An article that is a flooring material or a wall covering coated with a wear layer that is a heat-cured and radiation-cured coating composition, the composition including a polyvinyl chloride (PVC resin), an acrylic or methacrylic compound, and a radiation-reactive urethane oligomer, the composition being substantially or completely free of internal or external plasticizers.

This invention relates to a heat-curable and radiation-curable composition for coating sheet materials, more particularly but not exclusively for top coating of resilient vinyl flooring, materials, and to sheet materials coated with the cured composition. The invention also extends to a process for preparing such coated sheet materials.
Wear layer surfaces of vinyl flooring products are usually prepared from plastisols, which are dispersions of fine particles of resins in a plasticizer. Most plastisols for vinyl flooring products are formulated using polyvinyl chloride (PVC) emulsion resins mixed with primary and secondary plasticizers, extenders, stabilizers and other additives. After being applied to a substrate, for example a felt substrate or a glass fleece, by spread coating, the layer of plastisol is fused by heating to an elevated temperature. Wear layer surfaces of vinyl flooring products can also be prepared with a clear or colored powdered dry blend as described in French patent FR 2,542,260 published Sep. 14, 1984. These dry blend powders are prepared from polyvinyl chloride (PVC) suspension resins, plasticizers, stabilizers, extenders and other additives. They are prepared in a Henschel type mixer. The dry blend powder is applied to a felt or vinyl substrate and is fused by heating to an elevated temperature.
Clear wear layer surfaces can also be prepared by mixing polyvinyl chloride (PVC) suspension resins, plasticizers, stabilizers, extenders and other additives in a Banbury mixer and calendering or extruding the product to various gauges. This calendered sheet is then laminated to any one of various substrates, for example a PVC based film, a felt, a glass fleece, or the like.
Thermoplastic vinyl wear layers made from polyvinyl chloride (PVC) plastisols or from powdered dry blends or a high shear mixer (e.g. Banbury mixer) show various limitations and disadvantages, such as insufficient gloss retention, insufficient wear and abrasion resistance, stain resistance, scuff resistance, tear resistance, gauge resistance and resistance to various chemical agents. Some of these problems are additionally aggravated by migration of plasticizers towards the surface of the wear layer.
In order to improve wear properties of thermoplastic vinyl layers, various modifications to plastisol, dry blend and high shear mixer compositions have been proposed, mostly by changing the amount and type of plasticizers. Changing the amount and type of external plasticizers has not produced any substantial improvements. External plasticizers conventionally used for PVC compositions include dialkyl phthaiates, for example dioctyl phthalate. These conventional plasticizers have proven unsatisfactory for various reasons, one of which is that they have a tendency to migrate to the surface and exude from the surface. This leads to undesirable characteristics, including staining. It is also known to plasticize PVC internally. This is done, for instance, by copolymerizing a small amount of ethylene or propylene with the vinyl chloride, so that there is obtained PVC containing a small amount of ethylene or propylene incorporated into the polymer backbone. The small amount of ethylene or propylene may be up to about 10% of the total weight of the polyvinyl chloride (PVC) polymer. Internal plasticization has proved to be unsatisfactory in view of many limitations as to applications, formulations and performance. Plastisols having a resin component other than polyvinyl chloride (PVC) have also been proposed (see, for example, U.S. Pat. No. 4,210,567, U.S. Pat. No. 4,309,331 and U.S. Pat. No. 4,380,606), but this has not eliminated all the above mentioned problems.
To obtain a surface with acceptable wear properties, a thin top coat layer, usually made of a polyurethane, has been added over the plasticized polyvinyl chloride (PVC) coating (see, for example, U.S. Pat. No. 3,935,330, U.S. Pat. No. 4,100,318, U.S. Pat. No. 4,216,187, U.S. Pat. No. 4,217,396, U.S. Pat. No. 4,393,187 and U.S. Pat. No. 4,598,009). Although showing usually satisfactory mechanical resistance, these top coatings are not themselves free of problems.
The additional top coating and the process by which it is applied may adversely affect properties of an underlying foamable plastisol layer by damaging foam cells and causing reduction in the level of embossing. Also, since the polyurethane layer is expensive, it is usually thin. In some cases it may be too thin to prevent the migration of plasticizers from the base layer to the surf ace of the coating. Such migration may be prevented by increasing the thickness of the polyurethane top layer, but this makes the flooring material more expensive.
Most top layers of polyurethane are prepared by covering the polymer base layer, which may be formed for example from a polyvinyl chloride (PVC) plastisol, a polyolefin, a polyester, a polyamide, a polyepoxy or a polyacrylate, with a liquid composition of monomers (U.V. curable) or polymers (solvent or water based) which composition is subsequently cured at an elevated temperature or U.V. cured to produce a crosslinked, thermoset, mechanically resistant polyurethane coating. The liquid composition of monomers or polymers has a low viscosity which decreases with increasing temperature, before the top layer becomes solid by crosslinking. As a result, the top coating of polyurethane is usually of an uneven thickness, due to the low viscosity monomer or polymer composition flowing into any embossed valleys. Another disadvantage, with a foamable material, is that the hot melt viscosity of the polyurethane composition is too low to prevent the escape of gases from the underlying foamed or foaming plastisol layer. This results in blistering and pin holes of the polyurethane layer. To prevent this from happening, in the past a layer of a composition having a, high melt viscosity has been situated between the foamed or foaming plastisol layer and the polyurethane composition. A suitable composition having a high melt viscosity that has been used for this purpose is a plasticized high temperature melt viscosity PVC resin.
FR 2,379,323, published Sep. 1, 1978, discloses a top coat composition that contains, additionally to the usual polyurethane polymers, .an ethylenically unsaturated compound. After being applied to a foamable substrate but prior to being thermally cured, the composition is irradiated with U.V. light or an ionizing radiation or is heated to a low temperature by infrared radiation. This causes polymerization of the ethylenically unsaturated compound, which increases the hot melt viscosity of the composition and changes it to a solid state. The partially crosslinked composition creates a high temperature malt flow barrier film that prevents the escape of gases from the foamed underlayer when the latter is fused at a high temperature. The ethylenically unsaturated compounds used for this purpose are all very expensive monomers.
A similar two-step coating process is disclosed in U.S. Pat. No. 3,935,330. A coating composition, which comprises both thermally and radiation-curable components, is first partially cured by exposing it to an ionizing or non-ionizing radiation and the cure is then completed by a thermal treatment. Ionizing radiation is a radiation produced by an electron beam or electron generating sources. Non-ionizing radiation is a radiation produced by Carbon ARC, Tungsten filament lamps, sunlamps, lasers, Mercury arc, Xenon arcs or any other source of ultra violet and visible light radiation. Including thermally curable components into the coating composition and adding the step of thermal curing improves properties of the coating compared with coatings cured by radiation only. U.S. Pat. No. 3,935,330 is clearly concerned with coatings to be applied to wood and metal, and this method of processing is not practical for foaming products.
It is an object of the invention to provide a new composition that can be used, for example, for coating a wall covering or a tarpaulin or, more preferably, for preparing a wear layer for vinyl or other flooring materials, which wear layer is substantially free of disadvantages of wear layers known in the prior art and does not require an additional protective top coating.
It is another object of the invention to provide a method of coating a substrate with the new coating composition, to prepare resilient flooring materials substantially free of disadvantages of materials known in the prior art and which do not require an additional protective top coating.
Thus, according to one aspect, the invention provides a radiation-curable coating composition comprising a polyvinyl chloride (PVC) resin, an acrylic or methacrylic compound and a radiation-reactive urethane oligomer.
According to another aspect, the invention provides a heat-curable and radiation-curable coating composition which comprises a polyvinyl chloride (PVC) resin that is substantially or completely free from internal or external plasticizers, and an acrylic or methacrylic compound.
According to yet another aspect, the invention provides a transparent, radiation-curable flexible sheet composed of a polyvinyl chloride (PVC) resin that is substantially or completely free from internal or external plasticizers and is solvated with an acrylic or methacrylic compound.
According to another aspect, the invention provides an article comprising a material coated with a heat-cured and radiation-cured composition comprising a polyvinyl chloride (PVC) resin, an acrylic or methacrylic compound and a radiation-reactive urethane oligomer.
According to still another aspect, the invention provides an article comprising a material coated with a heat-cured and radiation-cured composition comprising a polyvinyl chloride (PVC) resin that is substantially or completely free from internal or external plasticizers, and an acrylic or methacrylic compound.
According to yet another aspect, the invention provides an article comprising a material coated with a transparent, radiation-curable flexible composition composed of a PVC resin that is substantially or completely free from internal or external plasticizers solvated with an acrylic or methacrylic compound.
According to yet another aspect, the invention provides a flooring material comprising a substrate and a top coating, said top coating prepared by thermal fusing and radiation-curing of a coating composition comprising from 35 to 140 parts by weight of a polyvinyl chloride (PVC) emulsion resin, from 30 to 80 parts by weight of an acrylic or methacrylic; compound and from 4 to 65 parts by weight of a radiation-curable urethane oligomer.
According to still another aspect, the invention provides a flooring material comprising a substrate and a top coating, said top coating prepared by thermal fusing and radiation-curing of a coating composition comprising from 75 to 140 parts by weight of a polyvinyl chloride (PVC) suspension resin, from 35 to 80 parts by weight of an acrylic or methacrylic compound and from 4 to 65 parts by weight of a radiation-reactive urethane oligomer.
According to another aspect, the invention provides a process for coating a,material, which process comprises applying to the material a coating composition comprising a polyvinyl chloride (PVC) resin, an acrylic or methacrylic compound and a radiation-reactive urethane oligomer, heating to heat-cure the coating composition and irradiating the composition to radiation-cure the coating composition. The composition can be applied to the material before or after it is heated.
According to yet another aspect, the invention provides a process for coating a material, which process comprises applying to the material a heat-curable and radiation-curable coating composition which comprises a PVC resin that is substantially or completely free from internal or external plasticizers, and an acrylic or methacrylic compound, heating to heat-cure the coating composition and irradiating the composition to radiation-cure the coating composition. The composition can be applied to the material before or after it is heated.
In one embodiment, the composition according to the invention is prepared and applied to a substrate as a low-viscosity mixture, in the manner known to those skilled in the art. After being applied to the substrate, the coating composition is heated to a temperature and for a period of time sufficient to fuse the composition, for example about 2 minutes at about 200xc2x0 C. The time and temperature required to gel and fuse the composition will depend upon the particular composition but can readily be determined by routine testing. If the substrate is a foamable substrate, for example, a plastisol,containing a heat-activated blowing agent, the fused coating composition and the expanded substrate can be chemically and/or mechanically embossed or otherwise formed. Thereafter, the coated composition is immediately exposed to a non-ionizing or ionizing radiation, for a period of time necessary to crosslink the crosslinkable components of the composition. The crosslinking freezes any embossing and transforms the flexible, thermoplastic layer of gelled composition into a clear, high modulus, stain and abrasion resistant, thermoset film.
In another embodiment, the composition is prepared as a dry blend or mixture. The dry blend composition is formed into a sheet on hot calender rolls to an appropriate thickness and laminated to a substrate. The substrate can be, for example, a felt, a glass fleece or a layer of a suitable polymeric material such as PVC, polyolefin, polyester, polyamide, polyepoxy, polyacrylate or the like. Infrared heating is usually used in the laminating step. The hot laminated film is then embossed and immediately exposed to an ionizing or non-ionizing radiation, for a period of time necessary to crosslink the reactive components. This freezes the design obtained by embossing and converts the flexible, thermoplastic film into a tough, high modulus, stain and abrasion resistant, clear film.
Another way to produce a sheet on hot calendar rolls is to use a high shear mixer such as a two roll mill, a Banbury mixer or an extruder. These items are used to transform the raw materials into a composition ready for application onto hot calender rolls. The Banbury mixer, two roll mill or extruder solvates the resin with the acrylic or methacrylic compound and radiation reactive oligomer and forms a hot high viscosity paste. This paste is then fed to calender rolls (Encyclopedia of PVC by NASS, second edition, vol. 3).
The composition according to the invention does not require any solvent or diluent components which might be released into the atmosphere during gelling and curing. The composition also requires no external nor internal plasticizers, so that no degradation of the coating due to migration of plasticizers towards the surface of the layer can occur. The compositions of the invention are therefore normally completely or substantially free of any internal or external plasticizer. Coatings prepared from the composition of the invention have a superior tensile strength, scuff resistance, chemical and stain resistance as well as excellent gloss retention.
The composition may contain a heat stabilizer, suitably in an amount from about 0.5 to 10 parts by weight.
Due to its outstanding mechanical, wear and stain resistance, the wear layer prepared from the composition of the invention does not require a top protective layer. This makes the resulting flooring material less costly than vinyl flooring materials comprising a polyurethane protective layer. The composition of the invention can be applied to thermoplastic vinyl layers, to provide a top protective layer. Such a layer possesses excellent wear properties and is less costly than traditional polyurethane protective layers. The composition of the invention can also be applied as a wear layer to materials other than thermoplastic vinyl.
The composition according to the invention can be prepared either in the form of a low viscosity paste, a dry blend mix or a PVC and monomer mix using a high shear mixer, such as a Banbury mixer.
In one embodiment of the invention, a low viscosity paste comprises from 35 to 140, preferably from 55 to 120, most preferably about 100 parts by weight of a PVC emulsion resin, from 30 to 80, preferably from 50 to 60, most preferably about 55 parts by weight of an acrylic or methacrylic monomer, from 0.5 to 65, preferably from 4 to 20, most preferably about 7.5 parts by weight of a urethane radiation-reactive oligomer, if required from 0.5 to 10, preferably from 1 to 7, most preferably about 6.0 parts by weight of a heat stabilizer and, if required, from 0.1 to 10, preferably from 0.75 to 4, most preferably about 1.0 parts by weight of a photoinitiator. The preferred low viscosity paste may contain further additives, such as an air release agent, a U.V. light stabilizer and an antioxidant. The amount of the air release agent is normally in the range of from 0.5 to 5.0, preferably from 0.5 to 3.0, most preferably about 0.5 parts by weight. The amount of the antioxidant is from 25 to 1,000, preferably from 100 to 700, most preferably about 500 ppm.
The low viscosity paste should have a viscosity of from 200 cps to 4000 cps, preferably from 600 cps to 2000 cps, most preferably about 800 cps, as measured by Brookfield viscometer HBT at 20 rpm and 26xc2x0 C.
In another embodiment of the invention, a dry blend mix comprises from 75 to 140, preferably from 85 to 130, most preferably about 100 parts by weight of a PVC suspension resin, from 35 to 80, preferably from 40 to 70, most preferably about 50 parts by weight of an acrylic or methacrylic monomer, from 0.5 to 65, preferably from 5 to 30, most preferably about 15 parts by weight of a urethane radiation-reactive oligomer, if required from 0.5 to 10, preferably from 1 to 6, most preferably about 4.0 parts by weight of a heat stabilizer and, if required, from 0.25 to 15, preferably from 1 to 4, most preferably about 2.0 parts by weight of a photoinitiator. The dry blend may contain further additives, such as a lubricant and a drying agent. The amount of the lubricant is normally from 0.5 to 3.5, preferably from 0.75 to 3.0, most preferably about 1.0 part by weight. The amount of the drying agent is normally from 1.0 to 10.0, preferably from 2.5 to 6.5, most preferably about 3.5 parts by weight.
The dry blend mixture can be prepared by admixing the various ingredients under high shear and subjecting them to gentle heat. As the mixture warms, the PVC particles absorb the liquid materials present, so that there is formed a dry powder composed of PVC particles in which the liquid materials are absorbed. The particles tend to be somewhat sticky, owing to residual amounts of liquid material on the surface of the particles. To combat this stickiness there can be added to the mixture a drying agent, for example a further small quantity of PVC powder or Cab-O-Sil. The dry blend mixture is then a stable powder, somewhat reminiscent of sand in appearance, that can be stored until required for use.
In another embodiment of the invention, a PVC suspension resin is mixed with the acrylic or methacrylic monomer, the radiation-reactive urethane oligomer, a heat stabilizer, if required, a photoinitiator, if required and a lubricant, if required, in a high shear mixer, such as a Banbury mixer, and then calendered on hot rolls to form a sheet which can be readily laminated. Apart from the presence of a lubricant, for example zinc stearate, the components and amounts present in the high shear mixture may be the same as the dry blend mixture. The effect of the high shear on these components, however, is to cause the formation of a hot viscous mass that must be used immediately. The high shear mixture is therefore fed directly from the high shear mixer to calender rolls to form the sheet.
PVC emulsion resins which may be used in the compositions of the invention are those which are normally used for clear layer applications. They should have a relative viscosity from 2.05 to 3.40, preferably from 2.30 to 2.65. Examples of resins that are suitable for use in compositions of the invention and are commercially available include Oxy 605, Oxy 75HC, Oxy 1755, Oxy 1757 and Oxy 80HC, all products of Occidental Chemical Ltd. Similar products are available from other manufactures, such as B. F. Goodrich, Borden Chemicals, Norsk Hydro (Pevikon resins), Solvic, Atochem, HUls and Goodyear. Oxy resins produced by Occidental Chemical Ltd. are preferred.
PVC suspension resins which may be used in compositions of the invention are polymers which have a relative viscosity from 1.56 to 2.52, most preferably about 1.6. Examples of such resins are Oxy 160 from Occidental Chemical Ltd. or VC 47B, VC 58, VC 95 PM, VC 100 PM and VC 100 T, products of Borden Chemicals. Similar resins are available from other manufactures, such as B. F. Goodrich, Borden Chemicals, Norsk Hydro (Pevikon resins), Solvic, Atochem, Htls and Goodyear. Of the above resins those produced by Borden Chemicals are preferred. Oxy 160, product of Occidental Chemical Ltd. is particularly preferred.
Acrylic (including methacrylic) compounds suitable for use in the compositions of the invention include mono-, di- and multi-functional acrylic monomers. Examples of suitable commercially available acrylic monomers include esters such as 2-phenoxyethyl acrylate (SR-339), tetrahydrofurfuryl acrylate (SR-285), isodecyl acrylate (SR-395), isobornyl acrylate (SR-506), 2-(2-ethoxy-ethoxy)ethyl acrylate (SR-256), polyethylene glycol 400 diacrylate (SR-344), tripropylene glycol diacrylate (SR-306), polyethylene glycol 200. diacrylate (SR-259), dipentaerythritol monohydroxy pentacrylate (SR-399), isodecyl methacrylate (SR-242), ethylene glycol dimethacrylate (SR-206), methacrylate terminated oligomer C14-C15 (SR-2100), ethoxylated trimethylol propane triacrylate (SR-454), ethoxylated bisphenol A dimethacrylate (SR-348), polyethylene glycol 600 dimethacrylate (SR-252), 1,6-hexanediol dimethacrylate (SR-239), isobornyl methacrylate (SR-423), tetraethylene glycol dimethacrylate (SR-209), trimethylol propane trimethacrylate (SR-350), triethylene glycol dimethacrylate (SR-205), polyethylene glycol dimethacrylate (SR-210) and diethylene glycol dimethacrylate (SR-231), all products of Sartomer. Of these, SR-209, SR-210, SR-423, SR-231, SR-205 and SR-206 are preferred. SR-209, SR-205, SR-210 and SR-231 are particularly preferred. High viscosity acrylic monomers and oligomers may be diluted with acrylic monomers and oligomers having lower viscosity to keep the viscosity of the paste composition within the acceptable range.
The radiation-reactive urethane oligomer component is mostly responsible for imparting toughness and gloss retention to the cured layer-of the composition of the invention. It is an essential component for applications where superior surface toughness is required, such as flooring materials. For flooring applications the radiation-reactive urethane oligomer should normally be included into the composition, in an amount of at least 4 parts by weight. For applications less demanding in terms of the surface properties of the coating, such as wall coverings, the amount of this relatively expensive component can be reduced or eliminated.
The radiation-reactive urethane oligomer component has terminal, ethylenically unsaturated double bonds and can be prepared as follows. A diisocyanate or triisocyanate is reacted with a polyol, suitably a diol or triol. Hydroxy groups of the polyol react with isocyanate groups of the diisocyanate to form a polyurethane prepolymer. The molar ratio of isocyanate to polyol is chosen so that the polyurethane prepolymer has isocyanate terminal groups. This prepolymer is then reacted with a hydroxyalkyl acrylate or methacrylate ester. The hydroxy groups of the acrylate or methacrylate ester react with the terminal isocyanate groups of the polyurethane prepolymer, so that there is formed a urethane oligomer having terminal acrylate or methacrylate moieties. When the composition of the invention is subjected to radiation a polymerization reaction occurs at the double bonds of the acrylate or methacrylate moieties, creating bonds between molecules of the urethane oligomer. It is of course possible to use mixtures of diisocyanates and triisocyantes and of diols and triols. Use of trifunctional reactants will lead to crosslinking and result in urethane oligomers of higher viscosity, which may limit the amounts of trifunctional reactants that can be used.
Suitable diisocyanates for use in preparing the polyurethane prepolymer include 2,4- and 2,6-toluene diisocyanate, 1,4-phenylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, xcex1,xcfx89-alkylene diisocyanates such as hexamethylene diisocyanate, and isophorone diisocyanate. Suitable polyols may be any oligomers that can be prepared with hydroxy terminal groups, for example polycarbonates, polyesters, silicone materials, polyhydroxyalkylacrylates, polyhydroxyalkylmethacrylates, elastomeric materials such as polybutadiene diacrylate and polyepoxy materials.
Of the possible polyols to be used in the preparation of the urethane oligomer, silicone materials are very expensive. Polyesters result in oligomers of high viscosity. Polyhydroxyalkyl acrylate and methacrylate polyols result in urethane oligomers that, when used in compositions of the invention, do not always display the degree of toughness desired for flooring. Polyepoxy materials display a tendency to yellow, and are also undesirably rigid for flooring applications. For use in flooring, where a degree of toughness in the final product is desirable, it is preferred that the polyol is an aliphatic polycarbonate polyol, more preferably a triol and most preferably a diol. Aromatic polycarbonate polyols are not widely available, are in general too viscous and have a tendency to yellow. Suitable polycarbonate polyols can be based on alkylene glycols, ether glycols and alicyclic glycols or a mixture thereof. Preferred alkylene glycols include xcex1,xcfx89-straight chain glycols having between 5 and 10, most preferably 6 carbon atoms. An example of a preferred alkylene glycol is 1,6-hexane diol. In the alkylene-glycol, one or more carbon atoms of the alkylene chain can be replaced by an oxygen atom, to form one or more ether linkages. An example of a preferred ether glycol is di-ethylene glycol.
Preferred alicyclic glycols include those having the following structure:
wherein:
x=1, 2 or 3
w=0 to 10
z=0 to 10
Preferably, x has the value 2, i.e., the alicyclic glycol is based on cyclohexane. It is also preferred that the substituents on the alicyclic ring are located in the 1,3- or 1,4- positions relative to each other. In the alicyclic glycol, one or more carbon atoms of the alkylene chain can be replaced by an oxygen atom to form one or more ether linkages. Also, one or more of the hydrogen atoms attached to a carbon atom of the alkylene chain can be replaced by a substituent that does not interfere with the course of the desired reaction, for example an alkyl group having between 1 and 4 carbon atoms. An example of a most preferred alicyclic glycol is 1,4-dimethanolcyclohexane.
Suitable polycarbonate polyols that are commercially available include KM10-1122, KM10-1733, KM10-1667 (all products of Stahl) and DESMOPHEN 2020E (product of Bayer).
Suitable hydroxyalkyl acrylates and methacrylates for reaction with the polyurethane prepolymer to form the polyurethane oligomer include hydroxyethyl, hydroxypropyl and hydroxybutylacrylates and methacrylates, of which the hydroxyethyl esters are preferred.
The urethane oligomers may have viscosity that is too high for convenient handling. If this is the case, the urethane oligomer can be mixed with an acrylic or methacrylic compound that can be used as a component of the composition. For example, a preferred urethane oligomer that is based on a polycarbonate polyol of molecular weight in the range of about 500 to 2000 forms with hydroxyethyl acrylate a urethane oligomer whose viscosity is higher than optimum for convenience of handling. This oligomer has been successfully used in a 3:1 by weight mixture with ethoxylated trimethylolpropane triacrylate. This mixture is commercially available from Stahl, U.S.A. of Peabody, Mass., under the designation U26253. It has a viscosity of about 100,000 cps at 60xc2x0 C. when measured with a Brookfield viscometer using spindle number 3 at 10 rpm, is slightly yellowish in colour and has a slightly sweetish odour. The product may contain a small quantity of hydroxyethyl acrylate, as this compound may be used in molar excess when reacted with the urethane prepolymer to ensure complete reaction of the prepolymer. Any small excess of hydroxyethyl acrylate that is present in the U26253 is incorporated into the composition of the invention and is crosslinked with the other components during the irradiation step and has no significant effect on the properties of the cured composition.
Desirably the urethane oligomer has a fairly high molecular weight, say about 100,000 or higher. At lower molecular weights the product obtained may be undesirably brittle.
Other examples of suitable urethane oligomers include urethane acrylates CN-966 and CN-953, CN-966 E75 (urethane acrylate with ethoxylated trimethylol propane triacrylate) and CN-964 H75 (urethane acrylate with 2-(2-ethoxyethoxy)ethyl acrylate), all products of Sartomer. Of the urethane oligomers, U26253 is preferred.
Although the presence of a urethane oligomer is necessary to yield a material having sufficient toughness to serve as a wear layer for flooring, for applications where such toughness is not required it is possible to dispense with the urethane oligomer. If the PVC resin and the acrylic or methacrylic compound are admixed and then heated, the acrylic or methacrylic compound solvates the PVC. It is possible to extrude the solvated PVC into a flexible, transparent sheet, for example. According to a further aspect of the invention, therefore,. there is provided a radiation-curable composition which comprises a PVC resin that is free of external and internal:plasticizers, and is solvated by an acrylic or methacrylic compound.
Heat stabilizers known to those skilled in the art include compounds of alkaline earth metals and transition metals. Examples of heat stabilizers suitable for the compositions of the invention are BZ 512 (product of Ciba-Geigy) and Synpron 0144 (product of Synthetic Products Co.). Barium zinc stabilizer BZ 512 is preferred.
Photoinitiators are normally required for compositions cured by non-ionizing U.V. radiation. They may not be necessary in the case when the acrylic or methacrylic monomer and the radiation reactive oligomer polymeric network shows sufficient reactivity or has a photoinitiator built-in, so that no extra photoinitiator has to be added. When present, the photoinitiators should ensure quick and complete crosslinking of the composition which has been partially cured by a thermal treatment. The preferred photoinitiators are derivatives of phenyl ketone. Examples of suitable photoinitiators are Irgacure 184, Irgacure 907, Irgacure 2959, Irgacure 500, Irgacure 651 and Irgacure 369 (products of Ciba-Geigy) and Darocur 4265, Darocur 1173, and Micure HP-8 (products of Merck). Of these, Irgacure 184 is preferred.
Of the auxiliary components of the compositions of the invention, sterically hindered phenols, for example Irganox 1010 (product of Ciba-Geigy), are preferred as antioxidants. Organically modified siloxanes, such as BYK 3105 (product of BYK Chemie), are preferred as air release agents. Fatty acids, for example stearic acid, and their salts, for example zinc stearate and magnesium stearate, are preferred as lubricant. Fumed silica or a fine particle emulsion PVC resin having relative viscosity of from 2.05 to 2.75 are preferred drying agents. Examples of suitable drying agents are Cab-O-Sil (product of Cabot Corporation) and Oxy 625 (product of Occidental Chemical Ltd.).
To prepare a low-viscosity paste, all the components are combined, thoroughly mixed to form a paste and the mixture is placed under vacuum, to eliminate any entrapped air. After the vacuum treatment, the paste is applied as a layer of a predetermined thickness to a substrate by conventional means, such as a reverse roll coater, a knife over roll, a screen coater, a spray gun or other applicable means. The substrate covered with the paste is then heated, for example in a circulating oven, to a temperature of from about 160xc2x0 C. to about 220xc2x0 C., preferably about 200xc2x0 C. Upon heating, the liquid ingredients initially solvate the PVC resin particles which then forms a solid homogeneous mass. As a result, the opaque layer of the paste is transformed into a clear thermoplastic film. When a composition of the invention is applied over a foamable thermoplastic vinyl plastisol layer, the composition has a sufficiently high melt viscosity that it serves as a barrier which prevents the escape of gases from the foamed underlayer when both films are fused. Consequently, and in contrast to the prior art, it is not necessary to provide an extra layer of a composition of high melt viscosity merely to avoid blistering and pin holes in the surface layer. The clear film, which leaves visible any underlying design, can be embossed or formed into any specific shape. The embossing can be done chemically or mechanically, in known manner. Once the shaping, if any, is terminated, the film is cured by exposing it to a non-ionizing or ionizing radiation, to crosslink the crosslinkable components and to freeze any design obtained by the embossing.
The crosslinking converts the flexible, thermoplastic film into a tough, stain and abrasion resistant layer. Since the film becomes transparent after the initial thermal treatment, even a thick film (10 mils or more) can be crosslinked quickly and completely by U.V. or E.B. irradiation. For U.V. radiation an inert gas, such as nitrogen, is used to displace oxygen which causes inhibition of the crosslinking on the surface. It is important that the film be completely crosslinked, since any remaining free monomers or oligomers will tend to migrate to the surface of the coating, adversely affecting its wear properties.
Dry blend mixtures formulated with PVC suspension resins are prepared suitably by heating the PVC suspension resin to approximately 50xc2x0 C.xc2x115xc2x0 C. while agitating in a high speed mixer, for example a Henschel mixer. The liquid portion of the composition, composed of the acrylic or methacrylic monomer and radiation reactive urethane oligomer, is then added gradually while the temperature is raised to about 80xc2x0 C.xc2x115xc2x0 C. At this temperature the resin absorbs all the liquid. The dry blend is then cooled to about 50xc2x0 C.xc2x115xc2x0 C., at which temperature drying agents may be added to ensure that the blend will remain dry when further cooled and stored.
The dry blend can be processed in various manners prior to irradiation. The mixture may be calendered on heated rolls (at a temperature of about 160xc2x0 C. to 220xc2x0 C., preferably about 200xc2x0 C.) to an appropriate thickness (usually from 2 to 30 mils), to form a sheet which is stripped from the last roll, cooled and stored. This rolled film can be subsequently laminated, for example onto a hot, printed tile sheet, embossed if required, radiation-cured and cooled. Alternatively, a layer of the dry blend mixture in the form of a powder may be applied to a substrate, for example a felt, using any known technique (squeegee, screen, etc.). The layer is then melted by heating to an elevated temperature by any suitable heating means, for example an air circulating oven or preferably by infrared. When heated to a temperature of from 160xc2x0 C. to 220xc2x0 C., preferably about 200xc2x0 C., by calendering, the initially opaque mixture becomes transparent, which facilitates the final radiation curing when a non-ionizing radiation, such as U.V. radiation, is used. Another aspect of the invention consists of adding the suspension resin and the acrylic or methacrylic monomer, radiation reactive urethane oligomer, stabilizer, photoinitiator and other additives like lubricants, into a high shear Banbury mixer or a two rolls intensive mixer and forming a sheet on calendar rolls.
By way of example, when a top protective layer is formed from a dry blend, the dry blend (20 mils) may be applied by knife coating over a felt substrate that has been coated with a printed or non-printed gelled vinyl film (10 mils). The coated felt substrate covered with the dry blend is then passed through an oven (for example 2 minutes at 200 xc2x0 C.) to melt the dry blend. If required, the product is cooled to room temperature. An embossing step, if present, is carried out on a textured cooling roll which reduces the temperature of the film. The following radiation curing step does not require any specific temperature.
The thermal gelling step can be carried out in an oven employing any suitable means for heat generation. For a low-viscosity-paste, this step is preferably carried out in a hot air circulating oven. For a dry blend mixture or a high shear Banbury mixing, the thermal gelling is preferably carried out on hot calender rolls, although an infrared heater or hot air oven can be used to melt the dry blend, if the blend is applied as powder to a substrate. A suitable residence time for the thermal gelling is about 2xc2x11 minutes for layers about 10 mils thick and at a temperature of about 200xc2x0 C.xc2x120xc2x0 C. This time will depend, in general, on the temperature, the thickness of the layer and the relative viscosity of the PVC resin.
The radiation curing of the thermally gelled film may be carried out with a non-ionizing or ionizing radiation. Any source providing a non-ionizing radiation of the wavelength between about 180 nm and about 400 nm, preferably between about 250 nm and about 400 nm, can be used. Examples of suitable sources are medium pressure mercury lamps, non-mercury lamps having spectra different from mercury lamps (xenon arc, krypton arc, carbon arc, sunlamps) and pulse U.V. sources. Of these, the medium pressure mercury lamp is preferred. Most medium pressure (1 to 2 atm) mercury vapor arc lamps can operate consistently at 100 or 200 Watts per linear inch. The U.V. irradiation is preferably carried out under nitrogen blanket to eliminate oxygen inhibition on the top surface of the cured coating. The radiation intensity is typically between 100 and 700 watt/sq.ft., preferably about 150 watt/sq.ft.
An electron beam can be used as a source of ionizing radiation. When an electron beam is used to crosslink the reactive components no photoinitiator is required. Also, when cured with the electron beam, the cured film can be colored or opaque. Such films may be preferred for some applications, such as inlaid floor coverings, wall coverings and the like.
Although originally developed for flooring applications, the compositions of the invention can be used for many other applications requiring a tough coating, laminated or not to a substrate, such as wall coverings, table cloths, boat tarpaulins and covers and the like. Felts, woven or non-woven fiberglass, woven or non-woven polyester, nylon, jersey, cotton fabrics and the like can be used as substrates. Felts or calendered PVC sheets are preferred for flooring applications. The compositions of the invention can also be used on non-supported PVC flooring products, for example resilient sheet vinyl floor covering as described in ASTM Standard F1303, classes B or C (vol. 15.04). They can be used on foamable PVC and ethylene-vinyl acetate (EVA) compositions. The PVC or EVA composition contains a heat-activated blowing agent. The composition of the invention is applied over the PVC or EVA foamable composition and the heat used to cure the composition of the invention also serves to activate the blowing agent, causing the PVC or EVA composition to foam.
The thickness of the cured layer depends on its intended application. For single wear layers for flooring materials, this thickness will be typically in the range of from 1 mil to 50 mils, preferably from 7 mils to 15 mils, most preferably about 10 mils. The same thickness can be used for protective layers applied on the top of conventional thermoplastic plastisol layers. In this case the preferred thickness is 5xc2x12 mils.

Curable coating composition for sheet goods


An electronic control device for a bistable solenoid valve, particularly for watering systems. The control device includes a power supply battery and a logic control unit, and provides low battery protection. A capacitor is set in parallel to the battery and a switch is operated by the logic control unit to effect, in a first operating position, charging of the capacitor and, in second and third operating positions, the application of control voltages having opposite signs from the capacitor to the solenoid valve for closing and opening the solenoid valve. The logic control unit is programmed in such a way that each request for opening of the solenoid valve brings about first the setting of the switch in the first operating position for charging the capacitor, then the switch is activated in the second operating position for closing the solenoid valve after a first preset time has elapsed following any previous closing control of the solenoid valve. The switch is then returned to the first operating position for a second charging of the capacitor and finally the switch is set in the third operating position to open the solenoid valve after a subsequent second preset time which is shorter than the first preset time.

1. Field of the Invention
The present invention concerns an electronic control device for a bistable solenoid valve with automatic low battery protection, particularly for watering systems.
2. Description of Related Art
Watering systems for lawns, gardens, kitchen gardens and cultivated spaces are generally based on the use of solenoid valves that determine the delivery of water in the various sectors to be watered.
The control of the solenoid valves is entrusted to programmable electronic control devices having various degrees of complexity that can be connected with mains power or operate with battery power, in which case, for power saving reasons, valves with bistable type electric actuators are essential.
With battery operated devices, the battery runs down and it is then necessary to detect the low or exhausted battery condition and to operate the solenoid valves in order to lock them in a closing position. In this way, considering that bistable type solenoid valves require driving controls of short duration, it is possible to prevent the opening of the solenoid valve whilst the battery still has sufficient energy to control the opening of the solenoid valve, but insufficient energy to subsequently close the solenoid valve, with the consequence that watering would continue without interruption until the moment in which someone notices the problem.
For such reason battery-operated control devices are usually provided with electronic circuits capable of detecting the battery voltage dropping to a minimum value, below which no further activation of the solenoid valves being controlled will occur.
In this way, the detection circuit determines the locking of the system when in reality the battery still has sufficient energy for several additional activations.
In addition, the detection circuit has a cost of its own, that obviously affects the total cost of the control device.
An object of the present invention is to realize a battery operated electronic control device for a bistable type solenoid valve, particularly but not exclusively for watering systems, that does not require a detection circuit for detecting a low or exhausted battery condition.
According to a first aspect of the invention such object has been attained with an electronic control device for bistable solenoid valve, comprising: a power supply battery; a capacitor in parallel with the battery; a switch having first switching means interposed between the battery and the capacitor and second switching means interposed between the capacitor and the bistable solenoid valve, said switch having a first operating position (rest position), in which the capacitor is connected to the battery to receive charge therefrom and is disconnected from the solenoid valve and second and third operating positions in which the capacitor is disconnected from said battery and is connected to the solenoid valve to transfer control voltages having opposite signs from the capacitor to the solenoid valve for respectively causing closing and opening of the solenoid valve; and a programmed logic control unit which controls said switch so that at each request for the opening of the solenoid valve the switch operates, in succession, first switching from said first operating position to said second operating position for the closing of the solenoid valve after a first preset time has elapsed from a previous valve closing operation, then switching to said first operating position and finally switching to said third operating position for the opening of the solenoid valve after a second preset time from said second switching, said second preset time being shorter than said first preset time.
According to a second aspect of the invention, there is provided an electronic control device for a bistable solenoid valve, comprising: a power supply battery; a capacitor in parallel with the battery; and a programmed logic control unit which at each request for opening of the solenoid valve controls, in succession, a first charge of the capacitor from the battery for a first preset time, a first discharge of the capacitor for a closing operation of the solenoid valve, a second charge of the capacitor from the battery for a second preset time which is shorter than said first preset time, and a second discharge of the capacitor for an opening operation of the solenoid valve.
Thus, as will be better seen hereinafter, it is possible to have a guarantee that at a certain point of discharging of the battery, or even in case of removal of the battery, a residual energy remains in the capacitor that is capable of allowing the closing of the solenoid valve without any further possibility of opening it again.

Electronic control device for a bistable solenoid valve with automatic low battery protection


A method for processing and laser ablation marking an imagewise exposed motion picture photographic film element which comprises a support having on a front side thereof one or more image-forming units comprising at least one light-sensitive silver halide emulsion layer is described, comprising processing the film to provide a developed photographic image with at least 100 mg/m2 of retained silver halide, and subsequently laser ablation marking the film to selectively ablate portions of the image forming units from the support.

The present invention relates in general to photography and in particular to a novel processed motion picture print film photographic element. More specifically, this invention relates to a motion picture print film which is processed after exposure thereof to result in a retained silver halide level of at least 100 mg/M2, which processed print film is capable of being marked with a laser with improved performance.
Marking of photographic film elements to provide, e.g., graphic elements, characters, bar codes or text is often desired in the photographic art. The showing of foreign language films in a motion picture theater, e.g., typically includes the simultaneous display of the translated dialogue in the form of marked subtitles along with display of the film scenes. A current frequently used method of subtitle marking, described in U.S. Pat. Nos. 4,854,696 and 5,367,348, involves embossing or etching the subtitle text into the film""s photographic emulsion image layer(s), after imagewise exposure of the film scenes and photographic processing to develop the imagewise exposed scenes. Marking is currently frequently done by laser ablation, wherein a laser beam of high energy travels along a determined path corresponding to the inscriptions to be formed on the film element. The majority of laser subtitling labs use an Argon laser with peak emissions at 488 and 514 nm. In such method, the photographic emulsion layer(s) coated onto the film support becomes ablated locally. Photographic color films comprise image dye-forming emulsion layers coated on a transparent support, and the marked or ablated areas comprise clear or low density areas surrounded by the unmarked dye-containing image areas. Similarly, for black and white films the marked or ablated areas comprise clear or low density areas surrounded by the unmarked image areas which contain silver metal. In the particular application of laser subtitling of photographic films, the quality of laser marked subtitles is dependent upon the density and color differences between the marks and the surrounding dye or silver image areas, and on the wavelength, power, and writing speed of the laser. The power and speed are selected to remove as much of image emulsion layers as possible without damaging or distorting the support. Laser subtitling is typically performed on the final color or black and white release print film intended for projection in a theater, but may also be performed on color intermediate or black and white films to form subtitle images which may then be optically printed onto another intermediate or black and white film to form a negative image, which may then be printed onto the final release print film.
Most laser subtitling systems were originally designed and optimized for marking motion picture films having acetate film base supports. A switch in the industry from acetate to polyester supports for motion picture print films has required the subtitling labs to make changes in their operations to reoptimize results, which has been a problem as thermoplastic polymer support materials, such as polyester, are more succeptible to support damage. There is an inherent conflict between using sufficient power to mark in low density image areas without causing significant base damage in the high density image areas, as due to the non-uniform release of gelatinous residues or to the damage of the support, undesired dark and/or colored spots may be observed when the film image is enlarged and projected on the screen in a theater, especially for print films having polyester film supports.
After imagewise (scene) exposure, silver halide motion picture photographic elements are typically processed using standard photographic processing procedures, such as Process ECP-2B for color print films, standard D-97 processing for black and white films, and ECN-2 for color negative and intermediate films. In such standard processes, residual (or retained) silver halide is typically minimized after image development to prevent the appearance of the developed image from changing, as such residual silver halide may be slowly photoreduced to silver metal. Silver salts are typically removed in a xe2x80x9cfixxe2x80x9d step or steps, wherein they are solubilized by complexation with a silver ligand. Where silver metal formed during image development is also desired to be removed (typically for color films where the image is formed with dyes), it is oxidized and converted back to a silver salt in a xe2x80x9cbleachxe2x80x9d step (optionally with a bleach accelerator), and then removed in a fix step. Alternatively, the bleach and fix may becomed into a single bleach-fix or xe2x80x9cblixxe2x80x9d step. Standard process ECP-2B for color print films, e.g., comprises prebath (10xe2x80x3), water rinse (20xe2x80x3), color developer (3xe2x80x2), stop bath (40xe2x80x3), first wash (40xe2x80x3), first fix (40xe2x80x3), second wash (40xe2x80x3), bleach (1xe2x80x2), third wash (40xe2x80x3), second fix (40xe2x80x3), fourth wash (1xe2x80x2), and final rinse (10xe2x80x3) steps, and then drying with hot air. Typical levels of retained silver in normally processed color print films in areas of high density are less than 150 mg/m2, and the typical level of retained silver halide in normally processed films is less than 50 mg/m2.
It would be desirable to provide a method for photographic processing and laser marking an imagewise exposed motion picture photographic film element in order to provide improved performance when the processed photographic film is marked by means of a laser beam.
In accordance with the present invention there is provided a method for processing and laser ablation marking an imagewise exposed motion picture photographic film element which comprises a support having on a front side thereof one or more image-forming units comprising at least one light-sensitive silver halide emulsion layer, comprising processing the film to provide a developed photographic image with at least 100 mg/m2 of retained silver halide, and subsequently laser ablation marking the film to selectively ablate portions of the image forming units from the support.
Motion picture film photographic elements processed in accordance with the invention comprise a support having on a front side thereof at least one silver halide emulsion layer. In preferred embodiments, the elements may include an antihalation undercoat in a subbing layer unit between the support and the silver halide emulsion layer(s), an outermost protective overcoat layer, an antistatic layer on either side of the support, and an outermost protective backcoat layer on the back side of the support.
While standard photographic processing is designed to minimize levels of retained silver halide in a processed photographic film, motion picture films are deliberately processed in accordance with the invention to result in a developed photographic image with at least 100 mg/m2 of retained silver halide, preferably from 100 to 1000 mg/m2, more preferably from 100 to 500 mg/m2 and most preferably from 100 to 250 mg/m2 of retained silver halide. Such levels of retained silver halide have surprisingly been found to result in improved performance when the processed films are subsequently laser ablation marked to selectively ablate portions of the image forming units from the support. Retained silver halide levels of less than 100 mg/m2 have little impact on laser ablation marking performance, while levels above 1000 mg/m2, may adversely effect minimum density and hues of the developed images. The most preferred range of 100 to 250 mg/m2 of retained silver halide provides optimum laser marking performance while minimizing impact on minimum density and hues of the developed images.
Special image processing techniques are known in the art which are designed to specifically retain a significant amount of silver metal (e.g., greater than 100 mg/m2, or even greater than 500 mg/m2) during the processing of color photographic silver halide print materials, such as by-passing the bleach step present in normal print processing so as to retain developed silver (see, e.g., B. Bergery, xe2x80x9cReflections: The Lab, Part IIxe2x80x9d, American Cinematographer, May 1993, pp. 74-78). The retained silver increases print opacity yielding higher black densities, with an accompanying decrease in color saturation. While the primary affect of this process is to leave silver in the film, some amount of silver halide also remains. The advantages of the invention attributable to retained silver halide, however, may be achieved in the absence of increased levels of retained silver metal, and laser subtitling results may in fact actually be better at lower retained silver metal levels. Accordingly, in preferred embodiments of the invention directed towards color print films, the retained silver metal after photographic processing is preferably less than 500 mg/m2, and more preferably less than 100 mg/m2.
Residual silver halide levels in accordance with the invention may be obtained by modifying standard photographic processing procedures. For example, fix solution steps may be skipped or shortened. Alternatively, higher retained silver halide levels may be achieved through other process variations, including lowering the temperature of the fixing solution or decreasing the amount of the active ingredient in the fix (e.g., sodium or ammonium thiosulfate), or adjusting the pH of the fixing solution. A high degree of regeneration or build-up of halide in the fix may also be used to reduce the activity of the fixer. Retained silver metal in combination with retained silver halide may be obtained, e.g., by skipping or reducing the time in either the bleach or the bleach accelerator solutions steps during processing, reducing the temperature of such solutions, reducing the concentration of bleach accelerator in an accelerator bath (where a two-part bleach solution is used) or the concentration of the active bleaching species in the bleach solution, adjusting the pH of the accelerator or bleach solution, or contaminating the bleach accelerator with thiosulfate or any other contaminant that deactivates the bleach.
The materials employed as the support member are synthetic high molecular weight polymeric materials. These materials may be comprised of various polymeric films, but polyester and cellulose triacetate film supports, which are well known in the art, are preferred. The advantages of the invention are particularly applicable when thermoplastic polymer supports, particularly polyester film supports such as poly(ethylene terephthalate), are used. For elements comprising acetate supports, processing to retain silver halide in accordance with the invention may advantageously allow good subtitling results to be obtained with lower power settings than previously required. The thickness of the support is not critical. Conventional support member thicknesses of from about 50 to 250 microns (2 to 10 mils, or 0.002 to 0.010 inches) can be employed, for example, with very satisfactory results.
The term xe2x80x9csubbing layer unitxe2x80x9d as used herein applies to layers of the photographic element coated between the support and the photographic emulsion layer closest to the support. Subbing layers coated between a support and the photographic imaging emulsion layers of a photographic element are conventionally employed in the art to provide improved adhesion of the imaging layers to the support, as well as other functionality such as antihalation or antistatic protection. As described in U.S. Pat. No. 4,132,552, e.g., it is often useful to employ a combination in the subbing layer unit of at least one hydrophobic xe2x80x9cprimerxe2x80x9d layer directly contacting the film support and at least one hydrophilic layer coated thereupon. Polyester support members, e.g., typically employ a primer layer between the functional layers and the polyester support. Such primer layers are well known in the art and comprise, for example, a vinylidene chloride/methyl acrylate/itaconic acid terpolymer or vinylidene chloride/acrylonitrile/acrylic acid terpolymer as described in U.S. Pat. Nos. 2,627,088; 2,698,235; 2,698,240; 2,943,937; 3,143,421; 3,201,249; 3,271,178 and 3,501,301. Additional polymers useful as primer layers in a subbing layer unit include styrene-butadiene copolymers, water-soluble polyesters and polyacrylic esters.
The hydrophilic layer which may be coated adjacent to the primer layer in a subbing layer unit preferably comprises a hydrophilic colloid to provide good adhesion to hydrophilic colloid layers coated thereover, and may also include an aqueous latex dispersion, optionally containing a cross-linking agent, a swelling agent, a matting agent or an antistatic agent. Hydrophilic colloids such as dextran, polyacrylamide, polyvinylalcohol and polyvinyl pyrrolidone may be used, but particularly preferred is gelatin, optionally in combination with at least one of the other hydrophilic colloids cited. Preferably hydrophilic layers are gelatinous layers. The gelatin used therein can be lime-treated or acid-treated gelatin. The preparation of such gelatin types has been described in e.g. xe2x80x9cThe Science and Technology of Gelatinxe2x80x9d, edited by A. G. Ward and A. Courts, Academic Press 1977, page 295 and next pages. The gelatin can also be an enzyme-treated gelatin as described in Bull. Soc. Sci. Phot. Japan, No. 16, page 30 (1966). Gelatin derivatives may be useful. Said derivatives have e.g. been described in U.S. Pat. Nos. 4,978,607; 5,378,598; 5,395,748 and 5,439,791 and in EP-A""s 0 628 860 and 0 666 498. Examples of the cross-linking (or hardening) agent include triazine compounds as described e.g. in U.S. Pat. Nos. 3,325,287; 3,288,775 and 3,549,377; dialdehyde compounds as described in U.S. Pat. Nos. 3,291,624 and 3,232,764; epoxy compounds as described in U.S. Pat. No. 3,091,537; vinyl compounds described in U.S. Pat. No. 3,642,486; aziride compounds described in U.S. Pat. No. 3,392,024; ethylene-imine compounds described in U.S. Pat. No. 3,549,378 and methylol compounds. Combinations of vinyl sulphonyl compounds and triazine compounds may be useful and particularly the combination set forth in U.S. Pat. No. 4,680,257.
Elements processed in accordance with the invention comprise one or more image-forming units comprising at least one light-sensitive silver halide emulsion layer coated on the element support. The invention is applicable to processing of color photographic print and intermediate film elements as well as black and white motion picture photographic film elements. While a single silver halide emulsion layer may typically be used in a black and white film element, a color photographic print or intermediate element will typically contain dye image-forming units sensitive to each of the three primary regions of the spectrum, in the form of a blue-sensitive layer having a yellow color coupler associated therewith, a green-sensitive layer having a magenta color coupler associated therewith, and a red-sensitive layer having a cyan color coupler associated therewith (i.e., separate yellow, magenta, and cyan dye image-forming units). Each unit may be comprised of a single light-sensitive layer, a pack of two light-sensitive layers with one being more light sensitive and the other being less light-sensitive, or a pack of three or more light-sensitive layers of varying light-sensitivity. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as is well known in the art.
A multicolor photographic print film element which may be processed in accordance with preferred embodiments of the invention comprises a support bearing, in order, a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler, optionally a first emulsion intercoat layer, a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, optionally a second emulsion intercoat layer, and a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler.
The silver halide emulsion layers of dye-image forming units and the emulsion intercoat layers will comprise a hydrophilic binder, typically gelatin. The intercoat layers positioned between adjacent dye image-forming units of photographic elements function to separate and prevent image spread between the adjacent image-forming units.
While processing of an element to result in at least 100 mg/m2 of retained silver halide in accordance with the invention advantageously leads to improved laser ablation marking performance, it is contemplated that laser ablation marking may be further improved by incorporating dispersed carbon particles into the layers coated on the emulsion side of the support as described in copending, commonly assigned U.S. Ser. No. 09/631,917 filed Aug. 3, 2000, the disclosure of which is incorporated by reference herein. Specifically, such elements may comprise in total from 5 to 30 mg/m2 of dispersed carbon particles, preferably at least 6 mg/m2, and preferably at most 22 mg/m2 and most preferably at most 20 mg/m2, where the majority of the dispersed carbon particles is contained in the emulsion layers and emulsion intercoat layers.
The light-sensitive silver halide emulsions employed in the emulsion layers of the photographic elements processed in accordance with the invention can include coarse, regular or fine grain silver halide crystals or mixtures thereof and can be comprised of such silver halides as silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chorobromoiodide, and mixtures thereof. The emulsions can be, for example, tabular grain light-sensitive silver halide emulsions. The emulsions can be negative-working or direct positive emulsions. They can form latent images predominantly on the surface of the silver halide grains or in the interior of the silver halide grains. They can be chemically and spectrally sensitized in accordance with usual practices. Photographic print films typically use relatively small grain, high chloride emulsions (e.g., emulsions having average grain size equivalent circular diameters of less than about 1 micron and halide contents of greater than 50 mole % chloride) in order to optimize print image quality and enable rapid processing. Such emulsions typically result in relatively low speed photographic elements in comparison to camera negative films. Low speed is compensated for by the use of relatively high intensity print lamps or lasers for exposing such print elements. For comparison purposes, it is noted that motion picture color print films, e.g., when rated using the same international standards criteria used for rating camera negative films, would typically have an ISO speed rating of less than 10, which is several stops slower than the slowest camera negative films in current use. The emulsions typically will be gelatin emulsions although other hydrophilic colloids can be used in accordance with usual practice. The compositions of typical light sensitive image recording layers used in print films are well known, and are not critical to the invention, as any of the silver halide materials used in conventional motion picture films may be used, such as those described, e.g., in Research Disclosure, Item 36544, September, 1994, and the references listed therein.
Dye-image-providing materials can be incorporated in the silver halide emulsion layer or in a separate layer associated with the emulsion layer. The dye-image-providing material can be any of a number known in the art, such as dye-forming couplers, bleachable dyes, dye developers and redox dye-releasers, and the particular one employed will depend on the nature of the element, and the type of image desired. Dye-image-providing materials employed with conventional color materials designed for processing with separate solutions are preferably dye-forming couplers; i.e., compounds which couple with oxidized developing agent to form a dye. Preferred couplers which form cyan dye images are phenols and naphthols. Preferred couplers which form magenta dye images are pyrazolones and pyrazolotriazoles. Preferred couplers which form yellow dye images are benzoylacetanilides and pivaloylacetanilides.
In accordance with a preferred embodiment of this invention, an antihalation undercoat layer is present as part of a subbing layer unit between the support and the emulsion layers, and is used to prevent light from being reflected into the silver halide emulsion layer(s) and thereby causing an undesired spreading of the image which is known as halation. Any of the filter dyes known to the photographic art can be used in the present invention as a means of reducing halation. Thus, for example, water-soluble dyes can be used for this purpose. Such dyes should be incorporated in the antihalation undercoat with a mordant to prevent dye diffusion. Alternatively, and preferably, a solid particle filter dye is incorporated in the antihalation undercoat.
Useful water-soluble filter dyes include the pyrazolone oxonol dyes of U.S. Pat. No. 2,274,782, the solubilized diaryl azo dyes of U.S. Pat. No. 2,956,879, the solubilized styryl and butadienyl dyes of U.S. Pat. Nos. 3,423,207 and 3,384,487, the merocyanine dyes of U.S. Pat. No. 2,527,583, the merocyanine and oxonol dyes of U.S. Pat. Nos. 3,486,897; 3,652,284 and 3,718,472, the enamino hemioxonol dyes of U.S. Pat. No. 3,976,661, the cyanomethyl sulfone-derived merocyanines of U.S. Pat. No. 3,723,154, the thiazolidones, benzotriazoles, and thiazolothiazoles of U.S. Pat. Nos. 2,739,888; 3,253,921; 3,250,617 and 2,739,971, the triazoles of U.S. Pat. No. 3,004,896, and the hemioxonols of U.S. Pat. Nos. 3,125,597 and 4,045, 229. Useful mordants are described, for example, in U.S. Pat. Nos. 3,282,699; 3,455,693; 3,438,779 and 3,795,519.
Preferred examples of solid particle filter dyes for use in antihalation undercoat layers include those which are substantially insoluble at aqueous coating pH""s of less than 7, and readily soluble or decolorizable in aqueous photographic processing solutions at pH of 8 or above, so as to be removed from or decolorized in a photographic element upon photographic processing. By substantially insoluble is meant dyes having a solubility of less than 1% by weight, preferably less than 0.1% by weight. Such dyes are generally of the formula:
Dxe2x80x94(X)n
where D represents a residue of a substantially insoluble compound having a chromophoric group, X represents a group having an ionizable proton bonded to D either directly or through a bivalent bonding group, and n is 1-7. The residue of a compound having a chromophoric group may be selected from conventional dye classes, including, e.g., oxonol dyes, merocyanine dyes, cyanine dyes, arylidene dyes, azomethine dyes, triphenylmethane dyes, azo dyes, and anthraquinone dyes. The group having an ionizable proton preferably has a pKa (acid dissociation constant) value measured in a mixed solvent of water and ethanol at 1:1 volume ratio within the range of 4 to 11, and may be, e.g., a carboxyl group, a sulfonamido group, a sulfamoyl group, a sulfonylcarbamoyl group, a carbonylsulfamoyl group, a hydroxy group, and the enol group of a oxonol dye or ammonium salts thereof. The filter dye should have a log P hydrophobicity parameter of from 0-6 in its non-ionized state. Such general class of ionizable filter dyes is well known in the photographic art, and includes, e.g., dyes disclosed for use in the form of aqueous solid particle dye dispersions as described in International Patent Publication WO 88/04794, European patent applications EP 594 973; EP 549 089; EP 546 163 and EP 430 180; U.S. Pat. Nos. 4,803,150; 4,855,221; 4,857,446; 4,900,652; 4,900,653; 4,940,654; 4,948,717; 4,948,718; 4,950,586; 4,988,611; 4,994,356; 5,098,820; 5,213,956; 5,260,179 and 5,266,454; the disclosures of each of which are herein incorporated by reference. Such dyes are generally described as being insoluble in aqueous solutions at pH below 7, and readily soluble or decolorizable in aqueous photographic processing solutions at pH 8 or above.
Preferred dyes of the above formula include those of formula:
[Dxe2x80x94(A)y]xe2x80x94Xn
where D, X and n are as defined above, and A is an aromatic ring bonded directly or indirectly to D, y is 0 to 4, and X is bonded either on A or an aromatic ring portion of D.
Exemplary dyes of the above formulas include those in Tables I to X of WO 88/04794, formulas (I) to (VII) of EP 0 456 163 A2, formula (II) of EP 0 594 973, and Tables I to XVI of U.S. Pat. No. 4,940,654 incorporated by reference above. Preferred examples of solid particle filter dyes include the following:
To promote adhesion of the antihalation undercoat to the support, primer layers as hereinabove described are advantageously employed, especially when the support is a polyester support.
The motion picture film elements processed in accordance with the present invention can contain additional auxiliary layers conventional in photographic elements, such as spacer layers, filter layers, pH lowering layers (sometimes referred to as acid layers and neutralizing layers), magnetic recording layers, timing layers, barrier layers, antistatic layers, and outermost protective overcoat and backcoat layers. The film elements can contain addenda conventional in the photographic art. Useful addenda are described, for example, in Research Disclosure, Item 36544, September, 1994. Useful addenda include spectral sensitizing dyes, desensitizers, antifoggants, masking couplers, DIR couplers, DIR compounds, antistain agents, image dye stabilizers, absorbing materials such as filter dyes and UV absorbers, light-scattering materials, coating aids, plasticizers and lubricants, and the like. To further improve laser subtitling performance or other print film properties, it is specifically contemplated that print films processed in accordance with the invention may incorporate anti-oxidant and UV absorbers as described in U.S. Pat. No. 5,981,155, the disclosure of which is incorporated by reference. Antioxidants in particular may be useful in combination with the invention.
Outermost protective overcoat and the outermost protective backcoat layers typically comprise film-forming binder and matting agent. The film-forming binder can be essentially any known polymeric binder. This includes hydrophilic colloids such as gelatin as well as hydrophobic polymers. Particularly preferred polymeric binders for use in the backcoat include aliphatic polyurethanes such as those described in U.S. Pat. No. 5,679,505 which is incorporated herein by reference.
In a particularly preferred embodiment the motion picture films processed in accordance with the invention may include an antistatic layer whose antistatic properties survive film processing. The antistatic layers may include a variety of electrically conductive metal-containing particles, such as metal oxides, dispersed in a binder material. Examples of useful electrically conductive metal-containing particles include donor-doped metal oxides, metal oxides containing oxygen deficiencies, and conductive nitrides, carbides, and borides. Specific examples of particularly useful particles include conductive TiO2, SnO2, V2O5, Al2O3, ZrO2, In2O3, ZnO, ZnSb2O6, InSbO4, TiB2, ZrB2, NbB2, TaB2, CrB, MoB, WB, LaB6, ZrN, TiN, WC, HfC, HfN, and ZrC. Examples of the patents describing these electrically conductive particles include; U.S. Pat. Nos. 4,275,103; 4,394,441; 4,416,963; 4,418,141; 4,431,764; 4,495,276; 4,571,361; 4,999,276; 5,122,445 and 5,368,995. Other useful electrically conductive materials for use in antistatic layers include:
Semiconductive metal salts such as cuprous iodide as described in U.S. Pat. Nos. 3,245,833; 3,428,451 and 5,075,171.
Fibrous conductive powders comprising, for example, antimony-doped tin oxide coated onto non-conductive potassium titanate whiskers as described in U.S. Pat. Nos. 4,845,369 and 5,116,666.
Conductive polymers, such as, the cross-linked vinylbenzyl quaternary ammonium polymers of U.S. Pat. No. 4,070,189, the conductive polyanilines of U.S. Pat. No. 4,237,194, and conductive polythiophenes of U.S. Pat. Nos. 4,987,042, 5,035,926; 5,354,613; 5,370,981; 5,372,924; 5,543,944 and 5,766,515.
A colloidal gel of vanadium pentoxide or silver-doped vanadium pentoxide as described in U.S. Pat. Nos. 4,203,769; 5,006,451; 5,221,598 and 5,284,714.
Typically, the antistatic layer is coated at a dry coverage of from 1 to 1000 mg/m2 based on total dry weight. The electrical resistivity of the antistatic layer is preferably from about 7 to about 11 log xcexa9/xe2x96xa1, more preferably from about 8 to 11 log xcexa9/xe2x96xa1, and most preferably from about 8.5 to 10 log xcexa9/xe2x96xa1.
The antistatic layer may be present on either side or both sides of the support material. The antistatic layer may be an internal layer that underlies the antihalation undercoat, protective overcoat, protective backcoat or the emulsion layers. Alternatively, the antistatic layer may be an outermost layer in which the electrically conductive material is included in the protective overcoat or protective backcoat.
The following examples are intended to illustrate the present invention but not to limit it in scope in any way.

Method of processing motion picture print film to provide improved laser subtitling performance, and processed motion picture print film


A sealant system 13 for a manifold 10 of a proton exchange membrane fuel cell includes low temperature cured or heat cured silicone rubber bridges 14, 14a, 14c between the end plates 9 to compensate for the uneven edges of various fuel cell component layers, and a layer 15 of silicone rubber foam or sponge, or a molded silicone rubber gasket 15a, extending across the bridges and along the end plates, around the entire contact perimeter surfaces of the manifold, to seal the manifold to the fuel cell. The cured silicone rubber may extend along the end plates between the bridges. A rubber strip 20 may be adhered to the silicone rubber bridges and end plates. The bridges may comprise a first layer 22 of low shrinkage self-leveling RTV liquid rubber with viscosity in the range of 10,000-20,000 cps and a second layer 14 of RTV liquid rubber.

This invention relates to a multi-part rubber/elastomer seal system for a proton exchange membrane (PEM) fuel cell reactant gas manifold.
A basic fuel cell comprises an anode electrode spaced apart from a cathode electrode with an electrolyte disposed therebetween in a compartment formed between the two electrodes; each electrode also includes a catalyst layer on the electrolyte side thereof. On the non-electrolyte side of the anode electrode is a reactant gas chamber for carrying a fuel, and on the nonelectrolyte side of the cathode electrode is a reactant gas chamber for carrying an oxidant. The electrodes are constructed so that the gas diffuses therethrough and comes into contact with the electrolyte in the catalyst layer thereby causing a well-known electrochemical reaction whereby hydrogen ions and electrons produced at the anode travel from the anode electrode through, respectively, the electrolyte and the external circuit to the cathode electrode where they react with oxygen to produce heat and water. This flow of electrons is the electric current produced by the cell.
In a fuel cell power plant a number of fuel cells are connected electrically in series through plates separating adjacent cells, thereby forming a cell stack assembly (CSA). These plates in combination with the electrodes adjacent thereto, generally define the reactant gas passages or chambers. The CSA is provided with external fuel and oxidant manifolds for simultaneous supply to and exhaust of gases from the individual cells. Accordingly, it is necessary to provide manifold-to-CSA seals to prevent leakage of the gases involved in the operation of the fuel cell stack assembly. Also, during operation of the CSA, the CSA and the manifold-to-CSA seals undergo compressive creep. Thus, since the CSA is made up of a series of cells, the edges of which are not aligned, and the surface of the stack is therefore rough, compressive creep of the stack and the manifold-to-CSA seals results in increased reactant leakage.
Seals for phosphoric acid fuel cells as shown in commonly owned U.S. Pat. No. 4,774,154, have successfully employed a composition which includes a high fluorine content fluorinated hydrocarbon elastomer, a carbon black filler, azodicarbonamide blowing agent and blowing agent promoter, and an epoxy or inorganic oxide acid acceptor. However, this composition cures in the range between 176xc2x0 C. and 204xc2x0 C. (350xc2x0 F. and 400xc2x0 F.). Since the proton exchange membrane is generally damaged above about 150xc2x0 C. (about 300xc2x0 F.), curing the prior seal compound would destroy a PEM fuel cell.
PEM fuel cells known to the prior art have utilized closed cell, neoprene rubber foam to accommodate the uneven surface of the side of the fuel cell stack. However, this material exhibits poor springback characteristics, resulting in increased leakage as a function of time and a requirement to continuously tighten the manifolds.
Objects of the invention include a manifold seal system for a PEM fuel cell stack assembly which can be effected at stack temperatures not exceeding 150xc2x0 C. (300xc2x0 F.), which is stable in the presence of hydrogen, oxygen and water, which has low creep and which is very compressible.
According to the present invention, a manifold seal system for a PEM fuel cell comprises at least two parts, including one or two layers of silicone rubber applied to provide smooth bridges between one stack end plate (sometimes referred to as xe2x80x9cpressure platexe2x80x9d), and the opposite end plate, there typically being one such bridge along each edge of the stack, another part comprising an elastomer adjacent to the reactant manifold, said elastomer having a low compression set (low creep), that is, below 25%, and a low compression modulus (being very springy), that is, capable of compressing about 25% under loads of less than 50 psi.
In one embodiment employing low temperature curing silicone rubber, an additional part comprises a rubber strip in contact with the end plates and in contact with the silicone rubber bridges; a bead of silicone rubber as used on the bridges may also be added under the rubber strip along the end plates, if required for leveling purposes. In accordance with one embodiment of the present invention, the cell bridges may comprise a two-part silicone rubber capable of curing at room temperature or a one-part silicone room temperature vulcanizing silicone rubber adhesive. In one embodiment, the bridges comprise two different room temperature curing silicone rubbers: first, a controlled quantity of a compatible liquid silicone rubber, having low shrinkage characteristics, a low viscosity and self-leveling capability is applied to the stack surface; this is followed by a higher viscosity, liquid rubber to fill the larger voids and crevices of the stack surfaces and to act as a bonding agent for the strip of pre-cured solid rubber.
In another embodiment, a bead of heat-cured silicone rubber sealant is applied between and on the end plates and cured with a heated platen, to a thickness determined either by shims or by volume/pressure control.
The elastomer may comprise closed cell silicone rubber foam of low to medium density, or closed cell silicone rubber sponge, but the preferred embodiment is a molded silicone rubber gasket. As used herein, xe2x80x9clow density foamxe2x80x9d means a foam that exerts a pressure of about 2-5 psi at a deflection of 25% while xe2x80x9cmedium density foamxe2x80x9d exerts a pressure of about 10-20 psi at a deflection of 25%. A low density foam also has a bulk density of about 0.15-0.25 grams per cubic centimeter and a medium density foam has a bulk density of 0.25-0.35 grams per cubic centimeter. The compression set of the seal material should be less than 35% after 72 hours at 190xc2x0 F.; this is defined as xe2x80x9clow compression setxe2x80x9d herein. The preferred range of thickness is between {fraction (1/16)} of an inch and {fraction (3/16)} of an inch.
The invention provides an effective seal to the fuel cell for all pressure differentials experienced by the seal during fuel cell operation, without leaking, and does not require periodic tightening of a manifold to maintain the seal over time. The sealing system of the invention allows easy removal of the manifold, should it be required.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.

Proton exchange membrane fuel cell external manifold seal