DESC:FIELD OF THE INVENTION

The present invention relates to selective crosslinked core-shell polymeric microcapsules preferably suitable as impact modifiers and formulations thereof comprising a low Tg vinyl and acrylic monomer based core crosslinked with crosslinkers including multifunctional urethane acrylate crosslinkers, and, vinyl and acrylic monomer based shell with relatively higher Tg, which polymeric impact modifier and formulations thereof when provided in select low dosage levels in coatings/ powder coatings enhances the direct and reverse impact performance in powder coatings without hampering the durability and/or storage stability of said powder coatings.

BACKGROUND ART
Polymers used for powder coatings are generally designed as high Tg (50 to 60 ?C) brittle solids to ensure optimum storage stability. Crosslinked systems are applied to the substrates of architectural, agricultural, automotive, furniture and electrical components to enhance durability, décor and protection. The coatings are subject to various mechanical impact and stresses during the service life.
The powder polymer glass transition temperature and crosslinking density can be optimized to get the desired direct/front impact performance. However, getting the desired reverse impact performance involves addition of a high amount of low glass transition temperature rubbery additive component (impact modifier).
Addition of high amounts of impact modifier will lead to increased costs and can hamper film durability.
In prior art rubbery materials such as hompolymers or copolymers of butadiene and silicone rubber are utilized in the core to provide toughness. Crosslinkers such as multifunctional acrylates are utilized in the preparation of the core.

On this reference is invited to WO2006132796A2 teaching core/shell impact modifier having as a core a copolymer or terpolymer having from 25 to 75 percent by weight of 2-ethylhexyl acrylate (2-EHA) monomer units with from 25 and 75 percent by weight of n-octyl acrylate (n-OA) monomer units. This core-shell impact modifier is used in performance polymers to improve low temperature impact performance.

CA2220411A1 is directed to a multistage core-shell particle consisting of a core, a first shell and optionally a second shell, substantially free from vinylically unsaturated compounds having at least two equally reactive double bonds, wherein: (i) the core contains a first (meth)acrylic polymer, (ii) the first shell contains a low Tg polymer comprising 0 to 25 % by weight of a styrenic monomer and 75 to 100 % by weight of a (meth)acrylic monomer, the (meth)acrylic monomer capable of forming a homopolymer having a glass transition temperature (Tg) in the range from -75 to -5 °C, and which first shell represents more than 65 % by volume of the combined volume of the core and first shell; (iii) the second shell, when present, contains a second (meth)acrylic polymer which may be the same or different from the first (meth)acrylic polymer, and (iv) the core and first shell together contain from 0.5 to 1.0 % by weight of a graft-crosslinker.

US2005119393A1 revolves around acrylic impact modifier having a core-shell structure that provides an acrylic impact modifier composition comprising (a) a rubber core containing an alkyl acrylate polymer comprising at least two layers having different cross-linking densities, and (b) a shell containing an alkyl methacrylate polymer; to a process for the preparation of the acrylic impact modifier; and to a poly(vinyl chloride) composition comprising it.

US2012164364A1 is based on acrylic polymer, modified with one or more hard core core/shell impact modifier, which is blended with one or more low melt viscosity polymer. The alloy formed by the blend has good impact properties, good melt processability, high modulus, high surface hardness, and excellent resistance to chemical attack.

WO2022204734A1 is directed to a photocurable composition including: about 45 to about 55 weight % of aromatic urethane di(meth)acrylate monomer having two urethane linkages and two acryloyloxy groups; about 20 to about 30 weight % of monofunctional (meth)acrylate monomer having acryloyl groups; about 8 to about 18 weight % of bifunctional (meth)acrylate monomer having ethoxy groups; about 5 to about 15 weight % of impact modifier having core-shell structure; about 0.2 to about 5.0 weight % of at least one kind of ultraviolet/visible (UV/Vis) light-photo-polymerization initiator; and at least one colorant.
There is thus a requirement of alternative impact modifier compositions adaptable to coatings/ powder coatings and effective at reduced dosage levels to impart desired reverse impact performance, without hampering the film durability or negatively affecting storage issues of such coatings.

OBJECTS OF THE INVENTION
The primary object of the present invention is to provide for alternative crosslinked core-shell polymeric microcapsules as polymeric impact modifiers and formulations thereof for end use and application in coatings/power coating that would show its efficacy at reduced dosage levels to impart desired reverse impact performance, without hampering the film durability of said coatings/ powder coatings.

It is another object of the present invention to provide for polymeric impact modifier formulations for coatings/powder coating which can provide desired direct and reverse impact performance as per ASTM D 2794 that evaluates the resistance of organic coatings to the effects of rapid deformation (impact).

It is yet another object of the present invention to provide for an impact modifier that would selectively utilize the toughness and durability of acrylic and polyurethane systems to enable said impact resistance in powder coatings without hampering the durability and/or storage stability of said powder coatings.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided impact modifier formulations comprising crosslinked core-shell polymeric microcapsules including part (A) low Tg -50 ?C-0?C based polymer core of vinyl and acrylic monomers crosslinked with monomers selected from multifunctional acrylic monomers, isocyanate monomers, and, part (B) relatively higher Tg 90 ?C-110?C based polymer shell of vinyl and acrylic monomers.

Preferably in said impact modifier formulations said crosslinked core-shell polymeric microcapsules are impact modifier microcapsules obtained of polymerization in water base by emulsion or suspension polymerization that is further spray dried or freeze dried or filtered to enable powder polymeric microcapsules as impact modifier resin having particle size in the range of 50 nm to 1 mm.

More preferably in said impact modifier formulations said crosslinked core-shell polymeric microcapsules as guided by Tg differentiating polymers include
50 to 95 wt.% of said part (A) low Tg (-50 ?C-0?C), C1-C8 vinyl and acrylic monomers including esters of acrylic or methacrylic acid based polymer core of monomers including Butyl Acrylate monomer, said core being cross-linked by 0.1 to 20 wt.% of monomers selected from said multifunctional acrylic monomers, isocyanate monomers and includes urethane acrylates, diacrylates, triacrylates, vinyl or allyl as crosslinkers, and,
5 to 50 wt.% of said part (B) higher Tg (90 ?C-110?C) vinyl and acrylic monomers based polymer shell including Polyvinyl alcohol, Methyl methacrylate monomers.
According to another preferred aspect of the present invention there is provided said impact modifier formulations wherein said urethane acrylate as a crosslinker is a reaction product of a diol or polyol with aliphatic, aromatic, or cycloaliphatic diisocyanate or polyisocyanate and hydroxy functional acrylate or methacrylate monomers, said polyols include polyethylene Glycol, polyTHF, polypropylene glycol, polytetramethylene glycol, polycaprolactone glycol and combinations thereof, and said diisocyantes include isophorone diisocyante, hexamethylene diisocyante, toluene diisocyante, methylenediphenyl diisocyanate and combinations thereof.

Preferably in said impact modifier formulations wherein said

microcapsules with EDGMA (ethylene glycol dimethacrylate) crosslinker at Core/Shell Ratio of 70:30 has core Tg of -45.4 °C and shell Tg of 90.8 °C;
microcapsules with EDGMA crosslinker at Core/Shell Ratio of 80:20 has core Tg of -44.1 °C and shell Tg of 94.1 °C;
microcapsules with PU-HEMA (urethane acrylate) crosslinker at Core/Shell Ratio of 70:30 has core Tg of -50.3°C and shell Tg of 103.3 °C;
microcapsules with PU-HEMA crosslinker at Core/Shell Ratio of 80:20 has core Tg of -50.6°C and shell Tg of 100.5 °C;
microcapsules with HDDA (Hexanediol diacrylate) crosslinker at Core/Shell Ratio of 70:30 has core Tg of -47.7 °C and shell Tg of 99.9 °C;
microcapsules with HDDA crosslinker at Core/Shell Ratio of 80:20 has core Tg of -47.2 °C and shell Tg of 94.9 °C.

According to another preferred aspect of the present invention there is provided said impact modifier formulations wherein said impact modifiers when involved in select low dosage levels of 0.4-0.9% in powder coatings could improve impact performance based on its flexibility greater than 100 cm and even greater than 160 cm of direct and reverse impact as per ASTM D2794 without hampering the durability and/or storage stability of said powder coatings, said powder coatings comprise polyester/epoxy, polyester/TGIC, polyester/primid, polyester/isocyanate and combinations thereof and also include polyacrylates, polyamides, polycarbonates, and fluoropolymers and combinations thereof.

According to another aspect of the present invention there is provided a method of manufacturing impact modifier formulations comprising crosslinked core-shell polymeric microcapsules suitable as impact modifier

comprising the steps of emulsion or suspension polymerization in presence of initiators said part A monomers in aqueous base followed by crosslinking and adding said Part B monomers and further polymerizing to obtain therefrom crosslinked core-shell polymer impact modifier formulation.

Preferably in said method of manufacturing impact modifier formulation said step of suspension polymerization in presence of said initiators to achieve said part A monomer based polymer core and crosslinking followed by adding said Part B monomers and further polymerizing include the following stages of reaction in inert atmosphere:

providing (i) a continuous phase of demineralized water, and monomers including polyvinyl alcohol under mild agitation ˜200 rpm till it achieves temperature 80°C;

providing (ii) a discontinuous phase of monomers including butyl acrylate monomers pre-mixed with initiator Azobisisobutyronitrile (AIBN);

adding said discontinuous phase of monomers (ii) into said continuous phase (i) above for a time period of 20 to 30 mins by maintaining vigorous agitation ˜350 rpm at a constant temperature of 80°C, followed by addition of said cross linkers together with AIBN and constantly stirring for 60 min, and thereafter adding said Part B monomers including methyl methacrylate with AIBN over a period of 15-20 mins, post which the reaction was maintained under vigorous agitation ˜350 rpm at a constant temperature of 80°C to obtain core shell microcapsules as an emulsion/suspension that was filtered, washed with water, followed by ˜8 hours of drying in oven at 60°C.

More preferably said method of manufacturing impact modifier formulation is provided wherein said Part B vinyl/acrylic resin shell is made in same reactor preferentially after preparation of Part A acrylic resin based crosslinked polymer core, and wherein said total polymerization process is carried out preferably for ˜5 h under a nitrogen atmosphere.

According to another preferred aspect of the method of manufacturing impact modifier formulation said crosslinker including urethane acrylate (PU-HEMA) crosslinker for addition in said process is pre-prepared including the following steps
providing Polypropylene glycol PPG-2000 (1 mol) with mild agitation followed by adding under stirring, IPDI (Isophorone diisocyanate, 2 mol) with DBTDL (Dibutyl tin dilaurate) at room temperature and raising the temperature gradually to 50°C to initiate the polymerization reaction for ˜1 hour and NCO content was observed, followed by increasing the reaction temperature after said ˜1 hour that is increased to 70 °C and polymerisation reaction was continued until ˜ 3 hours, further followed by addition of hydroxyethyl methacrylate (2 mol) and polymerization continued for another ˜1 hour at 70°C and the reaction cooled down to 40 °C and obtaining therefrom said urethane acrylate (PU-HEMA) crosslinker after a total polymerization time of ˜ 5 hours.

DETAILED DESCRIPTION OF THE INVENTION

As described hereinbefore, the present invention provides for selective crosslinked core-shell polymeric microcapsules suitable as impact modifiers and formulations thereof comprising a low Tg vinyl and acrylic monomer based core crosslinked with multifunctional urethane acrylate crosslinkers, and, vinyl and acrylic monomer based shell with relatively higher Tg, which polymer impact modifiers and formulations thereof when provided in select low dosage levels in coatings/ powder coatings enhances the direct and reverse impact performance in powder coatings without hampering the durability and/or storage stability of said powder coatings.

A selective crosslinked core-shell polymeric microcapsules crosslinked with crosslinkers including polyurethane crosslinkers and adapted as impact modifier preferably as a powder form of formulation is provided, which when applied in select low dosage levels in coatings/ powder coatings enhances the direct and reverse impact performance in powder coatings without hampering the durability and/or storage stability of said powder coatings.

The solution prescribed by core-shell polymer preferably in powder form of the present invention in powder coatings is based on selectively utilizing the toughness of polyurethanes via select polyurethane crosslinkers, which have not been reported in the prior state of the art as described above.

EXAMPLES:
The process to reach to said selective crosslinked core-shell polymer preferably in powder form is also provided including the steps of

(i) preparing Part A Acrylic resin via free radical polymerization (50% to 95% by weight) with low glass transition temperature (less than 0 deg C) by involving vinyl and acrylic monomers crosslinked by a multifunctional urethane acrylate crosslinker, wherein said part A acrylic resin is crosslinked by a urethane acrylic crosslinker or a urethane acrylate crosslinker including other vinyl, allyl and acrylic crosslinkers such as diacrylates and triacrylates;

(ii) Preparing Part B Acrylic resin via free radical polymerization (5 to 50% by weight) with high glass transition temperature (more than 50 deg C) by involving vinyl and acrylic monomers;

said Part B acrylic resin made in the same reactor preferentially after preparation of Part A acrylic resin, followed by drying of the polymer to obtain powder resin.

Said urethane acrylic crosslinker is a reaction product of a diol or polyol with aliphatic, aromatic, or cycloaliphatic diisocyanate or polyisocyanate and hydroxy functional acrylate or methacrylate monomers. The polyols include polyethylene Glycol, polyTHF, polypropylene glycol, polytetramethylene glycol, polycaprolactone glycol and their mixtures. The diisocyantes include isophorone diisocyante, hexamethylene diisocyante, toluene diisocyante, methylenediphenyl diisocyanate and their mixtures.

The percentage of the urethane functional crosslinker in the core of Part A Acrylic resin is 0.1 to 20% by weight.

The polymerization is done in water using emulsion or suspension polymerization, and the powder polymer impact modifier resin can be obtained by spray drying or freeze drying or filtration. Particle size of the impact modifier can be from 50 nm to 1 mm.

While the existing solutions to improve flexibility and impact performance of powder coatings lies in involving addition of impact modifiers with multiple shells, core using specialty long chain acrylic monomers such as stearyl acrylate, preparation of block copolymers by controlled radical polymerization, involving rubbery materials such as butadiene which involves polymerization under high-pressure which requires specialty equipment,
in which backdrop the present invention significantly finds that by involving polymerization of C1-C8 acrylic monomers (esters of acrylic or methacrylic acid), multifunctional urethane acrylate crosslinkers either alone or in combination with multifunctional acrylate, vinyl or allyl crosslinkers forming the core of the core-shell polymer guided by Tg differentiating polymer forming the shell, alternative polymer impact modifiers and composition thereof could be achieved, which when involved in select low dosage levels in powder coatings could improve impact performance without hampering the durability and/or storage stability of said powder coatings.

Polymeric impact modifier for coatings
Procedure for preparing the impact modifier:
The encapsulation was done using suspension polymerization technique. The polymerization reaction was performed in a four-neck glass reactor, stirring with digital control, temperature sensor, condenser for reflux and nitrogen gas tube. The synthesis process involved two phases: (i) a continuous phase containing demineralised water, polyvinyl alcohol and (ii) a discontinuous phase containing butyl acrylate and methyl methacrylate. The continuous phase was transferred to the glass reactor with mild agitation (200 rpm) till it achieves temperature of 80°C. The initiator was premixed with monomers. The butyl acrylate and crosslinker with AIBN was added to the continuous phase over 20 to 30 min. The reaction was maintained under vigorous agitation (350 rpm) at a constant temperature of 80°C. After constant stirring of 60 min, methyl methacrylate with AIBN was added to the reactor over 15 to 20 min. The reaction was maintained under vigorous agitation (350 rpm) at a constant temperature of 80°C. The polymerization process was carried out for 5 h under a nitrogen atmosphere. The obtained core shell microcapsules were filtered & washed with water, followed by 8 hours of drying in oven at 60°C.
Table 1: Experiments for preparation of core-shell impact modifier microparticles
Ingredients Exp-1
wt. (%) Exp-2
wt. (%) Exp-3
wt. (%) Exp-4
wt. (%) Exp-5
wt. (%) Exp-6
wt. (%)
Core shell ratio 70:30 80:20 70:30 80:20 70:30 80:20
Water 79.3 81.8 79.3 81.8 79.3 81.8
Polyvinyl alcohol 4.5 4.5 4.5 4.5 4.5 4.5
Butyl Acrylate 10 10 10 10 10 10
Azobisisobutyronitrile (AIBN) 0.5 0.5 0.5 0.5 0.5 0.5
EGDMA 0.2 0.2 - - - -
PU-HEMA - - 0.2 0.2 - -
HDDA - - - - 0.2 0.2
Methyl methacrylate 5 2.5 5 2.5 5 2.5
AIBN 0.5 0.5 0.5 0.5 0.5 0.5

Crosslinkers: EGDMA: ethylene glycol dimethacrylate, HDDA: Hexanediol diacrylate, PU-HEMA (urethane acrylate)
Synthesis of urethane acrylate (PU-HEMA) crosslinker:
The polymerization reaction was performed in a four-neck glass reactor, stirring with digital control, temperature sensor, condenser for reflux and nitrogen gas tube. PPG-2000 (1 mol) was added into the reactor with mild agitation. Under stirring stage, IPDI (2 mol) with DBTDL was added to reactor at room temperature. Gradually, the temperature was raised to 50°C to initiate the polymerization reaction for one hour and NCO content was checked. After an hour, the reaction temperature increased to 70 °C and polymerisation reaction was continued three hours to achieve desired NCO content of 3.43%. Hydroxyethyl methacrylate (2 mol) was added to the reactor and polymerisation was continued for another one hour at 70°C. After five hours of polymerization, final NCO content was checked to be <0.05 %. Reaction was cooled down to 40 °C and material was transferred to separate container.
Table 2: Formulation to synthesis PU-HEMA crosslinker:

Ingredients Weight %
Polypropylene glycol 2000 (PPG 2000) 73.87
IPDI (Isophorone diisocyanate) 16.52
Dibutyl tin dilaurate (DBTDL) 0.03
Hydroxyethyl methacrylate (HEMA) 9.59

Table 3: Glass transition temperature of microcapsules
Sr. No. Material Core/Shell Ratio Tg of Core Tg of Shell
1. Microcapsules with EDGMA crosslinker 70:30 -45.4 °C 90.8 °C
2. Microcapsules with EDGMA crosslinker 80:20 -44.1 °C 94.1 °C
3. Microcapsules with PU-HEMA crosslinker 70:30 -50.3 °C 103.3 °C
4. Microcapsules with PU-HEMA crosslinker 80:20 -50.6 °C 100.5 °C
5. Microcapsules with HDDA crosslinker 70:30 -47.7 °C 99.9 °C
6. Microcapsules with HDDA crosslinker 80:20 -47.2 °C 94.9 °C

Table 4: Impact resistance with & without 0.4% of impact modifier microcapsules in coating. The coating is a epoxy cured polyester powder coating
S.N. Coating type Trial Details DFT (µm) Impact Direct (height of column in cm) Impact Reverse
(height of column in cm)
1. Coating 1 Without impact modifier 60-70 100 Pass 50 Fail
2. Coating 2 0.4% of 70:30 with EGDMA 60-70 100 Pass 60 Pass
3. Coating 3 0.4% of 80:20 with EGDMA crosslinker 60-70 150 Pass 100 Pass
4. Coating 4 0.4% of 70:30 with PU-HEMA crosslinker 60-70 150 Pass 100 Pass
5. Coating 5 0.4% of 80:20 with PU-HEMA crosslinker 60-70 160 Pass 100 Pass
6. Coating 6 0.4% of 70:30 with HDDA crosslinker 60-70 100 Pass 50 Pass
7. Coating 7 0.4% of 80:20 with HDDA crosslinker 60-70 100 Pass 60 Pass

Table 5: Impact resistance with & without 0.8% of impact modifier microcapsules in coating. The coating is a epoxy-polyester powder coating
S.N. Coating type Trial Details DFT (µm) Impact Direct (height of column in cm) Impact Reverse
(height of column in cm)
1. Coating 1 Without impact modifier 60-70 100 Pass 50 Fail
2. Coating 8 0.8% of 70:30 with EGDMA 60-70 160 Pass 100 Pass
3. Coating 9 0.8% of 80:20 with EGDMA crosslinker 60-70 160 Pass 100 Pass
4. Coating 10 0.8% of 70:30 with PU-HEMA crosslinker 60-70 160 Pass 130 Pass
5. Coating 11 0.8% of 80:20 with PU-HEMA crosslinker 60-70 160 Pass 130 Pass
6. Coating 12 0.8% of 70:30 with HDDA crosslinker 60-70 100 Pass 80 Pass
7. Coating 13 0.8% of 80:20 with HDDA crosslinker 60-70 100 Pass 80 Pass

Key added advantages: The polymer impact modifiers and composition thereof of the present invention are prepared under ambient pressure via conventional techniques such as emulsion or suspension polymerization, and works improve flexibility and direct and reverse impact performance for all the variants of the reactive ingredients mentioned above enabling crosslinked core-shell polymeric microcapsules.

According to an aspect of the present invention there is provided a core-shell acrylic polymer composition comprising:

50% to 95% by weight Part A acrylic resin at its core based on vinyl and acrylic monomers with low glass transition temperature (less than 0 deg C) crosslinked by a multifunctional urethane acrylate crosslinker, said multifunctional urethane acrylate crosslinker including urethane acrylic crosslinker or urethane acrylate crosslinker including diacrylates and triacrylates, other vinyl or allylic crosslinkers.

5 to 50% by weight Part B acrylic resin based on vinyl and acrylic monomers with high glass transition temperature (more than 50 deg C).

According to another aspect of the present invention there is provided a method of preparation of said core-shell acrylic polymer composition comprising the step of

preparing Part A acrylic resin prepared via free radical polymerization (50% to 95% by weight) with low glass transition temperature (less than 0 deg C) by involving vinyl and acrylic monomers and crosslinking by a multifunctional urethane acrylate crosslinker, said crosslinkers being urethane acrylic crosslinker or a urethane acrylate crosslinker including diacrylates and triacrylates, other vinyl or allylic crosslinkers.

preparing Part B Acrylic resin prepared via free radical polymerization (5 to 50% by weight) with high glass transition temperature (more than 50 deg C) by involving vinyl and acrylic monomers.

According to another aspect of the present invention there is provided said process wherein Part B Acrylic resin is made in the same reactor preferentially after preparation of Part A acrylic resin followed by drying of the polymer to obtain powder resin.

According to yet another preferred aspect of the process there is provided said urethane acrylic crosslinker that is a reaction product of a diol or polyol with aliphatic, aromatic, or cycloaliphatic diisocyanate or polyisocyanate and hydroxy functional acrylate or methacrylate monomers.

According to another preferred aspect of the composition and process the percentage of the urethane functional crosslinker in the core is 0.1 to 20%.

According to another preferred aspect of the process of the present invention there is provided a process where polymerization is done in water using emulsion or suspension polymerization.

Preferably in said process the powder resin is obtained by spray drying or freeze drying or filtration to attain particle size of the impact modifier polymer of from 50 nm to 1 mm.

Preferably the above core-shell acrylic polymer composition of the present invention can be incorporated into powder coating composition to improve flexibility and direct and reverse impact performance.

According to another preferred aspect of the present invention there is provided said composition that comprises initiators, surfactants (ionic, non-ionic), colloidal stabilizers, defoamers, biocides, mineral fillers, processing aids and colorants.

Also the coating composition in powder form formulated with above core-shell acrylic polymer impact modifier can impart greater than 100 cm and even greater than 160 cm direct and reverse impact performance as per ASTM D2794.

The powder coating composition of the present invention includes polymers such as polyester/epoxy, polyester/TGIC, polyester/primid, polyester/isocyanate combinations. Other polymers used include polyacrylates, polyamides, polycarbonates, and fluoropolymers.

It is thus possible for the present advancement to provide for said selective crosslinked core-shell polymer impact modifiers and compositions thereof which when provided in select low dosage levels in coatings/ powder coatings enhances the direct and reverse impact performance in powder coatings without hampering the durability and/or storage stability of said powder coatings.
,CLAIMS:We Claim:

1. Impact modifier formulations comprising crosslinked core-shell polymeric microcapsules including part (A) low Tg -50 ?C-0?C based polymer core of vinyl and acrylic monomers crosslinked with monomers selected from multifunctional acrylic monomers, isocyanate monomers, and, part (B) relatively higher Tg 90 ?C-110?C based polymer shell of vinyl and acrylic monomers.

2. The impact modifier formulations as claimed in claim 1 wherein said crosslinked core-shell polymeric microcapsules are impact modifier microcapsules obtained of polymerization in water base by emulsion or suspension polymerization that is further spray dried or freeze dried or filtered to enable powder polymeric microcapsules as impact modifier resin having particle size in the range of 50 nm to 1 mm.

3. The impact modifier formulations as claimed in claims 1 or 2 wherein said crosslinked core-shell polymeric microcapsules as guided by Tg differentiating polymers include
50 to 95 wt.% of said part (A) low Tg (-50 ?C-0?C), C1-C8 vinyl and acrylic monomers including esters of acrylic or methacrylic acid based polymer core of monomers including Butyl Acrylate monomer, said core being cross-linked by 0.1 to 20 wt.% of monomers selected from said multifunctional acrylic monomers, isocyanate monomers and includes urethane acrylates, diacrylates, triacrylates, vinyl or allyl as crosslinkers, and,
5 to 50 wt.% of said part (B) higher Tg (90 ?C-110?C) vinyl and acrylic monomers based polymer shell including Polyvinyl alcohol, Methyl methacrylate monomers.
4. The impact modifier formulations as claimed in claims 1-3 wherein said urethane acrylate as a crosslinker is a reaction product of a diol or polyol with aliphatic, aromatic, or cycloaliphatic diisocyanate or polyisocyanate and hydroxy functional acrylate or methacrylate monomers, said polyols include polyethylene Glycol, polyTHF, polypropylene glycol, polytetramethylene glycol, polycaprolactone glycol and combinations thereof, and said diisocyantes include isophorone diisocyante, hexamethylene diisocyante, toluene diisocyante, methylenediphenyl diisocyanate and combinations thereof.

5. The impact modifier formulations as claimed in claims 1-4 wherein said

microcapsules with EDGMA (ethylene glycol dimethacrylate) crosslinker at Core/Shell Ratio of 70:30 has core Tg of -45.4 °C and shell Tg of 90.8 °C;
microcapsules with EDGMA crosslinker at Core/Shell Ratio of 80:20 has core Tg of -44.1 °C and shell Tg of 94.1 °C;
microcapsules with PU-HEMA (urethane acrylate) crosslinker at Core/Shell Ratio of 70:30 has core Tg of -50.3°C and shell Tg of 103.3 °C;
microcapsules with PU-HEMA crosslinker at Core/Shell Ratio of 80:20 has core Tg of -50.6°C and shell Tg of 100.5 °C;
microcapsules with HDDA (Hexanediol diacrylate) crosslinker at Core/Shell Ratio of 70:30 has core Tg of -47.7 °C and shell Tg of 99.9 °C;
microcapsules with HDDA crosslinker at Core/Shell Ratio of 80:20 has core Tg of -47.2 °C and shell Tg of 94.9 °C.

6. The impact modifier formulations as claimed in claims 1-5 wherein said impact modifiers when involved in select low dosage levels of 0.4-0.9% in powder coatings could improve impact performance based on its flexibility greater than 100 cm and even greater than 160 cm of direct and reverse impact as per ASTM D2794 without hampering the durability and/or storage stability of said powder coatings, said powder coatings comprise polyester/epoxy, polyester/TGIC, polyester/primid, polyester/isocyanate and combinations thereof and also include polyacrylates, polyamides, polycarbonates, and fluoropolymers and combinations thereof.

7. A method of manufacturing impact modifier formulations comprising crosslinked core-shell polymeric microcapsules suitable as impact modifier as claimed in claims 1-6
comprising the steps of emulsion or suspension polymerization in presence of initiators said part A monomers in aqueous base followed by crosslinking and adding said Part B monomers and further polymerizing to obtain therefrom crosslinked core-shell polymer impact modifier formulation.

8. The method of manufacturing impact modifier formulation as claimed in claim 7 wherein said step of suspension polymerization in presence of said initiators to achieve said part A monomer based polymer core and crosslinking followed by adding said Part B monomers and further polymerizing include the following stages of reaction in inert atmosphere:

providing (i) a continuous phase of demineralized water, and monomers including polyvinyl alcohol under mild agitation ˜200 rpm till it achieves temperature 80°C;

providing (ii) a discontinuous phase of monomers including butyl acrylate monomers pre-mixed with initiator Azobisisobutyronitrile (AIBN);

adding said discontinuous phase of monomers (ii) into said continuous phase (i) above for a time period of 20 to 30 mins by maintaining vigorous agitation ˜350 rpm at a constant temperature of 80°C, followed by addition of said cross linkers together with AIBN and constantly stirring for 60 min, and thereafter adding said Part B monomers including methyl methacrylate with AIBN over a period of 15-20 mins, post which the reaction was maintained under vigorous agitation ˜350 rpm at a constant temperature of 80°C to obtain core shell microcapsules as an emulsion/suspension that was filtered, washed with water, followed by ˜8 hours of drying in oven at 60°C.

9. The method of manufacturing impact modifier formulation as claimed in claims 7 or 8 wherein said Part B vinyl/acrylic resin shell is made in same reactor preferentially after preparation of Part A acrylic resin based crosslinked polymer core, and wherein said total polymerization process is carried out preferably for ˜5 h under a nitrogen atmosphere.

10. The method of manufacturing impact modifier formulation as claimed in claims 7-9 wherein said crosslinker including urethane acrylate (PU-HEMA) crosslinker for addition in said process is pre-prepared including the following steps
providing Polypropylene glycol PPG-2000 (1 mol) with mild agitation followed by adding under stirring, IPDI (Isophorone diisocyanate, 2 mol) with DBTDL (Dibutyl tin dilaurate) at room temperature and raising the temperature gradually to 50°C to initiate the polymerization reaction for ˜1 hour and NCO content was observed, followed by increasing the reaction temperature after said ˜1 hour that is increased to 70 °C and polymerisation reaction was continued until ˜ 3 hours, further followed by addition of hydroxyethyl methacrylate (2 mol) and polymerization continued for another ˜1 hour at 70°C and the reaction cooled down to 40 °C and obtaining therefrom said urethane acrylate (PU-HEMA) crosslinker after a total polymerization time of ˜ 5 hours.

Dated this the 6th day of March, 2024 Anjan Sen
(Applicants Agent)
IN/PA-199