SE465310B - PROCESS FOR PREPARATION OF PURPLE WITH PEOR - Google Patents

Description

465 310 10 l 25 20 25 30 35 plastic is mixed with 28 to 200 parts by weight of filler and 10 to 70 parts by weight of liquid or waxy hydrocarbon polymer, the plastic mixture is formed into a film, and the film is stretched in at least one direction by a factor of at least 1.2. However, this method has the disadvantage that certain fillers give poor extensibility and therefore do not give completely uniform pores and that the film produced can sound uncomfortable. In addition, the use of a hydrocarbon polymer makes the process unsatisfactory in that the polymer tends to "bloom" on the foil surface and give a sticky feeling.

Such porous foils are also useful as impermeable layers in sanitary napkins. Previously, a paper made waterproof by means of a polymer, for example polyethylene, has been used for this purpose. Sanitary napkins with such paper, however, have the disadvantage that they give an unpleasant feeling during long use by not letting water vapor through.

BRIEF DESCRIPTION OF THE INVENTION The present invention thus has for its object to provide an improved process for producing porous films.

Another object is to offer a process for producing porous foils with sufficient porosity and thus high moisture permeability and gas permeability while maintaining excellent resistance to water.

Another object of the invention is to provide a process for producing porous foils which are non-sticky and retain their mechanical strength.

A further object of the present invention is to provide an improved material for the manufacture of water-permeable layers in disposable diapers.

Another object of the invention is to provide an improved material for the manufacture of water-permeable layers in sanitary napkins. Other objects of the present invention will become apparent from the following description. These and other objects can be achieved by the inventive method of making porous foils comprising melting a plastic mixture consisting of a polyolefin polymer. , barium sulphate with an average grain diameter between 0 1 and 7 μm in an amount between 50 and 500 parts by weight per 100 parts by weight of polyolefin polymer and, if necessary, at least one substance selected from stabilizers, antioxidants, dyes, UV stabilizers and lubricants and / or other inorganic fillers and common organic modified additives in addition to the barium sulphate in an amount less than that of the added amount of barium sulphate, that a foil is produced from the molten plastic mixture and that the foil is stretched by a factor between 1.5 and 7.

Thus, in addition to polyolefin polymer, the mixture may comprise at least one additive selected from common stabilizers, antioxidants, dyes, UV absorbers and lubricants and / or in addition to barium sulfate the mixture may comprise other inorganic fillers (eg calcium carbonate and the like) or common inorganic or organic modifying additives in amounts which is less than the amounts of barium sulphate used (eg less than 20% of the amount of barium sulphate), but that the addition of liquid rubber, a hydroxylated saturated hydrocarbon polymer or a hydrocarbon polymer according to the above-mentioned Japanese Laid-Open Patents 47334 / '82, 203520 / * 82, 15538 / '83 and 149303 / '83 must be avoided in order to obtain a porous foil without a sticky surface.

According to the present invention, porous films without a sticky surface and with excellent properties which could not be produced with known technology can be produced without the use of any of the above-mentioned conventional additives. This can be done simply by specifying the type of filler, as well as the amount thereof and preferably its average grain size; preferably with an LDPE grade with a certain density and melt index and preferably with a linear LDPE (especially which comprises a copolymer of ethylene and hexene and / or octene) which preferably has a certain melt index and density; and by stretching the foil by a certain factor. DETAILED DESCRIPTION OF THE INVENTION The polyolefin plastics that can be used in the present invention include homopolymers such as polypropylene, LDPE, HDPE, linear LDPE, polybutene, etc .; copolymers such as ethylene-propylene copolymer, ethylene-butylene copolymer, ethylene-vinyl acetate copolymer, etc .; and mixtures between these.

Of these plastics, LDPE with a melt index of between 0.5 and 7 (0.5 to 8.5 for linear LDPE) and a density of between 0.915 and 0.935 is preferred. Any mixture of polyethylenes of different densities can be used, although it is preferable to use a single variety.

Melt index is preferably between 1 and 5. If melt index is less than 0.5 or greater than 7 (8.5 for linear LDPE), the plastic will be considerably more difficult to form into a film and may not be able to give an evenly thick film. On the other hand, the plastic becomes more difficult to stretch and stiffer and may not give rise to a soft foil if the density is lower than 0.915 or higher than 0.935.

Linear LDPE is a particularly suitable polyolefin plastic. This is a copolymer of ethylene and one or more alpha-olefins, and differs from LDPE produced in the conventional high pressure process.

Linear LDPE is produced by the low pressure process, and suitable alpha-olefins include butene, hexene, octene, decene and the like. The difference between LDPE produced according to the high-pressure process and that produced according to the low-pressure process is, from a structural point of view, that the former has strongly branched molecules while the latter is straight-chain.

Among the various LDPE copolymers, those with ethylene and hexene and / or octene are particularly preferred.

In the practice of the present invention, it is convenient to use barium sulfate having an average grain size of 0.1 to 7 microns, most preferably 0.5 to 5 microns. If the average grain size is less than 0.1 μm, well-defined pores cannot be obtained. If it is instead larger than 7 μm, the resulting foil becomes poorly stretchable, so that well-defined pores can hardly be produced, as well as not when the average particle diameter is too small.

The barium sulphate is added in amounts of between 50 and 500 parts by weight, preferably 100 to 400 parts by weight, per 100 parts by weight of polyolefin plastic. If less than 50 parts by weight are added, sufficient port density cannot be achieved, while the resulting foil cannot be fully stretched due to increased stiffness if more than 500 parts by weight are added, with the result that the port density decreases.

It is advantageous to surface treat the barium sulfate with a fatty acid or a metal salt of a fatty acid, silicone, silane, resin acid, or the like, as this improves the dispersion in the plastic and provides well-defined pores.

As long as the objects of the present invention are not counteracted, other inorganic fillers may be added, such as calcium carbonate and the like, or common inorganic or organic modifying additives in addition to the barium sulfate. However, these additives should be kept below 20% of the amount of barium sulphate.

The present method for producing porous films will be described in more detail below.

If necessary, add at least one substance selected from stabilizers, antioxidants, dyes, UV stabilizers and lubricants to a polyolefin plastic and barium sulphate. These ingredients are mixed in a Henschel mixer, supermixer or rotary mixer. The resulting mixture is then mixed and pelletized in a conventional extruder with one or two screws. Then these pellets (alone or together with polyolefin plastic pellets) are melted at a temperature higher than the melting point of the polyolefin plastic (preferably at 20 ° C or higher) but below its precipitation temperature, in a blow extruder or a T-die extruder, and formed to a foil. In some cases, said mixture can be formed directly into a foil with the extruder, instead of being pelletized first. Then the foil is stretched at least in a direction of 465 310 10 a factor of between 1.5 and 7 in a conventional manner, for example by rolling. The stretching can take place step by step and / or in several directions.

If the stretching takes place in two directions, however, it is suitable to stretch the film at the same time in both directions. To improve the pores I? dimensional stability, the foil can be tempered with heat after stretching.

The porosity is determined by the amount of barium sulphate added, the degree of stretching, etc. If the stretching factor is below 1.5, sufficient porosity can not be achieved, while if the stretching factor is above 7, a porous foil cannot be produced at a steady production rate, because the foil often transmits during stretching.

Porous foils produced by the present method are characterized by high porosity, excellent softness and slight mechanical weakening.

In addition, a porous film can be produced at a steady production rate because the affinity between the polyolefin plastic and the barium sulphate provides good extensibility and thus both good processability and pore distribution.

Especially when using linear LDPE as a plastic base, the resulting foil shows very little reduction in the mechanical strength.

It will then be possible to make porous foil with a smaller thickness (eg about 10 μm thick) than the previous technique allowed.

Furthermore, the film is not sticky on the surface, since the plastic mixture does not contain liquid rubber, hydroxylated saturated hydrocarbons or hydrocarbon polymers, as used in the prior art.

Accordingly, the porous film of the present invention has a sufficiently high porosity and thus good moisture permeability to moisture and gas while maintaining excellent water resistance, and can therefore be used in clothing and hygiene products. They can also be used for filtration because the pore distribution is so even.

The present invention is further illustrated by the following examples.

These examples are presented as illustrations only and should not be construed as limiting the scope of the invention. In the examples, the melt index (MI) has been determined according to ASTM D-1238 and the density according to ASTM D-1505.

In the examples, the properties of the foil have also been determined according to the following methods: 1) Mechanical strength and elongation Using a Tensilon test apparatus, a piece of foil measuring 25x100 mm with an elongation speed of 200 mm / min was tested.

The breaking strength and elongation at break were measured in the machine direction (MD) and in the transverse direction (TD). 2) Moisture permeability Moisture permeability was measured according to method D in ASTM E96. 3) Softness The softness was judged by the feeling and graded in the following degrees; very soft and smooth CU II fairly soft and smooth C = hard and coarse EXAMPLES 1-19 AND COMPARATIVE EXAMPLES 1-9 Each of the fillers in Table 1 was mixed with the corresponding plastic base in the amount indicated in Table 1 in a Henschel mixer. This mixture was kneaded well and pelleted using a twin-screw extruder. These pellets were then melted at a temperature 80 ° C higher than the melting point of the plastic base in a T-die extruder, and formed into a film. This film was stretched in one or two (Example 3) directions by the factor indicated in Table 1 so that a porous film was formed with the thickness given in Table 1. In Comparative Example 1 the film was not stretched, and in Comparative Examples 2 and 9 it could not stretched to a porous foil. In Comparative Examples 5 and 8, the film could only be stretched by a factor of up to 2. In Comparative Examples 3 and 7, samples could not be sampled due to recurring defects during stretching. 465 310 Mechanical strength, elongation, moisture permeability and softness were determined according to the above methods for the porous foils produced in the specified ways and the results are reported in Table 1. lv 46592510 9.

Table 1 Base plastic 1) Brand Melt- Density Type (manufacturer) index 2 (g / 10 min) (g / cma) I REFLON F-41 (Nippon §Example l LDPE Petrochemicals Co., 5.0 0.923 Ltd) šL II 2 II II II II II 3 II II II II MIRAsoN 45 (Mitsui "4" Polychemicals Co., 1.5 0.920 Ltd.) Il 5 II II II Il UBE POLYETHYLENE "6" F0l9I (Ube Kosan 0.9 0.912 KK) Neo-zex 4330 (Mitsuí Petrochemical Indus- "7" tries, Inc.) / UBE 3.0 0.940 POLYETHYLENE VF430 (Ube Kosan KK) = 2 / l "8 L-LDPE NUCG-5511 (Nippon 1.0 0.920 Unicar Co., Ltd.) II 9 II Il II II Ultzex 202OL (Mitsui "10" Petrochemical Indus- 2.1 "tries, Inc.) II II II II II II II Il II 'I n 13 unu H 10 Table 1 (cont.) Fillers Average 2) Stretch § EoIief_ __! Type Grain diameter Amount factor = thickness I (m), (phr) (m) I Basø4 0.8 150 4 40 II ll II 5 II i Il II II 2 X 2 II "1.2 130 5 50 II 5-0 II 'll n] __2 || 33) n II II 4 II II II II II "" 150 5 15 "4.2 50 6.5 40" 0.8 150 s "" 0.5 100 7 10 "" 300 3 40 465 310 ll Table 1 (continued) Breaking strength Elongation ( %) Moisture permeability- Soft- (kg / 25 mm) in lethality É. Lighet MD 'TD MD TD; 4.5 200 200 E 3,900 A 5.5 1.5 120 450; 3,000 A i 5.0 1.3 100 390 g "A 3.9 1.0 55 390 I 1,100 B 4. 5 H so zoo 2,000 _ c 3.5 1.2 100 420 3,900 C 2.5 0.8 80 400 5,000 A 7.8 1.4 pp 170 2,800 7 A 6.5 1.8 130 510 7,500 A 2.3 0.7 40 120 8,500 A 5.3 1.5 78 360 5,500 A 465 310 12 Table 1 (first) Base plastic 1) Type Brand (manufacturer) Melt index (g / io min) Density (g / cm *) Example 14 L-LDPE Ultzex 3010F (Mitsui Petrochemical Industries, Inc.) 1.3 0.930 Ultzex 202OL (Mitsui Petrochemical Industries, Inc.) 2.1 0.920 Ultzex 2010J (Mitsui Petrochem ical Industries, Inc.) 8.0 0.920 HDPE Hi-zex HZSOOOS (Mitsui Petrochemical Industries, Inc.) 0.9 0.954 PP MITSUI NOBLEN JS-G (Mitsui Toatsu Chemicals, Inc.) 0.890 EPC MLISUI NOBLEN MJS-G (Mätsui Toatsu Chemicals, Inc. .) f: 13 Table l (cont.) 465 510 Fillers g I Average 2) Stretch f Foil Type Grain diameter Amount factor 5 thickness i (m) (phr) i (m) 'ii BaSO4 5.0 150 5 É 50 š " 0.5 sbo 2 40 š 1 "0.8 200 3" S II II 5 II .hp-gm 465 310 14 Table 1 (continued) Breaking strength Elongation (%) Moisture permeability- Soft- (kg / 25 mm) slackness MD TD MD TD (g / m * / 24 hr) 1.5 1.4 110 400 6,700 A 5.0 1.0 35 20 5,000 A 5.5 1.4 105 420 4,700 A 8.0 2.2 70 400 4,500 C 10.3 2.5 90 350 4,900 C 9.1 2.3 88 520 4,000 C 15 Table 1 ( cont) 46§ * 31o Basplast 1)! Brand Melt- Density Type (manufacturer) index (g / lo min) (g / cma) Comparison-É L-LDPE; Ultzex 202OL (Mitsui Example 1 § I Petrochemical Indus- 2.1 0.920 É i tries, Inc.) II 2 | II Il II II i Il 3 I Il | Il II II .I l II 4 II II II II II 5 II II II II "6 f" NUCG-5511 (Nippon 1.0 "3 Unicar Co., Ltd.) II 7 II II II II n 8 nu gr n PETROSEN 207 (Toyo "9 LDPE Soda Manufacturing 8 0.924 Co., Ltd.) Footnotes: l) 2) 3), 5) and 7) Highest value while maintaining a straight line 4) and 6) No value could be determined due to recurring LDPE = low density polyethylene L -LDPE = linear low density polyethylene PP = polypropylene EPC = ethylene-propylene copolymer Parts by weight of filler per 100 parts by weight of base plastic fracture during stretch 465 510 16 Table 1 (cont.) I.

Filler in H É 'I [, = Average 2) * Stretch-Å Foil ~ E Type Grain diameter Amount factor f thickness I (m) (phr) ä (m) § ß! É l BaSO4 0.8 150 ¿Osträckt 50 É i "" 600 Osträckt - "" 150 Il 84) - cacos 1.0 "4 70 '1: \ f' Glas- 1.2 12o ¿2" g; 50 pearls f å ¿; §§ § BaSO "30 2 5; 40 4 š si :: \ znu 100 av '_ 7A Glas_ uu 2 I 60, beads BaSO4" 130 Unstretched - 465 310 17 Table l (continued) I Breaking strength Elongation (%) É Moisture genome - 01 Soft (kg / 25 mm) slack IT lighet MD TD MD f TD ¿(g / mf / 24 hr) «¿2.5 2.3 570 480 § 15 A š 4.3 0.8 20 100 3,000 C 1.5 0.7 140 290 30 C 4.5 1.0 105 430 15 C 1.0 0.5 40 100 40. C 465 310 "10 15 20 25 30 35 18 Porous foils prepared according to the present invention have high port density and excellent softness and show very little mechanical weakening, so they are very suitable as impermeable layers in disposable diapers. Although such impermeable layers are usually used as an outer layer in the diapers, a material that does not impede moisture passage (such as a regular foil with holes or an embossed foil) can be placed on top of the leakage-preventing layer to give a fabric-like surface.

In such disposable diapers, any common liquid absorbent can be used, such as fluff, fluff inside absorbent paper or the like, absorbent polymers with high water absorption, and so on.

As the liquid-permeable layer which is in direct contact with the skin, it is convenient to use a non-woven layer of fibers of polyester, nylon, polyolefin or the like.

In addition, adhesive tape can be used to attach the diaper and elastic bands (such as rubber) along the side edges to prevent leakage.

Disposable diapers are made by placing a liquid-absorbent material on said impermeable layer and placing a liquid-permeable layer on top of it.

In disposable diapers having a porous film of the present invention as the impermeable layer, the outermost impermeable layer has a large number of pores. Because these pores let water vapor through but stop water droplets, the baby's skin does not get moist but is kept dry, which reduces the risk of skin redness. In addition, they are not so easily torn apart and are soft enough not to make an unpleasant sound.

The following examples illustrate how the porous film of the present invention is used as a leakage preventing layer in disposable diapers.

H 10 15 20 25 30 35 465 510 19 EXAMPLES 20-22 and COMPARATIVE EXAMPLES 1o-14 Barium sulphate with an average grain diameter of 1.5 μm or each of the other fillers in Table 2 was mixed in a Henschel mixer with 100 parts by weight of LDPE with a melt index (MI) of 3 (Examples 20 and 21) or linear LDPE with an MI of 5 (Example 22 and Comparative Examples 10-14) in the amounts given in Table 2. This mixture was then kneaded and pelletized in a twin screw extruder. Then these pellets were melted at 130 ° C in a T-die extruder and formed into a film. The foil was stretched in a direction between a preheating roll with a temperature of 50 ° C and a stretching roll with a stretching factor given in Table 2, so that a perige foil with a girder was obtained.

The properties of the films thus obtained were determined and the results are presented in Table 2. Disposable diapers were made by applying a fluff filling and a non-woven layer of polyester to each of the porous films prepared according to Examples 20-22 and Comparative examples 10, 13 and 14, after which adhesive tape and elastic bands were added.

The disposable diapers of Examples 20-22 were superior in mechanical strength, moisture permeability and softness to Comparative Examples 10, 13 and 14, so that they only rustled insignificantly during use and felt comfortable to wear. When these disposable diapers were practically used on toddlers , the diapers in Examples 20-22 did not cause skin redness. The diapers according to Comparative Examples 10, 13 and 14, on the other hand, gave rise to pronounced or moderate (Comparative Example 13) skin redness.

EXAMPLE 23 By means of a machine for stretching in two directions, heated to 70 ° C, the foil according to Example 20 was stretched simultaneously in both the machine direction and the transverse direction (with the stretching factors 2 x 2), so that a porous foil with a thickness of 50 μm was obtained. The properties of this film were determined and the result is shown in Table 2. Disposable diapers with this porous film as an impermeable layer had as good properties as those of Example 20. 465 310 10 EXAMPLE 24 The same plastic mixture as in Example 22 was formed into a film. This was stretched in one direction by means of a roller, heated to 50 ° C, by a factor of 4 so that a porous foil with a thickness of 15 μm was obtained. The properties of this 1: 1 porous foil were determined and the result is given in Table 2.

On the outside of this porous foil, an LDPE foil with a thickness of 70 μm and with openings with a diameter of 1 mm (20 pcs / cm 2) was laid over its entire surface. Disposable diapers with this composite material as an impermeable layer had as good properties as the diapers of Examples 20-23. (br, * W 465 510 21 Table 2 I! "N Base plastic Filler H low | l Quantity Quantity H Type (weight Type (weight Ä parts) parts) ß Example 20 LDPE 100 BaSO4 150 E gl II II II II II s § "22 L-LDPE" "200 ¿" 23 LDPE "" 150 Ü "24 L-LDPE" "200 j Comparative-" "" 150 examples 10 II II II II H II II II II II II II II "14" "Glass 120 beads *) An attempt was made to stretch the foil no sampling was possible due to frequent breaks during stretching. by a factor of 8, but **) The foil could not be stretched by a factor greater than 2. 465 310 22 Table 2 (continued) I- š Breaking strengthš Moisture penetration-É Stretching - (MD / TD) similarity Softness factor (kg / as mm) s (g / m * / 24 hr) I 4 5 6.0 / 1.5 '3,500 A 5 6.5 / 1.3 f 4,200 A 3 5.5 / 1.3' 4,600 A 2 X 2 § 4.9 / 4.5 3,900 A 4 g e.7 / o.9 4,700 AI Unstretched '2.3 / 2.2 15 A Unstretched - - - 84) - - - 4 4.3 / 0.8 3,000 C 2 **) 1.5 / 0.7 30 C' wn) lO 15 20 25 30 35 465 310 23 COMPARATIVE EXAMPLE 15 120 parts by weight of calcium carbonate with an average grain diameter of 1.2 μm and 20 parts by weight of hydroxylated saturated hydrocarbon plastic (Liquid Polybutadiene GI-2000; Nippon Soda Co., Ltd.) were added to 100 parts by weight of linear LDPE with Mi = 5 and mixed in a Henschel mixer . This mixture was then kneaded and pelleted in a twin-screw extruder. Then these pellets were formed into a foil by means of a blow extruder with a hole diameter of 40 mm. The foil was rolled at 80 ° C by a factor of 3.0 so that a porous foil with a thickness of 50 μm was obtained.

This porous film varied in moisture permeability over its surface and had a certain degree of tack. Disposable diapers with this porous foil as a leak protection gave rise to a certain skin redness in toddlers.

COMPARATIVE EXAMPLE 16 The procedure of Comparative Example 15 was repeated, except that the hydroxylated saturated hydrocarbon polymer was liquid polybutadiene (Nisso PGB; Nippon Soda Co., Ltd.) or gummy EPR (Toughmer PO480; Mitsui Petrochemical Industries, Inc.). In this way, foil with a thickness of 50 μm was obtained. These foils were sticky on the surface and varied over the foil with respect to moisture permeability. Disposable diapers with one of these porous foils as leak protection gave rise to a slight reddening of the skin in young children.

Porous foils produced according to the present invention have a high port density and are very soft and in addition show a slight decrease in mechanical strength despite their insignificant thickness, so that they are well suited as leak-protective layers in sanitary napkins. Conventional sanitary napkins are constructed with a layer of liquid absorbent material such as fluff, cotton, absorbent plastic or the like which is partially covered by a paper layer made impervious to liquid by being treated with a synthetic polymer such as polyethylene or the like after which the whole structure is wrapped in a layer of non- woven. If porous foil according to the present invention is used as a leak-proof layer in sanitary napkins, this layer has a large number of holes which let water vapor through.

Therefore, the bandage keeps the skin dry and does not feel uncomfortable even with prolonged use. The following examples illustrate the use of the porous film of the present invention as a leak-proof layer in sanitary napkins.

EXAMPLES 25-27 Barium sulphate with an average grain diameter of 0.8 μm in the amounts given in Table 3 was added to 100 parts by weight of linear LDPE (L-LDPE) with MI = 2.1 and thus mixed in a Henschel mixer. This mixture was then kneaded and pelleted in a twin screw extruder.

These pellets were then melted at 230 ° C and formed into a film.

This was stretched in a direction between a preheating roller heated to 80 ° C and a stretching roller with a stretching factor according to Table 3 so that a porous foil with a thickness of 20 μm is obtained. The properties of this foil were determined and the result is shown in Table 3. Ties were made by partially covering a filling of fluff with each of the porous foils according to Examples 25-27, the whole was wrapped in a non-woven cloth and overlapping edges were sealed with heat. When these pads were compared to commercially available pads with a liquid impermeable layer of polyethylene coated paper by practical use for long periods of time, pads with layers of the present invention did not give rise to any unpleasant nausea. d 465 310 25 <ooN.v æ.o \ m.N m oow = = = ßw Hwnswxm <oowé móšó m om fi _. __ __ ww Hwaswxm <ooN_m oH \ Nm o oo fl wommm oo fi mmmA | A mw Hwaswxm 73 VN \ ~ E \ wv TE: mm \ wxv Anm fi wv T fi m fi mu noßxmm | mvx fi> v näs | wvxw> w fim æw Qæ æm v w Qm uwcm: Isocowßxsm mxmävm fi mvms fifl æm uwm fi ammm m flfl mnmë

Claims (15)

465 310 10 15 20 25 30 35 26 PATENT REQUIREMENTS A process for producing porous films, comprising melting a plastic mixture consisting of a polyolefin polymer, barium sulphate having an average grain diameter between 0.1 and 7 μm in an amount between 50 and 500 parts by weight per 100 parts by weight of polyolefin polymer and, if necessary, at least one substance selected from stabilizers , antioxidants, dyes, UV stabilizers and lubricants and / or other inorganic fillers or common organic modified additives in addition to barium sulphate in an amount less than that of the added amount of barium sulphate, that a film is produced from the molten plastic mixture and that the film stretched by a factor between 1.5 and 7. Process according to Claim 1, characterized in that the average grain diameter of the barium sulphate is between 0.5 and 5 μm. 3. A process according to claim 1, characterized in that the amount of barium sulphate is between 100 and 400 parts by weight per 100 parts by weight of polyolefin polymer. Process according to Claim 1, characterized in that the barium sulphate is surface-treated with a fatty acid, a metal salt of a fatty acid, silicone, silane or resin acid. Process according to Claim 1, characterized in that the polyolefin polymer is a polyethylene polymer. Process according to Claim 5, characterized in that the polyethylene polymer consists of low-density polyethylene with a melt index of between 0.5 and 7 and a density of between 0.915 and 0.935. Process according to Claim 6, characterized in that the low-density polyethylene consists of a single type of polyethylene polymer. Process according to Claim 6, characterized in that the low-density polyethylene consists of a mixture of polyethylene polymers with different densities. u. Q] 10 15 20 25 30 35 465 310 27 9. A method according to claim 7, characterized in that the melt index is between 1 and 5. 10. A method according to claim 5, characterized in that the polyethylene consists of linear low-density polyethylene. 11. A method according to claim 10, characterized in that the linear polyethylene has a melt index of between 0.5 and 8.5 and a density of between 0.915 and 0.935. Process according to Claim 10, characterized in that the linear low-density polyethylene is a copolymer of ethylene and hexene and / or octene. Porous foil which is waterproof but permeable to water vapor and gases, characterized in that it is produced by a process according to any one of claims 1-12. Use of porous foil according to claim 13 for anti-leakage layers in disposable diapers. Use of porous foil according to claim 13 for leakage prevention layers in sanitary napkins.