METHOD FOR PRODUCING OPEN-CELL RIGID FOAMS COMPRISING URETHANE GROUPS AND ISOCYANURATE GROUPS

Abstract

The invention provides a process for producing an open-cell rigid polyurethane foam by a slabstock foam process and also provides for the use of the rigid polyurethane foam obtained in vacuum insulation panels.

Claims

1. A process for producing an open-cell rigid polyurethane foam, the process comprising: performing a slabstock foam process by reacting a reaction mixture comprising a. a polyisocyanate; b. a compound comprising a group reactive towards at least one isocyanate group and having a functionality between 1.9 to 8; c. a catalyst; and d. a blowing agent; e. in the presence of a stabilizer e2) and a cell opener e1), wherein the cell opener e1) is a mixture of at least one macromolecular unsaturated hydrocarbon with an ester, and a weight ratio of the cell opener e1) to the stabilizer e2) is at least 0.2; and wherein i. the component b) comprises more than 1% by weight, based on a total weight of the component b), of a chain extender and/or crosslinking agent as the compound b-1) wherein the chain extender and/or crosslinking agent is at least one selected from the group consisting of an alkanolamine, a diol and triol, having a molecular weight of less than 400 g/mol and a functionality between 2 to 3 and ii. the blowing agent is a chemical blowing agent or a mixture of chemical blowing agents, and iii. an isocyanate index is from 130 to 215.

2. The process according to claim 1, wherein the component b-1) is a diol or triol.

3. The process according to claim 1, wherein the component b-1) is a diol.

4. The process according to claim 1, wherein the molecular weight of the component b-1) is between 60 to 300 g/mol.

5. The process according to claim 1, wherein the component b) further comprises component b-2).

6. The process according to claim 5, wherein the component b-2) is selected from the group consisting of a polyether alcohol and a polyester alcohol.

7. The process according to claim 5, wherein the component b) consists of components b-1) and b-2).

8. The process according to claim 1, wherein the blowing agent d) is selected from the group consisting of water and a mixture of water with one or more further chemical blowing agents.

9. The process according to claim 1, wherein the weight ratio of the cell opener e1) to the stabilizer e2) is from 0.2 to 10.

10. The process according to claim 1, wherein the open-cell rigid polyurethane foam obtained has a density of 30 to 100 g/1.

11. The process according to claim 1, wherein the reaction mixture is free foamed.

12. An open-cell rigid polyurethane foam obtainable by the process according to claim 1.

13. The open-cell rigid polyurethane foam obtainable by the process according to claim 1, having a density between 30-100 g/l.

14. A core material of a vacuum insulation panel, the core material comprising: an open-cell rigid polyurethane foam produced by the process according to claim 1.

Description

EXAMPLES

[0070] Measurement Methods:

[0071] Measurement of Hydroxyl Number:

[0072] Hydroxyl numbers are determined according to DIN 53240 (1971-12).

[0073] Viscosity Determination:

[0074] The viscosity of the polyols is determined, unless specified otherwise, at 25 C. according to DIN EN ISO 3219 (1994) using a Haake Viscotester 550 with plate/cone measurement geometry (PK100) using the PK 1 1 cone (diameter: 28 mm; cone angle: 1) at a shear rate of 40 1/s.

[0075] Compressive Strength:

[0076] Compressive strength is determined according to DIN ISO 844 EN DE (2014-11).

[0077] Open-Cell Content (OC) The determination of the open-cell content with corresponding measurement time was obtained in accordance with DIN EN ISO 4590.

[0078] Foam Density

[0079] The foam density was determined by measuring the foam density in the core in accordance with DIN EN ISO 845.

[0080] Starting Materials

[0081] a) Isocyanate (Polymer MDI)

[0082] Isocyanate 1 Lupranat M20 NCO content=31.8 g/100 g from BASF

[0083] b) Polyols [0084] Polyol 1 (b-2): OH number=490; prepared by addition of propylene oxide onto sucrose, and glycerol [0085] Polyol 2 (b-2): OH number=105; prepared by addition of propylene oxide onto propylene glycol [0086] Polyol 3 (b-2): OH number=250; prepared by addition of propylene oxide onto propylene glycol [0087] Polyol 4 (b-1): Monoethylene glycol (MEG) as chain extender [0088] Polyol 5 (b-1): Glycerol as chain extender [0089] Polyol 6 (b-2): OH number=490; prepared by addition of propylene oxide onto sorbitol [0090] Polyol 7 (b-2): OH number=42, prepared by addition of propylene oxide and ethylene oxide onto glycerol

[0091] c) Catalysts

[0092] Catalyst 1 (c-1): Polycat 58 (Evonik)

[0093] Catalyst 2 (c-2): Potassium acetate in MEG, 47% by weight (BASF)

[0094] Catalyst 3 (c-3): Dimethylcyclohexylamine (DMCHA)

[0095] d) Blowing Agents:

[0096] Water (d-1)

[0097] Cyclopentane 70: cyclopentane/isopentane (70:30%) (physical blowing agent)

[0098] f) Additives:

[0099] Stabilizer (e2): Tegostab B8870 from Evonik (stabilizer)

[0100] Cell opener (e1): Ortegol 501 from (Evonik)

[0101] Components a) to e) were mixed to give a polyol component and reacted with the isocyanate. The amounts of the feedstocks used can be found in table 1. C denotes comparative examples, IE denotes inventive examples. Mixing was effected in a mixing head (for example low-pressure or high-pressure process, the processing of IE 7 was effected in the high-pressure process) or by means of stirring in a reservoir vessel. The reaction mixture was discharged into a laboratory mold having side lengths 418 mm700 mm455 mm and allowed to cure there.

TABLE-US-00001 TABLE 1 C1 C2 IE1 IE2 IE3 C3 C4 IE4 Polyol 1 (b-2) [wt. %] 40.1 42.7 41.3 41.3 41.2 41.3 41.9 41.5 Polyol 2 (b-2) [wt. %] 40.1 42.7 41.3 41.3 41.2 41.3 41.9 41.5 Polyol 3 (b-2) [wt. %] 8.3 8.9 8.6 8.6 8.6 8.6 8.7 8.6 Polyol 4 (*) (b-1) [wt. %] 2.7 2.7 2.7 2.7 0.95 1.9 Polyol 5 (b-1) [wt. %] Polyol 6 (b-2) [wt. %] Polyol 7 (b-2) [wt. %] Catalyst 1 (c-1) [wt. %] 0.45 0.5 0.29 0.29 0.39 0.29 0.47 0.47 Catalyst 2 (.sup.i) (c-2) [wt. %] 0.64 0.7 0.93 0.93 0.93 0.93 0.95 0.94 Catalyst 3 (c-3) [wt. %] Cyclopentane 70 [wt. %] 6.8 Water (d-1) [wt. %] 0.5 1.26 1.66 1.66 1.85 1.66 1.95 1.93 Cell regulators (e) Stabilizer (e2) [wt. %] 0.82 0.87 0.83 0.83 0.83 0.83 0.85 0.85 Cell opener (e1) [wt. %] 2.27 2.42 2.34 2.34 2.34 2.34 2.37 2.35 Reaction parameters: Index 244 225 202 200 210 240 200 200 Sum of [wt. %] 100 100 100 100 100 100 100 100 b + c + d + e) (*) Component b-1) [wt. %] 0.34 0.37 3.22 3.22 3.22 3.22 1.45 2.38 Ratio of e1:e2 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 Isocyanate 1 [wt. %] 100 100 100 100 100 100 100 100 Cream time: [s] 55 55 55 35 55 70 45 47 Fiber time [s] 225 240 162 100 190 200 185 175 Core density [kg/m.sup.3] 67.5 87.2 65.9 55 64.6 76.3 60.8 60.3 Experimental results: Tmax [ C.] 147 164 180 190.1 169.6 172.3 165.6 168.7 OC (corr) [%] 93 19 95 100 93 99 78 91 Measurement [s] 1100 926 674 344 550 589 1708 821 time for OC Mixing iii) iii) iii) iv) iii) iii) iii) iii) Core discoloration no no no no no yes no no IE5 C5 IE6 IE7 IE8 IE9 C6 C7 Polyol 1 (b-2) [wt. %] 41.3 43.7 42.2 43.5 39.7 41.8 Polyol 2 (b-2) [wt. %] 41.3 41.3 41.3 41.3 41.3 41.3 20.0 20.0 Polyol 3 (b-2) [wt. %] 8.6 8.6 8.6 8.6 8.6 8.6 Polyol 4 (*) (b-1) [wt. %] 2.7 2.7 2.7 2.7 2.7 Polyol 5 (b-1) [wt. %] 2.7 Polyol 6 (b-2) [wt. %] 48.8 47.9 Polyol 7 (b-2) [wt. %] 25.0 25.0 Catalyst 1 (c-1) [wt. %] 0.29 0.29 0.29 0.29 0.29 0.29 Catalyst 2 (.sup.i) (c-2) [wt. %] 0.93 0.93 0.93 0.93 0.93 0.93 0.08 0.08 Catalyst 3 (c-3) [wt. %] 0.5 0.5 Cyclopentane 70 [wt. %] Water (d-1) [wt. %] 1.66 1.95 1.66 1.66 1.66 1.2 1.66 1.66 Cell regulators (e) Stabilizer (e2) [wt. %] 0.83 0.83 0.83 0.83 0.83 0.83 0.9 Cell opener (e1) [wt. %] 2.34 1.5 0.13 4 2.34 4 4 Reaction parameters: Index 200 200 200 200 200 200 160 160 Sum of [wt. %] 100 100 100 100 100 100 100 100 b + c + d + e) (*) Component b-1) [wt. %] 0.49 3.22 3.22 3.22 3.22 3.22 0.04 0.04 Ratio of e1:e2 2.8 1.8 0.2 4.8 2.8 4.4 Isocyanate 1 [wt. %] 100 100 100 100 100 100 100 100 Cream time: [s] 70 70 70 70 65 55 ii) 40 Fiber time [s] 202 168 172 170 169 148 190 Core density [kg/m.sup.3] 71.4 61.2 62.7 60.9 67.6 78.5 66.6 Experimental results: Tmax [ C.] 175.2 179 179 179 178.5 180 145 OC (corr) [%] 100 43 100 100 100 100 15 Measurement [s] 469 1843 470 986 493 492 1117 time for OC Mixing iii) iii) iii) iii) iii) iii) iii) iii) Core discoloration no no no no no no no

[0102] i) the actual MEG content is increased due to the amount in catalyst 2

[0103] ii) the foam collapses and as a result no PUR foam was obtained

[0104] iii) mixing in a reservoir vessel

[0105] iv) high-pressure mixing

[0106] To determine the course of curing, small foam blocks were foamed in a laboratory mold having a volume of approx. 0.5 dm.sup.3. The machine test was effected by foaming in a wooden mold of approx. 1500 l. The examples according to the invention show that it is possible to produce open-cell PUR/PIR foams based on chemical blowing agents (implementation examples IE 1 and 2). A sufficient open-cell content is necessary for vacuum and VIP applications. This can be achieved in particular by the use of chain extender polyols of the type b-1). The use of excessively small amounts (C4) leads to a reduced open-cell content.

[0107] The prerequisite for producing slabstock foams is that there is no core discoloration, since this leads to a deterioration of the properties and especially to an increased risk of fire. The maximum core temperature in combination with the resulting density is crucial here in particular.

[0108] Both cell openers (e1) and stabilizers (e2) have to be present, since otherwise either no open-cell rigid PUR foam or no rigid PUR foam at all is obtained, see C5 and C6. In this case the ratio of cell opener (e1) to stabilizer (e2) should also be taken into account, since this is important for the open-cell content and accessibility of the open cells. The accessibility of the open cells can be read from the measurement time for the level of open-cell content. The ratio of cell opener (e1) to stabilizers (e2) in this case has to exceed a minimum, see IE 8, IE 6 and 1E7, since otherwise an excessive amount of time is required for evacuating the rigid PUR foam.