Storage and / or transport of ethylenically unsaturated carboxylic acids

Abstract

The present invention relates to a method for storing and / or transporting an ethylenically unsaturated carboxylic acid, the ethylenically unsaturated carboxylic acid being protected with manganese(II) ions against undesired radical polymerization.

Description

[0001] Storage and / or transport of ethylenically unsaturated carboxylic acids

[0002] The present invention relates to a process for storing and / or transporting an ethylenically unsaturated carboxylic acid, wherein the ethylenically unsaturated carboxylic acid is protected with manganese(II) ions against unwanted radical polymerization.

[0003] Chemical compounds that contain one or more ethylenically unsaturated groups have a pronounced tendency toward radical polymerization. Such compounds are therefore also referred to as polymerizable compounds. Due to their tendency toward radical polymerization, these compounds are used as monomers for the production of polymers. However, the pronounced tendency of these compounds toward radical polymerization is disadvantageous in that it can lead to undesirable, spontaneous radical polymerization during storage and transport, as well as during chemical and / or physical processing, such as distillation or rectification, particularly under the influence of energy, such as heat and / or light.Such uncontrolled polymerizations can lead to the gradual formation of polymer deposits, for example, on heated surfaces, necessitating their removal and thus often resulting in a reduction in operating times. The uncontrolled polymerizations can even be explosive.

[0004] It is therefore common practice to add compounds that inhibit or at least slow down unwanted, spontaneous radical polymerization to ethylenically unsaturated compounds that have a tendency toward radical polymerization, or to mixtures containing such compounds, both during storage and transport and during chemical and / or physical processing. Such substances are referred to as polymerization inhibitors.

[0005] Polymerization inhibitors can be used as individual chemical compounds or as mixtures of compounds. Depending on the application, specific requirements apply to the polymerization inhibitor. For a polymerization inhibitor to be suitable as a transport and / or storage stabilizer for ethylenically unsaturated compounds, it is important that the efficiency of the polymerization inhibitor, i.e., the extent of polymerization inhibition, can be regulated.Under the storage and / or transport conditions of the ethylenically unsaturated compounds, the polymerization inhibitor should sufficiently prevent or slow down the undesired, spontaneous radical polymerization, whereas the desired radical polymerization of the ethylenically unsaturated compounds should be possible under appropriate polymerization conditions without the need to first separate the polymerization inhibitor used during storage and / or transport. If the stabilizer used during storage and / or transport is not separated during the desired polymerization, it is important that it does not adversely affect the desired polymerization, for example, by acting unintentionally as a regulator.

[0006] Measured by global production volume, acrylic acid is certainly one of the most important ethylenically unsaturated compounds. Acrylic acid is typically stabilized against unwanted, spontaneous radical polymerization during storage and / or transport with 0.018 to 0.022 wt.% hydroquinone monomethyl ether (MEHQ), based on the amount of acrylic acid. For adequate stabilization of acrylic acid against unwanted, spontaneous radical polymerization using MEHQ, it is necessary that oxygen is dissolved in the acrylic acid in sufficient quantities. Sufficient amounts of oxygen are usually dissolved in the acrylic acid when acrylic acid is stored and / or transported under an atmosphere containing 5 to 21 vol.% oxygen.During the desired polymerization of acrylic acid, the oxygen content dissolved in the acrylic acid is reduced, thereby reducing the efficiency of MEHQ to inhibit polymerization to such an extent that acrylic acid can be polymerized in the presence of MEHQ.

[0007] In addition to its use as a polymerization inhibitor during storage and / or transport of acrylic acid, MEHQ is also used as a polymerization inhibitor during storage and / or transport of methacrylic acid, acrylic acid esters and / or methacrylic acid esters or mixtures containing one or more of the aforementioned compounds.

[0008] Due to its wide use, MEHQ is one of the most important storage and / or transport stabilizers for ethylenically unsaturated compounds, especially for acrylic acid, methacrylic acid, acrylic acid esters and methacrylic acid esters.

[0009] Ethylenically unsaturated compounds are stored in suitable, permanently installed containers, such as storage tanks (see, for example, Acrylic Acid, A Summary of Safety and Handling, 4th Edition 2013, 7 Bulk Storage Facilities and Accessories). It is preferred that the ethylenically unsaturated compounds are stored in the respective containers for at least one hour, more preferably at least 10 hours, and most preferably at least 100 hours. Although the storage period is theoretically unlimited under appropriate conditions, the storage period is generally reduced to a minimum for economic reasons. It is preferred that the ethylenically unsaturated compounds are stored in the respective containers for a maximum of 180 days, more preferably for a maximum of 90 days, and most preferably for a maximum of 30 days.Particularly preferred ranges result from any combination of the previously mentioned lower and upper limits.

[0010] The transport of ethylenically unsaturated compounds usually takes place in suitable, transportable containers such as tanks or drums by ship, railcar and / or truck (see, for example, Acrylic Acid, A Summary of Safety and Handling, 4th Edition 2013, 9 Safe Transport of Acrylic Acid). Of course, the transportable containers can also be permanently installed on the corresponding means of transport, for example ship tanks or rail tank cars. It is also possible for the containers to be stored at a specific location for a certain period of time before being transported to another location. The transport of ethylenically unsaturated compounds can also take place in pipelines or hoses, for example after purification of the ethylenically unsaturated compound to the storage tank, during loading from the storage tank to a transportable container and / or during loading from one transportable container to another.It is preferred that the ethylenically unsaturated compounds remain in the respective containers for at least one hour during transport, more preferably at least 10 hours, and most preferably at least 100 hours. Although the duration is theoretically unlimited under appropriate conditions, the duration is generally reduced to a minimum for economic and safety reasons. It is preferred that the ethylenically unsaturated compounds remain in the respective containers for a maximum of 180 days during transport, more preferably for a maximum of 90 days, and most preferably for a maximum of 30 days. Particularly preferred ranges arise from any combination of the aforementioned lower and upper limits.

[0011] EP 0 398 633 A1 discloses a process for inhibiting the polymerization of acidic monomers with sources of manganese and phenylenediamines containing NH groups.

[0012] JP 5140027 discloses the use of mixtures of a) phenols, such as phenol, hydroquinone, p-methoxyphenol, cresol and catechol, b) manganese salts and c) sterically hindered phenols, such as 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butylphenol, 6-tert-butyl-m-cresol; 2,6-di-tert-butyl-p-cresol, 4-tert-butylcatechol, 2,4-dimethyl-6-tert-butylphenol, 2-tert-butylhydroquinone and 2-tert-butyl-4-methoxyphenol, for stabilizing acrylic acid, methacrylic acid and their esters.

[0013] US Pat. No. 6,207,859 discloses a process for storing and transporting α,β-unsaturated carboxylic acids. The α,β-unsaturated carboxylic acids are stabilized against unwanted radical polymerization with a phenol and a metal cation of at least divalent cation. The metal cation of at least divalent cation is removed after storage and transport.

[0014] The object of the present invention was to provide a process for storing and / or transporting ethylenically unsaturated carboxylic acids. The polymerization inhibitors should ensure sufficient stabilization of the ethylenically unsaturated carboxylic acids against unwanted radical polymerization. However, during the desired radical polymerization, there should be no need to separate the polymerization inhibitors from the mixture prior to polymerization. The polymerization inhibitors should therefore not act as polymerization regulators and / or polymerization inhibitors during the desired radical polymerization. Furthermore, the polymerization inhibitors should not lead to unwanted discoloration during the polymerization.

[0015] The object is achieved by a process for storing and / or transporting an ethylenically unsaturated carboxylic acid, wherein the ethylenically unsaturated carboxylic acid has a purity of at least 90% by weight, the mass of stored and / or transported ethylenically unsaturated carboxylic acid is at least 100 kg and the ethylenically unsaturated carboxylic acid has a temperature of less than 50°C during storage and / or transport, characterized in that the ethylenically unsaturated carboxylic acid contains from 0.000002 to 0.00005% by weight (20 to 500 ppb) of manganese(II) ions, based on the total amount of ethylenically unsaturated carboxylic acid.

[0016] The purity of the ethylenically unsaturated carboxylic acid is preferably at least 95% by weight, more preferably at least 98% by weight, most preferably at least 99% by weight.

[0017] The mass of stored and / or transported ethylenically unsaturated carboxylic acid is preferably at least 200 kg, more preferably at least 500 kg, most preferably at least 1,000 kg. The mass of stored and / or transported ethylenically unsaturated carboxylic acid is usually less than 10,000,000 kg.

[0018] The ethylenically unsaturated carboxylic acid has a temperature of preferably less than 45°C, more preferably less than 40°C, most preferably less than 35°C, during storage and / or transport. In the case of acrylic acid, the temperature during storage and / or transport should be at least 15°C. The ethylenically unsaturated carboxylic acid preferably contains less than 0.01 wt.% (100 ppm), preferably less than 0.001 wt.% (10 ppm), more preferably less than 0.0002 wt.% (2 ppm), most preferably less than 0.0001 wt.% (1 ppm) of phenols, in each case based on the total amount of ethylenically unsaturated carboxylic acid.

[0019] The ethylenically unsaturated carboxylic acid preferably contains substantially no phenol and / or substantially no phenylenediamine.

[0020] The ethylenically unsaturated carboxylic acid preferably contains from 0.000002 to 0.00005 wt.% (20 to 500 ppb), preferably from 0.000005 to 0.000045 wt.% (50 to 450 ppb), particularly preferably from 0.00001 to 0.00004 wt.% (100 to 400 ppb), very particularly preferably from 0.000015 to 0.000035 wt.% (150 to 350 ppb), in each case based on the total amount of ethylenically unsaturated carboxylic acid.

[0021] The ethylenically unsaturated carboxylic acids are preferably mono-, di- or triethylenically unsaturated C3 to Cs carboxylic acids.

[0022] Particularly preferred are acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, citraconic acid, methylenemalonic acid, crotonic acid, fumaric acid, mesaconic acid, itaconic acid and maleic acid, or any mixtures of two or more of the aforementioned ethylenically unsaturated carboxylic acids.

[0023] Acrylic acid and methacrylic acid are particularly preferred.

[0024] The ethylenically unsaturated carboxylic acids are typically stored and / or transported in stainless steel containers. Suitable stainless steels contain 16.5 to 19.5 wt% chromium and 8.0 to 13.5 wt% nickel.

[0025] The ethylenically unsaturated carboxylic acid is usually stored and / or transported under an oxygen-containing atmosphere.

[0026] The ethylenically unsaturated carboxylic acid is preferably stored in a container under an oxygen-containing atmosphere with an oxygen content of 5 to 10 vol.%, and the mixture in the container is regularly circulated, for example by completely pumping the tank contents around at least once a week. The relatively low oxygen content prevents flammable gas mixtures in the container. Circulation replaces consumed dissolved oxygen in the liquid ethylenically unsaturated carboxylic acid. The present invention further provides a process for radical polymerization, wherein at least one of the above-described ethylenically unsaturated carboxylic acids is polymerized by means of a polymerization initiator, and the use of one of the above-described ethylenically unsaturated carboxylic acids for radical polymerization by means of a polymerization initiator.

[0027] By means of the radical polymerization according to the invention, for example, water-soluble and water-swellable polyacrylic acids and their sodium salts are obtainable.

[0028] Radical polymerization itself is well known and is usually carried out in solution. Suitable polymerization initiators include all carboxylic acids that can decompose into radicals under the chosen reaction conditions, for example, thermal initiators, redox initiators, and photoinitiators. Suitable thermal initiators are peroxomono- and disulfates, as well as peroxomono- and diphosphates. Suitable redox initiators are sodium peroxodisulfate / ascorbic acid, hydrogen peroxide / ascorbic acid, sodium peroxodisulfate / sodium hypophosphite, sodium peroxodisulfate / sodium bisulfite, and hydrogen peroxide / sodium bisulfite.

[0029] Examples

[0030] Experiments on polymerization inhibition

[0031] The ethylenically unsaturated carboxylic acid used was double distilled to remove the polymerization inhibitor hydroquinone monomethyl ether (MEHQ). The resulting ethylenically unsaturated carboxylic acid was treated with the specified amount of the polymerization inhibitor. MEHQ and manganese(II) acetate were used.

[0032] 0.5 ml of each mixture was filled into a 1.8 ml ampoule and stored in a circulating air drying cabinet at the specified temperature.

[0033] In each test series, three ampoules of each mixture were filled and tested, with the mean time to complete polymerization being recorded visually. Table 1: Mixtures with acrylic acid

[0034] *) Comparison

[0035] Manganous ions have a comparable effect to MEHQ even at a thousand times lower concentration.

[0036] Experiments on polymerization

[0037] Under a nitrogen atmosphere, 450 g of water were placed in a reaction vessel. The reaction mixture was heated to 95°C with stirring. Once the temperature reached 95°C, three streams were added while stirring and maintaining the temperature.

[0038] Stream 1 : Dosage over 5 h, 500 g acrylic acid

[0039] Stream 2: Dosage over 4.75 h, 15 g sodium hypophosphite in 35 g deionized water Stream 3: Dosage over 5.25 h, 5 g sodium peroxodisulfate in 66.4 g deionized water

[0040] After addition of the three streams, the reaction mixture was stirred for another hour at 95°C. The reaction mixture was then cooled to room temperature and 80 g of water were added.

[0041] The acrylic acid used in stream 1 was stabilized with MEHQ or manganese(II) acetate.

[0042] The resulting polymers were analyzed by GPC (calibration with Na-PAA standard, eluent 0.01 mol / l phosphate buffer, pH 7.4 in distilled water, with 0.01 M NaN3). Table 2: Polymerization of acrylic acid

[0043] *) Comparison

[0044] The manganese(II) ions at the concentrations investigated lead to polyacrylic acids with a molecular weight comparable to that obtained when using the standard concentration of MEHQ.

[0045] Polymerization of sodium acrylate or sodium methacrylate

[0046] Under a nitrogen atmosphere, 52 g of deionized water and 60 g of aqueous sodium acrylate solution or aqueous sodium methacrylate solution (each

[0047] 37.2 wt.% and stabilized with 0.01 wt.% MeHQ or 0.0000057 wt.% manganese(II) acetate). Subsequently, 0.4 g of sodium peroxodisulfate dissolved in 10 g of deionized water was added and heated to 80°C with stirring. The reaction mixture was stirred at 80°C for 4 h and then cooled to ambient temperature.

[0048] In all experiments with MEHQ, the solution changed color during heating (at approximately 60°C).

Claims

Patent claims 1. A method for storing and / or transporting an ethylene unsaturated carboxylic acid, wherein the ethylene unsaturated carboxylic acid has a purity of at least 90 wt.%, the mass of the stored and / or transported ethylene unsaturated carboxylic acid is at least 100 kg, and the ethylene unsaturated carboxylic acid has a temperature of less than 50°C during storage and / or transport, characterized in that the ethylene unsaturated carboxylic acid contains 0.000002 to 0.00005 wt.% manganese(II) ions, based on the total amount of ethylene unsaturated carboxylic acid.

2. The method according to claim 1, characterized in that the ethylene unsaturated carboxylic acid contains less than 0.0001 wt% phenols, based on the total amount of ethylene unsaturated carboxylic acid.

3. The method according to claim 1, characterized in that the ethylene unsaturated carboxylic acid contains essentially no phenol and / or essentially no phenylenediamine.

4. Method according to one of claims 1 to 3, characterized in that the ethylene unsaturated carboxylic acid contains 0.000005 to 0.000045 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

5. Method according to one of claims 1 to 3, characterized in that the ethylene unsaturated carboxylic acid contains 0.00001 to 0.00004 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

6. Method according to one of claims 1 to 3, characterized in that the ethylene unsaturated carboxylic acid contains 0.000015 to 0.000035 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

7. Method according to one of claims 1 to 6, characterized in that the storage and / or transport of the ethylene unsaturated carboxylic acid extends over a period of at least 10 hours.

8. Method according to any one of claims 1 to 7, characterized in that the ethylene unsaturated carboxylic acid is acrylic acid and / or methacrylic acid.

9. Method according to any one of claims 1 to 8, characterized in that the ethylene unsaturated carboxylic acid is stored and / or transported in a steel container and the steel contains 16.5 to 19.5 wt.% chromium and 8.0 to 13.5 wt.% nickel.

10. A method according to any one of claims 1 to 9, wherein the ethylene unsaturated carboxylic acid is stored and / or transported under an oxygen-containing atmosphere.

11. A method according to any one of claims 1 to 10, wherein the ethylene unsaturated carboxylic acid is reacted under an oxygen-containing atmosphere with an oxygen content of 5 to 10% by volume is stored in a container and the ethylene unsaturated carboxylic acid in the container is regularly circulated.

12. A process for radical polymerization, wherein at least one ethylene unsaturated carboxylic acid is polymerized by means of a polymerization initiator, characterized in that the ethylene unsaturated carboxylic acid used contains 0.000002 to 0.00005 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

13. The method according to claim 12, characterized in that the ethylene unsaturated carboxylic acid contains 0.000015 to 0.000035 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

14. Use of an ethylene unsaturated carboxylic acid for radical polymerization using a polymerization initiator, characterized in that the ethylene unsaturated carboxylic acid used contains 0.000002 to 0.00005 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

15. The method according to claim 14, characterized in that the ethylene unsaturated carboxylic acid contains 0.000015 to 0.000035 wt% manganese(ll) ions, based on the total amount of ethylene unsaturated carboxylic acid.

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