Compositions – Compositions containing a single chemical reactant or plural... – Organic reactant
Reexamination Certificate
2001-06-21
2002-12-10
Cooney, Jr., John M. (Department: 1711)
Compositions
Compositions containing a single chemical reactant or plural...
Organic reactant
C252S182240, C521S170000, C521S174000
Reexamination Certificate
active
06491846
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for the in-situ production of a blend of polyether polyols, and specifically, a blend of one or more polyether monols and one or more polyether polyols, and to the in-situ formed blend of one or more polyether monols and one or more polyether polyols. It further relates to a process for the production of viscoelastic foams from these blends, and to the resultant viscoelastic foams. The process of the present invention requires a double metal cyanide (DMC) catalyst. The process uniquely employs a monol as the initial starter for epoxidation followed at a later stage in the polymerization by the continuous addition of a polyfunctional starter and continued addition of epoxide to yield a blend of a high equivalent weight polyether monol and a much lower equivalent weight polyether polyol in a single reactor batch. These in-situ formed blends of polyether monols and polyether polyols are suitable for the production of viscoelastic polyurethane foams.
Double metal cyanide (DMC) complexes are highly active catalysts for preparing polyether polyols by epoxide polymerization. Recent improvements have resulted in DMC catalysts that have exceptional activity. See, for example, U.S. Pat. No. 5,470,813.
While DMC catalysts have been known since the 1960s, commercialization of polyols made from these catalysts is a recent phenomenon, and most commercial polyether polyols are still produced with potassium hydroxide. One reason for the delayed commercial availability of DMC polyols is that conventional polyol starters, e.g., water, propylene glycol, glycerin, trimethylolpropane, and the like, initiate DMC-catalyzed epoxide polymerizations sluggishly (if at all), particularly in the typical batch polyol preparation process. Typically, the polyol starter and DMC catalyst are charged to a reactor and heated with a small amount of epoxide, the catalyst becomes active, and the remaining epoxide is added continuously to the reactor to complete the polymerization.
In a typical batch process for making polyols using either KOH or a DMC catalyst, all of the polyol starter is charged initially to the reactor. When KOH is used as the catalyst, it is well understood by those skilled in the art that continuous addition of the starter (usually a low molecular weight polyol such as glycerin or propylene glycol) with the epoxide will produce polyols having broader molecular weight distributions compared with products made by charging all of the starter initially. This is true because the rate of alkoxylation with KOH is substantially independent of polyol molecular weight. If low molecular weight species are constantly being introduced, the molecular weight distribution of the polyalkoxylation products will broaden.
Those skilled in the art have assumed that continuous addition of a starter in a DMC-catalyzed polyol synthesis would also produce polyols having relatively broad molecular weight distributions. Consequently, the DMC polyol synthesis art teaches almost exclusively to charge all of the starter to the reactor initially, and to add the epoxide continuously during the polymerization.
One exception is U.S. Pat. No. 3,404,109. This reference discloses a small-scale process for making a polyether diol using a DMC catalyst and water as a starter. This process describes charging a beverage bottle with DMC catalyst, all of the epoxide to be used, and water, and heating the capped bottle and contents to polymerize the epoxide. U.S. Pat. No. 3,404,109 further discloses that “when large amounts of water are employed to yield low molecular weight telomers, it is preferred to add the water incrementally because large amounts of water decrease the rate of telomerization.” (See column 7.) Incremental addition of the starter (i.e., water) is used to give a “practical” rate of reaction. Thus, the '109 patent charges all of the epoxide to the reactor initially, but adds the starter incrementally.
Interestingly, U.S. Pat. No. 3,404,109 also discloses that incremental addition of water “can also be employed to give telomers of a broader molecular weight distribution than those possible where all of the water is added at the beginning of the reaction.” In other words, the result expected from a DMC-catalyzed process is the same as the result obtained with a KOH-catalyzed process: i.e., the continuous or incremental addition of starter results in polyols with broad molecular weight distributions. Thus, one of ordinary skill in the art upon reading the '109 patent believes that the incremental addition of a starter to a DMC-catalyzed epoxide polymerization will produce polyols having a broader molecular weight distribution than would be obtained if all of the starter were charged initially.
U.S. Pat. No. 5,114,619 discloses a process for making polyether polyols that involves continuous addition of water and epoxide to a reaction mixture containing a barium or strontium oxide or hydroxide catalyst. A DMC-catalyzed process is not disclosed. The process of the '619 patent produces polyols with reduced unsaturation. The impact of continuous water addition in the presence of barium or strontium catalysts on polyol molecular weight distribution is not discussed. The '619 patent further notes that, unlike water, continuous addition of low molecular weight diols, triols, and polyoxyalkylene glycols does not reduce polyol unsaturation. In addition, substitution of KOH for the barium or strontium catalyst does not yield the improvement.
One consequence of charging all of the starter initially, as in a typical batch polyether polyol synthesis, is that reactors must often be used inefficiently. For example, to make a 4000 mol. wt. polyoxypropylene diol (4K diol) from a 2000 mol. wt. polyoxypropylene diol (2K diol) “starter,” the reactor is almost half full at the start of the reaction; to make 50 gallons of product, we would start with 25 gallons of 2K diol starter. A valuable process would overcome such “build ratio” limitations, and would permit efficient use of reactors regardless of the molecular weight of the starter or the product sought. For example, it would be valuable to have the option to charge our 50 gallon reactor with only 5 gallons of 2K diol starter, and still make 50 gallons of 4K diol product.
In addition to the process challenges of DMC catalysis, commercial acceptance of DMC-catalyzed polyols has been hindered by the variability of polyol processing and performance, particularly in the production of flexible and molded polyurethane foams. DMC-catalyzed polyols usually cannot be “dropped into” foam formulations designed for KOH-catalyzed polyols because the polyols do not process equivalently. DMC-catalyzed polyols often give too much or too little foam stability. Batch-to-batch variability in the polyols makes foam formulating unpredictable. The cause of this unpredictability in foam formulations with DMC-catalyzed polyols has not been well understood, and consistent results have remained elusive.
An improved process for making DMC-catalyzed polyols is described in U.S. Pat. No. 5,777,177. This process eliminates the need to separately synthesize a polyol starter by KOH catalysis, and enables the use of simple starters such as water, propylene glycol, and glycerin. This process also eliminates the problem of reactor fouling by polyol gels, makes efficient use of reactors, and overcomes build-ratio limitations.
While U.S. Pat. No. 5,777,177 discloses the use of an initial starter and the continuous addition of a second starter to produce polyether polyol with a narrow molecular weight distribution, it fails to disclose and/or suggest that this technology can be used to produce in-situ formed blends of polyols of significantly different and relatively narrow molecular weights in a single batch reactor. More specifically, it fails to disclose the in-situ production of a high molecular weight polyether monol and a very low molecular weight polyether polyol as disclosed and claimed in the present specification.
U.S. Pat. No. 5,689,
Hager Stanley L.
Reese, II Jack R.
Bayer Antwerpen N.V.
Brown N. Denise
Cooney Jr. John M.
Gil Joseph C.
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