RELEASE AGENTS FOR THE FOOTWEAR SECTOR - STATE OF THE ART White paper with studies on release agents for the footwear sector developed at ...
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RELEASE AGENTS
FOR THE
FOOTWEAR
SECTOR
STATE OF THE ART
White paper with studies on release agents for the
footwear sector developed at CONCENTROL R+D
laboratories
INDEX
Introduction ............................................................................................................................2
Types of release agents for polyurethane footwear soles ............................3
The choice of a footwear release agent .................................................................8
Water based release agents for phylon ................................................................12
Success Story - Footwear Sector..............................................................................13
Footwear sector: Concentrol's water-based mold release agents, for
single and dual density soles .......................................................................................14
!1
Introduction
to each manufacturer’s needs. Following we
At Concentrol we are experts in mold outline some of the advantages of
release agents, and one of our specialities is Concentrol’s release agents for footwear
mold release agents for shoe soles. The soles: firstly, we highlight the high release
knowledge and experience on the raw capacity, the perfect adhesion on bi-density
material used and on the needs of the soles, a level of shine and optimal surface
product are key to offering the best finish and compatibility with subsequent
solutions to manufacturers. treatments. Also we highlight the
differentiation of products according to
In the case of shoe soles, depending on what
whether they are polyether or polyester
footwear’s sole component (polyether or
soles.
polyester), one or other Concentrol
demolding agent is applied. Another of the goals achieved by our
footwear release agents is that they are
Needs according to types of soles solvent-based and water-based products
with low levels of rejection. In addition, they
Depending on the type of sole that is used, a
different release agent is required. Apart cause low mold fouling. Regarding the
from the material used (polyester or environment, we highlight the low emissions
polyether), we must bear in mind that of VOC and the possibility of DBT or tin free
products.
currently on the market we find two types of
soles (one density or two densities), which In order to present to our clients that the
require different injections. extensive range of water based, solvent
In any case, the objectives of the mold based and hybrid release agents offered by
release agent are the same: to achieve a Concentrol comply with all the rules and
regulations as well as the quality of their
high demolding power, impeccable finish in
performance and guarantee of results, we
terms of shine and uniformity of the surface,
low mold fouling and adaptation to the have prepared this document, which
complexity of the parts depending on includes the different studies with the
fashion. technical detail of the products.
In order to ease the process by eliminating
adhesive and sewing, thanks to the high
quality of our shoe release agents we can
make a direct injection of mono and bi-
density soles. The choice of a good release
agent is very important here, as the result
has to be a perfect sole, uniform shine,
excellent demolding, low fouling and, where
appropriate, good adhesion between the
sole and the midsole.
Main objectives
At Concentrol we work with the
commitment to always achieve the highest
quality in our products. Mold release agents
for shoe soles are one of our specialities and
we have achieved some of the main
features required by the product according
!2
Types of release agents for polyurethane footwear soles
INTRODUCTION
Polyurethane was introduced in the
footwear sector in the late 60s, and since Polyurethane type Hardness Density
then it has become a very popular material
for shoe manufacturers, since this material
allows to obtain quality shoes, comfortable
and durable, as well as light, at a low price.
Midsoles 280-450 g/l
Its appeal lies in the high amount of
footwear that is manufactured globally
every year. The "World Footwear Yearbook"
published that, in 2013 alone, 22 trillion pairs
of shoes were manufactured worldwide.
Polyester Outsoles 900-1100 g/l
Thanks to polyurethane technology, various
designs can be obtained, either from
moulding as units and their subsequent
combination with the body of the shoe, or
directly moulded into the shoe.
Monosoles 500-600 g/l
Polyurethane for shoe soles stands out for its
lightness and resistance to abrasion,
providing interesting mechanical properties.
Polyurethane soles are the result of a
Polyether 450 – 600 g/l
reaction between an isocyanate and a
polyol system.
The density will depend on the type of sole
Its hardness is imparted by hard segments
and its hardness:
in the polymer matrix and its density is the
result of CO2 generated by the reaction of
PU systems are based on both polyol
the isocyanate and water, as well as by the
polyester and polyether technologies. These
presence of small amounts of an expanding
technologies are suitable for different end
agent during mixing, as is the case of
uses and mean different processing
polyether systems.
characteristics.
The systems based on polyester offer
Example of polyurethane formation reaction:
greater chemical and abrasion resistance,
while polyether systems have a superior
resistance to hydrolysis.
Within the footwear sector, polyurethanes
Among the differences between the two
are found in a wide range of types. They can
production techniques is the processing
be used in shoes and sports boots, business
temperature: polyether-based systems are
and fashion shoe soles, as well as high
liquid at room temperature, while polyesters
quality safety shoes.
require approximately a temperature of
45°C.
Low density to compact polyurethane
Nowadays, polyether and polyester systems
systems are used for midsoles and outsoles.
are equally valued in the footwear industry,
so it is shoe sole producers that make the
choice according to their production
requirements, being polyester the most used
in safety footwear due to its chemical
resistance to agents such as oils or solvents.
Polyether, on the other hand, is ideal for
hydrolysis-resistant soles and to withstand
high humidity conditions, such as those
found in tropical climates.
!3Advantages of polyurethane soles: perchlorine at 120ºC in a rotating tub, over a
10 to 15-minute cycle, to eliminate any
• Low weight providing thermal and grease or dirt impurities that could interfere
abrasion resistance. with the bonding or finishing process.
• Flexible soles are produced that Current market:
enhance the comfort of the user by
correctly absorbing the impacts that • Asia is responsible for the
occur when walking, compared to manufacture of 87% of the world's
other materials such as EVA, PVC, footwear, with China being the
nylon or leather. leading country, producing 2 out of
3 pairs that are produced globally.
• Versatility of finishes: Easily • However, there is currently a
customizable with pigments or tendency for footwear
auxiliary elements. manufacturers to relocate Chinese
production to other areas such as
• Very mouldable material: Vietnam, Indonesia and Taiwan.
Polyurethane can be manufactured • In Europe it is more difficult to
with different densities to adapt to compete on price and the market is
different types of footwear, whether dominated by companies that
work or fashion. manufacture specialized footwear,
such as safety footwear.
In the following chart, the different • The same happens in the United
durability of footwear soles is shown States, where the production of
depending on the material they are made military footwear must also be
of: mentioned.
A manufacturer of shoe soles usually has a TYPES OF RELEASE AGENTS
very standardized process and puts its soles
through strict quality tests, in which, for The release agents used for the production
example, the parameters in the following of polyurethane soles are classified
table are measured: according to the process and material to be
demoulded:
Property Unit • Monodensity or Bidensity soles.
• Polyester or Polyether soles.
Tension Mpa
Tear kN/m Currently the largest consumption is of
solvent-based products, although there is
increasing interest in the use of water-based
Elongation %
release agents, whether ready for use or
concentrates to dilute.
Flexion % Choice should also be made according to
the wanted type of finish of the sole: Matte,
Abrasion Mg satin or glossy.
The main properties of a good release agent
When soles are painted or are to be must be:
adhered, the manufacturer usually does a
washing or "degreasing" process to remove • High demoulding power.
any remnants of the release agent that may
have been left superficially on the sole and • Provide a good finish to the sole in
that could interfere with adhesion with the terms of gloss or matte and
paint. uniformity.
A fairly common process is to insert • Low fouling of moulds and mould
demoulded soles into an automatic washing holders.
machine with a hot perchlorine jet. In this
process, the soles are exposed to
!4• Versatility for different sole designs.
Release agents for bidensity soles:
Bidensity footwear consists of an external
Release agents for Monodensity soles: polyurethane sole and a midsole, both
moulded and joined with one another during
Solvent-based release agents for the production process. The reason is to
monodensity soles consist of a dispersion of ensure that the outer sole has good
anti-adhesion agents in an aliphatic or resistance to abrasion or against oils, and an
isoparaffin type solvent base. inner sole that guarantees greater comfort
Lately, chlorinated solvents and the like to the user. In this way, comfort and safety
have been discontinued for toxicological are combined in a single sole.
reasons, since they could affect the health of These release agents are widely used for
workers. the safety footwear industry, where an
The concentration of active matter can vary impeccable finish and above all a good bond
greatly, from 2 to 60%. Being near the of soles is an indispensable requirement.
highest point the ideal concentration that Here, solvent-based or water-based release
allows a quick application of the release agents are used that contain an active
agent in rotating carousels, good material composed of special non-stick
demoulding and surface finish of the sole materials that create a homogeneous, stable
produced, and at the same time, emitting and consistent film on top of the mould,
the least amount of VOC's. facilitating demoulding and reducing
Water-based release agents are an consumption. These formulations achieve
emulsion, that is, they consist of anti- that the residue that remains on the mould
adhesion agents and additives emulsified in after several releases is minimal, thus
water by means of surfactant systems, lengthening the cleaning cycles.
which can be non-ionic, cationic or anionic These release agents facilitate the bonding
in nature. and gluing between two soles that come
For this reason they are more critical in from two injections of different density,
terms of transport and storage, being water producing soles with a satin finish and little
based, their viscosity can vary depending on or no greasy feel.
temperature, and in no case can they be In the case of solvent based, they work
subjected to temperatures below 0 °C, since perfectly in a wide range of temperatures,
this would cause a freezing process that and, unlike the release agents for
could destabilize the emulsion, breaking it monodensity soles, these are usually
and making it unrecoverable. formulated with high boiling point solvents
A similar effect can occur if the product is as a carrier for the active material, thus
subjected to high temperatures (> 50 °C), obtaining less flammable products and
for example during transport under sunlight drying a little slower making part of the
in countries with warm or tropical climates. solvent to act as an oil facilitating the
For their application it is recommended to lubrication of the sole in the mould.
use an airbrush gun with a 0.3 mm nozzle, In water bases, the factor to be taken into
as in the case of solvent based ones, but account is that the temperature of the
using an air pressure of 2.5 to 3 bars to aid moulds is adequate to facilitate drying,
drying. together with a good spray to obtain a good
The temperature of the mould should not be result.
less than 50ºC to aid drying, as it is also very In order to obtain a perfect atomization and
important to maintain an application distribution of the active ingredients on the
distance of 20 to 30 cm between the gun mould, as for monodensity soles, it is
and the mould, in order to form a uniform recommended that they be applied by
film on the surface that makes demoulding means of aerographic equipment with a 0.3
easier. mm nozzle.
Finally, in the case of water base it is If their electrostatic version is used, in
important that between the application of addition to maintaining the properties of the
the release agent and the injection / casting original product, a saving of 30% in
of polyurethane a minimum of 1 minute consumption is obtained, as well as the
passes, otherwise it may be convenient to corresponding reduction of VOC's emitted
use an air gun to speed up the drying and to the atmosphere.
reduce the times of the carousel cycle.
!5such as price reduction, reduction of VOC's
New factors that are currently taken into emitted to the atmosphere and better
account regarding the choice of a release working environment in the production line.
agent:
Electrostatic release agents
• Quantity of VOC's and FOG.
If the producer of soles or footwear wants to
• Flammability, with all that entails reduce consumption and VOC's without
regulation regarding the facilities changing the chemical nature of their
where it is used (ATEX), danger release agent, electrostatic release agents
according to flash point (Class) and are a possible solution.
aspects related to transportation The technical principle under which these
and storage. types of release agents operate is as follows:
Specific electrostatic spray guns are used.
• Toxicity of the products involved in They are connected to a negative pole,
its formulation and their implications while the working mould is connected to a
in the work environment, with positive pole. When applying a high voltage
particular reference to tin current, an electrostatic field is generated
compounds and solvents. between the electrode at the tip of the gun
and the mould. When the product is
• Final impact on the environment. atomized, the negatively charged particles
move towards the surface of the mould
under the influence of the electrostatic field.
Reduction of VOC's, TLV's and DNEL: The result is that, as opposing loads are
attracted, the mould attracts the release
To completely eliminate direct emission agent, efficiently covering its entire surface,
VOC's, the best solution is to change from a avoiding unnecessary losses and thus
solvent-based release agent to a water- providing a decrease in consumption.
based one. Any solvent-based release agent can be
Although this solution is still not very converted to electrostatic, guaranteeing a
integrated in shoe producers, there is an solution of sufficient, adjusted and adequate
upward trend to manufacture with water- conductivity that meets the needs of the
based release agents, especially if client or the application. Nowadays
consumption is high and there may be both electrostatic solutions do not present strong
economic and environmental savings. odours or additional toxicity, and they allow
to work electrostatically with solvents
known in the sector as classes I, II or III.
Hybrid release agents
The advantages of the use of electrostatic
release agents are, therefore: a significant
Between the solutions based on solvents and
reduction of the consumption, of 30 to 50%,
those based on water, there is one more
by avoiding the loss of material that does
option that is known as hybrid demoulders.
not enter the mould as a result of the
Hybrid demoulders or CO-SOLVENT MIX
dirtiness of the external parts (mould
50:50 demoulders are release agents in
supports, floors, etc.) and a significant
which the main material, that is, the carrier
reduction of emitted VOC's, improving the
of active ingredients, is half water, half
work environment.
solvent (approximately).
The considerations to take into account are
In terms of functionality and finishing of the
the greater difficulty in controlling their
unmoulded part they are like a solvent base,
application through robotic systems
with the main disadvantage that at least half
(although manual application is possible)
of their formulations contain VOC's.
and the need for specific equipment and
Even so, it is a good intermediate solution
pistols, larger and heavier than usual, which
for footwear manufacturers that are
means greater initial investment in
currently producing their soles with a
equipment.
solvent-based release agent and do not
want to take the step to change to water
based due to the inconveniences and
change in the way of working that entails. Tin-Free release agents:
The change from solvent to hybrid base
implies an improvement in certain aspects, In recent years both footwear
manufacturers and mould release agent
!6suppliers have been working to replace Auxiliary products:
organotin compounds with other
organometallic compounds, but with some For the footwear market based on
limitations regarding their effectiveness. polyurethane, there is a range of auxiliary
Most of the organometallic compounds that products such as mould cleaners, from the
have been used for a long time are based on most toxic but effective containing NMP and
tin and include, as the most used, dibutyltin NEP to cleaners without risk to health and
dilaurate (DBTDL). free of NMP.
The specialty chemical company Concentrol
It is possible to replace DBTDL as a catalyst has decades of experience in the
with other non-organotin substances using demoulding industry. A pioneer in its
specific knowledge acquired in the sector, commitment to research and development,
as well as with strong collaboration and Concentrol offers the market tailored
testing with customers, in order to adjust a solutions for each client using the latest
custom made product that meets all the technologies and knowledge of the sector to
requirements. achieve maximum efficiency and
performance. Contact us for more
information: marketing@concentrol.com
References:
http://www.polyurethanes.org
Huntsman – PU review April 2015
!7The choice of a footwear release agent
One of Concentrol’s strategic divisions is in order to find the most suitable release
mould release agents, and the release agent for his process are:
agents for polyurethane footwear soles
represents one of our flagship products in
this division. The high degree of Mould temperatures: The release agent must
specialization, thanks to innovation and be formulated with a carrier that dries fast
continuous improvement, has made our enough after applying it to the mould, in
products achieve a high reputation and we order to form a good film and release
currently provide service and coverage to a without issues.
wide variety of industrial sectors. In The correct mould temperatures are
addition, we are present in all continents imperative for catalyzing the reaction
with international clients that give us a between polyol and isocyanate at the
global strategic vision of the market, making correct level as the system is formulated,
us a reference worldwide. and to get a correctly cured PU shoe sole in
a defined cycle time not to disturb
The choice of the appropriate mould release productivity targets
agent depends on several factors that we
detail in this article. The base of the soles The type of Polyol used to produce footwear
with which we work, polyether or polyester, soles: polyester or polyether.
will determine the optimal solution, but we Polyesters are usually cheaper, and lower in
must also take into account the type of sole viscosity while Polyether polyols give better
to be manufactured, which can be of single abrasion resistance properties, but their
density or two densities, in which case it viscosity is higher, and they are more
requires different injections. The goal of the expensive.
release agent is always the same: to achieve Release agents are designed specifically for
a high demoulding power, a good gloss or each type of Polyol, meaning that typically a
matt finish according to customer release agent for polyester is not going to
requirements, and uniformity of the surface, release well enough on polyether or would
in addition to achieving the least fouling of cause pin holes or other undesired effects.
the mould and a great adaptability to the
pieces defined in the footwear design. The finish of the footwear sole is also critical
in order to choose a correct release agent,
The environmental, safety and health factors because its formulation will be quite
are also very important when dealing with different whether a shiny or matt surface is
release agents for polyurethane soles. desired. As a general rule, release agents
Emissions of gases into the atmosphere, formulated with a high concentration of
toxicity and flammability of the product are waxes give more satin/matt finish than the
important points to consider when choosing ones that contain just a mixture of silicones
a release agent, being the CO-SOLVENT MIX and resins.
50:50 or hybrid release agents a solution
that manufacturers opt for to reduce the Later processes like painting and
VOC’s emitted to the atmosphere and degreasing must also be considered,
improve the working environment in the because normally demoulded soles must be
production line. cleaned or degreased before painting them,
Here we outline all the factors to take into although some release agents can make this
account in the process of choosing a mould process easier and faster.
release agent for shoe soles.
Also in dual density processes it is important
The importance of mould release agents in
for the release agent to be designed
polyurethane footwear moulding processes
accordingly, in order not to interfere with
is well known, as it influences in a decisive
the bonding of the PU outsole and midsole.
way the appearance of the demolded soles,
All these factors mentioned above have to
in operations like painting or gluing and in
be known and studied by the release agent’s
profitability measured in scrap rates.
formulator in order to obtain a product that
The most common parameters, that are
performs in an excellent way optimizing
always considered by a footwear producer,
footwear production lines.
!8As a quick overview, a release agent is a Concentrated release agents have
chemical product, normally liquid, formed advantages compared to low solid content
mainly by a carrier (water or solvent), that ones, the main advantage is that the flow
has all the active material and additives rate of the product applied on to the mould
dispersed/emulsified in it. Its solid content is reduced, while also the overspray. This
can differ from some release agents to allows us to optimize the production and the
others, as we can have ready-to-use low- reduction of the cleaning cycles inside the
solid-content ones, usually formulated with a moulds and around them. Providing also a
fast evaporating solvent, like heptane, or better working environment with less
concentrated ready-to-use release agents solvent in the atmosphere.
with higher solid content in order to apply a
lower flow rate with the spraying However, to completely eliminate VOC’s the
equipment, and generally formulated with a best solution is to change from a solvent
lower volatile solvent, for example C9-C10 based release agent to water based one.
naphta, which also will take longer to dry.
Water based release agents, in some
However, when choosing a release agent families of polyurethane foam, have been
there are other factors, apart from the ones readily available for many years but their
mentioned above, that have to be taken into main disadvantage during past years was
consideration and are also important: that they give a greasy finish to the
demolded polyurethane item, not
All these factors intervene in the choice of a acceptable for many manufactures.
release agent and need to be taken into Improving this parameter without losing
account for the optimal operation of the line, release capacity has been one of the most
as well as its incidence in a balance between difficult challenges of the last several years.
safety, environmental & workers protection
with cost levels, to maximize productivity The trends in the markets is to work
while producing high-quality footwear items. constantly on this subject, improving water
based and co-solvent release agents,
VOC’s making them more dry-finish & solvent
based looking, while keeping their great
The European Union defines a Volatile release capacity and making it possible to
Organic Compound (VOC) as “any organic glue and paint on them.
compound having an initial boiling point less
than or equal to 250 °C (482 °F) measured Between solvent based and water based
at a standard atmospheric pressure of 101.3 there is an intermediate solution: Co-solvent
kPa.” 50:50 (hybrids)
The CO-SOLVENT MIX 50:50 are release
They are considered one of the most spread agents in which the main material, that is
out pollutants in the atmosphere, because the carrier of the active ingredients, is half
they are key substances to understand the water half solvent (approximately).
troposphere ozone formation together with
nitrogen oxides. In terms of functionality and finishing of the
demoulded part, they are like solvent based,
Related to release agents, there are some with the main disadvantage that at least half
VOC’s produced during polyurethane of their formulations contain VOC’s.
manufacture (stack emissions & direct Even so, it is a good intermediate solution
emissions) and there are several ways that for footwear manufacturers that are
they can be reduced with release agent’s currently producing their soles with a
technology. solvent based release agent and do not
want to take the step to change to water
The typical solvents used in release agents based on the inconveniences and change in
are aliphatic or isoparaffinic hydrocarbons. working methods that entails.
Reduction of VOC’s: The change from solvent based to hybrid
means an improvement in certain aspects,
The first step (and the easiest one) to such as price reduction, reduction of VOC’s
reduce VOC’s is to change from a low solid emitted to the atmosphere and better
content ready to use release agent to a working environment at the production line.
concentrated ready to use one.
!9Aside from water based release agents and converted to electrostatic, guaranteeing a
co-solvents, another solution to reduce sufficient, adjusted and adequate
VOC’s in the application stage of the release conductivity solution that satisfies the needs
agent is the use of Electrostatic Release of the customer or the application.
Agents. Nowadays, electrostatic solutions do not
present strong odours or additional toxicity,
Application systems and they allow us to work electrostatically
with solvents known in the sector as classes
• Application robots I, II or III. The advantages of using
electrostatic release agents are, therefore, a
Basically almost all release agents can be significant reduction of consumption, of
applied manually by spray gun or between 30 and 50%, by avoiding the loss of
automatically by robot. The main purpose to material that does not go into the mould as
use a robot is for cost savings. Nowadays a result of dirt from external parts (mould
robots can apply in all axes, assuring the holders, floors, etc.) and a significant
correct application of the release agent, as reduction of VOCs emitted, improving the
well as a human operator would do. work environment.
The considerations to be taken into account
Benefits: are the greater ease of controlling their
application through robotic systems
• Always the same application, it limits (although manual application is possible)
the risk of delamination in dual and the need for specific equipment and
density shoe soles due to excessive guns, larger and heavier than usual, which
application due to human error. means greater initial investment in
• Optimization of the release agent equipment.
consumption, which means longer As it is shown in the comparison graph, with
cleaning cycles and extends mould’s electrostatic release agents a 30-50%
operating life. reduction of the flow rate applied can be
• Easy to work electrostatic achieved, this means that also VOC’s are
application by robot rather than by being reduced this percentage. Also a lower
hand. impact on environment and an improvement
• The application speed can be in the workplace are achieved.
increased/adjusted without risk of
fatigue. All Concentrol’s solvent based release
• Cost reduction. agents can be adjusted to be used with
• More homogeneous production, as electrostatic equipment according to an
the same amount of release agents, electrical resistance value proposed by the
on the same areas of the mould, is customer, together with the equipment
consistently applied. supplier, that is usually around 200-500 MΩ.
Disadvantages:
• Robots can certainly handle their set
tasks, but they typically cannot
handle unexpected situations, quite
common in the PU industry, such as
when there are some problems in a
specific mould.
• Higher initial investment.
• Robots installed in workplaces still Flammability
require manual labour around them.
Training those employees on how to During the use of release agents, mainly
work with robots definitely has a solvent based ones, also ATEX (Explosive
cost attached to it. Atmosphere) has to be considered, although
Regarding the application technology on for a potentially explosive atmosphere there
release agents, we must consider also must be a combination of a flammable or
electrostatic technology, which works combustible substance with an oxidant at a
together with electrostatic release agents. given concentration and together with a
Any solvent-based release agent can be source of ignition. The risk becomes greater
!10and more complex when we are in a used in foaming reactions as these catalysts
confined space and with manipulation of also promote the isocyanate-water reaction.
these substances. Most organometallic compounds used for a
To avoid having to install ATEX facilities, long time are based on tin and include
there is only the solution of using water stannous octoate, dibutyltin dilaurate
based release agents, although regarding (DBTDL) and tin mercaptides. Certain salts
different flammability grades (known in the of lead, mercury and antimony have also
sector’s jargon as Class I, Class II & Class III), been used.
other solutions can be implemented, like Tin compounds, especially dibutyltin
concentrated class III release agent, dilaurate, are in widespread use in coatings
electrostatic release agent, wax pastes… as catalysts for the isocyanate/hydroxyl
However, despite having ATEX installation, reaction. As a general rule, organotin
there are advantages to some kind of catalysts are not selective, they catalyze the
solvent release agents compared with reaction of isocyanates with both hydroxyl
others. groups and water, and also catalyze the
In the polyurethane sector there is an old hydrolysis of ester groups.
known classification of solvents that are part The catalytic effect of metal salts is more
of the release agent as carriers of the active complex than that of amine, which
ingredients: compounds with either hydroxyl or
• Class I: Easily flammable: isocyanate. Tin and other metal catalysts
Substances whose flash Point is activate both polyol and isocyanate, first by
below 21ºC. the formation of a binary complex between
• Class II: Flammable: Substances the catalyst and polyol and then by the
whose Flash Point is between 21ºC joining of the isocyanate.
and 55ºC. Substituing DBTDL as catalyst with other
• Class III: Combustible. Substances non-organotin substances is possible using
whose Flash Point is over 55ºC. state-of-art knowledge together with strong
collaboration and trials with customers, in
Hazards and enviromental impact order to refine tailor-made products that
In addition to the flammability, the hazards meet all requirements.
of the products involved in the formulation
of the release agent, and their implications SUMMARY
in the work environment, may come from tin
compounds. To avoid the use of these CONCENTROL, with its range of release
restricted substances, a new variant of mold agents, is constantly working in all the points
release agents has been extended described above to improve its products
worldwide, the release agents without tin. and offer a solution, together with
Release agent’s suppliers have been working improvements on customer’s lines, like new
in the past years to substitute organotin equipment or changes in their processes.
compounds with other organometallic Each PU footwear line must be studied
compounds, mainly based of Bismuth or individually in order to recommend the most
Zinc, but with some limitations to their suitable release agent, spray gun, and other
effectivity. equipment facilities.
Also, amine-catalysts have been studied as
alternatives, but while amine catalysts exert This article was intended to inform of
some effect on the isocyanate-hydroxyl different factors which should be taken into
reaction, organometallic salts favour the account, besides its obvious function, when
isocyanate-hydroxyl reaction almost choosing a release agent for footwear
exclusively and are thus gelation catalysts. polyurethane, and also showing some of the
This means that metal-based catalysts solutions that CONCENTROL offers to its
typically accelerate the gelling reaction customers in order to achieve all their
between the isocyanate and the alcohol, targets.
whereas amine-based catalysts are mostly
!11Water based release agents for phylon
In recent years the footwear industry has Phylon is the most common process for
been growing at a constant pace thanks to creating soles for sports shoes. This process
the high demand for an aesthetic product, in starts with EVA already expanded, that is,
accordance with fashion, and, even so, with EVA foam, which contains gas bubbles
highly comfortable and durable. The inside. This foam is introduced into a mould
footwear industry can be classified by the with the design and final shape that the sole
type of user, purpose of the footwear, and will have. The mould closes and it is heated,
among other parameters, the material with melting EVA inside allowing the trapped gas
which it is manufactured. to expand further, making it easier for EVA
to fill the mould. The mould is cooled and the
In this article we will focus on the footwear EVA part is extracted.
material known as phylon, a modification of
EVA rubber, which by means of a The extraction of the phylon part is carried
thermoforming and cooling process out thanks to the presence of a release
achieves a less dense material, and, agent. This agent is applied by spray gun or
therefore, lighter. brush, providing the necessary lubrication to
be able to extract the part without causing
Before going into more detail about phylon, superficial damage. In addition, these
we will focus on EVA rubber to learn about products are responsible for the appearance
the origin of this new material that is and surface feel of the demoulded part.
expanding.
Concentrol’s demoulding department has
EVA rubber is a copolymer formed by the developed a concentrated product to dilute
repetition of ethylene and vinyl acetate in water for this process. The
monomers. The proportion used of these product CONCENTROL LP IADC-114-43
two components will determine the PHB can be diluted up to 1:100, depending on
properties and qualities of the material. the working conditions, maintaining a high
Generally between 10% and 40% vinyl demoulding efficiency and its stability at
acetate is used, and the rest is ethylene. The temperatures over 200ºC.
higher the percentage of vinyl acetate, the
higher the quality of EVA rubber, since with CONCENTROL LP IADC-114-43 PHB gives
a small percentage a hard and brittle parts a glossy finish (figure 1), but with the
polymer would be obtained. EVA is a soft addition of a Concentrol matting agent, it is
plastic that, thanks to its foaming process, is possible to achieve a satin or even matte
perfect for use as a shoe sole. shade (figure 2).
The foaming of EVA is done by introducing
gas into the polymer. A foaming agent,
azodicarboamide being the most common,
is introduced into EVA mixture. This, when
the mixture is heated, decomposes
producing gas that is trapped in the plastic.
The gas expands and EVA foam forms.
Once EVA foam is formed, shoe soles or
other parts of the shoe can be formed
through different methods. One of them, the
Figure 1: CONCENTROL LP IADC-114-43 PHB
hot compression process of EVA foam,
(original)
results in phylon.
Figure 2: CONCENTROL LP IADC-114-43 PHB
(Concentrol matting agent)
!12Success Story - Footwear Sector
What have we achieved? How we did it
Concentrol is going through an We designed a customized product, based
internationalization phase. Through our on a solvent-based product that is versatile
trade network, we want to offer our and with many possibilities. Bear in mind
chemical solutions to all the customers that that we are dealing with a high-end product
need them, offering the best technical and by Concentrol.
customer support for each case, which we
always treat in a personalized way. This is The new composition of the original product
the case of a Mexican customer, who was has achieved very good results to solve the
looking for a specific solution for the impediments that the customer faced. With
manufacture of their product. regard to the dirtying of the molds and the
imperfections that this caused, with the new
The protagonist of this success story is an product application production was
international customer who designs and improved so that while the molds had to be
manufactures soles of shoes. Their need is to washed three times a week, now they only
improve the production process. Their need be washed once. This has also led to a
problem was that the molds they used got reduction in costs, since production need
really dirty, the soles got stuck and the not be stopped as much as before. The
result they achieved was not uniform. quality of the result has also benefited.
The large growth of the business and its As for the painting process, the customer
premise of prioritizing quality above all now gets better results in less time, which
could not allow the imperfections of their also implies a substantial optimization. In
products. That is why this family-owned addition, we have managed to reduce the
company leader in the sector requests scrub that the customer had during the
Concentrol a tailor-made product that manufacture, because the product that we
allows them to optimize and improve the have offered reduces this problem thanks to
manufacturing process. its properties.
This customer wanted to maintain the Our solution
manufacture of soles with polyurethane,
with the aim of prioritizing quality and Consistency, quality and treatment and
better solidity results. The soles highly personalized services have been the
manufactured by the customer are complex keys to this recent success story.
and with demanding finish and quality.
At Concentrol we prioritize quality and focus
After analyzing the situation, Concentrol on excellence. When we find a customer
present to the company a custom solution. that works in our line, in this case a leading
Based on a product line that improves manufacturer in expansion, we work to be
performance, we adapt a formula that able to respond to their needs. We know
achieves a less dirty mold (more than twice that positive experiences that result in
the effectiveness of the product they used successful products benefit us in a
previously), with the added bonus of qualitative way and this makes our company
achieving more uniformity and a better- grow permanently.
performing painting and more uniform
result. That is why the company is committed to
invest more and more in R + D to offer new
chemical solutions, adapted to market
trends and specific for each sector.
Innovation is a fundamental part of
Concentrol’s DNA, as well as the
commitment to meet new challenges to
improve every day.
!13Footwear sector: Concentrol's water-based mold
release agents, for single and dual density soles
At Concentrol, we work day after day on the • Wide operating temperature range
constant improvement of production • Compatible with our additives for
processes and internal operations. All these gloss control
activities not only allow us to reduce costs, • Compatible with subsequent
but also give us the possibility of finding painting processes, with or without
solutions that are increasingly degreasing
sustainable, respectful with the natural • Tin-free formulation option
environment and with the work environment • RSL studies on demand (Restricted
and workers. Substances List)
The company has in its catalogue a wide • Availability of environmentally
range of products for the manufacture of all friendly cleaners
types of polyurethane footwear: mold
release agents, stabilizers, cleaners and WATER-BASED MOLD RELEASE AGENTS FOR
adhesives. Especially, we stand out in the DUAL DENSITY SOLES
making of solutions for polyurethane
footwear, with an increasing demand in the At Concentrol we have also specialized in
current market of the sector. the development of sustainable solutions for
After dedicating time and resources in polyurethane footwear with dual density
researching new solutions for polyurethane soles. As we have already seen with DSMs
footwear, more sensitive to the environment for single-density soles, the nature of the
and production personnel, we release agent allows for a series of benefits:
developed water-based release agents for • Homogeneous appearance without
footwear and polyurethane soles (DSM), defects
• Development of customized
both single-density and double-density.
products
Water-based mold release agents
• Longer cleaning cycles
are sustainable and environmentally friendly
• Control of the piece finish
products, thanks to lower flammability and a Regarding the properties of the product,
reduction in harmful properties and unlike water-based release agents for single
emissions of volatile organic compounds. density soles, these release agents adapt to
Therefore, we could say that they have a the characteristics of dual density
capacity to regulate emissions (they emit
soles, ensuring perfect adherence between
lower levels of VOCs).
the layers. Among their properties, we find:
• High mold release power
WATER-BASED MOLD RELEASE AGENTS FOR
• Minimal mold fouling
SINGLE DENSITY SOLES
• Wide operating temperature range
Firstly, we present the water-based mold
• Ensures perfect adhesion between
release agents aimed at the manufacture
layers
of single density polyurethane soles for Compatible with our additives for
•
footwear, both for polyester and polyether. gloss control
This Concentrol range has multiple benefits, • Compatible with subsequent
both with regard to the appearance, the painting processes, with or without
finish and the customization of the pieces; degreasing
as well as what affects the sustainability of • Tin-free formulation option
the product: • Availability of environmentally
• Homogeneous appearance without friendly cleaners
defects At the end of this article, two infographics
• Development of customized have been prepared that visually explain the
products properties and benefits of water-based
• Longer cleaning cycles mold release agents applied to polyurethane
• Control of the piece finish footwear.
Water-based release agents for single
density soles have the following properties:
• High mold release power
• Minimal mold fouling
!14OTHER CONCENTROL RANGES OF At Concentrol we work to devise and
POLYURETHANE FOOTWEAR MOLD RELEASE produce solutions that are fully adapted to
AGENTS the needs of our clients, taking into account
our commitment to society and the world in
The water-based release agents for PU which we live.
footwear are solutions that we have We are currently present in many countries,
developed in response to the climatic most of which are leaders in this sector such
emergency. It is the most sustainable range as China, India, Vietnam, Indonesia, Brazil,
of release agents and, moreover, more Turkey, Pakistan, Mexico, Italy, United
careful with the work environment. In States, Thailand, Russia, United Kingdom,
addition, at Concentrol we also have other Netherlands, Belgium, Morocco, Spain and
intermediate solutions for those clients who Portugal, among others.
still cannot take the step. Sustainability is a primary matter for the
protection of three fundamental pillars:
In our catalogue we have other options, caring for the environment, social
such as solvent-based mold release agents development and economic growth. For this
reason, we have invested resources (and will
and hybrid or co-solvent mold release
continue to do so) in developing efficient
agents (50% solvent-based, 50% water-
solutions for our clients, while ensuring the
based). In addition, in each one of them we safety of our team and the protection of the
adapt to the requirements and needs of the planet.
clients, also offering concentrated products, For more information, you can contact us
tin-free or suitable for electrostatic and we will be happy to present you the
applications. options that best suit your needs.
If you are interested in obtaining more information on
release agents for the footwear industry, contact us at
Concentrol or via the e-mail:
ydezabala@concentrol.com
!15You can also read
