Claims:We Claim:

1. TiO2-Polymer composites comprising polymer encapsulated stable particulate dispersion of TiO2 including TiO2 particles surface adsorbed with anionic dispersion agent providing a micellar like structure with matrix type encapsulation of said stable particulate dispersion of TiO2 particles in said composite.
2. TiO2-Polymer composites as claimed in claim 1 wherein said stable particulate dispersion of TiO2 comprise stable particulate dispersion of TiO2 including preferably adsorbed N-methyl-N-oleyl taurate (Hostapon TPHC).
3. TiO2-Polymer composites as claimed in anyone of claims 1 or 2 as aqueous dispersion suitable for use in paint formulations preferably including a broad distribution of particles at about 1500 nm corresponding to matrix type polymer or copolymer encapsulated TiO2 particles.
3. TiO2-Polymer composites as claimed in anyone of claims 1 or 2 comprising ~ 52 % non-volatile materials (NVM) having Tg in the range of 2 °C to about 16 °C and involving acrylic polymer or styrene-acrylic copolymer that is stable upon storage at 55 °C for 30 days with respect to settling, viscosity.
4. TiO2-Polymer composites as claimed in anyone of claims 1-3 comprising a polymer film with evenly distributed TiO2 particles preferably of Rutile grade showing excellent hiding enabling reduction of the levels of TiO2 by 10 % - 20 % in paint formulations.
5. A process for the preparation of TiO2-Polymer composites as claimed in anyone of claims 1-4 comprising providing TiO2-Polymer composites having matrix like encapsulated stably dispersed TiO2 particles in a polymer or a copolymer and having N-methyl-N-oleyl taurate (Hostapon TPHC) adsorbed onto the surfaces of said TiO2 particles favoring a miceller like structure for matrix like encapsulation of stably dispersed TiO2 particles in said composite in single stage emulsion polymerization process.
6. A process for the preparation of TiO2-Polymer composites as claimed in claim 5 comprising:
i) providing a stable aqueous dispersion of TiO2 by adsorbing an anionic dispersion agent onto the surface of said TiO2 particles;
ii) encapsulating said stable aqueous dispersion of TiO2 in polymer by carrying out single stage polymerization reaction in a reactor involving said stable aqueous dispersion of TiO2 as a seed in said polymerization reactor to thereby produce said TiO2-Polymer composites.
7. A process for the preparation of TiO2-Polymer composites as claimed in anyone of claims 5 or 6 as dispersion in the following steps comprising
(a) providing a stable aqueous dispersion of TiO2 by adding a selective amount of TiO2 to selective anionic dispersing agent of N-methyl-N-oleyl taurate (Hostapon TPHC) that gets adsorbed on the TiO2 surface;
(b) providing said stable aqueous dispersion of TiO2 in selective amounts as seed together with anionic surfactant, initiator and buffer solution;
(c) feeding a pre-emulsion comprising an aqueous dispersion of monomers or combinations thereof, selective amounts of anionic and non-ionic surfactants, for a period of about 4 hrs into the seed solution of step (b) having selective levels of anionic surfactant, thermal initiator and buffer until completion of polymerization and finally neutralizing to yield said TiO2-Polymer composites therefrom having matrix like encapsulated stably dispersed TiO2 particles in polymer or copolymer.
8. A process for the preparation of TiO2-Polymer composites as claimed in claim 7 wherein said step (c) optionally comprises
(I) feeding said pre-emulsion into said seed solution for about 1 hr until 20 % addition of the pre-emulsion is completed;
(II) adding remaining pre-emulsion together with cross-linkers including VTMO and polymerizing for about another 3 hrs until completion of polymerization and finally neutralizing to yield said TiO2-Polymer composites.
9. A process as claimed in anyone of claims 5-8 wherein said polymerization reaction was carried out in the temperature range of 72-82 °C to favour encapsulation of the TiO2 particles by acrylic polymer or styrene-acrylic copolymer.
10. A process as claimed in anyone of claims 5-9 wherein said providing stable aqueous dispersion of TiO2 involves providing 20 to 45 wt. % of TiO2 and 2 to 4.5 wt. % of anionic dispersing agent N-methyl-N-oleyl taurate (Hostapon TPHC) which is 7.5 wt. % to 10 wt. % Hostapon TPHC on TiO2, and de-ionized water to adjust the volume to 100 % and grinding at 500 rpm for 30 minutes and obtaining stable aqueous dispersion of TiO2 therefrom.
11. A process as claimed in anyone of claims 5-10 wherein the seed quantity is in the range of 1 % to 3 % active TiO2 dispersion and preferably involves ~ 0.3 % of non-ionic surfactant in combination with 3 % active TiO2 (9.99 % of 30 % TiO2 dispersion) dispersion.
12. A process as claimed in anyone of claims 5-11 wherein said monomer or combination of monomers include methacrylate monomer, a methyl methacrylate monomer, styrene monomer.
13. A process as claimed in anyone of claims 5-12 wherein said anionic surfactant in the pre-emulsion includes anionic surfactants Dowfax 2A1, Disponil FES32, and wherein said initiator include thermal initiators such as potassium persulphate.
14. A paint formulation comprising TiO2-Polymer composites comprising polymer encapsulated stable particulate dispersion of TiO2 including TiO2 particles surface adsorbed with anionic dispersion agent providing a micellar like structure with matrix type encapsulation of said stable particulate dispersion of TiO2 particles in said composite.
15. A paint formulation as claimed in claim 14 having pigment volume concentration in the range of 40-80 % adapted for reduction of TiO2 in said formulation in the range of 16-22 % on TiO2.

Dated this the 2nd day of May, 2016 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)
, Description:Field of Invention

The present invention particularly provides for TiO2-Polymer composites comprising polymer encapsulated stable particulate dispersion of TiO2 and more particularly, provides for a process of preparation of the same. Said polymer encapsulated stable particulate dispersion of TiO2 includes TiO2 particles surface adsorbed with anionic dispersion agent providing a micellar like structure with matrix type encapsulation of said stable particulate dispersion of TiO2 particles in said composite. Preferably, a stable aqueous TiO2 dispersion was achieved by N-methyl-N-oleyl taurate (Hostapon TPHC) as a dispersing agent followed by acrylic or styrene-acrylic copolymerization to encapsulate the TiO2 by single stage emulsion polymerization process leading to aqueous dispersion of polymer encapsulated TiO2 as TiO2-polymer composites. Such selective process resulted in matrix like encapsulation of TiO2 by polymer/copolymer favoring polymer encapsulated TiO2 composites that are useful in paint formulations leading to a significant reduction (10–20 % on TiO2) of TiO2 from the paint formulation.

Background Art

TiO2 is an opacifying pigment which gives hiding in the coatings. The spacing of the TiO2 particles in the film is crucial to obtain better hiding at low amount of TiO2 in the formulations. A better distribution of TiO2 particles can be achieved by using encapsulated TiO2 by polymer or TiO2-polymer composites.

Emulsion polymerization technique is generally used to prepare such polymer encapsulated particles or composites.

WO2012/116025 A1, and US Pat. Pub2014/0011943A1 claims polymer encapsulated titanium dioxide particles where, the TiO2/amphoteric polymer dispersion taken in vessel along with surfactant, and later redox emulsion polymerization was processed using redox couple, moreover, this prior art involves more than 1 stage polymerization.

EP Pat. Pub. 2343344A1 claims encapsulation of inorganic pigment particles with polymer particles prepared by mini-emulsion polymerization where, the dispersion of pigments particles and dispersion of polymerizable monomers were mixed and homogenized to get pigment encapsulated by monomer droplets which then was polymerized.

US Pat. Pub 8,703,865B2 claims method for production of polymer encapsulated pigments where, the organic pigment particles were encapsulated by mini-emulsion polymerization similar to the above mentioned prior art.

US Pat. Pub. 2010/0298483 A1 claims opacifying pigment particles where, the water soluble polymer was prepared first and then was mixed with TiO2 particles, and grinded at ~ 2000 rpm to prepare the pigment dispersion. In the second stage polymerization, this dispersion was taken in the vessel along with surfactant, then the polymerization was processed by adding monomers to encapsulate the pigment particles. This prior art involves more than 1 stage polymerization.

US Pat. Pub. 2006/0009546 A1 claims opacifying particles where the first polymer of rather low solid content (< 25 %) was mixed with TiO2 and grinded at ~ 5000 rpm to prepare the pigment dispersion of solid content of 63.7 % to 73.6 %. This polymer-TiO2 dispersion was further encapsulated with polymer by emulsion polymerization. This prior art also involves more than 1 stage polymerization.

An article in Journal of Polymer Science by Bedri Erdemetal.: Part A: Polymer Chemistry, Vol. 38, 4441-4450, 2000 report about the encapsulation of inorganic particles such as TiO2 particles. They employ mini-emulsion polymerization technique to encapsulate hydrophilic or hydrophobic particles of rather low particle sizes.

Research article British Polymer Journal Vol. 21, 133-140, 1989 by Carola H M Caris et al. report on the polymerization of MMA on the surface of inorganic submicron particles where, the TiO2 particles were first modified with Titanates as coupling/modifying agents prior to the encapsulation by conventional or mini-emulsion polymerization.

As apparent from the above state of the art, the same indicates the need of providing polymer encapsulated TiO2 or TiO2-Polymer composites made available through industrial friendly conventional emulsion polymerization in a single step using thermal initiators involving a simple processing method.

Summary of the Invention

Thus according to the basic aspect of the present invention there is provided TiO2-Polymer composites comprising polymer encapsulated stable particulate dispersion of TiO2 including TiO2 particles surface adsorbed with anionic dispersion agent providing a micellar like structure with matrix type encapsulation of said stable particulate dispersion of TiO2 particles in said composite.
Preferably said TiO2-Polymer composite is provided wherein said stable particulate dispersion of TiO2 comprise stable particulate dispersion of TiO2 including preferably adsorbed N-methyl-N-oleyl taurate (Hostapon TPHC).
According to another aspect of the present invention there is provided said TiO2-Polymer composites as aqueous dispersion suitable for use in paint formulations preferably including a broad distribution of particles at about 1500 nm corresponding to matrix type polymer or copolymer encapsulated TiO2 particles.
Preferably said TiO2-Polymer composites comprise ~ 52 % non-volatile materials (NVM) having Tg in the range of 2 °C to about 16 °C and involving acrylic polymer or styrene-acrylic copolymer that is stable upon storage at 55 °C for 30 days with respect to settling, viscosity.
Advantageously, said TiO2-Polymer composites is provided comprising a polymer film with evenly distributed TiO2 particles preferably of Rutile grade showing excellent hiding enabling reduction of the levels of TiO2 by 10 % - 20 % in paint formulations.
According to another aspect of the present invention there is provided a process for the preparation of TiO2-Polymer composites comprising providing TiO2-Polymer composites having matrix like encapsulated stably dispersed TiO2 particles in a polymer or a copolymer and having N-methyl-N-oleyl taurate (Hostapon TPHC) adsorbed onto the surfaces of said TiO2 particles favouring a miceller like structure for matrix like encapsulation of stably dispersed TiO2 particles in said composite in single stage emulsion polymerization process.
Preferably said process comprises:
i) providing a stable aqueous dispersion of TiO2 by adsorbing an anionic dispersion agent onto the surface of said TiO2 particles;
ii) encapsulating said stable aqueous dispersion of TiO2 in polymer by carrying out single stage polymerization reaction in a reactor involving said stable aqueous dispersion of TiO2 as a seed in said polymerization reactor to thereby produce said TiO2-Polymer composites.
More preferably said process for the preparation of TiO2-Polymer composites as dispersion comprises the following steps
(a) providing a stable aqueous dispersion of TiO2 by adding a selective amount of TiO2 to selective anionic dispersing agent of N-methyl-N-oleyl taurate (Hostapon TPHC) that gets adsorbed on the TiO2 surface;
(b) providing said stable aqueous dispersion of TiO2 in selective amounts as seed together with anionic surfactant, initiator and buffer solution;
(c) feeding a pre-emulsion comprising an aqueous dispersion of monomers or combinations thereof, selective amounts of anionic and non-ionic surfactants, for a period of about 4 hrs into the seed solution of step (b) having selective levels of anionic surfactant, thermal initiator and buffer until completion of polymerization and finally neutralizing to yield said TiO2-Polymer composites therefrom having matrix like encapsulated stably dispersed TiO2 particles in polymer or copolymer.
Preferably said step (c) optionally comprises
(I) feeding said pre-emulsion into said seed solution for about 1 hr until 20 % addition of the pre-emulsion is completed;
(II) adding remaining pre-emulsion together with cross-linkers including VTMO and polymerizing for about another 3 hrs until completion of polymerization and finally neutralizing to yield said TiO2-Polymer composites.
Preferably in said process said polymerization reaction was carried out in the temperature range of 72-82 °C to favour encapsulation of the TiO2 particles by acrylic polymer or styrene-acrylic copolymer.
According to another preferred aspect of the present invention there is provided said process wherein said providing stable aqueous dispersion of TiO2 involves providing 20 to 45 wt. % of TiO2 and 2 to 4.5 wt. % of anionic dispersing agent N-methyl-N-oleyl taurate (Hostapon TPHC) which is 7.5 wt. % to 10 wt. % Hostapon TPHC on TiO2, and de-ionized water to adjust the volume to 100 % and grinding at 500 rpm for 30 minutes and obtaining stable aqueous dispersion of TiO2 therefrom.
Preferably in said process the seed quantity is in the range of 1 % to 3 % active TiO2 dispersion and preferably involves ~ 0.3 % of non-ionic surfactant in combination with 3 % active TiO2 dispersion.
According to yet another preferred aspect of the present invention there is provided said process wherein said monomer or combination of monomers includes methacrylate monomer, a methyl methacrylate monomer, styrene monomer.
Preferably in said process said anionic surfactant in the pre-emulsion includes anionic surfactants Dowfax 2A1, Disponil FES32, and wherein said initiator includes thermal initiators such as potassium persulphate.
According to another aspect of the present invention there is provided a paint formulation comprising TiO2-Polymer composites comprising polymer encapsulated stable particulate dispersion of TiO2 including TiO2 particles surface adsorbed with anionic dispersion agent providing a micellar like structure with matrix type encapsulation of said stable particulate dispersion of TiO2 particles in said composite.
Preferably said paint formulation has pigment volume concentration in the range of 40-80 % adapted for reduction of TiO2 in said formulation in the range of 16-22 % on TiO2.

Brief Description of Figures

Figure 1: (a) Illustrates particle size distribution analyzed by dynamic light scattering (b) illustrates the FEGSEM images that indicate the matrix like encapsulated TiO2 by polymer;

Figure 2: (a) Illustrates the particle size distribution analyzed by dynamic light scattering; (b) illustrates the FEGSEM images that indicates matrix like encapsulated TiO2 by polymer;

Figure 3: (a) Illustrates the particle size distribution analyzed by dynamic light scattering (b) illustrates the FEGSEM images that indicates matrix like encapsulated TiO2 by polymer;

Figure 4: SEM images (a) and (b) for dry films of polymer encapsulated TiO2/TiO2-Polymer composites similar to example 1 and 2 which are prepared with 3.33 % of 30 % TiO2 dispersion as seed. These SEM images shows the aggregated/clustered TiO2 particles which are distributed throughout the polymer film;

Figure 5: Illustrates a schematic of encapsulation of TiO2 by emulsion co-polymer;

Figure 6: Illustrates polymer film without and with TiO2-Polymer composites showing excellent hiding.

Figure 7: a) Particle size distribution of TiO2 dispersion prepared with dispersing agent Hostaperm TPHC, b) TGA curves of neat TiO2 and TiO2 adsorbed with Hostapon TPHC

Detailed Description of the Invention

As discussed herein before, the present invention provides for TiO2-Polymer composites comprising polymer encapsulated stable particulate dispersion of TiO2 including TiO2 particles surface adsorbed with anionic dispersion agent providing a micellar like structure with matrix type encapsulation of said stable particulate dispersion of TiO2 particles in said composite.
A selective process of manufacturing the said TiO2-Polymer composites is also provided comprising the steps of preparation of aqueous TiO2 dispersions and then encapsulation by polymer.

Such process resulted in matrix like encapsulation of TiO2 by polymer. These TiO2-Polymer composites have found applications in coating formulations.

TiO2 is an opacifying pigment which gives hiding in the coatings. The spacing of the TiO2 particles in the film is crucial to obtain better hiding while employing low amount of TiO2 in the formulations. It was surprisingly found by way of the present invention a better distribution of TiO2 particles could be achieved by using encapsulated TiO2 by polymer or TiO2-polymer composites.

The present invention also thus provides a selective process of preparation of aqueous TiO2 dispersions and then the encapsulation by polymer. Such process resulted in matrix like encapsulation of TiO2 by polymer. These TiO2-Polymer composites have found applications in coatings formulations with better hiding as shown in Fig. 6 together with significant reduction of TiO2 use in paint formulations.

The present invention thus relates to a selective process of preparation of stable TiO2 dispersions using a dispersing agent. Selective amount of TiO2 dispersion was taken as seed in the reactor along with surfactant, initiator and buffer, followed by emulsion co-polymerization in a single step to encapsulate the stably dispersed TiO2. Thermal initiators like potassium persulphate (KPS), were used to initiate the polymerization which is cost effective as initiator. While the initiators like redox couples can also be used to process the emulsion polymerization at lower temperatures (< 50 °C), such redox polymerization generally results in high molecular weight and higher exotherm not suitable for some applications.

The FEGSEM images (Fig. 4a) evidenced the matrix like encapsulation. These polymer encapsulated TiO2 composites as TiO2-Polymer composites showed excellent hiding/opacity as is evident from Fig. 6.

According to a preferred embodiment of the present invention the process of preparing the TiO2-Polymer composites is as follows:

a) A stable aqueous dispersion of TiO2 was prepared by grinding a selective amount of TiO2 and selective amount of anionic dispersing agent Sodium-n-Methyl-n-Oleoyl Taurate (Hostapon TPHC) at ~ 500 rpm using zirconium beads. The grinding helped to break the agglomerated TiO2 into primary particle, and the anionic dispersing agent adsorbed on the TiO2 surface to result in a stable dispersion. Particle size analysis and thermo-gravimetric analysis confirmed the primary particle size and adsorption of surfactant on TiO2 respectively.

Figure 7a is provided revealing the particle size analysis of TiO2 dispersions where the particle distribution is centered at ~ 400 nm. Figure 7b reveals a thermo gravimetric analysis (TGA) curve to find the adsorption of dispersing agent on the TiO2. The TGA data for neat TiO2 and TiO2 dispersed with Hostapon TPHC is shown. The loss in weight of TiO2 dispersed with Hostapon TPHC evidences that the Hostapon TPHC adsorbed on TiO2.

Dispersions were prepared by employing 20 to 45 wt. % of TiO2, 2 to 4.5 wt. % of Hostapon TPHC, and de-ionized water to adjust the volume to 100 %. The stability of dispersion with > 45 wt. % of TiO2 was found to be low, also Hostapon TPHC below 7.5 wt. % on TiO2 do not produce stable dispersions and it was found that stability could be achieved until 10 wt. % Hostapon TPHC on TiO2.

b) The above prepared TiO2 dispersion was taken as seed in reactor to which anionic surfactant, buffer, initiator and de-ionized water were added. The styrene-acrylic or acrylic copolymerization was processed to encapsulate the TiO2 particles by feeding said pre-emulsion into said seed solution optionally comprising
feeding said pre-emulsion into said seed solution over a period of about 1 hours until 20 % addition of the pre-emulsion is completed followed by adding remaining pre-emulsion together with cross-linkers including VTMO until completion of polymerization of the mix at about 80 °C requiring about another 3 hrs, or
continuing feeding the pre-emulsion into the seed solution until completion of polymerization by carrying out polymerization of the mix at about 80 °C for about 4 hrs to obtain matrix like encapsulated stably dispersed TiO2 particles in polymer or copolymer as stable TiO2-polymer composite with different Tg therefrom.
The seed quantity was varied from 1 % to 3 % active TiO2 dispersion. In some cases the TiO2–Polymer composite prepared with effective 3 % TiO2, a little amount (~ 0.3 %) of non-ionic surfactant was required to overcome the settling observed after 12 hrs.

1 % to 3 % range of active TiO2 dispersion was found to be suitable as seed, even 3 % active TiO2 dispersion required 0.3 % of non-ionic surfactant. Composites prepared with 1 to 2 % active TiO2 dispersions are stable against any settling, whereas composite prepared with 3 % active TiO2 only showed settling overnight which could be overcome by use of 0.3 % of non-ionic surfactant.
Surfactant range in Pre-emulsion (PE) was also important for a successful emulsion polymerization wherein it was found as per Examples 2 and 3 that Dowfax 2A1 is in the range of 0.4 to 1.2 %, which when below 0.4 % the stability of the PE is low.
In Example 3, Disponil FES32 is in the range of 1 to 2 %, and Atpol A5720 is in the range of 0.5 to 1.5 % below and beyond which levels either there is some abnormality in processing, or the kettle hygiene is bad.
Surfactant range in the reactor is also an important factor for a successful emulsion polymerization with the above said seed wherein in Examples 2 Dowfax 2A1 is taken in the range of 0.06 to 0.6 % preferably in the range of 0.2 % wherein below 0.06 % very high amount of coagulum occurs and above 0.6 % increases the viscosity resulting in handling problems and hence preferable amount of 0.2 % is best suited.
Further in Example 3, Disponil FES32 is in the range of 0.3 to 0.9 %. Below 0.3 % a very high amount of coagulum occurs and hence preferably taken at 0.6% that was best suited. However, above 0.6 % the viscosity increases and causes handling issues.
It was also found that the polymerization process was favored when the temperature range for polymerization was maintained in the range of 72 to 82 °C wherein below 72 °C coagulation took place requiring a prolonged polymerization time.
The temperature is maintained to upto 82 °C, since beyond this temperature any large exotherm in polymerization reaction makes the reaction temperature difficult to control that may cause huge damages. Also, the desired polymerization could be effectively achieved in said temperature range.
In all the cases, with the above selective wt. % ranges employed, the polymerization processing, kettle/stirrer hygiene were good. In some cases, very slight amount of coagulum (< 0.3 %) was observed. Below examples describe the preparation of TiO2-polymer composite of different Tg at active 2 % TiO2 (6.66 % of 30 % TiO2 dispersion) dispersion as seed, in details.

Abbreviations

Hostapon TPHC=Sodium-n-Methyl-n-Oleoyl Taurate
Dowfax 2A1=Diphenyl oxyalkyl sulphonate
KPS=Potassium persulphate
SBC=Sodium bicarbonate
TDM=Tertiary dodecyl mercaptan
VTMO=Vinyl trimethoxysilane
TBHP=tert-butyl hydroperoxide
SFS=Sodium formaldehyde sulphoxylate
BA=Butylacrylate
ST=Styrene
MMA=Methylmethacrylate
MAA=Methacrylic acid
DI water=De-ionized water
FES32=Disponil FES32 an anionic surfactant
A5720=Atpol 5720, non-ionic surfactant
AMP 95= 2-Amino-2-methyl-1-propanol

Example 1: Preparation of TiO2 dispersions

Preparation of stable aqueous TiO2 dispersion consists of 30-50 g of TiO2 (R-900 grade from DuPont), 3-5 g of anionic dispersing agent Hostapon TPHC (from Clariant India), and de-ionized water to adjust the volume to 100 %. The mixture was ground at 500 rpm for 30 minutes to break the agglomerated TiO2 and stabilize with the dispersing agent.

Example 2: Low Tg film forming TiO2-Polymer composite

The polymerization was processed in a four-necked reactor which was equipped with metering devise, paddle stirrer, heating regulator and reflux condenser was charged with DI water (12.82 g), Dowfax 2A1 (0.20 g), KPS (0.14 g), TDM (0.02 g), SBC (0.15 g), and 30 % TiO2 dispersion (6.66 g). The temperature of the reactor was raised to 78±2 °C at the rate of 2 °C/min. Then the pre-emulsion (PE) prepared in a separate glass vessel by mixing DI water (22.17 g), Dowfax 2A1 (0.80 g), ST (8.33g), MMA (14.72 g), BA (24.94 g), TDM (0.03 g), MAA (0.88 g), and KPS (0.04 g), was fed over a period of 4 hrs. After 20 % completion of addition of PE, VTMO (0.33 g) and DI water (0.20 g) were added to the rest of the PE, and the addition of PE continued to the reactor. After 3 hrs of addition of PE, Dowfax 2A1 (0.50 g) and DI water (0.20 g) were added to the reactor, and then the PE addition was continued to the completion followed by the flushing with DI water (0.80 g). Once the flushing was completed, Dowfax 2A1 (0.15 g), and TBHP (0.04 g) in 0.40 g of DI water were added followed by the addition of solution of SFS (0.04 g) in 2 g of water added drop wise for a period of 30 min to polymerize the un- reacted monomers. Agitation was continued further for 1 hr at 78±2 °C. Then the content of the reactor was cooled to 40 °C and to which 15 % aqueous ammonia (0.70 g), Nipacide CFX (0.10 g), and 18 % Dapro DF4164 dispersion in water (0.021 g), and DI water (2.60 g) were added under agitation. The content of the reactor was filtered to remove any gel or coagulum. The filtered aqueous dispersion of polymer-TiO2 composite was found to have ~ 52 % non volatile materials (NVM). The theoretical Tg calculated by Fox equation was of ~ 03 °C. The particle size distribution analyzed by dynamic light scattering is shown Figure 1a. The FEGSEM images indicated the matrix like encapsulated TiO2 by polymer as shown in Figure 1b.

Example 3: High Tg film forming TiO2-Polymer composite

The polymerization was processed in a four-necked reactor which was equipped with metering devise, paddle stirrer, heating regulator, reflux condenser was charged with DI water (12.80 g), Dowfax 2A1 (0.20 g), KPS (0.14 g), TDM (0.02 g), SBC (0.15 g) and 30 % TiO2 dispersion (6.66 g). The temperature of the reactor was raised to 78±2 °C at the rate of 2 °C/min. Then the pre-emulsion (PE) prepared in a separate glass vessel by mixing DI water (22.09 g), Dowfax 2A1 (0.80 g), ST (8.33 g), MMA (18.50 g), BA (21.14 g), TDM (0.03 g), MAA (0.88 g), and KPS (0.04 g), was fed over a period of 4 hrs. After 20 % completion of addition of PE, VTMO (0.33 g) and DI water (0.20 g) were added to the rest of the PE, and the addition of PE continued to the reactor. After 3 h of addition of PE, Dowfax 2A1 (0.50 g) and DI water (0.20 g) were added to the reactor, and then the PE addition was continued to the completion followed by the flushing with DI water (2.40 g). Once the flushing was completed, Dowfax 2A1 (0.15 g), and TBHP (0.04 g) in 0.40 g of DI water were added followed by the addition of solution of SFS (0.04 g) in 2.00 g of water added drop wise for a period of 30 min to polymerize the un-reacted monomers. Agitation was continued further for 1hr at 78±2 °C. Then the content of the reactor was cooled to 40 °C and to which aqua ammonia (0.70 g), and Kathone (0.20 g), 18 % Tego foamex 8020 (0.02 g) and DI water (1.32 g) were added. The content of the reactor was filtered to remove any gel or coagulum. The filtered aqueous dispersion of TiO2-Polymer composite was found to have ~ 52 % nonvolatile materials (NVM). The theoretical Tg calculated by Fox equation was of ~ 15 °C. The particle size distribution analyzed by dynamic light scattering is shown Figure 2a. The FEGSEM images indicated the matrix like encapsulated TiO2 by polymer as shown in Figure 2b.

Example 4: High Tg non-film forming TiO2-Polymer composite
The polymerization was processed in a four-necked reactor which was equipped with metering devise, paddle stirrer, heating regulator, reflux condenser was charged with DI water (10.18 g), FES32 (0.60 g), KPS (0.13 g), and SBC (0.15 g) and 30 % TiO2 dispersion (6.66 g). The temperature of the reactor was raised to 78±2 °C at the rate of 2 °C/min. Then the pre-emulsion (PE) was prepared in a separate glass vessel by mixing DI water (24.87 g), FES32 (01.50 g), A5720 (1.00 g), ST (26.50 g), BA (20.20 g), TDM (0.05 g), MAA (1.50 g), and KPS (0.08 g), which was fed over the period of 4 hrs. Once the PE addition was completed, chaser catalyst TBHP (0.02 g) in 1.00 g of de-ionized water was added followed by the addition of solution of SFS (0.02 g) in 1.00 g of water was added drop wise for a period of 15 min to polymerize the un-reacted monomers. Agitation was continued further for 1 hr at 78±2 °C. Then the content of the reactor was cooled to 40 °C and to which AMP 95 (0.9 g), Kathone LX150 (0.20 g), and DI (1.92 g) were added. The content of the reactor was filtered to remove any gel or coagulum. The filtered aqueous dispersion of TiO2-Polymer composite was found to have ~ 52 % non-volatile materials (NVM). The theoretical Tg calculated by Fox equation was of ~ 16 °C. The particle size distribution analyzed by dynamic light scattering is shown Figure 3a. The FEGSEM images indicated the matrix like encapsulated TiO2 by polymer as shown in Figure 3b.

The particle size distribution (Figures 1a, 2a, and 3a) determined by the dynamic light scattering technique shows two distinct particle size distributions, a narrow distribution near 140 nm and a broad distribution near 1500 nm. The particle size distribution near 140 nm is for the usual emulsion polymer particles whereas, the broad distribution corresponds to the polymer encapsulated TiO2 particles. The FEGSEM images show particles of larger sizes (> 1 µ), and they appear as a matrix like encapsulation of TiO2 particles by the co-polymer. The SEM images of the dry films of polymer encapsulated TiO2-Polymer composites shows the aggregated/ clustered TiO2 particles which are distributed throughout the polymer film as shown in Figure 4. These SEM images correspond to Examples similar to 1 and 2 but with 3.33 g of 30 % TiO2 dispersions. TiO2 dispersion with 6.66 g, and 9.99 g also showed the similar behaviors. The aggregation/clustering of the TiO2 particles is probably due to the matrix like encapsulated particles.

Based on these observations, a schematic of the encapsulation of TiO2 by emulsion co-polymer is shown in Figure 5. Red color code indicates the TiO2 particles, blue headed and black tail represents dispersing agent/surfactants. The TiO2 particles stabilized (pigment dispersion) by selective dispersing agent of N-methyl-N-oleyl taurate (Hostapon TPHC) have tendency to aggregate because of the Van der Walls forces but instead micellar like structures are formed due to the presence of small amount of surfactant in the reactor, wherein the surfactants present in the reactor also have affinity towards the surfactant stabilized particles, such interactions resemble the micellar structure enabling effective encapsulation of such particles by co-polymerization based on using the TiO2 dispersion as seed with N-methyl-N-oleyl taurate (Hostapon TPHC) adsorbed onto TiO2 particle surface thus resulting in matrix like encapsulation of TiO2 particles by the copolymer upon emulsion polymerization.

When the polymerization process of the present invention was done under starving conditions, the same yielded large amount of coagulum which was not in acceptable specification range, and also the hiding was poor. Hence, a slightly higher surfactant in reactor was required.

Anionic surfactants e.g sodium dodecyl sulphate (SDS), sodium dodecyl benzene sulphonate (SDBS), Dowfax 2A1, Maxemul 6112 (co-polymerizable anionic surfactant with phosphate ester functionality), were also explored however, the stability of the dispersion was poor compared to the dispersion prepared with N-methyl-N-oleyl taurate (Hostapon TPHC) and hence the dispersion with other anionic surfactants was not effective as a seed in emulsion polymerization to realize the TiO2-Polymer composites of the present invention.

Additionally different processes were also explored to obtain the stable TiO2-Polymer composites such as : 1) A mini-emulsion polymerization wherein the TiO2 dispersion and monomers were mixed, ultra sonicated for ~ 25 min at 80 % amplitude followed by bulk polymerization whereby it was found that the processing was difficult as the viscosity became very high and a gel like mass was obtained. While increasing the amount of surfactant helped in better processing, still settling was observed in TiO2-polymer composite overnight; 2) Semi-continues emulsion polymerization under starving conditions yielded large amount of coagulum which was not in acceptable specification range, hence a slightly higher surfactant in reactor was employed; 3) Under starving conditions, the initiator dosage at regular time intervals were added, which also resulted in large amount of coagulum; 4) Different anionic surfactants were explored in the emulsion formulation to obtain better stability, and all resulted either in high coagulum, bits (tiny particles) in the dry film, poor kettle/stirrer hygiene. All the aforesaid processes failed to yield the desired TiO2-Polymer composites with matrix like encapsulated stably dispersed TiO2 particles.

It is thus a surprising finding of the present invention that stable TiO2-Polymer composites having matrix like encapsulated stably dispersed TiO2 particles in acrylic or styrene-acrylic copolymer and having N-methyl-N-oleyl taurate (Hostapon TPHC) adsorbed onto the surfaces of said TiO2 particles favoring a micellar like structure during emulsion polymerization process could only be advantageously achieved under only one/single stage emulsion polymerization process comprising the following steps:

a) initial preparation of stable aqueous dispersion of TiO2 which consists of selective known amount TiO2 and selective amount of selective anionic dispersing agent of N-methyl-N-oleyl taurate (Hostapon TPHC) and taking the dispersion as seed (instead of pre-emulsion) together with anionic surfactant, initiator and buffer solution;

b) preparing a pre-emulsion involving an aqueous dispersion of monomers or combinations thereof comprising methacrylate monomer, methyl methacrylate monomer, styrene monomer, and anionic and non ionic surfactants;

c) feeding said pre-emulsion into said seed solution optionally comprising
feeding said pre-emulsion into said seed solution over a period of about 1 hr until 20 % addition of the pre-emulsion is completed followed by adding remaining pre-emulsion together with cross-linkers including VTMO until completion of polymerization of the mix at about 80 °C requiring about another 3 hrs, or
continuing feeding the pre-emulsion into the seed solution until completion of polymerization by carrying out polymerization of the mix at about 80 °C for about 4 hrs to obtain matrix like encapsulated stably dispersed TiO2 particles in polymer or copolymer as stable TiO2-polymer composite with different Tg therefrom.

The above aqueous dispersion of polymer encapsulated TiO2 was neutralized with ammonia or AMP 95.

Stability results revealed that the sample upon storage at 55 °C for 30 days was stable w.r.t the settling, viscosity.
Significantly the polymer encapsulated TiO2 of the present invention as stable TiO2-polymer composites were characterized by FEGSEM images that confirm the matrix like encapsulation. The opacity/hiding was exceptionally higher in case of polymer encapsulated TiO2 compared to the neat polymer. Evaluation of these composites in paint formulation evidenced in a significant reduction of TiO2 from the paint formulations.

The TiO2 particles were found to be distributed uniformly in the polymer film and hence they show an excellent hiding, and an example is shown in Figure 6 where the polymer film without TiO2 and TiO2-Polymer composites were compared. These TiO2-Polymer composites are of great help in reducing the TiO2 by 10 % - 20 % from the paint formulations.

To conform to the abovesaid, the performance of the TiO2-Polymer composites were evaluated in paint formulation of various PVC levels e.g.

Low Tg film forming TiO2-Polymer composite was evaluated in paint formulation of PVC 41- 43 %. The contrast ratio and the whiteness are matched to the reference sample at 16 % of reduction of TiO2 (16 % on TiO2) from formulation which was compensated by CaCO3.

High Tg film forming TiO2-Polymer composite was evaluated in paint formulation of PVC 41- 43 %. The contrast ratio and the whiteness are matched to the reference sample at 16 % ofreduction of TiO2 (16 % on TiO2) from formulation which was compensated by CaCO3.

High Tg non-film forming TiO2-Polymer composite was evaluated in paint formulation of PVC 78-80 %. The contrast ratio and the whiteness are matched to the reference sample at 22 % of reduction of TiO2 (22 % on TiO2) from formulation which was compensated by CaCO3.

It is thus possible for the present advancement to provide for stable TiO2-Polymer composites having matrix like encapsulated stably dispersed TiO2 particles in polymers including acrylic or styrene-acrylic copolymer and having N-methyl-N-oleyl taurate (Hostapon TPHC) adsorbed onto the surfaces of said TiO2 particles favoring a micellar like structure during emulsion polymerization process that could only be advantageously achieved under only one/single stage emulsion polymerization process of the present invention. Advantageously, said TiO2 particles were found to be distributed uniformly in the polymer film and hence revealed an excellent hiding effect as per Figure 6 (with and without TiO2 Polymer composites) and also aid in reducing the use of such TiO2-Polymer composites by 10 % - 20 % in paint formulations.