Industrial minerals are traditionally a key factor in the
manufacture of detergents. In volume terms, sodium sulphate,
soda ash and zeolites play a major role, while considerably
lower quantities of bentonite-based speciality additives are
also used. Giving rise to innovative detergent formulations,
the demand for these additives has been growing at an
exceptionally high rate for many years. Worldwide sales of
laundry care products are currently recording average annual
growth rates of 2.5%, while the demand for bentonite-based
detergent additives is increasing at well over 3% a year.
Concentrated growth market
According to Euromonitor International, the global laundry care
market currently generates a sales volume in the order of some
$70bn, with detergents alone accounting for 75% of this figure.
The competitive environment is inevitably intense. A glance at
the market structure shows that the four largest suppliers
already hold a total market share of around 55%. In view of the
economic and ecological challenges facing the industry, this
concentration will no doubt continue to increase over the next
few years.
One of the main priorities for
manufacturers is ensuring the sustainability of their products
Ð in the broadest sense of the word. Apart from the
chemicals inherent in detergents, numerous other aspects also
determine their eco-balance. These range from the resources
used in production and the amount of packaging and transport
required, to the energy and water consumed during the actual
washing process. Added to these are challenges such as a
growing consumer demand for detergents that are as natural as
possible and for the most part hypoallergenic.
New statutory regulations are also
a response to the eco trend. These include for instance the
Registration, Evaluation and Authorisation of Chemicals (REACH)
directive, which has been in force in the European Union since
2008. In terms of ingredients, REACH now demands the highest
possible degree of transparency from manufacturers. At the same
time, new fabrics and performance textiles create a need for
ongoing development on the part of detergent producers. In the
search for solutions to this list of requirements, focus is
increasingly directed at speciality additives based on the
natural clay mineral bentonite. The reasons for this lie in the
mineral«s properties, which are both versatile and
exceptional.
Bentonite: origin & properties
The term bentonite stems from an American geologist by the name
of Knight. Around 1890, he discovered an unusual layer of clay
near Fort Benton in the US state of Wyoming and named the
material bentonite, after the place where it was found.
From a geological viewpoint,
bentonite is a sedimentary rock originating under certain
physical and chemical conditions from weathered drifts of
volcanic ash. Large deposits are found mainly in hollows and
fluvial plains in almost all parts of the globe. Conditions
influencing its creation did however vary from place to place,
giving rise to the many different qualities of bentonite found
today.
In most cases, the clay mineral was
formed by sedimentation - this being the reason for the
lenticular form of many bentonite beds, which are generally
found near the Earth’s surface.
Highly valued as an industrial
mineral, this clay owes its exceptional properties to its
chemical composition. In addition to accessory minerals, such
as quartz, feldspar, mica and calcite, bentonite essentially
consists of the clay mineral montmorillonite. In chemical
terms, this is a layered aluminium silicate made up mainly of
silicon, aluminium and oxygen atoms. The silicon and aluminium
ions are surrounded by oxygen ions, resulting in the formation
of three-layered silicate lamellae comprising a SiO4
tetrahedron on each outer side and an octahedral layer of
hydrated aluminium oxide in the centre. Bentonite is therefore
classed as a so-called triple-layered silicate. Each crystal is
made up of some fifteen to twenty of these lamellate
layers.
Inside each individual lamellate
stack, trivalent aluminium in the octahedral layer is replaced
by divalent ions, such as magnesium. This gives rise to an
excess negative charge which is neutralised by incorporating
exchangeable cations into the intermediate layer.
In addition to this exceptional
surface charge distribution, the lamellate structure of the
crystals is a key factor contributing to the mineral’s
specific properties. The individual crystal lamellae are only
one nanometer thick, their diameter reaching dimensions of
between 100 and 800 nanometers. This structure lends bentonite
inherent adsorptive and bonding powers which, compared with
other substances, are extremely high.
In order to utilise these
properties for technical applications, for instance in the
detergent industry, they are strengthened by way of selective
chemical after-treatment - this being referred to as
‘activation’. Depending on the intended application,
bentonite undergoes either acid or alkali activation, the
latter process also being used to manufacture detergent
bentonite.
The principle of alkali activation
is based on an ion-exchange reaction during which the
incorporated alkaline earth ions are replaced by alkaline ions.
These particles accumulate on the edges and intermediate layers
of the lamellae and hydrate upon contact with water. This
causes inner-crystalline swelling, accompanied by significant
expansion of the interlayer spacing. As a result, there is a
tremendous increase in the inner surface area, which explains
the high adsorption and retention capacity of activated
detergent bentonite. Added to this is a whole series of other
useful properties, which are outlined below based on specific
product-related examples.
Speciality bentonite for advanced 2-in-1
detergents
Among other things, bentonite-based speciality additives offer
a major economic and ecological benefit in 2-in-1 detergents.
The reason for these products is that, in the case of
conventional detergents, residue settles on textile fibres
during the laundry process, causing them to knot. This results
in a hard, scratchy feeling on the skin.
To prevent this effect the industry
initially developed fabric softeners, these liquid products
being added during the final rinse cycle. Their cationic
surfactants create a film around the fibres, making them
resistant to any deposits and subsequent knotting. Today, the
same effect can be obtained with 2-in-1 detergents -
without added softeners and surfactant-free. This is made
possible by using soft-touch bentonite, as offered for instance
by German bentonite producer Sud-Chemie AG - a subsidiary
of Clariant Group - under the Laundrosil
brand.
Laundrosil is added to the
manufactured product, forming an integral part of the detergent
mixture. Upon contact with water, the lamellae are released
from the additive’s crystal structure and attach
themselves to the textile fibres, forming a protective layer
measuring no more than a few thousandths of a millimetre. As a
result, fibres can no longer become entangled.
The advantages are far-reaching and
begin with wearing comfort. After washing, fabrics feel
pleasantly soft. Unlike softeners containing surfactants, the
soft-touch bentonite responsible for this feeling is however
guaranteed not to cause allergic reactions. Added to this is
another positive feature - whereas laundry treated with
fabric softeners is slightly hydrophobic, products such as
Laundrosil promote the water absorbing and releasing
properties of textiles. This creates a more pleasant body
climate.
Environment and cost considerations
are also convincing aspects of 2-in-1 detergents, since
consumers need only one product to achieve the same washing
performance and softness, based on a significantly lower
dosage. The final rinse cycle can also be entirely dispensed
with, thereby saving considerable water resources - even
in the case of modern automatic washing machines, by far the
largest amount of water is required for the rinse cycle.
There are also significant savings
to be gained by the manufacturer. Compared with producing a
combination of detergent and softener, the amount of energy
used and the costs incurred in manufacturing, packaging,
transporting and warehousing 2-in-1 detergents are considerably
lower. Speciality additives such as Laundrosil are
meanwhile so sophisticated that they can be used in both dry
detergent granules and liquid detergents. This is possible
thanks to special dispersions which ensure that the bentonite
particles remain stable, even in liquid solutions.
Even the reverse principle can
meanwhile be realised with the aid of bentonite, allowing
manufacturers to selectively combine certain advantages of
powder and liquid detergents. An ideal example of this is
Sud-Chemie’s Laundroclin product. Its
free-flowing granules utilise the high adsorption capacity of
bentonite and, depending on each manufacturer’s
requirements, contain up to 50% of liquid, non-ionic
surfactants, which are environmentally degradable. The granules
immediately disintegrate in the suds, promptly releasing the
active detergent ingredients. Other advantages of
Laundroclin include extremely easy dosing during the
manufacturing process, minimal cleaning of production equipment
compared with other solutions and an above-average level of
storage stability.
Challenges for industry suppliers
These and other bentonite-based additives increase value
creation in the detergent industry and make a significant
contribution to eco-friendly and economically attractive
innovations in this market segment. Of vital importance for
major, globally-positioned manufacturers are their additive
suppliers, who also maintain a worldwide presence, supplying
detergent additives of consistent high quality in all markets,
in line with required specifications.
Another group of bentonite-based
products - so-called pearls or speckles - draw
particular attention to the nature of this challenge. Today,
most washing powders are interspersed with these granules,
whereby their main purpose lies in the marketing sector thanks
to their individually defined colours. The vivid particles
symbolise the performance potential of each product,
strengthening its brand image. Specialised processing expertise
is needed for their manufacture, as previously activated
bentonite powder must be agglomerated to form larger customised
particles and then distinctively coloured to achieve the
desired optical differentiation from competitive
products.
Contributor: Dr Andreas Werner, Adsorbents business
line, Sud-Chemie AG, Clariant Group.
Spotlight on Sud-Chemie
Sud-Chemie is the world’s leading supplier of customised
detergent additives. The speciality chemical company recently
became part of the Clariant Group, after the Swiss chemicals
major acquired 96.15% of the company’s shares for
€2bn ($2.92bn) in April this year.
The company is a major global
supplier of bentonite with deposits in key regions such as Asia
and Latin America and an annual capacity of over 1m.
tonnes.
The Munich-based company’s bentonite-producing
adsorbents business represents 59% of annual sales of
€1.23bn (for 2010), with the remainder of the company
focused on speciality catalysts.