Europa,schesP_ MM M II II INI Ml M I M IN II I II J European Patent Office © Publication number: 0 398 147 B1 Office_„. europeen des brevets © EUROPEAN PATENT SPECIFICATION © Date of publication of patent specification: 09.11.94 © Int. CI.5: C08J 9/14, //(C08J9/14, C08L75:04) © Application number: 90108748.6 @ Date of filing: 09.05.90 © A foaming system for rigid urethane and Isoyanurate foams. ® Priority: 10.05.89 US 350184 © Proprietor: THE DOW CHEMICAL COMPANY (a Delaware corporation) @ Date of publication of application: 2030 Dow Center 22.11.90 Bulletin 90/47 Abbott Road Midland Michigan 48640 (US) © Publication of the grant of the patent: 09.11.94 Bulletin 94/45 @ Inventor: Smlts, Guldo Freddy Veldstraat 37 © Designated Contracting States: B-2110 Wljnegem (BE) AT BE CH DE DK ES FR GB GR IT LI LU NL SE Inventor: Grunbauer, Henri Jacobus Marie Schorploen 45 © References cited: NL-4501 HC Oostburg (BE) EP-A- 0 330 988 US-A- 3 583 921 US-A- 4 624 970 © Representative: Huber, Bernhard, Dlpl.-Chem. et al Patentanwalte H. Welckmann, Dr. K. Flncke F.A. Welckmann, B. Huber Dr. H. Llska, Dr. J. Prechtel, Dr. B. Bohm Postfach 86 08 20 uD-81635 \J i \J\J\J iviuMunchen ■ ■ vs ■ ■ v> ■ ■ (DE) QQ. yi^i— j 00 Oi oo Note: Within nine months from the publication of the mention of the grant of the European patent, any person ® may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition Q,. shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee LU has been paid (Art. 99(1) European patent convention). Rank Xerox (UK) Business Services (3. 10/3.09/3.3.3) EP 0 398 147 B1 Description This invention relates to rigid, closed-celled polyisocyanate-based foams, particularly polyurethane, polyurethane-isocyanurate and polyurethane-urea foams prepared using halocarbon blowing system com- 5 prising a first halocarbon component having a boiling point of at least 283 K and a second halocarbon component having a boiling point of less than or equal to 266 K. It is well-known to prepare such polyurethane foams by reacting an organic polyisocyanate with an active hydrogen-containing compound in the presence of a blowing agent or agents. Generally speaking, such blowing agents are volatile organic compounds which are liquids at room temperature. The poly- io merization reaction between the active hydrogen-containing compound and the polyisocyanate giving a polyurethane is exothermic as is the trimerization reaction of isocyanate giving an isocyanurate polymer. The reaction exotherm is sufficient to vaporize the blowing agent, which then becomes encapsulated in the liquid phase of the polymerizing reaction mixture resulting in the formation of cells. The formation of cells causes the reaction mixture to expand and form a foam which subsequently cures to become a rigid 75 closed-celled polyurethane foam. A problem frequently encountered is that of preventing an unacceptable degree of shrinkage of partially cured foam during the aging or curing period following manufacture. A further problem often encountered in cured foams, especially in applications where polyurethane foam may be exposed to subzero temperatures, below 0 ° C, for extended periods of time, is shrinkage or dimensional stability. 20 Such shrinkage or poor dimensional stability is frequently observed either where blowing agents used to impart the cellular structure to the foam have a high diffusion rate through the urethane polymer such as, for example, carbon dioxide. Or where the blowing agents employed have atmospheric boiling points such that when closed-celled foam containing these blowing agents are subjected for prolonged periods to low temperatures, the blowing agent condenses. The loss of, or condensation of blowing agent from the cell gas 25 leads to greatly reduced internal cell pressures and eventually resulting in shrinkage and/or poor dimen- sional stability of the foam. A further disadvantage of having condensed blowing agent present can be a potentially harmful effect for any polymer or other plastics material present, such as, for example, the polystyrene inner liner used in the production of some refrigeration units which can be attacked by the condensed blowing agent. 30 The shrinkage and poor dimensional stability of some polyurethane foams used for cold-insulation purposes may be controlled to an extent by for example increasing the foam density, but this leads to a more expensive product. Therefore, it is desirable to provide a process for the manufacture of polyurethane foams which have reduced susceptibility to shrinkage and improved dimensional stability. At the same time, it would be an 35 additional advantage if such a process could provide for a reduction or elimination of the commercial dependency on especially "hard" chlorofluorocarbon (CFC) blowing agents. The "hard" CFC blowing agents are those compounds in which all hydrogens of the carbon backbone have been replaced by a halogen, normally fluorine and chlorine, in contrast to "soft" CFCs which have at least one hydrogen atom remaining on the carbon backbone. Such "hard" CFCs are suspected of destroying the earth's protective 40 ozone layer by migrating up through the troposphere to the stratosphere and participating indirectly or directly in the chemical reactions of ozone. This invention accomplishes an improvement in dimensional stability of polyurethane foams. In a preferred embodiment, a significantly lower dependency on the use of "hard" CFC blowing agents can be obtained through selection of "soft" CFC blowing agents. 45 In one aspect, this invention is a process for preparing a rigid closed-celled polyisocyanate-based foam which comprises reacting an organic polyisocyanate with an active hydrogen-containing compound in the presence of water and a blowing agent characterized in that the water is present in from at least 1 .8 parts by weight per 100 parts by weight of active hydrogen-containing compound and water, and in that the blowing agent comprises: 50 (a) from 40 to 95 mole percent, based on components (a) and (b), of at least one halocarbon compound having a boiling point of at least 283K, and (b) from 5 to 60 mole percent, based on components (a) and (b), of at least one halocarbon compound having a boiling point of from 235K to 266K, and wherein the ratio of said boiling point of a component (a) to a component (b) is from 1.06:1 to 1.20:1 55 and wherein said blowing agent is free of any organic compound having a boiling point of 338K or greater. In a second aspect, this invention is an isocyanate-reactive composition comprising at least one active hydrogen-containing compound having an equivalent weight of from 50 to 700, water, and a blowing agent characterized in that the water is present in from at least 1.8 parts by weight per 100 parts by weight of 2 EP 0 398 147 B1 active hydrogen-containing compound and water, and in that the blowing agent is present in an amount of from 1 to 30 weight percent of total weight of the composition and blowing agent and in that the blowing agent comprises: (a) from 40 to 95 mole percent, based on components (a) and (b), of at least one halocarbon compound 5 having a boiling point of at least 283K, and (b) from 5 to 60 mole percent, based on components (a) and (b), of at least one halocarbon compound having a boiling point of from 235K to 266K , and wherein the ratio of said boiling point of a component (a) to a component (b) is from 1.06:1 to 1.20:1 and wherein said blowing agent is free of any compound having a boiling point of 338K or greater. io In a third aspect, this invention is a rigid, closed-celled polyisocyanate-based foam prepared according to the process of this invention and characterized in that the resulting foam contains within its cells a gaseous composition comprising: (a) from 30 to 85 mole percent, based on component (a) and component (b), of a mixture comprising: (1) from 40 to 95 mole percent, based on components (1) and (2), of at least one halocarbon is compound having a boiling point of at least 283K, and (2) from 5 to 60 mole percent, based on components (1) and (2), of at least one halocarbon compound having a boiling point of from 235K to 266K, and wherein the ratio of said boiling points of component (1) to component (2) is from 1.06:1 to 1.20:1 and wherein said composition is free of any compound having a boiling point of 338 K or greater; and 20 (b) from 15 to 70 mole percent, based on component (a) and (b), of carbon dioxide. It has been found surprisingly, that this invention provides for the use of combinations of low boiling point organic compounds with high boiling point organic compounds as blowing agent to provide polyure- thane foams with overall acceptable physical properties, including improved dimensional stability. The combination of a high boiling point and a low boiling point blowing agent are not normally employed for the 25 preparation of rigid, closed-celled, polyisocyanate-based foam. A further advantage is that in certain embodiments of this invention can also allow for the production of foam with good dimensional stability that contains reduced quantities of, or no "hard" CFC. In the process of this invention, a particular blowing agent composition is employed to prepare a blown, rigid, closed-celled polyisocyanate-based foam. 30 The blowing agent composition is characterized in that it comprises as a first component, at least one organic compound having a boiling point of at least 283 K at atmospheric pressure.