DE1187597B - Process for the purification of aqueous pentaerythritol solutions - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Number:
File number:
Registration date:
Display day:

C07c

German class: 12 ο - S / 03

1187 597
C20140IVb / 12o
November 9, 1959
February 25, 1965

Pentaerythritol is made from acetaldehyde and excess formaldehyde in aqueous alkaline Medium produced at elevated temperature. The mixture of pentaerythritol formed in this reaction, Sodium formate and unreacted formaldehyde is z. B. up to a pH of about 5 to 6 neutralized, then the formaldehyde is distilled off under pressure and then the solution concentrated at elevated temperature. The concentrated mixture will form crude pentaerythritol crystals refrigerated, which contain up to about 1% sodium formate. These crystals are usually found in recrystallized in hot water. The recrystallized pentaerythritol thus obtained is not like that pure or does not consist of crystals as large as would be desirable and is especially with 4 up to 9% dipentaerythritol formal contaminated. The usual with sulfuric acid and phthalic anhydride color tests carried out, the product changes color.

It is now already known that pentaerythritol containing dipentaerythritol formal with a cation-exchanging agent Bringing resin into contact. Not only is the formal hydrolyzed, but the sodium formate, which is also present, reacts with the ion exchange resin to form Formic acid and the sodium salt of the resin. The sodium salt of the resin formed in this reaction is no longer strongly acidic and therefore only has a weak hydrolysing effect on the formal. Consequently the resin gradually loses its ability to hydrolyze the dipentaerythritol formal, which immediately flows out of the exchanger bed. Then the entire resin bed must be regenerated.

The method according to the invention for the purification of aqueous pentaerythritol solutions, which dipentaerythritol formal and sodium formate, is made with the help of a strong cation-exchanging agent Resin carried out in the H + form, the hydrolysis of the dipentaerythritol formal taking place, and is characterized in that the purification takes place in two stages, with the pentaerythritol in the first stage in aqueous solution at a concentration of 25 to 45% at a temperature of more than 90 ° C is freed from sodium formate.

A process for the hydrolysis of the pentaerythritol formal contained in crude pentaerythritol obtained by crystallization by treatment with a cation exchanger in the H + form is known. However, in this known process, the ion exchange resin is quickly inactivated by the sodium formate which is also present and thus loses its ability to be used in hydro processes for purifying aqueous media
Pentaerythritol solutions

Applicant:

Canadian Chemical Company Limited,
Clover Bar, Alberta (Canada)

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald
and Dr.-Ing. Th. Meyer, patent attorneys,
Cologne 1, Deichmannhaus

Named as inventor:
John Cameron Clunie,
Montreal, Quebec (Canada)

Claimed priority:
V. St. v. America November 10, 1958
(772665)

lysis. In contrast, according to the invention, the sodium formate is first removed in a first stage and then the formal content is reduced by hydrolysis. This method has the advantage that only the cleaning bed needs to be regenerated from time to time to remove the sodium formate, while the cation exchanger used for hydrolysis remains practically unlimited in effectiveness.

Since the hydrolysis takes longer than the removal of the sodium formate, the contains The hydrolysis bed has more resin than the cleaning bed, usually about double to triple the amount. Are the If both resin beds are housed in vessels of the same cross-section, this is the depth of the hydrolysis bed two to three times as large as that of the cleaning bed, so that the contact time during the Hydrolysis is two to three times as great as that required for sodium formate removal.

In the preparation of pentaerythritol by the process described at the outset, recrystallization can be used be modified so that the pentaerythritol crystallizes out before the solution is cooled a process step is inserted in which the hot solution of the pentaerythritol initially with a cleaning bed and then with one

509 510M19

Hydrolysis bed of a strongly acidic cation exchange resin in the hydrogen form to remove the Sodium formate and reduction of the original formal content of the crude pentaerythritol of more than 2%, e.g. 4 to 9%, to less than 1%, based on the weight of the pentaerythritol will. The crystals are then removed from the mother liquor in any convenient manner severed. Details of a process for the preparation of crude pentaerythritol crystals, which suitable for treatment according to the invention are described in British Patent 757,564. This process results in a pentaerythritol having a low dipentaerythritol content, e.g. B. less than 5 ° / o.

When the recrystallization is carried out, the amount of water required to dissolve the crude Pentaerythritol crystals are used, preferably slightly more than the amount that is required to to achieve a saturated solution at the temperature of the treatment with the ion exchange resin. Pentaerythritol concentrations in the range from 25 to 45% are suitable.

A strongly acidic ion exchange resin should be used for the treatment. A class more suitable Resins form the sulfonated crosslinked aromatic resins that contain free sulfonic acid groups, z. B. sulfonated styrene-divinylbenzene copolymers or sulfonated phenol-formaldehyde resins.

The temperature used for the treatment with the resin is advantageously about 90 ° C or higher, e.g. B. between 90 ° C and the boiling temperature, which is about 105 ° C at atmospheric pressure. The contact time of the solution and the acidic resin during the hydrolysis treatment is between about 5 minutes and about 5 hours. A treatment time of 20 to 60 minutes is chosen, since this is usually sufficient to reduce the formal content to 0.6Vo or less, and Tile cleaning is sufficient for most purposes. During the treatment with the resin, the Temperature of the pentaerythritol solution can be maintained at the desired level in any way. For example, the resin layer can be traversed by heating coils.

After the treatment, the pentaerythritol solution is slightly acidic, mainly due to the Formic acid, which is released from the original sodium formate content. This sour Solution can be recrystallized directly, for example by cooling, without undue corrosion.

After the recrystallized pentaerythritol has been separated off from the mother liquor, it can be recycled to recover any pentaerythritol still dissolved therein. For example, the mother liquor can be added to the formaldehyde distillation residue in the process described in British Patent 757 564 so that it is concentrated with this residue and then cooled to form crude pentaerythritol crystals. The return of the mother liquor to the process is facilitated by the fact that it is free of ash, e.g. B. Na ⁺ , is.

example 1

A number of attempts were made with aqueous solutions of pentaerythritol with different Formal and sodium formate content carried out, with a sulfonated styrene-divinylbenzene copolymer as the ion exchange resin (Amberlite IR-120) with the following properties was used:

Active group -SO ₃ H

Form sodium form in pearls

Density, g / l 849

Moisture content,% 44 to 48

Pearl size, 0.45 to 0.6 mm

Total exchange capacity

Kilograms as CaCO ₃
^χ 5 per liter 1.87

Milliequivalent per cubic centimeter of wet resin 1.9

Milliequivalents per gram
dry resin 4.3

Maximum working temperature, ⁰ C

121

Effective working pH range 1 to 14

This resin was converted to the hydrogen form by washing with 10% aqueous H ₂ SO ₄ in an amount equivalent to at least twice the exchange capacity of the resin and then washed with distilled water until free of sulfate ions. A wet volume of 800 cm ^{3 of} resin was used in a column (resin height 42 cm). Pentaerythritol solutions were used which were prepared from crude crystalline pentaerythritol obtained by reacting acetaldehyde, excess formaldehyde and sodium hydroxide in an aqueous medium, followed by neutralization, distillation under pressure to remove the formaldehyde and evaporating the water and cooling. For the experiments described in this example, pentaerythritol from different product batches was used. To prepare the individual solutions, crude crystalline pentaerythritol was dissolved in the amount of water required for the desired concentration at 100 ° C. by stirring. The temperature was increased to about 104 ° C and the solution was filtered to remove any insoluble impurities and then passed through the resin column for the specified time at 100 ° C, then, if necessary, concentrated to a concentration of 40 ° / o and then cooled to room temperature, pentaerythritol crystals formed. The results are shown in the table below:

Mission I

Crude pentaerythritol with 0.18 percent by weight sodium formate and 7.1 percent by weight formals

concentration
the penta
erythritol solution
Vo Stay
Time
hours PH value
of
Product Formal
in the
product ash
in the
product
Vo 30th
35
40
40 1
1
1
Va 3.0
2.9
2.9
3.0 0.1
0.3
0.3
0.4 O O O O

Mission II

Pentaerythritol with 1.2 percent by weight sodium formate and 6.4 percent by weight formals

concentration
the penta
erythritol solution
° / o Stay
Time
hours PH value
of
Product Formal
in the
product
% ash
in the
product
% 40
40
40 1
V ₂
1 2.9
3.0
3.0 0.3
0.4
0.2 0
0
0

Use HI

Pentaerythritol with 0.33 percent by weight sodium formate and 6.1 percent by weight formals

concentration
the penta
erythritol solution
° / o Stay
Time
hours PH value
of
Product Formal
in the
product
% ash
in the
product
° / o 40
40
40
40
20th Vs
V ₂
2
³ U
1 3.0
2.9
3.0
3.0
2.9 0.6
0.2
0.3
0.4
0.4 O O O O O

From the above figures it can be seen that the reduction of the formal content of the pentaerythritol, even from a 40% pentaerythritol solution, to a satisfactory low value can be achieved in 1 hour, even in V ₂ hours. If the total exchange capacity of the resin is calculated, it is found that the resin is quick to hydrolyze

of the formal becomes ineffective. If insert I is used, turns, the resin is complete within 24 hours by reaction with the sodium formate or so far used that the residence time of the solution in the active resin is reduced so far,

^{time of solution is 3} Å hours during the entire working time of this hydrolysis column. In this way, a completely satisfactory product is continuously produced and only a relatively small amount of resin needs to be regenerated.

The following example illustrates the application of this principle in an industrial process,
ίο Example 2

The pentaerythritol solution contains 40% pentaerythritol and 25% sodium formate. It becomes that in example 1 The resin described is used in columns with a circular cross-section of 750 cm in diameter is housed. Two cleaning towers, each 360 cm high, are 225 cm high and one is only one Hydrolysis tower 750 cm high completely filled with resin. Pipes and valves are arranged so that the pentaerythritol solution can be passed into one of the cleaning towers before they are in the Hydrolysis tower crosses. The second cleaning tower is always regenerated.

100 ° C hot pentaerythritol solution is in an amount of 326kg / h. initially by one of the Purification towers and then through the hydrolysis tower. The draining pentaerythritol solution is free of sodium formate and contains less than 1% formals. The residence time in the hydrolysis tower is about 20 minutes.

After 8 hours, the pentaerythritol solution is passed to the second cleaning tower and the resin in the first cleaning tower regenerated with a 10% aqueous sulfuric acid and then with deionized Water washed. Then it can be made from the products of these examples again oil modified alkyd resins were clear. The alkyd resins were made in a conventional manner by heating a Reaction mixture made up of the following components

that the outflowing solution is still a considerable 40: 27% phthalic anhydride, 14.84% rei-part of the original formal. Will the nigt pentaerythritol, 58.14% soybean oil, 0.02% Flow rate adjusted so that the Aufent- black lead and xylene as a solvent in one holding time is initially 1 hour, then the amount of 5%, based on the total input, retention time after 12 hours

only V ₂ hours and the formal content of the product flowing off has risen from 0.3 to 0.4. With continued use of the resin, the residence time will soon be reduced to a value which is too short to achieve the desired degree of purification. As a result, it is often necessary to regenerate the resin after just 12 hours. When using inserts and III, with higher initial concentrations of sodium formate, the regeneration time is reached after less than 2 or 6 hours.

If, according to the invention, ^{200 cm 3 of 800 cm 3 of} resin are placed in a first purification column and 600 cm ³ in a second hydrolysis column, the process can be continued until the entire 200 cm ^{3 of} resin purification column is consumed by reaction with the sodium formate, which is the case after about 6 hours when using the inflow I. Then the 200 cm ^{3 of} resin are regenerated and meanwhile a second ^{column containing 200 cm 3 of} fresh resin is switched on. The 600 cm ^{3 of} resin in the second column are effective without a time limit and do not need to be regenerated. The residence

Claims (3)

Patent claims: 1. A process for the purification of aqueous pentaerythritol solutions containing dipentaerythritol formal and sodium formate with the aid of a strong cation-exchanging resin in the H ⁺ form, the hydrolysis of the dipentaerythritol formal taking place, characterized in that the purification takes place in two stages, the pentaerythritol is freed from sodium formate in the first stage in an aqueous solution in a concentration of 25 to 45% at a temperature of more than 90 ° C. 2. The method according to claim 1, characterized in that only the cleaning bed of first stage is regenerated from time to time. 3. The method according to claim 1 or 2, characterized in that the treatment with the Resin is made in the first stage at temperatures of 90 to 105 ° C. Documents considered: German Auslegeschrift No. 1034 611; U.S. Patent No. 2,629,746. 509 510/419 2.65 ι Bundesdruckerei Berlin