WO2004061021A1

WO2004061021A1 - Mineral dispersions containing carboxymethylcellulose acetate butyrate and their use as flatting agents in coating compositions

Info

Publication number: WO2004061021A1
Application number: PCT/US2003/039315
Authority: WO
Inventors: Ronald Todd Obie
Original assignee: Eastman Chemical Company
Priority date: 2002-12-27
Filing date: 2003-12-10
Publication date: 2004-07-22
Also published as: AU2003296466A1

Abstract

Mineral dispersions are disclosed that are useful matting agents for incorporation into coating compositions. The dispersions are especially useful to provide relatively low gloss and relatively clear UV cure coatings. The dispersions contain carboxymethylcellulose acetate butyrate, at least one solvent, and at least one mineral. Though a wide variety of minerals can be used, a preferred mineral is silica. Also disclosed are methods of making such dispersions.

Description

Mineral Dispersions Containing Carboxymethylcellulose Acetate Butyrate and Their Use as Flatting Agents in Coating Compositions

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to the use of carboxymethylcellulose acetate butyrate to disperse minerals, as well as to methods of dispersing minerals with carboxymethylcellulose acetate butyrate, and to the mineral dispersions and the dispersed minerals themselves.

Description of the Related Art

Coatings are typically used to protect and beautify surfaces. Coatings may also serve some temporary functional purpose. In order to obtain an aesthetically pleasing appearance, it is often desirable to reduce the gloss or to "matte'Or "flat" the coating.

Silica is the most commonly used mineral for gloss reduction in organic coatings. The matting efficiency of the silica is often dependent upon the nature of the silica used, such as its pore volume, surface area, and surface treatment. The ability to matte a particular coating is not only dependent upon the silica and its properties, but also on the type of coating being matted and the interaction of its components with the matting agent used. The cure properties of the coating can also play a significant role in the effectiveness of the matting agent. Finally, not only is it desirable to effectively matte a particular coating with the least amount of matting agent, it is also important that the resulting matted coating display a clear appearance rather than a hazy appearance. Other minerals that may be used for gloss reduction in coating compositions, with varying levels of success, include aluminum oxide, calcium carbonates, aluminum silicates, magnesium silicates, aluminum potassium silicates, calcium metasilicates, anhydrous sodium potassium aluminum silicates, sodium aluminosilicates, wollastonite, chlorite, mica, pyrophylite, barium sulfate, and feldspar, for example.

Although materials other than silica are effective in developing matte paint products, their use in semi-gloss paints and clear coatings is limited. This is at least partly because these minerals are often used to extend titanium dioxide in paint products, to produce a lower cost paint. Matting is inevitably a consequence of their presence. When already present as filler, they are therefore not as effective in controlling the degree of matting. In order to control the degree of matting or to lower the gloss of clear coatings, specifically processed synthetic silica is most often used, because of its clarity. Waxes may also be used to help lower gloss, but many times the clarity of the resulting composition suffers.

There are many forms of commercial synthetic silica matting agents used to impart matting properties to coatings. These silicas are typically made by one of three basic processes - gelation (silica gels); precipitation (precipitated silicas); and thermal methods (fumed silicas). Degussa, in their technical bulletin "Acematt Silicas for the Paint Industry," describe a number of fumed and precipitated silicas, both treated and untreated, for use in matting a variety of coating products. Similarly, Grace Davison and Fuji Silysia, in their technical bulletins Syloid 7000, Silica Flatting Agent for Solvent-Based Lacquers, and Sylysia, describe the use of silica gels, both treated and untreated, for use in matting a variety of coatings. In many coating applications in both solvent- and water-based systems, untreated silica gel particles form hard sediments when stored for extended periods. This can lead to varying levels of gloss when the coating composition is afterward applied. One way to avoid this effect is to add thixotropic agents to the compositions, in order to reduce the amount of settling that inevitably occurs. Another way to overcome the problems of sedimentation is to coat the silica, in order to reduce the affinity of the particles for one another, so that the particles can be easily redispersed just prior to application of the coating composition.

Traditionally, waxes have been used to coat silica particles, as have other similar thermoplastic coating materials that are insoluble in the solvents used. Such waxes include polyolefins, mineral waxes, paraffins, and other such materials. These materials must typically be applied at a temperature higher than the melting point of the wax, in order that an effective uniform coating be obtained. Aside from the significant energy costs of this process, another drawback is that the elevated temperature can result in the water being driven out of the silica, which is especially problematic when silica gel is being used.

U.S. Pat. No. 3,607,337 discloses a process for modifying silicic acids, gels and silicates by impregnation with a wax or a thermoplastic material such as polyethylene. The impregnation can occur either as the particles are being formed, or afterward by adding an aqueous emulsion or dispersion of the wax or thermoplastic material to an aqueous suspension or dispersion of the silicic acid, gel, or silicate particles.

U.S. Pat. No. 4,263,051 discloses treatment of finely divided silica with a reactive organopolysiloxane such as methyl hydrogen polysiloxane. These particles are said to be useful in known lacquers, varnishes, and other coating compositions.

U.S. Pat. No. 5,326,395 discloses a silica matting agent coated with a mixture of three waxes: a hard microcrystalline wax, a plasticizing monocrystalline wax, and a synthetic polyethylene wax. The use of this mixture is said to give the matting agent improved interaction with lacquers and improved sedimentation resistance.

U.S. Pat. No. 5,985,953 discloses compatibilized silicas for incorporation into natural and synthetic polymers in latex form or dry blending operations. The silicas are formed by the reaction of precipitated or fumed silica with organosilicon coupling compounds in aqueous suspension.

U.S. Pat. No. 6,103,004 discloses an aggregated silica gel produced from silica gel particles and a binding agent selected from synthetic or natural phyllosilicate, pyrogenic silicon dioxide, and organic polymers soluble or dispersible in water. The binding agent used can be carboxymethylcellulose. The aggregated silica gel is said to be suitable as a matting agent for coatings, as an antiblocking agent for polymer films, and as a beer clarifying agent.

WO 99/51692 discloses the use of urea-urethane derivatives to coat silica particles in order to improve the suspension properties of water-based coatings. However, the product is apparently ineffective in non-aqueous systems.

WO 01/04217 teaches the use of low pore volume silica gels coated with 15% to 30% paraffin to improve the matting efficiency in UV curable systems. There yet remains a need for matting agents that can be incorporated into a variety of coating compositions, and that allow for variance in gloss, particularly to obtain a very low gloss having excellent clarity. Especially advantageous would be a matting agent dispersion which can be readily dispersed in a variety of coating compositions.

BRIEF SUMMARY OF THE INVENTION

It has been found in the present invention that it is possible to use carboxymethylcellulose acetate butyrate dispersions containing minerals as matting agents for incorporation into coatings systems, resulting in tuneable gloss and clear appearance. Dispersion, or coating, may take place in organic solution, in water, or in 100% solids systems such as UV curable compositions.

DETAILED DESCRIPTION

The present invention relates to the use of carboxymethylcellulose acetate butyrate as a coating for minerals, and especially, to dispersions of minerals using carboxymethylcellulose acetate butyrate as a dispersant. The dispersed matting agents according to the invention, when matched with a suitable solvent, are especially advantageous when incorporated into a UV-curable composition.

UV-curable compositions are inherently difficult to matte because of their fast curing speeds, high solids content, and lack of high volumetric shrinkage, mechanisms known to those in the art to be of prime importance for obtaining matte finishes. In addition, when matte coatings are obtained, either by use of high levels of matting agent or by use of special matting agents, rheological difficulties, and/or stability problems, and/or clarity issues may inhibit commercialization of a coating system. Thus, the present invention provides a method for obtaining relatively low gloss and relatively clear UV cure coatings. According to the invention, carboxymethylcellulose acetate butyrate is used to wet out and to disperse mineral, and especially silica, matting agents.

Solvents useful in dispersions according to the invention include a wide variety of organic and water-based solvents that are miscible with the other components of the particular coating composition type selected. For example, water can advantageously be chosen as the solvent for use in water-based systems. As a further example, a preferred solvent for use in UV-curable acrylic systems is an acrylic monomer, and especially dipropylene glycol diacrylate, which can act both as a solvent and as a monomer that is polymerized into the system during the UV cure.

Thus, in a preferred embodiment, carboxymethylcellulose acetate butyrate is dissolved in an acrylate monomer to make a carboxymethylcellulose acetate butyrate-monomer solution. A mineral, for example silicon dioxide or aluminum oxide, is then dispersed in the carboxymethylcellulose acetate butyrate-monomer solution to make a mineral-carboxymethylcellulose acetate butyrate-monomer dispersion (MCM-dispersion). The MCM- dispersion is then added to a UV-curable coating. In an especially preferred embodiment, silica gel is used as the mineral of interest. The mineral, such as silica, is provided in the coating composition in the conventional amounts normally used in radiation-curable systems, which are from 1 to 25 weight percent based on the composition.

Other suitable minerals for use according to the invention include aluminum oxide, calcium carbonates, aluminum silicates, magnesium silicates, aluminum potassium silicates, calcium metasilicates, anhydrous sodium potassium aluminum silicates, sodium aluminosilicates, wollastonite, chlorite, mica, pyrophylite, barium sulfate, and feldspar, for example.

Monomers suitable for use in such UV-curable acrylic systems include those typically used. These compositions are well known and typically contain a mix of several photocurable acrylate or methacrylate monomers, which can be either monofunctional or polyfunctional. Among the acrylyl compounds typically used include acrylic acid, acrylamide, methyl acrylate, ethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, butoxyethoxyethyl acrylate, neopentyl glycol diacrylate, bicyclo [2.2.1]hept-2-yl acrylate, dicyclopentenyl acrylate, pentaerythritol mono- or di- or triacrylate or mixtures thereof, isodecyl acrylate, trimethylolpropane mono-, di-, or triacrylate or mixtures thereof, 2-phenoxyethyl acrylate, glycidyl acrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl acrylate, 2-(N,N-diethylamino)ethyl acrylate, trimethoxyallyloxymethyl acrylate, bicyclo [2.2.1]hept-2-en-5- ylmethyl acrylate, ethylene glycol diacrylate, bicyclo [2.2.1]hept-2-en-5,6- diyl diacrylate, vinyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, n-vinyl-2-pyrrolidinone (v-pyrol), acrylated epoxidized soybean oil, acrylated epoxidized linseed oil, (methyl carbamyl) ethyl acrylate, the reaction product of an aromatic or aliphatic polyisocyanate (such as tolylene diisocyanate) with a hydroxyalkyl acrylate (such as 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate). These and other compounds are well known in the art. Indeed, any photocurable compound containing the acrylyl group is suitable for use. Such coating compositions may also contain other polymerizable materials containing the ethylenically unsaturated group of the structure >C=C<. These and other compounds are disclosed in U.S. Pat. No. 3,966,572, incorporated herein by reference. These coating compositions will also contain a photosensitizer, activator, catalyst, or initiator, which can be used individually or in combination, with the total amount varying from about 0.01 to 20 percent by weight of the photocurable composition, a preferred amount being from 0.1 to 5 percent by weight, with an amount of from 0.5 to 2 percent by weight most preferred. With some combinations, a synergistic effect may be exhibited. These additives and the use thereof are well known in the art, and include practically any compound possessing the ability to function in such manner. Compounds suitable as photosensitizers include acetophenone, propiophenone, benzophenone, xanthone, thioxanthone, fluorenone benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 2- or 3- or 4- methylacetophenone, 2- or 3- or 4- methoxyacetophenone, 2- or 3- or 4-bromoacetophenone, 3- or 4-allylacetophenone, m- or p-diacetylbenzene, 2- or 3- or 4-methoxybenzophenone, 3,3'- or 3,4'- or 4,4'- dimethoxybenzophenone, 4-chloro-4'-benzylbenzophenone, 2- or 3- chloroxanthone, 3,9-dichloroxanthone, 2- or 3-chlorothioxanthone, 3-chloro- 8-nonylxanthone, 3-methoxyxanthone, 3-iodoxanthone, 2-acetyl-4- methylphenyl acetate, benzoin, alkyl, and aryl ethers of benzoin, the phenylglyoxal alkyl acetals, 2,2'-dimethoxy-2-phenylacetophenone, 2,2- diethoxyacetophenone, 2,2-diisopropoxyacetophenone, 1 ,3-diphenyl acetone, naphthalene sulfonyl chloride, toluene sulfonyl chloride. Suitable activators used in conjunction with photosensitizers include organic amines such as methylamine, decylamine, diisopropylamine, tributylamine, tri-2- chloroethylamine, ethanolamine, triethanolamine, methyldiethanolamine, 2- aminoethylethanolamine, allylamine, cyclohexylamine, cyclopentadienylamine, diphenylamine, ditolylamine, trixylylamine, tribenzylamine, N-cyclohexylethyleneimine, piperidine, 2-methylpiperidine, N-ethylpiperidine, 1 ,2,3,4-_^tetrahydropyridine, 2- or 3- or 4-picoline, morpholine, N-methylmorpholine, piperazine, N-methylpiperazine, 2,2- dimethyl-1 ,3-bis-[3-(N-morpholinyl)propionyloxy]-propane, 1 ,5-bis[3-(N- morpholinyl)propionyloxy]diethyl ether. Suitable catalysts and initiators include the diaryl peroxides, the hydroperoxides, the peracids and peresters, the azo compounds, or any other known free radical initiator or catalyst, such as di-t-butyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butyl hydroperoxide, peroxyacetic acid, peroxybenzoic acid, t- butyl peroxypivalate, t-butyl peracetate, and azobisisobutyronitrile. These and other suitable compounds are disclosed, for example, in U.S. Pat. No. 3,966,572, incorporated herein by reference.

The silica gel based MCM-dispersion according to the invention results in matte UV cure coatings that have low gloss (and tune-able gloss), excellent clarity, and excellent flow and leveling and appearance properties. In addition, the presence of the monomer-carboxymethylcellulose acetate butyrate solution improves the flow and leveling of the system.

The invention will be further understood by reference to the following examples of preferred embodiments, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

EXAMPLES

Example 1. Preparation of a silica/carboxymethylcellulose acetate butyrate dispersion

355.40 grams of dipropylene glycol diacrylate, available as Laromer DPGDA, from BASF Corporation, was charged to a stainless steel mixing vessel. 38.80 grams carboxymethylcellulose acetate butyrate, (CMCAB™ cellulose ester (Lot EMT00-065)), available from Eastman Chemical Co., Kingsport, TN, was added and mixed until it dissolved. To this mixture, 11.80 grams KIP100F photoinitiator, available from Sartomer Company, was added under agitation, and mixed well. To the above, 80.16 grams Syloid 7000, available from Grace-Davison, was added slowly with good agitation. This silica/CMCAB™ dispersion was mixed until smooth and uniform.

Example 2. Preparation of a UV-Curable Coating Composition

A stainless steel mixing vessel was charged with 268.28 grams Laromer PE55F, 243.56 grams Laromer PE44F, both polyester acrylates, available from BASF Corporation, 146.52 grams Ebecryl 264, aliphatic urethane triacrylate, 113.48 grams 1 ,6 Hexanediol diacrylate, both available from

UCB, and 154.88 grams PEG 400 diacrylate (known as Sartomer SR 344) and 33.60 grams Sartomer KIP 100F, both available from Sartomer Corporation. These items were then mixed thoroughly until uniform.

Example 3. Preparation of a Flat UV-Curable Topcoat

To a stainless steel mixing vessel, 75 grams of UV coating from Example 2 and 75 grams silica/CMCAB™ UV dispersion from Example 1 were added and mixed until uniform. To this mixture, 0.15 grams PolyFox T wetting agent available from Omnova Solutions, and 0.75 grams Tego Wet 500 wetting agent available from Degussa (Tego Chemie), was added. The resulting coating had a viscosity of 1820 centipoise as measured on a Brookfield RV DV-E Viscometer, using a #6 Spindle, at 100 rpm, and a 60 degree gloss of 14.5 as evaluated by A mil drawdown on Leneta Chart form N2A and cured through an American Ultraviolet UV curing unit, 1 pass at 13 FPM, 300 WPI mercury lamp.

Example 4. Flat UV Topcoat

40.10 grams UV Coating from Example 2, 32.08 grams Silica/CMCAB™ UV dispersion from Example 1 , and 0.22 grams Tego Airex 920 defoamer available from Degussa (Tego Chemie) was charged to, and mixed in, a stainless steel mixing vessel.

Example 5. UV Flooring Panel Development

The Flat UV Topcoat of Example 4 was loaded into the nip of a Burkle BKL200 mini roller coater equipped with a steel doctor roll and a rubber applicator roll. The doctor roll was subsequently turned off and the nip pressure and down pressure was adjusted so that approximately 0.3 mil of coating could be applied by passing a panel through the machine on the conveyor. A darkly stained oak veneer flooring panel was passed through the machine on the conveyor and the coating B-stage cured with an American Ultraviolet UV curing unit. The panel was again passed through the machine and the coating B-stage cured; the panel was passed a third time through the machine and the coating full cured. The coated panel was sponge sanded, and the sand dust wiped off. The sanded panel was passed through the applicator for a fourth time and the coating B-stage cured; the panel was passed through the applicator a 5^th and 6^th time, with B-Stage cure and full cure respectively. The resulting panel had a 20- degree gloss of 3.2, a 60-degree gloss of 21.3 and an 85-degree gloss of 75.0 and a clear, uniform, appearance.

Example 6. Carboxymethylcellulose acetate butyrate flatting base with 10 grit aluminum oxide

To a stainless steel mixing vessel, 59.23 grams dipropylene glycol diacrylate, available from BASF Corp as Laromer DPGDA, was added. 6.47 grams Carboxymethyl Cellulose Acetate Butyrate (CMCAB™ cellulose ester, Lot # EMT00-065), available from Eastman Chemical Company, Kingsport, TN, was added slowly and mixed until dissolved; 26.72 grams SPW 1200 aluminum oxide available from Treibacher Schleifmittel, was added slowly with agitation. After the batch was uniform, 2.30 grams Sartomer KIP 100F photoinitiator was added and mixed until dissolved. The resulting coating had a viscosity at 78F of 1630 centipoise as measured on a Brookfield RV DVE-E viscometer using a #6 spindle at 100 rpm.

Example 7. UV Cure Flat Topcoat with CMCAB™/AI₂O₃ Mixture

To a stainless steel mixing vessel, 87.50 grams of UV Coating from Example 2, 70.00 grams CMCAB™/Silica UV dispersion from Example 1, and 33.80 grams CMCAB™-AIO blend from Example 6 was added. The mixture was mixed until uniform and 0.19 grams PolyFox T, available from Omnova Solutions, and 0.96 grams Tego Wet 500 wetting agent, available from Degussa (Tego Chemie), was added. The resulting coating had a viscosity of 1690 centipoise at 80F on a Brookfield RV DVE Viscometer using a #6 spindle at 100 rpm, and a 60-degree gloss of 16.1 units when applied at VT. mil on Leneta Form N2A and cured by UV irradiation. Panels developed with this Example 7 coating as described in Example 5 resulted in coated panels with a 20-degree gloss of about 5.3, a 60-degree gloss of about 30.1 and an 85-degree gloss of about 75.2. The coated panels have a relatively clear, uniform appearance, with somewhat reduced mar resistance.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention, the scope of the invention being set forth in the following claims.

Claims

I claim:

1. A mineral dispersion, comprising: carboxymethylcellulose acetate butyrate; at least one solvent; and at least one mineral.

2. The mineral dispersion according to claim 1 , wherein the mineral comprises at least one member selected from the group consisting of silicic acid, silica gel, silicate particles, aluminum oxide, an aluminum silicate, a calcium carbonate, a magnesium silicate, an aluminum potassium silicate, a calcium metasilicate, an anhydrous sodium potassium aluminum silicate, sodium aluminosilicate, wollastonite, chlorite, mica, pyrophylite, barium sulfate, and feldspar.

3. The mineral dispersion according to claim 1 , wherein the mineral comprises at least one member selected from silica and alumina.

4. The mineral dispersion according to claim 1 , wherein the at least one solvent comprises at least one member selected from the group consisting of unsaturated monomers, volatile organic compounds, VOC- exerηpt organic solvents, and mixtures thereof.

5. The mineral dispersion according to claim 1, wherein the at least one solvent comprises an acrylate monomer.

6. The mineral dispersion according to claim 1 , wherein the dispersion further comprises at least one photoinitiator.

7. The dispersion according to claim 1, wherein the acrylate monomer comprises dipropylene glycol diacrylate; and wherein the at least one mineral comprises silica gel.

8. A UV-curable coating composition, comprising: the mineral dispersion according to claim 5; and at least one acrylate monomer or polymer.

9. A coating composition, comprising: the mineral dispersion according to claim 1 ; and one or more binders.

10. A method of coating a mineral, comprising: mixing carboxy methyl cellulose acetate butyrate and at least one solvent; and adding the mineral to the resulting mixture.

11. A method of flatting a coating composition, comprising adding to the coating composition, with stirring, the mineral dispersion according to claim 1.

12. A method of introducing carboxy methyl cellulose into a UV-curable coating composition, comprising adding to the UV-curable coating composition, with stirring, the mineral dispersion according to claim 1.

13. A method of providing a UV-curable acrylic composition with carboxyl and hydroxyl functionality, comprising adding to the UV-curable acrylic composition, with stirring, the mineral dispersion according to claim 1.