WO2022128166A1

WO2022128166A1 - Process for extracting at least one benzene sulfonamide plasticizer from a polyamide - associated polyamides uses and products

Info

Publication number: WO2022128166A1
Application number: PCT/EP2021/058519
Authority: WO
Inventors: Cyril Aymonier; Iulia BALANUTA; Marc VERGUGHT
Original assignee: Centre National de la Recherche Scientifique CNRS; Agiplast Italia Srl
Current assignee: Centre National de la Recherche Scientifique CNRS; Agiplast Italia Srl
Priority date: 2020-12-18
Filing date: 2021-03-31
Publication date: 2022-06-23
Anticipated expiration: 2023-06-18
Also published as: WO2022128167A1; WO2022128168A1

Abstract

The present invention relates to a process for at least partially extracting at least one benzene sulfonamide plasticizer from a polyamide containing such a plasticizer. According to the invention, said polyamide is contacted at least one time with a first solvent mixture comprising or consisting in supercritical carbon dioxide and a first polar cosolvent, said contact(s) being performed above 304.13 K, and above 7.3773 MPa, said first solvent mixture being liquid, at its critical point or in supercritical state.

Description

PROCESS FOR EXTRACTING AT LEAST ONE BENZENE SULFONAMIDE PLASTICIZER FROM A POLYAMIDE -ASSOCIATED POLYAMIDES USES AND PRODUCTS

Technical field of the invention

The present invention relates to a process for extracting at least one benzene sulfonamide plasticizer from a polyamide containing said plasticizer(s).

Offshore oil production uses flexible pipes for transporting the petroleum from the bottom of the see to the boat platform. There are some specific characteristics for these offshore pipes, like flexibility, high pressure and anticorrosion resistance. Multilayer system of pipes, composed basically of steel and thermoplastic polymer, satisfies all needful requirements. Polyamide 11 is a suitable polymer for this concept. Chemical and mechanical resistances of PA11 are explained by the strong intermolecular interactions between the chains via hydrogen bonds. During pipes lifetime, the hydrocarbons penetrate inside in the PA 11 matrix. Thereby instant mechanical recycling is not preferable, because the residual pollutions in the matrix will deteriorate the mechanical properties of polymer.

Moreover, offshore pipes need to be also flexible for spooling or to follow the flow lines for example. This property is achieved by the plasticization of virgin polymers. Incorporation of additive molecules destroys a part of hydrogen linkage and gives chain mobility. Usually off-shore pipes contain PA11 polymer modified by 12 wt.% of N-butyl benzene sulfonamide (BBSA). This plasticizer is harmful and toxic by simple contact. Despite the additives enhance the properties and lifetime of polymers, they can contaminate the environment and human health by simple migration. Hence, the control of these compounds is essential.

Prior art

Basically, the thermoplastic polymers can be successful recycled via mechanical method due to their properties. As regards plasticizers, the literature relates to supercritical extraction of additives from different thermoplastic matrixes, as HDPE, PP, PTFE. For the most part of works, supercritical CO2 solvent is used alone for the treatment, less often it is modified by an organic solvent. However, its quantity is too small in comparison with Soxhlet or conventional reflux methods. It is remarkable that is no information about the extraction of polyamide/nylon plasticizers.

Technical problems to be solved

One purpose of the present invention is to provide an environmentally friendly process for treating a polluted polyamide comprising at least one benzene sulfonamide plasticizer. Another purpose of the present invention is to provide a process as above-mentioned which does not use toxic or ecotoxic solvent and which does not produce waste.

Another purpose of the present invention is to provide a process enabling the recycling of offshore post-used pipes.

Another purpose of the present invention is to provide a process for treating a polyamide which enables the reuse of said recycled polyamide and more particularly the re-use of said polyamide in clothes, fabrics, or shoes manufacturing.

Brief summary of the invention

The present invention relates to a process for at least partially extracting at least one benzene sulfonamide plasticizer from a polyamide containing such a plasticizer, wherein said polyamide is contacted at least one time with at least one first solvent mixture comprising or consisting in supercritical carbon dioxide and a first polar cosolvent, said contact(s) being performed above 304.13 K, and above 7.3773 MPa, said first solvent mixture being liquid, at its critical point or in supercritical state.

The polyamide can be contacted several times with the same first solvent mixture or with at least two different first solvent mixtures. Each first solvent mixture can be identical or contain different first polar cosolvent or the same first polar cosolvent but in different weight amount.

According to the invention, the extraction of the plasticizer(s) can be total or only partial, depending on the first solvent mixture and the number of contacts.

The process of the invention can be used to recycle post-used polyamides or to treat newly produced polyamides but containing a too great amount (for instance more than 20% by weight) of benzene sulfonamide plasticizer(s).

Detailed description

Advantageously, said polyamide is contacted at least one time with at least one second solvent mixture after being contacted at least one time with said first solvent mixture(s), said second solvent mixture comprises or consists in supercritical carbon dioxide and at least one first solvent of said benzene sulfonamide plasticizer(s), said contact(s) being performed above 304.13 K, and above 7.3773 MPa , said second solvent mixture being liquid, at its critical point or in supercritical state. Preferably, the second solvent mixture is at its critical point or in supercritical state.

Again, the polyamide can be contacted several times with the same second solvent mixture or with at least two different second solvent mixtures. Second solvent mixtures can be different because they contain different plasticizer solvent or because they contain the same plasticizer solvent but in different volume. The second solvent mixture improves plasticizer(s) extraction.

Advantageously, the polyamide is contacted at least one time with at least one third solvent mixture, said third solvent mixture comprising or consisting in supercritical carbon dioxide and a second polar cosolvent, said contact(s) being performed above 304.13 K, and above 7.3773 MPa, said third solvent mixture being liquid, at its critical point or in supercritical state.

Advantageously, the third solvent mixture(s) is at its critical point or in supercritical state.

According to the invention, the polyamide can be contacted several times with the same third solvent mixture or with at least two different third solvent mixtures. Two third solvent mixtures can be different as regards the second cosolvent and/or as regards the volume of said second cosolvent.

The use of the third solvent mixture improves the extraction of the plasticizer(s) contained in the polluted polyamide and enables as the first solvent mixture a slight separation of the polymer chains. According to a particular embodiment, said polyamide is contacted at least one time with at least one first solvent mixture, then at least one time with at least one second solvent mixture, then contacted at least one time with at least one third solvent mixture and then contacted at least one time with at least one fourth solvent mixture containing at least one second solvent of said benzene sulfonamide plasticizer(s), said contact(s) being performed above 304.13 K, and above 7.3773 MPa, each of said first, second, third and fourth solvent mixtures being irrespectively one from the others, liquid, at its critical point or in supercritical state. According to this embodiment, plasticizer(s) can be removed in a sufficient manner.

According to a particular embodiment that can be combined with anyone of the embodiments of the present invention, said polyamide is contacted one time with one first solvent mixture, one time with one second solvent mixture, one time with a third solvent mixture and one time with a fourth solvent mixture.

The second polar cosolvent can be identical to said first polar cosolvent and/or the first solvent of said benzene sulfonamide plasticizer(s) can be identical to said second solvent of said benzene sulfonamide plasticizer(s).

Advantageously, the first and the third solvent mixtures are identical and the second and the fourth solvent mixtures are identical, and the polyamide is contacted one time with each solvent mixture. This can be sufficient to remove plasticizer(s). The resulting process is remarkably simple to perform. According to a variation that can be combined with anyone of the other embodiments, said first, second, third solvent and fourth mixture contains, independently one from the others, from 1% in volume to 20% in volume and in particular 2%, 3%, 4%, 5%, 6%, 7% 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17% 18%, 19% in volume of said first polar cosolvent, said first solvent of said benzene sulfonamide plasticizer(s), said second polar solvent and said second solvent of said benzene sulfonamide plasticizer(s), respectively. Polyamide can be contacted with said first polar cosolvent, said second polar cosolvent, said first or second solvent of said benzene sulfonamide plasticizer(s), before being contacted with supercritical carbon dioxide, said first, second polar cosolvents and said first and second solvent for said benzene sulfonamide plasticizer being liquid.

Advantageously, said polyamide is melted when contacted with said first, second, third or fourth solvent mixture. This improves the contact and the extraction of pollutants.

The process of the invention can be performed in a reactor (batch) or in a continuous manner. For example, it can be performed during extrusion of said polluted polyamide; it also can be performed in a fluidized bed comprising particles of at least one polyamide fluidized with said first, second, third or fourth solvent mixture.

Advantageously, said first polar cosolvent and said second polar cosolvent are chosen irrespectively one from the other among mixtures comprising or consisting in ethanol, acetic acid, water and mixtures of water and acetic acid, mixtures of ethanol and acetic acid and mixtures of ethanol, water, and acetic acid.

Accordingly, said first and/or said second polar cosolvent can consist in a mixture of ethanol and acetic acid and particularly in a mixture chosen among mixtures containing 1%, 10%, 20%, 25%, 30%, 50%, 60%; 75%, 80%, 85%, 90% in volume of ethanol.

The following mixtures are particularly suitable and can be used as first and/or second polar cosolvent: a mixture of 25% in volume of acetic acid and 75% in volume of ethanol. A mixture of 50% in volume of acetic acid and 50% in volume of ethanol or a mixture of 50% in volume of acetic acid and 50% in volume of water.

According to a particular embodiment which may be combined with anyone of the other embodiments, the first polar cosolvent consists in a mixture of 75% in volume of ethanol and 25% in volume of acetic acid.

According to another particular embodiment which may be combined with anyone of the other embodiments, the first polar cosolvent consists in a mixture of 75% in volume of ethanol and 25% in volume of acetic acid or in a mixture of 50% in volume of acetic acid and 50% in volume of ethanol or in a mixture of 50% in volume of acid acetic and 50% in volume of water and said second polar cosolvent consist in a mixture of 75% in volume of ethanol and 25% in volume of acetic acid.

The first and second solvent for said plasticizer(s) can be chosen, independently one from the other, among Ci to C4 alcohols, high volatile partially halogenated hydrocarbons and mixtures thereof and particularly is a mixture of at least two Ci to C4 alcohols more particularly contains methanol.

The first and the second solvent for said benzene sulfonamide plasticizer can be identical.

Preferably, said first and/or second solvent for said plasticizer(s) is methanol. This solvent is harmful but can be easily recycled with carbon dioxide after the process of the invention. Advantageously, regardless of the embodiment, the process according to the invention is performed at a temperature equal or superior to 170°C and equal or inferior to 280°C and particularly equal to 180°C, 185°C, 190°C, 200°C, 220°C, 240°C, 250°C or 270°C. 185°C and under a pressure equal or superior to 80 bars and equal or superior to 300 bars and, particularly equal to 230 bars.

Advantageously, it is performed at 185°C under 230 bars.

Polyamide can be chosen among aliphatic polyamides and particularly among PA6, PA 12, PA 11, PA 4.6, PA 6.6, PA 6.9, PA 6.10, PA 6.12, PA 10.10, PA 10.12, copolymers PA 6.6/6, PA 6/6.6/6.10, PEBA, semi-aromatic polyamides, aromatic polyamides, and mixtures thereof.

The polluted polyamide treated by the process of the invention can be in a multilayer structure, more particularly in a multilayer structure comprising on consisting of several layers of different polyamides chosen among the above-mentioned polyamides.

The plasticizer can be chosen among N-butyl benzene sulfonamide (BBSA), N-ethyl o/p toluene sulfonamide, p-toluene sulfonamide benzene sulfonamide, N-cyclohexyl p-toluene sulfonamide, toluene sulfonamide formaldehyde resin and mixtures thereof.

Advantageously, the weight amount of said plasticizer(s) and particularly BBSA in said polyamide can be from 1% up to 20% and particularly can be equal to 12%, 3% or 4%.

According to one embodiment, the polluted polyamide is PA 11 and it contains N-butyl benzene sulfonamide. This polyamide can come from an offshore pipe or from a part of a device or means of locomotion, said part being in contact with a hydrocarbon(s)-containing mixture.

The Inventors have established that the first and the third mixtures are able to separate the polyamide chains one from the other thereby enabling the solvent of said plasticizer(s) to penetrate and to dissolve said plasticizer(s). They have also established that extraction is improved when increasing the number of contacts between the polyamide and firstly a mixture enabling to separate the polymer chain and secondly a mixture enabling to dissolve the plasticizer(s).

The present invention also relates to a polyamide obtainable according to the process of the invention and particularly to a polyamide free from N-butyl benzene sulfonamide and having a molecular weight from 10⁶ to 10³ and particularly equal to 10⁶, 10⁵, 10⁴ or 10³ g/mol. Such a polyamide can be used for producing products that can touch the skin of a user without any risks caused by the presence of a plasticizer.

In all the present patent application, the molecular weight can be determined by any known method and more particularly using size exclusion chromatography.

Advantageously, said polyamide is PA 11.

The present invention also relates to a PA 11 obtainable according to the process of the invention and containing 20 weight% or less of said plasticizer(s) and particularly 4% by weight or less of said plasticizer(s) and particularly N-butyl benzene sulfonamide (BBSA) and having a molecular weight of 10⁶, 10⁵, 10⁴, 10³ g/mol or less.

The present invention also relates to the use of the polyamide according to the invention, to produce a product chosen among industrial tubes and particularly pneumatic tubes and hydraulic tubes, telecommunication cables and more particularly fiber optic cables and power cables, cable ties, particularly cable ties for aircraft systems, sport equipment, particularly balls, flying discs, nets, rackets, rods, tackles, sticks, bats, clubs, wickets, bases, footwear, paddles, protective equipment, helmets, shoes, in particular running shoes, ski shoes, soccer shoes, sole, fabrics, watches, and clothing.

The present invention also relates to a product chosen among sport equipment, particularly among balls, flying discs, nets, rackets, rods, tackles, sticks, bats, clubs, wickets, bases, footwear, paddles, protective equipment, helmets, shoes, in particular running shoes, ski shoes, soccer shoes, sole, fabrics, watches, and clothing, wherein said product comprises a polyamide according to the invention.

The present invention also relates to a product chosen among automotive parts in particular fuel/diesel tubes, hoses, automotive products, in particular fuel or diesel tubes, air brake tubes and air brake spirals, wherein said product comprises a polyamide according to the invention.

The present invention also relates to a product chosen among telecommunication cables and more particularly fiber optic cables and power cables, cable ties, particularly cable ties for aircraft systems wherein said product comprises a polyamide according to the invention.

Definitions

According to the present invention, the term “polyamide” refers to any polymer containing amide group in its repeating unit. According to the invention, it can be an homopolymer, a copolymer or a polymer mixture comprising more than 50% of polyamide(s) in mole percent. Preferably, it refers to an homopolymer and particularly to an aliphatic homopolymer or to a block copolymer and particularly poly(ether-block-amide) (PEBA). According to the invention, the polyamide can be also a semi-aromatic polyamide or an aromatic polyamide or a mixture of at least two types of polymers chosen among aliphatic, semi-aromatic and aromatic polyamides. The polyamide according to the invention is a non-reinforced polymer which means it is not a composite material.

The terms “high volatile partially halogenated hydrocarbons” refer to partially halogenated hydrocarbons which evaporate at 20°C under atmospheric pressure.

When a parameter is defined by a range of values, from a to b, for example, the lowest and the highest values - a and b- are also encompassed. The term “polluted polyamide” refers to a polyamide containing at least one benzene sulfonamide plasticizer, even if this plasticizer(s) has been consciously added for improving mechanical properties of the polyamide to make a particular product before production thereof. The polluted polyamide can comprise one or more benzene sulfonamide plasticizers. It can also contain pollutants.

The terms “free from A” mean that according to at least one technical analysis method, compound A cannot be found in the polyamide. Said technical analysis method can be chosen among CHNS elemental analysis, TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry), TGA coupled with FT-IR spectroscopy, gas-chromatography coupled with mass spectrometry and thermogravometric analysis coupled with mass-spectrometry, for instance.

The term “user” refers to a mammal which can be a human being or an animal.

Figures

Fig. 1 shows the scheme of the experimental set-up for the supercritical CO2 extraction.

Fig. 2 shows the TGA curves of virgin and polluted plasticized polymer, the top curve corresponds to RILSAN® BESNO P40 TL and the second curve to a polluted polymer from Brazil.

Fig. 3 shows the TGA curves of polluted polymer before and after the supercritical treatment, the curve with a peak at 448°C correspond to the polluted polymer before treatment and the other curve corresponds to the treated polymer.

Fig. 4 shows the TGA curves of polluted polymer before and after the supercritical treatment in 2 steps: a) scCCh and 5 vol. % of cosolvents (25 vol. % acetic acid and 75 vol. % ethanol), b) scCCh and 5 vol. % of methanol, the curve having a peak at 448°C corresponds to the polluted polymer non treated and the other curve corresponds to the treated polymer.

Fig. 5 shows the TGA curves of polluted polymer before and after the supercritical treatment in 4 steps: a) scCCh and 5 vol. % of cosolvents (25 vol.% acetic acid and 75 vol. % ethanol), b) scCCh and 5 vol. % of methanol; c) — a; d) — b, the curve having a peak at 448°C corresponds to the polluted polymer non treated.

EXEMPLES

1. Experimental set up

Experimental set-up for supercritical CO2 extraction is represented in Fig. 1. Bottle of CO2 gas is connected with the cryostat in order to send liquid CO2 in the reactor. Reactor is previously filled with the polymer to be treated and a mixture of cosolvent(s) and further heated to the working temperature. The pressure is controlled by installed manometer. After the treatment, which takes approximately 30 minutes, the supercritical CO2 drying is carried out also for 30 minutes. This process assumes continuous passage of CO2 towards eliminate the impurities charged in scCCL and liquid cosolvents. Then, the depressurization (still at 185°C) and cooling of reactor are realized.

The treatment of polluted polymer was carried out at high temperature and pressure. Choice of working temperature, namely 185°C, is explained by the melted state of polymer, which can be faster, and more efficiently treated by the scCCL; this also allows the treatment in the extruder. Established pressure 230 bar explains excellent power solvent of supercritical fluid CO2. Also, a mixture of polar cosolvents is added to the system.

2. Characterization of plasticized polymers before the supercritical treatment

For this project two types of polymers were investigated. First one is a commercial plasticized virgin polymer RILSAN® BESNO P40 TL (commercialized by Arkema) which is a polyamide PA 11 containing 12 wt.% of BBSA according to the provided information. And the second one is a polluted polymer issued from offshore pipes. Before the extraction processes of plasticizer, the characterization of these polymers was carried out by thermogravimetric analysis. In Fig. 2 are represented the TGA curves of virgin and polluted polymers.

Based on Fig. 2, first loss of mass until 180°C corresponds to the evaporation of humidity and evacuation of gases blocked in the matrix. Second loss of mass from 150°C to 350°C indicates the degradation of organic compounds, namely plasticizer BBSA. The peak of BBSA degradation is observed at nearly 230°C according to the derivates of TGA curves (short dashes). And the last loss of weight from 350°C to 550°C represents the degradation of polyamide 11 matrix. Comparing two TGA curves, the difference of the second losses is remarkable. The presence of 12 wt.% of plasticizer for virgin polymer RILSAN® BESNO P40 TL is confirmed. While the polluted polymer contains only 8 wt.% of plasticizers.

In order to prove the decomposition namely of BBSA molecule during the second loss of mass, the TGA coupled with FT-IR spectroscopy was performed. Obtained results for virgin and polluted polymers are similar (not shown). The intense absorption bands specific for BBSA were observed: the bands at 3077 cm'¹, 2890 cm'¹, 1415 cm'¹ and at 1356 cm'¹ is assigned to the C-H bond; and the bands at 1171 cm'¹ and 1092 cm'¹ corresponds to S=O bond.

Also, DSC analyses were carried out for virgin and polluted polymers (Fig. 3).

The melting temperature of virgin polymer (183°C) is lower than for polluted polymer (187°C). This change is related with the loss of the plasticizer from the polymer matrix. The T_g value for both polymers is 45°C and the rate of crystallization is about 18-19%. As a conclusion, TGA and DSC analyses confirm that polluted polymer is not degraded at the end of life. The presence of BBSA in polymers is proved by TGA coupled with FT-IR spectroscopy. During the use-life time the quantity of plasticizer decreases from 12 to 8 wt.% because of its solubility in oil and gas.

3. Characterization of plasticized polymers after the supercritical treatment

As was discussed previously, polyamide 11 matrix possesses excellent chemical and mechanical properties thanks to its molecular structure. Thereby the adding of cosolvent(s) in the system is necessary for an efficient extraction of plasticizer. The suitable solvent for BBSA is a polar molecule, like alcohol (Ci to C4) and high volatile partially halogenated hydrocarbons. Finally, polluted polymer was treated by supercritical CO2 fluid and 5 vol. % of methanol. In order to estimate the extraction of the plasticizer from the matrix, thermogravimetric analysis was performed (Fig. 4).

Before the supercritical treatment, polluted polymer contains 8 wt.% of BBSA. From 150 to 350°C is observed the loss of plasticizer with its degradation peak at 226°C. After the treatment by supercritical CO2 and 5 vol. % of methanol, the quantity of BBSA decreased from 8 to 3-4 wt.%. The loss of the BBSA is carried out from 150 to 300°C with the same degradation peak at 226°C. The same result was obtained when virgin polymer contained 12 wt.% of plasticizers was treated by the same solvent system: scCCh and 5 vol. % of methanol. The RILSAN® BESNO P40 TL lost 6 wt.% of BBSA during this type of extraction. Obviously, this solvent system can extract a half of all plasticizer’s quantity.

With the purpose to enhance the rate of the extraction another strategy was applied. At first, polluted polymer undergoes the supercritical treatment by CO2 and 5 vol. % of the mixture of polar cosolvents (25 vol. % acetic acid and 75 vol. % ethanol). Presence of these modifiers is necessary to break the hydrogen bonds between the polyamide chains. Hence, the polymer becomes less viscous. This property represents an advantage for next step. Second treatment of polluted polymer by scCCh and 5 vol. % of methanol will be more effective, because the methanol can easily penetrate through the matrix. The TGA result of these two consecutive treatments is represented in Fig. 4.

Double treatment of polluted polymer enhances the extraction rate of the plasticizer. But the extraction is not absolute, there is still 2 wt.% of BBSA, which are lost from 150 to 250°C according to TGA. Apparently, the bonding between polymer chains and BBSA are not totally destroyed. There are two types of hydrogen bonds formed between: i) the sulfonamide proton and the electron pairs of carbonyl group of polymers (S-N-H. . O=C), and ii) amide groups of polymers and the sulfonyl electron pairs of BBSA (N-H...O=S) [24], Hence, more aggressive attack of polymer’s matrix is necessary to destroy this attachment with BBSA molecules. In order to extract totally amount of plasticizer from the polyamide 11, polluted polymer was treated in four consecutive steps: a) scCCh and 5% vol. of cosolvents (25% vol. acetic acid and 75% vol. ethanol) b) scCCh and 5% vol. of methanol c) the same as step a d) the same as step b.

The TGA result of polluted polymer treated in this way is represented in Fig. 5.

Polluted polymer treated in four steps losses only 1,5 % wt. until 250°C, which corresponds to loss of the humidity and gases. Obtained result means that it is no more BBSA molecules in the polymer, which are degraded normally in this range of temperature. However, are observed some weight losses at 275°C and 343°C. These degradation peaks are assigned to the oligomers or other molecules formed due to the partially degradation of polyamide. Chopping or partially degradation of polyamide is expected because of aggressive treatment of polymer. Nevertheless, this type of process allows the total extraction of plasticizer.

Accordingly, the process according to the invention aimed to extract the plasticizer from the polyamide 11 matrix by supercritical technic. The interest of this project is related to the toxicity of BBSA molecules. Totally extraction of BBSA from the polymer allows its reuse in various applications without restrictions. In the literature are represented a lot of research works on additive supercritical extraction from different polymers. But there are no highlights on the plasticizer extraction from polyamides. Polyamide 11 matrix is difficult to treat because of molecular structure of polymer, namely the presence of intermolecular hydrogen bonds between the amide and carbonyl groups. In order to break these bonds and to facilitate the access into the matrix, initial treatment by supercritical CO2 and 5 vol. % of cosolvents (25 vol. % acetic acid and 75 vol. % ethanol) is required. This process makes the polymer less viscous and prepares it for following step. Second step involves the supercritical CO2 extraction with 5 vol. % of pure methanol. Methanol is a suitable solvent for BBSA plasticizer. As a result, these two consecutive steps do not allow the totally extraction of BBSA molecules and 2 wt.% of plasticizer remains in the matrix. However, the repetition of these 2 steps (4 steps in sum) is capable to extract all amount of BBSA according to TGA. The aggressive treatment provokes partially degradation of polyamide 11. But these changes can be converted into the advantage, like the possibility to extrude the polyamide for industrial applications.

Size Exclusion Chromatography have also been used on both polluted and treated polyamide (results not shown). SEC has shown that supercritical extraction with mixture of polar cosolvents cuts the chains of polymer (results not shown). Hence, its molecular weight decreases from 10⁴ to 10³g/mol. Moreover, it should be noted that the following cosolvent mixtures can also be used instead of the mixture of acetic acid 25% in volume and ethanol 75% in volume or can be used in combination with said acetic acid 25% in volume and ethanol 75% in volume cosolvent mixture. A mixture of acetic acid 50% and ethanol 50% can also remove partially BBSA with one contact. A mixture of acetic acid 50% in volume and water 50% in volume can also remove partially BBSA with one contact.

It should be noted that this detailed description concerns one specific example embodiment of the present invention, however in no way does this description limit the subject matter of the invention in any way: on the contrary, it aims to remove all possible imprecisions, or all incorrect interpretations of the claims provided hereafter.

It should also be noted that the reference signs placed in brackets in the claims provided hereafter are in no way limiting; the sole purpose of these signs is to improve the intelligibility and understanding of the claims provided hereafter, in addition to the desired scope of protection.

Claims

1. A process for at least partially extracting at least one benzene sulfonamide plasticizer from a polyamide containing such a plasticizer, wherein said polyamide is contacted at least one time with at least one first solvent mixture comprising or consisting in supercritical carbon dioxide and a first polar cosolvent, said contact(s) being performed above 304.13 K, and above 7.3773 MPa, said first solvent mixture being liquid, at its critical point or in supercritical state.

2. The process according to claim 1, wherein said polyamide is contacted at least one time with at least one second solvent mixture after being contacted at least one time with said first solvent mixture(s) and wherein said second solvent mixture(s) comprises or consists in carbon dioxide and at least one first solvent of said benzene sulfonamide plasticizer(s), said contact(s) being performed above 304.13 K, and above 7.3773 MPa, said second solvent mixture being liquid, at its critical point or in supercritical state.

3. The process according to claim 2, wherein said polyamide is contacted at least one time with at least one third solvent mixture after being contacted at least one time with said second solvent mixture, said third solvent mixture(s) comprising or consisting in supercritical carbon dioxide and a second polar cosolvent, said contact(s) being performed above 304.13 K, and above 7.3773 MPa, said third solvent mixture being liquid, at its critical point or in supercritical state.

4. The process according to claim 3, wherein said polyamide is contacted at least one time with at least one first solvent mixture(s), then at least one time with at least one second solvent mixture(s), then contacted at least one time with at least one third solvent mixture(s) and then contacted at least one time with at least one fourth solvent mixture containing at least one second solvent of said benzene sulfonamide plasticizer(s), said contact(s) being performed above 304.13 K, and above 7.3773 MPa , each of said first, second, third and fourth solvent mixtures being irrespectively one from the others, liquid, at its critical point or in supercritical state.

5. The process according to claim 4, wherein said second polar cosolvent is identical to said first polar cosolvent and/or wherein said first solvent of said benzene sulfonamide plasticizer(s) is identical to said second solvent of said benzene sulfonamide plasticizer(s).

6. The process according to claim 5, wherein said polyamide is contacted one time with said one first solvent mixture, one time with said second solvent mixture, one time with said third solvent mixture and one time with said fourth solvent mixture.

7. The process according to anyone of claims 1 to 6, wherein said first, second, third solvent and fourth mixture contains independently one from the others, from 1% in volume to 20% in volume and in particular 2%, 3%, 4%, 5%, 6%, 7% 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17% 18%, 19% in volume of said first polar cosolvent, said first solvent of said benzene sulfonamide plasticizer(s), said second polar solvent and said second solvent of said benzene sulfonamide plasticizer(s), respectively.

8. The process according to anyone of claims 1 to 7, wherein said polyamide is contacted with said first polar cosolvent, said second polar cosolvent, said first or second solvent of said benzene sulfonamide plash cizer(s), before being contacted with supercritical carbon dioxide, said first, second polar cosolvents and said first and second solvent for said benzene sulfonamide plasticizer being liquid.

9. The process according to anyone of claim 1 to 8, wherein said polyamide is melted when contacted with said first, second, third or fourth solvent mixture.

10. The process according to anyone of claims 1 to 9, wherein it is performed during extrusion of said polluted polyamide or in a fluidized bed comprising particles of at least one polyamide fluidized with said first, second, third or fourth solvent mixture.

11. The process according to anyone of claims 1 to 10, wherein said first polar cosolvent and said second polar cosolvent are chosen irrespectively one from the other among mixtures comprising or consisting in ethanol, acetic acid, water and mixtures of water and acetic acid, mixtures of ethanol and acetic acid and mixtures of ethanol, water, and acetic acid.

12. The process according to claim 11, wherein said first and/or said second polar cosolvent consist in a mixture of ethanol and acetic acid and particularly in a mixture chosen among mixtures containing 1%, 10%, 20%, 25%, 30%, 50%, 60%; 75%, 80%, 85%, 90% in volume of ethanol.

13. The process according to anyone of claims 2 to 12, wherein said first and/or said second solvent for said plasticizer(s) are chosen, independently one from the other, among Ci to C4 alcohols, high volatile partially halogenated hydrocarbons and mixtures thereof and particularly among mixtures of at least two Ci to C4 alcohols and more particularly among mixtures containing methanol.

14. The process according to claim 13, wherein said first and/or said second solvent for said plasticizer(s) is methanol.

15. The process according to anyone of claim 1 to 14, wherein it is performed at a temperature equal or superior to 170°C and equal or inferior to 280°C and particularly equal to 180°C, 185°C, 190°C, 200°C, 220°C, 240°C, 250°C or 270°C. 185°C and under a pressure equal or superior to 100 bars and equal or superior to 300 bars and, particularly equal to 230 bars.

16. The process according to anyone of claims 1 to 15, wherein said polluted polyamide is chosen among aliphatic polyamides and particularly among PA6, PA 12, PA 11, PA 4.6, PA 6.6, PA 6.9, PA 6.10, PA 6.12, PA 10.10, PA 10.12, copolymers PA 6.6/6, PA 6/6.6/6.10, PEBA, semi-aromatic polyamides, aromatic polyamides, and mixtures thereof.

17. The process according to anyone of claims 1 to 16, wherein said plasticizer is chosen among N-butyl benzene sulfonamide (BBSA), N-ethyl o/p toluene sulfonamide, p-toluene sulfonamide benzene sulfonamide, N-cyclohexyl p-toluene sulfonamide, toluene sulfonamide formaldehyde resin and mixtures thereof.

18. The process according to claim 17, wherein said polluted polyamide is PA 11 and wherein it contains N-butyl benzene sulfonamide.

19. The process according to claim 18 wherein said polyamide comes from an offshore pipe or from a part of a device or means of locomotion.

20. A polyamide obtainable according to the process of anyone of claims 1 to 19, wherein said polyamide is free from N-butyl benzene sulfonamide and wherein said polyamide has a molecular weight from 10⁶ tolO³ g/mol.

21. The polyamide according to claim 20, wherein said polyamide is PAI 1.

22. PA 11 obtainable according to the process of anyone of claims 1 to 19 and containing 20% by weight or less and particularly 4 % by weight or less of said plasticizer(s) and particularly N-butyl benzene sulfonamide and wherein said polyamide has a molecular weight of 10⁶, 10⁵, 10⁴ or 10³ g/mol.

23. Use of the polyamide according to anyone of claim 20 and 21, to produce a product chosen among industrial tubes and particularly pneumatic tubes and hydraulic tubes, telecommunication cables and more particularly fiber optic cables and power cables, cable ties, particularly cable ties for aircraft systems, sport equipment, particularly balls, flying discs, nets, rackets, rods, tackles, sticks, bats, clubs, wickets, bases, footwear, paddles, protective equipment, helmets, shoes, in particular running shoes, ski shoes, soccer shoes, sole, fabrics, watches, and clothing.

24. A product chosen among sport equipment, particularly among balls, flying discs, nets, rackets, rods, tackles, sticks, bats, clubs, wickets, bases, footwear, paddles, protective equipment, helmets, shoes, in particular running shoes, ski shoes, soccer shoes, sole, fabrics, watches, and clothing, wherein said product comprises a polyamide according to anyone of claims 20 to 22.

25. A product chosen among automotive parts in particular fuel/diesel tubes, hoses, automotive products, in particular fuel or diesel tubes, air brake tubes and air brake spirals, wherein said product comprises a polyamide according to anyone of claims 20 to 22.

26. A product chosen among telecommunication cables and more particularly fiber optic cables and power cables, cable ties, particularly cable ties for aircraft systems wherein said product comprises a polyamide according to anyone of claims 20 to 22.