Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1998-12-04
2002-04-16
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S015000, C528S031000, C528S033000
Reexamination Certificate
active
06372874
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the production of siloxane-polyoxyalkylene copolymers, referred to herein as “Copolymers”.
BACKGROUND OF THE INVENTION
The use of platinum catalysts for the addition of silanes or siloxanes with SiH groups to compounds with one or more olefinic double bonds, a reaction commonly referred to as hydrosilation or hydrosilylation, is well known. The addition reaction, however, proceeds without an appreciable formation of by-products, only if the compounds that have the olefinic double bond are free of groups which can react with the SiH group in competition with the addition reaction. This includes particularly the carbon-linked hydroxyl group. In practice it frequently happens that the hydrosiloxanes or hydrosilanes must be added to compounds with olefinic unsaturations, which also have hydroxyl groups or other reactive groups. An example of such a reaction is the addition of hydrosiloxane to an unsaturated alcohol or polyether. There is thus, a need for an economical process which, on one the hand, has a high activity to the addition of the SiH group to the olefinic double bond, and on the other hand, minimizes the side reactions.
Besides the aforementioned competing reaction in the form of the reaction of the SiH and COH groups, it is desired to also avoid disproportionation reactions within the silane or siloxane compounds. Such disproportionation reactions are understood to include a redistribution of the SiH groups, which are usually present in the mixture of silanes or siloxanes. Further side reactions or secondary reactions are the conversion of the allyl groups to propenyl groups, or the possible crosslinking of the addition compound that has terminal OH groups, via acetal formation with the propenyl ether groups. Both reactions generally are catalyzed by chloroplatinic acid (H
2
PtCl
6
.6H
2
O), and lead, on the one hand, to an inadequate conversion of the SiH groups and on the other hand, to an increase in viscosity of the end product.
The introduction of carboxylate salts of alkali and alkali earth metals—sodium propionate in particular—and solventless processing, have significantly improved the efficiency of copolymer production, as well as drastically cut batch cycle times. The use of sodium propionate often leads to the need for multiple catalysis or requirements of greater initial catalyst charge. Consistent with a longer induction period is greater selectivity to copolymers that are of the higher molecular weight analogs, which often give lower cloud points and reduced water solubility. Sodium propionate for the most part, is relatively insoluble in the reactants as well as the generated copolymers, and must be removed by post hydrosilation filtration. Sodium propionate in the presence of water, catalyzes dehydrocondensation potentially liberating hydrogen gas.
The use of sodium phosphate salts as buffers in solventless processes, have shown some improvement over sodium propionate. There is no detected inhibition in the rates of hydrosilation, and the resulting copolymers give water solubility and cloud points, that are comparable to those given by copolymers made in toluene. Sodium phosphate salts however, are very polar and dense, thus are hard to disperse throughout the reactant mixture. Settling is prone to occur, which severely limits their effectiveness.
U.S. Pat. No. 4,847,398 describes a process for the preparation of siloxane-oxyalkylene copolymers via a solventless hydrosilation in the presence of carboxylic acid salts. Although side reactions such as dehydrocondensation and acetal formation were much reduced by the use of these carboxylic acid salts, the rates of the hydrosilation reactions were somewhat inhibited, with the resulting Copolymers consisting of higher molecular weight analogs. This is evident in the relatively lower water solubilities that are characteristics of these copolymers.
U.S. Pat. No. 5,191,103 teaches the use of sterically hindered, nitrogen-containing and phosphorus-containing compounds as buffer-catalyst modifiers in the preparation of Copolymers. These amines and phosphines work to reduce dehydrocondensation and acetal formation and are often solids or high boiling liquids, which must either be removed by post hydrosilation filtration, or be allowed to remain in the resulting copolymer. As these compounds may be basic and cannot be removed by stripping, post hydrosilation neutralization is necessary in order to obtain a pH neutral copolymer. This need for additional processing lengthens the overall batch cycle time of the copolymer production, particularly where the buffer-catalyst modifier is solid, and limits their utilization in cosmetics and personal care applications, where the buffer-catalyst modifier is a high boiling liquid.
Separately, U.S. Pat. No. 4,292,434 teaches the use of a platinum catalyst that is specially modified, firstly by reaction with an olefin, and further with a primary or secondary amine. The need for pre-formation of the catalyst complex, prior to the hydrosilation, adds much additional expense, as well as lengthening the process time for the copolymer. Moreover, the catalyst package is more ideally suited for reactions involving monomeric or dimeric silicon compounds as opposed to polymeric silicones of the present invention.
SUMMARY
This invention disclosure describes an improved process for the preparation of Copolymers via a solventless hydrosilation of oxyethylene-rich polyethers in the presence of an ether, hydroxy or carbonyl modified amine as a buffer-catalyst modifier. The common side reactions such as dehydrocondensation and acetal formation are significantly reduced or eliminated, by the use of these amines. Undesirable side reactions such as acetal formations and dehydrocondensation are reduced or eliminated, when these amines are combined with the reactants. They are liquids at ambient temperature with boiling points ranging from 70° C. to 220° C. They are also completely miscible with the polyether-siloxane fluid admixture, thus are easily dispersed, without the risk of sedimentation. Rates of hydrosilation are minimally or not at all affected by these amines, thus there is virtually no induction period, and the resulting copolymers give comparable water solubility characteristics to those made in solvents. Since the amines have relatively low boiling points, optional removal by post hydrosilation stripping is possible, for Copolymers whose end-use is in cosmetics and or personal care applications. These amines unlike sodium propionate, do not catalyze the undesirable dehydrocondensation side reaction. When amines of the invention, are utilized, reduced levels of noble metal catalyst are possible during the hydrosilation, and the resulting copolymers possess water solubility characteristics that are equivalent to those of Copolymers prepared in solvent.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to an improved process for the preparation of Copolymers, and to products obtained by this process. These Copolymers are prepared by a hydrosilation reaction between (i) an organohydrogen-polysiloxane and (ii) at least one unsaturated polyoxyalkylene, in the presence of (iii) a modifier, which is a primary, secondary or tertiary amine with an alkyl group having a hydroxyl, ether, or carbonyl functionality and a boiling point below 220° C., preferably between 70° C. and 200° C., and more preferably 95° C. to 180° C. and (iv) a noble metal hydrosilation catalyst. The amine is believed to act as a buffer-catalyst modifier. The reaction is carried out in the presence of, or more preferably, in the absence of a solvent. Benefits include the elimination of need for post hydrosilation pH adjustments and filtration and extended solvent stripping, as well as improved per batch yields and significant reduction in batch cycle times. Reduced noble metal catalyst usage and the production of Copolymers that consistently give improved water solubility are achieved. A wider utilization of these copolymers in cosmetic, personal
Crompton Corporation
Dawson Robert
Ma Shirley S.
Robertson Jeffrey B.
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