MXPA96006271A - Gas generating compositions containing acid d, 1-tartar - Google Patents

Abstract

In gas generating compositions that use, as a fuel, at least in part, tartaric acid, aqueous processing is improved through the use of d, 1-tartaric acid on the naturally occurring 1-tartaric acid.

Description

GAS GENERATING COMPOSITIONS CONTAINING ACID d, 1 -TARTÁRIC The present invention is directed to gas generating compositions, and particularly to gas generating compositions containing d, 1-tartaric acid.

Background of the Invention U.S. Patent No. 3,785,149, the teachings of which are incorporated herein by reference, teaches the use of tartaric acid as a fuel in conjunction with a -oxidant, such as potassium perchlorate, as a generator. of gas for inflation of automotive air bags and the like. This patent teaches compacting tartaric acid and oxidant powders to form gas generating compositions. Tartaric acid is a desirable fuel in gas generating compositions as it contains only the elements of hydrogen, carbon and oxygen, and can be used in less nitrogen gas generating formulations, such as tartaric acid / potassium perchlorate compositions taught in the US PATENT No. 3,785,149. In compositions if nitrogen, undesirable nitrogen-containing gases, such as NO (particularly NO and NO) and NH-, are not formed. Likewise, tartaric acid is very high in oxygen content, whereby the weight ratio of fuel to oxidant can be relatively high so that a high volume of gas per generator weight is generated during combustion. Likewise, tartaric acid is relatively inexpensive and easily available. While tartaric acid is used alone as a single tibial combustion in various gas generating cushions disclosed in U.S. Patent No. 3,785,149, it is known to use tartaric acid in conjunction with other fuels in gas generating compositions. The present invention is directed to gas generating compositions in which the tartaric acid comprises at least about 10% by weight, generally at least about 20% by weight, up to 100%, of the total fuel content of a gas generating composition. gas. When the gas generating compositions are described using tartaric acid as a fuel, it is assumed that the J-tartaric acid is the form of the tartaric used. This is because j-tartaric acid, a natural product, is by far the most common and economical form of tartaric acid. J_-tartaric acid is produced by ferementation and is a secondary product of wine production. From a pyrotechnic point of view, there is no difference in operation independently of the tartaric acid form j_-, d_- or d, 1 -. Consequently, absent a stereochemistry designation, the gas generating compositions use tartaric acid as fuel, as in U.S. Patent No. 3,785,149, the use of J-tartaric acid is understood. When feasible for a particular gas generating composition, aqueous processing has advantages. In a typical aqueous gas generator processing, the various components dissolve and / or form in suspension in water, typically between about 10 to about 35% by weight of liquid. The suspension is dried and granulated to form pills or can be extruded. The pills or extruded particles, if desired, can subsequently be compacted into tablets. In general, prior to co-compaction, the gas generating composition is tested to ensure the proper composition. If the composition varies in content of acceptable limits, it can be formed in suspension again and reprocessed with additional ingredients. Examples of aqueous processing of gas generating compositions are found in U.S. Patent Nos. 4,994,212 and 5,084,218, the teachings of each of which are incorporated herein by reference. Water processing reduces the likelihood of premature combustion during the manufacture of pyrotechnic gas generating compositions. Likewise, water processing can produce very compact gas generating material, particularly when one or more of the gas generating components is soluable in water. The desirability of using, at least in part, a water soluble fuel in aqueous process gas generating material is taught, for example, in U.S. Patent No. 5,467,715, the teachings of which are incorporated herein by reference.

SUMMARY OF THE INVENTION In a gas generating composition comprising a fuel and an oxidant, wherein at least about 10% by weight, up to 100% by weight of the fuel is tartaric acid, it is found that aqueous processing is improved when used racemic acid od, 1-tartaric, instead of J-tartaric acid that occurs naturally.

Detailed Description of Certain Preferred Modes The gas generating compositions to which the present invention is directed contain a fuel and an oxidant. The present invention is directed to a wide variety of fuel / oxidant combinations. Accordingly, based on the total weight of most oxidant fuel, the fuel can vary from about 15 to about 60% by weight of the composition and the oxidant from about 40 to about 85 by weight of the compositions. The fuel, according to the invention, is at least in part, tartaric acid, but other fuels known in the art, particularly non-azide fuels, such as tetrazoles, triazoles, salts of dililturic acid and others are reported in the literature of patents and elsewhere can also be used in conjunction with tartaric acid as part of the gas generating composition. The compositions in the present invention can also be formulated with any conventional oxidant, such as alkali metal and alkali metal chlorides, perchlorates and nitrates as well as with transition metal oxides, such as CuO and Fe203. As noted above, with the aqueous processing of gas generating material, it is considered desirable, v. gr., as taught in U.S. Patent No. 5,467,715 that at least part of the material is soluble in water, e.g., a fuel component or an oxidizing component. Naturally occurring tartaric acid having a solubility in water at 20 ° C of 139 g / 100 ml would therefore seem to be particularly advantageous in aqueous processing. In contrast, d, l-tartaric acid, which has a solubility in water at 20 ° C. of only 20.60 g / 100 ml, would appear substantially less desirable for aqueous processing. In view of other disadvantages related to naturally occurring j-tartaric acid, that is, which is much less available (and consequently is more expensive), there is nothing to suggest the use of d, l-tartaric acid on the acid J_-tartaric in any gas generating composition. However, the applicants have found that in the. aqueous processing, the less soluble d, l-tartaric acid is advantageously advantageous over the highly soluble j-tartaric acid. It is found that the very high solubility of j-tartaric acid makes gas generating compositions that use this form very difficult to dry. The d, 1 -tartaric acid, on the other hand, is found to be sufficiently soluble in water to facilitate processing with water, and provides gas generating compositions that can be easily dried. This advantage is realized in the initial processing of the gas generating compositions, and also in the aqueous reprocessing of slightly ill-formulated gas generating material. In fact it is found that even where higher levels of water are required for processing the gas-generating material containing d, l-tartaric acid (in relation to the amount of water required if the form _1_- were used), the compositions containing the d, 1- form are dried much more easily. As a result, savings are made in both energy and labor costs. The advantages of using the d, 1- form of tartaric acid are realized whether the tartaric acid is the sole fuel, according to the formulations of U.S. Patent No. 3,785,149, or when the tartaric acid is used in conjunction With other fuels, the tartaric acid comprises at least about 10% by weight of the total fuel particularly when it comprises at least about 20% by weight of the total fuel. The invention will now be described in more detail through specific examples.

Example 1 According to the prior art, a suspension of 1609 g of potassium perchlorate and 1114 g of j-tartaric acid in 480 g was made. of water. This suspension was mixed in a high shear mixer. The suspension was poured to bande_ jas to a depth of approximately 1.90 cms. and dried in a vacuum oven at 90 ° C., which is the maximum drying of the mixture in accordance with the thermal measurements made accelerating the acceleration rate calorimetry (ARC). After 2.75 hours, the mixture was sieved through a 16 mesh screen and then dried for a further 3 hours. In accordance with the invention, d, 1 tartaric acid was replaced by j-tartaric acid in the formulation. In order to form a miscible suspension, the amount of water necessary to increase to 900 gr. However, the total drying time was reduced by 1 hour.

Example 2 A suspension of 26.9 kg was made. of potassium perchlorate and 18.6 kg. of _1_-tartaric acid in 8.0 kg. of water. Efforts to process this suspension in a modified spray dry apparatus to make pyrotechnic materials were satisfactory. D, l-tartaric acid was replaced by j-tartaric acid in the same formulations. The amount of water had to be increased to 16.4 kg. in order to make an efficient suspension. However, this suspension was easily processed in the spray drying apparatus to provide a spherical, dry pyrotechnic composition (less than 0.5 wt.% Moisture); yield of approximately 80%.

Claims (3)

CLAIMS:

1. - In a gas generating composition comprising fuel and oxidant, at least about 10% by weight of the fuel comprising tartaric acid, the improvement wherein the tartaric acid is d, l-tartaric acid.

2. A mixture of components to form a gas generating composition comprising fuel and oxidant, at least about 10% by weight of the fuel co-tempting tartaric acid, the improvement wherein the tartaric acid is d, l-tartaric acid .

3. A method that forms a gas generating composition comprising suspending fuel and oxidant in water, at least approximately 10% by weight of the fuel comprising tartaric acid, and subsequently drying the suspension to remove the water and in this way forming a gas generating composition is improved, where the tartaric acid is d, 1-tar-tartaric acid.