KR100347744B1 - Pigmented adhesive composition for laminating tissue paper products and methods for producing such compositions - Google Patents

Abstract

The present invention relates to an adhesive composition suitable for laminating absorbent paper products and a paper product laminated using the adhesive composition. The adhesive composition provides a visible signal and wet bond strength that retains the desired properties when the absorbent paper product is wet. The adhesive composition comprises a water soluble or water dispersible dry strength binder, a water soluble cationic wet strength resin and a pigment. Also disclosed are methods of making the adhesive composition. The method includes, as an essential step, providing energizing means capable of transmitting power of at least about 5 W / kg to the resin solution or dispersion when the pigment dispersion is added.

Description

Colored adhesive composition for laminating a tissue paper product and a method for manufacturing the same {PIGMENTED ADHESIVE COMPOSITION FOR LAMINATING TISSUE PAPER PRODUCTS AND METHODS FOR PRODUCING SUCH COMPOSITIONS}

Paper products are well known in everyday life. Certain types of paper products are referred to as tissues and are used as paper towels, cosmetic tissues, and toilet tissues.

Tissue paper products may include one or more layers, but may often contain two or more layers. As used herein, "ply" refers to a single sheet that has been removed from forming wires or similar devices and dried without the addition of additional fibers.

Of course, the plies can be laminated, where each layer can be made of different types of fibers. Lamination provides the advantage that the core layer can have strength in the tissue paper product by having a relatively strong fiber. The outside of the center layer may be short fibers that give the user a soft touch. Lamination can be advantageously made by US Pat. No. 3,994,771, commonly assigned to Morgan Jr., et al., Filed November 30, 1976, and incorporated herein by reference.

Often, two or more layers are joined together to produce a paper product. Joining multiple plies provides the advantage that the resulting stacks have a bending modulus lower than one ply of the same thickness. This in turn provides the advantage that a soft touch is perceived by the user. In addition, the absorbency and caliper are typically improved. Furthermore, combining three plies together can provide strength and flexibility, respectively, by allowing the paper product to have different center plies and outer plies in the stack.

Multiply tissue products are typically cellulosic. As used herein, “cellulosic” includes cotton linter, rayon, bagasse, more preferably wood pulp (eg, softwood (bark or softwood) or hardwood (pizza or deciduous)). (But not limited to) refers to a paper product comprising at least about 50% or at least about 50% by volume of cellulosic fibers, wherein the fibers can be recycled. The remainder of the fibers may be synthetic fibers such as polyolefins or polyesters. Cellular plies are often joined together by an adhesive. Bonding cellulosic plies with adhesives is well described in U. S. Patent No. 5,143, 776, commonly assigned to Givens on Sep. 1, 1992, which is incorporated herein by reference.

However, bonding multiple cellulosic plies of paper products with an adhesive can result in unsatisfactory performance. In particular, paper products used as paper towels, cosmetic tissues and toilet tissues should have adequate lap bond strength. As used herein, "ply bond strength" refers to the force required to separate two adjacent plies from each other, as described below.

Frequently, tissue paper products, especially paper towels, are wet when used. If the wet ply bond strength is insufficient, the ply separates during use and the paper product tears. While simply increasing the wet fold bond strength appears to be an easy problem, dry fold bond strength is directly related to wet fold bond strength. In the prior art, the dry fold bond strength becomes too large if the wet fold bond strength is increased to an appropriate level. Too high a dry lap bond strength typically decreases flexibility and absorbency.

U.S. Patent Application Serial No. 08 / 835,039, filed and filed on March 27, 1997, in the name of Neal et al., Is dried on adhesive bonds with a cationic wet strength resin that provides wet fold bond strength. A combination of nonionic adhesive materials that provide lap bond strength is described. This adhesive composition has been found to allow the multi-ply paper article laminated with the adhesive to have adequate wet ply bond strength without having too large dry ply bond strength.

It is also desirable for the laminated paper towel to provide a signal to the user that the wet paper bond strength is maintained when the paper product is wet in use. As is known in the art, many laminated paper towel products are provided with an aesthetically pleasing embossing pattern, wherein the laminating adhesive is placed on the distal end of such embossing to bond the plies together. It is also known that the embossing pattern disappears when the paper towel is wet. U.S. Patent Application Serial No. 08 / 749,708, filed on November 15, 1996 in the name of Steinhardt et al., Assigned an indicator means to maintain a satisfactory pattern when the paper towel is wet. Discloses the use of. One of the means disclosed in this patent application is a laminating adhesive further comprising an opaque agent such as titanium dioxide. However, commonly available titanium dioxide pigment dispersions also typically include anionic polymers to prevent such dispersions from agglomerating and settling. Combining cationic wet strength resins and anionic stabilized dispersions found to provide improved wet fold bond strength will result in adhesive compositions that further provide a visible signal of improved wet fold bond strength. However, the incompatibility of anionic and cationic materials is well known in the art.

Accordingly, there is a need for adhesive compositions that also include anionic stabilized pigment dispersions having improved and improved wet fold bond strength. There is also a need for a method of blending anionic stabilized pigment dispersions with cationic wet strength resins to form colored adhesive compositions. There is also a need for colored adhesive compositions having minimal pigment particle agglomeration and methods of minimizing such agglomeration to maximize the opacity of such colored adhesive compositions.

Applicants have found certain compositions and methods that meet these needs as will be readily apparent when reference is made to the following description in conjunction with the accompanying examples.

Summary of the Invention

The present invention provides an adhesive composition suitable for laminating multi-ply cellulosic paper products. The adhesive composition may comprise (a) about 2 to about 7 weight percent of a water soluble or water dispersible dry strength binder material, (b) about 0.05 to about 5 weight percent of a water soluble cationic wet strength resin, and (c) about 7 anionic stabilized pigment. To about 30% by weight, and (d) about 58 to about 91% by weight of water.

Preferably the adhesive composition is prepared using an energizing means that transfers at least about 5 W / kg to the adhesive composition. This transfer effectively separates the cationic wet strength resin from the anionic stabilized pigment (ie, the energizing means effectively maintains a positive charge density) to minimize aggregation and adhesive instability (e.g. coacervation) of the pigment particles. Sufficient energy is provided to the composition to be prepared below.

All percentages, ratios, and ratios herein are by weight unless otherwise specified.

The present invention is described in more detail below.

The present invention relates to adhesive compositions for laminating multi-ply cellulosic fibrous structures, such as tissue paper products, methods of making such adhesive compositions, and tissue products laminated using such adhesive compositions.

This specification concludes with the claims particularly pointed out and specifically clarified the subject matter regarded as the invention, but the invention can be better understood by reading the following detailed description and the appended examples.

As used herein, the term "comprising" means that various components, components or steps may be used jointly in the practice of the present invention. Accordingly, the term "comprising" encompasses the terms "essentially configured" and "consisted of", which are restrictive terms.

The present invention includes colored adhesive compositions suitable for joining two or more tissue plies to maximize the opacity of the pigment, methods of making such compositions, and paper products laminated using such compositions. As will be described later, the plies are cellulosic and they can be prepared according to the same or different production methods.

fold

Each ply may have a number of embossings that project outwardly from the plane of the ply to an adjacent ply. Similarly, adjacent plies may have opposing protrusions protruding toward the first ply. If a three-ply paper product is desired, the center ply may have embossing extending outward in both directions, but center plies without embossing or with unidirectional embossing may also be used.

The folds are assigned to Trokhan on January 20, 1987 and commonly assigned to U.S. Patent No. 4,637,859 and commonly assigned to Trocan on March 4, 1980, which are incorporated herein by reference. US Pat. No. 4,191,609, which is incorporated herein by reference. Alternatively, the plies can be fabricated using the uncreped but air-dried technique described in European Patent Application No. 0617164 A1, published September 28, 1994, or conventionally dried using felt as known in the art. Can be prepared.

In the present invention, each ply has a basis weight of about 8 to about 30 lb / 3,000 ft ² (13 to 48 g / m ² ) and preferably about 11 to about 18 lb / 3,000 ft ² (18 to 29 g / m ² ) And preferably have a composition of hardwood and / or softwood treated by any means well known in the art.

The fibers constituting the ply of the paper product are preferably cellulosic (e.g. cotton linter, rayon, bagasse, more preferably wood pulp (e.g. softwood (bark or softwood)) or hardwood (pizza or deciduous). ]to be. As used herein, laminated paper products are considered "cellulosic" if they comprise at least about 50% or at least about 50% by volume of cellulosic fibers, including but not limited to the aforementioned fibers. The remainder of the fibers that make up the laminated paper product may be synthetic fibers such as polyolefins or polyesters. Of wood pulp fibers comprising softwood fibers having a length of about 2.0 to about 4.5 mm and a diameter of about 25 to about 50 μm and hardwood fibers having a length of less than about 1.7 mm and a diameter of about 12 to about 25 μm. The cellulosic mixture has been found to work well with the laminated paper products described herein.

When wood pulp fibers are selected for the multiply paper products of the present invention, the fibers may be selected from chemical methods such as sulfite, sulfate and soda methods; And any pulping method, including mechanical methods such as the stone chain pulping method. Alternatively, the fibers can be made by a combination of chemical and mechanical methods, or the fibers can be made by a method of recycling waste paper. The form, combination and treatment of the fibers used are not critical to the invention. Hardwood fibers and softwood fibers may be laminated or homogeneously blended over the entire thickness of the laminated paper product.

Adhesive composition

The plies of the multiply paper product are bonded to each other using the colored adhesive composition prepared according to the invention. The adhesive composition is preferably applied to one or more embossings. Of course, the adhesive can be applied to both layers of embossing. Adhesives according to the present invention comprise a mixture of dry strength binders (eg, fully hydrolyzed polyvinyl alcohol adhesives), cationic wet strength resins (eg, thermosetting cationic resins) and anionic stabilized titanium dioxide slurries. Particularly preferred adhesive compositions comprise about 58 to about 90 parts water, 2 to 7 parts dry strength binder solids, 0.05 to 5 parts cationic wet strength resin solids and 7 to 30 parts titanium dioxide pigment. Each type of compound will be described in detail below.

Importantly, the adhesive composition should be applied to the plies in an appropriate amount to achieve satisfactory wet and dry ply bond strength and satisfactory signal strength in the post-treated laminated tissue product of the present invention. Suitable application methods are described below in the Ply Embossing and Lamination sections. It is also important to apply the components of the adhesive composition in the correct proportions. Those skilled in the art will appreciate that the absolute concentration of solid components of the composition may be at any limit, such as the viscosity of the composition, provided that the adhesive solids applied to the ply are sufficient to provide satisfactory wet and dry fold bond strength and satisfactory signal strength. It will be understood that it can be changed within). In particular, it is important that the ratio of dry strength binder solids to cationic wet strength resin solids is within an acceptable range to provide adequate wet ply bond strength without having too high dry ply bond strength. It is also important that the ratio of cationic charged material solids to anionic charged material solids is within an acceptable range to provide a stable adhesive composition with sufficient signal strength.

Specifically, Applicant has found the following.

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 fold bond strength and dry fold bond strength. Preferably, the ratio is less than about 4: 1.

2) The ratio of anionic charged material solids to cationic charged material solids should be such that the charge density of the final adhesive composition is at least about 25 micro equivalents / g (as will be understood by those skilled in the art). Likewise, the specific weight ratio will depend on the charge density of the individual materials). In preferred materials discussed herein, these are anionic charged pigment solids (pigment solids + anionic suspending aid solids) versus cationic solids (wet strength resin solids or other cations added to maintain net charge density). Sex-charged solids). Preferably the ratio of anionic solids to cationic solids is less than about 30: 1. More preferably the ratio is less than about 15: 1.

Dry strength binder material

The adhesive composition of the present invention comprises from about 2% to about 7%, preferably from about 3.5% to about 6.5% by weight of a dry strength binder material selected from the following group of materials as essential components: polyacrylamide (e.g., West New Jersey) Accostrength 711, manufactured by CyTec Industries, Patterson; Starch available from National Starch and Chemical Company, Bridgewater, NJ (e.g. RedoBOND 5320, 2005 and 3030) or Avebe America, Princeton, NJ Amylose 1100, 2200 or salbitose available from; Polyvinyl alcohol (eg, Evanol 71-30, supplied by DuPont Corporation, Wilmington, Delaware); And / or guar gum or soybean gum. Preferably, the dry strength binder material is selected from the group consisting of polyvinyl alcohols, starch-based resins, and mixtures thereof. The dry strength binder material serves to ensure that the multiply paper products of the present invention have the appropriate dry ply bond strength.

In a particularly preferred adhesive composition according to the invention, the dry strength binder comprises polyvinyl alcohol. The polyvinyl alcohol component may have any water soluble or water dispersible molecular weight sufficient to form an adhesive film. The weight average molecular weight is generally about 40,000 to about 120,000, more preferably 70,000 to 90,000. Polyvinyl alcohol in solid form is commercially available under several trade names, such as EVANOL (Dupont), GELBATOL (Monsanto), VINOL (Air Products) and POVAL (Kuraray). These grades have a degree of hydrolysis of about 80 to about 100%. Those skilled in the art will appreciate that the water solubility will be improved due to the decrease in the degree of hydrolysis and the molecular weight, but the adhesion is lowered. Therefore, the properties of polyvinyl alcohol will have to be optimized for the particular application. Particularly preferred polyvinyl alcohol is Ebanol 71-30 provided by DuPont Corporation, Wilmington, Delaware. Evaol 71-30 has a weight average molecular weight of about 77,000 and a degree of hydrolysis of about 99%.

Alternatively, the dry strength binder may comprise starch. In general, starches suitable for the practice of the present invention are characterized by the ability or water solubility to form stable dispersions that are hydrophilic. Examples of starch materials include corn starch and potato starch, but do not limit the range of suitable starch materials here. Preferred are waxy corn starch, which is industrially known as Amioka starch. Amioka starch differs from normal maize starch in that normal corn starch contains amplofectin and amylose, whereas amioka starch is completely amylopectin. Several unique properties of Amioca starch are further described in "Amioca-The Starch from Waxy Corn", HHSchopmeyer, Food Industries, December 1945, pp. 106-108 (Vol.pp. 1476-1478). . Starch may be granular or dispersed. Preferred starch, RediBOND, is a material that is dispersed for immediate use. Granular starch, such as amylose 1100, is preferably sufficiently cooked to cause swelling of the granules. More preferably, the starch granules are ripened and swollen at a point just prior to the dispersion of the starch granules. Such highly swollen starch granules will be referred to as "fully cooked". In general, the dispersion conditions may vary depending on the size of the starch granules, the crystallinity of the granules and the amount of amylose present. For example, fully cooked Amioka starch can be prepared by heating an aqueous slurry of about 4% consistency of starch granules at about 190 ° F. (about 88 ° C.) for about 30 to about 40 minutes. Another example starch material that can be used is a modified cationic, such as modified to have nitrogen-containing groups such as methylol groups and amino groups attached to nitrogen, available from National Starch & Chemical Company, Bridgewater, NJ. Or anionic starch. Given that these modified starch materials are more expensive than unmodified starch, unmodified starch materials are generally preferred.

Wet strength resin material

The adhesive composition of the present invention also contains from about 0.05% to about 5.0% by weight, preferably from about 0.1% to about 2.5% by weight of a wet strength resin material selected from the following group of materials as essential components: polyamide-epichlorohydrin resin , Glyoxalated polyacrylamide resin, styrene-butadiene latex; Insoluble polyvinyl alcohol; Urea-formaldehyde; Polyethyleneimine; Chitosan polymers and mixtures thereof. Preferably, the wet strength resin is a water soluble cationic resin selected from the group consisting of polyamide-epichlorohydrin resins, glyoxalated polyacrylamide resins, polyethyleneimine resins, and mixtures thereof.

Polyamide-epichlorohydrin resins are cationic wet strength resins that are known to be particularly useful. Preferably, the polyamide-epichlorohydrin resin comprises a water soluble polymeric reaction product of epichlorohydrin with a water soluble polyamide having a secondary amine group. The ratio of epichlorohydrin to secondary amine groups of the polyamide is preferably from about 0.5: 1 to about 2: 1. Preferably the water soluble polyamide is derived by reacting a polyalkylene polyamine with a saturated aliphatic divalent carboxylic acid having about 3 to 10 carbon atoms. The molar ratio of polyalkylene to divalent carboxylic acid is preferably from about 0.8: 1 to about 1.5: 1. Preferably the saturated aliphatic divalent carboxylic acid is adipic acid and the polyalkylene polyamine is diethylene triamine. Most preferably, the water soluble polyamide contains a repeating group of the formula:

In the above formula,

n and x are each 2 or more,

R is a divalent hydrocarbon radical of divalent carboxylic acid having about 3 to 10 carbon atoms.

Resins of this type are commercially available under the trade names KYMENE (Hercules Incorporated) and CASCAMID (Borden). An essential feature of these resins is that they are phase compatible with polyvinyl alcohol. That is, they are not phase-separated in the presence of aqueous polyvinyl alcohol.

Suitable forms of such resins are described in US Pat. No. 3,700,623, issued October 24, 1972, and 3,772,076, issued November 13, 1973, to Keim, which is incorporated herein by reference. . A useful source of polyamide-epichlorohydrin resin is Hercules Incorporated, Wilmington, Delaware, which is commercially available under the trade names Kymene 557H, Kymene 557LX and Kymene 557ULX, desirable.

Base-activated polyamide-epichlorohydrin resins that are also useful in the present invention are also sold under the tradename Kemen 450 by Hercules Incorporated, Wilmington, Delaware. An example of another salesperson of base-activated polyamide-epichlorohydrin resin is marketed under the Santores trademark, such as Santores 31 by Monsanto Company, St. Louis, Missouri. These types of materials are generally described in US Pat. No. 3,855,158, issued to Petrorovich on December 17, 1974; 3,899,388 to Petrovic, issued August 12, 1975; No. 4,129,528 to Petrovic, issued December 12, 1978; No. 4,147,586, issued to Petrobeach on 3 April 1979; And 4,222,921 to Van Eenam, issued September 16, 1980, all of which are incorporated herein by reference.

Glyoxalated polyacrylamide resins have also been found to be useful as wet strength resins. These resins are described in US Pat. No. 3,556,932 to Coscia et al. On January 19, 1971 and US Pat. No. 3,556,933 to Williams et al. On January 19, 1971, These are incorporated herein by reference. The salesman of the polyacrylamide resin is Cytec, of Stanford, Connecticut, and sells the resin under the trade name Parez 631NC.

Other water soluble cationic resins useful in the present invention are urea formaldehyde and melamine formaldehyde resins. More common functional groups of these multifunctional resins are nitrogen-containing groups such as methylol groups and amino groups attached to nitrogen. Polyethylenimine type resins may also be useful in the present invention.

Pigment

As described in the background section above, it is desirable to provide the user with an indication that desired properties such as wet lap bond strength are maintained when the paper product laminated by the adhesive is wet. As described above and as described in US patent application Ser. No. 08 / 749,708, which is also incorporated herein by reference, a laminating adhesive composition comprising a pigment may provide such a signal. Is a major factor in determining the opacity efficiency of. Table 1 below compares the refractive indices of pigments commonly used in the paper industry.

compound Refractive index Titanium dioxide Rutile 2.72 Anatase 2.55 Zinc oxide 2.02 Kaolin clay Filler 1.57 Calcined Kaolin Clay 1.57 Potassium carbonate Natural polishing 1.56 PCC-Analysis 1.66 Talc 1.57 Precipitated Silica 1.45

To be suitable for use as a pigment for the purposes of the present invention, such inorganic pigment material must have a refractive index of at least about 1.4. Preferably the refractive index is at least about 1.7. Particularly preferred inorganic pigment materials have a refractive index of at least about 2.0.

In addition to the refractive index, the particle size of the opacity agent also has a great effect on the opacity of the adhesive composition of the present invention. That is, for pigments of a predetermined concentration in the adhesive composition, compositions comprising pigments with smaller particle sizes will be more opaque. Pigments suitable for use in the present invention have an unsonicated median particle size of less than about 1.4 microns. Preferably the median particle size is less than about 0.8 micron. More preferably, the median particle size is less than about 0.6 microns. The method of measuring the intermediate particle size without sonication is described in the test method section below.

Particularly preferred pigment material is titanium dioxide (TiO ₂ ). The two crystalline forms of TiO ₂ are anatase and rutile. The rutile form is most opaque due to its high refractive index. In the papermaking field, it is known that a certain opacity can be achieved, typically with about 15-20% less rutile than Anatase. Titanium dioxide is commercially available in dry powder form and as a slurry in water. For the purposes of the present invention, the water slurry form is preferred because it is easily mixed with other components of the adhesive composition of the present invention and the pigment particles are more fully dispersed to provide good opacity.

In order to maintain the suspension of TiO ₂ , additional components are included in commercial TiO ₂ slurries. In particular, dispersion aids are used to prevent suspended TiO ₂ particles from clumping or precipitation. Dispersion aids come in two forms: stearic stabilizers and electrostatic stabilizers. Stearic stabilizers surround the TiO ₂ particles suspended with the absorbed polymer layer. Stearic interactions between different particulate polymer layers prevent the particles from getting close enough to aggregate. Typically, the stearically stabilized slurry is very viscous because of the absorbed polymer layer. Titanium dioxide particles can also be electrostatically stabilized by enclosing a charged class. This class may be cationic or anionic. Cationic TiO ₂ slurries are not common because the majority of TiO ₂ is used in the paint and paper industry and anionic slurries are required in this process. An example of a suitable anionic electrostatic suspending aid is sodium polyacrylate as described in US Pat. No. 4,503,172, issued to Farr et al. On March 5, 1985. Such materials are available as Dispex N40V manufactured by Allied Colloids, West Polk, Virginia.

A suitable commercial TiO ₂ slurry is Ti-Pure ™ RPS Vantage Rutile Paper Slurry, available from Dupont Company, Wilmington, Delaware. This material is an anionic stabilized slurry in the rutile form of TiO ₂ in water with a nominal TiO ₂ solids content of 71.5%. The unsonicated median particle size of this material is typically less than 0.5 micron.

When TiO ₂ pigments are used in accordance with the present invention it has been found that these TiO ₂ slurries provide a visible signal of properties in the desired wet use. Applicants have found that the colored adhesive composition according to the invention should comprise at least about 7% TiO ₂ solids in order to provide a satisfactory visible signal of the desired wetting properties. TiO ₂ solids content of at least about 30% no longer improves signal strength. Preferably the TiO ₂ solids content should be about 10 to about 30%. More preferably, the TiO ₂ solids content is about 15 to about 25%. Those skilled in the art will appreciate that when other pigments are used the amount of pigment needs to be adjusted to provide a satisfactory visual signal. As mentioned above, the relative index of refraction between TiO ₂ and potential replacement pigments can provide an initial index of how much control is needed.

Alternatively, organic coloring means, such as Ropaque HP91, from Rohm and Haas Corporation, Philadelphia, PA may be used to replace more than a portion of the titanium dioxide. Such organic coloring means are hollow polymeric spheres which serve as aqueous emulsions. Since the sphere is hollow, light bends several times while passing through the dispersion of the pigment. This multiple bend provides an apparent refractive index with hiding power comparable to TiO ₂ . Since such organic coloring means are also stabilized anionic, the problem of incompatibility with the cationic wet strength resins discussed above also affects the stability and opacity of the adhesive composition comprising the organic coloring means.

Another inorganic coloring means that can be used as a replacement for at least a portion of the titanium dioxide in the adhesive composition of the present invention is silica (eg, fumed silica, colloidal silica, etc.). Suitable fumed silica is AEROSIL 300 available from Degussa Corp., Ridgefield Park, NJ. As is evident from Example 5, the colored adhesive composition comprising such another inorganic coloring means provides the desired turbidity and viscosity as discussed above. Applicants also believe that replacing a portion of titanium dioxide with silica can reduce wear in the adhesive formulation and application device because of the small final particle size of the silica particles. For example, the AEROSIL 300 discussed above has a final particle size of 7 nm compared to the 0.5 micron of the TiO ₂ pigments discussed above.

Any cationic additive

As is well known, the cationic class carries a positive charge and the anionic class carries a negative charge. One measure of such charge is charge density. Methods of measuring charge density are provided in the Test Methods section below. Applicants have found that suitable adhesive compositions according to the invention should have a positive charge density. In other words, suitable adhesive compositions according to the invention are at least slightly cationic ((+) charge density). One of the advantages of the process of the present invention is that a portion of the blend is negatively charged during the addition of the remaining charged component of the composition by energizing one of the anionic or cationic components of the composition before starting to add another component. It is to prevent the state with density (this negative charge density has been found to increase the risk of coacervation, separation and opacity efficiency when the components are mixed under low energy conditions). By providing sufficient energy for the mixing step, the formation of a substantial portion of the blend with negative charge density and the resulting coacervation is significantly reduced.

Table 2 shows the charge density values of representative components suitable for use in the adhesive composition of the present invention.

ingredient Charge Density (Micro Equivalent / g) ^* Cationic material Kemen 557LX +3243 Readybond 5320 +264 Anionic material TiO ₂ Slurry (Ti-Pure RPS) -48 * 100% solids basis

The relative amount of these components in the composition will determine the charge density of the composition. For example, a composition comprising about 1.5% of chimen 557LX and about 23% of TiO ₂ prepared according to the method of the present invention has been found to have a charge density of about +185 microequivalents / g. On the other hand, a composition comprising about 0.3% chimen 557LX and about 23% TiO ₂ was found to have a charge density of about −1.7 microequivalents / g. Preferably, the charge density of the post-treated colored adhesive composition is at least about +25 micro equivalents per gram of dispersed solids. Preferably, the charge density is at least about +30 micro equivalents / g, more preferably at least about +50 micro equivalents / g.

As described below, the process of the present invention is particularly effective in minimizing pigment aggregation in the colored adhesive compositions prepared herein. However, it is still necessary to maintain the minimum (+) charge density in the post-treated adhesive composition to maximize the stability of the composition. For example, certain adhesive compositions may not include sufficient cationic wet strength resin to maintain positive charge density, which adds to the risk of coacervation and agglomeration. If the charge density contribution from the cationic material in the composition is insufficient, a material having a positive charge density (ie, cationic additive) may be added to the composition to compensate for this insufficient charge density. Suitable materials include cationic starch (Celquat L200 available from National Starch & Chemical Company, Bridgewater, NJ) and quaternary ammonium compounds (DP- from Witco Chemical Company, Dublin, Ohio). Available as SC-505-91). Particularly preferred cationic additives are relatively low molecular weight polyamines with high charge density. A particularly preferred material of this type is Cypro 515, available from Scitech, Stamford, Connecticut, with a charge density of about +6400 microequivalents / g (based on 100% solids). For example, when 0.6% of Cypro 515 is added to 0.3% of the Kymene 557LX solution prior to the addition of TiO _2, the composition after the addition of TiO _{2 results in} a charge density of +35 microequivalents / g instead of the above-1.7 microequivalents / g Have This charge density has been found to provide a suspension that is suitably stable for use as a laminating adhesive.

Adhesive manufacturer

As mentioned above, Kymene, a preferred wet strength resin, is highly cationic and therefore when it is mixed with an anionic stabilized TiO ₂ slurry, it is an anionic component of the adhesive composition (e.g. anionic). Pigment dispersion), resulting in layering and separation of the adhesive composition due to coacervation. Example 1 below shows this action.

Surprisingly, Applicants have found that by properly blending the components identified above, it is possible to overcome the well-known difficulties in preparing stable compositions comprising cationic and anionic materials.

In particular, Applicants are able to produce markedly stable colored adhesive compositions by using the methods described in detail below which energize one of the anionic or cationic components of the composition before adding the other of the components. I found out. The liquid substance is "energized" if the "energizing means" can provide at least about 5 W / kg when the liquid is blended. Preferably, the energizing means should be able to transfer at least about 15 W / kg when the liquid is blended. More preferably, the energizing means should be able to transfer at least about 25 W / kg when the liquid is blended. The method of measuring the transmitted energy (W / kg) is described in the Test Method column.

Suitable energizing means include batch mixers that provide high stirrer tip speeds (such as blenders available from Sunbeam Corp., Delray Beach, FL under the trade name Osterizer); Rotor / stator high shear mixers available from Charles Ross Son, Hofoge, NY; And in-line mixers available from Quadro Inc., Milburn, NJ as Quadro ZC. Particularly preferred energizing means is the Bredo Liquewipier model LOR supplied by Bredo Likwifier, Kansas City, Missouri.

Moreover, Applicants have found that when such a method is used, the median particle size of the pigment in the post-treated adhesive composition is comparable to the unsonicated median particle size in the original pigment dispersion. That is, the process of the present invention utilizes pigment dispersions in a highly efficient manner to provide an adhesive composition with maximum opacity.

This efficiency is a table comparing turbidity (the turbidity is a measure of opacity-the method of measuring turbidity is in the test method section) of the colored adhesive composition prepared according to the methods described in Examples 1 and 2 below. It is very clearly shown in 3.

Turbidity (NTU) Unsonicated medium particle size (microns) Compositions Prepared According to the Method of Example 1 1217 ^* 2 peaks (2.2, 17.1) Compositions Prepared According to the Method of Example 2 3467 ^* 0.5 * Measured at a concentration of 0.5 g of adhesive in 1000 ml water

As can be clearly seen, the adhesive composition prepared according to the method of Example 2 (method of the present invention) has a substantially higher turbidity (greater than the adhesive composition prepared according to the method of Example 1 (low energy mixing). Opacity) and lower median particle size.

Without wishing to be bound by theory, Applicants note that energizing one of the charged components of the composition prior to adding the component with the opposite charge causes the pigment particles to remain sufficiently separated, resulting in aggregation of the pigment particles (consequently, average pigment particle size). To increase). Applicants have found that, when colored adhesive compositions are prepared in accordance with the present invention, the pigment particles in such compositions have an unsonicated median particle size of about 2.5 times or less of the sonicated average particle size of the pigment in the pigment dispersion. I learned. Typically, the unsonicated average particle size of the pigment in the colored adhesive composition is less than about 1.5 times the unsonicated average particle size of the pigment in the pigment dispersion. Applicants believe that providing sufficient mechanical energy during addition of the second component to the first component minimizes the interaction between the anion class and the cationic class. That is, coacervation and a significant increase in the viscosity of the resulting composition (ie, layering and gelling) are minimized.

As discussed above, energizing the first component of the adhesive composition prior to adding any other component significantly minimizes coacervation and pigment particle aggregation, but the order of addition can affect the properties of the final adhesive composition. The following describes particularly preferred methods of making the adhesive composition of the present invention.

The first step of the preferred method is to provide the required amount of suitable cationic wet strength resin. For example, from about 0.05 parts to about 5 parts polyamide-epichlorohydrin resin can be provided to prepare 100 parts of the preferred adhesive composition of the present invention. Preferably, this resin is a solution comprising about 10 to about 15 weight percent resin solids. A particularly preferred method provides about 12 parts by weight of 12.5% by weight polyamide-epichlorohydrin resin solution. Optionally, if the desired concentration of the cationic wet strength resin is too low to maintain a suitable charge density (see above), one of the other cationic materials described above may be removed before energizing the cationic wet strength resin solution. Can provide.

The polyamide-epichlorohydrin resin solution is then energized by suitable means to provide mechanical energy as described above. When sufficient energy is provided by this energizing step, the resin solution is swirled. For example, the resin solution should not be so viscous that it converts a significant portion of the provided mechanical energy into thermal energy to significantly raise the temperature of the solution. In particular, the viscosity of the resin solution should be less than about 500 cP as measured according to the methods described in the Test Methods section below. More preferably, the viscosity should be less than about 300 cP.

As mentioned above, suitable energizing means can provide energy of at least about 5 W / kg to the resin solution provided by the first step. Particularly preferred energizing means for the purposes of the present invention is Bredo Leakewepher model LOR.

After energizing the cationic wet strength resin solution, the pigment dispersion is added thereto. To prepare 100 parts of the preferred colored adhesive composition described above, about 7 to about 30 parts of the pigment dispersion are added while continuously providing energy to the liquid. For the particularly preferred TiO ₂ dispersion described above, about 32 parts of 71.5% by weight of the dispersion are added.

Preferably, the pigment dispersion is added at a rate such that a large amount of material present in the mixing zone ensures the pigment dispersion in the cationic wet strength resin solution or the cationic wet strength solution. Otherwise, energy may be insufficient to maintain the separation of the pigment particles and to minimize coacervation. As used herein, the term "mixing zone" is a space in which energy is transferred from an energizing means to a liquid or dispersion that is energized from the selected energizing means selected. Applicants have found that a useful measure of the rate of addition is the Delivery Number. As used herein, “transfer number” is a unitless number that depends on the addition rate of the pigment dispersion, the shape of the stirrer and the rotational speed of the stirrer, and can be calculated according to the following equation:

Q = (PigWt / AddnTime) / nd ³ ρ

n = RotVel / 60

Where Q = number of transmissions

PigWt = weight of pigment dispersion added in Kg

AddnTime = time required to add pigment in seconds

r = pigment dispersion density (g / cm ³ )

RotVel = rotation speed of the stirrer (rpm)

d = diameter of stirrer (cm)

For example, in preparing a batch of the colored adhesive composition of the present invention, the following data was used:

PigWt = 36.97 Kg, AddnTime = 240 seconds, r = 2.2 g / cc (TiO ₂ slurry containing about 72% TiO ₂ solids), RotVel = 1800 rpm, d = 24.3 cm.

The number of transmissions generated is 1.63 × 10 ⁻⁴ . As can be seen from Example 3, this number of transmissions indicates that the pigment dispersion was added slowly enough to the mixing zone to prevent aggregation (ie, the unsonicated median particle size is less than about 1 micron).

The final step required in the preferred method is to add a dry strength binder solution (still adding energy to the liquid). The dry strength binder solution is preferably added after adding another component because the dry strength binder solution is typically high viscosity and difficult to energize such solutions without an unacceptable temperature increase. As mentioned above, the dry strength binder solution preferably comprises starch-based resin or polyvinyl alcohol in water. Preferably, the concentration of dry strength binder in such an aqueous solution is about 2 to about 14% and about 2 to about 7 parts of binder solids are added to the adhesive composition when preparing 100 parts of the post-treated adhesive composition.

Optionally, other ingredients may be added after blending the materials. For example, a portion of the dilution water can be added to adjust the final viscosity and solids content to compensate for the lot-to-lot changes in the individual raw materials.

Another adhesive manufacturing method

Order of addition

Although the foregoing method is preferred because it maximizes dispersion of pigment particles and minimizes particle aggregation, another method, in particular another order of addition, is also within the scope of the present invention. For example, 1) providing a dry strength binder solution; 2) energizing the dry strength binder solution; 3) providing an anionic stabilized pigment dispersion; 4) mixing the pigment dispersion with a dry strength binder solution to form a colored binder blend; 5) providing a cationic wet strength resin solution; And 6) mixing the wet strength resin solution with the colored binder blend is also contemplated by the applicant. Colored adhesive compositions prepared according to this other method have substantially improved opacity, reduced aggregation and stability compared to low energy mixing methods. In particular, for adhesive compositions comprising the preferred TiO ₂ pigments described above, the unsonicated intermediate pigment particle size is about 1.0 micron and the initial separation time is at least 24 hours. It is evident that these results are improved over the low energy mixing method of Example 1 when compared to the results shown in Table 2 above.

Energizing means

Another energizing means suitable for the purposes of the present invention is a mixer which provides energy to the liquid medium by forming ultrasonic vibrations (a suitable apparatus is a sonolator by Sonic Corp. of Stratford, Connecticut). Is prepared as). Sonolators are in-line systems that provide high frequency vibration by pumping dispersions of solids in liquids, blends of liquids or liquids at high linear velocities through shaped orifices. The liquid stream impinges against the cantilevered blades. Flow over the blades causes vibrations in the blades, causing cavitation in the stream, thereby converting the flow energy into mixed / dispersed energy.

5-ply embossing and lamination

After the papermaking process of forming the plies is finished, one or more plies can be embossed and laminated. Embossing / lamination is one means of obtaining a pattern useful for providing a visual indication of the desired properties when performing the embossing / lamination step using the colored adhesive composition of the present invention.

Embossing is the knob-to-knob embossing method illustrated in US Pat. No. 3,414,459, commonly assigned to Wells on Dec. 3, 1968, which is incorporated herein by reference. ; The nested embossing method illustrated in US Pat. No. 3,556,907 to Nystrand, issued January 19, 1971; Or according to the two-ply method illustrated in US Pat. No. 5,294,475, issued to McNeil, dated Mar. 15, 1994, and commonly assigned.

In the embodiments described and claimed herein, the embossing can be spaced at a pitch of 0.05 to 0.70 in and can have a distal end area of 0.001 to 0.100 in ² . Each embossing may be on a roll with a knob protruding from 0 to 0.120 inches from the plane of the roll. Embossing may be circular, oval or irregularly shaped.

Each embossing has a distal end, and the adhesive composition of the present invention is applied to at least a portion of the distal end to form a laminated tissue product according to the present invention. Preferably, the adhesive solid is applied to at least a portion of the distal end of the one or more tissue plies and laminated at a rate of about 12 to about 20 pounds of adhesive solids (6 to 10 g of adhesive solids per kilogram of paper). To form. More preferably, it is applied at a ratio of about 14 pounds of adhesive solids per ton of paper to about 18 pounds of adhesive solids (7 to 9 g per kg) per ton of paper. As used herein, the term "adhesive solids" refers to the non-aqueous components of the adhesive composition of the invention and includes dry strength resins, dry strength additives, TiO ₂ and any dispersing aid or other solids that may be added to the adhesive composition. do.

An embossing and laminating method for producing a laminated tissue product according to the present invention is shown in Example 4.

Applicants deem the following non-limiting examples to illustrate the invention.

Example 1

This example is intended to illustrate the properties of coacervated mixtures of cationic wet strength resins and anionically stabilized pigment dispersions and dry strength binder solutions prepared using conventional mixing methods.

Colored adhesive compositions were prepared according to the following method:

1) providing about 13 parts of a cationic wet strength resin solution comprising about 12.5% of a Kemen 557LX resin solids and having a pH of about 3.0; 2) Agitate the wet strength resin solution using a Lightnin Model TS2010 mixer (which is available from Lightnin, Rochester, NY, which provides about 1.7 W per kg of solution to the solution). To start; 3) 23 parts of 72% solids TiO ₂ dispersion (Ti-Pure RPS Vantage Rutile Paper Slurry from DuPont) with a pH of about 8.4 was added while stirring continued; 4) adding about 64 parts of a dry strength additive (ELVANOL 71-30 from DuPont) solution with about 7.4% resin solids while continuing to mix; 5) Add water as needed to provide 100 parts while continuing to mix.

Table 4 describes the property data obtained in the evaluation of this adhesive composition.

characteristic value pH 4.3 Unsonicated median particle size (μ) First peak 17.1 2nd peak 2.2 Turbidity ^* 1217 Initial detach time 4 hours * Measured at a concentration of 0.5 g of adhesive in 1000 ml of water

Example 2

This example uses the same materials, concentrations, and order of addition as Example 1, but provides a colored laminating adhesive composition suitable for joining two or more layers of tissue paper using the method of the present invention. Specifically, a laboratory blender (available from Sunbeam Corp., Delray Beach, FL) was used to energize the liquid at about 110 W / kg.

Table 5 describes the property data obtained in the evaluation of this adhesive composition.

characteristic value pH 4.3 Unsonicated median particle size (μ) 0.5 Turbidity 3467 Initial separation time More than 4 weeks

Example 3

This example shows the use of commercial scale mixing equipment to produce colored adhesive compositions in accordance with the present invention.

equipment:

Mixer: Bredo Likwipier Model LOR, size 50 gallons, 30Hp motor, speed adjustable (640-2300 rpm) available from Bredo Likwifier, Kansas City, MO.

Impeller: 1) Standard disc: part number 8-711-0004, 2) Uneven disc: part number 8-711-0691

Composition:

ingredient % Cationic Wet Strength Resin Solution 12 TiO ₂ dispersion 32 Dry strength additive solution 55 water One Sum 100

Table 6 describes the properties of some colored adhesive batches prepared according to various process conditions.

Conduct number Disc shape Batch size (kg) Speed (rpm) Number of transmissions Energy applied (W / kg) Unsonicated median particle size (μ) Turbidity (NTU) One Standard 116 1800 1.62 × 10 ^-4 35.2 0.679 3567 2 Unevenness 116 1800 1.62 × 10 ^-4 90.3 0.566 3721 3 Unevenness 230 1800 5.15 × 10 ^-4 88.1 0.577 Unmeasured

Example 4

This example discloses the properties of a multi-ply paper product laminated using the colored adhesive composition prepared according to the method of Example 2.

Such paper products can be made from two layers of cellulosic fibers commonly used in bounty brand paper towels sold by The Procter & Gamble Co., Cincinnati, Ohio. Each ply consists of 65% northern softwood kraft, 35% CTMP and has a basis weight of 14 lb / 3,000 ft ² . Each ply is embossed by an embossing method nested by an elliptical protrusion with a long axis of 0.084 in, a short axis of 0.042 in, and a protrusion height of 0.070 in at the winch end. The protrusions are spaced in a concentric diamond pattern at a 45 ^° pitch of about 0.118 inches. Two complementary plies are made and joined together at the contact nip of zero tolerance (clearance) being a one-piece laminate having about 33 projections / in ^2/1 ply is formed.

The method of Example 3 provides an adhesive composition having 5.75% total adhesive solids, of which 1.5% is chimen and 4.25% is polyvinyl alcohol. The adhesive composition also includes 23% TiO ₂ solids. This adhesive composition is applied to one layer of protrusions. The total solid of the adhesive composition is applied to the paper product. The resulting paper product has a wet ply bond strength of 5.5 g / in and a dry ply bond strength of 10.4 g / in. Methods for measuring wet fold bond strength and dry fold bond strength are described in the Test Methods section below.

In Table 7, the wet ply bond strength and the dry ply bond strength of paper towel products laminated with the adhesive composition prepared according to the present invention are compared with other commercially available paper towels.

sample Manufacturer Wet Fold Bond Strength (g / in) Dry lap bond strength (g / in) The present invention assignee 5.5 10.4 BOUNTY 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 * Data from US patent application Ser. No. 08 / 835,039

The wet ply bond strength and dry ply bond strength in Table 6 each represent the average of five or more samples. Of course, in the dry double bond strength test, each of the five samples represents an average of four specimens. As can be clearly seen from the data shown in Table 7, the adhesive composition of the present invention provides substantially improved wet ply bond strength while maintaining dry ply bond strength comparable to commercially available paper towels. When the paper towel laminated using the adhesive composition of the present invention is immersed in water, the pattern of the colored adhesive is clearly visible. When the commercially available paper towels described in Table 7 are similarly immersed, there is no visible pattern.

Example 5

This example shows the formulation of a colored laminating adhesive according to the invention comprising other materials. Table 8 shows the composition of the laminating adhesive according to the invention comprising other inorganic coloring materials and optional cationic additives.

ingredient Concentration (% by weight) Dry Strength Additives ¹ 4.5 Pigment ² 18.0 Cationic Wet Strength Resin ³ 0.3 Any Cationic Additive ⁴ 0.7 Other pigments ⁵ 1.0 water Sufficient amount to become 100% ELVANOL 71-302. Solids provided by Ti-Pure RPS Vantage Rutile Paper Slurry 3. Kymene 557LX4. Cypro 5155. Aerosil 300

The composition is prepared substantially in accordance with the preferred method of the present invention using a laboratory blender (asterizer) to energize the composition when blending the components. Evaluation of the post-treated composition showed that 1) there was no visible separation after 14 days; 2) exhibits turbidity-2600 NTU comparable to other compositions of the invention; 3) The composition was applied to the tissue substrate using a measurement rod (Paul N. Gardner Co., Inc., Pompano Beach, FL as size 8) to control the coating thickness. When applied, the whiteness of the thin layer of the adhesive composition of this example is comparable to that of the adhesive composition prepared according to Example 2 applied to the tissue substrate in the same manner, and 4) the viscosity is comparable to other compositions of the present invention. 170 cP.

Test Methods

Dry fold bond strength

Samples of four post-treated paper products are provided. Samples are cured for at least two weeks after preparation to fully cure the adhesive system. A 3 inch strip is cut from the center of each sample along the entire length of the sample. The two strips are cut in the machine direction and the other two are cut in the transverse direction (ie between the machine direction perforations or between the transverse edges). By slightly separating the strip along one of the 3 inch edges, each fold can be used independently of the other fold. The ply is separated by hand until the sample has a gauge length of 2 inches.

Each fold is placed in the jaw of the tensioner. A suitable tensile tester is Model 1451-24 supplied by Swing / Albert Corporation, Philadelphia, PA. Set the crosshead separation rate to 20 inches per minute and move 7.5 inches from the initial 2.0 inches separation. Data is recorded only for the last 6 inches of crosshead movement. All four samples are tested under tension. Four numbers are averaged to obtain a single ply bond strength representative of all four sampled products.

Care should be taken that the part of the sample to be separated by the tensioner does not come into contact with the lower jaw or the lower crosshead of the tensioner. If such a contact occurs, it will be recorded on the load cell and will show a very high reading. Similarly, care should be taken to avoid contacting the sample portion with the plies already separated by the tensile tester and the sample portion not yet separated. The occurrence of such a contact will present an error that increases the apparent fold bond strength. If any of the mentioned contacts occur, discard the data and test a new sample.

Wet Fold Bond Strength

Samples of four post-treated paper products are provided. Samples are cured for at least two weeks after preparation to fully cure the adhesive system. A 3-in strip (eg, between perforations of material to be converted to commercially available paper towels) is cut from the center of each sample along the entire length of the sample. The two strips are cut in the machine direction and the other two are cut in the transverse direction (ie between the machine direction perforations or between the transverse edges). Slight separation of the strip along one of the 3 inch edges allows each fold to be used independently of the other fold. The ply is separated by hand until the sample has a gauge length of 2 inches.

Separate the plies along one of the 3 inch edges of the sample. A portion of the sample that is not separated, that is, not located on the jaw of the tensioner, is immersed in distilled water. Immediately remove the sample from the water after immersion and dehydrate for 60 seconds on the dehydration frame. The spinneret is equipped with a nylon wire square mesh. The wire forming the mesh is 0.25 inch pitch, 0.015 inch diameter. The drying mold is oriented at an angle of 45 ^° to the horizontal. During drying on the drying mold, the sample is oriented so that the longer edge of the sample is arranged downward along the slope of the drying mold. The separated edges of the plies are flipped together in a drying mold to make the sample as smooth as possible, and the sample drains excess water as appropriate. After prepared in this manner, the samples are tested in a tensioner as described above for dry fold bond strength.

Viscosity

summary

The method is suitable for measuring viscosity as a function of shear rate. The sample is placed in a narrow annular space between two concentric cylinders. The inner cylinder is rotated at a controlled angular velocity, and the torque or force generated by the sample between the two cylinders is a measure of the viscosity of the sample disposed between them.

Device

Viscometers: Suitable viscometers are available as Model MCl from Paar Physica USA, Inc. of Edison, NJ.

Device installation

1) Install the viscometer according to the manufacturer's instructions.

2) Sample and device temperature should be 23 ± 1 ℃.

Way

1) Fill the sample to be evaluated into the outer cylinder with the indicated level.

2) Insert the outer cylinder into the viscometer with the inner cylinder at its center and lock the outer cylinder in place. After holding the outer cylinder in place, allow the sample to fill the annular space between the two cylinders for at least 10 seconds before the start of the viscosity scan.

3) Set the viscometer to scan from 10 to 1000 seconds ⁻¹ and use the ramp up / lamp down protocol for viscosity measurements. Make 50 measurements in the lamp up position and 50 measurements in the lamp down position.

Data recording and analysis

The viscosity is recorded from each of the two samples at a shear rate of 100 to 1000 seconds ⁻¹ in the ramp down portion of the protocol.

Charge density

summary

By measuring the electrical intensity (flowing intensity) between a pair of spatially separated electrodes, one can measure the charge density of a colloidal solution or dispersion, where one of the electrodes is used to adsorb particles of macromolecules or dispersion from Adjacent to the surface of the sample vessel, the other electrode is located in the free space of the sample vessel. The counterions for any charged particulate or macromolecular class are flowed by the oscillating piston to form the vibration intensity. Subsequently, the sample is titrated to zero streaming potential (ie isoelectric point) with a standard multi-electrolyte with opposite charge and the charge density is measured in microequivalents / g.

Device

Particle Charge Detector: A suitable device for measuring the charge density is available as a particle charge detector PCD 02 from MUTEK Analytic, Inc., Marietta, GA.

Titrator: A suitable titrator is a METTLER automatic end titrator model DL21 with two piston burettes, also available from Mutec Analytical, Marietta, GA.

Standard material

Standard polyelectrolyte solutions are also available from MUTEK Analytic. The cation standard is 0.001 N poly-diallyl-dimethyl-ammonium chloride. The anion standard is 0.001 N sodium polyethylene sulfate.

work

1) Install and calibrate the particle charge detector according to the manufacturer's instructions. Importantly, the ambient temperature should be at least 15 ° C., preferably about 25 ° C., for accurate measurements.

2) Install and calibrate the titrator according to the manufacturer's instructions.

3) Rinse the piston and sample cell of the particle charge detector with the sample. The sample is filtered (100 mesh filter) to remove large particles (although only a small portion of the charged class) that can interfere with the operation of the piston.

4) Insert the adjusted amount of sample into the rinsed sample cell. A preliminary titration may be necessary to determine the amount of sample that requires 0.5-15 ml of titrant. At least 10 ml of liquid is required to cover both electrodes. The sample is diluted with deionized water to provide a volume of at least 10 ml of sample requiring 0.5 to 15 ml of titrant.

5) Insert the piston into the sample vessel, place the vessel on the particle charge detector, contact the electrodes and allow the piston to engage the drive.

6) Turn on the piston and stabilize the flow strength (about 2 minutes).

7) Titrate the sample to the isoelectric point using a suitable polyelectrolyte solution. That is, the cationic sample is titrated with the anionic polyelectrolyte and the anionic sample is titrated with the cationic polyelectrolyte.

Data recording and analysis

1) Record the amount of titrant needed to titrate the sample to the isoelectric point.

2) Calculate the charge density q (micro equivalents / g) using the following equation:

q = V × C × 1000 / W

In the above formula,

V is the volume (ml) of the titrant required; C is the multiple electrolyte concentration (micro equivalents / g); W is the solids content of the sample (eg W = 0.01 g for a 10 ml sample of 0.1% TiO ₂ suspension).

3) Record each measurement result.

Particle size distribution

summary

The particle size distribution of the pigment particles formed by the method of the present invention can be measured using a light scattering device. Coherent and incoherent light sources are used depending on the expected particle size range.

Device

Suitable devices are available as Model LA910 from Horiba Instruments, Inc., Irvine, CA. Horiba LA910 uses a scattering system to measure particle size distribution (PSD). Coherent and non-coherent light sources are provided for the measurement of a wide range of PSDs. The device can measure four distributions (volume, number, area and length) for a given sample. Software is provided to the attached computer to control the device and convert the actual measured luminance data into any of the above-described distributions. The volume distribution is desirable for tracking structural changes. The median particle size is preferred as the single number descriptor of the PSD to provide adequate explanation in case of deviation from the normal distribution. Horiba LA910 has low-power ultrasonication (about 40 W) capability to separate aggregates. Measuring PSD without sonication is desirable to better understand any coagulation that may result from certain mixing methods.

Standard material

Calibration Standard Nanosphere Standard polystyrene particles are supplied by Duke Scientific of Palo Alto, CA. These standards are NIST traceable.

Device installation

Relative Refractive Index (RRI): 2.00 to 0.00i

Agitation: 3

Circulation: 4

Ultrasonication: None

Way

1) Install and calibrate the instrument according to the manufacturer's instructions.

2) Measure the particle size distribution against the blank (degassed deionized water) to check the instrument baseline by filling the sample cell with water and clicking on the measurement on the computer screen.

3) Put 150 ml of degassed deionized water into the sample cell and insert the cell into the device.

4) The sample is added dropwise until the light transmission scale (blue scale) measured by the device is about 70 to 75%.

5) Collect data from the sample and measure on a computer screen to determine the particle size distribution of the sample.

Data recording and analysis

1) Measure the particle size distribution on two or more samples.

2) Determine whether the distribution is polydisperse or monodisperse.

3) For monodisperse distributions, record the median particle size.

4) For polydispersion distributions, record the particle size defined by each peak in the distribution.

Turbidity

summary

Turbidity is a measure of the opacity / cloudiness of a liquid suspension. Turbidity is measured by measuring the amount of light scattered due to suspended particles.

Instrument

Turbidity meters: Suitable turbidity meters are available as Model 2100AN from Hachi Co., Robland, Colorado.

Standard material

StablCal Standards with turbidity values of non-turbidity turbidity units (NTUs) of less than 0.1, 20, 200, 1000, 4000 and 7500 are also available from Hachi Company.

Way

1) Install and calibrate the turbidity meter according to the manufacturer's instructions.

2) Dilute 0.4 g of the colored adhesive with 1000 ml of water and mix for 1 minute. Magnetic stirrers such as Corning Model PC-351 available from Coning Glass Works (Corning, NY) are suitable.

3) Allow the diluted sample to equilibrate for 1 minute.

4) Transfer the appropriate volume (˜30 ml) to the sample cell.

5) Measure turbidity according to the manufacturer's instructions.

6) Record the measured turbidity.

Data recording and analysis

1) Record the turbidity value in non-turbidity turbidity units (NTU).

Mixed energy

summary

It is used to measure current and voltage and to calculate the power transmitted to the energizing means.

Instrument

Power Analyzer: A suitable power analyzer is available as a Model 41B Power Harmonics Analyzer from Fluke Corp., Everett, Washington.

Amplifier Probes: Model 80I-1000s, also available from Fluke Corporation, is suitable.

Way

1) Correctly calibrate the power meter according to the manufacturer's instructions.

2) Place the amplifier probe around one of the three conductors of the electrical supply line to the energizing means. Attach the voltage probe to the other two conductors of the supply line. Fluke 41B calculates three-phase power readings from a simple single-phase measurement of balanced three conductor loads. The software included in the instrument is used to transmit and record power measurements in the Microsoft Excel spreadsheet (Fluke View Version 3.0).

3) Place a small amount of water around the seal of the base to measure power consumption with an empty tank. The power consumption over the entire speed range is measured and evaluated for the specific energizing means.

4) Record power readings from the power analyzer at least five times every 10 seconds through each addition step of the adhesive preparation method described above. If necessary, data acquisition hardware and software can be used on the sample and the power readings are automatically recorded.

Data recording and analysis

1) Calculate the net power for each addition step by subtracting power consumption at run speed from power consumption during material application.

2) Calculate the net power per unit mass for each step by dividing the net power by the mass of energized material after the addition step.

3) Record the net power per unit mass, and the net power for each addition step.

Claims (10)

2-7% by weight of a water soluble or water dispersible dry strength binder material; 0.05-5% by weight of water soluble cationic wet strength resin; And 58 to 91% by weight of water, Further comprising 7-30% by weight of anionic stabilized pigment suspended in the adhesive composition, Adhesive composition for laminating absorbent paper products. The method of claim 1, Wherein the dry strength binder material is selected from the group consisting of polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose resins, starch-based resins, and mixtures thereof. The method according to claim 1 or 2, An adhesive composition wherein the pigment is selected from the group consisting of kaolin, calcium carbonate, zinc oxide and titanium dioxide. The method according to claim 1 or 2, An adhesive composition, wherein a pigment slurry is provided to the adhesive composition as a dispersion in water, and the dispersion is stabilized using an anionic dispersion aid. The method according to claim 1 or 2, An adhesive composition wherein the water soluble cationic resin is selected from the group consisting of polyamide-epichlorohydrin resins, goxalated polyacrylamide resins, polyethyleneimine resins, and mixtures thereof. The method of claim 5, The polyamide epichlorohydrin resin comprises the reaction product of epichlorohydrin and a secondary amine group-containing polyamide, wherein the ratio of epichlorohydrin to polyamide secondary amine groups is from 0.5: 1 to 2: 1. Adhesive composition. An absorbent paper product comprising at least two ply papers, wherein the plies are adhesively laminated using the laminating adhesive composition according to claim 1. The method of claim 7, wherein An absorbent paper product comprising from 6 g of adhesive solids per kg of paper to 10 g of adhesive solids per kg of paper. The method according to claim 7 or 8, Absorbent paper product that is a paper towel. a) providing an aqueous solution or aqueous dispersion of the first resin; b) providing energizing means having the ability to transmit at least 5 W / kg of power to the first resin solution or dispersion; c) energizing a first resin solution or dispersion with said energizing means; d) providing an aqueous dispersion of pigment particles having an average particle size; e) mixing said pigment dispersion into a first resin solution or dispersion using said energizing means; f) providing an aqueous solution or dispersion of the second resin; And g) mixing the second resin aqueous solution or aqueous dispersion using the energizing means into a mixture of the pigment dispersion and the first resin solution to form a colored adhesive composition, The unsonicated median particle size of the pigment particles in the colored adhesive composition is 2.5 times or less the unsonicated median particle size of the pigment particles in the pigment dispersion. Process for preparing colored adhesive composition.