Marble powder in the Paper Industry
The use of marble in the paper industry is one of the most fascinating examples of the circular economy, transforming mineral residues into essential day-to-day components.
Marble powder is an “invisible hero” in various sectors.
It’s called Stone Paper, also known as Mineral Paper.
Marble is mainly composed of Calcium Carbonate (CaCO₃) and can be ground down until forming a very thin powder. This can have three principal functions in the industry:
1. A substitute for Cellulose as a Filler
Marble powder can be mixed directly with the paper pulp and can substitute the wood fiber (cellulose).
This helps in two ways:
- Cost reduction
It's significantly cheaper than wood fiber
- Opacity and whiteness
Marble gives paper a natural color and a higher opacity, preventing the ink from passing to the other side of the paper. This is ideal for front and back printing
2. Coating and shine
In high-quality papers like magazines or luxury leaflets, the calcium carbonate is used as a covering pigment
This helps in two ways:
- Softness
It fills up the irregularities between fibers, creating a smoother surface
- Printing quality
Better ink absorption, making images and colors clearer, more vibrant, and giving them a better shine
3. The innovative “Stone paper.”
This is a technology that can create paper without using trees or water
This helps in two ways:
- Composition
80% of Marble powder mixed with polyethylene resin
- Properties
The result is a highly durable, waterproof (can even be used underwater), tear-resistant, and 100% recyclable paper
4. Additional Environmental Benefits
- Neutralization
Marble has alkaline properties, helping to neutralize the natural acidity of the paper fabrication process, making the final product more durable and less prone to turning yellow with time
- Forrest preservation
By substituting cellulose for minerals, the pressure on Forestry is reduced
In Portugal, are there any factories that use this stone paper (Mineral paper) technology?
The scenery of stone paper factories in Portugal is currently in a transition phase between Academic investigation and industrial production.
Even though Portugal is a huge world producer of paper with cellulose, mineral paper is only being produced by very few or no companies.
- Project PPAPECO (Portugal Stone Paper) is the most relevant investigation led by the Polytechnic Institute of Leiria
Their objective is to create a circular economy that utilizes marble powder from extraction quarries like Pardais and Vila Viçosa to produce mineral paper.
- EmanaGreen
Is one of the main commercial references in Portugal for this technology. From notebooks, cards to maps made out 80% marble powder and resin.
- Traditional paper Industry
Big Portuguese companies already use ground marble (calcium carbonate) in their production of cellulose paper to increase whiteness and opacity, but not to create 100% mineral paper.
Stone paper opportunities in Pardais and Vila Viçosa
The marble region of Alentejo is seen as a “gold mine” for this technology, because it generates millions of tons of waste. This could well feed local factories of mineral paper. It would reduce the ecological footprint of the region drastically, eliminating the mountains of debris that characterize the landscape.
Other Industries that require Marble Powder
In the pharmaceutical and health industries, its purity makes it a valuable ingredient.
1. Pharmaceutical
- Anti-acids
Is the main component for heartburn medication. This acts in the stomach like a gastric acid neutralizer.
- Calcium Supplements
Used to treat and prevent osteoporosis, being a bioavailable source of calcium for the bones
- Excipient for Pills
It serves as a “filler” or neutral base to provide volume and form for many medicines, making it easier to digest
2. Health
- Toothpaste
Marble powder acts like a soft abrasive. It helps to remove bacterial plaque and superficial stains on the teeth without damaging the enamel.
3. Food Industry
There are rigorous norms and certifications for the marble powder used for human consumption.
To be considered “food grade”, it cannot just be grounded powder; it has to go through several processes of refinement to eliminate contamination and meet legal specifications
- Main norms and certifications
- E170 addictive code
In Europe, calcium carbonate food additive is qualified as E170. To be sold is has to respect the EU regulation No 213/2012 that establishes specifications of purity and limits the levels of heavy metals
- Food Chemicals Codex (FCC)
Is the international standard (used in the USA by the FDA) that defines the identity and purity criteria for food ingredients
- Good fabrication practices
Production should be in certified installations to control cross-contamination and full traceability of the batch
- Food safety certifications
Companies that process this powder need to have certifications such as FSSC 22000, ISO 22000, or IFS Food.
- Purity Certification
- For it to be safe for consumption, it should have a purity superior to 97% or 98%.
- Severe restrictions on Heavy metal limits for Arsenic (max 3 mg/kg), lead (max 1 mg/kg), and Mercury (max 0,3 mg/kg)
- Microbiological Control tests to guarantee the absence of bacteria such as Salmonella and E. coli
- Common Usage
When certification complies, this powder can be used as:
- Dye for cakes
- Anti-caking and stabilizing agent in doughs and breads
- Calcium supplement for plant-based drinks and diet pills
- Chewing Gum
4. Cosmetics and Personal Care
- Facial Powders & Makeup
Due to its capacity to absorb excess oils and confer a silky texture to the skin
- Sunscreens
In some formulas, it helps to create a barrier against UV rays
5. Environmental Protection (Unusual)
- Treatment for acid lakes
In countries with acid rains, the marble powder is released from Helicopters over lakes and forests to neutralize the pH levels of the water and save entire ecosystems
6. Plastic and Rubber Industry
Marble powder is much more than a simple “filler” to reduce costs. It acts like a functional reinforcing agent that transforms the mechanical properties of PVC pipes, making it a more robust material.
Here are the principal forms of how it makes PVC more resistant:
- Increased Hardness and Flexural Modulus
Pure PVC is naturally a polymer that can be deformed under pressure. The addition of fine particles of Calcium Carbonate creates a stiffer composite structure.
- Resistance to deformation
In pipes and window profiles, the powder prevents the material from folding or deforming easily under pressure or weight.
- Dimensional Stability
It reduces plastic shrinkage after molding, ensuring that the pieces hold their exact measures for longer.
- Better Resistance to Impact
Although it may seem contradictory, adding “stone” makes the plastic less brittle. Particle science explains this phenomenon:
- Energy Distribution
When PVC suffers an impact, the powder particles (especially micrometric or nanometric sizes) help to dissipate and distribute the energy of the force across the entire surface, instead of allowing a crack from spreading
- Tenacity
In controlled dosages (generally around 8 phr – parts per hundred resin), the material becomes more tenacious to withstand falls or impacts without cracking.
Marble powder helps PVC to perform better during manufacturing on extrusion machines.
- Polymer Flow
Facilitates the dispersion of other additives and promotes a more homogeneous flow of the molten plastic
- Thermal Conductivity
Calcium Carbonate has a higher thermal conductivity than pure PVC. This allows the plastic to heat up and cool down quicker and is more uniform during production, resulting in pieces with less internal tension and higher ultimate strength.
- Finish and Durability
- Surface Hardness
It increases resistance to scratches and surface wear.
- Opacity and Brightness
- Improves visual appearance, giving it a whiter and smoother finish
Fun facts:
The use of Calcium Carbonate of mineral origin is essential in the fabrication of Hard PVC pipes. It guarantees that the pipes support the water pressure and the weight of the earth without breaking for decades