US20130009333A1

US20130009333A1 - Process for making nonwoven webs

Info

Publication number: US20130009333A1
Application number: US13/635,144
Authority: US
Inventors: Lakshmi Krishnamurthy; Zuohong Yin; Joachim C Ritter; Joel M Pollino; Michael T Pottiger; John C Howe; David Matthews Laura, Jr.; Harry Vaughn Samuelson; Robert John Duff; Zheng-Zheng Huang
Original assignee: Individual
Current assignee: EIDP Inc
Priority date: 2010-03-22
Filing date: 2011-03-17
Publication date: 2013-01-10
Also published as: EP2550386A4; JP2013522495A; CA2792831A1; KR20130007619A; BR112012023944A2; WO2011119397A2; WO2011119397A3; EP2550386A2; CN102918191A

Abstract

A nonwoven web comprising bicomponent fibers. The fibers have continuous phases each of a first polyarylene sulfide (PAS) component and a polymer component. The polymer component may also be a second polyarylene sulfide. The first polyarylene sulfide component contains a tin or a zinc additive or both, and the first polyarylene sulfide component of any given fiber is at least partially exposed to the external surface of that fiber.

Description

FIELD

This invention relates to processes of making nonwoven webs, and in particular webs formed from polyarylene sulfides.

BACKGROUND

It is known that physical properties of a web can be improved by calendaring, which is the process of passing a sheet material through a nip between rolls or plates to impart a smooth, glossy appearance to the sheet material or otherwise improving selected physical properties.
Through the calendaring of paper or other fibrous materials, an effort is made to further improve the quality of paper formed or, in providing a standard level of quality, to achieve a higher running speed or increased bulk of the paper being produced. It is well known that the plasticity or molding tendency of paper or fiber may be increased by raising the temperature and/or the plasticizer content of the paper or fiber. A considerable change in mechanical properties, including plasticity, occurs when the temperature of the polymers contained in the paper rises to or beyond the so-called glass transition temperature (T.sub.g), at which point the material may then be more readily molded or formed or finished than it can below that temperature.
Many nonwoven fabrics are bonded to impart integrity to the fabric. While there are several bonding techniques available, thermal bonding processes prevail in the nonwovens industry both in volume and time devoted to the research and development of new products. These processes have gained wide acceptance due to simplicity and many advantages over traditional chemical bonding methods. Attractive features include low energy and raw material costs, increased production rates, and product versatility. Chemical simplification, since adhesive binders are not used, reduces concerns over the environment. U.S. Pat. No. 4,035,219 and U.S. Pat. No. 5,424,115 provide examples of point bonding of nonwoven webs to enhance physical properties.
U.S. Pat. No. 2,277,049 to Reed introduced the idea of using fusible fibers to make nonwoven fabrics by blending fusible and nonfusible fibers of similar denier and cut length and treating the web with either solvent or heat. The fusible fibers become tacky and act as a binder. A nonwoven fabric results after pressing and cooling the tacky web.
The use of temperatures near the melting point Tm of the fiber in a nanoweb is detrimental to the quality of the web. The small size of the fibers combined with the uneven heating inherent in calendaring machinery tend to produce uneven melting and bonding and render the web less effective for filtration and battery separator and other energy storage applications. The deficiency in the prior art in the area of strengthening of webs of low basis weight and comprising fine denier fiber is exemplified in EP 1 042 549, in which thermal bonding in a pattern is used to produce a less deformable web.
This invention overcomes the deficiencies in previous processes for making calendared webs by providing a process that provides a high strength product under less severe conditions that heretofore.

SUMMARY

This invention is directed to a nonwoven web comprising bicomponent fibers, said fibers comprising continuous phases each of a first polyarylene sulfide (PAS) component and a polymer component, in which the first polyarylene sulfide component contains a tin or a zinc additive or both and the first polyarylene sulfide component of any given fiber is at least partially exposed to the external surface of that fiber. By “partially exposed” is meant that at least a portion, of the component appears on an outside surface of the fiber. The entire outside surface of the fiber may be the first PAS component may also at least partially envelop the polymer component.
The invention is also directed to an improved process for manufacturing a nonwoven web comprising the steps of (i) spinning bicomponent fibers into a nonwoven web, said fibers comprising continuous phases each of a first polyarylene sulfide component and a polymer component, in which the first polyarylene sulfide component contains a tin or a zinc additive or both and the first polyarylene sulfide component of any given fiber is at least partially exposed to the external surface of that fiber, and (ii) calendaring the nonwoven web to bond at least a subset of the individual fibers. In a particular embodiment, the the nonwoven web is calendared for a time and temperature sufficient to bond at least a subset of the individual fibers.

DETAILED DESCRIPTION

Where the indefinite article “a” or “an” is used with respect to a statement or description of the presence of a step in a process of this invention, it is to be understood, unless the statement or description explicitly provides to the contrary, that the use of such indefinite article does not limit the presence of the step in the process to one in number.
Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

Definitions

As used herein the term “spunbond” refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments being rapidly reduced as by for example in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,542,615 to Dobo et al., which are each incorporated by reference in their entirety herein.
As used herein, the term “meltblown” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular die capillaries as molten threads or filaments into converging high velocity gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, in various patents and publications, including NRL Report 4364, “Manufacture of Super-Fine Organic Fibers” by B. A. Wendt, E. L. Boone and D. D. Fluharty; NRL Report 5265, “An Improved Device For The Formation of Super-Fine Thermoplastic Fibers” by K. D. Lawrence, R. T. Lukas, J. A. Young; and U.S. Pat. No. 3,849,241, issued Nov. 19, 1974, to Butin, et al, which patent is incorporated by reference hereto in its entirety.
As used herein the term “multicomponent fibers” refers to fibers which have been formed from at least two component polymers, or the same polymer with different properties or additives, extruded from separate extruders but spun together to form one fiber. Multicomponent fibers are also sometimes referred to as conjugate fibers or bicomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent fibers and extend continuously along the length of the multicomponent fibers. The configuration of such a multicomponent fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another, or may be a side by side arrangement, an “islands-in-the-sea” arrangement, or arranged as pie-wedge shapes or as stripes on a round, oval, or rectangular cross-section fiber. Multicomponent fibers are taught in, for example, U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 5,336,552 to Strack et al., and U.S. Pat. No. 5,382,400 to Pike et al. For two component fibers, the polymers may be present any desired ratios.
As used herein the term “biconstituent fiber” or “multiconstituent fiber” refers to a fiber formed from at least two polymers, or the same polymer with different properties or additives, extruded from the same extruder as a blend and wherein the polymers are not arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent fibers. Fibers of this general type are discussed in, for example, U.S. Pat. No. 5,108,827 to Gessner.
As used herein the term “nonwoven web” or “nonwoven material” means a web having a structure of individual fibers or filaments which are interlaid, but not in an identifiable manner as in a knitted or woven fabric. Nonwoven webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, air-laying processes and carded web processes. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm) or ounces of material per square yard (osy) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91).
By “partially envelops” is meant that that one component in a bicomponent or multicomponent fiber at least partially encloses a second component. One component may also appear on the external surface of the fiber.
“Calendering” is the process of passing a web through a nip between two rolls. The rolls may be in contact with each other, or there may be a fixed or variable gap between the roll surfaces. Advantageously, in the present calendering process, the nip is formed between a soft roll and a hard roll. The “soft roll” is a roll that deforms under the pressure applied to keep two rolls in a calender together. The “hard roll” is a roll with a surface in which no deformation that has a significant effect on the process or product occurs under the pressure of the process. The hard roll may have a pattern engraved on it or it may be unpatterned. An “unpatterned” roll is one which has a smooth surface within the capability of the process used to manufacture them. There are no points or patterns to deliberately produce a pattern on the web as it passed through the nip, unlike a point bonding roll.
Polyarylene sulfides (PAS) include linear, branched or cross linked polymers that include arylene sulfide units. Polyarylene sulfide polymers and their synthesis are known in the art and such polymers are commercially available.
Exemplary polyarylene sulfides useful in the invention include polyarylene thioethers containing repeat units of the formula —[(Ar¹)_n—X]_m—[(Ar²)_i—Y]_j—(Ar³)_k-Z]_l—[(Ar⁴)_o-W]_p— wherein Ar¹, Ar², Ar³, and Ar⁴are the same or different and are arylene units of 6 to 18 carbon atoms; W, X, Y, and Z are the same or different and are bivalent linking groups selected from —SO₂—, —S—, —SO—, —CO—, —O—, —COO— or alkylene or alkylidene groups of 1 to 6 carbon atoms and wherein at least one of the linking groups is —S—; and n, m, i, j, k, l, o, and p are independently zero or 1, 2, 3, or 4, subject to the proviso that their sum total is not less than 2. The arylene units Ar¹, Ar², Ar³, and Ar⁴may be selectively substituted or unsubstituted. Advantageous arylene systems are phenylene, biphenylene, naphthylene, anthracene and phenanthrene. The polyarylene sulfide typically includes at least 30 mol %, particularly at least 50 mol % and more particularly at least 70 mol arylene sulfide (—S—) units. Preferably the polyarylene sulfide polymer includes at least 85 mol % sulfide linkages attached directly to two aromatic rings. Advantageously the polyarylene sulfide polymer is polyphenylene sulfide (PPS), defined herein as containing the phenylene sulfide structure —(C₆H₄—S)_n— (wherein n is an integer of 1 or more) as a component thereof.
A polyarylene sulfide polymer having one type of arylene group as a main component can be preferably used. However, in view of processability and heat resistance, a copolymer containing two or more types of arylene groups can also be used. A PPS resin comprising, as a main constituent, a p-phenylene sulfide recurring unit is particularly preferred since it has excellent processability and is industrially easily obtained. In addition, a polyarylene ketone sulfide, polyarylene ketone ketone sulfide, polyarylene sulfide sulfone, and the like can also be used.
Specific examples of possible copolymers include a random or block copolymer having a p-phenylene sulfide recurring unit and an m-phenylene sulfide recurring unit, a random or block copolymer having a phenylene sulfide recurring unit and an arylene ketone sulfide recurring unit, a random or block copolymer having a phenylene sulfide recurring unit and an arylene ketone ketone sulfide recurring unit, and a random or block copolymer having a phenylene sulfide recurring unit and an arylene sulfone sulfide recurring unit.
The polyarylene sulfides may optionally include other components not adversely affecting the desired properties thereof. Exemplary materials that could be used as additional components would include, without limitation, antimicrobials, pigments, antioxidants, surfactants, waxes, flow promoters, particulates, and other materials added to enhance processability of the polymer. These and other additives can be used in conventional amounts.

Description

This invention is directed to a nonwoven web comprising bicomponent fibers, said fibers comprising continuous phases each of a first polyarylene sulfide (PAS) component and a polymer component, in which the first polyarylene sulfide component contains a tin or a zinc additive or both and the first polyarylene sulfide component of any given fiber is at least partially exposed to the outside of that fiber. By “partially exposed” is meant that at least a portion, of the component appears on an outside surface of the fiber. The entire outside surface of the fiber may consist of the first PAS component. The first PAS component may also at least partially envelop the second polymer component.
The invention is also directed to an improved process for manufacturing a nonwoven web comprising the steps of (i) spinning bicomponent fibers into a nonwoven web, said fibers comprising continuous phases each of a first polyarylene sulfide component and a polymer component, in which the first polyarylene sulfide component contains a tin or a zinc additive or both and the first polyarylene sulfide component of any given fiber is at least partially exposed to the outside of that fiber, and (ii) calendaring the nonwoven web for a time and temperature sufficient to bond at least a subset of the individual fibers.
The spinning process of the invention can be any nonwoven spinning process known to one skilled in the art, for example a spunbonding or meltblowing process.
The second polymer component can comprise any thermoplastic polymeric material. In further embodiments, the second polymer component can comprise a polymer selected from the group consisting or polyether ether ketone (PEEK), polyether ketone (PEK), polyester, polypropylene, polyamide, and mixtures thereof. The polyester is preferably polyethylene terephthalate (PET), polytrimethylene terephthalate, or polybutylene terephthalate (PBT). The second polymer component can further comprise a second PAS, which may further comprise a calcium salt additive, preferably calcium stearate. In one embodiment, the first PAS component of the sheath of the fibers comprises at least one tin(II) salt of an organic carboxylic acid. The polyarylene sulfide composition may comprise at least one tin additive comprising a branched tin(II) carboxylate selected from the group consisting of Sn(O₂CR)₂, Sn(O₂CR)(O₂CR′), Sn(O₂CR)(O₂CR″), and mixtures thereof, where the carboxylate moieties O₂CR and O₂CR′ independently represent branched carboxylate anions and the carboxylate moiety O₂CR″ represents a linear carboxylate anion. In one embodiment, the branched tin(II) carboxylate comprises Sn(O₂CR)₂, Sn(O₂CR)(O₂CR′), or a mixture thereof. In one embodiment, the branched tin(II) carboxylate comprises Sn(O₂CR)₂. In one embodiment, the branched tin(II) carboxylate comprises Sn(O₂CR)(O₂CR′). In one embodiment, the branched tin(II) carboxylate comprises Sn(O₂CR)(O₂CR″).
Optionally, the tin additive may further comprise a linear tin(II) carboxylate Sn(O₂CR″)₂. Generally, the relative amounts of the branched and linear tin(II) carboxylates are selected such that the sum of the branched carboxylate moieties [O₂CR+O₂CR′] is at least about 25% on a molar basis of the total carboxylate moieties [O₂CR+O₂CR′+O₂CR″] contained in the additive. For example, the sum of the branched carboxylate moieties may be at least about 33%, or at least about 40%, or at least about 50%, or at least about 66%, or at least about 75%, or at least about 90%, of the total carboxylate moieties contained in the tin additive.
In one embodiment, the radicals R and R′ both comprise from 6 to 30 carbon atoms and both contain at least one secondary or tertiary carbon. The secondary or tertiary carbon(s) may be located at any position(s) in the carboxylate moieties O₂CR and O₂CR′, for example in the position a to the carboxylate carbon, in the position w to the carboxylate carbon, and at any intermediate position(s). The radicals R and R′ may be unsubstituted or may be optionally substituted with inert groups, for example with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxylate groups. Examples of suitable organic R and R′ groups include aliphatic, aromatic, cycloaliphatic, oxygen-containing heterocyclic, nitrogen-containing heterocyclic, and sulfur-containing heterocyclic radicals. The heterocyclic radicals may contain carbon and oxygen, nitrogen, or sulfur in the ring structure.
In one embodiment, the radical R″ is a primary alkyl group comprising from 6 to 30 carbon atoms, optionally substituted with inert groups, for example with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxylate groups. In one embodiment, the radical R″ is a primary alkyl group comprising from 6 to 20 carbon atoms.
In one embodiment, the radicals R or R′ independently or both have a structure represented by Formula (I),
wherein R₁, R₂, and R₃are independently:
H;
a primary, secondary, or tertiary alkyl group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups;
an aromatic group having from 6 to 18 carbon atoms, optionally substituted with alkyl, fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups; and
a cycloaliphatic group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups;
with the proviso that when R₂and R₃are H, R₁is: a secondary or tertiary alkyl group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups;
an aromatic group having from 6 to 18 carbons atoms and substituted with a secondary or tertiary alkyl group having from 6 to 18 carbon atoms, the aromatic group and/or the secondary or tertiary alkyl group being optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups; and
a cycloaliphatic group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups.
In one embodiment, the radicals R or R′ or both have a structure represented by Formula (I), and R₃is H.
In another embodiment, the radicals R or R′ or both have a structure represented by Formula (II),
wherein
R₄is a primary, secondary, or tertiary alkyl group having from 4 to 6 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, and hydroxyl groups; and
R₅is a methyl, ethyl, n-propyl, sec-propyl, n-butyl, sec-butyl, or tert-butyl group, optionally substituted with fluoride, chloride, bromide, iodide, nitro, and hydroxyl groups.
In one embodiment, the radicals R and R′ are the same and both have a structure represented by Formula (II), where R₄is n-butyl and R₅is ethyl. This embodiment describes the branched tin(II) carboxylate tin(II) 2-ethylhexanoate, also referred to herein as tin(II) ethylhexanoate.
The tin(II) carboxylate(s) may be obtained commercially, or may be generated in situ from an appropriate source of tin(II) cations and the carboxylic acid corresponding to the desired carboxylate(s). The tin(II) additive may be present in the polyarylene sulfide at a concentration sufficient to provide improved thermo-oxidative and/or thermal stability. In one embodiment, the tin(II) additive may be present at a concentration of about 10 weight percent or less, based on the weight of the polyarylene sulfide. For example, the tin(II) additive may be present at a concentration of about 0.01 weight percent to about 5 weight percent, or for example from about 0.25 weight percent to about 2 weight percent. Typically, the concentration of the tin(II) additive may be higher in a master batch composition, for example from about 5 weight percent to about 10 weight percent, or higher. The tin(II) additive may be added to the molten or solid polyarylene sulfide as a solid, as a slurry, or as a solution.
In a further embodiment, the polyarylene sulfide composition of the sheath of the fibers of the invention further comprises at least one zinc(II) additive and/or zinc metal [Zn(O)]. The zinc(II) additive may be an organic additive, for example zinc stearate, or an inorganic compound such as zinc sulfate or zinc oxide, as long as the organic or inorganic counter ions do not adversely affect the desired properties of the polyarylene sulfide composition. The zinc(II) additive may be obtained commercially, or may be generated in situ. Zinc metal may be used in the composition as a source of zinc(II) ions, alone or in conjunction with at least one zinc(II) additive. In one embodiment the zinc(II) additive is selected from the group consisting of zinc oxide, zinc stearate, and mixtures thereof.
The zinc(II) additive and/or zinc metal may be present in the polyarylene sulfide at a concentration of about 10 weight percent or less, based on the weight of the polyarylene sulfide. For example, the zinc(II) additive and/or zinc metal may be present at a concentration of about 0.01 weight percent to about 5 weight percent, or for example from about 0.25 weight percent to about 2 weight percent. Typically, the concentration of the zinc(II) additive and/or zinc metal may be higher in a master batch composition, for example from about 5 weight percent to about 10 weight percent, or higher. The at least one zinc(II) additive and/or zinc metal may be added to the molten or solid polyarylene sulfide as a solid, as a slurry, or as a solution. The zinc(II) additive and/or zinc metal may be added together with the tin(II) salt or separately.

Examples

Bicomponent spunbond fabric was made from a poly(ethylene terephthalate) (PET) component and a poly(phenylene sulfide) (PPS) component. The PET component had an intrinsic viscosity of 0.633 dl/g and is available from PolyQuest, Wilmington, N.C. as PET resin grade PQB8A-065. The PPS component, available from Ticona Engineering Polymers, Florence, Ky. under the tradename Fortron® PPS was a mixture of 70 wt% grade 0309 C1 and 30 wt % grade 0317 C1.
The following materials were used in the examples. All commercial materials were used as received unless otherwise indicated. Tin(II) 2-ethylhexanoate (90%) and zinc oxide (99%) were obtained from Sigma-Aldrich (St. Louis, Mo.). Tin(II) stearate (98%) (Sn stearate) was obtained from Acros Organics (Morris Plains, N.J.). Zinc stearate (99%) (Zn stearate) was obtained from Honeywell Reidel-de Haen (Seelze, Germany). Tin(II) 2-ethylhexanoate is also referred to herein as tin(II) ethylhexanoate or SnEH.
Additive, if used, was melt blended with the PPS such that it comprised the required % of the total mass of the PPS component. The PET resin was dried in a through air dryer at a temperature of 120° C. to a moisture content of less than 50 parts per million. The PPS resins were dried in a through air dryer at a temperature of 115° C. to a moisture content of less than 150 parts per million. The PET polymers were heated in an extruder at 290° C. and the PPS resins heated in a separate extruder at 295° C. The two polymers were metered to a spin-pack assembly where the two melt streams were separately filtered and then combined through a stack of distribution plates to provide multiple rows of spunbond fibers having sheath-core cross sections. Such processing is well known to those skilled in the art. The PET component comprised the core and the PPS component comprised the sheath.
A spin pack assembly consisting of 2158 round capillary openings was heated to 295° C. and the PPS and PET polymers spun through each capillary at a polymer throughput rate of 2.2 g/hole/min. The PET component consisted of 70% by weight of the total weight of the spun bond fibers. The fibers were cooled in a cross flow quench extending over a length of 122 cm. An attenuating force was provided to the bundle of fibers by a rectangular slot jet. The distance between the spin-pack to the entrance of the jet was 147 cm. The fibers exiting the jet were collected on a forming belt traveling at 87.4 m/min. A vacuum was applied underneath the belt to help pin the fibers to the belt. The spunbond layer was then smooth-calendered by passing the web between two smooth metal to achieve filament to filament bonding. The bonding conditions were 135° C. roll temperature and 875 N/cm nip pressure. After thermal bonding, the spunbond sheet was formed into a roll using a winder.
In an additional step, the non-woven web was then smooth-calendered to achieve further densification of the already bonded non-woven web. The web was passed between 2 heated stainless steel rolls having a diameter of 76.2 cm at a nip pressure of 4200 N/cm. The line speed was 61 m/min and the rolls were heated to a surface temperature of 200° C. After calendaring, the spunbond sheet had a basis weight of 51 g/m².
The results of tensile testing on these samples are given in the table below, where SnEH is tin (II) ethylhexanoate, ZnO is zinc oxide, SnO is tin oxide, Zn Stearate is zinc stearate, and Sn Stearate is tin stearate. Tensile strength and work to break of the nonwoven sheets were measured on an Instron-type testing machine using test specimens 2.54 cm wide and a gage length of 18 cm, in accordance with ASTM D 828-97. Only the machine direction (MD) results are reported.

Results


	Additive and
	Level in	MD Tensile	MD Work to
Example	PPS layer.	Strength (kg/cm)	Break (kg · cm)

A	None	3.79	20.02
(Comparative)
1	1% Zn Stearate	3.80	19.86
2	0.5% SnEH	6.01	34.65
3	0.5%/0.13% Zn	4.21	23.22
	Stearate/ZnO
4	0.25% ZnO	4.30	24.29
5	0.25% SnO	5.06	28.45
6	0.66%/0.33% Zn	5.36	29.81
	Stearate/SnEH
7	0.5%/0.25% Zn	4.26	19.53
	Stearate/SnEH
8	1% Ca Stearate	3.93	18.88
9	0.5% Ca Stearate	3.53	18.70

The effect of the tin and/or zinc additives in raising the tensile strength and total energy to break of the web is clear from these examples.

Claims

1. A process for manufacturing a nonwoven web comprising the steps of (i) spinning bicomponent fibers into a nonwoven web, said fibers comprising continuous phases each of a first polyarylene sulfide (PAS) component and a polymer component, in which the first polyarylene sulfide component contains a tin or a zinc additive or both, and the first polyarylene sulfide component of any given fiber is at least partially exposed to the external surface of that fiber, and (ii) calendaring the nonwoven web.

2. The process of claim 1 in which the step of spinning is a spunbond process.

3. The process of claim 1 in which the polymer component comprises a polymer selected from the group consisting or polyether ether ketone (PEEK), polyether ketone (PEK), polyester, polypropylene, polyamide, and mixtures thereof.

4. The process of claim 3 in which the polyester comprises polyethylene terephthalate (PET), polytrimethylene terephthalate, or polybutylene terephthalate (PBT).

5. The process of claim 1 in which the second polymer component comprises a second polyarylene sulfide.

6. The process of claim 5 in which the second polyarylene sulfide is blended with a calcium salt.

7. The process of claim 6 in which the calcium salt is calcium stearate.

8. The process of claim 1 in which the tin additive is a branched carboxylate selected from the group consisting of Sn(O₂CR)₂, Sn(O₂CR)(O₂CR′), Sn(O₂CR)(O₂CR″), and mixtures thereof, where the carboxylate moieties O₂CR and O₂CR′ independently represent branched carboxylate anions and the carboxylate moiety O₂CR″ represents a linear carboxylate anion

9. The process of claim 8 in which tin additive further comprises a linear tin(II) carboxylate Sn(O₂CR″)₂

10. The process of claim 8 in which the sum of the branched carboxylate moieties O₂CR and O₂CR′ is at least about 25% on a molar basis of the total carboxylate moieties O₂CR, O₂CR′ and O₂CR″ contained in the tin additive.

11. The process of claim 8 in which the radical R″ is a primary alkyl group comprising from 6 to 30 carbon atoms.

12. The process of claim 11 in which the radical R″ is substituted with a group selected form the group consisting of fluoride, chloride, bromide, iodide, nitro, hydroxyl, carboxylate, and any combination thereof.

13. The process of claim 8 in which the radicals R and R′ independently or both have a structure represented by Formula (I),

wherein R₁, R₂, and R₃are selected from the group consisting of:

H;

a primary, secondary, or tertiary alkyl group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups;

an aromatic group having from 6 to 18 carbon atoms, optionally substituted with alkyl, fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups; and

a cycloaliphatic group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups;

with the proviso that when R₂and R₃are H, R₁is:

a secondary or tertiary alkyl group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups;

an aromatic group having from 6 to 18 carbons atoms and substituted with a secondary or tertiary alkyl group having from 6 to 18 carbon atoms, the aromatic group and/or the secondary or tertiary alkyl group being optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups; and

a cycloaliphatic group having from 6 to 18 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, hydroxyl, and carboxyl groups.

14. The process of claim 8 in which the radicals R and R′ independently or both have a structure represented by Formula (I), and R₃is H.

15. The process of claim 8 in which the radicals R and R′ independently or both have a structure represented by Formula (II),

wherein

R₄is a primary, secondary, or tertiary alkyl group having from 4 to 6 carbon atoms, optionally substituted with fluoride, chloride, bromide, iodide, nitro, and hydroxyl groups; and

R₅is a methyl, ethyl, n-propyl, sec-propyl, n-butyl, sec-butyl, or tert-butyl group, optionally substituted with fluoride, chloride, bromide, iodide, nitro, and hydroxyl groups.

16. The process of claim 8 in which the radicals R and R′ are the same and both have a structure represented by Formula (II), R₄is n-butyl, and R₅is ethyl.

17. The process of claim 1 in which the tin additive is present at a concentration of about 10 weight percent or less of the weight of the first polyarylene sulfide component.

18. The process of claim 1 in which the zinc additive comprises a zinc(II) additive or zinc metal [Zn(O)] or a mixture of both.

19. The process of claim 18 in which the zinc(II) additive is an organic additive or an inorganic additive or a mixture of both.

20. The process of claim 19, wherein the Zn(II) additive is selected from the group consisting of zinc oxide, zinc stearate, zinc sulfate and mixtures thereof.

21. The process of claim 1, wherein the zinc and tin additives are present at a total concentration of equal to or less than about 25 weight percent, based on the weight of the polyarylene sulfide.

22. The process of claim 21, wherein the Zn(II) additive and zinc metal are present at a total concentration of zero to about about 10 weight percent or less, based on the weight of the polyarylene sulfide.

23. The process of claim 5, wherein the first polyarylene sulfide, or the second polyarylene sulfide, or both are polyphenylene sulfide.

24. The process of claim 1 comprising calendaring the nonwoven web for a time and temperature sufficient to bond at least a subset of the individual fibers.