Filtration medium

Abstract

To provide a filtration medium comprising a fibrous web impregnated with a resin composition comprising lignin, and a method for producing the same.SOLUTION: A filter medium comprising a fibrous web impregnated with a resin composition comprising lignin, wherein the resin composition comprises lignin and a phenolic resin. The lignin has a pH of less than 7 and a weight-average molecular weight of less than 20, ASTMD4001 / mol, measured according to the 000g - 13 standard. A method of making a filter medium comprises impregnating a fibrous web with a lignin-containing resin composition and curing the impregnated fibrous web.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to filtration media, and more particularly to resin-impregnated filtration media such as may be used to filter fluids in automotive, industrial and domestic applications. [Background technology]

[0002] Filtration media used in automotive, industrial, and residential applications are generally formed by impregnating a fibrous substrate (such as paper) with a chemical binder, such as a phenol-formaldehyde (resole or novolac, or a blend of novolac and resole) resin or a latex resin. The resin provides the substrate with structural rigidity and resistance to tearing or puncture, which can occur when exposed to pressurized and heated fluids during filtration. After impregnation with the resin, the substrate is heat-cured to crosslink the resin and remove any excess solvent. The substrate can then be pleated, cut, and folded into the desired shape. The folded substrate can be assembled with additional support elements into a final shape, which can be cylindrical in some applications (e.g., oil and fuel filters for automobile engines) or panel-shaped in other applications (e.g., air conditioner filters). The assembled substrate can be subjected to a further heat treatment to secure it in place.

[0003] Conventional resole resins used in the above process are synthesized by the base-catalyzed reaction of bisphenol-A with phenol and formaldehyde. Conventional novolac resins used in the above process are synthesized by the acid-catalyzed reaction of cresol (methylphenol). These resins have desirable properties of water, oil, and chemical resistance, and are stable at high temperatures, making them particularly suitable for use in automotive filtration applications. However, a drawback of these resins is their tendency to emit toxic phenol and formaldehyde gases, which can have adverse health effects on exposed individuals and can be harmful to the environment.

[0004] A further drawback of conventional phenol-formaldehyde resins is that their starting materials are typically obtained from non-renewable hydrocarbon sources and their production requires large amounts of reagents, solvents, energy, and manufacturing inputs, making them environmentally and economically costly.

[0005] One alternative to using pure phenol-formaldehyde resin is to combine it with Vinsol® resin. Vinsol® resin is a thermoplastic lignin-based resin material derived from pine wood. As disclosed in U.S. Patent Nos. 5,629,999, 5,729,999, 5,729,999, and 5,729,999, it is composed of a complex mixture of high molecular weight phenolic compounds, rosin acids, neutral substances, and several minor components.

[0006] Patent Document 4 discloses a process for producing filter paper elements for use in automotive applications. The filter paper is impregnated with a resin varnish consisting essentially of a mixture of a thermosetting resole-type phenol-formaldehyde resin, water, resorcinol, and Vinsol® resin. Patent Document 4 discloses that the Vinsol® resin is preferably present in an amount of about 25 to 100 parts by weight of the phenol-formaldehyde resin solids, and the resorcinol is present in an amount of about 3 parts by weight.

[0007] A drawback of using Vinsol® resin to impregnate filtration media is its high density (~1.33 g / ml) and high viscosity (20-300 mPa·s at 25°C), making it difficult to impregnate the filtration media substrate. This can result in uneven or incomplete coating of the filtration media, potentially leading to structural failure during use. The high viscosity may be due to the high molecular weight of lignin, the primary component of Vinsol®, at 20,000 g / mol. An additional drawback of Vinsol® resin is its poor solubility in most solvent systems suitable for coating filtration media. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 5,656,733 [Patent Document 2] U.S. Patent No. 5,683,497 [Patent Document 3] U.S. Patent No. 5,702,521 [Patent Document 4] U.S. Patent No. 3,294,582 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, there is a need for a filtration medium that addresses at least some of the above-mentioned problems. More specifically, the present invention provides a filtration medium that is manufactured by a process that is more environmentally friendly and safer to operate than existing processes due to reduced emissions of phenol and formaldehyde. The present invention achieves this advantage while using a resin composition that has physical properties that allow it to be processed and impregnated efficiently and uniformly. It is a further object of the present disclosure that the filtration medium exhibits operational performance comparable to filtration media known in the art. [Means for solving the problem]

[0010] According to a first aspect of the present invention, there is provided a filtration medium comprising a fibrous web impregnated with a resin composition comprising lignin, wherein: the fibrous web comprises lignin in an amount of 0.1 to 30% by weight of the fibrous web; Lignin is 1.2 g / cm 3 or has a weight average molecular weight of less than 20,000 g / mol, as measured according to the ASTM D4001-13 standard.

[0011] The lignin may have a pH of less than 7, preferably between 3 and 5, or most preferably between 4 and 4.5. The resin composition may have a dynamic viscosity of less than 15 mPa·s, preferably from 5 to 13 mPa·s, and more preferably from 7.5 to 9.5 mPa·s, when measured according to the ISO2555:2008 standard.

[0012] The resin composition may have a pH of 4-7, preferably 5-6. Lignin is 1g / cm 3 less than 0.20 g / cm 3 ~0.75g / cm 3 , more preferably 0.25 g / cm 3 ~0.45g / cm 3 The density may be in the range of

[0013] The resin composition may further contain a formaldehyde scavenger having at least one primary or secondary amine functional group or being a polyamine, and the formaldehyde scavenger may be selected from urea, ammonia, melamine, dicyandiamide, polyethyleneimine, or polyvinylamine, and may preferably be urea.

[0014] The resin composition may also include an epoxy-based component, also known as a polyepoxide or epoxy resin, which may be selected from aromatic or aliphatic polyepoxides (such as reaction products formed from bisphenol and epichloride, from novolac and epichloride, or from aliphatic alcohols and epichloride), and may preferably be bisphenol A-diglycidyl ether.

[0015] The resin composition may comprise lignin and phenolic resin, preferably present in a weight ratio of lignin:phenolic resin of 1:1 to 1:9, preferably 1:1 to 1:4, more preferably 1:2.

[0016] The filtration medium can contain 10 to 50% by weight, preferably 10 to 40% by weight, and more preferably 10 to 30% by weight of the resin composition. The fibrous web may comprise at least 80%, preferably at least 90%, or more preferably at least 95% by weight of cellulosic fibers, based on the total weight of the fibers.

[0017] The fibrous web may comprise at least 80%, preferably at least 90%, or more preferably at least 95% by weight synthetic fibers, based on the total weight of the fibers.

[0018] The fibrous web can include a mixture of cellulosic and synthetic fibers. The synthetic fibers can be present in the fibrous web in an amount of up to 50% by weight, or preferably 10% to 30% by weight, of the total weight of fibers in the web.

[0019] The cellulose fibers may be selected from one or more of softwood fibers, hardwood fibers, vegetable fibers, and regenerated cellulose fibers. The filtration media may be selected from the group including oil filtration media, air filtration media, fuel filtration media, hydraulic filtration media, industrial filtration media, dielectric fluid filtration media, and water filtration media. The air filtration media may be used in heavy panel filters or duty air panel filters.

[0020] According to a second aspect of the present invention, there is provided a method for producing a filtration medium as defined above, comprising impregnating a fibrous web with a lignin-containing resin composition and curing the impregnated fibrous web.

[0021] The present invention will be better understood in light of the following examples and the accompanying drawings, which are provided in an illustrative manner and should not be construed in a limiting manner. [Effects of the Invention]

[0022] According to the present invention, a filtration medium including a fibrous web impregnated with a resin composition containing lignin and a method for producing the same are provided. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a graph showing the burst strength of cured resin compositions containing 10%, 20%, 30%, 40%, and 50% lignin. [Figure 2] 1 is a graph showing the burst strength of cured resin compositions containing 10%, 20%, 30%, 40%, and 50% lignin after aging at 160° C. for 24 hours. [Figure 3] 3 is a graph showing the curing speed of the resin compositions of FIGS. 1 and 2. [Figure 4] 1 is a graph showing the burst strength of a resin composition containing hexamine and paraformaldehyde. [Figure 5] 5 is a graph showing the burst strength of the resin composition of FIG. 4 after aging at 160° C. for 24 hours. [Figure 6] 1 is a graph showing formaldehyde and phenol emission levels for filtration media impregnated with phenol-formaldehyde resin and filtration media impregnated with phenol-formaldehyde resin containing 30% lignin according to the present invention. [Figure 7] 1 is a graph showing the filtration performance of an oil filter filtration media containing 30% lignin according to the present invention, measured in differential pressure (kPa) versus flow rate (L / min). [Figure 8] 8 is a graph showing the average filter efficiency versus particle size for the oil filter of FIG. 7. [Figure 9] 9 is a graph showing differential pressure versus time measured for the oil filters of FIGS. 7 and 8. [Figure 10] 1 is a graph comparing the hot oil burst strength at 140° C. of a filtration medium containing a 30% lignin resin composition and a filtration medium containing a resin composition without lignin. [Figure 11] 1 is a graph comparing the particle size filtration efficiency of (i) a flat filtration media impregnated with a phenol-formaldehyde resin containing 30% lignin according to the present invention and (ii) a flat filtration media impregnated with phenol-formaldehyde resin only. DETAILED DESCRIPTION OF THE INVENTION

[0024] As used in this specification and the appended claims, unless the context requires otherwise, the following terms are intended to be defined as follows: "Comprise" or variations thereof (e.g., "comprises" or "comprising") is understood to mean the inclusion of a stated integer or group of integers, but not the exclusion of other integers or groups of integers.

[0025] A "fiber" is a fibrous or filamentary structure with a high aspect ratio of length to diameter. "Staple fiber" means a fiber that naturally has regular, relatively short segments or individual lengths, or that has been cut or further processed into regular, relatively short segments or individual lengths.

[0026] "Fibrous" means a material composed primarily of fibers and / or staple fibers. The term "nonwoven" or "web" refers to a collection of fibers and / or staple fibers in a web or mat that are randomly interlocked, entangled, and / or bonded to one another to form a self-supporting structural element.

[0027] "Synthetic fibers" refers to fibers made from fiber-forming substances, including polymers synthesized from chemical compounds, modified or converted natural polymers, and siliceous (glass) materials. Such fibers can be produced by conventional melt spinning, solution spinning, solvent spinning, and similar filament-making techniques.

[0028] "Formaldehyde scavenger" means a compound capable of capturing gaseous emissions of formaldehyde. In the following, the term "water-soluble" must be understood as a compound in which at least 10% of the compound can be dissolved in water at atmospheric pressure and at room temperature (20° C.).

[0029] The present disclosure provides filtration media suitable for use in a variety of automotive, industrial and domestic fluid purification applications. The filtration medium includes a fibrous web impregnated with a resin composition containing lignin, wherein the lignin is present in the fibrous web in an amount of 0.1 to 30% by weight, preferably 0.1 to 20% by weight, or more preferably 0.1 to 15% by weight of the fibrous web.

[0030] Lignin is (i) 1.2 g / cm 3 and (ii) a weight average molecular weight of less than 20,000 g / mol, as measured in accordance with ASTM D4001-13, which is a standard test method for determining the weight average molecular weight of polymers by light scattering detection.

[0031] Lignin density is 1 g / cm 3 less than 0.20 g / cm 3 ~0.75g / cm 3 , more preferably 0.25 g / cm 3 ~0.45g / cm 3 , most preferably 0.35 g / cm 3 ~0.40g / cm 3 may be.

[0032] The pH of lignin is less than 7, preferably between 3 and 5, or most preferably between 4 and 4.5. The pH can be determined in a diluted 30% aqueous solution of lignin according to the procedure of ISO standard 10523:2008. This standard determines the pH of lignin by measuring the potential difference across two half-cells, one of which is a measuring electrode and the other a reference electrode. The potential of the measuring electrode is a function of the hydrogen ion activity of the measuring solution.

[0033] The low density, acidic pH, and relatively low molecular weight provide the disclosed lignin with a favorable low viscosity of less than 15 mPa·s, which allows the lignin to be dissolved in the resin composition and relatively easily impregnated into the fibrous web. Furthermore, the low viscosity of the resin can improve the uniformity and speed of impregnation of the fibrous web. This is in contrast to the commercially available Vinsol® resin, which has a viscosity of 1.33 g / cm. 3 It has a high density of 10 ...

[0034] Lignin can be obtained, for example, from the Kraft process. As is well known in the art, the Kraft process (also known as Kraft pulping or the sulfate process) is a process for converting wood into cellulose fiber pulp. In this process, wood chips are treated with a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (NaS) to break the bonds between lignin, hemicellulose, and cellulose. The method involves several mechanical and chemical steps, resulting in the formation of two product streams: a cellulose fiber stream and a lignin stream. The wood used in the Kraft process from which lignin is obtained can be softwood (i.e., from gymnosperms such as pine), hardwood (i.e., from angiosperms), or a combination thereof. Lignin obtained from the Kraft process is a renewable source of resin and has a lower environmental impact than resins obtained from oil-based hydrocarbon sources. Because Kraft lignin is a by-product of the Kraft process, minimal processing is required to obtain it.

[0035] In addition to containing lignin, the resin composition includes a phenolic resin (a phenol-formaldehyde resin such as a resole or novolac). The phenolic resin can be present in the resin composition in an amount of 50% to 90% by weight, preferably 60% to 90% by weight, or more preferably 70% to 90% by weight, based on the total weight of the phenolic resin. Resole resins may be formed by the base-catalyzed reaction of bisphenol A with phenol and formaldehyde. Novolac resins may be formed by the acid-catalyzed reaction of cresol (methylphenol).

[0036] The lignin and phenolic resin can be present in the resin composition in a weight ratio of lignin:phenolic resin of 1:1 to 1:9, preferably 1:1 to 1:4, more preferably 1:2. The weight ratio of lignin:phenolic resin does not change as the resin dries and remains substantially the same to allow for removal of the solvent used to impregnate the fibrous web after the drying step or to allow for crosslinking of the resin composition after the curing step.

[0037] The resin composition may also contain a crosslinking agent, such as hexamine, paraformaldehyde, or a dicyandiamide-formaldehyde condensate. The dicyandiamide-formaldehyde condensate is preferably a water-soluble thermosetting resin composition containing one described in U.S. Pat. No. 4,383,077. The dicyandiamide-formaldehyde condensate can be obtained by the method claimed in U.S. Pat. No. 4,383,077, and is preferably the dicyandiamide-formaldehyde condensate disclosed in the examples of U.S. Pat. No. 4,383,077. The crosslinking agent enables the resin composition to crosslink with the fibrous web during the curing process. The crosslinking agent may be present in the resin composition in an amount of up to 20% by weight, based on the total weight of the resin composition.

[0038] The resin composition can further contain a formaldehyde scavenger having at least one primary or secondary amine functional group or being a polyamine. The formaldehyde scavenger can be selected from urea, ammonia, melamine, dicyandiamide, polyethyleneimine, and polyvinylamine. Urea is particularly useful. The amine group of the formaldehyde scavenger can react with residual formaldehyde in the resin to convert it into a Schiff base compound, which has reduced volatility and toxicity. Because these types of reactions are typically acid-catalyzed, the resin composition preferably has a pH of less than 7. The resin composition typically has a pH of 4 to 7, preferably 5 to 6. More specifically, the use of a formaldehyde scavenger can reduce formaldehyde emissions to near zero.

[0039] According to a further embodiment, the resin composition may include an epoxy-based component, also known as a polyepoxide or epoxy resin. This epoxy-based component may be selected from aromatic or aliphatic polyepoxides (such as reaction products formed from bisphenol and epichloridrin, or from novolak and epichloridrin, or from aliphatic polyol and epichloridrin), and may preferably be bisphenol A-diglycidyl ether. This epoxy-based component may be used to partially or completely replace the phenolic resin, or to reduce the content of such compounds in the resin composition. For example, based on the total weight of the lignin, epoxy resin, and phenolic resin in the resin composition, the lignin is preferably present in an amount of 10 to 80 wt% (more preferably 25 to 50 wt%), the epoxy resin is preferably present in an amount of 10 to 80 wt% (more preferably 25 to 50 wt%), and the phenolic resin is preferably present in an amount of 10 to 80 wt% (more preferably 25 to 50 wt%). According to another embodiment, the resin composition contains less than 5% by weight (preferably 0% by weight) of phenolic resin, and the weight ratio of lignin:epoxy resin in the resin composition is, for example, 1:1 to 1:9. In either case, the weight ratio of lignin:epoxy resin (and the weight ratio of phenolic resin, if present) remains substantially the same as the resin dries, allowing for the removal of the solvent used to impregnate the fibrous web after the drying step or for the crosslinking of the resin composition after the curing step. The epoxy functional groups of the epoxy-based component can react with the lignin and phenolic resin and act as a crosslinker for the resin composition, similar to formaldehyde. Therefore, the addition of this epoxy-based component can reduce the formaldehyde content in the resin composition without adversely affecting the final properties of the filtration medium.

[0040] The resin composition has a dynamic viscosity of less than 15 mPa·s, preferably 5 to 13 mPa·s, and more preferably 7.5 to 9.5 mPa·s, when measured in accordance with ISO 2555:2008 (Standard protocol for determining the apparent viscosity of resins in a liquid or similar state using a rotational viscometer; also known as the Brookfield test method).

[0041] The inclusion of lignin in the resin composition advantageously reduces the amount of phenol and formaldehyde gases emitted from the resin. The reduction in these gas emissions may be correlated with the amount of lignin in the resin composition, with higher amounts of lignin resulting in greater reductions in emissions and lower amounts resulting in smaller reductions in emissions. Thus, the presence of lignin in the resin composition results in a more environmentally friendly product. It also reduces adverse health effects for workers operating the manufacturing process that produces these filtration media compared to manufacturing processes used to produce conventional filtration media known in the art. Without wishing to be bound by theory, it is believed that the release of phenol and formaldehyde from resole resins results from either the leaching of unreacted starting materials or the decomposition of the phenolic resin into its constituent components. The inclusion of lignin in the resin composition reduces the total amount of phenolic resin and its starting materials. Alternatively, or in addition, lignin may serve to protect the phenolic resin from degradation. The amount of phenol and formaldehyde released from the filtration medium can be measured as mg of phenol or formaldehyde released per kg of filtration medium. Filtration media impregnated with a lignin-containing resin composition can emit 50%, 60%, 70%, 80%, 90%, or 99% less phenol and / or formaldehyde than filtration media impregnated with a lignin-free phenolic resin. Furthermore, it should be noted that lignin is derived from renewable resources, in contrast to phenolic resins, which are sourced from fossil fuels. This further contributes to the environmentally friendly properties of the resin compositions described herein.

[0042] The resin composition may include polymers in addition to or alternative to the phenolic resin, such as styrene acrylic, acrylic, polyethylene vinyl chloride, styrene butadiene rubber, polystyrene acrylate, polyacrylate, polyvinyl chloride, polynitrile, polyvinyl acetate, polyvinyl alcohol derivatives, starch polymers, phenolic resins, and combinations thereof (including both water-based and solvent-based versions). In some cases, the additional or alternative resin may be in the form of a latex, such as an aqueous emulsion.

[0043] To strengthen the internal bonds between fibers, the fibrous web may contain binder fibers. These are bicomponent thermoplastic fibers that include a thermoplastic core fiber surrounded by a meltable coating of a thermoplastic polymer having a lower melting point than the core. Thus, when the low-melting coating softens or partially melts due to heating during processing of the fibrous web, it acts as a thermoplastic binder, thereby adhering to adjacent fibers in the web. The high-melting material forming the core can function as a structural material.

[0044] The resin composition may further include one or more additive components. The additive components may be dyes, fiber retention agents, separation aids (e.g., silicone additives and related catalysts), fire retardants, hydrophilic or hydrophobic agents, wetting agents, antistatic agents, or antimicrobial agents, which may be required to impart a desirable appearance to the filter media. When present, these additives may be present in an amount of more than 0 wt%, more than 0.01 wt%, more than 0.1 wt%, more than 1 wt%, more than 5 wt%, or more than 10 wt%, and / or less than about 30 wt%, less than 25 wt%, less than 20 wt%, less than 15 wt%, less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, or any combination thereof, based on the total weight of the resin composition, for example, in an amount of 0.01 wt% to 1 wt%. According to certain embodiments, the resin composition may contain 10% to 20% by weight of a flame retardant, such as phosphoric acid.

[0045] The filtration medium may contain 10 to 50% by weight, preferably 10 to 40% by weight, more preferably 10 to 30% by weight of the resin composition, with the remainder of the filtration medium mostly consisting of a fibrous web.

[0046] The fibrous web can comprise at least 80%, preferably at least 90%, or more preferably at least 95% by weight of cellulose fibers, based on the total weight of the fibers. The cellulose fibers can be selected from one or more of softwood fibers, hardwood fibers, plant fibers, and regenerated cellulose fibers.

[0047] Alternatively, the fibrous web can comprise at least 80 wt%, preferably at least 90 wt%, or more preferably at least 95 wt%, synthetic fibers, based on the total weight of the fibers. The synthetic fibers can be selected from one or more of synthetic polymer fibers, modified or converted natural polymer fibers, or siliceous (glass) fibers. Exemplary fibers suitable for the fibrous web include polyesters (e.g., polyalkylene terephthalates such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT)), polyalkylenes (e.g., polyethylene, polypropylene, etc.), polyacrylonitrile (PAN), and polyamides (nylons, e.g., nylon-6, nylon 6,6, nylon-6,12, etc.).

[0048] According to another alternative, the fibrous web can comprise a mixture of cellulosic and synthetic fibers. The synthetic fibers can be present in the fibrous web in an amount of up to 50% by weight, preferably 10% to 30% by weight, or preferably 15% to 25% by weight of the total weight of fibers in the web.

[0049] The filtration media may be selected from the group including air filtration media, fuel filtration media, oil filtration media, hydraulic filtration media, industrial filtration media, dielectric fluid filtration media, and water filtration media. The present disclosure extends to a method of making a filtration medium as defined herein, which method comprises impregnating a fibrous web with a lignin-containing resin composition, and drying and curing the impregnated fibrous web.

[0050] Once the lignin-containing resin composition is formed, it is transferred to an impregnation apparatus, where the resin composition is applied through a dosing roller to achieve a uniform degree of impregnation throughout the fibrous web. The amount of resin applied to the web depends on the end use of the filtration media. Once the resin has been applied to the fibrous web, the impregnated web enters a drying oven, where the solvent is removed during the drying process. This drying process is generally carried out at temperatures between 80°C and 150°C. The resin is then crosslinked to the fibrous web during the curing process by heating the impregnated web in a curing oven at temperatures between 120°C and 200°C, 150°C and 180°C, or 180°C and 200°C. Alternatively, curing can be achieved with ultraviolet or infrared radiation. Once fully cured, the impregnated fibrous web has achieved its final properties. These properties include its weight, thickness, corrugation, burst strength, explosion, permeability, pore size, resin content (%), humidity, and cure level. According to certain embodiments, the drying and curing steps can be performed simultaneously, i.e., in a single step, particularly when a cross-linking agent is used. Once the filtration medium is formed, it can be corrugated, cut, folded, pleated, subjected to additional curing steps, and assembled into a final use filtration product.

[0051] The filtration medium may be an air filtration medium. The air filtration medium may be configured to filter the interior air of the automobile. In particular, the filtration medium may be configured to filter particulates (such as dust, pollen, soot, bacteria, and PM2.5), gases (such as ozone, benzene, SOx, and NOx), or odors from the interior air. The filtration medium may include a layer of carbon (which may be activated carbon) to help filter undesirable gases and particulates from the interior air.

[0052] The air filtration media can be configured as an automobile air intake filter and can be configured to filter particulates (dust, pollen, soot, bacteria, PM2.5, etc.) from the air entering the automobile engine. The filtration media can optionally be treated to include one or more of a flame retardant layer, a water repellent layer, or a nanofiber layer, a microfiber meltblown layer, or a synthetic laminate layer to enhance strength and filtration performance.

[0053] The air filtration media can be configured for industrial filtration such as gas turbine intake filters, air-oil separation filters (e.g., for compressed air applications), air pollution control and particulate collection filter elements (e.g., those that can be used to reduce or eliminate particulate emissions into the atmosphere from industrial sources), or heating, ventilation, and air conditioning (HVAC) filter elements, among others.

[0054] The filtration media can be configured as a fuel filter element and can be configured to filter organic and inorganic impurities from the fuel. The fuel filter element may include multiple layers of filtration media and can be configured to separate and retain both particulate and water impurities from the fuel.

[0055] The filtration media can be configured as an oil filtration media. The oil filtration media can be configured to filter impurities such as soot, dust, and particulates from oil. In these embodiments, the filtration media can have high durability in hot oil, particularly high hot oil burst resistance.

[0056] The filtration media can be configured for use in filtering dielectric fluids used in electrical discharge machining (EDM) processes. The filtration media may be configured as a hydraulic filter media for use in hydraulic applications.

[0057] The filtration media can be configured for use in water filtration. The filtration media can be configured to filter contaminants from water at submicron levels, including organic acids, viruses, bacteria, cysts, cell debris, and trace pharmaceuticals. To improve filtration performance, the filtration media can be coated with an electrostatically charged layer or an activated carbon layer.

[0058] The present invention is further illustrated by the following non-limiting examples. [Example]

[0059] [procedure] Samples were prepared using a laboratory wet-laid handsheet mold using the TAPPI T205 procedure with the modifications described herein. The finished sample as described in the recipe was mixed with 2 liters of tap water and milled in a standard laboratory mill (Noram) at 1500 revolutions per minute. The furnish was then poured into a wet-laid mold, diluted with approximately 25 liters of tap water, agitated three times with a pedal agitator, and drained through a standard paper machine wire.

[0060] The handsheets were then dried by rolling three times on a couching roller, redried in a flatbed speed oven at 350°F (177°C) for 5 minutes, and then dried in an oven at 350°F (177°C) for 5 minutes. Raw physical data (raw basis weight, caliper, air permeability, etc.) were obtained for the oven-dried (OD) sheets immediately after oven drying.

[0061] The samples were then saturated with standard phenolic resin at a 25% by weight content based on the total weight of the sheet (the bath solids of the resin bath was 18% with methanol as the solvent). The samples were then air-dried at ambient conditions for 24 hours and cured at 350°F (177°C) for 5 minutes until they reached a saturated dried cured (SDC) level. The SDC basis weight was recorded immediately after curing, and other SDC data, such as SDC caliper and SDC air permeability, were then measured.

[0062] [Test method] The following test methods were used to obtain the data reported in the tables below. <Filtration performance> Filtration performance was determined using a multi-pass test, which required the recirculation of unfiltered fluid through the filter element and measured filtration performance according to various parameters. In some cases, a differential pressure multi-pass test was performed, as defined in the ISO 4548-12 standard.

[0063] <Differential pressure test> A differential pressure test involves mounting a test filter in a housing and measuring the pressure inside the test filter relative to the pressure around the test filter in the housing. The differential pressure determines how efficiently fluid passes through the filter. A high differential pressure indicates the filter is approaching capacity.

[0064] <Filtration efficiency> Defined in ISO 4548-12, filtration efficiency refers to a filter's ability to retain particles and is expressed as the percentage of particles of a given size that are retained by the filter under test. During testing, a particle counter is used to measure liquid or gas samples in front of and behind the filtration media. The particle concentration is measured, and filtration efficiency is calculated based on the difference in the amount of particles on either side of the filter.

[0065] <Flow Restriction Test> Defined in the ISO 4548-12 standard. This test procedure determines the contaminant capacity, particulate removal characteristics, and differential pressure of a filter. This test is intended for filter elements with an efficiency of less than 99% for particle sizes greater than 10 μm. This test corresponds to a multi-pass filtration test with continuous contaminant injection using an online particle counting method to evaluate the performance of full-flow lubricating oil filters for internal combustion engines. It is limited to steady-state conditions and does not accommodate variations in flow rate.

[0066] <Air permeability> The air permeability of the media is measured in accordance with TAPPI Standard T251cm-85 ("Air Permeability of Porous Paper, Fabric, and Pulp Handsheets") using a Textest AG (Model FX3300) at a water differential of 0.5 inches (2.7 mm) and is reported as air flow rate in units of cubic feet per square foot of sample area per minute (cfm / sf) (sometimes simply referred to as cfm).

[0067] <Mean Flow Pore (MFP) Size> Measured according to standard test procedure ASTM F-316. <Bursting strength> The pressure required to burst the media samples was measured using a Mullen® Burst Strength Tester according to TAPPI Standard T 403. Results are reported in pounds per square inch (psi) at media burst.

[0068] <Caliper> The caliper (thickness) of the SDC media was measured using an 89-100 caliper tester from Thwing-Albert Instrument Company in accordance with TAPPI Standard T411, "Caliper (Caliper) of Paper, Paperboard and Composite Paperboard," which is incorporated herein by reference in its entirety.

[0069] <rigidity> The stiffness of the OD and SDC media was obtained using a GURLEY™ bending resistance tester MOD 417 1D (Gurley Precision Instruments) according to TAPPIT489 om-92.

[0070] <Hot oil bursting strength> The hot oil burst strength of the medium sample is 7.07 cm 2Hot oil burst strength is the maximum hydrostatic pressure required to burst a media sample when a steadily increasing, controlled pressure is applied through a rubber diaphragm to an area of ​​14 cm x 10 cm. Hot oil burst strength was determined by placing a media sample (14 cm x 10 cm in size) in an oil bath of typical engine oil (such as MOBIL1™ motor oil) maintained at 140°C ± approximately 0.1°C for 144 hours. The media sample is then removed from the hot oil bath and allowed to cool for approximately 5 minutes while excess oil is wiped off the media sample. The dry sample is then tested using a MULLEN® Burst Strength Tester, and the results are reported in units of force per unit area at media burst, i.e., pounds per square inch (psi).

[0071] [Example 1] To optimize the amount of lignin in the resin, samples of phenolic (resole) resin containing 10%, 20%, 30%, 40%, and 50% (vol / vol) lignin were prepared as follows.

[0072] [Table 1]

[0073] The resin compositions were applied to filter paper samples, cured, and tested in triplicate according to the test methods described above. Their properties are summarized in Tables 1-5 below. In the following tables, "Target" refers to the target technical performance of the parameter.

[0074] [Table 2]

[0075] [Table 3]

[0076] [Table 4]

[0077] Figures 1 and 2 show the relative burst strength of resin compositions containing 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt% lignin after curing and aging at 160°C for 24 hours, respectively. Satisfactory results were obtained with lignin compositions up to 30 wt%. At levels of lignin above this, burst resistance decreased significantly.

[0078] FIG. 3 shows that the cure time at 165° C. of the resin composition increases with increasing lignin content. [Example 2] To identify preferred additives, resin compositions were prepared using hexamine and paraformaldehyde to evaluate the effect of these additives on burst strength and stiffness. Samples containing various amounts of lignin and hexamine or lignin and paraformaldehyde were prepared as shown in Table 6 below and tested according to the test methods described above.

[0079] [Table 5]

[0080] Figures 4 and 5 show that paraformaldehyde provides greater burst resistance than hexamine in the resin compositions tested. [Example 3] To compare the solubility of Vinsol and kraft lignin, four mixtures were prepared and evaluated.

[0081] [Table 6]

[0082] [Example 4] Tests were conducted to evaluate the ability of the solvent system disclosed in prior art document U.S. Patent No. 6,277,693 to dissolve Vinsol and lignin resin compositions. Solvent mixtures of ethanol, isopropanol, and water were prepared according to the amounts disclosed in U.S. Patent No. 6,277,693. Four different formulations (containing Vinsol and lignin) were prepared and their solubility evaluated.

[0083] [Table 7]

[0084] [Example 5] <Formation of filtration media> A resin composition was made according to the ingredients and amounts listed in Table 8.

[0085] [Table 8]

[0086] In the first step, lignin was dissolved in a resole resin. The resin / lignin mixture was transferred to a reactor, a cross-linking agent was added, and methanol and dye were added. The combined components were then mixed to produce a 64% solids content, 830.5 mPa s viscosity, and 1.107 g / cm density. 3 , and produced a dark solution with a pH of 5.53.

[0087] The resin composition was impregnated into the fibrous web using an applicator and a dosing roller to achieve uniform impregnation. The fibrous web contained more than 95% by weight of cellulose fibers. The impregnated fibrous web was analyzed, and the results are summarized in Table 9 below.

[0088] [Table 9]

[0089] [Example 6] The above impregnated filtration media was evaluated for formaldehyde and phenol emissions. The method for measuring free phenol or free formaldehyde in filter media paper involves UV-VIS spectroscopy. To measure free phenol in paper, a test is performed using 4-aminoantipyrine in the presence of ferricyanide (III) at a wavelength of 510 nm. To measure free formaldehyde in paper, a test is performed using the reaction of 3-methyl-2-benzothiazolinone hydrazone hydrochloride hydrate (MBTH) with iron (III) chloride hexahydrate at a wavelength of 628 nm. If the paper contains formaldehyde, this reaction produces a blue derivative.

[0090] The results are shown in Figure 6. These results indicate that the filter media impregnated with the resin containing 30% lignin reduced formaldehyde emissions by 80.3% and phenol emissions by 81.6% compared to the filter media impregnated with only resole resin.

[0091] [Example 7] An oil filter medium was prepared and impregnated with the lignin-containing resin composition disclosed above. The oil filter medium was subjected to flow restriction tests, filtration efficiency tests, and differential pressure tests as defined in the ISO 4548-12 standard. The results are shown in Figures 7, 8, and 9. The standard tests used correspond to a multi-pass filtration test with continuous contaminant injection and employ an online particle counting method to evaluate the performance of full-flow lubricating oil filter media for internal combustion engines. It was also noted that the oil filter medium was easy to pleat and did not produce smoke or odor during use.

[0092] [Example 8] Hot Oil Resistance Test at 140°C. The hot oil resistance test is performed as follows: Once the sample is fully cured, a MULLEN® bursting strength test is performed and the value of this test is recorded (initial resistance value). Five other paper samples are placed in an oil bath filled with approximately 12 liters of SLX OW30 or 5W-30 oil. The oil bath is adjusted to a temperature of 140°C. The paper samples are gradually removed from the oil bath. More specifically, one paper sample is removed from the oil bath after 24 hours, 48 ​​hours, 72 hours, 168 hours, and 500 hours. After removing the paper sample from the oil bath, excess oil is removed with absorbent paper and the sample is placed in a climate chamber adjusted to 25°C and 50% relative humidity for 2 hours. After this time in the climate chamber, the sample is subjected to a MULLEN® bursting strength test and the value obtained is recorded.

[0093] The results are shown in Figure 10. These results show that the resin composition containing lignin exhibited higher burst strength than the resin without lignin at all time intervals. [Example 9] The filtration efficiency of flat filtration media samples impregnated with (i) a 30% lignin-containing phenolic resin and (ii) a lignin-free phenolic resin was tested according to the test protocol defined above. The results are shown in Figure 11. These results indicate that the filtration media impregnated with the lignin-containing resin composition exhibited filtration efficiencies comparable to those of the filtration media impregnated with the lignin-free phenolic resin.

[0094] The invention can be further understood by reference to the following sections. 1. A filtration medium comprising a fibrous web impregnated with a resin composition comprising lignin, the fibrous web comprises lignin in an amount of 0.1 to 30% by weight of the fibrous web; Lignin is 1.2 g / cm 3 Filtration media having a density of less than 20,000 or a weight average molecular weight of less than 20,000.

[0095] 2. The filtration medium according to item 1, wherein the lignin has a pH of less than 7, preferably 3 to 5, and most preferably 4 to 4.5. 3. The filtration medium according to item 1 or 2, wherein the resin composition has a dynamic viscosity of less than 15 mPa·s.

[0096] 4. The filtration medium according to item 3, wherein the resin composition has a dynamic viscosity of 7.5 to 9.5 mPa·s. 5. Lignin is 1g / cm 3 less than 0.20 g / cm 3 ~0.75g / cm 3 , more preferably 0.25 g / cm 3 ~0.45g / cm 3 Item 5. The filtration medium according to any one of items 1 to 4, having a density of

[0097] 6. The filtration medium according to any one of items 1 to 5, wherein the resin composition further contains a formaldehyde scavenger having at least one primary or secondary amine functional group or being a polyamine.

[0098] 7. The filtration medium according to any one of items 1 to 6, wherein the resin composition further contains an epoxy-based component such as a polyepoxide or a polyepoxy resin. 8. The filtration medium according to any one of items 1 to 7, wherein the resin composition comprises lignin and a phenolic resin, preferably in a weight ratio of lignin:phenolic resin of 1:1 to 1:9, preferably 1:1 to 1:4, more preferably 1:2.

[0099] 9. The filtration medium according to item 8, wherein the phenolic resin is a resole resin. 10. The filtration medium according to item 8, wherein the phenolic resin is a novolac resin. 11. The filtration medium of any one of items 1 to 7, wherein the resin composition comprises lignin and latex resin, preferably in a weight ratio of lignin:latex resin of 1:1 to 1:9, preferably 1:1 to 1:4, more preferably 1:2.

[0100] 12. The filtration medium according to any one of items 1 to 11, comprising 10% by weight to 50% by weight of the resin composition. 13. The filtration medium according to any one of items 1 to 11, comprising 10% by weight to 40% by weight of the resin composition.

[0101] 14. The filtration medium according to any one of items 1 to 11, comprising 10% by weight to 30% by weight of the resin composition. 15. Lignin has a pH of 4-4.5 and a pH of 0.25 g / cm 3 ~0.45g / cm 3 Item 11. The filtration medium according to any one of items 1 to 10, wherein the resin composition contains lignin and a phenolic resin in a weight ratio of lignin:phenolic resin of 1:1 to 1:4, and the filtration medium contains 10% by weight to 30% by weight of the resin composition.

[0102] 16. Lignin has a pH of 4-4.5 and a pH of 0.25 g / cm 3 ~0.45g / cm 3 Item 11. The filtration medium according to any one of items 1 to 10, wherein the resin composition comprises lignin and a phenolic resin in a weight ratio of lignin:phenolic resin of 1:1 to 1:4, the resin composition further comprises a formaldehyde scavenger having at least one primary amine functional group, and the filtration medium comprises 10% by weight to 30% by weight of the resin composition.

[0103] 17. Lignin has a pH of 4-4.5 and a pH of 0.25 g / cm 3 ~0.45g / cm 3 Item 11. The filtration medium according to any one of items 1 to 10, wherein the resin composition comprises lignin and a phenolic resin in a weight ratio of lignin:phenolic resin of 1:1 to 1:4, the resin composition further comprises a formaldehyde scavenger having at least one secondary amine functional group, and the filtration medium comprises 10% by weight to 30% by weight of the resin composition.

[0104] 18. Lignin has a pH of 4-4.5 and a pH of 0.25 g / cm 3 ~0.45g / cm 3Item 11. The filtration medium according to any one of items 1 to 10, wherein the resin composition contains lignin and a phenolic resin in a weight ratio of lignin:phenolic resin of 1:1 to 1:4, and the resin composition further contains a formaldehyde scavenger which is a polyamine, and the filtration medium contains 10% by weight to 30% by weight of the resin composition.

[0105] 19. The filtration medium of any one of paragraphs 1 to 18, wherein the fibrous web comprises at least 80% by weight, preferably at least 90% by weight, and more preferably at least 95% by weight, of cellulose fibers, based on the total weight of the fibers.

[0106] 20. The filtration medium of any one of paragraphs 1 to 18, wherein the fibrous web comprises at least 80% by weight, preferably at least 90% by weight, and more preferably at least 95% by weight, of synthetic fibers, based on the total weight of the fibers.

[0107] 21. The filtration medium of any one of paragraphs 1 to 18, wherein the fibrous web comprises a mixture of cellulosic and synthetic fibers. 22. The filtration medium or method of paragraph 21, wherein the synthetic fibers are present in the fibrous web in an amount of 10% to 30% by weight of the total weight of fibers.

[0108] 23. The filtration medium of paragraph 19 or 21, wherein the cellulose fibers are selected from one or more of softwood fibers, hardwood fibers, plant fibers, and cellulose fibers. 24. The filtration medium of claim 23, wherein the cellulose fibers are regenerated cellulose fibers.

[0109] 25. The filtration medium of any one of paragraphs 1 to 24, wherein the filtration medium is selected from the group including oil filtration media, air filtration media, fuel filtration media, hydraulic filtration media, industrial filtration media, dielectric fluid filtration media, and water filtration media.

[0110] 26. Use of the filtration medium according to paragraph 25, wherein the air filtration medium is used in a heavy panel filter or a duty air panel filter. 27. A method for producing a filtration medium according to any one of items 1 to 14, comprising the steps of impregnating a fibrous web with a lignin-containing resin composition and curing the impregnated fibrous web.

Claims

1. A filtration medium comprising a fibrous web impregnated with a resin composition containing lignin, The resin composition comprises lignin and a phenolic resin.

2. 10. The filtration medium of claim 1, wherein the lignin has a pH of less than 7 and a weight average molecular weight of less than 20,000 g / mol as measured according to ASTM D4001-13 standard.

3. The lignin is 1.2 g / cm ３ 2. The filtration medium of claim 1, wherein the resin composition has a density of less than 1000 kJ / cm2 and a dynamic viscosity of less than 15 mPa·s when measured according to the ISO 2555:2008 standard.

4. The lignin is 1 g / cm ３ 3. The filtration medium of claim 1 or claim 2, having a density of less than 1000 .mu.m.

5. 3. The filtration medium of claim 1 or claim 2, wherein the resin composition further contains a formaldehyde scavenger having primary or secondary amine functionality or being a polyamine.

6. 3. The filtration medium of claim 1 or claim 2, wherein the resin composition comprises lignin and phenolic resin in a weight ratio of lignin:phenolic resin of 1:1 to 1:

9.

7. The filtration medium according to claim 1 or claim 2, comprising 10% by weight to 50% by weight of the resin composition.

8. 3. A method for producing the filtration medium of claim 1 or claim 2, comprising the steps of impregnating a fibrous web with a lignin-containing resin composition and curing the impregnated fibrous web.

9. 3. The filtration medium of claim 1 or claim 2, wherein the fibrous web comprises at least 95% by weight cellulosic fibers, based on the total weight of fibers.

10. 3. The filtration medium of claim 1 or claim 2, wherein the fibrous web comprises at least 95% by weight synthetic fibers, based on the total weight of fibers.

11. 3. The filtration medium of claim 1 or claim 2, wherein the fibrous web comprises a mixture of cellulosic and synthetic fibers.

12. 12. The filtration medium of claim 11, wherein the synthetic fibers are present in the fibrous web in an amount of up to 50% by weight of the total weight of fibers.

13. 10. The filtration medium of claim 9, wherein the cellulose fibers are selected from one or more of softwood fibers, hardwood fibers, plant fibers, and regenerated cellulose fibers.

14. 3. The filtration media of claim 1 or claim 2, wherein the filtration media is selected from the group including oil filtration media, air filtration media, fuel filtration media, hydraulic filtration media, industrial filtration media, dielectric fluid filtration media, and water filtration media.

15. 15. The filtration media of claim 14, wherein the filtration media is an air filtration media and is used in a heavy panel filter or a duty air panel filter.

Images