Multi-layered polymer based film structure for medical grade products

Technical field

The present invention relates to materials for the manufacture of medical grade products, and more particularly to a thin film product used for the manufacture of articles such as. B. plastic containers and medical tubing can be used.

State of the art

In the medical field, when medicines are contained, processed and stored in containers, transported and finally infused through tubing to patients in order to achieve a therapeutic effect, the materials used to manufacture the containers have a unique combination of properties. To visually inspect solutions for particulate contaminants, the container must e.g. B. be optically transparent. In order to infuse a solution from a container by compressing the container walls without introducing air into the container, the materials that form the walls must be sufficiently flexible. The material must remain functional over a wide temperature range. The material must remain functional at low temperatures while maintaining its flexibility and hardness because many solutions, e.g. B. certain premixed drug solutions, at temperatures such as. B. stored and transported from -25 to -30ºC to minimize drug degradation. The material must remain functional even at high temperatures to withstand the heat generated during sterilization, a process for which most medical packs and nutritional products are subjected to prior to transportation. The sterilization process generally involves exposing the container to steam at temperatures of typically 121 ° C and at an elevated pressure. The material must therefore be able to withstand the temperature and the pressure without significant deformation ("temperature resistance").

For ease of processing into useful articles, it is desirable that the material be weldable using radio frequency ("RF"), generally at approximately 27.12 MHz. The material should therefore have sufficient dielectric loss to convert the RF energy into thermal energy.

Another requirement is to minimize the environmental impact of the disposal of the article made from the material after its intended use. For such articles that are disposed of in a landfill, it is desirable to use as little material as possible to manufacture the article and to avoid the incorporation of low molecular weight leachable components. The material should therefore be light in weight and have good mechanical strength. Further advantages are created through the use of a material that can be recirculated to other useful articles by thermoplastic reprocessing of the article used.

Containers that are disposed of by incineration require the use of a material that avoids the risk of biological hazard and the formation of inorganic acids that are harmful to the environment, irritant and corrosive, or other products that are harmful, irritating or harmful any other way of complaining about the combustion should be avoided entirely.

It is also desirable that the material be free or low in low molecular weight additives, such as. B. plasticizers, stabilizers and the like, which could be released into the medication or biological fluids or tissues, making them dangerous for the patients who use such devices, or contaminating substances which are stored or processed in such devices. With containers containing solutions for transfusion, such contamination could enter the transfusion pathway and cause injury or death to the patient.

Traditional flexible polyvinyl chloride materials meet a number, and in some cases, most of the above requirements. Polyvinyl chloride ("PVC") also has the distinct advantage that it is one of the least expensive materials for manufacturing devices that meet the above requirements. PVC, however, can produce objectionable amounts of hydrogen chloride (or hydrochloric acid when contacted with water) during combustion, causing corrosion of the incinerator. PVC sometimes contains plasticizers that can leak into medicinal products or biological fluids or tissues that come into contact with PVC formulations. Many materials have therefore been proposed to replace PVC. However, most alternative materials are too expensive to manufacture and still do not meet all of the above requirements.

Many attempts have been made to develop a sheet material to replace PVC, but most attempts have been unsuccessful for one reason or another. For example, The multilayer film materials described in U.S. Patent 4,967,795 that are resistant to steam sterilization cannot be welded by radio frequency dielectric heating and cannot be assembled by this rapid, inexpensive, reliable, and well-feasible method. The European application EP 0310143 A1 describes multilayer films which meet most of the requirements and can be RF-welded. However, the components of the film described are crosslinked by irradiation and can therefore not be recirculated using standard methods for processing thermoplastics. Due to the radiation level, considerable amounts of acetic acid are released and captured in the material. In steam sterilization, acetic acid migrates into the packaging content as a contaminant and, by changing the pH value of the content, acts as a potential chemical reagent for the content or as a catalyst for the breakdown of the content.

The primary object of the present invention is to provide thermoplastic materials which, overall, are superior to materials previously known in the art or which have been used or sold commercially. The properties of such materials include flexibility, ductility and stretch recovery, not just at room temperature, but in a wide range from ambient to freezer temperatures. The material should be sufficiently optically transparent for a visual inspection, and be steam sterilizable at temperatures up to 121 ° C. It should be possible to subject the material to considerable stretching without showing whitening by stretching, which could be an indication of a physical and cosmetic deficiency. Another task is that the material is capable of being connected by means of RF processes. Another object is that the material is essentially free of low molecular weight leachable additives and can be disposed of by burning safely and without the formation of significant amounts of corrosive inorganic acids. Another task is that the material can be recirculated using standard methods for processing thermoplastics. In addition, it is desirable that the material contain regrind waste material accumulated during the manufacturing process in order to save material costs and reduce manufacturing waste. Finally, the material should be useful as an inexpensive alternative for various PVC formulations that are currently used for medical devices.

When more than one polymer is mixed to form an alloy composition, it is difficult to accomplish all of the above at the same time. In most cases, e.g. B. an alloy composition light; this does not meet the requirement for optical clarity. The light scattering intensity (measured by turbidity) depends on the size range of the components in the micrometer (µm) range and on the similarity of the refractive indices of the components. In general, the selection of components that can be processed sufficiently well in very small size ranges and yet show only a minimal refractive index deviation is a difficult task.

The present invention is provided to solve these and other problems.

Summary of the invention

Certain polymer-based multilayer structures are provided in accordance with the present invention. The films can become medical-grade items such as B. containers for storing medical solutions or blood products, blood bags and similar objects, or other products that are made up of multi-layer structures are processed.

An object of the present invention is to provide a multilayer film with the following physical properties:

(1) a modulus of elasticity less than 2758.10 & sup5; Pascals (40,000 psi), and particularly less than 1724.10 & sup5; Pascal (25000 psi) measured according to ASTM D-882;

(2) an elastic length recovery of more than or equal to 70%, and in particular more than or equal to 75%, after an initial deformation of 20%,

(3) an optical haze of less than 30%, and especially less than 15%, measured for a composition having a thickness of 0.229 mm (9 mil) according to ASTM D-1003,

(4) a loss factor at 1 Hz, measured at melt processing temperatures, of more than 1.0, and in particular more than 2.0,

(5) an elemental halogen content of less than 0.1%, and especially less than 0.01%,

(6) a low molecular weight water soluble fraction of less than 0.1%, and especially less than 0.005%.

(7) a maximum dielectric loss between 1 and 60 MHz and over a temperature range of 25 to 250 ° C greater than or equal to 0.05, and particularly greater than or equal to 0.1,

(8) an autoclave resistance measured by creep at 121 ° C under a load of 1862.10 & sup5; Pascal (27 psi) of less than or equal to 60%, and especially less than or equal to 20%, and

(9) no whitening after stretching at a moderate rate of about 50 cm (10 inches) per minute at about 100% stretch, and the presence or absence of whitening is determined.

The multilayer structure according to the invention is characterized as claimed in claim 1 and comprises a surface layer, preferably composed of a polypropylene copolymer with styrene and hydrocarbon block copolymers, and in particular a propylene copolymer with styrene / ethylene-butene-styrene ("SEBS") in one Range from 0 to 20% by weight of the surface layer. The structure also includes a radio frequency ("RF") sensitive layer adhered to the surface layer. The RF layer consists of a first component made of a polypropylene polymer, optionally a second component made of a non-propylene polyolefin (one containing no repeating propylene units), a third component made of a radio frequency sensitive polymer, and a fourth component from a polymeric compatibilizer. In alternative embodiments, additional layers, such as. B. Inner, waste and boundary layers to which surface and RF layers are added in order to provide additional or increased functionality of the resulting film structure.

The multilayer film structure according to the invention provides additional features that the compositions of the RF layer alone do not provide. The additional features of the multilayer film include excellent surface gloss and reduced stickiness to the outer surface of the film structure. In addition, the multilayer film structure has improved vapor barrier properties, higher strength and optical clarity, and is cleaner or less likely to blend into the contents of the containers.

The inner layer, which can be provided between the surface layer and the RF layer, consists of three components. Preferably, the first component is polypropylene, which forms about 40% of the inner layer, and the second component is ultra-low density polyethylene ("ULDPE"), which forms about 50% by weight of the inner layer, and the third component is a styrene / Hydrocarbon block copolymer, and in particular an SEBS block copolymer, which forms approximately 10% by weight of the inner layer.

The entire inner layer should have a thickness of 0.1 mm (4.0 mil).

For economic reasons, among other things, it is also desirable to re-incorporate waste material that has been obtained during the processing of the film material into the composition of the film structure. This can result in the use of significant amounts of waste material, expressed as a weight percent of the total layer structure, which significantly reduces the cost of the film product. The re-milled waste can either be incorporated into the structure described above as an additional separate layer located somewhere between the surface layer and the RF layer, or it can be mixed into the inner layer as an additional component. In any case, significant amounts of raw materials are saved by reprocessing the waste material.

In order to increase the gas barrier properties of the structure, it is expedient to install a barrier layer between the surface layer and the RF layer. The barrier layer can be attached to the surrounding layers using adhesive tie layers. The barrier layer can be selected from ethylene vinyl alcohols, e.g. B. those sold under the name Evalca (Evalca Co.), high-glass or crystalline polyamide, such as. B. Sclar PA® (Dupont Chemical Co.), acrylonitrile copolymers with a high nitrile content, e.g. B. are sold under the trade name Barex® by British Petroleum.

It has been found that films with the structure and composition mentioned above are flexible, optically clear, without whitening when stretched, and can be steam and radiation sterilized. In addition, the films are suitable for medical applications because the components that make up the film show minimal extractability to fluids and substances with which the composition comes into contact. In addition, the films are not harmful to the environment because they do not provide any harmful degradation products when burned. After all, the films represent an inexpensive alternative to PVC.

Additional features and advantages of the present invention are described in, and will be apparent from, the drawings and detailed description of currently preferred embodiments.

Brief description of the drawings

1 shows the cross section of a two-layer film structure according to the invention;

FIG. 2 shows the cross section of a three-layer film structure according to the invention, which has an inner layer attached to the film of FIG. 1;

Fig. 3 shows the cross section of the film of Fig. 1 with a solution contact layer;

Fig. 4 shows the cross-section of a four-layer structure according to the invention with a separate layer of waste material between the surface and the inner layer;

Figure 5 shows the cross section of a film structure using regrind waste as a separate layer between the inner and RF layers;

Fig. 6 shows the cross section of a film structure using regrind waste as a separate layer that separates the inner layer into two inner layers;

7 shows the cross section of a film structure according to the invention with 7 layers, including a barrier layer between the core and the RF layer and two connecting layers;

Fig. 8 shows the same structure of Fig. 6 except that the barrier layer is provided between the inner layer and the surface layer;

Fig. 9 shows the cross section of a film structure with a barrier layer dividing the inner layer; and

10 shows a container constructed from one of the film structures according to the invention.

Detailed description

1 shows a two-layer film structure 10 with a surface layer 12 and a layer 14 which is sensitive to radio frequency ("RF"). The surface layer 12 imparts temperature resistance and abrasion resistance and is preferably made of a polypropylene and in particular of a polypropylene copolymer with styrene and hydrocarbon - Block copolymers is mixed. The surface layer 12 is primarily a polypropylene copolymer which is mixed with an SEBS block copolymer in a range from 0 to 20% by weight. The surface layer 12 should have a thickness in the range of 0.005 to 0.008 mm (0.2 to 3.0 mil).

The RF sensitive layer 14 of the present invention should have a dielectric loss greater than 0.05 at frequencies in the range of 1 to 60 MHz within a temperature range of ambient to 250 ° C. The RF layer 14 preferably has 4 components. The RF layer 14 gives the film structure 10 RF weldability, flexibility, dimensional stability and compatibility. The first component of the RF layer 14 is selected from polypropylene copolymers, and preferably the propylene / α-olefin random copolymers ("PPE"). The PPEs have the required rigidity and resistance to deformation at sterilization temperatures of approx. 121ºC. As such, however, the PPEs are too stiff to meet the flexibility requirements. Good flexibility can be achieved when combined with certain low modulus polymers by alloying.

The low modulus copolymers may contain ethylene based copolymers such as e.g. B. ethylene / vinyl acetate ("EVA"), ethylene / a-olefins, or the so-called ultra-low density polyethylenes ("ULDPE") (typically less than 0.90 kg / l). These ULDPE include commercially available products sold under the trade name Tafmer® (Mitsui Petrochemical Co.) under the product name A485, Exact® (Exxon Chemical Company) under the product names 4023-4024, and Insite® technical polymers (Dow Chemical Co. ) are available. It has been found that polybutene-1 ("PB"), e.g. B. products sold by Shell Chemical Company under the product names PP-8010, PB-8310; thermoplastic elastomers based on SEBS block copolymers (Shell Chemical Company), polyisobutene ("PIB") the product names Vistanex L-80, L-100, L-120, L-140 (Exxon Chemical Company), ethylene alkyl acrylate, the methyl acrylate copolymers ( "EMA"), such as. B. the product names EMAC 2707 and DS-1130 (Chevron), and n-butyl acrylate ("ENBA") (Quantum Chemical) are acceptable copolymers. Ethylene copolymers such as e.g. B. the acrylic and methacrylic acid copolymers and their partially neutralized salts and ionomers, such as. B. Primacor® (Dow Chemical Company) and Suryln® (EI DuPont de Nemours & Company) are also useful. Typical ethylene-based copolymers have melting temperatures less than about 110ºC and are not suitable for sterilization at 121ºC. In addition, only a limited proportion of each component allows the flexibility and sterilizability to be met at the same time.

The first component is preferably selected from the group of propylene homopolymers and random copolymers with α-olefins, which are approximately 30 to 60%, in particular 35 to 45%, and primarily 45% of the weight of the film. Statistical copolymers of propylene and ethylene, in which ethylene is present in an amount in the range from 0 to 6%, and in particular in the range from 2 to 6%, based on the weight of propylene, are e.g. B. preferred as the first component.

The second component of the RF layer 14 gives the RF layer 14 flexibility and low temperature ductility and is selected from the group consisting of polyolefins that do not have repeating propylene units ("non-propylene based polyolefins"), including Ethylene copolymers including ULDPE, polybutene, butene / ethylene copolymers, ethylene / vinyl acetate copolymers with vinyl acetate contents of approx. 18 up to 50%, ethylene / methyl acrylate copolymers with methyl acrylate contents between approx. 20 to 40%, ethylene / n-butyl acrylate copolymers with an n-butyl acrylate content between 20 and 40%, ethylene / acrylic acid copolymers with an acrylic acid content of more than about 15%. Examples of these products are sold under product names such as Tafmer A-4085 (Mitsui), EMAC DS-1130 (Chevron), Exact 4023, 4024 and 4028 (Exxon). The second component is preferably either ULDPE, sold by Mitsui Petrochemical Company under the name Tafmer A-4085, or Polybutene-1, PB8010 and PB8310 (Shell Chemical Co.), and should be approximately 25 to 50%, in particular 35 to 45% , and primarily 45% by weight, based on the film.

The first and second components of the RF layer 14 can be replaced with a single component selected from high melting point flexible olefins such as e.g. B. such polypropylenes, which are sold by Rexene Company under the product name FPO. The melting point of this component should be greater than 130 ° C and the modulus less than 1379.10 & sup5; Pascal (20,000 psi). This component should make up 30 to 60% by weight of the RF layer.

In order to impart RF dielectric loss to the RF layer 14, certain known components with high dielectric loss are installed as the third component of the film structure 10. For example, EVA and EMA with sufficiently high comonomer levels showed significant loss properties at 27 MHz to allow the compositions to be weldable by a dielectric process. Polyamides as a class of materials and ethylene vinyl alcohol ("EVOH") copolymers (typically made by hydrolyzing EVA copolymers) both have high dielectric loss properties at suitable temperatures. Other active materials include PVC, vinylidene chlorides and fluorides, copolymers of bisphenol A and epichlorohydrins known as Phenoxys® (Union Carbide). Significant levels of these chlorine and fluorine containing polymers would make them environmentally harmful, however, because the combustion of such a material would form inorganic acids. The third component of the RF layer 14 is therefore preferably selected from the class of the polyamides.

The polyamides of the present invention are preferably selected from aliphatic polyamides from the condensation reaction of diamines with a carbon number in the range from 2 to 13, aliphatic polyamides from the condensation reaction of diacids with a carbon number in the range from 2 to 13, polyamides from the condensation reaction of dimeric fatty acids, and amide-containing copolymers (random, block or graft copolymers).

Polyamides such as B. nylon, are widely used in film materials because they give the film abrasion resistance. However, the nylon polymers are rarely found in a layer contacting medical solutions because they generally contaminate the solution by leaking into the solution. However, it has been found by the applicant of the present invention that various polyamides of dimeric fatty acids, e.g. B. sold by Henkel Corporation under the product names Macromelt and Versamid do not result in such contamination and are therefore the most preferred third component of the RF layer 14. The third component should be present in an amount of about 3 to 40%, especially 7 to 13%, and primarily 10% by weight, based on the RF layer 14.

The fourth component of the RF layer imparts compatibility between the polar and non-polar components of the RF layer 14. The fourth component was selected from styrene / hydrocarbon block copolymers, and preferably SEBS block copolymers, by maleic anhydride, epoxy, or Carboxylate functionalities are modified. The fourth component is primarily a SEBS block copolymer that is functionalized maleic anhydride. Such a product is sold by Shell Chemical Company under the product name Kraton RP-6509. The fourth component should make up approximately 5 to 40%, in particular 7 to 13%, and primarily 10% by weight of the RF layer 14.

It may also be expedient to incorporate a fifth component made of a SEBS block copolymer into the RF layer 14, which component is not modified by the above-mentioned functional groups, such as, for. B. the product sold by Shell Chemical Company under the product name Kraton G-1652. This component should be 5 to 40% by weight of the RF layer, in particular 7 to 13% by weight, and primarily 10% by weight.

The RF sensitive layer preferably has a thickness in the range of 0.002 to 0.229 mm (1 to 9 mils), and particularly 5.0 mil to 8.0 mils, and primarily 0.127 mm (5.0 mils). The surface layer has a density in the range of 0.005 to 0.076 mm (0.2 to 3.0 mil), and especially 0.5 mil.

FIG. 2 shows another embodiment according to the invention, which has an intermediate inner layer 16 between the surface layer 12 and the RF layer 14. The inner layer 16 gives the film structure 10 temperature resistance and flexibility and compatibility between the components of the film structure 10. Preferably, the inner layer has a thickness in the range from 0.013 to 0.254 mm (0.5 to 10 mil) and in particular from 0.025 to 0.102 mm (1 up to 4 mil). The inner layer 16 has three components. The first component is a polyolefin, and preferably a polypropylene, in an amount that is 20 to 60 percent by weight of the inner layer 16, preferably 35 to 50 percent by weight, and primarily 45 percent by weight of the inner layer 16 ,

The second component of the inner layer 16 is selected from the group consisting of compounds that give the inner layer 16 flexibility, including ULDPE, polybutene copolymers. The second component of the inner layer is preferably ULDPE or polybutene-1 in an amount of 40 to 60% by weight, in particular 40 to 50% by weight, and primarily 40% by weight.

The third component of the inner layer 16 is selected from the group of compounds that confer compatibility between the components of the inner layer 16 and comprises styrene / hydrocarbon block copolymers, and in particular SEBS block copolymers. The third component is preferably present in an amount from 5 to 40% by weight of the inner layer 16, and in particular from 7 to 15% by weight, and primarily from 15% by weight.

It is also possible to add as the fourth component to the inner layer 16 regrinded waste material obtained during the manufacture of containers. The waste material is dispersed over the entire inner layer 16. Waste can be added in an amount of preferably between about 0 to 50% by weight of the inner layer 16, and in particular in the range from 10 to 30% by weight, and primarily in the range from 3 to 12% by weight become.

FIG. 3 shows the film or film structure of FIG. 1 with a solution contact layer 17 which is attached to the side of the RF layer which is opposite to the surface layer 12. The solution contact layer 17 has three components that can be selected from the same first three components and with the same weight percentage range as indicated above for the inner layer 16. Preferably, the solution contact layer 17 has a thickness in the range of 0.005 to 0.025 mm (0.2 to 1.0 mil), and particularly 0.025 mm (1.0 mil).

FIG. 4 shows another embodiment of the multilayer film structure with the surface layer 12, inner layer 16 and RF layer 14 as described above and with an additional separate layer of waste material 20 between the surface layer 12 and the inner layer 16. FIG. 5 shows that separate waste material layer 20 between the inner layer 16 and the RF layer 20. In FIG. 6 the waste material layer 20 separates the inner layer 16 into first and second inner layers 16a and 16b. The regrind layer should preferably have a thickness in the range of 0.013 to 0.127 mm (0.5 to 5.0 mil), and particularly 0.025 mm (1.0 mil).

FIG. 7 shows another embodiment of the present invention with 7 layers, which has the surface layer 12, inner layer 16 and RF layer 14 discussed above, and with a barrier layer 26, which is present between and on the core layer 16 and the RF layer 14 with tie layers 28 attached to opposite sides of the barrier layer 26. 8 shows the barrier layer 26 between the inner layer 16 and the surface layer 12. In FIG. 9 the barrier layer 26 separates the core layer 14 into two inner layers 16a and 16b. The barrier layer 16 increases the gas barrier properties of the film structure 10. The barrier layer 26 is selected from the group consisting of ethylene vinyl alcohols, such as. B. under the name Evalca (Evalca Co.) marketed, highly glass-like or crystalline polyamide, such as. B. Sclar PA® (DuPont Chemical Co.), acrylonitrile copolymers with a high nitrile content, such as. B. Barex®, sold by British Petroleum. Preferably, the barrier layer 26 is made of ethylene vinyl alcohol and has a thickness in the range of 0.3 to 1.5 mils, and particularly 0.025 mm (1.0 mils).

The adhesive layers 28 can be selected from modified ethylene and propylene copolymers, such as those e.g. B. under the product names Prexar (Quantum Chemical Co.) and Bynel (DuPont), and should have a thickness in the range of 0.005 to 0.025 mm (0.2 to 1.0 mil) and in particular 0.013 mm (0.5 mil).

The above layers can be made by coextrusion, coextrusion coating, or other suitable method. However, the method for manufacturing the present structure is not part of the present invention, and the scope of the invention is therefore not limited to these embodiments.

The materials can be used to manufacture IV therapy bags, such as. B. the one shown in FIG. 10 and designated 30 can be used.

Films with various combinations of the above components and in percentages by weight as set forth in the examples below were tested using the following methods.

(1) Autoclavability

The sterilization resistance is measured by creep or increase in length of the sample at 121 ° C and under a load of 1862.10² Pascal (27 psi) for one hour. The sterilization resistance must be less than or equal to 60%.

(2) Low temperature and ambient temperature ductility

(A) Low temperature ductility

In an impact tester equipped with a low temperature chamber cooled with liquid nitrogen, foil samples with a size of 18 cm x 18 cm (7 x 7 inches) are placed on circular sample holders with a size of approx. 15 cm (6 inches) in diameter applied. A hemispherical impact head with load sensors is driven against the film at high speed (typically approx. 3 m / sec) and hits its center. The stress-displacement curves are recorded and the impact energy is calculated by integration. The temperature at which the impact energy rises dramatically and when the broken sample changes from a brittle to a ductile high deformation morphology is taken as a measure of the low temperature property of the film ("N.Temp").

(B) Mechanical module and resettability

The sterilized film sample with a certain geometry is mounted on a servohydraulically driven mechanical test device with cross heads to extend the sample. The sample is expanded to approximately 20% elongation at a crosshead speed of 25 cm (10 inches) per minute. At this point, the crossheads move back and forth in a direction opposite to the original direction used to stretch the sample. The stress-strain behavior is recorded with a digital recorder. The modulus of elasticity ("E (Kpsi)") is derived from the initial slope of the stress-strain curve, and the recovery from the excess of the sample dimension as a percentage of the sample elongation.

(3) RF processability

Connected to a Callahan 27.12 MHz, 2 KW radio frequency generator is a rectangular brass mold with a size of approx. 6.3 mm (0.25 inch) x 10 cm (4 inch), that of a flat brass electrode, which is also attached the generator is connected. After closing the mold in which there are two foils of the material to be tested, the solution sides of which are opposite, RF energy of different amplitudes and durations is applied. When the RF cycle is over, the mold is opened and the resulting composite is checked by manually pulling the two foils apart. The strength of the composite (versus film strength) and the nature of the defect (peel, tear, or adhesion defect) are used to assess the RF sensitivity of the material.

Alternatively, the film to be tested is first vacuum-sputtered with gold or palladium to a thickness of 100 angstroms to make the surface conductive, cut into circular slices and placed between the parallel electrodes of a dielectric capacitance measuring cell. Using an automatic Heward Packard 4092 RF bridge, the dielectric constant and dielectric losses are measured at various frequencies up to 10 MHz and temperatures up to 150 ° C. The dielectric loss allows the calculation of the heat generation in an RF field. The minimum required dielectric loss is obtained from the calculations and correlations with the RF welding tests.

When the RF welding behavior is obtained from the Callahan welding device, the following rating scale is applied:

(4) Optical clarity

Sterilized film samples are first cut into 5 x 5 cm (2 x 2 inch) squares, mounted on a Hunter colorimeter and their internal haze measured according to ASTM D-1003. Typically, these thicknesses require less than 30% internal haze, and preferably less than 20% ("% haze").

(5) Whitening when stretched

The sterilized film is stretched to about 100% stretch (twice the original length) at moderate speeds of about 50 cm (20 inches) per minute and the presence of stretch whitening (indicated by 1) or its absence (by 0 designated) determined ("stretching whitening")

(6) environmental compatibility

Environmental sustainability has three important characteristics:

(a) the material is free of low molecular weight plasticizers that could leak when disposed of in landfills,

(b) the material can be reused thermoplastic to produce useful articles after fulfilling its primary medical purpose, and

(c) when disposed of by incineration, no significant amounts of environmentally harmful inorganic acids are released ("environment"). The composition also contains less than 0.1% by weight halogens. To facilitate recirculation by melt processing, the resulting composition should have a loss factor greater than 1.0 at 1 Hz measured at processing temperatures.

(7) Solution compatibility

Compatibility with solutions is understood to mean that a solution contained in the film container is not contaminated by components which build up the composition (“L-Comp.”). The content of low molecular weight water-soluble fractions in the composition is less than 0.1%.

Using the tests described above, the following combinations were tested for the films listed below.