GB1563019A - Production of propylene glycol alginic acid esters - Google Patents

Description

(54) PRODUCTION OF PROPYLENE GLYCOL ALGINIC ACID ESTERS (71) We, MERCK & CO., Inc., a corporation duly organized and existing under the laws of the State of New Jersey, United States of America, of Rahway, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: The present invention relates to the production of propylene glycol alginate esters and provides a process for the preparation of propylene glycol alginate which comprises reacting an alginic acid which is neutralized to the extent of from about 0.2 mole % to about 17 mole % and has a solids content of from about 20 to about 80 weight percent with propylene oxide at a temperature from about 60"C. to about 140"C. and at a pressure sufficient to maintain the propylene oxide in liquid phase.

Preferably a 2 wt. % solution of the propylene glycol alginate product alginate in distilled water has a pH of from about 3.4 to about 4.9. most preferably 3.8 to 4.5. The reaction time is preferably no more than 2 hrs.

The partially neutralized alginic acid employed as a reactant may be prepared by partially neutralizing alginic acid by reaction with a base or basic salt or other material which when combined with the alginic acid will form a salt of the alginic acid, desirably a water soluble salt. Typical of such reactants are ammonium hydroxide, the alkyl amines, alkali metal and alkaline earth metal hydroxides and carbonates and basic salts. Examples of such bases and basic salts are sodium hydroxide, sodium bicarbonate, sodium carbonate, trisodium phosphate, potassium carbonate, potassium bicarbonate. ammonium hydroxide, ammonium carbonate, ammonia (NH3) and magnesium carbonate. Preferably about 3 to about 12 mole percent of the carboxyl groups in the alginic acid are neutralized.

Following the partial neutralization of the alginic acid, the solids content of the partially neutralized acid is adjusted to about 20 to about 80% by weight, i.e., a liquid content of about 80 to about 20 percent by weight. The liquid present in the partially neutralized acid is normally water but may be an admixture with a water miscible solvent, such as a lower alcohol, e.g., isopropyl alcohol.

The moisture content of the partially neutralized alginic acid may be reduced by gentle drying or by extraction with an alcohol or ketone.

The reaction time is increased (esterification rate decreased) considerably when the solids content of the partially neutralized alginic acid reactant is more than about 80% by weight.

It has been discovered that substantial benefits are obtained if the reaction is carried out with liquid propylene oxide in contact with the partially neutralized alginic acid.

The invention and its advantages are further illustrated by the following Examples: Example 1 Into a stainless steel bomb reactor fitted with a pressure gauge, an evacuation port and theremometer well was placed twenty-five grams of 30 percent solids alginic acid containing residual calcium at 2.2 equivalent percent and which had been further neutralized with NaOH for a total of 15.2 equivalent percent. The alginic acid fibers were covered by liquid propylene oxide, which was accomplished by using 130 gms. of liquid. The air over the liquid was removed by using a water aspirator. The bomb was then sealed and brought to temperature by partial immersion in a hot water bath at 89"C. The temperature rose to 79"C. within 5 minutes and was maintained at 800C. for 25 minutes.The pressure was at 5U psig. During this time no mechanical agitation was provided, because the fibers were being buffeted by the boiling liquid within the partially immersed bomb. After a total of 30 minutes of reaction, the bomb was removed from the bath and placed into a stream of cold water. The reaction temperature and pressure were reduced to ambient values within two minutes. The bomb was then opened and the contents placed on a vacuum filter where the fibers were washed with acetone.

The analysis was as follows: Ester (COOR where

84%, Na 13%, Ca 2.2%, and free acid (COOH) 0.8%; No product pH was obtained.

(Owing to the nature of the analytical procedures, the 'i%" given do not always add to Example 2 Into the stainless steel bomb was placed about 50 grams of 47 percent solids alginic acid that contained 2.1 equivalent percent sodium and 14.7 equivalent percent calcium; this partially neutralized acid was covered with liquid propylene oxide and the reaction was conducted as in Example 1 at an average temperature of 76"C. After 50 minutes the reactor was rapidly cooled and opened. After filtration, the product when dissolved in water gave a 1.6 percent solution viscosity of 18 cps. The solution was clear with only trace sediment or haze, and the pH was 3.9. Subsequent beer foam stability tests showed it to be the equal of the standard propylene glycol beer foam stabilizer.Free acidity and percent ester content were not obtained.

Example 3 Glycol production was measured for a liquid propylene oxide reaction. Into the bomb reactor was placed 10.7 g. of alginic acid, containing 4.4 equivalent percent of residual calcium, which was then further neutralized to a total of 17.6 equivalent percent using NaOH; percent solids not available. The fibers were covered with an excess of propylene oxide liquid and the bomb evacuated and sealed. The reaction was performed at 800C. The average pressure was 50 psig. and the time was 2 hours. The resultant product had an analysis as follows: pH 4.3. ester 72who. acid 10.6 ic. Na 13.4coo, calcium 4.4 equivalent percent. There was produced 0.15 grams of propylene glycol per gram of anyhdrous weight starting alginic acid.

Example 4 As a comparison to Example 2 another alginic acid with high neutralization was used.

This acid was 70 percent solids and contained 15 equivalent percent sodium and 2.4 equivalent percent calcium. The alginic acid was placed into the stainless steel bomb and reacted at 80"C. for 2 hours, at 50 psig. The reaction was terminated by rapid cooling. The filtered product has a 1 percent in water viscosity of 19 cps, equivalent to 35 cps for 1.6% solution; and a pH 4.2. The analysis showed it to contain 8.2 percent free acid and 74.4 percent ester. This product was not acceptably clear and free of sediment for some uses, and, thus, the 17.4 equivalent percent neutralization appears to be near the upper limit for this reaction.

Example 5 Into the stainless steel bomb was placed 12.2 g. of 74 percent solids alginic acid, i.e., 9.0 grams of anyhdrous weight algin and 3.2 grams of water. One hundred and thirty grams of liquid propylene oxide was added to this. The bomb was sealed and the reaction was run at a temperature of 85"C. After reaction termination the product had the following characteristics: Free acid 27.8 equivalent percent. ester 71.8 equivalent percent, sodium 0.2 equivalent percent, calcium 0.2 equivalent percent and glycol by-product 1.5 grams.

Example 6 Into a large stainless steel pressure vessel, fitted with a stirrer a propylene oxide inlet port and a pressure guage. was added through the inlet port partially neutralised alginic acid (metal and solids content as in the Table below) and 20.6 Ibs. of propylene oxide liquid.

Agitation was begun and the temperature was raised until the internal pressure reached 40 psig. No temperature could be taken but the boiling point of the liquid propylene oxide at 40 psig. is about 75"C. The reaction was run under these conditions for 2 hours and 10 minutes. The product was washed with isopropyl alcohol and centrifuged to remove liquid.

The product was then dried in a circulating air oven.

The analysis of the product was as follows: Free acid 4.25%, ester 88.0%, Na 0.4%, Ca 7.5% and pH 4.3.

Glycol production based on both what was found in the product and in the wash solvent amounted to 0.16 lbs./lb. of anhydrous alginic acid.

Example 7 Into the stainless steel bomb was placed 100 gms. of 34 percent solids alginic acid that contained as a residue 0.7 equivalent percent sodium and 0.3 equivalent percent calcium.

the acid was covered with liquid propylene oxide and the reaction was run with the temperature maintained at 710C. for 2 hours. The product had the following characteristics: ph .4, free acid 9.2 equivalent percent, ester 89.8 equivalent percent and calcium 0.3 equivalent percent.

Example 8 Into the stainless steel bomb was placed 100 gms. of the same 34 percent solids alginic acid as in Example 7, and the acid was covered with liquid propylene oxide. The reaction was run as in Example 7 except that the temperature was raised to 80"C. for the two hour reaction period.

The product had the following characteristics: pH 3.8, free acid 2.7 equivalent percent, ester 96X3 equivalent percent, sodium 0.7 equivalent percent and calcium 0.3 equivalent per cent.

Example 9 Into a stainless steel bomb was placed 30 gms. of 34 percent solids alginic acid that contained an additional 20 gms. of isopropyl alcohol. The alginic acid had 0.3 equivalent percent sodium and 0.2 equivalent percent calcium as residual partial neutralization. The acid was covered with liquid propylene oxide and the reaction was run for two hours attaining a temperature of 85"C. and a pressure of 47 psig. The product had the following characteristics: 3.6 pH, 3.6 equivalent percent free acid, 95.9 equivalent percent ester, 0.3 equivalent percent sodium and 0.2 equivalent percent calcium. The product was readily soluble and formed a clear solution in water.

Example 10 Into the bomb reactor was placed 50 grams of alginic acid at 34 percent solids. This acid had been washed three times with a 5 percent HCl solution to remove more of the residual sodium and calcium from the precipitation process. There still remained 0.3 equivalent percent sodium and 0.1 equivalent percent calcium. Liquid propylene oxide was added, and the reaction was made to proceed, as in Example 1. The average temperature of reaction was 85"C. and the average pressure was 51 psig. The reaction proceeded for 2 hrs. and produced a product of pH 3.8.

This product was for low viscosity applications and had a 1 percent viscosity in water of 9.0 cps. equivalent to 20 cps. at 1.6%. The solution was clear and the product had the following analysis: Free acid 2.2 equivalent percent, ester 97.4 equivalent percent, sodium 0.3 equivalent percent, calcium -01. equivalent percent. There was produced 1.53 Ibs. of glycol per pound of anhydrous alginic acid.

Comparative Examples 11-14 were carried out using gaseous propylene oxide reaction conditions.

Example 11 As a comparison to the liquid reactions of Examples 1-11, the following gaseous propylene oxide reaction was carried out to reveal the added time required to run a gaseous reaction versus a liquid reaction.

Into a glass tumbler reactor of 5 liters capacity and fitted with lifting vanes for agitation was placed 227 grams of 73.5 percent solids alginic acid. This acid contained 2.2 equivalent percent residual calcium and was further neutralized to 11.7 total equivalent percent with NaOH. The reactor was evacuated of air using a water aspirator, then when the evacuation was terminated, after about 3 minutes, there was introduced from an adjacent propylene oxide boiler, propylene oxide gas at about 3 psig. This proylene oxide pressure remained throughout the reaction. The tumbler was set in motion in a hot water bath and the fibers were iifted and dropped through the propylene oxide atmosphere. The reaction reached 81"C. in 10 minutes and averaged 80"C. for a total reaction time of 2 hours and 5 minutes.

At the end of this time the vessel was re-evacuated using a water aspirator, thus, terminating the reaction. The results of this reaction are listed below: 3.9 equivalent percent free acid; 85.2 equivalent percent ester; 9.5 equivalent percent Na; 2.2 equivalent percent Ca. pH is not available.

Example 12 One hundred grams of 70 percent solids alginic acid containing 9.6 equivalent percent calcium and 1.5 equivalent percent sodium was placed into a glass tumbler reactor as described in Example 12. The reaction proceeded at a temperature of 70"C. and a pressure of about 2 psig. for 3-1/2 hours. The product had a pH of 3.7 and an analysis as follows: Free acid 5.5%, ester 84.4%, sodium 1.5%, and calcium 8.6 equivalent percent.

The amount of glycol produced was 0.65 Ibs./lb. of anhydrous alginic acid.

Example 13 As a speed of reaction comparison to Example 10, a low neutralized alginic acid was used in a gaseous propylene oxide reaction. Into the same 5 liter tumbler reactor used in Example 11 was placed 240 grams of 71 percent solids alginic acid containing 0.5 equivalent percent residual Na and 2.6 equivalent percent residual Ca. The reaction was run in a like manner as Example 11 for 7 hours at 81"C. at about 2 psig. The product reached a pH of 3.1 and had the following analysis in equivalent percent: Free acid 9.1 percent, ester 87.8 percent, sodium 0.5 percent and calcium 2.6 percent. This product is under reacted after 7 hours time.

Example 14 The data for Example 14, which is summarized in the Table below, is taken from Example 1 of U.S. Patent 3,772,266.

Table The results of the above examples are more easily grasped and the benefit of the process of the instant invention more vividly displayed when set forth in tabular form. In the table, there are given for each Example the percent metal content of the partially neutralized alginic acid charge, the percent solids content of said acid charge, the temperature in "C. at which the reaction was carried out, the time in minutes of the reaction period, the percent free acid (nonreacted COOH groups), the 5toage of COOH groups reacted and the pH of a water solution of the ester product. Where information was not recorded, a NA (not available) is noted.

Table % % % % Example Metal Solids C. Pressure Psig Minutes Free Acid Reacted pH Liquid Propylene Oxide 1 15.2 30 80 50 30 0.8 99.2 NA 2 16.8 47 76 NA 50 NA NA 3.9 3 17.8 NA 80 50 120 10.6 89.8 4.3 4 17.4 70 80 50 120 8.2 91.8 4.2 5 0.4 74 8 NA 120 27.8 72.4 NA 6 7.9 56 75 40 130 4.2 95.9 4.3 7 1.0 34 71 NA 120 9.2 90.8 3.4 8 1.0 34 80 NA 120 2.7 97.3 3.8 9 0.5 34 85 47 120 3.6 96.6 3.6 10 0.4 34 85 51 120 2.2 97.8 3.8 Gaseous Propylene Oxide 11 11.7 74 80 3 125 3.9 96.9 NA 12 10.1 70 70 2 210 5.5 94.5 3.7 13 3.1 71 81 2 420 9.1 90.9 3.1 14* 19 70 60 14 135 3 97 4.4 * U.S. Patent 3,772,266 (Note: NA-Not Available)

Claims (8)

WHAT WE CLAIM IS:

1. A process for the preparation of propylene glycol alginate which comprises reacting an alginic acid which is neutralized to the extent of from 0.2 mole % to 17 mole % and has a solids content of from 20 to 80 weight percent with propylene oxide at a temperature from 60"C. to 1400C. and at a pressure sufficient to maintain the propylene oxide in liquid phase.

2. A process according to claim 1 wherein the alginic acid is partially neutralized by at least one species of ion selected from alkali metal, alkaline earth metal, ammonium, and alkylammonium ions.

3. A process according to claim 1 or 2 wherein a 2 weight percent solution of the propylene glycol alginate product alginate in distilled water has a pH of from 3.4 to 4.9.

4. A process according to claim 3 wherein a 2 weight percent solution of the propylene glycol alginate product alginate in distilled water has a pH of from 3.8 to 4.5.

5. A process according to claim 1, 2, 3 or 4 wherein 3 mole percent to 12 mole percent of the carboxyl groups of the alginic acid are neutralized.

6. A process according to any preceding claim wherein the reaction time is not more than 2 hours.

7. A process for the preparation of propylene glycol alginate substantially as described in any one of Examples 1 to 10.

8. Propylene glycol alginate when prepared by a process according to any preceding claim.