Chemistry: natural resins or derivatives; peptides or proteins; – Natural resins or derivatives – Tall oil or derivative used as starting material in process,...
Reexamination Certificate
2001-01-05
2003-06-24
Seidleck, James J. (Department: 1711)
Chemistry: natural resins or derivatives; peptides or proteins;
Natural resins or derivatives
Tall oil or derivative used as starting material in process,...
C530S201000, C530S215000, C530S212000, C530S210000, C530S216000, C530S214000, C530S217000, C530S221000
Reexamination Certificate
active
06583263
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to energy curable resin compositions used to formulate energy curable printing inks. More particularly, the invention relates to energy curable printing inks containing acrylated rosin and methods for preparing the rosin.
2. Description of Related Art
Resins, derived from natural products such as rosin esters are widely used as printing ink vehicles for flexographic and gravure printing inks. Maleic modified rosin-esters exhibit good pigment wetting, gloss retention, color retention and adhesion. Typically these esters are prepared from rosin, maleic anhydride and polyols, such as glycerol or pentaerythritol. In order to render these materials energy curable, acrylic groups are attached to free hydroxyl groups of the rosin ester. Since these hydroxyl groups are sterically hindered due to the bulky rosin moieties, the acrylation with acrylic acid is difficult, due to the severe reaction conditions necessary. Often these severe reaction conditions cause undesired polymerization of the acrylic functions at high temperatures due to their thermal instability. Therefore, an introduction of acrylic groups under mild conditions is typically required.
WO 87/04448 describes the esterification of fumarated rosin esters with hydroxyethyl acrylate at high temperatures above 200° C. At such temperatures there is a high risk of polymerization of acrylated functions even in the presence of an inhibitor.
U.S. Pat. No. 4,035,320 describes the reaction of special rosin esters, prepared with a large excess of polyols, along with acrylic acid. According to the nature of the described special rosin esters the acrylated compositions exhibit a mixture of low levels of acrylated rosin-esters and free acrylated polyols. However, the high excess of remaining hydroxyl functions after the reaction can affect the properties of the ink, since greater number of hydroxyl groups often give poor lithographic performance properties. To compensate for this the patent discloses that the free hydroxyl groups are capped by an additional reaction with acetic anhydride.
There continues, however, to be a need for methods to efficiently produce acrylated rosin esters, wherein the acrylate groups are connected directly to the rosin ester and are free of excess hydroxy groups and polymerized acrylate groups and where gellation, which can occur as a result of only partial polymerization during synthesis, is avoided.
SUMMARY OF THE INVENTION
The above described need is met by this invention, which is a method for preparing acrylated natural resin esters comprising: (a) esterifying one or more sterically hindered hydroxy groups of a natural resin ester, with 3-halopropionic acid at an esterification temperature of about at least 100° C. in an inert solvent to form a 3-halopropionate ester of the natural resin ester; and (b) reacting the resulting 3-halopropionate ester with an organic base at a reaction temperature of no more than about 100° C. thereby forming an acrylated natural resin ester that is free of polymerized acrylate groups and optionally free of excess hydroxy groups.
An added embodiment of this invention is an acrylated maleic-modified rosin ester comprising a maleic-modified rosin ester moiety and one or more acrylate moieties directly connected to the maleic-modified rosin ester moiety through an ester linkage; and, optionally, one or more hydroxy moieties; wherein the acrylated maleic-modified rosin ester contains about 30 equivalent % or more of the acrylate moieties based on the total equivalents of the acrylate moieties and hydroxy moieties and is substantially free of polymerized acrylate moieties.
Preferably the acrylated maleic-modified rosin ester contains about 40 equivalent % to about 75 equivalent % of the acrylate moieties based on the total equivalents of the acrylate moieties and the hydroxy moieties.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides a method for introducing acrylic functions into high molecular weight natural resins, such as rosin esters, under mild conditions, without the risk of gellation during the preparation. In particular, an acrylated natural resin ester is prepared by the invention by first esterifying one or more sterically hindered hydroxy groups of a natural resin ester, with a 3-halopropionic acid, such as 3-chloropropionic acid, at an esterification temperature of about at least 100° C. to form a 3-halopropionate ester of the natural resin ester. Next, the resulting 3-halopropionate ester is dehydrohalogenated by reacting it with an organic base at a reaction temperature of no more than about 100° C. to form the acrylated natural resin ester.
By the method of this invention, it was found, that roughly about 3 to 4 times more water is generated during the esterification with 3-chloropropionic acid than by direct esterification with acrylic acid. This finding indicates that a higher degree of esterification is achieved by using 3-chloropropionic acid instead of an acrylic acid and further illustrates the high efficiency of esterifying strong sterically hindered hydroxyl functions in natural resins in contrast to typical esterification methods using acrylic acid. Since the subsequent dehydrohalogenation of the esterified product proceeds at mild conditions (i.e. at a temperature of no more than about 100° C.) preferably at 25 to 80° C., there is low risk of forming uncontrolled polymerization products (i.e. gelling). Therefore, strong sterically hindered hydroxyl functions in natural resins can be more efficiently acrylated by the two step method of the present invention, than with the direct acrylation of natural resins with acrylic acid as taught in the prior art.
The first step of the present two step method comprises the esterification of a natural resin ester containing one or more sterically hindered hydroxy groups, with a 3-halopropionic acid at an esterification temperature of at least about 100° C. to form a 3-halopropionate ester of the natural resin ester.
Natural resin esters containing sterically hindered hydroxy groups, which may be used in the method of this invention, include rosin esters of polyols, maleated rosin esters of polyols, fumarated rosin esters, phenolic rosin esters. As used herein the term “polyol” is intended to include difunctional, trifunctional, tetrafunctional or polyfunctional hydroxy compounds such as ethylene glycol, propylene glycol, neopentyl glycol, 2-ethyl-2-butyl propanediol, polyethylene glycol, polypropylene glycol, glycerol, trimethylol ethane, trimethylol propane, trimethylol butane, pentaerythritol, dipentaerythritol, sorbitol, or a combination thereof, of which glycerol and pentaerythritol are preferred. Other natural resins derivatives, having sterically hindered hydroxyl groups, may also be used in the method of this invention such as for example derivatives of shellac, starch and dextrine. Of the natural resin esters, rosin esters are preferred, and maleated rosin esters are particularly preferred.
Rosin esters may be synthesized from commercial rosin such as China gum-rosin, along with trifunctional or tetrafunctional hydroxy compounds such as glycerol, pentaerythritol, and the like. Esters of rosin are commercially available and may be prepared as described in the “Printing Ink Manual”, Fifth Edition, Blueprint, London. The preparation of maleated rosin ester is specifically described in Example 1 which follows hereinafter.
The 3-halopropionic acids which may be used in the method of this invention may be 3-fluoropropionic acid; 3-chloropropionic acid; 3-bromopropionic acid; 3-iodopropionic acid; or a combination thereof. Preferably, the 3-halopropionic acid is 3-chloropropionic acid. The method of this invention is described hereinafter using 3-chloropropionic acid to esterify rosin esters or maleated resin esters, but the invention is not intended to be limited thereby.
The esterification of the rosin esters with 3-chloropropionic acid may be carried out by heating the 3-chloropropionic acid with the rosin esters, and optiona
Bissett Melanie
Persley Sidney
Seidleck James J.
Sun Chemical Corporation
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