FR2556648A1 - PROCESS FOR PRODUCING POROUS FILMS, FILMS OBTAINED AND THEIR USE - Google Patents

Abstract

PROCESS FOR THE PRODUCTION OF POROUS FILMS WHICH INCLUDES THE MIXTURE OF 100 PARTICULAR PARTICULAR DIAMETER OF 0.1 TO 7MICRONS BY WEIGHT OF A POLYOLEFINIC RESIN WITH 50 TO 500 PARTS BY WEIGHT OF BARIUM SULPHATE PREFERABLY HAVING AN AVERAGE PARTICULAR DIAMETER OF 0.1 TO 7MICRONS, THE FUSION OF THE RESIN COMPOSITION RESULTING AND THE FORMATION OF THIS IN THE FORM OF FILM, THEN THE STRETCHING OF THE FILM AT LEAST UNIAXIALLY ACCORDING TO A FACTOR OF 1.5 TO 7. AS A POLYOLEFINIC RESIN, A POLYETHYLENE RESIN HAVING AN INDEX CAN BE USED PREFERABLY. MELTING FROM 0.5 TO 7 AND A DENSITY OF 0.915 TO 0.935, AND MORE ADVANTAGEALLY A LINEAR LOW DENSITY POLYETHYLENE RESIN HAVING A MELTING INDEX OF 0.5 TO 8.5 AND A DENSITY OF 0.915 TO 0.935 AND WHICH IS PREFERENCE A COPOLYMER OF ETHYLENE AND HEXENE AND OR OF OCTEN. APPLICATION TO THE MANUFACTURING OF WATER-RESISTANT POROUS FILMS, PERMEABLE TO HUMIDITY AND GAS, USABLE IN PARTICULAR AS A WATERPROOF SHEET IN DISPOSAL DIAPERS AND HYGIENIC TOWELS.

Description

Process for producing porous films,

films obtained and their use.

  The present invention relates to a process

  improved to produce porous films. More particularly

  it relates to a process for the production of

  porous films which comprises mixing a polyurethane resin

  olefinic acid with barium sulfate as a filler, melting the resulting resin composition and placing it as a film, and then stretching the film at

less uniaxially.

  Conventionally, there are a large number of well known processes for the production of porous films by

  forming a film of a resin composition comprising

  polyolefin resin and any other

  incompatible charges, then stretching of this filmo For ex-

  ple, patent applications published before examination

  JA 47334/82 and 203520/82 describe a production process.

  of porous films which comprises melting a composition

  resin obtained by mixing a polyolefin resin

  with a load and a liquid rubber or a hydro-

  hydroxylated polysaturated carbide, forming a sheet or film of the molten resin composition, and then

  stretching this sheet or film. In addition, the

  patent application published before JA 15538 / '83

  describes a process for producing porous films which

  takes the fusion of a resin composition obtained by.

  mixture of linear resin of low density polyethylene

  with a filler and a liquid hydrocarbon polymer or

  the sheet or film is formed from the molten resin composition and then stretched from that sheet or film. However, the films produced by these methods are disadvantageous in that they provide a tacky surface due to the above component contained in addition to the polyolefin resin and the filler and in that they can be used in practice only at thick

  relatively important because of their low

mechanical resistance.

  In addition, it is disclosed in the copending patent application 149303/83 that such porous films can be used as waterproof sheets in disposable diapers. Porous films useful as water-proof sheeting sheets are produced by mixing parts by weight of a polyolefinic resin with 28 parts by weight of a filler and 10 to 70 parts by weight of a liquid or cerous hydrocarbon polymer. forming a film of the resulting resin composition and then stretching the film by a factor of 1.2 or

  more at least uniaxially. However, this method of

  Porous film production has drawbacks in that certain types of fillers provide poor drawability and thus fail to provide pores.

  completely uniform and that the resulting film tends to

  make an unpleasant noise. In addition, competitive use

  of a hydrocarbon polymer renders this compound unsatis-

  doing so because the hydrocarbon polymer tends to ooze at the

  film surface and causes a sticky feeling.

  Such porous films are also useful as waterproof sheets in sanitary napkins. In this connection, a sheet of paper which has been made impervious to liquids by means of

  a synthetic resin such as polyethylene. How-

  the resultant sanitary napkins have the disadvantage

  deny an unpleasant sensation during use.

  prolonged use because of their lack of permeability

with water vapor.

  Accordingly, the present invention obtains

  to provide an improved process for producing porous films. Another object of the present invention is to provide a method for producing porous films which have a sufficiently high porosity and thus offer high permeability to moisture and gases, while maintaining

  excellent resistance to water.

  Another object of the present invention is to provide

  a process for the production of porous films, the surface

  it's not sticky, which have excellent sweetness and

  have a low resistance reduction.

  The present invention furthermore aims to provide

  create an improved waterproof sheet useful in

to throw away.

  Another object of the present invention is to provide

  to form an improved waterproof sheet useful in sanitary napkins. Other objects of the present invention will be

  apparent from the following description:

  In accordance with the present invention, there is provided a method for producing porous films which comprises the

  melting of a resin composition consisting essentially of

  100 parts by weight of a polyolefinic resin and 50 to 500 parts by weight of barium sulfate, film forming of the molten resin composition, and then stretching of the film by a factor of 1.5. -7, at

less uniaxially.

  The expression "a composition comprising a resine

  essentially 100 parts by weight of a polyethylene resin

  olefinic acid and 50 to 500 parts by weight of barium sulfate "used herein indicates that the resin composition may further contain (1) at least one additive selected from

  stabilizing agents, anti-oxidants, dyes, absorbers

  bant ultraviolet light and common lubricants and / or

  (2) In addition to barium sulphate, other inorganic

  (in particular calcium carbonate and the like) or common inorganic and organic modifying agents in an amount less than that of the barium sulphate used (for example not more than 20% with respect to the amount of sulphate barium used), but the addition of liquid rubber, a hydroxylated hydrocarbon hydrocarbon or a hydrocarbon polymer as described in the patent applications published before examination indicated above JA 47334/82, 203520/82, 15538 / '83 and 149303 / '83, must be positively avoided in order to obtain a porous film without a surface

sticky.

  According to the present invention,

  produce porous films whose surface is not

  and which have excellent properties and do not

  could be obtained according to the prior art without using any of the additives described above

  used in the prior art. This can be done

  by determining the type of load; its quantity

  used and preferably its particle diameter

  way; preferably using a polyethylene resin

  low density ethene having a density and a fu-

  and more preferably a linear resin.

  re of low density polyethylene (especially a resin

  linear low-density polyethylene comprising a

  ethylene and hexene and / or octene polymer) which more preferably has a density and a melt index

  and stretching the film according to a specific factor

fic.

  Polyolefin resins which can be used

  in the present invention include homopoly-

  such as polypropylene, low density polyethylene, high density polyethylene, polyethylene

  linear low density, polybutylene, etc .; copo-

  polymers such as an ethylene-propylene copolymer, an ethylene-butylene copolymer, an ethylene-copolymer

  vinyl acetate, etc .; and their mixtures.

  Among these resins, low density polyethylene resins having a subscript are preferably used.

  melting point of 0.5 to 7 (0.5 to 8.5 for resins

  low density polyethylene) and a density of 0.915 to 0.935. Although it is better to use a

  resin alone, it is possible to use any kind of

  polyethylene resins having different densities.

  The melt index is preferably in the range of 1 to 5. If the melt index is less than 0.5 or greater than 7 (8.5 for linear low density polyethylene resins), the resin will have a markedly reduced ability to form a film and may fail to provide a film having a thickness

0 weak and uniform.

  On the other hand, if the density is less than

  0.915 or greater than 0.935, the resin will exhibit

  study at 1: reduced stretching and greater rigidity and can

  not succeed in providing a soft film.

  Particularly preferred polyolefin resins

  are linear resins of low polyethylene

  density. Linear resins of low-density polyethylene

  are copolymers of ethylene and one or more

  olefins, and they differ from the poly-

  Low density ethylene prepared according to the conventional method

  at high pressure. Linear polyethylene resins

  Densities are prepared by the low pressure process and useful olefins include butene, hexene, octene, decene and the like. The difference between low pressure polyethylene resins treated at high pressure and low density polyethylene resins treated at low pressure is that, from the point of view of

  view of the chemical structure, the former are poly-

  mothers strongly branched while the latter are straight chain polymers. Among these linear resins of low density polyethylene, it is particularly preferred

  copolymers of ethylene and hexene and / or octene.

  In the practice of the present invention, it is preferable

  fable to use barium sulfate with a diameter

  average particle size of 0.1 to 7 microns and preferably still

  0.5 to 5 microns.-If the average particle diameter

  less than 0.1 micron, we can not obtain

  are well defined. On the contrary, if this diameter is greater than 7 microns, the resulting film will have poor drawability and thus well defined pores may be present.

  difficult to obtain, just as in cases where the dia-

  average particle size is too low.

  Barium sulfate is used in an amount of 50 to 500 parts by weight, and preferably 100 to 400 parts by weight, per 100 parts by weight of the resin

  polyolefin. If the amount of barium sulphate used

  less than 50 parts by weight, it is not possible to obtain a sufficiently high porosity whereas if this

  amount is greater than 500 parts by weight, the film

  sultant can not be stretched completely because of his

  increased rigidity and will therefore reduce the

site.

  It is preferable to subject the sodium sulfate to

  ryum to a surface treatment with a fatty acid or a metal salt thereof, a silicone, a silaneun resin acid or the like, as this treatment is effective to improve its dispersibility in the resin and to produce

well-defined pores.

  In so far as the effects of this

  In addition to barium sulfate, other inorganic fillers such as calcium carbonate or the like or common inorganic and organic modifying agents can be used. However, these additives must be used in a quantity not exceeding 20% in relation to the amount of barium sulphate

Implementation.

  Now the process according to the present invention

  The production of porous films will be described

specific section below.

  Depending on the requirements, at least one additive selected from stabilizing agents, antioxidants, dyes, ultraviolet light absorbers and lubricants is added to a polyolefinic resin and barium sulfate. These ingredients are mixed in a Henschel mixer, super-mixer or rocker. Then, the resulting mixture is kneaded and granulated.

  using an ordinary single or double helix extruder.

  Then, with a swelling or T-die extruder, these granules (alone or mixed with polyolefin resin granules) are melted at a higher temperature.

  at the melting point of the polyolefinic resin (preferably

  20 C or more) and below the

  decomposition of it, then put in the form of a film.

  In some cases, the above mixture may be directly

  put in the form of a film with an extruder, instead of

  to be granulated. Then the film is stretched at least once

  axially according to a factor of 1.5 to 7 according to a conventional technique such as a draw on a cylinder, a widening or the like. This stretching can be performed in stages and / or in two or more directions. In the case of biaxial stretching, however, it is best to stretch

  the film simultaneously in both directions. In order to increase

  to bring about the morphological stability of the pores, the stretched film

can be annealed by heating.

  Porosity is determined by the amount of

  barium sulfate used, the draw factor and similar

  lar. If the stretching factor is less than 1.5, a sufficiently high porosity can not be obtained, while

  if this factor is greater than 7, it can not be

  a porous film on a regular basis because of its frequency

  break during the stretching process.

  The porous films produced according to the process of the present invention are characterized by high porosity, excellent softness and low

resistance.

  In addition, since the good affinity between the polyolefinic resin and the barium sulfate provides good drawability, not only good workability but also even distribution can be achieved.

  pores and thus regularly produce a porous film.

  In particular, when using as a base resin a

  linear resin of low density polyethylene, the film

  sultant has a very small reduction in resistance.

  Thus, it is possible to produce porous films that

  are thinner (eg about 10 microns thick)

  that those produced by the processes of art

prior.

  In addition, since the resin composition does not

  holds none of the liquid rubber, polysaccharide

  hydroxylated resins and hydrocarbon polymers used in

  processes of the prior art, the surface of the porous film

sultant is not sticky.

  Thus, the porous films according to the present

  invention have a sufficiently high porosity and manifest

  therefore have good permeability to moisture and gases while maintaining excellent water resistance, if

2556648 ,.

  although they can be used in clothes and in

  hygienic applications. In addition, they can also

  should be used as a filter media because of the

  regular distribution of their pores.

  The present invention is further illustrated by the following examples. However, these examples

  given by way of illustration and can not be

  avoid the scope of the present invention.

  In the examples, the melt index (MI): 10 is determined according to ASTM D-1238 and the density

according to ASTM D-1505.

  In the examples also, the properties of the film are evaluated according to the following procedures:

(1) Resistance and elongation.

  A piece of film measuring 25 mm (wide) x 100 mm (long) is evaluated with a tension speed of

  mm / minute, using a trac-

  Tensilon. Resistance and elongation at break are determined in the machine direction (MD) and in

the transverse direction (DT).

(2) Permeability to moisture.

  The permeability to moisture is evaluated according to

ASTM E96 (Method D).

(3) Sweetness.

  The softness to the touch is evaluated and attributed to

  drunk a note according to the following criteria: A = very soft and smooth B = rather soft and smooth C = hard and rough

  Examples 1 to 19 and Comparative Examples 1 to 9

  Each of the fillers listed in Table I is added to the corresponding base resin in the

  quantity indicated in Table I and then mixed with

  ci using a Henschel mixer. Then, with a

  double helix, the resulting mixture is closely

  mixed and granulated. Then, in a T-die extruder, these granules are melted at a temperature of 80 ° C higher than the melting point of the base resin and formed into a film. This film is stretched uniaxially or biaxially (example 3) according to a factor

  which is shown in Table I to provide a film capable of

  with the thickness given in Table I. However, the film is not stretched in Comparative Example 1 and

  can be stretched into a porous film in the examples

  In Comparative Examples 5 and 8, the film can be stretched only up to a factor of up to

  2. In Comparative Examples 3 and 7, it can not be

  hold sample because of frequent breaks in

during the drawing process.

  The characteristics of strength, elongation, moisture permeability and softness of porous films

  thus obtained shall be assessed in accordance with the procedures

  written above and the results are gathered in the

Table I.

/

TABLE I

  Base Resin Type 1) Trade Name Index TYP Density (Manufacturer) Melting (g / c3 (g / 10 min) REXLON F-41 (Nippon Example 1 LDPE Petrochemicals Co., 5I0 0923 Ltd.) "2

"3" 3 "".

  MIRASON 45 (Mitsui 4 Polychemicals Co., 1; 60920 Ltd.) Ir 5 Ir II 9

UBE POLYETHYLENE

  "6 F0191 (Ube Kosan 079 0 912 K.K.) Neo-zex 4330 (Mitsui

Petrochemical Indus-

"7 tries, Inc.) / UBE 3.0 07940

POLYETHYLENE VF430

  (Ube Kosan K.K.) = 2/1 8 L-LDPE NUCG-5511 (Nippon 0920 Unicar Co., Ltd.)

9 .. gl Dv ..

  Ultzex 2020L (Mitsui Petrochemical Indus- tries, Inc.), 11 ....., i

"1 2 ........

"13 ...

  - TABLE I (Continued) Filler Factor Thickness Diameter 2) of the film Particle type Stretch quantity of the film Average Particle Tye (μm) (P / 100 r). 1m) BaSO4 018 150 4 40 d. I, _, _ Z ,,,, t * 2X; -2 "I" n 1 72 130 5 50

"__ 5! 0 120"

"n 12" 33) h., 100 4 "i 150 5 15

"4 2 50 65 40

"., 0 8 150 5

"015 100 7 10

300 3 40

  l ,. TABLE I (cont'd) Resistance Elongation (%) Permeability (kg / 25 mm) at humidity DM DT DM DT (g / m2 / 24- h) O./f 1> 5 80 350 3 500 At t13 60 300 4 200 A

9 475 200 200 3 900 A

j51) 5 1200-

  LLLI. 1) 5120 and j0 3000 A 3! 9 01! 55 390 I 1 00 r

__ _ _

50,200 2,000 C

  f5 IrI8 130 510 I 5 00 A 2; 3 0d7 40 120 8 500 A '3r_5 i1 78 3620 5 500 A

___ _ _ _ _t_ _ _ __ _ _ _ _ _ _.

  I3 0; t 40 I2 (2 5000 ^ __ __ __ __ _ _ _ _ _ TABLE I (continued) Base resin Trade name Index Type (1) (melting) manufacturer Density (g / 10 min) <g / cm3 Ultzex 3010F (Mitsui Example 14 L-LDPE Petrochemical Industries (Inc.), Ultzex 2020L (Mitsui "Petrochemical Industries, Inc.) Ultzex 20100J" 16 (Mitsui Petrochemical 8001920 Industries, Inc.) , Hi-zex HZ5000S 17 HDPE (Mitsui Petrochemical 079 09954 Industries, Inc.)

MITSUI NOBLEN JS-G

  18 PP (Mitsui Toatsu 1; 5 0; 890 Chemicals, Inc.)

MITSUI NOBLEN MJS-G

  "19 EPC (Mitsui Todtsu Chemicals, Inc.) TABLE I (cont.) Charge Diameter 2) Thickness Factor Particulate Type Amount Idetirace of the average film (Pm) (P / 100 r) (IJm) DaSO 4 5.0 150 5 50

OS 500 2 40

* 0 8 200 3

"150 5

  TABLE I (continued) Resistance Elongation (%) Permeability (kg / 25 mm) Humidity Softness DM fDT DM DT (g / m / 24 h)

> 1 14 110 400 6 700 A

0 1.0 35 20 5000 A

5 l14 105 420 4 700 A;

870 2 2 70 400 4 500 C

3 2; 5 90 350 4 900 C

971 2) 3 88 520 4 000 C

  TABLE I (continued) Basic resin Type 1) Trade name Index Density Type C-merged type of melting3 ___ ___- (manufacturer) (g / 10 min) (g / cm3) Example Ultzex 2020L (Mitsui cpL-LDPE Petrochemical Indus- 2 1 0 920 tries, Inc.)

"2" ".

t. _ _

"3"

  If 4 i! 1-6, NUCG-5511 (Nippon Unicar Co., Ltd.). "

t 8 ....,. .

  PETROSEN 207 (Toyo 9 LDPE Soda Manufacturing 8 0, 924 Co., Ltd. otes 1) LDPE = low density polyethylene L-LDPE = linear low density polyethylene PP = polypropylene

  EPC = ethylene-propylene copolymer.

  2) Parts by weight of the load per 100 parts in

weight of the base resin.

  3), 5) & 7) The maximum value to which can be

  performed stretching on a regular basis.

  4) & 6) It is not possible to obtain any sample because of frequent breaks during the drawing process. TABLE I (continued) Load Diameter Factor Thickness

Diameter z) of film stretching

  Particulate Type Average Stretching Amount um) (P / 100 r) pm) BaSO 08 150 Unstretched 50 600 My Shot

-

  CaCO3 10 701 Balls 12 120 2 50 BaSO4 glass. 30 5 40

"100 86)

Balls "27) 60 of 2 60 glass

BaSO4 "130 Not drawn -

2556648.

  TABLE I (continued) Resistance (kg / 25 I tn Elongation (%) Perm6ab} i-1i t _________g at / 251 'humidityDD DM DT DM DT (g / m / 24 h) 2 75 2p3 570 480 15 A

4 3 0 8 20 100 3,000 C

1 5 0 7 140 290 30 C

  475 1j0 105 430 15 C-0 _ 0 4 j _-40 _ _

 0 075 1 40 C

  Porous films produced according to the process of the present invention have a high porosity and excellent softness and, moreover, they exhibit a slight reduction in strength, so that they are very suitable for use as a waterproof sheet. in

  disposable diapers. Although such a waterproof sheet is generally

  usually used as the outer layer of the disposable diaper, it can be superimposed on the outer side of

  the waterproof sheet a material (such as a perforated film

  or a sterically embossed sheet) does not alter its permeability to moisture so as to give it the appearance

fabric.

  In such disposable diapers, one can use

  any common products absorbing a liquid

  taking wadding composed of pulp fibers, this wadding being wrapped in absorbent paper or the like, polymeric absorbents having a high absorption rate

of water, or the like.

  As a liquid permeable sheet that will be

  in direct contact with the skin, it is preferable to use

  a non-woven fabric composed of polyester fibers,

  nylon fibers, polyolefin fibers or the like.

  In addition, pressure-sensitive ribbons may be used to secure the layer and resilient members (such as rubber elements) disposed along the side edges

to prevent any leakage.

  Discharge layers are prepared by disposing a liquid absorbent product on the waterproof sheet as described above, and then stacking on a sheet

permeable to the liquid.

  In disposable diapers using the porous film of the present invention as an etanzh sheet, the

  outer waterproof sheet offers a large number of pores.

  As these pores let the water vapor pass while retaining the water droplets, the baby's skin is not wet but kept dry, so that it has little tendency to develop the rash due to at the layer. Furthermore,

  they also have the advantage of being difficult to

  thanks to their high resistance and to be sufficiently

  soft to produce no unpleasant noise.

  The following examples illustrate the use of the porous film of the present invention as a sheet

reed in layers to throw.

  ii eeels 20 to 22 and comparative examples 10 to 14.

  Barium sulphate having a diameter is added. 1.5 micron average particle size or each of the other ihrs indicated in Table III at 100 parts of low density polyethylene (LDPE) odds having a subscript.

  ] .5 cl> merger (IF) of 3 (examples 20 and 21) or of poly-

  4-hydroxylamine (L-LDPE) having a melt index (IF) of 5 (Example 22 and Comparative Examples 14a), in an amount as indicated in the table

  ! then mixed with a Henschel mixer. In-

  The resulting mixture is intimately kneaded and formulated as granules using a double-blender. Then, using a T-die extruder, these granules are melted at 130 ° C. and put into the form of a shot. This film is uniaxially drawn to a heating cylinder heated to 50.degree. C. and a drawing cylinder according to a factor indicated in Table II so as to provide

  a porous wire having a thickness of 50 microns. Professionals-

  The porous films thus obtained are evaluated and the results shown in Table II. O-rolls are prepared by disposing a wadding and a non-woven polyester fabric on each of the porous films obtained in Examples 20 to 22 and in the corresponding examples 10, 13 and 14, and then arranging the ribbons.

  sensitive to, pressure and rubber elements.

2556648.

  The disposable diapers of Examples 20 to 22 are

  with regard to resistance, the permeation

  moisture and softness to those that are pre-

  trimmed in Comparative Examples 10, 13 and 14, so that they produce only a slight rustling current

  of use and seem comfortable to the touch. Lors-

  These disposable diapers are evaluated by using them as

  babies, examples 20 to 22 do not provoke

  no rash on the user's skin. At the

  milking, disposable diapers of comparative examples 10, 13

  and 14 cause a significant eruption or slight eruption

tion (Comparative Example 13).

Example 23.

  Using a heated biaxial stretching machine

  At 70.degree. C., the non-stretch film formed in Example 20 was simultaneously stretched both in the machine direction and in the transverse direction (by 2 × 2 factors) to provide a porous film having a thickness of microns. The properties of this porous film are evaluated and the results indicated in Table II. From layers to

  throw using this porous film as pre-sealed foil

  feel as good as those in Example 20.

Example 24.

  The same resin composition as used in Example 22 is formed into a film Uniaxially stretching this film by a factor of 4 using a cylinder heated to 50 C, to obtain a film porous having a thickness of 15 microns. The properties of this porous film are evaluated and the results provided

in Table II.

  We have on the outside of this porous film

  a LDPE film 70 microns thick, provided with

  tures 1 mm in diameter (20 / cm2) over its entire surface.

2556648.

  Disposable diapers using this composite product as a waterproof sheet also exhibit a performance

  as good as that of the layers of Examples 20 to 23.

TABLE II

  Base resin Charae Q'2antityj Quantit * Type (Type-parts divided by number) by weight)

o _ i10ts) -

-example20 LDPE 100 BaS04 150

21 .... _

"22 L-LDPE 200

23 LDPE _ 150

24 L-LDPE. 200

F3xnn e,]., It 51 the 150

comp. 1r.

  11, .... 600 "12 i.f. 150 "13 ... CaCO3> 14 __ _ _ _ Balls 2 _ glass | __" Lz4 ... H. 120 q O) We try to stretch the film by a factor of 8, but we can not have any sample in because of the 3 'frequent breaks occurring during the drawing process. ) The film can not be stretched by a factor of more than 2. TABLE II (cont.) Resistance Per: necability Factor [DM / DT] at moisture Softness of stretch 2 (kg / 25 mm) (g / m / 24 hrs)

4 6X0 / 175 3 500 A

615/1! 3 4.200 A

3 575/1 13 4 O00 A

-.........

2 X 2 4,9 / 4/5 3,900 A

4. 6.7 / 019 4 700 A

Unstretched 2) 3 / 2r2 15 A '-

Unstretched -

8>

8 *) ___

4 473/0; 8 3 -000 c

2 1; 5/017 30 C

Comparative Example 15

  120 parts by weight of calcium carbonate having a mean particle diameter of 1.2 micron are added

  and 20 parts by weight of a hydrocarbon polysaturated hydrocarbon

  Xylated (Liquid Polybutadiene GI-2000, Nippon Soda Co., Ltd.)

  to 100 parts by weight of linear low-density polyethylene

  (L-LDPE) having a melt index (MI) of 5,

  mixing is carried out using a Henschel mixer.

  Then the resulting mixture is intimately. kneaded and granulated with a double helix mixer. Then, these granules are formed into a film with a 40 mm diameter swelling extruder. This film is stretched on a 30 C cylinder by a factor of 3.0 to obtain a porous film having a thickness of 50 microns. The moisture permeability of this porous film varies depending on the site under study and the film surface is tacky. Disposable diapers using this film pro.eL.x as a waterproof sheet cause a slight eruption

slr the skin of babies.

rfxzPple comparative 16.

  The procedure described in Comparative Example 15 is repeated except that liquid polybutylidene (Nisso PBG, Nippon Soda Co. Ltd.) is used.

  or rubbery EPR (Toughmer P0480; Mitsui Petroche-

  mnica.l Industries, Inc.) as hydroxylated polysaturated hydrocarbon. Thus, films having a thickness

  50 microns. These porous films have a surface area

  Rim and their permeability to moisture varies depending on the site studied. Disposable diapers using each of

  these films porous as a waterproof sheet cause a slight

  z20 -aSer rash on baby's skin.

  Porous films obtained according to the process of the present invention have a high porosity and a

  excellent smoothness and, moreover, they show a low

  In spite of their small thickness, they are very suitable for use in comwie

  Ie waterproof in sanitary napkins. Services

  Conventional sanitary towels are constructed in such a manner that a liquid absorbent product, such as cotton wool, cotton, absorbent resin or the like, is partially covered with a paper film which has been rendered liquid-impermeable by a liquid-absorbing material. treatment with a zymetic resin such as polystyrene or the like and the resulting structure is then wrapped in a nonwoven fabric. In sanitary napkins employing the porous film of the present invention as a sheet

  waterproof, it offers a large number of pores that leave

  feel the water vapor. As a result, they can

  keep the skin of the user dry and do not

  there is no uncomfortable feeling, even if

prolonged

  The following examples illustrate the use of the porous film of the present invention as a sheet

  waterproof in sanitary napkins.

Examples 25 to 27

  Barium sulfate having an average particle diameter of 0.8 microns to 100 parts by weight of

  linear low density polyethylene (L-LDPE) having a

  amortization ratio (IF) of 2.1 in the indicated quantity

  in Table III, and then mixed with a mixture of

  Henschel. Then the resulting mixture is intimately

  mixed and granulated with a

  double helix mixer. Then, in a wire extrud-

  In T, these granules are melted at 230 C and put into form

  of a film. This film is stretched uniaxially between a cylinder

  preheat heated to 80 C and a draw roll, according to a factor shown in Table III, to provide

  a porous film having a thickness of 20 microns. Professionals-

  The properties of this porous film are evaluated and the results summarized in Table III. Sanitary napkins are prepared by partially covering a cotton pad with each of the porous films obtained in the examples.

  to 27, by wrapping the resulting structure in a fabric

  non-woven fabric and then sealing the

  overlapping. When comparing these sanitary napkins to commercially available napkins having a liquid impervious film coated with

  using them in practice for

  periods of time, it is found that the towels

2556648.

  hygienic products according to the present invention do not provoke

  no unpleasant feeling of lack of air.

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Claims (16)

  1. Production method for porous films   which comprises melting a resin composition   essentially as a polyolefinic resin and a load incompatible with it, the formation of   film of the molten resin composition and then the label   the film at least uniaxially,   in that the incompatible feed is barium sulfate, barium sulfate is used in an amount of 50 to 500 parts by weight per 100 parts by weight of   the polyolefin resin and the film is stretched according to a from 1.5 to 7.   2. Process according to claim 1, characterized   in that the average particle diameter of the sulphate of   barium is in the range of 0.1 to 7 microns.   3. Process according to claim 2, characterized   in that the average particle diameter of the sulphate of   barium is in the range of 0.5 to 5 microns.   4.Process according to one of claims 1 to 3, characterized   in that the barium sulphate is used in a quantity   from 100 to 400 parts by weight per 100 parts by weight polyolefin resin.   5. Process according to one of claims 1 to 4, characterized   in that the barium sulphate has been subjected to   superficial with a fatty acid or a metal salt   of it, a silicone, a silane or a resin acid.   6.Process according to one of claims 1 to 5, characterized   in that the polyolefinic resin is a resin of lyéthylene.   7. The process according to claim 6, characterized   in that the polyethylene resin is a low density polyethylene resin having a melt index   from 0.5 to 7 and a density of 0.915 to 0.935.   8. Process according to claim 7, characterized   in that the low density polyethylene resin is a unique resin.   9. A process according to claim 7, characterized   in that the low density polyethylene resin is a mixture of polyethylene resins having different densities.   10. Process according to one of claims 7 to 9, characterized   in that the melt index is in the range of 1 to 5.   11. A process according to claim 6, characterized   in that the polyethylene resin is a resin   low density polyethylene.   12. A process according to claim 11, characterized   in that the linear low density polyethylene resin has a melt index of 0.5 to 8.5 and a density of 0.915 to 0.935.   13.Procedure according to claim 11 or 12, characterized   in that the linear low density polyethylene resin is a copolymer of ethylene and hexene and / or octene.   14. Porous film having water resistance, moisture permeability and gas permeability,   as obtained by carrying out the process according to any one that claims 1 to 13.   15. Disposable diaper, characterized in that it comprises at least one porous film according to claim 14, as a waterproof sheet.   16. Sanitary napkin, characterized in that   it comprises at least one porous film according to the   dication 14, as a waterproof sheet.