Patent Application
20100286419
1. Brief Description of the Invention
The invention described herein involves improved thickening compositions often referred to as rheological additives, viscosity modifiers or thixotropes, used to impart rheological and viscosity modification properties to a wide range of oil and organic based systems used as paints and coatings. In many commercial applications, such a thickening rheological chemical is added to an oil or organic based paint or coating system, for example epoxy paint, to change or modify the rheological properties of the system. The invention also includes paints and coatings containing such additives.
In an important aspect the invention covers a rheological additive consisting of the reaction product of:
The invention is based on a discovery that certain castor based rheological additives, while imparting desirable rheology, impair recoatability and intercoat adhesion of the system in which they are utilized where such systems, after drying, is painted or coated over with a second paint or coating composition. The present invention shows that these undesirable side effects can be avoided by using the inventive additives.
Normally rheological additives should show no reactivity, so they do not react with any other ingredients in the systems in which they are used. Intercoat adhesion is defined as adhesion between adjacent layers of paint when more than one coat of paint or coating is applied to a substrate. Examples of such use are primer and topcoats in home painting and a series of paint coatings applied to automobiles and appliances.
We have concluded it is essential when using additives to structure their chemistry so that, at necessary dosage, they do not adversely affect paint and coating compositions used by customers in systems where more than one coat will be applied to a substrate.
2. Description of the Prior Art
It has been known in the art for many years to use various materials as rheological additives to, among other rheological properties, modify the viscosity of organic systems. Such systems can include paints and coatings, inks, construction materials and wood stains. Depending on the composition of the system, the products made with these thickeners are preferably useful as coatings and paints.
The present invention includes novel rheological additives as well as organic fluid composition containing such additives.
Rheology is defined as the science of the flow and deformation of matter. Rheological additives can be defined as substances added to liquid systems which change that system's flow and viscosity properties. Proper rheology for storage and application must be balanced with the requirement of many fluid systems to resist sagging and dripping during and following application. The term “thixotropy” describes a type of flow behavior in which a temporary reduction in a fluid's viscosity by the application of shear, such as through the use of a paintbrush or atomizing equipment; once the shear forces have been removed, such as following deposition of the liquid onto a surface), the system will regain its initial, higher viscosity.
For background, Japanese Patent Application No. 62-69957 describes a sag preventor for non-aqueous coating materials comprising a mixture of two different fatty acid amides wherein fatty acid amide (A) is obtained by reacting a mixture of at least one straight chain saturated fatty acid having 3-4 carbon atoms and 12-hydroxystearic acid (the molar ratio of the fatty acid and 12-hydroxystearic acid being 1:9-8:1) and ethylene diamine or hexamethylene diamine and fatty acid amide (B) is obtained by reacting a mixture of at least one straight chain saturated fatty acid having 6-22 carbon atoms and 12-hydroxystearic acid (the molar ratio of the fatty acid and 12-hydroxystearic acid being 0:10-8:2) and ethylene diamine, hexamethylene diamine, or xylylene diamine wherein the weight ratio of fatty acid amide (A) to fatty acid amide (B) is 100:00-20:80.
Products believed to be the reaction product of ethylene diamine, a monocarboxylic acid having ten carbon atoms and 12-hydroxystearic acid have been sold for many years as rheological additives. A product, designated comparative X, using this chemistry has been used as a comparative example to the invention hereof in the below following examples.
It is an object of the present invention to solve or substantially alleviate the problems created by prior art thickeners in thickening compositions for organic systems. It is, therefore, a more specific object of the present invention to an additive which will provide paints and coatings without affecting intercoat adhesion.
This invention provides amide compositions having at least two amide moieties per molecule which comprises reacting preferably by known condensation reactions, a diamine selected from ethylene diamine, hexamethylene and mixtures thereof diamine and mixtures thereof, one or more monocarboxylic acid of the formula:
R1—COOH
wherein R1 is a straight chain saturated aliphatic hydrocarbon radical of 3 to 7 carbon atoms and 12-hydroxystearic acid. The inventors have found that the inventive composition provides improved rheological and suspension properties to non-aqueous coating systems and more importantly the inventive composition does not cause intercoat adhesion failures of topcoats subsequently applied to primers.
In an important aspect the invention covers a rheological additive consisting of the reaction product of:
The invention preferably relates to a composition, which is obtained by reacting
A most preferably aspect of this invention relates to a rheological additive composition consisting of a reaction product of:
wherein the equivalent ratio of monocarboxylic acid and 12-hydroxystearic acid is 0.4:1.6 to 1.8:0.2 and there are 2 equivalents of ethylene diamine.
The term “equivalent(s)” is used and is intended to have its standard meaning as employed in the art (see for example Hawley's Condensed Chemical Dictionary 1987, 11th Edition). However, for additional clarity, equivalents refer to the number of reactive groups present in a molar quantity of a molecule, such that a mole of a diamine (e.g. ethylene diamine) has two equivalents of amine and a mole of 12-hydroxystearic acid has one equivalent of carboxylic acid. Furthermore a monoacid has only one reactive group and a diamine has only two reactive groups (preferably both primary amines), and a monocarboxylic acid has one carboxylic acid group and these are preferable, although not necessarily, the only reactive materials present in the reaction mixture.
The diamines of component a) useful for the present invention include ethylene diamine and hexamethylene diamine with the most preferred being ethylene diamine. Hexamethylene diamine is often referred to as hexane diamine. These are common chemicals and can be obtained from a large number of chemical manufacturers.
The chemicals useful for component b) include monocarboxylic acids of the formula R1—COOH where R1 is between 3 and 7. Such acids are commercially available and include butyric acid, pentanoic acid, hexanoic acid, heptanoic acid and octanoic acid. The monocarboxylic acid of the formula R1—COOH wherein R1 is C8 and above falls outside the preferred acids. A preferred acid is heptanoic acid with the most preferred hexanoic acid. These acids are commercially available for example from Acme Hardesty Company, Penta Manufacturing Company and Procter and Gamble Company and others.
Component (c) is 12-hydroxystearic acid. This acid is produced from hydrogenated castor oil and is a straight C1-8 carbon chain saturated fatty acid with an OH group attached to the 12th carbon atom. Suppliers of such products include, for example, CASCHEM, Inc and Acme-Hardesty Company.
Generally the rheological additives of the present invention are preferably prepared according to known condensation reaction. The diamine, monocarboxylic acid and 12-hydroxystearic acid are reacted together in stoichiometric amounts so that no excess of the acid or the amine is left unreacted. The order of the addition of the co-reactants is not generally important and these can be added either at ambient temperature or at reaction temperature. For example, the reactants may be charged in increments to a suitable reaction vessel equipped with a mechanical stirrer, a thermometer, a Dean-Stark adapter or other water collector and a nitrogen inlet. The vessel containing the reactants is heated under a blanket of nitrogen. The reaction may be carried out under atmospheric pressure or under vacuum. The reaction temperature to be used in the synthesis may be varied, but preferably ranges from ambient temperature to 300° C. under normal pressure. More preferably, the temperature ranges from ambient to 250° C., and most preferably from 120 to 220° C. Water is removed as condensate as the reaction progresses. After the completion of the reaction, the additive is cooled to 140-150° C. and discharged into a release box and allowed to cool overnight. The product is then cooled with liquid nitrogen, dried and ground cryogenically to a fine powder using a Brinkmann centrifugal mill.
The rheological additives used in the present invention may be synthesized with or without a catalyst. The catalyst, if used, may be selected from those, which are normally used for condensation reactions. Examples of such catalysts include, but are not limited to, sulfuric acid, orthophosphoric acid, p-toluene sulfonic acid, dibutytin dilaurate, tetraalkyl tin or titanium compounds, metal hydrides and the like. A preferred catalyst is orthophosphoric acid. The catalyst should generally be used in an amount of from about 0.001 to 2.5 percent by weight based on the total weight of the reactants.
Inventive paints and coatings can be prepared using present standard and diverse paint and coatings base formulations by merely replacing existing rheological additives with the inventive additives described above. Amounts of additives used are normally between 0.5 to 3.5% of the base formulation. Alkyd enamel paints, air drying alkyd paints, long oil alkyd baking paints, two-pack epoxy polyamide primer paints and pvc topcoats are preferred paint coating systems.
The following examples are illustrations designed to assist those skilled in the art to practice the present invention, but are not intended to limit the invention. Changes can be made without departing from the spirit of the invention. The various chemicals used in the examples were commercially obtained materials.
A number of additives were made using the teaching of this invention as follows.
To a 500-ml resin kettle equipped with a thermometer, a Dean-Stark adapter, a water-cooled condenser, a mechanical stirrer and a nitrogen inlet, 25.84 grams (0.43 mole, 0.86 equivalents) ethylene diamine, 49.95 grams (0.43 mole, 0.43 equivalents) hexanoic acid, 132.75 grams (0.43 mole, 0.43 equivalents) 12-hydroxystearic acid and 0.04 gram phosphoric acid as catalyst were charged. The mixture was heated to 200° C. with stirring under a blanket of nitrogen with a steady flow of the inert gas. Water starts to come off at 150°-155° C. After an hour at 200° C., aliquots are taken hourly and the acid and amine values are determined. The reaction is continued until the acid and amine values are below 10. The reaction product is cooled to 120° C. and is discharged into a release box and allowed to cool to room temperature. The product is then cooled under liquid nitrogen and ground cryogenically to a fine powder using a Brinkmann centrifugal mill.
The general procedure outlined in Example 1 was used, except that the reactants were replaced as indicated in Table 1.
All the materials prepared according to Examples 1-31 were incorporated by dispersing into a long oil alkyd baking enamel paint system at a loading of 7.2 pounds per hundred gallons (pphg) and a number of tests were conducted to demonstrate the effectiveness of the respective rheological additive as to common rheological properties of the type shown below.
After the paints were made, they were allowed to equilibrate at room temperature overnight, and the paint properties were measured as described below:
(1) Fineness of grind (indicative of dispersibility) was measured in Hegman units using a wide path Hegman gauge in accordance with ASTM D1210-79.
(2) Brookfield viscosities at 10 and 100 RPM were measured with a Brookfield Model RVT viscometer in accordance with ASTM D2196-81. From viscosity data, a Thixotropic Index (TI) was calculated as follows:
Thixotropic Index (TI)=10 RPM Viscosity÷100 RPM Viscosity
(3) Sag resistance was measured in mils using a Leneta Sag multi notch applicator at room temperature in accordance with ASTM D4400-84.
(4) In some instances Stormer viscosities were measured in Krebs Units (KU) with a Thomas Stormer Instrument, Model #09730-G15, in accordance with ASTM D562-81.
Gloss measurements were measured at 60° and/or 20° in accordance with ASTM D523-80. Drawdowns were prepared of paints according to Formulation A, and the 60° and/or 20° gloss determined after curing the film for 24 hours at room temperature. The preparation and components of the long oil alkyd baking enamel paint system are described in Formulation A. The results are set forth in Table 2.
Additionally, samples of rheological additives of the present invention were evaluated for Brookfield viscosities and intercoat adhesion in a two-pack epoxy primer. The preparation and components of the epoxy primer two component paint system are described in Formulation B. The results of the tests in a two-pack epoxy primer are set forth in Table 3. PVC topcoat formulation used for intercoat adhesion test is described in Formulation C. The intercoat adhesion test method and the spray conditions are described below.
The results of the intercoat adhesion in the two-pack epoxy primer are set forth in Table 4. The spray conditions used for intercoat adhesion test are set forth in Table 5.
Additionally, the samples of the rheological additives of the invention were evaluated in an air drying short oil alkyd paint system. The preparation and components of the short oil alkyd paint system are described in Formulation D. The results are set forth in Table 6.
In order to compare the rheological properties of the inventive additives with common prior art additives, several comparative examples were made and tested.
A long oil alkyd enamel paint was prepared according to the procedure described in Formulation A to which was added a rheological additive designated as Comparative X which uses the chemistry described above. The paint properties were evaluated and set forth in Table 2.
A two-pack epoxy primer was prepared according to the procedure described in Formulation B without a rheological additive. The intercoat adhesion properties were evaluated and are set forth in Table 4.
A two-pack epoxy primer was prepared according to the procedure described in Formulation B with Comparative X rheological additive. The paint properties were evaluated and set forth in Table 3 and intercoat adhesion properties were evaluated and set forth in Table 4.
An air drying short oil alkyd paint was prepared according to the procedure described in Formulation D without a rheological additive. The paint properties were evaluated and set forth in Table 6.
An air drying short oil alkyd enamel paint was prepared according to the procedure described in Formulation D with Comparative X rheological additive. The paint properties were evaluated and set forth in Table 6.
Discussion of Results: As may be seen from the data set forth above, the rheological additives of the present invention as described in the Inventive Examples are effective rheological additives providing excellent properties of high viscosity, anti-sagging and high thixotropic index and maintaining good gloss.
Discussion of Results: As can be seen from the data set forth above, the additives of the present invention are effective paint additives yielding excellent viscosity results and thixotropic index in the two pack epoxy primer.
One important aspect of this invention is to match prior art compositions in paint properties without affecting intercoat adhesion properties. Prior art compositions show poor intercoat adhesion whereas the inventive example exhibits no intercoat adhesion failures.
Test 2 and 3 were run to show the improved intercoat adhesion properties of this invention. It used the below-described method.
Test system: 2 part epoxy primer
Application and storage temperatures: 10° C., room temperature, 40° C.
Primer applied: 1 and 3 spray passes
Top coat: 1 and 3 spray passes
Discussion of Results: As can be seen from the data set forth above, the rheological additive of the present invention shows no intercoat adhesion failures using the cross hatch test as compared with the Comparative Example 3 where Comparative X was used and are equal to the Comparative Example 2 where no rheological additive at all was added to the primer formulation. In the tape test, the rheological additive of the present invention shows excellent intercoat adhesion properties as compared to the Comparative Example 2.
Discussion of Results: As may be seen from the data set forth above, the rheological additives of the present invention show high viscosity increase and excellent anti-sagging properties as compared to the comparative example containing no rheological additive. The inventive additives show comparable viscosity increase and anti-sag properties as compared to the comparative Example 5.
The above results demonstrate the ability of the current invention to make paint and coating products without affecting intercoat adhesion as compared with prior art Comparative X. The above results also demonstrate that making the product in this manner does not detract from its effectiveness in thickening an organic based paint.
In this regard, the inventive rheological additives of this invention do not adversely affect intercoat adhesion properties of topcoats, which are subsequently applied to primers. The rheological additives of the present invention also provide acceptable and adequate increases in viscosity, improved sag resistance and suspending properties when incorporated in various coating systems.
The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10936831 | Sep 2004 | US |
| Child | 12836907 | US | |
| Parent | 09589166 | Jun 2000 | US |
| Child | 10936831 | US |
