Description:FIELD OF THE INVENTION
The present invention provides chlorinated polyvinylchloride (CPVC) pipes and fittings suitable for transporting hot and cold water, while maintaining its quality and ensuring that it does not get contaminated with microbes of any kind. The invention also provides means for manufacturing the antimicrobial CPVC pipes and fittings.

BACKGROUND OF THE INVENTION
Drinking water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. Water transport involves moving safe drinking water from source to point of use, often using pipelines, ensuring water quality and safety throughout the process. Pipelines are a common and efficient way to transport large volumes of water, utilizing gravity flow or pumps to move water through a network of pipes.
CPVC pipes have conventionally been used for water transportation, but there has been no guarantee provided for maintenance of the microbial sterility of the water. While chlorine in the CPVC pipes contributes to some extent to preventing microbial growth, it does not ensure prevention and/or inhibition of growth of microbes of all kinds. Further, the conventional CPVC pipes cannot prevent formation and growth of biofilm on the interior surfaces of the pipes and/or at joints and fittings, which are typically difficult to access and clean. CPVC pipes with antimicrobial properties are commercially available.
FlowGuard Plus CPVC pipes (https://www.flowguard.com/en-in/blog/biofilm-formation) are commercially available, and these pipes are claimed to have low biofilm formation and low Legionella bacteria counts. However, the manufacturers provide testing by visual inspection, water testing and evaluations such as ATP (adenosine triphosphate) testing, to detect the presence and extent of biofilm formation, they do not provide any reports that indicate that the pipes meet ISO 22196 or ASTM standards. The ATP test measures how well a surface has been cleaned in terms of the removal of organic contamination. While ATP testing provides the quickest method to measure removal of organic contamination, it does not provide any indication about whether the pipes prevent growth and/or inhibit microbes. Also, other than the CPVC, no other components are known to be added to these pipes to provide antimicrobial properties.
Corzan CPVC pipes (https://www.corzan.com/en-us/blog/cpvc-is-a-top-achiever-in-antimicrobial-performance) are also commercially available which are free of plasticizers, and have been claimed to be resistant to biofilm growth due to the smooth internal surface of the pipes. They do not mention that their pipe material is antibacterial or anti-microbial, nor do they mention of any ASTM or ISO standard used to test these properties.

IFAN, another commercially available CPVC pipe brand, does mention about additive based CPVC fittings. However, it does not mention any ISO or ASTM standard to prove that the pipes are indeed effective in preventing or inhibiting microbes, and that these pipes can be used to transport water.
US9068072 discloses CPVC pipes containing "high rubber" impact modifier which contains more than 50 weight % of a pre-formed rubbery polydiene substrate such as a 1,3-diene polymer or copolymer thereof, in particular of butadiene and/or isoprene. These pipes have been taught to be useful in transporting hot and cold water under high pressure. However, nothing therein discloses or discusses the antimicrobial properties, if any, of the pipes.
EP0808851 relates to CPVC compound with a unique composition having good physical properties including heat deflection temperature, impact strength, tensile strength and modulus of elasticity. In particular, the invention relates to chlorinated polyvinyl chloride composition which at a minimum meets ASTM D 1784 cell class 23447, while maintaining suitable processability and good chemical resistance. Nothing therein teaches CPVC pipes with antibacterial or antimicrobial activity.
US20030157321 discloses plastic pipes and fittings made of CPVC formulation exhibiting suitable processability and meeting the base resin, impact strength, heat deflection temperature, tensile strength, and tensile modulus requirements of ASTM-D 1784, cell class 23448-B, with the proviso that said CPVC formulation is substantially free of chlorinated polyethylene. Nothing therein teaches CPVC pipes with antibacterial or antimicrobial activity.
WO2016100614 discloses a fitting for joining pipe sections prepared from a chlorinated vinyl chloride (CPVC) compound, wherein the CPVC compound comprises (A) at least one high molecular weight chlorinated vinyl chloride polymer resin (CPVC resin), wherein said high molecular weight CPVC resin is prepared by chlorinating a vinyl chloride resin having an inherent viscosity of about 0.79 or greater. However, the publication does not provide any teaching, motivation or suggestion for adding antimicrobial additives to the pipe, nor are the pipes tested for such activity.
KR100969655B1discloses a PVC pipe of an antimicrobial triple structure to improve impact resistance and strength against impact, and to stably and sanitarily supply drinking water using a water pipe with antimicrobial ability. The three-layer structure is made up of the outer layer, the center/core layer and the inner layer. The material of the outer layer and the inner layer is 100 parts by weight of PVC, 2 to 6 parts by weight of a composite heat stabilizer, 3 to 8 parts by weight of MBS-based impact modifier, 1 to 3 parts by weight of zeolite, vermiculite 1 to 8 parts by weight of a phosphate-based compound, 0.1 to 2 parts by weight of the lubricant composition. The material of the core layer is 100 parts by weight of PVC, 2 to 6 parts by weight of composite thermal stabilizer, 0 to 2 parts by weight of MBS impact modifier, 0.1 to 5 parts by weight of CaCO3, 0.2 to 3 parts by weight of lubricant, TiO2. While this publication does provide antimicrobial testing by ASTM standards, it must be noted that the pipes are made of PVC, and not CPVC. Also, the triple layered structure makes it a manufacturing complexity, which would then increase the cost.
CN109927353A discloses CPVC industrial pipe comprising a chlorinated polyvinyl chloride base pipe, an epoxy powder layer, an adhesive layer, a nano ceramic layer, a buffer layer, an antibacterial coating, an anti-corrosion layer and a protective layer which are sequentially arranged on the outer wall of the CPVC base pipe from inside to outside, and an inner liner layer arranged on the inner wall of the CPVC base pipe. The antibacterial coating comprises the following components in parts by weight: 20-30 parts of acrylic resin, 15-25 parts of methyl methacrylate, 10-15 parts of nano TiO2, 1-5 parts of a flatting agent, 1-5 parts of a defoaming agent, 10-15 parts of nano zinc oxide, 10-15 parts of polyvinyl alcohol, 5-10 parts of chitosan, 1-5 parts of a nano-silver ion antibacterial agent, 10-15 parts of ethyl acetate and 50-60 parts of deionized water. While this CPVC pipe has been described to have excellent corrosion resistance, good mechanical strength, excellent weather resistance and wear resistance, nothing in this publication provides any testing to ascertain the antimicrobial property of the pipe, and nothing assures that water transported therethrough would remain pure and will not be contaminated. It is important to note that this disclosure provides pipes with antibacterial coating – there is nothing that provides protection from other microbes such as fungi, virus and algae. Also, the coating is present on the top of the base CPVC pipe, and the antibacterial is not uniformly dispersed od distributed through the body of the pipe. It is possible that the antibacterial coating can wear out, get washed, or the coating film may lose its integrity, fully or partially, thereby exposing sections of the pipe to microbial attack.
WO2009154347A1 discloses a high tensile, impact resistant resin tube formed of a triple wall structure containing CPVC. It is described to include antimicrobial agents selected from zinc 2-pyridone-1-oxide, zirconium phosphate, silver ion antimicrobial agents, Ag 0.50%, SiO2 98.25%, water 0.25% and Al2 and a Silvix nanosilver composite powder. While the document identifies various antimicrobial agents, there is no actual testing of the antimicrobial activity of the pipes. Further, nothing therein describes pipes that would be resistant to contamination by bacteria, fungi, virus and algae.
The CPVC pipes and fittings known in the art do not seem to possess the desired antimicrobial properties for transportation and/or storage of water. Water stored during non-usage and water transported through the pipes will tend to have virus, bacteria, spores of fungi and algae, all of which grow in water and reach a level where it affects the health of the consumer. While claims have been made for addition of antimicrobials and biocides to pipes, there is the concern that such additives may not sufficiently prevent microbial growth against all of bacteria, fungi, virus and algae. Also, these additives may leach into water destroying the water quality and making it dangerous for human consumption. There is therefore a need for pipes that can maintain the sterility and quality of drinking water, while still not being difficult to manufacture. Further, the additives must not leach out, nor should they cause the pipes to break or become brittle over time. The present invention provides CPVC pipes and fittings that provide antimicrobial properties to the water being transported through them, and wherein the quality of water is maintained.

OBJECTIVE OF THE INVENTION
The objective of this invention is to maintain the health and hygiene of water by using pipes and fittings with antimicrobial properties, so that the water does not get contaminated with microbes. The antimicrobial property of the CPVC pipes and fittings refers to their ability to inhibit, prevent or eliminate the growth of microorganisms, such as bacteria, fungi, algae and viruses, in the water, or on the surfaces of the pipes and fittings that come into contact with the water.
The antimicrobial CPVC pipes and fittings include a chemical composition, added during the manufacturing process, that helps prevent the growth of microorganisms These added antimicrobials help in maintaining water quality, reducing biofilm formation, preventing contamination and extending the lifespan of safe water during storage and transportation.
When using antimicrobial additives in CPVC pipe fittings, manufacturers must navigate various regulatory requirements to ensure compliance. In many regions, products intended for contact with water are subject to stringent safety and performance standards. For example, in the United States, the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA) set guidelines for antimicrobial substances used in plumbing products. Manufacturers are required to conduct thorough testing to verify the efficacy and safety of their products, ensuring that any claims made regarding antimicrobial performance are substantiated. However, as discussed above, manufacturers of commercially available CPVC pipes do not provide details on antimicrobial properties of the pipes. Accordingly, there is a need for CPVC pipes that effectively provide antimicrobial properties that can inhibit or prevent the growth of virus, bacteria, fungi and/or algae, and which can maintain the water quality through its transport. It is also important that the pipes should not allow formation and growth of biofilm on the inside surfaces, as these cannot be cleaned effectively, and because biofilm formation is undesirable.
The present invention provides CPVC pipes with antimicrobial additives, wherein the additives are a crucial aspect of enhancing the safety and durability of the pipes, and wherein the additives are selected on the basis of their benefits, regulatory requirements and future trends, so as to provide high-quality products that meet the needs of a health-conscious market.
The antimicrobial CPVC pipes of the present invention are lead free, and hence, they pose no health hazard, and help in safe transportation of water. The CPVC pipes and fittings of the present invention are UV stabilized, ensuring protection from direct sunlight, thereby providing long life to the pipes and fittings. The pipes and fittings also have low thermal expansion, and are hence ideal for transportation of hot water up to 93°C to 95°C. Further, the insulating properties of the pipes result in high energy saving. The CPVC pipes are self-extinguishing and do not support combustion. As a result, they have an outstanding fire safety profile with LOI of 60 (Limiting Oxygen Index). The pipes and fittings can be used with electric and solar water heaters. They are 100% leak proof, allow easy jointing, and are hence plumber friendly.
Some of the benefits obtained with the use of the antimicrobial CPVC pipes and fittings of the present invention include :
• excellent resistance even under the harshest of water conditions
• unaffected by chlorine in water for potable water supply
• No scale, pit, or leach formation
• strong and durable
• provides antimicrobial activity against bacteria, fungi, virus and algae
• hot water compatible.
SUMMARY OF THE INVENTION
The present invention provides antimicrobial CPVC pipes and fittings suitable for transportation of hot and cold water, such that the water is protected from contamination by bacteria, fungi, virus and algae.
The present invention provides pipes and fittings for transportation of water comprising chlorinated polyvinyl chloride (CPVC) resin, one or more antimicrobial additive, processing aids, stabilizer, impact modifier, filler and lubricant, wherein the pipe (i) exhibits antibacterial activity gram-positive and gram-negative bacteria when tested as per ISO 22196 test method, (ii) is resistant to fungal attack at the end of 28 days of incubation when tested as per ASTM: G 21 test method, (iii) causes more than 95% reduction in viral activity when tested by ISO 21702 test method, and (iv) shows no growth of algae when tested as per ASTM: G 29 test method.
The antimicrobial CPVC pipes and fittings of the present invention include a suitable antimicrobial additive uniformly dispersed within the body of the pipe, i.e. dispersed or distributed through the CPVC resin, such that it is effectively available through the life of the pipes and fittings, and prevents contamination from the microbes.
In one embodiment of the present invention, the antimicrobial additive is selected from silver nanoparticles, copper (Cu), titanium dioxide (TiO2), Cu2O, CuO and mixtures thereof.
In one embodiment of the present invention, the antimicrobial additive is used in an amount ranging from about 0.01% to about 1.5% by weight of the CPVC resin. In a preferred embodiment of the present invention, the antimicrobial additive is silver nanoparticles in an amount of 0.2%.
In one embodiment of the present invention, the processing aid is selected from calcium stearate, zinc stearate and mixtures thereof. In one embodiment of the present invention, the processing aid is used in an amount ranging from about 1.5% to about 3% by weight of the CPVC resin.
In one embodiment of the present invention, the stabilizer is selected from methyltin, butyltin and octyltin; dialkyltin dicarboxylates; methyltin mercaptides and butyltin mercaptides; dialkyltin bis(alkylmercaptocarboxylate) including di-n-octyltin-S, S′-bis(isooctylmercaptoacetate); butylthiostaunoic acid; C4 to C6 alkyltin mercaptides and combinations thereof. In one embodiment of the present invention, the stabilizer is used in an amount ranging from about 0.4% to about 1.5% by weight of the CPVC resin.
In one embodiment of the present invention, the impact modifier used is selected from acrylic impact modifiers (AAM), methyl butadiene styrene (MBS), chlorinated polyethylene (CPE), acrylonitrile butadiene styrene (ABS), ethylene vinyl acetate copolymer (EVA) and combinations thereof. In a preferred embodiment of the present invention, the impact modifier used is methyl butadiene styrene (MBS) in an amount ranging from about 3% to about 4.5% by weight of the CPVC resin.
In one embodiment of the present invention, the lubricant used is selected from polyglycerols of dioleates, polyglycerols of trioleates, polyethylene of molecular weight less than 15000, polypropylene with molecular weight less than 15000, polyethylene wax, oxidized polyethylene wax and paraffin wax. In one embodiment of the present invention, the lubricant is polyethylene wax in an amount ranging from about 0.2% to about 1.5% by weight of the CPVC resin.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 represents types of CPVC pipe fittings.
Figure 1 A depicts Elbow fittings which are used to change the direction of flow between two pipes. Elbow fittings are usually 45 or 90 degrees, but there are also special types with longer radiuses.
Figure 1B depicts a coupler which is used to join two pipe pieces together when both pipes have the same diameter. Couplings are often used when a pipe is damaged or leaking.
Figure 1C depicts T-shaped fittings with two outlets that connect a pipe to a pipeline at a right angle.
Figure 1D depicts Cross fittings with four openings in four different directions that are used when four pipes meet at a point.
Figure 1E depicts Caps which are used to stop water flow at the end of a pipeline that doesn't need to be connected to another pipe.
Figure 1F depicts a Union which is similar to a coupling/coupler except is designed to allow quick and convenient disconnection of pipes for maintenance and fixture replacement.
Figure 1G depicts a Bushing also known as reducer bushing, which is used to connect pipes of different sizes. It is threaded and has an internal and external end. There are two types of bushings: plastic and brass.
Figure 1H depicts a Concealed valve for pipes which is used to regulate or cut off the water supply in a plumbing system. It is designed to be hidden behind walls or within fixtures, giving a clean and streamlined look.
Figure 1I depicts a Reducer which is used to connect pipes of different diameters, adjusting the flow capacity from larger to smaller pipes. There are two main types of reducers: concentric and eccentric.
Figure 1J depicts a ball valve to control the water flow and also save it.
Figure 1K depicts a tank adapter used to create an outlet for a water storage tank and is available in a variety of sizes.
Figure 2 depicts a typical antimicrobial CPVC pipe described herein.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides CPVC pipes and fittings for transport of water wherein the pipes are made of CPVC and contain suitable antimicrobial agent(s), impact modifiers, lubricants and stabilizers, and wherein the CPVC pipes prevent growth of bacteria, virus, fungus and algae.
Testing of the antimicrobial properties of the CPVC pipes and fittings of the present invention were conducted using various tests. For example, ISO 22196 testing standard described in Teresa Bento de Carvalho et al (Biology (Basel), 2024 Jan 20;13(1):59. doi: 10.3390/biology13010059 Assessing Antimicrobial Efficacy on Plastics and Other Non-Porous Surfaces: A Closer Look at Studies Using the ISO 22196:2011 Standard) was used for antibacterial testing. Antiviral testing was conducted as per ISO 21702 requirements (See https://cdn.standards.iteh.ai/samples/71365/2308a94aa39744c1b02ad44847bb942f/ISO- 21702-2019.pdf). Anti-algae testing was conducted to meet ASTM G29 requirements (See https://microchemlab.com/test/astm-g29-test-resistance algae/#:~:text=Summary%20of%20the%20ASTM%20G29%20Test&text=Test%20jars%20are%20stored%20in,for%20level%20of%20algal%20growth). Anti-fungal testing was conducted to meet ASTM G21 requirements (See https://store.astm.org/g0021-15r21e01.html). The present invention thus provides CPVC pipes and fittings meeting these above requirements for antimicrobial testing, wherein the microbes cover bacteria, fungus, virus and algae.
CPVC used for the manufacturing of the pipes is preferred over PVC (polyvinyl chloride) because it can withstand higher temperatures and pressure, and has significantly higher tensile strength. CPVC is a thermoplastic made by chlorination of polyvinyl chloride resin. Its chemical composition is two carbon atoms bonded to each other with two hydrogen atoms and two chlorine atoms bonded to this double carbon unit. This molecule then links with others to form polymer chains of CPVC. CPVC delivers superior resistance to degradation and provides a long service lifespan. CPVC is largely resistant to degradation from acid, alkali, and most inorganic chemicals. It is thermoplastic in nature and as a result the pipes have an inherent insulation that reduces condensation formation on the pipes. Its structure is stable and innately fire retardant. This stability also inhibits oxidation reactions.
The CPVC pipes and fittings of the present invention are prepared by mixing CPVC with antimicrobial additive. The antimicrobial additive may be added during the blending process in an extruder, or it may be pre-blended with the CPVC resin and then added to the extruder. This addition of the antimicrobial additive works differently from the currently available pipes, as it resists the growth of microorganisms in water, and also prevents formation of biofilm on the surface of the CPVC pipes and fittings. The antimicrobial additive is spread evenly over the surface of the pipes and fittings, and does not give any window for the growth of microorganisms in the water and/or on the surface of the pipes and fittings.
Antimicrobial additives suitable for use in the antimicrobial CPVC pipes of the present invention are defined as agents that are effective in preventing growth of microbes through the life of the pipe or fitting. The term “microbe” as used herein covers gram-positive bacteria, gram-negative bacteria, fungi, virus and algae. The bacteria against which the antimicrobial additives of the present invention are effective include Staphylococcus aureus, Escherichia coli, Vibrio cholerae, Salmonella species, Pseudomonas aeruginosa, Campylobacter species, fecal coliforms and Legionella species. The antimicrobial additives used in the present invention target waterborne viruses including noroviruses, hepatitis A and E viruses, adenoviruses, and enteroviruses. The typical fungi against which antimicrobial activity is targeted in the antimicrobial CPVC pipes of the present invention include Aspergillus niger, Penicillium funiculosum, Gliocladium virens, Chaetomium globosum and Aureobasidium pullulans. The algae against which antimicrobial activity is targeted include Chlorella pyrenoidosa and Scenedesmus species. It is important to note that the antimicrobial CPVC pipes and fittings of the present invention provide protection from all microbes so that the water transported through these pipes are not contaminated throughout the life of the pipes and fittings.
The antimocribial additive is used in an amount and type such that it provides protection from all microbes, and retain potability of the water being transporeted through the CPVC pipes. There are several types of antimicrobial additives that can be incorporated during the manufacturing of pipes. The most commonly used are silver-based compounds, which have well-documented antimicrobial properties. Silver ions are effective against a wide range of microorganisms and can disrupt their cellular processes, preventing growth and reproduction. In a preferred embodiment, metallic silver coated on inorganic nanoparticles, using additives in polyethylene wax, were used as the antimicrobial additive. It acts as an anti-microbial agent and fungicide. It is food-safe, human-safe and eco-friendly and does not release silver in the water being transported through the pipes. Typically, the silver nanoparticles in an amount of about 10%, such that the final product contains about 1-2%. Commercially available silver based antimicrobial additives that may be used in the antimicrobial pipes of the present invention include those provided by Microban, H&R Johnson, Addichem, Lifeline, Life Heiq, Bio-cote and the like. Other antimicrobial additives that may be used include zinc pyrithione (such as from Addichem), copper-based agents (such as those from Cupron and Lifeline), lead-based agents, quarternary ammonium compounds (such as from Biocote), various organic biocides (such as those from Microban) and mixtures thereof. Each of these additives has unique mechanisms of action and effectiveness against specific types of microbes. When selecting an antimicrobial additive for CPVC pipes that will be used for transport of potent water, manufacturers must consider factors such as compatibility, effectiveness and regulatory compliance to ensure optimal performance and safety. As discussed, these additives significantly reduce the risk of microbial contamination, thereby enhancing the safety of water transport systems. This is particularly crucial in applications such as water supply, where maintaining water quality is paramount. Secondly, antimicrobial additives can extend the lifespan of CPVC pipes and fittings by preventing the degradation associated with microbial growth. This leads to reduced maintenance costs and fewer system failures over time. Additionally, the use of antimicrobial CPVC can enhance marketability, as consumers increasingly prioritize health and safety in their purchasing decisions.
The antimicrobial additives that may be used in the manufacturing of the CPVC pipes of the present invention are selected from compounds containing silver, copper and/or zinc. These additives prevent or inhibit the development of microorganisms on the product surface, as well as kill the bacteria, virus, spores of fungus and algae. Silver containing compounds, such as silver nanoparticles, release silver ions that disrupt microbial cellular functions, effectively preventing their reproduction. While Zinc oxide nanoparticles have been reported to work by generating reactive oxygen species (ROS) that damage biological components in microbial cells, Zinc-based antimicrobials are not commonly used in industries due to their lower heat sustainability compared to other antimicrobials. Other inorganic antimicrobial additives like copper (Cu), titanium dioxide (TiO2), Cu2O, and CuO may be used. The antimicrobial additive is used in an amount ranging from about 0.01 to about 1.5kg per 100kg of the CPVC resin, also expressed as 0.01 to 1.5%, or PHR.
Filler that may optionally be used in the CPVC pipes of the present invention include calcium carbonate. While other agents could be used, most of these lead to damage to the machinery, except calcium carbonate. It is typically used in an amount ranging from about 1.5% to about 3%. The filler provides hardness to the CPVC pipes.
The CPVC pipes of the present invention include impact modifier in the form of microparticles, dispersed within the molecular structure of CPVC. When the CPVC products receive an impact, these microparticles in the molecular structure absorb the impact energy and prevent damage to the CPVC product. Examples of compounds that may be used as impact modifiers in the CPVC pipes of the present invention include acrylic impact modifiers (AAM), methyl butadiene styrene (MBS), chlorinated polyethylene (CPE), acrylonitrile butadiene styrene (ABS), ethylene vinyl acetate copolymer (EVA) and combinations thereof. The impact modifiers may be used in an amount ranging from about 3% to about 4.5%. In a highly preferred embodiment, MBS is used as the impact modifier. It is a tercopolymer of methyl methacrylate (M), butadiene (B) and styrene (S), which provides opaque CPVC products with high impact resistance, flexibility, good processability and reduced gelation time. In preferred embodiments, the MBS may be used in an amount ranging from about 1.5% to about 3%.
The CPVC pipes of the present invention include one or more lubricants. There are generally two types : (i) internal lubricants which assist the mixing and dispersion of the ingredients within the shearing action of an extruder, and (ii) external lubricants which assist the molten mass to move through the extruder. As the name suggests, internal lubricants, when included, are present within the body of the CPVC pipe, while external lubricants melt and coat the only the external surface of the pipe. Exemplary lubricants are polyglycerols of di- and trioleates, polyolefins such as polyethylene with molecular weight less than 15000, polypropylene with molecular weight less than 15000, polyethylene wax, oxidized polyolefins such as oxidized polyethylene wax and paraffin wax. In a highly preferred embodiment, polyethylene wax is used as a lubricant. The lubricant may be used in an amount ranging from 0.1% about to about 1.5%. The use of wax and lubricants, as described herein, as well as use of a controlled pipe extrusion process of the present invention helps in defined and reproducible inclusion of antimicrobial agent(s) agent in the extruded pipe and/or fitting, thereby providing it desired antimicrobial activity.
The CPVC pipes of the present invention include one or more stabilizers that act to prevent degradation from heat, as well as act as free radical quenchers or scavengers, which stop any chain reactions that can occur from the chlorine released from the CPVC resin at high temperatures in the extruders. Typically, stearates such as calcium stearate, zinc stearate and lead salts are used as stabilisers. However, lead compounds are avoided in the manufacturing of CPVC pipes used for transportation of water, so as to avoid any lead content in the water. In a preferred embodiment, the stabilizer used is calcium stearate, zinc stearate or a mixture of the same. Other stabilizing agents for CPVC formulations include alkyltin compounds such as methyltin, butyltin and octyltin; dialkyltin dicarboxylates; methyltin mercaptides and butyltin mercaptides; dialkyltin bis(alkylmercaptocarboxylate) including di-n-octyltin-S, S′-bis(isooctylmercaptoacetate); butylthiostaunoic acid; etc. and alkyltin stabilizers such as C4 to C6 alkyltin mercaptides. These stabilizers are generally present in amounts of from about 0.05 to 3% by weight.
The present inventors experienced significant challenges in manufacturing the CPVC pipes, wherein the amount of stabilizer was found to be critical to avoid the formation of gas. As can be understood and appreciated, when the process is carried out very high temperatures, as is needed for the pipe formation, the released chlorine gas can create a pressure in the system and lead to hazards such as blasts. Such eventualities were avoided by choosing the right kind and quantity of the stabilizer, and also by critically designing the process of manufacturing. The current inventors also found that pre-blending of the CPVC resin with the antimicrobial additive and stabilizer, followed by blending the mixture at a high temperature, and then cooling it, followed by addition of the other ingredients upon cooling, helps in obtaining uniform distribution of the antimicrobial additive throughout the body of the pipe. It is postulated that the butyl tin helps in coating the CPVC resin and the antimicrobial additive, thereby ensuring uniform distribution, and also preventing excessive gas formation in the system. The amount of the stabilizer was also critical to the entire process. In a preferred embodiment, the antimicrobial CPVC pipes of the present invention include butyl tin as the stabiliser, which imparts outstanding heat stability and clarity to mass and suspension of CPVC. The stabiliser is typically used in an amount ranging from about 0.4% to about 1.5%, and may include a mixture of calcium stearate and butyl tin in a highly preferred embodiment. In another highly preferred embodiment, about 1% of butyl tin is used as the stabilizer.
The CPVC pipes may use processing aids during manufacturing, such as acrylic polymers like methyl acrylate copolymers. Examples of process aids include Paraloid K- 120ND, K- 120N, K- 175; all available from Dow Chemical Company. The acrylic polymer used has excellent powder properties with larger particle size of spherical shape which results in greater efficiency in processing, ease of handling, effective weighing and a less dusty work environment. When used as a processing aid, the acrylic polymer provides good melt elasticity, strength and sizing. It promotes a wide processing window by offering flexibility to limit the number of processing aids for various applications. The acrylic processing aids impart superior rheological properties and process control, enhance overall physical properties, ease processing, and facilitate maximum production efficiencies. Other processing aids that can be used include low density polyethylene homopolymer, low density oxidized polyethylene copolymer and mixtures thereof.
A description of other types of processing aids which can be used in the compound can be found in The Plastics and Rubber Institute: International Conference on PVC Processing, Apr. 26-28 (1983), Paper No. 17. The CPVC pipes of the present invention may include antioxidants such as Irganox 1010 (tetrakis[methylene(3,5-di-tert-butyl-4-hydroxy-hydrocinnamate)] methane), Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and mixtures thereof. It may also include suitable pigments such as titanium dioxide, and carbon black. Examples of titanium dioxide is Tiona RCL-6 and RCL-4 from Cristal. An example of carbon black is Raven 410, available from Columbian Chemicals. Suitable inorganic fillers that may be used include talc, clay, mica, wollastonite, silicas, and other filling agents. These optional additives may be used in amounts conventional in the art.
The antimicrobial CPVC pipes of the present invention are manufactured by a technology that is unique, meets the requirements to provide desired product performance, and is environment friendly. The first step in the CPVC pipe manufacturing process is the preparation of raw materials. The raw materials used for CPVC pipes are the CPVC resin, suitable antimicrobial additive(s), impact modifiers, lubricants, stabilizers, processing aids, and optionally fillers. The raw materials are mixed in a predetermined ratio and fed into an extruder. The raw materials melt in the extruder and are then pushed through a die to form a continuous length of CPVC pipe. The diameter of the pipe is determined by the size of the die used. Once the CPVC pipe is extruded, it is cooled using a water bath which helps to maintain its shape. The cooling process also helps to improve the strength and durability of the pipe. After the cooling process, the CPVC pipe is passed through a sizing machine to ensure that it has the correct diameter and wall thickness. The pipe is then cut into specific lengths according to requirements.
Typically, the CPVC resin is mixed with the antimicrobial additive at a temperature ranging from about 80oC to about 140oC, for a cycle time ranging from about 5 minutes to about 30 minutes, at a mixing speed ranging from about 340 rpm to about 2880 rpm. The mixture is then typically extruded through an extruder at a temperature ranging from about 160oC to about 280oC. The CPVC Resin is mixed with necessary processing aids and antimicrobial additives at about 110oC to prepare a mixture where each material is mixed uniformly to yield pipes with uniform content.
In a highly preferred embodiment the anti-microbial additive is blended with a specific amount of the CPVC resin to ensure uniform dispersion, in a mixer having a capacity of about 300kg. The resulting mixture is then added to the main mixer along with other additives. Mixing is carried out at a temperature of about 115oC, for a cycle time of about 8 to about 10 minutes, at a mixing speed of about 1500 rpm. The molten mixture is then cooled to 45-50 oC for about 2-4 mins, while mixing. The material is then transferred to the extruder for pipe production, with the processing temperature in the extruder reaching up to about 200°C. The temperature and the cycle time is critical to ensuring uniform distribution of the antimicrobial additive in the body of the pipes and fittings. The mixed material is subjected to injection moulding to manufacture the pipes. As for the fittings, the mixed material is first processed into pellets using a pelletizer and then subjected to injection moulding for manufacturing the fittings. There are four stages in the cycle of injection moulding, namely clamping, injection, cooling and ejection stages.
The process is carried out using equipments conventional to the art, such as mixers wth capacities ranging from 50kg to 300kg or more; extruders such as those available from Theysohn Extrusionstechnik GmbH and the like; injection moulding machines may be automatic or semi-automatic and may be horizontal or vertical in functioning; pelletizers such as those available from Rajoo Bausano. A person skilled in the art would be aware of the conventional processes known for extrusion of the CPVC pipes using these equipments, and with the detailed description provided herein for the process and parameters, a skilled person can certainly manufacture the antimicrobial CPVC pipes and fittings of the present invention. As described above, the present invention provides antimicrobial pipes and fittings that meet regulatory standards for antimicrobial activity, and help protect the potent water, whether hot or cold, transported through these pipes.
In a preferred embodiment, the antimicrobial CPVC pipes of the present invention contain
(i) about 65% to about 90% by weight of CPVC resin,
(ii) MBS in an amount of about 2.5 to about 7% by weight of the CPVC resin,
(iii) an acrylic copolymer in an amount of about 0.2% to about 1.2% by weight of the CPVC resin,
(iv) polyethylene wax in an amount of about 0.24% to about 8% by weight of the CPVC resin,
(v) low density polyethylene (LDPE) homopolymer in an amount of about 0.75% to about 1.4% by weight of the CPVC resin,
(vi) low density oxidized polyethylene (LDOxPE) homopolymer in an amount of about 0.23% to about 0.75% by weight of the CPVC resin,
(vii) Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate in an amount of about 0.2% to about 0.65% by weight of the CPVC resin,
(viii) an external lubricant or a co-stabilizer in an amount of about 0.5% to about 1.8% by weight of the CPVC resin,
(ix) titanium dioxide in an amount of about 0.8% to about 3.4% by weight of the CPVC resin,
(x) colour in an amount of about 0.01% to about 0.06% by weight of the CPVC resin,
(xi) calcium stearate in an amount of about 0.02% to about 1.2% by weight of the CPVC resin,
(xii) silver nanoparticles in an amount of about 0.05% to about 0.22% by weight of the CPVC resin, and
(xiii) butyl tin in an amount of about 0.8% to about 3.7% by weight of the CPVC resin.
In a preferred embodiment, the antimicrobial CPVC pipes of the present invention meet BIS standards (IS 15778) such that the chlorine content in the resin is not less than 66.5%; the density of the pipe is between 1450kg/m3 and 1650 kg/m3; the opacity is 0.1% on transmission; the result of reversion test is less than 5%; the Vicat softening temperature is 110OC; the thermal stability of the pipes at 95OC at 3.6mPa is about 8760 hours; the tensile strength of the pipe is more than 50mPa; and at 95+2°C, test pressure of 1 mPa the fitting does not leak for 1000 hours.
In a preferred embodiment, the antimicrobial CPVC fittings of the present invention meet BIS standards (IS 17546) such that the chlorine content in the resin is not less than 55%; the density of the fittings is between 1450kg/m3 and 1650 kg/m3; the opacity is less than 0.2% on transmission; the Vicat softening temperature is note less than 103OC; the fittings do not show blisters, excessive delamination or cracking or signs of weld line splitting when tested in accordance with IS 12235 (Part 6); and at 95+2°C, test pressure of 1 mPa the fitting does not leak for 1000 hours.
The antimicrobial CPVC pipes and fittings of the present invention pass the tests for certification under NSF/ANSI 61, a global standard that sets benchmarks for evaluating water distribution products and materials, thus ensuring quality of the product and safety of the water transported through these pipes and fittings.
DEFINITIONS
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Unless the context indicates otherwise, it is specifically intended that the various features of the invention described herein can be used in any combination.
Moreover, the present invention also contemplates that in some embodiments of the invention, any feature or combination of features set forth herein can be excluded or omitted.
All publications, patent applications, patents, and other references mentioned herein are incorporated by reference herein in their entirety for all purposes.
As used herein, “a,” “an,” or “the” can mean one or more than one.
Also, as used herein, “and/or” refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative (“or”).
As used herein, the term “about,” as used herein when referring to a measurable value such as an amount of a compound or agent of this invention, time, temperature, and the like, is meant to encompass variations of ±10% of the specified amount.
As used herein, the term “ % by weight of the CPVC resin” is an amount equivalent to “per hundred units of the resin” or PHR, as is conventionally defined in the art, and relates to the amount of an excipient present per 100 units of the CPVC resin. It must be understood that the “% weight” of an excipient alway refers to the % by weight of the CPVC resin, in the present description and working examples.
The term “pipe” or “pipes” has been used herein to represent both pipes and fittings, and may be used interchangeably. Also, the reference to CPVC pipes, as described with respect to the present invention, refers to antimicrobial CPVC pipes, and the terms may be used interchangeable herein.
The present invention is further illustrated by reference to the following examples which is for illustrative purposes only, and does not limit the scope of the invention in any manner.
EXAMPLES
Comparative Example 1
The CPVC pipes of the present invention were prepared using raw materials as disclosed in Table A below.
Table A
Ingredients % by weight
CPVC resin 89.39
Acrylic copolymer 4.47
Oxidized polyethylene (OPE) wax 0.89
Low density polyethylene (LDPE) homopolymer 0.72
Low density Oxidized Polyethylene (LDOxPE) homopolymer 1.07
Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate 0.72
Methyl ethylene processing aid 0.40
Color 2.15
Calcium Stearate 0.01
Hydrotalcite 0.18

The CPVC resin and additives were mixed sequentially. The blend thus obtained was then passed through an extruder at about 160oC. The extruded material was then cooled and injection moulded to obtain pipes of defined size and diameter.
It wa observed that these pipes, which did not contain the antimicrobial additive, and which used a conventional process of mixing ingredients sequentially, yielded pipes that were brittle, and that were susceptible to microbial growth.
Example 1
The CPVC pipes of the present invention were prepared using raw materials as disclosed in Tables 1a, 1b, 1c below.
Table 1a
Ingredients % by weight
CPVC resin 82.2
MBS 4.11
Acrylic copolymer 0.83
Polyethylene wax 0.66
Low density polyethylene (LDPE) homopolymer 0.99
Low density Oxidized Polyethylene (LDOxPE) homopolymer 0.66
Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 0.37
Oxidized polyethylene (OPE) wax 0.99
Titanium dioxide 2.08
Colour 0.01
Calcium stearate 0.09
Silver nanoparticles 0.17
Butyl tin 1.98

Table 1b
Ingredients % by weight
CPVC resin 88.26
MBS 4.42
Acrylic copolymer 0.89
Polyethylene wax 0.70
Low density polyethylene (LDPE) homopolymer 1.06
Low density Oxidized Polyethylene (LDOxPE) homopolymer 0.70
Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 0.40
Oxidized polyethylene (OPE) wax 1.08
Titanium dioxide 2.08
Colour 0.01
Calcium stearate 0.09
Silver nanoparticles 0.17
Butyl tin 2.12

Table 1c
Ingredients % by weight
CPVC resin 90.86
MBS 4.55
Acrylic copolymer 0.91
Polyethylene wax 0.72
Low density polyethylene (LDPE) homopolymer 1.09
Low density Oxidized Polyethylene (LDOxPE) homopolymer 0.72
Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 0.41
Oxidized polyethylene (OPE) wax 1.09
Titanium dioxide 2.08
Colour 0.01
Calcium stearate 0.09
Silver nanoparticles 0.17
Butyl tin 2.18

The antimicrobial CPVC pipes were prepared by the process described below, using ingredients provided in Tables 1a, 1b, 1c above. The CPVC resin, antimicrobial additive and butyl tin were pre-blended and then mixed at about 80oC for about 10 minutes, at a mixing speed of about 340rpm, in a large tank of capacity 300kg to obtain a master blend. Once a homogenous mixture was obtained, the mster blend was cooled to about 45oC, while mixing, for about 2 to 4 minutes. The other materials were then added, sequentially. The mixture thus obtained was then passed through an extruder at about 160oC. The extruded material was then cooled and injection moulded to obtain pipes of desired size and diameter.
The pipes thus obtained had the desired antimicrobial activity, as demonstrated by tests conducted and described in the Examples below. Further, the pipes could be manufactured using higher temperatures such that the antimicrobial additive, lubricants, stabilizers and processing aids are uniformly mixed and dispersed through the body of the pipes, providing desired strength and properties, unlike the pipes of Comparative Example 1.
Example 2
The CPVC fittings of the present invention were also prepared using raw materials as disclosed in Table 2 below, using a process similar to that described in Example 1 above.
Table 2
Ingredients % by weight
CPVC resin 86.20
MBS 3.88
Acrylic copolymer 1.38
Polyethylene wax 0.69
Low density polyethylene (LDPE) homopolymer 1.03
Low density Oxidized Polyethylene (LDOxPE) homopolymer 0.52
Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 0.26
Titanium dioxide 2.07
Yellow Colour 0.01
Silver nanoparticles 0.17
Butyl tin 3.10

For fittings, the final blended material was first converted to pellets using a pelletizer and then injection moulded to obtain fittings of desired dimensions.
Example 3 : Antimicrobial testing of the CPVC pipes
A. Antibacterial testing
The antibacterial activity of the CPVC pipe of Example 1 was carried out using the test method described as per ISO 22196, against S. aureus ATCC 6538P and E. coli ATCC 8739. A CPVC pipe without the added antimicrobial additive was used as a control for the testing. 2.5x2.5cm2, 3mm pieces of both the test and control pipes were used. A test inoculum of S. aureus ATCC 6538P 2.70x106 CFU/ml and E. coli ATCC 8739 3.00x106 CFU/ml was used in Soya Casein Digest Lecithin Polysorbate (SCDLP) broth, wherein 0.1ml of the inoculum was added to 10ml broth. The test results are included in Table 3 below.
Table 3
Organism tested against Log of concentration of Inoculum on control sample after 24 hours Log of concentration of Inoculum on test sample (Example 1) after 24 hours Antibacterial activity
S. aureus ATCC 6538P 4.08 0.2 3.88
E. coli ATCC 8739 4.33 0.51 3.82

B. Antifungal testing
The antifungal activity of the CPVC pipe of Example 1 was carried out using the test method described as per ASTM: G21, against Aspergillus niger ATCC 9642 (8.50 x 105 spores/ml suspension), Penicillium funiculosum ATCC 11797 (8.13 x 105 spores/ml suspension), Gliocladium virens ATCC 9645 (8.48 x 106 spores/ml suspension), Chaetomium globosum ATCC 6205 (9.23 x 105 spores/ml suspension) and Aureobasidium pullulans ATCC 15233 (8.88 x 105 spores/ml suspension). The fungi culture was streaked on potato dextrose agar and incubated for 7 to 20 days. A spore suspension of each of the five fungi was prepared by using sterile solution containing wetting agent, using a nichrome wire to gently scrape the surface growth from the culture of test organisms. The spore suspension was poured into a sterile flask or tube containing 45ml of sterile water with wetting agent and 10 to 15 glass beads, cap and the flask was shaken. The suspension was filtered through sterile glass wool in a glass funnel into a sterile flask, followed by centrifugation of the filtered spore suspension aseptically. The supernatant was discarded. The spores were resuspended in sterile water and centrifuged, followed by dilution with nutrient salt medium to obtain a spore suspension of 1000000 ± 200000 spores/ml. This process was repeated for each organism used in the test. Specimen materials of 50 mms x 50 mms of CPVC pipe without antimicrobial additive (control) and CPVC pipe of Example 1 (test) were placed on nutrient salt agar. The test was performed in triplicate. Composite spore suspension was sprayed on the specimen. Observations were made on weekly basis for appearance and for the density of fungal growth. The filter paper control pieces had copious fungal growth at 2 weeks. At 4th week, samples were rated “0” to “4” as follows, when examined microscopically.
Growth on specimen Rating
None 0
Trace of growth (<10%) 1
Light growth (10 to 30%) 2
Medium growth (30 to 60%) 3
Heavy growth (60% to complete coverage) 4

The test results are included in Table 4 below.

Table 4
Sample Duration of the Test
Replicates Week 1 Week 2 Week 3 Week 4
CPVC Pipe of Example 1 Set I 0 0 0 0
Set II 0 0 0 0
Set III 0 0 0 0
CPVC Pipe without antimicrobial additive - 1 2 3 4

As can be seen from Table 4 above, CPVC Pipe of Example 1 was found to be resistant to fungal attack at the end of 28 days of incubation when tested as per ASTM: G 21 test method.

C. Antiviral activity
The antiviral activity of CPVC pipe of Example 1 was tested using Escherichia coli PHAGE MS2 (ATCC-15597-B1) (test virus) and Escherichia coli (ATCC-15597) (host cell), wherein a CPVC pipe without the added antimicrobial additive (untreated) was used as control. The test was carried out in triplicates by adding 0.4ml inoculum of virus to Soyabean Casein Digest Agar (SCDA) medium, to generate a viral titre of 2.6x1013. SCDLP was used as wash out medium. The contact period with the CPVC pipe of Example 1 and the untreated pipe was 24 hours. The results are recorded in Table 5 below.

Table 5
Virus Time Sample Logarithm of Infectivity titre of virus (Ig TCID50
CM2) Average titre
Infectivity of
Virus (Ig
TCID50
CM2) Pfu/ml Average Reduction in % Antiviral
Activity
E. coli
PHAGE
MS2 0 Hr Untreated 8.28 8.29 190000000 196666666.7
8.34 220000000
8.26 180000000
24 Hrs 8.34 8.35 220000000
240000000
210000000
Untreated 8.38 223333333.3
8.32
suspension (2.4 x108
PFU/ml) 0 Hr 8.30 20000000
21000000
23000000
Example 1 8.32 8.33 213333333.3
8.36
24 Hrs 6.92 8400000
Example 1 6.86 6.90 7300000 7866666.667 96.48
6.90 7900000
The antiviral activity was calculated using the formula
R= Ut-At
where,
R = Antiviral activity.
Ut = average of common logarithm from three control /untreated specimen after 24 hrs.
At = average of common logarithm from three treated specimen after 24 hrs.
Accordingly, the antiviral activity for the CPVC pipe of Example 1 was found to be 1.45.
D. Anti-algae activity
The anti-algae activity of CPVC pipe of Example 1 and an untreated CPVC pipe without the added antimicrobial additive was tested against Chlorella pyrenoidosa and Scenedesmus spp (1:1) as per ASTM: G29 test method. The test was conducted using 2.5 cm x 6.5 cm pieces of the untreated pipe and the pipe of Example 1, and placing them in a test chamber having a capacity of 500ml. The chamber was kept at room temperature and illuminated with cool white fluorescent bulb. At the end of 22 days of incubation, no growth was seen on the CPVC pipe of Example 1, while heavy growth was seen on the untreated sample.
, Claims:WE CLAIM :
1. A pipe for transportation of water comprising chlorinated polyvinyl chloride (CPVC) resin, one or more antimicrobial additive, processing aids, stabilizer, impact modifier, filler and lubricant, wherein the pipe (i) exhibits antibacterial activity gram-positive and gram-negative bacteria when tested as per ISO 22196 test method, (ii) is resistant to fungal attack at the end of 28 days of incubation when tested as per ASTM: G 21 test method, (iii) causes more than 95% reduction in viral activity when tested by ISO 21702 test method, and (iv) shows no growth of algae when tested as per ASTM: G 29 test method.
2. A pipe as claimed in claim 1 wherein the antimicrobial additive is selected from silver nanoparticles, copper (Cu), titanium dioxide (TiO2), Cu2O, CuO and mixtures thereof.
3. A pipe as claimed in claim 2 wherein the antimicrobial additive is used in an amount ranging from about 0.01% to about 1.5% by weight of the CPVC resin.
4. A pipe as claimed in claims above wherein the antimicrobial additive is 0.2% by weight of the CPVC resin of silver nanoparticles.
5. A pipe as claimed in claim 1 wherein the processing aid is selected from calcium stearate, zinc stearate and mixtures thereof.
6. A pipe as claimed in claim 5 wherein the processing aid is used in an amount ranging from about 1.5% to about 3% by weight of the CPVC resin.
7. A pipe as claimed in claim 1 wherein the stabilizer is selected from methyltin, butyltin and octyltin; dialkyltin dicarboxylates; methyltin mercaptides and butyltin mercaptides; dialkyltin bis(alkylmercaptocarboxylate) including di-n-octyltin-S, S′-bis(isooctylmercaptoacetate); butylthiostaunoic acid; C4 to C6 alkyltin mercaptides and combinations thereof.
8. A pipe as claimed in claim 7 wherein the stabilizer is used in an amount ranging from about 0.4% to about 1.5% by weight of the CPVC resin.
9. A pipe as claimed in claim 1 wherein the impact modifier used is selected from acrylic impact modifiers (AAM), methyl butadiene styrene (MBS), chlorinated polyethylene (CPE), acrylonitrile butadiene styrene (ABS), ethylene vinyl acetate copolymer (EVA) and combinations thereof.
10. A pipe as claimed in claim 9 wherein the impact modifier used is methyl butadiene styrene (MBS) in an amount ranging from about 3% to about 4.5% by weight of the CPVC resin.
11. A pipe as claimed in claim 1 wherein the lubricant used is selected from polyglycerols of dioleates, polyglycerols of trioleates, polyethylene of molecular weight less than 15000, polypropylene with molecular weight less than 15000, polyethylene wax, oxidized polyethylene wax and paraffin wax.
12. A pipe as claimed in claim 11 wherein the lubricant is polyethylene wax in an amount ranging from about 0.2% to about 1.5% by weight of the CPVC resin.
13. A fitting for pipes used for transportation of water comprising chlorinated polyvinyl chloride (CPVC) resin, one or more antimicrobial additive, processing aids, stabilizer, impact modifier, filler and lubricant, wherein the fitting (i) exhibits antibacterial activity gram-positive and gram-negative bacteria when tested as per ISO 22196 test method, (ii) is resistant to fungal attack at the end of 28 days of incubation when tested as per ASTM: G 21 test method, (iii) causes more than 95% reduction in viral activity when tested by ISO 21702 test method, and (iv) shows no growth of algae when tested as per ASTM: G 29 test method.
14. A method for preparing the antimicrobial CPVC pipe as claimed in claim 1 comprising:
(i) pre-blending and mixing CPVC resin, one or more antimicrobial additives and a stabilizer at a temperature ranging from about 80oC to about 140oC, for a time period ranging from about 5 minutes to about 30 minutes, at a mixing speed of about 340 rpm to about 2880 rpm to obtain a homogeneous mixture;
(ii) cooling the homogeneous mixture at a temperature ranging from about 30oC to about 60oC with continuous mixing to obtain a cooled homogeneous mixture;
(iii) mixing other additives sequentially with the cooled homogeneous mixture to obtain a homogeneous blend;
(iv) passing the homogeneous blend through an extruder at a temperature ranging from about 160oC to about 280oC to obtain an extruded material; and
(v) cooling and injection molding the extruded material to obtain the antimicrobial CPVC pipe.
15. A method for preparing antimicrobial CPVC fitting for pipes as claimed in claim 13, the method comprising:
i. pre-blending and then mixing CPVC resin, one or more antimicrobial additives, and a stabilizer at a temperature ranging from about 80oC to about 140oC, for a time period ranging from about 5 minutes to about 30 minutes, at a mixing speed of about 340 rpm to about 2880 rpm to obtain a homogeneous mixture;
ii. cooling the homogeneous mixture at a temperature ranging from about 30oC to about 60oC with continuous mixing to obtain a cooled homogeneous mixture;
iii. mixing other additives sequentially with the cooled homogeneous mixture to obtain a homogeneous blend;
iv. passing the homogeneous blend through an extruder at a temperature ranging from about 160oC to about 280oC to obtain an extruded material;
v. pelletizing the extruded material to obtain pellets; and
vi. injection molding the pellets to obtain the fitting.