METHOD FOR PRODUCING A RIGID POLYURETHANE-POLYISOCYANURATE FOAM

Abstract

The invention relates to a method for producing rigid polyurethane-polyisocyanurate (PUR/PIR) foams using partially trimerized isocyanate blends. The invention further relates to the rigid polyurethane-polyisocyanurate foams obtainable by said method and to the use thereof in manufacturing composite elements made of the rigid polyurethane-polyisocyanurate foams and suitable coatings. The invention also relates to the composite elements obtainable thereby.

Claims

1. A method of producing a rigid PUR-PIR foam by reacting a PUR-PIR system comprising: 1) an isocyanate component (A) comprising: 1.1) 15-25 wt % of isocyanurate groups; and 1.2) 30-55 wt % of monomeric MDI; 1.3) an NCO content of 23-30 wt %, all based on the total weight of the isocyanate component; and 2) a polyol formulation (B); in the presence of: 3) blowing agents (C); 4) catalysts (D); and optionally 5) further auxiliary and added-substance materials (E); wherein the isocyanate component (A) is obtained by a method comprising: (i) preparing an isocyanate blend (A2) by partially trimerizing an isocyanate mixture (A1) comprising oligomeric and monomeric MDI, wherein (A1) prior to trimerization comprises: a total monomeric MDI content of 55-80 wt % based on the total weight of (A1); and a viscosity of <30 mPas at 25 C.; and optionally (ii) blending the partially trimerized isocyanate blend A2 obtained in (i) with further isocyanates (A3); and wherein the system comprising the components (A) to (E) has an isocyanate index of 90 to 150.

2. The method of producing the rigid PUR-PIR foam of claim 1, wherein the isocyanate component (A) has an isocyanurate content of 18-25 wt %.

3. The method of producing the rigid PUR-PIR foam of claim 1, wherein the isocyanate component A comprises 35-45 wt % of monomeric MDI.

4. The method of producing the rigid PUR-PIR foam of claim 1, wherein the isocyanate mixture (A) is obtained by enriching a polymeric MDI with at least one of 4,4-MDI and TDI.

5. The method of producing the rigid PUR-PIR foam of claim 1, wherein the isocyanate mixture (A1) comprises 50-80 wt %, based on the total weight of (A1), of 4,4-MDI.

6. The method of producing the rigid PUR-PIR foam of claim 1, wherein the isocyanate mixture (A1) prior to trimerization has a viscosity of <28 mPas.

7. The method of producing the rigid PUR-PIR foam of claim 1, wherein the system has an isocyanate index of 100 to 140.

8. The method of producing the rigid PUR-PIR foam of claim 1, wherein the monomeric MDI in the isocyanate component (A) comprises at least 80 wt % of 4,4-diphenylmethane diisocyanate (4,4-MDI) based on the total weight of monomeric MDI.

9. The method of producing the rigid PUR-PIR foam of claim 1, wherein the polyol formulation (B) comprises a polyetherol based on at least one of ethylene oxide and propylene oxide.

10. The rigid PUR-PIR foam obtained with the method of claim 1.

11. The rigid PUR-PIR foam of claim 10, wherein the rigid PUR-PIR foam is an insulation foam in the manufacture of composite elements.

12. A composite element comprising a rigid foam layer comprising a the rigid PUR-PIR foam produced by the method of claim 8 and at least one facing layer.

13. The composite element of claim 12 wherein the facing layer comprises at least one material selected from the group of aluminum, steel, bitumen, paper, a mineral nonwoven, a nonwoven comprising organic fibers, a polymeric panel, a polymeric film/sheet, and a wooden panel.

14. The composite element of claim 13 further comprising an insulated pipe constructed of: a) a media pipe; b) a layer of insulating material comprising the rigid PUR-PIR foam; and c) a jacketing pipe.

Description

EXAMPLES

[0079] Starting Materials:

[0080] MDI-1: Desmodur 44V20 polymeric MDI from Bayer MaterialScience AG, viscosity at 25 C. is 200 +/40 mPas at an NCO content of 31.51 wt % (proportion of monomeric MDI: 43 wt %),

[0081] MDI-2: Desmodur 44 M, 4,4-MDI from Bayer MaterialScience AG

[0082] MDI-3: Desmodur 44V70, polymeric MDI from Bayer MaterialScience AG, viscosity at 25 C. is 200 +/40 mPas at an NCO content of 31.20.7 wt % (proportion of monomeric MDI: 30 wt %),

[0083] 2,4,6-Tris(dimethylaminomethyl)phenol: from Aldrich

[0084] Benzoyl chloride: from Aldrich

[0085] POLYOL FORMULATION: [0086] 56.85 parts of POLYOL 1: sugar-started polyether based on propylene oxide, OH number: 450 mg KOH/g; MW: 650 g/mol [0087] 21.91 parts of POLYOL 2: sugar-started polyether based on propylene oxide, OH number: 440 mg KOH/g; MW: 360 g/mol [0088] 12.39 parts of POLYOL 3, trimethylolpropane-started polyether based on propylene oxide, OH number: 370 mg KOH/g, MW: 450 g/mol [0089] 3.82 parts of POLYOL 4: propylene glycol-started polyether based on propylene oxide, OH number: 112 mg KOH/g, MW: 1000 g/mol [0090] 2.24 parts of water [0091] 1.90 parts of AK-8805 polyether polysiloxane from Jiangsu May sta Chemical Co. [0092] 0.88 part of Desmorapid 726b (dimethylcyclohexylamin from Covestro Deutschland AG) [0093] Molecular weight data (MW) reported in this invention relate to the number average molecular weight.

[0094] Measuring Procedures: [0095] Glass transition temperature DIN EN ISO 6721-2:2008 PlasticsDetermination of Dynamic Mechanical PropertiesPart 2: Torsion Pendulum Methods [0096] Thermal conductivity number DIN 52616:1977 Determination of Thermal Conductivity Using a Heat-Flow Meter [0097] Apparent density DIN EN ISO 845:2009 Cellular Plastics and RubbersDetermination of Apparent Density [0098] Isocyanate content (NCO %) EN ISO 11909:2007 Determination of Isocyanate Content [0099] Viscosity (eta) DIN EN ISO 3219:1994 PlasticsPolymers/Resins in the Liquid State or as Emulsions or Dispersions [0100] Hydroxyl number (OH number): determined as per the protocol of DIN 53240 (December 1971).

[0101] Storability was assessed for the rigid PUR-PIR foams qualitatively by keeping samples in the lab at room temperature for 3 months and evaluating them visually.

[0102] The mMDI content was determined via HPLC. The HPLC analyses were carried out using an Agilent 1200 or 1260 instrument. A UV/VIS diode array detector (DAD) was used for signal recognition. The solvents used were methanol and water of HPLC quality. A linear high-pressure solvent gradient at 1 ml/min is used to improve signal separation.

Example 1

Preparation of Isocyanate Mixture A1 (Isocyanate Mixture Before Trimerization)

[0103] MDI-1 and MDI-2 (batch size 3 kg, weight ratio 40:60) were transferred into a 5 1 three neck flask with stirrer under nitrogen for homogenization at room temperature. Isocyanate mixture A1 from Example 1 has a viscosity of about 25 mPas at 25 C. The isocyanate mixture obtained has an overall monomeric MDI content of about 77 wt % (based on the total weight of A1) and a 4,4-MDI content of about 75 wt % (based on the total weight of A1).

Example 2a

Preparation of Isocyanurate-Containing Isocyanate Blend A2

[0104] Isocyanate mixture A1 prepared in Example 1) is, under nitrogen, heated to a temperature of 60-80 C. and subjected to a trimerization reaction by catalysis of 2,4,6-tris(dimethylaminomethyl)phenol (1500 ppm). Samples of the reaction mixture are taken at intervals of about 15 minutes to determine the isocyanate content. A linear decrease in the NCO value over time under the reaction conditions allows an accurate estimation of the necessary reaction time (about 2 h) to reach the target NCO value. The reaction is stopped by admixture of benzoyl chloride (300 ppm) on reaching an isocyanate content of 26.2 wt %. The isocyanurate content (in weight percent) of isocyanate blend A2 thus obtained (isocyanurate % (A2)) is determined from the NCO decrease by the following computation:

isocyanurate % (A2)=(NCO % (A1)NCO % (A2))/(NCO % (A1)/2)*100

[0105] The isocyanurate content of isocyanate blend A2 thus obtained is 38 wt %, the viscosity is 4250 mPas at 25 C.

Example 2b

Preparation of Isocyanurate-Containing Isocyanate Blend A2

[0106] Isocyanate mixture A1 prepared in Example 1) is, under nitrogen, heated to a temperature of 60-80 C. and subjected to a trimerization reaction by catalysis of 2,4,6-tris(dimethylaminomethyl)phenol (1500 ppm). Samples of the reaction mixture are taken at intervals of about 15 minutes to determine the isocyanate content. A linear decrease in the NCO value over time under the reaction conditions allows an accurate estimation of the necessary reaction time (about 1 h) to reach the target NCO value. The reaction is stopped by admixture of benzoyl chloride (300 ppm) on reaching an isocyanate content of 29 wt %. The isocyanurate content of isocyanate blend A2 thus obtained (isocyanurate % (A2)) is determined from the NCO decrease by the following computation:

isocyanurate % (A2)=(NCO % (A1)NCO % (A2))/(NCO % (A1)/2)*100

[0107] The isocyanurate content of isocyanate blend A2 thus obtained is 21.7 wt %, the viscosity is 270 mPas at 25 C.

Examples 3a-3h*

Production of Rigid PUR-PIR Foams

[0108] Isocyanate component A is prepared by admixing in each case the amount reported in the table for the isocyanate blend from Example 2a with the amounts reported in the table for the isocyanates MDI-1, MDI-2 and/or MDI-3 to obtain isocyanate component A. The isocyanate component A is admixed with the POLYOL FORMULATION at an isocyanate index of 130 by addition of pentane as blowing agent, while the components used have been temperature regulated to room temperature. The amount of the blowing agent used in the examples was chosen such that the freely risen foam had approximately the same apparent densities of 28 to 30 kg/m.sup.3 and varied between 3.9 and 4.0 wt % based on the entire reaction mass, consisting of polyol formulation including added-substance materials, the isocyanate component and the physical blowing agent.

[0109] To determine their thermal conductivity number and their glass transition temperature, the foams were produced with an apparent density of about 60 kg/m.sup.3 in an aluminum mold temperature regulated to 40 C.

[0110] Examples 3-3h* reveal that the use of an isocyanurate-containing isocyanate blend A2) provides foams exhibiting distinct improvements in qualityevidenced by the glass transition temperature being increased and the thermal conductivity at the same time reduced versus Comparative Examples 3b* and 3h*. Comparative Example 3h* does not contain any pretrimerized isocyanate blend. In Comparative Examples 3d* and 3e* the isocyanurate content of isocyanate component A is too high, leading to unsatisfactory results in the storage test.

[0111] Example 3a came out particularly well in this series of tests because it leads to foams having the highest glass transition temperature and the lowest thermal conductivity number.

TABLE-US-00001 TABLE 1 Example 3a 3b* 3c* 3d* 3e* 3f 3g 3h* ISOCYANATE COMPONENT A) MDI-2 wt % 22.86 10.4 11 MDI-1 wt % 45.85 15.24 15.9 5 23 100 MDI-3 wt % 17 40 Isocyanate blend wt % 54.15 61.9 73.7 84 60 60 A2 from Example 2a Isocyanate blend 100 A2 from Example 2b Sum total of wt % 100 100 100 100 100 100 100 100 isocyanate component A Isocyanate content wt % 28.3 29 29.1 27.9 27.5 28.2 28.1 31.5 Monomeric MDI wt % 44.5 56.4 57.2 50.8 51.7 42.5 40.0 content as per HPLC Viscosity at 25 C. mPas 1170 270 280 900 1200 1350 1850 220 Polyisocyanurate wt % 21 21.7 21 27 30.8 22 22 0 content RIGID PUR-PIR FOAM Apparent density kg/m.sup.3 61 59 60 61 60 61 61 62 Thermal mW/m .Math. K 23.30 24.1 25.3 24.6 24.30 24.1 23.6 25 conductivity Glass transition C. >210 194.9 199.9 204.9 204.50 209.5 210 199 RT storage test for ok inhomogeneous, partly ok ok ok 3 months crystallized *comparative examples

Example 4

Production of Insulated Pipes

[0112] The components from Examples 3a and 3h were used to produce in each case composite jacketed pipes 6 m in length by the standard method using a 2K mixing and metering facility from Cannon.

[0113] The adherence of the foams to the jacketing pipe was assessed qualitatively and found to be equivalent. The axial interlaminar shear strength relative to the media pipe was measured to DIN EN ISO 253:2009. The foam from components 3a (in accordance with the present invention) had a shear strength of 0.48 MPa and that from 3h* had a shear strength of 0.45 MPa (comparative), both at a density of 651 kg/m.sup.3.