WO2008135680A2

WO2008135680A2 - Use of hydroxylamines as agents for destroying hydrophilic polymer and corresponding method for destroying such polymers

Info

Publication number: WO2008135680A2
Application number: PCT/FR2008/050455
Authority: WO
Inventors: Manuel Hidalgo; Bruno Van Hemelryck; Fabienne Vauloup
Original assignee: Arkema France
Priority date: 2007-03-15
Filing date: 2008-03-17
Publication date: 2008-11-13
Also published as: FR2913689B1; FR2913689A1; WO2008135680A3

Abstract

The invention relates to the use of at least one hydroxylamine as an agent for destroying hydrophilic polymers in the form of hydrogels or aqueous suspensions of hydrogels, said hydroxylamine having general formula (I), in which: R1 and R2 each represent independently of each other an alkyl radical at C1-C8, an alkyl radical at C1-C16 substituted by at least one hydroxyl, aryl, aralkyl or alkaryl radical, wherein either R1 or R2 can also represent hydrogen. The invention also relates to the corresonding method for destroying hydrophilic polymers in the form of hydrogels or aqueous suspensions of hydrogels.

Description

USE OF HYD ROXYLAM I N ES AS DESTRUCTIVE AGENTS OF

HYDROPHILIC POLYMERS AND CORRESPONDING METHOD OF

DESTRUCTION OF SUCH POLYMERS

The present invention is in the field of aqueous gels, also called hydrogels, based on organic polymers and, more particularly, it refers to a method of destroying such gels when they were formed accidentally or concomitantly with a manufacturing process or when the gels have been formed (and possibly) used and it becomes useful or necessary to destroy them. The term "hydrogel destruction process" is understood here to mean a method for greatly reducing their volume and / or their viscosity.

Some hydrophilic polymers, such as polymers based on acrylic acid and / or acrylamide, crosslinked or otherwise, form gels in contact with water.

These polymers find applications in the field of absorption of aqueous liquids - such as so-called Super Absorbent polymers (or SAP) - in the field of flocculation of suspended solids (flocculating polymers) or in the field. the rheology modification of water-based solutions or dispersions (thickening polymers). By way of examples, the following applications of these hydrophilic polymers may be mentioned:

- absorption of aqueous liquids in the field of hygiene (diapers, sanitary napkins, bodily fluids in hospitals, etc.);

- absorption of aqueous liquids in the field of cabling (protective sheathing of cables);

- flocculation of suspended solids in the field of wastewater and industrial wastewater treatment; rheological modification of paint formulations, for the oil extraction industry, etc. The destruction of gels accidentally or intentionally formed from these polymers is sometimes desirable to reduce their volume or decrease their viscosity. Thus, for example, the degradation or destruction of aqueous gels or suspensions of aqueous gels can be sought during manufacturing incidents, as part of the cleaning of manufacturing tools (reactors, containers, transfer lines), or in the case of polymer entrainment in aqueous effluents with the creation of bulky and compact gels that can cause clogging of the recovery network and water treatment. In other cases, gels formed during application, such as, for example, in the field of gelling absorption of aqueous fluids (for example, hygiene in a hospital environment), can become cumbersome and unwanted. because of their volume; it is then that it may be interesting to seek to destroy (degrade) them to facilitate their handling as waste.

In both cases, it is necessary to attack the polymer. This can be done physically (thermal destruction, radiolysis), physicochemical (contraction causing deflation by adding mineral salts), or even biochemically by bacterial treatment, as well as chemically: - the destruction of such polymers physically only most of the time is not applicable because it is too slow and / or because it requires the availability of sources of heat or radiation at the location of the gel, which is sometimes difficult to obtain for practical reasons; physicochemical destruction of the gels is often not very effective because it requires large amounts of salts and / or the preliminary preparation of solutions thereof and because it causes the deflation without degrading the polymer; bacterial destruction is often inefficient or far too slow for these poorly biodegradable polymers; the destruction of the gels by chemical etching of the polymer is effective but requires very aggressive chemical treatments by the nature of the agents (strong oxidants, strong concentrated bases) often used in large quantities. These latter treatments have the disadvantage of requiring manipulation of dangerous or aggressive products that may represent a risk for people, the environment and facilities. In the case of polyacrylic acids crosslinked and neutralized to various degrees, a known treatment of gels they form with water is the addition of concentrated salt solutions as explained in the articles entitled "Swelling and shrinking processes of sodium polyacrylate-type super-absorb gel in electrolyte solutions ", Sakohara, Shuji; Muramoto, Fujikazu; Asaeda, Masashi, Dep. Chem. Eng., Hiroshima Univ., Higashi-Hiroshima, 724, Japan Journal of Chemical Engineering of Japan (1990), 23 (2), 119-124, and "Calcium-induced shrinking of polyacrylate chains in aqueous solution", Huber, Klaus , Chem. Div., Ciba-Geigy AG, Basel, CH-4002, Switzerland, Journal of Physical Chemistry (1993), 97 (38), 9825-9830.

The salt may be for example, but not exclusively, sodium chloride, calcium chloride, aluminum sulfate. The effect of salt is manifested by a collapse of the polymer gel more or less slow depending on the salt concentration used. This type of treatment results in a volume contraction of the gel, without causing significant liquefaction by degradation of the gel. In addition, this salt treatment introduces the risk of corrosion in the facilities or may change the biological functioning of the water treatment plants by increasing the saline concentration. Finally, it is not very effective to allow a rapid reduction of the gelled volume. For polymers based on acrylamide, it is more usual to use chemical treatments with strong oxidants or strong bases (hydrolysis reactions).

It is also known that these polymers, often of high molecular weight, are degraded by mechanical effect (agitation) or when they are very dilute, but these two modes of destruction are impractical when it comes to eliminate a large volume of a gel based on acrylamide polymers. European Patent EP 0 514 649 B1 recalls that hydroxylamine-containing polyacrylamides (of formula NH 2 OH) or a hydroxylamine salt used to ensure their hydroxamation, tend to lose their viscosity rapidly for supposed reduction reasons. of their molecular masses, and this because of traces of hydroxylamine (or a salt thereof) not consumed during hydroxamation. It could be inferred from the teachings of this European patent application, which, moreover, claims treatments to prevent this degradation, that the direct use of NH ₂ OH could be an effective and slightly aggressive way to chemically destroy gels. hydrophilic polymers based on acrylamide. The use of NH 2 OH is however not conceivable in the context of an industrial treatment of gels because of its great instability. The use of its salts (hydrochloride or sulfate for example) also has drawbacks because it can cause corrosion in the same way as a treatment with a mineral salt such as NaCl or CaCl 2. Looking for a solution to the problems that have just been mentioned, the Applicant Company has found a new method for destroying gels formed from hydrophilic organic polymers. It has thus been discovered that the introduction of a hydroxylamine belonging to a particular family and, preferably, N, N-diethylhydroxylamine, into a gel or gel suspension formed from a hydrophilic polymer such as those which will be described below, leads to the degradation of the gel, and more quickly and more complete than with the addition of a mineral salt and without introducing a risk of corrosion of metal installations. The present invention therefore relates to a use of at least one hydroxylamine of general formula (I):

^R

N-OH

R ^{2 /} (I) wherein R ¹ and R ² each independently represent a C 1 -C 6 alkyl radical, a C 1 -C 16 alkyl radical substituted with at least one hydroxyl, aryl, aralkyl or alkaryl radical, one of R ¹ and R ² may further represent hydrogen, as a destructive agent for hydrophilic polymers in the form of hydrogels or aqueous suspensions of hydrogels.

By "aqueous suspensions of hydrogels" is meant fragments of hydrogels floating on or partially or totally immersed in water. The present invention is specifically concerned with the destruction, and not with the prevention of the formation of hydrogels, that is to say gels resulting from the adsorption of water by the hydrophilic functions of polymers. The alkyl radicals within the definition of R ¹ and R ² may be chosen from methyl, ethyl, isopropyl, n-propyl and n-butyl; the alkyl radicals substituted with at least one hydroxyl falling within the definition of R ¹ and R ² may be chosen independently from CH ₃ (CH ₂ ) HCH (OH) CH ₂ -, where n represents 0 to 10; aryl may be phenyl; aralkyl may be benzyl; and alkaryl is a tolyl radical. [0020] Advantageously, R ¹ and R ² may each be chosen from C ¹ -C 6 alkyl radicals, R ¹ and R ² preferably having a maximum total of 8 carbon atoms.

As examples of hydroxylamines of formula (I), there may be mentioned N, N-dialkylhydroxylamines, such as N, N-dimethylhydroxylamine, N, N-diethylhydroxylamine, N, N-di- n-propylhydroxylamine and N, N-di-n-butylhydroxylamine; N-alkyl-hydroxylamines, such as N-methylhydroxylamine, N-ethylhydroxylamine, N-isopropylhydroxylamine, N-n-propylhydroxylamine and N-n-butylhydroxylamine; and the N, N-bis-hydroxyalkylhydroxylamines of formula:

CH ₃ (CH ₂ ) _n CH (OH) CH _2χ

N-OH CH ₃ (CH ₂₎ _Y CH (OH) CH ₂ ⁷ With n and o independently represent 0 to 10, such as N, N-bis- (2-hydroxypropyl) hydroxylamine and N, N-bis - (2-hydroxybutyl) hydroxylamine.

A hydroxylamine of formula (I) which is particularly preferred is

N, N-diethylhydroxylamine. The hydroxylamine (s) of formula (I) are preferably used in the form of aqueous solutions.

The hydrophilic polymers which are at the origin of the hydrogels to be destroyed can be chosen in particular from:

(A) Absorbent or superabsorbent hydrophilic polymers; and (B) water-soluble polymers, these polymers may or may not be crosslinked and may or may not have undergone chemical modifications for a change in their properties, such as, for example, their affinity with water, their affinity with a substrate, their electric charge in solution or aqueous dispersion, etc. The polymers (A) may be crosslinked hydrophilic polymers obtained by radical polymerization of at least one unsaturated ethylenic monomer chosen in particular from (meth) acrylic acid, alkali metal salts (such as sodium and potassium) or the ammonium salts of (meth) acrylic acid, the esters of (meth) acrylic acid, maleic or fumaric acid and its salts, the esters of maleic or fumaric acid, the acid -acrylamido-2-methylpropanesulphonic acid or its salts, vinyl acetate, vinylpyrrolidone, vinylcaprolactam, dimethylaminoethyl (meth) acrylate, trimethylaminoethyl (meth) acrylate salts, acrylonitrile, maleic anhydride, acrylamide and methacrylamide, the crosslinking may have been carried out by using crosslinking monomers comprising at least two double bonds or crosslinking monomers comprising a double bond and at least one functional group the reagent or by addition of a non-polymerizable crosslinking agent comprising at least two reactive groups capable of reacting with the chemical functions of the monomer units used for the synthesis of the hydrophilic polymer.

Among the crosslinkers used, mention may be made of trimethylolpropane triacrylate, N, N-methylene-bis (meth) acrylamide, N-methylol (meth) acrylamide and (poly) ethylene glycol diglycidyl ether. The polymers (B) may be non-crosslinked hydrophilic polymers obtained by radical polymerization of at least one unsaturated ethylenic monomer chosen from acrylamide, methacrylamide, (meth) acrylic acid or its salts (such as alkali metal (sodium, potassium, etc.) or ammonium salts), 2-acrylamido-2-methylpropanesulphonic acid or its salts, alkyl esters of (meth) acrylic acid such as acrylate of methyl or ethyl and methyl or ethyl methacrylate, vinyl acetate, vinylpyrrolidone, maleic anhydride, maleic acid esters, dimethylaminoethyl (meth) acrylate, trimethylaminoethyl meth) acrylate and diallyldimethylammonium chloride. It is possible to mention, as examples of hydrophilic polymers forming gels that may be destroyed by the process of the invention, the polymers of (meth) acrylic acid and / or its salts, such as the sodium salts, of potassium or ammonium, polymers of acrylamide, copolymers of (meth) acrylic acid and / or its salts, such as those mentioned above, with acrylamide, copolymers of (meth) acrylic acid and / or its salts, such as those mentioned above, with an unsaturated ethylenic monomer other than acrylamide, copolymers of acrylamide with an unsaturated ethylenic monomer other than (meth) acrylic acid and / or its salts and copolymers (meth) acrylic acid and / or its salts with acrylamide and with a third ethylenic monomer.

The present invention also relates to a method for destroying at least one hydrophilic polymer in the form of a hydrogel or an aqueous hydrogel suspension, characterized in that said hydrogel or said suspension is brought into contact with each other. aqueous hydrogel with at least one hydroxylamine of general formula (I):

Services

N-OH

^R2 (I) wherein R ¹ and R ² each independently represent a C 1 -C 6 alkyl radical, a C 1 -C 16 alkyl radical substituted with at least one hydroxyl, aryl, aralkyl or alkaryl, one of R ¹ and R ² may additionally represent hydrogen, in an amount of 0.1% to 1000% by weight, in particular 1 to 50% by weight, of the pure (or) hydroxylamine (I) relative to to the dry polymer comprising the hydrogel or the aqueous hydrogel suspension.

More specifically, the method of the invention allows the destruction of the gel.

Without wishing to be bound by the theory, it has been observed that the very structure of the gel is partially or totally destroyed during the implementation of the method of the invention. There is therefore no or almost no destruction of the polymer chains, but destruction of the structure of the hydrogel formed by the polymer chains.

As indicated above, the (or) hydroxylamine (s) (I) is (or is) preferably implemented in the form of aqueous solution. The contacting of the hydrogel or the aqueous hydrogel suspension with the hydroxylamine or hydroxylamines is carried out by mechanical mixing or slow diffusion, at a temperature generally between room temperature and 100 ^° C., for example up to 50 ^° C. [0033] Examples of R ¹ and R ² , examples of compounds (I) as well as examples of hydrophilic polymers have been indicated previously. It is also possible to use, in combination with the hydroxylamine (s) of formula (I), at least one salt or oxide of a transition metal, such as salts or oxides of copper, cobalt or manganese, the percentage of said salt or metal salts up to 25% by weight relative to the weight of the dry polymer comprising the hydrogel or the aqueous suspension of hydrogel.

As examples of metal salts that can be used according to the invention, mention may be made of manganese triacetate (III). The destruction of the hydrophilic gels formed from the above-mentioned organic polymers can be substantially accelerated by the use of such a salt or metal oxide, which therefore plays the role of activator of the destruction of the hydrogel by the cation transition metal. Thus, the process of the present invention, as well as the use according to the present invention, are advantageously applicable in the various fields where the so-called Super Absorbent polymers (or SAP) are involved, and more particularly in the field of flocculation. suspended solids (flocculating polymers) or in the field of rheological modification of solutions or dispersions based on water (thickening polymers). More specifically, the fields in which the method and the use according to the present invention can be applied are hygiene (diapers, sanitary napkins, bodily fluids in a hospital environment, etc.), cabling (sheathing). cable protector), the treatment of industrial and waste water, the fields of rheological modification (for example for paint formulations, for the oil extraction industry), and more generally in all the fields where the the degradation or destruction of aqueous gels or suspensions of aqueous gels (cleaning of manufacturing tools, such as reactors, containers, transfer lines) is sought, or in case of training of polymers in aqueous effluents with the creation of bulky and compact gels that can cause clogging of the recovery network and / or water treatment.

The examples below illustrate the method of destroying hydrophilic gels of the invention without, however, limiting the scope thereof. In these examples, the percentages are by weight and the abbreviation DEHA has been used for N, N-diethylhydroxylamine. The hydrophilic polymers used were as follows:

SAP1 polymer: superabsorbent polymer marketed by the company ARKEMA under the trademark "AQUAKEEP", commercial grade D60, for diaper application

SAP2 polymer: superabsorbent polymer marketed by the company ARKEMA under the trademark "AQUAKEEP", commercial grade HP100, for diaper application. SAP3 polymer: superabsorbent polymer marketed by the company ARKEMA under the trademark "NORSOCRYL", commercial grade S35, for the cable application.

PA1 polymer: acrylamide-acrylic cationic copolymer modified with groups carrying ammonium functions, marketed by the company "SNF FLOERGER" as FO4800SH grade.

PA2 polymer: anionic copolymer of the sodium acrylamideacrylate type sold by the company SNF FLOERGER as an AN970SH grade.

PA3 polymer: anionic copolymer of the sodium acrlamideacrylate type marketed by the company SNF FLOERGER as a grade

AN934SH.

The test method used for the destruction of the hydrogels is as follows:

The hydrophilic polymer is swollen or dissolved, as the case may be, in a glass beaker or a plastic bottle in the presence of water (tap or deionized) at a rate of 1 g of dry polymer per 39 g of water, up to 'to the formation of a thick gel. This can be, depending on the case, a compact gel consisting of swollen (super) absorbent polymer particles or a spin gel consisting of a water-soluble polymer solution.

• The gels thus prepared are placed inside bottles of plastic (polystyrene). DEHA in liquid form (DEHA grade 85% in water) is added to the gel formed at the preferred concentration of 10% by weight of pure DEHA relative to the polymer.

• A reference is prepared consisting of an aqueous gel of identical polymer concentration, which will remain untreated or which will be treated with a saline solution, whose concentration is also expressed relative to the dry polymer; in the case of a reference treated with a saline solution, the salt concentration is chosen so as to have the same percentage by weight relative to the polymer as that used for pure DEHA. Unless otherwise specified, the gels do not undergo mechanical agitation. The plastic bottles containing treated or untreated gels (some references) are all closed with their lid (polyethylene) and placed, as appropriate, in an oven or on a bench exposed to light or in a closet protected from light. Quantification of the destruction of the gel by DEHA was carried out in the case of absorbent crosslinked polymers and in the case of non-crosslinked water-soluble polymers, by filtration of the treated gel using a stainless steel screen Standard AFNOR, carrying the Certification No. 434175 with 1 mm mesh. The quantification of the DEHA's effectiveness with respect to the destruction of the polymer gel is provided by the amount of product that has been able to pass through the sieve after treatment of the gel by contact with the destructive agent (DEHA or DEHA plus salt or metal oxide) for a certain time and relative to the reference.

To establish Table 1, for a selected gel and a treatment agent, each gel transformation measurement was carried out from a separate gel sample because of the difficulty in recovering quantitatively a gelled fraction retained on the filter for the next measurement. EXAMPLE 1

Follow-up in time of the destruction of super absorbent gels, protected from light; prepared gels with tap water

The gels are prepared by swelling 1 g of superabsorbent polymer SAP1, SAP2, SAP3 in 39 g of tap water.

In Table 1, is indicated the mass of product passing the sieve of

1 mm in% of the initial mass of gel, as a function of the contact time between the gel and the agent of destruction.

- Table 1 -

Table 1 indicates that a treatment of the gels with an aqueous solution of CaC ^ sheltered from the light produces no liquid phase recoverable by filtration through the sieve, while the treatment with DEHA produced from 4 hours a considerable destruction of the gels, whatever the grade of super absorbent, among the three grades of this example.

Two days later, the degradation is very predominant, while the reference saline solution produces no effect. EXAMPLE 2

Destruction from the light of the hydrophilic gel obtained from a superabsorbent polymer

The gels are prepared by swelling 1 g of SAP2 in 39 g of demineralised water.

In Table 2, is indicated the mass of product passing the sieve of

1 mm in% of the initial gel mass in%, after 5 months of static contact between the SAP2 gel with deionized water and the destructive agent, protected from light and at room temperature. Only a brief initial manual agitation was made.

- Table 2 -

Table 2 clearly shows the very clear superiority of treatment with DEHA gel SAP2 in the absence of light, compared with treatment with saline of CaC ^ under the same conditions.

EXAMPLE 3

Destruction by gel light obtained from a superabsorbent polymer

The gels are prepared by swelling 1 g of SAP2 in 39 g of tap water.

In Table 3, is indicated the mass of product passing the sieve of

1 mm in% of the initial mass of gel in%, after 5 months of static contact between the SAP2 gel with tap water and the destructive agent, in the laboratory light and at room temperature, after brief agitation initial manual. - Table 3

Table 3 shows that in the presence of light CaC ^ salt is capable of destroying a super absorbent gel, while this was not the case in the absence of light, but without equalizing the effectiveness DEHA which ensures almost complete destruction.

EXAMPLE 4

Accelerated destruction of a gel obtained from a superabsorbent polymer

The gels are prepared by swelling 1 g of SAP1, SAP2 or SAP3 in 39 g of tap water. The DEHA was first added to the gel, all stirred manually. A manganese salt was added as a 23% aqueous solution of manganese triacetate to the DEHA gel mixture. The manganese triacetate of Example 4 represents 0.5% relative weight of the dry polymer. The set was again shaken manually. In Table 4, is indicated the mass of product passing the sieve of 1 mm in% of the initial mass of gel, depending on the contact time between the gel and the destruction agent catalysed or not by the triacetate of manganese (III), in an oven at 40 ⁰ C (protected from light).

- Table 4 -

Table 4 shows an acceleration of the% of superabsorbent polymer gel destroyed by the DEHA in the presence of the metal salt (CH ₃ COO) ₃ Mn, regardless of the grade treated.

EXAMPLE 5

Destruction of hydrophilic polyacrylamide gels PA1, PA2 and PA3.

The gels are prepared by swelling 0.6 g of polyacrylamide in

59.4 g of water, with magnetic stirring.

The DEHA is added at a level of 10% relative to the dry polymer (0.06 g of pure DEHA, ie 0.0706 g of DEHA 85%). The mixture is placed in an oven at 40 ^° C.

In Table 5, is indicated the mass of product passing the sieve of

1 mm in% of the initial gel mass in%, for gels inflated with tap water or demineralized water, with 10% DEHA (samples (1), 25 (2), (3)) or without DEHA (samples T (4), T (5), T (6)), in an oven at 40 ^° C. (protected from light).

- Table 5 -

Table 5 clearly shows a significant destruction of the different grades of polyamides tested in the presence of DEHA. Destruction by DEHA is consistently greater when the gel has been inflated with tap water.

Claims

1. Use of at least one hydroxylamine of general formula (I)

R ¹

N OH

R '

(I) wherein R ¹ and R ² each independently represent a C 1 -C 6 alkyl radical, a C 1 -C alkyl radical substituted with at least one hydroxyl, aryl, aralkyl or alkaryl radical, one of R ¹ and R ² being furthermore, to represent hydrogen, as a destructive agent for hydrophilic polymers in the form of hydrogels or aqueous suspensions of hydrogels.

2. Use according to claim 1, characterized in that the alkyl radicals falling within the definition of R ¹ and R ² are chosen from methyl, ethyl, isopropyl, n-propyl and n-butyl; the alkyl radicals substituted by at least one hydroxyl falling within the definition of R ¹ and R ² are independently selected from CH ₃ (CH ₂ ) HCH (OH) CH ₂ - with n being 0 to 10; aryl is phenyl; aralkyl is benzyl; and alkaryl is a tolyl radical.

3. Use according to one of claims 1 and 2, characterized in that R ¹ and R ² are each chosen from C ¹ -C 6 alkyl radicals, R ¹ and R ² preferably having a maximum total of 8 carbon atoms.

4. Use according to any one of claims 1 to 3, characterized in that the hydroxylamines of formula (I) are chosen from N, N-dialkylhydroxylamines, N-alkylhydroxylamines, and N, N-bis-hydroxyalkylhydroxylamines. formula :

CH ₃ (CH ₂ ) _n CH (OH) CH _2χ

N OH CH ₃ (CH ₂₎ _Y CH (OH) CH ₂ ⁷ With n and 0 are independently O to 10.

5. Use according to any one of claims 1 to 4, characterized in that the hydroxylamines of formula (I) are chosen from N, N-dimethylhydroxylamine, N, N-diethylhydroxylamine, N, N-di-n propylhydroxylamine, N, N-di-n-butylhydroxylamine, N-methylhydroxylamine, N-ethylhydroxylamine, N-isopropylhydroxylamine, Nn-propylhydroxylamine, Nn-butylhydroxylamine, N, N-bis- hydroxypropyl) hydroxylamine and N, N-bis- (2-hydroxybutyl) hydroxylamine.

6. Use according to any one of claims 1 to 4, characterized in that the hydroxylamine of formula (I) is N, N-diethylhydroxylamine.

7. Use according to any one of claims 1 to 6, characterized in that the hydroxylamine or hydroxylamines of formula (I) are used in the form of aqueous solutions.

8. Use according to any one of claims 1 to 7, characterized in that the hydrophilic polymers which are at the origin of the hydrogels to be destroyed are chosen from: (A) absorbent or superabsorbent hydrophilic polymers; and

(B) polymers soluble in water, these polymers being optionally crosslinked and possibly having undergone chemical modifications in order to change their properties.

9. Use according to claim 8, characterized in that the polymers (A) are crosslinked hydrophilic polymers obtained by radical polymerization of at least one unsaturated ethylenic monomer chosen from (meth) acrylic acid, alkali metal salts or ammonium salts of (meth) acrylic acid, esters of (meth) acrylic acid, maleic or fumaric acid and its salts, esters of maleic or fumaric acid, acid

2-acrylamido-2-methylpropanesulphonic acid or its salts, vinyl acetate, vinylpyrrolidone, vinylcaprolactam, dimethylaminoethyl (meth) acrylate, salts of trimethylaminoethyl (meth) acrylate, acrylonitrile, maleic anhydride, acrylamide and methacrylamide, the crosslinking may have been effected by the use of crosslinking monomers comprising at least two double bonds or by crosslinking monomers comprising a double bond and at least one functional group reagent or by adding a non-polymerizable crosslinking agent comprising at least two reactive groups capable of reacting with the chemical functions of the monomer units used for the synthesis of the hydrophilic polymer.

10. Use according to claim 8, characterized in that the polymers (B) are hydrophilic non-crosslinked polymers obtained by radical polymerization of at least one unsaturated ethylenic monomer selected from acrylamide, methacrylamide, (meth) acrylic acid or its salts, 2-acrylamido-2-methylpropanesulphonic acid or its salts, alkyl esters of (meth) acrylic acid such as methyl or ethyl acrylate and methyl methacrylate or ethyl acetate, vinyl acetate, vinylpyrrolidone, maleic anhydride, maleic acid esters, dimethylaminoethyl (meth) acrylate, trimethylaminoethyl (meth) acrylate salts and diallyldimethylammonium chloride.

11. Use according to claim 8, characterized in that the hydrophilic polymers are chosen from polymers of (meth) acrylic acid and / or its salts, polymers of acrylamide, copolymers of the acid (meth) ) acrylic and / or its salts with acrylamide, copolymers of (meth) acrylic acid and / or its salts with an unsaturated ethylenic monomer different from acrylamide, copolymers of acrylamide with a different unsaturated ethylenic monomer (meth) acrylic acid and / or its salts and the copolymers of (meth) acrylic acid and / or its salts with acrylamide and with a third ethylenic monomer.

12. A method for destroying at least one hydrophilic polymer in the form of a hydrogel or an aqueous hydrogel suspension, characterized in that contacting said hydrogel or said aqueous suspension of hydrogel with at least one hydroxylamine of general formula (I):

Services

N-OH

R '

(I) wherein R ¹ and R ² each independently represent a C 1 -C 6 alkyl radical, a C 1 -C alkyl radical substituted with at least one hydroxyl, aryl, aralkyl or alkaryl radical, one of R ¹ and R ² being in addition, represent hydrogen in an amount of from 0.1% to 1000% by weight of the pure hydroxylamine (s) of formula (I) relative to the dry polymer comprising the hydrogel or the aqueous suspension hydrogel.

13. Process according to claim 12, characterized in that said hydrogel or said hydrogel suspension is brought into contact with an amount of 1% to 50% by weight of the hydroxylamine (s) of formula ( I) pure (s) relative to the dry polymer component hydrogel or aqueous suspension of hydrogel.

14. Method according to one of claims 12 or 13, characterized in that the hydroxylamine or hydroxylamines of formula (I) are used in the form of aqueous solution.

15. Process according to any one of Claims 12 to 14, characterized in that the hydrogel or the aqueous suspension of hydrogel is brought into contact with the hydroxylamine (s) of formula (I) by mixing mechanical or slow diffusion, at a temperature generally between room temperature and 100 ^° C.

16. Process according to any one of claims 12 to 15, characterized in that the alkyl radicals falling within the definition of R ¹ and R ² are chosen from methyl, ethyl, isopropyl, n-propyl and n-butyl; the alkyl radicals substituted with at least one hydroxyl falling within the definition of R ¹ and R ² are independently selected from CHs (CHb) _n CH (OH) CHb- with n being 0 to 10; aryl is phenyl; aralkyl is benzyl; and alkaryl is a tolyl radical.

17. Process according to any one of Claims 12 to 16, characterized in that R ¹ and R ² are each chosen from C ¹ -C 6 alkyl radicals, R ¹ and R ² preferably having a maximum total of 8 carbon atoms. carbon.

18. Process according to any one of Claims 12 to 17, characterized in that the hydroxylamines of formula (I) are chosen from N, N-dialkylhydroxylamines, N-alkylhydroxylamines, and N, N-bis-hydroxyalkylhydroxylamines. formula :

CH ₃ (CH ₂ ) _n CH (OH) CH _2χ

N-OH CH ₃ (CH ₂ ) _O CH (OH) CH ₂ ⁷ with n and o independently representing 0 to 10.

19. Method according to any one of claims 12 to 18, characterized in that the hydroxylamines of formula (I) are chosen from N, N-dimethylhydroxylamine, N, N-diethylhydroxylamine, N, N-di-n propylhydroxylamine, N, N-di-n-butylhydroxylamine, N-methylhydroxylamine, N-ethylhydroxylamine, N-isopropylhydroxylamine, Nn-propylhydroxylamine, Nn-butylhydroxylamine, N, N-bis- hydroxypropyl) hydroxylamine and N, N-bis- (2-hydroxybutyl) hydroxylamine.

20. Process according to any one of claims 12 to 19, characterized in that the hydroxylamine of formula (I) is N, N-diethylhydroxylamine.

21. Method according to one of claims 12 to 20, characterized in that the hydrophilic polymers which are at the origin of the hydrogels to be destroyed are chosen from:

(A) Absorbent or superabsorbent hydrophilic polymers; and (B) polymers soluble in water, these polymers being optionally crosslinked and possibly having undergone chemical modifications in order to change their properties.

22. Process according to claim 21, characterized in that the polymers (A) are crosslinked hydrophilic polymers obtained by radical polymerization of at least one unsaturated ethylenic monomer chosen from (meth) acrylic acid, alkali metal salts or ammonium salts of (meth) acrylic acid, esters of (meth) acrylic acid, maleic or fumaric acid and its salts, esters of maleic or fumaric acid, acid

2-acrylamido-2-methylpropanesulphonic acid or its salts, vinyl acetate, vinylpyrrolidone, vinylcaprolactam, dimethylaminoethyl (meth) acrylate, trimethylaminoethyl (meth) acrylate salts, acrylonitrile, maleic anhydride, acrylamide and methacrylamide, the crosslinking may have been carried out by the use of crosslinking monomers comprising at least two double bonds or by crosslinking monomers comprising a double bond and at least one reactive functional group or by addition of a non-polymerizable crosslinking agent having at least two reactive groups capable of reacting with the chemical functions of the monomer units for the synthesis of the hydrophilic polymer.

23. The method of claim 21, characterized in that the polymers (B) are non-crosslinked hydrophilic polymers obtained by radical polymerization of at least one unsaturated ethylenic monomer selected from acrylamide, methacrylamide, acid (meth). acrylic acid or its salts, 2-acrylamido-2-methylpropanesulphonic acid or its salts, alkyl esters of (meth) acrylic acid such as methyl or ethyl acrylate and methyl methacrylate or ethyl acetate, vinyl acetate, vinylpyrrolidone, maleic anhydride, maleic acid esters, dimethylaminoethyl (meth) acrylate, trimethylaminoethyl (meth) acrylate salts and diallyldimethylammonium chloride.

24. The method of claim 21, characterized in that the hydrophilic polymers are selected from hydrophilic polymers forming gels may be destroyed by the method of the invention, the polymers of (meth) acrylic acid and / or its salts, such as sodium, potassium or ammonium salts, polymers of acrylamide, copolymers of (meth) acrylic acid and / or its salts, such as those mentioned above, with acrylamide, copolymers of (meth) acrylic acid and / or its salts with an unsaturated ethylenic monomer different from acrylamide, copolymers of acrylamide with an unsaturated ethylenic monomer other than (meth) acrylic acid and / or its salts and copolymers of (meth) acrylic acid and / or its salts with acrylamide and with a third ethylenic monomer.

25. Process according to any one of claims 12 to 24, characterized in that, in combination with the hydroxylamine (s) of formula (I), at least one salt or oxide of a transition metal, such as that the salts or oxides of copper, cobalt or manganese, the percentage of said salt or metal oxides up to 25% by weight relative to the weight of the dry polymer component hydrogel or aqueous suspension of hydrogel. 0