CN1847474B - An extrusion die for meltblowing molten polymers - Google Patents

Abstract

An extrusion die for meltblowing molten polymers, comprising a row of die orifices, each die orifice comprising at least two independent polymer supply orifices entering from an inlet portion of the die, said Each of the polymer supply holes communicates with an independent extrusion capillary with an outlet at the outlet portion of the die, the gas supply holes enter from the inlet portion of the die and are arranged transversely relative to the polymer supply holes, the A gas supply hole communicates with a gas nozzle extending through the die and is arranged transversely with respect to an outlet of the extrusion capillary, wherein the extrusion capillary outlet and the gas nozzle communicate with the spinneret hole in the outlet portion of the die .

Description

Extrusion Dies for Meltblown Molten Polymers

This application is a divisional application of the invention patent application with the application number 01802291.X (PCT/US01/23972) and the filing date being July 31, 2001. the

technical field

The present invention relates to multicomponent meltblown fibers, multicomponent meltblown nonwoven fabrics and composite nonwoven fabrics comprising multicomponent meltblown fibers. The meltblown nonwovens of the present invention can be incorporated into composite fabrics suitable for use in garments, wipes, healthcare products, and pharmaceutical wraps. the

Background technique

In the meltblowing process, nonwoven fabrics are formed by extruding molten polymer through a die and attenuating the resulting fibers with a high velocity stream of hot air. During the production of webs composed of meltblown fibers, it is sometimes desirable to form the fibers from more than one polymeric material, where each material can have different physical properties and provide different characteristics to the meltblown web . A conventional method of forming such fibers is by spinning, in which polymeric materials are mixed in a molten state in a die cavity and extruded together in the form of a layered multicomponent polymer melt through a single spinning process. Holes, as described in US 6,057,256, which discloses meltblowing side-by-side bicomponent fibers onto a collector to form a cohesively entangled web. the

However, this approach has significant limitations due to compatibility constraints in the selection of polymeric materials that spin well together. the

Meltblown fibers have been incorporated into a variety of nonwoven fabrics, including composite laminates such as spunbond-meltblown-spunbond ("SMS") composite sheets. In SMS composites, the outer layer is a layer of spunbond fibers that provide strength to the overall composite, while the core layer is a layer of meltblown fibers that provide barrier properties. the

There is a need to provide a new method of forming melt-blown fibers and corresponding melt-blown nonwovens, which is more suitable for producing multi-component melt-blown fibers, and wherein the processing conditions for each polymer component can be independently optimize. the

Contents of the invention

The present invention relates to a method of forming multicomponent meltblown fibers comprising: extruding a first melt-processable polymer through a first extrusion orifice; simultaneously extruding a second melt-processable polymer through second extrusion orifice; after extrusion, melting the first and second melt-processable polymers into the extruded composite filaments; pneumatically attenuating the extrusion with at least one high velocity gas jet The resulting composite filaments are used to form the multicomponent meltblown fibers. The composite filaments can be cut with a jet of high velocity gas to form a plurality of fine, discrete multicomponent meltblown fibers. the

A second embodiment of the present invention relates to an extrusion die for meltblowing molten polymer comprising at least two separate polymer supply orifices entering from the inlet portion of the die, said polymer supply orifices being connected to the A separate extrusion capillary with an outlet at the outlet portion of the die communicates, said extrusion capillary fitting in the form of a composite hole, at least one gas supply hole entering from the inlet portion of the die, said gas supply hole being in contact with a gas supply hole extending through the die At least one gas nozzle of the head is connected, and the at least one gas nozzle is arranged concentrically around the outlet of the composite hole, wherein the extrusion capillary outlet and the gas nozzle are connected to the spinneret hole in the die outlet portion connected. the

In a third embodiment, the invention relates to an extrusion die for meltblowing molten polymer comprising an array of orifices, each orifice comprising at least two separate polymer supplies entering from the inlet portion of the die Each of the polymer supply holes communicates with a separate extrusion capillary with an outlet at the outlet portion of the die, and the gas supply holes enter from the inlet portion of the die and are laterally aligned with the polymer supply holes , the gas supply hole communicates with a gas nozzle extending through the die and is laterally aligned with the outlet of the extrusion capillary, wherein the extrusion capillary outlet and the gas nozzle are connected to the nozzle in the outlet portion of the die The pores are connected. the

Description of drawings

Figure 1 is a schematic cross-sectional view of a die according to a second embodiment of the present invention or a single die orifice according to a third embodiment of the present invention for producing meltblown fibers for use in nonwoven fabrics according to the process of the present invention. the

Figure 2 is a schematic view of a section 2 of the die of Figure 1 according to a second embodiment of the invention. the

Figure 3 is a schematic illustration of the die of Figure 1 used in the process of the present invention. the

FIG. 4 is a schematic diagram of another design of a die according to the second embodiment of the invention shown in FIG. 1 . the

FIG. 5 is an end view of an outlet according to a third embodiment of the present invention from the die of FIG. 1. FIG. the

Figure 6 is an end view of the outlet of another design of the die according to the third embodiment of the invention. the

Detailed ways

The invention relates to a method for forming multi-component melt-blown fibers and multi-component melt-blown nonwoven fabrics. the

As used herein, the term "polyolefin" means: any of a series of largely saturated open-chain polymeric hydrocarbons consisting only of carbon and hydrogen atoms. Typical polyolefins include polyethylene, polypropylene, polymethylpentene, and various combinations of ethylene, propylene, and methylpentene monomers. the

The term "polyethylene" (PE) as used herein is intended to include not only homopolymers of ethylene, but also copolymers in which at least 85% of the repeating units are ethylene units. the

As used herein, the term "polyester" is intended to include polymers in which at least 85% of the repeat units are condensation products of dicarboxylic acids and diols with linkages resulting from the formation of ester units. This includes aromatic, aliphatic, saturated and unsaturated dibasic acids and diols. The term "polyester" as used herein also includes copolymers (such as block copolymers, graft copolymers, random copolymers and alternating copolymers), mixtures and modifications thereof. A common example of a polyester is poly(ethylene terephthalate) (PET), which is the condensation product of ethylene glycol and terephthalic acid. the

The terms "meltblown fibers" and "meltblown filaments" as used herein refer to the extrusion of melt-processable polymers in the form of molten strands or filaments through a plurality of thin, usually circular capillaries into Fibers or filaments formed in a stream of heated gas (eg, air) at high velocity. The high velocity gas stream attenuates the filaments of molten thermoplastic polymer material to reduce their diameter to between about 0.5 and 10 microns. Meltblown fibers are generally discontinuous fibers, but can also be continuous. Meltblown fibers carried by a high velocity gas stream are typically deposited on a collecting surface so as to form a web of randomly dispersed fibers. the

As used herein, the terms "multicomponent fiber" and "multicomponent filament" refer to any filament or fiber composed of at least two different polymers, but are understood to include such items of things. The term "distinct polymers" means that each of said at least two polymers are arranged in distinct zones across the cross-section of the multicomponent fiber and along the length of the fiber. Multicomponent fibers differ from fibers extruded from a homogeneous melt mixture of polymeric materials in which regions of different polymers do not form. The at least two different polymer components usable herein may be chemically different, or they may be chemically the same polymer, but have different physical properties, such as intrinsic viscosity, melt viscosity, mold mouth expansion, density, crystallinity and melting or softening point. For example, the two components may be linear low density polyethylene and high density polyethylene. Each of the at least two different polymers may itself comprise a blend of two or more polymeric materials. Multicomponent fibers, also sometimes referred to as bicomponent fibers, include fibers formed from two components as well as fibers formed from more than two components. The terms "bicomponent web" and "multicomponent web" as used herein refer to a web comprising multiple component fibers or filaments. As used herein, the terms "multicomponent meltblown web" and "bicomponent meltblown web" mean a web comprising meltblown multicomponent fibers comprising at least two different A polymer component in which molten fibers are attenuated by a high-velocity heated gas stream and deposited onto a collection surface as a web of randomly dispersed fibers. the

As used herein, the term "spunbond" fibers means fibers formed by extruding molten thermoplastic polymer in the form of filaments from a plurality of fine, usually circular capillaries of a spinneret; The diameter of the extruded filaments is then rapidly reduced by drawing. Spunbond fibers are generally continuous and have an average diameter greater than about 5 microns. Spunbond nonwovens or nonwovens are formed by randomly layering spunbond fibers onto a collecting surface such as a perforated screen or belt. Spunbond fabrics can be bonded by methods known in the art, such as by hot roll calendering, or by passing the fabric under high pressure through a chamber of saturated steam. For example, the cloth can be thermal point bonded at a number of thermal bond points located on the spunbond fabric. the

As used herein, the term "nonwoven fabric, sheet or web" means a structure of individual fibers, filaments or threads arranged in a random manner to form a planar material with no recognizable pattern, as opposed to a braid . the

Figure 1 illustrates an extrusion die or spinblock according to a second or third embodiment of the invention for use in the meltblowing process of the invention, said scheme illustrating a two-component system for simplicity. Independently controlled multiple extruders (multiple extruders, not shown) feed separate molten polymer streams A and B to the die 10 through polymer supply ports 15a and 15b, where the polymer is passed through separate extruders. Outlet capillaries 16a and 16b, which in preferred embodiments are angled within the die so as to direct separate polymer streams toward a common longitudinal axis. However, the extrusion capillaries may be parallel to each other, but sufficiently close to each other to promote fusion of the molten polymer streams after exiting the individual extrusion capillaries. Preferably, the diameter of the extrusion capillary is less than about 1.5 mm, preferably less than 1 mm, more preferably less than about 0.5 mm. The outlets of these capillaries in the dietip 11 are arranged to promote fusion of the polymers as they exit through the spinneret holes 30 . Since extrusion capillaries 16a and 16b cooperate to form a single composite bicomponent polymer stream, they are collectively referred to as "composite holes". Bicomponent fibers formed by extruding a polymer stream through a composite orifice are attenuated by heated jets of gas supplied to the die through gas inlet 20 and delivered to the gas Nozzle 21, said gas nozzle is at an angle to the common longitudinal axis of the molten polymer streams exiting through the ends of extrusion capillaries 16a and 16b. The total included angle α between the gas nozzles 21 is preferably between approximately 60° and 90°. In this method, by using independently controlled extruders for different polymers, it is possible to individually control various processing parameters such as temperature, capillary diameter, and extrusion pressure for each polymer, so that the individual polymers Extrusion is optimized and still a single fiber comprising both polymers can be formed. the

Figure 2 is a simplified view of a section 2 of the die 10 in Figure 1, shown in plan view of a frustum, illustrating the preferred side-by-side configuration of the extrusion capillary outlet ends 16a and 16b, which will melt The polymer filaments are fed into an inverted cone of high-velocity gas formed by gas nozzles 21 arranged concentrically along the composite orifice. the

FIG. 3 is a diagram according to FIG. 1 illustrating the operation of the method of the invention through the extrusion die 10 . Polymers A and B are independently conveyed through extrusion orifices 15a and 15b and forced into extrusion capillaries 16a and 16b, respectively. The extruded filaments 40a of polymer A and the extruded filaments 40b of polymer B exit the end of the extrusion capillary, at which point it is believed that the transverse component of the force generated by the gas nozzle 21 will act, causing both The polymers are fused into bicomponent filaments 40. At about the same time, the longitudinal component of the force generated by the gas nozzle 21 will act to attenuate or stretch the filament to reduce the diameter of the stretched bicomponent filament to about 10 microns or less. As the bicomponent filaments exit the orifice 30, they can be chopped to form a plurality of fine, discrete bicomponent meltblown fibers 41. the

Fig. 4 is similar to Fig. 2 and is a schematic diagram of another modified design of the die head 10 according to the second embodiment of the present invention for forming bicomponent sheath-core fibers. In this embodiment, polymer A is extruded through a central extrusion capillary 16c, while polymer B is extruded through a series of extrusion capillaries, exiting the die through a series of curvilinear slots 16d that wrap around the capillaries. The ends of 16c are arranged concentrically. In this embodiment, the composite orifice includes a central extrusion capillary 16c and a curvilinear slot 16d. A plurality of heated gas nozzles 21 are arranged concentrically around the compound hole. In addition, the gas nozzle 21 may be replaced by an annular slot concentric with the composite hole. the

5 is an end view of the outlet of the die 10 shown in FIG. 1 in accordance with a third embodiment of the present invention, wherein a series of composite die holes are arranged in a row, each die hole includes capillary outlets 16a and 16b , and the molten polymer is extruded into a gas jet exiting through slots 21 that combine with the composite die holes to form spinneret holes 30 . As the polymer streams exit the composite die orifices, they will form a curtain of multicomponent meltblown filaments extending along the length of the die 10 . the

FIG. 6 is another design of the die head shown in FIG. 5 . The two vertically etched templates 60 and 60' are separated by a solid plate 64, thereby forming separate extrusion capillaries 62a and 62b. Gas nozzles, not shown in this figure, are arranged laterally adjacent to the die plates 60 and 60'. the

Those skilled in the art will recognize that the configuration and shape of the extrusion capillary can be modified in a number of ways for different reasons. For example, the method can be used to deliver more than two polymer components into the fiber by machining a pie-slice cross-section in the die lip to form a pie-slice cross-section. , Fibers of substantially circular cross-section. Likewise, those skilled in the art will recognize that, on a production scale, it may be necessary to use many extruder/die assemblies ("spinpacks") in order to obtain sufficient coverage of the collection surface to produce acceptable Non-woven or non-woven fabrics are acceptable. the

An advantage of carrying out the method according to the invention is that the various extrusion parameters can be controlled independently for different polymer components. Since each different polymer is conveyed through a different extrusion device, if one polymer component has significantly different physical properties from another polymer component, such as intrinsic viscosity, melt viscosity, die swell, or melting point/softening point, extrusion parameters such as temperature, pressure, and even extrusion capillary diameter can be varied to suit and optimize extrusion of various polymers. the

In prior art processes, when the polymers are mixed before the melts exit the die, an interface will exist between the two polymer melts. In this approach, the interface cannot be directly controlled and is influenced by many factors. Two examples of serious problems that will arise due to the lack of control over the interface are: 1) When using two similar polymers, as the polymers begin to mix, there may be diffusion at the interface, so the fiber is relatively because bicomponent fibers will be more melt blended fibers; and 2) if the polymers have a significant difference in melt viscosity, then the higher viscosity polymer will likely start to fill the die in disproportionate amounts The space available for the melts will create spinning problems due to the ability of the polymer melts to slide against each other along the interface, thus causing a velocity mismatch between the two melts as they exit the die. When the two polymers are kept separate until they exit the die, the melt is directly controlled and thus avoids the problems described above. the

It should be understood that melt-processable polymers useful in the method of the present invention include any polymer capable of being melt-processed, such as thermoplastics, including polyesters, polyolefins, polyamides, such as nylon-type polymers, polyurethanes Rubber, vinyl polymers such as styrene-type polymers, fluoropolymers such as ethylene-tetrafluoroethylene polymers, polyvinylidene fluoride, fluorinated ethylene-propylene polymers, perfluoro(alkylethylene base ether) polymers, etc. A preferred combination of polymers forming the bicomponent meltblown fibers and bicomponent meltblown nonwovens of the present method is polyethylene and poly(ethylene terephthalate). Preferably, the polyethylene is linear low density polyethylene having a melt index of at least 10 g/10 min (measured according to ASTM D-1238; 2.16 kg at 190°C), an upper melting point in the range of about 120-140°C, and a density in the range From 0.86-0.97 g/ ^cm3 . Meltblown nonwovens comprising bicomponent polyethylene/poly(ethylene terephthalate) meltblown fibers are particularly suitable for use in pharmaceutical end-use nonwovens because they are sterilizable by radiation. The bicomponent polyethylene/poly(ethylene terephthalate) meltblown nonwoven can be bonded to the spunbond layer typically used in said end use to provide strength, softness, Composite laminate with a good balance of breathability, and barrier properties. It is also believed that bicomponent polyethylene/poly(ethylene terephthalate) meltblown fibers have better properties than monocomponent polyethylene or poly(ethylene terephthalate) meltblown fibers. Other preferred polymer combinations for use in the post-coalescence spinning process of the present invention include polypropylene/poly(ethylene terephthalate), poly(hexamethylenediamine adipamide/poly( ethylene terephthalate), poly(hexamethylenediamine adipamide/polypropylene and poly(hexamethylenediamine adipamide/polyethylene). It is expected that if a certain These thermosetting polymers can also be used in the process of the invention if they remain molten during the process of the invention.

Typically, the fibers are deposited on a collecting surface, such as a moving belt or web, a scrim, or another layer of fibers. An air extraction device such as a suction box can be placed under the collector to aid in fiber deposition and gas removal. Fibers produced by meltblowing are typically high aspect ratio, discontinuous fibers having an effective diameter of about 0.5 to about 10 microns. As used herein, the term "effective diameter" of a fiber with an irregular cross-section is equal to the diameter of an imaginary circular fiber of the same cross-sectional area. Preferably, the meltblown web has a basis weight of between about 2 and 40 g/m ² , more preferably between 5 and 30 g/m ² , most preferably between 12 and 35 g/m ² .

Without being bound by theory, it is believed that the gas nozzle is capable of breaking or splitting the multicomponent filaments into even finer filaments. The resulting filaments are believed to include multicomponent filaments wherein each filament is made from at least two separate polymer components; both polymers substantially extend the length of the meltblown fiber, e.g. in a parallel configuration. It is also believed that some of the ruptured filaments may contain only one polymer component due to the splitting of the multicomponent fibers into individual monocomponent fibers. The degree of splittability between two or more different polymer components of a multicomponent meltblown filament can be controlled by selecting the polymer components to obtain the desired adhesion between different polymeric regions. knot degree. the

The fibers in the multicomponent meltblown nonwovens of the present invention are generally discontinuous fibers having an average effective diameter between about 0.5 and 10 microns, more preferably between about 1 and 6 microns, most preferably between Between about 2 and 4 microns. A multicomponent meltblown nonwoven is formed from at least two polymers spun simultaneously from a spinpack comprising an extrusion die as shown in the drawings herein. The fiber configuration in the melt-blown multi-component nonwoven fabric is preferably a two-component side-by-side arrangement, wherein most of the fibers are made of two parallel polymer components, and the content of each different polymer component is based on The desired properties of the cloth are between about 10 to 90% by volume, with the two polymer components extended and bonded over the majority of the length of each fiber. In addition, bicomponent fibers can be a sheath-core arrangement in which one polymer is surrounded by another polymer, the bicomponent fibers are circular pie slices with more than two different polymers section, or any other conventional bicomponent fiber structure. In a more preferred embodiment, the lower melting polymer is located on the surface portion of the fibers so as to enhance the bond between the meltblown fibers on the collecting surface. the

According to a preferred embodiment of the present invention, a low intrinsic viscosity polyester polymer and polyethylene are combined to produce a bicomponent meltblown nonwoven in a meltblown nonwoven production plant. The low viscosity polyester preferably comprises poly(ethylene terephthalate) having an intrinsic viscosity of less than about 0.55 dl/g, preferably from about 0.17 to 0.49 dl/g (measured using ASTM D2857 as described above), more Preferably from about 0.20 to 0.45 dl/g, most preferably from about 0.22 to 0.35 dl/g. The two polymers A and B described were melted, filtered and metered into a spin block. The molten polymers are extruded through separate extrusion capillaries within the spin block and exit the spin block through the spinneret holes where they are contacted by gas from the gas nozzles and forced into contact with each other, and are Attenuation is carried out in the machine direction to form high aspect ratio fibers. Meltblown bicomponent fibers can be cut by a heated gas jet to form discontinuous fibers, however, they can be continuous fibers. Preferably, the gas jet produces the desired side-by-side fiber cross section. the

Composite nonwoven fabrics incorporating the above multicomponent meltblown webs can be produced in-line by collecting the multicomponent meltblown fibers on different sheets such as spunbond fabrics, woven fabrics or foams. The layers can be joined using methods known in the art such as by thermal, ultrasonic and/or adhesive bonding. The meltblown layer and the other fabric or sheet layers preferably each comprise compatible polymeric components so that the layers can be bonded thermally, such as by thermal point bonding. For example, in a preferred embodiment, the composite laminate comprises a meltblown nonwoven and a spunbond, each comprising at least one substantially identical or identical polymer. Alternatively, the layers of the composite sheet can be produced independently and then laminated and bonded to form the composite sheet. It is also contemplated that more than one spunbond production unit can be used in series to produce webs made from different mono- or multi-component fiber blends. It is also contemplated that more than one meltblown nonwoven production unit can be used in series in order to produce a composite sheet with multiple meltblown layers. It is also contemplated that the polymer(s) used in the various cloth production devices may differ from each other. When it is desired to produce a composite sheet having only one spunbond layer and one layer of fine meltblown fibers, the second spunbond production unit can be shut down or eliminated. the

氟化学剂(得自DuPont，Wilmington，DE)或REPEARL氟化学剂(得自Mitsubishi Int.Corp.，New York，NY)。局部整饰方法可以与织物生产一起在线进行，或在独立的处理步骤中进行。另外，所述氟化学剂也可以作为添加至熔体中的添加剂而纺入纤维之中。  Optionally, a fluorochemical coating can also be applied to the composite nonwoven fabric, thereby reducing the surface energy of the fiber surface and thereby increasing the resistance of the fabric to liquid penetration. For example, fabrics may be treated with a topical treatment to improve liquid barrier properties, particularly low surface tension liquids. Many methods of spot-finishing treatments are well known in the art and include spraying, rolling, foam coating, dip-extrusion coating, and the like. Common finishing ingredients include ZONYL

Fluorochemicals (from DuPont, Wilmington, DE) or REPEARL Fluorochemicals (available from Mitsubishi Int. Corp., New York, NY). Partial finishing methods can be carried out in-line with fabric production, or in a separate processing step. Additionally, the fluorochemicals may also be spun into the fibers as additives added to the melt.

Test Methods

In the above description and in the examples that follow, the following test methods were used to determine the various listed properties and properties. ASTM refers to the American Society for Testing and Materials. the

Fiber diameters are measured by light microscopy and reported in mean microns. For each meltblown sample, the diameters of approximately 100 fibers were measured and averaged.

Basis weight is a measure of the mass per unit area of a fabric or sheet and is measured by ASTM D-3776, which is hereby incorporated by reference, and is reported in g/ ^m2 .

The intrinsic viscosity of the polyesters used herein is measured according to ASTM D2857 using 25 volume percent trifluoroacetic acid and 75 volume percent methylene chloride at 30° C. in a capillary viscometer. Frazier air permeability is a measure of the flow of air through a sheet at a specified pressure difference between the surfaces of the sheet and is measured in accordance with ASTM D737 and reported in ^m3 /min/ ^m2 , ASTM D737 Incorporated by reference.

Example

Composite sheets comprising an inner layer of meltblown fibers sandwiched between outer spunbond layers were prepared in Examples 1-4. The same spunbond outer layer was used in each of these examples and comprised bicomponent filaments with a sheath-core cross-section. the

The spunbond layer is made of bicomponent fibers of linear low density polyethylene (LLDPE) and poly(ethylene terephthalate) (PET); the melt index of the LLDPE is 27 g/10 min ( At a temperature of 190°C, measured according to ASTM D-1238), it is a blend of 20% by weight of ASPUN 6811ALLDPE and 80% by weight of ASPUN 61800-34 LLDPE (both from Dow); The intrinsic viscosity is 0.53dl/g, based on Crystar 4449 polyester form available from DuPont. The polyester resin was crystallized at a temperature of 180°C and dried at 120°C so that the water content before use was less than 50 ppm. In separate extruders, polyester was heated to 290°C and polyethylene to 280°C. The polymer was extruded, filtered and metered into bicomponent spinpacks maintained at 295°C with 4000 holes/meter (2016 holes in the spinneret pack) and designed to provide sheath-core filament cross-sections. The polymer was spun through a spinneret to produce bicomponent filaments with a polyethylene sheath and a poly(ethylene terephthalate) core. The total throughput of polymer per spin block capillary was 1.0 g/min. The polymer was metered to provide a filament of 30% polyethylene (sheath) and 70% polyester (core) by weight of fiber. The filaments were cooled in a 15 inch (38.1 cm) long quench zone with quench air supplied from two opposing quench boxes at a temperature of 12°C and a velocity of 1 m/sec. The filaments were fed into a pneumatic draw spinneret spaced 26 inches (66.0 cm) below the capillary opening of the spin block where the filaments were drawn. The resulting finer, stronger, substantially continuous filaments are deposited using vacuum suction onto a layup belt moving at a speed of 186 m/min to form a basis weight of 0.6 oz/ ^yd2 (20.3 g/ m ² ) of spunbond fabric. The fibers in the cloth had an average diameter of about 11 microns. Using a point bonding pattern, the resulting cloth was conveyed between two thermal bonding rolls at 100° C. and a nip pressure of 100 N/cm, so that the cloth was lightly bonded together for shipping. The lightly bonded spunbond is collected on a roller. The production method of the melt-blown layer used in each example will be described below.

Composite nonwoven sheets were prepared in Examples 1-4 by unrolling the bicomponent spunbond onto a kinematic belt and laminating the bicomponent meltblown nonwoven on top of the kinematic spunbond. The second roll of spunbond fabric is unrolled and laid on the spunbond-meltblown fabric to produce a spunbond-meltblown-spunbond composite nonwoven fabric. The composite cloth was thermally bonded between a textured oil hot metal calender roll and a smooth oil hot metal calender roll. Both rolls have a diameter of 466 mm. The engraving roll had a chrome-coated non-hardened steel surface with a diamond pattern, where each pattern had a spot size of 0.466 mm ² , a spot depth of 0.86 mm, a spot pitch of 1.2 mm, and a bonded area of 14.6%. Smooth rolls have hardened steel surfaces. The composite cloth was bonded at 120°C, a nip pressure of 350 N/cm and a line speed of 50 m/min. The bonded composite sheets are collected on rollers. The final basis weight of each composite nonwoven sheet was about 58 g/ ^m2 .

Example 1-4

聚(对苯二甲酸乙二酯)和以ASPUN6806得自Dow的线性低密度聚乙烯(LLDPE)，以并列型排列制备双组分纤维；其中所述聚(对苯二甲酸乙二酯)的特性粘度为0.53，含水量约1500ppm；所述LLDPE的熔体指数为100克/10分(根据ASTM D-1238测量)。在独立的挤压机中，将聚乙烯聚合物加热至450(232℃)并将聚酯聚合物加热至572

(300℃)。对两聚合物独立地进行挤出、过滤并计量至带有图6中所示模唇构型的双组分纺丝块中。所述模头由两个垂直蚀刻板60和60’形成，所述板带有在其中形成的平行凹槽62a和62b，所述凹槽的半径为0.2毫米。两块蚀刻板被2密耳厚的实心板64分开，以便使两种聚合物料流保持独立，直至它们排出挤出毛细管之后为止。其中之一的聚合物料流通过凹槽62a形成的毛细管供应，而另一聚合物料流通过凹槽62b形成的毛细管供应。挤出毛细管的出口孔以沿模唇长度方向每英寸30个孔的距离间隔开，其中模唇的长度约为21英寸(53厘米)。将纺丝块模头加热至572

(300℃)并以表1中给出的聚合物质量流速，通过毛细管对聚合物进行纺丝。将拉细空气加热至310℃并以9psi(62kPa)的气压通过两个1.5毫米宽的气道供应。两个气道在毛细管开口的约21英寸(53厘米)线路的长度上延伸，并且毛细管线每边一个的一个气道安置在毛细管开口后面1.5毫米。每个气道均以45度的角度与板64的平面取向，其中气道的两个轴向着挤出毛细管出口方向收敛，气道之间总的包括角为90度。利用两个不同的挤压机，将聚乙烯和聚(对苯二甲酸乙二酯)供至纺丝块。当聚乙烯排出挤压机时其温度为265℃，而聚(对苯二甲酸乙二酯)的温度为295℃。供至纺丝块的聚合物的质量流速对于每个实施例均不同，并列于表1中。将长丝收集在以52米/分运动的成型网上，其上表面位于模唇末端以下5.5英寸(14.0厘米)，以生产随后收集在罗拉上的熔喷法非织造布。在每个实施例中，所述熔喷法非织造布的单位重量均为11.7克/米²。  The bicomponent meltblown nonwovens in these examples were prepared using a post-coalescing meltblown process. Via Crystar from DuPont

Poly(ethylene terephthalate) and linear low density polyethylene (LLDPE) obtained from Dow as ASPUN6806 are arranged side by side to prepare bicomponent fibers; wherein the poly(ethylene terephthalate) The intrinsic viscosity is 0.53, and the water content is about 1500 ppm; the melt index of the LLDPE is 100 g/10 min (measured according to ASTM D-1238). In a separate extruder, the polyethylene polymer is heated to 450 (232°C) and heat the polyester polymer to 572

(300°C). The two polymers were independently extruded, filtered and metered into a bicomponent spinpack with the lip configuration shown in FIG. 6 . The die is formed from two vertically etched plates 60 and 60' with parallel grooves 62a and 62b formed therein, the grooves having a radius of 0.2 mm. The two etched plates were separated by a 2 mil thick solid plate 64 to keep the two polymer streams separate until after they exited the extrusion capillary. One of the polymer streams is supplied through the capillary formed by the groove 62a, while the other polymer stream is supplied through the capillary formed by the groove 62b. The exit holes of the extrusion capillary were spaced at a distance of 30 holes per inch along the length of the die lip, where the length of the lip was about 21 inches (53 centimeters). Heat the spinpack die to 572

(300°C) and at the polymer mass flow rate given in Table 1, the polymer was spun through a capillary. Attenuation air was heated to 310°C and supplied through two 1.5 mm wide air passages at 9 psi (62 kPa). Two air channels extend the length of approximately 21 inches (53 cm) of line of the capillary opening, and one air channel, one on each side of the capillary line, is positioned 1.5 mm behind the capillary opening. Each air channel is oriented at an angle of 45 degrees to the plane of plate 64, with the two axes of the air channels converging in the direction of the exit of the extrusion capillary, with a total included angle of 90 degrees between the air channels. Polyethylene and poly(ethylene terephthalate) were fed to the spin packs using two different extruders. The polyethylene had a temperature of 265°C as it exited the extruder, while the poly(ethylene terephthalate) had a temperature of 295°C. The mass flow rate of polymer supplied to the spin packs was varied for each example and is listed in Table 1. The filaments were collected on a forming wire moving at 52 meters per minute, the upper surface of which was located 5.5 inches (14.0 cm) below the end of the die lip to produce a meltblown nonwoven that was subsequently collected on rollers. In each embodiment, the unit weight of the melt-blown nonwoven fabric is 11.7 g/ ^m2 .

Example 5

A two-component melt-blown nonwoven is prepared using a linear low-density polyethylene (LLDPE) component and a poly(ethylene terephthalate) component; wherein the polyethylene has a melt index of 135 g/10 min (measured according to ASTM D-1238), available from Equistar as GA594; the reported intrinsic viscosity of the poly(ethylene terephthalate) is 0.53, measured as Crystar Polyester (Merge 4449) was obtained from DuPont. In separate extruders, LLDPE and poly(ethylene terephthalate) were heated to 260°C and 305°C, respectively. The two polymers were extruded separately and metered into two separate polymer dispensers. The planar melt stream discharged from each distributor is independently filtered and extruded through a two-component melt-blown die with two sets of linear independent holes, the first set extrudes LLDPE, the second set Poly(ethylene terephthalate) was extruded. The holes were arranged in pairs so that each LLDPE orifice was in close proximity to the poly(ethylene terephthalate) orifice, forming a linear array of composite orifices along the length of the die lip. The pairs of spinneret holes forming each composite spinneret hole are arranged so that the line passing through the centers of the two spinneret holes in each pair is perpendicular to the direction of the linearly arranged pair of holes, and between the two holes of the pair of holes The center point between is located at the apex of the die lip. The die had 645 pairs of capillary openings arranged in a 54.6 cm line. The die was heated to 305°C and LLDPE and poly(ethylene terephthalate) were spun at throughputs of 0.16 g/hole/min and 0.64 g/hole/min, respectively. Attenuated air was heated to 305°C and supplied through two 1.5 mm wide air passages at 5.5 psi. Two airways extend the length of the 54.6 cm line of the capillary opening, and one airway, one on each side of the capillary line, is positioned 1.5 mm behind the capillary opening. With the rate of 6.2 kg/hour and 24.8 kg/hour respectively, LLDPE and poly(ethylene terephthalate) are fed to the spinning combination to provide a bicomponent meltblown nonwoven fabric of 20 % by weight LLDPE and 80% by weight poly(ethylene terephthalate). The fabric was formed by collecting the meltblown fibers on a moving forming wire at a die to collector distance of 20.3 cm to produce a meltblown nonwoven fabric wound onto rollers. The basis weight of the melt-blown nonwoven fabric is 1.5 oz/yard ² (50.9 g/m ² ), and the Frazier air permeability of the sample is 86 ft ³ /min/ft ² (26.2 m ³ /min/m ² ).

Comparative example A

This example illustrates the formation of a bicomponent meltblown nonwoven in which two polymer streams are combined prior to exiting the die lip. The same polymer and spinning equipment as in Examples 1-4 were used except that the solid plate 64 shown in Figure 6 was removed to bring the two polymers into contact in the extrusion capillary. Polymer temperature and mass flow rate, die temperature, gas pressure and temperature were the same as used in Example 1. The basis weight of the melt-blown nonwoven fabric was 17 g/m ² .

Table 1

Meltblown conditions and properties of meltblown nonwovens

Example LLDPE mass flow rate (kg/h) PET mass flow rate (kg/h) Weight ratio (%PE) Frazier(m ³ /min/m ² ) of melt-blown nonwovens Size of fibers in meltblown nonwovens (μ) Frazier of composite sheet (m ³ /min/m ² ) 1 6 twenty four 20 23.2 2.8 10.4 2 12 18 40 -- -- 11.6 3 18 12 60 -- -- 17.4 4 twenty four 6 80 -- -- 9.4 5 6.2 24.8 20 26.2 - - A 6 twenty four 20 23.8 3.0 13.7

Claims (5)

1. An extrusion die for meltblowing molten polymer comprising a row of die orifices, each die orifice comprising at least two separate polymer supplies entering from an inlet portion of the die A gas supply hole enters from the inlet portion of the die and is arranged transversely with respect to said polymer supply hole, said gas supply hole communicates with a gas nozzle extending through the die and is opposite to a gas nozzle at the outlet portion of the die. The outlets of the independent extrusion capillaries of the outlets are arranged transversely, wherein the outlets of the extrusion capillaries and the gas nozzles communicate with spinneret holes in the outlet portion of the die, characterized in that each of the polymer supply holes communicated with the extrusion capillary. 2. An extrusion die for meltblowing molten polymers, comprising at least two separate polymer supply orifices entering from an inlet portion of the die, with an outlet at the outlet portion of the die Separate extrusion capillaries fit in the form of a composite orifice, at least one gas supply orifice is entered by the inlet portion of the die, the gas supply orifice communicates with at least one gas nozzle extending through the die and surrounds an opening of the composite orifice. The outlets are arranged concentrically, wherein said extrusion capillary outlet and said gas nozzle communicate with a spinneret hole in a die outlet portion, wherein said polymer supply hole communicates with said extrusion capillary. 3. An extrusion die according to claim 1 or 2, wherein said extrusion capillaries are angled relative to a common longitudinal axis. 4. An extrusion die according to claim 1 or 2, wherein said extrusion die comprises at least two gas nozzles, and wherein said extrusion capillary and said gas nozzles are at an angle relative to a common longitudinal axis . 5. The extrusion die according to claim 1 or 2, wherein said extrusion die comprises at least two gas nozzles, and wherein said extrusion capillaries are parallel to each other, and said gas nozzles are aligned with respect to a common longitudinal axis certain angle.

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