摘要:
A thermoplastic composition that contains a rigid renewable polyester and a polymeric toughening additive is provided. The toughening additive can be dispersed as discrete physical domains within a continuous matrix of the renewable polyester. An increase in the deformation force and elongational strain causes debonding to occur in the renewable polyester matrix at those areas located adjacent to the discrete domains. This can result in the formation of a plurality of voids adjacent to the discrete domains that can help to dissipate energy under load and increase impact strength. To even further increase the ability of the composition to dissipate energy in this manner, an interphase modifier may be employed that reduces the degree of friction between the toughening additive and renewable polyester and thus enhances the degree and uniformity of debonding.
摘要:
An oil-in-water emulsion that is environmentally friendly and also exhibits antimicrobial activity is provided. More specifically, the oil phase of the emulsion includes a botanical oil derived from a plant (e.g., thymol, carvacrol, etc.). Because the botanical oil tends to leach out of the emulsion during storage and before it is used in the desired application, a water-dispersible polymer is also employed in the aqueous phase of the emulsion to enhance long term stability of the oil and, in turn, antimicrobial efficacy. Without intending to be limited by theory, it is believed that the water-dispersible polymer can effectively encapsulate the botanical oil within the emulsion and inhibit its premature release. Once the emulsion is formed, water can then be removed so that it becomes a substantially anhydrous concentrate. In this manner, the water-dispersible polymer will not generally disperse before use and prematurely release the botanical oil. When it is desired, moisture may simply be re-applied to the concentrate to disperse the polymer and activate the release of the botanical oil. Of course, to provide the optimum degree of biocompatibility, the water-dispersible polymer is also a "biopolymer" that is biodegradable and/or renewable.
摘要:
A method for forming biodegradable fibers is provided. The method includes blending polylactic acid with a polyepoxide modifier to form a thermoplastic composition, extruding the thermoplastic composition through a die, and thereafter passing the extruded composition through a die to form a fiber. Without intending to be limited by theory, it is believed that the polyepoxide modifier reacts with the polylactic acid and results in branching of its polymer backbone, thereby improving its melt strength and stability during fiber spinning without significantly reducing glass transition temperature. The reaction-induced branching can also increase molecular weight, which may lead to improved fiber ductility and the ability to better dissipate energy when subjected to an elongation force. To minimize premature reaction, the polylactic acid and polyepoxide modifier are first blended together at a relatively low temperature(s). Nevertheless, a relatively high shear rate may be employed during blending to induce chain scission of the polylactic acid backbone, thereby making more hydroxyl and/or carboxyl groups available for subsequent reaction with the polyepoxide modifier. Once blended, the temperature(s) employed during extrusion of the blended composition can be selected to both melt the composition and initiate a reaction of the polyepoxide modifier with hydroxyl and/or carboxyl groups of the polylactic acid. Through selective control over this method, the present inventors have discovered that the resulting fibers may exhibit good mechanical properties, both during and after melt spinning.
摘要:
A biodegradable and renewable film that may be employed in a wide variety of applications is provided. The film is formed from a thermoplastic composition that contains at least one starch and at least one plant protein. Even at a high renewable material content, the present inventors have discovered that films may be readily formed from plant proteins and starches by selectively controlling the individual amount of the starch and plant proteins, the nature of the starch and plant proteins, and other components used in the film. Balancing the amount of starches and plant proteins within a certain range, for instance, can reduce the likelihood of plant protein aggregation and enhance the ability of the composition to be melt processed. The composition also contains at least one plasticizer that improves the thermoplastic nature of the protein and starch components. The selection of the plasticizer may also help reduce the tendency of the plant protein to aggregate during melt processing. For example, a relatively acidic plasticizer (e.g., carboxylic acid) may be employed in certain embodiments to minimize the formation of disulfide bonds in a gluten protein, and thereby decrease its tendency to aggregate.
摘要:
A method for forming a biodegradable polylactic acid suitable for use in fibers is provided. Specifically, a polylactic acid is melt processed in an extruder at a controlled water content to initiate a hydrolysis reaction. Without intending to be limited by theory, it is believed that the hydroxyl groups present in water are capable of attacking the ester linkage of polylactic acid, thereby leading to chain scission or 'depolymerization' of the polylactic acid molecule into one or more shorter ester chains. The extruder within which the polylactic acid is melt processed in a single screw extruder and contains a screw rotatably mounted and received within a barrel. The screw has a length-to-diameter ('L/D') ratio of from about 15 to about 50. With such a single screw extruder, the present inventors have discovered that the reaction components may be effectively mixed together in a highly efficient and cost-effective manner. Further, by selectively controlling the extrusion conditions (e.g., water content, temperature, shear rate, etc.), a hydrolytically degraded polylactic acid may be achieved that has a molecular weight lower than the starting polymer. Such lower molecular weight polymers have a higher melt flow rate and lower apparent viscosity, which are useful in a wide variety of fiber forming applications, such as in the meltblowing of nonwoven webs.
摘要:
A method for forming a fiber is provided. The method comprises supplying at least one aromatic polyester to a melt processing device and modifying the aromatic polyester with at least one polyether copolymer within the device to form a thermoplastic composition having a melt flow rate that is greater than the melt flow rate of the aromatic polyester. The polyether copolymer contains a repeating unit (A) having the following formula (A) wherein, x is an integer from 1 to 250, the polyether copolymer further containing a repeating unit (B) having the following formula (B) wherein, n is an integer from 3 to 20; and y is an integer from 1 to 150.
摘要:
A biodegradable fiber for use in forming a nonwoven web is provided. The fiber is formed from a thermoplastic composition comprising at least one polylactic acid in an amount from about 75 wt.% to about 99 wt.% and at least one polyether copolymer in an amount from about 1 wt.% to about 25 wt.%, wherein the polyether copolymer contains from about 40 mol.% to about 95 mol.% of a repeating unit (A) having the following formula. wherein, x is an integer from 1 to 250, the polyether copolymer further containing from about 5 mol.% to about 60mol.% of a repeating unit (B) having the following formula. wherein, n is an integer from 3 to 20; and y is an integer from 1 to 150. Such polyether copolymers have been found to improve a variety of characteristics of the resulting thermoplastic composition, including its ability to be melt processed into fibers and webs, as well as its sensitivity to moisture.
摘要:
A biodegradable, substantially continuous filament is provided. The filament contains a first component formed from at least one high melting polyester and a second component formed from at least one low melting polyester. The low melting point polyester is an aliphatic-aromatic copolyester formed by melt blending a polymer and an alcohol to initiate an alcoholysis reaction that results in a copolyester having one or more hydroxyalkyl or alkyl terminal groups. By selectively controlling the alcoholysis conditions (e.g., alcohol and copolymer concentrations, catalysts, temperature, etc.), a modified aliphatic-aromatic copolyester may be achieved that has a molecular weight lower than the starting aliphatic-aromatic polymer. Such lower molecular weight polymers also have the combination of a higher melt flow index and lower apparent viscosity, which is useful in the formation of substantially continuous filaments.
摘要:
A method for forming a biodegradable polylactic acid suitable for use in fibers is provided. Specifically, a polylactic acid is melt processed at a controlled water content to initiate a hydrolysis reaction. Without intending to be limited by theory, it is believed that the hydroxyl groups present in water are capable of attacking the ester linkage of polylactic acids, thereby leading to chain scission or "depolymerization" of the polylactic acid molecule into one or more shorter ester chains. The shorter chains may include polylactic acids, as well as minor portions of lactic acid monomers or oligomers, and combinations of any of the foregoing. By selectively controlling the hydrolysis conditions (e.g., moisture and polymer concentrations, temperature, shear rate, etc.), a hydrolytically degraded polylactic acid may be achieved that has a molecular weight lower than the starting polymer. Such lower molecular weight polymers have a higher melt flow rate and lower apparent viscosity, which are useful in a wide variety of fiber forming applications, such as in the meltblowing of nonwoven webs.
摘要:
The present invention can provide a distinctive method and process for making polymer fibers (62) and nonwoven fabric webs (60). The method can include providing a fiber material that exhibits a low crystallization rate. In a particular aspect, the fiber material can be subjected to an anneal-quench at an anneal-quench temperature that approximates a prime-temperature at which the polymer material most rapidly crystallizes. In another aspect, the fiber material can be subjected to a fiber-draw at a selected fiber-draw temperature, and in a further aspect, the fiber-draw temperature can be configured to approximate the prime-temperature of the polymer material. In still other aspects, the fiber material can be subjected to a relatively small amount of fiber-draw, and the fiber-draw can be provided at a relatively low fiber-draw speed.