The formation of an efficient nail polish may be based on the selection of a proper and an essential ingredient. The ingredients involved in the formation of a good variety of nail polish could be as follows:
FORMULATION OF NAIL LACQUERS
The formation of an efficient nail
polish may be based on the selection of a proper and an essential ingredient.
The ingredients involved in the formation of a good variety of nail polish
could be as follows:
S.N. Ingredients Example
1 Film
forming agents: Nitro cellulose, ethyl
cellulose, vinyl polymers
2 Resinous
substances: Aryl
sulphonamide-formaldehyde
3 Dissolving
solvent :
Ether, ethyl acetate, amyl acetate, butyl acetate
4 Dissolving
solvent/co-solvent: Ethyl alcohol, butyl
alcohol
5 Plasticizing
agents: d-butyl phthalate, n-butyl
stearate
6 Coloring
agent: 5% titanium dioxide (TiQ2)
7 Nacreous/pearly
pigments: Guanine crystal
8 Miscellaneous
substances: (1) suspending agent
(2)
perfumeries
1.
Film Forming Agents:
The selection of a film forming
agent is an important step in the formation
of a relevant type of nail lacquer. The most commonly used film forming
substance is nitrocellulose, due to the following properties.
·
The
films formed using nitrocellulose pigment stay flexible for a sufficient period
of time.
·
It
has good adherent property and hence does not allow any chipping and peeling.
·
Its
solvent retaining capacity is very low.
·
The
films formed by nitrocellulose are impermeable to water and air and hence fungal
infections can be eliminated.
·
It
imparts relevant transparency to the nail enamel.
·
When
compared to other film forming agents it is quite hard, tough and has good
abrasion resistance ability.
Other Film Forming Substances:
Several grades of nitrocellulose are available with varying viscosities but
only low viscosity grades are used for the preparation of nail polishes. The
degree of polymerization determines the viscosity which is necessary in order
to prepare a nail polish of required consistency.
Two types of grades of
nitrocellulose are readily used for nail polish preparation. They may be 'RS'
and ‘SS’ type. The most common used type is 'RS' grade with viscosity range 0.25
to0.5 cps. When nitrocellulose is used alone it produces a poor gloss and hence
in order to avoid this resins are added.
2.
Resinous Substances:
Resins enhance the glossy nature of
the nail polish and also impart adhesive
property.
·
Natural
resins such as benzoin, shellac, damar, sandarac and ester gums were used
initially but have been replaced' by synthetic resins as they provide good
gloss, better adhesion and also increased water resistance capacity.
·
The
most commonly used synthetic resin is sulphonamides-formaldehyde resin. it is a
polymer made by mixing equimolar proportions of formaldehyde and para toluene
sulphonamide.
·
The
two commercial types of aryl-sulphonamide-formaldehyde forms are santolite MHP
and santolite MS 80 percent.
·
The
santolite MHP forms a harder film and the santolite MS 80% provides good gloss,
flexibility and now property. But the resin combination is known to cause
certain allergic reactions and hence it has now been replaced by other
synthetic resins such as polystyrene, polyvinyl polyacrylic ester.
·
Acrylic
esters are compatible with nitrocellulose and they provide excellent gloss,
adhesion, durability, good flexibility etc.
3.
Solvent System:
The solvents normally used for
preparation of nail polishes may be volatile
organic liquids that can dissolve all the ingredients and make a homogenous and
uniform preparation. The solvent should be volatile enough in order to leave a
continuous, impermeable and hard film but the evaporation should not be too
rapid. The selection of a solvent plays an important role in order to provide a
balanced rate of evaporation.
Generally a mixture of solvents is preferred rather than a
single solvent. The solvents used for the formation of nail polishes are of the
following types.
(a)
Low Boiling Solvents: They include the solvents having
boiling point below 100°C. They take
more time to evaporate. Examples for low boiling solvents with their respective
boiling points are as follows:
Solvent Boiling point
Acetone 55°c
Butyl formate 96°c
Carbon disulphide 46°c
Carbon tetra chloride 77°c
Ethyl acetate 68°c
Methyl acetate 56°c
Isopropyl alcohol 80°c
Isopropyl acetate 92°c
(b)
Medium Boiling Solvents: these are solvents that have a
boiling point ranging between 100°C
to 150°C.The example of medium boiling solven ts with their boiling point are
as follows:
Solvent Boiling point
Amyl
formate 110°c
Butyl
alcohol 113°c
Diethyl
carbonate 126°c
Ethylene
glycol Monoethyl ether 135°c
Ethyl
lactate 135°c
Butyl
propionate 145°c
(c)
High Boiling Solvents: Liquids with boiling points more
than 150°C are r egarded as high boiling
solvents. Examples with their boiling points are as follows:
Solvent Boiling point
Cyclohexanone 154°c
Methyl
Cyclohexanone 160°c
Diacetone
alcohol 164°c
Methyl
hexalin 165°c
Ethyl
hexalin 185°c
Butyl
lactate 185°c
Cyclohexanone
pthalate 190°c
Generally, a combination of two or
more solvents is preferred over a single solvent. The solvent system used in
the preparation of nail polish influences the ease of its application. It also
influences its drying rate and hardening ability and other characteristic
properties of the film such as gloss shine etc,. The solvent combinations
should not have either too high or too low evaporation rates. Solvents that
evaporate very quickly may cause intense cooling. This may cause precipitation
of moisture from surrounding atmosphere making the film dull with unattractive
finish blushing. The phenomenon of blushing and blooming can be prevented during
the preparation of a nail polish by selecting a suitable solvent.
The viscosity of a nail lacquer is
also influenced by the boiling point of the solvent. Lower the boiling point of
the solvent, lower will be the viscosity of the resultant null lacquer and
hence better flow property. The rate of evaporation of solvents depends on many
factors such as specific heat, latent heat of evaporation, molecular weight, degree
of association etc, The solvent, with high boiling points generally provide at
brighter film than low boiling point solvent.
4.
Diluting Solvents/ Co-solvents:
They are not the actual solvents for
the dissolution of nitrocellulose
but are the co-solvents which increase the strength of the normal solvents. The
various reasons for the addition of diluents are to:
·
Maintain
the viscosity of the lacquer to form a stable film.
·
Increase
the solubility of the incorporated resins, thus working as a co-solvent.
·
Abate
the effect of freshly applied polish or a recently applied lacquer.
·
Reduce
overall cost of the product since the solvents used might he costly.
·
The
most commonly used diluents are alcohols such as ethyl alcohol, butyl alcohol
etc., they may also be used in combination with their esters. Example: Ethyl
alcohol with ethyl acetate etc,.
The quantity of diluent used may
also influence the formation of a good film. The limit for use of diluent may
he expressed in terms of tolerance ratio or dilution ratio. The dilution may he
defined as the maximum ratio of the diluent to the solvent (diluents/solvent)
that can be tolerated by nitrocellulose solution without causing precipitation
of nitrocellulose pigment.
Thus, selection of a proper
combination of diluent and the solvent system is necessary. The combination
should be such that the diluent should have a faster evaporation rate than the
solvent system which would prevent the precipitation of nitrocellulose due to
reduction in diluent solvent ratio. Thus, a clear, smooth and continuous film
may be formed rather than a rough and cloudy film. The other examples of
diluents beside alcohol are benzene, Xylene, toluene etc.
5.
Plasticizing Agents:
The plasticizing agent constitutes an important part in the formulation of nail polish
preparation. Plasticizers are used for the following purposes.
·
In
order to improve the flexibility of the nail lacquer and minimize its tendency
to shrink in order to form a uniform film.
·
The
nitrocellulose fibres alone make a dull and brittle film, but the addition of a
plasticizer increases the gloss and adhesive property. Example: Castor Oil.
Functionally plasticizers may be divided into two types:
(a)
Solvent
Plasticizers
(b)
Non-solvent
Plasticizers
(a)
Solvent Plasticizers: Solvent plasticizers, besides
imparting flexibility to the nail polish,
may also act as solvents for the dissolution of nitrocellulose. Many of
them are the high molecular weight esters that have low volatility and relatively
high boiling point. Example: butyl acetyl ricinoleate.
(b)
Non-solvent plasticizer: These are not compatible with
nitrocellulose and hence can’t be used
alone. They cannot act as solvents but only act as plasticizer.
·
The
ideal properties for the choice of a good plasticizer could be as follows:
·
It
should be compatible with other ingredients of the preparation.
·
It
should be able to impart flexibility and enhance the glossiness and adhesive
property of the nail polish.
·
It
should not evaporate quickly.
·
It
should not affect the stability of the preparation.
·
It
should not affect colour of the product.
·
It
should be non-irritating and non-toxic to the skin.
·
It
should be odourless and colourless.
·
It
should not cause any change in viscosity of the preparation.
The most commonly used plasticizers
are dibutyl phthalate, n-butyl stearate, butyl glycolate, tributyl phosphate,
resorcinol diacetate, castor triethyl citrate, dibutyl tartrate, dibutoxy ethyl
pthalate, butyl acetyl ricinoleate.
Dibutyl pthalate and glycolate
plasticizers are considered to be the best as They provide better hardness,
feel and adhesion to the nail. They generally contribute 5% of the total
mixture or as 25% to 30% in combination with the film forming agents.
The use of acetylated monoglycosides
along with other plasticizers may increase the stability and flexibility of the
Product thus improving the long lasting ability.
6.
Colouring Substances:
The colouring substances also form
an important component of the nail
lacquer as they are required to impart a desirable shade.
·
It
should also be able to opacify the nail lacquer so that the most delicate shade
may be able to cover the nail.
·
More
than 10 basic colours are required to produce large variety of sheds used in
polishes.
·
All
the colours must conform to the terms and conditions of the Drugs and Cosmetics
Act.
·
The
coloured substances are available as colouring agents and are incorporated with
the pigments and lakes.
·
They
are mostly available in the form of dispersion. The usual concentration is
between 3 to 5%. Examples: Lithopone or 5% titanium dioxide is incorporated
along with lakes to produce pastel shades. Iron oxides are used to produce
brown or tan shades. The dinitrobenzene pigments are used to produce brilliant
brown colours.
7.
Nacreous/ Pearlescent Substances:
They are used in order to produce an
iridescent or a nacreous appearance.
They have high refractive index and hence produce a glow when light falls on
then. The can be obtained either from nun-al or synthetic origin.
(a)
Natural Pigment: The example for the substance from
natural origin is guanine crystals. Chemically
they are 2-amino, 6-oxypurine crystals. They are obtained from the skin and the
scales of fish. They are marketed mostly in the form of suspensions or pastes.
(b)
Synthetic Pigments: Synthetic pigments can be obtained
from the coating of bismuth oxychloride
or titanium dioxide or the flakes or platelets of mica. They are less expensive
than natural pigments.
8. Miscellaneous Agent:
(a)
Suspending Agents: Suspending agents such as Bentone -
27 and Bentone-34 are most commonly
used in nail polishes in order to prevent settling of the pearlescent pigments,
thus avoiding sedimentation. The concentration of these substances varies
between 0.5 to 2%.
(b)
Perfumes: Perfumes are basically used to cover
the odour of other ingredients and to provide
a pleasant smell. Mostly synthetic perfumes are used in an optimum quantity of about 1% concentration. The formulae for the
preparation of nail lacquer are as follows:
Formula-1 Quantity for 100 g
Nitrocellulose (film former) 7 g
Dibutyl phthalate (plasticizer) 5 g
Polyvinyl acetate (resin) 8 g
Methylene chloride 29.4 g
Ethylene glycol monomethyl ether 28 g
(solvent)
Diethyl glycol monomethyl ether
(solvent) 2 g
Ethyl alcohol (diluents) 14 g
Perfume oil 6 g
Color 0.6 g
Formula-2 Quantity for 100 g
Nitrocellulose (film former) 10 g
Sentolite MHP (resin) 10 g
Dibutyl phthalate (plasticizer) 3 g
Ethyl alcohol (diluents) 6 g
Ethyl acetate (solvent) 20 g
Butyl acetate (solvent) 15 g
Toluene (solvent) 36
g
Formula-3 Quantity for 100 g
Nitrocellulose (film former) 4 g
Dibutyl phthalate (plasticizer) 4 g
Polypropyl methacrylate (resin) 18.6 g
Ethyl alcohol (diluents) 25.6 g
Butyl acetate (solvent) 23.9
g
Toluene (solvent) 23.4 g
Color 0.5 g
The Preparation Of Nail Lacquers
The preparation of nail polishes can be carried out as follows:
The film forming substance i.e.,
nitrocellulose is dissolved in a suitable solvent. Resins plasticizers can be
added directly or after dissolving them in small amouts of solvent.
The finely divided pigments are
added by forming dispersion of the pigment as they form aggregates. The
dispersion can be formed by milling the pigments in a ball null or a or triple
roller mill.
The dispersion of the pigments, nitrocellulose
and plasticizer are ground together in a solvent in order to form a plastic
mass.
The final mixing of the ingredients
for the manufacture of nail polishes is carried out in stainless steel tanks
with a stirrer.
Initially, the tank is charged with the
diluent and nitrocellulose (suitably wetted the diluent) is added to it.
The plasticizer and the resin are
added next and the mixing process continues.
The mixing process is carried out
till sufficiently uniform solution is formed. The clear lacquer is then
subjected to filtration and centrifugation in order to remove any particles.
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