MXPA99006203A - Thermoplastic composition - Google Patents

Abstract

Disclosed is a thermoplastic composition that comprises a unreacted mixture of an aliphatic polyester polymer and a multicarboxylic acid. One example of such a thermoplastic composition is a mixture of poly(lactic acid) and adipic 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.

Description

THERMOPLASTIC COMPOSITION Background of the Invention Field of the Invention The present invention relates to a thermoplastic composition comprising an unreacted mixture of an aliphatic polyester polymer and a poly-carboxylic acid The thermoplastic composition is capable of being extruded into fiber which can be formed into non-woven structures which can be used in a disposable absorbent product intended for the absorption of fluids, such as body fluids.

Description of Related Art Disposable absorbent articles currently find widespread use in many applications. For example in the child and infant care areas, the training underpants diapers have replaced the reusable cloth absorbent articles. Other typical disposable absorbent products include women's care products such as sanitary napkins or tampons, adult incontinence products and health care products, surgical covers or wound dressings. A typical disposable absorbent product generally comprises a composite structure that includes an upper sheet, a lower ho and an absorbent structure between the upper sheet and lower sheet. These products usually include some kind of restraint system for notching the product on the user Disposable absorbent products are typically used for one or more insults of liquid, such as urine, menstrual fluids or blood, during use. As such, the outer cover sheet materials of the disposable absorbent products are typically making of insoluble materials in liquid and liquid impervious such as polypropylene films, which exhibit sufficient strength and handling capacity so that disposable absorbent product retains its integrity during use by a user and does not allow the liquid to drain off. insults the product.

Although current disposable baby diapers and other disposable absorbent products have generally been accepted by the public, these products still need improvement in specific areas. For example, many disposable absorbent products can be difficult to discard. For example, attempts to discard water with many disposable absorbent products in a toilet inside a sewer system typically carry blockage from the toilet or from the pipes connecting the toilet to the sewer system. In particular, the outer cover materials, typically used in the disposable absorbent products generally do not disintegrate or disperse when disposed of with water discharge in a retret so that the disposable absorbent products can not be disposed of in this manner. If the outer covering materials are made too thin in order to reduce the overall volume of disposable absorbent product as to reduce the possibility of the block of a toilet or a sewer line then the outer covering material typically does not exhibit sufficient strength to to avoid tearing or breaking to subject the outer covering material to the normal user voltages by a user.

In addition, the disposal of solid waste has become a growing concern throughout the world. When the landfills are filled, there has been an increased demand for a reduction in the source of material in disposable products, the incorporation of more recyclable and / degradable components into disposable products, and the product design that can be disposed of by different means. to the incorporation in waste facilities of solid waste, such as landfills.

As such, there is a need for new materials that can be used in disposable absorbent products that generally retain their integrity and strength during use but after such use, the materials must be disposed of more efficiently. For example, the disposable absorbent product can be easily and efficiently discarded by composting. Alternatively, the disposable absorbent product can be easily and efficiently discarded in a liquid drainage system where the disposable absorbent product is capable of being degraded.

Although the aliphatic polyester prepared fibers are known, problems have been encountered with their use, and in particular, the aliphatic polyester polymers are known to have a relatively slow crystallization rate compared to, for example, polyolefin polymers, resulting in both in poor processability in the aliphatic polyester polymers. Aliphatic polyester polymers generally do not have good thermal dimensional stability Aliphatic polyester polymers usually suffer from severe heat shrinkage due to the relaxation of the polymer chain during the heat treatment processes below, such as thermal bonding and the lamination, unless s take an extra step, such as the settlement by heat. However, such a heat settling step generally limits the use of the fiber in non-woven formation processes in place, such as joined with spinning and melt blowing, where heat settling is very difficult to achieve. In addition, the use of processing additives may delay the biodegradation rate of the original material or the processing additives themselves, may not be biodegradable. It is therefore an object of the present invention to provide a thermoplastic composition which exhibits improved processing, 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 can be easily and efficiently formed into a fiber.

It is also an object of the present invention to provide a thermoplastic composition which is adapted for use in the preparation of non-woven structures.

It is an object of the present invention to provide a nonwoven or fiber structure that is easily degradable in the environment.

Synthesis of the Invention The present invention relates to a thermoplastic composition which is desirably biodegradable and which nevertheless is easily prepared and easily processed into desired end structures such as fiber or nonwoven structures.

One aspect of the present invention relates to the thermoplastic composition comprising a mixture of a first component and a second component.

An incorporation of such a thermoplastic composition comprises a mixture of an aliphatic polyester polymer and a poly-carboxylic acid, wherein the carboxylic acid has a total of carbon atoms that is less than about 30, and wherein the thermoplastic composition exhibits the desired properties. .

In another aspect, the present invention relates to a prepared fiber of the thermoplastic composition wherein the fiber exhibits the desired properties.

In another aspect, the present invention relates to a non-woven structure comprising a fiber prepared from the thermoplastic composition.

An incorporation of the nonwoven structure and a useful bottom sheet into a disposable absorbent product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a thermoplastic composition which includes a first component a second component. As used herein, the term "thermoplastic" is meant to refer to a material that softens when exposed to heat and returns essentially 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 succinate-co-adipate polybutylene, polyhydroxy butyrate-co valerate, polycaprolactone, polyethylene sulfonated terephthalate, mixtures of such polymers, or copolymers of such polymers.

In one embodiment of the present invention, it is desired that the aliphatic polyester polymer used be poly (lactic acid). The poly (lactic acid) polymer is generally prepared by the polymerization of lactic acid. However, it will be recognized by one skilled in the art that a chemically equivalent material can also be prepared by the polymerization of lactic acid, as used herein, the term "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 asymmetric molecules having two optical isomers mentioned, respectively, as the levogirator enantiomer (hereinafter referred to as "L") and dexogiratory enantiomer (hereinafter referred to as "D"). As a result, by polymerizing a particular enantiomer by using a mixture of the two enantomers, it is possible to prepare different polymers that are chemically similar so that they have different properties. In particular, it has been found that by modifying the stereochemistry of a poly (lactic acid) polymer, it is possible to control, for example, the melting temperature, the melt rheology, the crystallinity of the polymer. By being able to control such properties it is possible to prepare a multicomponent fiber exhibiting the desired melting strength, mechanical properties, smoothness and desired processing properties so as to be able to manufacture attenuated fibers accentuated by heat and crimps.

It is generally desired that the aliphatic polyester polymer be decent in the thermoplastic composition in an amount effective to result in the thermoplastic composition exhibiting the desired properties. The aliphatic polyester polymer will be present in the thermoplastic composition in a weight amount that is less than 100% by weight, beneficially from about 40% by weight to less than 100% by weight, more beneficially within about 50%. % p weight at about 95% by weight, suitably from about 60% by weight to about 90% by weight, m suitably from between about 60% by weight to about 80% by weight, and more suitably from about 70% p weight to about 75% by weight, wherein all per cent pro weight is based on the total weight amount of aliphatic polyester polymer and the muíticarboxli acid present in the thermoplastic composition.

It is generally desired that the aliphatic polyether polymer exhibit a weight average molecular weight that is effective for the thermoplastic composition to exhibit desirable melt strength, fiber strength, and desirable fiber spinning properties. In general, if the weight average molecular weight of an aliphatic polyether polymer is very high, this represents that the polymer chains are heavily entangled, which can result in a thermoplastic composition comprising that aliphatic polyester polymer which is difficult to process inversely, if weight The weight average molecular weight of an aliphatic polyether polymer is very low, this represents that the polymer chains are not sufficiently entangled, which may result in a thermoplastic composition comprising the aliphatic polyester polymer exhibiting a relatively weak melted strength, making the processing at very difficult speed. Thus, aliphatic polyester polymers suitable for use in the present invention exhibit average molecular weight weights and are beneficially from about 10,000 to about 2,000,000 more beneficially between about 50,000 to about 400,000 and suitably from about 100,000 to around 300,000. The weight average molecular weight for polymer or polymer mixtures can be determined using a method as described in the test methods section given herein.

It is also desired that the aliphatic polyester polymer exhibit a polydispersity index value that is effective for the thermoplastic composition exhibiting a desirable melt strength, fiber strength and fiber spinning properties. As used herein, the term "polydispersity index" is intended to represent the value obtained by dividing the average molecular weight of a polymer by the average molecular weight of a polymer number. In general, if the polydispersity index value of an aliphatic polyester polymer is very high, a thermoplastic composition comprising the aliphatic polyester polymer can be difficult to process due to the inconsistent processing properties caused by the polymer segments comprising the low molecular weight polymers having lower melt strength properties during spinning. Therefore, it is desirable that the aliphatic polyester polymer exhibits a polydispersity index value that is beneficially from 1 to about d 15. More beneficially from about 1 to about 4 and suitably from about 1 to about 3. The number average molecular weight for polymers or d polymer mixtures can be determined using a method as described in the test methods section given herein.

It is generally desired that the aliphatic polyester polymer be processable with melt. It is therefore desired that the aliphatic polyester polymer exhibit a melt flow rate that is beneficially between about one gram per 10 minutes to about 200 grams per 10 minutes suitably of between about 10 grams per 10 minutes around 100 grams per 10 minutes, and more appropriately d between about 20 grams per 10 minutes to about 4 grams per 10 minutes. The rate of melt flow of material can be determined, for example, according to method d test ASTM D1239-E incorporated herein in its entirety by reference.

In the present invention, it is desired that the aliphatic polyester polymer be biodegradable. As a result of this, the thermoplastic composition comprising the aliphatic polyester polymer, either in the form of a fiber or in the form of a non-woven structure, will be degraded when discarded to the environment and exposed to air and / or the water. As used herein, "biodegradable" is intended to represent that a material is degraded by the action of naturally occurring microorganisms such as bacteria, fungi, and algae.

In the present invention, it is desired that the aliphatic polyester polymer be compostable. As a result of this, the thermoplastic composition comprising the aliphatic polyester polymer, whether in the form of a fiber or in the form of a non-woven structure, will be compostable when discarded into the environment and exposed to the air and / or to the air. Water. As used herein, "compostable" is intended to represent that the material is capable of undergoing biological decomposition at a composted site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds, and biomass. a rate consistent with known compostable materials The second component in the thermoplastic composition is a multicarboxylic acid. A multicarboxylic acid is any acid comprising two or more carboxylic acid groups. Dicarboxylic acids, which comprise two carboxylic acid groups, are suitable for use in the present invention. It is generally desired that the multicarboxylic acid have a total number of carbon that is not very large because then the crystallization kinetics, at the rate at which it occurs at crystallization, may be slower than desired. Therefore, it is desired that the multicarboxylic acid have a total carbon atom that is beneficially less than about 30, more beneficially from about 3 to about 30 suitably from about 4 to about 20, and more suitably from about 5 to about 10. The polycyclic carboxylic acids include, but are not limited to, malonic acid, citric acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebasic acid and mixtures of acid acids.

It is generally desired that 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 more than 0% by weight beneficially from more than 0% by weight to about 60% by weight, more beneficially of between about 5% by weight about 50% by weight, appropriately between or around d % by weight to about 40% by weight, more suitably d between about 20% by weight to about 40% by weight, more suitably from about 25% by weight to about 30% by weight, where All percents by weight are based on the total weight amount of the aliphatic polyester polymer and the multicarboxylic acid present in the thermoplastic composition.

In order that the thermoplastic composition of the present invention be processed into a product, such as a fibr or a non-woven structure exhibiting the desired properties of the present invention, it has been found that it is generally desired that the multicarboxylic acid beneficially exist in a liquid state during thermal processing of the thermoplastic composition but that during cooling the processed thermoplastic composition, the multicarboxylic acid converts to a solid state or crystallizes before the aliphatic polyester polymer is returned to a solid state, crystallizes.

In the thermoplastic composition of the present invention, the multicarboxylic acid is believed to carry out important but distinct functions. First, when the thermoplastic composition is in a melted state, the multicarboxylic acid is believed to function as a process lubricant plasticizer that facilitates the processing of the thermoplastic composition while increasing the flexibility and strength of a final product such as a fiber. non-woven structure, through the internal modification of aliphatic polyester polymer. Although no attempt is made to be bound here, it is believed that the multicarboxylic acid replaces the secondary valence bonds by keeping the aliphatic polyester polymer chains together with the valences of multicarboxylic acid-to-aliphatic polyester polymer, thereby facilitating the movement of the polymer chain segment. This effect is evidenced, for example in a mixture of poly (lactic acid) and adipic acid where the melting temperature of the thermoplastic composition changes at lower temperatures with an increasing mixture ratio of adipic acid to poly (acid). lactic). With this effect, the out-of-torque required to overturn an extruder is generally reduced dramatically with the polymer processing of poly (lactic acid) alone. In addition, the process temperature required to spin the thermoplastic composition into a final product, such as a fiber or a nonwoven structure, is dramatically reduced in a general manner, thereby decreasing the risk of thermal degradation of the poly (lactic acid) polymer. ). Second, when a final product prepared from the thermoplastic composition such as a fiber or a non-woven structure is being cooled and solidified from its liquid to melted state, the multicarboxylic acid is believed to function as a nucleating agent. Aliphatic polyester polymers are known to have a very slow crystallization rate. Traditionally, there are two main ways to resolve this issue. One is the change of the cooling temperature profile in order to maximize the crystallization kinetics, while the other is to add a nucleating agent to increase the sites and the degree of crystallization The cooling process of the polymer extruded at room temperature is usually achieved by blowing air at room temperature or sub-ambient on the extruded polymer. This can be mentioned as cooling supercooling because the change in temperature is usually higher than 100 ° C and more frequently greater than 150 ° over a relatively short time frame (seconds) to make this common process. Furthermore, the ideal cooling temperature profile needed to be the only method of maximizing the crystallization kinetics of aliphatic polyesters in a real manufacturing process is very difficult due to the extreme cooling required within a very short period of time. Standard cooling methods can be used in combination with a second modification method. The second traditional method is to have a nucleating agent, such as solid particles, mixed with the thermoplastic composition to provide sites for initiation of crystallization during cooling. However, such solid nucleating agents generally agglomerate very easily in the thermoplastic composition which can result in blocking of the filters and orifices of the spinning organ during spinning. In addition, the nucleant effect of such solid nucleating agents usually rises to the level of aggregates of about 1% of such solid nucleating agents. Both of these factors generally reduce the ability or desire to add high weight percentages of such solid nucleating agents in the thermoplastic composition. . In the processing of the thermoplastic composition of the present invention, however, it has been found that the multicarboxylic acid generally exists in a solid 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 the cooling, where the multicarboxylic acid functions as a nucleating agent. S believes that with the cooling of the homogeneous melt, the multicarboxylic acid solidifies, crystallizes relatively more rapidly and completely just as it falls below its melted point since it is a relatively small molecule. The adipic acid has a melting temperature of about 162 ° and a crystallization temperature of about 145 ° C.

The aliphatic polyester polymer, being a macromolecule, has a relatively slow crystallization rate which means that when it cools it generally solidifies or crystallizes more slowly and at a lower temperature than its melting temperature. For example, poly (lactic acid) has a melting temperature d around 175 ° C and a crystallization temperature d around 121 ° C. During cooling, then, the multicarboxylic acid starts to crystallize before the aliphatic polyester polymer and generally acts as solid nucleant sites within the thermoplastic chiller composition.

It is generally desired that a thermally-processed thermoplastic composition or a product made from a thermoplastic composition, such as a fiber or a woven structure, exhibit a crystal size that is effective for the thermoplastic composition or a product made from the thermoplastic composition to exhibit desired properties. In an embodiment of the present invention, it is generally desired that a thermally processed thermoplastic composition or a product made from a thermoplastic composition, such as a fiber or non-woven structure, exhibit a main crystal size that is beneficially less than about 120 Angstroms , m Beneficially of less than about 110 Angstroms suitably less than about 100 Angstroms, suitably less than about 80 Angstroms, and suitably less than about 70 Angstroms. The main crystal size of a material can be determined according to the procedure described in the test methods section given here.

Although the main components of the thermoplastic composition of the present invention are described above, such a thermoplastic composition does not limit this and may include other components that do not adversely affect the desired properties of the thermoplastic composition. Exemplary materials, which may be used as additional components, will include, without limitation pigments, antioxidants, stabilizers, surfactants, flow promoting waxes, solid solvents, plastics, nucleating agents, particles and aggregates to improve processing of the thermoplastic composition. . An example of an optional component is a modified surface particle available, for example, from Burgess Pigment Company Sandersville, Georgia under the designation Burgess Polyclay Surface Modified Particle, or from Barretts Minerals Inc., Dillon, Montana, under the designation Modified Particle Surface Micropflexl200. . If such additional components are included in a thermoplastic composition, it is generally desired that such additional components be used in an amount which is beneficially less than about 5% by weight, more beneficially less than about 3% by weight, suitably less than about 1% by weight, where all percents by weight are based on the total weight amount of the aliphatic polyester polymer, the multicarboxylic acid, and the additional components present in the thermoplastic composition.

The thermoplastic composition of the present invention is generally simply a mixture of aliphatic polyester polymer, multicarboxylic acid and optionally any additional components. In order to achieve the desired properties of the thermoplastic composition of the present invention, it has been found to be critical that the aliphatic polyester polymer and the multicarboxylic acid remain essentially unreacted with each other so that a copolymer comprising each aliphatic polyether polymer and the Polycarboxylic acid does not form. As such, the aliphatic polyester polymer and the multicarboxylic acid remain distinct components of the thermoplastic composition.

In an embodiment of the present invention after dry blending together the aliphatic polyester polymer and the multicarboxylic acid to form a dry blend of thermoplastic composition, such dry blend of thermoplastic composition is stirred, stirred or otherwise beneficially blended to effectively mix uniformly the aliphatic polyester polymer and the multicarboxylic acid so that an essentially homogeneous dry mixture is formed. The dry blend can then be mixed with melt in, eg, an extruder to effectively uniformly mix the aliphatic polyester polymer and the multicarboxylic acid so that an essentially homogeneous melt is formed. The essentially homogeneous melted mixture can then be cooled and polietizada. Alternatively, the essentially homogeneous melt mixture can be sent directly to a spin pack or other equipment to form fibers or a non-woven structure. Alternating methods of mixing together the components of the present invention include adding multi-carboxylic acid to the aliphatic polyester in, for example, extruder which are being used to mix the components together. In addition, it is possible to initiate melting mixing of both of the components together at the same time. Other methods d mixed together of the components of the present invention are also possible and will be readily recognized by one skilled in the art. In order to determine whether the aliphatic polyester polymer and the multicarboxylic acid remain essentially unreacted, it is possible to use techniques, such as infrared analysis and nuclear magnetic resonance to evaluate the chemical characteristics of the final thermoplastic composition.

It is generally desired that the melting or softening temperature of the thermoplastic position is within a range that is typically found in most process applications. As such, it is generally desired that the temperature of melting or softening of the thermoplastic composition be beneficially between about 25 ° C about 350 ° C, more beneficially between about 55 ° to about 300 ° C and suitably from around 100 ° C to around 200 ° C.

The thermoplastic composition of the present invention has been found to exhibit generally improved processing properties as compared to the thermoplastic composition comprising the aliphatic polyester polymer but none of the multicarboxylic acid. As used herein, the improved processability of the thermoplastic composition was measured as a decline in the glass transition temperature (Tg). At the glass transition temperature, the polymers in the thermoplastic composition are believed to be a segment movement which means that there is sufficient energy, usually thermal energy, to allow the polymer to flow. A decline in the glass transition temperature meant that it takes less thermal energy to induce this segment movement and the resulting flow. If a thermoplastic composition is processed at a relatively lower temperature, the components of the thermoplastic composition will not be vulnerable to thermal degradation. Also if a thermoplastic composition has a lower glass transition temperature, then the process equipment such as an extruder, can typically be operated at lower energy settings ta as using less torsional force to turn the screw of the extruder. In general, then a thermoplastic composition having a lower glass transition temperature will generally require less energy to process and therefore be more economical to use.

In an embodiment of the present invention, the thermoplastic composition or a product made of such a thermoplastic composition such as a fiber or a non-woven structure will exhibit a glass transition temperature (Tg) which 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.

As used herein, the term "fibers" or "fibrous" is meant to refer to a material wherein the proportion of the diameter length of such a material is greater than about 10. Conversely, a "non-fiber" or "non-fibrous" material "is meant to refer to a material where the ratio of length to diameter of such material is about 10 or less.

The methods for making fibers are well known and do not need to be described in detail here. Polymer melt spinning includes the production of continuous filaments such as spunbond or meltblown and non-continuous filament bonding, such as shortened and artificial fiber structures. To form a bonded fiber with melt blown yarn, a thermoplastic composition is generally extruded and supplied to a distribution system where the thermoplastic composition is introduced into a spinner organ plate. The spun fiber is then cooled, solidified, pulled by an aerodynamic system and then formed into a conventional nonwoven. Meanwhile, to produce the shortened or cut the spun fiber is cooled, solidified and pulled, generally by a mechanical roller system to a diameter of intermediate filament and fibr harvested rather than being formed directly in a non-woven structure. Subsequently, the collected fiber can be "cold-pulled" at a temperature below the softening temperature, to the desired finished fiber diameter and can be followed by picking / texturing and cutting to a desirable fiber length. The fibers can be cut into relatively short stretches, such as short fibers, which will generally have lengths in the range d around 25 to about 50 millimeters and short fibers, which will be even shorter and will generally have lengths of less than about 18 millimeters. See, for example, U.S. Patent Nos. 4,789,592 issued to Taniguchi et al. And 5,336,552 issued to Strack et al., Both of which are hereby incorporated by reference in their entirety.

A problem encountered with preparing fibers from aliphatic polyester only polymers is that such fibers typically experience shrinkage during heat processing downstream. Heat shrinkage mainly occurs due to the thermally induced chain relaxation of the polymer segments in the amorphous phase and in the crystalline and complete phase. To overcome this problem, it is generally desirable to maximize the crystallization of the material before the bonding step so that the thermal energy goes directly to the melt rather than to allow chain relaxation and rearrange the incomplete crystal structure. One solution to this problem is to subject the material to a heat settling treatment. As such, when the fibers subjected to heat shrinkage reach the bonding roll, the fibers will not shrink substantially because such fibers are already fully or highly oriented. However, in the typical meltblown and meltblown processes, an on-line heat settling process is generally very difficult to achieve. The present invention generally alleviates the need, but does not prohibit, a settling step by heat because the use of the multicarboxylic acid in the thermoplastic composition generally allows the use of the values of spunbonding and meltblowing without a modification of main process. The mixing of aliphatic polyester polymer with a multicarboxylic acid generally therefore maximizes the crystallization of the aliphatic polyester polymer which generally minimizes the expected heat shrinkage of the aliphatic polyester polymer.

In addition, when a short fiber is prepared where in-line heat set is possible, in an embodiment of the present invention it is optional that the fibers prepared from the thermoplastic composition of the present invention suffer heat settlements. It is desired that such heat settling also reduces the possible heat shrinkage of the fiber. The settling by heat can be done when the fibers are subjected to a constant tension, which typically can be, but is not limited to about 10 to about 20 percent, at a temperature that is beneficially higher than about 50 degrees Celsius, more beneficially around 70 degrees Celsius, and adequately greater than about 90 degrees Celsius. It is generally recommended to use the highest possible heat setting conditions, including both the applied stress and temperatures, while not sacrificing fiber processability. However, a very high heat set temperature such as, for example, a temperature close to the melting temperature of a component of a fiber, can reduce the strength of the fiber and can result in the fiber being difficult to handle due to the stickiness.

In an embodiment of the present invention, it is desired that a fiber prepared from the thermoplastic composition of the present invention exhibit an amount of shrinkage, at a temperature of about 100 degrees centigrade and for a period of time of about 15 minutes, quantified a Heat Shrink value, which is beneficially less than about 15 percent, more beneficially less about 10 percent, suitably less than about 5 percent, and more adequately less than about percent, where the amount of shrinkage is based on the difference between the initial and final lengths of the fib divided by the initial length of the multiplied fiber po 100. The value of heat shrinkage for a fiber can be determined according to the procedure described in the test methods section given here.

The thermoplastic composition of the present invention is suitable for preparing fibers or n-woven structures that can 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 cleansers, bibs, wound dressings, and surgical layers or covers. Therefore, in another aspect, the present invention relates to a disposable absorbent product comprising ulticomponent fibers of the present invention.

In an embodiment of the present invention, the thermoplastic composition is formed in a fibrous matrix for incorporation into a disposable absorbent product. A fibrous matrix may take the form of, for example, a fibrous non-woven fabric. Fibrous non-woven fabrics can be made entirely from fibers prepared from the thermoplastic composition of the present invention or can be mixed with other fibers. The length of the fibers used may depend on the particular end use contemplated. Where the fibers will degrade in water, for example, in a toilet, it will be advantageous if the lengths are maintained at or below about 15 millimeters.

In one embodiment of the present invention, a disposable absorbent product is provided, which disposable absorbent product comprises a liquid pervious topsheet, a lower sheet attached to the liquid pervious topsheet, and an absorbent structure positioned between the topsheet permeable to the liquid-permeable sheet. liquid and the lower sheet, wherein the lower sheet comprises fibers prepared from the thermoplastic composition of the present invention.

Exemplary disposable absorbent products are described in U.S. Patent Nos. 4,710,187; 4,762,521; 4,770,656; and 4,798,603, the references of which are incorporated herein by this reference.

Absorbent products and structures according to all aspects of the present invention are generally subjected, during use, to multiple discharges of a body fluid. Therefore, absorbent products structures are desirably capable of absorbing multiple discharge of body fluids in amounts at which products and absorbent structures will be exposed during use. Insults or discharges are generally separated from one another for a period of time.

Test Methods Melting Temperature The melting temperature of a material was determined using differential scanning calorimetry. Differential scanning calorimetry, available from TA Instruments, Inc., of New Castle, Delaware under the designation Thermal Analyst 291 Differential Scanning Calorimeter (DCS), which was provided with a liquid nitrogen cooling accessory and was used in combination with the Thermal Analyst 2200 analysis software program, it was used to determine the melting temperatures.

The samples of material tested were in the form of fibers or resin pellets. It is preferred not to handle material samples directly, but rather to use tweezers and other tools so as not to introduce anything that could produce erroneous results. The material samples were cut, in the case of the fibers, or placed, in the case of the resin pellets, in an aluminum tray and weighed to an accuracy of 0.01 mg on an analytical balance. If necessary, a lid was placed on the sample of material on the tray.

The differential scanning calorimeter was calibrated using an indium metal standard and a baseline correction was carried out, as described in the manual for the differential scanning calorimeter. A sample of material was placed in the test chamber of the differential scanning calorimeter to test and an empty tray was used as a reference. All tests were run with 55 cubic centimeters / minute of nitrogen purge (industrial class) on the test chamber. The heating and cooling program is a two-cycle test that starts with the camera's balance at minus 75 degrees Celsius followed by the heating cycle from 20 degrees Celsius / minute to 220 degrees Celsius, followed by the cooling cycle at 20 degrees Celsius / minute at minus 75 degrees Celsius and then another heating cycle from 20 degrees Celsius / minute to 220 degrees Celsius.

The results were evaluated using a software analysis program where the glass transition temperature (Tg) of inflection, endothermic and exothermic peaks were identified and quantified. The transition temperature of the glass was identified as the area on the line where a different change in inclination occurs and then the melting temperature was determined using an automatic inflection calculation.

Apparent viscosity A capillary rheometer, available from Gottfer from Rock Hill, South Carolina, was used under the designation GÓttfer Rheograph 2003 capillary rheometer, which was used in combination with a WinRHEO analysis program (version 2.31) to evaluate the rheological properties of viscosity Apparent of the material samples. The placement of the capillary rheometer included a pressure transducer of 2,000 bars and a round hole capillary matrix of 30/1: 0/180.

If the sample of material being tested showed or is known to have sensitivity to water, the sample of material was dried in a vacuum oven above its glass transition temperature, for example above 55 or 60 degrees centigrade for the PLA materials, under a vacuum of at least 15 inches of mercury with nitrogen gas purge of at least 30 standard cubic feet per hour (SCFH) for the last 16 hours.

Once the instrument was heated and the pressure transducer was calibrated, the material sample was incrementally loaded into the column, packing the resin in the column with a stick each time to ensure consistent melting during the test. After loading the material sample, a melting time of 2 minutes precedes the test to allow the material sample to melt completely at the test temperature. The capillary rheometer automatically takes data points and determines the apparent viscosity (in pascal - seconds) at seven apparent cutoff rates (1 / second): 50, 100, 200, 500, 1000, 2000, and 5000. When you examine the The resulting curve is important that the curve is relatively smooth, if there are significant deviations of a general curve from one point to another, possibly due to the air in the column, the running test must be repeated to confirm the results.

The resulting rheology curve of apparent curtain rate against apparent viscosity produced to an indication of how the material sample will run at temperature in an extrusion process. Apparent viscosity values at a cut-off rate of at least 1,000 1 / second are of specific interest because these are typical conditions found in commercial fiber spinning extruders.

Molecular Weights Average Weight / Number A gel permeation chromatography (GPC) method was used to determine the molecular weight distribution of poly (lactic acid) samples whose weight average molecular weight (Mw) is between 800 to 400,000.

The gel permeation chromatography is put with two analytical columns PLgel mixed linear K 5 microns, at 7.5 x 300 millimeters in series. The temperatures of the column and the detector are 30 degrees centigrade. The mobile phase is tetrahydrofuran (THF) class HPLX. The pump rate is 0.8 millimeters per minute with an injection volume of 25 microliters. The total run time is 30 minutes. It is important to note that the new analytical columns should be installed every four months, a new guard column every month and a new online filter every month.

Polyester polymer standards, obtained from Aldrich Chemical Company, should be mixed in a solvent of dichloromethane (DCM): THF (10:90) both of HPLX class, in order to obtain concentrations of 1 mg / mL. Multiple polystyrene standards can be combined in a standard solution as long as their peaks do not overlap when they chromatograph. A standard range is around 687 400,000 should be prepared. Examples of standard mixtures with Aldrich polystyrenes of variable molecular weights (weight average molecular weight-Mw) and include: standard (401,340, 32,660, 2,727), standard 2 (45,730, 4,075), standard (95,800, 12,860) and standard 4 (184,200; 24,150; 687).

Next, prepare the supply verification standard. Dissolve 10 g of a PLA standard of 200,000 molecular weight, catalogs # 19245 obtained from Poliscience, Inc. to 100 ml of HPLC-type DCM to a glass jar with a Teflon-lined tap using an orbital shaker (at least 3 minutes). Pour the mixture on a dry clean glass plate and allow the solvent to evaporate first, then place in a preheated vacuum oven at 35 degrees centigrade and dry >14 hours under a vacuum of 25 mm d Hg. Then, remove the PLA from the oven and cut the film into small strips. Immediately grind the samples using a mill (W / 10 mesh grid) taking care not to add too much sample and cause the mill to freeze. Store a few grams of the sample milled in a dry glass jar in a desiccator, while the rest of the sample can be stored in the freezer in a jar of similar type.

It is important to prepare a new verification standard at the beginning of each new sequence and because the molecular weight is greatly affected by the sample concentration, great care should be taken in weighing and preparing. To prepare the verification standard weigh 0.0800 g + 0.00 g the standard PLA reference of 200,000 Mw in a dry and clean smear recipient. Then use a volumetric pipe or a dedicated repipet, add 2 milliliters of D to the container and tighten the lid tightly. Allow the sample to dissolve completely. Aremoly the sample on an orbital shaker, such as a Thermolyne Ro mixer (type 51300) or a similar mixer, if necessary. To evaluate if it is dissolved hold the container against the light at an angle of 45 degrees. Flip it slowly and watch the liquid flow this way down the glass. If the bottom of the container appears smooth, the sample is not completely dissolved. It may take several hours for the sample to dissolve. One dissolved v, add 18 ml of THF using a volumetric pipette a dedicated repipet, cover the container tightly mix.

The sample preparations begin by weighing 0.0800 g + 0.0025 g of the sample in a dry and clean smelling container (great care should be taken in weighing and preparing). Add 2 ml of DCM to the container with a volumetric pipette or a dedicated repipet and screw the cap tightly. Allow the sample to dissolve completely using the same technique described in the preparation of the verification standard mentioned above. Then add 18 ml of THF using a volumetric pipette or a dedicated repipet, cover the container tightly and mix.

Begin the evaluation by carrying out a test injection of a standard preparation to test the balance of the system. Once the equilibrium is confirmed inject the standard preparations. After that they are run, inject the standard preparation of verification. After the sample preparations. Inject standard check preparation after every 7 sample injections and at the end of the test. Be sure not to take more than two injections of any one of the container and those two injections should be done within 4.5 hours of each other.

There are 4 quality control parameters to evaluate the results. First the coefficient of correlation of the fourth order of regression calculated for each standard should not be less than 0.950 and no more than 1.050. Secondly, the relative standard deviation (RSD) of all the M's of the standard verification preparations should not be more than 5.0 percent. Third, the average of the ^, standard preparation injections of verification must be within 10 percent of the, on the first injection of standard preparation verification. Finally, record the lactic response for the standard injection of 200 microgram per milliliter (μg / mL) on an SQC data scheme. Using the outline control lines, the response must be within the defined SQC parameters.

Calculate the molecular statistics based on the calibration curve generated from standard polystyrene preparations and the Mark Houwink constants for PLA and polystyrene in THF at 30 degrees centigrade. Those are polestireno (K = 14.1 * 105, alpha = 0.700) and PLA (K = 54.9 * 105, alpha 0.639).

Heat Shrinkage of Fibers The equipment required for the determination of heat shrinkage includes: a convection oven (laboratory oven model Thelco 160 DM), 0.5 g (+/- 0.06 g sinking weight, half-inch union fasteners, masking tape, paper of graph with at least a quarter-inch square, a foam poster board (11 by 1 inch) or an equivalent substrate to join the graph paper and the samples, the convection oven must be capable of a temperature of 100 degrees centigrade Five samples are spun with melt at their respective spinning conditions, a bundle of 30 filaments is preferred, and mechanically pulled to obtain fibers with a jet stretch of 224 or greater. Only the fibers of this same jet stretch can be compared to one another in relation to their heat shrinkage. The jet stretch of a fiber is the ratio of the speed of the pull roller down divided by the rate of linear extrusion (distance / time) of the melted polymer leaving the spinning organ. Spun fiber is usually collected on a reel using a reel. The bundle of collected fibers was separated into 30 filaments, if a bundle of 30 filaments has not already been obtained, and cut into lengths of 9 inches.

The graph paper is curled over the poster board where one edge of the graph paper is matched with the edge of the poster board. One end of the bundle of fibers is taped, not more than 1 inch from the end. The taped end is attached to a poster board at the edge where the graph paper is matched so that the edge of the fastener rests on one of the horizontal lines of the graph paper while holding the bundle of fiber in place. (The taped end should be barely visible when secured under the bra). The other end of the bunch is pulled and aligned parallel to the vertical lines on the graph paper. Then, 7 inches down from the point where the fastener is having the fiber, prick the 0.5 g sinker to around the fiber bundle. Repeat the clamping process for doubled ca. Usually, 3 duplicates can be held at the same time the marks can be made on the graph paper to indicate the initial positions of the sinks. The samples are placed in the 100 ° C oven so that they hang vertically and do not touch the poster board. At intervals of 5, 10 and 15 minutes, quickly mark the new location of the sinkers on the graph paper and return the samples to the oven.

After the test is completed remove the poster board and measure the distances between the origin (where the fastener holds the fibers) and the marks at 5, 10, and 1 minutes with a 1/16 inch graduated ruler (about d 0.16 c). Three duplicates per sample are recommended. Calculate the averages, standard deviations and percent shrinkage. The percentage of shrinkage is calculated as s divide (initial length of the fiber length measured fiber by the initial length of the fiber and multiplied by 100. The values of heat shrinkage reported here use the target values at 15 minutes .

Crystal Size Determination The measurement of crystal sizes within a fiber sample was determined by ray diffraction using an x-ray machine available from Philips Inc., d. Mahwah, New Jersey, under the designation XRG-3000 machine, equipped with a copper tube. The photographs were obtained and a scheme was made using a wide angle goniometer. To determine the effective glass size of a fiber sample, a reflection pattern was obtained in the equatorial direction relative to the fiber, scanning through d the layer line (hkl). The plane (100) to around 16.4 ° 2Q s was selected to be consistent with all d dimension calculations. Using the Scherrer equation a principal dimension for the crystallites perpendicular to the plane (100) was calculated.

Biodeavability test The biodegradability test of the samples was carried out using Organic Waste. Systems of Gent, from Belgium using the modified standard ASTM 5338.92 or an equivalent ISO C 14855, test procedure. The modification of the AST 5338.92 method is that the test chambers are maintained at a constant temperature of 58 ° C through the test rather than using an incremental temperature profile.

EXAMPLES Ei emplo 1 A poly (lactic acid) (PLA) polymer d was obtained Chronopol Inc., of Golden Colorado. The poly (lactic acid) polymer had a L: D ratio of 100 to 0, a melt temperature of about 175 ° C, a weight average molecular weight of about 211,000, an average molecular weight d number of about 127,000, a polydispersity index d 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. Polymer (lactic acid) polymer blending with adipic acid involved the dry mixing of the components followed by the melting of these dots to provide vigorous mixing of the components, which was accomplished in a counter-rotating gemel screw extruder. . The mixing was carried out on either a BRABENDER twin screw combiner "33 ^ 3" or a twin screw extruder HAAKEMarca with mixing screws.

The conversion of the prepared mixtures to fiber s was carried out on a fiber spinning line. The spinning line consists of a 3/4 inch diameter extruder with a 24: 1 ratio screw of L: D (length: diameter) h heating zones which feed into a Koch® static mixer. 0.62 inches in diameter inside a spinning head (heating zones 4a and 5 through a spinner organ of 15 to 30 holes, where each hole has a diameter of about 500 micrometer. The temperatures of each heating zone are indicated sequence below the temperature profile section The fibr are air cooled at 13 ° C to 22 ° C and pulled towards aa by a mechanical pull roller to either a winding unit or a fiber pull unit (as in FIG. bonding process with Lurgi spinning.) The process conditions for several of the prepared fibers are shown in Table 1.

Table 1 * Not an example of the present invention The prepared fibers were evaluated for heat shrinkage, Tg, and main crystal size. The results of these evaluations are shown in Table 2. The current percentage of poly (acid-lactic acid) / adipic acid proportions were determined by using nuclear magnetic resonance as a ratio between peaks C and CH2.

Table 2 * It is not an example of the present invention Example 2 A poly (lactic acid) polymer was obtained from Chronopol Inc., of Golde 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 181,000 an average molecular weight number of about 115,000, a polydispersity index d about 1.57 and a residual lactic acid monomer value of about 2.3 per cent by weight.

Poly (lactic acid) polymer was mixed with various amounts of adipic acid. Mixing the poly (lactic acid) polymer with the adipic acid involved the dry blending of the components followed by the melted mixing of these together to provide vigorous mixing to the components, which was accomplished in a counter-rotating gemel screw extruder. Mixing was carried out on either a BRABENDEE "*" * gemel screw combiner or a HAAKE * "0 * twin screw extruder with mixing screws.

The conversion of the prepared mixtures into fibers was carried out in a domestic fiber spinning line. The spinning line consists of a 3/4-inch-diameter extruder with a 24: 1 ratio of L: D (length: diameter) screw and 3 heating zones that feed into a 0.62-inch Koch® static mixer. of diametr and then inside the spinning head (heating zones 4 * and 5 *) through a spinner organ of 15 to 30 holes, where each hole had a diameter of about 50 micrometers. The temperatures of each heating zone are indicated sequentially under the temperature profile section. The fibers are cooled by air at 13 ° C to 22 ° C and pulled down by the mechanical pull roller to either a fiber pull unit (co in the Lurgi spun bonding process). The process conditions for several of the prepared fibers are shown in Table 3.

Table 3 * It is not an example of the present invention.

The prepared fibers were then evaluated for heat shrinkage, Tg, and biodegradability. The results of these evaluations are shown in Table 4. The current percentage of the proportions of poly (lactic acid) polymer / adipic acid was determined by using nuclear magnetic resonance as the ratio between the CH and CH2 peaks.

Table 4 It is not an example of the present invention.

Those skilled in the art will recognize that the present invention is capable of many modifications without departing from the scope thereof. Therefore, the detailed description and the examples set forth are intended to be illustrative only and are not intended to limit in any way the scope of the invention as set forth in the appended claims.

Claims (27)

R E I V I N D I C A C I O N S

1. - A thermoplastic composition comprising a mixture of: to. an aliphatic polyester polymer having a weight average molecular weight that is from about d 10,000 to about 2,000,000, wherein the aliphatic polyester polymer is present in the thermoplastic composition in an amount by weight that is between about 50 percent by weight to about 59 percent by weight; Y b. a multicarboxylic acid having a carbon acid tota that is less than about 30, where the multicarboxylic acid is present in the thermoplastic composition in an amount by weight that is between about 5 weight percent to about 50 percent by weight wherein all percentages by weight are based on the total weight amount of aliphatic polyester polymer and multicarboxylic acid present in the thermoplastic composition

2. - The thermoplastic composition as claimed in clause 1 characterized in that the aliphatic polyester polymer is selected from the group consisting of pol (lactic acid), polybutylene succinate, polybutylene succinate-co-adipate, pol ihidroxibut irato-co -valerate, polycaprolactone, sulfonated polyethylene terephthalate, mixture of such polymers and copolymers of such polymers.

3. - The thermoplastic composition as claimed in clause 2, characterized in that the aliphatic polyester polymer is poly (lactic acid).

4. The thermoplastic composition as claimed in clause 2, characterized in that the aliphatic polyester polymer is present in the thermoplastic composition in an amount of weight that is between about 60% by weight about 90% by weight.

5. - The thermoplastic composition as claimed in clause 1 characterized in that the multicarboxylic acid is selected from the group consisting of malonic acid, citric acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, acid sebasic, and mixtures of such acids.

6. - The thermoplastic composition as claimed in clause 1 characterized in that the multicarboxylic acid is adipic acid.

7. - The thermoplastic composition as claimed in clause 1 characterized in that the multicarboxylic acid is present in the thermoplastic composition in an amount by weight that is between about 10% by weight to about 40% by weight.

8. - The thermoplastic composition as claimed in clause 1 characterized in that the multicarboxylic acid has a total of carbon atoms that is d between about 3 to about 30.

9. - The thermoplastic composition as claimed in clause 1 characterized in that the thermoplastic composition exhibits a glass transition temperature of less than about 55 ° C.

10. - The thermoplastic composition as claimed in clause 9 characterized in that the thermoplastic composition exhibits a glass transition temperature of less than about 50 ° C.

11. - The thermoplastic composition as claimed in clause 1 characterized in that the polymer is poly (lactic acid), polybutylene succinate, polybutylene succinate-co-adipate, polyhydroxybutyrate-co-valerate polycaprolactone, sulfonated polyethylene terephthalate, mixture of such polymers and copolymers of such polymers; multicarboxylic acid is selected from the group consisting of malonic acid, citric acid, sycyclic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and mixtures of such acids; and the thermoplastic composition exhibits a glass transition temperature which is less than about 55 ° C.

12. - The thermoplastic composition as claimed in clause 11 characterized in that the aliphatic polyester polymer is poly (lactic acid) and the multicarboxylic acid is adipic acid.

13. - The thermoplastic composition as claimed in clause 12 characterized in that the poly (lactic acid) polymer is present in the thermoplastic composition in an amount of weight that is between about 50 percent by weight to about 90 percent by weight. Weight Adipic acid is present in the thermoplastic composition in an amount by weight that is between about 10 percent by weight to about 40 percent by weight.

14. - A fiber prepared from a thermoplastic composition, the thermoplastic composition comprising a mixture of: to. an aliphatic polyester polymer having a weight average molecular weight that is from about d 10,000 to about 2,000,000, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 50 percent by weight to about 95 percent by weight; Y b. a multicarboxylic acid having a total carbon atoms that is less than about 30, wherein multicarboxylic acid is present in the thermoplastic composition in the amount of weight that is between about 5 percent by weight to about 50 percent by weight , where all percent by weight are based on total weight amount of the aliphatic polyester polymer and multicarboxylic acid present in the thermoplastic composition wherein the fiber exhibits a heat shrink value that is less than about 15 percent.

15. - The fiber as claimed in clause 14 characterized in that the aliphatic polyether polymer is selected from the group consisting of poly (lactic acid), polybutylene succinate, succinate-co-adipate polybutylene, polyhydroxybutyrate-co-valerate, polycaprolactone terephthalate of sulfonated polyethylene, mixtures of such polymers and copolymers of such polymers.

16. - The fiber as claimed in clause 15 characterized in that the aliphatic polyester polymer is poly (lactic acid).

17. - The fiber as claimed in clause 14 characterized in that the aliphatic polyester polymer is present in the thermoplastic composition in an amount by weight that is between about 60 percent po weight to about 90 percent by weight.

18. - The fiber as claimed in clause 14 characterized in that the multicarboxylic acid is selected from the group consisting of malonic acid, citric acid, succinic acid, glutaric acid, adipic acid, pimpinic acid, suberic acid, azelaic acid, sebacic acid , mixtures of such acids.

19. - The fiber as claimed in clause 18 characterized by the multicarboxylic acid and adipic acid.

20. - The fiber as claimed in clause 14 characterized in that the multicarboxylic acid is present in the thermoplastic composition in an amount by weight that is between about 10 percent by weight around 40 percent.

21. - The fiber as claimed in clause 14 characterized in that the multicarboxylic acid has a total of carbon atoms that is between about 3 about 30.

22. - The fiber as claimed in clause 14 characterized in that the thermoplastic composition exhibits a glass transition temperature that is less than about 55 ° C.

23. - The fiber as claimed in clause 22 characterized in that the thermoplastic composition exhibits a glass transition temperature that is less than about 50 ° C.

24. - The fiber as claimed in clause 14 characterized in that the aliphatic polyester polymer is selected from the group consisting of poly (lactic acid), polybutylene succinate, polybutylene succinate-co-adipate, polyhydroxybutyrate-co-valerate, polycaprolactone sulfonated polyethylene terephthalate, mixtures of such polymers and copolymers of such polymers; the multicarboxylic acid is selected from the group consisting of malonic acid, citric acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and mixtures of such acids, and the thermoplastic composition exhibits a glass transition that is less than about 55 ° C.

25. - The fiber as claimed in clause 24, characterized in that the aliphatic polyester polymer is poly (lactic acid) and the multicarboxylic acid and adipic acid.

26. - The fiber as claimed in clause 25 characterized in that the poly (lactic acid) polymer is present in the thermoplastic composition in an amount of weight that is between about 60 percent po weight to about 90 percent by weight and the adipic acid is present in the thermoplastic composition in an amount by weight that is between about 10 percent by weight to about 40 percent by weight.

27. - The fiber as claimed in clause 25 characterized in that the fiber exhibits a heat shrinkage value that is less than about 10 percent