JP7109888B2 - Method for producing cellulose acetate tow using spinneret - Google Patents

Description

priority claim
[0001] This application claims priority to U.S. Provisional Patent Application No. 62/344,479, filed Jun. 2, 2016, which is hereby incorporated by reference in its entirety. .

[0002] The present invention relates generally to a method of making cellulose acetate tow using a spinneret. In particular, the present invention produces cellulose acetate tow with controlled denier, denier per filament, rod-to-rod coefficient of variation, and/or yield by spinning a cellulose acetate dope through at least one spinneret. on how to.

[0003] Cellulose acetate fibers are commonly used in the manufacture of cigarette filters. To form fibers, cellulose acetate is dissolved in a solvent to form a cellulose acetate dope. The dope can then be spun through a spinneret to form filaments, which are then bundled to form a tow. The tow is typically baled, unbaled, and then subjected to several downstream processing steps to form filter rods and ultimately cigarette filters. Throughout the manufacture of cigarette filters, there is a requirement to maintain a defined yield in terms of filter rod pressure drop versus tow fiber weight in the filter. Numerous parameters are defined here, including denier per filament (a unit of measurement for the linear mass density of a fiber defined as its mass in grams per 9000 meters), and total denier (yarn denier). Affects yields. The cross-section of the filament can also affect the pressure drop across the rod. Therefore, it is desirable to have uniform denier per filament, total denier, and filament cross-section.

[0004] U.S. Patent Publication No. 2005/0126582 discloses a filter tow made from crimped endless cellulose acetate filaments whereby the filaments have at least the same filament titer of at least 600 filaments. Form a bundle of two connected fibers. Filament titers vary by at least 1 dtex per bundle. Additionally, US Patent Publication No. 2005/0126582 discloses a filter tow having a crimp ratio greater than 40%, said filaments comprising at least 22 crimp turns per unit filament length.

[0005] Chinese Patent Application No. 104651959 discloses a spinneret plate for producing diacetate fiber tow. The spinneret plate includes a spinneret plate body. A plurality of equally sized equilateral triangular spinneret holes are formed in the spinneret plate body. The centroids of all spinneret holes are arranged on the circumference of a plurality of concentric circles in the same plane. For each two adjacent spinneret holes on each circumference, the distance between their centers of gravity is identified as the circumferential distance of the spinneret holes, and the circumferential distances of spinneret holes on the same circumference are equal, and the two adjacent spinneret holes have the same circumferential distance. The distance between the circles thus formed increases gradually from the inside to the outside. The spinneret hole size and distribution distance are determined based on the size of the diacetate fiber tow that needs to be produced. The spinneret plate is simple in structure and reasonable in layout, and the extruded diacetate fiber tows are close to a "Y" shape and improve flue gas filtering performance.

[0006] US Patent Publication No. 2014/0026911, which is incorporated herein by reference in its entirety, discloses spinnerets with triarc holes that can be used to manufacture triarc filaments. In some cases, the triarc hole has a Y shape with three protrusions, each protrusion having an arc at the end of the protrusion that tapers from the end of the arc to the connection point of the adjacent arc. Triarc filaments, however, have a generally Y-shaped cross-section with a bulging or curved tip in the central portion. Additionally, triarc filaments may be useful in multiple applications including, but not limited to, filters, filters containing particulate additives, and smoking article filters.

[0007] US Patent No. 5,415,697 discloses a method and apparatus for cleaning the dope and unplugging the dope from the jet holes of spinneret plates used in the production of solvent-spun cellulose fibers. The method includes soaking the spinneret plate in a doping solvent, flushing the solvent through the jet holes in a first direction, and flushing the solvent through the jet holes in a reverse direction. The solvent is washed off in an ultrasonic water bath. The spinneret plate is then steam cleaned and then ultrasonically cleaned in a cleaning agent that removes cellulosic debris from the spinneret plate.

[0008] US Patent No. 5,011,541 discloses cleaning of contaminated spinneret components. A contaminated spinneret assembly is cleaned by striking the contaminated area with a high pressure jet of water. The water jet cleaning process is particularly effective for cleaning contaminated spinnerets when used in dry spinning spandex filaments.

U.S. Patent Publication No. 2005/0126582 Chinese Patent Application No. 104651959 U.S. Patent Publication No. 2014/0026911 U.S. Pat. No. 5,415,697 U.S. Pat. No. 5,011,541 U.S. Pat. No. 2,740,775 U.S. Patent Publication No. 2013/0096297 U.S. Patent Publication No. 2013/0192613 U.S. Patent No. 7,585,442 U.S. Patent No. 7,610,852 U.S. Patent Publication No. 2012/0302416

[0009] It has already been recognized that filament and tow uniformity is desired, as has another recognized need for spinneret cleaning, but it has A need exists for a method that addresses uniformity. In particular, the method desirably includes the step of improving filament uniformity during passage through the spinneret(s) to form filaments.

[0010] In one embodiment, the present invention is a method for reducing the rod-to-rod coefficient of variation in a plurality of cellulose acetate filter rods, wherein a cellulose acetate dope is passed through at least two spinnerets and spun to form filaments. forming, bundling the filaments to form a tow, crimping the tow, drying the tow, forming a plurality of filter rods from the tow, measuring the coefficient of variation between the rods, and Adjusting at least one of a spinneret, the total denier of the filaments, or the denier per filament to reduce the coefficient of variation between the rods to less than 5. In some embodiments, the number of spinnerets is decreased, while in other embodiments, the number of spinnerets is increased. In some embodiments, the total filament denier is decreased and the denier per filament is increased, while in other embodiments the total filament denier is increased and the denier per filament is decreased. The method may further comprise removing at least one of the at least two spinnerets from the method when the rod-to-rod coefficient of variation is 5 or greater, and cleaning the at least one spinneret.

[0011] In another aspect, the present invention provides a method for improving cross-sectional uniformity of cellulose acetate tow filaments, comprising spinning a cellulose acetate dope through a plurality of spinnerets to form filaments; bundling the filaments to form a tow, crimping the tow, drying the tow, forming a plurality of filter rods from the tow, measuring the yield of the rods by the weight of the tow (g/100 rod); and removing deposits and blockages from at least one of the plurality of spinnerets to maintain a rod yield within ±20 mm H ₂ O of a target rod yield. The cross section is selected from the group consisting of Y-shaped, R-shaped, X-shaped, K-shaped, C-shaped, O-shaped, I-shaped, circular, serrated, elliptical, polygonal, and dogbone-shaped. can be

[0012] In yet another embodiment, the present invention is a method of removing deposits and/or blockages from a cellulose acetate tow spinneret comprising: a) immersing the spinneret in acetone to remove the acetate; a) washing said spinneret in caustic and acid washes to remove organic and inorganic deposits; c) washing said spinneret with water or acetone to remove residues. The temperature of the acetone in the soaking step can range from 20-55° C. and the spinneret can be soaked for 5-60 minutes. The temperature of the acid in the acid wash can range from 20-60° C., and the spinneret can be washed in the acid wash for 5-90 minutes. The temperature of the caustic solution can range from 20-70° C., and the spinneret can be washed in the caustic solution for 5-180 minutes. In some aspects, greater than 90% of deposits and/or blockages are removed from the spinneret. The method may further comprise visually inspecting the spinneret for deposits and/or blockages after cleaning. Visual inspection may be performed under a microscope and/or with a light projector. The method may further include a solvent-based jet cleaning step. A jet cleaning step may be performed after steps a), b) and/or c).

[0013] In yet another embodiment, the present invention is a method of making a cellulose acetate tow bale, comprising dissolving cellulose acetate in a solvent to form a cellulose acetate dope; spinning through one spinneret to form filaments having a total denier of 10,000 to 100,000 and a denier per filament of 1 to 15; bundling the filaments to form a tow; , drying the tows, and packaging the tows into bales, wherein the total denier varies by less than 3% and the denier per filament varies by less than 10%; and directed to a method in which the denier index is less than 2.5:1.

[0014] The present invention can be better understood with reference to the accompanying non-limiting figures.

[0015] Figure IA illustrates a representative spinneret according to an embodiment of the present invention. [0016] Figure IB is a graph showing a partially occluded and/or deposited spinneret according to an embodiment of the invention; [0017] Fig. 5 is a graph showing rod yield as compared to a target yield line, in accordance with an embodiment of the present invention; [0018] Figure 4 shows a comparison of total denier and denier per filament over time according to an embodiment of the present invention;

I. Introduction
[0019] The present invention relates to improving the uniformity of filaments formed from cellulose acetate dopes. This uniformity can be quantified by making the filaments uniform in cross-section and/or having a predetermined ratio of total denier to denier per filament. Uniform filaments, as described herein, result in improved end products, such as cigarette filters. For example, uniform filaments result in a reduced coefficient of variation between rods in cigarette filters. Monitoring and maintaining the spinneret or spinnerets used to form the filaments allows this uniformity to be achieved during filament formation.

[0020] Accordingly, in some aspects, the present invention relates to reducing the rod-to-rod coefficient of variation in a plurality of cellulose acetate filter rods. The method includes passing a cellulose acetate dope through at least one spinneret and spinning to form filaments, bundling the filaments to form a tow, crimping the tow, drying the tow, and spinning a plurality of fibers from the tow. of filter rods, measuring the rod-to-rod coefficient of variation of the filter rods, and adjusting at least one of the number of spinnerets, the total denier of the filaments, and/or the denier per filament. to reduce the rod-to-rod variation to less than 5.

[0021] In a further aspect, the present invention is directed to a method of improving cross-sectional uniformity of cellulose acetate tow filaments. The method includes spinning a cellulose acetate dope through at least one spinneret to form filaments, bundling the filaments to form a tow, crimping the tow, drying the tow, filtering the tow, and filtering the tow. forming a rod, measuring the yield of the rod by the weight of the tow (g/100 rod), and removing deposits and/or blockages from at least one of the plurality of spinnerets to determine the yield of the rod; Including maintaining within ±20 mm H ₂ O of the target rod yield.

[0022] The present invention is also directed to a method of removing deposits and/or blockages from cellulose acetate tow spinnerets. The method includes soaking the spinneret in acetone to remove acetate, washing the spinneret in an acid wash to remove inorganic deposits, washing the spinneret in a caustic solution to remove organic material, and , including washing the spinneret with water or acetone to remove residue.

[0023] The present invention further includes a method of making a cellulose acetate tow bale. The method comprises dissolving cellulose acetate in a solvent to form a cellulose acetate dope, spinning the cellulose acetate dope through at least one spinneret to a total denier of 10,000 to 100,000, and forming filaments having a denier per filament of 10, bundling the filaments to form a tow, crimping the tow, drying the tow, and packaging the tow in a bale; In that case, the total denier varies by less than 3% across the bale, the denier per filament varies by less than 10% across the bale, and the ratio of the variation in total denier to the variation in denier per filament is The defined denier index is less than 2.5:1.
II. Preparation of cellulose acetate flakes
[0024] Cellulose acetate flakes are dissolved in a solvent to form a dope as described herein, US Pat. 775, and US Patent Publication No. 2013/0096297. Generally, acetylated cellulose is prepared by reacting cellulose with an acetylating agent in the presence of a suitable acidic catalyst. Acylating agents can include both carboxylic anhydrides (or simply anhydrides) and carboxylic acid halides, particularly carboxylic acid chlorides (or simply acid chlorides). Suitable acid chlorides include, for example, acetyl chloride, propionyl chloride, butyryl chloride, benzoyl chloride, and the like. Suitable anhydrides include, for example, anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and benzoic anhydride. Mixtures of these anhydrides or other acylating agents are also available for introducing different acyl groups into the cellulose. Mixed anhydrides such as acetic acid propionic anhydride, acetic acid butyric anhydride, etc. can also be utilized for this purpose in some embodiments.

[0025] Optionally, cellulose is thoroughly treated with an acetylating agent to produce derivatized cellulose with high DS values, most often with some additional hydroxyl group substitution (e.g., sulfate ester). acetylated. Extensive acetylation of cellulose means an acetylation reaction that is exhaustively carried out such that as many hydroxyl groups within the cellulose as possible undergo the acetylation reaction. When the cellulose acetate is intended for use in cigarette filters, the degree of substitution is less than 3.0, preferably 2.2-2.8 or 2.4-2.6.

[0026] Suitable acidic catalysts that promote acetylation of cellulose often comprise sulfuric acid or a mixture of sulfuric acid and at least one other acid. Other acidic catalysts that do not contain sulfuric acid are similarly available to facilitate the acetylation reaction. In the case of sulfuric acid, at least some hydroxyl groups within the cellulose may first be functionalized as sulfate esters during the acetylation reaction. Generally, most of such sulfate esters are cleaved during controlled partial hydrolysis used to reduce the amount of acetyl substitution. Other acidic catalysts are generally much less likely to react themselves with the hydroxyl groups of cellulose.

[0027] One of the highly desirable properties of acetylated cellulose is that it has several different properties depending on its intended end use, including, for example, films, flakes, fibers (e.g., fiber tows), non-deformable solids, and the like. The form is easily processable. In most cases, acetylated cellulose resulting from controlled partial hydrolysis precipitates as flake material.
III. Formation of cellulose acetate dope
[0028] The cellulose acetate dope is formed by dissolving the generally flaky cellulose acetate described herein in a solvent to form a dope solution. The solvent is the group consisting of water, acetone, methyl ethyl ketone, methylene chloride, dioxane, dimethylformamide, methanol, ethanol, glacial acetic acid, supercritical carbon dioxide, any suitable solvent capable of dissolving the above polymers, and combinations thereof. can be selected from In some aspects, the solvent is a combination of acetone and up to 5% by weight water. Pigments such as titanium dioxide may also be added to the dope. The dope may contain 20-30% by weight cellulose acetate and 70-80% by weight solvent. Pigments, if added, may be present from 0.1 to 5% by weight.

[0029] The dope may be heated to a temperature of, for example, 45-70°C to enhance mixing. Mixing can be carried out under ambient pressure or elevated pressure. High pressure is available when mixing occurs under a nitrogen blanket. Mixing time can range from 3 to 10 hours. Once the cellulose acetate is dissolved in the solvent, the dope is then filtered and degassed before being spun to form filaments. The degassing process can be performed under ambient pressure or elevated pressure. High pressure is available due to the nitrogen blanket. Filter sizes can vary and are selected according to downstream equipment and product specifications.
IV. Formation of cellulose acetate filaments and tows
[0030] To form filaments from cellulose acetate, a dope is formed as described above. The dope may comprise one or more cabinets and each cabinet may be spun in a spinner comprising a spinneret. The spinneret has holes that affect the rate at which the solvent evaporates from the filaments. Hole geometry and spinning parameters can be selected to form filaments of selected size, cross-sectional geometry, strength, and processability. Generally, the pores allow the formation of filaments of 25-75 micrometers in diameter. Various designs for holes are disclosed in US Patent Publication No. 2013/0192613, which is incorporated herein by reference in its entirety.

[0031] The spinneret may be in a cabinet operating at temperatures up to 100°C, but heat may be supplied by hot steam to evaporate the solvent. Over 90% of the solvent evaporates during the spinning process, leaving behind solid filaments of cellulose acetate. Filaments generally range from 1 to 15 denier per filament, such as 1 to 12 denier per filament, and are Y-shaped, R-shaped, X-shaped, K-shaped, C-shaped, O-shaped. It can have cross-sectional shapes including, but not limited to, letter-shaped, I-shaped, circular, serrated, elliptical, polygonal, and dogbone shapes. By modifying the temperature during the spinning process, as well as modifying the number of cabinets in the spinner, the strength of the filaments can be adjusted. For example, the filament can be easily damaged or broken as it first passes through the spinneret. However, as the filament moves further from the spinneret, the filament stiffens and the filament strength increases, allowing a stronger and larger airflow to continue to evaporate the solvent. Air flow through the spinner may be co-current or counter-current.

[0032] Once the filament passes through the spinneret, it is fed onto constant speed rolls where it may be further drawn. Additional spinning techniques are also available in lieu of dry spinning as described herein, including wet spinning and melt spinning. Optionally, a lubricant or finish can be added to the filaments. Representative lubricants or finishes include mineral oil, emulsifiers, and water, as disclosed in U.S. Pat. No. 7,585,442, which is incorporated herein by reference in its entirety. , but the lubricant or finish is not limited to these ingredients. Lubricants or finishes may be applied by spraying or wiping. Generally, a lubricant or finish is added to the filaments prior to forming the filaments into a tow.

[0033] The filaments are then bundled on rollers to form a tow. Generally, the tow can range in total denier from 10,000 to 100,000 and have a width of less than 8 cm (measured from horizontal edge to horizontal edge). In some aspects, once the tow is bundled, the tow may be plasticized before or during crimping. The plasticizer is typically sprayed onto the tow in liquid form, although other methods of plasticizer application are available. A plasticizer is selected that acts as a binder or hardener for the cellulose acetate. A large variety of plasticizers are available in amounts from 2 to 40% by weight. The amount of plasticizer used depends on the plasticizer itself, as well as the desired hardness of the plasticized tow.

[0034] In some preferred embodiments, the plasticizer is water, but numerous other plasticizers may also be utilized. Suitable plasticizers for use with the plasticized cellulose acetate described herein, in some embodiments, include, but are not limited to:

Formula 1 (wherein R1 is H, C ₁ -C ₄ alkyl, aryl, or C ₁ -C ₄ alkylaryl); Formula 2 (wherein R2 is H, C ₁ -C ₄ alkyl, aryl, or C ₁ -C ₄ alkylaryl, and R3 is H, C ₁ -C 4 alkyl, aryl, C ₁ -C ₄ alkylaryl, acyl, or C ₁ -C ₄ alkyl Formula 3 (wherein R4 and R6 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate) , acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ alkylamide, and R5 is H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, acyl, or C ₁ -C ₄ alkylacyl); Formula 4, wherein R7 is H, C ₁ -C ₄ alkyl, aryl, C ₁ -C 4 C ₄ alkylaryl, OH, C ₁ -C ₄ alkoxy, amine, or C ₁ -C ₄ alkylamine, wherein R8 and R9 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ to C ₄ alkylaryl, COOH, C ₁ to C ₄ alkyl carboxylate, acyl, C ₁ to C ₄ alkyl acyl, amine, C ₁ to C ₄ alkylamine, amide, or C ₁ to C ₄ Formula 5, wherein R10, R11, and R12 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkyl amine, amide, or C ₁ -C ₄ alkyl amide); Formula 6 (wherein R13 is H, C ₁ -C ₄ alkyl, aryl, or C ₁ -C ₄ alkylaryl, and R14 and R16 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ alkylamide Yes, R15 is , H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, acyl, or C ₁ -C ₄ alkyl acyl); Formula 7 (wherein R17 is H or C ₁ C ₄ alkyl, R18, R19, R20 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ alkylamide); Formula 8 (wherein R21 is H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkyl amine , amide, or C ₁ -C ₄ alkylamide, wherein R22 is H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, acyl, C ₁ -C ₄ alkylacyl, amine, or C ₁ -C ₄ alkylamine); Formula 9 (wherein R23 and R24 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH , C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkyl amine, amide, or C ₁ -C ₄ alkyl amide); (wherein R25, R26, R27 and R28 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl , C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkyl amine, amide, or C ₁ -C ₄ alkyl amide); Formula 11 (wherein R29, R30, and R31 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ alkylamide); Formula 12 (wherein R32 is H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl and R33 is H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, OH, C ₁ -C ₄ alkoxy, acyl, C ₁ -C ₄ alkylacyl, amine, or C ₁ -C ₄ alkylamine, and R34, R35, and R36 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH , C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkyl amine, amide, or C ₁ -C ₄ alkyl amide); Formula 12 (wherein R37, R38, R39, and R40 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl , C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ alkylamide); Formula 14 (wherein R41 is H, C ₁ - C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, OH, or C ₁ -C ₄ alkoxy, and R42 and R43 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl _{A triazine ( 1,2,3} , 1,2,4, or 1,3,5); independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, COOH, C ₁ -C ₄ alkyl carboxylate, a cyclic carbon or cyclic nitrogen that is an acyl, a C ₁ -C ₄ alkyl acyl, an amine, a C ₁ -C ₄ alkylamine, an amide, or a C ₁ -C ₄ alkylamide; independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, OH , C ₁ -C ₄ alkoxy, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C _{4 alkylaryl} , OH, C ₁ -C ₄ alkoxy, COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl, OH, C ₁ to C ₄ alkoxy, COOH, C ₁ to C ₄ alkyl carboxylate, acyl, C ₁ to C ₄ alkyl acyl, amine, C ₁ to C ₄ alkylamine, amide, or C ₁ to C ₄ Piperazines with R substituents derived from each of the cyclic carbons or nitrogens that are alkylamido; R44 and R46 are independently H, C ₁ -C ₄ alkyl, aryl, C ₁ -C ₄ alkylaryl , COOH, C ₁ -C ₄ alkyl carboxylate, acyl, C ₁ -C ₄ alkyl acyl, amine, C ₁ -C ₄ alkylamine, amide, or C ₁ -C ₄ alkylamide, and R44HN--R45-NHR46 wherein R45 is C ₁ -C ₁₀ alkyl; and combinations thereof. As used herein, "alkyl" means a C and H substituent that can be linear or branched (eg, t-butyl) and saturated or unsaturated. As used herein, "aryl" means an aromatic ring that can include phenyl, naphthyl, and heteroatom-containing aromatic rings.

[0035] Examples of suitable plasticizers for use in the plasticized cellulose acetates described herein include, in some embodiments, triacetin, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, triethyl Citrate, acetyl trimethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, tributyl-o-acetyl citrate, dibutyl phthalate, diaryl phthalate, diethyl phthalate, dimethyl phthalate, di-2-methoxyethyl phthalate, dioctyl phthalate (and isomers), dibutyl tartrate, ethyl-o-benzoylbenzoate, ethylphthalylethylglycolate, methylphthalylethylglycolate, n-ethyltoluenesulfonamide, o-cresyl-p-toluenesulfonate, aromatic diols, substituted aromatic diols, aromatic ethers, tripropionin, tribenzoin, polycaprolactone, glycerin, glycerol esters, diacetin, glycerol tribenzoate, glycerol acetate benzoate, polyethylene glycol, polyethylene glycol esters, polyethylene glycol diesters, di-2-ethylhexyl polyethylene Glycol esters, glycerol esters, diethylene glycol, polypropylene glycol, polyglycol diglycidyl ethers, dimethyl sulfoxide, N-methylpyrollidinone, propylene carbonate, C ₁ -C ₂₀ dicarboxylic acid esters, dimethyl adipate (and other dialkyl esters) , dibutyl malate, dioctyl malate, resorcinol monoacetate, catechol, catechol esters, phenol, epoxidized soybean oil, castor oil, linseed oil, epoxidized linseed oil, other vegetable oils, other seed oils, difunctionals based on polyethylene glycol glycidyl ethers, alkyl lactones (e.g. gamma-valerolactone), alkyl phosphate esters, aryl phosphate esters, phospholipids, aromatics (some of which are described herein, e.g. eugenol, cinnamyl alcohol, camphor, methoxyhydroxyacetophenone (including acetovanillone), vanillin, and ethyl vanillin), 2-phenoxyethanol, glycol ether , glycol esters, glycol ester ethers, polyglycol ethers, polyglycol esters, ethylene glycol ethers, propylene glycol ethers, ethylene glycol esters (e.g., ethylene glycol diacetate), propylene glycol esters, polypropylene glycol esters, acetylsalicylic acid, acetamino phen, naproxen, imidazole, triethanolamine, benzoic acid, benzyl benzoate, salicylic acid, 4-hydroxybenzoic acid, propyl-4-hydroxybenzoate, methyl-4-hydroxybenzoate, ethyl-4-hydroxybenzoate, benzyl-4-hydroxy benzoate, glyceryl tribenzoate, neopentyl dibenzoate, triethylene glycol dibenzoate, trimethylolethane tribenzoate, butylated hydroxytoluene, butylated hydroxyanisol, sorbitol, xylitol, ethylenediamine, piperidine, piperazine, hexamethylenediamine, Including, but not limited to, triazines, triazoles, pyrroles, etc., any derivatives thereof, and any combination thereof.

[0036] Examples of additional plasticizers suitable for utilization in the plasticized cellulose acetates described herein may include, in some embodiments, nonionic surfactants, which include are polysorbates (e.g. TWEEN® 20 or TWEEN® 80 available from SigmaAldrich), sorbitan esters (e.g. SPAN® products available from SigmaAldrich), polyethoxylated aromatics Hydrocarbons (e.g. TORITON® products available from SigmaAldrich), polyethoxylated fatty acids, polyethoxylated fatty alcohols (e.g. BRIJ® products available from SigmaAldrich), fluorinated interfaces Included are active agents, glucosides, and other nonionic surfactants with hydrocarbon tails ₍ e.g., C6 _- C22 alkyl groups) and hydrophilic head groups including hydroxyl and ester groups, and combinations thereof. but not limited to these. Several nonionic surfactants, alone or in combination with small molecule plasticizers, have been found to plasticize cellulose acetate. This is surprising since conventional plasticizers are small molecules. In contrast, nonionic surfactants with long hydrocarbon tail groups and possibly large head groups are bulky. For example, polyoxyethylene (20) sorbitan monolaurate was found to plasticize cellulose acetate, albeit significantly larger than conventional cellulose acetate plasticizers such as triacetin.

[0037] In some embodiments, the plasticizer may be bio-derived. For example, bio-derived triacetin, diacetin, tripropionin, glyceryl esters can be produced from glycerol, a by-product of biodiesel. Other examples of plasticizers that may be bioderived include vanillin, acetovanilone, gamma-valerolactone, eugenol, epoxidized soybean oil, castor oil, linseed oil, epoxidized linseed oil, and dicarboxylic esters (e.g., dimethyladipate, dibutyl malate), but are not limited to these. In some cases, the fragrant plasticizer is extractable from natural products and is therefore a bio-derived plasticizer.

[0038] In some embodiments, the plasticizer can be a semi-volatile to volatile plasticizer. Examples of some preferred semi-volatile to volatile plasticizers include glycerol esters (eg triacetin, diacetin, monoacetin), ethylene glycol diacetate, alkyllactones (eg γ-valerolactone), dibutylmalate, dioctyl Mention may be made, but is not limited to, malate, dibutyl tartrate, eugenol, tributyl phosphate, tributyl-o-acetyl citrate, and resorcinol monoacetate.

[0039] In some embodiments, more than one plasticizer is available. Additionally, a thermoplastic polymer may be included with the tow. Thermoplastic polymers include polyolefins (e.g., polyethylene and polypropylene), polyalphaolefins, polyesters, ethylene vinyl acetate copolymers, polyvinyl acetate, polyvinyl alcohol ("PVOH"), polyethyleneimine, polyacrylates, polymethacrylates, polyacrylamides, poly acrylonitrile, polyimide, polyamide, polyvinyl chloride, polysiloxane, polyurethane, polystyrene, polyetheramide copolymer, styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, Styrene-ethylene-propylene-styrene copolymers, butyl rubber, polyisobutylene, isobutylene-isoprene copolymers, acrylics, nitriles, and combinations thereof.

[0040] In some embodiments, the plasticizer is added to the tow before the crimper, such as at least 0.5 meters, such as at least 1 meter before entering the crimper. Numerous crimpers are known in the art, but they generally work by drawing the tow into the crimper, where rollers with some sort of groove or surface texture guide the crimp into the tow. . As described in U.S. Pat. No. 7,585,442, which is incorporated herein by reference in its entirety, the crimper comprises a stuffer box having a base frame and a top frame that moves relative to the base frame. It can be a crimper. The crimper includes a nip roller, cheek plates on the sides of the nip roller, doctor blades, flappers, and steam injectors.

[0041] The tow is pulled through the crimper by a pair of nip rollers, sometimes referred to as "crimp-guided" rollers, because the nip rollers crinkle or bend the tow as it passes through the nip. also, thus affecting the location of the crimp in the tow. One of the pair of nip rollers may be smooth, while the other nip roller may be grooved. The grooves can be of any type, including surface textures such as grooves, recesses, or other types of textures. The grooves are preferably of sinusoidal form, but may also be rectangular, triangular or semi-circular notches, grooves or ridges between which there is an axial line across the surface of the roller. There may or may not be a flat surface extending in the direction of (ie, horizontal to horizontal). These grooves range from 10 to 100 grooves per inch, preferably from 25 to 75 grooves per inch, most preferably from 25 to 75 grooves per inch. It can be 50 grooves. The groove depth (peak to trough) can range from 12.5 microns to 150 microns (0.5 mils to 5.0 mils), preferably from 25 to 50 microns (1 to 2 mils).

[0042] Each nip roller comprises steel/alloy bonded titanium carbide, tungsten carbide, HIPed or unHIPed MgO stabilized zirconia, or HIPed or unHIPed yttria stabilized zirconia, provided that can be made of metal or ceramic material, including but not limited to In some embodiments, the upper nip roller is smooth while the lower nip roller is grooved. The toe leaves the nip roller and enters the stuffer box. In some embodiments, the tow ends are lubricated prior to entering the stuffer box to minimize filament damage occurring between the nip rollers and cheek plates located on the sides of the nip rollers. can be This cheek plate can act as a guide to keep the tow between the nip rollers. A doctor blade is positioned adjacent the nip rollers and serves to guide the tow into the stuffer box and prevent the tow from sticking to the rollers.

[0043] The stuffer box may include steam injectors positioned adjacent the nip rollers in each side of the stuffer box. A steam injector injects steam, typically low pressure dry steam at a temperature of about 100° C., into the stuffer box to secure and lightly bond the tow crimp within the stuffer box channel.

[0044] The shape of the crimp may play a role in the processability of the final bale. Examples of crimp shapes can include horizontal, substantially horizontal, vertical, substantially vertical, an angle between horizontal and vertical, random, or any combination thereof, provided that: It is not limited to these. It should be noted that the terms "horizontal" and "vertical" refer to the general general crimp orientation, which may deviate +/- about 30 degrees from the shape.

[0045] The shape of the crimp can also be important to the processability of the final bale in subsequent processing steps, e.g. Horizontal crimp geometries may provide better filament cohesion than vertical and/or substantially vertical crimp geometries. To achieve horizontal crimping, at least one of three processing parameters, such as tow moisture content before crimping, tow thickness during crimping, and ratio of nip force to flap force during crimping, is adjusted. can be manipulated.

[0046] To achieve a horizontal and/or substantially horizontal crimp shape, crimping is performed on tows containing filaments with a lower weight percentage of total moisture, such as 5-25%. considered desirable. In some embodiments, a lower moisture weight percent is achieved by drying the tow prior to crimping, applying a finish emulsion with a higher solids concentration or lower moisture content, and separating control after applying a fine finish. reducing or eliminating any other moisture-contributing tow additions; altering the spinning conditions (increase temperature, speed, increase the airflow in the heating cabinet, change the dope concentration), or any combination thereof.

[0047] Additionally, a horizontal and/or substantially horizontal crimp shape is achieved by crimping narrower tows, i.e., reducing the total denier per inch of crimper nip roller width. obtain. In some embodiments, the total denier per inch of crimper nip roller width can be about 60,000 or less, about 50,000 or less, or about 40,000 or less. Suitable denier per inch of crimper nip roller width ranges from about 5,000, 10,000, 15,000, or 20,000 on the lower end to 60,000, 50,000, 40,000 on the upper end. , 35,000, or 30,000, but the total denier per inch of crimper nip roller width can range from any of the lower values to any of the upper values. , may include any subset therebetween.

[0048] Further, a horizontal and/or substantially horizontal crimp profile is achieved by crimping with a reduced nip force to flap force ratio, i.e., the ratio of applied nip force to applied flap force. obtain. In some embodiments, the ratio of nip force to flap force can be about 100:1 or less, about 50:1 or less, or about 25:1 or less. Suitable nip force to flap force ratios may range from a lower limit of about 3:1, 5:1, or 10:1 to an upper limit of about 100:1, 50:1, or 25:1, where: The nip-to-flap ratio can range from any of the lower limits to any of the upper limits, including any subset therebetween.

[0049] It should be noted that at least two of the above methods of achieving a horizontal and/or substantially horizontal crimp shape can be utilized in any combination. It should also be noted that when used in combination, the limits of the above parameters may be extended as synergistic effects may occur when used together. As a non-limiting example, a tow with a moisture content of about 27% w/w was processed at a total denier of about 25,000 per inch of crimper nip roll width with a nip force to flap force ratio of about 15:1. When crimped, a horizontal and/or substantially horizontal crimp shape can result.

[0050] Once the crimp is formed, the tow is directed to a dryer that dries and removes residual water and/or acetone. The dried tow is then fed into cans to form layers of tow. The dried tow may be placed in the can by a series of rollers, such as laying, layering, or aligning the tow within the can in a pattern. It should be noted that can can be used generally to refer to a container that can be of any shape, preferably square or rectangular, and of any material. The term "pattern" means any design that may or may not change during placement. In some embodiments, the pattern is substantially zigzag with a periodicity of about 1.6 cycles/m to about 19.7 cycles/m (about 0.5 cycles/ft to about 6 cycles/ft). can be In some embodiments, placing may include paddling the tow with a puddling index of about 10 m/m to about 40 m/m. The term "puddling" means placing a tow at least partially transversely thereon such that when placed, the tow's actual length is greater than its linear distance. The term "puddling index" means how many times the length of the tow corresponds to its linear distance when the tow is placed.

[0051] The layers of tow then move to a bale press where the bales are compacted and packaged for shipment. The cans are set in the press walls and then compressed by the platens. A typical tow bale compression and bale press design is disclosed in US Pat. No. 7,610,852, which is incorporated herein by reference in its entirety. Generally, the bale press includes two shaped platens selected to enable formation into a tow having a substantially flat surface that is maintained up to the packaging step. Such a substantially flat surface is advantageous as it allows the bales to be stacked during storage and shipping. In addition, a flat surface on the bale is advantageous in the debaling process described herein because the tows are less likely to become entangled and debaling can be achieved more efficiently.

[0052] In some embodiments, the packaging step may include at least one component such as wrapping material, vacuum ports (for vacuum release and/or vacuum suction), clamping elements, or any combination thereof. Suitable wrapping materials include air permeable materials, air impermeable materials, films (e.g. polymeric films, polyethylene films, plastic wrap), heat shrinkable films, cardboard, wood, textile materials (i.e., to form fabrics). non-woven materials (i.e., assemblies of random webs or mats of textile fibers held together by mechanical or chemical means, e.g. fusing thermoplastic fibers), foil materials (eg, metallic materials), etc., or any combination thereof. Suitable fastening elements include VELCRO®, pins, hooks, straps (eg, woven, non-woven, fabric, and/or metal), adhesives, tapes, hot-melt bonds, etc., or any combination thereof. can be, but are not limited to, In some embodiments, at least a portion of the packaging (including any components thereof) may be reusable.

[0053] In some embodiments, the bale has a height of about 76 cm (30 inches) to about 152 cm (60 inches), a length of about 117 cm (46 inches) to about 142 cm (56 inches), and a width of It can have dimensions ranging from about 89 cm (35 inches) to about 114 cm (45 inches). In some embodiments, the bale ranges in weight from 408 kg (900 lbs) to 953 kg (2100 lbs). In some embodiments, the bale can have a density greater than about 300 kg/m ³ (18.8 lb/ft ³ ).
V. Manufacture of tow for final product
[0054] The tow bales may be subjected to further processing to form final products, such as cigarette filters. Once baled, the tow is generally unveiled, bloomed, and formed into cigarette filters. Unbaling means removing the tow from the bale in which it was packaged. Depending on how the tow bales are crimped, compressed, and packaged, and on downstream manufacturing needs, tow unbaling can be performed at different speeds. The tow can be unbaled by picking it up from the tow bale and pulling it over the guides by rollers. The tow is then released or "bloomed" and formed into a rod, which is then wrapped with a paper called plugwrap. The filter rod is then cut to length and connected to tobacco.

[0055] During the blooming process, the tow can be released by using mechanical means, including pneumatic banding jets, and stretched under tension or semi-tension techniques using rollers. In some embodiments, air can be used to separate the filaments instead of mechanical means. If mechanical means are used, the blooming process can remove portions of the crimp. Therefore, if crimping is used to provide identification markings on the tow, the markings must be applied such that even if part of the crimp is removed, they are still readable.

[0056] The blooming process may include adding a plasticizer to the tow and curing the plasticized tow. Addition of a plasticizer allows softening of the fibers so that fiber-to-fiber bonds can form, which in turn hardens the filter to the desired hardness and consistency. In some embodiments, the plasticizer is applied to only one side of the bloomed tow, but should penetrate the tow. In other aspects, the plasticizer may be applied to each side of the tow. The plasticizer can be any plasticizer used in the art, including those disclosed in Section IV.

[0057] Once the tow is released, the tow is continuously fed to a device that forms a rod. Although one such apparatus is disclosed in U.S. Patent Publication No. 2012/0302416, which is incorporated herein by reference in its entirety, numerous apparatus for making tobacco rods are available in the art. known in the art. Molins PLC as well as Hauni-Werke Korber & Co. as manufacturers of rod making equipment. KG company is mentioned. The tow is formed into a cylindrical rod and wrapped with plug wrap. The plug wrap may be adhered with an adhesive to the rod, which is then connected to a smokable rod of tobacco.
VI. Observing and cleaning the spinneret
[0058] As described herein, the spinneret holes can become partially or completely occluded due to deposition and/or occlusion. Generally, the longer the run length of the process, the more deposits and/or blockages occur. Various constituents in the cellulose acetate dope can deposit on the spinneret, partially or completely blocking the spinneret pores over time. This deposition and/or blockage can be caused by several reasons. For example, if large particles remain after filtering, such particles can initiate blockage of the spinneret pores. If the cellulose acetate does not completely dissolve into the dope, the cellulose acetate can form deposits on the spinneret, at least partially plugging the pores. Regardless of the reason for the deposition and/or blockage, the once uniform spinneret pore sizes become different. As shown in FIG. 1A, a clean (and optionally new, unused) spinneret has uniformly sized pores. As shown in FIG. 1B, over time and use some of the pores become partially occluded. When the cellulose acetate dope is spun into filaments through partially closed holes, the filament cross-section and denier per filament differ from hole to hole.

[0059] The spinneret may be cleaned all at once or partially. For example, if 20 spinnerets are used to spin the dope, 5 spinnerets may be removed and cleaned if signs of deposition and/or blockage are observed. These spinnerets can then be replaced with new spinnerets or other process parameters can be adjusted to compensate for the spinneret reduction. Although less than ideal, if the yield varies significantly from the targets described herein, the entire process can be shut down to clean all spinnerets.

[0060] One indication of deposits and/or blockages accumulating during continuous operation of the process may be revealed by observation of the spinneret after cleaning. Observation can be, for example, visual inspection with the naked eye, under a microscope, or with a light projector or the like. If a light projector is used, pattern uniformity can be viewed. Additionally or alternatively, if a spinneret is suspected of having deposits and/or blockages, downstream measurements and testing of the tow and/or rods made from the tow are available to indicate so.

[0061] If the spinneret has deposits and/or blockages that have increased to interventional levels (eg, from impacting downstream products), special cleaning processes are available. First, the spinneret may be immersed in an acetone bath to remove the acetate from the spinneret. The acetone may be at a temperature of 20-55°C, such as 25-55°C, but may also be soaked for 5-60 minutes.

[0062] After treatment with the acetone bath, the spinneret may be air dried to allow the acetone to evaporate.
[0063] The spinneret may then be washed in a caustic solution to remove organic deposits. The caustic solution can be a commercial caustic cleaner such as OAKITE®, alkaline salts, diethylene glycol monobutyl ether, or other known caustic cleaning agents. Organic deposits can be organic salts and fatty acids. A caustic solution wash is generally carried out at a temperature of 20-70°C, eg 60-70°C. The spinneret can be washed in caustic solution for 5-180 minutes.

[0064] The spinneret may then be washed in an acid wash to remove inorganic deposits. The acid wash may contain sulfuric acid and/or nitric acid. The concentration of nitric acid may range from 5-20%, such as 10-20%, and the concentration of sulfuric acid may range from 40-90%, such as 55-80%, with the balance being water. Inorganic deposits may include pigments added to the cellulose acetate dope. Additionally, inorganic deposits may originate from the raw materials used to form the dope, or process equipment (eg, piping, vessels, pumps), but may also include metals, silica, and the like. Acid washing is generally carried out at a temperature of 20-60°C, eg 40-60°C. The spinneret can be washed in acid for 5-90 minutes. The spinneret may then be rinsed with hot water and/or hot acetone and then air dried. In some aspects, the caustic bath may be after the acid wash.

[0065] In some embodiments, the spinneret may be washed in an acid wash prior to washing in a caustic wash, ie the order of acid wash and caustic wash may vary.
[0066] Finally, the spinneret may be rinsed with water or acetone to remove any residue. Rinsing can be repeated until any visible residue is removed. If acetone is used, rinsing may be performed at a temperature of 20-50°C, such as 25-50°C. If a water rinse is used, the rinse may be performed at room temperature, eg 20-30°C. The spinneret can then be air dried.

[0067] Any of the above washing steps may be repeated if deposits and/or blockages are not removed after the initial cleaning. Additionally, lower temperatures can be used if the soak and rinse times are extended (eg, allowing overnight soaking at room temperature).

[0068] In some embodiments, an additional jet cleaning step may be included to aid in the removal of organic and inorganic deposits. A jet cleaning step may be included after soaking the spinneret in acetone, after caustic cleaning, after acid cleaning, and/or after washing the spinneret with water or acetone to remove residue. If the jet cleaning step follows a water or acetate wash (also called rinse), the spinner may be subjected to a final rinse with water or acetone. The jet cleaning step can be solvent-based jet cleaning. In some aspects, the solvent can be toluene, cyclohexane, dichlorobenzene, or other known solvents.

[0069] Greater than 90%, such as greater than 95%, greater than 97%, or greater than 99% of deposits and/or blockages are removed from the spinneret (including spinneret holes) after the above cleaning process has been performed on the spinneret. be done. The percentage of deposits and/or blockages removed is based on the percentage of spinneret holes that have some blockage (and not the percentage of blockage within individual holes). Removal of deposits and/or blockages can be quantified by visual inspection, for example, with the naked eye, under a microscope, and/or with a light projector. In some embodiments, a camera is also available to photograph the visual inspection. Preferably, the inspection is performed using a combination of cameras and light projectors.

[0070] In each of the above steps, the bath may be a static soak bath, an inert gas bubbling tank (eg, bubbled with nitrogen), an ultrasonic bath, and/or other agitation methods.
VII. Improved uniformity
[0071] As described herein, the present invention relates to improving the uniformity of tow products. Such improvements include reducing the coefficient of variation between rods, improving the cross-sectional uniformity of the filaments formed in the tow, and reducing the ratio of total denier variation to denier per filament variation. reduction. Each of these improvements enhances the performance of the final tow product, such as cigarette filters.
a. Coefficient of variation between rods
[0072] Especially for cigarette filters, the smoking experience from a particular type of cigarette should be uniform. One measure of this uniformity is pressure drop. Pressure drop, also called draw resistance, determines the amount of draw a smoker must apply to the cigarette in order to draw the smoke through the filter. The tobacco cylinder pressure drop in addition to the filter pressure drop must be within a range acceptable to consumers. Typically, the pressure drop (total across tobacco) is about 100 mm at the water gauge. The pressure drop across the filter rod is a measure of the static pressure difference across the filter rod at a defined volumetric airflow. Measurements may be performed in a temperature and relative humidity controlled laboratory (controlled to minimize the effects of temperature and relative humidity on the measurements). Measurements can be performed using commercially available filter rod test equipment that measures rod weight, circumference, and pressure drop at defined volumetric flow rates. The pressure drop is adjusted to the target circumference and the "coefficient of variation" is calculated. Statistical rules are used to determine if process adjustments are needed to adjust the pressure drop closer to the target or to reduce the coefficient of variation.

[0073] As described herein, uniform filaments formed into rods should have very similar pressure drops, i.e., rod-to-rod variation should be small, so the source of the tow, For example, the rod-to-rod coefficient of variation of filter rods consisting of a single bale can be measured as a means of determining the homogeneity of filaments spun through one or more spinnerets. The term "coefficient of variation" is a means of comparing the variance of two series by expressing the standard deviation as a percentage of the mean of the series. The coefficient of variation can be defined as:

[0074] Once the tow is formed into a filter rod in accordance with the present invention, the filter rod can be sampled to measure its pressure drop. Since a low coefficient of variation is desirable, the ability to adjust the coefficient of variation is also desirable. We have found that by adjusting at least one of a) the number of spinnerets, b) the total filament denier, or c) the denier per filament, the coefficient of variation between rods is less than 5, e.g. We have found that it can be reduced to less than 4, less than 3, or less than 2. The rod-to-rod coefficient of variation is preferably zero, but as a practical matter, the allowable rod-to-rod coefficient of variation may depend on the final product. For example, the rod-to-rod coefficient of variation allowed for so-called "super slim" cigarettes may exceed the rod-to-rod coefficient of variation allowed for regular cigarettes. Thus, in some embodiments, at least one of a) the number of spinnerets, b) the total filament denier, or c) the denier per filament when the coefficient of variation is 5 or more, such as 4 or more, or 3 or more It can be an opportunity to adjust one.

[0075] The tow manufacturer can be a different party than the cigarette filter manufacturer or the ultimate cigarette manufacturer, but the tow can be formed into rods for testing by any of these parties. For example, a tow manufacturer can sample tow in one or several bales and then form into rods to determine the coefficient of variation between rods.

[0076] As described herein, the cellulose acetate dope is spun through a spinneret to form filaments, which are then bundled and formed into tows. Denier per filament is determined by mass flow rate and drawdown. Since the filament cross-section is determined by the shape of the spinneret hole, and again the total denier is determined by the filament, the shape of the spinneret hole is an initial but important part of the final rod uniformity. . When adjusting the number of spinnerets, in some embodiments the number of spinnerets is increased. This spinneret increase can be implemented to increase manufacturing, average coefficient of variation, and increase total denier. In other aspects, the number of spinnerets may be reduced. This spinneret reduction may be performed when one or more cabinets are removed from the line for cleaning and/or inspection purposes, as described herein. In a further aspect, the total filament denier is increased. For example, the total filament denier can be increased to increase the minimum pressure drop. In a still further aspect, the total denier of the filaments is increased and the denier per filament is decreased and the denier per filament is increased. For example, the total denier of the filaments can be decreased while increasing the denier per filament to lower the minimum pressure drop.

[0077] In addition to the above adjustments to reduce the rod-to-rod coefficient of variation, the method of the present invention includes cleaning at least one of the spinnerets to remove deposits and/or blockages. The cleaning may be triggered by a rod-to-rod coefficient of variation greater than desirable, eg, greater than 2, greater than 3, greater than 4, or greater than 5. The spinneret may be cleaned according to the methods described herein, but is then thoroughly checked for remaining visible deposits and/or blockages.
b. filament cross section
[0078] The cross-section of the filaments and their uniformity also affect the final tow product, such as cigarette filters. As discussed herein, uniform pressure drop across the rods of tow source is a desirable quality for tow bales, and a low rod-to-rod coefficient of variation promotes pressure drop uniformity. reflect. However, most tow bales are sold by weight and pressure drop uniformity is irrelevant. Yield is calculated to assess the uniformity of the bale rod. Yield represents the relationship between pressure drop and weight (pressure drop divided by weight). Yield is often represented by a line on a graph, where the x-axis is weight and the y-axis is pressure drop. The bottom of the yield line is defined as the point where the rod forms a dent and the top of the yield line is defined as the point where the rod splits or mechanical roll wraps occur due to excessive tow. As shown in Figure 2, there is a target yield line. Upper and lower target yield limits are then typically set to within about ₂₀ mmH2O of the target. Weight is recorded as grams/100 rods. The weight of the tow can be adjusted on the rod maker to produce rods at the upper and lower limits for testing to ensure that the tow meets the target yield line. The samples in Figure 2 are roughly in line with the target yield line and within the upper and lower bounds. The same procedures and equipment are used to test the rods at the upper and lower limits used to test the rods for the coefficient of variation of pressure drop.

[0079] As described herein, the cellulose acetate dope is spun into filaments through the spinneret holes, so the cross-section of the filaments is determined by the shape of the spinneret holes. Over time, spinnerets are subject to deposition and/or blockage. When the measured yield deviates from the upper or lower target yield line, then one or more spinnerets are cleaned to remove deposits and/or blockages. After cleaning the spinneret(s), a yield remeasurement may then be performed to confirm that the yields are within set limits from the target yield line.

[0080] As described herein, adding spinnerets, removing spinnerets, adjusting the denier per filament, and adjusting the total denier may also improve yield, e.g. As the rod has a yield closer to the target yield line.
c. Denier Index: Ratio of variation in total denier to variation in denier per filament
[0081] Another way to check the uniformity of tow in a sample, eg, a bale, is to calculate the denier index. The Denier Index is a comparison of the variation in total denier and the variation in denier per filament. As described herein, rod uniformity can be achieved by adjusting the denier per filament, the total denier, or both. When one or both parameters are adjusted, it is desirable to maintain a predetermined ratio for variation between parameters to produce a uniform product. Denier per filament and total denier may vary depending on the final tow product, but the variation in total denier is less than 3%, such as less than 2.5%, less than 2%, or less than 1%. obtain. The variation in denier per filament may be less than 10%, such as less than 8%, less than 5%, or less than 3%. The ratio of the variation in total denier to the variation in denier per filament, ie, the Denier Index, is less than 2.5:1, such as less than 2:1, less than 1.5:1, less than 1:1, or less than 0.5:1. less than 6:1.

[0082] The invention will be better understood with reference to the following non-limiting examples.
VIII. Example

[0083] A cellulose acetate dope was prepared and spun through a spinneret as described herein. Over time, the yield fluctuated from the target yield and the denier per filament decreased, so more spinnerets were added to maintain the total denier. As shown in Figure 3, on the first day the denier per filament was about 2.85 and the total denier was 32,600 g/9000 meters. On day 14, the denier per filament decreased to 2.825 and the total denier increased to about 33,300. From the overall trend in Figure 3, the denier per filament decreased (indicating that the yield fluctuated from the target yield), but the addition of the spinneret kept the total denier while yielding within the target yield value. It is clear that

[0084] A cellulose acetate dope was prepared and spun through a spinneret as described herein. The total denier and denier per filament varied as shown in the table below, which shows FIG. 3 in tabular form. If the yield fluctuated outside the target yield, the denier per filament was reduced and the number of spinnerets was increased to maintain the total denier and bring the yield within the target yield value.

[0085] Total denier variation, denier per filament variation, and the ratio of total denier variation to denier per filament variation were obtained from the initial total denier and denier per filament numbers. Calculated based on variation. Measurements were carried out for about 6 months.

[0086] Although the invention has been described in detail, modifications within the spirit and scope of the invention will be apparent to those skilled in the art. Aspects of the present invention, and portions of various embodiments, and various features recited above and/or within the scope of the appended claims, in whole or in part, may be combined or interchanged. It should be understood that there is In the foregoing descriptions of various embodiments, those skilled in the art will recognize that embodiments referencing other embodiments can be appropriately combined with other embodiments. Furthermore, those skilled in the art will appreciate that the above description is for illustrative purposes only and is not intended to be a limitation on the present invention.
Specific aspects of the present invention are as follows.
[Aspect 1]
A method for reducing a rod-to-rod coefficient of variation in a plurality of cellulose acetate filter rods, comprising:
spinning the cellulose acetate dope through at least two spinnerets to form filaments;
bundling the filaments to form a tow;
crimping the tow;
drying the tow;
forming a plurality of filter rods from the tow;
measuring the coefficient of variation between the plurality of rods;
adjusting at least one of the at least two spinnerets, the total denier of the filaments, or the denier per filament to reduce the rod-to-rod coefficient of variation to less than 5;
method including.
[Aspect 2]
The method of aspect 1, wherein the number of spinnerets is reduced.
[Aspect 3]
The method of aspect 1, wherein the number of spinnerets is increased.
[Aspect 4]
The method of claim 1, wherein the total filament denier is decreased and the denier per filament is increased.
[Aspect 5]
The method of claim 1, wherein the total filament denier is increased and the denier per filament is decreased.
[Aspect 6]
A method according to aspect 1, wherein
removing at least one of the at least two spinnerets from the method when the coefficient of variation between the rods is 5 or more; and
cleaning the at least one spinneret to remove visible deposits and/or blockages;
The method further comprising
[Aspect 7]
A method for improving cross-sectional uniformity of cellulose acetate tow filaments comprising:
Spinning the cellulose acetate dope through multiple spinnerets to form filaments,
bundling the filaments to form a tow;
crimping the tow;
drying the tow;
forming a plurality of filter rods from the tow;
Measure the yield of the rod by the weight of the tow (g/100 rod), and
removing deposits and/or blockages from at least one of the plurality of spinnerets to maintain the yield within ±20 mmH ₂ O of the target yield;
method including.
[Aspect 8]
8. The method of aspect 7, wherein the cross section is Y-shaped, R-shaped, X-shaped, K-shaped, C-shaped, O-shaped, I-shaped, circular, serrated, elliptical, multi-shaped. A method selected from the group consisting of rectangular and dogbone shapes.
[Aspect 9]
A method of removing deposits and/or blockages from a cellulose acetate tow spinneret comprising:
a) removing the acetate by soaking the spinneret in acetone;
b) washing the spinneret with caustic and acid washes to remove organic and inorganic deposits, and
c) washing the spinneret with water or acetone to remove residue;
method including.
[Aspect 10]
A method according to aspect 9, wherein the temperature of the acetone in the soaking step is 20-55°C.
[Aspect 11]
A method according to aspect 9, wherein the spinneret is soaked for 5-60 minutes.
[Aspect 12]
A method according to aspect 9, wherein the temperature of the acid in the acid wash is 20-60°C.
[Aspect 13]
A method according to aspect 9, wherein the spinneret is washed in an acid wash for 5-90 minutes.
[Aspect 14]
The method of embodiment 9, wherein the temperature of said caustic solution is 20-70°C.
[Aspect 15]
The method of embodiment 9, wherein said spinneret is washed in said caustic solution for 5-180 minutes.
[Aspect 16]
10. The method of aspect 9, wherein greater than 90% of deposits and/or blockages are removed from the spinneret.
[Aspect 17]
10. The method of aspect 9, further comprising visually inspecting the spinneret for removal of deposits and/or blockages.
[Aspect 18]
18. The method of aspect 17, wherein said visual inspection is microscopic.
[Aspect 19]
18. The method of aspect 17, wherein the visual inspection uses a light projector.
[Aspect 20]
10. The method of aspect 9, further comprising a solvent-based jet cleaning step after steps a), b) and/or c).
[Aspect 21]
A method for producing a cellulose acetate tow bale comprising:
dissolving cellulose acetate in a solvent to form a cellulose acetate dope;
spinning the cellulose acetate dope through at least one spinneret to form filaments having a total denier of 10,000 to 100,000 and a denier per filament of 1 to 15;
bundling the filaments to form a tow;
crimping the tow;
drying the tow, and
packaging the tow into bales;
including
A method wherein the total denier of tows from said bale varies by less than 3%, the denier per filament of tows from said bale varies by less than 10%, and the denier index is less than 2.5:1.

Claims (6)

A method for reducing the coefficient of variation of rod-to-rod pressure drop in a plurality of cellulose acetate filter rods, comprising:
spinning the cellulose acetate dope through at least two spinnerets to form filaments;
bundling the filaments to form a tow;
crimping the tow;
drying the tow;
forming a plurality of filter rods from the tow;
measuring the coefficient of variation of the pressure drop across the plurality of rods;
adjusting at least one of the at least two spinnerets, the total denier of the filaments, or the denier per filament to reduce the coefficient of variation of the pressure drop between the rods to less than 5;
method including. 2. The method of claim 1, wherein the number of spinnerets is reduced. 2. The method of claim 1, wherein the number of spinnerets is increased. 2. The method of claim 1, wherein the total filament denier is decreased and the denier per filament is increased. 2. The method of claim 1, wherein the total filament denier is increased and the denier per filament is decreased. 2. The method of claim 1, wherein
removing at least one of the at least two spinnerets from the method when the coefficient of variation of the pressure drop across the rods is 5 or greater; and cleaning the at least one spinneret to remove visible deposits and/or or removing the blockage,
The method further comprising

Images