1. Field of the Invention
This invention relates to the manufacture of toothpastes and more particularly to a method of manufacturing a toothpaste which contains an abrasive system comprised at least in part of calcium carbonate.
2. The Prior Art
Dentifrices, such as toothpaste are generally extrudable pastes containing insoluble abrasives that aid in the removal of plaque, stains and other deposits from the teeth and help to polish them. Toothpaste compositions contain a variety of ingredients, the major types of ingredients generally being abrasive particulates,, a thickening agent, a liquid vehicle and surfactant. Other ingredients include flavoring agents and various other constituents for cosmetic, therapeutic or aesthetic effects.
Abrasives suitable for use in toothpaste compositions are generally finely divided, water-insoluble powdered materials such as silica, dicalcium phosphate dihydrate, calcium carbonate or calcined alumina. The toothpaste generally consists of a suspension of the abrasive in an aqueous humectant liquid phase. In order to hold the solid and liquid ingredients in the form of a stable paste with desirable rheological properties, the toothpaste invariably also includes a thickener or binder. A large number of different thickeners are known to the art and include, carboxymethylcellulose, xanthan gum, guar gum, carrageenan and mixtures thereof as thickener systems for toothpaste.
When preparing toothpastes, the toothpaste manufacturer encounters certain difficulties using abrasive powders and thickener systems to make a consumer acceptable toothpaste. For example, handling problems are encountered with the powdered abrasive where the particulate solids represent 10-60% by weight of the total toothpaste product and wherein the powders are low in bulk density which causes powder loss on debagging and during addition to the ingredient mixing tank. Also, upon the addition of the abrasive powder to the other ingredients in the mixing tank, there is a strong tendency towards lumping when combined with the water and humectant liquids present therein