MXPA99010297A - Pigmented adhesive composition for laminating tissue paper products and methods for producing such compositions - Google Patents

Abstract

An adhesive composition that is suitable for laminating absorbent paper products and paper products laminated using the adhesive composition are disclosed. The adhesive composition provides wet bond strength and a visual signal that desirable properties are maintained when the absorbent paper product becomes wet. The adhesive composition includes a water soluble or dispersible dry strength binder, a water soluble cationic wet strength resin, and a pigment. Also disclosed is a method of producing the adhesive composition. The method includes as an essential step, providing energizing means that can transfer at least about 5 watts per kilogram of power to a resin solution or dispersion as a pigment dispersion is added.

Description

PIGMENTED ADHESIVE COMPOSITION FOR LAMINATING TISU PAPER PRODUCTS AND METHOD TO PRODUCE SUCH COMPOSITIONS FIELD OF THE INVENTION The present invention relates to adhesive compositions for laminating multi-sheet cellulosic fibrous structures as tissue paper products, with methods for producing said adhesive compositions and laminated tissue products using such adhesive compositions.

BACKGROUND OF THE INVENTION Paper products are well known in everyday life. Certain types of paper products are known as tissue and are used for paper towels, facial tissues and toilet paper. The paper products may comprise a simple sheet, but often comprise two or more sheets. In the sense in which it is used herein, "sheet" refers to a simple sheet peeled from a forming mesh or the equivalent thereof, and dried without additional fibers being added to it. Of course a sheet may be layered with different types of fibers in each layer. The stratification provides the benefits that a core layer may comprise relatively strong fibers to impart strength to the tissue paper product. Outside the central layer may be shorter fibers that impart a soft touch to the user. The stratification may advantageously be carried out according to the jointly assigned U.S. Patent 3,994,771, issued November 30, 1976 to Morgan, Jr. et al., Which is considered part of the present, as a reference. . Often two or more sheets are put together to make a paper product. The joining of several sheets at the same time provides the advantage that the resulting laminate has a lower flexural modulus than a single sheet of equivalent thickness. This provides the benefit that the user perceives a softer tactile sensation. The absorbency and the gauge are usually also improved. In addition, joining three sheets allows the paper product to have different central and outer sheets in the laminate, to provide strength and softness, respectively. Multi-sheet tissue products are usually cellulosic. As used herein, the term "cellulosic" refers to a paper product comprising at least about fifty percent by weight or at least fifty percent by volume of cellulosic fibers, among which non-exclusive, cotton wool, rayon, bagasse and, more preferably, wood pulps, such as pulps of soft woods (gymnosperms or conifers) or hardwoods (angiosperms or deciduous), fibers that can be recycled are included. The balance of the fibers may be synthetic, for example, polyolefins or polyester. Cellulosic sheets are often joined by the use of an adhesive. The bonding of cellulosic sheets with adhesives is conveniently described in co-assigned U.S. Patent 5,143,776, issued September 1, 1992 to Givens, which is considered part of the present, as a reference. However, the joining of several cellulosic sheets in a paper product by adhesive can lead and thus has been an unsatisfactory performance. Particularly, paper products used as paper towels, facial tissues and toilet paper must have adequate sheet bonding strength. In the sense in which it is used in the present "sheet joining force" it refers to the force necessary to separate two adjacent sheets from one another as described below. Frequently, tissue paper products, in particular paper towels, become wet during use. If the binding strength of wet sheets is insufficient, the sheets are separated in use and the paper product is destroyed. While it might seem like an easy matter to simply increase the binding strength of wet foils, the strength of joining of sheets in dry is directly associated to the strength of joining of sheets in wet. In the prior art, as the binding force of wet sheets increases to the appropriate level, the bond strength of sheets in dry becomes too large. When the bond strength of dry sheets is too great, softness and absorbency are normally reduced. U.S. Patent Application Serial No. 08 / 835,039 assigned jointly, filed in the name of Neal et al., On March 27, 1997 discloses combinations of nonionic adhesive materials that provide bond strength of dry sheets to such adhesively bonded sheets and cationic wet strength resins that provide wet sheet bonding strength. It has been found that such adhesive compositions provide adhesively laminated multi-sheet paper products with adequate wet sheet bond strength without having a dry sheet bond strength that is too large. It is also desirable to provide the user with an indication that the laminated paper towel maintains its wet bonding strength when the paper product is wetted during use. As is known in the art, many rolled paper towel products are provided with an aesthetically pleasing embossing pattern with a laminating adhesive which is disposed at the distal ends of the embossing to join the sheets. It is also known that the embossing pattern disappears when the paper towel is moistened. United States Patent Application Serial No. 08 / 749,708 assigned jointly, filed in the name of Steinhardt, et al., On November 15, 1996 discloses the use of indicator means to maintain a pleasing pattern when the paper towel it gets wet. One of the means that is exposed therein is a laminating adhesive that further comprises an opacifier, such as titanium dioxide. However, the pigment dispersions of titanium dioxide which are commonly available, usually also comprise an anionic polymer which helps to prevent these dispersions from flocculating and sedimenting. Combining those anionically stabilized dispersions with cationic wet strength resins, as has been found to provide increased wet bond strength, would result in an adhesive composition that would further provide a visual indication of the increased wet bond strength. However, the incompatibility of anionic materials and cationic materials is well known in the art. Thus, there is a need for adhesive compositions also comprising an anionically stabilized pigment dispersion having improved and increased wet sheet bond strength. There is also a need for methods for mixing anionically stabilized pigment dispersions and cationic wet strength resins to form the pigmented adhesive compositions. There is still another need for pigmented adhesive compositions that have minimal agglomeration of pigment particles to maximize the opacifying strength of said pigmented adhesive compositions and methods that have the ability to minimize such agglomeration. Applicants have discovered certain compositions and methods that address those needs as will be readily apparent when taken with reference to the following description and when taken considering the examples that accompany it.

SUMMARY OF THE INVENTION The present invention provides a suitable adhesive composition for laminating a multi-sheet cellulose paper product. The adhesive composition comprises a mixture of: (a) between about 2% and 7% by weight of a water-soluble or water-dispersible dry strength binder material; (b) between about 0.05% and 5% by weight of a water-soluble cationic wet strength resin; (c) between about 7% and 30% by weight of an anionically stabilized pigment; and (d) between about 58% and 91% by weight of water. The adhesive composition is preferably manufactured using energizing media that transfers at least 5 watts per kilogram to the adhesive composition. Such transfer provides sufficient energy to the composition, as it is manufactured, to effectively remove the cationic wet strength resin and the anionically stabilized pigment (ie, the energizing media effectively maintain a positive charge density) by reducing at least the agglomeration of the pigment particles and the subsequent instability of the adhesive (for example, coacervation). All percentages, relationships and proportions P925 d herein they are by weight unless otherwise indicated. The present invention is described in more detail below.

DETAILED DESCRIPTION OF THE INVENTION Although this specification concludes with the claims that particularly point out and in a different manner claim the matter considered as an invention, it is considered that the invention will be better understood from the reading of the following detailed description and the attached example. In the sense in which the term "comprises" is used herein, it means that the various components, ingredients or steps can be used together in carrying out the present invention. Accordingly, the term "comprises" encompasses the more restrictive terms "consists basically of" and "consists of". The present invention comprises pigmented adhesive compositions which are suitable for joining two or more sheets of tissue, to maximize the opacifying properties of the pigment, the methods for producing those compositions and the laminated paper products using those compositions. The sheets are cellulose, as described below and may be made according to the same manufacturing process or according to different manufacturing processes.

The sheets Each sheet may have a plurality of reliefs projecting out of the plane of the sheet towards an adjacent sheet. In the same way the adjacent sheet may have opposite protrusions protruding towards the first sheet. If a three-sheet paper product is desired, the central sheet may have reliefs extending outward in both directions, although a central sheet may be feasible that has no reliefs or has reliefs without direction. The sheets may be made according to United States Patents assigned together 4,637,859, granted on January 20, 1987 to Trokhan or 4,191,609, granted on March 4, 1980 to Trokhan, which are considered hereby incorporated by reference. Alternatively, the sheets may be made using the non-creped air-drying technology described in European Patent Application 0 617 164 A1, published on September 28, 1994 or conventional drying using felts as is known in the art. . For the present invention, each sheet may have a basis weight of about 8 and 30 pounds per 3,000 square feet (13 to 48 g / m) and preferably between about 11 and 18 pounds per 3,000 square feet (18 and 29 g / m) ) and preferably has a composition of hard woods and / or softwoods processed by any of the means well known in the art. The fibers constituting the sheets of the paper product are preferably cellulosic, such as cotton wool, rayon or bagasse; and more preferably cellulose pulps, for example, from soft woods (gymnosperms or conifers) or hardwoods (angiosperms or deciduous). In the sense in which it is used in the present, a rolled paper product is considered "cellulosic" if the laminated paper product comprises at least 50 weight percent to at least 50 volume% of cellulosic fibers, including, but not limited to, the fibers listed above. The balance of the fibers comprising the rolled paper product may be synthetic, such as polyolefins or polyester. It has been found that a cellulosic mixture of wood pulp fibers comprises softwood fibers having a length of approximately between 2.0 and 4.5 millimeters and a diameter of approximately between 25 and 50 microns and hardwood fibers having a shorter length than approximately 1.7 millimeters and a diameter of approximately between 12 and 25 microns works well for the laminated paper products described herein. If cellulosic pulp fibers are selected for the multi-sheet paper products of the present invention, the fibers can be produced by any pulping process including chemical processes, such as sulfite, sulphate and soda processes; and mechanical processes such as mechanical pulp. Alternatively, the fibers may be produced by combinations of chemical and mechanical processes or may be produced by a process that recycles waste paper products. The type, combination and processing of the fibers are not critical to the present invention. The fibers of hardwoods and soft woods may be deposited throughout the thickness of the paper products laminated or mixed therein homogeneously.

The Adhesive Composition "The sheets of the multi-sheet paper product are adhesively bonded using a pigmented adhesive composition prepared according to the present invention The adhesive composition is preferably applied to the embossing of at least one sheet.Of course, the adhesive can be applied to the embossing of both sheets.

P925 the present invention comprises a mixture of a dry strength binder (eg, a fully hydrolyzed polyvinyl alcohol adhesive), a cationic wet strength resin (eg, a thermofix cationic resin) and a titanium dioxide paste anionically stabilized A particularly preferred adhesive composition comprises between about 58 and 90 parts of water, between 2 and 7 parts of dry strength binder solids, between 0.05 and 5 parts of cationic wet strength resin solids and between 7 and 30 parts of solids. titanium dioxide pigment. Each of these types of compounds will be described in detail below. Importantly, in order to achieve satisfactory wet and dry sheet bond strength and satisfactory signal strength in the laminated tissue finished product of the present invention, the adhesive composition must be applied to the sheets at a suitable level. Suitable application methods are discussed below in the Lamina and Lamination Embossing section. It is also important that the components of the adhesive composition are applied in the correct proportions. One skilled in the art will recognize that the absolute concentrations of the solid components of the composition can be varied within certain limits (for example, for P925 to control the viscosity of the composition) so long as the adhesive solids applied to the sheets are sufficient to provide satisfactory dry and wet sheet bond strength and satisfactory signal strength. Specifically, it is important that the proportion of dry strength binder solids and wet strength resin solids are within an acceptable range to provide adequate wet bond strength without having a dry sheet bond strength that It is too big. It is also important that the ratio of solids of cationically charged material and solids of anionically charged material be within an acceptable range to provide stable adhesive compositions having sufficient signal strength. Specifically, Applicants found that: 1) The ratio of dry strength binder solids to wet strength resin solids should not exceed about 6: 1 to have an acceptable balance between wet sheet bond strength and wet strength. bonding of sheets in dry. Preferably, the ratio is less than about 4: 1. 2) The ratio of solids of anionically charged material and solids of cationically charged material should be such that the charge density of the composition P925 final adhesive is at least 25 microequivalents per gram (as will be recognized by those skilled in the art, the specific weight ratios will depend on the charge density of the individual materials). For the preferred materials discussed herein, this means that the ratio of anionically charged pigment solids (solids pigment solids anionic suspension auxiliary) and cationic solids (wet strength resin solids or other cationically charged solids) added to maintain a net positive charge density) should be less than about 40: 1. Preferably, the ratio of anion solids to cationic solids is less than about 30: 1. More preferably, the ratio is less than about 15: 1.

Dry Strength Binder Materials The adhesive composition of the present invention contains as a basic component between about 2% and 7%, preferably between about 3.5% and 6.5% by weight of a dry strength binder material selected from the following group of materials: polyacrylamide (as Accostrength 711 produced by CyTec Industries of West Paterson, NJ); starch (such as RediBOND 5320, 2005 and 3030) available from National Starch and P925 Chemical Company; Bridgewater, NJ or Amylose 1100, 2200 or Salvitose available from Avebe America, Princeton, NJ; polyvinyl alcohol (such as Evanol 71-30, supplied by DuPont Corporation of Wilmington, DE); and / or guar or carob gum. Preferably, the dry strength binder materials are selected from the group consisting of polyvinyl alcohol, starch-based resins and mixtures thereof. The dry strength binder materials act to ensure that the multi-sheet paper products of the present invention have adequate sheet bond strength in dry. In the particularly preferred adhesive compositions according to the present invention, the dry strength binder comprises polyvinyl alcohol. The polyvinyl alcohol component can be of any molecular weight soluble in water or dispersible in water sufficient to form an adhesive film. In general, a weight average molecular weight of approximately between 40,000 and 120,000, more preferably between 70,000 and 90,000 is preferred. Polyvinyl alcohol in solid form is commercially available with several registered trademarks such as ELVANOL® (DuPont), GELVATOL® (Monsanto), VINOL® (Air Products) and POVAL® (KURARAY). These types have a degree of hydrolysis that varies between about 80 and 100%. Those skilled in the art P925 will appreciate that decreasing the degree of hydrolysis and molecular weight will improve the solubility in water but will reduce adhesion. Therefore, the properties of polyvinyl alcohol will have to be maximized for the specific application. A particularly preferred polyvinyl alcohol is Evanol 71-30, supplied by DuPont Corporation of Wilmington, DE. Evanol 71-30 has a molecular weight weight of about 77,000 and a degree of hydrolysis of about 99%. Alternatively, the dry strength binder may comprise a starch. In general, a suitable starch for carrying out the present invention is characterized by water solubility or the ability to form stable dispersions which are hydrophilic. Exemplary starch materials include corn starch and potato starch, although it is not intended thereby to limit the scope of suitable starch materials. Waxy corn starch which is industrially known as amioca starch is preferred. Amioca starch is distinguished from common starch in that it is only amylopectin, while common corn starch contains both amylopectin and amylose. Various unique characteristics of amioca starch are described more fully in "Amioca - The Starch from Waxy Corn", H.H. Schopmeyer, Food Industries, December 1945, p. 106- P925 108 (Vol.p. 1476-1478). The starch may be in granulated form or in dispersed form. A preferred starch, RediBOND, is presented as a dispersed ready-to-use material. Granulated starches such as Amylose 1100 are preferably cooked sufficiently to induce swelling of the granules. More preferably, the starch granules swell, for example, by cooking to a point just before the starch granule dispersion. Those very swollen starch granules will be referred to as "fully cooked". The conditions for dispersion in general can vary depending on the size of the starch granules, the degree of crystallinity of the granules and the amount of amylose present. Fully cooked amioca starch, for example, can be prepared by heating an aqueous paste of about 4% consistency of starch granules to about 190 ° F (about 88 ° C) for about 30 to 40 minutes. Other exemplary starch materials that may be used include modified anionic or cationic starches such as modified ones having nitrogen containing groups such as amino groups and methylol groups attached to nitrogen, available from National Starch and Chemical Company (Bridgewater, NJ). Whereas said modified starch materials are more expensive than starches without P925 Id modify, in general the latter have been preferred.

Resistance Wet Resin Materials The adhesive composition of the present invention also contains as a basic component between about 0.05% and 5.0%, preferably between about 0.1% and 2.5% by weight of a wet strength resin material selected from the following group of materials: polyamide-epichlorohydrin resins, polyacrylamide resins with glyoxal, styrene-butadiene latex; insolubilized polyvinyl alcohol; urea-formaldehyde; polyethyleneimine; chitosan polymers and mixtures thereof. Preferably, the wet strength resins are water-soluble cationic resins selected from the group consisting of polyamide-epichlorohydrin resins, glyoxal-modified polyacrylamide resins, polyethylene imine resins, and mixtures thereof. It has been found that polyamide-epichlorohydrin resins are cationic wet strength resins of particular utility. Preferably, the polyamide-epichlorohydrin resin comprises a reaction product of water-soluble polymeric epichlorohydrin and a water-soluble polyamide having secondary amino groups. The ratio of epichlorohydrin and groups P925 1 secondary amino acids of the polyamide is preferably between about 0.5 to 1 and 2 to 1. Preferably, the water-soluble polyamide is derived from reacting a polyalkylene polyamine and a saturated aliphatic dibasic carboxylic acid containing between 3 and 10 carbon atoms. Preferably, the molar ratio of polyalkylene and dibasic carboxylic acid is from about 0.8 to 1 to 1.5 to 1. Preferably, the saturated aliphatic dibasic carboxylic acid is adipic acid and the polyalkylene polyamine is diethylene triamine. With superlative preference, the water-soluble polyamide contains repeating groups of the formula O O -N (CnH2nH) x-CRC- wherein n and x are each 2 or more and R is the divalent hydrocarbon radical of the dibasic carboxylic acid containing between 3 and 10 carbon atoms. Resins of this type are commercially available under the trademarks KYMENE® (Hercules, Inc.) and CASCAMID® (Borden). A basic characteristic of these resins is that they are compatible in phase with the polyvinyl alcohol, ie there is no phase separation in the presence of aqueous polyvinyl alcohol. Suitable types of these resins are described in P925 U.S. Patents No. 3,700,623, issued October 24, 1972 and 3,772,076, issued November 13, 1973, both granted to Keim and considered part of this, as a reference. A commercial source of a useful polyamide-epichlorohydrin resin is Hercules, Inc. of Wilmington, DE, which markets said resins under the trademark Kymene® 557H, Kymene® 557LX and Kymene® 557ULX, with Kymene® 557LX being preferred. The base-activated polyamide-epichlorohydrin resins which are also useful in the present invention are also marketed by Hercules, Inc. of Wilmington, DE, which markets said resins under the trademark Kymene® 450. Other examples of commercial sources of polyamide resins -epichlorohydrin-activated bases are sold under the trademark Santo Res, as Santo Res 31, of Monsanto Company, St. Louis, MO. these types of materials are generally described in U.S. Patent Nos. 3,855,158, issued December 17, 1974; 3,899,388 granted to Petrovich on August 12, 1975; 4,129,528 granted to Petrovich on December 12, 1978; 4,147,586 granted to Petrovich on April 3, 1979 and 4,222,921 granted to Van Eenam on September 16, 1980, which are considered part of this by reference. It has been found that the resins of P925 polyacrylamide modified with glyoxal are also useful as wet strength resins. These resins are described in U.S. Patent No. 3,556,932 issued January 19, 1971, to Coscia et al. and No. 3,556,933 issued January 19, 1971 to Williams et al., which are considered hereby incorporated by reference. A commercial source of polyacrylamide resins is Cytec from Stanford, CT, which markets one of those resins under the trademark Parez ™ 631 NC. Still other water soluble cationic resins which find utility in this invention are the urea formaldehyde and melamine formaldehyde resins. The most common functional groups of these polyfunctional resins are nitrogen-containing groups, such as amino groups and methylol groups attached to nitrogen. Polyethylenimine type resins may also find utility in the present invention.

Pigment As discussed earlier in the section BACKGROUND OF THE INVENTION It is desirable to provide the user with an indication that desirable properties, such as bond strength of wet sheets, are retained when the products of adhesively laminated paper are P925 moisten. Also as noted above and as described in the aforementioned U.S. Patent Application Serial No. 08 / 749,708, the disclosure of which is considered hereinbefore, as a reference, laminating adhesive compositions comprising a pigment can provide said indication. As is well known, the refractive index is a main factor that determines the opacifying effectiveness of a pigment. Table 1 below compares the refractive index of pigments commonly used in the paper industry.

TABLE 1 Refractive Index Compound Titanium Dioxide Rutile 2.72 Anatase 2.55 Zinc Oxide 2.02 Kaolinic Clays 1.57 Calcined Clays 1.57 Natural Ground Calcium Carbonate 1.56 PCC-Calcite 1.66 P925 Talcum 1.57 Precipitated Silica 1.45 To be suitable in use as a pigment for the purposes of the present invention, said pigmenting materials should have a refractive index greater than about 1.4. Preferably, the refractive index is greater than 1.7. Particularly preferred inorganic pigment materials have a refractive index greater than about 2.0. In addition to the refractive index, the particle size of an opacifier also has a significant effect on the opacity of the adhesive compositions of the present invention. That is, for a given concentration of pigment in an adhesive composition, compositions containing pigments having a smaller particle size will be more opaque. Suitable pigments that are used in the present invention have a median particle size without sonication of less than about 1.4 microns. Preferably, the median particle size is less than about 0.8 microns.

More preferably, the median particle size is less than about 0.6 microns. A method to determine the median particle size without sonication is given later in the TEST METHODS section. A particularly preferred pigment material P925 is titanium dioxide (T102). There are two crystalline forms of Ti02: anatase and rutile. The rutile form is the most opaque due to its higher refractive index. In the paperma technique it is known that a given opacity can usually be achieved with approximately between 15% and 20% less rutile than anatase. Titanium dioxide is commercially available in both dry powder and paste in water form. For the purposes of the present invention, the paste in water is preferred due to the ease of mixing with other components of the adhesive composition herein and because the pigment particles are dispersed more completely to provide better opacity. So that the Ti02 remains suspended, additional components are included in the commercially available Ti02 pastes. In particular, dispersion aids are used to ensure that the suspended Ti02 particles do not flocculate or settle. The dispersion aids are of two types: spherical stabilizers and electrostatic stabilizers. Stearic stabilizers surround suspended particles of Ti02 with an adsorbed layer of a polymer. The spherical interaction between the layers of polymers in the different particles prevents them from getting so close that they can agglomerate. Normally, pasta Spherically stabilized P92S are very viscous due to the adsorbed polymer layer. The titanium dioxide particles can also be electrostatically stabilized by surrounding them with charged species. Said species can be both cationic and anionic. Because most Ti02 is used in the paper and paint industries and both require anionic pastes for their processes, cationic Ti02 pastes are rare. An example of a suitable anionic electrostatic suspending aid is the sodium polyacrylate described in U.S. Patent 4,503,172, issued in the name of Farrar, et al., On March 5, 1985. Said material is available as manufactured Dispex N40V. by Allied Colloids of Suffolk, VA. A suitable commercially available Ti02 paste is Ti-Pure® RPS Vantage Rutile Paper Slurry which is available from DuPont Company of Wilmington, DE. This material is an anionically stabilized paste of the rutile form of Ti02 in water having a nominal Ti02 solids level of 71.5%. The median particle size without sonication of this material is usually less than 0.5 microns. It has been found that a Ti02 paste of this type provides a visual indication of the desirable properties of wet use when the Ti02 is used as P925 the present invention. The Applicants have found that the pigmented adhesive compositions according to the present invention should comprise at least about 7% Ti02 solids to provide a satisfactory visual indication of desirable wet properties. Ti02 solids levels greater than about 30% do not provide further improvement in the intensity of the indication. Preferably the level of solids of Ti02 should be between approximately 10% and 30%. More preferably, the Ti02 solids level should be between about 15% and 25%. One skilled in the art will recognize that, if other pigments are used, the level of pigment will need to be adjusted to provide a satisfactory visual indication. As noted above, the relative refractive index between Ti02 and a potential substitution pigment can provide an initial indication of how large the adjustment is needed. Alternatively, organic pigment media, such as Ropaque HP91 from Rohm & Haas Corp., Philadelphia, PA, to replace at least part of the titanium dioxide. Said organic pigmenting means are hollow polymer spheres which are provided as emulsions in water. Since the spheres are hollow, the light deviates several times as it passes through a dispersion of those pigments. This multiple deviation provides an apparent Refractive Index that gives an opacifying power comparable to Ti02. Since, those organic pigment media are also anionically stabilized, the same issues of incompatibility with the cationic wet strength resins discussed above also affect the stability and opacity of adhesive compositions comprising organic pigmenting media. An alternative inorganic pigmenting medium which may be used as a substitute for at least a part of the titanium dioxide in adhesive compositions of the present invention is silica (eg, fuming silica, colloidal silica and the like). A suitable fuming silica is AEROSIL 300® which is available from Degussa Corp. of Ridgefield Park NJ. As is clearly evident from Example 5, the pigmented adhesive compositions comprising such alternative inorganic pigmenting media provide desirable haze and viscosity as discussed above. The Applicants further believe that replacing part of the titanium dioxide with silica has the potential to reduce wear in the mixing and application apparatus due to the small maximum particle size of the silica particles. For example, the AEROSIL 300® that P92S discussed above has a maximum particle size of 7 nanometers compared to 0.5 microns for the Ti02 pigment described above.

Optional Cationic Additives As is well known cationic species carry a positive charge and the anionic species carry a negative charge. One measure of these charges is the charge density. A method for measuring charge density is provided below in the TEST METHODS section. The Applicants have found that the adhesive compositions suitable in accordance with the present invention should have a positive charge density. That is, a suitable adhesive composition according to the present invention is at least slightly cationic (positive charge density). The applicants believe that one of the benefits of the method of the present invention is that by energizing one of the components of the anionic or cationic composition, before starting to add the other component, it avoids a situation where the portions of the mixture have a negative charge density during the addition of the remaining charged components of the composition (It has been found that said negative charge density, when the components are mixed under low energy conditions, increase the risk of coacervation, P925 separation and loss of opacifying efficacy). By providing sufficient energy in the mixing step, the formation of substantial portions of the mixture having a negative charge density and the resulting coacervation is significantly reduced. Table 2 presents load density values for representative components suitable for use in the adhesive compositions of the present invention.

TABLE 2 Component Load Density (Microequivalents / gram) * Cationic Materials Kymene®557 LX RediBond® 5320 +3243 Anionic Material +264 Ti02 Paste (TiPure® RPS) -48 * 100% solids base The relative amounts of such components in a composition will determine the charge density of the composition. For example, it has been found that a composition comprising approximately 1.5% Kymene 557LX and approximately 23% Ti02 prepared according to the method of the present invention has a charge density P925 of approximately +185 microequivalents per gram. On the other hand, it has been found that a composition comprising about 0.3% Kymene 557LX and about 23% Ti02 has a charge density of about -1.7 microequivalents per gram. Preferably, the charge density in the finished pigmented adhesive composition is at least about +25 microequivalents per gram of dispersed solid material. Preferably, the charge density is at least about +30 microequivalents per gram, more preferably, at least about +50 microequivalents per gram. As will be discussed below, the method of the present invention is particularly effective in minimizing the agglomeration of the pigment in pigmented adhesive compositions prepared therefrom. However, it is still necessary to maintain a minimum charge density in the finished adhesive composition to maximize the stability of the composition. For example, a particular adhesive composition may not contain sufficient cationic wet strength resin to maintain a positive charge density that increases the risk of coacervation and agglomeration. In order to compensate for this insufficient positive charge density, materials having a positive charge may be added to the composition.

P925 positive charge density (for example, cationic additives), if the charge density contribution from the cationic materials in the composition is insufficient. Suitable materials include: cationic starches (such as Celquat L200 which is available from National Starch and Chemical Co., Bridgewater, NJ) and quaternary ammonium compounds (such as those available from Witco Chemical Co. of Dublin), OH, as SC-505-91). A particularly preferred cationic additive is a relatively low molecular weight polyamine having a high charge density. A particularly preferred material of this type is Cypro® 515 having a charge density of about +6400 microequivalents per gram (100% solids base) and available from Cytec of Stamford, CT. For example, when 0.6% of Cypro® 515 is added to a solution of Kymene® 557 LX 0.3% before the addition of Ti02 and the composition, after the addition of Ti02 it has a charge density of +35 microequivalents per gram more than -1.7 microequivalents per gram as described above. It has been found that such a charge density provides a suitably stable suspension for use as a lamination adhesive.

Adhesive Fabrication As noted above, the wet strength resin, Kymene®, is highly cationic and therefore, when Kymene® is combined with anionically stabilized Ti02 pastes these can react with anionic components of the adhesive composition, for example with an anionically stabilized pigment dispersion, causing stratification and separation of the adhesive composition due to coacervation. Below, Example 1 demonstrates this behavior. Surprisingly, the Applicants have found that, by properly mixing the components identified above, they can solve the well-known difficulties in producing stable compositions by combining cationic and anionic materials. Specifically, the Applicants have found that by using the method described in detail below, wherein one of the components of the composition, the anionic or the cationic is energized before the other component is added, pigmented adhesive compositions can be produced. remarkably stable. A liquid material is "energized" if an "energizing medium" has the ability to provide at least 5 watts per kilogram as liquids P925 mix. Preferably, the energizing medium should have the ability to supply at least about 15 watts per kilogram as the liquids mix. More preferably, the energizing medium has the ability to supply at least 25 watts per kilogram as the liquids mix. In the TEST METHODS section, a method is provided to determine the energy delivered (watts per kilogram). Suitable energizers include: batch mixers that provide high speed at the tip of the agitator, for example, mixers such as those available from Sumbeam Corporation, of Delray Beach, FL under the trade name Osterizer; rotor / stator mixers of high tangential force, such as those available from Charles Ross & Son, Hauppauge, NY and line mixers such as those available from Quadro Inc., Millburn, NJ as the Quadro ZC model. A particularly preferred energizing medium is Breddo Likwiffer, Model LOR supplied by Breddo Likwiffer of Kansas City, MO. In addition, applicants have found that, when using these methods, the median particle size of the pigment in the finished adhesive composition is comparable to the median particle size of the pigment.

P92S pigment without sonicate in the original pigment dispersion. That is, the method of the present invention uses said pigment dispersions quite efficiently to provide the adhesive composition with maximum opacity. This efficiency is shown very clearly in Table 3 comparing turbidity (turbidity is a measure of opacity - a method for measuring turbidity is given in the TEST METHODS section) of pigmented adhesive compositions prepared according to the methods described later in Examples 1 and 2.

TABLE 3 Median Particle Size No Sonic Turbidity (NTU) (Mieras) Prepared composition 1217 * Two peaks (2.2, according to the method of 17.1) Example 1 Prepared composition 3467 * 0.5 according to the method of Example 2 * Measured at a concentration of 0.5 grams of adhesive in 1000 milliliters of water.

P925 As can clearly be seen, the adhesive composition prepared according to the method of Example 2 (method of the present invention) has a considerably higher turbidity (higher opacity) and a smaller particle size than the adhesive composition prepared according to the method of Example 1 (mixed low energy). Without being limited to the theory, the Applicants believe that energizing one of the charged components of the composition before adding the component having the opposite charge keeps the pigment particles sufficiently separated so that the agglomeration of the pigment particles (with the consequent increase in average particle size) is minimized. The Requesters have found that, when the pigmented adhesive compositions are prepared according to the present invention, the pigment particles in said compositions have an average particle size without sonication not greater than about 2.5 times the average particle size without sonication of the pigment in the pigment dispersion. . Normally, the average non-sonic particle size of the pigment in the pigmented adhesive composition is less than about 1.5 times the average non-sonic particle size of the pigment in the pigment dispersion. The Applicants further believe that by providing sufficient mechanical energy while P9? Adding the second component to the first one minimizes the interactions between the anionic and cationic species. That is, the coacervation and the resulting considerable increase in the viscosity of the composition (i.e., stratification and gelation) are minimized. While, as noted above, energizing a first component of the adhesive composition before adding any of the other components significantly reduces coacervation and agglomeration of pigment particles, the order of addition may affect the properties of the composition. final adhesive composition. A particularly preferred method of preparing the adhesive composition of the present invention is described below. ~ The first step of this preferred method is to provide the required amount of a cationic wet strength resin. For example, to prepare 100 parts of the preferred adhesive composition of the present invention, between about 0.05 parts and 5 parts of a polyamide-epichlorohydrin resin should be provided. Preferably, this resin is in a solution comprising between about 10% by weight and about 15% by weight resin solids. A particularly preferred method provides approximately 12 parts of a resin solution P925 polyamide-epichlorohydrin at 12.5% by weight. Optionally, if the desired concentration of cationic wet strength resin is too low to maintain an adequate charge density (see discussion above), one of the alternative cationic materials discussed above may be provided before energizing the resistance resin solution. wet cationic. The polyamide-epichlorohydrin resin solution is then energized by suitable means that provide it with mechanical energy as described above. It is important that the sufficient energy that is going to be supplied in this energizing step causes the resin solution to become turbulent. For example, the resin solution must not be so viscous that a considerable portion of the mechanical energy supplied is converted into thermal energy causing the temperature of the solution to increase substantially. Specifically, the viscosity of the resin solution should be less than about 500 centipoise when measured according to the method described below in the TEST METHODS section. More preferably, the viscosity should be less than about 300 centipoise. As noted above, the appropriate energizing medium has the ability to supply at least 5 watts per kilogram of energy to the resin solution P925 provided in the first step. A particularly preferred energizer for the purposes of the present invention is Breddo Likwiffer, Model LOR. After energizing the cationic wet strength resin solution, the pigment dispersion is added thereto. To produce 100 parts of the preferred pigmented adhesive composition described above, between about 7 and 30 parts of the pigment dispersion are added while continuing the supply of energy to the liquid. In the case of the particularly preferred Ti02 dispersion discussed above, between about 32 parts of dispersion are added to 71.5 weight percent. Preferably, the pigment dispersion is added at a rate which ensures that the mass of the material in the mixing zone comprises the cationic wet strength solution or a pigment dispersion in the cationic wet strength resin solution. Otherwise, there may be insufficient energy to maintain the separation of the pigment particles and minimize coacervation. In the sense in which it is used herein, the term "mixing zone" is determined by the geometry of the specific energizing medium selected and is the volume in which the energy is transferred from the energizing medium to the liquid or P925 dispersion that will energize. The Applicants have found that a useful measure of the rate of addition is the Supply Number. In the sense in which it is used in the present "Supply Number" it is a number without dimension that depends on the speed of addition of the pigment dispersion, the geometry of the agitator and the rotational speed of the agitator and can be calculated according to the following equation: Pigment Weight / Addition Time) Q = nd p Rotation Speed n = 60 where: Q = Supply Number Weight of Pigment = Weight of pigment dispersion added (kg) Addition Time = Time required to add the pigment (seconds) r = Density of pigment dispersion (g / cm) Rotation Speed = Rotational speed of the agitator (rpm) d = Diameter of the agitator (cm) For example, when preparing a batch of the pigmented adhesive composition of the present invention, P925 took the following data: Pigment Weight = 36.97 kg; Addition Time = 240 seconds r = 2.2 g / cc (Ti02 Paste, comprising approximately 72% Ti02 solids) Rotation Speed = 1800 rpm d = 24.3 cm The resulting Supply Number is 1.63 X 10". can observe from example 3, that Supply Number indicates that the pigment dispersion was added to the mixing zone slow enough to avoid agglomeration (ie the median particle size without sonication is practically less than 1 miera) The last step that is required in this preferred method is to add the dry strength binder solution (still continuing the power supply to the liquid.) The dry strength binder solution is preferably added after the other components because These solutions usually have a high viscosity and it is difficult to energize these solutions without an unacceptable temperature increase. The dry strength binder composition preferably comprises a resin based on starch or polyvinyl alcohol in water. Preferably, the concentration of the dry strength binder in that aqueous solution is between about 2% and 14% and between about 2 and 7 parts of binder solids are added to the adhesive composition when 100 parts of the finished adhesive composition are prepared . Optionally, other components may be added after mixing the above materials. For example, a portion of dilution water can be stored that allows control of the solids level and final viscosity to compensate batch by batch for the variation in the individual raw materials.

Methods of Manufacture of Alternative Adhesives Addition Order While the method described above is preferred because it provides maximum dispersion of the pigment particles and minimizes particle agglomeration, alternative methods, particularly alternative addition orders, are also within the scope of the present invention. For example, the Applicants also consider an order of addition comprising the following steps: 1) providing a dry strength binder solution; 2) energize the resistance binder solution in P925 dry; 3) provide an anionically stabilized pigment dispersion; 4) mixing the pigment dispersion in the dry strength binder solution to form a pigmented binder mixture; 5) provide a cationic wet strength resin solution; and 6) mixing the wet strength resin solution in the pigmented binder mixture. The pigmented adhesive compositions prepared according to this alternative method have considerably improved the opacity, the agglomeration reduction and the stability when compared to the low energy mixing methods. Specifically, the median non-sonic particle size for an adhesive composition comprising the preferred Ti02 pigment set forth above is approximately 1.0 micron and the initial separation time is greater than 24 hours. When these results are compared with the results shown in Table 2, above the improvement with respect to the low energy mixing method of Example 1 is obvious.

Energizing Medium An alternative energizing medium, suitable for the purposes of the present invention, is a mixer that supplies energy to a liquid medium generating ultrasonic vibrations therein (A suitable apparatus is produced by Sonic Corp. of Stratford, CT as Sonolator). The Sonolator is an in-line system that provides ultrasonic vibrations by pumping a liquid, a mixture of liquids or a solid dispersion in a liquid through an orifice that is formed at a high linear velocity. The liquid stream hits a lifting blade in the stream. The flow on the blade causes vibrations in the blade that produce cavitation in the current converting the energy of flow into mixing / dispersion energy.

Embossing and Lamination After the papermaking process in which a sheet is formed is finished, one or more sheets may be embossed and laminated. Embossing / laminating is one of the means that is useful for obtaining a pattern that is useful for providing a visual indication of the desirable properties when the embossing / laminating steps are carried out using the pigmented adhesive composition of the present invention. The embossing can be carried out according to the protuberance-to-protrusion embossing process illustrated by co-assigned US Patent 3,414,459, issued December 3, 1968 to Wells; the nested embossing process illustrated in the Patent of the P925 United States 3,556,907 issued on January 19, 1971 to Nystrand or a double sheet process illustrated in co-assigned United States Patent No. 5,294,475 issued March 15, 1994 to McNeil, which are considered part of the present as a reference. For the methods described and claimed herein, the reliefs may be spaced between 0.05 and 0.70 inches and may have an area at the distal end that varies between 0.001 and 0.100 square inches. Each relief may be drawn on a roller that has protrusions protruding from 0 to 0.120 inches from the plane of the roller. The reliefs can be round, oval or irregular in shape. Each of the reliefs has a distal end and the adhesive composition of the present invention is applied to at least a portion of the distal ends to form a laminated tissue product according to the present invention. Preferably, the adhesive solids are applied in a proportion of approximately 12 to 20 pounds of adhesive solids per ton of paper (6 to 10 grams of adhesive solids per kilogram of paper) to at least some of the distal ends in at least one of the sheets of tissue to form the laminated tissue product. More preferably, they apply between P925 approximately 14 pounds of adhesive solids per ton of paper and approximately 18 pounds of adhesive solids per ton of paper (7 grams per kilogram to 9 grams per kilogram). As used herein, the term "adhesive solids" refers to the non-aqueous components of the adhesive composition of the present invention and includes wet strength resins, dry strength additives, Ti02 and any dispersion aid or other solid materials that may be added to the adhesive composition. A particularly preferred method of embossing and lamination to produce laminated tissue products according to the present invention is described in Example 4. Applicants believe that the following, non-exclusive examples are illustrative of the present invention.

EXAMPLES Example 1 This example is intended to illustrate the properties of a coacervate mixture of a cationic wet strength resin, an anionically stabilized pigment dispersion and a dry strength binder solution made using a conventional mixing method.

P92S A pigmented adhesive composition was prepared according to the following method: 1) providing about 13 parts of a cationic wet strength resin solution comprising approximately 12.5% Kymene® 557LX resin solids and having a pH of about 3.0; 2) Begin agitation of the wet strength resin solution using a Lightnin Model TS2010 mixer which is available from Lightnin of Rochester, NY. Said mixer provides approximately 1.7 watts per kilogram of power to the solution; 3) with continuous stirring add approximately 23 parts of a Ti02 dispersion at 72% solids (TiPure® RPS Vantage Rutile Paper Slurry from DuPont) having a pH of about 8.4; 4) Add approximately 64 parts of a dry strength additive solution (ELVANOL 71-30 from DuPont) having approximately 7.4% resin solids with continuous mixing; and 5) add the necessary water with continuous mixing to give 100 parts. Table 4 lists the data obtained from the properties in the evaluation of this adhesive composition.

P925 TABLE 4 Property Value pH 4.3 Average particle size without sonication (μ) First Peak 17.1 Second Peak 2.2 Turbidity * 1217 Initial Separation Time 4 Hours * Measure at a concentration of 0.5 grams of adhesive in 1000 milliliters of water.

Example 2 This example employs the same materials, concentrations and order of addition as Example 1 but uses the method of the present invention to provide a pigmented laminated adhesive composition suitable for joining two or more sheets of tissue paper. Specifically, a laboratory mixer (Osterizer available from Sumbeam Corporation of Delray Beach FL) that energizes the liquid with approximately 110 watts per kilogram was used. Table 5 lists the data obtained from the properties in the evaluation of this adhesive composition.

P925 TABLE 5 Property pH Value 4.3 Median particle size without 0.5 sonicate (μ) Turbidity 3467 Initial Separation Time > 4 weeks Example 3 This example is intended to demonstrate the use of commercial scale mixing equipment for preparing the pigmented adhesive compositions according to the present invention. Apparatus: Breddo Likwiffer Mixer, Model LOR, Size 50 gallons, 30 Hp motor, adjustable speed (640-2300 rpm) available from Breddo Likwiffer of Kansas City, MO Rotor 1) Standard Disc - Part No. 8-711- 0004 2) Disc Teeth - Part No. 8-711-0691 Composition Component% Resistance Resin Solution in 12 Cationic Moisture Ti02 Dispersion 32 P925 Resistance Additive Solution in 55 Dry Total Water 100 Table 6 lists the properties of several batches of pigmented adhesive made according to the various process conditions.

TABLE 6 Corrida Disco Type Size Velocity Humerus of Ener ia Medium of Turbidity Batch No. (rpm) Addition Supply Size of (NTD) (kq) (Watt / a) Non Sonicate Particle (m) 1 Standard 116 1800 1.62 10 ~ 4 35.2 0.679 3567 2 Teeth 116 1800 1.62 10 ~ 4 90.3 0.566 3721 3 Teeth 230 1800 5.5 10 ~ 4 88.1 0.577 NA EXAMPLE 4 This example treats the properties of a multi-laminated paper product laminated using the pigmented adhesive composition prepared according to the method of Example 2. Such paper products may be made from two sheets of cellulosic fibers in the manner commonly used. on the Bounty brand paper towels marketed by The Procter & Gamble Company of Cincinatti, OH and the assignee of the present invention.

P925 Each sheet is made of 65 percent Kraft of softwoods from the north, 35 percent of CTPM, and has a basis weight of 14 pounds per 3,000 square feet. Each sheet is embossed with an embossing process nested by elliptically formed protuberances that have at the distal end an axis greater than 0.084 inches, a minor axis of 0.042 inches and a protrusion height of 0.070 inches. The protuberances are spaced in a concentric diamond pattern with a 45 degree tilt of approximately 0.118 inches. Two complementary sheets are made and joined to a coupling point with free space of zero, so as to form a unitary laminate having approximately 33 protrusions per square inch. The method of Example 3 provides an adhesive composition having 5.75% total adhesive solids, of which 1.5% is Kymene® and 4.25% is polyvinyl alcohol. The adhesive composition also comprises 23% solids of Ti02. This adhesive composition is applied to the protuberances of a sheet. The total solids of the adhesive composition are applied to the paper product. The resulting paper product has a wet sheet binding strength of 5.5 grams per inch and a dry sheet bond strength of 10.4 grams per inch. The methods to measure the strength of P925 binding of wet foils and the bond strength of dry foils are described below in the TEST METHODS section. In Table 7 the binding strength of wet sheets and the bond strength of dry sheets of paper towel products laminated with the adhesive compositions prepared according to the present invention are compared with other commercially available paper towels.

TABLE 7 Sample Manufacturer Bond Strength Bonding Strength in Wet Sheet Dry Sheets (gramcis / inch) (grams / inch) Present Assignee 5.5 10.4 Invention BOüNTY Assignee 3.9 10.1 BRAWNY * James River 3.1 10.1 SPARKLE * Georgia Pacific 3.0 7.0 MARDIS GRAS * Ft. Howard 3.4 7.6 VIVA 2-PLY * Scott 3.0 4.4 HI-DRI * Kimberly Clark 3.4 5.5 * United States Patent Application Data Series No. 08 / 835,039 Each of the bond strengths of dry and wet foil in Table 6 represents an average of at least five samples. Of course, for the dry bond strength test, each of the five samples represents an average of four specimens P925 test. As clearly demonstrated by the data shown in Table 7, the adhesive composition of the present invention provides substantially improved wet laminating bond strength while maintaining a dry lamella bonding strength comparable to commercially available paper towels. available. When the paper towels that are laminated using the adhesive compositions of the present invention are immersed in water, the pattern of the pigmented adhesive is clearly visible. When the commercially available paper towels listed in Table 7 are dipped in the same manner, there is no clearly visible pattern.

Example 5 This example is intended to demonstrate the formulation of a pigmented lamination adhesive according to the present invention comprising alternative materials. Table 8 lists the composition of a laminating adhesive according to the present invention which comprises both an alternative inorganic pigmenting material and an optional cationic additive.

P925 TABLE 8 Component Concentration (Percent in Weight) Dry Resistance Additive 4.5 Pigment 18.0 Wet Resistance Resin 0.3 Optional Cationic Additive 0.7 Pig. Alternati.vo5 1.0 Water QS 100% 1. ELVANOL® 71-30 2. Solids provided by Ti-Pure® RPS Vantage Rutile Paper Slurry 3. Kymene® 557LX 4. Cypro® 515 5. Aerosil® 300 The composition is practically prepared according to the preferred method of the present invention using a laboratory mixer (Osterizer) to energize the composition as the components are mixed. The evaluation of the finished composition shows: 1) there is no visible separation after 14 days; 2) turbidity comparable with the other compositions of the present invention - 2600 NTU; 3) the whiteness of a thin layer of the adhesive composition of the present example, when the composition is applied to a tissue substrate using P925 measuring rods (available from Paul N. Gardner Co. Inc. of Pompano Beach, FL in size 8) to control the thickness of the layer, is comparable with the whiteness of an adhesive composition prepared according to Example 2 applied to a substrate tissue in the same manner and 4) viscosity comparable with other compositions of the present invention - 170 centipoise.

TEST METHODS UNION FORCE OF DRY SHEETS Samples of four finished paper products are provided. The samples are aged for at least two weeks after having allowed the adhesive system to fully cure. A three-inch strip running the full length of the sample is cut from the center of each sample. Two of the strips are cut in the machine direction and the other two are cut in the direction transverse to the machine (for example, between perforations in the machine direction or between edges in the transverse direction to the machine). The strips are spread slightly along each of the three inch edges, so that each sheet is available independent of the other. The sheets are separated manually until the sample has a calibrating length P925 two inches. Each sheet is placed in the jaw of a tension machine. An appropriate strain gauge is a Model 1451-24 supplied by the Thwing / Albert Corporation of Philadelphia, Pennsylvania. Crosshead separation speed is set at 20 inches per minute and travels 7.5 inches from an initial clearance of 2.0 inches. Data is only recorded for the last six inches of crosshead travel. The four samples are tested for tension. The four numbers are then averaged to give a single sheet joining force representative of the product from which the four samples were taken. Care must be taken that the portion of the sample that is still to be separated by the tension machine does not come into contact with the lower jaw or with the lower crosshead of the tensioning machine. If that contact occurs, it will register in the load cell and give an erroneously high reading. In the same way, care must be taken that the portion of the sample that is still to be separated does not come into contact with the portion of the sample having the sheets already separated by the tension analyzer. If the contact occurs, the apparent sheet binding force will increase falsely. If each of the aforementioned contacts happens, the data P925 should be discarded and a new sample tested.

UNIONING FORCE OF SHEETS IN HUMID Samples of four finished paper products are provided. The samples are aged for at least two weeks after having allowed the adhesive system to fully cure. A three-inch strip running the full length of the sample (for example, between perforations for material that has been converted to commercial paper towels) is cut off from the center of each sample. Two of the strips are cut in the machine direction and the other two are cut in the direction transverse to the machine (for example, between perforations in the machine direction or between edges in the transverse direction to the machine). The strips are spread slightly along each of the three inch edges, so that each sheet is available independent of the other. The sheets are separated manually until the sample has a measured length of two inches. The sheets are separated along one of the three-inch edges of the sample. The portion of the sample that has not been separated, ie the portion that has not been placed in the jaws of the tension machine, is immersed in distilled water. After the dive, the P925 sample is immediately removed from the water and left to drain for 60 seconds on a drain rack. The draining grid is provided with a square mesh of nylon threads. The threads that form the mesh are 0.015 inches in diameter with a slope of 0.25 inches. The drying rack is oriented at an angle of 45 degrees in relation to the horizontal. While drying on the drying rack, the sample is oriented so that the longer edges of the sample are aligned in a descending manner with the slope of the drying rack. The separated edges of the sheet are put back together in the drying rack so that the sample is as uniform as possible and the sample adequately drains the excess water. After it has been prepared in this way, the sample is then tested in the tension machine as described above for the bond strength of dry sheets.

VISCOSITY Overview This method is suitable for measuring viscosity as a function of tangential velocity. The sample is placed in a narrow annular volume between two concentric cylinders. The inner cylinder rotates to a P925 controlled angular velocity and the resulting torque or force generated by the sample between the two cylinders is a measure of the viscosity of the sample placed between them.

Apparatus Viscometer A suitable viscometer is available from Paar Physica USA, Inc. of Edison, NJ as the Model MCI.

Preparation of the Apparatus 1) Calibrate the viscometer according to the manufacturer's instructions. 2) The temperature of the appliance and the sample must be 23 + 1 ° C.

Method 1) Fill the external cylinder to the level indicated with the sample to be evaluated. 2) Insert the outer cylinder into the viscometer making sure that the inner cylinder is centered on it and fix the external cylinder in place. Leave at least ten seconds after fixing the external cylinder in place so that the sample fills the annular volume between the two cylinders before it begins to register P925 5§ the viscosity. 3) Set the viscometer to make a sweep between 10 and 1000 seconds and use the ramp up / ramp protocol for the viscosity measurement. Fifty measurements are made in the ramp-up portion and fifty measurements in the ramp-down portion.

Data Logging and Analysis Record the viscosity of each of the two samples at the 100-second and 1000-second speeds "from the ramp-down portion of the protocol.

LOAD DENSITY Overview The charge density of a dispersion or colloidal solution can be measured by determining the electrical potential (flow potential) between a pair of spatially separated electrodes one of which is adjacent to a surface of a sample container where the particles of the dispersion or the macromolecules of a colloidal solution have been forced to absorb and the other of which is placed in the free volume of the sample container. The counterions of any charged macromolecular particulate or species are bound P925 to flow through an oscillating piston that fixes the electric potential. The sample is then titrated to a zero flux potential (ie, to the isoelectric point) with a standard polyelectrolyte having the opposite charge to measure the charge density in microequivalents per gram. Particle Load Detector Apparatus: A suitable apparatus for measuring charge density is available from MÜTEK Analytic, Inc. of Marietta, GA, as PCD 02 Particle Load Detector. Titrator: A suitable titrator is the end point titrator Mettler model DL21 automatic with two plunger burettes that is also available from MÜTEK Analytic, Inc. of Marietta, GA.

Standard Materials Polyelectrolyte standard solutions are also available from MÜTEK Analytic. The cationic standard is 0.001 N diallyl dimethyl ammonium polychloride. The anionic standard is sodium polyethylene sulfate 0.001 N.

Operation 1) Fix and calibrate the particle loading detector according to the manufacturer's instructions. It is very important that the ambient temperature must be greater than 15 ° C, P925 preference approximately 25 ° C, for accurate measurement. 2) Fix and calibrate the titrator according to the manufacturer's instructions. 3) Rinse the sample cell and the plunger of the particle charge detector with the sample. The sample can be filtered (100-mesh screen) to remove larger particles that may interfere with the operation of the plunger even if they are only a small portion of the loaded species. 4) Dispense a controlled amount of the sample into the sample cell that was rinsed. A preliminary titration may be necessary to determine the amount of sample that will require between 0.5 and 15 milliliters of titrant. At least 10 milliliters of liquid are required to cover both electrodes. Samples may be diluted with deionized water to provide a sample of at least 10 milliliters volume that requires at least 0.5 to 15 milliliters of titrant. 5) Insert the plunger into the sample container and place the container in the particle charge detector, making sure that the electrodes are in contact and the plunger is coupled with the drive mechanism. 6) Connect the plunger and let the flow potential stabilize (approximately 2 minutes).

P925 7) Titrate the sample to the isoelectric point using the appropriate polyelectrolyte solution. "That is, titrate cationic samples with the anionic polyelectrolyte and titrate anionic samples with the cationic polyelectrolyte.Record and ^ Data Analysis 1) Record the amount of titrant required to take the sample to the isoelectric point 2) Calculate the charge density q (microequivalents per gram) using the following equation: VxC lQQQ q = W Where: V is the volume of titrant required (milliliters); C is the concentration of polyelectrolyte (microequivalents per milliliter); and W is the solids content in the sample (for example, for a sample of 10 milliliters of a 0.1% Ti02 suspension, W = 0.01 grams) 3) Report the result of each measurement made.

DISTRIBUTION OF PARTICLE SIZE Overview The distribution of the particle size of the P925 pigment particles formed in the process of the present invention can be measured using a light scattering apparatus. Both coherent and non-coherent light sources are used, depending on the expected particle size range.

Apparatus A suitable apparatus is available from Horiba Instruments, Inc. of Irvine, CA as Model LA910. The Horiba LA910 measures the Particle Size Distribution (PSD) using a dispersion system. Both a coherent (laser) and a non-coherent light source are supplied for the measurement of a wide range of PSDs. This apparatus can determine four distributions (Volume, Number, Area and Length) for a given sample. Software for an associated computer is provided to control the apparatus and convert the luminous intensity data that is actually measured in any of the distributions identified above. Volume Distribution is preferred to follow structural changes. The median particle size is preferred as a unique numerical descriptor of the PSD to provide an adequate description in cases that deviate from the normal distribution. The Horiba LA910 has the ability to separate aggregates for a power of P925 low sonication (approximately 40 watts). The measurement of PSD without sonication is preferred to better understand any agglomeration that could result from a particular mixing process.

Materials Standard Calibration Pattern Nanosphere RM Standard Polystyrene particles supplied by Duke Scientific of Palo Alto, CA. These patterns are easy to find in NIST.

Preparation of the Relative Refraction Index Apparatus (RRI): 2.00-OOi Agitation 3 Circulation 4 Sonication Outside (Off) Method 1) Prepare and calibrate the instrument according to the manufacturer's instructions. 2) Measure the particle size distribution for a target (deionized, deaerated water) to verify the baseline of the instrument by filling the sample cell with water and pressing the measure option on the computer screen. 3) Place 150 milliliters of deaerated water, P925 deionized in the sample cell and enter the cell in the device. 4) Add the sample drop by drop until the scale of light transmission (blue scale) as determined by the apparatus is between approximately 70% and 75%. 5) Press the measure option on the computer screen to collect the sample data and determine the particle size distribution of the sample.

Registration and Data Analysis 1) Measure the particle size distribution for at least two samples. 2) Determine whether the distribution is monodisperse or polydispersed. 3) For monodisperse distributions report the median particle size. 4) For polydispersed distributions, report the particle size defined by each distribution peak.

TURBIDITY Overview Turbidity is a measure of the opacity of liquid suspensions. Turbidity is measured by determining the P925 amount of light scattering due to suspended particles.

Instrument Turbidimeter A suitable turbidimeter is available from HACH Comapny of Loveland, CO as Model 2100AN.

Materials Pattern The standard turbidity materials (StablCal Standards) that have turbidity values of < 0.1, 20, 200, 1000, 4000 and 7500 Nephelometric Turbidity Units (NTU) are also available from HACH Company.

Method 1) Prepare and calibrate the turbidimeter according to the manufacturer's instructions. 2) Dilute 0.4 grams of the pigmented adhesive with 1000 milliliters of water and mix for one minute. A magnetic stirrer such as the Corning Model PC-351 which is available from Corning Glass Works (Corning, NY) is suitable. 3) Allow the diluted sample to equilibrate for 1 minute. 4) Transfer an adequate volume (-30 milliliters) to the sample cell.

P925 5) Measure the turbidity according to the manufacturer's instructions. 6) Record the turbidity that was measured.

Registration and Data Analysis 1) Report the turbidity value in Nephelometric Turbidity Units, NTU.

MIXING ENERGY Overview The current and voltage are measured and used to calculate the power supplied to the energizing medium.

Instrument Power Analyzer A suitable power analyzer is available from Fluke Corp. of Everett, WA as Model 41B Power Harmonios Analyzer. Amperage Probe A Model 801-1000s is suitable, which is also available from Fluke Corp.

Method 1) Make sure that the potentiometer is calibrated according to the manufacturer's instructions.

P925 2) Place the amperage probe around one of the three conductors of the power supply line of the energizing medium. Connect the voltage probes to the other two conductors of the supply line. The Fluke 41B calculates a three-phase power output reading from a single single-phase measurement of a balanced three-conductor load. The power measurements were sent and recorded in a Microsoft Excel spreadsheet using the software supplied with the instrument (Fluke View version 3.0). 3) Measure the energy consumption with the empty tank by placing a small amount of water around the seal in the bottom. Measure the energy consumption in the full speed range for the specific energizing medium to be evaluated. 4) Record the power analyzer power reading every 10 seconds at least 5 times in each step of adding the adhesive manufacturing process described above. If desired, hardware and software for data acquisition can be used to automatically sample and record the power readings.

Record? _ Data Analysis 1) Calculate the Net Power for each addition stage by subtracting the energy consumption at the speed of the run, from the energy consumption while the material is added. 2) Calculate the Net Power per Unit of Mass for each stage dividing the Net Power among the mass of material to be energized after the addition step. 3) Report Net Power and Net Power per Unit of Mass for each stage of addition.

P925

Claims (2)

CLAIMS: 1. An adhesive composition for laminating an absorbent paper product, the adhesive composition comprising: between 2% and 7% by weight of a dispersible or water soluble dry strength binder material; between 0.05% and 5% by weight of a cationic resin of wet strength, soluble in water; between 58% and 91% by weight of water; which is characterized in that the adhesive composition also comprises between 7% and 30% by weight of a pigment suspended in the adhesive composition. 2. An adhesive composition according to claim 1, wherein the dry strength binder material is selected from the group consisting of polyvinyl alcohol, polyvinyl acetates, carboxymethyl cellulose resins, starch-based resins and mixtures thereof. An adhesive composition according to any of the preceding claims, wherein the pigment is selected from the group consisting of kaolin, calcium carbonate, zinc oxide and titanium dioxide. 4. An adhesive composition according to any of the preceding claims, wherein the pigment paste is supplied to the adhesive composition as a P925 dispersion in water and the dispersion is stabilized using an anionic dispersion aid. An adhesive composition according to any one of the preceding claims, wherein the water-soluble cationic resin is selected from the group consisting of polyamide-epichlorohydrin resins, glyoxal-modified polyacrylamide resins, polyethyleneimine resins and mixtures thereof. An adhesive composition according to claim 5, wherein the polyamide-epichlorohydrin resin comprises the reaction product of an epichlorohydrin and a polyamide containing secondary amino groups, the ratio of epichlorohydrin to secondary amino groups of the polyamide is between 0.5 and 2 a
1. l. 7. An absorbent paper product, the paper product comprising at least two sheets of paper, wherein the sheets are adhesively laminated using a lamination adhesive composition according to any of the preceding claims. 8. An absorbent paper product according to claim 7, wherein the product comprises between 6 grams of adhesive solids per kilogram of paper and 10 grams of adhesive solids per kilogram of paper. 9. An absorbent paper product according to claims 7 or 8, wherein the paper product is P925 a paper towel. A method for producing a pigmented adhesive composition, the method comprising the steps of: a) providing an aqueous solution or dispersion of a first resin; b) providing energizing medium characterized in that the energizing medium has the ability to transfer at least 5 watts per kilogram of power to the first resin solution or dispersion; c) energizing the first resin solution or dispersion with the energizing medium; d) provide an aqueous dispersion of pigment particles, the pigment particles have a mean particle size; e) mixing the pigment dispersion in the first resin solution or dispersion using the energizing medium; f) providing an aqueous solution or dispersion of a second resin; and g) mixing the second aqueous solution or dispersion of resin in the mixture of the first resin solution with the pigment dispersion using the energizing means to form the pigmented adhesive composition, wherein the median particle size without sonication of the particles of pigment in the adhesive composition Pigmented P925 is not greater than
2. 2.5 times the median particle size without sonication of the pigment particles in the pigment dispersion. P925