DESC:FIELD
The present disclosure relates to a process for the preparation of core-sheath-shell polymer particles.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Emulsion polymerization: Emulsion polymerization is a polymerization process, in which the monomers are stabilized via use of surfactants and are dispersed in an aqueous phase. The polymerization is initiated by free radicals obtained from the addition of an initiator that is soluble (or partially soluble) in the aqueous phase. The final product dispersed in an essentially aqueous medium, commonly known as latex.
Semi-continuous emulsion polymerization: is a process in which the monomer is added continuously or in increments, neat or in emulsion during the process of emulsion polymerization.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Titanium dioxide (TiO2) is one of the most efficient light scattering pigments, and as a result it is widely used to deliver opacity, especially in paint formulations. However, due to the cost of TiO2 and an energy intensive manufacturing process required to produce TiO2, alternative materials are required to minimize the usage of TiO2 and provide opacity to the coating.
Hollow core-sheath-shell polymer particles have shown a potential to replace TiO2 from the opaque coating formulations to produce coatings with low TiO2 concentration. Typically, the core-sheath-shell particles contains swollen core due to presence of water in the core. During the drying process of the paint containing swollen core-sheath-shell, the water in the core of this core-sheath-shell particles diffuses through the polymer shell and leaves an air void. Because of the difference in the refractive index between air and surrounding polymer, light is effectively scattered, contributing to film opacity. The void within the core-sheath-shell particles not only provides useful spacious compartments but also unique light scattering properties. These particles have been widely used in paper coatings, architectural coatings and so on.
However, core-sheath-shell particles produced using the conventional methods suffer from the primary drawback that, they are weak and non-robust. Hence, they are susceptible to rupturing if burnished, and once ruptured they lose a lot of their opacifying properties.
Therefore, there is felt a need to provide a process for the preparation of core-sheath-shell polymer particles that mitigates the drawback mentioned herein above.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the preparation of core-sheath-shell polymer particles.
Yet another object of the present disclosure is to provide core-sheath-shell polymer particles that are robust.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY:
The present disclosure relates to a process for the preparation of core-sheath-shell polymer particles. The process comprises the following steps:
i) A first monomeric system is polymerized in a first solvent by using at least one first surfactant in the presence of at least one first initiator and a crosslinking agent at first predetermined conditions to obtain a core in the form of latex.
ii) At least one second initiator is mixed with the core followed by adding a second monomeric system to obtain a mixture. The second monomeric system is polymerized on to the core in the presence of the second initiator from the mixture at second predetermined conditions to obtain a polymeric sheath coated core.
iii) Separately, a third monomeric system is mixed with at least one crosslinking agent, at least one second surfactant, at least one plasticizer, at least one redox initiator and at least one phase separating diluent at third predetermined conditions to obtain a pre-emulsion.
iv) A predetermined amount of the pre-emulsion and a predetermined amount of the polymeric sheath coated core are mixed and the pre-emulsion is polymerized at fourth predetermined conditions to obtain a crude core-sheath-shell polymer particles; wherein the core of the polymeric sheath coated core is neutralized by adding a base along with the pre-emulsion.
v) A chaser catalyst is added to the crude core-sheath-shell polymer particles at fifth predetermined conditions to obtain the core-sheath-shell polymer particles.
The first monomeric system comprises a monomer having a carboxylic acid functionality; the first monomeric system and the second monomeric system comprises at least one hydrophilic monomer and; the crosslinking agent in step i) and step iii) is ethylene glycol dimethacrylate .
Further, the present disclosure relates to core-sheath-shell polymer particles. The core-sheath-shell polymer particles comprises a) a polymeric core in the form of latex; b) a polymeric sheath layer coated on the core; and c) at least one polymeric shell layer coated on the polymeric sheath.
The core-sheath-shell polymer particles are characterized by having:
• a ratio of a mass of the core to the total mass of sheath and shell in the range of 1:5 to 1:25 and
• the amount of a crosslinking agent is in the range of 0.15 wt.% to 0.45 wt.% wherein the crosslinking agent is ethylene glycol dimethacrylate .
• the size of the core-sheath-shell polymer particles is in the range of 350 nm to 450 nm.
DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
Core-sheath-shell polymer particles are shown to be a viable option for reducing the usage of TiO2 from the opaque coating formulations. The hollow core-sheath-shell particles provides useful and unique optical properties. These particles find potential applications in the paper coatings and to some extent in leather, textiles and water based construction materials.
Core-sheath-shell particles produced by using conventional techniques are weak and non-robust. Hence, they are prone to rupturing upon application of the stress, and once ruptured they lose their optical properties and hence, they lose the ability to provide opacity to the coating composition.
The present disclosure provides a process for the preparation of core-sheath-shell polymer particles.
The process is described in detail as below:
In a first step, a first monomeric system is polymerized in a first solvent by using at least one first surfactant in the presence of at least one first initiator and a crosslinking agent at first predetermined conditions to obtain a core in the form of latex.
In accordance with the embodiments of the present disclosure, the first monomeric system comprises a monomer having a carboxylic acid functionality. In an exemplary embodiments the monomer having a carboxylic acid functionality is glacial methacrylic acid.
In accordance with the embodiments of the present disclosure, the first monomeric system comprises at least one hydrophilic monomer. In an exemplary embodiment, the hydrophilic monomer is glacial methacrylic acid.
In accordance with the embodiments of the present disclosure, the first monomeric system is a mixture of butyl acrylate in an amount in the range 5 wt.% to 10 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount in the range of 55 wt.% to 65 wt.% with respect to the total weight of the first monomeric system and glacial methacrylic acid in an amount in the range of 25 wt.% to 30 wt.% with respect to the total weight of the first monomeric system. In an exemplary embodiment, the first monomeric system is a mixture of butyl acrylate in an amount of 8.81 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount of 65.20 wt.% with respect to the total weight of the first monomeric system, and glacial methacrylic acid in an amount of 30.15 wt.% with respect to the total weight of the first monomeric system.
In accordance with the embodiments of the present disclosure, the crosslinking agent in step of synthesizing the core is ethylene glycol dimethacrylate .
In accordance with the embodiments of the present disclosure, the ethylene glycol dimethacrylate in step of synthesizing the core is in an amount in the range of 0.1 wt.% to 0.5 wt.% with respect to the total weight of the first monomeric system. In an exemplary embodiment, amount of the ethylene glycol dimethacrylate is 0.33 wt.%
The crosslinking agent added during the stage of the synthesis of the core helps in preventing collapse of voids during the drying of the paint film.
In accordance with the embodiments of the present disclosure, the first solvent is water. In an exemplary embodiment, the first solvent is demineralized water.
In accordance with the embodiments of the present disclosure, the first surfactant is selected from an anionic surfactant and a non-ionic surfactant,
Typically, the anionic surfactant of the present disclosure is sodium dodecyl benzene sulphonate and the non-ionic surfactants is alcohol ethoxylates.
Typically, the surfactants are used to create dispersion of monomers in the aqueous medium during the emulsion polymerization technique.
In accordance with the embodiments of the present disclosure, the amount of the anionic surfactant used for synthesizing the core is 0.4 to 0.6 wt.% of the total weight of the first monomeric system.
In accordance with the embodiments of the present disclosure, the first initiator is selected from potassium per-sulphate and ammonium per-sulphate. In an exemplary embodiment, the first initiator is potassium per-sulphate.
In accordance with the embodiments of the present disclosure, the first initiator is gradually introduced in two stages.
In accordance with the embodiments of the present disclosure, the first initator is not redox initiator.
Typically, the initiators are used to initiate the polymerization reaction by creating free radicles.
In accordance with the embodiments of the present disclosure, the first pre-determined conditions include a temperature is in the range of 60 oC to 100 oC, and a time period is in the range of 70 minutes to 150 minutes. In an exemplary embodiment, the first predetermined conditions include the temperature of 70 oC to 80 oC, and the time period of 90 minutes.
In accordance with the embodiments of the present disclosure, the synthesis of the core of the core-sheath-shell particles further involves the use of at least one first biocide.
In an exemplary embodiment, the first monomeric system is a mixture of butyl acrylate in an amount of 8.81 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount of 65.20 wt.% with respect to the total weight of the first monomeric system, glacial methacrylic acid in an amount of 30.15 wt.% with respect to the total weight of the first monomeric system, the crosslinking agent i.e ethylene glycol dimethacrylate in an amount of 0.33 wt.% with respect to the total weight of the first monomeric system, the first predetermined conditions include a temperature of 70 oC to 80 oC, time period of 90 minutes.
In accordance with the embodiments of the present disclosure, the core of the core-sheath-shell polymer particles is synthesized by an emulsion polymerization. In an embodiment, the core is synthesized by a semi-continuous emulsion polymerization.
In a second step, at least one second initiator is mixed in the core followed by adding a second monomeric system to obtain a mixture. The second monomeric system is polymerized on to the core in the presence of the second initiator from the mixture at second predetermined conditions to obtain a polymeric sheath coated core.
Composition of the sheath is important to the extent that it provide a complete covering to the core that is getting neutralized so that it allows neutralizer to enter and neutralize the high acid core and allows water to move out creating a void.
In accordance with the embodiments of the present disclosure, the second monomeric system comprises at least one monomer selected from butyl acrylate and methyl methacrylate. In an exemplary embodiment, the second monomeric system comprises a mixture of butyl acrylate, and methyl methacrylate.
In accordance with the embodiment of the present disclosure, the second monomeric system comprises a hydrophilic monomer is at least one selected from methacrylic acid and methacrylamide. In an exemplary embodiment, the hydrophilic monomer is a mixture of methacrylic acid and methacrylamide.
In accordance with the embodiments of the present disclosure, the second monomeric system is a mixture of methyl methacrylate in an amount in the range of 80 wt.% to 90 wt.% with respect to the total weight of the second monomeric system, butyl acrylate in an amount in the range of 5 wt.% to 10 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system, and methacryalamide in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system.
In an exemplary embodiment, the second monomeric system is mixture of butyl acrylate in an amount of 7.22 wt.% with respect to the total weight of the second monomeric system, methyl methacrylate in an amount of 88.75 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount of 2.74 wt.% with respect to the total weight of the second monomeric system and methacrylamide in an amount of 1.26 wt.% with respect to the total weight of the second monomeric system.
In accordance with the embodiments of the present disclosure, the second initiator is selected from potassium per-sulphate and ammonium per-sulphate. In an exemplary embodiment, the second initiator is potassium per-sulphate.
In accordance with the embodiments of the present disclosure, the second predetermined conditions include a temperature in the range of 60 oC to 100 oC, and a time period in the range of 60 minutes to 120 minutes. In an exemplary embodiment, the second predetermined conditions include the temperature of 80 oC, and the time period of 90 minutes.
In accordance with the embodiments of the present disclosure, a mixture of the second monomeric system and the hydrophilic monomers are gradually added to the core in step i) over a period in the range of 80 minutes to 100 minutes. In an exemplary embodiment, a mixture of the second monomeric system and the hydrophilic monomer is gradually added to the core in step i) over a period of 90 minutes.
In an exemplary embodiment, the second monomeric system is mixture of butyl acrylate in an amount of 7.22 wt.% with respect to the total weight of the second monomeric system, methyl methacrylate in an amount of 88.75 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount of 2.74 wt.% with respect to the total weight of the second monomeric system and methacrylamide in an amount of 1.26 wt.% with respect to the total weight of the second monomeric system, the second initiator is potassium per-sulphate, and the second predetermined conditions include the temperature of 80 oC, and the time period of 90 minutes.
Typically, the polymeric sheath coated on the core is hydrophilic in nature.
The composition and the amount of the second monomeric system and the processing temperature during the step of sheath polymerization is critical to get the stable uniform hollow core shell polymer particles.
Separately, a third monomeric system is mixed with at least one crosslinking agent, at least one second surfactant, at least one plasticizer, at least one redox initiator and at least one phase separating diluent at third predetermined conditions to obtain a pre-emulsion.
In accordance with the embodiments of the present disclosure, the third monomeric system comprises at least one monomer selected from styrene, butyl acrylate, methyl methacrylate, glacial methacrylic acid and methacryamide.
In accordance with the embodiments of the present disclosure, the third monomeric system is a mixture of styrene in an amount in the range of 70 wt.% to 80 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount in the range of 10 wt.% to 20 wt.% with respect to the total weight of the third monomeric system, butyl acrylate in amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the third monomeric system, glacial methacrylic acid in an amount in the range of 0.1 wt.% to 0.5 wt.% with respect to the total weight of the third monomeric system and methacrylamide in an amount in the range of 0.15 wt.% to 0.25 wt.% with respect to the total weight of the third monomeric system. In an exemplary embodiment, the third monomeric system is mixture of styrene in an amount of 78.41 wt.% with respect to the total weight of the third monomeric system, butyl acrylate in an amount of 1.08 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount of 13.33 wt.% with respect to the total weight of the third monomeric system, glacial methacrylic acid in an amount of 0.41 wt.% with respect to the total weight of the third monomeric system, methacrylamide in an amount of 0.19 wt.% with respect to the total weight of the third monomeric system.
In accordance with the embodiments of the present disclosure, the second surfactant is selected from an anionic surfactant and a non-ionic surfactant. In an exemplary embodiment, the second surfactant is sodium dodecyl benzene sulphonate.
In accordance with the embodiments of the present disclosure, the plasticizer is selected from linseed oil fatty acid and dehydrated castor fatty acid. In an exemplary embodiment, the plasticizer is a combination of linseed oil fatty acid and dehydrated castor fatty acid.
Linseed oil fatty acid and dehydrated castor fatty acid act as a plasticizing agent. They help in lowering the glass transition temperature of the polymeric sheath of the shell. Further, the addition of plasticizer also helps in facilitating the complete neutralization and provides stability to the hollow core-sheath-shell polymer particles and reduces the surfactant demand during the whole preparation process. Use of plasticizers also prevent the separation and settling of the core-sheath-shell polymer particle that is not observed during the neutralization stage.
In accordance with the embodiments of the present disclosure, the redox initiator is selected from tertiary butyl hydroperoxide and sodium formaldehyde sulfoxylate. In an exemplary embodiment, the redox initiator is a combination of tertiary butyl hydroperoxide and sodium formaldehyde sulfoxylate.
The redox initiators are used to polymerise the traces of monomer present after polymerisation process ensuring the unreacted monomers are minimal.
In accordance with the embodiments of the present disclosure, the phase separating diluent is iso-octane.
The phase separating diluent (isooctane) is used to make thermally stable hollow core-sheath-shell structures as it acts as a solvent to monomer however, acts as non-solvent to the resulting polymer. It also helps in promoting swelling of the core at the stage of neutralization. Because of the addition of phase separating diluent, the optical properties of the paint film/composition are not affected when kept at high temperature (50° C) due the stable hollow structure of the polymer. Addition of the diluent also helps in facilitating the complete neutralization of alkali added during the later stage of the preparation of core-sheath-shell polymer particles.
In accordance with the embodiments of the present disclosure, the third predetermined conditions include a temperature in the range of 60 oC to 100 oC and a time period in the range of 100 minutes to 200 minutes. In an exemplary embodiment, the third predetermined conditions include the temperature of 80 oC and the time period of 150 minutes.
In accordance with the embodiments of the present disclosure, the crosslinking agent used in the preparation of the pre-emulsion is Ethylene glycol dimethacrylate in an amount in the range of 5 wt.% to 15 wt.%. In an exemplary embodiment, the amount of Ethylene glycol dimethacrylate is 10.15 wt.%.
The crosslinking agent added during the stage of the preparation of the pre-emulsion stages helps in preventing collapse of voids during the drying of the paint film/composition.
In an exemplary embodiment, the third monomeric system is a mixture of styrene in an amount of 78.41 wt.% with respect to the total weight of the third monomeric system, butyl acrylate in an amount of 1.08 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount of 13.33 wt.% with respect to the total weight of the third monomeric system, glacial methacrylic acid in an amount of 0.41 wt.% with respect to the total weight of the third monomeric system, methacrylamide in an amount of 0.19 wt.% with respect to the total weight of the third monomeric system; the crosslinking agent is ethylene glycol dimethacrylate in an amount of 10.15 wt.%, the second surfactant is sodium dodecyl benzene sulphonate, the plasticizer is a combination of linseed oil fatty acid and dehydrated castor fatty acid, and the third predetermined conditions include the temperature of 80 oC and the time period of 150 minutes.
In accordance with the embodiments of the present disclosure, at least one second biocide, and at least one defoamer are added during the preparation of the pre-emulsion.
In the next step, a predetermined amount of the pre-emulsion and a predetermined amount of the polymeric sheath coated core is mixed and the pre-emulsion is polymerized at fourth predetermined conditions to obtain a crude core-sheath-shell polymer particles; wherein the core of the polymeric sheath coated core is neutralized by adding a base along with the pre-emulsion.
In accordance with the embodiments of the present disclosure, the fourth predetermined conditions include a temperature in the range of 70 to 90 ºC. In an exemplary embodiment, the temperature is 80 ºC.
In accordance with the embodiments of the present disclosure, the base is selected from sodium hydroxide, pottsium hydroxide and ammonia. In an exemplary embodiment, the base is sodium hydroxide.
In accordance with the embodiments of the present disclosure, the pre-emulsion is added to the sheath coated core particles in multiple stages (PE1, PE2 and PE3) to obtain a crude core-sheath-shell polymer particles having multiple shells. In an exemplary embodiment, the pre-emulsion is added in two stages to obtain the crude core-sheath-shell polymer particles having two shells. In another exemplary embodiment, the pre-emusion is added in three stages to obtain the crude core-sheath-shell polymer particles having three shells.
In an embodiment of the present disclosure, the base is added along with PE1 and PE2 (after 40 minutes from completion of the sheath coated core addition).
In another embodiment of the present disclosure, the base is added along with PE3 (after 85 minutes from the addition of PE1 and PE2).
In the next step, a chaser catalyst is added to the crude core-sheath-shell polymer particles at fifth predetermined conditions to obtain the core-sheath-shell polymer particles.
In accordance with the embodiments of the present disclosure, the chaser catalyst is at least one selected from tert-butyl hydroperoxide and sodium sulfoxide. In an exemplary embodiment, the chaser catalyst is a combination of tert-butyl hydroperoxide and sodium sulfoxide.
The chaser catalyst is added to stop the polymerization reaction by arresting the free unreacted monomers.
In accordance with the embodiments of the present disclosure, the fifth predetermined conditions include a temperature in the range of 80 oC to 90 oC for a time period in the range of 30 to 90 minutes. In an exemplary embodiment, the fifth predetermined conditions include the temperature of 85 oC for the time period of 60 minutes.
In accordance with the embodiments of the present disclosure, the sheath and the shell of the core-sheath-shell particles are permeable to the alkaline solutions.
In accordance with the embodiments of the present disclosure, the polymeric shell is hydrophobic in nature.
When the core-sheath-shell polymer particles are treated with the alkaline solution, the carboxylic acid functionalized core of the core-sheath-shell polymer particles are neutralized by the alkali which leads to the production of water in the core leading to the swelling of the core which can lead to the expansion of the core. The expansion of core particles can lead to the partial merging of outer periphery of the core with the inner periphery of sheath. Further, the enlargement of the sheath leads to the enlargement of the overall particles.
During the drying process of the paint composition/film containing swollen core-sheath-shell, the water in the core of this core-sheath-shell particles diffuses through the polymer shell and leaves an air void. Because of the difference in the refractive index between air and surrounding polymer, light is effectively scattered, contributing to film opacity. The void within the core-sheath-shell particles not only provides useful spacious compartments but also unique light scattering properties.
In another aspect, the present disclosure provides core-sheath-shell polymer particles. The core-sheath-shell polymer particles.comprises a) polymeric core in the form of latex, b) a polymeric sheath layer coated on the core, and c) at least one polymeric shell layer coated on the polymeric sheath.
In accordance with the embodiments of the present disclosure, the polymeric core is prepared by using a first monomeric system.
In accordance with the embodiments of the present disclosure, the first monomeric system is a mixture of butyl acrylate in an amount in the range 5 wt.% to 10 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount in the range of 55 wt.% to 65 wt.% with respect to the total weight of the first monomeric system and glacial methacrylic acid in an amount in the range of 25 wt.% to 30 wt.% with respect to the total weight of the first monomeric system. In an exemplary embodiment, the first monomeric system is a mixture of butyl acrylate in an amount of 8.81 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount of 65.20 wt.% with respect to the total weight of the first monomeric system, and glacial methacrylic acid in an amount of 30.15 wt.% with respect to the total weight of the first monomeric system.
In accordance with the embodiments of the present disclosure, the polymeric sheath layer is a polymer prepared by using a second monomeric system.
In accordance with the embodiments of the present disclosure, the second monomeric system is a mixture of methyl methacrylate in an amount in the range of 80 wt.% to 90 wt.% with respect to the total weight of the second monomeric system, butyl acrylate in an amount in the range of 5 wt.% to 10 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system, and methacryalamide in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system. In an exemplary embodiment, the second monomeric system is a mixture of butyl acrylate in an amount of 7.22 wt.% with respect to the total weight of the second monomeric system, methyl methacrylate in an amount of 88.75 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount of 2.74 wt.% with respect to the total weight of the second monomeric system and methacrylamide in an amount of 1.26 wt.% with respect to the total weight of the second monomeric system.
In accordance with the embodiments of the present disclosure, the polymeric shell layer is a polymer prepared by using a third monomeric system.
In accordance with the embodiments of the present disclosure, the third monomeric system is the third monomeric system is a mixture of styrene in an amount in the range of 70 wt.% to 80 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount in the range of 10 wt.% to 20 wt.% with respect to the total weight of the third monomeric system, butyl acrylate in amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the third monomeric system, glacial methacrylic acid in an amount in the range of 0.1 wt.% to 0.5 wt.% with respect to the total weight of the third monomeric system and methacrylamide in an amount in the range of 0.15 wt.% to 0.25 wt.% with respect to the total weight of the third monomeric system. In an exemplary embodiment, the third monomeric system is mixture of styrene in an amount of 78.41 wt.% with respect to the total weight of the third monomeric system, butyl acrylate in an amount of 1.08 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount of 13.33 wt.% with respect to the total weight of the third monomeric system, glacial methacrylic acid in an amount of 0.41 wt.% with respect to the total weight of the third monomeric system, and methacrylamide in an amount of 0.19 wt.% with respect to the total weight of the third monomeric system.
In accordance with the embodiments of the present disclosire, the core-sheath-shell polymer particles are characterized by having a ratio of a mass of the core to the total mass of sheath and shell in the range of 1:5 to 1:25 and the amount of a crosslinker is in the range of 0.15 wt.% to 0.45 wt.% wherein the crosslinking agent is ethylene glycol dimethacrylate ; and the size of the core-sheath-shell polymer particles is in the range of 350 nm to 700 nm. In an exemplary embodiment, the size of the core-sheath-shell polymer particles is 450 nm. In another exemplary embodiment, the size of the core-sheath-shell polymer particles is 660 nm.
In accordance with the embodiments of the present disclosure, the sheath and the shell of the core-sheath-shell particles are permeable to the alkaline solutions.
In accordance with the embodiments of the present disclosure, the polymeric shell is hydrophobic in nature.
The structural factors such as composition and core shell ratio and network structures are critical to obtain a stable hollow morphology.
During the drying process of the paint composition/film containing swollen core-sheath-shell, the water in the core of this core-sheath-shell particles diffuses through the polymer shell and leaves an air void. Because of the difference in the refractive index between air and surrounding polymer, light is effectively scattered, contributing to the composition/ film opacity. The void within the core-sheath-shell particles not only provides useful spacious compartments but also unique light scattering properties.
The core-sheath-shell particles of the present disclosure can be used to replace titanium oxide from the coating composition. Replacement of TiO2 by the particles of the present disclosure will lead to reduction in energy intensive manufacturing process required to produce TiO2.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
EXPERIMENTAL DETAILS
Experiment 1: Process for preparing core-sheath-shell polymer particles in accordance of the present disclosure:
The process for the preparation of core-shell polymer particles comprises the following steps:
Example 1:
Step (i): Synthesis of the core of the core-sheath-shell polymer particles in the form of latex: In a reactor, demineralized water as a solvent in an amount as shown in table 1 and fatty alcohol ethoxylate (having 30 moles of ethoxylation) and sodium dodecyl benzene sulphonate as surfactants in an amount as shown in table 1 were charged and heated to 70 °C. Further, a first monomeric system and ethylene glycol dimethyacrylic acid in an amount shown in the table 1 were charged to the reactor over 10 min and heated to 80 °C. Potassium persulphate (initiator) solution in an amount as shown in table 1 was charged over 10 min to obtain a mixture and the mixture was maintained at 80 °C for 40 min. Another dosage of Potassium persulphate (initiator) solution in an amount as shown in table 1 was charged after 40 minutes to obtain a reaction mixture. Further, the temperature of the reaction mixture was maintained at 80 °C and then cooled below 45 °C. Finally, CMIT based biocide was added to obtain a resultant mixture. Finally the resultant mixture was filtered to obtain the core in the form of latex.
Table 1: Names and amount of the ingradients used for the preparation of the core of core-sheath-shell particles.

Ingredients Example 1-a
Potassium persulphate initiator solution 0.02
Non-ionic Surfactant (alcohol ethoxylate ) 0.045
Butyl Acrylate 2.666
Dimeneralized Water 67.976
Anionic surfactant (Sodium dodecyl benzene sulphonate) 0.193
Ethylene glycol dimethyacrylic acid crosslinker 0.1
CMIT based biocide
(Chloromethylisothiazolinone) 0.1
Methyl methacrylate (MMA) 19.678
Glacial Methacrylic acid 9.102
Potassium persulphate initiator solution 0.12
Total 100

Step (ii): Preparation of a sheath coated core: To the core latex prepared in step (i), 10 ml of potassium per sulphate solution was added. Further, the second monomeric system as shown in Table 2 was added to the mixture of the core latex and the initiator solution over a period of 90 minutes to obtain a reaction mixture. Next, the reaction mixture was maintained at 80 °C for 40 minto obtain sheath coated core particles.
Table 2: Composition of the second monomeric system used for the preparation of the sheath coated core particles.
Ingredients Amount
Butyl Acrylate 0.342 g
Methyl Methacrylate 4.200 g
Methacrylic Acid 0.130 g
Meth acrylamide 0.06 g

Step (iii): Preparation of a pre-emulsion: The pre-emulsion was seaparately prepared by mixing a third monomeric system with at least one second surfactant, at least one crosslinking agent, at least one plasticizer and at least one phase separating diluent at 80°C for 150 minutes. The specific components/ingredinets and amounts are given in Table 3 below:
Table 3: Names and amount of the ingredients used for the preparation of the pre-emulsion
Ingredients Parts by weight
Methacrylamide 0.06
Butyl Acrylate 0.342
Styrene 24.7
Redox initiator 1 (tertiary butyl hydroperoxide) 0.02
Redox initiator 2 (sodium formaldehyde sulfoxylate) 0.02
Demineralized water(Sodium dodecyl benzene sulphonate) 62.519
Iso-octane 0.6
Anionic surfactant 0.125
Ethylene glycol dimethacrylate (EGDMA) crosslinker 0.32
CMIT based biocide
(Chloromethylisothiazolinone) 0.1
Methyl methacrylate (MMA) Monomer 4.2
Glacial Methacrylic acid 0.13
Defoamer 0.02
Potassium persulphate 0.19
Linseed Oil Fatty acid (LOFA) 0-0.5

Step (iv): 5 g of pre-mulsion was added to 5 g of polymeric sheath coated core, followed by polymerizing the pre-emulsion at 80°C to obtain a crude core-sheath-shell polymer particles. 4 mL of 10% NaOH solution was added to the reactor along with addition of pre-emulsion while forming crude core-sheath-shell polymer particles to neutralize the core.
Step (v): 0.04 g of mixture of tert-butyl hydroperoxide and sodium sulfoxide as a chaser catalyst was added to the crude core-sheath-shell polymer particles at 80 °C for 60 minutes to obtain the core-sheath-shell polymer particles.
Example 2-4: The Core-sheath-shell polymer particles were prepared by following the same procedure as in example 1 except that in step (iv), the pre-emulsion was added to the sheath coated core particles in multiple stages (PE1, PE2 and PE3) to obtain the crude core-sheath-shell polymer particles having multiple shells as given in table 4.
In Example 2, NaOH was added along with PE3 (after 85 minutes from the addition of PE1 and PE2) and in Examples 3-4, NaOH was added along with PE1 and PE2 (after 40 minutes from completion of the sheath coated core addition).
Moreover the components and their amounts present in the pre-emulsion were varied and these pre-emulsion with varied amounts of the ingredients (along with the ingredients present in table 3), were further used for addition in multiple stages to obtain the core-sheath-shell polymer particles.
Table 4 represents four examples having three different pre-emulsion compositions with varying quantities of EGDMA, iso-octane and LOFA.
Table 4: Preparation of the pre-emulsion that was added in three stages (PE1, PE2 and PE3)
Example 1 (R 5905)
PE1 PE2 PE3
EGDMA 0.16 0.16 0
ISO-OCTANE 0.12 0.24 0.24
LOFA 0 0 0

Example 2 (VSC 15)
PE1 PE2 PE3
EGDMA 0.16 0.16 0
ISO-OCTANE 0 0 0
LOFA 0 0.5 0


Example 3 (VSC 18)
PE1 PE2 PE3
EGDMA 0.16 0.16 0
ISO-OCTANE 0.12 0.24 0.24
LOFA 0.1 0.1 0

Example 4 (VSC 34)
PE1 PE2 PE3
EGDMA 0 0 0.3
ISO-OCTANE 0.12 0.24 0.24
LOFA 0.1 0.1 0
* PE1- pre-emulsion added in first stage; PE2- pre-emulsion added in second stage; PE3- pre-emulsion added in third stage
In example 1, ammonia was used as a base to neutralize the core and in examples 2-4, sodium hydroxide was used to neutralize the core.
The core-sheath-shell polymer particles of Example 1 has a particle size of 660 nm and the core-sheath-shell polymer particles of examples 2-4 has a particle size of 450 nm.
Experiment 2: Preparation of the paint composition by using the core-sheath-shell polymer particles prepared in Experiment 1 (Examples 1 to 4)
Paint compositions 1A-4A): Four paint compositions (1A-4A) were prepared by using the core-sheath-shell polymer particles prepared in Examples 1-4 respectively and the paint properties were studied as given in Table 5.
Table 5: Paint properties
Paint composition 1A
(R 5905) 2A
(VSC 15) 3A
(VSC 18) 4A
(VSC 34)
Neutralizer Liquor Ammonia NaOH NaOH NaOH
% NVM 31.77 31.42 31.50 31.22
Emulsion Viscosity (gms) 77 55 56 60
pH 8.5 6.9 7.0 6.9
Film appearance Smooth Smooth Smooth Smooth
Opacity against STD Batch Std Close to std Close to std Close to Std
Opacity against STD Batch
(after oven stability 50ºC) Std Better than Std Better than std Better than std
% Reducing Strength 100 97 97 98
% Reducing Strength *
(after oven stability 50ºC) 100 104 105 110
From Table 5, it is observed that % reducing strength values of paint compositions 2A-4A are less than that of paint composition 1A, which indicates that the color shades of the paint compositions 2A-4A are darker than that of paint composition 1A. Further, % reducing strength values after oven stability (at 50 ºC) of paint compositions 2A-4A are greater than that of paint composition 1A, which indicates that the color shades of the paint compositions 2A-4A are lighter than that of paint composition 1A.
It can be confirmed from above that, inspite of applying heat to the core-sheath particles upto 50 ºC, the core was much more stable from collapsing and it maintained its void structure. This was evident from the fact that shade had not darkened after oven stability test at 50 ºC. This is due to the fact that isooctane plays an important role by acting as a solvent for the monomeric system and a non-solvent for polymeric system, and LOFA acted as a plasticizer by making the layers soft, for efficient penenetration of alkali inside the core for neutralization and further water absorption in subsequent stages.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of,
? core-sheath-shell polymer particles that is stable and robust; and
? a simple process for the preparation of core-sheath-shell polymer particles.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising, will be understood to imply the inclusion of a stated element, integer or step,” or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

,CLAIMS:WE CLAIM:
1) A process for the preparation of core-sheath-shell polymer particles, said process comprising the following steps:
i) polymerizing at least one first monomeric system in a first solvent by using at least one first surfactant in the presence of at least one first initiator and a crosslinking agent at a first predetermined conditions to obtain a core in the form of latex;
ii) mixing at least one second initiator in said core followed by adding at least one second monomeric system to obtain a mixture; and polymerizing said second monomeric system on to the core in the presence of the second initiator from the mixture at a second predetermined conditions to obtain a polymeric sheath coated core;
iii) separately, mixing at least one third monomeric system, at least one crosslinking agent, at least one second surfactant, at least one plasticizer, at least one redox initiator and at least one phase separating diluent at third predetermined conditions to obtain a pre-emulsion;
iv) mixing a predetermined amount of the pre-emulsion and a predetermined amount of the polymeric sheath coated core and polymerizing the pre-emulsion at fourth predetermined conditions to obtain a crude core-sheath-shell polymer particles;
wherein the core of said polymeric sheath coated core is neutralized by adding a base along with said pre-emulsion;
v) adding at least one chaser catalyst to the crude core-sheath-shell polymer particles at fifth predetermined conditions to obtain the core-sheath-shell polymer particles;
wherein the first monomeric system comprises a monomer having a carboxylic acid functionality;
wherein the first monomeric system and the second monomeric system comprises at least one hydrophilic monomer, wherein said hydrophilic monomer is at least one selected from glacial methacrylic acid, methacrylic acid and methacrylamide and;
wherein the crosslinking agent in step i) and step iii) is ethylene glycol dimethacrylate.
2) The process as claimed in claim 1, wherein in step iv), the pre-emulsion is added to the sheath coated core particles in multiple stages to obtain a crude core-sheath-shell polymer particles having multiple shells.
3) The process as claimed in claim 1, wherein the first monomeric system comprises at least one monomer selected from methyl methacrylate, butyl acrylate, glacial methacrylic acid; and wherein the first solvent is water, the first surfactant is selected from an anionic surfactant and a non-ionic surfactant, the first initiator is selected from potassium per-sulphate and ammonium per-sulphate and the first pre-determined conditions include a temperature in the range of 60 oC to 100 oC and a time period in the range of 70 minutes to 150 minutes.
4) The process as claimed in claims 1 and 3, wherein the first monomeric system is a mixture of butyl acrylate in an amount in the range 5 wt.% to 10 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount in the range of 55 wt.% to 65 wt.% with respect to the total weight of the first monomeric system and glacial methacrylic acid in an amount in the range of 25 wt.% to 30 wt.% with respect to the total weight of the first monomeric system.
5) The process as claimed in claim 1, wherein the first initiator is gradually introduced in two stages.
6) The process as claimed in claim 1, wherein the second monomeric system comprises at least one monomer selected from butyl acrylate, methyl methacrylate, methacrylic acid and methacrylamide; wherein the second initiator is selected from potassium per-sulphate and ammonium per-sulphate; and wherein second predetermined conditions include a temperature in the range of 60 oC to 100 oC, and a time period in the range of 60 minutes to 120 minutes;
wherein the second monomeric system is gradually added to the core in step i) over a period in the range of 130 minutes to 170 minutes.
7) The process as claimed in claims 1 and 6, wherein the second monomeric system is a mixture of methyl methacrylate in an amount in the range of 80 wt.% to 90 wt.% with respect to the total weight of the second monomeric system, butyl acrylate in an amount in the range of 5 wt.% to 10 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system, and methacryalamide in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system.
8) The process as claimed in claim 1, wherein the third monomeric system comprises at least one monomer selected from styrene, butyl acrylate, methyl methacrylate, and glacial methacrylic acid;wherein the second surfactant is selected from an anionic surfactant and a non-ionic surfactant; wherein the plasticizer is selected from linseed oil fatty acid and dehydrated castor fatty acid; wherein the phase separating diluent is iso-octane; wherein the redox initiator is selected from tertiary butyl hydroperoxide and sodium formaldehyde sulfoxylate; and wherein the third predetermined conditions include a temperature in the range of 60 oC to 100 oC and a time period in the range of 100 minutes to 200 minutes.
9) The process as claimed in claims 1and 7, wherein the third monomeric system is a mixture of styrene in an amount in the range of 70 wt.% to 80 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount in the range of 10 wt.% to 20 wt.% with respect to the total weight of said third monomeric system, butyl acrylate in amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the third monomeric system, glacial methacrylic acid in an amount in the range of 0.1 wt.% to 0.5 wt.% with respect to the total weight of the third monomeric system and methacrylamide in an amount in the range of 0.15 wt.% to 0.25 wt% with respect to the total weight of the third monomeric system.
10) The process as claimed in claim 1, wherein the ethylene glycol dimethacrylate in step i) is in an amount in the range of 0.1 wt.% to 0.5 wt.% with respect to the total weight of the first monomeric system, and wherein the ethylene glycol dimethacrylate in step iii) is in an amount in the range of 5 wt.% to 15 wt.% with respect to the total weight of the third monomeric system.
11) The process as claimed in claim 1, wherein the fourth predetermined conditions include a temperature in the range of 70 oC to 90 oC.
12) The process as claimed in claim 1, wherein the chaser catalyst is selected from tert-butyl hydroperoxide and sodium sulfoxide; wherein the base is selected from sodium hydroxide and ammonia; and wherein the fifth predetermined conditions include a temperature in the range of of 80 oC to 90 oC for a time period in the range of 30 minutes to 90 minutes.
13) Core-sheath-shell polymer particles comprises:
a) a polymeric core in the form of latex;
b) a polymeric sheath layer coated on the core;
c) at least one polymeric shell layer coated on the polymeric sheath;
wherein said core-sheath-shell polymer particles are characterized by having:
• a ratio of a mass of the core to the total mass of sheath and shell is in the range of 1:5 to 1:25;
• the amount of a crosslinker is in the range of 0.15 wt.% to 0.45 wt.%, wherein said crosslinker is ethylene glycol dimethacrylate ; and
• the size of the core-sheath-shell polymer particles is in the range of 350 nm to 700 nm.
14) The core-sheath-shell polymer particles as claimed in claim 13, wherein the polymeric core is prepared by using a first monomeric system, wherein the first monomeric system is a mixture of butyl acrylate in an amount in the range 5 wt.% to 10 wt.% with respect to the total weight of the first monomeric system, methyl methacrylate in an amount in the range of 55 wt.% to 65 wt.% with respect to the total weight of the first monomeric system and glacial methacrylic acid in an amount in the range of 25 wt.% to 30 wt.% with respect to the total weight of the first monomeric system.
15) The core-sheath-shell polymer particles as claimed in claim 13, wherein the polymeric sheath layer is a polymer prepared by using a second monomeric system, wherein the second monomeric system is a mixture of methyl methacrylate in an amount in the range of 80 wt.% to 90 wt.% with respect to the total weight of the second monomeric system, butyl acrylate in an amount in the range of 5 wt.% to 10 wt.% with respect to the total weight of the second monomeric system, methacrylic acid in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system, and methacryalamide in an amount in the range of 1 wt.% to 5 wt.% with respect to the total weight of the second monomeric system.
16) The core-sheath-shell polymer particles as claimed in claim 13, wherein the polymeric shell layer is a polymer prepared by using a third monomeric system, wherein the third monomeric system is a mixture of styrene in an amount in the range of 70 wt.% to 80 wt.% with respect to the total weight of the third monomeric system, methyl methacrylate in an amount in the range of 10 wt.% to 20 wt.% with respect to the total weight of the third monomeric system, butyl acrylate in weight in the range of 1 wt.% to 5 wt.% with respect to the total total weight of the third monomeric system, glacial methacrylic acid in an amount in the range of 0.1 wt.% to 0.5 wt.% with respect to the total weight of the third monomeric system, and methacrylamide in an amount in the range of 0.15 wt.% to 0.25 wt% with respect of the total weight of the third monomeric system.

Dated this 01st day of June, 2021

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant