GB2312634A

GB2312634A - Making thermoformable laminates

Info

Publication number: GB2312634A
Application number: GB9708489A
Authority: GB
Inventors: Warella Racela Browall; Jr John S Rinaldi
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1996-05-02
Filing date: 1997-04-25
Publication date: 1997-11-05
Anticipated expiration: 2017-04-25
Also published as: DE19717433A1; FR2748276A1; GB2312634B; DE19717433B4; FR2748276B1; GB9708489D0; JP4246276B2; JPH1058531A

Description

2312634 60SI-1762 1 PROCESS FOR MAlaNG THERMOFORMABLE LAM W-ATES The

present invention relates to a process for producing thermaformable laminates comprising thermoplastic substrates and more particularly to thermoformable composite articles comprising a plurality of layers Wherein at least one layer is a hardcoat wherein the substrate 5 L; VUL 1 F isir said composite is a thermoplastic polymer.

LF1 M9 BackEEound of the Invention Multilayered thermoplastic larrunates formed from ermoplastc substrates have previously been produced by extruding or calendering these materials into thin sheets which are stacked and bonded by any of several cesses. Suitable thermoplastic materials found useful in producing such 10 laminates are, among others, ABS, polyvinyl chloride, acrylics, polycarbonates, polyolefins alloys and mixtures thereof.

One method employed to produce extruded products of the type described above comprises extruding a blend of a polycarbonate polymer, a polyethylene terephthalate and a non-acidic silica filler onto a moving is support such as a casting roll, to form an essentially non-oriented sheet. The roll may then be collected and thermoformed into a variety of useful shapes (U. S. Patent 4,107,251). Although these products may be quickly formed and inovely produced, they suffer, however, from poor abrasion resistance, poor weatherability and dull finishes generally caused by soft irregular 20 surfaces.

60SI-1762 2 In a further effort to overcome the disadvantage discussed above, attempts have been made, for example, to co-extrude an acrylic layer over a number of thermoplastic substrates (U. S. patent 4,100,237). Occasionally it is desirable to co-extrude polymers that are incompatible with one another such as a hydrocarbon polymer and ABS (U.S. patent 4,221,836). In this particular instance the problem of polymer incompatibility is solved by positioning an intermediate layer between the two incompatible polymers using a polymer that possesses a bonding factor and a melt viscosity intermediate between the two polymers being bonded.

This particular process suffers from some disadvantages, the most significant disadvantage being delarnination which has a tendency to accelerate in the presence of water. This tendency to delaminate in the presence of water leads to a poor weatherability. Further products manufactured using this technique are normally only manufactured in a small is variety of colors due to the effort and expense involved in changing the colors of materials utilized in a continuous extrusion line. This process has an additional disadvantage in that scrap materials can not be re-processed.

Various methods have thus been advanced to produce an integrated layer structure. U. S. patents 4,254,074 and 4,302,497 describe a product formed of a continuously cast sheet of a polymerized synthetic resin syrup that is integrally joined upon at least one side with a uniformly thick preformed film of polymerized resin. Consequently the fihn and the sheet are integrally joined to form a homogeneous product.

A different approach to laminated molded articles is demonstrated in U. S. patent 4,415,509 which coating an acrylic resin film onto the molding surface of a casting mold, introducing an acrylic monomer or partially polymerized acrylic product into the mold and then polymerizing the product. The film thus becomes integrated with and laminated upon the surface of the molded acrylic thermoplastic.

60SI-1762 Simultaneous coextrusion of two or more molten thermoplastics has resulted in the formation of laminates where the different thermoplastic materials inter diffuse at their interface creating a blended layer between the thermoplastic constituents (U.S. patent 4,415,519). These types of materials tend to be more resistant to delamination.

All of these approaches have tended to be unsatisfactory when used to produce laminates having desirable optical properties. For - example, polyacrylates and polycarbonates have found use as lightweight and durable lens materials for automobile headlamps and similar applications. However, the thermoplastics are soft and easily scratched and must additionally contain additives that stabilize the polymer against the degrading effects of the nvironment. Usually such optical materials are coated with a hardcoat to increase abrasion resistance and thus these formed thermoplastic optical articles are laminates and suffer from many of these same tlamination is problems.

Hardcoat compositions that have found particular use m coating polyacrylate and polycarbonate thermoplastic materials used for optical products have previously involved priming the thermoplastic substrate with a solution of an acrylic resin in a suitable solvent followed by applying a silicone hardcoat composition and thermally curing the laminate formed (U. S. patent 4,615,947). Monomeric hydroxy acrylates have been used to eliminate the priming composition and the step of applying a primer, however materials are not preferred because of their toxicity (ú patent 4, 486,504).

More recently it has been shown that it is possible to utilize a primerless silicone hardcoat composition that comprises a dispersion of an organic silicone containing phase with water and colloidal silica, a partial condensate of an organoalkoxysilane and an adhesion promoter selected from the group consisting of acrylated or methacrylated polyurethane and an acrylic copolymer (U.S. patent 5,503,935). Such a material yields a hardcoat 60SI-1762 4 having good primerless adhesion to thermoplastic substrates however such a primerless hardcoat works best if it is applied after the thermoplastic substrate is formed.

When coated thermoplastics are thermoformed, the coated or laminated thermoplastic frequently suffers from delan-dnation of the coating. In the case of optical laminates have been thermoformed another disadvantage may also occur, the formation of micro-cracks, i.e. n- ticrocrazing. A hardcoating on a thermoplastic substrate that has sufficiently good adhesion to withstand delamination usually is not flexible because it is hard io and thus when thermoformed, the coating tears microscopically, i.e. undergoing microcrazing, or alternatively it delaminates. This problem arises because thennoforming of thermoplastic polymers is both a convenient and rapid process for the manufacture of a wide variety of molded articles.

When optical properties such as clarity are not critical, one approach is has been to cast a polymerizable acrylic coating onto a sheet or laminate and thermally cure the coated laminate in several successive stages so that the coating is substantially polymerized (U.S. patent 4, 892,700). This process produces an additional layer between the coating and the substrate onto which the coating is applied, which is an interpenetration of the substrate by the coating. This apparently renders the coating more adherent to the substrate sheet or laminate enabling thermoforming without delamination.

Such an interpenetration layer has obvious problems when the coating to be applied and the substrate are optical materials. While there may be an acceptable match in optical properties such as clarity and refractive index, the interpenetration layer can be hazy. Alternatively if the interpenetration layer is clear it may possess the wrong refractive index, and thereby not possess desirable optical properties as an optical laminate.

60SI-1762 5 Summga of the Invention We now disclose a process for producing a therinoformable laminate comprising.

(a) depositing a hardcoat composition comprising an adhesion promoting compound selected from the group consisting of acrylated urethanes, methacrylated urethanes, and acrylic polyols onto a surface of a substrate comprising a thermoplastic thereby (b) forming a laminate; and (c) partially curing said laminate in one stage wherein no substantial trati n of said hardcoat into said substrate occurs.

We also disclose that the thermoformable laminate so produced may be simultaneously thermoformed and cured.

A preferred process is a process for producing a thermoformable laminate comprising:

(a) depositing a curable hardcoat composition comprising an adhesion promoting compound selected from the group consisting of acrylated urethanes, methacrylated urethanes, and acrylic polyols onto a surface of a substrate comprising a thermoplastic thereby (b) forming a laminate; and (c) partially curing said laminate in one stage at a temperature ranging from about 55 OC to about 105 oC wherein no substantial interpenetration of said hardcoat into said substrate occurs.

A more preferred process is a process for producing a thermoformable laminate comprising (a) depositing a curable hardcoat composition comprising an adhesion promoting compound selected from the group consisting of acrylated urethanes, methacrylated urethanes, and acrylic polyols onto a surface of a substrate comprising a thermoplastic thereby 60SI-1762 6 (b) forming a laminate; and (c) partially curing said laminate in one stage at a temperature ranging from about 55 OC to about 105 OC for a time ranging from about 5 minutes to about 30 minutes wherein no substantial interpenetration of said hardcoat into said s substrate occurs.

Detailed Description of the Invention

The present invention relates to a therinoforn-ting process whereby a single homogeneous thermoplastic substrate or a laminated substrate comprising thermoplastic materials is coated with a thermally curable hardcoat which is then partially cured and subsequently shaped by thermoforn-ting which simultaneously accomplishes the final cure of the hardcoat applied to the substrate. The substrate may comprise any of several thermoplastic polymers known in the art, for example, acrylonitrilebutadienestyrene (ABS), polyvinylchloride (PVC), polymethyhnethacrylate (P), polycarbonate, acrylates, polybutylene is terephthalate, polyethylene terephthalate, polyesters, polyethylene, polypropylene, polystyrene, polyolefins and the like. The thermoplastic substrates employed may be flexible or rigid depending on the ultimate application intended.

The process of the present invention is made possible by a particular coating composition. The coating compositions of the present invention comprise:

1) from about 20 parts by weight to about 30 parts by weight of an alkyl trialkoxy silane; 2) from about 0 parts by weight to about 10 parts by weight of a dialkyl dialkoxy silane, when the dialkyl dialkoxy silane is absent a primer will generally be required, when present, from about 2 to about 5 parts by weight of the dialkyl dialkoxy silane is preferred; 60SI-1762 7 3) from about 10 parts by weight to about 30 parts by weight-of an aqueous dispersion of colloidal silica where the solids level of the colloidal silica dispersion ranges from about 5 weight percent to about 50 weight percent and the particle size of the colloidal silica particles ranges from about s 4 nanometers to about 40 nanometers, preferably 4 nanometers to 30 nanometers and most preferably 4 nanometers to 24 nanometers; 4) from about 20 parts by weight to about 30 parts by weight of an alcohol having an odd number of carbon atoms and fewer than ten carbon atoms; 5) from about 20 parts by weight to about 30 parts by weight of an alcohol having an even number of carbon atoms and fewer than ten carbon atoms; 6) from about 1 part by weight to about 10 parts by weight of an ultraviolet stabilizing compound; and 7) from about 0.1 part by weight to about 10 parts by weight of an adhesion promoting compound.

This composition may additionally comprise other additives and compounds such as free radical initiators, antioxidants, dyes, flow modifiers, leveling agents, surface lubricants as well as additional quantities of alcohols, glycols, ethers, reactive silane species such as methyltrichloro, and hydrogen ion concentration adjusting compounds such as acids or bases. e. g. hydrochloric acid.. acetic acid and the like as acids and sodium hydroxide, potassium hydroxide, and ammonium hydroxide as bases.

The alkyl trialkoxy silane has the general formula:

RA(R80)35i while the dialkyl dialkoxy silane has the formula:

Rci(RDO)2Si.

The radicals RAP RB,, Rc and RD are hydrocarbon radicals that are each independently selected from the group of monovalent hydrocarbon radicals 60SI-1762 8 having from one to forty carbon atoms. Generally these radicals will be alkyl in nature, and when they are alkyl the more preferred radicals are radicals having a small number of carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isc>-butyl and the like, with methyl being most preferred. The radicals may also be alkaryl or aryl. When the radicals contain an aryl or alkaryl group the preferred radicals are phenyl, benzyl, phenethyl, and naphthyl, with phenyl being the most preferred.

While the radicals may be independently selected, generally RA and RB will be identical and Rc and RD will be identical. A particularly convenient io formulation is present when all four radicals, RA, RB,, Rc and RD are all identical. When RA, RB,, Rc and RD are all identical, a preferred radical is methyl.

The colloidal silica dispersion is an aqueous dispersion of colloidal silica having a solids content ranging from about 5 weight percent to about 50 is weight percent silica with the size of the colloidal silica particles dispersed therein ranging from about 4 nanometers to about 40 nanometers. It is preferable to use colloidal silica dispersions having a solids content ranging from about 5 to about 50 weight percent silica. It is also preferred that the size range of the silica particles dispersed as a colloid in the dispersion have a size ranging from about 5 nanometers to about 40 nanometers. U. S. patent 3, 986,997 also describes colloidal silica preparation useful in the practice of the present invention. Other finely divided oxides that may be employed with the colloidal silica or as a partial replacement for the colloidal silica include titanium dioxide (rutile, anatase or brookite), alun-dnum oxide (cty, or cerium oxide and antimony oxide.

Because it may be necessary to stabilize a colloidal silica dispersion with acids or bases, it may be necessary to adjust the pH of the hardcoat solution after the silica dispersion is incorporated therein. Generally a pH in the range of about 3 to about 8 is preferred and depending on the ingredients 60SI-1762 9 chosen and their proportions it may be necessary to add small quantities of acid or base to adjust the pH. Depending on the chemical sensitivities of the specific compounds employed, mineral acids may be used for pH adjustment if the compounds employed are not particularly susceptible to side reactions s catalyzed by strong acids otherwise weak acids such as acetic acid may be used. Likewise either strong bases such as sodium or potassium hydroxide may be used if the pH is too low unless the compounds are particularly susceptible to strongly alkaline bases in which case weaker bases such as ammonium hydroxide and the like may be employed. Since there are io teachings indicating that strongly alkaline bases may catalyze nuicrocrazing, the mono, di, tri, and tetra-alkyl ammonium hydroxides are the preferred bases for increasing the pH of the hardcoat solution. Additionally, tetra-alkyl ammonium salts, particularly tetra-n-butyl ammonium acetate catalyze an acceleration in the curing time of the hardcoat (US. patent 4,863,520).

is The solvents used as the basis of the formulation are low molecular weight alcohols, one being an alcohol having an odd number of carbon atoms and the other being an alcohol having an even number of carbon atoms. Thus a preferred alcohol nuixture useful as the solvent medium for the hardcoat compositions that enable the process of the present invention is a mixture of iso-propanol and n-butanol.

Since thermoplastics suffer from the degradative effects of ultraviolet radiation it is useful to add ultraviolet stabilizing compounds that are compatible with the compounds used in forming the hardcoat. A wide variety of ultraviolet stabilizing compounds useful for stabilizing polymers against the degrading effects of ultraviolet radiation are known in the art and may be incorporated into the compositions of the present invention to stabilize the compositions against the degrading effects of ultraviolet radiation (U. S. patents 4,278,804; 4,374,674; 4,419,405; 4, 299,746;4,495,360, and 4,525,425). Those ultraviolet stabilizing compounds or compositions taught 60SI-1762 10 by the prior art would be expected to function in a similar fashion in the compositions of the present invention provided they are soluble or miscible and further provided that there is no unwanted reactions of these stabilizing compounds or compositions with the other components of the composition. s Preferred ultraviolet stabilizing compounds are selected from the group consisting of

0 OH OH; 0 OH OCH3.

0 OH 0C8H17.

0 OH 0C12H23 0 OH 0 60SI-1762 0 OH 0C2H5 0 i - OCH3 OCH3 0 OH 0C2H5 SI-OC2H5 i 0C2H5 0 OH 0 0 OH CH3(CHCHD.CH3 0 with n such that the molecular weight is between 40,000 and 60,000; 2,4 -di-hydroxybenzophenone; a polybenzoylresorcinol having the formula:

60SI-1762 12 0 OH Al'I'5 1 R OH 0 where each A is independently a substituted or unsubstituted monocyclic or polycyclic aromatic radical, where the substituted monocyclic or polycyclic aromatic radical has substituents selected from the group consisting of hydrogen, halogens, alkoxy groups and one to 8 carbon alkyl groups and hydroxy groups with R either hydrogen or a one to ten carbon atom alkyl group; a polybenzoylresorcinol having the formula: 0 OH 0 AJ A OH I] At 0 where each A is independently a substituted' or unsubstituted monocyclic or polycyclic aromatic radical, where the io substituted monocyclic or polycyclic aromatic radical has substituents selected from the group consisting of hydrogen, halogens, alkoxy groups, one to 8 carbon alkyl groups and hydroxy groups; a sfiylated resorcinol having the formula: 0 OH RISi(OR2b OH R 0 where each R is independently a substituted or i s unsubstituted monocyclic or polycyclic radical, R' is carbon or a linear 60SI-1762 13 branched aliphatic chain having less than about ten carbon atoms and R2 is one to six carbon alkyl group; R4 0 11 R4 Rs-C-O-C N-OR3 R4 R4 where R3 is a four to twelve carbonatom alkyl group, each R4 is independently a one to five carbon atom alkyl group and R5 is a four to twelve carbon alkylene group; a bis-alkylene cyano-acrylate ester having the formula:

0 0 NC R7-A2-R7 W NX, 0 / \ 0,,c R6 6 J U J 0 where A' is a monocyclic or polycylcic cyclo-alkylene radical, each A2 is independently a substituted or unsubstituted aromatic radical, each R6 is independently a one to five carbon atom alkyl group, and each R7 is independently a one to four carbon atom alkylene group.

An essential component of the composition of the present invention is an adhesion promoter selected from the group consisting of acrylated urethanes, methacrylated urethanes and acrylic polyols.

is Acrylated and methacrylated urethanes, as used herein, refer to acrylated or methacrylated polyurethanes having an average molecular weight ranging from about 400 to about 1500. Specific useful acrylated urethanes are Actilane CB-32T" available from SNPE Chimie Co. of France, Ebecryl 8804Tm available from Radcure Specialties, Inc. Of Louisyfile, 20 Kentucky, and M-407m,a methacrylated urethane, available from Echo Resins 60SI-1762 14 & Laboratory of Versailles, Missouri. M-4071m is an adduct of isophorone diisocyanate and 2-hydroxymethyl methacrylate having a molecular weight of approximately 482.

Acrylic polyols, as used herein, are complex mixtures of polymerized and polymerizable acrylate species comprising:

1) from about 90 to about 99 weight percent of a styrene acrylic polymer; 2) from about 0.5 to about 5.0 weight percent of an ether ester, usually a glycol ether ester such as glycol ether acetate; 3) from about 0.1 to about 2.0 weight percent of a reactive site monorner selected from the group consisting. of dimethylamino, ethylmethacrylate, acrylic acid, butoxy methylacrylan-dde, glycidyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, N-methylol acrylamide, acetoacetoxyethyl methacrylate, acrylamide, 2-hydroxypropyl methacrylate, is and 2-hydroxypropyl acrylate, with hydroxyethyl methacrylate being a preferred species; 4) from about 0.05 to about 1.5 weight percent of a coating flexibilizing acrylate ester selected from the group consisting of ethyl acrylate, 2ethylhexyl acrylate, butyl acrylate, and methyl acrylate with methyl methacrylate being a preferred species; and 5) from about 0.05 to about 3.0 weight percent of a copolymerizable olefinic monomer such as styrene. The acrylic polyol may be considered to be an acrylic copolymer having hydroxyl functionalities in the range 30 to 160 per molecule, a number average molecular weight varying from about 1,000 to about 10,000 and an acid number of about 4 or less.

The acrylic polyol composition as used herein is preferably used in a range from about 0.25 to about 5.0 weight percent of the total coating composition. Commercially available acrylic polyol composition are sold by 60SI-1762 is S. C. johnson Wax of Racine, Wisconsin and are available under the tradenames of joncryl 500, 510, 587, 588, 901 and 906Tm.

The hardcoat composition of the present invention is then applied to the thermoplastic substrate of interest. The coating composition can be applied onto the substrate by any of several well-known methods such as sprayin& dipping, roll coating and the like. The hardcoat may also be applied by any of the several techniques as disclosed and taught in U. 5. patent 4,892,700. The substrate may be a single homogeneous phase of thermoplastic material or alternatively it may comprise a plurality of laminae one of which is a thermoplastic material. Suitable thermoplastic substrates include, but are not limited to, acrylic polymers including poly(methyl methacrylate), polyesters including poly(ethylene terephthalate), polycarbonates, polyamides, polyin-ddes, acrylonitrile-styrene copolymers, styrene acrylonitrile-butadiene copolymers, polyvinyl chloride, polystyrene, is polyphenylene ethers, polyphenylene sulfides, butyrates, polyethylene and other polyolefl= including crystalline polypropylene and crystalline syndiotactic polypropylene and the like.

Having been deposited on the substrate, the hardcoat is partially cured at temperatures ranging from about 55 to about 105 IC-, preferably from about 60 to about 100 OC, more preferably from about 80 to about 90 oC, and most preferably from about 80 to about 85 OC, for a time period ranging from about to about 30 minutes preferably from about 10 to about 25 minutes and more preferably from about 20 to about 22 minutes. By partial cure, Applicants define a process of polymerization or curing that ha been initiated or 9 but not completed or finally cured. Because the hardcoating composition of the process of the instant invention cures via thermal techniques, the extent of partial cure is operationally defined primarily by emperature ranges whereby the partial cure is achieved and secondarily defined by time of curing within a particular temperature range. Thus a partial cure process is a 60SI-1762 16 curing process conducted at a particular temperature for a particular time that does not produce a fully cured composition. This is generally accomplished by the application of heat since the compositions of the present invention are thermally cured. However, it is also possible to cure the compositions of the present invention by the use of infrared or microwave energy. The partially cured hardcoat affixes itself to the substrate in a more or less permanent fashion, allowing for a convenient intermediate storage of the partially cured hardcoated substrate until it is desired to shape the material by any of several therinoforming processes known in the art. Only one partial cure step is necessary The subsequent thermoforming step not only shapes the resulting thermoplastic laminate, but also completes the curing process begun in the step of partial curing.

The hardcoat applied to the substrate forms a distinct layer on an is exterior surface of the substrate or the laminate comprising the substrate thereby adding an additional layer to the material and rendering the material a laminate comprised of at least one thermoplastic lamina and a hardcoat. In contrast to other coating processes that form an interpenetration layer between the hardcoat and the lamina of the substrate to which the hardcoat is applied, the instant composition and process do not substantially form such an interpenetration layer, either as applied or upon subsequent thermoforming. As used in the previous sentence, the word substantially means that no interpenetration layer is detected by optical or electron microscopy up to a magnification factor of about 20,000.

The hardcoating may have a thickness ranging from about 0.05 to about 1.00 n-ffis thick, preferably from about 0.10 to about 0.50 mils thick, more preferably from about 0.10 to about 0.40 mils thick and most preferably from about 0.10 to about 0.20 mils thick.

60SI-1762 17 In the practice of the present invention it may be desirable to utilize a priming composition in order to improve the adherent properties of the hardcoat to the primer and in turn those of the primer to the substrate. As broadly conceived the process of the present invention is operable with or 5 without a primer as an intermediate layer or lamina between the hardcoat to and the substrate.

The substrate, which may be a homogeneous thermoplastic lamina or which may be a laminate comprising a plurality of laminae one of which laminae is a thermoplastic may vary in thickness from about 2 to about 5M mils thick, preferably from about 2 to about 250 mils, thick, more preferably from about 5 to about 190 mils, thick and most preferably from about 10 to about 125 mils thick.

A preferred embodhnent of the process of the instant invention consists of applying a partially curable hardcoat composition to a substrate is comprising a thermoplastic wherein the substrate is a sheet material. f9 a laminate by such application and partially curing the hardcoat producing a thennoformable hardcoated sheet. The thermoformable hardcoated -sheet may subsequently be simultaneously thermoformed and cured.

All United States patents referenced herein are herewith and hereby specifically incorporated by reference EMerimental The following examples are presented to illustrate the invention and are not to be construed as limiting the appended claims.

The following hardcoat compositions, as shown in Table 1, were evaluated for their suitability in the process of the present invention.

60SI-1762 18 Table 1: Hardcoat ComRositions Composition: I II III Component, WL% Methyl- 25.0 24.11 23.81 trimethoxy silane dimethyl- 0.0 2.63 2.60 dimethoxy silane Aqueous silica sol 15.01 18.012 17.762 n-butyl alcohol 26.0 24.32 24.06 i-propyl alcohol 26.0 24.32 24.06 acetic acid 0.17 0.24 1.40 ultra-violet 2-24 2.71 2.68 stabilizer methanol 2.00 2.43 2.40 flow control 0.10 0.05.05 additive tetra-butyl 0.15 0.16 0.16 ammonium acetate acrylic poly013 0.00 1.03 1.01 Notes:

1. Ludox AS-Wm 2. Nalcoag 2326Tm 3. Joncryl 587m The hardcoat formulations listed in Table 1 were applied to polycarbonate and polymethylmethacrylate sheets as the thermoplastic substrate. The hardcoats were applied both with and without the application of an intermediate primer layer. The primer utilized had a composition of 2-0 parts per hundred by weight (weight percent) polymethylinethacrylate and 0.5 parts per hundred by weight (weight percent) of Uvinol N-539 ultraviolet stabilizer dissolved in 97.5 parts per hundred by weight of a solvent consisting of 85 weight percent methoxy propylene glycol and 15 weight percent diacetone alcohol. When used, the primer was applied to the sheets and allowed to air dry before application of the hardcoat. The hardcoat was is applied to theprimed or unprimed sheets and partially cured in one step. Subsequently, the hardcoated sheets were drape thermoformed. Drape 60SI-1762 19 therrnoforming is a process wherein a thermoplastic material is brought into contact with a positive shaped surface, heated and allowed to flow and reshape to conform to the positive surface and then cooled. Alternatively drape thermoforming involves heating a thermoplastic, contacting the material with s a positive surface, allowing the material to flow and conform to the positive surface and then cooled. Drape thermoforming may be assisted by applying a differential pressure either by using an overpressure or a vacuum to accelerate the shaping process. All of the materials were drape thermoformed over a cylinder having a 1.25 inch radius of curvature. The resultant thennoformed hardcoated thermoplastic laminae were then evaluated for adherence of the hardcoat to the substrate and the occurrence of microcrazing. The results are summarized in Table 2. The sheets used varied in thickness form 1/ 16 inch to 3/16 inch thickness ( 62.5 to 187. 5 mils).

60SI-1762 20 Table 2. Thermoforming of Partially Cured Hardcoat ThermoRlastic Sheet Hardcoat I II HI Substrate Primed Substrate polycarbonate; polycarbonate; polycarbonate; adherent adherent adherent hardcoat, no hardcoat, no hardcoat, no n-dcrocrazing microcrazing microcrazing Unprimed polycarbonate; polycarbonate; polycarbonate; Substrate non-adherent adherent adherent hardcoat hardcoat, no hardcoat, no microcrazing microcrazing polymethyl methacrylate; adherent hardcoat, no microcrazing The results displayed in Table 2 indicate that a hardcoating composition containing an adhesion promoter partially cures in one step to form a hardcoat that can be simultaneously cured and thermoformed. When the hardcoat composition does not contain an adhesion promoter, a primer appears necessary. When the hardcoat is applied to a primed substrate comprising a thermoplastic, a partial cure accomplished in one step leads to a hardcoat that can be subsequently cured and thermoformed simultaneously as evidenced by the drape thermoforming experiments reported in Table 2.

60SI-1762 21

Claims

Claims

I. A process for producing a thermofon-nable laminate consisting essentially Of..
(a) depositing a hardcoat composition comprising an adhesion promoting compound selected from the group consisting of acrylated urees, methacrylated urethanes, and acrylic polyols onto a substrate comprising a thermoplastic thereby (b) forming a laminate; and (c) partially curing said laminate in one stage wherein no substantial interpenetration of said hardcoat into said substrate occurs.

21 The process of claim 1 additionally comprising simultaneously thermoforming and curing said laminate.
3. The process of dahn 2 wherein said substrate comprises polycarbonate.
4. The process of claim 2 wherein said substrate con polymethylmethacrylate.
5. The process of claim 3 wherein said adhesion promoter comprises an acrylic polyol.
6. The process of claim 4 wherein said adhesion promoter comprises an acrylic polyol.
7. A process for producing a thermoformable laminate comprising.

(a) depositing a hardcoat composition comprising an adhesion promoting compound selected from the group consisting of acrylated urethanes, methacrylated urethanes, and acrylic polyols onto a surface of a substrate comprising a thermoplastic thereby (b) forming a laminate; and (c) py curing said laminate in one stage wherein no substantial interpenetration of said hardcoat into said substrate occurs.

60SI-1762 22
8. The process of claim 7 additionally comprising simultaneously thermoforming and curing said laminate.
9. The process of claim 8 wherein said substrate comprises polycarbonate.
10. The process of claim 8 wherein said substrate comprises polymethylmethacrylate.
11. The process of claim 9 wherein said adhesion promoter comprises an acrylic polyol.
12. The process of claim 10 wherein said adhesion promoter comprises an acrylic polyol.
13. In a process for producing a laminate comprising preparing an acrylic composition comprising an acrylic monomer, depositing said acrylic composition onto a surface of a substrate comprising a thermoplastic, and curing said acrylic composition, the improvement comprising partially curing said acrylic composition in one step wherein said acrylic composition is a hardcoat composition wherein no substantial interpenetration of said hardcoat into said substrate occurs.
14. The process of claim 13 additionally comprising simultaneously thermoforming and curing said laminate.
15. The process of claim 14 wherein said substrate comprises polycarbonate.
16. The process of claim 14 wherein said substrate comprises polymethylmethacrylate.
17. The process of claim 15 wherein said adhesion promoter comprises an acrylic polyol.
18. The process of claim 16 wherein said adhesion promoter comprises an acrylic polyol.
19. The process of claim 11 wherein said hardcoat composition additionally comprises an ultraviolet stabilizer compound.
20. The process of claim 12 wherein said hardcoat composition additionally comprises an ultraviolet stabilizer compound.