Surfactant-free hydrophilic films and article there from

Abstract

A surfactant-free hydrophilic film comprising a polymeric composition with quaternary ammonium chloride monomers, such as [2-(acryloyloxy)ethyl] trimethylammonium chloride, is disclosed. The film is prepared via a pre-tenter coating process, anchored, and cured to achieve advanced water contact angles below 40 degrees. It is chemically stable across a pH range of 4 to 10 and mechanically resistant to abrasion. Ideal for applications like diagnostics and microfluidics, the invention includes methods for film preparation and use in fluid transport and biological assays.

Description

[0001] PA101091W002

[0002] SURFACTANT-FREE HYDROPHILIC FILMS AND ARTICLE THERE FROM

[0003] Technical Field

[0004] The present disclosure relates to surfactant-free hydrophilic films, particularly those designed for fluid transport and diagnostic applications. The invention further includes methods of manufacturing hydrophilic fdms as well as their use in medical diagnostics, microfluidic devices, and other fluid transport systems.

[0005] Background

[0006] In the field of material science and engineering, the development of hydrophilic films has gained significant attention due to their wide range of applications, including in medical devices, filtration systems, and diagnostic tools. Hydrophilic films are designed to attract and interact with water, making them ideal for applications where moisture management is crucial. Traditional hydrophilic films often rely on surfactants to achieve their water-attracting properties. However, the use of surfactants can introduce challenges such as reduced film stability, potential toxicity, and environmental concerns.

[0007] The demand for surfactant-free hydrophilic films has been growing as industries seek more sustainable and stable alternatives. These films need to maintain their hydrophilic properties without compromising on durability or safety. Achieving strong adhesion to various substrates while ensuring chemical and mechanical stability is a significant challenge in the development of these films. Additionally, the ability to control the film's thickness and hydrophilic properties through precise formulation and processing techniques is essential for meeting the diverse needs of different applications. As such, there is a continuous need for innovative solutions that address these challenges and provide reliable, high-performance hydrophilic films.

[0008] Summary

[0009] Accordingly, embodiments of the present invention address one or more of the issues identified above by providing a surfactant-free hydrophilic film. The film comprises a polymeric composition containing a quaternary ammonium chloride monomer, such as [2-(acryloyloxy) ethyl] trimethylammonium chloride, applied using a pre-tenter coating process. This innovative approach provides a uniform and durable hydrophilic layer that adheres strongly to a variety of substrates without requiring surfactants or crosslinking agents that may leach or interfere with sensitive applications.

[0010] Thus, disclosed herein are surfactant-free hydrophilic films and methods for manufacturing the same.In one embodiment, the hydrophilic film includes a polymeric composition dispersed in an aqueous medium, which is applied to a substrate through a pre-tenter coating process. This process involves stretching the coated substrate in at least one direction to enhance adhesion and film uniformity, followed by curing to stabilize the film. The pre-tenter coating process eliminates secondary manufacturing steps, reduces cost and ensures consistent performance.

[0011] In another embodiment, the hydrophilic film exhibits a low water contact angle (less than 40 degrees), making it ideal for fluid transport applications. The film also demonstrates chemical stability across a pH range of 4 to 10 and mechanical resistance to abrasion, ensuring durability in demanding environments.

[0012] The invention further includes hydrophilic films that are suitable for applications such as diagnostic test strips and microfluidic devices. By eliminating surfactants and leveraging advanced polymeric formulations, the film prevents interference with biological assays, ensuring reliable and accurate results.

[0013] Also disclosed herein is a method for manufacturing the hydrophilic film, involving steps such as preparing an aqueous dispersion of the polymeric composition, coating the substrate, , and curing the coated film. In the case of substrates that are oriented films, more preferred is to apply the polymeric composition prior to the cross-web stretching operation or pre-tenter. Pre-tenter coating may be conducted after the down-web stretch and before the cross-web stretch, or in a simultaneous biaxially stretched film, conducted prior to stretching the film in either the down-web and cross-web directions. The method provides a scalable and efficient approach to producing high-performance hydrophilic films for diverse applications.

[0014] The details of one or more examples of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description, claims, and accompanying drawings.

[0015] Detailed Description

[0016] The present invention relates to methods for manufacturing and utilizing surfactant-free hydrophilic films, particularly those with enhanced adhesion, durability, and hydrophilic properties. This invention further encompasses polymeric composition, pre-tenter coating processes, and hydrophilic films designed for applications in medical diagnostics, microfluidic devices, and fluid transport systems.

[0017] In the following description, reference is made to the accompanying figures that form a part thereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0018] In the following disclosure, the following definitions are adopted.As used herein, all numbers should be considered modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably.

[0019] The words "preferred" and "preferably" refer to embodiments described herein that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0020] Reference throughout this specification to "one embodiment," "certain embodiments," "one or more embodiments" or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as "in one or more embodiments," "in certain embodiments," "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0021] The term "hydrophilic film" herein refers to a polymeric film with a surface capable of attracting and interacting with water. It may exhibit advanced water contact angles of less than 40 degrees, facilitating efficient fluid transport in applications such as medical diagnostics and microfluidics.

[0022] The term "surfactant-free" implies that the hydrophilic film composition excludes any added surfactants or leachable materials that could interfere with sensitive applications, such as biological assays or fluid diagnostics.

[0023] The term “monomer” refers to a molecule capable of undergoing polymerization to form part of the essential structure of a polymer.

[0024] The term "pre-tenter coating process" refers to the application of a polymeric composition onto a substrate before the substrate undergoes stretching in one or more directions. This process enhances the adhesion, durability, and uniformity of the resulting hydrophilic film.

[0025] The term "fluid transport" refers to the movement of liquids, such as blood or reagents, across or through the surface of the hydrophilic film, facilitated by its water-attracting properties for applications in diagnostics and microfluidics.

[0026] The present invention provides a surfactant-free hydrophilic film comprising a polymeric composition, wherein the polymeric composition is securely anchored to a substrate through a pre-tenter coating process.

[0027] In one embodiment, the polymeric composition comprises a quaternary ammonium chloride monomer.

[0028] The polymer is synthesized by mixing the desired quaternary ammonium chloride monomer with an initiator (e.g., Vazo-67) and isopropyl alcohol (IP A) in a reactor under a nitrogen purge. The reaction isconducted at 65°C for a specified duration, followed by a charge of water at 1.25 times that of the IPA and removal of solvent under vacuum to yield a stable aqueous polymer solution that is typically about 2% IPA . The solution is then diluted to a specified concentration for use in formulations.

[0029] In a preferred embodiment, the quaternary ammonium chloride monomer is [2-(acryloyloxy)ethyl] trimethylammonium chloride.

[0030] Particles of the polymer have an average particle diameter of at least 20, 25, 30, 40, 50, or even 60 nm, and no more than 80, 90, 100, or even 120 nm, as determined by techniques known in the art, including light scattering.

[0031] The polymeric composition can be dispersed in an aqueous solvent, enabling a flexible application process, wherein "aqueous" means at least 50, 60, 70, 80, 90, or even 95% by weight of the liquid is water. In one embodiment, the aqueous liquid vehicle comprises 100% water by weight.

[0032] In a preferred embodiment, the polymeric composition may be diluted to 10% solids with DI water prior to coating.

[0033] In another embodiment, the concentration of the aqueous dispersion of [2-(acryloyloxy) ethyl] trimethylammonium chloride is from 0.05% to 25% by weight.

[0034] In addition, the surfactant-free hydrophilic film composition may include N-vinyl pyrrolidone as a useful monomer to enhance hydrophilicity, chemical stability, and mechanical performance. This combination contributes to durability and effectiveness across various applications.

[0035] The composition may also include coalescent solvents, such as glycol ethers or alcohols like octanol, isopropanol, ethanol, butanol, methanol, or hexanol, to optimize properties such as rheological behaviour, film-forming capabilities, and ink receptivity. These coalescent solvent scan be used in amounts up to 10% by weight, provided the film composition remains non-flammable.

[0036] The polymeric composition disclosed herein can be applied to a variety of substrates to form a wet-coated substrate. The substrate material can be a single-layer or multi-layer structure.

[0037] In one embodiment, the substrates may include sheets, fibers, or shaped objects. Preferred substrates are materials commonly used in adhesive products, such as paper, metal sheets and foils, nonwoven fabrics, and films of thermoplastic resins. Suitable thermoplastic resins include polyesters (e.g., polyethylene terephthalate), polyamides, polyolefins (e.g., polypropylene and polyethylene), polycarbonates, polyvinyl chloride, and polyethylene vinyl acetate. Other suitable materials include polymeric substrates such as polymethane, vinyl copolymers, olefin copolymers, acrylic polymers or copolymers, and polymer blends like polypropylene / polyethylene or polyurethane / polyester. The substrate selection depends on compatibility with the coating composition and intended application.

[0038] In an embodiment, the substrate material is selected from polyester, polyether, polyamide, polyolefin, polyacrylic acid, and glass. In a preferred embodiment, the substrate is a polyester such as polyethylene terephthalate.The polymeric composition can be applied to substrates using conventional coating techniques, such as wire-wound rod, direct gravure, offset gravure, reverse roll, air-knife, or trailing blade coating. Optional surface treatments, like corona treatment, may be performed prior to coating to enhance adhesion. While primers are generally unnecessary, they may be employed where additional bonding strength is required.

[0039] For oriented films, the polymeric composition is applied before stretching the film in the downweb and / or cross-web directions during the orientation process, which aligns polymer chains to improve mechanical strength and uniformity. In one embodiment, the coating is securely anchored to a substrate through a pre-tenter coating process, where the polymer becomes embedded into the substrate structure before stretching. This method reduces delamination risks and enhances mechanical durability under challenging conditions. After application, the wet-coated substrate is dried to produce a uniform surfactant-free hydrophilic film with consistent performance characteristics.

[0040] The thickness of the dried film may range from at least 10, 20, 30, 40,50, 60, 70, 80, 90, or even 100 nm, up to a maximum of 150, 200, 250, 300, 350, 400, 500 nm or even 1000 nm. The thickness of the dried film may be selected based on the nature of the substrate and may depend, in part, on any requirements for coating uniformity. For substrates that contain microfine features, thinner films ranging from about 10 nm to about 1000 nm may be suitable to reduce the likelihood and extent of filling in such microfine features. In certain embodiments, films ranging from about 50 nm to about 500 nm may be used in connection with substrates having microfine structures.

[0041] Additionally, curing is performed at temperatures ranging from 80°C to 220°C for 10 to 180 seconds. This step solidifies the polymeric coating, ensuring strong adhesion, uniform film formation, and enhanced hydrophilicity, durability, and chemical stability across a wide pH range.

[0042] The film is chemically stable across a pH range of 4 to 10, ensuring reliable and consistent performance without degradation. It exhibits a low advanced water contact angle of less than 40 degrees, highlighting its hydrophilic nature. The advanced dimensional contact angle ranges from 30 to 40 degrees, ensuring controlled surface properties for demanding applications such as medical diagnostics and microfluidics.

[0043] In other embodiment, a method for preparing the surfactant-free hydrophilic film is provided, which involves preparing an aqueous dispersion of a polymeric composition containing [2-(acryloyloxy)ethyl] trimethylammonium chloride. The aqueous dispersion is coated onto a suitable substrate, such as polyester or polyolefin films, using conventional coating techniques like wire-wound rod or gravure coating. The coated substrate undergoes a tenter process, where it is stretched in at least one direction to enhance the uniformity, mechanical strength, and adhesion of the hydrophilic layer. The coated and stretched substrate is then cured at 80°C to 220°C for 10 to 180 seconds to solidify the polymeric composition, ensuring strong adhesion, improved hydrophilicity, and chemical stability across a pH range of 4 to 10.In general, the surfactant-free hydrophilic film of the present disclosure may be used to transport fluids, including, e.g., biological fluids. Exemplary biological fluids include blood, urine, sweat, and saliva. Further, these films are particularly suited for biological assays or fluid diagnostics applications in diagnostic test strips and microfluidic devices, where efficient and controlled fluid movement is essential for accurate and reliable performance.

[0044] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0045] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

[0046] EXAMPLES:

[0047] Example 1: General Synthesis of Polymer

[0048] The synthesis of the polymer involves preparing a reaction mixture in a clean reactor equipped with a mechanical stirrer, thermocouple, nitrogen inlet / outlet, and condenser. Monomers are charged in desired compositions (100 parts total) along with Vazo-67 (0.5 parts) and isopropyl alcohol (200 parts). The solution is stirred at 150 rpm, purged with nitrogen, and polymerization is conducted at 65°C for 6 hours, followed by an additional charge of Vazo-67 (0.3 parts) and stirring for 12 more horns at the same temperature. After cooling to room temperature, DI water (200 parts) is mixed into the reaction, and isopropyl alcohol is distilled off under vacuum at 50°C, yielding a clear, viscous aqueous polymer solution.

[0049] The resultant polymer, typically with 33%-38% solids, is stable and ranges from colorless to slight amber in appearance. Unless otherwise noted, the polymers were stable (no ppt or flocculation noted) for at least a period of many months.

[0050] The exemplary compositions of the hydrophilic polymer include polymer Ex-1 and Ex-2, which are specifically designed to optimize hydrophilic, mechanical, and chemical properties for diverse applications. Polymer Ex-1 comprises [2-(acryloyloxy)ethyl] trimethylammonium chloride (QA) at 40% by weight, methyl methacrylate (MM A) at 22%, ethyl acrylate (EA) at 18%, acrylic acid (AA) at 10%, and DMAEMA at 10%. Similarly, polymer Ex-2 contains [2-(acryloyloxy)ethyl] trimethylammonium chloride(QA) at 30%, MMA at 33%, EA at 27%, and AA at 10%.

[0051] These compositions are tailored to balance adhesion, durability, and hydrophilicity, ensuring high performance in fluid transport systems and diagnostic applications. Variations in monomer ratios allow for fine-tuning the polymer’s properties to meet specific requirements while maintaining a surfactant-free formulation.

[0052] Example 2: Preparation of Test Coatings

[0053] For coating formulations, the polymers are diluted to 10% solids with DI water before application. Lab test coatings are prepared by drawing 10% solids formulations onto 24 mil cast polyester films using a #6 Mayer rod (15-micron wet coating thickness), drying at 80°C for 2 minutes, and then stretching using a Karo IV lab stretcher (Briikner Group Gmbh). The stretching process includes pre-heating at 100°C for 20 seconds, stretching simultaneously in down-web and cross-web directions to 3.0x3.0 at 40% continuous rate (respectively), followed by annealing at 220°C for 20 seconds. The utility of the hydrophilic film was demonstrated at other stretch ratios like 2.5x4.0 or 3.5x3.5.

[0054] Example 3: Evaluation of hydrophilic properties of various film types

[0055] This study evaluated the hydrophilic properties of various film types, including uncoated PET, 3M Microfluidic Diagnostic Film 9962, and exemplary compositions of Ex-1 and Ex- 2 (10% solids) coated on cast polyester film (20 mil) with a coating rod #6 and then tentered to 3.0 x 3.0 as described. Key parameters such as advanced water contact angle, dimensional contact angle, and surface energy were measured to assess the films' wetting and fluid transport capabilities. Results are tabulated in Table 1 below. Exemplary composition films of Ex-1 and Ex- 2, prepared using a pre -tenter roll coating process, demonstrated superior hydrophilic performance, making them suitable for applications requiring efficient fluid interaction and adhesion, such as medical diagnostics and microfluidics.

[0056] Table 1: Comparison of Properties of The Hydrophilic Films

[0057]

[0058] The results highlight the utility of the coated films of this invention with respect to their dropspreading and hydrophilic properties.

[0059] Example 4: Spreading Drop Test

[0060] The spreading drop test, an internal method developed at 3M, was conducted to evaluate the hydrophilic properties of various film samples, including 3M 9962 Diagnostic Film, Ex-1, Ex-2. The test uses a 3 -microliter drop of red dye, and the size of the dried droplet is assigned a value by comparison to a printed template of lower-case Courier New True Type leter "o's," ranging from font size 12 to font size 70. This method provides a straightforward evaluation of wetability and hydrophilicity by quantifying the spread of the droplet on the film surface. Results are tabulated in Table 2 below.

[0061] Table 2: Comparison of Spreading Drop Test Results

[0062]

[0063] The test highlights the suitability of these films for applications requiring efficient fluid transport, such as diagnostics or microfluidics for advanced fluid transport applications.

[0064] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0065] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

CLAIMS1. A surfactant-free hydrophilic film comprising a polymeric composition of a quaternary ammonium chloride monomer, wherein the polymeric composition is anchored to a substrate.

2. The surfactant-free hydrophilic film of claim 1, wherein the polymeric composition is applied to the substrate through a pre-tenter coating process.

3. The surfactant-free hydrophilic film of claim 1, wherein the quaternary ammonium chloride monomer is [2-(acryloyloxy)ethyl] trimethylammonium chloride.

4. The surfactant-free hydrophilic film of claim 1, wherein the polymeric composition is dispersed in an aqueous solvent.

5. The surfactant-free hydrophilic film of claim 4, wherein a concentration of the aqueous dispersion of [2-(acryloyloxy)ethyl]trimethylammonium chloride is from 0.05% to 25% by weight.

6. The surfactant-free hydrophilic film of claim 1, wherein the composition further comprises N-vinyl pyrrolidone.

7. The surfactant-free hydrophilic film of claim 1, wherein the film has a thickness ranging from 0.05 pm to 10 pm.

8. The surfactant-free hydrophilic film of claim 1, wherein the substrate is selected from the group consisting of polyester, polyether, polyamide, polyolefin, polyacrylic acid and glass.

9. The surfactant-free hydrophilic film of claim 8, wherein the polyester is polyethylene terephthalate.

10. The surfactant-free hydrophilic film of claim 1, wherein the substrate is a single-layer or a multilayer structure.

11. The surfactant-free hydrophilic film of claim 1, wherein the substrate is an oriented fdm that has been stretched in a down-web direction and / or a cross-web direction.

12. The surfactant-free hydrophilic fdm of claim 1, wherein the polymeric composition is cured at a temperature ranging from 80°C to 220°C for a duration of 10 sec to 180 sec.

13. The surfactant-free hydrophilic film of claim 1, wherein an advanced water contact angle of the film is less than 40 degrees.

14. The surfactant-free hydrophilic film of claim 1, wherein the film is chemically stable in a pH range of 4 to 10 and is mechanically resistant to abrasion.

15. The surfactant-free hydrophilic film of claim 1, wherein the film is used as a test strip for testing a fluid.

16. A method for preparing a surfactant-free hydrophilic film, the method comprising: preparing an aqueous dispersion of a polymeric composition including [2-(acryloyloxy)ethyl] trimethylammonium chloride; coating the aqueous dispersion onto a substrate to form a coated substrate; applying the coated substrate to a pre-tenter process, wherein the coated substrate is stretched in at least one direction; and curing the coated and stretched substrate.

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