EP0938347A1

EP0938347A1 - Superabsorbent composition for hygiene articles free from unpleasant smells

Info

Publication number: EP0938347A1
Application number: EP97913262A
Authority: EP
Inventors: Christian Gancet; Serge Nicolas; Yves Taupin
Original assignee: Carbonisation et Charbons Actifs CECA SA
Current assignee: Carbonisation et Charbons Actifs CECA SA
Priority date: 1996-11-13
Filing date: 1997-11-06
Publication date: 1999-09-01
Also published as: WO1998020915A1; FR2755612B1; FR2755612A1; AU5057798A; JP2001505237A; US6277772B1; CA2271982A1

Abstract

The invention concerns a superabsorbent composition containing a superabsorbent polymer powder, for instance polyacrylic and a zeolite powder exchanged with metal cations with bactericidal properties, in particular with silver ions. The hygiene articles incorporating them do not give off nor develop unpleasant smells though soaked with corporeal liquids.

Description

SUPERABSORBENT COMPOSITION FOR HYGIENE ARTICLES WHICH DOES NOT DEVELOP INCOMING ODORS.

Technical Field The present invention relates to the use of bactericidal zeolites containing metal ions to give hydrophilic superabsorbent polymers anti-odor properties.

Superabsorbent polymers (SAP) are used in the manufacture of diapers to improve their absorption capacity for liquids and urine in particular. When the absorbent article is impregnated with urine, it develops various strong and unpleasant odors, including the smell of ammonia coming from the hydrolysis of urea by the ureases of bacteria (Proteus, Acinetobacter, etc.) on the skin and in the digestive tract.

The search for a solution to the odor problem is all the more pressing since, nowadays, the absorption capacity of protective articles for body fluids is very significantly increased by incorporating superabsorbent polymers (SAP) into them. in particular hydrophilic polymers and copolymers of acrylic acid; at the same time, the duration of their retention in place is increased, all conditions favoring the development of microbial and enzymatic activity and the emission of odors which results therefrom.

Prior art

In order to remove these odors, many actions have been taken in the field of hygiene in general, in various ways. For example, extensive use has been made of odor or ammonia absorbents (US 3,340,875 at Scolt Paper Company, US 4,795,482 and 4,826,497 at Union Carbide) combined or not with deodorants, perfumes, etc. We also have recommended the use of oxidants (hydrogen peroxide, chlorine dioxide) as well as bactericides (quaternary ammoniums in particular), antibiotics, complexing agents, surfactants, both alone and in combination. These products pose the general problem of their irritant action on the skin and mucous membranes. Absorbents of odors or ammonia are certainly less dangerous in this respect, but they leave free field to a bacterial proliferation which remains worrying and which should be controlled from the start.

SUMMARY OF THE INVENTION It has now been found that it is possible to formulate superabsorbent polymers with zeolites exchanged by metal ions to make them absorbent compositions which, although soaked in urine or biological liquids, and maintained under the conditions of use, however, conducive to bacterial development, do not give rise to significant release of ammonia, nor to odor emissions, repulsive or simply unpleasant and which communicate this property to the hygiene articles which contain them. The invention thus consists of a superabsorbent composition intended for the production of hygiene articles of the linen, diaper and diaper type which do not develop unpleasant odors, comprising a superabsorbent polymer for water, saline solutions and body fluids. and zeolites exchanged with metal cations endowed with bactericidal properties in the proportion of 0.05% to 10%, preferably 0.1 to 5% relative to the superabsorbent composition.

Superabsorbent polymers are products that meet the definition of superabsorbents, as found in the book "Absorbent Polymer Technology, Studies in Polymer Sciences 8, Elsevier 1990", namely, dry materials capable of soaking up spontaneously from an aqueous fluid at least twenty times its own weight. Superabsorbent polymers within the meaning of the present invention are polymers which result from the polymerization with partial crosslinking of monomers water-soluble ethylenically unsaturated, in particular acrylic acid and methacrylic acid, as well as their alkaline salts, whether obtained by a polymerization process in solution or in reverse suspension. These polymers are endowed with a very high capacity for absorbing and retaining water and aqueous solutions, and today widely used commercially in the form of powders with particle sizes remaining between 100 and 800 μm. Literature is very rich; see for example EP-A-0312952 (The Dow Chem. Co.) and EP-A-0441507 (Sumitomo Seika Chem.).

Zeolites are microporous crystalline aluminosilicates whose structure is that of assemblies tetrahedra Si0 Al0 -and ₄ ^"and <3 ^ue 1 ^'on P ^was represented by a formula expressed as oxides

x M ₂ / _n O; A1 ₂ 0 ₃ ; y Si0 ₂ ; z H ₂ 0

in which M is an alkaline or alkaline earth cation of valence n, where x is a number less than or equal to 1, where y is between 2 and 30, and where z is a number which translates the hydration state of the zeolite. The bactericidal properties of zeolites exchanged with certain metal cations, themselves bactericidal, are known, and they have been used to prepare bactericidal fibers making it possible to manufacture articles of current consumption: socks, underwear, etc. in Japan (US 4,525,410 and 5,064,599, Kanebo). Recently, The Procter & Gamble Cy claimed an absorbent system controlling body odors by incorporating silver-exchanged zeolites in the perforated plastic film which envelops the absorbent (WO 95/24173). Others have housed a layer of such zeolites sandwiched between two sheets of superabsorbent polymer films (JP 63 156540, Dainippon Printing Co). Other patents describe the aqueous dispersion of silver-exchanged zeolites in textile layers (JP 63 097.159, Matsui), or have used them in impregnation of confetti dispersed in the absorbent components of hygiene articles (EP 0389015, Procter & Gamble). With the exception of the very curious synergy between a metallic zeolite and a far infrared radiating ceramic (JO63-210174, OTA), there is no published teaching of compositions containing a superabsorbent polymer and a metallic zeolite. The superabsorbent compositions of the invention are very easily prepared, compositions resistant to the emission of ammonia and of unpleasant odors when they are soaked in body fluids by simple mixing of superabsorbent polymer powder with a particle size between 100 and 800 μm , with a zeolite powder exchanged with metal cations, preferably with a particle size between 0.5 and 20 μm, at a rate of 0.05 to 10% and preferably from 0.1 to 5% by weight of zeolite exchanged with compared to the composition. These exchanged zeolites prepare themselves in a known manner from natural or synthetic zeolites.

More particularly, zeolites A are used for this purpose.

(LTA) or faujasites (FAU), or their mixture. The zeolite powder is suspended in water with stirring, and an aqueous solution of the metal ion with bactericidal property, in particular the Ag ⁺ , Cu ²⁺ , Zn2 + ions, is added thereto. It is recommended to disperse the exchangeable zeolite powder, preferably at pH 7-8 to avoid precipitation of the metal oxide or hydroxide. The useful quantity of Ag ⁺ ions fixed in the zeolite is between 0.01 and 10% by weight, relative to the zeolite, preferably between 0.05% and 5%. The amount of Cu ²⁺ , Zn ²⁺ ions is between 0.1 and 25%, preferably between 0.2 and 15% by weight.

The superabsorbent compositions of the invention gel on contact with water, aqueous saline solutions or body fluids such as the superabsorbents of the prior art, and the gels thus formed behave so substantially identical. They can therefore be used in place of ordinary superabsorbents in the manufacture of hygiene articles such as complete diapers or diapers for babies, children, adults or old men and women.

They do not suffer from any contraindication, the zeolites exchanged with the metal ions Ag ⁺ , Cu ²⁺ and Zn ²⁺ being rightly considered as harmless, on the one hand because these ions are strongly fixed inside zeolitic structure, and on the other hand, because these ions are traditionally and widely used in antiseptic compositions for the skin (Flanamazinc® and Sicazine® 1%; silver sulfadiazine at 1% with Ag content of 0.3% , Dermocuivre®; 0.2% copper sulphate, 10% zinc oxide). Hygiene articles such as complete diapers or diapers for babies, young children, adults or old men and women, comprising these compositions are also objects of the present invention. It is difficult to assess the real effectiveness of anti-odor products. But in the context of bacteria inhibitors to prevent the decomposition of urea into ammonia, one can estimate the effectiveness of the products of the invention, on the one hand, by their ability to limit, even eliminate the bacterial development and , on the other hand, by the release of ammonia in the presence of the various substances with which they are associated in the production of diapers and other sanitary articles, in particular superabsorbent polymers. The efficacy of these products is here quantified by counting the colonies of microorganisms per unit of volume (cfu / ml, set for colon forming units). But it is also necessary to decide on the overall satisfactory result by olfactory tests under conditions which accept the conditions of use of the products in which the superabsorbent composition presumed to inhibit odors is incorporated. They are made by soaking a change in urine under conditions standardized inoculation, by steaming the whole at mild temperature and by subjecting the object to a panel of noses for the global appreciation of its possible bad smells. Such tests are described in the examples given below, which illustrate the unexpected effectiveness of the products according to the invention. In these tests, the superabsorbent polymer used is a partially neutralized polyacrylic acid sold under the name AQUA-KEEP®D (Elf Atochem SA).

Examples

Example 1: Preparation of zeolites exchanged with silver.

100 g of zeolite X (SILIPORITE® G5 from CECA SA), counted in anhydrous equivalent, are placed in suspension in 300 cm ³ of water. The pH of the suspension is lowered from 10.5 to 7 by adding 18 cm ³ of 2N nitric acid. 50 cm ³ of a 0.188 molar silver nitrate solution are added to the suspension. The suspension is then stirred at room temperature for 3 hours. The zeolite thus exchanged with silver is dried at 100 ° C. for 2 hours, then ground using a RETSCH turbine mill equipped with a 0.08 mm grid. The sizes of the zeolite particles are between 0.5 and 20 μm. Under these exchange conditions, almost all of the money involved is exchanged in the zeolitic structure. In fact, only traces of silver are detected in the mother liquors and the washing waters. The zeolite exchanged with silver then contains 1.0% by weight of silver. X zeolites exchanged with 0.5 and 0.2% by weight of silver are prepared in the same way by dividing the molarity of the silver nitrate solution by 2 and 5 respectively. Example 2: Effect inhibiting odor and proliferation of bacteria.

Collection of urine.

The test can be carried out either on a real pooled urine sample, or on synthetic urine prepared when the time comes, according to the following composition:

For 1 1 of H ₂ 0:

Urea 25 g

NaCl 9 g

K ₂ S0 ₄ 4 g

(NH ₄ ) ₂ S0 ₄ 2.5 g

MgS0 0.6 g

Glucose 5 g

Ca (OCOCH ₃ ) ₂ 0.7 g

Yeast extract 5 g

Preparation of the inoculum

The inoculum is prepared with 20 ml of real or synthetic urine, 0.5 g of urea and either 2 g of contaminated fluff (already having an ammoniacal odor), or a selected bacterial strain. The mixture is incubated for

2 days, during which the collected urine is kept at

4 ° C.

At the time of the test, the inoculum has a marked odor, a sign of satisfactory growth.

In the case of isolated strains, the bacteria concentration, expressed in cfu / ml, is measured in order to carry out a reproducible sowing.

Sample preparation

8 hermetic polyethylene boxes are prepared as many times as there are products to be tested. In each box, place a 6 cm x 7.5 cm square of cellulose buffer (fluff) weighing approximately 3 g and containing approximately 0.75 g of superabsorbent dispersed in the mass, with or without the addition of anti-odor products to test. 30 ml of real or synthetic urine, inoculated at the rate of 10 ⁴ cfu / ml, are poured onto each square. The dishes are closed and incubated overnight at 37 ° C in an oven.

Odor evaluation

At the time of the test, the boxes are removed from the oven and offered randomly to the members of the jury who must note the odor between 0 and 5. The absence of NH3 odor is noted 0 and a very strong odor is noted 5. The average of the scores obtained is calculated for each product tested. The results are collated in the table below.

Counting of bacteria After evaluation of the odor, a count of microorganisms is carried out for each type of sample. To do this, the samples are diluted with 70 ml of sterile water and counted using Millipore plates. The result is expressed in cfu / ml.

Result

The control is made with the ordinary superabsorbent, Aqua-Keep®D (SAP). The superabsorbents of the invention are Aqua-Keep D / Zeolite X-Ag (SAP / X-Ag) compositions in variable quantities and at a rate of Ag. The following table relates panel notes (note 0 to 5) and bacteria count (cfu / ml).

Claims

1 - Superabsorbent composition intended for the production of hygiene articles such as linens, diapers or diapers, which soaked in body fluids do not give rise to emission or develop unpleasant odors, characterized in that it consists of:

- a superabsorbent polymer powder, with a particle size between 100 and 800 μm, and

- a zeolite A (LTA) or faujasite (FAU) powder or a mixture of the two, exchanged with cations with bactericidal properties taken from the group consisting of Ag, Cu, or Zn cations or a mixture of these cations , with a particle size between 0.5 and 20 μm.

2 - Composition according to claim 1 characterized in that the metal cation with bactericidal properties is silver and that its proportion in the zeolite is between 0.01 and 10% by weight, preferably between 0.05 and 5%.

3 - Composition according to claim 1 characterized in that the metal cation with bactericidal properties is copper or zinc and that its proportion in the zeolite is between 0.1 and 25% by weight, preferably between 0.2 and 15 %.

4 - Composition according to Claims 1 to 3, characterized in that the proportion of exchanged zeolite powder is between 0.05 and 10% by weight, preferably between 0.1 and 5% by weight relative to the superabsorbent composition .

5 - Hygiene items such as complete diapers or diapers for babies, young children, adults or old men and women, comprising the composition according to claims 1 to 4.