MXPA02004459A - Alkali neutralising superabsorbent products - Google Patents

Abstract

A superabsorbent article of the invention having improved odour control and microbial control, comprises a liquid impervious back layer, a liquid absorbing intermediate layer containing a partially neutralised, acidic hydrophilic polymer, especially a surface crosslinked polyacrylate, and a liquid pervious, non absorbing top layer, and is characterised by comprising an alkali neutralising agent which is evenly distributed in said absorbing intermediate layer.

Description

NEUTRALIZING PRODUCTS OF ALCALI NEUTRALIZING FIELD OF THE INVENTION The present invention relates to a superabsorbent article, which has improved odor control and prevents bacterial growth, and a method of producing said article BACKGROUND OF THE INVENTION Super-absorbent materials for use in baby diapers, feminine hygiene products and in incontinence diapers of various types are known in the art. These usually contain a highly crosslinked hydrophilic polymer, of the partially neutralized polyacrylate type. Without a problem, a problem with such hydrophilic particles is that the granulated polymers have a tendency to agglomerate, in "gel block", which reduces the porosity between particles and limits the speed of expansion. Therefore, currently many superabsorbent materials are of the advanced type, that is, with an additional surface crossover which results in a improved dispersion capacity and increased absorption rate - Surface crosslinking can be effected, for example, with diglycidyl compounds or alkylene carbonates at elevated temperature. This results in membrane-like surface properties and therefore improved water transport (expansion behavior) and better mechanical properties (higher absorption under load) (for a review, see for example, Buchholz and Graham, Modern Superabsorben t Polymer Technology, Wiley - VCH, .998, especially chapter 3: Commercial processes for the manufacture of superabsorben t polymers and chapter 5: The tructure and properti es of superab isorben t polyacrylates, and the references cited therein. ) A problem related to the use of superabsorbent materials is the odor caused by the components of the ori.na, especially ammonia and other alkaline nitrogen compounds. These components cause the superabsorbent materials to be available long before their maximum absorption capacity has been used. In addition, bacterial growth could lead to products that have a bad smell or are irritating to the skin. Therefore, there is a need for materials superabsorbents, which have control of odor and reduced bacterial growth when they come into contact with body fluids, and at the same time retain the characteristics of effective absorption and dispersibility of "modern" superabsorbent polymers It has been proposed to incorporate into diapers pH controlling agents or ammonia-absorbing agents to reduce the problems of odor and bacterial growth and skin irritation ("diaper rash"). EP-A 202,127 discloses absorbent articles of the first generation (which do not have surface cross-linking) that are based on highly neutralized polyacrylate, particulate (> 50%, especially> 65%), in which approximately 10% by weight of the pH control agents polymeric materials such as non-neutralized polyacrylic acid, cellulose phosphate, are distributed non-uniformly in discrete areas of the absorbent article. claim non-polymeric agents for pH control such as citric acid, but are not illustrated in EP-A 202,127. The distribution. non-uniform means that some zones should have a high acid / absorbent ratio of at least 10/1, while that other zones should have a low acid / absorbent ratio not greater than 1/10. It is indicated that the non-uniform distribution is necessary because it is not possible to achieve, without difficulty, a simple combination of agents for pH control with the superabsorbent polymer in the same structure, ie, only with a considerable reduction in the capacity of absorption. EP-A-311,344 describes incontinent absorbent articles for reducing diaper rash, which contain an antimicrobial agent and a pH regulating agent, which together maintain the pH of urine contaminated with Pro teus vulgaris, which contains bicarbonate absorbed, below 7.5. The pH regulating agent is partially neutralized acrylate JL other acid.

BRIEF DESCRIPTION OF THE INVENTION It has been surprisingly discovered that effective odor control can now be obtained by uniformly distributing an alkaline-neutralizing compound (to control pH) of low molecular weight in the absorbent article, and at the same time. time to retain the high absorption power of the non-acid absorbent polymers, including types with sub-surface crosslinking.

DETAILED DESCRIPTION OF THE INVENTION Therefore, the invention pertains to a superabsorbent article having improved odor control and microbial control, comprising a liquid-impervious 1-layer backing, an intermediate liquid-absorbing layer containing a partially neutralized acidic hydrophilic polymer, and a layer liquid-permeable non-absorbent top, and also comprising an alkali-neutralizing agent, wherein the alkali neutralizing agent is distinguished from the partially neutralized acidic hydrophilic polymer and distributed uniformly in said absolving intermediate layer. The superabsorbent polymer can be any type of hydrophilic polymer, typically based on synthetic polymers of unsaturated carboxylic acids, such as polyacrylate and / or polymaleate. Preferably the absorbent polymer is of the crosslinked type on the surface, i.e. of the type having particles with different relatively rigid outer layers and gelled bodies internally with high capacity for relatively weak expansion. Preferably the superabsorbent polymer is not acidic in itself, ie it is sufficiently neutralized in the case of acidic polymers and - without the alkali neutralizing agents it has a pH greater than 5, especially greater than 5.5, more especially higher 5.8, after moistening it, so that it has a sufficient absorbent capacity. Therefore, the acidic polymer has a degree of neutralization of at least 50%, especially between 60 and 80%. Suitable alkali neutralizing agents (acidifying agents) include dicarboxylic acids or polycarboxylic acids such as maleic acid, fumaric acid, oxalic acid, malonic acid, succinic acid and similar acid, and in particular hydroxy acids such as citric acid, gluconic acid, ascorbic acid, glycolic acid, glyceric acid, lactic acid, maleic acid, tartaric acid, salicylic acid and the like, as well as benzoic acid and phosphoric acid and other inorganic acids. These acids can be used in combination with their partially neutral salts (for example, monosodium citrate or morpho-potassium phosphate) to provide a buffering capacity for pH. In addition, they can be The absorption capacity can be expressed as free expansion capacity (FSC) and centrifugal holding capacity (CRC), and with absorption under load (AUL), or with other appropriate parameters, using a modified synthetic urine solution (SU) as the test liquid. The composition of this synthetic urine, which mimics urine also in the sense that it is regulated, is as follows: 300 mM urea, 60 mM KCl, 130 mM NaCl, 2.0 mM CaS04, 3.5 mM MgSO4, 29 mM KH2P04 , 5.3 mM Na2HP04, 1 mg / liter of Triton X-100 in deionized water The superabsorbent articles of the invention can be used to absorb liquids, especially body fluids containing various salts and non-ionic substances, together with alkaline components and / or that generate bad smell. The articles are particularly suitable in the form of hygienic absorbent articles, such as diapers, sanitary napkins, incontinence pads and the like.

Such articles can be produced entirely based on the individual superabsorbent polymers such as polyacrylates and polymaleates, but these can also contain a mixture of absorbent materials, such as different polyacrylates, cellulose derivatives and other polysaccharides. The absorbent article is preferably a stratified product, in which the superabsorbent polymer constitutes at least one layer. The absorbent layer can be placed between a liquid permeable top layer and a liquid impermeable bottom layer. In particular, the product can have four layers. The first may be a thin, non-woven layer of polyester fibers or other fibers. The second layer may be a filler that is used to acquire and disseminate abs orbited fluid such as urine. The third layer may consist of foamed pulp in which the superabsorbent polymer is spread as fine particles, especially 50-800 μm. The last layer may be a front sheet of a material such as polyethylene, which prevents leakage from the stratified absorption product. The product could also have three layers, in which the foamed layer and the absent layer are combined. In any form, the neutralizing compound is distributed evenly with the superabsorbent polymer through d to the foamed material.

EXAMPLE 1 Sanitary towels are produced that have an upper core and a lower core and a size of 10 x 28 cm. The upper core contains MS CTMP pulp (350 g / m2) and 15% by weight superabsorbent polymer (SAP), the lower core contains KEA pulp (310 g / m2) and 21% SAP. Therefore, the total weight of the cores is (0.10 x 0.28 x 350 x 15) + (0.10 x 0.28 x 310 x 1.21) g = 21.8 g. The apparent volume is 8 cm3 / g. SAP is highly neutralized polyacrylate (IM7100) or acid polyacrylate (30% neutralized (IM7110).) IM7100 has a better absorptive power than IM7110.

SAP, an acid is added in the amounts indicated below. The glusonic acid is added as a 50% solution (w / w), the citric acid is added as a powder or as a crushed tablet. The towel is placed in contact with modified synthetic urine (SU, see above) The absorption capacity (AC) in grams of liquid absorbed by the towel per gram of product (superabsorbent polymer plus pulp) is measured. The towel is placed on a Perspex test plate inclined at 30c, submerging the lower 2-3 cm in the test liquid (SU). The acquisition time is measured as the time needed to

Claims (2)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the content of the following is claimed as property: CLAIMS

1. - A superabsorbent articulate that has odor control and contri > 1 improved microbial, comprising a liquid-impermeable post-layer, an intermediate liquid-absorbent layer containing an acidic, partially neutralized hydrophilic polymer, of the cross-linked type, and a non-absorbent, liquid-permeable upper layer; The alkali neutralizing agent is distributed evenly in said absorbent intermediate layer, and said absorbent layer, after moistening it with neutral water, has a pH of 5.6 or less.

2. A euperabsorbent article according to claim 1, further characterized in that the alkali neutralizing agent is an organic acid selected from the group consisting of maleic, fumaric, oxalic, malonic, succinic, citric acid, gluconic, ascorbic, glycolic, glyceric, lactic, malic, tartaric and salicylic, especially citric, malic or lactic acid A euperabsorbent article according to claim 1, further characterized in that the acaling neutralizing agent is selected from the group consists of anhydrides, lactides and lactones, especially dilute, glycolide, but irolactone, valerolactone, gluconolactna and maleic anhydride. 4. - A superabsorbent article according to any of claims 1-3, further characterized by the alkali neutralizing agent being present in an amount of 0.2 to 1 parts by weight per parts by weight of hydrophilic polymer. 5. A euperabsorbent article according to any of claims 1-4, further characterized in that the article contains a cellulose vehicle material in an amount of 2 to 10 parts by weight per parts by weight of hydrophilic polymer. 6. A superabsorbent article according to any of the preceding claims, further characterized in that the hydrophilic polymer comprises polyacrylate 7. - A superabsorbent article of compliance with any of the preceding claims, further characterized in that the acid polymer has a degree of neutralization of at least 50%, especially between 60 and 80%. - A superabsorbent article according to any of the preceding claims, further characterized in that the absorbent layer, after wetting it with neural water, has a pH between 3.5 and 5.0. A superabsorbent article according to any of the preceding claims, further characterized by containing 2.5 to 10 g of hydrophilic polymer 10. A process for producing a superabsorbent article having improved odor control and improved microbial control, comprising mixing a neutralizing agent of alkali with a highly neutralized acidic hydrophilic polymer, with surface crosslinking, distributing the mixture in a fibrous carrier material, processing the carrier material in a layer and covering the layer of carrier material with a liquid impervious layer on the one hand and with a non-absorbent liquid-permeable layer on the other side.