DE102005036992A1 - Super absorbing powder, for e.g. nanofiber products, comprises polymer particles exhibiting a sourceable core and a superficially after-crosslinked shell in the presence of water - Google Patents

Abstract

A super absorbing powder (I) comprises polymer particles, which exhibit in the presence of water a sourceable core and a superficially after-crosslinked shell, where (I) is a sieve fraction of polymer particles, which were not minced after the superficial after-crosslinked of its shell. An independent claim is also included for a use of a nano-non-woven cloths (II) equipped with (I) to the absorption and retention of hydrophilic fluid for the uptake and/or retarded delivery of at least a fluid of body fluids, sweat of humans and animals, water (including cool water, condensation and water vapor), chemicals (including agro chemicals and pesticides), medicaments, biocides, germicide and fungicides, diagnostics, fire protection and fire-extinguishing agent, finery- and cleaning agents, hydraulic fluids, heating- and cooling fluids, waste water (including radioactively contaminated fluids) and perfumery.

Description

The The invention relates to a superabsorbent powder, in particular for absorption and retention of body fluids, consisting of polymer particles, one in the presence of water swelling core and a surface postcrosslinked shell and its use for finishing hygiene products based on textile fabrics of fine fibers or filaments with a diameter of less than 10 μm.

"Superabsorbents" are polymers Materials understood that up to a thousand times their mass Can absorb water, whereby they swell to form a gel. Since the water absorption and retention capacity the superabsorber by the "gel blocking" effect, the clumping the swollen or swollen superabsorbent particles, quickly strong limited, one already has various procedures for the superficial Postcrosslinking of the superabsorbent particles proposed to a from the inside to the outside increasing gradient of the degree of crosslinking of the particles, i. a less networked core and a more interconnected shell. Such modified superabsorbent and process for their preparation are from Ullmann's Encyclopedia of Industrial Chemistry, 6th Ed., Vol. 35, pp. 73 ff., 2003, as well known as their use for the equipment of hygiene products, including diapers and other incontinence products, sanitary napkins and wound dressings to be understood.

studies 15 million suffer in Western Europe and approximately in the US the same number of people with urinary incontinence. This health disorder occurs 10 times more common in women on as in men. Approximately 25% women aged 30-59 Years are at least temporary incontinent. But also 10-20% the younger ones Women over the age of 20 are affected. Become in Western Europe annually over 5.2 Billions of pieces Incontinence products such. B. adult diapers consumed. In US will be the annual Expenses for Incontinence products over $ 16.4 billion, of which about 35% in nursing homes attack. This gives rise to the great social and economic Importance of developing improved superabsorbents, specifically to the for such incontinence products used textile fabrics, mostly non-woven fabrics, adapted are.

incontinence products The primary task is to absorb urine, to absorb it firmly and effectively bind. It should keep moisture away from the skin and suppresses odor become. This is achieved by a multilayer structure of foil as liquid barrier to the outside, various nonwovens to control the distribution of liquid and superabsorbers for safe fluid absorption achieved.

Next this technical functionality is a certain wearing comfort, good fit, discretion (distribution channels, Volume, crackling / rustling) and hygienic handling he wishes.

incontinence products enable already less affected individuals a largely normal Everyday life. Nevertheless, mobility is limited and stay on an environment with a sanitary Infrastructure is limited, not least the social and professional Situation influences.

in the Trap stronger Incontinence occur these impairments Especially, as it is with today's materials and designs of incontinence products succeeds although the technical problems to master, but at the expense of comfort, fit, discretion and handling.

There Incontinence is a social taboo subject, has the socio-psychological Component of this disorder especially among younger ones Women have a special meaning that goes as far as isolation, loneliness and loss of self-confidence and autonomy.

Here can new materials for to remedy the use in novel incontinence products, especially the need after discretion by low volume, small thickness, low noise and high wearing comfort account.

It is already known from US Pat. No. 5,629,377 to use superabsorbent powders from superficially postcrosslinked polymer particles for finishing diapers and other incontinence products. However, it has been found that commercially available superabsorbent powders in combination with microfibrous webs, which are preferred for reasons of a dry skin surface as possible for users of these products, are not yet optimal. They were not easy to process, were not perfect in the fleece integrated structure and swelled when wetting from the nonwoven structure.

Of the Invention is based on the object, a special for the combination indicate superabsorbent powder suitable for ultrafine fiber webs, its use in the equipment of hygiene products for improved discretion, improved comfort and more economical manufacturing capabilities.

These Task is according to the invention in a Superabsorbent powder of the type mentioned solved in that the powder a sieve fraction of such polymer particles is that after the surface post-crosslinking their shell have not been crushed.

It that is surprisingly shown that the usual Superabsorbent powder even if they have an optimal grain size and a suitable particle size distribution for a certain ultra-fine fiber fleece had, therefore failed, because in the course of their production several times, even after their post-crosslinking, have been crushed, reducing the core / shell structure of the particles was injured and the gel blocking effect started again. Thereby were optimal water uptake and water retention values for ultrafine fiber webs unreachable, although with "normal" or coarser fiber webs useful results with the same conventional superabsorbent powders could be achieved. First as carefully sieved, not crushed Particles were selected as superabsorbent powder and in combination with Feinstfaservliesen were used, presented the desired optimal water absorption and water retention values.

If the sieve fraction used has a particle size distribution of d50 = 55 up to 100 μm and d100 = 100 to 150 μm have, according to the invention, the best Results achieved in combination with Feinstfaservliesen. The indication "d50 = 55 μm "means that 50% by weight the particles have a grain size of up to to 55 μm, So 55 microns or less, own, and "d100 = 100 μm "means that 100 wt .-% of the particles have a grain size of up to to 100 μm own, so no particle larger than 100 μm.

Preferably is the polymer that makes up the superabsorbent particles (Meth) acrylate or (meth) acrylic copolymer, particularly preferred Sodium polyacrylate.

The Superabsorbent powder of the selected Sieve fraction according to the invention for the equipment of hygiene products based on textile fabrics of fine fibers or filaments with a diameter of less than 10 μm used. Preferably, the fibers or filaments have one Diameter less than 1 μm. Such microfibers are referred to as micro or nanofibers.

The Use of superabsorbent powders to equip hygiene products based on nanofiber nonwovens, in particular of electrostatically Woven nanofibers manufactured hygiene products has become proved to be particularly advantageous, which will be explained in more detail below becomes.

Preferably The fibers or filaments consist of thermoplastic and hydrophilic or hydrophilized, melt-spinnable polymer, wherein polyurethane is particularly preferred.

When Hygienic products according to the invention preferably diapers and other incontinence products, sanitary napkins and wound dressings fluid absorbent equipped.

preferred Result of the use according to the invention is thus an elastic, superabsorbent fleece made of nanofibers for the Use in novel hygiene articles, especially in incontinence products with improved wearing comfort, secure odor retention and increased discretion. The hygiene article consists of a nonwoven fabric made of thermoplastic Polyurethane, in the superabsorbent powder of polyacrylate with a special particle size distribution and a special post-crosslinking is mechanically integrated. Of the Percentage of special superabsorbent can be up to 85% by weight of the total weight of the equipped Textile amount.

The Advantages of the invention prove in the discretion, the comfort and the production of the equipped textile fabrics or hygiene articles:

1. Improved discretion

Of the reason for Thickness and bulkiness of incontinence products lies primarily in the fact that superabsorbent powder (SAP) swells on contact with water and the particles among each other stick, making more water absorption difficult or prevented becomes (gel blocking). To prevent gel blocking, SAP has been so far always mixed with short cellulose fibers (pulp), which should keep the particles separated from each other. It can the share of SAP is 50% maximum. Pulp has a very low Density, is therefore very voluminous and increases considerably the volume of for the fluid intake required SAP / pulp amount.

Around to circumvent these disadvantages and to be able to do without pulp, thereby but at the same time a big one surface how to ensure SAP itself Various attempts have already been made, the superabsorbent not to be used as a powder, but in a different presentation, eg. As a foam, as a non-woven fabric or in the form coated with superabsorbent Fibers and nonwovens. However, these constructs were not used due to serious disadvantages such. B. strength loss after Wetting, brittleness / brittleness in the dry state or pronounced anisotropy of the wetting behavior.

Of the novel approach of the material according to the invention consists in the individual particles of superabsorbent powder with a defined particle size distribution into an elastic nonwoven structure so that the particles spatially are separated, wet on contact with water over the entire surface and three-dimensionally swell freely, due to the elasticity of the nonwoven matrix the Gelblocking is prevented, as this the increasing space requirements upon swelling of the superabsorbent can follow and thereby the particles largely separated from each other.

2. Improved comfort

By the elastic non-woven structure, which has a high proportion of superabsorbent contains is it possible, currently common, voluminous SAP / pulp mixtures to replace and the disadvantages of conventional To avoid incontinence articles. The thickness is reduced to 1/10. Due to the conformability, elasticity and small thickness of the material according to the invention are the designer of incontinence articles given all possibilities, laundry-like Combine comfort with discretion and technical performance.

3. Simplified Production process of hygiene products

Furthermore a simplification of the diaper manufacturing process is achieved by a diaper machine upstream consuming treatment plants were for pulp and plants for mixing SAP with Pulp are replaced by template the elastic, superabsorbent nonwoven in the form of webs, strips or roll goods. additionally any diaper construction is simplified because of construction elements how Tissue and Corewrap can be dispensed with. The diaper construction reduces to z. B. an elastic, breathable membrane, on the subject invention (elastic absorbent fleece) applied during the manufacturing process and the cover with a distribution and / or cover fleece. It already can in the manufacturing process of the material according to the invention this to a Membrane or foil as carrier material be applied and in the subsequent process step with conventional nonwovens be covered. In the composite thus obtained corresponds to the membrane or foil conventional backsheet, the material of the invention conventional Absorbent Core and the cover fleece the distribution layer or topsheet or both with suitable construction.

4. smell

conventional approaches for odor binding assume that volatile, mostly aminic compounds as a smell carrier formed by bacterial decomposition of urinary ingredients. Accordingly, by adjusting the degree of neutralization of the Superabsorber, by using pH buffers or bacteriostats tries to stop the multiplication and activity of microorganisms to command. Here is the use of bacteriostats or even Bactericides because of the associated risks of producing allergies, extremely controversial.

However, based on the fact that urine odor is essentially the smell of ammonia gas formed by enzymatic decomposition of urea, although the active enzyme is used by microorganisms for metabolizing urea, the activity and the appearance of the enzyme are not living cells is bound, the novel approach to solving this problem is conventional The incontinence article is not to combat microorganisms, but to block the efficacy of enzymes that break down urea by specific enzyme blockers.

Of the Replacement of conventional Allergy-producing cell toxins such as bactericides by known harmless enzyme blockers limited Odor-binding techniques not only on patients or cases, at which has a corresponding benefit / risk balance, but enables one wide application to improve the quality of life of incontinents.

The Enzyme blockers can be added to the spinning mass in the production of the elastic nonwoven and after diffusion at the surface the fibers can be effective, or they can subsequently in the form of an impregnation on the fiber surface be applied.

5. Textiles sheet

Out the literature, z. From US Pat. No. 4,043,331, it is known that with the technology of electrospinning polymers from solution too Nonwovens can be processed from continuous filaments. The Electrospinning is a still relatively uncommon experimental technology for the production of nonwovens. However, it offers the possibility like no other fleece laying technique, endless filaments of different types Polymers, including elastomers, with diameters in the nanometer range to produce and store in the form of a kind of spunbonded and during the Spinning process particles such. As grains or microcapsules (filled with Active ingredients, fragrances u. a., water or temperature activated) to integrate mechanically into the nonwoven structure. There is also the possibility the spinning solution Active ingredients such. As enzymes, enzyme blockers, vitamins, surfactants, wetting agents u. a. inflict, the diffusion due to diffusion to the surface of the spun fibers can unfold their effect there.

D. Smith et. al. report on an elastic nonwoven produced by the electrospinning method made of thermoplastic polyurethane with modifi ed strength of Grain Processing Corp., Muscatine, IA, with the trade designation "Waterlock" as superabsorbent filled is.

This Material already has interesting properties, but not the requirements in terms of specific absorption, speed the fluid intake and maximum filling level with absorber as a substitute for to meet an absorbent core in toiletries.

In Expectation, the requirements for replacement of the modified starch (Waterlock) of the existing material by polyacrylates, such as superabsorbent common in hygiene articles are, fulfill to be able to became commercial Superabsorbent powder on the for the incorporation in described nano-nonwoven appears necessary Grit size crushed and thus produced a superabsorbent containing nano-nonwoven. As expected although a compared to with modified starch (Waterlock) filled fleeces improved absorption behavior found, however, yielded higher filling ratios than 50% no measurable improvement in specific absorption as a result of gel blocking.

Surprised has now been found that particles of superabsorbent sodium polyacrylate suitable grain size, the not by crushing conventional Superabsorbent powder were prepared, but as a sieve fraction superficial postcrosslinked particles were recovered, despite compared to conventional Superabsorbent powder basically delayed Absorption of the total construct of preferably polyurethane nonwoven and superabsorbents clearly superior Lend properties. Only the use of superficially postcrosslinked Superabsorbent powder of polyacrylate or other suitable copolymers with intact core / shell structure and suitable grain size distribution allows fast fluid intake and distribution and high specific absorption at the same time high filling level of up to about 85% of the thermoplastic polyurethane and superabsorbent powder existing superabsorbent nonwovens with diameters of each Filaments in the nanometer to micrometer range.

The The invention is explained in more detail below with reference to examples:

test methods

A. Teabag absorption test (Tb)

The "tea bag" absorption test gives information about the Resistant fluid absorption. A defined amount of an SAP sample is converted into a commercial one Filled tea bags; the teabag is immersed in an excess of 0.9% saline for 30 minutes, then taken out; then you leave the Drain the bag for 10 minutes.

Of the Tb value in [g / g] is the ratio between the absorbed amount of water and the original one SAP amount.

B. Water retention test

Of the Test shows the water retention of the swollen SAP sample. Of the Puffed teabags from the Tb test are placed in a centrifuge and centrifuged at an acceleration of 250 g for 3 minutes.

Of the CRC value in [g / g] is the ratio between the withheld Amount of water and the original SAP amount.

C. Vertical Wicking Effect

Of the Test gives information about the Speed and preferential direction of propagation of water absorption. A 10 × 1 cm big Adhesive tape with adhering SAP sample is spaced from each 1 cm and vertical in a 0.9% NaCl solution until immersed to the first 1 cm mark; the liquid expansion is compensated by adjusting the strip to the mark. The time when the Distance of 1, 2, 3, 4 and 5 cm by rising of the solution reached the tape is measured.

Results

It were nonwovens made of thermoplastic polyurethane and various absorbent materials with different amounts the electrospinning process on a laboratory spinning or pilot spinning plant prepared and subjected to the tests described above.

In the experiments of the invention 3, 4, 6 and 7 came as superabsorbent (SAP) superficially cross-linked sodium polyacrylate powder with core / shell structure for use with a grain size distribution the sieve fraction of d50 about 100μ and d100 approx. 150μ, Tb about 38 g / g and CRC about 22 g / g.

Comparative test 5 was mechanically comminuted (and therefore not according to the invention) and thereafter sieved superabsorbent (SAP) with a particle size distribution of the sieve fraction from d50 about 55μ and d100 from 100μ, Tb about 38 g / g, CRC about 22 g / g performed.

Commercially available SAP in grain size fractions, as they are today in conventional Hygiene articles usual are proved to be too crude. They were not easily processed, were not properly integrated into the nonwoven structure and swelled when wetted out of the nonwoven structure. That's why already first preliminary tests with commercial SAP types set.

The Results of the experiments are summarized in Table 1.

It showed that through the use of superficially crosslinked sodium polyacrylate powder with core / shell structure at fill levels by 50% and a grain size of d50 = 100μ, d100 = 150μ the Water absorption rate reduced from 450 sec. To 80 sec and the water absorption from 29 g / g to 40 g / g or could be increased from 16 g / g to 22 g / g. At 50% filling level is yet no Gelblocking determine, rather surprisingly the Tb as well as the CRC value the theoretical values of the pure SAP. One on a larger pilot spinning line produced pattern of the same composition showed comparable good results and confirmed the reproducibility (experiment 6).

Furthermore, in experiment 5, it was found that there was a violation of the postcrosslinked shell of the SAP particles by mechanical comminution and a concomitant increase in the proportion of smaller particle sizes in the sieve fraction of the SAP adversely affects the speed of liquid absorption and liquid distribution in the web.

Further showed off the attempts that only the combination of elastic Fleece structure with superficial postcrosslinked SAP with intact core / shell structure and suitable grain size for the particularly desirable shaping the essential quality features like speed of fluid intake and distribution and absorption capacity (Tb, CRC) leads. It was surprising found that not a very fine powder is the best effect shows how was expected due to the fine nonwoven structure, but that there is an optimum particle size, which is much coarser is the dimensions of the fleece structures.

Table 1:

• (*) Pilot spinning line

Claims (11)

Superabsorbent powder, in particular for the absorption and retention of body fluids, consisting of polymer particles having a core which swells in the presence of water and a surface postcrosslinked shell, characterized in that the powder is a sieve fraction of such polymer particles which does not break up after the surface postcrosslinking of its shell have been. Superabsorbent powder according to claim 1, characterized that the Sieve fraction a particle size distribution of d50 = 55-100 μm and d100 = 100-150 microns has. Superabsorbent powder according to claim 1 or 2, characterized characterized in that Polymer is a (meth) acrylate or (meth) acrylic copolymer. Superabsorbent powder according to claim 3, characterized that this Polymer is sodium polyacrylate. Use of the superabsorbent powder according to a the claims 1 to 4 to the equipment of hygiene products based on textile fabrics made of ultra-fine fibers or filaments less than 10 μm in diameter. Use according to claim 5, characterized that the Fibers or filaments have a diameter of less than 1 micron. Use according to claim 5 or 6 for the equipment of Hygiene products based on nanofiber nonwovens. Use according to claim 7 for the equipment of made of electrostatically spun nanofibers hygiene products. Use according to one of claims 5 to 8, characterized in that the fibers or filaments te consist of thermoplastic and hydrophilic or hydrophilic, melt-spinnable polymer. Use according to claim 9, characterized that the Fibers or filaments made of polyurethane. Use according to one of claims 5 to 10 for the equipment of Incontinence products, sanitary napkins and wound dressings.