CA1256008A

CA1256008A - Microporous multi-layer bonded fabric for medical use and methods for its manufacture

Info

Publication number: CA1256008A
Application number: CA000485396A
Authority: CA
Inventors: Dieter Groitzsch; Erich Fahrbach
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1984-10-10
Filing date: 1985-06-26
Publication date: 1989-06-20
Also published as: JPS6197453A; CN1023885C; ES8606548A1; EP0178372A3; JPH0215655B2; ES542663A0; DE3584067D1; DE3437183A1; CN85104314A; DE3437183C2; US4618524A; EP0178372B1; EP0178372A2; BR8503118A

Abstract

ABSTRACT

A drapable microporous multi-layer bonded fabric designated for medical applications, especially for use in operation rooms, which contains a microfibre centre layer of hydrophobic fibres. This is covered on both sides by optionally non-woven laminates bonded together with a bonding agent. All layers are permanently secured together by means of impressing an elastically hydrophobic bonding agent. In this manner, the bonding paste penetrates in a rod-like fashion the entire cross-section of the multi-layer construction.
Also described is a process for the production of the multi-layer bonded fabric consisting of arranging a microfibre layer on top of a reinforcing material of non-woven fabric, and then applying a non-woven covering. The three-ply laminate is washed in hot water, squeezed out, and imprinted with the bonding paste. The imprinted material is then dried and is ready for use.

Description

' 12~:i61~0~

The invention re1ates to a microporous multi-layered bonded fabric for medical applications, e.g. as disposable operating room material. The multi-layered bonded fabric is a thorough1y waterproof composite bonded fabric, which contains a microfibre layer of water repellant fibres covered on both sides option~lly by a laminate of fabric bound with a bonding agent. the composite bonded fabric is soft and drapable.
All layers are joined permanently to each other. In addition, a process for the production of such a composite bonded fabric is proposed.

Multi-layered or composite bonded fabrics of the above-defined type have been recognized for medical applications and have also been used as disposable materials in operating rooms. The microfibre layer of hydrophobic fibres acts as a filter medium for the finest particles and bacteria. In order to prevent the incursion onto the surface of the fine fibres as well as materials to be filtered out, the microfibre layer is covered on both sides by a protective layer of non-woven material.
In this manner, the passage of bacteria is prevented. An entirely impenetrable water-tight laminate construction is provided.

Known are operating room materials, operating room smocks, and operating room covering materials which are covered by water repelling bonding materials, e.g. those based upon polypropylenes, or by film. The individual layers of the laminate construction are often poorly joined to each other, for which reason such products have only a limited applicability in areas requiring the use of large quantities of these materials. In the case of small pieces, e.g. surgical face masks, the laminate is held together by sewing or welding of the three-ply construction. Thermically welded non-woven material layers of synthetic fibres are also known.

- 2 - ~ ~5~008 The microfibre layer can be produced in a variety of ways, e.~. by means of electrostatic spinnin~ of dielectric polymer fibers from volatile solvents, or the electrostatic spinning from a molten mass or the blowing of a melt.
However, after the electrostatic spinnin~ method of low-boiling point solvents such as methylene chloride, only very hard and brittle polymers such as polycarbonate, polysulfone, cellulose triacetate and polystyrol or wastes can be worked to~ether. The stren~th of such a microfibre layer is very low. To overcome this problem, covering the layer on at least one side with ripstop reinforcin~ material is required. Where thermal weldin~ of such laminates is employed, very hard and brittle welding spots are produced which can cause discomfort to a user of a ~arment or other article made therefrom. Durin~
this brittlizin~ process, the additional dan~ers of dama~e and rip formation of the microfibre layer can arise through mechanical stressing.

The conventional multi-layered bonded fabrics have moreover the seriousdisadvantase of not bein~ drapable. The restricted ability to expand which is related to brittleness and the low workability of the bonded fabric makes possible the occurrence of dama~e to the filter layer in the presence of movement or mechanical influences durin~ use, e.~. as protective clothinK. In the case of thermally welded materials, most of the electrostatic fibre-based filtration capacity is lost durin~ heat treatment. When used in operation room robes and operation room coverin~ material, the breakin8 off, wearin~
off, or the intrusion of microfibres cannot be permitted.

Althou~h the sealin~ of the microfibre layer with a film coating certainly provides absolute protection a~ainst intrusion of bacteria, the wearin~
comfort is extraordinarily bad. Durin~ lon~er operations, heat build-up becomes a problem.

The invention addresses the problem of developin~ a microporous multi-layered bonded fabric for medical purposes, especially for use in operatin~ rooms. In this role the products should be soft, foldable and yet resistant to stresses occurrin~ during use. The material must therefore be waterti~ht, capable of breathing, i.e. permit the circulation of air, and should also allow the passa~e of moisture. The laminate constructions should not separate even ~ 3 - 125~0~

during mechanical stressing. The filter system of the microfibre layer must not fail during use. ~he penetsation by individual microfibres of the covering layer of non-woven material should furthermore be avoided.

The laminate construction suggested herein consists of a very drapsble non-woven reinforcing material, upon which a microfibre layer is arranged. It is advisable for the microfibre layer to be electrostatically spun. The process described in De-eS ~0 32 072 is preferred. The microfibre layer is then covered with a second very drapable non-woven material.

The bonded fabric laminates, as well as the reinforcement and the covering non-woven fabric, are dry or wet-laid non-woven fabrics. Where e~traordinary stresses are involved, spun non-woven materials are preferred. The ~aterials should ideally weigh from 10 to 40 g/m2.

~hould an e~tremely drapable fsbric be required, the use of bonding agent-free joined and lightly packed non-woven fibre materials is advantageous. The resistance against wear is improved by enrichment with a bonding agent. It is much preferred if the microfibre medium is covered with the same ~aterial on both sides.

The non-woven materials are usually waterproofed. At least one of the non-woven fabrics may consist of water-absorbent fibres according to a preferred embodiment. The printing paste is water-repellant and penetrates the entire triple laminate in the form of rod-like structures. The basic shape of this structure can be varied. The printing paste is thus transmitted through the laminate and enables 6 permanent bond of the laminate. In the case of relatively thin laminates, a single-sided pressing of the hydrophobic printing paste is sufficient to achieve suitable stsength. In cases where the laminate is thicker, a double-sided pressing of printing paste is appropriate. This is to be done so that each pressed-in mass of printing paste meets the other on the inside of the laminate. This can be achieved by the mirror-like application of both patterns which is technically possible if warp patterns are used on both sides, which are in the shape of bars shiftable at angles to one another. A mutual intersection and consequent touching is 125~i008 always ensured in this case. Ideally, the printing paste is applied as a watery past-emulsion. The resulting pressure is elastic to the desired degree.

The process for the production of the multi-layered bonded fabric firstconsists of applying the microfibre layer to the highly drapable non-woven fabric, which application can be by electrostatic spinning, a method which in particular has proven effective. The covering non-woven layer is then taken and the triple-layered laminate lightly pressed before rolling up.
The laminate is then washed in water at temperatures ideally above 600C, squeezed out, and then fed through a bath containing water repellant, squeezed out again, and then pressed with the hydrophobically active elastic bonding paste. The pressed material is then dried.

More particularly, the invention provides a microporous, multilayer nonwoven material, comprising:
a layer of nonwoven, microfiber material having a weight of from about 0.5 to about 60 g/m2, each microfiber thereof being hydrophobic and having a diameter of from about 0.1 to about 10 microns;
nonwoven layers covering opposite sides of the microfiber layer; and water-repellent past members penetrating through the layers in a pattern across the layers sufficient for bonding the layers together.

Washing of the laminate, before the water-repellant treatment, aids theremoval of undesirable foreign matter, e.g. spinning preparations on the fibres or emulsifiers in the case of non-woven covering fabrics joined by a bonding agent can be removed. Foaming agents, wetting agents and the like, if present, are also removed. The wash water should be at least 600C, in order for the microfibre medium to be thoroughly saturated.

_ 5 _ ~L2 5 ~ 3 The washed material is then squeezed out so that there remains a minimum residual moisture (equa1 to the amount of liquid absorbed) and brought to the water-repellant bath. The residual moisture, relative to the dry weight of the 1aminate, depends on the weight, thickness and construction of the laminate as well as the conditions of squeezing. So that the material can be accepted in the hydrophobic agent bath after passing through the impregnating bath, stronger pressing is required after washing than after the soaking with hydrophobic agent.

The following mathematical notations apply:

n = G (n + I) - l;

~9 = (n2 -nl) F gHM nl = Nl n2 = N2 gFM 9HM + AG;

Herein:

9HM is the dry weight of the semi-finished material in g/m2 9FM is the dry weight of the finished product in g/m2 ! --6-- ~L2~j00~3 a g is the weight of the finish in g/m2 Gt is the weight of the damp semi-finished materia1 after wash water has been squeezed out, in g/m2 ~2 is the weight of the damp semi-finished material after squeezing out after the second soaking (wet-in-wet soaking) n2 is the moisture absorbed (=residual moisture) after squee~ing out after the second soaking, relative to the weight of the ; semi-finished material in gHM

nl is the moisture absorbed aftersqueezing out the wash water, relative to the semi-finished material weight gHM
N2 as n2, expressed however in X
1 as nl, expressed however in Z.

From this it should be evident that n2 must be greater than nl .
(n2~ nl). Normally, the values for (n2 -nl) or nl should fluctuate within the following limits:
n2 -nl = 0.05 (N2-Nl = 50X) nl = 2.0 (Nl = 200X) in which case, for ener~:y efficiency-reasons, it i8 advantageous if nl is maintained as low as possible, i.e. to squeeze out the material as thoroughly as possible after washing without destroying it.

Intermediate drying is not necessary. The material may then be printed.

_7_ 1 ~5 ~ Q 8 It was surprising that the printing paste easily infiltrates the extremely fine microfibre layer and ensures a strong bond during the formation of the rod-like ridges. It was also surprising to discover that the printing paste easily penetrates the microfibre layer under pressing of the still damp material, wh~n it ought not to be too voluminous and difficult.
The weight of the microfibre layer preferably fluctuates therefore between o.s and 60 g/m2.

The printing paste consists essentially of a low-emulsifier polymer dispersion, which contains hydrophobic e1ement~ exclusively, especia11y hydrophobic monomers, as well as a thickener of high molecular weight which i~ low in solids, and a water repe11ant. su~h a printing paste which is very low in emulsifier, which contains none or only traces Of water-soluble agents, and in addition a hydrophobic agent, ensures the trouble-free penetra~ion of the microfilter medium and prevents leakage with relation to water or a deterioration of the water tigh~ness of the trip1e-1ayered construction.
.
The printing pattern is ideally applied as screen printing, in which case the arrangement of the printing spots is unlimited. In the case of very brittle polymers in the micro-fibre layer, which occur for example after the electrostatic spinning from a solution, it is desirable if the spaces between the elastic pressure joints are narrow.

The laminating together of the three 1ayers with the described join~ng by the printing paste give~ the material a high resistance to ripping, splitting and a flexibility, even in the presence of very hard and brittle polymer materials in the microfibre layer. According to the choice of microfibre materials and the components in the printing paste as well as the hydrophobic agent in the printing paste and the impregnation, the multi-layered bonded fabric can be tailored to suit the needs of the consumer. It is even possible to produce disposable articles from multi-purpose materials. To be able to withstand washing and cleaning, it :, 1256008 is important to employ meshable hydrophobic and bonding agents. Such agents and their qualities are known and are commercially available.

If voluminous and heavier materials are to be bond~d with the printing paste, it is advisable to add effective de-foamers, e.g. those based on silicon, to the hydrophobic bath. The printing paste is then employed in a foamy state. By virtue of the contact of the de-foamer-containing- and still damp composite bonded fabric, there results during the pressing process a spontaneous de-foaming in the presence of a significant lowering of the viscosity of the printing paste. In this manner, the infiltration or penetration of even thicker and more voluminous composite bonded fabrics is simplified.

Watertightness results from the pressing of the water-repellant-soaked material with the elastic hydrophobic printing paste. The difference between three ply laminate impregnated with water repellant and that without it becomes even more apparent if the weight of the covering fabric ! increases in relation to that of the microfibre layer. In the case of heavy composites, pressing on both sides suggests itself. The pressure points can be set so that each lies exactly opposite to the other on the opposite side. A rod-like printing pattern has proven itself, whereby the very slim rods are not symmetrically placed in relation to one another, but rather set at angles to one another, preferably at 90 because they touch each other at the intersection points and thereby ensure the strength of the laminate.

As a rule, the bonded fabrics used for covering are treated with water repellant. In order to improve the water-absorbancy, at least one of the laminates can consist of rayon-staple- or cellulose-containing non-woven fabrics. Such fabrics are relatively flat due to their high absorbancy and unwrinkled structure. They are therefore easily penetrated by the printing paste. These fabrics are comfortable to wear because of the high degree of moisture circu~ation and are always chosen when wearing comfort 9 ~5~iO~

i8 required.

The drspability of the fsbric used for covering can be improved by a mechanical softening process. This is partlcularly advantageous if the microfibre medium is surrounded by wet-laid non-woven covering material. The water repellant treatment of the covering fabric may be omitted if one or two absorbing surfaces are required in the structure. In this case, non-woven fabrics with a high rayon-staple or cellulose content are suitable, which are not bound over their entire surfaces, but rather over parts of their surfaces. ~fter washing, the absorbency of the fibres is at its heiBht.

Where swellable bonding agents are used, i.e. bonding agents whîch do not absorb because of added boundary-surface-active substances (tensides), but rather due to their polymer construction and low degree of intermesh, a joining of the fabrics over the entire surface is possible. If the water-soluble components are washed out, there is no decrease in absorbency.
The microfibre layer preferably consists of fibres with a diameter between 0.1 and 10 ~ m. The reinforcement strength depends on its later use and may fluctuate between 0.5 to 60 g/m2. With electrostatic spinning from the solution, weights of less than 1 g/m and microfibres with e~tremely even distribution, can be achieved. The ideal range of the microfibre application lies between 1 and 30 ~/m2.

The application of the microfibres is determined by the later requirements of: watertightness, impermeability of bacteria, water moisture permeability and the e~pected filterability. For a water tightness of 40 mbar, measured according to DIN-Standard 53 886/77, a microfibre covering of 8 g~m2 of 93 Weight- % polycarbonate and 7 Weight % polystyrol microfibres electrostatically spun from a solution with an average thickness of 4.5~um is sufficient, if the microfibre layer is covered on both sides with 20 g/m cellulose-rayon spin wet non-woven fsbric. Such a triple layer construction is described in E~ample 2.

In the drawings which are used to illustrate the present invention, 12560~13 Figures 1 to 4 show the construction of a multi-layer fabric, according to the invention; and Figures S and 6 are schematic drawin~s of production processes for manufacturing the multi-layer fabric.

Fi~ure 1 shows a cross-section through the three ply multi-layer fsbric, the microfibre layer of which is situated on top of the hydrophobic reinforcement fabric 2 snd is covered by the equally hydrophobic coverinK material 3.

The hydrophobic elastic printing paste shown at 4 ensures a solid bond.
Fi~ure la shows a top view of a multi-layer bonded fabric accordin~ to Figure 1. The pressure points 4 have the shape of patterns and are arranged on the water repellin~ non-woven coverin~ layer 3.

Figure 2 shows a triple-ply multi-layer fabric, in which the dlelectricmicrofibre medium 1 is arranged on an absorbent reinforcement fabric 5 and finished with a water repellant. The hydrophobic elastic 4 provides the bond. Figure 3 shows a multi-layer fabric of three layers which is absorbent on both sides. The dielectric microfibre medium 1 is located on top of the absorbent reinforcement fabric 5 and is covered with the equally absorbent coverinK fabric 6. The hydrophobic elastic through-rivetting of the printing paste ensures the seal.

Figure 4 clarifies the function of the hydrophobic elastic through-rivetted (rod-like) printing paste 4. The dielectric microfibre mediu~ 1 is surrounded by the coverings 2 and 3. The printing paste points 4 are variously arranged. Crossing each other are bonding pressure 4a, a bottom-applied bonding pressure 4b and a top-applied bonding pressure 4c.

Figure S shows a schematic for the production process of the triple-layer multi-layer fabric before the hydrophobing and printing. The reinforcement material 1 is taken from the roller 2 and given to the electrostatic spinning device 3. After leavin~ the spinner, the reinforcement material now covered 25~008 with the microfibre layer is lightly covered with the covering non-woven fabric 5 by light pressing. The triple-ply laminate is then pulled off the roller 7.

Figure 6 schematically illustrates the completion of the multi-layer bonded fabric. The triple-layer laminate 6 is washed in the washing machine 7 at temperatures of more than 60C. After leaving the washing marhine it is squeezed out with the help of rollers 8 and fed into a foulsrd throueh a bath 9 containing the desired wster-repelling a6ent. The hydrophobicslly finished multi-layer composition is once again drained of water through the rollers 10 and then printed with the hydrophobic elastic bonding paste with the aid of a printinK pattern 11 which features a rotary squeegy 12. The printed material is brought to the drier 14 and rolled over the roller 15.

, 1~5~008 The following examples illustrate the process according to the invention.

Example 1 (The zero-based test according to the state of the art) On a wet, non-woven material with a weight of 20 g/m2, consisting of 70 X
unground cellulose and 30 X rayon stap1e of 1 7/5 mm dtex, bonded with a hydrophobic emulsifier-poor polyacrylic acid ester dispersion of a medium soft film hardness (T300=approx. -14 C; T300 is that temperature at which the torsion module of an air-dried film has a value of 300 kg/cm2~ and with a bonding agent component of 30 X relative to the weight of the bonded fabric. Then, microfibres of 93 % polycarbonate and 7 X polystyrol were spun from a methylene chloride solution by the electrostatic spinning process .

The microfibre covering weighed 8 g/m2. The fineness of the fibres ranged from 1.9 to 9.4/um, at an average value of 4.5 ~m, 20 capillaries being measured.

After spinning, the second side of the microfibre layer was covered with the 20 9/m2 wet non-woven material, lightly pressed and rolled.

The water-tightness of the loose 3 ply laminate, measured according to DIN
53 886/77, was 20 mbar. The bonding strength of each of the three layers to each other was almost zero, as is shown in the following test report.

Highest tensile strength longitudjnally 33 N/5 cm; expansion at HTS
long:7X
Highest tensile strength laterally 14 N/5 cm; expansion at HTS lat Splitting strength 0.4 N*
Permeability of air 240 1/s.m2 at 0.5 mbar Thickness 0.60 mm * Splitting takes place within the micro layer. Shifting of the layers occurs when lightly touched with a hand.

-13- 125~Q~

Such a product, especially due to its very weak bonding ability, is suitable for use only in small-area applications, in for example disposab1e facemasks. In large-area applications, for example in protective garments or operating room covering cloths, the produçt of Example lb too sti~f, too hard, not easily drapable, and the laminate bonds are much too weak.

Example 2 The 48 g/m2 heavy bonded non-woven fabric with centred microfibre layer in example 1 is schematically represented in step 2.* It is first washed in a drum-washing machine at 60c, then continually washed at ~oom temperature and then squeezed out in a squeezer (roller pair) to a minimum dampness.

Then it goes through a watery soaking bath consisting of an 8 %

hydrophobic agent mixture, i.e. the described wet-in-wet soaking process is carried out.

The absorbed moisture, calculated on the air-dried non-woven fabric, was 35 ~ (= 1.34 9 solid/m2). For the hydrophobic agent, a zirconium salt containing paraffin emulsion, was employed. Immediately after the squeezing out of the water-repelling agent, the damp product is printed on one side by means of a 10 mesh round sieve pattern with a foam printing paste, aided by a magnetic pressure blade.

* worked off 1~ )08 Recipe forthe mixture: ( with a solid component of 40 ~) Solid Parts Liquid Parts Water 16.0 anionic foaming agent 0.8 4.0 green pigment colouring preparation0.5 1.0 weakly cationic hydrophobic agent (40 X) 12.0 30.0

3 X methyl cellulose- stock prolonger0.3 10.0 hydrophobic, very low in emulsifier polyacrylate dispersion 100.0 222.0 Total 113.2 283.0 The methyl cellulose has a medium substitutionability of 1.4-1.6 and a Hoppler-viscosity in a 2 % solution of 20,000 cps. The application of printing paste contained 10 g/m solids. The viscosity of the unfoamed mixture was 995 cps-Brookfield measured with spindle # 4 at 20 RPM. The mix~ure was foamed-up at a litre-weight of 200 9 (Weight of vessel: 200 g/litre).

After drying, the product was relatively stiff and was afterwards made soft and drapable by hand-crumpling.

The fol10wing data was recorded:

Total weight: 58 g/m2 Watertightness 40.5 mbar Highest tensile strength long.: 37 N/5 cm; expansion at HTS long. : 14 X
Highest tensile strength lat.: 20 N/5 cm, expansion at HTS lat. : 20 X
Thickness 0.44 mm Permeability of air 120 1/s.m2 at 0.5 mbar " " moîsture 35 mg/h.cm2 Splitting strength 1.6 N*

* shifting of the layers is no longer possible.

It is amazing to what extent the watertightness and partly the expansions in 'xample 2 and the splitting strength can be raised in relation to the zero-based test. In relation to this very high watertightness, Example 2 has a very high air permeability. Due to this fact, a material produced according to Example 2 could be employed as operation room covering material.

We know of no other process in which such a high watertightness combines with high air permeability at such a low weight of 58 g/m2. Hydrophobic disposable operating room covering cloths of bonded fabrics are found at watertightnesses of 17 to 23 mbar and in the weight range of 62 to 80 g/m2 and, according to the method of production and weight have an air-flow through value of approx. 30 to 250 l/s . m2 measured at an atmospheric pressure of 0.5 mbars.

Example 3 Production of the green reinforcing material for the spinning of the microfibres.

Upon a cross-laid pile of 7 g/m2 of fibre waste polyester of 1 7/38 mm dtex, x rayon staple dtex 1 3/40 mm = 70 x 30 is laid a lengthwise pile ~L% ~ Q O 8 weighing 7 g/m2 of 100 X rayon staple dtex 1 3/49 mm. The two ply fibre bond is secured with a bonding agent by means of foam impregnation. The plastic dispersion consists of 70 parts solid of a soft self-meshing polyacrylate (Acronal 35 D*) and 30 parts solid of an adhesive raw material (Acronal 80 D*).

To the impregnating mixture was added an anionic foamant, a sulfosuccinate-based surfactant, and green colouring. The ratio of fibre material to bonding agent was 74 : 26, and the weight of the reinforcing non-woven fabric was 19 g/m2. The non-woven reinforcing fabric had a very strong hydrophilic character. The non-woven reinforcing fabric was electrostatically spun with the polymer solution of example 1, only with this difference, that this time, the average fineness of the microfibres was 2.8 ~m with a mean deviation of 1.1 to 7.8 jum).

The microfibre coating was 8 g/m2. On the uncovered microfibre layer was laid a 10 g/m polyamide spun bonded fabric with a fine fibre titre (approx. 2.0 dtex) which was welded on part of its surface (24 X welded surface), and lightly pressed. Then, as example 1 has shown, it was washed, hydrophobically treated by the wet-in-wet process, pressed wet-in-wet, and dried with hydrophobic agent-containing foam paste. The application of hydrophobic agent was 0.8 g~m2 and 7 g/m2 of foaming paste, so that a finished material weight of 44.8 9/m2 resulted.

The strong meshing properties of the reinforcing non-woven fabric benefits the intermeshing of the microfibre layer during the washing process.

*Trade Mark ~6~)08 The following values were obtained:

Watertightness: 57 mbar Permeability of air 45 1/s.m2 at 0.5 mbar Water moisture permeability 26 mg/cm2 .h Highest tensile strength long. 116 N/5 cm Highest tensile strength lat. 52 N/S cm Rip propagation strength long. 6.4 N/5 cm Rip propagation strength lat. 8.3 N/S cm The material is so watertight, that it is impossible, even in the presence of high mechanical stressing, (such as pounding with the fist on a water puddle on the surface of the spread-out material) to cause water to penetrate. On the other hand, the ability to admit water moisture is great indeed. For this reason, a hydrophobic material finished according to example 3 could be employed as a drapable semipermeable laminate with a microporous microfibre insert in rain wear. The breathing activity and the great ability to allow water moisture to penetrate confer a comfortable wearing feeling without the danger of condensation buildup.
xample 4 This example differs from example 3 only infsofar that the weight of the microfibre covering was reduced from 8 g/m2 to 2.5 g/m .
he weight of the finished material was only 39 g/m2.

-18- ~ 2 ~ 0 0 ~3 The following values were obtained:

Watertightness: 24 mbar Permeability of air 182 l/s . m2 at 0.5mbar Highest tensile strength long. 98 N/5 cm Highest tensile strength lat. 48 N/5 cm Rip propagation long. 6.0 N
Rip propagation lat. 8.5 N
Drop coefficient 44.0 ~

The products manufactured according to example 4 feature a very high watertightness in relation to their very low weight. The draping ability (Drop coefficient) is very good and benefits from the low weight. The material can be used as disposable operating room covering material or disposable operation room smock material. With state-of-the-art processes, non-woven fabrics of at least 72 9/m2 are necessary. The saving in weight and therewith the saving in raw material is thus considerable.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A drapable microporous multi-layer bonded fabric which contains a microfibre layer of hydrophobic fibres, at least one side of which is covered by a bonding agent-joined non-woven fabric, in which all layers are permanently bonded to each other, characterized in that the microfibre layer consists of fibres with a diameter in the range of 0.1 to 10 µm, and the layers are bound by a pattern-shaped pressed-on hydrophobic bonding paste, whereby the bonding paste penetrates the combined cross-section of all the layers at the point of application of pressure.

2. A multi-layer bonded fabric according to claim 1, characterized in that both sides of the layer of hydrophobic fibres are covered by a bonding agent-joined non-woven fabric.

3. A multi-layer bonded fabric according to claim 1 or 2, characterized in that the bonding paste penetrates the cross-section of the layers in the form of continuous rod-forming ridges.

4. A multi-layer bonded fabric according to claim 1 or 2, characterized in that the bonding paste penetrates the cross-section of the layers in the form of intersecting ridges which are set at an angle to each other.

5. A multi-layer bonded fabric according to claim 1 or 2, characterized in that the bonding paste penetrates the cross-section of the layers in the form of intersecting ridges and the intersecting ridges are arranged at a 90°
angle to each other.

6. A multi-layer bonded fabric according to claim 1 or 2, characterized in that both non-woven covering fabrics are finished with water repellant.

7. A multi-layer bonded fabric according to claim 1 or 2, characterized in that at least one of both non-woven covering fabrics is constructed of hydrophilic fibres.

8. A multi-layer bonded fabric according to claim 1 or 2, characterized in that it is imprinted with an elastic hydrophobic bonding paste.

9. A process for producing a microporous multi-layer bonded fabric according to claim 1, characterized in that microfibres with a diameter in the range of 1-10 µm are applied upon a soft, drapable non-woven fabric in amounts of 0.5 to 60 g/m, the microfibre layer is then covered with an equally soft and drapable, bonded fabric laminate and the three-ply laminate so formed is loosely joined through light pressing, and washed in water at temperatures over 60 C, water is squeezed out to a residual moisture content N1 of 200 Weight-% at the highest, relative to the dry weight of the laminate and then when desired fed through a watery, hydrophobic agent-containing medium, and re-squeezed to a residual moisture content N2 of at least 50 Weight-%
relative to residual moisture content N1 and the damp laminate is then printed with a pattern on both sides with an elastic hydrophobic printing paste, whereby the printing paste at the pressure point completely penetrates the entire cross-section of the multi-layer bonded fabric.

10. A process according to claim 9, characterized in that the microfibres are spun from a solution onto the reinforcement non-woven fabric.

11. A process according to claim 9, characterized in that the triple-ply laminate is soaked with water-repelling agent before printing.

12. A process according to claim 11, characterized in that the three-ply laminate is not soaked with water-repelling agent before printing.

13. A process according to claim 12, characterized in that at least one of the two covering non-woven fabrics has been hydrophobically finished before washing.

14. A process according to claim 13, characterized in that at least one of the two non-woven fabrics consists of absorbent fibres.

15. A process according to claim 14, characterized in that the covering non-woven fabric is covered pattern-like with bonding agent.

16. A process according to claim 9, characterized in that at least one of the two non-woven coverings are bound on their entire surfaces with a swellable bonding agent in order to cover the microfibre layer.

17. A process according to claim 16, characterized in that the elastic and hydrophobic printing paste is imprinted on one side.

18. -A process according to claim 16, characterized in that the elastic hydrophobic printing paste is imprinted on both sides in such a way that pressure points occur which face each other in a mirror-like manner, whereby rod-forming ridges are formed, which penetrate the entire cross-section of the multi-layer bonded fabric.

19. A process according to claim 9, characterized in that the elastic hydrophobic printing paste is printed on both sides, that pressure points occur which are arranged at right angles to each other, whereby the printing paste penetrates the entire cross-section of the multi-layer bonded fabric in the form of bars arranged so as to be set-off from one another.

20. A process according to claim 19, characterized in that a watery printing paste is employed, which contains at the most 1.3 Weight-% emulsifiers, at the most 15.0 Weight-% hydrophobic agent, max. 1.0% high-molecular weight thickening agent, optionally pigment colouring, and up to 100 Weight-%
complete dry mass of the polymer dispersion constructed exclusively of hydrophobic monomer components, whereby the weight percentages are relative to the total weight of the dry mass of printing paste.

21. A process according to claim 20, characterized in that a watery foamed-up printing paste is employed.

22. A process according to claim 21, characterized in that the multi-layer bonded fabric is led through a medium containing hydrophobic agent which contains an anti-foaming agent selected from those based on silicon.

23. A microporous, multilayer nonwoven material, comprising:
a layer of nonwoven, microfiber material having a weight of from about 0.5 to about 60 g/m2, each microfiber thereof being hydrophobic and having a diameter of from about 0.1 to about 10 microns;
nonwoven layers covering opposite sides of the microfiber layer; and water-repellant paste members penetrating through the layers in a pattern across the layers sufficient for bonding the layers together.

24. The material of claim 23, wherein the paste members are elastic and rod-like.

25. The material of claim 24, wherein each rod-like paste member has at least one projection from each end along the layers, whereby the paste members may have been imprinted as bars onto opposite sides of the material with each bar penetrating into the material only far enough for contacting the bar from the other side.

26. The material of claim 25, wherein the projections from each end of the paste members are at an angle of about 90° to each other, whereby the bars were similarly oriented when imprinted.

27. The material of claim 23, wherein at least one of the covering nonwoven layers contains a water-repellent agent.

28. The material of claim 24, wherein at least one of the covering nonwoven layers contains a water-repellent agent.

29. The material of claim 25, wherein at least one of the covering nonwoven layers contains a water-repellent agent.

30. The material of claim 23, wherein at least one of the covering nonwoven layers contains hydrophilic fibers.

31. The material of claim 24, wherein at least one of the covering nonwoven layers contains hydrophilic fibers.