WO2000068207A1

WO2000068207A1 - Novel 6-amino-uracil derivatives, preparation and use thereof

Info

Publication number: WO2000068207A1
Application number: PCT/EP2000/004394
Authority: WO
Inventors: Etienne Hannecart
Original assignee: Solvay (Société Anonyme)
Priority date: 1999-05-10
Filing date: 2000-05-08
Publication date: 2000-11-16
Also published as: AR023895A1; BE1012673A3; AU5524400A

Abstract

The invention concerns novel 6-amino-uracil derivatives, their preparation and their use as stabilising agents for halogenated polymers.

Description

New 6-amino-uracil derivatives. their preparation and use

The present invention relates to new 6-amino-uracil derivatives, their preparation and their use in the stabilization of halogenated polymers.

Halogenated polymers, and more particularly polymers containing chlorine (including polymers of vinyl chloride), exhibit a set of interesting properties, in particular chemical inertness, good resistance to ultraviolet rays and excellent mechanical resistance.

However, in the context of certain uses requiring implementation in the molten state such as the manufacture of profiles or tubes, there is a slight degradation of the material which can be avoided by the use of stabilizing products.

However, in applications using these polymers in a very thick layer, for example of the order of several tens of mm, thermal degradation may appear at the heart of the material as a result of the severe thermal conditions to which it is subjected during shaping. thick pieces. Similarly, thermal stability problems arise when melted halogenated polymers of very high molecular weight (for example for the shaping of articles requiring very high mechanical strength) and / or copolymers whose stability intrinsic thermal is lower than that of the homopolymer. It is therefore currently desirable to have effective thermal stabilizers for halogenated polymers.

For the thermal stabilization of halogenated polymers, and more particularly polymers containing chlorine (including polymers of vinyl chloride), a multitude of very diverse thermal stabilizers have already been proposed. In practice, these are most often derivatives of heavy metals such as lead, calcium and / or zinc salts, barium and / or cadmium or organic derivatives of tin. However, heavy metal derivatives have the disadvantage of being toxic to living beings and of being harmful to the environment. Other organic derivatives have also been described as stabilizers in compositions comprising halogenated polymers, and more particularly polymers containing chlorine (including polymers of -. ? .

vinyl chloride). Belgian patent BE 687294 describes the use of stabilizing compositions for plastics comprising several stabilizers including a uracil derivative. The uracil derivatives are variously substituted by lower alkyl groups or by optionally substituted phenyl groups. Likewise, patent application EP 768336 describes stabilizing compositions comprising in particular heterocyclic uracil or thiouracil compounds in which the heterocyclic nitrogen atoms are substituted for example by alkyl groups comprising from 1 to 12 carbon atoms. These compounds are only obtained at the end of a long and costly synthesis process comprising several stages and which, moreover, involve toxic reagents. In addition, experience has shown that these compounds of the prior art only lead to poor stabilization of halogenated polymers and more particularly of polymers containing chlorine (including polymers of vinyl chloride). The present invention aims to provide effective stabilizers for halogenated polymers and more particularly polymers containing chlorine (including polymers of vinyl chloride).

To this end, the invention relates to new 6-amino-uracil derivatives corresponding to the general formula I

in which RI and RJ independently of one another represent a linear or branched alkyl group containing at least 14 carbon atoms.

In general, the new 6-amino-uracil derivatives correspond to the general formula I in which RI and R2 independently of one another represent a linear or branched alkyl group containing at most 24 carbon atoms, preferably at most 22 carbon atoms and in a particularly preferred manner, at most 20 carbon atoms.

A preferred class of new 6-amino-uracil derivatives correspond to the general formula I in which RI and RJ independently of one another represent a linear or branched alkyl group containing at least 16 carbon atoms.

Particularly preferred are the new 6-aminouracil derivatives which correspond to general formula I in which RI and R2 represent - J

each a linear or branched alkyl group containing 18 carbon atoms.

The invention also relates to a process for the preparation of new 6-amino-uracil derivatives. To this end, the invention relates to a process for the preparation of new 6-amino-uracil derivatives corresponding to the general formula I as defined above according to which an N, N'-disubstituted urea is reacted with cyanoacetic acid and the product obtained is then cyclized in basic medium.

By N, N'-disubstituted urea is intended to denote, for the purposes of the present invention, any disubstituted urea corresponding to formula II

in which RI and RJ are the same linear or branched alkyl groups as those defined above for the 6-amino-uracil derivatives corresponding to formula I.

In the process according to the invention, cyanoacetic acid is generally used in slight molar excess relative to the N, N'-disubstituted urea. This molar excess is usually less than or equal to a factor 2. Preferably, this molar excess is less than or equal to a factor 1.5. Excellent results are obtained with a molar excess less than or equal to a factor of 1.3.

Generally, the reaction between N, N'-disubstituted urea and cyanoacetic acid takes place in an organic solvent. The organic solvent is preferably an aliphatic or aromatic hydrocarbon. Among the organic solvents, there may be mentioned a petroleum ether fraction, toluene or xylenes, a chlorinated solvent such as chloroform or carbon tetrachloride or an acid derivative such as ethyl acetate or anhydride acetic. Acetic anhydride is particularly preferred.

In general, the amount of solvent involved is not critical. However, a solution that is too concentrated can affect the good dissolution of the reactants in the presence and the homogeneity of the solution, while a solution that is too dilute can reduce the speed of the reaction. An amount of 30 moles of solvent per mole of cyanoacetic acid is generally suitable.

Generally, the reaction between N, N'-disubstituted urea and cyanoacetic acid takes place at a temperature slightly above the ambient temperature. This temperature is usually greater than or equal to 30 ° C and preferably greater than or equal to 50 ° C. The reaction temperature is generally less than or equal to 150 ° C and preferably less than or equal to 100 ° C. Generally, the duration of the reaction between N, N'-disubstituted urea and cyanoacetic acid is a function of various parameters. Usually, the transformation of the reagents is followed by chromatographic or spectroscopic methods. Most often, the reaction is completed in less than 10 hours and preferably in less than 5 hours. Particularly preferably, the reaction is completed in less than 2.5 hours.

Generally, the cyclization of the product obtained by the reaction between N, N'-disubstituted urea and cyanoacetic acid takes place in basic medium. Usually, the cyclization of the product obtained by the reaction between N, N'-disubstituted urea and cyanoacetic acid is carried out by means of a basic solution comprising a base and a solvent. Usually, the committed base is a mineral base such as an alkali or alkaline earth metal hydroxide. Among these hydroxides, mention may be made of sodium hydroxide, potassium hydroxide, ammonium hydroxide or calcium hydroxide. Sodium hydroxide is particularly preferred. Usually the solvent is water or a solvent capable of dissolving the base. Alcohols are generally used for this purpose such as methanol, ethanol, butanol or t. butanol. Advantageously, methanol is used. Usually, the base concentration in the basic solution is greater than or equal to 1 mole / liter, preferably, the base concentration in the basic solution is greater than or equal to 2 moles / liter and advantageously, it is greater than or equal to 3 moles / liter. The base concentration in the basic solution is less than or equal to 10 moles / liter, preferably, the base concentration in the basic solution is less than or equal to 8 moles / liter and advantageously, this concentration is less than or equal to 5 moles /liter. The process for the preparation of the new 6-amino-uracil derivatives has the advantage of requiring only a few steps, it is therefore less expensive than the known processes and involves slightly toxic reagents.

The invention also relates to halogenated polymer compositions. To this end, the invention relates to halogenated polymer compositions comprising a halogenated polymer and a 6-amino-uracil derivative of general formula I as defined above. 3 -

By halogenated polymers is meant for the purposes of the present invention, both homopolymers and copolymers of halogenated monomers; in particular homopolymers of halogenated monomers such as vinyl chloride, vinylidene chloride, vinylidene fluoride, vinyl fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene; the copolymers which these halogenated monomers form with each other and the copolymers of one of these halogenated monomers with another ethylenically unsaturated monomer such as olefins such as ethylene, propylene and styrene, halogenated olefins, vinyl ethers, vinyl esters such as for example vinyl acetate as well as acrylic esters, nitriles and amides and esters, nitriles and methacrylic amides.

The amount of 6-amino-uracil derivative present in the composition depends, in general, on the nature, on the molecular weight, as well as, if necessary, on the extent of the thermal degradation of the halogenated polymers which is desired. stabilize. The 6-amino-uracil derivative is generally present in the composition in an amount of at least 0.05 parts by weight, preferably at least 0.1 parts by weight and particularly preferably at least 0.3 parts by weight per 100 parts by weight of halogenated polymer. In general, the 6-amino-uracil derivative is present in an amount of at most 5 parts by weight; preferably at most 3 parts by weight and particularly preferably at most 1.5 parts by weight per 100 parts by weight of halogenated polymer.

The halogenated polymer used in the compositions according to the invention is preferably chosen from polymers containing chlorine. The term “polymer containing chlorine” is intended to denote, for the purposes of the present invention, both homopolymers and copolymers of monomers containing chlorine, in particular homopolymers of monomers containing chlorine such as vinyl chloride and vinylidene chloride as well as copolymers involving vinyl chloride and vinylidene chloride and copolymers of vinyl chloride and / or vinylidene chloride with another ethylenically unsaturated monomer chosen from olefins, halogenated olefins, vinyl ethers, vinyl esters such as for example vinyl acetate as well as acrylic or methacrylic esters, nitriles and amides. The halogenated polymer used in the compositions according to the invention is very particularly preferably a polymer of vinyl chloride. The term “vinyl chloride polymer” is intended to denote, for the purposes of the present invention, both homopolymers of vinyl chloride and its copolymers with other ethylenically unsaturated monomers which can be polymerized by the radical route. As examples of common comonomers of vinyl chloride which can be used according to the invention, mention may be made of olefins, halogenated olefins, vinyl ethers, vinyl esters such as for example vinyl acetate, as well than acrylic or methacrylic esters, nitriles and amides. The comonomers are used in amounts not exceeding 50 mol%, most often not 35 mol% of the mixture of comonomers used in the copolymerization.

The halogenated polymers, and more particularly the polymers containing chlorine (including the polymers of vinyl chloride), entering into the compositions according to the invention can consist indifferently of virgin polymers or of used polymers (or of mixtures of these polymers) .

In the case of virgin polymers, these are most often in the form of powders whose particles have an average diameter of approximately 50 to 200 μm, and most often approximately 100 to 140 μm. In the case of used polymers, it is of course appropriate, prior to the incorporation of the new 6-amino-uracil derivative, to grind and / or to micronize the articles shaped into used halogenated polymers, with a view to reduce them to crushed particles (crushed) of reduced size. The grinds of used polymers preferably have an average diameter of not more than 5 mm and more particularly still 2 mm. The preparation of the compositions according to the invention does not present any particular problem. All the usual techniques making it possible to incorporate processing ingredients in thermoplastic polymers to form mixtures, in the form of powders or granules, can be used. Thus, the new 6-amino-uracil derivative can be mixed with the halogenated polymer from the polymerization stage, either by direct introduction into the polymerization medium, at the end of polymerization, or even by addition to the wet cake obtained by spin drying. or filtration of the aqueous dispersion coming from the polymerization. It is understood that this mode of incorporation is only suitable for compositions according to the invention consisting of virgin halogenated polymer. An advantageous procedure, which can be used in all cases, consists in adding the new 6-amino-uracil derivative to the polymer found. in the form of a powder (or of a ground product) during the manufacture of a premix (premix), at the same time as the other additives entering into the composition. The new 6-amino-uracil derivative can also be introduced directly into devices where the halogenated polymer is melted, such as screw extruders. In this case, the stabilized composition will be in the form of granules (compounds).

The compositions according to the invention are suitable for use by all the conventional techniques for transforming thermoplastic materials into a melt, such as extrusion and molding. In addition to the new 6-amino-uracil derivatives, the compositions according to the invention can contain the usual additives of halogenated polymers, such as lubricants, pigments, fillers, additives reducing the emission of fumes during combustion ("fumicide" agents), plasticizers, light stabilizers, etc. The new 6-amino-uracil derivatives used in the compositions according to the invention are of such efficiency that the compositions of halogenated polymers which contain them are suitable for the manufacture of very thick parts, such as plates or bars , that they allow the use of halogenated polymers with very high molecular weight and / or halogenated copolymers with lower thermal stability than that of homopolymers, but also that they allow the stabilization-discoloration of used and thermally degraded halogenated polymers thus making it possible to recycle crushed used articles.

The invention also relates to the use of the new 6-amino-uracil derivatives. To this end, the invention relates to the use of 6-aminouracil derivatives as stabilizers for halogenated polymers.

Preferably, the 6-amino-uracil derivatives are used as thermal stabilizers of halogenated polymers. The use of the new 6-amino-uracil derivatives as stabilizers for halogenated polymers has the advantage of preventing the coloration of the compositions or, as the case may be, of attenuating the coloration of the compositions (in the case of the stabilization of used polymers already degraded) when these are subjected to temperatures above the melting point of the halogenated polymers and sufficient to be able to transform them into shaped articles. The examples which follow are intended to illustrate the invention without however limiting its scope. Example 1

150 ml of acetic anhydride, 20 g (35.4 mmol) of N, N'-dioctadecylurea and 3.7 g (43.5 mmol) of cyanoacetic acid were introduced into a 250 ml three-necked flask under argon. . The solution was heated at 80 ° C for 2 hours and then evaporated to dryness on a Rotavapor. The oil obtained was taken up in 400 ml of tetrahydrofuran. 40 ml of a 4N sodium hydroxide solution were added with stirring. The solution obtained was then placed in an ice bath. The yellow crystals formed were filtered through a sintered glass filter and washed with twice 50 ml of methanol. After drying under vacuum in the presence of phosphorus hemipentoxide, 6-amino-1J-dioctadecyluracil was recovered, in the form of a yellow solid, with a yield greater than 92%. The melting point of the product obtained was 70-74 ° C. Example 2 A polymeric composition was prepared by mixing 80 parts by weight of PVC SOLNIC® S266RC (SOLVAY), 20 parts by weight of PNC SOLVIC® S 173TB (SOLVAY), 5 parts by weight of polybutylacrylate, 5 parts by weight of calcium carbonate, 4 parts by weight of TiO ₂ , and 1 part by weight of 6-amino-1,3-dioctadecyluracil. This composition was kneaded in a BRABEΝDER type kneader at 190 ° C. with a cam speed of 32 revolutions per minute and pancakes were taken after different kneading times, in order to assess their coloration.

After 3 minutes of mixing, the composition is white. After 7 minutes of mixing, the composition is still white. After 11 minutes of mixing, the composition is light beige. After 15 minutes of mixing, the composition is light brown. Examples 3-5 (comparative)

The same test as above was repeated either without added stabilizer (Example 3), either with 6-amino-1,3-dimethyluracil (Example 4) or with 6-amino-1J-dibutyluracil (Example 5). The results are shown in the table below. Board

(1): Coloring of pancakes removed after the number of minutes of mixing indicated in the column header.

Claims

R E V E N D I C A T I O N S

1 - New 6-amino-uracil derivatives corresponding to general formula I

2 - 6-Amino-uracil derivatives according to claim 1 characterized in that RI and RJ independently of one another represent a linear or branched alkyl group containing at most 24 carbon atoms.

3 - 6-Amino-uracil derivatives according to any one of claims 1 and 2 characterized in that RI and RJ independently of one another represent a linear or branched alkyl group containing at least 16 carbon atoms.

4 - 6-Amino-uracil derivatives according to any one of Claims 1 to 3, characterized in that RI and RJ represent a linear or branched alkyl group containing 18 carbon atoms.

5 - Process for the preparation of 6-amino-uracil derivatives according to any one of claims 1 to 4 in which an N, N'-disubstituted urea is reacted with cyanoacetic acid and the product obtained is then cyclized to basic environment.

6 - Halogenated polymer compositions characterized in that they comprise a halogenated polymer and a 6-amino-uracil derivative of general formula I according to any one of claims 1 to 4.

7 - Compositions according to claim 6, characterized in that the 6-amino-uracil derivative is present in an amount of at least 0.05 part by weight for

100 parts by weight of halogenated polymer. 8 - Compositions according to any one of claims 6 and 7, characterized in that the 6-amino-uracil derivative is present in an amount of at most 5 parts by weight per 100 parts by weight of halogenated polymer.

9 - Compositions according to any one of claims 6 to 8, characterized in that the halogenated polymer is chosen from polymers containing chlorine.

10 - Compositions according to any one of claims 6 to 9, characterized in that the halogenated polymer is a polymer of vinyl chloride.

11 - Use of 6-amino-uracil derivatives according to any one of claims 1 to 4 as stabilizers for halogenated polymers.