Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-12-15
2002-08-06
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S272000, C524S300000, C524S457000, C524S458000, C524S460000, C524S764000, C524S798000
Reexamination Certificate
active
06429247
ABSTRACT:
FIELD OF INVENTION
This invention relates to novel rosin-fatty acid vinylic emulsion compositions and the process for preparing the same. In particular, the invention relates to novel rosin-fatty acid vinylic emulsion compositions which exhibit properties that make them useful as water-borne vehicles for coatings on various substrates.
BACKGROUND OF THE INVENTION
Polymeric resins are commonly employed in a variety of different uses. For example, polymeric resins may be employed as support resins for ink formulations. Typical surfactant-based emulsion polymerization products generally do not have the rheology properties desired for graphic arts and coatings applications (i.e. film build, flow and leveling, and stability). It is, therefore, a common practice to add to the emulsion polymerization a low molecular weight water or alkaline soluble polymer (also referred to in the art as a resin) in place of, or in addition to, a surfactant in order to improve the stability and rheology properties of the emulsion.
Supported emulsions are commonly employed in paints, clear coatings, floor finishes, leather treatments, cement formulations, functional paper coatings, and graphic art applications. The latter encompasses pigmented (ink) and non-pigmented (overprints and functional coatings) formulations. A support emulsion is comprised of two polymers, one that represents the support resin and a second polymer that is dispersed into the support. The second polymer may be dispersed through agitation or actually be polymerized in the presence of the support resin. Supported emulsions add stability while enhancing the flow characteristics of the formulation (thereby resulting in higher gloss and clarity). Traditional polymer supports are commonly produced by the polymerization of acrylic acid or another vinylic acid and other vinyl monomers (see U.S. Pat. Nos. 4,839,413 and 5,216,064, which are hereby incorporated by reference). Other reactants and additives include initiators, solvents, and chain transfer agents. Upon completion of the reaction, any solvents employed may be removed yielding a support polymer. The support polymer then can be solubilized in a basic aqueous medium.
However, major problems exist with the traditional methods of producing polymer resins. For example, these methods require the use of environmentally adverse hydrocarbon solvents. Moreover, as these solvents are not usable or desirable in water-based ink or overprint formulations, the solvents must be stripped from the resulting acrylic polymers (thereby causing a yield loss). This stripping step also adds expense to the process due to both the losses of yield and the energy consumed in performing the stripping. Also, these methods must utilize chain transfer agents to regulate the molecular weight of the resulting support resin.
In the present invention, rosin-fatty acid vinylic polymers used as support resins for emulsion polymerization are produced preferably in bulk condition, thereby eliminating the costly stripping process for resin production. In addition, the resin polymerization can be performed at a higher temperature than traditional solution polymerization reactions. Moreover, as the present invention employs a lower amount of free radical initiator and little or no chain transfer agent, the resulting resins can be produced at a reduced cost (and unpleasant odors associated with chain transfer agents can be avoided).
Accordingly, one objective of this invention is to disclose a method of producing support resins comprised of rosin-fatty acid vinylic polymers and a method of producing emulsions using these rosin-fatty acid vinylic polymers as the support resins.
Although water-based inks are comprised of various components, the emulsion polymer (ink vehicle) is principally responsible for adhesion to the substrate. Adhesion is a quantitative description of the work of detachment between two phases under conditions of failure.
Polyolefin film substrates are difficult surfaces on which to achieve high adhesion due to their high surface energies and lack of functionality. Water-based inks in particular do not adhere well to film surfaces. Prior attempts to improve the adhesion of water-based inks include methods of increasing the polarity of the emulsion polymer vehicle through changes in monomer compositions including incorporation of vinyl chloride (see: Sisson et al., American Ink Maker, Vol. 78, pp. 44-47, August 2000 and U.S. Pat. No. 6,020,438). Amino-functional ink vehicles are also a way of obtaining adhesion to film substrates (U.S. Pat. No. 5,948,546). While these systems enhance adhesion, they have not found wide spread usage due to compatibility problems with the other ink components.
Therefore, an objective of this invention is to solve these problems by disclosing a rosin-fatty acid vinylic emulsion composition having improved adhesion to various substrates, including plastic, wood, metal, and flexible substrates like film and foil.
Alkyds generally are formed by the esterification polymerization of polyols and polybasic acid. The reaction mixture may also include monobasic acids, fatty acids and the like.
Due to their desired physical properties and low material costs, solvent-based alkyds have long been widely used as ingredients in coating compositions for various materials. For example, films resulting from aqueous alkyd coating compositions may be used as protective coatings for farm equipment and as a finish or refinish for trucks and automobiles. They are also extensively employed in architectural varnishes and enamels which require high gloss. However, rising health and environmentally concerns over the emission of organic compounds from solvent-based paints have resulted in strict regulation of the amount of volatile organic compounds (VOC) emitted from applied paints. In addition, rapid advances in technical innovation require improvements in the properties of coatings compositions. For example, it is desired that pigments be dispersed more effectively with higher stability in order to produce coating finishes having improved gloss (i.e., gloss at 60°) and distinctiveness-of-image gloss (i.e., gloss at 20°). Moreover, these coatings often exhibit problems with adhesion, flexibility, and resistance to corrosion and chemicals.
In an attempt to comply with the challenges of increased regulation and improved performance, industry has devoted much effort toward developing water-borne and high solid alkyds coatings which employ far lower amounts of organic solvents than conventional coatings. In spite of these substantial efforts, a need exists in the industry for such improved water-borne alkyds and high solid alkyds coatings.
High solid alkyds which employ less organic solvent than conventional alkyds often suffer from a dramatic increase in viscosity as the amount of solvent employed decreases. It has often been necessary for a high solid system to use lower molecular weight resins in order to maintain a workable paint viscosity. However, such systems tend not to develop the same hardness and through-dry in thick films in the same amount of time when compared to systems using higher molecular weight materials. Moreover, the additional functionality (which may build up the coating molecular weight after application) usually required for such high solid systems commonly results in adverse performance and higher production costs. One example of the use of additional functionality is to increase the level of unsaturated fatty acid to ensure sufficient crosslinking to achieve acceptable coating properties. One of the major drawbacks in the use of such high solid alkyds is the development of severe yellowing in the cured coatings due to the increased level of unsaturated fatty acid. U.S. Pat. No. 5,370,939 attempts to address this yellowing problem in alkyd coatings by teaching the incorporation of polyhydroxy based allyl ethers into alkyds to replace a part of or all of, the fatty acid. In U.S. Pat. No. 4,591,518, alkyd resins containing pendant polymerizable unsaturated groups attached to t
Shah Rajnikant
Sisson Thomas M.
Sisson Warunee S.
Egwim K C
McDaniel Terry B.
Reece IV Daniel B.
Schmalz Richard L.
Westvaco Corporation
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