Polyolefin-based articles printed by means of inks for PVC and processes for their manufacture

The invention relates to articles including at least one polyolefin, which are surface-treated and printed with inks for PVC, which are characterized by the surface presence of fluorine and oxygen in concentrations such that the oxygen/carbon atomic ratio (O/C), measured by ESCA spectroscopy at a depth of 1.5 nm, is at least 0.08 and that the fluorine/carbon atomic ratio (F/C) (measured in the same way) has a value of at least 90% of that of the O/C ratio and of not more than 290% of this ratio. It also relates to a process for their manufacture.

FIELD OF THE INVENTION 
The invention relates to polyolefin-based articles printed by means of inks 
for poly(vinyl chloride) (PVC) and to a process for their manufacture. 
TECHNOLOGY REVIEW 
In many applications, articles consisting of plastic, and in particular 
films, sheets and hollow bodies, are printed by means of conventional 
printing techniques such as silkscreen printing, photogravure or 
flexography. 
Inks have been developed specifically for printing on articles consisting 
of certain polymers exhibiting fairly specific surface polarity 
characteristics, such as a high surface tension, for example on articles 
based on polymethyl methacrylate (PMMA) or polyvinyl chloride (PVC); they 
are generally referred to as "inks for PVC". 
Inks for PVC are highly valued by printers because they impart to the 
printed designs a print quality which is superior to that generally 
obtained by means of other types of inks for plastics. As stated above, 
these inks can be employed on articles made of PVC, for example on PVC 
films. However, increasingly more frequent attempts are currently being 
made by plastics converters in order to substitute polyolefins (PO) for 
PVC. To meet this demand new surface treatment techniques have had to be 
developed by the plastics and paints industry in order to make it possible 
to print PO articles on conventional printing lines. In fact, because of 
their nonpolarity, some plastics such as polyolefins require, before they 
are printed, an appropriate surface treatment such as corona discharge, 
flaming, plasma treatment, fluorination or oxyfluorination, and the use of 
an ink adapted to these materials. Although these treatments increase the 
polarity of the surfaces thus treated, the inks employed for printing 
these articles remain specific to them; they are commonly referred to as 
"inks for polyolefins". Unfortunately, these inks are inefficient for 
printing articles made of PVC, to which they do not adhere. Similarly, 
inks employed for printing PVC generally do not adhere to polyolefin-based 
articles, even when the latter have been surface-treated. 
This situation obliges the printers to change an ink depending on whether 
they are printing PVC articles or polyolefin (PO) articles, and this 
involves complete cleaning of the plant. In addition, printers remain 
highly interested in inks for PVC, which in many cases give a superior 
print quality. 
There is therefore a continuing market demand either for a PO film 
printable both with inks for PVC and with inks for PO, or for a universal 
ink which is as effective as the inks for PVC but usable both on 
surface-treated PO supports and on PVC supports. Neither of these two 
solutions is available as present. 
Much work has been done to explain the adhesiveness of inks by the chemical 
modifications to which the articles surface-treated by treatments such as 
corona discharge or flaming are subjected at the surface. For example in 
the case of polyethylene articles, the adhesiveness and the degree of 
oxidation of the surface after the treatment have been correlated (The 
Effect of Corona and Ozone Treatment on the Adhesion of Ink to the Surface 
of Polyethylene--Polymer Engineering and Science, Jan. 1977, vol. 17, No. 
1, pp. 38-41). Plasma treatment has also been widely investigated; 
unfortunately, this technique is costly and remains restricted to 
noncontinuous treatments of products of high added value, and this rules 
out the continuous treatment of running products such as PO-based films. 
Special attention has been given in recent years to techniques involving 
fluorination (as described, for example, in U.S. Pat. No. 4,296,151) and 
oxyfluorination. Both these techniques, which can be practised 
continuously, are known to improve the adhesiveness of ink or of various 
coatings to PO-based articles. In a document (WO 93/24559) relating to 
packaging films exhibiting certain tribological properties and 
characteristics making them subsidiarily suited for certain types of 
printing it has furthermore been recommended to employ particular surface 
contents of oxygen and of fluorine. 
At the present time, however, despite all this work, no solution makes it 
possible to produce polyolefin-based articles which are printable equally 
well with inks for PVC or for PO. 
Furthermore, some of the surface treatments referred to above are effective 
only in the short term, that is to say that, for example, a polyolefin 
film treated by corona discharge is actually suitable for better quality 
printing with an ink for PO during the weeks that follow its treatment, 
but loses this property as time passes. This constitutes a considerable 
industrial and economic disadvantage, seeing that most articles are 
printed elsewhere than at their place of manufacture, or are stored before 
being printed, which means that a period of several months can sometimes 
separate their manufacture and their printing. 
SUMMARY OF THE INVENTION 
A first objective of the invention is therefore an article in which at 
least a surface region includes at least one polyolefin and which is 
surface-treated by means of oxygen and fluorine and printed by means of an 
ink for PVC.

DETAILED DESCRIPTION OF THE INVENTION 
More precisely, the invention relates to an article printed by means of an 
ink for PVC, in which at least a surface region includes at least one 
polyolefin and has been treated by means of oxygen and fluorine, 
characterized by the surface presence of fluorine and oxygen in 
concentrations such that the oxygen/carbon atomic ratio (O/C) measured by 
ESCA spectroscopy at a depth of 1.5 nm is at least 0.08, and that the 
fluorine/carbon atomic ratio (F/C), measured in the same way, has a value 
of at least 90% of that of the O/C ratio and of not more than 290% of this 
ratio. 
The articles aimed at within the scope of the present invention may be any 
type, especially films, sheets or plates, or else hollow bodies such as 
bottles, drums, storage containers, flasks, pipes and the like. The 
invention is particularly advantageous in the case of flat articles, 
especially in the case of films. These flat articles may be produced by 
any means, especially by calendering, by extrusion or by coextrusion, for 
example by blow-extrusion, extrusion-coating, extrusion with a flat die, 
and by related coextrusion techniques. In accordance with the invention at 
least one surface region of the article must include at least one 
polyolefin. This region preferably consists essentially of at least one 
polyolefin. One or several other parts of the article may consist 
essentially of one or several other materials such as a metal or a 
cellulose-based material. The invention applies to single-layer and 
multilayer articles. Thus, for example, the invention applies inter alia 
to multilayer articles in which at least the printed surface layer is 
polyolefin-based, it being possible for one or several other layers to 
consist essentially of one or several other materials. 
The abovementioned definition of the surface region refers to the surface 
of the article before its printing and not to the ink with which it may 
eventually be covered. 
In accordance with the invention the articles are printed by means of an 
ink for PVC. "Ink for PVC" is intended to mean an ink which, when applied 
onto a PVC substrate, adheres well to the latter, that is to say obtains a 
classification of "1" or "2" in the test defined by the ASTM standard 
D-3359 ("scotch tape test"). Nonlimiting examples of such inks are 
provided below, together with examples of printing processes. 
Polyolefins are intended to denote both olefin homopolymers and copolymers 
including at least 70% of units derived from olefins, any copolymer 
consisting of at least two different types of olefins, and mixtures of 
these homo- and/or copolymers. Olefins are intended to denote both 
monoolefins such as ethylene, propylene or butene, and olefins containing 
more than one double bond, for example diolefins such as butadiene. 
Propylene and ethylene polymers may be mentioned as nonlimiting examples 
of polyolefins. Both their homopolymers and their copolymers are thus 
intended to be denoted, it being optionally possible for the latter to 
include, besides propylene and/or ethylene, one or several other olefinic 
comonomers, the total quantity of the latter preferably remaining lower 
than 20% relative to the weight of the copolymer. Advantageous results 
have been obtained with articles in which the treated surface region 
consists essentially of a propylene polymer or of a mixture of 50 to 99% 
(relative to the total weight of the polymers) of at least one propylene 
polymer and of 50 to 1% of at least one ethylene polymer. 
In addition, one or several conventional inorganic fillers may be 
optionally added to this or to these polyolefins, such as calcium 
carbonate, titanium dioxide, mica and the like, as can be reinforcing 
fibres such as, for example, glass or carbon fibres, as well as one or 
several conventional additives such as stabilizers, lubricants, 
antioxidants and the like. 
Besides one or several polyolefins, fillers and additives as set out above, 
the articles concerned may optionally include one or several other 
polymers intended to impart particular properties to them, for example 
with a view to improving their impact strength. 
In the treated surface region the O/C atomic ratio is preferably higher 
than 0.1. The O/C ratio is furthermore generally lower than 0.40 and 
preferably lower than 0.30. The F/C atomic ratio is advantageously higher 
than 95% of the O/C ratio. It is preferably lower than 200% of this ratio. 
The ESCA spectroscopy (Electron Spectroscopy for Chemical Analysis) 
employed for measuring the oxygen and fluorine contents is described 
especially in "Practical Surface Analysis", vol. 1, D. Briggs and M. P. 
Seah Eds., J. Wiley & Sons Ltd, 1990. 
It should be noted that, in addition to the stability of their printability 
in the course of time, a particularly important advantage of the articles 
exhibiting these characteristics is that they are printable with all types 
of inks and especially with inks for PVC, in contrast to the articles 
known hitherto. 
A second objective of the present invention relates to a process enabling 
these articles to be manufactured and, more precisely, a process for 
surface treatment of an article intended to be printed, in which at least 
a surface region includes at least one polyolefin, including at least an 
oxidation stage and a fluorination stage, in conditions such that the said 
region contains fluorine and oxygen at the surface in concentrations such 
that the oxygen/carbon atomic ratio (O/C), measured by ESCA spectroscopy 
at a depth of 1.5 nm, is at least 0.08 and that the fluorine/carbon atomic 
ratio (F/C), measured in the same way, has a value of at least 90% of that 
of the O/C ratio and of not more than 290% of this ratio. 
This article is advantageously intended to be printed by means of an ink 
for PVC. 
The article concerned may be treated either over the whole of its surface 
or on one or several regions of its surface, corresponding to the above 
definitions. For example, in the case of a multilayer film in which only 
one of the two outer layers is polyolefin-based, it is possible to 
surface-treat only this layer or even a certain region of this layer, 
without departing from the scope of the present invention. The 
abovementioned values relating to the oxygen and fluorine concentrations 
quite obviously apply only to the regions including at least one 
polyolefin and which have actually been surface-treated. 
The surface treatment by means of oxygen and fluorine may be performed by 
any known method, continuously or noncontinuously, provided that it 
produces the abovementioned F/C and O/C ratios. In the surface-treated 
region the O/C atomic ratio is preferably higher than 0.1. The O/C ratio 
is furthermore generally lower than 0.40 and preferably lower than 0.30. 
The F/C atomic ratio is advantageously higher than 95% of the O/C ratio. 
It is preferably lower than 200% of this ratio. Concrete examples of 
surface treatment are given in the abovementioned documents U.S. Pat No. 
4,296,151 and WO 93/24559. 
This surface treatment process applies to any type of article, as defined 
above. It gives good results when applied to films. 
Fluorination is intended to denote any known treatment carried out by means 
of a gas mixture containing fluorine and enabling the latter to be 
chemically bonded to a plastic. Examples of this are given in the 
abovementioned documents U.S. Pat. No. 4,296,151 and WO 93/24559. A 
mixture of nitrogen and of 1 to 10% by volume of fluorine is preferably 
employed. Good results have been obtained by heating the vessel and/or the 
gas mixture during the fluorination stage. The duration of treatment is 
obviously related to all the operating conditions. The fluorination is 
generally of short duration. The fluorination period is advantageously not 
more than 12 seconds. It preferably does not exceed 4 seconds and still 
more preferably does not exceed 2 seconds. 
Oxidation is intended to denote any known treatment carried out enabling 
oxygen to be chemically bonded to a plastic. A well-known example of such 
treatment consists in employing a gas mixture containing oxygen. Other 
examples of oxidation stages will be given below ("energetic surface 
oxidation stages"). 
The oxidation stage and the fluorination stage may take place in any order. 
The fluorination and oxidation stages may be optionally combined. In 
practice it is furthermore very difficult, especially in plants operating 
continuously, to prevent the presence of traces of oxygen during the 
fluorination. 
According to an alternative form, the surface treatment process includes an 
oxyfluorination stage, that is to say a treatment by means of a gas 
mixture including oxygen and fluorine. This allows oxygen and fluorine to 
be incorporated simply and simultaneously at the surface of the treated 
articles. According to a particularly simple alternative form the process 
consists solely of an oxyfluorination stage. 
According to another alternative form the oxidation includes an energetic 
surface oxidation stage. This alternative form produces outstanding 
results. 
"Energetic surface oxidation" is intended to denote any high-energy 
oxidative treatment such as flaming, corona discharge, plasma treatment in 
the presence of oxygen, ozone treatment or else a stage of oxidation with 
oxygen with heating to a temperature below the melting temperature of the 
material of the region, as well as combinations of several of these 
treatments. 
When oxidation with oxygen with heating is adopted, the region is 
preferably brought to a temperature from 20.degree. to 90.degree. C. lower 
than the melting temperature of its constituent material. This heating may 
be produced by any known means, for example by infrared radiation or by 
blowing hot air. 
The energetic surface oxidation preferably includes a corona treatment. 
An oxidation with heating and a corona treatment are advantageously 
combined. 
The energetic surface oxidation and the fluorination may take place in any 
order. They may also be simultaneous, for-example using a cold plasma 
treatment, as described especially in J. Appl. Polym. Sc., Appl. Polym. 
Symp., vol. 46, 61 (1990) and in J. Appl. Polym. Sc., vol. 50, 585 (1993) 
or using oxyfluorination with heating. It is generally preferred that 
these treatments should be separated in time. In this case it is preferred 
very particularly that at least one fluorination stage should be preceded 
by at least one energetic surface oxidation stage. The intervals 
separating the various stages are immaterial, provided that the activation 
effect of a given stage still remains at the time of the following one. 
The surface treatment process may thus include an energetic surface 
oxidation stage followed by a fluorination stage a few days later. 
Nevertheless, in the particular case where the energetic surface oxidation 
includes an oxidation with heating, the oxidation with heating is in most 
cases rapidly followed by the fluorination stage, and both these 
treatments are preferably even simultaneous. However, especially for 
reasons of production efficiency, it is furthermore preferred to perform 
all of the surface treatment continuously, the various stages referred to 
above being carried out one following the other and without considerable 
intervals. In a particularly preferred manner the surface treatment is 
performed in line with the stages of manufacture of the articles 
(extrusion and the like). 
As stated above, the surface treatment process thus defined makes it 
possible to obtain articles in which at least a surface region includes at 
least one polyolefin to which the inks for PVC adhere well even when the 
printing takes place several months after their manufacture. 
A final objective of the present invention relates to a process of 
manufacture of a printed article in which at least a surface region 
includes at least one polyolefin, including a specific surface treatment 
as defined above and at least one stage of printing of this region by 
means of an ink for PVC. 
The printing may be done by any known process, for example by silk-screen 
printing, photogravure, flexography or by means of a doctor blade. 
It is furthermore clear that it is only in the case where the printing is 
done on the regions including at least one polyolefin, which have been 
surface-treated so as to produce the fluorine and oxygen concentrations 
shown, that the invention reveals its surprising advantages. 
EXAMPLES 
The present invention and the advantages which it provides are illustrated 
by the examples which follow, no limitation being implied. Examples 1R to 
8R, 14R to 17R and 19R are given by way of comparison. 
In these examples the printing of the films is performed by coating with 
the aid of a doctor blade which permits the deposition of a 6 .mu.m layer; 
the ink drying time (at ambient temperature) is set at 3 hours for all the 
inks employed. 
The surfaces of the treated films are evaluated by: 
measurement of the F and O surface contents expressed by the F/C and O/C 
atomic ratios determined by ESCA spectroscopy at a depth of 1.5 nm; the 
measurements are made with the aid of an SSI spectrometer (Surface 
Sciences Laboratories) employing the Al K.alpha. photon source; 
the total surface tension .gamma..sup.T and its dispersive and polar 
components (.gamma..sup.d and .gamma..sup.P respectively), which are 
calculated from the angles of contact of various liquids using the Kaelble 
method (Journal of Adhesion, vol. 2, p. 66, Apr. 1970); 
or by default (Ex. 12 and 13) the surface tension, measured with test inks 
according to ASTM standard D-2587-67 (version of 24.2.1984). 
EXAMPLE 1R 
A transparent polypropylene (PP) homopolymer film of 100 .mu.m thickness, 
extruded from Moplen.RTM. F30S resin (Himont) was employed. 
This film was treated by corona discharge with the aid of equipment of 
Ahlbrandt.RTM. trademark at a speed of 12 m/min. This system employs a 
generator of 5402 type (frequency 30 kHz; voltage 14 kV). The two 
electrodes, ceramic-coated, are at a distance of 3 mm from the 
counterelectrode. The output current is 5.6 A. 
EXAMPLE 2R 
A film identical with that employed in Example 1R was treated by flaming 
with the aid of equipment of Aerogen.RTM. trademark at a speed of 30 
m/min. The unit employs a burner of Aerogen AT533 type. The gas employed 
is propane. The oxygen content of the gas mixture is maintained at 
20.00.+-.0.02% by volume (measured with the aid of a paramagnetic cell of 
Servomex.RTM. 1420 type). The distance between the burner and the film 
surface is 30 mm. 
EXAMPLE 3R 
A film identical with that of Example 1R was treated by plasma discharge 
with the aid of equipment of Hitachi.RTM. trademark employing the radio 
frequency mode (13.56 MHz) at a speed of 12 m/min. The plasma-coupled 
voltage is 6.8 kV. The equipment is fitted with electrodes and treats only 
one face of the film. The pressure in the chamber is maintained at 1.33 
Pa. The gas employed is nitrogen, the flow rate of which is 100 ml/min. 
The results of Examples 1R to 3R appear in Table 2 below. 
In the case of the Examples 4R to 11, which follow, noncontinuous 
fluorination equipment from Fluorotech GmbH was employed. The samples of 
films are suspended in a cylindrical chamber into which nitrogen and 
fluorine are introduced. The temperature of the chamber was maintained at 
25.degree. C. An F.sub.2 /N.sub.2 mixture containing 10% of F.sub.2 was 
employed for the treatments. The purges at the beginning or at the end of 
the surface treatment cycle were performed with nitrogen. 
In the case of tests 4R to 11 the fluorination was performed 
noncontinuously and according to one of the following two cycles: a 
fluorination cycle (cycle 1--FIG. 1), and an oxyfluorination cycle (cycle 
2--FIG. 2). 
Without detailing their purge stages, these two cycles can be summarized as 
follows: 
cycle 1: exposure of the film to an F.sub.2 /N.sub.2 mixture containing 10% 
by volume of fluorine, at a total pressure of 400 mbar for 15 minutes, 
after having emptied the treatment chamber of the air which it contained; 
cycle 2: similar to cycle 1, but with the treatment chamber having been 
emptied only partially (200 mbar) of the air which it contained. 
In both cycles the total pressure was, however, slightly lower than 400 
mbar at the beginning and at the end of the treatment period, as a result 
of the progressive filling and draining of the treatment chamber. 
EXAMPLE 4R 
A transparent film of 100 .mu.m thickness, extruded from a 
polypropylene-polyethylene (PP-PE) copolymer (Moplen EP2C 30F resin from 
Himont) was employed. The film was fluorinated according to the surface 
treatment cycle 1 (fluorination). 
EXAMPLE 5R 
A film of 100 .mu.m thickness consisting of the same copolymer as in 
Example 4R but additionally filled with TiO.sub.2 (17.5% by weight 
relative to the polymer) was employed. The film was fluorinated according 
to the surface treatment cycle 1 (fluorination). 
EXAMPLE 6R 
A transparent PP homopolymer film of 100 .mu.m thickness, extruded from 
Moplen F30S resin and fluorinated according to surface treatment cycle 1 
(fluorination) was employed. 
EXAMPLE 7R 
A PP homopolymer film of 100 .mu.m thickness, filled with TiO.sub.2 
(17.5%), extruded from the same Moplen F30S resin and fluorinated 
according to surface treatment cycle 1 (fluorination) was employed. 
EXAMPLES 8R-9-10 
These examples differ from Examples 4R, 6R and 7R respectively only in the 
choice of the surface treatment cycle 2 (oxyfluorination). 
EXAMPLE 11 
In this example, in accordance with the invention, an extruded Eltex.RTM. 
XF714 (Solvay) high-density PE (HDPE) film of 150 .mu.m thickness was 
fluorinated according to surface treatment cycle 2 (oxyfluorination). 
EXAMPLES 12-13 
In the case of these tests, carried out continuously, the films passed 
through a chamber fed continuously, at a total pressure of 1 bar, with a 
treatment gas mixture containing an inert gas (nitrogen) and fluorine, 
also in the presence of oxygen. 
In Example 12, in accordance with the invention, a film identical with that 
of Example 1R was fluorinated in line at a speed of 5 m/min, in equipment 
such that the treatment period was 12 s. The treatment gas contained, by 
volume, 5% of fluorine and 95% of nitrogen. 
In Example 13, also in accordance with the invention, a film identical with 
that of Example 5R was fluorinated in line in the same conditions as in 
Example 12. 
The results of Examples 4R to 13 appear in Tables 1 and 2. 
Table 1 reproduces the values of the total surface tension .gamma..sup.T 
and of its dispersive and polar components .gamma..sup.d and .gamma..sup.P 
for Examples 4R to 11, as well as the total surface tension for Examples 
12 and 13. 
The adhesiveness of the inks for PVC and for PO was measured. These 
results, together with the F/C and O/C atomic ratios at 1.5 run, are given 
in Table 2. 
By comparing Tables 1 and 2 it can be seen that the total surface tension 
alone does not enable the measured adhesiveness levels to be predicted. It 
may be noted, however, that it appears advantageous for the polar and 
dispersive components of the total surface tension to be very high. 
TABLE 1 
______________________________________ 
Total surface tension .gamma..sup.T and its dispersive and polar 
components (.gamma..sup.d and .gamma..sup.p) for a series of films 
surface- 
treated according to the cycle shown in the column 
"Cycle". The data shown for Examples 12 and 13 are 
surface tensions measured with test inks according to 
ASTM standard D-2587-67. 
.gamma..sup.T 
.gamma..sup.d 
.gamma..sup.p 
Example Polymer Cycle (mN/m) (mN/m) 
(mN/m) 
______________________________________ 
4R PP-PE 1 41.1 29.1 12.0 
5R copo 1 27.5 21.7 5.8 
6R PP 1 35.0 26.7 8.3 
7R 1 30.0 22.3 7.7 
8R PP-PE 2 55.1 27.6 27.5 
copo 
9 PP 2 51.4 27.7 23.7 
10 2 45.5 25.5 20.0 
11 HDPE 2 54.6 33.1 21.5 
12 PP continuous 
55 
13 PE-PP continuous 
42 
copo 
______________________________________ 
TABLE 2 
______________________________________ 
F/C and O/C atomic ratios (1.5 nm) and adhesiveness of 
Inks for PVC and for PO with a series of films oxidized 
and fluorinated according to the prior art and treated 
according to the invention. 
Surface Compo- 
Ink adhesiveness (*) 
sition (ESCA) 
PO inks PVC inks 
Example O/C F/C A B C D E 
______________________________________ 
1R 0.12 0 1 1 1 3 1 
2R 0.16 0 1 1 1 3 1 
3R 0.22 0 1 1 1 4 2 
4R 0.09 0.27 1 3 1 3 2 
5R 0.05 0.53 1 5 1 2 3 
6R &lt;0.05 0.62 1 3 1 2 2 
7R 0.08 0.58 1 5 1 2 3 
8R 0.10 0.07 1 1 1 2 2 
9 0.12 0.14 1 1 1 2 1 
10 0.18 0.26 1 1 1 2 1 
11 0.29 0.28 1 1 1 1 1 
12 0.25 0.40 1 1 1 1 1 
13 0.12 0.14 1 1 1 1 1 
______________________________________ 
Inks for PO: 
A. Lorilleux .RTM. Pacific (waterbased) 
B. SICPA .RTM. Ethyflex (solventbased) 
C. SICPA .RTM. Brilloflex (waterbased) 
Inks for PVC: 
D. SICPA Sicpaleau (waterbased) 
E. SICPA Vinyloflex (solventbased) 
(*) Adhesiveness evaluated according to ASTM standard D3359: 
5. Very poor 
4. Poor 
3. Average 
2. Good 
1. Very good 
EXAMPLES 14R-16R--Aging tests 
A4 format samples of films 1R, 2R and 3R were placed with the treated face 
uppermost for 100 hours in a ventilated oven at 70.degree. C. After this 
aging the films were printed by means of the inks A and E; their 
adhesiveness was very poor (score "5" according to ASTM D 3359). 
Samples of the same films were also stored at ambient temperature for 12 
months; after this storage the adhesiveness of inks A and E was also very 
poor ("5"). 
On the other hand, films of Examples 9 to 11, in accordance with the 
invention, remain perfectly printable, this being both with inks for PO 
and with inks for PVC, after storage for 12 months at ambient temperature. 
Films of Examples 12 and 13, in accordance with the invention, also remain 
perfectly printable, both with inks for PO and with inks for PVC, after 
storage for 100 hours in a ventilated oven at 70.degree. C. 
EXAMPLE 17R 
An extruded film consisting of a mixture of PP (Eltex P HL001) and of PE 
(Eltex B 4020) (80:20 by weight) was treated continuously at a speed of 5 
m/min (corresponding to a treatment period of 12 s) by means of a gas 
mixture including (by volume) 10% of fluorine and 90% of nitrogen. 
EXAMPLE 18 
Before being fluorinated, the same film as in Example 17R was subjected to 
a corona treatment in the same conditions as in Example 1R but at a speed 
of 5 m/min. 
EXAMPLE 19R 
A calendered film consisting of an Eltex P KL 177 PP-PE copolymer including 
11 phr of TiO.sub.2 was treated continuously at a speed of 5 m/min by 
means of a gas mixture including (by volume) 5% of fluorine and 95% of 
nitrogen. 
EXAMPLE 20 
Before being fluorinated, the same film as in Example 19R was subjected to 
a corona treatment in the conditions mentioned in Example 18. 
The samples obtained according to Examples 17R to 20 were subjected to 
aging for 100 hours in a ventilated oven at 70.degree. C. The table which 
follows shows the initial surface tension (T.sub.0) and the surface 
tension after aging (T.sub.a) which are measured by means of test inks 
according to ASTM standard D-2587-67, together with the adhesiveness of 
the ink for PVC E, evaluated after the aging, according to ASTM standard 
D-3359. 
______________________________________ 
T.sub.O T.sub.a 
Example (mN/m) (mN/m) Adhesiveness of ink E 
______________________________________ 
17R 56 50 4 
18 56 54 1 
19R 40 32 4 
20 48 39 1 
______________________________________ 
Examples 18 and 20 show that the films which have been subjected to a 
corona treatment before their fluorination exhibit a surface tension which 
is more stable with time and higher. In addition, their printability is 
excellent, both with inks for PVC and for PO, in contrast to the films of 
Examples 17R and 19R.