Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C317/00—Sulfones; Sulfoxides

Definitions

• U.S. Patent 3,383,421 teaches the desirability of a mole ratio for phenol to sulfuric acid in excess of the stoichiometric 2:1 to avoid formation of such by-products as trifunctional sulfones.
• An initial amount of from 0.1 to 2 moles of liquid azeotrope former per mole of phenol may be used to regulate the reaction temperature.
• U.S. Patent 4,162,270 of Ogata et al there is described a similar process involving reaction of sulfuric acid with phenol having an unsubstituted ortho position to produce 4-4'dihydroxydiphenylsulfone.
• the reaction may commence in the presence of from about 0.1 to 5 parts of azeotrope-forming solvent by weight of the phenol. During reaction, however, essentially all the solvent is removed.
• the resultant condition leads to isomerization of by-product 2,4'-dihydroxydiphenylsulfone to the desired form of sulfone.
• the present invention involves an improved process for the preparation of bis(3,5-dialkyl-4-hydroxyphenyl) sulfone. This process comprises the steps of:
• phenol starting materials of the present invention are so-called "2-6-dialkyl phenols". They have the formula:
• R and R are each alkyl groups, most preferably having from 1 to 4 carbons.
• the preferred phenol in accordance with the present invention is 2,6-xylenol.
• the 2,6-dialkyl phenol and sulfuric acid reagents will react at a temperature in excess of about 155°C. to produce the desired diphenol sulfone product. Below this temperature, the primary reaction product is phenol sulfonic acid intermediate.
• These two reagents of phenol and sulfuric acid should be combined for reaction in essentially stoichiometric proportions of about 2:1, respectively. Variation of less than 2% from this ratio is preferred.
• the prior art has often avoided this ratio for varying different reasons. In accordance with the present process, however, this ratio leads to maximized yield and minimized impurities.
• the phenol and sulfuric acid should first be dissolved in an inert organic liquid.
• the manner or sequence of their addition is relatively unimportant.
• the sulfonating agent is added after the phenol has been dissolved in the organic liquid.
• the organic liquid is also employed to remove water formed during the sulfonating process. To satisfy this function it should be capable of forming an aqueous azeotrope which will vaporize during the reaction. Accordingly, the organic liquid should be one which forms an azeotrope having a boiling point of above about 155°C. The boiling point must also be below that employed in the reaction.
• Suitable organic liquids for the present process include hydrocarbons and halohydrocarbons, nonane, decane, dichloro- benzene and, preferably, nonane are representative of such liquids.
• the amount of organic liquid employed in accordance with _ the present process should be in excess of that required simply to perform its primary functions of dissolution and azeotropic removal of water. It has been discovered that an excess of this solvent enhances both the yield and purity of product diphenyl sulfone. Consequently, a weight ratio of organic liquid to phenol which is at least 0.7:1 to 10:1 desirably at least 1:1 is preferred.
• the solution of phenol and sulfuric acid in the organic liquid must as previously indicated, be heated to a temper ⁇ ature in excess of about 155°C. to commence production of bis(3,5-dialkyl-4-hydroxy ⁇ henyl) sulfone . .
• This temperature should also be above the boiling point of the aqueous azeotrope to ensure removal of water formed during the reaction. Due to the possibility of adverse side- reactions, a maximum temperature of 180°C more preferably 170°C should also be observed for the reaction. Although a fixed reaction temperature may be employed in the present process, this is not necessary.
• a gradually increasing temperature has the advantage of allowi greater control over the reaction rate. That temperature may even commence well below 155°C, so long as it rises to the temperature discussed above and is there maintained for at least a limited period of time.
• Such a graduated and successive temperature increase forms a preferred embodiment of this process.
• the solution of phenol to which the sulfuric acid is to be added is first heated to from about 40 to 80°C. After the acid is added, the reaction medium is heated quick to above the boiling point of the aqueous azeotrope of organic liquid. Thereafter, further heating to higher temperature is performed in an essentially step-wise manner to maintain a desirable reaction rate.
• the rate may well be above 30%, often 40% by weight of phenol per hour even with little increase in temperature. Subsequently, as the rate drops, higher temperatures are employed until the maximum desired temperature is reached. The latter temperature increases are usually made as the rate of consumption of phenol falls below about 3%, preferably 5% per hour.
• a significant advantage of the present process is that the reaction medium need not be maintained at a temperature in excess of 155°C. for an extruded period of time.
• yields of over 60% of diphenol sulfone are quickly achieved with minimal exposure to high temperature. This is particularly true where the foregoing embodiment of graduate temperature increases Is employed. In less than about 6 hours, for example, a yield in excess of about 85% may be obtained.
• Bis(3,5-dialkyl-4-hydroxyphenyl) sulfone formed pursuant to the present process is insoluble in the organic liquid. It therefore precipitates as a solid. Consequently, when the desired yield has been obtained, it may readily be separated (normally after first cooling to below 100°C.) by filtration or similar physical means.
• the separated, bis(3,5-dialkyl-4-hydroxyphenyl) sulfone may evidence contamination by impurities such as color bodies In accordance with the present invention, however, it has been found that this product is easily purified.
• the crude diphenyl sulfone may simply be washed with an alcohol such as methanol, ethanol, propanol or, preferably, isopropyl alcohol. These alcohols are desirably of neutral pH. The alcohol selectively dissolves impurities from the solid sulfone, leaving a refined product.
• EXAMPLE 2 In a one liter flask equipped with a thermometer, mechanical stirrer and Dean-Start trap/condenser is charged 136 g (1.115 moles) of xylenol and 240 ml of n- octane/dodencane (40/60) . The flask is heated to 50° - 60°C and 0.507 moles of concentrated sulfuric acid are added over a period of 5 minutes. Thereafter the reaction vessel is heated such that the water of reaction is removed continuously as formed by azeotropic distillation. The time-temperature extent of reaction (as measured by water removal) is shown below: Time (Hours) Temperature (°O) Extent of Reaction (%)
• Example 7 the profiles for both process A and B show a quick peaking and decline of reaction rate with time. Moreover, after only a low degree of reaction (even where high temperature is employed) little further reaction occurs. In contrast, the processes of the present invention (Examples 1-6) show more sustained rates of reaction. This is true even at much lower temperatures of reaction. As a result, substantially higher yields are obtained and under more mild conditions and shorter reaction times which correspondingly reduce the side-production of impurities.

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• 1982
  • 1982-04-30 WO PCT/US1982/000558 patent/WO1982003857A1/en not_active Ceased
  • 1982-04-30 JP JP57501789A patent/JPS58500612A/ja active Pending
  • 1982-04-30 EP EP19820901768 patent/EP0077823A4/de not_active Withdrawn

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