Washable marking compositions such as crayons have been known. See, for example, U.S. Pat. Nos. 4,212,786, 3,993,492, 4,978,390, and 5,084,098. Some of these compositions contain polyethylene glycol as an ingredient that contributes to the washability of the mark. Thus, for example, the '492 patent discloses a water soluble composition intended for making a variety of articles including crayons, lecture pencils, and the like. The composition contains a pigment, polyethylene glycols of different molecular weights, a non-ionic emulsifier, and a filler.
Although polyethylene glycol has been effective in improving the washability of the marks, some crayons made from such compositions have been found to have some drawbacks. For example, the crayons have diminished mechanical strength such as point strength. Thus, thin crayons, which are ideally suited for use by young children, tend to break rather easily. This reduced mechanical strength precludes the manufacture of thin crayons. Further, it is believed that manufacturers of crayons containing polyethylene glycol experience high reject rates due to the high melt-viscosity of these compositions particularly at low processing temperatures. In addition, flaking and rough writing or absence of smooth laydown are some of the problems encountered with these crayons.
Thus, there exists a need for a washable marking composition that offers a crayon having an enhanced mechanical strength. There further exists a need for a washable marking composition that can be manufactured into crayons more easily, with a reduced reject rate. There further exists a need for a washable marking composition whose crayon flakes less. There further exists a need for a marking composition that has smooth laydown properties.
These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
USPTO Backgrounds
USPTO Backgrounds