DESC:FIELD OF INVENTION:
The present invention relates to novel compound having UV-curing flame retardant properties suitable for use in coating application. More preferably, the present invention relates to a new phosphorus and silicon containing monoacrylate compound and synthesis process thereof. The said novel compounds can be employed as a part of base resin in an UV curing coating formulation.

BACKGROUND OF PRIOR ART:
In a world of increasingly stringent safety regulations, it is becoming more and more important to find new compounds with flame retardant (FR) properties. Plastics and wood are the main categories of products to which FR chemicals are often added. Flame-retardant chemicals are applied on substrate such as wood products to retard the spread of flame and limit smoke production from wood in fire situations. When such treatments applied to substrate enhances the fire performance of the products by reducing the amount of heat released during the initial stages of fire. The treatments also reduce the amount of flammable volatiles released during fire exposure. This results in a reduction in the rate of flame spread over the surface.
Organo-halogenated compounds have been most widely used as flame retardant materials either as reactive co-reactant or additives, particularly in the composite or in electronic equipment. However, halogenated flame retardant and its derivatives suffered from various disadvantages like corrosive fumes and carcinogenic substances.
There are various reports in literature of reactive flame retardants based on phosphorus, boron, nitrogen and silicon that were used for UV curable formulations.
There are generally two ways to incorporate reactive flame retardants into UV curing formulation either as an oligomer or reactive diluent.
The use of phosphorus containing materials as flame retardants is well known and they act by, forming phosphoric and polyphosphoric acids of low volatility which catalyse the decomposition of organic compounds to carbon (char) and water. Organophosphate flame retardants, including an aromatic phosphate and oligomeric phosphate, have both vapor- and condensed-phase flame retardant effects. When phosphate containing flame retarding compound is used in noncharring polymer such as a polyolefin, it is consider that vapor-phase flame retardant action due to scavenging of H radicals by phosphrous radicals is the main fire retardant mechanism. Some of the prior arts are disclosed below.
Patent no. US 3891727 discloses phosphorus containing oligomers exhibiting excellent fire retardant properties having -OCCO- linkages between phosphorus atoms, said oligomers obtained from the condensation of ß-haloalkyl esters of pentavalent phosphorus acids.
Pat App. No. EP1944351 A1 discloses fire retardant composition comprising a combination of an oligomeric or monomeric phosphate ester and a silica sol-gel.
JP 08199092 describes polyester resins for fire retardant powder coatings consisting of aromatic dicarboxylic acid component and aliphatic glycol component copolymerized with phosphorus containing compound.
JP 11293004 describes flame retardant polyester film made from polyester resin containing an aromatic dicarboxylic acid and a phosphorus compound. These resins are not copolymerizable by UV radiation.
Pat. No. US 9,382,402 discloses a flame-retardant silicone resin composition of crosslinking structure in which inorganic oxide particles dispersed in a polysiloxane resin having a condensation-reactive group are crosslinked with the polysiloxane resin by chemical bonds and inorganic particles.

Most of the authors have reported use of flame retardants materials as reactive diluents in UV formulations. Whereas, Lokhande et al. developed phosphorus and nitrogen containing reactive flame retardant and used as a reactive diluent for epoxy acrylate oligomer. Flame retardant studies revealed that coatings exhibited limiting oxygen index (LOI) of 34 and V-0 rating on UL-94. Later, Chambhare et al. authors developed boron containing reactive flame retardant to be used as reactive diluent. Authors concluded that the best formulation exhibited LOI value in the range of 25-28.
A flame-retardant epoxy resin based on a reactive phosphorus-containing monomer of DODPP and its thermal and flame-retardant properties are reported by Li-Ping Gao et. Al. A flame-retardant epoxy resin was synthesized based on a novel reactive phosphorus-containing monomer, 4-[(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphorinan-4-yl)oxy]-phenol (DODPP), and said epoxy resin containing 2.5% phosphorus, can reach UL-94 V-0 rating and a limiting oxygen index (LOI) value of 30.2%.
However, available flame retardant compounds suffer from several drawbacks: - low compatibility with the polymer matrix, negative impact on the physical and mechanical properties of the coating, pigmented additives reduce the UV reactivity of the resin, additive migration leads to a blooming of the surface and loss of FR effect. Flame retardant clear coats are not achievable with most of FR additives, halogen based flame retardant systems show undesirable side effects (corrosive fumes, toxicity, environmental issues, etc.).
It is observed that, in addition to LOI, the flame retardant compound must possess important characteristics to maintain other relevant properties of the formulation to which they are added such as adhesion, hardness, viscosity, stain resistance and its crucial to have balance of all these properties in a coating formulation.
Hence the present invention overcomes the above drawbacks by providing novel flame retarding compound. The inventors of the present invention investigated a new reactive flame retardant oligomer compound comprising phosphorus and silicon in the same molecule. The major advantage of this invention is application of coatings on wood substrate, wherein along with flame retardancy, other properties of coatings such as adhesion, hardness, stain resistance are equally important and its crucial to have balance of all these properties in a coating formulation.

OBJECTIVES OF THE INVENTION:
• The main objective of the present invention is to provide a new flame retardant compound for cellulosic substrates.
• Another objective of present invention is to provide a new flame retardant oligomer compound comprising phosphorus and silicon in the same molecule.
• Another objective of the present invention is to provide a process of synthesis of new flame retardant oligomer compound comprising phosphorus and silicon in the same molecule.

SUMMARY OF INVENTION:
The present invention provides a novel compound that is used as flame retardant for substrate like wood. More preferably, the present invention provides a phosphorus and silicon containing monoacrylate compound and synthesis process thereof.
Accordingly, the present invention provides a compound of the formula (I) ;
FORMULA (I)
As per present invention the preferred compound is:
2-(((4-(2-(4-((dimethoxyphosphoryl)oxy)phenyl)propan-2-yl)phenoxy)dimethylsilyl) oxy)ethyl acrylate.
The present invention also relates to process of preparation of compound of formula (I), Wherein, the reaction steps comprising:
a) Reaction of phosphorus oxychloride with bisphenol-A,
b) Reaction of step a) product with dichlorodimethyl silane ,
c) End capping of resultant chloride intermediate obtained in step b) with hydroxyethyl acrylate.

BRIEF DESCRIPTION OF DRAWINGS:
For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which:
FIGURE 1: Represent IR spectra of compound synthesized in Example 1.
FIGURE 2: Represent 1H-NMR spectra of compound synthesized in Example 1.

DETAILED DESCRIPTION OF THE INVENTION:
The present invention provides a novel compound that is used as flame retardant for substrate like wood. More preferably, the present invention provides a phosphorus and silicon containing monoacrylate compound and synthesis process thereof.
Accordingly, the present invention provides a compound of the formula (I) ;
FORMULA (I)

As per present invention the preferred compound is:
2-(((4-(2-(4-((dimethoxyphosphoryl)oxy)phenyl)propan-2-yl)phenoxy)dimethylsilyl) oxy)ethyl acrylate.
The present invention also relates to process of preparation of compound of formula (I).
The compound of Formula (I) of the present invention may be prepared by procedure as illustrated in scheme, reaction or examples mentioned herein.

Scheme: I
Wherein, the reaction steps comprising:
a) Reaction of phosphorus oxychloride with bisphenol-A,
b) Reaction of step a) product with dichlorodimethyl silane ,
c) End capping of resultant chloride intermediate obtained in step b) with hydroxyethyl acrylate.

The product of each step in the scheme above can be recovered by one of the conventional method including extraction, evaporation, precipitation, filtration and crystallization.

According to second aspect of the present invention, it provides a composition comprising the compound of formula (I) with one or more additives.
The uses of the phosphorus and silicon containing monoacrylate (Formula I) obtained by the production method of the invention are not particularly restricted but, when it is applied as the solution, the following uses may be mentioned among others: coating of a substrate which comprises applying it to the substrate, curing and drying the coatings layer.
The phosphorus and silicon containing monoacrylate (Formula I) in the form of the solution can be used as a coating composition after incorporation of one or more known formulating ingredients selected from among base resin such as epoxy acrylate resin, photo initiator, cross linking agents, solvent, film-forming auxiliaries and the like and/or further compounding of another suitable polymeric compound.
The various photo initiators include, but not limiting to, 2-Hydroxy-2-methyl propiophenone, 1- Hydroxycyclohexyphenyl ketone, 2-Hydroxy-4'-(2- hydroxyethoxy)-2- methyl propiophenone, Methylbenzoyl formate, Benzophenone, 4-chloro Benzophenone.
The various cross linking agents include, but not limiting to, 1,6-Hexanediol diacrylate, Ethylene glycol diacrylate (EGDA), Tetraethylene glycol diacrylate (TetEGDA), Ethylene Glycol Dimethacrylate, 99%
Triethylene glycol dimethacrylate, 1,1,1- Trimethylolpropane triacrylate, Pentaerythritol triacrylate.

It is understood that these schemes, preparation and examples are not intended to be limiting to the scope of the invention in any way.

Examples:
All chemicals were purchased from their distributors/suppliers as reagents, and unless otherwise indicated, used without further refinement. All FTIR data were recorded on Bruker FT-IR ATR respectively.
The present invention is explained in greater detail below, but it should be noted that the present invention is not at all limited to these examples.

Example 1: Synthesis of 2-(((4-(2-(4-((dimethoxyphosphoryl)oxy)phenyl)propan-2-yl)phenoxy)dimethylsilyl) oxy)ethyl acrylate:
One mole of phosphorus oxychloride was reacted with one mole of bisphenol-A, Wherein, phosphorus oxychloride is added dropwise to bisphenol-A at temperature range between 5 to 7 ºC and gradually increased upto 60 ºC for a period of 6 h. Further addition of dichlorodimethyl silane in dropwise at temperature range between 5 to 7 ºC and gradually increased upto 60ºC for a period of 6 h. The resultant chloride intermediate was then end capped with hydroxyethyl acrylate at temperature range between 50 to 60 ºC for a period of 4 h.. The product synthesized was confirmed by chemical as well as spectroscopic analysis. Yield=78.7 %.

FT-IR spectra are depicted in figure no. 1.
FT-IR ?= 1744 cm-1 (C=O) , 1606 cm-1 (C=C ), 1254 cm-1: (P=O), 823, 1436, cm-1: (C=C), 930 cm-1 (P-O-C), 1175, 1074 cm-1 (Si-O-C);
NMR spectra are depicted in figure no. 2.
NMR= (-CH3) Methyl protons attached to silicon could be observed at 0.67-0.82 ppm. Further, peaks at 1.67-1.80 ppm could be attributed to (-CH3) methyl protons. Protons present in the benzene ring of bisphenol A could be observed at chemical shifts 6.85-7.18 ppm. Chemical shifts at 4.23-4.39 showed the protons present in the ethoxy moiety in acrylate.

Example 2 : Application of Compound synthesized in example 1:
For application of coating on wood substrate, a commercial epoxy acrylate was partially replaced (5%, 10%, 15%, 20%, 25%) by this product as shown in table 1 and the effect of concentration of this acrylate oligomer on mechanical, chemical and flame retardant properties of the coatings was investigated and results are depicted in table 2, 3 and 4 respectively. Flame retardancy studies showed that maximum limiting oxygen index of 30 was obtained when concentration of monoacrylate component was 25%. The novel compound as disclosed in present invention is compatible with epoxy acrylate and polyurethane acrylate resins.

Formula Epoxy acrylate (%) P-Si-BPA (%) Reactive Diluent (TMPTA) % Photoinitiator (%) Phosphorus content (%) Silicon content (%)
P-Si-1 82 - 15 3 - -
P-Si-2 77 5 15 3 0.31 0.28
P-Si-3 72 10 15 3 0.61 0.55
P-Si-4 67 15 15 3 0.92 0.83
P-Si-5 62 20 15 3 1.22 1.10
P-Si-6 57 25 15 3 1.53 1.38
Table 1

Characterization:
A. Mechanical properties

Properties P-Si-1 P-Si-2 P-Si-3 P-Si-4 P-Si-5 P-Si-6
Gel content (%) 98.74 98.57 96.32 97.41 97.76 98.06
Gloss 125-130 95-100 85-95 80-85 80-90 80-85
Adhesion 5B 5B 5B 5B 4B 4B
Pencil Hardness 5H 6H 6H 5H 5H 4H
Water absorption (%) 1.65 1.48 1.27 1.21 1.08 0.98
Table 2

B. Chemical Properties
Properties P-Si-1 P-Si-2 P-Si-3 P-Si-4 P-Si-5 P-Si-6
Solvent Resistance
MEK >200 >200 >200 >200 >200 >200
Xylene >200 >200 >200 >200 >200 >200
Stain resistance
Permanent Marker Excellent Excellent Excellent Excellent Excellent Excellent
Ink Excellent Excellent Excellent Excellent Excellent Excellent
Silicon Wax Excellent Excellent Excellent Excellent Excellent Excellent
Coconut oil Excellent Excellent Excellent Excellent Excellent Excellent
Nail-Polish Excellent Excellent Excellent Excellent Excellent Excellent
Table 3

C. Flame retardant properties
Limiting oxygen index (ASTM D 2863): Dimension of samples 50 mm x 80 mm x 2 mm.
UL-94 test (ASTM D 4804):Sample dimensions 50 mm x 100 mm x 2 mm.

Coatings Limiting Oxygen Index UL-94
P-Si-1 17 VTM-2
P-Si-2 21 VTM-2
P-Si-3 23 VTM-1
P-Si-4 25 VTM-1
P-Si-5 28 VTM-1
P-Si-6 30 VTM-0
Table 4
Dated this 05th day of February 2018
Applicant’s Agent

Poonam Dhake Kolhe
A Patent Agent [Agent No.:IN/PA 1067]
FOR In10gible Innovation LLP
,CLAIMS:CLAIMS
I Claim;
1. A novel UV-curing flame retardant compound of the formula (I):

FORMULA (I).

2. The compound as claimed in claim 1, wherein the compound is 2-(((4-(2-(4-((dimethoxyphosphoryl)oxy)phenyl)propan-2-yl)phenoxy)dimethylsilyl) oxy)ethyl acrylate.
3. A process for preparing of compound of the formula (I) as claimed in claims 1 and 2, comprising steps of:
Step a) Reacting phosphorus oxychloride with bisphenol-A,
Step b) Reacting of step a) product with dichlorodimethyl silane,
Step c) End capping of resultant chloride intermediate obtained in step b) with hydroxyethyl acrylate,
Step d) purification.
4. The process as claimed in claim 1, wherein in step a) phosphorus oxychloride is added dropwise to bisphenol-A at temperature range between 5 to 7 ºC and gradually increased upto 60 ºC for a period of 6 h.
5. The process as claimed in claim 1, wherein in step b) dichlorodimethyl silane is added dropwise at temperature range between 5 to 7 ºC and gradually increased upto 60 ºC for a period of 6 h.
6. The process as claimed in claim 1, wherein step c) end capping is conducted at temperature range between 50 to 60 ºC for a period of 4 h.

Dated this 05th day of February 2018

Applicant’s Agent

Poonam Dhake Kolhe
A Patent Agent [Agent No.:IN/PA 1067]
FOR In10gible Innovation LLP