KR20070003782A - Optical brightener and method of preparing it - Google Patents

Abstract

The present invention relates generally to an improved method of preparing aqueous coating compositions including an optical brightener and a polyvinyl alcohol resin, the improvement being directed to cooking a slurry to dissolve the polyvinyl alcohol resin subsequent to the addition of optical brightener and polyvinyl alcohol resin to the slurry at a temperature above about 160‹F for at least about 5 minutes. The invention enables preparation with lower water content without compromising brightness and color. Particularly preferred is the addition of dry resin and/or dry brightener to provide high solids mixtures. Another aspect of the invention is a dry, particulate blend of brightener and PVOH resin. Disclosed is a method of preparing an optical brightener/PVOH aqueous concentrate comprising the sequential steps of: (a) providing an aqueous brightener composition including water and optical brightener active ingredient, wherein the optical brightener active ingredient is typically present in the aqueous brightener composition in an amount of from about 10% to about 25%; (b) admixing a polyvinyl alcohol resin with said aqueous optical brightener composition in an amount of about 1 part of dry polyvinyl alcohol resin per 0.5 to 10 wet parts of aqueous brightener composition to provide a nascent aqueous concentrate of polyvinyl alcohol resin and optical brightener; and (c) cooking the aqueous concentrate to dissolve the solids typically at a temperature of from about 175‹F to about 210‹F for a time of from about 10 minutes to about 120 minutes to provide a conked brightener/polyvinyl alcohol concentrate. ® KIPO & WIPO 2007

Description

Optical brightener and its manufacturing method {OPTICAL BRIGHTENER AND METHOD OF PREPARING IT}

Cross Reference to Related Application

This formal application is part of US Patent Application No. 10 / 731,495 filed December 9, 2003, entitled "Polyvinyl Alcohol and Optical Brightener Concentrate." , Claims priority based on the US patent application.

The present invention relates to novel methods and products for the preparation of mixtures of polyvinyl alcohol (PVOH) and light brighteners with high solids for easier drying and faster production rates. Coatings made from such compositions are particularly suitable for high quality coated paper.

In the paper industry, paper coating compositions or coating colors are used to impart the desired moisture resistance, physical properties and appearance to certain grades of finished paper. Generally, the coating composition is an aqueous dispersion consisting mainly of inorganic pigments such as clay, calcium carbonate or titanium dioxide, and pigment binders which are natural protein, starch or synthetic polymer emulsions. Styrene-butadiene and polyvinyl acetate are examples of such synthetic emulsion binders. The coating composition may also contain additives such as thickeners, wetting agents and lubricants.

The coating composition is typically applied to a continuous web of material by high speed coaters such as blade coaters, air knife coaters, rod coaters and roll coaters. It is advantageous to use faster coaters to increase productivity, to use higher solids coating compositions to reduce drying costs and to improve binder distribution.

High gloss coated grade paper typically includes an optical brightener (OB). In general, optical brighteners work by re-emitting in the blue-white visible region immediately after absorbing ultraviolet radiation. Examples of light brighteners include UVITEX® and TINOPAL® from Ciba Specialty Chemicals, BLANKOPHOR® from Bayer, and HOSTALUX® from Clariant. Trademarks) and LEUCOPHOR (registered trademark). Most OBs have an active ingredient belonging to a compound of stilbenes as represented by the formulas (A), (B) and (C) below.

Where

M can be H, an alkali metal, ammonium or magnesium,

R ₁ represents hydrogen, C ₁ -C ₅ alkyl, C ₁ -C ₅ alkoxy or halogen.

The compound also includes those of the following formula (B).

US Patent No. 5,057,570, issued to Air Products and Chemicals on October 15, 1991, describes a process for preparing paper coating compositions using partially hydrolyzed low molecular weight polyvinyl alcohol. have. The advantage of using this polymer is that no external heating is required and the polymer can be added as a dry solid to the aqueous pigment dispersion. This may be achieved at a rate of 1500 rpm for 5 minutes under high shear agitation, typically at room temperature.

US Patent No. 5,830,241 to Ciba Specialty Chemicals, issued November 3, 1998, describes a liquid formulation of a fluorescent whitening agent, low molecular weight polyethylene glycol, water and auxiliary compounds. The polyethylene glycol is in liquid form and acts as a nonvolatile solvent to stabilize the liquid formulation of the fluorescent brightener upon storage at elevated temperatures (50 ° C.). The low molecular weight polyethylene glycol has a low viscosity, resulting in a pumpable solution. A typical structure of the fluorescent brightener is as shown in Formula C, and a preferred carrier is polyvinyl alcohol (PVOH).

Wherein M is H, an alkali metal, ammonium or magnesium.

US Pat. No. 6,521,701, issued February 18, 2003 to Coatex SAS , Coatex SAS , contains polyvinyl alcohol in combination with homopolymers or copolymers of carboxylic acids in full acid form. Stable aqueous liquid polymer compositions have been described. Combinations of these polymers have been found to optimize water retention function, activate photobleach and control the viscosity of the coating color. This is all achieved without degrading the water retention properties.

US Pat. No. 6,620,294 to Ciba Specialty Chemicals, issued September 16, 2003, describes a stable aqueous solution of fluorescent brighteners containing polyvinyl alcohol. This aqueous solution is mixed with a wet press filter cake or dry powder of fluorescent brightener with modified or unmodified polyvinyl alcohol with or without any additives and heated until a homogeneous distribution is obtained. And by mixing.

OB alone also works well, but including PVOH enhances the performance of OB. In some cases, the papermaker purchases a standard PVOH grade in dry form and then prepares it for use by cooking it in a conventional batch vessel. The disadvantage of this method is that the water used for PVOH cooking dilutes the coating formulation by a significant amount, which can negatively affect the production rate. In addition, mills for cooking PVOH are expensive, and in many cases the cost is compounded by inadequate equipment or poorly trained operators. In general, PVOH is supplied to papermakers in various forms, i.e. 1) dry resins cooked in water to 20-30% solids by the consumer (advantage is the use of less expensive grades of PVOH, the disadvantages of which ), 2) PVOH, which is pre-cooked and delivered to the consumer as a 15-25% solid, which costs papermakers as it entails transporting most of the water), and 3) colored formulations It is supplied in a partially hydrolyzed grade of dry fine particle size which is added to the dry state. The last product is a relatively expensive ground material, but is convenient when cooking is not an option. See US Pat. No. 5,057,570. See also US Pat. No. 6,620,294, which describes a solution of PVOH and light brightener prepared by thoroughly mixing and heating a wet press cake or dry powder of fluorescent brightener with an aqueous solution of PVOH.

According to the present invention, both light brighteners and relatively inexpensive grades of PVOH are incorporated directly into water to form a slurry, and then the mixture is cooked to solubilize the materials to produce an aqueous brightener composition, thereby making products and manufactures previously impossible. It was found that it could offer an option. It is possible to use dry blends of PVOH resins and powdered optical brighteners, or to use either component in dry form.

Summary of the Invention

According to the invention, (a) providing an aqueous brightener composition consisting essentially of water and the optical brightener active ingredient, wherein the optical brightener active ingredient is typically present in the aqueous brightener composition in an amount of about 10 to about 25%. Present step; (b) mixing the polyvinyl alcohol resin with the aqueous optical brightener composition in an amount of about 0.5 parts by weight of the aqueous brightener composition or about 1 part by weight of the dry polyvinyl alcohol resin per 0.25 to 10 parts by weight of the polyvinyl alcohol resin and the optical brightener. Providing an initial aqueous concentrate of; And (c) cooking the aqueous concentrate, typically at a temperature of about 175 to about 210 ° F., for about 10 to about 120 minutes to dissolve substantially all of the solids of the PVOH resin, such as water, polyvinyl alcohol resin and photobleach There is provided a process for preparing a photo brightener / PVOH aqueous concentrate by a sequential step consisting of obtaining a cooked brightener / polyvinyl alcohol concentrate consisting essentially of the active ingredient. Typically, the polyvinyl alcohol resin is mixed in an amount of about 1 part of dry polyvinyl alcohol resin per 0.5-10 mole parts of the aqueous brightener composition.

The optical brightener active ingredient is generally present in the aqueous brightener composition in an amount of about 12 to about 20%, and the optical brightener / PVOH aqueous concentrate is typically based on the water, polyvinyl alcohol and photo brightener active ingredient contents of the concentrate. With a solids content of about 20 to about 75%. More typically, the polyvinyl alcohol is mixed with the aqueous photobleach composition in an amount of about 15 to about 55% PVOH based on the total weight of water, the optical brightener active ingredient and the polyvinyl alcohol resin, and the concentrate is about 30 to about Has a solids content of 60%. In addition, the aqueous concentrate is usually cooked at a temperature of about 185 to about 205 ° F. for about 20 to about 60 minutes to dissolve the solids. Suitable polyvinyl alcohol resins have a viscosity of about 2 or 3 to about 30 or 40 cps, most preferably in some cases polyvinyl alcohol resins have a viscosity of about 2 or 3 to about 5, 7 or 8 cps, or about 3 to about 4 cps Has

The polyvinyl alcohol resin is generally about 85 or 80 to about 99.5 mole% hydrolyzed, and typically the polyvinyl alcohol resin is about 85 to about 90 mole% hydrolyzed and has a degree of polymerization of about 50 to about 2500 or 2000. A degree of polymerization of about 50 to about 1700 is preferred, and a degree of polymerization of about 50 to about 300 is more preferred.

Most preferably, the polyvinyl alcohol resin is added to the aqueous polyvinyl alcohol brightener composition in substantially dry form, and sometimes the dilution step of the aqueous concentrate is convenient, depending on the process characteristics performed. Thus, the concentrate can also be applied directly to the paper substrate in a size press if desired.

The method includes adding polyethylene glycol to the aqueous concentrate, wherein the polyethylene glycol is added to the aqueous brightener composition in an amount of about 0.5 to about 2 parts by weight per dry part of the polyvinyl alcohol resin. Or adding to the initial or cooked aqueous concentrate.

A preferred method for preparing a color coat composition comprises the steps of (a) providing an aqueous brightener composition consisting essentially of water and the optical brightener active ingredient, wherein the optical brightener active ingredient is aqueous in an amount of about 10 to about 25%. Present in the brightener composition; (b) mixing the polyvinyl alcohol resin with the aqueous optical brightener composition in an amount of about 1 part dry polyvinyl alcohol resin per 0.25-10 mole parts of the aqueous brightener composition to prepare an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener. Providing; (c) cooking the aqueous concentrate at a temperature of about 175 to about 210 ° F. for about 10 to about 120 minutes to dissolve the solids, thereby cooking cooked brightener / polyvinyl consisting essentially of water, polyvinyl alcohol resin and photo brightener Providing an alcohol concentrate; And (d) mixing the cooked concentrate with an aqueous dispersion comprising a color pigment and a binder resin to produce a color coat composition. Typically, the polyvinyl alcohol resin is mixed in an amount of about 1 part of dry polyvinyl alcohol resin per 0.5-10 mole parts of the aqueous brightener composition.

The method further includes applying a color coat to the paper.

The optical brightener aqueous concentrate consists essentially of water, the optical brightener active ingredient and polyvinyl alcohol having a viscosity of about 3 or 2 to about 5 or 4 cps, wherein the aqueous concentrate is about 20 to about 75% solids, The polyvinyl alcohol resin is hydrolyzed about 85 or 80 to about 90 mole percent. Concentrates optionally include dispersants, productive colloids, solvents for such colloids, and / or auxiliaries such as cryoprotectants, sequestering agents, and the like, none of which are based on and novel to the concentrate. Does not affect features When referring to optical brightener / PVOH aqueous concentrates, the adjuvant further comprises small amounts of binders, plasticizers, fillers, water retention aids such as carboxymethyl cellulose and the like. Typically, the polyvinyl alcohol resin has a viscosity of 3-4 cps, and the aqueous concentrate is about 25 to about 65% solids. The optical brightener concentrate further comprises polyethylene glycol in some cases and the optical brightener active ingredient comprises a stilbene compound. The stilbene compound may be a sulfonated stilbene compound of the formula:

Wherein X and Y are independently selected from the residues shown in the table below.

Thus, the brightener active ingredient may be disulfonated, tetrasulfonated or hexasulfonated in various embodiments.

In another aspect of the invention, the optical brightener aqueous concentrate consists essentially of water, the optical brightener active ingredient, polyethylene glycol and a polyvinyl alcohol resin having a viscosity of about 2 to about 4 cps, wherein the aqueous concentrate is From about 20 to about 75% solids, and the polyvinyl alcohol resin is hydrolyzed from about 80 to about 90 mole percent.

In general, the present invention is directed to an improved method for preparing an aqueous composition comprising a light brightener and a polyvinyl alcohol resin, wherein the light brightener and polyvinyl alcohol resin are prepared at a temperature above about 160 ° F. for at least about 5 minutes. After addition, the PVOH-containing slurry is cooked to dissolve the polyvinyl alcohol resin. The present invention makes it possible to produce lower moisture content formulations without compromising brightness and color. Particular preference is given to adding a dry resin and / or a dry brightener to obtain a mixture of high solids. Another aspect of the invention is a method of providing PVOH and a light brightener to a color coat composition without external heating. Another aspect of the invention is a dry particulate blend of brightener and PVOH resin, the details of which are described later.

The invention is illustrated with reference to the various figures below.

1-4 are histograms showing Hunter Color data for the coatings of Examples 11, 12, Comparative F and Comparative G.

5-8 are histograms showing Hunter color data for coatings of Examples 17, 18, and Comparative Examples H-M.

The present invention is described in detail below with reference to a number of embodiments for illustrative purposes only. Modifications within the spirit and scope of the invention as disclosed in the appended claims will be apparent to those skilled in the art. In some cases, the optical brightener is added to the aqueous composition, such as the PVOH slurry, in substantially dry form; In other embodiments, the polyvinyl alcohol resin is added to the aqueous optical brightener solution in substantially dry form; In another embodiment, both the optical brightener and the polyvinyl alcohol resin are added to the water in substantially dry form to form a slurry.

In some preferred applications of the process of the invention, the slurry is cooked at a temperature of at least about 175 ° F. for at least 10 minutes after the addition of the optical brightener and polyvinyl alcohol resin. Typically, the slurry is cooked at a temperature of greater than about 160 ° F. for at least about 10 minutes after addition of the polyvinyl alcohol resin, the optical brightener and the polyvinyl alcohol resin; Typically, the slurry is cooked at a temperature above about 160 ° F. for at least about 20 minutes after the addition of the polyvinyl alcohol resin, the optical brightener and the polyvinyl alcohol resin. In many cases, the slurry is cooked at a temperature of about 175 to about 210 ° F. for about 10 to about 120 minutes after addition of the polyvinyl alcohol resin and the optical brightener. Perhaps most preferably, the slurry is cooked at a temperature of about 185 to about 205 ° F. for about 20 to about 60 minutes after addition of the polyvinyl alcohol resin and the optical brightener.

Suitable polyvinyl alcohol resins have a viscosity of about 2 to about 40 cps, typically polyvinyl alcohol resins have a viscosity of about 2 to about 8 cps, and more generally polyvinyl alcohol resins have a viscosity of about 3 to about 30 cps . About 3 to about 8 cps is the preferred range, and about 3 to about 7 cps is the more preferred range. Preferably, the polyvinyl alcohol resin is hydrolyzed from about 80 to about 99.5 mole percent, and typically the polyvinyl alcohol resin is hydrolyzed from about 85 to about 90 mole percent, and has a degree of polymerization of about 50 to about 2000. Typically, the polyvinyl alcohol resin has a degree of polymerization of about 50 to about 300.

In some preferred embodiments, the optical brightener active ingredient comprises a stilbene compound and may be a sulfonated stilbene compound such as a tetrasulfonated stilbene compound or a hexasulfonated stilbene compound. One preferred class is where the optical brightener active ingredient comprises a stilbene compound of the formula:

Wherein X and Y are independently selected from the residues shown in the table below.

In another aspect of the invention, there is provided a method for preparing an aqueous PVOH slurry; Adding dry particulate photobleach to the aqueous PVOH slurry; And cooking the slurry containing PVOH and the optical brightener at a temperature of greater than about 160 ° F. for at least 5 minutes to dissolve the PVOH resin to provide a process for preparing the optical brightener / PVOH aqueous concentrate.

In another aspect of the present invention, there is provided a method for preparing a dry powder optical brightener; Providing a dry polyvinyl alcohol resin; Dry blending the polyvinyl alcohol resin with the optical brightener in an amount of about 1 part dry polyvinyl alcohol resin per 0.05 to 1 part of the optical brightener; Mixing the dry blend with water to provide an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener; And cooking the aqueous concentrate at elevated temperature to dissolve the solids for a time sufficient to substantially dissolve both the polyvinyl alcohol resin and the optical brightener to include water, the polyvinyl alcohol resin, the optical brightener and optionally a small amount of adjuvants. Provided is a process for preparing a light brightener / PVOH aqueous concentrate comprising a sequential step comprising providing a cooked brightener / polyvinyl alcohol concentrate.

Another feature is a dry particulate blend of the optical brightener of polyvinyl alcohol resin, wherein the polyvinyl alcohol resin is 85 to 90 mole% hydrolyzed and has a degree of polymerization of about 50 to about 600. The polyvinyl alcohol resin is preferably 85 to 90 mol% hydrolyzed and has a degree of polymerization of about 185 to about 235. Even more preferably, the polyvinyl alcohol resin is hydrolyzed from 87 to 89 mole percent and has a viscosity of about 2 to about 8 cps.

Preferred “no cook” methods for preparing the color coat compositions include the steps of (a) preparing a pigment dispersion; (b) preparing a dry blend of the polyvinyl alcohol resin and the optical brightener, wherein the polyvinyl alcohol resin is hydrolyzed from about 85 to about 90 mole percent and at least about 99% of the particles pass through the 80 mesh sieve. Having a particle size; (c) adding a dry blend of polyvinyl alcohol resin and a light brightener to the pigment dispersion; And (d) shearing the pigment dispersion of the polyvinyl alcohol and the optical brightener to mix the dispersion and dissolve both the optical brightener and the polyvinyl alcohol resin without external heating.

(a) providing an aqueous brightener composition comprising water and a optical brightener active ingredient, wherein the optical brightener active ingredient is typically present in the aqueous brightener composition in an amount of about 10 to about 25%; (b) mixing the polyvinyl alcohol resin with the aqueous optical brightener composition in an amount of about 1 part dry polyvinyl alcohol resin per 0.25-10 mole parts of the aqueous brightener composition to prepare an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener. Providing; And (c) cooking the aqueous concentrate, typically at a temperature of about 175 to about 210 ° F., for about 10 to about 120 minutes to dissolve substantially all of the PVOH resin, so that the water, polyvinyl alcohol resin and photobleach active ingredient It further provides a method for preparing the optical brightener / PVOH aqueous concentrate by a sequential step consisting of providing a cooked brightener / polyvinyl alcohol concentrate consisting essentially of. Typically, the polyvinyl alcohol resin is mixed in an amount of about 1 part of dry polyvinyl alcohol resin per 0.5-10 mole parts of the aqueous brightener composition.

The optical brightener active ingredient is generally present in the aqueous brightener composition in an amount of about 12 to about 20%, and the optical brightener / PVOH aqueous concentrate is typically based on the water, polyvinyl alcohol and photo brightener active ingredient contents of the concentrate. With a solids content of about 20 to about 75%. More typically, the polyvinyl alcohol is mixed with the aqueous photobleach composition in an amount of about 15 to about 55% based on the total weight of water, the optical brightener active ingredient and the polyvinyl alcohol resin, and the concentrate is about 30 to about 60 Has a solids content of%. In addition, the aqueous concentrate is usually cooked at a temperature of about 185 to about 205 ° F. for about 20 to about 60 minutes to dissolve the solids. Suitable polyvinyl alcohol resins have a viscosity of about 2 or 3 to about 30 or 40 cps, most preferably in some cases polyvinyl alcohol resins have a viscosity of about 2 or 3 to about 7 or 8 cps, or about 3 to about 4 cps .

Polyvinyl alcohol resins are generally about 80 to about 99.5 mole% hydrolyzed, and typically polyvinyl alcohol resins are about 85 to about 90 mole% hydrolyzed and have a degree of polymerization of about 50 to about 2000. A degree of polymerization of about 50 to about 1700 is preferred, and a degree of polymerization of about 50 to about 300 is more preferred.

Most preferably, the polyvinyl alcohol resin is added to the aqueous brightener composition in substantially dry form, and sometimes the dilution step of the aqueous concentrate is convenient, depending on the process characteristics carried out. Thus, the concentrate can also be applied directly to the paper substrate in a size press if desired.

The method includes adding polyethylene glycol to the aqueous concentrate, wherein the polyethylene glycol is added to the aqueous brightener composition in an amount of about 0.5 to about 2 parts by weight per dry part of the polyvinyl alcohol resin, or The method may further comprise adding to the cooked aqueous concentrate.

One of the preferred methods for preparing a color coat composition is (a) providing an aqueous brightener composition consisting essentially of water and the optical brightener active ingredient, wherein the optical brightener active ingredient is present in an amount of about 10 to about 25%. Present in the aqueous brightener composition; (b) mixing the polyvinyl alcohol resin with the aqueous optical brightener composition in an amount of about 1 part dry polyvinyl alcohol resin per 0.25-10 mole parts of the aqueous brightener composition to prepare an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener. Providing; (c) cooking the aqueous concentrate at a temperature of from about 175 to about 210 ° F. for about 10 to about 120 minutes to dissolve the solids, thereby cooking cooked whitener / poly consisting essentially of water, polyvinyl alcohol resin and photobleach compound Providing a vinyl alcohol concentrate; And (d) mixing the cooked concentrate with an aqueous dispersion comprising a color pigment and a binder resin to produce a color coat composition. Typically, the polyvinyl alcohol resin is mixed in an amount of about 1 part of dry polyvinyl alcohol resin per 0.5-10 mole parts of the aqueous brightener composition.

The method further includes applying a color coat to the paper.

The optical brightener aqueous concentrate consists essentially of water, the optical brightener active ingredient and a polyvinyl alcohol resin having a viscosity of about 2 to about 4 cps, wherein the aqueous concentrate is about 20 to about 75% solids and the polyvinyl alcohol The resin is hydrolyzed from about 80 to about 90 mole percent. Concentrates optionally include dispersants, proliferative colloids, solvents for such colloids, and / or auxiliaries such as cryoprotectants, scenicizing agents, and the like, none of which affect the basis and novel characteristics of the concentrate. When referring to optical brightener / PVOH aqueous concentrates, the adjuvant further comprises small amounts of binders, plasticizers, fillers, water retention aids such as carboxymethyl cellulose and the like. Typically, the polyvinyl alcohol resin has a viscosity of 3-4 cps, and the aqueous concentrate is about 25 to about 65% solids. The optical brightener concentrate further comprises polyethylene glycol in some cases and the optical brightener active ingredient comprises a stilbene compound. The stilbene compound may be a sulfonated stilbene compound as indicated above.

In another embodiment of the invention, the optical brightener aqueous concentrate consists essentially of water, the optical brightener active ingredient, polyethylene glycol and polyvinyl alcohol having a viscosity of about 2 to about 4 cps, wherein the aqueous concentrate is about 20 to about 75% solids, and the polyvinyl alcohol resin is hydrolyzed from about 80 to about 90 mole percent.

The term used herein has its ordinary meaning unless a more specific or more general meaning is given below or is not clear in context.

Percent (%) means weight% unless specified as mole%.

"cps" means centipoise.

"Small amount" means less than 50% by weight with the moisture content excluded.

"PVOH" refers to polyvinyl alcohol resins typically prepared from polyvinyl acetate resins by well known saponification in the art. PVOH resins are derived from homopolymers of vinyl acetate, and copolymers of vinyl acetate with other ethylenically unsaturated monomers, and may include cationic moieties if desired. Preferably, the resin is at least 95 mole percent vinyl acetate derived. Suitable resins available from Celanese, Inc. include those of Table 1 below.

When the viscosity of the polyvinyl alcohol resin is specified, the viscosity is the viscosity of a 4% aqueous solution (weight / weight) of PVOH at 20 ° C.

Suitably, CIE L ^* , a ^* , b ^* and brightness values are used to specify the coated product made with the coating formulation of the present invention. L ^* , a ^* and b ^* values can be suitably measured using test methods such as TAPPI T 524 om-02, TAPPI T 527 om-02 or similar methods. TAPPI T 524 uses 45 ° directional illumination and vertical (0 °) viewing geometry. TAPPI T 527 uses diffuse illumination and vertical (0 °) viewing geometry. L ^* is a measure of increasing brightness from 0 for black to 100 for full white, a ^* represents green for positive values and green for negative values, and b ^* represents positive (+ In the case of), yellow and in the case of negative (-) are blue. (GE) Note that the brightness is measured according to TAPPI T 452 om-02. TAPPI T 452 uses 45 ° illumination and 0 ° observation geometry. Unless otherwise indicated, brightness values are recorded using ultraviolet (UV) radiation. To calculate brightness without UV, subtract the UV component from the UV brightness.

"Slurry" refers to an aqueous composition comprising undissolved solids.

"Color coat compositions" include aqueous pigment dispersions and optionally synthetic binder resins. Typical binder resins are styrene-butadiene latex or polyvinyl acetate emulsions. The polyvinyl alcohol resin is a binder resin, preferably used as a cobinder.

Aqueous pigment dispersions in which the concentrate of the present invention is combined typically consist of about 70-76% solids level in clay or calcium carbonate, or mixtures thereof. In general, at least a portion of the pigment comprises calcium carbonate, and in the clay portion, hydrous aluminum silicates such as clays commonly used for paper coating, such as kaolin group clays, hydrated silica clays and the like can be used. In addition to calcium carbonate and clay, other paper pigments such as titanium dioxide, blanc fixe ("barium sulphate"), lithopone, zinc sulfide or other coating pigments, such as various ratios, calcium carbonate and clay Up to 50% by weight, preferably up to 35% by weight of plastic, such as polystyrene, may be added. The composition may also contain other additives such as zinc oxide and / or small amounts of dispersants or stabilizers such as tetrasodium pyrophosphate.

Suitable low molecular weight, partially or mostly hydrolyzed polyvinyl alcohols for the practice of the invention may be hydrolyzed from 70 to 99.5 mole percent, preferably from 85 to 90 mole percent, most preferably from 87 to 89 mole percent And a degree of polymerization (DP) of from 50 to 600, preferably from 185 to 255. Another means for evaluating the DP of polyvinyl alcohol is its viscosity as an aqueous solution of 4% by weight at 20 ° C. Suitable polyvinyl alcohols have a viscosity of about 2 to 30 cps, preferably 3 to 4 cps. Such polyvinyl alcohols can be prepared by synthetic and saponification techniques well known to those skilled in the art to produce polyvinyl alcohol. Preferred polyvinyl alcohols having a viscosity of about 4 cps and hydrolysis of 87 to 89 mol% are sold by Celanes under the trade name CELVOL® 203. Another preferred polyvinyl alcohol is CELVOL® 502, which has a viscosity of about 3 cps. Polyvinyl alcohol is incorporated as a dry powder with dry OB. The optical brightener active ingredient consists of the stilbene class mentioned above and has the general structure of formulas (A), (B) and (C). Suitable stilbenes are disclosed in US Pat. No. 6,620,294 and US Pat. No. 5,830,241, which are incorporated herein by reference. Commercially available optical brighteners include UVITEX® and TINOPAL® from Ciba Specialty Chemicals, BLANKOPHOR® from Bayer, HOSTALUX® and LEUCOPHOR® from Clariant, and Paramount®. PARAWHITE® from Paramount) is included.

Next, the high solid aqueous pigment dispersion containing polyvinyl alcohol as a cobinder comprises: 100 parts by weight of a pigment containing clay and / or calcium carbonate and 0 to 35 parts by weight of a secondary pigment; 0.01 to 0.5 parts by weight of a dispersant or stabilizer; 1 to 30 parts by weight of a polymer binder emulsion (solid basis); 0.1 to 10 parts by weight of polyvinyl alcohol cobinder, preferably 0.5 to 2 parts by weight; 0.1 to 20 parts by weight of other cobinders; Defoamer 0 to 0.2 part by weight; And about 45 to 70 weight percent, preferably 60 to 70 weight percent or more, for water, typically high solids paper coating composition, sufficient to provide a desired level of solids. Can be used.

Coating compositions that can be prepared can be applied to the fiber paper web using any conventional coating apparatus, including a trailing blade coater, air-knife coater, roll coater, and the like.

As described below, PVOH can be cooked in the presence of OB delivered in about 17% solids without the addition of water.

The appearance of the final cooked blend, except for the viscosity, does not change.

Because of the viscosity, dilution is sometimes preferred. However, at 27% blended solids, relatively high solids solutions are advantageous for paper machines.

In all of the formulations discussed below, the pigments are predominantly calcium carbonate and clay, but may also comprise titanium dioxide. As is well known in the art, there are optionally other ingredients such as carboxymethyl cellulose, lubricants, dyes, antifoams. Units are expressed as dry // 100 pigments, except for OB. For the raw material, the pigments are delivered in dry or moisture pre-dispersed form, which may range from about 70 to 76% solids. Styrene butadiene latex is delivered in about 50% solids. PVOH can be delivered into solution before use in solid form to be cooked, or in liquid form at 15 to 30% solids. OB for coating is delivered in liquid form at about 17% active ingredient, most preferably tetrasulfonated or hexasulfonated.

Blends and coatings include 1/1, 2/1, 3.75 / 1 and 5/1 wet OB (TINOPAL®, tetrasulfonated form of Ciba) / dry PVOH (CELVOL® 203).

Formal operation in paper mills requires that PVOH and OB be added as liquids, respectively, into the blending tank. However, the present invention takes advantage of the water in the OB by adding dry PVOH to 100 parts of the OB slurry in the vessel while stirring and sufficiently dispersing the PVOH particles in a uniform manner. The contents are then heated to 185-205 ° F., preferably by steam heated water bath, depending on the grade of PVOH used. The temperature of the blend is fixed for 30 minutes, at which time the PVOH will dissolve entirely and the blend can be cooled or heated. The solid level is considered maximum since it was not diluted at all.

As set out below, in various embodiments, the method of the present invention produces a paper coating formulation having a higher overall coating solids than could be achieved by conventional methods. Using current methods using standard pigment dispersions of 70% or 76% solids content for the ratio of OB / PVOH shown, the maximum coating solids achievable by adding OB and PVOH (25% solids) respectively as a liquid is 64.4-70.0% (using 30% solids PVOH) and 69.0-70.2%.

In contrast, the process of the present invention adds dry PVOH to the OB solution. After adding dry PVOH, the blend is heated at a temperature of 185 to about 205 ° C. for 30 minutes to completely dissolve the PVOH. This solution is then added to a 70% or 76% pigment solid dispersion to achieve the final coated solids set forth below.

Color coat formulations are often expressed in dry and wet parts per 100 parts of dry pigment. Typically or "standard" coating formulations are as follows.

100 parts of dry pigments in 70% solids = 142.9 wet parts

14 latexes in 50% solids = 28 wet parts

0.34 parts with 17% active ingredient = 2 wet parts

1 part PVOH in 25% solids = 4 parts wet

Table 2 below shows the solids content for a standard formulation with a wet / dry part OB / PVOH ratio of 2/1 per 100 parts of pigment by conventional blending techniques.

In the present invention, the carrier water from the PVOH resin composition is removed, and the sample “dry” blend (2/1 wet OB / dry PVOH) has the composition shown in Table 3 below and has the benefit of a total of 1.1% solid phase.

The following are a number of additional examples and comparative examples that show the advantages of the solid phase realized by the present invention as opposed to conventional formulation techniques. These examples use the standard components specified above, various wet OB / dry PVOH ratios, and pigment solids content.

1/1 wet OB / dry PVOH

Comparative Example A

The color coat is combined with 70% or 76% pigmented solid dispersion and 25% or 30% PVOH solution. Solids that can be achieved using standard methods of mixing liquid OB (typically 17% solids) with liquid PVOH and adding to the pigment dispersion are shown in Table 4 below.

Example 1

Unlike the above, the present invention utilizes a solution prepared by adding dry PVOH to a 17% solution of OB to achieve the following concentrations. In this case, an OB / PVOH solution is prepared as follows.

83 parts of water and 17 parts of active ingredient OB are mixed with 100 parts of dry PVOH. Dry solids are (100 + 17) /200=58.5%. Cook as shown previously.

This solution is then added to the pigment dispersion to achieve the results shown in Table 5 below.

As can be seen from the table, there is an obvious solid phase advantage over the current practice.

2/1 humid OB / dry PVOH

Comparative Example B

Following the procedure outlined above, the maximum solids obtainable using conventional procedures are shown in Table 6 below.

Example 2

Dry PVOH is mixed with 17% of OB in the following manner.

83 parts of water and 17 parts of active ingredient OB are mixed with 50 parts of dry PVOH. Dry solids are (50 + 17) /150=44.7%. Then cook.

It is added to the pigment dispersion to achieve the results and solid phase advantages shown in Table 7 below.

3.75 / 1 Wet OB / Dry PVOH

Comparative Example C

Following the above procedure, the following maximum solids are achieved.

Example 3

The PVOH / OB mixture is according to the following manner.

83 parts of water and 17 parts of active ingredient OB are mixed with 26.7 parts of dry PVOH. Dry solids are (26.7 + 17) /126.7=34.5%. Then cook. The results are shown in Table 9 below.

5/1 humid OB / dry PVOH

Comparative Example D

Similarly, the current implementation yields the following maximum solids (%).

Example 4

The OB / PVOH solution is prepared in the following manner.

83 parts of water and 17 parts of active ingredient OB are mixed with 20 parts of dry PVOH. Dry solids are (20 + 17) /120=30.8%. Then cook.

The results are shown in Table 11 below.

The results of this example are summarized in Table 12 below.

Example 5

The combination of the present invention indicates no dilution was added in the blend. The viscosity at the 3.75 / 1 ratio was about 10,000 cps and above 23,000 cps at 2/1 because of the increased solids content. The blend at 5/1 ratio was initially about 4,000 to 5,000 cps for 3 days at 30.8% solids.

In some cases, it is desirable to achieve a standard target of 27% total solids by dilution of the formulations of the present invention. At this level, the viscosity of both PVOH / OB concentrates was between 2,000 and 4,000 cps, still showing the advantages of a solid phase over conventional practice as shown in Table 13 below.

Examples 6-10, and Comparative Example E

In these examples, it is shown that the novel method of the present invention does not impair the performance of the optical brightener. The formulation for paper coating was as follows.

CaCO ₃ / first clay pigment 75/25 case

14 styrene-butadiene latex binders

0.3 parts of carboxymethylcellulose water retention aids

OB (TINOPAL (registered trademark) PT) x wet department

PVOH (CELVOL 203 or 502) y parts

Solid 62%

The formulation was then coated onto paper using a cylindrical coater. Brightness tests are presented in Table 14 below.

The control is the basic liquid-liquid addition order of PVOH and OB, whereas Examples 6-10 are pre-cooked PVOH / OH blends in situ as indicated above. Both Example 6 and the control are combined with 3.75 / 1 wet OB / dry PVOH. The base paper has a brightness of 84.3 (standard-no UV). After coating, the brightness value for the paper (again-no UV) is improved to 85.3 and 85.6. UV brightness measurements indicate a significant improvement further significantly with 89.0 and 88.9 relative to each other. The a ^* values represent color shades for red or green, which are considered equal to each other. The b ^* value is important because it represents the desired blue-white with negative values and unwanted yellow with positive values. Negative values are preferred but their differences are not significant.

Examples 7 and 8 are formulated in 2/1 of wet OB / dry PVOH and compare the performance of two PVOH samples with different viscosity values. Both pre-cook with OB according to the present invention. Significant herein is that C-502 is implemented with C-203, and its viscosity is lower, allowing 27 to 30% higher blend solids in the light brightener concentrate for the benefit of higher coating color solid phase. Will be done.

According to the same procedure, Examples 9 and 10 were formulated in a wet OB / dry PVOH / polyethylene glycol 400 of 2/1/1 except that Example 10 had less than 2 parts of SBR.

Examples 11 and 12, and Comparative Examples F and G

According to the procedure shown previously, a color coat composition was prepared with wet OB / dry PVOH of about 3/1 and 1/1. The comparative example had a slightly lower solids and was prepared in a conventional manner.

In Table 15 below, 0.51 / 1 and 0.17 / 1 refer to the drying ratio of optical brightener to polyvinyl alcohol, and Comparative Examples F and G are typical optical brighteners such as TINOPAL (CELVOL® 203 polyvinyl alcohol). Trademark) Use PT optical brightener.

As can be seen in Table 15 below, the concentrates of the present invention appear to be equivalent or superior in critical optical measurements of UV brightness, blue-white “b” values and CIE whiteness.

The results are also presented graphically in Figures 1-4.

Examples 13-16

Additional 3/1 and 1/1 wet OB / dry PVOH concentrates were prepared and blended with a 75% clay / 25% calcium carbonate masterbatch as shown in Tables 16-19 below.

The optical test results of the coating on paper are shown in Tables 20 and 21 below.

Examples 17 and 18, and Comparative Examples H-M

In general, according to the procedure set forth above, the color coat by substantially conventional techniques (Examples H to M) and by adding dry OB powder according to the present invention and then cooking in situ (Examples 17 and 18) The composition was prepared.

The results are shown in Table 22 below and FIGS. 5 to 8.

Examples 19 and 20

The dry blends and solutions prepared according to the invention are as follows.

PVOH / OB aqueous concentrate with 3: 1 wet / dry ratio

Dry PVOH (10 g) is added to dry OB (5.1 g) and the resulting mixture is dry blended to obtain a homogeneous mixture of the two components. The dry blend is then slowly added to 40 ml of water. The resulting slurry is heated to a temperature of 200-210 ° F. with stirring for 30 minutes to completely dissolve the dry ingredients. The resulting solution is cooled to room temperature to give a 27.4% solid PVOH / OB concentrate. This example has an OB / PVOH ratio equivalent to a solution of 3 parts of optical brightener to 1 part of polyvinyl alcohol resin at 17% solids.

PVOH / OB Aqueous Concentrate with 1: 1 Wet / Dry Ratio

Dry PVOH (20 g) is added to dry OB (3.4 g) and the resulting mixture is dry blended to obtain a homogeneous mixture of the two components. The dry blend is then slowly added to 50 ml of water. The resulting slurry is heated to a temperature of 200-210 ° F. with stirring for 30 minutes to completely dissolve the dry ingredients. The resulting solution is cooled to room temperature to give 31.9% solid PVOH / OB concentrate. This example has an OB / PVOH ratio equivalent to a solution of 1 part of the optical brightener to 1 part of the polyvinyl alcohol resin at 17% solids.

A dry mixture of PVOH / light brightener powder can be added directly to the pigment dispersion, if desired, in preparing the color coat composition. Preferred embodiments use PVOH resins having a particle size of less than about 200 microns. In other words, 99% by weight of the resin particles pass through the 80 mesh sieve. The composition can easily dissolve in the coating slurry during mixing with shear applied without external heating.

Although the present invention has been described in connection with some embodiments, modifications to these examples within the spirit and scope of the invention will be apparent to those skilled in the art. In view of the foregoing discussions, relevant knowledge in the art, and references, including the previously discussed co-pending patent application, which is incorporated herein by reference in connection with the background and detailed description of the invention, further explanations are unnecessary. I think.

Claims (32)

(a) providing an aqueous brightener composition comprising water and a light brightener active ingredient; (b) mixing the polyvinyl alcohol resin with the aqueous optical brightener composition in an amount of about 1 part dry polyvinyl alcohol resin per 0.25 to 10 wet parts of the aqueous brightener composition, thereby initiating the polyvinyl alcohol resin and the optical brightener. Providing an aqueous concentrate; And (c) cook the aqueous concentrate at elevated temperature for a time sufficient to dissolve substantially all of the polyvinyl alcohol resin to dissolve the solids so that water, polyvinyl alcohol resin, optical brightener and optionally a small amount of auxiliary Providing a cooked brightener / polyvinyl alcohol concentrate comprising Method of producing a light brightener / PVOH aqueous concentrate comprising a sequential step consisting of. The method of claim 1, Wherein the optical brightener active ingredient is present in the aqueous brightener composition in an amount of about 10 to about 25%. The method of claim 1, Wherein the optical brightener / PVOH aqueous concentrate has a solids content of about 20 to about 75% based on the water, polyvinyl alcohol, and optical brightener active ingredient content of the concentrate. The method of claim 1, Mixing the polyvinyl alcohol with the aqueous photobleach composition in an amount of about 15 to about 55% PVOH based on the total weight of the water, the optical brightener active ingredient and the polyvinyl alcohol resin, and the concentrate is about 30 to Having a solids content of about 60%. The method of claim 1, Cooking the aqueous concentrate at a temperature of about 175 to about 210 ° F. for about 10 to about 120 minutes to dissolve the solid. The method of claim 1, Wherein the polyvinyl alcohol resin has a viscosity of about 2 to about 40 cps. The method of claim 1, Wherein the polyvinyl alcohol resin is hydrolyzed from about 80 to about 99.5 mole percent. The method of claim 1, The polyvinyl alcohol resin is added to the aqueous brightener composition in substantially dry form. The method of claim 1, Further comprising diluting the aqueous concentrate. The method of claim 1, Adding polyethylene glycol to said aqueous brightener composition or said initial or cooked aqueous concentrate. The method of claim 10, Adding polyethylene glycol to the aqueous brightener composition or the initial or cooked aqueous concentrate in an amount of about 0.5 to about 2 parts by weight per polyvinyl alcohol resin dry part. The method of claim 1, The optical brightener / PVOH concentrate contains a small amount of one or more adjuvants selected from dispersants, productive colloids, solvents for the colloids, cryoprotectants, sequestering agents, binders, plasticizers, fillers and water retention aids. How to include. The method of claim 1, And applying the optical brightener / PVOH concentrate directly to the paper substrate. (a) providing an aqueous brightener composition comprising water and a light brightener active ingredient; (b) mixing the polyvinyl alcohol resin with the aqueous optical brightener composition in an amount of about 1 part dry polyvinyl alcohol resin per 0.5 to 10 parts by weight of the aqueous brightener composition to prepare an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener. Providing; (c) cooking the aqueous concentrate at elevated temperature for a time sufficient to dissolve substantially all polyvinyl alcohol resin to dissolve the solid, thereby cooking comprising water, polyvinyl alcohol resin, optical brightener and optionally a small amount of auxiliary Providing a brightener / polyvinyl alcohol concentrate; And (d) mixing the cooked concentrate with an aqueous dispersion comprising a color pigment and a binder resin to produce a color coat composition Method for producing a color coat composition comprising a sequential step consisting of. The method of claim 14, Applying the color coat to a paper. The method of claim 14, The polyvinyl alcohol resin is added to the optical brightener composition in a substantially dry form. An optical brightener aqueous concentrate consisting essentially of water, a optical brightener active ingredient and a polyvinyl alcohol resin having a viscosity of about 2 to about 4 cps, wherein the aqueous concentrate is about 20 to about 75% solids and the polyvinyl alcohol resin Is an optical brightener aqueous concentrate that is hydrolyzed from about 80 to about 90 mole percent. The method of claim 17, The optical brightener aqueous concentrate wherein the optical brightener active ingredient comprises a stilbene compound. The method of claim 18, The optical brightener aqueous concentrate wherein the stilbene compound is a sulfonated stilbene compound. The method of claim 19, The optical brightener aqueous concentrate wherein the sulfonated stilbene compound is a tetrasulfonated stilbene compound. The method of claim 19, A light brightener aqueous concentrate wherein the sulfonated stilbene compound is a hexasulfonated stilbene compound. The method of claim 17, An optical brightener aqueous concentrate wherein the optical brightener active ingredient comprises a stilbene compound of the formula:

Wherein X and Y are independently selected from the residues shown in the table below.

An optical brightener aqueous concentrate consisting essentially of water, optical brightener active ingredient, polyethylene glycol and polyvinyl alcohol resin having a viscosity of about 3 to about 4 cps, wherein the aqueous concentrate is about 20 to about 75% solids, Wherein said polyvinyl alcohol resin is about 80 to about 90 mole percent hydrolyzed. A process for preparing an aqueous composition comprising a light brightener and a polyvinyl alcohol resin, wherein the slurry is cooked by addition of the light brightener and the polyvinyl alcohol resin at a temperature of greater than about 160 ° F. for at least about 5 minutes. Dissolving the resin. The method of claim 24, Adding the optical brightener to the slurry in substantially dry form. The method of claim 24, A polyvinyl alcohol resin is added to the optical brightener solution in substantially dry form to form a slurry. a) preparing a PVOH slurry; b) adding dry particulate photobleach to the PVOH slurry; And c) cooking the slurry containing PVOH and optical brightener at a temperature above about 160 ° F. for at least 5 minutes to dissolve the PVOH resin. Method of producing a light brightener / PVOH aqueous concentrate comprising a sequential step consisting of. a) providing a dry powder optical brightener; b) providing a dry polyvinyl alcohol resin; c) dry blending the polyvinyl alcohol resin with the light brightener in an amount of about 1 part dry polyvinyl alcohol resin per 0.05 to 1 part optical brightener; d) mixing the dry blend with water to provide an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener; And e) cooking the aqueous concentrate at elevated temperature to dissolve the solids for a time sufficient to substantially dissolve both the polyvinyl alcohol resin and the optical brightener to include water, the polyvinyl alcohol resin, the optical brightener and optionally a small amount of auxiliaries. Providing a cooked brightener / polyvinyl alcohol concentrate Method of producing a light brightener / PVOH aqueous concentrate comprising a sequential step consisting of. a) preparing an aqueous pigment dispersion; b) preparing a dry blend of the polyvinyl alcohol resin and the optical brightener, wherein the polyvinyl alcohol resin is hydrolyzed from about 85 to about 90 mole percent and at least about 99% of the particles pass through the 80 mesh sieve Having a size; c) adding a dry blend of polyvinyl alcohol resin and a light brightener to the pigment dispersion; And d) shearing the pigment dispersion containing polyvinyl alcohol and light brightener to mix the dispersion and dissolve both the light brightener and polyvinyl alcohol resin without external heating Method for producing a color coat composition comprising a. The method of claim 29, The method further comprises adding a latex binder to the pigment dispersion. The method of claim 29, Wherein the pigment dispersion contains an inorganic pigment selected from clay, calcium carbonate, titanium dioxide and mixtures thereof. Dry particulate blend of polyvinyl alcohol resin and optical brightener.

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