Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1997-06-10
2002-01-15
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S167000, C252S182270
Reexamination Certificate
active
06339110
ABSTRACT:
This invention relates to processes for the preparation of rigid polyurethane or urethane-modified polyisocyanurate foams, to foams prepared thereby, and to novel compositions useful in the process.
Rigid polyurethane and urethane-modified polyisocyanurate foams are in general prepared by reacting the appropriate polyisocyanate and isocyanate-reactive compound (usually a polyol) in the presence of a blowing agent. One use of such foams is as a thermal insulation medium as for example in the construction of refrigerated storage devices. The thermal insulating properties of rigid foams are dependent upon a number of factors including, for closed cell rigid foams, the cell size and the thermal conductivity of the contents of the cells.
A class of materials which has been widely used as blowing agent in the production of polyurethane and urethane-modified polyisocyanurate foams are the fully halogenated chlorofluorocarbons, and in particular trichlorofluoromethane (CFC-11). The exceptionally low thermal conductivity of these blowing agents, and in particular of CFC-11, has enabled the preparation of rigid foams having very effective insulation properties. Recent concern over the potential of chlorofluorocarbons to cause depletion of ozone in the atmosphere has led to an urgent need to develop reaction systems in which chlorofluorocarbon blowing agents are replaced by alternative materials which are environmentally acceptable and which also produce foams having the necessary properties for the many applications in which they are used.
A class of materials which have been used as alternative blowing agents with zero ozone depletion potential are hydrocarbons especially alkanes and cycloalkanes such as isobutane, n-pentane, isopentane, cyclopentane and mixtures thereof. However thermal insulation properties of hydrocarbon blown rigid polyurethane foams are not satisfactory. Another disadvantage of hydrocarbon blowing agents is their limited solubility in the standard isocyanate-reactive compositions.
It is an object of the present invention to provide hydrocarbon blown rigid polyurethane or urethane-modified polyisocyanurate foams having improved thermal insulation properties.
It is another object of the present invention to provide a process for making hydrocarbon blown rigid polyurethane or urethane-modified polyisocyanurate foams whereby the solubility of the blowing agent in the isocyanate-reactive composition is improved.
These objects are met by using in the process of making rigid polyurethane or urethane-modified polyisocyanurate foams from polyisocyanates and isocyanate-reactive components in the presence of hydrocarbons as blowing agent a tolylenediamine(TDA)-initiated polyether polyol in an amount of between 10 and 40% by weight based on the total isocyanate-reactive compounds.
Foams prepared by the process of the present invention show better thermal insulation than foams from the prior art prepared not using tolylenediamine (TDA)-initiated polyether polyols. Further the solubility of hydrocarbon blowing agents in the isocyanate-reactive composition is improved by using TDA-initiated polyether polyols.
Aromatic amine initiated polyether polyols such as TDA-initiated polyether polyols and diaminodiphenylmethane or polymethylene polyphenylene polyamine (DADPM)-initiated polyether polyols have been described as suitable isocyanate-reactive compounds for hydrocarbon blown rigid polyurethane foams (see, for example, EP 421269, WO 94/25514, EP 708127, U.S. Pat. Nos. 5,523,333, 5,523,332, 5,523,334 and EP 617068). None of these prior art documents suggests an improvement in thermal insulation properties or in hydrocarbon solubility by using TDA-initiated polyether polyols instead of DADPM-initiated polyether polyols. WO 96/23017 and EP 747411 (both citable under Article 54(3) EPC) describe the use of TDA-initiated polyols in hydrocarbon blown rigid polyurethane foams in an amount of at least 40% by weight based on total polyols.
The TDA-initiated polyether polyols for use in the present invention are obtained by the addition of alkylene oxides, such as ethylene oxide and/or propylene oxide to one or more of the various isomers of tolylene diamine such as 2,4-, 2,6-, 2,3- and 3,4-TDA. Preferably 2,3- and/or 3,4-TDA (ortho-TDA or vicinal TDA) is used as initiator with up to 25 wt % of total initiator of meta-TDA (2,4- and/or 2,6-TDA). Vicinal TDA is a pure isomer or mixture thereof, preferably containing 20 to 80 wt % 2,3-TDA and 80 to 20 wt % 3,4-TDA. Other co-initiators can be used additionally in an amount up to 60% by weight of total initiator, preferably between 5 and 10% by weight. In a preferred embodiment aliphatic amines are not used as co-initiator.
The alkylene oxides used are preferably 0 to 90% ethylene oxide, more preferably 20 to 80% ethylene oxide and 100 to 10%, preferably 80 to 20% propylene oxide.
The TDA-initiated polyether polyols for use in the present invention generally have OH numbers in the range 200 to 700, preferably 250 to 550 mg KOH/g, more preferably between 350 and 520 mg KOH/g and have functionalities in the range 2 to 8, preferably 3 to 6. The molecular weight is generally between 400 and 700.
Tolylene diamine initiated polyether polyols and methods for their preparation are fully described in the prior art, for example, in U.S. Pat. Nos. 4,243,759, 5,141,968, 4,391,728, 4,421,871, 4,562,290, 4,469,822, 4,397,966, DD 272307, DD 251151, DD 290202 and DD 290201.
A preferred TDA-initiated polyether polyol for use in the present invention is a polyether polyol of OH value 300 to 400 mg KOH/g, obtained by reacting o-TDA (containing up to 25 wt % of m-TDA) with propylene oxide. The amount of TDA-initiated polyol is preferably between 10 and 39% by weight based on the total isocyanate-reactive compounds, more preferably between 10 and 35% by weight, most preferably between 20 and 33% by weight.
In the case of blowing with solely cyclopentane as hydrocarbon the amount of TDA-initiated polyether polyol is preferably below 35% by weight, more preferably below 30% by weight, most preferably below 25% by weight based on total isocyanate-reactive compounds.
The hydrocarbon blowing agents for use in the present invention are preferably (cyclo)alkanes, preferably containing from 3 to 8 carbon atoms, such as cyclopentane, isopentane, n-pentane, neopentane, n-butane, cyclobutane, methylcyclobutane, isobutane, propane, cyclopropane, methylcyclopropane, n-hexane, 3-methylpentane, 2-methylpentane, cyclohexane, methylcyclopentane, n-heptane, 2-methylheptane, 3-ethylpentane, 2,2,3-trimethylbutane, 2,2-dimethylpentane, cycloheptane, methylcyclohexane, 2,2-dimethylbutane and 2,3-dimethylbutane. Particularly preferred hydrocarbons are the C5 and C6 (cyclo)alkanes such as cyclopentane, n-pentane and isopentane, and any mixtures thereof and mixtures of any of these with isobutane.
A preferred blowing agent is a mixture of isopentane and n-pentane in a weight ratio of between 75:25 and 25:75, most preferably at a ratio 8/3. Another preferred blowing agent is a mixture of cyclopentane and isopentane and/or n-pentane in a weight ratio cyclopentane:n/isopentane of between 80:20 and 20:80, preferably 60:40 wherein the weight ratio npentane:isopentane is preferably between 0:100 and 50:50.
Suitable isocyanate-reactive compounds which may be employed in admixture with the TDA-initiated polyether polyols include any of those known in the art for the preparation of rigid polyurethane or urethane-modified polyisocyanurate foams. Of particular importance for the preparation of rigid foams are polyols and polyol mixtures having average hydroxyl numbers of from 300 to 1000, especially from 300 to 700 mg KOH/g, and hydroxyl functionalities of from 2 to 8, especially from 3 to 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, trimethylolpropan
Barettini Silvio
Bazzo Walter
Cappella Andrea
Franco Maria Vittoria
Hoffmann Werner
Gorr Rachel
Imperial Chemical Industries PLC
LandOfFree
Process for rigid polyurethane foams does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for rigid polyurethane foams, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for rigid polyurethane foams will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2841790