Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-04-09
2002-03-19
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...
C521S131000, C521S172000, C252S182240
Reexamination Certificate
active
06359022
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to rigid, closed-cell polyurethane- and polyisocyanurate-based foams and to polyol based resin blends used to make such foams. In particular, the invention relates to polyol based resin blends containing a modified aromatic polyester polyol and a hydrocarbon blowing agent.
2. Description of the Related Art
Polyurethane and polyisocyanurate foams are commonly produced by preparing a resin blend (also known as “B component”) and subsequently mixing the resin blend with an isocyanate immediately prior to discharging the final foam-generating mixture. This resin blend typically contains a polyol or a mixture of polyols, catalysts, silicone or other cell-stabilizing surfactants, and one or more blowing agents which vaporize due to the heat of reaction, resulting in expansion of the foam. It may also contain water, as an additional blowing agent, which functions by chemically reacting with isocyanate to generate carbon dioxide; flame retardants; and other additives.
In such a foam producing process, the resin blend importantly is phase stable, resisting separation into layers of different composition. Often the resin blend is packaged for later sale or use, rather than being used immediately. Even if the resin blend ingredients are blended only by the end user, some time may elapse before the blend is completely consumed in the course of normal production. In some cases, this elapsed time may amount to as much as several days. In either type of application, if the ingredients separate into discrete layers, the resin blend will not perform correctly in use.
As another desirable feature in such a foam producing process, the resin blend ideally has a viscosity sufficiently low to allow easy pumping and mixing. A resin blend having high viscosity can cause difficulties in material transfer, as for example in transporting the resin blend from storage to the foam machine or from the machine holding tank to the mixing head. Excessive viscosity can also seriously obstruct efficient mixing with the isocyanate in the mixing head. For instance, in high-pressure impingement mixing, mixing efficiency may decline when the viscosity of the resin blend is greater than about 1000 to 2000 centipoise at the temperature of use. A resin blend viscosity of less than 1000 centipoise is thus preferred.
In an alternative process for producing polyurethane and polyisocyanurate foams, all ingredients of the resin blend except the blowing agent are combined into one pre-blend. The blowing agent is then either added to the pre-blend and mixed as the combination is transferred to the final mixing head, as by the use of an inline mixer, or the blowing agent is added at the final mixing head itself. The isocyanate, or a mixture of isocyanate and blowing agent, along with other optionally preferred ingredients, are simultaneously transferred to the mixing head, where they are mixed with the pre-blend and blowing agent and discharged to produce the polyurethane or polyisocyanurate foam. Although phase stability need not be maintained for more than a few seconds in such a process, the pre-blend nevertheless ideally mixes easily and uniformly with the blowing agent and the resulting resin blend ideally has a viscosity of less than 1000 centipoise to facilitate mixing with the isocyanate.
In certain circumstances, volatile hydrocarbons such as pentane and cyclopentane can be viable blowing agents for rigid foams. However, when such volatile hydrocarbons are used with existing polyols, poor phase stability and high resin blend viscosity generally result. Inadequate phase stability may be addressed by introducing the blowing agent in a separate stream at or near the mix head, or by constant agitation of the pre-mixed resin blend in a holding tank, as described in “Hydrocarbons Provide Zero ODP and Zero GWP Insulation for Household Refrigeration” by H. Ballhaus and H. Hahn, in
Proceedings of the Polyurethanes World Congress
1993, pages 33-39. However, these approaches are not useful for producing a phase-stable resin blend for later use, and also do not solve the problems of agitation and pumping difficulties associated with high viscosity.
U.S. Pat. No. 5,464,562 and U.S. Pat. No. 5,470,501 describe the use of certain polyoxyalkylene surfactants in combination with polyester polyols and hydrocarbon blowing agents, with improved phase stability. However, the stability described therein is of limited duration, consisting of only up to 3 hours when utilizing normal pentane and 4 days when utilizing cyclopentane. In addition, these disclosures are silent with respect to undesirable high resin blend viscosity.
Van der Wouden,
The Use of Polyester Polyols in CFC
-
Free Rigid Foams
, Utech '94, Paper 21, pp. 1-5, and van der Wouden, Performance of Oleochemical Based Polyester Polyols in Polyurethanes, Utech Asia '95, Paper 34, pp. 1-7 disclose that dimer acid-based polyester polyols can be added to hydrocarbon-incompatible polyether polyols to produce a hydrocarbon-soluble polyol blend.
SUMMARY OF THE INVENTION
The invention provides resin blends based on certain aromatic polyester polyols and hydrocarbon blowing agents. Resin blends of the invention have increased phase stability and lower viscosity compared to known blends and do not require the presence of nonionic surfactants. The absence of nonionic surfactants simplifies the composition and manufacture of the resin blends of the invention as compared to known blends. The absence of nonionic surfactants also eliminates a monohydroxyl material that can weaken polyurethane or polyisocyanurate foam structure by causing termination of polymer chains.
Thus, in a first aspect the invention provides a polyol based resin blend comprising:
(a) a polyol component comprising an aromatic polyester polyol reaction product formed by inter-esterification of:
(i) a phthalic acid based material;
(ii) a hydroxylated material having a functionality of at least 2; and
(iii) a hydrophobic material having:
(1) from one to six radicals, the radicals being selected from the group consisting of carboxylic acid groups, carboxylic acid ester groups, hydroxyl groups, and mixtures thereof;
(2) hydrocarbon groups totaling at least 4 carbon atoms for each radical present; and
(3) an average molecular weight of from about 100 to about 1000; wherein the hydrophobic material is substantially free of dimer acid; and
(b) a C
4
-C
7
hydrocarbon blowing agent.
In another aspect, the invention provides a polyol based resin blend comprising:
(a) a polyol component comprising:
(I) an aromatic polyester polyol reaction product formed by inter-esterification of:
(i) a phthalic acid based material;
(ii) a hydroxylated material having a functionality of at least 2; and
(iii) a hydrophobic material having: (1) from one to six radicals, the radicals being selected from the group consisting of carboxylic acid groups, carboxylic acid ester groups, hydroxyl groups, and mixtures thereof; (2) hydrocarbon groups totaling at least 4 carbon atoms for each radical present; and (3) an average molecular weight of from about 100 to about 1000; wherein the hydrophobic material is substantially free of dimer acid; and
(II) a polyether polyol; and
(b) a C
4
-C
7
hydrocarbon blowing agent.
In yet another aspect, the invention provides an aromatic polyester polyol reaction product formed by inter-esterification of:
(i) a phthalic acid based material;
(ii) a hydroxylated material having a functionality of at least 2; and
(iii) a hydrophobic material having:
(1) from one to six radicals, the radicals being selected from the group consisting of carboxylic acid groups, carboxylic acid ester groups, hydroxyl groups, and mixtures thereof;
(2) hydrocarbon groups totaling at least 4 carbon atoms for each radical present; and
(3) an average molecular weight of from about 100 to about 1000; wherein the hydrophobic material is substantially free of dimer acid.
In still another aspect, the invention provides polyurethane or polyisocyanurate foams fo
Hickey F. Leo
Rooney Kevin L.
Gorr Rachel
Stepan Company
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