WO1981001019A1

WO1981001019A1 - Respiratory mask and filtering material included therein

Info

Publication number: WO1981001019A1
Application number: PCT/FR1979/000118
Authority: WO
Inventors: L Giffard; J Neuveu
Original assignee: L Giffard; J Neuveu
Priority date: 1979-10-09
Filing date: 1979-11-30
Publication date: 1981-04-16
Also published as: IT8068536A0; IT1129291B; EP0036855A1

Abstract

New filtering material comprised by a needled felt of synthetic curled macro fibrilae, obtained by fibrilation of a laminated film with two olefine components of different natures, and subjected to a thermal treatment; said fibrilae having a rectangular cross section area and a titre comprised between 8 and 20dtex. Respiratory mask comprised of three shells (CI.MF.CE) of different shapes, the intermediate shell (MF) being made with the present new material and enclosed between the two outer shells welded thereon (SUS) at the periphery thereof, the marginal portion (A) of the intermediate shell (MF) filling a groove of the inner shell (CI) to form a bead (BR).

Description

FILTER MATERIAL AND RESPIRATORY MASK COMPRISING APPLICATION

Technical area-

The invention relates to a new filtration material, to respiratory masks comprising this filtering material and more particularly to respiratory masks -extremely light made of non-woven material and which are used during work in either a vitiated or aseptic atmosphere.

Pre-deviation technique

The nonwovens used for this purpose are felts formed of fibers, or even linear or wavy synthetic microfibers, of circular section, assembled together in a mat, generally by means of a binder, for example by impregnation, by spraying, by padding etc. In order to obtain passages or pores sufficiently small to retain the particles to be stopped, the mattresses of these nonwovens are formed from thermo-retractable fibers (PVC for example) and subjected to a heat treatment. It is taught that the diameter of the pores is substantially equal to that of the fibers making up the mattress. This theory led to the use of microfibers of circular section whose diameter is less than one micron.

The applicant has been manufacturing since 1965 (French patent No. 1438534) non-woven respiratory masks with a weight of 300 g / m ² (after shrinking).

It is now accepted (for example in the German utility model FREUDENBERG No. 76.00278 of December 16, 1976) that masks. monocoque constituted by a microfiber nonwoven with a weight of 300g / m ² after shrinking, did not have an efficiency greater than 50% under the test conditions of AFN0R NF standards (N 76 101 of May 1975 and S 76 201 of October 1975) while these prescribe a minimum efficiency of 85%, that is to say a retention power - such as 85% of particles with a diameter of 0.3 to 0.5 micron of a methylene blue aerosol, are stopped by the filter element. It was also observed that the increase in the grammage of the nonwoven only led to a barely noticeable improvement. 2 It is the same for the superposition of layers of such non-woven fabric.

The German utility model n ° 7600278 cited above proposes to constitute masks by means of a minimum of three layers, where the intermediate layers being produced in a sheet of extremely fine fibers (polycarbonate, polystyrene, polyvinyl chloride or mixtures thereof) obtained by an electrostatic process.

It seems that this 85% minimum efficiency still remains a problem awaiting a solution. Presentation of the invention

According to the invention, the filtering material is a non-woven mattress made of fibers having the particularity of being of rec tangular sections whose average titer is of the order of 10 dtex.

To facilitate understanding of what follows, the term "fiber" will be reserved for those of circular section while the word "fibril" will identify macrofibers with rectangular section like those obtained by a fibrillation process (for example according to the patent SHELL No. 1545.908 or French patent IT-.F. No. 2,306,818) from a laminated film with two different olefinic components (for example a pair: polypropylene / high density polyethylene homopolymer, or a pair: polypropylene homopolymer / propylene-ethylene random copolymer).

We know that according to these methods, the complex film is divided into a network (of structure analogous to that of expanded metal) by the action of a needle cylinder and that this process leads to fi¬ shines of approximately rectangular sections of which the edges are irregular and bearded.

If a couple is used, the two polymers of which have different thermal shrinkage coefficients and melting points, the heat treatment will initially produce three-dimensional crimping and, secondly, the self-agglomeration of the fibers, without 'it is necessary to use a binder.

Up to now, respiratory masks have never been produced, the filter element of which consists of a macro-fibrill mattress of rectangular section, because this use would have contradicted the theory of filtration which advocated the use of fibers with a diameter close to that of the particles to be retained and which as a result, tended to use increasingly fine microfibers (for example German utility model no. 76.00278 cited above).

However, this theory found its justification in the structure of traditional nonwovens. Indeed, the pores of these are formed by the gap left between two layers of fibers by an intermediate bed of the same fibers oriented differently, it being recalled that these fibers are straight, or at best wavy, that is to say to say of sinuous profile in a ^' plan.

The pore diameters of a traditional nonwoven are therefore necessarily equivalent to the diameter of the fibers of the intermediate bed with, as a corollary, the obligation to use micro-fibers to obtain micropores which can stop micro-particles.

On the contrary, in a mattress of macro-fibrils, the pores de¬ come from real cells whose dimensions are incomparable with the pores of traditional nonwovens.

Indeed, the helical crimp, sometimes thwarted for the same fibril, causes totally anarchic intervals to be created, therefore according to a completely random distribution, a cell which can differ from its neighbors depending on the position of the macro-fibrillum sepa- rant those of the "layers" immediately above and below from the case where the macro-fibril is flat, to the case where it is field through all the intermediate orientations. The shape and dimensions of the cells are further influenced on the one hand by the fact that helical crimping prohibits the stratification proper to nonwovens of micro-fibers, due to the Timber of the helices in each other ; and on the other hand by the barbs of the edges of the macro-fibrils.

It follows that these cells constitute veritable communicating chambers by airlocks. It is easy to identify a mattress of macro-fibrils compared to a traditional mattress. At identical grammage, the mattress of macro-fibrils is much thicker than the other.

The comparative tests carried out by the applicant showed him that the acro-fibrillary material had a very different behavior in terms of filtration than that of a microfiber mattress.

While the latter acts like a common sieve, the mail of which is made up of the pores of the nonwoven, the acrobatic mattress fibr llaire behaves like a succession of sieves separated by a multitude of relaxation chambers.

It follows that a mask made of a traditional nonwoven not only proves to be ineffective as observed in the tests, but it is quickly out of use because the solid particles in suspension in the air drawn in, obstructs quickly the pores of the preferential circuits which are created according to the law of least resistance to flow with as a consequence a notable increase in the pressure drop.

On the contrary, in a mask made of a macro-fibrillary nonwoven, the air loaded with particles relaxes in each cell of the mattress and abandons these particles as it goes along, the bigger the first, the more fine then. As these cells have dimensions much larger than that of a particle, they do not clog very quickly, retaining the macro-fibrillary nonwoven mask longevity and efficiency much greater than that of a non-woven mask. traditional woven.

The present invention therefore provides a satisfactory solution to the effectiveness of respiratory masks in order to reach the threshold of 85% and in particular by giving the macro-fibrillar material characteristics suitable for the intended use and in particular by reading , with this material, a mattress intended to be interposed between two shells of traditional nonwoven. Brief description of the drawings

Other features and advantages will appear on reading the description and the claims which follow, made with reference to the drawings in which:

- Figure 1 is an exploded view of a mask with three shells described as a preferred embodiment of the invention.

- Figure 2 is a theoretical vertical section of such a mask, being. specified that these figures are not to T scale.

- Figure Z is a view similar to Figure 2 showing an improvement.

Best way to realize the invention

As mentioned above, the invention is aimed firstly at a filtering material consisting of a felt of three-dimensional curly synthetic macro-fibrils, having an approximately rectangular section and a title of approximately 10 dtex.

MEDIUM TITLE 12 DTEX

THERMAL BEHAVIOR

% WITHDRAWAL

Tëtuve temperature

MACROFIBRILLE N ° 1 MACROFIBRILLE N ° 2

100 ° C 10% 20%

110 ° C 14.5% 25%

120 ° C 29% 32%

130 ° C 57% 57%

Area beyond which ther ocollage occurs

140 ° C 68% 66%

150 ° C 79% 11%

This felt is produced by ai mistletoe 11 stage of fibrils obtained by fibrillation of a laminated film with two constituents such as a homopolymer couple of propylene / high density polyethylene or of a homopolymer couple of propylene / propylene-ethylene random copolymer. The fibrils whose thermal behavior is highlighted in the preceding table are obtained from a laminated film, the fiber No. 1 corresponding to a pair: propylene homopolymer / propylene-ethylene statistical co¬ polymer, and the fiber n ° 2 to a couple: a terpol raère acid (ethylene-vinyl-acetate-homo olymer-Dronylene) / copolyroere, propylene-ethylene statistics mixture.

The heat treatment is applied to the felt after needling, it begins by revealing the three-dimensional helical crimp accompanied by the shrinkage. Above 130 ° C while this continues, the thermal inter-fi bonding which in turn stabilizes the mattress by melting the most fusible constituent.

Optionally, a mattress of macro-fibrils may contain, by addition at the time of coating, 20% of textile fibers or microfibers.

Unfortunately, such a mattress of macro-fibrils molded into a respiratory mask, has the drawback of insufficient rigidity and strength is to combine it with a more resistant support for example as already envisaged by the applicant in his French patent no. 1,503,573 of June 26, 1966, which described a mask comprising an outer shell carrying the cord and the deformable nasal bar and a removable inner shell made of filter material, these two shells being molded according to the same shape, to allow their nesting , so that it produces the subjection of the two shells without the need for other fixing means.

In the spirit of this old invention (which was aimed at economy), ^" the outer shell serving as a support for the inner shell and being able to be used several times (while the inner shell is replaced for each use), did not participate in the filtration, being carried out in a fabric with large mesh.

In terms of efficiency, this double-shell mask therefore behaved exactly like a single-shell mask.

For some applications, it is possible to envisage such a mask with two shells by making the filtering shell out of felt. macro-fibrillar as just described.

It appeared to the applicant that another category of mask could be created by combining the characteristics of the felt mattresses of micro-fibers and macro-fibrils. As can be seen in the accompanying drawings, three shells can be assembled: an outer shell CE, an inner shell CI and an intermediate shell MF.

The outer shell CE can be made of a fabric with large mail¬ and serve as a support as in the case of patent No. 1,503,573. It can also be made from a traditional nonwoven felt.

The inner shell is constituted by such a nonwoven, on the other hand the intermediate shell MF is made of felt of macro-fibrils, as previously described. . The different shells are thermoformed in dif¬ ferent molds so that their curvilinear profiles have dif¬ ferent arrows, so that they have only local contacts between them, for example at A and B so that 'They delimit enclosures such as VA1 and VA2 forming expansion chambers. CE and CI shells are welded together at their periphery

SHF by high frequency. The shell MF is wedged between CE and CI.

Advantageously, these shells CE and CI are molded in a veil of 300g / m ² .

The MF shell is made from a mat of fibrils like those referred to in the preceding table, with a final weight per m ² of 420 g and a thickness of 4 mm before thermoforming.

Of course, there could be several MF shells or several independent mattresses to form a single shell.

Finally, it is possible to fill the inter-fibril cells of the ^* mattress and, in the case of a mask, of the MF shell with a pulverulent material such as activated carbon powder.

It suffices for this to trap the particles of this powder during the coating operation (by dusting for example) before the heat shrinkage treatment. ^~ As seen in Figure 3 which shows a mask with three shells CI, CE and MF as previously described, we can take advantage of the presence of the intermediate filter shell MF in macro fabric fibrillary (therefore very thick) to produce by deformation of the wall of the shell CI, an external bead BR to this wall, bead which will constitute an excellent seal, provided that the shell MF is extended so that the marginal parts of its periphery A, are adjacent to the SUS weld (by high frequency or ultrasound), and placed inside the groove G02 forming this deformation.

A permeable but filtering seal is thus obtained which, contrary to known seals (for example French patent n ° 1.590.090) does not prevent the mask to be taseptic and does not soak up sweat like a sponge. .

Of course, the groove G02 can be formed at the same time as the shell CI.

It is also possible to envisage making the bead BR without preforming the groove G02.

In these ways, the constitution of the bead BR does not require any additional intervention to the operations necessary to obtain the mask without bead like that visible in FIG. 2.

Possibility of industrial applications The material which is the subject of the present invention can find application in all fields of filtration of gases loaded with solid particles.

Undoubtedly, we get the maximum benefit from this material in its application to respiratory masks, because it is in this area that optimal efficiency is often sought for health reasons where insufficient efficiency can have serious consequences.

O / I

Claims

1- Filtering material consisting of a felt of nonwoven synthetic fibers, needled and having undergone thermal shrinking, characterized in that the constituent fibers have an approximately rectangular section and a titer between 8 and 20 dtex.

2 - Material according to claim 1 characterized in that the smallest dimension of said rectangular section is greater than one micron or better greater than 10 microns.

3 - Material according to one of the preceding claims caracté¬ ized in that the constituent fibers are crimped, curled or wavy.

4 -'Material according to claim 3 characterized in that said fibers after heat treatment twist in helices.

5 - Material according to one of the preceding claims caracté¬ ized in that the constituent fibers of the felt are macro-fi¬ shines obtained from a laminated film with two constituents and fibril according to a known process (for example according to the SHELL process subject of patent 1,545,908 or of the ITF process described in patent 2,306,818).

6 - Material according to claim 5 wherein the macro-fi¬ shines are of olefinic nature characterized in that Tun of the film constituents is a propylene homopolymer. 7 - Material according to claim 6 characterized in that the second element of the couple is a random propylene-ethylene co-polymer.

8 - Material according to claim 5 wherein the macro-fi¬ shines are of olefinic nature characterized in that Tun of the constituents is formed of a random propylene-ethylene co-polymer, the second element of the couple being a ter -acid polymer (ethylene-vinyl acetate), mixed with a propylene homopolymer.

9- Material according to claim 6 characterized in that the second element of the couple is a high density polyethylene. 10 - Material according to one of the preceding claims in which the constituent macro-fibrils are subjected after needling to a heat treatment characterized in that in a first time, this treatment reveals the ideal hëlico ^' crimp of these fibrils then produces the three-dimensional retraction and finally the agglomeration of Dac fusion fibers, _

11 - Material according to one of the preceding claims, characterized in that its internal pores or cells enclose some of the additional filtering solids.

12 - Material according to claim 11 characterized in that said particles (for example activated carbon) are incorporated before the heat treatment, during the coating operation.

13 - As an application, a breathing mask with a filtering sheet of nonwoven synthetic fibers characterized in that it comprises at least one filtering sheet or mattress made of the material specified in one of the preceding claims.

14 - Mask according to claim 13 comprising a plurality of shells in non-ti ssêescaractérisé in that at least one of it is made of a tablecloth or mattress of macro-fibrils with two polyolefic constituents of rectangular section and d '' a title of 8 to 20 dtex.

15 - Mask according to claim 14 comprising three shells characterized in that the intermediate shell is made of a felt of macro-fibrils according to one of claims 1 to 12 including the inner shell being molded in a felt of traditional nonwoven.

16 - Mask according to claim 14 comprising three shells characterized in that the outer and inner shells are molded in a traditional nonwoven felt and the intermediate shell in a material according to one of claims 1 to 12 inclusive.

17 - Mask according to one of claims 15 or 16 characterized in that the weight per m ² (after shrinking) of the intermediate ply (or the total weight of the intermediate plies) in nonwoven of macro-fibrils is greater than 350 grams.

18 - Mask according to one of claims 15 to 17 characterized in that the thickness of this intermediate ply before thermo-for¬ mage (or the total thickness of the intermediate plies) is greater than 3 mm.

19 - Mask according to one of claims 15 to 17 characterized in that respectively the thickness and the weight per m ² of the sheet intermediate (or intermediate layers) are 4 mm and 420 grams.

20 - Mask according to one of the preceding claims characterized in that the fibrils of the intermediate sheet or sheets have a ti¬ be of about 10 dtex. 21 - Mask according to one of the preceding claims, characterized in that the intermediate sheet (or one of the intermediate sheets) includes solid particles which are completely filtering (activated carbon for example).

22 - Mask according to one of claims 13 to 21 comprising three shells characterized in that these three shells are thermoformed on three different molds so that their curvilinear profiles have different arrows, so that they have no them as local contacts defining pregnant forming ^rooms' relaxation. ^' • 23 - Mask according to claim 22 characterized in that the outer shells are welded by their periphery and enclose the intermediate shell, the marginal part of which produces a bead outside the inner shell, said bead forming a seal for the mask. 24 - Mask according to claim 23 characterized in that the inner shell comprises a preformed gutter, intended to rece¬ see said marginal part of the intermediate shell.