EP2323513B1 - Sweat-absorbing shoe sole inserts having improved sweat absorption - Google Patents

Description

The present invention relates to sweat-absorbent shoe insoles with improved perspiration absorption. It relates in particular to the use of particulate amorphous silica as an absorbent for sweat absorption in shoe insoles.

It is known that the human excretes about 100 liters of sweat per year via the feet, d. H. about 137 ml per day and per foot. Considering that a person in everyday work or even in his free time, for example, while skiing, wearing the same footwear for up to 10 hours continuously, about 60 ml of sweat per foot delivered to the footwear during this time. For humans, however, it is not only uncomfortable to have a constant feeling of damp feet. The moist and warm climate in the footwear also favors the growth of bacteria and the release of unpleasant odors.

There has been no lack of effort in the past to find ways to remedy the problems of the so-called "sweaty foot". Almost all approaches use an insole, which should absorb and store the absorbed sweat preferentially. Multilayer systems are often used for this purpose, with an upper layer in contact with the foot to ensure the transport of perspiration into the interior of the sole, a middle layer to store sweat, and a lower layer in contact with the shoe sole to absorb absorbed sweat. In order to cope with the high levels of secreted perspiration, the material for the middle layer of a shoe insole is usually selected for its ability to absorb and store aqueous fluids. However, activated carbon as a low-cost absorbent has only a comparatively small storage capacity. A comparatively high Storage capacity, in contrast, have so-called "superabsorbent" polymers which are capable of absorbing and storing a multiple of their own weight or volume of liquid. Superabsorbent salts are used, for example, in US Pat DE 691 08 004 T2 is used as the preferred absorbent in the cavities of the mid-layer of a shoe insert, with a membrane permitting the transfer of moisture from one cavity to the other. However, the disadvantage here is the strong swelling of the polymer particles, which can also lead to further fluid absorption being prevented by the so-called "gel blocking".

The DE 35 16 653 A1 describes a footwear in which the shoe interior limiting Shoe moldings are preferably equipped with a molecular sieve. Although molecular sieves are not prone to swell upon absorption of moisture, because of the very uniform pore or channel structure, molecular sieves release the liquid once taken up only under difficult conditions.

The shoe insoles of the prior art thus have the disadvantage that they either have an insufficient welding absorption capacity or tend to swell at the direct location of the sweat absorption. However, in no case can they guarantee that the sweat can be diverted from the direct location of the sweat absorption and distributed evenly over the surface of the shoe insoles. Furthermore, the prior art shoe insoles have the disadvantage that when attempting to regenerate the insoles for further applications, the absorbed perspiration is insufficiently desorbed again, i. H. consistently long drying times and / or high drying temperatures are required.

It was therefore an object of the present invention to provide a shoe insole which has a sufficient perspiration absorption capacity, but which does not swell due to sweat absorption and, moreover, ensures that The absorbed sweat can be spread effectively over the entire shoe sole volume and can be released to the environment just as effectively during regeneration.

Surprisingly, it has now been found that a shoe insole containing particulate amorphous silica satisfies the aforementioned requirements.

The subject of the present invention is therefore an insole having the features of claim 1.

Particulate or particles in the sense of the present invention refers to a three-dimensional body with a defined outer shape, which-depending on the size of the particle-can be determined by means of microscopic methods (light microscope, electron microscopes, etc.). The particles of the invention may be porous, d. H. Have pores and / or internal cavities.

For the purposes of the present invention, all commercially available particulate amorphous silicic acids can be used. The amorphous silica is preferably completely amorphous. In the context of the invention, however, it may also have a smaller crystalline fraction which is for example at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15, at most 10% or at most 5%. The crystalline fraction is determined in a known manner by means of X-ray diffraction. Suitable amorphous silicic acids are, for example, precipitated silicas and fumed silicas. Preference according to the invention is given to commercially available silicas from Evonik Degussa GmbH, which are available, for example, under the trade names Sipernat 2200, Sipernat 22, or Sipernat 50.

It has proved to be advantageous that the silica used according to the invention has a specific surface area (N ₂ ) according to ISO 5794-1 Annex D of between 5 and 500 m ² per g. The silica particularly preferably has a specific surface area of between 50 and 500 m ² , very particularly preferably between 150 and 500 m ² and particularly preferably between 185 and 475 m ² per g.

It has also proved to be advantageous that the silica used according to the invention has a DBP absorption (according to DIN 53601) of at least 180 g per 100 g. The DBP uptake of the silica is preferably in the range from 180 to 600 per 100 g, particularly preferably from 200 to 600 per 100 g, very particularly preferably from 200 to 500 per 100 g and particularly preferably from 250 to 400 per 100 g.

In particular, silicas are suitable whose product of the DBP absorption (according to DIN 53601) and tamped density according to ISO 787/11 at least 30,000 g / 100g * g / l, preferably at least 40,000 g / 100g * g / l, more preferably at least 50,000 g / 100g * g / l and most preferably at least 65,000 g / 100g * g / l.

Moreover, it has also proved to be advantageous that the average particle size d _{50 of} the silica in the range of 5 .mu.m to 500 .mu.m, preferably from 20 .mu.m to 450 .mu.m, more preferably from 30 to 400 .mu.m, and most preferably from 45 to 350 microns is. If the particles are too small, unwanted dust formation can occur. In turn, particles that are too large have the disadvantage that they are often mechanically unstable and have too deep pores, so that the absorption and desorption rates can become too low or parts of the absorbed sweat can no longer be desorbed.

The shoe insoles according to the invention may contain antibacterial agents. In the present invention, antibacterial active ingredients are understood as meaning chemical compounds or natural substances which are capable of inhibiting the growth of microorganisms, such as, for example, microorganisms. As bacteria, yeasts or molds to prevent. As antimicrobial agents known preservatives can be used such. As organic acids (sorbic acid, propionic acid, acetic acid, lactic acid, citric acid, malic acid, benzoic acid) and salts thereof, PHB esters and their salts, sodium sulfite and corresponding salts, nisin, natamycin, formic acid, hexamethylenetetramine, sodium tetraborate, lysozyme, alcohols, organohalogenated Compounds, parabens (methyl, ethyl, propyl, butyl, isobutyl, propylparaben), isothiazolones (benzisothiazolone, methylisothiazolone, octylisothiazolone), phenols, salicylates, nitriles, fragrances, flavors and other herbal or synthetic active substances with antimicrobial activity.

The shoe insoles according to the invention may contain fragrances, flavors or odorants, which are referred to collectively below as fragrances. Such materials are well known and commercially available. As used herein, they include natural (ie, substances extracted, for example, by extraction of plants such as flowers, herbs, leaves, roots, barks, woods, flowers, etc., or animal products), artificial (ie, a mixture of different natural oils or oil components ) and synthetic (ie synthetically produced) fragrant substances or mixtures of these substances. Such materials are often used in conjunction with other compounds such as fixatives, extenders, stabilizers and solvents. These auxiliaries or additives are used in the context of of the meaning of the term "perfume".

• Naturstoffe, wie Baummoos absolut, Basilikumöl, Zitrusfruchtöle (wie Bergamottenöl, Mandarinenöl, etc.), Mastix absolut, Myrtenöl, Palmarosaöl, Öle der Patschulipflanze, Petitgrainöl, insbesondere aus Paraguay, Wermutöl; Alkohole, wie Farnesol, Geraniol, Linalool, Nerol, Phenylethylalkohol, Rhodinol, Zimtalkohol; Aldehyde, wie Citral, Helional, α-Hexylzimtaldehyd, Hydroxycitronellal, Lilial (p-tert.-Butyl-α-methyldihydrozimtaldehyd), Methylnonylacetaldehyd; Ketone, wie Allylionon (1-(2,6,6-Trimethyl-2-cyclohexen-1-yl)-1,6-heptadien-3-on), α-Ionon, β-Ionon, Isomethyl-α-ionon, Methylionon; Ester, wie Allylphenoxyacetat, Benzylsalicylat, Cinnamylpropionat, Citronellyl-acetat, Citronellylethoxolat, Decylacetat, Di-methylbenzylcarbinylacetat, Dimethylbenzylcarbinylbutyrat, Ethylacetoacetat, Ethylacetylacetat, Hexenylisobutyrat, Linalylacetat, Methyldihydrojasmonat, Styrallylacetat, Vetiverylacetat, etc.; Lactone, wie γ-Undecalacton; verschiedene Bestandteile, die häufig zur Herstellung von Parfümen eingesetzt werden, wie Moschusketon, Indol, p-Menthan-8-thiol-3-on und Methyleugenol; und Acetale und Ketale wie Methyl- und Ethylacetale und -ketale, sowie die Acetale oder Ketale, die auf Benzaldehyd basieren, die Phenylethyl-Gruppen enthalten, oder Acetale und Ketale der Oxotetraline und Oxoindane.

Thus, perfumes are usually complex mixtures of a variety of organic compounds. Natural compounds include not only volatiles; these also include medium-volatile and moderately volatile substances. An exemplary composition of fragrances includes, among others, the following compounds:

• Natural substances, such as absolute tree moss, basil oil, citrus oils (such as bergamot oil, tangerine oil, etc.), absolute mastic, myrtle oil, palmarosa oil, patchouli oils, petitgrain oil, especially from Paraguay, wormwood oil; Alcohols, such as farnesol, geraniol, linalool, nerol, phenylethyl alcohol, rhodinol, cinnamyl alcohol; Aldehydes such as citral, helional, α-hexylcinnamaldehyde, hydroxycitronellal, lilial (p- tert -butyl-α-methyldihydrocinnamaldehyde), methylnonylacetaldehyde; Ketones, such as allylionone (1- (2,6,6-trimethyl-2-cyclohexen-1-yl) -1,6-heptadien-3-one), α-ionone, β-ionone, isomethyl-α-ionone, Methyl; Esters such as allylphenoxyacetate, benzylsalicylate, cinnamylpropionate, citronellyl-acetate, citronellylethoxolate, decylacetate, dimethylbenzylcarbinylacetate, dimethylbenzylcarbinylbutyrate, ethylacetoacetate, ethylacetylacetate, hexenylisobutyrate, linalylacetate, methyldihydrojasmonate, styrallylacetate, vetiverylacetate, etc .; Lactones, such as γ-undecalactone; various ingredients commonly used to make perfumes, such as musk ketone, indole, p-menthane-8-thiol-3-one and methyleugenol; and acetals and ketals such as methyl and ethyl acetals and ketals, as well as the acetals or ketals based on benzaldehyde containing phenylethyl groups, or acetals and ketals of the oxotetralines and oxoindanes.

Also suitable are: geranyl acetate, dihydromyrcenyl acetate (2,6-dimethyl-oct-7-en-2-yl acetate), terpinyl acetate, tricyclodecenyl acetate, tricyclodecenylpropionate, 2-phenylethyl acetate, benzyl acetate, benzyl benzoate, styrallylacetate , Amyl salicylate, phenoxyethyl isobutyrate, neryl acetate, trichloromethylphenyl carbinyl acetate, p- tert -butylcyclohexylacetate, isononylacetate, cedrylacetate, benzylalcohol, tetrahydrolinalool, citronellol, dimethylbenzylcarbinol, dihydromyrcenol, tetrahydromyrcenol, terpineol, eugenol, vetiverol, 3-isocamphylcyclohexanol, 2-methyl-3- (p- tert -butylphenyl) - propanol, 2-methyl-3- (p-isopropylphenyl) -propanol, 3- (p- tert -butylphenyl) -propanol, α - n- amyl cinnamaldehyde, 4- (4-hydroxy-4-methylpentyl) -3-cyclohexene carbaldehyde, 4- (4-methyl-3-pentenyl) -3-cyclohexene carbaldehyde, 4-acetoxy-3-pentyltetrahydropyran, 2-n- heptylcyclopentanone, 3-methyl-2-pentyl-cyclopentanone, n- decanal, n- dodecanal , Hydroxycitronellal, phenylacetaldehyde dimethylacetal, phenylacetaldehyde diethylacetal, geranonitrile, citronellonitrile, cedrylmethylether, isolongifolanone, Aubepine Nitrile, Aubepine, heliotropin, coumarin, vanillin, diphenyloxide, ionone, methylionone, isomethylionone, cis-3-hexenol and cis-3-hexenol Esters, musk compounds, which have inter alia an indane, tetralin or isochroman structure macrocyclic ketones, macrolactone musk compounds, ethylene brassylate, aromatic nitromuszo compounds, wintergreen oil, oregano oil, bay leaf oil, peppermint oil, mint oil, clove oil, sage oil, sassafras oil, lemon oil, orange oil, aniseed oil, benzaldehyde, bitter almond oil, camphor, cedar leaf oil, Marjoram oil, lemongrass oil, lavender oil, mustard oil, pine oil, pine oil, rosemary oil, thyme oil, cinnamon oil and mixtures of these substances. The fragrances mentioned can be used individually or as a mixture.

It has proven to be advantageous that the proportion of antibacterial agents and / or perfumes is between 0.01 to 10 wt .-% based on the total weight of all particles. The ideal ratio depends on the chemical nature and physicochemical properties of the antibacterial agents and fragrances as well as the silicic acid and can be determined for each material combination by simple series of experiments. Higher silica loading can cause insufficient sweat to be absorbed into the pores. With particular preference, the proportion of antibacterial agents and / or perfumes based on the total weight of all particles is in the range from 0.01 to 5% by weight, very particularly preferably in the range between 0.05 and 3 wt .-% and particularly preferably in the range between 0.5 and 3 wt .-%.

It has also proved to be advantageous that at least part of the silica according to the invention is present as a carrier for the antibacterial agents and / or perfumes. The proportion of silica particles present as carriers for the antibacterial agents and / or the fragrances is preferably between 5 and 40% by weight, based on the total weight of all particles, more preferably between 5 and 30% by weight, very particularly preferably between 5 and 20% by weight.

The shoe insoles according to the invention may additionally contain particulate superabsorbent polymers. For the purposes of the present invention, superabsorbent polymers are polymers (superabsorbent polymers, SAP) which are capable of absorbing a multiple of their own weight - up to 1000 times - of liquids (usually water or aqueous solutions). The product is used as a white, coarse-grained powder with particle sizes of 100 - 1,000 μm (= 0.1 - 1.0 mm).

Particularly suitable as superabsorbent polymers are polymers of (co) polymerized hydrophilic monomers, (graft) polymers of one or more hydrophilic monomers onto a suitable grafting base such as crosslinked cellulose or starch ethers, crosslinked carboxymethylcellulose, partially crosslinked polyalkylene oxide or natural products swellable in aqueous liquids such as guar derivatives, alginates and carragenans. Preference is given to polymers which are obtained by crosslinked polymerization or copolymerization of acid-group-carrying monoethylenically unsaturated monomers or derivatives thereof, in particular salts, esters or anhydrides. Such acid group-carrying monomers are, for example, monoethylenically unsaturated C ₃ -C ₂₅ -carboxylic acid, its salts or anhydrides. Preferably used monomers are acrylic acid, methacrylic acid, vinylsulfonic acid, acrylamidopropanesulfonic acid or mixtures of these acids. Particularly preferred are acrylic acid and methacrylic acid. To optimize properties, it is possible to use additional monoethylenically unsaturated compounds which do not carry any acid group but are polymerizable with the acid group-carrying monomers. These include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acids.

Crosslinkers may be compounds which have at least two ethylenically unsaturated double bonds. Examples of compounds of this type are N, N-methylenebisacrylamide, polyethylene glycol diacrylates and polyethylene glycol dimethacrylates.

Suitable superabsorbent polymers are described, for example, in the following reference: FL Buchholz, AT Graham (Ed.), Modern Superabsorbent Polymer Technology, Wiley-VCH, New York 1998 ,

In addition, the superabsorbent polymers can be used in combination with copolymers of C ₂ to C ₈ olefins or styrenes with anhydrides to improve the odor-binding properties.

It has proved to be advantageous for the particles of the superabsorbent polymers to have an average particle size d ₅₀ in the range from 5 μm to 300 μm, preferably from 20 μm to 150 μm, particularly preferably from 50 to 150 μm, and very particularly preferably from 50 μm 100 microns have.

The proportion of all particles is preferably at least 20% by volume, based on the total volume of the shoe insole according to the invention, more preferably at least 30% by volume and very particularly preferably at least 35% by volume.

The shoe insole comprises at least two layers, one of which is water and water permeable to water vapor and the other layer is impermeable to water and water vapor, the water- and water-vapor-impermeable layer contains recesses on its side inclined towards the water and water vapor permeable layer, both layers are firmly connected to one another such that the water and water vapor permeable layer forms the recesses on the surface thereof covered side of the water and water vapor-impermeable layer, the wells of the water-vapor-impermeable layer within this layer are interconnected by open channels, and the wells of the water and water vapor-impermeable layer containing a particulate amorphous silica to be used according to the invention. This embodiment is advantageous because the sole structure optimally supports the transport of perspiration within the absorbent and the sweat exchange (uptake and release) with the environment.

The present invention furthermore relates to the use of the shoe insole according to the invention in sports shoes, work boots or military shoes or boots.

pictures Figure 1: schematic representation of a shoe insole according to the invention

illustration 1 shows a shoe insole according to the invention in cross-section, comprising at least two layers 1 and 2, wherein layer 1 is water and water vapor permeable and layer 2 is impermeable to water and water vapor. Layer 2 contains 3 wells on surface. The layers 1 and 2 are connected together so firmly that surface 4 of layer 1 covers the depressions on surface 3 of layer 2. The recesses on surface 3 of layer 2 are interconnected within layer 2 by open channels. The depressions on surface 3 of layer 2 contain the absorbent 5 to be used according to the invention.

Hereinafter, the present invention will be explained in more detail by way of examples.

measurement methods Determination of the DBP number:

mit

• DBP = DBP-Aufnahme in g/100g
• V = Verbrauch an DBP in ml
• D = Dichte von DBP in g/ml (1,047 g/ml bei 20 °C)
• E = Einwaage an Kieselsäure in g
• K = Korrekturwert gemäß Feuchtekorrekturtabelle in g/100g

The DBP absorption (DBP number), which is a measure of the absorbency of a porous material, is determined in accordance with the DIN 53601 standard as follows: 12.5 g of the powdery or spherical material with 0-10% moisture content (if necessary, the moisture content is Drying at 105 ° C in a drying oven) are placed in the kneader chamber (article number 279061) of the Brabender Absorptometer "E" (without damping the output filter of the torque transducer). In the case of granules, the sieve fraction of 3.15 to 1 mm (stainless steel sieves from Retsch) is used (by gently pressing the granules with a plastic spatula through the sieve with 3.15 mm pore width). With constant mixing (rotary speed of the kneader blades 125 rpm), the mixture is dripped into the mixture at 25 ° C. through the "Dosimaten Brabender T 90/50" DBP at a rate of 4 ml per minute. The mixing takes place with only a small force requirement and is tracked on the basis of the digital display. Towards the end of the determination, the mixture becomes pasty, which is indicated by a steep increase in the power requirement. With a display of 600 digits (torque of 0.6 Nm), both the kneader and the DBP metering are switched off by an electrical contact. The synchronous motor for the DBP supply is coupled to a digital counter so that the consumption of DBP in ml can be read. The DBP recording is given in units of [g / 100g] without decimal places and is calculated using the following formula: $$\mathrm{DBP}=\left(\mathrm{V}*\mathrm{D}*\mathrm{100}\right)/\mathrm{e}*\left(\mathrm{G}/\mathrm{100}\mathrm{G}\right)+\mathrm{K}$$

With

• DBP = DBP uptake in g / 100g
• V = consumption of DBP in ml
• D = density of DBP in g / ml (1.047 g / ml at 20 ° C)
• E = weight of silica in g
• K = correction value according to the humidity correction table in g / 100g

The DBP image is defined for anhydrous, dried materials. When using moist materials, in particular precipitated silicas or silica gels, the correction value K must be taken into account for the calculation of the DBP absorption. This value can be determined from the following correction table. For example, a 5.8% water content of the material would mean a 33 g / 100 g supplement for DBP uptake. The moisture content of the material is determined according to the following method "Determination of moisture or dry loss". <b> Table 1: Moisture correction table for dibutyl phthalate uptake - anhydrous - </ b> % Humidity .0 .2 .4 .6 .8th 0 0 2 4 5 7 1 9 10 12 13 15 2 16 18 19 20 22 3 23 24 26 27 28 4 28 29 29 30 31 5 31 32 32 33 33 6 34 34 35 35 36 7 36 37 38 38 39 8th 39 40 40 41 41 9 42 43 43 44 44 10 45 45 46 46 47

Determination of moisture or dry loss

The moisture or even the dry loss (TV) of materials is determined following ISO 787-2 after 2 hours of drying at 105 ° C. This drying loss consists predominantly of water moisture.

execution

wobei A = Auswaage in g und E = Einwaage in g bedeuten.In a dry weighing glass with ground cover (diameter 8 cm, height 3 cm) 10 g of the powdery, spherical or granular material are weighed to exactly 0.1 mg (weight E). The sample is dried with the lid open for 2 h at 105 ± 2 ° C in a drying oven. Subsequently, the weighing glass is sealed and cooled in a desiccator with silica gel as a drying agent to 25 ° C. The weighing glass is weighed to the nearest 0.1 mg to determine the weight A on the precision balance. Determine the humidity (TV) in% according to $$\mathrm{TV}=\left(\mathrm{1}-\mathrm{A}/\mathrm{e}\right)*\mathrm{100}.$$

where A = weight in g and E = weigh in g.

Average particle size d ₅₀

The determination of the mean particle size d _{50 of} the silica is carried out according to the principle of laser diffraction on a laser diffractometer (Horiba, LA-920). To determine the particle size of powders, a dispersion having a weight fraction of about 1% by weight of SiO _{2 is} prepared by stirring the powder in water. Immediately following the dispersion, the particle size distribution is determined from a partial sample of the dispersion with the laser diffractometer (Horiba LA-920). For the measurement a relative refractive index of 1.09 has to be chosen. All measurements are carried out at 25 ° C. The particle size distribution as well as the relevant variables such. B. the average particle size d ₅₀ , are automatically calculated by the device and graphically displayed. The instructions in the operating instructions must be observed.

tapped density

The tamped density or bulk density is determined according to ISO 787-11.

SiO ₂ content

The determination of the SiO ₂ content is carried out according to ISO 3262-19. feature Silica No. * unit 1 2 3 4 5 6 7 8th 9 10 specific surface m ² / g 190 175 190 185 450 450 450 175 50 50 Average particle size d ₅₀ microns 110 8th 11.5 320 40 16 6 20 4.5 18 tapped density g / l 280 70 90 260 180 90 75 175 110 210 loss on drying % 6 6 6 5 6 6 3 6 5 6 PH value 6.5 6.2 6.5 6 6 6 6 6.3 9 9 DBP absorption g / 100 g 260 265 265 250 335 325 325 225 210 245 SiO ₂ content % 98 98 98 98 98.5 98.5 98.5 98 98.5 98 Tamped density * DBP Abs. g / 100g * g / l 72800 18550 23850 65000 60300 29250 24375 39375 23100 51450 * Silica No. 1: "Sipernat 22" from Evonik Degussa GmbH
Silica No. 2: "Sipernat 22 LS" from Evonik Degussa GmbH
Silica No. 3: "Sipernat 22 S" from Evonik Degussa GmbH
Silica No. 4: "Sipernat 2200" from Evonik Degussa GmbH
Silica No. 5: "Sipernat 50" from Evonik Degussa GmbH
Silica No. 6: "Sipernat 50 S" from Evonik Degussa GmbH
Silica No. 7: "Sipernat 500 LS" from Evonik Degussa GmbH
Silica No. 8: "Sipernat 320" from Evonik Degussa GmbH
Silica No. 9: "Sipernat 350" from Evonik Degussa GmbH
Silica No. 10: "Sipernat 360" from Evonik Degussa GmbH

test series

To carry out the experiments, a sole made of a water and water vapor impermeable PVC layer (layer 2), ie without water and water vapor permeable layer (layer 1) in shoe size 46 (about 30 cm in length) was used. Two series of experiments were carried out, using as absorbent on the one hand silicic acid No. 4 (Example 1), on the other silicic acid No. 4 and silicic acid No. 5 in the ratio of 95 to 5% by weight (Example 2). For comparison was based on DE 3516653 A1 a shoe insole filled with molecular sieve (Example 3, not according to the invention). It was a molecular sieve from Merck KGaA with a pore diameter of 0.5 nm and an average particle size of about 2 mm (sodium aluminum silicate, order number 195705). The absorbent was always added in the same amount (15 g) in the wells of the PVC layer. To simulate human perspiration, a saline solution consisting of 99% by weight of water and 1% by weight of saline (NaCl) was prepared. Of this solution, 60 ml each were added to the absorbent. The addition of the solution to the absorbent was carried out in the experiments at a constant rate (0.2 ml / min). The solution was added dropwise at one point, namely in the toe area, and the spread over time was determined. The loaded shoe soles were additionally assessed visually. It was evaluated how well the solution was absorbed by the respective absorbent. The rating was graded from 1 to 6, with a grade of 1 complete and a grade of 6 indicating no record. Table 3 summarizes the results. <b> Table 3: Propagation Kinetics and Visual Assessment </ b> Example no. 1 2 3 Time / min Spread / cm 0 0.0 0.0 0.0 10 2.0 2.0 2.5 20 2.8 3.0 3.2 30 3.8 3.7 4.0 60 6.6 5.2 6.2 90 8.6 7.0 8.2 120 10.2 9.5 11.2 150 12.3 11.5 13.7 180 16.0 14.2 18.0 210 21.0 18.0 21.6 240 23.0 22.0 25.0 270 25.5 26.0 25.6 300 25.5 26.0 25.6 visual assessment 2 1 5

The propagation speeds when using molecular sieve (Example 3) and amorphous particulate silicas (Examples 1 and 2) are initially comparable. However, while the use of amorphous particulate silicas, the liquid was almost completely absorbed by the absorbent, when using molecular sieve, the liquid was for the most part as a "free" liquid between the particles before. This finding clearly shows that both the absorption capacities (determined by pore volume) and the actual absorption rates (determined by wetting properties and pore sizes) are considerably more advantageous in amorphous particulate silicas compared to molecular sieves.

In addition, it was tested whether the soles loaded in the manner described above can be regenerated or dried overnight. For this, the soles were placed overnight in a drying oven with a temperature of 50 ° C (this corresponds approximately to the conditions of drying on a radiator) and measured the weight loss.

In the case of the molecular sieve-loaded sole (Example 3), a clear residual moisture of 17% by weight was still found after 12 h despite the "free" solution present. The residual moisture was determined gravimetrically.

The soles loaded with amorphous particulate silicas as absorbent (Examples 1 and 2) were completely dry under the same conditions (T = 50 ° C.) after just five hours.

The results confirm the advantages of using amorphous particulate silica as an absorbent in hygienic insoles, both in terms of sweat absorption (sweat absorption, redistribution in asymmetric sweat development) and drying (regenerability).

Claims (13)

1. Shoe insole containing particulate amorphous silica as adsorbent,
   the shoe insole comprising at least two layers (1, 2), the first layer (1) being water- and water vapour-pervious and the second layer (2) being water- and water vapour-impervious, the second layer (2) containing depressions on its surface (3), the two layers (1, 2) being fixed to one another in such a way that the surface (4) of the first layer (1) covers the depressions on the surface (3) of the second layer (2), the depressions on the surface (3) of the second layer (2) being joined to one another by open channels within the second layer (2), and the depressions on the surface (3) of the second layer (2) containing particulate amorphous silica.
2. Shoe insole according to Claim 1,
   characterized in that
   the particulate amorphous silica has a specific surface area in the range from 5 to 500 m² per g to ISO 5794-1 Annex D.
3. Shoe insole according to either of the preceding claims,
   characterized in that
   the particulate amorphous silica has a DBP absorption to DIN 53601 of at least 180 g per 100 g.
4. Shoe insole according to any one of the preceding claims,
   characterized in that
   the mean particle size (d₅₀) of the particulate amorphous silica is in the range from 5 to 500 µm.
5. Shoe insole according to any one of the preceding claims,
   characterized in that
   the product of DBP absorption to DIN 53601 and tamped density to ISO 787/11 for the particulate amorphous silica is at least 30 000 g/100g*g/l.
6. Shoe insole according to any one of the preceding claims,
   characterized in that
   the absorbent additionally contains active antibacterial ingredients and/or fragrances.
7. Shoe insole according to Claim 6,
   characterized in that
   the proportion of the active antibacterial ingredients and/or of the fragrances is in the range from 0.01 to 10% by weight based on the total weight of all particles.
8. Shoe insole according to either of Claims 6 and 7,
   characterized in that
   at least a portion of the particulate amorphous silica is present as a carrier for the active antibacterial ingredients and/or the fragrances.
9. Shoe insole according to Claim 8,
   characterized in that
   the proportion of the silica particles which are present as a carrier for the active antibacterial ingredients and/or fragrances is in the range from 5 to 40% by weight based on the total weight of all particles.
10. Shoe insole according to any one of the preceding claims,
    characterized in that
    the absorbent additionally contains particulate superabsorbent polymers.
11. Shoe insole according to Claim 10,
    characterized in that
    the mean particle size (d₅₀) of the particulate superabsorbent polymers is in the range from 5 to 300 µm.
12. Shoe insole according to any one of the preceding claims,
    characterized in that
    the proportion of all particles is at least 20% by volume based on the total volume of the insole.
13. Use of a shoe insole according to any one of the preceding claims in sports, work or military shoes or boots.

Images