As described above, the present invention provides an fire-retardant coating composition containing a substantially water-insoluble organic phosphates having phenolic base were used as fire retardant chemicals. The easiest way of protecting plywood is to apply coating of plywood surface with fire retardant chemicals. Other methods include -treating wood veneer with fire retardant chemicals before making plywood or dipping plywood, often under high pressure, in a solution of fire retardant. According to the present invention an excellent fire-retardant effect can be obtained with minor amounts of a fire-retardant coating composition, particularly in a process schedule, since the heat-insulating layer formed by other known process is very thick.
Additionally, the coating composition according to the present invention is particularly effective as a surface coating on veneer to provide a fire retardant property in use. Instead of using multivalent inorganic chemicals which interfere in bonding, organic phosphates having phenolic base are used as fire retardant chemicals. These chemicals having terminal phosphate groups are equally potent as fire retardant.
The veneers are not treated with chemicals as it seals the pores in the veneer and affect bonding. Instead, organophosphates are mixed with resin and applied on the veneer. Thus all surfaces of veneers get coated with fire retardant chemical along with resin. Being phenolic based, organo-phosphates do not interfere with the curing of the resin and remains ineffective to bonding.
The organo phosphates chemical herein used have the following properties:
Name: Tricresyl phosphate
Chemical formula: OP(OC6H4CH3)3
Alternative name: Tritolyl phosphate
Molecular mass: 568.37g/mole
Boiling point: 2550C
Melting point: - 400C
Appearance: Colourless liquid
It is a good plasticizer and major uses as flame retardant in plastic and rubber
Can be dispersed in phenol formaldehyde resin without any reaction. Due to presence of cresyl group having phenolic ring Tricresyl phosphate is compatible with phenol formaldehyde.
Further, the outer two layers of veneers which forms the faces of the plywood are not treated with resin so that after making plywood its surfaces remains free of resin and chemicals. A single stage phenol formaldehyde resin is being used as binder so that plywood becomes boil water proof (BWP grade).
The outer exposed surfaces of plywood are coated with colourless nano particle chemical which does not affect the natural colour of the veneer. The colourless chemical in nano particles enters into pores of surface veneer and the surface remains free and suitable for painting, but can resist flame due to presence of fire retardant chemicals in the pores of veneer.
The nano preservative chemicals herein referred is either from the group of
Chemical 1
Name : Borax
Chemical name: Disodium tetraborate octahydrate
Chemical formula : Na2B4O5(OH)4 . 8H2O
Boiling point: 15750C
Melting point: 7430C
Physical state: Colourless soft crystal
Non-toxic and anti-fungal
Used as fire retardant
Chemical 2
Name : Sodium fluoride
Chemical formula: NaF
Molecular weight; 41.9
Physical state: Colourless crystalline solid
Boiling point: 17040C
Melting point: 9930 C
An insecticide. Also act as fire retardant
In the manufacturing process of the veneers are treated with mild solution of NaOH to enhance the porosity of veneer surface so that resin containing fire retardant chemical penetrate into veneer. Veneers are dried to moisture content 6-8%.
Suitable construction of veneers for making particular thickness of plywood is formulated. Core veneers are coated with phenolic resin containing fire retardant chemicals. Glue core and panel core veneers arranged as required for making plywood. Face veneers are laid on either sides of the assembly, The whole assembly is pressed in a hydraulic press under high pressure and temperature.
The panel thus formed is trimmed to required size and both the surfaces are sanded to get smooth surfaces. The surfaces cleaned to remove any dust.
The plywood is dipped into a solution of nano particle of fire retardant chemicals. The plywood is subjected to moderate heat to facilitate nano particle completely absorb into the pores of the surface veneer. The surfaces of the plywood are buffed to remove any extraneous chemical deposit.
Testing of fire retardant plywood
As shown in Fig 1, the plywood is subjected to test as required for conformity to
IS : 5509 of Bureau of Indian Standards.
Following tests are performed:
i) Inflamability Tests
ii) Flame Penetration Test
iii) Rate of Burning
Plywood prepared as above conforms to the requirements of IS: 5509.
Inventive step
i) Unlike conventional method core and panel veneers are not treated with chemicals.
ii) Organo- phosphate is used as fire retardant chemical in place of inorganic phosphate
iii) Fire retardant chemical is applied along with resin.
iv) Since the fire retardant chemical is compatible with the resin, bonding is not affected so that plywood made with this resin gives strong water proof bond.
v) Surfaces are coated with nano chemical which does not discolour surfaces, but resist flame and permits painting.
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims:

1. A process of manufacture of boil water proof and fire retardant improved plywood conforming comprising the steps of:
treating the veneer with mild solution of NaOH;
assembling and resizing the veneers for making particular thickness of plywood;
coating the core veneers with phenolic resin containing fire retardant chemicals;
applying glue to core and panel core veneers and arranging the same for making plywood;
laying off the face veneers on either sides of the assembly;
pressing the whole assembly of veneers in a hydraulic press under high pressure and temperature.
trimming the pressed panel to required size and outer surfaces are sanded to get smooth surfaces.
dipping the plywood into a solution of nano particle of fire retardant chemicals and further heating the same in order to facilitate the nano particles to completely absorb into the pores of the outer surface veneer.
2. The process of manufacture of plywood as claimed in claim 1, wherein the treatment of NaOH solution is carried out in order to enhance the porosity of veneer surface so that resin containing fire retardant chemical penetrate into veneer.
3. The process of manufacture of plywood as claimed in claim 1, wherein the veneers are dried to moisture content 6-8% after the treatment of NaOH solution.
4. The process of manufacture of plywood as claimed in claim 1, wherein the outer surfaces are cleaned for removing any dust before applying a nano particle solution.
5. The process of manufacture of plywood as claimed in claim 1, further comprising the step of buffing the surfaces of the plywood in order to remove any extraneous chemical deposit.
6. The process of manufacture of plywood as claimed in claim 1, wherein the fire retardant chemical organic phosphate is phenolic base.
7. The process of manufacture of plywood as claimed in claim 1, wherein the nano particle chemical are Borax or Sodium Fluoride.
8. An improved fire retardant plywood comprising of :-
a plurality of veneers which are applied upon organophosphates mixed with resin such that all surfaces of veneers get coated with fire retardant chemical along with resin; a binder comprising of single stage phenol formaldehyde resin and colourless nano preservative chemical which does not affect the natural colour of the veneer;
Wherein the outer two layers of veneers which forms the faces of the plywood are not treated with resin; and the outer exposed surfaces of plywood are coated with colourless nano preservative chemical containing nano particles which enters into pores of surface veneer and the surface remains free suitable for painting.
9. The fire retardant improved plywood as claimed in claim 8, wherein outer exposed surface of the veneer surfaces remains free of resin.

10. The fire retardant improved plywood as claimed in claim 8, wherein the application of single stage phenol formaldehyde makes the plywood boil water proof (BWP grade).