POLYURETHANE RIGID FOAM, METHOD FOR PRODUCING SAME, AND USE THEREOF

Abstract

The invention relates to PUR rigid foams which can be obtained by reacting an organic polyisocyanate component B) in a specified viscosity range with a hydrogen-containing component A) which is reactive to isocyanate groups, at least containing a polyol component, water, and optionally stabilizers, catalysts, and other auxiliary agents and additives, in the presence of suitable propellants and to a method for producing same, having the steps of a) providing a mold, b) introducing the foam-forming reaction mixture of component A), the polyisocyanate component B), and propellants T) into the mold, and c) foaming the reaction mixture.

Claims

1. A rigid polyurethane foam obtainable by reaction of a foam-forming reaction mixture comprising: a component A) containing hydrogen atoms which are reactive toward isocyanate groups and comprising a polyol component A1), water A2) and optionally stabilizers A3), catalysts A4) and other auxiliaries and additives A5); at least one physical blowing agent T); and a polyisocyanate component B), wherein the polyol component A1) comprises the following components (i)-(iii), based on the total weight of the component A1): (i) 60-75% by weight of polyether polyol Ala) having a hydroxyl number of from 300 mg KOH/g to 600 mg KOH/g and a functionality of from 3.0 to 6.0, which is obtainable by addition of an epoxide onto one or more starter compound(s) selected from the group consisting of carbohydrates and bifunctional or higher-functional alcohols; (ii) 20-35% by weight of polyether polyol A1b) having a hydroxyl number of from 100 mg KOH/g to 550 mg KOH/g and a functionality of from 1.5 to 5.0, which is obtainable by addition of an epoxide or epoxide mixture onto an aromatic amine; (iii) 3-10% by weight of polyether polyol A1c) having a hydroxyl number of from 15 mg KOH/g to <300 mg KOH/g and a functionality of from 1.5 to 4.0, which is obtainable by addition of an epoxide or epoxide mixture onto one or more starter compound(s) selected from the group consisting of: carbohydrates and bifunctional or higher-functional alcohols, and wherein the polyisocyanate component B) contains at least 85% by weight (based on the total weight of B) polymeric MDI which has an NCO content of from 29.0% by weight to 32.0% by weight and a viscosity at 25 C. (EN ISO 3219, October 1994) of from 300 mPas to 750 mPa.Math.s and comprises, based on its total weight, from 25% by weight to 40% by weight of monomeric MDI.

2. The rigid polyurethane foam as claimed in claim 1, wherein the polyether polyol Ala) is obtainable by addition of an epoxide or epoxide mixture of ethylene oxide and propylene oxide onto one or more starter compound(s) selected from the group consisting of: mixtures of sucrose and propylene glycol, mixtures of sucrose and ethylene glycol, mixtures of sucrose, propylene glycol and ethylene glycol, mixtures of sucrose and glycerol, mixtures of sorbitol and propylene glycol, mixtures of sorbitol and ethylene glycol, mixtures of sorbitol, propylene glycol and ethylene glycol, and mixtures of sorbitol and glycerol.

3. The rigid polyurethane foam as claimed in claim 1, wherein the polyether polyol Alb) is a polyether polyol started on ortho-, meta- or para-toluenediamine or a mixture of isomeric toluenediamines.

4. The rigid polyurethane foam as claimed in claim 1, wherein the polyether polyol A1c) is a polyether polyol started on glycerol, mixtures of glycerol and propylene glycol, trimethylolpropane, mixtures of trimethylolpropane and propylene glycol, or propylene glycol.

5. The rigid polyurethane foam as claimed in claim 1, wherein the component A) contains 1.5% by weight of water A2).

6. The rigid polyurethane foam as claimed in claim 1, wherein the component A) contains 1.5% by weight of water A2) and 0.5-5% by weight of a stabilizer A3) selected from the group consisting of: polyether-polydimethylsiloxane copolymers.

7. The rigid polyurethane foam as claimed in claim 1, wherein the polymeric MDI has a viscosity at 25 C. (EN ISO 3219, October 1994) of 350-500 mPa.Math.s (EN ISO 3219, October 1994).

8. The rigid polyurethane foam as claimed in claim 1, additionally containing a catalyst A4) selected from the group consisting of: triethylenediamine, N,N-dimethylcyclohexylamine, dicyclohexylmethylamine, tetramethylenediamine, 1-methyl-4-dimethylaminoethylpiperazine, triethylamine, tributylamine, dimethylbenzylamine, N,N,N-tris(dimethylaminopropyl)hexahydrotriazine, tris(dimethylaminopropyl)amine, tris(dimethylaminomethyl)phenol, dimethylaminopropylformamide, N,N,N,N-tetramethylethylenediamine, N,N,N,N-tetramethylbutanediamine, tetramethylhexanediamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, bis(dimethylaminoethyl) ether, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane, bis(di-methylaminopropyl)urea, N-methylmorpholine, N-ethylmorpholine, sodium N-[(2-hydroxy-5-nonylphenyl)methyl]-N-methylaminoacetate, N-cyclohexylmorpholine, 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, triethanolamine, diethanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine and dimethylethanolamine.

9. A process for producing shaped bodies composed of rigid PUR foams as claimed in claim 1, comprising the steps: a) provision of a mold, b) introduction of the foam-forming reaction mixture composed of component A), polyisocyanate component B) and blowing agent T) into the mold, and c) foaming of the reaction mixture.

10. The process as claimed in claim 9, wherein the foam-forming reaction mixture is introduced into the mold under a variable injection pressure and/or in an amount which changes over time.

11. The process as claimed in claim 10, wherein step b) and/or step c) are carried out under reduced pressure.

12. The process as claimed in claim 11, wherein the reaction of the isocyanate component B) with the polyol is carried out at an index of from 100 to 150.

13. A composite system containing a rigid polyurethane foam as claimed in claim 1.

14. An insulation material comprising the composite system as claimed in claim 13.

15. A freezer system comprising the insulation material as claimed in claim 14.

16. The rigid polyurethane foam as claimed in claim 2, wherein the polyether polyol A1a) is obtainable by addition of propylene oxide onto one or more starter compound(s) selected from the group consisting of: mixtures of sucrose and propylene glycol, mixtures of sucrose and ethylene glycol, mixtures of sucrose, propylene glycol and ethylene glycol, mixtures of sucrose and glycerol, mixtures of sorbitol and propylene glycol, mixtures of sorbitol and ethylene glycol, mixtures of sorbitol, propylene glycol and ethylene glycol, and mixtures of sorbitol and glycerol.

Description

EXAMPLES

[0064] Starting Materials:

[0065] Polyol PA: Polyether polyol derived from sucrose, propylene glycol, ethylene glycol and propylene oxide and having a functionality of 4.7 and a hydroxyl number of 450 mg KOH/g.

[0066] Polyol PB: Polyether polyol derived from sorbitol, glycerol and propylene oxide and having a functionality of 5.5 and a hydroxyl number of 477 mg KOH/g.

[0067] Polyol PC: Polyether polyol derived from TDA and propylene oxide and having a functionality of 4 and a hydroxyl number of 360 mg KOH/g.

[0068] Polyol PD: Polyether polyol derived from propylene glycol and propylene oxide and having a functionality of 2 and a hydroxyl number of 112 mg KOH/g.

[0069] Stabilizer: Tegostab B 8522, Evonik Nutrition & Care GmbH

[0070] Catalyst KA: Pentamethyldiethylenetriamine Catalyst KB: N,N,N-Tris(dimethylaminopropyl)hexahydrotriazine

[0071] Catalyst KC: Tris(dimethylaminomethyl)phenol

[0072] Catalyst KD: N,N-Dimethylcyclohexylamine

[0073] Catalyst KE: Mixture of ethanediol and the salt of N,N,N-methanaminium and pivalic acid (50 parts by weight: 50 parts by weight)

[0074] Isocyanate IA: polymeric MDI containing 49.5% by weight of diphenylmethane 4,4-diisocyanate (mMDI), viscosity from 160 mPas to 300 mPas at 25 C., NCO content 31.3% by weight, Covestro Deutschland AG

[0075] Isocyanate IB: polymeric MDI containing 35.2% by weight of diphenylmethane 4,4-diisocyanate (mMDI), viscosity from 350 mPas to 450 mPas at 25 C., NCO content 31.1% by weight, Covestro Deutschland AG

[0076] Isocyanate IC: polymeric MDI containing 30.6% by weight of diphenylmethane 4,4-diisocyanate (mMDI), viscosity from 610 mPas to 750 mPas at 25 C., NCO content 30.9% by weight, Covestro Deutschland AG

[0077] Isocyanate ID: polymeric MDI containing 22.8% by weight of diphenylmethane 4,4-diisocyanate (mMDI), viscosity from 1500 mPas to 2500 mPas at 25 C., NCO content 29.0-32.0% by weight, Covestro Deutschland AG

[0078] Hydroxyl number (OH number): The determination of the OH number was carried out in accordance with the method of DIN 53240-2 (1998).

[0079] Isocyanate content: EN ISO 11909:2007 Determination of the isocyanate content

[0080] Viscosity: DIN EN ISO 3219:1994 Plasticspolymers/resins in the liquid state or as emulsions or dispersions

Experiments 1-6 (table 1)

[0081] On a high-pressure polyurethane metering machine model A40 from Cannon, the polyol formulation composed of the amounts of polyols, water, stabilizer, catalysts indicated in table 1 together with the blowing agent was mixed with the isocyanate in an FPL mixing head (from Cannon) having an outflow tube diameter of 18 mm and discharged. The circulation pressure for the components was regulated to about 150 bar and the container temperatures for the components were regulated to 20 C. The discharge rate of the mixture was set to 350 g/s.

[0082] The thermal conductivity was determined in accordance with DIN 52616 (1977). For this purpose, the polyurethane reaction mixture was poured into a 200205 cm mold with an introduced density of 37 kg/m.sup.3. After 6 minutes, the test specimen was taken from the mold and two test specimens having dimensions of 20203 cm were promptly cut from the molded body.

[0083] The compressive strength was determined in accordance with DIN EN 826 (2013). For this purpose, the polyurethane reaction mixture was poured into a 200205 cm mold with an introduced density of 36 kg/m.sup.3. After 5 minutes, the test specimen was removed from the mold and, after storage for 24 hours, 20 test specimens having a size of 554 cm were cut from various regions of the test specimen and the compressive strength was determined in accordance with the DIN standard indicated.

[0084] To determine the swelling behavior, the polyurethane reaction mixture was introduced into a mold which had been preheated to 45 C. and had the dimensions 70409 cm with an apparent density of 36 kg/m.sup.3 and removed from the mold after 5 minutes. The test specimen was stored for 24 hours and the thickness of the test specimen was subsequently determined.

[0085] The apparent core density was determined in accordance with DIN EN ISO 845:2009 (Cellular plastics and rubbersdetermination of apparent density).

TABLE-US-00001 TABLE 1 1* 2* 3* 4 5 6 Polyol formulation (parts by weight) Polyol PA 32.5 32.5 32.5 32.5 Polyol PB 32.5 65.0 32.5 32.5 65.0 32.5 Polyol PC 30.0 30.0 30.0 30.0 30.0 30.0 Polyol PD 5.0 5.0 5.0 5.0 5.0 5.0 Water 2.65 2.65 2.65 2.65 2.65 2.65 Stabilizer 2.0 2.0 2.0 2.0 2.0 2.0 Catalyst KA 0.6 0.6 0.6 0.6 0.6 0.6 Catalyst KB 0.5 0.5 0.5 0.5 Catalyst KC 0.4 0.4 0.4 0.4 Catalyst KD 0.85 0.85 0.85 0.85 0.85 0.85 Catalyst KE 0.8 0.8 Reaction system (parts by weight) Polyol formulation 100 100 100 100 100 100 Cyclopentane 14 14 14 14 14 14 Isocyanate IA 149 151 150 Isocyanate IB 149 151 149 Index 113 113 113 112 112 112 Properties Fiber time [s] 38 39 44 36 42 46 Free-foamed density [g/l] 23.3 22.9 22.3 22.8 23.7 23.1 Min. fill density [g/l] 31.8 30.9 30.9 32.0 32.2 31.8 Compressive strength at 36 kg/m.sup.3 159 170 165 162 163 154 [kPa] Apparent core density at 36 kg/m.sup.3 31.7 32.1 31.8 31.5 31.7 31.7 Thermal conductivity [mW/mK] 19.2 19.1 19.4 19.1 19.1 19.2 10 C. Swelling behavior after 24 h, 5 91.5 91.6 91.8 90.7 90.7 91.0 36 kg/m.sup.3 [mm] *Comparative examples

Experiments 7-10 (Table 2)

[0086] In a suitable vessel, a total of 100 g of the polyol formulation made up of the amounts of polyols, water, stabilizer, catalysts indicated in table 2 were admixed with cyclopentane and brought to 20 C. At the same time, the isocyanate component was likewise brought to 20 C. in a second suitable vessel. The required amount of the isocyanate component was subsequently added to the mixture of polyol formulation and blowing agent and all the constituents were mixed intensively with one another for 6 seconds. The reaction mixture was then poured into a test package (2020 cm) and the reactivity indicators were determined as follows:

[0087] The cream time corresponds to the time required by the reaction mixture until it begins to foam. To determine the fiber time, a wooden stick was dipped into the rising foam and pulled out again. The point in time at which the wooden stick draws threads on being pulled out of the foam corresponds to the fiber time of the foam.

[0088] To examine the flow properties of the foams, the reaction vessel was, after the stirring operation using an amount of the reaction mixture standardized for this method (265 g), introduced into a heatable rise tube (rigid foam rise tube) having a height of 150 cm and an internal diameter of 9.1 cm. The temperature of the rise tube was 35 C. The rise height and the pressure were detected as a function of time and corrected according to the respective prevailing air pressure to a standard pressure of 1013 mbar. The point in time at which a sudden pressure increase is detected corresponds to the gel point or the gel time of the foam. The following parameters need to be distinguished: tG (gel point, in s) and hG (height at the time of tG, in cm).

[0089] To determine the free-foamed density, a foam was produced as described above and this was subsequently stored for 24 hours at room temperature. A 101010 cm.sup.3 cube is cut from the center of the test specimen. The mass of the test specimen is determined by weighing and the apparent density is calculated as the ratio of mass to volume and is reported in kg/m.sup.3.

[0090] To determine the swelling behavior, the polyurethane reaction mixture was poured into a mold having the dimensions 222210 cm.sup.3 with overfilling by 25% and was removed from the mold after the indicated mold residence time (MRT). After 30 minutes, the thickness of the molded body was determined.

[0091] The compressive strength was determined in accordance with DIN EN 826 (2013). For this purpose, an amount of polyurethane reaction mixture which gave an introduced density of 36 kg/m.sup.3 was introduced into a 222210 cm.sup.3 mold. This molded body was removed from the mold after the indicated mold residence time (MRT). After 24 hours, 10 test specimens having the dimensions 555 cm.sup.3 were cut and the compressive strength of each of 5 test specimens was determined both in the thickness direction and also perpendicularly thereto.

[0092] The thermal conductivity was determined in accordance with DIN 52616 (1977). For this purpose, the polyurethane reaction mixture was poured into a 22226 cm.sup.3 mold with overfilling by 10%. This molded body was removed from the mold after 6 minutes. After a few hours, a test specimen having the dimensions 20203 cm.sup.3 was cut and the thermal conductivity was determined in accordance with the standard.

[0093] The apparent core density was determined in accordance with DIN EN ISO 845:2009 (Cellular plastics and rubbersdetermination of apparent density).

TABLE-US-00002 TABLE 2 1* 2 3 4* Polyol PA 32.50 32.50 32.50 32.50 Polyol PB 32.50 32.50 32.50 32.50 Polyol PC 30.00 30.00 30.00 30.00 Polyol PD 5.00 5.00 5.00 5.00 Water 2.65 2.65 2.65 2.65 Stabilizer 2.00 2.00 2.00 2.00 Catalyst KA 0.60 0.60 0.60 0.60 Catalyst KB 0.50 0.50 0.50 0.50 Catalyst KC 0.40 0.40 0.40 0.40 Catalyst KD 0.85 0.80 0.85 0.74 Polyol formulation 100 100 100 100 Cyclopentane 14.5 15.0 16.0 15.0 Isocyanate IA 149.0 95.0 Isocyanate IB 152.0 Isocyanate IC 153.0 Isocyanate ID 56.0 Index 113 113 113 113 Processibility Cream time [s] 9 9 9 9 Fiber time [s] 61 59 60 58 Gel time tG [s] 64 63 65 64 Flow height at tG 118.4 118.1 118.3 117 (1013 hPA) [cm] Foam properties Free-foamed density 23.3 23.3 22.4 23 [g/l] Compressive strength 144 18 147 24 152 27 142 18 at 36 kg/m.sup.3 [kPa] Apparent core density 32.2 0.3 32.6 0.4 31.9 0.3 32.2 0.3 at 36 kg/m.sup.3 Thermal conductivity 20.0 19.5 19.4 19.8 [mW/mK] 10 C. Swelling behavior, 1.4 0.6 1.2 1.4 MRT 5 min (10 cm) [mm] *Comparative examples

[0094] The experiments show that the inventive combination of polyols and isocyanates makes it possible to obtain rigid PUR/PIR foams which display equally good processibility in a discontinuous process and have a low thermal conductivity and a better swelling behavior than when using polymeric MDI in a different viscosity range. The lower values for the swelling behavior show that the shaped bodies composed of the rigid polyurethane foams according to the invention can be demolded after a shorter time.

Experiments 11-14 (Table 3)

[0095] Further polyurethane foams 11-14 which differ in terms of the composition of the polyol formulation were produced and tested in a manner analogous to experiments 7-10 (see table 3). The foams 11 and 12* were blown using cyclopentane, the foams 13 and 14* were blown using n-pentane.

[0096] Comparative experiments 12* and 14* contain a polyol system which in terms of its composition corresponds to systems of the prior art (US2012/0264842).

TABLE-US-00003 TABLE 3 11 12* 13 14* Polyol formulation 1 2 3 4 (parts by weight) Polyol PA Polyol PB 65.00 54.80 65.00 54.80 Polyol PC 30.00 19.40 30.00 19.40 Polyol PD 5.00 25.80 5.00 25.80 Water 2.65 2.65 2.65 2.65 Stabilizer 2.00 2.00 2.00 2.00 Catalyst KA 0.60 0.60 0.60 0.60 Catalyst KB 0.50 0.50 0.50 0.50 Catalyst KC 0.40 0.40 0.40 0.40 Catalyst KD 0.85 0.85 0.85 0.85 Reaction system (parts by weight) Polyol formulation 100.0 100.0 100.0 100.0 Cyclopentane 14.5 14.5 n-Pentane 13.5 13.5 Isocyanate IB 153.0 135.0 153.0 135.0 Index 113 113 113 113 Processibility Cream time [s] 9 9 7 7 Fiber time [s] 61 61 65 68 Gel time tG [s] 63 68 71 75 Flow height at tG 115.1 121.3 116.1 122.7 (1013 hPa) [cm] Foam properties Free-foamed density 23.7 22.2 24 22.8 [g/l] Compressive strength 189 20 147 17 183 16 162 15 at 36 kg/m.sup.3 [kPa] Apparent core density 31.6 0.4 30.7 0.3 31.9 0.4 31.2 0.3 at 36 kg/m.sup.3 Thermal conductivity 19.1 19.8 21 21.3 [mW/mK] 10 C. Swelling behavior, 0.1 1.6 0.2 0.8 MRT 5 min (10 cm) [mm] Swelling behavior, 1 2.3 1.1 1.6 MRT 4 min (10 cm) [mm]

[0097] The results show that the foams according to the invention are significantly better in terms of all properties reported than the comparative experiments using a polyol formulation from the prior art which is not according to the invention.