the polyurethane foam. Also described herein is an insulated pipe obtained by such a process and a method of using such an insulated pipe as insulated composite wall pipe for district heating or district cooling networks laid in the ground.

Claims

1. A process for producing a pipe insulated with polyurethane foam, comprising mixing (a) an isocyanate, (b) a polyol, (c) a blowing agent comprising at least one aliphatic, halogenated hydrocarbon compound (c1), made up of from 2 to 5 carbon atoms, at least one hydrogen atom and at least one fluorine and/or chlorine atom, where the compound (c1) comprises at least one carbon-carbon double bond, (d) a catalyst comprising N,N-dialkylbenzylamine, (e) optionally chain extenders and/or crosslinkers, and (f) optionally auxiliaries and additives, to give a reaction mixture, wherein the isocyanate index is in the range from 90 to 180, applying the reaction mixture to a pipe for media, and curing the reaction mixture to give the polyurethane foam.

2. The process according to claim 1, wherein the blowing agent (c1) is selected from the group consisting of trifluoropropenes and tetrafluoropropenes, pentafluoropropenes, chlorotrifluoropropenes, chlorodifluoropropenes and chlorotetrafluoropropenes and also mixtures of one or more of these components.

3. The process according to claim 1, wherein the blowing agent (c1) is selected from the group consisting of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (E)), cis-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd (Z)), trans-1, 1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz (E)), cis-1, 1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz (Z)), trans-1,3,3,3-tetrafluoroprop-1-ene (HFO-1234ze (E)), cis-1,3,3,3-tetrafluoroprop-1-ene (HFO-1234ze (Z)) and mixtures of one or more components thereof.

4. The process according to claim 1, wherein the density of the pipe insulation is from 30 to 200 kg/m3.

5. The process according to claim 1, wherein the proportion of blowing agent (c1), based on the total weight of the components (b) and (d), is from 10 to 30% by weight.

6. The process according to claim 1, wherein the proportion of N,N-dialkylbenzylamine is from 0.05 to 3% by weight, based on the total weight of polyols (b) and catalyst (e).

7. The process according to claim 1, wherein N,N-dimethylbenzylamine is used as N,N-dialkylbenzylamine.

8. The process according to claim 1, wherein the production of the insulated pipe is carried out at an isocyanate index of from 105 to 160.

9. The process according to claim 1, wherein the insulated pipe is produced by (A) providing a pipe for media and an outer pipe, wherein the pipe for media is arranged within the outer pipe and an annular gap is formed between pipe for media and outer pipe, (B) introducing the polyurethane reaction mixture into the annular gap and (C) allowing the polyurethane reaction mixture to foam and cure in the annular gap to give the polyurethane foam.

10. A pipe insulated with polyurethane foam, obtained by a process according to claim 1.

11. A method of using a pipe insulated with polyurethane foam according to claim 10, the method comprising using the pipe as insulated composite wall pipe for district heating or district cooling networks laid in the ground.

12. The process according to claim 1, wherein the blowing agent (c1) is selected from the group consisting of tetrafluoropropenes, pentafluoropropenes, and chlorotrifluoropropenes, wherein the unsaturated, terminal carbon atom bears more than one chlorine or fluorine substituent.

13. The process according to claim 1, wherein the blowing agent (c1) is selected from the group consisting of 1,3,3,3-tetrafluoropropene (HFO-1234ze); 1,1,3,3-tetrafluoropropene; 1,2,3,3,3-pentafluoropropene (HFO-1225ye); 1,1,1-trifluoropropene; 1,1,1,3,3-pentafluoropropene (HFO-1225zc); 1,1,1,3,3,3-hexafluorobut-2-ene, 1,1,2,3,3-pentafluoropropene (HFO-1225yc); 1,1,1,2,3-pentafluoropropene (HFO-1225yez); 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd); 1,1,1,4,4,4-hexafluorobut-2-ene and mixtures of two or more of these components.

Description

EXAMPLES

[0062] Table 1 below shows the constituents of a pipe insulation system for discontinuous processing:

TABLE-US-00001 TABLE 1 OH number Part by [mg weight/parts Material Type KOH/g] by weight Sucrose-initiated polyether 403 17.6 TDA-initiated polyether 390 30.0 Sorbitol-initiated polyether 490 12.0 Polyester having a 210 30.0 functionality of 2 Glycerol-initiated polyether 805 5.0 Water — 2.4 Silicone stabilizer Niax 40 3.0 Silicone L-6900 Trans-1-chloro-3,3,3- 22 trifluoropropene

[0063] A PMDI (Lupranat® M 20S: NCO content 31.5%, functionality: 2.7) is used as isocyanate. The polyol component is mixed with the isocyanate in a mass ratio of 100:150 using a hand mixer at a component temperature of in each case 20° C. The index of this foam is 152. Polyurethane foams were produced using different catalyst combinations. The catalyst combinations are indicated in Table 2; all amounts are in parts by weight.

TABLE-US-00002 TABLE 2 Ref. Ex. 1 Ex. 2 Ex. 3 N,N-dimethylcyclohexylamine 0.3 0.3 0.3 0.3 Dabco TMR-31 0.4 0 0 0.4 Potassium acetate w = 50% 0 0 0.2 0 N,N-dimethylbenzalamine 0 0.4 0.4 0.4 S-triazine 0.2 0.2 0 0.2 Cream time [s] 32 29 37 Fiber time [s] 180 170 190 Rise time [s] 290 260 300 Brittleness 6 1 1 1

[0064] Examples 1 to 3 display significantly improved values for the brittleness compared to the reference example without N,N-dimethylbenzalamine at similar curing rates.

[0065] As measure of the brittleness of the rigid polyurethane foam, the brittleness was assessed subjectively immediately after foaming by pressing the foam (brittleness subjective) and graded according to a system of grades from 1 to 6. 1 means that the foam is barely brittle, while 6 means that the foam has a high brittleness.

[0066] Pipes were also foamed using the foams of the reference example and example 3. The brittleness was assessed on taking off the end cap and was no different from the free-foamed specimens.