DE1177159B - Process for stabilizing stannous salts of aliphatic or aromatic carboxylic acids against oxidative degradation - Google Patents

Description

Process for stabilizing stannous salts of aliphatic or aromatic Carboxylic acids against oxidative degradation The present invention relates to Stabilization of stannous salts of aliphatic or aromatic carboxylic acids against oxidative degradation.

Stannous salts of such carboxylic acids are used as catalysts for production used by polyurethane foam and for curing silicones as well as for other purposes. These salts degrade in the presence of air, and their usefulness is limited especially if they are stored after the container containing them has been opened once. As far as is known, there is no method of stabilization the stannous salts of carboxylic acids to prevent their oxidative degradation.

According to the invention, a method for stabilizing stannous salts is provided proposed aromatic or aliphatic carboxylic acids against oxidative degradation.

It has been found that stannous salts can be more aromatic or aliphatic Carboxylic acids can be stabilized against oxidative degradation by adding the stannous salt a small amount of 4-tert-butylpyrocatechol is added.

Although the 4-tert-butyl pyrocatechol in sufficient quantities in Solution remains to stabilize the stannous salts at room temperature, can dissolve this connection only with difficulty at such temperatures. To create a solution it is preferred to heat liquid stannous salts to around 800 C and the stabilizing agent for a longer period of time, preferably for at least 30 minutes. To a breakdown To prevent during incorporation of the stabilizer, one should be in the presence an inert protective gas, with nitrogen being the cheapest gas in particular suitable. The stannous salts, which are solid substances at room temperature, are used for Melt heated and then stirred in the stabilizer in the manner indicated.

The technical grade stannous salts of carboxylic acids usually contain not exclusively divalent tin; thus contains, for example, commercially available Stannous octoate usually between 95 and 990 / o mustard +, and commercial stannooleate usually contains between 85 and 95 ovo Sn ++. These percentages and those as they are included in the examples, give the ratio of the bivalent Tin contained in the total tin content of the analyzed examples. 4-tert-butyl-pyrocatechol is an extremely effective inhibitor for the Degradation of the stannous salts of carboxylic acids. With this inhibitor one can more effective Protection for common use at levels as low as 0.02%, though too a prevention of degradation, albeit to a lesser extent, with even smaller ones Additional amounts can be achieved. It is preferred to add amounts between 0.05 and 0.20 / 0 should be used. It is not necessary to use more than 10 / o of the additive apply. Larger amounts of the additive can, however, be used without that the properties of the stannous salts are adversely affected. The percentages relate to weight. The maximum amount of stabilizer that the base material are incorporated, is in each case by its maximum solubility in the stannous salt as well as the difficulty of being able to dissolve larger amounts of the stabilizer, given.

According to the invention stabilizable stannous salts are z. B. stannous fumarate, Stannoglycolate, stannodiglycolate, stanno-12-hydroxystearate, stannoitaconate, stannolactate, Stannolevulinate, stannoline oleate, stannomalate, stannomaleate, stannoricinoleate, stannooleyl sarcosinate, Stannosalicylate, stannosebacate, stannosorbate, stannosuccinate, stannothioglycolate, Stannoversenate, Stanno - di - (3,5,5 - trimethylhexo &) tStannoabietat, Stannoacetat, Stannous monochloroacetate, stannous trichloroacetate, stannous acetate anhydride, stannous p-aminobenzoate, Stannobenzoate, Stannobutyrate, stannocaproate, stannocitrate, stannocaprylate, stannocyanoacetate, stannoformate. The following compounds are of particular technical interest: Stanno-2-ethylhexoate, Stannooctoate, stannooleate, stannonaphthenate, stannogluconate, stannostearate, stannotartrate, Stannocaproat. Stannomyristate, stannopalmitate, stannolaurate and stannooxalate.

The invention is explained in more detail in the following examples.

To determine the stabilizing effect, the following were used Table in the second column specified stannous salts with those in the third column specified amounts of 4-tert-butylpyrocatechol in the manner described above offset.

The salts that were liquid at room temperature (stannous 2-ethylhexoate, stannooleate and stannonic naphthenate) were then placed in 50 cc vials in such a way that the vials were about three-quarters full. The stannous salt (stannous stearate), which is solid at room temperature, was finely powdered after adding the specified amount of 4-tert.-butyl-pyrocatechol and spread openly in a thin layer on a base. The samples labeled (a) in the table are control samples. The samples identified by letters (b) and (c) were stabilized by adding the amounts of 4-tert-butyl-pyrocatechol indicated in the table. All samples were left to stand in the air for 6 or 7 days intermittently, during which they were also exposed to daylight during the day. ° o 4-tert-butyl- duration of o / o Sn + exposure No. Salt catechol and ventilation Before exposure After exposure in the salt ~ (Days) and ventilation and ventilation 1 (a) Stanno-2-ethylhexoate - 6 95.5 83.0 (b) the same 0.05 6 95.5 1 93.5 (c) the same 0.1 6 95.5 1 94.5 2 (a) the same - 6 95.5 1 83 (b) the same 0.01 6 95.5 89 (c) the same 0.025 6 95.5 92.5 3 (a) the same - 6 99 87 (b) the same 0.05 6 99 1 98 4 (a) Stannooleate - 6 88.5 1 78.5 (b) the same 0.05 6 88.5 87.0 (c) the same 0.1 6 88.5 86.5 5 (a) stannous stearate - 6 92S 90 (b) the same 0.1 6 92.5 92 6 (a) stannone naphthenate - 7 95.4 77.3 (b); the same 0.1 7 95.4 84.8 The information "O! O Sn ++" means the percentage of tin that is present in divalent form.

From the examples it can be seen that an amount of stabilizer of 0.05 to 0.10 / u a breakdown of the tin compounds after 6 or 7 days of exposure practically completely prevented. You can also use the stannous salts with depending on your Nature of various amounts of the stabilizer effectively stabilized against degradation will. These attempts were made under very aggressive conditions, such as those in the Practice will likely never occur, performed. In practice this is stannous salt namely stored in tightly closed vessels, even if a part of the vessel contents has been consumed, the further storage of the stannous salts in that corresponds to Air-only container does not undergo the aggressive conditions of a 6-day period extensive direct contact with air. 4-tert-butyl catechol is also available suitable. another Degradation of the partially degraded divalent organic To prevent tin salts. The degradation of salts that are solid at room temperature, such as stannous stearate, is less strong.

Claims (1)

Claim: Process for stabilizing aromatic stannous salts or aliphatic carboxylic acids against oxidative degradation, which is not possible n -z e i c h n e t that the salts 4-tert-butylpyrocatechol in an amount from 0.02 to 1 percent by weight, preferably 0.05 to 0.2% by weight, is added. Documents considered: German Patent No. 1 016 264; U.S. Patent No. 2,831,817.