MXPA98004436A - Process for the production of depoliurethane rigid foams in the presence of dehydrocarb blowing agents - Google Patents

Abstract

A process for the production of rigid foams characterized in that it comprises the reaction of: (a) an organic polyisocyanate, (b) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups, and (c) a blowing agent comprising isopentane and n-pentane in a ratio of 99: 1 to more than 80:20 parts by weight, under foamed foaming conditions

Description

PROCESS FOR THE PRODUCTION OF RIGID POLYURETHANE FOAMS IN THE PRESENCE OF BLOWN AGENTS HYDROCARBON FIELD OF THE INVENTION The present invention is directed to a process for the production of rigid polyurethane foams. More specifically, the present invention is directed to processes for the production of rigid polyurethane foams using a specific mixture of blowing agents.

BACKGROUND OF THE INVENTION Rigid polyurethane foams have many known uses, such as in building materials and as a thermal insulation medium for use in the construction industry as well as in refrigerated storage devices. The widespread commercial acceptance of rigid polyurethane foams as a means of thermal insulation is based on their ability to provide surprising and long-term initial thermal insulation, their superior structural properties and superior flame-retardant properties, all at relatively low densities.

It is known to prepare such rigid polyurethane foams by reacting a polyisocyanate and an isocyanate-reactive compound (usually a polyol) in the presence of a blowing agent. One class of materials which has been widely used as a blowing agent in the production of such foam are the fully halogenated chlorofluorocarbon (CFC) blowing agents, such as trichlorofluoromethane (CFC-11). The advantages of CFCs include their good thermal insulating properties, their relative non-flammability and their superior dimensional stability of the resulting foams. However, despite these advantages, CFCs are no longer favored because they have been associated with ozone depletion in the earth's atmosphere and therefore their use has been severely restricted. Hydrochlorofluorocarbons (HCFCs), such as chlorodifluoromethane (HCFC-22), 1-chloro-l, 1-difluoroethane (HCFC-142b), 1,1 l-trifluoro-2-dichloroethane (HCFC-123) and particularly 1, 1-dichloro-l-fluoroethane (HCFC-141b) has been considered a viable intermediate solution. However, it has been shown that HCFCs cause ozone depletion in the atmosphere and their use is under study. In fact, the widely disseminated production and use of HCFC-141b is currently scheduled to end in 2002.

Consequently, it has been observed that there is a need to develop processes for the production of rigid polyurethane foams and reaction systems for use therein which use blowing agents which have a zero potential of ozone depletion and which still Provide excellent thermal insulation and dimensional stability necessary for commercial applications. Several alkanes and cycloalkanes, such as n-pentane, n-butane and cyclopentane, have been investigated as possible blowing agents for rigid polyurethane foams. The use of such materials is described, for example, in U.S. Patent Nos. 5,096,933 and 5,444,101. However, these materials have not been found to produce rigid polyurethane foams having commercially attractive physical properties at densities which are low enough to make their use feasible. U.S. Patent Nos. 5,387,618 and 5,391,317 are also directed to polyurethane foams prepared in the presence of a physical blowing agent comprising 5-80 mole percent of an alicyclic C5.6 alkane and 95 to 20 mole percent of a mixture of isopentane and n-pentane in a molar ratio of 80:20 to 20:80. However, the formulations described in those patents have been found to produce foams having insufficient dimensional stability and thermal insulation properties. Consequently, it has been observed that there is still a need for a process for the production of rigid polyurethane foams which uses a blowing agent that has a zero potential of ozone depletion and which can be used to produce a rigid foam. polyurethane that has a long-term thermal insulation and excellent stability characteristics. Thus, an object of the present invention is to provide a process for the production of rigid polyurethane foams and a reaction system containing such a blowing agent. The present inventor has surprisingly found a process using a blowing agent consisting essentially of isopentane and producing rigid polyurethane foams having good thermal insulation and dimensional stability characteristics at densities which are much lower than those observed in foams produced with other isomers of pentane. Although the initial K-factor of the blown isopentane foam is generally higher than that of foams blown with HCFC-141b, cyclopentane and some mixtures of pentane, with an aged K-factor (ie, a long-term insulation value), of the foams produced according to the present invention is better than that of any of the above pentanes and at least equal to that of other pentane mixtures. In addition, the long-term insulation value of the rigid foams prepared with respect to the present process approximates a value close to that demonstrated by the foams blown with HCFC-141b. Importantly, isopentane has a zero potential for ozone depletion and therefore satisfies all current environmental concerns.

BRIEF DESCRIPTION OF THE INVENTION Therefore, the present invention is directed to a process for the production of rigid polyurethane foam comprising the reaction of (a) an organic polyisocyanate; (b) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups which are useful in the formation of rigid polyurethane or urethane-modified polyisocyanurate foams; (c) a blowing agent comprising isopentane and n-pentane in proportions from 99: 1 to more than 80:20 parts by weight under foaming conditions. Optionally, the process may further comprise the reaction components (a) to (c) with (c) water or another carbon dioxide generating agent. Components (a), (b), (c) and optionally (c), comprise a reaction system which is also within the scope of the present invention. The present invention is further directed to reaction systems which can be used in such processes. This reaction system comprises (a) an organic polyisocyanate; (b) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups; and (c) a blowing agent comprising isopentane and n-pentane in proportions from 99: 1 to more than 20:80 parts by weight. The present invention is further directed to rigid polyurethane foams prepared by the present process.

DETAILED DESCRIPTION OF THE INVENTION The blowing agent used in the present invention comprises isopentane and n-pentane in a ratio of 99: 1 to more than 80:20 parts by weight. Preferably, the blowing agent useful in the present invention comprises isopentane to n-pentane in a ratio of 98.5: 1.5 to 90:10, more preferably 97.5: 2.5 to 90:10 and much more preferably 97: 3 to 90:10 parts by weight. The total amount of blowing agent to be used in the present process to produce rigid polyurethane foams as needed for a particular purpose will be readily determined by those familiar with the art. However, typical amounts of the blowing agent will be from about 2 to about 15% and preferably from about 3 to about 10% by weight based on the total weight of the reaction system. Organic polyisocyanates suitable for use in the present invention include any of the polyisocyanates known in the art for the production of rigid urethane-modified polyurethane or polyisocyanurate foams. In particular, useful organic polyisocyanates include those having a functionality greater than 2.0, such as diphenylmethane diisocyanate (MDI) in the form of its 2,4'- and 4,4'-isomers and mixtures thereof, diisocyanate mixtures. of diphenylmethane and oligomers thereof (known as "crude" MDI) and polymeric MDI (ie, polyphenylene and polymethylene polyisocyanates). Polyisocyanates modified with carbodiimide groups, methane groups, allophanate groups, isocyanate groups, urea groups, biuret groups and oxazolidone groups can also be used in the process of the present invention. Isocyanate-reactive compositions containing a plurality of isocyanate-reactive groups suitable for use in the present invention include polyether polyols, polyester polyols and mixtures thereof having average hydroxyl numbers from about 100 to about 1000 and preferably from about 150 to about 700 KOH / g and hydroxyl functionalities from about 2 to about 8, and preferably from about 2 to about 6.

Suitable polyether polyols include reaction products of polyalkylene 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, trimethylolpropane, triethanolamine, pentaerythritol, sorbitol and sucrose.; polyamines, for example, ethylenediamine, tolylenediamine, diaminodiphenylmethane and polymethylenepolyphenylenepolyamines; aminoalcohols, for example, ethanolamine and diethanolamine; and mixtures thereof. Preferred initiators are diaminodiphenylmethane and polymethylenepolyphenylenepolyamines. Suitable polyester polyols include those prepared by reacting polycarboxylic acid and / or a derivative thereof or a polycarboxylic anhydride with a polyhydric alcohol. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and can be substituted (for example with halogen atoms) and / or unsaturated. Examples of suitable carboxylic anhydride acids include succinic acid, adipic acid, suberic acid, acelaic acid, sebasic acid, italic acid, isophthalic acid, terephthalic acid, trimellitic acid, italic acid, anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride. , endomethylenetetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids, such as those of oleic acid which can be mixed with monomeric fatty acids. Simple esters of polycarboxylic acids such as terephthalic acid, dimethyl ester, bis-glycol ester of terephthalic acid and mixtures thereof can also be used. Examples of suitable polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-, 1,4-, 1,2-, 2,3-butylene glycol, 1,6-hexanediol, 1, 8-octanediol, neopentyl glycol, cyclohexanedimethanol, 1,4-bis-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol, trimethyletylethylene, pentaerythritol , quinitol, mannitol, sorbitol, methyl glucoside, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycols and the like. The polyesters may contain some terminal carboxy groups although preferably, they end in hydroxyl. It is also possible to use lactone polyesters such as caprolactone or hydroxycarboxylic acids such as hydroxycaproic acid or hydroxyacetic acid.

Additional suitable polymeric polyols include polyether-terminated polyethylenes, polyamides, polyester amides, polycarbonates, polyacetals, polyolefins and polysiloxanes. The organic polyisocyanate component will generally be used in an amount from about 35 to about 65, preferably from about 50 to about 60, and more preferably from about 53 to about 57 percent by weight of the total system. The isocyanate-reactive composition will generally be used in an amount from about 19 to about 63, preferably from about 25 to about 50, and more preferably from about 29 to about 33 weight percent of the total system. The amounts of the polyisocyanate compositions and the isocyanate-reactive compositions will depend on the nature of the material to be produced and will be readily determined by those skilled in the art. The isocyanate reactive component of the present reaction systems may further comprise chain extenders and / or crosslinking agents. In general, useful chain extenders are those having a formula weight of less than about 750 and preferably about 62 to 750, and a functionality of approximately 2. Suitable chain extenders can be selected from polyols, for example ethylene glycol, diethylene glycol, butanediol, dipropylene glycol and tr ipropylene glycol; aliphatic and aromatic amines, for example, 4,4'-methylenedianilines having a lower alkyl substituent placed ortho to each N atom; certain compounds with imino functionality such as those described in the publications for European patent application Nos. 284253 and 359456; and certain enamine-functional compounds such as those described in European Patent Application Publication No. 359456 having two isocyanate-reactive groups per molecule. Suitable crosslinking agents include glycerol, oxyalkylated glycerol, pentaerythritol, sucrose, trimethylolpropane, sorbitol and oxyalkylated polyamines. The functionality of the crosslinking agents can vary from about 3 to about 8, and preferably from about 3 to about 4. The molecular weight of the crosslinking agents can vary between the same ranges as described above with respect to the chain extender. A preferred class of crosslinking agents includes oxypropyl derivatives of glycerol having an average number of molecular weight from about 200 to about 750, glycerol and mixtures thereof. The reaction systems of the present invention may further comprise water or other carbon dioxide generating agents such as hydrocarbyl monocarboxylic acids or polycarboxylic acids and cyclic ureas. When used, such carbon dioxide generating agents should be used in amounts from about 0.05 to about 2.0, and preferably from about 0.35 to about 1.0 weight percent based on the total weight of the reaction system. In order to reduce the cell size of the rigid polyurethane foam prepared according to the present invention and therefore improve the thermal insulation properties of the foam, an insoluble and inert fluorinated compound can be added to the isocyanate-reactive material. used in the present process. Such insoluble and inert fluorinated compounds include any of those described in the US NOS patents. 5,346,928, 4,981,871; 5,034,424; No. 4,972,002 and in European Patent Application No. 0508649. However, it is preferred to use a substantially valued, insoluble and inert compound having a boiling point of at least 208C at atmospheric pressure and preferably at least 40SC., and more preferably 60-1008C. Suitable compounds include substantially fluorinated or perfluorinated hydrocarbons, tertiary amines, aminoethers, and sulfones. The term "substantially fluorinated or perfluorinated" is considered to refer to compounds in which at least 50% of the hydrogen atoms are substituted by fluorine. Examples of preferred substantially fluorinated or perfluorinated compounds include perfluoro-n-pentane, perfluoro-n-hexane and perfluorinated alkyltetrahydrofurans. The insoluble and inert fluorinated compound should be used in an amount ranging from about 0.01 to about 5% by weight of the total system. The reaction system used in the present process may further comprise one or more auxiliary agents or additives as needed for particular purposes. Suitable auxiliary agents and additives include foam stabilizing agents or surfactants (e.g. organo-silicone polymers), catalysts (e.g., stannous octoate, dibutyltin laurate, tertiary amine), flame retardants (e.g., tris (2-chloroethyl) - phosphate and organophosphorus compounds), viscosity reducers, agents that improve compatibility, mold release agents, fillers or fillers, pigments and antioxidants. Suitable additives and the amounts thereof necessary for a particular purpose will be readily recognizable by those familiar with the art from the present disclosure. The present invention will now be illustrated with reference to the following non-limiting examples.

Example 1 Two samples are prepared containing the components described in tables 1, 2 and 3 using CFC-11, isopentane, n-pentane, cyclopentane and HCFC-141b as blowing agents as indicated. The "side A" of the system contains the polyisocyanate while the "side B" of the systems contains all the other ingredients. The B-side components are prepared by mixing all of the components together at room temperature in a high-speed mixer.

Table 1 Components Blown with CFC-Stepanpol "" PS-2502-A 100 100 OabooMR DC 193 2.5 2.5 -octoate in solution DEG 3 3 Debco "" TMR-30 1 1 CFC-1 1 45 43 Total blown, mls / am 24.45 23.36 index 250 250 Rubinate ™ 1850 148.25 148.25 Raactividtdas Cream time (seconds) 1 1 1 1 Gel time (seconds) 27 26 Completion of elevation (seconds) 66 65 Foam properties: Foam core density (pcf) 1.75 1 .83 Dim. Stab @ -20 ° F,% linear change -3.3 -1 Table 2 Component * 1 2 3 4 5 Stapan "" PS 2352 31.2 31.2 31.2 31 .2 32.87 TCPP 3 3 3 3 TEP 3 3 3 3 K-octoate in SDR 0.75 0.75 0.75 0.75 0.66 K-acetate an DEG 0.25 0.25 0.25 0.25 0.16 Polvcat "" 5 0.12 0.12 0.12 0.12 0.15 TegostabMR B84PI 0.82 TegostabMR B8466 1 1 1 1 Isopentane 5.66 1.89 n-pentane 5.66 1.89 Cyclopentane 5.66 1 .89 Ratio of s / rv / cycle 97.5: 2.5: 0.1: 99.9: 0.7: 10.3: 33:38:29 - 0 0 89 HCFC- 1 1 b 1 1 .66 Water 0.35 0.35 0.35 0.35 0.16 Total blown (ml / g) 22 22 22 22 24.36 index 275 275 275 275 250 RubinateMR 1850 54.69 54.69 54.69 54.69 53.51 Reactivities: Cream / gel time (seconds) 7/27 9/29 12/27 10/29 1 2/25 TFT / EOR time (seconds) 44/73 43/63 42/64 44/88 36/64 Foam properties: Foam core density (pcf) 1 .82 1 .89 1 .93 1 .92 1 .89 Estab. of the Dim (@ -29 ° C (-20 ° F,% change from -0.8 -0.1 -1 .5 -0.8 -0.7 linear) Thermal condfa'on (in BTU / pu / gada / ft'.hora'F / : Initial 0.158 0.159 0.154 0.55 0.143 4 weeks at eo ° C (140 ° F) 0.184 0.186 0.189 0.182 0.169 8 weeks at SO ^ C (140 ° F) 0.187 0.19 0.194 0.188 0.179 12 weeks at 60 ° C (140 ° F) 0.187 0.191 0.193 0.187 0.185 Table 3 Component * 6 7 8 9 10 Terete "" 2541 31.2 31.2 31.2 31.2 32.87 TCPP 3 3 3 3 TEP 3 3 3 3 K-octoate in SDR 0.75 0.75 0.75 0.75 0.66 K-acetate in DEG 0.25 0.25 0.25 0.25 0.16 Polycat "" 5 0.12 0.12 0.1 2 0.12 0.15 Tegostab "" B84PI 0.82 Tegostab "" B8466 1 1 1 1 Isopentane 5.66 1.89 n-pentane 5.66 1.89 Cyclopentane 5.66 1 .89 Ratio of iso / n cycle 97.5: 2.5: 0.1: 99.9: 0.7: 10.3: 8 33:38:29 - 0 0 9 HCFC -141b 1 1 .66 Water 0.35 0.35 0.35 0.35 0.16 Total blown (ml / g) 22 22 22 22 24.36 index 275 275 275 275 250 RubinateMn 1850 54.69 54.69 54.69 54.69 53.51 Reactivities: Cream / gel time (sec) 8/30 9/29 12/27 1 1/31 14/27 TFT / EOR time (sec) 44/73 41/63 39/62 51/72 44/68 Properties of the tack Foam core density (pcf) 1 .81 1 .88 1 .92 1 .91 1 .88 Estab. of Dim (@ 29 ° C (20 ° F>,% change from -0.5 -0.7 -2 -0.8 -4 line) Thermal Cond. * (in BTU in / ft. 'hour'F): Initial 0.165 0.163 0.160 0.159 0.147 4 weeks at 60 ° C (140 ° F) 0.193 0.196 0.199 0.191 0.180 8 weeks at 60 ° C (140 * F) 0.194 0.201 0.203 0.193 0.190 1 2 weeks at eO ° C (140 ° F) 0.195 0.201 0.201 0.195 0.193 RUBINATEMR 1850 is a highly functional poly-functional diphenylmethane diisocyanate, available from ICI Americas Inc. STEPANOL PS-2502-A is an aromatic polyester polyol available from Stepan Company. DABCOMR DC 193 is a silicone surfactant available from Air Products Inc. DABCOMR TMR-30 is a tertiary amine catalyst from Air Products Inc. STEPANMR PS 2352 a is aromatic polyester polyol available from Stepan Company. TERATE ™ 2541 is an aromatic polyester polyol available from Cape Industries. TCPP is tri (beta-chloropropyl) phosphate available from Great Lakes Chemical Corp (containing 32.5% Cl and 9.5% P). TEP is triethyl phosphate available from Focus Chemical Corporation containing 18.7% P). Potassium acetate is used as a 15% solution in DEG available from Air Products. Potassium octoate is used as a 15% solution in DEG available from Pelron Corp. POLYCATMR 5 is a catalyst that promotes polyurethane available from Air Products Inc.

TEGOSTABMR B8466 is a silicone surfactant available from Goldschmidt Corporation. The cyclopentane used in samples 1 to 16 is cyclopentane technical grade containing 77.5% cyclopentane, 9% n-pentane and 0.6% isopentane (the remainder are impurities), available from Phillips. The isopentane used in samples 1 to 10 contains 97.5% isopentane and 2.5% n-pentane and is available from Southhampton Refining Company. The isopentane used in samples 11 to 16 contains 99% isopentane and 0.4% n-pentane and is also available from Southampton Refining Company. The n-pentane used in samples 1 to 16 contains 99.6% n-pentane and 0.1% isopentane (the rest are impurities) and is available from Southhampton Refining Company. The CFC-11 used is available from ICI Americas Inc. The reactivity of each sample was measured by preparing free lift cup foam by mixing the ingredients indicated in tables 1, 2 and 3 using a propellant mixer of this speed room temperature. The physical properties of the core foam were measured in a free-lift foam made by mixing the ingredients and pouring them into a 17.8 x 17.8 x 38 cm (7"x 7" x 15") paper box immediately after mixing. The density of the foam core is measured according to the procedure established in ASTM D 1622 and the dimensional stability of the foams at -29SC (-20aF) using the method of long-term dimensional stability as described in "Factors Affecting the long-term dimensional stability of rigid foam for the construction industry "(Factors Affecting the Long Term Dimensional Stability of Rigid Foam for the Construction Industry", Daems, Rosobothom, Franco and Singh, 35th Annual SPI Technical / Marketing Conference, October of 1994. The thermal conductivity of the samples was measured according to the procedures set forth in ASTM C518 in a foam core formed from foam blocks of 38 x 38 x 36 cm (15"x 15" x 14"). The total blowing of the foam formulations was calculated using the following equation. my gas / gm = Sum of Weight of the goplartn component and 22400 Total weight of foam x molecular weight of the blowing component The foams shown in table 1 establish the reference point for the previous foam technology with respect to the concern of ozone depletion by the initial blowing agent CFC-11. It can be seen in Tables 2 and 3 that foam samples blown with isopentane according to the present invention (samples 1 and 6) provide dimensionally stable foams at relatively low density. A dimensionally stable foam, defined as a foam with% linear load less than or equal to 1% in the dimensional stability test, can be considered with the blowing agent described in this invention (samples 1 and 6, in tables 2 and 3) at a density similar to those blown by the blowing agent CFC-11 (Table 1). The use of CFC-11 has been severely restricted due to its association with the depletion of ozone in the earth's atmosphere. A dimensionally stable foam can also be manufactured at a lower density than that blown with the blowing agent HCFC-1 1b (Sample 5 and 10 in tables 2 and 3), whose use is currently intended to be completed in 2002. In addition, the blowing efficiency, measured by the density of the foam obtained for a given amount of blowing agent per unit weight of the formulation, is the lowest for the foams prepared according to the present invention. The excellent dimensional stability provided by the present blowing agent, combined against exceptional blowing efficiency, leads to the conclusion that rigid, structurally stable polyurethane foams can be made using smaller amounts of blowing agents. In addition, the aged K-factor of the foams prepared according to the present invention is better than that of any of the above methane and equivalent to the foams blown with the pentane mixture (Samples 4 and 9).

Example 2 Table 4 shows the formulation, reactivity and physical properties of samples 10 to 16 of rigid foam prepared with various mixtures of isopentane and n-pentane. The foams are prepared in the manner described above in Example 1. The thermal conductivity is measured by following the procedure set forth in ASTM C518. The density of the foam core and the dimensional stability at -29 C (-20SF) are measured using the following method mentioned in Example 1. It can be seen that the foams prepared using blowing agents containing mixtures of isopentane to n-pentane in proportions from 80:20 to 97: 3 (sample 13 to sample 15) are dimensionally stable at a density similar to that typical for CFC-11. Such stability is not possible with HCFC-141b, the intermediate blowing agent for the building insulation industry or any of the other mixtures evaluated. This excellent dimensional stability means that structurally stable rigid polyurethane foams can be made and can be used at a lower density if current processes and reaction systems are used. The initial K-factor of the foams prepared with mixtures of isopentane and n-pentane in the ratio 80:20 to 97: 3 (samples 13, 14 and 15) is slightly lower than those blown with pure isopentane or pure n-pentane. The aged K-factor, that is, the long-term insulation value of the foams, for the 90:10 (sample 14) and the 97: 3 (sample 15) mixtures of isopentane with respect to n-pentane, is better than for any of the other tested pentanes. The long-term insulation value of the 90:10 and 97: 3 isopentane mixtures with respect to n-pentane approximates a value very close to that of HCFC-141b.

Table 4 Component * 11 12 13 14 15 16 Stepan "" PS 2352 31.2 31.2 31.2 31.2 31 .2 31.2 TCPP 3 3 3 3 3 3 TEP 3 3 3 3 3 3 K-octoate in SDR 0.75 0.75 0.75 0.75 0.75 0.75 K-acatato in DEG 0.25 0.25 0.25 0.25 0.25 0.25 Polveat "" 5 0.12 0.12 0.12 0.12 0.12 0.12 TegostabMR B8466 1 1 1 1 1 1 Isopentane 0 2.83 4.53 5.09 5.49 5.66 n-pentane 5.82 2.83 1.13 0.57 0.17 0 Ratio of so / n-pentane 0: 100 50:50 80:20 90:10 97: 3 100: 0 Water 0.35 0.35 0.35 0.35 0.35 0.35 Total blown (ml / am) 22 22 22 22 22 22 index 275 275 275 275 275 275 Rubinate R 1850 54.69 54.69 54.69 54.69 54.69 54.69 Rottividmdas Cream / gel time (seconds) 8/28 8/28 8/30 8/28 7/27 8/29 TFT / EOR time (seconds) 41/65 41/64 44/65 38/65 44/63 38/63 Property of the - uma. Foam density of the foam (pcf) 1.82 1.83 1.83 1.83 1.82 1.81 Estab. of the Dim (@ -29 ° C (-20 ° F,% change -1.7 -2.2 -0.2 -0.1 -0.1 -0.8 linear) Cond. Témicaa (an BTU an / pia'.hora'F): Initial 0.169 0.163 0.157 0.157 0.157 0.162 4 weeks at 60"C (140 ° F) 0.198 0.192 0.185 0.184 0.184 0.192 8 weeks at 60 ° C (140 ° F) 0.203 0.196 0.192 0.189 0.187 0.195 12 weeks at eO "C (140 ° F) 0.205 0.199 0.193 0.191 0.187 0.197 Accordingly, it can be seen from the data set forth in Table 4 that the present process and the reaction systems used herein produce rigid foams from polyurethane having excellent dimensional stability as well as superior long-term insulation values (as demonstrated by the aged K-factor) compared to foams prepared with conventional processes.) The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and consequently reference may be made to the appended claims, instead of the preceding specification, as indicated by the scope of the invention.

Claims (17)

1. A process for the production of rigid polyurethane foams, characterized in that it comprises the reaction of: (a) an organic polyisocyanate; (b) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups; and (c) a blowing agent comprising a major proportion of isopentane and n-pentane in a ratio from 99: 1 to more than 80:20 parts by weight under foam foaming conditions.

2. The process according to claim 1, characterized in that it further comprises a carbon dioxide generating material that is selected from the group consisting of water, monocarboxylic acid, polycarboxylic acids and cyclic ureas with hydroxy functionality.

3. The process according to claim 2, characterized in that the carbon dioxide generating agent is water.

4. The process according to claim 1, characterized in that the blowing agent 28 comprises isopentane to n-pentane in a ratio of 98.5: 1.5 to 90:10 parts by weight.

5. The process according to claim 4, characterized in that the blowing agent comprises isopentane to n-pentane in a ratio of 97.5: 2.5 to 90:10 parts by weight.

6. The process according to claim 5, characterized in that the blowing agent comprises isopentane to n-pentane in a ratio of 97: 3 to 90:10 parts by weight.

7. The process according to claim 1, characterized in that the organic polyisocyanate is selected from the group consisting of 4,4 '-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate and diphenylmethane diisocyanate variants. .

8. The process according to claim 1, characterized in that the isocyanate-reactive composition is selected from the group consisting of polyether polyols, polyester polyols and mixtures thereof having average hydroxyl numbers from 100 to 1000 KOH / g and hydroxyl functionalities from 2 to 8.

9. A reaction system for the production of rigid polyurethane foams, characterized in that it comprises: (a) an organic polyisocyanate; (b) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups; and (c) a blowing agent comprising isopentane and n-pentane in a ratio of 99: 1 to more than 80:20 parts by weight.

10. The reaction system according to claim 9, characterized in that it also comprises a carbon dioxide generating material that is selected from the group consisting of water, monocarboxylic acids, polycarboxylic acids and cyclic ureas with hydroxy functionality.

11. The reaction system according to claim 10, characterized in that the carbon dioxide generating material is water.

12. The reaction system according to claim 9, characterized in that the blowing agent comprises isopentane to n-pentane in a proportion from 98.5: 1.5 to 90:10 parts by weight.

13. The reaction system according to claim 12, characterized in that the blowing agent comprises isopentane to n-pentane in a proportion from 97.5: 2.5 to 90:10 parts by weight.

14. The reaction system according to claim 13, characterized in that the blowing agent comprises isopentane to n-pentane in a proportion from 97: 3 to 90:10 parts by weight.

15. The reaction system according to claim 9, characterized in that the organic polyisocyanate is selected from the group consisting of 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate and variants of diphenylmethane diisocyanate.

16. The reaction system according to claim 9, characterized in that the isocyanate-reactive composition is selected from the group consisting of polyether polyols, polyester polyols and mixtures thereof having an average hydroxyl number from 100 to 1000 KOH / g and hydroxyl functionalities from 2 to 8.

17. A rigid polyurethane foam, characterized in that it is produced by the process according to claim 1.