Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/09—Carboxylic acids; Metal salts thereof; Anhydrides thereof
  • C08K5/092—Polycarboxylic acids
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
  • C08L101/16—Compositions of unspecified macromolecular compounds the macromolecular compounds being biodegradable
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/88—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polycondensation products as major constituent with other polymers or low-molecular-weight compounds
  • D01F6/92—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polycondensation products as major constituent with other polymers or low-molecular-weight compounds of polyesters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2203/00—Applications
  • C08L2203/12—Applications used for fibers

Definitions

• the present invention relates to a thermoplastic composition that comprises an unreacted mixture of an aliphatic polyester polymer and a multicarboxylic acid.
• the thermoplastic composition is capable of being extruded into fibers that may be formed into nonwoven structures that may be used in a disposable absorbent product intended for the absorption of fluids such as body fluids.
• Disposable absorbent products currently find widespread use in many applications. For example, in the infant and child care areas, diapers and training pants have generally replaced reusable cloth absorbent articles.
• Other typical disposable absorbent products include feminine care products such as sanitary napkins or tampons, adult incontinence products, and health care products such as surgical drapes or wound dressings.
• a typical disposable absorbent product generally comprises a composite structure including a topsheet, a backsheet, and an absorbent structure between the topsheet and backsheet. These products usually include some type of fastening system for fitting the product onto the wearer.
• Disposable absorbent products are typically subjected to one or more liquid insults, such as of water, urine, menses, or blood, during use.
• the outer cover backsheet materials of the disposable absorbent products are typically made of liquid- insoluble and liquid impermeable materials, such as polypropylene films, that exhibit a sufficient strength and handling capability so that the disposable absorbent product retains its integrity during use by a wearer and does not allow leakage of the liquid insulting the product.
• the outer cover materials are made very thin in order to reduce the overall bulk of the disposable absorbent product so as to reduce the likelihood of blockage of a toilet or a sewage pipe, then the outer cover material typically will not exhibit sufficient strength to prevent tearing or ripping as the outer cover material is subjected to the stresses of normal use by a wearer.
• the disposable absorbent product may be easily and efficiently disposed of by composting.
• the disposable absorbent product may be easily and efficiently disposed of to a liquid sewage system wherein the disposable absorbent product is capable of being degraded.
• fibers prepared from aliphatic polyesters are known, problems have been encountered with their use.
• aliphatic polyester polymers are known to have a relatively slow crystallization rate as compared to, for example, polyolefin polymers, thereby often resulting in poor processability of the aliphatic polyester polymers.
• the aliphatic polyester polymers generally do not have good thermal dimensional-stability.
• the aliphatic polyester polymers usually undergo severe heat- shrinkage due to the relaxation of the polymer chain during downstream heat treatment processes, such as thermal bonding and lamination, unless an extra step such as heat setting is taken.
• heat setting step generally limits the use of the fiber in in-situ nonwoven forming processes, such as spunbond and meltblown, where heat setting is very difficult to be accomplished.
• the use of processing additives may retard the biodegradation rate of the original material or the processing additives themselves may not be biodegradable.
• thermoplastic composition which exhibits improved processability, reduced crystal size, improved thermal dimensional-stability properties, and improved biodegradability. It is also an object of the present invention to provide a thermoplastic composition which may be easily and efficiently formed into a fiber.
• thermoplastic composition which is suitable for use in preparing nonwoven structures. It is also an object of the present invention to provide a fiber or nonwoven structure that is readily degradable in the environment.
• the present invention concerns a thermoplastic composition that is desirably biodegradable and yet which is easily prepared and readily processable into desired final structures, such as fibers or nonwoven structures.
• thermoplastic composition that comprises a mixture of a first component and a second component.
• thermoplastic composition comprises a mixture of an aliphatic polyester polymer and a multicarboxylic acid, wherein the multicarboxylic acid has a total of carbon atoms that is less than about 30, wherein the thermoplastic composition exhibits desired properties.
• the present invention concerns a fiber prepared from the thermoplastic composition wherein the fiber exhibits desired properties.
• the present invention concerns a nonwoven structure comprising a fiber prepared from the thermoplastic composition.
• One embodiment of such a nonwoven structure is a backsheet useful in a disposable absorbent product.
• thermoplastic is meant to refer to a material that softens when exposed to heat and substantially returns to its original condition when cooled to room temperature.
• the first component in the thermoplastic composition is an aliphatic polyester polymer. Suitable aliphatic polyester polymers include, but are not limited to, poly(lactic acid), polybutylene succinate, polybutylene succinate-co-adipate, polyhydroxybutyrate- co-valerate, polycaprolactone, sulfonated polyethylene terephthalate, mixtures of such polymers, or copolymers of such polymers.
• the aliphatic polyester polymer used is poly(lactic acid).
• Poly(lactic acid) polymer is generally prepared by the polymerization of lactic acid.
• a chemically equivalent material may also be prepared by the polymerization of lactide.
• poly(lactic acid) polymer is intended to represent the polymer that is prepared by either the polymerization of lactic acid or lactide.
• Lactic acid and lactide are known to be asymmetrical molecules, having two optical isomers referred to, respectively, as the levorotatory (hereinafter referred to as "L”) enantiomer and the dextrorotatory (hereinafter referred to as "D") enantiomer.
• L levorotatory
• D dextrorotatory
• the aliphatic polyester polymer be present in the thermoplastic composition in an amount effective to result in the thermoplastic composition exhibiting desired properties.
• the aliphatic polyester polymer will be present in the thermoplastic composition in a weight amount that is less than 100 weight percent, beneficially between about 40 weight percent to less than 100 weight percent, more beneficially between about 50 weight percent to about 95 weight percent, suitably between about 60 weight percent to about 90 weight percent, more suitably between about 60 weight percent to about 80 weight percent, and most suitably between about 70 weight percent to about 75 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer and the multicarboxylic acid present in the thermoplastic composition.
• the aliphatic polyester polymer exhibit a weight average molecular weight that is effective for the thermoplastic composition to exhibit desirable melt strength, fiber mechanical strength, and fiber spinning properties.
• the weight average molecular weight of an aliphatic polyester polymer is too high, this represents that the polymer chains are heavily entangled which may result in a thermoplastic composition comprising that aliphatic polyester polymer being difficult to process.
• the weight average molecular weight of an aliphatic polyester polymer is too low, this represents that the polymer chains are not entangled enough which may result in a thermoplastic composition comprising that aliphatic polyester polymer exhibiting a relatively weak melt strength, making high speed processing very difficult.
• aliphatic polyester polymers suitable for use in the present invention exhibit weight average molecular weights that are beneficially between about 10,000 to about 2,000,000, more beneficially between about 50,000 to about 400,000, and suitably between about 100,000 to about 300,000.
• the weight average molecular weight for polymers or polymer blends can be determined using a method as described in the Test Methods section herein.
• the aliphatic polyester polymer exhibit a polydispersity index value that is effective for the thermoplastic composition to exhibit desirable melt strength, fiber mechanical strength, and fiber spinning properties.
• polydispersity index is meant to represent the value obtained by dividing the weight average molecular weight of a polymer by the number average molecular weight of the polymer.
• the polydispersity index value of an aliphatic polyester polymer is too high, a thermoplastic composition comprising that aliphatic polyester polymer may be difficult to process due to inconsistent processing properties caused by polymer segments comprising low molecular weight polymers that have lower melt strength properties during spinning.
• the aliphatic polyester polymer exhibits a polydispersity index value that is beneficially between about 1 to about 15, more beneficially between about 1 to about 4, and suitably between about 1 to about 3.
• the number average molecular weight for polymers or polymer blends can be determined using a method as described in the Test Methods section herein.
• the aliphatic polyester polymer be melt processable. It is therefore desired that the aliphatic polyester polymer exhibit a melt flow rate that is beneficially between about 1 gram per 10 minutes to about 200 grams per 10 minutes, suitably between about 10 grams per 10 minutes to about 100 grams per 10 minutes, and more suitably between about 20 grams per 10 minutes to about 40 grams per 10 minutes.
• the melt flow rate of a material may be determined, for example, according to ASTM Test Method D1238-E incorporated in its entirety herein by reference.
• the aliphatic polyester polymer be biodegradable.
• the thermoplastic composition comprising the aliphatic polyester polymer, either in the form of a fiber or in the form of a nonwoven structure, will be degradable when disposed of to the environment and exposed to air and/or water.
• biodegradable is meant to represent that a material degrades from the action of naturally occurring microorganisms such as bacteria, fungi, and algae.
• the aliphatic polyester polymer be compostable.
• the thermoplastic composition comprising the aliphatic polyester polymer, either in the form of a fiber or in the form of a nonwoven structure, will be compostable when disposed of to the environment and exposed to air and/or water.
• compostable is meant to represent that a material is capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds, and biomass, at a rate consistent with known compostable materials.
• the second component in the thermoplastic composition is a multicarboxylic acid.
• a multicarboxylic acid is any acid that comprises two or more carboxylic acid groups. Suitable for use in the present invention are dicarboxylic acids, which comprise two carboxylic acid groups. It is generally desired that the multicarboxylic acid have a total number of carbons that is not too large because then the crystallization kinetics, the speed at which crystallization occurs, could be slower than is desired. It is therefore desired that the multicarboxylic acid have a total of carbon atoms that is beneficially less than about 30, more beneficially between about 3 to about 30, suitably between about 4 to about 20, and more suitably between about 5 to about 10.
• Suitable multicarboxylic acids include, but are not limited to, malonic acid, citric acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and mixtures of such acids.
• the multicarboxylic acid be present in the thermoplastic composition in an amount effective to result in the thermoplastic composition exhibiting desired properties.
• the multicarboxylic acid will be present in the thermoplastic composition in a weight amount that is greater than 0 weight percent, beneficially between greater than 0 weight percent to about 60 weight percent, more beneficially between about 5 weight percent to about 50 weight percent, suitably between about 10 weight percent to about 40 weight percent, more suitably between about 20 weight percent to about 40 weight percent, and most suitably between about 25 weight percent to about 30 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer and the multicarboxylic acid present in the thermoplastic composition.
• thermoplastic composition of the present invention In order for a thermoplastic composition of the present invention to be processed into a product, such as a fiber or a nonwoven structure, that exhibits the properties desired in the present invention, it has been discovered that it is generally desired that the multicarboxylic acid beneficially exists in a liquid state during thermal processing of the thermoplastic composition but that during cooling of the processed thermoplastic composition, the multicarboxylic acid turns into a solid state, or crystallizes, before the aliphatic polyester polymer turns into a solid state, or crystallizes.
• the multicarboxylic acid is believed to perform two important, but distinct, functions.
• the multicarboxylic acid is believed to function as a process lubricant or plasticizer that facilitates the processing of the thermoplastic composition while increasing the flexibility and toughness of a final product, such as a fiber or a nonwoven structure, through internal modification of the aliphatic polyester polymer.
• the multicarboxylic acid replaces the secondary valence bonds holding together the aliphatic polyester polymer chains with multicarboxylic acid-to-aliphatic polyester polymer valence bonds, thus facilitating the movement of the polymer chain segments.
• the multicarboxylic acid is believed to function as a nucleating agent.
• Aliphatic polyester polymers are known to have a very slow crystallization rate.
• the process of cooling the extruded polymer to ambient temperature is usually achieved by blowing ambient or sub-ambient temperature air over the extruded polymer.
• such solid nucleating agents generally agglomerate very easily in the thermoplastic composition which can result in the blocking of filters and spinneret holes during spinning.
• the nucleating affect of such solid nucleating agents usually peaks at add-on levels of about 1 percent of such solid nucleating agents. Both of these factors generally reduce the ability or the desire to add in high weight percentages of such solid nucleating agents into the thermoplastic composition.
• the multicarboxylic acid generally exists in a liquid state during the extrusion process, wherein the multicarboxylic acid functions as a plasticizer, while the multicarboxylic acid is still able to solidify or crystallize before the aliphatic polyester during cooling, wherein the multicarboxylic acid functions as a nucleating agent. It is believed that upon cooling from the homogeneous melt, the multicarboxylic acid solidifies or crystallizes relatively more quickly and completely just as it falls below its melting point since it is a relatively small molecule.
• adipic acid has a melting temperature of about 162°C and a crystallization temperature of about 145°C.
• the aliphatic polyester polymer being a macromolecule, has a relatively very slow crystallization rate which means that when cooled it generally solidifies or crystallizes more slowly and at a temperature lower than its melting temperature.
• poly(lactic acid) has a melting temperature of about 175°C and a crystallization temperature of about 121°C.
• the multicarboxylic acid starts to crystallize before the aliphatic polyester polymer and generally acts as solid nucleating sites within the cooling thermoplastic composition.
• thermoplastic composition or a product made from such a thermoplastic composition exhibits a crystal size that is effective for the thermoplastic composition or a product made from the thermoplastic composition to exhibit desired properties.
• a thermally processed thermoplastic composition or a product made from such a thermoplastic composition exhibits a Mean Crystal Size that is beneficially less than about 120 Angstroms, more beneficially less than about 110 Angstroms, suitably less than about 100 Angstroms, more suitably less than about 80 Angstroms, and more suitably less than about 70 Angstroms.
• the Mean Crystal Size of a material may be determined according to the procedure described in the Test Methods section herein. While the principal components of the thermoplastic composition of the present invention have been described in the foregoing, such thermoplastic composition is not limited thereto and can include other components not adversely effecting the the desired properties of the thermoplastic composition. Exemplary materials which could be used as additional components would include, without limitation, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, solid solvents, plasticizers, nucleating agents, particulates, and materials added to enhance processability of the thermoplastic composition.
• an optional component is a surface modified particulate available, for example, from Burgess Pigment Company of Sandersville, Georgia under the designation Burgess Polyclay surface modified particulate, or from Barretts Minerals Inc. of Dillon, Montana, under the designation
• Micropflex1200 surface modified particulate If such additional components are included in a thermoplastic composition, it is generally desired that such additional components be used in an amount that is beneficially less than about 5 weight percent, more beneficially less than about 3 weight percent, and suitably less than about 1 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer, the multicarboxylic acid, and the additional components present in the thermoplastic composition.
• thermoplastic composition of the present invention is generally simply a mixture of the aliphatic polyester polymer, the multicarboxylic acid, and, optionally, any additional components.
• thermoplastic composition dry mixture is beneficially agitated, stirred, or otherwise blended to effectively uniformly mix the aliphatic polyester polymer and the multicarboxylic acid such that an essentially homogeneous dry mixture is formed.
• the dry mixture may then be melt blended in, for example, an extruder, to effectively uniformly mix the aliphatic polyester polymer and the multicarboxylic acid such that an essentially homogeneous melted mixture is formed.
• the essentially homogeneous melted mixture may then be cooled and pelletized.
• the essentially homogeneous melted mixture may be sent directly to a spin pack or other equipment for forming fibers or a nonwoven structure.
• Alternative methods of mixing together the components of the present invention include adding the multicarboxylic acid to the aliphatic polyester in, for example, an extruder being used to mix the components together.
• Other methods of mixing together the components of the present invention are also possible and will be easily recognized by one skilled in the art.
• the melting or softening temperature of the thermoplastic composition be within a range that is typically encountered in most process applications. As such, it is generally desired that the melting or softening temperature of the thermoplastic composition beneficially be between about 25°C to about 350°C, more beneficially be between about 55°C to about 300°C, and suitably be between about 100°C to about 200°C.
• thermoplastic composition of the present invention has been found to generally exhibit improved processability properties as compared to a thermoplastic composition comprising the aliphatic polyester polymer but none of the multicarboxylic acid.
• the improved processability of a thermoplastic composition is measured as a decline in the glass transition temperature (Tg).
• Tg glass transition temperature
• the polymers in the thermoplastic composition are believed to begin segmental motion which means that there is enough energy, usually thermal energy, to allow the bulk polymer to flow.
• a decline in the glass transition temperature means that it takes less thermal energy to induce this segmental motion and the resultant flow. If a thermoplastic composition is processed at a relatively lower temperature, the components of the thermoplastic composition will not be as vulnerable to thermal degradation.
• thermoplastic composition has a lowered glass transition temperature
• process equipment such as an extruder
• a thermoplastic composition having a lowered glass transition temperature will generally require less energy to process and therefore be more economical to use.
• the thermoplastic composition or a product made from such a thermoplastic composition, such as a fiber or nonwoven structure will exhibit a glass transition temperature (Tg) that is beneficially less than about 55°C, more beneficially less than about 50°C, suitably less than about 45°C, and more suitably less than about 40°C.
• Tg glass transition temperature
• fiber or “fibrous” is meant to refer to a material wherein the length to diameter ratio of such material is greater than about 10.
• a nonfiber or “nonfibrous” material is meant to refer to a material wherein the length to diameter ratio of such material is about 10 or less.
• the melt spinning of polymers includes the production of continuous filament, such as spunbond or meltblown, and non-continuous filament, such as staple and short-cut fibers, structures.
• a thermoplastic composition is extruded and fed to a distribution system where the thermoplastic composition is introduced into a spinneret plate.
• the spun fiber is then cooled, solidified, drawn by an aerodynamic system and then formed into a conventional nonwoven.
• the spun fiber is cooled, solidified, and drawn, generally by a mechanical rolls system, to an intermediate filament diameter and collected fiber, rather than being directly formed into a nonwoven structure.
• the collected fiber may be "cold drawn” at a temperature below its softening temperature, to the desired finished fiber diameter and can be followed by crimping/texturizing and cutting to a desirable fiber length.
• Fibers can be cut into relatively short lengths, such as staple fibers which generally have lengths in the range of about 25 to about 50 millimeters and short-cut fibers which are even shorter and generally have lengths less than about 18 millimeters. See, for example, US Patent 4,789,592 to Taniguchi et al., and US Patent 5,336,552 to Strack et al., both of which are incorporated herein by reference in their entirety.
• the present invention generally alleviates the need for, but does not prohibit, a heat-setting step because the use of the multicarboxylic acid in the thermoplastic composition generally allows for the usage of existing spunbond and meltblown assets without major process modification.
• the blending of the aliphatic polyester polymer with a multicarboxylic acid therefore generally maximizes the crystallization of the aliphatic polyester polymer which generally minimizes the expected heat shrinkage of the aliphatic polyester polymer.
• the fibers prepared from the thermoplastic composition of the present invention undergo heat- setting. It is desired that such heat setting further reduce possible heat shrinkage of the fiber.
• This heat-setting can be done when the fibers are subjected to a constant strain, which typically can be, but is not limited to, about 10 to about 20 percent, at a temperature that is beneficially greater than about 50°C, more beneficially greater than about 70°C, and suitably greater than about 90°C. It is generally recommended to use the highest possible heat-setting conditions, including both applied strain and temperatures, while not sacrificing a fiber's processability.
• too high of a heat- setting temperature such as, for example, a temperature close to the melting temperature of a component of a fiber, may reduce the fiber strength and could result in the fiber being hard to handle due to tackiness.
• a fiber prepared from the thermoplastic composition of the present invention exhibit an amount of shrinking, at a temperature of about 100°C and for a time period of about 15 minutes, quantified as a Heat Shrinkage value, that is beneficially less than about 15 percent, more beneficially less than about 10 percent, suitably less than about 5 percent, and more suitably less than about 2 percent, wherein the amount of shrinking is based upon the difference between the initial and final lengths of the fiber divided by the initial length of the fiber multiplied by 100.
• the Heat Shrinkage value for a fiber may be determined according to the procedure described in the Test Methods section herein.
• thermoplastic composition of the present invention is suited for preparing fibers or nonwoven structures that may be used in disposable products including disposable absorbent products such as diapers, adult incontinent products, and bed pads; in catamenial devices such as sanitary napkins, and tampons; and other absorbent products such as wipes, bibs, wound dressings, and surgical capes or drapes.
• the present invention relates to a disposable absorbent product comprising the multicomponent fibers of the present invention.
• the thermoplastic composition is formed into a fibrous matrix for incorporation into a disposable absorbent product.
• a fibrous matrix may take the form of, for example, a fibrous nonwoven web. Fibrous nonwoven webs may be made completely from fibers prepared from the thermoplastic composition of the present invention or they may be blended with other fibers.
• the length of the fibers used may depend on the particular end use contemplated. Where the fibers are to be degraded in water as, for example, in a toilet, it is advantageous if the lengths are maintained at or below about 15 millimeters.
• a disposable absorbent product comprises a liquid-permeable topsheet, a backsheet attached to the liquid-permeable topsheet, and an absorbent structure positioned between the liquid-permeable topsheet and the backsheet, wherein the backsheet comprises fibers prepared from the thermoplastic composition of the present invention.
• Exemplary disposable absorbent products are generally described in US-A-4,710,187; US-A-4,762,521 ; US-A-4,770,656; and US-A-4,798,603; which references are incorporated herein by reference.
• Absorbent products and structures according to all aspects of the present invention are generally subjected, during use, to multiple insults of a body liquid. Accordingly, the absorbent products and structures are desirably capable of absorbing multiple insults of body liquids in quantities to which the absorbent products and structures will be exposed during use. The insults are generally separated from one anoth er by a period of time.
• the melting temperature of a material was determined using differential scanning calorimetry.
• a differential scanning calorimeter available from T.A. Instruments Inc. of New Castle, Delaware, under the designation Thermal Analyst 2910 Differential Scanning Calorimeter(DSC), which was outfitted with a liquid nitrogen cooling accessory and used in combination with Thermal Analyst 2200 analysis software program, was used for the determination of melting temperatures.
• the material samples tested were either in the form of fibers or resin pellets. It is preferred to not to handle the material samples directly, but rather to use tweezers and other tools, so as not to introduce anything that would produce erroneous results.
• the material samples were cut, in the case of fibers, or placed, in the case of resin pellets, into an aluminum pan and weighed to an accuracy of 0.01 mg on an analytical balance. If needed, a lid was crimped over the material sample onto the pan.
• the differential scanning calorimeter was calibrated using an indium metal standard and a baseline correction performed, as described in the manual for the differential scanning calorimeter.
• a material sample was placed into the test chamber of the differential scanning calorimeter for testing and an empty pan is used as a reference. All testing was run with a 55 cubic centimeter/minute nitrogen (industrial grade) purge on the test chamber.
• the heating and cooling program is a 2 cycle test that begins with equilibration of the chamber to -75°C, followed by a heating cycle of 20°C/minute to 220°C, followed by a cooling cycle at 20°C/minute to -75°C, and then another heating cycle of 20°C/minute to 220°C.
• Tg glass transition temperature
• a capillary rheometer available from G ⁇ ttfert of Rock Hill, South Carolina, under the designation G ⁇ ttfert Rheograph 2003 capillary rheometer, which was used in combination with WinRHEO (version 2.31) analysis software was used to evaluate the apparent viscosity rheological properties of material samples.
• the capillary rheometer setup included a 2000 bar pressure transducer and a 30/1 :0/180 round hole capillary die.
• the material sample being tested demonstrates or is known to have water sensitivity
• the material sample is dried in a vacuum oven above its glass transition temperature, i.e. above 55 or 60°C for PLA materials, under a vacuum of at least 15 inches of mercury with a nitrogen gas purge of at least 30 standard cubic feet per hour (SCFH) for at least 16 hours.
• SCFH standard cubic feet per hour
• the material sample is loaded incrementally into the column, packing resin into the column with a ramrod each time to ensure a consistent melt during testing.
• a 2 minute melt time precedes each test to allow the material sample to completely melt at the test temperature.
• the capillary rheometer takes data points automatically and determines the apparent viscosity (in Pascal-second) at 7 apparent shear rates (1 /second): 50, 100, 200, 500, 1000, 2000, and 5000.
• the resultant rheology curve of apparent shear rate vs. apparent viscosity produced gives an indication of how the material sample will run at that temperature in an extrusion process.
• the apparent viscosity values at a shear rate of at least 1000 1 /second are of specific interest because these are the typical conditions found in commercial fiber spinning extruders.
• Weight/Number Average Molecular Weights A gas permeation chromatography (GPC) method is used to determine the molecular weight distribution of samples of poly(lactic acid) whose weight average molecular weight (M w ) is between 800 to 400,000.
• the GPC is setup with two PLgel Mixed K linear 5 micron, 7.5 x 300 millimeter analytical columns in series.
• the column and detector temperatures are 30°C.
• the mobile phase is HPLX grade tetrahydrofuran(THF).
• the pump rate is 0.8 milliliters per minute with an injection volume of 25 microliters. Total run time is 30 minutes. It is important to note that new analytical columns must be installed every 4 months, a new guard column every month, and a new in-line filter every month.
• Standard of polystyrene polymers obtained from Aldrich Chemical Co., should be mixed into solvent of dichloromethane(DCM):THF (10:90), both HPLC grade, in order to obtain 1mg/mL concentrations. Multiple polystyrene standards can be combined in one standard solution provided that their peaks do not overlap when chromatographed. A range of standards of about 687 to 400,000 should be prepared.
• Standard mixtures with Aldrich polystyrenes of varying molecular weights(in weight average molecular weight-Mw) include: Standardl (401 ,340; 32,660; 2,727), Standard 2 (45,730; 4,075), Standard 3 (95,800; 12,860) and Standard 4 (184,200; 24,150; 687).
• the correlation coefficient of the fourth order regression calculated for each standard should be not less than 0.950 and not more than 1.050.
• the relative standard deviation (RSD) of all the M w 's of the check standard preparations should not be more than 5.0 percent.
• the average of the M w 's of the check standard preparation injections should be within 10 percent of the M w on the first check standard preparation injection.
• the required equipment for the determination of heat shrinkage include: a convection oven (Thelco model 160DM laboratory oven), 0.5g (+/- 0.06g) sinker weights, Vz inch binder clips, masking tape, graph paper with at least % inch squares, foam posterboard (11 by 14 inches) or equivalent substrate to attach the graph paper and samples.
• the convection oven should be capable of a temperature of 100°C.
• Fiber samples are melt spun at their respective spinning conditions, a 30 filament bundle is preferred, and mechanically drawn to obtain fibers with a jetstretch of 224 or higher. Only fibers of the same jetstretch can be compared to one another in regards to their heat shrinkage.
• the jetstretch of a fiber is the ratio of the speed of the drawdown roll divided by the linear extrusion rate (distance/time) of the melted polymer exiting the spinneret.
• the spun fiber is usually collected onto a bobbin using a winder. The collected fiber bundle is separated into 30 filaments, if a 30 filament bundle has not already been obtained, and cut into 9 inch lengths.
• the graph paper is taped onto the posterboard where one edge of the graph paper is matched with the edge of the posterboard.
• One end of the fiber bundle is taped, no more than the end 1 inch.
• the taped end is clipped to the posterboard at the edge where the graph paper is matched up such that the edge of the clip rests over one of the horizontal lines on the graph paper while holding the fiber bundle in place (the taped end should be barely visible as it's secured under the clip).
• the other end of the bundle is pulled taught and lined up parallel to the vertical lines on the graph paper.
• pinch the 0.5g sinker around the fiber bundle are then the attachment process for each replicate. Usually, 3 replicates can be attached at one time.
• Marks can be made on the graph paper to indicate the initial positions of the sinkers.
• the samples are placed into the 100°C oven such that they hang vertically and do not touch the posterboard. At time intervals of 5, 10, and 15 minutes quickly mark the new location of the sinkers on the graph paper and return samples to the oven.
• After the testing is complete remove the posterboard and measure the distances between the origin (where the clip held the fibers) and the marks at 5, 10 and 15 minutes with a ruler graduated to 1/16 inch (about 0.16 cm). Three replicates per sample is recommended. Calculate averages, standard deviations and percent shrinkage. The percent shrinkage is calculated as (initial length of the fiber - measured length of the fiber) divided by the initial length of the fiber and multiplied by 100.
• the Heat Shrinkage values reported herein use the values obtained at 15 minutes.
• Measurement of the crystal sizes within a fiber sample was determined by x-ray diffraction using an x-ray machine, available from Philips Inc. of Mahwah, New Jersey, under the designation XRG-3000 x-ray machine, outfitted with a copper tube.
• Photographs were obtained and a plot done using a wide angle goniometer.
• a reflection pattern was obtained in the equatorial direction relative to the fiber, scanning through the (hkl) layer line.
• the (100) plane at about 16.4° 2Q was selected so as to be consistent with all dimension calculations.
• a mean dimension for the crystallites perpendicular to the (100) plane was then calculated.
• a poly(lactic acid) polymer was obtained from Chronopol Inc., Golden, Colorado.
• the poly(lactic acid) polymer had an L:D ratio of 100 to 0, a melting temperature of about 175°C, a weight average molecular weight of about 211,000, a number average molecular weight of about 127,000, a polydispersity index of about 1.66, and a residual lactic acid monomer value of about 5.5 weight percent.
• the poly(lactic acid) polymer was mixed with various amounts of adipic acid.
• the blend of the poly(lactic acid) polymer with the adipic acid involved dry mixing the components followed by melt mixing them together to provide vigorous mixing of the components, which was achieved in a counter-rotating twin screw extruder. Mixing was conducted on either a BRABENDERTM twin screw compounder or a HAAKETM twin screw extruder with mixing screws.
• the spinning line consists of a 3/4" diameter extruder with a 24:1 L:D (length:diameter) ratio screw and 3 heating zones which feeds into a 0.62 inch diameter Koch® static mixer unit and then into the spinning head (4 th and 5 th heating zones) through a spinneret of 15 to 30 holes, where each hole has a diameter of about 500 micrometers.
• the temperatures of each heating zone is indicated sequentially under the temperature profile section.
• the fibers are air quenched at 13°C to 22°C and drawn down by a mechanical draw roll to either a winder unit or a fiber drawing unit (as in the Lurgi spunbond process).
• Table 1 The process conditions for several of the prepared fibers are shown in Table 1.
• a poly(lactic acid) polymer was obtained from Chronopol Inc., Golden, Colorado.
• the poly(lactic acid) polymer had an L:D ratio of 100 to 0, a melting temperature of about 175°C, a weight average molecular weight of about 181,000, a number average molecular weight of about 115,000, a polydispersity index of about 1.57, and a residual lactic acid monomer value of about 2.3 weight percent.
• the poly(lactic acid) polymer was mixed with various amounts of adipic acid.
• the blend of the poly(lactic acid) polymer with the adipic acid involved dry mixing the components followed by melt mixing them together to provide vigorous mixing of the components, which was achieved in a counter-rotating twin screw extruder. Mixing was conducted on either a BRABENDERTM twin screw compounder or a HAAKETM twin screw extruder with mixing screws.
• the spinning line consists of a 3/4" diameter extruder with a 24:1 L:D (length:diameter) ratio screw and 3 heating zones which feeds into a 0.62 inch diameter Koch® static mixer unit and then into the spinning head (4 th and 5 lh heating zones) through a spinneret of 15 to 30 holes, where each hole has a diameter of about 500 micrometers.
• the temperatures of each heating zone is indicated sequentially under the temperature profile section.
• the fibers are air quenched at 13°C to 22°C and drawn down by a mechanical draw roll to either a winder unit or a fiber drawing unit (as in the Lurgi spunbond process).
• Table 3 The process conditions for several of the prepared fibers are shown in Table 3.
• the prepared fibers were then evaluated for heat shrinkage, Tg, and biodegradability.
• the results of these evaluations are shown in Table 4.
• the actual percentage of the poly(lactic acid) polymer/adipic acid ratios were determined by using nuclear magnetic resonance as the ratio between CH and CH 2 peaks.

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• 1997
  • 1997-12-30 RU RU99116596/04A patent/RU2218368C2/ru not_active IP Right Cessation
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