Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F226/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen
  • C08F226/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen by a single or double bond to nitrogen
  • C08F226/04—Diallylamine
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents

Definitions

• the present invention relates to a cationic polymer more particularly a water absorbent polymer of the type commonly referred to as a "superabsorbent" .
• superabsorbents are typically slightly cross-linked hydrophillic polymers.
• the polymers may differ in their chemical nature but they share the property of being capable of absorbing and retaining even under moderate pressure amounts of aqueous fluids equivalent to many times their own weight.
• superabsorbents can typically absorb up to 100 times their own weight or even more of distilled water.
• Superabsorbents have been suggested for use in many different industrial applications where advantage can be taken of their water absorbing and/or retaining properties and examples include agriculture, the building industry, the production of alkaline batteries and filters.
• the primary field of application for superabsorbents is in the production of hygienic and/or sanitary products such as disposable sanitary napkins and disposable diapers either for children or for incontinent adults.
• superabsorbents are used, generally in combination with cellulose fibres, to absorb body fluids such as menses or urine.
• body fluids such as menses or urine.
• the absorbent capacity of superabsorbents for body fluids is dramatically lower than for deionised water.
• EP-A-0161762 relates to partially cross-linked copolymers of at least one diallylic quaternary ammonium salt, preferably a diallyldialkylammonium halide.
• the polymers are prepared by inverse suspension polymerisation with an oil phase as the continuous phase and an aqueous phase as the discontinuous phase.
• the polymers which are produced directly in salt form are said to be water-swellable polymers whose water absorbtion properties are not significantly diminished when used to absorb saline solutions.
• the specific example in EP-A- 0161762 relates to a material which has, on the basis of the results reported in the specification, a water absorption capacity in 0.9% by weight NaCl solution only about 20% of its absorption capacity in deionised water.
• the present 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, characterised in that the polymer has been produced by cationic polymerisation in an aqueous phase using a free radical catalyst.
• the present 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, characterised in that at least a substantial proportion of the functional groups are in basic form.
• the present invention provides a process for the production of a waterswellable, 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. It has surprisingly been found according to the present invention that polymerising a diallylic quaternary ammonium salt monomer together with a suitable cross-linking agent by cationic polymerisation in an aqueous phase produces a water-swellable, water- insoluble polymer having significantly improved properties as compared to the polymers of EP-A-0161762. More particularly, the polymer produced by cationic polymerisation in the aqueous phase shows improved water absorption in deionised water and/or in saline solution.
• the polymers of EP-A-0161762 are produced by inverse suspension polymerisation. It is to be expected that the different polymerisation methods as between EP-A-0161762 and the present invention, i.e. inverse suspension polymerisation as opposed to cationic polymerisation in the aqueous phase, will lead to differences in the final product. These differences may reside, for example, in uniformity of cross-linking and uniformity of molecular weight. Whilst these differences cannot be identified and defined, the differences in properties between the products and in particular the improved properties of the product according to the present invention, demonstrate that the products themselves are different.
• the present invention is applicable to any diallylic quaternary ammonium salt monomer which is suitable for the production of water-swellable polymers.
• the monomers have the formula
• R 1 and R 2 which may be the same or different, are each organic radicals which do not adversely affect the properties of the polymer and X is a suitable anion.
• R 1 and R 2 are each independently an optionally substituted saturated hydrocarbon group or aryl group.
• the saturated hydrocarbon group may be an alkyl group which may be straight or branched chain or cyclic.
• the aryl group also includes arylalkyl groups.
• the groups 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 the aryl group may be substituted by one or more suitable substituents selected from carboxyl, ester, hydroxyl, ether, sulphate, sulphonate, primary, secondary or tertiary amines or quaternary ammonium groups.
• R group is a hydrocarbon radical having from 1 to 20, preferably from 1 to 6 carbon atoms, more preferably the R group is methyl.
• suitable substituents include saturated hydrocarbon groups as defined above.
• the preferred groups for R 1 and R 2 are methyl groups.
• X may be any suitable anion which may be inorganic or organic.
• Suitable inorganic anions include halide
• Suitable organic anions include carboxylate such as acetate citrate, salicilate and propionate.
• the anion is a chloride or hydroxide ion.
• Preferred monomers are diallyl dimethyl ammonium chloride and dimethyl diallyl ammonium hydroxide.
• a particularly preferred diallylic quaternary ammonium salt monomer is dimethyldiallyl ammonium chloride.
• n is the number of monomer units.
• Suitable cross-linking agents are generally vinyl compounds with two or more polymerisable double bonds in the molecule.
• Specific examples of cross-linking agents include divinyl benzene and N,N-methylene bisacrylamide.
• the crosslinker should be employed in a sufficient quantity such that the absorbent gelling material (AGM) produced is insoluable when it is in contact with aqueous solutions, however the crosslinker must not be used in such quantities that it interferes with the ability of the AGM to absorb aqueous solutions.
• the amount of crosslinker used in mole % relative to the number of moles of monomer is in the range of from 0.01 to 20% and preferably in the range of from 0.05 to 5%.
• the cationic polymerisation according to the invention takes place in aqueous medium in the presence of a suitable free-radical initiator.
• a suitable free-radical initiator Any free radical initiator of the type conventionally used for cationic polymerisation can be used including organic peroxides, such as hydrogen peroxide, persulphates, such as ammonium persulphate and azo compounds, such 2,2- azobis (2-methyl propionamidine) dihydrochloride.
• Preferred free radical initiators include azo compounds and particularly azobisisobutyronitrile (“AZBN”) .
• the process for polymerization may be conducted as follows:
• a) was disareated with, for example, a vacuum pump. Thereafter b) and c) were added to a) with continuous stirring. The mixture was heating to approximately
• the product was cut to obtain smaller pieces and swelled by adding approximately 4 litres of distilled water thereto. After approximately 2 hours the swelled gel was filtered using, for example, a nonwoven fabric tissue filter.
• the gel was dried, for example, in a ventilated air oven at approximately 60°C for approximately 10 hours resulting in approximately lOOg of dried product.
• the product formed may be converted into basic form by swelling the product in distilled water, adding an alkali solution for example NaOH with continuous stirring, after approximately 1 hour the gel was filtered. Treatment with hydroxide and filtering was repeated until no further chloride ions were present in the washing waters; this may be measured by precipitation titration using silver nitrate (AgN03) .
• the gel was washed with distilled water until the washing water had a pH of 7.
• the product is dried, for example, in a ventilated air oven.
• solution polymerisation in aqueous medium requires addition of fewer components to the reaction medium, for example emulsifiers are not required, and this leads to less impurities in the final product.
• polymerisation proceeds better with a product of higher molecular weight being formed.
• the process according to the present invention leads to a product which can be used as an absorbent for water or saline in either salt or basic form.
• the basic form of the polymer may be obtained from the salt form of the polymer by conversion with alkali as described previously.
• the polymer according to the invention In use in absorbing saline, for example in the form of salt containing liquids such as urine or menses, there are considerable advantages in using the polymer according to the invention in basic form. In this case, at the same time as absorbing the liquid, the polymer also has a desalting effect on the liquid by virtue of the conversion of the polymer into the salt form. As the polymer according to the invention is a strong ion exchanger the polymer will spontaneously convert to the salt form of the polymer when in contact with saline solution.
• the absorbent according to the present invention is particularly suitable for use in applications where it is desired to absorb salt containing aqueous liquids.
• liquids include in particular menses and urine and the absorbent material can be used as the filling in catemenials and diapers generally in admixture with a fibrous absorbent such as cellulose fluff.
• the absorbent according to the present invention in base form can also be used in conjunction with an anionic superabsorbent in free acid form or a cation exchanger in acid form as described in our copending patent applications nos ... (internal reference DR 24) and ... ( internal reference DR 26) respectively.
• the base form is obtained by treatment of the polymer in Cl form with alkali (NaOH 0.01m) as follows:
• the above results show that the polymer according to the invention shows a surprisingly greater absorption that the polymer of EP-A-0161762 both in the case of deionised water and 0.9% NaCl solution.
• the polymer according to the invention can absorb liquid irrespective of whether it is in the salt or base form.
• the monomer solution was disareated by vacuum using a vacuum pump. Thereafter under continuous stirring the crosslinker solution and free radical intiator were added to the monomer solution, the temperature was adjusted to 60°C by placing the flask in a thermostatic bath for four hours.
• the solid product formed was cut using a spatula and transferred in 5 litre beaker containing 41 of distilled water, after two hours the swelled gel was filtered by a nonwoven tissue fabric filter.
• the gel was dried in a ventilated oven at 60°C for 12 hours.
• 60g of dried polymer was collected and called Fai 7 Cl.
• 20g of Fai 7 Cl was placed in a 10 litre beaker and swelled by adding 41 of distilled water, under continuous stirring.
• 500 ml of 0.01 M NaOH solution was added and after 30 minutes the gel was filtered using a nonwoven fabric tissue filter.
• the dried powder was tested for absorbence in deionized water and in a 1% NaCl solution according to the tea bag test as follows :
• AGM 0.3g of AGM was weighed into a tea bag envelope and allowed to swell in a 250ml beaker containing 150ml of
• A absorbency
• Wwet envelope containing the wet AGM in g
• Wdry envelope containing the dry AGM in g
• G dry AGM for the. test in g.

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• 1994
  • 1994-11-10 IT IT94TO000888A patent/IT1267493B1/it active IP Right Grant
• 1995
  • 1995-11-13 EP EP95940680A patent/EP0791019A4/en not_active Withdrawn
  • 1995-11-13 KR KR1019970703146A patent/KR970707182A/ko active IP Right Grant
  • 1995-11-13 CZ CZ19971407A patent/CZ291871B6/cs not_active IP Right Cessation
  • 1995-11-13 WO PCT/US1995/014676 patent/WO1996015162A1/en active IP Right Grant
  • 1995-11-13 AU AU42348/96A patent/AU4234896A/en not_active Abandoned
  • 1995-11-13 CN CN95197178A patent/CN1093139C/zh not_active Expired - Fee Related
  • 1995-11-13 HU HU9801032A patent/HU216321B/hu not_active IP Right Cessation
  • 1995-11-13 BR BR9509638A patent/BR9509638A/pt not_active Application Discontinuation
  • 1995-11-13 JP JP8516229A patent/JPH10509471A/ja not_active Ceased
• 1997
  • 1997-05-09 MX MX9703449A patent/MX213693B/es not_active IP Right Cessation

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