Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-11-06
2003-09-16
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S275000, C528S300000, C528S301000, C524S788000
Reexamination Certificate
active
06620904
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for preparing polyglycerols and polyglycerol esters, while minimizing formation of cyclic polyglycerols and polyglycerol esters.
BACKGROUND OF THE INVENTION
Polyglycerols and polyglycerol esters are well known in the art. They are commercially available as food, cosmetic, and pharmaceutical emulsifiers, and frequently used as textile lubricants, plastic anti-static agents, defoamers, anti-bloom agents for edible coatings, and anti-splattering agents in cooking oil.
Polyglycerols are commonly prepared by mixing glycerol with an alkali metal catalyst, such as sodium or potassium hydroxide, and then heating the mixture to an elevated temperature. This reaction causes the condensation or dehydration of two glycerol molecules &agr;-hydroxyl groups resulting in an ether bond between the glycerol molecules and the release of water. The unreacted &agr;-hydroxy groups remain available to react with the hydroxy groups of additional glycerol molecules and/or other polymerized molecules.
This method produces a mixture of linear, branched, and cyclic polyglycerols. Cyclic polyglycerols, however, often cause degradation of products into which they are incorporated, detrimentally affecting the taste, performance, and odor of the products. Therefore, there have been continuing efforts to find a method of preparing linear polyglycerols which produce little, if any, cyclic polyglycerols. Cyclic polyglycerols generally have significantly lower hydrophilic-lipophilic (HLB's) than similar linear polyglycerols. As a result, they typically act as emulsion breakers rather than emulsion builders. Also, the presence of cyclic polyglycerols and cyclic polyglycerol esters promotes free polyglycerol in high mono ester products to precipitate out of solution to produce a two phase system. This makes high mono ester products difficult if not impossible to manufacture on a commercial basis. Polyglycerol esters prepared with a low mole ratio of fatty acid to polyglycerol have a tendency not to be homogeneous at reaction temperature. The situation is worse when cyclic polyglycerols are brought into the system.
Harris, U.S. Pat. No. 2,258,892, describes a method for preparing polyglycerol ethers. The method comprises heating glycerol alone or in the presence of a catalyst to form polyglycerol and etherifying the polyglycerol with a particular alcohol, alkyl halide, alkyl sulphate, or mixture thereof to form a polyglycerol ether.
In U.S. Pat. No. 3,637,774, Babayan describes a process for preparing polyglycerols and esters thereof which have good color and little, if any, odor. The process involves the condensation of glycerol in the presence of an alkaline catalyst in an anhydrous medium at a temperature above 100° C. After the condensation has been completed, the reaction mixture is allowed to cool. It is then diluted with water and a bleaching agent is added. The temperature of the mixture is maintained below 100° C. for a time sufficient to bleach the product.
Many methods for enhancing the color, odor, and taste of polyglycerols and for reducing the concentration of cyclic polyglycerols in polyglycerol mixtures have been developed. For example, in the method described in Japanese Patent Publication No. 1125338, glycerol is condensed in the presence of an alkali catalyst and aluminum oxide or an aluminum oxide-based absorbent. Low-boiling point components, including unreacted glycerol, are then distilled off and the mixture condensed again to yield polyglycerols.
Japanese Patent Publication No. 61238749 discloses a method of preparing polyglycerols with low cyclic polyglycerol content. The method includes condensing glycerol in the presence of an alkali catalyst and an aluminum oxide absorbent.
Japanese Patent Publication No. 2172938 discloses a process for preparing polyglycerols having a low content of low molecular weight substances, including cyclic substances. The process involves condensation of glycerol in the presence of an alkaline catalyst at controlled temperature and pressure conditions.
Seiden et al., U.S. Pat. No. 3,968,169, disclose heating glycerol under reduced pressure in the presence of a catalytic amount of adjuvants capable of promoting the polymerization of glycerol to form polyglycerols. The condensation reaction is terminated by adding a neutralizing agent to the mixture. Unreacted glycerol and cyclic diglycerol are subsequently removed by distillation. The polyglycerol can optionally be esterified with a fatty acid to form a polyglycerol ester.
In Japanese Patent Publication No. 6279342, the content of cyclic polyglycerols in a crude polyglycerol mixture is reduced by first reacting the mixture with epichlorohydrin in the presence of a Lewis acid and then reacting it with an alkaline aqueous solution.
Jakobson et al., U.S. Pat. No. 4,960,953, disclose a process for preparing polyglycerols which are low in cyclic components. The process comprises reacting glycerol, diglycerol, or a high polyglycerol with epichlorohydrin at 90 to 170° C. to produce a crude chlorohydrin/ether mixture; adding an amount of a strong base at least substantially equivalent to the organically bound chlorine content of the chlorohydrin/ether mixture; and desalting the mixture and recovering the glycerol, diglycerol, and higher polyglycerol fractions.
Jakobson et al., U.S. Pat. No. 5,243,086, describe a process for the preparation of diglycerol and other polyglycerols substantially free of cyclic glycerol compounds. In this process, isopropylideneglycerol is reacted with &agr;-monochlorohydrin in the presence of at least one alkaline compound to yield monoisopropylidenediglycerol. The reaction mixture containing monoisopropylidenediglycerol is reacted with water in the presence of at least one acidic catalyst to yield diglycerol and other polyglycerols and acetone.
International Patent Publication No. WO 95/16723 disclose polymerizing glycerol, 2,2-dimethyl-1,3-dioxolane-4-methanol, glycidol, or glycerol carbonate in the presence of an anionic clay to form a polymer of glycerol.
There is a continuing need for more cost effective and faster methods of preparing polyglycerols containing little, if any, cyclic polyglycerols.
SUMMARY OF THE INVENTION
Applicants have discovered processes for preparing polyglycerols and polyglycerol esters in high yield and with minimal formation of cyclic polyglycerols and cyclic polyglycerol esters. Furthermore, the processes of this invention produce a high proportion of linear polyglycerols and polyglycerol esters. The linear polyglycerols have very desirable physical characteristics, including a clear appearance at melt, a desirable Gardner color, a mild odor, and a bland taste. The polyglycerols and polyglycerol esters prepared by the method of the present invention are well suited for use as cosmetic and food additives. Since few, if any, cyclic polyglycerols and polyglycerol esters are formed by the processes of this invention, costly and time consuming distillation steps to remove such by-products are not required.
More specifically, applicants have discovered that if a calcium containing compound, such as calcium hydroxide, is used in place of potassium or sodium hydroxide during polymerization of glycerol or esterification of polyglycerols, the formation of cyclic polyglycerols is greatly reduced.
One embodiment of the invention is a method of preparing a polyglycerol comprising polymerizing glycerol, polyglycerol, or a mixture thereof in the presence of a calcium containing compound, such as calcium hydroxide. Preferably, the calcium containing compound is present in a catalytically effective amount. Typically, less than about 8% by weight of cyclic polyglycerols are formed, based upon 100% by weight of total polyglycerols.
Another embodiment is a method of preparing a polyglycerol ester by esterifying or transesterifying a polyglycerol in the presence of a calcium containing compound. According to a preferred embodiment, the polyglycerol is esterified by reacting it with a fatty acid or a triglyceride
Acquah Samuel A.
Darby & Darby
Lonza Inc.
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