WO2021245702A1

WO2021245702A1 - An anti-microbial object and a process for manufacturing the same

Info

Publication number: WO2021245702A1
Application number: PCT/IN2021/050540
Authority: WO
Inventors: Dr Suvam Nag CHOWDHURY; Ashish Singh; Vinayak RAJE
Original assignee: Bajaj Electricals Ltd.
Priority date: 2020-06-04
Filing date: 2021-06-03
Publication date: 2021-12-09

Abstract

The present invention relates to an anti-microbial object and a process to make the same. Wherein, the article is made by coating at least 2 layers over a substrate, each layer containing silver particles physically distributed in between thermal cross-linked structure of resin coating the individual layers. The process includes mixing the silver particles with a polymer coat or a ceramic coat, impregnating the coats and imbibing antimicrobial qualities in each coat. The coats are then sequentially layered over the substrate using industrially acceptable coating techniques such a spray coating, PTFE coatings, Ceramic coatings, PEEK based polymer technology and sol-gel technology. The resultant objects made using this invention display antimicrobial activities of >99%.

Description

AN ANTI-MICROBIAL OBJECT AND A PROCESS FOR

MANUFACTURING THE SAME

FIELD OF THE INVENTION:

The present invention relates to an anti-microbial object. Particularly, the present invention relates to an antimicrobial object for home or commercial use having multiple coating layers impregnated with silver particles.

BACKGROUND OF I I II INVENTION:

Microbes are persistently present in the environment, when such microbes come in contact with mediums such as moisture and nutrients, they proliferate. If such favorable medium is found on kitchen articles, kitchen counters or cupboards, the microbes will thrive on such articles. Moreover, if the microbes are ingested by people using such articles for cooking or such other purposes, the person is likely to be infected resulting from minor to sever illnesses.

Unwashed kitchen articles can spread the microbes even to the clean washed kitchen articles or other uncontaminated surfaces that they come in contact with, thereby spreading the contamination. The microbes can pose a serious threat to health, produce malodors, cause discoloration of surfaces and objects, cause biofouling or produce mildew, inter alia.

The risk to health has become of utmost importance especially with recent scenarios such as a pandemic. Hygiene in the kitchen has become crucially necessary for not only industrial kitchens, hotels, restaurants, eateries and cafes, to maintain standards, but even in regular households with the scare of illnesses that are brought by microorganisms that thrive on unwashed kitchen articles, kitchen counters, gas stoves, unwashed walls, floors or such other areas and articles where traces of food or such medium that encourage microbial growth. An additional aspect of concern is while storing food in containers. Many believe that as long as food is stored in refrigerators there is not much to worry about. However, even in the refrigerators food products have a limited life span and most people especially in a regular household are unaware of the exact life span of such food products. Moreover, most people may not be able to identify a decaying food article unless the decay is fairly visible orodorous.

Focusing on heath and quality of life have become greatly important. While cleaning kitchen areas and articles may be performed regularly, there is always that negligence or mishap which can cost a human life.

The Turkey patent TR200909729U discloses cooking kitchen articles having antimicrobial effect prepared using silver nitrate and powdered paint mixture using screen printing method of the cooking surface of cookware.

Another, Chinese patent CN208799031U discloses a kitchen appliance, which relates to a kind of titanium alloy pot with antimicrobial effect.

There has been significant research in the field of anti-microbial cookware, home appliances, and the like. However, most of these simply include objects that have superficial antimicrobial surfaces. Therefore, as the object wears out with multiple usage the anti-microbial surface too wears out. Further, these inventions are restricted to cookware alone.

There is no object used in kitchens, homes, etc. that is antimicrobial at each layer. Moreover, there is no object that has anti-microbial qualities while allowing versatile forms such as ceramic, non-stick etc. and versatile applications such as home appliances, kitchen articles, kitchen material etc.

Therefore, there is a need to overcome at least one of the problems stated above. SUMMARY OF THE INVENTION

An aspect of the present invention provides an anti-microbial object for homes and kitchens. Wherein, the object is coated with at least a primer and top coat and optionally one or more middle layer(s). Each layer containing silver particles physically distributed in between thermal cross-linked structure of the resin present in the individual layers

An aspect of the present invention provides a process of layer by layer coating for anti-microbial object for home use comprising at least the following steps:

Subjecting the substrate to chemical treatment using industrially accepted techniques;

Physically blending Silver particles with the coating materials selected from but not limited to binder resin, PTFE resin, reinforcing agent, pigment(s), filler(s), sol solution, or combinations thereof;

Coating the impregnated layer(s) over the substrate;

Curing after application of each layer to establish thermal cross-linking of resin and thereby physical fixation of silver particles to the cross-linked resin.

BRIEF DECRIPTION OF DRAINGS:

Figure 1: shows an example of the ceramic coating of the present invention.

Figure 2: shows an example of the PTFE coating of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Various aspects of the present invention relate to an anti-microbial object for home use. Wherein, the object includes at least a substrate coated with a silver impregnated coating selected from but not limited to a Ceramic coating or a polymeric coating, wherein the silver particles present in the range of 0.1-1.0%, are physically distributed in between thermal cross-linked structure of the resin present in the individual layers.

In an embodiment of the present invention the substrate may be of a material selected from but not limited to Aluminum, Stainless Steel, iron, copper, brass, melamine plastic, stone, rubber, glassor a combination thereof. In an embodiment of the present invention the antimicrobial object includes at least a substrate coated with multiple layers of silver impregnated polymeric coat including at least a primer layer, at least one middle layer and a top coat; and wherein the primer layer forms a coating over the substrate, at least one middle layer is coated over the primer layer while the top coat is layered as the last coat.

Wherein the polymeric coat includes at least a primer layer including at least a heat resistant polymeric binder resin, reinforcing agent, 0.1-1.0% of silver particles; and wherein such heat resistant polymeric binder resin is selected from but not limited to PAI (Poly Amide Imide), PES (Polyether Sulphone), PPS (PolyPhenylene Sulfide), PTFE (polytetrafluoroethylene), or combinations thereof;

In an embodiment of the present invention, the binder resin is selected based on the substrate selected. The binder resin enhances adhesion between Metal substrate and Primer layer while the reinforcing agent strengthens the adhesion between the primer layer and the substrate and enhances the wear resistance of the coating. Wherein the middle layer and top coat include at least a PTFE (polytetrafluoroethylene) resin; at least one Pigment selected from but not limited to a glossy pigment, opaque pigment, matt pigment, inter alia; and 0.1-1.0% of silver particles

In a further embodiment of the present invention, the middle layer maybe selected from but not limited to a Ceramic coating, PTFE coating, PEEK, fluorocarbon solid, polymer based layer, colored Pigments, or a combination thereof.

In a further embodiment of the present invention, the top coat maybe selected from but not limited to Ceramic coating, PTFE coating, PEEK, special pigments such as glossy or matt pigments. The top coat enhances better Non-Stick Characteristics when blended with fluoropolymers (Non-stick prop)

In an embodiment of the present invention, the object consists of at least a substrate coated with a silver impregnated ceramic coat including at least a sol solution which is a colloidal disperse solution, containing alcohol, water, hydrolysis products of metal alkoxides having formula M(OR)4, where M is Si, Al, Ti or Zr or combination thereof; at least an inorganic pigment; at least a silicone component; 0.1-1.0% of silver particles; the metal alkoxides are hydrolyzed and form a gel solution which hardens into a glassy ceramic inorganic hard film on curing.

In an embodiment of the present invention, the object may be selected from but not limited to at least pan, pot, cooker, wok, skillet, bakeware, strainer, steamer, lid, screen, simmer ring, handle, stove, oven, microwave, mixer, grinder, cutter, kitchen counter, kitchen walls, iron for clothes, a paint, or any other kitchen articles, home appliance or parts thereof that are made of ceramic, metal, plastic, melamine or any type of polymeric material.

Another embodiment of the present invention, discloses a process for making an antimicrobial object characterized in that the process includes a layer by layer coating process comprising at least the following steps:

1. Subjecting a substrate to chemical treatment using industrially accepted techniques, wherein the substrate may be selected from but not limited to Aluminum, Stainless steel, MS, glass inter alia;

2.Physically blending Silver particles with a coating material selected from but not limited to a ceramic coat and a polymer coat to form an impregnated coat containing 0.1- 1.0% of silver particles;

3. Coating the impregnated coat over the substrate one layer at a time;

4. Curing after application of each layer to establish thermal crosslinking of resin and thereby physical fixation of silver particles to the cross-linked resin.

Wherein, the impregnated coat, specifically the impregnated polymer coat is layered by coating the substrate with a primary layer as the first layer, a top coat as the last layer and optionally coating the middle layer(s) over the primary layer prior to applying the top coat at least a primer and top coat, each layer containing silver particles physically distributed in between thermal cross-linked structure of resin contained in the individual layers In an embodiment of the present invention, the thermal crosslink is performed at 400°C for 10 mins for antimicrobial polymeric coat and at 220°C for 20 mins for ceramic coat.

In an embodiment of the present invention, the impregnated coating materials are layered over the substrate using process selected from but not limited to PTFE coatings, Ceramic coatings, PEEK based polymer technology and sol-gel technology, or such other industrially acceptable technology.

An embodiment of the present invention provides an anti- bacterial object. Wherein, the object is coated with at least a primer, at least one middle layer, and a top coat, each layer containing silver particles physically distributed in between thermal cross-linked structure of resin coating the individual layers.

In an embodiment of the present invention, Silver particulate is physically dispersed in between the thermal cross-linked structure of Resin without any chemical bonding.

Another embodiment of the present invention provides an anti-microbial substance. Wherein, the substance is a polymer based liquid containing pigments, impregnated with silver particles. The substance may include paints of various kinds containing silver particles in the range of 0.1 to 1.0%.

The physically dispersed silver particles of the present invention have a particle size preferably, but not limited to D98<40 pm and tapped density in the range of 0.1 - 1.0.

In an embodiment of the present invention, the silver particles are preferably used in the form of powder. The silver particles are directly added in the formulation of primer layer, middle layer and top coat in the range of 0.1 to 1.0% based on the level of antimicrobial properties required.

In yet another embodiment of the present invention provides a process of layer by layer coating for an anti-microbial object containing at least two layers including a primary layer and a top coat, the process comprising at least the following steps: Chemical Treatment:

Subjecting the substrate to chemical treatment using industrially accepted techniques, wherein the substrate may be selected from but not limited to Aluminum, Stainless steel, MS, iron, copper, brass, melamine plastic, stone, rubber, glassinter alia.

Physical Blending & Impregnation:

Physically blending Silver particles with resin and component Y;

Wherein:

The resin is a binder resin in case of a primer layer and a PTFE resin in case of a Middle layer or Top coat; and the Component Y is at least a reinforcing agent in case of a primer layer, at least a pigment in case of a middle layer and at least a special pigment in case of a top coat.

The reinforcing agent may be selected from but not limited to Carbon Blacks, Metal oxide, ceramic particles, Aluminum Flakes, Extenders Resin inter alia.

The resin may be selected from but not limited to Blended Fluoropolymer/ PTFE

The composition may further include a carrier selected from but not limited to water or a solvent

Physically blending Silver particles with resin and component Y to prepare impregnated coating layers namely Primary layer, Top coat and optionally one or more Middle layer(s), for polymeric coating;

Alternatively, the Silver particles are blended with a sol solution, which is a colloidal disperse solution, containing alcohol, water, hydrolysis products of metal alkoxides [M(OR)₄, where M = Si, Al, Ti, Zr for ceramic coating;

Coating:

• Coating the impregnated layers sequentially while coating the primer layer directly over the substrate and the top coat as the last layer, and optionally coating the middle layer(s) over the primary layer prior to applying the top coat for a polymeric coating. Wherein the coating techniques include industrially acceptable techniques selected from but not limited to PTFE coating, ceramic coating, sol/gel coating and spray coating, inter alia;

Curing:

• Thermal crosslink of said resin is performed after each layer is coated;

• Thermal crosslink is performed at 400°C for 10 mins for polymeric coating and at 220°C for 20 mins for sol-gel technology

• The crosslink of said resin acts as a net fixing the silver particles within the crosslinks.

In an embodiment of the present invention, the Silver particles are blended into the process of sol-gel wherein a colloidal disperse solution, containing alcohol, water, hydrolysis products of metal alkoxides [M(OR)4, with M = Si, Al, Ti, Zr], inorganic pigments and silicone components, that results by further hydrolysis and condensation reaction in an intermediate gel and finally in a glassy ceramic inorganic hard film. This results in an impregnated glassy ceramic inorganic hard film which is antimicrobial in nature. The impregnated glassy film can be deposited on a substrate material selected from but not limited to Aluminum, Stainless Steel, anodized surface inter alia,

After each layering, the coat undergoes curing at 400°C for lOmin for antimicrobial polymeric coating and at 220°C for 20 mins for sol-gel coating.

The physical mixing of silver particles with the resin, polymer and/or ceramic medium helps to increase efficiency of the microbial activity. The physical mixing enables the silver particles to be distributed in between thermal cross-linked structure of resin without any requirement of chemical bonding between silver and the resin.

In an embodiment of the present invention, the impregnated coat may be deposited on surfaces including but not limited to Aluminum, steel, other metallic or polymeric surfaces, inter alia. Figure 1 of the present invention shows an example of the ceramic coating wherein, substrate A is coated with first primer layer B and then top layer C. The primer layer B is sandwiched between the top coat layer C and the substrateA.

Figure 2 of the present invention shows an example of the PTFE coating wherein, a total of 3 layers are coated over the substrate A; the first layer is primer layer B, second is mid coat layer C and the top coat layer D.

WORKING EXAMPLES Example 1

The antimicrobial ceramic pan was prepared by physically mixing 1.0% Silver particles with a colloidal disperse solution containing alcohol, water, hydrolysis products of metal alkoxides [M(OR)4, with M = Si, Al, Ti, Zr], inorganic pigments and silicone components;

After further hydrolysis and condensation reaction an intermediate gel was formed which finally hardened into a glassy ceramic inorganic hard film impregnated with silver particles.

The impregnated glassy ceramic film was coated as a primer layer over Aluminum as substrate;

The ceramic layer was cured at 240°C for 20 mins

The resultant article displayed 99.3% antimicrobial activity.

Example 2

The antimicrobial non-stick tawa was prepared by mixing 0.17% Silver particles with PAI binder resin and carbon black to form a primer layer;

The primer layer was coated over the aluminum substrate body of the tawa;

The impregnated primer layer coated tawa was cured at 400 °C for 10 mins The impregnated primer layer is cured at 400 °C for 10 mins

0.3% Silver particles were mixed with PTFE and opaque pigments to form an impregnated middle layer;

The middle layer was coated over the of primer layer

The impregnated middle coat layered tawa was cured at 400 °C for 10 mins

0.5% Silver particles were mixed with PTFE and glossy pigments to form an impregnated top coat; The impregnated top coat waslayered over the middle coat and cured at 400 °C for 10 mins The resultant non-stick tawa displayed 99% antimicrobial activity through all its layers.

Example 3

The antimicrobial gas stove was prepared by forming a primary mix containing 0.2% Silver particles with PES binder resin and ceramic particles as reinforcing agent to form a primer layer; The primer layer was coated over the stainless steel body of the gas stove;

The impregnated primer layer coated object was cured at 400 °C for 10 mins

0.7% Silver particles were mixed with PTFE and glossy pigments to form an impregnated top coat;

The impregnated top coat was layered over the primary coat;

The impregnated top coat layered gas stove body was cured at 400 °C for 10 mins The resultant antimicrobial gas stove displayed 99% antimicrobial activity.

UTILITY

1. Silver dispersed Polymer and/or ceramic coated articles made using the present invention have at least >99% antimicrobial activity.

2. The present invention not only reduces the microbial count, but also inhibits further growth.

3. Enables malodor resistance in articles made using the present invention

4. Prevents spreading of bacteria on kitchen articles and thereby maintains a safe and healthy environment.

5. Microbial growth control in unwashed kitchen articles s, kitchen articles etc.

Experimental data:

Various combinations of the compositions as mentioned in the aforesaid embodiments were evaluated for the preparation of anti-microbial objects. The experiments were carried out to quantitatively assess the activity for Staphylococcus aureus and Escherichia coli by JIS Z 2801:2010 test method.

Test Conditions:

Neutralizer used: Buffered Saline with Tween 80-0.01% Contact Time: 24 hours at 37°C

Incubation Temperature: 37°C for Bacteria

Media and Reagent: Soyabean-caes in digest agar for Bacteria

Antimicrobial Activity The Standard Antimicrobial value of Evaluation R>2.0

1. Test Bacteria: Staphylococcus aureus ATCC 6538

2. Test Bacteria: Escherichia coli ATCC 8739

3. Test Bacteria: Staphylococcus aureus ATCC 6538

4. Test Bacteria: Escherichia coli ATCC 8739

Claims

Claims:

[CLAIM 1] An antimicrobial object characterized in that, said object includes at least a substrate coated with a silver impregnated coating selected from but not limited to a ceramic coating or a polymeric coating, wherein the silver particles present in the range of 0.1-1.0%, are physically distributed in between thermal cross-linked structure of the resin present in the individual layers.

[CLAIM 2] The antimicrobial object as claimed in claim 1, wherein said object includes at least a substrate coated with multiple layers of silver impregnated polymeric coat including at least a primer layer, at least one middle layer and a top coat; and wherein the primer layer forms a coating over the substrate, at least one middle layer is coated over the primer layer while the top coat is layered as the last coat.

[CLAIM 3] The antimicrobial object as claimed in claim 1 and 2, wherein the silver impregnated polymeric coat includes at least a primer layer including at least a heat resistant polymeric binder resin, reinforcing agent, 0.1 -1.0% of silver particles; and wherein such heat resistant polymeric binder resin is selected from but not limited to PAI (PolyAmide Imide), PES (Polyether Sulphone), PPS (PolyPhenylene Sulfide), PTFE (polytetrafluoroethylene), or combinations thereof.

[CLAIM 4] The antimicrobial object as claimed in claim 1 and 2, wherein the middle layer and top coating includes at least a PTFE (polytetrafluoroethylene) resin; at least one Pigment selected from but not limited to a glossy pigment, opaque pigment, matt pigment, inter alia; and 0.1-1.0% of silver particles;

[CLAIM 5] The antimicrobial object as claimed in claim 1, wherein the silver impregnated ceramic coating includes at least a sol solution which is a colloidal disperse solution, containing alcohol, water, hydrolysis products of metal alkoxides having formula M(OR)4, where M is Si, Al, Ti orZr or combinations thereof; at least an inorganic pigment; at least a silicone component; 0.1-1.0% of silver particles; the metal alkoxides are hydrolyzed and form a gel solution which hardens into a glassy ceramic inorganic hard film on curing.

[CLAIM 6] The antimicrobial object as claimed in claim 1, wherein said object may be selected from but not limited to at least pan, pot, cooker, wok, skillet, bakeware, strainer, steamer, lid, screen, simmer ring, handle, kitchen counter, kitchen walls, iron for clothes, a paint, or any other kitchen articles, home appliance or parts thereof that are made of ceramic, metal, plastic, melamine or any type of polymeric material.

[CLAIM 7] A process for making an antimicrobial object characterized in that the process includes a layer by layer coating process comprising at least the following steps: i. Subjecting a substrate to chemical treatment using industrially accepted techniques, wherein the substrate may be selected from but not limited to Aluminum, Stainless steel, MS, glass inter alia; ii. Physically blending Silver particles with a coating material selected from but not limited to a ceramic coat and a polymer coat to form an impregnated coat containing 0.1 -1.0% of silver particles; iii. Coating the impregnated coat over the substrate one layer at a time; iv. Curing after application of each layer to establish thermal crosslinking of resin and thereby physical fixation of silver particles to the cross- linked resin

[CLAIM 8] The process as claimed in claim 7, wherein the impregnated polymer coat is layered by coating the substrate with a primary layer as the first layer, a top coat as the last layer and optionally coating the middle layer(s) over the primary layer prior to applying the top coat;

[CLAIM 9] The process as claimed in claim 7, wherein the thermal crosslink is performed at 400°C for 10 mins for antimicrobial polymeric coat and at 220°C for 20 mins for ceramic coat resulting in at least the silver particles physically distributed in between thermal cross-linked structure of the resin.

[CLAIM 10] The process as claimed in claim 7, wherein the impregnated coating materials are layered over the substrate using process selected from but not limited to

PTFE coatings, Ceramic coatings, PEEK based polymer technology and sol- gel technology, or such other industrially acceptable technology.