CZ140797A3 - Cationic polymer - Google Patents

Abstract

The invention provides a water swellable, water-insoluble polymer comprising units derived from a diallylic quaternary ammonium salt monomer cross-linked by a suitable polyfunctional vinyl compound, at least a substantial proportion of the function groups being in basic form. The invention also provides a process for the production of a water-swellable, water-insoluble polymer which comprises polymerising a diallylic quaternary ammonium salt monomer and a suitable polyfunctional vinyl compound as cross-linking agent by cationic polymerisation in an aqueous phase using a free radical catalyst and polymers obtainable thereby. The water absorbent polymers are superabsorbents having improved water absorption properties particularly in respect of saliva solution.

Description

(57)

A water-swellable, water-insoluble polymer comprising units derived from a diallyl quaternary ammonium salt monomer crosslinked with a suitable polyfunctional wool compound, wherein at least a substantial proportion of the functional groups are in basic form. A process for making a water-swellable water-insoluble polymer comprises polymerizing a diallyl quaternary diammonium salt monomer and a suitable polyfunctional vinyl compound as crosslinking agent by cationic aqueous phase polymerization using a free radical catalyst to form a polymer. These mode-absorbing polymers are superabsorbents having improved water-absorbing properties, especially when it is a saline solution.

The ionic polymer catalyst

Technical field

The invention relates to a cationic polymer, in particular a water-absorbing polymer of the type commonly referred to as superabsorbent.

BACKGROUND OF THE INVENTION

These substances, currently referred to as superabsorbents, are usually slightly crosslinked hydrophilic polymers. Chemically, these polymers may vary, but share a common ability to absorb and retain, even at moderate pressure, water fluids in an amount equivalent to many times their own weight. For example, superabsorbents can usually absorb up to 100 times, or even multiple times, distilled water relative to their own weight.

Superabsorbents are designed for use in many different industrial applications benefiting from their ability to absorb and / or retain water, and examples of such applications include agriculture, the construction industry, the production of alkaline batteries and filters. However, the primary application field for superabsorbents is the production of sanitary and medical devices such as disposable sanitary napkins and diapers for either children or incontinent adults. In these sanitary and / or medical products, superabsorbents are generally used in combination with fibrous cellulose to absorb body fluids such as menstrual bleeding or urine. Unfortunately, the absorption capacity of superabsorbents is significantly lower for body fluids than for deionized water. It is generally believed that this effect results from the electrolyte content of body fluids and this phenomenon is often referred to as salt poisoning.

The properties of superabsorbents regarding water absorption and water retention are due to the presence of ionizable functional groups in the polymer structure. These groups may be carboxyl groups, the high proportion of which in the dry state is in the form of a salt, but which is subject to dissociation upon contact with water. Thus, in the dissociated state, the polymer chain will have a series of functional groups attached to the chain, where these groups have the same electrical charge and thus repel each other. This leads to the expansion of the polymer structure, which in turn allows for further absorption of water molecules, although this expansion is subject to the barriers provided by the cross-linking of the polymer structure, which must be sufficient to prevent dissolution of the polymer. The presence of significant concentrations of electrolytes in water is believed to interfere with the dissociation of functional groups and lead to an effect called salt poisoning. Although most commercially available superabsorbents are anionic superabsorbents, it is also possible to prepare cationic superabsorbents in which the functional groups are, for example, quaternary ammonium groups. These materials, in order to have the properties of superabsorbents, also require them to be in the form of a salt and are also influenced by the phenomenon of salt poisoning.

EP-A-0161762 relates to partially crosslinked copolymers with at least one diallyl quaternary ammonium salt, preferably diallyldialkylammonium halide. These polymers are prepared by inverse suspension polymerization using an oil phase as a continuous phase and an aqueous phase as a discontinuous phase. These polymers, which are produced directly in the form of a salt, are said to be polymers that increase the volume of water and whose water absorption parameters are not significantly reduced when used to absorb saline solutions. However, according to the specific example given in EP-A-0161762 and based on the results reported in the description, the material has a water absorption capacity using 0.9% NaCl solution only about 20% relative to the absorption capacity in deionized water.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a cationic polymeric water absorbent having improved water absorption parameters, in particular water absorption properties with respect to saline solutions.

According to one aspect of the invention, the invention provides a water-expansion and water-insoluble polymer comprising units derived from a diallyl quaternary ammonium salt monomer crosslinked with a suitable polyfunctional vinyl compound, characterized in that the polymer is produced by cationic aqueous phase polymerization using a catalyst with free radicals.

According to another aspect of the invention, the invention provides a water-bulking and water-insoluble polymer comprising units derived from a diallyl quaternary ammonium salt monomer crosslinked with a suitable polyfunctional vinyl compound, characterized in that at least a substantial proportion of functional groups is in basic form.

According to yet another aspect of the invention, the invention provides a process for producing a water-bulking and water-insoluble polymer comprising a monomer polymerizing diallyl quaternary ammonium salts and a suitable polyfunctional vinyl compound as crosslinker by cationic aqueous phase polymerization using a free radical catalyst.

Surprisingly, it has been found that the process of the invention provides cationic polymerization in the aqueous phase of a polymerizing monomer of a diallyl quaternary ammonium salt together with a suitable cross-linking agent, a water-bulking and water-insoluble polymer having significantly improved properties compared to polymers prepared according to EP-A- 0161762. In particular, the polymer produced by cationic aqueous phase polymerization has improved water absorption in deionized water and / or brine.

As already mentioned, the polymers of EP-A-0161762 are prepared by inverse suspension polymerization. It will be appreciated that the different polymerization methods used in EP-A-0161762 and the process of the invention, i.e. inverse suspension polymerization to cationic aqueous phase polymerization, will lead to differences in the final products. These differences may consist, for example, in uniformity of crosslinking and uniformity of molecular weight. Although these differences have not been identified and defined, the differences between these products, and in particular the improved properties of the product of the invention, demonstrate that they are different products.

The invention can be applied to any quaternary ammonium salt monomer suitable for the production of water-swellable polymers. In principle, these monomers have the following formula:

^CH 2 -CHR ¹ CH = CH 2

H, CN-CHR ^k in which R ¹ and R ² , which may have the same or different meanings, are organic radicals which do not adversely affect the properties of the polymer and X represents a suitable anion.

Preferably, each of R ¹ and R ^{2 is a} separate and optionally substituted saturated hydrocarbon or aryl group. The saturated hydrocarbon group may be, for example, a straight or branched chain alkyl group or a cyclic group. Said aryl also includes arylalkyl groups. Preferably, R ¹ and R ^{2 have} from 1 to 20 carbon atoms, more preferably from 1 to 6 carbon atoms. The saturated hydrocarbon group or aryl group may be substituted by one or more substituents selected from the group consisting of a carboxyl, ester, hydroxyl, ether, sulfate, sulfonate, primary, secondary or tertiary amine or quaternary ammonium group. In the case of the ester (-CO ^R) and ether (-OR) groups, the R group is a hydrocarbon radical of 1 to 20, preferably from 1 to 6 carbon atoms, and more preferably the R group is methyl. In the case of aryl groups, suitable substituents include saturated hydrocarbon groups as defined above. Preferably, R ¹ and R ^{2 are} methyl.

X may be any suitable anion, which may be inorganic or organic. Suitable inorganic anions include halide (especially fluoride, chloride, bromide and iodide), nitrate, phosphate, nitrite, carbonate, bicarbonate, borate, sulfate and hydroxide. Suitable organic anions include carboxylate such as acetate, citrate, salycilate and propionate.

A preferred anion is a chloride or hydroxide ion.

Preferred monomers are diallyldimethylammonium chloride and dimethyldiallylammonium hydroxide.

A particularly preferred diallyl quaternary ammonium salt monomer is dimethyldiallylammonium chloride.

Polymerization of the diallyl quaternary ammonium salt monomer in the presence of a free radical initiator yields a linear polymer according to the following scheme:

CH = CH R CH = CH ² I ² I L_

HjC —K® - CH ₂ i?

χθ

CH, -CH-CH-CH,

Kterémθ in which n represents the number of monomer units. To ensure that the polymer is insoluble when swelling with water, it is necessary to crosslink the polymer to a sufficient degree by introducing a suitable crosslinking agent into the polymerization reaction.

Generally, suitable crosslinking agents are vinyl compounds with one or more polymerizable double bonds in the molecule. Typical examples of crosslinking agents include divinylbenzene and Ν, Ν-methylenebisacrylamide. The crosslinking agent should be used in sufficient quantity to render the absorbent gelling material (AGM) insoluble upon contact with aqueous solutions, but the crosslinking agent must not be used in amounts that interfere with the ability of the AGM to absorb the aqueous solutions.

The amount of cross-linking agent used in mole% based on the number of moles of monomer is in the range of 0.01% to 20% and preferably in the range of 0.05% to 5%.

The cationic polymerization of the invention takes place in an aqueous medium in the presence of a suitable free radical initiator.

Any free radical initiator commonly used for cationic polymerization including organic peroxides such as hydrogen peroxide, peroxodisulfates such as ammonium peroxodisulfate and azo compounds such as 2,2-azobis- (2-methylpropionamidine) dihydrochloride can be used. Preferred free radical initiators include azo compounds and especially azo-bis (isobutyronitrile) (AZBN).

The polymerization process can be carried out as follows:

Prepare the following solutions:

(a) 60% aqueous monomer solution.

b) A solution of the crosslinking agent in distilled water at a concentration of about 230 g / l.

c) Free radical initiator solution in distilled water at a concentration of about 60 g / l.

Solution a) is vented, for example, by means of a vacuum pump. Thereafter, solutions b) and c) are added to solution a) with continuous stirring. The mixture is then heated to about 60 ° C. After about four hours a solid product formed. This product is cut into small pieces and allowed to swell by adding about 4 liters of distilled water. After about 2 hours, the swollen gel is filtered, for example using a nonwoven fabric filter. The gel is then dried, for example, in a hot-air oven at about 60 ° C for about 10 hours to give about 100 g of dried product.

The resulting product can be converted to base form by allowing it to swell in distilled water, adding a solution of an alkaline reagent such as NaOH with continuous stirring, and after about 1 hour the solution is filtered. The treatment with hydroxide and filtration are repeated until chloride ions are no longer present in the aqueous filtrates; these can be determined by precipitation filtration with silver nitrate (AgNO ₃ ). The gel is then washed with distilled water until the pH of the wash water reaches pH 7. The product is then dried, for example, in a hot-air oven.

Apart from the differences in the nature of the product, the process according to the invention, which comprises aqueous solution polymerization, has advantages over the suspension polymerization process of EP-A-0161762 in terms of the actual embodiment. In particular, polymerization in aqueous solution requires the addition of fewer components to the reaction medium, for example, it is not necessary to add emulsifiers, resulting in fewer impurities present in the final product. In addition, the polymerization proceeds better and produces a higher molecular weight product.

The process according to the invention results in a product which can be used as an absorbent of water or a saline solution, either in salt form or in basic form. The base form of the polymer can be obtained from the polymer in the form of a salt by conversion with an alkaline reagent as described above.

For use in absorbing salts, for example in the form of salt-containing fluids such as urine or menstrual bleeding, the use of the polymer of the invention in basic form provides significant advantages. In this case, at the same time as liquid absorption, the polymer also has a desalting effect on the liquid due to the conversion of the polymer to a polymer in the form of a salt. Since the polymer of the present invention is a strong ion exchanger, on contact with a saline solution, the polymer is spontaneously converted to a salt polymer.

The absorbent of the invention is particularly suitable for use in such applications where it is desirable to absorb salt-containing aqueous fluids. Examples of such fluids include, in particular, menstrual bleeding and urine, and the absorbent material can be used as a filler in sanitary or hygiene articles and diapers, generally in admixture with a fibrous absorbent such as cellulosic felt. The absorbent of the invention in base form can also be used in conjunction with an anionic free acid superabsorbent or a cationic ion exchanger in acid form as disclosed in our co-pending patent applications (internal DR 24) and (internal DR 26).

The invention is illustrated by the following examples.

DETAILED DESCRIPTION OF THE INVENTION

Example 1 g of a 60% aqueous solution of diallyldimethylammonium chloride is mixed with 0.0172 g of Ν, Ν-methylenebis (acrylamide) (crosslinking agent) under continuous stirring in a vacuum flask. Nitrogen was bubbled into the reaction vessel for 15 minutes, then 0.015 g of ammonium persulfate (free radical initiator) was added and the reaction mixture was heated to 70 ° C for 3 hours while stirring with a magnetic stirrer. until the magnetic rod is prevented from moving. The polymer forms gel solutions and becomes solid.

A large volume of deionized water is then added to the polymer and the polymer is allowed to swell for 24 hours to form a swollen gel. The swollen polymer is then dried in a forced-convection oven at 100 ° C for 10 hours, and the dried polymer is pulverized mechanically. The polymer thus obtained is in the form of a salt. The base form of the polymer is obtained by treating the polymer in Cl form with an alkaline reagent (NaOH 0.01 mol / l) as follows:

g of polymer is placed in a 10 liter vessel and 4 liters of distilled water are added. After swelling of the polymer, 500 ml of NaOH are added with stirring. After 1 hour, the gel is filtered through a nonwoven fabric filter. NaOH treatment and filtration are repeated until no chloride ions are present in the aqueous filtrate (argentometric titration). The gel is then washed with distilled water until the wash water is neutral (pH 7). This gel is then dried in a ventilated oven at 60 ° C to obtain the desired product.

The dried powder is tested for the absorption of deionized water and 0.9% sodium chloride solution by the procedure described below for Example 2, which is equivalent to that described in EP-A-0161762. The results are shown below:

absorption g / g (bag test) deionized 0.9% NaCl water

Polymer according to Example 1 in salt form 320 55 Polymer according to Example 1 in basic form 350 48 Polymer according to EP-A-0161762 160 31

The above results show that the polymer of the invention surprisingly has greater absorption to the polymer of EP-A-0161762, both for deionized water and for 0.9% NaCl solution. The polymer of the invention absorbs fluid regardless of whether it is a salt form or a base form.

Example 2

Preparation of Fai 7 OH

Weigh 133 g of a 60% aqueous dimethyldiallylammonium chloride solution (DMAC, available from Fluka) into a 250 mL flask.

0.2 g of bisacrylamide (BAC, available from Fluka) are separately weighed into a 5 ml tube and dissolved in 2 ml of distilled water.

Dissolve 0.12 g of ammonium persulphate (free radical initiator) in a 5 ml tube in 2 ml of distilled water.

The monomer solution is vented under vacuum using a vacuum pump.

The solution of the crosslinking agent and the free radical initiator is then added to the monomer solution with continuous stirring while the temperature is adjusted to 60 ° C by placing the flask in a tempered bath for four hours.

The solid product thus formed is then cut with a spatula and transferred to a 5 liter vessel containing 4 L of distilled water and then, after two hours, the swollen gel is filtered on a nonwoven fabric filter. The gel is dried in a ventilated oven at 60 ° C for 12 hours. 60 g of dry polymer, which was named Fai 7 Cl, were obtained. Place 20 g of Fai 7 Cl in a 10 liter flask and swell by adding 4 L of distilled water with continuous stirring. After the polymer swells (after 2 hours), 500 ml of 0.01 M NaOH solution is added and after 30 minutes the gel is filtered using a non-woven fabric filter. These processes (alkalization and filtration) are repeated until there are no chloride ions in the aqueous filtrate (chloride ions can be monitored by reaction with AgNO _a ). At this stage, the gel is washed with distilled water until the alkaline reaction of the wash liquid disappears.

Finally, the gel is dried in a ventilated oven at 60 ° C for 12 hours to give 10 g of the dried polymer named Fai 7 OH.

The dried powder was tested for absorption in ionized water and 1% NaCl solution by the infusion bag test as follows:

0.3 g of AGM is weighed into a sachet pouch and allowed to swell in a 250 ml beaker containing 150 ml of 1% NaCl solution (or deionized water) for 1 hour. The beaker is then removed but the package is left hanging for 10 minutes to allow the unabsorbed water to drip from the bag. The container containing the swollen AGM is then weighed and the amount of absorption calculated as follows:

A = (Wwet - Wdry) / G where:

A = absorption rate, Wwet = mass of the swell containing AGM in g, Wdry = mass of the dry AGM cartridge in g, G = mass of dry AGM used in the test in g.

Absorption rate g / g in the test bag Deionized water NaCl 1%

Claims (21)

KYKTEKTTOYZÉ CLAIMS A water-swellable, water-insoluble polymer comprising units derived from a diallyl quaternary ammonium salt monomer crosslinked with a suitable polyfunctional vinyl compound, characterized in that the polymer is produced by cationic aqueous phase polymerization using a free radical catalyst. 2. A water-swellable, water-insoluble polymer comprising units derived from a diallyl quaternary ammonium salt monomer crosslinked with a suitable polyfunctional vinyl compound, wherein at least a substantial proportion of the functional groups are in basic form. A water-swellable, water-insoluble polymer according to or 2, wherein the monomer has the formula of claim 1 CH ₂ = CH R ¹ CH - =: I ¹ i h] cN -CH ₂ AND R ² in which R ^x and R ² may be the same or different and each represents organic radicals which do not affect adversely the properties of the polymer and X is a suitable anion. The water-swellable water-insoluble polymer of claim 3, wherein R ¹ and R ² are each an independent and optionally substituted saturated hydrocarbon group or aryl group. The water-swellable water-insoluble polymer of claim 4, wherein the saturated hydrocarbon group or aryl group may be substituted with one or more suitable substituents selected from the group consisting of carboxyl, ester, hydroxyl, ether, sulfate, sulfonate, primary, secondary or tertiary amines; quaternary ammonium groups. The water-swellable water-insoluble polymer according to any one of claims 3 to 5, wherein the groups R ¹ and R ² and R groups in the ester and ether substituents have 1 to 20 carbon atoms, more preferably from 1 to 6 carbon atoms. The water-swellable water-insoluble polymer of claim 6, wherein R ¹ , R ² and R are methyl. A water-swellable water-insoluble polymer according to any one of claims 3 to 7, wherein X is a halide, nitrate, phosphate, nitrite, carbonate, bicarbonate, borate, sulfate or cartoxylate anion. The water-swellable water-insoluble polymer of claim 8, wherein X is a chloride or hydroxide anion. A water-swellable water-insoluble polymer according to any one of claims 3 to 9, wherein the monomer is dimethyldiallylammonium chloride or dimethyldiallylammonium hydroxide. The water-swellable water-insoluble polymer of claim 10, wherein the monomer is dimethyldiallylammonium chloride 12. A process for making a water-swellable water-insoluble polymer comprising polymerizing a diallyl quaternary ammonium salt monomer and a suitable polyfunctional vinyl compound as crosslinking agent by cationic aqueous phase polymerization using a free radical catalyst. The method of claim 12, wherein the crosslinking agent is a vinyl compound having two or more polymerizable bonds per molecule. The method of claim 13, wherein the crosslinking agent is divinylbenzene or N, N-methyl-bis-acrylamide. Process according to any one of claims 12 to 14, characterized in that the amount of crosslinking agent in mole percent based on the number of moles of monomer is in the range of 0.01 to 20%, preferably 0.05 to 5%. The process according to any one of claims 12 to 15, wherein the free radical initiator is an organic peroxide, persulfate or azo compound. 17. The process of claim 16 wherein the free radical initiator is hydrogen peroxide, ammonium persulfate or 2,2-azo- (2-methylpropionamidine) dihydrochloride. 18. The method of claim 17, wherein the free radical initiator is 2,2-azo- (2-methylpropionamidine) dihydrochloride. Use of a polymer according to any one of claims 1 to 12 for absorbing an electrolyte comprising aqueous liquids. Use according to claim 19, wherein the fluid is menstrual bleeding or urine. The use according to claim 19 or 20, wherein the polymer is in basic form and is used in conjunction with an anionic superabsorbent in the free acid form or a cation exchanger in acid form.