MXPA00002139A - Process for rigid polyurethane foams - Google Patents

Abstract

Process for preparing rigid polyurethane or urethane-modified polyisocyanurate foam using as blowing agent a mixture containing from 1 to 50 mole%1,1,1,3,3-pentafluoropropane and from 50 to 99 mole%isopentane and/or n-pentane.

Description

PROCESS FOR RIGID POLYURETHANE FOAMS DESCRIPTION OF THE INVENTION This invention relates to processes for the preparation of polyurethane foams or rigid modified urethane polyurethanes, to foams prepared in that way, and to novel compositions useful in the process. The polyurethane and rigid urethane modified urethane foams are generally prepared by reacting the appropriate poxy compound and appropriate isocyanate reagent (usually a polyol) in the presence of a blowing agent. One use of such foams is as a means of thermal insulation as for example in the construction of refrigerated storage devices. The thermal insulation properties of rigid foams are dependent on a number of factors including, for closed cell foams, the cell size and the thermal conductivity of the contents of the cells. A class of materials that has been widely used as a blowing agent in the production of polyurethane foams and modified urethane foam is the particular one for the former (CFC-11). The exceptionally low thermal conductivity of these blowing agents, and in particular of CFC-11, has allowed the preparation of rigid foams which have very effective insulating properties Recent concerns about the potential of c 1 orof 1 u Ocarbons to cause ozone depletion in the atmosphere have led to an urgent need to develop reaction systems where the blowing agents of C 1 orof 1 uorocar bu are replaced by alternative materials that are environmentally acceptable and that also produce foams that have the necessary properties for the many applications in which they are used Initially, the most promising alternatives appeared to be chlorine or carbon containing gases (HCFC) .US 4076644, for example, describes the use of 1, 1-dichloro-2, 2,2-trifluoroethane (HCFC-123) and 1,1-di chloro-1-fluoroethane (HCFC-141b) as blowing agents for the production of polyurethane foams. However, HCFCs also have some potential ozone reduction. There is therefore mounting pressure to find substitutes for HCFCs as well as CFCs. The alternative blowing types that are currently considered promising because they do not contain reduced ozone chloride are partially fluorinated hydrocarbons (HCF) and hydrocarbons (HC) .One of the most viable HCF candidates is 1, 1, 1 3, 3 -pen taf 1 uo r opr opane (HFC-245fa) as described in US 5496866 and EP 381986. With respect to HC, especially hydrocarbons of five carbon members are considered such as isopentane and n-pentane, as described in WO 90/12841. Currently a large amount of attention is given to blowing agent blends, which could, apart from a possible reduction in cost, also provide additional benefits such as reduction of foam density and conductivity. The US 5562857 discloses the use of mixtures containing from 50 to 70 mol% of HFC-245fa and from 30 to 50 mol% of isopentane as a blowing agent for rigid polyurethane foams. To provide a novel blowing agent mixture that does not contain chlorine and therefore zero ozone depletion potential performance foams that have good thermal insulation and physical properties. This object is known to be used in the process of making polyurethane foams or rigid modified urethane urethane polyisocyanates and isocyanate-reactive components a mixture containing from 1 to 40 mole% HFC-245fa and from 60 to 99% in moles of isopentane and / or n-pentane. Preferably the molar ratio of HFC 245f to / iso- and / or n-pentane is between 10/90 and 40/60. Preferably in side hydrocarbon only isopentane or n-pentane is used and more preferably only isopentane. But also mixtures of isopentane and n-pentane can be used; in these mixtures the molar ratio of i s open t ano / n-pentane is preferably between 80/20 and 20/80. Reactive isocyanate compounds suitable for use in the process of the present invention include any of those known in the art for the preparation of polyurethane or rigid urethane-modified polyurethane or polyurethane foams. Of particular importance for the preparation of rigid foams are polyols and polyol blends having average hydroxyl numbers of 300 to 1000, especially 300 to 700 mg of KOH / g, and hydroxyl functionalities of 2 to 8, especially 3. a 8. 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 initiators containing from 2 to 8 active hydrogen atoms per molecule . Suitable initiators include: polyols, for example glycerol, triethyl or 1-pyridone, triethanolamine, pentaerythritol, sorbitol and sucrose; polyamines, for example, eti 1 endi amine, to 1 i 1 endi ami na (TDA), di ami nodi f enilme t an (DADPM) ypo 1 ime ti 1 enp o 1 i -f in i 1 enp o 1 i ami nas; and ami noa 1 c oh or 1 e s, for example, ethanol amine and diethanolamine; and mixtures of such initiators. Other suitable polymeric polyols include polyesters obtained by the condensation of appropriate proportions of glycols and high functionality polyols with di-carboxylic acids or po 1 i c a rbox i 1 s. Additional suitable polymeric polyols include finished hydroxyl groups, polyamides, polymers, polyacids, polyolefins, and oxides.

The present blowing agent mixture is especially suitable for use in reactive isocyanate compositions containing polyether polyols, especially those derived from aliphatic or aromatic amine containing initiators, especially aromatic ones such as TDA and DADPM. A preferred reactive isocyanate composition contains from 10 to 75% by weight (based on total reactive isocyanate components) of initiating aromatic amine polyester polyols. Organic polyisocyanates suitable for use in the process of the present invention include any of those known in the art for the preparation of polyurethane foams or rigid modified urethane polyisocyanurates, and in particular aromatic polyisocyanates such as di fylcyanate diisocyanate in the form of its 2,4'-, 2,2'- and 4, 4'-isomers and mixtures thereof, the mixtures of diisocyanates of diuretic and non-methyl (MDI) and oligomers of the same as those known in the art as "crude" or polymeric MDI (polymethylene-p or 1 if in i 1 ene polyisocyanates) having an isocyanate functionality of more than 2, toluene diisocyanate in the form of its 2,4- and 2 , 6-isomers and mixtures thereof, 1, 5-naphthalene diisocyanate and 1,4-diisocyanate t-benzene. Other organic polyisocyanates that may be mentioned include the aliphatic diisocyanates such as isophorone diisocyanate, 1,6-diisocyanate, and 4,4'-diisocyanatodicyclohexylmethane. The amounts of the reactive isocyanate compositions and the reactive isocyanate compositions to be reactive will depend on the nature of the polyurethane foam or on the rigid urethane modified rigid urethane to be produced and will be readily determined. by those skilled in the art. Other known physical blowing agents for the production of rigid polyurethane foam can be used in small amounts (above 30% by weight of the physical blowing agent mixture) together with the blowing agent mixture of the present invention. Examples of these include di a 1 qu i 1 é teres, cic 1 or 1 qui 1 ene teresy ketones, ethers (per) f luorado s, c 1 orof 1 uo rocarburos, hydrocarbons pe fluoridated, hi dr o 1 orof luor o -carburos, others hi dr of luo r oca rbur os and other hydrocarbons. For example, a mixture of HFC-245fa, isopentane and cyclopentane can be used.

Analogously to the mixtures of the present invention of HFC-245fa- and other hydrocarbons (preferably linear alkanes) containing from 3 to 7 carbon atoms (such as cycloalkoxide, isobutane and n-hexane) can be used as an agent of blowing for rigid polyurethane foams. Generally water or other compounds developing carbon dioxide are used together with physical blowing agents. When water is used as typical amounts of chemical co-blowing agent are in the range of 0.2 to 5%, preferably 0.5 to 3% by weight based on the reactive isocyanate compound. The total amount of blowing agent to be used in a reaction system to produce cellular polymeric materials will be readily determined by those skilled in the art, but will typically be 2 to 25% by weight based on the total reaction system. In addition to the polyacidone anabolic reagent isocyanate compositions by 1 and the blowing agents, the foam-forming reaction mixture will commonly contain one or more conventional auxiliaries or additives for formulations for the production of polyurethane foams. polyurethane and modified rigid urethane urethane. Such optional additives include crosslinking agents, for example low molecular weight polyols such as triethanolamine, foam stabilizing agents, or surfactants, for example, copolymers of s i 1 oxano-oxy to qui 1Urethane catalysts, for example, tin compounds such as stannous octoate or styrene dilaurate 1-year or tertiary amines such as dimethyl ether, 1-amine, 1-amine or 1-amine, catalyze isocyanurate ct. quaternary ammonium or potassium salts, pyrorethands, for example, halogenated alkyl phosphates such as trisc-1-phosphate or op-opi-1, and reagents such as carbon black. Isocyanate rates of 70 to 140 will typically be used in operating the process of the present invention, but lower rates may be used, if desired. Higher indexes, for example 150 to 500 or even above 3000, can be used in conjunction with the catalyst to make foams containing isocyanurate bonds. These high index foams are usually made using polyester polyols as reactive isocyanate material.

In the operation, the process for making rigid foams according to the invention, a known edition, the prepolymer techniques emi-pr epo 1 i ro can be used together with the conventional mixing methods and the rigid foam can be produced in the form of supply plate, molders, cavity fillers, sprayed foam, hollow foam or laminates with other materials - such as board, gypsum board, plastics, paper or metal. It is convenient in many applications to provide the components for polyurethane production in re-metered formulations based on each of the primary reactive isocyanate and primary isocyanate components. In particular, many reaction systems employ an aqueous or reactive composition containing more additives such as the blowing agent and the catalyst in addition to the reactive component or components. Therefore, the present invention also provides a reactive or reactive composition comprising the present blowing agent mixture.

The various aspects of this invention are illustrated, but not limited to the following articles. The following reaction components are mentioned in the examples: Polyol 1: a p or 1 i e t p r 1 i or 1 of initiated sucrose of OH value 495 mg KOH / g. Polyol 2: a po 1 i e t 1 polymer of aromatic amine initiated with OH value 310 mg KOH / g. Polyols 3: a p o 1 t e rpo 1 i of aromatic amine initiated from OH value 500 mg KOH / g. Polyol 4: a p o 1 i e t t r r o 1 i or 1 glycerol initiated OH value 55 mg KOH / g. Arconato 1000: propylene carbonate available from Arco. L 900: a silicone surfactant available from Union Carbide. Polycat 8: an amine catalyst available from Air Products. Desmorapid PV: an amine catalyst available from Bayer. Isopentane: 99.7% pure isopentane available from Halterman. HFC-245fa: 1,1,1,3,3-pentafluoropropane available from PCR.

RUBINATE M: polymeric MDI available from Imperial Chemical Industries. RUBINATE is a trademark of Imperial Chemical Industries. EXAMPLE Rigid polyurethane foams were produced on a laboratory scale using a Heidolph RZR 50 type mixing device of the ingredients listed below in Table 1. The following properties were measured in the foam obtained: free elevation density measured in foams of cup, thermal conductivity (in a sample or core density approximately 33 kg / m3) according to standard DIN 53421, initial and then age for 5 weeks at room temperature (expressed as tension at 10% thickness). The results are also presented in Table 1.

In Figure 1 the initial lambda is arranged as a function of the blowing agent mixture composition. In figure 2 it is arranged for the aged lambda (at room temperature). From Figure 1 it is clear that the thermal conductivity of the blowing agent mixture is always lower than the mathematical average between the two extremes (expressed by the straight line in Figure 1). The deviation of the mathematical average is greater for the blowing agent mixture according to the invention (Foam B) than for the blowing agent mixture described in US 5562857 (Foam C). Thus the blowing agent mixtures according to the present invention produce foams of comparable thermal insulation values as the foams described in US 5562857 although more isopentane is used which inherently has a higher thermal conductivity than HFC-245fa. Also because the isopentane is less extensive than HFC-245fa the same embodiment is obtained at low cost. In addition other physical properties such as compressive strength of the foam are not affected pe r j udi c a lm e t e.

Claims (10)

1. Process for preparing polyurethane or rigid modified urethane urethane polyurethane foams, comprising the step of reacting an organic polymer with an isocyanate component reactive polyfunction 1 in the presence of water and a mixture of physical blowing agent containing 1, 1, 1, 3, 3 -pen taf 1 or r op r op an and isopentane and / or n-pentane characterized in that the molar ratio 1, 1, 1, 3, 3 -pentaf 1 uo r op r op a no / iso - and / or n-pentane is between 1/99 and 40/60.

2. Process according to claim 1, wherein the molar ratio 1,1,1,3,3-pen taf 1 uo r op r ope no / iso - and / or n-pentane is between 10/90 and 40 / 60

3. Process according to claim 1 or 2, wherein the mixture of physical blowing agent consists of 1, 1, 1, 3, 3 -pe n t a f 1 uo r op r opa and isopentane.

4. Process according to any one of the preceding claims, in which the reactive isocyanate composition po 1 i f uncinone 1 comprises po 1 i e t e rpo 1 i o 1 e s.

5. Process according to the claim 4, wherein the reactive isocyanate composition po 1 i f uni ona 1 contains from 10 to 75% by weight (based on the total reactive isocyanate components) of po 1 i e t or r 1 1 or 1 s of aromatic amine initiated.

6. Process according to the claim 5, in which the aromatic amine is selected from the group consisting of t i i n n am amine, diamino-di f in i lme t ano and po 1 im e t i 1 en pol i f en i 1 enpo i i am i na.

7. Process according to any of the preceding claims wherein the amount of water is between 0.2 and 5% by weight based on the total reactive isocyanate components.

8. Polyurethane foam or rigid modified urethane urethane obtainable by the method as defined in any of the preceding indications.

9. Polyfunctional reactive isocyanate composition 1 comprising water and a physical blowing agent mixture containing from 1 to 40% by moles of 1, 1, 1, 3, 3 -pen taff 1 or op opene and 60 to 99 mol% isopentane and / or n-pentane.

10. Reactive isocyanate composition po 1 if a 1 to 1 according to claim 9, in which the molar ratio 1,1,1,3,3-pen taph 1 or op oopane / iso - and / or n-pentane it is between 10/90 and 40/60.