FR2748276A1 - METHOD FOR MANUFACTURING HOT-FORMED LAMINATE LAMINATES - Google Patents

Abstract

Disclosed is a method of making hot-workable laminates, which comprises spreading a hard coating composition on a thermoplastic substrate, which may be a laminate consisting of several layers, and partially curing the coating. , in one step. Such a laminate can then be simultaneously cured and hot shaped, resulting in a hard, adherent coating which does not exhibit microcracks and has virtually no penetration into the substrate.

Description

METHOD FOR MANUFACTURING HOT-FORMED LAMINATE LAMINATES

  The present invention relates to a method for producing heat-moldable laminates comprising thermoplastic substrates, and more particularly to hot-formed composite articles having a plurality of layers, wherein at least one layer constitutes a hard coating and the substrate of said composite is in one

thermoplastic polymer.

  Heretofore, thermoplastic multilayer laminates formed from thermoplastic substrates have been produced by extrusion or calendering of these thin sheet materials which are stacked and glued together by one of the processes of which we have to do this. Suitable thermoplastic materials which can be used to produce such laminates are, inter alia, ABS, polyvinyl chloride, acrylic resins, polycarbonates and polyolefins, and the like.

  as alloys and mixtures of these materials.

  One of the methods used to obtain extruded products of the type described above is to extrude a mixture consisting of a polycarbonate type polymer, a poly (ethylene terephthalate) and a feedstock which is non-acidic silica, on a mobile support such as a roll of

  cast, to obtain a virtually unoriented sheet.

  The roll can then be recovered and shaped hot to give it various useful shapes (U.S. Patent No. 4,107,251). These products can be obtained quickly and inexpensively, but they suffer from poor abrasion resistance and poor weatherability, and have a dull final appearance, usually due to soft and irregular surfaces. In order to overcome the disadvantages mentioned above, attempts have been made, for example, to coextrude an acrylic resin layer over various thermoplastic substrates (U.S. Patent No. 4,100,237). It may be desirable, on occasion, to coextrude polymers that are incompatible with each other, such as a hydrocarbon polymer and ABS (U.S. Patent No. 4,221,836). In this particular case, the problem posed by the incompatibility of the two polymers is solved by placing between these two incompatible polymers an intermediate layer consisting of a polymer which has a bonding factor and a melt viscosity intermediate between those of the two polymers that we want

stick together.

  But this particular process suffers from some disadvantages. The most important disadvantage is delamination, which tends to accelerate in the presence of water. This tendency to delaminate in the presence of water causes poor resistance to atmospheric agents. Moreover, by using this technique, one can usually produce products in a small palette of colors, because of the work and costs involved in changing the colors of the materials used in a plant. extrusion operating continuously. This process has the additional disadvantage that the fact that

  can not reprocess discarded materials.

  Various methods have been proposed for obtaining a structure where several layers are integrated. U.S. Patent Nos. 4,254,074 and 4,302,497 disclose a product consisting of a continuously poured polymeric synthetic resin sheet which is adhered in one piece by at least one of its members. sides, to a polymeric resin film of regular thickness and formed beforehand. Therefore, the film and the sheet, glued in one piece, form a homogeneous product. A different approach for making laminated molded articles is provided in U.S. Patent No. 4,415,509; it consists in spreading an acrylic resin film on the molding surface of a casting mold, introducing into this mold an acrylic monomer or a partially polymerized acrylic compound, which is then polymerized to obtain the desired product. The film then integrates very well with the molded article in thermoplastic acrylic resin, forming a layer on the surface of

this one.

  Coextrusion or simultaneous extrusion of two or more molten thermoplastics leads to the formation of laminates where the different thermoplastics diffuse into one another at their interface, giving a mixed layer between the thermoplastic constituents ( U.S. Patent No. 4,415,519). The materials

  of this type tend to be more resistant to delamination.

  However, none of these approaches have given satisfactory results when attempts have been made to implement them to obtain laminates having certain desirable optical properties. For example, polyacrylates and polycarbonates have been used as lightweight and durable materials for automotive headlamps and in similar applications. But thermoplastics are soft and easy to scratch, and they must also contain adjuvants that stabilize the material.

  polymer with respect to the adverse effects of the environment.

  Usually, these optical materials are coated with a hard layer which increases their resistance to abrasion, and therefore the optical parts thus made of thermoplastics are laminates and suffer

  often delamination problems.

  Hitherto, cured coatings have been obtained, used in particular for coating polyacrylate or polycarbonate thermoplastics used in optical parts by first spreading a solution of an acrylic resin in a solvent on the thermoplastic substrate. then applying a curable silicone coating composition and then curing the formed laminate,

  under the action of heat (U.S. Patent No. 4,615,947).

  It has been proposed to use hydroxyacrylate type monomers in order to be able to dispense with the primer composition and to skip the application of a primer, but it is preferable to dispense with the use of these materials.

  because of their toxicity (U.S. Patent No. 4,486,504).

  More recently, it has been shown that it is possible to employ a curable silicone-based curable composition usable without primer, which composition contains an aqueous dispersion of a phase containing an organic silicone, as well as colloidal silica, a partial condensation product of an organoalkoxysilane, and an adhesion promoter selected from the group consisting of acrylic copolymers and polyurethanes bearing

  acrylate or methacrylate groups (U.S. Patent No. 5,503,935).

  Such a material provides a cured coating which has, even in the absence of primer, good adhesion to thermoplastic substrates, but such a cured coating usable without primer better plays its role if it is applied after having shaped the substrate thermoplastic. But when a form is given, under the action of heat, coated thermoplastics, it often happens that the coating of this coated or laminated thermoplastic material peels off delamination. In the case of hot-formed optical laminates, another disadvantage may also arise, namely the formation of microcracks. On a thermoplastic substrate, a cured coating that has good adhesion to resist delamination is usually not flexible because it is hard. Therefore, when such a material is shaped hot, microscopic tears appear in the coating, that is, it undergoes a microcracking, and it can also peel off the substrate. This is a problem because hot forming of thermoplastic polymers is a convenient and fast process for making parts.

moldings very diverse.

  If it is not important that the products obtained be provided with optical properties such as transparency, it is possible to cast a coating of polymerizable acrylic material on a sheet or laminate and heat-cure the coated laminate. , in several successive steps, so as to substantially polymerize the coating (US Patent No. 4,892,700). In this process, an additional layer is formed between the coating and the substrate on which the coating is applied, wherein the substrate and the coating penetrate into each other. This apparently allows the coating to better adhere to the substrate that constitutes the sheet or laminate, and therefore, to undergo a hot shaping without detaching from the substrate. But this interpenetration layer obviously poses problems when the applied coating and the substrate are optical materials. An acceptable compromise between optical properties such as transparency and refractive index can be achieved, but this interpenetration layer can be cloudy. On the other hand, if this interpenetration layer is transparent, it may have a poor refractive index and therefore not have the optical properties desirable for an optical laminate. The present invention relates to a method for producing a heat-formable laminate, which method comprises: (a) depositing, on a surface of a substrate comprising a thermoplastic material, a hard coating composition comprising a compound promoting the membership

  selected from the group consisting of urethanes

  acrylates, urethanes-methacrylates and acrylic polyols, (b) thereby forming a laminate, and (c) partially curing said laminate in a single step, with substantially no interpenetration occurring between said hard coating and said substrate. The heat-formable laminate thus produced can be

  simultaneously shaped hot and hardened.

  A preferred embodiment of the method of the invention is a method for producing a hot-workable laminate, which method comprises: (a) depositing, on a surface of a substrate comprising a thermoplastic material, a curable hard coating composition comprising an adhesion promoting compound selected from the group consisting of urethane acrylates, urethane methacrylates and acrylic polyols, (b) thereby forming a laminate, and (c) the partially curing this laminate in a single step, at a temperature of about 55 to about 105 C, with virtually no interpenetration occurring between said hard coating and said

substrate.

  An even more preferred embodiment of the method of the invention is a method for producing a hot-workable laminate, which method comprises: (a) depositing, on a surface of a substrate comprising a thermoplastic material a curable hard coating composition comprising an adhesion promoting compound selected from the group consisting of urethane acrylates, urethane methacrylates and acrylic polyols, (b) thereby forming a laminate, and (c) ) partially curing this laminate in a single step, at a temperature of about 55 to about 105 C for a period of about 5 minutes to about 30 minutes, virtually no interpenetration then occurring between said coating hard and said substrate. The present invention therefore relates to a hot forming process in which a heat-curable coating layer is spread on a simple and homogeneous thermoplastic substrate or on a laminated substrate comprising thermoplastic materials, the assembly is then partially cured, and it is subsequently shaped hot, while at the same time effecting the final hardening of the layer of coating spread over the

substrate.

  The substrate may be any of the many thermoplastic polymers known in the art, for example acrylonitrile / butadiene / styrene (ABS), polyvinyl chloride (PVC), poly (methyl methacrylate) (PMMA), polycarbonate, polyacrylate, poly (butylene terephthalate), poly (ethylene terephthalate), polyesters, polyethylene, polypropylene, polystyrene, polyolefins, etc. The thermoplastic substrates used can be flexible or rigid, depending on the final application

considered.

  What makes the process of this

  invention is a particular coating composition.

  The coating compositions used in the present invention contain: 1) from about 20 parts by weight to about 30 parts by weight of an alkyl-trialkoxysilane, 2) from about 0 parts by weight to about 10 parts by weight a dialkyl-dialkoxy-silane (if there is no dialkyl-dialkoxy-silane, a primary is usually used, if there is, it is preferable that there be some 2 to about 5 parts by weight), 3) from about 10 parts by weight to about 30 parts by weight of an aqueous dispersion of colloidal silica, the solids content of which is from about 5% by weight to about 50% by weight and the size of the colloidal silica particles is from about 4 nm to about 40 nm, preferably from 4 to 30 nm and more preferably from 4 to 24 nm, 4) from about 20 parts by weight to about 30 parts by weight of an alcohol the molecule of which contains an odd number of carbon atoms and less than ten), from about 20 parts by weight to about 30 parts by weight parts by weight of an alcohol whose molecule contains a number of carbon atoms even and less than ten, 6) from about 1 part by weight to about 10 parts by weight of an anti-UV stabilizer, and 7) from about 0.1 parts by weight to about 10 parts by weight

  weight of an adhesion promoting compound.

  This composition may further contain other adjuvants and compounds, such as free radical initiators, antioxidants, dyes, flow modifiers, leveling agents, surface lubricants, as well as alcohol supplements, glycols and the like. ethers, reactive silanes such as methyltrichlorosilane, and compounds for adjusting the concentration of hydrogen ions, i.e., acids or bases, for example hydrochloric acid, acetic acid or other acids, or sodium hydroxide, hydroxide

  of potassium, ammonium hydroxide or other bases.

  The alkyl-trialkoxysilane discussed above has the general formula: RA (RB 0) 3 Si and the dialkyl-dialkoxy-silane discussed above has the general formula: RCz (RDO> 2 The groups represented by RA, RB, Rc and RD are selected hydrocarbon groups, each independently of the others, in the group consisting of monovalent hydrocarbon groups having 1 to 40 carbon atoms. alkyl, and if so, the preferred alkyl groups are those which have a small number of carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, etc., with a These groups may also be aryl, aralkyl or alkaryl groups, in which case phenyl, benzyl, phenethyl and naphthyl groups are preferred, with particular preference being given to the phenyl group. each is independent of the others, but in general, RA and RB are identical, as are Rc and RD. Moreover, a particularly advantageous formulation is obtained when the four groups symbolized by RA, RB, Rc and RD are all identical, and if

  this is the case, it is preferred that it be methyl groups.

  The colloidal silica dispersion referred to above is an aqueous dispersion of colloidal silica whose solids content, that is to say silica, is from about 5% by weight to about 50% by weight. and wherein the size of the colloidal silica particles dispersed therein is from about 4 nm to about 40 nm, and preferably from about 4 nm to about 30 nm. U.S. Patent No. 3,986,997 also discloses a colloidal silica composition that can be used in the practice of the present invention. It is also possible to use other finely divided oxides, in addition to colloidal silica or in the place of a part thereof, and among these oxides, mention may be made of titanium dioxide in rutile form, anatase or brookite, aluminum oxide in alpha, gamma or xi form, cerium oxide and antimony oxide. Since it may be necessary to stabilize a colloidal silica dispersion with acids or bases, it may be necessary to adjust the pH of the hard coating composition after incorporating the silica dispersion therein. It is generally preferred that this pH is from about 3 to about 8, and depending on the ingredients selected and their proportions in the composition, it may be necessary to add thereto

  small amounts of acid or base, to adjust the pH.

  Depending on the various chemical reactivities of the particular compounds used, inorganic acids may be employed to adjust the pH of the composition if the compounds used are not particularly susceptible to side reactions catalyzed by strong acids; if this is not the case, weak acids such as acetic acid can be used. Similarly, if the pH value is too low, strong bases such as sodium hydroxide or potassium hydroxide can be used unless the compounds used are particularly sensitive to the action of bases. in which case weaker bases such as ammonium hydroxide or similar compounds may be used. But as there are references that indicate that strong bases can

  catalyze the reactions leading to the appearance of micro-

  cracks, it is preferable to use monoalkylammonium, dialkylammonium, trialkylammonium or tetraalkylammonium hydroxides to increase the pH of the hard coating composition. In addition, the salts of

  tetraalkylammonium, in particular tetra-n-

  butylammonium, accelerate by catalysis the hardening of the

  coating layer (U.S. Patent No. 4,863,520).

  The solvents used as the base of this composition are low molecular weight alcohols, one of which is an alcohol whose molecule contains an odd number of carbon atoms and the other is an alcohol whose molecule comprises an even number of carbon atoms. carbon atoms. It is a mixture of isopropanol and n-butanol which is preferably used as a solvent in coating compositions

  used in the process of the present invention.

  Since thermoplastic materials suffer the detrimental effects of ultraviolet radiation, it is useful to add anti-UV stabilizing compounds that are compatible with the compounds used to form the hard coating. Many anti-UV stabilizing compounds useful in stabilizing polymers against the deleterious effects of ultraviolet light are known in the art and can be incorporated into the compositions of the present invention to stabilize these compositions against the effects of UV radiation. Negative ultraviolet rays (US Pat. Nos. 4,278,804, 4,374,674, 4,419,405, 4,299,746, 4,495,360 and 4,525,425). It is expected that these anti-UV stabilizing compounds or compositions described in the prior art will play a similar role in the compositions of the present invention, provided they are soluble or miscible therein, and also that have no adverse reactions of these compounds or stabilizing compositions on the other components of said composition. Preferably, the anti-UV stabilizing compounds are selected from the group consisting of the compounds represented by the following formulas:

O OH

(2,4-dihydroxybenzophenone)> OH.

O OH

C OCH3

O OH

OC8H17;

O OH

OC n2H23.

O OH

O

O OH

0C2H5 0 <O Si -OCH3 OCH3

O OH

O C2H5

Si-OC2H5

OC2H5;

O OH

O

W 0 <\

O OH

CH3 (CHCH2), CH3

  where n is a number whose value is such that the molar mass of this compound is between 000 and 60,000, the polybenzoylresorcinols of formula:

O OH

A R

  Each A symbol represents, independently of the other, a monocyclic or polycyclic aromatic group, with or without substituents selected from the group consisting of halogen atoms, alkoxy groups, C1-C6 alkyl groups and the like. 8 and the hydroxy group, and the symbol R represents a hydrogen atom or a C 1 -C 10 alkyl group, the polybenzoylresorcinols of formula:

O OH O

A. A

  Each symbol A represents, independently of the others, a monocyclic or polycyclic aromatic group, optionally bearing substituents selected from the group consisting of halogen atoms, alkoxy groups, C1-C4 alkyl groups. and the hydroxy group, the silyl group resorcinols of formula:

O OH

  </ RISi (OR2) 3 OH OH wherein each R is, independently of the other, a monocyclic or polycyclic group with or without substituents, R 'represents a methylene group or a linear or branched aliphatic group comprising at most about 10 carbon atoms, and R2 represents a C1-C6 alkyl group compounds of formula: R4 fl R

R5 C "-O N-OR3

  R4 is R4 or R3 is C4-12alkyl, each R4 is, independently of the others, C1-5alkyl, and R8 is C4-1zalkyl, alkylene bis (cyanoacrylate) formula:

O O

NC R7-A2-R7 CN

O O

NR6 NR6

J I

  Al Al o A2 represents a monocyclic or polycyclic cycloalkylene group, each Al represents, independently of the other, an aromatic group with or without substituents, each R 6 symbol represents, independently of the other, a C 1 -C 5 alkyl group; , and each symbol R7 represents, independently of

  the other is a C1-4 alkylene group.

  An essential component of the composition used in the present invention is an adhesion promoter or adhesion promoting compound selected from the group consisting of urethanes-acrylates, urethanes-methacrylates and

acrylic polyols.

  In the sense in which these terms are used, "urethanes

  acrylates "and" urethanes-methacrylates "denote polyurethanes comprising acrylate or methacrylate functional groups and whose average molar mass ranges from about 400 to about 1500. Particular useful urethanes-acrylates are Actilane CB-32 available from SNPE Chimie Co. (France), Ebecryl 8804 (available from Radcure Specialties, Inc. (Louisville, Kentucky), and M-407, a urethane-methacrylate available from Echo Resins & Laboratory (Versailles, Missouri). is the product of the addition of 2-hydroxyethyl methacrylate to isophorone diisocyanate and

about 482.

  As used herein, the term "acrylic polyols" refers to complex mixtures of polymerized and polymerizable acrylates, comprising: 1) from about 90 to about 99% by weight of a styrene / acrylic polymer,

  2) from about 0.5 to about 5.0% by weight of an ether

  ester, which is usually a glycol ester ether such as a glycol ether acetate, 3) from about 0.1 to about 2.0% by weight of a reactive site-based monomer selected from the group consisting of with dimethylaminoethyl methacrylate, acrylic acid, butoxymethyl acrylamide, glycidyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, N-hydroxymethyl acrylamide, acetylacetoxyethyl methacrylate, acrylamide, 2-hydroxypropyl methacrylate and 2-hydroxypropyl acrylate, of which hydroxyethyl methacrylate is preferred, 4) from about 0.05 to about 1.5% by weight of an acrylate ester. , which serves to flexibilize the coatings and which is selected from the group consisting of ethyl acrylate, 2-ethylhexyl acrylate, butyl acrylate, methyl acrylate and methyl methacrylate, with a preference for the latter, and 5) from about 0.05 to about 3.0% by weight of one m onomère

  olefinic copolymerizable, such as styrene.

  This acrylic polyol may be considered as an acrylic copolymer which comprises from 30 to 160 hydroxy functional groups per molecule, whose number-average molar mass ranges from about 1000 to about 10,000 and which has an acid number less than or equal to It is preferred to use these acrylic polyols in an amount of from about 0.25 to about 5.0 percent of the total weight of the coating composition. Acrylic polyols sold by S.C. Johnson Wax (Racine, Wisconsin) are commercially available.

  the brands Joncryl 500, 510, 587, 588, 901 and 906.

  The hard coating composition used in the present invention is then spread on the thermoplastic substrate of interest. The coating composition can be spread on the substrate by applying one of a variety of well-known methods such as spraying, dipping, roll coating and the like. The coating composition can also be spread according to one of the various techniques disclosed in US Pat. No. 4,892,700. The substrate may constitute a single and homogeneous phase of a thermoplastic material, or it may comprise several layers of which one is a thermoplastic material. Suitable thermoplastic materials include, but are not limited to, acrylic polymers, including poly (methyl methacrylate), polyesters, including poly (ethylene terephthalate), polycarbonates, polyamides, polyimides, acrylonitrile / styrene copolymers, styrene / acrylonitrile / butadiene copolymers, polyvinyl chloride, polystyrene, polyphenylene ether, polyphenylene sulfide, polyethylene and other polyolefins, including crystalline polypropylene and crystalline syndiotactic polypropylene, and the

similar products.

  After spreading the coating composition on the substrate, it is partially cured at a temperature between about 55 and about 105 C, preferably between about 60 and about 100 C, more preferably between about 80 and about 90 C and most preferably between about 80 and about 85 C, for a period of about 5 to about 30 minutes, preferably about 10 to about 25

  minutes and better still from about 20 to about 22 minutes.

  The term "partial hardening" is used by the Applicant to refer to a polymerization or curing process that has actually started but has not been completed. Since the coating composition used in the process of the present invention cures under the action of heat, the degree of curing achieved is defined, in the course of operations, primarily by the temperature range in which the temperature is achieved. partially curing, and secondly by the time during which this curing is carried out in a particular temperature range. Therefore, a partial curing process is a curing process performed at a particular temperature for a particular period of time, which does not give a perfectly cured composition. In general, since the compositions of this invention cure under the effect of heat, their partial curing is accomplished by heating them. But it is also possible to cure the compositions used in the present invention

  under the action of infrared radiation or microwaves.

  The partially hardened coating layer adheres to it

  even to the substrate, more or less permanently, which allows the substrate having a partially hardened coating to be conveniently left for a certain time in the store, until the material is shaped according to one of the various hot forming processes known in the art. It is not necessary to perform more than one

partial hardening step.

  The next step of hot shaping not only gives a certain shape to the thermoplastic laminate thus obtained, but also to complete the curing process which began in the step of

partial hardening.

  The hard coating layer spread on the substrate constitutes a distinct layer which is on an outer surface of the substrate or laminate constituting the substrate; therefore, an additional layer was added to the material and this was made of a laminate consisting of a hard coating and at least one layer of thermoplastic material. Unlike other coating processes, in which a layer is formed which interpenetrates the hard coating and the substrate layer on which the hard coating is applied, the process of the present invention and the composition used in this process do not involve virtually no formation of such interpenetration layer, either after the spreading of the composition or after the subsequent hot forming step. As used in the preceding sentence, the term "practically" means that no interpenetrating layer is detected by optical microscopy or electron microscopy until a

magnification of about 20,000.

  The thickness of the hard coat layer may range from about 1.25 to about 25.4 μm (0.05 to 1.00 mil), preferably from about 2.5 to about 12.7 μm. (0.10 to 0.50 thousandths of an inch), more preferably from about 2.5 to about 10.2 μm (0.10 to 0.40 thousandths of an inch), and most preferably from about 2.5 to about 5.1 μm (0.10 to 0.20 thousandths of an inch). In the practice of the present invention, it may be desirable to use a primer composition to improve the adhesion properties of the hard coat to the substrate, taking advantage of the fact that the primer adheres well to the substrate and that the hard coating adheres well to the primary. But the method of the present invention, considered in all its scope, can be implemented with or without a primary layer constituting

  intermediate between the hard coating and the substrate.

  The substrate may consist of a layer of homogeneous thermoplastic material or a laminate comprising several layers, one of which is a thermoplastic material. The thickness of this substrate may vary from about 50 μm to about 12.7 mm (2 to 500 thousandths of an inch), preferably from about 50 μm to about 6.4 mm (2 to 250 thousandths of an inch), more preferably from about 125 μm to about 4.8 mm (5 to 190 thousandths of an inch), and most preferably from about 250 μm to about 3.2 mm (10 to 125 thousandths of an inch). A preferred embodiment of the method of the present invention comprises spreading a hard, partially curable coating composition onto a substrate which comprises a thermoplastic material and is in the form of a sheet, thereby forming a laminate and making partially curing the coating composition resulting in a heat-formable sheet having a partially cured coating layer. This sheet can then

  at the same time undergo hot forming and hardening.

  A particularly advantageous embodiment of the invention lies in a method of manufacturing a laminate, which comprises preparing an acrylic composition containing an acrylic monomer, depositing said acrylic composition on the surface of a substrate comprising a thermoplastic material, and curing this acrylic composition. According to this particular method, the acrylic composition which constitutes a hard coating composition is partially cured in a single step, and there is practically no penetration of said coating layer.

  hard coating in said substrate.

Examples

  The following examples are intended to illustrate

  the invention, but without limiting it in any way.

  The extent to which the following hard coating compositions, shown in Table 1, have been evaluated

  are suitable for the process of the present invention.

  TABLE 1: Hard Coating Compositions Composition: I II III Components% by weight methyl, 25, 24, 23,81 trimethoxy-silane dimethyl-O, 2,63, 2,6-dimethoxy-silane, aqueous sol of 15.0 (1) 18.01 (2) 17.76 <2) silica n-butanol 26.0 24.32 24.06 isopropanol 26.0 24.32 24.06 acetic acid 0.17 0.24 1.40 stabilizer 2.24 2.71 2.68 anti-UV methanol 2.00 2.43 2.40 adjusting agent 0.10 0.05 0.05 flow tetrabutyl acetate 0.15 0.16 0.16 ammonium polyol acrylic (3) 0.00 1.03 1.01 Notes: 1. Ludox AS-40 2. Nalcoag 2326 3. Joncryl 587 Q The hard coating formulations shown in Table 1 are spread on polycarbonate sheets or poly (methyl methacrylate), which act as a thermoplastic substrate. These formulations are spread out as well by interposing an intermediate layer of primer as by not interposing. The composition of the primer used is as follows: 2.0% by weight of poly (methyl methacrylate) and 0.5% by weight of UV stabilizer Uvinol N-539, dissolved in 97.5% by weight of a solvent consisting of 85% by weight of propylene glycol methyl ether and% by weight of diacetone alcohol. When interposing a primer layer, it is spread on the sheets and allowed to air dry before spreading over the hard coating composition. In a single step, the hard coating composition is spread on the sheets with or without a primer layer, and is partially cured. The sheets bearing this partially cured coating are then hot formed by draping. Draping hot forming is a process in which a thermoplastic material is contacted with a relief shaped surface, heated and allowed to flow and take the form of the raised surface, and then allowed to cool. . According to another possible procedure, the draping hot forming involves heating a thermoplastic material, bringing it into contact with a raised surface, allowing the material to flow and take the form of the raised surface, then cool it down. The draping hot forming operation can be facilitated by establishing a pressure difference, i.e., overpressure or vacuum, so that

  speed up the process of shaping by the material.

  In the present example, all test materials were hot-formed by draping them on a cylinder having a 31.75 mm (1.25 inch) radius of curvature. The hard-coated and hot-formed thermoplastic layers thus obtained were then evaluated for the adhesion of the hard coating to the substrate and the occurrence of microcracks. The results of these tests are collated in Table 2. The thickness of the sheets used varies from 1.59 to 4.76 mm (1/16 to 3/16 inches or 62.5 to 187.5

thousandths of an inch).

TABLE 2:

  Hot foaming of thermoplastic sheets with a partially hardcoated coating. Hard coat coated with polycarbonate; polycarlxIate; polycarfrIate; a primary coating hard hardcoat hard hard coating hard adherent adbérxt admrit

  no icro- no micro- no micro-

  fissures fissures fissures Substrate not bearing polycarbate; polycarboate; polycarbonate; No primer coating hard coat hard coating hard non adent adeeut adrt

no micro- no micro-

cracks fissures

_ _ __.

  Substrate bearing poly (ethiacrylate no methyl priara); hard coating adélvnt

no micro-

  The results summarized in Table 2 indicate that a hard coating composition containing an adhesion promoter partially cures, in a single step, to give a coating which can simultaneously undergo curing and hot forming. When the hard coating composition does not contain an adhesion promoter, it seems necessary to use a primer. When the hard coating composition is spread on a substrate comprising a thermoplastic material and carrying a primer, partial curing in a single step results in a coating layer which can then be cured and shaped at the same time. hot, as shown by the results of the draping hot forming tests,

  results summarized in Table 2.

Claims (9)

  A method of manufacturing a heat-formable laminate, characterized in that it comprises the steps of: (a) depositing, on a surface of a substrate comprising a thermoplastic material, a hard coating composition comprising a compound promoting adhesion, selected from the group consisting of urethanes-acrylates, urethanes-methacrylates and acrylic polyols, (b) thus forming a laminate, and (c) partially curing this laminate in one step, virtually none interpenetration not occurring   then between said hard coating and said substrate.   2. Method according to claim 1, characterized in that it further comprises the fact of simultaneously carrying out the   hot forming and curing said laminate.   3. Process according to claim 2, characterized in that   said substrate comprises a polycarbonate.   4. Method according to claim 2, characterized in that said substrate comprises a poly (methyl methacrylate). 5. Process according to claim 3, characterized in that   said adhesion promoter is an acrylic polyol.   6. Process according to claim 4, characterized in that   said adhesion promoter is an acrylic polyol.   Process according to claim 5, characterized in that said hard coating composition further contains an anti-UV stabilizer.   Process according to claim 6, characterized in that said hard coating composition further contains an anti-UV stabilizer. A method of manufacturing a laminate, which comprises preparing an acrylic composition containing an acrylic monomer, depositing said acrylic composition on the surface of a substrate comprising a thermoplastic material, and curing said acrylic composition, characterized in that this process comprises partially curing said acrylic composition in a single step, in that said acrylic composition constitutes a hard coating composition, and in that there is practically no penetration of said hard coating layer in said substrate.