The invention relates to an imaging support comprising an impermeable bottom layer wherein said bottom layer comprises polyester and a permeable upper layer said upper layer comprising polyester having a dry time of less than 10 seconds.

The present invention relates generally to an opaque image-recording element and, more particularly, the present invention relates to a recording element for an automated printing assembly such as a computer-driven ink-jet printer having excellent ink-receiving properties.
In a typical ink-jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye, and a large amount of solvent in order to prevent clogging of the nozzle. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol or a polyhydric alcohol or a mixed solvent of water and other water miscible solvents such as a monohydric alcohol or a polyhydric alcohol.
The recording elements or media typically comprise a substrate or a support material having on at least one surface thereof an ink-receiving or image-forming layer. The elements include those intended for reflection viewing, which usually have an opaque support, and those intended for viewing by transmitted light, which usually have a transparent support.
While a wide variety of different types of image-recording elements have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness. The requirements for an image-recording medium or element for ink-jet recording are very demanding. For example, the recording element must be capable of absorbing or receiving large amounts of ink applied to the image-forming surface of the element as rapidly as possible in order to produce recorded images having high optical density and good color gamut.
One example of an opaque image-recording element is described in U.S. Pat. No. 5,326,391. It consists of a layer of a microporous material which comprises a matrix consisting essentially of a substantially water-insoluble thermoplastic organic polymer, such as a linear ultra-high molecular weight polyethylene, a large proportion of finely divided water-insoluble filler of which at least about 50 percent by weight is siliceous and interconnecting pores. The porous nature of the image-recording element disclosed in U.S. Pat. No. 5,326,391 allows inks to penetrate the surface of the element to produce text and/or graphic images. However, the cost of producing these elements is relatively high. Also, the image density has been found to be of poor quality, i.e., the images have low optical densities and poor color gamut. U.S. Pat. No. 5,605,750 has already addressed the latter shortcomings of image density and color gamut via the application of an upper image-forming layer. This upper image forming layer is a porous, pseudo-boehmite having average pore radius of from 10 to 80 xc3x85. However, the high manufacturing cost of the article to form the absorbent layer is not solved in U.S. Pat. No. 5,605,750. This is due to the requirements for the porous substrate as described in U.S. Pat. No. 5,326,391. Thus, it can be seen that a need still exists in the art for the provision of an opaque image-recording element suitable for use in an ink-jet printer, which is capable of recording images (including color images) having fast dry times, high optical densities and good color gamut, but which is capable of being manufactured at a relatively low manufacturing cost. It is towards fulfilling this need that the present invention is directed.
There remains a need for an image-receiving member that has rapid absorption of ink and relatively low cost.
It is an object of the invention to overcome disadvantages of prior imaging supports.
It is another object of the invention to produce imaging supports that have short dry time for inks.
It is a further object of the invention to provide imaging supports that are dimensionally stable and low in cost.
These and other objects of the invention are accomplished by an imaging support comprising a base polyester layer and an ink permeable upper layer, said upper layer comprising of a continuous polyester phase having an ink absorbency rate resulting in a dry time of less than 10 seconds and a total absorbent capacity of at least 14.0 cm3/m2.
It is an object of the invention to provide an imaging member that has a high absorptive capacity for ink and is relatively low in cost.
The invention has numerous advantages over prior practices in the art. The imaging members of the invention may be made on readily available polyester film formation machines. The members of the invention preferably are made in one step with the permeable layer and the bottom base layer being coextruded, stretched, and integrally connected during formation. The imaging members are low in cost as the one step formation process leads to low manufacturing cost. The imaging members of the invention have rapid absorption of ink, as well as high absorbent capacity, which allows rapid printing and short dry time. Short dry time is advantageous, as the prints are less likely to smudge and have higher image quality as the inks do not coalesce prior to drying. The imaging members of the invention have the look and feel of paper, which is desirable to the consumer. The imaging members of the invention have a desirable surface look without pearlescence and present a smooth desirable image. The imaging member of the invention further is weather resistant and resistant to curling under differing humidity conditions. The imaging members of the invention further have high resistance to tearing and deformation. These and other advantages will be apparent from the detailed description below.
The term as used herein, xe2x80x9ctopxe2x80x9d, means the side or toward the side of the permeable polyester layer. The terms xe2x80x9cbottomxe2x80x9d and xe2x80x9cbasexe2x80x9d mean the side or toward the side of the base polyester.
The layers of the coextruded polyester sheet of this invention have levels of voiding, thickness, and smoothness adjusted to provide optimum ink absorbency, stiffness, and gloss properties. The polyester sheet has a voided layer to efficiently absorb the printed inks commonly applied to ink-jet imaging supports without the need of multiple processing steps and multiple coated layers. The coextruded polyester base of the invention contains a polyester layer to provide stiffness to the imaging support of the invention and to provide physical integrity to the highly voided absorbing layer. The thickness of the base layer is chosen to cause the total imaging support thickness to be 50 to 500 xcexcm depending on the required stiffness of the film. However, the thickness of the top layer is adjusted to the total absorbent capacity of the medium. A thickness of at least 28.0 xcexcm is needed to achieve a total absorbency of 14 cm3/m2. The rate at which inks are absorbed into the permeable layer is critical as discussed hereinbefore. The voiding should be such that the voids are interconnected or open-celled. This type of structure enhances ink absorption rate by enabling capillary action to occur. The sheet of the described invention has a permeable layer with an absorbing rate resulting in a dry time of less than 10 seconds.
Dry time is measured by printing a color line on the side of the top layer with an ink-jet printer at a laydown of approximately 15 cm3/m2 utilizing inks of the following formulation:
Where: EHMP=2-ethyl-2-(hydroxymethyl)-1,3-propanediol
This was accomplished utilizing an HP 722 ink-jet printer using standard HP dye-based ink cartridge (HP #C1823A) with the printed lines running in the direction of the sheet as it is conveyed through the printer. Dry time is measured by superposing a fresh printing paper on top of the printed line pattern immediately after printing and pressing the papers together with a roller press. If a particular printed line transfers to the surface of the fresh paper, its transferred length L could be used for estimating the dry time tD using a known linear transport speed S for the printer based on the formula       t    D    =      L    S
In a preferred embodiment of the invention, the ink absorbency rate results in a measured dry time of less than 1 second. The thickness of the voided layer should be such as to enable at least 14.0 cm3 of ink to be absorbed per 1 m2. The actual thickness can be determined by using the formula t=14.0/v where v is the void volume fraction defined as the ratio of voided thickness minus unvoided thickness to the voided thickness. The unvoided thickness is defined as the thickness that would be expected had no voiding occurred.
The polyester utilized in the top layer should have a glass transition temperature between about 50xc2x0 C. and 150xc2x0 C. preferably 60-100xc2x0 C., should be stretchable, and have an inherent viscosity of at least 0.50, preferably 0.6 to 0.9 dl/g. Suitable polyesters include those produced from aromatic, aliphatic, or cycloaliphatic dicarboxylic acids of 4-20 carbon atoms and aliphatic or alicyclic glycols having from 2-24 carbon atoms. Examples of suitable dicarboxylic acids include terephthalic, isophthalic, phthalic, naphthalene dicarboxylic acid, succinic, glutaric, adipic, azelaic, sebacic, fumartc, maleic, itaconic, 1,4-cyclohexane-dicarboxylic, sodiosulfoisophthalic, and mixtures thereof. Examples of suitable glycols include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 1,4-cyclohexane-dimethanol, diethylene glycol, other polyethylene glycols and mixtures thereof. Such polyesters are well known in the art and may be produced by well-known techniques, e.g., those described in U.S. Pat. Nos. 2,465,319 and 2,901,466. Preferred continuous matrix polymers are those having repeat units from terephthalic acid or naphthalene dicarboxylic acid and at least one glycol selected from ethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Poly(ethylene terephthalate), which may be modified by small amounts of other monomers, is especially preferred. Other suitable polyesters include liquid crystal copolyesters formed by the inclusion of a suitable amount of a co-acid component such as stilbene dicarboxylic acid. Examples of such liquid crystal copolyesters are those disclosed in U.S. Pat. Nos. 4,420,607; 4,459,402; and 4,468,510.
The base layer is substantially impermeable. In its preferred embodiment this base layer is comprised of poly(ethylene terephthalate) and its copolymers, which are lowest in cost and readily available.
Suitable particles for the microbeads used for void generation in the permeable layer during sheet formation are either commercially available inorganic fillers or polymerizable organic materials. The size of the microbeads is preferably in the range of 0.01 to 10 xcexc. Typical inorganic materials are silica, alumina, calcium carbonate, and barium sulfate. Typical polymeric organic materials are polystyrenes, polyamides, fluoro polymers, polycarbonates, or polyolefins.
Preferred polymers are cross-linked and are selected from the group consisting of an alkenyl aromatic compound having the general formula
wherein Ar represents an aromatic hydrocarbon moiety, or an aromatic halohydrocarbon moiety of the benzene series and R is hydrogen or methyl moiety; acrylate-type monomers including monomers of the formula
wherein R is selected from the group consisting of hydrogen and an alkyl moiety containing from about 1 to 12 carbon atoms and Rxe2x80x2 is selected from the group consisting of hydrogen and methyl; copolymers of vinyl chloride and vinylidene chloride, acrylonitrile and vinyl chloride, vinyl bromide, vinyl esters having the
wherein R is an alkyl group containing from 2 to 18 carbon atoms; acrylic acid, methacrylic acid, itaconic acid, citraconic acid, maleic acid, fumaric acid, oleic acid, vinylbenzoic acid; the synthetic polyester resins which are prepared by reacting terephthalic acid and dialkyl terephthalics or ester-forming derivatives thereof, with a glycol of the series HO(CH2)nOH, wherein n is a whole number within the range of 2-10 and having reactive olefinic linkages within the polymer molecule, the hereinabove described polyesters which include copolymerized therein up to 20 percent by weight of a second acid or ester thereof having reactive olefinic unsaturation and mixtures thereof, and a cross-linking agent selected from the group consisting of divinyl-benzene, diethylene glycol dimethacrylate, oiallyl fumarate, diallyl phthalate, and mixtures thereof.
Examples of typical monomers for making the cross-linked polymer microbeads include styrene, butyl acrylate, acrylamide, acrylonitrile, methyl methacrylate, ethylene glycol dimethacrylate, vinyl pyridine, vinyl acetate, methyl acrylate, vinylbenzyl chloride, vinylidene chloride, acrylic acid, divinylbenzene, arylamidomethyl-propane sulfonic acid, vinyl toluene, etc. Preferably, the cross-linked polymer is polystyrene or poly(methyl methacrylate). Most preferably, it is polystyrene, and the cross-linking agent is divinylbenzene.
Processes well known in the art yield nonuniformly sized particles, characterized by broad particle size distributions. The resulting beads can be classified by screening to produce beads spanning the range of the original distribution of sizes. Other processes such as suspension polymerization and limited coalescence directly yield very uniformly sized particles. Suitable slip agents or lubricants include colloidal silica, colloidal alumina, and metal oxides such as tin oxide and aluminum oxide. The preferred slip agents are colloidal silica and alumina, most preferably, silica. The cross-linked polymer having a coating of slip agent may be prepared by procedures well known in the art. For example, conventional suspension polymerization processes wherein the slip agent is added to the suspension is preferred. As the slip agent, colloidal silica is preferred.
It is preferred to use the xe2x80x9climited coalescencexe2x80x9d technique for producing the coated, cross-linked polymer microbeads. This process is described in detail in U.S. Pat. No. 3,615,972. Preparation of the coated microbeads for use in the present invention does not utilize a blowing agent as described in this patent, however.
The following general procedure may be utilized in a limited coalescence technique:
1. The polymerizable liquid is dispersed within an aqueous nonsolvent liquid medium to form a dispersion of droplets having sizes not larger than the size desired for the polymer globules, whereupon
2. The dispersion is allowed to rest and to reside with only mild or no agitation for a time during which a limited coalescence of the dispersed droplets takes place with the formation of a lesser number of larger droplets, such coalescence being limited due to the composition of the suspending medium, the size of the dispersed droplets thereby becoming remarkably uniform and of a desired magnitude, and
3. The uniform droplet dispersion is then stabilized by addition of thickening agents to the aqueous suspending medium, whereby the uniform-sized dispersed droplets are further protected against coalescence and are also retarded from concentrating in the dispersion due to difference in density of the disperse phase and continuous phase, and
4. The polymerizable liquid or oil phase in such stabilized dispersion is subjected to polymerization conditions and polymerized, whereby globules of polymer are obtained having spheroidal shape and remarkably uniform and desired size, which size is predetermined principally by the composition of the initial aqueous liquid suspending medium.
The diameter of the droplets of polymerizable liquid and, hence, the diameter of the beads of polymer, can be varied predictably, by deliberate variation of the composition of the aqueous liquid dispersion, within the range of from about one-half of a xcexcm or less to about 0.5 centimeter. For any specific operation, the range of diameters of the droplets of liquid and, hence, of polymer beads, has a factor in the order of three or less as contrasted to factors of 10 or more for diameters of droplets and beads prepared by usual suspension polymerization methods employing critical agitation procedures. Since the bead size, e.g., diameter, in the present method is determined principally by the composition of the aqueous dispersion, the mechanical conditions, such as the degree of agitation, the size and design of the apparatus used, and the scale of operation are not highly critical. Furthermore, by employing the same composition, the operations can be repeated, or the scale of operations can be changed, and substantially the same results can be obtained.
The present bead-formation method is carried out by dispersing one part by volume of a polymerizable liquid into at least 0.5, preferably from 0.5 to about 10 or more, parts by volume of a nonsolvent aqueous medium comprising water and at least the first of the following ingredients:
1. A water-dispersible, water-insoluble solid colloid, the particles of which, in aqueous dispersion, have dimensions in the order of from about 0.008 to about 50 vm, which particles tend to gather at the liquid-liquid interface or are caused to do so by the presence of
2. A water-soluble xe2x80x9cpromotorxe2x80x9d that affects the xe2x80x9chydrophilic-hydrophobic balancexe2x80x9d of the solid colloid particles; and/or
3. An electrolyte; and/or
4. Colloid-active modifiers such as peptizing agents, surface-active agents and the like; and usually,
5. A water-soluble, monomer-insoluble inhibitor of polymerization.
The water-dispersible, water-insoluble solid colloids can be inorganic materials such as metal salts or hydroxides or clays, or can be organic materials such as raw starches, sulfonated cross-linked organic high polymers, resinous polymers, and the like.
The solid colloidal material must be insoluble but dispersible in water and both insoluble and nondispersible in, but wettable by, the polymerizable liquid. The solid colloids must be much more hydrophilic than oleophilic so as to remain dispersed wholly within the aqueous liquid. The solid colloids employed for limited coalescence are ones having particles that, in the aqueous liquid, retain a relatively rigid and discrete shape and size within the limits stated. The particles may be greatly swollen and extensively hydrated, provided that the swollen particle retains a definite shape, in which case the effective size is approximately that of the swollen particle. The particles can be essentially single molecules, as in the case of extremely high molecular weight cross-linked resins, or can be aggregates of many molecules. Materials that disperse in water to form true or colloidal solutions in which the particles have a size below the range stated or in which the particles are so diffuse as to lack a discernible shape and dimension are not suitable as stabilizers for limited coalescence. The amount of solid colloid that is employed is usually such as corresponds to from about 0.01 to about 10 or more grams per 100 cubic centimeters of the polymerizable liquid.
In order to function as a stabilizer for the limited coalescence of the polymerizable liquid droplets, it is essential that the solid colloid must tend to collect with the aqueous liquid at the liquid-liquid interface, i.e., on the surface of the oil droplets. (The term xe2x80x9coilxe2x80x9d is occasionally used herein as generic to liquids that are insoluble in water.) In many instances, it is desirable to add a xe2x80x9cpromoterxe2x80x9d material to the aqueous composition to drive the particles of the solid colloid to the liquid-liquid interface. This phenomenon is well known in the emulsion art, and is here applied to solid colloidal particles, as an expanded of adjusting the xe2x80x9chydrophilic-hydrophobic balance.xe2x80x9d
Usually, the promoters are organic materials that have an affinity for the solid colloid and also for the oil droplets and that are capable of making the solid colloid more oleophilic. The affinity for the oil surface is usually due to some organic portion of the promoter molecule, while affinity for the solid colloid is usually due to opposite electrical charges. For example, positively charged complex metal salts or hydroxides, such as aluminum hydroxide, can be promoted by the presence of negatively charged organic promoters such as water-soluble sulfonated polystyrenes, alignates, and carboxymethylcellulose. Negatively charged colloids, such as Bentonite, are promoted by positively charged promoters such as tetramethyl ammonium hydroxide or chloride or water-soluble complex resinous amine condensation products, such as the water-soluble condensation products of diethanolamine and adipic acid, the water-soluble condensation products of ethylene oxide, urea and formaldehyde, and polyethylenimine. Amphoteric materials such as proteinaceous materials like gelatin, glue, casein, albumin, glutin, and the like are effective promoters for a wide variety of colloidal solids. Nonionic materials like methoxy-cellulose are also effective in some instances. Usually, the promoter need be used only to the extent of a few parts per million of aqueous medium, although larger proportions can often be tolerated. In some instances, ionic materials normally classed as emulsifiers, such as soaps, long chain sulfates and sulfonates and the long chain quaternary ammonium compounds, can also be used as promoters for the solid colloids, but care must be taken to avoid causing the formation of stable colloidal emulsions of the polymerizable liquid and the aqueous liquid medium.
An effect similar to that of organic promoters is often obtained with small amounts of electrolytes, e.g., water-soluble, ionizable alkalies, acids and salts, particularly those having polyvalent ions. These are especially useful when the excessive hydrophilic or insufficient oleophilic characteristic of the colloid is attributable to excessive hydration of the colloid structure. For example, a suitably cross-linked sulfonated polymer of styrene is tremendously swollen and hydrated in water. Although the molecular structure contains benzene rings which should confer on the colloid some affinity for the oil phase in the dispersion, the great degree of hydration causes the colloidal particles to be enveloped in a cloud of associated water. The addition of a soluble, ionizable polyvalent cationic compound, such as an aluminum or calcium salt, to the aqueous composition causes extensive shrinking of the swollen colloid with exudation of a part of the associated water and exposure of the organic portion of the colloid particle, thereby making the colloid more oleophilic.
The solid colloidal particles whose hydrophilic-hydrophobic balance is such that the particles tend to gather in the aqueous phase at the oil-water interface, gather on the surface of the oil droplets, and function as protective agents during limited coalescence.
Other agents that can be employed in an already known manner to effect modification of the colloidal properties of the aqueous composition are those materials known in the art as peptizing agents, flocculating and deflocculating agents, sensitizers, surface active agents, and the like.
It is sometimes desirable to add to the aqueous liquid a few parts per million of a water-soluble, oil-insoluble inhibitor of polymerization effective to prevent the polymerization of monomer molecules that might diffuse into the aqueous liquid or that might be absorbed by colloid micelles and that, if allowed to polymerize in the aqueous phase, would tend to make emulsion-type polymer dispersions instead of, or in addition to, the desired bead or pearl polymers.
The aqueous medium containing the water-dispersible solid colloid is then admixed with the liquid polymerizable material in such a way as to disperse the liquid polymerizable material as small droplets within the aqueous medium. This dispersion can be accomplished by any usual means, e.g., by mechanical stirrers or shakers, by pumping through jets, by impingement, or by other procedures causing subdivision of the polymerizable material into droplets in a continuous aqueous medium.
The degree of dispersion, e.g., by agitation, is not critical except that the size of the dispersed liquid droplets must be no larger, and is preferably much smaller, than the stable droplet size expected and desired in the stable dispersion. When such condition has been attained, the resulting dispersion is allowed to rest with only mild, gentle movement, if any, and preferably without agitation. Under such quiescent conditions, the dispersed liquid phase undergoes a limited degree of coalescence.
xe2x80x9cLimited coalescencexe2x80x9d is a phenomenon wherein droplets of liquid dispersed in certain aqueous suspending media coalesce, with formation of a lesser number of larger droplets, until the growing droplets reach a certain critical and limiting size, whereupon coalescence substantially ceases. The resulting droplets of dispersed liquid, which can be as large as 0.3 and sometimes 0.5 centimeter in diameter, are quite stable as regards further coalescence and are remarkably uniform in size. If such a large droplet dispersion be vigorously agitated, the droplets are fragmented into smaller droplets. The fragmented droplets, upon quiescent standing, again coalesce to the same limited degree and form the same uniform-sized, large droplet, stable dispersion. Thus, a dispersion resulting from the limited coalescence comprises droplets of substantially uniform diameter that are stable in respect to further coalescence.
The principles underlying this phenomenon have now been adapted to cause the occurrence of limited coalescence in a deliberate and predictable manner in the preparation of dispersions of polymerizable liquids in the form of droplets of uniform and desired size.
In the phenomenon of limited coalescence, the small particles of solid colloid tend to collect with the aqueous liquid at the liquid-liquid interface, i.e., on the surface of the oil droplets. It is thought that droplets which are substantially covered by such solid colloid are stable to coalescence while droplets which are not so covered are not stable. In a given dispersion of a polymerizable liquid the total surface area of the droplets is a function of the total volume of the liquid and the diameter of the droplets. Similarly, the total surface area barely coverable by the solid colloid, e.g., in a layer one particle thick, is a function of the amount of the colloid and the dimensions of the particles thereof. In the dispersion as initially prepared, e.g., by agitation, the total surface area of the polymerizable liquid droplets is greater than can be covered by the solid colloid. Under quiescent conditions, the unstable droplets begin to coalesce. The coalescence results in a decrease in the number of oil droplets and a decrease in the total surface area thereof up to a point at which the amount of colloidal solid is barely sufficient substantially to cover the total surface of the oil droplets, whereupon coalescence substantially ceases.
If the solid colloidal particles do not have nearly identical dimensions, the average effective dimension can be estimated by statistical methods. For example, the average effective diameter of spherical particles can be computed as the square root of the average of the squares of the actual diameters of the particles in a representative sample.
It is usually beneficial to treat the uniform droplet suspension prepared as described above to render the suspension stable against congregation of the oil droplets.
This further stabilization is accomplished by gently admixing with the uniform droplet dispersion an agent capable of greatly increasing the viscosity of the aqueous liquid. For this purpose, there may be used any water-soluble or water-dispersible thickening agent that is insoluble in the oil droplets and that does not remove the layer of solid colloidal particles covering the surface of the oil droplets at the oil-water interface. Examples of suitable thickening agents are sulfonated polystyrene (water-dispersible, thickening grade), hydrophilic clays such as Bentonite, digested starch, natural gums, carboxy-substituted cellulose ethers, and the like. Often the Sickening agent is selected and employed in such quantities as to form a thixotropic gel in which are suspended the uniform-sized droplets of the oil. In other words, the thickened liquid generally should be non-Newtonian in its fluid behavior, i.e., of such a nature as to prevent rapid movement of the dispersed droplets within the aqueous liquid by the action of gravitational force due to the difference in density of the phases. The stress exerted on the surrounding medium by a suspended droplet is not sufficient to cause rapid movement of the droplet within such non-Newtonian media. Usually, the thickener agents are employed in such proportions relative to the aqueous liquid that the apparent viscosity of the thickened aqueous liquid is in the order of at least 500 centipoises (usually determined by means of a Brookfield viscosimeter using the No. 2 spindle at 30 rpm.). The thickening agent is preferably prepared as a separate concentrated aqueous composition that is then carefully blended with the oil droplet dispersion.
The resulting thickened dispersion is capable of being handled, e.g., passed through pipes, and can be subjected to polymerization conditions substantially without mechanical change in the size or shape of the dispersed oil droplets.
The resulting dispersions are particularly well suited for use in continuous polymerization procedures that can be carried out in coils, tubes, and elongated vessels adapted for continuously introducing the thickened dispersions into one end and for continuously withdrawing the mass of polymer beads from the other end. The polymerization step is also practiced in batch manner.
The order of the addition of the constituents to the polymerization usually is not critical, but beneficially it is more convenient to add to a vessel the water, dispersing agent, and incorporated the oil-soluble catalyst to the monomer mixture, and subsequently add with agitation the monomer phase to the water phase.
The following is an example illustrating a procedure for preparing the cross-linked polymeric microbeads coated with slip agent. In this example, the polymer is polystyrene cross-linked with divinylbenzene. The microbeads have a coating of silica. The microbeads are prepared by a procedure in which monomer droplets containing an initiator are sized and heated to give solid polymer spheres of the same size as the monomer droplets. A water phase is prepared by combining 7 liters of distilled water, 1.5 g potassium dichromate (polymerization inhibitor for the aqueous phase), 250 g polymethylaminoethanol adipate (promoter), and 350 g LUDOX (a colloidal suspension containing 50% silica sold by DuPont). A monomer phase is prepared by combining 3317 g styrene, 1421 g divinylbenzene (55% active cross-linking agent; other 45% is ethyl vinyl benzene which forms part of the styrene polymer chain) and 45 g VAZO 52 (a monomer-soluble initiator sold by DuPont). The mixture is passed through a homogenizer to obtain 5 xcexcm droplets. The suspension is heated overnight at 52xc2x0 C. to give 4.3 kg of generally spherical microbeads having an average diameter of about 5 xcexcm with narrow size distribution (about 2-10 xcexcm size distribution). The mol proportion of styrene and ethyl vinyl benzene to divinylbenzene is about 6.1%. The concentration of divinylbenzene can be adjusted up or down to result in about 2.5-50% (preferably 10-40%) cross-linking by the active cross-linker. Of course, monomers other than styrene and divinylbenzene can be used in similar suspension polymerization processes known in the art. Also, other initiators and promoters may be used as known in the art. Also, slip agents other than silica may also be used. For example, a number of LUDOX colloidal silicas are available from DuPont. LEPANDIN colloidal alumina is available from Degussa. NALCOAG colloidal silicas are available from Nalco, and tin oxide and titanium oxide are also available from Nalco.
Normally, for the polymer to have suitable physical properties such as resiliency, the polymer is cross-linked. In the case of styrene cross-linked with divinylbenzene, the polymer is 2.5-50% cross-linked, preferably 20-40% cross-linked. By percent cross-linked, it is meant the mol % of cross-linking agent based on the amount of primary monomer. Such limited cross-linking produces microbeads which are sufficiently coherent to remain intact during orientation of the continuous polymer. Beads of such cross-linking are also resilient, so that when they are deformed (flattened) during orientation by pressure from the matrix polymer on opposite sides of the microbeads, they subsequently resume their normal spherical shape to produce the largest possible voids around the microbeads to thereby produce articles with less density.
The microbeads are referred to herein as having a coating of a xe2x80x9cslip agentxe2x80x9d. By this term it is meant that the friction at the surface of the microbeads is greatly reduced. Actually, it is believed this is caused by the silica acting as miniature ball bearings at the surface. Slip agent may be formed on the surface of the microbeads during their formation by including it in the suspension polymerization mix.
Microbead size is regulated by the ratio of silica to monomer. For example, the following ratios produce the indicated size microbead:
The microbeads of cross-linked polymer range in size from 0.1-50 xcexcm, and are present in an amount of 30-50% by volume in the feed stock for the porous layer prior to extrusion and microvoiding. However, the preferred size range for this invention is 0.5-5 xcexcm for best formation of an ink porous but smooth surface. Microbeads of polystyrene should have a Tg of at least 20xc2x0 C. higher than the Tg of the continuous matrix polymer and must be hard compared to the continuous matrix polymer. When using polymerizable organic materials, elasticity and resiliency of the microbeads generally result in increased voiding, and it is preferred to have the Tg of the microbeads as high above that of the matrix polymer as possible to avoid deformation during orientation. It is not believed that there is a practical advantage to cross-linking above the point of resiliency and elasticity of the microbeads.
The microbeads at the top (permeable) layer are at least partially bordered by voids. The void space in the supports should occupy at least 40%, preferably 50-70%, by volume of the top layer for best ink absorption with a stable layer. At this level of voiding the voids have been shown to be interconnected or open-celled. Any less voiding results in a closed cell structure, which does not lend itself to capillary action and, thus, fast ink absorbency rate is not achievable. Depending on the manner in which the supports are made, the voids may completely encircle the microbeads, e.g., a void may be doughnut-shaped (or flattened doughnut) encircling a microbead, or the voids may only partially border the microbeads, e.g., a pair of voids may border a microbead on opposite sides.
During stretching the voids assume characteristic shapes from the balanced biaxial orientation of paperlike films to the uniaxial orientation of microvoided/satinlike fibers. Balanced microvoids are largely circular in the plane of orientation, while fiber microvoids are elongated in the direction of the fiber axis. The size of the microvoids and the ultimate physical properties depend upon the degree and balance of the orientation, temperature and rate of stretching, crystallization kinetics, the size distribution of the microbeads, and the like.
The film supports according to this invention are prepared by:
(a) forming a mixture of molten continuous matrix polymer and microbeads uniformly dispersed throughout the matrix polymer, the matrix polymer being as described hereinbefore, the microbeads being as described hereinbefore,
(b) forming a two-layered sheet from the mixture by coextrusion of material in (a) with a base polyester layer and casting said sheet on a chill roll,
(c) orienting the cast sheet by stretching to form voids in the top layer at least partially bordering the microbeads on sides thereof in the direction, or directions of orientation.
The mixture may be formed by forming a melt of the matrix polymer and mixing therein the microbeads. When using microbeads of cross-linked polymer, it may be in the form of solid or semisolid microbeads. Due to the incompatibility between the matrix polymer and cross-linked polymer, there is no attraction or adhesion between them, and they become uniformly dispersed in the matrix polymer upon mixing.
After the microbeads are uniformly dispersed in the polymer matrix, the resin is used to form a layered film structure by the coextrusion process. Any one of the known techniques for coextruding cast polymer sheets can be employed. Such forming methods are well known in the art. Typical coextrusion technology is taught in W. J. Schrenk and T. Alfrey, Jr, xe2x80x9cCoextruded Multilayer Polymer Films and Sheets,xe2x80x9d Chapter 15, Polymer Blends, p. 129-165, 1978, Academic Press; and D. Djorjevic, xe2x80x9cCoextrusion,xe2x80x9d Vol. 6, No. 2, 1992 Rapra Review Reports. It is important that the cast, laminated sheet be subsequently oriented by stretching, at least in one direction. Methods of unilaterally or bilaterally orienting sheet or film material are well known in the art. Basically, such methods comprise stretching the sheet or film at least in the machine or longitudinal direction, after it is cast on a chill roll, by an amount of about 1.5-4.5 times its original dimension. Such sheet or film may also be stretched in the transverse or cross-machine direction by apparatus and methods well known in the art, in amounts of generally 1.5-4.5 times the original dimension. Stretching to these ratios is necessary to sufficiently void the top layer and to achieve desired levels of thickness uniformity and mechanical performance. Such apparatus and methods are well known in the art and are described, for example, in U.S. Pat. No. 3,903,234.
The voids of the top layer, or void spaces referred to herein, surrounding the microbeads are formed as the continuous matrix polymer is stretched at a temperature above its Tg. The microbeads are relatively hard under said temperature compared to the continuous matrix polymer. Also, due to the incompatibility between the microbead and the matrix polymer, the continuous matrix polymer slides over the microbeads as it is stretched, causing voids to be formed at the sides in the direction or directions of stretch, said voids elongate as the matrix polymer continues to be stretched. Thus, the final size and shape of the voids depend on the direction(s) and amount of stretching. If stretching is only in one direction, microvoids will form at the sides of the microbeads in the direction of stretching. If stretching is in two directions (bidirectional stretching), in effect such stretching has vector components extending radially from any given position to result in a doughnut-shaped void surrounding each microbead.
The preferred stretching operation simultaneously opens the microvoids and orients the matrix material. The final product properties depend on and can be controlled by stretching time-temperature relationships and the type and degree of stretch. For maximum top layer porosity and texture, the stretching is done just above the glass transition temperature of the matrix polymer. If the glass transition temperature of the polymeric microbead is in the vicinity of the glass transition temperature of the matrix polymer, both phases would stretch together and porosity would decrease. If the beads are solid during the stretching step, the materials are pulled apart leading to the formation of voids at the interfacial regions between the phases.
In general, void formation in the top layer occurs independent of, and does not require, crystalline formation in the matrix polymer. Porous opaque, microvoided films have been made in accordance with the methods of this invention using completely amorphous, noncrystallizing copolyesters as the matrix phase. Crystallizable/orientable (strain hardening) matrix materials are preferred for some properties like tensile strength and gas transmission barrier. On the other hand, amorphous matrix materials have special utility in other areas like tear resistance and heat sealability. The specific matrix composition can be tailored to meet many product needs. The complete range from crystalline to amorphous matrix polymers can be used in the practice of this invention. A preferred embodiment of the invention comprises polyethylene terephthalate or its copolymers as the continuous phase polyester of the top permeable layer, as these materials are generally lower in cost and have desirable mechanical properties. It is common to subject the stretched film to high temperature after the stretching steps to improve dimensional stability and mechanical performance. This heat treatment step is known as heat setting. It should be noted though that if the top layer is amorphous, care should be taken during the conventional heat setting step to ensure that the voids formed during the stretching steps not be sealed through coalescence of the amorphous molten polymer. Indeed, in case that the glass transition temperature of the amorphous matrix polymer in the top layer is considerably lower than the heat setting temperature, the heat setting step must be altogether eliminated or the heat setting temperature must be lowered closer to the glass transition temperature of said polymer.
The base layer can also be voided. However, the loading, of the microbeads in this layer should be less than 25% by volume to assure closed pores and stretchability of the laminate. At this loading level a closed cell structure is formed as described heretofore, allowing the base layer to be biaxially oriented and providing support and mechanical integrity to the top permeable layer.
The base layer can be filled with pigments. This would enable improvement in optical properties such as opacity. Typical pigments are talc, calcium carbonate, clay, titanium dioxide, gypsum, and silica. TiO2 is preferred for low cost and whiteness. The base layer can include tints and optical brighteners. This is commonly done to control whiteness of imaging support.
The support as heretofore described can be coated on the top layer with an ink receiving layer commonly used which contains mordanting agents to hold the ink dyes close to the top surface of the support, said ink receiving layer also containing UV absorbers and the like. Such layers are generally very thin and do not significantly reduce the absorbency rates of the support under said receiving layer.
Another embodiment of the invention is to laminate the heretofore described support to a paper on the base side of the support. In this embodiment the support heretofore described would comprise a thin base layer, as the paper would provide stiffness and a paper feel to the final laminated support.
In another embodiment of the invention a third permeable layer comprising the same materials as the heretofore described permeable layer is adjacent to the base layer on the opposite side of said first permeable layer. This layer could also be loaded to a level greater than 30% by volume and be ink permeable. It could be as thick as the top permeable layer to enable the same absorbing capacity or be thinner to lend a paper feel and have limited absorbing capacity. The final use of such a support would dictate the actual thickness of the film structure.


The invention concerns a method for melting a composition of raw materials including introducing the composition in an oven to form a layer (2) at the surface of the molten pool (4). An oxycombustion burner (10) is arranged above the pool and directed towards the composition layer (2) to produce a melting front (3). Parameters of the burner are adjusted to produce a large covering flame (12) causing an essentially radiation-based thermal transfer. Additionally, a plane containing a longitudinal section of the flame (Z-Z) and a horizontal direction perpendicular to the axis of the oven (X-X) intersects the melting front (3) at a height (h) included ranging between one third and half of the thickness of the composition (e). Such a method provides for a stable operation of the oven and is particularly adapted to a large-capacity oven.

The present invention relates to a method of melting a batch of raw materials using a burner placed in the crown of a furnace.
Many industrial processes include a step of melting raw materials, especially for producing materials that do not exist in the natural state, or that exist in the natural state in insufficient quantities or with a low level of purity. Metals and alloys are thus smelted in metallurgy. Likewise, glasses, frits and enamels are produced on an industrial scale by melting vitrifiable batches. In particular, industrial plants for manufacturing flat glass, especially of the soda-lime type, comprise melting furnaces of very large capacity and dimensions.
In the melting field, a mixture of raw materials, the proportions of which are determined according to the material that it is desired to obtain, is called a "batch". The batch is generally in the form of a substantially homogeneous powder, which is relatively dry and well separated.
To obtain a high output of molten material, a large-capacity furnace running continuously is used. The batch is continuously introduced into the furnace tank on a first side of the furnace and the molten material is discharged, also continuously, on a second side of the furnace, generally opposite the first side. One of the major challenges in installations of this type is to maintain continuity and stability of the melting conditions, from which, particularly, homogeneity of the molten material obtained results.
A charger is used to pour the batch into the tank on top of the fill level of the tank, in the form of a curtain of specified width. The flow of batch thus charged is approximately constant and uniformly distributed over the entire charging width. Given that the charged batch is less dense than the molten material, the batch, which is still pulverulent, stagnates on the surface of the melt. A batch layer that floats on the melt is thus formed. This layer is pushed slowly toward the downstream end of the furnace by the permanent flow of batch that continues to be poured in.
When the batch layer reaches a point in the tank where the temperature is high enough, the batch contained in the layer melts along a well-defined front. This melting front, usually called the "slope", is the boundary of the batch layer. In general, the shape and orientation of the melting front result from complex mechanisms that are poorly controlled. Convection of the molten liquid within the melt and the gas streams above the melt form part of these mechanisms.
Combustion heating is often used for such furnaces. To do this, one or more burners are placed above the furnace tank. The stability of the melting conditions then depends critically on many parameters, such as the arrangement of the burners, their number, the proportion of fuel to oxidizer used, the distance between the flame(s) of the burner(s), the fill level of the tank, etc.
When a burner of a type described in either of European Patent Applications 1 319 150 and 0 748 981 is used, a narrow flame is obtained. When this is directed toward the batch layer, a melting front is obtained in a limited flame-impact region. When the furnace is operating in a steady state, the melting front of the batch layer then has the shape of a V open toward the downstream end of the furnace. Different batch portions are therefore melted at locations in the furnace that correspond to different levels of advance along the charging direction. This causes deviations in the batch melting conditions. Furthermore, clumps of batch collapse randomly along the batch front, suddenly dropping into the melt. The slope is therefore eroded irregularly, causing uncontrolled movements of the melting front. The operation of the furnace is therefore unstable.
It is possible to place, perpendicular to the charging direction, several burners identical to the previous one in order to push the entire melting front into an upstream part of the furnace. The number of burners used makes such a solution expensive and difficult to implement, especially because of the frequency of the maintenance work on the burners that is therefore necessary.
One object of the present invention therefore consists in proposing a melting method that does not have the abovementioned drawbacks, or for which these drawbacks are reduced.
To do this, the invention proposes a method of melting a batch of raw materials, comprising the following steps:                the batch is introduced into a furnace in a charging direction parallel to a longitudinal central axis of the furnace, distributing the batch substantially continuously and uniformly over a defined charging width, so as to form a layer of the batch on the surface of the melt; and        an oxyfuel burner is placed above the melt, the burner being directed toward the batch layer so as to create a melting front of the batch present in the layer.
The method furthermore includes a step of adjusting the parameters of the burner, carried out so that:                the burner produces a flat flame having a horizontally elongate cross section;        the plane containing a longitudinal section of the flame and a horizontal direction perpendicular to the axis of the furnace intersects the batch melting front at a height between one third and one half of the thickness of the batch layer measured from the surface of the melt, and intersects the surface of the melt along a line perpendicular to the axis of the furnace; and        the flame transfers heat to the batch melting front essentially radiatively.
Thus, in a method according to the invention the parameters of the burner are adjusted so as to obtain a broad covering flame directed toward the melting front. Furthermore, given that the heat transfer from the flame to the batch melting front is essentially radiative, this transfer takes place over a substantial part of the width of the furnace at the melting front. The melting front therefore has a long straight portion oriented perpendicular to the longitudinal axis of the furnace.
A main part of the batch is thus melted at the same level of advance in the furnace, along the longitudinal axis of the latter. In addition, the melting conditions are substantially identical for batch portions located at different points on the straight part of the melting front. The batch is therefore melted in a continuous and uniform manner, under particularly stable conditions. In particular, sudden collapse of batch clumps no longer occurs in the straight part of the melting front.
This stability also results from the fact that the shape and orientation of the melting front are fixed by the nature of the flame generated by the burner. The configuration of the melting front now depends only slightly on uncontrolled effects, such as the convection of liquid material contained in the furnace tank, or such as the gas streams caused by the flame just above the batch layer. The batch melting conditions are therefore well controlled.
One advantage of a method according to the invention lies in the fact that the parameters of a single burner define the nature of the flame and thus the configuration of the melting front over a substantial distance perpendicular to the longitudinal axis of the furnace. A single burner is sufficient to fix the configuration of a large portion of the melting front, thereby making the method easy to implement. Furthermore, the reduced number of burners needed to heat the entire furnace makes the method particularly economical, both as regards the initial investment and as regards the maintenance work during operation of the furnace.
Preferably, the parameters of the burner are adjusted so that a longitudinal end of the flame does not touch the melting front of the batch. The flame is therefore short and the ratio of heat transfer that takes place radiatively to the total heat transfer from the flame is further increased. Thus, the straight portion of the melting front is even greater.
The inventors have observed that, when the burner parameters are adjusted according to the invention, the burner produces a particularly low-momentum flame. The expression "low-momentum flame" is understood to mean a flame which is sustained by injecting fluids, among which are the fuel and an oxygen-containing gas, which transmits a limited total momentum to said fluids. This momentum depends in particular on the geometrical and operational parameters of the burner.
For the sake of clarity, the dimensions of the devices shown in the figures are not in proportion with actual dimensions. In particular, measured dimensions in these figures that are associated with different actual directions are not transposed on the same scale. Furthermore, identical references used in the two figures denote identical elements.
As shown in FIG. 1, a furnace 100 comprises a tank 101, sidewalls 102 and a cover structure 103 called the crown. As an example, this furnace may be a glass production furnace.
The batch of raw materials is charged via a horizontal opening 104 made in one of the walls 102, over a length L. The batch is poured into the furnace in the form of a substantially continuous curtain 1 extending over the length L, which is called the charging width.
The molten batch forms a melt 4 contained in the tank 101. A spout 105 is provided in the wall of the furnace on the opposite side from the opening 104, via which spout the molten material flows out in the form of a continuous output stream 5.
The material contained in the furnace 100 moves overall from the charging opening 104 toward the spout 105 along the direction D, called the charging direction. The surface of the melt 4 is exposed in a downstream part of the furnace 100 and is covered in an upstream part of the furnace 100 by a still-solid batch layer 2, which floats on top of the melt. Between these two parts, the layer 2 has a sharp boundary 3 at which the batch contained in the layer 2 melts and is converted into liquid, which enters the melt 4. The boundary 3 of the layer 2 is the melting front of the batch.
In FIG. 1, X-X denotes the central longitudinal axis of the furnace 100. This axis is horizontal. The tank 101 has a rectangular base and the X-X axis intersects the width Lf of the furnace 100 at a point halfway along its width. P denotes the vertical plane that includes the X-X axis.
A method according to the invention uses an oxyfuel burner 10. As is known, such a burner produces a flame from an injection of a liquid or gaseous fuel and an injection of oxidizer consisting of a gas containing at least 60% oxygen by volume. Preferably, the oxygen-containing gas comprises at least 90% oxygen by volume. Such an oxyfuel burner is relatively compact and lightweight compared with an air-fuel burner. This makes it particularly easy to install it in a furnace. In particular, the burner 10 may be positioned through the holes 106 pierced in the crown 103 above the melt. Ducts 13 pass through the holes 106 in order to feed the burner 10 with oxygen-containing gas and with fuel. Thanks to the small dimensions and low weight of the burner 10, it is unnecessary to provide a quarl in the crown 103 for passage of the ducts 13. The design and construction of the crown 103 are thereby facilitated.
The burner 10 lies in the plane P. It is directed toward the batch layer 2 so as to produce one or more jets 11 of fuel and oxygen-containing gas that are distributed on each side of the plane P. To do this, the burner 10 may be inclined to the vertical direction, denoted by H in FIG. 1, and oriented downward. The angle between the mean exit direction F of the jets produced by the burner 10 and the direction H is denoted by α. The angle α is preferably between 30° and 75° and more particularly between 45° and 65°. In FIG. 1, the reference 12 denotes the flame produced by the burner 10.
The burner 10 may be of a model as described in U.S. Pat. No. 6,068,468. Such a burner possesses several fuel outlets and several oxygen-containing gas outlets. It is particularly suitable for obtaining a broad covering flame.
By suitably adjusting the burner 10, a principal mode of transferring the thermal energy produced by the flame 12 is adopted, this transfer taking place radiatively. Preferably at least 60% of the transfer of heat generated by the flame 12 takes place radiatively. A particularly large part of the melt therefore receives the heat produced by the flame 12. When the burner 10 thus regulated is directed toward the batch layer 2, the melting front 3 is located in the region of thermal impact by the flame 12. Given that this impact region is wide, the melting front 3 has a large straight portion perpendicular to the X-X axis in a part of the furnace facing the burner 10. In FIG. 1, d is the length of this straight portion of the front 3.
Since the burner 10 is centered with respect to the width of the furnace 100, the melting front 3 is symmetrical with respect to the plane P. In this way, the batch layer 2 is melted in the same way on both sides of the furnace 100 with respect to the plane P.
To further promote a radiative heating mode rather than a convective one, the burner 10 may furthermore be adjusted so as to generate a flame 12 that is short and luminous. To do this, the flame 12 is a low-momentum flame and has a fuel-rich zone. The use of an oxygen-fuel burner 10, instead of an air-fuel burner, is particularly appropriate for obtaining such combustion conditions. The temperature is then particularly high in the fuel-rich zone and the heat transfer to the furnace charge essentially takes place radiatively. The heat transfer from the flame to the batch layer therefore takes place with the flame a certain distance away from the batch layer, thereby making it easier to obtain a melting front having a large straight portion.
Certain parameters of the burner 10, which are adjusted so as to implement a melting method according to the invention, may be chosen from the following: the number, dimensions, positions and inclinations of the orifices for injecting fluids into the furnace 100, said fluids including a fuel and an oxygen-containing gas. Thus, the oxyfuel burner described in the publication EP-A1-0 754 912 is particularly suitable for implementing the method according to the invention.
To obtain a low-momentum flame 12, certain parameters of the burner 10 are adjusted so that the fluids injected into the furnace 100 by the burner have a total momentum of between 0.58 N and 5 N. Preferably, the total momentum of these fluids is between 1.2 N and 2.5 N.
FIG. 2 is a section through the furnace 100 in the plane P showing more precisely the geometric parameters of both the burner 10 and the flame 12. The flame 12 has a flattened shape, distributed symmetrically on either side of the plane P. F corresponds to the direction of the flame 12 in the plane P. The Z-Z axis, passing through the burner 10 and parallel to the direction F, intersects the melting front 3 at the point denoted A in the plane P. A is located at a height, measured from the surface of the melt 4, that lies between one third and one half of the thickness e of the batch layer 2. The distance between the end of the flame 12 and the melting front 3 is w. Since w is non-zero, the flame 12 does not touch the batch layer 2.
The inclined plane containing the Z-Z axis and a horizontal direction perpendicular to the plane P contains a longitudinal section of the flame 12. It intersects the surface of the melt 4 along a line perpendicular to the X-X axis passing through the point B.
When steady-state melting is established, the following equation relates the heating power P delivered by the flame 12 to the characteristics of the layer 2:P=ΔHρ2V,where ΔH denotes the average enthalpy of melting of the batch, ρ denotes the density of the batch in the layer 2 and V is the feed rate. It is therefore possible to adjust the power P of the burner 10 according to the desired output in the spout 105. The consumption of oxygen and fuel may thus be reduced to values just sufficient to melt the quantity of batch corresponding to the output. To give an example, it is possible to inject 10 Sm3/h of natural gas for 20 Sm3/h of oxygen via the burner 10, for a batch feed rate of 12 kg/h in the manufacture of glass.
According to an improvement of a method according to the invention, the position of advance of the melting front 3 on the surface of the melt 4, along the X-X axis, may also be used as a criterion for adjusting certain parameters of the burner 10. In particular, the fuel flow rate, the oxygen-containing gas flow rate, the fuel injection pressure, the oxygen-containing gas injection pressure and the angle α may be adjusted in this way.
Optionally, the method may furthermore include installing a system for detecting the position of advance of the melting front 3 along the X-X axis. Certain parameters of the burner may then be slaved to the position of advance of the melting front that is detected.
To give an example, the system for detecting the position of advance of the melting front 3 may comprise a laser (not shown). As soon as the laser beam is intersected or altered by movement of the melting front 3, a feedback signal is sent to an automatic control unit for controlling the parameters of the burner 10, so as to correct certain parameters in order to compensate for the movement of the front 3.
It has been shown that a melting method according to the invention has many advantages, among which the following may be recalled or mentioned:                the method provides particularly stable melting conditions;        it may be implemented in large-capacity furnaces;        the burner is simple to mount and requires only few fitments in the crown of the furnace;        the furnace equipment and maintenance costs are reduced;        the consumption of fuel and oxygen is reduced;        the molten material extracted from the furnace is very homogeneous;        the flame directed against the melting front constitutes a screen that prevents batch dust coming from the layer to propagate toward the downstream end of the furnace, to the outside of the furnace and through the flue;        the method is flexible and can be simply adapted when different batches are melted in succession in the same furnace. The burner parameters are only adjusted for each batch, so as to restore a straight shape of the melting front. Optionally, they may also be adjusted so as to displace the melting front along the charging direction to a suitable position for each batch; and        the method can be easily automated.
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.

Method for melting a composition of raw materials with an arched burner

L'Air Liquide Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude


The invention provides an aqueous, hard surface cleaner with significantly improved residue removal and substantially reduced filming/streaking, and the cleaner comprises:

1. Field of the Invention
The invention relates to a non-rinse, isotropic hard surface cleaner especially adapted to be used on glossy or smooth, hard surfaces, such as glass windows and the like, which removes soils deposited thereon, while significantly reducing the amount of residue caused by unremoved soil, cleaner, or a combination thereof. The inventive cleaner advantageously delivers an auditory xe2x80x9ccleanxe2x80x9d signal, the sound of a wicking implement, such as a cleaning cloth or sponge, squeaking or squealing when the cleaner is removed therewith from a smooth, glossy surface, such as a glass or mirrored surface.
2. Brief Statement of the Related Art
Cleaning hard, glossy surfaces such as glass windows has proven to be problematic. To remove soils deposited on such surfaces, the typical approach is to use an alkaline ammonium-based aqueous cleaner or other aqueous cleaners containing various mixtures of surfactants and other cleaning additives. Unfortunately, many of the ammonia-based cleaners have fairly poor soil removing ability, while many of the surfactant-based cleaners leave fairly significant amounts of residue on such hard, glossy surfaces. This residue is seen in the phenomena of streaking, in which the soil, cleaner, or both are inconsistently wicked off the surface, and filming, in which a thin layer of the residue actually clings to the surface desired to be cleaned.
Baker et al., U.S. Pat. No. 4,690,779, demonstrated a hard surface cleaner having improved non-streaking/filming properties in which a combination of low molecular weight polymer (e.g., polyethylene glycol) and certain surfactants were combined.
Church, U.S. Pat. Nos. 4,213,873 and 4,315,828, disclose hard surface cleaners containing water, a cleaning agent (ammonium hydroxide or an alcohol), and a lubricity agent, which is typically a polymer, but allegedly can include a mixture of ammonium carbonate and ammonium carbamate.
Corn et al., E.P. 0393772 and E.P. 0428816, describe hard surface cleaners containing anionic surfactants with ammonium counterions, and additional adjuncts. G.B. 2,160,887 describes a cleaning system in which a combination of nonionic and anionic surfactants (including an alkanolamine salt alkyl sulfate) is contended to enhance cleaning efficacy.
WO 91/11505 describes a glass cleaner containing a zwitterionic surfactant, monoethanolamine and/or beta-aminoalkanols as solvents/buffers for assertedly improving cleaning and reducing filming spotting.
Garabedian et al., U.S. Pat. Nos. 5,252,245, 5,437,807, 5,468,423 and 5,523,024, and Choy et al., U.S. Pat. No. 5,585,342, all of common assignment herewith, disclose improved glass and surface cleaners which combine either amphoteric or nonionic surfactants with solvents and effective buffers to provide excellent streaking/filming characteristics on glass and other smooth, glossy surfaces. These disclosures are incorporated herein by reference thereto.
The invention provides an aqueous, hard surface cleaner with significantly improved residue removal and substantially reduced filming/streaking, said cleaner comprising:
(a) an effective amount of at least one organic solvent with a vapor pressure of at least 0.001 mm Hg at 25xc2x0 C., and mixtures of such solvents;
(b) an effective amount of either at least one anionic surfactant, or a mixture of anionic and nonionic surfactants;
(c) an effective amount of a buffering system which comprises a nitrogenous buffer which will result in a pH of greater than 6.5; and
(d) the remainder as substantially all water.
The invention provides an all-temperature, improved glass and other hard surface cleaner having excellent streaking/filming performance as compared to the prior art. The improvement is especially striking when cleaning glass and other glossy, hard surfaces with the invention.
In another embodiment of the invention, the cleaner further comprises (e) an effective amount of an additional dispersant, namely, an n-alkylpyrrolidone. This particular adjunct has proven to be surprisingly effective at both dispersing highly insoluble organic materials, particularly, fragrance oils, while simultaneously enhancing or maintaining the effective minimization of streaking/filming of the surfaces cleaned with the inventive cleaner.
The invention further comprises a method of cleaning soils from hard surfaces by applying said inventive cleaner to said soil (such as by, e.g., using a pump or trigger sprayer to conveniently and effectively deliver metered amounts of the cleaner to the soiled surface), and removing both from said surface.
It is therefore an object of this invention to substantially eliminate filming which results from a residue of cleaner, soil, or both remaining on the hard surface intended to be cleaned.
It is another object of this invention to substantially eliminate streaking, which results from inconsistent removal of the cleaner, soil, or both, from the hard surface intended to be cleaned.
It is also an object of this invention to provide a cleaner for glass and other hard, glossy surfaces, which has virtually no filming or streaking.
The invention is an improved cleaning, substantially non-streaking/filming hard surface cleaner especially adapted to be used on glossy or smooth, hard surfaces, emblematic of which is glass. The cleaner benefits from the use of a novel surfactant which contributes unexpectedly to the complete removal of soils and the cleaner from the surface being cleaned. The cleaner itself has the following ingredients:
(a) an effective amount of at least one organic solvent with a vapor pressure of at least 0.001 mm Hg at 25xc2x0 C., and mixtures of such solvents;
(b) an effective amount of either at least one anionic surfactant, or, a mixture of anionic and nonionic surfactants;
(c) an effective amount of a buffering system which comprises a nitrogenous buffer which will result in a pH of greater than 6.5; and
(d) the remainder as substantially all water.
Additional adjuncts in small amounts such as fragrance, dye and the like can be included to provide desirable attributes of such adjuncts. In a further embodiment of the invention, especially when a fragrance is used, a further adjunct (e) a 1-alkyl-2-pyrrolidone is added in amounts effective, along with the anionic surfactant, to disperse the fragrance and to improve or maintain the reduced streaking/filming performance of the inventive cleaner.
In the application, effective amounts are generally those amounts listed as the ranges or levels of ingredients in the descriptions which follow hereto. Unless otherwise stated, amounts listed in percentage (xe2x80x9c%""sxe2x80x9d) are in weight percent of the composition, unless otherwise noted.
1. Solvents
The solvents useful in this invention are organic solvents with a vapor pressure of at least 0.001 mm Hg at 25xc2x0 C. and soluble to the extent of at least 1 g/100 ml water. The upper limit of vapor pressure appears to be about 100 mm Hg at 25xc2x0 C. Vapor pressure is a useful measure for determining the applicability of the given solvent, since one would select a solvent which will volatilize sufficiently so as to leave no visible residue. The organic solvent of the invention is preferably selected from C1-6 alkanol, C3-24 alkylene glycol ether, and mixtures thereof. However, other, less water soluble or dispersible organic solvents may also be utilized. It is preferred that a mixture of the C1-6 alkanol and C3-24 alkylene glycol ether solvents be used. The alkanol can be selected from methanol, ethanol, n-propanol, isopropanol, butanol, pentanol, hexanol, their various positional isomers, and mixtures of the foregoing. In the invention, it has been found most preferable to use isopropanol, usually in conjunction with a glycol ether. It may also be possible to utilize in addition to, or in place of, said alkanols, the diols such as methylene, ethylene, propylene and butylene glycols, and mixtures thereof. Other solvents, such as ketones, ethers, hydrocarbons and halides may be used. Other examples of solvents can be found in Kirk-Othmer, Encyclopedia of Chemical Technology 3rd, Vol. 21, pp. 377-401 (1983), incorporated by reference herein.
The alkylene glycol ether solvents can include ethylene glycol monobutyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and mixtures thereof. One particularly preferred glycol ether is ethylene glycol, monobutyl ether, also known as 2-butoxyethanol, sold as Dowanol EB from Dow Chemical, while another commercially available one is Butyl Cellosolve by Union Carbide. The use of these particular glycol ethers in the invention results in a very low to minimal foaming cleaner, both upon application (spraying) and removal from (wiping) a hard surface. Another preferred alkylene glycol ether is propylene glycol, t-butyl ether, which is commercially sold as Arcosolve PTB, by Arco Chemical Co. If mixtures of solvents are used, the amounts and ratios of such solvents used are important to determine the optimum cleaning and streak/film performances of the inventive cleaner. It is preferred to limit the total amount of solvent to no more than 50%, more preferably no more than 25%, and most preferably, no more than 15%, of the cleaner. However, in some of the compositions of this invention, no solvent may be present. A preferred range is about 1-15%, and if a mixed solvent system of alkanol/glycol ether is used, the ratio of alkanol to alkylene glycol ether should be about 1:20 to 20:1, more preferably about 1:10 to 10:1 and most preferably about 1:5 to 5:1.
As mentioned above, other, less water soluble or dispersible organic solvents may also be utilizable herein, although in a high water formulation, there may be a need for a further dispersant (e.g., hydrotrope or other emulsifier). These less water soluble or dispersible organic solvents include those conmmonly used as constituents for proprietary fragrance blends, such as terpene derivatives. The terpene derivatives herein include terpene hydrocarbons with a functional group. Effective terpenes with a functional group include, but are not limited to, alcohols, ethers, esters, aldehydes and ketones.
Representative examples for each of the above classes of terpenes with functional groups include but are not limited to the following: Terpene alcohols, including, for example, verbenol, transpinocarveol, cis-2-pinanol, nopol, iso-borneol, carbeol, piperitol, thymol, xcex1-terpineol, terpinen-4-ol, menthol, 1,8-terpin, dihydro-terpineol, nerol, geraniol, linalool, citronellol, hydroxycitronellol, 3,7-dimethyl octanol, dihydro-myrcenol, tetrahydro-alloocimenol and perillalcohol; Terpene ethers and esters, including, for example, 1,8-cineole, 1,4-cineole, isobornyl methylether, rose pyran, xcex1-terpinyl methyl ether, menthofuran, trans-anethole, methyl chavicol, allocimene diepoxide, limonene mono-epoxide, iso-bornyl acetate, nopyl acetate, a-terpinyl acetate, linalyl acetate, geranyl acetate, citronellyl acetate, dihydro-terpinyl acetate and neryl acetate; Terpene aldehydes and ketones, including, for example, myrtenal, campholenic aldehyde, perillaldehyde, citronellal, citral, hydroxy citronellal, camphor, verbenone, carvenone, dihyro-carvone, carvone, piperitone, menthone, geranyl acetone, pseudo-ionone, xcex1-ionone, xcex2-ionone, iso-pseudo-methyl ionone, normal-pseudo-methyl ionone, iso-methyl ionone and normal-methyl ionone.
Terpene hydrocarbons with functional groups which appear suitable for use in the present invention are discussed in substantially greater detail by Simonsen and Ross, The Terpenes, Volumes I-V, Cambridge University Press, 2nd Ed., 1947 (incorporated herein by reference thereto). See also, the commonly assigned U.S. Pat. No. 5,279,758, of Choy, incorporated herein by reference thereto.
2. Surfactants
The principal surfactants used in the inventive hard surface cleaner are anionic surfactants, for both cleaning and desirable foaming characteristics. The anionic surfactant is selected from alkyl sulfates, alkyl diphenyl oxide disulfonates, alkylbenzene sulfonates, alkylsulfonates, iseothionates, alkylethersulfates, xcex1-olefin sulfonates, alkyl taurates, alkyl sarcosinates and the like. Each of these surfactants is generally available as the alkali metal, alkaline earth and ammonium salts thereof. These surfactants can include both straight and branched alkyl chains, or mixtures thereof. The preferred anionic surfactants are alkyl sulfatesxe2x80x94more preferably C6-16 alkyl sulfatesxe2x80x94and alkyl diphenyl oxide disulfonates. One particularly preferred sulfate is sodium lauryl (C12) sulfate, available from Stepan Chetical Co., under the brand name Stepanol WAC. The alkyl diphenyl oxide disulfonates are atypical surfactants and preferably include an alkyl chain group of C6-20. The preferred alkyl diphenyl oxide disulfonates are from Dow under the brand name Dowfax. Especially preferred is Dowfax 3B2, an n-decyl diphenyloxide disulfonate. Pilot Chemical, with Calfax, is another source of the alkyl diphenyl oxide disulfonate surfactant.
In the invention, it was determined that the alkyl diphenyl oxide disulfonates are especially preferred. In addition to their improvement to cleaning performance, these surfactants enhance the inventive cleaners with the advantageous characteristic of an auditory signal when a hard surface is cleaned therewith. Specifically, when a cleaner formulated with said alkyl diphenyl oxide disulfonates is applied to a glossy hard surface, preferably glass or mirrored surfaces, and is then removed therefrom with the aid of a squeegee or wicking instrument, such as a cleaning cloth, sponge, or the like, a distinct xe2x80x9csqueakxe2x80x9d or squeal is heard, which signals the user that complete removal of the cleaner, and the soil, has been accomplished.
It is also preferred to add a nonionic surfactant to the formulation of this inventive hard surface cleaner, typically, in admixture with the anionic surfactant. These nonionic surfactants desirable for inclusion may be straight or branched chain and are selected from alkoxylated C6-16 alcohols, alkoxylated C6-16 alkyl ether phenols, and other C6-16 semi-polar nonionics, such as the trialkyl amine oxides. The alkoxylated alcohols include ethoxylated, and ethoxylated and propoxylated C6-16 alcohols, with about 2-10 moles of ethylene oxide, or 1-10 and 1-10 moles of ethylene and propylene oxide per mole of alcohol, respectively. The preferred ethoxylated alcohols include branched chain ethoxylated alcohols sold under the brand name xe2x80x9cTergitol,xe2x80x9d by Union Carbide, and those available under the brand name xe2x80x9cTriton,xe2x80x9d (also by Union Carbide) and from Shell Chemical Company under the trademark xe2x80x9cNeodol,xe2x80x9d and xe2x80x9cAlfonic,xe2x80x9d a trademark of Vista Chemical Company. A preferred straight chain alcohol is Alfonic 810-40. A preferred branched chain alcohol is Tergitol TMN-6. The preferred alkoxylated C6-16 alkyl ether phenols are typically either octyl-, or, more commonly, nonylphenols, with varying degrees of alkoxylation. Examples include the Tritons, from Union Carbide, such as Triton N-45, N-101 and N-57. Semi-polar amine oxides could be added, although, it is noted that these surfactants have themselves been used as the primary surfactant in the hard surface cleaners of Garabedian et al., U.S. Pat. No. 5,437,807. These have the general configuration:
wherein R is C6-24 alkyl, and Rxe2x80x2 and Rxe2x80x3 are both C1-4 alkyl, although Rxe2x80x20 and Rxe2x80x3 do not have to be equal. These amine oxides can also be ethoxylated or propoxylated. The preferred amine oxide is lauryl amine oxide, such as Barlox 12, from Lonza Chemical Company.
Other surfactants of interest include the semi-polar nonionic surfactant known as an alkylamidoalkylenedialkylamine oxide. Its structure is shown below:
wherein R1 is C5-20 alkyl, R2 and R3 are C1-4 alkyl, R1xe2x80x94Cxe2x80x94NHxe2x80x94(CH2)nxe2x80x94 or xe2x80x94(CH2)pxe2x80x94OH, although R2 and R3 do not have to be equal or the same substituent, and n is 1-5, preferably 3, and p is 1-6, preferably 2-3. Additionally, the surfactant could be ethoxylated (1-10 moles of EO/mole) or propoxylated (1-10 moles of PO/mole). These types of surfactants include Barlox C, from Stepan Company, and Varox, from Witco Chemical.
An amphoteric surfactant may also be desirable for addition in discrete amounts, although it is also observed that it has been used in comparative formulations against which the invention has been compared and in which the invention was found generally to have superior performance. The amphoteric surfactant is typically an alkylbetaine or a sulfobetaine. Especially preferred are alkylamidoalkyldialkylbetaines. These have the structure:
wherein Ra is C6-20 alkyl, Rb and Rc are both C1-4 alkyl, although Rb and Rc do not have to be equal, and m can be 1-5, preferably 3, and o can be 1-5, preferably 1. These alkylbetaines can also be ethoxylated or propoxylated. The preferred alkylbetaine is a cocoamidopropyldimethyl betaine called Lonzaine CO, available from Lonza Chemical Co. Other vendors are Henkel KGaA, which provides Velvetex AB, and Witco Chemical Co., which offers Rewoteric AMB-15, both of which products are cocobetaines.
The amounts of surfactants present are to be somewhat minimized, for purposes of cost-savings and to generally restrict the dissolved actives which could contribute to leaving behind residues when the cleaner is applied to a surface. In a preferred composition, the total amount of surfactant is present, in a range of about 0.001-10%, more preferably about 0.001-7.5%, and most preferably about 0.001-3%, total surfactant. In the typical hard surface cleaners of this invention, and where a mixture of anionic/nonionic/alkylpyrrolidone is used, the amounts added are generally about 0.001-2%, more preferably 0.002-0.75% anionic surfactant, generally about 0-1%, more preferably 0-0.75% nonionic surfactant and generally 0.005-2%, more preferably 0.01-1% alkylpyrrolidone surfactant, in the cleaner, although it is again most preferred not to exceed more than about 3% total surfactant. In fact, in a most advantageous execution of the invention, the total amount of surfactant should not exceed about 1%. The ratios of surfactants are generally about 1:1:10 to 1,000:1:1 anionic/nonionic/alkylpyrrolidone, when all three are present. If just two surfactants are used, the ratios will be about 1:1,000 to 1,000:1. However, in an especially preferred embodiment of this invention, when anionic and nonionic surfactants are combined, they are present in about a 1:1 ratio, for maximum foam control, streaking/filming performance and the delivery of the auditory signal.
3. Alkylpyrrolidones
The 1-alkyl-2-pyrrolidones can provide a dual function in this invention. First, one of the desirable adjuncts which are added to this system are fragrances, which are typically water-immiscible to slightly water-soluble oils. In order to keep this fairly immiscible component in solution, a co-solvent or other dispersing means was necessary. It was determined that 1-alkyl-2-pyrrolidones were particularly effective, along with the anionic surfactant, at so solubilizing the fragrance oils. The compound has the general structure:
wherein R4 is a C6-20 alkyl, or R5NHCOR6, and R5 is C1-6 alkyl and R6 is C6-20 alkyl. A particularly preferred alkyl pyrrolidone is lauryl (or n-dodecyl) pyrrolidone, sold by ISF Chemicals under the brand name Surfadone, such as Surfadone LP-300. Relatively low amounts of the alkyl pyrrolidone are used, preferably, about 0.001-2%, when the level of fragrance is from about 0.01-5%.
4. Buffer System
The buffer system comprises a nitrogenous buffer which is added to the aqueous hard surface cleaners of the invention so as to result in a pH of greater than 6.5, more preferably, between 7 and 14, most preferably between 7 and 13. The buffer can be selected from the group consisting of: ammonium or alkaline earth carbamates, guanidine derivatives, ammonium carbonate, ammonium bicarbonate, diammonium carbonate, ammonium hydroxide, ammonia (which forms ammonium hydroxide in situ when added to water) and mixtures thereof. Optionally and preferably, the co-buffer is selected from ammonium and alkaline earth metal hydroxides. A combination of ammonium carbamate and ammonium hydroxide is most preferred.
The nitrogenous buffer is a significant aspect of the invention. Because of its presence, greatly enhanced reduction in streaking and filming of hard surfaces is achieved after the inventive cleaner is used to clean the same. The preferred nitrogenous buffers are ammonium carbamate, ammonium bicarbonate, ammonium carbonate and ammonium hydroxide. Ammonium carbamate has the structure NH2COOxe2x88x92NH+4. Use of this particularly preferred buffer obtains outstanding reduction in filming/streaking. It is available from BASF Corp. Ammonium carbonate and bicarbonate are other, further desirable buffers. Mixtures of any of the foregoing can be used as the buffer in the buffering system. Most of these materials can be obtained from general chemical supply houses, e.g., Aldrich Chemicals.
Additionally, it is especially preferred to add, as a co-buffer, an ammonium or alkaline earth hydroxide. Most preferred is ammonium hydroxide, which volatilizes relatively easily after being applied, resulting in minimal residue. Ammonium hydroxide also emulsifies fatty soils to a certain extent.
The amount of nitrogenous buffer added should be in the range of 0.01-2%, more preferably 0.01-1%, by weight of the cleaner, while hydroxide, if present, should be added in the range of 0.00-1% by weight of the cleaner.
5. Water and Miscellaneous
Since the cleaner is an aqueous cleaner with relatively low levels of actives, the principal ingredient is water, which should be present at a level of at least about 50%, more preferably at least about 80%, and most preferably, at least about 90%. Deionized water is most preferred.
Small amounts of adjuncts can be added for improving cleaning performance or aesthetic qualities of the cleaner. Adjuncts for cleaning include additional surfactants, such as those described in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed., Volume 22, pp. 332-432 (Marcel-Dekker, 1983), which are incorporated herein by reference. Inorganic builders, such as silicates and phosphates, are generally avoided in this cleaner, especially those which will contribute a large amount of solids in the formulation which may leave a residue. Aesthetic adjuncts include fragrances, such as those available from Givaudan-Roure, Belmay, Bush Booke and Allen, Henkel KGaA, Firmenich, Dragoco, IFF, Quest and others, and dyes and pigments which can be solubilized or suspended in the formulation, such as diaminoanthraquinones. The choice of color is left to the formulator, although various shades and hues of yellow, purple, green and blue, as well as colorless, are preferred. As mentioned above, the fragrance oils typically require a dispersant, which role is fulfilled by the alkylpyrrolidone and by the anionic surfactant present. As previously noted, a fragrance is well dispersed by the alkylpyrrolidone while at least maintaining, if not improving, the non-streaking/non-filming performance of the inventive cleaner. The amounts of these cleaning and aesthetic adjuncts should be in the range of 0-2%, more preferably 0-1%.
An additional adjunct of interest herein is hydrotropes, specifically, short chain alkylaryl sulfonates, more specifically, C1-4 alkylaryl sulfonates, such as, without limitation, benzene, naphthalene, xylene, cumene and toluene sulfonates. These are typically alkali metal salts and, although it has been cautioned herein that the total level of alkali metal salts is to be limited, in fact, for certain purposes, such as hard surface cleaning (e.g., tile, composite materials such as Formica(copyright) and Corian(copyright) countertops, and the like), incorporation of hydrotropes in a discrete level may be quite acceptable. The preferred hydrotrope herein is alkali metal xylene sulfonate, wherein the alkali metal is potassium, sodium or lithium. An ammonium salt may also be acceptable. The amount of short chain alkylaryl sulfonate may be kept economically low, i.e., preferably about 0.01-2%, more preferably 0.02-1% and most preferably, about 0.05-1%. Preferred hydrotropes, among others, include sodium xylene sulfonate, sold in various active levels by Stepan Chemical Company under the brand name Stepanate SXS. Other preferred hydrotropes may be found from Colbom et al., U.S. Pat. No. 4,863,633, column 8, line 20 to column 10, line 22, which are incorporated by reference thereto.