Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. TITLE OF THE INVENTION
A FORMULATION AND A PROCESS FOR PREPARATION OF POLYURETHANE FOAM
2. APPLICANT (S)
NAME NATIONALITY ADDRESS
FLEETGUARD FILTERS PRIVATE LIMITED AN INDIAN COMPANY 136, PARK MARINA ROAD, BANER, PUNE, MAHARASHTRA, INDIA, PIN CODE - 411045
3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION
[001] The present invention pertains to the field of polyurethanes. Specifically, the present invention is directed towards a formulation devised for the preparation of a polyurethane foam, particularly a molding grade foam, intended for application in filter manufacturing and a process for preparation of the polyurethane foam from the formulation. The polyurethane foam of the present invention is characterized by good sealing capabilities, adhesion to filter media, including paper and perforated plated mild steel substrates, and demonstrates enhanced tear strength and elongation properties.
DEFINITIONS AND TERMINOLOGY
[002] The terms “formulation,” or “polyurethane formulation,” as utilized herein, are to be understood as synonymous, both referring to the specific composition employed in the preparation of polyurethane foam.
[003] The terms “filter” or “air filter,” for automotive or non-automotive applications, as referenced herein encompass not only air filters but also any other types of filters wherein the polyurethane foam of the present invention may be utilized. Moreover, while the filter is exemplified as being cylindrical or panel-shaped, the present invention extends to other filter configurations. The present invention is not restricted solely to filters, as the polyurethane foam disclosed herein may find utility in a variety of other applications.

BACKGROUND OF THE INVENTION
[004] Polyurethane foams, derived from the reaction between polyisocyanates or isocyanates and polyols, have found widespread applications in various industries, ranging from automotive components to furniture and construction materials. In the automotive sector polyurethane foams are used in manufacturing filters, both cylindrical and panel types. Polyurethane foams possess unique properties, such as adaptability to various shapes and sizes, which render the material ideal for creating effective seals and bonds in filters.
[005] However, the filter industry faces a challenge due to the differing requirements of cylindrical and panel filters. Cylindrical filters typically demand polyurethane foams with moderate to low tensile strength, elongation, tear strength, and hardness. In contrast, panel filters require foams with comparatively higher tear strength and elongation. Because of the divergent needs of the material properties the manufacturers are forced to maintain separate inventories of two distinct grades of polyurethane, one tailored for cylindrical filters and another for panel filters.
[006] The necessity of managing multiple polyurethane formulations presents several drawbacks. It increases inventory costs, complicates manufacturing processes, and reduces overall production efficiency. The need to switch between different formulations during production runs leads to longer changeover times and potentially higher rates of material waste. Furthermore, the maintenance of separate raw material streams for each formulation may strain storage capacities and complicate supply chain management.
[007] Attempts to address the afore-mentioned challenge by creating a single, versatile polyurethane formulation have encountered several obstacles. The conventional approach to increasing tear strength and elongation in polyurethane foams involves raising the foam density and increasing the concentration of chain extenders in the formulation. However, the method employing the increase in foam density and concentration of chain extenders often results in undesirable side effects, such as excessive increase in foam hardness. Additionally, the afore-mentioned modifications tend to drive up the overall cost of the polyurethane, negating potential savings from inventory reduction.
[008] The challenges extend beyond mere formulation issues. The production of two separate grades of polyurethane often requires manufacturers to invest in multiple dispensing machines or frequently recalibrate existing equipment, which not only increases capital expenditure but also introduces additional complexity into the manufacturing process, potentially leading to increased downtime and maintenance requirements.
[009] Moreover, the use of different polyurethane formulations for cylindrical and panel filters may lead to inconsistencies in the final product characteristics, which may complicate quality control processes and potentially impact the overall performance and durability of the manufactured filters.
[0010] In light of the afore-mentioned challenges, there is felt a need to provide a single formulation that may be used to produce polyurethane foam suitable for both cylindrical and panel filters. Such a formulation should be capable of yielding a polyurethane foam with increased tear strength and elongation, without significantly increasing hardness or density. Additionally, the formulation should facilitate reduced waste, simplified inventory management, and decreased production costs, while maintaining or improving the performance characteristics required for both types of filters.
OBJECTS OF THE INVENTION
[0011] Some of the objects of the present invention, of which at the minimum one object is fulfilled by at least one embodiment disclosed herein, are as follows.
[0012] An object of the present invention is to provide an alternative, which overcomes at least one drawback encountered in the existing prior art.
[0013] An object of the present invention is to provide a single formulation that may be used to produce polyurethane foam suitable for both cylindrical and panel filters.
[0014] Another object of the present invention is to provide a single formulation that eliminates the need for maintaining separate inventories of different polyurethane grades.
[0015] Another object of the present invention is to provide a formulation that, when reacted with an isocyanate compound, yields a polyurethane foam with increased tear strength and elongation without increasing hardness or density, meeting the requirements of both cylindrical and panel filters.
[0016] Still another object of the present invention is to provide a formulation that facilitates reduction in changeover time and process complexity in filter manufacturing, thereby increasing overall production efficiency.
[0017] Yet another object of the present invention is to provide a formulation that allows for the production of polyurethane foam with consistent properties, suitable for bonding filter media in both cylindrical and panel filters, thus simplifying quality control processes.
[0018] A further object of the present invention is to provide a formulation that contributes to cost reduction in filter manufacturing by minimizing raw material inventory, reducing waste, and potentially decreasing the need for multiple dispensing machines or frequent equipment recalibration.
[0019] Other objects and benefits of the present invention will be more apparent from the following description, which is not intended to bind the scope of the present invention.
SUMMARY OF THE INVENTION
[0020] The present invention relates to a polyurethane formulation designed for producing molding-grade foam for filter manufacturing. The foam exhibits excellent sealing, strong adhesion to filter media, including paper and perforated plated mild steel, and enhanced tear strength and elongation.
[0021] In accordance with a first aspect of the present invention, a formulation for preparation of polyurethane foam is disclosed.
[0022] In accordance with a first embodiment of the present invention, the formulation includes a first component and a second component. The first component includes a first polyol, a chain extender, a catalyst, and a blowing agent. The second component includes an isocyanate compound.
[0023] More specifically, the first polyol is in an amount in the range of 60 wt. % to 100 wt. %, wherein the first polyol being polyether polyol, the chain extender is in an amount in the range of 4 wt. % to 10 wt. %, the catalyst is in an amount in the range of 0.1 wt. % to 1 wt. %, and the blowing agent is in an amount in the range of 0.1 wt. % to 1 wt. %. The first component and the second component are mixed together to obtain the polyurethane foam.
[0024] In accordance with the present invention, a ratio of the first polyol to the isocyanate compound is in the range of 100:35 to 100:55.
[0025] In accordance with a second embodiment of the present invention, the formulation includes a first component and a second component. The first component includes a first polyol, a second polyol, a chain extender, a catalyst, and a blowing agent. The second component includes an isocyanate compound.
[0026] More specifically, the first polyol is in an amount in the range of 60 wt. % to 100 wt. %, wherein the first polyol being polyether polyol, the second polyol is in an amount in the range of 5 wt. % to 30 wt. %, the chain extender is in an amount in the range of 4 wt. % to 10 wt. %, the catalyst is in an amount in the range of 0.1 wt. % to 1 wt. %, and the blowing agent is in an amount in the range of 0.1 wt. % to 1 wt. %. The first component and the second component are mixed together to obtain the polyurethane foam.
[0027] In accordance with one embodiment of the present invention, the second polyol is a polycarbonate polyester polyol. In a specific embodiment, the polycarbonate polyester polyol is a compound sold by Covestro AG., under the trademark Desmophen® C 1200 series.
[0028] In accordance with one embodiment of the present invention, the ratio of the amount of the first polyol to the amount of the second polyol is in the range of 2 to 20, the ratio of the amount of the first polyol to the amount of the chain extender is in the range of 6 to 25, the ratio of the amount of the first polyol to the amount of the catalyst is in the range of 60 to 1000, and the ratio of the amount of the first polyol to the amount of the blowing agent is in the range of 60 to 1000.
[0029] In certain embodiments, the formulation of the present invention may include a pigment in an amount in the range of 0.1 wt. % to 5 wt. %. In accordance with one embodiment of the present invention, the pigment may be at least one selected from the group consisting of carbon black, pigment orange 5, pigment orange 34, and cadmium orange, but is not limited to the aforementioned pigment examples.
[0030] In accordance with one embodiment of the present invention the first polyol, which is polyether polyol, is at least one selected from the group consisting of polyether diol and polyether triol. In accordance with one embodiment of the present invention, the polyether polyol is having a molecular weight in the range of 2000 to 8000.
[0031] In accordance with one embodiment of the present invention, the polyether triol is polyalkyleneether triol. The polyalkyleneether triol is obtained by reaction of alkylene oxide with a trihydroxyl organic compound.
[0032] In one embodiment, the alkylene oxide comprises 2-4 carbon atoms. In a specific embodiment, the alkylene oxide is at least one selected from the group consisting of propylene oxide, and a mixture of propylene oxide and ethylene oxide.
[0033] In one embodiment, the trihydroxyl organic compound is at least one selected from the group consisting of 1,2,3-Propanetriol, 1,2,6-Hexanetriol, and mixtures thereof.
[0034] In accordance with one embodiment of the present invention, the chain extender is at least one selected from the group consisting of diols and diamines.
[0035] In accordance with one specific embodiment, the diol is at least one selected from the group consisting of 1,2-Cyclohexanediol, 1,6-Hexanediol, 1,3-Hexanediol, 2,2-Dimethyl-1,3-propanediol, 1,2-Propanediol, 2-(2-Hydroxyethoxy)ethanol, 1,4-Butanediol, 1,3-Butanediol, 2-[1-(2-Hydroxyethyl)phenoxy]ethanol, Ethane-1,2-diol, and 1,3-Propanediol.
[0036] In accordance with one specific embodiment, the diamine is at least one selected from the group consisting of 1,6-Hexanediamine, and 1,3-Diaminopentane.
[0037] In accordance with one embodiment of the present invention, the catalyst is at least one selected from the group consisting of amine-based catalyst and metal-based catalyst.
[0038] In accordance with one specific embodiment of the present invention, the amine-based catalyst is at least selected from the group consisting of Triethylenediamine, N-Cocomorpholine, Dimethylbenzylamine, Hexadecyl(dimethyl)amine, N,N-Dimethylethanolamine, Bis(2-dimethylaminoethyl)ether, N-Ethylmorpholine, N,N,N',N'-Tetramethyl-1,3-butanediamine, 1,4-Diazabicyclo[2.2.2]octane, 3-Dimethylamino-N,N-dimethylpropionamide, N-Methylmorpholine, N,N,N',N'-Tetramethylethylenediamine, Triethylamine, and salts of triethylene diamine.
[0039] In one embodiment, the blowing agent is water.
[0040] In one embodiment, the isocyanate compound is 1,1'-Methylenebis(4-isocyanatobenzene).
[0041] In accordance with a second aspect of the present invention, a process for preparation of the polyurethane foam based on the formulation as described herein above is disclosed. The process for the preparation of the polyurethane foam comprises the following steps:
[0042] Step 1: Charging a reactor with the first polyol in the amount ranging from 60 wt. % to 100 wt. %.
[0043] Step 2: Optionally adding a second polyol to the first polyol in the reactor, wherein the second polyol is a polycarbonate polyester polyol and is in the amount ranging from 5 wt. % to 30 wt. % and blending for 15 minutes.
[0044] Step 3: Adding the chain extender to the reactor in an amount ranging from 4 wt. % to 10 wt. % and blending for a time period in the range of 5 minutes to 30 minutes to obtain a first admix.
[0045] Step 4: Adding the catalyst to the first admix in the reactor in an amount ranging from 0.1 wt. % to 1 wt. % while mixing for a time period in the range of 5 minutes to 30 minutes to obtain a second admix.
[0046] Step 5: Adding the blowing agent to the second admix in the reactor in an amount ranging from 0.1 wt. % to 1 wt. % while blending for a time period in the range of 45 minutes to 75 minutes to obtain a third admix.
[0047] Step 6: Adding a pigment to the third admix into the reactor and blending for a time period in the range of 5 minutes to 30 minutes to obtain a fourth admix.
[0048] In each of the above steps of preparation of the polyurethane foam the temperature of all the intermediates is maintained at a temperature in the range of 20 to 50 °C throughout the blending process, while avoiding water contamination to obtain the first component.
[0049] Step 7: Finally, the first component is then mixed with the second component to obtain the polyurethane foam.
[0050] In accordance with the embodiments of the present invention, the polyurethane foam exhibits, a density in the range of 250 to 350 Kg/m3, a hardness in the range of 25 to 45 shore A, a tensile strength in the range of 5 to 20 Kg/cm2, an elongation in the range of 100 % to 200 %, tear strength in the range of 30 to 70 N/cm, and a compression set in the range of 2 to 50 %.
DETAILED DESCRIPTION
[0051] The present invention relates to polyurethanes, focusing on a formulation for molding grade polyurethane foam used in filter manufacturing, along with a process for preparation thereof. The resulting polyurethane foam offers superior sealing, strong adhesion to filter media, and enhanced tear strength and elongation.
[0052] Within the ensuing description and appended claims, a meticulous adherence to specialized lexicon and technical terminology is mandated, with interpretations thereof aligning with their conventional meanings ascribed within the pertinent field, unless explicitly redefined within this context.
[0053] Throughout the exposition and associated claims, it is crucial to underscore that the use of singular forms such as "a," "an," and "the" is intended to encompass plural references, thereby embracing diverse instances unless the context unequivocally necessitates a singular interpretation. Similarly, the inclusion of terms like "one," "a," "an," or "the" is deemed inclusive of both singular and plural manifestations, unless the context decidedly dictates otherwise.
[0054] Sequential designations, denoted by terms such as "first," "second," "third," and the like, serve exclusively to differentiate between various elements or components and do not imply any inherent sequence or hierarchical structure, unless explicitly stipulated or inferred from the context.
[0055] The term "may" conveys a sense of possibility or alternative rather than obligation, unless expressly mandated by the contextual milieu.
[0056] References to specific materials, compositions, or substances inherently encompass their functional equivalents unless explicitly specified otherwise by the context.
[0057] Expressions delineating spatial orientation such as "upper," "lower," "top," "bottom," "front," "rear," "side," and the like, serve solely to describe the relative positioning or orientation of elements or components within the disclosed embodiments and should not be construed as confining the invention to any particular spatial configuration unless explicitly declared or inferred from the context.
[0058] Terms such as "coupled," "connected," and "attached," including their variations, are utilized interchangeably and do not impose limitations on the nature of connection or attachment, unless explicitly necessitated by the context.
[0059] Numeric values specified within this discourse are inherently inclusive of a range extending approximately 10% below and above the stated value, unless an alternate range is expressly delineated.
[0060] Phrases such as "in one embodiment" are not indicative of identical embodiments but rather denote distinct instances that may represent different facets or aspects of the invention.
[0061] The terms "optional" or "optionally" signify that subsequent elements, steps, or features may or may not be encompassed within the scope of the invention, contingent upon specific embodiments or implementations.
[0062] When qualifiers like "substantially" or "essentially" are employed to characterize a characteristic or property, they encompass variations recognized by one skilled in the relevant field as not significantly altering the intended outcome or performance of the described embodiment.
[0063] The term "comprising," utilized herein, signifies inclusivity and openness, allowing for the incorporation of additional elements, features, components, process steps, sub-steps, and/or aspects as deemed suitable, unless explicitly stated otherwise.
[0064] Measurements and values disclosed herein are considered subject to modification by the term "about," intended to encompass deviations within a range extending approximately ±10% of the stated value, unless a different range is explicitly specified.
[0065] Disclosed herein, in accordance with a first aspect of the present invention, is a formulation utilized for preparation of polyurethane foam. The formulation of the present invention yields a polyurethane foam, and subsequent articles derived therefrom, that exhibits enhanced tear strength and elongation, along with a moderate increase in hardness, all without an accompanying increase in density. While the polyurethane foam of the present invention is particularly suited for the manufacture of cylindrical and panel-type filters, the use of the polyurethane foam is not limited to such applications and may be employed in a wide range of other products. The formulation further facilitates a reduction in both changeover and processing times, thereby eliminating the need for additional capital investment in separate machinery.
[0066] In accordance with the first aspect of the present invention disclosed is a formulation for preparation of polyurethane foam. The formulation comprises a first component and a second component, which, when combined, results in a polyurethane foam exhibiting the requisite properties. The first component comprises a first polyol, a chain extender, a catalyst, and a blowing agent, while the second component comprises an isocyanate compound. The formulation is specifically designed so that the ratio of the first polyol to the isocyanate compound is in the range of 100:35 to 100:55, ensuring the desired characteristics of the resulting foam.
[0067] In polyurethane synthesis, polyol compounds serve as the primary building blocks which react with isocyanates to form the polyurethane matrix. The polyol compounds determine the foam's structural formation, flexibility, and elasticity, influencing properties such as density, thermal stability, and mechanical strength.
[0068] In alignment with the above, in accordance with the embodiments of the present invention, the first polyol is incorporated in an amount ranging from 60 wt. % to 100 wt. %. The first polyol may be a polyether polyol. In a certain embodiment, the polyether polyol may have a molecular weight in the range of 2000 to 8000. The polyether polyol may encompass at least one polyether polyol selected from the group consisting of polyether diols and polyether triols. In a particular embodiment, the polyether triol is a polyalkyleneether triol. The selection of specific types of polyether polyols ensures the preparation of the polyurethane foam with the desired mechanical and chemical properties. More specifically, provision of both diols and triols to allow for customization of polyurethane properties. Diols produce linear, flexible chains ideal for soft foams and elastomers, while triols introduce branching and increase crosslinking density, resulting in more rigid and durable materials.
[0069] In one embodiment, the polyalkyleneether triol may be prepared via the reaction of an alkylene oxide with a trihydroxyl organic compound. The alkylene oxide is chosen from a subset of alkylene oxides possessing 2 to 4 carbon atoms. Specifically, the alkylene oxide may be at least one selected from the group consisting of propylene oxide, and a combination of propylene oxide and ethylene oxide in appropriate stoichiometric ratios. Furthermore, the trihydroxyl organic compound is at least one selected from the group consisting of 1,2,3-Propanetriol, 1,2,6-Hexanetriol and mixtures thereof. In accordance with one embodiment of the present invention, the amount of alkylene oxide is in the range of 80 wt. % to 95 wt. % and the amount of the trihydroxyl organic compound is in the range of 5 wt. % to 20 wt. %.
[0070] In the reaction of alkylene oxide with trihydroxyl organic compound to synthesize polyalkyleneether triol for producing polyurethanes the polyether chains are formed by adding alkylene oxide to the hydroxyl groups of the trihydroxyl compound, resulting in a branched molecule. By varying the alkylene oxide and trihydroxyl material, the properties of polyurethane such as molecular weight and functionality may be altered as desired. Polyalkyleneether triols aids in creating polyurethanes with customizable mechanical properties, good hydrolytic stability, and flexibility, making the triols suitable for various applications. The reaction between alkylene oxide and trihydroxyl organic compound is efficient, economically favorable, and environmentally friendly, with minimal by-products.
[0071] Chain extenders in polyurethane foam preparation are low-molecular-weight diols or diamines that react with isocyanates to extend polymer chains and create hard segments. The hard segments enhance the foam's rigidity, tensile strength, and thermal stability. By controlling the amount and type of chain extender, polyurethane foam properties such as toughness and flexibility may be suitably balanced, which enables the production of polyurethane foams with specific characteristics, making the polyurethane foam suitable for a wide range of applications. Thus, chain extenders aid to achieve the desired mechanical and thermal properties in polyurethane foams. In accordance with the embodiments of the present invention employs the chain extender is in an amount in the range of 4 wt. % to 10 wt. %, which enables to achieve the desired properties especially the hardness, and tensile strength of the final polyurethane foam.
[0072] In accordance with one embodiment of the present invention, the diols may be at least one selected from the group consisting of 1,2-Cyclohexanediol, 1,6-Hexanediol, 1,3-Hexanediol, 2,2-Dimethyl-1,3-propanediol, 1,2-Propanediol, 2-(2-Hydroxyethoxy)ethanol, 1,4-Butanediol, 1,3-Butanediol, 2-[1-(2-Hydroxyethyl)phenoxy]ethanol, Ethane-1,2-diol, and 1,3-Propanediol.
[0073] The above-mentioned diols are selected as chain extenders in polyurethane foam preparation due to the specific structural and chemical properties that influence the final material characteristics. Diols like 1,6-Hexanediol and 1,4-Butanediol vary in chain length, allowing control over the foam's flexibility and rigidity, while 1,2-Cyclohexanediol, having cycloaliphatic structure, adds rigidity and enhances thermal stability. Branched diols such as 2,2-Dimethyl-1,3-propanediol increase crosslinking density, improving hardness and chemical resistance. Diols with secondary hydroxyl groups, like 1,2-Propanediol, promote controlled polymer growth for uniform hard segments. Additionally, diols with ether linkages, such as 2-(2-Hydroxyethoxy)ethanol, introduce flexibility, while those with primary hydroxyl groups, like ethane-1,2-diol, ensure rapid chain extension, balancing flexibility, and strength in the polyurethane foam.
[0074] Further, in accordance with one embodiment of the present invention, the diamine may be at least one selected from the group consisting of 1,6-Hexanediamine, and 1,3-Diaminopentane. The reason for selecting the above recited specific diamines is the ability of the diamines to influence the material's properties. For example, 1,6-Hexanediamine, with long aliphatic chain, adds flexibility and toughness by forming long polymer segments. In contrast, 1,3-Diaminopentane offers a balance between rigidity and flexibility due to intermediate chain length. Diamines like 2-(2-Hydroxyethylamino)ethanol, which contain both amine and hydroxyl groups, enhance crosslinking, leading to improved mechanical strength and thermal stability. Multifunctional amines like 2,2,2-Tris(hydroxyethyl)amine further increase crosslinking density, resulting in a rigid, chemically resistant, and thermally stable polymer network, ideal for demanding applications.
[0075] In polyurethane foam preparation, amine-based catalysts accelerate urethane bond formation, influencing reaction speed and foam structure. The amine-based catalysts enable efficient polymerization and precise control over the foam's expansion and stability.
[0076] Metal-based catalysts facilitate blowing reaction by catalyzing the reaction between isocyanates and blowing agents like water, optimizing foam density and cell structure.
[0077] The afore-mentioned amine-based and metal-based catalysts aid in achieving the desired foam properties, including density, cell uniformity, and overall quality.
[0078] In line with the above discussion, the catalyst in accordance with the present invention is taken in an amount in the range of 0.1 wt. % to 1 wt. %.
[0079] In accordance with one embodiment of the present invention, the amine-based catalyst may be at least one selected from the group consisting of Triethylenediamine, N-Cocomorpholine, Dimethylbenzylamine, Hexadecyl(dimethyl)amine, N,N-Dimethylethanolamine, Bis(2-dimethylaminoethyl)ether, N-Ethylmorpholine, N,N,N',N'-Tetramethyl-1,3-butanediamine, 1,4-Diazabicyclo[2.2.2]octane, 3-Dimethylamino-N,N-dimethylpropionamide, N-Methylmorpholine, N,N,N',N'-Tetramethylethylenediamine, Triethylamine, and salts of triethylene diamine.
[0080] In some specific embodiments, the amine-based catalysts are chosen for specific roles in optimizing polyurethane foam preparation. For instance, Triethylenediamine (TEDA) and N,N,N',N'-Tetramethyl-1,3-butanediamine are selected for accelerating the urethane reaction between isocyanates and polyols, which ensures rapid polymerization and efficient foam formation. On the other hand, catalysts like Dimethylbenzylamine and N-Methylmorpholine are valued for their effectiveness in controlling reaction kinetics, balancing foam expansion with stabilization to achieve the desired foam density and cell structure. Thus, the afore-mentioned catalysts help adjust the properties of the polyurethane foam to meet specific application needs.
[0081] In polyurethane preparation, a blowing agent is incorporated which creates the foam's cellular structure by generating gas that expands the polyurethane matrix. In accordance with the embodiments of the present invention, water is used as the blowing agent due to advantageous properties thereof. When water reacts with isocyanates, carbon dioxide gas is produced as by product. Carbon dioxide gas forms bubbles within the polyurethane matrix, causing the polyurethane foam to expand and achieve cellular structure.
[0082] Water is preferred for several reasons. First, water is readily available and cost-effective compared to other blowing agents. Second, reaction of water with isocyanates is highly efficient, producing a consistent and controlled amount of carbon dioxide that ensures uniform foam expansion. Additionally, water is non-toxic and environmentally friendly, aligning with sustainability goals. Use of water in the blowing process results in a stable and predictable foam structure, making water an ideal choice for achieving the desired physical properties in polyurethane foams. In accordance with one embodiment of the present invention, the blowing agent is used in an amount in the range of 0.1 wt. % to 1 wt. %.
[0083] The second component is an isocyanate compound. The compound is chosen for polyurethane preparation due to high reactivity with hydroxyl groups in polyols. The reaction forms strong urethane bonds and aids in creating a durable and stable polymer network. The quick and efficient reaction between isocyanates and polyols ensures that the resulting polyurethane has desirable mechanical properties, such as strength and flexibility, which may be tailored to specific applications.
[0084] Further, the isocyanate compound 1,1'-Methylenebis(4-isocyanatobenzene), commonly known as MDI (Methylene Diphenyl Diisocyanate), is chosen for polyurethane preparation for several reasons. First, MDI offers excellent reactivity and versatility in forming polyurethane polymers, allowing for a wide range of material properties to be tailored. MDI includes two isocyanate groups attached to a methylene bridge, which facilitates efficient crosslinking with polyols, leading to strong and durable polymer networks.
[0085] Second, MDI's chemical stability contributes to consistent and predictable polymerization, reducing the likelihood of unwanted side reactions and ensuring high-quality, reliable foams, which enhances the material's performance in demanding applications, such as insulation and automotive components.
[0086] Lastly, MDI’s ability to form both rigid and flexible foams makes MDI highly versatile for various applications. Use of MDI enables the production of a range of polyurethane products with customized properties, from rigid insulation panels to flexible cushioning materials. This adaptability is a significant advantage in meeting diverse industrial needs.
[0087] In accordance with one embodiment of the present invention, the ratio of the first polyol to the isocyanate compound, is in the range of 100:35 and 100:55, and is chosen for enhancing polyurethane preparation. The specific ratio ensures a balanced reaction between polyol and isocyanate, preventing excess isocyanate from remaining unreacted, which could otherwise impact the foam's stability and quality. By maintaining the balanced reaction, polymerization process becomes more controlled and consistent.
[0088] Moreover, the chosen ratio directly influences the physical properties of the resulting foam. Ratio on the lower end of the range, such as 100:35, tend to produce more rigid and stronger foams, whereas higher ratio, like 100:55, yield more flexible and elastic foams. The flexibility in adjusting the ratio allows for tailoring the polyurethane foam to meet the specific needs of various applications, from insulation to cushioning.
[0089] Finally, the ratio of the first polyol to the isocyanate compound helps to manage the reaction kinetics, including the rate of foam expansion and final density. By controlling the afore-mentioned factors, uniform cell structure and high-quality foam is ensured thereby making the end products reliable and consistent.
[0090] In accordance with a second aspect of the present invention, the formulation includes a first component and a second component. The first component includes a first polyol, a second polyol, a chain extender, a catalyst, and a blowing agent. The second component includes isocyanate compound.
[0091] The first polyol, chain extender, catalyst, and blowing agent, along with the descriptions, are consistent with the first aspect previously outlined. To maintain brevity, those details are not repeated here.
[0092] The second polyol is present in an amount ranging from 5 wt. % to 30 wt. %. In one embodiment, the second polyol is a polycarbonate polyester polyol, specifically a compound sold by Covestro AG., under the trademark Desmophen® C 1200 series.
[0093] Polyester polycarbonate polyol enhances material properties. Specifically, polyester polycarbonate polyol improves mechanical strength and durability, offering increased resistance to impact, abrasion, and wear. Additionally, polyester polycarbonate polyol provides superior thermal stability, maintaining performance at high temperatures. The polyol also contributes to a uniform and controlled foam structure, optimizing cell size and density for precise application requirements. In summary, the inclusion of polycarbonate polyester polyol enhances both mechanical and thermal properties, ensuring high-quality and well-optimized polyurethane foams.
[0094] In accordance with an embodiment of the present invention, the ratio of the amount of the first polyol to the amount of the second polyol is in the range of 2 to 20, wherein the ratio herein enables control of flexibility and mechanical properties of the foam. Different polyols contribute different characteristics (such as flexibility, rigidity, or durability), and this specific range ensures a balance between these properties.
[0095] In accordance with an embodiment of the present invention, the ratio of the amount of the first polyol to the amount of the chain extender is in the range of 6 to 25, wherein the ratio enables controlling of the crosslinking density and, consequently, the hardness and elasticity of the foam. The chain extender typically increases the molecular weight between crosslinks, affecting the foam's mechanical properties, and this ratio ensures the desired balance.
[0096] In accordance with an embodiment of the present invention, the ratio of the amount of the first polyol to the amount of the catalyst is in the range of 60 to 1000, wherein the ratio allows for controlling the reaction rate. A higher ratio of polyol to catalyst slows down the reaction, providing better control over the foaming process and ensuring uniform cell structure and foam quality.
[0097] In accordance with an embodiment of the present invention, the ratio of the amount of the first polyol to the amount of the blowing agent is in the range of 60 to 1000, wherein the ratio determines the foam's density and cell structure. The blowing agent generates the gas that forms the foam cells, and wherein the ratio ensures that the correct amount of gas is produced to achieve the desired foam density and structure.
[0098] The formulation for synthesizing polyurethane foam may also include a pigment in an amount ranging from 0.1 wt.% to 5 wt.%. In one embodiment, the pigment may be at least one pigment selected from the group consisting of, but is not limited to, carbon black, pigment orange 5, pigment orange 34, and cadmium orange. Pigments serve to impart color to the polyurethane foam, allowing for customization of its appearance. Beyond aesthetics, pigments may enhance certain physical properties of the foam; for instance, carbon black not only provides a deep black color but also improves UV resistance, increasing the foam's durability when exposed to sunlight. The primary reason for incorporating pigments into polyurethane foam is to meet specific aesthetic or branding requirements, ensuring the final product aligns with desired color specifications for various applications, which is particularly important in industries like automotive and consumer goods, where visual appeal or color coding is essential.
[0099] In a third aspect of the present invention, a process for preparing polyurethane foam based on the previously described formulation is provided. The process involves several steps, beginning with charging a reactor with the first polyol in an amount ranging from 60 wt.% to 100 wt.%. Optionally, a second polyol in an amount in the range of 5 wt. % to 30 wt. %, which being a polycarbonate polyester polyol, is added to the reactor and blended with the first polyol for 15 minutes. Next, the chain extender is added to the kettle in an amount ranging from 4 wt.% to 10 wt.%, and the mixture is blended for 5 to 30 minutes to obtain a first admix. The catalyst is then added to this first admix in an amount ranging from 0.1 wt.% to 1 wt.% and mixed for 5 to 30 minutes to create a second admix. Following this, the blowing agent is introduced into the second admix in an amount ranging from 0.1 wt.% to 1 wt.% and blended for 45 to 75 minutes to form a third admix. A pigment is then added to this third admix and blended for 5 to 30 minutes to produce a fourth admix. Throughout the blending process, the temperature of all the four admixes is maintained between 20 to 50 °C, while ensuring that water contamination is avoided, to obtain first component. The first component is mixed with the second component which comprises an isocyanate compound, where the ratio of the first polyol to the isocyanate compound is maintained in the range of 100:35 to 100:55.
[00100] In accordance with a fourth aspect of the present invention, a process for manufacturing a filter using the formulation of the present invention to obtain the polyurethane foam is disclosed. The process involves several steps. Initially, the first component and the second component containing the isocyanate, are carefully filled into their respective tanks within the designated machinery. The temperature of each of the first component and the second component is maintained at around 25 °C to ensure favorable reaction conditions. Subsequently, first component and the second component are mixed in the predetermined ratio, following which the resulting mixture is dispensed into a filter cap mold.
[00101] The filter media block is then delicately immersed into the dispensed polyurethane within the mold, ensuring full contact and coverage. To achieve the desired structural integrity, a calculated load is applied to the media block, which is held under this pressure for a duration of 5 to 7 minutes. Following this curing period, the polyurethane cap is carefully demolded, completing the manufacturing process. Each step is executed with precision to maintain the quality and performance of the final filter product.
[00102] In accordance with a fifth aspect of the present invention, the polyurethane foam exhibits a density ranging from 250 to 350 Kg/m³, ensuring a balanced structure suitable for various applications. Its hardness falls within the range of 25 to 45 Shore A, providing the necessary rigidity while maintaining a degree of flexibility. The tensile strength of the foam is measured between 5 to 20 Kg/cm², indicating its ability to withstand stretching forces. Additionally, the foam demonstrates an elongation capacity of 100% to 200%, allowing it to stretch significantly without breaking. The tear strength is robust, ranging from 30 to 70 N/cm, reflecting the foam's resistance to tearing under stress. Lastly, the foam shows a compression set in the range of 2% to 20%, indicating its ability to retain its shape and dimensions after being compressed. These characteristics collectively define the performance and suitability of the polyurethane foam for its intended use.
EXAMPLES
[00103] The present invention is now described with reference to the following examples, which are provided solely for illustrative purposes and should not be construed as limiting the scope of the invention. These examples serve to enhance the understanding and explanation of the invention.
[00104] Experiment 1 (without polycarbonate polyester) polyurethane foam was prepared by employing the formulation described herein above. The present experiment 1 was carried out to achieve requirements of polyurethane foam for cylindrical and panel filter, wherein chain extender quantity was varied. The exact details of the formulation are tabulated in table I herein below:
Table I
Ingredients Specific compounds Examples
I II III IV V
First polyol Glycerol propoxylate-b-ethoxylate 100 100 100 100 100
Chain extender 1, 4 Butanediol 6 7 8 4 10
Catalyst Tetramethyl ethylenediamine 0.6 0.6 0.6 0.6 0.6
Blowing agent Water 0.35 0.45 0.48 0.25 0.75
First Polyol/MDI 100:39 100:40 100:43 100:41 100:53
[00105] The various properties of the polyurethane foam achieved by the above-mentioned compositions are listed in table II herein below.
Table II
Properties Examples
I II III IV V
Free rise density, Kg/m3 332 306 295 * 342
Hardness, Shore A 25-28 27-29 30-32 - 38-40
Tensile strength, Kg/cm2 6-8 8-9 11-12 - 13-15
Elongation, % 120 – 130 130-140 150-165 - 125-135
Tear strength, N/cm 30 - 34 34-36 35-40 - 45 -55
Compression set, % 18 - 20 6 - 7 3 -4 - 14-18
*Foam collapsed
[00106] The formulations described in Examples II and III are suitable for cylindrical filters. However, for panel filters, increasing the amount of chain extender enhances tensile strength and tear strength but reduces elongation. Additionally, this adjustment increases the compression set, which is undesirable for panel filter applications.
[00107] Experiment 2 (with polycarbonate polyester) Polyurethane foam was prepared by employing the formulation herein above to achieve properties of polyurethane foam suitable for both cylindrical and panel filters, wherein polycarbonate polyester was added in the formulation. The exact details of the formulation are tabulated in table III herein below:
Table III
Ingredients Examples
VI VII VIII IX X
First polyol Glycerol propoxylate-b-ethoxylate 90 85 75 95 70
Second polyol Desmophen® C 1200 Series 10 15 25 5 30
Chain extender 1, 4 Butanediol 8 8 8 8 8
Catalyst Tetramethyl ethylenediamine 0.6 0.7 0.7 0.6 0.7
Blowing agent Water 0.42 0.45 0.45 0.48 0.42
First polyol/MDI 100:43 100:44 100:43 100:44 100:44

Table IV
Properties VI VII VIII IX X
Free rise density, Kg/m3 316 303 302 330 310
Hardness, Shore A 40-42 38-40 34-36 42-44 34-36
Tensile strength, Kg/cm2 11-13 12-14 15-17 12-14 16-18
Elongation, % 150-160 155-165 170-180 130-150 180-190
Tear strength, N/cm 55-60 60-65 65-70 45-55 65-70
Compression set, % 5-6 6-8 3-4 3-4 2-3
[00108] Examples VIII and IX satisfy the requirements for both cylindrical and panel filter polyurethane foam, which exhibit increased tensile elongation and tear strength, along with a marginal increase in hardness, making them suitable for use in both cylindrical and panel air filters.
[00109] The present invention provides a single polyol formulation which may be used for manufacturing of both cylindrical and panel air filters which results in reduced inventory, wastage and changeover period and hence increases productivity.
TECHNICAL AND ECONOMICAL ADVANTAGES OF THE PRESENT INVENTION
TECHNICAL ADVANTAGES:
[00110] Enhanced Mechanical Properties: The formulation yields a polyurethane foam with increased tear strength and elongation without significantly increasing hardness or density. This balance of properties makes the foam suitable for a wider range of applications.
[00111] Versatility for Multiple Applications: The single formulation is suitable for both cylindrical and panel-type automotive air filters. This versatility allows manufacturers to use the same material for different filter designs, improving production flexibility.
[00112] Optimized Chemical Structure: The formulation incorporates specific polyols, chain extenders, and catalysts that allow for customization of the foam's properties. This enables manufacturers to tailor the balance between flexibility, strength, and stability, making the polyurethane suitable for diverse applications with optimized processing characteristics.
ECONOMIC SIGNIFICANCE:
[00113] Reduced Inventory Costs: The single formulation eliminates the need for separate polyurethane grades for different filter types. This reduction in inventory variety leads to lower storage costs, simplified stock management, and reduced risk of material obsolescence.
[00114] Simplified Manufacturing Processes: By using a single formulation for multiple applications, the invention streamlines manufacturing processes. This simplification may lead to fewer production line changeovers, reduced equipment requirements, and potentially lower training costs for operators.
[00115] Increased Production Efficiency: The formulation allows for reduced changeover times and decreased production costs. By eliminating the need to switch between different polyurethane grades, manufacturers may achieve longer production runs, minimize downtime, and potentially increase overall output without additional capital investment in separate machinery. , Claims:We claim:
1. A formulation for preparation of polyurethane foam, the formulation characterized by having:
- Part A comprising:
o A first polyol in an amount in the range of 60 wt. % to 100 wt. %, wherein the first polyol being polyether polyol;
o A chain extender in an amount in the range of 4 wt. % to 10 wt. %;
o A catalyst in an amount in the range of 0.1 wt. % to 1 wt. %; and
o A blowing agent in an amount in the range of 0.1 wt. % to 1 wt. %; and
- Part B comprising an isocyanate compound;
Wherein part A and part B are mixed together to obtain the polyurethane foam; and
Wherein a ratio of the first polyol to the isocyanate compound is in the range from 100:35 to 100:55.
2. The formulation as claimed in claim 1 includes a second polyol in an amount in the range of 5 wt. % to 30 wt. %, wherein the second polyol being a polycarbonate polyester polyol, wherein the polycarbonate polyester polyol is Desmophen® C 1200 series compound.
3. The formulation as claimed in claim 2, wherein
a. the ratio of the amount of the first polyol to the amount of the second polyol is in the range of 2 to 20;
b. the ratio of the amount of the first polyol to the amount of the chain extender is in the range of 6 to 25;
c. the ratio of the amount of the first polyol to the amount of the catalyst is in the range of 60 to 1000; and
d. the ratio of the amount of the first polyol to the amount of the blowing agent is in the range of 60 to 1000.
4. The formulation as claimed in claim 1
a. includes a pigment in an amount in the range of 0.1 wt. % to 5 wt. %; and
b. the pigment is one selected from the group consisting of carbon black, pigment orange 5, pigment orange 34, and cadmium orange.
5. The formulation as claimed in claim 1, wherein
a. the polyether polyol:
i. is one selected from the group consisting of polyether diol and polyether triol; and
ii. having a molecular weight in the range of 2000 to 8000;
b. the polyether triol is polyalkyleneether triol;
c. the polyalkyleneether triol being obtained by reaction of alkylene oxide with a trihydroxyl organic compound;
d. the alkylene oxide comprises 2-4 carbon atoms;
e. the alkylene oxide is one selected from the group consisting of propylene oxide, and a mixture of propylene oxide and ethylene oxide;
f. the trihydroxyl organic compound is one selected from the group consisting of 1,2,3-Propanetriol, 1,2,6-Hexanetriol, and mixtures thereof; and
g. the amount of the alkylene oxide is in the range of 80 wt. % to 95 wt. % and the amount of trihyroxyl organic compound is in the range of 5 wt. % to 20 wt. %.
6. The formulation as claimed in claim 1, wherein
a. the chain extender is one selected from the group consisting of diols and diamines;
b. the diol is one selected from the group consisting of 1,2-Cyclohexanediol, 1,6-Hexanediol, 1,3-Hexanediol, 2,2-Dimethyl-1,3-propanediol, 1,2-Propanediol, 2-(2-Hydroxyethoxy)ethanol, 1,4-Butanediol, 1,3-Butanediol, 2-[1-(2-Hydroxyethyl)phenoxy]ethanol, Ethane-1,2-diol, and 1,3-Propanediol; and
c. the diamine is one selected from the group consisting of 1,6-Hexanediamine, and 1,3-Diaminopentane.
7. The formulation as claimed in claim 1, wherein
a. the catalyst is one selected from the group consisting of amine-based catalyst and metal-based catalyst; and
b. the amine-based catalyst is one selected from the group consisting of Triethylenediamine, N-Cocomorpholine, Dimethylbenzylamine, Hexadecyl(dimethyl)amine, N,N-Dimethylethanolamine, Bis(2-dimethylaminoethyl)ether, N-Ethylmorpholine, N,N,N',N'-Tetramethyl-1,3-butanediamine, 1,4-Diazabicyclo[2.2.2]octane, 3-Dimethylamino-N,N-dimethylpropionamide, N-Methylmorpholine, N,N,N',N'-Tetramethylethylenediamine, Triethylamine, and salts of triethylene diamine.
8. The formulation as claimed in claim 1,
a. wherein the blowing agent is water; and
b. wherein the isocyanate compound is 1,1'-Methylenebis(4-isocyanatobenzene).
9. The formulation as claimed in claim 1, wherein the polyurethane foam exhibits:
a. A density in the range of 250 to 350 Kg/m3;
b. A hardness in the range of 25 to 45 shore A;
c. A tensile strength in the range of 5 to 20 Kg/cm2;
d. An elongation in the range of 100 % to 200 %;
e. A tear strength in the range of 30 to 70 N/cm; and
f. A compression set in the range of 2 to 50 %.
10. A process for preparation of the polyurethane foam based on the formulation as claimed in claim 1, wherein the process comprising the following steps:
a. charging a reactor with the first polyol in the amount ranging from 60 wt. % to 100 wt. %;
b. optionally adding a second polyol to the first polyol in the reactor, wherein the second polyol is a polycarbonate polyester polyol and is in the amount ranging from 5 wt. % to 30 wt. %, and blending for 15 minutes;
c. adding the chain extender to the reactor in an amount ranging from 4 wt. % to 10 wt. % and blending for a time period in the range of 5 minutes to 30 minutes to obtain a first admix;
d. adding the catalyst to the first admix in the reactor in an amount ranging from 0.1 wt. % to 1 wt. % while mixing for a time period in the range of 5 minutes to 30 minutes to obtain a second admix;
e. adding the blowing agent to the second admix in the reactor in an amount ranging from 0.1 wt. % to 1 wt. % while blending for a time period in the range of 45 minutes to 75 minutes to obtain a third admix; and
f. adding a pigment to the third admix into the reactor and blending for a time period in the range of 5 minutes to 30 minutes to obtain a fourth admix;
g. wherein the temperature of the first admix, the second admix, the third admix and the fourth admix is maintained at a temperature in the range of 20 to 50 °C throughout the blending process, while avoiding water contamination to obtain part A; and
h. wherein Part A is configured to be mixed with Part B comprising an isocyanate compound.
Dated this 30 September 2024
For the Applicant – Fleetguard Filters Private Limited

Deepak Pradeep Thakur
The Applicant’s Patent Agent
Reg. No. IN/PA – 3687
To,
The Controller of Patents
The Patent Office
At Mumbai