Using dyes for improving the optical properties of high yield pulps

作者：Liu H^*; Yang S; Ni Y

来源：Pulp & Paper-Canada, 2007, 108(10): 25-29.

• dyes
• optical properties
• high yield pulps
• yellowing
• brightness

High yield pulps (HYP) have found increased use in many paper grades, including printing and writing, coated and uncoated wood-free papers. The residual lignin and the other color substances cause the yellowish tint of HYP. To improve the pulp quality, dyes may be used to minimize or even eliminate the yellowish hue. In this paper we determined the effectiveness of using a basic dye to shade the yellowish hue of the HYP, and the results were compared to those obtained from a hardwood bleached kraft pulp (HBKP). The results showed that the basic dye can effectively increase the whiteness and decrease the yellowish color of the HYP, while the brightness decreased slightly. With a small amount of dye the HYP can get CIE whiteness and b* similar to those of a market HBKP. pH is an important parameter in determining the dye effectiveness and the acidic paper-making condition was found to have a small negative effect on HYP shading. The contact time had a significant effect on the HYP shading process, and the CIE whiteness increased and b* decreased with increasing the contact time until a plateau was reached. In contrast, the shading process for the HBKP was extremely fast. Our results also showed that the basic dye had a strong affinity with the HYP under the typical conditions of stock refining, and the loss of dyes front the HYP under such conditions is negligible.

• 出版日期2007-10
• 单位天津科技大学