Method for producing a hard polyurethane-polyisocyanurate foamed material

Abstract

The present invention relates to a process for producing a rigid polyurethane-polyisocyanurate foam C, comprising the step of reacting (i) an isocyanate-terminated prepolymer B with (ii) an activator component A comprising at least one trimerization catalyst A1 and at least one blowing agent A3 in a reaction mixture to form a foam, characterized in that—there is used an isocyanate-terminated prepolymer B obtained from a reaction of an isocyanate B1 having a mean isocyanate functionality of from ≧2.3 to ≦2.9 with a polyol component B2, and—the activator component A comprises water as the blowing agent A3 in an amount of from ≧5 wt. % to ≦50 wt. %,—the isocyanate index in the reaction mixture is in a range of from ≧400 to ≧500, and—the isocyanate content of the prepolymer B is in a range of from ≧21 wt. % to ≦30 wt. %, based on the total mass of the prepolymer B, and—wherein in the reaction of the prepolymer B and the activator component A a conversion contribution to polyisocyanurate of ≦75% is achieved. Rigid foams C so produced have good flame retarding properties while at the same time having good insulating properties and stability properties. The present invention relates further to a rigid polyisocyanurate foam C produced by the process according to the invention, to the use of such a rigid polyisocyanurate foam C in the production of heat-insulating structural components, and to a heat-insulating structural component comprising such a rigid polyurethane-polyisocyanurate foam.

Claims

1. A process for producing a rigid polyurethane-polyisocyanurate foam C, comprising the step of reacting (i) an isocyanate-terminated prepolymer B with (ii) an activator component A comprising at least one trimerisation catalyst A1 and at least one blowing agent A3 in a reaction mixture to form a foam, wherein the isocyanate-terminated prepolymer B is obtained from a reaction of at least one isocyanate B1 having a mean isocyanate functionality of from ≧2.3 to ≦2.9 with a polyol component B2, and the activator component A comprises water as the blowing agent A3 in an amount of from ≧5 wt. % to ≦50 wt. %, the isocyanate index in the reaction mixture is in a range of from ≧400 to ≦1500, the isocyanate content of the prepolymer B is in a range of from ≧21 wt. % to ≦30 wt. %, based on the total mass of the prepolymer B, and wherein in the reaction of the prepolymer B and the activator component A, less than or equal to 75% of the isocyanate groups of the isocyanate-terminated prepolymer B are converted to polyisocynanurate groups and wherein the prepolymer B and the activator component A are introduced individually from the outside of the device into a spray channel of a nozzle via inlets and are mixed in the spray channel, the spray channel having at least one mixing level into which at least one mixed gas is introduced through at least one tangentially arranged gas channel.

2. The process according to claim 1, wherein the reaction mixture does not contain any polyols having an OH number of <400 mg KOH/g.

3. The process according to claim 1, wherein the reaction mixture does not contain a flame retardant.

4. The process according to claim 1, wherein the process comprises the further step of spray applying the reaction mixture to a substrate.

5. The process according to claim 1, wherein the isocyanate-terminated prepolymer B is obtained from at least one isocyanate B1 selected from the group consisting of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, diisocyanato-dicyclohexylmethane and isophorone diisocyanate, and the polyol component B2 comprising at least one polyester polyol or polyether polyol.

6. The process according to claim 5, wherein the polyol component B2 comprising at least one polyether polyol that is the addition product of styrene oxide, ethylene oxide, propylene oxide, butylene oxide and/or epichlorohydrin on di- or poly-functional starter molecules.

7. The process according to claim 1, wherein at least one trimerisation catalyst A1 is selected from the group consisting of tin(II) acetate, tin(II) octoate, tin(II) ethylhexoate, tin(II) laurate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dioctyltin diacetate, tris-(N,N-dimethylaminopropyl)-s-hexahydrotriazine, tetramethylammonium hydroxide, sodium hydroxide, sodium N-[(2-hydroxy-5-nonylphenyl)methyl]-N-methylaminoacetate, sodium acetate, sodium octoate, potassium acetate, potassium octoate, and mixtures thereof.

8. A rigid polyurethane-polyisocyanurate foam C obtained by the process according to claim 1.

9. The rigid polyurethane-polyisocyanurate foam C according to claim 8, wherein the rigid polyurethane-polyisocyanurate foam C has a flame height of ≦150 mm, determinable in accordance with DIN 4102-1, using an edge flaming test and/or wherein the rigid polyurethane-polyisocyanurate foam C has a flame height of ≦150 mm, determinable in accordance with DIN 4102-1, using a surface flaming test.

10. The rigid polyurethane-polyisocyanurate foam C according claim 8, wherein the rigid polyurethane-polyisocyanurate foam C has a coefficient of thermal conductivity of ≦32 mW/(m×K), determinable in accordance with DIN 52616.

11. The rigid polyurethane-polyisocyanurate foam C according to claim 8, wherein the rigid polyurethane-polyisocyanurate foam C has a compressive strength of ≧0.20 MPa, determinable in accordance with DIN 826.

12. A method comprising utilising the rigid polyurethane-polyisocyanurate foam C according to claim 8 in the production of heat-insulating structural components.

13. A heat-insulating structural component comprising a rigid polyurethane-polyisocyanurate foam C according to claim 8.

Description

EXAMPLES

Glossary

(1) Isocyanate blend 1: Mixture consisting of 2,2′-MDI (0.4 wt. %), 2,4′-MDI (55 wt. %), 4,4′-MDI (44.6 wt. %), mean functionality of 2.0. Isocyanate blend 2: Mixture consisting of 2,2′-MDI (0.3 wt. %), 2,4′-MDI (4.2 wt. %), 4,4′-MDI (49.1 wt. %), 3-nuclear MDI (32.2 wt. %), 4-nuclear MDI (14.2 wt. %), mean functionality of 2.9. Polyol 1: Polyether polyol having a hydroxyl number of 37 mg KOH/g (DIN 53240) and an average OH functionality of 3. Obtained from the reaction of glycerol as starter component with ethylene oxide and propylene oxide, the ratio of ethylene oxide units (EO) to propylene oxide units (PO) in the polyether polyol being 71 wt. %/29 wt. %. Polyol 2: Polyether polyol having a hydroxyl number of 112 mg KOH/g (DIN 53240) and an average OH functionality of 2. Obtained from the reaction of propylene glycol as starter component with propylene oxide. Polyol 3: Poly(diethylene glycol adipate), acid number 0.5, OH number 112 mg KOH/g, average OH functionality of 2. Polyol 4: Polyether polyol having a hydroxyl number of 35 mg KOH/g (DIN 53240) and an average OH functionality of 3. Obtained from the reaction of glycerol as starter component with ethylene oxide and propylene oxide, the a ratio of ethylene oxide units (EO) to propylene oxide units (PO) in the polyether polyol being 13.5 wt. %/86.5 wt. %. Polyol 5: Polyether polyol having a hydroxyl number of 56 mg KOH/g (DIN 53240) and an average OH functionality of 2. Obtained from the reaction of propylene glycol as starter component with propylene oxide. PIR catalyst: Potassium acetate in diethylene glycol (1:3) (trimerisation catalyst) Blowing catalyst: Niax® A1 70 wt. % bis-(2-dimethylaminoethyl) ether dissolved in 30 wt. % dipropylene glycol (Momentive) Foam stabiliser: Tegostab® B 8645 (Evonik)

(2) In the tables below, the compositions of the isocyanate-terminated prepolymers B consisting of an isocyanate mixture B1 and a polyol B2 are shown, Examples 1 to 11 (Tables 1 to 3) being examples according to the invention, while Comparison Examples 12 to 15 (Table 4) do not show compositions according to the invention.

(3) TABLE-US-00001 TABLE 1 Example 1 2 3 Polyol OH number Polyol 1 37 27.46 9.11 27.72 Isocyanate NCO % Isocyanate blend 1 33.6 41.90 53.99 Isocyanate blend 2 30.8 27.94 36.00 72.28 Polyol OH number 37 37 37 Polyol functionality 3 3 3 Isocyanate NCO % desired 22 29 22 Isocyanate functionality 2.3 2.3 2.9 EO % in the prepolymer 21 7 20 EO % in the polyol 71 71 71 Hardness o.k. o.k. o.k. Bulk density free 93.2 55.1 130.3 Setting time 60 31 44 Bulk density test specimen kg/m.sup.3 — 64.3 — Coefficient of thermal mW/(m × K) — 24.9 — conductivity Fire test edge mm — 122 — Fire test surface mm 122 Torsion ° C. — >210 — Compressive strength in SR MPa — 0.39 — Compressive strength vertical 1 MPa — 0.38 — Panel no. 2 kg/m.sup.3 72.1 Fire test edge mm 115 Fire test surface mm 122

(4) TABLE-US-00002 TABLE 2 Example 4 5 6 7 Polyol OH number Polyol 4 35 9.91 5.386 Polyol 5 56 9.49 5.14 Isocyanate NCO % Isocyanate blend 1 33.6 54.04 54.31 Isocyanate blend 2 30.8 36.03 94.61 36.2 94.86 Polyol OH number 35 35 56 56 Polyol functionality 3 3 2 2 Isocyanate NCO % desired 29 29 29 29 Isocyanate functionality 2.3 2.9 2.3 2.9 EO % in the prepolymer 1 1 0.0 0.0 EO % in the polyol 13 13 0 0 Hardness o.k. o.k. o.k. o.k. Bulk density free 65.30 72.00 57.70 70.20 Setting time 45.00 50.00 51.00 53.00 Bulk density test specimen kg/m.sup.3 73.40 82.70 72.40 85.00 Coefficient of thermal conductivity mW/(m × K) 25.50 25.80 25.90 25.70 Fire test edge mm 123.00 78.00 128.00 76.00 Fire test surface mm 123.00 80.00 136.00 92.00 Torsion ° C. >210 >210 >210 >210 Compressive strength in SR MPa 0.47 0.62 0.41 0.52 Compressive strength vert. 1 MPa 0.67 0.93 0.61 0.60 Panel no. 2 kg/m.sup.3 84.9 82.2 Fire test edge mm 112 68 Fire test surface mm 118 80

(5) TABLE-US-00003 TABLE 3 Example 8 9 10 11 Polyol OH number Polyol 2 112 8.52 4.59 Polyol 3 112 8.52 4.59 Isocyanate NCO % Isocyanate blend 1 33.6 54.89 54.89 Isocyanate blend 2 30.8 36.59 95.41 36.59 95.41 Polyol OH number 112 112 112 112 Polyol functionality 2 2 2 2 Isocyanate NCO % desired 29 29 29 29 Isocyanate functionality 2.3 2.9 2.3 2.9 EO % in the iso 0 0 EO % in the polyol 0 0 Hardness o.k. o.k. o.k. o.k. Bulk density free 51.00 75.20 50.70 68.00 Setting time 76.00 98.00 52.00 54.00 Bulk density test specimen kg/m.sup.3 67.00 85.00 69.00 83.00 Coefficient of thermal conductivity mW/(m × K) 26.30 24.70 25.50 25.90 Fire test edge mm 134.00 84.00 122.0 74.00 Fire test surface mm 140.00 100.0 140.0 86.00 Torsion ° C. >210 >210 >210 >210 Compressive strength in SR MPa 0.44 0.54 0.42 0.55 Compressive strength vert. 1 MPa 0.56 0.64 0.47 0.69

(6) TABLE-US-00004 TABLE 4 Comparison Examples 12 13 14 15 Polyol OH number Polyol 1 37 66.81 45.42 65.65 48.14 Isocyanate NCO % Isocyanate blend 1 33.6 19.91 34.78 Isocyanate blend 2 30.8 13.28 23.20 34.35 51.86 Polyol OH number 37 37 37 37 Polyol functionality 3 3 3 3 Isocyanate NCO 9 15 9 15 % desired Isocyanate 2.3 2.3 2.9 2.9 functionality EO % in the iso 47 35 47 34 EO % in the polyol 71 71 71 71 Hardness too soft too soft too soft too soft Setting time — 180 60 170

(7) Test specimens were subsequently produced from the prepolymers B prepared according to the above-described tables using an activator component A.

(8) The activator components A each comprised as additives a blowing catalyst A2 (Niax A1; 7 wt. %, based on the total amount of activator component A), a PIR catalyst A1 (potassium acetate in diethylene glycol, 1:3; 39 wt. %, based on the total amount of activator component A), a foam stabiliser A4 (Tegostab B8465; 29 wt. %, based on the total amount of activator component A) as well as water as blowing agent A3 in an amount of 25 wt. %, based on the total amount of activator component A.

(9) Production of the Test Specimens:

(10) Three different types of test specimen were produced for the tests: 1. foam samples from the free foam, 2. foam samples from the foaming of panels in a hinged-lid mould, 3. foam samples from the foaming of lightly compressed panels in a hinged-lid mould for clarification of the fire properties with the same core density.

(11) The following reaction parameters apply generally for points 1. to 3.: raw material temperature 23° C. stirrer speed 2000 rpm (Pendraulik stirrer) stirring time 6 to 8 seconds activator component A was placed in the reaction vessel and the prepolymers B were added as the 2nd component, mould temperature for points 2+3 was 45° C. in each case all the foams were produced with an index of 800.

(12) With regard to 1., the activator component A in the specified amount was introduced into a paper cup and adjusted to a temperature of 23° C. The prepolymer B, already preheated, is added in the calculated amount for index 800 to the activator component A and mixing is carried out for 6-8 seconds at 2000 rpm. The reaction mixture is then poured into a paper package and the following properties are determined: reactivities (setting time) core bulk density (bulk density from the middle of the foam in kg/m.sup.3).

(13) With regard to 2., in order to produce the panels, a hinged-lid mould (1100 mm*300 mm*50 mm) was heated to 45° C. and lined with paper. The activator component A and the prepolymer B were mixed together in a large paper cup to give a total amount (maintaining the index 800) of 1080 g. The reaction mixture was then poured directly into the open hinged-lid mould, and the mould was closed.

(14) The following properties were determined from the resulting test specimens:

(15) TABLE-US-00005 core bulk density (in accordance with DIN EN ISO 845) compressive strengths (DIN 826) thermal conductivity (DIN 52616) fire behaviour (DIN 4102-1).

(16) With regard to 3., the hinged-lid mould mentioned under point 2 was reduced to dimensions of 700 mm*300 mm*50 mm by means of an insert and was likewise adjusted to a temperature of 45° C. and lined with paper. For the prepolymers B of Example 2, a charging bulk density of 85 kg/m.sup.3 was chosen.

(17) In order to achieve a comparable core bulk density for Examples 4 and 5, a charging bulk density of 90 kg/m.sup.3 was chosen for both. Foaming was carried out as under point 2. The following properties were determined from the resulting test specimens:

(18) TABLE-US-00006 core bulk density (in accordance with DIN EN ISO 845) fire behaviour (DIN 4102-1) PIR conversion by IR spectroscopy.

(19) In the case of the test specimens produced according to the invention, the hardness was determined by an experienced engineer and classified as hard. The brittleness was likewise determined by an experienced engineer and classified as good. In the case of the hardness in particular, it was possible to show in the comparison examples that the hardness was not sufficient. Specifically, the comparison examples with low NCO percent exhibited a comparatively lower hardness.

(20) Overall, it can be shown by examples that the establishment of the parameters according to the invention has an unexpected effect on the properties of the test specimens that are produced.

(21) For example, it can be seen from the results in respect of the panels produced as described under 2. that the fire result can be improved by increasing the functionality of the isocyanate. In principle, all the examples according to the invention show good flame retarding properties or fire protection properties, determinable in accordance with DIN 4102-1.

(22) By comparing Examples 4 with 6 and 5 with 7 it can further be shown that the compressive strength can be improved by increasing the polyol functionality.

(23) A comparison of Examples 4 and 5, for example, shows that the good flame retarding properties are not directly dependent on the bulk density of the rigid foam C.

(24) It could further be shown that the functionality of the isocyanate blends 1 and 2 has an immediate effect in the resulting foam density. In order to produce a foam having a particularly preferred density in a range of from 55 to 85 kg/m.sup.3, an isocyanate functionality of from ≧2.3 to ≦2.9 is advantageous.

(25) Moreover, it is apparent from the examples that such functionalities also make a positive contribution to the fire behaviour.

(26) A polyether (polyols 1, 2, 4 and 5) shows further improved fire results while at the same time exhibiting similar bulk densities, coefficients of thermal conductivity and compressive strengths.

(27) The above-mentioned examples were further tested for their total conversion or their specific conversion of the NCO groups to isocyanurate groups, urethane groups and urea groups as well as carbodiimide groups.

(28) The tests were carried out by spectroscopy using ATR-FTIR spectroscopy (MIRacle ATR-FTIR attachment in a Bruker VERTEX 70 spectrometer) of produced test specimens in their foam core. To that end, a thin disk was prepared from each test specimen and ten spectra, each at a spacing of 2 em, were recorded thereon in order to evaluate the uniformity.

(29) The result of the test is to be found in Table 5.

(30) TABLE-US-00007 TABLE 5 Examples 2 4 5 Isocyanate functionality 2.3 2.3 2.9 EO in the polyol % 71 13 13 Total NCO conversion * 87 82 70 Conversion contribution of the reaction to Isocyanurate % 63 62 53 Urethane/urea % 9.8 8.5 6.9 Carbodiimide % 14.9 11.1 11.1 Flame height - edge mm 115 112 68 flame height - surface mm 122 118 80

(31) In the following, differences within the examples according to the invention are discussed, all of which already exhibit good fire protection behaviour.

(32) It is clear that Example 5 with a comparatively higher NCO functionality of 2.9 has a lower conversion contribution of 53% to polyisocyanurate or to isocyanurate groups compared with Examples 2 and 4 (63% and 62%, respectively), which have a comparatively lower NCO functionality (2.3). Nevertheless, Example 5 exhibits an improved fire protection behaviour or flame retarding behaviour compared with Examples 2 and 4.

(33) Consequently, the prepolymer composition can affect the reaction as follows: The total NCO conversion and the conversion to isocyanurate is lower in the cases with higher NCO functionality than in cases of low functionality. The stronger crosslinking already applied in the starting materials can accordingly hinder the reaction in particular in the end phase. The total conversion tends to be higher in the two systems with the EO-rich prepolymer than in the systems with the PO-rich prepolymer.