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
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.
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
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
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
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