JPH0774282B2 - Method for producing acrylic coated polycarbonate articles - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an acrylic-coated polycarbonate article, particularly for providing a UV-cured protective coating on the surface of a polycarbonate substrate. Of the improved method.

[0002]

BACKGROUND OF THE INVENTION Polycarbonate films generally have acceptable strength and transparency, but lack high levels of abrasion resistance and chemical resistance. Radiation curable acrylic coatings and methods of applying them to polycarbonate substrates are known. For example, European Patent Application No. 86
EP 228,67 corresponding to 117,682
See issue 1. The conventional method of providing a radiation-curable acrylic coating on a polycarbonate film does not reach the desired degree of adhesion of the cured coating to the underlying polycarbonate.

In some of the conventional radiation curable acrylic coating compositions, the coating composition is
An amount of non-reactive solvent is used such that it reduces the viscosity of the composition during its application to the bone substrate. These non-reactive volatile components are removed from the coating by using a forced hot air drying system. Due to environmental and safety issues, it is important to use coating compositions containing significant amounts of non-reactive volatile components (eg solvents etc.) (eg 1% or more by weight of the total composition). Undesired. For this reason, a method for producing coated polycarbonate articles, i.e., radiation curable coatings containing few non-reactive volatile components, is applied to the polycarbonate.
There is a need for a method of applying a coated substrate to produce a coated article that exhibits good coating adhesion.

[0004]

OBJECTS OF THE INVENTION Accordingly, one object of the present invention is to
A primerless coated polycarbonate article with a high degree of adhesion between the cured coating and the polycarbonate substrate is treated with a non-reactive solvent like solvent. It is to manufacture without using a sex ingredient.

[0005]

SUMMARY OF THE INVENTION The present invention is a coating having excellent adhesion between the cured coating and the underlying polycarbonate substrate.
The present invention relates to a method for producing a coated polycarbonate film. The method of the present invention comprises: (i) applying an ultraviolet (UV) curable coating composition containing almost no non-reactive volatile component such as a solvent onto the surface of a thermoplastic resin substrate;
(Ii) uncured coating composition and substrate surface
By heating to a temperature selected from ˜150 ° F., a portion of the uncured coating composition is allowed to penetrate into certain areas under the surface of the thermoplastic resin substrate to allow the thermoplastic resin to co-exist with the thermoplastic resin under the surface. -
A coating composition penetrating region containing both of the coating composition is formed, and (iii) the coating composition thus applied is UV-cured by exposing the coating composition and the penetrating region to UV light. It consists of Upon UV curing of the coating composition, the subsurface penetration areas of the thermoplastic substrate provide an interlocking bond between the substrate and the cured coating.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The method of the present invention provides a UV cured coating on the surface of a thermoplastic resin substrate. The particular apparatus shown in Figure 1 is for applying and curing a coating material on a continuous thermoplastic film substrate. The substrate is preferably made of polycarbonate resin. The substrate used in the device of Figure 1 must be flexible and permeable to ultraviolet energy, and the properties of the polycarbonate substrate are unacceptable due to the transmission of radiation energy. Must not be affected by. The radiation energy source is selected to operate at ultraviolet frequencies. Preferred polycarbonate substrates for the method of the present invention include, for example, general
It is formed from a thermoplastic polycarbonate material such as Lexan® resin, a product of the Electric Company. Typical examples of the polycarbonate resin are U.S. Pat. No. 4,351,
No. 920 (incorporated) and by reaction of an aromatic dihydroxy compound with phosgene, or reaction of an aromatic dihydroxy compound with a carbonate precursor such as diarylecarbonate. can get. U.S. Pat. No. 4,351,920 also describes various methods for producing aromatic polycarbonate resins that can be used as substrates in the present invention. The preferred aromatic dihydroxy compound is 2,2-bis (4-hydroxyphenyl) propane [bisphenol-A]. The term aromatic polycarbonate resin means dihydroxyphenol,
It is intended to include polyester carbonates obtained from the reaction product of a carbonate precursor and a dicarboxylic acid (eg terephthalic acid or isophthalic acid). In some cases, certain amounts of glycols can also be used as reactants. The polycarbonate film can be prepared by a known method. Typically, molten polycarbonate is cast on an extrusion roll stack and both sides of the material are polished and pressed to a uniform thickness. Ultraviolet (UV) radiation is used as an energy source when curing coatings on polycarbonate substrates. With respect to the device of FIG.
The thickness of the bonnet film substrate can range from about 0.5 to about 30 mils, depending on the substrate's ability to retain flexibility. The thickness of the polycarbonate film is preferably 5-20 mils.

UV curable coating compositions generally include monomers and oligomers containing acrylic, methacrylic and vinyl unsaturation as well as other 100% solid convertible materials (eg, monomer soluble polymers and Elastomer, inorganic silica filler and pigment). This coating system is usually about 100 ~
It consists of a monomer having a molecular weight of 1000 and having a single unsaturation or two, three or more polyunsaturated sites. In the practice of the present invention, the coating contains few volatile, non-reactive components (<1%). The coating composition is preferably 99-100% by weight of the reactive component and the solid material, more preferably 99.9-100% by weight of the reactive component and the solid material, and 100% by weight of the reactive component. Most preferably the components and solid materials.
Solid materials include non-volatile solid materials such as polymeric substances and colloidal silica. A suitable polymer material is cellulose acetate butyrate. This coating composition is 100% when exposed to UV light.
Are preferably those that can be converted to solids. The coating composition may also contain a fixed amount of a latent UV blocker such as resorcinol monobenzoate. The composition also contains a photoinitiator in an amount effective to enable photocuring of the composition.

The preferred acrylic coating composition contains significant amounts of relatively low molecular weight aliphatic alkanediol diacrylates, which are polycarbonate groups by diffusion when exposed to and exposed to elevated temperatures. Penetrates below the surface of the material. A suitable aliphatic alkane diol diacrylate is 1,6-hexanediol diacrylate.
It is A preferred acrylate coating composition has from 5 to 5 parts by weight based on the total weight of the coating composition.
It contains 60% by weight of aliphatic alkanediol diacrylate. The aliphatic diol diacrylate preferably contains from 2 to 12 carbon atoms in its aliphatic portion. Suitable aliphatic diol diacrylates include ethylene glycol diacrylate, butanediol diacrylate, hexanediol diacrylate.
There are two types, tho, octane diacrylate, and decandiol diacrylate. A preferred coating composition is about 37 wt% trimethylolpropane triacrylate (TMPTA), about 15 wt% dipentaerythritol monohydroxypentaacrylate (DIPE).
PA), 37% by weight of 1,6-hexanediol diacrylate, about 9% by weight of cellulose acetate butyrate
(CAB) and about 2% by weight of the photoinitiator diethoxyacetophenone (DEAP). The preferred silica-filled acrylic coating is 22% 1,6-hexanediol diacrylate, 22% trimethylol.
Le Propane Triacrylate, 35% Functionalized Colloidal Silica, 7% Latent UV Absorber [eg. Applied Polymer Science (J. Appl.
ied Polymer Science) ", Volume 28 (1983) No. 1
The Siasorb (C) described on page 159 (incorporated)
yasorb) 5411 benzene sulfonate ester (BSEX)], and 3% photoinitiator [eg diethoxyacetophenone (DEAP)]. A suitable functionalized colloidal silica is Olson (Olso
n) et al., U.S. Pat. No. 4,455,205, Olson (Ol
U.S. Pat. No. 4,491,508, Ch.
U.S. Pat. No. 4,478,876 and Chang.
(Chung) U.S. Pat. No. 4,486,504 (incorporated). Aliphatic alkanediol diacrylate, especially 1,6-hexanediol diacrylate
The coating is capable of readily swelling a thermoplastic matrix such as polycarbonate and is therefore sufficient to enhance the adhesion between the coating and the substrate during curing of the coating composition. A sufficient amount of the coating composition facilitates rapid and proper penetration and diffusion into the area beneath the substrate surface. FIG. 3 shows an article made according to the present invention. The article has a cured acrylic coating and a polycarbonate substrate, and there are regions adjacent to the substrate surface that function to improve the adhesion between the coating composition and the substrate. To do.

An example of an apparatus suitable for applying and curing a coating on the surface of a polymeric substrate according to the method of the present invention is shown in FIG. In Figure 1, radiation curable
The coating material 10 is applied continuously by flowing it over the film surface at a controlled rate.

Substrate roll 12 is formed from a roll of uncoated substrate 14 wrapped around a core 16. The substrate 14 is unwound according to the movement of the casting drum 18 (described later). Coating material 1
0 can be applied to the surface of the base material 14 by dropping the material on the base material 14 using the applicator 20. As will be apparent to those skilled in the art, suitable adjustments may be made to this coating system to effectively coat the substrate. The coating material 10 can be applied to a number of well-known coating methods (eg, spray,
It may be applied to the base material 14 by any of a brush coating method, a curtain coating method, a dipping method and the like and other well-known roll coating methods (for example, a reverse roll coating method). The thickness of the radiation curable coating 10 applied to the substrate and the resulting cured hardcoat 21 thickness will depend on the end use application of the article and the desired physical properties. This thickness can range from about 0.05 to about 5.0 mils for non-volatile coating. A preferred thickness is about 0.2 to about 0.5 mil.

After the coating material 10 is applied to the base material 14, the coated base material 22 is guided to the nipple roll 24. The choice of material forming the nipple roll 24 used in the present invention is not critical. That is, this lo
The le can be made of plastic, metal (ie stainless steel, aluminum, etc.), rubber, ceramic material, and the like. The nipple roll 24 can include a sleeve. The sleeve is preferably formed of an elastic material such as tetrafluoroethylene or polypropylene, or any of the various rubber compounds currently available and blends thereof. The sleeve fits over the roll surface to provide a smooth surface that minimizes friction in contact with the substrate 22. The nipple roll 24 can be adjusted with respect to the position of the casting drum 18 (discussed below) and in some cases can be independently driven.

As shown in FIG. 1, the casting drum 18 is placed in the vicinity of the nip roll 24, and the outer peripheral surface of the nipple roll 24 and the outer peripheral surface of the drum 18 are nip 26 (described later). Are close to each other at the interface defining The pressure applied to the interface between the nipple roll 24 and the drum 18 can be adjusted by well known methods such as an air cylinder (not shown) attached to the axle 28 of the nipple roll 24, thereby The roll is selectively pressed against the drum 18. When the substrate does not pass through the nip 26, the pressure exerted at the interface is typically weaker than less than 5 pounds per linear inch. As will be described later, the pressure applied when the coated substrate is passing through the nip 26 can be readjusted according to various parameters.

The casting drum 18 surrounds the central axle 19 and is preferably made of a heat conducting material (preferably stainless steel or chrome plated steel). Further, the drum is preferably independently driven by an external power source (not shown).

On the surface 30 of the casting drum,
Various patterns or patterns can be provided depending on the pattern or pattern desired to be applied to the ting 10 and the resulting hard coat 21. For example, if a high degree of gloss is desired for hardcoat 21, surface 30 can be a well-polished chrome-plated surface. If a lower gloss of the hard coat 21 is desired, the surface 30 may be polished less well to give the coating a matte pattern. Similarly, a design pattern of a mirror image can be provided on the hard coat 21 by embossing a design pattern on the surface 30. The cured coating forms a hardcoat 21 which is a permanent mirror image of the casting drum surface 30.

Although a nitrogen atmosphere may be used to ensure anaerobic cure conditions for the coating composition, it is preferred to cure anaerobically without using such a nitrogen atmosphere. To minimize the amount of air present in the pre-cure coating 10 without using a nitrogen gas atmosphere, the nip 26
Carefully adjust the pressure that can act on the. The pressure applied to the nip 26 can be adjusted as described above. The precise pressure exerted on the nip 26 to obtain a constant coating thickness depends on the viscosity of the coating 10, the speed of the substrate, the design pattern on the surface 30 (if present). Depends on factors such as the degree of fineness and the temperature of the casting drum. Generally, a substrate with a thickness of 15 mils, with a thickness of 0.6 mils and 2
Acrylic-based coat with a viscosity of 20 centipoise
For coated substrates, coat the substrate at a speed of 50 feet / minute and a durometer (Shore A) 55 roll cover with a nip pressure of 25 lbs / inch. -Put on the coated substrate. Thus, the coating 10 is pressed into contact with both the substrate 22 and the casting drum surface 30, thereby ensuring that there is substantially no free diatomic oxygen in the coating during curing. Hard coating of hardened coating ensures almost complete hardening of the coating 21
Shows a pattern and / or a mirror image of the pattern on the surface 30 of the casting drum. Overcoating forms beads 31 of uncured coating composition material over the width of the drum over the nip. With this bead 31,
Ensures proper coating material enters through the nip 26 across the width of the drum.

After the substrate 22 coated with the coating 10 has passed through the nip 26, the coating is cured by UV energy. As shown in FIG. 1, the means 32 for transmitting ultraviolet energy causes the surface 3 of the substrate 22 opposite the surface 10 having the coating 10.
Ultraviolet energy is transmitted to 4. This radiation energy passes through the transparent base material 22 and is absorbed by the coating 10 which is compressed between the base material 22 and the drum surface 30. The preferred wavelength of UV radiation is from about 2900 to about 40.
It is 50 angstroms. The lamp system used to generate such UV radiation is a discharge lamp, such as xenon, a metal halide, a metal arc, or a high, medium or low pressure mercury vapor discharge lamp (each low pressure to a few millitorr to about It operates at a pressure of up to 10 atmospheres). The radiation dose applied to the coating 10 through the substrate 22 is about 2.0 to about 1.
The range may be 0.0 J / cm ² . A typical UV curing system suitable for the present invention is US Pat.
Linde medium pressure mercury lamp as described in US Pat. No. 7,529. The number of UV light lamps directed to the surface of the substrate is not critical, but the higher the number of lamps, the faster the production rate of the substrate with the coating 10. Normally, if the production line speed is about 50 feet / minute, then 30 for each coating of acrylic base with a thickness of about 0.5 mils.
Two lamps producing 0 watts / inch of radiant energy are sufficient. Such a curing procedure results in both polymerization of the polyfunctional acrylic monomer and crosslinking of the polymer to form a hard, non-sticky coating. The coating may be post cured by further exposure to UV light after leaving the surface of the casting drum.

After the coating material layer is applied to the substrate 22 and cured by the method of the present invention, the resulting product is a hard coated polycarbonate film article 38, which is After being sent to the idler rolls 40, 42 and 44, they are collected in a take-up roll 46. The take-up roll is usually driven independently to allow the hard coat coated polycarbonate article 38 to be separated from the drum surface 30.

The improvement according to the present invention is to heat the polycarbonate substrate 22 and the uncured coating composition 10 to a temperature of 90 to 150 ° F. prior to curing the coating composition 10. It is to be. Traditional coating methods use drying systems to remove non-reactive volatile components (eg, solvents) from the coating, but the purpose of such drying systems is to remove non-reactive volatiles. There is no clear reason why one of ordinary skill in the art has ever used such a system for coating compositions containing few unreactive volatiles. In the method of the present invention, the applied coating composition 10 is such that a sufficient amount of the coating composition diffuses into a region 47 below the surface 34 of the thermoplastic resin substrate 22. It is necessary to contact the thermoplastic resin substrate 22 at a sufficient temperature for a sufficient time after the application of the coating composition 10 and before its curing. Coating composition 10 preferably penetrates to a depth of 0.05-5 microns below the surface, more preferably 0.1-1 micron. Thus, the region 47 containing both the thermoplastic resin and the coating composition is formed. This region 47 is in close proximity to the coated surface 34 of the substrate. 1 for the substrate 22 and the coating composition 10
It is preferred to maintain contact at elevated temperatures of 90-150 ° F for ~ 5 seconds. This heating step does not significantly contribute to the curing of the coating composition. The infiltrated region 47 provides a mating matrix of the thermoplastic and cured coating 21 upon curing of the coating 10, which locks the coating 10 and substrate 22 together. Improve the adhesion between. The heating step of the substrate 22 and the coating 10 prior to the UV curing of the coating composition 10 can be performed by internally heating the drum 18. The drum can be internally heated with hot oil or the like (not shown). The coating composition of the present invention is a radiation curable composition rather than a thermosetting composition.

With the apparatus and preferred method of the present invention,
One of ordinary skill in the art will appreciate that a nitrogen atmosphere may alternatively be used alone.

[0020]

DESCRIPTION OF THE EMBODIMENTS The novel methods and articles of the present invention are illustrated in the following specific embodiments. This is for the purpose of illustrating particular embodiments only and is not intended to limit the broadest scope of the invention in any way.

FIG. 2 is a cross-sectional view of a coated article 48 made without the use of a heated casting drum. Note that the coating composition has not penetrated into the area below the surface 52 of the polycarbonate substrate 51, thus leaving no area for the cured coating to lock to the substrate 51. I want to.

FIG. 3 is a cross-sectional view of a coated polycarbonate article 38 made according to the method of the present invention.
Note that article 38 of Figure 3 has a region below the surface of the substrate into which some amount of the coating composition has migrated. Upon curing, this region serves to interlock and lock the cured coating with the polycarbonate substrate.

[0023] The following examples illustrate the improved process of the present invention. Example A is a comparative example, and Example B is an example of the improved adhesion achieved with articles made by the method of the present invention.

[0024]

[Table 1] Table 1 Curing speed Roll temperature Scribing adhesion Example ^(a) Feat / min F Tape test A 20 70 Fail B 20 115 Compliant (a) Examples A and B The coating composition was 0.75 grams of BSEX [Cyasorb (R)].
5411 # Benzenetriazole benzenesulfonate] and 0.3 grams DEAP (diethoxyacetophenone), 37.3 grams HDDA (hexanediol diacrylate), 37.3 grams TMP.
TA (trimethylolpropane triacrylate), 1
A mixture of 4.7 grams of DiPEPA (dipentaerythritol monohydroxypentaacrylate), 2.1 grams of DEAP (diethoxyacetophenone) and 8.6 grams of CAB (cellulose acetate butyrate). Obtained by adding to 10 grams.

[Brief description of drawings]

1 is a horizontal front view schematically showing an apparatus having a casting drum for carrying out the method of the present invention.

FIG. 2 is a cross-sectional view of a coated polycarbonate article without the use of a heated casting drum.

FIG. 3 is a cross-sectional view of a coated polycarbonate article made according to the method of the present invention.

[Explanation of symbols]

10 radiation curable coating material, 14 base material before coating, 18 casting drum, 20 applicator, 21 hard coat, 22 base material coated with coating material, 24 nipples, 32 light source, 38 polycarbonate film with hard coat, 47 area under the surface of thermoplastic resin substrate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B32B 27/08 8413-4F 27/16 8413-4F 27/30 A 8115-4F 27/36 102 7421 -4F C09D 4/02 PDS // C08L 69:00 (72) Inventor Dimitris Katsumbellis, No. 10429 (72) Inventor Stuart Robert, North East Gate, Mount Vernon, Indiana, USA Care, The Third United States, New York, Troy, Biscayne Bowlbird, No. 9 (72) Inventor Larry Nail Lewis United States, New York, Scotia, Harvest Drive, No. 7 (56) Reference Document JP-A-55-84331 (JP, A) JP-A -236244 (JP, A) European Patent Application Publication 228671 (EP, A)

Claims (9)

[Claims] 1. A surface of (a) a polycarbonate substrate,
A portion of the UV curable acrylic coating composition that is substantially free of non-reactive volatile components diffuses into the region of thickness 0.1-5 microns below the surface of the substrate.
Sufficient time 90 to 1 to form a region composed of the acrylic coating composition and the polycarbonate resin.
UV cured surface comprising contacting the composition at a temperature of 50 ° F. and (b) exposing the acrylic coating composition thus applied to sufficient UV to cause curing. A method of making a polycarbonate article having an acrylic coating. 2. The method of claim 1, wherein the cured acrylic coating composition comprises a solid. 3. The acrylic coating composition comprises:
A multifunctional acrylate monomer, a photoinitiator, and 20
The method of claim 1 comprising about 50% by weight of 1,6-hexanediol diacrylate. 4. The temperature is 110 to 130 ° F.,
The method of claim 1. 5. The method of claim 1, wherein the temperature is about 120 ° F. 6. The method of claim 1, wherein the cured acrylic coating forms a hardcoat having a thickness of 0.5-5 mils. 7. (a) An acrylic coating composition comprising a polyfunctional acrylic monomer and a photoinitiator and substantially free of non-reactive volatile components is applied to the surface of an aromatic polycarbonate substrate, (B) the applied coating composition together with the thermoplastic substrate applied with the coating composition, and a part of the coating composition in a region of a thickness of 0.05 to 5 microns below the surface of the substrate. Heated to a temperature of 90-150 ° F for a time sufficient to diffuse therein, and (c) sufficient ultraviolet light to cause curing of the applied coating composition under substantially anaerobic conditions. A method of making an acrylic-coated polycarbonate article, the method comprising exposing to light. 8. (a) On the surface of the polycarbonate substrate,
A part of the UV-curable acrylic coating composition diffuses into a region having a thickness of 0.1 to 5 μm below the surface of the base material to form the acrylic coating composition and the polycarbonate.
The composition is contacted at a temperature of 90 to 150 ° F. for a time sufficient to form a region of resin and (b) curing of the acrylic coating composition thus applied. A method for producing a polycarbonate resin article having a UV-cured surface acrylic coating, the method comprising exposing the same to sufficient UV light. 9. (a) UV cured thickness 0.5-5
A mill and an acrylic coating material layer, the (b) the thickness of 0.1 to 5 micron region consisting of the acrylic acrylic coating material was cured by UV adjacent to the coating and an aromatic polycarbonate resin, the cured composed of an aromatic polycarbonate resin substrate acrylic coating is bonded directly, aromatic polycarbonate article which is acrylic coated.