WO2011141522A1 - Biodegradable superabsorber - Google Patents

Abstract

The present invention relates to a superabsorbent material, comprising a biodegradable cross-linked copolymer. The copolymer comprises at least one constitutive unit A, wherein the unit A is derived from an olefinically unsaturated carboxylic acid, and at least one further constitutive unit B, wherein the unit B is suitable for inserting at least one biologically cleavable predetermined breaking point into the main chain of the cross-linked copolymer.

Description

 BIOABBAUBARER SUPERABSORBER

The invention relates to a superabsorbent material comprising a cross-linked copolymer having improved biodegradability and a process for its preparation.

Superabsorbents are weakly crosslinked, water-insoluble polymers that can absorb many times their own weight in water or aqueous solution to form a hydrogel. The superabsorbents currently used on

Polyacrylbasis are difficult to biodegrade, however. There

Superabsorbents primarily in the hygienic field in the form of disposable articles, such as e.g. Diapers or sanitary napkins are used, this is associated with a significant burden on the environment. This garbage, which can not be rotted or recycled, must be stored long-term in landfills or stored in landfills

Waste incineration plants are disposed of. In DE 40 29 591 and DE 40 29 592 it is proposed to use as an alternative to the conventional superabsorbent polysaccharide-acrylate hybrid systems. U.S. Patent No. 6900171 describes mainly linear polyacrylates in which biodegradability has been improved by incorporation of electron rich centers into the polymer backbone. However, all of these systems are only partially biodegradable.

In DE 42 07 465 has been proposed the biodegradability of

Superabsorbem by copolymerization of modified natural products such as starch, cellulose or protein molecules to improve. Although these polymers can be completely biodegraded, but their preparation is very expensive. There is therefore a need for superabsorbent materials that are biodegradable.

The object of the present invention is to provide a superabsorbent material which is stable during its use and biodegradable after fulfilling its task. T / EP2011 / 057641

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Another object of the present invention is to provide a superabsorbent material that can be degraded in a controlled manner. It is desirable to be able to control the biodegradation of the superabsorbent material in a targeted manner. Another object of the present invention is to provide a superabsorbent material whose degradation products are non-toxic to the environment. Furthermore, it is desirable that the superabsorbent material be degraded predominantly to carbon dioxide and water.

Another object of the present invention is to provide a superabsorbent material which, in addition to being biodegradable, has excellent swellability. It is also desirable to have the superabsorbent material in view of its physical properties, e.g. its water absorption capacity to adapt to the appropriate application. These and other objects are achieved by the subject matter of the independent claims. Preferred embodiments are in the dependent

Claims given.

A solution according to the invention consists in a superabsorbent material comprising a biodegradable, crosslinked copolymer, the copolymer comprising at least one constitutive unit A, wherein the unit A is derived from an olefinically unsaturated carboxylic acid, and at least one further constitutive unit B, wherein the unit B is suitable to insert at least one biologically cleavable breaking point in the main chain of the crosslinked copolymer. In addition, the biodegradable, crosslinked copolymer may comprise at least one further constitutive unit C, wherein the unit C is capable of introducing at least one biologically cleavable predetermined breaking point into the crosslinking bridges of the crosslinked copolymer. Biologically splittable predetermined breaking points represent weak points in the copolymer at which the polymer chain can be cleaved under the action of environmental influences. The invention makes it possible to insert specifically such predetermined breaking points in the crosslinked copolymer. Depending on the type of constitutive unit used, the predetermined breaking points can be inserted into the main chain of the crosslinked copolymer and / or into the crosslinking bridges of the crosslinked copolymer.

Preferably predetermined breaking points are present both in the main chain and in the cross-linking bridges. These predetermined breaking points may be, for example, a functional group which is sensitive to hydrolysis or oxidatively degradable. The oxidative degradation can e.g. be caused by ozone, by

 Solar radiation is formed. Further examples of such predetermined breaking points are functional groups in which the crosslinked copolymer is enzymatically

Microorganisms or photochemically can be split under the influence of sunlight. By the number and type of inserted into the copolymer

Predetermined breaking points, the degradation rate of the copolymer can be adjusted as desired.

In one aspect of the invention, the biodegradable, crosslinked copolymer is made entirely from synthetic monomers. An advantage of completely synthetic materials over superabsorbent polymers containing natural products such as starch or cellulose is that they can be produced with a defined, constant quality and thus always the same chemical

Composition and rate of degradation and have the same physical properties. In addition, the use of synthetic monomers allows a wide variation of the polymer structure and thus a targeted adaptation to the desired application. Brief description of the figures

Fig. 1 shows examples of predetermined breaking points in polymer systems and the biodegradation of such polymer systems.

Fig. 2 shows an example of ring opening upon copolymerization of a compound of the formula (I) and an acrylic acid monomer.

A "superabsorbent material" or a "superabsorber" is a

Polymer material capable of many times its own weight

To integrate water molecules into its structure, whereby the material swells strongly and forms a hydrogel. The term "copolymer" refers to a polymer which is composed of at least two different monomer units A "crosslinked copolymer" in the context of the invention is to be understood as meaning a copolymer in which at least one chain-shaped polymer or copolymer which is used in the context of the present invention "Main chain" is characterized by monomer or oligomer units, which in the context of the present invention as

"Networking bridges" are referred to each other.

The term "constitutive unit" describes the smallest, regular

repeating unit in a polymer that completely describes the structure of the polymer. The expression "wherein the constitutive unit X is derived from a compound according to formula Y" means that in the polymerization reaction a compound according to formula Y is used to form a polymer having a

to obtain constitutive unit X. In the context of the present invention, the terms "constitutive unit" and "unit" are used synonymously.

Under a "biologically fissile breaking point" is in the context of

The present invention is understood to mean a functional group in which the

Polymer chain under the influence of environmental influences hydrolytic, oxidative or can be degraded enzymatically. Examples of such biologically splittable predetermined breaking points are ether, ester, thioester, carbonyl, peroxy, hydrazo or ureylene groups and electron-rich centers such as double or

Triple bonds. Examples of environmental influences are the effects of

Moisture, sunlight, ozone or enzymes produced by microorganisms. Biodegradable breakpoints may be located in the backbone of the crosslinked copolymer and / or in the crosslinked bridges of the crosslinked copolymer. Biologically cleavable predetermined breaking points are preferably located both in the main chain and in the crosslinking bridges of the copolymer. Preferably, the biologically cleavable predetermined breaking point is a functional group which can be degraded hydrolytically or ozonolytically, more preferably hydrolytically. The polymer chain is first broken down into shorter fragments and finally degraded under near influence to final degradation products, which may consist of carbon dioxide, methane, water or other non-toxic compounds. The biodegradation of the crosslinked copolymer can be carried out, for example, by first cleaving the polymer chains into shorter chains under environmental conditions, preferably by hydrolysis, at the predetermined breaking points, and then the shorter chains of

Microorganisms are converted to C0 ₂ , water and / or biomass. In the context of the present invention, the expression "straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms" may comprise the following radicals:

Alkyl radicals may comprise straight-chain, branched or cyclic, optionally substituted radicals having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms and in particular lower alkyl radicals having 1 to 6, preferably 1 to 4 carbon atoms. Specific examples are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, n-pentyl, n-hexyl, dodecyl, octadecyl and cyclohexyl. The alkyl radicals may have one or more substituents from the group of halogens such as F, Cl and Br or acryloxy, amino, amide, aldehyde, alkoxy, alkoxycarbonyl, alkylcarbonyl, carboxy, cyano, epoxy, hydroxy, keto, methacryloxy , Mercapto, phosphoric acid, sulfonic acid or vinyl groups. Alkenyl and alkynyl radicals may include straight-chain, branched or cyclic, optionally substituted radicals having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and especially lower alkyl radicals having 1 to 6, preferably 1 to 4 carbon atoms. Special examples for

Alkenyl radicals are allyl, 1-methylprop-2-en-1-yl, 2-methyl-prop-2-en-1-yl, but-2-en-1-yl, but-3-en-1-yl, 1-methylbut-3-en-1-yl and 1-methylbut-2-en-1-yl.

 Specific examples of alkynyl radicals are propynyl, but-2-yn-1-yl, but-3-yn-1-yl and 1-methyl-but-3-yn-1-yl. Acyl radicals may optionally comprise substituted radicals of organic acids which are formally formed by cleavage of an OH group from the organic acid, for example radicals of a carboxylic acid or radicals derived therefrom such as the thiocarboxylic acid, optionally N-substituted iminocarboxylic acids or the radicals of carbonic acid monoesters, optionally N- substituted carbamic acids, sulfonic acids, sulfinic acids, phosphonic acids, phosphinic acids. The acyl radicals may contain one or more substituents from the group of halogens such as F, Cl and Br or acryloxy, amino, amide, aldehyde, alkoxy, alkoxycarbonyl,

 Alkylcarbonyl, carboxy, cyano, epoxy, hydroxy, keto, methacryloxy, mercapto, phosphoric acid, sulfonic acid or vinyl groups.

The term "optionally substituted" indicates that the radicals mentioned hereinafter can be optionally mono- or polysubstituted Suitable substituents are, for example, methyl, ethyl, propyl, butyl, hydroxyl or halogens, such as, for example, F, Cl, Br or I. Unless otherwise stated, percentages by weight are based on the total weight of the dry crosslinked copolymer, ie, for example, at a water content of less than about 0.1% by weight and / or after 12 hours of drying of the material, preferably at about 40 ° C. preferably in a convection oven, based. All numerical, range and property information and parameters given herein are, unless expressly stated otherwise, basically to be understood as being combinable with one another in any desired manner.

According to the invention, the superabsorbent material comprises a biodegradable, crosslinked copolymer comprising at least one constitutive unit A and at least one further constitutive unit B. The unit A is derived from an olefinically unsaturated carboxylic acid, and the unit B is suitable to have at least one biologically cleavable breaking point in to insert the backbone of the crosslinked copolymer. In addition, the crosslinked copolymer may comprise an optional unit C which is capable of introducing at least one further biodegradable breaking point in addition to the predetermined breaking points in the main chain

 Insert crosslink bridges of the crosslinked copolymer. Furthermore, the crosslinked copolymer may comprise an additional, optional D unit.

The constitutive unit A

The constitutive unit A is derived from an olefinically unsaturated carboxylic acid. Suitable carboxylic acid monomers for preparing the crosslinked copolymer according to the invention are carboxylic acids having at least one

Carboxyl group and at least one olefinic double bond. Preferably, a double bond in the olefinically unsaturated carboxylic acid is in the α-position to a carboxyl group. As a result, the double bond is activated and can be polymerized easier. The polymerizability of a

Double bond can also be facilitated by an end position in the molecule. But the double bond can also be found at any other position in the olefinic unsaturated carboxylic acid monomer. In addition, the olefinically unsaturated carboxylic acid monomer may comprise further double bonds, which may optionally also be polymerizable.

Examples of suitable olefinically unsaturated carboxylic acids are acrylic acid, methacrylic acid, ethylacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), ct-phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, 2-methyl-2-butenoic acid (angelic acid )

Cinnamic acid, p-chlorocinnamic acid, β-styrylacrylic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid or fumaric acid. Preferably, the olefinically unsaturated carboxylic acid monomer is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid, particularly preferred is acrylic acid. It is also possible to use mixtures of a plurality of olefinically unsaturated carboxylic acid monomers to prepare the copolymer of the invention. The olefinically unsaturated carboxylic acid monomers may be used in an amount of from 10 to 99 mole percent, based on the total content of the monomers employed, e.g. in an amount of 50 to 99 mol%, 60 to 98 mol% or from 70 to 97 mol%. Preferably, the olefinically unsaturated carboxylic acid monomers are used in an amount of 80 to 96 mol%, based on the total content of the monomers used.

According to one embodiment of the present invention, the crosslinked copolymer contains 10 to 99 mol% of the constituent unit A based on

Total amount of constitutive units of the crosslinked copolymer, preferably 50 to 99 mol%, 60 to 98 mol% or 70 to 97 mol%, and particularly preferably 80 to 96 mol%. The olefinically unsaturated carboxylic acid monomers can be used in the

Reaction mixture are at least partially neutralized, and thus the pH, the polymerization and ultimately the structure of the crosslinked copolymer of the invention are suitably modified. Preferably, at most about 80%, e.g. about 60 to 80%, and in exemplary embodiments neutralizes a maximum of 40% of the acid groups of the monomers. The (partial) neutralization can be achieved by adding at least one basic substance, e.g. an alkaline earth and / or alkali hydroxide, lime, alkylamines, or ammonia.

For example, KOH or NaOH can be used. Preferably, the (partial) neutralization is carried out with NaOH.

The constitutive unit B

The constitutive unit B is suitable, at least one biologically fissile

Insert predetermined breaking point in the main chain of the crosslinked copolymer.

To produce biologically cleavable breakpoints in the backbone of the crosslinked copolymer, the crosslinked copolymer comprises at least one constitutive unit B derived from a compound of formula (I)

wobei X und Y jeweils unabhängig voneinander ausgewählt sind aus der Gruppe umfassend -O-, -S-, -N= und -NR^a-, wobei R^a Wasserstoff oder geradkettiges, verzweigtes oder zyklisches, gegebenenfalls substituiertes Alkyl, Alkenyl, Alkinyl oder Acyl mit 1 bis 20 Kohlenstoffatomen ist, R ausgewählt ist aus der Gruppe umfassend Wasserstoff und geradkettiges, verzweigtes oder zyklisches, gegebenenfalls substituiertes Alkyl, Alkenyl, Alkinyl oder Acyl mit 1 bis 20 Kohlenstoffatomen,

wherein X and Y are each independently selected from the group consisting of -O-, -S-, -N = and -NR ^a -, wherein R ^{a is} hydrogen or straight, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl with 1 to 20 carbon atoms, R is selected from the group comprising hydrogen and straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms,

R ² and R ^{3 are} each independently selected from the group consisting of -CO-, -COO-, -O-CO-O-, -CONR ^b -, -HC = CH-, -O-, -S-, - SO-, -SO ₂ -, -CH ₂ - and -CHR ^C -, wherein R ^{b is} hydrogen or straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms and R ^{c is} hydrogen, hydroxy, Is halogen or straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms, and

R ^{4 is} either absent, in which case R ² and R ³ are linked via a single or double bond, or selected from the group comprising straight-chain or branched optionally substituted alkylene, alkenylene or alkynylene having 1 to 20 carbon atoms, these being CO, -COO-, -O-CO-O-, -CONR ^d -, -SiH ₂ -, -O-, -S-, -SO- or -S0 ₂ - may be interrupted groups, wherein R ^{d is} hydrogen or straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20

Carbon atoms.

Suitable compounds of the formula (I) are, for example, 2-methylene-1,3-dioxalane, 2-methylene-1,3-dioxepane, 2-methylene-4,7-dihydro-1,3-dioxepin, 6-methylene-1 , 1-dioxa-5,7-diazacyclohexadecane-12,16-dione, 2-methylene-1,3,6-triazocane, 2-methylene-1, 3,5,7-dioxadiazocane, 2-methylene-1, 3-dioxacycloundecane-4,1-dione, 2-methylene-1, 3,8,1-l-tetraazacyclopentadecane-9,10-dione, 3-methylene-1, 2,4,5-tetrazecane-6,10- dione, 2-methylene-1,3,3-dioxathiocane-6,6-dioxide, (Z) 2-methylene-1,3-dioxepin-4,7-dione, 2-methylene-1,3,3-dioxathiocane 6,6-oxide, 2

Methylene-1,3,7,10-tetraoxacyclotridecane, 2-methylene-1,3-diazonane, 2-methylene-1,3,3-dioxasilocane, 2-methylene-1,3-dioxecane-4-one, 6, 6-dimethyl-2-methylene-1,3,6- dioxasilocan. Preferably, the compound according to formula (I) is 2-methylene-1, 3-dioxalane, 2-methylene-1,3-dioxepan or 2-methylene-4,7-dihydro-1,3-dioxepin.

In the copolymerization with olefinically unsaturated carboxylic acid monomers, the compounds of the formula (I) undergo ring opening under β-bond cleavage, so that the following constitutive unit B is obtained within the polymer chain:

Depending on the meaning of X, X can have a single or

Double bond to be linked to the C atom. An example of such ring opening in the copolymerization of acrylic acid and 2-methylene-1,3-dioxalane is shown in FIG.

Optionally, the compound according to formula (I) can be further polymerisable

Contain double bonds which in the copolymerization with the olefinically unsaturated carboxylic acid monomer optionally additional

Form crosslink bridges between the main chains of the copolymer.

The compound according to formula (I) can be used in an amount of 0.1 to 50 mol%, based on the total content of the monomers used, for example in an amount of 0.5 to 40 mol%, 1 to 30 mol%. % or from 2 to 20 mol%. The compounds of the formula (I) are preferably used in an amount of from 5 to 15 mol%, based on the total content of the monomers used. According to one embodiment of the present invention, the crosslinked copolymer contains 0.1 to 50 mol% of constitutive unit B derived from a compound of formula (I) based on the total amount of constitutive

Units of the crosslinked copolymer, preferably 0.5 to 40 mol%, 1 to 30 mol% or from 2 to 20 mol%, and particularly preferably 5 to 15 mol%.

By incorporating compounds of formula (I) into the copolymer, predetermined breaking points can be generated in the backbone of the crosslinked copolymer which can be hydrolytically degraded.

According to a further embodiment, the crosslinked copolymer comprises at least two units B, the first unit B being derived from a compound of the formula (I) and the second unit B being derived from a compound of the formula (II),

 OD, where m is an integer> 0, and

R ⁵ to R ^{10 are} each independently selected from the group comprising hydrogen, halogen and straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20

Carbon atoms, -OR ^e , -COOR ⁶ , - NR ^* , -CO-CR and -SO ₃ R ^e , wherein each R ^e is hydrogen or straight chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 Carbon atoms. According to one embodiment, m is an integer between 1 and 10 or between 1 and 8. Preferably, m is an integer between 2 and 6.

Suitable compounds of the formula (II) are, for example, alkene compounds having 2 to 6 conjugated double bonds. Specific examples of compounds of the formula (II) are butadiene, isoprene, chloroprene,

Dimethyl butadiene, cyclohexadiene, butadiene carboxylic acid or

Butadiene dicarboxylic acid.

The compound of the formula (II) may be used in an amount of 0.1 to 50 mol%, based on the total content of the monomers used, e.g. in an amount of 0.5 to 40 mol%, 1 to 30 mol% or from 2 to 20 mol%. The compounds of the formula (II) are preferably used in an amount of from 5 to 15 mol%, based on the total content of the monomers used.

According to one embodiment of the present invention, the crosslinked copolymer contains 0.1 to 50 mol% of the constitutive unit B derived from a compound of the formula (II) based on the total amount of constitutive units of the crosslinked copolymer, preferably 0.5 to 40 mole%, 1 to 30 mole%) or from 2 to 20 mole%, and more preferably 5 to 15 mole%>.

By incorporating compounds of the formula (II) into the copolymer, it is additionally possible to generate predetermined breaking points in the main chain of the crosslinked copolymer, which can be decomposed ozonolytically.

According to a preferred embodiment, the ratio between the at least one constitutive unit A and the at least one constitutive unit B in the crosslinked copolymer is between 100: 1 and 2: 1, preferably between 50: 1 and 3: 1, more preferably between 35: 1 and 5: 1, more preferably between 15: 1 and 5: 1, and most preferably about 10: 1. As a result, the main chains of the crosslinked copolymer under the influence of environmental factors, preferably hydrolytically, broken down into fragments having preferably such chain lengths, which can be metabolized particularly well by microorganisms.

According to one embodiment, the ratio between the at least one unit A and the at least one unit B, is selected such that the main chains of the crosslinked copolymer under the influence of environmental influences, preferably hydrolytically, in fragments having a molecular weight between 500 and 6000, preferably between 600 and 3000, more preferably between 700 and 1500 and more preferably between 800 and 1000 cleaved.

Crosslinkers The main chains of the biodegradable, cross-linked copolymer are

 Networking bridges linked together. The crosslinking bridges can be generated by suitable crosslinkers.

Examples of suitable crosslinkers are compounds having at least two polymerizable double bonds or compounds having at least one polymerizable double bond and at least one further functional group which is reactive with acid groups. Suitable examples are mono-, di- and polyesters of acrylic acid, methacrylic acid, itaconic acid and

Maleic acid, mono-, di- and polyesters of polyhydric alcohols such as butanediol, hexanediol, polyethylene glycol, trimethylolpropane, pentaerythritol, glycerol and polyglycerol, as well as the resulting oxyalkylated homologs, e.g. Butanediol diacrylate, as well as the esters of these acids with allyl alcohol and its alkoxylated homologues. Further examples are N-diallylacrylamide, diallyl phthalate, triallyl citrate, trimonoallyl polyethylene glycol ether citrate,

Allylacrylamide and allyl ethers of diols and polyols and their oxethylates.

Also suitable, for example, diamines and their salts with at least two ethylenically unsaturated substituents such as di- and triallylamine and Tetraallylammonium. Particularly suitable are 1, 4-butanediol diacrylate (BDDA), methylenebisacrylamide and allyl methacrylate (ALMA).

In one embodiment, the crosslinked copolymer is a crosslinker selected from the group consisting of 1,4-butanediol acrylate,

Methylenbisacrylamid and allyl methacrylate crosslinked.

The crosslinker can be used in an amount of 0.00001 to 10 mol%, based on the total content of the monomers used, e.g. in an amount of 0.0001 to 8 mol%, 0.001 to 5 mol%, or 0.01 to 3 mol%, it is preferably used in an amount of 0.1 to 2 mol%.

According to one embodiment of the present invention, the crosslinked copolymer contains 0.0001 to 10 mol% constitutive units constituting crosslinking bridges between the main chains of the copolymer based on the total amount of constitutive units of the crosslinked copolymer, preferably 0.0001 to 8 mol%. , 0.001 to 5 mol% or from 0.01 to 3 mol%, and particularly preferably 0.1 to 2 mol%.

The optional constitutive unit C

According to an optional embodiment of the present invention, the biodegradable, crosslinked copolymer comprises at least one additional constitutive unit C, wherein the unit C is suitable for introducing at least one biologically cleavable predetermined breaking point into the crosslinking bridges of the crosslinked copolymer.

In one embodiment, the crosslinked copolymer comprises at least one unit C derived from a compound of formula (III)

HxCR ⁿ (4 _-X) where x is 0, 1 or 2 and

Each R is independently selected from radicals of the formula (IV)

wobei n eine ganze Zahl > 0 ist, Z ausgewählt ist aus der Gruppe umfassend -O- und -NH-,

where n is an integer> 0, Z is selected from the group comprising -O- and -NH-,

R ^{12 is} selected from the group comprising straight-chain or branched optionally substituted alkylene, alkenylene, alkynylene or arylene having 1 to 20 carbon atoms and

R ^{13 is} hydrogen or methyl. In one embodiment, x is equal to 2.

In another embodiment, n is an integer between 1 and 10 or between 1 and 8. Preferably, n is an integer between 2 and 4.

Examples of suitable compounds of the formula (III) are adipic acid bis [2- (2-methylacryloxy) ethyl] esters, fumaric acid bis [2- (2-methylacryloxy) ethyl] esters, itaconic acid bis [2- (2-methylacryloxy) ethyl] ester and maleic bis [2- (2-methylacryloxy) ethyl] ester.

wobei R jeweils unabhängig voneinander ausgewählt ist aus Resten der Formel (IV) According to a further embodiment, the unit C additionally or alternatively derived from a compound according to formula (V)

wherein each R is independently selected from radicals of the formula (IV)

wobei n eine ganze Zahl > 0 ist,

where n is an integer> 0,

Z is selected from the group comprising -O- and -NH-,

R ^{12 is} selected from the group comprising straight-chain or branched optionally substituted alkylene, alkenylene, alkynylene or arylene having 1 to 20 carbon atoms and R ^{13 is} hydrogen or methyl.

In another embodiment, n is an integer between 1 and 10 or between 1 and 8. Preferably, n is an integer between 2 and 4.

Examples of compounds of the formula (V) are zo-phthalic acid bis [2- (2-methylacryloxy) ethyl] esters, isophthalic acid bis [2- (2-methylacryloxy) ethyl] esters or terephthalic acid bis- [2- (2-methylacryloxy) ethyl] ester.

In a preferred embodiment, the moiety C is derived from the compound terephthalic acid bis [2- (2-methylacryloxy) ethyl] ester.

According to another embodiment of the present invention, the biodegradable, crosslinked copolymer at least one constitutive unit A, wherein the unit A is derived from an olefinically unsaturated carboxylic acid, at least one further constitutive unit B, wherein the unit B is adapted to insert at least one biodegradable breaking point in the main chain of the crosslinked copolymer, and at least one further constitutive unit C, wherein the unit C is adapted to insert at least one biologically cleavable predetermined breaking point in the crosslinking bridges of the crosslinked copolymer.

The compound of the formula (III) and / or the formula (V) may be used in an amount of 0.0001 to 10 mol% based on the total amount of the monomers used, e.g. in an amount of 0.001 to 8 mol%, 0.01 to 5 mol% or from 0.1 to 5 mol%. The compounds of the formula (III) are preferably used in an amount of 0.1 to 2 mol%, based on the total content of the monomers used.

According to one embodiment of the present invention, the crosslinked copolymer contains 0.0001 to 10 mol% of the constituent unit C based on

Total amount of constituent units of the crosslinked copolymer, preferably 0.001 to 8 mol%, 0.01 to 5 mol% or from 0.1 to 5 mol%, and particularly preferably 0.1 to 2 mol%.

By incorporating compounds of the formula (III) and / or (V) into the crosslinked copolymer, it is additionally possible to generate predetermined breaking points in the crosslinking bridges of the copolymer, which can be decomposed hydrolytically.

According to one embodiment, the ratio between the amount of compound used, from which the constitutive unit C is derived, to the amount of crosslinker used is between 1:50 and 50: 1, for example between 1: 2 and 40: 1 or between 1: 1 and 20: 1. PT / EP2011 / 057641

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The optional constitutive unit D

In addition, the biodegradable, crosslinked copolymer may comprise at least one further optional constitutive unit D, wherein the unit D in the

Main chain of the crosslinked copolymer is located. The additional optional constitutive unit D may be, for example, from

Derive compounds such as acrylonitriles or acrylamides. Suitable acrylonitriles are, for example, acrylonitrile, methacrylonitrile, ethylacrylonitrile or chloroacrylonitrile. Suitable acrylic acid amides are, for example, acrylamide, methacrylamide, N-methacrylamide, N-t-butylacrylamide, N-cyclohexylacrylamide and N-ethylacrylamide. Other suitable additional optional constitutive units may be used

For example, of compounds such as styrene, ethene, propene, butene or

Derive methyl (meth) acrylate. Preference is given to substituted N-acrylamides or N, N-disubstituted acrylamides.

The compound from which the constituent unit D is derived can be used in an amount of 0 to 10 mol%, based on the total content of the monomers used, e.g. in an amount of 0.0001 to 8 mol%, 0.001 to 5 mol%, or 0.01 to 3 mol%, it is preferably used in an amount of 0.1 to 2 mol%.

According to one embodiment of the present invention, the crosslinked copolymer contains 0 to 10 mol% of constitutive unit D, based on

 Total amount of constitutive units of the crosslinked copolymer, preferably 0.0001 to 8 mol%, 0.001 to 5 mol%, or 0.01 to 3 mol%, and particularly preferably 0.1 to 2 mol%.

According to a preferred embodiment, the ratio of the sum of the at least one unit A and the at least one unit D to the at least one constitutive unit B in the crosslinked copolymer is between 100: 1 and 2: 1, preferably between 50: 1 and 3: 1, more preferably between 35: 1 and 5: 1, even more preferably between 15: 1 and 5: 1 and particularly preferably at about 10: 1 The main chains of the crosslinked copolymer are decomposed under the action of environmental influences, preferably hydrolytically, into fragments with such chain lengths, which are particularly good for microorganisms

can be metabolized.

According to one embodiment, the ratio between the sum of the at least one unit A and the at least one unit D with respect to the at least one unit B is selected such that the main chains of the crosslinked copolymer are exposed to environmental influences, preferably hydrolytically, in fragments having a molecular weight between 500 and 6000, preferably between 600 and 3000, more preferably between 700 and 1500 and more preferably between 800 and 1000 cleaved.

In one embodiment, the biodegradable crosslinked copolymer of the present invention comprises 10 to 99 mole% of the compound from which a unit A is derived, and 1 to 50 mole% of the compound from which a unit B is derived, based on each Total content of the monomers used. According to another embodiment, the biodegradable, crosslinked copolymer of the invention comprises 10 to 99 mol% of the compound from which a unit A is derived, 1 to 50 mol% of the compound from which a unit B is derived, 0.0001 to

10 mol% of the compound from which a unit C is derived, 0 to 10 mol% of the compound from which derives a unit D, and 0.00001 to 10 mol% crosslinker, each based on the total content of the used monomers.

Preferably, the crosslinked copolymer of the present invention comprises 80 to 99 mol% of the compound from which a unit A is derived, 8 to 17 mol% of the compound from which a unit B is derived, and 0.5 to 4 mol -% of the

Compound from which a unit C is derived, in each case based on the

Total content of the monomers used. In a further preferred Embodiment includes the biodegradable, cross-linked, invention

Copolymer additionally 0.1 to 1 mol% of the compound from which derives a unit D, and / or 0.1 to 1 mol% of crosslinker, each based on the total content of the monomers used. The amounts of the above-mentioned compounds and crosslinkers are selected so that the total amount is 100 mol%.

In one embodiment, the biodegradable, crosslinked copolymer of the present invention contains from 10 to 99 mole percent of unit A and from 1 to 50 mole percent of unit B, each based on the total amount of constitutive units of the crosslinked copolymer. In another embodiment, the biodegradable, crosslinked copolymer of the present invention contains from 10 to 99 mole% of unit A and from 1 to 50 mole% of unit B, from 0.0001 to 10 mole% of constitutive unit C, from 0 to 10 mole%. % of the constitutive unit D, and 0.00001 to 10 mol% of the constitutive unit forming crosslinking bridges between the main chains of the copolymer, based in each case on the total amount of constitutive

Units of the crosslinked copolymer. Preferably, the crosslinked

 Copolymer of the present invention 80 to 99 mol% of unit A, 8 to 17 mol%) of unit B, and 0.5 to 4 mol% of unit C, each based on the total amount of constitutive units of the crosslinked copolymer , In a further preferred embodiment, the inventive,

biodegradable, crosslinked copolymer additionally 0.1 to 1 mol% of the unit D and / or 0.1 to 1 mol% of the constitutive unit which forms crosslinking bridges between the main chains of the copolymer, in each case based on the

Total amount of constitutive units of the crosslinked copolymer. The amounts of the above constitutive units are selected so that the

Total amount is 100 mol%. Preparation of the biodegradable, crosslinked copolymer

The biodegradable crosslinked copolymer of the present invention can be prepared by copolymerizing at least one olefinically unsaturated carboxylic acid monomer from which a constituent unit A is derived with at least one other monomer from which a constitutive unit B is derived, and at least one crosslinker.

According to one embodiment, the biodegradable, crosslinked copolymer of the present invention is prepared by copolymerizing at least one olefinically unsaturated carboxylic acid monomer, from which a constitutive unit A is derived, with at least one further monomer from which a constitutive unit B is derived, at least one crosslinker and at least one further monomer, from which a constituent unit C is derived produced.

According to another embodiment, an olefinically unsaturated

Carboxylic acid monomer, from which a constitutive unit A is derived, with at least two further monomers, of which two constitutive units B are derived, wherein the first monomer is a compound according to formula (I) and the second monomer is a compound according to formula (II ), and copolymerized at least one crosslinker.

According to another embodiment, an olefinically unsaturated

Carboxylic acid monomer, from which a constitutive unit A is derived, with at least two further monomers, of which two constitutive units B are derived, wherein the first monomer is a compound according to formula (I) and the second monomer is a compound according to formula (II ) is, at least one

Crosslinker and at least one other monomer from which a unit C is derived, copolymerized.

According to a further embodiment, an optional further monomer may be copolymerized, from which a unit D is derived. The crosslinked copolymers of the present invention can be prepared by known polymerization methods. For example, the

Polymerization in aqueous solution can be carried out as a gel polymerization. Other methods, such as e.g. the suspension polymerization are also common. Preferably, the polymerization is carried out in aqueous solution as a gel polymerization.

The polymerization can be carried out as a radical polymerization initiated by a free radical generator.

Suitable free-radical formers are, for example, peroxide compounds, organic peroxides, redox systems, azo initiators or photoinitiators. examples for

Peroxide compounds are potassium peroxodisulfate or hydrogen peroxide. Examples of organic peroxides are benzoyl peroxide or tert-butyl hydroperoxide. Examples of redox systems are potassium peroxodisulfate / sodium disulfide or

Hydrogen peroxide / hydroxylamine chloride, this is preferably the

Presented oxidizing agent. Examples of azo initiators are 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (VA-044) or azobisisobutyronitrile (AIBN). Examples of photoinitiators are benzoin, benzoin ethers, benzil,

Acetophenone derivatives and mixtures thereof.

Preferably, as a radical generator potassium peroxodisulfate sodium disulfide and 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (VA-044) or

Azobisisobutyronitrile (AIBN) used.

The radical generator can be used in an amount of 0.001 to 5 mol%, based on the total content of monomers.

The polymerization reaction can be carried out in a solvent. Suitable solvents are, for example, protic polar solvents, such as water, aqueous solutions, alcohols, such as methanol, ethanol; alkylamines,

Tetrahydrofuran, dioxane, and any mixtures thereof. Preferably Water used. Furthermore, these protic-polar solvents

optionally also in mixtures with aprotic and / or nonpolar

Solvents may be used, optionally with the addition of surfactants, emulsifiers or other amphiphilic substances in order to obtain a homogeneous reaction mixture as possible. However, other solvents may be used.

If appropriate, further additives can be added to the reaction solution in addition to the monomers and the radical generator.

According to one embodiment, additional cyclodextrins can be used in the gel polymerization in aqueous solution. Suitable cyclodextrins are, for example, α-, β- or γ-cyclodextrins or cyclodextrin derivatives, such as

CAVASOL ^® or CAVAMAX ^®. Particularly suitable are β-cyclodextrins such as HPBCD (hydroxypropyl-β-cyclodextrin), HEBCD (hydroxyethyl-β-cyclodextrin), DIMEB (heptakis (2,6-dimethyl) -β-cyclodextrin), TRIMEB

(Heptakis (2,3,6-trimethyl) -β-cyclodextrin), EPC (epichlorohydrin cross-linked cyclodextrin), HP-β-cyclodextrin, HE-β-cyclodextrin or per-Ac-β-cyclodextrin. Preferably, methylated β-cyclodextrin or methylated cyclodextrins such as TRIMEB, DIMEB, RAMEB are used. Particularly preferred is the randomly methylated RAMEB cyclodextrin (randomly methylated beta cyclodextrin). The cyclodextrins can be used in an amount of 0.1 to 15 mol%, 0.5 to 12 mol% or 1 to 10 mol%, based on the total content of monomers, preferably in an amount of 3 to 8 mol -%.

The polymerization temperature depends on the nature of the radical generator used and may for example be between 4 and 150 ° C. Preferably, the average reaction temperature of the polymerization reaction is maintained between about 50 ° C and 130 ° C, preferably from about 60 to 110 ° C, especially from about 70 to 100 ° C. The starting temperature of the reaction mixture can be between about 4 ° C and about 40 ° C, preferably at about 10 ° C to about 25 ° C, more preferably at 8 to 12 ° C are set.

The polymerization can be carried out in a protective gas atmosphere.

Examples of suitable shielding gases are nitrogen or argon. However, the polymerization can also be carried out under ambient air.

The starting compounds can be reacted by various methods. According to one embodiment, a mixture of all monomers from which the crosslinked copolymer is to be prepared, under

Polymerization conditions set. In such a one-step process, crosslinking, i. the formation of crosslink bridges, simultaneously with the chain growth of the main group of the copolymer. Alternatively, an oligomer, polymer or copolymer can also be prepared in a first step from at least two monomers and this can then be crosslinked in a second step with at least one further monomer. However, any other method is possible.

The water-absorbability of superabsorbent polymers is not only greatly affected by the compounds selected, their composition or

Degree of crosslinking, but also on the degree of neutralization of the polymer. The degree of neutralization indicates how many of those in the polymer

existing acid groups were neutralized by a base. The indication of 30% degree of neutralization therefore means that 30% of the acid groups present are neutralized. In general, the water absorbency is strongest when the carboxyl groups contained in the polymer are 75% neutralized. As the neutralizing agent, for example, sodium salts, potassium salts, ammonium salts or the salts of organic amines can be used.

Preferably, NaOH is used.

The degree of neutralization of the crosslinked copolymer may be less than 65%. Preferably, about 30% or 40% of the carboxyl groups of the crosslinked copolymer are converted into carboxylate groups, the counterion, depending on the neutralizing agent used, the corresponding alkali cation, the

Ammonium ion or by neutralization with an organic amine resulting quaternary cationic compound. Preferably, the counterion is Na ⁺ .

The neutralization can take place before or after the copolymerization.

For example, the olefinically unsaturated carboxylic acid monomer from which a constituent unit A is derived may be neutralized prior to polymerization. Alternatively, the polymerization reaction may be carried out first and then the resulting moist product may be neutralized thereafter.

The biodegradable, crosslinked copolymer obtained according to the present invention may optionally be washed, dried and pulverized to form the final product.

Optionally, the biodegradable, crosslinked copolymer obtained according to the invention can be postcrosslinked. For example, the product obtained can be sprayed in a mixer with a postcrosslinking agent. Suitable postcrosslinkers are, for example, solutions of Al compounds in water or of long-chain diols or long-chain diamines in organic solvents. Examples of postcrosslinkers are diethylene glycol,

Triethylene glycol, polyethylene glycol, glycerin, polyglycerol, propylene glycol, diethanolamine, triethanolamine or polyoxypropylene. The postcrosslinkers may be used in an amount in the range of 0.001 to 20 mol%, 0.01 to 10 mol% or 0.1 to 5 mol% based on the total content of the monomers used. The postcrosslinking reaction can be carried out at elevated temperature, eg at 40, 60, 80 or 100 ° C. Following the postcrosslinking reaction, the product obtained can be dried again and sieved.

Use of Crosslinked Copolymers As a superabsorbent material, the biodegradable, crosslinked copolymer of the present invention can be used, for example, as a piece or in the form of powder, flakes, films, fibers or sheets. In addition to that

biodegradable, crosslinked copolymer, the superabsorbent material may contain other materials, e.g. Paper, cellulose fibers, perfumes, dyes, disinfectants or antibacterial agents. The superabsorbent material may also contain physical blends with wood, minerals or soil.

According to one embodiment, the superabsorbent material may be used to absorb liquids. These liquids may be, for example, water, aqueous solutions or body fluids such as e.g. Include blood, urine or feces. For example, the superabsorbent material can be used in medical products and personal care products. Examples of medical products are surgical wound material, surgical sponges and swabs or bandages. Examples of sanitary products are sanitary drapes, diapers, tampons, sanitary napkins, napkins, toilet paper, paper towels or small animal bedding and litter.

According to a further embodiment, the superabsorbent material planting and potting soil can be added as a soil additive.

According to another embodiment, the superabsorbent material may be used as packaging material. For example, it can be used as packaging material for foods such as meat, sausage or fish. According to one embodiment, the superabsorbent material is referred to as Packaging material used for substances that are introduced into the soil and should be released after a certain time. Examples of such substances are nutrients for plants. For example, the superabsorbent material can be used in the form of a biodegradable bag which contains a substance to be introduced into the soil and, after being introduced into the soil there after a certain time, is decomposed by environmental influences, thus releasing the contents of the bag.

embodiments

The swellability of the copolymers produced is defined as the uptake of liquid in grams per gram weight of the copolymer in the dried state and is reported in g / g. The swelling capacity was determined by means of a modified teabag test. Demineralized water (demineralized water) was used as the test solution.

The tea bag test is carried out as follows: 1 g of the sample (original state) is placed in a tea bag with a size of 80x120 mm and the teabag sealed. Then it is completely immersed in a beaker filled with demineralised water. After the designated time, for example after 24 hours, the tea bag is removed, allowed to drain for 30 minutes on a glass rod and weighed. The amount of water absorbed by the product then results as the difference between the weight of the tea bag before and after the swelling process, whereby the water taken up by the pure tea bag must be taken into account. Taking into account the water content of the product used can be the Determine swellability of the dry product. The specified

Swelling capabilities always refer to the dry product.

The hydrodynamic diameter was determined by means of dynamic light scattering. The molecular weight was determined by gel permeation chromatography (GPC), the concentration of the samples being 1 mg / ml.

The viscosity was determined using a HAAKE MARS II Rheometer (Thermo Fisher Scientific Inc.) at a temperature of 23 ° C. As a sensor PP35 Ti (cone-plate construction) was used, and the moment of inertia was 1,676 x 10 ^"6 kg / m ^2.

Example 1: Polymerization of isoprene-acrylic acid copolymer with

Terephthalic acid bis [2- (2-methyl-acryloyloxy) ethyl] ester and RAMEB-CD

Preparation of terephthalic acid bis [2- (2-methyl-acryloyloxy) ethyl] ester

976 mg of hydroxyethyl methacrylate (HEMA) (7.5 mmol) are dissolved in 15 ml of pyridine. Terephthalic acid dichloride is emulsified in 30 ml of pyridine and added dropwise with stirring to the dissolved HEMA, whereby the acid dichloride dissolves completely during the dropwise addition. After a reaction time of 2 h, the mixture is heated under reflux at an oil bath temperature of 1 15 ° C to boiling. On the following day, the cooled solution is mixed with 50 ml of water and extracted three times with 50 ml of diethyl ether. The combined organic phases are washed with demineralized water (demineralized water), dilute HCl and again with deionised water. The solvent is concentrated at a pressure of 60 mbar and a bath temperature of 40 ° C on a rotary evaporator. Polymerization of isoprene and acrylic acid with terephthalic acid bis [2- (2-methyl-acryloyloxy) ethyl] ester and RAMEB-CD

2.62 g of RAMEB-CD (2 mmol) are placed in a 50 ml two-necked flask and dissolved with 4 ml of demineralized water. After stirring for one hour, 136.2 mg of isoprene (2 mmol) are added and stirred again for one hour. Thereafter, 1.44 g of acrylic acid (0.02 mol) are added and 0.001 mol of terephthalic acid bis [2- (2-methyl-acroyloxy) -ethyl] ester). Thereafter, with external cooling, 0.08 g of 50% sodium hydroxide solution (0.01 mol) was added and the reaction solution was cooled to 10 ° C. The solution is then flushed for 15 minutes with a gentle stream of argon. The initiator used is a redox system. For this purpose each 1

Mol% potassium peroxodisulfate and sodium disulfite dissolved in 2 ml of deionized water and the solutions were added successively to the reaction mixture. The reaction proceeds at room temperature for 24 h. The following day, reaction mixture at a pressure of 65 mbar and a bath temperature of 40 ° C on

Concentrated rotary evaporator and dried the product.

Swellability of the resulting dry copolymer in deionized water: 17.5 g / g ozonolytic degradation

In a cold trap, 100 mg of the product are initially charged and filled with methylene chloride until the inlet tube is immersed in the solution. The cold trap is connected by gas hoses with the ozone generator and then introduced nitrogen for 10 min. The heterogeneous system is cooled to -74 ° C and finally purged with oxygen for 170 min. Subsequently, the

Ozone generator started. The introduced oxygen is converted to ozone. As soon as the ozonolysis of the heterogeneous system is complete, it will turn to color

Excess of ozone blue. After stopping the ozone generator, the solution is purged with oxygen until it decolorizes. Finally, 2 ml of dimethyl sulfate are added to the solution. The reaction mixture is at Thawed at room temperature and stirred overnight. Subsequently, the

Solvent at atmospheric pressure and a bath temperature of 40 ° C concentrated.

The proof that a degradation has taken place, results from the measurement of the hydrodynamic diameter. Hydrodynamic diameter before ozonolytic degradation: 170 nm

Hydrodynamic diameter after ozonolytic degradation: 150 nm

The reduction in hydrodynamic diameter indicates the ozonolytic degradation.

Example 2: Polymerization of isoprene-acrylic acid copolymer with

Terephthalic acid bis [2- (2-methyl-acryloyloxy) -ethyl] ester

Terephthalic acid bis [2- (2-methyl-acryloyloxy) -ethyl] ester is prepared as described in Example 1.

Polymerization of isoprene and acrylic acid with terephthalic acid bis [2- (2-methyl-acrylo-yloxy) ethyl] ester 4 ml of demineralized water are placed in a 50 ml two-necked flask and 136.2 mg of isoprene (2 mmol) are added with stirring and stirred again for an hour.

Subsequently, 1.44 g of acrylic acid (0.02 mol) are added and 0.001 mol of terephthalic acid bis [2- (2methyl-acroyloxy) -ethyl] ester). Thereafter, under external cooling, 0.08 g of 50% sodium hydroxide solution (0.01 mol) and the reaction mixture cooled to 10 ° C. The solution is then flushed for 15 minutes with a gentle stream of argon. The initiator used is a redox system. For this purpose, each 1 mol% of potassium peroxodisulfate and sodium disulfite are dissolved in 2 ml of deionized water and these solutions are added successively to the reaction mixture. The reaction proceeds at room temperature for 24 h. The following day, the Reaction mixture concentrated at a pressure of 65 mbar and a bath temperature of 40 ° C and the product was dried.

Swellability of the resulting dry copolymer in deionized water: 86.5 g / g.

Ozonolytic degradation In a cold trap, 100 mg of the product are initially charged and filled with methylene chloride until the inlet tube is immersed in the solution. The cold trap is connected by gas hoses with the ozone generator and then introduced nitrogen for 10 min. The heterogeneous system is cooled to -74 ° C and finally purged with oxygen for 170 min. Subsequently, the

Ozone generator started. The introduced oxygen is converted to ozone. As soon as the ozonolysis of the heterogeneous system is complete, it will turn to color

Excess of ozone blue. After stopping the ozone generator, the solution is purged with oxygen until it decolorizes. Finally, 2 ml of dimethyl sulfate are added to the solution. The reaction mixture is at

Thawed at room temperature and stirred overnight. Subsequently, the

 Solvent at atmospheric pressure and a bath temperature of 40 ° C concentrated.

The proof that a degradation has taken place, results from the measurement of the hydrodynamic diameter.

Hydrodynamic diameter before ozonolytic degradation: 170 nm Hydrodynamic diameter after ozonolytic degradation: 150 nm

The reduction in hydrodynamic diameter indicates the ozonolytic degradation. Example 3: Polymerization of 2-methylene-l, 3-dioxalane with acrylic acid and hydrolytic degradation

Preparation of 2-methylene-1,3-dioxalane

Stage 1: Synthesis of 2-chloromethyldioxalane 4 g of p-toluenesulfonic acid monohydrate (21 mmol) and ethylene glycol 21 g (338.32 mmol) are initially introduced into a 100 ml two-necked flask and 95.92 g

Chloroacetaldehyde dimethyl acetal (770 mmol) was added. The mixture was refluxed for 1.5 h at 11 1 ° C. Add 30.5 g of cyclohexane to 48.58 g of chloroacetaldehyde dimethyl acetate (389.98 mmol), and add to the mixture and reflux to remove the cyclohexane-methanol azeotrope. There were two phases in the water separator. The lower phase was removed until no longer formed.

Step 2: Elimination reaction to 2-methylene-1,3-dioxalane

29.99 g of 1,4-diazobicyclo [5.4.0] undec-7-ene (DBU) (197 mmol) and 40 g

2-Chloromethyldioxolane (326 mmol) are each dissolved in 50 ml of diethyl ether. In a three-necked flask with dropping funnel, septum, Schliffhermometer and

Magnetic stirrer, the 2-chloromethyldioxolan / diethyl ether mixture is introduced and cooled to 0 ° C by means of ice bath. From the dropping funnel is the

DBU / diethyl ether mixture slowly added dropwise, so that the temperature does not exceed 5 ° C. After completion of the dropwise addition, the product is stirred after 15 minutes and then warmed to room temperature. The solvent is removed on a rotary evaporator at 40 ° C and 12 mbar. It remains a reddish-yellow liquid back. Ring-opening polymerization of 2-methylene-1,3-dioxalane with acrylic acid

In a three-necked flask with magnetic stirrer, reflux condenser and oil bath 21.64 g of 2-methylene-l, 3-dioxalane (250 mmol) are added and added to 150 ml of deionized water and 1 mol% of 1,4-butanediol diacrylate. 87.53 g of acrylic acid

(1250 mmol) are also added and neutralized to a degree of neutralization of 30% with 33% sodium hydroxide solution. Subsequently, the

Reaction mixture cooled to 10 ° C and an aqueous solution of 1.7 g of sodium peroxodisulfate in 15 ml of water and then add a solutions of 0.2 g of potassium disulfite in 5 ml of deionized water. The temperature of the reaction mixture rises to about 95 ° C during the reaction. After cooling, the resulting product is dried in a drying oven at 70 ° C.

Swellability of the resulting dry copolymer in deionized water after 24 h: 342.6 g / g

Hydrolytic degradation 100 ml of the product are placed in a 50 ml flask and combined with a

10% KOH solution. The reaction mixture is refluxed for 24 h at an oil bath temperature of 100 ° C. The next day the product is completely dissolved.

Example 4: Polymerization of 2-methylene-l, 3-dioxalane with acrylic acid and the hydrolytic degradation

2-Methylene-1,3-dioxalane is prepared as described in Example 3. Ring-opening polymerization of 2-methylene-L3-dioxalane with acrylic acid

In a three-necked flask with magnetic stirrer, reflux condenser and oil bath, 10.8 g of 2-methylene-l, 3-dioxalane (125 mmol) are added and added to 150 ml of deionized water and 1 mol% of 1,4-butanediol diacrylate. 87.53 g of acrylic acid (1250 mmol) are also added and neutralized to a degree of neutralization of 30% with 33% sodium hydroxide solution. The reaction mixture is cooled to 10 ° C and then added a solution of 1.7 g of sodium peroxodisulfate in 15 ml of deionized water and then a solution of 0.2 g of potassium bisulfite in 5 ml of deionized water. The temperature of the reaction solution rises during the reaction to about 95 ° C. After cooling, the resulting product is dried in a drying oven at 70 ° C.

Swellability of the resulting dry copolymer in deionized water after 24 h:

H6.6 g / g.

Hydrolytic degradation

In a 50 ml flask, 100 mg of the product are introduced and treated with a 10% KOH solution. The reaction mixture is refluxed for 24 h at an oil bath temperature of 100 ° C. The next day the product is completely dissolved.

Example 5: Polymerization of 2-methylene-4,7-dihydro-1,3-dioxepin with

Acrylic acid in water and hydrolytic degradation Preparation of 2-methylene-4,7-dihydro-L3-dioxepin

Step 1: Synthesis of 2-chloromethyl-4,7-dihydro-1,3-dioxepin

4 g of p-toluenesulfonic acid monohydrate (21 mmol) and 29.78 g of butenediol (338 mmol) are introduced into a 100 ml two-necked flask and 95.92 g

Chloroacetaldehyde dimethyl acetal (770 mmol) was added. The mixture was taken Reflux cooling heated at 111 ° C oil bath temperature for 1.5 h. 48.58 g

Chloroacetaldehyde dimethyl acetate (389.98 mmol) is added with 30 mL of cyclohexane and added to the mixture and refluxed to remove the cyclohexane-methanol azeotrope. There were two phases in the water separator. The lower phase was removed until no longer formed.

Step 2: Elimination reaction to 2-methylene-4,7-dihydro-1,3-dioxepin

29.99 g of 1,4-diazobicyclo [5.4.0] undec-7-ene (DBU) (197 mmol) and 48.44 g of 2-chloromethyldioxolane (326 mmol) are each dissolved in 50 ml of diethyl ether. In a three-necked flask with dropping funnel, septum, Schliffhermometer and

Magnetic stirrer, the 2-chloromethyldioxolan / diethyl ether mixture is introduced and cooled to 0 ° C by means of ice bath. From the dropping funnel is the

Slowly added dropwise DBU / diethyl ether mixture, so that the temperature does not rise above 5 ° C. After completion of the dropwise addition, the product is stirred after 15 minutes and then warmed to room temperature. The solvent is removed on a rotary evaporator at 40 ° C and 12 mbar. It remains a reddish-yellow liquid back.

Ring-opening polymerization of 2-methylene-4H-dihydro-1,3-dioxepin with acrylic acid

In a three-necked flask with magnetic stirrer, reflux condenser and oil bath, 28.03 g of 2-methylene-4,7-dihydro-l, 3-dioxepin (250 mmol) and 150 ml of deionized water and 1 mol% of 1,4-butanediol diacrylate added. To the

Reaction mixture 87.53 g of acrylic acid (1250 mmol) are added and neutralized this to a degree of neutralization of 30% with 33% sodium hydroxide solution. Subsequently, the reaction mixture is cooled to 10 ° C, an aqueous solution of 1.7 g of sodium peroxodisulfate in 15 ml of deionized water and then add a solutions of 0.2 g of potassium bisulfite in 5 ml of deionized water. The Temperature of the reaction mixture increases during the reaction 95 ° C. To

Cooling the resulting product in a drying oven at 70 ° C is dried.

Swellability of the resulting dry copolymer in deionized water after 24 h:

290.5 g / g. Hydrolytic degradation

In a 50 ml flask, 100 mg of the product are introduced and treated with a 10% KOH solution. The reaction mixture is refluxed for 24 h at an oil bath temperature of 100 ° C. The next day the product is completely dissolved. Example 6 Comparison of the Hydrolytic Degradability of the Copolymer of the Invention and a Comparative Copolymer

Sample A (Prior Art): Commercially available superabsorbent material from butanediol acrylate cross-linked acrylic acid

Sample B (according to the invention): Superabsorbent material according to Example 5 Hydrolytic degradation

In a 50 ml flask 100 mg of the sample are presented and mixed with a 10% KOH solution. The reaction mixture is heated to 80 ° C for 4 h.

Subsequently, the viscosity of the sample is determined. T EP2011 / 057641

- 38 -

Results of the viscosity measurement

Sample A: 0.06 mPa s

Sample B: 0.005 mPa-s

The superabsorbent material of the present invention (Sample B) exhibits a significantly lower viscosity as compared to the prior art superabsorbent material (Sample A) which does not have biodegradable break points. The lower viscosity of sample B compared to sample A shows that the superabsorbent material according to the invention is readily hydrolytically degradable.

Example 7 Comparison of the Hydrolytic Degradability of the Copolymer of the Invention and a Comparative Copolymer

Sample A (Prior Art): Commercially available superabsorbent material from butanediol acrylate cross-linked acrylic acid

Sample B (According to the Invention): Superabsorbent Material According to Example 5 Hydrolytic Degradation 100 mg of the sample are placed in a 50 ml flask and admixed with a 10% strength KOH solution. The reaction mixture is heated to 100 ° C for 10 h. Subsequently, the molecular weight of the sample is determined.

Results of molecular weight determination

Sample A: 64650 g / mol

Sample B: 4941 g / mol

The superabsorbent material of the present invention (Sample B) exhibits a significantly lower molecular weight as compared to the prior art superabsorbent material the technique (sample A), which has no biologically fissile predetermined breaking points. The lower molecular weight of sample B compared to sample A shows that the superabsorbent material according to the invention has good hydrolytic degradability and the polymer chains have been split into shorter fragments.

Claims

claims A superabsorbent material comprising a biodegradable crosslinked copolymer comprising  at least one constitutive unit A, wherein the unit A is derived from an olefinically unsaturated carboxylic acid, and  at least one further constitutive unit B, wherein the unit B is adapted to insert at least one biologically cleavable breaking point in the main chain of the crosslinked copolymer, and is derived from a compound according to formula (I)

wherein X and Y are each independently selected from the Group comprising -O-, -S-, -N = and -NR ^a -, wherein R ^{a is} hydrogen or is straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms, R ^{1 is} selected from the group comprising hydrogen and straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl and acyl having 1 to 20 carbon atoms, R ² and R ^{3 are} each independently selected from the group consisting of -CO-, -COO-, -O-CO-O-, -CONR ^b -, -HC = CH-, -O-, -S-, - SO-, -SO ₂ -, - CH ₂ - and -CHR ^C -, wherein R ^{b is} hydrogen or straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms and R ^{c is} hydrogen, hydroxy, Is halogen or straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms, and R ^{4 is} either absent, in which case R ² and R ³ are linked via a single or double bond, or is selected from the group comprising straight-chain or branched optionally substituted alkylene, alkenylene or alkynylene having 1 to 20 carbon atoms, said may be interrupted by -CO-, -COO-, -O-CO-O-, -CONR ^d -, -O-, -S-, -SO- or -SO ₂ - groups, where R ^{d is} hydrogen or straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms. A superabsorbent material according to claim 1, wherein R ^{1 is} -H or -C = CH. 3. Superabsorbent material according to claim 1, wherein the compound of formula (I) is selected from the group consisting of 2-methylene-l, 3-dioxalane, 2-methylene-1, 3-dioxepan, 2-methylene-4,7 dihydro-1,3-dioxepin, 6-methylene-1,11-dioxa-5,7-diazacyclohexadecane-12,16-dione, 2-methylene-1,3,6-triazocane, 2-methylene-1,3 , 5,7-dioxadiazocane, 2-methylene-1,3-dioxacycloundecane-4,1-dione, 2-methylene-1,3,8,1-tetraazacyclopentadecane-9,10-dione, 3-methylene-1 , 2,4,5-tetrazecane-6,10-dione, 2-methylene-1,3,3-dioxathiocane, 6,6-dioxide, (Z) -2-methyl-1,3-dioxepin-4,7- dione, 2-methylene-l, 3, 6-dioxathiocane-6,6-oxide, 2- Methylene-1,3,7,10-tetraoxacyclotridecane, 2-methylene-1,3-diazonane, 2-methylene-1,3,6-dioxasilocane, 2-methylene-1,3-dioxane-4-one, 6, 6-dimethyl-2-methylene-1,3,6-dioxasilocane. A superabsorbent material according to any one of the preceding claims, wherein the crosslinked copolymer comprises at least two units B, wherein the first unit B is derived from a compound of formula (I) and the second unit B is derived from a compound according to formula (II) .

where m is an integer between 1 and 10, and R ⁵ to R ^{10 are} each independently selected from the group comprising hydrogen, straight-chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms, - OR ^e , -COOR ⁶ , - NR !; , -CO-CR ₂ ^e and -SO ₃ R ^e , wherein each R ^e is hydrogen or straight chain, branched or cyclic, optionally substituted alkyl, alkenyl, alkynyl or acyl having 1 to 20 carbon atoms. 5. Superabsorbent material according to claim 4, wherein the compound according to formula (II) is selected from the group consisting of butadiene, isoprene, Chloroprene, dimethyl butadiene, butadiene carboxylic acid or butadiene dicarboxylic acid. 6. A superabsorbent material according to any one of the preceding claims, wherein the cross-linked copolymer comprises at least one further unit C, wherein the unit C is adapted to insert at least one biologically cleavable breaking point in the cross-linking bridges of the cross-linked copolymer. Superabsorbent material according to claim 6, wherein the unit C is derived compound of formula (III) H _X CR _(4-x)  (ΠΙ), where x is 0, 1 or 2 and Each R ¹¹ is independently selected from residues of Formula (IV)

where n is an integer between 1 and 10,  Z is selected from the group comprising -O- and -NH-, R ^{12 is} selected from the group comprising straight-chain or branched optionally substituted alkylene, alkenylene, alkynylene or arylene having 1 to 20 carbon atoms and R ^{13 is} hydrogen or methyl. A superabsorbent material according to claim 7, wherein the compound of formula (III) is selected from the group consisting of adipic acid bis [2- (2-methylacryloxy) ethyl] ester and fumaric acid bis [2- (2) methylacryloxy) ethyl ester. A superabsorbent material according to claim 7, wherein the moiety C is derived from the compound terephthalic acid bis [2- (2-methylacryloxy) ethyl] ester. 10. Superabsorbent material according to one of the preceding claims, wherein the unit A is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. A superabsorbent material according to any one of the preceding claims, wherein the crosslinked copolymer comprises at least one further unit D inserted in the backbone of the crosslinked copolymer. A superabsorbent material according to claim 11, wherein the constituent unit D is derived from a compound selected from the group consisting of acrylonitrile, methacrylonitrile, ethylacrylonitrile, chloroacrylonitrile, Acrylamides, methacrylamide, N-methacrylamide, N-t-butylacrylamide, N-cyclohexylacrylamide, N-ethylacrylamide, styrene, ethene, propene, butene or Methyl (meth) acrylate. A superabsorbent material according to any one of the preceding claims, wherein the crosslinked copolymer is crosslinked with a crosslinker selected from the group consisting of 1,4-butanediol acrylate, methylenebisacrylamide and allyl methacrylate. The superabsorbent material according to any one of the preceding claims, wherein the superabsorbent material additionally comprises paper, cellulosic fibers, fragrances, dyes, disinfectants or antibacterial agents. A process for the preparation of a biodegradable, crosslinked copolymer comprising the copolymerization of at least one olefinically unsaturated carboxylic acid monomer, from which a constitutive unit A is derived, with at least one further monomer, of which is a constitutive unit B according to one of claims 1 to 3 and at least one crosslinker. 16. The method according to claim 15, wherein at least one further monomer is copolymerized, from which a constituent unit B according to one of claims 4 or 5 is derived, and / or at least one further monomer is copolymerized, from which a constitutive unit C according to any one of claims 6 to 9 derived, and / or at least one further monomer is polymerized, from which a constitutive unit D according to any one of claims 11 or 12 derived. 17. Use of a superabsorbent material according to any one of the preceding claims 1 to 14 for the absorption of liquids, preferably for the absorption of water, aqueous solutions and body fluids. 18. Use of a superabsorbent material according to one of the preceding claims 1 to 14 as a packaging material. A hygiene product containing a superabsorbent material according to any one of claims 1 to 14, wherein the hygiene product is preferably selected from sanitary drapes, diapers, tampons, sanitary napkins, napkins,  Toilet paper, paper towels or bedding and litter for small pets. A medical product containing a superabsorbent material according to any one of claims 1 to 14, wherein the medical product is preferably selected from surgical wound material, surgical sponges and swabs or bandages. 21. A packaging material containing a superabsorbent material according to any one of claims 1 to 14. 22. Plant or potting soil containing a superabsorbent material according to any one of claims 1 to 14.