WO2025238446A1

WO2025238446A1 - Coating comprising methyl methacrylate copolymer with silicon-oxygen groups and articles

Info

Publication number: WO2025238446A1
Application number: PCT/IB2025/054005
Authority: WO
Inventors: Naota SUGIYAMA; Chad M. AMB; Mahfuza B. Ali; John P. Baetzold; Zhihui Miao; Koji Saito; Keisuke Kato; Ken Egashira; Lijun Zu; Masami Miura; Shinsuke KONDO
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2024-05-17
Filing date: 2025-04-16
Publication date: 2025-11-20
Anticipated expiration: 2026-11-17

Abstract

An article is described comprising a substrate comprising a protective layer comprising a methyl methacrylate copolymer comprising at least 50 wt.% of polymerized units of methyl methacrylate; 2-20 wt.% of polymerized units of (meth)acrylate comonomer(s) wherein a homopolymer thereof has a Tg less than 90°C; and less than 5 wt.% of polymerized units of (meth)acrylate monomer(s) comprising at least one Si-O group. When the (meth)acrylate monomer(s) comprising at least one Si-O group is a -Si(OR¹)m group wherein R¹ is hydroxyl or a C1-C4 alkyl group and m ranges from 1-3, the article may be prepared by moisture curing the -Si(OR¹)n group(s) of the copolymer. Also described are methyl methacrylate copolymers. Methods of thermoforming and a thermoformed article.

Description

COATING COMPRISING METHYL METHACRYLATE COPOLYMER WITH SILICON-OXYGEN GROUPS AND ARTICLES

Summary

Industry would find advantage in protective coatings having a combination of strctchability and abrasion resistance. It is also desirable for protective coatings to be cleanable such as exhibited by permanent marking removal, low dirt pick up and high contact angles.

In one embodiment, a method of making a protective layer is described comprising providing a coating solution comprising an organic solvent and a copolymer. The copolymer comprises at least 50 wt.% of polymerized units of methyl methacrylate; 2-20 wt.% of polymerized units of (meth)acrylate comonomer(s) wherein a homopolymer thereof has a Tg less than 90°C; and less than 5 wt.% of polymerized units of methacrylate monomer(s) comprising a -SiCOR^m group wherein R¹ is hydroxyl or a C 1 -C4 alkyl group and m ranges from i -3. The method further comprises applying the coating solution to a substrate, removing the organic solvent, and moisture curing the -Si(OR' )ri group(s) of the copolymer.

In another embodiment, an article is described comprising a substrate comprising a protective layer comprising a methyl methacrylate copolymer comprising at least 50 wt.% of polymerized units of methyl methacrylate; 2-20 wt.% of polymerized units of (meth)acrylate comonomer(s) wherein a homopolymer thereof has a Tg less than 90°C; and less than 5 wt.% of polymerized units of (meth)acrylate monomer(s) comprising at least one Si-0 group.

In some embodiments, the article is suitable for thermoforming.

Also described are methyl methacrylate copolymers. In some embodiments, the copolymer comprises less than 10 wt.% of polymerized units of acrylate comonomer. In some embodiments, the copolymer comprises less than 10 wt.% of polymerized units of (meth)acrylate comonomer having a Tg less than 0°C.

Brief Description of the Drawings

FIG. 1 is a cross-section schematic view’ of an article comprising a substrate and a protective coating layer;

FIG. 2 is cross-section schematic view’ of another article comprising a release liner, an adhesive layer, a transparent organic polymer film, and a protective layer;

FIGs. 3-4 are cross-section schematic view’s of graphic articles comprising a colored or printed layer.

Detailed Description

Methyl methacrylate (MMA) homopolymer or in other words poly(meth methacrylate) is reported to have a glass transition temperature of 105°C. As evidenced by the forthcoming comparative examples, protective coatings comprising methyl methacrylate homopolymer exhibits low stretchability, yet good abrasion resistance. Good abrasion resistance is evidenced by low’ haze values after abrasion testing. Various copolymers of MMA and butyl acrylate (BA) have been described. With reference to CE-6 of the forthcoming examples, although 10 wt.% of BA can improve the stretchability, the abrasion resistance is compromised. Industry would find advantage in protective coating comprising MMA copolymers having improved flexibility wherein the abrasion resistance is equal to or better than MMA homopolymer. In some embodiments, the properties of the protective layer described herein are similar to PMMA copolymer protective coatings comprising fluorinated components, such as described in US9296692. However, the presently described protective coating layer, article, and copolymer can provide such attributes while lacking fluorine atoms. Such protective coatings are especially usefi.il for flexible organic polymer films.

The protective coating composition comprises a methyl methacrylate copolymer comprising at least 50 wt.% of polymerized units of methyl methacrylate. In typical embodiments, the amount of polymerized units of methyl methacrylate is at least 55, 60, 65, 70, 75, or 80 wt.% based on the total amount of monomers of the MMA copolymer. Notably, the forthcoming examples comprise at least 80, 81 . 82. 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93 wt.% of polymerized units of methyl methacrylate. However, it is contemplated that a portion of the MMA may be replaced with a different monomer having a Tg about equal to or greater than MMA (e.g. at least 95, 100 or 105°C).

The methyl methacrylate copolymer further comprises polymerized units of at least one (meth)acrylate comonomer having a Tg less than methyl methacrylate. It is particularly surprising that the PMMA copolymer can comprise polymerized units of a lower Tg (meth)acrylate without compromising the abrasion resistance. Notably, the abrasion resistance can be equal to or better than PMMA homopolymer.

In typical embodiments, methyl methacrylate copolymer further comprising polymerized units of at least one (meth)acrylate comonomer, wherein a homopolymer thereof has a Tg no greater than 90, 85, 80, 75, 70, 65, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 0°C. In some embodiments, the Tg of a homopolymer of the (meth)acrylate comonomer is at least 10, 15, 20, 25, 30, 35, 40, 55, 50, 55, 60, 65, 70, 75, 80, or 85°C. Although 10 wt.% of butyl acrylate (Tg = -54°C) or n-hexyl methacrylate, can also improve the stretchability, the abrasion resistance is decreased. However, it is contemplated that smaller concentrations of lower Tg (meth)acrylate comonomers can be utilized. In some embodiments, (meth)acrylate comonomers having a Tg less than 0°C may be present in combination with (meth)acrylate comonomer(s) having a Tg greater than 0°C. In some embodiments, the methyl methacrylate copolymer comprises less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt.% or zero of (meth)acrylate comonomers having a Tg less than 0°C. In some embodiments, the methyl methacrylate copolymer comprises less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt.% or zero of acrylate comonomers, such as butyl acrylate. In some embodiments, the methyl methacrylate copolymer comprises less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt.% or zero of (meth)acrylate comonomers that are crystalline solids at ambient temperature (25°C). High amount of crystalline comonomers can contribute to higher haze values.

The Tg of the homopolymer of various monomers is known and is reported in various handbooks (Polymer Handbook , 4^th edition, edited by J. Brandrup, E.H. Immergut, and E.A. Grulke, associate editors A. Abe and D.R. Bloch, J. Wiley and Sons, New York, 1999). The Tg of the homopolymer of various monomers is also often reported by the supplier (e.g. Sigma Aldrich).

Glass Transition Temperature (Tg) of the Homopolymer of Monomers

In some embodiments, the (meth)acrylate comonomer may be represented by the formula:

HaC^RJCOOR² wherein R^! is methyl or hydrogen and R² is an alkyl with 1 to 24 carbon atoms.

In some embodiments, R¹ is methyl. In other words the comonomer is a methacrylate comonomer.

In some embodiments, the alky group may have less than 22, 18, 16, 14, 12, 10, 8, or 6 carbon atoms. In some embodiments, the alkyl group is a straight-chain alkyl group with 1 to 5 carbon atoms, such as in the case of methyl, ethyl, and butyl.

Although 10 wt.% of branched alkyl (meth)acrylate monomers such as isobutyl methacrylate can improve the stretchability, the abrasion resistance decreases or the protective layer exhibits a white appearance after stretching. However, smaller concentrations (less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt.%) of branched (meth )acrylatc comonomers, such as isobutyl methacrylate, can be utilized.

In some embodiments, the alkyl group of the comonomer further comprises a hydroxyl group. Such comonomer may be represented by the formula:

H₂C=CR¹C(O)OR²OH wherein R¹ is methyl or hydrogen and R" is an alkyl with 1 to 5 carbon atoms.

In some embodiments, R¹ is methyl. In other words the comonomer is a methacrylate comonomer. In some embodiments, the alkyl group is a straight-chain alkyl group, such as in the case of methyl, ethyl, and butyl.

The OH group may be a terminal group or a pendent group. When the -OH group is a terminal group R² may be referred to as an alkylene group with 1 to 5 carbon atoms. It is surmised that the -OH group may participate in moisture curing with -OH or alkoxy groups of the alkoxy silane methacrylate monomer.

A single (meth)acrylate comonomer or combination of two or more (meth)acrylate comonomers may be utilized. The methyl methacrylate copolymer typically comprises at least 1, 2, 3, 4, or 5 wt.% of lower Tg (mcth)acrylatc comonomer(s) (i.e. having a Tg less than MMA as previously described), based on the total amount of monomers of the MMA copolymer. The amount of lower Tg (meth)acrylate comonomer(s) is typically no greater than 20, 19, 18, 17, 16, or 15 wt.%. In some embodiments, the amount of (meth)acrylate comonomer(s) is no greater than 14, 13, 12, 11, or 10 wt.%. In some embodiments, the amount of (meth)acrylate comonomer(s) is no greater than 9, 8, 7, 6, or 5 wt.%.

The MMA copolymer further comprises polymerized units of a (meth)acrylate monomer having at least one Si-0 group. The S-0 group may be hydrolysable (e.g. alkoxy ) silane group, a polysiloxane (e.g. polydimethyl siloxane “PDMS” moieties), or a combination thereof. Various (meth)acrylate monomer(s) comprising at least one Si-0 group are commercially available from suppliers such as Shin- Etsu Silicones, Aldrich, Gelest, and Momentive.

In some embodiments, the amount of polymerized units of a (meth)acrylate monomer(s) comprising at least one Si-0 group is at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 wt.% based on the total amount of monomers of MMA copolymer. In some embodiments, the amount of polymerized units of a (meth)acrylate monomer(s) comprising at least one Si-0 group is at least 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 wt.% based on the total amount of monomers of MMA copolymer. In some embodiments, the amount of polymerized units of a (meth)acrylate monomer) s) comprising at least one Si-0 group is no greater than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt.% based on the total amount of monomers of MMA copolymer.

In some embodiments, the MMA copolymer is moisture curable. The moisture curable MMA copolymer comprises polymerized units of a (meth)acrylate monomer(s) comprising hydrolysable (e.g. alkoxy) silane groups in an amount as just described.

Such monomer may have the general structure: wherein

R^! is hydrogen or C1-C4 alkyl,

R^z is C 1 -C 12 alkyl, and

R'^: is hydrogen or methyl , n ranges from 1-12, and m ranges from 1 io 3 In some embodiments, n is at least 1, 2, or 3. In some embodiments, n is no greater than 8, 6, or 4. In some embodiments, m is 2. In some embodiments, m is 3. In some embodiments, R¹ is methyl. In other words the comonomer is a methacrylate comonomer. In some embodiments, the (meth)acrylate monomer(s) comprising (e.g. alkoxy) silane groups further comprises other linking groups such as an amino or urethane group.

Representative (mcth)acrylare alkoxy silanes include (3-methacryloyloxypropyl) trimethoxysilane; (3-acryloyloxypropyl)trimethoxysilane; (3-methacryloyloxyethly)trimethoxysilane; (3- acryloyloxyethyljtrimethoxysilane; ( 3 -acryloyloxypropyl)methyldimethoxysilane; (methacryloyloxymethyl)methyl diethoxysilane; (methacryloyloxymethyl)methyl diethoxysilane; methacryloyloxypropyl- methyldiethoxysilane; methacryloyloxypropylmethyldimethoxysilane; methacryloyloxy-propyldimethylethoxysilane; and methacryloyloxypropyldimethylmethoxysilane.

In some embodiments, the MMA copolymer comprises polymerized units of a (meth)acrylate monomer comprising a polysiloxane group in an amount as previously described. Such monomer may be monofunctional, i.e. comprising a single methacrylate or acrylate group. In other embodiments, such monomer may be difunctional i.e. comprising a polysiloxane (e.g. PDMS) backbone and (meth)acrylate terminal groups. The (meth)acrylate monomer typically has a molecular weight of at least 1000, 2000, 3000, or 5000 g/mole. In some embodiments, the polysiloxane (.e. polydimethylsiloxane) group or (meth)acrylate monomer has a molecular weight no greater than 25,000; 20,000; 15,000, or 10,000 g/mole.

When the MMA copolymer is moisture curable, a (mcth )acrykatc monomer comprising a polysiloxane group is optional, but may be present in combination with the alkoxy silane (meth)acrylate monomer. When the MMA copolymer is not moisture curable, a (meth)acrylate monomer comprising a polysiloxane group may be the only (meth)acrylate monomer comprising at least one Si-0 group, such as illustrated by Example 20.

In some embodiments, the MMA copolymer further comprises polymerized units of (3- methacryloyloxypropyl)trimethoxysilane (Silane A174), polysiloxane (e.g. PDMS) methacrylate (KF- 2012), or a combination thereof.

The protective layer may comprise additives provided that the inclusion of such does not detract from the stretch ability and abrasion resistance. To enhance durability of the hardcoat layer, especially in outdoor environments exposed to sunlight, a variety of commercially available ultraviolet absorbers and light stabilizers can be added, such as described W02009/005975 and available as the trade designation TINUVIN (e.g. product numbers 123, 292, 200, 477, 479, 1130). In some embodiments, the protective layer comprises at least 1, 2, 3, 4, or 5 wt.% of ultraviolet absorbers and light stabilizers. In some embodiments, the protective layer exhibits good weatherability. As illustrated by the forthcoming examples in some embodiments the AE is less than 3, 2, 1, 0.5, or 0. 1 . In some embodiments, the 60 and/or 20 degree gloss is at least 75, 80, 85, 90, 95 or 100%.

The protective layer may comprise additives to adjust the surface appearance, or gloss levels, provided that the inclusion of such does not detract from the stretchability and abrasion resistance. To adjust the gloss levels of the hardcoat layer, a variety of matting agents may be added, as described in the technical document ACEMATT™ “Matting agents for the coating industry”. Alternatively or in addition to matting agents, the top surface of the protective layer may be structured by casting onto a textured release liner. This approach will result in a texture on the surface of the protective layer, which is useful in adjusting the gloss level. In some embodiments, the 60 degree gloss is less than 25 gloss units.

The protective layer may comprise silane or siloxane additives. Such alkoxy silane additives are similar to the (meth)acrylate alkoxy silane additives except that the (meth)acylate group is typically replaced with an alkoxyl silane group and there is a R³ group. A representative alkoxy silane additive is l,6-bis(trimethoxysilyl)hexane (KBM-3066). The amount of silane or siloxane additives that lack a (methjacrylate group may be at least 1, 2, 3, 4, or 5 wt.%. In some embodiments, the amount of silane or siloxane additives is no greater than 10, 9, 8, 7, 6, or 5 wt.%.

The protective coating typically comprises little or no silica nanoparticles. When present the amount is typically less than 5, 4, 3, 2, or 1 wt.%. Protective layers comprising the MMA copolymer and 5 wt.% of silica nanoparticles can exhibit a white appearance when stretched.

In some embodiments, the total amount of additives is no greater than 25, 20, 15, 10, or 5 wt °/o of the total protective layer.

The MMA copolymer can be prepared by solution polymerization within a suitable organic solvent that dissolves the monomers. A suitable solvent includes for example ethyl acetate or 90%/ 10% wt./wt. blend of ethyl acetate/isopropanol. Alcohol may be utilized to dissolve the alkoxy silane (methjacrylate monomer. The MMA copolymer is typically a random copolymer.

The MMA copolymer at a concentration of at least 10, 20 or 30 wt.% is soluble in organic solvent prior to moisture curing. After moisture curing (e.g. at 120^cC for 16 horns) at least 5 wt.% of the copolymer is insoluble in a (e.g. 20 wt.%) copolymer mixture with organic solvent. In some embodiments, the amount of moisture cured MMA copolymer that is insoluble in organic solvent is at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 wt.%. As evident by the forthcoming examples, high concentrations of solvent insoluble crosslinked MMA copolymer can be obtained with an alkoxy silane (methjacrylate monomer content of about 2 wt.%. Smaller concentrations can be utilized to obtain less crosslinked protective layers. When the MMA copolymer is prepared from a polysiloxane (methjacrylate monomer in the absence of a (methjacrylate monomer comprising hydrolysable (e.g. alkoxy) silane groups, the MMA copolymer is soluble in the organic solvent. Protective layers comprising highly crosslinked MMA copolymers can have better durability and chemical resistance.

The molecular weight of the MMA copolymer may' have a weight average molecular weight of a t l e a s t 5 0 , 00 ; 60 , 000 ; 70 , 000 ; 80 , 000 , or 8 5 , 000 g/ mo l e . T he molecular weight of the MMA copolymer may range up to 100,000; 150,000; 200,000; 250,000; 300,000; 350,000; 400,000; 450,000, or 500,000 g/mole. Weight average molecular weights of the acrylic polymer can be measured, for example, by gel permeation chromatography (i.e., size exclusion chromatography (SEC) using the test method described in the examples. The MMA organic solvent copolymer solution can be diluted to the desired viscosity with additional organic solvent.

The protective coating can be applied as a single or multiple layers to a substrate using conventional film application techniques. Thin films can be applied using a variety of techniques, including dip coating, forward and reverse roll coating, wire wound rod coating, and die coating. Die coaters include knife coaters, slot coaters, slide coaters, fluid bearing coaters, slide curtain coaters, drop die curtain coaters, and extrusion coaters among others. Many types of die coaters are described in the literature. Although it is usually convenient for the substrate to be in the form of a roll of continuous web, the coatings may be applied to sheets or individual parts.

After applying the protective coating solution, the solvent is removed by evaporation and condensation techniques. Laboratory samples can be dried for 90 seconds at 60°C in air followed by placing the coated substrate in an oven at 120°C for 10 minutes in air. Moisture curing of the alkoxy silane group occurs during drying and can be accelerated with heat or a catalyst.

Although the protective coating described herein can be applied to any substrate, it is particularly advantageous for uses wherein flexibility in combination with good abrasion resistance is of importance. The thickness of the protective coating layer is typically at least 1, 2, 3, 4, or 5 microns. Notably a 5 micron protective coating layer was utilized for the test results reported in the forthcoming examples. The protective coating typically has a thickness of no greater than 75, 50, 25, or 10 microns.

The physical properties of the protective layer and MMA copolymer can be evaluated with the test methods described in the forthcoming examples.

The organic polymeric film together with the MMA copolymer protective layer can be stretched 150% at 23 ^CC without cracking. The protective layer (e.g. at a thickness of 5 microns or less) can be stretched 150% at 23°C without cracking.

The protective layer (e.g. MMA copolymer) is also typically cleanable. In some embodiments, the cleanable protective layer exhibits permanent marker removability. In some embodiments, the cleanable protective layer exhibits dirt pick up of less than 10. In some embodiments, the cleanable protective layer exhibits dirt pick up of less than 10 or 5 after wiping 3 times with water. In some embodiments, the cleanable protective layer exhibits a static contact angel with water of at least 75, 80, 85, 90, 95, 100, or 105 degrees.

The protective layer may be disposed on various articles. FIG. 1 is an illustrative article of a protective layer 102 comprising a MMA copolymer as described herein disposed on a substrate 104. The substrate can be various objects, a release liner, or an organic polymer film. Due to the high transparency, e.g. initial haze less than 2 or 1%, the protective layer is particularly useful for transparent substrates, including more rigid substrates such as glass.

With reference to FIG. 2 illustrative protective film articles typically comprise a protective layer 202, 302, 402 comprising a MMA copolymer as described herein disposed on a major surface of (e.g. transparent) organic polymer film substrate 201, 301, 401. The (e.g. transparent) organic polymer film substrate 201, 301, 401 typically has a first major surface parallel to a second major surface and a thickness in the direction orthogonal to the major surfaces. An (e.g. pressure sensitive) adhesive layer 203 is disposed on the opposing major surface of the (e.g. transparent) organic polymer film substrate 201. A release liner 204 is typically disposed on the opposing surface of the adhesive layer 203, 303, 403. During use, the release liner is removed, exposing the underlying adhesive layer. The adhesive layer is utilized to adhere the protective film to a surface of an object. The adhesive layer may be a continuous or discontinuous layer.

In some embodiments, the article may be characterized as a graphic film article. Graphic film articles are used for various purposes including to provide information, advertising and decorative uses. In one embodiment, the article may be characterized as a paint protection film or paint replacement film (e.g. for vehicles). With reference to FIGs 3-4, graphic film articles further comprise a graphic, i.e. a colored, decorative, or printed layer 305, 405. The images can be formed with various printing methods such as ink jet printing process, a thermal mass transfer printing process, electrostatic printing, gravure printing, offset printing, screen printing, and the like. The inks can be water-based, organic-solvent based, or inks comprising (meth)acryl monomers that can be cured by exposure to ultraviolet radiation.

The graphic, i.e. a colored, decorative, or printed layer 305, 405 may be printed or coated onto a (e.g. transparent) organic polymer film substrate 301, 401. Alternatively, the graphic, i.e. a colored, decorative, or printed layer 305, 405 may be a separate film layer that is bonded to (e.g. transparent) organic polymer film substrate 301, 401.

In some embodiments, the graphic is between the (e.g. transparent) organic polymer film substrate 301 and the adhesive layer 303, as depicted in FIG. 3. Due to the high transparency of the protective layer 302 and the transparent organic polymer film substrate 301, the underlying graphic can be seen through the protective layer and substrate 301.

In other embodiments, the graphic is between the protective layer 402 and the adhesive layer 403, as depicted in FIG. 4. Due to the high transparency of the protective layer, the underlying graphic can be seen through the protective layer.

Common (e.g. transparent) organic polymer films for graphic film articles include for example poly(meth)acrylate, polyolefin, polyester, polyamide, and/or polycarbonate film. More flexible organic polymer films include for example polyurethane, polylactic acid (PDA) film, and vinyl film such as, for example, a polyvinyl chloride (PVC) film, a PVC blend film, or a plasticized PVC film. In some embodiments, the PLA film comprises a polylactic acid polymer, a second polymer (e.g. polyvinyl acetate), and plasticizer as described in WO2016/105998. In some embodiments, the poly(meth)acrylate further comprised polyvinyl acetal (e.g. butyral) as described in WO2016/094277. In some embodiments, the film has a thickness from about 10 to about 250 microns (about 0.5-10 mils).

The (e.g. transparent) organic polymer films may contain a variety of coatings or surface treatments. Among the suitable surface treatments that can be applied to one or both surfaces of the substrate are, for example, corona treatment, plasma treatment or flame treatment. Usefill coatings include, for example, primer coatings such as chemical primer layers, ink receptive coatings, and the like. Various adhesives have been used to bond graphic films to an object, including for example heat activated and pressure sensitive adhesives. Heat activated adhesives are typically non-tacky at room temperature but become tacky and capable of bonding to a substrate at elevated temperatures. These adhesives usually have a thermal transition glass transition temperature (T_g) or melting point (T_m) above room temperature.

The protective film may comprise various (e.g. pressure sensitive) adhesives such as natural or synthetic rubber-based pressure sensitive adhesives, acrylic pressure sensitive adhesives, vinyl alkyl ether pressure sensitive adhesives, silicone pressure sensitive adhesives, polyester pressure sensitive adhesives, polyamide pressure sensitive adhesives, poly-alpha-olefins, polyurethane pressure sensitive adhesives, and styrenic block copolymer based pressure sensitive adhesives. Pressure sensitive adhesives generally have a glass transition temperature of less than 25°C and have a storage modulus (E’) as can be measured by Dynamic Mechanical Analysis at room temperature (25°C) of less than 3 x 10⁶ dynes/cm at a frequency of 1 Hz.

The (e.g. pressure sensitive) adhesives may be organic solvent-based, a water-based emulsion, hot melt (e.g. such as described in US 6,294,249), as well as an actinic radiation (e.g. e-beam, ultraviolet) curable (e.g. pressure sensitive) adhesive.

Typically, the adhesive layer has a thickness of 10-200 micrometers. In some embodiments, the adhesive layer has a thickness of 10-100 micrometers or even 25-75 micrometers (1-3 mils).

In some embodiments, the protective layer described herein is provided on a thermoplastic substrate and is suitable for thermoforming.

Thermoforming is a manufacturing process in which a thermoplastic sheet (also referred to as a film) is heated to a temperature where it becomes soft and flexible. Then the sheet is pressed into and stretched over a mold using air (both vacuum and compressed) pressure. The thermoforming process is usually segmented into thin-gauge (typically less than 5 mm) and thick-gauge markets. Thin gauge thermoforming as the name implies uses thin plastics and is used to manufacture rigid or disposable packaging items such as plastic cups, food containers, lids, or blisters, while thick gauge thermoforming is typically used to form more durable cosmetic permanent parts such as vehicle door inside panels and electronics packaging. In some embodiments, vacuum forming may be used in combination with thermoforming, also known as dual vacuum thermoforming (DVT).

The most common thermoplastics used in thermoforming are acrylic (PMMA), acrylonitrile butadiene styrene (ABS), cellulose acetate, polyolefins such as low density polyethylene (LDPE), high density' polyethylene (HDPE), polypropylene (PP); polystyrene (PS), polyvinyl chloride (PVC), polyesters, and polyamides including nylons. All of these classes include polymers that can be melted, formed into films, and re-shaped via thermoforming into different forms.

Themiofomiable composite panels are thermoplastic materials — e.g. polypropylene (PP), nylon 6, polyetherimide (PEI), polyphenylenesulphide (PPS) — reinforced with some type of fiber, and then supplied to customers as solid sheets, which are then thermoformed into shaped structures.

The invention is illustrated by the following non-limiting examples: Table 1 Materials

Method for Determine Molecular Weight

The GPC equipment consisted of a 1260 Infinity II liquid chromatography system (comprised of isocratic pump, autosampler, column compartment and variable wavelength UV/vis detector) from Agilent Technologies (Santa Clara, CA) operated at a flow rate of 1 .0 mL/minute. The SEC column set was comprised of two PLgel 5 um MIXED-C (300 millimeter (mm) length x 7.5 mm internal diameter) and a PLgel 5 um guard column (50 millimeter (mm) length x 7.5 mm internal diameter) all from Agilent Technologies. The detection consisted of a miniDAWN 3 angle Light Scattering detector and an OPTILAB differential refractive index detector, both from Wyatt Technology Corporation (Santa Barbara, CA). The samples were prepared by dissolving the polymers in tetrahydrofuran at a 5.0 mg/mL concentration. The sample solutions were filtered through a 0.2 micron polytetrafluoroethylene filter (VWR International, West Chester, PA. USA). The resulting solution were injected into the GPC instrument and the data were collected and analyzed using software ASTRA version 8 from Wyatt Technology Corporation. The column compartment, UV/vis detector, and differential refractive index detector were set to 40 °C. The solvent and eluent (or mobile phase) consisted of tetrahydrofuran (stabilized with 250 parts per million of butylated hydroxytoluene) OMNISOLV grade from EMD Millipore Corporation, Burlington, MA. The relative molar mass data was determined from the DIR data and is reported relative to EasiCal PS-I PL2010- 0501 and PL2010-0505 polystyrene standards (PS) in the range of Mp = 580 to Mp= 2,403,000 g/mol from Agilent Technologies. The calibration curve was constructed in the ASTRA software, using all of the PS standards except for the Mp=6,570,000, owing to it being outside the upper molecular weight resolution limits of the columns.

Method for Determining Haze

Examples and Comparative Examples were measured by using a haze meter (obtained under the trade designation “haze-guard plus” from BYK). Optical properties were determined on as prepared samples (i.e., initial optical properties) and after subjecting the samples to steel wool abrasion resistance testing. The “Haze Test” is comparing the difference in haze values before and after the subjecting the samples to steel wool abrasion resistance testing.

Method for Determining Steel Wool Abrasion Resistance

Examples and Comparative Examples ware evaluated by the surface changes after the steel wool abrasion test using 3 cm diameter circular head with #0000 steel wool after 10 cycles at 1kg grams load and at 60 cycles/min. rate. The strokes were 85 mm long. The instrument used for the test was an abrasion tester (obtained under the trade designation “5800 HEAVY DUTY LINEAR ABRASER” from TABER INDUSTRIES). After the steel wool abrasion resistance test was completed, the samples were observed for the presence of scratches and their optical properties (percent transmittance, haze. A Haze or delta Haze (i.e., haze after abrasion test-initial haze) were measured again using the method described above.

Method for Determining Static Water Contact Angle

Static water contact angles of each sample were measured using a Rame-Hart goniometer (Rame-Hart Instrument Co., Succasunna, New Jersey). The static contact angle was measured from an optical photograph image after 2.0 microliter deionized water (H2O) was dropped on the surface via a steel syringe needle of 0.028” (0.71 mm) outer diameter into or out of sessile droplets. The measurement of the contact angles followed ASTM D7334-08 (reapproved 2022) with the following exceptions and specifications.

Method for Dirt Pick-up Resistance

First, the film to be evaluated is cut into 2 cm widths and laminated on a white painted steel plate. The a, b and L values of the surface are measured by Ci6X Handheld Spectrophotometer from X- Rite, Incorporated, and the initial E value is calculated by measured a, b and L values. The white plate with the film is placed on the side wall of the metal paint can with PVC tape. 49.5 g of sand (EMD Milipore Co. SX0070 CAS#14808-60-7), 0.1 ml brake fluid and 0.5 g contaminant (SDL ATLAS synthetic soil from SDL ATLAS) are added into the paint can. The paint can is tumbled with 80 rpm for 24 hours. The plate is removed and then the a, b and L values are measured and AE value is calculated as a performance of dirt pick up resistance. The plate is wiped 3 times by water-soaked cotton and then the a, b and L values are measured and AE value is calculated. Lower values indicate better dirt pick up resistance.

Method for Permanent Marker Cleanability

The cleanability is evaluated by using a black permanent marker under trade name “Sharpie” from Newell Office Brands, GO, USA), where a circle with a diameter of 30 mm is drawn. After 10 min the sharpie is wiped off with 50 g/cm² of presser by IPA soaked polyester wipers under trade name “Texwipe TX1009 from ITW Company, NC, USA.

Pass indicates that when wiped three times with an IPA soaked wiper, all the black permanent marker ink is removed when evaluated by visual inspection (i.e. without a microscope). Fail indicates that black permanent marker remains present.

Method for Determining Strctchabi litv

The film is cut into pieces having a width of 20 mm and a length of 60 mm. The pieces were fixed at 5 mm along the width from each edge, providing a testing area length of 50 mm. The film was elongated 150% by hand stretching at a rate of about 10 mm/sec (i.e. the film was stretched along it’s length from 50 mm to 125 mm).

Pass indicates that cracks or whiteness were not observed after elongation when evaluated by visual inspection. Fail indicates that cracks or whiteness were observed.

Dual Vacuum Thermoforming (DVT)

The PMMA films with a protective layer as described herein were applied to a 5 micron thick polycarbonate covered with a 3M colored graphic film. The films were thermoformed using the DVT method described in JP 2023-080776, filed June 8, 2023; incorporated herein by reference.

The conformability and weatherability of the protective layer was evaluated according to the following criteria: Pass indicates that cracks and color changing were not observed when visually inspected after the thermoforming process. Fails indicate that cracks, color change or film break were observed after .

Method for Determining Weather Resistance

Weather resistance is evaluated by an accelerated weathering test using Super Xenon Weather Meter SX75 from Suga Test Instruments Co., Ltd. with irradiation 180Wm-2, up to 750MJ accumulated energy of 300-400nm light (toPass about 1200 hours), using filter glass which cut under 300nm light. The 60 degree gloss, 20 degree gloss and E value of the samples before and after the accelerated test are measured using GMX-203 from MURAKAMI COLOR RESERCH LABOLATORY and Datacolor 600 from Datacolor International respectively. The measured values are used to calculate gloss retention and AE, which are used as evaluation indexes.

Table 2 - Comparatives Examples

The results show that PVC has high stretchability and a haze after steel wool abrasion of less than 10. PVC does not exhibit permanent marker cleanability or low dirt pick up (e.g. less than 10). PMMA coatings CE-2, CE-3, and CE-4 have low stretchability, yet exhibit permanent marker cleanability and low dirt pick up.

Preparation of methyl methacry late copolymer

Copolymer samples were prepared as follows. The % by weight of the components listed in the tables were charged to a (4 oz, 120 mL) Boston round glass heavy weight bottle in relative compositions found in the tables. The monomer concentration was 30% in either ethyl acetate or 90%/ 10% wt/wt. blend of ethyl acetate/isopropanol (if an alcohol monomer was used with a silane monomer) using 0.3% of Vazo 67 with respect to solids. The bottle was purged with nitrogen gas (1.2 liters per minute for 90 seconds) bubbling through the liquid, then sealed with a polytetrafluoroethylene lined metal cap. The cap was wrapped with electrical tape to secure it before placing the bottle in a safety cage with lid, using sponges to fill unoccupied space in the cage. Finally, the cage was secured with retaining bars in a water-filled launderometer tank at 70°C and agitated at 15 rpm. After approximately 22 hours, the bottle was removed from the launderometer. Coating solutions were produced by dilution of the polymer solutions by i : 1 wt/wt dilution using 85% MEK/15% methoxypropanol solvent to produce 15% wt/wt coating solutions.

The following examples were prepared using 8518 PVC substrate and 15 wt.% coating solutions, respectively. The coating solutions were applied to the substrate using Mayer Rod #22. After drying for 90 seconds at 60°C in air, the coated substrate was placed in an oven at 120°C for 10 minutes in air. The protective coating layer with thickness of approximately 5um on the PVC substrate was produced for each sample.

Table 3 - Comparatives Examples

Table 4 - Examples Table 5 - Examples

Coating solutions prepared same as above except 31 ,67g of 30% wt/wt polymer solutions produced above was combined with 6.0 g methoxypropanol, and 28.3 g MEK. The KBM3066 was added. The final amounts are described in Table 6.

Table 6 - Examples

Table 7 - Examples

Method for Determining Moisture Curing Crosslinking

6.0 grams of a polymer solution having 30 wt.% in ethyl acetate with and without 0.005 grams of XK-678 catalyst were weighed on an aluminum pan and the pan placed in an oven at 120°C for 16 hours to form a dry polymer.

The dry polymer was then placed in a glass jar in the prescribed amount and 10 g of ethyl acetate was added. The glass jar was closed and stirred at room temperature for an hour and then placed in an oven at 120^cC for 2 hours. The percent of undissolved polymer was then calculated from the weight of the polymer before dissolving in the solvent. The amount of polymer that remains undissolved is the amount of crosslinked polymer.

The previously described coating solutions were also applied to SOI 4G (PMMA) film.

Conformability of Thermoformed PMMA Films and Weather Resistance.

Claims

What is claimed is:

1. A method of malting a protective layer comprising providing a coating solution comprising an organic solvent and a copolymer comprising: at least 50 wt.% of polymerized units of methyl methacrylate;

2-20 wt.% of polymerized units of (meth)acrylate comonomer(s) wherein a homopolymer thereof has a Tg less than 90°C; and less than 5 wt.% of polymerized units of methacrylate monomer(s) comprising a -SiCOR^m group wherein R¹ is hydroxyl or a C1-C4 alkyl group and m ranges from 1-3; applying the coating solution to a substrate; and removing the organic solvent and moisture curing the -Si(OR‘)n group(s) of the copolymer.

2. The method of claim 1 wherein the copolymer is soluble in organic solvent prior to moisture curing.

3. The method of claims 1-2 wherein after moisture curing at 120°C for 16 hours, at least 25, 50, 75, or 90 wt.% of the copolymer is insoluble in a 20 wt.% copolymer solution of the organic solvent.

4. The method of claims 1-3 wherein the substrate is an organic polymer film or a release liner.

5. The method of claim 4 wherein after moisture curing the organic polymer film together with the protective layer can be stretched 150% at 23°C -without cracking.

6. The method of claim 5 wherein after moisture curing the copolymer at a thickness of 5 microns can be stretched 150% at 23 °C without cracking.

7. The method of claims 1-6 wherein the (meth)acrylate comonomer(s) comprise a linear or branched alkyl group comprising 1 -24 carbon atoms.

8. The method of claim 7 wherein the alkyl group further comprises a hydroxyl substituent.

9. The method of claims 1-8 wherein the methacrylate monomer(s) comprising a -Si(OR^!)m groups has the general structure: wherein

R¹ is hydrogen or C1-C4 alkyl, is Cl -Cl 2 alkyl, and

R ' is hydrogen or methyl, n ranges from 1-12, and m ranges from 1 to 3.

10. The method of claims 1-9 wherein the coating composition further comprises a polysiloxane having a (meth)acrylate group.

11 . The method of claims 1-10 wherein the moisture cured copolymer film has a haze after steel wool abrasion of no greater than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1%.

12. The method of claims 1-11 wherein the protective layer has one or more of the following properties: i) permanent marker removability: ii) dirt pick up of less than 10; iii) dirt pick up of less than 5 after wiping 3 times w’ith water; iv) a static water contact angle of at least 75, 80, 85, 90, 95, 100, or 105 degrees.

13. An article comprising: a substrate comprising a protective layer comprising a methyl methacrylate copolymer comprising: at least 50 wt.% of polymerized units of methyl methacrylate;

2-20 wt.% of polymerized units of (meth)acrylate comonomer(s) wherein a homopolymer thereof has a Tg less than 90°C; less than 5 wt.% of polymerized units of (meth)acrylate monomer(s) comprising at least one Si-0 group.

14. The article of claim 13 wherein the Si-0 group is a -SiCOR^m group wherein R is hydrogen or a Cl- C4 alkyl group and m ranges from 1-3.

15. The article of claims 13-14 wherein the Si-0 group is a polysiloxane.

16. The article of claims 13-15 further characterized by claims 2-12.

17. A methyl methacrylate copolymer comprising at least 50 wt.% of polymerized units of methyl methacrylate;

18. The methyl methacrylate copolymer of claim 17 further characterized by claims 2-12 and 15.

19. The method, article, or copolymer of the previous claims wherein the protective layer lacks fluorine atoms.

20. The method, article, or copolymer of the previous claims wherein the copolymer comprises less than 10 wt.% of polymerized units of acrylate comonomer and/or less than 10 wt.% of (meth)acrylate comonomers having a Tg less than 0°C.

21. The method, article, or copolymer of the previous claims wherein the copolymer comprises at least 80, 85 or 90 wt.% of polymerized units of methyl methacrylate

22. A method of use comprising: providing the article of claims 13-16 and thermoforming the article.

23. A thermoformed article ofc laims 13-16.