Field of the Invention:

The invention relates to coating compositions more particularly, the present invention pertains to compositions of protective corrosion and abrasion resistant underbody coatings for application in the automotive industry. The composition is provided in a ready to use formula meeting varied market application practices.

Background of the Invention

The currently marketed underbody coatings are spray products expected to provide corrosion and abrasion resistance to the car underbody. However, these are asphalt based products and do not have fuel resistance. Further, these coatings are sensitive to dirt cleaning solvents often used in car garages when the car is serviced or repaired. There are wide ranges of synthetic resins available to the paint industries, they are essentially polymers made from a glycerol, fatty acid and phthalic anhydride.

Underbody coats are applied on vehicle chassis. They are highly pigmented to give good obliterating power and to give good build or film thickness. However these known coating compositions do not exhibit anti-corrosion and anti-abrasion properties. These may be used only for decorative coating applications without desired anti- corrosion or anti-rub property. Although the underbody coating products pass all the internal quality tests, certain problems are encountered with these coatings. For instance, it is common practice that whenever an automobile is serviced or repaired, the vehicle is subjected to a diesel wash process wherein the cleaning is afforded by a water diesel mix to clear the dirt and grime from the underbody. This often results in the softening of the underbody coating which eventually causes surface peeling and flaking of the coating. Moreover the unstable viscosity under the prevalent application conditions result in sagging, overspray and a non-uniform coating. Therefore these products are susceptible to failure in such harsh durability conditions.

Some of the other serious disadvantages of the prior art asphaltic-type compositions is their tendency to become brittle, crack and separate from the substrate forming a pocket which can trap corrosive salt water and keep it in contact with the metal substrate over an extended period of time.

Polyvinylchloride (PVC) underbody coating compositions have been also widely used in the last decade as a chipping resistant and anti-rust protective coating and sealant for automobile under coatings.

However, in spite of the attractive characteristics of such automobile underbody car coatings which are known from e.g. US patent No. US5520961, JP06316664 the required recycling of automobile parts as much as possible due to increasing environmental pressure is not possible, as the PVC and auxiliaries included in said compositions, will cause the formation of hydrochloric acid and other toxic and/or environmental charging compounds, e.g. dioxines, when said compositions are burnt for recycling automobile parts.

Some of the other conventional underbody coatings, mainly two part curable compositions have been discussed in JP05320546, JP04154876, US4804734, EP280981. However, the major disadvantage encountered with these prior art compositions is the necessity of using them as a two-part system. Two-part systems obviously require an excessive amount of labor time and equipment utilization.

Particularly in view of the widespread use of these products, the significance attached to this problem is great: given the fact that, the manufacturers of such coating compositions have warranty liabilities on durability failures for these products, they have to face adverse economic consequences.

Hence there is a need to provide a composition which will materially alleviate the difficulties associated currently known automobile undercoating compositions and more particularly to lower the costs associated therewith, increase the efficiency of the respective operations related to applicability such as sprayability, brushability, providing a textured finish and affording a ready to use formula. Objective of the Invention

The objective of the present invention is to provide coating compositions, more particularly to underbody coating compositions comprising synthetic resins to achieve superior fuel resistance and improved mechanical properties such as good adhesion, tensile strength, quick drying characteristics, durability and imparting an orange peel appearance to meet varied market application practices.

Accordingly, one aspect of the present invention relates to a corrosion and abrasion resistant underbody coating composition comprising a polymeric binder, filler and an anti-corrosive pigment.

Another aspect of the present invention pertains to a polymeric binder for underbody coating compositions. It has been found, surprisingly, that the binders of the present invention allow the formulation of underbody coating compositions superior to those formulated from conventional binders. This is true in terms of the all of the properties related to a superior quality product being satisfied by the current invention. A further aspect of the present invention relates to a process for the preparation of underbody coating composition.

In accordance to a significant embodiment of the invention, the composition exhibits superior physical properties with regard to drying time, adhesion, fuel and water resistance, mar resistance (hardness) and salinity resistance.

Further advantages achieved by the present invention are minimum unit production cost without any compromise on the product quality.

Other features and advantages of the present invention will become apparent following detailed description proceeds. Brief description of the drawings

The present invention is illustrated in the accompanying drawings:

FIG 1 shows the illustration of superior fuel resistance demonstrated by Formula 1 [FIG 1(a)], Formula 2 [FIG 1(a)] of the present invention over Formula 5 [FIG 1(c)]

FIG 2 shows the orange peel texture appearance [FIG 2(a)] demonstrated by compositions of the present invention before [FIG 2(b)] and after application [FIG 2(c)].

DETAILED DESCRIPTION OF INVENTION

For purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about".

Corrosion is herein defined as an electrochemical process that seeks to reduce the binding energy in metals. It is a chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the metal and its properties. The process of corrosion is an anodic reaction process, whereby metal- dissolving ions are generated. The process occurring at the anodic site is the dissolution of metal as metallic ions, and converting these ions into insoluble corrosion products, such as rust.

Metal or metallic is defined herein as any substance susceptible to corrosion.

The coating compositions of the present invention have broad utility for protecting metallic substrates susceptible to corrosion, including ferrous substrates such as iron [Fe] and steel as well as Aluminum[Al] ,Copper [Cu], Magnesium [Mg] , and alloys thereof as well as other conventional metals employed in any structural applications where corrosion may occur due to contact by atmospheric moisture, water, salinity, humidity or other corrosives normally present in urban or industrial environments. Therefore, although it will be appreciated by those skilled in the art that the coating composition of the present invention may be applied to any type of metallic substrate, it is especially suited for use on preferably ferrous surfaces and will be described in connection therewith. The present invention relates to coating compositions for providing corrosion resistance on metallic substances, and more particularly, to such a coating composition that is especially useful for preventing abrasion and corrosion on vehicle underbodies and interior body parts. Importantly, the composition of the present invention may be used inside frames, hidden supports and to cover many irregular surfaces which cannot be coated with the typical, more viscous compositions of the prior art.

The composition of the present invention is essentially a "one-part" system which means all the necessary ingredients are composed in a single ready to use composition for application.

This invention is directed to an underbody coating composition comprising a polymeric binder, a filler and an anti-corrosive pigment especially designed for the automotive market.

One of the principle aspects of the present invention relates to a polymeric binder for underbody coating composition comprising a rosin modified alkyd resin and an oil soluble maleic resin with a drier material. Preferably, the binder comprises 80% by weight of a rosin modified alkyd resin and 20% by weight of an oil soluble maleic resin with a drier material.

The term "alkyd" is referred to a polyester modified by the addition of fatty acids and other components. Alkyd resins are essentially polymers derived from polyols and a dicarboxylic acid or carboxylic anhydride. Alkyd resins are of two types, drying and non- drying. Both types are typically produced from dicarboxylic acids or anhydrides, such as phthalic anhydride or maleic anhydride, and polyols, such as trimethylolpropane, glycerine or pentaerythritol. There are two general methods for their production which being (a) simple addition (b) Condensation polymerization. The resin prepared in accordance with the present invention comprises a linseed oil polymer, raw rosin, phthalic, pentaerythrotil, oil soluble maleic resin and mineral oil.

All of the above raw materials are charged into the vessel together and heated to a reaction temperature of about 40°C. The components react quite easily with each other to give an alkyd resin.

Drier combination is used to accelerate the conversion of coating from liquid form to dry film. Driers are primarily heavy metal soaps of organic acids. Some of the preferred drier combinations employed in context with the present invention are selected from the group comprising

(1) Cobalt Octoate: Acts as a "Surface Drier ". It is primarily an oxidation catalyst and has a tendency to cause surface wrinkling, hence to provide uniform drying.

(2) Manganese Octoate: It has both oxidizing and polymerizing properties and produce hard film.

(3) Zirconium Octoate: Acts as an active cross-linking agent and improves hardness of dried film as well as its adhesions.

In one of the embodiments of the present invention the drier combination (1) is present in the composition of the present invention in an amount of upto 5 parts of the binder mixture, or in some cases upto 4 parts of the binder mixture, or in some cases 3 parts of the binder mixture with the parts being considered based on the total weight of the resin combination. Preferably, in order to appreciate the advantageous attributes of the present invention, the anti-corrosive composition comprises 4 parts of the binder mixture.

To increase the rate of cure of the composition, that is to accelerate the conversion of coating from liquid form to dry film it is preferred to add about 4 parts of a drier combination, based on the weight of the binder. Typical driers that are used are, for example Manganese octate, metal salts of a 6-12 carbon atom saturated aliphatic monocarboxylic acid, such as nickel octoate, cobalt octoate, zirconium octate, nickel caprylate, nickel-2-ethylhexoate, and nickel naphthenate, cobalt naphthenate, manganese naphthenate, lead tallate; and the like.

Fillers- Inorganic fillers are solids that are present in a finely divided form in the composition. Fillers have two tasks; on the one hand they are to bring down the cost of a product in the conventional sense and ensure that, in comparison with products that are not filled, it has improved or additional, new properties, and on the other hand the use of fillers is often to facilitate the ease of production. In addition to the cost-lowering effect, fillers also have an influence upon the rheology, that is, thickening and, if applicable, thixotropy, by means of controlled adjustment of a time-dependent structural viscosity, for example by means of kaolin, talc and wollastonite. In general, the flow behavior is also affected by fillers. Although any of the aforementioned, or other, mineral fillers may be employed for such purpose, particularly preferred mineral filler in view of the present invention is silica.

The amount of filler used depends on the particular polymeric material, the filler and the property requirements of the finished products. The filler may be an inorganic filler commonly used such as silica, talc, calcium carbonate etc, however, in view of the workability of the coating. The filler in preference for the workability of the present invention is selected from the group comprising ground silica, fumed silica, precipitated silica, silicic anhydride and the like. Ground silica offers low binder demand for high loadings that giver better filling and bonding. Silica is used to improve mar resistance and abrasion resistance. They also function as anti-blocking and anti-slip agents.

In one of the embodiments of the present invention the filler mixture is present in the coating composition of the present invention in an amount of upto 60 % of the mixture, or in some cases upto 50% of the mixture, or in some cases 40% parts of the mixture, or in some cases 30% parts of the mixture with the parts, or in some cases 20% parts of the mixture, or in some cases 10% parts of the mixture, the % being considered based on the total weight of the coating composition. In one of the embodiments of the present invention the anti-corrosive pigment is present in the coating composition of the present invention in an amount of about 1 to 6 parts of the mixture with the parts being considered based on the total weight of the coating composition. Preferably, the anti-corrosive pigment comprises 5-6 parts based on the total weight of the coating composition.

A preferred anti-corrosive pigment employed in the present coating composition is preferably an Oxyamino phosphate of magnesium [OAPM]. The most important parameter of the protection mechanism by OAPM forms a continuous film which is composed of oxidized Magnesium and Phosphorus helping to maintain the surface potential below the corrosion values thus improving the cathodic surface protection.

In the curable compositions of the present invention, there may further be added, when necessary, various additives such as dehydrating agents, physical property modifiers, storage stability improving agents, antioxidants, adhesion promoters, lubricants, pigments, flame retardants each in an adequate amount. Accordingly, one such additive is Wood fiber Cellulose that provides high fiber strength and texture to the composition. In accordance with one aspect of the present invention the wetting agent is a salt of unsaturated polyamine amides and lower molecular weight acidic polyesters. Preferably, the wetting agent is Anti tera U.

The wetting step primarily consists of replacing the adsorbed materials on the surface of the pigment / filler and inside the agglomerates (water, oxygen, air) by the binder solution.

The role of the dispersing agents is to enhance the dispersion process and ensure a fine particle size in order to stabilize pigments in the binder solution.

The complete wetting out of pigment / filler helps to enhance the technical performance of a liquid coating that depends very much on interaction between the pigment particles and the binder system. Dispersing additives, which adsorb on the pigment surface, facilitate liquid/solid interfacial interactions and help to replace the air/solid interface by a liquid medium/solid interface.

In the formulation of coatings, it is well-known that rheological modifiers may be added to control the flow properties of the final product for a particular application. The rheological modifier utilized in the improved coating composition of the present invention advantageously performs the functions of both an anti-sag additive as well as a flow control agent.

The rheological additive of the present invention improves the sag resistance of a coating composition. Following application on a surface, the coating must maintain sufficient viscosity during the drying process to prevent unsightly runs and drips until the coating is dry. The rheological additive of the present invention was determined to increase the sag resistance of a coating composition, compared to a composition without the rheological additive and compared to a composition having a known rheological additive.

A preferred diluent/carrier is mineral oil.

The proportion of mineral oil may vary according to the desired consistency of the composition. Examples of mineral oil include mineral turpentine oil, spindle oil, machine oil, cylinder oil, turbine oil lubricating oils, light oils, brake fluids, antifreeze or synthetic lubricating oils and the like.

The present invention provides improved underbody coating compositions which may be easily applied by conventional spraying systems. Other modes of application are roller coating, brushing, sprinkling, flow coating, dipping, electrostatic spraying and the like.

In a preferred embodiment of the present invention, the coating composition comprises at least

(a) upto 50 parts of silica (b) up to 0.5 parts of a wetting and dispersive additive

(c) upto 2 parts of a rheological modifier

(d) upto 6 parts of a pigment

(e) Upto 22 parts of mineral turpentine oil

(f) Upto 2 parts of wood fiber cellulose.

The thickness of the coating, preferably of an undercoat is not particularly limited, however, usually ranges from 100 μηι to 500 μηι thickness. If the thickness is less than 100 μηι, the coating is likely to become susceptible to corrosion whereas if it exceeds 500 μηι, liquid dropping may occur.

Compositions of the present invention can be applied to a substrate to be treated by conventional coating techniques such as, for example, spray coating, brush coating, dip coating, direct roll coating, reverse roll coating, curtain coating, and combinations thereof, among other methods. Preferably, compositions of the present invention are applied by a paint spray gun.

Compositions of the present invention may be applied as a single coating, for example, as a clear coat and/or a topcoat; as a basecoat in a two-coat composition; or as a layer of a multi-component coating, for example, as a primer layer, basecoat and/or topcoat layer, and/or as a clear coat layer. Compositions of this invention are useful, for example, as a primer, a basecoat, a topcoat, and/or a clear coat applied either directly onto the substrate surface itself or disposed onto prior underlying coating(s) and/or treatment(s), e.g., an inorganic or organic treatment, a primer, and/or basecoat material, disposed on the substrate surface to achieve a desired result.

According to a further aspect of the invention a test metal panel coated with a control composition and a composition as per the current invention were subjected to various tests to evaluate the effect on flexibility, drying time, fuel resistance, water resistance, mar resistance (hardness), 5% salt spray resistance, and 1 mm cross cut test. The flexibility of the coatings are tested by conducting a Mandrel bend test for flexibility. These test methods cover the determination of the resistance to cracking (flexibility) of attached organic coatings on substrates of sheet metal or rubber-type materials. The coating materials under test are applied at uniform thickness to panels of sheet metal or rubber- type materials. After drying or curing the coated panels are bent over a mandrel and the resistance to cracking of the coating is determined.

The water resistance of coatings is tested by partial or complete immersion of coated test specimens in distilled or de-mineralized water at ambient or elevated temperatures. Although the apparatus and procedure could be employed in immersion tests using solutions of various materials in water, this practice is limited to tests in water alone.

Coated specimens are partially or wholly immersed in water in a container that is resistant to corrosion. The exposure conditions are varied by selecting (a) the temperature of the water and (b) the duration of the test. Water permeates the coating at rates that are dependant upon the characteristics of the coating and upon the temperature of the water. Any effects such as color change, blistering, loss of adhesion, softening or embrittlement are observed and reported.

Corrosion resistance test is conducted on a metal test panel and a coating of the composition prepared in accordance with the current invention. More specifically the corrosion resistance test is the salt spray test. The salt spray test is a standardized test method used to check corrosion resistance of coated samples. The appearance of corrosion products is evaluated after a period of time. Test duration depends on the corrosion resistance of the coating; the more corrosion resistant the coating is, longer the period in testing without showing signs of corrosion.

More particularly this test method covers the treatment of previously painted or coated specimens for accelerated and atmospheric exposure tests and their subsequent evaluation in respect to corrosion, blistering associated with corrosion, loss of adhesion at a scribe mark, or other film failure. This method therefore provides a means of evaluating and comparing basic corrosion performance of a substrate, pretreatment or coating system or combination thereof, after exposure to corrosive environments.

The composition of the present invention is subjected to a fuel resistance test to assess the fuel resistance of the coating.

Yet another test method is directed towards assessing the mar resistance (hardness) of the coating. This test method covers the determination of the mar resistance on smooth flat surfaces. The materials under test are applied at uniform thickness to flat panels of uniform surface texture. After drying/curing, the mar resistance is determined by pushing the panels beneath a rounded stylus or loop that is loaded in increasing amounts until the coating is marred. The mar resistance is ascertained in terms of load in kilograms at the mar failure end point. In order to assess the adhesion of coating films to metallic substrates by applying and removing pressure-sensitive tape over cuts made in the film. These test methods are used to establish whether the adhesion of a coating to a substrate is at a generally adequate level. The following examples illustrate certain embodiments and aspects of the present invention and not to be construed as limiting the scope thereof. All parts and percents therein are by weight unless otherwise indicated.

EXAMPLE 1

The polymeric binder composition were prepared as tabulated in Table 1 to evaluate the performance attributes such as drying time, fuel resistance and mar resistance (hardness) at various ratios by measure in weight % of component (1) i.e., rosin modified alkyd resin and component 2 i.e., oil soluble maleic resin retaining the drier component at a constant weight %. TABLE 1

EXAMPLE 2: The composition of the present invention was prepared by adding 80% by weight of a rosin modified alkyd resin and 20% by weight of an oil soluble maleic resin with the drier material (polymer binder) into a vessel. After the addition was completed, the wetting and dispersive additive, rheological modifier additives were slowly added to the vessel. All the ingredients were mixed with high speed stirring for one hour (1000+10 RPM)

The stirrer was turned off and subsequently black oxide, OAPM and ground silica were added in the order listed below and mixed until the mixture was completely homogenized. (1500+10 RPM)

a. Black Oxide - Mixing time 20 minutes

b. Pigment OAPM - Mixing time 10 minutes

c. Silica Mixing time 20 minutes

When the product was totally homogenized, the stirrer was turned off and approximately 500 ml of the sample was collected for the tests.

In order to demonstrate the superiority and/or non-obviousness of the compositions prepared in accordance with the present invention, the polymeric binder compositions as tabulated in table 1 were combined with other ingredients like ground silica, wetting and dispersing additive, rheological modifier additives, black oxide, mineral turpentine oil and wood fiber cellulose to yield the finished product. The finished products were also compared to some of the currently marketed formulations and control formulations to evaluate the superior performance attributes of such as flexibility, water resistance, fuel resistance, mar resistance, corrosion resistance and adhesion test.

TABLE 2

TABLE 3

^: - 'Undershield' (marketed product) TABLE 4

^: - 'Undershield' (marketed product) ; **- 'BodySchultz ' (marketed product)

EXAMPLE 1: FLEXIBILITY TEST

The test was conducted in accordance to ASTM D522 - 93a (Standard Test Methods for Mandrel Bend test of Attached Organic Coatings). The coating compositions under test were applied at uniform thickness to test metal panels. After drying and curing, the coated panels were bent over a mandrel and the resistance to cracking of the coating is determined. Formulations 1-4 representing compositions prepared in accordance with the present invention exhibited superior resistance to cracking.

EXAMPLE 2: WATER RESISTANCE TEST

The test was conducted in accordance to ASTM D870-09 (Testing water resistance of coatings using water Immersion). The tank was filled with water to a depth such that the test specimens were immersed approximately three quarters of their length. Water resistance is measured in terms of the days of water resistance passed by each of the individual test specimens. EXAMPLE 3: FUEL RESISTANCE TEST

The test was conducted in accordance to ASTM D4752-10. The test metal panel was coated with the coating composition and dried. The dried panel was immersed after 48 hours in petrol for 30 minutes. Fuel resistance was measured in a rating of 0 to 5, 0 being the worst rating and 5 being the best. Formulations 1-4 representing the compositions prepared in accordance with the present invention exhibited superior fuel resistance.

EXAMPLE 4: MAR RESISTANCE

The test was conducted in accordance to ASTM D5178. Mar resistance is calculated in terms of the resistance exhibited by the surface of the coating to permanent deformation resulting from the application of a dynamic mechanical force. Mar resistance is comparatively measured in terms of the load in kilograms at the mar failure end point. Formulations 1-4 representing the composition prepared in accordance with the present invention exhibited a mar resistance of 3.5-6 kg.

EXAMPLE 5: CORROSION RESISTANCE TEST: 5% SALT SOLUTION IN SALT SPRAY TEST

The test was performed in an apparatus for testing consisting a closed testing chamber, where a salted solution (mainly, a solution of sodium chloride) was atomized by means of a nozzle. This produces a corrosive environment of dense saline fog in the chamber such that the metal parts exposed were attacked under accelerated corroding atmosphere.

The metal test piece was exposed to standardized 5% solution of NaCl known as NSS (neutral salt spray). The results are represented as testing hours in NSS without appearance of corrosion products.

The results of the 5% salt spray test are tabulated in Table 2 with the composition of the present invention prepared according to Formulations 1-4 passed 800-1000 hours of corrosion resistance. EXAMPLE 6: ADHESION TEST

The test was conducted in accordance to ASTM D3359-09. The procedure comprises for assessing the adhesion of coating films to metallic substrates by applying and removing pressure-sensitive tape over cuts made in the film. The adhesion strength was determined in accordance with test methods D1000 or D3330/D3330M in terms of adhesion ratings. The composition of the present invention prepared according to Formulations 1-4 passed the 1mm cross cut test exhibiting superior coating adhesion.

While the present invention has been described herein with some specificity, and with reference to certain preferred embodiments thereof, those of ordinary skill in the art will recognize numerous variations, modifications and substitutions of that which has been described which can be made, and which are within the scope and spirit of the invention. It is intended that all of these modifications and variations be within the scope of the present invention as described and claimed herein, and that the invention be limited only by the scope of the claims which follow, and that such claims be interpreted as broadly as is reasonable.