PRODUCTION OF POLYAMIDE POWDERS BY ESTER AMINOLYSIS

Abstract

A method for producing a polycondensate powder dispersion, characterised in that it includes at least one step of polycondensation: i) of at least one diester and at least one diamine, and/or ii) at least one amino ester, while stirring, in a solvent that can solubilise both the diamine and the diester and/or the amino ester but not the polyamide that forms during the polycondensation, at a temperature between 30° C. and the boiling temperature of the solvent, in order to produce a powder precipitate dispersed in the solvent.

Claims

1. A process for producing a polycondensate powder dispersion, wherein the method comprises at least one step of polycondensation: i) of at least one diester and at least one diamine, and/or ii) of at least one amino ester, with stirring, in a solvent that can dissolve both the diamine and the diester and/or the amino ester, but not the polyamide which forms during the polycondensation, at a temperature included in the range of from 30° C. to the boiling point of said solvent, such that a powder precipitate dispersed in the solvent is obtained, wherein the powder precipitate comprises particles of free powder which have a spheroidal shape, a D50 measured according to ISO standard 13320-1:1999 included in the range of from 1 to 200 μm, and traces of ester chain ends.

2. The process for producing a powder dispersion as claimed in claim 1, wherein the method also comprises a step of separation of the solvent and of recovery of the powder.

3. The process as claimed in claim 1, wherein said polycondensation is carried out in the presence of a polycondensation catalyst, the content of which is included in the range of from 0.01 mol % to 50 mol %, relative to the number of moles of all of the reagents.

4. The process as claimed in claim 1, wherein said at least one diester is of formula:
R.sub.1—(CH.sub.2).sub.m—R.sub.2, wherein m represents an integer ranging from 0 to 36, and R.sub.1 and R.sub.2 represent identical or different ester functions of general formula COOR.sub.3, wherein R.sub.3 represents a saturated or unsaturated, linear or branched alkyl chain of from 1 to 5 carbon atoms and/or
R.sub.1—(C.sub.6H.sub.4).sub.n—R.sub.2, wherein n represents an integer ranging from 1 to 2, and R.sub.1 and R.sub.2 represent identical or different ester functions of general formula COOR.sub.3, wherein R.sub.3 represents a saturated or unsaturated, linear or branched alkyl chain of from 1 to 5 carbon atoms.

5. The process as claimed in claim 1, wherein said at least one primary or secondary diamine is chosen from aliphatic diamines having from 6 to 12 carbon atoms, said diamine possibly being a saturated aryl or cyclic diamine.

6. The process as claimed in claim 1, wherein said at least one amino ester corresponds to the general formula R.sub.5—(CH.sub.2)—R.sub.6, wherein p represents an integer ranging from 0 to 36, R.sub.5 represents a primary or secondary amine function, and R.sub.6 represents an ester function of general formula COOR.sub.7, wherein R.sub.7 represents an alkyl chain of from 1 to 5 carbon atoms.

7. The process as claimed in claim 3, wherein the polycondensation catalyst is chosen from sodium hydride, potassium hydride, sodium, sodium stearate, ortho-phosphoric acid, stearic acid, ethanol, phenol, sodium methoxide, sodium ethoxide, and mixtures thereof.

8. The process as claimed in claim 1, wherein the solvent is chosen from linear alkanes, cycloaliphatic alkanes, halogenated solvents and mixtures thereof.

9. The process as claimed in claim 1, wherein the polycondensation is characterized by a simultaneous precipitation in the form of polycondensate powders.

10. The process as claimed in claim 1, wherein the stirring is at a speed included in the range of from 1 to 2000 rpm.

11. A polycondensate powder which can be obtained according to the process of claim 1.

12. The powder as claimed in claim 11, wherein the powder comprises from 0 to 50 mol %, of a polycondensation catalyst, relative to the number of moles of polycondensate.

13. The powder as claimed in claim 11, wherein the powder comprises traces of a polycondensation solvent, wherein the solvent is chosen from linear alkanes, cycloaliphatic alkanes, halogenated solvents and mixtures thereof.

14. The powder as claimed in claim 11, wherein the powder comprises traces, relative to the total weight of the powder, of alcohol of formula R.sub.3OH and/or R.sub.7OH, wherein R.sub.3 and R.sub.7 each represent an alkyl chain from 1 to 5 carbon atoms.

15. The powder as claimed in claim 11, wherein the polycondensate is an oligomer having a number-average molar mass included in the range of from 300 g/mol to 5000 g/mol.

16. The powder as claimed in claim 11, wherein the polycondensate is a polyamide having a number-average molar mass of between 5000 and 30 000 g/mol.

17. A product comprising the powder as claimed in claim 11, wherein the product is chosen from coatings, paints, anticorrosion compositions, paper additives, powder agglomeration by electromagnetic radiation-induced melting or sintering for producing objects, electrophoresis gels, multilayer composite materials, packaging, toys, products in the textile, automobile and/or electronics industry, and cosmetic, pharmaceutical or perfumery products.

18. A method of using oligomer powder as claimed in claim 15, as an ester and/or amine reactive synthon in polymer chain extension reactions, either alone or as an additive for powder agglomeration by electromagnetic radiation-induced melting or sintering for producing objects or as a polyamide reinforcement.

19. An oligomer or polymer powder dispersion, wherein the dispersion comprises: from 0.1% to 99.9% by weight of particles of powder which have a spheroidal shape, a D50 measured according to ISO standard 13320-1:1999 included in the range of from 1 to 200 μm, and which comprise traces of ester chain ends; and from 0.1% to 99.9% by weight of solvent wherein the solvent can dissolve both diamine and diester and/or amino ester, but not polyamide which forms during polycondensation, relative to the total weight of the dispersion.

20. A cosmetic and/or perfumery composition, wherein the composition comprises: from 0.1% to 99.9% of particles of powder which have a spheroidal shape, a D50 measured according to ISO standard 13320-1:1999 included in the range of from 1 to 200 μm, and which comprise traces of ester chain ends, and from 0.1% to 99.9% of a medium which is acceptable in cosmetics and/or in perfumery, relative to the total weight of the composition.

21. The composition as claimed in claim 20, said composition being a colored, noncolored or transparent product chosen from the following products: makeup products for the human face and body; care products for the human face and body; hair products; perfumery products.

22. The polycondensate powder as claimed in claim 11, wherein the polycondensate powder comprises particles of free powder comprise 10 to 4000 meq/kg of ester chain ends, relative to the weight of polycondensate.

Description

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0049] The invention is now described in greater detail and in a nonlimiting manner in the description which follows.

[0050] Unless otherwise indicated, the proportions or percentages indicated are by weight.

[0051] For the purposes of the invention, the term “polycondensate” is intended to mean both an oligomer and/or a polyamide obtained by polycondensation.

[0052] For the purposes of the invention, the term “polyamide” is intended to mean the products of condensation of amino esters and/or diesters with diamines and, as a general rule, any polymer formed by units linked to one another by amide groups.

[0053] For the purposes of the invention, the term “oligomer” is intended to mean a chemical molecule consisting of one to four monomers.

[0054] For the purposes of the invention, the term “monomer” is intended to mean a repeating unit of the oligomer or of the polyamide. The case where a repeating unit consists of the combination of a diester with a diamine is particular. It is considered that it is the combination of a diamine and of a diester, that is to say the diamine.diester pair (in equimolar amount), which corresponds to the monomer. This is explained by the fact that, individually, the diester or the diamine is just one structural unit, which is not sufficient on its own to form a polymer.

[0055] The invention envisions producing a polycondensate powder from at least one diester and at least one diamine, and/or at least one amino ester, as defined above.

[0056] According to one particular embodiment of the invention, a single diamine diester pair is used, so as to form a homopolyamide.

[0057] According to one preferred embodiment of the invention, two or more diamine diester pairs are used, so as to form a copolyamide (CoPA).

[0058] According to another particular embodiment, a single amino ester having a single index n is used so as to form a homopolyamide.

[0059] According to an even more preferred embodiment, two or more amino esters having different indices n are used, so as to form a CoPA.

[0060] According to the process of the invention, introduced for example into a reactor are the monomer(s) included in the range of from 20% to 75%, preferably 30%, by weight of at least one diester and at least one diamine and/or of at least one amino ester, in a dispersion solvent, relative to the total weight of dispersion. The solvent may comprise in particular one or more of the following compounds: linear alkanes, cycloaliphatic alkanes, halogenated solvents and mixtures thereof. The solvent preferably comprises a solvent of Shellsol type. The term “solvent of Shellsol type” is intended to mean a solvent consisting of a hydrocarbon fraction.

[0061] It is also possible to introduce into the medium a polycondensation catalyst, the content of which is included in the range of from 0 to 50 mol %, preferably from 0.01 mol % to 50 mol %, preferably from 0.01 mol % to 30 mol %, preferably from 0.01 mol % to 20 mol %, relative to the number of moles of all of the reagents. The use of a catalyst has an advantageous effect on the control of the polymerization and on the precipitation of the powders. According to one advantageous embodiment of the process of the invention, an acid catalysis and a basic catalysis can alternatively be used. Preferably, a basic catalysis, preferably comprising sodium methoxide, is used.

[0062] The reaction temperature is included in the range of from 30° C. to the boiling point of the solvent, preferably from 50° C. to 120° C., preferably from 80° C. to 110° C., preferably equal to 100° C.

[0063] Stirring is applied to the reaction medium, preferably included in the range of from 1 to 2000 rpm, preferably 150 rpm, preferably 310 rpm. This stirring can be carried out by any system sufficient to bring about the dispersion of the PA powders in the solvent, including by shear.

[0064] According to one advantageous embodiment of the invention, the stirring is carried out by means of a paddle stirring system, preferably by means of a paddle and counter-paddle stirring system.

[0065] This step lasts for example at least one hour, or at least two hours, or at least three hours, or at least four hours, or at least five hours.

[0066] The temperature is preferably constant. Alternatively, this temperature can vary for example in a monotone or cyclic manner or in steps. A temperature increase phase can be provided for at the beginning of the process or before. Preferably, said phase lasts less than 30 minutes, or less than 20 minutes, or less than 15 minutes, or less than 10 minutes.

[0067] The ester aminolysis results, according to the process of the invention, in the formation of a polycondensate. According to the invention, the ester aminolysis, by reaction of at least one diamine and at least one diester and/or of at least one amino ester, leads directly to the synthesis of polycondensate.

[0068] Parasitic reactions can theoretically be observed, such as a cyclization of the diester, an intramolecular cyclization, an intermolecular cyclization or an N,N′-dimethylation. The alkylation of the amines by the esters, originating from the competition of the acyl-alkyl groups (N-alkylation), leads to the interruption of the formation of the polyamide, since there is permanent formation of nonreactive chain ends. Without being bound by any theory, the inventors think that, by virtue of the process according to the invention, only the last reaction is possible at low temperature (temperature below 200° C.), all the other reactions being linked to a high temperature (greater than or equal to 200° C.). The lower the reaction temperature, the less the N-alkylation occurs. Advantageously, the process according to the invention makes it possible to reduce or even prevent the parasitic reactions.

[0069] Simultaneously with the polycondensation, a dispersion of powder in the solvent forms. The reaction medium opacifies, marking the start of the formation of a powder, preferably after one hour.

[0070] The powder dispersion can be stored in this state or else the powder can be separated from the dispersion solvent and recovered. Preferably, the polycondensate is thus recovered in powder form.

[0071] Where appropriate, the separation step can be carried out according to any liquid-solid separation techniques, preferably by solvent evaporation.

[0072] Various additives can also be introduced into the medium, in particular organic fillers, such as PA, or mineral fillers, such as silica; and/or surfactants.

[0073] Advantageously, an organic or mineral filler, preferably silica, is added to the reaction medium to assist with the precipitation by making it possible to control the size distribution of the particles. Use may be made of a 5 μm hydrophilic silica (Sipernat 320DS), but use is preferably made of a hydrophobic silica consisting of agglomerates which are smaller than one micrometer in size (Aerosil R972). The addition of silica has an advantageous effect on the size of the polycondensate powder. In the absence of such a filler, the powder tends to form agglomerates which coalesce, and in this case it proves to be difficult, or even impossible, to control the size distribution of the particles, and thus to obtain a powder with a D50 of less than 100 μm, or even a D50 of less than 200 μm.

[0074] Advantageously, various types of surfactants can be added to the reaction medium. These surfactants make it possible to stabilize the growing particles in the reaction medium. They may for example be sodium stearate or butanol, preferably butanol.

[0075] The number-average molar mass of the polyamide obtained can be determined by size exclusion chromatography, using hexafluoroisopropanol (HFIP) as solvent and eluent, and a refractometric detection. The number-average molar mass of the polyamide obtained can also be determined by NMR (nuclear magnetic resonance), or else by quantitative determination of the chain ends. NMR is preferably used to determine the number-average molar mass.

[0076] The characteristics of the powders of polyamide, which is the subject of the invention, are in particular: [0077] the mean particle diameter of from 1 to 200 μm, preferably from 1 to 100 μm, even more advantageously from 5 to 60 μm; [0078] the narrow particle size distribution by volume. The particle size distribution by volume of the powders is determined according to the usual techniques, for example using a Coulter LS 230 particle size analyzer, according to ISO standard 13320-1:1999. On the basis of the particle size distribution by volume, it is possible to determine the volume mean diameter (“D50”) and also the particle size dispersion (standard deviation) which measures the width of the distribution. It is one of the advantages of the process described that it makes it possible to obtain a tight or narrow (dispersion) particle size distribution by volume; [0079] the spheroidal shape of the particles, that is to say in the shape of a spheroid, which has a shape similar to that of a sphere; [0080] the particle surface porosity, measured by the apparent specific surface area (also called SSA). The particles of the invention have an SSA measured according to the BET method ranging from 1 to 20 m.sup.2/g, preferably from 2 to 10 m.sup.2/g, preferably from 3 to 6 m.sup.2/g. The BET (Brunauer-Emmet-Teller) method is a method known to those skilled in the art. It is in particular described in The journal of the American Chemical Society, vol. 60, page 309, February 1938, and corresponds to international standard ISO 5794/1. The specific surface area measured according to the BET method corresponds to the total specific surface area, that is to say that it includes the surface area formed by the pores.

EXAMPLES

[0081] The following examples illustrate the invention without limiting it.

Example 1—Precipitation Polymerization of a PA 6.10

[0082] A dibutyl sebacate/hexamethylenediamine reaction mixture is prepared in a 1:1 weight ratio. The reaction mixture is introduced into a glass reactor in an amount of 30% by weight in Shellsol. Sodium methanolate is added to the reaction medium in an amount of 17 mol % relative to one of the monomers. The reaction is carried out with stirring at 150 rpm and heated up to a temperature of 100° C. The reaction time is 7 hours.

[0083] The medium is then filtered so as to recover the PA 6.10 powder, and then the powder is washed with ethanol, and then with water and finally oven-dried at 75° C.

[0084] The powder is analyzed by .sup.1H NMR and DSC.

[0085] The total yield by weight is 72%. This yield by weight is calculated by calculating the ratio of the weight of powder obtained after washing and drying to the weight of powder theoretically expected at the end of reaction.

[0086] The PA 6.10 powder obtained has a molar mass of approximately 1200 g/mol.

[0087] The PA 6.10 powder obtained has a melting point (M.sub.p) equal to 201° C. and a viscosity of 0.23 (according to Arkema method: 0.5 g/dl in metacresol at 25° C.).

[0088] The D50 of the powder is then measured according to ISO standard 13320-1:1999. The mean diameter of the powder particles obtained is 80 μm.

TABLE-US-00001 TABLE 1 .sup.1H NMR analysis of example 1 Molar ratio Ex. 1 Secondary amide 76.12% Ester 3.79% Acid 5.76% Primary amine 11.60% Alcohol 2.72%

[0089] The NMR analyses clearly show the production of a polyamide from a diester and from a diamine.

Tests: Influence of the Catalyst Concentration and of the Temperature Profile on the Synthesis Yield by Weight

[0090] Tests were carried out by varying the catalyst concentration. The conditions used are identical to those of example 1. The results are presented in the following table (the higher the yield by weight, the more efficient the reaction).

TABLE-US-00002 TABLE 2 Influence of the catalyst concentration on the yield Test Catalyst [mol %] Yield by weight 1 17 72% 2 9 20% 3 40 72%

[0091] According to the yields by weight obtained under the conditions of example 1, it is possible to conclude that there is an optimal loading of sodium methanolate (reaction catalyst): approximately 17 mol %. Indeed, with less catalyst (9 mol %), the reaction gives a lower yield by weight; and with more catalyst (40 mol %), there is no improvement observed compared to 17 mol %.

[0092] Tests were carried out by varying the reaction temperature. The results are presented in the following table (the higher the yield by weight, the more efficient the reaction).

TABLE-US-00003 TABLE 3 Influence of the thermal profile on the action of the sodium methanolate Precipitation Test Catalyst [%] Thermal profile yield by weight 1 17 100° C. over the 72% course of 7 h 4 17 100° C. over the 72% course of 15 h 5 17 80° C. over the 52% course of 15 h 6 17 120° C. over the 13% course of 7 h

[0093] According to the yields by weight obtained, it is possible to conclude that there is an optimal synthesis temperature: 100° C. Indeed, it appears that, with a lower temperature (80° C.) or a higher temperature (120° C.), the reaction is less efficient.

[0094] Tests were carried out by varying the stirring speed of the reaction medium. The results are presented in the following table (the higher the yield by weight, the more efficient the reaction).

TABLE-US-00004 TABLE 4 Influence of the stirring speed on the particle size Test Stirring speed [rpm] Mean diameter [μm] 1 150 100 7 310 80

[0095] The stirring speed has a direct effect on the size of the polycondensate powder particles; the faster the stirring, the smaller the particles.

Example 2—Oil/Water Emulsion of the Polycondensate Powder According to the Invention

[0096] A formulation A for a cosmetic cream, of the oil-in-water type, having the following composition by weight is prepared: [0097] Water 83.44%. [0098] Chlorphenesin: 0.28%. [0099] Xanthan gum: 0.2%. [0100] Hydroxyethyl acrylate and copolymer of sodium acryloyldimethyl taurate: 0.5%. [0101] Arachidyl alcohol and behenyl alcohol and arachidyl glucoside: 3.0%. [0102] Caprylic/capric triglycerides: 5.0%. [0103] Cyclohexasiloxane: 1.0%. [0104] Phenoxyethanol and ethylhexylglycerol: 0.5%. [0105] Antioxidant: 0.08%. [0106] Glycerol: 3.0%. [0107] Composition according to the invention: 3.0%.

[0108] A formulation B for a pressed cosmetic powder for smoothing out imperfections, having the following composition by weight, is prepared: [0109] Octyldodecyl xyloside: 5.0%. [0110] Isostearyl isostearate: 3.0%. [0111] Talc: 44.7%. [0112] Mica: 30.0%. [0113] Talc and disodium stearoyl glutamate/aluminum hydroxide: 5.0%. [0114] Cellulose: 5.0%. [0115] Salicylic acid: 0.2%. [0116] Pigments: 2.1%. [0117] Composition according to the invention: 5.0%.

[0118] In the two formulations above, the composition according to the invention is produced from particles of copolyamide 6112.

[0119] The particles have a volume-mean diameter D50 of 10 μm.

[0120] The composition has a pH included in the range of from 5 to 9, for example of 7.5.