An ink jet printing method, comprising the steps of: A) providing an ink jet printer that is responsive to digital data signals; B) loading the printer with an ink jet recording element comprising a non-absorbing substrate; C) loading the printer with an ink jet ink composition comprising an aqueous ink jet ink composition comprising: a pigment, a polymer binder containing less than 25% of hydrophilic monomer by weight of the total polymer, which is dispersible but insoluble in aqueous media, at least one surfactant, and a humectant; and D) printing on the ink jet recording element accompanied by a heating step using the ink jet ink composition in response to the digital data signals.

This invention related to ink jet printing method using an ink jet ink and ink receiver combination wherein the ink is an aqueous inkjet ink comprises a pigment and a polymer binder, and the receiver comprises a non-absorbing substrate, e.g. an untreated vinyl.
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets on a substrate (paper, transparent film, fabric, etc.) in response to digital signals. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging and large format printing for outdoor applications such as banners, signage, displays, posters, billboard and bus wraps.
This technique of printing is well suited for printing on a variety of surfaces (receivers) including porous and non-porous surfaces. Porous inkjet receivers have the advantage of large fluid intake and this provides fast printing speed. However, in some applications, such as banners, signage, displays, posters, billboard and bus wraps, these porous receivers suffer from durability issues such as lightfastness, waterfastness, abrasion resistance and weather resistance. In order to overcome these problems, the prints are usually post treated by methods such as lamination, which adds to the cost considerably. Historically, in order to overcome these problems, solvent based inks or UV curable inks were developed for printing on non-absorbing substrates such as vinyl to achieve the desired durability. U.S. Pat. No. 4,106,027 describes such a solvent-based ink that is suitable for printing images on non-absorbing receivers with improved adhesion and durability. EP 0 882 104 B1 describes a UV curable inkjet ink composition for better durability of the print on non-absorbing substrate. A significant environmental, health and safety concern with both of these types of ink is the evaporation of solvent or UV monomer during printing.
U.S. Pat. No. 6,087,416 describes the use of an aqueous based pigment ink for printing on non-absorbing vinyl substrate. That ink contains a grafted copolymer binder that is soluble in the aqueous vehicle but insoluble in water. However, the problem with the ink is that, due to the soluble nature of the binder in the ink vehicle, the ink viscosity is high and the printing reliability is poor. In addition, the printed images are not durable to solvents.
U.S. Pat. No. 4,762,875 described a printing ink containing pigment and polymer additives for plastics and metal surfaces. However, there is a problem with this invention that the solid content for this ink is high, therefore the viscosity of the ink is too high for inkjet ink applications; in addition, the additives used in this invention is hydrophilic in nature therefore the resulted coatings has poor water resistance.
Therefore, there is a need for an ink jet printing method that uses an aqueous based inkjet ink to provide good waterfastness, lightfastness, abrasion resistance, good adhesion to non-absorbing substrates including untreated vinyl, and that can be printed reliably through a piezo or thermal printhead.
The present invention discloses an ink jet printing method that uses an aqueous based inkjet ink to provide good waterfastness, lightfastness, abrasion resistance, good adhesion to non-absorbing substrates including untreated vinyl, and that can be printed reliably through a piezo or thermal printhead. The invention discloses an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading said printer with an ink jet recording element comprising a non-absorbing substrate;
C) loading said printer with an ink jet ink composition comprising an aqueous ink jet ink composition comprising:
a pigment;
a polymer binder containing less than 25% of hydrophilic monomer by weight of the total polymer, which is dispersible but insoluble in aqueous media;
at least one surfactant; and
a humectant; and
D) printing on said ink jet recording element accompanied by a heating step using said ink jet ink composition in response to said digital data signals.
The method used in the present invention is suited for printing on a variety of non-absorbing substrates. The receivers that may be used in the present invention include any substrate that is essentially non-porous and has very low or no fluid absorbing capacity. Usually, these substrates are hydrophobic. Examples of such non-absorbing substrates are metal such as aluminum, copper, stainless steel and alloy etc.; plastics such as vinyl, polycarbonate, polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polystyrene, cellulose; and other substrates such as ceramics, glass.
In order to achieve good image durability when printing aqueous based inks onto a non-absorbing substrate, the polymeric binder in the ink composition needs to be essentially hydrophobic, capable of providing good adhesion strength to the non-absorbing substrate, and also not be easily re-dispersible in water after drying. In addition, in order to provide good ink storage stability and prevent potential nozzle clogging, the hydrophobic polymer binder also needs to be sufficiently stable as a dispersion and compatible with other ink components, such as surfactant, colorants and humectants. Therefore, the polymer binders need to be dispersible in aqueous ink environment but not soluble to achieve low ink viscosity and print durability to both water and solvents. Furthermore, the ink should have sufficiently low surface tension to have good wettability to the non-absorbing substrate.
The pigment used in the current invention can be either self-dispersible pigment such as those described in U.S. Pat. No. 5,630,868, encapsulated pigments as those described in the pending U.S. patent application Ser. No. 09/822,723, filed Mar. 30, 2001, or can be stabilized by a dispersant. The process of preparing inks from pigments commonly involves two steps: (a) a dispersing or milling step to break up the pigment to the primary particle, and (b) dilution step in which the dispersed pigment concentrate is diluted with a carrier and other addenda to a working strength ink. In the milling step, the pigment is usually suspended in a carrier (typically the same carrier as that in the finished ink) along with rigid, inert milling media. Mechanical energy is supplied to this pigment dispersion, and the collisions between the milling media and the pigment cause the pigment to deaggregate into its primary particles. A dispersant or stabilizer, or both, is commonly added to the pigment dispersion to facilitate the deaggregation of the raw pigment, to maintain colloidal particle stability, and to retard particle reagglomeration and settling.
There are many different types of materials which may be used as milling media, such as glasses, ceramics, metals, and plastics. In a preferred embodiment, the grinding media can comprise particles, preferably substantially spherical in shape, e.g., beads, consisting essentially of a polymeric resin. In general, polymeric resins suitable for use as milling media are chemically and physically inert, substantially free of metals, solvent and monomers, and of sufficient hardness and firability to enable them to avoid being chipped or crushed during milling. Suitable polymeric resins include crosslinked polystyrenes, such as polystyrene crosslinked with divinylbenzene, styrene copolymers, polyacrylates such as poly(methyl methylacrylate), olycarbonates, polyacetals, such as Derlin(trademark), vinyl chloride polymers and copolymers, polyurethanes, polyamides, poly(tetrafluoroethylenes), e.g., Teflon(trademark), and other fluoropolymers, high density polyethylenes, polypropylenes, cellulose ethers and esters such as cellulose acetate, poly(hydroxyethylmethacrylate), poly(hydroxyethylacrylate), silicone containing polymers such as polysiloxanes and the like. The polymer can be biodegradable. Exemplary biodegradable polymers include poly(lactides), poly(glycolids) copolymers of lactides and glycolide, polyanhydrides, poly(imino carbonates), poly(N-acylhydroxyproline) esters, poly(N-palmitoyl hydroxyprolino) esters, ethylene-vinyl acetate copolymers, poly(orthoesters), poly(caprolactones), and poly(phosphazenes). The polymeric resin can have a density from 0.9 to 3.0 g/cm3. Higher density resins are preferred inasmuch as it is believed that these provide more efficient particle size reduction. Most preferred are crosslinked or uncrosslinked polymeric media based on styrene.
Milling can take place in any suitable grinding mill. Suitable mills include an air jet mill, a roller mill, a ball mill, an attritor mill and a bead mill. A high speed mill is preferred. By high speed mill we mean milling devices capable of accelerating milling media to velocities greater than about 5 meters per second. Sufficient milling media velocity is achieved, for example, in Cowles-type saw tooth impeller having a diameter of 40 mm when operated at 9,000 rpm. The preferred proportions of the milling media, the pigment, the liquid dispersion medium and dispersant can vary within wide limits and depends, for example, up on the particular material selected and the size and density of the milling media etc. After milling is complete, the dispersion of active material is separated from the grinding media by simple sieving or filtration. With either of the above modes the preferred amounts and ratios of the ingredients of the mill grind will vary widely depending upon the specific materials and the intended applications. The contents of the milling mixture comprise the mill grind and the milling media. The mill grind comprises pigment, dispersant and a liquid carrier such as water. For aqueous ink jet inks, the pigment is usually present in the mill grind at 1 to 50 weight %, excluding the milling media. The weight ratio of pigment to dispersant is 20:1 to 1:2. The high speed mill is a high agitation device, such as those manufactured by Morehouse-Cowles, Hockmeyer et al.
The dispersant is another ingredient in the mill grind. It can be either a small molecule or a polymer. Preferred dispersants used in the present invention include sodium dodecyl sulfate, acrylic and styrene-acrylic copolymers, such as those disclosed in U.S. Pat. Nos. 5,085,698 and 5,172,133, and sulfonated polyesters and styrenics, such as those disclosed in U.S. Pat. No. 4,597,794. Other patents referred to above in connection with pigment availability also disclose a wide variety of dispersants. The dispersant used in the examples is potassium N-methyl-N-olcoyl taurate (K-OMT).
The milling time can vary widely and depends upon the pigment, mechanical means and residence conditions selected, the initial and desired final particle size, etc. For aqueous mill grinds using the preferred pigments, dispersants, and milling media described above, milling times will typically range from 1 to 100 hours. The milled pigment concentrate is preferably separated from the milling media by filtration.
The pigment particles useful in the invention may have any particle sizes which can be jetted through a print head. Preferably, the pigment particles have a mean particle size of less than about 0.5 micron, more preferably less than about 0.2 micron.
A wide variety of organic and inorganic pigments, alone or in combination, may be selected for use in the present invention. Colorant particles which may be used in the invention include pigments as disclosed, for example in U.S. Pat. Nos. 5,026,427; 5,086,698; 5,141,556; 5,160,370; and 5,169,436, the disclosures of which are hereby incorporated by reference. The exact choice of pigments will depend upon the specific application and performance requirements such as color reproduction and image stability. Pigments suitable for use in the present invention include, for example, azo pigments, monoazo pigments, disazo pigments, azo pigment lakes, xcex2-Naphthol pigments, Naphthol AS pigments, benzimidazolone pigments, disazo condensation pigments, metal complex pigments, isoindolinone and isoindoline pigments, polycyclic pigments, phthalocyanine pigments, quinacridone pigments, perylene and perinone pigments, thioindigo pigments, anthrapyrimidone pigments, flavanthrone pigments, anthanthrone pigments, dioxazine pigments, triarylcarbonium pigments, quinophthalone pigments, diketopyrrolo pyrrole pigments, titanium oxide, iron oxide, and carbon black. Typical examples of pigments which may be used include Color Index (C. I.) Pigment Yellow 1, 2, 3, 5, 6, 10, 12, 13, 14, 16, 17, 62, 65, 73, 74, 75, 81, 83, 87, 90, 93, 94, 95, 97, 98, 99, 100, 101, 104, 106, 108, 109, 110, 111, 113, 114, 116, 117, 120, 121, 123, 124, 126, 127, 128, 129, 130, 133, 136, 138, 139, 147, 148, 150, 151, 152, 153, 154, 155, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 179, 180, 181, 182, 183, 184, 185, 187, 188, 190, 191, 192, 193, 194; C. I. Pigment Orange 1, 2, 5, 6, 13, 15, 16, 17, 17:1, 19, 22, 24, 31, 34, 36, 38, 40, 43, 44, 46, 48, 49, 51, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69; C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 21, 22, 23, 31, 32, 38, 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 49:3, 50:1, 51, 52:1, 52:2, 53:1, 57:1, 60:1, 63:1, 66, 67, 68, 81, 95, 112, 114, 119, 122, 136, 144, 146, 147, 148, 149, 150, 151, 164, 166, 168, 169, 170, 171, 172, 175, 176, 177, 178, 179, 181, 184, 185, 187, 188, 190, 192, 194, 200, 202, 204, 206, 207, 210, 211, 212, 213, 214, 216, 220, 222, 237, 238, 239, 240, 242, 243, 245, 247, 248, 251, 252, 253, 254, 255, 256, 258, 261, 264; C.I. Pigment Violet 1, 2, 3, 5:1, 13, 19, 23, 25, 27, 29, 31, 32, 37, 39, 42, 44, 50; C.I. Pigment Blue 1, 2, 9, 10, 14, 15:1, 15:2, 15:3, 15:4, 15:6, 15, 16, 18, 19, 24:1, 25, 56, 60, 61, 62, 63, 64, 66; C.I. Pigment Green 1, 2, 4, 7, 8, 10, 36, 45; C.I. Pigment Black 1, 7, 20, 31, 32, and C.I. Pigment Brown 1, 5, 22, 23, 25, 38, 41, 42. In a preferred embodiment of the invention, the pigment is C.I. Pigment Blue 15:3, C.I. Pigment Red 122, C.I. Pigment Yellow 155, C.I. Pigment Yellow 74, C.I. Pigment Black 7 or bis(phthalocyanylalumino)tetraphenyldisiloxane as described in U.S. Pat. No. 4,311,775, the contents of which are incorporated herein by reference.
In the case of organic pigments, the ink may contain up to approximately 20% pigment by weight, but will generally be in the range of approximately 0.1 to 10%, preferably approximately 0.1 to 5%, by weight of the total ink composition for most ink jet printing applications. If an inorganic pigment is selected, the ink will tend to contain higher weight percentages of pigment than with comparable inks employing organic pigments.
The polymers used in the current invention are essentially hydrophobic polymers of any composition that can be stabilized but not dissolved in water-based ink medium. They can be either polymer latex or water dispersible polymer. Such hydrophobic polymers are generally classified as either condensation polymer or additional polymers. Condensation polymers include, for example, polyesters, polyamides, polyurethanes, polyureas, polyethers, polycarbonates, polyacid anhydrides, and polymers comprising combinations of the above-mentioned types. Addition polymers are polymers formed from polymerization of vinyl-type monomers including, for example, allyl compounds, vinyl ethers, vinyl heterocyclic compounds, styrenes, olefins and halogenated olefins, unsaturated acids and esters derived from them, unsaturated nitrites, vinyl alcohols, acrylamides and methacrylamides, vinyl ketones, multifunctional monomers, or copolymers formed from various combinations of these monomers. Most of monomer units in the polymer used in the invention may be hydrophobic, and the content of the hydrophilic monomer is less than 25% by weight of the total polymer, more preferably less than 10% by weight of the total polymer, most preferably less than 5% by weight of the total polymer.
In a preferred embodiment of the invention, the polymer latex or water dispersible polymer is a styrene/acrylic polymer, a polyester or a polyurethane.
The polymer can be prepared in aqueous media using well-known free radical emulsion polymerization methods and may consist of homopolymers made from one type of the above-mentioned monomers or copolymers made from more than one type of the above-mentioned monomers. Polymers comprising monomers which form water-insoluble homopolymers are preferred, as are copolymers of such monomers. Preferred polymers may also comprise monomers which give water-soluble homopolymers, if the overall polymer composition is sufficiently water-insoluble to form a latex. The polymer can be prepared by emulsion polymerization, solution polymerization, suspension polymerization, dispersion polymerization, ionic polymerization (cationic, anionic), Atomic Transfer Radical Polymerization, and other polymerization methods known in the art of polymerization.
The first class of preferred polymer include those styrene/acrylic polymers prepared by free-radical polymerization of vinyl monomers in aqueous emulsion. The polymer latex can be homopolymer or copolymer or cross-linked polymers comprising ethylenically-unsaturated hydrophobic monomers which form water-insoluble homopolymers are preferred, as are copolymers of such monomers, which may also comprise ethylenically-unsaturated hydrophilic monomers which give water-soluble homopolymers, if the overall polymer composition is sufficiently water-insoluble to form a latex.
The styrene/acrylic polymers can be made via emulsion polymerization, dispersion polymerization, suspension polymerization, grand milling, or solution/bulk polymerization and then post-emulsification. Detailed information about the process and the stabilizers can be found in xe2x80x9cEmulsion Polymerization and Emulsion Polymersxe2x80x9d (P. A. Lovell, M. S. El-Aasser, John Wiley and Sons Ltd., England, 1997), incorporated herein by reference.
The ethylenically-unsaturated monomers which can be used in the invention include, for example, the following monomers and their mixtures: acrylic acid, methacrylic acid, ethacrylic acid, methyl acrylate, ethyl acrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, propyl acrylate, propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, octadecyl methacrylate, octadecyl acrylate, lauryl methacrylate, lauryl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyhexyl acrylate, hydroxyhexyl methacrylate, hydroxyoctadecyl acrylate, hydroxyoctadecyl methacrylate, hydroxylauryl methacrylate, hydroxylauryl acrylate, phenethylacrylate, phenethyl methacrylate, 6-phenylhexyl acrylate, 6-phenylhexyl methacrylate, phenyllauryl acrylate, phenyllaurylmethacrylate, 3-nitrophenyl-6-hexyl methacrylate, 3-nitrophenyl-18-octadecyl acrylate, ethyleneglycol dicyclopentyl ether acrylate, vinyl ethyl ketone, vinyl propyl ketone, vinyl hexyl ketone, vinyl octyl ketone, vinyl butyl ketone, cyclohexyl acrylate, 3-methacryloxypropyl-dimethylmethoxysilane, 3-methacryloxypropyl-methyldimethoxysilane, 3-methacryloxypropyl-pentamethyldisiloxane, 3-methacryloxypropyltris-(trimethylsiloxy)silane, 3-acryloxypropyl-dimethylmethoxysilane, acryloxypropylmethyldimethoxysilane, trifluoromethyl styrene, trifluoromethyl acrylate, trifluoromethyl methacrylate, tetrafluoropropyl acrylate, tetrafluoropropyl methacrylate, heptafluorobutyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, N,N-dihexyl acrylamide, N,N-dioctyl acrylamide, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl methacrylate, piperidino-N-ethyl acrylate, vinyl propionate, vinyl acetate, vinyl butyrate, vinyl butyl ether, and vinyl propyl ether ethylene, styrene, vinyl carbazole, vinyl naphthalene, vinyl anthracene, vinyl pyrene, methyl methacrylate, methyl acrylate, alpha-methylstyrene, dimethylstyrene, methylstyrene, vinylbiphenyl, glycidyl acrylate, glycidyl methacrylate, glycidyl propylene, 2-methyl-2-vinyl oxirane, vinyl pyridine, aminoethyl methacrylate, aminoethylphenyl acrylate, maleimide, N-phenyl maleimide, N-hexyl maleimide, N-vinyl-phthalimide, and N-vinyl maleimide poly(ethylene glycol) methyl ether acrylate, polyvinyl alcohol, vinyl pyrrolidone, vinyl 4-methylpyrrolidone, vinyl 4-phenylpyrrolidone, vinyl imidazole, vinyl 4-methylimidazole, vinyl 4-phenylimidazole, acrylamide, methacrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, N-methyl methacrylamide, aryloxy dimethyl acrylamide, N-methyl acrylamide, N-methyl methacrylamide, aryloxy piperidine, and N,N-dimethyl acrylamide acrylic acid, methacrylic acid, chloromethacrylic acid, maleic acid, allylamine, N,N-diethylallylamine, vinyl sulfonamide, sodium acrylate, sodium methacrylate, ammonium acrylate, ammonium methacrylate, acrylamidopropanetriethylammonium chloride, methacrylamidopropane-triethylammonium chloride, vinyl-pyridine hydrochloride, sodium vinyl phosphonate and sodium 1-methylvinylphosphonate, sodium vinyl sulfonate, sodium 1-methylvinyl-sulfonate, sodium styrenesulfonate, sodium acrylamidopropanesulfonate, sodium methacrylamidopropanesulfonate, and sodium vinyl morpholine sulfonate, allyl methacrylate, allyl acrylate, butenyl acrylate, undecenyl acrylate, undecenyl methacrylate, vinyl acrylate, and vinyl methacrylate; dienes such as butadiene and isoprene; esters of saturated glycols or diols with unsaturated monocarboxylic acids such as, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, pentaerythritol tetraacrylate, trimethylol propane trimethacrylate and polyfunctuional aromatic compounds such as divinylbenzene.
The hydrophilic monomer is selected from the group consisting of acrylic acid, methacrylic acid, chloromethacrylic acid, maleic acid, allylamine, N,N-diethylallylamine, vinyl sulfonamide, sodium acrylate, sodium methacrylate, ammonium acrylate, ammonium methacrylate, acrylamidopropane-triethylammonium chloride, methacrylamidopropane-triethylammonium chloride, vinyl-pyridine hydrochloride, sodium vinyl phosphonate and sodium 1-methylvinylphosphonate, sodium vinyl sulfonate, sodium 1-methylvinyl-sulfonate and sodium styrenesulfonate.
In a preferred embodiment of the invention, the ethylenically-unsaturated monomers are halogenated. Examples are vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide and vinylidene bromide, chloromethacrylic acid and the like.
The second class of polymer used in the invention may be water dispersible polyesters. The water-dispersible polyester ionomer polymers used in this invention have the following general formula:
wherein:
A is the residue of one or more diol components which together comprise 100 mole % of recurring units and is represented by the following structure:
xe2x80x94Oxe2x80x94(CHR2CHR3O)mxe2x80x94R1xe2x80x94(OCHR2CHR3)nxe2x80x94Oxe2x80x94
wherein:
m and n independently represent an integer from 0-4;
R1 represents S, an alkylene group of 1 to about 16 carbon atoms; a cycloalkylene group of 5 to about 20 carbon atoms; a cyclobisalkylene group of about 8 to about 20 carbon atoms, a bi- or tri-cycloalkylene group of about 7 to about 16 carbon atoms, a bi- or tri-cyclobisalkylene group of about 9 to about 18 carbon atoms, an arenebisalkylene group of from 8 to about 20 carbon atoms or an arylene group of 6 to about 12 carbon atoms, a carbinol-terminated polydimethylsiloxane segment; and
R2 and R3 each independently represents H, a substituted or unsubstituted alkyl group of about 1 to about 6 carbon atoms or a substituted or unsubstituted aryl group of about 6 to about 12 carbon atoms;
B is the residue of a diacid component which comprises 8 to 50 mole % of recurring units and is represented by one or more of the following structures:
wherein:
M+ represents alkali metals, such as Li, Na and K; ammonium groups 5 such as ammonium, methylammonium, triethylammonium, tetralkylammonium, aryltrialkylammonium, etc.; phosphonium groups such as triphenylphosphonium; tetrabutylphosphonium; heteroaromatic ammonium groups such as pyridinium, imidazolium and N-methylammonium; sulfonium groups; guanidinium groups; amidinium groups, etc.; and
D is the residue of a diacid component which comprises 50 to 92 mole % of recurring units and is represented by one or more of the following structures:
wherein p represents an integer from 2 to 12.
Some typical diols which A in the above formula represents include ethylene glycol, diethylene glycol, triethylene glycol, thiodiethanol, cyclohexanedimethanol, bisphenol A, trans-1,4-cyclohexanediol, dodecanediol, cis-exo-2,3-norbomanediol, 5-norbornene-2,2-dimethanol, hydroquinone bis(2-hydroxyethylether), carbinol terminated polydimethylsiloxane, MW=1000 (DMS-C15), (Gelest Inc.), etc.
Examples of water dispersible polyesters useful in the invention include Eastman AQ(copyright) polyesters, (Eastman Chemical Company). Eastman Polyesters AQ 29, AQ 38, and AQ 55 are composed of varying amounts of isophthalic acid, sodium sulfoisophthalic acid, diethylene glycol, and 1,4-cyclohexanedimethanol. These thermoplastic, amorphous, ionic polyesters are prepared by a melt-phase condensation polymerization at high temperature and low pressure, and the molten product is extruded into small pellets. The solid polymer disperses readily in water at 70xc2x0 C. with minimal agitation to give translucent, low viscosity dispersions containing no added surfactants or solvents. Varying the amount of ionic monomers, i.e., sulfoisophthalic acid, can control the particle size. The particle sizes range from 0.02 to 0.1 xcexcm.
The third class of polymer used in the invention may be an aqueous dispersible polyurethane. Useful polyurethanes are disclosed in U.S. Pat. No. 6,268,101, the disclosure of which is hereby incorporated by reference. These materials may be prepared as described in xe2x80x9cPolyurethane Handbook,xe2x80x9d Hanser Publishers, Munich Vienna, 1985. Examples of aqueous dispersible polyurethanes are Witcobond(copyright) polyurethane dispersion such as W-240, W-232 and W-254 by Crompton Corp. or Sancure(copyright) polyurethane by BF Goodrich Company.
The polymer employed in the invention in general has a Tg of xe2x88x9250 to 150xc2x0 C., preferably 5 to 100xc2x0 C., most preferably 10 to 80xc2x0 C.
The polymer latex employed in the invention in general have an average particle size of less than 2 xcexcm, preferably less than 0.5 xcexcm, more preferably less than 0.25 xcexcm.
The polymer latex used in the invention is present in the ink jet ink generally from 0.1% to 20% by weight, preferably from 0.5% to 10% by weight.
The aqueous carrier medium for the ink composition is water or a mixture of water and at least one water miscible co-solvent. Selection of a suitable mixture depends on requirements of the specific application, such as desired surface tension and viscosity, the selected pigment, drying time of the pigmented ink jet ink, and the type of paper onto which the ink will be printed. Representative examples of water-miscible co-solvents that may be selected include (1) alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol; (2) ketones or ketoalcohols such as acetone, methyl ethyl ketone and diacetone alcohol; (3) ethers, such as tetrahydrofuran and dioxane; (4) esters, such as ethyl acetate, ethyl lactate, ethylene carbonate and propylene carbonate; (5) polyhydric alcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol and thioglycol; (6) lower alkyl mono- or di-ethers derived from alkylene glycols, such as ethylene glycol mono-methyl (or -ethyl) ether, diethylene glycol mono-methyl (or -ethyl) ether, diethylene glycol mono-butyl (or -ethyl) ether, propylene glycol mono-methyl (or -ethyl) ether, poly(ethylene glycol) butyl ether, triethylene glycol mono-methyl (or -ethyl) ether and diethylene glycol di-methyl (or -ethyl) ether; (7) nitrogen containing cyclic compounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone; and (8) sulfur-containing compounds such as dimethyl sulfoxide, 2,2xe2x80x2-thiodiethanol, and tetramethylene sulfone.
The amount of aqueous carrier medium is in the range of approximately 70 to 99 weight %, preferably approximately 90 to 98 weight %, based on the total weight of the ink. A mixture of water and a polyhydric alcohol, such as diethylene glycol, is useful as the aqueous carrier medium. In a preferred embodiment, the inks contain from about 5 to about 60 weight % of water miscible organic solvent based on the total weight of the aqueous carrier medium.
Jet velocity, separation length of the droplets, drop size and stream stability are greatly affected by the surface tension and the viscosity of the ink. The ink jet inks suitable for use with ink jet printing systems and to apply to non-absorbing substrates, especially high surface energy hydrophobic surfaces, should have a surface tension in the range of about 20 dynes/cm to about 60 dynes/cm and, more preferably, in the range 20 dynes/cm to about 35 dynes/cm. Control of surface tensions in aqueous inks is accomplished by additions of small amounts of surfactants. The level of surfactants to be used can be determined through simple trial and error experiments, usually about 0.1% to about 6%, preferably, 0.5% to about 4% by weight of the total ink composition. Anionic, cationic and nonionic surfactants may be selected from those disclosed in U.S. Pat. Nos. 5,324,349; 4,156,616 and 5,279,654 as well as many other surfactants known in the ink jet ink art. Commercial surfactants include the Surfynols(copyright) from Air Products; the Zonyls(copyright) from DuPont and the Fluorads(copyright) from 3M. Preferred surfactants can be silicon surfactants or fluorinated surfactants. Preferred silicon surfactants are available from BYK-Chemie as BYK surfactants, and from Crompton Corp, as Silwet(copyright) surfactants. Commercially available fluorinated surfactants can be the Zonyls(copyright) from DuPont and the Fluorads(copyright) from 3M, they can be used alone or in combination with other surfactants.
A humectant is added to the composition employed in the process of the invention to help prevent the ink from drying out or crusting in the orifices of the ink jet printhead. Polyhydric alcohols useful in the composition employed in the invention for this purpose include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol and thioglycol. The humectant may be employed in a concentration of from about 10 to about 50% by weight of the entire ink composition. In a preferred embodiment, diethylene glycol or a mixture of glycerol and diethylene glycol is employed a concentration of between 10 and 20% by weight of the entire ink composition.
The ink has physical properties compatible with a wide range of ejecting conditions, i.e., driving voltages and pulse widths for thermal ink jet printing devices, driving frequencies of the piezo element for either a drop-on-demand device or a continuous device, and the shape and size of the nozzle.
A penetrant (0-10% by weight) may also be added to the ink composition employed in the process of the invention to help the ink penetrate the receiving substrate, especially when the substrate is a highly sized paper. A preferred penetrant for the inks employed in the present invention is n-propanol at a final concentration of 1-6% by weight.
A biocide (0.01-1.0% by weight) may also be added to prevent unwanted microbial growth which may occur in the ink over time. A preferred biocide for the inks employed in the present invention is Proxel(copyright) GXL (Zeneca Colours Co.) at a concentration of 0.05-0.5% by weight. Additional additives which may optionally be present in ink jet inks include thickeners, conductivity enhancing agents, anti-kogation agents, pH buffering agents, drying agents, and defoamers.
Ink jet inks made using polymers employed in this invention are employed in ink jet printing wherein liquid ink drops are applied in a controlled fashion to an ink receiving substrate, by ejecting ink droplets from plurality of nozzles, or orifices, in a print head of ink jet printers.
Commercially available ink jet printers use several different methods to control the deposition of the ink droplets. Such methods are generally of two types: continuous stream and drop-on-demand.
In drop-on-demand systems, a droplet of ink is ejected from an orifice directly to a position on the ink receiving layer by pressure created by, for example, a piezoelectric device, an acoustic device, or a thermal process controlled in accordance digital data signals. An ink droplet is not generated and ejected through the orifices of the print head unless it is needed. Ink jet printing methods, and related printers, are commercially available and need not be described in detail.
To accelerate the printing speed and increase durability, an extra heating step can be added during the process of printing the ink composition of this invention. This heating step can be employed either during printing or after printing. In a preferred embodiment, heating is employed both during and after printing. Heating will help fluids to spread on a non-absorbing substrate as well as to accelerate its evaporation. Heating can also help ink components to penetrate into the non-absorbing substrate by swelling mechanism. The heating step during printing can be achieved using a heating means so that the non-absorbing substrate is heated to elevated temperature during the process of printing. The substrate is preferably heated to between 30xc2x0 C. and 90xc2x0 C., more preferably between 40 to 70xc2x0 C. During the heating step after printing, the printed substrate is heated to elevated temperature using a heating means where substrate is heated to a temperature range between 50xc2x0 C. and 150xc2x0 C., more preferably between 80 to 120xc2x0 C. Various methods may be used for the means of heating, for example, using light irradiation, a hot air source or an electrical heater. For the heating step during printing, an electrical heater or an infrared lamp is preferred. For the heating step after printing, light irradiation such as an infrared lamp is preferred. Optionally, an infrared absorbing material can be employed in the ink of the present invention to assist the heating by an infrared lamp.
The following examples illustrate the utility of the present invention.

Inkjet printing method for an ink/receiver combination


The present invention relates to a paper tissue, and in particular to facial tissue, and disposable handkerchiefs. Claimed and described is a paper tissue comprising at least two plies, characterized in that the paper tissue has a physiological surface smoothness parameter of less than 700 microns, preferably from 650 microns to 50 microns, more preferably from 650 microns to 300 microns and in combination has a caliper per ply of more than 0.09 mm, preferably from 0.09 mm to 0.5 mm, more preferably from 0.1 mm to 0.2 mm. In one preferred embodiment a three-ply tissue with embossed middle ply is provided. Further is a related process claimed and described.

The present application is a 371 application of International Application No. PCT/US00/32197 filed Nov. 22, 2000, which claims priority to European Application No. 99123568.0 filed Nov. 26, 1999.
The present invention relates to paper tissue, and in particular to facial tissue, and disposable handkerchiefs. In one preferred embodiment a three-ply tissue with embossed middle ply is provided.
Paper webs or sheets, sometimes called tissue or paper tissue webs or sheets, or herein called paper tissue, find extensive use in modern society. Such items as facial and toilet tissues are staple items of commerce, all of which are herein referred to as paper tissue. It has long been recognised that important physical attributes of these products are their strength and thickness/caliper, their softness and smoothness, their absorbency, and their lint resistance. Research and development efforts have been directed to the improvement of each of these attributes without seriously affecting the others as well as to the improvement of two or three attributes simultaneously.
Softness and smoothness relate to the tactile sensation perceived by the consumer when holding a particular product, rubbing it across the skin, or crumpling it within the hands. This tactile sensation is a combination of several physical properties. One of the more important physical properties related to the softness and smoothness is generally considered by those skilled in the art to be the surface structure of the paper tissue from which the tissue product is made and which is best captured by the physiological surface smoothness (PSS) parameter as known e.g. from U.S. Pat. No. 5,855,738. As important for the tactile sensation of consumers is the thickness/caliper of a tissue product.
Strength is the ability of the product to maintain physical integrity and to resist tearing, bursting, and shredding under use conditions.
Absorbency is the measure of the ability of a product to absorb quantities of liquid, particularly aqueous solutions or dispersions. Overall absorbency as perceived by the consumer is generally considered to be a combination of the total quantity of a liquid a given mass of paper tissue will absorb at saturation as well as the rate at which the mass absorbs the liquid.
Lint resistance is the ability of the fibrous product, and its constituent webs, to bind together under use conditions, including when wet. In other Words, the higher the lint resistance is, the lower the propensity of the web to lint will be.
WO97/44528 discloses a multi-ply tissue product with high absorbency. Example 4 discloses a product where a patterned, relatively textured ply is disposed between two substantially unpatterned, relatively untextured plies.
EP 0 264 676 discloses a process for the manufacture of multi-ply paper sheets. Example 3 discloses a three-ply product made from wet-formed paper, where the inner web is provided from embossed paper with a weight of 18 g/m2 and the outer webs are provided from calendered paper with a weight of 14 g/m2. The plies are assembled by a cellulose ether adhesive applied by nozzles.
U.S. Pat. No. 5,855,738 discloses a process for making smooth paper tissue comprising a calendering step.
Relatively thick disposable paper products, namely in the form of paper handkerchiefs and facial tissues, are known. For example, Tempo(trademark), sold by The Procter and Gamble Company, has a caliper of about 0.3 mm. A high caliper conveys the idea of high dry and wet strength to the consumer. A high wet strength, also referred to as wet burst strength, in particular prevents tearing or bursting which in turn results in contamination of the user""s hand with mucus or other bodily fluids.
Even thicker disposable paper products are known and typically used as kitchen towels, such as Bounty(trademark), sold by The Procter and Gamble Company, which has a caliper of about 0.7 mm and a wet burst strength which is greater than 200 g. However such kitchen towels to a considerable extent owe their caliper to embossing over the whole surface which results in a surface texture which is rough and does not provide a suitably smooth wiping surface for blowing the nose.
Other products with high wet burst strength and typically a relatively high caliper are those produced by through-air-drying. Though-air-drying facilities, however, are not available on conventional paper making machines and the provision of such equipment means a considerable financial investment.
In theory, the wet strength and caliper of a product can be increased by increasing the number of plies to 5, 6 or even more (instead of embossing or the like) and thereby maintaining a smooth outer surface. However, this approach would be very costly and also lead to a stiff product, hence compromising tactile perception.
In attempting to provide a very smooth surface it is common in the art to subject paper tissue to calendering. However, calendering always means a trade-off of caliper and softness for smoothness (as discussed e.g. in U.S. Pat. No. 5,855,738).
In view of the prior art there remains a need for a tissue product, in particular a facial tissue, which:
combines optimal strength, namely wet burst strength, absorbency and lint resistance
further gives an ideal tactile sensation of softness, smoothness and thickness
is cost effective to manufacture and preferably can be manufactured on conventional paper machines
optionally provides skin care benefits
The present invention relates to a paper tissue, and in particular to facial tissue, and disposable handkerchiefs. Claimed and described is a paper tissue comprising at least two plies, characterised in that the paper tissue has a physiological surface smoothness parameter of less than 700 microns, preferably from 650 microns to 50 microns, more preferably from 650 microns to 300 microns and in combination has a caliper per ply of more than 0.09 mm, preferably from 0.09 mm to 0.5 mm, more preferably from 0.1 mm to 0.2 mm. In one preferred embodiment a three-ply tissue with embossed middle ply is provided. Further is a related process claimed and described.
According to the present invention, a cellulose fibrous structure is wet-laid using principles and machinery well-known in the art of paper-making. A suitable pulp furnish for the process of making the paper tissue substrate preferably contains papermaking fibres consisting essentially of cellulose fibres (commonly-known as wood pulp fibres) or cellulose-derived fibres (including, for example, rayon, viscose). Fibres derived from soft woods (gymnosperms or coniferous trees) and hard woods (angiosperms or deciduous trees) are contemplated for use in this invention. The particular species of tree from which the fibres are derived is immaterial. The wood pulp fibers can be produced from the native wood by any convenient pulping process. Chemical processes such as sulfite, sulphate (including the Kraft) and soda processes are suitable. Mechanical processes such as thermochemical (or Asplund) processes are also suitable. In addition, the various semi-chemical and chemi-mechanical processes can be used. Bleached as well as unbleached fibers are contemplated for use. Preferably no non-cellulosic fibres, such as latex, fibres are used.
The paper tissue according to the present invention may contain, as a highly preferred component a wet strength chemical agent. Preferably up to about 3.0%, preferably at least 0.5%, and more preferably at least 0.8% by weight, on a dry fiber weight basis, of wet strength chemical agent, such as water-soluble permanent and temporary wet strength resin, are contained.
Wet strength resins useful herein can be of several types. For example, Wesffelt described a number of such materials and discussed their chemistry in Cellulose Chemistry and Technology, Volume 13, at pages 813-825 (1979).
Usually, the wet strength resins are water-soluble, cationic materials. That is to say, the resins are water-soluble at the time they are added to the papermaking furnish. It is quite possible, and even to be expected, that subsequent events such as cross-linking will render the resins insoluble in water. Further some resins are soluble only under specific conditions, such as over a limited pH range. Wet strength resins are generally believed to undergo a cross-linking or other curing reactions after they have been deposited on, within, or among the papermaking fibres. Cross-linking or curing does not normally occur so long as substantial amounts of water are present.
Of particular utility are the various polyamide-epichlorohydrin resins. These materials are low molecular weight polymers provided with reactive functional groups such as amino, epoxy, and azetidinium groups. The patent literature is replete with descriptions of processes for making such materials, including U.S. Pat. No. 3,700,623, issued to Keim on Oct. 24th 1972, and U.S. Pat. No. 3,772,076, issued to Keim on Nov. 13th 1973.
Polyamide-epihydrochlorin resins sold under the trademarks Kymene 557 H and Kymene LX by Hercules Inc. of Wilmington, Del., are particularly useful in this invention. These resins are generally described in the aforementioned patents to Keim.
Base-activated polyamide-epichlorohydrin resins useful in the present invention are sold under the Santo Res trademark, such as Santo Re 31, by Monsanto Company of St. Louis, Mo. These types of materials are generally described in U.S. Pat. No. 3,855,158 issued to Petrovich on Dec. 17th 1974; U.S. Pat. No. 3,899,388 issued to Petrovich on Aug. 12th 1975; U.S. Pat. No. 4,129,528 issued to Petrovich on Dec. 12, 1978; U.S. Pat. No. 4,147,586 issued to Petrovich on Apr. 3rd 1979; and U.S. Pat. No. 4,222,921 issued to Van Eenam on Sep. 16th 1980.
Other water-soluble cationic resins useful hererin are the polyacrylamide resins such as those sold under the Parez trademark, such as Parez 631NC, by American Cyanamid Company of Sandford, Conn. These materials are generally described in U.S. Pat. No. 3,556,932 issued to Coscia et al on Jan. 19th 1971; and U.S. Pat. No. 3,556,933 issued to Williams et al on Jan. 19th 1971.
Other types of water-soluble resins useful in the present invention include acrylic emulsions and anionic styrene-butadiene latexes. Numerous examples of these types of resins are provided in U.S. Pat. No. 3,844,880. Meisel Jr et al, issued Oct. 29th 1974. Still other water-soluble cationic resins finding utility in this invention are the urea formaldehyde and melamine formaldehyde resins. These polyfunctional, reactive polymers have molecular weights on the order of a few thousand. The more common functional groups include nitrogen containing groups such as amino groups and methylol groups attached to the nitrogen. Although less preferred, polyethylenimine type resins find utility in the present invention.
More complete descriptions of the aforementioned water-soluble resins, including their manufacture, can be found in TAPPI Monograph Series No. 29, xe2x80x9cWet Strength in paper and Paperboard, Technical Association of the Pulp and Paper Industry (New York; 1965).
Temporary wet strength agents, such as modified starch may also, optionally, be used. Combinations of permanent and temporary wet strength agents may be used.
The present invention may contain dry strength chemical agents, preferably at levels up to 3% by weight, more preferably at least 0.1% by weight, on a dry fiber weight basis. A highly preferred dry strength chemical agent is carboxymethyl cellulose. Other suitable dry strength chemical agents include polyacrylamide (such as combinations of Cypro(trademark) 514 and Accostrength(trademark) 711 produced by American Cyanamid of Wayne, N.J.); starch (such as corn starch or potato starch); polyvinyl alcohol (such as Airvol(trademark) 540 produced by Air Products Inc. of Allentown, Pa.); guar or locust bean gums; and polyacrylate latexes. Suitable starch materials may also include modified cationic starches such as those modified to have nitrogen containing groups such as amino groups and methylol groups attached to nitrogen, available from National Starch and Chemical Company (Bridgewater, N.J.).
Chemical softening compositions, comprising chemical debonding agents are optional components of the present invention. U.S. Pat. No. 3,821,068, issued Jun. 28th, 1974 teaches that chemical debonding agents can be used to reduce the stiffness, and thus enhance the softness, of a paper tissue web. U.S. Pat. No. 3,554,862, issued on Jan. 12th 1971 discloses suitable chemical debonding agents. These chemical debonding agents include quaternary ammonium salts.
Preferred chemical softening compositions comprise from about 0.01% to about 3.0% of a quaternary ammonium compound, preferably a biodegradable quaternary ammonium compound; and from about 0.01% to about 3.0% of a polyhydroxy compound; preferably selected from the group consisting of glycerol, sorbitols, polyglycerols having an average molecular weight of from about 150 to about 800 and polyoxyethylene glycols and polyoxypropylene glycols having a weight average molecular weight from about 200 to 4000. Preferably the weight ratio of the quaternary ammonium compound to the polyhydroxy compound ranges from about 1.0:0.1 to 0.1:1.0. It has been discovered that the chemical softening composition is more effective when the polyhydroxy compound and the quaternary ammonium compound are first premixed together, preferably at a temperature of at least 40xc2x0 C., before being added to the papermaking furnish. Either additionally, or alternatively, chemical softening compositions may be applied to the substantially dry paper tissue web, for example by means of a printing process (N.B. all percentages herein are by weight of dry fibres, unless otherwise specified).
Examples of quaternary ammonium compounds suitable for use in the present invention include either unmodified, or mono- or di-ester variations of:well-known dialkyldimethylammonium salts and alkyltrimethyl ammonium salts. Examples include the di-ester variations of di(hydrogenated tallow)dimethyl ammonium methylsulphate and di-ester variations of di(hydrogenated tallow)dimethyl ammonium chloride. Without wishing to be bound by theory, it is believed that the ester moity(ies) lends biodegradability to these compounds. Commercially available materials are available from Witco Chemical Company Inc. of Dublin, Ohio, under the tradename xe2x80x9cRewoquat V3512xe2x80x9d. Details of analytical and testing procedures are given in WO95/11343, published on Apr., 27th 1995.
Examples of polyhydroxy compounds useful in the present invention include polyoxyethylene glycols having a weight average molecular weight of from about 200 to about 600, especially preferred is xe2x80x9cPEG-400xe2x80x9d.
The paper tissue of the present invention may be made by common methods well-known to the person skilled in the art, such as by dewatering suitable pulp using, for example, one or more papermakers felts and/or belts. For the present invention conventional papermaking processes are preferred. Any process referred to herein as conventional is a paper-making process which does not comprise a step of through-air-drying. Alternatively, papermaking processes comprising a through-air-drying step can be utilised. Such processes are described in the patent literature referred to hereinafter with regard to through-air-dried tissue.
According to the present invention a paper tissue is provided from at least 2 plies which is thick but smooth and hence has a physiological surface smoothness parameter of less than 700 microns, preferably from 650 microns to 50 microns, more preferably from 650 microns to 300 microns and in combination has a caliper per ply of more than 0.09 mm, preferably from 0.09 mm to 0.5 mm, more preferably from 0.1 mm to 0.2 mm. According to the present invention it has been found that the caliper per ply is a relevant parameter in expressing how much caliper is provided in a cost effective way, i.e. per one ply. Any combination of ranges given above for the PSS parameter and the caliper per ply is within the scope of the present invention.
Preferably the paper tissue has a low ratio of caliper per ply over the PSS parameter, the ratio being lower than 6500 microns/mm, more preferably lower than 5000 microns/mm, yet more preferably lower than 3000 microns/mm.
A paper tissue according to the present invention has a first and a second surface, the surfaces being mutually opposed to each other, and a thickness orthogonal to the first and second surface. The thickness is also referred to a caliper of the tissue.
The caliper of a tissue according to the present invention is preferably from 0.1 mm to 1 mm, more preferably from 0.2 mm to 0.5 mm.
Moreover, a paper tissue according to the present invention has preferably a wet burst strength greater than 100 g, preferably from 150 g to 500 g, more preferably from 250 g to 400 g.
In one preferred embodiment of the present invention a paper tissue is provided from two plies. In one preferred two-ply embodiment of the present invention one ply is provided from a calendered paper tissue while the other ply is provided from a textured, preferably embossed paper tissue. Without wishing to be bound by theory, the following is believed: The embossing increases the overall caliper of the product and thereby also the caliper per ply. The calendering typically increases the smoothness of the respective ply and thereby a surface is provided with a low PSS parameter.
xe2x80x9cCalenderedxe2x80x9d, as used herein, comprises high pressure calendering, high pressure calendering denoting a calendering using a pressure per contact length of at least 3 kN/m, more preferably 5 kN/m to 50 kN/m, yet more preferably 10 kN/m to 25 kN/m. Calendering with higher pressure increases the smoothness of paper tissue and hence decrease the PSS parameter.
In accordance with the present invention preferably single plies are subjected to calendering, but alternatively several plies at a time or a whole multi-ply paper tissue may be calendered.
Alternatively other techniques known is the art to increase the smoothness of paper tissue can be used, such as the selection of appropriate Fourdrinier wires, felts, and belt in the dewatering stages, further creping under the appropriate conditions (glue content, glue composition, blade impact angle, creping aides). Further surface treatments, for example with a lotion, as disclosed hereinafter, are within the scope of the present invention.
xe2x80x9cTexturedxe2x80x9d, as used herein, for a paper tissue refers to a paper tissue which is either through-air-dried, or bulk embossed, or comprises regions of different basis weights or is dried with a texture or creped under the appropriate conditions (glue content, glue composition, blade impact angle, creping aides), as explained hereinafter.
xe2x80x9cBulk embossedxe2x80x9d, as used herein, refers to an embossing which increases the caliper of the paper tissue by at least 5%, preferably 15%, more preferably 25% as compared to the caliper of the paper tissue before the bulk embossing. Preferably bulk embossing provides a pattern of embossed and unembossed areas, which is imparted to only a limited number of plies of the multi-ply paper tissues of the present invention in one process step, preferably only to one ply in one process steps. The outermost embossed areas of the pattern preferably extends over at least 75%, preferably 85%, more preferably 95% of the total surface area of the embossed paper plies. Knob to knob embossing is well known in the art as illustrated by commonly assigned U.S. Pat. No. 3,414,459, issued Dec. 3, 1968 to Wells. The texture may also be imparted to the paper tissue by nested embossing as illustrated by U.S. Pat. No. 4,320,162, issued Mar. 16, 1982 to Schulz et al. Alternatively, the texture may be imparted to the paper tissue by dual ply lamination embossing as illustrated by commonly assigned U.S. Pat. No. 5,468,323, issued Nov. 21, 1995 to McNeil. Preferably such bulk embossing pattern is provided by steel-to-steel knob-to-knob embossing, the knobs preferably having an elliptical cross section and a height in the range of 0.5 mm to 3 mm, more preferably in the range of 1 mm to 2 mm. Preferably the bulk embossing provides a ratio of embossed areas to unembossed areas of from 1:1 to 1:20, more preferably 1:2 to 1:15, yet more preferably a ratio of from 1:5 to 1:10.
To obtain the texture on either, or both, of the first and second opposed surfaces, the tissue may be alternatively through-air-dried. Through-air-dried tissue is disclosed in commonly assigned U.S. Pat. No. 4,529,480, issued Jul. 16, 1985 to Trokhan; U.S. Pat. No. 4,637,859, issued Jan. 20, 1987 to Trokhan; U.S. Pat. No. 5,364,504, issued Nov. 15, 1994 to Smurkoski et al.; U.S. Pat. No. 5,529,664, issued Jun. 25, 1996 to Trokhan et al.; U.S. Pat. No. 5,679,222 issued Oct. 21, 1997 to Rasch et al.; U.S. Pat. No. 5,714,041 issued Feb. 3, 1998 to Ayers et al.; U.S. Pat. No. 5,906,710, issued May 25, 1999 to Trokhan. Alternatively, the paper tissue may be through-air-dried and made as disclosed in U.S. Pat. No. 5,429,686 issued Jul. 4, 1995 to Chiu et al. and U.S. Pat. No. 5,672,248 issued Sept. 30, 1997 to Wendt et al.
Alternatively, the paper tissue may be textured by providing various regions of differing basis weights, so that a multi-basis weight paper tissue is presented. Multi-basis weight paper tissue is disclosed in commonly assigned U.S. Pat. No. 5,245,025, issued Sep. 14, 1993 to Trokhan et al.; U.S. Pat. No. 5,527,428 issued Jun. 18, 1996 to Trokhan et al.; U.S. Pat. No. 5,534,326 issued Jul. 9, 1996 to Trokhan et al.; U.S. Pat. No. 5,654,076, issued Aug. 5, 1997 to Trokhan et al.; U.S. Pat. No. 5,820,730, issued Oct. 13, 1998 to Phan et al.; U.S. Pat. No. 5,277,761, issued Jan. 11, 1994 to Phan et al.; U.S. Pat. No. 5,443,691, issued Aug. 22, 1995 to Phan et al.; U.S. Pat. No. 5,804,036 issued Sep. 8, 1998 to Phan et al.; U.S. Pat. No. 5,503,715, issued Apr. 2, 1996 to Trokhan et al.; U.S. Pat. No. 5,614,061, issued Mar. 25, 1997 to Phan et al.; U.S. Pat. No. 5,804,281 issued Sep. 8, 1998 to Phan et al.; and U.S. Pat. No. 5,900,122 issued May 4, 1999 to Huston.
Alternatively, the paper may be conventionally dried with a texture, for example, according to commonly assigned U.S. Pat. No. 5,549,790, issued Aug. 27, 1996 to Phan; U.S. Pat. No. 5,556,509, issued Sept. 17, 1996 to Trokhan et al.; U.S. Pat. No. 5,580,423, issued Dec. 3, 1996 to Ampulski et al.; U.S. Pat. No. 5,609,725, issued Mar. 11, 1997 to Phan; U.S. Pat. No. 5,629,052 issued May 13, 1997 to Trokhan et al.; U.S. Pat. No. 5,637,194, issued Jun. 10, 1997 to Ampulski et al.; U.S. Pat. No. 5,674,663, issued Oct. 7, 1997 to McFarland et al.; U.S. Pat. No. 5,693,187 issued Dec. 2, 1997 to Ampulski et al.; U.S. Pat. No. 5,709,775 issued Jan. 20, 1998 to Trokhan et al.; U.S. Pat. No. 5,776,307 issued Jul. 7, 1998 to Ampulski et al.; U.S. Pat. No. 5,795,440 issued Aug. 18, 1998 to Ampulski et al.; U.S. Pat. No. 5,814,190 issued Sep. 29, 1998 to Phan; U.S. Pat. No. 5,817,377 issued Oct. 6, 1998 to Trokhan et al.; U.S. Pat. No. 5,846,379 issued Dec. 8, 1998 to Ampulski et al.; U.S. Pat. No. 5,855,739 issued Jan. 5, 1999 to Ampulski et al.; U.S. Pat. No. 5,861,082 issued Jan. 19, 1999 to Ampulski et al., 5,871,887 issued Feb. 16, 1999 to Trokhan et al.; U.S. Pat. No. 5,897,745 issued Apr. 27, 1999 to Ampulski, et al.; and U.S. Pat. No. 5,904,811 issued May 18, 1999 to Ampulski et al.
In a highly preferred embodiment of the present invention a paper tissue is provided from three plies. Preferably at least one ply is calendered and at least one ply is textured, preferably embossed. More preferably two plies are calendered and an embossed preferably is disposed there-between. This particular embodiment has the advantage of providing a smooth surface to the user on either side. Alternative embodiments of the present invention are for example those with any number of textured, preferably embossed plies disposed between two outer calendered plies, one of these being a four ply paper tissue with two embossed plies disposed between two calendered plies.
When two or more plies of paper tissue are combined to form the paper tissue, the plies may, optionally, be attached together by means, for example, of gluing or embossing, herein referred to as xe2x80x9cattachment embossingxe2x80x9d. Gluing is less preferred because it tends to result in a stiffer, less soft product. xe2x80x9cAttachment embosssingxe2x80x9d, as used herein, refers to an embossing by which all plies of a multi-ply tissue according to the present invention are embossed in one process step. Preferably the attachment embossing does not or at least not to a large extent affect the smoothness of any calendered ply. Therefore, preferably the tissue has an unembossed surface over a major part of the surface area of the tissue, preferably on the first and the second surface. As used herein, this means that the tissue has one or more regions not comprising an attachment embossing and, optionally, one or more regions comprising an attachment embossing, and that the region not comprising an attachment embossing is at least 50%, and as much as 99%, of the surface area of the tissue. Most commonly the regions comprising an attachment embossing lie close to the edge of the tissue (for example along two or four edges); and a regions comprising an attachment embossing may also be used for decorative purposes (for example to create a pattern or to spell out a logo or brand name). The region not comprising an attachment embossing is the continuous region between and/or around the region comprising an attachment embossing. Attachment embossing is preferably done by steel-to-steel pin-to-pin embossing.
If glue is to be used to attach the plies of a multi-ply paper tissue, according to the present invention the glue is preferably applied unevenly over the surfaces of the plies to be attached. Therefore the glue is preferably not applied by means such a spraying nozzle, since such nozzles apply the glue evenly with no preference for particular areas of the tissue, even when the glue is applied as to form a discontinuous net.
A textured, preferably embossed, paper tissue comprises raised portions. In one preferred embodiment of the present invention the glue to applied only to these raised portions of the paper tissue. Since primarily these raised portions are in context with adjacent plies, in particular with adjacent calendered plies, application of glue to these raised portions is sufficient as to ensure good attachment, but avoids the application of an amount of glue, which easily impart stiffness to the paper tissue.
One preferred method of applying glue to a tissue ply is to apply the glue by print rolling. Alternatively glue may be applied by melt blowing, so as to form areas of preferential glue applications, e.g. strips of glue.
The paper tissue and preferably one or both surfaces, most preferably both surfaces of the tissue may, optionally, be further treated with a lotion. A lotion can contribute to the smoothness of the paper tissue, and hence decrease its PSS parameter.
The lotion may comprise softeningidebonding agents, emollients, immobilizing agents and mixtures thereof. Suitable softening/debonding agents include quaternary ammonium compounds, polysiloxanes, and mixtures thereof. Suitable emollients include propylene glycol, glycerine, triethylene glycol, spermaceti or other waxes, petrolatum, fatty acids, fatty alcohols and fatty alcohol ethers having from 12 to 28 carbon atoms in their fatty acid chain, and mixtures thereof. Suitable immobilizing agents include polyhydroxy fatty acid esters, polyhydroxy fatty acid amides and mixtures thereof. Other optional components include perfumes, antibacterial actives, antiviral actives, disinfectants, pharmaceutical actives, film formers, deodorants, opacifiers, astringents, solvents and the like. Particular examples of lotion components include camphor, thymol and menthol.
A process according to the present invention may utilise any paper tissue made by any method known in the art, preferred methods are disclosed herein.
The process comprises a step of supplying the paper tissue by unwinding at least two plies, preferably three plies, from a corresponding number of parent rolls. The process comprises a further step of applying a texture pattern to at least one ply, preferably by bulk embossing as disclosed herein. The process also comprises a step of high pressure calendering at least one ply using calendering pressures as disclosed herein. Further the process comprises a step of juxtaposing said plies to form a multi-ply tissue.
A more preferred process further comprises a step of applying lotion to the plies, which will form the outer plies of the mulit-ply paper tissue, most preferably the lotion is applied only to the surfaces which will form the outer surfaces of the multi-ply tissue. Moreover a preferred process comprises a step of attaching the juxtaposed plies by embossing, referred to and described above as attachment embossing. Optionally the present process may also comprise the application of glue, preferably only to the raised portions of the textured plies.
Caliper is measured according to the following procedure: The tissue paper is preconditioned at 21xc2x0 to 24xc2x0 C. and 48 to 52 percent relative humidity for two hours prior to the caliper measurement. If the caliper of toilet tissue is being measured, 15 to 20 sheets are first removed and discarded. If the caliper of facial tissue is being measured, the sample is taken from near the center of the package. The sample is selected and then conditioned for an additional 15 minutes.
Caliper of the multi-ply paper tissue, as used herein, is the thickness of the paper when subjected to a compressive load of 14.7 g/cm2. Preferably, caliper is measured using a low load Thwing-Albert micrometer, Model 89-11, available from the Thwing-Albert Instrument Company of Philadelphia, Pa. The caliper per ply is the total caliper of the multi-ply paper tissue divided by the number of plies comprised. For a single ply tissue caliper per ply and caliper are identical. Decorated regions, perforations, edge effects, etc., of the tissue should be avoided if possible.
The wet burst strength is measured using an electronic burst tester and the following test conditions. The burst tester is a Thwing-Albert Burst Tester Cat. No. 177 equipped with a 2000 g load cell. The burst tester is supplied by Thwing-Albert Instrument Company, Philadelphia, Pa. 19154, USA.
Take eight paper tissues and stack them in pairs of two. Using scissors, cut the samples so that they are approximately 228 mm in the machine direction and approximately 114 mm in the cross-machine direction, each two finished product units thick.
First age the samples for one to two hours by attaching the sample stack together with a small paper clip and xe2x80x9cfanxe2x80x9d the other end of the sample stack to separate the sheets, this allows circulation of air between them. Suspend each sample stack by a clamp in a 107xc2x0 C. (xc2x13xc2x0 C.) forced draft oven for 5 minutes (xc2x110 seconds). After the heating period, remove the sample stack from the oven and cool for a minimum of three minutes before testing.
Take one sample strip, holding the sample by the narrow cross direction edges, dipping the centre of the sample into a pan filled with about 25 mm of distilled water. Leave the sample in the water four (4.0xc2x10.5) seconds. Remove and drain for three (3.0xc2x10.5) seconds holding the sample so the water runs off in the cross direction. Proceed with the test immediately after the drain step. Place the wet sample on the lower ring of the sample holding device with the outer surface of the product facing up, so that the wet part of the sample completely covers the open surface of the sample holding ring. If wrinkles are present, discard the sample and repeat with a new sample. After the sample is properly in place on the lower ring, turn the switch that lowers the upper ring. The sample to be tested is now securely gripped in the sample holding unit. Start the burst test immediately at this point by pressing the start button. The plunger will begin to rise. At the point when the sample tears or ruptures, report the maximum reading. The plunger will automatically reverse and return to its original starting position. Repeat this procedure on three more samples for a total of four tests, i.e., 4 replicates. Report the results, as an average of the four replicates, to the nearest gram.
For the physiological surface smoothness measurement, which reports the PSS parameter, a sample of the paper tissue is selected which avoids wrinkles, tears, perforations, or gross deviations from macroscopic monoplanarity. The sample is conditioned at 22 to 24xc2x0 C. and 48 to 52% relative humidity for at least two hours prior to testing. The sample is placed on a motorised table and magnetically secured in place. Either face of the sample may be selected for the measurement, provided all traces are taken from the same face.
Physiological surface smoothness is obtained by scanning the paper tissue sample in any direction with a profilometer to obtain the Z-direction displacement as a function of distance. The Z-direction displacement is converted to an amplitude versus frequency spectrum by a Fourier Transform. The spectrum is then adjusted for human tactile response using a series of filters. The peak heights of the filtered amplitude frequency curve are summed from 0 to 10 cycles per millimeter to give the result.
The paper tissue sample is approximately 100 millimetersxc3x97100 millimeters in size and mounted on a motorised table. While any suitable table will suffice, a table with surface tester model KES-FB-4NKES-SE, available from Kato Tech Company Limited of Koyota, Japan, or a CP3-22-01 DCI Mini Precision table using a NuStep 2C NuLogic Two Axis Stepper Motor Controller in the closed loop control mode have been found suitable. The table has a constant drive motor which travels at the rate of 1 millimeter per second. The sample is scanned 30 millimeters in the forward direction transversely indexed one millimeter, then reversed. Data are collected from the centre 26 millimeters of the scan in both the forward and reverse directions. The first and last 2 millimeters of each scan are ignored and not used in the calculations.
The profilometer has a probe with a tip radius of 2.54 microns and an applied force of 0.20 grams. The gauge range is calibrated for a total Z-direction displacement of 3.5 millimeters. Over the scan distance of the sample, the profilometer senses the Z-direction displacement of the stylus in millimeters. The output voltage from the gauge controller is digitised at a rate of at least 20 points per second. Over the entire 26 millimeter scan range, 512 pairs of time surface height data points are obtained for both the forward and reverse directions of a scan. The profilometer is mounted above the sample table such that the surface topography can be measured. A suitable profilometer is a EMD 4320 WI Vertical Displacement Transducer, having an EPT 010409 stylus tip, and an EAS 2351 Analog Amplifier. This equipment is obtainable from Federal Products of Providence, R.I.
The digitised data pairs are imported into a standard statistical analysis package for further analysis. Suitable software analysis packages included SAS of Cary, N.C., and preferably LabVIEW Instrument Control Software 3.1 available from National Instruments of Austin, Tex. When using the LabVIEW software, raw data pairs linking surface height and time from the individual scans are centered about the mean using the Mean.vi analysis tool in the LabVIEW software. The 512 data points from each of the 16 traces are converted to 16 amplitude spectra using the Amplitude and Phase Spectrum.vi tool. Each spectrum is then smoothed using the method described by the PROC Spectra Method of the SAS software. LabVIEW smoothing filter values of 0.000246, 0.000485, 0.00756, 0.062997, 0.00756, 0.000485, 0.000246 are utilized. The output from this tool is taken as the Amp Spectrum Mag (vrms).
The amplitude data are then adjusted for human tactile response using a series of frequency filters designed from Verrillo""s data on vibrotactile thresholds as a function of vibration frequency as set forth in the Journal of Acoustical Society of America, in the article entitled xe2x80x9cEffect Of Contactor Area On The Vibrotactile Thresholdxe2x80x9d, Vol. 35, 1962 (1963). The aforementioned data are reported in a time domain as cycles per second and converted to the spatial domain in cycles per millimeter. The conversion factor and filter values are found in the procedure set forth in the 1991 International Paper Physics Conference, TAPPI Book 1, more particularly the article entitled xe2x80x9cMethods For The Measurement Of The Mechanical Properties Of Paper tissuexe2x80x9d by Ampulski, et al., and found at page 19, utilizing the specific procedure set forth at page 22 entitled xe2x80x9cPhysiological Surface Smoothnessxe2x80x9d. The response from the filters are set at 0 below the minimum threshold and above the maximum response frequencies and varies from 0 to 1 therebetween as described by the aforementioned Ampulski et al. article.
The physiologically adjusted frequency amplitude data are obtained by multiplying the amplitude spectra described above by the appropriate filter value at each frequency. A typical amplitude spectrum and filtered amplitude spectrum are illustrated in FIG. 5 of the aforementioned Ampulski et al. article. The Verrillo-adjusted frequency amplitude curve is summed point by point between 0 and 10 cycles per millimeter. This summation is considered to be the physiological surface smoothness. The eight forward and eight reverse physiological surface smoothness values thus obtained are then averaged and reported in microns.
Physiological surface smoothness measurements using the SAS software is described in commonly assigned U.S. Pat No. 4,959,125, issued Sep. 25, 1990 to Spendel; U.S. Pat. No. 5,059,282, issued Oct. 22, 1991 to Ampulski et al.; U.S. Pat. No. 5,855,738, issued Jan. 5, 1999 to Weisman et al., and U.S. Pat. No. 5,980,691, issued Nov. 9, 1999 to Weisman et al.
Either face of the tissue may be selected for the smoothness measurement, provided all traces are taken from the same face. If either face of the tissue meets any of the smoothness criteria set forth herein, the entire sample of the tissue is deemed to fall within that criterion. Preferably both faces of the tissue meet the above criteria.