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Specialty Minerals Precipitated Calcium Carbonate Products for Paperboard Applications

Specialty Minerals Inc. (SMI), a wholly owned subsidiary of Minerals Technologies Inc., provides the technology and products to advance the science of papermaking. By concentrating on precipitated calcium carbonate (PCC) for the paper industry, SMI leads the way in new product innovation, implementation of alkaline papermaking, cost reduction through higher filler usage and machine productivity, enhanced paper quality and environmentally-friendly industrial practices.  

SMI’s satellite plant program has reduced papermaking material and processing costs by locating PCC manufacturing plants on site at the paper mill. In addition to freight and inventory economies, all of our PCC products reflect SMI’s commitment to quality and performance and can be tailored to meet the unique needs of a specific application or even the needs of a distinct paperboard within a specific application. We can control processing parameters (degrees of freedom) to customize PCC particle shapes, particle sizes, particle distribution, surface area, and surface chemistry. All of these are designed to optimize individual board performance.

Control over these “five degrees of freedom” allows us to manufacture a wide range of PCC products that are optimized to meet the unique and dynamic needs of almost every board application. We offer distinct families of products targeted toward a primary papermaking need, which allow for optimization within the family to address secondary papermaking requirements. We continue to research alternate PCC morphologies and methods of PCC manufacture in order to generate products with new and exciting benefits.

The following family of PCCs can be used in a wide variety of uncoated and coated paperboard applications including various linerboards, coated containerboard, pre-coated or top-coated bleached paperboard, and white top linerboard.

PCC products for filling uncoated paperboards:

Albacar® Precipitated Calcium Carbonate (PCC) Family

Albacar® precipitated calcium carbonates (PCCs) are a family of ideal mineral fillers for papermaking settings where maximum caliper and brightness are required. Its unique scalenohedral (or rosette) morphology, average particle size, and particle size distribution are controlled during synthesis to provide economical paper opacity, brightness, and bulk. Optimized filler bulk helps maintain paper grade stiffness. In addition, Albacar® PCC maximizes light scattering (opacity and brightness) which minimizes the need for costly alternative minerals and optical brighteners. This mineral filler is recommended for use in uncoated fine papers and coating base stock.

Specialty Minerals Inc. (SMI) manufactures three grades of Albacar® PCC as shown in the selector chart. In general, these scalenohedral calcite crystals have similar properties but differ in particle size and surface areas. These differences yield desirable properties that the papermaker can exploit to his advantage. For example, the smaller particle size Albacar® HO PCC is used where opacity and brightness are more important. The larger particle size Albacar® LO PCC is the filler of choice where improved sheet strength and added bulk are desired.

 

You can request technical data and Material Safety Data Sheets (MSDS) for Albacar® PCC products. Contact Us

Albafil® Precipitated Calcium Carbonate (PCC) Family

The Albafil® precipitated calcium carbonates (PCCs) from Specialty Minerals Inc. (SMI) represent a set of economical fiber substitutes that improve wet press efficiency, reduce dryer steam demand, and allow more bonding within the wet fiber web. Hence, Albafil® PCCs provide papermakers with higher productivity through fewer web breaks and faster machine speeds, while significantly improving sheet quality. Albafil® PCC’s particle size and shape also provide superior optical properties over ground calcium carbonate (GCC) and chalk.

Albafil® PCC is available in a range of closely controlled particle sizes that can be customized to suit an individual mill’s requirements. The narrow particle size distribution of Albafil® PCC, coupled with its prismatic shape, produces the best filler for higher mineral content alkaline papers. Its smaller average particle size scatters light more effectively than any natural ground filler, producing a more opaque and brighter sheet.

SMI manufactures four slurry grades of Albafil® PCC as shown in the selector chart. In general, these calcite crystals have similar properties but differ in particle sizes and surface areas. The smaller particle sizes can be used where opacification and porosity controls are desired. The larger particle sizes provide highest dry strength and excellent internal sizing

For neutral or slightly acid papermaking systems, SMI has patented the AT® PCC system, which allows papermakers to use PCC in environments down to pH 6.5. The paper machine wet end environment is buffered to protect the PCC from acid dissolution.

AT® Precipitated Calcium Carbonate System

Specialty Minerals Inc. (SMI) precipitated calcium carbonate (PCC) filler pigments permit papermakers manufacturing wood-containing papers to cost-effectively attain high brightness and opacity demanded by today’s publishers. Traditionally, paper utilizing virgin or deinked mechanical pulps was made under acidic conditions in part due to fiber darkening. Mechanical (groundwood) pulps used in the wet end contain lignin, a naturally occurring material that darkens with increasing pH. This alkaline darkening reduces the effectiveness of PCC at increasing paper brightness. If the pH of a mechanical papermaking system is controlled to about 6.5 to 7.5, alkaline darkening is minimized and PCC is much more effective. The problem with this pH range is that calcium carbonate is soluble and significant amounts of PCC will dissolve.

SMI offers the AT® PCC (acid-tolerant) system utilizing a patented technology that allows PCC to exist in weakly acidic to weakly alkaline conditions without significant dissolution or stability problems. The AT® PCC system can be used with a number of different PCC fillers that outperform clay and other fillers. The AT® PCC system allows mechanical papermakers to realize brightness and opacity characteristics compared to PCC in woodfree papers, which are typically made under alkaline production environments.

The AT® Precipitated Calcium Carbonate System
The AT® PCC system from SMI is a three component system consisting of appropriate amounts of calcium carbonate (precipitated or ground calcium carbonate and/or chalk), a weak acid, and a chelant. The weak acid buffers the water of the paper machine at the desired pH level (typically 6.8 to 7.2). When stable, the buffer system will resist pH changes in either direction because buffering species are capable of consuming both H+ and OH- ions. PCC is prevented from significantly dissolving in the system because of the common ion effect. Once the system reaches equilibrium, the presence of dissolved calcium ions in the water inhibits further PCC dissolution.

While increased dissolved calcium levels help inhibit calcium carbonate dissolution, they also accelerate the decomposition of soluble buffering species which can precipitate as calcium salts. The chelant addresses this issue by serving a dual function. First, the chelant stabilizes the buffering species by binding calcium ions. The chelant has a higher affinity for calcium ions than the soluble buffering species which allows for greater increases in dissolved calcium before the buffering species precipitate as calcium salts. Second, the chelant acts as a scale inhibitor. The chelating agent, in addition to binding calcium ions, inhibits the formation of calcium salts by reacting with the surface of calcium salt crystal inhibiting further crystal growth. This action prevents deposit formation on the paper machine. The chelant is usually added to the filler either separately or as part of the filler dispersant package.

Pointers for Understanding the Chemistry of the AT® Precipitated Calcium Carbonate System

  • When running the AT® PCC system, it is important to consider the entire papermaking system. Chemical dosages will be determined by the degree of unbuffered fresh water entering the system although filler loading and alkalinity will affect acid demand.
  • If the AT® PCC system is not run properly, poor brightness response or scaling issues may result.  Warning signs that the system may not be running properly are large variations in pH, increases in acid demand, and sharp increases in dissolved calcium.
  • Chelant use is critical for this application to run properly. SMI has identified several preferred chelating agents for this application.
     

The AT® PCC system does not stabilize PCC against dissolution by strong acids. Contact with strong acid (e.g. HCl or H2 SO4) should be avoided throughout the paper mill to minimize dissolution and calcium ion buildup.

In addition to its incorporation into printing and writing papers, Albafil® PCC is also widely used as a filler in cigarette papers to control the burn rate.

 

You can request technical data and Material Safety Data Sheets (MSDS) for Albafil® PCC products. Contact Us

Megafil® Precipitated Calcium Carbonate (PCC) Family

The Megafil® family of precipitated calcium carbonates (PCCs) from Specialty Minerals Inc. (SMI) act as functional additives and fiber substitutes in the paper web, offering a balance of improved dry strength properties and internal sizing advantages. In conjunction with the paper fibers, the solid prismatic crystals of Megafill® PCC create a uniform structure, which promotes greater paper stiffness and strength. In fact, the specific particle shape of Megafill® PCCs interferes less with fiber-to-fiber bonding than other common minerals.

Megafil® PCC also reduces wet end chemical usage. In many instances, this pigment can significantly increase internal sizing response with the same level of synthetic size. It promotes easier drying during high speed paper production, creates a denser, flatter sheet than with traditional PCC fillers and develops a smoother substrate for subsequent coating operations. As with all PCC products from SMI, Megafil® PCCs are practically non-abrasive, high in brightness and display excellent first pass retention. Importantly, all of these benefits are made possible with improved paper machine speed and runnability.

There are three slurry grades of Megafil® PCC from SMI as shown in the selector chart. In general, these calcite prismatic crystals have similar properties but differ in particle sizes and surface areas. These differences give rise to desirable properties that can be exploited to the papermaker’s advantage. For example, the smaller particle size Megafil® 1000 PCC is used where optics and paper porosity are more important, while the larger particle size Megafil® 3000 PCC is recommended where strength and caliper control are needed.

 

You can request technical data and Material Safety Data Sheets (MSDS) for Megafil® PCC products. Contact Us

Opacarb® Precipitated Calcium Carbonate (PCC) Family

Opacarb® precipitated calcium carbonates (PCCs) are a family of Specialty Minerals Inc.’s (SMI’s) products designed for coated paper and paperboard applications. With a range of aragonite particle sizes and narrow particle-size distributions, Opacarb®  PCCs are tailor-made to maximize fiber coverage and light scatter. From glossy to matte finishes, Opacarb® PCC provides both brightness and opacity increases not attainable with other commercial calcium carbonates.

Opacarb® PCC is ideal as a precoat or a topcoat pigment for offset and rotogravure printing on paper or board. Color print images are sharp and vibrant due to its narrow particle-size distribution, which provides an optimal coating structure for porosity control.

 

You can request technical data and Material Safety Data Sheets (MSDS)  for Opacarb® PCC products. Contact Us

We continue to research and test new PCCs in our laboratories. Many of these products are designed to meet the changing demands of manufacturers of uncoated and coated papers and paperboards. New generations of high brightness, cost-efficient PCCs are capable of providing very high filler contents to enhance surface properties.

Backed up by multiple state-of-the-art laboratory facilities and access to pilot scale coating machines, we forge partnerships with our paperboard customers to create solutions for paper manufacturing problems. For example, SMI can assist in engineering plant design, optimizing paperboard machine runnability, tackling wet-end chemistry problems, and creating the best cost-performance benefits.