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Optimizing Water and water vapor barrier properties of water-based barrier coatings

Functional coatings are applied to paper and paperboard substrates to provide resistance, or a barrier, against media such as oil and grease (oil and grease resistance; OGR), water, water vapor (moisture vapor transmission rate; MVTR), and oxygen, for applications such as food packaging, food service, and other non-food packaging. Typical functional barrier coatings can be created by applying a solid coating or extruded film, a solvent-based coating, or a water-based coating to the paper substrate using various means of coating applicators. Today, there is increasing interest in developing recyclable and more sustainable approaches to producing these types of packages. This paper focuses on water-based barrier coatings (WBBC) for water resistance and MVTR for medium barrier performance. The main goal was to improve the performance of existing barrier polymers using additives such as waxes. Barrier coated systems were evaluated in single layer laboratory coating studies. This paper reviews examples of improving the performance of barrier polymers studied, including styrene butadiene and styrene acrylate, using wax additives. Regulatory challenges with paraffin waxes have resulted in the focus on bio-waxes. The results showed that small amounts of bio-wax can significantly improve barrier properties, especially for water resistance and MVTR. The choice of the best combination of binder and wax is essential. The influence of the bio-wax additive on blocking tendency, coldset glue strength, or heat seal strength is negligible.

The influence of precoating layers on the performance of water-based barrier coatings, TAPPI Journal January 2025

Cellulose nanofibrils (CNF) on paper have been demonstrated to be an effective barrier against oxygen and grease and have been shown to improve the barrier performance of dispersion-based barrier coatings. The potential to produce paper grades that have good oxygen, grease, and moisture barrier properties is clear, but a better understanding of the synergies between CNF, other coating layers, and water-based barrier coatings (WBBC) is needed to optimize these systems. Different coat weights of a commercial WBBC were applied to papers that have a range of different qualities and thicknesses of CNF precoating layers. The same WBBC was also applied to pigmented coated paper, with various types of pigments and latex levels. Samples were characterized in terms of grease resistance, water vapor transmission rate (WVTR), and oxygen transmission rate (OTR) before and after folding. The results were contrasted to cases where the WBBC was applied to the paper with no precoating layer. When the WBBC is applied on a CNF layer or the pigmented coating layer, the performance of the WBBC for the water vapor barrier improves a significant amount compared to when the WBBC is applied to the base paper with no precoating layer. This improvement likely comes from these precoating layers filling in the large paper pores, which leads to the WBBC forming a continuous layer at low coat weights. Folding decreases the moisture barrier performance to some degree, but the grease resistance is not influenced by folding when a CNF precoating layer is involved. Oxygen barrier properties are moderate for the CNF layer alone and are less than 5 cm3/m2/day when WBBC is coated on the CNF layer. This result likely comes from the barrier coating’s ability to repair defects in the CNF layer to stop the easy passage of oxygen in defect regions of the sample.

Anthraquinone pulping of kudzu (pueraria lobata), TAPPI Journal December 2024

Authors: Peter W. Hart, Brian N. Brogdon, and Jeffrey S. Hsieh | TAPPI J. 76(4): 162(1993) - ABSTRACT: Kudzu was pulped underpulping conditions for kraft, kraft-AQ, soda, and soda-AQ processes. Anthraquinone addition increlased the carbohydrate content of the brownstock pulp for all cooks. Anthraquinone addition lowered the broumrtock kappa number while reducing the chemical demand. Brownstock ~om selected pulping sequences was tested to determine tear strength, tensile strength, burst strength, and~eeness. The broumstock was also subjected to a CED bleaching sequence. For the bleached pulps, viscosity and average fiber length were determined.

Understanding the risks and rewards of using 50% vs. 10% strength peroxide in pulp bleach plants,TAPPI Journal December 2024

Authors: Alan W. Rudie and Peter W. Hart | TAPPI J. 17(11): 601(2018) - ABSTRACT: The use of 50% concentration and 10% concentration hydrogen peroxide were evaluated for chemical and mechanical pulp bleach plants at storage and at point of use. Several dangerous occurrences have been documented when the supply of 50% peroxide going into the pulping process was not stopped during a process failure. Startup conditions and leaking block valves during maintenance outages have also contributed to explosions. Although hazardous events have occurred, 50% peroxide can be stored safely with proper precautions and engineering controls.  For point of use in a chemical bleach plant, it is recommended to dilute the peroxide to 10% prior to application, because risk does not outweigh the benefit. For point of use in a mechanical bleach plant, it is recommended to use 50% peroxide going into a bleach liquor mixing system that includes the other chemicals used to maintain the brightening reaction rate. When 50% peroxide is used, it is critical that proper engineering controls are used to mitigate any risks.

Editorial: Carl Houtman: A government research perspective

Statistical determination of the effects of enzymes on bleached pulp yield, TAPPI JOURNAL, August 2005, Vol. 4(8) (80 KB)

Statistical determination of the effects of enzymes on bleached pulp yield, TAPPI JOURNAL, August 2005, Vol. 4(8) (80 KB)

Characterization of tensile fracture properties of paper, TAPPI JOURNAL, February 2000, Vol. 83(2)

Characterization of tensile fracture properties of paper, TAPPI JOURNAL, February 2000, Vol. 83(2)

Environmentally benign psas featured at recycling symposium, TAPPI JOURNAL, February 2000, Vol. 83(2)

Environmentally benign psas featured at recycling symposium, TAPPI JOURNAL, February 2000, Vol. 83(2)

Influence of coating rheology on final coating properties, TAPPI JOURNAL, February 2000, Vol. 83(2)

Influence of coating rheology on final coating properties, TAPPI JOURNAL, February 2000, Vol. 83(2)

Oxalic acid formation during ecf and tcf bleaching of kraft pulp, TAPPI JOURNAL, February 2000, Vol. 83(2)

Oxalic acid formation during ecf and tcf bleaching of kraft pulp, TAPPI JOURNAL, February 2000, Vol. 83(2)