Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Having discontinuous gas or vapor phase – e.g. – foam:
Reexamination Certificate
2001-11-29
2002-11-05
Foelak, Morton (Department: 1711)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Having discontinuous gas or vapor phase, e.g., foam:
C516S010000, C521S088000, C521S097000, C521S098000, C521S131000
Reexamination Certificate
active
06476080
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a blowing agent composition containing a hydrofluorocarbon (HFC) having a boiling point of 30° C. or higher and lower than about 120° C. (mid-range low-boiling HFC), a HFC having a boiling point lower than 30° C. (low-range low-boiling HFC), and at least one component selected from low-boiling alcohols and low-boiling carbonyl compounds. The present invention further relates to polymeric foams and the use of such a blowing agent composition to produce polymeric foams, and foamable polymer compositions comprising a polymer that has such blowing agent compositions dispersed therein.
2. Description of Related Art
Low-boiling alcohols are useful components in blowing agent compositions for preparing polymeric foams. “Low-boiling alcohol” and “LBA” are interchangeable terms herein and refer to an alcohol having a boiling point lower than about 120° C. LBAs can plasticize a polymer (see, e.g., U.S. Pat. No. 4,663,360 column 12 lines 50-52), facilitating polymer expansion at lower pressures than a non-plasticized polymer. Furthermore, LBAs tend to maintain or increase foam cell sizes even at relatively high concentrations, concentrations where other blowing agents tend to act as nucleators and reduce foam cell sizes. As a result, one may use relatively high concentrations of alcohol to reduce foam density without reducing foam cell size. Reducing density without reducing cell size is attractive for preparing thermally insulating polymeric foam.
Unfortunately, alcohols have drawbacks when used as blowing agents. An alcohol can react with halogenated components that are present in the foam, such as halogenated flame retardants, to produce a corrosive acid. The acid tends to corrode metal equipment. Furthermore, alcohols can escape into the atmosphere whereby they contribute undesirably to volatile organic compound (VOC) emissions.
Low-boiling carbonyl compounds, such as ketones and aldehydes, can facilitate production of a polymeric foam similarly to alcohols, but do so without significantly contributing to acid production. “Low-boiling carbonyl compound” and “LBC” are interchangeable terms and refer to an aldehyde or ketone that has a boiling point lower than about 120° C. Unfortunately, residual LBCs can also escape into the atmosphere whereby they contribute undesirably to volatile organic compound (VOC) emissions.
Blowing agents comprising HFCs are gaining popularity as regulations encourage replacing hydrochlorofluorocarbon (HCFC) and chlorofluorocarbon (CFC) blowing agent components, both of which can contribute to ozone depletion. HFCs have a thermal conductivity lower than most polymers or blowing agents (other than HCFCs and CFCs) so HFC residuals in a polymeric foam can lower the foam's thermal conductivity.
Unfortunately, low-range low-boiling HFCs tend to escape from polymeric foam thereby causing an undesirable increase in polymeric foam thermal conductivity and organic emissions over time. Exploration of mid-range low-boiling HFCs such as 1,1,1,3,3-pentafluorobutane (HFC-365 mfc) as blowing agents is underway. Mid-range low-boiling HFCs can also reduce polymeric foam thermal conductivity and tend to reside within polymeric foam longer than low-range low-boiling HFCs.
A blowing agent composition that benefits from the advantages of a LBA and/or LBC compound yet has less of the detrimental affects of the alcohol and/or carbonyl compound is desirable. A blowing agent composition that further comprises HFCs to reduce the thermal conductivity through a polymeric foam is also desirable, particularly if a mid-range low-boiling HFC partially replaces a low-range low-boiling HFC.
DEFINITIONS
“Hydrofluorocarbon” and “HFC” are interchangeable terms and refer to an organic compound containing hydrogen, carbon, and fluorine, the compound being substantially free of halogens other than fluorine.
“Boiling point” refers to the boiling point at one atmosphere pressure.
“Mid-range low-boiling hydrofluorocarbon”, “mid-range low-boiling HFC”, and “MRLB HFC” are interchangeable terms and refer to a HFC that has a boiling point of 30° C. or higher and lower than about 120° C.
“Low-range low-boiling hydrofluorocarbon”, “low-range low-boiling HFC”, and “LRLB HFC” are interchangeable terms and refer to a HFC that has a boiling point lower than 30° C.
“Fresh” refers to within one month, preferably within one week, more preferably within one day, still more preferably within one hour, most preferably immediately after manufacture.
“LBA and/or LBC” means “LBA, LBC, or LBA and LBC”.
A polymeric foam or blowing agent composition that is “essentially free” of a specified component or components refers to a polymeric foam or blowing agent composition, respectively, that contains ten weight-percent (wt %) or less, preferably five wt % or less, more preferably one wt % or less, still more preferably 0.5 wt % or less, most preferably zero wt % of the specified component(s).
BRIEF SUMMARY OF THE INVENTION
In a first aspect, the present invention is a blowing agent composition comprising: (a) at least one hydrofluorocarbon having a boiling point of 30° C. or higher and lower than about 120° C.; (b) at least one hydrofluorocarbon having a boiling point lower than 30° C.; and (c) at least one component selected from low-boiling alcohols and low-boiling carbonyl compounds. Embodiments of the first aspect include compositions that are essentially free of low-boiling carbonyl compounds and compositions that contain at least one of ethanol, acetone, and additional blowing agents. One preferred embodiment of the first aspect further comprises carbon dioxide at a concentration of less than 50 weight-percent of the composition. Another preferred embodiment of the first aspect comprises 1,1,1,3,3-pentafluorobutane, 1,1,1,2-tetrafluoroethane, ethanol, and carbon dioxide, wherein carbon dioxide is less than 50 weight-percent of the composition.
In a second aspect, the present invention is a process for preparing polymeric foam comprising the steps: (a) forming a foamable polymer composition from a polymer and the blowing agent composition of the first aspect; and (b) expanding said foamable polymer composition into a polymeric foam.
In a third aspect the present invention is a polymeric foam that comprises: (a) a polymer; (b) a hydrofluorocarbon having a boiling point of 30° C. or higher and lower than about 120° C; (c) a hydrofluorocarbon having a boiling point lower than 30° C; and (d) at least one component selected from low-boiling alcohols and low-boiling carbonyl compounds.
In a fourth aspect, the present invention is a foamable polymer composition comprising a polymer that has the blowing agent composition of the first aspect dispersed therein.
Surprisingly, low foam thermal conductivity and ease of processing associated with a blowing agent composition consisting of a LRLB HFC and a LBA and/or LBC is achievable by partially replacing at least one of the LRLB HFC, LBA and LBC with a MRLB HFC. Furthermore, one may achieve a lower foam thermal conductivity 90 days after formation by partially replacing at least one of LRLB HFC, LBA, and LBC with a MRLB HFC in the foam's blowing agent composition.
The blowing agent compositions of the present invention are particularly useful for preparing thermally insulating polymeric foam.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a blowing agent composition comprising at least one MRLB HFC, at least one LRLB HFC, and at least one component selected from LBAs and LBCs.
Suitable LBAs include aliphatic alcohols having from one to five carbons (C
1
-C
5
) such as methanol, ethanol, n-propanol, and isopropanol. LBAs may or may not be anhydrous, but anhydrous (containing less than 1 weight-percent (wt %) water based on weight of alcohol) is preferred. The LBA is preferably ethanol or isopropanol, more preferably anhydrous ethanol.
Suitable LBCs include any ketone or aldehyde that has a boiling point lower than about 120° C. Illustrative LBCs include acetone, 2-butano
Duffy John D.
Griffin Warren H.
Foelak Morton
Mork Steven W.
The Dow Chemical Company
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