DE3331749A1 - Soft film made of polpropylene - Google Patents

Abstract

Transparent, non-tacky, soft film made from polypropylene which contains, per 100 parts per weight, from 0.01 to 2 parts per weight of an additive from the group consisting of organic acids, derivatives thereof, sorbitol derivatives, pigments and finely divided powders of inorganic materials, and is from 20 to 60 per cent by weight soluble in boiling n-heptane and whose crystalline component has a monoclinic crystal structure.

Description

The invention relates to a transparent, non-adhesive, soft film made of polypropylene and a method for its manufacture. In particular, it concerns a transparent, soft film non-adhesive on the surface, which is designed in such a way that the crystalline portion of the low-crystalline polypropylene, which contains an additive, essentially having a monoclinic crystal structure is present.

So far, soft foils in particular have proven to be those enforced from polyvinyl chloride or polyolefins, the former having the disadvantage that they are unreacted Contain monomers and plasticizers on foods can transmit, so that the latter have spread to a greater extent.

In most cases it is used as the starting material for the Production of soft polyolefin films predominantly uses ethylene, while those films are their main starting material Propylene is predominantly in the form of hard films made of highly crystalline polypropylene.

The object of the present invention is to create a soft film for its production the main raw material used is propylene. It has been shown that this task by the Application of a low crystalline polypropylene or polymeric propylene can be dissolved.

In general, the highly crystalline polypropylene is processed into foils with the help of a deformation process, in which the melted resin quickly with water

MEER MÜLLER STEINMEISTER Toy.O Soda ... - 1931

or quenched on the surface of a chilled roll, d. H. using a water cooling blow molding process or a casting process.

On the other hand, low crystalline polypropylene gives instantaneous results using the deformation methods described above However, after being deformed into the sheet, it is a soft sheet with excellent transparency the disadvantage of blocking, as it contains a large amount of amorphous components. These components continue to migrate over time to the surface of the film and lead to a deterioration in transparency and the gloss, with increased blocking effects occurring at the same time, so that finally the surface

II, I) I. i »j whü, vjaa ZUi l'Yihji. ' has that ULtitu. "Kleibäulyoüiiuhai: - · Adopts leu and the adhesion of dusts becomes inevitable, which affects the practical application of the material.

To solve this problem, a method has already been proposed by the applicant (see the August 18 Japanese Patent Application No.

), with which the surface adhesive properties the film can be reduced in that the crystal structure of the crystalline portion of the low crystalline Polypropylene essentially corresponds to the monoclinic system.

The present invention and thus the solution to the problem addressed above is based on the knowledge that a transparent, soft, non-stick film made of polypropylene or polymeric propylene can be obtained by adding an additive to the crystalline portion of the low crystalline To give polypropylene a monoclinic crystal structure.

TER MEER · MÜLLER · STEiKMEISTER ^; Toyo Soda ... - 1931

The low-crystalline polypropylene used according to the invention includes propylene homopolymers and copolymers of no more than 10% by weight of any other than propylene Olefins such as ethylene, butylene, pentene, hexene etc. and propylene. Furthermore, the polymer used according to the invention is a low crystalline, which 20 to Contains 60% by weight of a fraction soluble in boiling n-heptane.

If the soluble portion is more than 60% by weight, the surface tack properties of the film can be impaired can only be improved with difficulty according to the teaching of the invention. On the other hand, when the proportion is less than 20% by weight the problem of surface tack properties Although neglected, the result is, however, a hard film, so that this case according to the invention is excluded.

The portion soluble in boiling n-heptane is generally referred to as atactic polypropylene, with the polymer used according to the invention of the in boiling n-heptane soluble portion not less than 30 wt .-% must be insoluble in boiling diethyl ether. If this insoluble portion is less than 30% by weight, the surface tack properties can deteriorate can only be improved badly.

The low crystalline polypropylene used in the invention has a melt index (melt flow rate) of 0.01 to 50 g / 10 min (ASTM D-1238-73, 19O ⁰ C, 2160 g). If the melt index is less than 0.01 g / 10 min, the processing temperature becomes abnormally high and brings about difficulties in terms of the heavy load on the motor in the processing machine and other problems. On the other hand, leaves with one

TER MEER ■ MÜLLER ■ STEIhiMEISTE R Ύρνρ Soda ... - 1931

Schnielz index of more than 50 g / 10 min the processability in the film formation and it can change the surface tack properties cannot be improved. Furthermore, the molecular weight distribution, which is determined by the ratio of weight average molecular weight results in number average molecular weight, not particularly critical, but is preferably in In terms of physical properties and processability of the material in the range of 3 to 20.

The process for producing the one used according to the invention low crystalline polypropylene is also not particularly critical provided the above mentioned conditions are met. For example, it is possible to mix the in To produce boiling n-heptane soluble part with the insoluble part, although it is economical For reasons, it is preferred to form the material in one operation in the polymerization stage.

The conventional one-step process for preparing the material comprises in the polymerization step the homopolymerization of propylene or its copolymerization with a comonomer in the presence of a Ziegler-

25 Natta catalyst made from a transition metal compound and an organometallic compound in gas phase, bulk, slurry or solution.

The control of the fraction soluble in boiling n-heptane and the fraction insoluble in boiling n-heptane or the melt index of the material is determined by the selection of various factors, such as the production method, the type and the amount of catalyst used gate component, the added amount of an electron donor

TER MEER · MÜLLER ■ STEINMEISTER: T-OVO Soda ... - 1931

nors, the amount of hydrogen added, the polymerization temperature and the polymerization pressure.

As the industrially most important process for the production of the polymer, which is preferably used according to the invention a simplified procedure is recommended. This procedure allows for ash removal and to forego the extraction by using a solvent-free polymerization process, i. H. a Polymerization process in the gas phase or in bulk is used in which a highly active catalyst is used, which consists of a titanium compound present on a magnesium compound as a carrier and a organic aluminum compound.

The fact that the low crystalline polypropylene with the help of this simplified process with low Cost can be made and the fact that from the polymer deemed unsuitable and not being used effectively is a material with diverse Film properties can be formed according to the invention are essential.

According to the invention, organic additives are used as additives Acids and their derivatives, sorbitol derivatives, various pigments and finely divided inorganic materials used, these additives alone or in combination of two or more than two materials this type can be used. 30th

Specific examples of the organic acids are succinic acid, glutaric acid, adipic acid, suberic acid, Sebacic acid, salicylic acid, thioglycolic acid, benzoic acid, p-isopropylbenzoic acid, p-tert-butybenzoic acid, Diphenylacetic acid, monophenylacetic acid, phenyldimethyl-

TER MEER MÖLLER STEINMKISTER, ToyoSoda - 1931

acetic acid and the like. Examples of derivatives of organic acids are sodium benzoate, aluminum benzoate, Aluminum p-tert-butyl benzoate, calcium adipate, amine salts benzoic acid or ß-phenylacetic acid, sodium glutaminate and the same. Dibenzylidene sorbitol can be mentioned as sorbitol derivatives, while inorganic pigments are used Pigments and phthalocyanine and quinacridone organic pigments can be used, such as titanium dioxide in the rutile form, cadmium red, sewer soot, iron oxide, cyanine blue, Cyanine green, polyazo yellow etc.

As finely divided inorganic materials, talc, Use hydrotarsite and the like. As combinations of an organic acid or a salt of an organic Acid and other compounds can be combined with phthalic acid and phthalic anhydride Use calcium and / or barium stearate.

The amount of additive used according to the invention is 0.01 to 2 parts by weight, preferably 0.02 to 1 part by weight per 100 parts by weight of the low crystalline polypropylene. When the amount of the additive is less than 0.01 part by weight, transparency and maintenance can be achieved the improvement of the surface tackiness not be achieved, while on the other hand the use of an amount of additive of more than 2 parts by weight is not preferred for practical reasons, more in view of the coloring caused by the additive than the fact that no further increase in the effect can be achieved.

Various conventional methods can be used to mix the additive with the low crystalline polypropylene will. For example, they can be mixed in a dry state with the help of a blender or mixer.

TER MEER · MÜLLER. STEINMEISf ER

-Toyo soda

. - 1931

10 15

or one can shape the materials into pellets by means of extrusion molding by melting and mixing. The formation of the films according to the invention from the non-adhesive, low-crystalline polymer can be achieved by ^{melting the material at a temperature in the range from 180 to 280 °} C. and allowing it to cool slowly to form a film. As the film-forming method generally used in an industrial scale, there can be mentioned, for example, the air-cooling blowing method using an air cooling system, the compression molding method in which the polymer melted under pressure and heat is slowly cooled by means of a cooling press under increasing pressure, and the like. In these methods, the material is processed under such conditions that the crystalline portion of the polymer adopts a monoclinic crystal structure.

20 25

According to the invention, by adding the additive to the low crystalline polypropylene and by processing it with slow cooling so that its more crystalline Share adopts a monoclinic crystal structure, transparency and surface tack properties of the film compared to a film obtained without the additive.

It is well known that by adding the additives used according to the invention to highly crystalline polypropylene products, formed by injection molding and the like, transparency and mechanical Strength can be improved. When processing into a film, however, the transparency even when using these additives cannot be improved, so the use of these materials has not been considered suitable so far.

35

TER MEER -MÜLLER STEINMEISTER Toyo Soda ... - 1931

If, however, in contrast, according to the invention, these additives are added to low-crystalline polypropylene and this is shaped into a film, the crystalline portion of which has a monoclinic crystal structure there is a surprising improvement in the optical properties resulting from the highly crystalline The knowledge gained from polypropylene could not be foreseen, and in addition, according to the invention can also improve the surface tack properties.

The reason that the films according to the invention with monoclinic crystal structure formed from the low-crystalline polypropylene containing the additive

have been found to have excellent optical properties is not clear; however, it is believed that this is due to the fact that the additive is easier to use in a low crystalline polymer than in a highly crystalline one Polypropylene can be dispersed evenly, due to the fact that the rate of crystallization of the material is slowed down accordingly and therefore easily fine spherical with the help of the additive Crystals can be formed, and ultimately due to the fact that the external opacity of the Slide is remarkably small. The reason for the improvement in surface tack properties appears based on the fact that the area with crystalline structure and the area with amorphous structure through The effects of the additive are closely interwoven, forming a structure that will only change with time little changed, which is supported by the fact that the monoclinic structure is a stable structure is.

If necessary, to the inventively used

TER MEER MÜLLER STEIKMEISTER Toyo Soda ... - 1931

- 11 -

use low-crystalline polypropylene various auxiliaries, such as antioxidants, flame retardants, Lubricants, antiblocking agents, antistatic agents, ultraviolet light absorbers and the like are added, without thereby departing from the scope of the invention.

The invention is explained in more detail below with reference to the accompanying drawing. In the drawing demonstrate

1 shows the X-ray diffraction diagram of the film obtained according to Example 1,

2 shows the X-ray diffraction diagram of the slowly cooled film according to Example 17 with a monoclinic Crystal structure and

3 is an X-ray diffraction diagram of the film of the comparative example 3, which is a smectic

Has structure.

In the drawing, the ordinate shows the diffraction intensity and the abscissa shows the diffraction angle 2θ (in Degree).

In the examples, the properties were determined using determined by the following methods:

30 a) Melt flow rate

This property is measured using the conditions of ASTM regulation D-1238 (190 ^° C., 2160 g).

TER MEER -MÜLLER · STEINMOISTER Toyo Soda,,. - 1931

b) Evaluation of the surface tack properties

The surface condition of the film is observed every hour in an atmosphere with the desired temperature. Then, the stickiness properties are evaluated using the following standard of evaluation: A: No change
B: Slight blocking
C: Heavy blocking
D: Surface is sticky.

c) turbidity

The haze is measured using ASTM D-1003.

d) gloss

The gloss is determined using ASTM D-2457.

e) 5_% ₌ module

This parameter is determined using a No. 1 specimen of Japanese Standard JIS K-6301 with a Jaw spacing of 40 mm and a deformation rate of 50 mm / min measured.

example 1

A stainless steel polymerization vessel is charged Steel with an internal volume of 100 1 with 0.85 g of a mixture of a catalyst component (a), which is by treating 16.8 g of anhydrous magnesium chloride

35 rid with 2.1 g of ethyl benzoate and 2.7 g of titanium tetrachloride

TER MEER MÜLLER STEINMEISTER Toyo Soda ... - 1931

- 13 -

has formed in a ball mill with an internal volume of 0.8 1 over 20 hours under a nitrogen atmosphere, and 0.5 g of triethylaluminum is added as a further catalyst component (b), after which hydrogen is used to control the molecular weight to a pressure of 0.147 bar ( 0.15 kg / cm ² ) and finally introduces 25 kg of liquid propylene in order to carry out a bulk polymerization reaction at a polymerization temperature ^{of 70 ° C. for one hour.} 10

After the reaction has ended, unreacted propylene is flushed out and 10.5 kg of polypropylene are obtained in the form of a white powder.

This polypropylene product contains 39% by weight of the fraction soluble in boiling n-heptane, with 50% by weight of the the fraction soluble in boiling n-heptane is insoluble in boiling diethyl ether. The melt index of the polypropylene product is 3.47 g / 10 min, while the molecular weight distribution (weight average molecular weight / number average Molecular weight) is 11.

To 100 parts by weight of the low-crystalline polypropylene obtained with the aid of the process described above 0.15 part by weight of benzoic acid and 0.1 part by weight of 2,6-di-tert-butyl-p-cresol and 0.1 part by weight are added Tetrakis / inethylene-3- (3 ', 5' -di-tert-butyl-4'-hydroxyphenyl) propionate / methane as stabilizers and mixes in a V-mixer for 10 minutes.

The mixture is then mixed and extruded with the aid of an extruder to form pellets desired composition.

The pellets obtained in this way from the low-

TER MEER ■ MÜLLER · STEINMEISTER ToyÖ Soda ... - 1931

crystalline polypropylene composition, the proportion of which is soluble in boiling n-heptane, 39% by weight and its melt index 3.47 g / 10 min, are extruded with the aid of an extruder with a barrel inner diameter of 40 mm and an L / D ratio of the screw of 28 and extruded through a spiral ring die and formed into one by means of the air cooling blow molding process Processed film, which has excellent transparency and very low surface tack.

The 5% modulus of this film is 192.3 N / mm ² (1960 kg / cm ² ) in the machine direction and 193.3 N / mm ² (1970 kg / cm ² ) in the transverse direction, which values are small in comparison to values of 445.4 N / mm ² (4540 kg / cm ² ) in the machine direction or 443/4 N / mm ² (4520 kg / cm ² ) in the transverse direction of a highly crystalline commercial polypropylene, which means that the invention Slide is soft.

In the molding conditions by the air-cooling Blasverformungsverfahrens, wherein the temperature of the annular die is at 22O ⁰ C, results in a pulling speed of 10 m / min and a blow ratio of 1.5 to give the film in the form of a hose with good stability obtained, which leads to a good, practical product, since the formation of wrinkles and thickness unevenness does not occur.

Examples 2 and 3 30 and Comparative Examples 1 and 2

The measures of Example 1 are repeated, with the difference that the additive is used in the amounts given in Table I.
35

333,749 "

TER MEER · MÜLLER · STEINMEISTER ToyO Soda 1931

- 15 -

Comparative example 3

The low-crystalline polypropylene obtained in Example 1 (which has not been mixed with the additive) is melted and extruded from a spiral ring die with the aid of an extruder with an internal cylinder diameter of 65 mm and an L / D ratio of the screw of 28 to one Foil with a thickness of 40 μm which has good transparency but shows blocking because of the water cooling blow molding process.

Furthermore, the transparency of this material decreases over time, because the sticky component on the surface the foil blooms.

Examples 4 to 13

Films are formed according to the procedure of the example 1, with the difference that the additives given in Table II below are added to the additives given there Sets in.

The results of the investigation of the optical properties and the surface tack in an atmosphere with a temperature of 25 ^° C. or 50 ^° C. within one month after processing into films are the same for Examples 1 to 3 and Comparative Examples 1 and 2 as those from The crystal structures determined by the X-ray diffraction of the films are given in Table I, while the corresponding results of Examples 4 to 14 are summarized in Table II.

It can be seen that the films according to the invention the Foien of the comparative examples with regard to the trans-

TER SEA. MÜLLER. STEINMEISTEFi: Toyö Soda ... - 1931

parence and the surface tack properties are considerable are superior.

TABLE I.

No. of the example Additive Art Used Optical Own Surface tack properties 25 ° C / 50 °
After 1 C)
After 1 After 1 Crystal structure or the Ver
same example p (Parts by weight) schafi
Cloudiness ; en
shine (
Immediately Day week month Benzoin 0.15 (%) after
Manufacturing A / A A / A A / A example 1 acid 4.1 117 A / A nionoclinic Benzoin 0.05 A / A A / A AWAY Example 2 acid 8.0 102 A / A monoclinic Benzoin 0.50 A / A A / A A / A Example 3 acid 11.2 82 A / A ironoclinic _ - AWAY A / C A / D Comparison 37.3 31 A / A monoclinic example 1 Benzoin 0.005 AWAY A / C A / D Comparison acid 35.5 35 A / A monoclinic example 2 - - B / D D / D D / D Comparison 3.0 130 B / B smectic example 3

TABLE II

No. of the case
game or
Comparison
for example Additive
Art Use
te amount
(Weight
"Parts) Optical
scha
Cloudiness
(%) Own
ften
shine Surfaces]
Immediately
after
Manufacturing the rest
(25 ° C /
To
1 day keitseig
50 ⁰ C)
After 1
week teams
After 1
month crystal
structure Example 4 Glutaric acid 0.15 4.8 115 A / A A / A A / A A / A ionoclinic Example 5 Adipic acid 0.15 3.5 121 A / A A / A A / A A / A monoclinic Example 6 Diphenylacetic acid 0.15 6.7 110 A / A A / A A / A A / A monoclinic Example 7 p-tert-butylbenzoic acid 0.15 15.0 75 A / A A / A AWAY AWAY monoclinic Example 8 Sodium L-glutaminate 0.15 3.0 130 A / A A / A A / A A / A monoclinic Example 9 Alundniunibenzoate 0.15 4.5 113 A / A A / A A / A A / A monoclinic Example 10 Dibenzylidene sorbitol 0.15 18.0 70 A / A VA AWAY AWAY monoclinic Example 11 Dibenzylidene sorbitol
Hydrotalsite 0.15
0.10 3.0 129 A / A A / A A / A A / A monoclinic Example 12 Cyanine blue 0.10 6.5 111 A / A A / A A / A A / A monoclinic Example 13 talc 0.20 15.3 74 A / A A / A A / A AWAY monoclinic

TER MEER MÜLLER - STEINMEISTER Toyo Soda ... - 1931

- 19 -

Example 14

The steps of Example 1 are repeated, but using 0.45 g of catalyst component (a) and 4.7 g of triisobutylaluminum as catalyst component (b), applying a hydrogen pressure of 0.049 bar (0.05 kg / cm ² ) and replacing it the additive by 0.3 parts by weight of aluminum benzoate, with the aid of the air-cooling blow molding process, a film is formed from the low-crystalline polypropylene composition which contains 56% by weight of the fraction soluble in boiling n-heptane, of which 40% by weight are insoluble in boiling diethyl ether, and which has a melt index of 4 g / 10 min.

This film has a haze of 2.4%, a gloss of 145% and, even after one month of storage in an atmosphere of 40 ^° C., shows no surface tack and has sufficient softness, since it has a modulus of 68.7 N / mm ² (700 kg / cm ² ) in the machine direction and 69.2 N / mm ² (705 kg / cm ² ) in the cross direction.

If the additive is not used, the film has a haze of 28%, a gloss of 40% and is opaque and shows surface ^{tack after a storage period of 3 weeks at a temperature of 40 ° C.}

Example 15-30 and Comparative Example 4

The measures of Example 1 are repeated, with the The difference is that 0.95 g of a magnesium chloride carrier is present as catalyst component (a) Titanium catalyst used, which can be treated by treating

TERMEER-MULLEFi-STEINMClSTEiR TOVO Soda ... - 1931

of 20 g of anhydrous magnesium chloride with 5.5 ml of isobutyl vinyl ether and 3 ml of silicon tetrachloride for 42 hours in a ball mill with an internal volume of 0.8 1 in a nitrogen atmosphere, by washing with η-hexane and further reacting in 150 ml of titanium tetrachloride for 2 hours 80 ^° C. and filtration is obtained by using 0.5 g of triethylaluminum as catalyst component (b) and applying a hydrogen pressure of 0.196 bar (0.20 kg / cm ² ). In this way, using an air-cooling blow-molding process, a film made of a low-crystalline polypropylene with a melt index of 3.5 g / 10 min, the proportion of which is soluble in boiling n-heptane is 25% by weight, of which 65% by weight are insoluble in boiling diethyl ether.

The optical properties and the change in surface tack properties in an atmosphere with a temperature of 70 ^° C. as a function of time are given in Table III below, together with the corresponding values of a comparative example which was carried out without the use of the additive.

TABLE III

No. of the example or comparative example

Additive

Example 15

Comparative example 4

Art

Benzoic acid

Amount used (parts by weight)

0.15

Optical properties

Cloudiness

6.4

36.4

Surface tack properties
(70 ⁰ C)

Direct
after
Manufacturing

To
Day

After 1
week

After 1
month

Crystal structure

monoclinic

monoclinic

3 ΕΠ Z

TER MEER MÖLLER STEINMEISTER: 'C ¹ OVO Soda ... - 1931

Example 16

Example 15 is repeated with the difference that one works at a hydrogen pressure of 0.147 bar (0.15 kg / cm ² ) and gradually introduces ethylene into the polymerization mixture. In this way, by random copolymerization of propylene with ethylene, 9.5 kg of a white powder with an ethylene content of 4.5% by weight and a proportion of 50% by weight soluble in boiling n-heptane, of which 60% by weight. -% are insoluble in boiling diethyl ether. The melt index of the material is 2.5 g / 10 min.

Following the procedure of Example 1, but using of 0.005 parts by weight of adipic acid as an additive, the material is shaped into pellets, which are then removed with the aid of the Air cooling blow molding process can be processed into a film.

Examination of this film shows that it has a haze of 6.8%, ^{has no surface tack even after one month in an atmosphere with a temperature of 60 °} C. and has a monoclinic crystal structure in X-ray diffraction.

A film is then produced in the same way without the use of adipic acid. However, after two weeks in an atmosphere with a temperature of 60 ^° C., this film shows surface tack in addition to the fact that it is opaque

Is 30 because the haze is 35%.

Example 17

The pellets from Example 1 are produced with the aid of a heating press at a distance of 100 .mu.m for 5 minutes

TER SEA ■ MÜLLER · STEIh ¹ MHIS-TER

Toyo soda

. - 1931

- 23 -

melted, after which the material could be formed using the following four methods to form foils with a Thickness of 100 μΐη lets cool:

(1) Turn off the heater of the heating press to slowly cool the film.

10

(2) The mixture is cooled slowly, the film at a pressure of 98.1 bar (100 kg / cm ²⁾ for 10 minutes, by adjusting the temperature of the heating press to 5O ⁰ C.

15 20 25

(3) It discourages the film at a pressure of 98.1 bar (100 kg / cm ²⁾ during 10 minutes in a set at 0 ⁰ C from cooling press.

(4) The film is placed in water for the purpose of quenching

brought in.

These films is left for one hour in an oven which is heated at 1O ° C intervals from 50 ⁰ C to 160 ⁰ C, respectively, to the temperature noted at which the Oberflächenklebrigkeitseigenschaften occur. The results obtained of the films produced according to the above procedures are as follows: (1) No surface tack (melting of the material at 16O ⁰ C), (2) 150 ⁰ C, (3) 70 ⁰ C and (4) 70 ° C .

When examining these films by X-ray diffraction, it can be seen that in the case of the method

(1) and (2) the crystalline portion is monoclinic, while in the case of the according to the method (3) and (4) is smectic. It is recognizable that in the case of a material with a monoclinic crystal structure a higher temperature is required, to create the surface tack properties than in the case of materials with a smectic structure.

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Claims (1)

Soft polypropylene film Priority: September 06, 1982, Japan, No.P 57-154047 Claims (i.) Transparent, non-adhesive, soft film made of polypropylene, which per 100 parts by weight 0.01 to 2 parts by weight of an additive from the organic acids, their Derivatives, sorbitol derivatives, pigments and finely divided powders made from inorganic materials and has a proportion of 20 to 60% by weight soluble in boiling n-heptane and is more crystalline Share has a monoclinic crystal structure. TER MEER> MÜLLER 'STEirvMfelSTER "ToVO Soda ... - 1931 - 0 - 2. Folic) according to claim 1, el a by ge - k e η η ζ ο i c h η e t that the in boiling diethyl ether insoluble portion is not less than 30% by weight of the boiling n-heptane soluble portion. 5 3. Film according to claim 1, characterized in that the polypropylene has a melt index of 0.01 to 50 g / 1.0 min, measured according to ASTM regulation D-1238-73 (190 ⁰ C, 2160 g). ^^^ f4.) Process for the production of the soft film according to Claims 1 to 3, characterized in that the polypropylene is produced with the aid of a simplified, solvent-free polymerization process using a highly active catalyst from a titanium compound present on a magnesium compound as a carrier and an organic aluminum compound. 20 5. The method according to claim 4, characterized in that the polypropylene is under Melting at a temperature in the range from 180 to 280 ° C formed into a film and then formed cools slowly, so that the crystalline part with a ner monoclinic crystal structure.