Advantages of HEC application in toothpaste:
(1)Combined with CMC, to meet the requirements of modern toothpaste production process, so that the time of wetting, hydration and expansion of adhesive is shorter than in the past, suitable for dry production process.
(2) The particle size is less than CMC, and the paste appearance is bright, delicate and textured.
(3) Good dispersity, smooth taste and rich foam.
(4) The dispersity and thixotropy of toothpaste were greatly improved due to the introduction of hydroxyl group in the molecule. Good for pumping and filling, reduce the pressure of extruding paste, reduce the phenomenon of trailing.
Characteristics of HEC application in toothpaste:
1. Influence of pH on hydration time. HEC will agglomerate immediately if added directly to water (cold or hot), so special care should be taken. The results show that the pH of aqueous solution has a certain influence on the hydration time of HEC, and the hydration time is proportional to pH. The hydration time of HEC was 40min at pH 8 and 80min at pH 7.
Therefore, for calcium carbonate or calcium hydrogen phosphate formulations, the hydration time of HEC is basically the same as that of CMC alone, and the paste preparation time does not need to be extended. For silicon dioxide formulation, the addition time of acid-base regulator can be adjusted to shorten the hydration time of HEC. In alkaline environment, the hydration time of HEC is generally 30min under appropriate shear action.
2. Influence of temperature on hydration time. Temperature directly affects the degree of physical and chemical change between substances. Studies show that hydration time is inversely proportional to temperature. Therefore, the HEC hydration time can be shortened by using the heat generated during the paste making process. The system only needs to be kept within a relatively stable temperature range. Generally, the temperature of the system is 30-50 °C. The hydration time of HEC at 35°C is significantly shorter than that at 5°C.
3.HEC has better anti-electrolyte ability than CMC, but it can also be degraded by enzymes. The anionic CMC is sensitive to high concentration of ions, which reduces the bonding properties of CMC. Too high pH (pH>9. 7) or too low pH (pH≤5.0) will reduce the performance of CMC, so that the application of CMC in high-quality, special effect toothpaste is limited. By using non-ionic HEC as adhesive (thickener), the performance of the adhesive against high concentration of ions is enhanced, the storage stability of the paste is greatly improved, and the storage time of the toothpaste is prolonged.
Because HEC has good compatibility with CMC, it can be used in high-salt toothpaste. The process requirements are:
② The replacement degree Ms of HEC applied to toothpaste should be in the range of 1.8 ~ 2.5.
② The use method of HEC is the same as CMC, and can be mixed evenly with CMC, and then operate according to the actual process.