Flexible thermoplastic and compressible tube made of this material

A flexible package is provided made of plastic, having a wall made of a thermoplastic blend containing a first and of a second polymer, wherein the first polymer is a propylene homopolymer (PP) and the second polymer is a copolymer of propylene (PP) and of ethylene (PE), and a method for producing the package by injection molding of the blend in a suitable mold. The package can be an injection-moulded tube, and is particularly suitable for the packaging of small volumes of cosmetic and/or dermatological products.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a thermoplastic blend and to a 
compressible package of the tube type, obtained using this blend. The 
invention relates more particularly to the production of flexible plastic 
tubes by injection moulding, wherein the tubes are compatible with the 
product contained therein and the walls of which have sufficient 
flexibility to be compressed manually, without leaving folded areas after 
the compression. The package of the invention is intended, in particular, 
to contain a cosmetic, pharmaceutical, dermo-pharmaceutical product or 
certain food products. 
2. Discussion of the Background 
Currently, most of the packages used, particularly in the cosmetic field, 
such as tubes or bottles intended to contain a cream or a shampoo, are 
made of plastic. In order to manufacture them, thermoplastic polymers, 
such as suitable polyolefins, are generally used in an extrusion or 
extrusion blow-moulding process with the aid of conventional industrial 
equipment. 
The thermoplastic polyolefins used are generally low-density polyethylenes, 
intended in particular for the manufacture of tubes, and high-density 
polyethylenes or polypropylenes which are intended for the manufacture of 
bottles. In particular, polypropylenes have good water-vapour 
impermeability properties, have the advantage of being compatible with 
most chemicals. 
SUMMARY OF THE INVENTION 
Accordingly, one object of the present invention is to provide a 
thermoplastic composition that is sufficiently fluid to allow the 
production, by injection moulding, of packages, such as compressible 
tubes, especially those having a wall that is thin and sufficiently 
flexible to be manually compressed in order to dispense the product. 
Another object of the present invention is to provide a material that gives 
better resistance to creasing of the wall brought about by compressing the 
tube, and in reducing, or even eliminating, the formation of white regions 
in a previously creased wall region. 
These and other objects of the present invention have been satisfied by the 
discovery of a combination of a particular copolymer with a conventional 
polypropylene homopolymer to form a thermoplastic blend that can be used 
for the manufacture, by injection moulding, of a package having the 
desired properties. This blend furthermore has good compatibility with the 
products intended to be stored in the package, in particular in the 
presence of certain surfactants.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The packages provided by the present invention are generally of the type 
having a compressible peripheral envelope open at a first free end, which, 
after filling with the product to be dispensed, is intended to be closed 
by pinching, followed by heat sealing of its free edges. Generally, the 
second end of the envelope is joined, for example by means of a region 
forming a shoulder, to a neck having a sufficient thickness to be rigid 
with a channel for dispensing the product passing through the neck. 
Usually the cross-section of the envelope is circular or oval, but other 
shapes are also possible, such as a polygonal shape. Preferably, the neck 
carries a closure means, such as a thread for fixing a closure cap, or a 
clip-on flange for fastening a dispensing capsule. The envelope must have, 
in its entirety, a shape suitable for it to be demoulded after injection 
moulding of the thermoplastic blend in a suitable mould. 
The actual moulding of a package of the type mentioned above, by injection 
of a material such as polypropylene having a melt flow index suitable for 
injection moulding, causes no problems in practice. However, a package 
obtained in this way conventionally has two major drawbacks: 
on the one hand, the walls of the envelope are not sufficiently flexible to 
be manually compressed, and it is therefore difficult to drain the tube, 
and, 
on the other hand, the walls do not resume their initial shape after the 
envelope has been compressed and have undesirable visible folded regions 
which have, moreover, a whitish colour which is aesthetically 
unattractive. 
The present invention therefore provides a flexible plastic package having 
a wall made of a thermoplastic blend comprising a first polymer and a 
second polymer, wherein the first polymer is a propylene homopolymer (PP) 
and, the second polymer is a copolymer of propylene (PP) and of ethylene 
(PE). 
More particularly, the present invention provides a tube produced by 
injection-moulding the blend in a suitable mould. 
According to one preferred embodiment of the present invention, the 
thermoplastic blend has a melt flow index (ISO 1133 standard, at 
230.degree. C., 2.16 kg) of approximately 25 g/10 min. Because of this 
relatively high flow index, the blend is particularly suitable for 
injection-moulding thin-walled articles. 
According to another preferred embodiment of the present invention, the 
first polymer has a melt flow index (ISO 1133 standard) of from 20 g/10min 
to 200 g/10min (grades 20 to 200), preferably from 75 g/10 min. to 125 
g/10 min., more preferably of 100 g/10 min. The first polymer is present 
in the mixture in a preferred amount of less than or equal to 50 wt. %, 
and preferably from 20 wt. % to 35 wt. %, with respect to the total weight 
of the blend. 
Preferably, the second polymer (copolymer) has a melt flow index (ISO 1133 
standard) of from 5 g/10 min to 20 g/10min (grades 5 to 20), more 
preferably from 6 g/10 min to 10 g/10 min, most preferably 8 g/10 min. The 
second polymer has a preferred flexural modulus, according to the ASTM 
D790 standard of less than or equal to 200 MPa. The second polymer is 
present in the blend in an amount of greater than or equal to 50 wt. %, 
preferably from 65 wt. % to 80 wt. %, with respect to the total weight of 
the blend. 
According to a particularly preferred embodiment of the present invention, 
the second polymer is a copolymer of propylene and of ethylene, having a 
flexural modulus, according to the ASTM D790 standard, of less than 200 
MPa, such as the PP/PE copolymer sold by the company Montell under the 
brand name ADFLEX.RTM.. 
The thermoplastic blend of the present invention can be used, in 
particular, for the injection moulding of any thin-walled plastic article 
which has to be flexible. 
When this article is a flexible tube, it preferably has a relatively rigid 
head, consisting of a shoulder and a neck which is provided with a 
dispensing hole, and a compressible peripheral wall connected to the 
shoulder. The peripheral wall is flexible and forms a compressible body of 
the tube, in which the product is packaged. A cap may be provided in order 
to seal the dispensing orifice during the storage period. According to one 
preferred aspect of the present invention, the compressible wall is 
approximately cylindrical, or has an oval or polygonal cross-section. When 
the cross-section is circular, the external diameter of the tube is 
preferably from 10 mm to 50 mm, more preferably from 25 mm to 35 mm. 
Preferably, the wall has a thickness of from 0.2 mm to 1.0 mm, more 
preferably from 0.4 mm to 0.7 mm, most preferably approximately 0.5 mm. 
Within the indicated flow index conditions of the blend, as well as of the 
above-noted wall thickness, it is easily possible to mould tubes of which 
the length of the compressible wall, measured along the axial dimension, 
is less than 15 cm. Preferably, the tube dimensions are chosen such that 
the wall length/wall diameter ratio of the tube is less than or equal to 
4. According to the present invention, such a package is obtained by 
injecting the blend, when hot, into a suitable mould. 
Thus, after pinching and sealing of that end of the compressible wall which 
is opposite the dispensing head, a volume is obtained which may range from 
approximately 5 ml to approximately 250 ml, preferably from 30 ml to 100 
ml, and more preferably from 60 ml to 80 ml. This volume is intended to 
contain the product, such as a cosmetic or dermatological product. The 
volume can be varied depending on the cross-section of the tube and on its 
length. 
The present invention is described below with respect to an illustrative 
embodiment, which is provided for improving understanding of the present 
invention and is not intended to be limiting thereof. 
Denoted by the reference 1 in FIG. 1 is a packaging assembly according to 
the present invention, in the form of an open tube obtained by injection 
moulding. The tube 1, of axis A, has a cylindrical body formed by a 
cylindrical sidewall 3 provided with an open end 3a. On the opposite side 
from the end 3a, the body is surmounted by a dispensing head 2 having a 
frustoconical shoulder 2a which is extended by a cylindrical neck 2b 
having a smaller diameter than the diameter of the body 3. The neck 2b has 
an external thread 2c capable of engaging with a sealing cap (not shown). 
The head 2 is provided with a dispensing orifice 2d of smaller diameter 
than the diameter of the neck 2b. 
In order to fill the tube 1, the neck 2 is closed off by a cap and the 
assembly is turned upside down so that the open end 3a is uppermost. A 
suitable amount of product is then poured into the tube. By means of a 
heated clamp, the free end 3a is pinched and, at the same time, a weld 12 
is made, as shown in FIG. 2, in order to close off the bottom of the tube. 
EXAMPLES 
Having generally described this invention, a further understanding can be 
obtained by reference to certain specific examples which are provided 
herein for purposes of illustration only and are not intended to be 
limiting unless otherwise specified. 
An open tube 1, as shown in FIG. 1, was obtained by injecting a molten 
blend of two polymers into a suitable mould. The injection-moulding 
temperature was approximately 220.degree. C. This blend comprised: 
20% of a polypropylene homopolymer, grade 100 (sold by the company Montell 
under the brand name MOPLEN EPN31MA), and 
80% of a copolymer of propylene and of ethylene, grade 8 (sold by the 
company Montell under the brand named ADFLEX X100G). This tube included 
the head 2 and the sidewall 3. The height of the wall 3, along the axis A, 
was approximately 9 cm, with the thickness of the said wall 3 being 
approximately 0.5 mm. 
After filling the tube with the product, the open end 3a of the tube was 
pinched and is closed off by heat sealing. The tube 11 in its final form, 
as shown in FIG. 2, was then obtained. It may be seen that the end 3a, 
having a sealing strip 12, was now closed off. Because of the small 
thickness of the wall 3, the tube 11 would be easily deformed, by 
compressing it, by a user wishing to remove a dose of product. 
The cost of manufacture of a tube according to the present invention is 
substantially less than the cost of a tube manufactured by extrusion. 
The present application is based on French Priority Application Serial No. 
97-01227, filed with the French Patent Office on Feb. 4, 1997, the entire 
contents of which are hereby incorporated by reference. 
Obviously, additional modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practised otherwise than as specifically described herein.