Concentrol, through its Additives Division, works on the development of products for the PSA sector. These are pressure-sensitive adhesives, which are made of resins that modify the cohesion and adhesion parameters.

Within PSAs we find different products: resin dispersions, antifoaming agents, wax and silicone emulsions, silicone surface additives and other auxiliary products.


What are PSAs?

Self-adhesives (known as PSA) can bond a variety of materials such as papers, plastics, metals, wood, and glass. A PSA adhesive is a solid that does not require activation by water, solvent, or heat.

They are permanently tacky at room temperature and can be used as a replacement for a multitude of fasteners. Their ease of application makes these adhesives widely used in many manufacturing processes.

Within the broad world of self-adhesive, the self-adhesive label market represents an enormous and growing volume. Concentrol has been working in this sector for years, developing and manufacturing products such as: resin dispersions, antifoaming agents, wax and silicone emulsions and silicone surface additives.


How are they made?

The manufacturing process of a self-adhesive (PSA) consists of four phases: siliconation, adhesivation, conditioning and complex formation.

Briefly, the support (paper) is passed through a head where the silicone is added, to obtain the silicone paper. Subsequently, this is introduced into another head where the adhesive is added and finally a sheet is attached to form the self-adhesive itself.

  • Siliconation

Siliconation consists of applying a silicone layer to the backing paper that will allow us to apply the adhesive and transfer it to the sheet, protecting the adhesive until its final use and allowing the sheet to be easily detached from the support. Ultimately, siliconation allows us to give the paper a non-stick treatment to prevent the support and the sheet from sticking together.

The layer of silicone applied to the support can vary, depending on the support itself and the final product, although in general it is usually around 1.1 to 1.3 g / m2. Subsequently, the support (paper), already siliconized, enters a drying tunnel where crosslinking and polymerization are carried out at very high temperatures.

Siliconation is a very important process, since it intervenes in a very marked way in the release, which is the property that measures the separation force between the sheet and the support. It is vitally important for the reel where the label stripping occurs and for automatic application of labels in the labeler.

If the release is too high, it can cause label roll breakage and stop the production process, as well as label dispensing failures. On the contrary, if the release is very low, labels may come off the support.

  • Adhesivation

It is the phase in which the adhesive is applied to the silicone support. Subsequently, drying is carried out to eliminate the water or solvent it contains. The amount of adhesive applied to the support ranges from 10 to 25 g / m2, depending on the end use that is going to be given.

  • Conditioning

In the conditioning, a moisture reconditioning operation is carried out on the product by passing it through a steam ramp at low pressure, since drying in the siliconation and adhesivation phases are undesirable effects.

  • The formation of the complex

This is the last phase of the process and is carried out when the support is joined to the sheet. This process occurs when the adhesive is sufficiently dry and the support has the necessary degree of moisture.

To join the adhesive support with the sheet, it is passed between two contact rollers, leaving both layers adhered. Because the support has a non-stick treatment obtained by the silicone, the adhesive remains only stuck to the sheet.


How are adhesive technologies classified?

The technologies are classified according to the composition of the adhesives, with four main groups: aqueous emulsions (acrylics), solvent-based, hot melt and UV crosslinking.

The technologies are classified according to the composition of the adhesives, with four main groups: aqueous emulsions (acrylics), solvent-based, hot melt and UV crosslinking.

Aqueous (acrylic) emulsions

These are acrylic polymers dispersed in water. They are the most widely used. Acrylic adhesive generally has good physical properties for a wide range of  long-term exterior applications.

These adhesives can be acrylic-based, made with acrylic cross-linked polymers, although they are much more expensive, or with acrylics modified with tacking resins (wide range by Concentrol) that are used to improve bonding properties , offering greater initial adhesion and greater bonding ability to low energy surfaces, although there is a loss of resistance to UV light and solvents.

These type of products has numerous advantages: they are easy to handle, non-flammable and have a low level of contamination, good resistance to sunlight, oxygen and heat, little tendency to migrate, and offer adhesion, cohesion and tack. However, it has low adhesion to nonpolar substrates and at low temperatures.

Solvent based

They are acrylic polymers in a petroleum or solvent based solution. They usually have good tack and adhesion, as well as good adhesion on nonpolar surfaces. They have a high cost, are hazardous and are not very ecological.


They are mixtures of rubber with resins, plasticizers and other additives that are applied at the time of producing the self-adhesive complex in molten form by means of heat at temperatures above 120 ºC. In this process there is no intervention of water and solvents.

These adhesives provide good tack, excellent adhesion to wet substrates, as well as good adhesion to polar substrates. However, the following disadvantages should be mentioned: they have poor heat resistance, suffer from frontal migration and age worse (oxygen and UV rays).

UV Crosslinking

This is a newer technology. They are 100% solid adhesives that are applied molten and are subsequently cross-linked with ultraviolet radiation (therefore, they are thermostable).

It is less used and one of its advantages is that it is suitable for many applications. However, it does not perform well on nonpolar substrates and at low temperatures.


What are the applications of self-adhesive?

Self-adhesives have a wide variety of applications in a multitude of sectors. Within this broad world, we are going to focus on one of the major market segments: PSA self-adhesive labels. However, the largest market is for self-adhesive tapes.

The self-adhesive label segment is clearly dominated by products based on water-based acrylic emulsions, the most important sectors being: packaging, food and beverages, electronics and laminates, medicine and pharmaceuticals, automotive and transport, and construction, among others.

Mainly the type of application, as well as the volume and intensity of the labelling, will mark the type of support. In most cases it will be automatic labelling, or sheets for manual labelling, with different characteristics due to the manipulation as well as the  pressure applied when sticking the labels.


What materials are used to make the self-adhesive?

The raw materials involved in the manufacture of a self-adhesive backing are the backing, the adhesive and the release paper.

The supports differ mainly by their supply, either on reels or paper sheets.

The reel is a complex paper self-adhesive in width and length. There are also reels with Kraft support, although they are not useful for automatic application, so they are transformed into sheets. They are normally used in laser quality.

The paper sheets are sheets of greater grammage (eg: 80-130 g / m2), which depend on whether they are with or without cut and the type of sheet. For the sheets to have a good behaviour in the dies, the regularity of the gauge is very important.

As we have already mentioned, there are four different types of technologies. At Concentrol we are basically focused on acrylic adhesives (aqueous emulsions).

Acrylic polymers are widely used in the manufacture of PSA adhesives. Typical acrylic monomers, such as acrylic acid, methyl methacrylate, 2-ethylhexyl acrylate, butyl acrylate, and other monomers, when polymerized, form permanently sticky acrylic polymers.

In this way, properties of heat stability, better resistance to oxidation and heat, as well as to ultraviolet radiation are obtained, and they adhere well to polished surfaces, such as paper, glass, polyester and polycarbonate plastics. Its main weakness is its bonding to low surface energy surfaces, such as polyethylene and polypropylene.

These acrylic adhesives can be made with cross-linked acrylic polymers, resulting in more expensive base adhesives, although with good resistance to heat and oxidation. They have a lower initial adhesion and require a longer settling period to obtain maximum adhesion. However, they are less prone to adhesive edging and maintain a more consistent level of removability on removable labels.

Adhesives with tackifying resins are modified acrylic adhesives, in an approximate ratio of 20% tackifier / 80% acrylic, which enables us to obtain better costs. In addition to higher initial adhesion and higher bonding ability to low energy surfaces, there is also a loss in UV light and solvent resistance. CONCENTROL has a wide range of tackifying resins that allow our clients to make modified acrylic self-adhesive with excellent results.

Regarding the sheet, it is the front material of the self-adhesive that ends up becoming a label. Depending on the quality and substrate, as well as other parameters, different types of sheet are used: coated paper with different finishes; calendered offset paper; aluminium foil; metallized paper; cellulose acetate, polyvinyl chloride, polypropylene, polyethylene and polyolefin fiber films; and thermo paper.


What parameters should we control for proper operation?

For the correct functioning of the complex, it is vitally important to control the following parameters: peel – adhesiveness, quick stick, rolling ball, cohesion and release.


The peel is a measure of the adhesion capacity, from which the adhesive is defined, and can be:

  • Removable: They are those that can be detached once applied.
  • Permanent: They cannot be detached once applied.
  • Super permanent: These are those used when the substrate where we apply the label presents adhesion difficulties.

Peel is the force required to detach at 180º and 300 mm / min a 25 mm wide strip adhered with the pressure exerted by a 2 kg roller on a plate of different materials after certain application times.

Quick stick and Rolling ball

There are two tests to measure the tack of the adhesive.

Tack is very important in automatic applications. A high tack indicates that the adhesive will stick when it comes into contact with the substrate.

In manual applications, tack is not so important, since the person who sticks the label can give the necessary pressure so that it is well attached.

Quick stick is a test that measures the force necessary to immediately detach at 300 mm / min a 190 x 25 mm loop of adhesive sheet glued on a stainless steel plate.

Rolling ball is a test that measures the distance in centimetres, travelled by a stainless steel ball with a diameter of 11.1 mm. It falls down a 30º inclined plane and rolls over the sample, being braked by its adhesive film. The shorter the rolling ball, the higher the tack. 


Cohesion indicates the resistance of the adhesive to flow. This is a major problem when trying to guillotine the self-adhesive sheets, because if the adhesive is not coherent enough, it can flow around the edges and the sheets stick together.

To measure cohesion, the bond strength or fragmentation of the adhesive film is analysed in two parts by applying a couple of forces. The test is based on the time required for a 1 kg weight to internally fracture the adhesive film of a sample strip stuck on a glass plate 2º from the vertical.


It measures the separation force between the sheet and the support and is of great importance for the moment of printing and stripping, as well as in the automatic application of labels.

To analyse the release, we work with two speeds: low speed (300mm / min) and high speed (150m / min).


Concentrol’s range of pressure sensitive adhesives

Silicone emulsions

Silicone emulsions usually contain a silicone component (typically silicone oil), water, and the emulsifiers required to obtain a stable emulsion. From a chemical perspective, a silicone component is a finite chain of silicon and oxygen atoms bonded together. In addition to these bonds, silicone itself has two other bonds to organic groups. In most cases, these organic groups are methyl groups (CH3) that give the silicone component its characteristic semi-organic behavior.

Silicone polymer micro emulsions are especially recommended for self-adhesive formulations and, after their incorporation into the formula, improve the guillotine cutting and punching process of paper and film reels, specially at high speeds. Furthermore, due to the wetting of the surface, they improve the rheology of the PSA on rollers. At low doses it does not adversely affect adhesion.

They are products that offer good characteristics: thermal and dilution stability, surface wetting, APEO Free, compatibility with anionic and non-ionic surfactants, easy application, they do not yellow over time. 

Wax emulsions allow achieving removable properties and, in general, to modify cohesion. 

Resin dispersions

The main purpose of the EMULTROL® range of resin dispersions is to improve the properties of cohesion, tack and sticking of self-adhesives based on polymeric dispersions of acrylic resin, PVA, EVA, SBR, NBR, natural latex, polychloroprene and aqueous polyurethane dispersions. They increase adhesion and tack on non-polar substrates and low energy surfaces, improving their wetting capacity. They can also be used in applications on porous and polar supports such as paper and cardboard.

Concentrol’s resin dispersions offer a number of advantages: APEO Free, Flexible R&D, flexible manufacturing batches, and products suitable for indirect food contact.

Antifoaming agents

Many water-based acrylic adhesives (PSA) tend to foam due to their aqueous composition. Foam can be critical, both in the formulation process of the adhesive and in its application. Applying a small amount of antifoamer allows to eliminate and prevent foam in the adhesive with maximum compatibility, with no adverse effects on dispersion performance and a lasting effect over time.

In the development of antifoaming agents for self-adhesive paper, special consideration has been taken to achieve good effectiveness without worsening the wetting of the adhesive formulations.

Antifoaming agents are effective (doses less than 50-100 ppm), durable, they act as antifoamers and defoamers, are safe (many comply with the European and American FDA Regulations) and have low surface tension for effective foam control in various processes. Oil antifoamers specially developed for PSA are used, as they have recirculating deaeration properties. Concentrol antifoamers are APEO Free, offer high performance, are very effective and have a good price/effectiveness ratio.

Silicone surface additives

Silicone surface additives are well known products for offering special properties in paints, inks and coatings. These additives are organo-functional silicones, most of them composed of copolymers of polysiloxane and non-hydrolyzable polyether. Although they are silicone-based products, unlike traditional silicone oils, they are very easy to use, their compatibility with most coating formulations is high, and typical defects such as craters or compatibility problems are not expected ( painting, adhesion, etc.) with their use.

Our range improves wetting without increasing foam formation, using doses of up to ten times less than those of traditional wetting agents. We also offer special finishes, smoother coatings, reduction of friction or more resistance to abrasion and scratches etc. They are APEO Free products and have a good price/effectiveness ratio.

At Concentrol we work to develop the best solutions for our clients. With the aim of offering the best possible product with the best value for money on the market, we develop solutions in our laboratories and we are committed to R&D.