MXPA98008750A - Coextruded multilayer films for sterilizable fluid containers - Google Patents

Abstract

The films, foils, sheets and the like, flexible and transparent, fully formed of polyolefins, suitable in particular for the manufacture of infusional solution containers with the aid of forming, filling and sealing processes, comprise two terminal layers (A) and (C) of different polymeric composition, and"n"intermediate substrates B1, B2, ...Bi...Bn having gradients of ethylenic content and of softening temperature (fig. 1).

Description

MULTIPLE COATED COAT FILMS, FOR FLUID AND STERILE FILLING CONTAINERS FIELD OF THE INVENTION The present invention concerns films, sheets, thin metal sheets and similar composite materials, flexible and transparent, of several coextruded layers having a high compatibility and adhesion between layers, suitable, in particular, for manufacturing, by means of forming-filling processes - it is bundled (F-LL-S), of containers, especially of fluid bags, particularly of solutions for infusion that must be sterilized in autoclave, with steam, at temperatures of approximately 120 ° C or higher, and that must have, In addition to transparency and good welding resistance, high resistance to puncture and falls, the films comprise at least: an outer layer (A) that comes into contact with the welding medium, during the F-LL-S process and that It has a melting temperature of at least 130 ° C and high strength REF. : 28568 mechanics to hold the filled container, during the sterilization phase; an inner layer (C) which is intended to come into contact with the fluids and, once the container is formed and filled, is responsible for the hot or cold welding seals; and a complex intermediate layer (B) between layers (A) and (C) which is particularly important for adhesion, transparency, mechanical strength, shock absorption, etc., the layer consists substantially of olefinic polymers in the absence of adhesives and crosslinking compounds.

BACKGROUND OF THE INVENTION In the patent application (Swiss Patent Application No. 3771/93, corresponding to EP-A-0658421) a co-extruded multilayer film is described, substantially of the previous type, that is to say that it has the characteristics indicated as prior art in the preamble of the present specification and relevant claim 1. In the application (the description of which is intended to be incorporated herein), the outer layer (A) and the inner layer (C) have the same symmetrical composition (i.e. , the same polyolefin is thermophilic (PO-STERI) while the intermediate layers (B), (not ther able, with melting point below 121 ° C and thickness of 50 to 200 microns) consisted of polyolefins selected from the group consisting of thermoplastic polyolefins, copolymers of ethylene -but with a density below 0.9 g / m3 and relevant mixtures.The materials of the layers (A and C) (which have a thickness of 10 a 80 micron is) were selected from: polymers and copolymers of propylene with ethylene and / or butylene; polymers or copolymers of ethylene with an alpha-olefin having six carbon atoms; relevant mixtures with or without lower amounts of elastomers. The following symbols will be used to indicate: PP, propylene polymers and PE ethylene polymers, which can be linear (L) and have a density (D) low (B), medium (M), or high (A) ).

In the layers of example (A) and (C) they were both and at the same time PP or C8-PEBDL (low density polyethylene, linear, with a small amount of octene, (8)) while (B) could also be a polyolefin material, recovered and re-granulated. Similarly, in EP-A-0216506 (classified X, ie considered relevant in the EP-A-0658421 Search Report), medical pouches formed with laminates consisting of layers (A) and (C) are described. identical and selected from PEBD, HDPE or ethylene-alpha olefin copolymers with a density of at least 0.920 g / cm3 while (B) is an ethylene-alpha olefin copolymer having a density below 0.935 g / cm3. The need to have layers (A) and (C) of symmetrical composition was attributed, in general, to the fact that, in doing so, the difficulties of the intermediate layer (B) were reduced to confer adequate compatibility and adhesion between the layers. layers (A) and (C) that only by having the same composition were already compatible. However, experience has shown that it is neither easy nor safe to confer, with a single layer (even if it is very thick) of the material (B), an adequate adhesion, particularly after sterilization, to the layers (A) and (C), no matter that its composition is the same. Indeed, in the case of bags for infusion solutions, the problems to be solved are twice as high and concern not only the most appropriate evaluation and selection of pairs (A) and (C), for example, in terms of the viscosity, but also the problems in terms (fi) of the acceptance by the "FARMACOPEA" for which the values of adhesion between layers must be respected being very high and critical, indispensable to guarantee an acceptable behavior of the structure. There is also the common request for bags that accommodate ever-increasing volumes of solution which must therefore show increasing resistance characteristics.

BRIEF DESCRIPTION OF THE INVENTION The main objective of the present invention is to provide co-extruded films and relevant containers having a "maximum maximorum" of characteristics, in particular an optimal combination of excellent values: of the adhesion between the end layers (A) and (C) of different composition; of compatibility, transparency, softness, resistance to drops, resistance of the seal, absence of transfer of decomposition products in the solutions, etc. This and other objects are achieved with the films and related containers, which have the features described in the claims. It has indeed been found that, through the advantageous use of layers (A) and (C) of different composition and, among them, of a discrete series of substrates Bl, B2 ... Bn critically distributed with gradients as well as their content of ethylene units, monomeric, combined (E), as well as its melting temperature (softening), it is possible to obtain films and bags capable of satisfying even the most instigating demands. of resistance, ease of working in machine, presentation, etc., in addition to the specific requirements of the Pharmacopoeia.

BRIEF DESCRIPTION OF THE DRAWINGS The different aspects and advantages of the invention will become apparent in a clearer form from the following description made with reference to both the examples and the accompanying drawings, in which: Figure 1 is a cross-sectional view , schematic, of a multilayer film according to the invention, and Figures 2 and 3 are diagrams representing emblematically the spatial variation of the ethylene content, respectively, of the melting temperatures, in the different layers.

DESCRIPTION OF THE PREFERRED MODALITIES Only in order to fix the ideas, in Figure 1 a composite film is represented which comprises, according to a first characteristic of the invention, two terminal layers (A) and (C) asymmetric, ie of different composition ( and of also different characteristics) and a discrete number of "n" intermediate substrates Bl, B2 ... Bi ... Bn-1, Bn, which have gradients of ethylene content and melting temperature or softening (Tfr) . According to another preferred feature of the invention: a number of central substrates Bl ... B c that form virtually a core or center CO have the minimum softening temperature and gradients in the content of E and the softening, minimum and including n; - a number "ms" of substrates from Bl to B s that form virtually an upper core Bs, show an increasing ethylene content and decreasing melting temperatures, from the maximum temperature (T ax) of (A) (approximately 140 ° C) up to the minimum temperature (Tmin) below the sterilization temperature (121 ° C Tester.); a number of substrates placed under the substrates of the core CO show increasing ethylene contents and softening temperatures which also increase from the minimum temperature mentioned above (Tmin, below 121 ° C) to the temperature of the layer ( C) (Te at least equal to the sterilization temperature Tester., Ie 121 ° C). Obviously, ms + me + mi = n. Figure 2 shows the terminal layers (A), (C) and the intermediate layer (B) consisting of a sequence of secondary layers (Bl, B2 ... Bn). Layer (A) consists substantially of monomeric propylene units, possibly combined with lower amounts of ethylene; preferably (A) is selected from: PP homopolymers with low PE content; in the limit case it could also be HDPE mixed with block copolymers of PP-PE, layer C consists substantially of combined units of ethylene possibly with lower amounts of alf-olefins; preferably C is selected from: PEBDL preferably in the form of copolymer with an alpha-olefin which is primarily octene and, subordinate, butene, hexene; mixtures of LDPE and LDPE prepared with a high pressure process. The central layer B, ie the sequence of secondary layers (Bl, B2 ... Bn) must show a high affinity with the terminal layers (ie A "and C") to ensure perfect compatibility and adhesion of the entire structure , both at high temperature and at room temperature. Only in this way is it possible to reach a maximum in the mechanical characteristics of the structure (including resistance to puncture and falls) involving all layers in this function of support and absorption of stress, particularly deformation. According to a further feature of the invention, the number of substrates is as high as possible, however they should preferably form perfectly compatible successive pairs; this allows passing through successive stages from the affine face (A) of PP to the affine side (C) of PE, maintaining a perfect cohesion and transparency. In practical experience it has been investigated that if, on the one hand, "n" can not be infinite and, on the other hand, only a substrate of (B) is not enough to ensure the optimal combination of the desired characteristics, they begin to appear particularly satisfactory results with two, better, with three, substrates possibly repeated several times; with these repetitions it is possible to create the sequence of suitable characteristics to optimize the adhesion between layers and the homogeneity of the structure. In this structure (described here with general terms) the parameters that can give an indication of the affinity of the materials present in the successive layers, are the ethylene content (EC) and the softening point, even if other primary characteristics are of fundamental importance (degree of crystallinity, morphology in the solid state, contact angle, etc.). In practice, for the PP-PE copolymers particularly adapted to form the substrates, the products with an increasing content of ethylene have been selected and for the linear PE the products with an increasing copolymer content have been preferred, in order to achieve an optimum of adhesion between the two terminals. Surprisingly it has been investigated that there is a good compatibility between the random copolymers richer in ethylene and the so-called polyethylenes with very low densities (PEDMB) and these mixtures can cause the end of the passage through the structure similar to the PP and those more similar to the PE. These mixtures, which can already be obtained through simple physical mixing and successive extrusion, are further improved through a preliminary phase of mixing in the melt mixture and can be made more convenient for the use described above if they are added synthetic elastomers such as SBS, SEBS and similar polymers, or polyolefin rubbers such as copolymers of PP-PE-EPDM. In the examples it is reported that some of these structures have contributed to achieve the desired characteristics of adhesion between layers and sealing strength, resistance to puncture and falls, transparency after steam sterilization and ease of working on machines, requested for the specific use of flexible bags. As a further object of the invention concerning the coextruded multiple layer structures, suitable structures for flat head coextrusion called "melt extrusion" are reported in the following examples. In any case the invention can not be limited to this technique but can also be incorporated by coextrusion with blown followed by rapid tubular cooling or by sequential coextrusion from separate heads, which allows the extrusion in successive stages of different materials that , once cooled, they roll up like a single sheet.

Experimental part In a particularly simple embodiment, the structures of the invention have been produced in a fusion coextrusion line, consisting of 5 single screw extruders with independent controls, capable of melting and feeding, with good precision, up to 5 different materials with the desired reciprocal flows: the molten materials are then sent in convoy, even separately, to a system of parallelization of layers and stabilization of the desired sequences that are then fed to a flat nozzle for the final formation of the sheet in a molten state. At the outlet of the screw nozzle the sheet is rapidly cooled by contact with a rotating cylinder through which a cooling liquid flows internally, and the linear velocity of the cylinder with respect to the speed of the melt leaving the nozzle screw allows to control the thickness of the multi-layer structure at will. It is possible that the outermost layers are provided with conventional agents to facilitate the displacement or to avoid blocking, to improve the ease of machining of the bags. Referring to the film samples of the examples, the bags are conventionally formed and filled with solutions for infusion and then sterilized in an autoclave at 121 ° C and a back pressure of 2 bar for each total cycle (heating, sterilization and cooling) of 60 minutes. The following structures (particularly the simple structures summarized in Table 1) are manufactured at the same extrusion rate and keeping the total thickness of 200 microns constant. The main functional characteristics of the films thus obtained are analyzed and validated in accordance with conventional methods, 72 hours after extrusion. The simple materials cited in the Table correspond to the following types and characteristics: A) PP COPO: random copolymer of PP-PE with an ethylene content of 3 to 3.5, (IFEF) (melt flow index) measured at 230 ° C, between 9 and 12; melting point of 148-152 ° C. Typical commercial polymers are: BOREALIS RE 764 or DAPLEN KFC 2004; Bl) PP COPO with high ethylene content: it is again a random copolymer of PP-PE but with high content of ethylene (7-10%), IFEF at 230 ° C of 12, melting point of 132 ° C. The typical commercial product is DAPLEN MFC 2110 SB; B2) Compound PP: Random copolymer with low ethylene content (less than 15%) mixed and homogenized with block copolymers of the type SEBS, EPDM. The elastomer content can be between 20 and 30% and the IFEF at 230 ° C can be between 2 and 8. There is a version obtained entirely in the polymerization phase but with similar characteristics called ADFLEX C 200 F manufactured by the MONTELL Company. B3) PEDMB: very low density (0.900 g / cm3) linear polyethylene, generally obtained by the copolymerization of ethylene with comonomers such as butene, hexene or other fine alpha-olenes in the presence of specific catalysts. The product used in these analyzes is the "CLEARFLEX" CLDO marketed by the company "POLIMERI EUROPA" with a content of comonomers below 20%, IFEF at 190 ° C of 3 and a melting point of 115 ° C. C) PEBDL: linear polyethylene (analogous to the previous PEDMB) prepared by polymerization is ethospecific ethylene with small amounts (below 10%) of comonomers of the alpha-olefin type. In a preferred embodiment two additional substrates B4 and B5 were added, as follows: B4) PEDM: medium density polyethylene prepared with a conventional process (at high pressure) in an autoclave and characterized by a relatively high density (d = 0.933 g / cm3) ) which imparts particular stiffness characteristics to the film. IFEF a 190 ° C = 2.5 - 3.5. B5) LDPE: Copolymer with butene or hexene at parity of all other conditions. As anticipated, optimal results are obtained by repeating, several times, substrates formed of pairs such as B1-B2, B2-B3, B3-B4 or of terns such as B1-B2-B3, B2-B3-B4, B3-B4-B5, etc.

Comparative Examples In addition to the examples according to the invention, two products are reported in the Table, which have structures that do not correspond to those of the invention, (examples 4 and 5) so they have poor properties which confirms that a composition is needed particular to achieve the characteristics required for the specific use in the bags. The spatial variations (Y axis) of the content of ethylene monomer units, combined (E on the X axis in Figure 2), respectively, of the temperature of the softening-softening are represented emblematically in the diagrams of figures 2 and 3. (Tfr in the X axis of figure 3). Significantly, the variations of these two important parameters are more marked (stronger) in the two main areas A-As and C-Ci above and below the core CO in which, on the contrary, E and Tfr can vary even in a negligible value. The gradients of E and Tfr are generally present in those main areas A-As and C-Ci but could be minimal or negligible in the central area CO. In the figures the curves formed by stripes represent other possible laws of variation of E and Tf r. From figure 2 it is clear that in the central zone BC the ethylene E content can be constant (curve 2, gradient zero = GR = 0) or vary 1 inealment e (curve 3, constant gradient GR = cost) or have no linear variations (variable gradient GR = var.). From the foregoing it will be observed that numerous variations and modifications can be made without departing from the true spirit and scope of the novel concept of the invention.

TABLE 1 IV) or It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (7)

1. Films, sheets, thin metal sheets and similar, flexible and transparent composite materials, consisting of several co-extruded layers having high compatibility and adhesion between layers, suitable, in particular, for manufacturing, by means of forming-filling-sealing processes ( F-LL-S), of containers, especially of fluid bags, particularly of solutions for infusion that must be sterilized in autoclave, with steam, at temperatures of approximately 120 ° C or higher, and which must have, in addition to transparency and good welding resistance, high resistance to puncture and falls, the films comprise at least: - an outer layer (A) that comes in contact with the welding medium, during the F-LL-S process and having a melting temperature of at least 130 ° C and high mechanical strength to hold the filled container, during the sterilization phase; - an inner layer (C) which is intended to come into contact with the fluids and, once the container is formed and filled, is responsible for the hot or cold welding seals; and a complex intermediate layer (B) between layers (A) and (C) which is particularly important for adhesion, transparency, mechanical strength, shock absorption, etc., the layer consists substantially of olefinic polymers in the absence of adhesives and crosslinking compounds; characterized in that: the layers (A) and (C) have heterogeneous compositions, the layer (A) consists substantially of a polymer formed of combined monomer units of propylene possibly with small proportions of combined monomer units of ethylene or alpha-olefins; layer (C) consists substantially of ethylene units combined possibly with small proportions of alpha-olefins; and the layer (B) consists of a discrete number n of substantially polymeric layers comprising a number of more substrates on the top (A-As) close to (A), an "e" number of central substrates forming a central core (BB) of the intermediate layer (B) between (A) and (C), and a "mi" number of layers in the inner part C-Ci between assemblies B-Bc and C-Ci, where ms + mi + e = n, and at least the layers or substrates "ms" and "me" of the upper parts (A -As) and lower C-Ci, respectively, have gradients of the content of combined monomer units, of ethylene, and of the softening temperature.

2) The films according to claim 1, characterized in that the outer layer (A) is formed substantially of combined monomer units of propylene, possibly with smaller proportions of combined units of ethylene not greater than 4%; layer (C) is formed substantially of combined monomer units of ethylene, possibly with lower proportions of an alpha-olefin; all the "ms" and "me" substrates, in the A-As and C-Ci zones of (B) show: increasing contents of monomeric ethylene units but increasing softening temperatures (Tfr) in A-As from the maximum temperature of softening (Tmax) from (A) to the minimum temperature (Tmin) in the core (CO, BB), respectively increasing softening temperatures in the C-Ci zones, from the minimum core temperature of the layer (C) to at least the sterilization temperature of 121 ° C.

3) The films according to claim 2, characterized in that "me" is between 6 and 8, "ms" is equal to at least 2, and "mi" is between 2 and 10.

4) The films according to at least one of the preceding claims, characterized in that the layer (A) is selected from the group consisting of propylene polymers having an ethylene content of less than 3.5%, and has thicknesses that are found between 10 and 80 microns, the layer (C) is selected from the group of ethylene polymers having an alpha-olefin content of less than 10%, the higher substrates "ms" have melting temperatures decreasing from 140 ° C to approximately 90 ° C, the lower substrates "mi" have increasing temperatures of 90 ° C to at least 121 ° C.

5) The films according to at least one of the preceding claims, characterized in that: the layer (A) is formed of a random copolymer of PP (polypropylene) with a PE content (polyethylene) below 3.5; - layer (C) is a LDPE (linear density polyethylene) with an alpha-olefin content below 10%; - the layer (B) comprises at least a first substrate B2 consisting of a compound of a random PP copolymer and an elastomeric modifier selected from the terpolymers of monomeric t-butyl-propyl-ene-diene, EPDM or SEBS; and - the substrates, B3, B4, B5, B6, B7 etc., are formed by polyethylenes selected from: PEDMB and PEBDL of the polymeric type having lower proportions of an alpha-olefin, and MDPE.

6) Multilayer films, composite, characterized in that they are substantially in accordance with Table 1.

7) Containers, particularly fluid bags, that is, especially for medical solutions, can be sterilized by autoclaving with steam at 121 ° C or more, consisting of multi-layer, co-extruded, physical films. at least one layer of which has substrates showing softening temperatures below 121 ° C, characterized in that the thicknesses of the outer (A) and inner (C) layers (which during sterilization at 121 ° C or more, is say when at least a large portion of the "n" substrates of the intermediate layer (B) is in partial melting conditions and impart mechanical strength to the container), they increase as the weight of the fluid contained in the bag increases and the total thickness of (B), and they are of over 40 microns when the total thicknesses of (B) are above 50 microns and, for fluid quantities of at least 1 liter, the number "n" of substrates (B) also increases as the last amount of the fluid increases.