WO2023047205A1

WO2023047205A1 - Methods of making smooth thermoformed articles

Info

Publication number: WO2023047205A1
Application number: PCT/IB2022/057667
Authority: WO
Inventors: Ta-Hua Yu; Timothy J. Hebrink; Ryan BIRRINGER
Original assignee: 3M Innovative Properties Company
Priority date: 2021-09-23
Filing date: 2022-08-16
Publication date: 2023-03-30

Abstract

The present disclosure provides a method of making an article (200A, 210B, 430A, 440A, 440B, 450C). The method includes a) obtaining a tool (560) shaped to include at least one of a protrusion or a concavity, in which a surface of the protrusion and/or a concavity has a microstructured texture (214B); b) disposing a smooth film on at least a portion of the tool (560) including the protrusion and/or the concavity; and c) thermoforming a thermoplastic polymer onto the tool (560) to form an article (200A, 210B, 430A, 440A, 440B, 450C) shaped to include a curve (208A, 218B) having a smooth surface. The curve (208A, 218B) is an inverse of the protrusion or the concavity of the tool (560). The method minimizes imparting undesired microstructured texture (214B) from a tool (560) to a final article (200A, 210B, 430A, 440A, 440B, 450C) during the thermoforming process.

Description

METHODS OF MAKING SMOOTH THERMOFORMED ARTICLES

Field

The present disclosure generally relates to thermoforming methods of making articles.

Summary

In a first aspect, a method of making an article is provided. The method includes a) obtaining a tool shaped to include at least one of a protrusion or a concavity, wherein a surface of the protrusion and/or the concavity has a microstructured texture having a height of 10 to 150 microns; b) disposing a smooth film on at least a portion of the tool including the protrusion and/or the concavity; and c) thermoforming a thermoplastic polymer onto the tool to form an article shaped to include a curve having a smooth surface. The curve is an inverse of the protrusion and/or the concavity of the tool.

Certain articles with microstructured surfaces can be challenging to clean for removal of non-bacteria (e.g., staining) contaminants. This is surmised to be due at least in part to the bristles of a brush or fibers of a (e.g., nonwoven) wipe being larger than the space between microstructures. Methods according to at least certain embodiments of the present disclosure can provide thermoformed articles having fewer and/or smaller microstructures on their surfaces than the tool employed during the thermoforming process, e.g., achieving a smoother exterior surface.

The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples may be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.

Brief Description of the Drawings

FIG. 1 is a flow chart of an exemplary method according to the present disclosure.

FIG. 2A is a photograph of an article prepared by an exemplary method of the present disclosure;

FIG. 2B a photograph of an article prepared by a comparative method;

FIG. 3 is an optical micrograph image of an interior surface of the article of FIG. 2A and of an interior surface of the article of FIG. 2B;

FIG. 4A is a photograph of an article polished by a comparative method; FIG. 4B is a photograph of an article prepared and polished by an exemplary method of the present disclosure;

FIG. 4C is a photograph of an article prepared and polished by an exemplary method of the present disclosure; and

FIG. 5 is a generalized schematic perspective view of a tool comprising a plurality of protrusions and concavities, having a shape of a dental arch.

While the above-identified figures set forth various embodiments of the disclosure, other embodiments are also contemplated, as noted in the description. In all cases, this disclosure presents the invention by way of representation and not limitation. The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

Detailed Description

Glossary:

As used herein, the term “arch” refers to a semicircular shape.

As used herein, “curvature radius” is the reciprocal of the curvature of a curve.

As used herein, “concavity” refers to a surface or an object that has a concave shape.

As used herein, “smooth” with respect to a surface refers to the surface being essentially free of microstructures that have a height of 10 microns or greater, for instance microstructures having a height of up to 1 millimeter.

As used herein, “surface roughness” refers to the smoothness of a material surface and is quantified as “Ra”, which refers to the average surface roughness and is defined as the integral of the absolute value of the distance from the mean elevation. The mean elevation is the arithmetic average of the height profile of the surface. The function z(x) refers to the difference between the height and the mean elevation at a position x measured over an evaluation length /:

The term “Rq” represents the root mean square value of the ordinate values z(x) within the sampling length I

The term “Rsk” refers to the quotient of the mean cube value of the ordinate values z(x) and the cube of R within the sampling length I

The elevation can be measured using an optical profilometer (e.g., a Wyko NT3300 optical profilometer from Veeco Instruments Inc., Plainview, New Jersey). Topography maps can be obtained using confocal laser scanning microscopy (CLSM), e.g., a Keyence VK-X200. CLSM is an optical microscopy technique that scans the surface using a focused laser beam to map the topography of a surface. CLSM works by passing a laser bean through a light source aperture which is then focused by an objective lens into a small area on the surface and image is built up pixel-by-pixel by collecting the emitted photons from the sample. It uses a pinhole to block out- of-focus light in image formation. Dimensional analysis can be used to measure various parameters using SPIP 6.7.7 image metrology software according to the manual (see htps://www.iniagemet.com/media-library/si.Epport-documents).

As used herein, “integral” refers to being made at the same time or being incapable of being separated without damaging one or more of the (integral) parts.

As used herein, “draw down” as used herein means extending a molten resin as it is being thermoformed. The draw down is characterized by a draw down ratio (DDR), which is the ratio of the surface area of a part to the footprint of the part. In general, the draw-down ratio for thermoplastic materials used herein is suitably from 1. 1 to 3.

As used herein, the term “essentially free” in the context of a composition being essentially free of a component, refers to a composition containing less than 1% by weight (wt.%), 0.5 wt.% or less, 0.25 wt.% or less, 0.1 wt.% or less, 0.05 wt.% or less, 0.001 wt.% or less, or 0.0001 wt.% or less of the component, based on the total weight of the composition. The term “essentially free” in the context of a feature of a structure (e.g., a surface of a layer), refers to a structure having less than 5% by area of the component, 4% or less, 3% or less, 2% or less, or 1% or less by area of the component, based on the total area of the structure.

As used herein, “masking film” refers to a protective substrate.

As used herein, “thermoplastic” refers to a polymer that flows when heated sufficiently above its glass transition point and become solid when cooled.

As used herein, “thermoset” refers to a polymer that permanently sets upon curing and does not flow upon subsequent heating. Thermoset polymers are typically crosslinked polymers.

The words “preferred” and “preferably” refer to embodiments of the disclosure 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 disclosure. In this application, terms such as “a”, “an”, and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a”, “an”, and “the” are used interchangeably with the term “at least one.” The phrases “at least one of’ and “comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

As used herein, the term “or” is generally employed in its usual sense including “and/or” unless the content clearly dictates otherwise.

The term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements.

Also herein, all numbers are assumed to be modified by the term “about” and preferably by the term “exactly.” As used herein in connection with a measured quantity, the term “about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used. Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within +/- 20 % for quantifiable properties). The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within +/- 10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as same, equal, uniform, constant, strictly, and the like, are understood to be within the usual tolerances or measuring error applicable to the particular circumstance rather than requiring absolute precision or a perfect match.

Although articles with specific microstructure features are useful for reducing the initial formation of a biofilm, particularly for medical articles; in the case of other articles, such microstructured surfaces can be difficult to clean. It has been found that smooth surfaces exhibit better non-microorganism contaminant removal when cleaned than some types of microstructured surfaces. The article is typically not a sterile implantable medical article. Rather, the smooth surface typically comes in contact with people and/or animals as well as other contaminants (e.g., dirt). Some representative articles include for example surfaces or component of a medical article, a dental article, an orthodontic article (e.g., an orthodontic aligner), a vehicular article, an electronic article, a personal care article, a cleaning article, an athletic article, a food preparation article, a child care article, or an architectural article. In a first aspect, a method of making an article is provided. The method comprises: a) obtaining a tool shaped to comprise at least one of a protrusion or a concavity, a surface of the protrusion and/or the concavity having a microstructured texture having a height of 10 to 150 microns; b) disposing a smooth film on at least a portion of the tool including the protrusion and/or the concavity; and c) thermoforming a thermoplastic polymer onto the tool to form an article shaped to comprise a curve being an inverse of the protrusion or the concavity of the tool, wherein the curve has a smooth surface.

It has been discovered that it is possible to form an article that includes a smooth curved surface, thermoforming on a tool that has a surface with a microstructured texture. For instance, the surface of a custom tool formed by additive manufacturing will exhibit the texture as an artefact (i.e., not an engineered design of the tool surface) due to the limitations of the resolution of the particular additive manufacturing technique. For instance, fused deposition modeling (FDM) and selective laser sintering (SLS) printers typically print Z-axis layers at a thickness of 100 to 300 microns, while stereolithography (SLA) currently provides a minimum Z-axis layer thickness of 25 microns. Indeed, smoothing processes have been developed to remove texture/roughness from articles made by additive manufacturing methods, such as sanding, contact with a solvent, adding a coating, and/or heat treatment. An advantage of forming an article according to the present disclosure includes being able to employ a (e.g., standard) thermoplastic polymer with any custom- made tool (such as a dental arch prepared for a particular individual) to create an integral custom article having a smooth surface despite the microstructured texture present on the surface of the tool. The smooth curved surface of a thermoformed article is accomplished by including a smooth fdm located between the tool and the thermoplastic polymer. Tools can readily be formed via additive manufacturing (e.g., using a digital scan of the desired shape), or other processes. In certain methods, step a) of the method comprises making the tool using an additive manufacturing process, e.g., stereolithography (SLA). Moreover, one or more dimensions of the tool may be compensated to take into account the presence of the smooth fdm disposed between the tool and the thermoplastic polymer to result in a thermoformed article having the desired size, e.g., the tool may be made smaller in at least one dimension than if a smooth fdm was not going to be employed during the thermoforming process.

In contrast to a curved surface, a flat surface has a curvature radius of infinity. In some embodiments, the curve comprises a minimum curvature radius of 0.5 mm, such as 0.5 mm or greater, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, 8.5 mm, 9.0 mm, 9.5 mm, or 10.0 mm or greater; and 20.0 mm or less, 19.5 mm, 19.0 mm, 18.5 mm, 18.0 mm, 17.5 mm, 17.0 mm, 16.5 mm, 16.0 mm, 15.5 mm, 15.0 mm, 14.5 mm, 14.0 mm,

13.5 mm, 13.0 mm, 12.5 mm, 12.0 mm, 11.5 mm, or 11.0 mm or less.

Referring to FIG. 1, the method of making a microstructured article comprises a Step 110 to a) obtain a tool shaped to comprise at least one of a protrusion or a concavity, a surface of the protrusion and/or the concavity having a microstructured texture having a height of 10 to 150 microns; and a Step 120 to b) dispose a smooth fdm on at least a portion of the tool including the protrusion and/or the concavity. The method further comprises a Step 130 to c) thermoform a thermoplastic polymer onto the tool to form an article shaped to comprise a curve being an inverse of the protrusion and/or the concavity of the tool, wherein the curve has a smooth surface. Accordingly, a smooth surface can be imparted to an article having at least one curved surface by thermoforming a thermoplastic polymer onto a tool having a protrusion, in which a smooth film is disposed between at least one of a protrusion or a concavity and the thermoplastic polymer.

Variations in how the steps of the method are performed are contemplated. For instance, the smooth film may be attached to the thermoplastic polymer and steps b) and c) may be performed at least partially simultaneously. Optionally, the smooth film is disposed on the tool according to step b) by thermoforming the smooth film onto the tool simultaneously with step c). In some methods, the smooth film is attached (e.g., by thermoforming) to an exterior surface of the tool, including over at least a portion of a protrusion and/or a concavity, prior to step c). In some embodiments, vacuum forming may be used in combination with thermoforming, also known as dual vacuum thermoforming (DVT).

Any tool shape can be used to provide a portion of material that extends beyond, above, or below a planar surface, to impart a curve into a final article thermoformed onto at least one of a protrusion or a concavity of the tool, in which the (e.g., first) curve of the article is the inverse of the protrusion or the concavity. Referring to FIG. 5, one suitable example is a dental arch comprising a plurality of protrusions, namely a tool 560 having a shape of a dental arch in which numerous protrusions are present; e.g., each tooth 565, as well as the overall curved arch shape. Moreover, the tool 560 further includes one or more areas having a concave shape; e.g., concavities 567 of some of the teeth. The presence of a concavity will result in an outwardly curved inverse shape on the thermoformed article. This is a case of a tool having a plurality of protrusions and a plurality of concavities. Any tool according to the present disclosure may include one or more protrusions, one or more concavities, or at least one of each of a protrusion and a concavity. Dental arches are well known to be used as a tool in forming a dental tray for an individual (e.g., a dental tray can include a dental aligner, a night guard, a mouth guard, a treatment tray, complete or partial dentures, a tooth cap, or the like). A dental aligner may allow for repositioning misaligned teeth for improved cosmetic appearances and/or dental function. A night guard may be worn by a user to minimize damage to teeth during tooth grinding. A mouth guard may be, for example, a sports mouth guard that may or may not be formed to a user’s mouth with heat. A treatment tray may allow administration of a medication to oral surfaces, e.g., teeth whitening, remineralization, gum disease treatments, or the like. In some embodiments, the dental tray may provide aesthetic appeal by providing color (e.g., whitening).

In methods of the present disclosure, a smooth fdm is disposed on some or all of a tool, including on one or more protrusions or one or more concavities. Depending on the specific application, the smooth film may be disposed on 50% or greater of a surface of the tool, such as 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% or greater of a surface of the tool; and 100% or less, 98%, 93%, 88%, 83%, 78%, 73%, 68%, 63%, 58%, or 53% or less of a surface of the tool.

FIG. 2A is a photograph of an article 200a made by an exemplary thermoforming method. In this example, the thermoplastic polypropylene polymer is shaped to comprise more than one curve that comprises a smooth surface, namely each curve that is an inverse of a protruding portion of a tooth and the curve of the dental arch. As such, depending on the specific article being formed, the thermoplastic polymer may suitably be shaped to comprise a second curve that comprises a smooth surface, a third curve, a fourth curve, etc.

FIG. 2B is a photograph of an article 210b made by a comparative thermoforming method. In this example, the thermoplastic polypropylene polymer was thermoformed directly on the dental arch tool (i.e., without a smooth film disposed between the dental arch tool and the thermoplastic polymer). Comparing the appearance of an exterior surface 212b the article 210b to an exterior surface 202a of the article 200a in FIG 2A, it can be seen that the article 200a has a more transparent appearance while the article 210b has a more hazy/opaque appearance. Accordingly, methods according to the present disclosure may result in forming articles having improved aesthetics than articles formed without employing a smooth film, as it is often more desirable to have a clear article than a hazy article.

FIG. 3 is an optical micrograph image including portions of interior surfaces of the articles 200a and 210b. More particularly, the articles 200a and 210b were placed adjacent to each other to show the difference in smoothness of their interior surfaces formed from thermoforming. The article 210b formed by a comparative method lacking the presence of a smooth film disposed between the dental arch tool and the thermoplastic polymer has a microstructured texture 214b formed on an interior surface 216b of a curve 218b of the article 210b. In contrast, the article 200a formed by an exemplary method including a smooth film disposed between the dental arch tool and the thermoplastic polymer has a smooth texture 204a formed on an interior surface 206a of a curve 208a of the article 200a. Referring back to FIG. 1, the method often further comprises a Step 140 to d) remove the article from the tool. In some preferred embodiments, the method additionally comprises a Step 150 to e) subject the article to polishing. It has also been discovered that including a masking film on an exterior major surface of the thermoplastic polymer advantageously protects the thermoplastic polymer from experiencing surface damage during certain polishing procedures. Stated another way, the thermoplastic polymer comprises a first major surface that comes into contact with the smooth film and optionally a masking film is attached to a second major surface opposite the first major surface of the thermoplastic polymer. In some cases, a smooth film is provided on one major surface of the thermoplastic polymer and a masking film is provided on the opposing major surface of the thermoplastic polymer. The masking film comprises a first major surface that is in contact with the thermoplastic polymer and optionally the first major surface of the masking film is smooth. Often, a difference in optical clarity can be observed between articles polished with or without a masking film disposed on the exterior surface of the thermoformed article. Moreover, by minimizing surface damage to the article, the article is more durable than an article having surface damage from processes such as polishing.

Referring to FIG. 4A, a photograph is provided of an article 430a that was thermoformed by an exemplary method, removed from the dental arch tool, separated from the smooth film, then polished (i.e., the article 430a was polished by the “Procedure 2 for Polishing” described in detail below while lacking any smooth film or masking film disposed on the major surface(s) of the article). Each of the exterior surface 432a and the interior surface 436a of the article 430a was thus contacted with ceramic polishing material during the polishing process and is shown in the photograph to have a hazy appearance.

In contrast to the article 430a of FIG. 4A, FIG. 4B is a photograph an article 440b that was formed by the same exemplary thermoforming method as article 430a except that a masking film was present on the exterior surface of the thermoplastic polymer. Further, the masking film remained attached to the exterior surface 442b of the article 440b during polishing by the “Procedure 2 for Polishing”. The exterior surface 442b was thus protected from direct contact with ceramic polishing material during the polishing process. The smooth film used in the thermoforming method, however, had been separated from the article 440b and was no longer in contact with (e.g., disposed on) the interior surface 446b of the article 440b during the polishing procedure. After polishing, the masking film was removed and the exterior surface 442b of the article 440b that was formed and polished according to an exemplary method is shown in the photograph to have a less hazy (i.e., more transparent) appearance than that of the article 430a.

Referring to FIG. 4C, a photograph is provided of an article 450c that was formed by the same exemplary thermoforming method as the article 440b. Further, the smooth film remained atached to the interior surface 456c of the article 450c during polishing by the “Procedure 2 for Polishing”. Stated another way, each of the interior surface 456c and the exterior surface 452c was protected from direct contact with ceramic polishing material during the polishing process (i.e., by the smooth fdm and the masking film, respectively). After polishing, each of the smooth film and the masking film was removed and both the interior surface 456c and the exterior surface 452c of the article 450c that was formed and polished according to another exemplary method is shown in the photograph to have a less hazy (i.e., more transparent) appearance than either the article 430a or the article 440a. Accordingly, employing a protective film on a surface of an article during polishing can advantageously preserve clarity of the article, with the use of protective films on each of the two major surfaces providing greater protection than the use of a protective film on just one of the two major surfaces.

Referring again to FIG. 1, in any method according to the present disclosure, a Step 160 may be included, to f) remove at least one of the smooth film or the masking film (if a masking film is present) from the article. Typically, removing the masking film occurs after one or more polishing steps. Removing the smooth film is performed after at least step c) and preferably after any polishing. Optionally, removing the smooth film and/or the masking film may be a final step in making the article, for instance to maintain protection of exterior surface(s) of the thermoplastic polymer from (e.g., physical) damage during various manufacturing steps.

While in the example articles shown in FIGS. 2-4 include a portion of a curve comprising the smooth surface comprises an interior portion of the article, in certain articles according to the present disclosure a portion of a curve comprising the smooth surface comprises an exterior portion of the article (e.g., a handle of a utensil or tool, a vehicle steering wheel, etc.).

Smooth Film

In some cases, a smooth film is provided on a major surface of the thermoplastic polymer. By definition, the “smooth” film requires a major surface of the film to be smooth such that a surface of the film is essentially free of microstructures that have a height of 10 microns or greater. The smooth surface of the smooth film assists in imparting a smooth surface to the thermoplastic polymer during the thermoforming of the thermoplastic polymer on a tool that has a microstructured texture. The smooth film does not necessarily have to have any peel strength to maintain contact of the film with the thermoplastic polymer but can optionally exhibit the same range of peel strength as described below with respect to the masking film.

Typically, the smooth film has a thickness of 32 microns or greater, 35 microns, 37 microns, 40 microns, 45 microns, 50 microns, 55 microns, 60 microns, 65 microns, 70 microns or 75 microns or greater; and 125 microns or less, 120 microns, 115 microns, 110 microns, 105 microns, 100 microns, 95 microns, 90 microns, 85 microns, or 80 microns or less. In some cases, the smooth film has a thickness of 32 microns to 125 microns. Having a thickness of less than 32 microns tends to allow transfer of at least some of the microstructured texture of the tool to the curve surface of the resulting article. Having a thickness of greater than 125 microns tends to interfere with imparting the desired overall geometry of the tool to the resulting article.

For successful use in thermoforming processes, the smooth film may comprise a material that exhibits an elongation at break of 100% or greater, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190% or 200% or greater, and 400% or less. Typically, the smooth film comprises a material that exhibits a Shore A hardness of 60 or greater, 65, 70, 75, or 80 or greater; and 100 or less. Durometer hardness is a measured value of the resistance of a material to indentation, and is typically performed according to ASTM D2240, such as the Shore A hardness.

Suitable materials for the smooth film include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), copolymer of ethylene vinyl acetate (EVA), copolymer of ethylene and acrylic acid (EAA), copolymer of ethylene and ethylene ethyl acrylic acid salt such as Surlyn, polypropylene, polypropylene copolymer, polyvinyl chloride (PVC), nylon and polyester. The preferred primary polymer on the surface of a masking film to affect the adhesion level (e.g., peel strength) to substrates is a styrene-ethylene-butylene- styrene block copolymer, a styrene-ethylene-propylene block copolymer, or blends thereof, such as Kraton-G polymers available from Kraton Corporation. A secondary polymer such as polyolefins (homopolymers or copolymers), stryenes, butylenes, polymethylpentene and polyoxymethylene, and mixtures thereof, can be blended at varying ratios with the primary polymer to provide the desired level of adhesion to substrates.

Polyesters or copolyester may include linear, branched or cyclic segments on the polymer backbone. Suitable polyesters and copolyesters may include ethylene glycol on the polymer backbone, or be free of ethylene glycol. Suitable polyesters include, but are not limited to, copolyesters with no ethylene glycol available under the trade designation Tritan from Eastman Chemical, Kingsport, TN, polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyclohexylenedimethylene terephthalate (PCT), polycyclohexylenedimethylene terephthalate glycol (PCTg), poly(l,4 Cyclohexylenedimethylene) Terephthalate (PCTA), polycarbonate (PC), and mixtures and combinations thereof. Suitable PETg resins, which contain no ethylene glycol on the polymer backbone, can be obtained from various commercial suppliers such as, for example, Eastman Chemical, Kingsport, TN; SK Chemicals, Irvine, CA; DowDuPont, Midland, MI; Pacur, Oshkosh, WI; and Scheu Dental Tech, Iserlohn, Germany. For example, EASTAR GN071 PETg resins and PCTg VM318 resins from Eastman Chemical have been found to be suitable. Masking Film

The same materials may be suitable for each of the smooth film and the (e.g., optional) masking film for use in any method of the present disclosure, namely the same polyolefins (e.g., polyethylenes and/or polypropylenes) and copolyesters described above with respect to the smooth film.

To maintain direct contact of the masking film with the major surface of the thermoplastic polymer during processing such as polishing, preferably the masking film has an average peel strength to the thermoplastic polymer of greater than 0.2 Newtons per inches (N/in), 0.25 N/in, 0.35 N/in, 0.50 N/in, 0.65 N/in, 0.75 N/in, or 0.9 N/in or greater; and 7 N/in or less. The average peel strength is determined as described below in the “Peel Strength Test”. The thickness of the masking film is typically with the same range as the smooth film, described above (e.g., a thickness of 32 microns to 125 microns).

Thermoplastic Polymers

Suitable thermoplastic polymers for use in making the thermoformed article comprise a material that exhibits a draw down ratio of greater than 1.1, such as 1.2 or more, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 2.1, 2.2, or 2.3 or more; and 3.0 or less, 2.9, 2.8, 2.7, 2.6, 2.5, or 2.4 or less. Optionally, suitable thermoplastic polymers comprise a material that exhibits an elongation at break of 50% or greater, such as 55% or greater, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% or greater; and 400% or less. Elongation at break can be determined by ASTM D638-10, using test specimen Type V. It is preferred that the thermoplastic polymers possess the following properties: having thermal transition points such as glass transition temperatures between 70°C and 140°C, an elongation at break greater than 100%, stain resistance, crack resistance, resistance to stress relaxation and good optical clarity.

Some example suitable thermoplastic polymers include for instance and without limitation, a polypropylene, a polyester, a co-polyester, a polycarbonate, a thermoplastic polyurethane, a polyethylene, a polypropylene and polyethylene copolymer, an acrylic, a cyclic block copolymer, a polyetheretherketone, a polyamide, a polyethylene terephthalate, a polybutylene terephthalate, a poly etherimide, a polyethersulfone, a polytrimethylene terephthalate, silicone urethane copolymer, fluoropolymer, or any combination thereof. Polyurethanes may be formed from aromatic or aliphatic isocyanates combined with polyester or polyether polyols or a combination thereof. In some favored embodiments, the thermoplastic polymer comprises a polypropylene, such as under the trade designation “INVISACRYL C” from Great Lakes Dental Technologies (Tonawanda, NY). Suitable polyesters include, but are not limited to, copolyesters available under the trade designation TRITAN from Eastman Chemical, Kingsport, TN, polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyxlohexylenedimethylene terephthalate (PCT), polycyclohexj'lenedimethylene terephthalate glycol (PCTg), polycarbonate (PC), and mixtures and combinations thereof. Suitable PETg and PCTg resins can be obtained from various commercial suppliers such as, for example, Eastman Chemical, Kingsport, TN; SK Chemicals, Irvine, CA; DowDuPont, Midland, MI; Pacur, Oshkosh, WI; and Scheu Dental Tech, Iserlohn, Germany. For example, EASTAR GN071 PETg resins and PCTg VM318 resins from Eastman Chemical have been found to be suitable. Suitable polypropylene or polypropylene copolymer include, but are not limited to, Essix C+ from Dentsply Sirona, Charlotte, NC, and HardCast Material and INVISACRYL C from Great Lakes Dental Technologies, Tonawanda, NY.

Optional Additives & Coatings

The thermoplastic polymer material of the article may contain other additives such as antimicrobial agents (including antiseptics and antibiotics), dyes, mold release agents, antioxidants, plasticizers, thermal and light stabilizers including ultraviolet (UV) absorbers, fdlers, (e.g., for certain applications the fdlers are radioopaque), pigments, and the like.

Suitable antimicrobials can be incorporated into or deposited onto the polymers. Suitable preferred antimicrobials include those described in US Publication Nos. 2005/0089539 and 2006/0051384 to Scholz et al. and US Publication Nos. 2006/0052452 and 2006/0051385 to Scholz. The surfaces of articles of the present disclosure also may be coated with antimicrobial coatings such as those disclosed in International Application No. PCT/US2011/37966 to Ali et al.

Articles

Since one useful object is to provide an article having a surface with increased nonmicroorganism contaminant (e.g., dirt) removal when cleaned, the article is typically not a (e.g., sterile) medical article such as nasal gastric tubes, wound contact layers, blood stream catheters, stents, pacemaker shells, heart valves, orthopedic implants such as hips, knees, shoulders, etc., periodontal implants, dentures, dental crowns, contact lenses, intraocular lenses, soft tissue implants (breast implants, penile implants, facial and hand implants, etc.), surgical tools, sutures including degradable sutures, cochlear implants, tympanoplasty tubes, shunts including shunts for hydrocephalus, post-surgical drain tubes and drain devices, urinary catheters, endotraecheal tubes, heart valves, wound dressings, other implantable devices, and other indwelling devices. The medical articles just described may be characterized as single use articles, i.e., the article is used once and then discarded. In contrast, the articles and surfaces described herein include those where the surface is exposed to the surrounding (e.g., indoor or outdoor) environment and is subject to being touched or otherwise coming in contact with one or more people and/or animals.

In some embodiments, one or more surfaces of the article comes in direct (e.g., skin) contact with (e.g., multiple) people and/or animals during normal use of the article. In other embodiments, the surface may come is close proximity to people/or animals in the absence of direct (e.g., skin) contact.

Representative articles that would be cleaned during normal use and/or are amenable for use providing a smooth curved surface of the article include various interior or exterior surfaces or components of a medical article, a dental article, an orthodontic article, a vehicular article, an electronic article, a personal care article, a cleaning article, an athletic article, a food preparation article, a child care article, or an architectural article. More particularly, some examples of representative articles of these categories may include the following: a) vehicular articles (e.g., automobile, bus, train, airplane, boat, ambulances, ships), such as head rests, dashboards, door panels, window shutter (e.g., of an airplane), gear shifter, seat belt buckle, instrument and button panels, arm rests, railings, luggage compartments, steering wheels, handlebars, etc.); b) medical articles or dental articles including (e.g., non-sterile) surfaces of a medical, dental, or laboratory facility or medical, dental, or laboratory equipment (e.g., defibulators, ventilators and CPAPs (especially masks thereof), face shields, crutches, wheelchairs, bed rails, breast pump devices, IV pole and bags, dental tools (e.g., hand tools used during dental cleaning and restoration procedures), curing lights (e.g., for dental materials), exam tables, etc.; c) orthodontic articles including aligners (e.g., clear tray aligners), retainers, splints, class II and class III correctors, sleep apnea devices, bite openers, bands, brackets, buccal tubes, cleats, buttons, other attachment devices, etc.; d) electronic articles including housings and cases of electronic devices (e.g., phones, laptops, tablets, or computers) as well as keyboards, mouses, projectors, printers, remote control devices, locks, chargers (including cords & docking stations), fobs, video and arcade games, slot machines, automatic teller machines; and point of sale electronic devices such as credit card readers, keypads, stylists, cash registers, barcode scanner, payment kiosks, etc.; e) personal care articles including toothbrushes, eye glass frames, shoes, clothing, handbags, etc.; f) cleaning articles including vacuums, mops, scrub brushes, dusters, toilet bowl cleaners, plungers, brooms, etc.; g) athletic articles including helmets, guards, balls and hand-held equipment for various sports including baseball, lacrosse, tennis, football, basketball, soccer, and golf, etc.; h) food preparation articles appliances (e.g., microwaves, stoves, ovens, blenders, toasters, coffee makers, refrigerators), grills, utensils (e.g., especially handles thereof), condiment bottles, salt & pepper shakers, galleys, carts, cutting boards, lunch boxes, thermoses, tables and chairs (especially for public dining in restaurants, dorms, nursing homes, and prisons), etc.; i) child care articles including toys, pacifiers, bottles, teethers, car seats, cribs, changing tables, playground equipment, etc.; and j) architectural articles including railings, countertops, desktops, cabinets, lockers, window sills, electrical modulators (e.g., light switches, dimmers, and outlets), components of furniture (e.g., desks, tables, chairs, seats and armrests); handles (e.g., knob, pull, levers including locks) of articles including furniture, doors of buildings, turn styles, appliances, vehicles, shopping carts and baskets, surfaces and components of lavatories (e.g., sink, toilet surfaces (e.g. levers), drain caps, shower walls, bathtub, vanity, countertop), etc.

In select cases, the article comprises an orthodontic article, such as an orthodontic aligner.

Exemplary Embodiments

In a first embodiment, the present disclosure provides a method of making an article. The method comprises a) obtaining a tool shaped to comprise at least one of a protrusion or a concavity, a surface of the protrusion and/or the concavity having a microstructured texture having a height of 10 to 150 microns; b) disposing a smooth film on at least a portion of the tool including the protrusion and/or the concavity; and c) thermoforming a thermoplastic polymer onto the tool to form an article shaped to comprise a curve being an inverse of the protrusion or the concavity of the tool, wherein the curve has a smooth surface.

In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the smooth film is thermoformed onto the tool prior to step c).

In a third embodiment, the present disclosure provides a method according to the first embodiment, wherein the smooth film is attached to the thermoplastic polymer and steps b) and c) are performed at least partially simultaneously.

In a fourth embodiment, the present disclosure provides a method according to the third embodiment, wherein the smooth film is thermoformed onto the tool simultaneously with step c).

In a fifth embodiment, the present disclosure provides a method according to the method of any of the first through fourth embodiments, wherein the thermoplastic polymer comprises a first major surface that comes into contact with the smooth film and a second major surface opposite the first major surface, and wherein the thermoplastic polymer further comprises a masking film attached to the second major surface.

In a sixth embodiment, the present disclosure provides a method according to the fifth embodiment, wherein the masking film comprises a first major surface in contact with the thermoplastic polymer and wherein the first major surface of the masking film is smooth.

In a seventh embodiment, the present disclosure provides a method according to the fifth embodiment or the sixth embodiment, wherein the masking film has a thickness of 32 microns to 125 microns.

In an eighth embodiment, the present disclosure provides a method according to the method of any of the fifth through seventh embodiments, wherein the masking film has an average peel strength to the thermoplastic polymer of greater than 0.2 N/in as determined by the “Peel Strength Test”.

In a ninth embodiment, the present disclosure provides a method according to the method of any of the fifth through eighth embodiments, wherein the masking film comprises a polyolefin or a copolyester.

In a tenth embodiment, the present disclosure provides a method according to the method of any of the fifth through ninth embodiments, wherein the masking film comprises a polyethylene or a polypropylene.

In an eleventh embodiment, the present disclosure provides a method according to the method of any of the first through tenth embodiments, wherein the smooth film has a thickness of 32 microns to 125 microns.

In a twelfth embodiment, the present disclosure provides a method according to the method of any of the first through eleventh embodiments, wherein the smooth film comprises a polyolefin or a copolyester.

In a thirteenth embodiment, the present disclosure provides a method according to the method of any of the first through twelfth embodiments, wherein the smooth film comprises a polyethylene or a polypropylene.

In a fourteenth embodiment, the present disclosure provides a method according to the method of any of the first through thirteenth embodiments, wherein the tool is formed by additive manufacturing.

In a fifteenth embodiment, the present disclosure provides a method according to the method of the fourteenth embodiment, wherein step a) comprises making the tool using an additive manufacturing process.

In a sixteenth embodiment, the present disclosure provides a method according to the method of any of the first through fifteenth embodiments, further comprising: d) removing the article from the tool; and e) subjecting the article to polishing.

In a seventeenth embodiment, the present disclosure provides a method according to the method of any of the first through sixteenth embodiments, further comprising: f) removing at least one of the smooth film or the masking film from the article.

In an eighteenth embodiment, the present disclosure provides a method according to the method of any of the first through seventeenth embodiments, wherein the thermoplastic polymer comprises a polypropylene, a polyester, a co-polyester, a polycarbonate, a thermoplastic polyurethane, a polyethylene, a polypropylene and polyethylene copolymer, an acrylic, a cyclic block copolymer, a polyetheretherketone, a polyamide, a polyethylene terephthalate, a polybutylene terephthalate, a poly etherimide, a polyethersulfone, a polytrimethylene terephthalate, silicone urethane copolymer, fluoropolymer, or any combination thereof.

In a nineteenth embodiment, the present disclosure provides a method according to the method of the eighteenth embodiment, wherein the thermoplastic polymer comprises a polypropylene.

In a twentieth embodiment, the present disclosure provides a method according to the method of any of the first through nineteenth embodiments, wherein the article is a medical article, a dental article, an orthodontic article, a vehicular article, an electronic article, a personal care article, a cleaning article, an athletic article, a food preparation article, a child care article, or an architectural article.

In a twenty-first embodiment, the present disclosure provides a method according to the method of any of the first through twentieth embodiments, wherein the article is an orthodontic aligner.

In a twenty-second embodiment, the present disclosure provides a method according to the method of the twenty-first embodiment, wherein the protrusion or the concavity comprises a dental arch.

EXAMPLES

The following Examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims.

Unless otherwise noted or otherwise apparent from the context, all parts, percentages, ratios, and the like in the Examples and the rest of the specification are provided on the basis of weight. Solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company (Milwaukee, WI) unless otherwise noted. Materials

TRITAN MX710. An amorphous copolyester (obtained under the trade designation “TRITAN MX710” from Eastman Chemical Co., Kingsport, TN).

ECDEL 9967. A copolyester ether elastomer (obtained under the trade designation “ECDEL 9967” from Eastman Chemical Co., Kingsport, TN).

A 5 -layer ABCBA (TRITAN MX710 / ECDEL 9967 / TRITAN MX710 / ECDEL 9967 / TRITAN MX710) smooth tooling fdm. The 5 -layer ABCBA smooth tooling fdm was extruded using a pilot scale coextrusion line equipped with a feedblock and fdm die. The skin layer (A) extruder was fed with the first rigid resin, TRITAN MX710. The skin layer (A) extrusion melt temperature was controlled at 505 °F (262.8 °C). The throughput was 4.3 Ibs/hr (1.95 kg/hr). The core layer (C) extruder was also fed with the first rigid resin, TRITAN MX710, and the extrusion melt temperature was controlled at 550 °F (287.8 °C). The core layer extrusion throughput was 11.6 Ibs/hr (5.26 kg/hr). The middle layer (B) extruder was fed with a second thermoplastic elastomeric resin, ECDEL 9967, and the extrusion temperature was controlled at 470 °F (243.3 °C). The middle layer extrusion throughput was 5.54 Ibs/hr (2.51 kg/hr). The extruded sheet was cast onto and chilled on a cast roll and the overall sheet thickness was controlled at 3.5 mils (0.0889 mm). A 125 mm diameter hollow punch was used to cut out individual discs for thermoforming from the 5 -layer smooth tooling film.

Polypropylene disc, 125 mm diameter, 1.02 mm thick (obtained under the trade designation “INVISACRYL C” from Great Lakes Dental Technologies (formerly Great Lakes Orthodontics), Tonawanda, NY).

ESSIX ACE copolyester disc, masked on both sides with smooth masking films, 125 mm disc diameter, 0.875 mm copolyester thickness, and 0.051 mm masking film thickness (obtained under the trade designation “ESSIX ACE” from Dentsply Sirona, Charlotte, NC).

GT FLEX copolyester disc, masked on both sides with smooth masking films, 125 mm disc diameter, 0.75 mm copolyester thickness, and 0.047 mm masking film thickness (obtained under the trade designation “GT FLEX” from Good Fit Technologies, Boston, MA).

GT FLEX PRO copolyester disc, masked on both sides with smooth masking films, 125 mm disc diameter, 0.8 mm copolyester thickness, and 0.052 mm masking film thickness (obtained under the trade designation “GT FLEX PRO” from Good Fit Technologies, Boston, MA). Inspection Methods

The articles were visually inspected and examined with a digital microscope (obtained under the trade designation “KEYENCE VHX-1000” from Keyence Corporation of America, Itasca, IL).

Peel Strength Test

The 180-degree peel strength of a smooth film affixed to a thermoplastic polymer substrate was measured per the test method, conditioning, and specimen preparation guidelines outlined in ASTM D903-98. One-inch-wide (2.54 cm) peel test strips were fabricated by scoring the smooth film at 1-inch (2.54 cm) width using a sharp razor blade and removing excess film material from the thermoplastic substrate. Peel strength values were reported in units of Newtons per inch of film width; these units can be converted to ASTM D903 SI units of kgf per mm of film width by dividing by a factor of 249.

Procedure 1 for Thermoforming

To thermoform, a 125 mm diameter substrate was heated for a specific time and then pulled down over a rigid-polymer dental arch model on a pressure molding machine (obtained under the trade designation “BIOSTAR VI” from Scheu-Dental GmbH, Iserlohn, Germany). The specific heating times were set at 30 seconds for copolyester discs (ESSIX ACE and GT FLEX), 40 seconds for 3.5 mils (0.089 mm) smooth 5 -layer tooling film and 70 seconds for polypropylene disc (INVISA CRYL C). The BIOSTAR VI chamber behind the film was pressurized to 90 psi (620.5 kPa) for 15 seconds of cooling time, after which the chamber was vented to ambient pressure and the formed article and arch model were removed from the instrument and cooled down to room temperature under ambient condition. The model with thermoformed substrate was removed from the machine and excess film was trimmed using an ultrasonic cutter (obtained under the trade designation “SONIC-CUTTER NE80” from Nakanishi Incorporated, Kanuma City, Japan).

Procedure 2 for Polishing

Polishing was performed in a centrifuge barrel deburring, finishing, and tumbling machine (obtained under the trade designation “LC-600” from Richwood Industries, Huntington Beach, CA). The tumbling barrel was filled three-quarters-full with round ceramic polishing media (obtained under the trade designation “MC-SL6” from United Surface Solutions, Santa Fe Springs, CA). Water and 3 drops of hand soap (obtained under the trade designation “EPREDIA SOFTCIDE” from Thermo Fisher Scientific, Waltham, MA) were added to the barrel until level with the top of the polishing media. The test parts were added to the barrel before the lid was secured to the top of the barrel. The barrel and counterbalancing barrel fdled with water were loaded into the tumbling machine and secured in place. The tumbling machine was run at 150 rpm for 10 minutes. The barrels were then removed from the machine. The barrel containing the test parts was opened and the parts were removed from the barrel by reaching into the media using gloved hands. The polishing media was rinsed clean with tap water and the barrel returned to storage. The retrieved samples were washed in tap water and carefully dried with a paper towel.

Example 1

A 0.089 mm thick 5-layer smooth tooling fdm was punched into a 125 mm disc. The disc was thermoformed onto a rigid-polymer dental arch model by Procedure 1. A polypropylene disc (INVISACRYL C) was then thermoformed over the smooth tooling fdm on the rigid-polymer dental arch model using the conditions of Procedure 1. After trimming with the ultrasonic cutter, the polypropylene tray was separated from the tooling fdm and the dental arch model by hand. The polypropylene tray had high clarity, and a smooth surface was evident on the cavity side of the polypropylene tray when examined by digital microscope.

Example 2

A copolyester disc with masking fdms (GT FLEX) was thermoformed by Procedure 1 onto a rigid-polymer dental arch model with a heating time of 30 seconds having the tooling fdm in contact with the dental arch model. After trimming with the ultrasonic cutter, the tray with masking fdms was separated from the dental arch model by hand. The tray with masking fdms was polished with the ceramic polishing media as described in Procedure 2. The masking fdms were removed from the tray after polishing and the tray had good clarity.

Comparative Example 1

A polypropylene disc (INVISACRYL C) was thermoformed by Procedure 1 onto a rigid- polymer dental arch model with a heating time of 70 seconds. After trimming with the ultrasonic cutter, the tray was separated from the dental arch model by hand. The inverted structure of the surface texture of the rigid-polymer dental arch model was evident on the surface of the cavity side of the polypropylene tray when examined by digital microscope.

Comparative Example 2

A copolyester disc with masking films (ESSIX ACE) was thermoformed by Procedure 1 onto a rigid-polymer dental arch model with a heating time of 30 seconds. After trimming with the ultrasonic cutter, the tray was separated from the dental arch model by hand. Masking films were observed to be cracked and the inverted structure of the surface texture of the rigid-polymer dental arch model was observed on the surface of the cavity side of the tray when examined by digital microscope.

Comparative Example 3

Masking films were removed from a copolyester disc (GT FLEX). The disc was thermoformed by Procedure 1 onto a rigid-polymer dental arch model with a heating time of 30 seconds. After trimming with the ultrasonic cutter, the tray was separated from the dental arch model. The inverted structure of the surface texture of the rigid-polymer dental arch model was observed on the surface of the cavity side of the tray. The tray had hazy appearance after polishing with ceramic polishing media as described in Procedure 2.

Peel Strength of Smooth Films

Each of the films of ESSEX ACE, GT FLEX, AND GT FLEX PRO were tested for average peel strength according to the above “Peel Strength Test”. The results are shown below in Table 1:

Table 1. Average Peel Strength of Films

Claims

What is claimed is:

1. A method of making an article, the method comprising: a) obtaining a tool shaped to comprise at least one of a protrusion or a concavity, a surface of the protrusion and/or the concavity having a microstructured texture having a height of 10 to 150 microns; b) disposing a smooth film on at least a portion of the tool including the protrusion and/or the concavity; and c) thermoforming a thermoplastic polymer onto the tool to form an article shaped to comprise a curve being an inverse of the protrusion or the concavity of the tool, wherein the curve has a smooth surface.

2. The method of claim 1, wherein the smooth film is thermoformed onto the tool prior to step c).

3. The method of claim 1, wherein the smooth film is attached to the thermoplastic polymer and steps b) and c) are performed at least partially simultaneously.

4. The method of any of claims 1 to 3, wherein the thermoplastic polymer comprises a first major surface that comes into contact with the smooth film and a second major surface opposite the first major surface, and wherein the thermoplastic polymer further comprises a masking film attached to the second major surface.

5. The method of claim 4, wherein the masking film comprises a first major surface in contact with the thermoplastic polymer and wherein the first major surface of the masking film is smooth.

6. The method of claim 4 or claim 5, wherein the masking film has a thickness of 32 microns to 125 microns.

7. The method of any of claims 4 to 6, wherein the masking film has an average peel strength to the thermoplastic polymer of greater than 0.2 N/in.

8. The method of any of claims 1 to 7, wherein the smooth film has a thickness of 32 microns to 125 microns.

9. The method of any of claims 1 to 8, wherein the smooth film comprises a polyolefin or a copolyester.

10. The method of any of claims 1 to 9, wherein the smooth film comprises a polyethylene or a polypropylene.

11. The method of any of claims 1 to 10, wherein the tool is formed by additive manufacturing.

12. The method of any of claims 1 to 11, further comprising: d) removing the article from the tool; and e) subjecting the article to polishing.

13. The method of any of claims 1 to 12, further comprising: f) removing at least one of the smooth film or the masking film from the article.

14. The method of any of claims 1 to 13, wherein the thermoplastic polymer comprises a polypropylene, a polyester, a co-polyester, a polycarbonate, a thermoplastic polyurethane, a polyethylene, a polypropylene and polyethylene copolymer, an acrylic, a cyclic block copolymer, a polyetheretherketone, a polyamide, a polyethylene terephthalate, a polybutylene terephthalate, a poly etherimide, a polyethersulfone, a polytrimethylene terephthalate, silicone urethane copolymer, fluoropolymer, or any combination thereof.

15. The method of any of claims 1 to 14, wherein the article is a medical article, a dental article, an orthodontic article, a vehicular article, an electronic article, a personal care article, a cleaning article, an athletic article, a food preparation article, a child care article, or an architectural article.

16. The method of any of claims 1 to 15, wherein the article is an orthodontic aligner.