Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-08-09
2002-10-01
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...
C521S114000, C521S170000, C521S174000
Reexamination Certificate
active
06458862
ABSTRACT:
The present invention relates to the use of hydrofluoropolyethers (HFPE) as foaming agents in substitution of trichloro-fluoromethane (CFC 11). Said foaming agents are used to prepare polymeric foams, specifically polyurethane foams.
More specifically the present invention relates to the use of hydrofluoropolyethers as foaming agents, characterized by low GWP values (Global Warming Potential) and by ODP (Ozone Depletion Potential) and VOC (Volatile organic Compounds) values equal to zero to be used in substitution of CFC 11 for preparing polymeric foams, specifically rigid closed cell polyurethanes.
The foamed polymer application is well known. For illustrative purposes the application concerning polyurethanes is hereinafter reported. In particular, as it is known, foamed polyurethanes represent a class of materials widely used for applications concerning the furnishing, car and in general transport, building and cooling industry.
Polyurethanes are polyaddition products between isocyanates and polyols; depending on the precursor features, it is possible to obtain flexible, rigid foams, or foams having intermediate characteristics.
The former are used in the furnishing and car sector, while rigid closed cell polyurethanes are widely used in the thermal insulation field for building and cooling industry.
All the polyurethane foams require a foaming agent for their preparation in order to obtain cellular structures, density, mechanical and insulation properties suitable for any application type.
In particular, the rigid polyurethane insulating properties are given by the presence of closed cells internally containing foaming agent vapours characterized by low thermal conductibility values.
As known, the main foaming agent used for the preparation of rigid foamed polyurethanes has been CFC 11.
A great part of the technology relating to rigid polyurethanes for the thermal insulation has been for a long time developed and optimized for the use of this foaming agent.
CFC 11 is characterized by particular chemical physical properties such as to be advantageously used in the previously described sector and allows, furthermore, a simple, cheap and safe use since it is chemically stable, non flammable and non toxic.
CFCs and specifically CFC 11 have, however, the drawback to show a high destroying power on the stratospheric ozone layer, therefore, the production and commercialization have been subjected to rules and then banned since Jan. 1, 1995.
The need is therefore particularly felt to identify alternative products able to replace CFC 11 in the mentioned application fields while respecting and protecting the environment.
In the foamed polyurethane field, the use versatility of these products, which allows applications in different fields with the use of suitable technologies and raw material formulations, has made impossible the identification of a single product valid for the replacement of CFC 11 in all applications.
The alternative solutions which now result widely used foresee the use of hydrocarbons (n-pentane, iso-pentane and cyclo-pentane) or of HCFC 141b (1,1-dichloro-1-fluoroethane: CCl
2
FCH
3
).
Hydrocarbons, due to their high flammability, have not a generalized use and require large investments to avoid fire and explosion risks in plants and rooms wherein they are used or stored.
Furthermore, these foaming agents constitute an atmospheric pollution source since, if exposed to the sun light in the presence of nitrogen oxides, they undergo oxidative degradation phenomena, with formation of the so called ozone-rich “oxidizing smog”. Due to this negative characteristic, these products are classified as VOC compounds (Volatile Organic Compound).
HCFC 141b, which has been and is one of the most valid substitutes for above applications, has however the drawback to be moderately flammable and especially to be characterized by an ODP value equal to 0.11 (CFC 11 has ODP=1) and therefore it has been subjected to restricted use.
Besides, another drawback of all the above mentioned substitutes is that they are characterized by thermal conductibility values higher than CFC 11, with consequent decrease of the insulating power of the foaming agents.
There was a need to have available substitutes able to furtherly limit or overcome the above mentioned environmental and safety problems and which allow a simpler and generalized use as foaming agents, with the possibility to obtain results similar to those obtained with CFC 11.
The Applicant has unexpectedly found that the hydrofluoropolyethers (HFPE) object of the present invention are characterized by chemical-physical properties such to be suitable as substituent of CFC 11, they are non flammable, have an environmental impact expressed in ODP and VOC equal to zero, and low GWP values.
It is therefore an object of the present invention hydrofluoropolyether foaming agents:
difluoromethoxy-bis(difluoromethyl ether) (indicated as HFPE1) of formula HCF
2
OCF
2
OCF
2
H; and/or
1-difluoromethoxy-1,1,2,2-tetrafluoroethyl difluoromethyl ether (indicated as HFPE2) of formula HCF
2
OCF
2
CF
2
OCF
2
H.
The main characteristics of the hydrofluoropolyethers of the present invention are reported in Table 1 in comparison with CFC 11 and HCFC 141b. The hydrofluoropolyethers are characterized by a combination of chemical-physical properties such as:
chemical inertia
high thermal stability
suitable boiling temperature
low thermal conductibility
suitable solubility in polyols
low solvent power towards the polyurethane matrix such as to be particularly suitable, as pure fluids or in admixture with each other, for the CFC 11 replacement in the foamed polymer field, specifically in the rigid polyurethanes field.
The preliminary studies on the acute toxicity show that the hydrofluoropolyethers reported in Table 1 have a low biologic activity.
It has been found by the Applicant that the particular hydrogen atom distribution on the terminal ends and the presence of an ethereal bond prevents dehydrofluorination reactions, which would lead to toxic olefins formation and avoids the acidity formation which would imply metal material corrosion phenomena and inactivation of basic catalysts generally used in foaming agent formulations, specifically in polyurethane formulations.
These decomposition reactions which are typical of hydrofluorocarbons (ex: HCFC 141b, HCFC 123: 1,1 dichloro-2,2,2 trifluoro ethane, HCFC 22: chlorotrifluoro methane) and of some hydrofluorocarbons, are favoured by the presence of basic catalysts used in foaming agent formulations, specifically in polyurethane formulations; they are catalyzed by metals and by heat.
In order to avoid or limit the decomposition of these foaming agents, it is necessary to use stabilizers and/or select less reactive polyols.
Another advantage of the foaming agents of the present invention consists in that they do not require stabilizers as an essential component, and that they can be used also with the catalysts and the most reactive polyols. At any rate stabilizers can be added as optional components.
It has been found by the Applicant that the particular chemical structure of the present invention hydrofluoropolyesters confers a good solubility in the polyols, such as to guarantee the foaming agent preparation with sufficiently low densities without having an excessive solvent power towards the polymeric matrix of the final foaming agent.
The invention HFPE have an ODP value equal to zero and a low GWP value. It has been found that the presence of the hydrogen atoms on the molecule end groups favours the decomposition reactions in the atmosphere and limits the half-life time thereof, with consequent benefit on the direct greenhouse effect generated by the product.
The suitable combination of the above mentioned hydrofluoropolyether properties allows to obtain foams having good properties in terms of thermal conductibility, density, morphology, dimensional stability, mechanical resistance and fire-reactivity.
It has been found that hydrofluoropolyethers having an higher molecular weight, with boiling tempera
Basile Giampiero
Musso Ezio
Visca Mario
Arent Fox Kintner Plotkin & Kahn
Ausimont S.p.A.
Cooney Jr. John M.
LandOfFree
Foaming agents does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Foaming agents, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Foaming agents will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2968066