Sterilization pouch containing porous nonwoven fabric

Abstract

A porous nonwoven fabric for manufacturing sterilization articles, particularly pre-formed sterilization barrier systems, is disclosed, comprising fibers formed in part from metallocene polypropylene and 0.1 to 1.4% by weight of titanium dioxide relative to the total weight of the nonwoven fabric.

Description

Technical Field

[0001] The present invention relates to nonwoven materials used in the manufacture of sterilization items, and more particularly, but not limited thereto, to nonwoven materials used in the manufacture of preformed sterile barrier systems, particularly sterilization pouches.

Background Art

[0002] In order to sterilize medical devices (reusable or disposable), it is known practice to use preformed sterile barrier systems (pre-SBS) that meet certain standards, particularly ISO 11607 (Packaging for terminally sterilized medical devices) and NF EN 868, particularly Part 9, which describes the requirements and test methods for uncoated polyolefin-based nonwoven materials. These preformed sterile barrier systems are composed of polymer films, particularly multilayer films, typically multilayer films based on polypropylene (PP) and polyethylene terephthalate (PET), and porous nonwoven materials, and can be manufactured by heat sealing. One side of the pre-SBS is left unsealed so that an instrument can be inserted and sterilized.

[0003] Once the instrument is inserted, the molded sterilization barrier system can be heat-sealed at its opening, and the entire assembled system is placed in a sterilization chamber, such as an autoclave or sterilization chamber, into which a disinfectant is injected. This disinfectant may be vapor, formaldehyde, hydrogen peroxide (in particular when excited by an electromagnetic field, in which case referred to as gas plasma sterilization), or ethylene oxide. Sterilization can also be achieved by irradiation.

[0004] Therefore, the porosity of the nonwoven fabric allows the disinfectant to penetrate into the system and disinfect its contents.

[0005] When the instrument is to be used, medical staff open the system by separating the nonwoven fabric from the polymer film. During this process, it is desirable that no fibers detach from the nonwoven fabric to ensure the sterility of the packaging system. In fact, detachment of fibers can pose a risk of contamination of the surgical field.

[0006] Therefore, the seal strength between the polymer film and the nonwoven fabric must be sufficient to ensure the integrity of the sterile contents of the system and to withstand the pressure during the sterilization cycle, but it must not be too high to avoid the risk of tearing and fiber shedding upon opening.

[0007] British Patent No. GB2449418 describes the use of metallocene polypropylene (PP) to manufacture a porous nonwoven fabric that can be used to manufacture sterilizable packaging. Fillers other than fluorinated compounds, antistatic agents, colorants, or antimicrobial agents are not envisioned.

[0008] U.S. Patent Application Publication US2018 / 0327948A1 describes a stretchable SMMS-type nonwoven article comprising a spunbond layer containing metallocene polypropylene mixed with other polymers, e.g., PE, PC, and 0.25 wt% TiO2. Such materials are unsuitable for manufacturing sterile pouches because they do not meet the standard NF EN 868-9, particularly in terms of mechanical strength and aseptic opening. Section 2.2.1 of the standard specifies a tensile strength of at least 2.5 kN / m in the machine direction (MD) and at least 1.5 kN / m in the cross direction (CD).

[0009] U.S. Patent Application Publication No. US2022 / 0195645A1 describes a nonwoven fabric comprising a two-component fiber containing a polymer which may contain metallocene PP, with CaCO3 and TiO2 filler content in several mass percent. [Overview of the project] [Problems that the invention aims to solve]

[0010] There is a need for further improvements to porous nonwoven fabrics used in the manufacture of sterilized articles, particularly pre-molded sterilization barrier systems, to facilitate their opening by peeling, while ensuring sufficient seal strength, good quality of the imprints left on the nonwoven fabric, and the absence of tearing to guarantee sterility. [Means for solving the problem]

[0011] The present invention is directed toward satisfying this need and achieves this need by proposing a porous nonwoven fabric intended for producing sterilized articles, in particular pre-formed germicidal barrier systems, wherein the porous nonwoven fabric comprises fibers at least partially formed from metallocene polypropylene and contains 0.1% to 1.4% by mass, preferably 0.1% to 0.8% by mass, of titanium dioxide based on the total weight of the nonwoven fabric.

[0012] The present invention allows for adjustment of the sealing force. This improves the peelability and ease of use when opening the sterilization barrier system. Because the opening force is constant and appropriate, it is easy to open, without tearing of the nonwoven fabric, and the sterile state is maintained. The quality of the imprint formed on the nonwoven fabric when the sterilization barrier system is opened is also improved (the imprint can be more uniform, whiter, without transparent areas (i.e., without transparency), and without any detached fibers).

[0013] Remarkably, the requested content allows for the adaptation and improvement of sealing performance while simultaneously maintaining good mechanical properties and sterility.

[0014] In fact, a titanium dioxide content exceeding 1.4% by mass results in a significant decrease in tear strength in the mechanical direction, as well as a decrease in tensile strength in both the mechanical and intersecting directions.

[0015] At concentrations of less than 0.1%, a transparent imprint is produced on the porous nonwoven fabric, particularly at sealing temperatures of 150°C to 160°C. Furthermore, because the sealing force is not adjusted, the nonwoven fabric may tear or the fibers may peel off if the germicidal barrier system is opened.

[0016] The nonwoven fabric according to the present invention conforms to standards ISO 11607 and ISO 10993. It also conforms to standards DIN 58953-6 (the latter describing tests relating to 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 porous materials to prevent bacterial intrusion). According to the latter method, a completely impermeable control sample (number of bacterial intrusions = 0) is exposed to 1 million cfus (colony-forming units). 6 The logarithm of is 6. 10 samples were subjected to the same test as the control sample. 1 If the intrusion of 1 cfu (log 10=1) is tolerated, the LRV (Log Reduction Value) is 5 (6-1=5). Therefore, a higher LRV value indicates that the porous material has higher resistance to bacteria and microorganisms.

[0017] When the nonwoven fabric is used to manufacture sterile pouches, the nonwoven material must meet the requirements of standard NF EN 868-9. In particular, the pouch must have a sterile opening, and according to this standard (section 2.2.1), in the case of polypropylene-based materials, the nonwoven fabric must have a tensile strength of at least 2.5 kN / m in the mechanical direction MD (measured according to EN ISO 1924-2) and at least 1.5 kN / m in the transverse direction CD (measured according to EN ISO 1924-2).

[0018] According to one or more advantageous features of the present invention, considering them individually or in combination, are as follows: - The nonwoven fabric contains 0.1% to 1% by mass of titanium dioxide, particularly more than 0.25% by mass of titanium dioxide, better 0.4% to 1% by mass of titanium dioxide, and even better 0.4% to 0.6% by mass of titanium dioxide. - The nonwoven fabric is of the spunbond type. The non-woven fabric does not contain any inorganic filler other than titanium dioxide, especially in an amount of 0.1% by mass or more, or strictly less than 0.1% by mass, or contains only titanium dioxide as an inorganic filler and does not contain calcium carbonate as a filler, which is advantageous in preventing the occurrence of false positives in biocompatibility tests. - The titanium dioxide has a number average size of 100 to 1000 nm, - The fiber is entirely formed from metallocene polypropylene with respect to one or more polymer materials constituting it.

[0019] According to another aspect of the present invention, the present invention also relates to an article comprising a non-woven fabric according to the present invention as defined above, especially a formed sterilization barrier system, especially a sterilization pouch, a surgical drape, a protective garment, or a pouch for transporting an active ingredient.

[0020] Preferably, the article is a sterilization pouch.

[0021] According to another aspect of the present invention, the present invention also relates to a process for closing an article according to the present invention, in which the non-woven fabric is heat-sealed to a thermoplastic support.

[0022] The sealing is preferably carried out at a temperature of 135°C to 165°C, more preferably 150°C to 160°C.

[0023] The present invention can be more clearly understood by reading the following detailed description, non-limiting examples of its implementation, and examining the accompanying drawings.

Brief Description of the Drawings

[0024] [Figure 1] Figure 1 is a front view of the non-woven fabric side of an example of a sterilization pouch according to the present invention. [Figure 2] Figure 2 is a partial schematic cross-sectional view of the pouch. [Figure 3]Figure 3 is a table showing the mechanical properties of the non-woven fabrics obtained for different titanium dioxide contents. [Figure 4] Figure 4 is a table showing the measured sealing force and other findings for different sealing temperatures and different titanium dioxide contents.

Mode for Carrying Out the Invention

[0025] Figures 1 and 2 show one example of the sterilization pouch 1 according to the present invention, which includes a porous non-woven fabric 2 heat-sealed to a support film 3 made of a non-porous thermoplastic material based on polypropylene PP and PET.

[0026] Figure 1 shows a pouch sealed along a weld line 4 extending only on three sides, and thus, an opening 5 for inserting the instrument to be sterilized is provided. After the instrument is inserted, the non-woven fabric is heat-sealed to the support along a closure line 6, and then, the pouch is sterilized.

[0027] On the side opposite to the opening 5, the pouch 1 has an area 7 where the non-woven fabric covers the support without being sealed thereto, and thus, when the user opens the pouch, those parts can be grasped by hand and peeled off.

[0028] This sterilization barrier system can be sterilized using the following various methods: Moist heat: The sterilizing agent is steam (temperature: 121°C to 134°C, 18 to 30 minutes, under pressure), Ethylene oxide: Temperature 30 to 60°C, relative humidity over 30%, ethylene oxide concentration 200 to 800 mg / L for 16 to 18 hours. Here, ethylene oxide is a toxic substance, and thus, a degassing time needs to be provided after sterilization. Ionizing radiation (gamma rays, beta rays, or electron beams), Formaldehyde: Formaldehyde can be used in gaseous form. Gas plasma: Hydrogen peroxide (H2O2) is diffused in gaseous form into a chamber and then plasma-generated by an electromagnetic field. This generates ions, free electrons, and numerous free radicals with very strong bactericidal activity. This method allows for sterilization at low temperatures and does not require degassing.

[0029] Metallocene PP

[0030] Within the meaning of the present invention, the term "polypropylene" includes propylene homopolymers, propylene copolymers obtained by copolymerization of propylene with at least one α-olefin comonomer, and derivatives of propylene homopolymers or propylene copolymers, in particular derivatives of propylene homopolymers or propylene copolymers to which reactive functional groups have been grafted by reaction with maleic anhydride or acrylic acid (e.g., maleic acid-modified polypropylene). The copolymer may be a block copolymer or a random copolymer.

[0031] Polypropylene (regardless of its form) may be isotactic or syndiotactic.

[0032] In the context of this invention, the term "metallocene PP" refers to polypropylene obtained by a metallocene catalyst.

[0033] Polypropylene is produced using metallocene catalysts, rather than via the Ziegler-Natta process (the use of this type of catalyst for the production of polyolefins is well known to those skilled in the art, as described in U.S. Patent Nos. US 5571619, US 5322728, and US 5472775).

[0034] The nonwoven fabric is preferably manufactured from metallocene polypropylene (PP) in accordance with the teachings of British Patent No. GB2449418.

[0035] Metallocene PP generally has a fairly narrow molecular weight distribution (MWD), preferably less than 3, and particularly less than 2.5, enabling the production of fibers with an average diameter of less than 25 microns, particularly in the range of 10 to 20 microns.

[0036] The resulting nonwoven fabric is formed by a technique known as spunbond, which is known in itself. The formation of metallocene polypropylene fibers can be carried out as described in British Patent No. GB2449418 (this process is also described in U.S. Patent Nos. US3821062, US3563838, U.S. Patent Application Publication No. US2021 / 0301425, and U.S. Patent Application Publication No. US2019 / 145032). Titanium dioxide (TiO2) is incorporated during the production of polypropylene fibers by mixing with metallocene PP, particularly by dry blending. Titanium dioxide is preferably in the form of a masterbatch.

[0037] The PP used may, in particular, be Metocene HM562S having a melt flow index of 30 g / 10 min measured at 230°C under a weight of 2.16 kg (according to standard ASTM D1238).

[0038] According to the present invention, the porous nonwoven fabric may undergo a calendering step. Several parameters of this calendering step, such as temperature (typically about 130°C to 160°C), speed (typically more than 10 m / min), and pressure (typically more than 30 bar), may be varied.

[0039] The mass content of titanium dioxide in the nonwoven fabric is 0.1% to 1.4%, preferably about 0.5%.

[0040] Such content provides advantageous properties for manufacturing the pouch, as detailed with reference to the tables in Figures 3 and 4.

[0041] The fibers of the nonwoven fabric may have an average diameter in the range of 10 to 25 microns.

[0042] The titanium dioxide may have an average size in the range of 100 nm to 1 μm.

[0043] Official Exam

[0044] Various samples were prepared using porous nonwoven fabrics made of metallocene PP (Metocene HM562S) and TiO2 (average diameter of 300 nanometers), and a 12 μm laminated polymer film PET 12 μm / PP.

[0045] The nonwoven fabric has a density of 93 g / m². 2 It has a weight-average molecular weight (measured according to standard ISO 536).

[0046] A 5cm x 15cm strip was prepared for each sample. The PP side of the PET / PP film was heat-sealed to the porous nonwoven fabric.

[0047] Pairs of film (PET / PP) and porous nonwoven fabric were heat-sealed using a laboratory heat sealer, with the hot jaw pressed against the PET side. The following different sealing temperatures of 150°C, 155°C, and 160°C were tested at a constant pressure of 5 bar and a time of 0.3 seconds.

[0048] The sealing force was measured for 10 samples using a tensile testing machine in accordance with the standard ASTM F88 / F88M-2021 (Technical B).

[0049] Tensile tests were performed on 10 samples using a tensile testing machine in accordance with the standard ASTM D882-18.

[0050] Tear tests were performed on 10 samples using a tensile testing machine in accordance with the standard ASTM D1938-19.

[0051] These film (PET / PP) and porous nonwoven fabric pairs were sealed using a laboratory heat sealer, allowing for examination of the imprint quality upon opening.

[0052] Pouches, such as the one shown in Figure 1, were also manufactured using an FFS ("Form-Fill-Seal") machine. Three sealing temperatures, 150°C, 155°C, and 160°C, were used, and the speed was set to 15 pouches per minute. These pouches were used to evaluate the feel upon opening and the quality of the imprint.

[0053] The table in Figure 3 shows that tear strength significantly decreases in tests with content of 1.5% or more, and reaches a relative maximum at 0.5%.

[0054] The table in Figure 4 compares the sealing force for different sealing temperatures and different titanium dioxide mass contents.

[0055] These results are also evaluated in the form of comments in the last two columns of the table in Figure 4.

[0056] At concentrations below 0.1%, a lack of whiteness in the imprint, as well as a transparent appearance, can be observed at sealing temperatures of 150°C, 155°C, and 160°C.

[0057] With titanium dioxide content of 0.19%, 0.27%, 0.5%, and 0.8%, there was no "transparency" after peeling, and a good feeling upon opening while maintaining sterility.

[0058] At a concentration of 1.5%, the sensation upon opening is poor.

[0059] The best results were obtained with a titanium dioxide content of 0.27% to 0.5% by weight at 155°C to 160°C. In fact, a very good opening feel was observed, a homogeneous and white imprint was obtained while maintaining sterility, and very good mechanical properties (especially tear strength) were also obtained.

[0060] Needless to say, the present invention is not limited to the embodiments described above.

[0061] For example, nonwoven fabrics according to the present invention can be used in the manufacture of pre-formed germicidal barrier systems, such as pouches, breathable tape bags, or hospital packaging sheaths, among other items.

[0062] Metallocene PP can be mixed with at least one other thermoplastic, among other possible types, such as grafted or ungrafted polyethylene (low density or linear low density), or polybutene. The proportion of one or more other polymers in the mixture is selected to maintain the desired properties.

Claims

1. A sterilization pouch comprising a porous nonwoven fabric containing fibers at least partially formed from metallocene polypropylene, and 0.1% to 1.4% by mass of titanium dioxide relative to the total weight of the nonwoven fabric, wherein the nonwoven fabric does not contain inorganic fillers other than titanium dioxide in an amount of 0.1% by mass or more.

2. The pouch according to claim 1, comprising 0.1% to 1% by mass of titanium dioxide.

3. The pouch according to claim 1 or 2, comprising 0.4% to 1% by mass of titanium dioxide.

4. A pouch according to any one of claims 1 to 3, comprising 0.4% by mass to 0.6% by mass of titanium dioxide.

5. A spunbond type pouch according to any one of claims 1 to 4.

6. The pouch according to any one of claims 1 to 5, wherein the titanium dioxide has a number average size of 100 to 1000 nm.

7. The pouch according to any one of claims 1 to 6, wherein the fiber is formed entirely from metallocene polypropylene with respect to one or more polymer materials constituting it.

8. The pouch according to any one of claims 1 to 7, wherein the nonwoven fabric has a tensile strength of at least 2.5 kN / m in the mechanical direction MD (measured according to EN ISO 1924-2) and a tensile strength of at least 1.5 kN / m in the intersecting direction CD (measured according to EN ISO 1924-2), in accordance with the standard EN ISO 1924-2 (Section 2.2.1).

9. A method for closing a pouch according to any one of claims 1 to 8, wherein the nonwoven fabric is heat-sealed to a thermoplastic support.

10. The method according to claim 9, wherein the sealing is performed at a temperature of 135°C to 165°C, more preferably 150°C to 160°C.

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