FIELD OF INVENTION
This invention relates to new class of phosphorus containing epoxy ester resins,
which are useful as curing components for melamine formaldehyde resin in the
manufacturing of intumescent fire retardant resins, paints, and clear coatings. The
invention also includes the process for preparation of phosphate ester resin and for the
preparation of water based intumescent fire retardant clear coating compoitions.
Selection of amino melamine resin relates to potentially intumescent fire retardant
water base clear coatings for combustible (wooden and fabric) substrates to protect
from fire or heat. This coating can also protect a wide variety of substrates to prevent
flame propagation without loss of their aesthetic properties.
BACKGROUND
Fire is one of the most difficult things to control. Protection against fire is important
for saving lives, as well as minimizing financial losses. The danger of fire exists
wherever we work or dwell, high altitude is also no exception.
This invention relates to fire retardant intumescent clear coating and, more
particularly, to melamine resin as binder which are rendered fire retardant and
intumesecent by use of certain phosphate ester resins. Fire retardant coatings are not
new. The prior art includes references to fire proofing compositions which may be
applied in the form of paint and coating to retard fire and flame spread. Many fire
retardant coatings have little or no flow and, hence do not provide desirable
smoothness to qualify for protective and decorative coating applications. Another
serious limitation of many of the prior art fire retardant coating compositions is their
lack of washability. Upon exposure to washing, as for example, to remove dirt spots
by periodic cleaning with soap solution, the films get dissolved. Many prior art
intumesent fire retardant coatings are also significantly less effective than desired in
providing resistance to flame spread and in creating an insulating barrier between the
source of flame and combustible material.
US3497469 describes intumescent clear coating by using solvent based polyurethane
binders and organo phosphorus compound. However the used binder and solvents are
highly flammable, hence the coatings based on such resins and solvents are not
recommended.
US3883463 and US4764539 disclose the use of a flame retardant binder such as
polymer latex comprising of vinyl phosphates, vinyl halides and other derivatives of
acrylic acids. However, such halogens containing fire retardant systems may produce
a large amount of toxic gases while burning, and will be harmful to human beings.
US4210452 discloses the use of an intumesecent coating containing cyclic nitrogen
compound, phosphorous polyol, phosphorous acid and water. Although it has good
flame retardant property, it requires 30 h for curing at room temp or to be baked at
70-170 ° C for 20 minutes for complete curing. Hence such type of coatings is not
recommended for big structures, because it is difficult to heat big structures.
US4247435 mentions about an intumescent coating composition having Carbon
source and ammonium polyphosphate. These types of coatings, due to their poor film
appearances are not recommended for structures where aesthetics is of primary
importance.
US5108832 discloses an intumescent curable composition which contains a flexible
polyepoxide resin, curing agent and additives such as zinc, boron and Phosphorous
elements. But the use of boron related compounds are not recommended due to its
hazardous nature to human beings.
IN232744 discloses the intumescent fire retardant paint composition which comprises
of water based acrylic resin, ammonium polyphosphate, pentaerytritol,
dicyandiamide, etc. Since the composition contains water soluble compounds, paint
composition is not recommended for exterior purpose and is also not suitable for the
areas where humidity is high.
US6084008 discloses a fire retardant coating composition which comprises of
expandable graphite, an absorbent material, a polymeric binder, a carbonific material,
a blowing agent, etc. Since the materials used for making the coating compositions
are costly hence such type coating will not be cost effective.
US7417091 discloses polymer binders for intumescent coatings by using a blend of
p-methylstyrene repeat units and 2-ethylhexylacrylate repeat units copolymer and
some rheology modifier additives. But the use of such additives may affect the fire
retardance properties of the coatings.
US7820736 discloses an epoxy and vinyl ester resin based intumescent coating
composition for steel substrates with coating thickness of centimeter range. The use
of this type of coating will not only increase the weight of the structure but also
increase the cost of the coating.
Zhiling Ma et al, 2012 published synthesis and characterization of water borne
intumescent varnish based phosphate resin and melamine urea formaldehyde resin.
But the intumesent varnish was prepared by using phosporous pentoxide which is
highly hygroscopic and it requires extra care during handling.
The said prior art described systems do not provide intumescent fire retardant clear
coating composition so as to provide protection for wooden structures. Most of these
priorly known coatings are pigmented ones. The incorporation of pigments and
additives in to the binder are done by using paint mixing equipments. To achieve
sufficient fire retardancy, a high loading of additive and pigments are required which
results in the detrimental influence on the physical and mechanical properties of the
coating. Water based emulsions coating systems described in the prior art are
susceptible to moisture in high humid environments. Also some coating systems
described in prior art need baking after application of coating to the substrates, but
which is not possible in the case of extreme large structures such as ships, trains and
buildings. Some of the prior art described coatings itself wherein the solvents used
are highly flammable and can also cause environmental pollution.
Water borne fire retardant clear coating not only protects wooden furniture from fire
but also produces low carbon. Hence there is a need for development of water based
intumescent clear coating with improved transparency which can also be used for
protection of wood, metal and plastic materials.
Intumescent fire retardant coatings are used to protect structures from fire in view of
its excellent fire retarding property and thermal insulation capability through
formation of carbonaceous foam. Since conventional intumescent paints are not
fulfilling the requirement of aesthetic appearance of the substrates. Hence there is
need to develop intumescent fire retarding clear coating which can be applied by
brushing and can from smooth uniform film and also remain stable during normal
storage conditions.
The present inventors have surprisingly found that when all the intumescent
ingredients are incorporated into the polymer backbone during its synthesis, then it
forms clear transparent coating films without disturbing the aesthetic appearance of
the substrate. The present invention also uses water as solvent making coating eco
friendly and economic. The present invention thus provides a liquid coating
composition thereby avoiding the use of powder coating which requires high
temperature baking/curing of the coating in oven which is not feasible in cases of
large structures such as ships, buildings etc. Hence, the coating can be applied on all
type of substrate such as wood, plastic and metals.
OBJECT OF INVENTION
The primary object of the invention is to develop water based intumescent fire
retardant clear coating for protection of metallic and wooden structures and also
simultaneously provide aesthetic appearance to the structures.
Another object of the invention is to describe a process for preparation of water based
intumescent fire retardant clear coating which uses Melamine resin as a binder.
Yet another object of the invention is to provide phosphate ester epoxy resins.
Yet another object of the invention is to provide a process for preparation of
phosphate ester resin which is required for curing of melamine resin and also
improves application and film formation properties of intumescent fire retardant clear
coating at ambient conditions.
Yet another object of the invention is to provide a process for preparation of
intumescent fire retardant clear coatings composition which utilizes water as solvent
to achieve moderate evaporation rate and less porous coating with proper leveling and
is also eco friendly in nature.
SUMMARY OF INVENTION
According to another aspect of the present invention, there is provided Phosphate
ester epoxy resin comprising:
i. mixture of polyol and butanol;
ii. polyphosphoric acid;
iii. mixture of epoxy resins.
According to another aspect of the present invention, there is provided a process for
the preparation of phosphate ester epoxy resin comprising the steps of
i. Adding a mixture of polyol and butanol to the reaction flask;
ii. Adding polyphosphoric acid to the reaction mixture slowly by maintaining the
temperature in the range 50-70°C;
iii. Increasing the temperature of the reaction mixture to 120-140°C;
iv. Maintaining the reaction temperature until the acid value becomes constant;
v. Adding a mixture of epoxy resins to the phosphate ester acid;
vi. Maintaining the reaction temperature at 60°C till the acid value decreases to
250±30 mg KOH/g resin.
According to another aspect, the present invention provides Intumescent fire retardant
clear coating compositions comprising a phosphate ester resin as a curing agent for
amino melamine resins.
According to yet another aspect of the present invention, there is provided
Intumescent fire retardant clear coating composition comprising
a. phosphate ester epoxy resin comprising
i. mixture of polyol and butanol;
ii. polyphosphoric acid;
iii. mixture of epoxy ester resin
b. melamine formaldehyde resin and
c. water
According to yet another aspect of the present invention there is provided a process
for the preparation of intumescent fire retardant coating composition comprising the
steps of:
i. Adding a mixture of polyol and butanol to the reaction flask;
ii. Adding polyphosphoric acid to the reaction mixture slowly by maintaining the
temperature in the range 50-70°C;
iii. Increasing the temperature of the reaction mixture to 120-140°C;
iv. Maintaining the reaction temperature until the acid value becomes constant;
v. Adding a mixture of epoxy resins to the phosphate ester acid;
vi. Maintaining the reaction temperature at 60°C till the acid value decreases to
250±30 mg KOH/g resin;
vii. Adding 50% by weight of water to the above mixture along with the curing
agent which is selected from melamine formaldehyde resin to form intumescent
fire retardant clear coating composition.
DESCRIPTION OF INVENTION
According to this invention intumescent fire retardant clear coating composition
based on phosphate ester resin as curing agent for protection of wooden structures is
disclosed. The phosphate ester curing agent is synthesized by condensation reaction
of polyphosphoric acid and a combination of polyol used in combination which is
further reacted with a base resin such as melamine resins (HMM).
Phosphate ester epoxy resin comprising:
i. mixture of polyol and butanol;
ii. polyphosphoric acid;
iii. mixture of epoxy resins.
Phosphate ester resin was synthesized using Polyphosphoric acid, Pentaerytritol (PE),
Butyl alcohol (BA), epoxy resins. The formation of phosphate ester resin was
confirmed by FTIR spectroscopy and acid value determination. This resin was diluted
with water to make 50 wt% solution and used as curing agent for amino melamine
resins such as melamine formaldehyde (HMM) formaldehyde resins.
The following two epoxy resins were used in combination in this invention
A process for the prepartaion of phosphate ester resin comprising the steps of
i. Adding a mixture of polyol and butanol to the reaction flask;
ii. Adding polyphosphoric acid to the reaction mixture slowly by maintaining the
temperature in the range 50-70°C;
iii. Increasing the temperature of the reaction mixture to 120-140°C;
iv. Maintaining the reaction temperature for 4-7 hours until the acid value
becomes constant;
v. Adding a mixture of epoxy resins to the phosphate ester acid;
vi. Maintaining the reaction temperature at 60°C till the acid value decreases to
250±30 mg KOH/g resin
A process for the preparation of intumescent fire retardant coating composition
comprising the steps of:
i. Adding a mixture of polyol and butanol to the reaction flask;
ii. Adding polyphosphoric acid to the reaction mixture slowly by maintaining the
temperature in the range 50-70°C;
iii. Increasing the temperature of the reaction mixture to 120-140°C;
iv. Maintaining the reaction temperature for 4-7 hours until the acid value
becomes constant;
v. Adding a mixture of epoxy resins to the phosphate ester acid;
vi. Maintaining the reaction temperature at 60°C till the acid value decreases to
250±30 mg KOH/g resin,
vii. Adding 50% by weight of water to the above mixture along with the curing
agent which is selected from melamine formaldehyde resin to form
intumescent fire retardant clear coating composition.
The detailed description of the process is given below.
The synthesis of curing agent involves the following steps. Initial step
involves synthesis of phosphate ester acid. For this purpose, mixture of pentaerytritol
and butanol was added into a four necked glass flask equipped with a stirrer, a reflux
condenser and a thermometer. The poly phosphoric acid was added to the reaction
mixture slowly to control the exothermic reaction, maintaining temperature in the
range of 50-70°C. After the complete addition of poly phosphoric acid the
temperature was increased to 120-140 °C and the reaction was continued for about 4-
7 h until the acid value becomes constant. In the second step, a mixture of Neopentyl
Glycol and Butane diol based epoxy resins were added to above synthesized
phosphate ester acid and the reaction was carried out at 60°C to further decrease the
acid value, and water was added to the above reaction mixture when acid value
stabilizes. The 50 weight % solution in water of above curing agent was used to cure
melamine resins for making intumescant clear coatings.
The phosphate epoxy ester resin is cured with a curing agent in the ratio of 1:1.
The mixture of polyol and butanol is in the ratio 1:1.7 to 12.2.
The polyol is selected from pentaerythritol or dipentaerytritol.
The epoxy ester resin comprises a mixture of Neopentyl Glycol diglycidyl ether and
Butane diol diglycidyl ether based epoxy resin in 1:1 ratio.
The acid value of the fire retardant coating composition is in the range of 225±10 mg
KOH/g resin. The Initial acid value is 710 ±10 mg KOH/g resin, after continuing the
reaction for about 4-7 h, the acid value is 605 ±10 mg KOH/g resin, after the addition
of Neopentyl glycol and butane diol diglycidyle ether epoxy resin and heating at
60°C the acid value is 250±30 mg KOH/g resin, the acid value at the point when
water is added to the reaction mixture is 250±30 mg KOH/g resin. Thus the reaction
is continued till the acid value is in the range of 250±30 mg KOH/g resin.
The binder material consists of Phosphate ester resin in the range of 20-25 weight %,
Melamine formaldehyde resins (98% solid) 40-50 weight %, water 20-25 weight
%, and were mixed to produce the Intumescent clear lacquer. The present
invention therefore provides Intumescent fire retardant clear coating composition
comprising
a. 20-25 weight% phosphate ester epoxy resin;
b. 40-50 weight % Melamine formaldehyde resin and
c. 20-25 weight% water.
Intumescent fire retarding clear coatings, according to the present invention has 70-75
weight % binder which includes phosphate ester resin and the melamine resin, 25-30
weight % water for diluting the binder material.
The thickness of the intumescent fire retardant clear coating that needs to be applied
is 225±25 micron.
The intumescent fire retardancy of painted specimens demonstrated that a higher
phosphorous content is beneficial to the intrinsic fire retardancy of coated specimens.
The high quality char formation is another benefit to intrinsic fire retardancy of
coated specimens.
Intumescent fire retardant clear coating composition of the present invention can be
applied with brush and film formation takes palce at ambient temperature conditions
without disturbing aesthetics of substrates especially patterns available on wooden
articles.
Further Intumescent fire retardant clear coating composition of the present invention
produces glossy tough durable films when applied on painted surfaces and wooden
components as also provides films with good resistant to solvents after curing.
The advantages of the intumescent fire retardant clear coating composition of the
present invention are as follows:
> Present coating composition provides clear transparent coating films without
disturbing the aesthetic appearance of the substrate;
> Present coating composition uses water as solvent medium thereby making
the coating ecofriendly and economic;
> Avoids the use of additive and pigments
> Avoids the use of powder coating;
> Does not require high temperature baking/curing of the coating in oven.
> The coating can be applied on all type of substrate such as wood, plastic and
metals;
> Present coating composition can be used in humid environment.
Process for preparation of clear intumescent fire retardant coatings for protection of
fabric and wooden structures and evaluated according to the present invention has the
following composition in wt%
Example-l
The mixture of pentaerytritol 12 g and butanol 26 g was added into a four necked
glass flask. The poly phosphoric acid 80 g was added to the reaction mixture
slowly/in small quantity to maintain temperature at 50-70 °C. After the complete
addition of poly phosphoric acid the temperature was increased to 120-140°C and the
reaction was continued for about 4-7 h until the acid value stopped decreasing. A
mixture of Neopentyl Glycol 35 g and Butane diol 35 g based epoxy resins were
added to the above reaction mixture. The reaction was carried out at 60°C to further
decrease the acid value. The 50 wt % solution in water of above curing agent was
mixed with 50 g of melamine resins.
Example-2
The mixture of pentaerytritol 16 g and butanol 30 g was added into a four necked
glass flask. The poly phosphoric acid 80 g was added to the reaction mixture
slowly/in small quantity to maintain temperature at 50-70 °C. After the complete
addition of poly phosphoric acid the temperature was increased to 120-140°C and the
reaction was continued for about 4-7 h until the acid value stopped decreasing. A
mixture of Neopentyl Glycol 35 g and Butane diol 35 g based epoxy resins were
added to the above reaction mixture. The reaction was carried out at 60°C to further
decrease the acid value. The 50 wt % solution in water of above curing agent was
mixed with 50 g of melamine resins.
Example-3
The mixture of pentaerytritol 20 g and butanol 34 g was added into a four necked
glass flask. The poly phosphoric acid 80 g was added to the reaction mixture
slowly/in small quantity to maintain temperature at 50-70 °C. After the complete
addition of poly phosphoric acid the temperature was increased to 120-140°C and the
reaction was continued for about 4-7 h until the acid value stopped decreasing. A
mixture of Neopentyl Glycol 35 g and Butane diol 35 g based epoxy resins were
added to the above reaction mixture. The reaction was carried out at 60°C to further
decrease the acid value. The 50 wt % solution in water of above curing agent was
mixed with 50 g melamine resins.
The clear coating composition was evaluated for following characteristics.
1. Volatile matter, as per IS: 101 (Part 2/ Sec-2) 1986
2. Weight per liter, as per IS: 101 (Part l/Sec-7) 1987
3. Drying time as per IS: 101 (Part 3/ Sec-1) 1986
a. Surface Dry
b. Hard Dry
4. Cross hatch adhesion, as per ASTM D 3359-B-97
5. Abrasion Resistance,[weight loss (in mg)/1000 cycles], as per ASTM D 4060-10
6. Impact test, as per, as per ASTM G-14-04(2010)
7. Scratch resistance test,[tolerance weight in kg] as per IS: 101(Part-5/Sec-2) 1988
8. Fire retardant properties, as per Appendix-A
a. Flame spreading length
b. Char height
c. Afterglow
d. After flaming
Appendix- A
FIRE TEST FOR INTUMESCENT FIRE RETARDANT PAINT
1. Out line of the method The apparatus consisting of a two foot tunnel inclined at
38° to the horizontal in which painted panel placed facing downwards to form the
roof of the tunnel as shown in figure 2. Paint under test should be applied at the
recommended dry film thickness which is 225±25 micron.
2. Evaluation of the compositions for fire test
2 foot-tunnel test: The frame of the tunnel is fabricated from %" x 3A"x 1/8" angle
iron mounted on a 5" x 26" base plate. The sample holding rack utilizes a 30 "x 4"
specimen size. An asbestos backing plate of 30" x 4" is used to prevent the test
specimen from warping during the fire test. A small opening at the lower end of the
tunnel is provided with a mirror to observe the propagation of the flame. Temperature
at the back of the panel is measured by inserting thermocouple through a small
hole at the top cover which is located right above the burner. A Bunsen burner is
used at the lower end of the inclined tunnel and the distance between the burner top
and test specimen is about 1.5 inch.
3. Procedure: The intumescent clear coating is applied on the wooden panels
(Himalayan fir) of size 30"x4"x0.4". Two coats of paint is applied to build up a film
thickness of 175 ± 25 microns and allowed to dry for 3 days at ambient conditions.
The panel is positioned in the inclined top and the asbestos plate which is of the size
of the test specimen is placed above the painted panel. Mark the coated panel in such
a way that '0' mark is positioned exactly above the tip of the burner and further
marking are made in 1" succession till end of the panel as shown in figure -1. Panel is
exposed to flame for ten minutes with pressure 2.0 lbs / square inch and the following
observations are to be noted.
(a)Char height: Maximum height of char in millimeter at a point directly above
the burner.
(b)Flame spread length: Only flame extending along the surface of the test panel
should be recorded as flame spread length.
(c) After glow
(d) After flaming
Evaluation of the clear coating composition for the following characteristics yielded
the below results
Coating parameters determined were as follows
UL-94 test and LOI result for composition provided in example 2.
1. The UL-94 test utilizes specimens having the dimensions 125 X 12.7 X 3 mm
were clamped vertically to stand in place and twice ignited from below for
about 30 sec. The average after burning time and the formation of burning
polymer droplets are evaluated as follows.
2. LOI test results are as follows: Carried out as per ASTM D 2863
We claim
1 • Phosphate ester epoxy resin comprising:
i. mixture of polyol and butanol;
ii. polyphosphoric acid;
iii. mixture of epoxy resins.
2. A process for the preparation of phosphate ester epoxy resin comprising the steps
of
i. Adding a mixture of polyol and butanol to the reaction flask;
ii. Adding polyphosphoric acid to the reaction mixture slowly by maintaining
the temperature in the range 50-70°C;
iii.Increasing the temperature of the reaction mixture to 120-140°C;
iv. Maintaining the reaction temperature until the acid value becomes
constant;
v. Adding a mixture of epoxy resins to the phosphate ester acid;
vi. Maintaining the reaction temperature at 60°C till the acid value decreases
to 250±10 mg KOH/g resin.
3. A process for the preparation of phosphate epoxy ester resin as claimed in claim 2
wherein the reaction is continued till the acid value is in the range of 250±30 mg
KOH/g resin.
4. Intumescent fire retardant clear coating composition comprising
a. phosphate ester epoxy resin comprising
i. mixture of polyol and butanol;
ii. polyphosphoric acid;
iii. mixture of epoxy resins;
b. melamine formaldehyde resin and
c. water.
5. Intumescent fire retardant clear coating composition as claimed in claim 4
comprising
a. 20-25 weight% phosphate ester epoxy resin;
b. 40-50 weight % Melamine formaldehyde resin and
c. 20-25 weight% water.
6. A process for the preparation of intumescent fire retardant coating composition
comprising the steps of:
i. Adding a mixture of polyol and butanol to the reaction flask;
ii. Adding polyphosphoric acid to the reaction mixture slowly by maintaining the
temperature in the range 50-70°C;
iii. Increasing the temperature of the reaction mixture to 120-140°C;
iv. Maintaining the reaction temperature until the acid value becomes constant;
v. Adding a mixture of epoxy resins to the phosphate ester acid;
vi. Maintaining the reaction temperature at 60°C till the acid value decreases to
250±10mgKOH/g resin;
vii. Adding 50% by weight of water to the above mixture along with the curing
agent which is selected from melamine formaldehyde resin to form intumescent
fire retardant clear coating composition.
7. A process for the preparation of intumescent fire retardant coating composition as
claimed in claim 6 wherein the phosphate epoxy ester resin is cured with a curing
agent in the ratio of 1:1.
8. The mixture of polyol and butanol as claimed in any one of the preceding claims
is in the ratio 1:1.7 to 1: 2.2.
9. The polyol as claimed in any one of the preceding claims wherein the polyol is
selected from pentaerythritol or dipentaerytritol.
10. The epoxy resin as claimed in any one of the preceding claims comprises a
mixture of Neopentyl Glycol diglycidyl ether and Butane diol diglycidyl ether
based epoxy resin in 1:1 ratio.