JP2007514041A - Optical brightener and method for producing the same - Google Patents

Abstract

The present invention generally relates to an improved method for producing an aqueous coating composition comprising a fluorescent brightener and a polyvinyl alcohol resin, the improvement being after the fluorescent brightener and polyvinyl alcohol resin are added to the slurry. Heating at a temperature in excess of about 160 ° F. (about 71.1 ° C.) for at least about 5 minutes to dissolve the polyvinyl alcohol resin. According to the present invention, it is possible to produce with a low moisture content without compromising whiteness and color. It is particularly preferred to add a dry resin and / or a dry brightener to provide a mixture with a high solids content. Another aspect of the present invention is a dry, granular blend of brightener and PVOH resin. A method for producing an optical brightener / PVOH aqueous concentrate, comprising: (a) preparing an aqueous brightener composition comprising water and an optical brightener active ingredient, wherein the optical brightener active ingredient is Present in the aqueous brightener composition, usually in an amount of about 10% to about 25%; (b) 0.25-10 parts of the aqueous brightener composition in an amount of about 1 part of dry polyvinyl alcohol resin per wet part. Mixing the polyvinyl alcohol resin and the aqueous optical brightener composition to provide an initial aqueous concentrate of the polyvinyl alcohol resin and optical brightener; and (c) the aqueous concentrate is typically about 175 ° F. Heating at a temperature of about 79.4 ° C. to about 210 ° F. for about 10 minutes to about 120 minutes to dissolve the solids to provide a heated optical brightener / polyvinyl alcohol concentrate. Disclosed is a method comprising the above.

Description

  The present invention relates to a novel process for producing a mixture of high solids content polyvinyl alcohol (PVOH) and optical brightener for easier drying and faster production rates, and its products. Coatings made with the present composition are particularly suitable for high quality coated paper.

  Paper coating compositions, or coating colors, are used in the paper industry to impart the desired moisture resistance, physical properties and appearance to specific grades of finished paper. In general, the coating composition is an aqueous dispersion composed mainly of mineral pigments such as clay, calcium carbonate or titanium dioxide and pigment binders of natural proteins, starches or synthetic polymer emulsions. Styrene-butadienes and polyvinyl acetate are examples of such synthetic emulsion binders. The coating composition can also include additives such as thickeners, wetting agents and lubricants.

  The coating composition is usually applied to a continuous web of material by a high speed coating machine such as a blade coater, air knife coater, rod coater and roll coater. It is advantageous to use a fast coater to increase productivity and to use a high solids content coating composition to reduce drying costs and improve binder dispersibility.

  A high brightness coated grade of paper usually contains an optical brightener (OB). Optical brighteners usually function by absorbing ultraviolet light and immediately reentering the visible blue-white range. Examples of optical brighteners include UVITEX® and TINOPAL® (Ciba Specialty Chemicals), BLANKOPHOR® (Bayer) and HOSTALUX® and LEUCOPHOR® (Clariant). Can be mentioned. Most OBs (fluorescent brighteners) have the following structures A, B and C:

{Wherein M may be H, alkali metal, ammonium or magnesium, R ₁ represents hydrogen, C ₁ -C ₅ alkyl, C ₁ -C ₅ alkoxy or halogen} as shown in stilbene species The active ingredient belonging to the compound of

  Such compounds have the following structure B:

Also included.
US Pat. No. 5,057,570 (Air Products and Chemicals, Oct. 15, 1991) describes a process for producing paper coating compositions using partially hydrolyzed, low molecular weight polyvinyl alcohol. The advantage of using this polymer is that no external heating is required and that it can be added to the aqueous pigment dispersion as a dry solid. This can usually be achieved at room temperature at a speed of 1500 rpm for 5 minutes under high shear stirring.

  US Pat. No. 5,830,241 (Ciba Specialty Chemicals, November 3, 1998) describes liquid preparations of fluorescent whitening agents, low MW polyethylene glycol, water and auxiliary compounds. This polyethylene glycol is liquid and functions as a non-volatile solvent to stabilize the liquid formulation of the drug when stored at high temperatures (50 ° C.). This low MW polyethylene glycol has a low viscosity and is therefore a liquid that can be pumped by suction. The general structure of the fluorescent whitening agent is as follows:

{Wherein M is H, alkali metal, ammonium or magnesium and polyvinyl alcohol (PVOH) is the preferred carrier}.
US Pat. No. 6,521,701 (Coatex SAS, 18 February 2003) describes a stable aqueous liquid polymer composition comprising polyvinyl alcohol in combination with a copolymer or homopolymer of a fully acidic form of a carboxylic acid. This combination of polymers has been found to optimize the moisture retention function, thereby activating the optical brightener and adjusting the viscosity of the coating color. This is all achieved without degrading the moisture retention function.

  US Pat. No. 6,620,294 (Ciba Specialty Chemicals, September 16, 2003) describes a stable aqueous solution of a fluorescent whitening agent comprising polyvinyl alcohol. This solution is optionally mixed with optional additives to mix a wet press filter cake or dry powder of fluorescent whitening agent with an aqueous solution of denatured or non-denatured polyvinyl alcohol, heated and homogeneous It can be produced by mixing until a dispersion is obtained.

  OB alone works well, but adding PVOH improves its performance. In some cases, papermakers use standard PVOH grades sold in dry form, which are then made for use by heating in conventional batch containers. The disadvantage of this method is that the water used in PVOH heating can significantly dilute the coating formulation, which can negatively impact production rates. In addition, the mill is expensive to heat PVOH, and in many cases the cost is further increased by problems with improper equipment or less trained operators. PVOH is usually provided to papermakers in various forms. (1) Dry resin, which is heated in water at a solids content of 20% to 30% by the consumer, the advantage of this is that an inexpensive grade of PVOH can be used, the disadvantages are (2) PVOH preheated at a solids content of 15% to 25% and delivered to the consumer, which includes mostly water transportation costs and is costly for papermakers; and ( 3) Dried, finely grained, partially hydrolyzed grade, which is added dry to the pigmented formulation. These latter products are relatively expensive ground materials, but are advantageous when heating is not an option. See U.S. Pat. No. 5,057,570. Also described is a solution of PVOH and fluorescent whitening agent produced by thoroughly mixing and heating a wet presscake or dry powder of fluorescent whitening agent and an aqueous solution of PVOH. See also Patent No. 6,620,294.

  In accordance with the present invention, both an optical brightener and a relatively inexpensive grade of PVOH are added directly to water to form a slurry, which is then heated to stabilize the material and produce an aqueous brightener composition. It has been found to provide products and manufacturing options that were not previously feasible. It is possible to use a dry blend of PVOH resin and powdered optical brightener, or use the dry form of each component.

Summary of the Invention

  In accordance with the present invention, a method of making an optical brightener / PVOH aqueous concentrate comprising: (a) providing an aqueous brightener composition essentially comprising water and an optical brightener active ingredient, wherein said aqueous brightener composition comprises The optical brightener active ingredient is usually present in the aqueous brightener composition in an amount of about 10% to about 25%; (b) dry polyvinyl alcohol per 0.25-10 wet parts of the aqueous brightener composition Mixing a polyvinyl alcohol resin and the aqueous optical brightener composition in an amount of about 1 part resin to provide an initial aqueous concentrate of the polyvinyl alcohol resin and the optical brightener; and (c) the aqueous concentrate. Is heated at a temperature of about 175 ° F. (about 79.4 ° C.) to about 210 ° F. (about 98.8 ° C.) for about 10 minutes to about 120 minutes to dissolve substantially all of the PVOH resin, water, polyvinyl Providing a heated fluorescent brightener / polyvinyl alcohol concentrate consisting essentially of an alcohol resin and an optical brightener active ingredient That provides the method according to the sequential steps. Usually, the polyvinyl alcohol resin is mixed in an amount of about 1 part dry polyvinyl alcohol resin per 0.5 to 10 wet parts of the aqueous brightener composition.

  The optical brightener active ingredient is typically present in the aqueous brightener composition in an amount of about 12% to about 20%, and the optical brightener / PVOH aqueous concentrate is usually present in the concentrate. Solid content of about 20% to about 75% based on water, polyvinyl alcohol and optical brightener active ingredient content. Further, the polyvinyl alcohol is mixed with the aqueous optical brightener composition in an amount of about 15% to about 55% PVOH based on the mixing weight of water, the optical brightener active ingredient and the polyvinyl alcohol resin, and concentrated. The solids content of the product is about 30% to about 60%. Similarly, the aqueous concentrate is usually heated at a temperature of 185 ° F. (about 85 ° C.) to 205 ° F. (about 96.1 ° C.) for about 20 minutes to about 60 minutes to dissolve the solids. Suitable polyvinyl alcohol resins have a viscosity of about 2 or 3 cps to about 30 or 40 cps. Most preferably, optionally the polyvinyl alcohol resin optionally has a viscosity of from about 2 or 3 cps to about 5, 7 or 8 cps or from about 3 cps to about 4 cps.

  The polyvinyl alcohol resin is typically about 85 or 80 to about 99.5 percent hydrolyzed on a mole percent basis, and typically the polyvinyl alcohol resin is about 85 percent to about 90 percent hydrolyzed on a mole percent basis, Has a degree of polymerization of 50 to about 2500 or 2000. More preferably, the degree of polymerization is from about 50 to about 1700, but the degree of polymerization is from about 50 to about 300.

  Most preferably, the polyvinyl alcohol resin is added to the aqueous polyvinyl alcohol brightener composition in substantially dry form. The dilution stage of the aqueous concentrate may also be convenient depending on the processing characteristics desired. Thus, the concentrate can be applied directly to the paper support during size pressing if desired.

  The method further includes adding polyethylene glycol to the aqueous concentrate, wherein the polyethylene glycol is added to the aqueous brightener composition, or to an initial or heated aqueous concentrate from about 0.5 to Add in an amount of about 2 parts by weight.

A preferred method of producing a color coat composition includes the following sequential steps:
(A) preparing an aqueous brightener composition comprising water and an optical brightener active ingredient, wherein the optical brightener active ingredient is usually in the amount of about 10% to about 25% of the aqueous brightener composition. Present in the whitener composition;
(B) Aqueous whitening agent composition 0.25-10 parts of polyvinyl alcohol resin and the aqueous fluorescent whitening agent composition are mixed in an amount of about 1 part of dry polyvinyl alcohol resin per wet part to obtain a polyvinyl alcohol resin and a fluorescent whitening agent. Providing an initial aqueous concentrate with;
(C) heating the aqueous concentrate at a temperature of about 175 ° F. (about 79.4 ° C.) to about 210 ° F. (about 98.8 ° C.) for about 10 minutes to about 120 minutes to dissolve the solids, Providing a heated optical brightener / polyvinyl alcohol concentrate consisting essentially of an alcohol resin and an optical brightener compound; and (d) mixing the heated concentrate with an aqueous dispersion comprising a color pigment and a binder. Thus, a color coat composition is produced. Usually, the polyvinyl alcohol resin is mixed in an amount of about 1 part dry polyvinyl alcohol resin per 0.5 to 10 wet parts of the aqueous brightener composition.

The method further includes applying the 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 from about 3 or 2 cps to about 5 or 4 cps, wherein the aqueous concentrate is a solid About 20 to about 75% and the polyvinyl alcohol resin is hydrolyzed from about 85 or 80 to about 90 percent on a molar basis. This concentrate optionally contains dispersants, protective colloids, said colloidal solvents, and / or auxiliaries such as antifreeze agents, sequestering agents, all of which are basic and novel properties of the concentrate. Do not change. When referring to the optical brightener / PVOH aqueous concentrate, the aid includes a small amount of a binder, plasticizer, filler, water retention aid such as carboxymethylcellulose. Typically, the polyvinyl alcohol resin has a viscosity of 3 cps to 4 cps and the aqueous concentrate is about 25 to about 65 percent solids. The optical brightener concentrate further optionally includes polyethylene glycol and the optical brightener active ingredient includes a stilbene compound. This stilbene compound has the formula:

{Wherein X and Y are independently selected from the following table:

} May be a sulfonated stilbene compound.
Thus, the brightener active ingredient may be disulfonated, tetrasulfonated or hexasulfonated in various ways.

  In a further 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 cps to about 4 cps, said aqueous concentrate. Is about 20 to about 75% solids and the polyvinyl alcohol resin is hydrolyzed from about 80 to about 90 percent on a molar basis.

  The present invention further relates to an improved method for producing an aqueous composition comprising an optical brightener and a polyvinyl alcohol resin, wherein the improvement is obtained by adding PVOH after adding the optical brightener and the polyvinyl alcohol resin. The slurry is heated to a temperature above about 160 ° F. (about 71.1 ° C.) for at least about 5 minutes to dissolve the polyvinyl alcohol resin. According to the present invention, it is possible to produce with a low moisture content without compromising whiteness and color. It is particularly preferred to add a dry resin and / or a dry brightener to provide a mixture with a high solids content. Another aspect of the present invention is a method for providing PVOH and optical brightener to a color coat composition without the use of external heating. Yet another aspect of the present invention is a dry, granular blend of brightener and PVOH, the details of which are described below.

The invention will be described in connection with various figures.
The invention will now be described in detail with reference to a number of aspects that are for illustrative purposes only. Variations within the spirit and scope of the present invention as set forth in the appended claims will be apparent to those skilled in the art. Optionally, the optical brightener is added to the aqueous composition such as PVOH slurry in substantially dry form; in other embodiments, the polyvinyl alcohol resin is added to the aqueous optical brightener composition in substantially dry form. In yet another aspect, both the optical brightener and the polyvinyl alcohol resin are added to water in a substantially dry form to form a slurry.

  In some preferred applications of the process, the slurry is heated at a temperature of at least about 175 ° F. (about 79.4 ° C.) for at least 10 minutes after the addition of the optical brightener and the polyvinyl alcohol resin. Typically, the slurry is heated for at least about 10 minutes at a temperature above about 160 ° F. (about 71.1 ° C.) after the addition of the polyvinyl alcohol resin, the optical brightener and the polyvinyl alcohol resin; The polyvinyl alcohol resin, the optical brightener and the polyvinyl alcohol resin are added and heated at a temperature above about 160 ° F. (about 71.1 ° C.) for at least about 20 minutes. In many cases, after adding the polyvinyl alcohol resin and the optical brightener, the slurry is about 175 ° F. (about 79.4 ° C.) to about 210 ° F. (about 98.8 ° C.) for about 10 minutes to about 120 minutes, Heat. Perhaps most preferably, the aqueous composition is about 20 minutes to about 185 ° F. (about 85 ° C.) to about 205 ° F. (about 96.1 ° C.) after addition of the polyvinyl alcohol resin and the optical brightener. Heat for about 60 minutes.

  Suitable polyvinyl alcohol resins have a viscosity of about 2 cps to about 40 cps. Typically, the polyvinyl alcohol resin has a viscosity of about 2 cps to about 8 cps, and the polyvinyl alcohol resin has a viscosity of about 3 cps to about 30 cps. About 3 cps to about 8 cps are preferred, and viscosities from about 3 cps to about 7 cps are also preferred. Preferably, the polyvinyl alcohol resin is about 80 to about 99.5 percent hydrolyzed on a mole percent basis. Typically, the polyvinyl alcohol resin is about 85 percent to about 90 percent hydrolyzed on a mole percent basis and has a degree of polymerization of about 50 to about 200. 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, which may be a sulfonated stilbene compound, such as a tetrasulfonated stilbene compound or a hexasulfonated stilbene compound. One preferred type is that the optical brightener active ingredient has the formula:

{Wherein X and Y are independently selected from the following parts:

} Of the stilbene compound.
In another aspect of the invention, an aqueous PVOH slurry is provided; dry particulate optical brightener is added to the aqueous PVOH slurry; and the slurry comprising PVOH and optical brightener is about 160 ° F. ( A method for producing an optical brightener / PVOH aqueous concentrate comprising sequential steps, wherein the PVOH resin is dissolved by heating at a temperature greater than about 71.1 ° C. for at least 5 minutes.

  In another aspect of the invention, a dry powder fluorescent whitening agent is provided; a dry polyvinyl alcohol resin is provided; the polyvinyl alcohol resin and the fluorescent whitening agent are dried polyvinyl per 0.05 to 1 part of the fluorescent whitening agent. Dry blend in an amount of about 1 part alcohol resin; mix the dry blend with water to provide an initial aqueous concentrate of polyvinyl alcohol resin and optical brightener; and the aqueous concentrate to the polyvinyl Heat at high temperature to dissolve the solid for a time sufficient to dissolve substantially all of the alcohol resin and the optical brightener to dissolve water, polyvinyl alcohol resin, optical brightener and optionally a small amount of aid. A process for producing a fluorescent brightener / PVOH aqueous concentrate comprising sequential steps is provided, which provides a heated brightener / polyvinyl alcohol concentrate comprising the agent.

  Yet another feature is a dry, granular blend of polyvinyl alcohol resin and optical brightener, where the polyvinyl alcohol resin is hydrolyzed 85-90 mol% and has a degree of polymerization of about 50 to about 600. . The polyvinyl alcohol resin is preferably 85-95 mol% hydrolyzed and has a degree of polymerization of about 185 to about 235. More preferably, the polyvinyl alcohol resin is hydrolyzed 87-89 mol% and has a viscosity of about 2 cps to about 8 cps.

A preferred “no cook” process for producing a color coat composition comprises (a) producing a pigment dispersion; (b) producing a dry blend of a polyvinyl alcohol resin and an optical brightener, wherein The polyvinyl alcohol resin has a fine particle size such that about 85 mol% to about 90 mol% is hydrolyzed and at least about 99% of the particles pass through an 80 mesh screen;
c) adding the blend of polyvinyl alcohol resin and optical brightener to the pigment dispersion; and d) applying a shear force to the pigment dispersion containing the polyvinyl alcohol and optical brightener to Each step of mixing the dispersion and dissolving the optical brightener and polyvinyl alcohol resin without using external heating is included.

  A method for producing an optical brightener / PVOH aqueous concentrate, comprising: (a) preparing an aqueous brightener composition comprising water and an optical brightener active ingredient, wherein the optical brightener active ingredient is Present in the aqueous brightener composition, usually in an amount of about 10% to about 25%; (b) 0.25-10 parts of the aqueous brightener composition in an amount of about 1 part of dry polyvinyl alcohol resin per wet part. Mixing the polyvinyl alcohol resin and the aqueous optical brightener composition to provide an initial aqueous concentrate of the polyvinyl alcohol resin and optical brightener; and (c) the aqueous concentrate is typically about 175 ° F. Heat for about 10 minutes to about 120 minutes at a temperature of about 79.4 ° C. to about 210 ° F. (about 98.8 ° C.) to dissolve substantially all of the PVOH, water, polyvinyl alcohol resin and optical brightener activity Fluorescent whitening in sequential steps to provide a heated fluorescent whitening agent / polyvinyl alcohol concentrate consisting essentially of components / Further provides preparation method of the PVOH aqueous concentrate. Usually, the polyvinyl alcohol resin is mixed in an amount of about 1 part dry polyvinyl alcohol resin per 0.5 to 10 wet parts of the aqueous brightener composition.

  The optical brightener active ingredient is typically present in the aqueous brightener composition in an amount of about 12% to about 20%, and the optical brightener / PVOH aqueous concentrate is usually present in the concentrate. Solid content of about 20% to about 75% based on water, polyvinyl alcohol and optical brightener active ingredient content. Further, the polyvinyl alcohol is usually mixed with the aqueous fluorescent brightener composition in an amount of about 15% to about 55% PVOH based on the combined weight of water, optical brightener active ingredient and polyvinyl alcohol resin, The concentrate has a solid content of about 30% to about 60%. Similarly, the aqueous concentrate is typically heated at a temperature of 185 ° F. (about 85 ° C.) to 205 ° F. (about 96.1 ° C.) for about 30 minutes to about 60 minutes to dissolve the solid. Suitable polyvinyl alcohol resins have a viscosity of about 2 or 3 cps to about 30 or 40 cps. Most preferably, the polyvinyl alcohol resin optionally has a viscosity of about 2 or 3 cps to about 7 or 8 cps, or about 3 cps to about 4 cps.

  The polyvinyl alcohol resin is typically about 80 to about 99.5 percent hydrolyzed on a mole percent basis, and typically the polyvinyl alcohol resin is about 85 percent to about 90 percent hydrolyzed on a mole percent basis, and about 50 Has a degree of polymerization of ˜2000. More preferably, the degree of polymerization is from about 50 to about 1700, as is the degree of polymerization from about 50 to about 300.

  Most preferably, the polyvinyl alcohol resin is added to the aqueous brightener composition in substantially dry form. The dilution stage of the aqueous concentrate is also convenient depending on the processing characteristics sought. Thus, the concentrate can be applied directly to the paper support during size pressing if desired.

  The method further includes adding polyethylene glycol to the aqueous concentrate, wherein the polyethylene glycol is added to the aqueous brightener composition, or to an initial or heated aqueous concentrate from about 0.5 to Add in an amount of about 2 parts by weight.

One preferred method of producing the color coat composition includes the following sequential steps:
(A) providing an aqueous brightener composition consisting essentially of water and an optical brightener active ingredient, wherein the optical brightener active ingredient is typically in an amount of about 10% to about 25%. Present in the aqueous brightener composition;
(B) Aqueous whitening agent composition 0.25-10 parts of polyvinyl alcohol resin and the aqueous fluorescent whitening agent composition are mixed in an amount of about 1 part of dry polyvinyl alcohol resin per wet part to obtain a polyvinyl alcohol resin and a fluorescent whitening agent. Providing an initial aqueous concentrate with;
(C) heating the aqueous concentrate at a temperature of about 175 ° F. (about 79.4 ° C.) to about 210 ° F. (about 98.8 ° C.) for about 10 minutes to about 120 minutes to dissolve the solids, Providing a heated optical brightener / polyvinyl alcohol concentrate consisting essentially of an alcohol resin and an optical brightener compound; and (d) an aqueous dispersion comprising the heated concentrate, a color pigment and a binder resin. Mix to produce a color coat composition. Usually, the polyvinyl alcohol resin is mixed in an amount of about 1 part dry polyvinyl alcohol per 0.5 to 10 wet 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, an optical brightener active ingredient, and a polyvinyl alcohol resin having a viscosity of about 2 cps to about 4 cps, wherein the aqueous concentrate is about 20 to about solids. 75% and the polyvinyl alcohol resin is hydrolyzed from about 80 to about 90 percent on a molar basis. This concentrate optionally contains dispersants, protective colloids, said colloidal solvents, and / or auxiliaries such as antifreeze agents, sequestering agents, all of which are basic and novel properties of the concentrate. Do not change. When referring to the optical brightener / PVOH aqueous concentrator, the auxiliaries include small amounts of binders, plasticizers, fillers, water retention aids such as carboxymethylcellulose. Typically, the polyvinyl alcohol resin has a viscosity of 3 cps to 4 cps and the aqueous concentrate is about 25 to about 65 percent solids. The optical brightener concentrate further optionally includes polyethylene glycol and the optical brightener active ingredient includes a stilbene compound. The stilbene compound may be a sulfonated stilbene compound as described above.

  In a further 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 cps to about 4 cps, wherein said aqueous The concentrate is about 20 to about 75% solids and the polyvinyl alcohol resin is about 80 to about 90 percent hydrolyzed on a molar basis.

As used herein, terms have their ordinary meanings unless a more specific or more general meaning is given below or is clear from the context.
%, Percent or Percent is weight percent unless a mole percent is specified.

cps means centipoise.
“Small amount” means less than 50% by weight excluding moisture.
“PVOH” means a polyvinyl alcohol resin commonly produced in the art from polyvinyl acetate resin by saponification. PVOH resins are derived from homopolymers of vinyl acetate as well as copolymers of vinyl acetate and other ethylenically unsaturated monomers and may optionally contain cationic sites. Preferably the resin is vinyl acetate derived from 95 mole percent or more. The following resins are available from Celanease, Inc.

When specifying the viscosity of the polyvinyl alcohol resin, the viscosity is that of a 4% (w / w) aqueous solution of PVOH at 20 ° C.
Preferably, CIE L *, a *, b * and brightness are used to characterize the coated product made with the coating formulation of the present invention. L *, a *, b * values can be suitably tested using test methods such as TAPPI T 524 om-02, TAPPI T 527 om-02 or similar methods. TAPPI T 524 includes 45 ° illumination and right (0 °) viewing geometry. TAPPI T 527 includes diffuse illumination and 0 ° viewing geometry. L * is a measure of whiteness that increases from 0 for black to 100 for full white; a * indicates red for positive, green for negative; b * for positive When it is yellow or negative, it shows blue. Note that (GE) whiteness is measured according to TAPPI T 452 om-2. TAPPI 452 includes 45 ° illumination and 0 ° viewing geometry. Unless otherwise noted, whiteness values are reported by ultraviolet (UV) irradiation. To calculate whiteness without using UV, the UV component is subtracted from the UV whiteness.

“Slurry” refers to an aqueous composition containing undissolved solids.
The “color coat composition” includes an aqueous pigment dispersion and optionally a synthetic binder resin. Usually, the binder resin is a styrene-butadiene latex or a polyvinyl acetate emulsion. The polyvinyl alcohol resin is preferably a binder resin used as a co-binder.

  The aqueous pigment dispersion to be mixed with the concentrate of the present invention usually consists of clay or calcium carbonate or a mixture of the two at a solid level in the range of about 70-76%. Usually, at least a part of the pigment contains calcium carbonate, and for the clay part, any clay conventionally used in paper coatings such as hydrous aluminum silicates such as kaolin-type clays, hydrated silica clays, etc. should be used. Can do. In addition to calcium carbonate and clay, titanium dioxide, precipitated barium sulfate (blanc fixe), lithopone, sulfide, in various proportions up to 50% by weight, preferably up to 35% by weight, based on calcium carbonate and clay Other paper pigments such as zinc or other coating pigments including plastics such as polystyrene. In addition, the composition may contain minor amounts of other additives such as zinc oxide and / or dispersants or stabilizers such as tetrasodium pyrophosphate.

  Suitable low molecular weight, partially or nearly hydrolyzed polyvinyl alcohols for the practice of the present invention are 70-99.5 mol%, preferably 85-90 mol%, most preferably 87-89 mol% hydrolyzed. It may have a degree of polymerization (DP) in the range of 50 to 600, preferably 185 to 255. Another means for evaluating the DP of polyvinyl alcohol is the viscosity of a 4 wt% aqueous solution at 20 ° C. Suitable polyvinyl alcohols have a viscosity in the range of about 2-30 cps, preferably 3-4 cps. Such polyvinyl alcohols can be produced by synthesis and saponification methods known to those skilled in the art of producing polyvinyl alcohol. A preferred polyvinyl alcohol having a viscosity of about 4 cps and a hydrolysis rate of 87-89 mol% is commercially available from Celanese under CELVOL® 203. Another preferred polyvinyl alcohol is CELVOL® 502, which has a viscosity of about 3 cps. Polyvinyl alcohol is blended with dry OB as a dry powder. The optical brightener active ingredient is the stilbene species described above and has the general structure of structures A, B and C. Suitable stilbenes are disclosed in US Pat. No. 6,620,294 and US Pat. No. 5,830,241, the disclosures of which are hereby incorporated by reference. Commercially available optical brighteners include UVITEX® and TINOPAL® (Ciba Specialty Chemicals), BLANKOPHOR® (Bayer) and HOSTALUX®, LEUCOPHOR® (Clariant) and PARAWHITE (registered trademark) (Paramount).

  Using a high solids aqueous pigment dispersion containing polyvinyl alcohol as a co-binder, 100 parts of pigment and clay containing 0 to 35 parts of clay and / or calcium carbonate; 0.01 to 0.5 part of dispersant or stabilizer; polymer 1 to 30 parts binder emulsion (solid base); 0.1 to 10 parts polyvinyl alcohol co-binder, preferably 0.5 to 2 parts; 0.1 to 20 parts other co-binders; 0 to 0.2 parts deformer; and desired Producing a paper coating composition comprising a sufficient amount of water to provide a solid level, usually about 45-70% by weight, preferably 60-70% by weight, or more for high solids paper coating compositions Can do.

  The prepared coating composition can be applied to the fibrous paper web using any conventional coating equipment, including trailing blade coaters, air-knife coaters, roll coaters, and the like.

As described below, PVOH can be heated in the presence of OB as purchased at ~ 17% solids without the addition of water.
Other than viscosity, the appearance of the resulting heat blend does not change.

Dilution may be desirable due to viscosity. However, with a solid blend of 27%, the papermaker benefits from a relatively high solid solution.
For all formulation examples described below, the pigments are primarily calcium carbonate and clay, but may include titanium dioxide. As known to those skilled in the art, other components such as carboxymethylcellulose, lubricants, dyes, deformers may optionally be included. Except for OB, the unit is expressed as dry part / 100 pigment. With respect to the raw materials, the pigments are transported in a predispersed or dry form in water that can vary from about 70% to 76% solids. Styrene butadiene latex is transported at about 50% solids. PVOH can be transported in solid form to be heated in solution before use, or in a liquid system of 15% to 30% solids. The coating OB is transported in liquid form with about 17% active ingredient, with tetra- or hexasulfonated species being most preferred.

Blends and coatings include 1/1, 2/1, 3.75 / 1 and 5/1 wet OB (Ciba TINOPAL® PT, tetrasulfonated form) / dry PVOH (VELVOL® 203) It is done.
In normal operation with a paper mill, it is necessary to add PVOH and OB, respectively, as liquids to the compounding tank. However, in the present invention, the water of OB is skillfully used by adding dry PVOH to 100 parts of OB slurry in the container while stirring to sufficiently disperse the PVOH particles in a uniform manner. The contents are then preferably heated by a steam heated water bath to 185 ° F. (about 85 ° C.) to 205 ° F. (about 96.1 ° C.) depending on the PVOH grade used. The temperature of the blend is held for 30 minutes, at which point the PVOH is completely dissolved and the blend can be cooled or used hot. Since no dilution is performed, the above solid level is considered maximum.

  As shown below, in various examples, the method of the present invention results in a paper coating composition that includes an overall higher coating solid than can be achieved by conventional methods. Using the current method for the indicated OB / PVOH ratio and using a standard pigment dispersion of 70% or 76% solids, the maximum coating solids that can be achieved by adding OB and PVOH concentrate (25% solids) as liquids Varies from 64.4% to 70.0% and from 69.0% to 70.2% (using 30% solid PVOH).

  In contrast, the method of the present invention adds dry PVOH to the OB solution. After the dry PVOH is added, the blend is heated at a temperature in the range of 185 ° F. (about 85 ° C.) to about 205 ° F. (about 96.1 ° C.) for 30 minutes to completely dissolve the PVOH. This solution is then added to the 70% or 76% solids pigment dispersion to achieve the final coating solid shown below.

The color coat formulation may be expressed as a dry part and a wet part per 100 parts of dry pigment. A typical or “standard” coating formulation is as follows:
70% solids and 100 parts dry pigment = 142.9 wet parts;
14 dry parts latex = 28 wet parts with 50% solids;
17% active ingredient and 0.34 dry parts = 2 wet parts;
25% solids, 1 dry part PVOH = 4 wet parts.

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

  In the context of the present invention, carrier water from the PVOH resin composition is removed and the same “dry” formulation (2/1 wet OB / dry PVOH) has the composition shown in Table 3, The solid effect is 1.1%.

  The following are a number of additional examples and comparative examples that demonstrate the solid effects achieved with the present invention over conventional compounding methods. In these examples, the standard ingredients described above are used with varying wet OB / dry PVOH ratios and pigment solids content.

1/1 wet OB / dry PVOH
Comparative example series A
Color coats are made with either 70% or 76% solid pigment dispersion and 25% or 30% PVOH solution. The solids that can be achieved using standard methods of mixing liquid OB (usually 17% solids) and liquid PVOH and adding to the pigment dispersion are shown in Table 4 below.

Example series 1
In contrast to the above, the present invention uses a solution prepared by adding dry PVOH to a 17% solution of OB to obtain the following concentrations: In this case, the OB / PVOH solution is prepared as follows: 83 parts water and 17 parts active ingredient PB + 100 parts dry PVOH. Dry solid = (100 + 17) /200=58.5%; heated as above.

  Subsequently, this solution was added to the pigment dispersion, and the results shown in Table 5 were obtained.

As can be seen from the above table, there is a clearer solid effect than the implementation by the current method.
2/1 wet OB / dry PVOH
Comparative Example Series B
The maximum solids that can be achieved using conventional methods according to the above procedure are shown in Table 6.

Example Series 2
Dry PVOH is mixed with 17% OB according to the following formulation: 83 parts water and 17 parts active ingredient OB + 50 parts dry PVOH. Dry solid = (50 + 17) /150=44.7%. Then heat.

  This is added to the pigment dispersion to obtain the results and solid effects shown in Table 7.

3.75 wet OB / dry PVOH
Comparative Example Series C
According to the above, the following maximum solid is obtained.

Example Series 3
The PVOH / OB mixture follows the following formulation: 83 parts water and 17 parts active ingredient OB + 26.7 parts dry PVOH. Dry solid = (26.7 + 17) /126.7=34.5. Then heat. The results are shown in Table 9.

5/1 wet OB / dry PVOH
Comparative example series D
Similarly, the current method yields the following maximum% solids:

Example Series 4
This OB / PVOH solution is prepared as follows: 83 parts water and 17 parts active ingredient OB + 20 parts dry PVOH. Dry solid = (20 + 17) /120=30.8%, followed by heating.

  The results are shown in Table 11.

  The results of the above examples are summarized in Table 12 below.

Example Series 5
The above formulation of the present invention indicates that it is not diluted with the blend. Due to the increase in solids, the viscosity at the 3.75 / 1 ratio was ˜10,000 cps, with 2/1 exceeding 73,000 cps. The blend at a 5/1 ratio was ˜4,000 to 5,000 cps in the first 3 days at 30.8% solids.

  In some cases, it is desirable to achieve the standard goal of a total of 27% solids by diluting the formulations of the present invention. At this level, the viscosity of all PVOH / OB concentrates fluctuated from 2,000 to 4,000 cps, still showing a solid effect over conventional methods as shown in Table 13 below.

Examples 6-10, Comparative Example Series E
These examples show that the novel process of the present invention does not compromise the performance of the optical brightener. The formulation for the paper coating composition is as follows:
75/25 drying section CaCO ₃ /No.1 clay pigment;
14 Drying part styrene-butadiene latex binder;
0.3 dry part carboxymethylcellulose water retention aid;
x Wet section OB (TINOPAL (registered trademark) PT);
y Drying section PVOH (CELVOL203 or 502);
Solid ~ 62%.

The formulation was then coated on paper using a cylinder coater. The whiteness test results are shown in Table 14 below.
The controls are the basic liquid-liquid addition order of PVOH and OB, but Examples 6-10 are in-situ preheated PVOH / OB blends as described above. Example 6 and the control are both formulated with 3.75 / 1 wet OB and dry PVOH. This base paper has a whiteness of 84.3 (standard-no UV). After coating, the whiteness value of the paper (again-no UV) increases to 85.3 and 85.6. This UV whiteness measurement shows a significant improvement to 89.0 and 88.9, which can be comparable to each other. This a * value indicates color shading to red or green, which are considered equal to each other. The b * value is important because the desired blue-white shows a negative value and the undesirable yellow shows a positive value. Negative values are desirable and the difference is not important.

  Examples 7 and 8 blend OB / dry PVOH at 2/1 and compare the performance of the two PVOH samples with various viscosity values. All were preheated together with OB as in the present invention. What is striking here is that C-502 functions similarly to C-203 and has a low viscosity, which means that high whitening agent concentrates can be as high as 27-30% blend solids for high coating color solid effects That is.

  Following a similar procedure, Examples 9 and 10 were formulated with 2/1/1 wet OB / dry PVOH / polyethylene glycol 400, except that Example 2 had less 2 parts SBR.

Examples 11 and 12 and Comparative Examples F and G
According to the above procedure, the color coat composition was prepared with about 3/1 and 1/1 wet OB / dry PVOH. The comparative example was a slightly lower solid and was prepared by conventional methods.

  In Table 15, 0.51 / 1 and 0.17 / 1 refer to the dry ratio of optical brightener to polyvinyl alcohol, and in Comparative Examples F and G, TINOPAL® PT fluorescence along with CELVOL® 203 polyvinyl alcohol. Typical optical brighteners such as brighteners are used.

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

The results are also shown graphically in FIGS.
Examples 13-16
Further 3/1 and 1/1 wet OB / dry PVOH concentrates were prepared and blended with the 75% clay / 25% calcium carbonate masterbatch described in Tables 16-19 below.

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

Examples 17 and 18, Comparative Examples H to M
In general, following the above procedure, the color coat composition is heated substantially in accordance with conventional methods (Examples H to M) and in accordance with the present invention with dry OB powder followed by heating in-situ (Example 17, 18).

  The results are shown in Table 22 below and FIGS.

Examples 19 and 20
The following are dry blends and solutions prepared according to the present invention.
3: 1 wet / dry ratio PVOH / aqueous concentrate Dry PVOH (10 grams) was added to dry OB (5.1 grams) and the resulting mixture was dry blended to produce a homogeneous mixture of the two components. The dry blend is then slowly added to 40 ml of water. The resulting slurry is heated with stirring at a temperature of 200 ° F. (about 93.3 ° C.) to 210 ° F. (about 98.8 ° C.) for 30 minutes to completely dissolve the dry ingredients. The resulting solution is cooled to room temperature to produce a 27.4% solid PVOH / OB concentrate. This example has an OB / PVOH ratio equal to a solution of 3 wet parts of optical brightener to 1 dry part polyvinyl alcohol resin in 17% solids.

1: 1 wet / dry ratio PVOH / OB aqueous concentrate Dry PVOH (20 grams) was added to dry OB (3.4 grams) and the resulting mixture was dry blended to produce a homogeneous mixture of the two components. . The dry blend is then slowly added to 50 ml of water. The resulting slurry is heated with stirring at a temperature of 200 ° F. (about 93.3 ° C.) to 210 ° F. (about 98.8 ° C.) for 30 minutes to completely dissolve the dry ingredients. The resulting solution is cooled to room temperature to produce a 31.9% solid PVOH / OB concentrate. This example has an OB / PVOH ratio equal to a solution of 1 part wet to 1 part polyvinyl alcohol resin of optical brightener in 17% solids.

  The dry mixture of PVOH / fluorescent brightener powder can be added directly to the pigment dispersion, optionally producing a color coat composition. In a preferred embodiment, PVOH resin with a particle size of less than about 200 microns is used. That is, 99% by weight of the resin particles pass through an 80 mesh screen. This composition can be readily dissolved in the coating slurry during mixing by applied shear in the absence of external heating.

While the invention has been described with reference to several embodiments, modifications to these embodiments will be apparent to those skilled in the art within the spirit and scope of the invention. In view of the above discussion, related recognition in the art, and references including the above-discussed copending applications in connection with the background and detailed description, the entire disclosure of which is hereby incorporated by reference. This is not necessary.

FIG. 1 is a histogram showing Hunter color data for the coatings of Examples 11 and 12 and Comparative Examples F and G. FIG. 2 is a histogram showing Hunter color data for the coatings of Examples 11 and 12 and Comparative Examples F and G. FIG. 3 is a histogram showing Hunter color data for the coatings of Examples 11 and 12 and Comparative Examples F and G. FIG. 4 is a histogram showing Hunter color data for the coatings of Examples 11 and 12 and Comparative Examples F and G. FIG. 5 is a histogram showing Hunter color data for the coatings of Examples 17 and 18 and Comparative Examples H-M. FIG. 6 is a histogram showing Hunter color data for the coatings of Examples 17 and 18 and Comparative Examples H-M. FIG. 7 is a histogram showing Hunter color data for the coatings of Examples 17 and 18 and Comparative Examples H-M. FIG. 8 is a histogram showing Hunter color data for the coatings of Examples 17 and 18 and Comparative Examples H to M.

Claims (32)

A method for producing an optical brightener / PVOH aqueous concentrate comprising:
a) providing an aqueous brightener composition comprising water and an optical brightener active ingredient;
b) Aqueous brightener composition 0.25 to 10 A polyvinyl alcohol resin and the aqueous fluorescent brightener composition are mixed in an amount of about 1 part of dry polyvinyl alcohol resin per wet part to obtain a polyvinyl alcohol resin and a fluorescent brightener; And c) heating the aqueous concentrate at an elevated temperature for a time sufficient to dissolve substantially all of the polyvinyl alcohol resin to dissolve the solids, water, polyvinyl alcohol Said process comprising sequential steps, providing a heated optical brightener / polyvinyl alcohol concentrate comprising a resin, an optical brightener and optionally a small amount of auxiliary. 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 optical brightener / PVOH aqueous concentrate has a solids content of about 20% to about 75% based on the water, polyvinyl alcohol resin and optical brightener active ingredient content of the concentrate. The method described in 1. The polyvinyl alcohol is mixed with the aqueous optical brightener composition in an amount of PVOH of about 15% to about 55% based on the mixed weight of the water, the optical brightener active ingredient and the polyvinyl alcohol resin, The method of claim 1, wherein the concentrate has a solids content of about 30 to about 60%. The method of claim 1, wherein the aqueous concentrate is heated at a temperature of about 175 ° F (about 79.4 ° C) to about 210 ° F (about 98.8 ° C) for about 10 minutes to about 120 minutes. The method of claim 1, wherein the polyvinyl alcohol resin has a viscosity of about 2 cps to about 40 cps. The method of claim 1, wherein the polyvinyl alcohol resin is hydrolyzed from about 80 to 99.5 percent on a mole percent basis. The method of claim 1, wherein the polyvinyl alcohol resin is added to the aqueous optical brightener composition in substantially dry form. The method of claim 1, further comprising diluting the aqueous concentrate. The method of claim 1, further comprising adding polyethylene glycol to the aqueous optical brightener composition or the initial or heated aqueous concentrate. 11. The method of claim 10, wherein the polyethylene glycol is added to the aqueous fluorescent brightener composition or the initial or heated aqueous concentrate in an amount of about 0.5 to about 2 parts per dry part of the polyvinyl alcohol resin. The optical brightener / PVOH concentrate is at least one selected from a dispersant, a productive colloid, a solvent for the colloid, an antifreeze, a sequestering agent, a binder, a plasticizer, a filler, and a water retention aid. The method according to claim 1, comprising a small amount of an auxiliary agent. The method of claim 1, further comprising adding the optical brightener / PVOH concentrate directly to the paper support. A method for producing a color coat composition comprising:
(A) providing an aqueous brightener composition comprising water and an optical brightener active ingredient;
(B) Aqueous brightener composition 0.5 to 10 parts by weight of polyvinyl alcohol resin and the aqueous fluorescent brightener composition are mixed in an amount of about 1 part of dry polyvinyl alcohol resin per wet part to obtain a polyvinyl alcohol resin and a fluorescent brightener. Providing an initial aqueous concentrate with;
(C) Heating the aqueous concentrate at a high temperature for a time sufficient for substantially all of the polyvinyl alcohol resin to dissolve to dissolve the solid, water, polyvinyl alcohol resin, fluorescent brightener and To provide a heated fluorescent brightener / polyvinyl alcohol concentrate containing a small amount of an auxiliary agent; and (d) a color coat composition by mixing the heated concentrate with an aqueous dispersion containing a pigment and a binder resin. Said method comprising sequential steps of providing an article. 15. The method of claim 14, further comprising applying the color coat to paper. 15. The method of claim 14, wherein the polyvinyl alcohol resin is added to the aqueous fluorescent brightener composition in a substantially dry form. An optical brightener aqueous concentrate consisting essentially of water, an optical brightener active ingredient, and a polyvinyl alcohol resin having a viscosity of from about 2 cps to about 4 cps, said aqueous concentrate comprising from about 20 to about 75% Wherein the polyvinyl alcohol resin is hydrolyzed from about 80 to about 90 percent on a molar basis. The optical brightener concentrate of claim 17, wherein the optical brightener active ingredient comprises a stilbene compound. 19. The fluorescent whitening agent concentrate of claim 18, wherein the stilbene compound is a sulfonated stilbene compound. 20. The fluorescent brightener concentrate of claim 19, wherein the sulfonated stilbene compound is a tetrasulfonated stilbene compound. 20. The fluorescent whitening agent concentrate of claim 19, wherein the sulfonated stilbene compound is a hexasulfonated stilbene compound. The optical brightener active ingredient has the formula:

{Where X and Y are independently listed below:

18. The optical brightener concentrate of claim 17 comprising a stilbene compound selected from: An optical brightener aqueous concentrate consisting essentially of water, an optical brightener active ingredient, and a polyvinyl alcohol resin having a viscosity of about 3 cps to about 4 cps, said aqueous concentrate comprising about 20 to about 75% Wherein the polyvinyl alcohol resin is hydrolyzed from about 80 to about 90 percent on a molar basis. In a method for producing an aqueous composition comprising an optical brightener and a polyvinyl alcohol resin, after adding the optical brightener and the polyvinyl alcohol resin to the slurry, a temperature of about 160 ° F. (about 71.1 ° C.) And heating the slurry for at least about 5 minutes to dissolve the polyvinyl alcohol. 25. The improved method of claim 24, wherein the optical brightener is added to the slurry in a substantially dry form. 25. The improved method of claim 24, wherein the polyvinyl alcohol resin is added in a substantially dry form to the fluorescence enhancer solution to form a slurry. A method for producing an optical brightener / PVOH aqueous concentrate comprising:
a) preparing a PVOH slurry;
b) drying, adding granular optical brightener to the PVOH slurry; and c) heating the slurry containing PVOH and optical brightener at a temperature above about 160 ° F. (about 71.1 ° C.) for at least 5 minutes. Said method comprising sequential steps of dissolving the PVOH resin. A method for producing an optical brightener / PVOH aqueous concentrate comprising:
a) preparing a dry powder optical brightener;
b) preparing a dry polyvinyl alcohol resin;
c) dry blending the polyvinyl alcohol resin and the optical brightener in an amount of about 1 part dry polyvinyl alcohol resin per 0.5 to 1 dry part of the optical brightener;
d) mixing the dry blend with water to provide an initial aqueous concentrate of polyvinyl alcohol resin and fluorescent brightener; and e) adding the aqueous concentrate to the polyvinyl alcohol resin and fluorescent whitening. Heated whitening agent / polyvinyl alcohol concentrate containing water, polyvinyl alcohol resin, fluorescent whitening agent, and optionally a small amount of auxiliary agent, heated for a time sufficient for substantially all of the agent to dissolve Providing said method comprising sequential steps. A method for producing a color coat composition, comprising:
a) producing an aqueous pigment dispersion;
b) producing a dry blend of polyvinyl alcohol resin and optical brightener, wherein the polyvinyl alcohol resin is hydrolyzed from about 85 mol% to about 90 mol% and at least about 99% of the particles are 80 mesh Having a fine particle size that passes through a sieve of
c) adding the blend of polyvinyl alcohol resin and optical brightener to the pigment dispersion; and d) applying a shear force to the pigment dispersion containing the polyvinyl alcohol and optical brightener to The method comprising the steps of mixing the dispersion and dissolving the fluorescent brightener and polyvinyl alcohol resin without the use of external heating. 30. The method of claim 29, further comprising adding a latex binder to the pigment dispersion. 30. The method of claim 29, wherein the pigment dispersion comprises a mineral pigment selected from clay, calcium carbonate, titanium dioxide and mixtures thereof. Dry, granular dry blend of polyvinyl alcohol resin and optical brightener.

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