ITTO950924A1 - METHOD TO STABILIZE HYDROXYKETONE-BASED PRODUCTS SUBJECT TO INSTABILITY AND COLOR DEVELOPMENT PROBLEMS. - Google Patents

Abstract

The present invention relates to a method for stabilizing products based on hydroxyketones, such as for example a diaceton-alcohol, which have a high instability and color development which make it difficult to transport them over long distances or on intercontinental trips that cause the color development, i.e. the transition from colorless to yellowish shades, for example, thus being in disagreement with national or international specifications. The method is based on the addition of said p-terbutyl-catechol compounds in solid form or in solution preferably in storage tanks or in containers, so as to achieve a color stability (which is the most sensitive item) for at least 100 days.

Description

DESCRIPTION

of the patent for Industrial Invention

The present invention relates to a method for stabilizing solvent based on hydroxyketones such as for example a diaceton-alcohol, which have serious problems of instability with the passage of time, the condition worsening with their storage and transport to very distant locations.

The products based on hydroxyketones that are taken into consideration, such as for example diacetonalcool (I) which have the following structural formula:

(THE)

contain hydroxyl groups close to a ketone group. This proximity makes the molecule more unstable and reactive.

The Applicant is a manufacturer of ketone-based solbents. and hydroxy keton, essentially diacetone alcohol, hereinafter referred to as DAA, which finds several uses in the chemical industry, such as for example as a solvent in several types of inks and paints, thinners and retardants, substances for agricultural protection, products for wood processing, electrical insulation paints, leather products and raw materials for several organic syntheses. The DAA produced by the Applicant follows internal specifications similar to those contained in the ASTM D 262787 standard, whose characteristics are the following:

In 1980, colorless distilled diaceton alcohol was found to present problems when stored for long periods. It presented a "degradation" that was perceptible as a "development" of color (a darkening that acquired a yellowish (or even yellow) hue), turbidity in the miscibility tests with water and an increase in the dose of water in the stored product, which It was disqualified for commercial use. Until then, the Richièdente had not encountered any problems, as domestic customers were purchasing and using the DAA in a period of less than 30 days. The problem only became evident with a mass export of DAA on tankers. At that time the DAA was exported to France and the cargo arrived in Europe with out-of-specification colors, ie yellowish.

A first immediate solution was to devise special storage and export barrels As the price of each barrel was US $ 30.00 and a ton of DAA required five barrels to contain it, this amounted to US $ 150.00 / ton of DAA on its transport cost, which made this commercial operation impossible.

Studies were therefore carried out to try to correlate this "degradation" problem with process variables (resin duration time, quantity of heavy impurities in the finished product, quality of the catalyst, etc.), and other assays were devised to identify storage variables that could increase degradation (O2 of the atmosphere, material used in the manufacture of reservoirs, temperature, action of sunlight, etc.) and still other assays in an attempt to provide stabilizing agents to prevent degradation.

In 1982, with an improvement in the production process that obtained a DAA with a color below 5 on the Pt / Co color scale, the quality of the final product was considerably increased, thus satisfying the needs of the domestic customer who used this product in less than or up to 30 days. The studies performed during this time provided important conclusions, for example, that it was necessary to keep the DAA stored in an inert atmosphere, such as nitrogen, that the material in the tank has no influence on the color development of the product and that the ideal solution was to find a stabilizer.

Several agents or substances have been examined for this purpose, such as phenol, bisphenol A, thymol and several others. Among all these, TBC (para-terbutyl-catechol) was the most preferred for the results obtained in terms of stability in general and, in particular, for the development of color.

The choice of this stabilizer was due to the fact that it has an antioxidant and antipolymerizing effect on the diaceton - alcohol molecules due to the possibility that the development of color was associated with a self-condensation of the DAA molecules or with its oxidation possibly through mechanisms to free radicals, which cause its degradation into heavier and more colored products that have a negative impact on its application as a solvent, thus placing the product out of specification. For this reason, the first and main purpose has been to develop a stabilization method for hydroxyketone-based solvents which may not cause any change in the color of the product or which at least delays its process for as long as possible.

In examining the state of the art, we found some documents that deal with the inversion of the stabilizer during the distillation of the product, and some documents that deal with the stabilizers for the final product in order to prevent the development of color. These stabilizers known to technicians are BHT (2,6-di-tert-butyl-4-methyl-phenol) and BHA (3-terbutyl-4-hydroxy-anisole).

In practice, BHT is sold by Shell under the trade name of IONOLR.

No document has been found dealing with the stabilization of hydroxyketone-based solvents, essentially TBC.

The object of the present invention is to develop a stabilization method for hydroxyketone-based solvents, which are very unstable and subject to storage and transport for long periods, and which exhibit a degradation such as color change, generally from colorless to hue. yellowish, passing through yellow, and able to reach a dark brown color in the most severe cases, consequently being specific Hearts.

Another object of the present invention is to stabilize the hydroxyketone-based solvent about the other characteristics mentioned both in the manufacturer's quality control specifications (applicant's internal specifications) and in the ASTM D 2627-87 standard, such as for example neutralization index (acidity), water, evaporation residue (non-volatile material), etc.

The Applicant has developed a stabilization method for hydroxyketone-based products subject to problems of instability and color development, characterized by the fact that 15 to 200 ppm of 4-terbutyl is added to each ton of finished product to be preserved. catechol (TB) in both solid and solution form.

With the addition of TBC to the hydroxyketone-based solvent, a greater color stability is obtained for 120 days, and 100 days for the other characteristics, for example miscibility in water, while without the stabilizer the color stability is lower than SO days. Regarding the stability of DAA with TBC used as stabilizer, it is possible to consider that all the specification characteristics are higher than 100 days for the DAA stabilized with a stabilizer commercially found for this purpose; it has been noted that this can vary between 27 and 35 days. Thus, it can be said that the stability provided by the TBC is clearly superior as regards the stability when this comes from other stabilizing agents already known to those skilled in the art.

The invention relates to the stabilization of hydroxyketone-based solvents, such as for example diaceton - alcohol (DAA or 1-hydroxy-2propanone), 2-hydroxy-1,2-diphenyl-hephanone, 4-hydroxy-3-hexanone, 2-hydroxy-3-hexanone, 1,1,1,5,5,5-hexafluoro-4-hydroxy-4-methyl-2-pentanone, 1,1,1-trifluoro-4-hydroxy-4-methyl- 2-pentanone, 1-bromo-4-hydroxy-4-methy1-2-pentanone, 1,5-dichloro-1,1,5, -tetrafluoro-4-hydroxy-4-methy1-2-pentanone, 5 , 5,5-trifluoro-4-hydroxy-4- {trifluoro-methyl) -2-pentanone, 5-chloro-4- (c1orodifluoromethyl) -5,5-difluoro-4-hydroxy-2-pentanone, 5-chloro -4- {chloromethyl) -4-hydroxy-2-pentanone, 5,5-difluoro-4-hydroxy-5-nitro-4- (trifluorometi1-2-pentanone, 5,5-difluoro-4-hydroxy-5- nitro-4- (trifluorometi1) -2-pentanone, 1-chloro-5,5,5-trifluoro-4-hydroxy-4- (trifluoro-methi1) -2-pentanone, 1-bromo-5,5,5- trifluoro-4-hydroxy-4- (trifluoromethyl) -2-pentanone, conjugated mono acid of 4-hydroxy-4-methyl-2-pentanone, 3-chloro-4-hydroxy-4-methyl-2-pentanone, 1,1 , 1,3,5,5,5-heptafluoro-4-hydroxy-4- (trifluoromethi l) -2-pentanone, 4-hydroxy-3-iodine-4-methyl-2-pentanone, lithium salt of 5,5,5-trifluoro-4-hydroxy-4- {trifluoromethi1) -2-pentanone, 1 , 1,1,5,5,5-hexafluoro-4-hydroxy-4-methyl-2-pentanone, and several others, which are all unstable compounds which degrade easily in contact with oxygen, due to temperature increases , in sunlight, etc., that is, they present an oxidation or a self-condensation thus originating heavier compounds which cause an alteration of the color and, in more serious cases, these can change from yellow to dark brown.

This stabilization is achieved by incorporating TBC (tert-butylcatechol) in an amount of approximately 15 to 200 ppm. of TB, preferably.

The addition of TBC is done in the storage tank itself. If the TBC is in the form of an 85% solution, which is found commercially, it is necessary to calculate the volume of solution needed to obtain a mixture of, for example, 100 ppm of TBC per ton of solvent. For this, it is necessary to take into account the volume of the tank or its mass in order to calculate the volume of TBC solution to be added.

The contents of the tank should preferably be subjected to homogenization, which can be achieved by recirculating it, or by other mixing methods already known to those skilled in the art.

It is important that the TB is stored in solution in a place protected from light and rendered inert (an inert atmosphere), and must not be subjected to heating, as otherwise this also degrades the TB which can acquire a yellowish hue and, in more drastic cases, a dark brown color, which affects the quality of the product in which it is incorporated. For this reason, care must be taken to add good quality TB, i.e. a colorless TB.

The first tests, carried out in 1986, with 100 mg of purified solid state TBC per tonne of DAA confirmed the color stabilization of the DAA for up to 3 months, as indicated in the following Table I.

TABLE I

In 1987 the test was performed using 100 ppm of commercial TBC (85% aqueous solution) per ton of DAA and the results are shown in the following Table II.

TABLE II

As can be seen from the previous Tables, the choice of TBC in solid or solution form is not clearly reflected in the final characteristics of the stabilized product. An essential condition is that the TBC must have a colorless shade and a quality according to its specifications. Below are some examples by way of illustration, which thus do not limit the scope of the present invention.

EXAMPLE 1

The DAA contained in a tank is homogenized and stored in 6 barrels, occupying 2/3 of the volume of the barrel.

The barrels are numbered 1, 1A, 2, 2A, 3 and 3A. No addition of stabilizer (TBC) is made to barrels 1 and 1A.

Barrels 2 and 2A are weighed and stabilizer (TBC) is added so that its final concentration is 50 ppm.

Barrels 3 and 3A are weighed and stabilizer (TBC) is added to these so that its final concentration is 100 ppm.

The product in the barrels is homogenized and a. sample from each barrel for a complete analysis, that is, all items of the specification (time equal to zero days).

The barrels are then placed in a covered place under a nitrogen atmosphere.

The attached figure 1 illustrates the diagram for making barrels 1, 2, 3 and 1A, 2A and 3A inert with the addition of nitrogen.

Some pieces of carbon steel are placed in the barrels for this material to come into contact.

Each week, a sample is taken from each barrel and analyzed for color and miscibility in water.

Full analyzes are performed on days 58 and 125.

Below is a list of the attached tables which indicate the characteristics of the samples with the passage of time.

Table III - Color development (Pt / Co) Table IV - Acidity development

Table V - Development of non-volatile substances Table VI - Development of the percentage of water

Table VII - Development of the starting point of the distillation interval

(° C) (SP)

Table VIII Development of miscibility in water

(Note: L = clear;

NL = not clear).

CONCLUSIONS

The use of a stabilizer prevents the degradation of the AAD with the passage of storage time.

The TBC-free product exhibits a remarkable development and goes out of specification in 125 days for the items: color, non-volatile substances, acidity and miscibility in water.

TBC prevents the development of color and acidity in DAAs and reduces the rate of degradation for non-volatile substances and miscibility.

For the water and DP (dry point of the distillation range) items, the development rate is the same between products with and without TBC, but maintained in specification beyond 125 days.

EXAMPLE 2

The DAA used for the test was freshly manufactured and according to the specification of the ASTM D 2627-87 standard.

The test is performed in two carbon steel barrels vented to the atmosphere and exposed to the elements.

The color entry is analyzed weekly (see Table X) and the other entries every 30 days approximately (see Table IX).

The product that does not contain TBC leaves the specification regarding color in 50 days of storage, while the product with TBC does not show any color development in 190 days of storage (Table X). L and LIMP mean "CLEAR" and NL and N mean "NOT CLEAR".

Again according to the results of Table VIII, there is a development of acidity of the product without stabilizer, which goes out of specification for a storage of 75 days, the products with TBC started the test with a higher acidity, but does not show any development.

There is development of the water content in the two barrels, which is made worse by being vented to the atmosphere and exposed to the elements.

After turbidity appears in the test, the TBC analysis exhibits interference and makes it difficult to determine the end point of the analysis.

There is a development of turbidity in the product that does not contain 100 ppm of TBC in DAA between 75 and 99 days.

There is an increase in the non-volatile substance in the DAA without stabilizer, while there is no increase in the DP (dry point) of the distillation interval.

The SP (starting point) of the distillation interval of the product with TBC shows a drop, but remains in accordance with the specification in 190 days.

TABLE III

COLOR DEVELOPMENT (Pt / Co)

NCA - - IT COULD NOT BE ANALYZED

TABLE IV

DEVELOPMENT OF ACIDITY

TABLE V

DEVELOPMENT OF NON-VOLATILE SUBSTANCES

TABLE VI

DEVELOPMENT OF THE PERCENTAGE OF WATER

TABLE VII

SP DEVELOPMENT IN THE DISTILLATION INTERVAL

TABLE VIII

DEVELOPMENT OF MISCIBILITY IN WATER

TABLE XI

ANALYSIS FOR THE DEVELOPMENT OF DAA QUALITY IN BARRELS

TABLE X

Claims (1)

CLAIMS 1. Method for stabilizing hydroxyketone-based products subject to instability and color development problems, in which 15 to 200 ppm of 4-tert-butyl-catechol (TBC) are added to each ton of finished product to be preserved. solid or in solution. 2. Method for stabilizing hydroxyketone-based products subject to instability and color development problems according to claim 1, wherein the hydroxyketone-based product to be preserved is preferably diaceton-alcohol. 3. A method for stabilizing ketone-based products subject to instability and color development problems according to claim 1, in which the addition of TBC preferably occurs in the storage tank or container.