Working side by side with customers and investing heavily in R&D resources are key elements to meeting the needs of the sector. Concentrol is divided into four major areas of knowledge and activity: Performance Materials, Food Processing Aids, Additives and Adhesives. These four company divisions allow us to cover a wide range of businesses on a global scale.
At the Additives division, Concentrol devises and manufactures solutions for paper manufacturers, such as antifoaming agents and wax emulsions, among other auxiliary products, such as antistatic agents and dispersants.
In this article we are going to focus on wax emulsions or sizing agents, which is what these additives are called in the paper manufacturing sector. Wax emulsions are used mainly in coated paper and thermal paper, both belonging to the category of printing and writing paper.
Coated paper
Coated paper is made with more short fibre than long fibre and, subsequently, the load is attached to the fibre by means of a binding agent, which can be synthetic or natural (usually calcium carbonate). Next, a coating layer is applied on the cellulose, in order to generate better printing and definition results. This is due to the fact that ink remains on the surface and, consequently, the result after going through the press is brighter and more colourful.
The most common option is white coated paper, because if the coating cracks, the background colour is not visible. There is the option of a matte or semi-matte finish.
Thermal paper
When heat is applied to thermal paper, it darkens. In this type of products we distinguish several parts:
- Base or support paper: As its name suggests, it is the base on which all the chemical layers of the paper will go.
- Pre-coat or “under coating”: It is used as an undercoat to guarantee the uniformity of the surface on which the following coats are applied. It helps the equitable distribution of all materials, and a higher resolution when printing.
- Thermal layer: It is the upper layer, composed of many chemical components among which are the colorant, a co-reactant and a sensitizer.
Wax emulsions: definition, characteristics and properties
Wax emulsions are thermodynamically unstable suspensions of small wax particles (dispersed phase) homogeneously distributed in water (continuous phase or dispersing phase). These are stabilized by emulsifying agents that form films on the surface of the droplets (surfactants) or that impart mechanical stability to them.
Wax-based emulsions are used as additives and, being in liquid form, are easily incorporated into formulations by simple mixing. They are typically formulated to have a certain ionic charge, to be compatible with the other ingredients in such formulations.
Wax emulsions can be anionic, non-ionic or cationic depending on the emulsifier. Due to their dissolution behaviour, the pH of the emulsions is a good indication of the character of the emulsifying system.
Wax emulsions are capable of providing certain properties depending on the requirements of the application. Waxes have a wide range of functionalities that allow them to solve a wide range of performance problems, modifying the results of the products. Among the most outstanding properties we find the improvement in non-adherence (lubrication), water repellence (waterproofing) and glossy finishes.
- Gliding properties are obtained when using a hard wax. This is explained by the fact that solid-state wax crystals are the main factor responsible for the sliding characteristic. Therefore, adapting the particle size of the emulsion is crucial to maximize the effects of the wax on the surface.
- In terms of water resistance, paraffin waxes, including refined and partially refined (containing around 5% oil), work extremely well, especially on porous surfaces, as they quickly and easily penetrate pores and substrate cracks, giving a highly hydrophobic property to the treated surface. The choice of the emulsifier-dispersant system is important, as it directly, positively or negatively, influences the hydrophobic behaviour of the wax film.
- To achieve a glossy effect, the emulsions must have a very small particle size and this is obtained when the emulsion is cooled quickly to induce the formation of very small wax crystals. These are less capable of scattering light, so the film will reflect light in a more mirror-like way.
As a consequence of the mentioned properties, wax emulsions are used, among many other sectors, in the production of paper. They are added to the coating mix to reduce dust formation during calendering, and to paper coatings to increase water repellence, to improve flexibility and to increase gloss.
Wax emulsions or sizing additives for papermaking
Below is a brief outline of Concentrol’s star products for this sector.
- EMULTROL CM-2469 SPL:
Sizing additive especially suitable for coatings for the production of thermal paper. It is an anionic-non-ionic aqueous emulsion of paraffin stabilized with protective colloid. In the treatment of paper, it confers water-repellent properties, maintaining the dimensional stability of the paper and has excellent compatibility with the materials that make up the coating.
Additionally, it ensures a good bonding with the base cellulosic substrate. They also act as lubricants and non-stick agents during the passing of the coating mix through the calenders.
Complies with FDA regulations, chapters 21 CFR 175.300, 176.170 and 176.180.
- EMULTROL CPM-1379:
It is a sizing additive for the surface treatment of paper, and mainly for coated paper. It is an aqueous emulsion of modified paraffin of a mainly non-ionic character. In coating mixes this sizing agent gives shine and non-stickiness.
In addition, it provides water-repellence properties and maintains the dimensional stability of the paper. Due to its clearly non-ionic character, it presents good compatibility with numerous emulsified products of different active materials, although it must be checked in each case.
Complies with FDA regulations, chapters 21 CFR 175.300, 176.170 and 176.180.
At Concentrol we manufacture products tailored to the needs of the sector and legal requirements. The firm commitment to research allows us to have an expert team specialized in each area of activity. This is our formula to develop products with the best value for money on the market.
Thanks to the company’s investment in R&D, we can offer customized solutions to our clients, with a global reach. Currently, our products reach the 5 continents of the world with customers from 82 different countries. For more information, our team of experts will be happy to hear from you.
Author: Carlota Clarasó, Technical Manager of Concentrol.
