MXPA97004251A

MXPA97004251A - Polycylate lamina excertaating lactic acid, to be used in absorbent articles

Info

Publication number: MXPA97004251A
Application number: MXPA/A/1997/004251A
Authority: MX
Inventors: Larsson Bjorn; Lagerstrom Erik
Original assignee: Moelnlycke Ab
Priority date: 1994-12-13
Filing date: 1997-06-09
Publication date: 1998-07-03

Abstract

The present invention relates to surface material for an absorbent article including the material a surface layer which excreta lactic acid and / or a physiologically acceptable acid derivative thereof when the surface layer is submerged in a volume of water, being 1: 100 the ratio in weight enters the surface layer and the volume of water, in an amount such that the lactic acid and / or the derivative excreted within a period of time of at most 20 hours will confer the water volume a pH of at most 3

Description

POLYLACTIC SHEET THAT EXCRETS LACTIC ACID, TO BE USED IN ABSORBING ITEMS The present invention relates to a material of its surface for absorbent articles in the form of tampons, sanitary napkins, diapers or incontinence guards, for example, preferably tampons and sanitary napkins. It is known that a rich flora of bacteria, mainly producing lactic acid, occur in the urogenital region of healthy women, both before and after menopause. These bacteria have anti-metabolism properties against different existing uropatdgens, which are believed to be due to their ability to produce different antimetabolites. An especially important antimetabolite is, of course, lactic acid, which has an inhibitory effect on different pathogenic microorganisms - by lowering the pH in the urogenital environment. It is also known that lactic acid production is disturbed in conjunction with menstruation, resulting in a decrease in the amount of lactic acid produced. This, of course, will result in a higher pH value, which favors the microorganisms that generate - substances of bad smell, among other things. The development of microorganisms is also susceptible to irritation of the skin and the mucous membrane in the urogenital region. The methods provided by the known techniques for counteracting these problems involve to a wide extent the use of different tampons and sanitary napkins which have been impregnated with different substances that lower the pH value in the present context. For example, Swedish patent documents SE 9100364-0 and SE 8505491-4 describe tampons and compresses that have been impregnated with cultures of live lactic acid bacteria. Even though this type of technical solution might at first appear to be benevolent and sympathetic, since lactic acid bacteria are used that occur naturally-in the urogenital region, a closer study of these descriptive deaths reveals that the technique applied is to the - once very complicated and highly sensitive. For example, it is necessary to isolate bacterial cultures and determine their type before they can finally be incorporated into the tampon or compress with. help of some type of adhesive. Another disadvantage presented with this technique, as stated in the European patent document EP-A1 0.130.356, is that the pH value in the vagina in conjunction with a menstruation is already located in the region. alkaline when the tampon or compress is applied. This inhibits the growth of lactic acid bacteria and thereby reduces their production of lactic acid, or at least results in this production - I greatly fluctuating. The last-mentioned document, EP-A1 0,130,356, in turn describes a tampon whose absorbent body is impregnated with a buffer solution containing citrate. Naturally, a buffer solution of this kind should be considered foreign to the body, at least - in the present context, although the most serious disadvantage with this technical solution lies, also in this case, in the - additional and complicated elaboration operations which are caused by the actual impregnation process in the manufacture of the tampons. Other technical solutions are described in U.S. patent documents. US-A 3,794,034 and DE-AI 2,309,575. These solutions, however, are also hindered by the same disadvantages. A somewhat different technical solution is described in British patent document GB-A-2,107,192, which refers to a ta pdn which may have for example a poly (lactic acid) incorporated in its absorbent mass. It is proposed that this polymer be mixed in the fibrous pulp of the absorbent mass, in a powder, granule or fiber form. This technical solution therefore also needs the application - of at least one additional step in the manufacture of the buffer, specifically the stage in which the poly (lactic acid) is mixed in the fibrous pulp. The purpose of the buffer is to decrease the pH value within the buffer, while, on the other hand, the pH value outside the buffer is allowed to assume values as high as 4.5. PCT patent document WO 91/08726 also describes the use of poly (lactic acid) in absorbent articles, more specifically in the upper and lower sheets of such articles. These sheets, however, are intended exclusively to fulfill a specific purpose, namely that the absorbent article will have to be considered -as it represents an article that is biologically degradable after use. This document makes no mention of the possibility that poly (lactic acid) could be used to adjust the pH value in order to counteract bad odors or an irritation of the skin and mucous membrane. Japanese patent document JP 61-149,160 discloses the use of poly (lactic acid) in absorbent articles for medical purposes. In this case, the poly (lactic acid) is present in the form of a sponge. The only reason given to use precisely poly (lactic acid) is to make the sponge biologically degradable. WO 90/01521 discloses plastic films composed, inter alia, of poly (lactic acid). However, these films of plastic material are intended exclusively for conventional purposes of packaging. The document gives no indication that the film could be used in absorbent articles. There is a clear need for tampons and sanitary napkins biodegradable, with which bad smells and the risk of skin irritation and membra na mucosa in the urogenital region of the user could be to counteract and control of a continuously when the article is in use, and can also be produced in a simple way. The object of the present invention is to create an absorbent article that satisfies this need. This object is achieved, according to the present invention, with the aid of a surface material of the kind mentioned in the introduction, which has the characteristic features set out in the characterizing part of the following claim 1. A surface material of the invention is capable of ensuring that the concentration of lactic acid and / or a lactic acid derivative in the urogenital region of a menstruating woman, using an absorbent article provided with said surface material, is sufficient during use, and remain sufficient during such use, to establish a pH value of at most 4.0 in this region. Different embodiments of the present invention will be apparent from the following claims - subordinated. The outer layer of the surface material will preferably be composed essentially of at least one polyester based on lactic acid or, as this polymer is also called, a polylactide, ie a polymer of the formula H.CH. CH-? i J HO-CH-CO / - -0-CH-C0--7n-0-CH-COOH where n is the number of monomer units in the average polymer chain. The numerical average molecular mass, M, is preferably at most 50,000, and most preferably at most 40,000. It should be noted that the term "lactic acid based polyester" as used in the present context will also include polymers of the above formula wherein one or more hydrogen atoms are replaced by one or more appropriate groups, for example methyl or ethyl. The aforementioned surface layer can be the outermost layer of the surface material, although it can also form a predominant part of the surface material or of all of said material. The surface material can be composed of an outer layer of the an-tedicha class, which has been deposited on a substrate consisting of a high molecular weight polylactide, ie a polylactide for which M > 50,000, although the substrate - may also be composed of some other suitable material, for example a polymer, such as polyethylene, polypropylene, a polyester or other similar; it can also be conceived - that the substrate includes or consists of mixtures of such polymers. The surface material, or in certain cases by at least the substrate, will conveniently have the properties that are normally required of a surface material with respect to its liquid permeability, softness, mechanical strength, stretchability and others. These properties can be imparted to the substrate by introducing different additives, such as for example a softener. According to a preferred embodiment, the lactic acid-based polyester is modified to include relatively large areas of an amorphous material, since it has been found that an amorphous material will hydrolyze more rapidly than a crystalline material, probably because of its greater permeability to water and steam, respectively, which means that the amorphous material will be converted more quickly into lactic acid or a lactic acid derivative. Examples of known methods for adjusting - the crystallinity of a polyester based on lactic acid, for example to obtain a practically amorphous polyester, are described in WO 94/07941 (see for example Example p. 26 in said document). The lactic acid based polyester will naturally contain a given amount of monomers and / or oligomers needed by the laws of nature, for example an α-lactide when the polyester is a polylactide; the concentration in equilibrium with respect to the lactide is usually about 1-3 weight percent, calculated in relation to the polylactide. Since there is reason to suppose that the monomer will decompose rapidly to form the lactic acid and / or a lactic acid derivative instead of the corresponding polyester, the polyester layer is preferably modified to have a higher concentration of monomers and / or oligomers that the concentration in equilibrium. This higher concentration is preferably greater by 10% in units, more preferably by 5% in units than the corresponding concentration in equilibrium. When the polyester is a polylactide, the concentration of monomer or oligomer, ie the concentration of lactide, will preferably be -5-30 weight percent, more preferably 10-25 weight percent, calculated in relation to the polylactide. By an "oligomer" is meant herein a polymer which contains at least 10 monomeric units. Known methods for achieving the above-mentioned increases in concentration are described, for example, in WO 90/01521, see for example page 11, lines 24-32, or page 18, lines. In another preferred embodiment, the The upper sheet or surface layer includes an agent that accelerates the polypolysis of the polyester and / or the conversion of the polyester and / or its monomers / oligomers to form lactic acid and / or a lactic acid derivative., at least when it is taking -the absorbent article. Examples of such agents are mentioned in JP-A 4,168,149 and include enzymes such as lipase, α-lyase, cellulase and enzymes to dehydrogenate lactic acid. By treating the polyester in the surface layer with water and / or water vapor, the polyester can be pre-hydrolyzed so that the polyester will be converted to the lactic acid and / or a lactic acid derivative in a greater extent. that what would otherwise happen, at least when the article is in use. Other embodiments of the present invention will be apparent from the dependent claims of claim 1. In addition to the above methods for modifying a lactic acid-based polyester with the intention of producing more lactic acid during the use in question, there are a number of other known methods for a person skilled in the art in order to achieve such modification, as will be apparent from page 9, lines 17-25, of WO 92/04412. The present invention is described below in greater detail with reference to an Example.

EXAMPLE Different surface stratified materials, which included a polylactide, were immersed in water at room temperature. The pH of the water was measured immediately - after having submerged the material and also after the material had remained submerged for about 20 hours. About 0.4 g of material - in about 40 ml of water in each test - were immersed. It was then possible to calculate the amount of lactic acid released, based on this data. A polylactide film consisting of about 95% polymerized L-lactic acid was used as a reference material; this film is then cited as Film 1. In addition to this film, a non-woven thermally bonded and carded material, a spunbonded non-woven material, cut-off fibers and a non-woven thermally bonded and bonded material made from of these staple fibers; all these polylactide materials were essentially the same type unmodified as that of Film 1.

The surface layer was used as its surface material according to the present invention, in three tests. These surface layers comprised polylactide films that had been modified to include a high concentration of monomer or oligomer. One film had a monomer or oligomer concentration of about 24 weight percent and is referred to below as Film 2. The corresponding concentration in another film referred to as Film 3 was about 11 weight percent. A third film had a concentration of approximately 14 weight percent. The following table sets forth the pH values and the calculated amount of lactic acid liberated as a percentage by weight, based on the original weight of the material implied in the tests carried out with the above materials.

TABLE Lactic acid released Lactic acid released MM x pH immediately in percent in pH after in percent in n Material not mind then weight immediately immersion dumps after 20 homodified 1,000 immersion after immersion for 20 hours immersion flush Film 1 60/135 5, 9 3.2 0.6 Non-woven material thermally bonded and carded 62/137 4.5 0.03 3.5 0.3 Spunbonded non-woven material 85/180 5.8 4.3 0.05 Fibers cut 65/140 4.5 0.03 3.4 0.3 Non-woven material thermally bonded and carded, made of staple fibers 68/139 4.3 0.05 3.1 0.6 TABLE (Continuation) Modified Modified Material, in percent by weight, within the frameworks Film 2 (24%) 37/92 2.8 1.3 2.6 2.5 Film 3 (11%). 35/107 4.0 0.1 3.0 0.9 Film 4 (14%) 33/94 3.7 0.2 0.2 2.9 1.2 i Mn = the numerical average molecular mass Mw = the weighted average molecular mass From the Table it will be observed that the unmodified materials gave the volume of water in question a pH value of at least 3.1 after a treatment for 20 hours, while all the modified materials gave a value of pH of 3.0 or less during a corresponding period of time. The difference in lactic acid released is even more spectacular: in the case of unmodified materials, the highest value was 0.6%, after the lowest value for the modified materials was 0.9%. It will also be observed from the Table that the values of a obtained immediately with the unmodified materials were not less than 4.3 (corresponding to 0.05% of liberated lactic acid), while the highest value of the pH of the Modified materials did not exceed 4.0 (corresponding to 0.1% released lactic acid). Of course, the present invention should not be considered as restricted to the above-described exemplifying embodiments of the same or to the Example, and it will be understood that the invention is restricted only by the following claims, within which scope other embodiments will be conceivable. to a person expert in this -technique. For example, the surface materials of the invention can be used to counteract malodors generated during the use of incontinence pads or protectors.

Claims

1. A surface material for an absorbent article, which includes a surface layer consisting mainly of a lactic acid-based polyester that excretes lactic acid and / or a physiologically acceptable acid derivative thereof, when the surface layer is immersed in a volume of water, in which the weight ratio between the surface layer and the volume of water is 1: 100, in an amount such that the lactic acid and / or the derivative that is excreted within a period of time of at most 20 hours - it will give the water volume a pH of at most 3.0, characterized because before being submerged in the volume of water, the surface layer has a concentration of monomer and / or oligomers (s) that is essentially greater than the equilibrium concentration of monomer and / or oligomer (s) corresponding to the amount of polyester that is present, with the concentration of monomer and / or oligomer (s) being 5% -30 percent by weight calculated with relationship to the polyester.

2. Surface material according to claim 1, characterized in that the concentration of monomer and / or oligomer (s) is 10-25 weight percent, calculated - relative to the polyester.

3. Surface material according to claim 1 or claim 2, characterized in that the polyester-based lactic acid when the surface layer is immersed in said volume of water, is partially converted into and / or out of the surface material. in-lactic acid, and / or the physiologically acceptable acid derivative thereof, said acid and / or said derivative then being excreted.

4. Surface material according to claim 3, characterized in that when the surface layer is immersed in the volume of water, the polyester is partially depolymerized to give a monomer and / or an oligomer which is or is then converted ( s) in lactic acid.

5. Surface material according to claim 3 or claim 4, wherein at least a part of the total amount of the polyester has the formula »Characterized in that the number average molecular mass, M, of this polyester is at most 50,000.

6. Surface material according to claim 5, characterized in that the M is at most 40,000.

7. Surface material according to any one of the preceding claims, characterized in that the concentration of monomers and / or oligomer (s) exceeds the equilibrium concentration up to 10 units of%.

8. Surface material according to claim 7, characterized in that the concentration of mono mer and / or oligomer (s). exceeds the equilibrium concentration to more than 5 units of%.

9. Surface material according to any one of the preceding claims, characterized in that the polyester is a polylactide, and the monomer and / or the oligomer or the oligomers are or are lactides.

10. Surface material according to any one of the preceding claims, characterized in that the surface layer includes an agent that accelerates the conversion of the polyester to lactic acid and / or a lactic acid derivative, at least when the surface layer Surface material according to any one of the preceding claims, characterized in that the surface layer includes an agent that accelerates both the depolymerization of the polyester and the conversion of the polyester and its monomer. in lactic acid and / or a lactic acid derivative, at least when the surface layer is submerged in said volume of water.