2. Alkaline Paper making & QPC

Summary

This lecture focuses on the process of alkaline paper making and its impact on paper quality, stability, and durability. It explores the historical issues with paper deterioration, particularly with modern paper making compared to older techniques. The importance of cellulose purity and pH levels in paper production is discussed, along with the advantages of using alkaline sizing agents over acidic ones. The session also highlights how alkaline paper making can improve paper strength, printability, and productivity, while reducing costs. Additionally, it emphasizes key paper characteristics and testing methods to ensure quality control.

Takeaways

• 😀 The topic discussed is the alkaline paper-making process and its impact on paper quality, productivity, and costs.
• 😀 The issue of paper degradation and damage, especially to documents over 100-200 years old, led to the investigation of paper quality.
• 😀 Paper made from wood pulp (groundwood) contains high lignin, which causes faster aging compared to paper made with chemically processed pulp.
• 😀 Alkaline paper-making improves paper stability and longevity by reducing the presence of lignin, which leads to less yellowing and degradation.
• 😀 pH levels in paper-making are crucial: acid-based papers are less durable, while alkaline papers are more stable and last longer.
• 😀 In the 1800s, acidic sizing agents like Alum were used, but they caused rapid degradation in stored paper, prompting the search for better alternatives.
• 😀 Alkaline paper-making uses more stable and durable sizing agents like calcium carbonate, which helps in achieving better paper quality and lower costs.
• 😀 Calcium carbonate is a cost-effective alternative to traditional agents like Titanium dioxide (TiO2), offering similar optical properties at a much lower price.
• 😀 The relationship between paper-making process and quality control involves ensuring optimal pH levels (7-10) and low lignin content to achieve high-quality, long-lasting paper.
• 😀 Alkaline paper-making not only improves durability but also enhances paper strength, printability, and reduces friction, leading to smoother printing surfaces.
• 😀 Key paper properties such as roughness, brightness, opacity, porosity, and internal bonding are crucial for assessing paper quality and ensuring it meets customer needs.

Q & A

What is the focus of the second meeting in the transcript?

The focus of the second meeting is on 'alkaline paper making' and its relationship to paper quality, specifically how it impacts the durability and stability of paper, including the factors that affect paper's aging and longevity.

Why is there a concern about the deterioration of paper in libraries?

In the 1980s, it was observed that documents aged between 100-200 years were deteriorating, whereas older documents were in much better condition. This discrepancy raised questions about the quality of modern paper and the causes of its rapid deterioration.

What are the two key factors that affect the stability of paper?

The two key factors affecting the stability of paper are cellulose purity and the pH level of the paper.

What is the difference between groundwood pulp and chemical pulp in paper production?

Groundwood pulp is produced mechanically, retaining high lignin content, which accelerates aging and yellowing. In contrast, chemical pulp undergoes a chemical process that reduces lignin content, leading to better longevity and stability of the paper.

How does pH affect the quality of paper?

The pH of the paper determines its acidity or alkalinity. Paper made with acidic conditions tends to deteriorate more quickly, while paper made in alkaline conditions is more durable, resistant to aging, and less prone to yellowing.

What discovery in the 1990s improved paper-making processes?

In the 1990s, it was discovered that paper made using alkaline processes, as opposed to acidic ones, improved paper stability. This led to the widespread adoption of alkaline paper-making technologies.

What are the benefits of using alkaline paper-making techniques?

Alkaline paper-making increases paper stability, strength, reduces friction, improves printability, and lowers the cost of production. It also results in less paper deterioration over time.

What are some recommended parameters for achieving optimal paper permanence?

For optimal paper permanence, the pH of paper production should be between 7 and 10, the fiber should contain no more than 1% lignin, and the brightness retention should ensure that after 50 years, the brightness remains at 90%.

Why is calcium carbonate used in alkaline paper-making?

Calcium carbonate is used in alkaline paper-making as a filler because it is inexpensive, provides optical brightness, and helps maintain the alkaline nature of the paper. It is much cheaper than titanium dioxide, which was previously used.

How do the alkaline paper-making processes contribute to cost reduction in paper production?

Alkaline paper-making reduces production costs by lowering refining energy, enhancing fiber bonding, decreasing the need for mechanical defibrillation, and reducing the need for costly additives like titanium dioxide.