How to choose the correct sandpaper base paper?

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When it comes to producing coated abrasives, the three key elements are the base paper, the abrasive, and  the adhesive. Among these, the base paper is the most varied and differently used  material, as different paper is used for producing water-resistant sandpaper, dry sandpaper, wood sandpaper, paper-backed sanding belts, and more. The quality of the base paper also has the biggest impact on the final overall product quality. This article aims to shed light on the selection process of the base paper, offering insights to help manufacturers stabilize and enhance their product quality.

Current State of Base Paper Manufacturing Companies

As a specialized industrial paper used for sandpaper production, the market for base paper is relatively niche. The annual domestic demand for base paper is less than 20,000 tons. However, with the accelerated industrialization in China, there has been significant growth in recent years.

Common Misconceptions in Base Paper Selection

1. One-size-fits-all approach for Coarse and Fine Grit Sandpaper

It's crucial to understand that coarse and fine grit sandpapers have significant differences in terms of grit concentration, bottom adhesive application, and double adhesive application. Therefore, they have distinct requirements for the base paper. Coarse grit sandpaper necessitates a base paper with a bias towards higher weight. On the other hand, fine grit sandpaper requires a base paper with a bias towards lower weight. Additionally, fine grit sandpapers demand a smoother surface with no visible paper fibers, as the fine grit particles and lower adhesive levels call for higher smoothness.

2. Alignment Between Base Paper and Adhesive

The selection of base paper and adhesive should be in harmony. Different qualities of sandpaper (A-grade, B-grade, latex-backed) require adjustments in the production process. For instance, A-grade paper, used for producing silicon carbide transparent sandpaper, should be paired with epoxy resin adhesive. B-grade paper, utilized for regular water-resistant sandpaper, pairs best with alkyd resin adhesive. Latex-backed paper, used for dry sanding super coating paper, requires either epoxy or phenolic resin adhesive. It's crucial to avoid mismatching these components, as it can lead to issues with wear resistance and durability.

3. Proper Identification of Base Paper Sides

Base paper has a distinction between the front and back sides. The side facing the wire part of the papermaking machine is referred to as the back, while the other side is called the front. The front side tends to be smoother and more even. Due to variations in equipment and requirements of coated abrasive manufacturers, the two sides of the base paper can have significant differences in oil absorption and smoothness. Therefore, it's imperative to select and use the appropriate side of the base paper based on the specific requirements for producing coarse and fine grit sandpapers.

4. Temperature Tolerance of Base Paper

The manufacturing process of base paper determines its temperature tolerance. Ordinary water-resistant sandpaper typically requires a tolerance of 70-80°C, which can be achieved using rosin as the adhesive. However, for A-grade base paper or latex-backed paper, which might undergo processes exceeding 100°C, it is vital to use appropriate adhesives to prevent brittleness and ensure longevity.

5. Relying Solely on Tensile Strength

While tensile strength is an essential parameter, it should not be the sole determining factor. Other physical indicators, such as weight, density, folding endurance, absorption, and moisture content, should also be considered. These factors collectively contribute to the overall quality and performance of the base paper.

Requirements for Sandpaper Base Paper

1. External Quality: The base paper should have uniform coloration, particularly for uncolored paper where each batch must match. Excessive dust, wrinkles, transparency, or holes are unacceptable. This is especially crucial for colored papers, where any blemishes are highly noticeable.

2. Internal Quality: The base paper should be made from 100% sulfate coniferous wood pulp, as opposed to 'sandwich paper' which incorporates waste paper pulp during the paper making process. It should have an appropriate weight for the specific type of sandpaper being produced.

Selecting the right base paper is a critical step in the coated abrasive manufacturing process. By understanding the nuances and avoiding common misconceptions, manufacturers can ensure that their products meet the highest quality standards.