Sterilization bag and process for closing a bag.

Abstract

Disclosed is a porous non-woven fabric for producing sterilization articles, in particular preformed sterile barrier systems, comprising fibers formed at least in part of metallocene polypropylene, and between 0.1 and 1.4% of titanium dioxide by weight relative to the total weight of the non-woven fabric.

Description

1 / 12 “STERILIZATION BAG AND PROCESS FOR CLOSING A BAG” TECHNICAL AREA

[001] The present invention relates to nonwoven materials used in the manufacture of sterilization items and, more particularly, but not exclusively, in the manufacture of pre-formed sterile barrier systems, notably sterilization bags. Background of the Invention

[002] To sterilize medical equipment (reusable or disposable), it is common practice to use preformed sterile barrier systems (pre-SBS) that meet certain standards, including ISO 11607 (Packaging for terminally sterilized medical devices) and NF EN 868, in particular part 9, which describes the requirements and test methods for uncoated polyolefin-based nonwoven materials. These preformed sterile barrier systems may consist of a polymer film, notably a multilayer film, typically based on polypropylene (PP) and polyethylene terephthalate (PET), and a porous nonwoven material, produced by heat sealing. One side of the pre-SBS is left unsealed to allow insertion of the instrument to be sterilized.

[003] Once the instrument has been inserted, the pre-formed sterile barrier systems can be thermally sealed at their opening, and the entire assembly placed in a sterilization chamber, such as an autoclave or sterilization chamber, where a sterilizing agent is injected. This agent can be steam, formaldehyde, hydrogen peroxide (especially when excited with an electromagnetic field, in which case this is called gas-plasma sterilization) or ethylene oxide. Sterilization can also be achieved by irradiation.

[004] The porosity of nonwoven fabric allows the sterilizing agent to penetrate the system to sterilize its contents. Petition 870250082370, dated 12 / 09 / 2025, page 47 / 62 2 / 12

[005] When the instrument is used, the medical team opens the system by separating the nonwoven fabric from the polymer film; during this operation, it is desirable that no fibers of the nonwoven fabric are lifted in order to ensure the asepsis of the packaging system. In fact, lifting fibers can lead to the risk of contamination of the surgical field.

[006] The sealing force between the polymer film and the nonwoven fabric must therefore be sufficient to ensure the integrity of the sterile contents of the system and withstand the pressurizations during sterilization cycles, but not too high to avoid the risk of tearing and fiber release when opened.

[007] Patent application GB 2 449 418 describes the use of metallocene polypropylene (PP) for the manufacture of a porous nonwoven fabric that can be used in the manufacture of sterilizable packaging. No fillers other than fluorinated compounds, antistatic agents, dyes or antimicrobials are foreseen.

[008] US patent application 2018 / 0327948 A1 describes an elastic nonwoven article of the SMMS type, composed of continuously spun layers containing metallocene polypropylene mixed with other polymers such as PE, PC and 0.25% by weight of TiO2. This material is not suitable for the manufacture of sterilization bags, as it does not meet the NF EN 868-9 standard, mainly in terms of mechanical strength and aseptic opening. The aforementioned standard specifies, in section 2.2.1, a tensile strength in the machine direction (MD) of at least 2.5 kN / m and in the transverse direction (CD) of at least 1.5 kN / m.

[009] US patent application 2022 / 0195645 A1 describes a nonwoven fabric comprising two-component fibers comprising polymers that may include metallocene PP, with a filler content of several percent by mass of CaCO3 and TiO2. Petition 870250082370, dated 12 / 09 / 2025, pp. 48 / 62 3 / 12 Field of Invention

[0010] There is a need to further improve porous nonwoven fabrics used in the manufacture of sterilization articles, especially pre-formed sterile barrier systems, in order to facilitate their opening by peeling, while ensuring sufficient sealing strength, good quality of the impression left on the nonwoven fabric and no tearing to ensure asepsis. Brief Description of the Invention

[0011] The invention aims to meet this need and achieves it by proposing a porous nonwoven fabric intended for the manufacture of sterilization articles, notably pre-formed sterile barrier systems, comprising fibers formed at least partially of metallocene polypropylene, and between 0.1% and 1.4% and preferably between 0.1% and 0.8% of titanium dioxide by mass relative to the total weight of the nonwoven fabric.

[0012] Thanks to the invention, the sealing forces can be adjusted. This improves the ease of peeling and the user experience when opening the sterile barrier system. The opening forces are constant and moderate, ensuring easy opening without tearing the nonwoven fabric and maintaining asepsis. The quality of the impression formed on the nonwoven fabric when the sterile barrier system is opened is also improved (the impression can be more uniform, whiter, without transparent areas (i.e., no transparency) and without any raised fibers).

[0013] Surprisingly, the claimed content makes it possible to adapt and improve sealing performance while maintaining good mechanical performance and preserving sterility.

[0014] In fact, a titanium dioxide content greater than 1.4% by mass leads to a significant decrease in tear resistance in the machine direction and also to a decrease in tensile strength in both directions. Petition 870250082370, dated 12 / 09 / 2025, pp. 49 / 62 4 / 12 machine as well as in the transverse direction.

[0015] A content lower than 0.1% results in a transparent impression on porous nonwoven fabric, especially at sealing temperatures between 150 °C and 160 °C. Furthermore, the sealing forces are not adjusted, which can cause tearing in the nonwoven fabric or lifting of fibers when the sterile barrier system is opened.

[0016] The nonwoven fabric according to the invention conforms to ISO 11607 and ISO 10993 standards. It also conforms to DIN 58953-6 (the latter describes tests for the microbial barrier properties of medical devices to be sterilized), ASTM F2101 (measurement of bacterial filtration efficiency, BFE) and ASTM F1608 (measurement of the ability of a porous material to prevent bacterial penetration). According to the latter method, a completely impermeable control sample (bacterial penetration = 0) is exposed to one million CFU (colony forming units). The number 10⁶ has a logarithmic value of 6. If a sample subjected to the same test as the control sample allows the penetration of 10¹ CFU (log 10 = 1), its LRV (Logarithmic Reduction Value) is 5 (6 - 1 = 5). Thus, the higher the LRV value, the more resistant the porous material will be to bacteria and microorganisms.

[0017] When nonwoven fabric is used for the manufacture of a sterilization bag, the nonwoven material must meet the requirements of NF EN 868-9. In particular, the bag must have an aseptic opening and the nonwoven fabric must have a tensile strength in the machine direction (MD) (measured in accordance with EN ISO 1924-2) of at least 2.5 kN / m and in the transverse direction (CD) (measured in accordance with EN ISO 1924-2) of at least 1.5 kN / m, in accordance with this standard (section 2.2.1) for polypropylene-based materials.

[0018] According to one or more advantageous characteristics of Petition 870250082370, dated 12 / 09 / 2025, pp. 50 / 62 5 / 12 invention, considered individually or in combination: - the nonwoven fabric comprises between 0.1% and 1% by mass of titanium dioxide, notably more than 0.25% by mass of titanium dioxide, better still between 0.4% and 1% by mass of titanium dioxide, better still between 0.4% and 0.6% by mass of titanium dioxide, - The nonwoven fabric is of the continuously spunbonded type. - The nonwoven fabric does not contain any mineral filler other than titanium dioxide, notably in an amount greater than or equal to 0.1% by mass, notably strictly less than 0.1% by mass, or even contains only titanium dioxide as a mineral filler, the absence of calcium carbonate as a filler being advantageous insofar as it avoids the creation of false positives in biocompatibility. Titanium dioxide has an average numerical size between 100 and 1000 nm, - the fibers are formed entirely, with respect to the polymeric material(s) of which they are composed, from metallocene polypropylene.

[0019] According to another aspect thereof, the invention also relates to an article, notably a system of preformed sterile barriers, notably a sterilization bag, surgical drape, protective garment or bag for transporting an active ingredient, comprising a nonwoven fabric according to the invention, as defined above.

[0020] Preferably, the item is a sterilization bag.

[0021] According to another aspect thereof, the invention also relates to a process for closing an article according to the invention, in which the nonwoven fabric is thermally sealed to a thermoplastic support.

[0022] Sealing is preferably performed at a temperature Petition 870250082370, dated 12 / 09 / 2025, pp. 51 / 62 6 / 12 between 135°C and 165°C, even better between 150°C and 160°C. Brief Description of the Drawings

[0023] The invention may be better understood by reading the detailed description that follows, by non-limiting examples of its implementation, and by examining the accompanying drawing, in which: [Fig. 1] shows a front view, non-woven side, of an example of a sterilization pouch according to the invention; and [Fig. 2] is a partial schematic cross-section of the bag. Detailed Description of the Invention

[0024] Figures 1 and 2 show an example of a sterilization bag (1) according to the invention, comprising a porous nonwoven fabric (2) thermally sealed to a support film (3) made of a nonporous thermoplastic material based on polypropylene PP and PET.

[0025] Figure 1 shows the bag sealed along a weld line (4) that extends on only three sides, thus providing an opening (5) for the insertion of an instrument to be sterilized. The nonwoven fabric is thermally sealed to the support along a closure line (6) after the instrument is inserted, and the bag is then sterilized.

[0026] On the opposite side of the opening (5), the bag (1) has an area (7) where the non-woven fabric covers the support without being sealed to it, so that the user can hold it with their hands to separate it when opening the bag, peeling it off.

[0027] This sterile barrier system can be sterilized using several methods: - with moist heat: the sterilizing agent is steam (temperature: 121°C-134°C for 18-30 minutes, under pressure), - with ethylene oxide: temperature between 30 and 60 °C, with relative humidity above 30% for 16 to 18 hours and ethylene oxide concentration of Petition 870250082370, dated 12 / 09 / 2025, pages 52 / 62 7 / 12 Ethylene (200 to 800 mg / L). Ethylene oxide is a toxic agent; therefore, a desorption period must be observed after sterilization. - using ionizing radiation (gamma rays, beta sterilization or electron beam), - with formaldehyde: formaldehyde can be used in gaseous form, - with gaseous plasma: using hydrogen peroxide (H2O2) in gaseous form, diffused into the chamber and converted into plasma by an electromagnetic field. This generates ions, free electrons, and numerous free radicals with very strong bactericidal activity. This method allows sterilization at low temperatures and does not require desorption. PP METALOCENE

[0028] In the sense of the invention, the term “polypropylene” encompasses a propylene homopolymer, propylene copolymers obtained by copolymerization of propylene with at least one alpha-olefin comonomer, and propylene homopolymers or propylene copolymer derivatives that are functionalized, notably by grafting a reactive function after interaction with maleic anhydride or acrylic acid, for example, maleated polypropylene. A copolymer may be block or random.

[0029] Polypropylene (regardless of its form) can be isotactic or syndiotactic.

[0030] In the context of the invention, the term “metallocene PP” refers to polypropylene obtained by metallocene catalysis.

[0031] Polypropylene is produced using metallocene catalysis instead of the Ziegler-Natta process (the use of this type of catalysis for the production of polyolefins is well known to those skilled in the art, as described in US patents 5,571,619, 5,322,728 and 5,472,775).

[0032] Nonwoven fabric is preferably made of Petition 870250082370, dated 12 / 09 / 2025, pages 53 / 62 8 / 12 metallocene polypropylene (PP) according to the teachings of GB 2 449 418 patent.

[0033] Metallocene PP generally has a fairly narrow molecular weight distribution (MWD), preferably with an MWD value less than 3, notably less than 2.5, and allows the production of fibers with an average diameter less than 25 microns, notably in the 10-20 micron range.

[0034] The nonwoven fabric obtained is formed by a technique known as continuous spinning, which is known in itself. The formation of metallocene polypropylene fibers can be carried out as described in patent application GB 2,449,418 (this process is also described in documents US 3,821,062, US 3,563,838, US 2021 / 0301425 and US 2019 / 145032). Titanium dioxide (TiO2) is incorporated during the production of polypropylene fibers by mixing with metallocene PP, mainly by dry mixing. The titanium dioxide is preferably in the form of a masterbatch.

[0035] The PP used may notably be Metocene HM562S with a melt flow index of 30 g / 10 min measured at 230 °C under a weight of 2.16 kg (according to ASTM D1238 standard).

[0036] According to the invention, the porous nonwoven fabric can undergo a calendering step. During this step, several parameters can vary, such as temperature (typically around 130 °C and 160 °C), speed (typically greater than 10 m / min) and pressure (typically greater than 30 bar).

[0037] The mass content of titanium dioxide in nonwoven fabric is between 0.1% and 1.4%, preferably around 0.5%.

[0038] This content provides advantageous properties for the manufacture of the bag, as will be detailed with reference to tables 1 and 2.

[0039] The fibers of nonwoven fabric can have an average diameter ranging from 10 to 25 microns. Petition 870250082370, dated 12 / 09 / 2025, pages 54 / 62 9 / 12

[0040] Titanium dioxide can have an average size ranging from 100 nm to 1 μm. Comparative tests

[0041] Several samples were produced using porous nonwoven fabric composed of metallocene PP (Metocene HM562S) and TiO2 (average diameter of 300 nanometers) and a 12 μm PET 12 μ / PP laminated polymer film.

[0042] The nonwoven fabric has an average basis weight of 93 g / m2 (measured according to ISO 536 standard).

[0043] Strips measuring 5 cm x 15 cm were prepared for each sample. The PP side of the PET / PP film was thermally sealed to the porous nonwoven fabric.

[0044] Pairs of film (PET / PP) and porous nonwoven fabric were thermally sealed using a laboratory thermal sealer, with the hot jaw pressed against the PET side. Different sealing temperatures were tested: 150, 155 and 160 °C, at a constant pressure of 5 bar, for a period of 0.3 seconds.

[0045] Sealing forces were measured on 10 samples using a tensile testing machine in accordance with ASTM F88 / F88M-2021 (technique B).

[0046] Tensile tests are performed on a tensile testing machine in accordance with ASTM D882-18 standard on 10 samples.

[0047] Tear tests are performed on 10 samples using a tensile testing machine in accordance with ASTM D1938-19.

[0048] These pairs of film (PET / PP) and porous nonwoven fabric, sealed in a laboratory heat sealer, also allowed studying the print quality at the opening.

[0049] Bags like those shown in Figure 1 were also produced on an FFS (Form-Fill-Seal) machine. Three were used. Petition 870250082370, dated 12 / 09 / 2025, pages 55 / 62 10 / 12 sealing temperatures: 150, 155, and 160 °C, and the speed was set to 15 bags per minute. These bags were used to evaluate the feel upon opening and the print quality.

[0050] Table 1 illustrates the mechanical characteristics of the nonwovens obtained for different titanium dioxide contents and shows that tear resistance is significantly reduced for tests with contents of 1.5% or more, and that it reaches a relative maximum at 0.5%. Table 1 Physical properties of PP-based nonwoven films 0.05% TiO2 0.19% TiO2 0.27% TiO2 0.50% TiO2 0.8% TiO2 1.5% TiO2 2% TiO2 average average average average average average Tensile strength [kN / m] Machine direction 4.5 6.2 3.5 3.4 3.2 1.9 0.8 Cross direction 4.6 3.4 3 2.9 2.8 1.7 0.9 Elongation [%] Machine direction 61.5 40.7 32.3 29.2 25.3 17.2 11.2 Cross direction 133 34.5 28.2 27.2 24.3 18.2 12.5 Tear [mN] Machine direction 135 22 30 41 82 63 8560 5523 2342 1621

[0051] Table 2 illustrates the measured sealing forces and other findings for different sealing temperatures and different titanium dioxide contents and compares the sealing forces for different sealing temperatures and different titanium dioxide mass contents. Table 2 TiO2 content [%] Sealing temperature [°C] Sealing force [N / 15mm] (5x15 cm2 coupon) Impression on nonwoven fabric after opening (5x15 cm2 coupon and bag in Figure 1) Feel on opening (5x15 cm2 coupon and bag in Figure 1) Comments 0% TiO2 150 3.1 Transparency Moderate Some fiber elevation Non-aseptic opening 155 3.4 Transparency Poor - increased Non-aseptic opening Petition 870250082370, dated 12 / 09 / 2025, pages 56 / 62 11 / 12 T1O2 content [%] Sealing temperature [°C] Sealing strength [N / 15mm] (5x15 cm2 coupon) Impression on nonwoven fabric after opening (5x15 cm2 coupon and bag in Figure 1) Feel on opening (5x15 cm2 coupon and bag in Figure 1) Aseptic fiber comments 160 4.0 Poor transparency - increased fibers Non-aseptic opening 0.05% T1O2 150 3.1 Moderate transparency some fiber elevation Non-aseptic opening 155 3.6 Poor transparency - tearing Non-aseptic opening 160 4.1 Poor transparency - tearing Non-aseptic opening 0.19% T1O2 150 1.9 Good, white and homogeneous Good Bacterial barrier OK (according to ASTM F2101) LRV OK (according to (with ASTM F1608) In accordance with EN 868 (part 5 and part 9) 155 2.5 Good, white and homogeneous Good 160 2.9 Good, white and homogeneous Good 0.27% T1O2 150 1.9 Good, white and homogeneous Good 155 2.3 Good, white and homogeneous Good 160 2.7 Good, white and homogeneous Good 0.50% T1O2 150 1.8 Good, white and homogeneous Good 155 2.1 Good,White and homogeneous Good 160 2.4 Good, white and homogeneous Good 0.80% T1O2 150 1.8 Good, white and homogeneous Good 155 1.8 Good, white and homogeneous Good 160 2.1 Good, white and homogeneous Good 1.5% T1O2 150 1 Non-homogeneous Poor Not compatible with EN 868 part 5 Low sealing resistance 155 1.1 Non-homogeneous Poor 160 1.2 Non-homogeneous Poor

[0052] The results are also evaluated in the form of comments in the last two columns of table 2. Petition 870250082370, dated 12 / 09 / 2025, pages 57 / 62 12 / 12

[0053] For a content lower than 0.1%, a lack of whiteness in the print may be observed, as well as a transparent appearance, for sealing temperatures of 150, 155 and 160 °C.

[0054] There is no “transparency” after peeling, a good feel when opening, maintaining sterility, for titanium dioxide contents of 0.19%, 0.27%, 0.5% and 0.8%.

[0055] The opening feeling is bad with a content of 1.5%.

[0056] The best results are obtained with titanium dioxide contents of 0.27% and 0.5% by weight, at 155 °C and 160 °C. In fact, an excellent feel is observed when opening, as well as a homogeneous and white impression, preserving sterility, and also excellent mechanical performance (notably tear resistance).

[0057] Needless to say, the invention is not limited to the examples described.

[0058] For example, the nonwoven fabric according to the invention can be used in the manufacture of pre-formed sterile barrier systems, such as pouches, breathable tape bags or hospital packaging sheaths, among other items.

[0059] Metallocene PP can be blended with at least one other thermoplastic, for example, grafted or ungrafted polyethylene (low density or linear low density), or polybutene, among other possibilities. The proportion of the other polymer(s) in the blend is chosen to maintain the desired properties. Petition 870250082370, dated 12 / 09 / 2025, pp. 58 / 62

Claims

1 / 2 Claims 1. STERILIZATION BAG (1), characterized by comprising a porous nonwoven fabric (2) comprising fibers formed at least partially of metallocene polypropylene and between 0.1% and 1.4% titanium dioxide by mass relative to the total weight of the nonwoven fabric, the nonwoven fabric being free of any mineral filler other than titanium dioxide in an amount greater than or equal to 0.1% by mass.

2. BAG (1), according to claim 1, characterized by comprising between 0.1% and 1% by mass of titanium dioxide.

3. BAG (1), according to any one of claims 1 to 2, characterized by comprising between 0.4% and 1% by mass of titanium dioxide.

4. BAG (1), according to any one of claims 1 to 3, characterized by comprising between 0.4% and 0.6% by mass of titanium dioxide.

5. BAG (1), according to any one of claims 1 to 4, characterized in that it is of the continuous spinning type.

6. BAG (1), according to any one of claims 1 to 5, characterized in that the titanium dioxide has a numerical mean size between 100 and 1000 nm.

7. BAG (1), according to any one of claims 1 to 6, characterized in that the fibers are formed entirely, with respect to the polymeric material(s) constituting them, of metallocene polypropylene.

8. BAG (1), according to any one of claims 1 to 7, characterized in that the nonwoven fabric has a tensile strength in the machine direction, measured in accordance with EN ISO 1924-2, of at least 2.5 kN / m and in the transverse direction, measured in accordance with EN ISO 1924-2, of at least 1.5 kN / m in accordance with section 2.2.1 of the standard. Petition 870250082370, dated 12 / 09 / 2025, p. 59 / 62 2 / 2 9. PROCESS FOR CLOSING A BAG (1), as defined in any one of claims 1 to 8, characterized in that the nonwoven fabric is thermally sealed to a thermoplastic support (3).

10. PROCESS, according to claim 9, characterized in that the sealing is carried out at a temperature between 135 °C and 165 °C, preferably between 150 °C and 160 °C. Petition 870250082370, dated 12 / 09 / 2025, pp. 60 / 62

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