Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-03-08
2001-11-13
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S163000, C521S167000, C521S170000, C521S172000
Reexamination Certificate
active
06316513
ABSTRACT:
This invention relates to a novel process for the production of substantially closed-cell rigid polyurethane foams.
Due to their low thermal conductivity, rigid polyurethane foams are used for insulation applications in refrigeration and freezing appliances, in industrial equipment, tank farms, pipelines, shipbuilding and in the construction industry. A summary review of the production of rigid polyurethane foams and the use thereof is given in
Kunststoff-Handbuch,
volume 7 (Polyurethane), 2nd edition 1983, edited by Dr. Günter Oertel (Carl Hanser Verlag, Munich).
The thermal conductivity of a largely closed-cell rigid polyurethane foam is largely dependent upon the nature of the blowing agent or cell gas used. Completely halogenated chlorofluorocarbons (CFCs), inparticular trichlorofluoromethane (R11), which has particularly low thermal conductivity, had proved particularly suitable for this purpose. These substances are chemically inert and non-toxic. However, due to their elevated stability, completely halogenated chlorofluorocarbons reach the stratosphere, where, due to their chlorine content, they play a part in breaking down the ozone present there (for example Molina, Rowland,
Nature
249 (1974) 810; first interim report of the German Parliament's commission of enquiry,
Vorsorge zum Schutz der Erdatmosphäre
[precautions for the protection of the earth's atmosphere] of 02.11.1988, German Parliament, public relations department, Bonn).
Formulations containing a lower R11 concentration have been proposed in order to reduce the R11 content in rigid polyurethane foams.
It has also be proposed (for example EP 344 537, U.S. Pat. No. 4,931,482) to use partially fluorinated hydrocarbons (hydrofluoroalkanes) which still contain at least one carbon-hydrogen bond as a blowing agent. Substances from this class of compounds contain no chlorine atoms and thus have a ODP value (ozone depletion potential) of zero (by way of comparison: R11: ODP=1). Typical representatives of this class of substances are, for example: 1,1,1,4,4,4-hexafluorobutane (R356) or 1,1,1,3,3-pentafluoropropane (245fa).
It is furthermore known to use hydrocarbons, either pure or as a mixture (U.S. Pat. No. 5,391,317), such as n- or i-pentane, 2,2-dimethylbutane, cyclopentane or cyclohexane as blowing agents. It is also known to use hydrocarbons in conjunction with water as blowing agents (EP 0 421 269).
It is moreover known that, by virtue of their chemical structure, unsubstituted hydrocarbons are highly non-polar and thus mix very poorly with the polyols conventionally used in rigid foam production. Complete miscibility is, however, an important prerequisite for the conventional production technique in which the polyol and isocyanate components are mechanically foamed. In addition to the reactive polyether- or polyesterpolyols, the polyol component also contains blowing agents and auxiliaries such as activators, emulsifiers and stabilisers in dissolved form. It is known that polyol formulations containing aminopolyethers exhibit particularly high alkane solubility (WO 94/03515).
It is also known that hydrocarbon-blown rigid foams have poorer thermal conductivities than rigid foams blown with R11 or with reduced quantities of R11, which is due to the higher thermal conductivities of hydrocarbon gases. (Thermal conductivities of the gases at 20° C.: R11: 8 mW/mK; cyclopentane: 10 mW/mK; n-pentane, 13 mW/mK; i-pentane, 13 mW/mK).
The object of the present invention was to provide hydrocarbon-blown rigid polyurethane foams which have thermal conductivities of the same low level as foams blown with reduced quantities of R11.
It has surprisingly been found that polyol formulations based on a certain polyol mixture yield foams having thermal conductivities which are at the same, low level as foams blown with reduced quantities of R11, in particular if cyclopentane is used as the blowing agent.
The present invention accordingly provides a process for the production of rigid polyurethane foams having low thermal conductivity from polyols and polyisocyanates together with blowing agents and optionally foam auxiliaries, characterised in that the rigid polyurethane foam is obtained by reacting
A. a polyol component containing
1. at least one polyesterpolyol of a molecular weight of 100 to 30000 g/mol having at least two isocyanate-reactive hydrogen atoms,
2. compounds of a molecular weight from 150 to 12500 g/mol containing at least two isocyanate-reactive hydrogen atoms, the molecules of which compounds contain at least one tertiary nitrogen atom,
3. compounds of a molecular weight from 150 to 12500 g/mol containing at least two isocyanate-reactive hydrogen atoms,
4. catalysts,
5. water,
6. blowing agent and
7. optionally auxiliary substances and additives with
B. an organic and/or modified organic polyisocyanate having an NCO content of 20 to 48 wt. %.
It is surprising that the combination according to the invention of a polyesterpolyol with the stated aminopolyethers and a further polyol in the polyol component of hydrocarbon-blown foams should result in such a low thermal conductivity.
Polyol formulations according to the invention contain at least one polyesterpolyol of the molecular weight from 100 to 30000 g/mol, preferably of 150 to 10000 g/mol, particularly preferably of 200 to 600 g/mol, prepared from aromatic and/or aliphatic mono-, di- or tricarboxylic acids and polyols containing at least two hydroxyl groups. Examples of dicarboxylic acids are phthalic acid, fumaric acid, maleic acid, azelaic acid, glutaric acid, adipic acid, suberic acid, terephthalic acid, isophthalic acid, decanedicarboxylic acid, malonic acid, glutaric acid, succinic acid and fatty acids such as stearic acid, oleic acid, ricinoleic acid. Both the pure mono-, di- or tricarboxylic acids and any desired mixtures thereof may be used. Instead of the free mono-, di- and tricarboxylic acids, it is also possible to use the corresponding mono-, di- and tricarboxylic acid derivatives, such as for example mono-, di- and tricarboxylic acid esters of alcohols having 1 to 4 carbon atoms or mono-, di- and tricarboxylic anhydrides or triglycerides. The following are preferably used as the alcohol component for esterification: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, glycerol, trimethylolpropane or mixtures thereof.
According to the invention, polyol formulations may also contain polyether esters, as may, for example, be obtained by reacting phthalic anhydride with diethylene glycol and subsequently with ethylene oxide (EP-A 0 250 967).
Polyol formulations according to the invention contain at least one compound of the molecular weight from 150 to 12500 g/mol, preferably of 200 to 1500 g/mol, containing at least two isocyanate-reactive hydrogen atoms, the molecules of which compound contain at least one tertiary nitrogen atom. These compounds are obtained by polyaddition of alkylene oxides, such as for example ethylene oxide, propylene oxide, butylene oxide, dodecyl oxide or styrene oxide, preferably propylene oxide or ethylene oxide, onto starter compounds. The starter compounds used are ammonia or compounds containing at least one primary or secondary or tertiary amino group, such as for example aliphatic amines such as ethylenediamine, ethylenediamine oligomers (for example diethylenetriamine, triethylenetetramine or pentaethylenehexamine), ethanolamine, diethanolamine, triethanolamine, N- methyl- or N-ethyldiethanolamine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-hexamethylenediamine, aromatic amines such as phenylenediamines, tolylenediamines (2,3-tolylenediamine, 3,4-tolylenediamine, 2,4-tolylenediamine, 2,5-tolylenediamine, 2,6-tolylenediamine or mixtures of the stated isomers), 2,2′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane or mixtures of these isomers.
Polyol formulations according to the invention
Eisen Norbert
Heinemann Torsten
Klan Walter
McCullough Dennis
Bayer Aktiengesellschaft
Brown N. Denise
Cooney Jr. John M.
Gil Joseph C.
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