Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2001-04-27
2003-11-04
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S200000, C502S156000
Reexamination Certificate
active
06642171
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to double metal cyanide (“DMC”) complex catalysts which are especially useful in the polymerization of epoxides and show significant activity. The invention further is directed to methods for preparing such DMC catalysts.
BACKGROUND OF THE INVENTION
DMC compounds are known catalysts for epoxide polymerization. Conventional DMC catalysts are prepared by reacting an aqueous solution of a metal salt and metal cyanide salt to form a precipitate of the DMC compound. The catalysts are highly active and are especially useful in the production of polyether, polyester, and polyetherester polyols having low unsaturation. Many of such polyols are useful in the production of polyurethane coatings, elastomers, sealants, foams, and adhesives.
DMC catalysts were disclosed over 30 years ago by General Tire. U.S. Pat. No. 3,427,256 discloses a composition containing two metals selected from a wide variety of metals along with an organic complexing agent selected from an ether with only ether functionality, a sulfide with only sulfide functionality, an amide with only amide functionality and a nitrile with only nitrile functionality wherein the complexing agent serves to activate the catalyst. This patent also discloses a method for washing the DMC with the organic complexing agent. U.S. Pat. No. 3,427,334 discloses DMC compositions containing the same metals set forth in U.S. Pat. No. 3,427,256 with organic complexing agents selected from alcohols with only hydroxyl functionality, aldehydes with only aldehyde functionality, ketones with only ketone functionality, and methods for the washing and drying of the catalyst. U.S. Pat. No. 3,427,335 discloses DMC compositions containing, as the organic complexing agent, ethers which also may contain halogen, esters with only ester functionality, cyclic ethers with only cyclic ether functionality, and methods for precipitating the catalyst and washing and drying it. U.S. Pat. No. 3.404,109 discloses a DMC catalyst composition of formula Zn
3
[Co(CN)
6
]
2
.1.7 glyme .1.2 H
2
O .1.2 ZnCl
2
. This gives a mole fraction Zn/Co of 2.1. In each of these patents, the DMC is first precipitated without organic complexing agent followed by washing with a complexing agent/water mixture. General Tire further describes similar DMC/glyme catalysts in several research articles published in the open scientific literature. See, for example, R. J. Herold et al., Polym. Prepr., Amer. Chem. Soc., Div. Polym. Chem., “Hexacyanometallate Salt Complexes for Epoxide Polymerization” (1972) 13(1), 545-550, discussed in further detail below.
U.S. Pat. Nos. 4,477,589 and 4,472,560 disclose DMC catalyst compositions and a process for polymerizing epoxides with such catalysts, respectively. This improved DMC technology is also discussed in a research paper. See J. Kuyper et. al., J. Catal, “Hexacyanometallate Salts Used as Alkene—Oxide Polymerization Catalysts and Molecular Sieves,” (1987), 105(1), 163-174, discussed in detail below. The compositions of the DMC and associated organic complexing agents in the '560 patent are similar to those described in t he patents of the preceding paragraph and further include, as additional complexing agents or activators, an acid such as HCl and a salt, such as ZnSO
4
, generally added to the reactor with the DMC catalyst just prior to polymerization. U.S. Pat. No. 4,477,589 discloses an acid modified DMC prepared initially without organic complexing agent, followed by the addition of sodium hydroxide to form the intermediate hydroxide salt, isolation, and lastly neutralization by HCl with and without glyme organic complexing agent. In both patents, the ethers or glymes are the preferred organic activating agent. These patents further disclose the use of Zn and Co in the presence of glyme, HCl, and ZnSO
4
.
A method where the DMC catalyst is precipitated in the presence of the organic complexing agent, is also taught later in a Japanese Patent (JP 4,145,123) and in U.S. Pat. No. 5,712,216. Japanese Patent JP 4,145,123 teaches DMC catalysts coordinated with tert-butanol, prepared by stirring an aqueous solution containing zinc chloride, potassium cyanocobaltate, and the tert-butanol ligand. This catalyst had a substantially improved catalytic life over the DMC/glyme catalyst.
U.S. Pat. No. 5,158,922 discloses an improved process for making easily filtered DMC catalysts by controlling the order of reagent addition, the reaction temperature, and the stoichiometric ratio of the reactants. This patent teaches the use of at least about a 100% stoichiometric excess of the metal salt relative to the metal cyanide salt and glyme, as organic complexing agent. Zinc hexacyanocobaltate catalysts prepared by this procedure generally have zinc chloride to zinc hexacyanocobaltate molar ratios of about 0.6 or more; i.e., a mole fraction Zn/Co>1.8. It further discloses compositions having as little as 0.2 moles of metal salt per mole of DMC compound (Zn/Co=1.6). While the procedure described in the '922 patent (large excess of zinc chloride) works well with glyme, it is stated in U.S. Pat. No. 5,627,122 that this excess is less satisfactory for use with other complexing agents, including tert-butyl alcohol. When tert-butyl alcohol is used, the catalyst precipitate becomes gelatinous and difficult to isolate. In addition, the activity of these catalysts for epoxide polymerizations, although high compared with KOH catalysts, is still somewhat less than desirable.
U.S. Pat. Nos. 5,470,813 and 5,712,216 disclose improved methods for making DMC catalysts in the presence of an organic complexing agent, preferably t-butanol. The '813 Patent uses a homogenization method wherein a water soluble metal salt is intimately mixed with a water soluble metal cyanide salt. The homogenizer used is not described. In the examples, t-butanol, as complexing agent, is slowly added after the other salts are mixed. Contrasting examples with “normal” mixing fail to show the same activity. U.S. Pat. No. 5,712,216 discloses a method where the organic complexing agent is initially present in the reactant solutions, eliminating the need for homogenization. Here, all of the included examples only show data for reduced unsaturation, with no demonstration of improved activity.
U.S. Pat. Nos. 5,482,908 and 5,627,120 teach improvement of the activity of the DMC catalyst by the use of two complexing agents. The first complexing agent, in an amount of from 5 to 80 wt. %, is a polyether polyol. U.S. Pat. No. 5,482,908 covers polyols having a number average molecular weight of greater than 500 Da (preferred is poly(propylene oxide) polyol with molecular weight between 2,000 and 4,000). U.S. Pat. No. 5,627,120 covers polyols having a number average molecular weight less than 500 Da, and may contain, as polyol activator, the monomethyl ether of tripropylene glycol with t-butanol. In each case, the second organic complexing agent is t-butanol. A stated advantage is the reduction of Co and Zn in the final polyol, reported to be ≦5 ppm.
Companion patents include U.S. Pat. Nos. 5,589,431 and 6,018,017. U.S. Pat. No. 5,589,431 discloses a method for producing polyols and compositions of matter for polyols produced with the catalysts of U.S. Pat. No. 5,470,813. U.S. Pat. No. 6,018,017 discloses polyols as being limited to triols and higher functionality polyols, produced from the catalysts of U.S. Pat. No. 5,712,216.
U.S. Pat. No. 5,627,122 discloses a “crystalline” DMC complex catalyst which comprises a DMC compound, an organic complexing agent, and a metal salt, wherein the catalyst contains less than about 0.2 moles of the metal salt per mole of DMC compound; i.e., mole fraction Zn/Co<1.6. Organic complexing agents include alcohols, aldehydes, ketones, ethers, esters, amides, ureas, nitrites, sulfides, and mixtures thereof. With low levels of ZnCl
2
, these catalysts are very active and reportedly produce polyols with very low unsaturation. WO 99/19063 discloses a “substantially crystalline” DMC catalyst that incorporat
Grieve Robin L.
O'Connor James M.
Locke Liddell & Sapp LLP
Synuthane International, Inc.
Wood Elizabeth D.
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