AU2008209665B2 - Process for making rigid urethane-modified polyisocyanurate foams - Google Patents

Abstract

Process for preparing rigid urethane-modified polyisocyanurate foams from polyisocyanates and polyfunctional isocyanate-reactive components in the presence of a blowing agent, a metal salt trimerisation catalyst and a functionaliscd carboxylic acid.

Description

P/00/01 I Regalation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A DIVISIONAL PATENT ORIGINAL Name of Applicant: HUNTSMAN INTERNATIONAL LLC Actual Inventor(s): Joern KUESTER, Roberto FARE and David, Alexander FERGUSON Address for Service: Houlihan 2 , Level 1, 70 Doncaster Road, Balwyn North, Victoria 3104, Australia Invention Title: PROCESS FOR MAKING RIGID URETHANE-MODIFIED POLYISOCYANURATE FOAMS The following statement is a full description of this invention, including the best method of performing it known to 1 2 PROCESS FOR MAKING RIGID URETHANE-MODIFIED POLYISOCYANURATE FOAMS The present application is a divisional application from Australian patent application number 5 2002324070. The entire disclosures of Australian patent application number 2002324070 and its corresponding International application, PCT/EPO2/09541, are incorporated herein by reference. This invention relates to processes for the preparation of rigid urethane-modified 10 polyisocyanurate foams, to foams prepared thereby and to compositions useful in said processes. Rigid urethane-modified polyisocyanurate (PIR) foams are in general prepared by reacting a stoichiometric excess of polyisocyanate with isocyanate-reactive compounds (usually a 15 polyol) in the presence of a blowing agent, surfactants and catalysts. One use of such foams is as a thermal insulation medium as, for example, in buildings. Urethane-modified polyisocyanurate foams exhibit better fire retardancy, reduced smoke emission in fire situations and greater thermal stability than polyurethane foams in general, 20 due to the presence of the isocyanurate groups. Higher index PIR foams are increasingly desirable in construction applications due to more stringent fire regulations and the need for low smoke systems. However it has been shown to be very difficult to achieve good isocyanurate conversion with slow reacting foam systems as 25 is the case in thick (20 cm) lamination panels and in discontinuous panels. Another disadvantage of PIR foams in general is their poor adhesion to facer materials in building panels. 30 It is an aspect of the present invention to provide PIR systems that give good isocyanurate conversion, especially at slow speeds (string time ± 90 seconds). The present invention involves a method for making rigid urethane-modified polyisocyanurate foams from polyisocyanates and polyfunctional isocyanate-reactive 35 components in the presence of blowing agents and in the presence of a trimerisation catalyst and a carboxylic acid.

3 The present invention also includes a process for preparing rigid urethane-modified polyisocyanurate foam comprising the step of reacting an organic polyisocyanate with a polyfunctional isocyanate-reactive component at an isocyanate index of 150 to 450% in the 5 presence of a hydrocarbon and/or water as blowing agent/s and a trimerisation catalyst, selected from potassium acetate or potassium 2-ethylhexanoate or a mixture thereof, wherein the process is carried out in the presence of lactic acid. A good isocyanurate conversion can be achieved in lamination systems over a range of 10 panel thicknesses, using the same polyol masterbatch. The slow reaction speed required for high thickness panels is achieved by employing lactic acid together with a trimerisation catalyst, which is either potassium acetate or potassium 2-ethythexanoate. Good isocyanurate conversion leads to good fire properties. At the same time compressive 15 strength and dimensional stability of the foam is optimised. But also in faster systems (string time between 30 and 40 seconds) the use of lactic acid in combination with a trimerisation catalyst, which is either potassium acetate or potassium 2 ethyihexanoate, leads to improved processing for PIR foams and a higher isocyanurate 20 conversion. The lactic acid is generally used in an amount ranging from 0.05 to 5% by weight based on the i socyanate-reactive composition, preferably about 0.1% to 2%. 25 The trimerisation catalyst being potassium acetate is commercially available as Polycat 46 from Air Products and Catalyst LB from Huntsman Polyurethanes and, most preferably, being potassium 2-ethylhexanoate is commercially available as Dabco K15 from. Air Products. In a preferred embodiment, both potassium acetate and potassium 2-ethylhexanoate are used 30 as trimerisation catalysts in the process of the present invention. The trimerisation catalyst is generally used in an amount ranging from 0.5 to 5% by weight based on the isocyanate-reactive composition, preferably about I to 3%.

4 In general an almost stoichiometric ratio of acid/metal salt is used, especially if Dabco K1 5 or Catalyst LB are used as metal salt trimerisation catalyst. A particularly preferred combination is lactic acid together with Dabco K15 as the 5 trimerisation catalyst. The reaction is typically carried out an isocyanate index of 150 to 450%, preferably at an isocyanate index of 180 to 300%. The term isocyanate index as used herein is meant to be the molar ratio of NCO-groups over reactive hydrogen atoms present in the foam 10 formulation, given as a percentage. In terms of "excess isocyanate", which is the weight percentage of isocyanate in the total formulation which is not used for the OH/NCO reaction, this means between 10 and 60%. 15 The rigid urethane-modified polyisocyanurate foam produced according to the process of the present invention generally is closed-celled, i.e. the open cell content is less than 20%. Suitable isocyanate-reactive compounds to be used in the process of the present invention include any of those known in the art for the preparation of rigid polyurethane or urethane 20 modified polyisocyanurate foans. Of particular importance for the preparation of rigid foams are polyols and polyol mixtures having average hydroxyl numbers of from 160 to 1000, especially from 200 to 700 mg KOH/g, and hydroxyl functionalities of from 2 to 8, especially from 2 to 6. Suitable polyols have been fully described in the prior art and include reaction products of alkylene oxides, for example ethylene oxide and/or propylene oxide, with 25 initiators containing from 2 to 8 active hydrogen atoms per molecule. Suitable initiators include: polyols, for example glycerol, trimethylolpropane, triethanolamine, pentaerythritol, sorbitol and sucrose; polyamines, for example ethylene diamine, tolylene diamine (TDA), diaminodiphenylmethane (DADPM) and polymethylene polyphenylene polyamines; and aminoalcohols, for example ethanolamine and diethanolamine; and mixtures of such 30 initiators. Other suitable polymeric polyols include polyesters obtained by the condensation of appropriate proportions of glycols and higher functionality polyols with dicarboxylic or polycarboxylic acids, DMT-scrap or digestion of PET by glycols. Still further suitable 5 polymeric polyols include hydroxyl-terminated polythioethers, polyamides, polyesteramides, polycarbonates, polyacetals, polyolefins and polysiloxanes. Preferably the isocyanate-reactive composition contains at least 30 wt%, preferably at least 60 5 wt% of polyester polyols. In a particularly preferred embodiment of the present invention almost all of the isocyanate-reactive compounds are polyester polyols. Suitable organic polyisocyanates for use in the process of the present invention include any of those known in the art for the preparation of rigid polyurethane or urethane-modified 10 polyisocyanurate foams, and in particular the aromatic polyisocyanates such as diphenylmethane diisocyanate in the form of its 2,4'-, 2,2'- and 4,4'-isomers and mixtures thereof, the mixtures of diphenylmethane diisocyanates (MDT) and oligomers thereof known in the art as "crude" or polymeric MDI (polymethylene polyphenylene polyisocyanates) having an isocyanate functionality of greater than 2, toluene diisocyanate in the forn of its 15 2,4- and 2,6-isomers and mixtures thereof, 1,5-naphthalene diisocyanate and 1,4-diisocyanatobcnzene. Other organic polyisocyanates, which may be mentioned, include the aliphatic diisocyanates such as isophorone diisocyanate, 1,6-diisocyanatohcxane and 4,4'-diisocyanatodicyclohexylmethane, 20 The quantities of the polyisocyanate compositions and the polyfunctional isocyanate-reactive compositions to be reacted will depend upon the nature of the rigid polyurethane or urethane modified polyisocyanurate foam to be produced and will be readily determined by those skilled in the art. 25 Suitable hydrocarbon blowing agents include lower aliphatic or cyclic, linear or branched hydrocarbons such as alkanes, alkenes and cycloalkanes, preferably having from 4 to 8 carbon atoms. Specific examples include n-butane, iso-butane, 2,3-dimethylbutane, cyclobutane, n pentane, iso-pentane, technical grade pentane mixtures, cyclopentane, methylcyclopentane, neopentane, n-hexane, iso-hexane, n-heptane, iso-heptane, cyclohexane, methylcyclohexane, 30 1-pentene, 2-methylbutene, 3-methylbutene, 1-hexene and any mixture of the above. Preferred hydrocarbons are n-butane, iso-butane, cyclopentane, n-pentane and isopentane and any mixture thereof, in particular mixtures of n-pentane and isopentane (preferred weight ratio 6 3:8), mixtures of cyclopentane and isobutane (preferred weight ratio 8:3), mixtures of cyclopentane and n-butane and mixtures of cyclopentane and iso- or n-pentane (preferred weight ratio between 6:4 and 8:2). 5 Generally, water or other carbon dioxide-evolving compounds are used together with the physical blowing agents. Where water is used as the chemical co-blowing agent typical amounts are in the range from 0.2 to 5%, preferably from 0.5 to 3% by weight based on the isocyanate-reactive component. 10 Water can also be used as the sole blowing agent with no additional physical blowing agent being present. The blowing agents ate hydrocarbons and/or water. Since lactic acid itself also shows a blowing capacity, when water is used as a blowing agent in combination with hydrocarbons, 15 it is present in less than about 1%, which improves cure and adhesion of the foam. The total quantity of blowing agent to be used in a reaction system for producing cellular polymeric materials will be readily determined by those skilled in the art, but will typically be from 2 to 25% by weight based on the total reaction system.. 20 In addition to the polyisocyanate and polyfunctional isocyanate-reactive compositions and the blowing agents, the foam-forming reaction mixture will commonly contain one or more other auxiliaries or additives conventional to formulations for the production of rigid polyurethane and urethane-modified polyisocyanurate foams. Such optional additives include crosslinking 25 agents, for examples low molecular weight polyols such as triethanolamine, surfactants, fire retardants, for example halogenated alkyl phosphates such as tris chloropropyl phosphate, and fillers such as carbon black. In particular in the present invention additives can be used to further improve the adhesion of 30 the foam to the facer material. These include triethylphosphate, mono- and polyethyleneglycol and propylene carbonate, either alone or mixtures thereof 7 In operating the process for making rigid foams according to the invention, the known one shot, prepolymer or semi-prepolymer techniques may be used together with conventional mixing methods. 5 It is convenient in many applications to provide the components for polyurethane production in pre-blended formulations based on each of the primary polyisocyanate and isocyanate reactive components. In particular, many reaction systems employ a polyisocyanate-reactive composition which contains the major additives such as the blowing agent, the catalyst and the surfactant in addition to the polyisocyanate-reactive component or components. 10 Therefore the present invention also provides a polyfunctional isocyanate-reactive composition which contains the isocyanate-reactive components, the trimerisation catalyst, the lactic acid, optionally in combination with the blowing agent, further catalysts and surfactants. 15 The various aspects of this invention are illustrated, but not limited by the following examples. In these examples the following ingredients are used: 20 Polyol 1: an aromatic polyester polyol available from Stepan under the name Stepanpol PS 2352 Polyol 2: a sucrose initiated polyether polyol of OH value 155 mg KOH/g Polyol 3: an aromatic amine initiated polyether polyol of OH value 310 mg KOH/g Polyol 4: an aromatic PET-based polyester polyol 25 Poyol 5: a sucrose/amine initiated polyether polyol of OH value 585 ing KOHI/g TEP: triethylphosphate TCPP: tris chloropropyl phosphate DEEP: diethyl ethyl phosphonate PEG 300: polyethyleneglycol of MW 300 30 DC 5357: silicone surfactant available from Air Products DC 193: silicone surfactant available from Air Products L6900: silicone surfactant available from Crompton OSi 8 Niax Al: amine catalyst available from Air Products Jeff[at PMDETA: amine catalyst available from Huntsman Performance Chemicals JeffTcat TR90: amine catalyst available from Huntsman Performance Chemicals SFB: dimethylcyclohexylamine catalyst (DMCHA) available from Bayer 5 Catalyst LB: potassium acetate catalyst available from Huntsman Polyurethanes Dabco K15: potassium 2-ethylhexanoate trimerisation catalyst available from Air Products Isocyanate: polymeric MDI Example 1 10 Rigid polyisocyanurate foam panels of varying thickness (indicated between brackets) were prepared at an isocyanate index of 200% IFom the ingredients listed in table 1 below. The reaction profile was followed in terms of cream time (CT) which is the time it takes for the foam to start expanding, full cup time (FC) which is the time it takes the rising foam to 15 reach the top-rim of the cup, string time (ST) which is the time it takes to pull the first strings from the foam and end of rise time (ER) which is the time it takes for the foam not to grow anymore in rise-direction. Closed cell content (CCC) of the obtained foam was measured according to standard ASTM D2856 and core density according to standard DIN 5320. 20 The reaction to fire was measured by the B2 flame spread test according to standard DIN 4102. This is an indicator for the isocyanurate conversion: low isocyanurate conversions result in poor fire performance. Table 1 25 Foam No. 1 (4 cm) 2 (10 cm) 3 (20 cm) 4 (10 cm) 5 (20 cm) Polyol 1 pbw 7.24 7.02 6.66 7.53 7.15 Polyol 2 pbw 4.46 4.32 4.1 4.63 4.4 Polyol 3 pbw 10,03 9.72 9.22 10.42 9.91 TEP pbw 4.9 4.97 5.12 5.1 5.28 PEG 300 pbw 4.68 4.54 4.3 4.86 4.62 9 DC 5357 pbw 1.11 1.19 123 1.27 1.32 Niax Al pbw 0.02 0.02 0.02 0.02 0.02 SFB pbw 0.45 0.43 0.41 0.46 0.44 Dabco K15 pbw 0.67 0.39 0.15 0.67 0.68 Water pbw 0.94 1.02 1.13 0.81 0.88 Lactic acid pbw 0.22 0.37 Isocyanate pbw 65.5 66.38 67.65 64 64.9 CT sec 9 12 15 12 16 FC sec 27 37 52 41 56 ST sec 33 49 73 48 75 ER see 55-60 80 85 CCC % 86 88 87 88 86 Density kgI/m 41.6 39.8 40.4 42.1 37 B2 cm 13 14 18 13 12 The results given in table 1 indicate that reducing the speed of the system by decreasing the K15 level is detrimental to isocyanurate conversion. However the LLe of lactic acid in combination with K15 as in foams nos 4 and 5 give enhanced isocyanurate conversion. 5 Using this approach it is possible to achieve the same degree of isocyanurate conversion for slower systems (50 sec string time for 10 cm thickness; 70 sec string time for 20 cm thickness) as it is for fast systems (30 sec string for 4 cm thickness). Example 2 10 Rigid polyisocyanurate foams were prepared at an isocyanate index of 170% from the ingredients listed in table 2 below. Properties were measured as in Example 1 above. The results are presented in Table 2. 15 Table 2 10 Foam No. 6 7 8 9 Polyol 5 pbw 29 29 29 29 Polyol 4 pbw 44 44 44 44 TCPP pbw 20 20 20 20 Water pbw 2 2 2 2 DMCHA pbw 1 1 1 1 DC 193 pbw 1 1 1 Jeffcat PMDETA pbw 0.3 0.3 0.3 0.3 Dabco K15 pbw 1.7 1.7 Catalyst LB pbw 1.7 1.7 Lactic acid pbw 1 1.2 Salicylic acid pbw 1.7 2.1 Isocyanate pbw 180 180 180 180 CT see 11 15 16 16 FC see 22 34 31 37 ST see 29 43 36 45 ER sec 70 85 80 90 Density g/l 47.5 56.6 45.7 55.9 CCC % 95.3 93.2 94.2 93.4 B2 cm 8 8.5 8.7 9 Example 3 5 Rigid polyisocyanurate foams were prepared at an isocyanate index of 230% from the ingredients listed in table 3 below. Properties were measured as in Example 1 above. The results are presented in Table 3.

11 Table 3 Foam No. 10 Polyol 4 pbw 84 DEEP pbw 10 Water pbw 0.7 Jeffeat TR90 pbw 0.8 L6900 pbw 1.6 Jeffcat PMDETA pbw 0.2 Dabco K15 pbw 1.2 Catalyst LB pbw 0.3 Lactic acid pbw 1.2 n-pentane pbw 7 Isocyanate pbw 158 CT see 22 ST see 85 Density g/l 36.5 CCC % 94 B2 cm 12 Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this 5 specification, they are to be interpreted as specifying the presence of the stated features, integers, steps or components referred to, but not to preclude the presence or addition of one or more other feature, integer, step, component or group thereof. Further, any prior art reference or statement provided in the specification is not to be taken 10 as an admission that such art constitutes, or is to be understood as constituting, part of the common general knowledge in Australia.

Claims (11)

1. Process for preparing rigid urethane-modified polyisocyanurate foam comprising the step of reacting an organic polyisocyanate with a polyfunctional 5 isocyanate-reactive component at an isocyanate index of 150 to 450% in the presence of a hydrocarbon and/or water as blowing agent/s and a trimerisation catalyst, selected from potassium acetate or potassium 2-ethylhexanoate or a mixture thereof, wherein the process is carried out in the presence of lactic acid.

2. Process according to claim 1, wherein where water is used as the co 10 blowing agent it is present in an amount in the range of between about 0.2 to 5% by weight based on the isocyanate-reactive component.

3. Process according to claim 1 or claim 2, wherein said lactic acid is used in an amount ranging from 0.05 to 5% by weight based on the isocyanate-reactive component. 15

4. Process according to any one of claims 1 to 3, wherein the blowing agent comprises water.

5. Process according to any one of claims 1 to 4, wherein water is present in an amount of below 1% by weight based on the isocyanate-reactive component.

6. Process according to any one of the preceding claims, wherein the 20 trimerisation catalyst is potassium 2-ethylbexanoate.

7. Process according to any one of the preceding claims, wherein the trimerisation catalyst is a mixture of potassium acetate or potassium 2-ethylhexanoate.

8. Process according to any one of the preceding claims, wherein the trimerisation catalyst is used in an amount ranging from 0.5 to 5% by weight based on the 25 isocyanate-reactive component.

9. Process according to claim 7, wherein the trimerisation catalyst is used in an amount ranging from 1 to 3% by weight based on the isocyanate-reactive component.

10. Rigid urethane-modified polyisocyanurate foam obtained by the process as defined in any one of the preceding claims. 30

11. Process according to any one of claims I to 8, substantially as hereinbefore described with reference to any of the Examples.