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CLEARCOAT COMPOSITIONS COMPRISING CELLULOSE ESTERS AND FUMED SILICAS

IP.com Disclosure Number: IPCOM000238407D
Publication Date: 2014-Aug-25

Publishing Venue

The IP.com Prior Art Database

Related People

Eastman Chemical Company: OWNER [+3]

Abstract

This disclosure illustrates the improved appearance, circulation and storage stability achieved by the use of cellulose ester rheology additives, alone or in combination with certain type of fumed silicas in automotive clearcoats.

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This is the abbreviated version, containing approximately 18% of the total text.

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85707US01

CLEARCOAT COMPOSITIONS COMPRISING CELLULOSE ESTERS AND FUMED SILICAS

    This invention illustrates the improved appearance, circulation and storage stability achieved by the use of cellulose ester rheology additives, alone or in combination with certain type of fumed silicas in clearcoats, especially automotive original equipment manufacturer (OEM) clearcoats that do not require hardeners, catalysts, or activators.

    In order to control the rheology of liquid coating systems, organically modified bentonites, silicas and polyamide waxes are predominantly used. A disadvantage of these substances is that they are mostly dry solids which have to be brought into the form of a semi-finished product using solvents, a portion of binder resins and through a grinding process. Another disadvantage of these types of rheology control additives is that they lead to turbidity and haze in liquid clearcoats. They do not provide the necessary level of optical clarity to the resulting finishes, particularly when the coatings are designed for ambient temperature curing.

    Other widely used rheology control agents are sag control agents (SCAs). The obvious advantage of SCAs is that they can be directly added to a formulation without any grinding or other preparation steps. However, there are several shortcomings associated with SCA, particularly in clearcoat formulations, including optical clarity, shear stability, and storage stability. SCAs are opaque in general and may reduce the optical clarity of a clearcoat. Since an isocyanate and an amine adduct forms crystalline particles or needle like structures suspended in the resin in which it is prepared, they are opaque and clearcoats containing SCAs may also appear opaque. A clearcoat containing a SCA typically has to be baked above a certain temperature (in most cases, above 100C) to form a clear transparent film. Automotive OEM clearcoats are often recirculated for long period of time in the application plant. In the recirculation process, the clearcoats undergo shear stress that leads to variations in the rheological properties due to the instability of the SCAs. Consequently, variations in rheological properties can cause irregularities in the application. A clearcoat containing SCA tends to form layer separation during storage because of settling of SCA. Proper agitation during the storage and application is needed.

    Solus™ 2100 cellulose ester and a variety of other cellulose esters were tested in several automotive OEM 1K clearcoat formulations as the sole rheology modifier. It was found that cellulose esters offered excellent flow/leveling properties as well as reasonable sag resistance. However, in some applications where high film build (˃ 40µm) is preferred, cellulose esters as the

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85707US01

sole rheology additive may not provide sufficient sag resistance, which could compromise appearance for clearcoats applied on vertical surfaces. Our research has found that...